Fracture Behavior of Inhomogeneous Biological Materials and Interfaces Biological materials like bone, nacre, human tooth layers are inhomogeneous materials made up of soft collagen, and hard, hydroxyapatite (HAP) mineral arranged in such a fashion so that these materials have higher strength and toughness, the measure of crack resisting behavior in materials, at the same time, which is exclusive in nature for different class of materials available for different application areas. The interfaces in these biological materials are designed in such a fashion so that the load transfer between the constituents takes place so smoothly, therefore, become a region of strength, not susceptible to failure like in other man-made materials and composites. It is important to understand these aspects of biological materials so that they can be mimicked to the novel materials to satisfy the growing need of different industries
"Nature, through millions of years, has evolved mechanically superior materials which have recently become a rich source of inspiration. Virtually all hard biological materials are composites where stiff, elongated inclusions are bound together through a soft polymeric "glue". In some of these composites such as nacre and bone, the stiff component is a hard and stiff minerals (aragonite in nacre and hydroxyapatite in bone) forming mineral-polymer composite while for others, such as tendon and plant cell wall, a stiff and strong polymer (collagen in tendon and cellulose in plant cell wall) constitutes the inclusion part of the polymer-polymer composite. These building blocks are bonded by softer organic materials, and the overall properties of these natural materials are highly dependent on the properties of these "weaker" interfaces. While the mechanical properties and the role of inclusions are well studied and understood, there is far less work reported in literature on the mechanics and properties of weak biological interfaces, and their composition, structure and mechanics are poorly understood. In this study the mechanical properties of weak biological interfaces in mollusk nacre are measured and their mechanics of deformation and fracture is characterized. To this end, first, the fracture toughness of interfaces within three different types of nacre (namely top shell, pearl oyster, and red abalone) is, for the first time, determined through combing the result of chevron notch fracture test, micrographs obtained from scanning electron microscope, and linear elastic fracture mechanics concept. The results revealed that fracture toughness of polymeric interfaces within nacre is indeed extremely low, in the order of the toughness of the mineral inclusions. A novel experimental method called Rigid Double Cantilever Beam (RDCB) is developed to measure the fracture toughness of very soft polymeric and biological interfaces. The method not only determines the fracture toughness of interfaces but also yields their cohesive strength, extensibility and stiffness. The method is successfully implemented on three engineering adhesives, and their fracture toughness and cohesive law are reported. The RDCB test is also used to study the effect of substrate, and chemical treatment on the interfacial fracture toughness and cohesive properties of a biological adhesive fibrin network. An eight-chain based model is then proposed to elucidate the bell-shaped cohesive law of fibrin interfaces. The new method can be used to characterize the cohesive behavior of other important proteins such as bone osteopontin. Finally, an improved fracture mechanics based criterion is developed to predict the failure of biological and engineered staggered composites. The model captures the nonuniform distribution of shear stresses along the interfaces, and the resulting stress fields within the inclusions. The criterion can be applied for a wide array of material behavior at the interface and will lead to optimal designs for the interfaces, in order to harness the full potential of bio-inspired composites. " --
This book is a collection of 13 chapters divided into seven sections: Section I: "General Foundations of the Stress Field and Toughness" with one chapter, Section II: "Fractography and Impact Analysis" with two chapters, Section III: "Toughness Fracture" with three chapters, Section IV: "Fracture Behavior" with two chapters, Section V: "Natural and Hydraulic Fractures" with two chapters, section VI: "Fatigue" with one chapter and Section VII: "Fracture Biomaterials and compatible" with two chapters. This book covers a wide range of application of fracture mechanics in materials science, engineering, rock prospecting, dentistry and medicine. The book is aimed towards materials scientists, metallurgists, mechanical and civil engineers, doctors and dentists and can also be well used in education, research and industry.
Mechanics of Biological Systems and Materials represents one of eight volumes of technical papers presented at the Society for Experimental Mechanics Annual Conference & Exposition on Experimental and Applied Mechanics, held at Uncasville, Connecticut, June 13-16, 2011. The full set of proceedings also includes volumes on Dynamic Behavior of Materials, Mechanics of Time-Dependent Materials and Processes in Conventional and Multifunctional Materials, MEMS and Nanotechnology; Optical Measurements, Modeling and, Metrology; Experimental and Applied Mechanics, Thermomechanics and Infra-Red Imaging, and Engineering Applications of Residual Stress.
Mechanics of Biological Systems and Materials, Volume 5: Proceedings of the 2012 Annual Conference on Experimental and Applied Mechanics represents one of seven volumes of technical papers presented at the Society for Experimental Mechanics SEM 12th International Congress & Exposition on Experimental and Applied Mechanics, held at Costa Mesa, California, June 11-14, 2012. The full set of proceedings also includes volumes on Dynamic Behavior of Materials, Challenges in Mechanics of Time-Dependent Materials and Processes in Conventional and Multifunctional Materials, Imaging Methods for Novel Materials and Challenging Applications, Experimental and Applied Mechanics, MEMS and Nanotechnology and, Composite Materials and Joining Technologies for Composites.
