here is a rendering of the printed wing I have been designing. My idea is to create a rapid prototype/carbon fibre composite material which I can use in UAV applications. The concept is to be able to print the RP parts directly from CAD data and then cover in carbon fibre pre-preg. The use of RP allows quick design changes and iterations without tooling. The RP is used in the same way a structural foam would be used.This concept is for a UAV around the 20kg weight size, I'm not sure it would be possible to make it light enough for smaller UAV applications.........
I am hoping to produce the physical parts in the next few days. Part of the callenge is to create a lightweight structure that will build easily on the RP machines and something which will skin up ok in CF. I may need to do a couple of iterations before it is acceptable.
I'll post some pictures of the finished parts as soon as I have them....
For the honeycomb areas, it would be possible to use laser cut parts to come to very near the same design. Then you could choose from sheet foams like depron, styrene sheet, woods, balsa, lite ply... Could keep costs down and allow enough weight savings to allow other design changes, like sheeting under the skin.
It was mentioned above as well, what material does your RP use? Can it handle the curing temps and pressures?
Have you done any FEA with the core 45° off current?
When using prepreg is a high vaccum needed during cure?(I'm not a composites guy)
Thanks for your reply,
you are right about what you say, the honeycomb structure is no good for wing designs as I have shown it...You are also right that its hard to beat Balsa as a lightweight material......but thats not quite what I was trying to do....I wanted to design a small UAV <10kg you can print off, something that needs no modelmaking skills and something that is strong enough to be catapault launched or crashed a few times without falling apart...I am looking at combining printed parts with CF coated printed parts....I have some single skinned CF bits that are simple to make but really strong and tough...Lets not forget that the plated RP parts I have made are over 10 x stiffer than the plastic substrate...surely they could be used for spars etc?
I see what you are trying to do Oliver and it is indeed pause for thought, but going for broke with printing the entire thing, I am struggling to see how you can avoid winding up with an airframe with next-to-no payload.
On the other hand, a series of printed ribs with more three-dimensional detail than can be achieved by simple laser-cut balsa might be a good compromise solution, especially if you can clip/slide them on to a couple of (for example) laser-cut balsa or tubular CF spars. This structure could then be relatively easily skinned in balsa or EPP/EPO sheeting.
You are right......as with everything the design is a compromise....if you print parts from the standard ABS material it's hard to make them stiff and strong enough....
This link shows somebody doing what I have wanted to do for ages but not got round to doing...make an entire airframe...http://www.stratasys.com/Resources/Case-Studies/Aerospace-FDM-Techn...
As you can see they had a few issues with strength, my idea is to use the printed parts and then selectively metalise them to add stiffness and strength The key is to optimise the design with FEA to understand the loads and only add material where it's needed ...the wings are much more of a challenge....I think the best option is to print a thin skin hollow aerofoil and then fill it with pourable foam, from the work I have done already I think a single skin of CF is all you need.
This new approach to construction also works better when you tailor the airframe design to exploit the strengths of the process. Blended body/wing designs that allow maximum payload space work well with this process, high wing monoplanes perhaps less so.....
I think this approach will give you a durable airframe that will survive multiple hard landings something balsa and foam UAV's just cannot do (in my experience...!)
Print, Build, Fly the future of UAV Construction......
If you're talking about pourable foam mouldings, consider using the printed part as a disposable mould - print from PLA or some form of disolvable material. Pour the foam interior and then strip off the printed material - a la shell moulded casting.