What is the Shear Modulus for G10?

jahall4 · Apr 20, 2019

Given the common use of the material for fins you would think a value (or a range of values) would be readily available, but after more than an hour of looking no joy. A link would be most appreciated.

Thanks in advance.

JJSR · Apr 20, 2019

I would think it would depend on what glue/epoxy used and if it's through the wall or surface mounted.

Steve Shannon · Apr 20, 2019

https://www.professionalplastics.com/professionalplastics/PhenolicG-10FR4DataSheets.pdf

19,000 psi

blackjack2564 · Apr 20, 2019

They may look the same for any given thickness, but supplier/manufacturer makes HUGE difference in quality/flex.

Need to get specs from them.
Are you trying to figure out flutter issues with this info?

Steve Shannon · Apr 20, 2019

Here’s a different site that lists 21,500 psi.
https://www.industries3r.com/images/absolucatalog/documents/NEMA G10_FR4 - Industries 3R ENG.pdf

Keep in mind that G10 is an older NEMA standard material, but the standard is not based on shear strength so it can vary.

jahall4 · Apr 20, 2019

Steve Shannon said:
https://www.professionalplastics.com/professionalplastics/PhenolicG-10FR4DataSheets.pdf

19,000 psi

Great example of the problem, this sounds way low I now have figures ranging from 19,000 - 1,600,000 psi

jahall4 · Apr 20, 2019

blackjack2564 said:
They may look the same for any given thickness, but supplier/manufacturer makes HUGE difference in quality/flex.

Need to get specs from them.
Are you trying to figure out flutter issues with this info?

Yes, sure am, and have not found a single manf that specifies "Shear Modulus".

Steve Shannon · Apr 20, 2019

jahall4 said:
Great example of the problem, this sounds way low I now have figures ranging from 19,000 - 1,600,000 psi

Where did you see 1.6 Megapsi?
All the sources I found list right around 20k psi.

Steve Shannon · Apr 20, 2019

I apologize; my answers are all shear strength, not shear modulus.

jahall4 · Apr 21, 2019

Steve Shannon said:
Where did you see 1.6 Megapsi?
All the sources I found list right around 20k psi.

In a NASA SLI CDR that has some incorrect calculations

. 20K psi is probably shear strength not modulus.

heada · Apr 21, 2019

McMaster-Carr part 9910T63

"Flexural Strength 45,000-55,000 psi"

If you have a MIL-Spec, you can search their site with the spec and find stuff that way too.

blackjack2564 · Apr 21, 2019

Maybe this will help.
From personal experience pushing minimum diameter rockets to limit with commercial motors.
38mm min. diam. fins carbon plate just glued to surface. 1/16
54mm 1/8 in fins. G-10... M-2.3 surface mount no T-T
75mm 3/16 carbon fins Hysol epoxy M-2.6 surface mount no T-T [would use 1/8 carbon if did over]

4in airframe through wall 75mm mount. 3/16 G-10 just external fillets....any motor you can stick in it. No issue M-2.1

Fin shape and material are most important to success. [and glue]
Most 4in rockets with a 75mm motor mount will not come apart with any commercial motor you can stick in it that I know of, as long as proper build technique used. [3/16 fins]

tfish · Apr 21, 2019

some cut and paste from an old email of mine...
____________________________________________________

Here are some of the specs from McMaster. https://www.mcmaster.com/#8667k243/=1bhdwzr
G10/FR4 .125"
Max Temp 265F
Compression strength 35,000
Flexural Strength 45,000

I found a new source, where the material seems to have better specs. https://accurateplastics.acculam.com/Asset/Acculam®EpoxyglasG11,FR5.pdf
G11/FR5 .125"
Max Temp 356F
Compression Strength 65,000
Flexural Strength 75,000

There is a $75 min order. They also don't tell you the shipping costs until after is ships. (same as McMaster?)
I ordered two .125" x12x24 sheets plus one .062" x12x12. came to $75.94

Shipping was $23.52 from Yonkers New York

Info only....
_____________________________________________________________________

I normally use .097 'G10'..mostly because a buddy of mine gave me several sheet of surplus mil spec stuff he got from Loockheed. I'm working on a project that I wanted/needed better stuff. That's how I came across the above.

Tony

jderimig · Apr 21, 2019

jahall4 said:
Yes, sure am, and have not found a single manf that specifies "Shear Modulus".

That is because shear modulus is not commonly measured. Young's or Elastic modulus is and G is then often approximated (usefully) with the Poisson's ratio formula.

jahall4 · Apr 21, 2019

heada said:
McMaster-Carr part 9910T63

"Flexural Strength 45,000-55,000 psi"

If you have a MIL-Spec, you can search their site with the spec and find stuff that way too.

