Measurement of the conductivity temperature dependence of CFRP and its application in anticipating lightning strike thermal effect

The carbon fiber reinforced polymer (CFRP) of aircraft skin structure suffers from a sharp temperature rise which is induced by lightning strikes. The temperature rise has an important influence on the electrical conductivity of composites which in turn affects the generation process of Joule heat. In this paper, two kinds of heating experiments, using hot air gun to directly heat one surface of specimen and conducting direct current into the material, were carried out to unidirectional ZT7H/5229D carbon fiber/epoxy laminates. In the two heating experiments, the temperature-dependent conductivity during heating-cooling cycle (thermal cycle) were measured, respectively. A high pulse current injection experiment was carried out. The instantaneous temperature of the material surface during the current action was measured firstly using an all-fiber transient high temperature probe. The measured temperature-dependent conductivity were applied to the simulation model, and the instantaneous temperature of the high pulse current injection experiment was simulated. The results show that the temperature-dependent conductivity of the two kinds of heating experiments have a good consistency. The electrical conductivity before and after heating and during the whole thermal cycle are influenced by the hysteresis loop, decomposition and matrix thermoset. The temperature field of CFRP under lightning current injection can be predicted accurately through the simulation model on the basis of measured temperature-dependent conductivity.