Large apparent internal deformation of carbon fibres under tension observed by in-situ microbeam small-angle X-ray scattering

Abstract A single fibre tensile in-situ microbeam small-angle X-ray scattering study was performed on the polyacrylonitrile-based carbonised fibres. There was no remarkable skin-core difference in the scattering profiles for the fibres tested. Meanwhile, we found that the chord length of the scattering objects shows an immense, yet reversible, increase of as much as 30–35% before the fibre fails at the macroscopic tensile strain of 2–2.5%. We believe this anomalous behaviour in the apparent length of the scattering objects reflect the complicated internal nanostructure of the carbonised fibres.