MAJOR PROJECT REPORT
on
INVESTIGATING THE MECHANICAL PROPERTIES OF
LIGNIN, KEVLAR AND S-GLASS REINFORCED EPOXY
COMPOSITE MATERIAL
Major project report submitted in partial fulfillment of the requirements for the
award of the degree of
BACHELOR OF TECHNOLOGY
in
MECHANICAL ENGINEERING
by
CHAPPATI BALARAJASEKAR
(218W5A0302)
KUMPATI PAVAN RAJ
(208W1A0331)
DEVADULA GIRISH
(208W1A0316)
KADDALA PAVAN KUMAR
(208W1A0324)
Under the Supervision of
P. GOPINADH CHOWDARY M TECH
Assistant Professor
DEPARTMENT OF MECHANICAL ENGINEERING
VELAGAPUDI RAMAKRISHNA
SIDDHARTHA ENGINEERING COLLEGE
(AUTONOMOUS) VIJAYAWADA - 520007
i
DEPARTMENT OF MECHANICAL ENGINEERING
V.R. SIDDHARTHA ENGINEERING COLLEGE
CERTIFICATE
This is to certify that the thesis entitled “INVESTIGATING THE
MECHANICAL PROPERTIES OF LIGNIN, KEVLAR AND S-GLASS
REINFORCED
EPOXY
COMPOSITE
MATERIAL”
submitted
by
CHAPPATI BALARAJASEKAR (218W5A0302), KUMPATI PAVAN RAJ
(208W1A0331), DEVADULA GIRISH (208W1A0316), KADDALA PAVAN
KUMAR (208W1A0324), to V. R. SIDDHARTHA ENGINEERING COLLEGE,
Vijayawada under the jurisdiction of JNTU Kakinada in partial fulfillment of the
requirements for the award of the degree of Bachelors of Technology is a record of
bonafide research work carried out by them under my supervision and guidance. This
work has not been submitted elsewhere for the award of any degree.
P. Gopinadh Chowdary
Dr. N. Vijaya Sai
Assistant Professor
(Head of The Department)
Department of Mechanical Engineering
V.R. Siddhartha Engineering College, Vijayawada – 520007
ii
ACKNOWLEDGEMENT
We would like to express our deepest gratitude and appreciation to our
supervisor P. Gopinadh Chowdary, Assistant Professor inspired, encouraged and
supported us at all levels of this study.
We also take the opportunity to acknowledge the contribution of Dr. N.
VIJAYA SAI, Head of the department MECHANICAL ENGINEERING, for his
support and assistance during the development of the project.
We would like to express our sincere thanks to Dr. A. V. RATNA PRASAD,
Principal, V.R. SIDDHARTHA ENGINEERING COLLEGE, for their valuable
guidance and supporting for completing our project.
We would like to extend our warm appreciation to all my friends for sharing
their knowledge and valuable contributions in the project.
Finally, we would like to thank one and all who have directly or indirectly
contributed for the successful completion of this project work.
TEAM OF MINI PROJECT:
CHAPPATI BALARAJASEKAR
(218W5A0302)
KUMPATI PAVAN RAJ
(208W1A0331)
DEVADULA GIRISH
(208W1A0316)
KADDALA PAVAN KUMAR
(208W1A0324)
iii
DECLARATION
We here by declare that the project titled “INVESTIGATING THE
MECHANICAL PROPERTIES OF LIGNIN, KEVLAR AND S-GLASS
REINFORCED EPOXY COMPOSITE MATERIAL” is a bonafide work duly
completed by us. It does not contain any part of the project or thesis submitted by any
other candidate to this or any other institute or university. All such materials that have
been obtained from other sources have been duly Acknowledged.
iv
ABSTRACT
This study focuses on the determination of mechanical properties of lignin,
epoxy, Kevlar and S-Glass composite material. A composite is produced from these
four materials would be an innovative and fascinating Material. Combining them
results in a unique blend of properties that make it incredibly versatile and durable.
The lignin is the naturally available renewable material and Kevlar is a tough material
which can hold its properties at elevated temperatures. S-Glass is also a best material
in combining with epoxy. So, the properties of the S-Glass can be brought into the
final composite material. Also, there is no study conducted on the composite made of
epoxy – lignin – Kevlar– S-Glass and therefore the study on this material would give
important information about the resulting composite material which might help to the
industrial applications and in the material science technology. The main objective of
our study is to find out the mechanical properties and benefits of composite obtained
from epoxy, lignin, Kevlar and S-Glass.
This project focuses on the making of composite materials by mixing Kevlar
fibers, lignin, epoxy resin and S-Glass fibers. The primary objective is to obtain good
reasonable mechanical properties of Kevlar and S-Glass along with the sustainable and
abundant lignin as a reinforcing agent within an epoxy matrix. The fabrication process
involves careful optimization of the composite composition to achieve balance
between strength, flexibility and other types of properties.
The study tells us a comprehensive material characterization including tensile
strength and flexural strength. Additionally, the environmental impact and
v
recyclability of the composite materials will be maintained at safe to ensure a
sustainable approach to composite design and manufacturing.
The outcomes of this project include the formulation of high-performance
composite materials suitable for structural applications in aerospace, automotive, and
construction industries. The integration of lignin as a bio-based component aims at
contributing to reduce the environmental footprint of composite materials, aligning
with the principles of green and sustainable engineering. Overall, this project attempts
to advance the field of composite materials and promote the development of
environmentally friendly alternatives for different applications.
vi
TABLE OF CONTENTS
Section No:-
Description
Page No:-
Chapter 1
Introduction
1
1.1
Composite materials
1
1.2
Need of composite materials
2
1.3
Types of composite materials
3
1.4
Natural composite materials
4
Chapter 2
Literature review
5
Chapter 3
Problem identification
18
3.1
Research needs
18
3.2
Problem definition
19
Chapter 4
Selection of materials
20
4.1
Epoxy
20
4.2
lignin
21
4.3
Kevlar
22
4.4
S-Glass
24
Chapter 5
Methodology and preparation of
25
composite material
5.1
Steps involved
25
5.2
Previous study
25
vii
5.3
Composition calculation
27
5.4
Mould preparation
29
5.5
Mould solidification
31
5.6
Cutting into specimens
33
Chapter 6
Experimentation
35
6.1
Standards used
35
6.2
Universal testing machine
36
6.3
Tensile test
38
6.4
Flexural test
40
Chapter 7
Results and discussion
43
7.1
Tensile
43
7.2
Flexural
45
Chapter 8
Conclusion
48
Chapter 9
References
50
viii
LIST OF FIGURES
Sl.No Fig. No:-
Caption
Page No:-
1
4.1
Epoxy (Liquid Gel)
21
2
4.2
Lignin (Powder form)
22
3
4.3
Kevlar (Mat laminate)
23
4
4.4
S-Glass (Mat laminate)
24
5
5.1
Lignin volume % vs Young’s
26
Modulus
6
5.2
Lignin volume % vs Peak Strength
26
7
5.3
Foam sheet
30
8
5.4
Mould
30
9
5.5
Fabrication of composite material
32
10
5.6
Cut specimens
33
11
6.1
AE 30 KN UTM
37
12
6.2
Tensile test
38
13
6.3
Flexural test
40
14
7.1
Plot of Tensile Strength of
43
composite materials
15
7.2
Plot of Young’s Modulus of
composite materials
ix
44
16
7.3
Plot of Flexural Strength of
45
composite materials
17
7.4
Plot of Flexural Modulus of
46
composite materials
LIST OF TABLES
Sl.No Table No:-
Caption
Page No:-
1
5.1
Composite table
27
2
6.1
Tensile properties of composite
39
materials
3
6.2
Flexural properties of composite
materials
x
41
CHAPTER-1: INTRODUCTION
1.1 COMPOSITE MATERIALS
Composite materials are materials made from two or more constituent materials
with significantly different physical or chemical properties. These materials are
combined to produce a new material with enhanced characteristics that surpasses those
of the individual components. Composites are widely used in various industries due to
their exceptional strength, stiffness, lightweight nature, and resistance to corrosion and
fatigue. One of the most common types of composite materials is fiber-reinforced
composites, which consist of a matrix material reinforced with high-strength fibers
such as carbon, glass and aramid. These fibers provide tensile strength and stiffness,
while the matrix material, typically a polymer resin like epoxy, provides support and
protection for the fibers.
