UNIVERSITI TEKNOLOGI MALAYSIA -...
Transcript of UNIVERSITI TEKNOLOGI MALAYSIA -...
PSZ 19:16 (Pind. 1/97)
UNIVERSITI TEKNOLOGI MALAYSIA
BORANG PENGESAHAN STATUS TESIS♦
JUDUL: ANALYSIS ON THE FRONTAL NON-CRUSH ZONE OF A UTM____
RACING CAR_________________________________________________
SESI PENGAJIAN: 2005/2006
Saya LIM SHI YEE__________________________________
(HURUF BESAR)
mengaku membenarkan tesis (PSM/Sarjana/Doktor Falsafah)* ini disimpan di Perpustakaan Universiti Teknologi Malaysia dengan syarat-syarat kegunaan seperti berikut:
1. Tesis adalah hakmilik Universiti Teknologi Malaysia. 2. Perpustakaan Universiti Teknologi Malaysia dibenarkan membuat salinan untuk tujuan
pengajian sahaja. 3. Perpustakaan dibenarkan membuat salinan tesis ini sebagai bahan pertukaran antara
institusi pengajian tinggi. 4. **Sila tandakan (√ )
SULIT (Mengandungi maklumat yang berdarjah keselamatan atau
kepentingan Malaysia seperti yang termaktub di dalam AKTA RAHSIA RASMI 1972)
TERHAD (Mengandungi maklumat TERHAD yang telah ditentukan oleh organisasi/ badan di mana penyelidikan dijalankan)
TIDAK TERHAD
Disahkan oleh __________________________________
____________________________________ (TANDATANGAN PENULIS) (TANDATANGAN PENYELIA)
Alamat Tetap: EN. RAZALI BIN SULAIMAN______ 45, KAMPUNG AMAN, 86600
PALOH, JOHOR Nama Penyelia Tarikh: 27 MAY 2006___________ Tarikh: __27 MAY 2006_____________
√
CATATAN: * Potong yang tidak berkenaan. ** Jika tesis ini SULIT atau TERHAD, sila lampirkan surat daripada pihak berkuasa/organisasi
berkenaan dengan menyatakan sekali sebab dan tempoh tesis ini perlu dikelaskan sebagai SULIT atau TERHAD
♦ Tesis dimaksudkan sebagai tesis bagi Ijazah Doktor Falsafah dan Sarjana secara penyelidikan, atau disertai bagi pengajian secara kursus dan penyelidikan, atau Laporan Projek Sarjana Muda (PSM).
UTM(FKM)-1/02
Fakulti Kejuruteraan Mekanikal
Universiti Teknologi Malaysia
PENGESAHAN PENYEDIAAN SALINAN E-THESIS
Judul tesis : …………………………………………………………………………………………… ANALYSIS ON THE FRONTAL NON-CRUSH ZONE OF A UTM RACING CAR
……………………………………………………………………………………………..
Ijazah : …………………………………………………………………………………………… IJAZAH SARJANA MUDA KEJURUTERAAN MEKANIKAL
Fakulti : …………………………………………………………………………………………… FAKULTI KEJURUTERAAN MEKANIKAL
Sesi Pengajian : …………………………………………………………………………………………… 2005/2006
Saya_________________________________________________________________________________ LIM SHI YEE
(HURUF BESAR)
No. Kad Pengenalan _______________ mengaku telah menyediakan salinan e-thesis sama seperti tesis
asal yang telah diluluskan oleh panel pemeriksa dan mengikut panduan Penyediaan Tesis dan Disertasi
Elektronik (TDE), Sekolah Pengajian Siswazah, Universiti Teknologi Malaysia, November 2002.
831221-01-6178
(Tandatangan pelajar)
(Tandatangan penyelia sebagai saksi)
Alamat Tetap:
45, KAMPUNG AMAN, Nama Penyelia: EN. RAZALI BIN SULAIMAN Fakulti: Kejuruteraan Mekanikal
86600 PALOH, JOHOR
Tarikh: __ ______________ _____________ Tarikh: ___ __________________ _______________27 MAY 2006 27 MAY 2006
Nota: Borang ini yang telah dilengkapi hendaklah dikemukakan kepada FKM bersama penyerahan CD.
SUPERVISOR’S DECLARATION
“I hereby declare that I have read this thesis and in my opinion this thesis
is sufficient in terms of scope and quality for the award of the degree of
Bachelor of Mechanical Engineering”
Signature : .......................................................
Name of Supervisor : . . ... ...................... ....... .....................EN. RAZALI BIN SULAIMAN
Date : 27 MAY 2006
ANALYSIS ON THE FRONTAL NON-CRUSH ZONE OF A UTM RACING
CAR
LIM SHI YEE
A thesis submitted in fulfillment of the
requirements for the award of the degree of
Bachelor of Mechanical Engineering
Faculty of Mechanical Enginnering
Universiti Teknologi Malaysia
MAY 2006
ii
I declare that this thesis entitled “Analysis on the frontal non-crush zone of a UTM
racing car” is the result of my own research except those cited in references.
