Material Modeling of Polylactide

Computational modeling of stents can provide insight into critical locations (high stress/strain regions), help with design iterations/optimization, and reduce the need for bench-top testing. This study focuses on the developmental efforts to create a material model that can capture the mechanical response of poly-L-lactide (PLLA), the backbone of Abbott Vascular’s ABSORB Bioresorbable Vascular Scaffold (BVS). PLLA is an anisotropic, viscoplastic material. Its material behavior maybe affected by temperature, environment, and processing; thereby, introducing substantial challenges in modeling its response. A new test protocol was developed for performing material characterization experiments that can capture the anisotropic material response using a dog-bone shaped specimen. The Parallel Network (PN) model from Veryst Engineering is an advanced modular constitutive model framework. The PN model allows for specific anisotropic and isotropic hyperelastic and viscoplastic components to be combined to capture the experimentally observed response of PLLA. The material model (PN model) was calibrated to experimental data from the dog-bone material testing. A validation experiment (single ring tensile test) was performed and the fidelity of the computational model was tested by comparing its predictions to the single ring tensile test data.