Introduction to composite materials

1. Composite material

2. Composite material is a material which is produced
from two or more constituent materials. These
constituent materials have notably dissimilar
chemical or physical properties and are merged to
create a material properties unlike the individual
elements. Within the finished structure, the
individual elements remain separate and distinct.
What is a composite Material?

3. • Composites can be very strong and stiff, yet very light in
weight, so ratios of strength -to - weight and
stiffness -to - weight are several times greater than steel or
aluminum.
• Fatigue properties are generally better than for common
engineering metals.
• Toughness is often greater too
• Composites can be designed that do not corrode like steel
• Possible to achieve combinations of properties not attainable
with metals, ceramics, or polymers

4. • The tensile strength of composite material is 4-6 times
higher than conventional materials such as steel,
aluminum, etc.
• They have better torsion and stiffness properties.
• They are 30-45% lighter than aluminum structures
designed for the same functional requirements.
• As they are lightweight, strong, stiff, and tough, Composites
are mainly used for making Fuselage and wings of an
aircraft
• Composites make less noise during operation and provide
less vibration.

5. 1. Traditional composites – composite materials that occur in
nature or have been produced by civilizations for many
years
Examples: wood, concrete
2. Synthetic composites - modern material systems normally
associated with the manufacturing industries, in which the
components are first produced separately and then
combined in a controlled way to achieve the desired
structure, properties, and part geometry

6. Nearly all composite materials consist of two phases:
1. Primary phase - forms the matrix within which the secondary
phase is imbedded
2. Secondary phase - imbedded phase sometimes referred to as a
reinforcing agent, because it usually serves to strengthen the
composite
The reinforcing phase may be in the form of fibers, particles, or
various other geometries

7. 7
:
-- Matrix - is continuous
-- Dispersed - is discontinuous and
surrounded by matrix
Fig.1

8. Composite Structural Organization: the design
variations

9. Functions of matrix
 Binds fibre
 Act as medium
 Protect fibre
 Prevent propagation of cracks.

10. Essentials of matrix phase
 It should be ductile
 Bonding strenth should be high
 Corrosion resistant

11. Classification of dispersed phase
 The dispersed phase can be fibre particle etc.
 Fibres:
1.Glass fibres
2.Carbon fibres
3.Aramid fibres(Aromatic)
 Particles (metallic or non metallic)
 Whiskers: thin crystals with high impact ratio e.g. graphite,
silicon carbide etc.

12. • It increases the mechanical properties of the composite.
• It provides strength and stiffness to the composite material
in one direction as reinforcement carries the load along the
length of the fiber
• It also increases the Co-efficient of thermal expansion and
the conductivity.

13. • Open Molding
•Closed molding
•Cast polymer molding

14. Open Molding / Hand layup
• Fiber reinforcements are placed by hand in a mold and resin is
applied with a brush or roller
• This process is used to make both large and small items, including
boats, storage tanks, tubs and showers.

15. Closed Molding
• Reinforcement material is loaded into a closed mold, the mold is
clamped, and resin is pumped in (through injection ports) under
pressure.
• This process produces complex parts with smooth finishes

16. Cast polymer Molding
• A mixture of resin and fillers are poured into a mold (typically without
reinforcements) and left to cure or harden.
• These molding methods sometimes use open molding and sometimes
use closed molding.

17. • Composites are more brittle than wrought metals and thus
are more easily damaged.
• Many of the polymer-based composites are subject to attack
by chemicals or solvents, just as the polymers themselves are
susceptible to attack.
• Composite materials are generally expensive
• Manufacturing methods for shaping composite materials are
often slow and costly

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