Caractérisation et modélisation des propriétés mécaniques des biocomposites à fibres courtes aléatoires

Abstract

This study consists in characterizing the mechanical properties in tensile, bending and impact resistance of three biocomposite materials. The materials to be characterized are composed of the same matrix (polypropylene (PP) / polyolefin elastomer (POE), PP / POE [95 wt%: 5 wt%]) reinforced by three different reinforcements. Formulations (F1), (F2) and (F3) are respectively reinforced with 30wt% biochar, 30wt% miscanthus and the third reinforcement is a mixture between 15wt% biochar and 15wt% miscanthus. To improve the adhesion between the reinforcements and the matrix, 3wt% of modified polypropylene anhydride (MAPP) was added to the composites. Experimental results showed that the three reinforcements improve the Young's modulus of the matrix. Formulation (F2) exhibited the best tensile and flexural properties over the other two materials. In fact, miscanthus fibers increased the Young's modulus of the matrix by 107% and the tensile strength by 10,51%. These tensile properties are better than those of the commercial material RTP 132 UV. The hybrid bicomposite (F3) also increased the Young's modulus of the matrix by 70% and maintained almost the same tensile strength of the PP / POE. Biocomposite reinforced with biochar (F1) improved matrix stiffness by 34% but decreased matrix strength by 8%. By contrast, these reinforcements have decreased the impact resistance of the matrix. Comparing the experimental results of the unnotched Izod impact test of the three biocomposites, the formulation reinforced by biochar (F1) showed the best resilience but still remains far from the resilience of the commercial material. Numerical homogenization using the finite element method is used to predict the Young's modulus of these randomly reinforced biocomposites. Digimat® commercial software was used to generate the 3D representative volume element (VER) and evaluate the Young's modulus of the composite. The critical size of the VER is about twice the length of the fiber using the periodic boundary conditions. In this study, the numerical results showed a good agreement with the experimental results of the biocomposites.

Date	2 Oct 2018
Original language	French
Awarding Institution	École de technologie supérieure
Supervisor	Anh Dung Ngô (Supervisor) & Manjusri Misra (Co-supervisor)