Hole-making and Drilling Technology for Composites: Advantages, Limitations and Potential PDF
Preview Hole-making and Drilling Technology for Composites: Advantages, Limitations and Potential
Hole-Making and Drilling Technology for Composites Woodhead Publishing Series in Composites Science and Engineering Hole-Making and Drilling Technology for Composites Advantages, Limitations and Potential Edited by A.B. Abdullah S.M. Sapuan An imprint of Elsevier Woodhead Publishing is an imprint of Elsevier The Officers’ Mess Business Centre, Royston Road, Duxford, CB22 4QH, United Kingdom 50 Hampshire Street, 5th Floor, Cambridge, MA 02139, United States The Boulevard, Langford Lane, Kidlington, OX5 1GB, United Kingdom © 2019 Elsevier Ltd. All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. 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To the fullest extent of the law, neither the Publisher nor the authors, contributors, or editors, assume any liability for any injury and/or damage to persons or property as a matter of products liability, negligence or otherwise, or from any use or operation of any methods, products, instructions, or ideas contained in the material herein. Library of Congress Cataloging-in-Publication Data A catalog record for this book is available from the Library of Congress British Library Cataloguing-in-Publication Data A catalogue record for this book is available from the British Library ISBN: 978-0-08-102397-6 For information on all Woodhead publications visit our website at https://www.elsevier.com/books-and-journals Publisher: Matthew Deans Acquisition Editor: Gwen Jones Editorial Project Manager: Joshua Mearns Production Project Manager: Joy Christel Neumarin Honest Thangiah Cover Designer: Miles Hitchen Typeset by SPi Global, India List of contributors A.B. Abdullah School of Mechanical Engineering, Universiti Sains Malaysia, Nibong Tebal, Malaysia J. Abdullah School of Mechanical Engineering, Engineering Campus, Universiti Sains Malaysia, Nibong Tebal, Malaysia M.S. Abdullah School of Mechanical Engineering, Universiti Sains Malaysia, Nibong Tebal, Malaysia H.Y. Chan School of Mechanical Engineering, Universiti Sains Malaysia, Nibong Tebal, Malaysia K. Debnath Department of Mechanical Engineering, National Institute of Technology Meghalaya, Shillong, India M.H. Hassan School of Mechanical Engineering, Engineering Campus, Universiti Sains Malaysia, Nibong Tebal, Malaysia N. Ishak School of Mechanical Engineering, Universiti Sains Malaysia, Nibong Tebal, Malaysia S. Kachhap National Institute of Technology Patna, Patna, India A. Krishnamoorthy School of Mechanical Engineering, Sathyabama Institute of Science and Technology, Chennai, India R. Kumar Indian Institute of Technology Roorkee, Roorkee, India J. Lilly Mercy School of Mechanical Engineering, Sathyabama Institute of Science and Technology, Chennai, India S. Norisam School of Mechanical Engineering, Universiti Sains Malaysia, Nibong Tebal, Malaysia S. Prakash School of Mechanical Engineering, Sathyabama Institute of Science and Technology, Chennai, India x List of contributors S. Ramesh Department of Mechanical Engineering, KCG College of Technology, Chennai, India Z. Samad School of Mechanical Engineering, Universiti Sains Malaysia, Nibong Tebal, Malaysia S.M. Sapuan Department of Mechanical and Manufacturing Engineering, Universiti Putra Malaysia, Serdang, Malaysia N.A. Sheikh Department of Mechanical Engineering, International Islamic University, Islamabad, Pakistan A. Singh National Institute of Technology Patna, Patna, India K.F. Tamrin Department of Mechanical and Manufacturing Engineering, Universiti Malaysia Sarawak (UNIMAS), Kota Samarahan, Malaysia P.V. Siva Teja Department of Mechanical Engineering, Dhanekula Institute of Engineering and Technology, Vijayawada, India M.S.M. Zain School of Mechanical Engineering, Universiti Sains Malaysia, Nibong Tebal, Malaysia Review of hole-making technology 1 for composites M.S. Abdullah, A.B. Abdullah, Z. Samad School of Mechanical Engineering, Universiti Sains Malaysia, Nibong Tebal, Malaysia 1.1 Introduction Composite material can be used for a great number of applications in modern structures because of its high modulus, strength, light weight, durability, corrosion resistance, design flexibility, and so on. However, due its nonhomogeneity and high- abrasivity, machining composite material is a major problem [1–4]. In many man- ufacturing industries, conventional machining processes such as drilling remain the primary method of hole-making in composites. Generally in the aviation manufacturing industry, most aircraft structures, such as stabilizers, wings and fuselage, consist of a great number of varying types of holes (e.g., round, counterboring, countersinking, honing, reaming, lapping, sanding, etc.) with different diameters, depths and surface