Composite Basics - Textile Scholar

 

Composite Materials:

• Made from two or more constituent materials
• Materials having significantly different physical or chemical properties
• Produced material has different characteristics from the individual components

 

Classification Of Composites based on Matrices

What are Composites?

Why Composites ?

 

1. A composite is a mixture of two or more phases (materials)
2. A better or unique combination of properties is realized when different materials (or phases) are combined
3. The primary needs for all the advanced composites are:
4.  Light weight, higher operating temperatures, greater stiffness, higher reliability and affordability

 

What makes a material a Composite?

 

• Composite materials are formed by combining two or more materials that have quite different properties.
• The different materials work together to give the composite unique properties, but within a composite you can easily tell the different materials apart – they do not dissolve or blend into each other
• Composites can be produced using three classes of materials: Polymers, Metals & Ceramics ( Also natural composites are made from wood, bamboo,shells, bones, other tissues & Natural Fibres like cotton, jute, wool etc.)

 

Making a Composite:

 

Most composites are made up of just two materials. One material (the Matrix or Binder) surrounds and binds together a cluster of fibres or fragments of a much stronger material (the reinforcement)

Examples:

1) In case of mud bricks, the two roles are taken by the mud and the straw; in concrete, by the cement and the aggregate; in a piece of wood, by the cellulose and the lignin.

2) In fibreglass, the reinforcement is provided by the fine threads or fibres of glass, often woven into a sort of cloth , and the matrix is a plastic.

 

Two phase composite:

• Matric is the continuous phase and surrounds the reinforcements
• Reinforcement is the dispersed phase, which normally bears the majority of stress

 

What is Matrix in composite?

• Matrix is made from Metal, Polymer or Ceramic
• It is in Continuous phase
• Some ductility is desirable
• Binds the reinforcements (fibres/particulates) together
• Mechanically supporting the reinforcements
• Load transfer to the reinforcements
• Protect the reinforcements from surface damage due to abrasion or chemical attacks
• High bonding strength between fibre and matrix is important 

What is Reinforcements in composite?

 

• A reinforcement is the strong, stiff integral component which is incorporated into the matrix to achieve desired properties
• The term ‘reinforcement’ implies some property enhancement
• Different types of reinforcements:
• Fibres or filament: Continuous fibres, discontinuous fibres, whiskers
• Particulates reinforcement may be of any shape, ranging from irregular to spherical, plate- like or needle-like nanoparticles
• They have a low ductility

 

 

Polymer

A large molecule (macro-molecule) composed of repeating structural units (monomer) typically connected by covalent chemical bonds

Glass Fibre plays an Important role in Composites (in glass composites)

 

Polymer Matrix Composite (PMC):

• Consisting of a Polymer (resin) Matrix and Fibre
• Very popular due to their low cost and simple fabrication

 Applications of PMCs

Fibres in PMCs

 

Various forms:

1. Discontinuous (chopped)
2. Continuous or woven as a fabric

 

Fibre used:

• Principal fibre materials in FRPs are Glass, Carbon & Kevlar 49.
• Less common fibres include Boron, SiC, Al₂O₃  and steel.;
• Glass is the most common fibre material in today’s FRPs; It’s use to reinforce plastics dates from around 1920

 

Polymer Processing:

 

Forming Processes for Thermosetting Matrix Composites:

1. Pultrusion
2. ResinTransfer Molding
3. Hand Layup and Spray up techniques
4. Filament Winding
5. Autoclave Molding

 

Forming Processes for Thermoplastic Matrix Composites:

1. InjectionMolding
2. DiaphragmForming
3. Film stacking
4. Thermoplastic tape laying