Micromechanics of Deformation of High Modulus Polymer Fibres and Composites

Abstract

A Raman microscope has been used to investigate the deformation of high-modulus polymer fibres such as poly(p-phenylene terephthalamide) (Kevlar 49), substituted polydiacetyelene single crystal fibres and poly(p-phenylene benzobisthiazole) (PBT) fibres. Well-defined intense Raman spectra can be obtained from individual fibres and the spectra for the different fibres show characteristic bands due principally to the stretching modes of back-bone bonds. It has been found that for each type of fibre most of the bands are strain sensitive moving by up to -20 cm -1/% strain. The reasons for this strain sensitivity are discussed in relation to the deformation of bonds in the individual molecules. The way in which the strain-induced band shift can be used to follow the micromechanics of deformation in composites reinforced with high modulus fibres is described.