An experimental study on the effects of matrix cracking to the stiffness of glass/epoxy cross plied laminates

Three independent measurement techniques are applied to characterize glass fiber laminates. The effects of distributed fatigue damage to the stiffness related behavior of cross plied laminates are quantified. Tensile and flexural stiffness reduction is obtained from quasi-static testing. Vibration testing shows the degradation of flexural and in-plane shear stiffnesses. The reduction of the phase velocity of symmetric S0 mode is observed from the experimental dispersion curves of Lamb waves. However, the mutual agreement of these results is less satisfactory than was earlier seen for virgin laminates. The phenomena causing the discrepancies are proposed and discussed.