Modifying carbon nanotube fibers: A study relating apparent interfacial shear strength and failure mode

Achieving high strength in fiber reinforced structural composites requires effective load transfer between the high-performance fiber reinforcement, e.g., carbon nanotube (CNT) yarn, and the matrix. Various processing approaches to enhance the interaction between CNT fiber and the matrix were investigated. The apparent interfacial shear strengths (IFSS) of pristine CNT yarns, post-treated CNT yarns (cross-linked, functionalized, and polymer incorporation by resistive heating), and pre-infiltrated polymer/CNT composite fibers measured using single fiber pull-out tests were used to screen the efficacy of the processing methods. Pristine CNT yarns had a low apparent IFSS (20 MPa). Improved wet-out of the fiber eliminated the dry-core shear failure mode. The hierarchical microstructure of carbon nanotube fibers necessitates consideration of matrix/fiber interfaces within the reinforcement to improve interfacial shear strength and prevent failure within the reinforcement. [Display omitted]