3RD-ORDER STIFFNESS CONSTANTS OF TEXTURED HEXAGONAL CRYSTALLITE AGGREGATES WITH AN ORTHOTROPIC MACROSCOPIC SYMMETRY

Voigt-type averaging is carried out to obtain the effective second- an d third-order elastic stiffness constants of textured hexagonal (6/mmm , 6m2BAR or 6mm point group) crystallite aggregates with orthotropic m acroscopic symmetry. The second-order constants agree with previously reported results. The third-order constants are presented in a compact formula. The formula relates the effective third-order stiffness cons tants to the crystallite orientation distribution coefficients (CODCs) and the single-crystal third-order stiffness constants. If any two of these three sets of parameters are known, information of the third se t can be inferred. The sensitivity of the effective third-order stiffn ess constants to changes of the CODCs is also given.