Composite material
•(or composites for short) are engineered
materials made from two or more constituent
materials with significantly different physical
or chemical properties and which remain
separate and distinct within the finished
structure.
TYPES
•Two types of constituent materials:
- MATRIX and REINFORCEMENT
The matrix material surrounds and supports the
reinforcement materials by maintaining their relative
positions. The reinforcements impart special physical
(mechanical and electrical) properties to enhance the
matrix properties.
Material properties – A COMBINATION OF THE
TWO
Two Natural composites:
BONE
and
WOOD
COMPOSITES
Particle Reinforced
Large
Dispersion
Particle Strengthened
Fibre Reinforced
Continuous
(Aligned)
Aligned
Discontinuous
Structural
laminates
(short)
Randomly Oriented
Sandwich
panels
Earliest examples
The most primitive composite materials
comprised straw and mud in the form
of bricks for building construction.
The ancient brick-making process can
still be seen on Egyptian tomb
paintings in the Metropolitan Museum
of Art
Modern composites
• The most advanced examples are used
on spacecraft in demanding
environments.
• The most visible applications:
roadways in the form of either steel and
portland cement concrete, Mastic
asphalt and asphalt concrete.
• Engineered composite materials must be
formed to shape.
• This involves placing the reinforcements
while manipulating the matrix properties to
achieve a melding event at or near the
beginning of the component life cycle.
• Various methods used according to the end
item design requirements.
• These methods are commonly named
moulding or casting processes,with
numerous variations
• The principle factors:
1. The natures of the chosen matrix and
reinforcement materials.
2. Quantity of material to be produced. Large
quantities to justify high capital expenditures
for rapid and automated manufacturing
technology.
Small production quantities with lower capital
expenditures but higher labour costs at a
correspondingly slower rate.
Mechanics
• A polymer matrix material called a resin or
resin solution.
• There are many different polymers available
depending upon the starting raw ingredients.
Broad categories, each with numerous
variations. The most common categories are
known as polyester, vinyl ester, epoxy,
phenolic, polyimide, polyamide, and others.
• The reinforcement materials: fibers & ground
minerals.
• Fibers transformed into a textile material
such as a felt, fabric, knit or stitched
construction.
• Advanced composite materials: a
category comprising carbon fiber
reinforcement and epoxy or polyimide
matrix materials.
• These are the aerospace grade
composites and typically involve
laminate molding at high temperature
and pressure to achieve high
reinforcement volume fractions. These
advanced composite materials feature
high stiffness and/or strength to weight
ratios.
• One component - a strong fibre such as
fiberglass, quartz, kevlar, Dyneema or carbon
fiber that gives the material its tensile
strength
• another component (called a matrix)- a resin
such as polyester, or epoxy that binds the
fibres together, transferring load from broken
fibers to unbroken ones and between fibers
that are not oriented along lines of tension.
• The matrix chosen - flexible, prevents the fibers
from buckling in compression.
• Some composites use an aggregate instead of,
or in addition to, fibers.
• In terms of stress, fibers to resist tension,
the matrix to resist shear, and all materials
present serve to resist compression,
including any aggregate.
• Composite materials - divided into two
main categories:
1.Short fiber reinforced materials
2. continuous fiber reinforced materials
Continuous reinforced materials will often constitute
a layered or laminated structure.
Shocks, impact, loadings or repeated cyclic stresses
can cause the laminate to separate at the interface
between two layers, a condition known as
delamination. Individual fibers can separate from the
matrix e.g. fiber pull-out.
