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Proceedings Paper

Accelerated characterization for long-term creep behavior of polymer
Author(s): Rongguo Zhao; Chaozhong Chen; Qifu Li; Xiyan Luo
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Paper Abstract

Based on the observation that high stress results in increasing creep rate of polymeric material, which is analogous to the time-temperature equivalence, where high temperature accelerates the process of creep or relaxation of polymer, the time-stress equivalence is investigated. The changes of intrinsic time in polymer induced by temperature and stress are studied using the free volume theory, and a clock model based on the time-temperature and time-stress equivalence is constructed to predict the long-term creep behavior of polymer. Polypropylene is used for this work. The specimens with shape of dumbbell are formed via injection molding. The short-term creep tests under various stress levels are carried out at ambient temperature. The creep strains of specimens are modeled according to the concept of time-stress equivalence, and the corresponding stress shift factors are calculated. A master creep curve is built by the clock model. The result indicates that the time-stress superposition principle provides an accelerated characterization method in the laboratory. Finally, the time-dependent axial elongations at sustained stress levels, whose values are close to the tensile strength of polypropylene, are measured. The three phases of creep, i.e., the transient, steady state and accelerated creep phases, are studied, and the application and limitation of the time-stress superposition principle are discussed.

Paper Details

Date Published: 25 August 2009
PDF: 6 pages
Proc. SPIE 7375, ICEM 2008: International Conference on Experimental Mechanics 2008, 73751D (25 August 2009); doi: 10.1117/12.839057
Show Author Affiliations
Rongguo Zhao, Xiangtan Univ. (China)
Chaozhong Chen, Xiangtan Univ. (China)
Qifu Li, Xiangtan Univ. (China)
Xiyan Luo, Xiangtan Univ. (China)

Published in SPIE Proceedings Vol. 7375:
ICEM 2008: International Conference on Experimental Mechanics 2008
Xiaoyuan He; Huimin Xie; YiLan Kang, Editor(s)

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