Effects of strain and damage on strain-sensing ability of carbon fiber cement

The strain-sensing ability of carbon fiber cement, as based on piezoresistivity, remains in the presence of damage, although the gauge factor (fractional change in resistance per unit strain) is affected by strain and damage. The longitudinal gauge factor is diminished by compressive strain by up to 70% and by damage by up to 25%. The magnitude of the transverse gauge factor is diminished by strain by up to 60% and by up to 25% by minor damage not accompanied by irreversible strain, but it is increased by up to 120% by major damage accompanied by irreversible strain. The gauge factor, whether longitudinal or transverse, is reduced in magnitude as the specimen size increases (by 13 to 51mm).