Early fatigue damage in carbon-fibre composites observed by electrical resistance measurement

Early fatigue damage during the first tenth (or less) of the fatigue life w as observed in carbon fibre composites by d.c. electrical resistance measur ement. The damage was most severe in the first loading cycle and the increm ental damage in each subsequent cycle diminished cycle by cycle. For the co ntinuous carbon fibre carbon-matrix composite, the resistance increased irr eversibly du ring early fatigue due, to matrix damage and possibly fibre fr acture as well. For the short carbon fibre polymer-matrix and cement-matrix composities, the resistance decreased irreversibly during early fatigue du e to matrix damage near the junction of adjacent fibres and the resulting i ncrease in the chance that adjacent fibres touched one another. (C) 1998 Kl uwer Academic Publishers.