Fibre-reinforced polymer (FRP) composites are preferred over single phase materials for various application due to their unique properties such as high strength to weight ratio and corrosion resistance. Unfortunately, machining of FRP materials has become more difficult and challenging due to the significant difference between the mechanical properties of the matrix and fibre. Thus, it causes rapid and severe tool wear and brings about significant surface and subsurface damage of the machined parts. For example, a machined component may have cracked matrix, fractured fibre, and delaminated parts.
Many non-traditional methods have been developed to overcome these difficulties. However, the applications of conventional traditional methods like water-jet cutting and laser cutting are confronted by several limitations. The former is environmentally unfriendly and produces poor quality surfaces due to the high speed while the latter is associated with high laser been energy produced by thermal damages. Recently, elliptic vibration-assisted (EVA) cutting has been developed for fabricating FRP. It works on the principle of application of ultrasonic vibrations on the cutting tool for effective removal of chips, longer tool life, and good surface finish. Despite the improvements, tool wear mechanism and their effects on material removal, machining process, and surface integrity have not been fully explored.
Dr. Weixing Xu and Professor Liangchi Zhang at The University of New South Wales (School of Mechanical and Manufacturing Engineering) investigated the effects of tool wear mechanism in the fabrication of FRP composites on chip formation, material removal, cutting forces and machined surface integrity. They performed both theoretical and experimental studies on the traditional and EVA cutting techniques using a 3D microstructure-based finite element model for simulating the material removal processes. Their research work is now published in journal, Composite Structures.
The authors found out that friction-induced flank wear was the most dominant tool wear mechanism in both EVA and traditional methods for FRP composites fabrication. However, it was significantly minimized when ultrasonic vibrations were introduced to the cutting tool. Consequently, the effects of tool wear were observed in cutting forces, chip formation, materials removal mechanism and surface finish of the machined composites, in contrast to the normal assumption that it mainly influences chip removal and cutting forces.
Based on the experimental results, the accuracy of the novel model in assessing the effects of tool wear mechanisms can be ascertained. For example, in most traditional cutting methods, fresh cutting edges form larger chips than worn out edges. Also, bending fractures on the machined surfaces induced by friction results in poor surface quality. Nevertheless, the vibration-assisted machining technique has proved to be a potential solution. The induced vibrations reduced tool-workpiece contact time which was vital for reducing tool wear during machining processes.
The study by Weixing Xu and Liangchi Zhang will pave the way for the development of more advanced and effective methods with limited tool wear for the fabrication of FRP composites materials with the desired surface finish integrity in the future.
Xu, W., & Zhang, L. (2018). Tool wear and its effect on the surface integrity in the machining of fibre-reinforced polymer composites. Composite Structures, 188, 257-265.Go To Composite Structures