Examples
• Fiber Reinforced Polymers or FRPs:
– Classified by type of fiber:
• Wood (cellulose fibers in a lignin and hemicellulose matrix)
• Carbon-fiber reinforced plastic or CFRP
• Glass-fiber reinforced plastic or GFRP
– Classified by matrix:
• Thermoplastic Composites
– short fiber thermoplastics
– long fiber thermoplastics or long fiber reinforced
thermoplastics
– glass mat thermoplastics
– continuous fiber reinforced thermoplastics
• Thermoset Composites
• Reinforced carbon-carbon (carbon fiber in a graphite matrix)
• Metal matrix composites or MMC:
– White cast iron
– Hardmetal (carbide in metal matrix)
– Metal-intermetallic laminate
• Ceramic matrix composites:
– Bone (hydroxyapatite reinforced with collagen
fibers)
– Cermet (ceramic and metal)
– Concrete
• Organic matrix/ceramic aggregate composites
– Asphalt concrete
– Mastic asphalt
– Mastic roller hybrid
– Dental composite
– Syntactic foam
– Mother of Pearl
• Chobham armour
• Engineered wood
– Plywood
– Oriented strand board
– Wood plastic composite (recycled wood
fiber in polyethylene matrix)
– Pykrete (sawdust in ice matrix)
• Plastic-impregnated or laminated paper or
textiles
– Arborite
– Formica (plastic)
• Buckypaper Composites
Road design
• consists of two important technical
aspects:
• geometrical road design
• structural road design
• Once these activities are completed,
construction of the pavement can begin. First the
native soil, known as the subgrade, is
compacted. Weak soils may also be stabilized
with additives such as portland cement and
quicklime, or dug out and replaced with imported
soils.
• Then a base course consisting of gravel or
crushed stone is usually placed on the subgrade
and compacted. On top of the base course is
placed a surface course which typically consists
of asphalt concrete or portland cement concrete.
This surface course strengthens the pavement
structure by spreading out the vehicle loads
applied to the subgrade. It also provides a
smooth and high-friction surface for vehicles to
drive on.
• Modern roads, and indeed many ancient ones, such as
those built by the Romans, feature a convex transverse
profile known as superelevation or camber. This is
designed to allow water to drain away from the road to
its edges. Water is then carried away by gutters to drains
placed at intervals. Some roads don't have gutters and
water simply drains away to a naturally porous verge, or
into ditches. Modern roads that carry motor traffic also
employ camber in curves to aid traffic stability by
allowing them to "bank into" the bend to some extent.
• On the side of the road there may be retroreflectors on
pegs, rocks or crash barriers, white toward the direction
of the traffic on that side of the road, and red toward the
other direction. In the road surface there may be cat's
eyes: retroreflectors that protrude slightly, but which can
be driven over without damage.
• Road signs are often also made retroreflective or even
illuminated in rare circumstances. For greater visibility of
road signs at daytime, sometimes fluorescence is
applied to get very bright colors.
All-weather road - an unpaved road that is constructed of material
(particularly gravel) that does not create mud during rainfall.
Unpaved road - a road without a bound surface layer (such as asphalt
concrete or portland cement concrete).
Types of unpaved roads include dirt roads and gravel roads. Unpaved
roads are much cheaper to construct than paved roads, but may be
more expensive to maintain especially when they have high traffic
volumes. The cost of operating a vehicle on an unpaved road is also
much higher than on a paved road.
An unusual road at London Heathrow Airport, England. A British
Airways Boeing 777-200 is being towed across a public road on its way
to the maintenance hangars
.
Reinforced carbon-carbon
• Reinforced Carbon-Carbon
(carbon-carbon or RCC) is a
composite material consisting
of carbon fiber reinforcement
in a matrix of graphite, often
with a silicon carbide coating
to prevent oxidation. It was
developed for the nose cones
of intercontinental ballistic
missiles, and is most widely
known as the material for the
nose cone and leading edges
of the space shuttle.
• Carbon-carbon is well-suited to structural
applications at high temperatures, or where
thermal shock resistance and/or a low coefficient
of thermal expansion is needed. While it is less
brittle than many other ceramics, it lacks impact
resistance; Space Shuttle Columbia was
destroyed after one of its RCC panels was
broken by the impact of a piece of foam
insulation from the Space Shuttle External Tank.
This was a catastrophic failure partly because
original shuttle design requirements did not
consider such a violent impact to be likely.
• The material is made in three stages:
• First, material is laid up in its intended final shape, with
carbon filament and/or cloth surrounded by an organic
binder such as plastic or pitch. Often, coke or some
other fine carbon aggregate is added to the binder
mixture.
• Second, the lay-up is heated, so that pyrolysis
transforms the binder to relatively pure carbon. The
binder loses volume in the process, so that voids form;
the addition of aggregate reduces this problem, but does
not eliminate it.
