RTV Sealant modeling

[egal]

Dr. Bergstorm ,

Do you have any suggestions on how to model room temperature vulcanization (RTV) silicone rubber sealant? I searched through the website and can not find anything related. There are some restrictions to choose material model using gasket element.

Thanks

[Jorgen]

Hello egal,

The simplest approach is to use a hyperelastic material model (e.g. the 8-chain model, the Gent model, or the Yeoh model). If you need to also capture viscous effects (hysteresis, or energy dissipation), then you can try either a linear viscoelastic model, or if you want to be more accurate the Bergstrom-Boyce (BB) model. Note that linear viscoelasticity is only accurate for small strains, but that the BB model can work for both small and large strains.

- Jorgen

[egal]

Thanks!
The problem is, RTV is something liquid firstly. It is used on the mating surface of two parts and then cures in the room temperature like adhesives to combine the two parts with good sealing performance.

If I try to use hyperelastic model. which kind of tests I need to do for RTV?
It is so hard to test this material because it has to be tested after it is cured between two metal parts. The single tension, pure shear tests,cyclic tests are not easy to be performed accurately because it is hard to set gauge length in INSTRON or MTS machine.

[Jorgen]

I recommend (a minimum of) uniaxial tension or compression. You might be able to create suitable compression specimens if you design a specific mold.

If that does not work, then you can try to use microhardness indentation testing. You can find the hyperelastic parameters from the indentation testing through "trial-and-error" FE simulations (called 'solving the reverse problem') of the indentation setup.

- Jorgen

[egal]

Because the RTV will slip in plane and be compressed, I will try to get uniaxial compression and pure shear test data.

What is microhardness indentation testing? I have never heard about that.

Thanks

[Jorgen]

Microhardness testing is a simple test in which a very small indenter is pressed into the surface of a test specimen. During the test the force-displacement response of the indentor is carefully measured.

The test is useful for comparing the stiffness of different materials, and if you are careful, it can also be used quantitatively and for material model characterization.

- Jorgen