Electrical Resistance Change Measurement with Elevated Temperature due to Joule Heating for the Detection of Delamination in Graphite/Epoxy Composites

Abstract

Delamination cracks in a graphite/epoxy composite change the thermal expansion properties in the damaged regions. We detect this change by measuring the electrical resistance in the affected areas while heating. The proposed damage detection method is effective even when a damaged electrode is used, in contrast to the traditional method, which requires highly reliable electrodes to prevent an increase of the inherent electrical resistance. The proposed damage detection method is thus feasible for a variety of environments that might cause the degradation of the electrode. Heating of the composite is performed by Joule heating of the graphite fibers rather than general heating using an outside heat source. Graphite fibers, due to their high electrical conductivity, are used not only as the damage sensor but also as the heat source. The influences of delamination and electrode defects on a heated cross-ply beam are examined by simulation. The electrical resistance change after Joule heating is also experimentally measured. As a result, we proved that delamination detection is possible even with a damaged electrode.