We propose a new approach for constructing strain-based
rupture criterion for ascending
thoracic aortic aneurysm. The
rupture metric is formulated using an effective strain, which is a measure of net strain that the
collagen bundles experience after fiber uncrimping. The effective strain is a function of the total strain and the waviness properties of the
collagen fibers. In the present work, the waviness properties are obtained from fitting biaxial response data to constitutive models that explicitly consider the
collagen waviness and fiber recruitment. Inflation test data from 10 ascending
thoracic aortic aneurysm specimens are analyzed. For each specimen, tension-strain data at ∼2300 material points are garnered. The effective strain fields in the configuration immediately before
rupture are computed. It is found that the hotspots of the effective strain match the
rupture sites very well in all 10 samples. More importantly, the values of effective strain at the hotsopts are closely clustered around 0.1, in contrast to a much wider distribution of the total strain. The study underscores the importance of considering the fiber recruitment in formulating strain-based
rupture metric, and suggests that ϵ¯≈0.1, where ϵ¯ is the effective strain metric defined in this work, can be considered as a criterion for assessing the imminent
rupture risk of
ascending aortic aneurysms. STATEMENT OF SIGNIFICANCE: We advocate to use effective strain in
ATAA rupture assessment. The effective strain is a measure of net strain in the
collagen network after waviness uncrimping. We analyzed bulge inflation data of
ATAA samples. It was found that, while the total strains at
rupture varied from sample to sample, the effective strains were closely clustered around 0.1. And the hotspots of effective strain matched the
rupture sites well. The work underlines the importance of considering
collagen fiber waviness and recruitment when evaluating the
rupture risk using strain, and suggests a new direction for developing sharper
rupture metrics.