Thermo-Elastic Constants of Symmetric Laminates with Cracks and Local Delaminations in Off-Axis Ply

Analytical expressions for in-plane thermo-elastic constants of symmetric laminates containing intralaminar cracks in off-axis plies and local delaminations at ply interfaces are presented. Exact relationships called GLOB-LOCdel model that links laminate stiffness to characteristics of cracks with delaminations were presented in Varna et al., 2025. The effect of a crack is described by normalized average opening (COD) and sliding displacements (CSD) of its faces, which are larger in the presence of local delaminations. The CSD dependence on delamination length was analyzed in the paper cited above, where simple fitting functions were presented. In the present paper, FEM is used to analyze the COD dependence on delamination length and crack density for different material systems in balanced laminates with cracked 90-ply, revealing the most significant parameters. Then, the obtained approximate COD and CSD expressions are used in the GLOB-LOCdel model to predict thermo-elastic constants of multidirectional laminates. The results are in good agreement with direct FEM calculations in the literature. When calculating COD and CSD, homogenization over adjacent plies to estimate the constraint on the damaged ply is suggested and validated with FEM data from literature.