Detection of Damage by Measurement of Electrical Resistance in CFGFRP Composites.

Abstract

CFGFRP (carbon fiber-glass fiber-reinforced plastics) composites are materials with a self-diagnostic function for detecting latent damage. Three type of carbon fiber bundles with different ultimate elongations and one type of glass fiber bundle with a large ultimate elongation were tested as conductive fibers and insulating fibers, respectively. Electrical resistance increased with increasing strain, and a tremendous change was seen at the transition point where the carbon fiber bundles fractured. Data obtained by the acoustic emission method were measured simultaneously, and these changes showed results similar to changes in the electrical resistance. Permanent, residual strain and residual electrical resistance were observed even after the removal of load, and these changes were dependent on the maximum strain applied in the past. Latent damage of CFGFRP composites can be detected by a method based on the measurement of their changes in residual electrical resistance after unloading. The method based on measuring changes in the electrical resistance of the CFGFRP composites during and after loading is simple in terms of technique and manageable in terms of cost for detecting latent damage and preventing fatal fracture.