CREEP BEHAVIOUR OF DONAX GRANDIS FIBRE-REINFORCED
POLYMER COMPOSITES IN HYGRIC CONDITION
NUR TAHIRAH BINTI RAZALI
This project is submitted in partial fulfilment of requirement for the degree of
Bachelor of Engineering with Honours
(Mechanical Engineering and Manufacturing System)
Fakulti Kejuruteraan Universiti Malaysia Sarawak
2006
1
Dedicate To,
My Loving Family and My Love Ones...
11
ACKNOWLEDGEMENT
In the name of ALLAH, the Most Gracious and the Most Merciful
I would like to take this opportunity to give my acknowledgement to the entire
individual that guide and help me a lot throughout this completion of my final year
project.
Here by, I would like to express my great appreciation and deepest gratitude to
my project supervisor, Madam Mahshuri bt. Yusof, for her valuable guidance,
advices, encouragement and opinion in conducting the experiment and writing this
report.
I would like to express my thanks to my beloved family and my beloved one
for all their blessing and their continuous support. Also thanks to my friends for their
help while doing this project.
Last but not least, I also want to state my gratitude to the supporting staff that
helps me a lot in completing this project through contributing their ideas and
information.
Nur Tahirah binti Razali
Faculty of Engineering
Universiti Malaysia Sarawak.
(2005/2006)
111
ABSTRACT
The compressive creep test have been conducted for Donax Grandis fibre-
reinforced polymer composite in 10% and 20% fibre volume fraction in hygric
condition. This experimental study was taken to determine the effect of creep
behaviour of Donax Grandis fibre-reinforced polymer composite by applying various
load at hygric condition. Two test equipments were used to obtain the results and they
are testometric machine and data logger. The testometric machine was performed for
the tensile test to obtain the load that will be applied to the creep test. The creep test
was utilized both machines where the testometric machine used to applied the
constant load that have been choose from tensile test and stop at the required load.
Next the data logger took place to record the slow deformation for the creep in
voltage values. Then convert the voltage values to obtain force values. The force
values then convert to stress values and finally convert the stress values into strain
values. The graphs for creep strain versus time at constant stress were built. Results
showed that at higher stress, the strain also increase and take longer recovery time
compared to the lower stress. Longer recovery time indicate that the creep occurrence
is significant compared to the shorter recovery time. It is desired to obtain shorter
recovery time since it indicates better creep resistant. Both 10% fibre volume fraction
and 20% fibre volume fraction showed the same result that is creep occurrence is
significant at higher stress.
iv
ABSTRAK
Ujian mampatan kerayapan telah dijalankan untuk bahan komposit berasaskan
poliester dari Donax Grandis dengan komposisi 10% dan 20% gentian dalam keadaan
basah. Ujukaji ini telah dijalankan bagi menentukan sifat kerayapan gentian komposit
poliester dari Donax Grandis dalam mod mampatan dengan mengenakan pelbagai nilai
beban dalam keadaan basah. Dua alatan telah digunakan untuk mendapat keputusan
ujikaji iaitu mesin testometric and perakam Picolog. Mesin tetometric telah digunakan
untuk menjalankan ujikaji regangan untuk mendapat nilai beban yang akan digunakan
dalam ujikaji kerayapan. Kedua-dua alatan ini digunakan dimana mesin testometric
digunakan untuk mengenakan beban yang telah didapati dalam ujikaji regangan dan
dihentikan pada nilai beban yang dikehendaki. Kemudian perakam Picolog digunakan
untuk mengambil nilai perubahan perlahan bagi ujikaji kerayapan dalam nilai voltan.
Nilai voltan akan ditukar ke nilai kuasa. Nilai kuasa akan ditukar ke nilai tekanan dan
seterusnya nilai tekanan ditukar ke nilai ketegangan. Graf ketegangan kerayapan
melawan masa pada kadaran tekanan tetap telah dibuat. Keputusan menunjukkan pada
tekanan tinggi, nilai ketegangan meningkat dan masa pemulihan agak lama berbanding
pada nilai tekanan yang rendah. Masa pemulihan yang lama menunjukkan bahawa
kerayapan adalah jelas berbanding dengan masa pemulihan yang pendek. Masa
pemulihan yang pendek ialah nilai yang diingini kerana menunjukkan kalis kerayapan
yang lebih baik. Kedua-dua nilai bagi 10% komposisi gentian dan 20% komposisi
gentian menunjukkan keputusan yang sama iaitu kerayapan berlaku dengan jelas pada
tekanan yang tinggi.
