DEFORMATION MICROMECHANICS IN HIGH-VOLUME-FRACTION ARAMID EPOXY COMPOSITES/

It is shown that Raman spectroscopy is an excellent technique for anal ysis of the relationship between structure and deformation processes i n both high-performance fibres and fibre-reinforced composites. It is demonstrated that Raman spectroscopy can be used to follow molecular d eformation processes in Kevlar 49 aramid fibres through stress-induced band shifts. The shift of Raman bands in a high-volume-fraction unidi rectional composite is analysed and it is found that there are signifi cant variations in local fibre strain due to imperfections in the comp osite microstructure. Furthermore, it is shown that it is possible to map the local fibre strain distributions around a hole in the composit e. The distributions of axial fibre strain have also been mapped in bo th a plain weave and a four-harness satin weave Kevlar 49/epoxy compos ite. Complex distributions of local fibre strain that follow the patte rn of the repeat units of the woven structures are found. The power of the Raman technique to follow composite micromechanics is therefore d emonstrated.