Cohesive Mixed-Mode Damage Model Applied to the Simulation of the Mechanical Behaviour of a Repaired Sandwich Beam

Delamination caused by low velocity impact is one of the most frequent cases of damage in sandwich composite materials. When delamination is present the ability of the material to withstand structural loading is limited [1, 2]. In many cases, a local repair of a damaged sandwich structure is preferable over replacement for economical, mechanical and environmental reasons. Bonded repairs are widely used in composite structures, taking over mechanical fastening methods because of the low weight penalty of the process and more uniform stress distributions. The behavior of a repaired sandwich beam loaded under four point bending is simulated using the ABAQUS software. Both overlap and scarf repair, suitable for sandwich structures, were simulated considering two dimensional nonlinear material and geometrical analysis. Special developed interface finite elements including a trapezoidal cohesive mixed-mode damage model appropriate for ductile adhesives (figure 1) were used in order to simulate the adhesive layer. The proposed model is intended to replace the continuum finite elements traditionally used to simulate the adhesive layer, thus reducing the computational effort necessary to obtain results.