Finite element analysis of non-linear composite materials by use of overlay systems

Abstract

An ‘overlay’ model is employed in the description of the non-linear behaviour of materials. The solid is assumed, for mathematical convenience only, to be composed of several layers or overlays, each of which undergoes the same deformation. The total stress field is obtained by summing the different contributions of each overlay. By assigning simple but different deformation properties in each overlay a composite behaviour can be obtained which exhibits many of the characteristics encountered in a practical material. The model is employed in the solution of several numerical examples and compared with alternative approaches where possible. It is then shown how the model can be extended to strain-softening situations by the introduction of a cracking overlay. Finally the overlay approach is compared with experimental results for the cyclic loading of a thick ring.