Mode separation of energy release rate for delamination in composite laminates using sublaminates,

Individual energy release rates for delamination in composite laminates do not exist according to two- or three-dimensional elastic theory due to the oscillatory characteristics of the stress and displacement fields near the delamination tip (Sun, C.T., Jih, C.J., 1987. Engng. Fracture Mech. 28. 13-20; Raju, I.S., Creus Jr., J.H., Aminpour, M.A., 1988. Engng. Fracture Mech. 30, 383-396.) In this paper, sublaminates governed by transverse shear deformable laminate theory are adopted to model such delamination. Oscillatory singular stresses around the delamination tip are avoided as a result. Instead, stress resultant jumps are found in the sublaminates across the delamination tip. It transpires that mode I, II and III energy release rates can then be obtained using the virtual crack closure technique. The results produced by this approach for a homogeneous double cantilever beam and an edge-delamination in a nonhomogeneous laminate show good agreement with those available in the literature. The approach produces both total and individual components of energy release rate for delamination, which converge as the sublaminate division is refined and the sizes of the delamination tip elements decrease. (C) 2001 Elsevier Science Ltd. All rights reserved.