Prepared a Glass Fiber Reinforced Plastic board and determined the optimal drilling conditions that would cause the least delamination using Design of Experiments.

1. d
ABSTRACT
The main objective of the project is to prepare a GFRP - Glass Fiber
Reinforced Plastic (composite material) using glass fiber woven with a
binder called bisphenol as a matrix, with the help of a Mechanical Press. The
next step is to perform drilling operation on the composite using different
drill bit materials such as High Speed Steel, Tungsten Carbide and Poly-
Crystalline Diamond. The parameters such as feed of the operation and the
spindle speed of the machine are varied and the test is undertaken.
Simultaneously a dynamometer is attached to the drilling machine to check
the torque and thrust force. The drilled holes are then subjected to a device
called Profile Projector to study the delamination factor of the holes. The last
test is called Flexure test (which is a bending test) in which the strength of
the specimen is tested using the UTM - Universal Testing Machine. After
obtaining all the data, the values are tabulated and graphs are plotted
accordingly.
18

2. APPENDIX 3
TABLE OF CONTENTS
CHAPTER NO. TITLE PAGE NO.
ABSTRACT iii
LIST OF TABLE
LIST OF FIGURES
LIST OF SYMBOLS
xvi
xviii
xxvii
1. INTRODUCTION
1
1.1 GENERAL 1
1.2 . . . . . . . . . . . . . 2
1.2.1 General 5
1.2.2 . . . . . . . . . . . 12
1.2.2.1 General 19
1.2.2.2 . . . . . . . . . . 25
1.2.2.3 . . . . . . . . . . 29
1.2.3 . . . . . . . . . . . . 30
1.3 . . . . . . . . . . .. . . . . . . 45
1.4 . . . . . . . . . . . . . . . . . . 58
2. LITERATURE REVIEW
69
2.1 GENERAL
75
2.2 . . . . . . . . . . 99
2.2 ……………. 100
18

3. 1. INTRODUCTION
1.1. INTRODUCTION TO COMPOSITE MATERIALS
Composite materials or Composites are materials made from two or
more constituent materials with significantly different physical or chemical
properties, that when combined, produce a material with characteristics
different from the individual components. The individual components
remain separate and distinct within the finished structure. Composites, unlike
metals are not homogeneous, anisotropic and consist of both unique resins
and fibers. Composites are normally manufactured in near net shape
processes but they require secondary machining operations for assembly.
Hence drilling, cutting and machining composites in any post processing
operations to get to final shape or configuration is different from other
materials.
1.2. HISTORY OF COMPOSITE MATERIALS
The earliest man-made composite materials were straw and mud
combined to form bricks for building construction. This ancient brick-
making process was documented by Egyptian tomb paintings. Wattle and
daub is one of the oldest man-made composite materials, over 6000 years
old. Concrete is also a composite material and is used more than any other
man-made material in the world. As of 2006, about 7.5 billion cubic meters
of concrete are made each year—more than one cubic meter for every person
on Earth.
18

4. 1.3. CLASSIFICATION OF COMPOSITE MATERIALS
Composite materials are usually classified by the type of
reinforcement they use. This reinforcement is embedded into a matrix that
holds it together. The reinforcement is used to strengthen the composite. For
example, in a mud brick, the matrix is the mud and the reinforcement is the
straw. Common composite types include random-fiber or short-fiber
reinforcement, continuous-fiber or long-fiber reinforcement, particulate
reinforcement, flake reinforcement, and filler reinforcement.
1.3.1. METAL MATRIX COMPOSITES
A metal matrix composite is a composite material with at least two
constituent parts, one being a metal. The other material may be a different
metal or another metal, such as ceramic or organic compound. When at least
three materials are present, it is called a hybrid composite. A metal matrix
composite is complementary to a cermet. They are made by dispersing a
reinforcing material into a metal matrix. The reinforcement surface can be
coated to prevent a chemical reaction with the matrix.
1.3.2. CERAMIC MATRIX COMPOSITES
Ceramic Matrix Composites are subgroup of composite materials as
well as a subgroup of technical ceramics. They consist of ceramic fibers
embedded in a ceramic matrix, thus forming a ceramic fiber reinforced
ceramic material. The matrix and fibers can consist of any ceramic material,
whereby carbon and carbon fibers can also be considered a ceramic material.
1.3.3. POLYMER MATRIX COMPOSITES
18

5. Polymer Matrix Composite is the material consisting of a polymer
(resin) matrix combined with a fibrous reinforcing dispersed phase. They are
very popular due to their low cost and simple fabrication methods. Use of
non-reinforced polymers as structure materials is limited by low level of
their mechanical properties. The reinforced fibers may be arranged in
unidirectional fibers or roving or chopped strands. They are used for
manufacturing secondary load bearing aerospace structures, boat bodies,
canoes, kayaks, automotive parts, radio controlled vehicles, sport goods,
bullet proof vests and other armor parts, brake and clutch linings
1.4. FIBER REINFORCED COMPOSITES
A fiber-reinforced composite (FRC) is a composite building material
that consists of three components: (i) the fiber as the discontinuous or
dispersed phase, (ii) the matrix as the continuous phase, and (iii) the fine
interphase region, also known as the interface. This is a type of advanced
composite group, which makes use of rice husk, rice hull, and plastic as
ingredients. This technology involves a method of refining, blending, and
compounding natural fibers from cellulosic waste streams to form a high-
strength fiber composite material in a polymer matrix. The designated waste
or base raw materials used in this instance are those of waste thermoplastics
and various categories of cellulosic waste including rice husk and saw dust.
FRC is high-performance fiber composite achieved and made possible
by cross-linking cellulosic fiber molecules with resins in the FRC material
matrix through a proprietary molecular re-engineering process, yielding a
product of exceptional structural properties.
Through this feat of molecular re-engineering selected physical and
structural properties of wood are successfully cloned and vested in the FRC
product, in addition to other critical attributes to yield performance
properties superior to contemporary wood.
18

