Nanomechanics of advanced polymer fibres

The micro/nano-structural evolution before and after tensile/compressive loading, fatigue and ultimately, failure has been studied by Raman (and IR) microspectroscopy for PBO, PET, PA66, PP, silk and hair using three probes: the low wavenumber collective modes at <150 cm−1 as representatives of the crystalline/ordered and amorphous chains, the stretching and bending modes, as representative of the C–C/C–N polymeric backbone, and the localized vibrations (OH, NH) to probe the inter-macromolecule segment distance. The wavenumber and bandwidth distribution across fibre diameters reveal different types of skin/core heterogeneity. The in situ analysis at different strain/pressure levels shows that amorphous chains in the fibre accommodate the stress differently. The post mortem analysis shows that amorphous domains can be highly stressed during the failure and the remnant stress can be measured.