Download or read book Multi fidelity Modeling of Interfacial Micromechanics for Off Aligned Polymer Carbon Nanotube Nanocomposites written by Reed Kopp and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Recent initiatives to stimulate development of next-generation rotorcraft featuring leap-ahead improvements in speed, payload, range, and durability, such as Clean Sky and Future Vertical Lift, have revitalized research efforts directed toward advanced, unconventional designs that emphasize lower operations and sustainment costs. Accordingly, soft-inplane damperless bearingless and hingeless rotor concepts have garnered significant interest. However, soft-inplane designs are susceptible to aeromechanical instabilities, such as air and ground resonance, which can potentially induce catastrophic blade vibrations without sufficient blade damping. To ensure stability, current composite blades typically require auxiliary damping sources that incur weight, volume, complexity, and maintenance penalties. Alternatively, one promising approach for achieving new lightweight, low vibration rotorcraft structures is passive damping engineered intrinsically into a structure via polymeric nanocomposites.In this study, a multi-fidelity modeling effort is employed to investigate the interfacial load transfer micromechanics, including strain energy storage and dissipation, of an off-aligned discontinuously-reinforced polymer/carbon nanotube nanocomposite. The effects of off-alignment angle on nanocomposite mechanical properties is of primary interest. The methodology in this study is separated into two independent modeling tracks: a simplified analytical micromechanics model and a high-fidelity 3D finite element model. Both model types explore transverse fixed and transverse free boundary conditions applied to the representative volume element, which correspond to applied strain and applied stress external loading conditions, respectively. Each model accounts for interfacial shear stress variations along the azimuthal direction of the nano-inclusion surface that are a result of nonzero and non-right alignment angles with respect to the applied loading. The analytical micromechanics models examine non-embedded fiber conditions, for which matrix end material effects are neglected, in the preslip and postslip regimes and embedded fiber conditions, for which matrix end material effects are included, in the preslip regime. The non-embedded micromechanics model is based on principles from an extended Cox model for discontinuous fiber reinforcement and generalized shear lag analysis for off-aligned discontinuous fibers; furthermore, the energy dissipation, which is based on principles of a simple amplitude-dependent friction damper, is assumed to be caused only by interfacial slip friction between constituents and is functionally dependent on the interfacial shear force acting over slipped portions of the matrix/nano-inclusion interface. In order to isolate the effects of azimuthal interfacial shear stress variation, a comparison of the current non-embedded model with an alternative non-embedded analytical model that employs an interfacial shear magnitude approach is performed. The embedded analytical micromechanics model is based on principles from a modified Cox model that extends the non-embedded approach to account for finite matrix end material and nonzero fiber end normal stress. The finite element model is implemented in the preslip regime for an embedded fiber with limited off-alignment angle range.The material properties employed by each model reflect those of a realistic multi-walled carbon nanotube/poly-ether-ether-ketone nanocomposite architecture. In the preslip regime, the FEM and analytical model predictions for interfacial shear and nano-inclusion normal stress distributions generally display good agreement, which is improved by including inclusion end stress effects in the analytical models. For the transverse fixed boundary condition, the non-embedded analytical model predicts reduced interfacial slip damping capacity as off-alignment increases, with initiation of slip becoming impossible at relatively high off-alignment angles. However, for the transverse free boundary condition, the non-embedded analytical model predicts that zero interfacial slip damping occurs comparatively at more moderate off-alignment angles, with nonzero damping occurring at both lower and higher off-alignment angles. The phenomena of extrema in interfacial slip damping with respect to alignment angle is due to the relative strain behavior between nanocomposite constituents caused by elastic stiffness mismatch. The alternative azimuthal magnitude non-embedded analytical model generally underpredicts storage modulus and greatly overpredicts loss modulus (for nonzero and non-right off-alignments) compared with the corresponding properties predicted by the current non-embedded analytical model because the alternative azimuthal magnitude approach assumes a greater interfacial slip surface area for a given off-alignment angle and strain magnitude compared to the current approach. Overall, the results demonstrate that nano-inclusion alignment angle substantially affects nanocomposite stiffness and interfacial damping and that azimuthal variation of the interfacial shear is a critical feature of nanocomposite mechanics. The outcome of this multi-fidelity modeling study is an array of qualified nanocomposite mechanical property prediction methods spanning a wide range of practical off-alignment angles, applied dynamic strain amplitudes and static strain magnitudes, loading and fiber embedment conditions, and nano-inclusion geometries and concentrations.

