A NOVEL METHOD FOR MEASURING DIRECT COMPRESSIVE PROPERTIES OF CARBON-FIBERS USING A MICROMECHANICAL COMPRESSION TESTER

A novel method has been developed for measuring direct compressive pro perties such as strength and elasticity of a series of mesophase-pitch -based and PAN-based carbon fibres about 10 mum in diameter by uniaxia l and transverse compression tests using a micro-mechanical tester. Th e fibres were shaped into cylindrical specimens, with their size ratio of length to diameter kept at about 2 to 3, by separating them from a ''thin film'' made by polishing the cut faces of a strand of carbon f ibres with epoxy resin as a matrix. Individual cylindrical specimens w ere stood up or laid down on a glass plate without any fixer for the m easurements of axial and transverse compression properties of fibres, respectively. The fibres exhibited non-linear elasticity, with the com pressive modulus decreasing with compressive deformation. The direct a xial compressive strengths of pitch-based carbon fibres were found to be marginally lower than the indirect ones, whereas there was no signi ficant difference between the two strength values for PAN-based fibres . The pitch-based fibres exhibited smaller average values of axial com pressive strength than the PAN-based fibres. The transverse compressiv e strength, which decreases with an increase in elasticity of carbon f ibres, exhibited a considerably lower average value than that of the a xial compressive strength. Further, the axial compressive strength was found to be smaller than the direct tensile strength for the fibres.