Composite materials lecture.ppt

Design and Product
Development Engineering with
Advanced Composite Materials
Dr. Padmanabhan Krishnan
Professor, Higher Academic Grade
School of Mechanical Engineering
Vellore Institute of Technology-University
Vellore 632014.
Email: padmanabhan.k@vit.ac.in
(M) 9840032002

My Journey
B.Sc Physics, Madras Presidency College. 1984.
M.Sc, Physics and Materials Science,
Annamalai University , Chidambaram, 1986.
M.Sc [Engg], Composite Materials and
Mechanics, IISc, Bangalore, 1991.
Ph.D [Engg], Composite Materials
and Mechanics, IISc, B’lore, 1995.
Life Fellow of 6 Organizations.

3
Mythological Connection
To Composites

4
The Indian Composite
gods are bottom up
The western deities
& daemons are top down
Though there are exceptions !

Contents
Definition and Product Applications
Micro, Meso and Macromechanics
Modelling and Simulation
Composites in Electronic Packaging
Composites in Dentistry
Bi-material Composite Applications
Metal Matrix Polymer Fibre Reinforced Composites.
Self Reinforced Composite Applications
Sandwich Composites and Applications
Composites in Music
Composites in Ballistics
Reuse, Recycle and Refuse…….
Summary, Acknowledgements and References.

Definition
A composite material is a multi-
component system with at least a matrix
and a reinforcement.
The desired properties must be better than
at least one of the constituents.
The constituents are normally physically
separable , with a line of heterogeneity
between them, called the interface.

Composite Product
Applications-General

Composites in Wind Energy
www.suzlon.com , www.ge.com
Vestas RRB

Composites in Storage
Corrosion and weathering free thermoset and thermoplastic matrix
glass fibre reinforced composite storage tanks, pressure vessels and
containers are cheaper and more durable than conventional containers

Biomedical Composites
s
75X106 cyles of heart beat
78 x 106 cycles of heart beat
over 25 years

Composites in Dentistry
Acrylics, Acrylic esters, Bis-
GMA, PMMA derivatives,
Ceramic filled composites
Can you make out the
difference ?
Ref: K. Padmanabhan , Programme overview, NIST ceramics machining
consortium, I th Chapter, Gaithersburg, USA, October 8-9, 1998.

Composites in Automobiles
Italian automobile with carbon fibre composite chassis

All Composite Engines
Aluminium Composite Engine
Composite Engine Manifold

All composite Aircrafts
Indian Hansa-All composite aircraft
VTOL Aircraft
Ref: B.K. Parida, RMVGK Rao and K. Padmanabhan , Proceedings of the third joint
National Aerospace Laboratories- Chinese Aircraft Establishment workshop on
composites, April 22-24, Bangalore, India, 1996, p9. & NAL website

Composites - Sports & Leisure
Carbon fibre-nylon matrix – rigid foam
tennis racquet
Composite Yatch

Composites in Defense
A Bulletproof Vest A missile material case

Composites in Space
All aluminium alloy and carbon composites

Micromechanics is where design
begins as I don’t claim to know
nanomechanics !
Design is defined
as the complete
information
required to
produce a
product or
render service
- Anonymous

The Single Fibre-Resin Micro Bond
A drop of the cured resin on the
fibre surface showing adhesion
Fibre pullout test through a micro
vise design fixture

Micro bond Bundle Pull-out Test- A
Mesomechanical Test
Ref: K. Padmanabhan , Final project report to the Singapore –MIT Alliance ,
Singapore, November 2002

Interface Tests
Single fibre pullout test
Single fibre push out test, brittle materials
Micro bond single fibre pullout test
Multiple fibre pullout test and Micro bond
multiple fibre pullout test, Statistically
averaged results, More precise, Less
difficult, Mesomechanical in nature.
Interlaminar shear strength test, ILSS.

Multiple Fibre Pullout
Ref: K. Padmanabhan , Toyobo Confidentiality Report, 2002.
Ref: C. Y. Yue and K. Padmanabhan , Composites B, 30(1999) p205.
Micro bond Matrix slab

Modelling and Analysis
Carbon Fibre and Zylon™ Fibre /epoxy
Matrix Embedded Composite Systems
Cylindrical Assemblage
Model
Matrix
Pull Out Through a Micro vise
• Micromechanics
le

Pull out of Fibre Tows
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The Width: Thickness must be > 5:1
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The Y intercept will be positive only when the width : thickness of the
fibre tow in pull out is at least 5:1 , in perfect agreement with the ASTM
Guidelines on ILSS test specimen’s W/t dimensional ratios.

