Association between multiaxial mechanical properties and microstructure of porcine descending aorta

The descending thoracic aorta (DTA) is a crucial large blood vessel, and its inherent mechanical properties are fundamental to cardiovascular system stability. This study provides a pilot characterization of the biaxial mechanical behavior and microstructural features of the porcine DTA through biaxial tensile testing and histopathological analysis. The porcine DTA exhibited pronounced nonlinear hyperelastic behavior characterized by marked anisotropy: higher compliance in the longitudinal direction and greater stiffness in the circumferential direction. The experiment also found that the porcine DTA exhibited progressive mechanical damage beyond 40% strain, as evidenced by stress softening across loading cycles. Three hyperelastic constitutive models-the classical two-fiber-family HGO model, the fiber-dispersion Holzapfel model, and the four-fiber polynomial model-were evaluated for their ability to characterize the DTA mechanical response. All three models captured the essential anisotropic and nonlinear features, with performance generally increasing with model complexity. Cross-validation on independent strain ratios confirmed predictive robustness across all models. This study advances understanding of the mechanical properties and load-induced microstructural response of the porcine DTA, provides comparative validations for constitutive models with differentiated prediction accuracy and computational complexity, and establishes a foundation for computational modeling applications.