Making Composites

What is matrix?

What is reinforcing fibre?

Three different ways to make composites

Conditions for manufacturing composites

 

 


 

 

 

Making Composites

Composites are made by combining two or more different materials. Most composites have two  constituent materials: a matrix (binder) and reinforcing fibre. The reinforcing fibre is usually much stronger and stiffer than the matrix, and gives the composite its good properties. The matrix holds the reinforcing fibre in an orderly pattern. Because the reinforcing fibre is usually discontinuous, the matrix also helps to transfer load among the reinforcements.back to top


 

What is matrix?

The matrix is the majority of the composites volume. Matrices are usually polymers because they are lightweight, inexpensive, and are easy to process and mold. Thermosetting polymers such as epoxies are very attractive as matrices because they dont readily flow. The matrix is sometimes a metal. Aluminum is commonly used because it is lighter than most other metals of the same volume. back to top


 

What is reinforcing fibre?

There are 2 types of reinforcing fibre - particulate, and fibrous. A particle has roughly equal dimensions in all directions, though it does not have to be spherical. Gravel, micro-balloons, and resin powder are examples of particulate reinforcements. Fibrous reinforcements (chopped fibres or whiskers) vary in length from a few millimeters to a few centimeters and most fibres are only a few microns in diameter.back to top


 

Three different ways to make composites

1. Filled composites
One of the materials is embedded into a matrix of the other. For example, in reinforced concrete, cement is the matrix; stones and the iron rods are the reinforcing fibre.

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2. Fibre composites

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Fibres are embedded into a matrix of the other material.
The glass fibre is the reinforcing fibre and plastic is the matrix.

 

Making fibre-reinforced composites is a laborious process with many steps:

Fiber Alignment
a)
Fine fibres must be woven together into larger bundles called yarns. The fibres or yarns are then aligned into regular patterns of a mat or a tape.


Fiber Alignment

Fiber Molding
b)

The mat or tape are then woven into a larger mat or aligned into a longer stripe.


Fiber Molding

Poly Infiltration
c)

The polymer chains must completely infiltrate around the reinforcing fibres to realize full reinforcing capability. Pressure is then applied to force the polymer chains to flow around the fibres.


Poly Infiltration

Crosslinking
d)

The chains are then cross-linked to form the fibre-reinforced composite.


Crosslinking

 

3. Laminated or sandwich composites
  One material is bonded to or coated on the surface of the other, e.g. plywood and corrugated cardboard.

Plywood

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Condition for manufacturing composites

Successfully manufacturing a composite requires the correct combination of temperature, pressure, and curing time. To find the best process for each specific material, several curing processes are tried and the resultant materials tested.back to top


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