Composites Vacuum Bagging Wet Layups

Why vacuum bag a layup?

Items Needed for a Carbon Fiber Vacuum Infusion Layup

Vocabulary and Notes:

Process:

1. Construct and prepare the mold for a lay-up. For more information check out https://uwarg-docs.atlassian.net/wiki/x/DoDDm.

2. Apply the release agent (need to go into specifics) you are using to the mold.

   1. WARG commonly uses wax. Another release agent should only be used if discussed as a mech team.

   2. For wax, apply 5 layers waiting 5-10 minutes between layers for it to dry and develop a slight haze. Buff off and apply the next layer.

3. Cut carbon fiber fabric to correct size for the mold, add about 1”-2” extra on each side.

   1. Easiest method to get a straight cut is to pull on fiber out and follow the gap that is created with CF shears.

4. Place the first sheet of carbon into the mold. Have help!

   1. This sheet is visible on the outside, so keep that in mind.

   2. Choose the sheet that looks the cleanest and has fibers orientated the correct direction.

   3. Use a small amount of 3M Super77 spray adhesive to stick the piece of fabric into place, ensuring there are no air gaps between the mold and the fabric.

   4. Trim the excess fabric that is not in contact with the mold. Make sure no stray fibers end up in the layup.

5. Place the remaining sheets of fabric, keep in mind orientation if a pattern is being followed. Trim excess as needed.

6. Place peel ply over top of the carbon fiber, using many pieces if needed for complicated shapes.

   1. Duct tape can be used to stick the peel ply down. Do not stick duct tape to carbon fiber directly.

7. Plan the path for the resin to flow. This is one of the most important steps and needs to be thought out. (Will include examples after we do it ourselves. Will find some online diagrams too)

8. If the part is large, use an infusion mesh to help the resin spread quickly and evenly.

   1. Duct tape can once again be used to secure this; however, stop 2-3 inches before the resin outlet.

   2. UWFE suggests placing breather material around sharp edges on the mold to absorb excess resin, other sources mention breather material is not needed Vacuum Infusion.

9. Place vacuum inlets and outlets, including spiral tubing according to plan from step 9.

10. Enclose the lay-up in a vacuum bag. There are many methods that can be used. Some common ones are shown below.

    1. Place sealant tape along the surface you choose to close the bag onto (can be a mold, the bag itself, or a table). Leave the tape that is facing outwards covered.

    2. Include pleats around complex surfaces to allow extra bag material to wrap around the shape.

    3. Only peel off the outer side of tape when approaching that area with the bag.

11. Place resin lines onto the inlets and outlets.

    1. Include a line clamp on the outlet line.

12. Set up the resin trap and vacuum pump.

    1. Check for leaks now. With vacuum infusion, there is unlimited time to search for leaks. Ensure there are zero. (Will add more details of how to tell if there is a leak)

13. Now catalyze the resin and set up the inlet bucket.

14. Watch the flow of the resin and time how fast it infuses. Marking on the bag can help learn about the process for future infusions and whether to change viscosities of resin.

15. After the part is fully cured, unwrap it and remove all disposable items (spiral tubing, peel ply, infusion mesh). Remove the part from the mold/surface being careful with the edges.

It is highly recommended everyone interested in composite layups reads the resources used to help create this introduction document. As WARG is beginning with vacuum infusion, there is a lot to learn and add to this knowledge base.

Resources Used:

Vacuum Infusion Equipment and Methods - Part One - Fibre Glast

→ pdf of link above and more readable: Vacuum Infusion - The Equipment and Process of Resin Infusion

How to Choose a Vacuum Pump for Composites - Explore Composites!