The versatility of composite materials makes them invaluable in aerospace,
automotive, marine, construction, and sporting goods industries, among others. In
1
aerospace, composite materials are used to manufacture aircraft components such
as wings, fuselages, and engine components, enabling aircraft to be lighter and more
fuel-efficient without sacrificing structural integrity. In the automotive industry,
composites are employed to produce body panels, chassis components, and interior
parts, contributing to weight reduction and improved fuel economy. Additionally,
composite materials are widely utilized in sporting goods like tennis rackets, golf
clubs, and bicycles, where the combination of strength and lightness enhances
performance and durability, revolutionizing the design and capabilities of modern
equipment.
1.2 NEED OF COMPOSITE MATERIALS
Composite materials fulfill a crucial need in modern industries by offering the
combination of strength, lightweight properties and customization options which are
not achievable with traditional materials alone. Their exceptional strength-to-weight
ratio makes them essential in weight-sensitive applications like aerospace, automotive,
and marine industries, where they contribute to improved fuel efficiency, performance
and durability. Additionally, the ability to tailor their properties to specific
requirements enhances their versatility across various sectors, driving innovation in
product design and manufacturing processes. Moreover, composite materials play a
vital role in promoting sustainability with their renewable and recyclable components
offering environmentally friendly alternatives to traditional materials. As industries
continue to seek solutions to meet evolving challenges, the need for composite
materials will only grow, driving ongoing research, development and integration
across diverse sectors.
2
1.3 TYPES OF COMPOSITE MATERIALS
Composite materials come in various types, each offering unique properties and
advantages suited to specific applications. One common classification is based on the
type of reinforcement used:
1. Fiber-Reinforced Composites: These composites consist of a matrix material
reinforced with fibers. The fibers, typically made of materials such as carbon,
glass, or aramid, provide strength and stiffness, while the matrix material, often
a polymer resin like epoxy, provides support and protection. Fiber-reinforced
composites are widely used in aerospace, automotive, sporting goods and
construction industries.
2. Particulate Composites: In this type, the matrix material is reinforced with
particles or fillers, such as ceramics, metals or polymers. Particulate
composites offer improved mechanical properties, thermal conductivity, or
electrical conductivity, depending on the type of particles used. They find
applications in automotive components, electronics and structural materials.
3. Laminar Composites: Laminar composites consist of layers of materials
bonded together. Each layer may have different properties, allowing engineers
to tailor the composite's characteristics. These composites are commonly used
in aircraft structures, wind turbine blades, and high-performance sports
equipment.
These types of composite materials demonstrate the versatility and adaptability of
3
composites, making them essential in a wide range of industries and applications.
1.4 NATURAL COMPOSITE MATERIALS
Natural composite materials are formed by combining natural fibers with a matrix
material, often derived from renewable resources. These composites harness the
inherent properties of natural fibers, such as cellulose, lignin, or proteins, along with a
matrix material, typically a natural resin or polymer. Examples of natural composites
include wood, bamboo, straw bale and coconut oil.
These
materials
offer
several
advantages,
including
sustainability,
biodegradability and low environmental impact. Natural composites find applications
in various industries, such as construction, automotive, packaging and consumer
goods. For instance, they are used in automobile interiors and structural components
due to their lightweight nature and eco-friendly properties.
Natural composite materials are increasingly gaining attention as sustainable
alternatives to synthetic composites, with ongoing research and development focused
on optimizing their properties and expanding their applications. Their renewable
nature and reduced environmental footprint make them promising solutions in the
quest for more eco-friendly materials across diverse industries.
4
CHAPTER-2: LITERATURE SURVEY
1. Thielemans, W., Can, E., Morye, S. S., & Wool, R. P. (2002). Exploratory
research delved into innovative applications of lignin, exploring its use as a
filler and comonomer in thermosetting unsaturated polyesters and vinyl esters.
Different lignin types (pine kraft, hardwood, ethoxylated, and maleinated) were
examined for solubility in various resin systems to assess compatibility. When
employed as a filler, lignin led to an elevated glass-transition temperature,
while the modulus at 20°C decreased due to its plasticizing effect. This
approach aimed to remedy surface defects on natural fibers and enhance the
bond strength between the resin and fiber. Optimal improvements were
observed, dependent on the amount of lignin applied to cover the fibers. These
findings underscore lignin's potential as a versatile component in resin systems,
offering promising avenues for innovative applications in composite materials
and reinforcing natural fibers.
2. Goyat, M. S., Ray, S., & Ghosh, P. K. (2011). An innovative ultrasonic dual
mixing process, combining ultrasonic mixing with impeller stirring, was
6
employed to disperse sub-25 nm Al2O3 particles in epoxy resin.
Characterization of the resulting nanoparticulate-epoxy composite was
conducted using TEM, AFM, DTA, TGA, and FTIR, comparing it with epoxy
without particles. The dual mixing process induced the formation of a selforganized hexagonally arranged lattice of nano-sized cavities at 40% and 55%
amplitudes, leading to an increase in the glass transition temperature of the
epoxy. In contrast to stirring, the ultrasonic dual mixing method resulted in
linear clusters of nanoparticles, reducing particle agglomeration and decreasing
cluster size with increasing amplitude. The arrangement of cavities in the
nanoparticulate-epoxy composite appeared somewhat disturbed compared to
the neat epoxy without particles. Notably, the composite processed at a 55%
amplitude exhibited the most significant improvements in glass transition
temperature and thermal stability. This enhancement was attributed to
extensive hydrogen bonding between the epoxide groups in the epoxy resin and
the free OH groups on the nanoparticle surface, particularly under ultrasonic
dual mixing conditions at a high amplitude of 55%. This bonding constrained
polymer chain movement, contributing to the observed improvements in
composite properties.
3. Rashid Azrin Hani Abdul, Ahmad Roslan, Mariatti Jaafar, Mohd Nazrul
Roslan, Saparudin Ariffin (2011). This study focuses on assessing the highspeed impact and flexural properties of hybrid textile reinforced epoxy
composites. Samples were crafted from coir yarn, Kevlar yarn, as well as a
blend of the two with varying warp/weft orientations, alongside pure epoxy for
comparison. The woven samples were produced using a handloom, while
7
composite specimens were prepared using hand lay-up techniques. The
findings revealed that woven Kevlar composite samples demonstrated superior
impact resistance, albeit with lower flexural properties. Notably, the composite
plate composed of woven coir yarn (warp) and Kevlar yarn (weft) exhibited
flexural and impact strengths of 17 MPa and 67 kJ/m² respectively, closely
resembling those of woven Kevlar composites.
