Metallurgy is a domain of materials science and engineering that studies the physical and chemical behavior of metallic elements, their inter-metallic compounds, and their mixtures, which are called alloys.
Metallurgy can also be described as the technology of metals, the way in which science is applied to the production of metals and the engineering of metal .
Metallurgy is a domain of materials science and engineering that studies the physical and chemical behavior of metallic elements, their inter-metallic compounds, and their mixtures, which are called alloys.
Metallurgy can also be described as the technology of metals, the way in which science is applied to the production of metals and the engineering of metal .
Image result for metal matrix composites
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A metal matrix composite (MMC) is composite material with at least two constituent parts, one being a metal necessarily, the other material may be a different metal or another material, such as a ceramic or organic compound. When at least three materials are present, it is called a hybrid composite.
Adhesion is one of the significant parameter which leads to mechanical wear. This presemntation gives brief information about adhesion, molecular interaction between two mating surfaces and factors affecting adhesion. Study of interfacial forces between mating surfaces helps in selection of surface materials to prevent adhesion. Failure of lubricant’s basic function relates to failure of separation of two surfaces which results in adhesion between sliding surfaces. Adhesion is not observed between two surfaces casually placed together due to existing oxide film and contaminants. Surface energy, reduced roughness, high hardness can depress adhesion.
Metal matrix composites (MMCs) possess significantly improved properties including highspecific strength; specific modulus, damping capacity and good wear resistance compared to unreinforced alloys. There has been an increasing interest in composites containing low density and low cost reinforcements. Among various discontinuous dispersoids used, fly ash is one of the most inexpensive and low density reinforcement available in large quantities as solid waste by-product during combustion of coal in thermal power plants. Hence, composites with fly ash as reinforcement are likely to overcome the cost barrier for wide spread applications in automotive and small engine applications.
Image result for metal matrix composites
www.slideshare.net
A metal matrix composite (MMC) is composite material with at least two constituent parts, one being a metal necessarily, the other material may be a different metal or another material, such as a ceramic or organic compound. When at least three materials are present, it is called a hybrid composite.
Adhesion is one of the significant parameter which leads to mechanical wear. This presemntation gives brief information about adhesion, molecular interaction between two mating surfaces and factors affecting adhesion. Study of interfacial forces between mating surfaces helps in selection of surface materials to prevent adhesion. Failure of lubricant’s basic function relates to failure of separation of two surfaces which results in adhesion between sliding surfaces. Adhesion is not observed between two surfaces casually placed together due to existing oxide film and contaminants. Surface energy, reduced roughness, high hardness can depress adhesion.
Metal matrix composites (MMCs) possess significantly improved properties including highspecific strength; specific modulus, damping capacity and good wear resistance compared to unreinforced alloys. There has been an increasing interest in composites containing low density and low cost reinforcements. Among various discontinuous dispersoids used, fly ash is one of the most inexpensive and low density reinforcement available in large quantities as solid waste by-product during combustion of coal in thermal power plants. Hence, composites with fly ash as reinforcement are likely to overcome the cost barrier for wide spread applications in automotive and small engine applications.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
This book was originally prepared in 2012 and updated recently in 2015. The
objective of the present book is to present a complete and up ± to ± date coverage of
composite laminates properties and literature reviews through the usage of a wide
spectrum of old and recent bibliography.
The material presented in this book is intended to serve as an introduction and
literature review of composite laminated plates. In chapter one, the introduction was
presented from the points of view of fundamental definitions of fibrous composite
laminates and micromechanical properties of fibers and matrix materials. At the end
of the chapter the objectives of the present work were cited.
Chapter two contains a comprehensive literature review which includes
continuous developments in the theories of laminated plates. Also, a survey of
numerical techniques which could be used in the analysis of laminated plates.
Chapter three contains the conclusion of the present book. In this chapter the
important observations and findings were explained clearly.
The book is suitable as a review on theories of plates, numerical and / or
analytical techniques subjected to bending, buckling and vibration of laminated
plates.
