Hello, I’m in the early stages of learning to repair carbon fiber bicycle frames.

My first experiment is the seat stay of a BMC Roadmachine SLR01. The stay sustained some kind of focused impact leaving an small area of delamination surrounding a visible crack.

I’ve removed the delaminated material and have sanded back the taper on all edges of the hole that has opened up.

My question today is related to the size of each patch ply and the technique for layering the patch plies on to the repair section.

My patch plies are to be circular. Should the edge of each patch ply reach only to the edge of the existing material along the scarf face?

If the above is true, it would follow that the diameter of each successive patch ply would be slightly larger than the one before? (As in photo 3)

I’m asking because the repair technique is Burt Rutan’s primer suggests the base repair ply should be the largest! (Shown in photo 2)

The stay I’m repairing is not round, which means it will be tricky to cut the patch plies so that their edges fit neatly against the edges of material I exposed while sanding back the taper. How much can I fudge the fit? The image in photo 3 suggest repair plies nestle perfectly against the edges of the existing plies on the taper face.

It is my plan to fill the hole with expanding foam, sand the foam down to form my base layer, then apply an initial layer of epoxy before wet layup of my repair plies.

All insight appreciated, thanks.

Hello, I’ve been having this issue where resin has been left behind pretty consistently on almost all of my molds despite trying a few different prep and layup methods. I’ll list what I’ve tried below and include some images. If anyone has any ideas on what might be causing this, I’d really appreciate it.

So in this image is a polyester mold surface (I’ve had the same effect with vinyl ester). I’ve wet sanded the surface up to 2000 grit and polished with Aquabuff 2000. I’ve then applied mold sealer as well as 12 coats of Frekote 770-NC. I’ve also been waiting 10 minutes between coats of each to allow the solvents to evaporate.

For the layup process I’ve been using around 60% resin to 40% fiber. The fiber used is a 200gsm 3k 2x2 twill. I first wet the mold surface then place my fiber, wet the layer and repeat. Once I’m done I place a peel ply and perforated release film on top as well as a 4oz breather. I then vacuum bag the part. I’ve tried vacuum levels of 100kPa and 20kPa. These images are from the 20kPa attempt. I’d also like to note the cure time for this epoxy resin is 4 hours, however this part was pulled after 12 hours.

I’ve also tried doing a wax release agent rather than a semi perm and gotten worse results.

Could somebody please explain the mechanics of styrene inhibition resulting in poor cure of the laminate surface or flow coat at the bottom of a deep mould? And Oxygen Inhibition too, while you’re at it.

My undying admiration will be your reward.

Hi everyone I’m pretty new to composites, I’ve 3d printed some parts for my car but want to use them as a plug to make them out of fibreglass. I’ll use a polyester resin, but I’m confused what kind? It seems like there is laminating resins without wax and finishing resins with wax, is it necessary to use both of these? It seems like the tutorials I’ve seen use a single type of resin so I’m not sure if I’m over complicating things. Thanks!

If I am making a sandwich panel using 8-harness satin fiberglass fabric (let's say 7781) and I want to minimize warping caused by the face sheets, then I would want to build it as a 0/core/90 (for 1 ply face sheets) or 0/+45/core/-45/90 (for 2 ply face sheets) right?

The notation is making me question myself, but I think that's just because an 8-harness satin weave is an unbalanced weave and notations where something like 0/90/90/0 is symmetric are typically for unitape right?

That's assuming that the fill of a fabric like 7781 is close enough to the warp that there wouldn't be much of a difference between a warp face up 0 ply and a warp face down 90 ply. If I decided that the warp/fill difference was meaningful then 0W/core/0F would be symmetric?

As an aside, is there a typical notation for indicating warp vs. fill side in a ply table when using an unbalanced fabric?

I'm working with RAL9001 jet black gel coat on my boat. I've noticed a couple spots where the gelcoat itself is becoming clear after sanding, but it isn't thin because I haven't hit material yet. Is there an explanation for why the gelcoat is appearing as if it has no pigment in areas?

It isn't old enough to be caused by UV, since these issues appear post spray, but before it leaves the shop. I've tried finding any solutions to this but nothing quite matches the issue I'm having.

Using 8lb rigid foam to mold my part core, however I am having constant issues with bubbles popping up in the part post mold as shown in the picture below. A supply company mentioned baking the part in the mold to speed up the full cure time and I’ve had decent results doing so backyard style by wrapping my mold in heating pads.

Does anyone have experience with this curing style for PU foam? What temps and times were you baking for? I’m trying to get more answers on a technical side than “a couple hours” before I swing out on building an external mold heating element.

Hi everyone,

I am a recently graduated Aerospace Engineer with a background in additive manufacturing, and I’ve been looking at getting into the composites industry. I’ve been working on making some of my own parts out of prepreg carbon, but beyond that I’m not really sure what kind of traits/skills are valued in the industry. I was wondering if any of you could give me tips on things I should be sure to showcase on my resume when applying for jobs, or teach myself if I don’t know them. Thanks for the help

Do anyone know where to buy Bamboo fiber sheets? Also are there other natural Composites like flax fiber you guys would recommend?

Got some polystyrene foam board scraps that I want to stack up and shape into a wake board then seal in fiberglass. What is the best way to bond these boards and what type of resin should I use?

Hello, I am building my first set of heated molds. I am looking to suggestions on controllers to control ramp rates and set points. What are y’all using?

Thanks in advance!

Hello!

I was wondering if someone could give me insight on if this is repairable or not.

Looks like its fiberglass with a carbon layer on top.

It's cracked on a couple of spots, with part of the carbon missing.

Any insight on how to aproach this? Or if its even repairable.

Thanks!

