Akihiko Kitano

In-situ health monitoring of CFRP composites using electrical characteristics

The increase in electrical resistance of Carbon Fiber Reinforced Plastic (CFRP) composites caused by mechanical damage are studied experimentally and analytically. Considering the contacts of misaligned conducting carbon fibers of CFRP, we proposed a discrete network model as an equivalent electrical circuit for CFRP. This model incorporates both an electrical ineffective length, over which broken fibers carry no current, and the Weibull- Poisson statistics of fiber breakage. The model is also used to explain experimental data showing that the resistance change does not depend on the gage length of specimen and that the resistance and electrical ineffective length are controlled by the fiber volume fraction.

Quantitative evaluation of CFRP and CFGFRP hybrid composites as a maximum strain memory sensor

This paper studies the correlation between mechanical deformation, damage behavior and the change of electric resistance for unidirectional CFRP and CFGFRP (carbon fiber/glass fiber reinforced plastics) composites. This study is performed using experimental and numerical methods, and the results of two methods are compared. The change of electrical resistance is measured under the condition of simple tension and repeated loading-unloading, and the failure process of two types of CFRP is investigated using an optical microscope. A Monte Carlo simulation is performed to predict the change in electrical resistance due to strain and damage (fracture) of carbon fibers. Through these studies, it is revealed that the change of electrical resistance had a close relation with the damage process and there is a good agreement between experimental and predicted results. It is also suggested that this detecting technique is applicable to the health- monitoring of composite structures.