Characterizing the strain rate effect on Mode I delamination of CFRP composites using acoustic emission

The strain rate effect on Mode I delamination in carbon-fiber-reinforced polymer (CFRP) composites remains a subject of significant debate, and conventional testing methods struggle to effectively characterize its mechanical behavior under different loading rates. This study aims to investigate the strain rate effect on Mode I delamination in CFRP composites using acoustic emission (AE) techniques. Macro-mechanical and microscopic morphology analyses indicate that the interlaminar failure mode shifts from fiber/matrix debonding and matrix cracking at lower loading rates to interlaminar brittle fracture of the matrix at higher loading rates. Meso-scale AE data further reveal the influence of Mode I delamination loading rate on damage source energy and activity. Additionally, AE peak frequency data suggest that an increase in loading rate alters the damage modes in the delamination process, shifting from matrix cracking to interfacial effect-driven damage. Furthermore, experimental data combined with a derived semi-empirical strain rate effect model confirm a positive correlation between AE energy-weighted centroid frequency and the interlaminar strain rate effect. These findings demonstrate that, within the scope of this study, AE technology is an effective approach for characterizing the strain rate effect on Mode I delamination in CFRP composites.