MODELING AND SIMULATION OF TIME-DEPENDENT INELASTIC SOFT TISSUE BEHAVIOR
Martin, Caitlin Marie
MetadataShow full item record
Over long periods of time, soft collagenous tissues undergo irreversible microstructural changes including elastin degradation and collagen fiber un-crimping owing in part to the natural aging process and mechanical fatigue damage. These changes are accelerated in tissue-derived medical devices which lack regenerative repair abilities, and have deleterious effects on physiological function. Methods to predict collagenous tissue property changes in response to various factors could facilitate the design of durable tissue-based devices and the development of enhanced diagnostic and preventative treatment methods. However, most of the biomechanics work on soft collagenous tissues reported in the literature thus far, whether experimental, theoretical, or computational, is confined to static, instantaneous tissue property characterization. As such, only the recoverable or elastic behavior of tissue is considered, although from a thermodynamics stand point, permanent changes in tissue structure and material properties represent dissipative, inelastic effects. Thus, the objective of this dissertation was to develop a theoretical and computational framework to describe the time-dependent inelastic behavior of soft tissues such that the effects of mechanical fatigue damage and aging in soft tissues could be accurately modeled. The framework was implemented in a finite element solver and applied to investigate the effects of aging on the human ascending aorta, and the effects of leaflet fatigue damage in bioprosthetic heart valves. The results from these studies may offer scientific rationale for the design of improved devices and diagnostic methods.