Characterisation of electrical resistance for CMC materials up to 2000 K

Carbon based composites are used in thermal protection systems (TPS) for atmospheric re-entry. The electrical properties of this semiconductor material can be used for health monitoring, as electrical resistivity changes with damage, strain and temperature. In this work the electrical resistivity as a function of the material temperature is analysed, eliminating effects of thermal electricity, and the thermal coefficient of electrical resistance is determined. In the linear region, for material temperatures up to 523 K the thermal coefficient of electrical resistance is found to be Cα=-6.67·10-41/K and in the non-linear region it is Cβ=3.89·10-1. A sensor network is applied for local and time resolved monitoring of the 320 mm × 120 mm × 3 mm panel shaped samples. Since the TPS is used for atmospheric re-entry it needs to be characterised for a wide range of temperatures, in this case up to 2000 K. Therefore, experiments in an inductively heated test bench were conducted.