how can apply the material that not exist in the materials library?
Solidworks allows you to create and save custom materials. If you know enough of the materials properties to suit your purpose, simply create a custom material and save it to the custom materials library and it will be there for you to apply.
For example, we often use engineered plastic that isn't quite the same density as the nearest matching default library plastic, so we adjust the density and save it as a custom material to apply to the appropriate parts.
I usually just pick something known to be close until such time that we have better detail. All we really use material properties for is estimating things such weight so it isn't super crucial.
thank you for your helpful explaining ... what we have to do if we have no properties of material ??
for example new plastic that we have no information about ?