1

CHAPTER 1

INTRODUCTION

1.1 Background

Failure in building structure is a critical matter that need to be taken seriously. There are

many factors affecting the strength of the structure making it essential for regular

maintenance. Besides error in building design, when the structure in a building is

suppressed by load which exceeding its limit capacity, the failure of structural may

occurred as well. Besides, the change in existing practice of the building do also resulting

in new imposed loading that may exceed in the initial design. As these failures may

produce cracks, they may also have been exposed to harsh conditions which can weaken

the structure and causing it to deteriorate. Hence, strengthening of structural will be

necessary in order to prevent these problems from getting worse.

Researchers had developed few techniques and solutions to overcome these

structural failures. At first, an external reinforcement using epoxy bonded steel plates

have been introduced. This method consists of using steel plates bonded to the tension

face of the subjected reinforced concrete beams using epoxy. This steel plates were

2

effectively strengthen the beams, however other materials are sought to replace steel after

they discovered the disadvantages of using steel. It is found that the steel is prone to

corrosion due to moisture content in air and the installation process is rather difficult to

execute due to factors such as its heavyweight and abundantly precautions.

Then, an alternative method using fibre reinforced composite plate had been

developed to replace steel plate in external reinforcement. This method is similar to the

steel plate method which involving epoxy resin bonding on the surface of reinforced

concrete structural. The inherent properties of composite materials in the plate include

high specific tensile strength, good fatigue, corrosion resistance and simple installation.

Theoretically, these fibre composite plate do have a higher ultimate strength and lower

density. Furthermore, the fibre reinforced composite plate takes a lower cost and it does

not corrode. This bring more advantages in becoming external reinforcement.

Years ago, the composite materials used in development of composite plates are

man-made materials consisting two distinctive component materials and the resulting

material being different from the component materials. Hence, this material is generally

described as a rational combination of two or more materials to yield a product that is

more efficient from its components. The components are fibre phase which provides

strength, and the other one is fibre binder in matrix phase. The matrix used in composite

materials like epoxy acts as a binder and bond the fibres in the intended position which

provides the composite material its structural integrity by giving shear transfer capability.

This leads to the development of glass and carbon fibre reinforced plate, CFRP and

GFRP. Later in recent, biocomposite materials combining natural or plant fibre with

polymer matrices is introduced to replace the man-made fibre due to several factors

focusing on environment and sustainability, as biofibre plates are eco-friendly.

In this research study, kenaf fibre is chosen as the materials in developing biofibre

reinforced composite plate as an external reinforcement as they are likely environmental

friendly and economical. It is clearly that this biocomposite can help to reduce the

increasing cost of using petroleum-based material. Kenaf fibre comes with high flexural

strength and tensile strength, making it as one of the choices in extruded, moulded and

3

non-woven products. The fibre has replace the glass fibres in utilized as reinforcement

material for polymeric composites. Plant fibres are certainly have more advantages

compared to glass and carbon fibres as they are cost effective, have lower density,

renewable, recyclable, abrasive and biodegradable. This method is the best solution to the

main problem as it promotes the sustainability development and green development.

Recently, people are alert on the materials chosen for structural upgrading has

additional function in efficiency and sustainability. The materials should have fulfil these

criteria such as environmental friendly, sustainable, recyclable, reusable, renewable and

beneficial to local economy by generating income along low in cost. Waste disposal has

been a major issue in modern cities as more lands are required in land filling. This

problem is due to the expansion world population and needs of raw materials in satisfy

demands on world market is growing well. So, by practicing sustainable development

along with green building, these problems stand a chance to be reduced to minimum.

Figure 1.1 shows the general flow of the background on the introduction of fibre

composite materials to the structural industry.

FIGURE 1.1: General flow of the background of natural fibre composite plate

Strengthening of RC beam

Steel Plate

Carbon Fibre Composite Plate

Natural Fibre Composite Plate

4

1.2 Statement of the Problem

Cracked and weakened reinforced concrete beams will disturb the structure's stability and

worsen it. However, reconstructing or rebuilding the reinforced concrete beam is not one

of the top choice because it will definitely increase the cost and time. One of the best

solution would be rehabilitation of the cracked and weakened beams, by means a suitable

repair is adequate enough to solve this matter. So, the rehabilitation can be done by using

external reinforcement such as reinforced composite plate on the beam.

Carbon fibre reinforced plate (CFRP) and glass fibre reinforced plate (GFRP) are

able to replace steel plate effectively due to its high specific tensile strength, lower

density, corrosion resistance and easier installation. In spite of that, they have their own

disadvantages. When it comes to costing, these materials are significantly expensive

compare to other fibres. Furthermore, this man-made materials are not biodegradable,

brittle and hazardous as well.

Health hazardous due to manufacturing carbon fibre is one of the major problems

in nowadays. The disadvantages of carbon are its high price and brittle property. When it

compare to resins, fibres are distinctively inert. The main hazard of carbon is the

mechanical irritation, either of the skin or the respiration. The very small particle of

carbon can easily inhaled and thus respiratory problems or worse. But the size of kenaf

fibre is relatively bigger than carbon, too large to be inhale. Mechanical irritation

occurred when itching after direct contact with glass and carbon. Most fibres have a

sizing that can cause chemical irritation.

The carbon is hazardous when it is subjected to a fire after a crash. It produces

dangerous and hazardous compounds such as acids, cyanides and any other threat

compounds that bond with the fibres, which are carried by the smoke and flames into the

air. This poses a serious threat to anyone involving the fire extinguishment or any other

people nearby. The fibres will infiltrate into the skin and dissolve into the bloodstream.

Thus us compounded by the fact that the body does not recognize carbon as a foreign

elements and will not attempt to repels it. This proves that the carbon particle is

hazardous to human being and may bring harm to human health once it is not handled in

5

the right way. Moreover, these materials doubtlessly need extra precaution when being

handled.

Thus, to overcome this issue, biofibres was introduced to the industry. Biofibres

material do offer many advantages topping the problems encountered by previous

solution. These biofibres are renewable, recyclable, biodegradable, lightweight, non-

hazardous, higher flexural and tensile strength, relatively low density and non-toxic.

Further investigation on the development of natural fibre has been conducted by many

researchers in the world. Various green fibres are being used including jute, hemp, coir,

sisal and also kenaf.

1.3 Purpose of the Study

External reinforcing of reinforced concrete structures has slowly gained the popularity in

the industry because it is much easier and time effective compared to reconstructing the

whole deteriorating structure. In the beginning, steel plate are been used but some other

problems might occurred due to its natural properties.

The usage of steel plates might not be as efficient as expected, leading to the main

purpose of the study, which is to assess the effectiveness of kenaf fibre reinforced

composite plate as external reinforcement instead of steel plates in strengthening the

structural beams.

1.4 Objectives of the Study

The main objectives of the research study are as follow:

1. To investigate the physical properties of kenaf fibre reinforced composite plate.

2. To investigate the mechanical property of uncoated and coated kenaf fibre

reinforced composite plates at different weathering conditions.

6

1.5 Research Question

The research questions of this research study are:

1. What is the factors affecting the strength of kenaf fibre reinforced composite

plates?

2. How will kenaf fibre reinforced composite plates will be affected its strength by

the presence of water content?

3. How effective the epoxy resin in resisting water molecule from diffusing into

kenaf fibre reinforced composite plates?

4. What difference can be made by coated and uncoated kenaf fibre reinforced

composite plate?

5. Does long exposure to water content surface can affected the strength of kenaf

fibre reinforced composite plate?

1.6 Scope of Research

The scope of studies is determined in order to accomplish the objective of the research

study. Many studies have been performed to investigate on the structural properties of

natural fibre composite plates. However, the research study will focus on kenaf fibre only.

The collected kenaf fibres are raw materials which were purchased from LKTN

(Lembaga Kenaf dan Tembakau Malaysia).

On the other hand, the material chosen as bonding matrix phase would be epoxy

resin, model EPOXY BBT-7892 purchased from Berjaya Bintang Timur Sdn. Bhd. This

epoxy resin is consisting two liquid components which are resin and hardener. This model

is specifically designated for hand lay-up fabricating process in composite applications.

