Could someone explain me the underlined:
"Of the different facets of a materialís behaviour, rheological behaviour is needed for the Mechanics of Materials."
Does it mean "rheological behaviour of the different facets of a materialís behaviour"?
No. It means that, when one is considering the mechanics of a material, then from all of the different facets of that material's behaviour, one has to focus on the rheological behaviour of that material.
I'm not a teacher of English, but I have spoken it for (almost) all of my life....