This PDF file contains the front matter associated with SPIE Proceedings Volume 8409, including the Title Page, Copyright information, Table of Contents, and Introduction, and Conference Committee listing.

In this paper, the variational principle of functionally graded circular plate is presented by the variational integral method taking temperature change into account. The vibration governing equation is illustrated, which will be benefit for the numerical simulation with finite element method in further investigations. The numerical results show that the natural frequency increases as the graded coefficient increases in the chosen domain. It can be observed that the vibration characteristics are influenced by the temperature changes obviously. Moreover, the natural frequency is larger for thicker FGM circular plates, while it is lower for thinner ones. Furthermore, the first four vibration mode shapes with different thickness of FGM circular plate are illustrated.

The amplitude-frequency response of the simple supported SMA laminated beam under harmonic excitation is studied. The nonlinear dynamic equation of the beam was constructed in the authors' recent researches, in which the generalized restoring force caused by SMA layers is the piecewise function of state variable. The dynamics equation of the beam is solved by average method at first, and the amplitude-frequency response equation with piecewise characteristics is obtained. Finally, the constrained bifurcation theory is introduced to study the relationship between the responses and the parameters of the system. Through calculation, it is found that there are 10 qualitatively different kinds of amplitudefrequency response curves corresponding to 10 regions in the parameter space which is composed by the amplitude of harmonic excitation and elastic modulus of substrate. The results can guide directly the design of the SMA laminated beams to make them vibrating as the desirable mode.

Thermal-response amorphous polymer is a typical soft active material where the glass transition occurs as temperature changes. In the process of glass transition, the amorphous polymer will go through the transitions between the glassy state and the rubber state. Furthermore, as subjected to a combining load of the mechanics and temperature, the materials will experience deformation and glass transition simultaneously and exhibit some peculiar macroscopic response. To describe this behavior, we consider the evolution of natural configurations as the main mechanism for such thermo-mechanical behavior, and develop a thermo-mechanical constitutive model of polymer under mechanical and thermal loads. As application the proposed model, we investigate the uniaxial thermo-mechanical behavior of the soft active polymers. It is shown that the model is effective for describing the coupling behavior of material evolution with large deformations in the glass transition region.

Temperature stability and durability of magnetorheological fluids are important for engineering application. The damper with magnetorheological fluids were put in environment of -40°C to 130°C and the forces were measured under different currents. Durability was evaluated by performance experiments of 2×10⁶, 3.5×10⁶,and 5×10⁶ cycles. The results show that magnetorheological fluids have ideal temperature stability and durability.

A traditional solid-state sintering method was used to fabricate 0.55Pb(Ni_1/3Nb_2/3)O₃-0.45Pb(Zr_0.3Ti_0.7)O₃ (0.55PNN-0.45PZT) relaxor-ferroelectric ceramics with CuO as sintering aid. The influence of xCuO additions (x=0.0, 0.2, 0.4, 0.6, 0.8 wt.%) on the microstructure and electrical properties of the 0.55PNN-0.45PZT ceramics was investigated. X-ray diffraction patterns demonstrated that all specimens formed a typical perovskite structure with pseudo-cubic phase. Cu²⁺ ions entered into the B sites in ABO₃ structure for the PNN-PZT solid solution ceramics. The additions of CuO improved the sinterability of the 0.55PNN-0.45PZT ceramics. The grain size and density of these specimens increased slightly with increasing amounts of CuO addition. The specimen with 0.4 wt.% CuO addition achieves the maximum value of density ρ~8108 kg/m3. Meanwhile, the piezoelectric, dielectric and ferroelectric properties also enhanced significantly with increasing amount of CuO addition. Excellent properties, d₃₃~777 pC/N, k_p~55%, ε₁ r~7365, tanδ~2.9%, p_r~18.86 μC/cm², and E_c~3.52 kV/cm were obtained for the 0.55PNN-0.45PZT ceramics with 0.4 wt.% CuO addition sintered at 1125°C for 2 h.

For several decades, morphotropic phase boundary (MPB) in ferroelectric materials has attracted constant interest due to its great enhancement of piezoelectric properties. However, such a MPB has been studied merely in ferroelectric system, not in ferromagnetic system. Recently, we reported the magnetic MPB in a ferromagnetic system of TbCo₂-DyCo₂ and correspondingly a larger magnetostriction (i.e. a piezoelectricity-like phenomenon in ferromagnets) occurs near MPB. Very surprisingly, such a MPB in TbCo₂-DyCo₂ system has been ever regarded as a spin reorientation transition (SRT) where the spontaneous magnetization (Ms) gradually rotates from <111> in TbCo₂-rich phase to <001> of DyCo₂-rich phase and vice versa. But, our experiment of synchrotron x-ray diffractometry demonstrates the MPB region is the coexistence of TbCo₂ and DyCo₂ phases and hence the Ms cannot rotate gradually from <111> to <001>¹. Thus, the process of magnetization rotation near MPB in a ferromagnetic system of TbCo₂-DyCo₂ remains obscure due to a lack of in-situ observation of magnetic moment rotation. In the present work, by using a method of Monte Carlo simulation, we successfully reproduce the observed effects and furthermore clarify the magnetization rotation process near the magnetic MPB of TbCo₂-DyCo₂ systems. Namely, the direction of magnetization changes discontinuously from <111> to <001> near the MPB via the phase transition process from TbCo₂-rich phase to DyCo₂-rich phase. Our simulation provides an effective way to understand the origin of the magnetic MPB.

This work studies the effect of doping with magnesium trisilicate for LiFePO₄/C cathode materials by a solid-state method. The samples were synthesized by two-step processing. Firstly, it was heated at 360 °C for 10 hours and then was calcined at 700°C for 10 hours. All the annealing processing was carried out in argon atmosphere. The phase structure, morphology and element distribution of prepared samples were characterized by XRD and scanning electron microscope and energy dispersive spectrometer. The results show that Mg²⁺ and Si⁴⁺ co-doped LiFe_0.99Mg_0.01P_0.985Si_0.015O₄/C cathode materials exhibit higher capacity and rate capability than the unsubstituted LiFePO₄/C cathode. For example, LiFe_0.99Mg_0.01P_0.985Si_0.015O₄/C exhibit discharge capacity of 146 mAh·g^-1 compared to 140mAh·g^-1 for unsubstituted LiFePO₄/C at 0.5C. Especially, at 5C rate, the discharge capacity of LiFe_0.99Mg_0.01P_0.985Si_0.015O₄/C was remarkably exceeded that of unsubstituted LiFePO₄/C cathode materials. The better performances of the cathode were attributed to the increase of electronic conductivity and the improved migration of lithium ion.

Polythiophene /multi-wall carbon nanotubes (MWNT) composites were prepared by ball-mailing. The morphology and internal structure of the composites were evaluated by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD). Their thermoelectric properties, i.e., the electrical conductivity, the Seebeck coefficient and the thermal conductivity, were investigated in detail. The remarkably increased electrical conductivity, the slightly increased Seebeck coefficient and the relatively insensitive thermal conductivity with increasing MWNT content led to an obvious enhancement in the thermoelectric figure of merit. The results showed that the MWNT were uniformly dispersed in the polymer matrix, and that increasing the electrical conductivity is the key factor for enhancing the thermoelectric figure of merit. This study suggested a simple way to improve the thermoelectric performances of conducting polymers.

Acoustic Emission (AE) evaluation is one of the fast growing non-destructive techniques, owing to its ability to reveal in advance of any impending failure of a building structure. This capability makes the so called passive ultrasonic technique a very good tool in structural health monitoring; especially for composite structures. In metallic structures, AE technique is currently well established and able to provide accurate and consistent results. However, in composites, the challenge for a reliable AE results is huge due to the orthotropic behaviour of the materials. The present study investigates the energy attenuation of AE signals in thin composite plate and utilized the attenuation pattern into non-velocity based source location detection. Standard Hsu-Nielsen source location testing was applied on a glass fibre epoxy resin laminate and a single channel AE system was used to acquire AE signals with the support from AEWin software for signal analysis. Form the results; a new AE signals energy attenuation model for composite laminate was proposed. Then, a linear source location algorithm utilizing AE signals energy attenuation patterns was developed and tested for the composite specimen. The results revealed that the source location algorithm provides reasonably accurate results of source location for glass fibre epoxy resin laminate.

The acoustical parameters of porous materials such as tortuosity factor, viscous and thermal characteristic length, and static flow resistivity, are very important, but not obtained directly from the conventional experimental measurements. Hence, in this study, the methods based on the Johnson-Champoux-Allard model and including the simulated annealing generic algorithm and successive quadratic programming are put forward so as to determine the acoustical parameters of a kind of sintered fibrous metal. And the corresponding results are compared to each other. It is found that the determination of the acoustical parameters of the sintered fibrous metals employing the simulated annealing generic algorithm is not only accurate, but also has good robust properties. Moreover, the work shows that utilizing the successive quadratic programming method can also obtain good results provided that the optimization variables are chosen appropriately. Finally, some calculated and measured results are given and discussed to verify the validity of the presented methods further.

The transfer matrix method, based on plane wave theory, of multi-layer equivalent fluid is employed to evaluate the sound absorbing properties of two-layer-assembled and three-layer-assembled sintered fibrous sheets (generally regarded as a kind of compound absorber or structures). Two objective functions which are more suitable for the optimization of sound absorption properties of multi-layer absorbers within the wider frequency ranges are developed and the optimized results of using two objective functions are also compared with each other. It is found that using the two objective functions, especially the second one, may be more helpful to exert the sound absorbing properties of absorbers at lower frequencies to the best of their abilities. Then the calculation and optimization of sound absorption properties of multi-layer-assembled structures are performed by developing a simulated annealing genetic arithmetic program and using above-mentioned objective functions. Finally, based on the optimization in this work the thoughts of the gradient design over the acoustic parameters- the porosity, the tortuosity, the viscous and thermal characteristic lengths and the thickness of each samples- of porous metals are put forth and thereby some useful design criteria upon the acoustic parameters of each layer of porous fibrous metals are given while applying the multi-layer-assembled compound absorbers in noise control engineering.

Vibration-based piezoelectric energy harvesters through the conversion of vibration energy to electrical energy has gained increasing attention over the past decade because of the reduced power requirements of small electronic components, especially in industrial condition monitoring applications where sensors may be embedded in machines. The structure parameters of cantilevered piezoelectric energy harvesters are of importance to maximize the output power in accordance with the characteristics of the ambient vibrations. Therefore, a piezoelectric cantilevers optimization method using finite element analysis and SPICE is proposed. This paper models piezoelectric cantilever using Hamilton principle and extracts the vibration modal parameters to establish the circuit model in SPICE. The numerical analysis is addressed to study the effect of parameters. Finally, the optimization analysis and experiment are carried out. The results verify that the optimized cantilevered piezoelectric energy harvesters can produce a 56V peak open-circuit voltage, and that the proposed method is suitable for optimization design of piezoelectric energy harvester.

Bulk metallic glasses are a new type of advanced materials. They are characterized by their topologically disordered atomic structures. The lack of long-range translational symmetry in the atomic arrangement in bulk metallic glasses contributes to a range of unique and outstanding mechanical properties. For example, the yield strength of metallic glasses can be as large as twice that of corresponding crystalline alloys. However, the major issue to hinder metallic glasses application is the apparent brittleness. Unlike crystalline alloys, metallic glasses show abrupt failure with zero macroscopic plasticity. Various methods are being investigated in material engineering to improve the plasticity of bulk metallic glasses. The most recent progress is to develop shape memory bulk metallic glass composites, a combination of metallic glass and shape memory alloy. The large stress-induced transformation strain in shape memory alloy leads to the increase in the plasticity of the new composite material. The stress-strain behaviour of shape memory bulk metallic glass composites was investigated in this paper by using the finite element method. A unit cell model, which includes shape memory alloy phase and metallic glass phase, under uniaxial tension were numerically simulated. The effects of phase volume fraction, transformation stress and strain on the stress-strain behaviour of this new composite material were examined in this research.

The fatigue failure of a super-elastic NiTi alloy was observed by uniaxial stress-controlled cyclic tests. During the cyclic loading a hysteresis loop with a varied but stabilized size after certain cycles was obtained, which is similar to plastic shakedown. The material exhibits unique brittle fracture with a large transformation strain. The fatigue life of the material greatly depends on the applied peak nominal stress, the nominal stress amplitude and the mean nominal stress. A relation between the dissipation energy at the stabilized stage of cyclic loading and the number of cycles at failure was derived from the experimental results. Based on the obtained experimental results, a uniaxial fatigue failure model based on the energy approach was proposed to predict the fatigue life. It was shown that the proposed model provides good predictions to the uniaxial fatigue lives of super-elastic NiTi alloys with different types of cyclic stressing.

