How Interleaved High-Loading Particles Alter the Fracture Pathway and Boost Toughness in CFRP Composites

Carbon fiber-reinforced polymer (CFRP) composites are widely used in the aerospace industry owing to their high specific strength and modulus. To further expand their utility, structure-function integration is increasingly pursued by incorporating high-loading functional fillers into their interlaminar resin-rich regions. However, the interlaminar behavior of such highly filled composites is complex, and their Mode I interlaminar fracture characteristics and crack propagation mechanism remain poorly understood. To fill this gap, specimens with varying high particle mass fractions were fabricated via a multi-layer resin film infusion (MLRFI) process, to systematically investigate the effects of highly filled particles on their Mode I interlaminar fracture behavior and crack propagation mechanism. Results show that 33.3 vol% filler loading only induced local crack deflection with limited toughening effect. At 50 vol% filler loading, the crack propagation mode shifted from interlaminar-dominated to synergistic interlaminar-intralaminar propagation, fully activating energy dissipation mechanisms and increasing Mode I fracture toughness by 70.5%. Conversely, excessive 60 vol% filler loading introduced numerous weak interfaces, leading to an interlaminar-dominated crack path and reduced fracture resistance. Furthermore, a high-fidelity embedded finite element model (EFEM) was established, which reveals how interleaved high-loading particles mediates composite damage evolution, providing a reliable reference for interlaminar cracking prediction in such composites.