Signature : .............................................
Name of Author : LIM SHI YEE
Date : 27 May 2006
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To my beloved dad and mum.
For their infinite love and support.
To my dearest siblings.
Cloud, snow, sun and wind.
My world would not be complete without them.
To 5SMM coursemates.
The good old days that we had through the years.
iv
ACKNOWLEDGEMENT
First and foremost, I would like to grab the opportunity to express my sincere
appreciation and gratitude to my project supervisor, Mr. Razali Bin Sulaiman for his
valuable advices; consistent assistance and guidance. His continued support and
motivation is the main key to succeed in this project.
In addition, I would like to thank Mr. Shukur Abu Hassan for his knowledge
and information. Special thanks to my friends who have been giving me their helping
hands and invaluable ideas.
Lastly, my deepest gratitude and love goes to my family for their continuous
encouragement and financial support.
v
ABSTRACT
The main objective of this project is to study the crash performance of the
front bulkhead and design a structure to be incorporated in the frontal non-crush zone
of a UTM racing car. Composite honeycomb core structure was designed and
produced using carbon fiber reinforced plastic by using filament winding process. A
finite element honeycomb model was developed and then the simulation was
completed using LS-DYNA software. Quasi-static test was done on the composite
honeycomb structure using hydraulic press machine. Interpretation of results by LS-
DYNA analysis was used to predict the deformation and failure of the structure and
after that compare it with the experimental results derived from the testing. The
feasibility of both experimental and computational results was discussed. Further
improvements to get better results from analysis and testing were discussed as well.
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ABSTRAK
Objektif utama project ini adalah untuk mengkaji prestasi perlanggaran
bahagian hadapan ‘bulkhead’ dan untuk mereka satu struktur baru bagi dipersatukan
di bahagian hadapan ‘non-crush zone’ bagi kereta perlumbaan UTM. Struktur teras
‘Honeycomb’ komposit telah direka dan dicipta dengan menggunakan gentian
karbon diperkuatkan dengan plastik melalui proses belitan filamen. Satu model
‘Honeycomb’ daripada Kaedah Unsur Terhingga telah dibangunkan dan simulasi
tersebut telah disempurnakan dengan perisian LS-DYNA. Mesin penekanan
hydraulik telah digunakan untuk melakukan ujian Quasi-statik ke atas struktur
‘Honeycomb’ komposit. Selepas itu, keputusan yang telah diintepretasi melalui
analisis LS-DYNA digunakan untuk menjangkakan perubahan bentuk dan kegagalan
bagi struktur dan seterusnya dibandingkan dengan keputusan eksperimen yang
diperoleh daripada ujian-ujian yang telah dijalankan. Kemudian, kesesuaian dan
kemunasabahan kedua-dua keputusan daripada eksperimen dan simulasi
diperbincangkan. Cadangan-cadangan selanjutnya untuk mendapatkan keputusan
yang lebih baik daripada analisis dan ujian dibincangkan juga.
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TABLE OF CONTENTS
CHAPTER ITEM
PAGE
TITLE
DECLARATION
DEDICATION
ACKNOWLEDGEMENT
ABSTRACT
ABSTRAK
TABLE OF CONTENTS
LIST OF TABLES
LIST OF FIGURES
i
ii
iii
iv
v
vi
vii
x
xi
1 INTRODUCTION 1
1.1 Objectives 4
1.2 Scope 5
2 BACKGROUND 6
2.1 Formula SAE 6
2.2 Finite Element Analysis (FEA) Software
2.2.1 LS-DYNA (LSTC)
7
8
2.3 Composite Honeycomb Structure
2.3.1 Conventional Way of Producing a
Honeycomb Structure
10
10
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2.3.2 The Proposed Composite Honeycomb
Structure Making Process
11
3 LITERATURE REVIEW 13
3.1 Carbon Fiber Reinforced Plastic (CFRP) 13
3.2 Filament Winding 16
4 COMPUTATIONAL ANALYSIS 19
4.1 LS-DYNA 19
4.2 Hexagon Analysis 20
4.3 Honeycomb Core Model 20
5 EXPERIMENTAL ANALYSIS 22
5.1 Quasi-Static Test for Hexagons
5.1.1 Instron Machine
22
25
5.2 Quasi-static Test for Composite Honeycomb
Structure
5.2.1 Hydraulic Press Machine
5.2.2 Displacement Transducer
5.2.3 Load Cell
26
26
28
28
6 RESULTS 29
6.1 Initial Testing Results for Hexagons 29
6.2 LS-DYNA Analysis Results for Hexagon
6.2.1 Material Plastic Kinematics (Steel)
6.2.2 Material Composite Damage (Composite)
33
33
34
6.3 LS-DYNA Analysis Results for Honeycomb Core 35
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6.4 Composite Honeycomb Testing Results 36
7 CONCLUSIONS 39
7.1 Comparison of Results 39
7.2 Conclusions 40
8 DISCUSSIONS AND RECOMMENDATIONS 41
8.1 LS-DYNA Analysis 41
8.2 Test Rig 42
8.3 Honeycomb Size 42
REFERENCES 43
APPENDIX 44
x
LIST OF TABLES
TABLE NO. TITLE PAGE
Table 3.1 Comparison between carbon fiber and steel 15
Table 3.2 Comparison of materials 17
