Re: [PSUBS-MAILIST] Glass microspheres idea

["Sean T. Stevenson" <cast55@telus.net>]

Glass microspheres in an epoxy matrix constitutes syntactic foam, a material
commonly used for solid buoyancy in deep ocean vehicles.  If you need such a
buoyant cavity filler material, this is a much better idea than simply using the
spheres without an interstitial matrix material.  The epoxy acts to distribute
load across more surface area of an individual sphere, preventing the point
loads you refer to.  It also retains the spheres in a manner that makes the
cured cavity volume tolerant to damage - i.e. you can sustain an impact or
puncture to the cavity without losing your filler, and without adversely
affecting the buoyancy of the affected cavity.  The solid foam is then removable
when you wish to inspect or repair a space.

Density of the glass microsphere / epoxy matrix, and hence its buoyancy, is
controlled by varying the size and type of glass spheres, as well as the volume
ratio of these spheres to the surrounding epoxy matrix.  Denser foams are
required for deeper applications, and consequently require larger displacement
volumes than less dense foams.  While quite brittle, a cured piece of syntactic
foam can be structural - i.e. it has a decent compressive strength, and it can
be cut and shaped just like wood - just be sure to wear protective clothing and
a respirator - you don't want to be breathing glass dust.

I would not recommend simply pouring raw microspheres into a cavity and sealing it.

-Sean



Quoting djackson99@aol.com:

> I was wondering about using glass microspheres and air as a filler in a
> fiberglass compartment. For example, build a figerglass tank, then fill it
> with 10,000 psi glass bubbles and seal it off. I know each sphere would be
> loaded at points of contact with it neighbors but I seems like it would work
> to at least 3000 ft. 
>  
>  Please let me know what you think.
>  
>  Here is a link to 3M's Selection Guide:
> 
http://multimedia.mmm.com/mws/mediawebserver.dyn?FFFFFFoMYRUF&i2Fsi2FFFSzlqBeeeeD-
> 
>  
>  Doug J
>  Tulsa, Ok
>  www.submarineboat.com
>  
> ________________________________________________________________________
> AOL now offers free email to everyone.  Find out more about what's free from
> AOL at AOL.com.
> 







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