Geometric Control Of Fracture And Topological Metamaterials

This thesis reports a rare combination of experiment and theory on the role of geometry in materials science. It is built on two significant findings: that curvature can be used to guide crack paths in a predictive way, and that protected topological order can exist in amorphous materials. In each, the underlying geometry controls the elastic behavior of quasi-2D materials, enabling the control of crack propagation in elastic sheets and the control of unidirectional waves traveling at the boundary of metamaterials. The thesis examines the consequences of this geometric control in a range of materials spanning many orders of magnitude in length scale, from amorphous macroscopic networks and elastic continua to nanoscale lattices.

Geometry and topology have emerged as powerful tools for understanding a wide range of phenomena in condensed matter physics. Often, geometric and topological constraints drive the order and dynamics of soft mechanical systems-systems in which material behavior is energetically accessible at room temperature in tabletop experiments. Here, we investigate the role of geometry and topology in the mechanics of quasi-two-dimensional elastic materials.

This book pursues optimal design from the perspective of mechanical properties and resistance to failure caused by cracks and fatigue. The book abandons the scale separation hypothesis and takes up phase-field modeling, which is at the cutting edge of research and is of high industrial and practical relevance. Part 1 starts by testing the limits of the homogenization-based approach when the size of the representative volume element is non-negligible compared to the structure. The book then introduces a non-local homogenization scheme to take into account the strain gradient effects. Using a phase field method, Part 2 offers three significant contributions concerning optimal placement of the inclusion phases. Respectively, these contributions take into account fractures in quasi-brittle materials, interface cracks and periodic composites. The topology optimization proposed has significantly increased the fracture resistance of the composites studied.

This book lays down the foundation on the mechanics and design of auxetic solids and structures, solids that possess negative Poisson’s ratio. It will benefit two groups of readers: (a) industry practitioners, such as product and structural designers, who need to control mechanical stress distributions using auxetic materials, and (b) academic researchers and students who intend to produce unique mechanical and other physical properties of structures using auxetic materials.

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.

The topology optimization method solves the basic enginee- ring problem of distributing a limited amount of material in a design space. The first edition of this book has become the standard text on optimal design which is concerned with the optimization of structural topology, shape and material. This edition, has been substantially revised and updated to reflect progress made in modelling and computational procedures. It also encompasses a comprehensive and unified description of the state-of-the-art of the so-called material distribution method, based on the use of mathematical programming and finite elements. Applications treated include not only structures but also materials and MEMS.

A crucial element of structural and continuum mechanics, stability theory has limitless applications in civil, mechanical, aerospace, naval and nuclear engineering. This text of unparalleled scope presents a comprehensive exposition of the principles and applications of stability analysis. It has been proven as a text for introductory courses and various advanced courses for graduate students. It is also prized as an exhaustive reference for engineers and researchers. The authors' focus on understanding of the basic principles rather than excessive detailed solutions, and their treatment of each subject proceed from simple examples to general concepts and rigorous formulations. All the results are derived using as simple mathematics as possible. Numerous examples are given and 700 exercise problems help in attaining a firm grasp of this central aspect of solid mechanics. The book is an unabridged republication of the 1991 edition by Oxford University Press and the 2003 edition by Dover, updated with 18 pages of end notes.

This work reviews the current state of the art in metallic microlattice structures, manufactured using the additive manufacturing processes of selective laser melting, electron beam melting, binder jetting and photopolymer wave guides. The emphasis is on structural performance (stiffness, strength and collapse). The field of additively manufactured metallic microlattice structures is fast changing and wide ranging, and is being driven by developments in manufacturing processes. This book takes a number of specific structural applications, viz. sandwich beams and panels, and energy absorbers, and a number of conventional metallic materials, and discusses the use of additive manufactured metallic microlattice structures to improve and enhance these structural performances. Structural performances considered includes such non linear effects as plasticity, material rupture, elastic and plastic instabilities, and impact loading. The specific discussions are put into the context of wider issues, such as the effects of realisation processes, the effects of structural scale, use of sophisticated analysis and synthesis methodologies, and the application of existing (conventional) structural theories. In this way, the specific discussions are put into the context of the emerging general fields of Architectured (Architected) Materials and Mechanical Metamaterials.