DOCSLIB.ORG

Post-Buckling of Web-Core Sandwich Plates Based on Classical Continuum Mechanics

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Post-Buckling of Web-Core Sandwich Plates Based on Classical Continuum Mechanics This is an electronic reprint of the original article. This reprint may differ from the original in pagination and typographic detail. Romanoff, Jani; Jelovica, Jasmin; Reddy, J. N.; Remes, Heikki Post-buckling of web-core sandwich plates based on classical continuum mechanics Published in: MECCANICA DOI: 10.1007/s11012-020-01174-6 Published: 01/06/2021 Document Version Publisher's PDF, also known as Version of record Published under the following license: CC BY Please cite the original version: Romanoff, J., Jelovica, J., Reddy, J. N., & Remes, H. (2021). Post-buckling of web-core sandwich plates based on classical continuum mechanics: success and needs for non-classical formulations. MECCANICA, 56(6), 1287-1302. https://doi.org/10.1007/s11012-020-01174-6 This material is protected by copyright and other intellectual property rights, and duplication or sale of all or part of any of the repository collections is not permitted, except that material may be duplicated by you for your research use or educational purposes in electronic or print form. You must obtain permission for any other use. Electronic or print copies may not be offered, whether for sale or otherwise to anyone who is not an authorised user. Powered by TCPDF (www.tcpdf.org) Meccanica https://doi.org/10.1007/s11012-020-01174-6 (0123456789().,-volV)( 0123456789().,-volV) RECENT ADVANCES IN COMPUTATIONAL MECHANICS AND INNOVATIVE MATERIALS Post-buckling of web-core sandwich plates based on classical continuum mechanics: success and needs for non-classical formulations Jani Romanoff . Jasmin Jelovica . J. N. Reddy . Heikki Remes Received: 21 January 2020 / Accepted: 10 May 2020 Ó The Author(s) 2020 Abstract The paper investigates the post-buckling element models of the actual 3D-geometry. Finally, response of web-core sandwich plates through classi- the physical limits of the classical continuum mechan- cal continuum mechanics assumptions. The compres- ics are discussed in the present context. sive loading is assumed to be in the direction of the web plates. Equivalent Single Layer (ESL) plate Keywords Plate theory Á Post-buckling Á Structural formulation is used with the kinematics of the First design Á Sandwich Structures order Shear Deformation Theory (FSDT). During the initial, membrane-dominated loading stages, it is observed that the effect of finite size of the periodic microstructure is barely influences the plate responses. 1 Introduction At the higher loads, when bending is activated, the finite size of the microstructure activates secondary There is constant need to study new materials and shear-induced bending moments at the unit cells of the structural configurations for thin-walled structures. plate. A method to capture the envelope of the Weight reduction and strength increase enable lighter maximum values of these bending moments is and often more sustainable structural solutions that presented. The findings are validated with the shell can be used in civil, naval and aeronautical applica- tions. Structural efficiency in terms of strength-to- weight and stiffness-to-weight is obtained by posi- J. Romanoff (&) Á H. Remes tioning of the material according to the load-carrying Marine Technology, Department of Mechanical mechanism of the structure. In bending dominated Engineering, School of Engineering, Aalto University, applications, this often results in plates with periodic Otakaari 4, 00076 Aalto, Finland e-mail: jani.romanoff@aalto.fi microstructure, for example, single-sided stiffened plates and sandwich panels with visibly discrete core; J. Jelovica see Fig. 1. The periodic structure allows integration of Department of Mechanical Engineering, University of functions to the panel(e.g. air-conditioning and cable British Columbia, Applied Science Lane, Vancouver Campus, 2054-6250, Vancouver, BC V6T 1Z4, Canada tracks). Thus, unidirectional stiffening system with coarse spacing becomes attractive structural alterna- J. N. Reddy tive; Refs. [1–13]. These unidirectional plates, espe- Department of Mechanical Engineering, Center of cially in the form of steel sandwich plates, have been Innovation in Mechanics for Design and Manufacturing, Texas A&M University, J. Mike Walker’66, 180 Spence found to have excellent mechanical properties for Street, College Station, TX 77843, USA 123 Meccanica Fig. 1 Examples of periodic sandwich panels structural failures under different extreme loads. (Figures from: explosions Valdevit et al. [18]; full-scale ship collisions Ehlers et al. [37] and quasi-static plate punch experiments Ko¨rgesaar et al. [38]) buckling, bending and impact loads [14–21]. These the fact that often the failure of these panels occurs structures