Indian Rail Steel- Pearlitic and Bainitic Rails and comparisionMukuldev Khunte
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Synthetic fiber production is a fascinating and complex field that blends chemistry, engineering, and environmental science. By understanding these aspects, students can gain a comprehensive view of synthetic fiber production, its impact on society and the environment, and the potential for future innovations. Synthetic fibers play a crucial role in modern society, impacting various aspects of daily life, industry, and the environment. ynthetic fibers are integral to modern life, offering a range of benefits from cost-effectiveness and versatility to innovative applications and performance characteristics. While they pose environmental challenges, ongoing research and development aim to create more sustainable and eco-friendly alternatives. Understanding the importance of synthetic fibers helps in appreciating their role in the economy, industry, and daily life, while also emphasizing the need for sustainable practices and innovation.
The Roman Empire A Historical Colossus.pdfkaushalkr1407
The Roman Empire, a vast and enduring power, stands as one of history's most remarkable civilizations, leaving an indelible imprint on the world. It emerged from the Roman Republic, transitioning into an imperial powerhouse under the leadership of Augustus Caesar in 27 BCE. This transformation marked the beginning of an era defined by unprecedented territorial expansion, architectural marvels, and profound cultural influence.
The empire's roots lie in the city of Rome, founded, according to legend, by Romulus in 753 BCE. Over centuries, Rome evolved from a small settlement to a formidable republic, characterized by a complex political system with elected officials and checks on power. However, internal strife, class conflicts, and military ambitions paved the way for the end of the Republic. Julius Caesar’s dictatorship and subsequent assassination in 44 BCE created a power vacuum, leading to a civil war. Octavian, later Augustus, emerged victorious, heralding the Roman Empire’s birth.
Under Augustus, the empire experienced the Pax Romana, a 200-year period of relative peace and stability. Augustus reformed the military, established efficient administrative systems, and initiated grand construction projects. The empire's borders expanded, encompassing territories from Britain to Egypt and from Spain to the Euphrates. Roman legions, renowned for their discipline and engineering prowess, secured and maintained these vast territories, building roads, fortifications, and cities that facilitated control and integration.
The Roman Empire’s society was hierarchical, with a rigid class system. At the top were the patricians, wealthy elites who held significant political power. Below them were the plebeians, free citizens with limited political influence, and the vast numbers of slaves who formed the backbone of the economy. The family unit was central, governed by the paterfamilias, the male head who held absolute authority.
Culturally, the Romans were eclectic, absorbing and adapting elements from the civilizations they encountered, particularly the Greeks. Roman art, literature, and philosophy reflected this synthesis, creating a rich cultural tapestry. Latin, the Roman language, became the lingua franca of the Western world, influencing numerous modern languages.
Roman architecture and engineering achievements were monumental. They perfected the arch, vault, and dome, constructing enduring structures like the Colosseum, Pantheon, and aqueducts. These engineering marvels not only showcased Roman ingenuity but also served practical purposes, from public entertainment to water supply.
Instructions for Submissions thorugh G- Classroom.pptxJheel Barad
This presentation provides a briefing on how to upload submissions and documents in Google Classroom. It was prepared as part of an orientation for new Sainik School in-service teacher trainees. As a training officer, my goal is to ensure that you are comfortable and proficient with this essential tool for managing assignments and fostering student engagement.
June 3, 2024 Anti-Semitism Letter Sent to MIT President Kornbluth and MIT Cor...Levi Shapiro
Letter from the Congress of the United States regarding Anti-Semitism sent June 3rd to MIT President Sally Kornbluth, MIT Corp Chair, Mark Gorenberg
Dear Dr. Kornbluth and Mr. Gorenberg,
The US House of Representatives is deeply concerned by ongoing and pervasive acts of antisemitic
harassment and intimidation at the Massachusetts Institute of Technology (MIT). Failing to act decisively to ensure a safe learning environment for all students would be a grave dereliction of your responsibilities as President of MIT and Chair of the MIT Corporation.
