Vacuum Infusion Process: Step-by-Step Guide for High-Quality Composites

Vacuum Infusion

What Is Vacuum Infusion?

Vacuum infusion (also known as resin infusion) is an advanced composite manufacturing process that uses vacuum pressure to draw resin into dry reinforcement materials such as carbon fibre, fibreglass, or Kevlar.

By removing air and evenly distributing resin, this process produces stronger, lighter, and more consistent composite parts—making it a preferred method in marine, automotive, and industrial applications.

Key Benefits of Vacuum Infusion

  • High fibre-to-resin ratios (typically ~60/40)
  • Reduced voids and defects
  • Superior surface finish
  • Lower material waste
  • Consistent repeatability across production runs
 

Why Resin Selection Matters

Choosing the correct resin is critical for a successful vacuum infusion process. The mould, reinforcement, and resin system must be compatible.

Important: Using epoxy resin on a polyester-based mould can cause serious damage to both the mould and the final part.

Our technical team can help you select the right materials and optimise your process, reducing cost, waste, and production time.

Step-by-Step Vacuum Infusion Process

Mould Preparation

  • Apply a high-quality release agent with even coverage
  • Add gelcoat if required and allow it to fully cure
  • Apply vacuum tape around the mould perimeter

 

Lay-Up of Reinforcement

  • Cut reinforcement (carbon fibre, fibreglass, or Kevlar) to size
  • Place multiple layers as required for strength
  • Ensure complete and even coverage

 

Apply Peel Ply

  • Lay a single layer over the reinforcement
  • Cut slightly larger than the reinforcement
  • Avoid overlapping edges

 

Peel ply helps create a clean, bondable surface after curing.

Infusion Mesh and Feed Lines

  • Place infusion mesh on top of the peel ply
  • Match mesh size to peel ply, with slight excess for feed lines
  • Add resin feed line along one edge
  • Position vacuum line on the opposite side

Tip: Complex shapes may require multiple feed lines for even flow

Vacuum Bagging

  • Use a vacuum bag 50–70% larger than the part
  • Press firmly onto vacuum tape, avoiding wrinkles
  • Insert resin and vacuum hoses through sealed incisions
  • Connect:
    • Resin feed → resin pot
    • Vacuum → catch pot → pump

 

Leak Check & Vacuum Setup

  • Turn on the vacuum pump
  • Ensure the bag tightens evenly
  • Check vacuum gauge (should reach ~100%)

If pressure drops, inspect and reseal leaks—especially around hose entry points.

Resin Infusion

  • Mix resin and catalyst accurately
  • Stir thoroughly (including edges and base of container)
  • Unclamp resin feed and allow resin to flow into laminate

Infusion time varies (typically up to 1 hour depending on part size)

  • Monitor resin flow carefully
  • Clamp feed once reinforcement is fully saturated
  • Maintain vacuum during curing

Curing and Finishing

  • Allow the part to fully cure (temperature-dependent)
  • Turn off vacuum and remove:
    • Vacuum bag
    • Tape
    • Infusion mesh
    • Peel ply

Peel ply may require force to remove—avoid using tools that could damage the surface.

  • Trim and finish the part as required

Common Vacuum Infusion Applications

Vacuum infusion is widely used for:

  • Marine components (hulls, decks)
  • Automotive parts (body panels, structural elements)
  • Industrial composite structures
  • Carbon fibre manufacturing

Improve Your Vacuum Infusion Process

Looking to improve efficiency or introduce vacuum infusion into your manufacturing?

We offer:

  • Product selection guidance
  • Process optimisation support
  • Free technical audits

 

Contact our team today to get started

Frequently Asked Questions

What is vacuum infusion used for?

Vacuum infusion is used to manufacture high-performance composite parts with excellent strength, consistency, and surface finish.

What materials are used in vacuum infusion?

Common materials include:

  • Reinforcements: carbon fibre, fibreglass, Kevlar
  • Resins: epoxy, vinyl ester, polyester

What is the ideal resin-to-fibre ratio?

A typical target is 60% fibre / 40% resin, delivering optimal strength and weight.

Why is vacuum pressure important?

Vacuum pressure removes air and ensures complete resin saturation, reducing voids and improving structural integrity.

Do you offer technical support?

Yes — our experts provide hands-on support, process audits, and material recommendations.

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