A Constitutive Model for the Nonlinear Viscoplastic Behavior of Thermoplastic Olefin

摘要

A tangent constitutive model was developed in this article to address the nonlinear viscoplastic behavior of compound grade thermoplastic olefin (TPO). The TPO was commonly blends of polypropylene matrix, rubber, and inorganic filler. The constitutive model for TPO was obtained from the combination of the mechanical behavior of the matrix and fillers. In a multiphase material, the rate-dependent behavior of polypropylene matrix was presented by a physically based constitutive model for large strain deformation, while the deformation behavior of rubber and talc were captured by Hooke's law. The average strain of each phase, as well as the strain of the voids caused by cavitation of rubber and debonding of talc, was determined by the Mori-Tanaka method, in conjunction with a tangent modulus approach. To test the applicability of the developed model, it was applied to calculate the rate dependent stress-strain relations of TPO. The model was predictive of the initial rate-dependent stiffness, yield, and strain hardening response in large strain deformation. The constitutive model was incorporated into a finite element code to predict the large strain deformation behavior of TPO. The initiation of necking and neck propagation were obtained and confirmed by experimental observation.