The nature of failure of thick-section laminated composites containing pre-existing edge delamination

An analytical and experimental investigation was performed to study the compression failure of thick-section laminated composites containing a pre-existing semicircular edge delamination. A three-dimensional linear finite element model was developed to predict the stress field acting along the delamination front for a laminate of arbitrary thickness and stacking sequence, and a semi-circular edge delamination of arbitrary location and size. Experimentally; thick-section E-glass fabric/vinylester laminated composite specimens containing either a single or multiple simulated semi-circular edge delamination(s) were tested in compression and in four-point bending loading conditions to ascertain the dominant failure mode. In specimens containing only a single simulated edge delamination, experimental results have shown that the failure mode depends on the depth of the initial delamination. The failure mode changed from in-plane (shear-dominated) fracture to sublaminate buckling with the consequence of delamination growth as the depth of the initial delamination decreased. However, in the specimen containing multiple simulated edge delaminations, delamination growth occurred without sublaminate buckling, possibly indicating that multiple delaminations have a larger effect on the stress state than a single delamination does.