Correlation between mechanical scales and analysis scales of topographic signals under milling process of natural fibre composites

This article aims to find the relation between the multiscale mechanical structure of natural fibre reinforced plastic composites and the analysis scales in the topographic signals of machined surfaces as induced by profile milling process. Bamboo, sisal and miscanthus fibres reinforced polypropylene composites were considered in this study. The multiscale process signature of natural fibre reinforced plastic machined surfaces based on wavelet decomposition was determined. Then, the impact of wavelet function was inspected by testing different wavelet shapes. Finally, the analysis of variance was carried out to exhibit the contribution rate of fibre stiffness and tool feed on the machined surface roughness at each analysis scale. Results demonstrate that studying the machining of natural fibre reinforced plastic requires the selection of the relevant scales. They show also the insignificance of the wavelet choice. This study proves that the contribution rate of fibre stiffness and tool feed on machined surface roughness is significantly dependent on the analysis scales, which are directly related to the mechanical properties of natural fibres structure inside the composite.