Self-Assembled Polydopamine for Enhanced Fracture Toughness of Carbon Nanofiber-Reinforced Phthalonitrile Composites

This study investigates how cracks spread in carbon fiber (CF) reinforced phthalonitrile (PN) composites (CFRPN) and ways to modify them. The dominance of plasticity in crack propagation within CFRPN presents potential safety hazards in real-world scenarios. Given the demands of the molding process and operational conditions, it is imperative that interfacial modification materials exhibit exceptional resistance to high temperatures. This research implements a high-temperature-stable interfacial modification strategy, employing self-assembled polydopamine (PDA) as the sizing agent for CF fabrics, aimed at enhancing the interfacial crack growth stability and ensuring high-temperature resistance. Experimental results indicate that PDA treatment significantly improves the type I interlaminar fracture toughness and interlaminar shear strength (ILSS) of CFRPN. Scanning electron microscopy analysis further reveals that after the PDA coating, cracks predominantly propagate through the PN resin rather than at the interface between the fiber and resin. Therefore, using PDA as a sizing agent for CF not only strengthens the interface bonding between PN and CF but also effectively inhibits the unstable crack propagation, thereby significantly enhancing the composite’s load transfer efficiency, interfacial type I fracture toughness, and ILSS.