Enhanced interlaminar fracture toughness of CFRP using UHMWPE fiber veils modified with polydopamine and graphene oxide

• Novel application of UHMWPE fiber veils for interlaminar toughening of CFRP. • GPPE Veil led to a 90.6 % increase in G Ic and a 69.8 % increase in G IIc . • The enhanced adhesion of PDA and GO contributes to improved fracture toughness. Carbon fiber-reinforced polymer (CFRP) laminates are prone to delamination due to their inherently low interlaminar fracture toughness. This study, for the first time, investigates the use of ultra-high molecular weight polyethylene fiber (PE) veils to enhance the interlaminar fracture toughness of CFRP and explores the influence of polydopamine (PDA) and graphene oxide (GO) on their toughening efficacy. PE, PDA-modified PE (PPE), and GO/PDA-modified PE (GPPE) veils with an areal density of 10 g/m 2 were fabricated using a wet-laying technique and subsequently introduced as interlayers in unidirectional CFRP laminates via a prepreg hot-pressing process. Mode I and Mode II interlaminar fracture toughness (G Ic and G IIc ) of the CFRPs were evaluated using double cantilever beam and end-notched flexure tests, respectively. The results demonstrated that while all three PE veils improved the interlaminar fracture toughness compared to the pristine CFRP laminates without interlayers, the incorporation of the GPPE veil yielded the largest increase in G Ic and G IIc by 90.7 % and 69.8 %, respectively. Analysis of the toughening mechanisms revealed that PDA modification improved the interfacial adhesion between the PE fibers and the epoxy matrix, promoting fiber bridging and pull-out. The introduction of GO further contributed to the toughness through additional nanoscale mechanisms such as crack deflection and pinning, exhibiting a synergistic effect with PDA. This research presents an effective strategy for developing high-toughness CFRPs.