Comparison of models for transverse ply cracks in composite laminates

Ply-level transverse cracking often results in the loss of strength and stiffness and changes in the coefficients of thermal expansion (CTE), and it also provides pathways for moisture or other corrosive agents. In stiffness critical structures, the loss of stiffness and/or change in CTE may result in the loss of structural functionality. These matrix-dominated failure modes can lead to delamination and fiber breakage in highly loaded plies and eventually to failure of the laminate. It is vitally important that predictive methods are developed that will be accepted, following thorough validation, by the composites engineering community. This paper is one attempt to achieve sound validation for four different methods of prediction, one of which is finite-element analysis. The three distinct cross-ply laminate models discussed here have been shown to be consistent with each other, and with FEA predictions. Additionally, model predictions for the effective moduli of transversely cracked laminates have been shown to be in good agreement with experimental measurements. The excellent correlation of the model predictions and the agreement with experimental data provides the basis for these models to be seriously considered for use in the development of new design tools and procedures.