Equiv. approach to model sandwich panel
Equiv. approach to model sandwich panel
(OP)
hi to all experts,
wondering if anyone had experience in modeling a composite material using equivalent approach, which means converting the composite to non-composite. can this approach model all behaviours, i.e. bending, axial behaviours etc, accurately?
thank you very much
wondering if anyone had experience in modeling a composite material using equivalent approach, which means converting the composite to non-composite. can this approach model all behaviours, i.e. bending, axial behaviours etc, accurately?
thank you very much





RE: Equiv. approach to model sandwich panel
1. An unsymetric lamination has bending and extension coupling.
2. The equivalent model would also have to take into account the properties of the individual plies, as well as the failure index that you would choose.
I personally have found it difficult to use micro mechanics to accurately predict the properties of the individual plies let alone the entire lamination with core. A good book on composites is Mechanics of Composite Materials by Robert Jones.
RE: Equiv. approach to model sandwich panel
actually mine is a linear system, so wondering if the axial and bending effects can be uncoupled. since young's modulus of axial and bending effects are different, so will use the respective E's to get axial and bending stress respectively.
will try to look for the book recommended. thanks v much :)
RE: Equiv. approach to model sandwich panel
Check out http://femci.gsfc.nasa.gov/hcplate/. Your software probably provides an obscure menu somewhere to allow you to fully control these described membrane and bending stiffness parameters yourself, to model the sandwich. E.g., see NASTRAN PSHELL link at bottom of above page.
I believe the above link is a recommended method described as "Method 2(b)" in the following excellent article. Modeling Sandwich, http://groups.google.com/groups?selm=3scsf5%2425u%40news.engr.udayton.edu. Note he claims the transverse shear factor should be, say, 0.08 or less (?). I don't believe you'll find the "MIL-HDBK-23A" (circa 1968) he references, on-line. It might be many MB, and might not be as good as modern text book references.
Also, here's another link, just in case it might help a little. http://www.oneoceankayaks.com/Sandcore.htm. Good luck.
RE: Equiv. approach to model sandwich panel
those sites are really wonderful.
just wondering if u have used SAP2000 to model sandwich panel before? i'm currently playing around with 2 methods, one is using the equivalent approach and the other one is to directly model the composite panel. Did this by constraining nodes on the 3 layers tog. using rigid body constraints. have u ever come across this method?
thanks so much for ur help once again and truly appreciate it.
RE: Equiv. approach to model sandwich panel
I haven't tried your second method (I used a laminate element, so far). What about making all three layers coincident, which automatically connects them, then applying z' offsets to face sheet layer elements, if possible? I assume you're referring to offset face sheets in your second method; otherwise it probably would be far from the correct answer. If the strain (not stress) distribution is really as nonlinear as Brockman claims, then any of these plate methods, including the laminate element, of course might be somewhat inaccurate. For more study on the subject, a few more references were listed in Thread507-14199. Good luck.
RE: Equiv. approach to model sandwich panel
RE: Equiv. approach to model sandwich panel
RE: Equiv. approach to model sandwich panel
just to add on the comment u made on my 2nd method, i tried comparing my model with a calculated answer (formula gotten from J.M.Davis book on Lightweight Sandwich Construction). tried varying the mesh density and my results seemed to tell me that there is an 'optimum mesh density'. the more i meshed the stiffer the panel became till it became stiffer than the actual caluclated answer. probably this is what u are referring to as results being dramatic.
also, u mentioned z-offset, what does a z-offset do anyway? what i'm doing is just physically offsetting the individual layers.
thanks so much.....
RE: Equiv. approach to model sandwich panel
There is also an "offset" paramater for beam elements. A beam offset is same as above, except you can offset in y' and/or z' directions. Plate element z offsets don't show up on the screen, but they're in the mathematical definition during the solve, whereas most products do show beam offsets on the screen. Good luck.