Ply thickness effect on in-situ transverse shear strength and microcrack propagation in carbon fiber-reinforced polymer

This study employs micro-scale finite element modeling to investigate thickness-dependent in-situ transverse shear strength and damage mechanisms in cross-ply carbon fiber-reinforced polymer (CFRP) laminates. A computationally efficient representative volume element (RVE) model is developed, comprising a 90° ply with randomly dispersed fibers, matrix, and interlaminar resin regions embedded between 0° plies. The constitutive behavior is characterized using the Drucker–Prager model for matrix plasticity and bilinear cohesive models for interface debonding. The results demonstrate that the in-situ transverse shear strength increases by 43.74% when the ply thickness decreases from 125 μm to 60 μm, while further reduction to 40 μm causes strength fluctuations within 6.6%. Across the 125-40 μm thickness range, the strength variation remains below 10% with interlaminar resin thickness varying from 0 to 3.5 μm. These findings provide a quantitative theoretical foundation for optimizing ply thickness design and establishing reliability prediction models in CFRP laminated composites subjected to transverse shear loading.