Sample records for sandwich construction

  1. Sandwich Construction with Carbon Foam Core Materials

    Microsoft Academic Search

    SANGWOOK SIHN; BRIAN P. RICE

    2003-01-01

    To study suitability of the emerging ultralightweight carbon foams in load-carrying structures, the state-of-the-art carbon foams from various manufacturers were evaluated as core material in a sandwich construction. The carbon foams were firstly characterized by measuring compressive and shear mechanical properties. The carbon foam possessed highly anisotropic properties between in-plane and through-the-thickness directions. The foams aged at 316°C (600°F) for

  2. Structural sandwich construction is used in many air and space vehicles, cargo containers, boats and ships. Connection of the sandwich construction component to a framework or substructure

    E-print Network

    Vel, Senthil

    , boats and ships. Connection of the sandwich construction component to a framework or substructure vehicles, ships, boats, cargo containers and residential construction. Sandwich construction provide

  3. Composite sandwich constructions for absorbing the electromagnetic waves

    Microsoft Academic Search

    Po Chul Kim; Dai Gil Lee

    2009-01-01

    RAS (radar absorbing structures) is a key component for weapon systems such as aircrafts, warships, and missiles to achieve both the stealth performance by absorbing EM (Electromagnetic) waves incident on and load bearing capability. In this work, the RAS was fabricated as sandwich constructions composed of nanocomposite, carbon fabric\\/epoxy composite, and PVC foam. The nanocomposite composed of E-glass fabric, epoxy

  4. Measurement and analysis of the structural performance of cellular metal sandwich construction

    Microsoft Academic Search

    H. Bart-Smith; J. W. Hutchinson; A. G. Evans

    2001-01-01

    The bending performance of sandwich construction with thin cellular metal cores has been measured and simulated. A mechanism map has been generated to characterize the predominant failure phenomena based upon collapse load criteria for face yielding, core shear and indentation. A previously developed constitutive law for the core material has been incorporated into numerical simulations. Comparisons have been made with

  5. Construction of double- and triple-decker sandwich compounds from half-sandwich compounds: a theoretical assessment.

    PubMed

    Zhang, Mei; Zhang, Xueying; Meng, Lingpeng; Li, Qingzhong; Li, Xiaoyan

    2015-08-01

    The viability and properties of double- (Cp2M) and triple-decker (Cp3M2) sandwiches formed from half-sandwiches (CpM, Cp?=?C5H5; M?=?Li, Na, K, Be, Mg, Ca, Fe, Co, Ni, Cu, and Zn) are discussed based on the geometry, energy, HOMO-LUMO gap, and topological properties. The calculated results show that the alkali metals and transitional metals (Fe, Co, Ni) with more unpaired electron are more inclined to form high-symmetry sandwich complexes than the alkaline earth metals. The Cp2M and Cp3M2 symmetries for M?=?Cu and Zn are low. In Cp2M and Cp3M2, the electrostatic and ? orbital interactions are dominant. For Cp3M2, the contributions of orbital interaction to the total M-C interaction and of ?-type interaction to the orbital interaction are larger than those in Cp2M. The nature of the M-C bond is well correlated to its bond length. The shorter the M-C bond, the more covalent it is. PMID:26164558

  6. Flexural and impact properties of sandwich panels used in surfboard construction

    SciTech Connect

    Manning, J.A.; Crosky, A.G.; Bandyopadhyay, S. [Univ. of New South Wales, Kensington (Australia). School of Materials Science and Engineering

    1993-12-31

    Surfboards represent a particularly simple example of sandwich panel construction and are conventionally made from a preshaped low density polyurethane foam core encased in an E-glass/polyester skin. They are made to minimum weight and thickness and as a result suffer durability problems. The boards are particularly prone to denting due to impact damage, causing principally cosmetic problems. More importantly, they frequently snap under normal service conditions. Recently, there has been considerable interest in the use of higher performance materials for the skins, notably S-glass and epoxy resin, to improve the durability of surfboards. This work examines the failure of simple parallel faced panels fabricated to simulate a section of a surfboard. It is shown that when loaded in four point bending, the panels fail by compression of the core and that this mode of failure produces the same characteristics as seen in service failures. Further, the flexural strength is dominated by the behavior of the core and is not improved appreciably by the use of S-glass or epoxy resin. On the other hand, the impact resistance is improved by the use of S-glass and further improved if epoxy resin is used as the matrix.

  7. Multi-scale modeling of time-dependent response of smart sandwich constructions

    Microsoft Academic Search

    Jeong Sik Kim; L. Arronche; A. Farrugia; A. Muliana; V. La Saponara

    2011-01-01

    Polymer and polymer based composite structures exhibit time-dependent response, leading to their being described as viscoelastic bodies. The rate of creep (or stress relaxation) in viscoelastic bodies increases with increasing the temperature of the bodies. In this study, we are interested in analyzing the time-dependent response of smart sandwich composites comprising of glass fiber reinforced polymer (GFRP) skins, polyurethane foam

  8. Fabrication and characterization of microscale sandwich beams

    E-print Network

    Kenis, Paul J. A.

    Fabrication and characterization of microscale sandwich beams Francisco Arias, Paul J.A. Kenis, Cambridge, Massachusetts 02138 (Received 10 July 2000; accepted 20 November 2000) Microscale sandwich beams structurally efficient, lightweight microscale beams and panels. I. INTRODUCTION Sandwich construction

  9. Composite sandwich construction with syntactic foam core - A practical assessment of post-impact damage and residual strength

    NASA Technical Reports Server (NTRS)

    Hiel, C.; Dittman, D.; Ishai, O.

    1993-01-01

    An account is given of an inspection method that has been successfully used to assess the postimpact damage and residual strength of syntactic (glass microspheres in epoxy matrix) foam-core sandwich panels with hybrid (carbon and glass fiber-reinforced) composite skins, which inherently possess high damage tolerance. SEM establishes that the crushing of the microspheres is responsible for the absorption of most of the impact energy. Damage tolerance is a function of the localization of damage by that high impact energy absorption.

  10. Sandwich Courses

    ERIC Educational Resources Information Center

    Overy, B. B.

    1972-01-01

    A look at the responsibilities that a college takes on in offering sandwich courses, i.e., courses (primarily technical) which alternate academic study with field experience. A primary problem is finding suitable industrial training situations. Greater involvement of small firms and specialized industries is one answer. (Author/JB)

  11. Sandwich Courses

    ERIC Educational Resources Information Center

    Topping, J.

    1975-01-01

    Describes programs which alternate a study period in college and a training period in industry. Called "sandwich courses" in Britain and "cooperative courses" in America, these programs are considered by many educators to be among the most significant educational developments of our time. (MLH)

  12. ADVANCEMENTS IN ENGINEERED COMPOSITE SANDWICH CORE MATERIALS

    Microsoft Academic Search

    Eric J. Lang

    Results are presented for product and design innova tions involving TYCOR ® fiber-reinforced- foam (FRF) core technology for composite sandwich construction. Low-cost FRF core-preforms used with infusion molding processes provide light, stiff composite sandwich panels and structures. Product design innovations were tested that provide more balanced primary (\\

  13. FAILURE MECHANISMS OF COMPOSITE SANDWICH STRUCTURES

    Microsoft Academic Search

    E. E Gdoutos

    Sandwich construction is of particular interest and widely used, because the concept is very suitable and amenable to the development of lightweight structures with high in-plane and flexural stiffness. Sandwich panels consist typically of two thin face sheets (or facings, or skins) and a lightweight thicker core. They display various failure modes under general bending, shear and in-plane loading. The

  14. Collapse Mechanism of Foam Cored Sandwich Structures Under Compressive Load

    Microsoft Academic Search

    S. Manjunath Yadav; K. V. Arun; S. Basavarajappa; Narendranath S; Santosh Kumar

    2011-01-01

    In this work the moisture absorption capability, compressive properties, collapse modes of various types of composite sandwich structures are reported. The tested sandwich structures were constructed with varieties of hybridized skin materials and different compositions of the core materials. The moisture absorption, Flatwise compression and Edgewise compression tests are conducted for core as well as sandwich structures. Comparisons of results

  15. Failure Modes and Optimization of Sandwich Structures for Load Resistance

    Microsoft Academic Search

    Stephen R. Swanson; Jongman Kim

    2003-01-01

    Sandwich construction using foam cores is used in applications, and an understanding offailure loads is an important part ofthe design process. Tests on sandwich beam specimens with embedded strain gages show that the simpler analysis procedures can be in error by large factors, while an elasticity solution from the literature gives good agreement with the experiments. Comparisons with laboratory tests

  16. Design of sandwich beams for concentrated loading

    NASA Astrophysics Data System (ADS)

    Kim, Jongman

    Although sandwich construction offers well-known advantages for high stiffness with light-weight, the problem of designing a sandwich structure to withstand localized loading such as might result from accidental impact, for example, is important. The review of the literature and experimental results performed by the author has shown that current design and analysis procedures are not suitable for predictions of the response of sandwich structures for concentrated loading. To investigate the response of sandwich structures to concentrated loading, experiments were carried out on beam specimens with polyurethane foam core with various densities and thickness, and faces made of AS4/3501-6 carbon/epoxy fiber composite of various thickness under three point loading, which gives a concentrated loading. Overall deformation was measured, along with strains from both surface and embedded gages. Additionally, compression tests and torsion tests have been done for the polyurethane foam used as core in the sandwich beam to characterize its yield properties. Many theories, including classical theory, first order shear deformation theory, higher order theory, elasticity and FE analysis, were compared with the three-point bending experiments. A two-dimensional elasticity solution, which is suitable for sandwich beams under simply support boundary conditions, was used to obtain the strain/stress distribution, failure prediction and optimization work. The common failure modes of sandwich beams have been observed, including core failure in compression and shear failure in core, delamination, and fiber failure in the face. The failure modes can be predicted for sandwich beams under localized loading using elasticity theory and the failure is controlled by a failure mode with the lowest load. An algorithm developed by Swanson and Kim was used to predict the optimum design of sandwich structures for strength to weight under concentrated loading and compared with experimental yield or failure loads of sandwich beams. This optimization procedure was applied to the sandwich beam with equal thickness faces and unequal thickness faces. The yield load and stiffness were varied with the mass of the beam and thickness ratio of top face to bottom face. The optimum conditions for resistance to concentrated loading give different core properties as compared to those of optimum stiffness.

  17. Design of Sandwich Structures

    E-print Network

    Petras, Achilles

    Failure modes for sandwich beams of GFRP laminate skins and Nomex honeycomb core are investigated. Theoretical models using honeycomb mechanics and classical beam theory are described. A failure mode map for loading under 3-point bending...

  18. Force protection using composite sandwich structures

    Microsoft Academic Search

    R. L. Sierakowski; M. L. Hughes

    2006-01-01

    In the recent past, advances have been made in the attempt to utilize composite materials as components in protective structures such as those employed by the Air Force to secure critical military assets. In such applications, where lightweight materials that exhibit large levels of energy absorption and high strength\\/stiffness characteristics are desirable, composite sandwich constructions offer an attractive solution.In an

  19. Homogenization of sandwich structures

    Microsoft Academic Search

    T. Rabczuk; J. Y. Kim; E. Samaniego; T. Belytschko

    2004-01-01

    SUMMARY A homogenization method is proposed for sandwich structures consisting of two plates interlaced with beams and shells in a periodic, lattice structure. The proposed method is a quasi-continuum approach where the constitutive response is obtained from the generalized forces of the interlacing elements. Buckling is studied as part of this model. Comparison of the homogenized model with fully discrete

  20. Graph Sandwich Problems

    Microsoft Academic Search

    Martin Charles Golumbic; Haim Kaplan; Ron Shamir

    1995-01-01

    The graph sandwich problem for property ? is defined as follows: Given two graphs G1 = (V, E1) and G2 = (V, E2) such that E1 ? E2, is there a graph G = (V, E) such that E1 ? E ? E2 which satisfies property ?? Such problems generalize recognition problems and arise in various applications. Concentrating mainly on

  1. Sandwich Courses, United Kingdom.

    ERIC Educational Resources Information Center

    Brewer, Malcolm

    1990-01-01

    Describes the history and current status of sandwich courses offered by all polytechnics and many colleges and universities in the United Kingdom--in which periods of full-time, academically related employment alternate with periods of formal coursework. Topics include responsibilities for placement, pay, assessment, and international placements.…

  2. Salads, Sandwiches and Desserts.

    ERIC Educational Resources Information Center

    Marine Corps Inst., Washington, DC.

    Developed as part of the Marine Corps Institute (MCI) correspondence training program, this course on salads, sandwiches, and desserts is designed to provide Marine food service personnel with a general background in the proper techniques for the preparation of these items. Introductory materials include specific information for MCI students and a…

  3. Influence of reinforcement type on the mechanical behavior and fire response of hybrid composites and sandwich structures

    Microsoft Academic Search

    James William Giancaspro

    2004-01-01

    Lightweight composites and structural sandwich panels are commonly used in marine and aerospace applications. Using carbon, glass, and a host of other high strength fiber types, a broad range of laminate composites and sandwich panels can be developed. Hybrid composites can be constructed by laminating multiple layers of varying fiber types while sandwich panels are manufactured by laminating rigid fiber

  4. HYBRID-SANDWICHED REINFORCEMENT WITH GEOSYNTHETICS

    NASA Astrophysics Data System (ADS)

    Yasuhara, Kazuya; Yamazaki, Shinji; Sakakibara, Tsutomu

    Advantageous aspects of sandwich-type reinforced earth structures combined with geosynthetics and sand mat are highlighted in this paper. Those aspects were elucidated by two kinds of laboratory tests : (1) large consolidation tests for improvement of hydraulic conductivity and (2) model footing tests on improvement of bearing capacity and deformation characteristics for reinforced earth structures, including both vertical permeability and horizontal transmissibility characteristics of geosynthetics results from both laboratory tests indicated the following: i) Hydraulic conductivity of geosynthetics used for this type of earth reinforcement can be maintained for a long period. Such conductivity sometimes disappears, particularly because of clogging when geosynthetics are adopted in embankment construction using fine-grained soils. This fact indicates that the sand mats which are laid above and beneath geosynthetics play a salient role in preventing clogging of geosynthetics that occurs by intrusion of fines from cohesive soils. ii) Sandwich-type reinforcement combined with geosynthetics and sand mats increases stability and decreases deformation of earth structures. In particular, the sandwich structure is effective for providing toughness, which has remained an important issue for reducing infrastructural maintenance and costs. In the later part of the paper, conventionally available stability analysis was carried out to propose the design procedure for reinforced earth structures and at the same time numerical analysis was also conducted to ensure the applicability of the hybrid-sandwiched earth reinforcement newly proposed in the current paper. Finally, based on the horizontal placement by means of HBS described in the current paper, the vertical drain procedure using the sandwich structures for accelerating consolidation and increasing stability of soft soils is also suggested for the future research and investigation.

  5. Composite Sandwich Panels

    NSDL National Science Digital Library

    Finn, Brian

    This module, created by Brian D. Finn of the University of Washington, "investigates the fundamental aspects of designing composite sandwich panels." These boards are commonly used to create surfboards, wake boards, and corrugated cardboard. They are also heavily implemented in the aerospace industry; this includes items such as wing flaps, aircraft floors and overhead storage bins. The module features an abstract, objective, curriculum overview, procedures, mathematical calculations and references. In the end, students will learn to build, test and analyze the strength of these composite materials.

  6. Implementing timed automata specifications: the "sandwich" approach

    E-print Network

    Paris-Sud XI, Université de

    1 Implementing timed automata specifications: the "sandwich" approach Raymond Devillers model. The implementation is then "sandwiched" between the original specification and the new model prototype is `sandwiched' between the original specification and the new model. More precisely, we propose

  7. Noise transmission through nonlinear sandwich panels

    NASA Astrophysics Data System (ADS)

    Vaicaitis, R.; Hong, H.-K.

    1983-04-01

    An analytical study is presented to predict the noise transmission through nonlinear double wall sandwich panel systems subject to random loading. Viscoelastic and nonlinear spring dash-pot models are chosen to characterize the behavior of the core. The noise transmission through this panel system is determined into an acoustic enclosure of which the interiors are covered with porous absorption materials. The absorbent boundary conditions of the enclosure are accounted for by a two-step transformation of the boundary effect into a wave equation which governs the acoustic pressure field. The nonlinear panel response and interior acoustic pressure are obtained by utilizing modal analyses and Monte Carlo simulation techniques. Numerical results include the nonlinear response time histories and noise reduction. It is found that by proper selection of the dynamic parameters and damping characteristics, the noise transmission can be significantly reduced by the double wall sandwich construction.

  8. The quasi-static and dynamic responses of metallic sandwich structures

    E-print Network

    St-Pierre, Luc

    2012-06-12

    -dense materials. Adapted from Russell (2009). . 2 1.2 Examples of sandwich structures in nature: bird skulls of (a) a magpie and (b) a long-eared owl. Adapted from Gibson et al. (2010). . . . . . 3 1.3 Examples of sandwich structures in industrial applications: (a... and very resistant to bending and breaking. The skull of birds present a variety of sandwich topologies. For example, the skull of a magpie is a double sandwich construction (see Fig. 1.2(a)) whereas the skull of larger birds, such as owls, is a multiple...

  9. Sandwich structures for high temperature applications: Microstructural development and mechanical performance

    Microsoft Academic Search

    Fardad Azarmi

    2008-01-01

    There has been a great deal of interest in the development of sandwich structures as viable engineering constructions. It is due to their unique structural, physical, and mechanical characteristics such as light weight, high strength to weight ratio, high bending stiffness, excellent thermal and acoustical insulation. Although the service temperature for most applications of sandwich structures is low, the outstanding

  10. Thermomechanical response of metal foam sandwich panels for structural thermal protection systems in hypersonic vehicles

    Microsoft Academic Search

    Joseph F. Rakow

    2005-01-01

    Sandwich panels with metal foam cores are proposed for load-bearing structural components in actively cooled thermal protection systems for aerospace vehicles. Prototype acreage metal foam sandwich panels (MFSP's) are constructed and analyzed with the central goal of characterizing the thermomechanical response of the system. MFSP's are subjected to uniform temperature fields and equibiaxial loading in a novel experimental load frame.

  11. Failure of sandwich beams consisting of alumina face sheet and aluminum foam core in bending

    Microsoft Academic Search

    Kapil Mohan; Yip Tick Hon; Sridhar Idapalapati; Hong Pheow Seow

    2005-01-01

    Applications of sandwich structures, comprising alumina face sheets and aluminum foam core, depend critically on their mechanical performance. Four point bend tests are performed on sandwich beams with varying geometries to identify competing failure modes, such as core indentation, face sheet cracking and core shear. Analytical formulae for the identified failure modes are obtained. A failure mode map was constructed

  12. On the dynamic response of sandwich composites and their core materials

    Microsoft Academic Search

    Hassan Mahfuz; Tonnia Thomas; Vijay Rangari; Shaik Jeelani

    2006-01-01

    Sandwich composites are being aggressively pursued as structural materials by various defense and commercial industries. These include navy, air force, army, automotive and sporting industries to name a few. In the context of structural load bearing members and absorbing dynamic loads, foam core sandwich composites offer unique advantages over traditional composites. The cellular construction of the foam materials not only

  13. Large inelastic response of unbonded metallic foam and honeycomb core sandwich panels to blast loading

    Microsoft Academic Search

    M. D. Theobald; G. S. Langdon; G. N. Nurick; S. Pillay; A. Heyns; R. P. Merrett

    2010-01-01

    Sandwich panels constructed from metallic face sheets with the core composed of an energy absorbing material, have shown potential as an effective blast resistant structure. In the present study, air-blast tests are conducted on sandwich panels composed steel face sheets with unbonded aluminium foam (Alporas, Cymat) or hexagonal honeycomb cores. Honeycomb cores with small and large aspect ratios are investigated.

  14. Characterization of sandwich panels for indentation and impact

    NASA Astrophysics Data System (ADS)

    Shazly, M.; Bahei-El-Din, Y.; Salem, S.

    2013-07-01

    The integrity of sandwich structures which are susceptible to impact may deteriorate significantly due to collapse of the core material and delamination of the face sheets. The integration of a thin polyurethane interlayer between the composite face sheet and foam core is known to protect the core material and substantially improve the resistance to impact. The objective of the present work is to characterize the response of sandwich panels, as well as that of the constituents to impact. In particular, the response of polyurethane and foam samples under a range of quasi-static and dynamic loading rates is determined experimentally. Furthermore, the response of sandwich panels to quasi-static indentation and low velocity impact is examined to quantify the extent of damage and how it is affected by the integration of polyurethane interlayers in their construction. This information is useful in the modelling of high velocity impact of sandwich panels; an effort which is currently underway. The results illustrate the benefit of using polyurethane interlayers within the construction of sandwich panels in enhancing their performance under quasi-static indentation and impact loads.

  15. Facesheet Delamination of Composite Sandwich Materials at Cryogenic Temperatures

    NASA Technical Reports Server (NTRS)

    Gates, Thomas S.; Odegard, Gregory M.; Herring, Helen M.

    2003-01-01

    The next generation of space transportation vehicles will require advances in lightweight structural materials and related design concepts to meet the increased demands on performance. One potential source for significant structural weight reduction is the replacement of traditional metallic cryogenic fuel tanks with new designs for polymeric matrix composite tanks. These new tank designs may take the form of thin-walled sandwich constructed with lightweight core and composite facesheets. Life-time durability requirements imply the materials must safely carry pressure loads, external structural loads, resist leakage and operate over an extremely wide temperature range. Aside from catastrophic events like tank wall penetration, one of the most likely scenarios for failure of a tank wall of sandwich construction is the permeation of cryogenic fluid into the sandwich core and the subsequent delamination of the sandwich facesheet due to the build-up of excessive internal pressure. The research presented in this paper was undertaken to help understand this specific problem of core to facesheet delamination in cryogenic environments and relate this data to basic mechanical properties. The experimental results presented herein provide data on the strain energy release rate (toughness) of the interface between the facesheet and the core of a composite sandwich subjected to simulated internal pressure. A unique test apparatus and associated test methods are described and the results are presented to highlight the effects of cryogenic temperature on the measured material properties.

  16. Ultralight asymmetric photovoltaic sandwich structures

    Microsoft Academic Search

    Julien Rion; Yves Leterrier; Jan-Anders E. Månson; Jean-Marie Blairon

    2009-01-01

    This work evaluated the possibility of using silicon solar cells as load-carrying elements in composite sandwich structures. Such an ultra-light multifunctional structure is a new concept enabling weight, and thus energy, to be saved in high-tech applications such as solar cars, solar planes or satellites. Composite sandwich structures with a weight of ?800g\\/m2 were developed, based on one 140?m thick

  17. Failure of sandwich beams with metallic foam cores

    Microsoft Academic Search

    T. M. McCormack; R. Miller; O. Kesler; L. J. Gibson

    2001-01-01

    Sandwich beams with metallic foam cores can fail by several modes: face yielding, face wrinkling, core yielding and indentation. We estimate the initial failure load, corresponding to the first deviation from linearity in the load–deflection curve as well as the peak load for each mode. Failure mode maps are constructed which illustrate the dominant failure mode for practical beam designs.

  18. Fatigue performance of sandwich beams with a pyramidal core

    Microsoft Academic Search

    F. Côté; N. A. Fleck; V. S. Deshpande

    2007-01-01

    Sandwich beams have been manufactured from AISI type 304 stainless steel faces and AL6XN pyramidal core, and subjected to both monotonic and cyclic three-point bending in order to assess their monotonic and cyclic strengths. Collapse mechanisms maps for monotonic loading, and fatigue maps for cyclic loading are constructed with the aid of simple analytical models for the competing failure modes.

  19. INVESTIGATION OF CORE CLOSEOUTS IN FIBER-REINFORCED SANDWICH LAMINATES

    E-print Network

    INVESTIGATION OF CORE CLOSEOUTS IN FIBER-REINFORCED SANDWICH LAMINATES by Russell Lee Evertz .............................................................................................................4 Sandwich Theory .....................................................32 Sandwich Termination Effects

  20. INNOVATIVE 3-D FRP SANDWICH PANELS FOR BRIDGE DECKS TAREK K. HASSAN (1)

    E-print Network

    construction technology made of composite materials. Currently, foam and honeycomb core sandwich composites, crushing and buckling instability are major concerns. This paper presents two innovative alternative and fiber composites. Light weight, High strength and excellent corrosion characteristics made fiber

  1. Elastic Coupling Effects in Tapered Sandwich Panels with Laminated

    E-print Network

    Vel, Senthil

    Elastic Coupling Effects in Tapered Sandwich Panels with Laminated Anisotropic Composite Facings theory for the analysis of tapered sandwich panels with laminated anisotropic facings is presented. Unlike sandwich panels of uniform depth, the response of tapered sandwich panels is counterintuitive

  2. Comment: Industrial Training and Sandwich Courses

    ERIC Educational Resources Information Center

    Brookes, D.

    1973-01-01

    Discusses the purposes and benefits of sandwich courses, which are now an established feature of the British system of higher education. These courses provide students with a period of industrial experience sandwiched between academic periods in college. (JR)

  3. Graph Sandwich Problems Martin Charles Golumbic

    E-print Network

    Kaplan, Haim

    Graph Sandwich Problems Martin Charles Golumbic Dept. of Math. and Computer Science Bar@math.tau.ac.il November 1992, revised January 1994 1 #12; Running head: Graph Sandwich Problems. Correspondence to: Ron­Aviv 69978, Israel. email: shamir@math.tau.ac.il 2 #12; ABSTRACT The graph sandwich problem for property \\Pi

  4. GEODESIC HAM-SANDWICH CUTS Prosenjit Bose

    E-print Network

    Hurtado, Ferran

    GEODESIC HAM-SANDWICH CUTS Prosenjit Bose Erik D. Demaine Ferran Hurtado John Iacono§ Stefan contains r red points and b blue points in its interior. Let n = m + r + b. A ham-sandwich geodesic and the blue points. We present an O(n log k)-time algorithm for finding a ham-sandwich geodesic. We also show

  5. Geodesic Ham-Sandwich Cuts Prosenjit Bose

    E-print Network

    Iacono, John

    Geodesic Ham-Sandwich Cuts Prosenjit Bose School of Computer Science Carleton University jit and b blue points in its interior. Let n = m+r+b. A ham-sandwich geodesic is a shortest path in P. We present an O(n log k)-time algorithm for finding a ham-sandwich geodesic. We also show

  6. DESIGN OF SANDWICH STRUCTURES WITH CURVATURE

    E-print Network

    Paris-Sud XI, Université de

    DESIGN OF SANDWICH STRUCTURES WITH CURVATURE Vincent Manet 1 , Woo-Suck Han 1 , and Alain Vautrin 1 for the analysis of sandwich structures. This method is based on Reissner's functional which is applied locally as in 3D, is assessed in 2D for the computation of an U-type sandwich beam for which both the ratio

  7. Sandwich Theorems, extension principles and amenability

    E-print Network

    Boccuto, Antonio

    Sandwich Theorems, extension principles and amenability A. BOCCUTO - D. CANDELORO 1. Introduction. In the literature, a lot of results have been found, dealing with Hahn- Ba- nach extension principles, sandwich to the existence of sandwich invariant homomorphisms, and this 1 #12;is in turn equivalent to amenability

  8. GEODESIC HAM-SANDWICH CUTS Prosenjit Bose

    E-print Network

    Iacono, John

    GEODESIC HAM-SANDWICH CUTS Prosenjit Bose Erik D. Demaine Ferran Hurtado§ John Iacono¶ Stefan contains r red points and b blue points in its interior. Let n = m + r + b. A ham-sandwich geodesic and the blue points. We present an O(n log k)-time algorithm for finding a ham-sandwich geodesic. We also show

  9. Wrinkling Prevention Methods for Sandwich Panel Structure

    NASA Astrophysics Data System (ADS)

    Dahara, Koichiro; Sanmaru, Kazuya; Yano, Toshihiro; Noguchi, Hiroshi

    In this paper, we proposed a method for preventing the wrinkling of the facings of a sandwich panel whose outer and inner facings were at different temperatures. By using this method, the wrinkling of the outer facing of a sandwich panel structure, such as a sandwich panel refrigerator box, could be prevented. In order to prevent the facings of the structure from wrinkling, it was necessary to determine the wrinkling strength using a compressive test, and to reduce the thermal stress of the sandwich panel structure to less than the wrinkling strength. It was observed that a sandwich panel structure with slits in the facing reduced the thermal stress. In this study, we used sandwich panel containers to examine whether this proposed method could prevent a sandwich panel from wrinkling.

  10. Quasicircular orbits of conformal thin-sandwich puncture binary black holes

    SciTech Connect

    Hannam, Mark D. [Center for Gravitational Wave Astronomy, University of Texas at Brownsville, 80 Fort Brown, Brownsville, Texas 78520 (United States)

    2005-08-15

    I construct initial data for equal-mass irrotational binary black holes using the conformal thin-sandwich puncture approach. I locate quasicircular orbits using the effective-potential method, and estimate the location of the innermost stable circular orbit (ISCO). The ISCO prediction is consistent with results for conformal thin-sandwich data produced using excision techniques. These results also show that the ISCOs predicted by the effective-potential and ADM-Komar mass-comparison methods agree for conformal thin-sandwich data, just as they did for Bowen-York data.

