Direct measurement of the axial poisson's ratio of single carbon fibres

Abstract A new method of determination of the axial Poisson's ratio of single carbon fibres is presented. The proposed method, based on a laser diffractographic technique, provides measurements of the axial Poisson's ratio with an accuracy of 5·7%. Measurements on three types of carbon fibres demonstrates that the grand mean value of the axial Poisson's ratio takes values in the range 0·26–0·28. Moreover, analysis of changes in the fibre diameter with elongation, measured in nine different directions in the plane of a fibre cross-section, displays the anisotropic nature of the axial Poisson's ratio.