composite material: property and characteristic.ppt

Composite material

1. COMPOSITE MATERIALS
Technology and Classification of Composite Materials
Metal Matrix Composites
Ceramic Matrix Composites
Polymer Matrix Composites
Guide to Processing Composite Materials
©2002 John Wiley & Sons, Inc. M P Groover, “Fundamentals of Modern Manufacturing
2/e”

2. Composite Material Defined
A materials system composed of two or more physically 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
Wood (a natural composite as distinguished from a synthesized composite)
©2002 John Wiley & Sons, Inc. M P Groover, “Fundamentals of Modern Manufacturing
2/e”

3. Why Composites are
Important
Composites can be very strong and stiff, yet very light
in weight, so ratios of strength-to-weight and
stiffness-to-weight are several times greater than steel
or aluminum
Fatigue properties are generally better than for
common 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
©2002 John Wiley & Sons, Inc. M P Groover, “Fundamentals of Modern Manufacturing
2/e”

4. Disadvantages and Limitations of
Composite Materials
Properties of many important 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
©2002 John Wiley & Sons, Inc. M P Groover, “Fundamentals of Modern Manufacturing
2/e”

5. One Possible Classification of
Composite Materials
1.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
©2002 John Wiley & Sons, Inc. M P Groover, “Fundamentals of Modern Manufacturing
2/e”

6. Components in a Composite
Material
Nearly all composite materials consist of two phases:
1.Primary phase -forms the matrixwithin which the
secondary phase is imbedded
2.Secondary phase -imbedded phase sometimes referred
to as a reinforcingagent, because it usually serves to
strengthen the composite
 The reinforcing phase may be in the form of fibers,
particles, or various other geometries
©2002 John Wiley & Sons, Inc. M P Groover, “Fundamentals of Modern Manufacturing
2/e”

7. Our Classification Scheme for
Composite Materials
1.Metal Matrix Composites(MMCs) -mixtures of ceramics
and metals, such as cemented carbides and other
cermets
2.Ceramic Matrix Composites(CMCs) -Al
2O
3and SiC
imbedded with fibers to improve properties, especially
in high temperature applications
The least common composite matrix
3.Polymer Matrix Composites(PMCs) -thermosetting
resins are widely used in PMCs
Examples: epoxy and polyester with fiber reinforcement,
and phenolic with powders
©2002 John Wiley & Sons, Inc. M P Groover, “Fundamentals of Modern Manufacturing
2/e”

8. Functions of the Matrix Material
(Primary Phase)
Provides the bulk form of the part or product made of
the composite material
Holds the imbedded phase in place, usually enclosing
and often concealing it
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 the reinforcing agent
©2002 John Wiley & Sons, Inc. M P Groover, “Fundamentals of Modern Manufacturing
2/e”

9. The Reinforcing Phase
(Secondary Phase)
Function is to reinforce the primary phase
Imbedded phase is most commonly one of the following
shapes:
Fibers
Particles
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 with
polymer
©2002 John Wiley & Sons, Inc. M P Groover, “Fundamentals of Modern Manufacturing
2/e”

10. Figure 9.1-Possible physical shapes of imbedded phases in
composite materials: (a) fiber, (b) particle, and (c) flake
©2002 John Wiley & Sons, Inc. M P Groover, “Fundamentals of Modern Manufacturing
2/e”

11. Fibers
Filaments of reinforcing material, usually circular in
cross-section
Diameters range from less than 0.0025 mm to about
0.13 mm, depending on material
Filaments provide greatest opportunity for strength
enhancement of composites
The filament form of most materials is significantly
stronger than the bulk form
As diameter is reduced, the material becomes oriented in
the fiber axis direction and probability of defects in the
structure decreases significantly
©2002 John Wiley & Sons, Inc. M P Groover, “Fundamentals of Modern Manufacturing
2/e”

12. Continuous vs. Discontinuous
Fibers
Continuous fibers-very long; in theory, they offer a
continuous path by which a load can be carried by the
composite part
Discontinuous fibers(chopped sections of continuous
fibers) -short lengths (L/D = roughly 100)
Important type of discontinuous fiber are whiskers-hair-
like single crystals with diameters down to about 0.001
mm (0.00004 in.) with very high strength
©2002 John Wiley & Sons, Inc. M P Groover, “Fundamentals of Modern Manufacturing
2/e”

13. Fiber Orientation –Three
Cases
One-dimensionalreinforcement, in which maximum
strength and stiffness are obtained in the direction of
the fiber
Planarreinforcement, in some cases in the form of a
two-dimensional woven fabric
Randomor three-dimensional in which the composite
material tends to possess isotropic properties
©2002 John Wiley & Sons, Inc. M P Groover, “Fundamentals of Modern Manufacturing
2/e”