are, however, challenging in terms of first locally in the microstructural level in the face and structural analysis. The direct inclusion of the web-plates or at the welds by yielding or buckling, see microstructure to computational models of the entire Fig. 1. This means that certain level of accuracy is structure leads to expensive pre-processing, analysis needed in the analysis of structural details. and post-processing times (i.e., computationally inten- Homogenization is the alternative method for a sive). The problem compounds if the geometry direct modeling of both micro- and macrostructure. In changes and analysis is needed to be repeated several terms of plates, it has been discussed by several times(e.g., during structural optimization or reliability authors(see, e.g., Refs. [1, 3, 4, 11–14, 20–36]). In analysis [18, 20]). Further complications are caused by plates, the main idea is to reduce the mathematical 123 Meccanica description to Equivalent Single Layer (ESL) repre- the problem at hand. We assume that the microstruc- sentation in which the deformations and stress resul- ture is linearly-elastic. Thus, at micro-scale, analyti- tants (forces and moments) are computed for known cal, stiffness and strength formulations are possible load and boundary conditions. In periodic sandwich and the prevailing physics can be explained in panels, the closed unit cells, including the interacting parametric form. Then we show how to eliminate the face and web plates, form a structure that warps in microstructural elements from the plate model. This bending due to the out-of-plane shear. With this elimination allows solution of the macro-scale prob- phenomenon included, Libove and Hubka [1] pre- lem with the classical ESL-FSDT formulations that sented an ESL-theory for corrugated-core sandwich can be found from numerous textbooks and the finite plates which follows First order Shear Deformation element implementations from several commercial Theory (FSDT). They derived the equivalent shear codes. Then, at the post-processing stage we focus on stiffness and provided series solutions to prevailing assessment of stress concentrations at faces, webs and differential equations for bending. After this work, welds and reconsider the finite size of the microstruc- several papers have been written for other microstruc- ture. This shows the limitations of this paper and also tures [26–30, 33, 37, 38] where the stiffness param- the commercial FSDT-ESL FE-codes on capturing the eters change, but the differential equations remain the prevailing post-buckling behavior. It also motivates same. The approach has been also validated to extensions to the non-classical continuum mechanics geometrically moderate non-linear global deforma- formulations. tions [26–28]. However, the problem arises in the assessment of stresses. As the local, microstructural length-scale can be close to that of macro-structural, 2 Theory the local oscillations of stresses within microstructure can have significant contribution to the overall stress 2.1 Notations state caused by macroscopic plate behavior. It has been experimentally shown that the out-of-plane shear The plate is assumed to consist of structural elements damages the periodic structures from plate edges or with small thickness representing the face and web close to point loads, thus the secondary stresses plate(s). This justifies the use of Kirchhoff hypothesis induced by shear need to be carefully assessed locally at the face and web-plates. The thicknesses of [20–22], see also Fig. 1. These findings are based on the top and bottom face plates are denoted by tt and tb, bending of plates. This situation can also occur during respectively, and these are positioned in the xy-plane. in-plane compression after buckling when the initially The web plates are in the xz-plane and have thickness membrane-dominated responses are complemented tw, spacing s, and height hc. The plate has two with out-of-plane responses [39]. coordinate systems, namely: global xyz and local xlylzl The objective of this study is to present the (see Fig. 2). The origin of the global coordinate phenomena related to post-buckling response of system is located at the geometrical mid-plane of the web-core sandwich plates and thereby extending the plate and the origin of the local coordinate is located at work presented in Ref. [39]. Primary focus is on the the geometrical mid-planes of face or the web plates bending responses due to the von Ka´rma´n strains. The under consideration. ESL formulation based on the FSDT is utilized in order to show the connection between in- and out-of- 2.2 Classical, homogenized FSDT for periodic plane deformations. In post-buckling regime, bending plates occurs, which activates secondary normal stresses of the microstructure. As the unit cell to plate length The deformation of the periodic
Load more

Recommended publications
