Stiffness loss due to delaminations has not been as thoroughly investigated as their initiation and growth. O'Brien (1985)
was apparently the first who examined the influence of matrix crack tip delamination on the laminate stiffness and strength. The linear degradation of the laminate modulus with delamination area, observed for graphite/epoxy laminates (O'Brien, 1985
), was predicted also for glass/epoxy laminates using a simple rule of mixture analysis (Caslini, Zanotti, & O'Brien, 1987
). A simple 1-D shear lag analysis using the concept of interlaminar shear layer (Fukunaga, Chou, Peters, & Schulte, 1984
) was extended by Ogihara and Takeda (1995)
to the laminates ...