Experimental investigation on the thermo-mechanical deformation of thermo-induced shape memory polyurethane

The influences of loading conditions on the shape memory effect (SME) of thermo-induced shape memory polyurethane (TSMPU) are investigated by series of thermo-mechanical deformation experiments. The variables related to mechanical responses and the strain contours are extracted to analyze the SME. It is shown that the recovery ratio gradually decreases and the residual strain gradually accumulates with the increase of number of cycles. Then, the internal stress is obtained from the experimental results under different deformation histories. It is unexpectedly found that there is a linear relationship between the internal stress and recovery ratio under the same peak strain with different strain rates and number of cycles. Meanwhile, the formation and release of internal stress as the deformation mechanism can reasonably reflect the influence of deformation history on the SME. The experimental results are useful to deepen the understanding of SME and establish a constitutive model considering the thermo-mechanical deformation history of TSMPU.