Composite materials

Composite Materials
mkpq55.mp@gmail.com 1
1.Introduction
Many modern technologies require materials with unusual combination of
properties that cannot be made by conventional metal alloys. This is especially true
for materials that are needed for aerospace, satellites, submarines and other
transportation applications.
We require materials those are stronger than steel, lighter than aluminum and
stiffer than titanium. These anxieties can be contented by “composites”.
Composites are combination of two materials in which one of the materials,
called reinforcing phase, is in the form of fibers, sheets or particles that are embedded
in the other material called the matrix phase.
Thus a composite material posses a unique combination of properties, such as
stiffness , strength, hardness, weight, conductivity &corrosion resistance etc. that are
not possible by individual materials.

Composite Materials
2.TYPES OF COMPOSITE MATERIALS
Composites
Particle-reinforced Fiber- reinforced Structure
Large Dispersion Conti- Disconti- Laminates Sandwich
Particle strengthened nuous nuous Panels
(aligned) (short)
Aligned Randomly oriented
2.1 Particle Reinforced Composite
Large particle and dispersion-strengthened composites are the two
classifications of particle-reinforced composites
Fig. Particulate composites
 Large Particle Composites
The term “large” is used to indicate that particle matrix interactions cannot be
treated on the atomic or molecular level; rather, a continuous mechanism is used. For
most of these composites, the particulate phase is harder and stiffer than the matrix.
The degree of the reinforcement or improvement of the mechanical behavior depends
on strong bonding at the matrix particle inter phase.

Composite Materials
 Dispersion Strengthened Composites
For Dispersion Strengthened Composites the particles are normally much
smaller having diameters between 0.01 and 0.1 micrometer. The mechanism of
strengthening is similar to that of precipitation hardening. Thus plastic deformation is
restricted such that yield and tensile strengths, as well as hardness, improve.
Metals and metal alloys may be strengthened and hardened by uniform
dispersion of several volume percents of fine particles of very hard and inert material.
The dispersed phase may be metallic or non- metallic; oxide materials are often used.
2.2 Fiber-Reinforced Composites
Fig . Fiber composites
Technologically, the most important composites are those in which the
dispersed phase is in the form of fiber. Design goals are Fiber-Reinforced
Composites often include high strength and/or stiffness on weight basis. Fiber
reinforced composites with exceptionally high specific strengths and module
have been produced that utilize low-density fiber and matrix material.
Fiber length significantly affects the properties of Fiber-Reinforced
Composites. For critical length it gives maximum strength but any increase in
the length is useless. If the length is less than critical length then, it reduces the
strength. Depending on the fiber lengths these are classified as continuous and
discontinuous, whereas discontinuous (short) fibers may be aligned or
randomly oriented in the matrix.

Composite Materials
 Continuous And Aligned Fiber Composites
The properties of a composite having its fibers continuous and aligned
are highly anisotropic i.e. dependent on direction in which they are measured.
 Discontinuous And Aligned Fiber Composites
The reinforcement efficiency of Discontinuous and Aligned Fiber Composites
are lower than Continuous and Aligned Fiber Composites even though they are
becoming increasingly more important in commercial market. Chopped glass fibers
are used more extensively; however carbon and carbide discontinuous are also
employed. This short fiber composite can be produced having modulus of elasticity
and tensile strength that approaches 90% and 50% respectively, of their continuous
fiber parts.
 Discontinuous And Randomly Oriented Fiber Composites
Normally when the fiber orientation is random, short and
discontinuous fibers are used.
2.3 Structural Composites
A Structural Composite is normally composed of both homogeneous and
composite materials. The properties of which depend, not only on the properties of the
constituent materials but also on the geometrical design of the various structural
elements. Laminar composites and sandwiched panels are the two most common
structural composites.

Composite Materials
 Laminar or Layered Composites
Laminar or layered composites are those having distinct layers of materials
bonded together in some manner and include thin coatings. Plywood is probably the
most common material in this category and is an example of laminate material.
Strength and fracture resistance are improved properties are some what
uniform within the plane of the sheet. Swelling and shrinkage tendencies are
minimized and large pieces are now available at reasonable cost.
 Sandwich Panels
Sandwich Panels composites consist of two strong outer sheets, or faces,
separated by a layer of less dense material or core, which has lower stiffness and
lower strength. The faces bear most of the plane loading and also any transverse
bending stresses. Typical face material includes aluminium alloy, fiber reinforced
plastics, titanium, steel and plywood.
Sandwich material is a laminar structure composed of a thick, low density,
core, placed between thin high-density surfaces. Corrugated cardboard is an example
of sandwich structure.