4. Singh, Thingujam Jackson, and Sutanu Samanta (2015). In recent years,
the interest of using the fibre reinforced composites (FRCs) has increased due
to its potential for replacing the traditional materials in various applications.
Kevlar fibre, due to its unique properties such as higher strength to mass ratio
and modulus, has become very popular as reinforcement in composite
materials and its application has growth considerably. However, for enhancing
its properties in various applications, a proper characterization is very
important. Many researches have been conducted in recent years, for
characterization of Kevlar fibre and its composites. In this paper, a state-of-the
art review of these characterizations is presented.
5. Audrey Llevot, Etienne
Grau, Stéphane Carlotti, Stéphane Grelier
(2016). In contemporary times, there is significant interest in synthesizing
(semi)aromatic polymers from lignin derivatives, owing to the pivotal role of
aromatic compounds in polymer manufacturing and lignin's status as the
primary source of aromatic biobased substrates. Lignin deconstruction yields
various phenols with diverse chemical structures, with vanillin and ferulic acid
being prominent examples. Depending on the phenolic substrates involved,
8
different chemical modifications and polymerization pathways are explored,
resulting in (semi)aromatic polymers exhibiting a broad spectrum of
thermomechanical properties. This review comprehensively examines the
synthesis and characteristics of both thermoset (vinyl ester resins, cyanate
ester, epoxy, and benzoxazine resins) and thermoplastic polymers (polyesters,
polyanhydrides,
Schiff
base
polymers,
polyacetals,
polyoxalates,
polycarbonates, and acrylate polymers) derived from vanillin, ferulic acid,
guaiacol, syringaldehyde, or 4-hydroxybenzoic acid.
6. Naseem, A., Tabasum, S., Zia, K. M., Zuber, M., Ali, M., & Noreen, A.
(2016). Lignin and its derivatives, including sulfonate, phenolic, organosolv,
Kraft, and sodium sulfonate lignin, exhibit a myriad of valuable properties such
as
high
thermal
stability, antioxidant capabilities, biodegradability,
antimicrobial actions, and adhesive properties. These characteristics make
them versatile for a wide range of applications. Derived materials from
chemically modified lignin, like coatings, paints, plastics, resins, rubber
packaging, and fuel production, benefit from the excellent mechanical and
physicochemical properties of these lignin derivatives. This review emphasizes
the multi-purpose nature of lignin-based materials and their extensive
industrial applications, shedding light on recent advancements in addressing
various technical and scientific aspects.
7. Yang, S., Chalivendra, V. B., & Kim, Y. K. (2017). In this study Kevlar fibers
have been widely used as impact-resistant reinforcement in composite
materials. The paper studies the impact behavior as well as damage tolerance
9
of Kevlar/filled epoxy matrix. Two different fillers, cork powder and nano
clays Cloisite 30B, were used in order to improve the impact response of these
laminates. For better dispersion and interface adhesion matrix/clay nano clays
were previously subjected to a silane treatment appropriate to the epoxy resin.
The fillers adding increases the maximum impact load but the opposite
tendency was observed for the displacement.
8. Nair, S. S., Kuo, P.-Y., Chen, H., & Yan, N. (2017). In a pioneering study,
high residual lignin-containing cellulose nanofibrils (LNFCs) derived from
alkali-treated bark fibers were used to reinforce epoxy resins. Mechanical
fibrillation resulted in LNFC aqueous suspensions with an average fibril
diameter of 62.5 ± 24.7 nm. Incorporating 20–36 wt% of LNFCs into pure
epoxy remarkably doubled the tensile modulus and strength of the resulting
composites, surpassing mechanical properties reported in the literature for
similar cellulose nanofibril loadings. The composites exhibited high thermal
stability, with only a slight reduction in thermal degradation temperatures
compared to neat epoxy resin. Furthermore, these novel composites
demonstrated exceptionally low water absorption and water vapor transmission
rates. The water vapor barrier efficiency of the composites significantly
outperformed both pure LNFC films and cured neat epoxy, exhibiting an
increase of more than 156 times and eight times higher, respectively.
9. Suthan, R., V. Jayakumar, and S. Madhu (2018). In this study the Kevlar
fiber reinforced polymer composites are rapidly growing in manufacturing
applications such bicycle tires and racing sails to body armor, bullet proof
10
vests, military helmets, walking boots etc. Kevlar epoxy composite material
using the Kevlar fiber and epoxy resin LY-556 was fabricated with manual
hand layup procedure. The mechanical characteristics like tensile, impact
strength and flexural rigidity were evaluated. With the results obtained it is
found that kevlar epoxy composite provides better mechanical characteristics
than aluminum. In this work, the possibility of replacing aluminum with Kevlar
reinforced epoxy composite material is investigated for various applications
viz. manufacturing of bus body frame, bullet proof vests, automobile body,
sports applications, fire proof clothing, military helmets etc. Also, the FE
analysis is carried out with MIDAS NFX software to correlate the test results
with FEA.
10. Xu, Y., Dayo, A. Q., Wang, J., Wang, A., Lv, D., Zegaoui, A., … Liu, W.
(2018). A groundbreaking self-exothermic curing agent, formed by blending
4,4’-diaminodiphenylmethane (DDM) and acrylic acid (AA), efficiently cures
E51 epoxy resin at room temperature. The curing agent's chemical structure
was characterized using 1H nuclear magnetic resonance (1H NMR) and
Fourier-transform infrared (FTIR). Curing behavior was investigated via
differential scanning calorimetry (DSC) and FTIR, confirming completion of
the curing reaction in just 3 hours due to the high reactivity of acryl amide
groups and substantial heat release from the DDM and AA reaction. For rapid
prototyping high-performance composites, 5 wt% NaOH-treated short hemp
fibers (TF) were incorporated into the room temperature curing epoxy resin.
Mechanical properties were examined, revealing increased tensile strength
with higher TF content, coupled with decreased elongation at break. Compared
11
to cured neat epoxy resin, the composite with 7.5 wt% TF exhibited significant
improvements: a 233% increase in impact strength, a 52% rise in flexural
modulus, and an impressive 213% enhancement in Young's modulus. Dynamic
mechanical analysis (DMA) and thermogravimetric analysis (TGA) explored
the effect of fiber content on thermal properties, while scanning electron
microscopy (SEM) highlighted excellent adhesion between TF and room
temperature-cured epoxy resin. This research presents a novel curing agent,
advancing the development of high-performance composites with rapid
prototyping capabilities and superior mechanical and thermal characteristics.
11. Arvind Singh Negi1, Jitendra Kumar Katiyar2, Sandeep Kumar3, Nitin
Kumar1 and Vinay Kumar Patel (2019). The current research delves into
examining the physical, mechanical, and wear characteristics of epoxy
composites reinforced with KMnO4-treated hemp fiber (3, 6, and 9 wt%), in
comparison with Kevlar-5 wt%/epoxy and carbon-5 wt%/epoxy composites.
Findings indicate that the carbon-hemp reinforced epoxy composite exhibits
superior tensile strength (83.33 MPa at 6 wt% hemp), impact resistance (12
Joule at 6 wt% hemp), and hardness (49.4 Hv at 9 wt% hemp) compared to
other composites. Integrating hemp into Kevlar and carbon fiber-based epoxy
composites notably enhances tensile strength, elongation, impact resistance,
hardness, and abrasion wear resistance properties. Particularly, Kevlar-hemp
fiber epoxy composites display superior elongation and abrasion wear
resistance properties compared to carbon-hemp reinforced epoxy composites
at equivalent weight percentages. Optimal composite performance is
determined through a multi-criteria TOPSIS technique, highlighting that the
12
epoxy composite reinforced with 6 wt% hemp fiber and 5 wt% carbon fiber
offers the most favorable overall physical, mechanical, and abrasive wear
performance.
