Approche XFEM-CZM couplée à USDFLD pour la prédiction de l’endommagement dans les structures renforcées par composite gradués

Abstract

A bi-graded composite patch is analyzed in this study. The aim of this bi-gradation concept is to enhance the reinforcement of a notched aluminum plate by tailoring the stiffness distribution through gradation parameters. The approach involves grading three different types of fibers, all with the same volume fraction and within the same epoxy matrix. The patch debonding, caused by adhesive failure, as well as the crack initiation and propagation in the plate, are simulated respectively using the Cohesive Zone Model (CZM) and the Extended Finite Element Method (XFEM), both implemented in the ABAQUSVR finite element code. The CZM model accounts for both shear and normal separation modes in the adhesive layer. Using FGM-based functions, the bi-gradation of the composite patch is defined along the thickness at the fiber scale, with each layer formulated through a power-law volume fraction

between the fibers and the matrix. Three concepts are proposed and analyzed. In Concept C-1,

the central region of the patch consists of CFRP-1 fibers, which are graded toward Glass- Epoxy and CFRP-2 fibers at the outer surfaces. Concept C-2 features CFRP-2 fibers in the center, graded toward CFRP-1 and Glass-Epoxy at the extremities, with Glass-Epoxy located at the adhesive interface. In Concept C-3, the core is made of Glass-Epoxy fibers, graded toward CFRP-1 and CFRP-2 at the outer surfaces, with CFRP-2 placed at the adhesive interface. These various gradation configurations aim to improve the patch’s ability to absorb loads transferred through the adhesive joint and to investigate how the gradation influences damage mechanisms, particularly debonding. The analysis, conducted under various loading conditions, demonstrates a competitive interaction between adhesive debonding and crack initiation in the notched plate, confirming the effectiveness of the proposed bi-graded composite patch designs.