A MULTI-SCALE MODEL FOR BENDING STIFFNESS OF CNT STRANDS IN CNT FIBERS

AI Azad and R Dargazany and R Mirzaeifar and S Mall, PROCEEDINGS OF THE ASME INTERNATIONAL MECHANICAL ENGINEERING CONGRESS AND EXPOSITION, 2017 VOL 14, UNSP V014T11A030 (2018).

Carbon Nanotube (CNT) fibers are 3D-woven hierarchical assemblies of CNTs which show excellent mechanical and electrical properties. There is a tremendous loss of mechanical performance in the scale transition from individual CNT to fibers, over which we have limited understanding. Our knowledge of load transfer across different length scales is scarce and inconclusive. Here, the objective is to explore the load transfer mechanism (LTM) of CNT fibers, by identifying the contribution of defects on mechanical performance of fibers at various length scales. A micromechanical-based constitutive model is developed to describe bending-tensile properties of strands as an assembly of twisted yarns. The model associates the strand response to two states of deformation referred to as stick and slip states. Several inelastic features were considered in calculation of the response of strands, such as local jamming, evolution of the void area between yarns, and friction. The model is validated against different sets of experiments.

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