Atomic force microscope imaging of the surface roughness of SCS- and TiB2-coated SiC fibres and uncoated sapphire fibres

Abstract

To understand the role of fibre surface roughness on the toughening of composite materials, it is imperative to characterize the fibre surface structure properly. This paper presents nanometre scale images of the surfaces of SCS- and TiB₂-coated SiC fibres, and of uncoated sapphire fibres, obtained by atomic force microscopy. It is found that SCS and TiB₂ coatings deposited on SiC fibres using chemical vapour deposition methods produce fibres exhibiting surface structures that are tri-fractal over several decades of length scale. The sapphire fibre exhibited a surface structure with two scales of periodic roughness, of wavelength 60 μm and 100 nm. A roughness analysis of the experimentally obtained data at different resolutions demonstrated that the magnitudes of the conventional parameters root mean square (r.m.s.) height σ, r.m.s. slope σ′, and r.m.s. curvature σ″ for the same surface varied in some cases by more than an order of magnitude.