Examining the Behavior of Epoxy Filler Composites

A Research Paper

Presented to the

Science Department

Eleanor Roosevelt High School

In Partial Fulfillment

Of the Requirements for

Research Practicum

By

Amir Baiyina

May, 2013

Abstract: Examining the Behavior of Epoxy Filler Composites

Amir Baiyina May, 2013

Epoxy is a widely used potting material in electronics. With the technology era evolving, this material is a necessity for electronic components to be efficiently used and examined. Protection is important to both the developers and the consumers.

In this current experiment, the curing behavior of Allied High Tech Products, Inc. Epoxy was tested at various distributions using glass filler. Strain and temperature change were the primary variables being tested in order to determine which distribution yielded the most suitable environment for a sample of silicon. The three trial groups comprised: no filler, 30% filler, and 50% filler. In order to formulate the epoxy, a resin and hardener were combined and stirred uniformly for each filler distribution. The strain and temperature were measured using strain gauges and thermocouples. The results showed that as the filler distribution increased, there was an apparent decrease in strain and temperature change.

i

Acknowledgements

I would like to give special thanks to CALCE and UMD for the internship

opportunity. To Bhanu Sood, I would like to humbly thank you for your great patience

and guidance throughout this past year. For finding an awesome, interesting project, I am

appreciative. I also give many thanks to Swapnesh Patel for his unwavering willingness

to always lend a helping hand with my project whenever it was needed. In addition, I

thank Giovanni Flores for taking me under his wing and familiarizing me with the lab

equipment. I give great thanks to the entire CALCE family.

ii

Biographical Outline

Personal Data:

Name: Amir I. Baiyina

Date of Birth: January 31, 1995

Place of Birth: Cheverly, MD

City of Residence: Greenbelt, MD

College Attending: University of Pennsylvania, The Wharton School of Business

Major: Finance, Economics

Academic Achievements:

Cumulative GPA: 4.0+

ERHS Science Fair Third Place, Chemistry

AP Scholar with Honor

Activities:

National Honor Society

Spanish Honor Society

Varsity Basketball Team

Dem’ Raider Boyz Step Team

Our Town Lead Actor

Coffee House Performer, Vocalist

iii

Table of ContentsAbstract.................................................................................................................................iAcknowledgements.............................................................................................................iiBiographical Outline..........................................................................................................iiiList of Tables and Figures...................................................................................................vChapter One.........................................................................................................................1Chapter Two........................................................................................................................4Chapter Three....................................................................................................................12Chapter Four......................................................................................................................14Chapter Five.......................................................................................................................19Literature Cited..................................................................................................................21Appendix............................................................................................................................23

iv

List of Tables and Figures

Table 4.1............................................................................................................................15Table 4.2............................................................................................................................15Figure 4.1...........................................................................................................................17Figure 4.2...........................................................................................................................18

v

Chapter One

The Problem and Its Setting

Introduction to the Problem

Epoxy (polyepoxide) is a staple in the world of modern technology. It is typically

molded and used to protect vital circuits and chips that control operation. Protection of

the motherboard can lead to a longer life for the electronic. With technology’s evolution,

people have become accustomed to instant gratification. Additionally, functionality and

durability are critical to electronics’ success in the market. Because of this great demand,

it is essential that the hardware responsible for electronics existence is protected.

Being that epoxy is a “thermosetting polymer,” it can be cured. There are two

common epoxies: the one-part and the two-part. One-part epoxies are usually cured when

the resin (epoxide) is put under certain temperature conditions (usually high), which

activate an internal chemical reaction. Contrarily, two-part epoxies can usually be cured

at room temperature by means of mixing the resin with a hardener. Electronics

experience various stresses and perform under different conditions throughout its

lifetime. Therefore, the hardware must be able handle these situations. (May, 1973)

Statement of the Problem

The purpose of this experiment is to determine which epoxy filler composite

produces the most effective molds while maintaining optimum performance for the

component. Three different filler distributions will be tested: no filler, 30% filler, and

50% filler. A silicon substrate will serve as the component that is being molded.

Hypothesis

If filler distribution affects the strain and temperature during an epoxy’s cure, then

higher filler distributions will yield lower strain and temperature changes and provide the

most appealing environment for the silicon substrate.

Variables and Limitations

Independent variables.

1. Allied High Tech Products, Inc. Epoxy

a. Epoxy Resin

b. Epoxy Hardener

2. Glass filler: two size distributions

a. 30% filler

b. 50% filler

Dependent variables.