Different condition of kenaf fibre reinforced composite plate are fabricated which

is correctively uncoated and coated composite plates. This is carried out in order to

determine the best form of kenaf fibre composite plate is to use as application on external

reinforcement. The kenaf fibres are uniformly distributed in one direction during the

7

fabrication process in order to provide a better tensile strength. Tensile strength testing for

the mechanical property of the product will be based on ASTM standard D3039. Physical

properties of the fibre plates, for example moisture content and density will be also carry

out.

1.6 Outline of the Thesis

This thesis will provide an overview on the development of kenaf fibre reinforced

composite plate and also focused on the investigation of the tensile properties of kenaf

fibre reinforced composite plate, each uncoated and coated with different weathering

conditions.

In the chapter one, a general idea on the background of fibre reinforced plate will

be briefly explained with problems occurred. Reasons of the application of this

technology on strengthening will stated as well. This chapter summarizes the purpose and

gives an overview on this research study.

Chapter two will explain about the literature review of the study, providing

relevant information to support the study. There would be a deliberation on the

classification and characteristics of the natural fibres including kenaf fibre including

applications of materials applied on the research. Several methods of fabrication will be

discussed to clarify the execution of the study.

On the next chapter, a research methodology will be illustrate as detailed

procedure on conducting the development of kenaf fibre reinforced composite plate will

be explained thoroughly. The method used to fabricate the kenaf fibre reinforced

composite plate is the hand lay-up method. Then, the methodology will be continued with

the preparation on the physical properties test and the mechanical property test of the

product. In the end of the chapter, a proper research plan will be presented too.

Chapter four will focusing on the analyzing the results and outcomes from the

experimental and laboratory work. The targeted output of this study is mainly on the

8

uncoated and coated kenaf fibre with various weathering conditions. This resulted will be

recorded from the mechanical property test. Besides, physical properties test will help the

study to elucidate the characteristics of kenaf fibre reinforced composite plate,

concentrating at the density, water content and water absorption. The analysis of results

will be explained fully with assistance of tables and graphs. Next, problems occurred

during laboratory work will be discussed.

Finally, on chapter five, a conclusion will be made based on the objective declared

in the thesis. Then, recommendations for improvement of future research will be included

in this chapter.

9

CHAPTER 2

LITERATURE REVIEW

2.1 Introduction

Nowadays, as an interest growth in green development, a quite amount of researchers

have been study on the replacement of man-made fibres with green or natural fibres.

Thus, the use of green fibres in building structural has further accepted by the industries.

There are several properties that are required for construction purposes such as high

specific strength and modulus, low cost, low density, absence of health threats, easy

modifications and sustainability.

2.2 Natural Fibres

Natural fibres have become increasingly used in many applications not only

because they are environmental friendly, but it is also because of their various desirable

properties including stiffness. Natural fibres has been used on many products such as

cloths, carpets, ropes, paper, mats and also building materials. The synthetic fibres mostly

10

produced from non-renewable resources and poses many problems. For an example,

health risks rise up in the application of petroleum based products either from direct or

indirect exposure such as water and air pollution. It is clearly natural fibre is helping in

the needs of achieving sustainable development. Natural fibres can be extracted from

leaves, bark and fruit of the plants itself. Natural fibres such as cotton, hemp, kenaf, sisal

and others are widely used in numerous industries.

FIGURE 2.1: Hemp and cotton

The use of natural fibres and epoxy matrix is highly beneficial. It is because its

strength and toughness of the resulting composites are greater than those of the

unreinforced plastics. Plus, cellulose-based natural fibres are technically durable, low in

cost, lightweight, abundant and renewable. Recently, natural fibres reinforced polymer

materials are used commercially such as automotive, sporting good, marine, electrical,

industrial, construction, household appliances and even aerospace structure. Table 2.1

will show the advantages and disadvantages of natural fibre.

11

TABLE 2.1: Advantages and disadvantages of natural fibres

Advantages Disadvantages

Producible with low investment at low

cost, which makes the material an

interesting product for low-wage

countries.

Thermal recycling is possible, as glass

causes problems in combustion

furnaces.

Low specific weight, resulting in a

higher specific strength and stiffness

than glass.

Benefits on being designated for

bending stiffness.

Renewable resources, the production

requires little energy as CO2 is used

while oxygen is given back to the

environment.

Price can fluctuate by harvest results or

agricultural politics.

Lower durability, fibre treatments can

improve this issue.

Have moisture absorption that causes

swelling of the fibres.

Lower strength properties, particularly

its impact strength.

2.3 Kenaf Fibre

Kenaf fibres have history of cultivation in some areas in the world such as India,

Bangladesh, United States of America, South Africa, Vietnam, Thailand, Indonesia, and

even in Malaysia. Known as Hibiscus Cannabinus, it is a tropical crop related to jute or

cotton, and it has been incorporated in various applications, successfully. The stems of

kenaf are able to produce two types of fibre, which are coarser fibre in the outer layer

(bast fibre) and a finer fibre in the core. The harvesting time of kenaf fibre only takes

about 150 days. This shows that this fibre are more efficient in producing wood products,

reducing the demand of of timber, and leads to the solutions of deforestation activities.

12

It is an annual or biennial herbaceous plant growing to 1.5-3.5 m tall with a

woody base. The stems are 12 cm diameter, often but not always branched.

The leaves are 1015 cm long, variable in shape, with leaves near the base of the stems

being deeply lobed with 3-7 lobes, while leaves near the top of the stem are shallowly

lobed or unlobed lanceolate. The flowers are 815 cm diameter, white, yellow, or purple;

when white or yellow, the centre is still dark purple. The fruit is a capsule 2 cm diameter,

containing several seeds.

Initially, kenaf leaves were consumed in human and animal diets, and the bast was

used as bags and the sails for Egyptian boats. They were also used as rope, twine, coarse

cloth and also paper. Other than that, in 1992, California, Texas, Louisiana and

Mississippi used kenaf for animal bedding and food. Nowadays, kenaf fibre is widely

used including in engineering wood, insulation, clothing-grade cloth. soil-less potting

mixes, animal bedding, packing material, and also oil and liquid absorbent.

FIGURE 2.2: Kenaf fibres

13

2.3.1 Properties of Kenaf Fibre

The physical properties of natural fibres are depending on the type of fibre itself. Kenaf

filament consist of discrete individual fibres sized 2-6 mm. Their properties are

depending on the sources, age, separating technique and even the history of the fibres.

The stem is straight and it is also unbranched, composed of an outer layer, which is bark,

and a core. The process of separation of the stem into bark and core is considerably easy,

either by chemical or enzymatic retting.

The performance of the materials is presented in terms of their mechanical

properties. Tensile properties, flexural properties, compression properties, impact

properties, and wear behaviour are important to determine and for the sake of validity of

the kenaf ability, focusing under extreme and critical conditions, which are the connection

between the material and the engineering performances. It is proven that the kenaf fibre is

able to demonstrate an equivalent tensile strengths. Besides, the flexural strength of kenaf

also is remarkably high compared to other fibres such as hemp, coir, and sisal.

Plasticization is one of the sign of humidity aging, which contributes to long-term

failure of an organic matrix. This is due to the water absorption property of the fibre.

Plus, the humidity aging also may cause defects to the mechanical properties and

dimensional stability of composites. Hence, this became one of the major concerns in

developing solutions towards green technology. In kenaf side, it will reach its equilibrium

at a certain specific immersion time. However, it will change its magnitude of absorption

at a certain time, where it may solve few obstacles. This means that the penetrability of

water, causing it to become active as water penetrating into the interface through voids

induced by swelling of the kenaf fibres, resulting the ability of the kenaf to neutralize the

acidity itself.

14

TABLE 2.2: Advantages and disadvantages of kenaf fibres as natural fibres

Advantage Disadvantage

High specific strength

Renewable

Low cost

Less health risk

Good heat conductor

Low impact strength

High moisture absorption

Low durability

Quality varies

Poor heat resistance

2.4 Epoxy Resin

Matrix materials have been used in structural industry for a long time. However, they can

be classified into two main categories. The categories are consist of thermoplastic

polymer and thermosetting polymers. Thermoplastic polymer is a type of plastic that

changes its properties depending on temperature. It will become soft when heated and

smoothly hardened when cooled. Under a certain temperature, they have a significant

structural strength, but they will soften then melt upon heating. Thermoplastic polymer

are such as polyethylene, polypropylene and vinyl.

