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Old 02-02-2010, 10:48 AM   #21
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Some follow-up questions:
* What was the approx foam thickness?
* Do you have a gut feeling on how much of a stiffness and strength difference nomex aramid honeycomb of the same thickness would make?
* Are there any unique problems with honeycombs? Like earlier delamination due to the smaller contact area between the core and reinforcements?
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Old 02-02-2010, 11:27 AM   #22
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Excelent post TET! I really like to see that power of using core. Beautiful!
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Old 02-02-2010, 07:59 PM   #23
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Also, please notice the first two test. Fiberglass vs Carbon. Show that to customers that don't understand why real carbon parts are more expensive and so much stronger.
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Old 02-03-2010, 05:26 AM   #24
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Quote:
Originally Posted by tpita View Post
Some follow-up questions:
* What was the approx foam thickness?
* Do you have a gut feeling on how much of a stiffness and strength difference nomex aramid honeycomb of the same thickness would make?
* Are there any unique problems with honeycombs? Like earlier delamination due to the smaller contact area between the core and reinforcements?

problems with honeycomb are mostly in the realm of infusions. You can't really use it in a VARTM/RTM part because the resin will just fill the holes. It's mostly used in pre-preg, or the skin layers are bonded on the core with film adhesive.
Also, when bending it, say down a simple 45deg bend. The sides of the core that aren't being bent down, will in fact bend UP. Foam cores if flexible enough, will just bend one way. There is a name to this effect, but I do not recall it.
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Old 02-03-2010, 08:11 AM   #25
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Quote:
Originally Posted by riff42 View Post
problems with honeycomb are mostly in the realm of infusions. You can't really use it in a VARTM/RTM part because the resin will just fill the holes. It's mostly used in pre-preg, or the skin layers are bonded on the core with film adhesive.
Also, when bending it, say down a simple 45deg bend. The sides of the core that aren't being bent down, will in fact bend UP. Foam cores if flexible enough, will just bend one way. There is a name to this effect, but I do not recall it.
Film adhesive, not plain expoxy? How does that work? For all types of honeycombs or just metals?

I didn't really grasp the bending point.
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Old 02-04-2010, 07:02 AM   #26
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Quote:
Originally Posted by tpita View Post
Film adhesive, not plain expoxy? How does that work? For all types of honeycombs or just metals?

I didn't really grasp the bending point.
film adhesive normally has a carrier layer (FB scrim, or even a woven layer), so it won't flow like an epoxy. You can just lay the sheet of film adhesive over the core like a layer of fabric, and cure it.

as for the core... Let me try to explain this way. Visualize you are holding a 12" square honeycomb core. Grab 2 sides, and bend the core down. The 2 opposing sides will curve UPwards. Verses a sheet of paper, you bend the 2 sides down, and it has a nice simple curve.
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Old 02-05-2010, 07:09 PM   #27
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Quote:
Originally Posted by riff42 View Post
film adhesive normally has a carrier layer (FB scrim, or even a woven layer), so it won't flow like an epoxy. You can just lay the sheet of film adhesive over the core like a layer of fabric, and cure it.

as for the core... Let me try to explain this way. Visualize you are holding a 12" square honeycomb core. Grab 2 sides, and bend the core down. The 2 opposing sides will curve UPwards. Verses a sheet of paper, you bend the 2 sides down, and it has a nice simple curve.
So what you're saying is if I bend paper it'll look like a U but if I bend foam core itll look like W?

If possible could you show a picture? I'm extremely interested in this effect
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Old 02-06-2010, 06:54 AM   #28
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I will see what I can find in the store room and take some pics....I did find this link.
http://www.cstsales.com/media/VacBag..._Honeycomb.jpg
you can look at the edges, and see that the bend core isn't flat on the rounded side. Best I can find :-/
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Old 02-06-2010, 01:29 PM   #29
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Quote:
Originally Posted by riff42 View Post
I will see what I can find in the store room and take some pics....I did find this link.
http://www.cstsales.com/media/VacBag..._Honeycomb.jpg
you can look at the edges, and see that the bend core isn't flat on the rounded side. Best I can find :-/
OHHHH I see what you're saying.

If I have a square piece of core and I put my hands on the left and right sides, when if I bend those downward the side facing me will bend up.

Although I'm not an expert I think that has to because of the bending moment. The top surface is under tension and the bottom section is under compression. Therefore the top will pull and the bottom will push to maintain equilibrium? Definitely interesting though. Thanks for sharing that information
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Old 02-07-2010, 05:38 AM   #30
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Suuuuure!!! something like that I think there are some honeycombs (as noted while look for pics) that are designed to bend smoothly. Shaped non-traditional, but gets the job done.
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