The volume provides a comprehensive understanding of the macroscopic failure behavior of solids from the description of the microscopic failure processes and their coupling with the microstructure. Several fundamental questions were addressed: the relation between the microstructural features of materials and their fracture properties and crack trajectories; the role of damage mechanisms and non-linear deformations near the crack tip on the failure behavior of solids; and finally the role of dynamic inertial effects during fast fracture was more briefly evoked. The chapters provide a pedagogical overview of recently developed concepts and tools, that permit to perform the transition from small scales to large ones in fracture problems, thus introducing basic rules for the rational design of tough solids.
"Hard biological materials such as seashells, bone and teeth boast unusual combinations of stiffness, strength and toughness even though they are made of weak constituents. Until now, such high performance cannot be matched in most modern engineering materials. Behind such performance is the unique arrangements of brittle building blocks bonded with weak interfaces that makes up the microstructure. These fine tune architectures generate nonlinear deformation and channel cracks into powerful toughening configurations. Therefore, the question of how to arrange brittle building blocks with polymeric interfaces to produce high performance material is of great importance in developing the ‘next’ generation of materials. In this dissertation, a computational tool is developed to study the deformation and fracture behavior of hard biological materials. Modeling the fracture behavior of hard biological materials is a challenging problem because of the computational cost associated with capturing multiple toughening mechanisms that act together during crack propagation at multiple length scales; some of them involving large volumes of material. Therefore, we chose to use the discrete element method (DEM) which reduced the computational time by several orders as compared to the conventional finite element method (FEM). We first focused on the deformation of staggered arrangements of rigid tablets; an arrangement often found in nacre, collagen and spider silk. Specifically, we studied the combined effects of statistics, tablet arrangement, and interface properties on the mechanical properties such as stiffness, strength and energy absorption. We found that statistical variations have a negative effect on all properties, in particular on the ductility and energy absorption because randomness precipitates the localization of deformations. However, the results also showed that the negative effects of random microstructures can be partially offset by interfaces with large strain at failure accompanied by strain hardening. We also explored, with large DEM models (450,000 tablets), the effects of interface properties and statistical variations on fracture mechanics: crack deflection, crack bridging, volumetric process zones of different size and shapes, transient and steady-state crack propagation regimes and full crack resistance curves (R-curves). We found that moderate statistical variations in the microstructure increase toughness because the crack gets pinned into tougher regions. However, higher statistical variations generate very weak regions which can be activated far from the main crack, leading to discontinuous cohesive zones, sparse process zones, and an overall decrease in toughness. We finally expanded the design space by exploring material designs inspired from Voronoi tessellations, regular polygons, and brick and mortar structures. We identified several toughening mechanisms including crack deflection, crack tortuosity, crack pinning and process zone toughening. Our results showed that periodic architectures can achieve higher toughness compared to random microstructures, the toughest architectures are also the most anisotropic, and tessellations based on brick and mortar structure are the toughest. Our findings were summarized as design guidelines and material selection charts for developing high performance materials"--
Market: Students and researchers in geophysics, astronomy, and astrophysics. This book reports on the timely Earth Observing System (EOS) Program's wide range of scientific investigations, observational capabilities, vast data and information system, and educational activities. Because its primary goal is to determine the extent, causes, and regional consequences of global climate change, this program provides the scientific knowledge needed by world leaders to formulate sound and equitable environmental policies.
Supports the use and development of strong, fracture-resistant, and mechanically reliable ceramic materials The Fracture of Brittle Materials thoroughly sets forth the key scientific and engineering concepts underlying the selection of test procedures for fracture toughness, strength determination, and reliability predictions. With this book as their guide, readers can confidently test and analyze a broad range of brittle materials in order to make the best use of existing materials as well as to support the development of new materials. The authors explain the importance of microstructure in these determinations and describe the use of quantitative fractography in failure analysis. The Fracture of Brittle Materials is relevant to a broad range of ceramic materials (i.e., any inorganic non-metal), including semiconductors, cements and concrete, oxides, carbides, and nitrides. The book covers such topics as: Basic principles of fracture mechanics underlying brittle material tests and analysis procedures Theory and mechanisms of environmentally enhanced crack growth Fracture mechanics tests to determine a material's resistance to fast fracture Test and analysis methods to assess the strength of ceramics Methods to analyze the fracture process based on quantitative measurements of the fracture surface Effect of a material's microstructure Methods for predicting the lifetime of brittle components under stress Throughout the book, figures and illustrations help readers understand key concepts and methods. Replete with real-world examples, this text enables engineers and materials and ceramics scientists to select and implement the optimal testing methods for their particular research needs and then accurately analyze the results.
