Teruyuki Nakatsuji

Hybrid composites with self-diagnosing function for preventing fatal fracture

Design of intelligent material with self-diagnosing function for preventing fatal fracture of the structural material is achieved by hybrid composites consisting of fiber tows or powders in carbon material with a small value of ultimate elongation and glass fiber tows with a large value of ultimate elongation. CPGFRP/GFRP (carbon powder dispersed in glass-fiber-reinforced plastics/glass-fiber-reinforced plastics) composites are superior to CFGFRP (carbon-fiber and glass-fiber-reinforced plastics) composites in respect of their capability of damage monitoring by measuring change in electrical resistance from the early stage of damage, but the former is inferior to the latter as an application because of the difficulties of mass production and high cost. CFGFRP composites are already commercially used as sensor rods for diagnosing the health of concrete structures in skyscrapers in the architectural field or in security walls for preventing an invader in the security field. A method based on monitoring damage by measuring changes in the electrical resistance of structural materials is promising for improving the reliability of material.

Materials design of CFGFRP-reinforced concretes with diagnosing function for preventing fatal fracture

When concretes reinforced by CFGFRP (carbon fiber-glass fiber reinforced plastics) composites containing three types of carbon fiber bundles with different ultimate elongation values are subject to two-point loading tests, the electrical resistance increases linearly with the increase of load, strain and deflection of CFGFRP-reinforced concretes during loading and unloading but when the maximum value of the previous load is exceeded, the increase of electrical resistance becomes non-linear. This behavior is an effective way of knowing the magnitude of the maximum load during loading and unloading. The change in electrical resistance of CFGFRP reinforced concretes during loading increases largely when the carbon fiber bundle is fractured and is maintained thereafter against the increase of external load due to the presence of glass fibers. This behavior can also be used to prevent fatal fracture. Change in electrical resistance can supply better information for damage in concrete structures than strain or ...

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

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.