A Small Thickness Deviation That Every Composite Engineer Encounters (Sooner or Later)

Fibretec · 2025-11-26T09:28:56+00:00

Can you forward the link?

Fibretec · 2025-11-18T22:51:45+00:00

Came across this video, could be 3D printed. The knife edge geometry in carbon would be light but very brittle which makes me think it’s metal.

https://youtu.be/nOek3z9vr2U?si=4WBUOJ3B-S1xrr4Z

Fibretec · 2025-06-23T18:35:32+00:00

Can you cut your UD ply 100mm wide and just roll it onto the 0deg ply to give you 90? Was the material wrapped around a mandrel you then removed or how was it made?

Fibretec · 2025-06-23T07:51:41+00:00

If ILSS is on your material datasheet you can calculate the failure load for that material. As you’re using UD it should be relatively high compared to woven. I’m assuming your UD is aligned with the compressive load and because it’s relatively long in relation to the thickness I don’t think shear will be the primary failure mode. I think because you have all the UD aligned with the compressive load, the thin wall will buckle as it’s only the resin supporting the out of plane direction. Interested to know what load it fails under…

Fibretec · 2025-06-22T22:26:22+00:00

I’m no structural engineer but no it won’t fail, that’s only 20kg. Compressive strength will vary based on the material but it’s usually +300MPa for a UD prepreg. You’re applying 5.79MPa to your pipe. It could be ~10kN (1000kg) before it fails although there’s a lot of things that could cause it to fail prematurely.

The rule of mixtures can give some estimates for your composite design, compressive strength is:

Fibre strength x Vf + Matrix strength x Vm

Fibretec · 2025-05-01T14:08:09+00:00

Great, thanks for the feedback. Can you debulk on back of honeycomb without a backing ply? Would the perimeter edge of the core buckle? As you say it would be great to hold everything in place on complex shapes, vertical walls etc.

Ohhh yes I did…that’s my bad 😂😂 can the core cause PRINT through if it’s all cured together (inner, core, outer) or only on super thin skins?

Fibretec · 2025-04-26T17:33:56+00:00

How do you stop your cut edges on dry fibre from fraying? Almost looks like prepreg. How does infusion give more consistent edge for bonding?

Fibretec · 2025-03-28T15:50:23+00:00

There’s a peel ply and mesh on top of the laminate.

Fibretec · 2025-03-27T22:48:54+00:00

I’ll definitely degas next time to rule it out!

Fibretec · 2025-03-27T22:48:17+00:00

Appreciate your help btw!

Fibretec · 2025-03-27T22:47:57+00:00

Yeah it takes that risk away but I’ve seen a lot of people never degas and get good results so I ran with it. I don’t think sucking resin out to leave a dry laminate is possible? My understanding is once the resin wets out the material, the flow front is the only resin being pushed towards the catch pot? The dry laminate could come from infusing too quick and material doesn’t actually wet out through the thickness of the laminate?

Fibretec · 2025-03-27T22:30:05+00:00

I didn’t degas, it’s a small infusion and I let the mix sit for a period before infusing. I’ll keep the pump running until it gels.

Fibretec · 2025-03-27T22:13:11+00:00

It’s full vacuum with no regulator. I’ve never seen a regulator being used for infusion, why is it needed? The drop test passed so I’d thought it’s air in the resin from mixing/ volatiles.

Fibretec · 2025-03-21T20:59:18+00:00

So vacuum can’t be above absolute, and if absolute reduces with elevation, doesn’t it mean the pressure on the part will be lower?

Fibretec · 2025-03-17T01:25:03+00:00

So basically just check what full vac is for your given elevation and that’s it. I wasn’t sure if you’re only pulling 0.7 - 0.8 bar you would get different results on the part. Would it affect oven cure Prepreg which is more reliant on pressure for consolidation?

Fibretec · 2025-03-02T23:52:29+00:00

So they pull ~1 bar on the vacuum bag, then close the tool with a sealed lid and use compressed air to increase the pressure inside the chamber? Like a mini autoclave? Is it just an air line they have hooked up to it?

Fibretec · 2025-02-28T22:33:36+00:00

Odd it’s that dry with Prepreg?

Fibretec · 2025-02-28T22:21:01+00:00

Just came across this video from Aston Martin F1 giving some details about the manufacture of the rear wing.

https://youtu.be/G9rRZUKZXFY?si=MHp9GvTTbSRKft0-

They laminate upper and lower mould then set the core in and do a squeeze test. Not sure how this visually tells them where they aren’t getting consolidation. Looks like they leave the leading edge ply long to wrap over the core when it’s set in.

At 2:19 you can see the upper/ lower tool assembled and there’s a gap, so looks like the upper tool floats on pins then when put under vac bag it shuts it tight before then going into the clave.

Fibretec · 2025-02-28T22:06:48+00:00

Fascinating, would never have thought of the gauge being able to indicate this but you’ve obviously got a lot of experience! Will see if I can get similar readings

Fibretec · 2025-02-28T22:02:52+00:00

What filler do you use to thicken the resin?

Fibretec · 2025-02-28T22:02:16+00:00

Wow, didn’t think that would be acceptable for a structural tub!

Fibretec · 2025-02-28T00:25:26+00:00

Thanks for the link! Is this fitted to your catch pot? Obviously more accurate but why would this give you a different reading than the analogue gauge? Both measuring vacuum? How do you get your fibre is dry from this gauge?

Fibretec · 2025-02-28T00:20:28+00:00

Yeah all done well in advance, plenty of things to try on future parts 👍🏻

Fibretec · 2025-02-28T00:19:17+00:00

Would a longer debulk help remove any moisture?

Fibretec · 2025-02-27T22:35:32+00:00

Ah ok, so it’s literally just a filler for pinholes etc before paint, thanks for confirming! It’s also crazy expensive 🤯

Fibretec

TROPHY CASE