V
TABLE OF CONTENTS
NO. CONTENTS
CONFIRMATION LETTER OF PROJECT REPORT
SUBMISSION
APPROVAL SHEET
TITLE PAGE
DEDICATION
ACKNOWLEDGEMENT
ABSTRACT
ABSTRAK
TABLE OF CONTENTS
LIST OF TABLES
LIST OF FIGURES
1.0 CHAPTER 1: INTRODUCTION
1.1 Introduction
1.2 Natural Composite
1.3 Scope and Objective
PAGES
1
ii
111
iv
V
vi
ix
X1
I
3
5
vi
2.0 CHAPTER 2: LITERATURE REVIEW
2.0 Introduction 6
2.1 Types of Fibres 6
2.2 Types of Resins 9
2.2.1 Unsaturated Polyester Resins 13
2.2.2 Epoxy Resins 14
2.3 Creep Definition 16
2.3.1 Creep Behaviour 17
2.3.2 Creep Characteristics in Natural Fibre-Polymer 19
Composites
2.3.3 Creep Parameter 21
2.3.3.1 Temperature 22
2.3.3.2 Fibre Content 24
2.3.3.3 Fibre-Matrix Bonding 25
2.3.3.4 Effect of Moisture Content of Polymeric 26
Composite Materials
3.0 CHAPTER 3: METHODOLOGY
3.0 Introduction
3.1 Fibre Processing
3.2 Fibre-Reinforce Lamination
3.3 Fibre Volume Fraction and Weight Fraction
3.4 Curing Process
3.5 Compression Test Specimens
3.6 Tabbing on Test Specimens
37
37
40
41
42
43
44
vii
3.7 Number of Test Specimens 45
3.8 Cutting the Composite Laminate 46
3.9 Moisture Absorption Parameters 47
3.10 Test Equipment 48
3.11 Experimental Procedures and Data Collection 51
4.0 CHAPTER 4: RESULTS AND DISCUSSION
4.0 Introduction 53
4.1 Data Collection 53
4.2 Data Conversion 55
4.2.1 Converting Voltage Values into Force 56
4.2.2 Converting Force into Stress and Strain Values 57
4.3 Creep Test on 10% and 20% Fibre Volume Fraction 60
Specimens
4.4 Creep Compliance 62
5.0 CHAPTER 5: CONCLUSIONS AND RECOMMENDATIONS
5.0 Introduction
5.1 Conclusions
5.2 Recommendations
63
63
64
REFERENCES 66
APPENDICES 71
viii
LIST OF TABLES
TABLE DESCRIPTION
NO.
Table 2.1: Relative proportions of the major constituents and
properties of some of the common natural fibres.
(Matthews and Rawlings, 1999)
PAGE
7
Table 2.2: Properties of asbestos fibres. (Matthews and Rawlings, 1999) 8
Table 2.3: Comparison of Typical Ranges of Property Values for 12
Thermosets and Thermoplastics.
(Matthews and Rawlings, 1994).
Table 2.4: Some Typical Properties of Thermosets. 15
(Matthews and Rawlings, 1994)
Table 3.1: Curing Characteristics of Unsaturated Polyester Resin 42
With Its Hardener.
Table 3.2: Dimensions and Test Condition Adopted for Compression 43
Test (Hodgkinson, 2000)
Table 3.3: Numbers of Test Specimens Prepared According to the 46
Test Type and Volume Fraction Used.
ix
Table 4.1: Load That Applied on Test Specimen 55
Table 4.2: Readings from Testometric and Picolog Recorder with 56
The Value of Force Represent by 1V of 20% Fibre
Volume Fraction at 35 N Load
x
LIST OF FIGURES
FIGURE DESCRIPTION
NO.
PAGE
Figure 1.1: Examples of natural fibre from banana, palm, kantala and 3
coir. [www. aem. eng. ua. edu/people/hague/research. asp]
Figure 1.2: Primary Composition of Bone. [www. uthscsa. edu]
Figure 2.1: Stress-strain Curves for a Range of Fibres.