On the other hand, thermosetting, also known as thermoset, is a type of polymer

material that irreversibly cures, as it takes heat to do the curing. Other than that, this type

of polymer also cured by a chemical reaction, or irradiation, such as electron beam

processing. Initially in liquid or malleable form, thermosetting polymer cannot be

reheated and melted back to liquid form once it is hardened. Example of thermosetting

polymers are epoxy, polyester, silicone and alkyd.

Thermoset materials are basically stronger than thermoplastic materials. This can

be explained by the three dimensional network of bonds, which is cross-linking. Also,

thermoset materials are better in withstand the higher temperature applications up to the

decomposition temperature. However, since it is non-reformable, the chances for

recycling the material is close to zero. Thus, for this fabrication of kenaf composite plate,

thermosetting material, epoxy is used.

15

In general, uncured epoxy resins have only poor mechanical, chemical and heat

resistance properties. However, excellent properties can be obtained by curing. Curing is

a process of reacting the linear epoxy resin with suitable curatives to form three-

dimensional cross-linked thermoset structures, such as hardeners. Curing of epoxy resins

is an exothermic reaction, hence it may produces sufficient heat to cause thermal

degradation if not controlled. So, epoxy resins has becomes one of the best option in

producing composite plate due to its better bonding between fibres ad matrix, along with

compatible sizing, its ability to cure at room temperature and good creep resistance.

As stated, epoxy can be cured by adding hardener and each hardener gives

different cure profile and impacts different properties to finish products. This can be

elaborated with the relation between the selection of hardeners with the rate of curing

time, and also the volume ratio of epoxy resin and the hardener. However, it cost higher

than other matrix materials. Epoxy also provides higher viscosity then most polyester,

causing a slightly higher degree of difficulty in execution. The table below shows the

advantages and disadvantages of epoxy resin.

TABLE 2.3: Advantages and disadvantages of epoxy resin

Advantage Disadvantage

Wider range of properties

Lower shrinkage during curing time

Absence of volatile elements during

cure

Ability to resist chemical and solvents

Provides great adhesion to wide variety

reinforcement

Higher cost

Longer curing time

16

2.5 Natural Fibre Reinforced Composite

A composite material is made by mixing two or more materials or elements or even by a

unique combination of properties. For thousand years ago, the wattle and daub is a prove

of man-made composite materials that has been applied as building materials, resulting

them one of the earliest composite materials been developed ever. Besides, the most

common composite materials are Portland cement concretes and asphalt concretes, which

are widely used in construction industries nowadays.

Practically, the natural fibre reinforced composites are composite materials made

from natural fibres and polymer matrix such as epoxies. Biocomposites are hybrid

materials made of polymer resin reinforced by natural fibres, providing a significantly

high mechanical and physical performances. The short and discontinuous natural fibre

composites can be considered as a success, but the application of long continuous fibres

are widely encountered lately. The long continuous fibres is basically more advanced for

capital-intensive materials and products. The structural properties can be modified by

changing the direction of the fibres in the resin, increasing the strength.

Within the bonding in the composite plate, the poor capabilities and drawbacks of

the individual elements will be solved. This can be shown by its high in stiffness and

strength with a low weight and excellent corrosion resistance. Since the excellence

performance takes up a considerably long duration, this technology gains a higher

demands compared to wool and metal.

2.6 Fabrication Methods

The fabrication methods are able to influence the performance of composite that

produced, although the mixing product of fibres and matrix itself resulting higher

performances in any properties. This shows the importance of fabrication method in the

manufacturing of the composites. In a nutshell, there are so many methods are used in the

industry, varying techniques, advantages, limitations and specific characteristics of final

production. Nevertheless, these hand lay-up, resin transfer moulding, Seemann composite

17

resin infusion moulding process (SCRIMP) and compression moulding can be considered

as the upfront in the industry as the fabrication methods.

2.6.1 Hand Lay-Up Method

This method is the simplest yet the most executed in the industry. The hand lay-up

method is applied to manufacture a significant amount of fibre reinforced polymer

composite products. The process consists of chopped or continuous fabric which

impregnated or soaked with resin using handheld rollers, brushers and other related

apparatus. The fabric layer are stacked on each other, with each layer being applied with

matrix, which is the resin. Open mold is used for the hand lay-up process. By this way, it

can save cost because it can be easily modifiedto develop products with different shape

and surface texture.

In the open mold process, the surface of mold is applied with several layers of

wax or glycerin so that the products are easily removed. It is also sprayed with a

pigmented polyester resin called gel coat. On top of the gel coat, fibre layers will be

saturated by resin and catalyst at the suitable room temperature are located. To achieve a

proper and uniform wetting on the reinforcement, each fibres will be pressed by using

hand rollers. "Prepreg", also known as pre-impregnated reinforcement of resin is carried

out to ensure the consistent control over reinforcement to resin ratio by weight or volume.

This method may take a longer time and it involves a lot of labor-intensive steps even

though the procedures are simple. Still, there are possibilities of the variation throughout

the process. In spite of its simplicity in the execution, a good ventilation and protective

equipment are essential for the participated workers.

18

FIGURE 2.3: Hand lay-up method

2.6.2 Resin Transfer Moulding (RTM)

Unlike the hand lay-up method, this resin transfer moulding is a close mould process,

whereby the mould are kept under a low pressure. The preformed fibre reinforcement is

placed in the mould throughout the fabrication process and they will be infused with resin

and catalyst, as the fibres themselves will pumped into the closed mould under low

pressure. Next, the mould is heated and cured in order to create a composite part. The

surfaces of the mould is then utilized in the process by coating it with gel coat, or even

applied with a veil to create a the best quality of smooth surface of final product.

In the fabrication process, the complex shapes can be made in one operation with

or without inserts. The process can be automated with limited void content. On the

19

brighter sides, this method can release the less hazardous emissions. The resin commonly

used for this method are polyester, vinyl, ester, epoxies and others. This process also

consisting a mineral fillers, which are nanoclays. The mineral fillers will exfoliate to

enhance fire retardancy, mechanical properties, durability and surface finish.

Furthermore, a good controlling system in the process under low pressure

provides a high product strength with minimal fibre damages. Due to its high production

rate and ability to produce complex shapes, it is more preferable in the automobile

industry. Figure below shows the process of resin transfer moulding method.

FIGURE 2.4: Resin transfer moulding process

20

2.6.3 Seemann Composite Resin Infusion Moulding Process (SCRIMP)

The Seemann composite resin infusion moulding process (SCRIMP) is actually a

vacuum-assisted resin transfer moulding process that produces parts for aerospace,

transportation, and infrastructure applications. SCRIMP is applied for co-moulding

composite skins and core in one piece without using autoclave. It is similar to the resin

transfer moulding which contributes in performing parts using dry fibres and core.

However this process does not need two sided mould or resin pressure, unlike the resin

transfer moulding.

Based on the figure below, the fibre layer including any core is saturated, or

soaked in one infusion step, which leads to the elimination of the weaker secondary bonds

and relatively longer times that are associated with the resin transfer moulding process.

Fabric preform acts as an effective breather layer, eliminating the trapped air voids in the

resin infusion process. Resin infused through the fibre layers are spread evenly and the

fibres will be saturated. This method is applied in the manufacturing of composite parts

like those with single skin and cored construction as well as complex three-dimensional

truss parts.

FIGURE 2.5: Seemann composite resin infusion moulding process (SCRIMP)

21

2.6.4 Compression Moulding

The compression moulding is a technique off moulding which a preheated polymer is

placed into an open, heated mould cavity. The good thing is, this method can be used for

both thermosetting polymer, as well as thermoplastic polymer for the sake of

manufacturing purposes. Throughout the process, matrix materials including the fibres are

applied directly in the mould cavity and then will be compressed under a certain pressure.

The mould is closed with a top plug and forces are applied to perform the compression

process of the involving materials to contact all area of mould evenly.

The thermosetting polymer will be cured through heating process. On the other

hand, the thermoplastic polymer will soften up and form into the mould cavity shape with

heat and pressure. The controlling of the temperature, pressure and time residence are

depending on the properties of employed materials and the dimension of product

required. The compression moulding is high in volume and pressure plastic moulding

method, which is suitable for complex moulding and high strength products. Thus, this

method can be considered as one of the top choices in the automotive industry for

manufacturing parts, due to its time cnsuming and high production rate.