Composite Materials
3. MANUFACTURING TECHNOLOGY
A major new breakthrough in composites manufacturing technology is not
likely to occur in the foreseeable future. Most likely, there will be incremental
improvements to existing manufacturing technologies. For composites to become
competitive with metals, cost reduction has to occur besides durability,
maintainability and reliability. Some of the manufacturing technology developments
expected to occur in the foreseeable future is described below.
 Filament Winding
Improvements in automation, speed, variable thickness, pad-up insertion,
consistent quality, flexibility in fiber orientation, control of resin and void content and
shapes other than cylinders are expected in near future. A combination of robotic and
traditional filament winding (7 to 10-axis windings) system is being developed to
wind complex multi-axes shapes, such as T and elbow shapes.
 Resin Transfer Molding
This technique has to be improved for handling large & complex designs with
varying skin thickness ranging from less than 1/4" to more than 1". Further, there is
scope for developing a new cost-effective resin system.
 Pultrusion
Pullers
Fig. Pultrusion process
Pre forming
die
Cutting die

Composite Materials
For pultrusion to become an acceptable & popular composite manufacturing
technology, it must be possible to pultrude complex multi-element cross sections,
such as J-stiffened panels and constant airfoil section.
 Continuous Sandwich Panel
Presently this method is limited to making flat constant sandwich panels.
Future improvements will improve quality and speed of fabrication for fabricating
complex shapes and variable thickness.
 3-D Weaving
The advantages of 3-D weaving to obtain a 3-D fabric are widely known, but
the cost has been prohibitively high. A few automated and semi-automated systems
have been created or are under development to reduce cost.
These manufacturing methods have great potential for high volume
production, especially when combined with the use of thermoplastics. Application is
limited to small to medium size parts. Sports goods & industrial products will benefit
from this group of technologies.

Composite Materials
4. COMPOSITES - TYPICAL PROPERTIES
 DesignFlexibility
With their huge design flexibility, composites have a decisive advantage over
conventional materials in many applications. Today, composite materials are
everywhere from modern homes and offices to the harsh conditions of outer space.
 High Strength and Stiffness to Weight Ratio
Characteristic high strength and stiffness to weight ratios make composite
structures ideal for many applications. This is particularly true where movement is
involved, such as automobiles, ships, and aircraft, where reduced weight means
significant reduction in operating costs.
 Corrosion Resistance
Composites created with anti-corrosive properties are widely used in marine
applications, where the salty environment would degrade conventional materials.
 Reduced Manufacturing Costs
Another quality of composites is the ability to produce a part in its final shape
without the need for additional machining. The fiberglass hull of a boat is one
example. The ability to consolidate multiple parts into a single composite component
further reduces manufacturing costs.
 Unique Attributes
One unique attribute of composites is that the design engineer may choose the
properties of the material as the optimum component shape is being determined. This
is in contrast to conventional design methods, where the component design must
conform to the material’s properties.

Composite Materials
For example, the engineer can specify the orientation of the fibers to obtain the
required strength. Some portion of the fibers may be oriented in the direction of the
principal load, while others are configured to carry shear and off-axis loads.
Processing methods – in temperature curing cycles, vacuum pressures, and other
factors – also allow great variability in the properties of the end product.
 Convenient Shapes, Unpredictable Properties
The ability to create a composite in its final shape is efficient for
manufacturing but complicates testing. There is often no clear relationship between
the properties of a test specimen and the properties of the final product. Therefore
testing must be performed at different stages of production to measure the properties
in both the constituent materials and the final component or structure.
 Tension
Figure 1 shows a tensile load applied to a composite. The response of a
composite to tensile loads is very dependent on the tensile stiffness and strength
properties of the reinforcement fibers, since these are far higher than the resin system
on its own.
Figure 1 – Illustrates the tensile load applied to a composite body.

Composite Materials
 Compression
Figure 3 shows a composite under a compressive load. Here, the adhesive and
stiffness properties of the resin system are crucial, as it is the role of the resin to
maintain the fibers as straight columns and to prevent them from buckling.
Figure 2 - Illustrates the compression load applied to a composite body.
 Shear
Figure 3 shows a composite experiencing a shear load. This load is trying to
slide adjacent layers of fibers over each other. Under shear loads the resin
plays the major role, transferring the stresses across the composite. For the
composite to perform well under shear loads the resin element must not only
exhibit good mechanical properties but must also have high adhesion to the
reinforcement fiber. The interlinear shear strength (ILSS) of a composite is
often used to indicate this property in a multiplayer composite (‘laminate’).
Figure 3 - Illustrates the shear load applied to a composite body