1. Temperature

2. Strain/Pressure

Control treatments.

1. No filler

Regulated conditions.

1. Size of fillers

2. Filler type

3. Number of epoxy combinations: 3

4. Use of the same strain and temperature gauges.

2

Research was conducted in the Center for Advanced Life Cycle Engineering

(CALCE) at the University of Maryland in College Park, MD under the supervision of

Bhanu Sood.

Limitations.

1. Not being able to control the consistencies of the various epoxy brands

and filler types.

Assumptions

1. The strain and temperature gauges are fully functional and working properly.

2. Epoxy and filler measurements are exact throughout the experiment.

3. The curing process will not be affected by any outside sources.

Statistical Analysis

In order to accumulate statistics, a t-test will be performed on the strain and

temperature data collected throughout the experiment. The p-value recovered from the t-

tests will determine if the following tests wither accepted or rejected the null hypothesis.

Definition of Terms and Abbreviations

1. Curing: the toughening or hardening of a polymer material by cross-linking

polymer chains - chemical additives, ultraviolet radiation, electron beam or heat.

2. Epoxy: a thermosetting polymer that reacts with itself or something else in

order to create a solid mold.

3. Thermosetting polymer: polymer material that irreversibly cures.

3

Chapter Two

The Review of the Related Literature

Introduction

Computers have undoubtedly proven their worth in the modern world, especially

within the last decade. Several major societies’ fast paced operations have become

particularly dependent on the use of these devices. In the digital age, computers are

critical to everyday devices such as automobiles, cell phones, and portable tablets. The

compactness of modern computers has made that possible.

Also, the presence of these products allows for work to get done effectively and

efficiently. However, computers were not always so convenient. The first computer,

ENIAC (Electrical Numerical Integrator and Calculator), occupied a gigantic room. In

the 1950’s, there were two devices that evolved the computer: the transistor and the

vacuum tube. Now, the majority of society carries around compact cell phones that have

a plethora of capabilities. Within a great number of these devices, epoxy resins play a

vital role in maintaining their operation. (Augarten, 1984)

Motherboards and their Significance

A motherboard is the major circuit board found internally within electronics.

There are various optical drives and disks that are connected to interfaces located on the

board. Essentially, it is the nervous system of the computer. Motherboards come in

different sizes or footprints which have direct impacts on the type of system that the

board is able to fit into. It is very important that the motherboard has an adequate source

of power for operation and that this power source has proper connections.

The Central Processing Unit (CPU), Random Access Memory (RAM), and

various disk or optical drives are all plugged into interfaces on a motherboard. Again,

when all these devices are connected, the overall computer is able to operate. Without

motherboards, the world of technology would not be where it is today. These critical

components have allowed for electronics to operate at high levels and speeds and because

of its presence technology continuously evolves. (R., K., 2012)

Thermosetting Polymers and Epoxy

Thermosetting polymers are known to release a significant heat of reaction during

processing. This chemical reaction that occurs during the curing of these polymers has a

great effect on the modeling of thermoset composites. It is vital to include an accurate

cure kinetic model in the process of thermoset composites. The differential scanning

calorimeter is an experimental tool for thermal analysis that is used all over primarily for

detecting any heat that flows from samples. It provides information on heat that is either

generated or absorbed from the samples as either a function of time or maybe even

temperature. (Kamal, 1973)

Based on experiments that were conducted, the glass transition temperature of the

100%-cured prepeg was found to be 199 degrees Celsius. Also, the presence of fibers

appeared to increase the prepeg’s temperature just slightly over that of the neat epoxy.

The AS4 fibers played little to no role in the curing behavior as well. The doubled staged

cure kinetics model that was isothermally-based accurately predicted the total energy that

was released and also the degree of the cure for similar scans. This experimentation is

5

important in the real world because technology drives the modern generation. Therefore,

companies seek to create the best products and part of getting the best product is being

able to engineer something that will work under a variety of conditions and last. That is

where epoxy becomes a major factor. (May, 1973)

Applications of Copolymers and Epoxy

Epoxy resins are a staple in the world of thermosetting polymers and are widely

used for numerous situations because of their great electrical and mechanical properties.