FIGURE 2.6: COMPRESSION MOULDING

22

CHAPTER 3

RESEARCH METHODOLOGY

3.1 Introduction

This chapter generally describes and discusses the overall plan of the experiment program

to develop the kenaf fibre reinforced composite plate. The main focus on this research

study is on the difference in strength between uncoated and coated kenaf fibre composite

specimens. This will define the effects of water existence in the reinforced fibre plate.

The research plan will includes the determination of kenaf fibre reinforced composite

plate, physically and mechanically including its development.

Data that have been gathered will be analyzed to detect the effect of water

existence to kenaf fibre reinforced composite plate. Hence, there would be various

conditions will be tested on the specimens, uncoated and coated.

23

3.2 Research Plan

The research plan in this study is primarily divided into three main components which is

including the fabrication of kenaf and the testing upon the specimens. Thus, the

components are fabrication of kenaf fibre reinforced composite plate, physical properties

tests on the specimens, and mechanical property test on the specimens. The proper

procedure will be explained thoroughly. Besides, the optimum load for compaction will

calculated.

First of all, after kenaf fibres is purchased from LKTN (Lembaga Kenaf dan

Tembaga Malaysia), after an appropriate preparation of the fibre, the fabrication of kenaf

fibre reinforced composite plate will be carried out. The execution of fabrication will be

done with using hand lay-up method. By this, the first objective has been achieved.

After 16 plates have been developed, the plates will be tested physically and

mechanically. In the beginning, physical properties tests will be carried out. There would

be three tests in order to find the physical properties of kenaf fibre reinforced composite

plates, which are density, moisture content and water absorption. This step is tally with

the second objective of the research study. Furthermore, the density test will be following

ASTM D3800 while moisture content and water absorption test will be following ASTM

D5229.

Step three, another specimens of kenaf fibre composite plate will be tested on its

mechanical property, which is tensile strength. In this study, only tensile property will be

determined, since the main objective of the development of kenaf fibre reinforced

composite plate is to overcome the external tension applied on the concrete beam.

Concrete structure can withstand compression effectively, but not tension force. To

investigate the tensile strength of the kenaf fibre plate specimens, ASTM D3039 will be

followed. By this, the last objective of the research study is achieved.

Throughout the fabrications and physical and mechanical properties test,

observations will be made. The data will be monitored and recorded for the next analysis.

The main target of the tests is to find the relation between the strength of the kenaf fibre

24

reinforced composite plate with the water existence. Ergo, conclusion will be made

wholly. On the conclusion, further recommendations also will be stated.

FIGURE 3.1: General flow of research plan

25

3.2 Fabrication of Kenaf Fibre Reinforced Composite Plate

In fabricating kenaf fibre reinforced composite plate, the hand lay-up method will be used

because it is the most suitable method among all.

For each plate, there will be five layer of kenaf fibre weighed 12g each, making it

total 60g of kenaf fibre for each plate. The size of plate is 400mm x 80mm x 6mm. The

mould used is made of steel, and matrix material is epoxy resin. The fabrication process

will end with compaction of the plate with an optimum load.

3.3.1 Material Preparation

3.3.1.1 Kenaf Fibre

Kenaf bast fibres have been selected as the material of fibre phase in the fabrication of

kenaf fibre reinforced composite plate. The bast is used due to the distribution of the

fibres. The fibre composite plate bond on the tension surface of beam must provide ample

tensile strength in order to achieve external reinforcement. Hence, the fibres are preferred

to be long and continuous along the plate so that a better tensile strength can be provided.

Moreover, the fibres are needed to uniformly distributed in one direction. However, kenaf

core fibre does not obey the long and continuous characteristics as they are short and thin

walled.

During the preparation of the fabrication process, the fibres have to be handle

properly in order to accomplish the requirements; continuous, uniformly distributed,

unidirectional. disintegrate and straighten. There are several methods can be applied with

assisting tools such as clips, and comb. The fibre first is cleaned to remove dirt and others

to maximize the quality. The discontinuous fibre is also need to be removed, as tensile

strength may drop due to its existence. All the unwanted are removed by combing. This

combing technique is also usable to straightening the curly parts of the fibres. Despite

combing, there are still curly parts that need to be done, hence, cellophane tape and clips

26

are used by fixing the fibres at both ends by using this. Plus, this fixing can ensure the

fibres are not overlapping each other, and they also won't be twisted.

FIGURE 3.2: Kenaf fibre

The strength of kenaf fibre composite plate depends on the bonding between

matrix and fibres. If fibres are not disintegrated properly, gaps will existed between

fibres, causing the plate to inexact. There will be conditions where some parts of fibre

will not fully soaked with epoxy, resulting air voids within fibres.

3.3.1.2 Epoxy Resin

Matrix materials have been used in structural industry for a long time. However, they can

be classified into two main categories. The categories are consist of thermoplastic

polymer and thermosetting polymers. Thermoplastic polymer is a type of plastic that

changes its properties depending on temperature. It will become soft when heated and

smoothly hardened when cooled. Under a certain temperature, they have a significant

structural strength, but they will soften then melt upon heating. Thermoplastic polymer

are such as polyethylene, polypropylene and vinyl.

27

On the other hand, thermosetting, also known as thermoset, is a type of polymer

material that irreversibly cures, as it takes heat to do the curing. Other than that, this type

of polymer also cured by a chemical reaction, or irradiation, such as electron beam

processing. Initially in liquid or malleable form, thermosetting polymer cannot be

reheated and melted back to liquid form once it is hardened. Example of thermosetting

polymers are epoxy, polyester, silicone and alkyd.

Thermoset materials are basically stronger than thermoplastic materials. This can

be explained by the three dimensional network of bonds, which is cross-linking. Also,

thermoset materials are better in withstand the higher temperature applications up to the

decomposition temperature. However, since it is non-reformable, the chances for

recycling the material is close to zero. Thus, for this fabrication of kenaf composite plate,

thermosetting material, epoxy is used.

The epoxy purchased consists of two component liquid, which is the resin and the

hardener. For application in fabricating the kenaf composite plate, the mixing ratio of

resin and hardener is 5:1. Averagely, 250g of resin will be mixed to 50g of resin in a

suitable container. This measurement usually enough for making one composite plate.

Safety precautions such as wear rubber gloves are required when mixing the epoxy, as

skin irritation may occurred when directly contact to the skin. Since the material is

corrosive, precaution needs to be taken seriously. Furthermore, masks are needed as the

ammonia-like smell are definitely unpleasant. The epoxy is mixed manually using stick

for about 5 minutes before applied to the fibres.

28

FIGURE 3.3: Epoxy resin; a) Resin and b) Hardener

FIGURE 3.4: Mixing epoxy resin

A

B

29

3.3.2 Steel Mould Preparation

In order to produce a well performance fibre composite plate with required dimensions

using epoxy resin, a mould will be needed. Problems such as leak of epoxy may occur

during fibre composite fabrication due to narrow spaces between the middle frame and

bottom plate. This can cause the thickness of kenaf fibre composite plate not constant

thus will affect the performance. Silicone sealant is one of the best way to solve this. The

spaces will completely covered by this sealant. The silicone sealant is applied before the

fabrication process started. Then the plate is applied with a layer of grease to prevent the

fibre composite bonded on the steel mould surface and it also makes it easier to remove

the plate once it is done.

FIGURE 3.5: Preparing the mould

3.3.3 Hand Lay-out Method

The hand lay-up method is used to produce a significantly large number of fibres

reinforced polymer composite products in the industry. Thus, before starting the

30

fabrication, the fibre, epoxy resin and mould must be prepared thoroughly. The following

will be details of procedures in fabricating the kenaf fibre reinforced composite plate.

First step, the surface of the mould will applied with a thin layer of grease. The

thin grease layer is essential because it would prevent the completed kenaf fibre

reinforced composite plate from sticking to the mould and hard to removed. Then, the

mould surface with thin layer of grease is pre-coated with prepared resin mix. The epoxy

resin is spread evenly on the centre part of mould surface with assisting tool such as

spatula and scrapper. The amount of epoxy resin used in this first layer is depends on the

required fibre composite plate size.

