I can talk about foam in a slightly different sense. I can take a chunk of blue 2 pcf foam with cross section 3-1/4x7 inches and it will stand between 2600 and 4000 inch pounds of bending moment. This average looking 63 year old can not quite break it in two with his hands. Other higher density foams are stronger, roughly in proportion with their density, but that is still close to nothing. In comparison, I have a 3-1/4 by 7 inch fiberglass channel that is designed to carry over 850,000 inch pounds of bending, 11,700 pounds of shear, and take whatever torsional deformation the wing generates. That is 300 times more strength than if we used solid foam in the same dimension, and is on the order of what we need in our airplanes.

Plastic foams do so little for strength that we can ignore it in our computations. Plastic foam allows us to make reasonably light, precisely dimensioned composite parts of incredible stiffness and strength so we include it...

Billski

Plastic foams do so little for strength that we can ignore it in our computations. Plastic foam allows us to make reasonably light, precisely dimensioned composite parts of incredible stiffness and strength so we include it...

Billski

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