Table 3.3 Possibilities in manufacturing 18
Table 7.1 Comparison between analysis results and testing results 39
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LIST OF FIGURES
FIGURE NO. TITLE PAGE
Figure 1.1 Body frame of a UTM racing car 2
Figure 1.2 Hexagonal honeycomb structure 3
Figure 1.3 Cross section view of honeycomb structure being
installed in the non-crush zone
3
Figure 2.1 The process of making honeycomb structure from
corrugated plats
10
Figure 2.2 The proposed composite honeycomb structure making
process
11
Figure 2.3 Sandwich structure 12
Figure 3.1 Carbon Fiber composite 13
Figure 3.2 Comparison of mechanical properties between steel and
carbon fiber reinforced epoxy resin
15
Figure 3.3 Filament winding 16
Figure 3.4 Schematic diagram of making a hexagon from a mandrel 17
Figure 4.1 Solid modeling of honeycomb core 21
Figure 5.1 Hexagon with 30º degree winding angle (side view) 23
Figure 5.2 Hexagon with 55º degree winding angle (side view) 23
Figure 5.3 Hexagon with 80º degree winding angle (side view) 24
Figure 5.4 Instron machine 25
Figure 5.5 The setting of hexagon with strain gauge connected to
data logger
25
Figure 5.6 The setting of composite honeycomb testing 26
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Figure 5.7 Hydraulic press machine (Yasui YHP-50A) 27
Figure 5.8 Base (support) 27
Figure 5.9 Presser 27
Figure 5.10 Gauge 27
Figure 5.11 Displacement transducer 28
Figure 5.12 Load cell 28
Figure 6.1 Deformed shape of hexagon with 30º winding angle 29
Figure 6.2 Deformed shape of hexagon with 55º winding angle 30
Figure 6.3 Deformed shape of hexagon with 80º winding angle 30
Figure 6.4 Graph of force against deflection for 30 degree winding
angle
31
Figure 6.5 Graph of force against deflection for 55 degree winding
angle
31
Figure 6.6 Graph of force against deflection for 80 degree winding
angle
32
Figure 6.7 Graph force against time for hexagon (steel) 33
Figure 6.8 Graph force against time for hexagon (composite) 34
Figure 6.9 Graph force against time for honeycomb model 35
Figure 6.10 Deformation of composite honeycomb after compression
testing
36
Figure 6.11 Deformed honeycomb core (top view) 37
Figure 6.12 Deformed honeycomb core (side view) 37
Figure 6.13 Graph of force against deflection for honeycomb
compression testing
38
CHAPTER 1
INTRODUCTION
Safety is the most concerned issue in designing a formula racing car. During
a frontal impact, the whole car is exposed to a considerable longitudinal deceleration.
A high quantity of kinetic energy is being carried. This energy should be dissipated
as smoothly as possible in order to reduce the deceleration to which the driver is
exposed. Thus, the frontal impact structure at the front of the Formula racing car is
designed to be a crushable structure to dissipate as much kinetic energy as possible in
the case of frontal impact. But there must be a very strong non-crush zone after the
crushable nose cone to protect the driver’s leg. This non-crush zone is shown in
figure 1.1 which is shaded in red color.
2
Figure 1.1: Body frame of a UTM racing car
Hexagonal composite honeycomb is chosen to be installed at the frontal non-
crush zone of the racing car. Honeycomb is a type of cellular material with a two-
dimensional array of hexagonal cells as shown in figure 1.2 [1]. The honeycomb
comprises of many small hexagons produced by carbon fiber reinforced plastic
through filament winding process.
3
Figure 1.2: Hexagonal honeycomb structure
The front bulkhead is assumed to be totally crushed but the honeycomb
structure acts as a non-crush zone to protect the driver’s leg with the least
deformation is desired when the frontal impact occurred. The cross section of this
structure is shown in figure 1.3. The crushable nose cone is not studied in this
research.
Figure 1.3: Cross section view of honeycomb structure being installed in the
non-crush zone
4
Experimental and numerical investigations towards this honeycomb structure
were implemented in this project but initially a testing and simulation on a single
composite hexagon was being carried out. Crash modeling and simulation were used
during the design phase to study the response of the structures to dynamic crash
loads and to predict the driver responses to impact with probability of injury. A finite
element model of a hexagon was developed using the non-linear, explicit dynamic
code LS-DYNA. Simulation of hexagon responses to the crash impact was done to
compare with the numerical model. At the same time, crash test was performed on
the single hexagon using Instron Machine, with the whole process controlled by the
computer. Comparison between numerical data and the experimental results was
done to see the differences.
