V. Keryvin; M. Ueda; G. Kermouche; Y. Marthouret; S. Sao-Joao
Composites Science and Technology 272 (2025) 111362
The longitudinal compressive mechanical behaviour of polyacrylonitrile (PAN)-precursor T300 carbon fibres
was assessed using micro-pillar compression testing, with direct comparison to published data on entire fibre
compression. Micro-pillars, fabricated via focused ion beam (FIB) milling, exhibited compressive modulus,
strength, and failure strain values closely matching those of whole fibres, thereby validating this microscale
technique for accurate stiffness and strength measurements. A progressive reduction in stiffness with increasing
compressive strain — indicative of non-linear elasticity — was directly observed and quantified under
compression for the first time. Although the failure modes of micro-pillars differed from those of intact
fibres, the results support the hypothesis of a mechanically homogeneous fibre microstructure and suggest the
presence of a stabilising outer sheath that delays failure initiation. These findings reinforce the methodological
basis for small-scale mechanical testing of carbon fibres and carry implications for multiscale modelling and
the prediction of compressive strength in unidirectional composite plies.