FIGURE 3.6: Fabrication process of kenaf fibre reinforced composite plate

Step two, the prepared kenaf fibre layer will be applied on the epoxy resin mix

surface. Minor forced is applied on the centre part which covered with epoxy resin using

scrapper. Gentle movement is recommended in this procedure to avoid fibres from comes

off. The kenaf fibre layer is pressed from centre to both sides of plate in order to spread

the epoxy resin mix into each part of mould. This is also to ensure the kenaf fibres are

31

completely soaked with epoxy. Besides, this will increase the bonding between epoxy

resin and fibres as well as preventing air voids trapped in the composite plate. The air

voids in the plate can definitely decrease the strength of the composite plate. Throughout

the execution, the fibres must kept in the same direction.

Step one and two can be repeated four more times to complete the plate. However,

before proceed to the next step, kenaf fibres are pulled from both ends to ensure that

fibres are straighten by pulling the ends in opposite directions during the epoxy resin mix

is in elastic form. This is to ensure the direction of the kenaf fibres, preventing them from

curled up and disturb the strength of the product.

For step three, once the fibres are totally applied with epoxy resin mix, the mould

is closed and sealed with top plate. The designated holes on top of plate allow the trapped

air voids within mould released from the epoxy resin mix. Additional loads applied on the

top plate gives compression force on fibre composite to ensure the fibres and epoxy resin

are compressed. This will increase the performance of fibre composite plate produced.

Heavy objects such as bricks are place on top plate of mould to give external loadings.

FIGURE 3.7: Summary of fabrication process of kenaf fibre reinforced composite plate

32

Lastly, the fibre composite is left to dry for about 24 hours with room temperature.

The plate will be removed from the mould gently. Figure 3.7 is a summary of the

procedure of the fabrication of a kenaf fibre reinforced composite plate.

3.3.4 Load Compression

After the fabrication process is done, the mould filled with kenaf fibre and epoxy resin

mix must be compressed until the product is dry. Therefore, an optimum load of

compression must be set in order to standardize the compression criteria. The optimum

load of compression is important to maintain the quality of the product kenaf fibre

reinforced composite plate along with preventing the mould from break or damage due to

excessive load applied.

To determine the optimum compression load, in the beginning of the compression,

the weight of the load must be applied gradually. Starting from 10kg, another load will be

added increasingly until the top plate is touched the mould. Right after they are in contact,

there will be no more loads need to be applied, by means, the total load applied is the

optimum load for compression. Figure 3.8 shows the illustration when the top plate is

touched the mould.

FIGURE 3.8: Determination of optimum compression load

33

From the compression process, it is found that the optimum compression load for

a plate is 50kg. Hence the compression pressure acting on the steel mould can be

calculated.

Compressive Pressure =

=

= 20.83 kN/m2

3.3.5 Lessons Learnt and Precautions

In producing the kenaf fibre reinforced composite plate, there are few lessons that I have

learnt from the errors and problems that I have faced.

It is clear that the compaction process is very important in producing high strength

of kenaf composite plate. However, since the plate has a long dimension, then the

compaction occurred is possibly uneven. This will affected the strength of the plate since

there will be still air bubbles trapped in the epoxy mix resin and kenaf fibres. The error

that I have made is, I put loads at the center of the top plate. This caused the compaction

focused on the center part of the plate, leading to uneven compaction of the plate. Thus,

the solution is, to do the compaction, the first load has to be on both end sides of plate, or

the first load has to be as long as the top plate. Then the other load can be placed as usual.

This will guarantee the even compaction of the kenaf fibre reinforced composite plate.

34

FIGURE 1.9: Error; load focused on the center of the top plate

FIGURE 3.10: The proper way; the first load is as long as the top plate

FIGURE 3.11: The first loads are placed at the end of plates

35

In compaction of the fibre, there are possibilities that the fibres spilled out. This is

due to the amount of kenaf fibre used in fabricating the fibre reinforced composite plate.

The spilled fibres can cause the plate to decrease its strength, due to lacking amount of

kenaf fibre in the composite plate. This happened when the loads are pressed the top

plate, the kenaf fibres at the top are dispersed to the sides. Supposedly, with a proper

procedure and a great, ample pressure in compaction, this problem can be prevented. The

reality stated that the dispersed fibres cant be prevented since it will move to side since

the epoxy is not fully hardened yet. So, the solution is, when preparing the epoxy and

kenaf fibre in the plate, it is best to leave spaces at both sides inside the plate. This will

help the dispersed kenaf at the top to fill the space provided. Hence by this way, the

strength of the plate can still maintained.

FIGURE 3.12: Spilled fibres

FIGURE 3.13: Leaving spaces at sides to prevent fibre spills

Spilled Fibres

36

When opening the plate and separate the kenaf fibre composite plate from the

mould, it would be hard to separate them especially when removing the top plate. This is

because the epoxy resin have a very high cohesion strength and the dry product of epoxy

will make it harder to remove as it is very high in strength resistance. Apparatus such as

scrapper, nail and hammer are needed to remove the plate from the mould. This can cause

the metal mould scratched off, or even worse, the fibre plate to break. So, to solve this,

after the mould is applied with grease, gently cover them with plastic cover. This is also

need to apply on the top plate. When the curing time is completed, they will be easier to

remove.

Safety is very important. It is a compulsory for us to make sure the safety is

guaranteed throughout the fabrication of the plate. Precautions can be taken to prevent

from any problems. When it comes to handling the epoxy resin, precautions such as

wearing gloves, goggle and face mask are strictly compulsory. This is because the epoxy

resin is an exothermic material. It produces heat and gas when the hardener is mixed with

the epoxy resin. The gas produces may cause problem when it is inhaled directly

especially to asthmatic patient. When laying the fibres in the plate, spread the epoxy resin

using scrapper instead of bare hands. Besides from protecting hand from possible

irritation, the scrapper do provides a better, even spread on the fibres. When placing the

load on the plate for the compaction process, precautions also need to take. The plate

mould need to be placed on the ground so that it is easy to place the loads, and it would

cause less problem if the loads fall, because the ground is near.

3.3.6 Sample Specimens

After all composite plates have been developed, which the total is 12 plates, the plates

will be sent to timber factory to cut them into specimens. There are three specimens are

produced from one plate, making 48 specimens in total. The dimensions for each

specimens is 250mmx15mmx6mm. Then, 18 specimens will be coated with a layer of

epoxy resin mix. These specimens will be used in mechanical property test which is

tensile strength test, in a category 'Coated'. The other 18 uncoated specimens are also will

37

be tested on the same test. The rest of the specimens will be tested on the physical

properties test, which are density, moisture content and water absorption. Three

specimens for the water absorption test are also coated.

FIGURE 3.14: Sample specimens

3.3.7 Uncoated and Coated Specimens

From these 18 specimen plates, they will be divided by half. Half of them will directly be

tested in various environment, which they will be left at indoor, outdoor and in the water

for 7 days, 14 days and 28 days. After they undergo these conditions then they will be

tested its strength. These sample plates are in category Uncoated specimens.

When the plate is cut into smaller size of specimen plates, there would be exposed

surface area(s) occurred at the sample plate. Hence, for the other half plates, they will be

coated by epoxy resin to cover the exposed surface. This will be carried out to determine

the effects of exposed area to the strength of the kenaf fibre reinforced composite plates.

After that the Coated specimens will undergo the same procedure as the Uncoated

specimens. All data will be recorded and tabulated for analysis of the kenaf fibre

reinforced composite plate.

Theoretically, water content does affect the strength of the kenaf fibre. The

presence of water will weaken the inner bond in the fibres thus make it easier to break.

So, the exposed surface area will exposed to water moisture in the air as well. The

38

comparison will be made between the coated specimens and the uncoated specimens to

determine the effect of moisture content in the air towards the exposed surface area of

kenaf fibre reinforced composite plate. Figure 3.15 shows the flow chart of the tensile

test.

FIGURE 3.15: Flow chart for physical properties tests and mechanical property test

3.4 Physical Properties Tests

The physical properties of composite varies based on the materials and fabrication

method have been applied for the manufacturing process. Application of composite for

industrial is depending on the physical properties which gives unique features to

composite. So, physical tests are performed in order to determine the required physical

properties including density, moisture content and water absorption of the kenaf fibre

reinforced composite plates.

39

3.4.1 Density

The density of the kenaf fibre reinforced composite plate is important to compare its

usefulness with other external reinforcement in the industry. Theoretically, when the

density of a material is high, the weight of the material definitely will be high. As

mentioned before, lightweight materials are preferable for an easy installment and

maintenance. For this research study, the density test procedure is applying Archimedes's

method.

