Time-Dependent Strain Distribution in Polymers under Complex Stress History: Experimental Study by Moire Fringe Method and Finite Element Predictions

A combination of experimental and computational methods are developed, for predictions of nonlinear viscoelastic creep of polymers in sheet form, subjected to inhomogeneous stress states and stress history. A recently proposed multiaxial constitutive model for glassy polymers was implemented in a commercial finite element (FE) package. The model was tested by means of creep experiments on PMMA at elevated temperature, using specimens with a central circular hole. The experiments were performed using a tensile creep machine, and the geometric Moire fringe method was employed for measuring strain distribution. The results obtained from the experiment and FE analysis were compared.