finishes [1]. Commonly these aircraft structures require assembly and therefore a number of holes need to be drilled. Most of the joints involved in the assembly are mechanical joints, such as bolted connections, rivet connections and pin connections, therefore mechanical joint efficiency is highly dependent on the quality of the holes [5]. With advances in processing techniques, the development of new hole-making technology, which is now integrated with the digital computer, has improved the efficiency and productivity of hole-making in terms of cutting time and hole quality. This chapter reviews the existing technologies in hole-making for composite pan- els, and the advantages and limitations of these technologies. The chapter begins with a brief introduction to hole-making technology, followed by a discussion of machining and nonmachining technologies. 1.2 Hole-making for composite laminates Hole-making technology can be divided into machining and nonmachining technol- ogy. The machining technology can be further divided into traditional and nontradi- tional machining. Drilling and milling are the traditional machining methods used for composites. The difference between the two methods is the approaching mechanism; for example, in drilling, the drill bit is rotated and fed the stationary workpiece and the volume of the workpiece is removed to produce a circular hole. Since drilling is a primary method of making holes [6], we will focus on this first. Many types of drilling technologies have evolved to meet the demand for composite materials. Hole-Making and Drilling Technology for Composites. https://doi.org/10.1016/B978-0-08-102397-6.00001-5 © 2019 Elsevier Ltd. All rights reserved. 2 Hole-Making and Drilling Technology for Composites Hole-Making Technology Machining Nonmachining Traditional Nontraditional Punching machining machining Milling Drilling AWJM EDM Laser Fig. 1.1 Technologies in hole-making. In nontraditional machining, methods such as Wire EDM, laser and Abrasive Water Jet Machining (AWJM) are being used. In nonmachining, to date only punching tech- nology is being used for hole-making in composite materials. Fig. 1.1 summarizes the hole-making technologies that have been developed to date. 1.2.1 Machining Machining (i.e., drilling) remains the preferred method of hole-making in composite materials across industries, although it is obvious that drilling in composite mate- rial is not the same as drilling in metallic material [7]. Composite material is very abrasive and since the mechanical drilling operation involves direct contact between tool and workpiece, the tool suffers extreme wear and creates a great amount of heat, which induces residual stress that leads to degradation of both tool life and the quality of workpiece [2]. The mechanical drilling operation can be divided into five types: conventional drilling, high-speed drilling (HSD), grinding drilling, vibration-assisted twist drilling (VATD), and orbital drilling (OD). As an alternative to drilling, punching also shows potential for producing holes in composites. 1.2.1.1 Conventional drilling Most drilling operations use twist drill bits and other special drill bits (step drill bit, center drill bit and dagger drill bit) as the cutting tools. However, the twist drill bit is the most widely used [8]. In conventional drilling, multiple stages of drilling need to be executed before the hole reaches its specified size or diameter. If the diameter of the hole is relatively large, a pilot hole with a small diameter may have to be drilled first and then enlarged to the final size with a larger tool [9]. This is to avoid a concentration Review of hole-making technology for composites 3 of high stress at the hole boundary on the workpiece material and to keep the damage to a minimum [10, 11]. The research on conventional drilling in composite laminates includes a number of experiments studying input variables, such as drilling parame- ters (spindle speed and feed), drill bit geometry, drill bit material, type of composite material and diameter size, and output variables, such as hole quality (delamination, surface roughness and roundness), thrust force and bearing strength of the hole [12]. 