Figure 1.

Schematic describing model configurations and kinematics. The glycosaminoglycan (GAG), other matrix (MAT), and collagen (COL) reference configurations ${\kappa }_0^{\mathit{GAG}},{\kappa }_0^{\mathit{MAT}}$, and ${\kappa }_0^{\mathit{COL}}$, respectively, are identical to the solid matrix (SM) reference configuration κ_R. Due to the GAG swelling pressure, both the GAG and SM stresses T^GAG and T^SM are not zero in κ_R. Consequently, a swelling deformation gradient tensor F_sw maps κ_R to a stress-free SM configuration κ₀. Mechanical testing was simulated by prescribing the experimental deformation gradient tensor F_exp that maps κ₀ to the deformed equilibrium configuration κ.