  11. Algorithms for Ham-Sandwich Cuts

    Microsoft Academic Search

    Chi-yuan Lo; Jirí Matousek; William L. Steiger

    1994-01-01

    Given disjoint setsP\\u000a 1,P\\u000a 2, ...,P\\u000a \\u000a d\\u000a inR\\u000a \\u000a d\\u000a withn points in total, ahamsandwich cut is a hyperplane that simultaneously bisects theP\\u000a \\u000a i\\u000a . We present algorithms for finding ham-sandwich cuts in every dimensiond>1. Whend=2, the algorithm is optimal, having complexityO(n). For dimensiond>2, the bound on the running time is proportional to the worst-case time needed for constructing a level

  12. Development of biobased sandwich structures for mass transit application

    NASA Astrophysics Data System (ADS)

    Munusamy, Sethu Raaj

    Efforts to increase the biobased content in sandwich composites are being investigated to reduce the dependence on synthetically produced or mined, energy-intensive materials for numerous composite applications. Vegetable oil-based polyurethane foams are gaining recognition as good substitutes for synthetic counter parts while utilizing bast fiber to replace fiberglass is also gaining credence. In this study, soy oil-based polyurethane foam was evaluated as a core in a sandwich construction with facesheets of hybridized kenaf and E-glass fibers in a vinyl ester resin matrix to replace traditionally used plywood sheeting on steel frame for mass transit bus flooring systems. As a first step towards implementation, the static performance of the biobased foam was compared to 100% synthetic foam. Secondly, biobased sandwich structures were processed and their static performance was compared to plywood. The biobased sandwich composites designed and processed were shown to hold promise towards replacing plywood for bus flooring applications by displaying an increase of 130% for flexural strength and 135% for flexural modulus plus better indentation values.

  13. The behavior of sandwich structures of isotropic and composite materials

    Microsoft Academic Search

    J. R. Vinson

    1999-01-01

    The Behavior of Sandwich Structures of Isotropic and Composite Materials provides a unique presentation of mathematics, descriptions and analysis of techniques in the growing field of sandwich structures. Everything is covered, from a background of sandwich structures, to thermoelastic problems of sandwich structures, sandwich shell theory and much more. This test is ideal for the engineer-in-training, as well as the

  14. Compressive strength after blast of sandwich composite materials.

    PubMed

    Arora, H; Kelly, M; Worley, A; Del Linz, P; Fergusson, A; Hooper, P A; Dear, J P

    2014-05-13

    Composite sandwich materials have yet to be widely adopted in the construction of naval vessels despite their excellent strength-to-weight ratio and low radar return. One barrier to their wider use is our limited understanding of their performance when subjected to air blast. This paper focuses on this problem and specifically the strength remaining after damage caused during an explosion. Carbon-fibre-reinforced polymer (CFRP) composite skins on a styrene-acrylonitrile (SAN) polymer closed-cell foam core are the primary composite system evaluated. Glass-fibre-reinforced polymer (GFRP) composite skins were also included for comparison in a comparable sandwich configuration. Full-scale blast experiments were conducted, where 1.6×1.3?m sized panels were subjected to blast of a Hopkinson-Cranz scaled distance of 3.02?m?kg(-1/3), 100?kg TNT equivalent at a stand-off distance of 14?m. This explosive blast represents a surface blast threat, where the shockwave propagates in air towards the naval vessel. Hopkinson was the first to investigate the characteristics of this explosive air-blast pulse (Hopkinson 1948 Proc. R. Soc. Lond. A 89, 411-413 (doi:10.1098/rspa.1914.0008)). Further analysis is provided on the performance of the CFRP sandwich panel relative to the GFRP sandwich panel when subjected to blast loading through use of high-speed speckle strain mapping. After the blast events, the residual compressive load-bearing capacity is investigated experimentally, using appropriate loading conditions that an in-service vessel may have to sustain. Residual strength testing is well established for post-impact ballistic assessment, but there has been less research performed on the residual strength of sandwich composites after blast. PMID:24711494

  15. Compressive strength after blast of sandwich composite materials

    PubMed Central

    Arora, H.; Kelly, M.; Worley, A.; Del Linz, P.; Fergusson, A.; Hooper, P. A.; Dear, J. P.

    2014-01-01

    Composite sandwich materials have yet to be widely adopted in the construction of naval vessels despite their excellent strength-to-weight ratio and low radar return. One barrier to their wider use is our limited understanding of their performance when subjected to air blast. This paper focuses on this problem and specifically the strength remaining after damage caused during an explosion. Carbon-fibre-reinforced polymer (CFRP) composite skins on a styrene–acrylonitrile (SAN) polymer closed-cell foam core are the primary composite system evaluated. Glass-fibre-reinforced polymer (GFRP) composite skins were also included for comparison in a comparable sandwich configuration. Full-scale blast experiments were conducted, where 1.6×1.3?m sized panels were subjected to blast of a Hopkinson–Cranz scaled distance of 3.02?m?kg?1/3, 100?kg TNT equivalent at a stand-off distance of 14?m. This explosive blast represents a surface blast threat, where the shockwave propagates in air towards the naval vessel. Hopkinson was the first to investigate the characteristics of this explosive air-blast pulse (Hopkinson 1948 Proc. R. Soc. Lond. A 89, 411–413 (doi:10.1098/rspa.1914.0008)). Further analysis is provided on the performance of the CFRP sandwich panel relative to the GFRP sandwich panel when subjected to blast loading through use of high-speed speckle strain mapping. After the blast events, the residual compressive load-bearing capacity is investigated experimentally, using appropriate loading conditions that an in-service vessel may have to sustain. Residual strength testing is well established for post-impact ballistic assessment, but there has been less research performed on the residual strength of sandwich composites after blast. PMID:24711494

  16. A numerical study of periodic sandwich propellants with oxygenated binders

    NASA Astrophysics Data System (ADS)

    Zhou, Xu; Jackson, T. L.; Buckmaster, J.

    2003-06-01

    We examine sandwich propellants constructed from sheets of pure ammonium perchlorate (AP) interleaved with an AP/binder blend, and construct solutions numerically using a code that fully couples gas-phase and solid-phase processes via an unsteady moving interface. This code has been used elsewhere to simulate the burning of random packs of spherical AP particles embedded in binder. We show that for a stoichiometric configuration, variations of the burning rate with ? (a measure of the oxygenation of the AP/binder blend) are not monotonic, but display a weak maximum; and variations of the burning rate with sandwich thickness are monotonic for small ?, but display a minimum for large ? (e.g. ? = 0.5). When the equivalence ratio is varied, the burning rate displays a maximum on the fuel-lean side when ? is small, on the fuel-rich side when ? is large. These results, and the manner in which the sandwich topography varies with the different parameters, suggest that the configuration could be invaluable for validating the model ingredients and parameter values of heterogeneous propellant combustion codes.

  17. Facesheet Wrinkling in Sandwich Structures

    NASA Technical Reports Server (NTRS)

    Ley, Robert P.; Lin, Weichuan; Mbanefo, Uy

    1999-01-01

    The purpose of this paper is to provide a concise summary of the state-of-the-art for the analysis of the facesheet wrinkling mode of failure in sandwich structures. This document is not an exhaustive review of the published research related to facesheet wrinkling. Instead, a smaller number of key papers are reviewed in order to provide designers and analysts with a working understanding of the state-of-the-art. Designers and analysts should use this survey to guide their judgement when deciding which one of a wide variety of available facesheet wrinkling design formulas is applicable to a specific design problem.

  18. The behavior of sandwich structures of isotropic and composite materials

    SciTech Connect

    Vinson, J. (Univ. of Delaware, Newark, DE (United States). Mechanical Engineering Dept.)

    1999-01-01

    The Behavior of Sandwich Structures of Isotropic and Composite Materials provides a unique presentation of mathematics, descriptions and analysis of techniques in the growing field of sandwich structures. Everything is covered, from a background of sandwich structures, to thermoelastic problems of sandwich structures, sandwich shell theory and much more. This test is ideal for the engineer-in-training, as well as the practical engineer who desires a comprehensive understanding of sandwich structures technology.

  19. Metal sandwich plates optimized for pressure impulses

    Microsoft Academic Search

    John W. Hutchinson; Zhenyu Xue

    2005-01-01

    Survival of a plate against an intense, short duration impulsive loading requires the circumvention of failure modes, including those associated with excessive overall deflection and shear-off at supports and webs. All-metal sandwich plates have distinct advantages over comparable weight monolithic plates, especially for intense water loadings. A recently developed mechanics of dynamically loaded sandwich plates by N. A. Fleck and

  20. Impact resistance of composite laminated sandwich plates

    Microsoft Academic Search

    Chun-Gon Kim; Eui-Jin Jun

    1992-01-01

    Investigated are the effects of face layup sequence and core density of a sandwich plate on the impact delamination area of the laminated facesheet. The sandwich plate is made of graphite\\/epoxy faces and Nomex honeycomb core. The size and shape of delamination due to impact at each interply location have been measured by the room temperature deply technique. The shape

  1. On Debond Failure of Foam Core Sandwich

    Microsoft Academic Search

    L. A. CARLSSON

    Face\\/core debond fracture toughness has sandwich beams with a foam core made from cross-linked PVC has been examined experimentally\\u000a and analytically using a recently proposed test method called Tilted Sandwich Debond (TSD) test. In this paper we will present\\u000a a brief summary of research accomplishments in this area.

  2. Structural response of pyramidal core sandwich columns

    Microsoft Academic Search

    Francois Cote; Russell Biagi; Hilary Bart-Smith; Vikram S. Deshpande

    2007-01-01

    An experimental and analytical investigation is carried out to examine the in-plane compressive response of pyramidal truss core sandwich columns. The identified failure mechanisms include Euler buckling, shear buckling and face wrinkling. The operative mechanism is dependent on the properties of the bulk material and geometry of the sandwich columns and analytical formulae are derived for each of these modes.

  3. Properties of polyurethane foam/coconut coir fiber as a core material and as a sandwich composites component

    NASA Astrophysics Data System (ADS)

    Azmi, M. A.; Abdullah, H. Z.; Idris, M. I.

    2013-12-01

    This research focuses on the fabrication and characterization of sandwich composite panels using glass fiber composite skin and polyurethane foam reinforced coconut coir fiber core. The main objectives are to characterize the physical and mechanical properties and to elucidate the effect of coconut coir fibers in polyurethane foam cores and sandwich composite panels. Coconut coir fibers were used as reinforcement in polyurethane foams in which later were applied as the core in sandwich composites ranged from 5 wt% to 20 wt%. The physical and mechanical properties found to be significant at 5 wt% coconut coir fiber in polyurethane foam cores as well as in sandwich composites. It was found that composites properties serve better in sandwich composites construction.

  4. Sandwich structures for high temperature applications: Microstructural development and mechanical performance

    NASA Astrophysics Data System (ADS)

    Azarmi, Fardad

    There has been a great deal of interest in the development of sandwich structures as viable engineering constructions. It is due to their unique structural, physical, and mechanical characteristics such as light weight, high strength to weight ratio, high bending stiffness, excellent thermal and acoustical insulation. Although the service temperature for most applications of sandwich structures is low, the outstanding properties make sandwich constructions attractive for use in high temperature service conditions as well. The overall performance of sandwich constructions depends on the material properties of skin and core, and their geometrical characteristics. An investigation of the characteristics of sandwich structures suitable for high temperature application is presented. The objective of the investigation was to develop a process for producing sandwich structures by depositing alloy 625 skins on Ni foam cores using air plasma spraying (APS), and to characterize the structure and mechanical behavior of the constituents and the sandwich structure. The experimental investigation consisted of optimization of deposition process parameters, microstructural and mechanical characterization of sandwich constituents and testing of mechanical performance of sandwich structures under flexural loading conditions. The responses of the as-received foam, as-sprayed coating, and as-fabricated sandwich structure to heat treatment were investigated. Available analytical models and numerical simulations linking the mechanical properties of the Ni alloy foam, the alloy 625 coating, and the sandwich structure to their physical properties and microstructures were compared with the results of mechanical testing to understand the behavior of the sandwich structure in terms of the properties of the constituents. An empirical model was developed to predict deposition parameters which simultaneously minimize the oxide content and the porosity in the alloy 625 coating. The optimum spraying conditions produced a coating with less than 4% oxide and less than 3% porosity. The elastic modulus of the as-sprayed coating increased from ˜10% of the value of conventionally processed alloy 625 material to ˜25% of that value after a 5 hour heat treatment at 1100°C. The ductility of the as-sprayed samples was as low as 1% compared to 15--20% for conventionally processed materials. The elastic modulus and yield stress of the as-received Ni alloy foam samples was also improved significantly by heat treatment. The mechanical behavior of sandwich structures with skin thickness of 0.5 and 0.1 mm were examined under four point bending test. The flexural rigidity of the sandwich structures increased after heat treatment for both skin thicknesses, however the rigidity was found to be lower in all cases than the rigidity predicted by analytical models based on the measured properties of the constituents. The dominant failure mode observed for the sandwich samples with skin thicknesses of 0.1 mm and 0.5 mm were core yielding and skin indentation, respectively.

  5. Feedback sandwiches affect perceptions but not performance.

    PubMed

    Parkes, Jay; Abercrombie, Sara; McCarty, Teresita

    2013-08-01

    The feedback sandwich technique-make positive comments; provide critique; end with positive comments-is commonly recommended to feedback givers despite scant evidence of its efficacy. These two studies (N = 20; N = 350) of written peer feedback with third-year medical students on clinical patient note-writing assignments indicate that students think feedback sandwiches positively impact subsequent performance when there is no evidence that they do. The effort necessary to produce feedback sandwiches and students' unwarranted confidence in their performance impact have implications for teaching about how to give feedback. PMID:22581568

  6. A SANDWICH THEOREM FOR CONVEXITY PRESERVING MAPS WIESLAW KUBIS

    E-print Network

    Kubis, Wieslaw

    A SANDWICH THEOREM FOR CONVEXITY PRESERVING MAPS WIESLAW KUBI´S Abstract. We state a "sandwich. A similar "sandwich" type theorem is valid for maps of arbitrary linearly ordered spaces (see below using the notion of convexity structures. Then one can look for sandwich type theorems for classes

  7. Impact response of three-dimensional multifunctional sandwich composite

    Microsoft Academic Search

    A. S. Vaidya; U. K. Vaidya; N. Uddin

    2008-01-01

    Sandwich composite materials are characterized by high strength and low weight benefits. Traditional applications of sandwich structures primarily utilize polymeric foams and honeycomb as core materials. The primary concern with traditional core sandwich is however, the dissimilarity of the facesheet and core material, core to facesheet delamination under low velocity impact and space inaccessible core. This research presents multifunctional sandwich

  8. A shell finite element for viscoelastically damped sandwich structures

    Microsoft Academic Search

    El mostafa Daya; Michel Potier-Ferry

    2002-01-01

    In this paper, a shell finite element is proposed for viscoelastically damped sandwich structures, in which a thin viscoelastic layer is sandwiched between identical elastic layers. The sandwich finite element is obtained by assembling three elements throughout the thickness of the sandwich structure. Using specific assumptions and displacement continuity at the interfaces, one reduces to eight the number of degrees

  9. Conformal Thin-Sandwich Solver for Generic Initial Data

    E-print Network

    William E. East; Fethi M. Ramazano?lu; Frans Pretorius

    2012-11-06

    We present a new scheme for constructing initial data for the Einstein field equations using the conformal thin-sandwich formulation that does not assume conformal flatness or approximate Killing vectors. This includes a method for determining free data based on superposition, as well as a way to handle black hole singularities without excision. We numerically solve the constraint equations using a multigrid algorithm with mesh refinement. We demonstrate the efficacy of the method with initial data solutions for several applications: a quasicircular binary black hole merger, a dynamical capture black hole-neutron star merger, and an ultrarelativistic collision.

  10. Precast concrete sandwich panels subjected to impact loading

    NASA Astrophysics Data System (ADS)

    Runge, Matthew W.

    Precast concrete sandwich panels are a relatively new product in the construction industry. The design of these panels incorporates properties that allow for great resilience against temperature fluctuation as well as the very rapid and precise construction of facilities. The concrete sandwich panels investigated in this study represent the second generation of an ongoing research and development project. This second generation of panels have been engineered to construct midsized commercial buildings up to three stories in height as well as residential dwellings. The panels consist of a double-tee structural wythe, a foam core and a fascia wythe, joined by shear connectors. Structures constructed from these panels may be subjected to extreme loading including the effects of seismic and blast loading in addition to wind. The aim of this work was to investigate the behaviour of this particular sandwich panel when subjected to structural impact events. The experimental program consisted of fourteen concrete sandwich panels, five of which were considered full-sized specimens (2700 mm X 1200mm X 270 mm) and nine half-sized specimens (2700mm X 600mm X 270 mm) The panels were subjected to impact loads from a pendulum impact hammer where the total energy applied to the panels was varied by changing the mass of the hammer. The applied loads, displacements, accelerations, and strains at the mid-span of the panel as well as the reaction point forces were monitored during the impact. The behaviour of the panels was determined primarily from the experimental results. The applied loads at low energy levels that caused little to no residual deflection as well as the applied loads at high energy levels that represent catastrophic events and thus caused immediate failure were determined from an impact on the structural and the fascia wythes. Applied loads at intermediate energy levels representing extreme events were also used to determine whether or not the panels could withstand multiple impacts. It was shown that panels impacted on the fascia wythe are capable of withstanding multiple impacts of energy levels in excess of 16 000 J while panels that were impacted on the structural wythe are capable of resisting a single impact delivering an energy level of 10 000 J or multiple impacts from an energy level of 5 000 J. A Single Degree of Freedom (SDOF) model was developed to predict the maximum deflection of the panels and it provided a good approximation of the deflection observed during the experimental program. A high degree of composite action between the two wythes was determined to exist from the results of high speed video imaging and through SDOF modelling.

  11. Fabrication and mechanical testing of glass fiber entangled sandwich beams: A comparison with honeycomb and foam sandwich beams

    Microsoft Academic Search

    Amir Shahdin; Laurent Mezeix; Christophe Bouvet; Joseph Morlier; Yves Gourinat

    2009-01-01

    The aim of this paper is the fabrication and mechanical testing of entangled sandwich beam specimens and the comparison of their results with standard sandwich specimens with honeycomb and foam as core materials. The entangled sandwich specimens have glass fiber cores and glass woven fabric as skin materials. The tested glass fiber entangled sandwich beams possess low compressive and shear

  12. Debonding in foam-core sandwich panels

    Microsoft Academic Search

    T. C. Triantafillou; L. J. Gibson

    1989-01-01

    The strain energy release rate is used to give a criterion for debonding in structural sandwich beams with isotropic faces\\u000a and a foam core. The critical strain energy release rate of the interface is measured on double-shear specimens and the results\\u000a of the debonding analysis are compared with experiments on sandwich beams with aluminium faces and foamed polyurethane cores.\\u000a The

  13. Fracture behavior of some lightweight sandwich structures

    SciTech Connect

    Lee, J.R.; Park, S.J. [Korea Research Inst. of Chemical Technology, Taejeon (Korea, Republic of). Polymer and Composite Materials Lab.

    1995-10-01

    The mechanical flexural properties of foams and honeycombs are studied using three-point bending tests. It is suggested that the role of adhesives and their interface properties are considered with various attached skin and core structures for high performance light weight composites. The results of acoustic emission analysis on the foam core sandwich structures are also identified. In compared foam sandwich structure with that of honeycomb, more enhanced role of interface are observed in foam cores.

  14. Compression facing wrinkling of composite sandwich structures

    Microsoft Academic Search

    E. E Gdoutos; I. M Daniel; K.-A Wang

    2003-01-01

    A thorough investigation was conducted of face wrinkling failures of sandwich columns under compression and beams in three- and four-point bending and cantilever beams under end loading. The beams were made of unidirectional carbon\\/epoxy facings and aluminum honeycomb and closed-cell PVC foam cores. The constituent materials were fully characterized. Face wrinkling failures were observed in sandwich columns and beams with

  15. Local slamming impact of sandwich composite hulls

    Microsoft Academic Search

    Z. Qin; R. C. Batra

    2009-01-01

    We develop a hydroelastic model based on a {3,2}-order sandwich composite panel theory and Wagner’s water impact theory for investigating the fluid–structure interaction during the slamming process. The sandwich panel theory incorporates the transverse shear and the transverse normal deformations of the core, while the face sheets are modeled with the Kirchhoff plate theory. The structural model has been validated

  16. Use of GFRP Grid for Innovative Concrete Sandwich Panels Jonathan G. Soriano1

    E-print Network

    , Young C. You2 , and Junhee Kim2 1 North Carolina State University, Raleigh, North Carolina, USA 2 Korea Institute of Construction Technology, Gyeonggi-Do, Korea Abstract Glass fiber reinforced polymer (GFRP at the North Carolina State University focused on the behavior of insulated concrete sandwich wall panels

  17. Experimental study of acoustical characteristics of honeycomb sandwich structures

    NASA Astrophysics Data System (ADS)

    Peters, Portia Renee

    Loss factor measurements were performed on sandwich panels to determine the effects of different skin and core materials on the acoustical properties. Results revealed inserting a viscoelastic material in the core's mid-plane resulted in the highest loss factor. Panels constructed with carbon-fiber skins exhibited larger loss factors than glass-fiber skins. Panels designed to achieve subsonic wave speed did not show a significant increase in loss factor above the coincidence frequency. The para-aramid core had a larger loss factor value than the meta-aramid core. Acoustic absorption coefficients were measured for honeycomb sandwiches designed to incorporate multiple sound-absorbing devices, including Helmholtz resonators and porous absorbers. The structures consisted of conventional honeycomb cores filled with closed-cell polyurethane foams of various densities and covered with perforated composite facesheets. Honeycomb cores filled with higher density foam resulted in higher absorption coefficients over the frequency range of 50 -- 1250 Hz. However, this trend was not observed at frequencies greater than 1250 Hz, where the honeycomb filled with the highest density foam yielded the lowest absorption coefficient among samples with foam-filled cores. The energy-recycling semi-active vibration suppression method (ERSA) was employed to determine the relationship between vibration suppression and acoustic damping for a honeycomb sandwich panel. Results indicated the ERSA method simultaneously reduced the sound transmitted through the panel and the panel vibration. The largest reduction in sound transmitted through the panel was 14.3% when the vibrations of the panel were reduced by 7.3%. The influence of different design parameters, such as core density, core material, and cell size on wave speeds of honeycomb sandwich structures was experimentally analyzed. Bending and shear wave speeds were measured and related to the transmission loss performance for various material configurations. The shear modulus of the core showed maximum influence on the wave speeds of the samples, while cell size did not have a significant influence on wave speeds or on transmission loss. Skin material affected wave speeds only in the pure bending regime. Honeycomb sandwich structures with a subsonic core and thus reduced wave speed showed increased transmission loss compared to samples without a subsonic core.

  18. Mechanical and thermal buckling analysis of rectangular sandwich panels under different edge conditions

    NASA Technical Reports Server (NTRS)

    Ko, William L.

    1994-01-01

    The combined load (mechanical or thermal load) buckling equations were established for orthotropic rectangular sandwich panels under four different edge conditions by using the Rayleigh-Ritz method of minimizing the total potential energy of a structural system. Two-dimensional buckling interaction curves and three-dimensional buckling interaction surfaces were constructed for high-temperature honeycomb-core sandwich panels supported under four different edge conditions. The interaction surfaces provide overall comparison of the panel buckling strengths and the domains of symmetrical and antisymmetrical buckling associated with the different edge conditions. In addition, thermal buckling curves of these sandwich panels are presented. The thermal buckling conditions for the cases with and without thermal moments were found to be identical for the small deformation theory.

  19. Analysis of Stainless Steel Sandwich Panels with a Metal Foam Core for Lightweight Fan Blade Design

    NASA Technical Reports Server (NTRS)

    Min, James B.; Ghosn, Louis J.; Lerch, Bradley A.; Raj, Sai V.; Holland, Frederic A., Jr.; Hebsur, Mohan G.

    2004-01-01

    The quest for cheap, low density and high performance materials in the design of aircraft and rotorcraft engine fan and propeller blades poses immense challenges to the materials and structural design engineers. The present study investigates the use of a sandwich foam fan blade mae up of solid face sheets and a metal foam core. The face sheets and the metal foam core material were an aerospace grade precipitation hardened 17-4 PH stainless steel with high strength and high toughness. The resulting structures possesses a high stiffness while being lighter than a similar solid construction. The material properties of 17-4 PH metal foam are reviewed briefly to describe the characteristics of sandwich structure for a fan blade application. A vibration analysis for natural frequencies and a detailed stress analysis on the 17-4 PH sandwich foam blade design for different combinations of kin thickness and core volume are presented with a comparison to a solid titanium blade.

  20. Analysis of Stainless Steel Sandwich Panels with a Metal Foam Care for Lightweight Fan Blade Design

    NASA Technical Reports Server (NTRS)

    Min, James B.; Ghosn, Louis J.; Lerch, Bradley A.; Raj, Sai V.; Holland, Frederic A., Jr.; Hebsur, Mohan G.

    2004-01-01

    The quest for cheap, low density and high performance materials in the design of aircraft and rotorcraft engine fan and propeller blades poses immense challenges to the materials and structural design engineers. Traditionally, these components have been fabricated using expensive materials such as light weight titanium alloys, polymeric composite materials and carbon-carbon composites. The present study investigates the use of P sandwich foam fan blade made up of solid face sheets and a metal foam core. The face sheets and the metal foam core material were an aerospace grade precipitation hardened 17-4 PH stainless steel with high strength and high toughness. The stiffness of the sandwich structure is increased by separating the two face sheets by a foam core. The resulting structure possesses a high stiffness while being lighter than a similar solid construction. Since the face sheets carry the applied bending loads, the sandwich architecture is a viable engineering concept. The material properties of 17-4 PH metal foam are reviewed briefly to describe the characteristics of the sandwich structure for a fan blade application. A vibration analysis for natural frequencies and P detailed stress analysis on the 17-4 PH sandwich foam blade design for different combinations of skin thickness and core volume %re presented with a comparison to a solid titanium blade.

  1. Fatigue studies of polyurethane sandwich structures

    NASA Astrophysics Data System (ADS)

    Sharma, S. C.; Krishna, M.; Narasimha Murthy, H. N.; Sathyamoorthy, M.; Bhattacharya, Debes

    2004-10-01

    The fatigue characteristics of polyurethane foam-cored (PUF) composite sandwich structures were investigated using three-point bending tests carried out according to ASTM C 393. Three types of specimens (epoxy/glass-PUF-epoxy/glass, polyester/glass-PUF-polyester/glass, and epoxy/glass-PUF-polyester/glass) were considered for investigation. Experimental results indicate that degradation of stiffness occurs due to debonding and sliding between the skin and the foam during fatigue cycles. Epoxy/glass-PUF-epoxy/glass sandwich structures exhibit higher bending strength along with higher stiffness degradation than the other two types of sandwich panels, due to higher initial fatigue loading. The lowest fatigue properties have been obtained for the polyester/glass-PUF-polyester/glass sandwich panel specimens. Better performance of the epoxy/glass-PUF-epoxy/glass sandwich panels is most likely due to the superior properties of the outer thin skins. Most of the specimens fail within the foam region and not at the skin level. This situation is possibly due to debonding between the foam and the skin. The fatigue damage development in the foam and skin has been investigated using scanning electron microscopy.

  2. Galactosylated electrospun membranes for hepatocyte sandwich culture.

    PubMed

    Chien, Hsiu-Wen; Lai, Juin-Yih; Tsai, Wei-Bor

    2014-04-01

    In this work, we developed a galactocylated electrospun polyurethane membrane for sandwich culture of hepatocyte sandwich culture. The electrospun fibrous membranes were bio-functionalized with galactose molecules by a UV-crosslinked layer-by-layer polyelectrolyte multilayer deposition technique. The galactosylated electrospun membranes were employed as a top support membrane for the sandwich culture of HepG2/C3A cells on a collagen substrate. Our results demonstrate that HepG2/C3A cells covered by the galactosylated PU membranes form multi-cellular aggregates and lead to improved albumin secretion ability compared to the control membranes (unmodified PU or poly(ethylene imine)-modified PU). Our study reveals the potential of galactosylated electrospun membranes in the application of liver tissue engineering and the regeneration of liver-tissue substitutes. PMID:24583260

  3. High Strain Rate Response of Sandwich Composites with Nanophased Cores

    NASA Astrophysics Data System (ADS)

    Mahfuz, Hassan; Uddin, Mohammed F.; Rangari, Vijaya K.; Saha, Mrinal C.; Zainuddin, Shaik; Jeelani, Shaik

    2005-05-01

    Polyurethane foam materials have been used as core materials in a sandwich construction with S2-Glass/SC-15 facings. The foam material has been manufactured from liquid polymer precursors of polyurethane. The precursors are made of two components; part-A (diphenylmethane diisocyanate) and part-B (polyol). In one set of experiments, part-A was mixed with part-B to manufacture the foam. In another set, TiO2 nanoparticles have been dispersed in part-A through ultrasonic cavitation technique. The loading of nanoparticles was 3% by weight of the total polymer precursor. The TiO2 nanoparticles were spherical in shape, and were about 29 nm in diameter. Sonic cavitation was carried out with a vibrasound liquid processor at 20 kHz frequency with a power intensity of about 100 kW/m2. The two categories of foams manufactured in this manner were termed as neat and nanophased. Sandwich composites were then fabricated using these two categories of core materials using a co-injection resin transfer molding (CIRTM) technique. Test samples extracted from the panel were subjected to quasi-static as well as high strain rate loadings. Rate of loading varied from 0.002 s-1 to around 1300 s-1. It has been observed that infusion of nanoparticles had a direct correlation with the cell geometry. The cell dimensions increased by about 46% with particle infusion suggesting that nanoparticles might have worked as catalysts during the foaming process. Correspondingly, enhancement in thermal properties was also noticed especially in the TGA experiments. There was also a significant improvement in mechanical properties due to nanoparticle infusion. Average increase in sandwich strength and energy absorption with nanophased cores was between 40 60% over their neat counterparts. Details of manufacturing and analyses of thermal and mechanical tests are presented in this paper.