  • Lightweight Highly Tunable Jamming-Based Composites
    SOFT ROBOTICS Volume 00, Number 00, 2020 ª Mary Ann Liebert, Inc. DOI: 10.1089/soro.2019.0053 Lightweight Highly Tunable Jamming-Based Composites Yashraj S. Narang,1,2 Buse Aktasx,1 Sarah Ornellas,3 Joost J. Vlassak,1 and Robert D. Howe1,4 Abstract Tunable-impedance mechanisms can improve the adaptivity, robustness, and efficiency of a vast array of en- gineering systems and soft robots. In this study, we introduce a tunable-stiffness mechanism called a ‘‘sandwich jamming structure,’’ which fuses the exceptional stiffness range of state-of-the-art laminar jamming structures (also known as layer jamming structures) with the high stiffness-to-mass ratios of classical sandwich com- posites. We experimentally develop sandwich jamming structures with performance-to-mass ratios that are far greater than laminar jamming structures (e.g., a 550-fold increase in stiffness-to-mass ratio), while simulta- neously achieving tunable behavior that standard sandwich composites inherently cannot achieve (e.g., a rapid and reversible 1800-fold increase in stiffness). Through theoretical and computational models, we then show that these ratios can be augmented by several orders of magnitude further, and we provide an optimization routine that allows designers to build the best possible sandwich jamming structures given arbitrary mass, vol- ume, and material constraints. Finally, we demonstrate the utility of sandwich jamming structures by integrating them into a wearable soft robot (i.e., a tunable-stiffness wrist orthosis) that has negligible impact on the user in the off state, but can reduce muscle activation by an average of 41% in the on state.
    [Show full text]
  • Dynamic Responses of Flexible-Link Mechanisms with Passive/Active Damping Treatment Jean-François Deü, Ana Cristina Galucio, Roger Ohayon
    Dynamic responses of flexible-link mechanisms with passive/active damping treatment Jean-François Deü, Ana Cristina Galucio, Roger Ohayon To cite this version: Jean-François Deü, Ana Cristina Galucio, Roger Ohayon. Dynamic responses of flexible-link mech- anisms with passive/active damping treatment. Computers and Structures, Elsevier, 2008, 86 (3-5), pp.258-265. 10.1016/j.compstruc.2007.01.028. hal-01519381 HAL Id: hal-01519381 https://hal.archives-ouvertes.fr/hal-01519381 Submitted on 7 May 2017 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Distributed under a Creative Commons Attribution| 4.0 International License Dynamic responses of flexible-link mechanisms with passive/active damping treatment J.-F. Deü, A.C. Galucio, R. Ohayon Conservatoire National des Arts et Me´tiers (CNAM), Structural Mechanics and Coupled Systems Laboratory, Case 353, 292 rue Saint Martin, 75141 Paris Cedex 03, France This work presents a finite element formulation for non-linear transient dynamic analysis of adaptive beams. The main contribution of this work concerns the development of an original co-rotational sandwich beam element, which allows large displacements and rota- tions, and takes active/passive damping into account.
    [Show full text]
  • Analysis Methods Used on the NASA Composite Crew Module (CCM)
    Analysis Methods used on the NASA Composite Crew Module (CCM) Craig Collier1, Phil Yarrington2, Mark Pickenheim3 [email protected] Collier Research Corp., Hampton, VA Brett Bednarcyk4 NASA Glenn Research Center, Cleveland, OH Jim Jeans5 Genesis Engineering Solutions, Inc., Lanham, MD The process in use by a national team from NASA research centers and industry partners for the analysis and design of a full scale composite crew module is presented. Methods, failure analyses, and design sizing approaches used by the team are identified. The HyperSizer® software coupled with FEA was used for trade studies of crew module shape configurations, material selections, sandwich panel dimensions, and composite layups and is being used for final analyses and stress report margins-of-safety. Different types of analyses were performed throughout the design maturity and their impacts to the evolving design discussed. These analyses include shell and backbone panel buckling, composite strength to damage tolerance criteria, laminate interlaminar shear, ply drop-offs, sandwich panel specific failures such as facesheet wrinkling, core shear, and core crushing, flat wise tension, core taper ramp downs, and adhesively bonded joints and bolted joints. © 2008 Collier Research Corporation. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. 1, 2, 3 Senior Research Engineers, Hampton, Virginia; AIAA Senior Member, [email protected] 4 Materials Research Engineer, AIAA Senior Member, [email protected] 5 Senior Engineer, [email protected] 1 American Institute of Aeronautics and Astronautics Fig.1, Ares I Crew Launch Vehicle that launches the NASA Crew Module. Fig.2, The Crew Module (CM) interfaces with the Service Module (SM) and the Launch Abort System (LAS).