• Third, the voids are gradually filled by forcing a carbonforming gas such as acetylene through the material at a
high temperature, over the course of several days. This
long heat treatment process also allows the carbon to
form into larger graphite crystals, and is the major
reason for the material's high cost, exceeding $100,000
per panel.
Metal matrix composite
• A metal matrix composite (MMC) is a
type of composite material with at least
two constituent parts, one being a metal.
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. An MMC is
complementary to a cermet
• Composition
MMCs are made by dispersing a reinforcing
material into a metal matrix. The reinforcement
surface can be coated to prevent a chemical
reaction with the matrix. For example, carbon
fibers are commonly used in aluminum matrix to
synthesize composites containing low density
and high strength. However, carbon reacts with
aluminum to generate a brittle and water-soluble
compound Al4C3 on the surface of the fiber. To
prevent this reaction, the carbon fibers are
coated with nickel or titanium boride.
• Matrix
• The matrix is the monolithic material into which
the reinforcement is embedded, and is
completely continuous. This means that there is
a path through the matrix to any point in the
material, unlike two materials sandwiched
together. In structural applications, the matrix is
usually a lighter metal such as aluminum,
magnesium, or titanium, and provides a
compliant support for the reinforcement. In high
temperature applications, cobalt and cobaltnickel alloy matricies are common.
• Reinforcement
The reinforcement material is embedded into the matrix. The
reinforcement does not always serve a purely structural task
(reinforcing the compound), but is also used to change
physical properties such as wear resistance, friction
coefficient, or thermal conductivity.
The reinforcement can be either continuous, or discontinuous.
Discontinuous MMCs can be isotropic, and can be worked with
standard metalworking techniques.
• Continuous reinforcement uses monofilament wires or fibers
such as carbon fiber or silicon carbide. Because the fibers are
embedded into the matrix in a certain direction, the result is an
anisotropic structure in which the alignment of the material
affects its strength.
• One of the first MMCs used boron filament as reinforcement.
Discontinuous reinforcement uses "whiskers", short fibers, or
particles. The most common reinforcing materials in this
category are alumina and silicon carbide.
Manufacturing and forming
methods
•
•
•
•
•
•
•
•
•
•
•
•
MMC manufacturing can be broken into three types: solid, liquid, and vapor.
Solid state methods
Powder blending and consolidation (powder metallurgy): Powdered metal
and dicontinuous reinforcement are mixed and then bonded through a
process of compaction, degassing, and thermo-mechanical treatment
(possibly via hot isostatic pressing (HIP) or extrusion).
Foil diffusion bonding: Layers of metal foil are sandwiched with long fibers,
and then pressed through to form a matrix.
Liquid state methods
Electroplating / Electroforming: A solution containing metal ions loaded with
reinforcing particles is co-deposited forming a composite material.
Stir casting: Discontinuous reinforcement is stirred into molten metal, which
is allowed to solidify.
Squeeze casting: Molten metal is injected into a form with fibers preplaced
inside it.
Spray deposition: Molten metal is sprayed onto a continuous fiber substrate.
Reactive processing: A chemical reaction occurs, with one of the reactants
forming the matrix and the other the reinforcement.
Vapor deposition
Physical vapor deposition: The fiber is passed through a thick cloud of
vaporized metal, coating it. [1]
Applications
• Carbide drills are often made from a tough cobalt matrix with hard
tungsten carbide particles inside.
• Some tank armors may be made from metal matrix composites, probably
steel reinforced with boron nitride. Boron nitride is a good reinforcement
for steel because it is very stiff and it does not dissolve in molten steel.
• Some automotive disc brakes use MMCs. Early Lotus Elise models used
Aluminum MMC rotors, but they have less than optimal heat properties
and Lotus has since switched back to cast-iron. Modern highperformance sport cars, such as those built by Porsche, use rotors made
of carbon fiber within a silicon carbide matrix because of its high specific
heat and thermal conductivity. 3M sells a preformed aluminum matrix
insert for strengthening cast aluminum disc brake calipers [2], allowing
them to weigh as much as 50% less while increasing stiffness.
• Toyota has since used metal matrix composites in the 2ZZ-GE engine
block, and the Porsche Boxster and 911 use MMCs to reinforce the
engine's cylinder sleeves. (Lotus uses the 2ZZ-GE in later Elise S2
versions). The 2ZZ-GE engine is actually designed and built by Yamaha,
as were the Iron-block Toyota 4A-GE, etc. Prior, Honda had already used
Aluminum MMC in its high-performance engine blocks such as the H22
and later the K20.