6. This material, unlike other composites, can be recycled up to 20 times,
allowing scrap FRC to be reused again and again.
The failure mechanisms in FRC materials include delamination, intra-
laminar matrix cracking, longitudinal matrix splitting, fiber/matrix de-
bonding, fiber pull-out, and fiber fracture.
1.4.1. CARBON FIBER REINFORCED PLASTIC
Carbon fiber reinforced plastic is an extremely strong and light fiber-
reinforced polymer which contains carbon fibers. The polymer is most often
epoxy, but other polymers, such as polyester, vinyl ester or nylon, are
sometimes used. The composite may contain other fibers, such as aramid e.g.
Kevlar, Twaron, aluminum, or glass fibers, as well as carbon fiber. The
strongest and most expensive of these additives, carbon nanotubes, are
contained in some primarily polymer baseball bats, car parts and even golf
clubs where economically viable. Carbon fiber is commonly used in the
transportation industry; normally in cars, boats and trains
Although carbon fiber can be relatively expensive, it has many
applications in aerospace and automotive fields, such as Formula One. The
compound is also used in sailboats, rowing shells, modern bicycles, and
motorcycles, where its high strength-to-weight ratio and very good rigidity is
of importance. Improved manufacturing techniques are reducing the costs
and time to manufacture, making it increasingly common in small consumer
goods as well, such as certain ThinkPad’s since the 600 series, tripods,
fishing rods, hockey sticks, paintball equipment, archery equipment, tent
poles, racquet frames, stringed instrument bodies, drum shells, golf clubs,
helmets used as a paragliding accessory and pool/billiards/snooker cues.
1.4.2. GLASS FIBER REINFORCED PLASTIC
18

7. Glass Fiber Reinforced Plastic is a fiber reinforced polymer made of a
plastic matrix reinforced by fine fibers of glass.
Fiberglass is a lightweight, extremely strong, and robust material.
Although strength properties are somewhat lower than carbon fiber and it is
less stiff, the material is typically far less brittle, and the raw materials are
much less expensive. Its bulk strength and weight properties are also very
favorable when compared to metals, and it can be easily formed using
molding processes.
The plastic matrix may be epoxy, a thermosetting plastic (most often
polyester or vinyl ester) or thermoplastic. Common uses of fiberglass include
high performance aircrafts (gliders), boats, automobiles, baths, hot tubs,
water tanks, roofing, pipes, cladding, casts, Surfboards, and external door
skins. Fiberglass is an immensely versatile material which combines its light
weight with an inherent strength to provide a weather resistant finish, with a
variety of surface textures.
The development of fiber reinforced plastic for commercial use was
being extensively researched in the 1930s. It was particularly of interest to
the aviation industry. Mass production of glass strands was accidentally
discovered in 1932 when a researcher at the Owens-Illinois directed a jet of
compressed air at a stream of molten glass and produced fibers. Owens
joined up with the Corning Company in 1935 and the method was adapted
by Owens Corning to produce its patented "Fiberglas". A suitable resin for
combining the "Fiberglas" with a plastic was developed in 1936 by du Pont.
The first ancestor of modern polyester resins is Cyanamid's of 1942.
Peroxide curing systems were used by then.
During World War II it was developed as a replacement for the
molded plywood used in aircraft radomes (fiberglass being transparent to
microwaves). Its first main civilian application was for building of boats and
sports car bodies, where it gained acceptance in the 1950s. Its use has
18

8. broadened to the automotive and sport equipment sectors as well as aircraft,
although its use there is now partly being taken over by carbon fiber which
weighs less per given volume and is stronger both by volume and by weight.
Fiberglass uses also include hot tubs, pipes for drinking water and sewers,
office plant display containers and flat roof systems.
Fiberglas is also used in the telecommunications industry for
shrouding the visual appearance of antennas, due to its RF permeability and
low signal attenuation properties. It may also be used to shroud the visual
appearance of other equipment where no signal permeability is required,
such as equipment cabinets and steel support structures, due to the ease with
which it can be molded, manufactured and painted to custom designs, to
blend in with existing structures or brickwork. Other uses include sheet form
made electrical insulators and other structural components commonly found
in the power industries.
Because of fiberglass's light weight and durability, it is often used in
protective equipment, such as helmets. Many sports utilize fiberglass
protective gear, such as modern goaltender masks and newer baseball
catcher's masks.
1.5. TYPES OF REINFORCING GLASS FIBERS
Glass-reinforced composites gain their strength from thin glass fibers
set within their resin matrix. These strong, stiff fibers carry the load while
the resin matrix spreads the load imposed on the composites. A wide variety
of properties can be achieved by selecting the proper glass type, filament
diameter, sizing chemistry and fiber forms (e.g., roving, fabric, etc.).
Fibers made primarily from silica-based-glass containing several
metal oxides offer excellent thermal and impact resistance, high tensile
strength, good chemical resistance and outstanding insulating properties.
18