This Congress will not stand idly by and allow an environment hostile to Jewish students to persist. The House believes that your institution is in violation of Title VI of the Civil Rights Act, and the inability or
unwillingness to rectify this violation through action requires accountability.
Postsecondary education is a unique opportunity for students to learn and have their ideas and beliefs challenged. However, universities receiving hundreds of millions of federal funds annually have denied
students that opportunity and have been hijacked to become venues for the promotion of terrorism, antisemitic harassment and intimidation, unlawful encampments, and in some cases, assaults and riots.
The House of Representatives will not countenance the use of federal funds to indoctrinate students into hateful, antisemitic, anti-American supporters of terrorism. Investigations into campus antisemitism by the Committee on Education and the Workforce and the Committee on Ways and Means have been expanded into a Congress-wide probe across all relevant jurisdictions to address this national crisis. The undersigned Committees will conduct oversight into the use of federal funds at MIT and its learning environment under authorities granted to each Committee.
• The Committee on Education and the Workforce has been investigating your institution since December 7, 2023. The Committee has broad jurisdiction over postsecondary education, including its compliance with Title VI of the Civil Rights Act, campus safety concerns over disruptions to the learning environment, and the awarding of federal student aid under the Higher Education Act.
• The Committee on Oversight and Accountability is investigating the sources of funding and other support flowing to groups espousing pro-Hamas propaganda and engaged in antisemitic harassment and intimidation of students. The Committee on Oversight and Accountability is the principal oversight committee of the US House of Representatives and has broad authority to investigate “any matter” at “any time” under House Rule X.
• The Committee on Ways and Means has been investigating several universities since November 15, 2023, when the Committee held a hearing entitled From Ivory Towers to Dark Corners: Investigating the Nexus Between Antisemitism, Tax-Exempt Universities, and Terror Financing. The Committee followed the hearing with letters to those institutions on January 10, 202
Biological screening of herbal drugs: Introduction and Need for
Phyto-Pharmacological Screening, New Strategies for evaluating
Natural Products, In vitro evaluation techniques for Antioxidants, Antimicrobial and Anticancer drugs. In vivo evaluation techniques
for Anti-inflammatory, Antiulcer, Anticancer, Wound healing, Antidiabetic, Hepatoprotective, Cardio protective, Diuretics and
Antifertility, Toxicity studies as per OECD guidelines
Model Attribute Check Company Auto PropertyCeline George
In Odoo, the multi-company feature allows you to manage multiple companies within a single Odoo database instance. Each company can have its own configurations while still sharing common resources such as products, customers, and suppliers.
Operation “Blue Star” is the only event in the history of Independent India where the state went into war with its own people. Even after about 40 years it is not clear if it was culmination of states anger over people of the region, a political game of power or start of dictatorial chapter in the democratic setup.
The people of Punjab felt alienated from main stream due to denial of their just demands during a long democratic struggle since independence. As it happen all over the word, it led to militant struggle with great loss of lives of military, police and civilian personnel. Killing of Indira Gandhi and massacre of innocent Sikhs in Delhi and other India cities was also associated with this movement.
1. Mukuldev Khunte-MME 6th Semester
01UG15050023
Name-Mukuldev Khunte
Dept. of Metallurgical & Materials Engineering (6th
Semester)
Roll No-01UG15050023
Subject- Engineering Polymers & Composite Assignment
Q. Define composite material. Classify this material as per their parametric level. What are the fundamental properties of
a composite material.
Answer –Definition-A material which is composed of two or more materials at a microscopic scale and have chemically distinct
phases. And Heterogeneous at a microscopic scale but statically homogeneous at macroscopic scale. Constituent materials have
significantly different properties.
Composite materials are commonly classified at following two distinct levels:
• The first level of classification is usually made with respect to the matrix constituent. The major composite classes include
Organic Matrix Composites (OMCs), Metal Matrix Composites (MMCs) and Ceramic Matrix Composites (CMCs). The term
organic matrix composite is generally assumed to include two classes of composites, namely Polymer Matrix Composites (PMCs)
and carbon matrix composites commonly referred to as carbon-carbon composites.
