Fracture analysis of interleaved composites with self-same resin-rich layers using mechanical testing, acoustic emission, and micro-visualization

The interlaminar toughness of composite materials remains a critical challenge, limiting their broader application in industries requiring high load-bearing capacity and resistance to delamination. This study investigates innovative interleaving methods to enhance the fracture performance of thermoplastic composites. Using self-same resin-rich layers (RRL), fracture tests under Mode-I loading conditions quantify strain energy release rates for crack initiation and propagation. Digital Image Correlation (DIC) was employed to monitor crack tip propagation, while acoustic emission data was recorded to analyze strain energy release during crack growth. The fracture performance improvement of interleaved components was limited. The results further underscore the critical role of strong fiber-matrix bonding and the predominance of fiber bridging during fracture in reference samples under separation forces (Mode I). These factors contribute to their high GIc values, to the extent that the introduction of an interlaminar resin layer—designed to promote increased matrix plastic deformation at the crack tip—fails to yield significant improvement in GIC values.