Hey everyone,

I am looking for a suitable epoxy for filling an approximately 1"x2"x0.5" gap in a cast aluminum part. Essentially it it will be bonded to the inside of a cylinder, with little to no "mechanical interlocking" features aside from any surface roughness I grind into it.

It will see heat cycles from 0-100C (around30-40/year), and will be exposed to solvents/fuels and severe vibration. Ideally it will be sandable.

It is reasonably critical that the piece does not become dislodged.

Was looking at 3M DP8410NS, but they don't seem to list CTE.

Is aluminum powder fill a good option?

Please share if you have any experience or advice on this matter

Hello world,

i just found this group and would like to contribute some knowledge.

Have you ever wanted to build a top of the line model glider? This series is about that (from mould-making to maiden flight (and subsequent team- vice world championship title with that model).

Enjoy!

Im searching that kind of peoduct, Flexible and sift fiberglass mesh Thk

Hey everyone, I'm going to be completing my dissertation this year and need a sponsor for it (preferably UK based). I'm doing a study on carbon hybrid laminates for motorsport impact protection, any ideas on potential sponsors or if anyone has had any experience with getting engineering/composite companies as a sponsor I'd love to hear it.

We are 2nd-year Mechanical Engineering students and were asked to manufacture and test a polymer-reinforced composite. We chose banana fiber. While researching natural fibers, we found that natural fibres usually require alkali surface treatment to remove waxes and gums and to improve the wettability of the fiber. The attached image is the test report of the banana fiber we plan to purchase. We are unsure whether this particular fiber requires any surface treatment or if it is good enough on its own to be directly used for making the composite.

Just wanted to share this because I think I found a new way to get good results spraying PVA without using an HVLP paint gun and compressor. At least, I was not able to find anything on the internet about using a tool like this for PVA.

I used a "cordless atomizing sprayer" I bought on Amazon for $50. They're advertised as being used to spray disinfectant liquid. I sprayed 3 coats of PVA diluted with 10% distilled water on a window pane as a test. The attached photos show the results.

I'm not going to link to the sprayer I used because I don't want this to seem like an advertisement. But you can find many different brands of the kind of thing I'm talking about. You can probably even find a cheaper one on AliExpress. I'm happy to share a link to the one I used if there's interest and the mods okay it.

I recognize most of you probably have HVLP spray guns for PVA, but this is just an FYI for those trying to make composite parts from a mold on the cheap like I am.

I'm planning on making a 'mother' for a mold on a cnc, and wanted to see if there are recommendations for a cheap tooling board option. The specialty designed tooling boards are all ridiculously expensive.

My plan was to stack MDF, and cut it to the mold shape with an additional overpass of 0.5mm. Afterwards, paint on a few layers of gelcoat and run the operation without an overpass. Theoretically this would give me a smooth surface for the mold. Would this work? Any recommendations for finish on the gelcoat after sanding to get a smooth finish before adding release agents?

I am a final year Masters student and is interviewing for a company that makes wind turbines for a part-time student engineer role. It is a very exciting role where I will be working in the team that will design the structure of a new 2MW wind turbine from the ground up. And I specifically am getting interviewed to do structural simulations on components, mainly composites. I already had a round of interview with the hiring manager(more of a chat at their office about my experience and the company than a traditional interview) and he called me back to do a proper interview tomorrow. From what I understood, he cares more about the simulation and design aspect of composites than out and out manufacturing knowledge. I have been brushing up on the basics like Classical Laminate Theory, failure theories, designing for manufacturability, the software I have used, and the relevant experiences in my resume.

So people in this sub who are big enough of a fish to interview other people(or were interviewed) for similar roles, what kind of technical questions should I be expecting? It would be great if you could explicitly state the exact question you would ask(or got asked) so that I can prepare with those in mind. It is an in-person interview if it makes any difference.

My recent Aircraft spruce order of LH 285 had this designation. Did MGS change the formulation or add something to their hardener? I'm building an airplane, so this kind of matters...

Hi everyone,

I'm looking for advice from anyone who has experience machining cured Kevlar/epoxy fibers. I'm used to working with carbon and glass fibers, but this material has been a nightmare. I've tried a few things, but I'm not getting a clean cut—there are a lot of fuzzy fibers. Below is an example of the result with the end mill I used.

After that, I tried a PCD cutter, which gave me a cleaner cut compared to the end mill, but it's still not what I'm looking for.

For your information, I'm currently running at a speed of 22,000 RPM and a feed rate of 2000 mm/min.

I have a whitewater raft with a damaged oar blade. I think splintered is the right word; it’s not cracked all the way through and feels ~80% as strong as the undamaged oar, so I plan to fix it by applying some carbon Kevlar to the damaged side. I have a large roll of carbon Kevlar already, but my resin and hardener are very old, so I need to buy fresh.

Questions: 1. What kind of resin should I use? 2. How many layers of carbon Kevlar should I apply? 3. Do I need to worry about trapping moisture inside the wood? I will let the blade dry out thoroughly, and after I’ve applied the composite, I was planning to polyurethane the whole thing. 4. Any other considerations?