12. Tanveer Ahmed Khan, Jung-Hun Lee, Hyun-Joong Kim (2019). Lignin,
the second most abundant component of plant material, holds great promise as
a natural resource for adhesive and coating applications. Traditionally,
adhesive and coating materials have been sourced from nonrenewable
petroleum-based sources. However, with increasing demand and diminishing
resources, the chemical industry has turned its attention towards renewable
alternatives. In the past decade, significant research efforts have been dedicated
to exploring various methods and techniques for harnessing lignin's potential
as adhesives and coatings, owing to its renewability. This chapter provides an
in-depth exploration of lignin recovery processes, methodologies for
synthesizing valuable lignin-based chemical products, and its potential
applications as adhesive raw material or energy source. Additionally, it covers
the utilization of lignin in polymer composites and the development of ligninbased coatings. Key topics addressed include the structure and processing of
lignocellulosic biomass for lignin extraction, polymers incorporating lignin as
a macro monomer, synthesis of monomers and polymers from monolignol,
production of polymers from lignin-derived chemicals like vanillin, and the
application of lignin-based coatings across various products. Intended for
polymer scientists, engineers, and students, this chapter offers valuable insights
into the ongoing research and advancements in utilizing lignin for adhesive and
coating purposes.
13
13. Lu, Wenyu, Wenfan Yu, Baoxu Zhang, Xiaohang Dou, Xiangsheng Han,
and Hongzhen Cai (2021). Transforming crop straw wastes into functional
wood-plastic composites is considered as a cost efficient and eco-friendly way
for
agricultural
wastes
recycling.
However,
the
lacking
of
promising mechanical strengths and functionalities have been the main
hindrances for their actual applications in structural and engineering
constructions.
14. Prakhash, N., P. Sakthivel, M. Dhivakar Karthick, P. Swaminathan, and
D. Zunaithur Rahman (2021). This research investigated the use of Kevlar,
Banana Fabric fiber as possible to improve the impact properties. These fibers
have high mechanical resistance such as tensile strength and comparative
compressive strength addition to that high thermal resistance, corrosion
resistance. Kevlar is about five times lighter than steel in terms of the same
tensile strength. It is the strongest textile fiber available today.
15. Xiang Zhen, Huiwen Li, Zhongbin Xu, Qingfeng Wang, Shunni Zhu, Zh
ongming Wang, Zhenhong Yuan (2021). This study presents a novel and
environmentally friendly approach for producing lignin-based epoxy
thermosets, addressing a current lack of efficient methods for utilizing
industrial lignin. The proposed strategy involves a one-pot synthesis to create
phenolated lignin incorporated novolac epoxy networks (PLIENs). The
resulting PLIENs demonstrated superior mechanical and thermal properties
compared to epoxy resins produced through conventional methods.
14
Interestingly, increasing lignin loading did not significantly compromise the
thermal-mechanical performance of the cured epoxy resins. While the glass
transition temperature (Tg) of PLIENs was slightly reduced compared to
conventional petroleum-based epoxy resins (DGEBA), PLIENs exhibited
higher flexural strength and storage modulus than DGEBA. Notably, the char
yield of PLIENs at 800 °C reached 28.9%, significantly surpassing DGEBA's
6.9%. This suggests that lignin contributes to enhancing the flame retardancy
of epoxy resins. The findings of this research offer a promising and
commercially viable approach for the production of lignin-based epoxy
thermosets,
providing
valuable
insights
for
the
development
of
environmentally sustainable materials.
16. Xin Zhao, Zeyu Zhang, Jinyin (2022). Formaldehyde reacts with the ortho
phenolic hydroxyl groups present in p-hydroxyphenyl and guaiac-based
structures within lignin, leading to the attachment of hydroxymethyl groups by
displacing the hydrogen atom at the ortho-position carbon. This process yields
hydroxymethylated modified lignin (HMKL). Through various analyses
including
infrared
spectroscopy,
hydrogen
NMR
spectroscopy,
thermogravimetric (TG), and derivative thermogravimetric (DTG) analysis, it
is confirmed that the hydroxymethylation modification of alkali lignin is
successful. Subsequently, lignin nanoparticles (LNPs) are fabricated using the
acid precipitation self-assembly method in an ethylene glycol solution
containing hydroxymethylated modified lignin. Scanning electron microscopy
15
and dynamic light scattering (DLS) analysis are employed to determine the
particle size and shape of the lignin nanoparticles.
17. Yashas
Gowda
T.
G., Vinod
A., Madhu
P., Sanjay
Mavinkere
Rangappa, Suchart Siengchin, Mohammad Jawaid (2022). This study
focuses on evaluating the performance of hybrid fiber composites for
engineering applications by combining two natural fibers with different
synthetic fibers. Specifically, the research investigates the impact of stacking
sequence on the mechanical and thermal properties of flax, Kevlar, carbon, and
carbon-Kevlar hybrid fiber reinforced epoxy composites. Using a hand layup
technique, four-layered composite laminates with varying stacking sequences
were fabricated. Mechanical properties including tensile, flexural, interlaminar
shear, and impact tests, as well as thermal behavior, water absorption, contact
angle measurement, and scanning electron microscopy, were analyzed. In
essence, this research endeavors to contribute to the understanding of how
different stacking sequences influence the properties of hybrid fiber
composites, thus informing their potential for diverse engineering applications.
18. Ghaiskar, Ahamad and Mohammad Damghani Nouri (2022). This study
explores the concept of sustainability by comparing the behavior of neat hemp
fabrics with polymer matrix composites reinforced with these fabrics under
high-velocity
impact.
With
a
focus
on
incorporating
stable
and
environmentally friendly fillers into polymer composites, the research
investigates the use of lignin fillers as alternatives to black carbon. Ligninbased rubber matrix composites were fabricated to examine their performance.
16
Scanning electron microscope analysis confirmed the effective dispersion of
lignin among the yarns, contrasting with the distribution of black carbon. The
interaction between lignin and rubber facilitated uniform filling of gaps
between the yarns. High-velocity impact tests were conducted on one to three
layers of samples using a gas gun with hemisphere projectiles at velocities
ranging from 20 to 160 m/s. The evaluation was based on energy absorption
and failure mechanisms. Results indicate that coating natural hemp woven
fabric with the diluted rubber matrix significantly influences the ballistic
performance and energy absorption of the composites. The green composite
comprising lignin-based rubber matrix exhibited superior energy absorption
capacity compared to the black carbon-based rubber matrix composite.
Consequently, lignin-based rubber composites are proposed as highperformance green composites, offering lower weight and higher energy
absorption.
