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Maybe, but it wouldn't be very strong and would dent easily. You could certainly fiberglass over an outdoor countertop more heavily - or lightly if the underlying structure is plywood or something strong. Plenty of boats have decks made out of plywood with fiberglass (ideally in epoxy) over - works great!

@@ExploreComposites yea im trying to find a substrate to do a outdoor kitchen on..the epoxy and top coat i have that figured it out..tricoya is 385$ waterproof my wow that price for a 4x10 im almost thinking solid surface/corian

Depends on where you are located - but they can be hard to source in small quantities. Some sources at the bottom this article: explorecomposites.com/articles/tooling/machinable-tooling-boards/

Pretty sure its Airtech release coated nylon: compositeenvisions.com/wp-content/uploads/2018/03/Model-511-bleeder-lease-b-tds.pdf

Sure, usually with a heated table in these videos because I don't have a good oven setup. Pretty essential with any higher performance epoxy. How hot and how long depends on material and target Tg and service requirements.

Yes! Been there, struggled with that. It's the worst. I keep coming back to wood (but mostly MDF) as about the ideal cheap tooling material. Harder to shape, but stable (ish) and uniform.

@@ExploreComposites Yeah, I've built MDF tooling before. Glued up a large block, CNC machined it, sanded, then coated, sanded and polished polyester tooling resin (duratec). Still, the hairs from the MDF prevented part release. Had to demold the parts using a hammer and chisel. Every time, lol!

That sounds interesting - could the preforms be 3D or just flat sheets?

That's a good tip. It will wick up naturally if viscosity gets low enough (not going to happen here) but agree - glue out in the middle of a cell just sitting there isn't helping!

Yes, for these little panels it certainly would! The sure are handy - I just don't have one yet. I like being able to see through the bag for showing what's going on - that's probably one benefit of disposable consumables for demos like this.

You and me both! I have always wanted to do more specific mechanical testing of samples and hope to do it in the future. It does take a bit of doing to get to the point where the data collected in useful!

The table is "home made" from out of date prepreg and 2" vented aluminum honeycomb. I have a bunch of them I made years ago - super handy but not a readily available product and expensive materials! The aluminum core is excellent for heat transmission to the tool face while staying stiff and having matching CTE to carbon parts.

It comes in varying densities - and the light stuff will dent with a finger. This will easily dent with fingernail pressure but quite stiff and brittle over larger areas.

I haven't. My concern is that it would be very hard to get the top layer of fabric to go up and over each rib gracefully without a lot of bridging. A short-fiber chopped reinforcement might work well though.

@@ExploreComposites Ah true. The bridging, at the expense of a little extra weight might add significant torsional rigidity (much like bead rolling on a flat automotive panel). Hopefully vacuum bagging will minimise the effect. Might be worth experimenting with

Thanks for the info - that makes sense. I will have to experiment with it more. I wonder if the hot-wire process itself makes for an improved bond where the melting has happened?

Depends on temperature but probably up near 800 or 1000cps at room temperature. The styrene and breaking down reinforcement (mat) binders make it feel much thinner in use than the viscosity in a cup would lead you to expect.

Not really, but I'd like to. The problem is that doing mechanical testing right takes a lot of work and some equipment I don't have. I do a little core shearing in a newer sample - #43b - but it's nothing special!

It would machine nicely with the right cutters. I have machined many similar pieces...

What about the layers do you want to calculate? Analyzing a tapered or contoured part can be a bit of work - is it the composite properties you're after?

@@ExploreComposites no, in my case it is just the fitting/shape of the part. I would like to precut the layers and with an easy shape like a cube, this would be rather easy (lots of squares). But how many? And when I have like an organic landscape shape, do I need to have a CAD model and slice it in layers? Or could a plaster model, grinded down work as well as an template? And finally my most important question: is there an upper limit for compressing fibers? Could I (theoretically) press 100 layers under a 300 tons press or at which point would the fibers break. Because I saw a video, where they tried to break a (cured) carbon fiber cube under an hydraulic press with many, many layers and they could not break the cube.

