Numerical Evaluation of Upper and Lower Bounds to the Collapse Limit Load for Composite Laminates

This paper proposes a procedure based on the limit analysis theory to define the load bearing capacity of laminates made of composite material. To apply the limit analysis theory on structures made of materials, which can, in general, exibit limited ductility and often characterised by a failure criteria rather than by a yield one, the actual material is effectively replaced with a perfectly plastic one, making the failure criteria playing the role of yield condition [

1

]. Grounding on these assumptions, the kinematic approach for limit analysis of anisotropic composite laminates under plane stress conditions is applied for the direct evaluation of an upper bound on the collapse load multiplier, moreover the static approach is utilized to define a lower bound to the same limit load. In the present formulation the limit analysis is performed via a numerical procedure known as Elastic Simulation Method [

2

]. The numerical procedure, successfully applied to Von Mises [

2

,

3

] and Drucker- Prager materials [

4

], is here suitably modified to ac- count for the specific form of the yield function assumed to deal with anisotropic materials. The effectiveness of the proposed procedure is verified by a few simple numerical examples.