• The second level of classification refers to the reinforcement form - fibre reinforced composites, laminar composites and
particulate composites. Fibre Reinforced composites (FRP) can be further divided into those containing discontinuous or
continuous fibres.
• Fibre Reinforced Composites are composed of fibres embedded in matrix material. Such a composite is a discontinuous fibre
or short fibre composite if its properties vary with fibre length. On the other hand, when the length of the fibre is such that any
further increase in length does not further increase, the elastic modulus of the composite, the composite is continuous fibre
reinforced
• Laminar Composites are composed of layers of materials held together by matrix. Sandwich structures fall under this category.
• Particulate Composites are composed of particles distributed or embedded in a matrix body. The particles may be flakes or in
powder form. Concrete and wood particle boards are examples of this category.
fundamental properties of a composite material
1. Specific Strength-This is simply the rigidity or hardness of a material regarding its weight. For example, several composites
such as fiberglass share comparable impact resistance (bangability) with steel and titanium at a fraction of the weight employed.
2. Expense-Many composites can be manufactured with less cost than their traditional metal counterparts.
3. Application-Because composites are composed of 2 or more "phases", they can be formulated to meet the needs of a specific
application with considerable ease.
4. Processability-As most of you know, metal processing requires high amounts of thermal energy (heat). Plastics and plastic
based composites require less heat to mould or process the products. There is a constant desire to produce composites which can
be processed at low temperatures but when cured or set-up (paint drying or a mould cooling), they are very impact resistant and
very heat resistant or fire retardant.
Q-Advantage and Limitation of Composite Material.
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01UG15050023
Answer- Advantages of Composite Materials
1. Composites reduced the overall structural member weight by 20-50%.
2. Composites are very corrosion and fatigue resistance.
3. Composites have tolerable mechanical properties.
4. Composites have lower assembly costs because it requires very few fasteners, bolts etc.
Disadvantages of Composite Materials
1. Composites have high recurring costs.
2. Composites are higher non-recurring costs.
3. Composites have higher material costs.
4. Composites have very expensive repairs and maintenance.
5. Composites needed isolation to prevent adjacent aluminium part galvanic corrosion
Q-State the law of mixture and stablish this. What is the significance of this law.
Answer- Composite stiffness can be predicted using a micro-mechanics approach termed the rule of mixtures. Assumptions
1. Fibres are uniformly distributed throughout the matrix.
2. Perfect bonding between fibres and matrix.
3. Matrix is free of voids.
4. Applied loads are either parallel or normal to the fibre direction.
5. Lamina is initially in a stress-free state (no residual stresses).
6. Fibre and matrix behave as linearly elastic materials
Rule of mixture is the simple’s relation between the properties of a composite and those of its constituents. The simplest is the
linear mixture rule, e.g.
Ec = v1E1 +v2E2
for the modulus. Ec is the composite modulus v1 is the volume fraction of component 1 with modulus E1 (say the matrix) and v2,
E2 are the corresponding quantities for component 2 (say, the reinforcement). This is true physically is you have parallel phases
and the force is parallel with the phases. The other extreme is the reciprocal mixture rule:
1/Ec = v1/E1 + v2/E2
in this case the elements are in series. The real situation is somewhere in-between. Formally the two extremes can be combined
Q-Determine the young’s Modulus in Transvers and Longitudinal direction in an isostrain condition. Discuss Critical
Length of fiber.