Ferromagnetic shape memory alloys (FSMAs) are a special type of smart materials which can commonly display strains of about 6 % by applying an external magnetic field. The large magnetic induced strain and the possibility of non-contact actuation make those materials promising active elements for actuators. The effectiveness of those materials as active elements was experimentally proved in previous works, and it was demonstrated that despite the non-linear and hysteretic response of FSMA materials, they can be successfully controlled, achieving positioning accuracies of the order of a nanometer. In this work, a new actuator based on FSMA is proposed. Two orthogonal applied magnetic fields allow to simultaneously control both the contraction and the expansion of the material. As considerably high magnetic fields are necessary to operate the material, in order to reduce the actuator size, a pulse operation mode is used, which involves higher currents (up to 250 A) during a short time (4-12 ms). A specific high power electronic module is designed for this purpose and magnetic fields up to 0.4 Tesla are achieved. Preliminary positioning experiments are shown.

Deformation recovery capability is one of the important indexes to examination shape memory effect of the shape memory polymers (SMPs). And the shape memory characteristic of SMPs is closely related to different phase states and mechanical properties above and below the glass transition temperature (T_g). In this paper, we investigated the strain recovery response of a thermoset shape memory epoxy resin modified by polyurethane (PU) through uniaxial compression experiments under various isothermal conditions and strain rates and developed a "three-phase" constitutive model based on phase transition concept, which including stationary phase, active phase and frozen phase. This model established the mutual transformation relationships between frozen phase and active phase of SMPs by introducing temperature switch function, which presents the stain storage and release process of SMPs under loading and changing temperature environment. Besides, the proposed model represents the SMPs deformation process of viscous hysteresis response by employing the rheological elements description of the three phases. The numerical results agree very well with experiment results of stress-strain response curve of isothermal compression/unloading test, which validated this model can predict the finite deformation behavior of SMPs.

This paper presents the design, fabrication and experimental characterization of a valveless micropump actuated by an ionic-polymer-metal-composite (IPMC) soft actuator. The performance of the IPMC varies over time, therefore on-line iterative feedback tuning (IFT) is used to adaptively tune the PID controller to control the bending deflection of the IPMC to ensure a constant pumping rate. The pump rate is higher at lower frequencies for a given applied voltage to the IPMC. A maximum flow rate of 130 μl/min is achieved at 0.1 Hz.

The demand for single cell manipulation to allow scientist to carry out medical researcher is fast increasing. To facilitate this advanced manipulation systems are required to permit both precise and safe handling of the biological cells. Current devices can achieve a high level of precision at the micro/nano scale but as a consequence are highly rigid and this stiffness puts the target cells at risk as there is no compliance or back-drivability. Ionic polymer-metal composites (IPMCs) are naturally compliant, giving them a 'soft touch', and now with recent advances in their fabrication and control IPMCs are showing major promise as safe and accurate cell manipulators. This paper presents the development of an optimally tuned force controller for a 2 degree-of-freedom (2DOF) IPMC actuated micro-manipulator. The control system has been implemented to demonstrate the ability to control the manipulator's applied force as a step towards implementing a truly safe system with active compliance control. The controller is adaptively tuned using a model-free iterative feedback tuning (IFT) approach which is ideal for operation in unknown cellular environments as well as for controlling the complex time-varying behavior of the IPMC actuators themselves. The IFT algorithm tunes the force controller by minimizing the design criteria, a least squares error, by 25% in the horizontal direction and 46% in the vertical direction. Experiments then show that the manipulator can accurately track a reference trajectory up to 4gf or ~40mN in both DOF.

A novel flexible strain sensor was developed using a conducting polymer coated on rubber for large strain measurements. A coating of the conducting polymer, polypyrrole, was deposited on a strip of natural rubber through the process of vapour phase polymerisation while the rubber is in a stretched state. This process involves depositing a layer of oxidant on the rubber surface, followed by exposure to pyrrole monomer vapours that polymerize on the oxidantcoated rubber to produce polypyrrole. The change in electrical resistance of the strain sensor was recorded while cyclic strain from 0% to 20% was exerted on it. The gauge factor of the strain sensor was calculated to be 1.86. From repeated electrical resistance-strain measurements, the repeatability of the strain sensor was studied. A hysteresis was observed in a single extensionretraction strain cycle. Further study showed that the observed hysteresis is dependent on the strain rate where lower strain rate resulted in higher hysteresis and vice versa for a higher strain rate. There is also an electrical resistance drift between consecutive extension-retraction cycles. Owing to the flexibility of the rubber, the strain sensor can be used in complex configurations. The strain sensor can also be mounted or attached directly on surfaces to provide low-profile installation where space constraint is an issue. These characteristics offer advantages over traditional strain sensors to be used in applications that were not previously possible.

Nanometer spherical spinel lithium manganates with about 20nm in diameter were synthesized for the first time by explosive method. The water-solubility explosive was prepared using a simple facility at room temperature. The growth of lithium manganate via detonation reaction was investigated with respect to the presence of an energetic precursor, such as the metallic nitrate and the degree of confinement of the explosive charge. For detonation of the water-solubility explosive, the detonation pressure, the detonation temperature and the adiabatic gamma were 2-5 GPa, 2000-3000 K and close to 3. The inherent short duration, high heating rate (10¹⁰-10¹¹ K/s) and high cooling rate (10⁸-10⁹ K/s) prevent the lithium manganate crystallites from growing into larger sizes and induce considerable lattice distortion.

In this study, formaldehyde, one of the major volatile organic compounds, is chosen as the target pollutant. The polytetrafluoroethylene (PTFE) filter, a low cost and commonly used material in industry, is employed as the substrate for nano TiO₂ photocatalyst coating at room temperature, which has been scarcely used compared to ceramics or glass beads. Furthermore, a specific experimental set-up that is similar to actual air purification system is developed for the testing. The degradation mechanisms of photolysis reaction, adsorption and photocatalytic oxidation reaction on volatile organic compounds are present respectively. The influences of three aspects mentioned above are compared by a serial of experimental data. The high efficiency of volatile organic compounds on the degradation of formaldehyde is assured. Furthermore, the purification characteristics of three kinds of activated carbon filters and PTFE filter with nano TiO₂ are evaluated with the method of fuzzy mathematics. In the end, the result shows that the filter with nano TiO₂ has the optimal comprehensive performances.

An experimental study is reported in this paper demonstrating monitoring of surface-fatigue crack propagation in a welded steel angle structure using Lamb waves generated by an active piezoceramic transducer (PZT) network which was freely surface-mounted for each PZT transducer to serve as either actuator or sensor. The fatigue crack was initiated and propagated in welding zone of a steel angle structure by three-point bending fatigue tests. Instead of directly comparing changes between a series of specific signal segments such as S0 and A0 wave modes scattered from fatigue crack tips, a variety of signal statistical parameters representing five different structural status obtained from marginal spectrum in Hilbert-huang transform (HHT), indicating energy progressive distribution along time period in the frequency domain including all wave modes of one wave signal were employed to classify and distinguish different structural conditions due to fatigue crack initiation and propagation with the combination of using principal component analysis (PCA). Results show that PCA based on marginal spectrum is effective and sensitive for monitoring the growth of fatigue crack although the received signals are extremely complicated due to wave scattered from weld, multi-boundaries, notch and fatigue crack. More importantly, this method indicates good potential for identification of integrity status of complicated structures which cause uncertain wave patterns and ambiguous sensor network arrangement.

The effect of elevated temperature on the modulus of glass/epoxy composites was studied. Dynamic mechanic analysis (DMA) was carried out to investigate the storage modulus, loss modulus, loss factor and glass transition temperature. Static flexural modulus was also tested by control force mode in DMA. The effect of elevated temperature on the modulus of the composites was evaluated between 30°C and 120°C. A new temperature-dependent model both for the dynamic storage modulus and static flexural modulus was proposed. The model only needed one parameter to fit the experiment data and showed good accordance with experimental results. The physical meaning for the parameter of the model was given.

ZnO films with exceptional homogeneity and surface smoothness have been hydrothermally grown by using lateral epitaxial overgrowth (LEO). A thin ZnO seed layer film was beforehand grown in water at 90°C on a MgAl₂O₄ (111) substrate as a buffer layer. The LEO method using a mask with an optimized ratio of window to wing was then employed to reduce threading dislocations at the boundaries of crystal mosaic in the epitaxial films. The dislocations arose from unmasked window and coalescence of masked wings while they were seldom present in the wing area. The average dislocation density significantly reduced from 1.4 x 10⁹ to 2.3 x 10⁸ cm^-2 via the LEO. However, it decreased slightly to 1 x 10⁸ cm^-2 after a double LEO applied for further dislocation reduction since new threading dislocations were produced at the coalescence of wings from the LEO.

Thermal energy storage plays an important role in heat management because of the demand for developed energy conservation, and has applications in diverse areas, from buildings to textiles and clothings. In this study, we aimed to improve thermal characteristics of polyurethane rigid foams that have been widely used for thermal insulation in electrical water heaters. Through this work, paraffin waxes with melting point of 55~65°C act as phase change materials. Then the phase change materials were incorporated into the polyurethane foams at certain ratio. The polyurethane/phase change composite materials used as insulation layers in electrical water heaters performed the enthalpy value of 5~15 J/g. Energy efficiency of the electrical water heaters was tested according to the National Standard of China GB 21519-2008. Results show that 24 h energy consumption of the electrical water heaters manufactured by traditional polyurethane rigid foams and polyurethane/phase change material composites was 1.0612 kWh and 0.9833 kWh, respectively. The results further show that the energy-saving rate is 7.36%. These proved that polyurethane/phase change composite materials can be designed as thermal insulators equipped with electrical water heaters and have a significant effect on energy conservation.

Metallic oxide/carbon composite has been extensively studied and widely used for energy storage in supercapacitor and lithium ion battery. In this paper, we synthesized nanograins-grafted nanorods of MoO₂/carbon composites through a facile chemical reaction process without any template. Well crystallized MoO₂ with monoclinic structure was identified in the XRD pattern. MoO₂ nanograins with the size of 30-50nm were grown on the carbon nanorods, which were a few microns in length. Coupling of the rods-like carbon with good conductivity and the well distributed redox-active MoO₂ leads to improved electrochemical performance. The cyclic voltammogram measurement shows that the as-prepared nanocomposites exhibit a broad potential window of 1.3V, which is extremely desired for supercapacitor application. The symmetrical supercapacitor of the nanograins-grafted nanorods of MoO₂/carbon composites can work even at a high electric potential of 1.2V in aqueous electrolyte which seems impossible for many other metallic oxide and carbon composites.

In this paper, vibration characteristics of piezoelectric fiber composite beams are presented. An asymptotic method based on virtual work principle is introduced first. The primary variables in thermo-electro-mechanical problems are asymptotically expanded in terms of the small parameter, which is done by taking the geometric slenderness of the beams. This subsequently renders a set of recursive virtual works at each order, in which the virtual works are separated into two parts: 2D microscopic problems and 1D macroscopic problems. These microscopic and macroscopic problems are systematically associated with each other, and thus the boundary conditions are affected by both of them. Cantilever beams under multiphysics environment are taken as a test-bed in order to illustrate the significance of edge effects and asymptotical correctness to the vibration characteristics of the beams. For the displacement prescribed boundary such as the clamped boundary, the stress weighted average conditions are applied to obtain the accurate prediction, which are known to be a good approximation (possibly the best candidate up to date).

Carbon fiber reinforced plastics (CFRP) cables were initially most investigated to replace steel cables. To further explore the advantages of FRP cables, the potential ability of vibration control is studied in this paper emphasizing the designable characteristic of hybrid FRP cables. Fiber reinforced vinyl ester composites and fiber reinforced epoxy composites were prepared by the pultrusion method. Due to the extensive application of fiber reinforced composites, the temperature spectrum and frequency spectrum of loss factor for the composite were tested using dynamic mechanical analysis (DMA) equipment. The damping properties and damping mechanism of the composite were investigated and discussed at different temperatures and frequencies. The result indicates that the loss factor of the composites is increasing with the increase of the frequency from 0.1Hz to 2 Hz and decreasing with the decrease of the temperature from -20°C to 60°C. The loss factor of the carbon fiber composite is higher than that of the glass fiber for the same matrix. The loss factor of the vinyl ester composite is higher than that of the epoxy composite for the same fiber.