14. Figure 9.3 -Fiber orientation in composite materials:
(a) one-dimensional, continuous fibers; (b) planar, continuous fibers in
the form of a woven fabric; and (c) random, discontinuous fibers
©2002 John Wiley & Sons, Inc. M P Groover, “Fundamentals of Modern Manufacturing
2/e”

15. Materials for Fibers
Fiber materials in fiber-reinforced composites:
Glass –most widely used filament
Carbon –high elastic modulus
Boron –very high elastic modulus
Polymers -Kevlar
Ceramics –SiC and Al
2O
3
Metals -steel
The most important commercial use of fibers is in
polymer composites
©2002 John Wiley & Sons, Inc. M P Groover, “Fundamentals of Modern Manufacturing
2/e”

16. Particles and Flakes
A second common shape of imbedded phase is
particulate, ranging in size from microscopic to
macroscopic
Flakesare basically two-dimensional particles -small
flat platelets
The distribution of particles in the composite matrix is
random, and therefore strength and other properties of
the composite material are usually isotropic
Strengthening mechanism depends on particle size
©2002 John Wiley & Sons, Inc. M P Groover, “Fundamentals of Modern Manufacturing
2/e”

17. The Interface
There is always an interfacebetween constituent phases in a
composite material
For the composite to operate effectively, the phases must bond where
they join at the interface
©2002 John Wiley & Sons, Inc. M P Groover, “Fundamentals of Modern Manufacturing
2/e”
Figure 9.4 -Interfaces between phases in a composite material:
(a) direct bonding between primary and secondary phases

18. Interphase
In some cases, a third ingredient must be added to achieve bonding of
primary and secondary phases
Called an interphase, this third ingredient can be thought of as an
adhesive
©2002 John Wiley & Sons, Inc. M P Groover, “Fundamentals of Modern Manufacturing
2/e”
Figure 9.4 -Interfaces between phases: (b) addition of a third
ingredient to bond the primary phases and form an interphase

19. Figure 9.4 -Interfaces and interphases between phases in a
composite material: (c) formation of an interphase by solution
of the primary and secondary phases at their boundary
©2002 John Wiley & Sons, Inc. M P Groover, “Fundamentals of Modern Manufacturing
2/e”
Another Interphase
Interphase consisting of a solution of primary and
secondary phases

20. Properties of Composite
Materials
In selecting a composite material, an optimum combination of
properties is usually sought, rather than one particular property
Example: fuselage and wings of an aircraft must be lightweight and be
strong, stiff, and tough
Several fiber-reinforced polymers possess this combination of properties
Example: natural rubber alone is relatively weak
Adding significant amounts of carbon black to NR increases its strength
dramatically
©2002 John Wiley & Sons, Inc. M P Groover, “Fundamentals of Modern Manufacturing
2/e”

21. Properties are Determined by
Three Factors:
1.The materials used as component phases in the
composite
2.The geometric shapes of the constituents and resulting
structure of the composite system
3.The manner in which the phases interact with one
another
©2002 John Wiley & Sons, Inc. M P Groover, “Fundamentals of Modern Manufacturing
2/e”

22. Figure 9.5 -(a) Model of a fiber-reinforced composite material
showing direction in which elastic modulus is being estimated
by the rule of mixtures (b) Stress-strain relationships for the
composite material and its constituents. The fiber is stiff but
brittle, while the matrix (commonly a polymer) is soft but
ductile.
©2002 John Wiley & Sons, Inc. M P Groover, “Fundamentals of Modern Manufacturing
2/e”

23. 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
©2002 John Wiley & Sons, Inc. M P Groover, “Fundamentals of Modern Manufacturing
2/e”

24. Fibers Illustrate Importance of
Geometric Shape
Most materials have tensile strengths several times
greater as fibers than in bulk
By imbedding the fibers in a polymer matrix, a
composite material is obtained that avoids the problems
of fibers but utilizes their strengths
The matrix provides the bulk shape to protect the fiber
surfaces and resist buckling
When a load is applied, the low-strength matrix deforms
and distributes the stress to the high-strength fibers
©2002 John Wiley & Sons, Inc. M P Groover, “Fundamentals of Modern Manufacturing
2/e”

25. Other Composite Structures
Laminar composite structure –conventional
Sandwich structure
Honeycomb sandwich structure
©2002 John Wiley & Sons, Inc. M P Groover, “Fundamentals of Modern Manufacturing
2/e”

