This article sucks 

for one thing, it focuses exclusively on solid material - what about fluids and solids? For another, the most important concepts are buried under mountains of crap - the most simple, basic and important concepts, like ductile materials failing under shear and brittle failing under normal, fluids supporting normal but flowing under shear ... that should be in the intro. Instead, the article drones on and on with graduate level tensor math that should be spit into other articles.