Composite Materials

ME 2302 : Introduction to Materials Science and
Manufacturing Engineering
Part A: Engineering Materials
Composite Materials
Dr. Ruwan Gallage
WHY STUDY Composites?

Many of our modern technologies require materials with unusual
combinations of properties that cannot be met by the conventional
metal alloys, ceramics, and polymeric materials. This is especially
true for materials that are needed for aerospace, underwater, and
transportation applications.
For example, aircraft engineers are increasingly searching for

structural materials that have low densities, strong, stiff, abrasion
and impact resistant, and are not easily corroded.
Boeing 787
What is composite material?

There are no universally accepted definition. If a material satisfied
the following condition is called as composite ;
(a) It consists of two or more physically and/or chemically distinct ,
suitably arranged or distributed phases.
(b) It has properties that are different from either parent material.
(c) It is manufactured. (Except wood, bone)
Many composite materials are composed of just two phases; one is
termed the matrix, which is continuous and surrounds the other
phase, often called the dispersed phase (fiber or particles).
Example for composite materials use in Engineering are concrete,

chip board, fiber reinforced composite, etc.
Composites that occur in nature:

Wood consists of strong and flexible cellulose fibers surrounded
and held together by a stiffer material called lignin.
Bone is a composite of the strong yet soft protein collagen and
the hard, brittle mineral apatite.
(a) Classification of composites according to the

reinforcement geometry
1. Fiber-reinforced composites
2. Particulate composites
3. Structural composites ( Laminar, sandwich)
Particles
(Carbon)
matrix:
(Rubber)
Automobile tires
Excellent strength-to-weight ratio, stiffness and fatigue resistance

Consist of two phases: the fiber and matrix
Types of fibers
1. Glass fibers: Glass fibers are silica (~50 %) based. Quite cheap and use for
reinforcement of plastics (Fiberglass)
2. Carbon fibers: Carbon is a very light element. Graphite form is
considered for carbon fibers.
3. Ceramics fibers: Commonly use Al2O3 fibers, SiC fibers. Possibility to use at
high temperature , Chemically inert.
4. Organic fibers: Kevlar (commercial name)
5. Metallic fibers: Wire form of Ti, W, Ta, Mo etc.
The fiber are responsible for handling the applied load.
1. Fiber-reinforced composite
Types of matrix
1. Polymeric materials: Polyester resin (commonly use due to low
cost), epoxy resins, vinyl ester resin
2. Metal : Super alloys, Aluminum (Al), Magnesium(Mg),
Titanium(Ti), Cupper(Cu ) and their alloys
3. Ceramics: Alumina (Al2O3,), Zirconia (ZrO2)

The matrix must
- be able to transfer the mechanical load to the fiber,
- be able to protect the individual fibers from surface damage
as a result of mechanical abrasion or chemical reactions with
the environment,
- has adequate adhesive bonding forces between fiber to
minimize fiber pull-out to get the ultimate strength of
composite
Impact of the fiber amount and orientation on performance of

composite
Most fiber reinforced composite contain 35 % to 50% of fibers by

volume. (When fiber fraction exceeds about 80%, there is not
enough matrix materials to completely surrounded the fiber and
transfer the load effectively.)
Aligned fibers results in the more

reinforcing in aligned direction than any
other direction.
Randomly oriented fibers are isotropic and
providing same properties in all direction.
Produce more easier and inexpensive
Fabric fibers results in higher strength and
ability to withstand loads in multiple
directions. More complicated and
manufacturing process is expensive.
2. Particulate composites
Cannot provide the same strength as fiber reinforced composites
but much easier to manufacture and inexpensive
Contain large number of particles called aggregates that help to

withstand composite in compressive loads. Possessing the same
properties in all direction (Isotropic)
Most common particulate composites are Portland cement

concrete and Asphalts concrete (Mineral aggregates with tar and
binders, etc., use for constructing roadways and parking lots.) .
Concrete
Asphalts concrete
3. Structural composites ( Laminar, Sandwich)

