2. Structure
Amorphous Glass Quasi-Crystal Polycrystalline Crystals
Type of materials
Element
Organic Inorganic
Quasicrystal, is a structure that is ordered but not periodic.
3.
4. ā¢ Examples of naturally occurring composites
Wood: Cellulose fibers bound by lignin matrix
Bone: Stiff mineral āfibersā in a soft organic matrix permeated with holes filled
with liquids
Granite: Granular composite of quartz, feldspar, and mica
5. Some examples of manāmade composites
Concrete: Particulate composite of aggregates (limestone or granite), sand,
cement and water
Plywood: Plywood: Several layers of wood veneer glued together
Fiberglass: Fiberglass: Plastic matrix reinforced by glass fibers Cemets:
Ceramic and metal composites
Fibrous composites: Variety of fibers (glass, kevlar, graphite, nylon, etc.)
bound together by a polymeric matrix
These are not composites! composites!
ā¢ Plastics: Even though they may have several āfillersā, their presence does
not alter the physical properties significantly.
ā¢ Alloys: The alloy is not macroscopically heterogeneous, especially in terms
of physical properties.
ā¢ Metals with impurities: The presence of impurities does not significantly
alter physical properties of the metal.
6.
7. Industrial use
Automotive industry: Lighter, stronger, wear resistance, rustāfree, aesthetics,
Car body ā Brake pads
Aerospace: Lighter, stronger, temperature resistance, smart structures, wear
resistance, Rocket, Missiles
Sports: Lighter, stronger, toughness, better aesthetics, higher damping
properties
8.
9.
10. The matrix is basically a homogeneous and monolithic material in which a
fiber system of a composite is embedded. It is completely continuous. The
matrix provides a medium for binding and holding reinforcements together
into a solid. It offers protection to the reinforcements from environmental
damage, serves to transfer load, and provides finish, texture, color, durability
and functionality.
There are three main types of composite matrix materials:
Ceramic matrix - Ceramic matrix composites (CMCs) are a subgroup of
composite materials. They consist of ceramic fibers embedded in a ceramic
matrix, thus forming a ceramic fiber reinforced ceramic (CFRC) material.
The matrix and fibers can consist of any ceramic material. CMC materials
were designed to overcome the major disadvantages such as low fracture
toughness, brittleness, and limited thermal shock resistance, faced by the
traditional technical ceramics.
11. Metal matrix -
Metal matrix composites (MMCs) are composite materials that contain at least
two constituent parts ā a metal and another material or a different metal.
The metal matrix is reinforced with the other material to improve strength and
wear. Where three or more constituent parts are present, it is called a hybrid
composite.
In structural applications, the matrix is usually composed of a lighter metal such
as magnesium, titanium, or aluminum.
Typical MMC's manufacturing is basically divided into three types: solid, liquid,
and vapor. Continuous carbon, silicon carbide, or ceramic fibers are some of the
materials that can be embedded in a metallic matrix material.
MMCs are fire resistant, operate in a wide range of temperatures, do not absorb
moisture, and possess better electrical and thermal conductivity. They have also
found applications to be resistant to radiation damage, and to not suffer from
outgassing.
12. Polymer matrix -
Polymer matrix composites (PMCs) can be divided into three sub-types,
namely, thermoset, thermoplastic, and rubber.
Polymer is a large molecule composed of repeating structural units
connected by covalent chemical bonds.
PMC's consist of a polymer matrix combined with a fibrous reinforcing
dispersed phase. They are cheaper with easier fabrication methods.
PMC's are less dense than metals or ceramics, can resist atmospheric and
other forms of corrosion, and exhibit superior resistance to the conduction of
electrical current.
24. Carbon based reinforced
Carbon and carbon bond
Carbon (6) contains four electrons in its outer shell (2Px,2Py,2Pz). Therefore, it can form
four covalent bonds with other atoms or molecules.
The most common oxidation state of carbon in inorganic compounds is +4, while +2 is
found in carbon monoxide and transition metal carbonyl complexes.
30. C or graphite fiber are fibers about 5 to 10 micrometers, made of
carbon.
Carbon fibers have several advantages including high stiffness, high
tensile strength, low weight, high chemical resistance, high temperature
tolerance and low thermal expansion.
Note: 1020 steel (low carbon); 6061 is a precipitation-
hardened aluminium alloy, containing magnesium and silicon.
