z direction(out of plane)properties for composites 5

[alleak]

For an ansys analysis i need to know z direction(out of plane)material properties of on filament wound carbon/epoxy composite.but in handbooks i saw only the properties in x,y&xy directions.how can i have these properties.any help would be appreciated.

Cheers

alleak

 

[SWComposites]

What specific material system do you have? There is some thru-thickness shear data in Mil-Handbook-17. Other values can be estimated from the im-plane values.

 

[alleak]

Hi SWComposites ;
It is necessary at least to enter Ez & Strenght in Z direction and it is sufficient to enter other modulus and strenghts relating to z direction.

Cheers

alleak

 

[SWComposites]

I don't understand your reply. What material are you analyzing? What are the in-plane properties that you are using for your analysis?

 

[alleak]

I am analysing a 3d composite(carbon/epoxy) pressure vessel and i want to obtain tsai-wu failure criterian.I have only these properties1,2 or x,y are in plane 3 or z is out of plane)
MODULUS: E1,E2,G12
STRENGHT: Xt,Xc,Yt,Yc,S
POISON RATIO:NU12
but there are more properties required by ansys,if i leave other blank ansys shows an error,until i use a value for modulus E3,and strenghts Zt,Zc,now ansys will solve the problem.I think this is because The Tsai-Wu failure criteria used in ansys are 3-D versions of the failure criterion.plus these there are other properties which leaving them blank does not make an error in ansys but this may influnce on the results.these properties are:
G23,G13,NU23,NU13,Zt,Zc,Syz,Sxz




Cheers

alleak

 

[SWComposites]

You are obviously using solid elements in your model, therefore you will need to enter a full set of 3D stiffness properties. You will have to look in the Ansys manual regarding what strength properties for the failure criteria are required, but I suspect that a 3D set is required also. Now, as to what values to enter, you need to answer the following questions (which I will ask for the third and last time):
- what specific material are you using (fiber, resin, vendor)?
- what values are you entering for the in-plane properties? I know what the variables are; what is needed is the actual values.

 

[alleak]

I used shell elements(shell 99 which is Linear Layered Structural Shell)and i mentioned that in ansys manual The Tsai-Wu failure criteria used are 3-D versions of the failure criterion .so strenghts in all directions(x,y,z,xy,xz,yz)are required.
your questions:
1-carbon fibers are TC-42 from TAIRYFIL co.
2-epoxy resin is LY5052,and hardener is HY5052,these are from CIBA co.
3-Wf(fiber weight ratio)is 0.625 so Vf(fiber volume ratio)is 0.5
4-values entered first are:
modulus:
Ex=1.103e11 pa
Ey=1.52e10 pa
Gxy=4.9e9 pa
poison ratio:
PRxy=0.25
strenght:
XTenstrs=1.918e9 pa
XComstrs=-1.569e9 pa
YTenstrs=2.74e8 pa
YComstrs=-1.245e9 pa
XYShstrs=6.895e7
by these values ansys shows an error
so i entered :
Ez=Ey
ZTenstrs=YTenstrs
ZComstrs=YComstrs
and i got a result but other values which may affect the final results are left blankG23,G13,NU23,NU13,Zt,Zc,Syz,Sxz )

Cheers

alleak

 

[SWComposites]

Ok, assuming this is a unidirectional tape material (which it appears to be by the stiffness properties that you listed), I recommend the following based on other typical carbon fiber/epoxy materials (room temperature/ambient properties):

YT and YC appear to be way too high for a carbon/epoxy tape. I would use something like:

YT = 8 ksi (5.52E7 pa)
YC = -40 ksi (-2.76E8 pa)

for the thru-thickness properties:

EZ = 1.3 msi (8.97E9 pa)
(note your value for EY of 2.2 msi seems too high for an epoxy material at room temperature)
G13 = G12 = 4.9E9 pa
G23 = 0.67*G12 = 3.28E9 pa
NU13 = NU12 = 0.25
NU23 = [EZ/2/G23]-1 = 0.365 (assumes material is isotropic in the 2-3 plane)
ZT = YT = 8 ksi (5.52E9 pa)
ZC = YC = -40 ksi (-2.76E8 pa)
SXZ = SYZ = 5 ksi (3.45E7 pa)

Hope this helps.

 

[alleak]

Thanks a lot for your consideration.The values i mentioned are based on this book:
Hyer M.W.,"Stress Analysis of Fiber Reinforced Composite Materials"McGrawHill 2001
perhaps these are for another kind of carbon/epoxy.
but i want to know how did you guess Ez and other formula,where are they from.are they from a reference or they are from your own experiments.

Cheers

alleak

 

[SWComposites]

I did not "guess" anything. My recommendations are based on 20+ years of experience with composite materials and a lot of test data. Unfortunately, I do not have data for your specific material system (TC42/5052). Data published in textbooks is usually of unknown pedigree and of questionable value. One source of composite material data is Mil-Handbook-17 (copies of which can be purchased at

http://www.astm.org)

Volume 2 contains data for a number of carbon/epoxy material systems, though not your specific material.

 

[RvL04]

Hi Alleak;

Why don't you get your materials tested? You can get the material results in all directions you need. Some materials testing labs (like

http://www.axelproducts.com)

can help you out with that quite easily!

Ron

 

[RPstress]

SW: where did you get your 2/3 factor for G23 from? We've seen various values recommended for this over the years, but have not got a "definitive" one. It can have a significant effect on buckling predictions.

 

[SWComposites]

RP: there is some thru-thickness shear stiffness data (G13, G23) in Mil-Handbook-17, Volume 2, Rev F for a couple of carbon fiber/epoxy materials. I based my factor on this data and other proprietary data which I have access to.

 

[RPstress]

Ah. Thanks. I hadn't spotted that snippet in MIL-HDBK-17. I'm always finding stuff in there that I didn't know was there.

 

[clocklight]

you can assume the fiber is isotropic. so the properties you need input are only E and v. The composite will be transversely isotropic in this case.