26. Laminar Composite Structure
Two or more layers bonded together in an integral piece
Example: plywoodin which layers are the same wood, but grains are
oriented differently to increase overall strength of the laminated
piece
©2002 John Wiley & Sons, Inc. M P Groover, “Fundamentals of Modern Manufacturing
2/e”
Figure 9.7 -Laminar composite
structures: (a) conventional laminar
structure

27. Sandwich Structure –Foam Core
Consists of a relatively thick core of low density foam bonded on both
faces to thin sheets of a different material
©2002 John Wiley & Sons, Inc. M P Groover, “Fundamentals of Modern Manufacturing
2/e”
Figure 9.7 -Laminar
composite structures: (b)
sandwich structure using foam
core

28. Sandwich Structure –Honeycomb Core
An alternative to foam core
Either foam or honeycomb achieves high strength-to-weight and
stiffness-to-weight ratios
©2002 John Wiley & Sons, Inc. M P Groover, “Fundamentals of Modern Manufacturing
2/e”
Figure 9.7 -Laminar
composite structures: (c)
sandwich structure using
honeycomb core

29. Other Laminar Composite
Structures
Automotive tires-consists of multiple layers bonded together
FRPs-multi-layered fiber-reinforced plastic panels for aircraft,
automobile body panels, boat hulls
Printed circuit boards-layers of reinforced plastic and copper for
electrical conductivity and insulation
Snow skis-composite structures consisting of layers of metals,
particle board, and phenolic plastic
Windshield glass-two layers of glass on either side of a sheet of
tough plastic
©2002 John Wiley & Sons, Inc. M P Groover, “Fundamentals of Modern Manufacturing
2/e”

30. Metal Matrix Composites
(MMCs)
A metalmatrix reinforced by a second phase
Reinforcing phases:
1.Particlesof ceramic (these MMCs are commonly called
cermets)
2.Fibersof various materials: other metals, ceramics,
carbon, and boron
©2002 John Wiley & Sons, Inc. M P Groover, “Fundamentals of Modern Manufacturing
2/e”

31. Cermets
MMC with ceramiccontained in a metallic matrix
The ceramic often dominates the mixture, sometimes
up to 96% by volume
Bonding can be enhanced by slight solubility between
phases at elevated temperatures used in processing
Cermets can be subdivided into
1.Cemented carbides –most common
2.Oxide-based cermets –less common
©2002 John Wiley & Sons, Inc. M P Groover, “Fundamentals of Modern Manufacturing
2/e”

32. Cemented Carbides
One or more carbidecompounds bonded in a metallicmatrix
The term cermetis not used for all of these materials, even though it
is technically correct
Common cemented carbides are based on tungsten carbide (WC),
titanium carbide (TiC), and chromium carbide (Cr
3C
2)
Tantalum carbide (TaC) and others are less common
Metallic binders: usually cobalt (Co) or nickel (Ni)
©2002 John Wiley & Sons, Inc. M P Groover, “Fundamentals of Modern Manufacturing
2/e”

33. Figure 9.8 -Photomicrograph (about 1500X) of cemented carbide
with 85% WC and 15% Co (photo courtesy of Kennametal Inc.)
©2002 John Wiley & Sons, Inc. M P Groover, “Fundamentals of Modern Manufacturing
2/e”

34. Figure 9.9 -Typical plot of hardness and transverse rupture
strength as a function of cobalt content
©2002 John Wiley & Sons, Inc. M P Groover, “Fundamentals of Modern Manufacturing
2/e”

35. Applications of Cemented
Carbides
Tungstencarbidecermets (Co binder) -cutting tools are
most common; other: wire drawing dies, rock drilling
bits and other mining tools, dies for powder metallurgy,
indenters for hardness testers
Titanium carbidecermets (Ni binder) -high
temperature applications such as gas-turbine nozzle
vanes, valve seats, thermocouple protection tubes,
torch tips, cutting tools for steels
Chromium carbidescermets (Ni binder) -gage blocks,
valve liners, spray nozzles, bearing seal rings
©2002 John Wiley & Sons, Inc. M P Groover, “Fundamentals of Modern Manufacturing
2/e”

36. Ceramic Matrix Composites
(CMCs)
A ceramicprimary phase imbedded with a secondary phase,
which usually consists of fibers
Attractive properties of ceramics: high stiffness,
hardness, hot hardness, and compressive strength; and
relatively low density
Weaknesses of ceramics: low toughness and bulk tensile
strength, susceptibility to thermal cracking
CMCs represent an attempt to retain the desirable
properties of ceramics while compensating for their
weaknesses
©2002 John Wiley & Sons, Inc. M P Groover, “Fundamentals of Modern Manufacturing
2/e”

