A modified shear lag analysis, taking into account the concept of interlaminar shear layer, is employed to predict the onset of a transverse carck and multiple transverse cracking. Based on this analysis the effect of transverse cracks on the stiffness reduction and change in the coefficient of thermal expansion in cross-ply laminated composites is also evaluated. This analysis involves a construction of admissible displacement fields which satisfy equilibrium and boundary conditions on laminate and transverse crack surfaces. The energy concept is utilized to assess the layer thickness effect and constraining effect on transverse cracking behavior.
Some results of this study show that the onset of a transverse crack and change of thermomechanical properties of laminated composites due to multiple transverse cracking are influenced profoundly by the thickness of transverse cracking layer. However, the constraining effect is negligible for the laminate with a constant thickness of transverse cracking layer. The effect of thermal residual stresses and Poisson's effect are also considered in this failure analysis. The thermal residual stresses influence significantly the transverse cracking in graphite/epoxy composites. However, Poisson's effect is negligible in transverse cracking behavior.
Predictions of the onset of a transverse crack and laminate stiffness reduction due to transverse cracks are compared with experimental results. The present failure analysis is simple, yet its results show reasonable agreement with experimental results.
Finally, experiment of damage developments due to thermal loading only is performed for carbon/epoxy cross-ply laminated composites. The major failure mode is transverse cracking and this results in local 0/90 interface delamination and free edge delamination in thick laminated composites.