It is conventional practice in the study of elasticity to determine the response of a structure to a known force. Such problems are referred to as direct problems as they involve determination of unknown effects of a known cause. The identification problem of determining the force acting on a structure from measurements of response of the structure to force using different types of sensors is the inverse problem. In many practical situations, it is difficult to perform direct measurements of external forces acting on an existing vibrating structure. Instead, the structural response may then be measured from a proper sensor like strain gauges, accelerometers, vibrometers, etc., and position and magnitude of exciting forces be calculated from measured response. Unfortunately, the results from the inverse process are often highly sensitive to noise in the measurements of response and errors in the model of the structure leading to ill conditioning. This paper presents force identification for a cantilever beam subjected to impact force. The acceleration response is used as the input for the prediction. The force prediction algorithm using inverse Frequency Response Function method is developed to determine the history of impact force amplitude by minimizing an objective function using least square method. Results have shown that the general inverse technique can be used to identify unknown forces using response data. Best results are obtained when accelerometer is located close to the location of the unknown forcing function. The developed methodology can be easily extended to other structures for impact force prediction.

The possibility as a vibration sensor of Electro-Active paper (EAPap) based on piezoelectricity was investigated in the present paper. The EAPap was fabricated by regenerating and tape casting cellulose. The gold, silver and aluminum were deposited on both sides of the cut cellulose film using a thermal evaporator. The sample was coated by thin laminating film for packaging. The simple aluminum cantilevered beam was used for the vibration testing and EAPap was attached on the beam. The original EAPap sensor without grounding and shielding has greatly affected by the surrounding noise such as power noise especially. The power noise reduced dramatically with grounding and shielding of EAPap. The impulsive response of EAPap provided correct dynamic characteristics of the beam. Forced response of EAPap presented that gold and silver electrodes are suitable for EAPap sensor but aluminum electrode provides too many noise due to high resistance. PVDF provided similar characteristics of EAPap, which results EAPap has high potential as a vibration sensor.

Most of the currently available vibration-based identification approaches for structural damage detection are based on eigenvalues and/or eigenvectors extracted from vibration measurements and, strictly speaking, are only suitable for linear system. However, the initiation and development of damage in engineering structures under severe dynamic loadings are typical nonlinear procedure. Studies on the identification of restoring force which is a direct indicator of the extent of the nonlinearity have received increasing attention in recent years. In this study, a date-based time domain identification approach for general nonlinear system was developed. The applied excitation and the corresponding response time series of the structure were used for identification by means of standard least-square techniques and a power series polynomial model (PSPM) which was utilized to model the nonlinear restoring force (NRF). The feasibility and robustness of the proposed approach was verified by a 2 degree-of-freedoms (DOFs) lumped mass numerical model equipped with a shape memory ally (SMA) damper mimicking nonlinear behavior. The results show that the proposed data-based time domain method is capable of identifying the NRF in engineering structures without any assumptions on the mass distribution and the topology of the structure, and provides a promising way for damage detection in the presence of structural nonlinearities.

CFRP composite material has superior specific strength and rigidity compared to metallic material, and is widely adopted in the various fields. Exceptional corrosion resistance enables the acceptance in maritime structural members such as ship and oildrilling machineries. However, CFRP composite material has the weakness in hygrothermal environment and crash environment. Especially, moisture ingress into composite material under hygrothermal environment can change molecule arrangement and chemical properties. In addition, interface characteristics and component material properties can be degraded. An experimental investigation was carried out to study the crash evaluations of CFRP composites to dynamic crushing by impact loading. We have made a collapse experiment to research into the difference of absorbed energy and deformation mode between moisture absorbed specimen and non-moisture absorbed specimen. As a result, the effect of moisture absorption and impact loads of approximately 30~50% reduction in strength are shown.

The measurement of stress of concrete structures under impact loading and other strong dynamic loadings is crucial for the monitoring of health and damage detection. Due to its main advantages including availability, extremely high rigidity, high natural frequency, wide measuring range, high stability, high reproducibility, high linearity and wide operating temperature range, piezoelectric (Lead Zirconate Titanate, PZT) ceramic materials has been a widely used smart material for both sensing and actuation for monitoring and control in engineering structures. In this paper, a kind of stress sensor based on piezoelectric ceramics for impact stress measuring of concrete structures is developed. Because the PZT is fragile, in order to employ it for the health monitoring of concrete structures, special handling and treatment should be taken to protect the PZT and to make it survive and work properly in concrete. The commercially available PZT patch with lead wires is first applied with an insulation coating to prevent water and moisture damage, and then is packaged by jacketing it by two small precasted cylinder concrete blocks with enough strength to form a smart aggregate (SA). The employed PZT patch has a dimension of 10mm x 10mm x 0.3mm. In order to calibrate the PZT based stress sensor for impact stress measuring, a dropping hammer was designed and calibration test on the sensitivity of the proposed transducer was carried out with an industry charge amplifier. The voltage output of the stress sensor and the impact force under different free falling heights and impact mass were recorded with a high sampling rate data acquisition system. Based on the test measurements, the sensibility of the PZT based stress sensor was determined. Results show that the output of the PZT based stress sensor is proportional to the stress level and the repeatability of the measurement is very good. The self-made piezoelectric stress sensor can be easily embedded in concrete and provide reliable stress sensing under dynamic loadings.

Launch vehicles, satellites and aircrafts often experience harsh vibration and pyroshock loads during the flight including maneuvering and separation events, which may cause the malfunction of equipped electronic devices. Furthermore, this minor malfunction can generate catastrophic failure of the whole mission. To prevent malfunction of the electronic devices from severe shock and vibration loads, elastomeric isolators are commonly applied between the electronic device and the equipment bay structure in the aerospace fields. However, this rubber type elastomeric material is vulnerable to the low-frequency vibration load which involves large amount of displacement due to its low stiffness. Recently, the present authors proposed new type of isolator, called as pseudoelastic hybrid mesh isolator. This talk introduces the key features of this new pseudoelastic hybrid mesh isolator which shows better isolation performance throughout all frequency range than conventional isolators.

In order to study the application of detonation synthesis method in preparing nanoscale ceria(CeO₂), ceria powder was synthesized by detonation method. The synthesis experiment was carried out in explosion containment vessel by initiating the emulsion explosive in which Ce(NO₃)₃·6H₂O acted as the main oxidant. The phase composition, crystal form, appearance and microstructure of the as-synthesized products were characterized by X-ray diffraction(XRD) and Transmission Electron Microscope(TEM). The result from XRD test indicated that the nanoscale ceria belonged to cubic phase. The mean size of ceria grain was 26nm based on the calculation result according to Scherrer equation. The result from TEM test presented that the as-synthesized ceria grain was spherical by appearance, and the size was uniform. According to TEM test result, the mean size of ceria grain was between 20nm and 30nm, which coincided with calculation result perfectly.

The present study attempts to investigate the synergistic effects of graphene nanoplatelets and multi-wall carbon nanotubes on mechanical and physical properties when used as nano-fillers in a conventional aerospace epoxy system. Towards this direction, 0.5 % w.t. graphene nanoplatelets (GNPs) consisting of several graphene sheets with an overall average thickness of 10 nanometers and average diameter of 5 microns are homogenously dispersed along with 0.3 % w.t. multi-walled carbon nanotubes with average diameter about 10-15 nm and length larger than 500 nm. The dispersion of the hybrid GNP/MWCNTs epoxy mixture was achieved using a Torus Mill™ device under vacuum which introduced high shear forces by a high-speed rotating disc and reduced the nano-particle agglomerates due to the milling effect generated by zirconium dioxide beads. Furthermore using same dispersion technique non-hybrid nano-composites were produced with: (a) 0.5% w.t. GNP and (b) 0.3% w.t MWCNTs. Also neat epoxy samples were produced. The experimental campaign started with SEM microscopy in order to gain an insight for the homogeneous dispersion of both nano-fillers. Furthermore electrical & thermal conductivity and glass transition temperature (Tg) measurements were conducted. Finally tensile and flexure tests were performed. The nano-composites doped only with GNPs exhibited the highest tensile and flexural modulus with hybrid material recording the worst performance. On the contrary experimental results indicate that the presence of GNP proved beneficial for further increase of thermal and thermo-mechanical properties of nano-composites doped only with carbon nanotubes.

Theoretical intensity of carbon fibre is about 180GPa. However, the maximum intensity of carbon fibre in the available products hardly reaches 1/20 of the theoretical value. Based on micro damage principle of composites and microstructure of carbon fibre, this paper focused relationship between the actual intensity of carbon fibre and crystallization, orientation and pore conditions; searched for the analysis and calculation methods, and discussed the main factors which affected the intensity. Through novel theoretical analysis method and calculation algorithms, the theoretical obtained results were consistent with the experimental results. It is revealed that the pore density, size and orientation determine the carbon fibre intensity, which provides theoretical basis to improve the carbon fibre production.

Focus is here made on the approximate modal coupling evaluation and response analysis of the piezoceramic materials d₁₅ shear-mode response. Hence, different evaluation techniques of the effective modal coupling are assessed and twodimensional (2D) plane strain and plane stress free-vibration problems, under short-circuit and approximate, without equipotential (EP) constraints, and accurate, with EP, open-circuit electric conditions, are investigated with ANSYS^r 2D and three-dimensional finite elements for a literature shear-mode piezoceramic sandwich beam benchmark with different filling foams. It is shown that the EP physical constraints reduce dramatically the effective coupling, and the plane stress and strain results depend strongly on the filling foam stiffness.

In this paper, modeling and numerical analysis of a three dimensional shell structure made of shape memory alloy (SMA) are introduced. As a new smart material, SMA material has been applied in many fields due to two significant macroscopic phenomena which are called the shape memory effect (SME) and pseudoelasticity. The material of SMA exhibits two-way shape memory effect (TWSME) after undergoing especial heat treatment and thermo-mechanical training. This work investigates the numerical simulation and application of the SMA component: SMA strip, which has been pre-curved in the room temperature. The component is expected to extend upon heating and shorten on cooling along the curve. Hence the shape memory effect can be used to change the shape of the structure. The return mapping algorithm of the 3-D SMA thermomechanical constitutive equations based on Boyd-Lagoudas model is used in the finite element analysis to describe the material features of the SMA. In this paper, the ABAQUS finite element program has been utilized with a user material subroutine (UMAT) which is written in the FORTRAN code for the modeling of the SMA strip. The SMA component which has a certain initial transformation strain can emerge considerable deflection during the reverse phase transformation inducing by the temperature.

Most hydrogels exhibit coupled chemo-mechanical behaviors when in an aqueous environment with changing salt concentrations. This work presents a theoretical framework and a numerical procedure to describe the coupled mechanical deformation and solvent diffusion of such ion-sensitive hydrogels. A new variational formulation for the coupled governing equations is formulated by implementing the coupled formulations in a finite element procedure in Eulerian frame and further the time-dependent concurrent process of mechanical deformation and solvent diffusion is numerically investigated. The proposed numerical method is demonstrated by analyzing several chemo-mechanical coupling phenomena of initially-swollen hydrogels, such as transient free-swelling and indentation with a spherical punch. The results show that the present model is capable of simulating transient free-swelling and solvent migration in such smart materials subjected to externally-applied mechanical forces.

Shape memory polymer(SMP) is a class of smart materials used in intelligent biomedical devices and industrial application as sensors or actuators for their ability to change shape under a predetermined stimulus. Carbon nanotube (CNT)/shape memory polymer (SMP) composites demonstrate good mechanical properties and shape memory effect. In this work, a model of CNT/SMP composite shell with a vaulted cross-section was established. This composite shell structure could further elevate the recovery stress of CNT/SMP composites. The folding properties of CNT/SMP composite shell structure were analyzed by finite element method and the influence of structural parameters on the buckling behavior of the shell was studied using the energy conservation principle. The results indicate that vaulted cross-section shell had unique mechanical properties. The structural parameters, such as the vaulted radius and the total length have a great impact on buckling moment of the shell. This shell structure is expected to achieve effective control of buckling and deploying process, relying on the special shape memory property of SMP and high elastic modulus CNTs. Moreover, it could also largely avoid the vibration problem during the deploying process.

