Damage to composite materials in aerospace structures

The purpose of research in this area is to gain better understanding of damage phenomena involving composite materials and structures. The long-term goal is to supply local or structural sizing tools for the design of aeronautical or aerospace structures. These studies are carried out in the more general framework of the “Composite materials and structures” research group of the Clement Ader Institute.

Processes and Materials: (1 PhD thesis defended, 3 in progress)

In the area of processes, current activities concern the control of damage due to the drilling of laminated composites, as well as the control of porosity content in thick composites manufactured by autoclave molding. In the area of materials, the team’s on-going focus is on crack propagation in laminated composites (primarily delamination cracks and more recently through-the-thickness cracks in thin laminates) and on characterization of damage laws for materials. Environmental effects such as temperature and wet ageing are being investigated to determine the durability of materials and structures.

Structural details and sizing of structures: (2 PhDs defended, 2 in progress and 2 post-doctoral studies).

This theme concerns sizing of structural details (i.e. ply drop-off zones, joint zones ; bolted, bonded and stitched zones). Characterization of damage phenomena through fatigue or static tests enables us to develop numerical models aimed at understanding and predicting the mechanical behavior of these very critical structural zones. Part of this research is also dedicated to composite structure optimization through the use of heuristic methods.

Impact behavior and damage tolerance: (3 PhDs defended, 1 in progress)

The purpose of this research is to model damage generated by impacts on composite materials and structures and to evaluate residual strengths. Models of impact behavior for low to intermediate speeds are based on either a micro-mechanics approach for short-fiber composites or a mesoscopic approach for laminated composites. The identification of energy absorption mechanisms during the crushing of composites plates led to a numerical model consistent with observations. Characterization of damage processes and residual strengths of impacted composite tubes led to an optimized tube design.