Load Displacment curve ?? the slope of the curve is E1 or E2 or E12?

[Timoko]

Hallo guys,

it may be a simple question, i had to compare experimental result with FEM. in experiment my structure is less stiff than FEM for the case of compression 400mm specimen with 10mm thickness (orthotropic).
1- Why?
2-what is delta(F)/delta(u)=E. what is E in case of orthotropic material? E1, E2, E12???
3-how to find it analytically?

best regards.

 

[rb1957]

1) "less stiff" ... in the elastic range, or plastic ?

2) how have you modelled the speciemn ? plates, solids ??

another day in paradise, or is paradise one day closer ?

 

[Timoko]

Orthotropic material is brittle so when its breaks you dont actually have to much placticity. it is plate.

 

[rb1957]

ok, you're using plate elements, with a very simple loading.

E1 and E2 refer to different directions based on the material (like grain directions). so which direction suits the loading direction ? (are you loading along the grain or across it or ?)

E12 is shear, no? (and so not relevent to a compression test)

are you confident in your material property data ?

another day in paradise, or is paradise one day closer ?

 

[Timoko]

sorry, but i dont think you have understand my question!

thanks in advance.

 

[rb1957]

there are lots of reasons why an FEM can be more stiff than the real world. all i know about your model is your accertion that it exists and i think you've used plate elements. i don't know how much stiffer it is ... 1%, 10%, 100% ?

is "what is delta(F)/delta(u)=E." a question ? E is stress/strain ... stress could be "F", or "F" could be load. "delta(u)" is probably not strain, probably it is deflection (change in length).

i'm not sure what you mean by E1, E2, E12, and countered with a more traditional engineering expression ("1" could be the direction of load, and "2" could be the transverse direction, in any case E12 looks more like G.

E is easy to find analytically, once you know what it is.

sorry i couldn't understand your question; we try to help here.

another day in paradise, or is paradise one day closer ?

 

[stressebookllc]

rb1957, it looks to me like he is doing a coupon test of a laminate specimen. I think he is doing a bare compression test.

Assuming you are using a 2D orthotropic material (PCOMP seems suitable here):
E1 - Individual ply material's primary material angle Young's Modulus
E2 - Individual ply material's secondary material angle Young's Modulus
E12 - In plane shear Modulus

Just trying to help here too...

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