Coupled mechanical and conductivity measurements: Damage detection

This paper reports in situ measurements of electrical resistivity during mechanical solicitation of insulator-conductor composite. Electrical and mechanical behaviors will be discussed on 3 examples namely (i) unidirectional carbon fiber reinforced polymers (CFRP), (ii) stick-like whiskers reinforced soft thermoplastics and (iii) carbon nanotubes reinforced soft thermoplastics. Resistivity measurements are described as a useful tool to monitor the damage of these composites. In the case of composite materials consisting in reinforced insulated matrix by electrically conducting fibers or fillers, resistivity (or conductivity) measurements show classically several features such as strong anisotropy in long fiber composites or the existence of continuous direct current (DC) conducting pathway for short fiber or particulate composites. Moreover, and this is the topic discussed here, in terms of mechanical stress/strain properties, the fibers or fillers conducting network may exhibit resistivity changes due to fiber ruptures, delamination, filler-filler debonding within filler network, etc.