High-strength carbon nanotube fibers by twist-induced self-strengthening

High-strength carbon nanotube (CNT) fibers are strongly desired as they offer both excellent mechanical and electrical properties compared to traditional fiber materials. Here, we adopt twisting and compression as two complementary steps to tailor the fiber structure and obtain extraordinary mechanical properties. We have fabricated twist-compressed ribbon-like CNT fibers with predefined, uniform, relative large ribbon thicknesses (9-20 μm). Tensile tests show highly reproducible mechanical behavior of our fibers with a distinct self-strengthening stage during loading, leading to ultimate strengths up to 3.3-3.7 GPa in 9 μm-thick fibers at a gauge length of 10 mm, and strengths of 2.5-3.0 GPa at the same thickness but larger gauge length (100 mm). Whereas the compression step effectively reduces the cross-sectional area, twist-aligned CNTs and their re-orientation are responsible for producing large Poisson's ratio and achieving high strength. Controlled fabrication of thick, uniform, high-strength CNT fibers is critical for high load-bearing capacity and will facilitate many practical applications.

232