1.2.1.2 High-speed drilling In a single aircraft there are thousands of holes that need to be drilled, mostly for mechanical fasteners like rivets and bolts [13]. The continuous development of cut- ting tools (material and geometry) has reduced cutting time and improved produc- tivity in hole-making [12]. There are several basic requirements to take into account in HSD, namely, concentricity (related to tool material behavior when operating at different cutting speeds), tool material, coating material, flute geometry and coolant delivery [14]. HSD technology has been widely studied and employed in many ar- eas of composite drilling. It is supposed to produce less delamination damage in a short time with single-shot drilling [15]. Similar to conventional drilling, HSD is the most promising drilling operation that leads to better performance and improves the quality of the hole. Unlike other drilling operations, HSD is carried out at very high spindle speed and results in reduction of delamination [16, 17]. However, increasing the speed literally increases the power consumption of the machine operation as well as the tooling cost due to excessive tool wear, and causes the total machining cost to become very expensive [18]. As the speed goes higher, usually 5–10 times more than conventional drilling, the rate of temperature increases making the composite lam- inates prone to thermal damage [19]. At the higher temperature, which exceeds the epoxy melting temperature, the heat from the friction contact between the tool and the workpiece softens the epoxy matrix making it evaporate, known as matrix burnout, and causes only the fiber to be left. This results in interlaminar delamination [20]. Not only that, it is also shortens the tool life span. Because the temperature signifi- cantly affects the hole quality and tools, coolant is used to combat temperature issues. Nowadays, most applications of HSD incorporate a high-pressure coolant flow system to avoid catastrophic thermal damage to the workpiece instead of removing chips. Yet the aerospace manufacturing industry is moving toward HSD under dry conditions with optimum cutting parameters due to economic and environmental reasons [21]. Dry drilling conditions might be a better choice for thin composite laminates because the short engagement time may limit heat buildup. 1.2.1.3 Grinding drilling Grinding drilling, also known as core drilling, is one of the drilling operations that best reduces delamination damage. Grinding drilling focuses on the periphery of the hole. There is no chisel edge acting on the predrilling like with a normal drill bit since the center of the drill bit is hollow. The absence of chisel edge reduces thrust force and hence delamination [22, 23]. It was found that increasing the number of teeth of the cutting tool can reduce the cutting force. The easiest way to achieve an unlimited 4 Hole-Making and Drilling Technology for Composites number of teeth is by coating the cutting tool with a certain grit size of material. Tsai and Hocheng [24] proposed coating it with diamond material. Diamond material has an extremely high thermal conductivity, which can remove heat from the cutting edge and extend tool life. The research suggests that diamond material is preferable because it provides high abrasive wear resistance. The different grain size of coated material also influences the surface quality of the hole and the heat distribution over the matrix of the hole boundary. The result of the investigation shows that increasing the grain size results in lower thermal load and allows the heat to dissipate more efficiently. However, it was shown that finer grains result in better surface quality of the hole [25]. There are different types of geometry for core drill bits and each of them serves different purposes. Fig. 1.2 shows different designs of core drill bits. An improvement of the cutting mechanism in micro-core drilling has been made by introducing a shear mechanism at the cutting edge of the core drills using novel tool design (defined cutting edge using polycrystalline diamond (PCD)). The conventional core drills (randomly distributed micro grains) use an electroplated diamond abrasive micro-core drill that produces an abrasive/rubbing action that results in random cutting edge geometry (negative rake angle, protrusions, densities). This deficiency of random cutting edge geometry is not a good solution for machining parameters. According to the research, a novel micro-core drill reduces drilling force and temperature by 36% and 11%, respectively, compared with conventional core drills. In addition to these findings, the evaluation of the shearing action of the novel micro-core drill found it produces holes with superior edge definition and surface quality [26]. Fig. 1.3 shows a conceptual image of a laser-generated PCD core drill. 1.2.1.4 Vibration-assisted twist drilling VATD is another branch of vibration cutting that uses vibration in the drilling process. There are three directional modes of vibration that occur in the drilling process, namely, axial, lateral and torsional. The drill moves in these three directions when it is run on the surface of the workpiece. When it comes to composite laminates, the typical dam- age that has been recognized as the major damage when drilling is d elamination [27]. Fig. 1.2 Different design types of core drill bits (A) abrasive tools [25] and (B) hollow grinding [12].
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