Failure behavior of scarf-bonded woven fabric CFRP laminates

Abstract

We report on the mechanical analysis of scarf-bonded woven fabric CFRP laminates. The study focuses on the effect of the scarf angle on the failure behavior of the repaired composite structures. Composite panel manufacturing was based on twill carbon/epoxy prepregs and followed standardized lay-up and curing procedures. We tensile tested scarf-bonded specimens with scarf angles of 1.9°, 2.8°, and 5.7°. The results show that the tensile strength decreases with increasing scarf angle. There are mainly three types of failure, depending on the scarf angle. The failure type is predominantly cohesive for 5.7°, fiber failure for 1.9°, and a mixture of these for 2.8°. Finite element analysis through cohesive zone modeling accurately predicts the experimentally observed response and provides further insight into the failure behavior. Stress concentration distribution over the bonding area plays an important role in the failure type of the repaired specimens. An additional investigation on the effects of adhesive defects showed that a defect fraction of 10% over the bond area can reduce the strength by almost 20%.