Fiberglass Material Properties

[E-Boogie]

Good morning all,

I have been asked by a subdivision of our company to structural integrity of a fiberglass building during a loading condition (picking up a motor with a chain hoist mounted to the roof). My understanding of composites needs work. I will be running an FEA simulation using Inventor NASTRAN. NASTRAN will allow you to compile a composite. The problem is defining material properties. I could be missing something simple but I have not found what I'm looking for in my search so far.

The fiberglass will be sprayed onto an insulation board in random directions. I need to define the material properties for the fiberglass laminate.

Information given by resin data sheet
Typical Properties of a 1/8" Laminate (4 plies of 1.5 OZ/FT^2):
Flexural Strength = 22,300 psi
Flexural Modulus = 11.7 x 10^5 psi
Tensile Strength = 12,700 psi
Tensile Modulus = 13.3 x 10^5 psi
Tensile Elongation = 1.1%
Barcol Hardness = 44 - 48

Since the fiber orientation will be random I would think the material is transverse isotropic.

Here are the values that I need to define the material in Inventor:
Young's Mod 1: *I would think this is equal to my tensile modulus
Young's Mod 2: *I would think this is equal to my flexural modulus
Poisson's Ratio 12:
Poisson's Ration 23:
Shear Modulus:
Yield Strength: *will the yield and tensile strength be the same in this case? Will a fiberglass laminate yield (elastically) or will it break (plastically)?
Tensile Strength: *given

The glass will be C glass fiber if this helps.

Thank you very much for your help!

 

[EdStainless]

If this is sprayed chopped fiber then all properties in the plane should be the same.
But you data sheet talks bout plies, and you are talking about spray. Could be very different fiber orientations.
Put a piece of Saran wrap on a board, have them spray and cure as usually, cut some test samples.


= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

 

[rb1957]

"Young's Mod 1: *I would think this is equal to my tensile modulus
Young's Mod 2: *I would think this is equal to my flexural modulus"

not the way I understand it ...
E1 and E2 are Young's modulus in the two in-plane directions ... your data is probably E1, and E2 is ?? AS Ed suggests, chopped fibre properties are probably the same in both directions.
use tensile or flexural depending on whether the laminate is in bending or axial load.

Are you planning to verify your FEA somehow ?


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

 

[E-Boogie]

Thanks for the replies guys!

Ed I feared that was the best option to truly understand the material properties. I was wondering if there was any way to manipulate the information that I have to fill in missing material properties. I think I will follow this path.

rb your explanation makes sense. I am missing information. For verification I was planning on doing a hand calc treating the building roof as a beam fixed on each end, translate the distributed weight over the plate to point loads in the bolts fixing the mounting plate to the roof, and then stress calculations based on the force results and material thicknesses (roof, plates, bolts.) I should probably do a deflection calculation as well.

 

[rb1957]

is this chopped fiber ?

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

 

[E-Boogie]

Yes sir this is a chopped fiber. Strands will be between 2" and 3" long.

 

[rb1957]

ok, so like Ed suggests E1 = E2 (properties the same in all directions).
nu12 = n21 = ?
nu13 = nu23 = ?
I don't know poisson for resin bulk with chopped fiber ... maybe the same as resin ??
shear modulus = ? (isn't there a relationship between E, nu, and G ?)
Ftu, fty easy to measure with a test (several samples)

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

 

[EdStainless]

But if all of the in-plane properties are equal that leaves the thickness (thinness?).
If you built a layer 1/4" thick and then cut 1/4" x 1/4" strips from it you will quickly find which direction is which.
In directional lams the x and y can often be 2-6 times different in modulus.
In your case the through thickness direction will be very low.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

 

[E-Boogie]

rb,
There definitely is a relationship between E, nu, G but I only have one of the three values. E= (2*G)(1+nu)
I do not have a value for nu or G.
The information I listed is the extent of the information that I was given.

I have found the same thing about directional properties.

Thank you very much for your help. I will be asking for a lab test of specimen samples.