A mixed-enhanced strain method: Part II: Geometrically nonlinear problems

In Part 1 of this paper we presented a mixed-enhanced approach to formulating elements for application to geometrically linear problems. In the present work we consider an extension to the geometrically nonlinear case. A mixed deformation gradient is presented and enhancements developed, resulting in a formulation which produces coarse mesh accuracy in bending dominated problems and locking-free response in the near incompressible limit. As in Part 1, variational stress recovery is permissible, due to the mixed fields present. Representative simulations illustrate the performance of the formulation in the setting of incompressible hyperelasticity.