Contents lists available at ScienceDirect Composite Structures journal homepage: www.elsevier.com/locate/compstruct Tool wear and its effect on the surface integrity in the machining of fibre- reinforced polymer composites Weixing Xu, Liangchi Zhang ⁎ Laboratory for Precision and Nano Processing Technologies, School of Mechanical and Manufacturing Engineering, The University of New South Wales, NSW 2052, Australia ARTICLE INFO Keywords: Fibre reinforced polymer (FRP) composite Tool wear Wear mechanism Surface integrity Vibration-assisted cutting ABSTRACT This paper investigates, both experimentally and theoretically, the tool wear in the cutting of fibre-reinforced polymer composites as well as its effect on the surface integrity of the machined composites. It was found that the main mechanism is friction-caused flank wear, and that the introduction of ultrasonic vibration to the cutting tool can drastically reduce its wear rate. It was identified that tool wear not only influences cutting forces and chip formation as usually understood, but also affects significantly the material removal mechanisms and surface integrity of the machined composites. The study revealed that in a traditional cutting process, the chip formed by a fresh cutting edge is larger than that by a worn cutting edge, and that friction-induced bending fracture can occur in a machined subsurface as the tool wears out. The vibration-assisted cutting, however, reduces tool wear due to the much shortened tool-workpiece contact time in each cycle of the tool vibration. 1. Introduction Fibre-reinforced polymer (FRP) composites have high ratios of stiffness/modulus-to-weight and strength-to-weight, and are of high corrosion resistance, which are not usually possessed by single-phase materials [1,2]. As such, FRP composites have been utilized con- siderably by automotive, aerospace, marine and construction industries [3,4]. The machining of an FRP composite, however, is challenging due to the significant difference of the fibre and matrix mechanical prop- erties [5–7]. Severe tool wear takes place rapidly in the machining [8–11], and significant subsurface damage occurs in the machined FRP components, such as delamination, fibre-matrix debonding, matrix cracking, fibre pull-out, and fibre fracture [12–15]. To overcome these difficulties, numerous of non-traditional methods have also been stu- died [16–18]. For instance, water-jet cutting was found to be high cutting efficiency [19,20]. But, the problems accompanied by the pro- cess are its environmental attack and the low surface quality of the machined components, such as the matrix damage and delamination caused by the high speed impact, and the large kerf angle induced by abrasive erosion. Laser cutting has no mechanical forces, and can be easier controlled in fabricating parts with complex geometries [21,22]. However, it is only adequate to thin laminate and the significant thermal damage occurs because of the high energy laser beam. There- fore, the applications of the above methods to the fabrication of FRP composites are confronted with various limitations. Vibration-assisted machining was reported to have significantly improved cutting performances on the machining of alloys and cera- mics [23–26]. To fabricating FRPs, a technique, named as elliptic vi- bration-assisted (EVA) cutting, has also been developed by applying microscale ultrasonic elliptic vibrations onto the cutting tool [27–29]. The EVA cutting has confirmed that the high frequent tool vibration can facilitate chip removal, and produce high surface integrity. The cutting forces can be greatly reduced, and tool life can be largely extended. However, the mechanisms of the tool wear and its effect on material removal in EVA cutting of FRPs are unclear. Tool wear is a result of complicated physical, chemical and thermo- mechanical phenomena in the cutting process, and is produced by the contact and relative sliding between the cutting tool and the workpiece, and between the tool and the chips. Numerous experimental and nu- merical investigations have been carried out to understand and predict the tool wear and its effect on the machining process. Monitoring the cutting process, such as chipping, cutting forces and tool/workpiece temperature, can help analyse the tool wear/life [30,31]. However, it is hard to reveal the tool-workpiece interaction in the contact zone. Many predictive equations/theories have been proposed; nevertheless, mas- sive experiments are necessary for establishing an accurate model, which makes the process costly and time consuming [32,33]. Numerical simulation, such as the finite element (FE) modelling, is effective [34,35]. This is because an appropriate model can accurately predict the cutting process, such as tool-workpiece interaction, tool wear and https://doi.org/10.1016/j.compstruct.2018.01.018 Received 25 September 2017; Received in revised form 12 December 2017; Accepted 9 January 2018 ⁎ Corresponding author. Tel:. +61 2 9385 6078; fax: +61 2 9663 1222. E-mail addresses: weixing.xu@unsw.edu.au (W. Xu), liangchi.zhang@unsw.edu.au (L. Zhang). Composite Structures 188 (2018) 257–265 Available online 10 January 2018 0263-8223/ © 2018 Elsevier Ltd. All rights reserved. T