Answer- Elastic Behaviour—Longitudinal Loading Let us now consider the elastic behaviour of a continuous and oriented
fibrous composite that is loaded in the direction of fiber alignment. First, it is assumed that the fiber–matrix interfacial bond is
very good, such that deformation of both matrix and fibers is the same (an isostrain situation). Under these conditions, the total
load sustained by the composite Fc is equal to the sum of the loads carried by the matrix phase Fm and the fiber phase Ff, or
Fc = Fm + Ff (16.4)
From the definition of stress, Equation 6.1, F sA; and thus expressions for Fc, Fm, and Ff in terms of their respective stresses (sc,
σm, and σf) and cross-sectional areas (Ac, Am, and Af) are possible. Substitution of these into Equation 16.4 yields
σσcAc = σmAm + σfAf (16.5)
and then, dividing through by the total cross-sectional area of the composite, Ac, we have
where AmAc and AfAc are the area fractions of the matrix and fiber phases, respectively. If the composite, matrix, and fiber phase
lengths are all equal, AmAc is equivalent to the volume fraction of the matrix, Vm, and likewise for the fibers,
Vf AfAc. Equation 16.6 now becomes
3. Mukuldev Khunte-MME 6th Semester
01UG15050023
σc = σmVm + σfVf
The previous assumption of an isostrain state means that
€c =€m+ €f
(16.7)
(16.8)
16.9 yields an expression for the modulus of elasticity of a continuous and aligned fibrous composite in the direction of alignment
(or longitudinal direction), Ecl, as
since the composite consists of only matrix and fiber phases; that is, Vm Vf 1.
Thus, Ecl is equal to the volume-fraction weighted average of the moduli of elasticity of the fiber and matrix phases. Other
properties, including density, also have this dependence on volume fractions. Equation 16.10a is the fiber analogue of Equation
16.1, the upper bound for particle-reinforced composites.
It can also be shown, for longitudinal loading, that the ratio of the load carried by the fibers to that carried by the matrix is
Elastic Behavior—Transverse Loading
A continuous and oriented fiber composite may be loaded in the transverse direction; that is, the load is applied at a 90 angle to
the direction of fiber alignment as shown in Figure 16.8a. For this situation the stress s to which the composite as well as both
phases are exposed is the same, or
σc = σm= σf= σ (16.12)
This is termed an isostress state. Also, the strain or deformation of the entire composite c is
€c= €mVm + €fVf (16.13)
but, since sE,
where Ect is the modulus of elasticity in the transverse direction. Now, dividing through by s yields
(16.15)
which reduces to
(16.16)
Equation 16.16 is analogous to the lower-bound expression for particulate composites, Equation 16.2.
Ecl= EmVm + EfVf
Ecl = Em(1 – Vf )+ EfVf
Ff
Fm
EfVf
=
EmVm
1/Ect =Vm/Em+vfEf
4. Mukuldev Khunte-MME 6th Semester
01UG15050023
Figure 16.6 The
deformation pattern in
the matrix surrounding
a fiber that is subjected
to an applied tensile
load.
Critical Length of fiber- The mechanical characteristics of a fiber-reinforced composite depend not only on the properties
of the fiber, but also on the degree to which an applied load is transmitted to the fibers by the matrix phase. Important to the
extent of this load transmittance is the magnitude of the interfacial bond between the fiber and matrix phases. Under an
applied stress, this fiber–matrix bond ceases at the fiber ends, yielding a matrix deformation pattern as shown schematically
in Figure 16.6;in other words, there is no load transmittance from the matrix at each fiber extremity.
Some critical fiber length is necessary for effective strengthening and stiffening of the composite material. This critical
length lc is dependent on the fiber diameter d and its ultimate (or tensile) strength s*f , and on the fiber–matrix bond strength
(or the shear yield strength of the matrix, whichever is smaller) tc according to
ss
When a stress equal to s*f is applied to a fiber having just this critical length, the stress–position profile shown in Figure
16.7a results; that is, the maximum fiber load is achieved only at the axial center of the fiber.As fiber length l increases, the
fiber reinforcement becomes more effective; this is demonstrated in Figure 16.7b, a stress–axial position profile for l 7 lc
when the applied stress is equal to the fiber strength. Figure 16.7c shows the stress–position profile for l 6 lc.
