Analysis of single lap adhesive composite joints with delaminated adherends

Polymer composites have high potential for applications in repair of aerospace structures. Adhesively bonded composite patches minimize balance and clearance problems on control surfaces and can be readily formed to complex aircraft contours. Delamination in composites can be detrimental to joint performance and durability and should be accounted for in joint design. In this work, a simple engineering model is developed for cracked adhesive joints with arbitrary orthotropic laminated adherends. Joints with unidirectional and cross-ply adherends are analyzed and compared as an example. Variations of the strain energy release rates with the crack location and size are calculated. It is shown that joints with the cross-ply adherends have higher energy release rates than the joints with the unidirectional adherends. Experimental observations of the delamination growth are also performed and found to corroborate the theoretical predictions.