Classification of Materials | Isotropic Material | Homogeneous Material | Specific Strength and Its Units

Classification of Materials
An isotropic material:
Has a stress-strain relationship that is inde­pendent of the orientation of the coordinate system at a point. An isotropic material is the one having the same elastic properties (E,µ)  in all directions at any one point of the body.

A Homogeneous Material:

A material is said to be homogeneous if the material elastic properties (E,µ) are the same at all points in the body.

Specific Strength:

This quantity is defined as the ratio of the ultimate (or tensile) strength to specific weight, i.e., weight per unit volume.  we have

And,
In the SI system, we have

So that in either system specific strength has units of length. This parameter is useful for comparisons of material efficiencies.