Abstract：A constitutive model for shape memory polymer is established by constructing a multi-axial compressible strain energy with thermal-coupled property to obtain relationships between stress-strain、stress-temperature and strain-temperature. Three invariants based on Hencky strain are introduced to (i) simulate compressible condition; (ii) applicable to at least two deformation mode, i.e. uniaxial tension and compression and bi-axial tension; (iii) effective for multi-axial case. By using explicit method to (i) give out the explicit formulations of free energy and entropy to prove that the constitutive equations satisfy the thermodynamic conditions; (ii) give out the shape functions of stress-strain、stress-temperature、and strain-temperature. The multi-axial model can automatically reduce to their uniaxial case, respectively. The model result can accurately match the experiment data by adjust parameters in the shape functions. The new constitutive model can accurately guide engineer designing for the shape memory polymer.
2020, Vol. 41 
