Aeroshell Mid Design Cycle Crisis

(like mid-life crisis)

Core

• Pros

  • Stiffer

  • Higher rigidity

  • Easier mounting due to thicker panels

  • Less bulkheads needed

• Cons

  • Harder layup (chances of wrinkling, dimpling, bridging etc), core has to be cut and shaped

  • Heavier

  • What to do with edges/corners?

    • Min curvature radius increases massively meaning potential shell redesign/ reassessment of how stuff fits together

  • Harder to sim

No Core

• Pros

  • Light

  • Easy to manufacture

  • Sims are easier

  • No redesign needed

• Cons

  • Bulkheads are needed (which are also hard to sim)

  • Much less stiff/strong

  • Harder mounting

Core Options

• Nomex

  • 1/16th inch thick nomex

  • 1 ply on either side, most likely 0,0 due to symmetry

    • Is symmetry a big enough issue to not have a 45?

    • 45 is only needed if torsional rigidity is necessary which shouldn’t be a common loading case for us (?)

  • Min curvature radius would become 1.5 inches which is way too much (source: chat )

  • This means we would have to taper core and have solid laminate at edges

    • This would require sanding core from 1/16th inch to .01 inches for about an inch

    • This would also up layup complexity as we would need to add a ply or 2 of laminate to reinforce bridge between core and rest of part at edge

  • Also research says to use a caul/pressure intensifier (some rigid material placed on top of breather so that pressure is more evenly distributed)

    • Helps significantly in reducing resin pooling and wrinkles, something which is a major issue w/ Nomex layups

• Foam

  • Rohacell 31 - 2mm

  • Rohacell 71 - 3mm

  • Leaning towards Rohacell 31 just because its closer to thickness to the 1/16th nomex, it does have lower strength properties though and is something that needs to be validated through sims

  • Easy to taper due to higher rigidity

  • Doesn’t soak up too much resin

  • Would also require the extra ply to help with ramp

  • Could also bend the core using heat in theory but idk if I would really want to do that given that we haven’t tested it before

  • Very easy to layup in comparison to nomex

  • Most likely also 0,0

• No Core; bulkhead maxing

  • .25-.5 inch thick Nomex honeycomb, 2 ply on either

  • 2 to 4 bulkheads running length of part, 5 to 6 for width

  • Design is based on idea that by limiting space between bulkheads, deflection is limited to radius between that square (assuming bulkheads are perfectly rigid)

Top Shell SA: 7 m^2

Middle Shell SA: 3.1 m^2

Design Options

• Top Shell Nomex

  • Weight: 14.67 lbs

  • Price: $545

  • Prep Difficulty: High (tapering nomex is very annoying)

  • Layup Difficulty: High (layup with nomex in general since it has issues with bridging and wrinkling)

• Top Shell Rohacell

  • Weight: 16.32 lbs

  • Price: $709.66

  • Prep Difficulty: High (Tapering Rohacell is easy but will need to be heat formed to right shape)

  • Layup Difficulty: Easy

• Top Shell Bulkheads

  • Weight: 19.84 lbs

  • Price: N/A

  • Prep Difficulty: Easy

  • Layup Difficulty: Easy

• Middle Shell Nomex

  • Weight: 7.16 lbs

  • Price: $246.72

  • Prep Difficulty: Hell (Both sides sanded for nomex)

  • Layup Difficulty: Very High (2 tapers on nomex, one for curve and one for bottom flange)

• Middle Shell Rohacell

  • Weight: 7.23 lbs

  • Price: $314.72

  • Prep Difficulty: Hell but slightly less (heatformed, but at least taper is easy)

  • Layup Difficulty: Easy

• Middle Shell Bulkheads

  • Weight: 17.35 lbs

  • Price: N/A

  • Prep Difficulty: Easy

  • Layup Difficulty: Easy

* Note, price is only accounting for core, not CF and resin, as that should be relatively constant. Also, it doesn’t account for shipping either. Can change that if needed. Also, am currently using rough estimates for SA, and also a 50% volume fraction. Also weight doesn’t account for reinforcement plies.