AUSTRALIAN DEVELOPMENTS IN THE ANALYSIS OF COMPOSITE STRUCTURES WITH MATERIAL AND GEOMETRIC NONLINEARITIES

To achieve the potential cost savings resulting from the use of compos ites in 'primary' structural components, i.e. wing fuselage skins, it is important that composite structures be used outside the linear regi me. However, before this can be achieved a computational methodology c apable of analysing the detailed local stress states in conditions whe re there are both geometrically and material nonlinearities is necessa ry. This paper presents one such approach in which the 'global structu re' is modelled by employing plate-type finite elements and the local details are modelled with solid 3D finite elements. A coupling techniq ues based on multi-point constraints is then employed to connect the 2 D and local 3D models. The approach presented allows for significant c hanges in finite element mesh density and enables the connection of ve ry detailed local models with less detailed global models. To illustra te 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 metho dology is then used to analyse the post-buckling response of both a sh ear 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 m ethodology provides a viable computational tool for determining the lo cal 3D stress states for structures undergoing complex nonlinear defor mation states. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.