Background and Purpose: An aortic aneurysm is a localized and permanent dilation of the aortic wall that has a risk of rupture, which can lead to life-threatening consequences. Reliable predictors to assess rupture risk of aneurysms are currently lacking. Changes in the composition and organization of the aortic wall, as seen in aneurysmal tissue, may influence how the vessel responds to mechanical stress. Studying rupture characteristics in aneurysmal tissue with varying wall structures may, therefore, support the identification of more reliable indicators of rupture risk.
This study aims to characterize the rupture behavior of healthy porcine aortic tissue using a custom-designed symmetry-constraint compact tension (SymconCT) test. The SymconCT setup is a modified version of a compact tension test specifically designed to analyze fracture behavior in soft biological tissues. Rupture behavior is evaluated under both longitudinal and circumferential tensile loading to assess mechanical response in different loading directions. Healthy porcine aortic tissue was chosen for testing the SymconCT setup before application in diseased human tissue due to its close anatomical similarity to the human aorta.
Methods: The recently designed SymconCT test setup was developed for soft tissue rupture analysis. In this setup, rupture is initiated from a notch at a fixed location on the sample. To prevent buckling of the soft tissue during loading, the SymconCT incorporates a pre-straining beam opposite the notch, enabling controlled crack propagation. Eight healthy porcine aortic samples (five circumferential, three longitudinal) were tested under tensile loading in longitudinal or circumferential directions. Digital Image Correlation was used to evaluate the deformation field. Fracture behavior was characterized by ultimate stress, ultimate strain, strain at the crack tip, initiation energy, and dissipation. Crack trajectories were reconstructed based on maximal strain localization.
Results: Orientation-dependent fracture behavior was observed. Circumferential samples showed higher ultimate stress (289.2 ± 58.4 kPa vs. 184.6 ± 29.8 kPa) and ultimate strain (157 ± 9.1% vs. 111 ± 42.4%) compared to longitudinal samples. Initiation energy was almost twice as high in circumferential samples (21.78 ± 5.99 mJ/mm vs. 11.04 ± 4.12 mJ/mm). Energy dissipation was also higher in circumferential samples (1.34 ± 0.42 mJ/mm² vs. 0.98 ± 0.12 mJ/mm²). Longitudinal samples fractured in relatively straight pathways, whereas circumferential samples exhibited more zigzagging fracture paths.
Conclusion: The custom-designed SymconCT setup successfully captured rupture behavior in healthy porcine aorta tissue. It facilitated a stable rupture progression, demonstrating the method's capability of soft tissue fracture testing. The results reveal orientation-dependent fracture behavior of healthy arterial tissue, with increased resistance observed when samples were loaded along the circumferential direction. This study design provides a foundation for future studies into rupture risks in aneurysmal tissue with disrupted fiber architectures.