Viscoelastic Properties of Porcine Pericardium Under Biaxial Tensile Creep and Stress Relaxation: Application for Novel Aortic Valve Bioprosthesis Design

This study quantified time-dependent biaxial viscoelastic behavior of Landrace porcine pericardium to support durable aortic valve bioprosthesis design and long-term FSI simulation. Square pericardium specimens (10 mm × 10 mm) were harvested from 51-week-old pigs, mounted for equibiaxial loading, and tested in PBS at 37°C. The authors performed biaxial tensile creep tests by sustaining a 0.5 N equibiaxial load for 30 minutes, and biaxial stress relaxation tests by imposing a constant 10% equibiaxial strain for 30 minutes. Across seven experiments, the radial direction was more compliant (higher strain), but the time-dependent creep evolution in circumferential and radial directions was statistically similar at 1, 60, 300, 900, and 1800 seconds; after 30 minutes, mean creep deformation was 3303 × 10^-6 (circumferential) and 5192.9 × 10^-6 (radial). Stress relaxation showed higher stresses in the circumferential direction than radial direction, with both directions relaxing at similar rates; after 30 minutes, stresses were ~15.28 kPa (circumferential) and ~9.6 kPa (radial). To enable computational use, viscoelastic constitutive parameters were identified using Prony-series representations: a generalized Kelvin–Voigt model for creep (R² ≈ 0.96 circumferential and 0.98 radial) and a generalized Maxwell model for stress relaxation (R² ≈ 0.89 circumferential and 0.75 radial), optimized via the Levenberg–Marquardt algorithm. The resulting parameter sets are positioned as inputs for finite element and FSI simulations to predict long-term leaflet fatigue, sealing, and performance in novel aortic valve bioprostheses.