They have great resistance to water heat and chemicals. Tests were conducted to try and

explore the curing properties of a commercial epoxy resin after the addition of a SG

copolymer. The spectra of the commercial epoxy will be recorded using a Bruker AC200

and the molecular weight of the SG copolymer was determined by gel permeation. There

are no human subjects, only epoxy and other chemicals are being tested. The samples

were prepared through mixing and the mixture was then degassed in a vacuum. These

samples were pre-cured at 140 degrees Celsius for one hour and then cured at 160

degrees Celsius for four hours. The results clearly indicated that the hydrosilyation

reaction was successful. The results also showed that the addition of the SG copolymer to

the epoxy resin increased the mobility of the crosslinked network and therefore increases

the thermal stability. Dynamic mechanical thermal analysis (DMA) was the analytic

technique that was used. It measured the the viscoelastic properties and also obtain

information about the microstructure of crosslinked networks.The main point taken away

from this article is that the curing process of an epoxy resin was stabilized through the

addition of a polymer. This is important because this finding sheds light on the efficiency

of the epoxy curing process. (Hou, 2000)

6

Epoxies are often molded to protect important electrical components so thermal

stability is definitely essential to their environment. I feel as if the addition of the

copolymer was very interesting because of the ultimate results that the chemical reaction

displayed. The weakness would have to be the exploration of only one kind of copolymer

though. (McMichael, 1999)

One-part Epoxies

The reaction of a one-part epoxy is often initiated from an external source such as

temperature. Often times, these epoxies are placed at very high temperatures when in

their liquid form, and there are internal reactions that occur that result in a time-efficient

cure. In a particular experiment, the goal was to prepare a microencapsulated epoxy and

latent curing agent as well as evaluating the feasibility of this two-component repair

system for producing self-healing epoxy. The objective was to improve healing

efficiency. The bisphenol-A epoxy resin acted as the healing agent to be encapsulated.

The matrix of these composites were imported from China. There were no human

subjects used in this experiment. All materials were commercial so no further purification

occurred. In order to test the healing capabilities that of the fiber glass composites. 16 x

14 plain weave glass was imported. The main findings of the study included the fact that

the latent curing agent was able to successfully dissolve in the given epoxy and it was

cured at 130-180 degrees Celsius. Also it was concluded that the fracture toughness of

epoxy that contains microencapsulated epoxy and latent hardener depends on the contents

within them. Overall, it was found that the glass fabric laminates that were using the self-

healing epoxy in its curing process yielded a healing efficiency of 68%. This shows that

the addition of microencapsulated epoxies and latent curing agents could produce an

7

epoxy that is more prone to last longer and protect electronic components when applied

to most situations. (Yin, 2007)

Two-Part Epoxies

Diglycidyl ether of bisphenol-A-type is an epoxy resin that has two functions.

This epoxy was cured with different of types of curing agents. These agents contained a

difference in ratios. So basically, the authors were trying to discover the different effects

that the chemical structure of a hardener would have on the curing and behavior of epoxy

resins. The crosslink process of the epoxy resins and hardeners were followed by a

viscosimetry and also differential scanning calorimetry. There were no human subjects

involved in experimentation. The gelation time and also the activation energy of the

epoxy materials were discovered to be heavily dependent on the actual structure of the

harderner. However, the heat of the reactions did not seem to change much when the

hardeners were varied. (De Nograro, 2003)

Overall, the key point that should be taken away is that the chemical structure of

the hardener in a two-part epoxy system can have significant effects on the curing of the

epoxy. This is important because epoxies are heavily used in modern technology so

convenience and efficiency are very significant factors that must be considered due to the

time and cost that accompanies the development of new electronics. (Lee, 2000)

Epoxy and Fillers

The function of fillers in the curing of epoxy is to ultimately produce a stronger

final result. Physically, they resemble tiny grains of sand and the particle sizes vary. The

different mechanical properties when silica-filled epoxies were tested. Silica filled epoxy

are often chosen in the technological field because of their low costs, varying cure

8

temperatures, curing rates, and pretty good adhesion to substrates. However, epoxy resin

without filler happened to reduce the opportunity for solder bumps to contact copper so

the fillers must be carefully chosen so that this will work properly.

