The role of intralaminar damages on the delamination evolution in laminated structures

Delamination is a major failure mode affecting laminated composite structures. This failure mechanism, if not properly monitored, can lead to uncontrolled cracks growth and premature structural collapse. Thus, predicting delamination propagation is mandatory to determine the structural integrity. At present, delamination has been extensively investigated in laminated composite structures but only a few studies have been performed on how the intralaminar damages influence the interfacial release energy and, consequently, the delamination evolution. In this paper, the well-established SMart-Time XB delamination simulation tool, has been coupled with a Hashin Criteria based User-Material Subroutine (UserMat) to study the role of the intra-laminar damages in delamination propagation. A benchmark case based on the mixed-mode I/II Single Leg Bending (SLB) specimen for delamination evolution assessment under quasi-static loading has been investigated. Subsequently, a composite material plate, characterized by an artificial circular delamination, under compression has been considered. This study proved to be valuable by underlining the influence of fibre and matrix breakage on the interlaminar damages evolution. Interestingly, taking into account the effect of intralaminar flaws changes the local energy release rates values on the delamination front and, consequently, the crack shape and evolution.