An enriched shell element formulation for modeling of inter- and intralaminar crack propagation in laminates

In traditional finite element modeling of progressive failure in laminated fiber reinforced polymers, inter- and intralaminar cracks are normally treated in different ways. Interlaminar cracks are normally described explicitly by building up the laminate using stacked elements (solids or shells) connected by cohesive interface elements. Intralaminar cracks, one the other hand, are more often accounted for by using a continuum damage approach, (e.g. a smeared crack approach). In this paper, we propose a modeling concept which instead can accurately represent both intralaminar and interlaminar cracks with an extended kinematical representation, whereby cracks can be explicitly accounted for without excessive use of degrees of freedom. With this concept, we aim to take one step closer to more efficient FE analyses of progressive laminate failure, since only one shell element through the thickness is required, and where arbitrary inter- and intralaminar crack propagation are accounted for only in areas where it is needed. We show that the current shell formulation proposed can be utilized to describe the kinematics of a laminate containing multiple inter- and intralaminar cracks. Thus, we see significant potential for this modeling concept in analyses in which computational efficiency is of major importance.