Probabilistic approach of thermoplastics composites mechanical behaviour assemblied by laser welding ; Approche probabiliste du comportement mécanique des composites thermoplastiques assemblés par soudage laser

Thermoplastic composite materials are more and more used in many fields of application as a result of their recyclability and their joining capabilities by polymer fusion, witch is called welding. Among these assembly types, the laser welding offers better alternatives. Because, beyond the high level mechanical strength and the good aesthetic appearance it provides, this assembly technique will not create damage within the composite material, like certain methods such riveting, drilling or bolting.The purpose of this study is to propose a probabilistic failure model of laser beam assembly of a continuous fibres thermoplastic composite.A detailed description of the material is first performed by a multi-scale approach, which was aiming to predict the macroscopic behaviour of the based composite knowing the local fluctuations of its microstructure.The mechanical characterisation of the assembly is then conducted through multi-axial tests using a special device (Arcan-Mines) which takes into account the confinement of the laser weld seam. This enables proposing a generalized Drucker-Prager élasto-plastic model.Acoustic emission tests allowed making the assumption of weak link model within the weld seam. The failure is then evaluated through the Weibull statistical model.Probabilistic failure criterion based on the first and the second invariants of stress tensor is finally proposed ; Les matériaux composites à matrice thermoplastique occupent de plus en plus un large domaine d'application grâce à leur aptitude à être recyclés et à être assemblés par fusion du polymère, encore appelée soudage. Parmi ces modes d'assemblage, le soudage laser propose de meilleures alternatives. Car, outre le fait qu'elle assure une meilleure tenue mécanique et un meilleur aspect esthétique, cette technique d'assemblage ne crée pas d'endommagement au sein du composite, à l'instar de certaines méthodes comme le rivetage, le vissage ou le boulonnage.L'objectif de ce travail est de proposer un modèle de rupture probabiliste de l'assemblage ...