Review on spectral decomposition of Hooke’s tensor for all symmetry groups of linear elastic material

The spectral decomposition of elasticity tensor for all symmetry groups of a linearly elastic
material is reviewed. In the paper it has been derived in non-standard way by imposing the
symmetry conditions upon the orthogonal projectors instead of the stiffness tensor itself. The
numbers of independent Kelvin moduli and stiffness distributors are provided. The corresponding
representation of the elasticity tensor is specified.