The micro-vibration control is necessary to vibration-sensitive precise apparatus and facilities under random environment disturbance. The composite structures with magneto-rheological visco-elastomer (MRVE) can effectively control the micro-vibration under certain external magnetic fields. In this paper, the fabrication of an MRVE by dispersing iron particles in viscous liquids, degassing the mixture and making it cured in molds is introduced firstly. The experimental study on the mechanical properties of MRVE and the effects of external magnetic field and vibration frequency on the MRVE properties is performed, and the results are given. Then the micro-vibration response of a sandwich plate with MRVE core under random support motion excitations is studied to evaluate its response reduction capacity. The differential equations of motion of the sandwich plate are derived from the dynamic equilibrium, constitutive and geometric relations. The Galerkin method is applied to convert the partial differential equations into ordinary differential equations. The expressions of frequency-response function, response power spectral density and root-mean-square velocity spectrum in terms of the one-third octave frequency band for micro-vibration are obtained and calculated. Finally, numerical results are given to illustrate the micro-vibration response reduction capacity of the MRVE sandwich plate under random support motion excitations.

The Gr/Epoxy laminated composite materials have high specific stiffness and strength for applications in the aerospace and industries. It is important to monitor the curing residual stress to ensure the reliability of composite materials. Fiber Bragg Grating (FBG) sensors are small and compatible with polymeric materials so that they can be easily embedded into the internal sensing site of a composite structure without introducing significant defections. This study embedded 4 FBGs into different laminae of composite materials to monitor the internal residual strain during the curing process. The curing residual strain was assessed via changes in the shape of the optical spectra, intensity attenuation and shifts in wavelengths of FBGs. Utilizing this approach we can monitor curing residual strains in different layers of the composite during the curing process.

Among structural health monitoring techniques, Lamb waves is frequently used as diagnostic tools to detect damage in plate-like structures. Lamb waves usually excited by piezoelectric transducers essentially involve exciting the structure with high frequency guided-waves and processing the difference in structural response with respect to a baseline signal for the pristine condition to detect damage. As a kind of baseline free method, time reversal (TR) method applied to ultrasonic detection and focusing with arrays of transducers has been proposed. The decomposition of the time reversal operator (DORT) method is a selective detection and focusing technique using an array of transmit-receive transducers. Unlike body waves, the propagation of Lamb waves is complicated due to their dispersive and multimode characteristics. So Lamb wave is hard to locate different scatterers on the plate using DORT method because of the asymmetry of the time reversal transfer matrix. In this paper, a proposed approach based on the DORT method is developed to distinguish and locate two simulated damages on the aluminum plate using Lamb wave through finite element simulation on the commercial finite element code ANSYS platform. The behavior of reflected waves is analyzed by studying the eigenvalues and eigenvectors of the time reversal transfer matrix, showing that the number of significant eigenvalues is not exactly the number of damage targets and two significant eigenvalues correspond to one target. This method, which uses PZT array and operates under multi-modes pulse-echo mode, can estimate the position of the damaged zone in 2D image by numerically backpropagating selective eigenvector using the S0 and/or A0 Lamb wave propagation analytical solution.

Some structures are vulnerable to localized internal damages incurred by impact of small objects. Previous work showed that the whereabouts of an impact event on a 0.8m×0.8m square aluminum plate can be located by analyzing the differential time-of-flight among signals picked up by a four-FBG (fiber Bragg grating) array. However, good location accuracy was obtained only when the impact position was well within the envelop of the sensor arrays. In the current work, it will be demonstrated when an impact occurs within ±60o on either sides of the FBG axis, the signal is strong and the time-of-flight can be measured accurately so that an impact can be located accurately to better than 1 cm. Beyond that range, the signal became heavily attenuated and masked by noises and the location errors could be larger than 20 cm. To investigate the possible directions for improvement on the system accuracy, FBG rosettes with two mutually perpendicular FBGs are used to replace single FBGs to alleviate the angular sensitivity problem. It was shown that with the rosette array, good location accuracy can virtually be extended to all over the plate.

Piezoelectric paint is a composite piezoelectric material, due to its outstanding properties consisting of flexibility and conformability, it has been a great interest in structural health monitoring applications recently. The normal piezoelectric ceramics offer high piezoelectric properties, but are difficult to adhere on curly structural surfaces. For normal polymers, it offers high flexibility but missing the ability to transform the mechanical energy into the electrical energy, and vice versa. The piezoelectric paint combines the features of both, so it could be distributed on both even and uneven structural surface, as a sensor or actuator. This work starts with the development of the piezoelectric paint, followed by a systematic characterization of its mechanical and piezoelectric properties, which includes microstructure, Young's modulus, sensitivity and piezoelectric charge constant d_a1. The characterization results helps to understand the performance of the piezoelectric paint more deeply. Finally, a refinement method is demonstrated to improve the piezoelectricity of the paint. The results showed that the piezoelectricity was greatly improved and therefore its applications in structural health monitoring is widely expanded.

Scaffold for cell therapy was prepared with poly (lactide-co-glicolide, PLA/PGA (10:90). By using melt-spinning and draw texturing process, we could prepare microfibrous bulky suture which had heterogeneous macropore. Microfibrous structure has great potentiality as biomimicking architecture for cell growth and maintaining cell functions. The result of cell seeding showed that pore size, pore distribution, and fiber fineness of sutures were suitable as a biocompatible scaffold in vitro for NIH 3T3 Fibroblast cell. Also, we expect that prepared scaffold for cell-therapy will provide numerous benefits as a noninvasive alternative for tissue engineering applications.

Quasiperiodic crystals (QCs) are a new class of materials that exhibit long-range aperiodic translational order and high rotational symmetries. Unlike periodically arranged photonic crystals (or photonic band-gaps), PQCs possess unique light localization and transport properties related to their complex, multi-fractal energy spectra. Advances in 2D photonic structures are expected in the introduction of non linear and/or active functionality into a 2D PQC. One-dimensional semiconductor nanostructures are likewise promising materials both in fundamental research and in practical applications. CdSe/CdS rods present the appealing characteristics of strong and tunable light emission from green to red, are highly fluorescent and show linearly polarized emission. These characteristics open the way to a new class of hybrid devices based on polymers and colloidal NRs in which the unique optical properties of the inorganic moiety are combined with the processability of the host matrix to develop new high performing optical devices such as organic light-emitting diodes, ultra-low threshold lasers and non-linear devices. One of the challenges of these applications is the incorporation of inorganic nanoparticles into organic polymer matrices, since this is usually accompanied by phase separation, aggregation of nanoparticles, loss of transparency and luminescence quenching due to exciton energy transfer. In this paper two-dimensional (2D) hybrid PQCs which consist of air rods in a nanocomposite prepared by incorporating CdSe/CdS core/shell nanorods (NR) in a polymer are proposed and experimentally demonstrated. Scanning electron microscopy and far field diffraction are used to characterize the experimental structures.

Recently, neural prosthetic electrodes covered with polyimide (PI) have been developed for chronic recording and stimulation of nervous system function. However, when these devices are implanted onto the nerve trunk, nerves might be damaged by the presence of the electrode due to the mechanical mismatch between the stiff probe and the soft biological tissue. Consequently, newly formed tissue layer may isolate the electrode from neural tissue, resulting in poor signal detection. In this study, we found a method to solve this problem. As the method, we designed and prepared poly(ethylene glycol) (PEG)-grafted PI film to function cell fouling resistance. The PEG-grafted PI film was characterized by X-ray photoelectron spectroscopy (XPS) and static water contact angle measurements. Protein adsorption experiment was carried out to evaluate protein fouling resistance because protein adsorption is closely related to cell adhesion. In vitro cell behavior on PEG-grafted PI film was evaluated by confocal laser scanning microscopy (CLSM) and CCK assays. The results showed that PEG-grafted PI film has characteristics of protein and cell fouling resistances as compared to bare and hydrolyzed PI films under in vitro. We suggested that PEG-grafted PI film can be useful for a neural implantable electrode.

Nanoporous anodic aluminum oxide (AAO) templates are fabricated using an anodization method. The mean diameter of the nanoporous anodic aluminum oxide templates is 100 nm. A molded plastic thin film with nano-structure is fabricated using AAO template as a mold insert by nanoimprint. The surface properties of the molded plastic thin film obtained using various processing parameters in nanoimprint are discussed. The contact angle of the molded polycarbonate (PC) thin film with the nano-structure exceeds that without the nano-structure. The molded PC thin film (with nano-structure) with a hydrophobic surface is formed, and has a water contact angle of 128.5°. The use of anodic aluminum oxide to prepare a mold insert for nanoimprint supports the formation of a nano-structure in the molded PC thin film, and effectively increases its reflectance.

Today, in a world context characterized by high pollution levels and increasingly limited natural resources, even in the building sector, focusing on environmental issues, through energy saving and a more rational use of these resources, both during construction and management, is fundamental. An important contribution in this direction is given by the knowledge of the durability of products and building components, especially when innovative products are applied and no information are available on the reliability and service life. The research concerns the evaluation of the durability of cement-based photocatalytic coatings ("rasanti" in the Italian diction), containing different types of pigments, used for the external finishing of the buildings envelope and applied in low thicknesses on different supports. These products were prepared using photocatalytic cements by Italcementi (TX Active^R) The investigated aspects are: the photocatalytic properties, conferring self-cleaning attitude and reduced maintenance to the treated surfaces, and the colorimetric ones, meaning the conservation of colour and giving aesthetic quality to the building envelope. The paper presents some results carried out on TX Active^R cement-based coatings, performed according to the ISO 15686 methodology, aimed at defining the Reference Service Life, through accelerated ageing tests in climatic chamber and the corresponding monitoring of photocatalytic and colorimetric properties. The photocatalytic tests were carried out according to the UNI 11247-2010, in terms of NOx abatement capability, and the colour measurements were taken on the CIELAB colour space.

Recently, a terahertz ray (T-ray) technique has emerged as one of the most promising new powerful nondestructive evaluation (NDE) techniques, and new application systems are under processing development for the area applications. In this study T-ray technique will be adopted for the characterization of the FRP composite solid laminates as an imaging and useful nondestructive evaluation (NDE) tool. So, in order to detect and evaluate the flaws in FRP solid composite laminates a new time-domain spectroscopy system was utilized. Various experimental measurements in reflection and through-transmission modes were made in order to map out the T-ray images. Especially in this characterization procedure, we estimated the electromagnetic properties such as the refractive index and a couple of techniques were proposed to measure the refractive index. It is found that estimations of properties with the proposed different ways are in good agreement with known data. Furthermore woven CFRP Honey comb sandwich panel with Al wire were observed in reflection mode and limitations will be mentioned in the T-ray processing.

Aerospace structures are often made out of (Carbon) fiber reinforced polymers. In order to enhance their physical properties especially on thermal and electrical conductivity, the polymer matrix materials are to be enriched with different types of fillers such as CNTs or Carbon black. Results from different related investigations show benefits on the one side but also some problem areas which are to be observed. Shape memory polymers (SMP) are applied to the structures to compensate possible shape deviations due to curing stresses, where fillers are to be used to reduce if not avoid creep effects in these SMP.

In the present study, a simple approach has been presented to in situ deposition of Pd-doped well-crystallized SnO₂ nanocrystals on the surface of multiwalled carbon nanotubes (MWCNTs) in the ethanol solution of SnCl₂. The morphology, microstructure and surface chemistry of the as-prepared nanocomposites were characterized by high resolution transmission electron microscope (HRTEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), respectively. The HRTEM and XRD results show that the well-crystallized SnO₂ nanocrystals with uniform crystal size (about 5 nm) tightly and homogenously coat on the entire surface of the MWCNTs. The carboxylic function groups on the MWCNTs surface may supply nucleation sites for facilitating the in situ deposition of SnO₂ nanocrystals. The XPS results reveal that the chemical states of the nanocomposites and the dopant of Pd mainly exists in two chemical states as Pd²⁺ and Pd⁴⁺. The response of the 2.5 at% Pd-doped SnO₂/MWCNTs nanocomposites to 1000 ppm NO at the temperature of 250 °C behaviors better, whose response time is about 70 s and the sensitivity is about 4.62.

