COMPRESSIVE PROPERTIES OF UNIDIRECTIONAL CARBON-FIBER LAMINATES .1. A COMPACT FLEXURE BEAM FOR COMPRESSION TESTING

A new compact flexure beam has been developed which is suitable for the compression testing of unidirectional laminates. The method gives very high failure strains for APC 2 laminates, i.e. 1.73%, and low coefficients of variation, i.e. 3.3%. It is essential that the compressive and tensile moduli be monitored during the test, since these are found to vary with strain. With APC 2 having a fibre volume fraction of 0.61, the secant modulus decreases from a rule of mixtures value of 145 GPa at a tensile strain of about 0.4% to 102 GPa at a compressive strain of 1.7%. In consideration of the high strength values obtained (1.8 GPa), it is suggested that the method should be considered for adoption by ISO, ASTM and other standards associations.