Electrical properties and surface roughness of carbon fibre reinforced polymer under progressive surface abrasion

Two key technologies to reduce aircraft emissions are lightweight structures and the electrification of propulsion systems. Achieving high power density is a barrier to aviation electrification. Carbon fibre reinforced polymer (CFRP) is used in over 50% of state-of-the-art aircraft structures due to its lower density. CFRP offers ten times higher strength depending on the fibre and superior mechanical properties compared to aluminium. Replacement of metallic equipment casings and cable raceways with CFRP offers the opportunity to increase power density. However, the use of CFRP for these applications will give rise to new failure modes where the CFRP forms part of the electrical bonding network (pathway to current return) on the aircraft. Historically, the most common failure mode for aircraft systems is a short circuit due to abrasion of cable insulation. For electrical failures through CFRP, the outer layer of epoxy must also be abraded for an electrical connection to be made between the metallic cable conductor and the carbon fibres. The electrical resistance added to the fault path by CFRP components will vary with the level of abrasion on the surface of the CFRP. This paper describes the capture of datasets [1] which correlate the change in electrical resistance for unidirectional [0°] and woven CFRP with the level of surface abrasion. This data enables users to characterise the failure mode regarding impact on electrical fault response and subsequent resilient electrical power system design and may facilitate the relation between imaging data and a non-destructive evaluation of electrical properties. Further, the methodology to capture datasets relating electrical properties of CFRP with increasing levels of surface abrasion can be replicated for different CFRP layups.