Fractographic analysis of scarf repaired carbon/epoxy laminates submitted to tensile strength

Abstract

This study presents the main fractographic aspects and failure modes involved on the fracture of scarf repaired laminates submitted to tensile test, using scanning electron microscopy (SEM) technique. A detailed analysis of the fractographic aspects was carried out correlating them to the failure modes, the local crack propagation, and the mechanical performance of the scarf joint. SEM analyses showed cohesive failure of the adhesive film associated with a strong mechanical anchoring between the adhesive and the laminate, as well as a good patch ply consolidation on the adhesive interface, showing the joining mechanism efficiency. Fiber pull-out mechanism associated with the translaminar fracture, combined with intralaminar fracture were the predominant failure modes observed in the parent laminate and in the patch repaired region, evidencing the complexity on crack growing in woven fabric composite materials. Fractographic analyses provide evidences that justify the good mechanical behavior of the repaired laminates that is attributed to high interfacial shear strength of the scarf joint and overall good quality of the repair manufacturing process.