Measurement the longitudinal mechanical properties of high-performance fibres

Measurement of the longitudinal-compression modulus for aramid and carbon fibres is introduced. The 'micro-composite method' is used to measure the stress-strain property of the fibres in longitudinal compression. The micro-composite is a uniaxial fibre and epoxy-resin composite of cylindrical shape, 5 mm in length and 1 mm in diameter. This small size realizes the high-volume fraction of the fibre, around 0.85, and causes compact packing of the fibres in the matrix. This compact packing may prevent buckling of the fibres during compression. The stress-strain curve in longitudinal compression is superimposed on the tensile stress-strain curve obtained by the extension of a single fibre. The two curves obtained by these very different methods are smoothly connected, and the full stress-strain curve covering the compression and extension is introduced for high-performance fibres such as aramid fibres and carbon fibres.