Advanced nonlinear three-dimensional finite element shell formulations for composite structures

In recent years, an increasing interest in the use of advanced composites in a wide variety of engineering applications is taking place. This trend arises from the superior advantages that composite offer in terms of their specific strength and stiffness properties in comparison with traditional metallic materials. More particularly, these composite materials have been extensively used in slender structures in the aeronautical and the aerospace industries. From the numerical point of view, the mechanical responses of such structural components have been accomplished by means of standard finite element shell models, which typically neglect three-dimensional effects along the thickness direction. However, it has been amply observed that these three-dimensional features play a significant role in the onset and propagation of different damage mechanisms in composite structures, namely debonding and delamination processes at critical locations. In this presentation, we address the development and finite element implementation of advanced shell formulations for composite structures. Two main composite typologies are considered in this work: unidirectional laminates, whose heterogeneous material disposition is taken into account by means of the so-called Equivalent single Layer (ESL) approach and Functionally Graded Materials (FGM) that allows a continuous and smooth variation of the material properties over the thickness directions of the shell. Representative numerical simulations evaluating the applicability of such developments through standard benchmark problems and correlation with industrial applications are provided.