Modelling Mode I Crack Initiation in Composites under Fatigue Loading Using Interface Elements

Modelling quasi-static crack growth with interface elements is a widely accepted technique [1-2]. Interface elements are inserted into the finite element mesh along possible crack paths. The interface elements are characterised by a traction-displacement curve. When a specific maximum stress is reached, the interface element undergoes a softening process until the critical fracture energy has been dissipated. Recently, the applications of interface elements have been extended to high-cycle fatigue (HCF) loading using Paris-law based fracture criteria [3-4]. Although the results obtained from these models are in reasonable agreement with experimental observations, a significant macroscopic crack must be present before the technique can be applied. Applications of this technique can be extended further by the development of a crack initiation law, hence allowing a total fatigue life model to be formed. This paper presents new numerical models for the initiation phase that have been implemented into the explicit finite element (FE) code LS-DYNA.