(Matthews and Rawlings, 1999)
4
9
Figure 2.2: Stress Strain Curve for an Ideal Resin System. 10
[http: //www. netcomposites. com]
Figure 2.3: Strain Vs Time Behaviour During Creep Under Constant 17
Load (Dowling, 1993)
Figure 2.4: Strain Vs Time Behaviour During Creep Under Constant 22
Load (Dowling, 1993)
Figure 2.5: Creep Modulus of Hard Wood Fibre-PP Composites at 23
Different Temperatures (Bledzki and Faruk, 2003)
xi
Figure 2.6: Effect of Coupling Agent On The Strength of Epoxy 30
LaminatesmAs A Function of The Time Exposed to Boiling
Water. Volan A, Methacrylatochromic Chloride; A-1100,
Triethoxysilyl Propylamine; Z-6040, Glycidoxypropyl
Trimethoxysilane; Y- 4086,3,4-Epoxycyclohexylethyl
Trimethoxysilane (Matthews and Rawlings, 1999
Figure 2.7: The Beneficial Effect of a Silane Coupling Agent on 30
Interfacial Behaviour in The Presence of Water According
to Plueddemann (Plueddemann, 1974): (a) Hydrolysis of
The Covalent M-O Bond; (b) Shear Displacement at The
Polymer-glass Interface Without Permanent Bond Rupture.
(Matthews and Rawlings, 1999)
Figure 2.8: Hygric Strains in Unidirectional AS4/3501-6 Carbon/ 35
Epoxy Composite As A Function of Moisture
Concentration. (Daniel and Ishai, 1994).
Figure 3.1: (a). Separate the skin from inner core; (b). Submerged 38
the separated parts into the lake. (Cheing T. K., 2004)
Figure 3.2: (a). Drying the tow of fibre in force air concentration oven; 39
(b)Periodically weight measurement of the tow of fibre
during drying process. (Cheing T. K., 2004)
xii
Figure 3.3: Fibre-Reinforcement Lamination Process 40
(Daniel and Ishai, 1994).
Figure 3.4: Specimen geometries for determination of compression 44
properties of unidirectional (orthogonal), ASTM-D3410.
W= specimen width, LT = end-tab length, GL = gauge
length, h= specimen thickness, A= end-tab thickness.
(Hodgkinson, 2000)
Figure 3.4: Cutting of The Individual Specimens of Desired Width 47
From The Tabbed Specimens. (Adam et. al., 2002)
Figure 3.5: Testometric (Chieng Y. K., 2004) 48
Figure 4.1: Tensile Test Result for 10% Fibre Volume Fraction 54
Figure 4.2: Tensile Test Result for 20% Fibre Volume Fraction 54
Figure 4.3: Force Versus Time Chart for 20% Fibre Volume Fraction 57
at 35N Load
Figure 4.4: Stress Versus Time Chart for 20% Fibre Volume Fraction 58
at 35N Load
xiii
Figure 4.5: Strain Versus Time Chart for 20% Fibre Volume Fraction 59
at 35N Load
Figure 4.6: Compressive Creep Curves for 10% Fibre Volume Fraction 60
Under 8.3 MPa and 12.5 MPa Stresses.
Figure 4.7: Compressive Creep Curves for 20% Fibre Volume Fraction 61
Under 2.92 MPa and 4.1 MPa Stresses
xiv
Chapter 1 Introduction
CHAPTER 1
INTRODUCTION
1.1 Introduction
Composite material has been defined as material that are consists of two or more
physically and/or chemically distinct suitably arranged or distributed phases, with an
interface separating them. In practice, most composites have bulk phases, which are
continuous called the matrix, and one dispersed, non-continuous phase called the
reinforcement that is usually harder, stronger and stiffer. The reinforcement is usually in
fibre form. [33]
The concept of composite material is to combine different materials to produce a
new material with performance unattainable by the individual constituents. For examples,
by adding straw to mud for building stronger mud walls, carbon black in rubber, steel
rods in concrete, cement mixed with sand and fibreglass in resin. While in nature, the
examples are coconut palm leaf, cellulose fibres in a lignin matrix (wood), and collagen
fibres in an apatite matrix (bone).
PKMSP 1 8929
Chapter 1 Introduction
Reinforcements are not necessarily in the form of long fibres. They can be
particles, whiskers, discontinuous fibres, sheets and many more. A great majority of
materials is stronger and stiffer in the fibrous form than in any other form. This explains
the emphasis on using fibres in composite material design. Fibres used in advanced
composites have very high strength and stiffness but low density. They also should be
very flexible to allow a variety of methods or processing and have high aspect ratio
(length/diameter) that allows a large fraction of the applied to be transferred via the
matrix to the fibres. Fibres are added to a ductile matrix such as polymers and metals,
usually to make it stiffer, while fibres are added to a brittle matrix such as ceramics to
increase toughness.
