Self-monitoring of strain and damage by a carbon carbon composite

A carbon-carbon composite was found to be able to sense its own damage and dynamic strain, as its electrical resistance increased irreversibly upon damage and increased reversibly upon tensile strain. Even damage after the first cycle of tensile loading within the elastic regime was detected. The reversible resistance increase upon cyclic tension was mainly due to dimensional changes, but it was partly due to a phenomenon that intensified as damage increased. The gage factor, which is the reversible part of the fractional resistance change per unit reversible strain, was 1.2-2.4.