Panel D-Matrix Calculations

[kshea]

I'm using the AIAA paper AIAA 94-1579 to calculate the D matrix of a stiffened panel, however I can't match the HyperSizer calculated stiffness results.  Other than the papers on Thermoelastic Formulation of Stiffened Composite Panels, is there any documentation on how you calculate the D-matrix?

Related to the same problem, how does HyperSizer account for the panel width in excess of the stringer spacing? For example, an 11" panel with 3" stiffener spacing results in... 3 stiffeners or 4?  If 3, what happens to the other 2" -- is that spread evenly into the D-matrix as an effective stiffener spacing of 3.66" or is the excess just ignored?  If 4 stringers, what happens to the missing skin width?

[Ryan]

There will be a new Thermoelastic Stiffness Formulation methods document included in the next release of the software.

You should be able to get close the the HyperSizer symmetric D11 term by computing the EI of the panel (Optimization Requirements Frame of Computed Properties Tab). The D11 term exported to FEA is the bending stiffness with respect to the midplane of the facesheet (as opposed to the 'neutral axis' of the panel). These ABD terms are shown in the Computed Results frame of the Computed Properties tab. This D11 term will be inflated because is describes the bending resistance away from the 'neutral axis.'

HyperSizer does not consider the effect of uneven stiffener spacing. Rather it always computes the stiffness of a single stiffener+skin span unit.

-Ryan