  4. Insert Design and Manufacturing for Foam-Core Composite Sandwich Structures

    NASA Astrophysics Data System (ADS)

    Lares, Alan

    Sandwich structures have been used in the aerospace industry for many years. The high strength to weight ratios that are possible with sandwich constructions makes them desirable for airframe applications. While sandwich structures are effective at handling distributed loads such as aerodynamic forces, they are prone to damage from concentrated loads at joints or due to impact. This is due to the relatively thin face-sheets and soft core materials typically found in sandwich structures. Carleton University's Uninhabited Aerial Vehicle (UAV) Project Team has designed and manufactured a UAV (GeoSury II Prototype) which features an all composite sandwich structure fuselage structure. The purpose of the aircraft is to conduct geomagnetic surveys. The GeoSury II Prototype serves as the test bed for many areas of research in advancing UAV technologies. Those areas of research include: low cost composite materials manufacturing, geomagnetic data acquisition, obstacle detection, autonomous operations and magnetic signature control. In this thesis work a methodology for designing and manufacturing inserts for foam-core sandwich structures was developed. The results of this research work enables a designer wishing to design a foam-core sandwich airframe structure, a means of quickly manufacturing optimized inserts for the safe introduction of discrete loads into the airframe. The previous GeoSury II Prototype insert designs (v.1 & v.2) were performance tested to establish a benchmark with which to compare future insert designs. Several designs and materials were considered for the new v.3 inserts. A plug and sleeve design was selected, due to its ability to effectively transfer the required loads to the sandwich structure. The insert material was chosen to be epoxy, reinforced with chopped carbon fibre. This material was chosen for its combination of strength, low mass and also compatibility with the face-sheet material. The v.3 insert assembly is 60% lighter than the previous insert designs. A casting process for manufacturing the v.3 inserts was developed. The developed casting process, when producing more than 13 inserts, becomes more economical than machining. An exploratory study was conducted looking at the effects of dynamic loading on the v.3 insert performance. The results of this study highlighted areas for improving dynamic testing of foam-core sandwich structure inserts. Correlations were developed relating design variables such as face-sheet thickness and insert diameter to a failure load for different load cases. This was done through simulations using Computer Aided Engineering (CAE) software, and experimental testing. The resulting correlations were integrated into a computer program which outputs the required insert dimensions given a set of design parameters, and load values.

  5. Supersonic flutter of composite sandwich panels

    NASA Astrophysics Data System (ADS)

    Shiau, Le-Chung

    1992-12-01

    A flutter-motion equation is presently derived for a 2D composite sandwich panel considering the total lateral displacement of the plate as the sum of the displacement due to bending of the plate, and that which is due to shear deformation at the core. The effects of core thickness and stacking sequence of the faces on the flutter boundary of the plate are discussed; it is shown that the sandwich panel greatly improves the flutter boundary over that of a composite laminate panel, provided it has sufficient core thickness.

  6. An Instrument for the Control of Sandwich Courses.

    ERIC Educational Resources Information Center

    Dunster, D. F.

    1982-01-01

    Defines sandwich courses as those with practical periods sandwiched between academic periods. Describes a study that indicates that students need preparation for the practical periods to give them the best chance of obtaining a good learning experience. (JOW)

  7. Mechanical behavior of dip-brazed aluminum sandwich panels

    E-print Network

    Hohmann, Brian P. (Brian Patrick)

    2007-01-01

    An experimental study was carried out to determine the mechanical behavior of sandwich panels containing cellular cores of varying shape. Compression and four point bend tests were performed on sandwich panels with square ...

  8. Dynamic ham-sandwich cuts in the plane

    E-print Network

    Abbott, Timothy G.

    We design efficient data structures for dynamically maintaining a ham-sandwich cut of two point sets in the plane subject to insertions and deletions of points in either set. A ham-sandwich cut is a line that simultaneously ...

  9. A parameterized algorithm for Chordal Sandwich Pinar Heggernes

    E-print Network

    Fomin, Fedor V.

    A parameterized algorithm for Chordal Sandwich Pinar Heggernes Federico Mancini Jesper Nederlof, the Chordal Sandwich problem asks whether there exists a chordal graph (V, E F ) such that F F. This problem. As many related problems, Chordal Sandwich is NP-complete. In this paper we show that the problem becomes

  10. An Unavailability Analysis of Firewall Sandwich Configurations Steve Goddard

    E-print Network

    Goddard, Steve

    An Unavailability Analysis of Firewall Sandwich Configurations Steve Goddard Computer Science to this problem is to use firewall sandwiches, comprising multiple firewall processors running in parallel. A firewall sandwich system needs load-balancing processes executing on separate processors to manage the flow

  11. THE BORSUK-ULAM AND HAM SANDWICH THEOREMS BRIAN LIBGOBER

    E-print Network

    May, J. Peter

    THE BORSUK-ULAM AND HAM SANDWICH THEOREMS BRIAN LIBGOBER Abstract. In this paper I describe the way the Ham Sandwich theorem. Contents 1. Introduction 1 2. A Theorem of Many Monikers 1 3. A Measure Theoretic Approach to Lyustenik-Shnirel'man 4 4. Tucker's Lemma: Detour De Force 6 5. The Ham Sandwich

  12. Strength optimization of metallic sandwich panels subject to bending

    E-print Network

    Zok, Frank

    Strength optimization of metallic sandwich panels subject to bending H.J. Rathbun, F.W. Zok *, A A general methodology for the design of strong, lightweight sandwich panels is described and implemented with the weight of a solid panel. Ã? 2005 Elsevier Ltd. All rights reserved. Keywords: Sandwich panels; Lightweight

  13. STATIC ANALYSIS OF SANDWICH PLATES BY FINITE ELEMENTS

    E-print Network

    Paris-Sud XI, Université de

    STATIC ANALYSIS OF SANDWICH PLATES BY FINITE ELEMENTS V. MANET, W.-S. HAN AND A. VAUTRIN ´Ecole des. Introduction Sandwich plates being more and more involved in structural components, it becomes essential computational methods developed in order to describe the mechanical behaviour of sandwich plates in a more

  14. Hybrid finite elements for the computation of sandwich plates

    E-print Network

    Paris-Sud XI, Université de

    Hybrid finite elements for the computation of sandwich plates Vincent Manet, Woo-Suck Han and Alain sandwich structure in an accurate way, especially at interfaces, where the equilibrium state is satisfied Introduction The sandwich plate have become an important structural component for industrial applications

  15. Algorithms and Complexity of Sandwich Problems in Graphs

    E-print Network

    Shamir, Ron

    Algorithms and Complexity of Sandwich Problems in Graphs (extended abstract) Martin Charles and E 1 ` E 2 . Given such two graphs, the graph G = (V; E) is called a sandwich graph for the pair G 1 ; G 2 if E 1 ` E ` E 2 . In other words, G must be ``sandwiched'' between G 1 and G 2 . We define

  16. Physical Maps and Interval Sandwich Problems: Bounded Degrees Help

    E-print Network

    Shamir, Ron

    Physical Maps and Interval Sandwich Problems: Bounded Degrees Help Haim Kaplan \\Lambda Department@math.tau.ac.il. Abstract The problems of Interval Sandwich (IS) and Intervalizing Colored Graphs (ICG) have received a lot. Consider the following problem: INTERVAL SANDWICH (IS): INSTANCE: A triple S = (V; E; F ), where V is a set

  17. Strongly chordal and chordal bipartite graphs are sandwich monotone

    E-print Network

    Heggernes, Pinar

    Strongly chordal and chordal bipartite graphs are sandwich monotone Pinar Heggernes Federico Mancini Charis Papadopoulos R. Sritharan§ Abstract A graph class is sandwich monotone if, for every pair. In this paper we show that strongly chordal graphs and chordal bipartite graphs are sandwich monotone, answering

  18. Structural performance of metallic sandwich beams with hollow truss cores

    E-print Network

    Wadley, Haydn

    Structural performance of metallic sandwich beams with hollow truss cores H.J. Rathbun a , F.W. Zok of sandwich beams with hollow truss lattice cores made from a ductile stainless steel. The trusses but lower stretch resistance. For bend-dominated loadings of the sandwich beams, the core in the diamond

  19. Homogenization of cellular sandwich panels Arthur Lebee a

    E-print Network

    Paris-Sud XI, Université de

    Homogenization of cellular sandwich panels Arthur Leb´ee a , Karam Sab* a aUniversit´e Paris in [1] is applied to cellular sandwich panels. This theory is the extension of Reissner-Mindlin theory to heterogeneous plates. Its application clarifies common assumptions made in sandwich theory. It also enables

  20. SEVERAL RELATED MODELS FOR MULTILAYER SANDWICH PLATES Scott W. Hansen

    E-print Network

    SEVERAL RELATED MODELS FOR MULTILAYER SANDWICH PLATES By Scott W. Hansen IMA Preprint Series # 1966://www.ima.umn.edu #12;SEVERAL RELATED MODELS FOR MULTILAYER SANDWICH PLATES Scott W. Hansen Iowa State University, Ames sandwich plates consisting of alternating stiff and compliant layers are derived. Two main types of models

  1. The use of Ansys to calculate sandwich Vincent Manet

    E-print Network

    Paris-Sud XI, Université de

    The use of Ansys to calculate sandwich structures Vincent Manet ´Ecole des Mines de Saint sandwich beam subjected to a uniform pressure using different modellings offered by the software Ansys 5's moduli of layers using Plane 82 elements. Key words: Ansys, sandwich structure, interface stresses, local

  2. Mon Tues Wed Thu Fri Sat Sandwich of the Week

    E-print Network

    Collins, Gary S.

    Mon Tues Wed Thu Fri Sat Sandwich of the Week Grilled Ham & Pepperjack 1 Closed Labor Day 2 Chicken Caesar Wrap 3 Shrimp Po' Boy 4 Chef's Salad & Taco Bar 5 Chef's Choice Sandwich of the Week Grilled 12 Chef's Choice Sandwich of the Week Grilled Salami & Pepperjack 15 Greek Hummus Pita 16 BBQ Pork 17

  3. Uncertainties in structural dynamics for composite sandwich panels

    E-print Network

    Boyer, Edmond

    Uncertainties in structural dynamics for composite sandwich panels C. Chen(1) , D. Duhamel(2) , C sandwich panels constituted of two thin carbon-resin skins and one high stiffness closed-cell foam core. Each skin is constituted of two unidirectional plies [60/-60]. Such light composite sandwich panels

  4. Static Analysis of Sandwich Plates by Hybrid Finite Elements

    E-print Network

    Paris-Sud XI, Université de

    Static Analysis of Sandwich Plates by Hybrid Finite Elements V. Manet and W.-S. Han Materials 42023 Saint-Etienne Cedex 2 France August 31, 1996 Abstract As sandwich plates become more and more into acount. The present work concerns the development of hybrid sandwich finite elements mod- elling

  5. ICTP/IAEA Sandwich Training Educational Programme Fellowship Application

    E-print Network

    ICTP/IAEA Sandwich Training Educational Programme Fellowship Application INSTRUCTIONS The Applicant/IAEA Sandwich Training Educational Programme Fellowship Application (Part I) (The Applicant should complete to #12;ICTP/IAEA Sandwich Training Educational Programme Fellowship Application (Part I) (The Applicant

  6. Buckling Analysis of Debonded Sandwich Panel Under Compression

    Microsoft Academic Search

    David W. Sleight; John T. Wang

    1995-01-01

    Abstract A sandwich panel with initial through - buckling of its faceskin when subject to an in faceskin is modeled as a beam on a Winkler elastic foundation in which the springs of the elastic foundation represent the sandwich foam difference methods are used to predict the critical buckling load for various debond lengths and stiffnesses of the sandwich foam

  7. Impact and post impact behavior of composite sandwich panels

    Microsoft Academic Search

    Patrick M. Schubel; Jyi-Jiin Luo; Isaac M. Daniel

    2007-01-01

    Assessing the residual mechanical properties of a sandwich structure is an important part of any impact study and determines how the structure can withstand post impact loading. The damage tolerance of a composite sandwich structure composed of woven carbon\\/epoxy facesheets and a PVC foam core was investigated. Sandwich panels were impacted with a falling mass from increasing heights until damage

  8. Finite Element Modeling of the Buckling Response of Sandwich Panels

    Microsoft Academic Search

    Cheryl A. Rose; David F. Moore; Norman F. Knight; Charles C. Rankin

    2002-01-01

    A comparative study of different modeling approaches for predicting sandwich panel buckling response is described. The study considers sandwich panels with anisotropic face sheets and a very thick core. Results from conventional analytical solutions for sandwich panel overall buckling and face-sheet-wrinkling type modes are compared with solutions obtained using different finite element modeling approaches. Finite element solutions are obtained using

  9. Face layer wrinkling in sandwich shells— theoretical and experimental investigations

    Microsoft Academic Search

    M. A. Stiftinger; F. G. Rammerstorfer

    1997-01-01

    Wrinkling of the face layers is one of the typical failure modes in sandwich structures. Different aspects of this phenomenon are investigated in this paper: analytical considerations concern the determination of wrinkling loads for anisotropic elastic sandwiches under uniaxial as well as biaxial loading. Finite element calculations are carried out to investigate the postbuckling behaviour of isotropic sandwiches, with different

  10. Structurally graded core junctions in sandwich beams: fatigue loading conditions

    Microsoft Academic Search

    Elena Bozhevolnaya; Ole Thybo Thomsen

    2005-01-01

    Sandwich beams with inclusion of different core materials were the subject of the experimental study [Bozhevolnaya E, Thomsen OT. Structurally graded core junctions in sandwich beams: quasi-static analysis. Compos Struct, in press], which focused on the static performance of such sandwich elements. The concept of structurally graded core junctions, suggested in [Bozhevolnaya E, Thomsen OT. Structurally graded core junctions in

  11. Manufacturing and applications of structural sandwich components

    Microsoft Academic Search

    Kicki F. Karlsson; B. Tomas Åström

    1997-01-01

    Techniques to manufacture sandwich components for structural applications are summarized and discussed in terms of processing steps, characteristics of both technique and manufactured components, and application examples. The emphasis is on the commercially most common manufacturing techniques, though less common processing routes are briefly discussed as well. The intentions of this review are twofold: first, the paper aims to provide

  12. Engineering Sandwich Courses in British Technological Universities

    ERIC Educational Resources Information Center

    Moore, J. P.; Urry, S. A.

    1971-01-01

    The development of sandwich courses, a review of their progress and a consideration of the problems associated with their operation are described. These courses are integrated so that industrial training is required and is interspersed between academic segments. (Author/TS)

  13. Career Counseling for the Sandwich Generation.

    ERIC Educational Resources Information Center

    Byrd, Virginia

    The Sandwich Generation refers to individuals who have multiple caregiving responsibilities for children under 18, as well as parents, grandparents or other aging relatives. Employees who are the caregivers cannot help but bring the stress of the situation to the workplace. Existing research suggests that these responsibilities take a toll on…

  14. The Future of the Integrated Sandwich Course

    ERIC Educational Resources Information Center

    Rankin, John

    1972-01-01

    Sandwich courses' survival depends on devising a procedure to assess industrial training meaningfully. The author proposes a list of specific procedures in such an assessment, including regular student inverviews with an assessment panel consisting of both his academic and industrial teachers. (Author/JB)

  15. Geometrically exact sandwich shells: The dynamic case

    Microsoft Academic Search

    L. Vuquoc; H. Deng; X. G. Tan

    2001-01-01

    In this paper, we present a finite element formulation for the dynamic analysis of our geometrically exact multilayer shell model developed earlier. The dynamics of the motion of sandwich shells is referred directly to an inertial frame. This model accommodates large deformation and large overall motion. The layer directors at a point in the reference surface are connected to each

  16. Self-healing composite sandwich structures

    Microsoft Academic Search

    H. R. Williams; R. S. Trask; I. P. Bond

    2007-01-01

    Impact damage can degrade the flexural strength of composite sandwich structures by over 50% due to a loss of skin support inducing localized skin buckling. Various self-healing methodologies have been applied to laminated composites but the concept of delivering a healing agent from a remote reservoir to a region of damage via a vascular network offers the potential for a

  17. Feedback Sandwiches Affect Perceptions but Not Performance

    ERIC Educational Resources Information Center

    Parkes, Jay; Abercrombie, Sara; McCarty, Teresita

    2013-01-01

    The feedback sandwich technique-make positive comments; provide critique; end with positive comments-is commonly recommended to feedback givers despite scant evidence of its efficacy. These two studies (N = 20; N = 350) of written peer feedback with third-year medical students on clinical patient note-writing assignments indicate that students…

  18. Fatigue characteristics of foam core sandwich composites

    Microsoft Academic Search

    Basir Shafiq; Amilcar Quispitupa

    2006-01-01

    In situ AE and post test microscopic analysis of quasi-static and flexural fatigue testing of sandwich composites indicated core damage to be the predominant failure activity while fiber rupture served as a precursor to catastrophic failure. Multiple crack initiation sites were observed under fatigue loading conditions in the vicinity of the notch tip. Both modes I and II cracking was

  19. Cellular Metal Truss Core Sandwich Structures**

    E-print Network

    Wadley, Haydn

    . Introduction Cellular metals have attracted interest as alternatives to honeycomb when used as the cores rigidity. Honeycomb core sandwich structures are the current state-of-the-art choice for weight sensitive of the porosity can trap moisture leading to corrosion. In space ap- plications, their skins are susceptible

  20. Fiber Composite Sandwich Thermostructural Behavior: Computational Simulation

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.; Aiello, R. A.; Murthy, P. L. N.

    1986-01-01

    Several computational levels of progressive sophistication/simplification are described to computationally simulate composite sandwich hygral, thermal, and structural behavior. The computational levels of sophistication include: (1) three-dimensional detailed finite element modeling of the honeycomb, the adhesive and the composite faces; (2) three-dimensional finite element modeling of the honeycomb assumed to be an equivalent continuous, homogeneous medium, the adhesive and the composite faces; (3) laminate theory simulation where the honeycomb (metal or composite) is assumed to consist of plies with equivalent properties; and (4) derivations of approximate, simplified equations for thermal and mechanical properties by simulating the honeycomb as an equivalent homogeneous medium. The approximate equations are combined with composite hygrothermomechanical and laminate theories to provide a simple and effective computational procedure for simulating the thermomechanical/thermostructural behavior of fiber composite sandwich structures.

  1. Ultrasonic Spectroscopy of Stainless Steel Sandwich Panels

    NASA Technical Reports Server (NTRS)

    Cosgriff, Laura M.; Lerch, Bradley A.; Hebsur, Mohan G.; Baaklini, George Y.; Ghosn, Louis J.

    2003-01-01

    Enhanced, lightweight material systems, such as 17-4PH stainless steel sandwich panels are being developed for use as fan blades and fan containment material systems for next generation engines. In order to improve the production for these systems, nondestructive evaluation (NDE) techniques, such as ultrasonic spectroscopy, are being utilized to evaluate the brazing quality between the 17-4PH stainless steel face plates and the 17-4PH stainless steel foam core. Based on NDE data, shear tests are performed on sections representing various levels of brazing quality from an initial batch of these sandwich structures. Metallographic characterization of brazing is done to corroborate NDE findings and the observed shear failure mechanisms.

  2. Thermographic Inspection of Metallic Honeycomb Sandwich Structures

    NASA Technical Reports Server (NTRS)

    Taylor, John O.; Dupont, H. M.

    1998-01-01

    The X-33/VentureStar has a Thermal Protection System (TPS) consisting mainly of brazed metallic honeycomb sandwich structures. Inspection of these structures is changing as a result of the extremely thin (less than 200 microns) skins, the small critical defect size (less than 2 mm long by 100 microns wide) and the large number (more than 1000) of parts to be inspected. Pulsed Infrared Thermography has been determined to be the most appropriate inspection method for manufacturing inspection based on performance comparison with other methods, cost, schedule and other factors. The results of the assessment of the different methods will be summarized and data on the performance of the final production inspection system will be given. Finite difference thermal methods have been used to model the whole inspection process. Details of correlation between the models and experimental data will be given and data on the use of pulsed infrared thermography on other metallic honeycomb sandwich structures will be given.

  3. Optimal parameters of sandwich composite plates

    NASA Astrophysics Data System (ADS)

    Kriutchenko, V. E.

    1992-12-01

    A method is proposed for calculating the optimal parameters of sandwich plates of specified stiffness loaded in flexure. The objective function is the plate mass, with the elastic and inertial characteristics of the layer used as the optimization parameters. An analytical relationship is established between the normalized thickness of a plate and its mass; an expression is obtained for the optimal plate thickness, which corresponds to the minimum mass for a fixed cylindrical stiffness.

  4. Fatigue Behaviour of Polymer Composite Sandwich Beams

    Microsoft Academic Search

    R. A. Shenoi; S. D. Clark; H. G. Allen

    1995-01-01

    The static and flexural fatigue characteristics of foam cored polymer composite sandwich beams are investigated. The skins of the beams are made from hybrid glass-aramid fibres set in epoxy resin and the core materials are linear and cross-linked polymer foams. The applied load in a ten-point configuration approximates a uniformly distributed load throughout the span of the beam which is

  5. The durability of structural sandwich elements

    Microsoft Academic Search

    K. Berner; J. M. Davies; A. Helenius; L. Heselius

    1994-01-01

    Structural sandwich elements typically have two thin metal faces and a lightweight core. The core may be polyurethane or polyisocyanurate\\u000a foamedin situ, or it may be formed from either rigid plastic foam or mineral wool slabstock. It is particularly in the latter case that\\u000a durability problems may arise which have not been properly addressed by the industry. This paper considers

  6. Testing Falling Peanut Butter Sandwich Myth

    NSDL National Science Digital Library

    Twin Cities Public Television, Inc.

    2006-01-01

    In this activity related to rotational inertia (page 1 of the PDF), learners will use a bit of scientific experimenting to test if open-faced peanut butter sandwiches really do always land peanut butter side down. Learners will also test other variables, such as drop height, size of bread slice, and whatever else learners can think of, to arrive at some sound conclusions. Relates to the linked video, DragonflyTV: Microgravity.

  7. Structural response of all-composite pyramidal truss core sandwich columns in end compression

    Microsoft Academic Search

    Ming Li; Linzhi Wu; Li Ma; Bing Wang; Zhengxi Guan

    2011-01-01

    With the equivalent mechanical properties of composite materials, analytical formulae of critical load for an all-composite sandwich column with pyramidal truss core are derived. Four failure modes are considered: macro Euler buckling, macro shear buckling, face-sheet wrinkling and face-sheet crushing. Failure mechanism maps are constructed with the four competing failure modes, and the relationship between the failure mechanism maps and

  8. Self-healing sandwich composite structures

    NASA Astrophysics Data System (ADS)

    Fugon, D.; Chen, C.; Peters, K.

    2012-04-01

    Previous research demonstrated that a thin self-healing layer is effective in recovering partial sandwich composite performance after an impact event. Many studies have been conducted that show the possibility of using Fiber Bragg Grating (FBG) sensors to monitor the cure of a resin through strain and temperature monitoring. For this experiment, FBG sensors were used to monitor the curing process of a self-healing layer within a twelve-layer fiberglass laminate after impact. First, five self-healing sandwich composite specimens were manufactured. FBG sensors were embedded between the fiberglass and foam core. Then the fiberglass laminate was impacted with the use of a drop tower and the curing process was monitored. The collected data was used to compare the cure of the resin and fiberglass alone to the cure of the resin from a self-healing specimen. For the low viscosity resin system tested, these changes were not sufficiently large to identify different polymerization states in the resin as it cured. These results indicate that applying different resin systems might increase the efficiency of the self-healing in the sandwich composites.

  9. Mode I Toughness Measurements of Core/Facesheet Bonds in Honeycomb Sandwich Structures

    NASA Technical Reports Server (NTRS)

    Nettles, Alan T.; Ratcliffe, James G.

    2006-01-01

    Composite sandwich structures will be used in many future applications in aerospace, marine and offshore industries due to the fact that the strength and stiffness to mass ratios surpass any other structural type. Sandwich structure also offers advantages over traditional stiffened panels such as ease of manufacturing and repair. During the last three decades, sandwich structure has been used extensively for secondary structure in aircraft (fuselage floors, rudders and radome structure). Sandwich structure is also used as primary structure in rotorcraft, the most common example being the trailing edge of rotor blades. As with other types of composite construction, sandwich structure exhibits several types of failure mode such as facesheet wrinkling, core crushing and sandwich buckling. Facesheet/core debonding has also been observed in the marine and aerospace industry. During this failure mode, peel stresses applied to an existing facesheet/core debond or an interface low in toughness, results in the facesheet being peeled from the core material, possibly leading to a significant loss in structural integrity of the sandwich panel. In an incident during a test on a liquid hydrogen fuel tank of the X-33 prototype vehicle, the outer graphite/epoxy facesheet and honeycomb core became debonded from the inner facesheet along significant areas, leading to failure of the tank. As a consequence of the accident; significant efforts were made to characterize the toughness of the facesheet/core bond. Currently, the only standardized method available for assessing the quality of the facesheet/core interface is the climbing drum peel test (ASTM D1781). During this test a sandwich beam is removed from a panel and the lip of one of the facesheets is attached to a drum, as shown in Fig. 1. The drum is then rotated along the sandwich beam, causing the facesheet to peel from the core. This method has two major drawbacks. First, it is not possible to obtain quantitative fracture data from the test and so the results can only be used in a qualitative manner. Second, only sandwich structure with thin facesheets can be tested (to facilitate wrapping of the facesheet around the climbing drum). In recognition of the need for a more quantitative facesheet/core fracture test, several workers have devised experimental techniques for characterizing the toughness of the facesheet/core interface. In all of these cases, the tests are designed to yield a mode I-dominated fracture toughness of the facesheet/core interface in a manner similar to that used to determine mode I fracture toughness of composite laminates. In the current work, a modified double cantilever beam is used to measure the mode I-dominated fracture toughness of the interface in a sandwich consisting of glass/phenolic honeycomb core reinforced with graphite epoxy facesheets. Two specimen configurations were tested as shown in Fig 2. The first configuration consisted of reinforcing the facesheets with aluminum blocks (Fig. 2a). In the second configuration unreinforced specimens were tested (Fig. 2b). Climbing drum peel tests were also conducted to compare the fracture behavior observed between this test and the modified double cantilever beam. This paper outlines the test procedures and data reduction strategies used to compute fracture toughness values from the tests. The effect of specimen reinforcement on fracture toughness of the facesheet/core interface is discussed.