19. Sathvik
Kangokar
Mukesh, Nuthan
Bettagowda, Jagadeesh
Praveenkumara, Yashas Gowda Thyavihalli Girijappa (2022). This
research involves the fabrication of hybrid epoxy composites reinforced with
natural fibers using the hand lay-up method, with flax and Kevlar serving as
reinforcement and epoxy as the binding material. The study aims to examine
how stacking sequence and hybridization affect the mechanical, water
absorption, and morphological properties of the polymer composites. The
findings indicate that the neat Kevlar-reinforced composite demonstrates
maximum tensile strength, modulus, and impact strength of 189.94 MPa,
2345.35 MPa, and 37.16 kJ/m2 respectively, alongside minimal water
17
absorption behavior. Conversely, the hybrid composite, with Kevlar as outer
layers and flax as core layers, exhibits maximum flexural strength, modulus,
and interlaminar shear strength of 360.76, 37124.2, and 213.51 MPa
respectively. However, the neat natural flax-reinforced epoxy composite
displays higher water absorption percentage due to its more hydrophilic nature.
Scanning electron microscope analysis demonstrates the effective bonding and
adhesion of both Kevlar and flax fabrics with the epoxy matrix.
18
CHAPTER-3: PROBLEM IDENTIFICATION
3.1 RESEARCH NEEDS
Research needs for epoxy, lignin, Kevlar and S-Glass composite materials vary
based on their unique properties and potential applications. For epoxy composites,
there's a need for research focused on developing novel formulations to enhance
mechanical properties, such as strength, toughness and fatigue resistance, while also
improving environmental sustainability by exploring bio-based alternatives to
traditional epoxy resins.
In the case of lignin composites, research is needed to optimize extraction
methods and processing techniques to effectively utilize this abundant renewable
resource as a reinforcing filler in composite materials. Additionally, understanding the
compatibility of lignin with different matrix materials and its impact on composite
performance is crucial.
For Kevlar composites, research efforts may focus on improving
manufacturing processes to reduce costs and increase production efficiency while
19
exploring new applications that capitalize on Kevlar's exceptional strength and impact
resistance.
Similarly, for S-Glass composites, research needs include advancing
fabrication techniques to enhance fiber-matrix bonding, optimizing fiber orientation
for specific applications and investigating potential hybridization with other
reinforcing materials to further improve mechanical properties and tailor performance
characteristics to meet the demands of various industries.
3.2 PROBLEM DEFINITION
The composite materials have good scope in future. Thus, in this study we
aimed towards making the composite materials. Problem definition in the context of
epoxy, lignin, Kevlar, and S-Glass composite material making involves identifying
specific challenges or issues that need to be addressed in the production process. This
could include factors such as optimizing material compatibility, improving
manufacturing efficiency, enhancing mechanical properties, reducing costs or
exploring sustainable alternatives. Each material presents its unique set of challenges,
such as developing effective bonding techniques for epoxy composites, optimizing
lignin extraction and processing methods, improving scalability and cost-effectiveness
in Kevlar production and enhancing fiber-matrix adhesion and composite strength in
S-Glass materials. Accurately defining these problems is essential for guiding project
and development efforts aimed at overcoming these obstacles and advancing
composite material manufacturing capabilities.
Thus, the main objective of our project is to obtain the mechanical properties
20
of the epoxy, lignin, kevlar and s-glass composite material.
21
CHAPTER-4: SELECTION OF MATERIALS
4.1 EPOXY
Form
– Liquid
Density
– 1.16 g/m³
Heat distortion temperature
– 50°c
Modulus of elasticity
– 5 Gpa
Flexural strength
– 60 Mpa
Tensile strength
– 73 Mpa
Applications
– decorative items, surface coatings.
Epoxy is most versatile material that is used in making of the composites. Up
to now many composites are prepared in combination of epoxy and other
reinforcement materials. Epoxy resins are mostly used in structural and industrial
applications. There are several applications like composite preparation, surface
coatings and electrical laminates. Epoxy resins are a type of strong and stiff material
that can handle high temperatures, stay in shape and resist getting tired from repeated
22
use.
Fig. 4.1: Epoxy (liquid Gel)
They are known for their strength, stiffness, ability to withstand heat, stable
shape and resistance to wear and tear. Epoxy resins are cured with the help of hardeners
or curing agent to form the cross-linking structures with the other compounds in the
mixture. Epoxy generally contains of aliphatic amines which have low viscosity, high
reaction with other compounds and can be used easily.
4.2 LIGNIN
Form
– Powder
pH value
– 8.0 to 10.0(50g/L, 20°c)
Methoxyl Group
– 10.0 to 12.0 % (calcd.on anh.substance)
Ignition residue (Sulfate)
– 20.0 to 29.0 % (calcd.on anh.substance)
Water max.
– 10.0%
Tensile strength
– 5-8 Mpa
Applications
- Functional Surfaces and Coatings, Bio composites
23
Fig. 4.2: Lignin (Powder form)
Lignin and its bio polymers have shown vast traits like high thermal stability,
biodegradability, antioxidant, antimicrobial actions, adhesive properties etc. It is the
second most available natural resource after cellulose. Most important chemical
function groups in lignin structure are aromatic, hydroxyl, methoxyl and carbonyl
groups. Hence lignin can be used in polymer composites synthesis as raw, organic and
bio-based material. Additionally, polyphenolic structure in the molecular composition
of lignin results in reduction of cost of production of composites and helps to blend
well with other polymers as a modifier. It is theoretically possible to replace petroleum
based with lignin due to its similarity in structure for the synthesis of epoxy resin.
4.3 KEVLAR
Form
- Matt
24
Breaking Strength
- 226N
Breaking tenacity
- 2.92GPA
% Elongation
- 3.5%
Tensile Modulus
- 86GPA
Applications
– body armours, ropes, cables.
Fig. 4.3: Kevlar (mat laminate)
The use of Kevlar fiber can improve the impact properties when used as
reinforcement material. These fibers have high mechanical resistance such as tensile
strength and comparative compressive strength in addition to that high thermal
resistance and corrosion resistance. Kevlar is about five times lighter than steel in
terms of the same tensile strength. It is the strongest textile fiber available today.
Kevlar fibers have advantages of mechanical properties like tensile strength, Young
modules, toughness , low density , high dimensional and thermal stabilities (degrading
temperature >500 °C), making them favorable candidates as reinforcing fillers in crop
straw-thermoplastic polymer composites . Kevlar fibers have been applied to plastic
polymers directly.
25
4.4 S-GLASS
Tensile strength
- 4.6 Gpa
Modulus
- 86.8 Gpa
Density
- 2.46 g/cc
Coefficient of thermal expansion
- 23-27 *10^7/0c
Dielectric constant
- 5.0-5.1 *10^10 Hz
Applications
– composite materials, sports equipment.
Fig. 4.4: S-glass (Mat laminate)
S-Glass, also known as "Strength Glass," is a high-performance composite
material renowned for its exceptional strength, stiffness and thermal resistance. It is
primarily composed of silica (SiO2). S-Glass fibers are significantly stronger and
stiffer than traditional E-Glass fibers, making them ideal for applications requiring
superior mechanical properties. S-Glass is commonly used in aerospace, military and
high-end sporting goods, where its excellent tensile strength and modulus offer
advantages in weight reduction and structural integrity. Additionally, its resistance to
high temperatures and harsh environments makes S-Glass a preferred choice in
26
demanding engineering and industrial applications.
27
CHAPTER-5: METHODOLOGY AND
PREPARATION OF COMPOSITE MATERIAL
5.1 STEPS INVOLVED
In this study, we will make composites of epoxy with lignin, kevlar and SGlass as its reinforcement materials. This study gives the data about the composite
made with epoxy-lignin-Kevlar- S-Glass, which tells how reinforcement materials
effecting the mechanical properties of composite according to their composition. The
experimental tests are conducted to obtain the mechanical properties of the material.