Interfacial Parameters
Interfacial shear strength,τ
Interfacial frictional stress, τf
Fibre/matrix coefficient of friction, µ
Matrix shrinkage pressure, Po
Pressure due to Poisson expansion, pa
Contact pressure
Interfacial wear

Non-linear Quasistatic
Analysis
Surface to surface
contact
CAM is anisotropic
and matrix is isotropic
Only failure and post
failure conditions were
considered due to
relevance and precision
Model has dihedral
symmetry
Solid 8 noded brick 185 element
Hex swept volumes

Zylon Fibre
www.toyobo.co.jp
ZYLON consists of rigid-rod chain molecules of poly(p-
phenylene-2,6-benzobisoxazole)(PBO).
Tensile Strength : 5.8 GPa
Tensile Modulus : 270 GPa
Ref: K. Padmanabhan , Toyobo Confidentiality Report, 2002.

Results of ANSYS Analysis
37 MPa
Zylon/epoxy shear stress at CAM interface

FEM Analysis Results
Carbon/epoxy shear stress at CAM interface

31
Nano Structuring of
Kevlar Surface

32
0.51 nm
Schematic diagram of Kevlar® 49 fiber
showing the radially arranged
pleated sheets
Microstructure of aramid fiber
Kevlar fibers

34
Kevlar Fibre Nano
Structuring
Ref: C. Y. Yue and K. Padmanabhan , Composites B, 30(1999) p205

35
Kevlar Fibre Nano Structuring
10 Min Methanol
And Water Washing

36
XPS of Treated Kevlar Surfaces

37
SEM of Treated Kevlar Surfaces

38
Kevlar Fibre/ Epoxy Composites
- Interfacial Results

Meso and Macromechanics
in Composites Design
39

Mesomechanical Unit Cells of Fabric
in a Composite
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Microbond Bundle Pull out Test-
A New Mesomechanical Test Method
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Fractography
Fig. The fibre bundle after the shear pull out of the bond. b) SEM picture
of the resin microbond droplet sheared out of the fibre bundle. Notice
that the drop is still intact in this case.

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Fractography
Fig. : SEM fractograph of the microbond sheared through the fibre
bundle. Notice the micro vise mark on the resin droplet due to
compressive stresses near the exit. b) A completely sheared out intact
drop from the bundle of fibres due to pull out.

A Polyethylene Self Reinforced
Polymer Microbond Bundle Pull-Out
8/17/2022
ICONS 2018, December 14-17, 2018,
IIT, Chennai. 45

Cohesive Zone Modelling and
Toughness
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Cohesive Zone Modelling
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Machining Surface Integrity and
Structural Integrity
- The Micromechanical and
Mesomechanical Fundamentals
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Importance in Small Scale & Microtesting
 Machining Surface Integrity
to be high
 Surface cracks should be
smaller than interior cracks.
 Small cross section
demands very few &
smaller defects/ cracks
 Subcritical phenomena to
be understood and
implemented.
 Quasi-static and fatigue
sensitive.
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Micro buckling and Design
Micro buckling can be
prevented by choosing
higher fibre diameter,
higher fibre elastic
modulus and high
interfacial bond strength
between fibre and matrix
Boron fibres are the best
for design against micro
buckling

Macromechanics
Transversely isotropic
composite needs 5
independent elastic
constants for efficient
modelling (UD/00 )
Layered orthotropic
composite needs 9
independent elastic
constants for efficient
modelling

3 D Braided Structures
3 D braided ,knitted, stitched and fibre
preform structures have enabled easy
manufacturing of net shape FRPs. The
modelling and performance analysis of
such structures poses challenges
Ref: Padmanabhan .K, Singapore- MIT Alliance Research Fellow Report, 2002.

