huangyhg

deflection max orthotropic sandwich
hi all,
i ask me how calculate the max deflection of the sandwich plate with skin orthotropic (with a simple expression, please, not with the kl plate theorie).
methods can i have seen in the hexcel catalog, structure composite daniel gay, the bruhn or other books taking the assumption that the skins are in isotropic material.
my question is.
can i use these formulas taking the highest young modulus of the orthotropic skin to calculate the max deflection of the plate?
i believe that methods aplication can give a correct approach but considering the plate as a beam with the highest young's modulus in the longitudinal axis.
but i don't sure. i wait your suggestions.
thanks.
ps:sorry for the mistakes, i know, i'm unpardonable


generally, to calculate deflections of anisotropic materials, you would use the modulus of elasticity that applies to the material in the direction of stress that relates to the deflection being considered. so, if i understand your question correctly, the answer would be maybe. you asked about the highest young's modulus, but you can only use the young's modulus that applies to your specific direction, which may or may not be the highest one.
however, you also talked about a sandwich plate, which indicates there may be different materials that make up the depth of your bending
i recommend that you post in the composite engineering forum on this site. you can search the site for it.
as you have mentioned there are many differing authors in the field of composites and so the approaches can also differ.
i would recommned using roark's formulas for stress and strain which will be based on plate theory but will not cover the anisotropic nature of the problem.
to use beam theory i would think the ratio of length to width should be on the order of 2 or higher.
regards,
qshake
eng-tips forums:real solutions for real problems really quick.

i think you need to get an equivalent modulus of elasticity of the different plates. assuming the plates are properly bind together, that (the entire assemblage) is subjected to a common compressive force, the resulting deflection is uniform (each plate shortens the same amount), from that relationship, you should be able to solve e(equiv).
i guess the friction in between plates may have some influence on how these plates behave, but i am not positive on that.
"highest" modulus ??? ... lower would be better.
i think you want to conservatively consider your orthotropic skin as being isotropic by assuming the lower modulus. sounds ok to me.

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