3-D Thermoelastic Moduli and Saturation Crack Density for Cross-Ply Laminates with Transverse Cracks

For stiffness critical structures, such as those found in space applications, the structural design and functionality may depend on several stiffness components. In this work we study the effect of transverse cracking on the effective Young's moduli, the effective Poisson ratios and the effective coefficient of thermal expansion for glass/epoxy and graphite/epoxy cross-ply laminates. In particular, included in the study are the effect of prescribed boundary conditions on the representative volume element used to describe the problem, the effect of variable crack spacing, and the interaction of transverse crack stress fields. The analysis is accomplished by the use of a model based on Reissner's variational principle that has been shown to accurately model stress fields and energy release rates in flat laminates. The present model predictions are compared to shear lag and finite element predictions from the literature and found to be in good agreement with published experimental data. A criterion to estimate the limiting density for pure transverse cracking damage is presented. Additionally, it is shown that for large crack densities, the model accurately recovers the limiting theory ply-discount effective property values.