Download or read book Mechanics of Composite Hybrid and Multifunctional Materials Volume 5 written by Piyush R. Thakre and published by Springer. This book was released on 2018-10-15 with total page 324 pages. Available in PDF, EPUB and Kindle. Book excerpt: Mechanics of Composite, Hybrid, and Multifunctional Materials, Volume 5 of the Proceedings of the 2018 SEM Annual Conference & Exposition on Experimental and Applied Mechanics, the fifth volume of eight from the Conference, brings together contributions to this important area of research and engineering. The collection presents early findings and case studies on a wide range of areas, including: Recycled Constituent Composites Nanocomposites Mechanics of Composites Fracture & Fatigue of Composites Multifunctional Materials Damage Detection & Non-destructive Evaluation Composites for Wind Energy & Aerospace Applications Computed Tomography of Composites Manufacturing & Joining of Composites Novel Developments in Composites

Download or read book Micromechanics Modeling of the Multifunctional Nature of Carbon Nanotube polymer Nanocomposites written by Gary Don Seidel and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The present work provides a micromechanics approach based on the generalized self-consistent composite cylinders method as a non-Eshelby approach towards for assessing the impact of carbon nanotubes on the multi-functional nature of nanocom-posites in which they are a constituent. Emphasis is placed on the effective elastic properties as well as electrical and thermal conductivities of nanocomposites con-sisting of randomly oriented single walled carbon nanotubes in epoxy. The effective elastic properties of aligned, as well as clustered and well-dispersed nanotubes in epoxy are discussed in the context of nanotube bundles using both the generalized self-consistent composite cylinders method as well as using computational microme-chanics techniques. In addition, interphase regions are introduced into the composite cylinders assemblages to account for the varying degrees of load transfer between nanotubes and the epoxy as a result of functionalization or lack thereof. Model pre-dictions for randomly oriented nanotubes both with and without interphase regions are compared to measured data from the literature with emphasis placed on assessing the bounds of the effective nanocomposite properties based on the uncertainty in the model input parameters. The generalized self-consistent composite cylinders model is also applied to model the electrical and thermal conductivity of carbon nanotube-epoxy nanocomposites. Recent experimental observations of the electrical conductivity of carbon nanotube polymer composites have identifed extremely low percolation limits as well as a per-ceived double percolation behavior. Explanations for the extremely low percolation limit for the electrical conductivity of these nanocomposites have included both the creation of conductive networks of nanotubes within the matrix and quantum effects such as electron hopping or tunneling. Measurements of the thermal conductivity have also shown a strong dependence on nanoscale effects. However, in contrast, these nanoscale effects strongly limit the ability of the nanotubes to increase the thermal conductivity of the nanocomposite due to the formation of an interfacial thermal resistance layer between the nanotubes and the surrounding polymer. As such, emphasis is placed here on the incorporation of nanoscale effects, such as elec-tron hopping and interfacial thermal resistance, into the generalized self-consistent composite cylinder micromechanics model.

