EXPERIMENTAL AND NUMERICAL STUDY OF DELAMINATION CAUSED BY LOCAL BUCKLING OF THERMOPLASTIC AND THERMOSET COMPOSITES

Experimental and numerical studies of delamination caused by local buc kling have been carried out on thermoset and thermoplastic carbon-fibr e composites. The propagation of delamination appears only after the a ppearance of macrocracks in the buckling plies. In the first part of t his work, acoustic emission (Felicity ratio) is used to qualify damage accumulation before propagation of delamination. The second part deal s with the determination of the initiation of delamination by two nume rical methods, the first of which allows us to calculate the global re stitution energy rate (virtual crack-extension method) and the second its partition into modes I, II and III (modified crack-closure integra l). A mechanical failure criterion is then applied to a stacking seque nce and two materials. This criterion is compared with an interfacial stresses criterion determined by the finite-element method. (C) 1998 P ublished by Elsevier Science Ltd. All rights reserved.