Laminate Sample #22: Vacuum-Bagged Kevlar / Epoxy with Aluminum Honeycomb Core
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- Опубліковано 5 вер 2020
- This 22nd Laminate Sample is a bit of an odd mix - maybe not that practical but worth a look for educational purposes. I wanted to show some Kevlar and discuss how it handles and what it is good for... but I also wanted to do a one-shot honeycomb cored panel with wet epoxy instead of prepreg.
You'd probably want to mix your Kevlar (aramid) fiber with some e-glass or carbon to get the best useful performance, but this shows the process and gives an idea of what you can expect. Most notably, the thicker Proset 135 resin doesn't run too badly into the honeycomb cells and the 1/8" / 3mm cell honeycomb doesn't leave dimples in the bag-side surface. Carbon on aluminum honeycomb can have corrosion issues and sometimes a glass scrim is used to isolate the materials - here a scrim might help the not-so-sticky Kevlar adhere better to the epoxy.
Kevlar is very strong in tensile loading and not remarkable in compression - here it just buckles but doesn't break even when the epoxy cracks away from the fibers. Try that with carbon - which will just explode! Kevlar is tough stuff though and if you have things that need to stay together when damaged or resist abrasion - it is totally worth looking into!
More practical composites knowledge (and someday a page with more about this sample) at: explorecomposites.com - Навчання та стиль
The close up shots at various times of the video were really good- very informative- thanks.
There is a lot of education value in your videos. Thank you.
Your content is always enjoyed - thanks for sharing. That's a very respectable breakage pattern you had when peeling away the skin from the honeycomb.
It seemed stuck but I've only really used Kevlar as prepreg or in infusion - and not sure ever directly against honeycomb - glad it wasn't terrible! Thanks!
I found a specialty tin snips (designed for cutting stainless steel) that do a pretty good job cutting laminated kevlar. The ones I have are made by Midwest. They make a very clean cut for trimming.
Oh that is a neat idea - I guess if they cut stainless then 1/16" Kevlar sheet is no big deal!
uhmwpe next? thanks for uploading. feel like there is somthing special about combining aramid and polyeth
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
Can sandwich structures be constructed without the use of Adhesives
Can we manufactuer the core with 0.5m foil thickness?
I see that the honeycomb didn't stick to the laminate nicely it got delaminated very quickly can you please tell me any method by which I can bond laminate to honeycomb structure and tell for both laminate as upper laminate will cause great issue
It’s harder with honeycomb because you have less bonding area - ideally just resin fillets from the facesheet to the cell walls. This sample had decent adhesion to the honeycomb but the kevlar doesn’t stick that well. Best option is to use toughened bonding adhesive (ideally prepreg film with prepreg laminate) and do tests. Chunks of core should stay stuck to the laminate - not a clean break.
You must properly prepare aluminum core before bonding. Usually a vapor degrease and sometimes primer.
If we join the Face sheet and the core using another technique instead of bonding them can we achieve the same properties?
I am not sure what would work - maybe some type of welding with aluminum face sheets. What do you have in mind? Glue is pretty great at attaching different materials like this.
Two sheets of 0,5mm carbon fiber on each side, instead of Kevlar, would be more stronger?
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.
@@ExploreComposites OK, thank you for your response!
Why do you not use full vacuum?
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.