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Transcript of Giris Composite Materials
8/2/2019 Giris Composite Materials
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COMPOSITE MATERIALS
Dr.Suat CANOĞULLARI
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©2002 John Wiley & Sons, Inc.M P Groover, “Fundamentals of
Modern Manufacturing 2/e”
Composite Material Defined
A materials system composed of two or morephysically distinct phases whose combination
produces aggregate properties that are
different from those of its constituents
• Examples:
– Cemented carbides (WC with Co binder) – Plastic molding compounds containing fillers
– Rubber mixed with carbon black
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©2002 John Wiley & Sons, Inc.M P Groover, “Fundamentals of
Modern Manufacturing 2/e”
One Possible Classification of
Composite Materials1. Traditional composites – composite materials that
occur in nature or have been produced by
civilizations for many years
– Examples: wood, concrete, asphalt
2. Synthetic composites - modern material systems
normally associated with the manufacturing
industries, in which the components are first
produced separately and then combined in a
controlled way to achieve the desired structure,
properties, and part geometry
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©2002 John Wiley & Sons, Inc.M P Groover, “Fundamentals of
Modern Manufacturing 2/e”
Why Composites are Important
• Composites are strong, stiff, light in weight, sostrength-to-weight and are several times greaterthan steel or aluminum
• Fatigue properties are generally better than forcommon engineering metals
• Toughness is often greater too
• Composites can be designed that do not corrode like
steel• Possible to achieve combinations of properties not
attainable with metals, ceramics, or polymers alone
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©2002 John Wiley & Sons, Inc.M P Groover, “Fundamentals of
Modern Manufacturing 2/e”
Disadvantages and Limitations of Composite Materials
• Composites are anisotropic - the properties differ depending
on the direction in which they are measured – this may be an
advantage or a disadvantage
• Many of the polymer-based composites are subject to attack
by chemicals or solvents, just as the polymers themselves are
susceptible to attack
• Composite materials are generally expensive
• Manufacturing methods for shaping composite materials are
often slow and costly and
• Gradually they have a low temperature strength against to
metals
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©2002 John Wiley & Sons, Inc.M P Groover, “Fundamentals of
Modern Manufacturing 2/e”
Components in a Composite Material
All composite materials consist of two phases:
1. Primary phase - forms the matrix within which
the secondary phase is imbedded2. Secondary phase - imbedded phase sometimes
referred to as a reinforcing agent , because it
usually serves to strengthen the composite
The reinforcing phase may be in the form of fibers,
particles, or various other geometries
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©2002 John Wiley & Sons, Inc.M P Groover, “Fundamentals of
Modern Manufacturing 2/e”
Composite Materials
1. Metal Matrix Composites (MMCs) - mixtures of ceramics and metals, such as cemented carbides andother cermets
2. Ceramic Matrix Composites (CMCs) - Al2O3 and SiCimbedded with fibers to improve properties,especially in high temperature applications
– The least common composite matrix
3. Polymer Matrix Composites (PMCs) - thermosettingresins are widely used in PMCs
– Examples: epoxy and polyester with fiberreinforcement, and phenolic with powders
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©2002 John Wiley & Sons, Inc.M P Groover, “Fundamentals of
Modern Manufacturing 2/e”
Functions of the Matrix Material
• Provides the bulk form of the part
• Holds the imbedded phase in place
• When a load is applied, the matrix shares the load
with the secondary phase, in some cases deforming
so that the stress is essentially born by thereinforcing agent
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Matrix Considerations
End Use Temperature
Toughness
Cosmetic Issues
Flame Retardant
Processing MethodAdhesion Requirements
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©2002 John Wiley & Sons, Inc.
