CHARACTERIZATION OF COMPRESSIVE PROPERTIES OF HIGH-PERFORMANCE POLYMER FIBERS WITH A NEW MICROCOMPRESSION APPARATUS

A microcompression apparatus to measure the compressive stress-strain curve of individual fibres has been developed. Illustrative results were obtained for a series of mesophase-pitch-based carbon fibres. A series of optical micrographs of a P100 fibre were taken as it failed in compression. The ultimate compressive strength (UCS) for any given type of fibre tended to cluster around two average values. The reason for this clustering is uncertain, but the two values may correspond to more and to less 'perfect' fibres. P55 exhibited a higher average UCS of 600 MPa and a lower average of UCS of 300 MPa. P75 had a higher average UCS of 600 MPa and a lower average UCS of 300 MPa. P100 gave a higher average UCS of 400 MPa and a lower average UCS of 150 MPa. The compressive modulus for P75 was 470 GPa. The fibres exhibited non-linear elasticity, with the compressive modulus decreasing as the compressive strain increased.