Download or read book Analytic and Computational Micromechanics of Clustering and Interphase Effects in Carbon Nanotube Composites written by Daniel Carl Hammerand and published by . This book was released on 2006 with total page 87 pages. Available in PDF, EPUB and Kindle. Book excerpt: Effective elastic properties for carbon nanotube reinforced composites are obtained through a variety of micromechanics techniques. Using the in-plane elastic properties of graphene, the effective properties of carbon nanotubes are calculated utilizing a composite cylinders micromechanics technique as a first step in a two-step process. These effective properties are then used in the self-consistent and Mori-Tanaka methods to obtain effective elastic properties of composites consisting of aligned single or multi-walled carbon nanotubes embedded in a polymer matrix. Effective composite properties from these averaging methods are compared to a direct composite cylinders approach extended from the work of Hashin and Rosen (1964) and Christensen and Lo (1979). Comparisons with finite element simulations are also performed. The effects of an interphase layer between the nanotubes and the polymer matrix as result of functionalization is also investigated using a multi-layer composite cylinders approach. Finally, the modeling of the clustering of nanotubes into bundles due to interatomic forces is accomplished herein using a tessellation method in conjunction with a multi-phase Mori-Tanaka technique. In addition to aligned nanotube composites, modeling of the effective elastic properties of randomly dispersed nanotubes into a matrix is performed using the Mori-Tanaka method, and comparisons with experimental data are made. Computational micromechanical analysis of high-stiffness hollow fiber nanocomposites is performed using the finite element method. The high-stiffness hollow fibers are modeled either directly as isotropic hollow tubes or equivalent transversely isotropic effective solid cylinders with properties computed using a micromechanics based composite cylinders method. Using a representative volume element for clustered high-stiffness hollow fibers embedded in a compliant matrix with the appropriate periodic boundary conditions, the effective elastic properties are obtained from the finite element results. These effective elastic properties are compared to approximate analytical results found using micromechanics methods. The effects of an interphase layer between the high-stiffness hollow fibers and matrix to simulate imperfect load transfer and/or functionalization of the hollow fibers is also investigated and compared to a multi-layer composite cylinders approach. Finally the combined effects of clustering with fiber-matrix interphase regions are studied. The parametric studies performed herein were motivated by and used properties for single-walled carbon nanotubes embedded in an epoxy matrix, and as such are intended to serve as a guide for continuum level representations of such nanocomposites in a multi-scale modeling approach.

Download or read book Multiscale Modeling of Multifunctional Carbon Nanotube Reinforced Polymer Composites written by AHMED ROWAEY Rowaey Abdelazeam ALIAN and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In this thesis, novel multiscale modeling techniques have been successfully developed to study multifunctional nanocomposite polymeric materials. Interfacial, mechanical, electrical, and piezoresistive properties of carbon nanotube (CNT)-reinforced polymer composites were investigated using molecular dynamics (MD), micromechanics, and coupled electromechanical modeling techniques. Additionally, scanning electron microscopy was used to determine the morphology and dispersion state of a typical CNT-epoxy composite. Based on these measurements, realistic nanocomposite structures were modeled using representative volume elements (RVEs) reinforced by CNTs with different aspect ratios, curvatures, orientations, alignment angles, and bundle sizes. At the nanoscale level, the interfacial shear strength was determined via pull-out MD simulations. Additionally, the stiffness constants of a pure polymer, pristine and defective CNTs, and an effective fiber consisting of a CNT and a surrounding layer of polymeric chains were determined using the constant-strain energy minimization method. The obtained atomistic mechanical properties of the composite constituents were then scaled up using Mori-Tanaka micromechanical scheme. Monte Carlo simulations were conducted to determine the percolation and electrical conductivity of RVEs containing randomly dispersed CNTs. An advanced search algorithm was developed to identify percolating CNT networks and transform them into an equivalent electrical circuit formed from intrinsic and tunneling resistances. A solver based on the modified nodal analysis technique was then developed to calculate the effective conductivity of the RVE. Finally, the electrical model was coupled with a three-dimensional finite element model of the RVE to determine the coupled electromechanical behavior of the composite under tensile, compressive, and shear loads from the resistance-strain relationship. The outcome of the developed modeling approach revealed that: the elastic modulus of a nanocomposite reinforced with well-dispersed straight CNTs was found to increase almost linearly with the increase of their volume fraction and double at CNT volume fraction of 5.0 %; the combined effect of CNT waviness and agglomeration results in a significant reduction in the bulk properties of the nanocomposite; CNTs with grain boundaries perpendicular to the tube axis experience 60% reduction in its mechanical strength; and the nanocomposite gauge factor can reach up to 3.95 and is sensitive to loading direction and CNT concentration.

