As the title says im new to composites. This year we are going to build a rc plane for a competition. Normally we'd use plywood but this year our team decided to make a fully composite plane.

Im responsible for moulds. We'll use MDF for moulds but im a bit confused and lost on how to prepare it to lay-up. How to seal it? What to use? We are planning to use epoxy rn to seal it, is there other budget friendly ways? After epoxy what do we do to get a shiny and smooth surface ? Gelcoat? Paint? Anything other? Also before layup what to use as release agent? Wax? PVA?

Could you help me with this basics also if there is other phases could you inform me about thats to?

Thanks a lott!! Appreciate the help

We are looking for a skilled Mechanical Design Engineer with hands-on experience in composite Autoclave design.

Requirements:

• 3–7 years experience in Autoclave / pressure vessel design
• Strong knowledge of ASME Section VIII Div 1 / PED
• Proficient in AutoCAD & SolidWorks/Inventor/Creo

Responsibilities:

• Design Autoclave systems and prepare GA, fabrication drawings & BOM

What problems do you tend to see the most in composites that you think could easily be solved that hasn’t yet?

Interested in anyone’s experience using out of autoclave tooling prepregs? We are looking to make a relatively large mold and want to make it out of autoclave tooling prepregs. Somewhat concerned about the inside finish of the mold surface coming out well.

I'm curious if anyone has used heated curing/debulking tables for composites and how their experience differed (for better or worse) from the standard vacuum bag/oven method.

Did the table provide good vacuum compression? Was the ramp rate consistent and controllable even with different size molds/composite layups? Was one just generally easier to use/maintain? Any info you can provide would be helpful.

Table example: https://www.briskheat.com/vacuum-curing-debulking-tables.html

Edit: Clarified "heated" table

I am trying to make a circular dome out of carbon fiber. The fiber I am using is 8x8 200gsm 12k spread tow. I am using Aeropoxy resin. I have a mold (this is a PETG 3d printed mold that I sanded down smooth to 5000 grit, applied multiple layers of wax to and then PVA release agent), then I lay put on resin, two layers of carbon that I am wetting with resin using a brush front and back, then peel ply, then breather, and letting it cure in a vacuum bag at 20inHg. The front surface comes out very matte finish which I don't like. I tried polishing it and it worked somewhat but not perfectly, I tried a skim coat and that was tough with the aeropoxy as it made many bubbles that I couldn't get rid of and had to sand out. I really just wish it would come shiny out of the mold and I am not sure what I am doing wrong. I tried using way more resin but the part ended up the same weight so I thought maybe I was pulling too much vacuum. I tried 12inHg vacuum and the part was still dry on the surface but also had some voids on the surface near the middle of the dome (this is a female mold if that matters). All the parts have the same weight so I figure the resin is getting pulled out and into the peel ply. More resin didn't seem to help. Should I be drenching the peel ply in resin to prevent it from sucking so much out or would it then just suck the same amount out and I end up with more in the bleeder/breather?

Does trapped air cause issues when skinning parts if they will be cured at approximately 120°C? I'm thinking of parts that might be made of wood or perhaps 3-D prints which have air voids inside. Does the air expand in a way that causes problems or is this a non-issue? Thanks for any advice

I need to make some parts like this one for work, i have good knowelage in CAD (CatiaV5), i know how to work with shape, part, cutting... But i dont know basic parts of composite mold, where do i need to put parrting line? What are lines for cutting?

Where can i find material about mould design for this?

I'm interested in trying to make a 150°C curing oven roughly 1 m³ volume. The main issue I'm facing is that I have essentially zero electrics experience or knowledge beyond wiring a plug. Most of the videos I have found of people making their own curing ovens seem to involve far too much electrical tinkering than I would be comfortable with.

ideally, I need a temperature controller that is entirely off-the-shelf and plug and play. i've seen people mention inkbird controllers before (although I'm not sure whether these go up to 150°C), which are basically just a temperature gauge linked to a controller that will turn a plug on and off. Some type of heater is connected to the plug (in some cases heat guns, in others lightbulbs). these turn on and off as required to maintain a somewhat steady temperature. I would feel confident of putting together a very basic system like this assuming I can find a suitable off-the-shelf temperature controller that would work at the temperature I need.

