Electric resistance measurement–based structural health monitoring with multifunctional carbon fibers: Predicting, sensing, and measuring overload

Abstract Polymer matrix composites that also contain carbon fiber reinforcement can be given a secondary function in addition to load bearing due to the electrical conductivity of the reinforcing fiber. We investigated how to measure the deformation of a composite by measuring the resistance of the carbon fiber and indicate its current or previous overload. We found that the resistance of the carbon fiber bundle initially increases linearly and then progressively during the testing of the specimens, and finally, when the fiber bundle snaps, the circuit breaks. We have shown by cyclic testing that overload exceeding reversible deformation can be detected and measured by examining the first derivative of the resistance change with respect to deformation. Based on our results, electric measurements of either an only carbon fiber-reinforced composite or a hybrid composite can be used to detect a possible previous overload of a component with an unknown load history.