UTM is used to find the tensile strength and modulus of the material. Bending test is
also conducted to find the flexural strength.
5.2 PREVIOUS PROJECT
Previously, we have conducted a study on lignin and epoxy composite material.
The results obtained from that study helped us in this project by reducing the number
of variations required to get the valuable research data of the composite material. In
our previous study, we made various samples by varying the lignin weight percentage
28
content in steps of 5 and upto 20%. The peak strength and young’s modulus of those
test specimens obtained as shown in the figure 5.1 and figure 5.2.
Lignin volume.% vs Young's Modulus
Youngs Modulus - MPa
1200
1000
800
888.95
918.12911.13
1,116.20
990.81
880.38
940.11
725.14
600
400
200
0
5
10
15
20
Lignin Volume %
YOUNGS MODULUS OF CG
YOUNGS MODULUS OF FGM
Fig. 5.1: Lignin Volume % vs Young’s modulus
Lignin volume % vs Peak Strength
37.35
40
32.64
Peak Strength - MPa
35
30
25
36.98
28.55
28.16
23.14
25.04
24.84
20
15
10
5
0
5
10
15
20
Lignin Volume%
PEAK STRENGTH OF GC
PEAK STRENGTH OF FGM
Fig. 5.2: Lignin Volume % vs Peak Strength
GC represents general composite material and FGM represents functionally
graded material. In both the material and properties, the highest values are obtained at
29
the lignin composition of 15%. By taking our previous project as a reference, it
simplified our project for some part. We have selected the composition for the material
in which lignin of 15%wt is taken constant in all the samples.
5.3 COMPOSITION CALCULATION
We made the composite material by measuring proper v/v% composition of
epoxy and corresponding reinforcement materials as shown in the table 5.1. Eight
composites were made based on the reinforcement materials embedded in the
composite. All eight composite materials with respective composition content are
shown in the table 5.1. The volume percentage we have taken for the lignin is obtained
by taking the reference from the results we obtained from our previous project.
We choose 15% lignin for all the composite samples, this is because we got
good mechanical properties of the composite material at 15% in our previous project.
Table 5.1: Composition Table
S.no
Sample
Epoxy
Lignin
Hardener
(g)
(g)
(g)
1
Pure epoxy
155.52
0
17.28
2
15%lignin
132.19
25.92
14.68
3
15%lignin + 1
124.92
24.49
13.88
124.92
24.49
13.8
117.65
23.06
13.07
layer Kevlar
4
15%lignin + 1
layer S-Glass
5
15%lignin + 2
30
layers Kevlar
6
15%lignin + 2
117.65
23.06
13.07
117.65
23.06
13.07
117.65
23.06
13.07
layers S-glass
7
15%lignin + 1
layer Kevlar + 1
layer S-Glass
8
15%lignin + 1
layer S-Glass +
1 layer Kevlar
MOULD DIMENSIONS:
Length of the mould = 20 cm
Breadth of the mould = 18 cm
Thickness of the mould = 0.4 cm
Total volume of the mould = 20*18*0.4= 144 cm^3
Total mas of epoxy in the mould = 1.2*144 = 172.8 g
1 – PURE EPOXY:
90% volume is epoxy = 144*0.9= 129.6 cc
10% volume hardener = 144*0.1 = 14.4 cc
Mass of epoxy = density*Volume=1.2*(90% of 144) =155.52 g
Mass of hardener = density*Volume= 0.98*14.4 = 14.11 g
31
2 – 15% LIGNIN:
15% mass lignin = 172.8*0.15= 25.8 g
85% mass = 90% epoxy + 10% lignin = 147 g = 132.2 g epoxy + 14.8 g hardener
3 – 15% LIGNIN + 1 LAYER KEVLAR:
1 layer kevlar volume = 18*20*0.022= 7.92 cc
Epoxy, hardener and lignin volume = 144 - 7.92 = 136.08
15% lignin = 136.08*1.2*0.15 = 24.9g
Epoxy = (136.08*1.2-24.9)*0.9= 124.92g
Hardener = 136.08*1.2*0.1= 13.8g
4 - 15% LIGNIN + 1 LAYER S-GLASS:
Same as in sample 3
5 - 15%LIGNIN + 2 LAYERS KEVLAR:
2 layers volume = 0.022*2*18*20 = 15.84 cc
Epoxy, Lignin and Hardener = 144-15.84 = 128.16 cc
15% lignin= 128.16*1.2*0.15= 23.06g
Epoxy = (128.16*1.2-23.06)*0.9= 117.65g
Hardener = 13.07g
The same calculation is used for sample 6, 7 and 8 as in 5.
5.4 MOULD PREPARATION
A mould of 20cm x 18cm x 0.4cm dimensions is made using the below
materials. Such type of 8 molds were made for producing the composites of different
32
proportions. The following materials are used for making one mould:
1. A plywood of 30cm*30cm
2. OHP sheet
3. 8 small nails
4. Fevikwik
5. Knife
6. Foam sheet (Fig. 5.1)
7. Hammer
1. Firstly, take the plywood and place in on the flat floor.
2. Then place the OHP sheet on the plywood exactly at the center of the board.
3. Now cut a foam sheet of inside 18cm*20cm and outside 21cm*23cm and place
this piece on the OHP sheet so that rectangular foam sheet fits perfectly.
4. Now take the nails and place it on the Hallow OHP sheet as shown in the figure
5.2.
5. Then hold the hammer and blow on the nail head so that it passes through OHP
sheet, foam sheet and plywood. This makes the mould rigid.
6. Finally, use fevikwik between the OHP sheet and Foam sheet so that no gap
forms and perfect seal occurs.
7. Leave the mould for few hours to form a good seal that fevikwik makes.
33
Fig. 5.3: Foam sheet
Fig. 5.4: Mould
5.5 COMPOSITE SOLIDIFICATION
The lignin, epoxy and hardener were measured carefully by using the
electronic laboratory weighing machine. The measured quantities were mixed in a
flask thoroughly till uniform distribution is obtained. While stirring, the air bubbles
may form in the mixture and forms air voids in the final composite. To avoid such
defects, we should stir the mixture slowly.
Fig. 5.5.1
Fig. 5.5.2
34
Fig. 5.5.3
Fig. 5.5.4
Fig. 5.5.5
Fig. 5.5.6
Fig. 5.5: Fabrication of composite material
After mould preparation, the mixture was poured into the mould and placed in
a closed box. Now it will be ready for the solidification.
Similarly, eight composites of such composites were made based on the
reinforcement materials content in the composite material. The composite material was
prepared by pouring the mixture into the mould. It takes a minimum of 24 hours to
solidify completely so that bond forms between them. The table shows the composite
35
composition.
The above procedure is only for composite materials with no kevlar and SGlass. For making composite materials with kevlar and S-Glass laminates, we should
place the laminates between the two layers of Epoxy-lignin mixture. Thus, forming the
composite material with first layer and third layer of epoxy-lignin and second layer of
kevlar laminates. Similarly, S-Glass composite also made with same procedure. For
making composite materials with two laminates, we can use the same method by
pouring the epoxy-lignin mixture between the laminates.
5.6 CUTTING INTO SPECIMENS
The composite material formed is now ready to cut into specimens for tensile
and flexural test. The shape of the tensile and flexural test specimens is of simple
rectangular cross-section but not the dimensions. For tensile test, a specimen of
13mm*165mm was used in which gauge length is “-----”. For flexural test, a specimen
of 25mm*100mm was used in which the load applied at center.
