Machinability study on polyetheretherketone (PEEK) unreinforced and reinforced (GF30) for applications in structural components J. Paulo Davim a, * , Pedro Reis a ,V  ıtor Lapa a , C. Conceic ß~ ao Ant  onio b a Department of Mechanical Engineering, University of Aveiro, Campus Santiago, 3810-193 Aveiro, Portugal b Department of Mechanical Engineering, Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465 Porto, Portugal Abstract Composites such as polyetheretherketone (PEEK) used in structural components, are generally manufactured by extrusion, and for this fact, these recent materials need additional machining operations. One of the major concerns in machining is to reach a good surface roughness and dimensional precision. So the aim of this paper is the study of the cutting parameters (cutting velocity and feed rate) under machining force (F m ), specific cutting pressure (K s ), surface roughness (R a ) and International dimensional precision (IT) in PEEK unreinforced and reinforced (GF30). A plan of experiments, based on the methodology of Taguchi, was established considering turning with prefixed cutting parameters in the PEEK workpiece. The analysis of variance was preformed to investigate the cutting characteristics of PEEK using a polycrystalline diamond cutting tool. Ó 2003 Elsevier Ltd. All rights reserved. Keywords: Polyetheretherketone; Polycrystalline diamond; Turning; Taguchi methodology; Analysis of variance 1. Introduction Composite materials show advantages in structural application due to their high specific strength and directional properties and they are the most commonly used material in structural components in industry. Polyetheretherketone (PEEK) usually designed by PEEK is a recent thermoplastic with exceptional high temperature properties. The structure of this polymer produces mechanical properties similar to bronzes plus radiation resistance and low flammability. Reinforced with glass or carbon fibers, the mechanical properties are further enhanced. The 30% carbon fiber reinforced provides maximum rigidity and load bearing capability. This thermoplastic presents a melting point of 335 °C and a glass transition at 143 °C. PEEK is applied in fields of applications such as aeronautical, biomechanics and it is strongly applied in the aerospace industry, re- placing aluminium because of its superior performance at high temperature [1–3,5]. Rahman et al. [3] presents a study of machinability carbon/PEEK composites and conclude that the smooth surface finish of the workpiece is caused by some form of polymer softening action rather than determined by the tool geometry of the cutter. Chambers and Bishop [4] have investigated the ma- chining of carbon/epoxy and carbon/PEEK using dif- ferent cutting tools manufactured by cemented carbide and polycrystalline diamond (PCD) and concluded that the PCD cutting tool gave the best overall performance. Various points of view are held in order to reach high tool life ratios during application of carbides and PCD tools in the cutting of thermoplastics. However, it is unanimously reported that longer tool lives and better cutting results and surface qualities can be obtained with PCD tools [5]. 2. Experimental procedure 2.1. Means and materials Machining issues were performed under different cutting conditions, with the purpose to reach the * Corresponding author. Fax: +351-234-370953. E-mail address: pdavim@mec.ua.pt (J. Paulo Davim). 0263-8223/$ - see front matter Ó 2003 Elsevier Ltd. All rights reserved. doi:10.1016/S0263-8223(03)00085-0 Composite Structures 62 (2003) 67–73 www.elsevier.com/locate/compstruct