Prediction of Poisson's ratio degradation in hygrothermal aged and cracked [θm/90n]s composite laminates

The Poisson ratio reduction of symmetric hygrothermal aged [<i>&#952;_m</i>/90</i>_n</i>]<i>_s</i> composite laminates containing a transverse cracking in mid-layer is predicted by using a modified shear-lag model. Good agreement is obtained by comparing the prediction models and experimental data published by Joffe <i>et al</i>. (2001). The material properties of the composite are affected by the variation of temperature and transient moisture concentration distribution in desorption case, and are based on a micro-mechanical model of laminates. The transient and non-uniform moisture concentration distribution give rise to the transient Poisson ratio reduction. The obtained results represent well the dependence of the Poisson ratio degradation on the cracks density, fibre orientation angle of the outer layers and transient environmental conditions. Through the presented study, we hope to contribute to the understanding of the hygrothermal behaviour of cracked composite laminate.