After the experimental and numerical investigation towards single composite
hexagon was done, the strongest composite hexagon was chosen to continue with the
further study for honeycomb structure. Simulation towards the honeycomb structure
was carried out by importing the structure modeling done by Solidworks into LS-
DYNA. Besides, compression test was done in the honeycomb structure using
hydraulic press machine after the maximum force to crash the structure was
predicted by LS-DYNA. After that, both results were compared to see the feasible of
the results derived.
1.1 Objectives
The main objective of this project is to study the crash performance of the
front bulkhead and design a structure to be incorporated in the frontal non-crush zone
of a UTM racing car. Interpretation of results by LS-DYNA analysis is used to
predict the deformation and failure of the structure and after that compare it with the
experimental results derived from the testing.
5
1.2 Scope
A study of crash phenomenon was carried out. Besides, a detailed analysis on
LS-DYNA program was also done. A finite element hexagon structure was
developed using LS-DYNA. The scope of this project is focused on modeling and
simulation of the structure using LS-DYNA analysis and testing on the structure
itself. Apart from that, results of the testing and LS-DYNA analysis was investigated,
compared and thoroughly discussed.
CHAPTER 2
BACKGROUND
2.1 Formula SAE
Formula SAE began in 1981 with 4 universities entering the competition and
has now evolved to a 4-day, 140 University event held annually in Detroit, Michigan.
The Formula SAE competition is for SAE student members to conceive, design,
fabricate and compete with small formula-style racing cars. The restrictions on the
car frame and engine are limited so that the knowledge, creativity, and imagination
of the students are challenged. The cars are built with a team effort over a period of
about one year and are taken to the annual competition for judging and comparison
with approximately 120 other vehicles from colleges and universities throughout the
world. [2]
The competition challenges students to design and manufacture a single seat,
open wheel style racecar for a potential customer, the weekend autocross enthusiast.
The car must have exceptional handling, acceleration and braking capabilities. It
must be attractive, comfortable and most of all safe for the driver. It must be
affordable, reliable, easy to maintain, and well designed for manufacture. With these
criteria, the competition touches upon virtually every area of engineering design.
7
The judging of the racecars begins with team presentations on the
marketability, manufacturability and engineering design of the vehicle. Once the
vehicles have past the technical safety inspection they compete in five dynamic
events. These events include a skid pad to test turning ability, a 100m-acceleration
run, an autocross event that tests speed, acceleration and handling, and an endurance
race where fuel economy and reliability are challenged.
In total, over 140 engineering schools participate in the Formula SAE
competition making it the largest and most prestigious student design competition in
the world.
2.2 Finite Element Analysis (FEA) Software
Finite element analysis (FEA) software uses a numerical technique to model
and analyze complex structure by solving boundary-value problems. Finite element
analysis involves the use of finite element (FE) software to study mechanical parts
and components that undergo significant strains and stresses. [1] There is a lot of
finite element software in the market such as ALGOR, NASTRAN, ABACUS,
COSMOS, I-DEAS, RADIOSS and LS-DYNA. The most commonly used software
for crash analysis is RADIOSS and LS-DYNA.
RADIOSS is explicit Finite Element Analysis software, developed by
MECALOG and dedicated to performing dynamic, non linear structural analysis
involving large strains. RADIOSS is widely used by industrial companies worldwide
to perform crash analysis simulations and significantly reduce the amount of physical
testing required in a variety of fields.
LS-DYNA is a multi-purpose, explicit and implicit finite element program
used to analyze the nonlinear dynamic response of structures. It has fully automated
contact analysis capability and a wide range of constitutive models to simulate a
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whole range of engineering materials. LS-DYNA has many solution procedures to
simulate the physical behavior of 2D and 3D structures: nonlinear dynamics, thermal,
failure, crack propagation, contact, quasi-static, Eulerian, arbitrary Lagrangian-
Eulerian, fluid-structure interaction, multi-physics coupling, etc.
2.2.1 LS-DYNA (LSTC)
LS-DYNA by Livermore Software Technology Corporation (LSTC) is a
general purpose transient dynamic finite element program capable of simulating
complex real world problems. LS-DYNA is optimized for shared and distributed
memory Unix, Linux, and Windows based, platforms. It is an explicit finite element
code, which uses a Langrangian formulation. The equations of the motion are
integrated in time explicitly using central differences. The method requires very
small time steps for a stable solution, thus it is particularly suitable for impact and
crash simulation. [3] The code contains materials model for metals and composites.
It has also easy and efficient contact algorithms.
LS-DYNA comes with LS-PrePost and LS-OPT. LS-PrePost is an advanced
interactive program for preparing input data for LS-DYNA and processing the results
from LS-DYNA analyses. LS-OPT allow the users to structure the design process,
explore the design space and compute optimal designs according to the specified
constraints and objectives.
