Finite element analysis on thermo-mechanical behavior of styrene-based shape memory polymers

Tensile tests at various temperatures are conducted to detect the relationship of material strain and stress of the styrene-based shape memory polymers (SMP).The material elastic modulus and yielding limit stresses at the temperatures of 25°C, 30°C,40°C and 50°C are determined according to the results of tensile tests. In order to describe the glass transition behavior of the styrene-based SMP, a new material parameter function is supposed based on the results of the tensile tests. The styrene-based SMP is assumed as an isotropic material, then a threedimensional thermo-mechanical constitutive equation of SMP is developed based on Tobushi' s one-dimensional thermo-mechanical constitutive equation. In order to perform finite element analysis on SMP by using ABAQUS, a UMAT subroutine for ABAQUS is programmed with Fortran codes based on the three-dimensional constitutive equation and the new material parameter function. The shape memory thermo-mechanical process of styrene-based SMP is numerically simulated by ABAQUS coupled with the UMAT subroutine, which includes deformation at a high temperature upon loading, shape fixity due to cooling and shape recovery through heating. Numerical results show that the thermo-mechanical behavior of SMP can be well simulated by ABAQUS coupled with the UMAT subroutine.