Fibers for which l W lc (normally l 7 15lc) are termed continuous; discontinuous or short fibers have lengths shorter than this.For
discontinuous fibers of lengths
s*f
dlc =
2tc
5. Mukuldev Khunte-MME 6th Semester
01UG15050023
Figure 16.7
Stress–position profiles when fiber length l (a) is equal to the critical length lc, (b) is greater than the critical length, and (c) is less than the
critical length for a fiber-reinforced composite that is subjected to a tensile stress equal to the fiber tensile strength s*f .
0 l 0
significantly less than lc, the matrix deforms around the fiber such that there is virtually no stress transference and
little reinforcement by the fiber.These are essentially the particulate composites as described above. To affect a
significant improvement in strength of the composite, the fibers must be continuous.
Q- Discuss stress Strain diagram of a composite material.
Answer- Tensile Stress–Strain Behavior—Longitudinal Loading Mechanical responses of this type of composite
depend on several factors to include the stress–strain behaviors of fiber and matrix phases, the phase volume fractions,
and, in addition, the direction in which the stress or load is applied. Furthermore, the properties of a composite having
its fibers aligned are highly anisotropic, that is, dependent on the direction in which they are measured.
us first consider the stress–strain behavior for the situation wherein the stress is
* *
c ccc
* *
*
*
*
cc
c
6. Mukuldev Khunte-MME 6th Semester
01UG15050023
Figure (a) Schematic stress–strain curves for brittle fiber and ductile matrix materials. Fracture stresses and strains for both materials are
noted. (b) Schematic stress–strain curve for an aligned fiber-reinforced composite that is exposed to a uniaxial stress applied in the direction of
alignment; curves for the fiber and matrix materials shown in part (a) are also superimposed.
in this figure are fracture strengths in tension for fiber and matrix, s*f and sm*, respectively, and their corresponding
fracture strains, *f and *;m furthermore, it is assumed that m* 7 *f , which is normally the case.A fiber-reinforced
composite consisting of these fiber and matrix materials will exhibit the uniaxial stress–strain response illustrated in
Figure 16.9b; the fiber and matrix behaviors from Figure 16.9a are included to provide perspective. In the initial Stage
I region, both fibers and matrix deform elastically; normally this portion of the curve is linear. Typically, for a
composite of this type, the matrix yields and deforms plastically (b) while the fibers continue to stretch elastically,
inasmuch as the tensile strength of the fibers is significantly higher than the yield strength of the matrix.This process
constitutes Stage II as noted in the figure; this stage is ordinarily very nearly linear, but of diminished slope relative to
Stage I. Furthermore, in passing from Stage I to Stage II, the proportion of the applied load that is borne by the fibers
increases.
The onset of composite failure begins as the fibers start to fracture, which corresponds to a strain of approximately *f
as noted in Figure b. Composite failure is not catastrophic for a couple of reasons. First, not all fibers fracture at the
same time,since there will always be considerable variations in the fracture strength of brittle fiber materials . In
addition, even after fiber failure, the matrix is still intact inasmuch as *f 6 m* a. Thus, these fractured fibers, which are
shorter than the original ones, are still embedded within the intact matrix, and consequently are capable of sustaining a
diminished load as the matrix continues to plastically deform.
Q-What are fibers and Whiskers ?
Answer- A fiber has: –
•High length‐to‐diameter diameter ratio. – Its diameter approximates its crystal size.
• Modern composites exploit the fact that small scale samples of most of the materials are much stronger than
bulk materials. Thus, thin fibers of glass are 200‐500 times stronger than bulk glass.
• Several types of fibers are available commercially. Some of the more commonly used fibers are made from
materials such as carbon, glass, Kevlar, steel, and other metals.
• Glass is the most popular fiber used in composites since it is relatively inexpensive. It comes in two principal
varieties; E‐glass, and S‐glass. The latter is stronger than the former.
applied along the direction of alignment, the longitudinal direction, which is
indicated in Figure a To begin, assume the stress versus strain behaviors for fiber
and matrix phases that are represented schematically in Figure 16.9a; in this
treatment we consider the fiber to be totally brittle and the matrix phase to be
reasonably ductile.Also indicated
I
II
7. Mukuldev Khunte-MME 6th Semester
01UG15050023
• Fibers are significantly stronger than bulk materials because: – They have a far more “perfect” structure, i.e.
their crystals are aligned along the fiber axis. – There are fewer internal defects, especially in direction normal to fiber
orientation, and hence there are lesser number of dislocations.