Carbon fiber reinforce polymer (CFRP)
31. 1. In CFRP the reinforcement is carbon fiber, which provides its strength. The matrix
is usually a polymer resin, such as epoxy, to bind the reinforcements together.
2. Because CFRP consists of two distinct elements, the material properties depend on
these two elements.
3. Reinforcement gives CFRP its strength and rigidity, measured
by stress and elastic modulus respectively.
4. Unlike isotropic materials like steel and aluminum, CFRP has directional strength
properties.
5. The properties of CFRP depend on the layouts of the carbon fiber and the
proportion of the carbon fibers relative to the polymer.
6. The fibers carry the mechanical loads, while the matrix material transmits loads to
the fibers and provides ductility and toughness as well as protecting the fibers from
damage caused by handling or the environment. It is the matrix material that limits
the service temperature and processing conditions.
Resin example (Thermosets ): Bisphenol-A (E51) diglycidylether with a hardener of 4-
methyl-1,3 cyclohexane diamine (HTDA); Polyester resin; acrylic polymers;
polyurethane adhesives
32. The two different equations governing the net elastic modulus of composite
materials using the properties of the carbon fibers and the polymer matrix can
also be applied to carbon fiber reinforced plastics.
The following equation is valid for composite materials with the fibers
oriented in the direction of the applied load.
is the total composite modulus, and are the volume fractions of the
matrix and fiber respectively in the composite, and and are the
elastic moduli of the matrix and fibers respectively.
Note:
An elastic moduli/elastic modulus is a quantity that measures an object or
substance's resistance to being deformed elastically (i.e., non-permanently) when a
stress is applied.
34. Fiber orientation type
The strength and stiffness of a composite buildup depends on the orientation sequence of
the plies, the layer orientation of fiber reinforced polymer composite materials needs to be
designed correspondingly.
While the fibers in a unidirectional material run in one direction and the strength and
stiffness is only in the direction of the fiber; the fibers in a bidirectional material run in two
directions and the strength and stiffness is in two direction of the fiber.
The layers should require 0Ā° plies to respond to axial loads, Ā±45Ā° plies to react to shear
loads, and 90Ā° plies to react to side loads. Since the strength design requirements are a
function of the applied load direction, ply orientation and ply sequence have to be true
Layer orientation
35. Molding
One method of producing CFRP parts is by layering sheets of carbon fiber cloth
into a mold in the shape of the final product. The alignment and weave of the
cloth fibers is chosen to optimize the strength and stiffness properties of the
resulting material. The mold is then filled with epoxy and is heated or air-cured.
The resulting part is very corrosion-resistant, stiff, and strong for its weight.
Production method
36. Vacuum bagging
For simple pieces of which relatively few copies are needed (1ā2 per day), a vacuum
bag can be used. A fiberglass, carbon fiber, or aluminum mold is polished and waxed, and
has a release agent applied before the fabric and resin are applied, and the vacuum is pulled
and set aside to allow the piece to cure (harden). There are three ways to apply the resin to
the fabric in a vacuum mold.
37. Compression molding
A quicker method uses
a compression mold. This is a
two-piece mold usually made out
of aluminum or steel that is
pressed together with the fabric
and resin between the two. The
benefit is the speed of the entire
process.
38. Properties of CFRP Composites
Composite materials, reinforced with carbon fiber, are different than other FRP
composites using traditional materials such as fiberglass or aramid fiber. The properties
of CFRP composites that are advantageous include:
Light Weight: A traditional fiberglass reinforced composite using continuous glass
fiber with a fiber of 70% glass (weight of glass / total weight), will commonly have a
density of 0.065 pounds per cubic inch.
Meanwhile, a CFRP composite, with the same 70% fiber weight, might typically
have a density of 0.055 pounds per cubic inch.
Increased Strength: CFRP composites are much stronger and stiffer per unit of
weight. This is true when comparing carbon fiber composites to glass fiber, but even
more so when compared to metals.
A carbon fiber structure of equal strength āwill often weigh 1/5th that of steel.
An aluminum structure of equal strength would likely weigh 1.5 times that of the
carbon fiber structure.
Aramid fibers are a class of heat-resistant and strong synthetic fibers, The name is a blend of
"aromatic polyamide.
39. Disadvantages of CFRP Composites
Cost: CFRP composites are cost-prohibitive in many instances. Depending on the current
market conditions (supply and demand), the type of carbon fiber (aerospace vs.
commercial grade), and the fiber tow size, the price of carbon fiber can vary
dramatically.
