How would forged chopped tow compare to this for hard point mountings ? And those white lines in the cross-section, is that the stitching? Ive seen them on monocoques.
The table is "home made" from out of date prepreg and 2" vented aluminum honeycomb.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
XPS foam has a coating on it due to the manufacturing process. That coating should be removed via sanding or hot wire so the epoxy will form a good bond.
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?
Can you help me? Do you know the name of the material at 0:40 in this video? Thank you very much! ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-sxUSqV-acNA.htmlsi=r1apnNRr3bbs2PlC
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!
Please make a video on how to calculate carbon fiber layers when you have a 3dimensional oart with different thicknesses like an orthotic in-sole (flat at the front, individual at the middle and rather thick at the end).
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.
... So any comments on bulk CTE after nearly a year? I'd imagine most of the strength & rigidity comes from the woven outer plies, and 18% fiber volume means 82% resin in the core - could have a substantial CTE impact unless that's the uncompressed figure?
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.
XPS foam is a polystyrene foam. Epoxy as we all know is exothermic meaning that it generates heat. Foam and heat do not mix . That being said. There is a way that you could’ve done it if you would’ve used a penetrating epoxy with a slow hardening on the foam And put it in your vacuum sealer and basically allowed that to cure with just the epoxy, sanded it, and then add your other substrate with your fiberglass, obviously sanding to create a mechanical bond, you would’ve not had delamination. It would’ve been a solid structure way more solid than you did.
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.
If I've just did a layer of laminating polyester fiberglass, when can I add another layer of laminating polyester fiberglass without having to sand? Between 0 minutes and 24 hours, will I be fine?
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?
okay when you said "we are relying on the resin to form little fillets in the honey comb", that made no sense to me, like it would make tiny little cut away's, but then i thought of the auto cad symbol for fillet and instantly knew what you were talking about with that right angle bond lol. wait is fillet vs fill-ey a different word or just different pronunceations? lol
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
Do you think this would make a quality backing plate/solid core replacement in a PE hand layup vs G10? Say a solid glass core section under a windlass or stanchion.
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.
how would you add a non compressible mounting point somewhere on the panel? is a hole drilled in the foam core and filled with graphite powder mixed with resin or some sort of metal insert better? do i need a specific kind of graphite powder? i'm building a front splitter for a car that needs to withstand substantial downforce
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.
I’m curious how it would perform with the same core thickness in LW-PLA. Obviously I would use the foam core for strictly flat panel layups, but LW-PLA might work great for curved surfaces in aviation. Maybe this idea could be done in episode 49/50?? This idea could work great for having replaceable panels, kinda like fenders, hoods, or doors, on aircraft to make repairs easier.
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.
Stiffer maybe, and stronger in some ways - but not as resistant to hammers! Carbon might also have long term galvanic issues with the aluminum core. But yes, carbon would be a more practical and common choice here.
I meant that that piece of Nomex is of a density that is 40kg per cubic meter - but yes, the little piece is light! And the reason to do both sides it to see how it comes out... which in this case isn't ideal.
@@MaartenOosterbaan I was trying to get two "finished" sides - but I only got two pin-hole filled but flat sides. With honeycomb cores and thin skins, the bag side laminate gets pushed into the holes in the honeycomb leaving a dimpled (and rough from peel ply) surface. Also resin in the "top" skin can drain out into the honeycomb cells leaving the laminate dry.
I am not sure I understand the exact issue - does too much resin bleed out, or is it migrating under the bag to places you don't want it (where?) leaving dry areas? A couple of ideas: 1. Perforated release film (hole patterns can sized vary by product) is necessary for limiting bleed. Laps should only be 10-15mm (1/2"). 2. Use less vacuum - half or even less can be plenty to consolidate. 3. Allow resin to start to gel (slightly) before pulling vacuum. Some wet-layup resins specify a time to first compaction or some other thing - so the resin isn't sitting uncured and very liquid for a long time under vacuum. 4. Sometimes you are best off dividing a lamination into multiple curing steps - especially if there is core or things are complicated.
