I have sandwich panel, and made a spread sheet with all Hoffman required values.
But question are:
- What sign to use for stress allowable values?
- What sign to use for applied stresses (normal stresses)?
I have some elements with signma1 value greater than compressive stress allowable value for a ply in a sandwich panel.
But I use all positive allowables and absolute applied stress values, I get positive margin even through sigma1 (compressive) is more than allowable compressive stress along direction 1?
Just to clear, if I use as it is stress values but positive allowable values, results seem OK.
Yes, this is possible with interactive failure theories.
BUT, none of the interactive failure theories work, ie, correlate to test data. See the failure criteria papers by Hinton.
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