Nonlinear response of graphite structures

A nonlinear constitutive relation for graphite under three-dimensional stress states is presented for the finite element stress analysis. In the constitutive formulation, graphite is assumed to be transversely isotropic and an incremental stress-strain law is utilized in conjunction with a loading function which is used to specify the elastic or elastic-plastic state of deformations. The loading function is also used to define the strain-hardening of the material starting from the initial yielding state to the failure (or fracture) state. Therefore, by using this constitutive relation, not only the nonlinear load-deformation response of graphite is determined, but also its failure load and corresponding failure mode can be predicted