    [Show full text]
  • Analysis of Sandwich Beam
    View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by International Journal of Science Engineering and Advance Technology (IJSEAT) International Journal of Science Engineering and Advance ISSN 2321-6905 Technology, IJSEAT, Vol 2, Issue 12 December-2014 Analysis of Sandwich Beam M Siva Prasad#1, P Satish Reddy #2, Matta Manoj #3, N.Guru Murthy #4 ME Department, Prasiddha College of Engg and Technology, Anathavaram 1 [email protected], [email protected], [email protected], [email protected] Abstract- Sandwich beams are composite systems materials. In general, these structures require high having high stiffness-to-weight and Strength-to- reliability assurance for which, the prediction of the weight ratios and are used as light weight load maximum load that the structure can withstand. bearing components. The use of thin, strong skin sheets adhered to thicker, lightweight core materials A sandwich structured composite is a special class of has allowed industry to build strong, stiff, light, and composite materials that is fabricated by attaching durable structures. Due to the use of viscoelastic two thin but stiff skins to a light weight but thick polymer constituents, sandwich beams can exhibit core. The core material is normally low strength time-dependent behaviour. This study examines the material, but its higher thickness provided the behaviour of sandwich beams driven by the sandwich composite with high bending stiffness with viscoelastic rubber core. Finite element (FE) method overall low density. Open and closes cell structured is used to analyze the overall transient responses, foams like polyvinylchloride, polyurethane, harmonic responses and the static responses of the polyethylene or polystyrene foams, and honey combs sandwich systems subject to a concentrated point are commonly used core materials.
    [Show full text]
  • Flexural Analysis and Composite Behavior of Precast Concrete Sandwich Panel
    FLEXURAL ANALYSIS AND COMPOSITE BEHAVIOR OF PRECAST CONCRETE SANDWICH PANEL Thesis Submitted to The School of Engineering of the UNIVERSITY OF DAYTON In Partial Fulfillment of the Requirements for The Degree of Master of Science in Civil and Environmental Engineering By Behnam Naji Dayton, Ohio December, 2012 FLEXURAL ANALYSIS AND COMPOSITE BEHAVIOR OF PRECAST CONCRETE SANDWICH PANEL Name: Naji, Behnam APPROVED BY: Elias Toubia, Ph.D. Steven Donaldson, Ph.D. Advisory Committee Chairman Committee Member Assistant Professor Assistant Professor Civil and Environmental Engineering Civil and Environmental Engineering Thomas Whitney, Ph.D. Committee Member Assistant Professor Civil and Environmental Engineering John G. Weber, Ph.D. Tony E. Saliba, Ph.D. Associate Dean Dean, School of Engineering School of Engineering & Wilke Distinguished Professor ii ©Copyright by Behnam Naji All rights reserved 2012 iii ABSTRACT FLEXURAL ANALYSIS AND COMPOSITE BEHAVIOR OF PRECAST CONCRETE SANDWICH PANEL Name: Naji, Behnam University of Dayton Advisor: Dr. Elias Toubia Several experimental studies have shown the effect of core shear contribution in precast concrete sandwich wall panels. Due to the complex nature of such construction, quantifying the contribution of the core on the behavior of the precast concrete sandwich wall panel subjected to lateral load and in-plane loads is still a challenge. Based on engineering judgment and experience, current design practices assume a certain percentage in composite action between the faces (wythes) of the sandwich panel. In this study, a general equation for the deflection of a simply supported sandwich panel under in-plane and lateral loads was developed. The formulated equation includes all mechanical properties of the core and the thick similar faces.