37. Polymer Matrix Composites
(PMCs)
A polymerprimary phase in which a secondary phase is
imbedded as fibers, particles, or flakes
Commercially, PMCs are more important than MMCs or
CMCs
Examples: most plastic molding compounds, rubber
reinforced with carbon black, and fiber-reinforced
polymers (FRPs)
FRPs are most closely identified with the term
composite
©2002 John Wiley & Sons, Inc. M P Groover, “Fundamentals of Modern Manufacturing
2/e”

38. Fiber-Reinforced Polymers
(FRPs)
A PMC consisting of a polymermatriximbedded with
high-strength fibers
Polymer matrix materials:
Usually a thermosetting(TS) plastic such as unsaturated
polyester or epoxy
Can also be thermoplastic(TP), such as nylons
(polyamides), polycarbonate, polystyrene, and
polyvinylchloride
Fiber reinforcement is widely used in rubberproducts such
as tires and conveyor belts
©2002 John Wiley & Sons, Inc. M P Groover, “Fundamentals of Modern Manufacturing
2/e”

39. Fibers in PMCs
Various forms: discontinuous (chopped), continuous, or
woven as a fabric
Principal fiber materials in FRPs are glass, carbon, and
Kevlar 49
Less common fibers include boron, SiC, and Al
2O
3, and
steel
Glass (in particular E-glass) is the most common fiber
material in today's FRPs; its use to reinforce plastics
dates from around 1920
©2002 John Wiley & Sons, Inc. M P Groover, “Fundamentals of Modern Manufacturing
2/e”

40. Common FRP Structure
Most widely used form of FRP is a laminar structure,
made by stacking and bonding thin layers of fiber and
polymer until desired thickness is obtained
By varying fiber orientation among layers, a specified
level of anisotropy in properties can be achieved in the
laminate
Applications: parts of thin cross-section, such as aircraft
wing and fuselage sections, automobile and truck body
panels, and boat hulls
©2002 John Wiley & Sons, Inc. M P Groover, “Fundamentals of Modern Manufacturing
2/e”

41. FRP Properties
High strength-to-weight and modulus-to-weight ratios
Low specific gravity -a typical FRP weighs only about 1/5 as much as
steel; yet, strength and modulus are comparable in fiber direction
Good fatigue strength
Good corrosion resistance, although polymers are soluble in various
chemicals
Low thermal expansion -for many FRPs, leading to good dimensional
stability
Significant anisotropy in properties
©2002 John Wiley & Sons, Inc. M P Groover, “Fundamentals of Modern Manufacturing
2/e”

42. FRP Applications
Aerospace–much of the structural weight of todays
airplanes and helicopters consist of advanced FRPs
Automotive–somebody panels for cars and truck cabs
Continued use of low-carbon sheet steel in cars is
evidence of its low cost and ease of processing
Sports and recreation
Fiberglass reinforced plastic has been used for boat hulls
since the 1940s
Fishing rods, tennis rackets, golf club shafts, helmets,
skis, bows and arrows.
©2002 John Wiley & Sons, Inc. M P Groover, “Fundamentals of Modern Manufacturing
2/e”

43. Figure 9.11 -Composite materials in the Boeing 757
(courtesy of Boeing Commercial Airplane Group)
©2002 John Wiley & Sons, Inc. M P Groover, “Fundamentals of Modern Manufacturing
2/e”

44. Other Polymer Matrix Composites
In addition to FRPs, other PMCs contain particles, flakes, and short
fibers as the secondary phase
Called fillerswhen used in molding compounds
Two categories:
1.Reinforcing fillers–used to strengthen or otherwise improve mechanical
properties
Examples: wood flour in phenolic and amino resins; and carbon black in
rubber
2.Extenders–used to increase bulk and reduce cost per unit weight, but
little or no effect on mechanical properties
©2002 John Wiley & Sons, Inc. M P Groover, “Fundamentals of Modern Manufacturing
2/e”

45. Guide to Processing
Composite Materials
The two phases are typically produced separately
before being combined into the composite part
Processing techniques to fabricate MMC and CMC
components are similar to those used for powdered
metals and ceramics
Molding processes are commonly used for PMCs with
particles and chopped fibers
Specialized processes have been developed for FRPs
©2002 John Wiley & Sons, Inc. M P Groover, “Fundamentals of Modern Manufacturing
2/e”