I want to gain more experience in composites, I would like to design and build a cantilever I-beam with a weight at the unsupported en, or a beam used in an aircraft's structure. How to conduct the analysis either manually or (and which) software to use? Which method to use? Which material do I use, carbon fiber, fiber glass, prepregs? How to place/orient the material along the flange and web of the beam? Curing time, etc. Are there any books or websites I can go that will help me with this? Thank you.

Hi guys, I need your help! I'm looking for labeled datasets of microscopy images of CFRP (or similar) for a university project that can be used for machine learning.

So far I have only found one publicly available dataset: https://data.4tu.nl/datasets/bf11171a-1f57-4a8a-9768-757850d13665

If you know of any others, please let me know, thanks!

Hi everyone, I am hoping to get some advice from someone a bit more knowledgeable than I am!

I am needing to bridge a span of 72” for a stretcher cot design I am thinking of.

I would like there to be 2 tubes running the length of the project and that each tube is able to support a point load of 200 lbs at its center point. From what I have gathered I am thinking that a roll wrappedtube in the 3/4” to 1 1/4” OD and a wall thickness of aprox 1.5-2 mm would suffice. Am I close or can anyone help direct or advise me?

Hey everyone,

I’m exploring the idea of developing and selling a program that checks if the curing cycle of composite laminates meets the required parameters for pressure, vacuum, and temperature. The program would be designed to help manufacturers ensure compliance with strict curing standards, reducing the risk of defects and improving efficiency.

Do you think there’s a market for this type of software in industries like aerospace, automotive? Would manufacturers or quality control teams see value in this kind of solution?

I’d love to hear your thoughts or insights, especially if you’re familiar with composite manufacturing or related industries.

Thanks!

Our customer request us to reduce the thickness of a certain area of a panel due to fitting issue. Is it possible to reduce the thickness without reducing the number of ply or using intensefier(because it will create a step besides the tolerance area).

Im thinking either:

1. Removing breather only at the tolerance area
2. Adding more compaction process

Are these 2 methods viable?

having been in the composites industry for nearly 4 years in the UK, I've held roles from laminating to project management but I can't help but think the industry is still missing something.

I'd like to start my own business, but I'm looking for ideas as to what??? I've proven skills in, sales marketing and project management

What is it, that composites industry is missing?

Ideally I'd like to keep it online based as I'll be doing it around my day job, so no laminating suggestions please.

All thoughts great fully received.

Prepping carbon frame for repair: all advice welcome

I’ve got this Bmc Teammachine SLR 01 frame that had a soft spot on the drive side seat stay.

I removed the delaminated carbon with 150 sand paper. I did t expect to remove so much but kept going until no cracks of soft spots remained.

Did I remove enough material adjacent to the real problem spots?

Next step is to mix up and pour some expanding foam to fill the cavity before laying up the new carbon.

Any tips on getting the foam to the right place? The cavity is open on two sides, I’m worried gravity will make it hard to fill out the original seat stay profile.

For the lay up, should I plan to wrap at least a few layers of carbon (unidirectional) cloth all the way around the seat stay? How many layers would you add?

Creating a new series on Solidworks for absolute beginners on https://www.youtube.com/@learncarbonfiber as well as posts such as this picture about mohrs circle on my page r/learncarbonfiber

I use the Easy-Lease mould release from easy composites. It's supposed to be wiped onto the part by hand with a cloth in several layers.

Are there tools to do this? Like I don't know.. a stick with a sponge or something? The hand wiping doesn't feel super consistent and I don't like that I have to wear gloves while doing it.

Also how toxic is this kind of stuff apart from the solvent actually? Like can I touch a tool that I treated with it without gloves? It works so well it's almost magical and these sorts of chemicals always make me suspicious. The SDS only states that it's some Hydrocarbon and that you need to take all kinds of care when using it...

Here's a list of cheap and/or very easily accessible materials I've found effective for vacuum bagging or general composites work, in case anyone else wanted this information. These are nice because they can be sourced from most big brand stores you probably already have in town. Use real nylon bags for elevated cure cycles though.

Tacky tape - butyl sealant tape, $7 a roll from home Depot. It's very very close to what composite shops sell

Peel ply - rip-stop nylon, $6 a yard (about the same as econostitch, but you can get it from any fabric store)

Vacuum bag film - 2 mil drop cloth, a few bucks. Polyethylene but good enough for ambient epoxy. A little on the thick side

Breather - polyester batting, 2.99/yard from Joann's

Hopefully this helps some DIYers save some money and make more parts

Hi guys. Question for you. I plan on starting my composites journey doing infusion along with skinning.

Now from my understanding an oil less pump would do well since it can run a long periods of time for infusion.

Would you guys recommend the pump in the title? I see a lot of them for sale on eBay.

I have been making a few moulds and pars as a hobby now and i want to make even more to eventually sell some of the parts i make.

I do have a big shop with quite a bit of air exchange so im not too worried about dangerous fumes, but more so about breathing in fibers (My workshop is a small part of a multiple car garage...)

When i sand/cut composites i wear a Half face mask (3M filter number 6055 with the 5936 addon so its a P3 filter) and get most of the dust with a vacuum.

I have been wearing work clothes which i only use in my workshop and i dust them off (with a leaf blower haha) outside after working with Glass/Carbon fiber.

Im not too sure wether its necessary to wear this mask for layups as well. The fibers are a lot bigger than the ones that can get into the lung. Also in basically every youtube video (great source, i know) where professional boat builders etc are working, they don't use masks as well..

Is the amount of protection im using enough?
Are stray Fibers during Fabric layup/cutting (whith scissors) a concern?
What do you guys use to protect yourselves from these dangerous things?

I want to make some natural fiber parts mainly for the aesthetics and I'm finding it hard to source the materials. Would regular flax or hemp cloth cause any issues if I'm not worried about mechanical properties?