9. Fibers can also be produced from carbon, boron and aramid. While
these materials offer high tensile strength and are stiffer than glass, they cost
significantly more. For that reason, carbon, boron and aramid are typically
reserved for high-tech application demanding exceptional fiber properties for
which the customer is willing to pay a premium. An alternative is to use
hybrid fiber (combining an expensive fiber with glass fiber), which improves
overall cost yet cost less than using premium fibers alone.
1.5.1. E-GLASS FIBER
E-glass is a popular fiber made primarily of silica oxide, along with
oxides of aluminum, boron, calcium and other compounds. Named for its
good electrical resistance, E-glass is strong yet low in cost, and accounts for
over 90% of all glass fibers reinforcements, especially in aircraft radomes,
antennae and application where radio-signal transparency is desired. E-glass
is also used extensively in computer circuit boards where stiffness and
electrical resistance are required.
In addition to E-glass, several other types of glass can be used for
composite reinforcement. The most popular are high strength glass and
corrosion resistant glass.
1.5.2. HIGH STRENGTH GLASS FIBER
High- strength, carbon or other advanced fibers are used in application
requiring greater strength and lower weight. High-strength glass is generally
known as S-type in the United States, R-glass Europe and T-glass in Japan.
S-glass was originally developed for military application in the 1960’s and a
lower cost version, S-2 glass, was developed for commercial applications.
High- strength glass has appreciably higher amounts of silica oxide,
aluminum oxide and magnesium oxide than E-glass. S-2 glass is
approximately 40-70% stronger than E-glass.
18

10. 1.5.3. CORROSION RESISTANT GLASS FIBER
When glass fibers are exposed to water, they become eroded to
leaching. To protect against water erosion, a moisture- resistant coating such
as silane compound is coated on to the fibers during composite formation
provides additional protection. The result is corrosion-resistant glass (called
C-glass)
Some types of glasses perform better than others when exposed to
acids or bases. Both C-glass and S-2 glass offer good corrosion resistance
when exposed to hydrochloric or sulfuric acid. E-glass and S-2 glass resist
sodium carbonate solution better than C-glass.
1.6. MACHINING OF GLASS FIBER REINFORCED COMPOSITES
Machining of GFRPs (Glass fiber reinforced plastics) differs
significantly from machining of conventional metal and alloys. In the former
the material behaviors depend on diverse fiber and matrix properties, fiber
orientation and relative volume of matrix and the fibers. The tool
continuously encounters alternate matrix and fiber material whose response
to machining can vary greatly. For example in a glass/epoxy composite the
tool encounters a low temperature soft epoxy matrix and brittle glass fibers.
Conventional machining of GFRPs (Glass fiber reinforced plastics) is
difficult due to the presence of comparatively high volume fraction of hard
fibers in the matrix, their orientation and diverse fiber and matrix properties.
The earliest of the literature in FRP (Fiber reinforced plastics)
machining was by Wason. He was of the opinion that the best way to saw
FRP plates was by diamond tipped circular saw with large amount of cutting
fluid. The speed should be high and feed rate slow. Mackrin also stated that
diamond wheel may be used for cutting GFRP. The most significant work in
18

11. the machining of GFRP is by Konig, Wulf, Grab and Willerscheid. They
have identified that the major problems associated with different FRPs
namely glass, carbon and Kevlar reinforced ones. They found that type of
fiber used for reinforcement is the major factor which determines the
machinability of the composite.
1.6.1. DRILLING OF FRP
Drilling is far the most important item of machining and it is very
important because it is often a final operation during assembly. Any defects
lead to rejection of the part. In the aircraft industry for example drilling
associated delamination accounts for 60% of all part rejections during the
final assemble of an aircraft. The economic impact of this is significant
considering the value associated with the part when it reaches the assemble
stage.
2. LITERATURE REVIEW
Glass Fiber Reinforced Plastic refers to a plastic which has been
reinforced with glass fibers. It uses a plastic matrix, which may be an epoxy
resin, a thermosetting or thermoplastic resin to bind the glass fiber together
and improve its mechanical properties. It is far less brittle than carbon fiber
18

12. reinforced plastic and less expensive than metals. Its bulk strength and
weight properties are very favorable compared to metals. Morton [1]
discusses about GFRP, how it is fabricated, the advantages of using GFRP
and design considerations to be considered in using equipment are made
from them in his article. Also he discusses the different resins that can be
used for its fabrication. He discusses the thermosetting resins (epoxies,
polyesters, vinyl esters). He discusses the hand layup method of fabrication
that is being used for this project to apply resin on thin glass fiber mats
stacked on top of another till desired dimensions are achieved. This is the
most basic of fabrication techniques. It is also referred to as ‘contact
molding’. The author continues to mention about the strength characteristics
of GFRP and its various properties that make it preferable in various fields
of application like corrosion resistance, weight advantages, high strength,
inexpensiveness and flexibility. A lot of research has been conducted to
achieve efficient drilling of composites materials. Drilling tests were carried
out on GFRPC composites in order to verify the effect of machining
parameters on cut quality. Experiment results showed that, the quality index
was strongly affected by cutting speed to feed ratio (V/s). In particular large
damage zones were observed when low V/s values were adopted. However
beyond a limiting value, extend of the damage is no longer influenced by
V /s. A ratio of V/s greater than 150 was suggested in order to obtain best cut
quality in drilling of GFRPC.
The type of drill used has an important influence on the various
process parameters. Here the influence of three drill types of same diameter
is studied. Davim et al. [2] gives details about the study on a straight flute
jobber length type drill and a twist type drill used for composite drilling. The
drills used are of the same diameter (here 5 mm) and varies only in their
type. The “jobber length” drill has a 118 degree point angle. Important
results obtained showed that the Twist drill presents less specific cutting
18