Download or read book Damping in Carbon Nanotube Nanocomposites by Interfacial Slippage and Thermally Augmented Polymer Relaxation written by Frank Gardea and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The present work investigates the damping potential of carbon nanotube (CNT) reinforced polymer matrix composites through integrated experiments and continuum modeling techniques. Both "passive" and "active" damping are studied. The passive damping here refers to the inherent capability of a composite to damp vibrations in the absence of external stimuli, such as electrical signals, by exploiting different damping mechanisms introduced by the presence of the nanoscale reinforcements. Among the targeted passive damping mechanisms in nanocomposites is a 'slip-stick' mechanism in which the interactions between the filler and polymer results in energy dissipation in a frictional mode along the interface. Microstructural design of nanocomposites, such as the development of CNT alignment, was pursued here to enhance the contribution of interfacial sliding to damping, relative to other mechanisms such as stress concentrations within the matrix and matrix plasticity. A micromechanics model was used to provide additional insight into the experimental observations by showing that the nonlinear variation of damping with dynamic strain can be attributed to slip-stick behavior. The dependence of the interfacial load-transfer reversibility on the dynamic strain history and characteristic time scale was experimentally investigated to demonstrate the relative significance of van der Waals (vdW) interactions, mechanical interlocking, and covalent bonding on shear interactions. In this effort, we also studied the controllability of energy dissipation capability in nanocomposites via electrical signals, referred to as active damping. This mechanism benefits from the electrically conductive network of CNTs, as well as their high surface to volume ratio, to thermally enhance viscous phenomena, such as chain relaxation in polymers. For active damping, the thermomechanical response of the polymer is targeted and studied as a potential damping source within the nanocomposite. By taking advantage of the polymer relaxation resulting from an increase in temperature, the composite shows the potential for damping enhancement. However, the non-uniform temperature distribution in the composite sample has a large effect on the overall damping enhancement. The non-uniformity of the temperature distribution, both locally and globally, was studied via experiments and multi-resolution models to further shed light on this phenomenon. This effort clearly points to the significance of interface phenomena, both friction between filler and matrix and energy transfer from the fillers to the matrix, in controlling the damping mechanisms in nanocomposites and presents insights, both qualitative and quantitative, into the origins of these effects. The electronic version of this dissertation is accessible from http://hdl.handle.net/1969.1/155748

Download or read book Carbon Nanotube Reinforced Polymers written by Roham Rafiee and published by Elsevier. This book was released on 2017-10-06 with total page 588 pages. Available in PDF, EPUB and Kindle. Book excerpt: Carbon Nanotube-Reinforced Polymers: From Nanoscale to Macroscale addresses the advances in nanotechnology that have led to the development of a new class of composite materials known as CNT-reinforced polymers. The low density and high aspect ratio, together with their exceptional mechanical, electrical and thermal properties, render carbon nanotubes as a good reinforcing agent for composites. In addition, these simulation and modeling techniques play a significant role in characterizing their properties and understanding their mechanical behavior, and are thus discussed and demonstrated in this comprehensive book that presents the state-of-the-art research in the field of modeling, characterization and processing. The book separates the theoretical studies on the mechanical properties of CNTs and their composites into atomistic modeling and continuum mechanics-based approaches, including both analytical and numerical ones, along with multi-scale modeling techniques. Different efforts have been done in this field to address the mechanical behavior of isolated CNTs and their composites by numerous researchers, signaling that this area of study is ongoing. - Explains modeling approaches to carbon nanotubes, together with their application, strengths and limitations - Outlines the properties of different carbon nanotube-based composites, exploring how they are used in the mechanical and structural components - Analyzes the behavior of carbon nanotube-based composites in different conditions

