Rubber sheet deflection?????

[14erclimberIA]

I'm working on a project that is going to require a rubber sheet (10'-0 long x 2'-0) to be adhered 6" onto a horizontal steel plate with the remaining 1'-6 of width then cantilever off the the side. How do I find out what the minimum DURO and thickness of material I need to achieve a minimum amount of downward delflection under the sheet own self weight? We would be satisfied with 4-6 inches of deflection, does anyone have any suggestions? Do there exist any charts or equations, etc, related to this?

 

[SealGuru]

Most stress strain-curves in rubber are done in compression. Also remember that rubber is non-linear in stress-strain.
Your best bet is to do finite element analysis (FEA). Input the "E" (slope) and choose a K factor around .5. If you have access to Cosmos, they have rubber properties in there already that should get your pretty close.
It might be easier to get 1" inch strips of rubber with various sizes and test them. That will be the most accurate as well.
if you find that the thickness required to get your deflection is too think, you can have your rubber sheet fabric reinforced. Basically, fabric is molded with the rubber and thus makes it a lot stiffer in bending.

Best,
Michael
Engineer
Mykin Inc

http://mykin.com

Michael Chou

http://mykin.com

 

[glass99]

Hi 14erclimberIA,

I have found the Gent formula to be useful. It relates shore A hardness to young's modulus. I did some lab testing recently, and found it to be somewhat accurate (between 10% and 70% error for the silicone rubber I was testing).

 

[glass99]

I meant to add, you can find the Gent formula on Wikipedia:

http://en.wikipedia.org/wiki/Shore_durometer