The silica-filled epoxy resin composites were supplied by The Packaging

Resource Center at Georgia Tech. The samples being tested had the same resin matrix but

were filled with spherical silica particulate by 0, 14, 21, 28, 33, and 39% filler volume

fractions. The mean diameter of silica particulate was about 4 μm. The curing condition

was 250°C for 40 min. In order to investigate the thermo-mechanical behaviors there was

a six-axis mini tester that was developed by Wayne State University. There were curves

tested both at room temperature as well as 115 degrees Celsius. And the results showed

that the mechanical behaviors of the materials were extremely sensitive to the silica filler

contents. At room temperature, it was shown that the materials became stronger with the

addition of silica filler into the epoxy matrix. However at 115 degrees it was shown that

the behaviors of the materials varied. Overall, the application of fillers into the world of

epoxy is very significant due to the various effects that they have on them. This study

showed that the addition of a silica-filler at room temperature actually strengthened the

cure of the epoxy resin. Furthermore, as technology continues to evolve, materials that

are stronger and lighter and more efficient are often the goal. (Wang, 2002)

Issues with Epoxy

Epoxy polymers are thermosetting materials that have many useful properties

such as high failure strength and good performance at high temperatures. That is one of

the main reasons why epoxies are often used for fiber-reinforced materials. However, one

major issue that accompanies this problem is that the material is relatively brittle and it

9

has poor resistance against the formation of cracks.The materials that were used in

experimentation were mainly based on a epoxy formulation that was one-part and cured

at very high temperatures. It was a standard diglycidyl ether of bis-phenol A. There were

also nano-particles of silica that were utilized. To determine the properties of the

matrices, the formulations were cured by mixing together the epoxy and silicone. There

were no human subjects used during experimentation. The main finding was that the

nano-silica phase as well as the rubber phase toughened matrices. The pure epoxy’s data

showed no toughening phase to that of the epoxy that contained the rubber particles.

Also, there were experiments done where the rubber and the silica were both added to see

if any additional toughness would result. The article did not display any particular use of

an analytical technique.The synergistic effects of having a structure with several phases

based on nano-SiO2 particles as well as micro rubbery domains are evident through this

experiment. Also, the addition of these rubber and silica particles did not have any

detrimental effects on the modulus of the epoxy itself. The understanding of these

mechanisms could potentially lead to increases in the mechanical performance of epoxy

polymers and also the development of composite materials produced at low costs in the

manufacturing industry. (Kinloch, 2005)

Summary

Epoxy (polyepoxide) is a “thermosetting polymer” which is formed when a resin

(epoxide) and a hardener (polyamine) react with each other. This substance is extremely

vital to the world of electronics. The range of situations that epoxy can be applied to is

quite vast. This includes generators, motors, insulators, and transformers. Many epoxy

systems are specifically used in industrial tooling to produce molds that can be used to

10

replace metal. This lowers overall costs and is chiefly more efficient. Now, in order for

epoxy to be created, two chemicals must react: a hardener and an activator (as stated

above). Therefore, epoxy can be considered a copolymer. The process of polymerization

can be referred to as “curing.” This procedure can be controlled through filler sizes, size

distributions, cure temperatures, as well as temperature rates. With this knowledge, the

most effective epoxy under various circumstances can be experimented.

11

Chapter Three

Materials and Methods

Materials

1. Allied High Tech Products, Inc. Epoxy Resin (125 grams)

2. Allied High Tech Products, Inc. Epoxy Hardener (15 grams)

3. Glass Filler

a. 30% distribution

b. 50% distribution

4. One-inch Diameter Molding Container (5)

5. Thermocouple (5)

6. Strain Gauge (5)

7. Three-inch Wooden Mixer

Methods

Five molding containers of one-inch diameters were obtained. 1 mL of release

agent was obtained and spread uniformly throughout the inside of each container. 125

grams of Allied High Tech Products, Inc. Epoxy Resin were measured and placed into a

cup. 15 grams of Allied High Tech Products, Inc. Epoxy Hardener were also measured

and placed into the same cup. A wooden stick was then stirred in a counterclockwise

motion to mix the two liquids together until the solution was uniform and contained no

air bubbles. The 140-gram Resin-Hardener solution was then set aside.

Five strain gauges and five silicon substrates were then obtained. One strain

gauge was attached to each individual substrate and taped down into each molding

container. Five thermocouples were also obtained and taped onto the sides of each

container with the end of the wire hanging inside the middle of the container. 28 grams of

the Resin-Hardener solution were then placed into each of the five containers. 8.4 grams

of the glass filler (30% filler) were placed into one of the molding containers and stirred

counterclockwise with a wooden stick until the solution was uniform. Then 14 grams of

the same glass filler (50% filler) were placed into another cup and stirred in a

counterclockwise motion until the solution was uniform.

Three out of the five containers were left without any added filler material. Each of

the five prepared samples’ strain gauges and thermocouples were then attached to a

DELL computer and the Labview program was prepared for data collection. Each of the

samples was left to cure for a 24-hour period. After 24 hours, data collection was stopped

and the data for each sample was extracted.

