The electrical peformance of carbon fibre composite joints

Abstract

The proposed use of Carbon Fibre Composite material in future aircraft projects has led to the initiation of many research
programmes internationally. Much of the work is concentrated around the electrical performance and properties the material.
Investigations have shown that Carbon Fibre Composites possess poor electrical conductivity relative to metals, which influences the electromagnetic properties of a structure comprised of Carbon Fibre Composite materials. The internal electromagnetic environment of a structure for a given impinging electromagnetic field is a function of the structure's material, its joints or seams, size, shape, and number of areas that have low conductivity. The level of electromagnetic field penetration for a given structure constructed from Carbon Fibre Composites is an important consideration in the
electromagnetic hazard protection design of the systems. This problem must be addressed with confidence in order to produce design specifications for equipment, optimise system installation and understand system integration within the structure. The aim of this research is to further the understanding of the electrical current flow, both A.C. and D.C., through practical aircraft standard joints constructed in Carbon Fibre Composite. The investigations incorporate consideration of the D.C. conditions of the joint and measurements in the frequency band 1MHz to 50MHz utilising a dual plate transmission line. The results of these investigations show that a current flow through a jointed structure can be predicted using a theoretical finite difference model. The behaviour of current flow through the C.F.C. material was also assessed using simple theory, and shown to have good agreement with measurements of the D.C. properties of the material and joints. Finally, it was demonstrated that measurements of the A.C. properties of the, joint up to 50MHz can be attained by utilising a simple dual plate transmission line test jig.