Multiscale models for the degradation, damage, and failure of collagen-based soft tissues

Abstract

Multiscale computational models for the deformation, degradation, and failure of soft tissues can inform the work of tissue engineers, clinicians who treat soft tissue injuries, and biologists who study the growth and development of soft tissues. Increasingly, mechanical models for tissues that couple multiple length scales include microstructural information in their design. Multiscale tissue models are revealing fundamental insights into how and why tissues deform, degrade, and fail in response to loading. The rapid growth in computational resources available to researchers (such as through academic supercomputing facilities) has also lead to an increase in the complexity and fidelity of multiscale models for tissue mechanics that may not have been possible even a decade ago. The finite element method has served as a popular modeling approach to couple the material properties of tissues at varying length scales. In the present dissertation, a series of multiscale models which couple a macroscale finite element continuum to deterministic microscale fiber networks were used to simulate the degradation, damage, and failure of collagen-based tissues and tissue analogs. The models build on previous work that has focused primarily on the pre-failure mechanics of tissues. Enzymatic degradation was modeled by changing the effective diameter of microscale collagen fibers over time to mimic the action of strain-dependent collagenases. Mechanical failure and damage were modeled via the failure of discrete collagen fibers in a tissue based on a critical stretch criterion. Related research on the mechanical role of non-fibrillar matrix in tissues and on the mechanics of networks of varying topology was also conducted that will largely shape future research on the failure of multicomponent tissues and tissues of varying microstructure.