Raw carbon fiber on a price-per-pound basis can be anywhere between 5-times to 25-
times more expensive than fiberglass. This disparity is even greater when comparing
steel to CFRP composites.
Conductivity: Carbon fiber is extremely conductive, while glass fiber is in-sulative.
Many applications use glass fiber, and cannot use carbon fiber or metal, strictly because
of the conductivity.
40. Composites in defence
Indian composites industry, has been growing
with a lower rate of 5 per cent per annum
compared to the global rate of 12 percent per-
annum.
About 5 percent composites are being used in
defence and military sector, which is likely to
increase.
The Garden Reach shipyard using carbon fibre
to build Anti-Submarine Warfare.
The Integrating the carbon composite
superstructure with the steel hull has helped
reduce the total weight of the vessel by 30%
and has increased its stealth capability.
https://www.sciencedirect.com/journal/defence-technology/vol/14/issue/4
41. Major applications of Composites
Aerospace
1. Aircrafts Structural parts like - Control surfaces,
wing parts, fuselage panels, radome, interior parts,
equipment cases, etc.
2. Helicopters - Structural parts like - Control surfaces,
floor panels, cabins, rotary wings etc.
3. Space Vehicles Structural Parts: Composite antennae
& reflectors, Bus structures, Towers & Sub systems,
Deployable booms & Masts, etc.
4. Compression Moulded Kevlar parts for Engines.
Land System
Personal Armour, Light weight Bullet Proof Jackets
Commando / Tactical Vests and Jackets
Floatation Jackets for Naval force
Riot gear; Bullet proof helmets/Ultra light weight
Vehicle Protection
Car Blanket
Bullet Proof Vehicles
Ballistic Barrier
Land Systems - Containers to transport sensitive
equipment like missiles; Shelters for storage under
special conditions; Panels for the battle tank/ armoured
vehicles such as escape hatch etc.
The figure below depicts an
estimated breakup of composites
market in various defence
segments:
Marine Systems
High speed boats/Naval vessels
Sail boats/Fishing boats
Syntactic foams
Other sector includes: - Railways,
Wind Energy, and Medical
42. It is a known fact that in the aircraft industry that there are more than hundred thousand
mounting holes on a single small aircraft and more than a million holes on larger ones.
Thus, from manufacturers' point of view, drilling process constitutes the 40% of all
machining operations during the assembly (riveted, bolted) of components.
However, failures such as fiber rupture, resin-fiber de-bonding, surface
irregularities, micro-crack formation and deformations around drilling regions are
commonly encountered during the machining of CFRP composite materials due to the
presence of two or more phases.
The surface quality depends on the cutting parameters, tool geometry and cutting forces.
Therefore, correct selection of cutting parameters is essential in the machining
of polymer matrix composites.
Problem
43. It is also almost impossible to find a single monolithic material with the required property
profile for engineering applications.
Moreover, material properties are greatly affected by the working environment (such as
temperature, pressure, humidity, etc.) and the nature of loading (gradual, fluctuating,
impact, fatigue, etc.).
There is need, therefore, to combine two or more materials, as alloys or composites so
as to utilise the different useful properties offered by the different materials.
Metal matrix composites can be classified into several distinct classes, generally defined
with reference to the type, shape and method of their reinforcements.
Metal- matrix composites
44. Particle-reinforced MMCs:
Particulate-reinforced MMCs, these composites generally contain equi-axed ceramic
reinforcements, mainly oxides (e.g. alumina, Al2O3), carbides (e.g. silicon carbide, SiC) or
borides (e.g. titanium bromide, TiB2), with an aspect ratio less than 5 and present in
volume fraction less than 30%. They can be produced by blending metal and the ceramic
powders, followed by solid-state sintering or by liquid-metal techniques such as stir
casting, squeeze infiltration and in situ processes.
Continuous fibre-reinforced MMCs: These contain either relatively fine continuous fibres,
usually of Al2O3, SiC or carbon, with a diameter below 20 Ī¼m, or coarser fibres or
monofilaments.
The former can be either parallel or pre-woven prior to infiltration to form a composite,
while the bending flexibility of the latter limits the range of shapes that can be produced.
