Effect of patch hybridization on the compression behavior of patch repaired glass/epoxy composite laminates using acoustic emission monitoring

This article investigates the compressive response of damaged glass/epoxy composite laminates repaired using hybrid external patches. Hybrid external patches based on glass and Kevlar woven fabrics bonded on both faces of the damaged parent laminate were considered. Five different kinds of plain weave woven fabrics with a different ratio between glass and Kevlar fibers (100/0, 75/25, 50/50, 25/75, and 0/100) were used as the external patches. The intention of using these hybrid patches is to build up a patch of optimum stiffness that facilitate to restrict the critical adhesive or cohesive failure on the joints unlike high stiff glass fibers or extensive fiber micro-buckling of the external patches unlike low stiff Kevlar fibers under compression loading and consequently to produce repaired laminates with a strain to failure and residual strength nearly close or similar as that of virgin or normal components. The virgin and damaged specimens were taken as the reference specimens for comparison of residual mechanical properties and damage mechanisms. Damage evolution and the failure progression of the repaired glass/epoxy specimens were monitored using real-time Acoustic Emission (AE) monitoring technique. Specimens repaired with the equal volume fraction of glass and Kevlar fibers in the external patches presented the most favorable residual compressive response by effectively releasing the stress concentration in the damaged area. POLYM. COMPOS., 39:1922-1935, 2018. (c) 2016 Society of Plastics Engineers