A colloidal shear thickening fluid (STF) was prepared by dispersing submicron silica particles in Polyethylene glycol 200(PEG200) with ball-milling technique. Kevlar/STF composites were fabricated by soaking Kevlar in the solution of STF diluted by ethanol. The rheological behavior of the fluid with various concentrations and the effect of dilution ratio on stab resistant properties of Kevlar/STF composites were studied. The result shows that the initial viscosity and the highest viscosity of the fluid increase as the weight fraction of SiO₂ increasing with the weight fraction ranging from 50% to 60%, while the critical shear rate decrease as the weight fraction increasing. The fluid has notable shear thickening behavior at SiO₂ weight fraction of 59%. Two solutions with 1:0.5 and 1:1weight ratio of STF:ethanol were used to fabricate Kevlar/STF composites. It is found that the composites fabricated by solution with dilution ratio 1:1 show better stab resistant properties. The Kevlar/STF composites exhibit better stab resistant properties than the neat Kevlar with the same areal density.

A fiber Bragg grating (FBG) sensors system utilizing a multi-wavelength erbium-doped fiber lasers (EDFL) with frequency shifter is proposed. The system is one fiber laser cavity with two FBG sensors as its filters. One is for strain sensing, and the other one is for temperature compensation. A frequency shifter is used to suppress the mode competition to lase two wavelengths that correspond with FBGs. The wavelength shift of the EDFL represents the sensing quantity, which is demodulated by Fiber Fabry-Perot (FFP) filter. The sensor's response to strain is measured by experiment. Because of exploiting the dual-wavelength fiber laser with a frequency shifter forming the feedback as the light source, many advantages of this system are achieved, especially high signal-to-noise ratio, high detected power, and low power consuming comparing with conventional FBG sensor system utilizing broadband light as the light source. What's more, this structure is also easy to combine with FBG array.

In order to reduce effective load and lower the launch cost, many light-weight flexible structures are employed in spacecraft. The research of active control on flexible structural vibration is very important in spacecraft design. Active vibration control on a flexible beam with smart material piezoelectric pieces bonded in surface is investigated experimentally using independent modal space control method, which is able to control the first three modes independently. A comparison between the systems responses before and after control indicates that the modal damping of flexible structure is greatly improved after active control is performed, indicating remarkable vibration suppression effect. Dynamic equation of the flexible beam is deducted by Hamilton principle, and numerical simulation of active vibration control on the first three order vibration modes is also conducted in this paper. The simulation result matches experimental result very well. Both experimental and numerical results indicate that the independent modal control method using piezoelectric patch as driving element is a very effective approach to realize vibration suppression, which has promising applications in aerospace field.

In vehicle industry, the design of vehicle should be inclined towards the safety performance aspect, at the same time; it also should have weight loss of a vehicles structural member. In this study, experimental investigations are performed for Al/CFRP Hybrid structural members. They are cured by heating to the appropriate curing temperature (130°C) by means of a heater at the vacuum bag of the autoclave. Because the CFRP is an anisotropic material whose mechanical properties, such as strength and elasticity, change with its stacking condition, special attention was given to the effects of the stacking condition on the collapse behavior evaluation of the Al/CFRP Hybrid structural members. The collapse mode and energy absorption capability of the Al/CFRP Hybrid structural members was analyzed with change of the fiber orientation. The stacking condition were selected to investigate the effect of the fiber orientation angle (±15°, ±45°, 90°, 0°/90°and 90°/0° where 0°direction coincides with axis of the member)on the energy absorption of the Al/CFRP Hybrid structural members. The collapse mode and energy absorption capability of Al/CFRP Hybrid structural members was analyzed with change of the fiber orientation of CFRP.

The lanthanum-modified lead zirconate titanate(PLZT) actuator activated by high-energy lights can introduce actuation and control effects without hard-wired connections. A novel controlling algorithm for multi-modal vibration control of beam structures via photostrictive actuators is proposed in this paper. Two pairs of photostrictive actuators are laminated with the beams and the alternation of light irradiation is in accordance with the changing of the corresponding modal velocity direction. A binary-coded GA is used to optimize the location and size of photostrictive actuators to maximize the modal force index and guarantee the overall modal force index induced by two pairs of photostrictive actuator is positive. The control effect of multiple vibration modes of the beam under irradiation of set light intensity/variable light intensity is analyzed. Numerical results demonstrate that the method is rational and efficient, and the use of strategically positioned actuator patches can control the first two bending modes that dominate the structural vibration effectively.

Considering the nucleation process was asymmetrical and not synchronous due to the effects of defects in polycrystalline ferroelectric system, a mulriple Kolmogorov-Avrami-Ishibashi (MKAI) model was proposed based on the classical KAI model. Moreover, the switching kinetics of Bi_3.15Nd_0.85 Ti₃O₁₂ ferroelectric films was investigated using the MKAI model. The simulation results indicates that the MKAI model was more consistent and exactly with experimental results.

Pb(Zr_0.52Ti_0.48)O₃ (PZT) thin films were coated onto Pt/Ti/SiO₂/Si substrates by a sol-gel method and then crystallized by 2.45 GHz microwave irradiation in the magnetic field. The crystalline phases and microstructures as well as the electrical properties of the PZT films were investigated as a function of the annealing temperature from 550 to 750°C for 60 s. The crystallization behavior of the PZT films annealed at 650°C for different times were also investigated. X-ray diffraction and transmission electron microscopy reveal that the pyrochlore phase is formed initially but that it transforms into the perovskite phase very quickly. The ferroelectric and dielectric properties of the PZT films are correlated to the crystallization behavior. The annealing time to obtain perovskite PZT films with good electrical properties at 650°C is only 60 s, and is much shorter than that in conventional furnace annealing process. The reasons for the reduction of annealing time in the rapid microwave annealing process are also discussed.

Rutting is one of the most serious problems on asphalt pavements. Decrease the surface temperature of the asphalt pavement is an effective method to solve the rutting problem on asphalt pavements. In this study, nano sized particles filled polymer composite was developed as an overlay to reflect the solar energy and decrease the surface temperature of asphalt pavements. The overlay was composed of acrylic or epoxy resin filled with nano TiO₂ or nano TiNO₂. The solar reflection of the nano particle filled polymers was tested and the results showed that solar reflection effectiveness of the epoxy/TiO₂ composite reached the highest value. The results of outdoor temperature test indicate that the solar-reflective overlay could decrease the surface temperature of asphalt pavements about 10 °C when the pavement temperature is about 60 °C. Pavement skid resistance was also tested, which expressed by micro/macrotexture depth and the results of which showed that both matrix was qualified after coated with aggregates on the surface.

We demonstrated the monitoring of the liquid-solid phase transition, including a supercooling process, based on embeded FBGs. A FBG concentration sensing scheme is proposed by observing the embeded-FBGs' response to the phase transition. The freezing of the salt solution and the Glucose solution are measured and the results show the correlation between the solute's concentration and the embeded-FBGs' response.

Piezoelectric material, such as, Lead Zirconate Titanate (PZT) can be use as sensing and/or actuating element for structural health monitoring due to its direct and converse piezoelectric effects. In this study, several fabricated PZT impedance transducers encapsulated by cement were embedded into a plain concrete beam to detect the surface crack damage. By monitoring the electromechanical (EM) admittance spectra of the embedded transducers, the structural surface crack damage was investigated. From the experimental results it is found that the shape of the electrical admittance spectra curve of the embedded PZT transducers hardly changes before and after surface crack is of presence, and the EM admittance spectra exhibits tiny change in amplitude with the increase of crack depth, which indicate that the embedded PZT transducers into concrete are insensitive to surface crack damage.

NiTi endodontic rotary instruments subjected to alternating tension and compression stress in root canals may fracture without prior warning. Once broken, extracting the fractured part from the canal is a difficult job and is annoying to both the patient and the dentist. Warning of an imminent fracture during clinical use will be a great help to avoid medical and legal complications. A monitoring system employing Fiber Bragg Grating (FBG) sensors has been attempted. The reason of using FBG is its small size which is very promising in integrating with the handpiece of the endodontic equipment. When cracking developed in an rotary instrument, we expect the natural vibration frequency of the instrument changes. If we can pick up the stress wave transmitted through the structural components of the rotary instruments, we may be able to detect the occurrence of a crack. In the current work, we found that we can successfully locate the operation period in the time domain by picking up and analyzing the sound wave using FBG. Furthermore, by employing Fast Fourier Transform (FFT) on the signal, we can reveal the energy variation and the frequency shifting phenomenon in specific section of frequency domain. For some characteristic frequencies, it was found that the energy and frequency varied in a well-defined pattern during the period of crack growth. It is hoped that with these information, the fatigue failure of rotary instruments can be closely monitored to avoid/alleviate the occurrence of unexpected fracture during clinical use.

Optimization of growth parameters has permitted to create monolithic nanocomposites with buried nanocrystals (NCs) of iron and chromium disilicides and polycrystalline nanocomposites with buried Mg₂Si NCs (3-40 nm) on the base of reactive deposition epitaxy (RDE), solid phase epitaxy(SPE) and molecular beam epitaxy (MBE), which demonstrated wonderful thermoelectrical properties and the possibility of strong light emission with wavelength of 1.2 - 1.6 microns in the mesa-diode structures with p-n junction at direct and back bias. Doping process of Mg₂Si nanocrystals inside nanocomposite layers was developed on the base of ordered surface phases of metals on a silicon substrate. Nanocomposite layers with n- and p-type conductivity have been successfully grown. The huge increase of Zeebeck coefficient in the Si-p/β-FeSi₂ NCs/Si-p and Si/Mg₂Si NCs/Si nanocomposites has been found.

In this paper, a small seamless morphing wing aircraft of MTOW=51 kg is investigated. The leading edge (LE) and trailing edge (TE) control surfaces are positioned in the wing section in span wise. Based on the studying results of aeroelastic wing characteristics, the controller should be designed depending on the flight speed. Compared with a wing of rigid hinged aileron, the morphing wing produces the rolling moment by deflecting the flexible TE and LE surfaces. An iteration method of pseudo-inverse allocation and quadratic programming allocation within the constraints of actuators have be investigated to solve the nonlinear control allocation caused by the aerodynamics of the effectors. The simulation results will show that the control method based on control allocation can achieve the control target.

With the development of new materials, the study of the interaction of multi-physical fields is more and more important. Many experiments have shown that chemo-mechanical coupling exists in a lot of smart materials. In this paper, a theoretical model is proposed for the uniaxial strain state of chemo-mechanical materials. It is assumed that the smart material is an isotropic continuum. Based on the coupled governing equations, the displacement function and concentration function are derived and then the stress and chemical potential are obtained. This study not only reveals the mechanism of chemo-mechanics, but also provides a foundation to the numerical simulation.

A series of montmorillonite (DK2) modified shape memory polyurethane-epoxy (UEP) composites had been prepared. The effect of DK2 modification on the morphological, mechanical and thermal properties of epoxy/polypropylene/Montmorillonite nano-composites were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), tensile test, scanning electron microscope (SEM) and dynamic mechanical analysis (DMA). The shape memory performance was investigated by fold-deploy shape memory tests. The XRD and TEM results indicated the formation of exfoliated structure for epoxy/polypropylene nano-composites had been prepared using 2~ 3wt.% DK2. On the other hand, a mixture of intercalated and exfoliated structure was found in 4~5wt.% DK2/ epoxy/polypropylene polymers. Further more, the toughness, tensile strength, enlongation at break had been improved by adding DK2, while glass transition temperature, storage modulus and shape recovery ratio was unaffected. The composite materials possessed excellent shape memory properties, they could fully recover their original shapes within 3 min under the maximum bending angle of 180°, and there were little effect by fold-deploy ten times.

This study presents a novel type of optically driven lever-based micro-actuator fabricated using two-photon polymerization 3D-microfabrication technique. The lever is composed of a beam, an arch, and a sphere. First, optical tweezers is applied on the spheres to demonstrate the actuation of the lever. A spring is jointed at the lever for verifying the induced forces. Under the dragging by laser focusing, the lever simultaneously turns and results a torque like a mechanical arm. Then, the demonstration of a photo-driven micro-transducer with a mechanical arm and a gear is preformed. The experimental result indicates that our design enables precise manipulation of the mirco-actuator by optical tweezers at micron scale. This study provides a possibility for driving micron-sized structured mechanisms, such as connecting rods, valves. It is expected to contribute on the investigation of "Lab-on-a-chip".