Data Collection and Analysis

The data for this experiment were collected through the use of strain gauges to

measure apparent strain and thermocouples to do the same for temperature. During data

collection, strain gauges and thermocouples were attached to silicon substrates and placed

inside the filler before being connected to Dell computers. There was a program on the

computer called Labview that was programmed to collect data over a specified period of

time. The data was then analyzed and placed into table form using the program MatLab

which allowed the data to be comprehended more efficiently.

13

Chapter Four

Results

Data

Strain and temperature data were collected in the Center for Advanced Life Cycle

Engineering (CALCE) laboratory with strain gauges, thermocouples, and Labview

computer software. The strain data is measured in microstrain and the temperature data is

measured in degrees Celsius.

In the in-laboratory testing, an increase in filler distribution seemed to yield a

decrease in the magnitude of strain and temperature stresses, and the statistics revealed

supported this notion. After examination of general trends, the 50% filler was shown to

provide the least stressful environment out of the samples tested. This may be due to the

filler’s effects of decreasing molecule velocity during the cure process. There were errors

in some of the original samples. This is due to faulty equipment and the air-conditioning

system in the laboratory in the overnight setting.

In-Laboratory Study

Table 4.1: These are the measurements made using the strain gauges in microstrain units

throughout various filler distributions.

Strain (microstrain) Filler Type

No Filler 30% Filler 50% Filler

Minimum Compression -0.223 ~~~ -0.331

Maximum Compression -143 -0.716 -0.677

Maximum Elongation ~~~ 0.25 ~~~

Table 4.2: These are the measurements made using the thermocouples in degrees Celsius

throughout various filler distributions.

Temperature (Celsius)

Temperature (Celsius) Filler Type

No Filler 30% Filler 50% Filler

Minimum Temp. 22.344 24.206 23.610

Maximum Temp. 28.709 29.777 29.704

Temp. Range 6.365 5.571 6.094

Data Analysis

15

Based on the data collected, general trends showed that an increase in filler

distribution within the epoxy did, in fact, yield an increase in both the overall strain and

temperature stresses; therefore, the null hypothesis was rejected. Two T-Tests were run

on the data sets of strain and temperature for comparison of 30% and 50% filler

distributions. The respective p-values of the one-tail and two-tail for strain were 6.68E-09

and 1.34E-08. Alternatively, the respective p-values of the one-tail and two-tail for

temperature were 5.65E-12 and 1.13E-11. All critical values are clearly less than the

alpha-value of 0.05 which certifies that the null hypothesis is rejected and the

experimental data is statistically significant. The sample that contained no filler

experienced strains with the greatest magnitudes. As the filler distribution increased,

there was a visible decrease in the magnitude of the overall strain.

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Figure 4.1: This graph shows the strain experienced in filler distributions of 30% and

50% over time.

Table 4.3: This table shows the statistical values of the strain data after performing a t-

test.

Strain T-Test 30% Filler 50% FillerMean 2.07E-06 -1.7E-05Variance 2.24E-10 8.42E-11Observations 38 38Hypothesized Mean Difference 0Df 61t Stat 6.555994P(T<=t) one-tail 6.68E-09t Critical one-tail 1.670219P(T<=t) two-tail 1.34E-08t Critical two-tail 1.999624  

17

Figure 4.2: This graph shows the temperature changes experienced in filler distributions

of 30% and 50% over time.

Table 4.4: This table shows the statistical values of the strain data after performing a t-

test.

Temperature T-Test 30% Filler 50% FillerMean 26.51479 26.92626Variance 0.823813 1.017128Observations 513 513Hypothesized Mean Difference 0Df 1013t Stat -6.8687P(T<=t) one-tail 5.65E-12t Critical one-tail 1.646359P(T<=t) two-tail 1.13E-11t Critical two-tail 1.962309  

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Chapter Five

Conclusions

Summary

In this study, strain and temperature changes of a two-part epoxy’s chemical

reaction were tested statistically at three different distributions. The purpose was to

conclude which composite yielded the most appealing curing environment for a silicon

substrate. The data was collected at the Center for Advanced Life Cycle Engineering at

the University of Maryland. Labview was the program utilized to achieve this goal. Data

was further analyzed by two statistical t-tests. The fillers themselves were scaled using a

digital balance. Strain gauges and thermocouples were placed into the liquid epoxy itself

to complete the measures. The null hypothesis of the experiment predicted that lower

filler distributions would yield lower strain and temperature, while the alternative yielded

that higher filler distributions would.

