Laminate Sample #32: Infused Spread-Tow Carbon with 2mm Cork Core

[@ExploreComposites]

CORRECTION: Because I forgot to switch part of the spreadsheet from imperial to metric, the estimate of the weight showing reduced resin uptake is wrong. The bit at 0:24 is just wrong. The actual error was 0.16% - which is way to close so just luck. Sorry for the confusion. The datasheet from Amorim linked in the description is actually spot on!

[@GrantOakes]

I never would have thought of cork as a core material. As always, your videos are very informative!

[@MJTVideos]

Cork is cheap so that’s definitely a benefit. A cork and basalt laminate would be pretty cool too, since it is natural and more affordable

[@ExploreComposites]

May have to try that one! Still trying to get my head around where Basalt makes sense. I just don't have enough experience with it...

[@richm7936]

Congrats on 1k subs. Keep up the good work.

[@ExploreComposites]

Thanks! Its fun to know that people are interested and good for motivation too.

[@TWX1138]

So I've been watching your materials library videos with an interest in vehicle applications, specifically tonneau covers, canopy shells, and full-slide-in cabover campers. Right now these sorts of accessories are either fiberglass, or sheet metal skin over some kind of moderately lightweight metal square-tubing, or in some more exotic designs, some kind of thick foam-composite, either using fiberglass or aluminum skins over a 1" or 2" thick panel, with all flat panels with aluminum extrusions for corners/joints. The trouble with most of these existing solutions is weight, or is a lack of thermal advantages if lightweight (ie sheet metal over metal frame). Some of your various samples give me ideas, though since you're not doing performance characteristics on your samples (testing for load carrying capacity, max elastic deformation, threshold for plastic deformation, threshold for structural compromise, etc) it's obviously hard to say what exact processes would yield the best possible result. This looks incredibly lightweight for its stiffness though, I'm curious if building a 'big mac' structure with a layer of carbon, layer of cork, another layer of carbon, another layer of cork, and a final layer of carbon might result in some other kind of properties for stiffness relative to weight where it still comes in under half a pound per square foot yet results in something that a 4' wide by 8' long panel could be tread upon without support away from the edges.

[@ExploreComposites]

Thats a tough order the 4x8 sheet walk-able at under half s pound per square foot. Some surfboard manufacturers put higher density foam over low density like your ‘big mac’ idea. The higher density helps with point loading and crush resistance. Shear may still be an issue with thick super low density cores but worth looking into. Have some very light/thick core on the future samples list and am excited to see how it works.

[@TWX1138]

@@ExploreComposites I look forward to your future samples. If it's any consolation I know that I don't *_really_* know anything about composites, and that there are considerable startup costs for equipment and supplies to just get started learning in-earnest, even possibly more costs and learning if one takes an approach similar to the guy on Throttle Stop Garage for making fiberglass molds for large 3d parts. Perhaps someday I'll actually have the time and budget to start experimenting on my own; definitely would be building on the work of others. It just seems like many of the current techniques used for fiberglass parts are ripe for replacement with better techniques in a paradigm-shift, especially if low-cost materials like these cores can be readily cut and shaped to fit well into 3d molds. Suddenly a camper shell on a truck that previously weighed 300+ pounds and taking a third of the payload capacity of a mid-sized pickup could be cut down to under a hundred pounds, that would be useful since the truck could safely carry 200+ pounds more cargo.

[@SuperYellowsubmarin]

Once resin hits the MTI hose, it will not let air through anymore. Also, as it will prevent resin through the line, one needs to be careful to stop resin feed BEFORE the resin is all the way on the MTI otherwise resin will keep pooling at the inlet with no chance of getting out the vac line. It seems to me semi-permeables such as MTI are slightly misunderstood. They are not magic tricks to get your infusion perfect just letting you close the resin when it hits the hose all the way. It just lets you get away with a very uneven flow front without sucking resin in the vacuum line. So it's useful when resin flow is very uncertain, the mold does not provide enough distance for a proper resin break, fasttracking may occur, ...

[@ExploreComposites]

That all makes really good sense. I have worried about how to know what you have the "right" amount of resin in the part given the time it takes to fill and even out across the pressure differential after clamping the feed - especially without the "overflow" volume in something like spiral-wrap. I'm pretty new to MTI hose and semi-permeables in general but very interested in the possibilities!

[@carbonarne675]

you can often use a liquid vax in top of chemical release agent to give the tackytape some surace to bond to... what also helps is oten a little heat... what you did worked out great but it might help or something else

[@ExploreComposites]

It just makes me nervous putting sealant tape over release coatings. Wax seems much safer than this Zyvax Watershield which is really not-sticky. Had a bad experience once with a bag un-sticking while cooking a prepreg part bc of release on the mold edge so I’m scared now!

[@gutierrezivan447]

So I work in aerospace and there's this thing that happens when you have core involved. When you use core it takes a really long time to completely suck all the air out for example when we do rohacell sandwich panels we keep it under vaccum for about 2 hours before we leak check it for the oven. It's best to leave it under vaccum for a couple hours to really take out all the air.

[@ExploreComposites]

I think you’re totally right. This would have benefitted from more time under the bag before infusing. Does it take two hours for the vacuum to stabilize and boil off moisture before you get a reliable leak check? Assuming for prepreg?

[@gutierrezivan447]

@@ExploreComposites I wouldn't know much having to do with moisture since we'd bake our core for a while before using to make sure it was completely dry but maybe that's something you can experience with as well. But its quite significant the difference. One thing we started using that helped a lot was this little turbine fan thingy that was spliced into the vaccum line. When it was spinning it meant air was still being drawn from the layup and when it was perfectly still it meant the laminate no longer had any air in it

[@sealpiercing8476]

@@ExploreComposites Not a composites guy but I do higher-end vacuum stuff. Natural materials and most plastics take ages to get really dry at room temperature, and they usually have more water content than you'd expect. What's worse, something like cork will become an even _more_ effective insulator under vacuum, so removing that water takes some heat input but the heat hasn't got any way to get where it needs to go, if you just pump on it and wait. So, how long it takes depends mainly on how thoroughly dewatered you need it. At one extreme, if I'm doing a vacuum tube that's supposed to stay under vacuum for years, I'll quite happily heat it at 500 C for a few hours for no other reason than to degas it, unless some material of construction forces me to stay cooler. If you just need to be able to see whether air is leaking in, I'd try degassing it 20 C hotter than you intend to do the infusion and see if it helps. If it's a big problem, bake it as high as your setup can easily tolerate--the hotter you work, the faster the dewatering goes.

[@garthlee8166]

Many Thanks, cork was an eye opener many Thanks 10/10

[@adishukri1526]

What release agent are you using?

[@ExploreComposites]

Zyvax Watershield water-bourne polymer.