High-speed drilling of thick woven carbon fiber reinforced epoxy laminates

Composite materials are widely used in the aerospace industry. It is a great challenge to achieve high-quality parts with reduced damage level when drilling the faces of composites. This is due to several factors including the heterogeneity of the material, its sensitivity to heat, and its abrasiveness. The objective of this study was to characterize the drilling of thick woven carbon fiber reinforced epoxy by investigating the effect of the drilling parameters (speed and feed) on the final quality of the drilled holes in terms of geometrical errors, surface roughness, thermal damage (matrix burning), as well as delamination and fiber tearing. Orbital drilling was compared with conventional drilling performed with three different cooling modes, namely dry cooling, air cooling, and minimum quantity lubrication (MQL). All the drills and end mills were made of solid carbide. The material used is a woven carbon fiber epoxy composite with a thickness of 19.05 mm. It was found that MQL offered the best hole diameter error, whereas the orbital drilling outperformed the other techniques in eliminating delamination and improving surface finish. This is mainly attributed to the lower cutting forces and the enhanced cooling effect.