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

iii

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.

vi

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.

vii

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

viii

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

ix

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

xi

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

xii

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

8

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.

9

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.

28

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.

33

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.

35

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.

36

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

44

APPENDIX