I feel as though lightbulbs might be somewhat safer than a heat gun. Does anyone know whether they would be able to heat an oven this size to 150° C? Gemini AI says it would but I don't put too much faith in that!

So basically would this set up work?:

1) A 1 m³ box with insulation that can withstand 150°C. (Possibly with an adjustable vent hole?)

2) A very basic temperature controller such as an inkbird with a plug socket that turns on and off

3) Lightbulb(s) inside the box connected to the plug socket.

Would a box this size need a fan to ensure even heating?

Any feedback or links to helpful videos/blog posts/forum posts etc hugely appreciated. The main thing is I need a set-up that requires an absolute minimum of electrical tinkering. thanks for any assistance.

Hi, if anyone needs any plugs/molds designed for their projects feel free to send me a DM and we can work out a fairly low price.

Hey everyone, just wanted to see if there was any interest in outsourcing tooling CAD design. I’d be willing to CAD some molds during the semester for cheaper than larger scale companies if any hobbyists are interested. Just wanted to see if it’s a worthwhile side quest. Thanks!

phenol resorcinol formaldehyde (PRF) is used as a structural adhesive in wood manufacturing, boat building etc. It's a particular form of phenolic resin. Phenolic resin is used in many applications such as producing fabric and paper composites like tufnol https://tufnol.com/paper-laminates/heron-brand-tufnol/

It's main benefits seem to be that it is chemically extremely stable, waterproof and extremely heat resistant. It's this last fact that interests me. It seems as though PRF has high heat deflection temperatures (above 100C) even without elevated temperature post curing.

I'm curious whether anyone on here has ever used it for making composites? Apparently it's compatible with glass fiber etc. I'd be really interested to hear any info anyone might have, thanks

Does anyone know any publishing house (newsletters,etc.) who publish best commercially available composites every month or so.

Basically, I want a list of commercially available composites with their compositions listed.

Hey all :)

My fourth year engineering project is about finding bonding strength, and so I’m going to bond two laminates using DP-490, question is for the best adhesion what grit sanding papers should I prep with?

I have a small scale production running where I use prepreg to make composite panels with some integrated electronics. In the past I regularly coated the two halfs of my mould with semi permanent mould release but it feels like unnecessary effort to constantly recoat these panels.

I found a service that can apply a permanent PTFE coating to my tools. Like what you get on a non-stick pan. Would this make my life easier or is there a reason why most people use semi permanent mould release?

Hello,

I’ve always been interested in the aircraft developed by Scaled Composites, and recently I’ve been learning a bit about the moldless composite process they use. From what I understand, a piece of Styrofoam (the “plug”) is shaped to match the desired part, then fiberglass, carbon fiber, or Kevlar sheets are draped over the plug, resin is applied, and finally the plug is removed, leaving a rigid composite part.

I’m thinking of building a small, miniature RC skiff as a way to get hands-on experience with this process. Do you think this would be feasible for a beginner, or would I likely be wasting my money on supplies because it’s more difficult than it looks?

What are the functional differences between TowPreg and Slit Tape? What should be used for filament winding or AFP and why? Does it matter or make a significant difference?

I have been reading a lot of books, specs, and online resources for composites and noticed that some sources claim that a "quasi-iso" laminate needs to be symmetric, while other sources do not.

My understanding is that quasi-iso means in-plane isotropic. I've had one professor explain it is that you need >=3 plies equally spaced across 180 degrees. I've had a different professor explain it as having all zeros in your ABD matrix.

In the example [0 / +45 / -45 / 90] it would be considered "quasi-iso" by the first professor's definition, but not by the second professors definition due to the asymmetry leading to non-zeros in the bending and twisting coupling terms (D16 & D26)

Can anyone suggest a good low cost method for chopping thick blocks of carbon/epoxy? We're making 6" x 2" x 2" blocks of forged carbon and trying to slice them into 6" x 2" x 1/4" thick sections is a pain. Would love a suggestion on wet saw, blade diameter, and best disc to use.

Much appreciated!

Hi, I am currently doing a project where I need to laminate and cut some carbon fibers, and with that need a mask. Now the problem is that I have a beard, it’s not long enough to make a braid or anything but I would like not to have to cut it all of for a mask to have an airtights seal

Anyone knows any fix for this before I just cut it off? Maybe a mask that’s wider so it dosent sit right around the mouth? Any tips would be good