13. pressure and thrust force than the Jobber length drill considering the same
cutting parameters (cutting speed and feed rater). The Twist drill produces
less damage on the GFRP composites than the Jobber length drill as well as
has better performances.
Delamination is the cracking of the composites laminate due to the
contact with the drill bit. It is a major problem associated with drilling fiber-
reinforced composite material that, in addition to reducing the structural
integrity of the material, also results in poor assembly tolerance and has the
potential for long performance deterioration. In the machining composites
parts, a finish comparable to metals cannot be achieved because of
inhomogeneity and anisotropy of materials. Tsao et al. [3] mentions that
induced delamination can occur at both entrance and exit planes of work
piece. A rapid increase in feed rate at the end of drilling will cause cracking
around the exit edge of the hole. Tsao et al. [3] mentions that delamination in
drilling have been correlated to thrust force during exit of the drill. A
significant portion of the thrust is due to the chisel edge. Increasing the
chisel edge length, results in the rise of thrust force. The candle stick drill
and saw drill have a smaller center than the twist drill; thus, a smaller extent
of the last laminate is subjected to a bending force. Experiments indicate that
there exists s critical thrust force below which no delamination occurs.
Above that level, matrix cracks are generated by interface delamination
growing from the crack tips.
Davim and Reis et al. [2] mentions that the hole surface quality
(surface roughness and dimensional precision) is strongly dependent on
cutting parameters, tool geometry and cutting forces (thrust force and
torque). The author studied the work developed by other authors drew the
conclusion from drilling of glass fiber reinforced plastics manufactured by
hand layup method that the specific cutting pressure decreases with the feed
rate and slightly with the cutting speed, and the thrust force increases with
18

14. the feed rate. The feed rate is the cutting parameters which has greater
influence on specific cutting pressure. The damage increases with both
cutting parameters, which means that the composite damage is lesser for
higher cutting speed and for lower feed.
JOURNALS REFERRED
“Effects of special drill bits on drilling-induced delamination of
composite materials”
Introduction
Drilling is the most frequently employed operation of secondary
machining for fiber-reinforced materials owing to the need for joining
structures. Delamination is among the serious concerns during drilling.
Practical experience proves the advantage of using such special drills as saw
drill, candle stick drill, core drill and step drill. The experimental
investigation described in this paper by Hocheng, Tsao et al. [3] examines
the theoretical predictions of critical thrust force at the onset of delamination,
and compares the effects of these different drill bits. The results confirm the
analytical findings and are consistent with the industrial experience.
Ultrasonic scanning is used to evaluate the extent of drilling-induced
delamination. The advantage of these special drills is illustrated
mathematically as well as experimentally, that their thrust force is distributed
toward the drill periphery instead of being concentrated at the center. The
allowable feed rate without causing delamination is also increased. The
analysis can be extended to examine the effects of other future innovative
drill bits.
Results
The experimental results of the drilling-induced delamination while
using special drills have been presented. The results are compared with the
theoretical predictions of critical thrust force at the onset of delamination,
18

15. and are consistent with the industrial experience as well. Due to the different
drill geometry, these drills show different levels of the drilling thrust force
which varies with the feed rate. The advantage of these special drill bits lies
in their higher threshold feed rate at the onset of delamination. Among the
five drills, the core drill offers the highest critical feed rate followed by the
candle stick drill, saw drill and step drill, while the traditional twist drill
allows for the lowest feed rate. In other words, the core drill, candle stick
drill, saw drill and step drill can be operated at larger feed rate or in shorter
cycle time without delamination damage compared to the twist drill.
“The effect of vibratory drilling on hole quality in polymeric
composites”:-
Introduction
Arul et. al. [4] mentions that anisotropy of fiber-reinforced plastics
(FRP) affects the chip formation and thrust force during drilling.
Delamination is recognized as one of the major causes of damage during
drilling of fiber reinforced plastics, which not only reduces the structural
integrity, but also has the potential for long-term performance deterioration.
It is difficult to produce good quality holes with high efficiency by
conventional drilling method. This research concerning drilling of polymeric
composites aims to establish a technology that would ensure minimum
defects and longer tool life. Specifically, the authors Arul, Vijayraghavan
Malhotra et al. conceived a new drilling method that imparts a low-
frequency, high amplitude vibration to the work piece in the feed direction
during drilling. Using high-speed steel (HSS) drill, a series of vibratory
drilling and conventional drilling experiments were conducted on glass fiber-
reinforced plastics composites to assess thrust force, flank wear and
delamination factor. In addition, the process-status during vibratory drilling
was also assessed by monitoring acoustic emission from the work piece.
18

16. From the drilling experiments, it was found that vibratory drilling method is
a promising machining technique that uses the regeneration effect to produce
axial chatter, facilitating chip breaking and reduction in thrust force.
Results
The results of vibratory drilling studies on woven glass fabric
composite using high speed steel drill were presented. Some of the
observations are:-
• The thrust in vibration drilling is smaller than that in the conventional
drilling, which indicates that the vibration drilling method is suitable
for defect constrained drilling of polymeric composites.
• The trend of variation of thrust, flank wear, delamination factor, AE
power and AE rms with number of holes for conventional and
vibration drilling are similar.
• Good correlation between thrust and delamination factor indicates that
on-line monitoring of thrust can facilitate defect-constrained drilling.
In conventional drilling, increase of thrust and delamination factor around
30 holes, indicates that 30 is the limiting number of holes to be drilled and in
vibratory drilling 50 is the limiting number of holes to be drilled for defect
tolerance.
“Fiber reinforced composites in aircraft construction”
Introduction
Fibrous composites have found applications in aircraft from the first
flight of the Wright Brothers' Flyer 1, in North Carolina on December 17,
1903, to the plethora of uses now enjoyed by them on both military and civil
aircrafts, in addition to more exotic applications on unmanned aerial vehicles
(UAVs), space launchers and satellites. Their growing use has risen from
18