Failures and Multiple Causes
In nature, most of the real environment failures
are due to multiple causes.
As enough standard procedures are available
for failures due to a single cause, the obvious
move is to develop the understanding as well as
standard procedures for failures due to multiple
causes.
An understanding of these failures leads to a
better fracture control that aids superior designs
with advanced composite materials

Multiscale Modelling
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Statistical Reliability
55
(c)2003 Brooks/Cole, a division of Thomson Learning, Inc. Thomson Learning™ is a trademark used herein under license.
Figure The Weibull distribution describes the fraction of the samples
that fail at any given applied stress. It will be interesting to see the
Weibul distribution plots for multiscale materials.
1- Probability (Failure) = P ( Reliability )

My Experience With Product
Design and Engineering of
Composite Materials
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A Design Paradox: The more
you learn the less freedom you
have to use what you know-
David G Ullman.
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Composites in Microelectronic
Packaging

Composites in Microelectronic
Packaging
The BOM includes Copper lead frame,
Gold wires for bonding, Silver –epoxy
for die attach, Silicon die and Epoxy
mould composite with Phenolics, Fused
silica powder and Carbon black powder
as the encapsulant materials.

60
3D Model 64L
With encapsulation
Without encapsulation

61
Analysis
• Electric-Thermal Analysis
• Thermal – Structural Analysis
• Materials used
• Lead Frame and Leads - Copper
• Wire bonding - Gold
• Die - Silicon
• Adhesive for lead frame
and die - Silver Epoxy
• Encapsulation - Carbon black and
• fused silica particles
• filled epoxy and
• phenolic resin –
• a multiscale composite !
Ref: Padmanabhan Krishnan, A SPEL-SVCE Joint Project, 2007- 2010.

A TQLMP IC Chip Is A
Bottom-up Integral
Assembly In Product
Architecture On A
Copper Based Lead
Frame Platform.
62

Thermal – Structural Results
Displacement Vector sum Von mises stress
Stress intensity XY Shear stress

Non Destructive Evaluation
Ultrasonic C-Scan NDT
can do depth profiling of
composites delamination
and damage profiling
Scanning acoustic microscope
can sense delaminations of
micron dimensions ( shown as
red areas) in TQLMP IC
packages. FEA techniques are
also NDE techniques.

Fatigue Durability of
Microelectronic Chips
65

66
Coffin-Manson's Equation
• Fatigue is the most common failure mode in IC
packaging,
• IC device dissipate heat to it’s surroundings during
operation, differential thermal expansion generates
stresses in the interconnecting structure.
• These stresses produce instantaneous elastic and
plastic strain in the material joint.
• The mechanical properties of material change strongly
over the normal temperature range of operation.
• Above the room temperature, mechanical built-in
stresses that result from thermal mismatch with the
other materials will relax and vanish over time.

67
Coffin-Manson Equations
• Cyclical plastic deformations change the grain
structure, weaken the joints and can lead to fatigue.
• The time of the joint fracture depends on relative
deformation (strain), temperature and frequency of
deformation.
• A simplified relationship is given by the Coffin-
Manson's formula;
N0.5 × δp = constant
• Where
• N – number of cycles,
• δp -relative deformation

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Coffin-Manson Fatigue vs CTE

Plastic Strain
69
Total strain ≈ 0.00097656
Shear stress XY plane ≈
1.504614MPa
Estimated plastic strain ≈
0.00083977
Fig : Total equivalent strain (36L)

Coffin Manson Plots for the ICs
70
The weakest bi material interface at which delaminations occur first is the
copper lead frame-encapsulant pad area. Most of the preconditioning
experiences have revealed that more than 90 % of the failures occur in
the pad area interface. The following plot , thus, is a Coffin –Manson
fatigue graph created to predict the life time of IC packages investigated
here.
Fig: The Coffin-Manson Plot for three ICs. Plastic Strain vs. No: of cycles

Fatigue Life Prediction
• As the plastic strain reduces with cycling
and only a small value of strain remains
after a few tens of cycles at MOT, thereby
slowly embrittling the encapsulant in the
process, the overall deformation /strain
simulated or measured for a single steady
state cycle would be very high. With
cycling the total deformation/ strain
reduces and reaches a steady but low
value . The plot resembles an endurance
S-N plot for ferrous materials with a limit.
The fatigue life of the ICs are expected to
be higher.
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72
Summary and Conclusions
• Modelling of some µDual and TQLMP IC packages
was accomplished.
• Thermo-mechanical analysis of IC packages after
Joule heating using FEM software was carried out.
• Die shear tests, JEDEC Tests, Scanning Acoustic
Microscopy, Hygro-thermal behaviour analyses and
Validation through Failure theories for all the
packages were done for static and fatigue design
durability during operation at MOT.
• The operation of the ICs at an elevated temperature
(125 Celsius) above the MOT was also analyzed
with the help of FEM, JEDEC tests and SAM.