  10. Sandwich panels with Kagome lattice cores reinforced by carbon fibers

    Microsoft Academic Search

    H. L. Fan; F. H. Meng; W. Yang

    2007-01-01

    Stretching dominated Kagome lattices reinforced by carbon fibers were designed and manufactured. The sandwich panels were assembled with bonded laminate skins. The mechanical behaviors of the sandwich panels were tested by out-of-plane compression, in-plane compression and three-point bending. Different failure modes of the sandwich structures were revealed. The experimental results showed that the carbon fiber reinforced lattice grids are much

  11. Aptamer-based Sandwich Assay and its Clinical Outlooks for Detecting Lipocalin-2 in Hepatocellular Carcinoma (HCC)

    PubMed Central

    Lee, Kyeong-Ah; Ahn, Ji-Young; Lee, Sang-Hee; Singh Sekhon, Simranjeet; Kim, Dae-Ghon; Min, Jiho; Kim, Yang-Hoon

    2015-01-01

    We validated a single-stranded, DNA aptamer-based, diagnostic method capable of detecting Lipocalin-2 (LCN2), a biomarker from clinically relevant hepatocellular carcinoma (HCC) patient serum, in the sandwich assay format. Nine aptamers (LCN2_apta1 to LCN2_apta9) for LCN2 were screened with SELEX processes, and a sandwich pair (LCN2_apta2 and LCN2_apta4) was finally chosen using surface plasmon resonance (SPR) and dot blotting analysis. The result of the proposed aptamer sandwich construction shows that LCN2 was sensitively detected in the concentration range of 2.5–500?ng mL?1 with a limit of detection of 0.6?ng mL?1. Quantitative measurement tests in HCC patients were run on straight serum and were compared with the performance of the conventional antibody-based ELISA kit. The aptamer sandwich assay demonstrated an excellent dynamic range for LCN2 at clinically relevant serum levels, covering sub-nanogram per mL concentrations. The new approach offers a simple and robust method for detecting serum biomarkers that have low and moderate abundance. It consists of functionalization, hybridization and signal read-out, and no dilution is required. The results of the study demonstrate the capability of the aptamer sandwich assay platform for diagnosing HCC and its potential applicability to the point-of-care testing (POCT) system. PMID:26039737

  12. Aptamer-based Sandwich Assay and its Clinical Outlooks for Detecting Lipocalin-2 in Hepatocellular Carcinoma (HCC).

    PubMed

    Lee, Kyeong-Ah; Ahn, Ji-Young; Lee, Sang-Hee; Singh Sekhon, Simranjeet; Kim, Dae-Ghon; Min, Jiho; Kim, Yang-Hoon

    2015-01-01

    We validated a single-stranded, DNA aptamer-based, diagnostic method capable of detecting Lipocalin-2 (LCN2), a biomarker from clinically relevant hepatocellular carcinoma (HCC) patient serum, in the sandwich assay format. Nine aptamers (LCN2_apta1 to LCN2_apta9) for LCN2 were screened with SELEX processes, and a sandwich pair (LCN2_apta2 and LCN2_apta4) was finally chosen using surface plasmon resonance (SPR) and dot blotting analysis. The result of the proposed aptamer sandwich construction shows that LCN2 was sensitively detected in the concentration range of 2.5-500?ng mL(-1) with a limit of detection of 0.6?ng mL(-1). Quantitative measurement tests in HCC patients were run on straight serum and were compared with the performance of the conventional antibody-based ELISA kit. The aptamer sandwich assay demonstrated an excellent dynamic range for LCN2 at clinically relevant serum levels, covering sub-nanogram per mL concentrations. The new approach offers a simple and robust method for detecting serum biomarkers that have low and moderate abundance. It consists of functionalization, hybridization and signal read-out, and no dilution is required. The results of the study demonstrate the capability of the aptamer sandwich assay platform for diagnosing HCC and its potential applicability to the point-of-care testing (POCT) system. PMID:26039737

  13. Stochastic micro-vibration suppression of a sandwich plate using a magneto-rheological visco-elastomer core

    NASA Astrophysics Data System (ADS)

    Ying, Z. G.; Ni, Y. Q.; Ye, S. Q.

    2014-02-01

    Magneto-rheological visco-elastomer (MRVE) is used to construct sandwich plates for micro-vibration control. The micro-vibration response of a sandwich plate with an MRVE core under stochastic support motion excitation is studied to evaluate the vibration suppression capability. The dynamic behavior of MRVE in micro-vibration is characterized by a non-homogeneous complex modulus dependent on the vibration frequency and controllable by an applied magnetic field, in which the effect of the localized magnetic field distribution is considered. The partial differential equations for the coupled transverse and longitudinal motions of the sandwich plate are derived from the dynamic equilibrium, constitutive and geometric relations. A frequency-domain solution method for the stochastic micro-vibration response of sandwich plates is developed based on the Galerkin method and random vibration theory. The partial differential equations are first converted into ordinary differential equations according to the Galerkin method. Then the expressions for the frequency-response function, response power spectral density and root-mean-square velocity spectrum in terms of the one-third octave frequency band for micro-vibration are obtained. Finally, numerical results are given to illustrate the high response reduction capacity of the MRVE sandwich plate under stochastic support motion excitation, and the influence of the MRVE parameters and localized magnetic field placement on the micro-vibration response.

  14. Impact and Blast Resistance of Sandwich Plates

    NASA Astrophysics Data System (ADS)

    Dvorak, George J.; Bahei-El-Din, Yehia A.; Suvorov, Alexander P.

    Response of conventional and modified sandwich plate designs is examined under static load, impact by a rigid cylindrical or flat indenter, and during and after an exponential pressure impulse lasting for 0.05 ms, at peak pressure of 100 MPa, simulating a nearby explosion. The conventional sandwich design consists of thin outer (loaded side) and inner facesheets made of carbon/epoxy fibrous laminates, separated by a thick layer of structural foam core. In the three modified designs, one or two thin ductile interlayers are inserted between the outer facesheet and the foam core. Materials selected for the interlayers are a hyperelas-tic rate-independent polyurethane;a compression strain and strain rate dependent, elastic-plastic polyurea;and an elastomeric foam. ABAQUS and LS-Dyna software were used in various response simulations. Performance comparisons between the enhanced and conventional designs show that the modified designs provide much better protection against different damage modes under both load regimes. After impact, local facesheet deflection, core compression, and energy release rate of delamination cracks, which may extend on hidden interfaces between facesheet and core, are all reduced. Under blast or impulse loads, reductions have been observed in the extent of core crushing, facesheet delaminations and vibration amplitudes, and in overall deflections. Similar reductions were found in the kinetic energy and in the stored and dissipated strain energy. Although strain rates as high as 10-4/s1 are produced by the blast pressure, peak strains in the interlayers were too low to raise the flow stress in the polyurea to that in the polyurethane, where a possible rate-dependent response was neglected. Therefore, stiff polyurethane or hard rubber interlayers materials should be used for protection of sandwich plate foam cores against both impact and blast-induced damage.

  15. Experimental investigation and constitutive modeling of metallic honeycombs in sandwich structures

    E-print Network

    Mohr, Dirk, 1976-

    2003-01-01

    Traditionally, honeycomb sandwich structures are designed in the elastic range, but recent studies on the crushing of sandwich profiles have shown their potential in crashworthiness applications. Thin sandwich sheets also ...

  16. Einstein constraints: Uniqueness and nonuniqueness in the conformal thin sandwich approach

    SciTech Connect

    Baumgarte, Thomas W. [Department of Physics and Astronomy, Bowdoin College, Brunswick, Maine 04011 (United States); Murchadha, Niall O [Physics Department, University College, Cork (Ireland); Pfeiffer, Harald P. [Theoretical Astrophysics, California Institute of Technology, Pasadena, California 91125 (United States)

    2007-02-15

    We study the appearance of multiple solutions to certain decompositions of Einstein's constraint equations. Pfeiffer and York recently reported the existence of two branches of solutions for a particular family of background data in the extended conformal thin-sandwich decomposition. We show that the Hamiltonian constraint alone, when expressed in a certain way, admits two branches of solutions with properties very similar to those found by Pfeiffer and York. We construct these two branches analytically for a constant-density star in spherical symmetry, but argue that this behavior is more general. In the case of the Hamiltonian constraint this nonuniqueness is well known to be related to the sign of one particular term, and we argue that the extended conformal thin-sandwich equations contain a similar term that causes the breakdown of uniqueness.

  17. The Einstein constraints: uniqueness and non-uniqueness in the conformal thin sandwich approach

    E-print Network

    Thomas W. Baumgarte; Niall Ó Murchadha; Harald P. Pfeiffer

    2006-10-25

    We study the appearance of multiple solutions to certain decompositions of Einstein's constraint equations. Pfeiffer and York recently reported the existence of two branches of solutions for identical background data in the extended conformal thin-sandwich decomposition. We show that the Hamiltonian constraint alone, when expressed in a certain way, admits two branches of solutions with properties very similar to those found by Pfeiffer and York. We construct these two branches analytically for a constant-density star in spherical symmetry, but argue that this behavior is more general. In the case of the Hamiltonian constraint this non-uniqueness is well known to be related to the sign of one particular term, and we argue that the extended conformal thin-sandwich equations contain a similar term that causes the breakdown of uniqueness.

  18. Modeling of Sandwich Sheets with Metallic Foam

    SciTech Connect

    Mata, H.; Jorge, R. Natal; Fernandes, A. A.; Parente, M. P. L. [IDMEC-FEUP, Faculdade de Engenharia da Universidade do Porto, Rua Dr. Roberto Frias 4200-465 Porto (Portugal); Santos, A. [INEGI, Faculdade de Engenharia da Universidade do Porto, Rua Dr. Roberto Frias 4200-465 Porto (Portugal); Valente, R. A. F. [Universidade de Aveiro, Campus Universitario de Santiago 3810-193 Aveiro (Portugal)

    2011-08-22

    World-wide vehicles safety experts agree that significant further reductions in fatalities and injuries can be achieved as a result of the use of new lightweight and energy absorbing materials. On this work, the authors present the development and evaluation of an innovative system able to perform reliable panels of sandwich sheets with metallic foam cores for industrial applications. The mathematical model used to describe the behavior of sandwich shells with metal cores foam is presented and some numerical examples are presented. In order to validate those results mechanical experiments are carried out. Using the crushable foam constitutive model, available on ABAQUS, a set of different mechanical tests were simulated. There are two variants of this model available on ABAQUS: the volumetric hardening model and the isotropic hardening model. As a first approximation we chose the isotropic hardening variant. The isotropic hardening model available uses a yield surface that is an ellipse centered at the origin in the p-q stress plane. Based on this constitutive model for the foam, numerical simulations of the tensile and bulge test will be conducted. The numerical results will be validated using the data obtained from the experimental results.

  19. Modeling of Sandwich Sheets with Metallic Foam

    NASA Astrophysics Data System (ADS)

    Mata, H.; Jorge, R. Natal; Santos, A.; Fernandes, A. A.; Valente, R. A. F.; Parente, M. P. L.

    2011-08-01

    World-wide vehicles safety experts agree that significant further reductions in fatalities and injuries can be achieved as a result of the use of new lightweight and energy absorbing materials. On this work, the authors present the development and evaluation of an innovative system able to perform reliable panels of sandwich sheets with metallic foam cores for industrial applications. The mathematical model used to describe the behavior of sandwich shells with metal cores foam is presented and some numerical examples are presented. In order to validate those results mechanical experiments are carried out. Using the crushable foam constitutive model, available on ABAQUS, a set of different mechanical tests were simulated. There are two variants of this model available on ABAQUS: the volumetric hardening model and the isotropic hardening model. As a first approximation we chose the isotropic hardening variant. The isotropic hardening model available uses a yield surface that is an ellipse centered at the origin in the p-q stress plane. Based on this constitutive model for the foam, numerical simulations of the tensile and bulge test will be conducted. The numerical results will be validated using the data obtained from the experimental results.

  20. Stress Analysis of Thick Laminated Composite and Sandwich Plates

    Microsoft Academic Search

    James M. Whitney

    1972-01-01

    Because of the relatively soft interlaminar shear modulus in high per formance composites, laminated plate theory based on the Kirchhoff hypothesis becomes inaccurate for determining gross plate response and internal stresses of thick composites and sandwich type laminates. In this paper a procedure is developed for accurately calculating the mechanical behavior of a thick laminated composite or sandwich plate of

  1. A Preliminary Analysis of the Earnings of Sandwich Course Students

    ERIC Educational Resources Information Center

    Hanson, C.; Marshall, V. C.

    1977-01-01

    The sandwich course system in the United Kingdom has much in common with cooperative education programs in the United States, involving a blend of academic study with work experience. Examines whether the sandwich course system has achieved its objectives, e.g., to provide practical experience in the application of theoretical concepts covered in…

  2. A Cost Basis for Resource Allocation for Sandwich Courses.

    ERIC Educational Resources Information Center

    Taylor, Bryan J. R.

    1984-01-01

    The use of a computer-based resource allocation procedure for cooperative education ("sandwich" coursework) at the University of Bath in Great Britain is discussed. Costs of undergraduate sandwich courses are compared with those of the more traditional 3-year, full-time undergraduate courses in British universities. Distinction is made between…

  3. Low velocity impact behavior of composite sandwich panels

    Microsoft Academic Search

    Patrick M. Schubel; Jyi-Jiin Luo; Isaac M. Daniel

    2005-01-01

    Composite sandwich structures are susceptible to low velocity impact damage and thorough characterization of the loading and damage process during impact is important. The objective of this work is to study experimentally the low velocity impact behavior of sandwich panels consisting of woven carbon\\/epoxy facesheets and a PVC foam core. Instrumented panels were impacted with a drop mass setup and

  4. An integrated assembly method of sandwich structured ceramic matrix composites

    Microsoft Academic Search

    Alberto Ortona; Simone Pusterla; Sandro Gianella

    2011-01-01

    Sandwich structured composites have been widely studied and applied at ambient temperature in aeronautical, automobile and naval applications. For high temperature applications, an integrated ceramic sandwich structure could take advantage of multiple functions such as skin stiffness and core insulation. For thermo-structural applications, skins must be made of ceramic matrix composites (CMC) because of their strength, their resistance to high

  5. Active Vibration Suppression of Sandwich Beams using Piezoelectric Shear Actuators

    E-print Network

    Vel, Senthil

    Active Vibration Suppression of Sandwich Beams using Piezoelectric Shear Actuators Senthil S. Vel1 of the piezoelectric actuators to cause transverse shear deformation of the sandwich beam. Active vibration suppression actuators. An exact analysis of the free vibration, forced vibration and active vibration suppression

  6. Stability of functionally graded shape memory alloy sandwich panels

    Microsoft Academic Search

    Victor Birman

    1997-01-01

    The stability of sandwich panels subjected to the simultaneous action of a uniform temperature and a uniaxial compression is considered. At elevated temperatures, the buckling load can be increased by using shape memory alloy (SMA) fibers in resin sleeves embedded within the core, at the midplane of the sandwich panel. The best results are achieved when the spacing of SMA

  7. Gourmet Sandwiches Flying Cow Club $5.50

    E-print Network

    Oklahoma, University of

    Gourmet Sandwiches Flying Cow Club $5.50 Turkey, ham bacon, lettuce, tomatoes, onions, cheese, mayo & the kitchen sink on three slices of toasted bread. Calories 823 California Turkey $5.50 Shaved turkey breast, Sodium 1,514 mg Better Turkey Sandwich $4.75 Sliced turkey, lettuce, tomatoes & red onions on a ciabatta

  8. Creep of sandwich beams with metallic foam cores

    Microsoft Academic Search

    O. Kesler; L. K. Crews; L. J. Gibson

    2003-01-01

    The steady state creep deflection rates of sandwich beams with metallic foam cores were measured and compared with analytical and numerical predictions of the creep behavior. The deflection rate depends on the geometry of the sandwich beam, the creep behavior of the foam core and the loading conditions (stress state, temperature). Although there was a considerable scatter in the creep

  9. Analysis of crack kinking in foam core sandwich beams

    Microsoft Academic Search

    Tomohiro Yokozeki

    2011-01-01

    The crack kink angle and the steady state crack location of the core crack in sandwich beams are predicted by using the analytical formulation of energy release rates associated with core cracking in a double cantilever sandwich beam. The predicted analytical results are compared with experimental results available in the literature. It is demonstrated that the present analysis is in

  10. Practical Instruction in Tissue Culture and Cytogenetics for Sandwich Students.

    ERIC Educational Resources Information Center

    Williams, D. C.; Bishun, N. P.

    1973-01-01

    Describes the training and practical techniques taught to students involved in a sandwich course at the Tissue Culture and Cytogenetics Unit of the Marie Curie Memorial Foundation, Surrey, England. Students spend a minimum of six months involved in the sandwich course before returning to university for a final academic year. (JR)

  11. Fatigue of foam core sandwich beams—1: undamaged specimens

    Microsoft Academic Search

    M Burman; D Zenkert

    1997-01-01

    The present paper addresses the fatigue characteristics of two cellular foam core materials as used in load carrying sandwich structures. The fatigue loading studied is a constant shear stress which corresponds to the main type of loading that the core in a sandwich structure exhibits. Based on results from testing stress-life curves are presented for a number of stress ratios

  12. Corrugated skin in a foam core sandwich panel

    Microsoft Academic Search

    Jack Reany; Joachim L. Grenestedt

    2009-01-01

    Sandwich plates with one corrugated and one flat skin were studied with the goal to find configurations with higher strength and\\/or stiffness and reduced weight. A procedure for calculating homogenized orthotropic plate stiffnesses of the sandwich was developed and applied to a number of different profiles. The corrugations lead to increased bending stiffness in one direction but reduced in another.

  13. Nonlinear Flexural Deflection of Thermoplastic Foam Core Sandwich Beam

    Microsoft Academic Search

    Kwang Joon Yoon; C. K. Kim; Hoon C. Park

    2002-01-01

    Nonlinear flexural deflection behavior of foam core sandwich beams hasbeen experimentally investigated. The experimental data were compared with the predicted results obtained from a proposed analytical method and the finite element analysis. Sandwich beams with thermoplastic foam core and carbon\\/epoxy fabric faces were manufactured using the vacuum bagging process. To investigate the effect of the face thickness on the nonlinear

  14. Static indentation and unloading response of sandwich beams

    Microsoft Academic Search

    Dan Zenkert; Andrey Shipsha; Karl Persson

    2004-01-01

    This paper deals with analysis of foam core sandwich beams subject to static indentation and subsequent unloading (removal of load). Sandwich beams are assumed continuously supported by a rigid platen to eliminate global bending. An analytical model is presented assuming an elastic-perfectly plastic compressive behaviour of the foam core. An elastic part of indentation response is described using the Winkler

  15. Compressive Strength of Stainless-Steel Sandwiches at Elevated Temperatures

    NASA Technical Reports Server (NTRS)

    Mathauser, Eldon E.; Pride, Richard A.

    1959-01-01

    Experimental results are presented from crippling tests of stainless-steel sandwich specimens in the temperature range from 80 F to 1,200 F. The specimens included resistance-welded 17-7 PH stainless-steel sandwiches with single-corrugated cores, type 301 stainless-steel sandwiches with double-corrugated cores, and brazed 17-7 PH stainless-steel sandwiches with honeycomb cores. The experimental strengths are compared with predicted buckling and crippling strengths. The crippling strengths were predicted from the calculated maximum strength of the individual plate elements of the sandwiches and from a correlation procedure which gives the elevated-temperature crippling strength when the experimental room-temperature crippling strengths are known. Photographs of some of the tested specimens are included to show the modes of failure.

  16. Development, testing, and numerical modeling of a foam sandwich biocomposite

    NASA Astrophysics Data System (ADS)

    Chachra, Ricky

    This study develops a novel sandwich composite material using plant based materials for potential use in nonstructural building applications. The face sheets comprise woven hemp fabric and a sap based epoxy, while the core comprises castor oil based foam with waste rice hulls as reinforcement. Mechanical properties of the individual materials are tested in uniaxial compression and tension for the foam and hemp, respectively. The sandwich composite is tested in 3 point bending. Flexural results are compared to a finite element model developed in the commercial software Abaqus, and the validated model is then used to investigate alternate sandwich geometries. Sandwich model responses are compared to existing standards for nonstructural building panels, showing that the novel material is roughly half the strength of equally thick drywall. When space limitations are not an issue, a double thickness sandwich biocomposite is found to be a structurally acceptable replacement for standard gypsum drywall.

  17. Vibration and formability characteristics of aluminum-polymer sandwich materials

    NASA Astrophysics Data System (ADS)

    Somayajulu, Thamma S. V.

    Metal/polymer/metal sandwich materials are finding increasing use in the automotive industry primarily as lightweight alternatives to steel and aluminum alloys. In addition to low density they also offer other functional benefits e.g. improved vibration damping. In order to exploit such beneficial characteristics it is necessary to examine the manufacturability of these materials. In this work the vibration characteristics and formability were examined in selected materials, chosen from a group of aluminum/polypropylene/aluminum sandwich materials. First, a systematic study was carried out on vibration characteristics of square sandwich plates using 3D finite element models and usefulness of such a 3D displacement field in understanding the damping mechanisms as well as their contributions toward the modal damping were discussed. Second, a study of stretch formability of several sandwich materials was conducted. Since the knowledge of tensile properties is essential for understanding the formability, those properties were determined by performing uniaxial tensile tests on several aluminum/polypropylene/aluminum (HyliteRTM) sandwich materials and their constituent materials. The phenomena of diffused necking and deformation of material up to and beyond the point of necking were systematically investigated. Furthermore, the formability of sandwich materials was assessed by comparing the experimentally determined forming limit diagrams (FLDs) of monolithic 5182 aluminum and several sandwich materials. In addition to the experimental research, theoretical modeling was carried out to predict formability based on the concept of growth of pre-existing defects. One such model, known as M-K analysis, was utilized on the basis of defects existing in (i) the aluminum skins and (ii) the overall thickness of the sandwich. The experimental and theoretical results suggest that the levels of forming limit in sandwich materials are far less than those for monolithic materials of equivalent stiffness. This result may be related to smaller defect factor in the skin of the sandwich materials.

  18. FLAMBAGE ET EFFET D'ECHELLE DANS LES STRUCTURES SANDWICH BUCKLING AND SCALE EFFECTS IN SANDWICH STRUCTURES

    E-print Network

    Boyer, Edmond

    FLAMBAGE ET EFFET D'ECHELLE DANS LES STRUCTURES SANDWICH BUCKLING AND SCALE EFFECTS IN SANDWICH for both global and local buckling. In a perfect framework, analytical critical loads are extracted eigenvalue can correspond to the occurrence of global and local buckling (wrinkling). Then local and global

  19. Impact damage in aircraft composite sandwich panels

    NASA Astrophysics Data System (ADS)

    Mordasky, Matthew D.

    An experimental study was conducted to develop an improved understanding of the damage caused by runway debris and environmental threats on aircraft structures. The velocities of impacts for stationary aircraft and aircraft under landing and takeoff speeds was investigated. The impact damage by concrete, asphalt, aluminum, hail and rubber sphere projectiles was explored in detail. Additionally, a kinetic energy and momentum experimental study was performed to look at the nature of the impacts in more detail. A method for recording the contact force history of the impact by an instrumented projectile was developed and tested. The sandwich composite investigated was an IM7-8552 unidirectional prepreg adhered to a NOMEXRTM core with an FM300K film adhesive. Impact experiments were conducted with a gas gun built in-house specifically for delivering projectiles to a sandwich composite target in this specic velocity regime (10--140 m/s). The effect on the impact damage by the projectile was investigated by ultrasonic C-scan, high speed camera and scanning electron and optical microscopy. Ultrasonic C-scans revealed the full extent of damage caused by each projectile, while the high speed camera enabled precise projectile velocity measurements that were used for striking velocity, kinetic energy and momentum analyses. Scanning electron and optical images revealed specific features of the panel failure and manufacturing artifacts within the lamina and honeycomb core. The damage of the panels by different projectiles was found to have a similar damage area for equivalent energy levels, except for rubber which had a damage area that increased greatly with striking velocity. Further investigation was taken by kinetic energy and momentum based comparisons of 19 mm diameter stainless steel sphere projectiles in order to examine the dominating damage mechanisms. The sandwich targets were struck by acrylic, aluminum, alumina, stainless steel and tungsten carbide spheres of the same geometry (19mm diameter) and surface finish. A peak absorbed energy for perforation of 34.5J was identied regardless of the projectile density. The effect of composite panel manufacturing methods on the impact damage and energy absorption of the panel was also investigated. Specifically, damage related to pre-cured facesheets is compared to the co-cured facesheets used throughout the study.

  20. Calibration of an analytical thermal model for an epoxy-based composite sandwich design

    NASA Astrophysics Data System (ADS)

    Reinarts, Thomas R.; Davis, Darrell; Stuckey, Charles I.

    2001-02-01

    An epoxy-based sandwich configuration was designed to meet the structural and thermal requirements of a nose cap for the space shuttle solid rocket boosters (SRB's). This project was suspended in late 1999, but the information gathered during this work is unique in the sense that portions of graphite-epoxy layers were modeled at temperatures exceeding their glass transition temperatures. This work presents the results of the thermal model calibration efforts. A symmetric sandwich configuration was chosen that includes an inner and outer structural skin with a graphite-epoxy composite, Hexcel's AGP370-8H/3501-6 (AS4/3501-6), and a center epoxy-based syntactic core. 3M SC350G, that provides thermal protection. Each graphite-epoxy section consists of seven layers, each layer with a 0°, 90°, or +/-45° graphite fiber orientation. Three flat panels (0.305×0.483 m top view dimensions) using this sandwich construction were fabricated and exposed to an aerothermal environment in the Marshall Space Flight Center (MSFC) Improved Hot Gas Facility (IHGF). Each of these panels had ten interstitial thermocouples in the panel. The exact locations of the thermocouples and thickness of the different layers were determined by X-ray evaluation. A 1-D model was generated that used the outer surface IR measured temperature as a boundary condition, and the predicted temperatures were compared with the measured temperatures, calibrating the code. .

  1. Human umbilical cord mesenchymal stromal cells in a sandwich approach for osteochondral tissue engineering

    PubMed Central

    Wang, Limin; Zhao, Liang; Detamore, Michael S.

    2013-01-01

    Cell sources and tissue integration between cartilage and bone regions are critical to successful osteochondral regeneration. In this study, human umbilical cord mesenchymal stromal cells (hUCMSCs), derived from Wharton’s jelly, were introduced to the field of osteochondral tissue engineering and a new strategy for osteochondral integration was developed by sandwiching a layer of cells between chondrogenic and osteogenic constructs before suturing them together. Specifically, hUCMSCs were cultured in biodegradable poly-l-lactic acid scaffolds for 3 weeks in either chondrogenic or osteogenic medium to differentiate cells toward cartilage or bone lineages, respectively. A highly concentrated cell solution containing undifferentiated hUCMSCs was pasted onto the surface of the bone layer at week 3 and the two layers were then sutured together to form an osteochondral composite for another 3 week culture period. Chondrogenic and osteogenic differentiation was initiated during the first 3 weeks, as evidenced by the expression of type II collagen and runt-related transcription factor 2 genes, respectively, and continued with the increase of extracellular matrix during the last 3 weeks. Histological and immunohistochemical staining, such as for glycosaminoglycans, type I collagen and calcium, revealed better integration and transition of these matrices between two layers in the composite group containing sandwiched cells compared to other control composites. These results suggest that hUCMSCs may be a suitable cell source for osteochondral regeneration, and the strategy of sandwiching cells between two layers may facilitate scaffold and tissue integration. PMID:21953869

  2. Transmission Loss and Absorption of Corrugated Core Sandwich Panels With Embedded Resonators

    NASA Technical Reports Server (NTRS)

    Allen, Albert R.; Schiller, Noah H.; Zalewski, Bart F.; Rosenthal, Bruce N.

    2014-01-01

    The effect of embedded resonators on the diffuse field sound transmission loss and absorption of composite corrugated core sandwich panels has been evaluated experimentally. Two 1.219 m × 2.438 m panels with embedded resonator arrangements targeting frequencies near 100 Hz were evaluated using non-standard processing of ASTM E90-09 acoustic transmission loss and ASTM C423-09a room absorption test measurements. Each panel is comprised of two composite face sheets sandwiching a corrugated core with a trapezoidal cross section. When inlet openings are introduced in one face sheet, the chambers within the core can be used as embedded acoustic resonators. Changes to the inlet and chamber partition locations allow this type of structure to be tuned for targeted spectrum passive noise control. Because the core chambers are aligned with the plane of the panel, the resonators can be tuned for low frequencies without compromising the sandwich panel construction, which is typically sized to meet static load requirements. Absorption and transmission loss performance improvements attributed to opening the inlets were apparent for some configurations and inconclusive for others.

  3. Development and Mechanical Behavior of FML/Aluminium Foam Sandwiches

    NASA Astrophysics Data System (ADS)

    Ba?türk, S. B.; Tano?lu, M.

    2013-10-01

    In this study, the Fiber-Metal Laminates (FMLs) containing glass fiber reinforced polypropylene (GFPP) and aluminum (Al) sheet were consolidated with Al foam cores for preparing the sandwich panels. The aim of this article is the comparison of the flexural properties of FML/Al foam sandwich panels bonded with various surface modification approaches (silane treatment and combination of silane treatment with polypropylene (PP) based film addition). The FML/foam sandwich systems were fabricated by laminating the components in a mould at 200 °C under 1.5 MPa pressure. The energy absorbtion capacities and flexural mechanical properties of the prepared sandwich systems were evaluated by mechanical tests. Experiments were performed on samples of varying foam thicknesses (8, 20 and 30 mm). The bonding among the sandwich components were achieved by various surface modification techniques. The Al sheet/Al foam sandwiches were also consolidated by bonding the components with an epoxy adhesive to reveal the effect of GFPP on the flexural performance of the sandwich structures.