• At larger scales, the degree of structural perfection within a material sample is far less that what is present at
small (micro and Nano) scales. For this reason fibers of several engineering materials are far stronger than their
equivalent bulk material samples.
Whiskers
• Whiskers are similar in diameter to fibers, but in general, they are short and have low length‐to‐ diameter ratios,
barely exceeding a few hundreds.
• Thus, the difference in mechanical properties of a whiskers vis‐à‐vis bulk material is even more pronounced.
This is because the degree of perfection in whiskers whiskers is even higher vis‐à‐vis that in fibers.
– Whiskers are produced by crystallizing materials on a very small scale.
– Internal alignment within each whisker is extremely high.
• Modern composites composites derive much of their desired desired properties properties by using fibers and
whiskers as one of the constituent materials.
• Fibers made from carbon, E‐glass, S‐glass, and Kevlar are commonly used in modern composite structures
Q-Classify Fibers as per individual parameters.
Answer-
Textile fibers have been used to make cloth for several thousand years. First manufactured fiber was
produced commercially on 1885 and was produced from fibers of plants and animals. Wool, flax, cotton
and silk were commonly used textile fibers. Textile fibers are characterized by the flexibility, fineness
8. Mukuldev Khunte-MME 6th Semester
01UG15050023
and large length in relation to the maximum transverse dimension. On the basis of origin fibers can be
classified broadly into three types:
I. Natural fibers: Fibers which grow or develop and come from natural resources like plant and
animals.
II. Manufactured (or man-made) fibers: Fibers produced by industrial processes, whether from
natural polymers transformed upon the action of chemical reagents or through polymers obtained
by chemical synthesis (synthetic fibers).
III. Mineral Fibers: Asbestos is the only naturally occurring mineral fiber that was used extensively
for making industrial products but is now restricted due to its suspected carcinogenic effect.
Q- What are matrix? classify as per dimensional cases.
Answer- Fibers or particles embedded in matrix of another material are the best example of modern-day composite
materials, which are mostly structural In matrix-based structural composites, the matrix serves two paramount
purposes viz., binding the reinforcement phases in place and deforming to distribute the stresses among the
constituent reinforcement materials under an applied force.
Q-What are the significance of fiber and matrix ?
Answer-A fiber is characterized geometrically not only by its very high length-to-diameter ratio but by its near-
crystal-sized diameter. Strength sand stiffnesses of a few selected fiber materials are arranged in increasing average
S/p and E/p. The common structural materials, aluminum, titanium, and steel, are listed for the purpose of comparison.
However, a direct comparison between fibers and structural metals is not valid because fibers must have a
surrounding matrix to perform in a structural member, whereas structural metals are Yeady-to-use'.
A whisker has essentially the same near-crystal-sized diameter as a fiber, but generally is very short and stubby,
although the length-to- diameter ratio can be in the hundreds. Thus, a whisker is an even more obvious example of the
crystal-bulk-material-property-difference paradox. That is, a whisker is even more perfect than a fiber and therefore
exhibits even higher properties. Whiskers are obtained by crystallization on a very small scale resulting in a nearly
perfect alignment of crystals. Materials such as iron have crystalline structures with a theoretical strength of 2,900,000
9. Mukuldev Khunte-MME 6th Semester
01UG15050023
psi (20 GPa), yet commercially available structural steels, which are mainly iron, have strengths ranging from 75,000
psi to about 100,000 psi (570 to 690 MPa).
Q-Discontinous and randomly oriented fiber composite.
Answer-Fiber Geometry
Some common geometries for fiber-reinforced composites:
• Aligned
The properties of aligned fiber-reinforced composite materials are highly anisotropic. The longitudinal tensile
strength will be high whereas the transverse tensile strength can be much less than even the matrix tensile
strength. It will depend on the properties of the fibers and the matrix, the interfacial bond between them, and
the presence of voids.
