Abstract
A detailed experimental study is performed on the piezo-resistive damage sensing capability of electrically conductive carbon fiber and carbon nanotube-infused glass fiber composites after freshwater and saltwater ingression under quasi-static tension and under low temperatures. The electrical resistance is recorded via a two-point probe measurement technique for carbon fiber and a four-point probe measurement technique for glass fiber.
The carbon fiber composites on average absorbed 1.7% of their initial mass as either freshwater or saltwater. The glass fiber composites absorbed 2.1% on average of their initial mass as freshwater or saltwater. Mechanical and electrical properties of carbon fiber composites showed a dependency on both water ingression and testing temperature.
Water-infused carbon fiber composites exhibited a unique electrical behavior where, after severe delamination the frayed lamina fibers could bridge the delamination and regenerate lost electrical connections. Lower temperatures allowed more severe delamination to occur within the composite. The glass fiber composites infused with 0.5% by weight (wt) and 95% purity carbon nanotubes were not conductive and did not detect internal damages.