Coupled effects of fiber orientation and delamination on mechanical performance of composite laminates exposed to asymmetrical environmental conditions

This study presents a coupled analytical approach to predict stiffness degradation in composite laminates affected by transverse cracking and delamination under asymmetrical environmental conditions. A modified shearlag model incorporating both parabolic and progressive shear stress distributions is used to quantify relative and total stiffness loss. The theoretical framework builds on Classical Laminate Theory (CLT), extended to include stress perturbations and interface damage. This choice ensures compatibility with laminate-level mechanical behavior while enhancing local damage representation. Model predictions are validated against experimental data for T800H/3631 laminates, showing strong agreement across varying crack densities and temperatures. The results confirm that fiber orientation, delamination ratio, and environmental gradients significantly influence stiffness degradation. Compared to previous models based solely on CLT or simplified degradation factors, the present approach captures the interactive effects of damage and asymmetric moisture diffusion more realistically. These insights inform the design of more durable aerospace composite structures operating in harsh hygrothermal environments.