The solution types of LY-DYNA includes nonlinear dynamics, rigid body
dynamics, quasi-static simulations, normal modes, linear static, thermal analysis,
fluid analysis, finite element analysis(FEM), underwater shock, failure analysis,
crack propagation, real-time acoustic, design optimization, implicit springback,
multiphysics coupling, structural-thermal coupling, adaptive re-meshing, smooth
particle hydrodynamics and element-free meshless method.
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It is widely used in the automotive industry for crashworthiness and occupant
safety. It predicts car’s behavior in a collision and the effects of the collision upon
the car’s occupants. Besides, it also eliminates the experimental testing of prototypes,
thus saving time and expense.
LS-DYNA can also be applied for sheet metal forming, military and defense
application, and in the aerospace industry to simulate bird strike, jet engine blade
containment and structural failure.
10
2.3 Composite Honeycomb Structure
2.3.1 Conventional Way of Producing a Honeycomb Structure
Figure 2.1: The process of making honeycomb structure from corrugated plats
Figure 2.1 shows the conventional way of making honeycomb structure.
Firstly, the corrugated plats are connected together by using adhesive at the indicated
place. After that, layer by layer the corrugated plates are added to form a honeycomb
structure.
Corrugated Plat
Adhesive
11
2.3.2 The Proposed Composite Honeycomb Structure Making Process
The hexagons used in making honeycomb structure were produced using
filament winding process. A hexagonal mandrel was used in the filament winding
process. After that, the hexagons were then cut into the desired size. The cut
hexagons were combined together using adhesive to form a honeycomb structure.
Each stages of the honeycomb making process until the complete honeycomb
structure were shown in figure 2.2.
Combined Hexagons Honeycomb core
Hexagons + Epoxy Hexagons cut according desired size
Figure 2.2: The proposed composite honeycomb structure making process
12
After the composite honeycomb core was done, two plats were added to the structure
to form a sandwich structure before installing it into the non-crush zone of the racing
car. The sandwich structure is shown in figure 2.3.
Plat Sandwich structure
Figure 2.3: Sandwich structure
CHAPTER 3
LITERATURE REVIEW
3.1 Carbon Fiber Reinforced Plastic (CFRP)
Figure 3.1: Carbon Fiber composite
Carbon fiber composite, particularly those with polymeric matrices, have
become the dominant advanced composite materials for aerospace, automobile,
sporting goods, and other applications due to their high strength, high modulus, low
density, and reasonably cost. [4] Technically the term ‘carbon fiber’ is used to refer
to carbon filament thread, or to felt or woven cloth made from carbon filaments as
shown in figure 3.1. The fiber-polymer composite made with carbon filament is more
properly termed carbon fiber reinforced plastic (CFRP or CRP). It is becoming
14
increasingly common in small consumer goods as well, such as laptops, tripods, and
fishing rods.
Carbon fibers are usually grouped according to the modulus band in which
their properties fall. These bands are commonly referred to as: high strength (HS),
intermediate modulus (IM), high modulus (HM) and ultra high modulus (UHM). The
filament diameter of most types is about 5-7mm. Carbon fiber has the highest
specific stiffness of any commercially available fiber, very high strength in both
tension and compression and a high resistance to corrosion, creep and fatigue. Their
impact strength, however, is lower than either glass or aramid, with particularly
brittle characteristics being exhibited by HM and UHM fibers.
Carbon fiber composites are among the strongest materials yet devised. The
strength is provided by the fibers themselves, but the epoxy resin matrix is essential
to bond the fibers together in the correct orientation, protect them from damage, and
enable successive layers to be laminated.
The resin must function as an adhesive, be soft enough during the production
process to avoid damaging the delicate fibers, and when hardened be able to function
over wide temperature ranges. Figure 3.2 compares the strength and density of a
carbon fiber composite with the equivalent properties of steel normalized at 100.
Weight for weight, carbon fiber reinforced epoxy resin is 5 times stronger than steel.
15
Figure 3.2: Comparison of mechanical properties between steel and carbon
fiber reinforced epoxy resin
You can also notice on table 3.1 that carbon fibers are 3 times stronger and
more than 4 times lighter than steel.
Table 3.1: Comparison between carbon fiber and steel
Tensile strength Density Specific strength
Carbon fiber 3.50 1.75 2.00
Steel 1.30 7.90 0.17
16
3.2 Filament Winding
Filament winding is one of the oldest composite manufacturing methods. It
was probably the first method to be automated, and remains today one of the most
cost effective methods for mass production. Filament winding is also somewhat
unique, being one of very few processes that do not build up the composite one
uniform ply at a time.
Figure 3.3: Filament winding
Filament Winding is the process of winding resin-impregnated fiber or tape
on a mandrel surface in a precise geometric pattern. This is accomplished by rotating
the mandrel while a delivery head precisely positions fibers on the mandrel surface
as shown in figure 3.3. By winding continuous strands of carbon fiber, fiberglass or
other material in very precise patterns, structures can be built with properties stronger
than steel at much lighter weights.
