CHAPTER - 01
(POLYMER COMPOSITE)
Think Life......Without Composite.......🤔🤔
(BASICS OF COMPOSITE)
Composite:
A composite material is made by combining two or more distinct materials to create a new one with superior properties.
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A composite material is a type of material that is created by combining two or more constituent materials with dissimilar chemical or physical properties. In combining these two materials, the resulting composite material will have new properties superior to the original components.
- These materials typically consist of a matrix and reinforcement (Fiber).
- The matrix binds the reinforcement, which usually provides strength and rigidity.
- Composites are often used in advanced technology applications, such as in aircraft, race yachts, and skis.
Advantages (Why composite materials are extensively used ?)
The main benefits of composite materials is of course the enhanced properties that they can offer compared to traditional material which make them the best choice for applications in demanding industries that require properties. Several advantages also giving below-
- High strength/weight ratio
- Excellent Rigidity
- Lower Cost
- Design versatility. & unlimited moulding size.
- Ease of fabrication
- Wide range of manufacturing techniques
- Excellent water resistance.
- Chemical resistance.
- Weathering resistance.
Components of Composite:
Matrix (Resin)
- The continuous phase that surrounds the reinforcement.
- It can be made of polymers, metals, or ceramics.
- It transfers load to the reinforcement and protects it from damage.
- Examples: Epoxy (Polymer Matrix), Aluminum (Metal Matrix), Silicon Carbide (Ceramic Matrix).
- Unsaturated Polyester Resins: Most common for FRP; cured using catalysts like cobalt naphthenate.
- Epoxy Resins: Low shrinkage, high durability, but slow curing and hard to release from molds
- Vinyl Ester Resins: Part epoxy, cures like polyester, resistant to chemicals and heat.
- Urea Formaldehyde Resin: Light color, good electrical and tracking resistance, used in light fixtures and decorative laminates.
- Phenolic Resins (Resol & Novalac): Excellent thermal, electrical, and chemical resistance.
- Melamine Formaldehyde Resin: Translucent, used for tabletops, resists hot water.
- Silicone Resins: High thermal stability, poor mechanical strength, costly, limited commercial use.
- Furan Resins: Great chemical resistance, low smoke emission.
- The material that provides strength, stiffness, and other desired properties.
- Fibers (glass, carbon, aramid), particles (silicon carbide, alumina), or even nanomaterials (carbon nanotubes).
- Glass Fiber: Inexpensive, compatible with polyester and epoxy, widely used in industry.
- Types of Glass Fiber:
- A-Glass (Alkali)- Base for glass fibers.
- E-Glass (Electrical)- For electrical properties.
- C-Glass (Chemical-Resistant)- For chemical durability.
- R & S-Glass- High strength, aerospace applications.
- Carbon Fiber: High strength-to-weight ratio, ideal for aerospace and machinery parts.
- Aramid Fiber: Up to 30% lighter than glass, 50% lighter than aluminum, excellent impact and fatigue resistance, used with epoxy.
- Asbestos Fiber: Adds stiffness
- Additives in plastics are substances added to enhance or modify the properties of the base polymer.
- These can improve performance, processing, or aesthetics.
There are matrix (resins) are used for making various types of products-
- Key Additives
- Catalyst (Hardener): Ensures uniform curing by dispersing throughout the resin.
- Accelerators/Promoters: Boost reaction rate with catalysts.
- Inhibitors: Extend resin shelf life.
- Curing Agents: Cross-link polymers, creating thermosetting structures.
- Fillers: Reduce cost; add rigidity, impact resistance, decrease flammability, and improve other properties.
- Pigments/Dyes: Color FRP, compatible with resin.
- Additional Additives
- Lubricants: (e.g., Zinc stearate) prevent mold release issues.
- Light Stabilizers:Protect against UV degradation (e.g., phenyl salicylate).
- Release Agents: Ensure easy demolding (e.g., Wax, PVA).
- Matrix Raw Materials:
- Resins like epoxy, polyester, thermoplastics (PEEK), metals like aluminum or magnesium, ceramics.
- Reinforcement Raw Materials:
- Glass fibers (from silica), carbon fibers (from polyacrylonitrile), natural fibers (jute, flax), aramid fibers (Kevlar), and nanoparticles (carbon nanotubes).
*Processing Methods of Composite:
- Contact Moulding Process
- Hand lay-up process
- Spray up process
- Vacuum bag
- Pressure bag Autoclaves.
- Matched Moulding Process
- Cold press
- Hot press or compression moulding
- Transfer moulding
- Resin transfer moulding
- Injection moulding
- Continuous Process
- Continuous laminating
- Pultrusion
- Other Processes
- Filament Winding
- Centrifugal Casting
- Sandwich construction
*General Characteristics of Composite
- Mechanical Strength and Rigidity: Reinforcements provide load-bearing capabilities, making composites ideal for structural applications.
- Thermal Stability and Conductivity: Matrix choice and filler additives dictate thermal properties, essential in aerospace and electronics.
- Fatigue and Impact Resistance: Resilient materials like aramid and carbon fibers withstand high stresses, critical for automotive and aerospace safety.
- Environmental Resistance: Many composites resist UV radiation, corrosion, and chemicals, increasing durability.
Structure & Properties:
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- Microstructure: Composite structure depends on fiber arrangement (random, aligned, woven) and matrix-fiber bonding, affecting mechanical behavior.
- Physical Properties: Composites show anisotropy, meaning properties vary by direction of fiber alignment. Layering techniques improve multidirectional strength.
- Chemical Properties: Matrices and fibers can be tailored for chemical resistance or to withstand specific environments (e.g., underwater).
- Electrical Properties: Some composites (e.g., carbon-reinforced) are electrically conductive, while others (e.g., fiberglass) offer insulation.
Processing Behavior:
- Moldability: Thermoset matrices are irreversible once cured, offering rigidity, while thermoplastics allow re-melting and reshaping.
- Flow and Fiber Orientation: In molding processes like injection and RTM, flow rates and pressures are optimized to maintain fiber orientation and uniformity.
- Curing and Cross-Linking: Heat and catalysts trigger cross-linking in thermosets, while thermoplastics require heating without cross-linking for shaping.
Applications:
- Aerospace: Lightweight composites like carbon fiber-reinforced polymers are used in aircraft bodies and wings to reduce weight and fuel consumption.
- Automotive: Composites improve fuel efficiency by reducing vehicle weight.
- Construction: Glass fiber-reinforced composites are used for bridges, panels, and roofs due to their corrosion resistance and strength.
- Sporting Goods: Bicycles, tennis rackets, and helmets use composites for their strength and lightweight nature.
- Marine: Boat hulls are made from composites for their water resistance and durability.
