Good Morning Joshua,
Thank you for your email. We appreciate your interest in DragonPlate.
Without knowing which product your are looking at, I can only speculate about the specifications.
Your density seems high compared to what we typically use. We use 0.06 lb/in3 (~1700 kg/m3).
Your modulus also seems high. The raw carbon is typically around 34 Msi (~230 GPa). We do offer higher modulus
options as well (57 Msi and 110 Msi). Depending on the composition of the tube you are looking at, the final modulus
using 34 Msi carbon fiber can vary from 5 Msi (34 GPa) to 17 Msi (117 Gpa). This would be higher if you use the higher
modulus options available.
Your poisson ration of 0.2 seems appropriate.
thschrader wrote: ↑Wed Aug 15, 2018 6:46 pmAccording to your FEM help-request in this forum:
https://forum.freecadweb.org/viewtopic. ... 0&start=10
A year ago I have written a FEM beginner manual
https://www.dropbox.com/s/vr6pxaj1bt4ph ... l.doc?dl=0
You can simulate the wind on your glider with the FreeCAD cfd workbench
https://forum.freecadweb.org/viewtopic. ... &start=110
Your model can be simulated (calculated), as Harry has shown above.
HarryvL wrote: ↑Thu Aug 09, 2018 11:15 amOh it's an airplane frame
Just a few questions and observations then:
Where do you plan to attach your 4 engines?
How do you attach the wings and what is their composition?
In a conventional design the plane derives strength and stiffness from ribs, stringers and skin (like a thin-wall composite beam) or an monocoque stress-skin. Is it your intent that in your design the stiffness comes from a bending frame of 0.5" tubes?
Anyway, pending a better understanding of how your design works, I would in the first instance model your frame as simple beam elements (available in FreeCAD)
Where to apply static loads and supports depends on where your engines sit and the flight mode (lift off and landing vs horizontal flight). Also in a very skinny design (which you are aiming for (?) dynamic loads need to be considered.
Finally, you may well find that appurtenances (like the wings) provide much greater strength and stiffness than the skinny tubular structure itself.
Hope this helps.
HarryvL wrote: ↑Thu Aug 09, 2018 9:51 pmso ....
With E= 234422 N/mm^2, OD=25.4mm and ID=20.3mm, EI=E*π/64 *(OD-ID)^4=234422*π/64*(25.4-20.3)^4 = 7.66E6 Nmm^2
All your tubes have the same EI, but you have 2 lengths (pcft_24: L=610mm and pcft_98: L=2489mm).
Finally you have put (only!!) 1 N of load on each element, giving a uniformly distributed load of pcft_24: q=1/610=0.00164 N/mm and pcft_98: q=1/2489=0.00040177 N/mm
Putting it all together, the deflections of your tubes are:
I am a bit rusty, so it is quite possible I made a few mistake here ... but is only to demonstrate that 3D elements make no sense for the full model.