Amorçage et propagation initiale de délaminages dans les reprises de plis de matériaux composites stratifiés carbone-époxy

For composite laminates thickness optimisation, this article is focused on the thickness variation problems in laminates manufactured with plies drop-offs. The ends of plies within the laminates infer three-dimensional stresses and singularities. Some tests were achieved on specific test pieces for 9 to 5 plies transitions. With optical investigations, these tests showed non-stationary delamination for a particular strength. Some radiographies were done to watch the extent of delaminated areas, and a finite element model enabled us to define an initiation criterion in the ends of the plies with the energy restitution rates and to determine the characteristics of delaminations growing, as analogy to singularities of geometrical accidents