Composites-Everything you need to know

Composites are materials formed by combining two or more different materials to achieve better properties.
They consist of a reinforcement and a matrix that work together to improve strength and durability.
Composites are lightweight, strong, and resistant to corrosion.
They are widely used in aerospace, automotive, construction, and marine applications.

COMPOSITES

1. Definition

A composite material is an engineered material made by combining two or more physically and chemically different materials to produce a material with superior properties compared to the individual constituents.

A composite generally consists of:

Matrix → continuous phase (binds and protects reinforcement)
Reinforcement → discontinuous phase (provides strength and stiffness)

2. Need for Composites

Conventional materials (metals, polymers, ceramics) often cannot meet modern engineering demands such as:

High strength with low weight
Corrosion resistance
High fatigue life
Tailored properties

Composites overcome these limitations.

3. Constituents of Composites

3.1 Matrix Materials

The matrix:

Holds reinforcement in position
Transfers load to reinforcement
Protects reinforcement from environment

Types of matrix materials:

a) Polymer Matrix

Epoxy, polyester, nylon
Lightweight, corrosion resistant

b) Metal Matrix

Aluminum, magnesium, titanium
High temperature resistance

c) Ceramic Matrix

Silicon carbide, alumina
High thermal and wear resistance

3.2 Reinforcement Materials

Reinforcement improves:

Strength
Stiffness
Wear resistance

Forms of reinforcement:

Fibers (glass, carbon, aramid)
Particles (SiC, Al₂O₃)
Flakes

4. Classification of Composites

4.1 Based on Reinforcement Geometry

a) Particulate Composites

Reinforcement in particle form
Isotropic properties
Example: Concrete, Al–SiC

b) Fiber-Reinforced Composites

Continuous or short fibers
Example: GFRP, CFRP

c) Laminar Composites

Layered structure
Example: Plywood, laminated glass

d) Structural Composites

Load-bearing structures
Example: Sandwich panels

4.2 Based on Matrix Material

Type	Matrix	Example
PMC	Polymer	GFRP
MMC	Metal	Al–SiC
CMC	Ceramic	SiC–SiC

5. Manufacturing Methods of Composites

5.1 Hand Lay-Up

Fibers placed manually
Resin applied
Low cost, labor intensive

5.2 Compression Molding

High pressure and temperature
Good surface finish

5.3 Filament Winding

Fibers wound on rotating mandrel
High strength components

5.4 Pultrusion

Continuous process
Uniform cross-sections

5.5 Resin Transfer Molding (RTM)

Resin injected into closed mold
Better quality and repeatability

6. Properties of Composites

High strength-to-weight ratio
Excellent fatigue resistance
Corrosion resistance
Tailorable directional properties
Good thermal and electrical insulation

7. Advantages of Composites

Lightweight
High stiffness and strength
Long service life
Design flexibility
Reduced maintenance

8. Limitations of Composites

High initial cost
Complex manufacturing
Difficult inspection and repair
Recycling challenges
Anisotropic behavior

9. Applications of Composites

Aerospace

Aircraft wings, fuselage
Helicopter blades

Automotive

Body panels
Drive shafts

Marine

Boat hulls
Propellers

Construction

Bridge decks
Reinforced concrete

Sports & Medical

Tennis rackets
Prosthetic limbs

10. Failure of Composites

Fiber breakage
Matrix cracking
Delamination
Fiber–matrix debonding

11. Comparison with Conventional Materials

Property	Metals	Composites
Weight	High	Low
Corrosion	Poor	Excellent
Strength	Moderate	Very high
Cost	Lower	Higher

12. Conclusion

Composites are advanced engineering materials essential for modern industries due to their superior performance, lightweight nature, and customizable properties. Proper design, material selection, and manufacturing are crucial for their successful application.