Conclusion and Discussion

According to the data, the series of experiments involving the examination of the

Allied High Tech Products, Inc. Epoxy Resin and Hardener’s curing process signify that

the addition of glass filler material to this thermosetting polymer yields a visible overall

decrease in the strains and temperature changes experienced by the silicon substrate.

Chemically, the addition of glass filler material reduced the original expansion rates of

the epoxy samples. The relative filler distributions decreased these rates based on their

sizes. Furthermore, the decrease in expansion rates yielded the apparent decreases in

temperature due to the fact that less expansion means slower moving molecules which

ultimately signify temperature drops. With that being said, the conclusions drawn during

this experimentation process can certainly be applied to the real world. Electronic

technology commonly utilizes epoxy and fragile materials of small sizes. Therefore, the

epoxy’s hardening process must definitely be considered when handling these

components that are often very expensive. The attention to an epoxy’s cure could

determine the success or failure of a project.

Recommendations

The results of this study should be used as a measure of strain and temperature

caused by various epoxy filler composites. Because the results showed behavior for only

one epoxy brand and filler type, the data did not indicate that epoxy behavior would be

consistent with brand. Also, great caution and care should be applied when handling

strain gauges and thermocouples so that data is collected most accurately.

Future Implications

Further study should be conducted to determine the behaviors of various other

filler types and distributions. Epoxy type could also most definitely be varied to compare

how different companies’ products react with these filler materials. Another implication

of this study is the testing of stresses that other potting materials place on components as

well. Overall, this experiment concludes that there is an average decrease in strain and

temperature stresses from no filler to 30% filler to 50% filler.

20

Literature Cited

Augarten, S. (1984). Bit by bit: An illustrated history of computers. New York: Ticknor & Fields.

De Nograro, F. F., Guerrero, P., Corcuera, M. A., & Mondragon, I. (2003). Effects of chemical structure of hardener on curing evolution and on the dynamic mechanical behavior of epoxy resins. Journal of applied polymer science, 56(2), 177-192.

Hou, S. S., Chung, Y. P., Chan, C. K., & Kuo, P. L. (2000). Function and performance of silicone copolymer. Part IV. Curing behavior and characterization of epoxy–siloxane copolymers blended with diglycidyl ether of bisphenol-A. Polymer, 41(9), 3263-3272.

Kamal, M. R., & Sourour, S. (1973). Kinetics and thermal characterization of thermoset cure. Polymer Engineering & Science, 13(1), 59-64.

Kinloch, A. J., Mohammed, R. D., Taylor, A. C., Eger, C., Sprenger, S., & Egan, D. (2005). The effect of silica nano particles and rubber particles on the toughness of multiphase thermosetting epoxy polymers. Journal of materials science, 40(18), 5083-5086.

Lee, C. L., & Wei, K. H. (2000). Curing kinetics and viscosity change of a two‐part epoxy resin during mold filling in resin‐transfer molding process. Journal of applied polymer science, 77(10), 2139-2148.

May, C. A., & Tanaka, Y. (1973). Epoxy resins; chemistry and technology. New York: M. Dekker.

McMichael, K. (1999). Chemistry 240. Retrieved from http://chemistry2.csudh.edu/rpendarvis/Polymer.html

R., K. (2012, September 07). What is a motherboard?. Retrieved from http://www.wisegeek.org/what-is-a-motherboard.htm

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Yin, T., Rong, M. Z., Zhang, M. Q., & Yang, G. C. (2007). Self-healing epoxy composites–Preparation and effect of the healant consisting of microencapsulated epoxy and latent curing agent. Composites Science and Technology, 67(2), 201-212.

Wang, H., Bai, Y., Liu, S., Wu, J., & Wong, C. P. (2002). Combined effects of silica filler and its interface in epoxy resin. Acta materialia, 50(17), 4369-4377.Wolfe. (2009, 16 3). Homepage. Retrieved from http://hopage.cs.uri.edu/faculty/wolfe/book/Readings/Reading03.htm

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Appendix

Filler 2

Filler 1

Type 2 (36)

Filler 3

No Filler (Control)

Filler 2

Filler 1

Type 3 (36)

Filler 3

No Filler (Control)

EPOXY (108)

Filler 2

Filler 1

Type 1 (36)

Filler 3

No Filler (Control)

*Original layout of experimentation (changed due to lack of materials and finances)

23