Performance of a Cohesive Layer Model in the Prediction of Interfacial Crack Growth in Sandwich Beams

A cohesive layer model is employed for the prediction of initiation and tracking of interfacial crack growth in sandwich composite beams. A feature of the model is that it can be used for geometrically non-linear problems as it is formulated in terms of appropriate stresses and strains. Two types of sandwich specimens are selected for study: a sandwich beam specimen carrying a delamination at the top facing core interface with its bottom edge restrained, and a delaminated column specimen carrying axial compression. The beam was used to investigate the influence of the properties of cohesive layer material on its ability to predict the onset and progress of crack growth. It is found that the cohesive layer model is fairly robust and is not sensitive to change in parameters other than the critical strain energy release rate in the opening mode. Thus there is wide a latitude in the selection of parameters of the cohesive layer. The compression specimen exhibited a variety of phenomena, viz. delamination buckling, stable delamination growth, intervention of overall buckling, and finally unstable crack growth as the specimen sheds the load. The finite element analysis coupled with the cohesive layer model was able to follow all these stages of sandwich beam behavior. Good agreement between the model predictions and experimental results is found to exist in all the cases studied.