Composite Materials
5.COMPARISON WITH OTHER STRUCTURAL MATERIALS
Due to the factors described above, there is a very large range of mechanical
properties that can be achieved with composite materials. Even when considering one
fiber type on its own, the composite properties can vary by a factor of 10 with the
range of fiber contents and orientations that are commonly achieved. The comparisons
that follow therefore show a range of mechanical properties for the composite
materials. The lowest properties for each material are associated with simple
manufacturing processes and material forms (e.g. spray lay-up glass fiber), and the
higher properties are associated with higher technology manufacture (e.g. autoclave
molding of unidirectional glass fiber prepreg), such as would be found in the
aerospace industry.
For the other materials shown, a range of strength and stiffness (modulus)
figures are also given to indicate the spread of properties associated with different
alloys, for example.
Figure– Tensile Strength of Common

Composite Materials
fig. Specific strengths of materials
The above Figures clearly show the range of properties that different
composite materials can display. These properties can best be summed up as high
strengths and stiffness combined with low densities. It is these properties that give rise
to the characteristic high strength and stiffness to weight ratios that make composite
structures ideal for so many applications. This is particularly true of applications,
which involve movement, such as cars, trains and aircraft, since lighter structures in
such applications play a significant part in making these applications more efficient.
The strength and stiffness to weight ratio of composite materials can best be
illustrated by the following graphs that plot ‘specific’ properties. These are simply the
result of dividing the mechanical properties of a material by its density. Generally, the
properties at the higher end of the ranges illustrated in the previous graphs are
produced from the highest density variant of the material.

Composite Materials
6. ADVANTAGES OF COMPOSITES
Different materials are suitable for different applications. When composites
are selected over traditional materials such as metal alloys or woods, it is usually
because of one or more of the following advantages:
 Cost
1. Prototypes
2. Mass production
3. Maintenance
4. Long term durability
5. Production time
6. Maturity of technology
 Weight:
1. Light weight
2. Weight distribution
 Strength and Stiffness:
1. High strength-to-weight ratio
2. Directional strength and/or stiffness
 Dimension:
1. Large parts
2. Special geometry
 Surface Properties:
1. Corrosion resistance
2. Weather resistance
 Thermal Properties:
1. Low thermal conductivity
2. Low coefficient of thermal expansion
 Electric Property:
1. High dielectric strength
2. Non-magnetic 3. Radar transparency

Composite Materials
7.APPLICATIONS OF COMPOSITES
The unique properties created in the formation of composite materials, are
useful for wide range of engineering applications. The most important uses of
composite material in today’s society are in commercial aerospace, defense, space
technology, recreation and general engineering and industrial structures.
 Aerospace Industry:
Composites make up to 80% of the structural rate of some aircrafts. The
excellent strength to weight and stiffness to weight characteristics of composites are
ideal for use in aircrafts, where minimum weight is essential.
The weigh gained by using composites as an alternative to aluminium has
meant that an increased payload can be carried and fuel consumption has decreased.
This has meant that the cost of building a commercial plane has fallen and
consequently the cost of air travel has become affordable to more people.
Composite materials are also suited to use them in aircraft, as they are durable
and often highly resistive to environmental corrosion, weathering and fire. This means
that they will have a much longer working life than previously used aluminium alloys
and will also have high safety standards.
.
 Formula 1 Racing Cars
The car must weight a maximum of 605 kilos, and therefore the weight is
an important consideration. The designer needs the maximum stiffness with least
possible weight. This means that the composite materials are ideal. Another
improvement brought by the use of composites is that the can be molded to fit
complicated shape; many fewer pieces are needed to construct the car. The
composite pieces are fixed with an epoxy resins instead of metal bolts, which
offers further weight decrement and aerodynamic advantages.

Composite Materials
 Transportation Infrastructure
Composite materials are being used increasingly in the design of high-speed
transport vehicles, such as railway industry and fast ship construction. The resulting
improvements are very significant.
1. Train Construction
Composite material and fabric materials are increasingly used in modern trend
construction, providing significant cost reduction. The reduction in the weight of the
frame allows high speed as well as reducing energy consumption. It also allows low
center of gravity, giving enhanced stability and reduces the starting and stopping
inertia.
The high stiffness of materials means that the supporting framework becomes
unnecessary, increasing the passenger room in the train. The train construction is
made from panels which are quick to fit and inter changeable. Therefore if there is
any damage to the panels they can be replaced easily.
2. Fast Ship Construction
Naval architects are rapidly adopting the latest construction techniques using
composites. Whether for structural or non-structural applications, their aim is to
improve the performance and decrease weight.

Composite Materials
8. FAILURES OF COMPOSITES MATERIALS
 Layer cracking:
This occurs in multi-angle when the load direction is perpendicular to that of the
fibers, the amount of stress on the material increases due to transverse tension.
Small cracks appear in the matrix of the layer and as the load increases they can be
transferred to other layers.
 De-lamination:
This usually occurs at plate edges where out of planeloads can be placed on
some off angle layers. This causes de-lamination. It can be avoided by altering
stacking sequence.
 Fiber breakage:
Discontinuities in an individual fiber cause weakness and when subjected to
tensile stress or compressive buckling can cause fiber fracture. This leads to matrix
cracking and due to high stress these cracks lead to fracture. These breaks can
intrude into other layers a sizable weakness.
 Interfacial de-bonding:
Some fiber composites have an applied coating which protect the fiber from
the corrosion and act as a primer, to help the bond between the matrix and fiber this
inter face can de-bond under stress so the matrix can no longer transfer the stress to
fiber causing weakness.

