Effect of Delaminations on Opening of Transverse Matrix Cracks

Abstract

The use of advanced composite materials for cryogenic fuel tanks reduces the mass of the structure but the leakage of fuel can become a problem. Since the amount of leakage increases with the crack opening, it is essential that we understand the factors that affect the crack opening. In previous studies by the authors, the opening and the degradation behavior of lamina properties due to transverse matrix cracking had been studied extensively. It has been found that the opening of transverse matrix cracks can be directly related to changes in effective moduli. This paper extends the earlier work to include the additional opening due to the delaminations induced at the tips of the transverse matrix crack. Finite element models have been built for seven delamination configurations. The opening and the stiffness degradation of laminates have been obtained as functions of the crack density and the delamination length. The effect of some factors such as adjacent ply orientation, ply thickness, and temperature on the opening have been studied. It has been found that the crack opening due to transverse crack-induced delaminations is still directly related to reduction in effective moduli. The opening increases almost linearly with the delamination length. A simple formula has been developed to predict the opening. The prediction of the opening obtained using this formula agreed very well with the finite element predictions.