Will Nylon Work for My Application?

[Ghadeer 0]

Hello Ultimaker Community!

 

I am working on building a shape shifting airfoil for my university graduation project (See example here) and I am in the process of designing a corrugated section that will flex up and down to give the desired airfoil profile. I came up with a part (shown in attached pic). Where I expect it to be able to bend (not too  much though) in the directions of arrows as shown. The material thickness is around 6 mm (into the page) with a height of 6 mm and total width of 30 mm. I am considering buying the Ultimaker Nylon filament, but I also want to get your opinions if you think this will work before I buy it. 

 

Sincerely,

Ghadeer 

 

 

 

 

Edited February 21, 2019 by Ghadeer

[geert_2 556]

No experience with nylon. However, I regularly print carabiner hooks in PLA and PET, and use them daily, just to learn how the materials flex and behave on the long term. The PLA ones always crack in the same place. The PET ones are more flexible and survive. Unless I pull too hard, and then they fracture too, usually at random places (not necessarily in the corners).

 

So, if you would already have PLA or PET, try these materials first, and see how the model flexes and where it breaks. It gives an idea of the stress concentrations and weak points. Then, nylon will just be stronger and easier to flex than PET, and unlikely to break.

 

Would a real full-scale model also be in nylon? Or rather in composite, thus much harder and stiffer than nylon (in which case it might behave more like PLA or PET, althoug much stronger)?

 

Anyway, it looks like a very interesting project, which might also be usefull for composite airplanes. A question: how much turbulence do the little ribs create? And doesn't that disturb the smooth airflow and spoil the efficiency of the wing? Or will these ribs be covered with an extra plate later on? Would this flexible shape be more efficient than the crude profile changes achieved by traditional flaps and ailerons in airplane wings?

 

Left and center: PLA/PHA-blend (colorFabb). Right: PET (ICE). The PET is more flexible and survives repeated opening well. The PLA/PHA show the usual point of faillure.

 

 

[Ghadeer 0]

Thank you geert for the elaborated answer.

 

I agree with prototyping with available materials to see the stress concentrators, which will help me in refining my design. I have already ordered the nylon filament, so even if it didn't work, I am sure it will be useful for other projects. 

 

To answer your questions, the 3D Printed nylon piece is only used in a part of the wing rib (the flexing points) and not the whole rib frame. The rest of the rib will be mostly made out of wood (since the project targets miniature UAVs that dont need very strong wing). The rib will be covered with elastomeric skin (similar to Latex material), which is smooth and can stretch as the rib profile changes. The efficiency of the flexible rib wing is part of the investigation, but according to AFTI/F-111 mission adaptive flight wing program, it can increase range by 20-30% of a plane. It all comes down to how much weight the system adds, and if that additional weight will be compensated by performance increase. So it really depends on the design/materials the flexible wing consists of. 

 

 

 

[CapableQuad 10]

I print mostly with nylon, I have not used Ultimaker nylon though, I use Matterhackers Pro nylon. I don't know how they compare with their properties but I know the Matterhackers nylon prints great on my UM3 with "generic" the nylon setting.

Now in regards to your shape, I print small prosthetic devices normally between 15mm to 125mm in dimension, mostly between 1.5mm to 10mm thick. The reason I like nylon is that it is semi-flexible and somewhat indestructible. I think your shape should work fairly well, you will have to experiment with the thickness of the web to get degree of stiffness (or bendi-ness) that you want.

A caveat with nylon is the degree that it uptakes moisture into the filament. I use a food dryer to keep it dry, many people underestimate how much this can affect the printing process. After it is printed moisture is not an issue. The other issue with nylon parts are that they are difficult (but not impossible) to glue to other material.

I hope this helps.

[Ghadeer 0]

5 hours ago, CapableQuad said:

I print mostly with nylon, I have not used Ultimaker nylon though, I use Matterhackers Pro nylon. I don't know how they compare with their properties but I know the Matterhackers nylon prints great on my UM3 with "generic" the nylon setting.

Now in regards to your shape, I print small prosthetic devices normally between 15mm to 125mm in dimension, mostly between 1.5mm to 10mm thick. The reason I like nylon is that it is semi-flexible and somewhat indestructible. I think your shape should work fairly well, you will have to experiment with the thickness of the web to get degree of stiffness (or bendi-ness) that you want.

A caveat with nylon is the degree that it uptakes moisture into the filament. I use a food dryer to keep it dry, many people underestimate how much this can affect the printing process. After it is printed moisture is not an issue. The other issue with nylon parts are that they are difficult (but not impossible) to glue to other material.

I hope this helps.

Thank you CapableQuad for your answer. I am now more confident about the Nylon material. The gluing is also what concerns me, as i will be gluing the nylon to different material types such as wood and rubber.

[geert_2 556]

You will definitely need to chemically "activate" the surface before glueing, and use a glue designed for plastics and nylon. Otherwise bonding may not withstand high loads and repeated flexing.

 

Maybe you could also look into mechanical bondings, in addition to glue? For example dovetails (I hope that is the correct word in English), recessed screws, recessed rivets flush with the surface, sewing (like in the old days of book-binding), or so?

 

Another option that just comes to my mind: polyurethanes are usually easier to glue than nylon, and some of them are also flexible and durable. Maybe you could ask a couple of samples?

 

It will take some experimenting and pioneering, but it looks like an interesting project. Lots of people have looked into wings that can deform, but I hadn't seen your approach yet. So, feel free to post the results of how you solved the problems, and what the efficiency of the wing is.

 

[Brulti 177]

@Ghadeer I've printed quite a lot with UM Nylon, for myself and for customers, and did mechanical parts for engines and such. It should work without problem for your needs. As @CapableQuad said, be sure to keep your nylon dry and use a drybox when printing, it does absorb humidity quite a lot, though not as badly as PVA.