Current Work
• Independently working on
converting CNSL (Cashew Nut
Shell Liquid ) in to a state of
the art encapsulant material.
It shows more promise than
epoxies or phenolics due to a
high hygrothermal resistance,
rodent, termite, and chemical
resistance at superior
mechanical and dielectric
properties. Any filling or
modification are possible due
to high wetting and
processing ease. They are
bio-derived and cost effective.
74

Cashew Nut Shell Liquid Resin
(CNSL) for Composite
Applications
75
CNSL Resin is cured with formaldehyde at 120 degree Celsius .
It is rodent and termite resistant and possesses thermal resistance Up to 250
degree Celsius. It is increasingly used for composite applications in lieu of
epoxies and phenolics. Electronic packaging applications are possible.

76
Multiscale Composites in
Dentistry

Composites in Prosthodontics
Tooth is a functionally graded
composite material with enamel
and dentin. In the third maxillary
molar the occlusal stress can
be 2-3 MPa.
The masticatory heavy chewing
stress will be around 193 MPa.
A composite restorative must with
stand this with an FOS and with
constant hygrothermal attack.

78
Multi Scale Composites for
Dentistry
• Bis GMA, UDMA, Methacrylic Esters
contain glassy particles that are
mostly less than 1 micron in size
• Esters and acrylates/ceramic filler
(barium alumina silica glass, glassy
microfillers, 0.1 to 10 microns size)
restorative composites.
• Multi scale composites are also
useful as luting cements, crown and
bridge materials and cements and
veneer materials.

79
Wear Data for Restoratives
• Aesthetics, Shade, Reliability
• Most of the composites show a
logarithmic wear rate, linear wear
rate is unwelcome !
• Wear of less than 200 microns in 10
years is acceptable.
• Wear volume will be 0.5 to 0.8 cu.
mm per annum, enamel vs
restoratives.
• Coeff of Friction is ~ 0.1 to 0.35.

Hygrothermal Behaviour
Fibre reinforced plastics are known for
environmental attacks that reduce their function.
Mechanical properties degrade over time !
Moisture plays havoc at elevated temperatures,
in the presence of voids, defects and in low Tg
plastics .
Diffusion and osmotic pressure are the driving
mechanisms for hygrothermal attack
Evaluation methods and surface preservation
Important in marine, biomedical, aeronautical,
electronic and automobile applications

Design for Hygrothermal
Durability

ASTM STP D 5229 M Rule
The MOT( Maximum Operating Temperature)
of the material, device/component should be
at least 25 º Celsius lower than the lowest Tg
(normally wet) of the material attained after
hygrothermal equilibration. All the polymeric
materials and their composites must satisfy
this rule in order to qualify for certification for
reliability and durability.
Ref: Padmanabhan. K, Need to Revise Dental
Standards, Current Science, August, 2006.

Asymmetrically Hybridized Bi-
Material Composite Applications
In Skis

Asymmetric Hybridization
Designs

Asymetrically Hybridized Composite Laminates

Applications of Asymmetrically
Hybridized Bi-material Composites

Polymer Fibre Reinforced Metal
Matrix Composites for High
Temperature Applications and
Light-weighting

Relevance and scope
 This research work finds its relevance from the growing needs of industries which are interested in
developing newer materials, and continuously improving the performance of existing ones by way of
replacing existing materials that are limited by their existing properties, especially, and the strength,
specific strength, modulus, and specific modulus, and for areas of lightweight structures such as in
aircraft and automobiles.
 Since the possibility of using high-performance polymer fibres, namely PBO, and
p-aramid as a reinforcement in a metal matrix were less attempted, it shows promising applications
due to the properties of the polymer fibres.
 This research work becomes significant in the creation and advancement of knowledge in metal-
plastic systems by way of developing PRMMCs by conventional processing technique like liquid
infiltration, and novel method like HVOF thermal spray deposition.
 The fibre architecture was compatiblized with metal matrices by metallizing.
8/17/2022 Kumaran D Ph.D. work, 2021. 88
Ref: Kumaran, D, Rajadurai, A & Padmanabhan, K 2020, ‘Processing and
evaluation of thermal-sprayed high-performance polymer fiber reinforced
Zn metal matrix compo-sites’, Journal of Composite Materials,
https://doi.org/10.1177/0021998320913097

