Download or read book Mechanical Instability in Soft Materials written by Xudong Liang and published by . This book was released on 2018 with total page 134 pages. Available in PDF, EPUB and Kindle. Book excerpt: We are surrounded by soft materials in a variety of physical and chemical states, which can be easily deformed under external stimuli. When subjected to sufficiently large compression, electric voltage, gravity or impact, soft materials may undergo mechanical instabilities of various types. The instability modes can be either linear or nonlinear, depending on the form of perturbation when the instability set in. When the material is a pressurized dielectric elastomeric film under high voltage, snap-through instability is linear with finite change of volume, while the bulge-out mode is nonlinear with a localized deformation. In terms of surface instability, wrinkles are linear instability mode with undulations finite in space with infinitesimal strain deviating from the smooth state, while creases are localized nonlinear modes with large strain deviating from smooth state. If a soft material is subjected to high speed impact, both the viscoelastic behaviors of the material and inertial effect are involved, and the mechanical instability is coupled with the wave propagation, finally leading to highly nonlinear instability mode. We start with the instability analysis of a pressurized dielectric elastomeric film subjected to high voltage. By adopting ideal dielectric elastomer (DE) constitutive model, we show that linear perturbation analysis can capture the shape bifurcation in a spherical DE balloon. However, nonlinear bulge-out shape with a highly localized deformation appears as constraints of the boundaries of the film is applied. A competition between the surface instability modes between the wrinkle and crease is studied in both experiment and theoretical analysis under a deformation mode called eversion, and crease is shown to form prior to wrinkle with lower critical strain to set in. A transition between the wrinkle and crease instability happens when gravity becomes important. We measure the dynamics of soft elastomeric blocks with stiff surface films subjected to high-speed impact, and observe wrinkles forming along with, and riding upon, waves propagating through the system.
Download or read book Instability Driven Reconfigurable Soft Materials written by Gaojian Lin and published by . This book was released on 2018 with total page 175 pages. Available in PDF, EPUB and Kindle. Book excerpt: Mechanical instability, a deformation mode involving abrupt switching between two distinct equilibrium structural configurations, has historically been viewed as a failure mechanism in engineering and materials science. Since the pioneering work in harnessing spontaneous buckling for surface micro-patterning in 1998, tremendous research interest has focused to utilize, rather than avoid, buckling instability in soft materials at small scale for achieving unique properties and multifunctionality. The benefit of small-scale bucking instability in soft materials and structures lies in the reversible dynamic tunability of the buckled structural or surface configuration in response to different external stimuli, which enables the coupling of structural or surface reconfiguration with dynamically tunable properties, such as mechanical, optical, wetting, and electrical properties. In this dissertation, I explore the fundamental mechanics and functionality of surface-based buckling and hierarchical wrinkling on substrates in multifunctional opto-electronic devices and smart windows. I will first explore the benefits of classical plate buckling in soft materials. The challenge lies in the intrinsic indeterminate characteristics of buckling in terms of its buckling orientation, which could lead to geometric frustration and random global structures. To address this challenge, I introduce cuts-based geometrical imperfection to guide the deterministic buckling in arrays of parallel active polymeric plates on rigid substrates. After introducing patterned cuts, the originally random phase-shifted buckling transits to a prescribed buckling with controllable phases. The design principle for cut-directed deterministic buckling in plates is revealed through both mechanics model and finite element simulation. By harnessing cut-directed buckling for controllable contacts and interactions in buckled parallel plates, I demonstrate the array of parallel plates as a multifunctional platform for selectively steering the electronic and optical pathways on demand, as well as the potential application in design of mechanical logic gates. I then explore the hierarchical wrinkling of thin films on soft substrates via sequential wrinkling for design of a potential multifunctional smart window with combined structural color and water droplet transport control. The self-similar hierarchical wrinkles with both nanoscale and microscale features are generated on a pre-strained poly(dimethylsiloxane) (PDMS) elastomer through sequential strain release and multi-step oxygen plasma treatment. I exploit the criteria for generating self-similar hierarchical wrinkles through both simplified theoretical model and experiments. I show that the hierarchically wrinkled elastomer displays both opaqueness and iridescent structural color. I further show its ability in control of water droplet transport on demand through mechanical stretching and release. I further extend the study of self-similar hierarchical wrinkling to the dynamic wetting behavior of multiscale self-similar hierarchical wrinkled surfaces on PDMS substrates through combined plasma and ultraviolet ozone (UVO) treatment. The generated surface structure shows an independently controlled dual-scale roughness with level-1 small-wavelength wrinkles resting on level-2 large-wavelength wrinkles, as well as accompanying orthogonal cracks. By tuning the geometry of hierarchical wrinkles, I explore the small degree of wetting anisotropy in hierarchical wrinkled surfaces, defined as the contact angle difference between the parallel and perpendicular directions to the wrinkle grooves through both experimental characterization (confocal fluorescence imaging) and theoretical analyses. I find that the measured larger apparent contact angle than the theoretically predicted Wenzel contact angle is attributed to the three-phase contact line pinning effect of both wrinkles and cracks, which generates energetic barriers during the contact line motion. I reveal that the observed small degree of wetting anisotropy in the hierarchical wrinkled surfaces arises from the competition between orthogonal wrinkles and cracks in the contact line pinning.