• The F-16 Fighting Falcon uses monofilament silicon
carbide fibres in a titanium matrix for a structural
component of the jet's landing gear.
• Specialized Bicycles have used aluminium MMC
compounds for their top of the range bicycle frames for
several years.
• MMCs are nearly always more expensive than the more
conventional materials they are replacing. As a result,
they are found where improved properties and
performance can justify the added cost. Today these
applications are found most often in aircraft components,
space systems and high-end or "boutique" sports
equipment. The scope of applications will certainly
increase as manufacturing costs are reduced.
• MMCs are resistant to fire, can operate in wider range of
temperatures, do not absorb moisture, have better
electrical and thermal conductivity, are resistant to
radiation, and do not display outgassing.
• BUT, MMCs tend to be more expensive, the fiberreinforced materials may be difficult to fabricate, and the
available experience in use is limited.
Concrete.
• Concrete is a construction material that consists, in its most
common form, of Portland cement, construction aggregate
(generally gravel and sand) and water.
• Concrete does not solidify from drying after mixing and placement;
the water reacts with the cement in a chemical process known as
hydration. This water is absorbed by the cement, which hardens,
bonding the other components together and eventually creating a
stone-like material.
• Concrete is used more than any other man made material on the
planet[1]. It is used to make pavements, building structures,
foundations, motorways/roads, overpasses, parking structures,
brick/block walls and footings for gates, fences and poles.
• As of 2005 about six billion cubic meters of concrete are made each
year, which equals one cubic meter for every person on Earth.
Concrete powers a US$35 billion industry which employs over two
million workers in the United States alone. Over 55,000 miles of
freeways and highways in America are made of this material. China
currently consumes 40% of world cement production.
Composition
• The composition of concrete is determined initially during
mixing and finally during placing of fresh concrete. The
type of structure being built as well as the method of
construction determine how the concrete is placed and
therefore the composition of the concrete mix (the mix
design).
• Cement
• Main article: Portland cement
• Portland cement is the most common type of cement in
general usage. It is a basic ingredient of concrete, mortar
and plaster
• Water
• Potable water can be used for
manufacturing concrete. The w/c ratio
(mass ratio of water to cement) is the key
factor that determines the strength of
concrete. A lower w/c ratio will yield a
concrete which is stronger, while a higher
w/c ratio yields a concrete with a lower
strength
Aggregates
• The water and cement paste hardens and develops
strength over time. In order to ensure an economical and
practical solution, both fine and coarse aggregates are
utilised to make up the bulk of the concrete mixture.
Sand, natural gravel and crushed stone are mainly used
for this purpose. However, it is increasingly common for
recycled aggregates (from construction, demolition and
excavation waste) to be used as partial replacements of
natural aggregates, whilst a number of manufactured
aggregates, including air-cooled blast furnace slag and
bottom ash are also permitted.
Admixtures
• Admixtures are materials in the form of powder
or fluids that are added to the concrete to give it
certain characteristics not obtainable with plain
concrete mixes. In normal use, admixture
dosages are less than 5% by mass of cement,
and are added to the concrete at the time of
batching / mixing. The most common types of
admixtures are:
• Accelerators speed up the hydration (hardening) of the
concrete.
• Retarders slow the hydration of concrete.
• Air-entrainers add and distribute tiny air bubbles in the
concrete, which will reduce damage during freeze-thaw
cycles.
• Plasticizers can be used to increase the workability of
plastic or "fresh" concrete, allowing it be placed more
easily, with less consolidating effort. Superplasticisers
allow a properly designed concrete to flow in place even
around congested reinforcing bars, see self
consolidating concrete described below. Alternatively,
they can be used to reduce the water content of a
concrete (water reducers) while maintaining workability.
This improves its strength and durability characteristics.
• Pigments can be used to change the colour of concrete,
for aesthetics.
• Additions
• Additions are very fine inorganic materials that usually have
pozzolanic or latent hydraulic properties. They are added at the
concrete mixer to improve the properties of concrete. The term is not
used when the materials are added at the factory as constituents of
blended cements.