There are 2 different geometries for aligned fibers:
1. Continuous & Aligned
The fibers are longer than a critical length which is the minimum length
necessary such that the entire load is transmitted from the matrix to the
fibers. If they are shorter than this critical length, only some of the load is
transmitted. Fiber lengths greater that 15 times the critical length are
considered optimal. Aligned and continuous fibers give the most effective
strengthening for fiber composites.
2. Discontinuous & Aligned
The fibers are shorter than the critical length. Hence discontinuous fibers are
less effective in strengthening the material, however, their composite
modulus and tensile strengths can approach 50-90% of their continuous and
aligned counterparts. And they are cheaper, faster and easier to fabricate
into complicated shapes.
• Random
This is also called discrete, (or chopped) fibers. The strength will not be as high as with aligned fibers,
however, the advantage is that the material will be istropic and cheaper
• Woven
The fibers are woven into a fabric which is layered with the matrix material to make a laminated structure.
Q-How does a fiber orientation related with stress distribution?
Answer-When considering the effect of fibre orientation on the strength of a composite material made up of a
continuous aligned fibres embedded in a matrix, it should be recognised that there are 3 possible modes of failure...
1. Tensile fracture parallel to the fibres (whether the fibres fail or the matrix fails will depend on the particular
combination of fibre and matrix materials as well as the volume fraction of fibres),
2. Shear failure of the matrix as a result of a large shear stress acting parallel to the fibres ,
3. Tensile failure of the matrix or fibre/matrix interface when stressed perpendicular to the fibres.
10. Mukuldev Khunte-MME 6th Semester
01UG15050023
We have already determined suitable expressions for the strength of a composite when tested parallel to the fibres,
We'll call this strength X. We also know the tensile strength of the matrix material which we'll call Y. The shear
strength of the matrix can be determined using the Tresca criteria and is simply Y/2. In order to examine the effect of
orientation on strength we need to make use of Mohr's Circle to establish the state of stress aligned parallel and
perpendicular to the fibres and then to equate these stresses with the appropriate failure stress of the composite in each
those directions.
For failure to occur, the applied stress must be increase until either
These equations are plotted out below and since failure is a "weakest link" phenomenon, fracture will occure at
whichever criterion is reached first and so the mechanism of failure changes from tensile failure of the fibres to shear
of teh matrix to tensile failure of the matrix as the fibre angle is increased from 0 to 90°.
11. Mukuldev Khunte-MME 6th Semester
01UG15050023
Q-What is Transformational Toughening in case of ceramic matrix composite (CMC). Why toughening is
required for CMC and what are the characteristics of it?
Answer-Ceramic Matrix Composites
Significant research effort has been directed toward the development of tough ceramics, since such materials have the
potential to open up a large range of specialised engineering applications. Toughness can be significantly improved
with the production of ceramics with a very small flaw size (< 50µm) in accordance with the Griffith theorem.
However, producing such ceramics, and non-destructive testing for flaw size, is very difficult. An alternative solution
is to engineer the microstructure of ceramics in such a way as to inhibit crack propagation. To this end, a family of
toughened ceramics known as ceramic matrix composites (CMCs) is now undergoing development. Toughness values
as high as 10 to 20 MPa.m½ have been achieved, which is comparable with some metals.
Fibre reinforcement combines crack bridging, fibre pull-out, and crack deflection mechanisms. As an overall
toughening technique, it appears to give the greatest improvement. Further, the use of metal fibres adds the toughening
mechanism that comes from the plasticity of the metallic phase.
Several toughening mechanisms have been engineered into ceramics. These include:
1. Crack deflection
2. Crack pinning
3. Crack bowing
4. Plasticity in metallic phase
5. Transformation toughening
6. Compressive matrix residual stresses
7. Matrix microcracking
8. Frictional interlocking
9. Crack bridging
10. Fibre pull-out