Table Of ContentHole-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. Details on how to seek permission, further information about the
Publisher’s permissions policies and our arrangements with organizations such as the Copyright Clearance
Center and the Copyright Licensing Agency, can be found at our website: www.elsevier.com/permissions.
This book and the individual contributions contained in it are protected under copyright by the Publisher
(other than as may be noted herein).
Notices
Knowledge and best practice in this field are constantly changing. As new research and experience
broaden our understanding, changes in research methods, professional practices, or medical treatment may
become necessary.
Practitioners and researchers must always rely on their own experience and knowledge in evaluating and
using any information, methods, compounds, or experiments described herein. In using such information
or methods they should be mindful of their own safety and the safety of others, including parties for whom
they have a professional responsibility.
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].
