Modification of duel functioning PDA-PAADA capsules on interface and resin towards CFRPs with high strength and toughness

The interfacial bonding performance of the optimized CF/epoxy composites exhibits a high bonding strength which is comparable to the epoxy matrix. Considering the development of the CFRPs, how to break the limitation of the improvement of fiber/matrix adhesion by the matrix strength is a new meaningful focus for interfacial modification in the future. This paper takes a novel approach to break this established constraint by applying polydopamine and dopamine-modified poly (acrylic acid) (PDA-PAADA) capsules on CFs to produce variable behaviors. This is inspired by the polymeric capsules that possess the designability, controlled load-release, and deformability properties. Such PDA-PAADA capsules could serve as an effective strengthening component for the matrix in CFRP while optimizing fiber/matrix adhesion. Compared with existing interface modification methods of CF/epoxy composites, the realization of capsule inter-phase with variable behavior results in a breakthrough improvement in the interfacial strength. The ILSS of the prepared CFRP is up to 117 MPa, much higher than the matrix strength by 25.76%. Meanwhile, the CFRPs also acquire excellent impact toughness (110 kJ/m²). This brings a new vision to interface modification technology for CFRPs.