Thermodynamic and viscoelastic constitutive model of TPI/HDPE hybrid shape memory polymer

In recent years, shape memory smart materials have developed rapidly, and more and more novel shape memory polymers have been developed and applied. In sharp contrast to the rapid development of shape memory smart materials, its theoretical research is obviously lagging behind. Therefore, it is necessary to clearly understand and master the thermodynamic dynamic response mechanism of shape memory polymers. In view of the fact that the influence of thermodynamic properties of hybrid shape memory polymer under the coupling effect of multiple factors is still very vague, a novel hybrid shape memory polymer composites (SMPC) thermodynamic viscoelastic constitutive model is proposed for the first time by combining the macroscopic phenomenological viscoelastic theory with the microscopic phenomenological phase transition model, and a microstructure composed of two parts of reversible phase and stationary phase in parallel is constructed. At the same time, a three-dimensional parameter equation with temperature effect and capable of describing the coordinated changes of various parameters in the phase transition process is established. Through the validation of the model, it can be found that the variation trend of the simulation curve is in good agreement with the experimental curve during the whole static loading process, and the error of the fracture stress is less than 2%. Through the dynamic evolution of multi-content and wide-temperature range, the consistency between the simulation results and the experimental results is successfully proved, and the microscopic mechanism of the macroscopic static mechanical behavior of the hybrid SMPC is revealed. The model established in this paper can accurately describe the internal phase change of the mixed matrix, and realize the effective prediction of the stress-strain response under the coupling effect of the matrix composition and the external environment. The proposal of this model provides a new idea for the exploration of hybrid SMPC thermodynamic viscoelastic theory, and also provides an important theoretical reference for the development and application of novel hybrid shape memory materials in the future.