Interface design against delamination in CFRP: Interleaving or fibre bridging due to interlayer thickness and volume density of micro-/nano- aramid pulp fibers

This study aims at an optimum interface design against delamination in unidirectional carbon fiber-reinforced polymers (UD-CFRP) by incorporating ultra-thin micro-/nano- Aramid pulp (AP) interlayers with various AP lengths, volume densities, and thicknesses. Experimental results indicate that even reduction of interlayer thickness alone (while keeping other interleaving conditions unchanged) can significantly enhance the fracture toughness G IC by up to 190%. Nano-AP fibers primarily contribute to crack-bridging toughening, while micro-AP fibers facilitate fibre bridging across UD carbon fiber plies. SEM analysis reveals the key toughening mechanism of fibre bridging across the ply interface. These findings suggest that optimal AP interlayer properties (thickness, volume density, and fiber length) can be tailored for improved delamination resistance in CFRPs. AP-interleave toughening can be adopted in pre-preg manufacturing; therefore, this research methodology can potentially be transferred to industrial production for more reliable and delamination resistance CFRP.