Etude du comportement en rupture des composites

Abstract

This thesis falls within the field of materials mechanics and focuses on the fracture behaviour of polymer matrix composites reinforced with natural fibers. Two research directions are explored. The first involves studying the effect of natural ageing on the flexural mechanical properties of an Alfa/polyester composite. This composite is developed using two types of Alfa fibers (coarse and fine) at three different weight fractions (10%, 20%, and 30%). The second axis investigates the effect of artificial ageing through ultraviolet (UV) radiation on a flax/epoxy-based composite and its hybrid versions. The adopted methodology is based on three-point bending tests and optical microscopy observations for the analysis of fracture mechanisms. Additionally, a numerical simulation using the finite element method in Abaqus is implemented to validate the experimental results and deepen the analysis of mechanical behaviour. The results highlight the significant impact of ageing, whether natural or UV- induced, on the mechanical performance of biocomposites. These degradations directly affect flexural strength and fracture mechanisms, underlining the need to consider such phenomena for the sustainable development of natural fiber-based composite materials.