• Fly ash: A by product of coal fired elgenerating plants, it is used to
partially replace Portland cement (by up to 60% by mass). The
properties of fly ash depend on the type of coal burnt. In general,
silicious fly ash is pozzolanic, while calcareous fly ash has latent
hydraulic properties.
• Ground granulated blast furnace slag (ggbs): A by product of steel
production, is used to partially replace Portland cement (by up to
80% by mass). It has latent hydraulic properties.
• Silica fume: A byproduct of the production of silicon and ferrosilicon
alloys. Silica fume is similar to fly ash, but has a particle size 100
times smaller. This results in a higher surface to volume ratio and a
much faster pozzolanic reaction. Silica fume is used to increase
strength and durability of concrete, but generally requires the use of
superplasticizers for workability
Characteristics
• During hydration and hardening, concrete
needs to develop certain physical and
chemical properties. Among other
qualities, mechanical strength, low
moisture permeability, and chemical and
volumetric stability are necessary.
• Workability
• Workability (or consistency, as it is known in Europe) is the ability of
a fresh (plastic) concrete mix to fill the form / mould properly with the
desired work (vibration) and without reducing the concrete's quality.
Workability depends on water content, chemical admixtures,
aggregate (shape and size distribution), cementitious content and
age (level of hydration)
• Curing
• Because the cement requires time to fully hydrate before it acquires
strength and hardness, concrete must be cured once it has been
placed. Curing is the process of keeping concrete under a specific
environmental condition until hydration is relatively complete. Good
curing is typically considered to use a moist environment which
promotes hydration, since increased hydration lowers permeability
and increases strength, resulting in a higher quality material.
Allowing the concrete surface to dry out excessively can result in
tensile stresses, which the still-hydrating interior cannot withstand,
causing the concrete to crack.
• Strength
• Concrete has relatively high compressive strength, but
significantly lower tensile strength (about 10% of the
compressive strength). As a result, concrete always fails
from tensile stresses — even when loaded in
compression. The practical implication of this is that
concrete elements subjected to tensile stresses must be
reinforced. Concrete is most often constructed with the
addition of steel or fiber reinforcement. The
reinforcement can be by bars (rebar), mesh, or fibres,
producing reinforced concrete. Concrete can also be
prestressed (reducing tensile stress) using internal steel
cables (tendons), allowing for beams or slabs with a
longer span than is practical with reinforced concrete
alone.
• Elasticity
• The modulus of elasticity of concrete is a funcion of the modulus of
elasticity of the aggregates and the cement matrix and their relative
proportions. The modulus of elasticity of concrete is relatively linear at
low stress levels but becomes increasing non-linear as matrix cracking
develops. The elastic modulus of the paste may be in the order of 10
GPa and aggregates about 45 to 85 GPa. The concrete composite is
then in the range of 30 to 50 GPa.
• Expansion and shrinkage
• Concrete has a very low coefficient of thermal expansion. However if
no provision is made for expansion very large forces can be created,
causing cracks in parts of the structure not capable of withstanding the
force or the repeated cycles of expansion and contraction.
• As concrete matures it continues to shrink, due to the ongoing reaction
taking place in the material. Brickwork made of clay tends to expand
for some time after manufacture of the bricks, and the relative
shrinkage and expansion of concrete and brickwork require careful
accommodation when the two forms of construction interface.
• Cracking
• Concrete is placed while in a wet (or plastic) state, and therefore can
be manipulated and molded as needed. Hydration and hardening of
concrete during the first three days is critical. Abnormally fast drying
and shrinkage due to factors such as evaporation from wind during
placement may lead to increased tensile stresses at a time when it
has not yet gained significant strength, resulting in shrinkage cracks.
The early strength of the concrete can be increased by keeping it
damp for a longer period during the curing process. Minimizing
stress prior to curing minimizes cracking. High early-strength
concrete is designed to hydrate faster, often by increased use of
cement, which increases shrinkage and cracking.
• Creep
• Creep is the term used to describe the permanent movement or
deformation of a material in order to relieve stresses within the
material. Concrete which is subjected to forces is prone to creep.
