Enclosures made of CARBON FIBER laminates ??? - Page 3 - diyAudio
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Old 22nd August 2007, 10:41 AM   #21
tinitus is offline tinitus  Europe
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Dave, you are right ... if there is the least small drag between the two drivers there is a big risk of ripping the magnets and poleplares apart
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Old 25th August 2007, 01:27 AM   #22
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Taking it a step further would use ready rod as common bolts for the drivers
That is actually what is in my (current) plan, in a slightly different application, for whenever I actually comes around to start building the thing. Hopefully later this fall.......
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Old 25th August 2007, 01:53 AM   #23
SY is offline SY  United States
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Epoxy-carbon composites typically have densities similar to dense hardwoods or even higher. There are some specialty low-mass composites, but those are pretty exotic- usually, wood is lighter for a given part size. Not as strong, though, which is why CF composites are useful in bikes and airplanes.

CF composites also tend to be more "ringy" than wood. Something worth exploring is loading the resin with hollow microspheres, which can help damp things and drop the density significantly. If you can run the process reasonably hot, something like a 3-4% addition of Expancel into the resin during impregnation could prove useful. Then during layup and cure, raise the heat to the expansion temp of the spheres and the composite will puff up like Jiffy Pop. Well, maybe not that much, but you can easily get a 40-50% expansion.
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Old 25th August 2007, 02:16 AM   #24
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Quote:
Originally posted by OzMikeH
the large chunk of aluminium would cost as much as the drivers!
Can't see why a length of sonotube wouldn't work. Stiff and well damped.
I plan to build my 2 x 18" lower bass enclosures this way and otherwise similar to the drawing above with the threaded rods.
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Old 26th August 2007, 01:23 AM   #25
Daveis is offline Daveis  United States
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How thick/many layers would you need to get the same strength and deadness as 3/4" MDF ?

Are the chemicals you work with safe enough to not need a respirator?
(Seem to remember plastics solvents are bad to breathe)
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Old 26th August 2007, 03:11 AM   #26
JinMTVT is offline JinMTVT  Canada
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the prepeg i use has already been half cured..
so no it is not 100% safe, but i only use a small vent by convection on my oven and it is more than sufficient..

but for using prepegs for boxes, one would require a pretty big oven that could be controlled pretty accuratly
( our cure cycle as some ramps and is 130C for 1.5hour...
the epoxy goes back to semi-liquid and then starts curing when it hits 120c+ , then you need some time to let it solidify when bringing the temp down )

MDF is what, 3-4KPSI ? CF is roughly 300KPSI in TS
and half that in Comp S
so not much is required if you use some aluminum or balsa core to get a few times more stiff than 3/4 MDF

thing is that, because it will be seriously lightweight
you want to consider using something like 1"thick core,
as the weight incresase will be marginal, but stiffness will be multiplied VS .5 or .75" thick ..

probably 1-2 layers of CF inside and out would be more than sufficient ..

corners will need more attention and different use of CF

also the contour of the driver's hole would require attention to detail, as CF composites surface is very fragile because it is only the resin that is holding up,
so it is not very hard ( 6-8K PSI for the epoxy i believe)
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