Download or read book Computational Methods to Study Mechanical Instabilities in Soft and Multi physics Media written by Berkin Dortdivanlioglu and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Predictive modeling of complex materials is gaining more and more attention each day as the complexity of problems increases rapidly with innovations in fabrication and monitoring technologies. At the same time, these innovations are revealing unsolved fundamental problems both in nature and engineered systems, mainly because of high nonlinearities in material and geometry, multiple physics, and multiple length and time scale behavior. In this thesis, we focus on developing computational tools to model soft and multiphysics materials as well as to capture geometrical and material instabilities observed in these complex materials. We show that the developed computational schemes successfully pinpoint the onset and simulate the evolution of instabilities in soft materials under large deformations, extending the fundamental understanding of the complex bifurcation response of bilayer materials and commonly observed instability modes of buckling, wrinkling, period-doubling, and creasing. Through fundamental studies on the transient nature of poroelastic instabilities, we address the influence of solvent diffusion on instabilities for stimuli-responsive materials such as hydrogels. Particularly, we discuss the numerical modeling aspects of hydrogels along with dissipative fluid transport phenomena through developing new numerically stable mixed isogeometric hydrogel models. We also introduce a new structural stability criteria for hydrogels with a saddle-point formulation, enabling computational studies designed to elucidate the diffusion-driven swelling-induced instabilities of hydrogels. Equipped with the developed accurate and efficient methods, we draw stability diagrams highly relevant to designing functional and tunable soft hydrogel devices over a wide range of length scales.
Download or read book Material Instabilities in Elastic and Plastic Solids written by Henryk Petryk and published by Springer. This book was released on 2014-05-04 with total page 390 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book collects recent theoretical developments in the area of material instability in elastic and plastic solids along with related analytical and numerical methods and applications. The existing different approaches to instability phenomena in metal single crystals, polycristals and in geomaterials are presented with the emphasis laid on mutual relations and on unifying concepts, including elliptictly loss and the energy criterion. Quasi-static bifurcation, initiation of single or multiple shear bands and post-critical strain localization are examined along with dynamic phenomena as wave propagation, moving shocks, internal snap-through and instability of flutter type. This gives an overview of a variety of material instability problems, methods and applications.
Download or read book Electro and Magneto Mechanics of Soft Solids written by Kostas Danas and published by Springer Nature. This book was released on with total page 185 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Nonlinear Solid Mechanics written by Davide Bigoni and published by Cambridge University Press. This book was released on 2012-07-30 with total page 549 pages. Available in PDF, EPUB and Kindle. Book excerpt: Addresses behaviour of materials under extreme mechanical conditions and of failure in terms of non-linear continuum mechanics and instability theory.
Download or read book Analysis of Dynamic Surface Instabilities in Soft Hydrogel Cylinders Subject to Laser driven Shock loading written by Daniel N. Pickard and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Soft materials subject to both static and dynamic loading are known to exhibit a variety of mechanical instabilities which may lead to intricate surface deformation patterns. In particular, creases and wrinkles have been found to play an important role in the morphogenesis of soft tissues and tumor growth. Soft matter instabilities are also relevant to a number of manufacturing and engineering applications such as the fabrication of microlenses, and the development of soft robots, actuators and ŕexible electronics. Static instabilities in soft matter have been well studied theoretically, and they are known to result from bifurcations of equilibrium due to loss of convexity of the nearly-incompressible elastic strain energy function in the large deformation range. Under dynamic loading, soft solids exhibit many instabilities that are well known in ŕuids, including Rayleigh-Taylor, Faraday and Richtmyer-Meshkov instabilities.
Download or read book Mechanics of Soft Materials written by Konstantin Volokh and published by Springer. This book was released on 2016-06-17 with total page 158 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides a concise introduction to soft matter modelling. It offers an up-to-date review of continuum mechanical description of soft and biological materials from the basics to the latest scientific materials. It includes multi-physics descriptions, such as chemo-, thermo-, electro- mechanical coupling. It derives from a graduate course at Technion that has been established in recent years. It presents original explanations for some standard materials and features elaborated examples on all topics throughout the text. PowerPoint lecture notes can be provided to instructors.
