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Wet Layup, Resin Infusion, Resin Transfer Moulding, Pre Preg

What are Composites?

A composite is defined as a mixture of two or more materials that when combined give properties superior to those of the individual components. Composites are composed of a matrix and reinforcement, the matrix would normally be resin and the reinforcement a fibre.

Common Composites

Commonly known composites are Fibreglass and Carbon Fibre. The resin (matrix) supports, bonds together and protects the fibres. Transfers applied load and stresses and imparts toughness to the composite. The temperature rating of the composite material is generally defined by the resin service temperature. The fibres (reinforcement) provide the strength and stiffness to the composite material.

Manufacturing Method

There are 4 main methods normally used to manufacture composite parts:

1. Wet Layup

Resin applied to the mould (brushed on), then fibre sheets are added, then more resin is brushed into the fibre, with the fibres being consolidated with a roller to ensure all trapped air is removed. The process is repeated building up to the required thickness, the part is the left to cure

2. Resin Infusion.

Reinforcement fibres added to the mould and layered to follow the mould contours, resin infusion consumables are added to aid resin flow. A vacuum bag is placed over the complete mould, sealed and a vacuum applied. A defined quantity of Resin is then allowed to enter the vacuum bag and flows in covering and saturating the fibres the fibres and the inlet valve is closed. The part is then left to cure under vacuum.

3. Resin Transfer Moulding

Similar to Resin Infusion. However this time there is an upper and lower mould, held together with a mechanical or hydraulic press and resin is injected in under pressure. This results in a parts with a parts with a good resin surface finish on both sides of the part.

4. Pre Preg

The sheets of Carbon Fibre come ready prepared with resin already pre-impregnated into the fibres. The Pre preg plys are added to the mould, pre preg consumable are added to aid in pulling a vacuum and ensuring pre preg plys are evenly compressed. A vacuum bag is added and sealed with vacuum applied and the mould cured under a vacuum in the oven.

Advantages & Disadvantages

Each method has its own advantages and disadvantages. Orthogonal normally utilise Pre Preg or Resin Infusion for most parts, occasionally employing compression moulding for small solid Carbon Fibre parts like brake levers.

With the Infusion and Pre Preg methods the fibre plys are individually oriented so that the warp (strongest fibre orientation) is aligned to provide the best overall strength or maximum strength in a particular direction.

Orthogonal Moulds

We make our own moulds in-house utilising either CAD files and 3D printed moulds or mould building from the actual part using epoxy moulds, to provide an extremely strong and very lightweight part for just about any application.

If you are interested in learning more about composites or have a project that you believe would benefit from the use of composites, please get in touch.


CF Pre Preg and Mould ready in Vacuum Bag for Vacuum and Oven


Example Carbon Fibre Bike Lower Socket, produced using 3D printed Mould and Pre-Preg Carbon Fibre/ Vacuum Bagging Process.

© Orthogonal Engineering Ltd
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