We must be very careful during cutting operation because any small mistake
or movement leads to unexpected dimensions of the test specimen. In order to achieve
perfect cutting, we should mark the raw piece accurately with steel rule. During the
operation, the work piece must be held tightly on the bench vice which would reduce
the vibrations.
36
Fig. 5.6: Cut specimens
The figure 5.9 shows the cut specimens for flexural and tensile test. The
specimens were cut using disc saw because it has precise cutting motion and produce
less vibration. During the cutting operation, we should take safety measures. The
following are the safety measures we should take:
1. Don’t touch the circular disc saw during the operation.
2. Wear apron and gloves so that jamming of the cloths doesn’t occurs.
3. Wear mask and eye glasses.
4. Hold the work piece on the bench vice.
5. Cut the work piece slowly, as the kevlar and S-Glass are prone to get suck by
the disc saw.
37
CHAPTER-6: EXPERIMENTATION
6.1 STANDARDS USED
The test pieces were cut from the obtained composites of standard size.
Generally, ASTM D790 standard can be used for reinforced composites and plastic
composites to calculate flexural strength. ASTM D3039 standard can be used for
tensile strength. So, the cut pieces with above standards and number of such pieces
were used for average values. ASTM 3039 and ASTM D790 are both standards
established by the American Society for Testing and Materials (ASTM) to evaluate the
mechanical properties of composite materials, particularly in terms of tensile and
flexural properties respectively. ASTM D3039 outlines the standard test method for
tensile properties of polymer matrix composite materials. It specifies the procedure for
determining the tensile strength, tensile modulus, and other mechanical properties of
composite materials under tension. This standard is crucial for assessing the strength
and durability of composite materials used in various industries such as aerospace,
38
automotive and construction.
On the other hand, ASTM D790 defines the standard test method for flexural
properties of unreinforced, reinforced plastics and electrical insulating materials. This
standard provides guidelines for measuring the flexural strength, flexural modulus and
other flexural properties of materials under a bending load. It has been widely used to
evaluate the stiffness and resistance to bending of materials like plastics, composites
and electrical insulators.
Both standards play essential roles in quality control, material selection and
design optimization processes across industries where composite materials are
prevalent. Adhering to these standards ensures consistency, reliability and
comparability of test results, facilitating the development and advancement of
composite materials for diverse applications.
6.2 UNIVERSAL TESTING MACHINE
The AE 30KN universal testing machine is a robust and versatile instrument
used in materials testing laboratories to evaluate the mechanical properties of various
materials under tension, compression and bending. With a maximum load capacity of
30 kilonewtons (kN), it can accurately measure the tensile strength, yield strength,
elongation and other crucial parameters of metals, plastics, composites and other
materials. Fig. 6.1 shows the AE 30KN UTM.
Equipped with advanced features such as precision load cells, displacement
sensors and intuitive software interfaces, the AE 30KN ensures precise and reliable
36
test results. It’s high-resolution data acquisition system captures real-time force and
displacement data, allowing for detailed analysis of material behavior during testing.
Fig. 6.1: AE 30KN UTM
The machine's design incorporates rigid frames and components to minimize
deflection and ensure precise alignment, essential for accurate test results.
Additionally, its user-friendly interface enables operators to easily set up test
parameters, monitor testing progress, and analyze results efficiently.
The AE 30KN tensile test machine is widely used in research and development,
quality control, and production environments across industries such as aerospace,
automotive, construction, and manufacturing. Its ability to perform a wide range of
37
standard and customized tests makes it a valuable asset for evaluating the mechanical
performance and reliability of materials used in various applications. Overall, the AE
30KN universal testing machine stands as a dependable tool for assessing material
strength and quality with precision and consistency.
6.3 TENSILE TEST
Fig. 6.2: Tensile test
Tensile Testing is a form of tension testing and is a destructive engineering and
materials science test whereby controlled tension is applied to a sample until it fully
38
fails. This is one of the most common mechanical testing techniques. It is used to find
out how strong a material is and also how much it can be stretched before it breaks.
This test method is used to determine yield strength, ultimate tensile strength, ductility.
strain hardening characteristics, Young's modulus and Poisson's ratio. The different
hybrid composite specimens are tested in the tensometer to find out the tensile
properties. The dimension of the specimen is 165 mm × 10.2 mm × 5 mm and a span
length of 70 mm was employed.
FORMULA
TS= F/A
Where,
TS-tensile strength.
F=load(N)
A=area(mm)
E-TS/ E
Where,
E= Tensile modulus
TS=tensile strength
CALCULATION
Table 6.1: Tensile properties of composite materials
S.no
Sample
Tensile stress
Young’s modulus
(MPa)
(MPa)
1
Pure epoxy
19.4856125
821.5784746
2
15%lignin
28.5496153
1116.2019236
39
3
15%lignin + 1 layer Kevlar
44.5316452
1983.5726433
4
15%lignin + 1 layer S-Glass
36.5615462
1548.6515472
5
15%lignin + 2 layers Kevlar
67.5586425
2385.5165792
6
15%lignin + 2 layers S-glass
53.6511346
2181.8457762
7
15%lignin + 1 layer Kevlar + 1
61.5195528
2264.5146357
59.1845951
2289.1626654
layer S-Glass
8
15%lignin + 1 layer S-Glass + 1
layer Kevlar
The above table shows the readings of all eight composite materials obtained
from conducting the tensile test on the UTM. For each sample, we have taken 4 test
specimens such that the average values can be found. We have conducted the tests very
carefully and taken all the safety measures and precautions to get accurate and precise
values. As said, we got the sound values which are well comparable and reasonable.
This data gives us useful information in the material science and helps to the further
improvements in composite materials.
6.4 FLEXURAL TEST
Fig. 6.3: Flexural test
40
Flexural testing measures the force required to bend a beam of plastic material
and determines the resistance to flexing or stiffness of a material. The flexural test
measures the force required to bend a beam under three-point loading conditions. The
data is often used to select materials for parts that will support loads without flexing.
Flexural modulus is used as an indication of a material's stiffness when flexed. The
flexural test can be done on tensometer. The dimension of the specimen is 100 mm ×
9.3 mm × 5 mm and a loading span of 40 mm was employed.
FORMULA
F=3pl/bd?
Where,
F =Flexural strength (MPa)
P=failure load (N)
L =effective span of beam (mm)
b = breadth of beam (mm)
d= thickness (mm)
CALCULATION
Table 6.2: Flexural properties of composite materials
S.no
Sample
Flexural stress
Shear modulus
(MPa)
(MPa)
1
Pure epoxy
40.1545655
736.1518153
2
15%lignin
92.6452985
3915.8416528
41
3
15%lignin + 1 layer Kevlar
136.1554317
5864.58415397
4
15%lignin + 1 layer S-Glass
112.4851813
4685.1682546
5
15%lignin + 2 layers Kevlar
158.1486167
7895.5485943
6
15%lignin + 2 layers S-glass
142.6845153
6648.8751759
7
15%lignin + 1 layer Kevlar + 1 layer
149.1542486
7195.1845162
152.5485783
7108.5844981
S-Glass
8
15%lignin + 1 layer S-Glass + 1
layer Kevlar
We have conducted the flexural tests on all the test specimens of eight
composite material. this test is conducted in the same way as that of tensile test, but in
this case the specimen is held like simply supported beam and load is applied at the
center of the specimen. In this test also, we got very reasonable readings and can
contribute to the additional information required to the composite materials and
material science.
