Optimum consolidation of self-reinforced polypropylene composite and its time-dependent deformation behavior

A systematic investigation was carried out to determine the optimum consolidation process conditions of a co-extruded polypropylene self-reinforced composite (SRC) considering its structural characteristics and static and time-dependent deformation behavior. It was observed that very little change in the processing condition influenced significantly the mechanical behavior of consolidated SRCs, e.g., the peel strength can be improved by approximately 30% within 10° change in temperature, the reason for which was investigated with structural analysis such as DSC and XRD and mechanical tests, including T-peel, tensile, and creep tests. A creep potential with three orthotropic material parameters was utilized to describe the anisotropic and nonlinear time-dependent deformation behavior of the SRC. Combined with the creep potential, the creep test of an off-axis coupon specimen with the fiber orientation of 22.5° was found to represent the anisotropic and nonlinear creep behavior of other off-axis specimens within a reasonable error.