Monofilaments are large diameter (100ā150 Ī¼m) fibres, usually produced by chemical
vapour deposition (CVD) of either SiC or boron (B) into a core of carbon fibre or tungsten
(W).
45. Whisker- and short-fibre-reinforced MMCs: These contain reinforcements with an
aspect ratio of greater than 5 but are not continuous. Short Al2O3 fibre-reinforced MMCs
have been dominantly used in pistons. Whisker-reinforced composites, produced by either
powder metallurgy or squeeze infiltration into a fibre preform, are generally produced to
net/near-net shape. However, usage of whiskers as reinforcements is being restricted due
to perceived health hazards.
Hybrid MMCs: Hybrid MMCs essentially contain more than one type of reinforcement,
for example, a mixture of particle and whisker, a mixture of fibre and particle or a mixture
of hard and soft reinforcements. With the discovery of carbon nanotubes (CNT),
composites with superior mechanical properties over those of carbon have been produced.
46. Notes
The general rule is that mechanical properties (strength and stiffness) increase as
reinforcement length increases and Particulates are the limit of short fibers
In theory whiskers should have superior properties because of their higher aspect
ratio. However they tend to break up into shorther lengths during processing.
Another disadvantage of using whisker reinforcement is that they may oriented by
some processes like rolling and extrusion, producing composites with anisotropy.
It is also more difficult to pack whiskers than particulate (lower
reinforcement/matrix ratio).
Fiber diameters range from less than 2.5 micrometers to 130 micrometers
Particulates size from microscopic to macroscopic
Flakes are 2D particles like small flat platelets
The distribution of particles in the composite matrix is random so the properties
of the composite are usually isotropic
Fibers and flakes are usually oriented so the properties of the composites are
anisotropic
47. Continuous fibers - very long; in theory, they offer a continuous path by which a load
can be carried by the composite part
ā¢ Discontinuous fibers (chopped sections of continuous fibers) ā
short lengths (L/D ) <100.
Whiskers are important type of discontinuous fiber ā hair-like single crystals with
diameters down to about 0.001 mm (0.00004 in.) with very high strength
48.
49. The most abundant metallic element in the Earthās crust (8% of the earth crest).
Aluminium has light-weight combined with good thermal/electrical conduction, high
reflectivity, and reasonably good strength and resistance to corrosion.
The strength of aluminium alloys can equal (and sometimes exceed) the strength of normal
construction steel.
Automotive industry, Aerospace, marine, rail, packaging, thermal management, building
and construction, sports and recreation, etc
Aluminium matrix composites (AMCs) are potential materials for various applications due
to their good physical and mechanical properties.
AMCs are considered as light weight high performance aluminium centric material
systems.
The addition of reinforcements into the Al metallic matrix improves the stiffness, specific
strength, wear, creep and fatigue properties compared to the conventional engineering
materials.
The reinforcement in AMCs could be in the form of continuous/discontinuous fibres,
whisker or particulates, in volume fractions ranging from a few percent to 70%.
Aluminium
50. Typical microstructures of AlMMCs. (a) Al/Al2O3 platelets. (b) Al/Al2O3 continuous fibres.
(c) Al/SiCp. (d) Al/graphite with 20 vol.% graphite flakes taken along the basal plane.
51. Classified into two main groups, namely,
(1) Liquid-state processes and
(2) Solid-state processes.
(3) Gaseous Processes
Manufacturing
The liquid-state processes are
further classified into liquid-
metal-mixing processes and
liquid-metal-infiltration
processes.
liquid-metal mixing is the primary
compositing route for producing
materials considered for high-
volume automotive applications,
liquid-metal infiltration for high-
volume electronic packaging
applications and solid-state
processing for high-performance
aerospace applications.
52.
53.
54. Liquid-metal-mixing processes
The liquid-metal-mixing process involves
the incorporation of reinforcement
particles or short fibres into a molten or
semi-solid aluminium matrix through a
stirring process.
In stir casting technique, the process
involves the incorporating of ceramic
particulate into liquid aluminium melt and
allowing the mixture to solidify.
It is crucial to ensure that good wettability
between the particulate reinforcement and
the liquid aluminium alloy melt is
achieved.
Generally it is possible to incorporate up
to 30% ceramic particles in the size range
from 5 to 100 Ī¼m in a variety of molten
aluminium alloys.
Liquid-metal-infiltration processes
In the liquid-metal-infiltration process, the
molten aluminium or its alloy is moved into a
preform of the reinforcement, either as a
packed bed or a rigid, free-standing structure.
