Journal of Materials Processing Technology 173 (2006) 345–351 CO 2 laser cutting of a carbon/carbon multi-lamelled plain-weave structure F.A. Al-Sulaiman, B.S. Yilbas ∗ , M. Ahsan ME Department, KFUPM, Dhahran 31261, Saudi Arabia Received 30 November 2005; accepted 6 December 2005 Abstract Laser cutting of composite structure consisting of 64 layers of plain-weave carbon/carbon fibers with 0 ◦ orientation is carried out. The influence of laser power on the kerf size is examined experimentally as well as analytically. The scale law analysis is introduced to predict the kerf width. The striation formation on the kerf edges is examined using a scanning electron microscopy (SEM). It is found that kerf width size increases with increasing laser power intensity. The orientation of the carbon fiber axis relative to the axis of workpiece movement during cutting has significant effect on the kerf size. Use of nitrogen as assisting gas suppresses the oxidation reactions taking place in the cutting section. This, in turn, minimizes the side ways burning and edge irregularities in the cutting section. © 2006 Elsevier B.V. All rights reserved. Keywords: Carbon/carbon fibers; Cutting; Kerf width size 1. Introduction Laser cutting of composites find wide application in industry due to improved end product quality, low cost and short pro- cessing time. In laser cutting operation, an assisting gas is used to protect the cutting section from the exothermic reactions. In this case, an inert gas emerging from the nozzle co-axially with a laser beam and impinging onto the workpiece surface is employed. Impinging gas has a shielding effect protecting the cutting section from the oxidation reactions. The end product quality is influenced significantly by the high temperature com- bustion reactions taking place in the cutting section. Moreover, when cutting thick workpieces, the assisting gas may not have enough pressure to shield the cutting edges from the combustion reactions when it reaches the bottom of the workpiece. This, in turn, results in sideways burning at the bottom edge of the work- piece. Consequently, investigation into the end product quality of laser cutting of composites is necessary. Considerable research studies are carried out to examine laser cutting process. Ivarson et al. [1] studied oxidation dynamics and striation formation in laser gas assisted cutting process. They showed that cyclic cutting events were associated with ∗ Corresponding author. Fax: +966 3 860 2949. E-mail address: bsyilbas@kfupm.edu.sa (B.S. Yilbas). the temporal behavior of oxidation reactions. Laser cutting of polymeric materials was examined by Fenoughty et al. [2]. They indicated that the laser could be effectively used in high speed cutting of thin laminates. Laser cutting by stainless steel was considered by Sheng and Joshi [3]. They formulated the cutting section profile and computed the cutting section geometry. Grum and Zulijan [4] investigated heat affected zone in laser cutting process. They indicated that the heat transfer rates in the cut- ting front influenced the quality of cut. Cenna and Mathew [5] conducted extensive review on laser cutting of fiber-reinforced plastics. They suggested that simulation of laser cutting param- eters was required not only to reduce the heat affected zone but also to improve the laser cut quality with respect to surface quality and dimensional accuracy. Laser induced damages in composite structures were studied by Uhlmann et al. [6]. They introduced analytical methods including conductivity models for anisotropic composite materials. Laser grooving of fiber- reinforced composite material was studied by Pan and Hocheng [7]. They indicated that thermal conductivity changes with the fiber orientation in the composite and it is the main factor affecting the cutting performance. Laser cutting of compos- ite materials was considered by Shanmugam et al. [8]. They compared the end product quality due to water jet and laser cutting situations. The analysis of laser cutting parameters for fiber-reinforced plastics composite materials was carried out by Cenna and Mathew [9]. They indicated that the predictions of 0924-0136/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.jmatprotec.2005.12.004