Performance assessment of a hybrid intermittent-progressive grinding strategy for bi-directional carbon fibre reinforced composites

Abstract

In today’s era, fibre reinforced composites (FRCs) due to their superior mechanical properties are preferred over metals in various applications such as sports, automotive, aerospace, etc. Even though high-quality fabrication procedures for near-net FRC structures are reported, their employment in many of the functional applications demands machining operations to yield controlled geometric tolerances and surface finish. To meet surface integrity without severe damages, machining using abrasive grains may be a potential solution. However, owing to non-homogeneous and anisotropic nature of FRCs, continuous engagement of abrasive grains may lead to undesirable effects of grinding force such as fibre pull-out, fibre breakage, matrix failure etc. Intensity of these damages, which are sensitive to the type of fiber and fibre orientations, is observed to be proportional to the depth of cut maintained by the cutting edge. While grinding bi-directional and multi-directional carbon fibre laminate composites using conventional abrasive tools, the aforementioned surface defects become a serious concern. Present paper aims to investigate the performance of a hybrid grinding strategy for bi-directional carbon fibre-epoxy composites, introduced with a title “Eccentric Sleeve Grinding (ESG)”, combining the merits of both intermittent and progressive cutting, solely using a conventional surface grinding machine and non-super abrasive wheel. Cost-effective eccentric sleeves for grinding wheel assembly and associated control over cutting scheme have been adopted in the proposed technique to achieve minimal damage material removal. Eccentric sleeve grinding experiments on 0/90° bi-directional carbon fibre reinforced composite (CFRC) at a range of depth of cut has been carried out and assessed the machining performance using indices such as grinding force, grinding efficiency in terms of force ratio, grinding wheel wear and surface defects. Superior tribological behavior was observed in ESG through the enhancement of grinding force ratio, in addition to significant reduction in normal grinding force, grinding wheel wear and surface roughness. Microscopic analysis of composite surfaces after ESG could illustrate the effectiveness of progressive-intermittent cutting to yield a favorable surface topography, without severe damages as observed in conventional surface grinding at same depth of cut.