Influence of ply thickness on transverse cracking onset, damage progression in thin ply composites and impact on mechanical performance

Abstract

Composite structures employing thin ply materials have gained significant attention in aerospace and high-performance applications. These materials offer the potential for improved mechanical performance and enhanced resistance to damage compared to composite laminates with thicker plies due to the added transverse strength that can potentially reduce microcracking. However, in quasi-isotropic layup structures, stress concentrations may develop due to the irregular arrangement of the individual layers stacked up in different orientations, leading to various forms of damage initiation and progression. The type and direction of loading, as well as factors such as ply thickness and ply stacking orientation play critical roles in this configuration. Recent studies have demonstrated the ability of thin ply laminated composites to mitigate damage progression, such as transverse micro-cracking, structural delamination’s, and splitting under static, fatigue and impact loadings. This work investigates and quantifies the damage characteristics in carbon fiber/toughened epoxy thin-ply laminates with single ply thicknesses of 70 µm for different laminate sequences under quasi static loading conditions. The results show that addition of thin plies within the composite laminate enhanced the mechanical performance. This improvement is achieved by reducing the damage progression in the thicker plies as a result of the suppression of transverse crack intensity.