“…Governing equations, formulated in terms of finite differences, were solved numerically using an eigen-value technique. Zhang, Soutis, and Fan (1994a) and Zhang et al (1994b) used a 2-D improved shear lag analysis to predict the strain energy release rate for edge and local delaminations in balanced symmetric [AEq m /90 n ] s laminates. For edge delamination, they were able to capture a zigzag delamination pattern, that is, edge delamination switching from one (q/90) interface to another through a matrix crack, and improve O'Brien's formula for strain energy release rate for edge delamination (O'Brien, 1982) incorporating the effect of matrix cracking.…”