This process makes high strength, hollow and generally cylindrical products
such as pipes, storage tanks, and pressure vessels. Reinforcement fibers are drawn
through a liquid resin bath and wound round onto a rotating mandrel at one or more
precisely defined wind angels so that the resulting products have the combination of
mechanical properties in both the hoop and axial directions. After the winding is
17
completed, the composite product is hot cured and removed from the mandrel. The
schematic diagram of making a hexagon from a rotating mandrel is shown in figure
3.4.
Figure 3.4: Schematic diagram of making a hexagon from a mandrel
Table 3.2: Comparison of materials
18
Comparison between carbon fiber, aluminum and steel is shown in Table 3.2
while table 3.3 shows the possibilities of filament winding in manufacturing.
Table 3.3: Possibilities in manufacturing
Filament winding machines operate on the principles of controlling machine
motion through various axes of motion. The most basic motions are the spindle or
mandrel rotational axis, the horizontal carriage motion axis and the cross or radial
carriage motion axis. Additional axes may be added, typically a rotating eye axis or a
yaw motion axis, and when the pattern calls for more precise fiber placement further
additional axes may be added.
Filament winders are not limited to producing cylindrical shapes, in fact, the
flexibility of these machines allow for the manufacturing of almost any geometric
shape imaginable.
CHAPTER 4
COMPUTATIONAL ANALYSIS
4.1 LS-DYNA
LS-DYNA was used to analyze and predict the crash behavior of my
composite honeycomb model. The reason LS-DYNA was chosen as the analysis
software in my project is that it has fully automated contact analysis capability
(contact algorithm) which is useful when surfaces of the structure contact to each
other during the deformation. [5] This is an important capability in compression.
First of all, the simulation of a single hexagon is being done followed by the
composite honeycomb model. An initial material was chose to run the simulation
which is Material Plastic Kinematic [6]. After the trial, Material Composite Damage
[6] was used in the model simulation.
20
4.2 Hexagon Analysis
A finite element hexagon model was being developed using LS-DYNA pre-
processor. This hexagon was modeled by six shell elements with wall thickness
equals to 3mm. The height of the model is 50mm. The material chosen for the first
analysis is Material Plastic Kinematic. The model was then meshed using
quadrilateral elements type.
Next, a moving rigid wall with an impact velocity equal to 100mm/s was then
developed 2mm above the hexagon model to represent the impact mass. The material
used is Material Rigid [6]. After that, Contact Automatic Surface to Surface is
defined between the surfaces of rigid wall and hexagon while Contact Automatic
Single surface is defined for the hexagon’s surface itself. Besides, the termination
time is set to 0.03 seconds. Then, the analysis was started using the LS-DYNA
solvers. The second simulation was finished with Material composite damage.
The deformed shape of the hexagon can then be shown at different response
time in the post processor of LS-DYNA. Different graphs of the simulation can also
be found after the analysis was completed at the Post-processor of LS-DYNA.
4.3 Honeycomb Core Model
The solid modeling of the honeycomb structure was being done using
Solidworks. Then the model was imported into LS-DYNA to do simulation. The
model is shown in figure 4.1.
21
Figure 4.1: Solid modeling of honeycomb core
All the hexagons that formed the honeycomb are same size. The same
materials were used in the simulation of this structure. Then, the same procedures
with hexagon were used once again to simulate this honeycomb structure using LS-
DYNA. The deformed shape can be seen clearly at the Post-Processor. Total energy
was calculated and various graphs were plotted.
CHAPTER 5
EXPERIMENTAL ANALYSIS
5.1 Quasi-static Test for Hexagons
In order to carry out the compression testing on the hexagons with different
degree of winding angle, the apparatus needed are Instron Machine (figure 5.4), load
cell (figure 5.12), data logger (figure 5.5), strain gauges and others. The purpose of
this initial testing on the hexagons is to get the physical properties of carbon fiber
which is required to be used as input values for hexagon and honeycomb models in
LS-DYNA simulation. There are three different degree of winding angle which is 30º
winding angle (figure 5.1), 55º winding angle (figure 5.2) and 80º winding angle
(figure 5.3).
23
Figure 5.1: Hexagon with 30º winding angle (side view)
Figure 5.2: Hexagon with 55º winding angle (side view)
24
Figure 5.3: Hexagon with 80º winding angle (side view)
25
5.1.1 Instron Machine
This machine is used to carry out quasi-static testing for single hexagons with
different degree of winding angle which is 30º, 55º and 80º. Strain gauges were fixed
on each of the hexagon and connected to the data logger.
