Effects of thermal rates on the thermomechanical behaviors of amorphous shape memory polymers |
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Authors: | Francisco Castro Kristofer K Westbrook Kevin N Long Robin Shandas H Jerry Qi |
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Affiliation: | (1) State Key Laboratory of Polymer Materials and Engineering of China, Polymer Research Institute, Sichuan University, Chengdu, 610065, China; |
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Abstract: | Shape memory polymers (SMPs) are polymers that can recover a large pre-deformed shape in response to environmental stimuli,
such as temperature, light, etc. For a thermally triggered (or activated) amorphous SMP, the pre-deformation and recovery
of the shape require the temperature of the material to traverse the glass transition temperature T
g under constrained or free conditions. In this paper, effects of thermal rates on the thermomechanical behaviors of amorphous
SMPs are investigated. Under uniaxial compression, during a temperature cycle (cooling followed by heating), the stress decreases
to zero as the temperature decreases to below the glass transition temperature, and increases to a value larger than the initial
stress (termed stress overshoot) as the temperature is raised above the glass transition temperature. These observations are
examined by a thermoviscoelasticity model that couples the nonequilibrium structural relaxation and temperature dependent
viscoelastic behavior of the material. In addition, using this model, stress-temperature behaviors during temperature cycles
with various thermal rate conditions and tensile loading conditions are studied. |
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Keywords: | |
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