Elastic Modulus Of Common Foams                last revision:   5 May 03
 measurement via 3-point bending test
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foam            rho        E11    E22    E33    E33/rho     data source
type         (lb/ft^3)    (psi)  (psi)  (psi)  (in/10^6)
----------    -------    ------ ------ ------   --------    ------------
Spyder foam     2.30             4000   6900      5.18      Mark Drela
Spyder foam     2.36      1218   3358   7027      5.14      Phil Barnes

Hi-Load 60      2.25      1100   3400   6000      4.61      Mark Drela
Hi Load 60a     2.30      1229   2819   6212      4.67      Phil Barnes
Hi Load 60b     2.30      1412   2888   6412      4.82      Phil Barnes

Dow blue        1.75      2000    640   2500      2.47      Mark Drela

Foamular 250a   1.63      2317   1899   2372      2.51      Phil Barnes
Foamular 250b   1.63      2430   1972   2476      2.62      Phil Barnes

Foamular 400a   1.98      2788   2946   2941      2.54      Phil Barnes
Foamular 400b   1.98      2920   3088   3087      2.67      Phil Barnes

Foamular 600a   3.04      4927   4927   5108      2.90      Phil Barnes
Foamular 600b   3.04      4716   4807   5251      2.98      Phil Barnes

Grey Foam a     1.54      2894   1054    640      0.72      Phil Barnes
Grey Foam b     1.54      2845   1105    588      0.66      Phil Barnes

Stylite a       1.93      1877   2906   3489      3.12      Phil Barnes
Stylite b       1.93      1847   2854   3416      3.06      Phil Barnes

Rohacell 31     1.90      5120   5120   5120      4.66      CST
Rohacell 51     3.10      9950   9950   9950      5.55      CST

4.7lb balsa     4.70    160000                              Mark Drela

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Definitions
-----------

rho = density
E11 = modulus along  sheet (8' dimension)
E22 = modulus across sheet (2' dimension)
E33 = modulus across thickness
E/rho = specific modulus


Different numbers for the same foam is most likely due to
variation between foam batches, and to measurement uncertainty.


For composite foam core applications, the relevant modulus is E33.
The larger this number, the greater the resistance to buckling 
failure of the compression-side skin.  E33 also indicates
resistance to dents.

For bare foam wings (slow fliers, etc), the relevant modulus
is either E11 (span is along foam sheet), or E22 (span is
across foam sheet).  The larger this number, the greater
the bending stiffness of the wing.