A330 floor panels with cutouts substantiation

[brailos]

Hello,

Does anyone has experience in making a substantiation report regarding the creation of cutouts in a floor panel?
I have a few ideas how to approach this presuming i have the data about the honeycomb core and the fasteners used to fix it to the floor.

- Try to find the loads that the panels are subjected to : loads from seats + load from floor structure and make an FEM analysis before the cutout and after the cutout+reinforcements and compare the results
- with an analytical approach : get the shear allowables of the fasteners used on the longest side to fix the panels , multiply the shear allowable with the number of fasteners on that side and that way trying to get an idea of the maximum load the panel should withstand and somehow prove that the panel with the cutout can withstand the same load
- in a similar manner i can just calculate the strength of the panel before the cutout with the formulas from Bruhn and find a way to calculate the strength of the panel with the cutout and reinforcements.

If anyone has done this before please give me some guidance, or if you know some method of how i can approach this. As some of you may know it is kind of hard to find loads and allowables..i have been browsing airbusworld for 2 days and all i could find was just the name of the fastener and the facing materials of the sandwich panels..i am still searching for the core details...

Amy input is much appreciated.

 

[dwallace1971]

An equivalent strength approach (your third option) might be the most practical as loads are often hard to come by. Have you checked out the SRM for your aircraft? Also, Hexcel has good information on anaylyzing honeycomb panels along with properties for the cores they manufacture.

D.

"On the human scale, the laws of Newtonian Physics are non-negotiable"

 

[ncaero]

Are the floorboards considered in the analysis of the overall fuselage of A330? In my experience (older helos), some a/c do and some don't. I guess if they're not considered by the OEM analysis of the fuselage, then you only have to worry about equipment/personnel loads; if they are considered, then I suppose it's more complicated.

 

[brailos]

Well, from my knowledge the floor panels act as shear panels in the floor structure(crossbeams and stringers). In case of a load in FWD direction the crossbeams do not take any load, they just "bend", and that load is supported by these panels. I have to prove that the cutouts+reinforcement will have the same shear strength as before.

Meanwhile i went for the following solutions:

- i take the shear allowable for the fasteners used to fix each panel, multiply the shear allowable with the number of fasteners on a side, and i get the shear strength of the panel. I know it probably overestimated. After that it is simple, i calculate the shear that the cutout was supposed to withstand and use a doubler with the same capacity of withstanding shear.

- a buckling analysis of the panel without the cutout (with just a unit load) will output an RF; i make the same analysis with the cutout + reinforcement using a beam along the cutout and if i get a RF close to the initial one, i think it is a pretty solid proof.

Depending on what information i can get my hands on i will apply one of the above solutions. For the first one i only need the fastener specs and the thickness of the facings. For the second one i need the specifications for the facings and honeycomb core materials.

Please correct me if i am wrong.

 

[YoungTurk]

What about normal loads? Assumint you have a pressurized part 25 aircraft, these would include (a) rapid decompression (b) cargo / contents at gust or emergency landing and / or (c) passenger / occupant aisle loads. You may also need to consider combinations of these loads (see 25.365).

You can determine worst case decompression loads by applying the maximum difference between the cabin operating pressure and the atmospheric pressure (usually a constant value after some altitude).

Cargo loads and aisle loads may be contained in the aircraft product specification.