Measurement of 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.