COMPOSITE LAMINATES

1. PROJECT ON
“FATIGUE LIFE PREDUCTION OF WOVEN GFRP
COMPOSITE LAMINATES WITH IMPACT
DAMAGE”
PRESENTED BY
DILEEP KUMAR H.A KIRAN KUMAR A DILIP V
1KN13ME014 1KN13ME021 1KN13ME015
Work Under the Guidance of
SHERYAS P.S
Assistant Professor
Department Of Mechanical Engineering
K N S Institute of Technology, Bangalore:-560064
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2. ABSTRACT
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 Composite materials have become viable alternative to metallic structures in
aircrafts and automotive sectors. These structures prone to impact and fatigue loads.
 The objective of this work is to investigate the effect of low velocity impact and
tension-tension type fatigue on woven glass fibre/epoxy polymer composite laminate.
 The impact damage and fatigue life is inter-linked in this work.
 The laminates were prepared by hand layup process having thickness 2mm.
 The specimens were subject to low-velocity impact at different energy levels (7.85,
15.7 and 23.54 Joules).

3. INTRODUCTION
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 In the recent day‟s composite materials are widely used in all the fields like
aerospace, automobile, etc. because they have more strength to weight ratio.
 A composite is a structural material which consists of combining two or more
constituents.
 One constituent is called the reinforcing phase and the one in which it is embedded is
called the matrix.
 The use of composites has evolved to commonly incorporate a structural fiber and
plastic, this is known as Fiber Reinforced Plastics (FRP)
 Common types of fibers used in FRP composite includes: Glass fiber, Aramid fiber,
Carbon fiber, Boron fiber, Basalt fiber, Natural fiber(wood, flax, hemp..) etc.
 Common plastic resins used in composites includes: Epoxy, Polyester, Vinyl ester,
Polyurethane and Polypropylene etc.

4. CLASSIFICATION OF COMPOSITE
Geometry of Reinforcement:
 Particulates Type:
Particulates type of composite is formed by adding particles of different size
and shape into matrix in random fashion
 Flake Type:
Flake Type of Composite consists of flat reinforcement of matrices.
 Fibers Type:
The matrices reinforced by continuous or discontinuous fibers.
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5. Types of Glass Fibers:
 A-glass: In A-glass, “A” stands for Appearance. It used to improve surface
appearance.
 C-glass: In C-glass, “C” stands for corrosion. It used in chemical environments,
such as storage tanks.
 D-glass: In D-glass, “D” stands for Dielectric. It used for applications requiring low
dielectric constants, such as radomes.
 E-glass: In E-glass, “E” stands for Electrical because it was designed for electrical
applications. However, it is used for many other purposes now, such as decorations
and structural applications.
 S-glass: In S-glass, “S” stands for Silica. It retains its strength at higher temperature,
higher fatigue strength. It is used mainly for aerospace applications.
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6. Types of matrix
 Polymer matrix composites:
Polymer matrix composite consists of polymer (e.g. Epoxy, polyester,
urethane) reinforced by thin-diameter fibers (e.g., glass, graphite, aramids, boron).
 Metal matrix composites:
Metal matrix composites (MMC‟s), as the Name impies, have a metal matrix.
Ex of matrices in such composites include aluminium, magnesium, and titanium.
Typical fibres include carbon and silicon carbide.
 Ceramic matrix composites:
Ceramic matrix composites (CMCs) have a ceramic matrix such as alumina
calcium alumina silicate reinforced by fibers such as carbon or silicon carbide.
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7. BENEFIT OF COMPOSITES
 Light weight
 High strength
 Corrosion and chemical resistance
 Elastic
 Non- conductive
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8. Sporting Goods:
Automobiles:
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APPLICATIONS OF COMPOSITES IN VARIOUS
INDUSTRIES