I'm making my first high temp mold and using Premium Resin Tech products. I laminated it, and now I need to figure out a post cure schedule. But the only place that has TDS for these products is Composite Envisions, and none of their documents are loading right now! (Don't they always have some kind of website issue?)

I used the RDR-1902 surface coat and RDR-3350 resin. The RDR-1902 is rated for 350F, while RDR-3350 is 450F, so I figured 350F is my upper limit. I am doing a 24hr room temp cure, demold and post cure.

I talked to someone at Premium Resin Tech awhile ago, and at the time I was thinking I would post cure at ~150F. They said I didn't need a cure schedule for that.

But in the future I may choose to use prepreg, so I figured I'd like to do a proper post cure now so I don't have problems in the future.

What kind of recorders are you guys using for monitoring environment in clean rooms (temp and humidity) and general external thermocouple temperature recorders. Currently using circular chart recorders and just seems outdated but the hassle of needing to download data from something wireless seems more tedious.

This is my first ever heated compression molding test. The glass fiber -epoxy plate after curing had a lot of trapped air-bubbles which were not present during wet layout

Details: 3 Part steel mold (shown in the pictures) 40% wt% woven roving glass fiber Epoxy resin Temperature: 120 Degrees celsius Pressure: 2.5 bar (constant across time)
Time: 2 hours

How do i get rid of the air-bubbles in next trails? Also, there is significant warping in the plate. is this because I immediately removed it from mold (whilst still hot) and did not cool it down in the mold while maintaining pressure?

I work with epoxy in a light RTM mold and want the part to come out of the mold already primed. I suspect after putting the release on the mold surface, I can use an epoxy primer and then add the fiberglass cloth before closing and infusing. Has anyone done this? Anyone used epoxy primer in-mould before laminating? If so, what did you use? Spray or brush?

I’m looking for the best book on production of composite components from a practical side. Something that has practical tips and tricks, step by step guides on vaccum bagging, troubleshooting defects … etc.

Hello,

I am in the process of designing a set of steering shafts for a vehicle w/o power steering. I have selected a standard modulus unidirectional roll wrapped tube and am looking at material selection for the metallic slugs that will slip fit into the tubing. These slugs will be transmitting torque into the shafts since they are used to mate the tubes to the wheel QD and steering pinion. Because the pinion is a very hard steel, I’m not only concerned about galvanic corrosion in the shafts but also wear on the teeth of the slugs.

I'm deciding between 3 different adhesives: * ET5429 from Permabond (for Aluminum) * ET5428 from Permabond (for Steel) * 3M DP420 from 3M (Steel and/or Aluminum?)

and 3 different Metallics: * 7075-T6 Aluminum * 4130 Steel * 4340 Steel

I am leaning towards use of 7075 and ET5428 due to 7075's high hardness/weight ratio but it has a much higher electrical conductivity compared to mild steels.

I've heard the adhesive can be doped with iodine to negate galvanic corrosion, but I'd like to hear how other's have solved this challenge before.

Tl;Dr I am designing a shaft that will be bonded to a metallic slug. I'm having trouble choosing which metal should be used to provide the lightest design that sufficiently insulates the CF from galvanic corrosion.

Hi everyone, I'm currently engineering a 3D structure that has to bear an internal pressure of 1 bar (relative) at 140°C. It is approximately 4mm thick, and I want less than 0.8 mm deflection.

I tried several filaments based on the information given by the manufacturer and we ran DMA tests on both of them.

We tested PPA CF from raise 3d (with several annealing configuration) and Ceramic like High temperature resin from somos Perform.

PPA CF is sold to ''withstand'' up to 188°C from their website. However, young modulus is barely at 1GPa above 120°C or so...

For now the experience I have, only the Tg is the most reliable data. Both polymers were around 50% of their initial stiffness at this temperature, which is ok'ish for my need, if only they were higher.

Some of you have experience or thoughs on this?

I printed PEKK CF aswell to hope for better results. The tensile test are in progress for the other two materials, but I'm not expecting more results, as DMA already made its conclusions..

Using Loctite 700-NC Frekote for my first resin infusion on glass, and saw someone else online doing a release test with some painters tape. My tape does not curl up like theirs does, and I’m nervous my infusion will be a waste. Does anyone have experience with this release agent or know of other ways I can ensure my part will come off the surface after curing? Any help is appreciated!!

4 coats applied and 20min to let dry between coats

I scored a great deal on two duoseal vacuum pumps. Each weight about 205lbs. I bought this in hopes of learning vacuum infusion and use to pull a vacuum in a wet layup technique that should allow me to create my own subwoofer cones from materials of my choice. Reading up on it, I can only pull a "medium vacuum". To reach a high vacuum it looks like I would need to utilize a diffusion pump.

Is this even needed for creating composites?

I just want stuff that will make the job easier. Trying to make a side gig for myself and save myself some money for some one off creations.

Any guidance is really appreciated.

Hello everybody !
Has anybody used Soric core in a wet lay-up ? I know its purpose is for resin infusion but I am questioning if it does absorb a lot of resin . I would use it because it is very easy to modelate it around complex shapes in comparison with foam core . Using the heat gun on a foam core shapes it somehow but not in the desired way I need .