Spirally Ag-coated short carbon fiber as a reinforcing filler for rigid polyurethane

High-performance materials often require high toughness and strength. Unfortunately, in most composites, toughness and strength are almost mutually exclusive. The simple combination of brittle carbon fibers (CFs) and rigid polyurethane (RPU) obviously cannot meet the standards of high-performance materials. In this paper, the spiral CFs (SS-CFs) were obtained by the electrodeposition. From the point of view of fracture mechanics, fracture resistance increases with crack propagation. This spiral structure provides more crack propagation paths, resulting in more energy consumption, which can lead to materials properties that are much higher than simple mixture. The results showed that the interfacial shear strength, tensile toughness, tensile strength, and impact toughness of SS-CFs/RPU composites were increased by 73.6%, 77.2%, 103.3% and 85.0%, respectively, compared with the pristine CFs/RPU composites. The main strengthening mechanisms of the materials were the pinning effect and the effective increase of the crack propagation pathway by the convex SS-CFs. At the same time, due to the deposition of the silver coating on the CF surface, the modified CFs composites also had excellent electrical conductivity and electromagnetic shielding performance. This means that our materials have a wide range of applications.