Cellular piezoelectret film is actually the voided charged polymer film. They show very large piezoelectric effect in the film thickness direction, and have great potential in the application of flexible electromechanical sensor. In this paper, cellular piezoelectret film is considered as a composite where the voids containing charges of opposite polarities are viewed as inclusions, while the polymer as matrix. We develop a micromechanical model to find the effective electromechanical moduli of cellular piezoelectret film. Sensitivity analysis is presented for effective electromechanical moduli with respect to void parameters. Furthermore, this micromechanical formulation is extended to include the viscoelastic deformation of polymer matrix. Temporal evolution of the effective properties, including elastic modulus and piezoelectric d₃₃ coefficient in the film thickness, of cellular piezoelectret film can be obtained.

By using electroactive monomers it is possible to produce gels that respond to oxidation or reduction by swelling and deswelling in the presence of solvent. By the inclusion of an appropriate biasing element such as a spring, it is possible to produce linear, reversible actuation. The process can be driven electrochemically in a standard cell, with driving voltages under ± 1 V. For many systems, the intrinsic conductivity of the gel, leading to poor or no performance. This can be overcome by blending conductive carbon nanotubes at 1% concentration, which give reasonable conductivity without affecting mechanical performance. Extensions of up to 40% are possible, against an external pressure of 30 kPa. The process is slow, taking up to 160 minutes per cycle due to slow ionic diffusion. The electrochemical cell can be cycled many times without degradation.

In this paper, conducting polymer and ionic liquid cellulose electroactive paper composites (CPILEAPap is prepared and characterized. The CPIL_EAPap was prepared by dispersing ionic liquid in regenerated cellulose solution. The film obtained from the solution is then coated with polypyrrole electrodes. Electromechanical performance was assessed by measuring the bending displacement of the composite film. The bending displacement of the actuator was compared at different humidity conditions. In addition, morphological and structural studies were undertaken using FTIR and SEM analysis. Preliminary results show good displacement of the bender actuator which decreases with increasing % relative humidity. Additional work is being undertaken to further quantify and characterize the structural features that are important for actuation and humidification.

The dynamic response of a dielectric elastomer actuator with an electrode-elastomer-electrode sandwich structure is modeled and analyzed. The equation of motion is derived by thermodynamic considerations. Due to the exact formulation of the inertia term in three dimensions, the equation of motion involves particularly a quadratic dependence on the first derivative of the deformation. Numerical solutions of the model are presented to show the dynamic response of the DEA, e.g. the vibration under constant electric potential, the oscillation under harmonic electric loadings, and particularly the resonance phenomenon.

Bolted joints are of great importance in steel structures. Any levels of looseness or even failure in the bolted joints if not earlier be found in time, will continuously change the connection strength and stiffness, causing cumulative damage to the structure, or even resulting in a sudden structural failure. Thus, it is crucial to develop efficient detection approach for early looseness in bolted joint. In particular, electro-mechanical impedance (EMI)-based damage detection technique which uses smart piezoelectric Lead Zirconate Titanate (PZT) patches has emerged as a potential tool for local damage detection of engineering structures. This paper presents a feasibility study on the application of an EMI-based bolted joint looseness detection with PZT patches. One steel specimen and an aluminum specimen were designed and the bolt looseness damage was introduced by loosening some connection bolts. Impedance measurement for each PZT sensor on the two sides of bolted joint with different distances from the loosened bolts was carried out on. A quantitative identification method based on a statistical damage index, the root mean square deviation (RMSD) of the EMI over different frequency bands, was proposed to assess the presence of damage. Results showed the RMSD can detect the existence of looseness damage and the sensitivity of the PZT sensors are investigated for the bolted joint structure. Also, the sensitive region of the PZT patches in different frequency ranges for both specimens were discussed. The proposed approaches have great potential to be applied in practice for the looseness detection in bolted joints.

Floatation or levitation, as well as free suspension are intriguing phenomenon. Both require minimum in energy. However, as Lord Kelvin observed only composite systems of diamagnets with permanent and induced magnets can achieve stable equilibrium. Permanent magnets, in contrast to electromagnets retain their ability to attract and hold magnetic objects without any external energy expenditure. This persistent property similar to superconductors is entirely quantum mechanical. Recently M.V. Berry, A.K. Geim and others have re-instigated interest in the stability criteria of these systems. In this work, stability in the horizontal plane is guaranteed by the localization of the holding field. Smart response gives rise to vertical stability. Smartness causes the net force to be repulsive when the object is too close and attractive when far. Here we report for the first time, the production of smart response in a system with diamagnetic and ferromagnetic constituents. The restoring force, F is strongly asymmetric and non-linear with displacement (z); F(z) is non-harmonic, does not follow hook's law. Two types of diamagnetic materials bismuth and pyrolytic graphite were investigated. Consistent with the higher susceptibility, the later provides a factor of two stronger repulsive forces under ambient conditions. Also, for the first time we show that this smart system is extremely un- harmonic. For stable equilibrium, restoring force is essential and sufficient however harmonic behavior is not essential.

Piezoelectric cantilevers energy harvesting made by micro-electromechanical system (MEMS) technology can scavenge power from low-level ambient vibration sources. The developed cantilevers energy harvesting are featured with resonate frequency and power output in microwatt level, which is sufficient to the self-supportive sensors for in-service integrity monitoring of large social and environmental infrastructures at remote locations. In this paper, piezoelectric energy harvesting based on thick-film piezoelectric cantilevers is investigated to resonate at specific frequencies of an external vibration energy source, which creating electrical energy via the piezoelectric effect. Our cantilever device has a multiple structure with a proof mass added to the end. The thick film lead zirconate titanate Pb(Zr,Ti)O₃ (PZT) coated on the top of Au/Cr/SiO₂/Si substrates by sol-gel-spin method. The thickness of the PZT membrane was up to 2μm and the cantilevers substrates thickness 50μm, wideness 1.5mm, length 4mm. The Au/Ti top electrode is patterned on top of the sol-gel-spin coated PZT thick film in order to employ the d31 mode. The prototype energy generator has a measured performance of 0.74μW effective electrical power, and 4.93 DC output voltages to resistance load. The effect of proof mass, beam shape and damping on the power generating performance are modeled to provide a design guideline for maximum power harvesting from environmentally available low frequency vibrations. A multiple structure cantilever is designed to achieve compactness, low resonant frequency and minimum damping coefficient, simultaneously. This device is promising to support networks of ultra-low-power sensor.

As an intelligent material, polymer gel is able to respond to external stimulus, including temperature, chemical concentration, pH, etc. The theoretical framework of chemo-mechanical coupling behavior for intelligent polymer gel is emphasized in this paper. Analytical solutions of the displacement and concentration function are found for one dimensional chemo-mechanical coupling problem. It is shown that the present chemo-mechanical theory can be applied to model chemo-mechanical coupling behavior of intelligent polymer gel. This study has important significance to reveal the mechanism of chemo-mechanical coupling behavior of the polymer gel.

A distributed optical fiber Raman temperature sensor system was established, and a new temperature calibration method was presented. A Thermoelectric Controller (TEC) module was used as a dynamic multi-temperature reference to solve the nonlinear problems caused by temperature drift of Avalanche Photodetector (APD) gain and nonlinear response of Raman effect. The information of temperature fields along the fiber could be demodulated linearly regardless the environmental temperature variations. Compared with the traditional calibration methods, the proposed sensor system was more accurate and stable, and was suitable for engineering applications. The expermental results show that the measurement error of the system was less than 1°.

The circuit model was applied to predict the pin load distribution of composite multiple bolt-joint structure. The load, flexibility and deformation of the mechanics model were equivalent to the current, resistance and voltage of the circuit model, respectively. Based on the above assumption, it could be found that the Hooke's law and the deformation compatibility equation in the origin mechanics model transformed into the Ohm's law and the voltage balance equation in the new circuit model. This approach translated the complex model of composite multiple bolt-jointed into a simple circuit model which consisted of some series circuits and parallel circuits. The analysis of the new circuit model had formed n-1 independence voltage balance equations and a current balance equation, thus, the current and load of each bolt could be calculated. In the new model, power sources which were added as required in some branch circuits could also simulate the clearance or interference in the origin model. Compared with the result of the multiple bolt-joints composite laminate test, the new approach could make an excellent performance to estimate the load distribution.

Electrochromism is the phenomenon displayed by some color changing materials when a burst of charge is applied. Viologens (Vio) are cathodic electrochromic materials, and triphenylamines (TPA) are anodic electrochromic materials. Here, we reported a new electrochromic compound composed of Vio, TPA and phosphonic acid groups, thus the molecules can be anchored on electrode, which will lead to faster switching speed and high stability. An electrochromic device was assembled using the new Vio as primary electrochromes and Prussian blue as secondary electrochromes. The device exhibits high transparency. In addition, it shows fast switching speed and good stability.

Vanadium pentoxide films have been synthesized by ultrasonic spraying using self-fabricated equipment. Experimental condition is easy to control without the presence of high temperature, electric field, and vacuum. The substrate on which the film deposits does not require high conductivity and the obtained film is good in uniformity. The method is especially effective to process large area films. In this study, the obtained films were investigated for their structural, surface morphological, electrochemical and optical properties. Compared with electrodeposited vanadium pentoxide films, sprayed ones exhibit relatively poor charge storage capacity, but a similar transmittance value. Under comprehensive consideration, the ultrasonic spraying method is preponderant choice for preparing large area films for electrochromic devices.

This study deals with the development of two vision estimation algorithms for robot vision control scheme. One is the Extended Kalman Filtering algorithm, and the other is the Newton-Raphson algorithm. The Newton-Raphson (N-R) algorithm consists of vision system model, camera parameters estimation scheme and joint angle estimation scheme. The Extended Kalman Filtering (EKF) algorithm consists of vision system model, process model and measurement model. In addition, the process and the measurement models include the camera parameters estimation scheme and the joint angle estimation scheme, respectively. The vision system model includes six camera internal and external parameters. Each algorithm has its strengths and weaknesses. The Newton-Raphson algorithm is based on iterations and can concurrently handle large amounts of data. On the other hand, it takes a lot of processing time and accordingly is not easy use for real-time robot control. The Extended Kalman Filtering algorithm is based on recursion and thus is faster, but it requires very accurate selection of initial values. In this study we use Monte-Carlo method for estimating initial values. Finally, the results of both algorithms are compared experimentally by tracking the moving target.

Anodic physical deposition is a method that joins technical simplicity, environment friendly, non-toxic, low investment cost, and ease in morphology control. Nanoporous ZnO with high internal rough surface and polycrystalline nature has been prepared via a simple chemical technique. Anodization of Znic (Zn) foil was studied in a mixed of ammonium sulfate and sodium hydroxide solution under the affect of various anodization durations. The as-prepared samples were studied by X-ray diffraction (XRD), and energy dispersive analysis of X-rays (EDX). An optical characterization by a Raman spectrometer was performed to investigate their optical properties. The PL and Raman results revealed both good compromise with the features of our samples and dormant for forthcoming utilizations for example smart sensors system and other modern solid state technologies. The formation of porous structures has been confirmed by Raman spectroscopy and scanning electron microscopy investigations.

Fluorophthlocyanine thin films were used as n-type semiconductor in organic solar cell. Heterojunction solar cells of cupper hexadecafluorophthalocyanine (F₁₆CuPc) / copper phthalocyanine (CuPc) and F₁₆CuPc / zinc phthalocyanine (ZnPc) deposited with PEDOT-PSS on ITO as electrode were fabricated and characterized. Comparison between CuPc and ZnPc as p-type semiconductor on photovoltaic performance was studied. Light-induced charge separation and charge transfer was investigated by current density and optical absorption. Internal microstructure in active layer was measured by transmission electron microscopy, X-ray and electron diffractions. The F₁₆CuPc thin film in the deposited active layer worked for electron-accepting layer as n-type semiconductor. The photovoltaic performance was original in charge transfer from CuPc to F₁₆CuPc in active layer.

In this study, a cross-flow laser with maximum out power of 5kW was applied to the welding of Fe-Mn-Si shape memory alloys (SMA). The optimal welding processing parameters of 1mm thick Fe-Mn-Si SMA were established by orthogonal experiment. With the optimal processing parameters, power 1600W, welding speed 2.2m/min, defocusing distance 0.6mm, the tensile strength of the welded joint can achieve 93.5% of the base material, and the weld undercut and reinforcement transfer smoothly on the surface of the welding seam and the cross-section of the welding seam morphology presents "X" shape. The fracture appears in the weld fusion zone, so this area is weak during the laser welding. By the metallographic observation, the weld center structure is small equated, and the region of fusion zone is thick cellular crystal that decreases the strength of the welded joint, and the X-ray diffraction (XRD) test proves that the laser welding promotes the grain refinement. The micro-hardness analysis shows that the hardness of the fusion zone is lower than the other area clearly which is also associated to the weld structure. By the fracture scanning electron microscope (SEM) analysis, it is found that the fracture of Fe-Mn-Si SMA shows many small dimples with the optimal parameters, and the result is accorded with the base material which belongs to plastic fracture.