Creep can sometimes reduce the amount of cracking that occurs in
a concrete structure or element, but it also must be controlled. The
amount of primary and secondary reinforcing in concrete structures
contributes to a reduction in the amount of shrinkage, creep and
cracking.
• Because it is a fluid, concrete can be
pumped to where it is needed. Here a
concrete transport truck is feeding
concrete to a concrete pumper, which is
pumping it to where a slab is being poured
Types of concrete
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Regular concreteRegular concrete is the lay term describing concrete that is produced by
following the mixing instructions that are commonly published on packets of cement,
typically using sand or other common material as the aggregate, and often mixed in
improvised containers. This concrete can be produced to yield a varying strength from
about 10 MPa to about 40 MPa, depending on the purpose, ranging from blinding to
structural concrete respectively. Many types of pre-mixed concrete are available which
include powdered cement mixed with an aggregate, needing only water.
High-strength concrete
High-strength concrete is concrete with a compressive strength generally greater than
6,000 pounds/square inch (40 MPa). High-strength concrete is made by lowering the watercement (w/c) ratio to 0.35 or lower. Often silica fume is added to prevent the formation of
free calcium hydroxide crystals in the cement matrix, which might reduce the strength at
the cement-aggregate bond.
Low w/c ratios and the use of silica fume make concrete mixes significantly less workable,
which is particularly likely to be a problem in high-strength concrete applications where
dense rebar cages are likely to be used. To compensate for the reduced workability,
superplasticizers are commonly added to high-strength mixtures. Aggregate must be
selected carefully for high-strength mixes, as weaker aggregates may not be strong
enough to resist the loads imposed on the concrete and cause failure to start in the
aggregate rather than in the matrix or at a void, as normally occurs in regular concrete.
In some applications of high-strength concrete the design criterion is the elastic modulus
rather than the ultimate compressive strength.
Self-compacting concretes
During the 1980s a number of countries including Japan, Sweden and France developed a
range of concretes that were self-compacting. These self-compacting concretes (SCCs) are
characterised by their extreme fluidity, behaving more like a thick fluid that is self-leveling,
as opposed to the traditional concrete that needs consolidating, normally by vibration or
packing.
• Shotcrete
• Shotcrete uses compressed air to shoot (cast) concrete
onto (or into) a frame or structure. Shotcrete is frequently
used against vertical soil or rock surfaces, as it
eliminates the need for formwork. It is sometimes used
for rock support, especially in tunnelling. Today there are
two application methods for shotcrete: the dry-mix and
the wet-mix procedure. In dry-mix the dry mixture of
cement and aggregates is filled into the machine and
conveyed with compressed air through the hoses. The
water needed for the hydration is added at the nozzle. In
wet-mix, the mixes are prepared with all necessary water
for hydration. The mixes are pumped through the hoses.
At the nozzle compressed air is added for spraying. For
both methods additives such as accelerators and fiber
reinforcement may be used. [3]
• The term Gunite is occasionally used for shotcrete, but
properly refers only to dry-mix shotcrete, and once was a
proprietary name.
•
•
•
Pervious concrete
With pervious or "no fines" concrete, carefully controlled amounts of water
and cementitious materials are used to create a paste that forms a thick
coating around aggregate particles. A pervious concrete mixture contains
little or no sand (fines), creating a substantial void content. Using sufficient
paste to coat and bind the aggregate particles together creates a system of
highly permeable, interconnected voids that drains quickly. Typically,
between 15% and 25% voids are achieved in the hardened concrete, and
flow rates for water through pervious concrete are typically around 480 in./hr
(0.34 cm/s, which is 5 gal/ft²/ min or 200 L/m²/min), although they can be
much higher. Both the low mortar content and high porosity also reduce
strength compared to conventional concrete mixtures, but sufficient strength
for many applications is readily achieved.
Pervious concrete pavement is a unique and effective means to address
important environmental issues and support sustainable growth. By
capturing rainwater and allowing it to seep into the ground, porous concrete
is instrumental in recharging groundwater, reducing stormwater runoff, and
meeting US Environmental Protection Agency (EPA) stormwater
regulations. The use of pervious concrete is among the Best Management
Practices (BMPs) recommended by the EPA, and by other agencies and
geotechnical engineers across the country, for the management of
stormwater runoff on a regional and local basis. This pavement technology
creates more efficient land use by eliminating the need for retention ponds,
swales, and other stormwater management devices. In doing so, pervious
concrete has the ability to lower overall project costs on a first-cost basis.