42
CHAPTER – 7: RESULTS AND DISCUSSION
7.1 TENSILE TEST
Tensile Strength (MPa)
Tensile Strength (MPa)
80
67.56
70
36.56
40
20
59.18
44.53
50
30
61.52
53.65
60
28.55
19.49
10
0
Pure epoxy 15%lignin 15%lignin + 15%lignin + 15%lignin + 15%lignin + 15%lignin + 15%lignin +
1 layer
1 layer S2 layers 2 layers S1 layer
1 layer SKevlar
Glass
Kevlar
glass
Kevlar + 1 Glass + 1
layer S- layer Kevlar
Glass
Various composites
Fig. 7.1: Plot of tensile strength of composite materials
The above figure shows us the tensile test data of all eight composite materials.
All those values are obtained and these are very reasonable when compared to the past
literatures and research studies, but these values are somewhat lower than we expected.
In the above bar charts, the trend goes of the values gone same as expected. The pure
43
epoxy has shown a tensile strength of 19.49 MPa. Since the kevlar has high mechanical
properties compared to other materials, our results have shown the same thing and we
got high tensile strength in the samples consist of kevlar mat.
Tensile strengths are conducted according to the ASTM D3039. The samples
shown different types of values, in which the highest value obtained to the 2-layer
kevlar composite of 67.5586425 MPa. Remaining composites have shown decrease in
mechanical properties by decrease in number of layers in the composite. Here, Kevlar
and s-glass combination has given second highest values of 61.5195528 MPa and
59.1845951 MPa.
Using only kevlar mat in lignin-epoxy matrix gives higher strength than S-glass
mat in the same composite. This is because, the pure kevlar mat has higher strength
than S-glass mat. Hence, the results have also shown the same properties.
Young's Modulus (MPa)
Young's Modulus (MPa)
3000
2,385.52
2500
1,983.57
2000
1,548.65
1500
1000
2,181.85 2,264.51 2,289.16
1,116.20
821.58
500
0
Pure
epoxy
15%lignin 15%lignin 15%lignin 15%lignin 15%lignin 15%lignin 15%lignin
+ 1 layer + 1 layer S- + 2 layers + 2 layers + 1 layer + 1 layer SKevlar
Glass
Kevlar
S-glass Kevlar + 1 Glass + 1
layer Slayer
Glass
Kevlar
Various composites
Fig. 7.2: Plot of Young’s Modulus of composite materials
The above figure shows the young’s modulus of the all the composite
materials. The above bar chart also shown the same trend as that of tensile strength
44
and we have obtained 2-layer kevlar with highest young’s modulus giving 2385.52
MPa. Again, the pure epoxy shown the least value of 821.58 MPa which is the average
value when compared to the previous literatures. The second highest values are
obtained for materials made of S-Glass giving 1548.65 MPa (1 layer S-Glass) and
2181.85 MPa (2-layer S-Glass). Thus, we got decent mechanical properties in the
tensile test.
7.2 FLEXURAL TEST
Flexural Strength
Flexural Strength (MPa)
180
160
140
120
100
80
60
40
20
0
158.15
142.68
136.16
149.15
152.55
112.49
92.65
40.15
Pure epoxy 15%lignin 15%lignin + 15%lignin + 15%lignin + 15%lignin + 15%lignin + 15%lignin +
1 layer
1 layer S- 2 layers 2 layers S- 1 layer
1 layer SKevlar
Glass
Kevlar
glass
Kevlar + 1 Glass + 1
layer S- layer Kevlar
Glass
Various composites
Fig. 7.3: Plot of Flexural Strength of composite materials
The above figure shows the data of flexural strength of all eight composite
materials. Pure Epoxy: This sample exhibited the lowest flexural strength at 40.15
MPa and a moderate flexural modulus of 736.15 MPa. Pure epoxy is a common
baseline material in composite testing, known for its decent mechanical properties
but often improved upon with additives.
45
15% Lignin: Adding 15% lignin significantly increased the flexural strength to
92.65 MPa, indicating lignin’s reinforcement effect. The flexural modulus also rose
substantially to 3915.84 MPa, showing that lignin contributes to stiffness in the
composite.
Flexural Modulus (MPa)
Flexural Modulus ( MPa )
9000
8000
7000
6000
5000
4000
3000
2000
1000
0
7,895.55
6,648.88
7,195.18
7,108.58
5,864.58
4,685.17
3,915.84
736.15
Pure epoxy 15%lignin 15%lignin + 15%lignin + 15%lignin + 15%lignin + 15%lignin + 15%lignin +
1 layer
1 layer S- 2 layers 2 layers S- 1 layer
1 layer SKevlar
Glass
Kevlar
glass
Kevlar + 1 Glass + 1
layer S- layer Kevlar
Glass
Various composites
Fig. 7.4: Plot of Flexural Modulus of composite materials
15% Lignin + 1 Layer Kevlar: Incorporating Kevlar on top of the lignin further
enhanced both flexural strength (136.16 MPa) and flexural modulus (5864.58 MPa).
Kevlar is renowned for its high tensile strength and impact resistance, which is
reflected in these results.
15% Lignin + 1 Layer S-Glass: Similarly, adding a layer of S-Glass to the
lignin composite increased strength (112.49 MPa) and stiffness (4685.17 MPa). SGlass is known for its high strength-to-weight ratio, contributing to the composite's
mechanical properties.
46
15% Lignin + 2 Layers Kevlar and 15% Lignin + 2 Layers S-Glass: Doubling
the layers of reinforcement (Kevlar or S-Glass) further improved the flexural strength
and flexural modulus, with values peaking at 158.15 MPa and 7895.55 MPa for Kevlar,
and 142.68 MPa and 6648.88 MPa for S-Glass, respectively.
Combined Reinforcements: The samples with combined reinforcements (1
layer Kevlar + 1 layer S-Glass or vice versa) showed comparable flexural strength and
modulus values, highlighting the synergistic effects of different reinforcing materials.
Overall, the trend shows that adding reinforcing materials like lignin, Kevlar
and S-Glass enhances the composite's mechanical properties, with variations in the
number and type of layers affecting the degree of improvement.
47
CHAPTER-8: CONCLUSION
In conclusion, the flexural test results for the different composite samples
reveal notable trends and insights into their mechanical properties:
1. Pure Epoxy: This sample demonstrated the lowest flexural strength and
modulus
values,
indicating
its
baseline
performance
without
any
reinforcements.
2. 15% Lignin: The addition of lignin significantly increased both flexural
strength and modulus compared to pure epoxy, showcasing lignin's potential
as a reinforcing agent.
3. Kevlar and S-Glass Reinforcements: Introducing Kevlar and S-Glass layers on
top of the lignin composite further enhanced the mechanical properties. Kevlar
contributed to high tensile strength, while S-Glass added stiffness.
4. Layering Effects: Doubling the layers of Kevlar or S-Glass led to notable
improvements in flexural strength and modulus, highlighting the impact of
layering on composite performance.
5. Combined Reinforcements: Samples with combined Kevlar and S-Glass
48
reinforcements showed comparable strength and modulus values, indicating
synergistic effects between different reinforcing materials.
Overall, the data suggests that the mechanical properties of composite
materials can be significantly enhanced by incorporating reinforcements such as
lignin, Kevlar, and S-Glass, with variations in layering and combinations leading to
different levels of improvement. These findings are crucial for designing composites
with tailored mechanical properties for specific applications in various industries,
including aerospace, automotive, and construction.
49
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