Engineering Values for model materials.

[mc71]

I have been playing with foamies for a while now and experimenting with building techniques but I want to know just how far I can push the limits.

I was wondering if anyone had some basic engineering values (modulus of elasticity and yield points etc.) for depron, styrofoam etc.

Matt

[Ollie]

Here are some data on styrofoam compression strength and density:

Foamular:
Type Compressive Strength Compressive Modulus
Flexural Strength Density

FOAMULAR 150 15 psi min. N/A
60 psi min. 1.4 pounds/cubic foot (approx.)
FOAMULAR 250 25 psi min. N/A
75 psi min. 1.8 pounds/cubic foot (approx.)
FOAMULAR 400 40 psi min. 1400 psi min.
115 psi min. 2.04 pounds/cubic
foot (avg.)
FOAMULAR 600 60 psi min. 2200 psi min.
140 psi min. 2.4 pounds/cubic foot
(avg.)


HiLoad:
Type Compression Strength Minimum Density

High Load 40 40 psi min. 1.8 pounds/cubic foot
High Load 60 60 psi min. 2.2 pounds/cubic foot
Grayboard 15 psi min. 1.35 pounds/cubic foot

From my limited experience with High Load 60, the above density for seems low, and I might better agree with the following data found in the same article:

Type Weight Compression Strength
High Load 60 2.8 pounds/cubic foot 60x60x60 psi
Spyder foam 2.3 pounds/cubic foot 45x15x15 psi
Interesting to note the better three dimensional properties of High Load vs. Spyder foam.

White expanded polystyrene is available in several densities and strengths. Type I is 1 pounds/cubic foot @ 10 psi. Type II is 1.5 pounds/cubic foot @ 15 psi. Type IX is 2.0 pounds/cubic foot @ 25 psi.

[Ollie]

Here is more data:




Elastic Modulus Of Common Foams 2 May 03
================================================== ======

foam rho E11 E22 E33 E33/rho
brand (lb/ft^3) (psi) (psi) (psi) (in/10^6)
---------- ------- ----- ----- ----- -------
Spyder 2.30 ? 4000 6900 5.18
Hi-Load 60 2.25 1100 3400 6000 4.61
Dow blue 1.75 2000 640 2500 2.47
Rohacell 31 1.90 5120 5120 5120 4.66
Rohacell 51 3.10 9950 9950 9950 5.55

4.7lb balsa 4.70 160000 ? ? 58.80 (E11/rho)

---------------------------------------------------


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

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


For foam core applications, the relevant modulus is E33.

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).

From Phil Barnes measurements:
foam type..rho....E11....E22....E33....E33
Hi Load 60a.......2.30...1229...2819...6212...4.67
Hi Load 60b.......2.30...1412...2888...6412...4.82
Foamular 400a......1.98...2788...2946...2941...2.54
Foamular 400b......1.98...2920...3088...3087...2.67
Foamular 250a......1.63...2317...1899...2372...2.51
Foamular 250b......1.63...2430...1972...2476...2.62



foam type.......rho....E11....E22....E33....E33/rho

Hi Load 60a.....2.30...1229...2819...6212...4.67
Hi Load 60b.....2.30...1412...2888...6412...4.82
Foamular 400a...1.98...2788...2946...2941...2.54
Foamular 400b...1.98...2920...3088...3087...2.67
Foamular 250a...1.63...2317...1899...2372...2.51
Foamular 250b...1.63...2430...1972...2476...2.62

Foamular 600a...3.04...4927...4927...5108...2.90
Foamular 600b...3.04...4716...4807...5251...2.98
Grey Foam a.....1.54...2894...1054...640...0.718
Grey Foam b.....1.54...2845...1105...588...0.660
Stylite a.......1.93...1877...2906...3489...3.12
Stylite b.......1.93...1847...2854...3416...3.06
Spyder foam.....2.36...1218...3358...7027...5.14

[mc71]

Wow, thanks Ollie.

That is a huge wealth of information, where did you find it?

Matt

[Ollie]

Matt,

I copied it into my files several years ago. I'm not sure but, I think it came from the R/C Soaring Exchange.

[markdrela]

The original files are here, along with modulus measurement method and application info:

http://groups.yahoo.com/group/Allegro-Lite/files/Skin_Stress/