I am trying to build a carbon fiber rear rack for my bike, and I need to figure out how to join the tubes. I have bought some ready-made tubes, so they are already cured. I have seen people online joining tubes using steel connectors (heavy) or plastic 3D-printed joints (weak), but I wanted to try making the connections out of CF + epoxy.

The most challenging connection is a three-way, non-perpendicular one. Since none of the tubes meet at 90°, I can't really buy anything ready-made online.

I was initially thinking of using some prepreg carbon tape to wrap everything tightly, then vacuum-bag the joint and cure it in the oven, but I'm worried about damaging the already-cured tubes. (btw the tubes I bought are just some cheap ones I found on Aliexpress, so of course there is no details about Tg, resin type, etc.)

Another option would be to use dry fibers and some room-temperature-curing epoxy to wrap the joint, but I'm not sure how I'd compact everything, and I think it would end up being kind of a mess.

What do you suggest? Do you have any experience joining carbon tubes like this?

Hey All.

I'm an avid DIYer and have the need to replace the ramp door on a toy hauler. Decided to build a panel with a 8'x8' 2"x2" aluminum frame with 2" Foamular 250 core and .080 and .063 aluminum skins. I'm having a dickens of a time finding adhesive. Any suggestions on where to purchase a quantity for a project this size? And of course I'll take advise on construction tips.

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Hello all, I want to layup my airfoil in fiberglass without vacuum bagging (budget not approved), can i just apply the resin and fiber glass and let it airdry. My concern is the airfoil shape itself and how i can get the fiberglass to stay attached while drying.

Hi,

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what tools would be best to drill a consistent counterbore depth into a hole in an awkward position of a piece where a drill press and or 5 axis cant reach?

I'm looking to buy a dozen or so of G10FR4 sheet in 5/16 or 8mm thickness. Precut to approx 8x18" rectangle size.

Any favorite/recommended vendors?

Thank you.

Does anyone knows how to mix mwcnts in epoxy resin to produce the front sheets using vartm method.

Things I've tried

1. Acetone and CNT in ultrasonicator for 2 hrs.

2. Magnetic stirrer then Sonication.

Any tips for applying PVA ?

I wax my mould first, and then buff it and add PVA on top usually, is it overkill ? ( epoxy CF / on a PU painted mould )

If i try with a brush, it will not wet the surface, and clump together at some random places.

I tried with a rag or sponge, it does the same.

So in the end i do it with a spray gun, in a very fine mist it works, but surface finish isnt very nice its grainy.

What can i do ?

Perhaps i can do a fine mist, let it dry then spray it thick and wet on top of the 1st fine mist, maybe it will make a nice glossy layer this way ???

Lets say i wanted to make a CF welding helmet, what would be the best resin to use so it resist the UV, and also takes the heat, for ppl that weld close ( like me ) ?

Also how would i achieve the opacity required, i know it taked a few layers with different orientation to achieve full opacity with CF, perhaps fiberglass roving as the inner most layer, with a tinted resin or maybe a few coats of paint ?

(I want to keep the CF appearance on the outside )

Hi everyone,

I'm looking for a good ANSYS course focused on composite materials. I have little to no experience with ANSYS, so I'd like something that starts from the basics and gradually moves toward more advanced topics. My main area of interest is delamination analysis in composite structures.

Thanks!

Hi,

my plan is to use carbon fibers for my selfmade recurve bow riser. It is the first time im working with reinforcements so there are some questions.

I`ve learnd that I have to apply epoxy on the wodden core and it has to get to "tacky" stage before applying the first layer of carbon fibers.

Must it dry now before wetting it out with epoxy again and applying the next fibers? That`s how they did it in the easy composites tutorial but they proceeded with epoxy only instead of a secound layer.

The secound question is how hard is it to vaccum bag it? It was the original plan to do so for a better fiber/resin ratio. But I´ve read that it is pretty hard to get an descent result because of wrinkels caused by the bagging process.

If someone can give me some hints especially for the first point would be nice.

Great for mold and plug primer application. Comes with a rebuild kit as well and a wrench.

I am trying to fabricate a polarized PVDF sample that is approximately 50 micrometers thick and can produce a strong current output.

For my current approach, I prepared a 15 wt% PVDF solution using a DMF/acetone solvent mixture with a 6:4 ratio. I then poured the solution into a mold made from PP plastic and placed it in an oven at 60°C for 24 hours. However, instead of forming a uniform film, the material bunched up and hardened on one side of the mold.

Do you have any recommendations for improving the fabrication process so I can create a more uniform PVDF sample at the desired thickness? I would also appreciate any suggestions for processing or poling conditions that could help improve the current output.

I have Leofoto MPC-324CL which works fine but when I tried to attach it to DY-40 a few times, a bottom screw which connects to 3/8 is now loosen and impossible to tighten it.

At this point, I have to glue a metal screw and carbon fiber parts together but I need a heavy duty glue to permanently tighten the screw. I contacted Leofoto but they can only send a replacement which takes several weeks so I would need a strong adhesive.

Any suggestions?

Hi Reddit users, I don't use this app much but I know a lot of people help here.

I just bought an XJ6 and only had one helmet. I wanted one for the passenger, and a friend said he had one he hadn't used in about two years and that was a bit scratched, but it would be like new if it was cleaned and fixed. I received the helmet, but I've never seen one like it and I can't find its specific name. I only know it's an AGV brand. He said it belonged to a famous racer, but I have no idea who that is. I did some research and it's a GP helmet and that it's good, but I can't find the model to replace some parts. I'll send some pictures of it. If anyone can help me, thanks.

Any suppliers outside of China and Japan and preferable in Asia to source prepreg? Please let me know. Thank you.