Re: [PSUBS-MAILIST] In my search for a simple, cheap pressure hull ...

[Ian Roxborough <irox@ix.netcom.com>]

Hi all,

I've thinking along the GRP lines for a while.
Thought I'd pass along some information, mainly
the material definition of GRP so any body using
Alec Smyth's useful little spreadsheet can compare
GRP to steel.

Material definition for GRP (fiberglass matting):

E = Young's Modulus : 65GPa or 9427121 psi
Poisson's Ratio : 0.35
Yield Stress : 1200MPa or 174039 psi
Density : 2.1 g/cm^3 or 0.06387 lbs/in3

The above data is from the book "Pressure Vessels
external pressure technology" by Carl T. F. Ross.

I think testing many vessels to collapse depth is
key before trusting your life to a GRP based pressure
vessel.

Somebody meantioned using a cardboard tube as the
frame for constructing a GRP pressure vessel.  Another
more durable and maybe more useful method would be
to use a section of large diameter corrugated polyethylene
(or other plastic or GRP) piping, similar to piping
used for drains in some areas.  Done correctly, the
corrugations will form GRP hoops giving greater strength
to the pressure vessel (the same as steel hoops on a metal
pressure vessel).

I'm hoping to start destructively testing some
smaller GRP pressure vessels some time next year.
If we share our test results we should be able to
plot some nice curves and accurately compare the
practical results to the math side of things.

I'll also post a bio at some point as well.

Ian.

On Wed, 7 Nov 2001 07:37:52 +1000
"Walter Starck" <wstarck@ozemail.com.au> wrote:

> Phil,
> 
> It would seem a fairly simple thing to lay up a series of small
> composite vessels and test to collapse depth to get some idea of
> variability and relative strength of  various resins, fibers, and
> laminates.  Do you know if this has been done and if so are the results
> accessible?
> 
> Walter Starck
> Golden Dolphin Video CD Magazine
> of  diving and underwater photography
> www.goldendolphin.com
> 

-- 
Stop killing everything.