This thread is great for us old engineering types. Remember all the material testing I did as a newbe engineer.
Next challange is to actually plot load deflection curves remembering that this stuff is probably very rate sensitive ;^).
Ever want an Instron in your basement? I did.
Jack Iafret "Keeper of the Nostalgia Rules"
From: [EMAIL PROTECTED] To: [EMAIL PROTECTED] Subject: [RCSE] Foam Rating(s) Date: Fri, 12 Nov 2004 17:44:25 EST
Following up on compression strength of foam for vac bagging, picked up some
Dow Scoreboard in Tulsa, lugged it back to the wilderness, and then panicked
when it measured slightly lower bulk density than Owens Foamular 150.
However, a check of the Dow website indicates Scoreboard, Square Edge, etc., have a
min rating of 25psi.
(_http://dowbp-us-residential.buildscape.com/items/?type=products_
(http://dowbp-us-residential.buildscape.com/items/?type=products) )
A small cantilever was set up in the basement and lead shot was added until
a 1" square piece of each type of foam deflected 25%. This is a somewhat
arbitrary rating but it provides a relative comparison. A very rough calculation
back to loading at this deflection gives:
White (virgin) beaded foam ~ 16 psi Foamular 150 ~ 21 psi Dow Scoreboard ~ 29 psi
It's noteworthy that the white foam remains crushed but the others are
gradually springing back. The amount of deflection is continuous with weight so,
in effect, the initial modulus of Scoreboard > Foamular 150 > Virgin beads.
Bulk density is not a good rating factor.
Not sure what this implies for specific max vac for each material - other
than rank ordering them a bit - but if you've got a kid that needs a science
fair project this school year ..........
- Dave R
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