The influence of layer thickness on the stress intensity factor of a crack lying in an elastic (viscoelastic) layer embedded in a different elastic (viscoelastic) medium (mode III analysis)

We consider here a problem in which an elastic (or viscoelastic) composite is composed of two dissimilar materials. One of these (medium 2) is contained in a layer sandwiched between semi-infinite half spaces of medium 1. In order to study the possibility of fracture within the layer (medium 2) we consider the response to remote applied loads of a finite length crack in medium 2. As a first step, mode 3 deformation is considered and we investigate how the stress intensity factor (SIF) varies with the thickness (2h) of the inside layer and the different properties of the two elastic (viscoelastic) media. Formulae for the SIF as a function of the thickness of the inside layer and the elastic constants are derived. Analytical results for small and large h are obtained as a function of the material properties and verified by numerical analysis. (C) 1996 Elsevier Science Ltd