Optimisation des propriétés mécaniques de composites à base de fibres naturelles : application à un composite de fibre de lin avec un mélange de polyéthylène/polypropylène d'origine post-consommation

Authors: Toupe, Jean Luc
Advisor: Rodrigue, Denis; Trokourey, Albert
Abstract: In this thesis, we tried to optimize the mechanical properties (flexural and tensile moduli, impact strength, and tensile stress at yield) of a flax fiber/postconsumer plastic composite by combining two optimization paths (phase compatibilization and manufacturing process optimization) while taking into account the material production costs. In the first part, the composite was optimized by phase compatibilization. To do this, the best additive was first determined by analyzing the effect of several additives of different types (conventional coupling agent, elastomeric additive, and mixture of elastomeric additive/coupling agent), on the mechanical, morphological and physical (density) properties. Then, material composition was optimized to improve the mechanical properties. An objective function (quality/cost ratio) was defined to simultaneously account for all the mechanical properties and production costs. In the second part, the effectiveness of combining two optimization paths was analyzed. First, the manufacturing process parameters (extrusion followed by injection) were optimized using the optimum composite composition obtained in the first part (combination of both optimization paths). The quality/cost ratio was also used as objective function. Thereafter, the effect of the combined optimizations on the microstructure (fiber dimensions, matrix crystallinity and matrix molecular properties) and mechanical properties of the composite was investigated. The results showed that the best additive was EO-g-MAH/MAPP of the category “mixture of elastomeric additive/coupling agent”. In addition, the composition and the manufacturing conditions of the composites were optimum when the overall mechanical performance was improved by giving priority to stiffness, and simultaneously to stiffness and resilience, respectively. On the other hand, the combination of both optimization paths, besides good fiber-matrix interfacial adhesion, promoted an optimum balance between components degradation and composite homogeneity (good fiber and additives dispersion in the matrix), leading to better mechanical properties. This optimization procedure was able to improve all the mechanical properties of the composite, as well as being effective in terms of performance and costs.
Document Type: Thèse de doctorat
Issue Date: 2015
Open Access Date: 23 April 2018
Permalink: http://hdl.handle.net/20.500.11794/25985
Grantor: Université Laval
Collection:Thèses et mémoires

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