14 - Competing cohesive layer models for prediction of delamination growth

Abstract

Publisher Summary The cohesive layer methodology has proven to be a powerful tool for the study of delamination growth in laminated composites. It is based on the postulation of a layer of cohesive material between the surfaces liable to delaminate and an energy release criterion for its decohesion. A majority of the investigators have used cohesive layers of zero thickness, although there is an implicit recognition of a cohesive zone upstream of the crack tip which must necessarily have some thickness, however small. The cohesive law takes the form of a relationship between the relative displacements between the delaminating layers and the interlaminar stresses. This chapter summarizes the results of an investigation on the relative merits of these types of models, using test cases of delamination in a double cantilever beam and a pre-cracked laminate under low velocity impact. It presents the comparison between the two distinctly different cohesive layer models, one having finite thickness and governed by a stress-strain relationship (UMAT model) and the other having zero initial thickness and governed by stress-relative displacement relationship (UEL model).