Analyse et modélisation des mécanismes d'endommagement et de déformation en fatigue multiaxiale de matériaux composites : polyamide renforcé par des fibres courtes

摘要

The current work focuses on a new micromechanical high cycle fatigue visco-damage model for short glass fiber reinforced thermoplastic composites, namely: PA66/GF30. This material, extensively used for automotive applications, has a specific microstructure which is induced by the injection process. The multi-scale developed approach is a modified Mori-Tanaka method that includes coated reinforcements and the evolution of micro-scale damage processes. Their description is based on the experimental investigations of damage mechanisms previously performed by the team. Damage chronologies have been proposed involving three different local degradation processes: fiber-matrix interface debonding/coating degradation, matrix microcracking and fiber breakage. Their occurrence strongly depends on the microstructure. The developed model integrates these damage kinetics and accounts for the complex matrix viscoelasticity and the reinforcement orientation distributions induced by the process. Each damage mechanism is introduced through an evolution law involving local stress fields computed at the microscale. The developed constitutive law at the representative volume element scale is implemented into a C++ scientific library, SMART+, and is designed to work with Finite Element Methods. The model identification is performed via reverse engineering, taking advantage of the multiscale experimental results: in-situ SEM tests as well as quantitative and qualitative μCT investigations.