Detailed investigation on elastoplastic deformation and failure of carbon nanotube fibers by monotonic and cyclic tensile experiments

Monotonic and cyclic tensile loading experiments were conducted for analyzing elastoplastic deformation and failure of carbon nanotube (CNT) fibers. The deformation stages of the CNT fibers under tensile loads consist of a short elastic stage and a long-lasting plastic stage, while the elastic stage of the CNT fibers can be generally divided into two parts: a perfect-elastic stage and an elastic-like stage. Microstructural evolution for each deformation stage was interpreted by means of scanning electron microscope photos. An elastic limit and an offset yield point were discovered through the cyclic loading experiments. The elastic strain limit of the CNT fibers was determined at about 0.35% and the offset yield strain at about 1.2% for quasi-static loading. The effect of strain rates on the deformation and failure mode of CNT fibers was investigated as well.