Experimental observation of tensile behavior of patch repaired composites

This work concerns notched composite plates repaired with external circular patches. Their load carrying capability and failure process under tensile loading were investigated experimentally. In the case of a strong adhesive joint, the stiffness of the patches has to be optimized to release high stress concentration and obtain the best repair performance. It was found that the damage progression of the repairs depends not only on the patch stiffness but also on the stacking sequence. With visual inspection and acoustic emission, three modes of damage and failure process for patch repaired specimens were identified. Theses damage models are essential for the development of a numerical design tool for the optimization of external patch repairs.