Download or read book Micromechanics of Composite Materials written by Jacob Aboudi and published by Butterworth-Heinemann. This book was released on 2013 with total page 1032 pages. Available in PDF, EPUB and Kindle. Book excerpt: Summary: A Generalized Multiscale Analysis Approach brings together comprehensive background information on the multiscale nature of the composite, constituent material behaviour, damage models and key techniques for multiscale modelling, as well as presenting the findings and methods, developed over a lifetime's research, of three leading experts in the field. The unified approach presented in the book for conducting multiscale analysis and design of conventional and smart composite materials is also applicable for structures with complete linear and nonlinear material behavior, with numerous applications provided to illustrate use. Modeling composite behaviour is a key challenge in research and industry; when done efficiently and reliably it can save money, decrease time to market with new innovations and prevent component failure.

Download or read book Mechanics of Composite Materials written by Jacob Aboudi and published by Elsevier. This book was released on 2013-10-22 with total page 341 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the last decade the author has been engaged in developing a micromechanical composite model based on the study of interacting periodic cells. In this two-phase model, the inclusion is assumed to occupy a single cell whereas the matrix material occupies several surrounding cells. A prominent feature of the micromechanical method of cells is the transition from a medium, with a periodic microstructure to an equivalent homogeneous continuum which effectively represents the composite material. Of great importance is the significant advantage of the cells model in its capability to analyze elastic as well as nonelastic constituents (e.g. viscoelastic, elastoplastic and nonlinear elastic), thus forming a unified approach in the prediction of the overall behaviour of composite material. This book deals almost exclusively with this unified theory and its various applications.

Download or read book Continuum Micromechanics written by P. Suquet and published by Springer. This book was released on 2014-05-04 with total page 352 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents the most recent progress of fundamental nature made in the new developed field of micromechanics: transformation field analysis, variational bounds for nonlinear composites, higher-order gradients in micromechanical damage models, dynamics of composites, pattern based variational bounds.

Download or read book Titanium Alloys written by W Sha and published by Elsevier. This book was released on 2009-04-29 with total page 588 pages. Available in PDF, EPUB and Kindle. Book excerpt: Given their growing importance in the aerospace, automotive, sports and medical sectors, modelling the microstructure and properties of titanium and its alloys is a vital part of research into the development of new applications. This is the first time a book has been dedicated to modelling techniques for titanium.Part one discusses experimental techniques such as microscopy, synchrotron radiation X-ray diffraction and differential scanning calorimetry. Part two reviews physical modelling methods including thermodynamic modelling, the Johnson-Mehl-Avrami method, finite element modelling, the phase-field method, the cellular automata method, crystallographic and fracture behaviour of titanium aluminide and atomistic simulations of interfaces and dislocations relevant to TiAl. Part three covers neural network models and Part four examines surface engineering products. These include surface nitriding: phase composition, microstructure, mechanical properties, morphology and corrosion; nitriding: modelling of hardness profiles and kinetics; and aluminising: fabrication of Ti coatings by mechanical alloying.With its distinguished authors, Titanium alloys: Modelling of microstructure, properties and applications is a standard reference for industry and researchers concerned with titanium modelling, as well as users of titanium, titanium alloys and titanium aluminide in the aerospace, automotive, sports and medical implant sectors. - Comprehensively assesses modelling techniques for titanium, including experimental techniques such as microscopy and differential scanning calorimetry - Reviews physical modelling methods including thermodynamic modelling and finite element modelling - Examines surface engineering products with specific chapters focused on surface nitriding and aluminising