In this paper, numerical study is performed to reveal the influences of the cell size on the steady state thermal performance of hexagonal metallic honeycomb sandwich panel, by using the semi-empirical Swann and Pittman formula and the Finite Element Method (FEM), respectively. Based on the same material volume of honeycomb core, two types of hexagonal honeycomb core, i.e., size variation of core cell with a constant core height and height variation of core with a constant side length of hexagonal cell, are considered to establish the panel's thermal analysis model, which including the conduction and radiation coupling. Comparisons between the temperature distribution results from both methods show that FEM can reveal the size effect of the honeycomb cell on the thermal performances of sandwich panel while the Swann and Pittman formula can not. At the same time, numerical results show that for the core with constant height, the panel thermal performance analyzed by FEM has a tendency of being close to the results obtained from Swann and Pittman formula as the core cell size decreases; whereas, if the hexagonal cell with constant side length is concerned, the greater the core height, the worse the thermal conductive performance of sandwich panel. Besides, analyses based on both methods also show that the temperature distribution of the lower surface of panel becomes gradually uniform when the wall thickness of hexagonal cell decreases.

Piezoelectric composites find increasing applications in the field of smart materials, mainly as sensors and transducer. However, accurately predicting its performance is still a challenging task. In this paper, we analyzed the electromechanical properties of a three-phase piezoelectric composite with titanate piezoelectric ceramics powders (PZT-5H) and carbon black embedded in an epoxy matrix by a finite element numerical method. A homogenizing micromechanical model is applied, which is capable to provide various property parameters of the piezoelectric composite, such as dielectric constant, piezoelectric constant. The calculation verifies that the electric network formed by the conducting-phase carbon black(CB) can effectively improve the electromechanical performance of the piezoelectric composites. The effect of different content of the carbon black is also taken in consideration in the simulation. A good fit between the calculation and the experimental results clearly shows that the homogenizing modeling is able to accurately predict the electromechanical properties of the three-phase piezoelectric composite. This work will contribute to optimize the material function design and analyze the effect of conduct phase on the piezoelectric composites.

In order to improve the concentration efficiency and eliminate the optical aberration, the umbrella-shaped keel structure has been introduced into the deployable structure concentrator, which can overcome the shortcomings such as the low concentration ratio and ineliminable superimposed folds. A deployable solar parabolic concentrator, possessing the collapsible umbrella-shaped keel and aperture radius of 4.9m has been designed. Its finite element model has been established, the ANSYS software has been adopted to perform the structure and static analysis. Under the influence of solar wind and films surface tension, the maximum deformation of the umbrella fabric is only 0.941mm, the radius of spot size is 6.37cm, geometry concentrator ratio could achieve 5908, only 1.3% reduced than the standard parabolic. The maximum stress is 1.6 MPa, which are much smaller than the tensile strength of Kevlar material. Power density of the concentrator is 8149227.24W/m², the weight of the system is 0.38Kg per kW. The results indicated that the influence of films tension and solar wind on the working shape of concentrator bas been offset to a large extent by the umbrella-shaped keel. The new umbrella-shaped keel concentrator has available for the solar thermal thruster (STP) system, which has the advantage of high geometry concentrator ratio, structure stability, small envelope volume, light weight and deployable perfectly, as well as the selected structure and materials are appropriate.

A series of transparent and super-hydrophilic TiO₂/SiO₂ composite films with high adhesion to the glass were fabricated by dipping methods. The sol was prepared using peroxotitanium complex (PTC) as precursor by sol-gel process at low temperature. The properties of transmittance, hydrophility and adhesion were characterized by ultraviolet-visible spectrophotometer, water contact angle and the tape test, and the structure was analyzed by Fourier transform infrared spectroscopy (FTIR). The relationship of structure, surfactant and the compound action of TiO₂/SiO₂ was investigated. The results indicated that the fabricated films achieved excellent transmittance to slide glass of over 90%. Because of the poor adhesion of pure TiO₂ film, the TiO₂/SiO₂ composite film with polyvinyl alcohol (PVA) as the surfactant was prepared. The tape test indicated that the composite film had a steady adhesion on the surface of glass. At the same time, the water contact angle of the films was blow 5° after exposed to the UV light. Furthermore, the glass insulators with TiO₂/SiO₂ composite film were placed in the outdoor environment, and it showed self-cleaning ability after water drenching. It was proved from the experiments that the transparent TiO₂/SiO₂ hybrid films with self-cleaning property possessed potential application in the fields of outdoor glass constructions, suspended glass disk insulators and auto windshields.

Due to the mechanical flexibility, tunable properties and easy processing, polymer based composites, especially the electroactive polymer composites based on the poly(vinylidene fluoride), which can be applied in the sensors, transistors and the capacitors, have been widely investigated. In this paper, all-organic composite films composed of cobalt phthalocyanine and poly(vinylidene fluoride) with high dielectric permittivity are simply synthesized by solution casting on the glass. The dielectric property over the broad frequency from 1Hz to 10⁷Hz is investigated. The high dielectric permittivity 86.4(10²Hz), about 9 times of the pure poly(vinylidene fluoride), is achieved when the fraction of the cobalt phthalocyanine is 20wt% that is similar to other semiconductors reinforced polymer composites. The significant increase of the dielectric constant and the dielectric loss tangent can be explained by the threshold theory. The origin of dramatically enhancement of dielectric permittivity and dielectric loss tangent over the low frequency is the Maxwell-Wagner-Sillars polarization. The results show that the dielectric property is very sensitive to the fraction of cobalt phthalocyanine. Additionally, when the fraction of the cobalt phthalocyanine was 10wt%, the dielectric permittivity and the conductivity of composite films are 17.1 and 1.1×10^-6s/cm respectively which indicated that it is potentially applied in the capacitors.

In this paper we repot the field demonstration of fiber laser seismic system. The structure of the fiber laser geophone, the seismic towed array, the interrogator system, and the test results are given. The results show that the four-element fiber laser seismic array have good performance.

Graphene sheets were carbon materials with high surface area, and excellent electrical properties. One of the most promising applications of those materials is in polymer nanocomposites. Their multifunctional properties may create new applications of polymer nanocomposites. In this paper, graphene sheets were prepared by oxidation-reduction method. The graphite was oxidized by potassium permanganate and sulphuric acid. The graphene oxide nanosheets, which were exfoliated from graphite oxide by ultrasound in water, were reduced by hydrazine hydrate, and the graphene nanosheets were obtained. Thereafter, the graphene sheets were dispersed in N,N-dimethylacetamide by simple sonication treatment. The graphene sheets/polyimide nanocomposites were synthesized by in situ polymerization using N,N'-dimethylformamide, graphene sheets and pyromellitic dianhydride. It was observed from transmission electron microscopy of graphene oxide sheets and graphene sheets that the very thin sheets were obtained by exfoliation of graphite. The result of FT-IR spectral analysis for graphene sheets shows the functional groups on the graphene sheets surface were almost the same as graphite, and that means the graphene sheets were complete reduced by hydrazine hydrate. A homogeneous dispersion of graphene sheets was achieved in polyimide as evidenced by scanning electron microscopy.

The stress induced martensitic transformation and shape memory effect in an Fe-17Mn-5Si-10Cr-5Ni shape memory alloy with different deformation condition is studied by XRD analysis, metallographical and TEM observation. The results show that the shape recovery ratio rapidly increases with the time increase, when the suspend loading time T< 10min; although the amount of the stress induced martensitic increases, the shape recovery ratio decreases, when the suspend loading time T>10min, which reason is the stabilization of the stress induced martensitic. Suspending loading 10min can effective improve the shape recovery ratio.

Monitoring techniques based on fiber Bragg grating sensor have proved to exhibit meaningful benefits when compared with the current solutions of an electric nature in recent years. In this study, several fiber Bragg grating (FBG) strain sensors were embedded into a prestressed concrete dual-room box-girder when construction at a prefabrication workshop to monitor strain of concrete girder during prestressing tension. All FBG sensors are alive during monitoring, which shows the advantages of robust surviving capability and long-term on-line monitoring performance. From the monitoring results it is found that the variances in strain at the measurement sites are small and almost is linear with time in certain one tension process, and the strain at the measurement sites almost synchronously and linearly change with the increase of the prestress. It is also found that the changes in strain at the measurement sites during the final tension are larger than that during the early tension.

In this paper application of Ionic Polymer Metal Composite (IPMC) as actuator in a deformable ring capable of locomotion is studied. Such a deformable ring moves as a result of gravitational force acting on its body when its shape changes. It can be used in exploration, search and rescue missions in future, where using conventional robots with rigid bodies and actuators is impossible. Large deformation induced by small stimulating voltage, low stiffness the sensing characteristics that in future work can be used in feedback control make IPMC a good choice for such an application. In this work first a model for IPMC is introduce that can be used in simulating deformation of IPMC in different arrangements of actuators. Since in this research we used our own fabricated IPMC, next we present characterization tests and identification results for model's parameters. Then using this model in simulation possibility of generating locomotion using body deformation in a ring made of IPMC is confirmed. Finally result of experiment on deformable ring is presented and possibility of implementation of the proposed design is confirmed. Based on this work, more accurate models can be developed to get better compatibility between experiment and simulation results. Also by modifying fabrication techniques, a deformable ring with faster and steadier movement can be made in future.

This paper presents an experimental study on monitoring of fatigue crack under complex environment using guided waves. An experimental set-up consisting of an electrical oven, a MTS testing machine and a monitoring system is established to perform the study. First, the combined effects of temperature, load and vibration on the propagation of guided waves in metallic structure is studied. Then, a statistical approach is proposed to detect fatigue crack under these combined effects. Damage feature is extracted after the guided wave signals are processed by Fourier transform. A Monte Carlo procedure is employed to estimate the probability density functions of the feature before and after cracking, respectively. By comparing the probability density functions, the probability of existence of fatigue crack is determined. Experimental study on a fatigue coupon under combined effects of temperature, load and vibration is conducted to demonstrate the effectiveness of the proposed method.

Material characterization of several resin systems for high temperature carbon fiber reinforced composites was performed through a series of the tensile test, the dynamic mechanical analysis (DMA) test, and the strand test. The modified tensile specimens and the DMA specimens were used to evaluate the tensile and thermal analysis properties of resin systems. The strand specimens were used to evaluate the tensile properties and load transfer efficiencies of the specimens. Four types of resin systems were considered. One was a conventional resin system currently used for filament wound structures and other three were high temperature resin systems. According to the tensile and DMA test results, the tensile modulus decreases slightly and the tensile strength decreases rapidly until the temperature reaches glass transition temperature. The tensile modulus and tensile strength are almost negligible above glass transition temperature. The tensile modulus obtained from the tensile test is consistent with that from the DMA test at different temperatures. From the strand test results, considering, the load transfer efficiency is found to be around 87 to 90 % of the tensile strength of T800H-12K carbon fibers for all resin systems except the specimen with the Type 2. Finally we found that the Type 4 is the best candidate for high temperature resin system applicable to filament wound structures in the view of the glass transition temperature as well as the tensile properties.

Works on the absorption of collision energy in the structural members are carried out widely with various material and cross-sections. And, with ever increasing safety concerns, they are presently applied in various fields including railroad trains, air crafts and automobiles. In addition to this, problem of lighting structural members became important subject by control of exhaust gas emission, fuel economy and energy efficiency. CFRP(Carbon Fiber Reinforced Plastics) usually is applying the two primary structural members because of different result each design parameter as like stacking thickness, stacking angle, moisture absorption ect. We have to secure the data for applying primary structural members. But it always happens to test design parameters each for securing the data. So, it has much more money and time. We can reduce the money and the time, if can ensure the CFRP material properties each design parameters. In this study, we experiment the coupon test each tension, compression and shear using CFRP prepreg sheet and simulate non-linear analyze at the sources - test result, Caron longitudinal modulus and matrix poisson's ratio using GENOAMQC is specialized at Composite analysis. And then we predict the result that specimen manufacture changing stacking angle and experiment in such a way of test method using GENOA-MCQ.

