The effect of the transcrystalline layer on the performance of fibre reinforced composite materials has been attributed to its better elastic/mechanical properties, which in turn result from a higher degree of crystalline order in the transcrystalline phase. For the aramid and carbon fibre reinforced nylon 66 composites, atomic force microscopy reveals radial regularity in the transcrystalline layer relative to the fibre, and X-ray diffraction investigations of the isolated layer suggest that the polymer chain is oriented predominantly perpendicular to the fibre axis.