Download or read book From Multiscale Modeling to Meso Science written by Jinghai Li and published by Springer Science & Business Media. This book was released on 2013-03-22 with total page 497 pages. Available in PDF, EPUB and Kindle. Book excerpt: Multiscale modeling is becoming essential for accurate, rapid simulation in science and engineering. This book presents the results of three decades of research on multiscale modeling in process engineering from principles to application, and its generalization for different fields. This book considers the universality of meso-scale phenomena for the first time, and provides insight into the emerging discipline that unifies them, meso-science, as well as new perspectives for virtual process engineering. Multiscale modeling is applied in areas including: multiphase flow and fluid dynamics chemical, biochemical and process engineering mineral processing and metallurgical engineering energy and resources materials science and engineering Jinghai Li is Vice-President of the Chinese Academy of Sciences (CAS), a professor at the Institute of Process Engineering, CAS, and leader of the EMMS (Energy-minimizing multiscale) Group. Wei Ge, Wei Wang, Ning Yang and Junwu Wang are professors at the EMMS Group, part of the Institute of Process Engineering, CAS. Xinhua Liu, Limin Wang, Xianfeng He and Xiaowei Wang are associate professors at the EMMS Group, part of the Institute of Process Engineering, CAS. Mooson Kwauk is an emeritus director of the Institute of Process Engineering, CAS, and is an advisor to the EMMS Group.

Download or read book The Applicability of the Generalized Method of Cells for Analyzing Discontinuously Reinforced Composites written by and published by . This book was released on 2001 with total page 40 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Graphene and Nanoparticles Hybrid Nanocomposites written by Abou el Kacem Qaiss and published by Springer Nature. This book was released on 2021-04-27 with total page 350 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book covers the recent research on nanomaterials and nanotechnology based on the hybridization of graphene with other nanoparticles. With their simple synthesis, nanoscale dimensions, high aspect ratio, mechanical, electrical and thermal properties, graphene and its hybridized materials have witnessed a great interest, and the chapters in this book cover the spectrum of research from the preparation and synthesis of novel nanocomposites to their potential use in aeronautic, automative, energy and environmental applications. Written by respected researchers from both industry and academia, this book is of interest to researchers and students working on nanomaterials.

Download or read book Science and Application of Nanotubes written by D. Tománek and published by Springer Science & Business Media. This book was released on 2005-12-17 with total page 393 pages. Available in PDF, EPUB and Kindle. Book excerpt: This series of books, which is published at the rate of about one per year, addresses fundamental problems in materials science. The contents cover a broad range of topics from small clusters of atoms to engineering materials and involve chemistry, physics, materials science, and engineering, with length scales ranging from Ångstroms up to millimeters. The emphasis is on basic science rather than on applications. Each book focuses on a single area of current interest and brings together leading experts to give an up-to-date discussion of their work and the work of others. Each article contains enough references that the interested reader can access the relevant literature. Thanks are given to the Center for Fundamental Materials Research at Michigan State University for supporting this series. M. F. Thorpe, Series Editor E-mail: thorpe@pa. msu. edu East Lansing, Michigan V PREFACE It is hard to believe that not quite ten years ago, namely in 1991, nanotubes of carbon were discovered by Sumio Iijima in deposits on the electrodes of the same carbon arc apparatus that was used to produce fullerenes such as the “buckyball”. Nanotubes of carbon or other materials, consisting ofhollow cylinders that are only a few nanometers in diameter, yet up to millimeters long, are amazing structures that self-assemble under extreme conditions. Their quasi-one-dimensional character and virtual absence of atomic defects give rise to a plethora of unusual phenomena.

Download or read book Analysis and Performance of Fiber Composites written by Bhagwan D. Agarwal and published by Wiley-Interscience. This book was released on 1990-10-08 with total page 480 pages. Available in PDF, EPUB and Kindle. Book excerpt: Having fully established themselves as workable engineering materials, composite materials are now increasingly commonplace around the world. Serves as both a text and reference guide to the behavior of composite materials in different engineering applications. Revised for this Second Edition, the text includes a general discussion of composites as material, practical aspects of design and performance, and further analysis that will be helpful to those engaged in research on composites. Each chapter closes with references for further reading and a set of problems that will be useful in developing a better understanding of the subject.

Download or read book Fiber Matrix and Interface Properties written by Christopher J. Spragg and published by ASTM International. This book was released on 1996 with total page 206 pages. Available in PDF, EPUB and Kindle. Book excerpt: Emphasizing fiber-matrix adhesion and its characterization in composite materials, reports results from applying the most commonly used test methods, such as fragmentation, pull-out, and indentation, to high-performance composites and their constituents. The 13 papers were presented at a symposium i