    [Show full text]
  • Sandwich Structures 7: Advancing with Sandwich
    SANDWICH STRUCTURES 7: ADVANCINGWITH SANDWICH STRUCTURES AND MATERIALS Sandwich Structures 7: Advancing with Sandwich Structures and Materials Proceedings of the 7th International Conference on Sandwich Structures, Aalborg University, Aalborg, Denmark, 29-31 August 2005 Edited by O.T. THOMSEN Aalborg University, Aalborg, Denmark E. BOZHEVOLNAYA Aalborg University, Aalborg, Denmark and A. LYCKEGAARD Aalborg University, Aalborg, Denmark A C.I.P. Catalogue record for this book is available from the Library of Congress. ISBN-10 1-4020-3444-X (HB) ISBN-13 978-1-4020-3444-2 (HB) ISBN-10 1-4020-3848-8 (e-book) ISBN-13 978-1-4020-3848-8 (e-book) Published by Springer, P.O. Box 17, 3300 AA Dordrecht, The Netherlands. www.springeronline.com Printed on acid-free paper The cover depicts the ICSS-7 logo, by Kjeld Moseholm and Anders Lyckegaard. © Institute of Mechanical Engineering, Aalborg University, Denmark. Used by permission. All Rights Reserved © 2005 Springer No part of this work may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, microfilming, recording or otherwise, without written permission from the Publisher, with the exception of any material supplied specifically for the purpose of being entered and executed on a computer system, for exclusive use by the purchaser of the work. Printed in the Netherlands. TABLE OF CONTENTS Preface xvii KEYNOTE LECTURES Sandwich structures: Past, present, andfuture 3 J.R. Vinson Sandwich structures technology in commercial aviation 13 A.S. Herrmann, P.C. Zahlen and I. Zuardy Damage assessment and damage tolerance of FRP sandwich structures 27 B.
    [Show full text]
  • A Simple and Accurate Sandwich Plate Theory Accounting for Transverse Normal Strain and Interfacial Stress Continuity ⇑ X
    Composite Structures 107 (2014) 620–628 Contents lists available at ScienceDirect Composite Structures journal homepage: www.elsevier.com/locate/compstruct A simple and accurate sandwich plate theory accounting for transverse normal strain and interfacial stress continuity ⇑ X. Wang, G. Shi Department of Mechanics, Tianjin University, Tianjin 300072, China article info abstract Article history: This paper presents a simple and accurate sandwich plate theory accounting for the transverse normal Available online 2 September 2013 strain and interfacial stress continuity. A refined cubic polynomial is used for the transverse shear func- tion and a linear function is adopted for the transverse normal strain. The Heaviside step function and Keywords: stress continuity coefficients are employed respectively to enforce the interfacial continuity of the in- Sandwich plate theory plane displacements and transverse stresses. By the enforcement of the traction conditions on the plate Transverse shear function surfaces, there are only five independent field variables in the present sandwich plate theory. The varia- Transverse normal strain tional consistent equilibrium equations and boundary conditions in terms of both displacements and Interfacial stress continuity stress resultants are derived by utilizing the variational principle. The analytical solutions of the bending Analytical solution analyses of sandwich plates with different aspect ratios and stiffness ratios are solved to demonstrate the accuracy of this new sandwich plate theory. The resulting analytical solutions of deflections, normal stresses and transverse shear stresses are compared with the 3D elasticity solutions, the numerical results and the results given by other sandwich plate theories. The comparison study shows that this equivalent single layer sandwich plate theory is not only simple, but also capable of achieving the accu- racy of layerwise sandwich plate theories.