  4. Dorsal and ventral stimuli in sandwich-like microenvironments. Effect on cell differentiation.

    PubMed

    Ballester-Beltrán, José; Lebourg, Myriam; Salmerón-Sánchez, Manuel

    2013-11-01

    While most of the in vivo extracellular matrices are 3D, most of the in vitro cultures are 2D--where only ventral adhesion is permitted--thus modifying cell behavior as a way to self-adaptation to this unnatural environment. We hypothesize that the excitation of dorsal receptors in cells already attached on a 2D surface (sandwich culture) could cover the gap between 2D and 3D cell-material interactions and result in a more physiological cell behavior. In this study we investigate the role of dorsal stimulation on myoblast differentiation within different poly(L-lactic acid) (PLLA) sandwich-like microenvironments, including plain material and aligned fibers. Enhanced cell differentiation levels were found for cells cultured with dorsal fibronectin-coated films. Seeking to understand the underlying mechanisms, experiments were carried out with (i) different types of dorsal stimuli (FN, albumin, FN after blocking the RGD integrin-binding site and activating dorsal cell integrin receptors), (ii) in the presence of an inhibitor of cell contractility, and (iii) increasing the frequency of culture medium changes to assess the effect of paracrine factors. Furthermore, FAK and integrin expressions, determined by Western blotting, revealed differences between cell sandwiches and 2D controls. Results show a stimuli-dependent response to dorsal excitation, proving that integrin outside-in signaling is involved in the enhanced cell differentiation. Due to their easiness and versatility, these sandwich-like systems are excellent candidates to get deeper insights into the study of 3D cell behavior and to direct cell fate within multilayer constructs. PMID:23744752

  5. The behavior of bonded doubler splices for composite sandwich panels

    NASA Technical Reports Server (NTRS)

    Zeller, T. A.; Weisahaar, T. A.

    1980-01-01

    The results of an investigation into the behavior of adhesively bonded doubler splices of two composite material sandwich panels are presented. The splices are studied from three approaches: analytical; numerical (finite elements); and experimental. Several parameters that characterize the splice are developed to determine their influence upon joint strength. These parameters are: doubler overlap length; core stiffness; laminate bending stiffness; the size of the gap between the spliced sandwich panels; and room and elevated temperatures. Similarities and contrasts between these splices and the physically similar single and double lap joints are discussed. The results of this investigation suggest several possible approaches to improving the strength of the sandwich splices.

  6. Elastic Coupling Effects in Tapered Sandwich Panels with Laminated Anisotropic Composite Facings

    Microsoft Academic Search

    Senthil S. Vel; Vincent Caccese; Huyue Zhao

    2005-01-01

    A newly developed theory for the analysis of tapered sandwich panels with laminated anisotropic facings is presented. Unlike sandwich panels of uniform depth, the response of tapered sandwich panels is counterintuitive. For example, prior studies have demonstrated that a tapered cantilever sandwich beam having constant dimensions at the clamped edge and subjected to a tip load has an optimum taper

  7. Comptes Rendus des JNC 17 -Poitiers 2011 tude des dformations locales dans un matriau sandwich

    E-print Network

    Boyer, Edmond

    sandwich sollicité en flexion 3 et 4 points Study of the local strains in a sandwich material under 3 and 4) dans un matériau sandwich à âme PVC et peaux composites. Ce matériau est soumis à un chargement de, the evolution of the local shear strain (at micron level) inside a sandwich material, with PVC core

  8. The Graph Sandwich Problem for a coNP property Marcus Schaefer

    E-print Network

    Schaefer, Marcus

    The Graph Sandwich Problem for a coNP property Marcus Schaefer School of CTI DePaul University 243 # F # we say that the graph G is sandwiched between graphs F and F # . The graph sandwich problem that there is a coNP­complete graph property for which the graph sandwich problem is # p 2 ­complete. 1 Introduction

  9. TEMPERATURE DEPENDENT CREEP EXPANSION OF Ti-6Al-4V LOW DENSITY CORE SANDWICH STRUCTURES

    E-print Network

    Wadley, Haydn

    TEMPERATURE DEPENDENT CREEP EXPANSION OF Ti-6Al-4V LOW DENSITY CORE SANDWICH STRUCTURES Douglas T for the low cost manufacture of porous metal sandwich structures. These porous cored sandwich structures technique for the production of Ti-6Al-4V porous cored sandwich structures. Their process began

  10. An experimental comparison of half-scale rockfall protection sandwich structures

    E-print Network

    Paris-Sud XI, Université de

    An experimental comparison of half-scale rockfall protection sandwich structures A. Heymann1, 3 , S in building a sandwich cellular structure for this purpose. Cellular structures are efficient technological the behaviour of three sandwich structures based on half-scale experiments. The 1.5 m high cellular sandwich

  11. The Graph Sandwich Problem for a coNP property Marcus Schaefer

    E-print Network

    Schaefer, Marcus

    The Graph Sandwich Problem for a coNP property Marcus Schaefer School of CTI DePaul University 243 we say that the graph G is sandwiched between graphs F and F . The graph sandwich problem consistsNP-complete graph property for which the graph sandwich problem is p 2-complete. 1 Introduction We say a graph G

  12. A Ham Sandwich Is Better than Nothing: Some Thoughts about Transitivity

    ERIC Educational Resources Information Center

    Roberts, Tim S.

    2004-01-01

    There is an old joke that says that given the choice between eternal happiness and a ham sandwich, one should choose the ham sandwich. The proof is quite simple: (1) nothing is better than eternal happiness; (2) a ham sandwich is better than nothing; and therefore, it straightforwardly follows from (1) and (2) that (3) a ham sandwich is better…

  13. Compressive and shear buckling analysis of metal matrix composite sandwich panels under different thermal environments

    Microsoft Academic Search

    W. L. Ko; R. H. Jackson

    1993-01-01

    Combined inplane compressive and shear buckling analysis was conducted on flat rectangular sandwich panels using the Raleigh-Ritz minimum energy method with a consideration of transverse shear effect of the sandwich core. The sandwich panels were fabricated with titanium honeycomb core and laminated metal matrix composite face sheets. The results show that slightly slender (along unidirectional compressive loading axis) rectangular sandwich

  14. Measuring Moisture Levels in Graphite Epoxy Composite Sandwich Structures

    NASA Technical Reports Server (NTRS)

    Nurge, Mark; Youngquist, Robert; Starr, Stanley

    2011-01-01

    Graphite epoxy composite (GEC) materials are used in the construction of rocket fairings, nose cones, interstage adapters, and heat shields due to their high strength and light weight. However, they absorb moisture depending on the environmental conditions they are exposed to prior to launch. Too much moisture absorption can become a problem when temperature and pressure changes experienced during launch cause the water to vaporize. The rapid state change of the water can result in structural failure of the material. In addition, heat and moisture combine to weaken GEC structures. Diffusion models that predict the total accumulated moisture content based on the environmental conditions are one accepted method of determining if the material strength has been reduced to an unacceptable level. However, there currently doesn t exist any field measurement technique to estimate the actual moisture content of a composite structure. A multi-layer diffusion model was constructed with Mathematica to predict moisture absorption and desorption from the GEC sandwich structure. This model is used in conjunction with relative humidity/temperature sensors both on the inside and outside of the material to determine the moisture levels in the structure. Because the core materials have much higher diffusivity than the face sheets, a single relative humidity measurement will accurately reflect the moisture levels in the core. When combined with an external relative humidity measurement, the model can be used to determine the moisture levels in the face sheets. Since diffusion is temperaturedependent, the temperature measurements are used to determine the diffusivity of the face sheets for the model computations.

  15. Academic Accreditation of Work-Based Learning in the Construction Environment

    ERIC Educational Resources Information Center

    McLernon, Tim; Hughes, David

    2004-01-01

    This paper examines the contribution of work-based learning (WBL) to the education of construction students. The research draws on the experiences of part-time students and students on sandwich courses in a School of the Built Environment. The sandwich courses include a year in industry as the penultimate year of a four-year programme. This WBL…

  16. Multifunctional composite sandwich structures utilizing embedded microvascular networks

    NASA Astrophysics Data System (ADS)

    Tye, Jordan

    Sandwich composites possess exceptional specific flexural strengths, but currently lack the capability for multifunctional use of the volumes encapsulated within their cores. The objectives of this research are to (1) fabricate sacrificial fiber with increased production rates and decreased degradation times, (2) integrate sacrificial fibers into sandwich composite skins, and (3) transport, store, and recover fluid from cells within a honeycomb composite core. Melt-mixing and extrusion of PLA and tin (II) oxalate catalyst is used to increase production rates by five orders of magnitude and reduce evacuation times by a factor of four, while substantially lowering costs and eliminating hazardous chemical waste. Sacrificial fibers are woven into and fully evacuated from sandwich composite structures. Finally, fluid is successfully transported via the patterned microvascular pathways and stored within the core compartments, enabling sandwich composites suitable for applications such as structural fluid storage, heat dissipation, and damage sensing.

  17. Modelling of crack deflection at core junctions in sandwich structures

    NASA Astrophysics Data System (ADS)

    Jakobsen, J.; Andreasen, J. H.; Thomsen, O. T.

    2009-08-01

    The paper treats the problem of crack propagation in sandwich panels with interior core junctions. When a face-core interface crack approaches a trimaterial wedge, as it may occur at a sandwich core junction, two options exist for further crack advance; one is for the interface crack to penetrate the wedge along the face-core interface, and the second is deflection along the core junction interface. Crack deflection is highly relevant and a requirement for the functionality of a newly developed peel stopper for sandwich structures. The physical model presented in this paper enables the quantitative prediction of the ratio of the toughnesses of the two wedge interfaces required to control the crack propagation, and the derived results can be applied directly in future designs of sandwich structures. The solution strategy is based on finite element analysis (FEA), and a realistic engineering practice example of a tri-material composition corresponding to face and core materials is presented.

  18. The fatigue behaviour and damage development of 3D woven sandwich composites

    Microsoft Academic Search

    H. Judawisastra; J. Ivens; I. Verpoest

    1998-01-01

    In this paper, the bending fatigue behaviour and damage development during fatigue of polyurethane (PUR)-epoxy 3D woven sandwich composites is investigated. 3D sandwich fabrics are produced by a velvet weaving technique. It allows relatively easy production of delamination-resistant sandwich panels, compared to more traditional sandwich structures with honeycomb or foam cores. In this paper, the 3D sandwich fabrics made of

  19. Collapse of truss core sandwich beams in 3-point bending

    Microsoft Academic Search

    V. S Deshpande; N. A Fleck

    2001-01-01

    Sandwich beams, comprising a truss core and either solid or triangulated face-sheets, have been investment cast in an aluminium–silicon alloy and in silicon brass. The macroscopic effective stiffness and strength of the triangulated face-sheets and tetrahedral core are estimated by idealising them as pin-jointed assemblies; tests show that this approximation is adequate. Next, the collapse responses of these sandwich beams

  20. Impact Testing on Composites Laminates and Sandwich Panels

    Microsoft Academic Search

    Claudio Scarponi; Giuseppe Briotti; Renato Barboni; Antonio Marcone; Michele Iannone

    1996-01-01

    The purpose of this work was the evaluation of the behavior of fiber-reinforced composites and sandwich panels for aeronautical applications under impact.Experimental tests were performed on several specimen configurations, based on different quasi-isotropic lay-up and materials such CFRP, CFRTP and a syntactic foam as the core of sandwich panels. Considering the high specific mechanics characteristics of such a foam and

  1. Graphite\\/epoxy honeycomb core sandwich permeability under mechanical loads

    Microsoft Academic Search

    David E. Glass; V. V. Raman; Venki S. Venkat; Sankara N. Sankaran

    1999-01-01

    The air permeability of two honeycomb core sandwich materials as a function of applied shear stress was characterized. The honeycomb core sandwich specimens were provided to Analytical Services and Materials, Inc. by The Boeing Company for evaluation. The core material for the test specimens was either Hexcel HRP-3\\/16-8.0 or DuPont Korex-1\\/8-4.5 and was nominally 1.27 cm (0.5 in.) thick. The

  2. The response of clamped sandwich beams subjected to shock loading

    Microsoft Academic Search

    D. D. Radford; N. A. Fleck; V. S. Deshpande

    2006-01-01

    The dynamic response of monolithic and sandwich beams made from stainless steel is determined by loading the end-clamped beams at mid-span with metal foam projectiles. The sandwich beams comprise stainless-steel pyramidal cores (with no axial stretch resistance), stainless-steel corrugated cores (with a high stretch resistance) and an aluminium alloy metal foam. High-speed photography is used to measure the transient transverse

  3. Experimental investigation of thermal effects in foam cored sandwich beams

    Microsoft Academic Search

    R K Fruehmann; J M Dulieu-Barton; O T Thomsen; S Zhang

    \\u000a Polymer foam cored sandwich structures are commonly used in applications where mechanical loads and elevated temperatures\\u000a form the normal service conditions. The temperature sensitivity of the mechanical properties of the polymer foam cores leads\\u000a to compromised mechanical performance of the overall sandwich structure at elevated temperatures. So far this phenomenon has\\u000a primarily been investigated using analytical techniques. The present paper

  4. Impact performance of nanophased foam core sandwich composites

    Microsoft Academic Search

    M. V. Hosur; A. A. Mohammed; S. Zainuddin; S. Jeelani

    2008-01-01

    In this study, sandwich panels were fabricated with neat and nanophased foam core and three-layered plain weave carbon fabric\\/Sc-15 epoxy composite face sheets. Neat and nanophased foam cores with Nanocor® I-28E nanoclay at a loading of 0.5% and 1% by weight were prepared. Sandwich panels were then fabricated using co-injection resin transfer molding process. Samples of size 100mm×100mm were then

  5. Half-Metallic Sandwich Molecular Wires with Negative Differential Resistance and Sign-Reversible High Spin-filter Efficiency

    NASA Astrophysics Data System (ADS)

    Wang, Lu; Yan, Xin; Zhou, Jing; Lu, Jing; Gao, Zhengxiang; Gao, Xingfa; Nagase, Shigeru; Sanvito, Stefano; Maeda, Yutaka; Akasaka, Takeshi; Mei, Wai-Ning

    2011-03-01

    Using density functional theory and non-equilibrium Green's function method, we construct organometallic nanowires that consist of Fe or V atoms sandwiched between composite molecules (Cp * FeCp * , where Cp * is C5 (CH3)5) . For the first time, we demonstrate that half-metallicity, negative differential resistance, and sign-reversible high spin-filter capability can coexist remarkably in one organometallic nanowire (FeCp * wire). This renders FeCp * wire promising in electronics and spintronics.

  6. A study of structurally efficient graphite-thermoplastic trapezoidal-corrugation sandwich and semi-sandwich panels

    NASA Technical Reports Server (NTRS)

    Jegley, Dawn C.

    1993-01-01

    The structural efficiency of compression-loaded trapezoidal-corrugation sandwich and semi-sandwich composite panels is studied to determine their weight savings potential. Sandwich panels with two identical face sheets and a trapezoidal corrugated core between them, and semi-sandwich panels with a corrugation attached to a single skin are considered. An optimization code is used to find the minimum weight designs for critical compressive load levels ranging from 3,000 to 24,000 lb/in. Graphite-thermoplastic panels based on the optimal minimum weight designs were fabricated and tested. A finite-element analysis of several test specimens was also conducted. The results of the optimization study, the finite-element analysis, and the experiments are presented.

  7. Foam core materials for structural sandwich panels

    SciTech Connect

    Huang Jongshin.

    1991-01-01

    The author first investigates the creep of polymer foam cores. Models for the creep of linear and nonlinear viscoelastic polymer foams are proposed. Experimental results for the creep of a rigid polyurethane foam are compared to the mode; agreement is good. The results indicate that creep can limit the design of building panels with polymer foam cores. Next, he studies the potential of using ceramic foams as a core material in building panels. Ceramic foams have a high stiffness, high creep resistance, low cost, and are incombustible. Ceramic foams, however, have a low fracture toughness and tensile strength. Assuming that the variability of cell wall modulus of rupture follows a Weibull distribution, there is a cell size effect on both the fracture toughness and tensile strength. Both the tensile strength and fracture toughness of ceramic foams can be improved by controlling the cell size. Since cell wall deformation of cellular materials is primarily by bending, the mechanical properties of cellular materials may be improved by making cell walls into sandwich structures. Hollow-sphere composites are made by introducing thin-walled hollow spheres into a matrix.

  8. Numerically simulating the sandwich plate system structures

    NASA Astrophysics Data System (ADS)

    Feng, Guo-Qing; Li, Gang; Liu, Zhi-Hui; Niu, Huai-Lei; Li, Chen-Feng

    2010-09-01

    Sandwich plate systems (SPS) are advanced materials that have begun to receive extensive attention in naval architecture and ocean engineering. At present, according to the rules of classification societies, a mixture of shell and solid elements are required to simulate an SPS. Based on the principle of stiffness decomposition, a new numerical simulation method for shell elements was proposed. In accordance with the principle of stiffness decomposition, the total stiffness can be decomposed into the bending stiffness and shear stiffness. Displacement and stress response related to bending stiffness was calculated with the laminated shell element. Displacement and stress response due to shear was calculated by use of a computational code write by FORTRAN language. Then the total displacement and stress response for the SPS was obtained by adding together these two parts of total displacement and stress. Finally, a rectangular SPS plate and a double-bottom structure were used for a simulation. The results show that the deflection simulated by the elements proposed in the paper is larger than the same simulated by solid elements and the analytical solution according to Hoff theory and approximate to the same simulated by the mixture of shell-solid elements, and the stress simulated by the elements proposed in the paper is approximate to the other simulating methods. So compared with calculations based on a mixture of shell and solid elements, the numerical simulation method given in the paper is more efficient and easier to do.

  9. ?-Cyclodextrin cuprate sandwich-type complexes.

    PubMed

    Bagabas, Abdulaziz A; Frasconi, Marco; Iehl, Julien; Hauser, Brad; Farha, Omar K; Hupp, Joseph T; Hartlieb, Karel J; Botros, Youssry Y; Stoddart, J Fraser

    2013-03-18

    Three structures, based on ?-cyclodextrin (?-CD) and metal ions (Cu(2+), Li(+), Na(+), and Rb(+)), have been prepared in aqueous and alkaline media and characterized structurally by single-crystal X-ray diffraction. Their dimeric assemblies adopt cylindrical channels along the c axes in the crystals. Coordinative and hydrogen bonding between the cylinders and the solvent molecules lead to the formation of two-dimensional sheets, with the identity of the alkali-metal ion strongly influencing the precise nature of the solid-state structures. In the case of the Rb(+) complex, coordinative bonding involving the Rb(+) ions leads to the formation of an extended two-dimensional structure. Nonbound solvent molecules can be removed, and gas isotherm analyses confirm the permanent porosity of these new complexes. Carbon dioxide (CO2) adsorption studies show that the extended structure, obtained upon crystallization of the Rb(+)-based sandwich-type dimers, has the highest CO2 sequestration ability of the three ?-CD complexes reported. PMID:23432138

  10. REIS, ENGIN MURAT. Characteristics of Innovative 3-D FRP Sandwich Panels. Foam and honeycomb core sandwich composites are widely used in structural

    E-print Network

    ABSTRACT REIS, ENGIN MURAT. Characteristics of Innovative 3-D FRP Sandwich Panels. Foam and honeycomb core sandwich composites are widely used in structural applications. Nevertheless, possibilities encountered in traditional FRP panels. The panels consist of GFRP laminates and foam core sandwich where top

  11. Impact damage analysis of balsawood sandwich composite materials

    NASA Astrophysics Data System (ADS)

    Abdalslam, Suof Omran

    In this study, a new composite sandwich structure with a balsa wood core (end grain and regular balsa) in conjunction with E-glass/epoxy face sheets was proposed, fabricated, impact tested, and modeled. The behavior of the sandwich structure under low velocity impact and compression after impact was investigated. Low velocity impact tests were carried out by drop-weight impact tower at different energy levels (8J-35J) to evaluate the impact response of the sandwich structure. Visual inspection, destructive and non destructive evaluation methods have been conducted. For the sandwich plate with end grain core, the damage was very clear and can be visually detected. However, the damage in regular balsa core was not clearly visible and destructive evaluation method was used. Compression testing was done after subjecting the specimens to impact testing. Impact test results; load-time, load-deflection history and energy absorption for sandwich composites with two different cores, end grain and regular balsa were compared and they were investigated at three different impact energies. The results show that the sandwich structures with end grain core are able to withstand impact loading better than the regular balsa core because the higher stiffness of end grain core informs of sustaining higher load and higher overall energy. The results obtained from compression after impact testing show that the strengths of sandwich composites with end grain and regular balsa cores were reduced about 40% and 52%, respectively, after impact. These results were presented in terms of stress-strain curves for both damaged and undamaged specimens. Finite element analysis was conducted on the sandwich composite structure using LS-DYNA code to simulate impact test. A 3- D finite element model was developed and appropriate material properties were given to each component. The computational model was developed to predict the response of sandwich composite under dynamic loading. The experimental and finite element results were matched better for maximum load. However progressive damage accumulation could not predicted well due to lack of sophisticated material damage models in FEA codes.

  12. Sandwich mapping of schistosomiasis risk in Anhui Province, China.

    PubMed

    Hu, Yi; Bergquist, Robert; Lynn, Henry; Gao, Fenghua; Wang, Qizhi; Zhang, Shiqing; Li, Rui; Sun, Liqian; Xia, Congcong; Xiong, Chenglong; Zhang, Zhijie; Jiang, Qingwu

    2015-01-01

    Schistosomiasis mapping using data obtained from parasitological surveys is frequently used in planning and evaluation of disease control strategies. The available geostatistical approaches are, however, subject to the assumption of stationarity, a stochastic process whose joint probability distribution does not change when shifted in time. As this is impractical for large areas, we introduce here the sandwich method, the basic idea of which is to divide the study area (with its attributes) into homogeneous subareas and estimate the values for the reporting units using spatial stratified sampling. The sandwich method was applied to map the county-level prevalence of schistosomiasis japonica in Anhui Province, China based on parasitological data collected from sample villages and land use data. We first mapped the county-level prevalence using the sandwich method, then compared our findings with block Kriging. The sandwich estimates ranged from 0.17 to 0.21% with a lower level of uncertainty, while the Kriging estimates varied from 0 to 0.97% with a higher level of uncertainty, indicating that the former is more smoothed and stable compared to latter. Aside from various forms of reporting units, the sandwich method has the particular merit of simple model assumption coupled with full utilization of sample data. It performs well when a disease presents stratified heterogeneity over space. PMID:26054518

  13. Response of fiber reinforced sandwich structures subjected to explosive loading

    SciTech Connect

    Perotti, Luigi E. [California Institute of Technology, Pasadena; El Sayed, Tamer [King Abdullah University of Science and Technology (KAUST), Thuwal, Kingdom of Saudi Arabia; Deiterding, Ralf [ORNL; Ortiz, Michael [California Institute of Technology, Pasadena

    2011-01-01

    The capability to numerically simulate the response of sandwich structures to explosive loading constitutes a powerful tool to analyze and optimize their design by investigating the influence of different parameters. In order to achieve this objective, the necessary models for foam core and fiber reinforced materials in finite kinematics have been developed together with a finite element scheme which includes C1 finite elements for shells and cohesive elements able to capture the fracture propagation in composite fiber reinforced materials. This computational capability has been used to investigate the response of fiber reinforced sandwich shells to explosive loading. Based on the dissipated fracture energy resulting from these simulations, a factorial design has been carried out to assess the effect of different parameters on the sandwich shell response creating a tool for its optimization.

  14. Analysis and test of a damped composite sandwich structure

    NASA Astrophysics Data System (ADS)

    Searle, Ian R.; Martin, Thomas; Ikegami, Roy

    1996-05-01

    Composite sandwich panels are increasingly attractive structural components for modern space structures. Their light weight, high stiffness, and 'manufacturability' make them ideal for primary structure. One disadvantage of sandwich panels is the low damping, typically on the order of 0.5 percent. This problem has been addressed during the course of designing an all composite spacecraft bus. A visco-elastic treatment and a constraining layer have been applied to a composite sandwich panel. Analysis and tests were performed on the panel in both the damped, and the un-damped configuration. A five-fold increase in the panel damping was achieved, and some valuable lessons learned. These lessons, the modeling methods, test and analysis results are presented.

  15. Improvement Noise Insulation Performance of Polycarbonate Pane using Sandwich Structure

    NASA Astrophysics Data System (ADS)

    Shen, Min; Nagamura, Kazuteru; Nakagawa, Noritoshi; Okamura, Masaharu

    Polycarbonate (PC) laminates offer the possibility of designing strong and light weight panes application in automobile. However, the noise insulation performance of PC pane is worse than glass pane because of its high rate of stiffness to low weight. In this work, a new ultra-thin(less than 10mm) sandwich pane is proposed to obtain high transmission loss(TL). The sandwich structure consists of two thin laminates plates of the same PC material and a thin lightweight damping core bonded between those plates. Then TL is predicted using decoupled equations representing symmetric and anti-symmetric motions for a sandwich PC pane. The effects of various structural and material parameters on noise insulation performance are investigated with numerical examples. Numerical results show that the shear rigidity has evident effect on coincidence frequency and proposed structure has better noise insulation properties than single layer PC pane of equivalent thickness.

  16. Vibration and dynamic stability of a traveling sandwich beam

    NASA Astrophysics Data System (ADS)

    Yang, Wen-Pei; Chen, Lien-Wen; Wang, Ching-Cheng

    2005-07-01

    The vibration and dynamic stability of a traveling sandwich beam are studied using the finite element method. The damping layer is assumed to be linear viscoelastic and almost incompressible. The extensional and shear moduli of the viscoelastic material are characterized by complex quantities. Complex-eigenvalue problems are solved by the state-space method, and the natural frequencies and modal loss factors of the composite beam are extracted. The effects of stiffness and thickness ratio of the viscoelastic and constrained layers on natural frequencies and modal loss factors are reported. Tension fluctuations are the dominant source of excitation in a traveling sandwich material, and the regions of dynamic instability are determined by modified Bolotin's method. Numerical results show that the constrained damping layer stabilizes the traveling sandwich beam.

  17. Actively cooled plate fin sandwich structural panels for hypersonic aircraft

    NASA Technical Reports Server (NTRS)

    Smith, L. M.; Beuyukian, C. S.

    1979-01-01

    An unshielded actively cooled structural panel was designed for application to a hypersonic aircraft. The design was an all aluminum stringer-stiffened platefin sandwich structure which used a 60/40 mixture of ethylene glycol/water as the coolant. Eight small test specimens of the basic platefin sandwich concept and three fatigue specimens from critical areas of the panel design was fabricated and tested (at room temperature). A test panel representative of all features of the panel design was fabricated and tested to determine the combined thermal/mechanical performance and structural integrity of the system. The overall findings are that; (1) the stringer-stiffened platefin sandwich actively cooling concept results in a low mass design that is an excellent contender for application to a hypersonic vehicle, and (2) the fabrication processes are state of the art but new or modified facilities are required to support full scale panel fabrication.

  18. ['Sandwich PhD': considerations for a successful experience abroad].

    PubMed

    Salvetti, Marina de Goes; Bueno, Mariana; Gastaldo, Denise; Kimura, Amélia Fumiko; Pimenta, Cibele Andrucioli de Mattos

    2013-03-01

    International PhD internship, named "Sandwich PhD" in Brazil is an opportunity to improve research abilities, to become known in academic area and to establish and/or increase work opportunities in an international context. In this article, we describe key factors regarding the planning and development of the "Sandwich PhD" as experienced by professors and students involved in the collaboration between the School of Nursing, University of São Paulo and Lawrence S. Bloomberg Faculty of Nursing, University of Toronto, Canada. We also present the participation of PhD students' network as an alternative to the "Sandwich PhD". An international experience, when well-planned and developed correctly, promotes students' personal and professional development and favors the internationalization of Brazilian graduate programs and research groups. PMID:23781743

  19. Structural Performance of Eco-Core Sandwich Panels

    NASA Astrophysics Data System (ADS)

    Shivakumar, Kunigal; Chen, Huanchun

    Eco-Core, a fire resistant core material for sandwich composite structures developed under the US Navy (ONR) program, was used to study its performance as a sandwich beam with glass/vinyl ester face sheet. Performance of Eco-Core was compared with balsa and PVC core sandwich panels. Test specimens were designed to simulate shear, flexural, and edgewise compression loadings. These tests were conducted on Eco-Core as well as balsa and PVC sandwich composite specimens. Failure loads and modes were compared with each other and the analytical prediction. Both Eco-Core and balsa cored sandwich beams had similar failure modes in all three test conditions. In the case of transversely loaded (four-point) beams Eco-Core specimens failed by core shear for span/depth (S/d) ratio less than 4 and the failure mode changed to core tension for S/d >4. This is attributed to weak tensile strength of the core material. An expression for core tension failure load based on beam theory was derived. On the other hand, ductile materials like PVC failed by core indentation. Under edgewise compression, face sheet microbuckling and general buckling are the two potential failure modes for Eco-Core and balsa core sandwich composites. For specimen length/depth ratio L/d <7 the failure is by face sheet microbuckling, for 7 ?L/d ?13 the failure is a combination of face sheet microbuckling, debonding and buckling, and for L/d >13 the failure is by general buckling. Predictions from the existing equations agreed well with the experiment for both core materials. For PVC core, wrinkling/shear buckling and general buckling are the potential failure modes. For L/d ?8.5 the failure is wrinkling and for L/d >8.5 the failure is general buckling.

  20. The extended high-order sandwich panel theory

    NASA Astrophysics Data System (ADS)

    Phan, Catherine N.