Coating Methods
Figure: Schematic diagram of the thermal spray process
8/17/2022 Kumaran D, Ph.D. work, 2021 89

Results and discussion
PRMMC by liquid infiltration
Text
8/17/2022 Kumaran D, Ph.D. work
Figure: Stacked frame-wound fibres
with constraining block placed
Figure: Cast unreinforced matrix material
Figure: Polymer reinforced metal matrix composite
Figure: Cold compressed PRMMC Figure: Samples of PRMMC test specimens for further finishing
90

Self Reinforced Polymer
Composites
91

Self Reinforced Polymer Composites
 Improved energy efficiency and reduced fuel consumption
have become increasingly important in order to stay
competitive in the transport industry.
 Aerospace industry sees constant pressure to reduce fuel
consumption.
 The use of light weight composites have helped in this
regards.
 A light polymer matrix is reinforced with the same
material as polymer fibres.
 Varieties of Pseudo-SRCs are also possible. Some of the
SRCs like that of PE and PP float on water.
92

Applications
 Air, sea and road cargo containers for light-weighting.
 Biomaterials
 Personal baggage and luggage
 Electronic packaging
 Marine Structures
 Low loss Electronic Structures
 Automobile interiors
 Aircraft interiors
 Polyethylene and Polypropylene SRCs float on water
despite their shape.
93
Ref: Sharan Chandran M , Doctoral Student Thesis , SMEC, VIT Vellore, 2020.

Correlation (PE)
Test
Method
t/A
ratio
(s/mm2)
pullout test 0.32 43.75 0.625
Tension 0.373 7,075.446 4,178.571
in-plane shear 0.0288 71,468.75 26,041.67
Quasi- static
flexural 0.45 311.2222 1,088.889
PE 600 0.00033 6,763,061 92,109,000
PE 900 0.00031 7,861,345 139,418,200
PE 1200
0.00026
3 9,706,751 167,868,600
95

Test
Method
Stress evolution
coefficient
(Stress/t/a)
(N/s)
Strain evolution
coefficient
(Strain/t/a)
(m2/s)
Pullout 31.25 3.125
Tension 49.017 0.0267
Inplane 46.875 0.3125
Flex 92.22 0.1111
96
Correlation….

High Impact Applications
98
UHMWPE fibres and films like XF 23 and 33 , especially cross plied XPE have led
the breakthroughs in ballistic helmet and vest technology : Ref; X Chen (2016)

Passenger Aircraft Accidents And SRCs
99

Influence of Conventional and Unconventional
Machining Induced Structural Changes
on the Mechanical Characterization of
Self Reinforced Polymer Composites
Deepa A – PhD Work (2021)

Methodology
 Selection of Material
 DSC and TGA analysis of samples before fabrication.
 Hot Compaction Method
 Optimization of Machining parameters
 Cutting of samples using Conventional and
unconventional Machining
 Mechanical Testing.
 FTIR & SEM analysis
 Correlation of results.
101

Machining
 Conventional Machining
 Unconventional Machining
 Laser cutting
 Type of Machine : CO2 Laser
 Machine power : 1000W
 Material : Polyethylene
 Nozzle diameter : 1.7mm
 Speed : 420 mm/min
 Abrasive Water jet cutting
 Feed rate : 1000mm/min
 Orifice – 0.1 to 0.3 mm
 Pressure – 2500 to 4000 bar
 Abrasive flow - 0.1 to 1.0 Kg/min
 Stand off distance – 1 to 4 mm
102

SEM Images
103
a) Conventional b) Laser c) AWJ

Lessons from Machining
Induced Structural Changes
 A suitable method of machining has to
be chosen and optimized for superior
structural health reliability of
composites and mechanical properties
for product development as these
composites are sensitive to the
machining methods and parameters.
104

Design Optimization of Rigid
Polymer Foam Sandwich
Composites
105

Sandwich Composites
Indian sandwiches like Samosa, Vada, Bonda and other
stuffed items are end-capped and fried. On the contrary,
the western sandwiches , burgers and hot dogs are mostly
open ended and contain green matter. A ludicrous blend
has more avenues.

