Carbon nanotubes (CNTs) have been used as an in-situ sensor to detect the initiation of micro-cracks and their accumulations in the fiber reinforced polymer composites. CNTs form electrically conductive networks throughout the polymer matrix when dispersed in the composites and act as a sensor when the conductive networks break due to some damages. This methodology was applied to three-dimensional (3D) braided composites, aiming to investigate a feasibility of detecting the matrix failure in 3D braided composites. Tensile specimens were prepared using 3D braided glass and ultra high molecular weight polyethylene (UHMWPE) performs and vinyl ester containing multi-walled CNTs (0.5 wt %) via vacuum assisted resin transfer molding (VARTM). The electrical resistance of the composites was then measured during the tensile testing and analyzed with the microscopic observation of their cross-sections. Finally, it was determined whether the resistance change can reflect the initiation and accumulation of the micro-cracks and micro-delaminations in the braided composites.
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