Not the same thing, Shear Moduluses are typically 6 and 7 digits for the type of materials we use in HPR

jahall4 · Apr 21, 2019

jderimig said:
That is because shear modulus is not commonly measured. Young's or Elastic modulus is and G is then often approximated (usefully) with the Poisson's ratio formula.

Yep, That's what I'm finding out. The hobby needs a Wiki!

jderimig · Apr 21, 2019

jahall4 said:
Yep, That's what I'm finding out. The hobby needs a Wiki!

You can measure modulus with your PC.

Get a rectangular sample of the material.
Clamp to the edge of the table leaving an overhand.
"Pluck" the sample, record the sound using your PC recorder.
Run an oscilloscope app and find the frequency.
Calculate E using the mechanics formulas.

jahall4 · Apr 21, 2019

tfish said:
some cut and paste from an old email of mine...
____________________________________________________

Here are some of the specs from McMaster. https://www.mcmaster.com/#8667k243/=1bhdwzr
G10/FR4 .125"
Max Temp 265F
Compression strength 35,000
Flexural Strength 45,000

I found a new source, where the material seems to have better specs. https://accurateplastics.acculam.com/Asset/Acculam®EpoxyglasG11,FR5.pdf
G11/FR5 .125"
Max Temp 356F
Compression Strength 65,000
Flexural Strength 75,000

There is a $75 min order. They also don't tell you the shipping costs until after is ships. (same as McMaster?)
I ordered two .125" x12x24 sheets plus one .062" x12x12. came to $75.94

Shipping was $23.52 from Yonkers New York

Info only....
_____________________________________________________________________

I normally use .097 'G10'..mostly because a buddy of mine gave me several sheet of surplus mil spec stuff he got from Loockheed. I'm working on a project that I wanted/needed better stuff. That's how I came across the above.

Tony

Thx! Good info, I commonly use McMaster's G10, but if they can't provide a Shear Modulus that may stop. If Accurate Plastics really has a glass that much stronger it may be worth the extra change.

jahall4 · Apr 21, 2019

jderimig said:
You can measure modulus with your PC.

Get a rectangular sample of the material.
Clamp to the edge of the table leaving an overhand.
"Pluck" the sample, record the sound using your PC recorder.
Run an oscilloscope app and find the frequency.
Calculate E using the mechanics formulas.

John your sort of making my point

but it would be interesting to see if it works.

jahall4 · Apr 21, 2019

blackjack2564 said:
Maybe this will help.
From personal experience pushing minimum diameter rockets to limit with commercial motors.
38mm min. diam. fins carbon plate just glued to surface. 1/16
54mm 1/8 in fins. G-10... M-2.3 surface mount no T-T
75mm 3/16 carbon fins Hysol epoxy M-2.6 surface mount no T-T [would use 1/8 carbon if did over]

4in airframe through wall 75mm mount. 3/16 G-10 just external fillets....any motor you can stick in it. No issue M-2.1

Fin shape and material are most important to success. [and glue]
Most 4in rockets with a 75mm motor mount will not come apart with any commercial motor you can stick in it that I know of, as long as proper build technique used. [3/16 fins]

Yep, you have summed it up pretty good, that's what I figured before I began this quest and what I'm finding out... except for the NASA SLI TEAM who documentiend in their CDR that their fins would flutter at Mach 75

jderimig · Apr 21, 2019

jahall4 said:
Thx! Good info, I commonly use McMaster's G10, but if they can't provide a Shear Modulus that may stop. If Accurate Plastics really has a glass that much stronger it may be worth the extra change.

The problem is that G10 is probably anisotropic. So a modulus spec doesn't mean anything unless its accompanied with an orientation. What the about the modulus in the other orientations?

jahall4 · Apr 21, 2019

jderimig said:
The problem is that G10 is probably anisotropic. So a modulus spec doesn't mean anything unless its accompanied with an orientation. What the about the modulus in the other orientations?

I'm sure it is some, but not nearly as anisotropic as say plywood so you assume the worst case (orientation) and use that in your calculations.

cptcolo · Oct 1, 2019

jahall4,

You could assume it is isotropic. From Dave Steinberg - Vibration Analysis for Electronic Equipment 3rd Ed, p 131: G-10 epoxy fiberglass has modulus, E = 2,000,000 psi CW, Poisson's Ratio, nu = 0.12. Shear Modulus, G = E/(2*(1+nu)) = 892,857 psi

Charley

jahall4 · Oct 1, 2019

cptcolo said:
jahall4,

You could assume it is isotropic. From Dave Steinberg - Vibration Analysis for Electronic Equipment 3rd Ed, p 131: G-10 epoxy fiberglass has modulus, E = 2,000,000 psi CW, Poisson's Ratio, nu = 0.12. Shear Modulus, G = E/(2*(1+nu)) = 892,857 psi

Charley

Wow, Charley, thanks for following up on such and old post!

What is the Shear Modulus for G10?

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