    The contribution of this thesis is an extended high-order sandwich panel theory (EHSAPT) for sandwich beams/wide panels, in which the axial stresses are taken into account as well as the shear and transverse normal stresses in the core, and its validation. The general nonlinear formulation of EHSAPT is given in Chapter 2. Validation of the present theory is made by comparison with elasticity solutions and experimental data. The accuracy of EHSAPT is assessed for the standard class of structural analysis problems which include: static loading, static instability (global buckling and wrinkling), free vibrations, and dynamic loading. In Chapter 3 the static response to a half-sine distributed load applied to the top face sheet of a simply supported sandwich beam/wide panel is solved. Validation is made with elasticity, and Euler-Bernoulli beam, first order shear deformation theory, and HSAPT were also included for comparison. In Chapter 4 the static global buckling critical load is determined for a simply supported sandwich beam/wide panel under edgewise loading. Validation is made with elasticity, and Allen's formula and HSAPT are included for comparison. In Chapter 5 the static wrinkling critical load of a simply supported sandwich beam/wide panel is investigated. Validation includes comparison with elasticity, experimental results reported in literature, and recently acquired experimental results. Results using Hoff-Mautner's wrinkling formula and HSAPT are also shown. In Chapter 6 the free vibrations of a simply supported sandwich beam/wide panel are explored, and the predicted antisymmetric and symmetric natural frequencies are compared to experimental results found in the literature and with elasticity. The last validation of EHSAPT is made for the dynamic response to a half-sine distributed load with an exponential time decay applied to the top face sheet of a simply supported sandwich beam. Results are compared with elasticity. The response from using HSAPT is also shown. Chapter 8 presents results from an impact experiment upon a sandwich panel and comparison with EHSAPT. Finally, Chapter 9 gives overall comments on the future work that can be done with EHSAPT.

  1. Home/EU Undergraduate Full time/Sandwich 120 credits 3,145 1,255

    E-print Network

    Variable Fee Old System Students Part Time Course Codes Home/EU Undergraduate Full time/Sandwich and Part Time students 10 Overseas Full Time/Sandwich 200 * Overseas Part time Refer to Student Life Office

  2. Active Vibration Suppression of Sandwich Beams using Piezoelectric Shear Actuators: Experiments and

    E-print Network

    Vel, Senthil

    Active Vibration Suppression of Sandwich Beams using Piezoelectric Shear Actuators: Experiments assessment of the vibration suppression of smart structures using piezoelectric shear actuators. Experimental of the sandwich beam. Active vibration suppression is achieved using either positive position feedback or strain

  3. Two types of novel tetra-iron substituted sandwich-type arsenotungastates with supporting lanthanide pendants.

    PubMed

    Chen, Lijuan; Zhang, Fang; Ma, Xing; Luo, Jie; Zhao, Junwei

    2015-07-01

    Two classes of novel tetra-iron substituted sandwich-type arsenotungastates (ATs) with supporting lanthanide (Ln) pendants KNa2 [Ln(H2O)7][Fe4(H2O)10(B-?-AsW9O33)2]·21H2O [Ln = La(III) (), Pr(III) (), Nd(III) (), Sm(III) ()] and [Ln(H2O)8]2[Fe4(H2O)8(l-thr)2(B-?-AsW9O33)2]·20H2O [Ln = La(III) (), Pr(III) (), Nd(III) (), Sm(III) (), Eu(III) (), Gd(III) (), Tb(III) (), Dy(III) (), Er(III) ()] (l-thr = l-threonine) have been synthesized by the hydrothermal reaction of the [As2W19O67(H2O)](14-) precursor with Fe(3+) cations and Ln(3+) cations in the presence of l-thr or l-leucine and l-alanine, and further characterized by elemental analyses, IR spectra and single-crystal X-ray diffraction. Structural analyses indicate that display the inorganic 2-D sheet architecture constructed from tetra-iron sandwiched AT [Fe4(H2O)10(B-?-AsW9O33)2](6-) fragments by bridging [Ln(H2O)7](3+) cations whereas the molecular structures of the isostructural consist of an organic-inorganic hybrid tetra-iron substituted sandwich-type AT [Fe4(H2O)8(l-thr)2(B-?-AsW9O33)2](6-) fragment and two pendant [Ln(H2O)8](3+) cations. As far as we know, represent the rare inorganic 2-D extended ATs based on transition-metal substituted sandwich-type polyoxometalate units and Ln linkers and are the first Fe-Ln heterometallic ATs with amino acid ligands. The solid state photoluminescence (PL) measurements of and have been performed at room temperature. The PL emission of is mainly derived from the characteristic (5)D0 ? (7)F2 (J = 4-0) transitions of the Eu(III) cations whereas the PL behavior of stems from the common contribution of the (5)D4 ? (7)FJ (J = 5-3) transitions of the Tb(III) ions and oxygen-to-metal (O ? W) charge-transfer transitions of AT segments. The thermogravimetric (TG) analyses of and have been investigated. PMID:26066321

  4. STRAIN MONITORING AND DETECTION OF BARELY VISIBLE DAMAGE IN FOAM-CORE SANDWICH STRUCTURES

    E-print Network

    Paris-Sud XI, Université de

    STRAIN MONITORING AND DETECTION OF BARELY VISIBLE DAMAGE IN FOAM-CORE SANDWICH STRUCTURES Juho To detect indentation or low-velocity impact induced damage in foam-core sandwich structures, a fiber into the sandwich structures and the strains are measured using a Rayleigh scattering based monitoring system which

  5. Dynamic Ham-Sandwich Cuts of Convex Polygons in the Plane Timothy Abbott

    E-print Network

    Dynamic Ham-Sandwich Cuts of Convex Polygons in the Plane Timothy Abbott Erik D. Demaine Martin L structure for dynami- cally maintaining a ham-sandwich cut of two non- overlapping convex polygons in the plane. Given two non-overlapping convex polygons P1 and P2 in the plane, the ham-sandwich cut of P1

  6. Effect of core topology on projectile penetration in hybrid aluminum/alumina sandwich structuresq

    E-print Network

    Wadley, Haydn

    Effect of core topology on projectile penetration in hybrid aluminum/alumina sandwich structuresq H 2013 Keywords: Sandwich panels Ballistics Cellular structures a b s t r a c t A series of hybrid sandwich structures were fabricated by shrink-fitting precision-ground prisms of alumina (CoorsTek grade AD

  7. Dynamic compression of metallic sandwich structures during planar impulsive loading in water

    E-print Network

    Wadley, Haydn

    Dynamic compression of metallic sandwich structures during planar impulsive loading in water K Accepted 7 May 2009 Available online 21 May 2009 Keywords: Sandwich panels Underwater impulsive loading response of rigidly supported stainless steel sandwich panels subject to a planar impulsive load in water

  8. Bounded Degree Interval Sandwich Problems \\Lambda Haim Kaplan y Ron Shamir z

    E-print Network

    Kaplan, Haim

    Bounded Degree Interval Sandwich Problems \\Lambda Haim Kaplan y Ron Shamir z Abstract The problems of Interval Sandwich (IS) and Intervalizing Colored Graphs (ICG) have received a lot of attention recently: Interval Sandwich (IS): INSTANCE: A triple S = (V; E; F ), where V is a set of vertices, and E and F

  9. Metal sandwich plates subject to intense air shocks Ashkan Vaziri, John W. Hutchinson *

    E-print Network

    Hutchinson, John W.

    Metal sandwich plates subject to intense air shocks Ashkan Vaziri, John W. Hutchinson * Division for plates subject to high intensity air shocks are employed to assess the performance of all-metal sandwich­structure interaction in the design and assessment of sandwich plates subject to water shocks. Square honeycomb

  10. Performance of metallic honeycomb-core sandwich beams under shock loading

    E-print Network

    Hutchinson, John W.

    Performance of metallic honeycomb-core sandwich beams under shock loading H.J. Rathbun a , D honeycomb core sandwich and solid monolithic beams have been subjected to high-pressure, short. The experiments have been designed to achieve two objectives: (i) to demonstrate the benefits of sandwich

  11. Quantitation of Rat Lacrimal Secretion: a Novel Sandwich ELISA with High Sensitivity

    E-print Network

    Quantitation of Rat Lacrimal Secretion: a Novel Sandwich ELISA with High Sensitivity SANDHYA SANGHI®cantly on current methods, a rat- and mouse-speci®c sandwich ELISA was developed. For this purpose, chickens, and subsequently optimized for use in a sandwich ELISA. Both antisera detected a wide range of different rat tear

  12. Measurement of relevant elastic and damping material properties in sandwich thick-plates

    E-print Network

    Paris-Sud XI, Université de

    Measurement of relevant elastic and damping material properties in sandwich thick-plates Marc R to measure relevant elastic and damping properties of the constituents of a sandwich structure, possibly) by comparing the results on different plates made of the same sandwich material. Key words: Elasticity

  13. Ham-Sandwich Cuts for Abstract Order Types Stefan Felsner1

    E-print Network

    Felsner, Stefan

    Ham-Sandwich Cuts for Abstract Order Types Stefan Felsner1 and Alexander Pilz2 1 Institut f Technology, Graz University of Technology, Austria, apilz@ist.tugraz.at. Abstract. The linear-time ham-sandwich for the mentioned sub-algorithm. This yields a linear-time ham-7 sandwich cut algorithm even in our restricted

  14. Experimental characterization and numerical simulations of a syntactic-foam/glass-bre composite sandwich

    E-print Network

    Corigliano, Alberto

    sandwich Alberto Corigliano a, *, Egidio Rizzi b , Enrico Papa a a Dipartimento di Ingegneria Strutturale results of an experimental and numerical investigation on the mechanical behaviour of a composite sandwich primarily designed for naval engineering applications. The skins of the sandwich are made of glass

  15. Compressive response of glass fiber composite sandwich structures A.J. Malcom a,

    E-print Network

    Wadley, Haydn

    Compressive response of glass fiber composite sandwich structures A.J. Malcom a, , M.T. Aronson b reinforcement B. Mechanical properties a b s t r a c t Sandwich panels with crushable foam cores have attracted absorbing, glass fiber composite sandwich structure and explore it is through thickness (out

  16. arXiv:1108.5604v2 The asymmetric sandwich theorem

    E-print Network

    Simons, Stephen

    arXiv:1108.5604v2 [math.FA] 22 Sep 2011 The asymmetric sandwich theorem S. Simons Department the asymmetric sandwich theorem, a generalization of the Hahn{Banach theorem. As applications, we derive various of linear functionals in various situations. The main results of Section 2 are the asymmetric sandwich

  17. On The So-Called "Huber Sandwich Estimator" and "Robust Standard Errors" David A. Freedman

    E-print Network

    Sekhon, Jasjeet S.

    On The So-Called "Huber Sandwich Estimator" and "Robust Standard Errors" by David A. Freedman Abstract The "Huber Sandwich Estimator" can be used to estimate the variance of the MLE when the underlying, and robustification is unlikely to help much. On the other hand, if the model is seriously in error, the sandwich may

  18. The impulsive response of sandwich beams: analytical and numerical investigation of regimes of behaviour

    E-print Network

    Fleck, Norman A.

    The impulsive response of sandwich beams: analytical and numerical investigation of regimes the impulsive response of sandwich beams based on the relative time-scales of core compression and the bending/stretching response of the sandwich beam. It is shown that an overlap in time scales leads to a coupled response

  19. Mechanical behavior and failure of composite pyramidal truss core sandwich columns

    E-print Network

    Vaziri, Ashkan

    Mechanical behavior and failure of composite pyramidal truss core sandwich columns Jian Xiong a of pyramidal truss core sandwich panels made of carbon fiber composite under axial compression made of fiber reinforced composite. The response of the sandwich panels under axial compression

  20. On the computation of interface stresses by finite elements for sandwich materials

    E-print Network

    Paris-Sud XI, Université de

    On the computation of interface stresses by finite elements for sandwich materials Vincent Manet to compute interface stresses of a sandwich structure. The robustness of the method is terms of convergence emphasized. Key words: sandwich structure, interface stresses, post-processing, local Reissner 1 Introduction

  1. Metallic sandwich panels subjected to multiple intense shocks Hamid Ebrahimi, Ashkan Vaziri

    E-print Network

    Vaziri, Ashkan

    Metallic sandwich panels subjected to multiple intense shocks Hamid Ebrahimi, Ashkan Vaziri Available online 11 January 2013 Keywords: Sandwich panels Honeycomb core Folded plate core Multiple shocks Ductility Dynamic response a b s t r a c t The mechanical response and fracture of metal sandwich panels

  2. ETUDE ET MODELISATION DU COMPORTEMENT ELASTIQUE D'UNE STRUCTURE SANDWICH DE TYPE CARTON ONDULE

    E-print Network

    Paris-Sud XI, Université de

    ETUDE ET MODELISATION DU COMPORTEMENT ELASTIQUE D'UNE STRUCTURE SANDWICH DE TYPE CARTON ONDULE sandwich de type carton ondulé. La démarche adoptée est double. Elle aborde le problème d'une part, d. ABSTRACT The main goal of this study is to determine the homogenised properties of sandwich structure

  3. Structural performance of near-optimal sandwich panels with corrugated cores

    E-print Network

    Zok, Frank

    Structural performance of near-optimal sandwich panels with corrugated cores L. Valdevit a , Z. Wei of steel sandwich panels with corrugated cores in both transverse and longitudinal loading orientations has. Keywords: Lightweight structures; Sandwich panels; Corrugated core; Imperfection sensitivity 1

  4. On the computational complexity of Ham-Sandwich cuts, Helly sets, and related

    E-print Network

    Boyer, Edmond

    On the computational complexity of Ham-Sandwich cuts, Helly sets, and related problems Christian and certain decision versions of the ham-sandwich cut problem are W[1]-hard (and NP-hard) if the dimension, combinatorial geometry, ham-sandwich cuts, parameterized complexity Digital Object Identifier 10.4230/LIPIcs

  5. Bayesian sandwich posteriors for pseudo-true parameters Peter Hoff1

    E-print Network

    Washington at Seattle, University of

    Bayesian sandwich posteriors for pseudo-true parameters Peter Hoff1 and Jon Wakefield1 Technical a misspecified model can provide consistent estimation for this parameter. Furthermore, the well-known sandwich performance. With this in mind, we present a Bayesian sandwich posterior distribution, whose likelihood

  6. Riesz spaces, integration and sandwich Abstract -Some definitions of integrals are introduced, for functions

    E-print Network

    Boccuto, Antonio

    Riesz spaces, integration and sandwich theorems A. BOCCUTO Abstract - Some definitions of integrals-type convergence theorems are proved. Finally, some sandwich-type and Hahn-Banach type theorems are given, sandwich theorems. A.M.S. Classification: 28A70 - 43A07 1. Introduction. In the literature, there are many

  7. Finite element analysis of the dynamic response of clamped sandwich beams subject to shock loading

    Microsoft Academic Search

    X. Qiu; V. S. Deshpande; N. A. Fleck

    2003-01-01

    The finite element (FE) method is employed to analyse the response of clamped sandwich beams subject to shock loadings. Pressure versus time histories representative of shock loadings are applied uniformly to the outer face of the sandwich beam; an impulse applied uniformly to the outer face of the sandwich beam is shown to model adequately shock loadings. Material elasticity and

  8. Dynamic Ham-Sandwich Cuts in the Plane Timothy G. Abbott

    E-print Network

    Dynamic Ham-Sandwich Cuts in the Plane Timothy G. Abbott Michael A. Burr Timothy M. Chan§ Erik D Seyboth¶ Vincent Yeung Abstract We design efficient data structures for dynamically maintaining a ham-sandwich- sandwich cut is a line that simultaneously bisects the cardinality of both point sets. For general point

  9. Deformation and Failure Modes of I-Core Sandwich Structures Subjected to Underwater Impulsive Loads

    E-print Network

    Espinosa, Horacio D.

    Deformation and Failure Modes of I-Core Sandwich Structures Subjected to Underwater Impulsive Loads modes of sandwich structures when subjected to impulsive blast loading. In particular, performance distribution of the mass per unit area in the design of sandwich structures is investigated by comparing

  10. Sandwich masking eliminates both visual awareness of faces and face-specific brain activity through a

    E-print Network

    Sandwich masking eliminates both visual awareness of faces and face-specific brain activity through a sandwich-masking paradigm, a commonly used approach for attenuating conscious awareness of visual stimulus without awareness. The electrophysiological measures revealed that the sandwich masking abolished

  11. Impedance of a ferromagnetic sandwich strip A. Sukstanskii, V. Korenivski, and A. Gromov

    E-print Network

    Haviland, David

    Impedance of a ferromagnetic sandwich strip A. Sukstanskii, V. Korenivski, and A. Gromov-layer sandwich, consisting of two metallic ferromagnetic layers separated by a non-magnetic conductive layer, including the ferromagnetic resonance. Two sandwich strip structures are analyzed, both having thickness

  12. Performance of sandwich plates with truss cores Nathan Wicks *, John W. Hutchinson

    E-print Network

    Hutchinson, John W.

    Performance of sandwich plates with truss cores Nathan Wicks *, John W. Hutchinson Division in revised form 30 January 2003 Abstract Sandwich plates with truss cores fashioned from straight struts have to opportunities afforded by their open architecture, the truss core sandwich plates meet or exceed the load

  13. Additivity of Cation-Interactions: An ab Initio Computational Study on -Cation-Sandwich Complexes

    E-print Network

    Sussman, Joel L.

    Additivity of Cation- Interactions: An ab Initio Computational Study on -Cation- Sandwich Complexes- sandwiches are the sums of the two corresponding TMA- systems. The contribution of electron correlation- sandwiches and to estimate their binding energies. Morokuma decomposition analysis on the binding energy

  14. Compression and impact testing of two-layer composite pyramidal-core sandwich panels

    E-print Network

    Vaziri, Ashkan

    Compression and impact testing of two-layer composite pyramidal-core sandwich panels Jian Xiong a.e., with different relative densities) were fabricated: 1.25%, 1.81%, and 2.27%. Two-layer sandwich panels Sandwich panels with low-density cores have attracted signifi- cant interest as multifunctional structures

  15. Impact testing and simulation of composite sandwich structures for civil transportation

    Microsoft Academic Search

    L Torre; J. M Kenny

    2000-01-01

    The impact response of sandwich panels with an improved structure to increase their impact resistance is investigated herein. In order to compare the impact performance of sandwich structures, a specific and instrumented ball drop tester was designed and developed. Two different sandwich structures are analyzed: the first type is a classical structure composed by a glass fiber-polyester matrix-composite skin and

  16. A multifunctional heat pipe sandwich panel structure Douglas T. Queheillalt a,*, Gerardo Carbajal b

    E-print Network

    Wadley, Haydn

    A multifunctional heat pipe sandwich panel structure Douglas T. Queheillalt a,*, Gerardo Carbajal b by multifunctionally utilizing the core as a heat pipe sandwich panel. Its interior consists of a 6061 aluminum was used to guide the design of the heat pipe sandwich panel. We describe the results of a series

  17. Manufacturing and testing of a CFRC sandwich cylinder with Kagome cores

    Microsoft Academic Search

    Hualin Fan; Daining Fang; Liming Chen; Zheng Dai; Wei Yang

    2009-01-01

    Filament winding and twice co-curing processes were proposed to make a carbon fiber reinforced composite (CFRC) sandwich cylinder with Kagome cores. Axial compression was carried out to reveal the stiffness and load capacity of the fabricated sandwich cylinder. Compared with the stiffened cylinder with similar dimensions and mass, the sandwich cylinder is shown to be stiffer and stronger by several

  18. Large Deflection of Geometrically Asymmetric Metal Foam Core Sandwich Beam Transversely Loaded by a Flat Punch

    Microsoft Academic Search

    QINGHUA QIN; JIANXUN ZHANG; ZHENGJIN WANG; T. J. WANG

    2011-01-01

    The objective of this work is to study the large deflection of geometrically asymmetric metal foam core sandwich beam under transverse loading by a fiat punch. A yield criterion is proposed for geometrically asymmetric metal foam core sandwich structures, and then analytical solution for the large deflection of a fully clamped slender sandwich beam is obtained, in which the interaction

  19. Co-cure bonding method for foam core composite sandwich manufacturing

    Microsoft Academic Search

    Chang Sup Lee; Dai Gil Lee; Je Hoon Oh

    2004-01-01

    The conventional manufacturing of composite sandwich structures is completed by adhesive joining separately prepared composite faces to cores. The joining process during sandwich fabrication is most difficult process, which requires strict quality control. The joining process can be eliminated when the sandwich structures are manufactured by co-cure method inside a mold using the large coefficient of thermal expansion (CTE) of

  20. Failure Modes of Foam Core Sandwich Beams under Static and Impact Loads

    Microsoft Academic Search

    Tae Seong Lim; Chang Sup Lee; Dai Gil Lee

    2004-01-01

    In recent times, sandwich structures have been widely used in load bearing structures due to their high specific stiffness and high specific strength. Some sandwich structures, such as those used in high speed transportations, are required to have high impact energy absorption characteristics also. Since sandwich structures can fail in various modes, in this article, the static failure modes and

  1. Compression Response of a Sandwich Fuselage Keel Panel With and Without Damage

    NASA Technical Reports Server (NTRS)

    McGowan, David M.; Ambur, Damodar R.

    1997-01-01

    Results are presented from an experimental and analytical study of a sandwich fuselage keel panel with and without damage. The fuselage keel panel is constructed of graphite-epoxy skins bonded to a honeycomb core, and is representative of a highly loaded fuselage keel structure. The face sheets of the panel contain several terminated or dropped plies along the length of the panel. The results presented provide a better understanding of the load distribution in damaged and undamaged thick-face-sheet composite sandwich structure with dropped plies and of the failure mechanisms of such structure in the presence of low-speed impact damage and discrete-source damage. The impact-damage condition studied corresponds to barely visible impact damage (BVID), and the discrete-source damage condition studied is a notch machined through both face sheets. Results are presented from an impact-damage screening study conducted on another panel of the same design to determine the impact energy necessary to inflict BVID on the panel. Results are presented from compression tests of the panel in three conditions: undamaged; BVID in two locations; and BVID in two locations and a notch through both face sheets. Surface strains in the face sheets of the undamaged panel and the notched panel obtained experimentally are compared with finite element analysis results. The experimental and analytical results suggest that for the damage conditions studied, discrete-source damage influences the structural performance more than BVID.

  2. Vibration and acoustic properties of honeycomb sandwich structures subject to variable incident plane-wave angle pressure loads

    NASA Astrophysics Data System (ADS)

    Yan, Jiaxue

    Honeycomb structures are widely used in many areas for their material characteristics such as high strength-to-weight ratio, stiffness-to-weight, sound transmission, and other properties. Honeycomb structures are generally constructed from periodically spaced tessellations of unit cells. It can be shown that the effective stiffness and mass properties of honeycomb are controlled by the local geometry and wall thickness of the particular unit cells used. Of particular interest are regular hexagonal (6-sided) honeycomb unit cell geometries which exhibit positive effective Poisson's ratio, and modified 6-sided auxetic honeycomb unit cells with Poisson's ratio which is effectively negative; a property not found in natural materials. One important honeycomb meta-structure is sandwich composites designed with a honeycomb core bonded between two panel layers. By changing the geometry of the repetitive unit cell, and overall depth and material properties of the honeycomb core, sandwich panels with different vibration and acoustic properties can be designed to shift resonant frequencies and improve intensity and Sound Transmission Loss (STL). In the present work, a honeycomb finite element model based on beam elements is programmed in MATLAB and verified with the commercial finite element software ABAQUS for frequency extraction and direct frequency response analysis. The MATLAB program was used to study the vibration and acoustic properties of different kinds of honeycomb sandwich panels undergoing in-plane loading with different incident pressure wave angles and frequency. Results for the root mean square intensity IRMS based on normal velocity on the transmitted side of the panel measure vibration magnitude are reported for frequencies between 0 and 1000 Hz. The relationship between the sound transmission loss computed with ABAQUS and the inverse of the intensity of surface velocity is established. In the present work it is demonstrated that the general trend between the STL pressure response and the inverted intensity metric have similar response characteristics over both the stiffness frequency region and the resonance frequency region, showing that an increase in IRMS corresponds to a decrease in STL. The ABAQUS model was used to verify the MATLAB program for natural frequencies and mode shapes, and to compute the STL on the top surface of the honeycomb sandwich structure. Resonant peaks in the frequency response of intensity and STL are identified with natural frequencies and mode shapes of the honeycomb sandwich structure. A unique feature of this research is the ability to apply the time-harmonic acoustic pressure as a load on the transmitting surface of the honeycomb sandwich panel with variable incident angle ranging between 0° to 90°. When the incident angle is nonzero, the pressure load is complex valued, with sinusoidal distribution, and frequency dependent. The finite element implementation of the complex-valued variable incident pressure distribution is programmed in MATLAB to give complete control of the angle, frequency and distribution. Commercial finite element software such as ABAQUS has limited ability to directly apply frequency dependent and distributed real and imaginary pressure distributions in a direct steady state frequency analysis over a large number of frequency evaluations. In the present work, IRMS results for a family of honeycomb sandwich panels with systematic increment in internal cell wall angle, subject to incremental changes in incident angle pressure loads are studied and compared. Results show that for honeycomb sandwich panels with both positive and negative internal cell wall angle, on average, intensity for the nonzero incident angles is higher than the 0° normal incident angle. For the honeycomb sandwich panels with positive internal angle, the intensity consistently increases with larger nonzero incident angles. Furthermore, under the same incident angle pressure load, the intensity of honeycomb panel with positive internal angle is consistently larger than honeycomb panels with

  3. Star cell type core configuration for structural sandwich materials

    DOEpatents

    Christensen, Richard M. (Danville, CA)

    1995-01-01

    A new pattern for cellular core material used in sandwich type structural materials. The new pattern involves star shaped cells intermixed with hexagonal shaped cells. The new patterned cellular core material includes star shaped cells interconnected at points thereof and having hexagonal shape cells positioned adjacent the star points. The new pattern allows more flexibility and can conform more easily to curved shapes.

  4. Fabrication and structural performance of periodic cellular metal sandwich structures

    Microsoft Academic Search

    Haydn N. G. Wadley; Norman A. Fleck; Anthony G. Evans

    2003-01-01

    Metallic sandwich panels with periodic, open-cell cores are important new structures, enabled by novel fabrication and topology design tools. Fabrication protocols based on the sheet forming of trusses and shell elements (egg-boxes) as well as textile assembly have allowed the manufacture of robust structures by inexpensive routes. Topology optimization enables control of failure mechanisms at the truss length scale, leading

  5. The Response of Metallic Sandwich Panels to Water Blast

    Microsoft Academic Search

    Yueming Liang; Alexander V. Spuskanyuk; Shane E. Flores; David R. Hayhurst; John W. Hutchinson; Robert M. McMeeking; Anthony G. Evans

    2007-01-01

    Metallic sandwich panels subject to underwater blast respond in a manner dependent on the relative time scales for core crushing and water cavitation. This article examines the response at impulses representative of an (especially relevant) domain: wherein the water cavitates before the core crushes. Three core topologies (square honeycomb, I-core, and corrugated) have been used to address fundamental issues affecting

  6. A comparative study of impulse-resistant metal sandwich plates

    Microsoft Academic Search

    Zhenyu Xue; John W. Hutchinson

    2004-01-01

    The performance of metal sandwich plates under impulsive blast loads is compared to that of solid plates made of the same material and having the same weight. Three core geometries are considered: pyramidal truss, square honeycomb and folded plate. Plates of infinite length and clamped along their sides are subject to uniform impulsive load. The momentum impulse is applied to

  7. Preliminary assessment of sandwich plates subject to blast loads

    Microsoft Academic Search

    Zhenyu Xue; John W. Hutchinson

    2003-01-01

    The question motivating the present study is whether metal sandwich plates with sufficiently strong cores are able to sustain substantially larger blast loads than monolithic solid plates of the same material and total mass. Circular plates clamped at their edges are considered under blast loads large enough to produce substantial deflections. The material is elastic–perfectly plastic. Material strain-rate dependence and

  8. The Workplace Supervision of Sandwich Degree Placement Students.

    ERIC Educational Resources Information Center

    Saxton, Judy; Ashworth, Peter

    1990-01-01

    Discusses the role of the supervisor who is directly responsible for a sandwich placement student in the workplace. Identifies and examines seven supervisory styles, highlights ways in which effective workplace supervision can enrich placement experience, and discusses placement management guidelines. (JOW)

  9. A Graduate Sandwich Programme for Practising Administrators: A Canadian Experiment.

    ERIC Educational Resources Information Center

    Murphy, Peter J.