M P Groover, “Fundamentals of
Modern Manufacturing 2/e”
The Reinforcing Phase
(Secondary Phase)
• Function is to reinforce the primary phase
• Imbedded phase is most commonly one of thefollowing shapes:
a) Fibersb) Particles
c) Flakes
• In addition, the secondary phase can take the form
of an infiltrated phase in a skeletal or porous matrix
– Example: a powder metallurgy part infiltrated withpolymer
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11
Types of Fibers
Fiber Glass
Graphite Fiber
Kevlar Fiber
Kevlar/Carbon Hybrid
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Composite Survey
Large-
particle
Dispersion-
strengthened
Particle-reinforced
Continuous
(aligned)
Aligned Randomlyoriented
Discontinuous
(short)
Fiber-reinforced
Laminates Sandwich
panels
Structural
Composites
Adapted from Fig.16.2, Callister 7e .
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• Elastic modulus, E c , of composites:-- two approaches.
• Application to other properties: -- Electrical conductivity, se : Replace E in the above equations
with se .
-- Thermal conductivity, k : Replace E in above equations with k .
Adapted from Fig. 16.3,Callister 7e . (Fig. 16.3 isfrom R.H. Krock, ASTM Proc , Vol. 63, 1963.)
Composite Survey
lower limit: 1
E c = V m
E m +
V p
E p
c m m
upper limit: E = V E + V p E p
“rule of mixtures”
Particle-reinforced Fiber-reinforced Structural
Data:Cu matrixw/tungstenparticles
0 20 4 0 6 0 8 0 10 0
150
20 0
250
30 0350
vol% tungsten
E (GPa)
(Cu) ( W)
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Composite Survey: Fiber
• Fibers themselves are very strong
– Provide significant strength improvement to
material
Properties are Determined by Three Factors:
• The materials,• The geometric shapes of the constituents and
• Resulting structure of the composite system
Particle-reinforcedFiber-reinforced Structural
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©2002 John Wiley & Sons, Inc.
M P Groover, “Fundamentals of
Modern Manufacturing 2/e”
Figure 9.5 - (a) Model of a fiber-reinforced composite material showingdirection in which elastic modulus is being estimated by the rule of mixtures (b) Stress-strain relationships for the composite material andits constituents. The fiber is stiff but brittle, while the matrix(commonly a polymer) is soft but ductile.
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©2002 John Wiley & Sons, Inc.
M P Groover, “Fundamentals of
Modern Manufacturing 2/e”
Figure 9.6 - Variation in elastic modulus and tensile strength as a function
of direction of measurement relative to longitudinal axis of carbon
fiber-reinforced epoxy composite
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Fiber Alignment
alignedcontinuous
aligned randomdiscontinuous
Adapted from Fig.16.8, Callister 7e .
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Composite Strength: Longitudinal Loading
Continuous fibers - Estimate fiber-reinforced compositestrength for long continuous fibers in a matrix
• Longitudinal deformation
sc =
smV m +
s f V f but
c =
m =
f
volume fraction isostrain
E ce = E m V m + E f V f longitudinal (extensional)modulus
m m
f f
m
f
V E
V E
F
F f = fiber
m = matrix
Remembering: E = s / and note, this modelcorresponds to the“upper bound” for
particulate composites
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Composite Strength: Transverse Loading
• In transverse loading the fibers carry less of theload and are in a state of ‘isostress’
s
c
= s
m
= s
f
= s
c
= m
V m
+
f
V f
f
f
m
m
ct E
V
E
V
E
1transverse modulus
Remembering: E = s / and note, this modelcorresponds to the “lower
bound” for particulate
composites
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An Example:
Note: (for ease of conversion)
6870 N/m2 per psi!
UTS, SI Modulus, SI
57.9 MPa 3.8 GPa
2.4 GPa 399.9 GPa
(241.5 GPa)
(9.34 GPa)
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• Stacked and bonded fiber -reinforced sheets-- stacking sequence: e.g., 0º/90º or 0 /45 /90º
-- benefit: balanced, in-plane stiffness
Adapted from Fig.16.16, Callister 7e .
Composite Survey: Structural
Particle-reinforced Fiber-reinforced Structural
• Sandwich panels -- low density, honeycomb core-- benefit: light weight, large bending stiffness
honeycomb adhesive layer
face sheet
Adapted from Fig. 16.18,Callister 7e . (Fig. 16.18 isfrom Engineered Materials
Handbook , Vol. 1, Composites , ASM International, Materials Park, OH, 1987.)