Delamination identification of cross-ply graphite/epoxy composite beams using electric resistance change method

Detection of delaminations is a difficult task for visual inspections. Difficulty of detection underlines the importance of development of smart structures for monitoring delaminations of graphite/epoxy laminated composites. This study employs an electric resistance change method for identification of delamination location and size; applicability of the method is investigated experimentally using beam-type specimens fabricated from cross-ply laminates. On the specimen surface, multiple electrodes are mounted by co-curing copper foil to measure electric resistance changes. Interlamina shear tests are conducted to create a practical delamination crack in a beam-type specimen. Five beam specimen types were made and tested. A large number of tests were conducted to obtain a data set for solving inverse problems to estimate delamination location and size from measured electric resistance changes. Response surfaces are employed for a solver of inverse problems instead of well-known artificial neural networks. As a result, the method successfully identifies delamination location and size for these beam type specimens. To obtain practically efficient estimation performance, at least five electrodes are indispensable for these beam type specimens. (C) 2002 Elsevier Science Ltd. All rights reserved.