Besides holding the fibres together, the matrix also transferring the applied load to
the fibres. It is of great importance to be able to predict the properties of a composite,
given the component properties and their geometric arrangement. Fibres reinforced
composite materials typically exhibit anisotropy, that is, some properties vary depending
upon which geometric axis or plane they are measured along. For a composite to be
isotropic in a specific property, such as Young's modulus, all reinforcing elements,
whether fibres or particles have to be randomly oriented. This is not easily achieved for
discontinuous fibres, since most processing methods tend to impart a certain orientation
to the fibres.
Most research in engineered composite materials has been done since 1965, and it
has come out with material such as aerospace structure, building structure, motor
PKMSP 2 8929
Chapter 1 Introduction
structure and other composite material that meets the performance requirements.
Moreover the usage of composite material can decrease or saving in weight and cost. [27]
1.2 Natural Composite
Other form of composite that are very popular nowadays and easily available
from the natural resources is natural composite (natural fibres). The examples of natural
fibres are cotton, flax, jute, hemp, ramie, wood, straw, hair, wool, palm, banana and silk.
In recent years, use of natural fibres as reinforces in the fibre thermoplastic composites
has been of great interest, particularly to automotive industry. These fibres have many
advantages such as low density, high specific strength and modulus, relative non-
abrasiveness, ease of fibre surface modification, wide availability and renew ability. [32]
Figure 1.1: Examples of natural fibre from banana, palm, kantala and coir.
[311
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Chanter 1 Introduction
Jute is an attractive natural fibre for use an reinforcement in composite because of
its low cost, renewable nature and much lower energy requirement for processing. The
scope for using jute fibre in place of the traditional glass fibres in different forms partly
or fully as reinforcing agents in composites stems from the higher specific modulus and
lower specific gravity of jute (- 40 Pa and 1.29 respectively) compared with those of
glass (-30 Gpa and 2.5 respectively). [30]
Bone is one of the examples of natural composites that are important in the
medical sector. Figure 1.2 shows that the bone is composed primarily of calcium-based
mineral and an organic material known as collagen. Collagen, a fibrous protein found in
skin, tendon, bone and dentin, appears to be a key component that determines the ability
of bone to withstand sudden impacts. [29]
Bone: composite of calcium minerals
and collagen
Figure 1.2: Primary Composition of Bone.
[29]
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Chapter 1 Introduction
The use of natural fibres for technical composite applications has recently been
the subject of intensive research in Europe. Many automotive components are already
produced in natural composites, mainly based on polyester and fibres like flax, hemp or
sisal. [28]. The adoption of natural fibre composites in this industry is lead by motives of
price, weight reduction and marketing, rather than technical demands. The range of
products is restricted to interior and non-structural components like door upholstery or
rear shelves.
1.3 Scope and Objective
The aim of this study is to investigate the creep behaviour of Donax Grandis
polyester composites. The effects of applying various load and fibre contents on the creep
behaviour of material will also be investigated in this study.
To achieve these objectives, the fibre from Donax Grandis are extracted and
processed prior to composite panel fabrication. Then, the fibres are mixed with resin in
two different fibre volume fractions (10% and 20%) and hot pressed to obtain a
composite panel. Then the panels are cured, cut and tabbed before performing
compressive creep test according to ASTM D3410.
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Chapter 2 Literature Review
CHAPTER 2
LITERATURE REVIEW
2.0 Introduction
Several results that have been done by the researches and other
information based on types of fibres, types of resins and any useful
information about creep that available were reviewed here.
2.1 Types of Fibres
Essentially, fibres can be classified into two main groups that are
natural fibres and synthetic fibres. However, according to Ghoshs (2004),
fibres are basically classified into three groups with respect to their origin,
which are natural fibres, semi-synthetic or artificial fibres and synthetic fibres.
Natural fibres are mainly extracted from plant (bast fibres and leaf fibres) and
animal. Artificial fibres are chemically modified natural polymers where only
the side groups are partly, significantly or fully modified by a chemical
process, while synthetic fibres are completely man-made and nature are unable
to synthesize these fibres.
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Chapter 2 Literature Review
According to Matthews and Rawlings (1999), fibres can be categorized
into natural fibres and synthetic fibres. Natural fibres are basically extracted
from plant and animal. The fibres that extracted from plant are essentially
micro-composites consisting of cellulose fibres in an amorphous matrix of
lignin and hemicelluloses and often have a high length to diameter ratio, called
the aspect ratio, of greater than 1000. Table 2.1 shows the relative proportion
of the major constituents and properties of some of the common natural fibres.
