Effect of S2-Glass/Epoxy Thickness on Buckling of GLAREs Under Pre-Cyclic Hygrothermal Loading

Glass-reinforced aluminum laminates (GLAREs) are widely used in aerospace structures due to their superior characteristics. However, their buckling response, especially under severe environmental conditions, is not yet fully understood. This study investigates the buckling behavior and damage evolution of GLAREs under varying polymer-composite ply thickness and hygrothermal preconditioning. Experimental and finite element analyses are conducted on two different configurations, with and without hygrothermal cycling, to assess load–displacement responses, critical buckling loads, and damage mechanisms. A strong correlation is observed between numerical predictions and experimental measurements, with deviations in critical buckling loads within ±6%. Doubling the S2-glass/epoxy ply thickness improves structural performance, raising the specific critical buckling load by up to 49%, highlighting the synergistic effects of ply thickness and laminate density. Hygrothermal preconditioning degrades buckling resistance in thinner laminates but, when coupled with increased non-post-cured S2-glass/epoxy ply thickness, enhances the buckling load-bearing capacity. Damage observations reveal delamination at metal–composite interfaces as the dominant failure mode, typically initiating at specimen edges. Longitudinal fiber rupture and buckling occur mainly in highly stressed glass-epoxy layers, whereas aluminum layers exhibit ductile damage at large deflections. Finite element damage and cohesive-interface analyses confirm these trends and demonstrate the mitigating effect of hygrothermal preconditioning on delamination.