The resting procedure is referred to standard testing method ASTM D3800 and

apparatus are including thermometer, stirrer, balance, balance stand, suspension wire and

water are used. The specimen size for this test are not specifically stated, but I have used

the specimens with the same size as other tests which is 250mm x 15mm x 6mm. The

suspension wire is weighed in the air first. Then, the weight of suspension wire with the

specimen is weighed. The suspension wire with specimen is then immersed in the water

and weighed again. All the readings are recorded in a table. The weight of the suspension

wire in the water is also recorded. Three specimens are used and average density is

calculated.

FIGURE 3.16: Weighing the specimen in the air

40

FIGURE 3.17: Weighing specimen in the water

3.4.2 Moisture Content and Water Absorption

Moisture content test is conducted to investigate the initial water content in the fibre

plate. The apparatus used for the testing including oven, measuring weight, glove and

container, besides the specimen itself. The initial weight of three specimens are measured

and later on oven-dried at 150C temperature for 24 hours. Once the oven-dried

specimens are removed from the oven, the specimens are weighed again and the average

moisture content of kenaf fibre reinforced composite plate can be determined.

Moisture absorption test is a crucial test which is to determine the amount of

moisture can the kenaf fibre reinforced composite plate absorb. The specimens will be

tested within two conditions, which are uncoated and coated. This is also to determine the

effectiveness of epoxy resin mix in coating the exposed surface of the fibre plate and the

ability of the epoxy resin in water resistance. So for this test, three uncoated and three

coated specimens are used and then the average moisture absorption of uncoated and

coated specimens are determined separately.

The specimens prior to testing were dried in an oven at 150C and then were

allowed to cool to a room temperature. They then are kept in desiccators. The weights of

41

the specimens are then recorded before being submerged into the water for 48 hours.

After that, the specimens were taken out from the moist environment and all surface

moisture was removed with a clean dry cloth or any drying materials. The specimens

weights are measured again. The weight difference before and after submerging in the

water is calculated as it is representing the water absorption. Hence, the percentage

weight gain or the water absorption of the specimens is measured by this equation:

Water Absorption. % Mt = ( )

From the equation, the Wo and the Wt denote the oven-dry weight and the weight

after the specimens being submerged in the water for 48 hours respectively.

3.5 Mechanical Property Test

The performance of a material can be determined by its properties and behavior under

mechanical properties which includes tensile, compressive, shear and other properties in

the environment. These properties will be a critical criteria when selecting the suitable

materials in a given application as well as designing a structure with the selected

materials. These mechanical properties are measured by a laboratory tests first before

being used in the industry. Thus for this kenaf fibre reinforced composite plate, only

tensile property will be determine. By book, the concrete is able to withstand compression

force effectively, but poorly in resisting tension. When applied tension on concrete, the

structure will break or damage. In other words, concrete beam can withstand a big

compression but very small tension. This is leading to the invention of the external

reinforcement, to externally withstand tension force of the structure.

42

3.5.1 Tensile Strength

Tensile testing is a material test where the sample is subjected to tension force until

reaching the failure state. The test result will be used to select the material whether it is

appropriate for the application in the structure industry. However, understanding on the

background theory of tensile test is crucial before conducting the test. It is because it is

challenging to obtain a valid tensile property from a tensile test. The conduction of tensile

test will be based on standard ASTM D3039.

According to the standard, minimum of five straight sided specimens for each test

condition is required. The width of straight sided specimen is 15 mm and overall length

must be 250mm. These explains the dimension of the specimens which is mentioned

before. The tab material used in this test will be aluminium with 1mm thick and 50mm

length. The fibre composite plate is cut to 250mm x 15mm x 6mm as stated previously.

Each test conditions is conducted with at least three specimens to obtain an accurate

average reading. The testing of tensile strength will be using the Universal Testing

Machine (UTM) model INSTRON 8801.The composite plate specimens are subjected to

the testing machine to ensure that the specimens is tight to prevent errors during the

testing.

FIGURE 3.18: Specimen for tensile test

43

FIGURE 3.19: Universal testing machine (UTM) INSTRON 8801

FIGURE 3.20: Consequences when the composite plate are not well made

3.6 Presence of Water

As mentioned before, water plays a crucial role in weaken the strength of kenaf fibre

reinforced composite plate. Humidity aging is initially known for being a main factor of

long-term failure of organic matrices when they are exposed to atmosphere or when

44

having a contact in liquid form. The presence of water that have been absorbed into the

composite plate may cause the plate to swell, causing degradation of the intermolecular

strength by hydrolysis, osmotic cracking and also changes of water state that leads to

hydrothermic shock. These will disturb the durability of the plate gradually.

The penetration of water is done by three mechanisms. The first mechanism is

consisting the diffusion of water into the very small voids that are already present in

between the polymer chain. Then, the voids are becoming some sort of capillary transport

which transmit the water molecules to all voids to fill. This is because the voids

represents the incomplete moisture. Lastly, when the fibre plate starts swelling, the

transportation of micro-cracks in the plate. Although matrix such as epoxy resin are

completely water resistant, the epoxy is possible to moisturized, thus provides a higher

moisture to be transported throughout the plate, internally.

Focusing internally, when talking about kenaf fibre material, the fibre is

hydrophilic, meaning that the material is likely to contact with water. Although the rate of

absorption will reach its equilibrium at a certain stage, with a small amount of water

presence will weaken the internal strength right away.

45

CHAPTER 4

RESULT AND ANALYSIS

4.1 INTRODUCTION

This chapter basically elaborates the collected data and discussion on the analysis from

the laboratory testing. The tests are divided into two main categories which are physical

tests and mechanical test on both uncoated and coated kenaf fibre reinforced composite

plate specimens. The physical test is conducted to measure the physical properties of the

kenaf fibre reinforced composite plate which are density, moisture content and water

absorption, while only tensile strength test is conducted for mechanical property.

4.2 Physical Properties of Kenaf Fibre Reinforced Composite Plate

4.2.1 Density

The density of kenaf fibre is determined by using Archimedes's Method based on ASTM

D3800.

46

4.2.1.1 Procedures

1. The suspension wire is weighed in the air.

2. The weight of suspension wire with the specimen is weighed and recorded.

3. The suspension wire with specimen is immersed in the water and weighed again.

The data is recorded.

4. The weight of the suspension wire in the water is recorded.

5. All the readings are recorded in a table.

6. Three specimens are used and average density is calculated.

4.2.1.2 Results

Results are observed and recorded. The density is calculated by using these equations:

Vspecimen (cm3) = Wspecimen - Wsubmerged

water

specimen = Wspecimen

Vspecimen

where

Wspecimen = Weight of the specimen in the air, in g.

Wsubmerged = Weight of the specimen in the water, in g.

water = Density of water, 1 g/cm3

specimen = Density of the specimen in g/cm3

47

TABLE 4.1: Density of kenaf fibre reinforced composite plate

Sample Weight in air (g) Weight in water (g) Density (g/cm3) Density

(kN/m3)

1 27.32 8.83 1.477 14.77

2 31.38 8.43 1.367 13.67

3 30.29 6.75 1.286 12.86

Average 1.376 13.76

Steel usually have a density range between 77.50 kN/m3 to 80.50 kN/m

3 [_]. Due

to high density, leading to higher weight, the application of the steel plate too reinforced

the beam externally would be rather difficult and intricate, as an advanced machineries is

required to lift and move the steel plates.

Carbon fibre reinforced plate (CFRP) rather have much lower density than steel,

ranged 17.50 kN/m3 to 19.50 kN/m

3 [_]. This explains the broad uses of this plate in the

industry nowadays. CFRP has a very high water resistant, electrically conductive and

does not creep. These values promise a long term in aging the stability of the building. It

is known that water does play an important role in weaken the structure of a building. As

for steel, the presence of water will make it rust, and thus corrodes to failure. Along with

its high weight due to its density, making it as a second choice, after fibre reinforced plate

even though steel has a very high tensile strength. Furthermore, CFRP is highly resistant

to many chemical solutions. The installation process then would be so much easier as

there would not be any restrictions to the surface of the fibre plate.

