Temperature and rate dependent thermomechanical modeling of shape memory polymers with physics based phase evolution law

• A physics based phase evolution law for amorphous shape memory polymer is developed.
• The constitutive model is validated using experimental results in the literature.
• The model can account for the effect of both internal and external parameters.
• The principle and approach can be extended to semicrystalline shape memory polymers.

The thermomechanical constitutive models are critical for shape memory polymers (SMPs) in analyzing their shape memory behaviors under different conditions. Recently, the phase evolution modeling approach proposed by Liu et al. (2006) has been extended and widely used due to its simplicity and generality. However, the lack of physical explanation has become its major limitation. In this study, a phase evolution law was proposed from the physics perspective. The shape memory polymer was then treated as a frozen-phase matrix with active-phase inclusions embedded in it and the Mori-Tanaka approach was used to predict the effective mechanical properties. The theoretical predictions were compared with available experimental results and reasonable agreement was found. The influence of the intrinsic material structures and the thermomechanical conditions on the shape memory behavior were evaluated by parametric studies.

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