Nano structural analysis on stiffening phenomena of PAN-based carbon fibers during tensile deformation

Abstract

The effects of inner microstructures, including crystallite size, orientation and defects on the stiffening phenomena of PAN-based T300 carbon fibers under tension were explored. Single-fiber tensile test was conducted on three types of fiber: as received, 1400 and 1600 C heat treated. The distribution of crystallite orientation in a fiber from core to skin was obtained by using transmission electron microscopy. The observations indicate the load-transfer between crystallites depends on the crystallite entanglement. The slide-lock of the entangled junctions among the loosely compacted crystallites is responsible for the increasing elastic modulus during tension. The sharp drop of tensile strength (-36%) of the fiber after heat treated at 1600 degrees C was attributed to the increasing of crystallite size, nanopore defects and a higher misalignment of crystallites in the core region. (C) 2014 Elsevier Ltd. All rights reserved.