Monitoring deformation processes in high-performance fibres using Raman spectroscopy

It is demonstrated that Raman spectroscopy is a powerful technique for the analysis of the relationship between structure and deformation processes in high-performance fibres. A brief review is presented of the developments in instrumentation that have enabled Raman spectroscopy to become so powerful for such studies. Examples are given of the application of the technique to follow molecular deformation processes in different aramid fibres. It is demonstrated that the behaviour is consistent with the deformation being controlled by a uniform stress series-type model where deformation takes place through a combination of crystal stretching and crystal rotation. The stress-induced Raman band shifts are a direct measure of crystal stretching. It is further demonstrated that the deformation of polyester fibres can be interpreted in a similar way. The Raman technique is extended to the analysis of the relationship between structure and mechanical properties on carbon fibres where it is again shown that the behaviour can be modelled successfully by a uniform stress model.