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Hi, I'm Elizabeth (Maylin) Rawson, the 2023-2024 Aeroshell lead. I made this article based on my own experience as lead conducting and managing the composite manufacturing of Daybreak (2022-2024). This document is primarily for aeroshell management to understand how to choose and acquire materials in preparation for a layup. This is also helpful for aeroshell members who want to understand more about the materials that we use.

To future aeroshell leads: try to ensure you get as many donations as possible. Composites are very expensive; I spent roughly $17000 in 2023-2024 (very few donations). Please work with your operations lead in advance to acquire materials.

My favorite places to buy materials, especially fabrics, are Composite Envisions and Fiberglast. As of the time I'm writing this I know that we have a 20% discount code from Fiberglast. However, I actually prefer Composite Envisions because you can buy basically everything you need there which means that you can order in bulk. Additionally, their clearance section is better. If you buy from their 2nd quality fabrics, their fibers can get really cheap and rival Fiberglast. 

Fibers

Fiber type

FiberUsesProsCons
Carbon fiberUsed for the exterior of the car
  • Lightweight
  • Conductive → does not allow radio waves to travel through it
    • Communicate with data acquisition on where they're placing the radio to make sure that you don't have carbon fiber surrounding it
FiberglassTypically used for making molds
  • Flexible
  • Cheaper than other fibers
  • Non-conductive → allows radio waves to travel through it
  • Heavy 
KevlarRequired in the canopy by regulations
  • Fireproof
  • Shatterproof
  • Difficult to cut: you need a $30 diamond dremel bit

Weave

WeaveAppearanceDefinitionUsesProsCons
Plain weavePlain Weave Carbon Fiber Diagram
  • Flat sheets
  • Tubes
  • Bulkheads
  • Panels
  • Poor with curved geometry/complex contours
Plain weave (spread tow)

Spread Tow Plain Weave Carbon Fiber Diagram Checker Weave

Like your regular plainweave, but 
  • Flat sheets
  • Tubes
  • Bulkheads
  • Panels

  • Poor with curved geometry/complex contours
  • More expensive than regular plain weave
Twill weave (2x2)2x2 Twill Weave Carbon Fiber Diagram
  • Flexible 
  • Can conform to complex contours
  • Less fabric stability than plain weave
Twill weave (3x3, 4x4, etc)4x4 Twill Weave Carbon Fiber DiagramTwill weave with less formability than standard 2x2 twill weave. We have historically rarely used this

  • More expensive than regular twill weave
  • Less fabric stability than 2x2 twill weave

Tow: A bundle of fiber that is identified by the number of carbon filaments they contain. Each "k" stands for a thousand fibers.

Tow

1k

3k

6k

12k




Density

Fabric orientation

Fabric OrientationPictureDefinitionUsesProsCons
0-90


  • Molds
  • Uses significantly less material
  • Cheaper
  • Easier to cut and prep
  • Weaker along the 45 degrees diagonal

45-90

(Quasi-isotropic)


  • Sturdier composites
  • Aeroshell
  • Stronger along the 45 degrees diagonal

  • Harder to cut and prep
  • Uses significantly more material
  • More expensive



  1. After you have determined all of your fabric qualities, you need to calculate how much fiber you are going to use. The best way to do this is to go into the CAD file of the aeroshell and then create rectangular sketches that are the size of the fiber rolls that you plan to buy. 
    1. Make sure you have 3-5 inches of overlap for each layer of fiber.
  2. Find the area of these rectangular sketches
  3. Know how much ply you want in your composite, and then multiply the area by the number of ply.
  4. Then, add 50% to the final amount you get.
    1. You will always need more than you think. People will never cut fiber optimally or lay down fiber optimally. When I ordered material, I had a 30% buffer and it was not enough.

Resin 

  • Pot life determines how long you have to work with the resin in a pot/bucket before it starts to cure. Most laminating resins that cure at room temperatures have a really low pot life.
    • Higher pot life gives more leniency.

Mold Smoothers

Vacuum Materials

  • Breather: 
    • Breather is separated by density. Which one you choose is not that important as long as its roll width is wide enough for the composite you want to make. I chose based on price.
  • Tacky tape
    • We use any kind of yellow tacky tape. Yellow tacky tape performs well in hotter temperatures and it is higher quality.
    • Avoid gray tacky tape. It can be used for test composites or smaller composites but I would strongly advise against using these for anything that's important.

PPE

Leads, encourage your facilities lead beforehand to buy protective gear. This way three teams don't have to buy stuff, rather OB buys stuff.



Step-by-step guide


References: 
https://www.elevatedmaterials.com/carbon-fiber-weaves-what-they-are-and-why-to-use-them/



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