Microstructural Effects in Tayloring the Response of Engineered Bio-Materials

University Of Virginia Main Campus, Charlottesville VA

Investigators

Abstract

The goal of this research is to establish fundamental microstructure-property understanding needed for the development of a new generation of bio-engineered materials characterized by wavy microstructures, whose targeted performance is attained through micro-structural evolution based on the survival-of-the-fittest principles. Toughness, extensibility and adaptability may be realized through the exploitation of various arrangements of wavy microstructures, yet fundamental understanding of these architectural features vis-a-vis material response is lacking. Recent micro-structural simulation studies by the PI and co-workers demonstrated that layer thickness has a substantial impact on the homogenized response of periodic multi-layers with wavy microstructures in the inelastic domain. The proposed investigation addresses this recently discovered effect, and related effects, for the first time in engineered materials that mimic biological material response in the finite-deformation domain, including certain tissues. In particular, the investigation will answer the following questions, which have not been yet addressed, in the analysis and development of engineered materials with stiffening characteristics for bio-medical applications: (1) what is the effect of layer thickness on the homogenized and local responses of a wavy periodic multilayer in the finite-deformation domain?; (2) can targeted response of an engineered material with wavy microstructure be achieved using more than one microstructure?; (3) can connection between complexity and simplicity be established through an evolutionary design? The investigation employs a computational approach based on a novel homogenization technique called the parametric finite-volume direct averaging micromechanics (FVDAM) theory developed by the PI, his students and collaborators. This theory is particularly well suited for robust analysis, simulation and optimization of heterogeneous materials with accuracy comparable to the finite-element method, which presently is the computational standard, but with substantially greater efficiency. Experimentally measured response of three types of mitral valve chordea tendinea, which exhibit different levels of stiffening caused by different crimp patterns of the fibril bundles arranged in wavy layers, is employed in support of the verification and microstructural optimization component of the investigation. The intellectual merit stems both from the knowledge that will be generated and from further development of the theoretical tools necessary to accomplish it. Very little work based on first principles has been reported which is aimed at addressing the effect of microstructure in biological tissues on the overall response. The investigation will establish this connection for a particular material system that plays a significant role in biomedical applications. Further, the proposed theoretical enhancements of the parametric FVDAM theory will produce a paradigm shift in the theory's evolution, with the potential to replace the prevailing computational standard in the analysis and design of heterogeneous materials. The resulting computational technology will be readily employed in applications across several interdisciplinary boundaries, including traditional and emerging engineered materials with bio-inspired architectures. The theoretical enhancements involve the incorporation of finite-deformation capability into the FVDAM framework and the concomitant development of stable and accurate algorithms for the solution of structural mechanics problems in the finite-deformation domain, which continue to be a focus of the numerical engineering community. The proposed research is an important step in the parametric FVDAM theory?s continued development needed to realize its full potential across disciplinary boundaries. The broader impacts stem from the wide range of applications in which materials and structural components with wavy multilayer patterns are utilized across several scales and disciplines, ranging from corrugated structural panels to the rapidly developing nanotechnology areas. Microstructures with wavy architectures can potentially enhance certain performance characteristics such as stiffness, thermal stability and toughness. Yet, little systematic data is available addressing these issues in both the infinitesimal and finite-deformation domains. Moreover, the developed computational technology will be made available to the pertinent communities in the form of a Graphical User Interface to facilitate analysis, design and development of material systems for a wide range of applications, enabling material scientists and structural mechanicians alike to investigate what-if scenarios in pursuit of optimized and durable material microstructures. Concurrently, it will serve a greater educational purpose through training of both undergraduate and graduate students. Undergraduate students recruited from traditionally under-represented groups through the PI?s contact as an instructor in undergraduate courses, as well as through the well-known Center for Diversity at the University of Virginia, will be involved in the GUI?s testing and applications as summer interns who will further exploit this experience in their senior theses.