9. IMPACT LOADING
 In mechanics, an Impact is a high force or shock applied over a short time period
when two or more bodies collide.
 The effect depends critically on the relative velocity of the bodies to one another.
 A high-velocity collision (an impact) does not provide sufficient time for these
deformations and vibrations to occur.
 Impact resistance will be decreased with an increase in the modulus of elasticity,
which means that stiffer materials will have less impact resistance
The following are the different types of impacts in mechanics
 High velocity impact.
 Low velocity impact.
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LOW VELOCITY IMPACT
 The impact velocity is less then 15m/s such impacts is known as Low Velocity
Impact
 Damage involves extensive interplay, matrix cracking and interplay delaminations
depending on the extent of the damage.
 The damage is mostly embedded inside the materials, it is very difficult to detect
several new techniques are available like.,
 C-scan
 X-ray
 The following are the different types of impactors available:
 Charpoy/Izard type
 Pendulum type
 Drop weight/Instrumented type

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FATIGUE CHARACTERISTICS
 Fatigue occurs when a material is subjected to repeat loading and unloading.
 Fatigue analysis, is a very important tool for designers to use in the prediction of
relative magnitudes of fatigue lives of structures at potentially critical points.
 Factors that affect fatigue-life:
 Cyclic stress state
 Geometry
 Surface quality
 Material Type
 Residual stresses
 Direction of loading
 Grain size
 Environment etc…

12. OBJECTIVES
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1. To prepare the Woven type GFRP composite laminate thickness of 2mm.
2. To investigate parameters effect on the low velocity impact for 2mm thickness.
3. Evaluate the damage parameters on low velocity impact.
4. Analyzing the fatigue life for post impacted composite laminates.
5. Evaluating the relationship b/w impact velocity v/s no. of failure cycles.

13. METHODOLOGY
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1. Preparing the woven type of glass fibre reinforced polymer composite laminates
using hand-layup process.
2. Preparing the specimen as per ASTM standards.
3. Impact test is conducted for the laminates at different Height of Fall for 2mm
thickness.
4. The fatigue test is conducted for the impacted and unimpacted laminates.
5. Tabulating the test results for both impact and fatigue test.
6. Plotting the Curves for impact velocity v/s no. of cycles.

14. Flow Chart:

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SPECIMEN FABRICATION
Hand Lay-Up
 Combining of the reinforced fiber and resin is known as composite fabrication
 Hand lay-up molding is used for the production of parts of any dimensions it as
shown in fig

16. Cont..
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The hand layup molding method consists of applying the following elements
successively onto a mold surface.
 Release agent (Gel coat)
 A layer of liquid thermosetting Resin, of viscosity between 0.3 and 0.4 Pa.s.
 A layer of reinforcement in the form of chopped strand mat or woven roving.
 Impregnation of the reinforcement is done by hand using a roller or a brush.
 This operation is repeated for each layer of reinforcement in order to obtain the
desired Thickness of the laminate.

17. Fig: 1.2 Finished Composite Laminate For Impact Test As Per ASTM Standard
Fig: 1.1 Woven Type Weaved Glass Fibers

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EXPERIMENTAL INVESTIGATION
Low Velocity Impact
 The impact tests on composite laminates could be performed in various test methods.
 However, the most widely used among these are,
a. Drop/falling weight test method.
b. Penetrating impact test method using pneumatic guns.
 The tests were performed using an instrumented falling weight testing machine with
no energy storage device and is primarily used to investigate the impact behavior
under lower acceleration.
 The test specimen are prepared according to ASTD standard

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Fig : 1.3 Schematic Diagram of Specimen Being Impacted.
Fig :1.4 Specimen Clamping Apparatus

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Fig : 1.5 Falling Weight Impact Test Equipment Setup

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Fatigue Testing
 At the ends of the laminates Aluminum is used as tabing for the purposes of holding
the specimen to test machine.
 The hydraulic computer controlled Fatigue testing machine is used.
 The fig.1.6 shows the schematic diagram for fatigue machine fixtures. In this one is
movable other one is fixed. The two jaws are operated by hydraulically because it
holds the specimen very rigidly and handling is easy
Fig. 1.6 Schematic diagram showing the fatigue test machine fixtures

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RESULTS AND DISCUSSION
Low Velocity Impact
 This work, variation of impact parameters such as contact force, displacement,
impact velocity, and absorbed energy versus time or deflection is examined in order
to figure out damage process of woven fabric composites in an impact event.
 The study is expected to be helpful in understanding the overall response of woven
fabric composite plates under impact loading.
 The experimental tests were performed on three specimens for thickness of 2mm.
 Tests were performed two times at three energy levels determined by the falling
height, namely 500, 1000 and 1500 mm. The corresponding values of the nominal
impact velocities are 3.132, 4.429 and 5.425 m/s.
 From an energy point of view, Fig. shows six curves of force versus displacement
and force versus time of the dart at various levels of impact energy.

