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Hi all!
Usually, one would model a rubber as incompressible (##\nu \rightarrow \infty## or equivalently ##\kappa \rightarrow \infty##, where ##\nu## is Poisson ratio and ##\kappa## is bulk compressibility). However, I am trying to use rubber in an application where performance will improve the closer ##\nu## gets to 0.5. Are there any commercially available elastomers that are exceptionally incompressible (better than other elastomers)? (I know that relying on consistent material properties from something like rubber is generally a bad idea, but if this works it would be very convenient.)
For background, the reason I am doing this is to achieve a joint that is stiff axially and compliant tangentially. My thought was to use a thin disk-shaped pad of rubber. According to this reference (publisher link, open-access link), the axial stiffness of a thin cylindrical pad of rubber should scale like ##\frac{1}{1-2\nu}##, which will tend towards infinity as ##\nu \rightarrow 0.5##. In contrast, the transverse stiffness does not scale like this and does not explode as ##\nu \rightarrow \infty##. (See equations 3-3a (axial) and 3-3c (shear) in the linked reference for the exact formulae.) I've verified this trend with finite-element simulations (at least using a linear elastic material model, still working on a hyperelastic material model). But, this only works if the rubber's Poisson ratio is very close to 0.5 (the closer, the better). Hence my question above.
I realize that wires satisfy the same criteria above (stiff axially, compliant tangentially). But the rubber pads would be much simpler to implement in my application. Wires are my plan B if this rubber pad idea doesn't pan out.
Thanks in advance for your input!
Usually, one would model a rubber as incompressible (##\nu \rightarrow \infty## or equivalently ##\kappa \rightarrow \infty##, where ##\nu## is Poisson ratio and ##\kappa## is bulk compressibility). However, I am trying to use rubber in an application where performance will improve the closer ##\nu## gets to 0.5. Are there any commercially available elastomers that are exceptionally incompressible (better than other elastomers)? (I know that relying on consistent material properties from something like rubber is generally a bad idea, but if this works it would be very convenient.)
For background, the reason I am doing this is to achieve a joint that is stiff axially and compliant tangentially. My thought was to use a thin disk-shaped pad of rubber. According to this reference (publisher link, open-access link), the axial stiffness of a thin cylindrical pad of rubber should scale like ##\frac{1}{1-2\nu}##, which will tend towards infinity as ##\nu \rightarrow 0.5##. In contrast, the transverse stiffness does not scale like this and does not explode as ##\nu \rightarrow \infty##. (See equations 3-3a (axial) and 3-3c (shear) in the linked reference for the exact formulae.) I've verified this trend with finite-element simulations (at least using a linear elastic material model, still working on a hyperelastic material model). But, this only works if the rubber's Poisson ratio is very close to 0.5 (the closer, the better). Hence my question above.
I realize that wires satisfy the same criteria above (stiff axially, compliant tangentially). But the rubber pads would be much simpler to implement in my application. Wires are my plan B if this rubber pad idea doesn't pan out.
Thanks in advance for your input!