• Cellular concrete
• Aerated concrete produced by the addition of an air entraining agent
to the concrete (or a lightweight aggregate like vermiculite ) is
sometimes called Cellular concrete. See also aerated autoclaved
concrete.
• Roller-compacted concrete
• Roller-compacted concrete, sometimes called rollcrete, is a lowcement-content stiff concrete placed using techniques borrowed
from earthmoving and paving work. The concrete is placed on the
surface to be covered, and is compacted in place using large heavy
rollers typically used in earthwork. The concrete mix achieves a high
density and cures over time into a strong monolithic block. [4] Rollercompacted concrete is typically used for concrete pavement, but has
also been used to build concrete dams, as the low cement content
causes less heat to be generated while curing than typical for
conventionally placed massive concrete pours.
• Asphalt concrete
• Strictly speaking, asphalt is a form of concrete as well, with
bituminous materials replacing Portland cement as the binder.
Cermet
• Cermet is an abbreviation for "'ceramic" and "metal." A CerMet is a
composite material composed of ceramic (cer) and metallic (met)
materials. A Cermet is ideally designed to have the optimal
properties of both a ceramic, such as high temperature resistance
and hardness, and those of a metal, such as the ability to undergo
plastic deformation. The metal is used as a binder for an oxide,
boride, carbide, or alumina. Generally, the metallic elements used
are nickel, molybdenum, and cobalt. Depending on the physical
structure of the material, cermets can also be metal matrix
composites, but cermets are usually less than 20% metal by volume.
• It is used in the manufacture of resistors (especially potentiometers),
capacitors, and other electronic components which may experience
high temperatures.
• Some types of cermet are also being considered for use as
spacecraft shielding as they resist the high velocity impacts of
micrometeoroids and orbital debris much more effectively than more
traditional spacecraft materials such as aluminum and other metals.
• One application of these materials is their use in vacuum tube
coatings which are key to solar hot water systems.
• Cermets are also used in dentistry as a material for fillings and
prostheses.
Bone
• Matrix
• The matrix comprises the other major constituent of
bone. It has inorganic and organic parts. The inorganic is
mainly crystalline mineral salts and calcium, which is
present in the form of hydroxyapatite. The matrix is
initially laid down as unmineralized osteoid
(manufactured by osteoblasts). Mineralisation involves
osteoblasts secreting vesicles containing alkaline
phosphatase. This cleaves phosphate groups and acts
as the foci for calcium and phosphate deposition. The
vesicles then rupture and act as a centre for crystals to
grow on.
• The organic part of matrix is mainly Type I collagen. This
is made intracellularly as tropocollagen and then
exported. It then associates into fibrils. Also making up
the organic part of matrix include various growth factors,
the functions of which are not fully known. Other factors
present include GAGs, osteocalcin, osteonectin, bone
sialo protein and Cell Attachment Factor.
Engineered wood
• Engineered wood, also called composite
wood, includes a range of derivative wood
products which are manufactured by
binding together wood strands, particles,
fibers, or veneers with adhesives to form
composite materials. These products are
engineered to precise design
specifications which are tested to meet
national or international standards.
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Types
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Glued laminated timber
Veneer-based
– Plywood
– Laminated veneer lumber (LVL)
– Stamina wood
Parallam
Parallel strand lumber
Particle-based
– Oriented strand board (OSB)
– Waferboard
– Particleboard (chipboard)
Fiberboard
– Insulation board
– Homasote
– Masonite
– Medium-density fiberboard (MDF)
– Hardboard
Mineral-bonded particleboard and fiberboard
– Cement board
– Fiber cement siding
– Gypsum board
– Papercrete
Strawboard
Wood-plastic composite
Plywood
• Plywood was the first type of engineered wood to be invented. It is
made from thin sheets of wood veneer, called plies or veneers.
These are stacked together with the direction of each ply's grain
differing from its neighbors' by 90° (cross-banding). The plies are
bonded under heat and pressure with strong adhesives, usually
phenol formaldehyde resin, making plywood a type of composite
material. A common reason for using plywood instead of plain wood
is its resistance to cracking, shrinkage, twisting/warping, and its
general high degree of strength.
