Abstract
Translaminar reinforcements in the form of stitching is an effective solution to suppress delaminations in laminated composites. An analytical study is conducted on the unidirectional graphite/epoxy laminates to examine the effects of stitching and the various geometric parameters associated with stitching on the apparent interlaminar fracture toughness. End-notched flexure tests were conducted to study the Mode II fracture toughness of the laminates. Shear deformable beam theory was applied to model the sublaminates where the stitches were smeared as equivalent foundation springs. Only elastic behavior of this equivalent spring system was assumed. Load-deflection patterns were obtained and the fracture toughness, GIIc, as a function of the apparent crack propagation was computed. The fracture toughness, GIIc was determined by evaluating the area under the load-deflection curve at every instant of crack propagation. The effects of mechanical properties of the smeared stitches on the crack extension was studied. The analytical model was verified by comparing with the experimental results. The effects of stitch stiffness, density, initial starter crack length and various geometric parameters were examined.
