Experimental calibration of constitutive model for an amorphous shape memory polymer under large deformations

The aim of the present study is the experimental calibration of the recent model proposed by the authors which describes the thermomechanical behavior of glassy polymers under large deformations. For such this purpose a series of thermomechanical experiments has been conducted with lightly-linked epoxy specimens, for which large deformations are achievable in the rubbery state. Three experimental series have been carried out on the DMA testing machine in the regime of regulated axial compression load and changed temperature with the axial contraction measuring. The aim of the first experimental series was to prove the elastic potential choice for describing the behavior of the concerned material. For this purpose the samples in rubbery state were deformed under constant loading rate. It was concluded that the Peng-Landel elastic potential could be applied for the accurate description of the epoxy resin deformation process. The second series included several adjusting experiments for the model parameters determination. The samples were heated with the constant temperature rate under the constant compression load. The comparison of results for different rates and load levels is given. Also the procedure of the parameters determination is described. Some parameters were taken as the material constants, for other ones the linear approximation of the dependence on the temperature rate and the load level was made. The third series presents the verification experiment for which a shape memory thermomechanical cycle was chosen. The experimental data were approximated with the numerical model based on the parameters which were found from the adjusting experiments. A good agreement between the experimental and numerical results is shown. A brief review of the most spread experimental schemes for the shape memory cycle is also given in the paper.