HOW TO EXPERIEMENT FOR SHEAR MODULUS IN COMPOSITE

[sharpedge]

Hi ya all,
Just wondering if any could help with information on best way to test for Shear modulus and Poisson ratios in composite. And is there a way one can use a FE method to test for this?,..

Cheers.

 

[xerf]

You can build a FE model of a composite sample (RVE =representative volume element. Basically, one should model the micro-structure of the composite.

Then one can subject the RVE to constant macro-strain/stress.

Based on the FE solution, one can average the micro-stress/strain components and establish obtain for example the effective shear and bulk moduli from the averaged micro-stress/strain components.

 

[GBor]

I don't have the test procedures off the top of my head, but there are standard procedures for shear. Generally, testing is performed to generate these properties. You can approximate them, but you need to perform the test if there isn't available test data already BEFORE expecting an FEA to give accurate results. Mil-HNDBK-17, I think, is very helpful for this. I know you can purchase an electronic copy at

http://www.materials-sciences.com.

Garland E. Borowski, PE
Borowski Engineering & Analytical Services, Inc.
Lower Alabama SolidWorks Users Group
Magnitude The Finite Element Analysis Magazine for the Engineering Community

 

[SWComposites]

Tensile test per ASTM D3039 for Poission's ratio, using biaxial strain gages or extensometers

In-plane shear test per ASTM D7078 for shear modulus, or tensile test of +/-45 laminate per ASTM D3518.

See ASTM D4762 for a guide to the various test standards for composites.

You cannot "test" with FEA; you can make "predictions" of structural response.

 

[sharpedge]

Cheers guys for your valuable post, my only worry is there seems to be several test methods for carrying out shear modulus on composite, how do I know which is most appropriate.

Many thanks.

 

[SWComposites]

It depends -
What specific material are you testing?
What is the ply thickness?
What do you want to use the shear modulus for?
At what temperature do you want to test?
Which test methods are you considering?
Do you need the non-linear shear stress-strain curve, or just this initial linear shear modulus?
What capabilities does your lab have?
Which test fixtures do you have?

 

[Tmoose]

Our folks came to rely heavily on this test to determine the interlaminar shear strength of the stuff we made and had made.

http://www.compositesworld.com/hpc/issues/2006/July/1350

The test beam had to be made with a process and materials REALLY representative of what we were doing.