48

FIGURE 4.1: Carbon fibre reinforced plate (CFRP)

Moving to glass fibre reinforced plate (GFRP), the density of GFRP is 17.7 kN/m3

[_]. It also has a considerably low density compared to steel, which also helps the

installation to be easier and faster. Comes with fairly high Young's modulus and

strength, which are bonus in reinforcing the beam externally. However, there are several

issues that have been carried along. GFRP is basically expensive to produce, same as

CFRP, as it must be processed directly to shape by laying up partially. Then they requires

hot pressing, which is also expensive, to cure the layers of the glass fibres. Other than

that, it is difficult to shape, means the fabrication process is rather complicated than other

fibre reinforced plate. It also cannot be recycled, showing the uses of this GFRP is not

supporting sustainable development, which what are we fighting for nowadays.

49

FIGURE 4.2: Glass fibre reinforced plate (GFRP)

Based on the density test, kenaf fibre reinforced composite plate has the lowest

density among all., which is 13.76 kN/m3. As we all know, density is important in

indicating it usefulness regarding comfort, support and durability. This result shows that

the kenaf fibre plate is lightweight, making it easy for installation and other uses.

Although steel do have a huge difference of tensile strength, but due to the steel's density,

it may cause a burden. Kenaf fibre is absolutely great substitute for external

reinforcement because it also has high tensile strength. On the other hand, CFRP and

GFRP have their own disadvantages that kenaf fibre plate can overcome, making it

eligible to substitute them.

FIGURE 4.3: Kenaf fibre reinforced composite plate

50

4.2.2 Moisture Content

The moisture content of fibre is determined by laboratory testing based on the standard

testing method ASTM 5229. Three specimens are prepared during the test in order to

determine the average value of moisture content of kenaf fibre.

4.2.2.1 Procedures

1. The initial weight of three specimens are measured separately.

2. The specimens are oven-dried at 150C temperature for 24 hours.

3. The specimens are weighed again.

4. The average moisture content of kenaf fibre reinforced composite plate are

determined.

4.2.2.2 Results

The specimens need to be oven-dried for 24 hours to remove the moisture content in the

plate initially. The moisture content of the three specimens are calculated thoroughly

using these equations:

Moisture Content (%) = ( )

where

W0 = Initial weight of the specimen, in g.

Wt = Final weight of the specimen, after oven-dried, in g.

51

TABLE 4.2: Moisture content of kenaf fibre composite plate

Sample Initial Weight (g) Final Weight (g) Moisture Content

(%)

1 32.5 31.59 2.88

2 30.4 29.6 2.70

3 33.2 32.33 2.69

Average 2.76

Based on the result, it is shown that the composite plate does absorb water, and

this can cause swelling of the materials. This also shows the possibilities of the

degradation of matrix or interfacial properties in the material. Theoretically, low moisture

content composites resulting in a higher and better performance. Inside the plate, the

existing moisture may leads to void development, and this may weaken the structure as it

would interfere the bonding between the epoxy resin and the fibre.

4.2.3 Water Absorption

Moisture absorption test is conducted in order to find the water absorption behavior of the

composite plate. It is based on the standard ASTM 5229. These specimens will be tested

under two conditions, which are coated and uncoated. Here we can foresee the role of

epoxy resin in resisting water absorption.

4.2.3.1 Procedures

1. The uncoated and coated specimens are oven-dried at 150C and then were

allowed to cool to a room temperature.

2. The weights of the specimens are then recorded.

3. The specimens are submerged in water for 48 hours.

52

4. The specimens were taken out from the moist environment and all surface

moisture was removed with a clean dry cloth

5. The specimens weights are measured again.

6. The water absorption of the specimens are calculated and recorded.

4.2.3.2 Results

In this test, the differences of the water absorption between uncoated and coated

specimens plays an important role, as it tells the effectiveness of the epoxy resin as a

coater. The water absorption of the specimens are calculated using this equations:

Water Absorption (%) = ( )

where

W0 = Initial weight of the specimen, in g.

Wt = Final weight of the specimen, after oven-dried, in g.

TABLE 4.3: Water absorption of uncoated and coated kenaf fibre composite plate.

Type Sample Initial Weight (g) Final Weight (g) Water Absorption(%)

Uncoated

1 29.9 29.96 0.2

2 32.52 32.56 0.12

3 29.37 29.91 0.13

Average 0.15

Coated

1 33.03 33.03 0

2 33.01 32.02 0.03

3 37.56 37.58 0.05

Average 0.03

53

Water absorption is one important topic to discuss in developing kenaf fibre

reinforced composite plate. Since the existence of moisture in the fibre is able to disrupt

the strength of the product, as it would disturb the bonding between the elements, an

addition of moisture or water content from surrounding is something to prevent or reduce

to minimum. This concern is supported with the fact that the air in the atmosphere does

contain moisture, Also when this external reinforcement technique is applied, the plate

will be exposed to air and there are many possibilities that this plate will be exposed to

other liquid forms of inert and thus nullified its function, not mentioning other chemical

solution that have a high potential in spoil its strength.

In order to solve this issue, one needs to block the access of water or any other

liquid form of inert to penetrate the external reinforcement. One of the most effective way

is by coating the plate using its matrix, which is epoxy resin. As discussed before, epoxy

resin, a thermosetting material has a wide usage since it is waterproof, high specific

strength, heat resistance, strongly adhesive and chemical resistance. In order to make it

cost effective and minimize the waste disposal, we can use the excess epoxy resin used to

fabricate the kenaf fibre reinforced composite plate. This supports the sustainable

development as well although epoxy resin cannot be recycled, by using it to the

maximum. Thus, by coating the plate, it will increase the chance of the plate's life. Water

absorption testing is mainly to determine the effectiveness of coated kenaf fibre

composite plate in resisting water absorption.

So based on the results of the water absorption test, it clearly shows that the epoxy

resin is effectively minimize the water absorption of the composite plate. The water

absorption of uncoated kenaf fibre composite plate is 0.15% while coated plate shows

0.03% of water absorption, which is close to zero. Technically, if the fibre plate is coated

properly, it is possible that it will not absorb any water or other liquid. In this case, the

reason that there is still water have been absorbed by the coated kenaf fibre plate is

because it is not coated fully. Double coat would give a better performance. Back to the

result, it clearly shows the impressive performance of coated specimens compared to

uncoated one because there is a reasonably big gap between the values.

54

FIGURE 4.4: Differences of water absorption of uncoated and coated specimens

From the chart above, it shows an obvious differences in water absorption

between the two types of specimen. It became a matter because this test only conducted

where the specimens are only submerged in the water for 48 hours. The usage of this

external reinforcement are meant to be effective for a long time. Imagine that the coated

kenaf fibre reinforced composite plate is used for reinforcement, logically it surely can

stand a higher load and last much longer than the uncoated type. Thus, in my opinion it is

essential for kenaf composite plate to be coated before applied, as it does not cause any

extra cost of materials.

4.3 Mechanical Properties of Kenaf Fibre Reinforced Composite Plate

Besides physical properties such as density, moisture content and water absorption,

mechanical properties is also important in determining the capability of kenaf fibre

reinforced composite plate to be used as external reinforced in construction. In fact,

mechanical properties will help to justify the strength and uses of this fibre plate. This

mechanical properties test also will elaborate the effectiveness of epoxy resin in

0.15

0.03

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Uncoated Coated

Wat

er

Ab

sorp

tio

n (

%)

Water Absorption

55

preventing the specimens from weaken its inner strength due to presence of water and

moisture. So for this mechanical property, only tensile strength tests are conducted. I have

used approximately 36 specimens, uncoated and coated including specimens as dummy,

for me to practice on how to use the machine for the testing and for the trial. These

specimens are divided into two main components, which are indoor and water condition.

Through this, it will emphasize and focus to the effects of presence of water in the kenaf

fibre composite plate.

4.3.1 Tensile Strength Test

As mentioned above, only tensile strength test is conducted to obtain the mechanical

property of the specimen. This is due to the reality that concrete beam has a significantly

low tensile strength even though it can withstand a very high compressive stress.

Concrete has a constant of elasticity at a low stress but it will start to decrease gradually

at a higher stress levels as there would be developments of matrix cracking. Tension also

contributes to the development of crack on the concrete besides shrinkage. Tension

cracking on the concrete beam is commonly happened when a transversely applied load is

placed on the surface of the beam causing compression, and the opposite surface is

enforced by tension. This is due to induced bending. In such a way, the surface that

enforced with tension would likely to crack.

