Modeling of soft composites under three-dimensional loading

The finite deformation response of fiber-reinforced hyperelastic solids under three-dimensional loading is studied through finite element simulations. The composites are modeled using representative volume elements with random fiber arrangement and periodic boundary conditions. Different matrices and volume fractions are considered. It is found that the shear stiffness of composites with Neo-Hookean components depends on the direction of the applied deformation even when the fibers are not stretched, which indicates a clear dependance on not only the I‾1 and I‾4 invariants, but also on I‾5. This anisotropy increases with the fiber concentration. The effect of using an Ogden matrix with increased nonlinearity is also discussed. Finally, the simulations are compared with suitable homogenization techniques available in the literature. A prediction using two different values of the shear stiffness is able to accurately model the response regardless of the loading direction.