Unit 3: Composite Materials
Course Code: CHM-DSM-351
Paper Name: Advance Materials (Minor)
Table of Contents
1. What are Composite Materials?
A composite is a material made from two or more constituent materials with significantly different physical or chemical properties. When combined, they produce a material with characteristics different from the individual components.
Key Advantages:
- High Strength-to-Weight Ratio: Very strong but much lighter than metals.
- Corrosion Resistance: They do not rust like steel.
- Design Flexibility: Can be molded into complex shapes easily.
2. The Two Main Phases
A composite material is generally made of two distinct parts:
- Matrix (Continuous Phase): The primary material that surrounds and holds the reinforcement in place. It protects the reinforcement from the environment and transfers the load to it.
- Reinforcement (Dispersed Phase): The material added to the matrix to improve its properties (like strength or stiffness).
3. Classification by Matrix
Composites are usually named after the type of matrix they use:
| Classification | Matrix Material | Typical Properties |
|---|---|---|
| PMC (Polymer Matrix) | Resins (Epoxy, Polyester) | Lightweight, low cost, used in sports and aerospace. |
| MMC (Metal Matrix) | Aluminum, Magnesium | High strength at high temperatures, used in engine parts. |
| CMC (Ceramic Matrix) | Silicon Carbide, Alumina | Extreme heat resistance, used in jet engines and brake discs. |
4. Types of Reinforcements
Reinforcements come in different shapes, which changes how the composite behaves:
- Fiber Reinforcement: Long, thin strands (Carbon fiber, Glass fiber). These provide the highest strength in the direction of the fiber.
- Particle Reinforcement: Small bits of material (like sand or metal particles). These improve wear resistance.
- Laminar Composites: Sheets of material glued together (like Plywood or high-tech laminates).
5. Applications
- Aviation: Modern planes like the Boeing 787 are over 50% composite to save fuel.
- Construction: Fiber-reinforced concrete and bridge cables.
- Automotive: Carbon fiber parts in high-performance cars.
6. Exam Focus: Tips and FAQs
Frequently Asked Questions
Q: Is an alloy a composite?
A: No. An alloy is a homogeneous mixture (uniform throughout), while a composite has macroscopically distinct phases you can often see under a microscope.
Q: Why is the Matrix important if the Reinforcement is the strong part?
A: Without the matrix, the reinforcement would just be a pile of loose fibers or dust. The matrix binds them and allows them to share the weight/load.
Q: What is the most common reinforcement used in PMCs?
A: Glass fiber (resulting in Fiberglass) and Carbon fiber.