Normally composed of both homogeneous materials 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 composite
Composed of two-dimensional sheets or panels
that have a preferred high-strength directional
arrangement of fibers. (such as found in wood
and continuous and aligned fiber-reinforced
plastics). The layers are stacked and
subsequently cemented together such that the
orientation of the high-strength direction varies
with each successive layer.
Sandwich composite
. Consists of two outer sheets that are separated and adhesively bonded to a
thicker core.
The outer sheets are made of a relatively stiff and strong material, typically
aluminum alloys, fiber-reinforced plastics, titanium, steel, or plywood; they impart
high stiffness and strength to the structure, and must be thick enough to
withstand tensile and compressive stresses that result from loading.
The core material is lightweight. Core materials typically fall within three
categories: rigid polymeric foams (i.e., phenolics, epoxy), wood and honeycombs
(b) Classification of composites according to the matrix

materials:
1. Polymer-matrix composite (PMC)
2. Metal-matrix composite (MMC)
3. Ceramic-matrix composite (CMC)
Fracture surface of a SiC fibrereinforced Cu metal matrix

composite
1. Polymer- matrix composite (PMC)

Polymer resin as the matrix, with fibers as the reinforcement medium.
These materials are wildly used in various applications, as well as in the
largest quantities, due to room-temperature properties, ease of
fabrication, and cost.
1.1 Glass Fiber-Reinforced Polymer Composites (Fiberglass)
It is readily available and may be fabricated into a glass-reinforced

plastic economically using a wide variety of composite-manufacturing
techniques.
When coupled with the various plastics, it can be used in a variety of
corrosive environments.
Applications: Automotive and marine bodies, plastic pipes, storage
containers, and industrial floorings. (The transportation industries are
utilizing these to decrease vehicle weight and boost fuel efficiencies)
1.2 Carbon Fiber-Reinforced Polymer Composites
Carbon fibers have the highest specific modulus and specific

strength of all reinforcing fiber materials.
At room temperature, carbon fibers are not affected by

moisture or a wide variety of solvents, acids, and bases.
These fibers exhibit a diversity of physical and mechanical

characteristics.
Expensive than other composites ( However, manufacturing

processes have been developed that are relatively inexpensive
and cost effective)
Applications: Sports equipment (fishing rods, golf clubs),

pressure vessels, and aircraft structural components.
2. Metal - matrix composite (MMC)

Ductile metal as the matrix, with fibers as the reinforcement medium.
May be utilized at higher service temperatures than their base metal
counterparts.
Some of the advantages of these materials over the polymer-matrix

composites(PMC) include higher operating temperatures,
nonflammability, and greater resistance to degradation by organic fluids.
Much more expensive than PMC.
Applications: Automobile industries (some engine components aluminum-alloy matrix with carbon fibers), extruded stabilizer bars,
transmission components.
3. Ceramic- matrix composite (CMC)

Ceramic materials are inherently resilient to oxidation and
deterioration at elevated temperatures. Some of these materials would
be ideal candidates for use in high-temperature applications, specifically
for components in automobile and aircraft gas turbine engines.
Referencess:
1. http://en.wikipedia.org/wiki/Ceramic_matrix_composite
2. http://en.wikipedia.org/wiki/Metal_matrix_composite
3. http://en.wikipedia.org/wiki/Composite_material

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ME 2302 : Introduction to Materials Science and

Dr. Ruwan Gallage

WHY STUDY Composites?

For example, aircraft engineers are increasingly searching for

What is composite material?

Example for composite materials use in Engineering are concrete,

Composites that occur in nature:

(a) Classification of composites according to the

Excellent strength-to-weight ratio, stiffness and fatigue resistance

The fiber are responsible for handling the applied load.

3. Ceramics: Alumina (Al2O3,), Zirconia (ZrO2)

Impact of the fiber amount and orientation on performance of

Most fiber reinforced composite contain 35 % to 50% of fibers by

Aligned fibers results in the more

Contain large number of particles called aggregates that help to

Most common particulate composites are Portland cement

3. Structural composites ( Laminar, Sandwich)

(b) Classification of composites according to the matrix

Fracture surface of a SiC fibrereinforced Cu metal matrix

1. Polymer- matrix composite (PMC)

It is readily available and may be fabricated into a glass-reinforced

1.2 Carbon Fiber-Reinforced Polymer Composites

Carbon fibers have the highest specific modulus and specific

At room temperature, carbon fibers are not affected by

These fibers exhibit a diversity of physical and mechanical

Expensive than other composites ( However, manufacturing

Applications: Sports equipment (fishing rods, golf clubs),

2. Metal - matrix composite (MMC)

Some of the advantages of these materials over the polymer-matrix

Much more expensive than PMC.

3. Ceramic- matrix composite (CMC)

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