    1983-01-01

    Describes the graduate cooperative program, or sandwich course, that offers administrators the learning experiences they need to induce educational and social change, to develop effective skills for anticipating and managing the future, to deal with political and emotional groups, and to study issues in broader terms. (JOW)

  10. Low velocity impact damage in composite sandwich beams

    Microsoft Academic Search

    C. T. Sun

    1996-01-01

    Impact damage in sandwich beams consisting of graphite\\/epoxy face sheets and Rohacell foam core was investigated. Low velocity impact tests were conducted to investigate damage mechanisms and damage modes in the face sheet and the core. The major modes of failure included local ’yielding‘ of the core, matrix cracking and delamination in the face laminate. A finite element analysis was

  11. Geometrically-exact sandwich shells: The static case

    Microsoft Academic Search

    L. Vu-Quoc; H. Deng; X. G. Tan

    2000-01-01

    The present formulation offers a general method for analyzing the static response of geometrically-exact sandwich shells undergoing large deformation. The layer directors at a point in the reference surface are connected to each other by universal joints, and form a chain of rigid links. Finite rotations of the directors in every layer are allowed, with shear deformation independently accounted for

  12. Emission imaging of AP\\/HTPB propellant sandwich combustion

    Microsoft Academic Search

    B. T. Chorpening; M. Q. Brewster

    2002-01-01

    Ultraviolet emission imaging (305-315 nm) was used to study the combustion of sandwiches of ammonium perchlorate (AP) and hydroxyl-terminated polybutadiene (HTPB) in nitrogen at pressures up to 32 atm, with binder layers from 50 to 450 µm in thickness. The emission imaging was combined with a novel backlighting technique to allow determination of the corresponding surface shape during combustion. The

  13. Modular container assembled from fiber reinforced thermoplastic sandwich panels

    DOEpatents

    Donnelly, Mathew William (Edgewood, NM); Kasoff, William Andrew (Albuquerque, NM); Mcculloch, Patrick Carl (Irvine, CA); Williams, Frederick Truman (Albuquerque, NM)

    2007-12-25

    An improved, load bearing, modular design container structure assembled from thermoformed FRTP sandwich panels in which is utilized the unique core-skin edge configuration of the present invention in consideration of improved load bearing performance, improved useful load volume, reduced manufacturing costs, structural weight savings, impact and damage tolerance and repair and replace issues.

  14. Pulsed terahertz inspection of non-conducting sandwich composites

    NASA Astrophysics Data System (ADS)

    Lopato, P.; Chady, T.

    2013-01-01

    Pulsed terahertz inspection enables accurate, contactless and safe for operating personnel evaluation of non-conducting structures. In this paper we present results of pulsed terahertz testing of various sandwich composite structures incorporating glass and basalt fibers based skin materials and spherecore and balsa wood based core materials. Various Time-Frequency Distributions (TFD) are utilized in order to obtain most valuable defects response.

  15. Cyclodextrin Cuprate Sandwich-Type Complexes Abdulaziz A. Bagabas,*,,

    E-print Network

    Cyclodextrin Cuprate Sandwich-Type Complexes Abdulaziz A. Bagabas,*,, Marco Frasconi, Julien Iehl on -cyclodextrin (-CD) and metal ions (Cu2+ , Li+ , Na+ , and Rb+ ), have been prepared in aqueous and alkaline+ complex, coordinative bonding involving the Rb+ ions leads to the formation of an extended two

  16. A sandwich ELISA to detect VHSV and IPNV in turbot

    Microsoft Academic Search

    M. Vázquez Brañas; J. Coll Morales; A. Estepa

    1994-01-01

    The recent demonstration that reared turbot (Scophthalmus maximus L) is a natural host for salmonid rhabdoviruses has made their rapid detection relevant to these fish species. A unique protocol to select and use non-competitive monoclonal antibodies (Mabs) for two high-sensitivity sandwich ELISAs has been developed to detect both infectious pancreatic necrosis virus (IPNV) and viral haemorrhagic septicaemia virus (VHSV) in

  17. Crack path in foam cored DCB sandwich fracture specimens

    Microsoft Academic Search

    L. A. Carlsson; R. C. Matteson; F. Aviles; D. C. Loup

    2005-01-01

    A simple laminated beam analysis is presented for analysis of the propagation path of a core crack in symmetric and unsymmetric double cantilever beam (DCB) sandwich fracture specimens with a polymer foam core. The analysis determines the sign of shear stress ahead of the crack tip from the discontinuity of bending strain in the legs of the DCB specimen, and

  18. Undergraduate Sandwich Placements: a fresh look at skills

    Microsoft Academic Search

    Ian Winfield; Nick Ellis

    1993-01-01

    This paper chronicles the design and delivery of a course preparing Business Studies Sandwich undergraduates to find and undertake a one year supervised placement period. The paper describes both the development of specific job?getting skills and the process of preparing students for the placement experience itself.

  19. Fracture properties of high performance carbon foam sandwich structures

    Microsoft Academic Search

    G. Reyes; S. Rangaraj

    2011-01-01

    This paper investigates the fracture properties of high performance sandwich structures based on tough carbon fiber reinforced polyetheretherketone (PEEK) skins bonded to a carbon foam core. Single cantilever beam tests on pre-cracked samples indicated that an excellent level of adhesion can be achieved between the skin and core materials. In all specimens, the crack propagated within the carbon foam providing

  20. Novel design of foam core junctions in sandwich panels

    Microsoft Academic Search

    E. Bozhevolnaya; A. Lyckegaard; O. T. Thomsen

    2008-01-01

    An improved design of core junctions in sandwich panels\\/beams is proposed. The improved\\/novel design consists of a specific geometrical shaping of the boundary of the adjoined core materials, which substantially diminishes the local stress concentrations at core junctions subjected to transverse shear loading. Two groups of the beams with conventional butt junctions and modified (spline shaped) junctions are manufactured and

  1. Carbon Foam Core Composite Sandwich Beams: Flexure Response

    Microsoft Academic Search

    M. D. Sarzynski; O. O. Ochoa

    2005-01-01

    The possibility of utilizing an open-cell carbon foam in structural applications is assessed through integrated testing and computational analysis. The structural elements considered are sandwich beams with carbon-epoxy laminate face sheets and carbon foam core subjected to bending loads. The primary damage mode observed is the formation of shear cracks in the carbon foam core at a measured axial strain

  2. Size effects in metallic foam core sandwich beams

    Microsoft Academic Search

    O Kesler; L. J Gibson

    2002-01-01

    Foams exhibit size effects: if the specimen dimensions are of the same order as the cell size, the moduli and strength depend on specimen size. Metallic foams have particularly large cells (typically 2–20 mm), potentially giving rise to size effects when they are used in sandwich beams. Previous studies have shown that the shear strength of metallic foams bonded to

  3. Damage Tolerance of Sandwich Plates With Debonded Face Sheets

    NASA Technical Reports Server (NTRS)

    Sankar, Bhavani V.

    2001-01-01

    A nonlinear finite element analysis was performed to simulate axial compression of sandwich beams with debonded face sheets. The load - end-shortening diagrams were generated for a variety of specimens used in a previous experimental study. The energy release rate at the crack tip was computed using the J-integral, and plotted as a function of the load. A detailed stress analysis was performed and the critical stresses in the face sheet and the core were computed. The core was also modeled as an isotropic elastic-perfectly plastic material and a nonlinear post buckling analysis was performed. A Graeco-Latin factorial plan was used to study the effects of debond length, face sheet and core thicknesses, and core density on the load carrying capacity of the sandwich composite. It has been found that a linear buckling analysis is inadequate in determining the maximum load a debonded sandwich beam can carry. A nonlinear post-buckling analysis combined with an elastoplastic model of the core is required to predict the compression behavior of debonded sandwich beams.

  4. Damage Tolerance of Sandwich Plates with Debonded Face Sheets

    NASA Technical Reports Server (NTRS)

    Avery, John L., III; Sankar, Bhavani V.

    1998-01-01

    Axial compression tests were performed on debonded sandwich composites made of graphite/epoxy face-sheets and aramid fiber honeycomb core. The sandwich beams were manufactured using a vacuum baccrin2 process. The face-sheet and the sandwich beam were co-cured. Delamination between one of the face sheets and the core was introduced by using a Teflon layer during the curing process. Axial compression tests were performed to determine the ultimate load carrying capacity of the debonded beams. Flatwise tension tests and Double Cantilever Beam tests were performed to determine. respectively, the strength and fracture toughness of the face-sheet/core interface. From the test results semi-empirical formulas were derived for the fracture toughness and ultimate compressive load carrying capacity in terms of the core density. core thickness. face-sheet thickness and debond length. Four different failure modes and their relation to the structural properties were identified. Linear buckling analysis was found to be inadequate in predicting the compressive load carrying capacity of the debonded sandwich composites.

  5. Electronic and optical properties of metal-nanoparticle filled graphene sandwiches

    NASA Astrophysics Data System (ADS)

    Zaniewski, Anna M.; Schriver, Maria; Gloria Lee, J.; Crommie, M. F.; Zettl, A.

    2013-01-01

    We sandwich gold nanoparticles between graphene sheets and contrast the electronic and optical properties of these hybrid structures to those of single layer graphene with and without gold nanoparticle overlayers, and laminated unfilled double layers. Undecorated graphene has the highest sheet resistance while filled sandwiches have the lowest. The optical extinction spectrum for sandwiches is redshifted and broadened compared to decorated single layer graphene. We also find that the presence of gold nanoparticles in sandwiches shifts the work function relative to unfilled double-layer graphene. The low sheet resistance and favorable optical properties of metal-filled sandwiches make them attractive candidates for optoelectronic applications.

  6. Compressive and shear buckling analysis of metal matrix composite sandwich panels under different thermal environments

    SciTech Connect

    Ko, W.L.; Jackson, R.H.

    1993-06-01

    Combined inplane compressive and shear buckling analysis was conducted on flat rectangular sandwich panels using the Raleigh-Ritz minimum energy method with a consideration of transverse shear effect of the sandwich core. The sandwich panels were fabricated with titanium honeycomb core and laminated metal matrix composite face sheets. The results show that slightly slender (along unidirectional compressive loading axis) rectangular sandwich panels have the most desirable stiffness-to-weight ratios for aerospace structural applications; the degradation of buckling strength of sandwich panels with rising temperature is faster in shear than in compression; and the fiber orientation of the face sheets for optimum combined-load buckling strength of sandwich panels is a strong function of both loading condition and panel aspect ratio. Under the same specific weight and panel aspect ratio, a sandwich panel with metal matrix composite face sheets has much higher buckling strength than one having monolithic face sheets.

  7. Compressive and shear buckling analysis of metal matrix composite sandwich panels under different thermal environments

    NASA Technical Reports Server (NTRS)

    Ko, William L.; Jackson, Raymond H.

    1993-01-01

    Combined inplane compressive and shear buckling analysis was conducted on flat rectangular sandwich panels using the Raleigh-Ritz minimum energy method with a consideration of transverse shear effect of the sandwich core. The sandwich panels were fabricated with titanium honeycomb core and laminated metal matrix composite face sheets. The results show that slightly slender (along unidirectional compressive loading axis) rectangular sandwich panels have the most desirable stiffness-to-weight ratios for aerospace structural applications; the degradation of buckling strength of sandwich panels with rising temperature is faster in shear than in compression; and the fiber orientation of the face sheets for optimum combined-load buckling strength of sandwich panels is a strong function of both loading condition and panel aspect ratio. Under the same specific weight and panel aspect ratio, a sandwich panel with metal matrix composite face sheets has much higher buckling strength than one having monolithic face sheets.

  8. A three-node C deg element for analysis of laminated composite sandwich shells

    NASA Technical Reports Server (NTRS)

    Martin, C. Wayne; Lung, S. F.; Gupta, K. K.

    1989-01-01

    A three-node flat shell element with C deg rotation fields has been developed for analysis of arbitrary composite shells. The element may consist of any number of orthotropic layers, each layer having different material properties and angular orientation. The formulation includes coupling between bending and extension, which is essential for analysis of unsymmetric laminates. Shearing deflections are included, since laminated and sandwich construction frequently results in shear stiffness much smaller than bending stiffness. Formulation of the element is straightforward, and calculation of its stiffness matrix is simple and fast. Convergence of solutions with mesh refinement is uniform for both thin and thick shells and is insensitive to element shape, although not as rapid as some other elements that lack one or more capabilities of the newly developed element. An experimental verification of the shall element is reported in the appendix.

  9. Analyses of sandwich beams and plates with viscoelastic cores

    NASA Astrophysics Data System (ADS)

    Wang, Gang

    A hybrid damping scheme using passive constrained damping layers (PCLD), and surface bonded piezoceramic actuators was proposed for interior cabin noise and vibration control in helicopters. In order to evaluate the performance of these treatments, we need to understand the dynamic behavior of sandwich structures. The analyses of sandwich structures are complicated by the frequency dependent stiffness and damping properties of viscoelastic materials. The methods developed in this thesis specifically deal with finite element methods and assumed modes methods to this problem. A spectral finite element method (SFEM) was developed in the frequency domain for sandwich beam analysis. The results of natural frequencies and frequency responses for two cantilevered beams with different span of PCLD treatments were presented and validated by experimental results and other analyses; including the assumed modes method (AM), and conventional finite element method (CFEM). The SFEM method implicitly accounts for frequency dependent stiffness and damping of viscoelastic materials. However, CFEM and AM method have to use additional internal dissipation coordinates to account for these properties. The Golla-Hughes-McTavish (GHM) damping method was used in both analyses. Also SFEM improves accuracy of frequency predictions compared to the results of CFEM and AM method because of its higher order interpolation functions. We expected to extend SFEM method to two-dimensional sandwich plate structures. But it is extremely difficult to solve the governing equations for a sandwich plate. An alternative method was developed to update the traditional AM method by using plate mode shapes. The plate mode shape functions were solved directly based on the Kantorovich variational method for both transverse bending and in-plane vibration of isotropic rectangular plates. These plate mode shapes were employed to calculate sandwich plates in AM method. The results of natural frequencies; loss factors and frequency response functions were calculated and validated by experimental data and the results by using beam and rod mode shapes. The comparable results were achieved for both analyses with less modes in the case of using plate mode shapes.

  10. Sandwich pressurization systems for smoke control

    SciTech Connect

    Marchant, R. (South Australian Metropolitan Fire Service, Adelaide (Australia))

    1992-11-01

    Australian building legislation has in the past paid little attention to smoke control within multi-story buildings apart from the old Australian Standard 1668, Fire Precautions in Buildings with Air Handling Systems. The objective of that standard was to prevent the migration of smoke to other parts of a building by way of the installed air-conditioning ductwork. However, there was no requirement in the old AS-1668 or in Australian building regulations (AMUBC) to minimize smoke spread through a multi-story building by connecting paths other than the air-conditioning ductwork (building service, elevator and ventilation shafts). This paper reports that because the old standard only applied to buildings employing a central air handling plant, in those early days (before some authorities woke up to the loophole) it was possible to construct a multi-story building with individual on-floor (unitary) air conditioners, to save the expense of a smoke control system. Occupants would then, for their safety, rely solely upon required stair pressurization systems to provide smoke-free paths of egress. Local ad hoc tests have demonstrated that smoke will migrate from the fire floor to other parts of a building via transfer paths such as elevator shafts, construction joints and ventilation ducts. The traditional AS-1668 modus operand, at time of fire, consists of running the building air-conditioning plant in what we now call the purge mode. Using economy cycle dampers, all floors (including the fire floor) are supplied with 100% fresh air and exhausted to atmosphere. This is usually accomplished via a return air shaft, using either dedicated smoke spill fans or the air-conditioning return air fans.

  11. Development of aircraft lavatory compartments with improved fire resistance characteristics. Phase 2: Sandwich panel resin system development

    NASA Technical Reports Server (NTRS)

    Anderson, R. A.; Arnold, D. B.; Johnson, G. A.

    1979-01-01

    A NASA-funded program is described which aims to develop a resin system for use in the construction of lavatory wall panels, sidewall panels, and ceiling panels possessing flammability, smoke and gas emission, and toxicity (FS&T) characteristics superior to the existing epoxy resin. Candidate resins studied were phenolic, polyimide, and bismaleimide. Based on the results of a series of FS&T as well as mechanical and aesthetic property tests, a phenolic resin was chosen as the superior material. Material and process specifications covering the phenolic resin based materials were prepared and a method of rating sandwich panel performance was developed.

  12. Development of lightweight graphite/polyimide sandwich panels.

    NASA Technical Reports Server (NTRS)

    Poesch, J. G.

    1972-01-01

    Lightweight graphite/polyimide composite honeycomb core and sandwich panels were fabricated and tested. Honeycomb cores of 1/4-in. and 3/8-in. cell sizes of hexagonal configuration were produced from thin plus or minus 45 deg cross plied sheets of prepreg producing core weights between 1.8 and 3.6 lb/cu ft. Thin gauge prepreg using Hercules graphite tow and Monsanto Skybond 710 polyimide resin were manufactured to produce cured ply thicknesses of 0.001 to 0.002 in. Graphite core properties measured at temperatures from -150 to 600 F are reported. Core properties which are superior to available materials were obtained. Sandwich panels weighing less than 0.5 lb/sq ft were designed and fabricated which meet the support structure loads for the shuttle orbiter thermal protection system.

  13. Impact load mitigation in sandwich beams using local resonators

    E-print Network

    Sharma, B

    2015-01-01

    Dynamic response of sandwich beams with resonators embedded in the cores subjected to impact loads is studied. Using finite element models the effectiveness of various local resonator frequencies under a given impact load is compared to the behavior of an equivalent mass beam. It is shown that addition of appropriately chosen local resonators into the sandwich beam is an effective method of improving its flexural bending behavior under impact loads. The effect of a given local resonance frequency under different impact load durations is also studied. It is demonstrated that the choice of appropriate local resonance frequency depends on the impact duration. Further, by performing transverse impact experiments, the finite element models are verified and the advantage of using internal resonators under impact loading conditions is demonstrated.

  14. Bismaleimide resins for flame resistant honeycomb sandwich panels

    NASA Technical Reports Server (NTRS)

    Stenzenberger, H. D.

    1978-01-01

    Bismaleimide resins are prime candidates for nonflammable aircraft interior panels. Three resin types with different structures and processing characteristics were formulated. Resin M 751 was used to fabricate 100 kg of glass fabric prepregs which were used for the preparation of face sheets for honeycomb sandwich panels. Prepreg characteristics and curing cycles for laminate fabrication are provided. In order to advance beyond the current solvent resin technology for fibre and fabric impregnation, a hot melt solvent-less resin system was prepared and characterized. Preliminary tests were performed to develop a wet bonding process for the fabrication of advanced sandwich honeycomb panels by use of polybismaleimide glass fabric face sheets and polybismaleimide Nomex honeycomb core. B-stage material was used for both the core and the face sheet, providing flatwise tensile properties equivalent to those obtained by the state-of-the-art 3-step process which includes an epoxy adhesive resin.

  15. Metal/dielectric/metal sandwich film for broadband reflection reduction.

    PubMed

    Jen, Yi-Jun; Lakhtakia, Akhlesh; Lin, Meng-Jie; Wang, Wei-Hao; Wu, Huang-Ming; Liao, Hung-Sheng

    2013-01-01

    A film comprising randomly distributed metal/dielectric/metal sandwich nanopillars with a distribution of cross-sectional diameters, displayed extremely low reflectance over the blue-to-red regime, when coated on glass and illuminated normally. When it is illuminated by normally incident light, this sandwich film (SWF) has a low extinction coefficient, its phase thickness is close to a negative wavelength in the blue-to-red spectral regime, and it provides weakly dispersive forward and backward impedances, so that reflected waves from the two faces of the SWF interfere destructively. Broadband reflection-reduction, over a wide range of incidence angles and regardless of the polarization state of the incident light, was observed when the SWF was deposited on polished silicon. PMID:23591704

  16. Metal/dielectric/metal sandwich film for broadband reflection reduction

    PubMed Central

    Jen, Yi-Jun; Lakhtakia, Akhlesh; Lin, Meng-Jie; Wang, Wei-Hao; Wu, Huang-Ming; Liao, Hung-Sheng

    2013-01-01

    A film comprising randomly distributed metal/dielectric/metal sandwich nanopillars with a distribution of cross-sectional diameters, displayed extremely low reflectance over the blue-to-red regime, when coated on glass and illuminated normally. When it is illuminated by normally incident light, this sandwich film (SWF) has a low extinction coefficient, its phase thickness is close to a negative wavelength in the blue-to-red spectral regime, and it provides weakly dispersive forward and backward impedances, so that reflected waves from the two faces of the SWF interfere destructively. Broadband reflection-reduction, over a wide range of incidence angles and regardless of the polarization state of the incident light, was observed when the SWF was deposited on polished silicon. PMID:23591704

  17. Metal/dielectric/metal sandwich film for broadband reflection reduction

    NASA Astrophysics Data System (ADS)

    Jen, Yi-Jun; Lakhtakia, Akhlesh; Lin, Meng-Jie; Wang, Wei-Hao; Wu, Huang-Ming; Liao, Hung-Sheng

    2013-04-01

    A film comprising randomly distributed metal/dielectric/metal sandwich nanopillars with a distribution of cross-sectional diameters, displayed extremely low reflectance over the blue-to-red regime, when coated on glass and illuminated normally. When it is illuminated by normally incident light, this sandwich film (SWF) has a low extinction coefficient, its phase thickness is close to a negative wavelength in the blue-to-red spectral regime, and it provides weakly dispersive forward and backward impedances, so that reflected waves from the two faces of the SWF interfere destructively. Broadband reflection-reduction, over a wide range of incidence angles and regardless of the polarization state of the incident light, was observed when the SWF was deposited on polished silicon.

  18. Star cell type core configuration for structural sandwich materials

    DOEpatents

    Christensen, R.M.

    1995-08-01

    A new pattern for cellular core material used in sandwich type structural materials is disclosed. The new pattern involves star shaped cells intermixed with hexagonal shaped cells. The new patterned cellular core material includes star shaped cells interconnected at points thereof and having hexagonal shape cells positioned adjacent the star points. The new pattern allows more flexibility and can conform more easily to curved shapes. 3 figs.

  19. Fibrin Glue Sandwich Prevents Pancreatic Fistula following Distal Pancreatectomy

    Microsoft Academic Search

    Susumu Ohwada; Tetsushi Ogawa; Yoshifumi Tanahashi; Seiji Nakamura; Izumi Takeyoshi; Toshihiro Ohya; Toshiroh Ikeya; Kenji Kawashima; Yoshiyuki Kawashima; Yasuo Morishita

    1998-01-01

    . Pancreatic fistula is a major form of morbidity following pancreatic resection. We conducted a nonrandomized clinical\\u000a trial comparing the sealing and sandwich techniques of spraying fibrin glue to prevent pancreatic fistula following distal\\u000a pancreatectomy. The pancreas was transected with a scalpel to identify and suture the main pancreatic duct and its small branches.\\u000a In the sealing group, fibrin glue

  20. Formability of Aluminum 5182Polypropylene Sandwich Sheet for Automotive Application

    Microsoft Academic Search

    Kee Joo Kim; Cheol-Woong Kim; Byung-Ik Choi; Chang Won Sung; Heon Young Kim; Si-Tae Won; Ho-Yeun Ryu

    2008-01-01

    The AA5182\\/polypropylene\\/AA5182 (AA\\/PP\\/AA) sandwich sheet is the material fabricated by adhering two aluminum skins to one polypropylene core. When it has the same flexural rigidity as a steel sheet, it is 65% lighter than the steel sheet and 30% lighter than an aluminum alloy sheet. Therefore, it is notified exclusively as good substitutive materials for a steel body to improve

  1. Compression after impact strength of composite sandwich panels

    Microsoft Academic Search

    G. A. O. Davies; D. Hitchings; T. Besant; A. Clarke; C. Morgan

    2004-01-01

    Two types of sandwich panels with carbon epoxy skins and aluminium honeycomb core were subjected to low velocity impacts and then the damaged panels tested for their compression-after-impact (CAI) strength. One type of panel was found to be a very robust energy absorber, i.e. a thick-skin thin-core option. The other panels with their thin skins and thick core were found

  2. Flow-through amperometric immunosensor: fast ‘sandwich’ scheme immunoassay

    Microsoft Academic Search

    A. L Ghindilis; R Krishnan; P Atanasov; E Wilkins

    1997-01-01

    A flow-through immunosensor based on a high-surface-area carbon immunoelectrode has been developed. Dispersed carbon material serves as a carrier for immobilized antibodies and at the same time as an electrode material. The ‘sandwich’ scheme of immunoassay has been used. Iodine formed as a result of the enzymatic oxidation of iodide by a peroxidase label has been detected amperometrically. The immunosensor

  3. Creep response of sandwich beams with a metallic foam core

    Microsoft Academic Search

    C. Chen; N. A. Fleck; M. F. Ashby

    2002-01-01

    The creep response of metallic foam sandwich beams in 3-point bend is investigated numerically for the case of a metallic foam core and two steel faces. The face sheets are treated as elastic, while the foam core is modeled by a viscoplastic extension of the Deshpande-Fleck yield surface. This power-law creeping constitutive law has been implemented within the commercial finite

  4. Impact Behaviour of Metal Foam Cored Sandwich Beams

    Microsoft Academic Search

    S. McKown; R. A. W. Mines

    Previous work on the drop weight impact behaviour of polymer composite sandwich beams subject to three point bending has been\\u000a concerned with beams with polymeric cores (Divinycell H100, H200) and pre-preg UD glass epoxy skins (SP Systems SE84) laid\\u000a up in a cross ply form [1,2]. In the work, a mass of 1.49 kg was dropped from a height of

  5. Numerical Investigation of Crack Propagation in Sandwich Structures

    Microsoft Academic Search

    E. E. Theotokoglou

    Low-density foam core sandwich composite find an increasing use as structural materials. They are often used for high performance\\u000a structural applications such as in the hull forms of racing yachts, patrol crafts, lifeboats and catamaran ferries. There\\u000a is a growing emphasis on selecting different materials and their behavior under flexural loading. In addition, fracture mechanics\\u000a analyses of low-density foam core

  6. Development of mature BDNF-specific sandwich ELISA.

    PubMed

    Lim, Yoon; Zhong, Jin-Hua; Zhou, Xin-Fu

    2015-07-01

    Mature brain-derived neurotrophic factor (mBDNF) plays a vital role in the nervous system, whereas proBDNF elicits neurodegeneration and neuronal apoptosis. Although current enzyme-linked immunosorbent assay (ELISA) has been widely used to measure BDNF levels, it cannot differentiate mBDNF from proBDNF. As the function of proBDNF differs from mBDNF, it is necessary to establish an ELISA assay specific for the detection of mBDNF. Therefore, we aimed to establish a new mBDNF-specific sandwich ELISA. In this study, we have screened and found a combination of antibodies for a sandwich ELISA. A monoclonal antibody and sheep anti-BDNF were chosen as capture and detection antibody for sandwich ELISA respectively. The new ELISA showed no cross-reactivity to human recombinant NT-3, NT-4, nerve growth factor and negligible cross-reactivity (0.99-4.99%) for proBDNF compared to commercial ELISA kits (33.18-91.09%). The application of the new mBDNF ELISA was shown through the measurement of mBDNF levels in different brain regions of rats and in the brain of ?-site amyloid precursor protein cleaving enzyme 1 (BACE1)(-/-) and WT mice and compared to western blot. Overall, this new ELISA will be useful for the measurement of mBDNF levels with high specificity. As the function of proBDNF differs from mBDNF (mature BDNF), it is necessary to establish an ELISA specific for the detection of mBDNF. Here, we present a novel sandwich ELISA which detects mBDNF with high specificity. This new ELISA will be useful for the measurement of mBDNF levels with high specificity in various human and animal tissues. proBDNF, precursor of BDNF; BDNF, brain-derived neurotrophic factor; NT-3, neurotrophin-3; NT-4, neurotrophin-4; NGF, nerve growth factor. PMID:25824396

  7. Failure behavior of composite sandwich structures under local loading

    Microsoft Academic Search

    V. Rizov

    2009-01-01

    Usually when analyzing the mechanical response of foam-cored fiber-reinforced composite sandwich structures to localized static\\u000a loading, the face sheets are treated as a linear-elastic material and no damage initiation and growth is considered. However,\\u000a practice shows that at higher indentation magnitudes damage develops in the face sheet in the area of contact with the indentor,\\u000a which could lead to local

  8. Size Effects in Impact Damage of Composite Sandwich Panels

    NASA Technical Reports Server (NTRS)

    Dobyns, Alan; Jackson, Wade

    2003-01-01

    Panel size has a large effect on the impact response and resultant damage level of honeycomb sandwich panels. It has been observed during impact testing that panels of the same design but different panel sizes will show large differences in damage when impacted with the same impact energy. To study this effect, a test program was conducted with instrumented impact testing of three different sizes of sandwich panels to obtain data on panel response and residual damage. In concert with the test program. a closed form analysis method was developed that incorporates the effects of damage on the impact response. This analysis method will predict both the impact response and the residual damage of a simply-supported sandwich panel impacted at any position on the panel. The damage is incorporated by the use of an experimental load-indentation curve obtained for the face-sheet/honeycomb and indentor combination under study. This curve inherently includes the damage response and can be obtained quasi-statically from a rigidly-backed specimen or a specimen with any support conditions. Good correlation has been obtained between the test data and the analysis results for the maximum force and residual indentation. The predictions can be improved by using a dynamic indentation curve. Analyses have also been done using the MSC/DYTRAN finite element code.

