ABSTRACT
An isotropic material is one which has identical mechanical, physical, thermal, and electrical properties in every direction. Isotropic materials involve only three elastic constants; the modulus of elasticity, E; the shear modulus, G; and Poisson's ration, v. Any of the components can be isotropic or anisotropic, and the construction may or may not be midplane symmetric. The rapidly increasing use of anisotropic materials, such as composite materials, has resulted in a materials revolution. Having defined all of the elastic stress and strain tensor components, the stress-strain relations are now used to derive the anisotropic stiffness and compliance matrices. On the surface of the control element there can exist both normal stresses and shear stresses. Materials which have three mutually-orthogonal planes of elastic symmetry are called "orthotropic". There are several sets of equations for obtaining the composite elastic properties from those of the fiber and matrix materials. A piezoelectric material is one of several intelligent materials used to develop adaptive structures.
