A procedure for the constitutive analysis of creep phenomena in polymeric materials

A specific procedure is proposed for the univocal and fast identification of viscoelastic parameters of polymeric materials by the processing of experimental results from creep tests. Mechanical tests were developed on polymethylmethacrylate and polycarbonate samples according to different stress and temperature conditions. The creep stresses and the temperatures were defined to characterize the mechanical response within the standard domain of application of the specific polymeric materials. The experimental data were post-processed to provide the experimental relationship between creep modulus and time at the different temperatures. Such experimental relationship was interpreted by specific model formulations, which were developed starting from the standard theory of linear visco-elasticity. Elastic and viscous parameters were identified by the minimization of discrepancy between model and experimental results. The trend of constitutive parameters with temperature was finally evaluated.