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2.8.4 Simple Solid Mixtures
In the simplest type of non-reactive constrained mixtures of solids all constituents share the same reference configuration , in which case and . For this type of mixture where does not evolve, it is convenient to set for all and scale the material properties of to properly reflect the contribution of each constituent to the mixture. Thus, the relation of eq.(2.8.3-8) reduces to This type of non-reactive mixture of solids is represented in FEBio using the material “solid mixture”.
When each constituent of a solid mixture is modeled using an uncoupled formulation to enforce nearly isochoric responses, the strain energy density of this type of mixture is given by where is the volumetric energy component, is the distortional energy component, and is the distortional part of the deformation gradient, as described in Section 2.4.3↑. This type of non-reactive mixture of uncoupled solids is represented in FEBio using the material “uncoupled solid mixture”.