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There is a constant demand from the industry to provide better, more situation dependent construction materials; materials which are able to satisfy strength requirements while also able to accommodate other design requirements such as ductility, fracture resistance, thermal resistance/insulation, etc. Functionally graded materials (FGMs) are one such material. This study investigates the fracture process of sustainable concrete, fiber reinforced concrete, and of functionally graded concrete slabs. Both two-dimensional and three-dimensional problems are analyzed. The primary focus of the thesis is on sustainable, functionally graded concrete slabs, emphasizing the computational/mechanical aspects of fracture. A model of the slabs is developed; which incorporates a variety of cohesive zone models (CZMs) into an implicit, nonlinear finite element scheme. Intrinsic cohesive zone elements, with traction-separation relationships defined along the crack surface, are utilized to simulate mode I fracture of the slabs. Based on the load to crack mouth opening displacement (CMOD) relationships of the slab, one is able to optimize concrete properties and placement to reach predefined goals. A parametric study is conducted on the fracture parameters of the slab; the results of which show that the variations in the CZMs have a direct correlation with the overall behaviour of the slab. Additionally, in conducting the experiments for the slabs, a new fracture test for concrete is developed. The attractive feature of the test is that it uses a specimen geometry which is easily obtained from in-situ concrete in the field. Technology exists which allows us to extract cylindrical cores from concrete structures at relative ease. This study proposes a specimen geometry which can easily be developed from these cylindrical cores called the disk-shaped compact tension (DCT) specimen. A series of experiments are conducted on the specimen, and computational simulations are carried out. A parametric study is done; the results of which, show that the specimen geometry is able to predict the mode I fracture properties of concrete, with both virgin and recycled aggregates, with relative accuracy and ease.
Scientific research on functionally graded materials (FGM's) looks at functions of gradients in materials comprising thermodynamic, mechanical, chemical, optical, electromagnetic, and/or biological aspects. This collection of technical papers represents current research interests with regard to the fracture behaviour of FGM's. The papers provide a balance between theoretical, computational, and experimental techniques. It also indicates areas for increased development, such as constraint effects, full experimental characterization of engineering FGM's under static and dynamic loading, development of fracture criteria with predictive capability, multiphysics and multiscale failure considerations, and connection of research with industrial applications.
Functionally graded materials are generally two-phase composites with continuously varying volume fractions. Used as coatings and interfacial zones, they help to reduce mechanically and thermally induced stresses caused by the material property mismatch and to improve the bonding strength. In this project some basic problems concerning fracture mechanics of graded materials are identified, general analytical methods for solving the related crack problems are developed, the singular behavior of the solutions for typical material nonhomogeneities is examined, and solutions of some benchmark problems are obtained. The results are intended to provide technical support for material scientists and engineers who are trying to develop methods for processing these materials and for design engineers who are interested in using them in technological applications. Typical applications of functionally graded materials include thermal barrier coatings of high temperature components in gas turbines, surface hardening for tribological protection, and as interlayers in microelectronic and optoelectronic components. The results found show that by eliminating the discontinuities in material property distributions the mathematical anomalies regarding the crack tip stress oscillations for the interface cracks and the nonsquare root singularities for cracks intersecting the interfaces are also eliminated. From the viewpoint of fracture mechanics the importance of this result lies in the fact that in analyzing the components involving functionally graded materials one can use the existing crack tip finite element modeling developed for ordinary square root singularities and apply the energy balance based theories of conventional fracture mechanics.
Presenting original results from both theoretical and numerical viewpoints, this text offers a detailed discussion of the variational approach to brittle fracture. This approach views crack growth as the result of a competition between bulk and surface energy, treating crack evolution from its initiation all the way to the failure of a sample. The authors model crack initiation, crack path, and crack extension for arbitrary geometries and loads.
Mechanics of Functionally Graded Material Structures is an authoritative and fresh look at various functionally graded materials, customizing them with various structures. The book is devoted to tailoring material properties to the needed structural performance. The authors pair materials with the appropriate structures based upon their purpose and use.Material grading of structures depending upon thickness, axial and polar directions are discussed. Three dimensional analysis of rectangular plates made of functional graded materials and vibrational tailoring of inhomogeneous beams and circular plates are both covered in great detail. The authors derive novel closed form solutions that can serve as benchmarks that numerical solutions can be compared to. These are published for the first time in the literature. This is a unique book that gives the first exposition of the effects of various grading mechanisms on the structural behavior as well as taking into account vibrations and buckling.
Mechanical responses of solid materials are governed by their material properties. The solutions for estimating and predicting the mechanical responses are extremely difficult, in particular for non-homogeneous materials. Among these, there is a special type of materials whose properties are variable only along one direction, defined as graded materials or functionally graded materials (FGMs). Examples are plant stems and bones. Artificial graded materials are widely used in mechanical engineering, chemical engineering, biological engineering, and electronic engineering. This work covers and develops boundary element methods (BEM) to investigate the properties of realistic graded materials. It is a must have for practitioners and researchers in materials science, both academic and in industry. Covers analysis of properties of graded materials. Presents solutions based methods for analysis of fracture mechanics. Presents two types of boundary element methods for layered isotropic materials and transversely isotropic materials. Written by two authors with extensive international experience in academic and private research and engineering.
This book provides readers with an incisive look at cutting-edge peridynamic modeling methods, numerical techniques, their applications, and potential future directions for the field. It starts with an introductory chapter authored by Stewart Silling, who originally developed peridynamics. It then looks at new concepts in the field, with chapters covering dual-horizon peridynamics, peridynamics for axisymmetric analysis, beam and plate models in peridynamics, coupled peridynamics and XFEM, peridynamics for dynamic fracture modeling, and more. From there, it segues into coverage of cutting-edge applications of peridynamics, exploring its biological applications, modeling at the nanoscale, peridynamics for composites delamination and damage in ceramics, and more, concluding with a chapter on the application of artificial intelligence and machine learning in peridynamics. Covers modeling methods, numerical techniques, applications, and future directions for the field Discusses techniques such as dual-horizon peridynamics, damage modeling using the phase-field approach, and contact analysis of rigid and deformable bodies with refined non-ordinary state-based peridynamics Looks at a range of different peridynamic applications such as ice modeling, fiber-reinforced composite modeling, modeling at nanoscale, and more