23. Cont.…….
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 This figure allows us to clearly detect the transition from rebound to perforation, in
the perforation cases the curve „„folds‟‟ onto itself toward decreasing displacement,
while in the rebound cases the displacement is increasing.
 The transition case is shown by the fifth curve (corresponding to 1000 mm of falling
height and 5.125 m/s of nominal impact velocity) that evidences very little rebound
of the dart after the maximum penetration has been reached.
 Fig. i. iii and v indicates the time histories of the dart displacement and force.
 Fig. ii, iv and vi indicates the histories of the force and time.
 The force history showed two thresholds, the first one at about 360 N, where the
curve sharply changed its look and a deviation was visible, the second one was at
1260 N, where the curve sharply dropped down and then started again to grow but
with a slope lower than the previous one.

24. Cont.…….
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 The first threshold is the indication of the first material damage. The second
threshold occurs at the first lamina failure.
 The force versus displacement graph i & v shows a closed loop.
 The area under the curve is the absorbed energy that was progressively transferred
from the dart to the plate, when the saturation of the load carrying capacity of the
plate was reached.
 The shaded area represents the energy absorbed by specimens during impact tests
resulting in closed type curves
 For specimens having rebounding, i.e. closed type curves, the absorbed energy can
also be calculated from the initial kinetic energy minus the rebound kinetic energy
using the initial and rebound velocities. Fig. iii Indicates graphs for a case of
perforation.

25. Cont.…….
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 At this time the energy balance can be formulated and thus obtain the whole energy
dissipated by the specimen in order to initialize and propagate fractures inside the
material.
 Another measurable characteristic time can be defined when the dart velocity
becomes zero, at this time the dart has reached its „„maximum penetration‟‟.
i.
ii.

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iii.
v.
iv.
vi.

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Fatigue Life of The Composites After Impact:
 Fatigue is nothing but applying the cyclic load on the work.
 In Tension- Tension fatigue each fatigue cycle the tensile fatigue load is applied, this
causes the local buckling and displacement of the impact damage site.
 In the tension phase of fatigue cycle the crack could be seen to open very slightly
and after a few hundred cycles the 2 cracks would join across the impact indentation.
 In later stages of fatigue test some of surface plies would delaminate from the
damage plies and buckle during the tension phase of the cyclic loading.
 Fig.1.8 shows Log of No. of cycle‟s v/s Impact velocity (m/s) for fatigue life time
curve, under Tension-Tension fatigue loading for 2 mm thickness of woven glass
fiber reinforced polymer composite laminates with and without impact loadings
respectively.

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3
3.5
4
4.5
5
5.5
6
0 1 2 3 4 5 6
LogforNo.Ofcycles
Impact Velocity (m/s)
Fig: 1.8 Log of No. of cycle’s v/s Impact velocity (m/s) for fatigue life time
curve, under Tension-Tension fatigue loading for 2mm thickness

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CONCLUSIONS
The investigation of the effect of low velocity impact and tension-tension type
fatigue on woven glass fiber/epoxy polymer composite laminate has led to the
following conclusions:
1) These impact tests have shown that the dynamic response of the laminates depends
on the elastic properties of the fiber material.
2) The force versus displacement and the time versus force curves for each case have
been drawn.
3) The laminate sustained the impact with delimitation on the outer layer at an impact
velocity up to 3.132 m/sec, whereas, at impact velocity of 4.429 m/sec, the laminates
sustained catastrophic failure.

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SCOPE OF FUTURE WORK
Following are the some recommended future work:
 Different fiber and resign material can be selected with different orientations of fiber.
 In low-velocity impact mass and height of fall can be varied with different types of
impactor can be used.
 For fatigue test tension-compression test also be done with various frequency and
stress ratios.

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