Processing of co-bonded scarf repairs: Void reduction strategies and influence on strength recovery

Partially impregnated prepreg are attractive materials for scarf bonded repairs as they can be consolidated with vacuum assisted pressure only. Several air evacuation strategies were evaluated for cobonded scarf repairs of monolithic composites skins. Various void levels were measured in the bondline by digital radiography, and tensile tests were performed to assess the repairs strength recovery. Most of the entrapped air could be evacuated prior to cure for the method using a textured adhesive film. This repair strategy consistently led to a significant reduction in bondline porosity and exhibited the highest strength recovery. Overall, it was found an average linear reduction in tensile strength recovery of 4.5% per 1% areal void content in the adhesive. Additionally, a change in final failure mode was observed from cohesive failure for porous bondlines, to net-section tensile failure in case of void-free bondlines.