Download or read book Challenges in Mechanics of Time Dependent Materials Volume 2 written by Meredith Silberstein and published by Springer Nature. This book was released on 2021-04-05 with total page 101 pages. Available in PDF, EPUB and Kindle. Book excerpt: Challenges in Mechanics of Time-Dependent Materials, Volume 2 of the Proceedings of the 2020 SEM Annual Conference& Exposition on Experimental and Applied Mechanics, the second volume of seven from the Conference, brings together contributions to this important area of research and engineering. The collection presents early findings and case studies on fundamental and applied aspects of Experimental Mechanics, including papers in the following general technical research areas: Characterization Across Length Scales Extreme Environments & Environmental Effects Soft Materials Damage, fatigue and Fracture Inhomogeneities & Interfaces Viscoelasticity Research in Progress
Download or read book Mechanics of Soft Materials written by Konstantin Volokh and published by Springer. This book was released on 2019-06-11 with total page 167 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides a concise introduction to soft matter modelling, together with an up-to-date review of the continuum mechanical description of soft and biological materials, from the basics to the latest scientific materials. It also includes multi-physics descriptions, such as chemo-, thermo-, and electro-mechanical coupling. The new edition includes a new chapter on fractures as well as numerous corrections, clarifications and new solutions. Based on a graduate course taught for the past few years at Technion, it presents original explanations for a number of standard materials, and features detailed examples to complement all topics discussed.
Download or read book Soft Solids written by Alan D. Freed and published by Springer Science & Business Media. This book was released on 2014-03-10 with total page 391 pages. Available in PDF, EPUB and Kindle. Book excerpt: This textbook presents the physical principles pertinent to the mathematical modeling of soft materials used in engineering practice, including both man-made materials and biological tissues. It is intended for seniors and masters-level graduate students in engineering, physics or applied mathematics. It will also be a valuable resource for researchers working in mechanics, biomechanics and other fields where the mechanical response of soft solids is relevant. Soft Solids: A Primer to the Theoretical Mechanics of Materials is divided into two parts. Part I introduces the basic concepts needed to give both Eulerian and Lagrangian descriptions of the mechanical response of soft solids. Part II presents two distinct theories of elasticity and their associated theories of viscoelasticity. Seven boundary-value problems are studied over the course of the book, each pertaining to an experiment used to characterize materials. These problems are discussed at the end of each chapter, giving students the opportunity to apply what they learned in the current chapter and to build upon the material in prior chapters.
Download or read book Instability driven Pattern Transformations in Soft Architected Materials written by Nitesh Arora (Ph.D.) and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Soft elastomers provide an excellent material platform for developing compliant devices, including soft robots, sensors, and wearable devices, due to their ability to sustain large elastic deformations. However, by designing structured-soft materials, we can extend their capabilities beyond merely a material platform. The structural design, which can be tailored for desired material properties, can involve features such as microscale patterns, hierarchical arrangements, or inclusions within the soft matrix. When soft architected materials are subjected to large deformations, they often develop elastic (reversible) instabilities. The phenomenon is associated with sudden and dramatic microstructural transformations. Opposed to the traditional approach of designing to curb the onset of instability, this thesis focuses on harnessing instability-induced structural reconfigurations to design stimuli-responsive materials with switchable functionalities. The post-transformation behavior of such tunable materials is dictated by the admissible buckling configurations; therefore, they play a crucial role in the design of these materials. This thesis provides a detailed study of the instability phenomenon occurring at different length scales in a variety of soft architected materials. First, we show that in 3D fiber composites, the non-linear stiffening behavior of phases dictates the interplay between the long-wave and microscopic instabilities, and defines the wavelength of the buckling patterns. Then, we experimentally illustrate that the fiber composites switch the orientation of their buckling plane, depending on their in-plane periodicity and material properties. Next, we investigate a composite system consisting of a magnetoactive layer embedded into an inactive elastomeric matrix. With this material system, we show that instability-induced reconfigurations can be triggered via a remotely applied magnetic field. In addition to elucidating the mechanisms associated with magneto-mechanical instability, the study also outlines the strategy and benefits of harnessing two-field physics for controlling bifurcations in a material system. We also introduce a novel design framework for achieving desired structural transformations that are encoded magnetically. The framework utilizes the rich interplay of magnetic interactions and instability phenomenon. We showcase the diversity of the admissible reconfigurations through a series of information embedding demonstrations, including alphabet shape matching and Morse code. Finally, by employing this framework, we design a magneto-mechanical metamaterial in which we can program the deformation field to attain local material densification. Furthermore, we demonstrate its application as a strain-tunable vibration absorber.
