777 Floor Panel Stress Analysis
777 Floor Panel Stress Analysis
(OP)
Hi,
I am very green to this stress analysis field and I am hoping to get guidance from this forum.
I am doing 777 floor panel strength substantiation. Floor panel material BMS4-20 Type III. Loading is console load from seats which in Z direction. For conservative analysis I am considering it as a panel with all edges simply supported and load applied in middle. But I couldnt find any formula or theory to calculate bending moment/ bending stress. Does anyone of you know how to do this? or Do you know any other methodology to do strength substantiation of these kind of panles?
Thanks
I am very green to this stress analysis field and I am hoping to get guidance from this forum.
I am doing 777 floor panel strength substantiation. Floor panel material BMS4-20 Type III. Loading is console load from seats which in Z direction. For conservative analysis I am considering it as a panel with all edges simply supported and load applied in middle. But I couldnt find any formula or theory to calculate bending moment/ bending stress. Does anyone of you know how to do this? or Do you know any other methodology to do strength substantiation of these kind of panles?
Thanks





RE: 777 Floor Panel Stress Analysis
There is an old story that while the 747 floor was fine - women with high heels would destroy them. Keep that in mind.
RE: 777 Floor Panel Stress Analysis
RE: 777 Floor Panel Stress Analysis
Garland E. Borowski, PE
Star Aviation
RE: 777 Floor Panel Stress Analysis
"There is an old story that while the 747 floor was fine - women with high heels would destroy them...."
Boeing made their improved floor panels, BMS4-23, to better handle in service wear (impact and rolling load).
BMS4-20 is graphite epoxy face with nomex core.
BMS4-23 is fiberglass flame retardent epoxy face with aluminum honeycomb core.
One of my co-workers said that the 777 has composite graphite floor beams with BMS4-23 floor panels. Maybe the type floor panels are a customer option.
RE: 777 Floor Panel Stress Analysis
Thanks
RE: 777 Floor Panel Stress Analysis
RE: 777 Floor Panel Stress Analysis
I know E doesnt belong to bending moment. But it is belong to bending stress and in Roark you will get bending stress not bending moment.
Regards!
RE: 777 Floor Panel Stress Analysis
RE: 777 Floor Panel Stress Analysis
Thanks a lot again. Again the problem is how one should calculate bending moment of the panel which is simply supported on all four edges and loading is concentrated load in middle.
RE: 777 Floor Panel Stress Analysis
RE: 777 Floor Panel Stress Analysis
I would think that you could conservatively reduce this to a 2D beam problem. Assume a unit width (in the short direction), and then treat the plate as a s-s beam, length = long dimension, Upper face sheet = Upper chord, Lower face sheet = lower chord, and core is the shear web. Calculate the max moment for this beam (where the load is applied). \
Then assume that the face-sheets carry axial load only, and the core carries shear only.
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Nert
RE: 777 Floor Panel Stress Analysis
RE: 777 Floor Panel Stress Analysis
NB: for uniform isotropic plates you don't need E to find moments/stresses. The *relative* stiffness along and across the plate (and indeed the ratios of those to the plate torsional stiffness, provided nu is about 0.3) is unchanged by E.
Note that if the sandwich panel face sheets are not quasi-isotropic then the Roark plate analysis is wrong. In this instance the Es *are* necessary to find the moment distribution/stress. Also, if you get into the detail then the core shear stiffness will also change the bending moments (even with isotropic face sheets), because the shear modulus along the ribbon direction is more than it is across the ribbon (the core being honeycomb). The plate stiffness is the inverse of the sum of the bending and shear flexibilties.
Audacious: you should be being supervised by someone knowledgeable who can give this sort of advice while you build up your own basic knowledge. As GBor says, a good set of static stressing manuals would help. Roark is good, but it is not the be all and end all.