Composite Materials
9.FUTURE SCOPE
1) Improvements are being made in the methods of fabrication, in quality
assurance, in reliability and in the predictability of the behavior of composite
materials during their service life.
2) Extensive developments in metal matrix composites are found in aerospace
application requiring strength and stiffness at elevated temperatures
particularly continuous fiber reinforced titanium alloys.
3) Developments are taking place in techniques for three-dimensional
reinforcement of composites and for improvement in their resistance to
compression, buckling and impact.
4) Efforts are being made to increase the toughness and improve elongation
capabilities of epoxy resin matrices.
5) Major developments in ceramic matrix composites are expected in the area of
improving the strength, toughness and failure resistance under impact
loadings.
6) An important area of study is reduction in the costs of raw materials and
fabrication of composite materials.
7) One more important area of research is the use of fiber-reinforced polymers in
high cycle fatigue application.

Composite Materials
10.CONCLUSION
The composite materials are the materials having high strength to
weight ratios, non-corrosive nature, and low specific gravities, high damping
characteristics etc. Therefore composite materials have great potential in next
decades.
Advanced designed guidelines for industrial use required to reduce the
cost for the development of new structural components. In future there will be era of
materials. i.e. composites material only.

Composite Materials
REFERENCE
BOOKS
1. O.P. Khanna,“Materials science & Metallurgy”
2. Kalpakjian “Manufacturing Engg.& Technology”
3. P.C. Sharma “ProductionTechnology”
WEBSITES
1.www.Google.com
2.www.azom.com
3.www.instron.com

Composite Materials
Additional Ingredients to make good compost
 Soil with a clay component – to hold nutrients and reduce nutrient loss
 Gypsum – to add Sulphur essential to activate the nutrients on soil particles
 Rock Dust – can add up to 5%
 Rock Phosphate – for phosphorous – up to 5%
 Lime – a sprinkle unless the ph is too low.
 Wood Ash – but not too much or it will raise your ph too high
 Worm teas, comfrey teas, nettle teas
 Sawdust, used hay, straw
 Paper, Corn Stalks
 Manures, Blood, and Bone
Basically, anything that is biodegradable as long as you keep that carbon-
nitrogen balance, water balance, aeration, and Ph correct.
You can put meat products in your compost as long as you bury them deep
enough to prevent rats and other vermin getting at them. But this can be
tricky.
I personally find putting a Compote into your compost pile makes
disposing of all your kitchen waste, (especially meat products), super
easy. This way you can lock up your meat, dairy, eggs, and anything
biodegradable inside your Compote inside your heap. This improves the
overall nutrient content of your compost. It will bring the worms as well
who in turn improve your compost nutrient mix. Or plant a few
Compotes in your garden if you couldn’t be bothered with a compost heap,
which generally speaking is a lot of hard work.
So what makes good compost?
In the end, don’t worry too much about your compost (unless it turns into
a big smelly mess). It is still the best way to nourish your plants, dispose
of waste, and help the environment even though each particular batch may
not be perfect. But it does require large quantities of materials to
produce a small amount of compost. Understanding how all the elements
in your soil and your compost interact with each other to produce great
soil is a complex process that is even more complex to describe.
Basically, it comes down to always mixing as many different materials as
you can in your compost heap. This will ensure you have a pretty good
chance of producing “good compost” that is nutrient rich to make your
plants grow.

Composite Materials
What not to put in your Compost heap?
Gum leaves, as well as Pine needles, contain a chemical that stops any
other seed from growing under that tree. This means that particular tree
can utilize all the available water and nutrients they need to grow and
don’t have to share resources with other trees. This is important because
these trees are usually found in dry, nutrient-poor areas where there is
likely to be competition for any available water and nutrients.
For this reason, Gum leaves & Pine needles should NOT be added to a
compost heap.
Of course, there are all the other “usual” suspects that don’t work well in
a worm farm or outdoor compost heaps such as Meat, Dairy, Eggs, Oil,
Onions and any citrus waste. But you can put all these items in a Compote
if you own a Compote.
http://agriculture.vic.gov.au
https://www.farmwest.com/
http://www.teravita.com
https://www.agweb.com

Composite Materials
www.apal.com.au
Bob James
Lovel, H. 2014; Quantum Agriculture Biodynamics and Beyond;
Quantum Agriculture Publishers; 2014

Composite materials

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