Self diagnosis function of fiber reinforced composite with conductive particles

The electrically conductive fiber reinforced plastics (FRP) and ceramics matrix composites (CMC) have been designed and fabricated in order to introduce the self-diagnosis function which means the combination of reinforcement and damage diagnosis function into structural materials. The electrical conductivity was achieved by adding conductive fiber or particles into these composites. The composites with percolation structure consisting of carbon particles were found to have the advantages in response of conductivity to a small strain and in detectable strain range, comparing to the composites containing carbon fiber. A part of resistance change in the elongated composites with carbon particles remained after unloading despite its elastic deformation. The residual resistance increased with increasing applied maximum strain, showing that the composite possesses the function to memorize the previous maximum strain. The CMC materials containing TiN particles as a conductive phase indicated not only the fine response of resistance to slight deformation but also the increase in residual resistance during cyclic deformation at a constant load, suggesting that the composite have the ability to diagnose a cumulative damage through measurements of the residual resistance. These results suggest that the self-diagnosis functions peculiar to these composites are suitable for health monitoring techniques for many structural materials.