Hence the reinforced concrete beams are invented to support the beam from

failure due to tensile stress applied. Along with the fact that concrete needs to reinforced

at the tension area, kenaf fibre reinforced composite plate is designed to reinforced the

concrete beam form tension externally. In such a degree, kenaf composite plate will

provide an extra reinforcement from the surface to hold the tensile stress.

To obtain tensile strength of the specimen, A tensile strength test tallied to ASTM

D3039 is carried out. The specimens are subjected to tension force until it reached the

state of failure, which is breaking. Machinery that responsible in finding the tensile

strength of the composite plate is Universal Testing Machine (UTM) model INSTRON

56

8801. The size of specimens each is 250mm x 15mm x 6mm and it is crucial to have a

specimen with thickness of less than 10mm, because that's the maximum size of specimen

the machine can hold.

FIGURE 4.5: Universal Testing Machine (UTM) INSTRON 8801

The UTM INSTRON 8801 is connected to computer nearby, as the results of the

tensile strength of specimens are directly transferred to the compute using a specific

software. In the software, a basic set up is needed such as setting up the size of specimen,

type of specimen, and also the rate of tension force applied on the specimens. The rate is

definitely versatile as we can decide what rate to be used. Theoretically, the lower the

rate, the more accurate the reading. However, if the rate is too small, the graph of result

obtain will not be smooth and too disturbed, thus a proper rate is essential. Also, the stress

and strain needs to be reset prevent the zero errors. For this test, I have used 5mm/min of

rate for the tension force. After the result is procured, we can save them into a desirable

folder.

57

FIGURE 4.6: Specimens for tensile strength test

FIGURE 4.7: Zero error happened when the stress and strain is not reset

4.3.1.1 Procedures

Conducting tensile strength test using UTM INSTRON 8801 can be considered as quite

intricate. This is because first, the specimen must be placed vertically without any slant as

Zero error

58

it would disrupt the results. Secondly, we have to reset the tensile strain and stress few

times as they would normally unstable. So the strain and stress must be at the initial value

which is zero, then the testing can be proceed. Plus, if the specimens aren't placed

properly or the characteristics disobey the requirements, the machine will shut off

immediately resulted from a gradually decreased pressure. However, thanks to the lab

technician for helping my partner and I in guiding us to conduct the test properly.

Therefore, the procedure of the testing for each specimen is described below.

1. The specimen holders are set at ample length suit for the specimen.

2. The upper and lower grip holder are aligned in parallel.

3. The specimen is gripped firmly.

4. The stress and strain of tension is reset to zero value.

5. The testing started until the specimen reach its failure state.

6. The 'finish' button is clicked and the graph of tensile development is obtained.

7. The files are saved in a specific folder.

FIGURE 4.8: The technician guided us to set up the machine.

59

FIGURE 4.9: Setting up the rate of tension, specimens' dimension and type of specimens.

FIGURE 4.10: The specimens after failure

60

4.3.2 Effects of the Presence of Water

As mentioned before, water plays a crucial role in weaken the strength of kenaf fibre

reinforced composite plate. The disruption of the structure of the plate happens when the

presence of water is exist between the fibres and the matrix resin. It will disturb the

cohesion and bonding between the fibres and the epoxy resin, and leading to decrease of

stability of the plate. Initially, when there is no water molecule, the cohesion and bonding

are in completely stable. The plate would not stand a higher tension when there is a

presence of water molecules. Thus, a further steps need to be taken in order to prevent the

plate from absorbing water.

4.3.3 Uncoated and Coated Specimens

Since water is likely to disrupt the stability of the strength of the composite plate, a proper

solution for this problem should be made. There are various ways to prevent the

composite plate from being affected by water molecules, such as pretreatment of the

fibres, and as well as by coating the specimens.

For the properties determination by various testing, after the curing of the

fabricated kenaf fibre reinforced composite plate, the plate needs to be cut into smaller

specimens. Initially when the plate is completely dried, there are also exposed inner fibre

to the atmosphere. This increases the chances of moisture absorption. It worsen the case

when the plate is cut into smaller pieces as bigger surface area is exposed. So, the water

molecules even from the atmosphere would easily diffused into the fibres in the plate.

61

FIGURE 4.11: Cross section of kenaf fibre composite plate after being cut into smaller

pieces

FIGURE 4.12: Penetration of water into the exposed surface

By coating the cut specimens, the water absorption can be prevented because of

the epoxy's characteristics. Besides having a high flexural strength and others, epoxy

resin is effectively waterproof. The covered exposed surface will prevent from the water

to be absorbed. Besides prevent the inner structure of the plate being filled with water

molecules, it will also acts as an extra shield and strengthener for the plate. This

theoretically will increase the tensile strength of the plate.

This explains the effectiveness and advantages of using epoxy resin as addition

coating. Although there are many other choices such as polyester and silicone, epoxy

resin provides a better strength. Besides, we can reuse the excessive epoxy resin that has

been used of the fabrication of the kenaf fibre reinforced composite plate. The fact that

the epoxy resin is not recyclable, at least we can decrease its waste disposal to the

minimum.

62

FIGURE 4.13: When the specimen is coated, the water cannot penetrate the specimen

4.3.4 Indoor Condition

As stated before, for the mechanical property test, the tensile strength test are conducted

under two conditions, indoor and water. For the indoor condition, 6 uncoated and 6

coated specimens are used, excluding the dummy specimens. The specimens are placed in

indoor for 7, 14 and 28 days. Although the specimens are not exposed to water directly,

the atmosphere itself contains water moisture. So, this test will determine whether the

moisture from the atmosphere can affect the strength of the plate or not. A definition of

textbook tells that the rate of water absorption from the air is not as slow as in the water,

due to the quantity of water molecules in the air. For the testing, I have placed the

specimens in my room, as it is indoor. We are neglecting the outdoor condition because

theoretically the water content in the air indoor and outdoor are likely the same.

4.3.5 Water Condition

For this condition 20 specimens, uncoated and coated are used, excluding the dummy

specimens. The specimens are submerged in water for 1, 3, 7, 14 and 28 days. Since the

water molecules are in maximum capacity in this condition, it is decided that we test them

in more variables of days. The results according to days of testing will make it clearer in

justifying the effects of water absorption in disturbing the strength structure of kenaf fibre

reinforced composite plate.

63

4.3.6 Results

The result obtained from the tensile strength test are tabulated in two different table

according to the indoor and water conditions. For each state of specimen, let say for this

kenaf fibre reinforced composite plate, in indoor condition for 7 days testing per se, there

would be 2 specimens will be tested and a higher value of tensile stress is chosen. This is

because there are possibilities of error that can be made, such as zero error and others.

Thus it would be safe to have more than one specimens for each conditions. Furthermore,

a backup specimens are essential since the UTM INSTRON 8801 is rather sensitive to

handle. The table below shows parts of the tensile strength test's result.

TABLE 4.4: Results obtained from the tensile strength test

Maximum

Load (kN) Modulus (Mpa)

Maximum Tensile

Extension (mm)

Tensile Strain at Break

(%)

9.5 9807.46 2.16568 0.86627

TABLE 4.5: Maximum tensile stress for specimens under INDOOR condition

Condition: Indoor

Days of testing Condition Specimen Max. Tensile Stress (MPa)

7

Uncoated KIU7-1 69.36

Uncoated KIU7-2 51.37

Coated KIC7-1 75.09

Coated KIC7-2 60.6

14

Uncoated KIU14-1 63.19

Uncoated KIU14-2 59.63

Coated KIC14-1 73.16

Coated KIC14-2 67.96

28

Uncoated KIU28-1 51.61

Uncoated KIU28-2 36.25

Coated KIC28-1 74.77

Coated KIC28-2 40.53

64

From the results from the table above, the shaded result is the chosen one, as the

value is higher. Note that for uncoated specimens, as the days of testing increase, the

tensile stress can handled by the specimens is decrease. This shows that the longer the

surface exposed to the atmosphere, the weaker the specimens can be. The decrease of the

value in the results explains the role of water moisture content in weaken the structure of

the plate. The next tables will show a clearer vision of the decreasing tensile stress by

day. However, the maximum tensile stress for coated specimens to endure are almost

constant by days.

TABLE 4.6: Simplified result for UNCOATED specimens under INDOOR condition

Days of Testing