17. their high specific strength and stiffness, when compared to the more
conventional materials, and the ability to shape and tailor their structure to
produce more aerodynamically efficient structural configurations. In this
paper, Soutis et al. [5] gives a review of recent advances using composites
in modern aircraft construction is presented and it is argued that fiber
reinforced polymers, especially carbon fiber reinforced plastics (CFRP) can
and will in the future contribute more than 50% of the structural mass of an
aircraft. However, affordability is the key to survival in aerospace
manufacturing, whether civil or military, and therefore effort should be
devoted to analysis and computational simulation of the manufacturing and
assembly process as well as the simulation of the performance of the
structure, since they are intimately connected.
Results
The application of carbon fiber has developed from small-scale
technology demonstrators in the 1970s to large structures today. From being
a very expensive exotic material when first developed relatively few years
ago, the price of carbon fiber has dropped to less than £10/kg, which has
increased applications such that the aerospace market accounts for only 20%
of all production. The main advantages provided by CFRP include mass and
part reduction, complex shape manufacture, reduced scrap, improved fatigue
life, design optimization and generally improved corrosion resistance. The
main challenges restricting their use are material and processing costs,
impact damage and damage tolerance, repair and inspection, dimensional
tolerance, size effects on strength and conservatism associated with
uncertainties about relatively new and sometimes variable materials.
Carbon fiber composites are here to stay in terms of future aircraft
construction, since significant weight savings can be achieved. For
secondary structures, weight savings approaching 40% are feasible by using
composites instead of light metal alloys, while for primary structures, such
18

18. as wings and fuselages, 20% is more realistic. These figures can always
improve but innovation is the key to making composites more affordable.
“Influence of cutting parameters on thrust force and torque in drilling
of E-glass/polyester composites”
Introduction
Reinforced plastics find wide application in all manufacturing fields
due to their distinct properties such as low weight, high strength and
stiffness. Although components are produced to near net shape, machining is
often needed to fulfill the requirements related to tolerances of assembly
needs. Among all the machining processes, drilling is the most indispensable
method for the fabrication of products with composite panels. The
performance of these products is mainly dependent on surface quality and
dimensional accuracy of the drilled hole. Murthy et al [6] studies the effect
of process parameters such as spindle feed, drill diameter and point angle
and material thickness on thrust force and torque generated during drilling of
GFRP composite material using solid carbide drill bit. Full factorial Design
of Experiments (DoE) has been adopted and the results indicate that spindle
speed is the main contributing factor for variation in thrust force and drill
diameter is the main contributing factor for variation for variation in torque.
The optimum combination of process parameters settings has been found out
using the integration on Taguchi method and Response Surface
Methodology.
Results
Thrust force is significantly influenced by spindle speed and they are
inversely proportional. Hence while working on glass fiber reinforced
composites by using solid carbide drills, higher spindle speed are
recommended for process parameter ranges under consideration. Cutting
torque is significantly influenced by drill diameter. Higher the drill diameter,
18

19. larger the thrust force and cutting torque required. Thrust force increases
whereas cutting force decreases with the increase in drill point angle. Both
thrust force and cutting torque increase with the increase in feed rate and
material thickness. Integrating taguchi method and RSM can be very
effective in process parameter optimization, as combining of the results of
the two methods can not only optimize the parameters, but also, indicate the
values of response, through which process parameter selection can be refined
and results justified. The results are based on the preselected range of values
of speed, feed, material thickness drill diameter and drill point angle and
hence the inference drawn cannot be completely generalized. The inferences
drawn from this study is of great significance to the practitioners in
minimizing tool wear and cutting energy, as solid carbide tool is being
widely used in machining GFRP
3. EXPERIMENTAL DETAILS AND PROCEDURE
3.1. INTRODUCTION
Major constituents in a fiber reinforced composite material are
reinforcing fiber and the matrix which hold the fibers. Fibers are the
principal constituents; they occupy a large volume fraction and the major
portion of load acting on a composite. For this experimental study we select
E type glass fiber and Bisphenol as the reinforcing fiber and the matrix
respectively. In previous studies done in institutions outside, they used epoxy
resins and other resins to hold the fibers. We use Bisphenol to study how it
differs from other resins and the different properties that it imbibes to the
final GFRP that is prepared.
The most common form in which GFRP’s are used in structural
application is called laminated. It is obtained by stacking a number of thin
layers of fibers and matrix and consolidating them to the desired thickness.
The fiber orientation in each layer as well as the stacking sequence of
18

20. various layers can be controlled to generate a wide range of physical and
mechanical properties for the composite laminate.
The design of experiment was done by taking three input parameters
namely the drill material, spindle speed and feed rate.
We discuss the details of the experimental procedure and the different
equipment’s and tools used in this study as follows:
3.2. PROCEDURE
• Manufacture GFRP using woven glass fiber and Bisphenol as matrix.
• Acquire tools, drill bits (HSS, Tungsten Carbide, PCD)
• Drill GFRP with the drill bits at varying cutting speed and feed rate
• Find thrust force and torque by attaching 9257B Kistler Dynamometer
to drilling equipment.
• Perform wear test, flexural strength test, hardness test on GFRP
• Optimize thrust force, torque and minimize delamination (both entry
and exit) in the holes using Design of Experiments and Response
Table Methodology
• Find optimal machining parameters for obtaining best quality drilled
hole.
3.3. MANUFACTURING METHOD FOR GFRP – HAND LAYUP
METHOD
The GFRP is prepared in the laboratory at room temperature using
woven glass fiber mats and using Bisphenol along with promoters and
catalysts to progress the method at room temperature.
18