Still, the strength and stiffness of these fibres are low compared to the
synthetic fibres.
Table 2.1: Relative proportions of the major constituents and properties
of some of the common natural fibres. (Matthews and Rawlings, 1999)
Density
p
(Mg/m)
Cellulose
(%)
Hemi-
celluloses
(%)
Lignin
(%)
Young's
Modulus
Ef
(GPa)
Tensile
strength
6Tf
(MPa)
Specific
modulus
[(GPa) /
(Mg/m3)]
Specific
strength
[(Mpa) /
(Mg/m)]
Wood 1.5 40 40 20 - 500 - 333
Jute 1.3 72 14 14 55.5 442 43 340
Hemp - 71 22 7 - 460 - -
Sisal 0.7 74 - 26 17 530 24 757
According to Ghoshs (2004), natural fibres such as jute, hemp, kenaf,
sisal and wool are widely used in clothing and garment industry, non-apparel
areas such as twines and ropes, nets, shopping bags, mats or carpets and
geotextiles. Asbestos, another type of natural fibre, of mineral origin
PKMSP 7 8929
Chapter 2 Literature Review
commonly used for heat insulation purposes and making structural composites
for housing, municipal, transport and related sectors. According to Matthews
and Rawlings (1999), asbestos can be divided into two classes, which are
chrysotile and crocidolite. Chrysotiles have good flexibility, stiffness and
strength, while crocidolite has good stiffness and tensile strength but their
flexibility is poor. Table 2.2 shows the properties of chrysotile and crocidolite.
Table 2.2: Properties of asbestos fibres. (Matthews and Rawlings, 1999)
Property Chrysotile Crocidolite
Young's Modulus (GPa) 160 190
Tensile Strength (MPa) 3100 3500
Density (Mg/M3) 2.56 3.43
Specific modulus [(GPa)/(Mg/m )] 62.5 55.4
Specific Strength [(MPa)/(Mg/m )] 1211 1020
Maximum service temperature (°C) 600 400
Matthews and Rawlings (1999) mentioned that synthetic fibres can be
classified as synthetic organic fibres and synthetic inorganic fibres. Examples
of synthetic organic fibres are Aramid, which consist of Kevlar, Twarlon and
Technora, and Polyethylene that consist of Spectra and Dyneema. Meanwhile,
synthetic inorganic fibres are Glass, Alumina, Boron, Carbon, and Silicon
based fibres. Figure 2.1 shows the stress-strain curves for a range of fibres to
make a comparison between the organic and inorganic synthetic fibres.
PKMSP 8 8929
Chapter 2 Literature Review
5
4
Cabon(HS)
Polyethylene 51000
123 Tensile strain (%)
Figure 2.1: Stress-strain Curves for a Range of Fibres.
(Matthews and Rawlings, 1999)
2.2 Types of Resins
Wright (2000) defined resins as any class of solid, semi-solid, or liquid
organic material, generally the product of natural or synthetic origin with a high
molecular weight and with no melting point. Besides holding the fibres together,
matrix also transfer the applied load to the fibres.
According to the NetComposites web page, any resin system that will be used
in a composite material will require good mechanical properties, good adhesive
properties, good toughness properties and good resistance to environmental
degradation.
PKMSP 9 8929
Chapter 2 Literature Review
Figure 2.2 shows the stress-strain curve for an ideal resin system. The curve
shows high ultimate strength, high stiffness and high strain to failure, which means
that the resin initially stiff but at the same time will not suffer from brittle failure.
High adhesion between resin and reinforcement fibres is necessary to ensure that the
loads are transferred efficiently and will prevent cracking or fibre/resin debonding
when stressed. Toughness is a measure of a material's resistance to crack propagation.
Generally the more deformation the resin will accept before failure the tougher and
more crack resistant the material will be. Conversely, a resin system with a low strain
to failure will tend to create a brittle composite, which cracks easily. It is important to
match this property to the elongation of the fibre reinforcement. Good resistance to
the environment, water and other aggressive substances together with an ability to
withstand constant stress cycling are properties that essential to any resin system and
important for use in a marine industry.
Ultimate Tensile Strength plastic deformation
Tensile Stress Elastic
Deformation
i
Failure
Strain (%)
i
Strain to Failure
Figure 2.2: Stress Strain Curve for an Ideal Resin System. 1331
PKMSP 10 8929