Figure 5.4: Instron machine
Figure 5.5: The setting of hexagon with strain gauge connected to data logger
26
5.2 Quasi-static Test for Composite Honeycomb Structure
The apparatus used in accomplishing the testing are Hydraulic press machine,
load cell (figure 5.12), displacement transducers (figure 5.11), strain gauges, end
plates, data logger and others. The setting of the testing is shown in the figure 5.6.
6mm End plate
Honeycomb structure
Load cell
Base
Displacement transducer
Strain gauge
50mm
Figure 5.6: The setting of composite honeycomb testing
5.2.1 Hydraulic Press Machine
Hydraulic press machine model Yasui YHP- 50A was used to compress the
composite honeycomb structure which placed on the base. This hydraulic press is
able to provide a maximum pressure of 39.24MPa or 35 ton. The hydraulic press
machine (figure 5.7) consists of base (figure 5.8), presser (figure 5.9) and gauge
(figure 5.10).
27
Figure 5.7: Hydraulic press machine Figure 5.8: Base (support)
(Yasui YHP-50A)
Figure 5.9: Presser Figure 5.10: Gauge
In this testing, the maximum pressure of this machine was achieved. Due to
this limitation, the testing was being stopped at the load of 35 ton and all the data
were collected using the data logger.
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5.2.2 Displacement Transducer
Figure 5.11: Displacement transducer
5.2.3 Load Cell
Figure 5.12: Load cell
CHAPTER 6
RESULTS
6.1 Initial Testing Results for Hexagons
From the initial hexagons testing results, graphs force against deflection for
each winding angle were plotted. Deformed shape for each specimen was also shown
in figure 6.1, 6.2 and 6.3.
Figure 6.1: Deformed shape of hexagon with 30º winding angle
30
Figure 6.2: Deformed shape of hexagon with 55º winding angle
Figure 6.3: Deformed shape of hexagon with 80º winding angle
Graphs for 30, 55 and 80 degree winding angle are shown in figure 6.4, 6.5
and 6.6 as followed.
31
30 Degree Winding Angle
-2000
200400600800
10001200140016001800
0 2 4 6 8 10 12 14 16Deflection (mm)
Forc
e (k
gf)
Figure 6.4: Graph of force against deflection for 30 degree winding angle
55 Degree Winding Angle
-500
0
500
1000
1500
2000
0 2 4 6 8 10 12 14 16
Deflection (mm)
Forc
e (k
gf)
Figure 6.5: Graph of force against deflection for 55 degree winding angle
32
80 Degree Winding Angle
-2000
200400600800
1000120014001600
0 2 4 6 8 10 12 14 16 18 20 22 24 26
Deflection (mm)
Forc
e (k
gf)
Figure 6.6: Graph of force against deflection for 80 degree winding angle
From the graphs plotted, we found out that the hexagon with 80º winding
angle is the strongest compared to the other two degree of winding angle. Results
show that hexagon with higher degree of winding angle can support the higher load
and can absorb more energy before it fails.
Thus, the hexagon with 80º winding angle was chosen for the honeycomb
core testing. The composite honeycomb was made up of hexagons with 80º winding
angle. Besides, the properties of this winding angle are used as the input values for
the hexagon simulation in LS-DYNA.
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6.2 LS-DYNA Analysis Results for Hexagon
6.2.1 Material Plastic Kinematics (Steel)
Figure 6.7: Graph force against time for hexagon (steel)
From the graph plotted above (figure 6.7), the maximum crushing load is
about 42.5kN which denoting that in order to create the first collapsed hinge, 42.5kN
is needed. For the places in the graph indicating ‘A’, hinges were produced at those
places. Higher energy is needed to produce a hinge. Thus, after many hinges were
created and a maximum is reached, the model will fail.
34
6.2.2 Material Composite Damage (Composite)
Figure 6.8: Graph force against time for hexagon (composite)
From figure 6.8, the maximum crushing load is 13kN. It can be seen that, it
took about 13kN to produce the first collapse hinge. After the first hinge is produced,
the others hinges were created subsequently with lesser force compared to the first
hinge. The model collapsed after many hinges were created.
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6.3 LS-DYNA Analysis Results for Honeycomb Core
Figure 6.9: Graph force against time for honeycomb model
From figure 6.9, it can be seen that the maximum crushing load is 1000kN.
This means that, LS-DYNA predicts a crushing load of 1000kN for composite
honeycomb structure. This indicates that, in order to produce the first collapse hinge,
a load of 1000kN is needed!
Apparently, this crushing load is too high for Instron machine, thus the
hydraulic press machine was chosen to carry out the compression testing.
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6.4 Composite Honeycomb Testing Results
After the compression testing was done, the data was collected by the data
logger. Graph was plotted using the data collected. The deformation of the structure
was shown as followed.
35 mm (min) 6mm End plate
Figure 6.10: Deformation of composite honeycomb after compression testing
From figure 6.10, it can be seen that the maximum penetration is about
15mm. The total load that was used to perform this failure is 35 ton which is the
maximum load for the hydraulic press machine. Apart from that, it can be seen that
the end plates were bent due to the insufficient thickness used. It was not strong
enough to act as a rigid plate. Thus, the honeycomb core deformed unevenly due to
the bending of end plate. This is one of the reasons that cause the big difference in
results between analysis and testing.