21. Fig.1 Molding process
 Mold is treated with a release agent-to prevent sticking.
 Gel coat layers are placed on the mold- to give decorative and
protective surface.
 Put the reinforcement (woven roving's or chopped strand mat).
 The thermosetting resin is mixed with a curing agent, and applied with
brush or roller on the reinforcement.
 The part is allowed to cure and then disassembled from the mold.
 Since this process is not typically performed under the influences of
heat and pressure, simple equipment and tooling can be employed.
3.4. TOOLS USED
We use three different drill bits of increasing hardness to test the
effect of drill bit material on the output parameters.
HSS (High Speed Steel), Tungsten Carbide and PCD (Poly Crystalline
Diamond)
18

22. Fig.2 HSS
Fig.3 Tungsten Carbide
18

23. Fig. 4 PCD
Fig. 5 Parts of Twist Drill
We use 5mm diameter twist drill bits.
Nomenclature of drill bit is as follows.
18

24. Axis: The imaginary straight line which forms the longitudinal center line of
the drill
Body: The portion of the drill extending from the shank or neck to the outer
corners of the cutting lips
Chisel Edge: The edge at the end of the web that connects the cutting lips
Clearance: The space provided to eliminate undesirable contact between the
drill and the work piece
Clearance Diameter: The diameter over the cut away portion of the drill
lands
Drift: A flat tapered bar for forcing a taper shank out of its socket
Flutes: Helical or straight grooves cut or formed in the body of the drill to
provide cutting lips, to permit removal of chips, and to allow cutting fluid to
reach the cutting lips
Flute Length: The length from the outer corners of the cutting lips to the
extreme back end of the flutes; it includes the sweep of the tool used to
generate the flutes and, therefore, does not indicate the usable length of the
flutes
Helix Angle: The angle made by the leading edge of the land with a plane
containing the axis of the drill
Land: The peripheral portion of the body between adjacent flutes
Lead: The axial advance of a leading edge of the land in one turn around the
circumference
Lips: The cutting edges of a two flute drill extending from the chisel edge to
the periphery
Margin: The cylindrical portion of the land which is not cut away to provide
clearance
Neck: The section of reduced diameter between the body and the shank of a
drill Oil Grooves: Longitudinal straight or helical grooves in the shank, or
18

25. grooves in the lands of a drill to carry cutting fluid to the cutting lips Oil
Holes or Overall Length.
Point: The cutting end of a drill, made up of the ends of the lands and the
web; in form it resembles a cone, but departs from a true cone to furnish
clearance behind the cutting Point Angle: The angle included between the
cutting lips projected upon a plane parallel to the drill axis and parallel to the
two cutting lips
Shank: The part of the drill by which it is held and driven
Tang: The flattened end of a taper shank, intended to fit into a driving slot
in a socket
Taper Drill: A drill with part or all of its cutting flute length ground with a
specific taper to produce tapered holes; they are used for drilling the original
hole or enlarging an existing hole
Taper Square Shank: A taper shank whose cross section is square
Web: The central portion of the body that joins the lands; the extreme end of
the forms the chisel edge on a two-flute drill.
Point angle =118°
Cutting edge angle = 59°
Helix angle =25°
Clearance angle =6°
Process
Parameters
Spindle
Speed (rpm)
Feed
(mm/rev)
Drill Bit
Level 1 450 0.04 HSS
Level 2 852 0.08
TUNGSTEN
CARBIDE
Level 3 1250 0.12 PCD
Table 1: The varying input parameters factor
We use the above sets of spindle speed, feed rate and drill bit to
perform a run test on the GFRP prepared. The spindle speeds and feed rate
values are selected in such a way to keep the settings as low, medium and
18

26. high. The previous tests done in other journals influenced us to select the
appropriate values.
The drilling machine was modified so as to measure the thrust and
torque during the drilling cycle. For this a dynamometer was attached to
drilling machine. For proper measurement of the thrust and torque was fixed
in such a way that the axis of the drill bit passes through the center of the
dynamometer.
3.5. EQUIPMENTS USED
The important equipment’s used in experimentation include
3.5.1. Drilling Machine
The drilling machine used for the experiment is a radial upright type
drilling machine. The machine can be used as an automatic feed machine or
a manual feed machine. The control that allows its use as an automatic feed
machine. The upper lever allows selection of automatic feed in three levels –
0.04mm/rev, 0.08mm/rev and 0.12mm/rev. Once the required level is
selected the lower has to be pulled forward for the machine to start automatic
operation.
The drilling machine can be operated either on a belt drive or a geared
drive. In the case of the belt drive the drive is taken directly from the drive
motor of the drilling machine to it spindle through a belt drive. In the other
case a geared drive also comes into picture. To prevent damage to the
machine change over from belt drive to geared drive or vice versa should be
done only when motor is switch off. Presently the machine is in belt drive;
pull the lever to the blue colored area for the geared drive.
It depends also on the rpm of the drive motor used for the drilling
machine. A 960 rpm or a 1440 rpm motor can be used with this drilling
18

