Compressive behavior of CFRP laminates repaired with adhesively bonded external patches

摘要

Composite patches can be used to reinforce and repair both cracked composite and metallic aircraft structures. The repair of a composite structure with a composite patch may use mechanical fastening, which often introduces undesirable stress concentrations or adhesive bonding, external or flush patches. To ensure a reliable and durable bond, various parameters such as the quality of surface preparation and the design of the composite patch (size, shape, stiffness) are very important. This paper describes the teasing of bonded external patch repaired CFRP laminates loaded in compression. It is found that the critical failure mechanism is fibre microbuckling in the 0 deg pies accompanied by matrix cracking and delamination, triggered by failures at the adhesive/adhered interface. A three-dimensioanl finite element analysis is performed to estimate the stress field in the repaired region. The calculated stresses are then used with the maximum stress and average stress failure criteria to predict damage ignition, mode and location. Carefully designed external patch repairs can recover more than 80 /100 of the undamaged compressive strength.