I built a couple of surfboards with XPS, wet layup e-glass and epoxy. I used a couple of techniques to encourage good skin bonding, like a row of 10-12 exacto blades to score grooves, and initially it was ok but they all delammed eventually. My understanding is that XPS has around 10 percent polyethylene added. This keeps it from sticking as it's extruded. It also keeps anything from actually chemically bonding to the foam, so physical bonding helps. Over time it seems to lose it's grip, perhaps because cycling slowly breaks all the weak surface bonds that initially stuck to the PE. Another issue is that it's closed-cell enough to trap air pockets that will expand with heat and grow with cycles. Too bad, that foam's physicals are really good. Thanks and the library is awesome!
Thank you for the information about XPS - I didn't know about the PE added or consider the trapped air expansion risk. I came off as pretty down on it in this video, but only because I was trying to get more from it than it can offer. If you're building super light stuff with little risk of impact - it can be great!
This is a complicated and long process that is only applicable to aerospace work. The waste is considerable and certainly can't be considered a green process.
Oh for sure! So much composites work is very wasteful especially as things move up the performance/weight curve. It is a fundamental problem that needs lots of attention and effort!
Yes, my arm kind of hides it but it the spiral is fit over the tube for the last foot or so. It is probably overkill here but is a good inexpensive solution when you have room for a decent sized resin/vacuum break to keep resin from just rushing into the vacuum outlet side.
You are right - it is a hydraulic flow control and says "Parker Par Trol PN600B -40BT" and "MAX 2000 PSI" which is more than vacuum is ever going to give it. I don't recall where I got it from, but it was part of something I bought used because I never purchased it by itself or even considered what it might be besides a vacuum regulator. Thank you for making me learn!
“See air through” lol. Light. A couple of tips, firstly you didn’t use nearly enough epoxy. Second, after you’ve gotten it uniform, don’t try to mash it down. Just put the first piece of plastic on top, then roll it out. Pick up the plastic and make sure you don’t see any air lol. If you do see through, put a few shreds on, place plastic back down and roll again. Repeat until uniform. THEN, vacuum seal.
Air - didn't notice that - come to think of it, I see air everywhere! Your idea about squishing between plastic and checking for uniform coverage and adding more as needed is great! I've never made anything this way before and was really just playing around to see. All my "chopped carbon" stuff has been prepreg or infused/injected so you saw me being pretty clueless here. Your advice is always welcome - thank you!
Not very strong really a speed record holding aircraft from California was built using this very same foam in the wings so get your bloody facts straight 😢
i have a Dresser vacuum pump DC2 high volume oil pump. I am having trouble finding the info on the required oil type? What should i be looking for in a oil. My unit looks low and want to flush and replace. Thanks
I’m no expert here - use what the manufacturer suggests if you can find it. Not much out there on a Dresser DC2 though! Most (rotary vane) vacuum pump oil is ISO68 viscosity mineral oil and unless you’re using a special pump generic vacuum pump oil should work ok. You won’t likely ruin the pump with the wrong oil but it may not last as long or work as well.
Thank you. This is just the video I have been looking for. Took about a month to find this video but it answered my question about making a boat out of purple foam. :)
I used XPS as a foam core in a few windsurfing boards. They were exceptionally light and lasted very well. I did use on of the denser grades. I would not hesitate in using this again. It certainly is worth considering for other uses, say a small dinghy / yacht tender. I would not use it for the main structure on a yacht, but for non critical parts, perhaps. Particularly if you were after good insulation, for the least cost
I haven't found an easy source for higher density XPS, but I bet it would work pretty well even at 2-3 pound density. Compression strength and peel-resistance is probably closely correlated with density. Hoping to try some out soon!
It isn’t good! Cutting dry fiber in direct sunlight is always an eye-opener - lots of little glass or carbon “sparkles” floating around. Dust mask or respirator is a good choice. Not asbestos (amiante) level dangerous though.
