There are certain classes of materials that are not supported by Smart Slice. Specifically flexible materials and support materials are not supported.
The purpose of Smart Slice is to evaluate the structural performance (part stiffness and strength) of plastic parts manufactured using the FFF 3D printing method. Hence, support materials are not evaluated by Smart Slice because they are removed once the part is printed and therefore do not contribute to the stiffness or strength of the part. Flexible and rubber-like materials are not supported because they exhibit highly nonlinear stiffness behavior and are therefore ill-suited for linear finite element simulations.