Adhesively Bonded Patch Repair of Composite Laminates

Abstract

Damaged composite laminates repaired using adhesively bonded patches have been studied. A special adhesive element is developed to examine the stress distribution in the bonded region. Utilizing the adhesive element, one is able to incorporate the regular elements in the laminate and patch. It has the advantage of reducing the adhesive bonding problem to a two-dimensional in-plane problem, and avoiding the need for refined meshes in the adhesive. The special adhesive element is derived based on the assumption of constant shear stress through the thickness of the adhesive. The damaged area of the composite laminate is simulated as a hole. The repair efficiency is evaluated by comparing the stress concentration factor in the damaged hole before and after repair. The effects of the thickness, size and material properties of both patch and adhesive on the stress distribution are presented through a parametric study. Numerical results indicate that a stiffer and thicker patch is able to carry higher loads, and, consequently, reduce the load across the damaged area yielding less stress concentration in the damaged hole. For a high shear modulus and thin thickness of the adhesive layer, less loads are transferred to the patch resulting in a high stress concentration in the damaged hole.