    [Show full text]
  • Diab Guideline to Core and Sandwich
    Guideline to Core and Sandwich Introduction to sandwich This document has been written to spread knowledge about sandwich and understanding of its behavior. 1.1 Why sandwich? It has long been known that by separating two materials below). This distinction, along with many other drivers with a lightweight material in between it will increase the such as the environmental benefits, extreme cost savings, structure’s stiffness and strength at very low weight and and freedom of design, are causing sandwich to become cost (see further explanation in “The sandwich principle” more and more popular in structural design. 1.1.1 Weight benefits One of the most driving reasons to use sandwich is that solution enables faster and smaller robots. Within the concept enables lightweight construction. The energy- theatre, it enables fast set changes between scenes. In saving benefits are described in the previous section, construction, a bridge or façade facilitates fast, effective but it also enables faster and more effective solutions in installation. In transportation, lower weight in containers many cases. Sports equipment is one segment for which or vessel construction enables higher payloads. Clearly, strength and speed are important. Another is racing, such the benefits of lightweight solutions go on and on. as sailing, speed boats etc. In industry, a lightweight 1.1.2 Environmental benefits Obviously, anything that moves consumes energy, and environmental impact of material choice in the beginning the heavier it is, the more energy consumed. Since using (energy) and in the end (recycling) of a vessel’s life cycle sandwich makes structural designs lighter, sandwich is minor (as long as the material choice saves weight) in solutions are extremely environmentally friendly.
    [Show full text]
  • Free Vibration of Flexible Soft-Core Sandwiches According to Layerwise Theories Differently Accounting for the Transverse Normal Deformability
    ORIGINAL ARTICLE Free Vibration of flexible soft-core sandwiches according to layerwise theories differently accounting for the transverse normal deformability Ugo Icardia* Andrea Urracia a Dipartimento di Ingegneria Meccanica e Aerospaziale - Politecnico di Torino - Corso Duca degli Abruzzi 24, 10129 Torino, Italy. E-mail: [email protected], [email protected] * Corresponding author https://doi.org/10.1590/1679-78255624 Abstract This study aims to generalize a previously developed accurate and inexpensive 3-D zig-zag theory up to an arbitrary representation form and to determine which simplifications are yet accurate in determining transverse shear and normal stress/deformation effects on vibrations of soft-core sandwiches with not moving middle/neutral plane (pumping). Natural frequencies are calculated using displacements assumed differently across the thickness, having fixed d.o.f., not yet explored forms of representation and zig-zag functions differently accounting for the transverse normal deformability and that partially or fully fulfill physical constraints. Applications are presented for sandwich plates and beams with length-to-thickness ratios and material properties of faces and core varying within an industrial range, for which layerwise effects are very important and so suited to the evaluation of theories. Analytical solutions are found using the same trial functions and expansion order for all theories, so to evaluate their accuracy under the same conditions. The choice of the representation form and of zig-zag functions is shown immaterial if displacement field coefficients are recomputed across the thickness by enforcing the fulfillment of all physical constraints (using symbolic calculus). Furthermore, it is shown that assigning a specific role to each coefficient is immaterial, as well as exchanging the order of representation of in-plane and transverse displacement components and even that zig-zag functions could be omitted.
    [Show full text]
  • Stress Analysis of Tapered Sandwich Panels with Isotropic Or Laminated Composite Facings Huyue Zhao
    The University of Maine DigitalCommons@UMaine Electronic Theses and Dissertations Fogler Library 2002 Stress Analysis of Tapered Sandwich Panels with Isotropic or Laminated Composite Facings Huyue Zhao Follow this and additional works at: http://digitalcommons.library.umaine.edu/etd Part of the Mechanical Engineering Commons Recommended Citation Zhao, Huyue, "Stress Analysis of Tapered Sandwich Panels with Isotropic or Laminated Composite Facings" (2002). Electronic Theses and Dissertations. 309. http://digitalcommons.library.umaine.edu/etd/309 This Open-Access Thesis is brought to you for free and open access by DigitalCommons@UMaine. It has been accepted for inclusion in Electronic Theses and Dissertations by an authorized administrator of DigitalCommons@UMaine. STRESS ANALYSIS OF TAPERED SANDWICH PANELS WITH ISOTROPIC OR LAMINATED COMPOSITE FACINGS I BY Huyue Zhao B.S. Huazhong University of Science and Technology, 1996 M.S. Huazhong University of Science and Technology, 2000 A THESIS Submitted in Partial Fulfillment of the Requirements for the Degree of Master of Science (in Mechanical Engineering) The Graduate School The University of Maine December, 2002 Advisory Committee: Senthil Vel, Assistant Professor of Mechanical Engineering, Co-Advisor Vincent Caccese, Associate Professor of Mechanical Engineering, Co-Advisor Donald A. Grant, RC. Hill Professor of Mechanical Engineering Michael "Mick" Peterson, Assistant Professor of Mechanical Engineering LIBRARY RIGHTS STATEMENT I In presenting this thesis in partial hlfillment of the requirements for an advanced degree at The University of Maine, I agree that the Library shall make it freely available for inspection. I hrther agree that permission for "fair use" copying of this thesis for scholarly purposes may be granted by the Librarian.