37
Figure 6.11: Deformed honeycomb core (top view)
Figure 6.12: Deformed honeycomb core (side view)
38
GRAPF FORCE (F) AGAINST DEFLECTION (d)
050
100150200250300350400
0 10 20 30
DEFLECTION,d (mm)
FO
RC
E,F
(k
N)
Figure 6.13: Graph of force against deflection for honeycomb compression
testing
From the graph derived from compression testing above (figure 6.13), it
clearly shows that the force used to crush the composite honeycomb is still
increasing. This denotes that the specimen did not fail completely and more energy is
needed to totally crush the composite honeycomb core. Each small peak that
achieved in the graph indicating hinges that created on the structure. Each of these
hinges contributed to the failure of this structure. The deformation of structure is
shown in figure 6.11 and 6.12.
CHAPTER 7
CONCLUSIONS
7.1 Comparison of Results
From the results that we get from both the simulation and testing, comparison
was shown in table 6.1.
Table 7.1: Comparison between analysis results and testing results
Method LS-DYNA (kN) Testing (kN)
Hexagon 13 15
Honeycomb 1000 350
From table 6.1, it can be seen that the value that predicted by LS-DYNA for
the hexagon is close to the testing value which is 13kN and 15kN respectively. As
for the honeycomb core, the values for both analysis and testing varied in a big
40
difference. The results for honeycomb core from analysis and testing will be
compared in a single graph to see the feasibility of the results obtained.
7.2 Conclusions
Throughout the study and testing, it can be concluded that a composite
structure that produced through filament winding process can designed and
constructed to be used as a structural member in the non-crush zone of a racing car.
This proposed honeycomb structure design can be developed further to be installed
in the non-crush zone of the racing car which protects the driver’s legs during a
frontal collision. This can be proven through the analysis and testing done on the
honeycomb model and structure respectively.
Apart from that, LS-DYNA can be used to predict and analyze the structural
performance of the honeycomb structure. Material composite damage which was
chosen to be the material of the honeycomb structure produced feasible results too.
CHAPTER 8
DISCUSSIONS AND RECOMMENDATIONS
For this project, there are some improvements can be done towards LS-
DYNA analysis and test rig to obtain better results for comparison between
computational results and analysis results. Besides, the size of the honeycomb could
be made smaller for higher strength.
8.1 LS-DYNA Analysis
For the LS-DYNA analysis, the main capability is the contact algorithm
which cannot be found on other software. The Contact Automatic Surface to Surface
and Contact Automatic Single surface functions were useful in the honeycomb
analysis as the honeycomb surface touch each others during the compression. Beside
that, the honeycomb surface touches the rigid wall during the compression too. Thus,
with these capabilities, more feasible results were obtained.
Besides, Material Composite Damage was chosen as the material to analyze
for the honeycomb model. The results obtained are feasible and valid to be used as a
42
reference. For further research, Material Enhanced Composite Damage [5] can be
chosen to do analysis as it is more complicated compared to Material Composite
Damage.
8.2 Test Rig
Although the predicted result by the LS-DYNA for the honeycomb structure
is 1000kN, but due to the limitation of Hydraulic press machine, the maximum load
can be produced is only 350kN. There is no other bigger machine in UTM which can
produce higher load. Thus, the testing was completed up to the machine limitation.
Although the results obtained cannot be compared completely with the simulation
results but we managed to compare the trends of the graph obtained from both
simulation and testing.
8.3 Honeycomb Size
The size of the hexagons in the honeycomb is determined by the mandrel
used during the filament winding process. The proposed hexagon diameter is the
smallest diameter that can be made by the manufacturer so far due to the mandrel
available. But definitely, it could be made smaller for better strength. The smaller the
hexagon size used in forming the honeycomb together with the epoxy, the stronger
the honeycomb will be.
43
REFERENCES
1. Ruan, D. et al. (2003). “In-plane Dynamic Crushing of Honeycombs-A Finite
Element Study”, International Journal of Impact Engineering, 28, pp. 161-182
2. Society of Automotive Engineers, Inc. (2005). “2005 Formula SAE®”, United
States of America: 2005 Formula SAE® Rules
3. Bisagni, C. et al. (2004). “Progressive Crushing of Fiber-reinforced Composite
Structural Components of A Formula One Racing Car”, Composite Structures
4. Chung, Deborah D. L. (1994). “Carbon Fiber Composites”, United States of
America: Butterworth-Heinemann
5. Livermore Software Technology Corporation (2001). “LS-DYNA Volume I”,
Livermore: Keyword User’s Manual
6. Livermore Software Technology Corporation (2001). “LS-DYNA Volume II”,
Livermore: Keyword User’s Manual
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APPENDIX