Sandwich Core Materials
Foam
Honey
comb

Sandwich Showing Core and
Skin –Core Interfacial Failure
Tensile face
Core failure
Ref: ASTM C 393/C393M-06, ASTM D7249/ D 7249 M-06, ASTM D7250/
D7250M-06

Design Optimization
Ref: 1. G.R. Froud ,Composites, July, 1980, p 133.
2. RMVGK Rao et al in Jl. Of Reinforced Plastics and Composites,
Vol:25, No: 6, 2006, p 663.
3. Padmanabhan.K, ARDB SP , Project Report Number : CR 1650/001, Dec 2016.

Design Optimization for Strength
Glass-Epoxy Skin Showing
Buckling Delamination Type
Of Failure on the Compressive
Face.
Carbon-Epoxy Skin Showing
Buckling Delamination Type
Of Failure on the Compressive
Face. We found that Froud’s theory
didn’t provide optimized solutions
for any sandwich composite.

112
Flexural Behaviour of Sandwich Composite Panels Fabricated
Through Different Vacuum Bagging Techniques
Dual Modified
Bagging
Core shear failure and
interface debonding

• Existing Theories on Sandwich Design Optimization
• L.J. Gibson et al developed an analytical method for finding the values of
core thickness, face thickness and core density which minimize the weight
of a foam core (polyurethane) sandwich beam of given stiffness and span
length.
Maximum stiffness occurs when skin weight is one fourth of core weight (
Metal skin rigid polymeric foam core
• G.R. Froud, on his article on the mechanical properties in bending
applications of sandwich constructions, has suggested
The maximum flexural rigidity occurs when,
Core weight = 2/3*total weight
If it is assumed that the failure of a sandwich structure occurs due to tensile
failure in the skin, the core must not fail in shear before tensile failure in
the skins is attained.
The maximum bending strength is obtained when
Core weight = total weight of skins .

114
Major Findings
• Existing theories on DO of sandwich composites for
strength and stiffness(Froud, Gibson) found at fault
• Dependent mainly on actual parameters – material
properties, weight ratio, span to depth ratio, shear flow,
elastic-plastic mismatch
• Foam Mechanical property outcomes – Compressive and
Tensile , significant to failure as Literature absent for
failure in foams across densities.
• Poisson’s ratio decreases with density up to a point
• Cell wall structures and density key to foam failure
mechanism
• FEM techniques applied and results partly achieved –
Tension, Compression, mode 2 shear (No previous
publications)
• DO found to be case specific with no general theory
acceptable as of now
• Ranking by FMEA done for factors decisive in DO for
strength and stiffness like elastic material properties
,geometry, span to depth ratio

Failure Modes For Strength
Optimization
115
Core shear failure : Slip stick mechanism and
Interfacial de-bonding with the face sheets. Many
optimized strength specimens failed in this mode
as more energy is consumed in the fracture
process in bending and fracture resistance leads
to high stresses and moments.

Light Weight Structures
It is possible to design and fabricate a sandwich panel that can support
an elephant’s weight and be light enough to be carried by one person

117
NOVEL PRESSURE BOX PROTOTYPE
Based on our investigations
with modified and multiple
bag fabrications, the idea
evolved into a more stable
solution in the form of a
pressure box which is an
economic variant for an
autoclave. As these
sandwich composites cannot
be fabricated at pressures
exceeding 5 Bars, due to
crushing, a mobile pressure
box was found useful which
could be carted in to an
oven, for post curing

Applications of Polymer
Sandwich Composites
118

Design and Development of
Composite Swarmandal and 5th
Century BC Sengottu Yazh
119

PRODUCT AND ITS FUNCTIONALITIES
( COMMERCIALLY AVAILABLE ) : SWARAMANDAL
• ‘Indian zither’ - most commonly used as an accompanying instrument for vocal Hindustani Classical
Music. (Zither : german instrument, cittern family).
• Swara (notes), and Mandal (group), representing its ability to produce a large number of notes.
• Traditionally made from ‘Tun’ wood.
• Measures from twenty-four to thirty inches in length, and twelve to fifteen inches in width.
• Singer may choose to employ any number of strings from 21 to 36.

INNOVATIONS: THE VACUUM BAGGING PROCESSES
A schematic diagram of the room temperature vacuum bagging process used here is shown with
the produced Carbon- Silk- Fly Ash/ Epoxy Matrix composite laminate parts in the next figure.