    [Show full text]
  • Carbon Foam Characterization
    CARBON FOAM CHARACTERIZATION: SANDWICH FLEXURE, TENSILE AND SHEAR RESPONSE A Thesis by MELANIE DIANE SARZYNSKI Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE December 2003 Major Subject: Mechanical Engineering CARBON FOAM CHARACTERIZATION: SANDWICH FLEXURE, TENSILE AND SHEAR RESPONSE A Thesis by MELANIE DIANE SARZYNSKI Submitted to Texas A&M University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Approved as to style and content by: _________________________________ _________________________________ Ozden Ochoa Paul Roschke (Chair of Committee) (Member) _________________________________ _________________________________ Harry Hogan Dennis O’Neal (Member) (Head of Department) _________________________________ William Schneider (Member) December 2003 Major Subject: Mechanical Engineering iii ABSTRACT Carbon Foam Characterization: Sandwich Flexure, Tensile and Shear Response. (December 2003) Melanie Diane Sarzynski, B.S., Texas A&M University Chair of Advisory Committee: Dr. Ozden Ochoa The focus of this research is characterizing a new material system composed of carbon and graphite foams, which has potential in a wide variety of applications encompassing aerospace, military, offshore, power production and other commercial industries. The benefits of this new material include low cost, light weight, fire-resistance, good energy absorption, and thermal insulation or conduction as desired. The objective of this research is to explore the bulk material properties and failure modes of the carbon foam through experimental and computational analysis in order to provide a better understanding and assessment of the material for successful design in future applications. Experiments are conducted according to ASTM standards to determine the mechanical properties and failure modes of the carbon foam.
    [Show full text]
  • Creep Behaviour of Geometrically Nonlinear Soft Core Sandwich Panels
    20th International Conference on Composite Materials Copenhagen, 19-24th July 2015 CREEP BEHAVIOUR OF GEOMETRICALLY NONLINEAR SOFT CORE SANDWICH PANELS Ehab Hamed1 and Yeoshua Frostig2 1Centre for Infrastructure Engineering and Safety, School of Civil and Environmental Engineering, University of New South Wales, NSW 2052, Sydney, Australia Email: [email protected], web page: http://www.unsw.edu.au 2Faculty of Civil and Environmental Engineering, Technion – Israel Institute of Technology, Haifa 32000, Israel. Email: [email protected], web page: http://www.technion.ac.il Keywords: Buckling, Creep, High-order, Sandwich panels, Viscoelasticity. ABSTRACT This paper investigates the effects of creep of the core material on the global geometrically nonlinear behavior of sandwich panels under axial and lateral loading conditions. The theoretical model combines the concepts of the hereditary (convolution) integral of viscoelasticity based on the principle of superposition, with the high-order sandwich theory. From the expansion of the relaxation moduli into Prony series, an incremental exponential law that corresponds to the rheological generalized Maxwell model is obtained, and which allows for a step-by-step time analysis that accounts for the change in deformations and stresses with time. The results show that creep of the core can lead to a significant reduction in the global buckling capacity of sandwich panels. 1 INTRODUCTION Sandwich panels that are made of metallic or laminated composite face sheets and a soft core find a wide spread use in many engineering applications. Under service conditions, sandwich panels can be subjected to different load scenarios, one of them being axial compression that is combined with lateral loading/effects due to imperfections, self-weight, and other effects.
    [Show full text]