• Types of plywood
• . Softwood plywood is usually made either of Douglas fir or spruce,
pine, and fir, and is typically used for construction and industrial
purposes. Decorative plywood is usually faced with hardwood,
including red oak, birch, maple, lauan (Philippine mahogany) and a
large number of other hardwoods.
• Plywood meant for indoor use generally uses the less expensive
urea-formaldehyde glue which has limited water resistance, while
outdoor and marine grade plywood are designed to withstand rot
and use a water resistant phenol-formaldehyde glue to prevent
delamination
• Plywood production
• Plywood production requires a good log, called a peeler, which is
generally straighter and larger in diameter than one required for
processing into dimensioned lumber by a sawmill. The log is peeled
into sheets of veneer which are then cut to the desired dimensions,
dried, patched and glued together to form the plywood panel. The
panel can then be patched, resized, sanded or otherwise refinished,
depending on the market it was intended for.
• History
• Plywood has been made for thousands of years; the earliest known
occurrence of plywood was in ancient Egypt around 3500 BC when
wooden articles were made from sawn veneers glued together
crosswise. This was originally done due to a shortage of fine wood.
Thin sheets of high quality wood were glued over a substrate of
lower quality wood for cosmetic effect, with incidental structural
benefits. This manner of inventing plywood has occurred repeatedly
throughout history. Many of the great English furniture makers such
as Sheridan used veneer as a raw material.
• Plywood is used in any application that needs
high quality wooden sheet material. -means
resistance to cracking, breaking, shrinkage,
twisting and warping.
• Plywood is also used as an engineering material
for stressed skin applications. -used in this
fashion for marine and aviation application since
the WW II era.
• Most notable is the British De Havilland
Mosquito bomber which was primarily made out
of wood. Plywood is currently used in stressed
skin applications quite succesfully, as in this
contemporary RJ.03 IBIS homebuilt aircraft
project.
Formica (plastic)
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Formica is a brand of composite materials
manufactured by the Formica Corporation based in
Cincinnati, Ohio, United States. In common use, the
term refers to the company's classic product, a heat
resistant, wipe-clean, plastic laminate of paper or
fabric with melamine resin.
Formica was invented in 1912 by Daniel J. O'Conor
and Herbert A. Faber, then working at Westinghouse.
They originally conceived it as an electrical insulator
as a substitute "for mica", hence the name they chose
when they left Westinghouse to set up their own
company in 1913.
In its early years, Formica manufactured insulation
along with other products such as phenolic composite
gears, developing its classic range of surfacing
laminates from the late 1920s. During World War II it
manufactured plastic-impregnated wooden airplane
propellers. Post-war, engineering uses declined,
ceasing in 1970 in favour of decorative laminates.
In the last quarter of the 20th century, after a
management buyout from its then owners American
Cyanamid, it diversified with products such as solid
surfacing, metal laminates and flooring materials.
Buckypaper
• Buckypaper is a thin sheet made from nanotubes that
are 250 times stronger than steel and 10 times lighter. It
is being developed by Dr. Ben Wang with other
professors and students from the Florida State University
research group the Florida Advanced Center for
Composite Technologies (FAC2T). The project has
already attracted research funding from the Army
Research Lab and Air Force Office of Scientific
Research.
• The name "Buckypaper" derives from buckyballs and
shows great promise as a building material for
everything from aerospace vehicles, body armor and
next-generation electronics and displays.
• Background
• Buckypaper is made from carbon nanotubes —
amazingly strong fibers about 1/50,000th the diameter of
a human hair that were first developed in the early
1990s. Buckypaper owes its name to
Buckminsterfullerene, or Carbon 60 — a type of carbon
molecule whose powerful atomic bonds make it twice as
hard as a diamond. Sir Harold Kroto, now a professor
and scientist with FSU's department of chemistry and
biochemistry, and two other scientists shared the 1996
Nobel Prize in Chemistry for their discovery of
Buckminsterfullerene, nicknamed "buckyballs" for the
molecules' spherical shape. Their discovery has led to a
revolution in the fields of chemistry and materials
science — and directly contributed to the development of
buckypaper.
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