DETAILS OF RESEARCH CARRIED OUT AND THE
STAGE OF THE PROPOSED PRODUCT
The impulse hammer test set up and experimentation to determine the Natural frequencies,
Damping factors, Resolution and Signal strengths of the Fabricated Composite Laminates

INNOVATIONS: BONDED ASSEMBLY OF SWARMANDAL
• The relevant laminates were thus prepared through vacuum bagging and tested.
• The specimens obtained were subjected to vibrational tests by the impulse hammer
technique at Sri Venkateshwara College of Engineering (SVCE), Sriperumbudur.
• Carbon fibre with silk, epoxy and fly ash as the best material for instrument construction.
• Final product prepared using the selected composite, facing a lot of challenges during
practical assembly and material procurement.
• Final Stages of Assembly:
123

INNOVATIONS: BONDED ASSEMBLY OF SWARMANDAL…
124

SEMI FINISHED PRODUCT : SWARMANDAL
A semi finished Carbon- Silk- Fly ash/Epoxy Matrix Swarmandal During Tests

SWARMANDAL ACOUSTIC CHARACTERISTICS
THE IMPULSE HAMMER TEST FOR QUALIFICATION
The best material was selected based on qualitative as well as quantitative factors such as
the resultant amplitudes, resolution or clarity, and optimum difference of the first natural
frequencies with the lowest frequency of the bass string of the instrument (F#, 92.5 Hz). The
final material thus selected was that of carbon fibre, silk and fly ash, with epoxy resin.

Product and its functionalities (Commercially Viable ) :
The Sengottu Yazh
• A harp used in ancient Tamil music, which is the ancestor of modern day Veena.
• An open-stringed polyphonous instrument, with gut strings, with a wooden boat-shaped skin-covered
resonator and an ebony stem.
• Thiruvalluvar, the legendary Tamil poet, mentions yazh in his work Thirukkural (around 200 BC). Many
other mentions also exist in sangam literature.
• Periyazh which is almost extinct but for a few museum pieces , has 21 strings.

Project Details
 The PI for the project is Prof. Padmanabhan Krishnan
 The sanctioned amount is Rs. 2 lacs
 Sanctioned Equipment/Consumables list
 A model wooden Swarmandal from a Kanpur supplier .Rs. 20,000/-
 Spare parts kit for Swarmandal and Yazh : Rs. 30,000/-
 Epoxy Resins, CNSL Resin, Hardeners, Fillers and Fibres for Swarmandal and Yazh: Rs.
50,000/-
 Cost of manufacture and bonding : Free at VIT.
 Outsourcing charges for musical assembly and testing : Rs. 25,000/-
 Visits to museums and musical artists for models and promotion: Rs. 25,000/-
 Cost of publishing and patenting : Rs. 2 lacs.
 Projected Cost Overrun : Rs. 1.5 lacs ( A later requirement )

Proposed Functionalities & Background of the
Product:
 The Yazh is an ancient musical instrument dating prior to 3rd century BC which was used
mainly in Tamil Folk/Traditional Music.
 This project aims to recreate the same instrument with the use of some modern-day
materials such as Carbon fibre / Epoxy composite.
 It has been found experimentally with impulse hammer test that the Carbon fibre / Epoxy
composite has a better natural frequency of vibration, resolution and signal strength than
the wood.
 That is the main reason for the use of carbon fibre / epoxy composite for the
manufacturing of a musical instrument with it.
 The sweetness and somewhere sharpness of the sound lies beneath the material and
design of this instrument.
 Many papers are published on the acoustic properties of the carbon Fibre composite, in
this project we have used those properties to regenerate an old and flourished
instrument with much enhanced properties.

Sengottu Yazh:
Courtesy: Chennai Egmore
Museum

Vaccum Bagging Process
Thermocol mould for shells. Greased Mould
Layers of Carbon
fibre

Vacuum bagging for Top plate and the
shells

The Strengthening of the top plate with
hard wood:
The two padak wood plates were bonded
with epoxy under the top plate for better
strength without increasing the weight.

