Constitutive Modeling of the Tensile Behavior of Recycled Polypropylene Based Composites

Abstract

The effect of reprocessing on the quasi-static uniaxial tensile behavior of two commercial polypropylene (PP) based composites is experimentally investigated and modeled. In particular, the studied materials consist of an unfilled high-impact PP and a talc-filled high-impact PP. These PP composites are subjected to repeated processing cycles including a grinding step and an extrusion step to simulate recycling at the laboratory level, the selected reprocessing numbers for this study being 0, 3, 6, 9 and 12. Because the repeated reprocessing leads to thermo-mechanical degradation by chain scission mechanisms, the tensile behavior of the two materials exhibits a continuous decrease of elastic modulus and failure strain with increasing number of reprocessing. A physically consistent three-dimensional constitutive model is used to predict the tensile response of non-recycled materials with strain rate dependence. For the recycled materials, the reprocessing effect is accounted by incorporating the reprocessing sensitive coefficient into the constitutive model for Young’s modulus, failure strain, softening and hardening equations. Our predictions of true stress - true strain curves for non-recycled and recycled 108MF97 and 7510 are in a good agreement with experimental data.

Modeling the mechanical response of polymers and nano‐filled polymers: Effects of porosity and fillers content

“…As a result, Wang et al 1 have modified the Richeton model to account for the effect of nanofillers. In fact, a three-phase model was developed by incorporating the Richeton model into the Ji model and by making use of the Takayanaigi homogenization scheme.…”

“…17 Ji et al 18 have developed a model which takes into account the interface between the polymer and the nanofillers. Therefore, the three-phase model of Wang et al, 1…”

“…For instance, the stiffness of a polymer increases with increasing the volume fraction of nanofillers. 1 Polymer nanocomposites have become one of the most interesting candidate materials for membranes, especially in water treatment applications. Nanofillers are not only used to give more mechanical strength, but also to functionalize the polymer-based membranes to improve the removal of pollutants such as heavy metals.…”

“…Previously reported studies mainly established models for the prediction of the mechanical behavior for polymers and polymer nanocomposites. 1,3,4 For the general cases, two of the most comprehensive models for the mechanical behavior of polymers are: (a) the cooperative model which predicts the yield stress, and (b) the statistical model which predicts the elastic modulus for polymers. 5,6 Ahzi and coworkers 1,3,4 have extended these two approaches to polymer nanocomposites by incorporation of the nanofillers effects using a composite formulation approach.…”

“…1,3,4 For the general cases, two of the most comprehensive models for the mechanical behavior of polymers are: (a) the cooperative model which predicts the yield stress, and (b) the statistical model which predicts the elastic modulus for polymers. 5,6 Ahzi and coworkers 1,3,4 have extended these two approaches to polymer nanocomposites by incorporation of the nanofillers effects using a composite formulation approach. We note that these modeling approaches for the mechanical response of polymers and polymer nanocomposites accounts for the effect of both temperature and strain-rate/frequency.…”