Comparison of the electrical resistance and potential techniques for the self-sensing of damage in carbon fiber polymer-matrix composites

The electric potential method, which involves measuring the potential at a distance from the line of current application, is effective for damage sensing of carbon fiber polymer-matrix composites when the distance is sufficiently small, such as 1.0 min (8 laminae) in the through-thickness direction. It is ineffective when this distance is 2.1 mm (16 laminae). The electrical resistance method, which involves measuring the potential on the line of current application, has no thickness limitation. However, it suffers from current path distortion upon damage and the consequent reduced sensitivity for damage. A minor phenomenon of the measured resistance decreasing with increasing damage is observed for the regions of the composite not containing the point of impact. The major phenomenon of the resistance increasing with damage overshadows this minor phenomenon for the region containing the point of impact.