What is the end goal of your simulation? Are you trying to calculate the max. force required to pull the silicone joint out? If that is the case, then you may want to apply a displacement boundary condition and calculate the reaction force on it to answer your question.
Now coming to a bigger question, how is the silicone joint held inside? You defined a bonded contact between them but in reality is it glued to it or is it similar to a push pin where the friction is holding them together?
- If this is a press-fit assembly, then you don't need any failure models. You'll need to start by solving for interference fit first so that contact pressure is developed and friction will be sufficient to hold them together. Then in the second step, you can apply the displacement and measure the force required to remove the silicone joint.
- If there is a glue, then cohesive zone material modeling is the way to go. You'll need the max. shear bond strength of the glue and the max. distance at which it fails. I'd recommend you read about it in the help documentation to gain insight.
- If you want to model the failure of silicone, then Mullins effect is not the way forward. You'll need to use explicit solve (Explicit STR or ANSYS LS DYNA) and turn on element erosion so the elements are deleted when they meet a user-defined criteria (e.g., max. strain).
Also, if you're reducing it to a 2-D model make sure that you're using the appropriate 2-D behavior. For instance, 2-D axisymmetric would not be suitable for what you're doing, plane strain is probably what you want.