Crystallographic data on axially compressed Kevlar 49 fibres

Axially compressed Kevlar 49 fibres have been examined by X-ray diffraction methods. The most prominent effect of axial compression is the anisotropic deformation of the unit cell. Whereas the c-axial length, which correspond s to the chain axis, undergoes contraction, the basal plane dimensions mani fest enlargement. The deformations increase with the extent of axial compre ssion. The half-widths and the azimuthal spread of reflections also exhibit changes. The compression induced structural changes provide qualitative su pport to the experimentally observed reduction in tensile strength and modu lus.