THE NATURE OF FAILURE OF THICK-SECTION LAMINATED COMPOSITES CONTAINING PREEXISTING EDGE DELAMINATION

An analytical and experimental investigation was performed to study th e compression failure of thick-section laminated composites containing a pre-existing semicircular edge delamination. A three-dimensional li near finite element model was developed to predict the stress field ac ting along the delamination front for a laminate of arbitrary thicknes s and stacking sequence, and a semi-circular edge delamination of arbi trary 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 simul ated edge delamination, experimental results have shown that the failu re mode depends on the depth of the initial delamination. The failure mode changed from in-plane (shear-dominated) fracture to sublaminate b uckling with the consequence of delamination growth as the depth of th e initial delamination decreased. However, in the specimen containing multiple simulated edge delaminations, delamination growth occurred wi thout sublaminate buckling, possibly indicating that multiple delamina tions have a larger effect on the stress state than a single delaminat ion does.