Study of synergistic and competitive mechanisms on toughening CFRP composites with intrinsic and extrinsic multiscale interleaves

Abstract

Delamination damage is a common failure mode of carbon fiber reinforced polymer (CFRP) laminates, which severely limits their application. This paper proposes a novel interlaminar toughening structure based on intrinsic and extrinsic multiscale toughening mechanisms using nanoscale multi-walled carbon nanotubes (MWCNTs) and microscale core-shell rubber (CSR). The resin sample M-0.5/C-8, containing 0.5 wt% MWCNTs and 8 wt% CSR, exhibited significant improvements in fracture toughness, with increases of 183.3 % in the mode-I critical stress intensity factor (KIC, Resin) and 412.0 % in the critical energy release rate of resin (GIC, Resin). However, its flexural strength and modulus decreased by 3.1 % and 3.3 %, respectively. Introducing MWCNTs and CSR into the interlayers of the CFRP, the interleaved toughened CFRP laminate exhibited a 123.3 % improvement in the mode-I critical energy release rate (GIC, Comp) and a 79.6 % increase in the mode-II critical energy release rate (GIIC, Comp) during the crack propagation stage, without sacrificing flexural performance. This remarkable enhancement in interlaminar fracture toughness results from the simultaneous triggering of nanoscale extrinsic toughening and microscale intrinsic toughening during crack growth. The flexural properties and fracture toughness of Epoxy/MWCNTs/CSR composites were also investigated to understand the properties transformation from resin matrix to CFRP. Morphological characterization and numerical analysis were used to analyze the synergies and constraints between two energy dissipation behaviors.