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 the increasing amount 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 good agreement with experimental data and can be useful for industries and companies which are looking for a model able to predict the recycling effect on mechanical behavior of polymer-based materials.
Highlights
Polypropylene (PP)-based composites are increasingly utilized in the automotive industry, in particular, for both exterior and interior components
We found that the ethylene octene copolymer (EOC) inclusions stabilize the tensile elongation at the break up to three recycling numbers due to a decrease of their size and the homogenization of their shape during the reprocessing
For the purpose of mathematical simplicity as mentioned previously, we considered that the physic meaning parameters, CR, N, and Rs, are not depending on the strain rate and they are selected in accordance with the experimental curves at a strain rate of 0.001s−1
Summary
Polypropylene (PP)-based composites are increasingly utilized in the automotive industry, in particular, for both exterior and interior components. The experimental characterization indicates the evolution of different properties of the composite during the mechanical recycling, the modeling of mechanical responses of recycled PP-based composites is less investigated To this end, a micromechanical modeling may enable us to predict the maximum reprocessing number, until which the quality of the material would be retained for a targeted application. The main objective is to experimentally determine and model the tensile behavior of two commercial PP-based composites as a function of the number of mechanical reprocessing. These two materials are commonly used for the manufacturing of car bumpers in the automotive industry, requiring optimizing their end-of-life scenarios and utilization. The analysis of the recycling-dependent tensile behavior has guided the development of a constitutive model, including the recycling correlative physical parameters
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