The world, coming into the 21st century, is preparing a new revolution called a knowledge-based society after the industrial society. The interest of the world is concentrated on information technology, Nano-technology and biotechnology. In particular, the Nano-technology of which study was originally started from an alternative for overcoming semiconductor micro-technology. It can be applied to most industry subject such as electronics, information and communication, machinery, chemistry, bioengineering, energy, etc. They are emerging into the technology that can change civilization of human beings. Specially, ultra precision machining is quickly applied to Nano-technology in the field of machinery. Lately, with rapid development of electronics industry and optic industry, there are needs for super precision finishing of various core parts required in such related apparatuses. This paper handles stability of a super precision micro cutting machine that is a core unit of such a super precision finisher, and analyzes the results depending on the hinge type and material change, using FEM analysis. By reviewing the stability, it is possible to achieve the effect of basic data collection for unit control and to reduce trials and errors in unit design and manufacturing.

The recent trend in vehicle design is aimed at improving crash safety and environmental-friendliness. To solve these issues, the needs for lighter vehicle to limit exhaust gas and improve fuel economy has been requested for environmental-friendliness. Automobile design should be made for reduced weight once the safety of vehicle is maintained. In this study, composite structural members were manufactured using carbon fiber reinforced plastic (CFRP) which are representative lightweight structural materials. Carbon fiber has been researched as alternative to metals for lightweight vehicle and better fuel economy. CFRP is an anisotropic material which is the most widely adapted lightweight structural member because of their inherent design flexibility and high specific strength and stiffness. Also, variation of CFRP interface number is important to increase the energy absorption capacity. In this study, one type of circular shaped composite tube was used, combined with reinforcing foam. The stacking condition was selected to investigate the effect of the fiber orientation angle and interface number. The crashworthy behavior of circular composite material tubes subjected to static axial compression under same conditions is reported. The axial static collapse tests were carried out for each section member. The collapse modes and the energy absorption capability of the members were analyzed.

This study investigated on improving of cooling performance of the thermoelectric cooling system by a vibrating from the piezoelectric actuator. Experiment was carried out to investigate cooling performance of the thermoelectric cooling system for the cases; one without the piezoelectric actuator and the other with the piezoelectric actuator. Temperature measurement experiment and flow visualization experiment were performed to compare cooling performance for the cases, respectively. Cooling performance of the thermoelectric cooling system was improved by the piezoelectric actuator when the results of temperature measurement and flow visualization were compared, because forced convection was generated by vibrating (acoustic streaming) from the piezoelectric actuator and the cold air in cooling region was actively circulated by impulsive convection.

The infrared thermographic nondestructive inspection technique is a quality inspection and stability assessment method used to diagnose the physical characteristics and defects by detecting the infrared ray radiated from the object without destructing it. Recently, the nondestructive inspection and assessment that use the ultrasound-infrared thermography technique are widely adopted in diverse areas. The ultrasound-infrared thermography technique uses the phenomenon that the ultrasound wave incidence to an object with cracks or defects on its mating surface generates local heat on the surface. Aiming to establish a convergence non-destructive evaluation system, this study used the control technology of an ultrasound exciter as an association technology that satisfies various required conditions in order to control the ultrasound excitation time and output, and performed basic research for establishing a convergence non-destructive system by applying the Lock-in technology that improves the infrared thermography detectability. Also it compared and analyzed the test result by using COMSOL Multiphysic, a finite element analysis program.

Steel rebar is the most employed reinforcements in concrete structures and is subjected to damage due to environmental factors. Therefore it is meaningful to develop suitable non-destructive damage detection methods for steel rebar in engineering structures. Lead Zirconate Titanate (PZT) is one of the most effective types of piezoelectric material, and it has been widely used both sensors and transducers for the structural health monitoring (SHM) of engineering structures. Based on the coupling effect of PZT patches surface-bonded on a structural member, the electromechanical impedance (EMI) based structural damage detection has been employed to detect local damage of civil engineering structures. This paper presents the results of the experimental study on the EMI based damage detection for steel rebar specimens under different damage scenarios by analyzing the changes in the piezoelectric admittance spectrum of PZT patches surface-bonded on the steel rebar specimens. A damage index called the root mean square deviation of admittance (RMSDD) is employed to evaluate the extent of damage of the steel beam. Based on the analysis on the relationship between the damage index and the distance of the PZT sensor from the damage, the sensitivity of the PZT sensors and their sensing region is discussed. The results shows that the location and level of the damages could be quantitatively identified by converting the admittance measurements into the scalar damage index.

The simulation of multiphase solidification process can be handled by combining the VOF (Volume of Fluid) transport equation, in which the continuum mechanics model is used to simulate the melt/solid interface and the conservation of mass, momentum, and energy. Because the melt phase, the solid phase, and the melt/solid interface are controlled by a single control equation; if the enthalpy model based on porosity concept represents the processing of the phase transformation range, it is possible to solve the problem of phase transformation in the same way as solving the single-phase problem. Once the energy field of enthalpy for each step in time is resolved, the position of the interface can be precisely calculated with the use of VOF equation. This type of novel VOF method can be applied to find out the conditions of vertical Bridgman crystal growing located on the earth or under microgravity.

Force field based simulation has been employed to predict the deformation mechanisms of auxetic nano-materials having tetrahedral framework. The structure of α-quartz was studied in detail for subjecting to uniaxial loading along the Z direction. The cooperative dilation and rotation of tetrahedra acting concurrently were demonstrated to be the main deformation mechanism of α-quartz, confirming previous analytical model. Slight tetrahedral distortion also existed for undeformed and deformed structure.

A developed process model including the effects of chemical and thermal strains and the cure related elastic material behavior is established in order to simulate the cure process before cooling stage more realistically. A three-dimensional finite element method is used to analyze the effect of the curing related parameters on residual stresses in the cure progress of polymer composites. The obtained results show that the density, the specific heat, the thermal conductivity and the anisotropic chemical shrinkage have different influences on the final residual stresses before cooling stage.

The nanocrystalline sodium niobate(NaNbO₃) and sodium tantalite(NaTaO₃) powders with perovskite structure were synthesized by the solvthermal method with glycol as solvent. These powders were characterized by powder X-ray diffraction(XRD), Raman spectroscopy, Scanning electron microscopy (SEM) and transmission electron microscopy(TEM). Rietveld refinement of X-ray diffraction data and Raman spectroscopy confirm that the nanoparticles of NaNbO₃ and NaTaO₃ have orthorhombically distrorted structures with Pmc2₁ and Pbnm space groups, respectively. The SEM photograph shows that NaTaO₃ and NaTaO₃ powder are cubic morphology. The TEM and the SAED pattern confirmed that the nanoscale NaTaO₃ is single-crystal structure. In addition, the influence of the concentration on the NaTaO₃ powder characteristics was also detailed investigated.

With the rapid application of the composite structure in the aerospace industry, more load-bearing structures and components are used with composites instead of conventional engineering materials. However, the composite structures are inevitably suffered damages in the complex environment, the composites structures repair become more important in the airplane maintenance. This paper describes the composites patch repair progress. Firstly, the flaws and damages concerned to composite structures are concluded, and also the repair principles are presented. Secondly, the advantages and disadvantages for different repair methods are analyzed, as well as the different bonded repair and their applicability to different structures is discussed. According the recent research in theory and experiment, the scarf repair effects under different parameters are analyzed. Finally, the failure mechanisms of repair structure are discussed, and some prospects are put forward.

A palladium silver (Pd-Ag) film coated LPG for hydrogen sensing is represented in this paper. This hydrogen sensor is a LPG coated with Pd-Ag film, and the thick of the film is about 70nm. When the sensor is exposed to hydrogen, the refractive index of Pd-Ag will change, and it will cause the shift of the resonance wavelength of LPG. Therefore, the concentration of hydrogen can be monitored by measuring the shift of resonance wavelength of LPG. The preliminary experiment shows that Pd-Ag film coated LPG has an obvious response to 3~4% hydrogen, with a response time of a few minutes at 4% hydrogen.

Stability of magnetorheological (MR) fluids are important in practical application, such as oxidation resistance, antiwear properties, temperature independence, stability of sedimentation and aggregation. Ferrous particles surface nitriding and different additives were used to improve MR fluid's stability .The synthesis process and properties of MR fluid were described briefly.

Crack monitoring plays a great role in modern structural health monitoring. A new scheme of the sensor is developed in this paper. The finite element model (FEM) of the sensor was established, and the output characteristics of the sensor were analyzed by FEM. It was shown that the sensor was sensitive to cracks, and could be used to monitor the propagation of cracks initiating from the edge of the hole. Finally, the sensor was prepared on a specimen, and the feasibility of the sensor to monitor cracks was demonstrated by experiment.

The effects of heat treatment on microstructures and mechanical properties of the Mg-5Zn-xEr alloys (x = 0.63, 1.25, 6.3 wt.%) have been investigated by using XRD, DSC, SEM and TEM. The investigation suggested that the kinds of the secondary phases had a great effect on microstructures and ageing responses of the alloys. It was found that the Mg-5Zn-0.63Er alloys which contained the secondary phase of I-phase exclusively displayed the optimal ageing responses at 175°C for 36 h when it had been solution treated at 480°C for 10 h. However, the Mg-5Zn-1.25Er alloy including both W-phase and I-phase exhibited its good ageing behaviors at 175°C for 10 h after solution treated 520°C for 10 h. Meanwhile, the Mg-5Zn-6.3Er alloy presented its preferable ageing responses at 175°C for 18 h after solution treated at 520°C for 10 h. The peak hardness was ascribed to the presence of the β'₁ phase which precipitateed during aging process.

The importance of Carbon Fiber reinforced plastics (CFRP) has been generally recognized, and the CFRP composite laminates are widely used. When ultrasonic inspection is applied on actual aircraft components, the part geometry often lacks flat and parallel faces and the benefit of a backwall echo maybe unavailable. So, it is very necessary to detect flaws and defects in the CFRP composite solid laminates due to the flaws of CFRP composite laminates affecting the properties of the laminate. Firstly, we used miniature potted angle beam transducers (designed for generating mode-converted shear waves or Rayleigh waves in steel) on solid laminates of composites. A pair of such transducers was mounted in a holder in a nose-to-nose fashion to be used as a scanning probe on composites. Secondly, a method was utilized to determine the porosity content of a composite lay-up by processing micrograph images of the laminate. The results from the image processing method are compared with existing data. C-scan images of CFRP samples, which were based on the impacted samples were then produced by combining the pitch-catch probe with a portable manual scanner known as the Generic Scanner ("GenScan"). The signal amplitude of pitch-catch C-scan images was also correlated to the volume percent of porosity in carbon composite laminates. Finally, a simulation was performed with the numerical Wave-2000 Code for predicting the ultrasonic wave in the sample.

TiNi shape memory alloys exhibit superior shape memory effect, superelasticity, and high damping capacity. The damping behaviour of a ternary TiNiCu₇ alloy were characterized by dynamic mechanical analyzer (DMA) instrument, dynamic mechanical thermal analysis (DMTA) and differential scanning calorimetry (DSC) equipment. The loss factor Tanδ, storage modulus E' and loss modulus E" of shape memory alloy aging followed by furnace cooling and air cooling were Measured. It shows that test method and cooling rate of aging have significant effect on the results of damping capacity of TiNi SMA. Internal friction values (Q^-1) corresponding to cubic B2 parent phase to rhombohedral R phase transformation are as high as 0.14 for the TiNiCu7 alloy measured by DMA in single cantilever mode, lower than that of 0.21 measured by DMTA in three-point bending mode.

Prognostics and Health Management (PHM) technologies for potential application on aircraft have been maturing rapidly recently since it can ensure safety, equipment reliability, and reduction of costs. The service life prediction of aircraft engine is vital part of PHM technology. Research on practical and verifiable prediction methods for service life of bearing plays a critical role in improving the reliability and safety of aircraft engines. In the paper, the concept of Grade-Life (GL) is introduced to describe the service life of the bearing. A grade-life prognostic model of aircraft engine bearing, which is based on the fuzzy logic inference, is proposed. Firstly, the mathematical model is discussed, which is used to predict the physics-based GL (PGL). Then, the diagnostic estimation model based on SVM is given in details, which is exploited to predict the empirical GL (EPL). Thirdly, a fuzzy logic inference method is adopted to fuse two GL predicted results. Finally, the grade-life prognostic model is verified by the run-to-failure data acquired from accelerated life test of an aircraft bearing. The results accredit that this model provides for a more practical and reliable prediction for service life of bearings.