27. machine. When using the different drive motor the spindle speeds available
are
960 rpm, Geared drive – 65 rpm, 95 rpm, 140rpm, 205 rpm, 300 rpm
960 rpm, Belt drive- 390 rpm, 570 rpm, 840 rpm, 1230 rpm, 1800 rpm
1440 rpm, Geared drive- 100 rpm, 142 rpm, 210 rpm, 310 rpm, 450 rpm
1440 rpm, Belt drive- 600 rpm, 852 rpm, 1260 rpm, 1860 rpm, 2700 rpm
3.5.2. Dynamometer
A drill tool dynamometer was used to measure the thrust force and
torque occurring during the drilling operation. It is designed to be directly
mounted on the top of the drilling machine. It is basically a strain gauge
based sensor. This dynamometer consists of 2 strain gauge based sensor; one
measured the thrust force acting on the dill tool, while the other one
measures the twisting force (torque) acting on the drill tool. The
dynamometer has to be mounted in such a way that the drilling machine
passes through the axis of the dynamometer; this will ensure accurate torque
readings. Before starting experiment the instrument has to be put in “ON”
position for about 10min for initial warm-up. Adjust the potentiometer in the
front panel till the display reads “0” for thrust force as well as torque
3.5.3. Profile Projector
The profile projector is used for measuring the drilled holes after
completing the drilling operation. The GFRP piece is mounted on the work
table of the profile projector. The specimen is focused by adjusting the
position of the table to get a clear sharp image. The focusing should be done
properly to ensure that the damage area around the drilled hole is clearly
visible. A magnified image of the GFRP piece is obtained on the screen.
Magnification on the range of 10x, 20x and 50x are possible using the
instrument. Going for a higher magnification allows for easier measurement
18

28. of the drilled holes. Both linear and angular measurements can be done
using the profile projector.
3.5.4. Variable Speed and Feed Controller
3.6. DELAMINATION FACTOR
Delamination is a mode of failure for composite materials. It is caused
due to weak bonding of constituents. It reduces the structural integrity of
material and results in poor assembly tolerance and long term performance
deterioration.
Delamination causes layers of the glass fibers to separate after
repeated cyclic stresses. This makes the material lose the mechanical
toughness.
Delamination factor is determined by the ratio of maximum
diameter (D max) of Delamination and the diameter of the hole (D)
Fd = D max/D
18

29. Fig.6 Delamination Factor
Fig.7 Delamination Entry
Fig.8 Delamination exit
3.7. TESTS PERFORMED ON GFRP
Composite materials emerge as a promising alternative to correct the
deficiencies caused by steel reinforcements in concrete structures. The
advantageous properties of fiber reinforced polymer (FRP) such as high
strength to weight ratio, and corrosion and fatigue resistance create an
interest in engineers.
For wide acceptance and implementation in construction, full
characterizations of the mechanical properties of GFRP specimens are
needed. In particular, it is necessary to define the mean value and
18

30. distribution of the tensile strength of GFRP bars for reinforced concrete,
which engineers can use for design purposes and composite manufacturers
for quality control.
3.7.1. FLEXURAL STRENGTH TEST
Flexural strength, also known as modulus of rupture, bend strength or
fracture strength, a mechanical parameter for brittle material, is defined as a
materials ability to resist deformation under load. The transverse bending
test is most frequently employed, in which a rod specimen having either a
circular or rectangular cross section is bent until fracture using a three point
flexural test technique. The flexural strength represents the highest stress
experienced within the material at its moment of rupture. It is measured in
terms of stress, here given the symbol σ.
Fig.9 Three Point Flexure Test
When an object formed of a single material like a wooden beam or
steel rod, is bent, it experiences a range of stresses across its depth. At the
edge of the object on the inside of the bend, the stress will be at its maximum
compressive stress value. At the outside of the bend, the stress will be at its
maximum tensile value. These inner and outer edges of the beam or rod are
18

31. known as ‘extreme fibers’. Most materials fail under tensile stress before
they fail under compressive stress, so the maximum tensile stress value that
can be sustained before the beam or rod fails is its flexural strength.
For a rectangular sample under a load in a three point bending setup
σ = (3FL) / (2bd²)
F is the load (force) at the fracture point (N)
L is the length of the support span (mm)
b is width (mm)
d is thickness (mm)
4. TABULATION AND GRAPHS
4.1. TABULATION
RESPONSE TABLE FOR DELAMINATION ENTRY
Drill Bit Material Speed (rpm) Feed (mm/rev)
Exp. No HSS TC PCD 450 852 1250 0.04 0.08 0.12
1 1.059 1.059 1.059
2 1.068 1.068 1.068
3 1.11 1.11 1.11
4 1.058 1.058 1.058
5 1.09 1.09 1.09
6 1.099 1.099 1.099
7 1.035 1.035 1.035
8 1.068 1.068 1.068
9 1.095 1.095 1.095
10 1.04 1.04 1.04
11
1.06
5
1.065 1.065
12
1.08
5
1.085 1.085
13
1.03
5
1.035 1.035
14
1.06
2
1.062 1.062
15
1.07
5
1.075 1.075
16
1.01
5
1.015 1.015
17
1.04
3
1.043 1.043
18
1.06
8
1.068 1.068
19 1.02 1.02 1.02
20 1.026 1.026 1.026
21 1.031 1.031 1.031
22 1.012 1.012 1.012
23 1.015 1.015 1.015
24 1.029 1.029 1.029
25 1.01 1.01 1.01
26 1.016 1.016 1.016
27 1.022 1.022 1.022
TOTAL 9.697
9.48
8
9.181 9.504 9.475 9.372 9.284 9.453 9.614
AVERAGE 1.077
1.05
4
1.020 1.056 1.052 1.041 1.031 1.050 1.068
18

32. Table 2: Response table for Delamination Entry
RESPONSE TABLE FOR DELAMINATION EXIT
Drill Bit Material Speed (rpm) Feed (mm/rev)
Exp.
No
HSS TC PCD 450 852 1250 0.04 0.08 0.12
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
Table 3: Response table for Delamination Exit
RESPONSE TABLE FOR THRUST FORCE
Drill Bit Material Speed (rpm) Feed (mm/rev)
Exp.
No
HSS TC PCD 450 852 1250 0.04 0.08 0.12
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
Table 4: Response table for thrust force
18

