Spider & AeroWeave
Spider
Hey, I've been thinking about how to design a composite that keeps weight low while still handling the stresses of high‑altitude flight. What if we start by mapping the load distribution and then see which materials can meet those specs?
AeroWeave
Sounds solid. Map the loads first, then do a quick stress‑to‑density check on carbon‑fibers, maybe some glass‑reinforced polyimide, and compare with the latest aluminum alloys. Cut out anything that gives you a margin less than 2‑3%. Keep the layers thin and stagger the fibers so the composite breathes under low pressure. The key is to get the high‑strength fibers at the right angles where the stress peaks. Once you’ve nailed that, the weight will follow. Need help crunching those numbers?
Spider
Got it, I’ll line up the load map, run the density check on the fibers, and flag anything below that 2‑3% safety margin. I’ll keep the layers thin, stagger the fibers, and target the stress peaks. Let me know the exact load data so I can crunch the numbers.
AeroWeave
Here’s a quick load sketch for a typical high‑altitude aircraft. Use it to pull the numbers for your composite.
1. **Static limits**
• +3 g vertical load (max maneuver)
• –1 g vertical load (negative G for stall recovery)
• +2 g side‑load (rudder‑induced turn)
2. **Dynamic pressure (q) at cruise**
• Altitude 30 000 ft, Mach 0.75 → q ≈ 0.9 psi (≈6 kPa)
• Lift coefficient (Cl) ≈ 0.8 at cruise → lift ≈ 0.8 × q × S
3. **Pressure gradients across the wing**
• Root (inner panel) ~ 150 psi peak compressive
• Tip (outer panel) ~ 80 psi peak tensile
4. **Safety factor target**
• Structural FS ≥ 1.5 for all loading paths
Pull the wing area, air density, and your planned C‑L values to convert these to stress in MPa. Then you’ll see which fiber orientations and stack sequences keep the safety margin above 2–3 %. Let me know if you need a deeper dive into the stress equations.
Spider
Sounds good. I’ll take those load figures, plug in the wing area and density at 30 000 ft, and work out the stresses in MPa. Then I’ll test a few fiber angles and stack orders to keep the safety factor above 1.5 and the margin over 2‑3 %. Let me know the exact wing span and planform you’re using, and I’ll run the numbers.
AeroWeave
Here’s a sample you can run with. 30‑meter span, a straight‑taper planform that starts at a 4‑meter root chord and tapers to about 1.2 meters at the tip. The wing area works out to roughly 90 square meters. Plug those into the load map and the pressure data for 30 000 ft and you’ll get the stress numbers you need. Adjust the taper or chord if you’re aiming for a different wing loading, but this should give you a solid baseline.
Spider
Okay, I ran the numbers with the 30 m span and 90 m² area.
*Dynamic pressure at 30 000 ft is 6 kPa.*
*Lift = 0.8 × 6 kPa × 90 m² ≈ 432 kN,* giving an average wing load of about 4.8 kPa.
But the pressure gradient is what matters for the composite.
Root compressive peak ≈ 150 psi ≈ 1.03 MPa.
Tip tensile peak ≈ 80 psi ≈ 0.55 MPa.
With a target safety factor of 1.5, the required material strength is at least:
Root: 1.5 × 1.03 MPa ≈ 1.55 MPa.
Tip: 1.5 × 0.55 MPa ≈ 0.83 MPa.
That’s well below what a high‑modulus carbon fiber can deliver (tensile > 3 GPa, compressive > 2 GPa).
So the key is orientation: keep the high‑strength fibers in ±45° stacks at the root where the compressive load peaks, and align them more longitudinally near the tip to handle the tensile peak. Keeping the layers thin and staggering the fibers will also reduce buckling risk under the low‑pressure environment. If you need the exact stacking sequence or a weight estimate, let me know.