Aeronautical carbon fibre composites with high electrical conductivity and fracture toughness utilizing functionalized interleaves

Abstract

Carbon fibre reinforced polymers (CFRP) are extensively used in current advanced aircraft due to their light weight, high strength to weight ratio and good corrosion resistance. Future aeronautical CFRPs are likely to be highly integrated material systems with excellent mechanical properties and additional functionalities. This thesis focuses on the concept of structural-functional integration for CFRPs, by combining high fracture toughness and electrical conductivity with balanced mechanical properties.
Firstly, fracture toughness is significantly improved via interleaving the carbon-epoxy plies with a polyamide toughening layer. A high temperature rosin-sourced epoxy was formulated as the green matrix resin. The effects of interleaving on fracture toughness, impact resistance, toughening mechanisms and in-plane mechanical properties are investigated. The Mode I and Mode II interlaminar fracture toughness values were both significantly improved by interleaving along with the CAI residual strength with only a modest reduction in in-plane mechanical properties.
Proprietary electroless copper-nickel plated polyester veils were also evaluated as interleaves, forming a bi-continuous network in interlaminar regions, also improving the Mode I and Mode II interlaminar fracture toughness values. The resulting electrically conductive network yielded major improvements in the through-thickness electrical conductivity of laminates and this was also dependent on compaction. A series-resistor model was applied to estimate the through-thickness electrical conductivity for a given conductive network. Compaction had a lower influence on flexural and interlaminar shear properties although a 20% decrease in interlaminar shear strength was noted for FIT specimens due to the low intra-ply shear resistance of interlayers.

Date of Award	Mar 2023
Original language	English
Awarding Institution	University of Nottingham
Supervisor	Xiaosu Yi (Supervisor), Xiaoling Liu (Supervisor) & Chris Rudd (Supervisor)