Comparative study on flexural performances of carbon fiber reinforced polymers with micro‐, micro‐/nano‐, and nano‐sized aramid fiber interlayers

Abstract Delamination restricts the out‐of‐plane loading capacity of carbon fiber reinforced polymers (CFRPs), posing a challenge in their structural applications. While interlaminar reinforcement using aramid fibers has emerged as a promising method to alleviate delamination issues, the effects of aramid fiber size and areal density on the flexural properties of reinforced CFRPs remain underexplored. This study investigated the reinforcing potential of different aramid fiber forms, including short aramid fibers, aramid pulp, and aramid nanofibers, through a three‐point bending test on CFRPs. The results revealed that short aramid fibers and aramid pulp provided better reinforcing effects than aramid nanofibers as their fiber lengths were optimal for the bridging mechanism. Specimens reinforced with 0.16 g/m² short aramid fibers attained the highest flexural strength, with a 20.9% improvement compared to unmodified specimens. Increasing the areal reinforcement density led to thicker interlayers, which negatively impacted flexural strength. These findings provide valuable insights for optimizing the use of aramid fibers in the industrial manufacturing of CFRPs, considering both reinforcing effects and process efficiency. Highlights Different‐sized aramid fibers were used for interlaminar reinforcement of CFRPs. Influence of interlayer thickness on flexural properties was investigated. Up to 20.9% improvement in flexural strength was achieved. Potential applications of different‐sized aramid fibers were discussed.