Damage tolerance of few-layer graphene modified CFRP: From thin-to thick-ply laminates

Abstract

Low impact resistance and high notch sensitivity are significant drawbacks of carbon-fibre-reinforced plastics (CFRP). The addition of carbon nanoparticles (CNP), a third phase, reduces this deficit through additional energy-consuming mechanisms. The influence of CNP modification on strength and damage behaviour cannot be separated from the effect of layer thickness because it controls the stress state in the entire laminate. This study investigates the influence of few-layer graphene (FLG) modification on CFRP with layer thicknesses varying from ultra-thin-ply (28μm, 30g/m2) to thick-ply (220μm, 240g/m2). The mode I and mode II inter-laminar energy release rates increased significantly with the FLG modification. It also increased the damage initiation stress for notched laminates of all layer thicknesses, thereby increasing the useable design space. The FLG modification also increased the ultimate notched strength for the ultra-thin ply laminates, thereby reducing the high notch sensitivity which is the limiting factor for their application. In the case of low-velocity impact damage, the modification of thick-layer laminates improves the residual compressive strength. FLG modification leads to a considerable improvement in the compressive strength. The selection of CNP was based on a comprehensive investigation of the fracture toughness of the prepreg resin/CNP nanocomposites. The particle loading and type was selected for FLG with a 25μm sheet size and 0.05 wt %.