Infiltration is a liquid state method of
composite materials fabrication, in which a
preformed dispersed phase (ceramic particles,
fibers, woven) is soaked in
a molten matrix metal, which fills the space
between the dispersed phase inclusions.
In order for the preform to retain its integrity
and shape, it is often necessary to use silica-
and alumina-based mixtures as a binder.
Some degree of pressure is needed to overcome
the wetting and capillary resistance, and this
can vary from atmospheric to thousands
of Pascal.
55. Solid-state processes
Solid-state processes involve the mixing of reinforcement (particles or whiskers)
into a solid-state matrix.
These materials are primarily employed in higher-performance applications,
(aerospace and automotive markets).
Initially, ceramic-whisker materials were produced, and subsequently, ceramic-
particulate-reinforced materials followed.
These materials, while expensive (reinforcement and processing costs),
developed dramatically improved properties over the base metal.
However, due to the health risks posed by whisker-reinforced MMCs,
particulate-reinforced MMCs have replaced them in many applications, leaving
the whisker-reinforced MMCs for specialised military applications [23].
Particulate reinforcement, besides being of lower cost, also exhibited
improvements in strength and stiffness almost as high as those obtained in
whisker-reinforced materials.
http://www.substech.com/dokuwiki/doku.php?id=solid_state_fabrication_of_metal_matri
x_composites
56. Solid state fabrication of Metal Matrix Composites is the process, in which Metal Matrix
Composites are formed as a result of bonding matrix metal and dispersed phase due to
mutual diffusion occurring between them in solid states at elevated temperature and
under pressure.
Low temperature of solid state fabrication process (as compared to Liquid state fabrication
of Metal Matrix Composites) depresses undesirable reactions on the boundary between
the matrix and dispersed (reinforcing) phases.
Metal Matrix Composites may be deformed also after sintering operation by
rolling, Forging, pressing, Drawing or Extrusion. The deformation operation may be either
cold (below the recrystallization temperature) or hot (above the recrystallyzation
temperature).
Deformation of sintered composite materials with dispersed phase in form of short fibers
results in a preferred orientation of the fibers and anisotropy of the material properties
(enhanced strength along the fibers orientation).
There are two principal groups of solid state fabrication of Metal Matrix Composites:
Diffusion bonding
Sintering
57. Diffusion Bonding is a solid state fabrication method, in which a matrix in form of foils
and a dispersed phase in form of long fibers are stacked in a particular order and then
pressed at elevated temperature.
The finished laminate composite material has a multilayer structure.
Diffusion Bonding is used for fabrication of simple shape parts (plates, tubes).
Variants of diffusion bonding are roll bonding and
wire/fiber winding:
Roll Bonding is a process of combined Rolling (hot
or cold) strips of two different metals
(e.g. steel and aluminum alloy) resulted in
formation of a laminated composite material with
a metallurgical bonding between the two layers.
Wire/fiber Winding is a process of combined
winding continuous ceramic fibers and metallic
wires followed by pressing at elevated
temperature.
58. Sintering
Sintering fabrication of Metal Matrix Composites is a process, in which a powder of a
matrix metal is mixed with a powder of dispersed phase in form of particles or short
fibers for subsequent compacting and sintering in solid state (sometimes with some
presence of liquid).
Sintering is the method involving consolidation of powder grains by heating the āgreenā
compact part to a high temperature below the melting point, when the material of the
separate particles diffuse to the neighboring powder particles.
In contrast to the liquid state fabrication of Metal Matrix Composites, sintering method
allows obtaining materials containing up to 50% of dispersed phase.
When sintering is combined with a deformation operation, the fabrication methods are
called:
Hot Pressing Fabrication of Metal Matrix Composites
Hot Isostatic Pressing Fabrication of Metal Matrix
Composites
Hot Powder Extrusion Fabrication of Metal Matrix
Composites
Hot Pressing Fabrication of Metal Matrix Composites
Hot Pressing Fabrication of Metal Matrix Composites
59. Hot Pressing Fabrication of
Metal Matrix Composites ā
sintering under a
unidirectional
pressure applied by a hot
press;
60. Hot Isostatic Pressing Fabrication of Metal
Matrix Composites ā
sintering under a pressure applied from
multiple directions through a liquid or gaseous
medium surrounding the compacted part and
at elevated temperature;
