Nondestructive sensing evaluation of single carbon fiber/polymer composites using electro-micromechanical technique

Cure monitoring and nondestructive strain-stress sensing of carbon fiber composites were evaluated by the measurement of electrical resistance, The difference in the electrical resistivity (DeltaR) during curing occurred by residual stress due to matrix contraction. As curing temperature increased, electrical resistivity of steel fiber increased, whereas that of carbon fiber decreased due to intrinsic electrical properties of each fiber. Residual stress built in the fiber is the highest at the fiber axis direction, whereas that of built in the matrix is relatively higher at the circumference and radius directions. For the strain-stress sensing, as curing temperature increased, apparent modulus increased and the elapsed time is shorter to reach to the maximum load. The strain at low temperature was larger than that of higher temperature case until the load reached at the maximum value. Furthermore, the dependence of other parameters such as curing agent composition, embedded length, fiber surface treatment was investigated under cyclic loads. The apparent modulus of the electrodeposited Fiber composite was higher than that of the untreated case. Electrical resistivity was responded well quantitatively with the change of temperature, curing and strain-stress sensing, and thus electro-micromechanical technique can be feasible nondestructive evaluation.