Extrinsic Factors Affecting Anisotropic Electrical Conduction in Carbon/Epoxy Laminates Using Solid Electrodes

The lack of an in-depth understanding of electrical conduction behaviour in anisotropic carbon fibre-reinforced laminates was reflected by the fact that there was no measurement standard. Various ad hoc experimental techniques were used, involving a range of extrinsic parameters with little or no rigorous control. Not only were the widely varying values of electrical conductivity, if not incorrect values, generated, but also the effects of extrinsic parameters were attributed erroneously to those of intrinsic parameters. This predicament was compounded by different techniques used in measurements of volume and surface electrical conduction. This paper formulated the most effective experimental method, using two well-argued solid electrodes, to evaluate electrical conduction with rigorous control of all extrinsic parameters. Its main objectives were to investigate anisotropic volume and surface electrical conduction with focus on the effects of electrode-specimen contact resistance, clamping pressure, conductive paint, contact face preparations, lay-ups, and specimen dimensions. Unique results and data trends provided the step-changing understanding of electrical conduction such that the contributions of extrinsic factors were clearly established. The specifical findings showed that (1) 2-probe method was the only viable technique to measure both volume and surface conductivities, (2) all conductivity values were dependent on clamping torques and contact face machining, (3) the conductive paint enhancement effect was an artefact, and (4) obtaining surface conductivities by multiplying volume conductivities with laminate thickness was incorrect.