Preliminary experimental study on the electrical impedance analysis for in-situ monitoring of the curing of carbon/epoxy composite material for aeronautical and aerospace structures

International audienceThis paper concerns the electrical characterization of T700/M21 unidirectional composite materials using sensors developed specifically for this study. It proposes a reliable and reproducible protocol for the characterization of the material during curing. Prior to the characterization, an analysis was carried out to assess the impact of parasitic access elements (resistance of the electrode/fibre interface or of the feed wire), which was reduced to a minimum by appropriate dimensioning of the electrodes. A study of the electrical conduction in relation to the direction of the fibres made it possible to establish a suitable approach to homogenized measurement of the material. Thermo-electric coupling by self-heating was also evaluated, with a view to obtaining measurements that were not influenced by this phenomenon. Finally, the use of electrical impedance spectral analysis allowed in-situ monitoring of the curing process. The results obtained are compared with those of a rheological analysis of the same material. These results highlight the value of the proposed protocol and demonstrate that, with the aid of these sensors, complete automation of the manufacturing process of composite structures is feasible (optimization of the cure cycle by real-time automatic control)