33. RESPONSE TABLE FOR TORQUE
Drill Bit Material Speed (rpm) Feed (mm/rev)
Exp.
No
HSS TC PCD 450 852 1250 0.04 0.08 0.12
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
Table 5: Response table for torque
4.2. GRAPHS
DELAMINATION ENTRY GRAPHS
18

34. 1.045
1.05
1.055
1.06
1.065
1.07
1.075
1.08
1.085
0 500 1000 1500
HSS: SPEED VS DELAMINATION ENTRY
DELAMINATION
Fig.10 Speed vs Delamination Entry (HSS)
1.03
1.04
1.05
1.06
1.07
1.08
1.09
1.1
0 0.05 0.1 0.15
HSS: FEED VS DELAMINATION ENTRY
DELAMINATION
Fig.11 Feed vs Delamination Entry (HSS)
18

35. Fig. 12 Speed vs Delamination Entry (TC)
Fig.13 Feed vs Delamination Entry (TC)
18

36. Fig.14 Speed vs Delamination Entry (PCD)
Fig.15 Feed vs Delamination Entry (PCD)
18

37. Fig.16 Drill Bit Material vs Delamination Entry
DELAMINATION EXIT GRAPHS
Fig.17 Speed vs Delamination Exit (HSS)
18

38. Fig.18 Feed vs Delamination Exit (HSS)
Fig.19 Speed vs Delamination Exit (TC)
18

39. Fig.20 Feed vs Delamination Exit (TC)
Fig.21 Speed vs Delamination Exit (PC)
18

40. Fig.22 Feed vs Delamination Exit (PCD)
Fig.23 Drill Bit Material vs Delamination Exit
18

41. THRUST FORCE GRAPHS
Fig.24 Speed vs Thrust Force (HSS)
0
20
40
60
80
100
0 0.05 0.1 0.15
HSS: FEED VS THRUST FORCE
THRUST
Fig.25Feed vs Thrust Force (HSS)
18

42. 56
58
60
62
64
66
68
0 500 1000 1500
TUNGSTEN CARBIDE: SPEED VS THRUST
FORCE
THRUST
Fig.26 Speed vs Thrust Force (TC)
Fig.27 Feed vs Thrust Force (TC)
18

43. Fig.28 Speed vs Thrust Force (PCD)
Fig.29 Feed vs Thrust Force (PCD)
18

44. Fig.30 Drill Bit Material vs Thrust Force
TORQUE GRAPHS
Fig.31 Speed vs Torque (HSS)
18

45. Fig.32 Feed vs Torque (HSS)
Fig.33 Speed vs Torque (TC)
18

46. Fig.34 Feed vs Torque (TC)
Fig.35 Speed vs Torque (PCD)
18

47. Fig.36 Feed vs Torque (PCD)
Fig.37 Drill Bit Material vs Torque
18

48. 4.3. TEST RESULTS
4.3.1. FLEXURAL STRENGTH
Fig.38 Flexural Strength Graph
The peak load obtained is 6.8 KN
Flexural strength
σ = (3FL) / (2bd²)
= 3x6800x500/ (2x100x10x10)
= 510 N/mm2
Flexural Strength is found out as 510.00 N/mm2
5. SUMMARY AND CONCLUSION
18

49. A brief summary and main conclusion drawn from this study are
presented in this chapter. The main highlight of this work is that this study
was conducted based on the composites manufacturing and drilling point of
view. The samples for machining were prepared so that the required fiber
orientation 60% by volume could be given. The drilling machine was
modified so that it could measure thrust force and torque value. The
influence of the input parameters on the damage factor and thrust force and
torque is found out and how it is checked to obtain better quality drill hole.
5.1. CONCLUSIONS
From the data received after optimizing the output parameters by
adjusting the input parameters, we come to these following conclusions. The
spindle speed, feed and drill bit material has influence on the final outcome
of the quality of the drilled hole. The drill bit material is most influential
parameter in the output parameters according to study done.
It is observed that the delamination factor or the damage factor, thrust
force and the torque increases as the feed rate is increased while it decreases
with the increase of spindle speed. Also as the hardness of the drill bit
increases, the delamination decreases both at the entry and exit level. It is
also observed that delamination exit is more than the delamination entry. To
achieve minimum delamination, thrust force and torque during drilling
process, we see that we need to reduce the feed rate and increase the spindle
speed. Thus we select the drill bit material as PCD, feed rate as 0.04 mm/rev
and the spindle speed as 1250 rpm to achieve the best quality drilled hole.
REFERENCES
18

50. [1] “Fiber-Glass Reinforced Plastics for Corrosion Resistance” :- Ted R.
Morton, Beetle Plastics, Inc. 1974
[2] “Experimental study of drilling glass fiber reinforced plastics (GFRP)
manufactured by hand lay-up”:-J.Paulo Davim, Pedro Reis - Composites
Science and Technology 64(2004) 289-297
[3] “Effects of special drill bits on drilling-induced delamination of
composite materials” :- H. Hocheng, C.C. Tsao – International Journal of
Machine Tools &Manufacture 46 (2006)
[4] “The effect of vibratory drilling on hole quality in polymeric composites”
:- S. Arul, L. Vijayraghavan, S.K. Malhotra, R. Krishnamurthy –
International Journal of Machine tools & Manufacture 46 (2006) 252-259
[5] “Fibre reinforced composites in aircraft construction”:-C.Soutis –
Progress in Aerospace Sciences 41 (2005) 143-151
[6] “Process Parameters Optimization in GFRP drilling through integration
of Taguchi and Response Surface Methodology” Murthy B.R.N, Lewlyn
L.R. Rodrigues and Anjaiah Devineni – Research journal of Recent Sciences
Vol1 (6) June 2012
18