Influence of the Fibre-Matrix Interface on the Matrix Crack Development in Carbon-Epoxy Cross-Ply Laminates: Experimental and Numerical Validation

Carbon-fibre-reinforced composites rely heavily on the fibre-matrix interface for effective load transfer and damage tolerance. This study investigates how varying levels of fibre surface treatment influence the mechanical behaviour of carbon-epoxy cross- ply laminates (02/902)s. Tensile tests combined with finite element modelling in COMSOL Multiphysics examined stiffness, strength, strain to failure, and matrix crack evolution. Results show that moderate treatment (≈10% of standard duration) optimizes interfacial bonding, improving stiffness and strength while maintaining ductility. Excessive treatment increases brittleness, leading to rapid crack propagation and reduced energy absorption. The FEM model, incorporating cohesive zone and progressive damage laws, showed strong correlation with experiments (R² > 0.975). These findings highlight that balanced surface treatment is critical: insufficient bonding weakens composites, while over-strengthening eliminates beneficial energy dissipation.