Download or read book Competition Between Wrinkling Buckling and Creasing Instability Modes on the Surfaces of Soft Materials and Patterned Bilayers written by Tetsu Ouchi and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis broadly aims to examine how different surface instability modes compete with each other across various length scales and to apply the resulting fundamental understanding to enable switchable liquid/gas permeation and electrical sensing devices. To this end, Chapter 2 describes a new model for the crease nucleation and growth phenomenon. There have been discrepancies between experiments and theories in critical strains of creasing, especially for systems with high elastocapillary number. In this chapter, we resolved the discrepancy by verifying our new model, which properly takes the surface tension effects into account. Chapter 3 describes acceleration induced surface instabilities. Although wrinkling frequently appears in a bilayer system, it has rarely been observed in a single layer system. In this chapter, we demonstrated rotational acceleration induced wrinkling instabilities on the surface of a single layer gel. Chapter 4 discusses the interplay between surface instability modes originating from a patterned bilayer with characteristic length-scales comparable to those of the instability modes. While applications, such as flexible electronics, have surfaces with in-plane heterogeneity (e.g. metal electrode patterns on PDMS), a fundamental understanding of surface instabilities with in-plane heterogeneity have not been understood well. In this chapter, we successfully controlled critical strains, locations, and types of surface instabilities by changing the micro-pattern geometries, leading to a rich set of surface topographies composed of multiple surface instability modes. Chapter 5 describes the effects of geometrical singularities in the form of notch structures on the development of surface morphology under compression. Although creasing leads to reversible surface self-contact, its applications are limited partly due to the large activation strain required for the crease formation and the difficulties in controlling crease position. In this chapter, reversible surface self-contact was induced by the stress concentration associated with notch structures, and mechanically gated electrical switches with small and tunable activation strains and high on/off ratios were demonstrated. Chapter 6 discusses the fabrication of devices for switchable liquid/gas permeation and electrical sensing and their performance. Devices consisting of large active area surfaces with impermeable conductive patterns were fabricated, which enabled switchable liquid/gas permeation and electrical resistivity under mechanical compression.
Download or read book On the Stability of Elastic Equilibrium written by Warner Tjardus Koiter and published by . This book was released on 1967 with total page 226 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Mechanics and Thermomechanics of Rubberlike Solids written by Guiseppe Saccomandi and published by Springer Science & Business Media. This book was released on 2004-03-30 with total page 270 pages. Available in PDF, EPUB and Kindle. Book excerpt: This work gives for the first time an interdisciplinary and deep approach to the mathematical modelling of rubber-like materials considering both the molecular and phenomenological point of views. It contains an introduction to the suitable numerical techniques and an overview of experimental techniques and data with a short survey on some industrial applications. Elastic and inelastic effects are discussed in details. The book is suitable for applied mathematicians, mechanical engineers, civil engineers, material scientists and polymer scientists.
Download or read book Soft Matter in Plants written by Kaare Jensen and published by Royal Society of Chemistry. This book was released on 2022-09-09 with total page 258 pages. Available in PDF, EPUB and Kindle. Book excerpt: Plants offer some of the most elegant applications of soft matter principles in Nature. Understanding the interplay between chemistry, physics, biology, and fluid mechanics is critical to forecast plant behaviour, which is necessary for agriculture and disease management. It also provides inspiration for novel engineering applications. Starting with fundamental concepts around plant biology, physics of soft matter and viscous fluids, readers of this book will be given a cross-disciplinary and expert grounding to the field. The book covers local scale aspects, such as cell and tissue mechanics, to regional scale matters covering movement, tropism, roots, through to global scale topics around fluid transport. Focussed chapters on water stress, networks, and biomimetics provide the user with a concise and complete introduction. Edited by internationally recognised leading experts in this field with contributions from key investigators worldwide, this book is the first introduction to the subject matter and will be suitable for both physical and life science readers.
Download or read book Indentation based Characterization of the Mechanical and Adhesion Properties of Soft Materials written by Michael J. Wald and published by . This book was released on 2015 with total page 258 pages. Available in PDF, EPUB and Kindle. Book excerpt: Instrumented indentation is also used to measure the adhesion properties of soft materials. While advancing and receding contact adhesion properties have been shown to differ, current indentation techniques are limited to characterizing receding contact due to mechanical and material instabilities between the indenter and the specimen. To address this, a modified nanoindentation method was developed to collect force and displacement measurements during both advancing and receding contact while avoiding instability. A finite element-based inverse method was developed to extract elastic and adhesion properties from spherical indentation tests on a thin film. Nanoindentation experiments on PDMS thin films were completed at various displacement rates and a finite element based-inverse analysis was used to extract the elastic and adhesion properties. In contrast with previous indentation adhesion studies which only characterized adhesion during separation, this work demonstrated that the rate dependence of both advancing and receding contact adhesion can be quantified using nanoindentation.
