Australian developments in the analysis of composite structures with material and geometric nonlinearities

Abstract

To achieve the potential cost savings resulting from the use of composites in ‘primary’ structural components, i.e. wing fuselage skins, it is important that composite structures be used outside the linear regime. However, before this can be achieved a computational methodology capable of analysing the detailed local stress states in conditions where there are both geometrically and material nonlinearities is necessary. This paper presents one such approach in which the ‘global structure’ is modelled by employing plate-type finite elements and the local details are modelled with solid 3D finite elements. A coupling techniques based on multi-point constraints is then employed to connect the 2D and local 3D models. The approach presented allows for significant changes in finite element mesh density and enables the connection of very detailed local models with less detailed global models. To illustrate this analysis methodology a range of nonlinear structural problems involving both geometrical and material nonlinearities are considered. The methodology is first validated by considering a plate bending and a post-buckling problem for which the solutions were known. The methodology is then used to analyse the post-buckling response of both a shear and an axially loaded composite stringer/skin panel. In both cases the computed results correlated very well with experimental results. The results from these test cases suggest that the proposed analysis methodology provides a viable computational tool for determining the local 3D stress states for structures undergoing complex nonlinear deformation states.