The twenty-first century provides engineers with a host of challenges and opportunities. Our oldest, culturally important structures must be retrofitted, protected, and preserved. Structures built during the industrial boom of the twentieth century are approaching the end of their lives. In most cases, we still need these bridges, buildings, highways, and dams. As such, these structures must be inspected, assessed, maintained, and managed in a way that is cost effective, practical, and safe.¹ At the same time, new materials, architectural concepts, and the desire for sustainable, energy efficient, and eco-friendly design are pushing the science of construction. Indeed, it is an exciting time to be an engineer.

Multifunctional sensor-embedded materials can help engineers meet these challenges. While performing a traditional protective or load-carrying role, these materials also gather and carry information for structural health monitoring (SHM). For aircraft, such materials could help reduce the ∼400km of cabling required in a modern large airframe.² For civil structures, such materials could provide the next evolutionary step in the design and operation of infrastructure.³

The 2009 L'Aquila (central Italy) and 2010 Haiti earthquakes have provided powerful and striking images of seismic damage. Nearly every week, smaller events occur that lead to embankment failures, bridge collapses, washouts, sinkholes, and settlement problems, as shown in Figure 1. Risk is an inherent part of engineering and cannot be eliminated. Most structures in seismic areas have already been subjected to mild earthquakes and contain minor levels of damage. There is a need for innovative solutions to mitigate risk in areas prone to natural hazards.

Figure 1. Structures at risk: geotechnical failures and inhabited masonry structures in historic areas (Pavia and Venice, Italy).

The polyfunctional technical textiles against natural hazards (POLYTECT) project is made up of 27 partners from 12 countries and is coordinated by D'Appolonia SpA from Genova, Italy. The project aims to provide reinforcing strength and monitoring capability for geotechnical and masonry applications through the industrial production of multifunctional technical textiles. More information on the project and its partners is available from its website⁵ and from an online news item,⁴ as seen in Figure 2. POLYTECT is developing many novel products, several of which are shown in Figure 3. These include fiber-optic, piezoelectric, and chemically sensitive textile fibers; novel sensor interrogation systems, hardware and data processing techniques, as well as nanoparticle-based mortars and adhesives. It is also integrating sensors into warp-knitted textiles for geotechnical and masonry applications, in both 2D and rope-like structures. Project partners evaluate these products in the laboratory, develop numerical models for their use, and undertake field testing.

Figure 2. The Euronews international news network has made a short ‘Futuris’ program about the POLYTECT project and the L'Aquila earthquake, which is available online.⁴ (Image courtesy of Euronews.)

Engineers can benefit from multifunctional textile products that are versatile, low cost, and provide high performance. Textiles can be mass produced, and both weaving and warp-knitting lend themselves to the inclusion of fiber-optic sensors along their length. Experience in the field is showing a preference for a multifunctional product that incorporates monitoring (rather than one that requires the planning and purchase of stand-alone monitoring systems).

One POLYTECT product is a ‘seismic wallpaper.’ Sensor-embedded reinforcing strips or wide-area-coverage multiaxial textiles can be applied to and integrated with the surface of a masonry structure (see Figure 3). Uniaxial strips made of stiff fibers are applied with epoxy resin. Wide-area textiles made of more flexible fibers and are applied using mortar compound. Both approaches demonstrate significant increases in strength, and the wide-area solution provides notable increases in structural ductility. Embedded sensors can be used for static and dynamic measurements (depending on the fiber-optic technique employed). In the event of an earthquake, the risk of collapse and falling debris is reduced, and engineers have a tool to begin damage assessment.

Figure 3. Several POLYTECT products: A multi-channel stackable interrogation system (Interlab), a sensor embedded multiaxial textile (STFI), novel fiber-optic sensors (Smartec), and a sensor-embedded filter mat (Extreme Materials).

In geotechnical applications, fiber-optic sensors can be used to provide distributed strain and temperature measurements over kilometers.⁶ This is useful for slope stability problems, areas prone to sinkholes, or pipelines that leak.⁷ When integrated into textiles, the sensors become protected and interact better with the soil, providing more accurate measurements. Field tests show that the sensors survive normal compaction operations, harsh weather environments, and remain functional several years after installation. One field test proved extremely helpful to the repair of a slope in need of stabilization and monitoring. In this case, the underground sensor measurements provided immediate feedback on whether the repair was successful (and subsequently indicated if the repair held, reducing the slope's threat to the nearby community). This field test and one at the reconstruction of a railway embankment are shown in Figure 4.

Figure 4. Uniaxial strip reinforcement of a single-story structure and its analysis (by the Institute of Mechanics of Materials and Geostructures, Greece) and the integration and testing of wide-area multiaxial textiles (Karlsruhe Institute of Technology, Germany).

Figure 5. The emplacement of sensor-embedded geotextiles at a railway embankment (Saxon Textile Research Institute, Germany) and at the repair of a slope that needed stabilization and monitoring (University of Kassel, Germany).

POLYTECT has teamed with the European Research Centre for Training and Research in Earthquakes (EUCENTRE) and the Structural Engineering Research Center (SERC) in India. In the coming months, full-scale multi-story structures will be retrofitted with POLYTECT textiles and evaluated using shaking table tests. With respect to geotechnical applications, sensor-embedded textiles will be installed at a Romanian landfill site to help manage the site as a bioreactor.

The POLYTECT project is supported by the European Commission 6th Framework Programme.