Hierarchical enhancement of carbon fiber reinforced polymer laminate with randomly hybridized carbon nanotubes and aramid-pulp micro/nano-fibers

In this study, inspired by human teeth, random hybrid carbon nanotubes (CNTs) and aramid-pulp micro/nano-fibers (AP) with different mixing ratios were experimentally interleaved into carbon fiber reinforced polymer (CFRP) panels to form a gradient interface for hierarchical enhancement and synthetic effects. Due to different out-of-plane movability or penetrability of the CNTs, AP, and resin, 3rd and 4th order bio-inspired gradient interfaces between the carbon-fiber plies were formed in situ. According to flexural testing, hybrid CNT/AP-interleaved CFRP with a CNT of 3.6 gsm and an AP of 2.4 gsm showed an improvement of 47.35% in flexural strength. Furthermore, the synthetic effects of hybrid CNT/AP-interleaving were investigated by analyzing the mer3its and demerits of the CNT- or AP-interleaving methods. It was identified that the hybridization of multiple length-scale fibers as interleaves can be used to produce more hierarchical enhancements and synthetic effects. The new insights into multi-scale strengthening mechanisms were systematically revealed from the models of hierarchical fiber-bridging. And the graded penetration mechanisms of multi-scale fiber-reinforced CFRP laminates were analyzed.Highlights The in situ gradient interfaces form by Z-direction penetration of CNT/AP. CNT/AP-interleaving can form hierarchical enhancements and synthetic effects. Multi-scale strengthening via fiber-bridging and graded penetrations achieved. More fiber-bridging occur at sub-surface regions of the carbon-fiber plies. Bio-inspired hybrid CNT and AP strengthen CFRP panels for flexural resistance of CFRP laminates. image