You're right, there's a lot of resin and the carbon mat does act a lot like a core. Even at 18% FVF, the carbon probably keeps the CTE low but it is hard to know how much the uniform face plies are doing the work. I'd shoot for about 1/3-1/2 the thickness in structural face plies and use the recycled mat as a core to increase thickness and stiffness of the tool shell. It can be a challenge to wet through though, so testing is important and slow filling helps. Resin is still cheaper than carbon but not by as much!

I think you're right - though I would have had to start from one edge and work across. Without any holes through, the air would only be able to escape if worked all the way across the surface to an edge.

This is interesting - the way it failed looked very much like failure of the foam, but if your penetrating epoxy could get a better (deeper) grip, maybe it would be tougher. Usually penetrating epoxies have very low viscosity and that helps make them penetrate - do you think this would help here? Thanks!

@@ExploreComposites FINNFOAM has been used to make at least 2 boats, believe deeper penetration of epoxy helped but really vacuum infusing it is the way to go, only that would cause it to deform under pressure.

Me neither Jerry, me neither! Thanks!

A good rule of thumb is "after it has hardened and cooled off and as long as it's still tacky on the surface - best not to go more than a day or two". Depends a ton on the temperature, resin type, humidity and probably lots of other stuff.

I think I was trying not to push too hard on the top skin - to avoid pushing the fiber down into each honeycomb cell. Not sure it would have happened anyway - Kevlar isn't sure stretchy! For bagged wet layup half vacuum is often plenty.

I'd love to learn more about uhmw polyethylene fiber - do you mean like Spectra or Dyneema? Do you know where I could find more information about aramid/uhmwpe hybrid fabrics?

@@ExploreComposites google this S0734743X15001773

I guess it can be spelled with one or two L's depending on where you're from. I'd say "fill-ay" for a piece of a fish and "fill-it" for an inside radius thing.

​@@ExploreComposites :p found a super cheap source of g10 0.5mm, 40 cents a slice as lifepo4 battery insulation sheets. more videos on that please if you get the time =] thanks for your time

Sure, especially if you need a really big or odd-shaped piece when G10 gets less cost effective and practical. Also look into Coosa / Penske / Airex PXc high density core. Also aluminum backing plates and just dropping core out of the laminate in that area - though you'll probably want to thicken up the 'glass too. Infusion maximizes fiber content, but a hand-laid plate would be ok too and maybe cheaper - certainly easier.

The fibers are really long and might be too hairy and clumpy to cut a decent fillet of a normal size. You can buy shorter chopped/milled carbon - 1mm or so - that might make decent fillets if mixed with silica or some other filler.

It is a hassle to buy a small amount of Rohacell - and $$$! These were from a job I worked on long ago where we used quite a bit of it.

Drilling and backfilling with filled resin works. It needs to be a sizable fill completely touching each skin. Core can be dug back with an L-shaped tool in a drill. You can also mold it in with G10 of carbon plate if location is predictable. G10 tubes work well for through fasteners as compression bushings too - sized right they can be tapped too. Assuming carbon because you say graphite filler (silica filler is good too) but aluminum inserts or tapping plates are common with glass laminates but no good long term with carbon.

You really have to test to be sure, but estimating the volume of perforations and flow grooves is pretty easy if you measure with a caliper and do lots of multiplication. Plain foam surfaces take up resin inversely proportional to density of the foam because high density core has smaller cells. Nothing like a few square meters of test panel to get it figured pretty well including surface flow and feed lines.

Mostly so the mold will be air tight and the vacuum bag will work. It also helps support the fairing and primer.

Thanks for the suggestion! I have been wanting to try LW-PLA for a while but hadn't considered it for a core. Next time I order filament I'll try to get some. Could probably be printed as a skinned honeycomb and just get laminated over with a light layer of fiber on each side...

@@ExploreComposites For an outside skin on aircraft or cars I don’t think the comb would be necessary. For stringers and ribs I would use 3D formed reinforcement, like half a circle to hopefully match up with some carbon tube. I haven’t drawn it on F360 yet but that’s how I’m imagining it in my head. I’m thinking carbon tube for transferring loads between 3d printed panels and along the fuselage.