Machining operation for arch:
 A special type of cutting tool, commonly known as pineapple cutter was used to
drill the holes Into the yazh arch and this cutter was also used to give the trimming
operations where ever it was required.
 The speciality of the tool is that it can chip and smoothen the edge
simultaneously. This is mainly achieved by its Dual helical diamond shaped
cutting edges

The finished Yazh and the Inventor

A Few Firsts……
 The fifth Centuary Sengottu Yazh was revived using Carbon Silk Epoxy
composites.
 First ever Composite Sengottu Yazh fabricated.
 Use of silk for Dampening the frequencies by widening of amplitude curve
of the natural frequency.
 State of the art vacuum bagging method followed.
 A double helical Diamond patterned pineapple router used for machining of
the composite laminates, shells and beams
 Natural Frequencies, Mode shapes and harmonics of the plate, shell and
arch determined through impulse hammer technique.
 Custom made brass bridges using EDM.
 Rigorous analysis of Impedence, conductance, admittance and decay time
done with related physics
 FEM approach adopted for natural frequencies and harmonics analysis
 First ever Composite Sengottu Yazh to be filed for Patent

The Product Architecture of
the Swarmandal and
Sengottu Yazh is a
Common Bottom-up and
Integral Bonded Assembly.

References:
 https://rechneronline.de/musik/frequency-string.php
 https://wahiduddin.net/calc/calc_guitar_tension_from_size.htm
 https://www.gauging.com/customer-resources/film-calculators/calculate-film-thicknessgauge-by-
weight/
 (Springer Study Edition) Neville H. Fletcher, Thomas D. Rossing (auth.) - The Physics of Musical
Instruments-Springer New York (1991)
 Reconstruction of the Swaramandal using Carbon Fiber Epoxy Composites, project report submitted
by SAATTWIK DIKSHIT (12BME0085), SMEC, VIT Vellore.

Ballistic Helmet Design and
Development for the Indian Army

High Temperature High Pressure
Compression Moulding Press for Zero
Defect Parts

An Ultrasonic NDT Test of a Kevlar
Laminate at a Sample 2 mm depth
Indicates Zero Defects

146
An out come of my defense application project with Concord Helmets.

147
Ballistic Grade Polymer Composite Helmets

The Finished Product for the Army
148

Uses
• Ballistics
&
• Defense

More information….
Just type
Padmanabhan Krishnan, VIT, in LinkedIn,
Research gate, Facebook, You tube or
Google Scholar……
Or write to me for papers or reports…
Padmanabhan.k@vit.ac.in
Whatsapp Number (m) 8610904298 or
9840032002.

– All my Co-workers, Managements,
Co-Authors, Sponsors, Organizers
and Participants as the list runs to a
few hundred.
Acknowledgements

Bibliography
P,K. Mallick, Fibre reinforced composites, Marcel and
Dekker Inc., New York .
Derek Hull and T.W. Clyne, ` An Introduction to
composite materials’, Cambridge solid state science
series, 1996.
E.J. Barbero, `Introduction to composite materials
design’, Taylor and Francis ,MI.
J.K. Kim and Y.W. Mai, `Engineered interfaces in fibre
reinforced composites ‘, Elsevier, 1998.
www.wikipedia.org
Rao Tummala, Microsystems Packaging,McgrawHill.

Bibliography
Sanjay K Mazumdar, Composites Manufacturing, CRC
Press, 2002.
Geoffrey Pritchard, Reinforced Plastics Durability,
Woodhead publishing,Cambridge, England, 1999.
Skinner’s Science of Dental Materials , R.W. Phillips, A
Prism India ed, 1994.
ASTM Standards Handbooks Vols: 08.01,08.02 and
08.03, PA, USA.
www.astm.org
ANSYS Analysis Manuals, 2020.
Rayner M Mayer, Design with Reinforced Plastics,
Design Council, London.

Bibliography
K. Padmanabhan, S.Subeesh, K. Balaguru and T.
Karthik , ` 3D Modelling and Failure Analyses of IC
packages’, in ANSYS Users’ Conference CD, 6 & 7
November 2008, Bangalore.
K. Padmanabhan, S.Subeesh, K. Balaguru and T.
Karthik , ` An Analyses of Reliability and
Hygrothermal Effects in IC packages’, in ANSYS
Users’ Conference CD, 6 & 7 November 2008,
Bangalore. BEST PAPER AWARD
K. Padmanabhan, D. Sanjay and S Subeesh,` Design
and electro-hygrothermo-mechanical reliability
analyses of a leadless quad IC package’, in the

Thirukkural For Project Planning
ப ொருள்கருவி கொலம் வினையிடபைொடு ஐந்தும்
இருள்தீர எண்ணிச் பெயல். (675)
धन साधन अवसर तथा, स्थान व ननश्चित कर्म ।
पााँिों पर भ्रर् क
े बिना, वविार कर कर कर्म ॥ (६७५)
Do an act after a due consideration of the (following) five, viz. money,
means, time, execution and place.

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