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Process to be used for Aerobody Production: Vacuum Infusion Process

This process requires a lot of preparation and preplanning in order to be done properly.  The initial selection of materials to be used for the process is very important including molds, vacuum lines and the actual material to be infused with resin.  Some of the important aspects of the process that have to be accounted for are the amount of time required for the infusion to be completed in and the speed at which the resin and hardener will spread throughout the material.  This leads to the consideration of the viscosity of the resin, the permeability of the material and the additional flow media within the material to aid in the infusion process.

The viscosity of the resin is important, as it determines how much times is required for the infusion to be completed and how well and even it spreads throughout the material.  The recommended viscosity is at less than 400 centipoise, however higher viscosities can be used, but curing time must be a lot longer to allow for the spreading to occur.  Alternatively, additional time can be allowed instead to allow higher viscosity resins to be used.

The permeability of the material is also important, due to it also determining the efficiency at which the resin and hardener spreads through the material.  The currently selected type of material will be sufficient for this, as the weaved fibres allow for easy spreading of the resin.  However looser weaves are recommended for easier spreading.

The flow media to be used has to also be considered.  Even though infusion can be done without any flow media throughout the material, it will take much more time to properly spread the resin and hardener throughout the mold.

Fibreglass types:

Fibreglass is a type of composite material that can be used in order to form parts.  Even though fibreglass is generally made of the one material, glass, there are many specifications and types that change its material properties and the process by which a part can be created.

Fibreglass is designated by 3 / 4 letters.  The 1st letter defines the type of glass within the fibreglass, where E is Electrical and S is high-Strength.  The 2nd letter indicates the type of strand that the fireglass material is composed of, for instance Continuous.  The 3rd or both the 3rd and 4th letter indicate the thickness of the strands.

Additionally, fibreglass weave is separated into two types: the vertical is warp and the horizontal is called fill / woof / weft.



Resins + hardeners:

As mentioned before, the viscosity of the resin and hardener is important to consider for the Vacuum Infusion Process.  This means that either the resin has to be lower than 400 centipoise or the hardener used has to be have a higher curing time.

The pot life given for the resin is the amount of time it takes for the resin to double in viscosity.  Additionally, the work life is the amount of time that the resin remains workable and spreadable, after which the curing time is the time required for it to fully solidify.

The current resin that is to be used is the West System 105 Epoxy Resin (http://www.westsystem.com/wp-content/uploads/User-Manual-2015.pdf).  It has a viscosity of 1000 centipoise, very thick for the vacuum infusion process.  However this can be compensated for by the resin hardener used.  The most likely hardener to be used is the West System 209 Extra-Slow Cure Hardener.  This has the following characteristics:

  • Mix ratio: 3 parts resin - 1 part hardener
  • Pot life at 72°F / 22°C: 40-50min
  • Cure to solid state: (72°F / 22°C) 20-24 hours, (95°F / 35°C) 6-8 hours
  • Cure to working strength: (72°F / 22°C) 4-9 days

The temperature is a major factor to the curing time, with a reduction to ca. 1/3 of the curing time at 35°C.  It is probably most efficient to perform the infusion at 22°C, but after that is completed the curing should be completed at 35°C.


Flow Media:

Flow media is the medium that is additionally inserted into the material to help the vacuum infusion process by allowing the resin and hardener to spread through the material faster.  The flow media can be chosen to only aid in the infusion, but also can be chosen to also structurally function as core material to strengthen the material additionally.

The most probable flow media to be used is the FibreGlast Divinycell DIVINYMAT (http://www.fibreglast.com/product/DIVINYMAT_01024_A/Vacuum_Bagging_Vacuum_Infusion).  It functions as both flow media and as the structural core for the material itself.

Composite contacts:

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