Silicone Gasket Expansion from Compression

[Stamos87]

Hi Everyone!
I have a gasket that I am designing to go into an aluminum backshell for a high speed cable. I am trying to determine the size of the groove I should make. The gasket is silicone and 1/32" thick. The width x length is 4mm x 77mm. If I add 20% compression, how will that change the outside dimensions? I'm sure there is a formula for this. That would be helpful as well. I'm also not sure of what hardness to get. I am guessing 50A or 60A.

Any help would be greatly appreciated. Thank you!

 

[Luis.Tormento]

Due to elastomer characteristic, you will never have the same sizes for an elastomer, only a range for it. This change depends on production process, filler mixing, temperature of curing and curing process. My sggestion is that you produce your aluminum backshell with the silicone inside, to avoid dimensions variaation.

 

[acspain]

Elastomers are considered incompressible, the volume will stay the same. So you need to allow enough space in the groove to accommodate the material moving due to the compression. If the temperature of the application changes, you will also need to allow space for the elastomer to expand into, as generally the elastomer has a larger coefficient of expansion than the housing. In my previous work, we would test the compound for mechanical and expansion properties to feed a FEA model to determine how the gasket would move due to compression and temperature.

Hardness does not strictly correlate with elasticity. It is possible to compound an elastomer with differing hardness and have the same elasticity. Compare 100% Modulus or Tensile Strength instead.