The transverse cracking in advanced composite laminates is the predominant damage mechanism in the initiation stage due to low transverse strength. The transverse cracks result in a redistribution of layer stresses which can affect the stiffness reduction of laminated composites and interlaminar stresses which can induce the delamination. In this study, cross-ply laminates with various thickness of transverse cracked layer are analyzed and tested for the evaluation of progressive transverse cracking and the stiffness reduction of laminate due to transverse cracking.
A refined two-dimensional analysis method, taking into account the crack opening deformation, is proposed for the evaluation of stress distributions and the prediction of stiffness reduction in transverse cracked cross-ply laminates. The interlaminar stresses which play an important role in laminate failure are evaluated using the concept of interface layer. A series expansion of the displacements is employed and the thermal residual stresses and Poisson's effects in the laminate are taken into consideration in the formulation. The stress distributions and the stiffness reductions due to transverse cracks are compared with finite element results and experimental data, respectively. The proposed method represents well the characteristics of the stress distributions. The predicted laminate stiffness reductions are in excellent agreement with experimental data for various materials. The proposed analysis can be applied as a basis for the prediction of the induced delamination onset by using appropriate failure criteria.
There are two mechanisms in transverse cracking ; Transverse crack is formed from the through-the-thickness flaw or from the partial crack. The progression of transverse crack are consisted of 3 stages and the saturated transverse crack density remarkably increased as the thickness of transverse cracked layer decreases. The progression of transverse crack under static or cyclic loading is represented well by the proposed parameter except the case of small transverse crack density. Specially, the relation between the normalized transfer stress and the transverse crack density is linear except the case of very small transverse crack density.
