Electrothermal Behaviour of Constrained Carbon/Epoxy Laminates Under Various Electric Currents

Although induced Joule heating in carbon/epoxy laminates has been studied, how it can affect their anisotropic electrical conduction has not been well established. The objectives of this work were to ascertain the electrical current-temperature relationship, the effect of induced temperatures on specimen sizes, clamping torques, and electrical conductivity of, and the Lorenz proportionality constants between, thermal and electrical conductivities, all verified with analytical corroborations. A 2-probe method was used in electrical conduction measurements with machined specimens in various dimensions. The specific contributions of elevated temperatures to the electrical conduction through specimen size and clamping torque were ascertained. The thermal conductivities of laminate samples were measured using differential scanning calorimetry. From test results, a parabolic relationship between induced temperature and electrical current was found in both in-plane and through-the-thickness directions. The temperatures in the small specimens rose parabolically. Increasing clamping torques led to linear reductions in temperatures. Over the range of temperatures, the effect of induced temperatures on the electrical conductivity was very small, because the rising of temperatures did not alter the electrical conduction mechanisms. The proportionality constants between thermal and electrical conductivities were established for the first time. This means that just one kind of these measurements needs to be conducted for the same laminates.