  9. Vibration Characteristics Determined for Stainless Steel Sandwich Panels With a Metal Foam Core for Lightweight Fan Blade Design

    NASA Technical Reports Server (NTRS)

    Ghosn, Louis J.; Min, James B.; Raj, Sai V.; Lerch, Bradley A.; Holland, Frederic A., Jr.

    2004-01-01

    The goal of this project at the NASA Glenn Research Center is to provide fan materials that are safer, weigh less, and cost less than the currently used titanium alloy or polymer matrix composite fans. The proposed material system is a sandwich fan construction made up of thin solid face sheets and a lightweight metal foam core. The stiffness of the sandwich structure is increased by separating the two face sheets by the foam layer. The resulting structure has a high stiffness and lighter weight in comparison to the solid facesheet material alone. The face sheets carry the applied in-plane and bending loads (ref. 1). The metal foam core must resist the transverse shear and transverse normal loads, as well as keep the facings supported and working as a single unit. Metal foams have ranges of mechanical properties, such as light weight, impact resistance, and vibration suppression (ref. 2), which makes them more suitable for use in lightweight fan structures. Metal foams have been available for decades (refs. 3 and 4), but the difficulties in the original processes and high costs have prevented their widespread use. However, advances in production techniques and cost reduction have created a new interest in this class of materials (ref. 5). The material chosen for the face sheet and the metal foam for this study was the aerospace-grade stainless steel 17-4PH. This steel was chosen because of its attractive mechanical properties and the ease with which it can be made through the powder metallurgy process (ref. 6). The advantages of a metal foam core, in comparison to a typical honeycomb core, are material isotropy and the ease of forming complex geometries, such as fan blades. A section of a 17-4PH sandwich structure is shown in the following photograph. Part of process of designing any blade is to determine the natural frequencies of the particular blade shape. A designer needs to predict the resonance frequencies of a new blade design to properly identify a useful operating range. Operating a blade at or near the resonance frequencies leads to high-cycle fatigue, which ultimately limits the blade's durability and life. So the aim of this study is to determine the variation of the resonance frequencies for an idealized sandwich blade as a function of its face-sheet thickness, core thickness, and foam density. The finite element method is used to determine the natural frequencies for an idealized rectangular sandwich blade. The proven Lanczos method (ref. 7) is used in the study to extract the natural frequency.

  10. Lightweight composites for modular panelized construction

    NASA Astrophysics Data System (ADS)

    Vaidya, Amol S.

    Rapid advances in construction materials technology have enabled civil engineers to achieve impressive gains in the safety, economy, and functionality of structures built to serve the common needs of society. Modular building systems is a fast-growing modern, form of construction gaining recognition for its increased efficiency and ability to apply modern technology to the needs of the market place. In the modular construction technique, a single structural panel can perform a number of functions such as providing thermal insulation, vibration damping, and structural strength. These multifunctional panels can be prefabricated in a manufacturing facility and then transferred to the construction site. A system that uses prefabricated panels for construction is called a "panelized construction system". This study focuses on the development of pre-cast, lightweight, multifunctional sandwich composite panels to be used for panelized construction. Two thermoplastic composite panels are proposed in this study, namely Composite Structural Insulated Panels (CSIPs) for exterior walls, floors and roofs, and Open Core Sandwich composite for multifunctional interior walls of a structure. Special manufacturing techniques are developed for manufacturing these panels. The structural behavior of these panels is analyzed based on various building design codes. Detailed descriptions of the design, cost analysis, manufacturing, finite element modeling and structural testing of these proposed panels are included in this study in the of form five peer-reviewed journal articles. The structural testing of the proposed panels involved in this study included flexural testing, axial compression testing, and low and high velocity impact testing. Based on the current study, the proposed CSIP wall and floor panels were found satisfactory, based on building design codes ASCE-7-05 and ACI-318-05. Joining techniques are proposed in this study for connecting the precast panels on the construction site. Keywords: Modular panelized construction, sandwich composites, composite structural insulated panels (CSIPs).

  11. Thermomechanical response of metal foam sandwich panels for structural thermal protection systems in hypersonic vehicles

    NASA Astrophysics Data System (ADS)

    Rakow, Joseph F.

    Sandwich panels with metal foam cores are proposed for load-bearing structural components in actively cooled thermal protection systems for aerospace vehicles. Prototype acreage metal foam sandwich panels (MFSP's) are constructed and analyzed with the central goal of characterizing the thermomechanical response of the system. MFSP's are subjected to uniform temperature fields and equibiaxial loading in a novel experimental load frame. The load frame exploits the mismatch of coefficients of thermal expansion and allows for thermostructural experimentation without the endemic conflict of thermal and mechanical boundary conditions. Back-to-back strain gages and distributed thermocouples capture the in-plane response of the panels, including buckling and elastic-plastic post-buckling. The out-of-plane response is captured via moire interferometry, which provides a visualization of evolving mode shapes throughout the post-buckling regime. The experimental results agree with an analytical prediction for critical temperatures in sandwich panels based on a Rayleigh-Ritz minimization of the energy functional for a Reissner-Mindlin plate. In addition, a three-dimensional finite element model of the non-linear thermomechanical response of the panel-frame experimental system is developed and the results are shown to agree well with the experimentally identified response of MFSP's. Central to analytical and numerical characterization of MFSP's is an understanding of the response of metal foam under shear loading. The shear response of metal foam is captured experimentally, providing density-dependent relationships for material stiffness, strength, and energy absorption. Speckle photography is employed to identify microstructural size effects in the distribution of strain throughout metal foam under shear loading. In addition, a micromechanical model is established for the density-dependent shear modulus of metal foam, which allows for the coupling of cell-level imperfections with unit cell response. Through experiments, MFSP's are subjected to dynamic through-the-thickness thermal gradients, constrained deformation, and active cooling. In capturing the response of the cooled and uncooled panels, control and actuation of thermostructural deformation in actively cooled MFSP's is demonstrated. The finite element model of the panel-frame system is extended to the actively cooled experiments and is shown to agree well with the experimental results.

  12. Dynamic models for low-velocity impact damage of composite sandwich panels – Part B: Damage initiation

    Microsoft Academic Search

    Michelle S. Hoo Fatt; Kyong S. Park

    2001-01-01

    Equivalent single and multi degree-of-freedom systems are used to predict low-velocity impact damage of composite sandwich panels by rigid projectiles. The composite sandwich panels are symmetric and consist of orthotropic laminate facesheets and a core with constant crushing resistance. The transient deformation response of the sandwich panels subjected to impact were predicted in a previous paper, and analytical solutions for

  13. Development of a satellite structure with the sandwich T-joint

    Microsoft Academic Search

    Byoung Jung Kim; Dai Gil Lee

    2010-01-01

    In this study, a monocoque satellite structure composed of many composite sandwich panels, which consist of two carbon fiber\\/epoxy composite faces and an aluminum honeycomb core, was designed to reduce structural mass and to improve static and dynamic structural rigidity. To join composite sandwich panels with T-shape joints, a new I-shape side insert, which was fixed inside the composite sandwich

  14. Dynamic models for low-velocity impact damage of composite sandwich panels – Part A: Deformation

    Microsoft Academic Search

    Michelle S. Hoo Fatt; Kyong S. Park

    2001-01-01

    Equivalent single and multi degree-of-freedom systems are used to predict the low-velocity impact response of rigidly supported, two-sided clamped, simply supported and four-sided clamped composite sandwich panels. The composite sandwich panels have orthotropic facesheets and are symmetric. Analytical solutions for the transient deformation response of the sandwich panels are presented in this paper, and analytical predictions of impact damage initiation

  15. Impact tests on steel–concrete–steel sandwich beams with lightweight concrete core

    Microsoft Academic Search

    J. Y. Richard Liew; K. M. A. Sohel; C. G. Koh

    2009-01-01

    This paper studies the impact performance of Steel–Concrete–Steel (SCS) sandwich beams consisting of a lightweight concrete core sandwiched between two face plates that are connected by J-hook connectors. Impact tests were carried out by dropping free weights on to sandwich beams to investigate their structural response against impact loads. Test results revealed that the proposed J-hook connectors provide an effective

  16. A new approach to develop high temperature foam core sandwich structures using air plasma spraying

    Microsoft Academic Search

    F. Azarmi; T. Coyle; J. Mostaghimi; L. Pershin

    2009-01-01

    Foam core sandwich structures exhibit mechanical performance comparable to conventional materials at much lower weight and\\u000a potentially lower cost. An advanced production technique for manufacturing foam core sandwich structures with high temperature\\u000a constituents is introduced. Skin and core are the main components of a sandwich beam. The various manufacturing processes\\u000a are available to join skins and core to make a

  17. Experimental evaluation of two 36 inch by 47 inch graphite/epoxy sandwich shear webs

    NASA Technical Reports Server (NTRS)

    Bush, H. G.

    1975-01-01

    The design is described and test of two large (36 in. x 47 in.) graphite/epoxy sandwich shear webs. One sandwich web was designed to exhibit strength failure of the facings at a shear load of 7638 lbs/in., which is a characteristic loading for the space shuttle orbiter main engine thrust beam structure. The second sandwich web was designed to exhibit general instability failure at a shear load of 5000 lbs/in., to identify problem areas of stability critical sandwich webs and to assess the adequacy of contemporary analysis techniques.

  18. Combined-load buckling behavior of metal-matrix composite sandwich panels under different thermal environments

    SciTech Connect

    Ko, W.L.; Jackson, R.H.

    1991-09-01

    Combined compressive and shear buckling analysis was conducted on flat rectangular sandwich panels with the consideration of transverse shear effects of the core. The sandwich panel is fabricated with titanium honeycomb core and laminated metal matrix composite face sheets. The results show that the square panel has the highest combined load buckling strength, and that the buckling strength decreases sharply with the increases of both temperature and panel aspect ratio. The effect of layup (fiber orientation) on the buckling strength of the panels was studied in detail. The metal matrix composite sandwich panel was much more efficient than the sandwich panel with nonreinforced face sheets and had the same specific weight.

  19. Smart Composite Sandwich Structures for Future Aerospace Application -Damage Detection and Suppression-: a Review

    NASA Astrophysics Data System (ADS)

    Takeda, Nobuo; Minakuchi, Shu; Okabe, Yoji

    Sandwich structures with advanced composite facesheets are attracting much attention as a solution to maximize the potential of composite materials. However, the composite sandwich structures are prone to damage, such as impact damage and debonding. Although these damages are difficult to detect using conventional nondestructive inspection method, they cause significant reduction in the mechanical properties. Hence, several researchers have attempted to detect and suppress the damages using smart sensors and actuators. In this paper recent developments on smart technologies to improve reliability of the composite sandwich structures are reviewed. First, the state-of-the-art sandwich technology in aerospace application is presented. Next, typical damages in composite sandwich structures are described, which is essential to effectively apply the smart technologies to sandwich structures. Then, smart technologies which have been applied to sandwich structures are briefly shown with focusing specific properties of sandwich structures. It includes damage detection using dynamic response, wave propagation and optical fiber sensors. Finally, a smart honeycomb sandwich concept is also presented.

  20. Performance of Pre-Stressed Sandwich Composites Subjected to Shock Wave Loading

    NASA Astrophysics Data System (ADS)

    Wang, E.; Shukla, A.

    2010-06-01

    The present paper experimentally studies the dynamic behaviour of prestressed sandwich composites under blast loading. The in-plane static compression loadings are implemented on the sandwich composites before they are subjected to the transverse shock wave loading. Three different pre-stress levels are chosen. 3-D realtime deformation data are captured by two high-speed photography systems: a backview Digital Image Correlation (DIC) system and a side-view camera system. The results show that pre-stresses can induce local buckling in the front face-sheet of sandwich composites, consequently reduce the blast resistance of sandwich composites.

  1. Energy absorption capabilities of composite sandwich panels under blast loads

    NASA Astrophysics Data System (ADS)

    Sankar Ray, Tirtha

    As blast threats on military and civilian structures continue to be a significant concern, there remains a need for improved design strategies to increase blast resistance capabilities. The approach to blast resistance proposed here is focused on dissipating the high levels of pressure induced during a blast through maximizing the potential for energy absorption of composite sandwich panels, which are a competitive structural member type due to the inherent energy absorption capabilities of fiber reinforced polymer (FRP) composites. Furthermore, the middle core in the sandwich panels can be designed as a sacrificial layer allowing for a significant amount of deformation or progressive failure to maximize the potential for energy absorption. The research here is aimed at the optimization of composite sandwich panels for blast mitigation via energy absorption mechanisms. The energy absorption mechanisms considered include absorbed strain energy due to inelastic deformation as well as energy dissipation through progressive failure of the core of the sandwich panels. The methods employed in the research consist of a combination of experimentally-validated finite element analysis (FEA) and the derivation and use of a simplified analytical model. The key components of the scope of work then includes: establishment of quantified energy absorption criteria, validation of the selected FE modeling techniques, development of the simplified analytical model, investigation of influential core architectures and geometric parameters, and investigation of influential material properties. For the parameters that are identified as being most-influential, recommended values for these parameters are suggested in conceptual terms that are conducive to designing composite sandwich panels for various blast threats. Based on reviewing the energy response characteristic of the panel under blast loading, a non-dimensional parameter AET/ ET (absorbed energy, AET, normalized by total energy, ET) was suggested to compare energy absorption capabilities of the structures under blast loading. In addition, AEweb/ET (where AEweb is the energy absorbed by the middle core) was also employed to evaluate the energy absorption contribution from the web. Taking advantage of FEA and the simplified analytical model, the influences of material properties as well as core architectures and geometries on energy absorption capabilities (quantified by AET/ ET and AEweb/E T) were investigated through parametric studies. Results from the material property investigation indicated that density of the front face sheet and strength were most influential on the energy absorption capability of the composite sandwich panels under blast loading. The study to investigate the potential effectiveness of energy absorbed via inelastic deformation compared to energy absorbed via progressive failure indicated that for practical applications (where the position of bomb is usually unknown and the panel is designed to be the same anywhere), the energy absorption via inelastic deformation is the more efficient approach. Regarding the geometric optimization, it was found that a core architecture consisting of vertically-oriented webs was ideal. The optimum values for these parameters can be generally described as those which cause the most inelasticity, but not failure, of the face sheets and webs.

  2. Hail Ice Impact of Lightweight Composite Sandwich Panels

    NASA Astrophysics Data System (ADS)

    Luong, Sean Dustin

    There is a growing demand for the usage of composite sandwich structures in the aircraft industry. Aircraft may suffer damage from a variety of impact sources such as ground service equipment, runway debris, bird strike, or hail ice. The damage response of hail ice impacts on composite sandwich structures is not well understood and they can often result in core damage without visually detectable surface damage. This seed damage may grow and lead to large-scale failure of the structure through repetitive operational loading, such as ground-air-ground cycles of aircraft (causes core internal pressurization). Therefore, it is necessary to understand the types of damage that can occur as a result of impacts. This study explores the effect of high velocity hail ice impact on damage formation in lightweight composite sandwich panels, particularly at a level that produces barely visible external damage. Panels consisting of two different facesheet thicknesses (1.19 and 1.87 mm) were impacted at angles of 25, 40, and 90 degrees at speeds of 25 and 50 m/s. The tests revealed three different core damage modes. Any level of measurable surface damage was an indicator of the presence of internal core damage, but internal damage could also be present without measurable surface damage. Thus, visual inspection alone was not a reliable method of damage detection. No clear relationship was found between impact energy levels and internal damage state since, for example, both 83 and 20.5 J tests produced core fracture, while a 16 J test did not produce any core damage. All core damage occurred at a depth of 3-5 mm from the impact-side facesheet.

  3. Deformation and fracture of impulsively loaded sandwich panels

    NASA Astrophysics Data System (ADS)

    Wadley, H. N. G.; Børvik, T.; Olovsson, L.; Wetzel, J. J.; Dharmasena, K. P.; Hopperstad, O. S.; Deshpande, V. S.; Hutchinson, J. W.

    2013-02-01

    Light metal sandwich panel structures with cellular cores have attracted interest for multifunctional applications which exploit their high bend strength and impact energy absorption. This concept has been explored here using a model 6061-T6 aluminum alloy system fabricated by friction stir weld joining extruded sandwich panels with a triangular corrugated core. Micro-hardness and miniature tensile coupon testing revealed that friction stir welding reduced the strength and ductility in the welds and a narrow heat affected zone on either side of the weld by approximately 30%. Square, edge clamped sandwich panels and solid plates of equal mass per unit area were subjected to localized impulsive loading by the impact of explosively accelerated, water saturated, sand shells. The hydrodynamic load and impulse applied by the sand were gradually increased by reducing the stand-off distance between the test charge and panel surfaces. The sandwich panels suffered global bending and stretching, and localized core crushing. As the pressure applied by the sand increased, face sheet fracture by a combination of tensile stretching and shear-off occurred first at the two clamped edges of the panels that were parallel with the corrugation and weld direction. The plane of these fractures always lay within the heat affected zone of the longitudinal welds. For the most intensively loaded panels additional cracks occurred at the other clamped boundaries and in the center of the panel. To investigate the dynamic deformation and fracture processes, a particle-based method has been used to simulate the impulsive loading of the panels. This has been combined with a finite element analysis utilizing a modified Johnson-Cook constitutive relation and a Cockcroft-Latham fracture criterion that accounted for local variation in material properties. The fully coupled simulation approach enabled the relationships between the soil-explosive test charge design, panel geometry, spatially varying material properties and the panel's deformation and dynamic failure responses to be explored. This comprehensive study reveals the existence of a strong instability in the loading that results from changes in sand particle reflection during dynamic evolution of the panel's surface topology. Significant fluid-structure interaction effects are also discovered at the sample sides and corners due to changes of the sand reflection angle by the edge clamping system.

  4. Measuring Core/Facesheet Bond Toughness in Honeycomb Sandwich Structures

    NASA Technical Reports Server (NTRS)

    Nettles, A. T.

    2006-01-01

    This study examines two test methods to evaluate the peel toughness of the skin to core debond of sandwich panels. The methods tested were the climbing drum (CD) peel test and the double cantilever beam (DCB) test. While the CD peel test is only intended for qualitative measurements, it is shown in this study that qualitative measurements can be performed and compare well with DCB test data. It is also shown that artificially stiffening the facesheets of a DCB specimen can cause the test to behave more like a flatwise tensile test than a peel test.

  5. Water intrusion in thin-skinned composite honeycomb sandwich structures

    NASA Technical Reports Server (NTRS)

    Jackson, Wade C.; O'Brien, T. Kevin

    1988-01-01

    Thin-skinned composite honeycomb sandwich structures from the trailing edge of the U.S. Army's Apache and Chinook helicopters have been tested to ascertain their susceptibility to water intrusion as well as such intrusions' effects on impact damage and cyclic loading. Minimum-impact and fatigue conditions were determined which would create microcracks sufficiently large to allow the passage of water through the skins; damage sufficient for this to occur was for some skins undetectable under a 40X-magnification optical microscope. Flow rate was a function of moisture content, damage, applied strain, and pressure differences.

  6. Adhesion characterization and defect sizing of sandwich honeycomb composites.

    PubMed

    Ndiaye, Elhadji Barra; Maréchal, Pierre; Duflo, Hugues

    2015-09-01

    Defects may appear in composite structures during their life cycle. A 10MHz 128 elements phased array transducer was investigated to characterize join bonds and defects in sandwich honeycomb composite structures. An adequate focal law throughout the composite skin gives the ultrasonic dispersive properties of the composite skin and glue layer behind. The resulting B-scan cartographies allow characterizing locally the honeycomb adhesion. Experimental measurements are compared in good agreement with the Debye Series Method (DSM). In the processed C-scan image, flaws are detectable and measurable, localized both in the scanning plane and in the thickness of the composite skin. PMID:26138595

  7. Mathematical Modelling of Shear Effect of Sandwich Beam

    NASA Astrophysics Data System (ADS)

    Magnucka-Blandzi, Ewa

    2010-09-01

    This paper is devoted to simply supported sandwich beams with a metal foam core. The mechanical properties of the isotropic core of the beam are varied in a normal direction in relation to the middle plane of symmetry. Mathematical modelling of shear effect is presented. The fields of displacement for the flat cross section of the beam are defined. Basing on the principle of the stationary of the total potential energy the system of four partial differential equations is obtained. One way for solving the system of equilibrium equations is proposed.

  8. Sandwich antibody arrays using recombinant antibody-binding protein L.

    PubMed

    Seo, Jin-soo; Poulter, C Dale

    2014-06-10

    Antibody arrays are a useful for detecting antigens and other antibodies. This technique typically requires a uniform and well-defined orientation of antibodies attached to a surface for optimal performance. A uniform orientation can be achieved by modification of antibodies to include a single site for attachment. Thus, uniformly oriented antibody arrays require a bioengineered modification for the antibodies directly immobilization on the solid surface. In this study, we describe a "sandwich-type" antibody array where unmodified antibodies are oriented through binding with regioselectively immobilized recombinant antibody-binding protein L. Recombinant proL-CVIA bearing C-terminal CVIA motif is post-translationally modified with an alkyne group by protein farnesyltransferase (PFTase) at the cysteine residue in the CVIA sequence to give proL-CVIApf, which is covalently attached to an azido-modified glass slide by a Huisgen [3 + 2] cycloaddition reaction. Slides bearing antibodies bound to slides coated with regioselectively immobilized proL-CVIApf gave stronger fluorescence outputs and those where the antibody-binding protein was immobilized in random orientations on an epoxy-modified slide. Properly selected capture and detection antibodies did not cross-react with immobilized proL-CVIApf in sandwich arrays, and the proL-CVIApf slides can be used for multiple cycles of detected over a period of several months. PMID:24841983

  9. Sandwich Composite, Syntactic Foam Core Based, Application for Space Structures

    NASA Technical Reports Server (NTRS)

    Hodge, Andrew J.; Kaul, Raj K.; McMahon, William M.; Reinarts, Thomas

    2000-01-01

    The current Solid Rocket Booster (SRB) launch vehicle has several metal based components that require a Thermal Protective System (TPS) be applied to the exterior surface to ensure its structural integrity and to protect the interior hardware from aerodynamic heating. TPS materials have distinct disadvantages associated with their use. One disadvantage to the application of TPS is that it can act as a debris source to the Space Shuttle Orbiter during flight and it also adds weight to the system without directly contributing any structural strength. One of the specific areas examined under this program was to replace a metal/TPS system with polymer based composites. A polymer matrix based sandwich composite was developed which had both structural and insulative properties to meet the high aerodynamic structural and heating load survival requirements. The SRB Nose Cap was selected as a candidate for this application. The sandwich system being qualified for this application is a carbon/epoxy outer and inner skin with a high strength-low thermal conductivity syntactic foam core.

  10. Communicative Language Teaching through Sandwich Stories for EFL Children in China.

    ERIC Educational Resources Information Center

    Ji, Yuhua

    1999-01-01

    Presents a discussion of two problems with communicative language teaching textbooks for English-as-a-foreign-language children in China. Provides an explanation of the rationale for the use of stories and sandwich stories, and gives a demonstration of sandwich stories being used in the classroom. (Author/VWL)

  11. BA Business Studies Degree: Employment Experiences of "Sandwich" Degree Graduates versus 1-Year "Conversion" Programme Graduates.

    ERIC Educational Resources Information Center

    Kiely, Julia A.; Ruhnke, Julia

    1998-01-01

    Comparison of 38 business studies graduates in a four-year sandwich program (with one-year job placement) and 23 with a two-year diploma, one-year conversion to bachelor's program showed that sandwich graduates were more successful in job placement and salary. The conversion group were disadvantaged by lack of work experience and lower academic…

  12. One-dimensional response of sandwich plates to underwater shock loading

    Microsoft Academic Search

    V. S. Deshpande; N. A. Fleck

    2005-01-01

    The one-dimensional shock response of sandwich plates is investigated for the case of identical face sheets separated by a compressible foam core. The dynamic response of the sandwich plates is analysed for front face impulsive loading, and the effect of strain hardening of the core material is determined. For realistic ratios of core mass to face sheet mass, it is

  13. A Liquid Crystal Sandwich Screen For Real-Time 3-D Color Display

    NASA Astrophysics Data System (ADS)

    Nithiyanandam, N.

    1983-12-01

    A sandwich type volumetric screen is proposed for 3-D color image display based on sectional imaging. Each slice of the sandwich displays one section of the image. The slice consists of a back-illuminator and a front liquid crystal matrix screen. A modulated composite color light source of three primary colors illuminates the back-illuminator.

  14. Mechanical response of carbon fiber composite sandwich panels with pyramidal truss cores

    E-print Network

    Wadley, Haydn

    Mechanical response of carbon fiber composite sandwich panels with pyramidal truss cores Tochukwu panel designs offers novel opportunities for ultralight structures. Here, pyramidal truss sandwich cores-predicts the measurements. The CFRP pyramidal cores investigated here have a similar mechanical performance to CFRP

  15. Numerical and Experimental Analysis of the Dynamic Behavior of Aluminum-Composition Cork Sandwich Beams

    Microsoft Academic Search

    Rui A. S. Moreira; Francisco J. Q. de Melo; Jose´ Dias Rodrigues

    2010-01-01

    This work is devoted to the analysis of the static and dynamic properties of composition corks used as damping cores in sandwich structures. A mixed displacement-stress beam finite element is formulated, implemented and used as a valuable numerical tool in an inverse identification methodology, where the core material is characterized from the free vibration response of the sandwich beam. The

  16. Enhanced transmittance and fields of a thick metal sandwiched between two dielectric photonic crystals

    Microsoft Academic Search

    Gui-Qiang Du; Hai-Tao Jiang; Li Wang; Zhan-Shan Wang; Hong Chen

    2010-01-01

    We demonstrated that transmittance and field intensities of a thick metal sandwiched between two dielectric photonic crystals (PCs) can be enhanced by more than two orders of magnitude and by nearly 20 times, respectively, compared to a single metal layer with the same thickness. Under the tunneling mechanism, the light can enter the sandwiched structure without reflection and localizes at

  17. The high velocity impact response of composite and FML-reinforced sandwich structures

    Microsoft Academic Search

    G. Reyes Villanueva; W. J. Cantwell

    2004-01-01

    The high velocity impact response of a range of novel aluminium foam sandwich structures has been investigated using a nitrogen gas gun. Tests were undertaken on sandwich structures based on plain composite and fibre-metal laminate (FML) skins. Impact testing was conducted using a 10 mm diameter projectile at energies up to that required to achieve complete perforation of the target.

  18. Integration of Mechanics and Acoustics in a Sandwich Fuselage. Part IV

    Microsoft Academic Search

    M. J. L. van Tooren; L. A. Krakers; A. Beukers

    2005-01-01

    Until now only the stiffened skin structural concept has been discussed. A different structural concept is the sandwich concept. Sandwiches consist out of layers. The outer layers are called facings and are generally thin and of high density. These facings are supposed to resist most of the edgewise loads and flat-wise bending moments. The inner layer is called the core

  19. Cohesive layer models for predicting delamination growth and crack kinking in sandwich structures

    Microsoft Academic Search

    S. El-Sayed; S. Sridharan

    2002-01-01

    There are potentially two types of fracture that sandwich structures with strong and stiff facing sheets and lightweight cores are liable to suffer. These are the delamination growth at the face-sheet core interface and crack kinking into the sandwich core, respectively. The paper proposes computational models to simulate these failure mechanisms. The models employ the cohesive layer concept and are

  20. Mechanical behavior of carbon fiber composite lattice core sandwich panels fabricated by laser cutting

    E-print Network

    Vaziri, Ashkan

    molding [12­14], pultruded unidirectional fiber-rein- forced composite rods without helical forming [15Mechanical behavior of carbon fiber composite lattice core sandwich panels fabricated by laser and prototyping of low-density carbon fiber sandwich panel cores based on laser beam cutting (LBC). Using LCB

  1. Porous tissue grafts sandwiched with multilayered mesenchymal stromal cell sheets induce tissue regeneration for cardiac repair

    Microsoft Academic Search

    Chun-Hung Chen; Hao-Ji Wei; Wei-Wen Lin; Iwen Chiu; Shiaw-Min Hwang; Chung-Chi Wang; Wen-Yu Lee; Yen Chang; Hsing-Wen Sung

    2008-01-01

    Aims To provide the basis for uniform cardiac tissue regeneration, a spatially uniform distribution of adhered cells within a scaffold is a prerequisite. To achieve this goal, a bioengineered tissue graft con- sisting of a porous tissue scaffold sandwiched with multilayered sheets of mesenchymal stromal cells was developed. Methods and results This tissue graft (sandwiched patch) was used to replace

  2. Modelling the flexural behaviour of sandwich composite materials under cyclic fatigue

    Microsoft Academic Search

    A El Mahi; M Khawar Farooq; S Sahraoui; A Bezazi

    2004-01-01

    In this work the fatigue behaviour of the sandwich composite materials in three point bending has been studied. A stiffness reduction approach was adopted which was further based on the interpolation by the empirical functions of our test results, whose coefficients depends on the material properties and loading conditions. This approach permitted to predict the fatigue life of the sandwich

  3. Deformation and Fracture of Impulsively Loaded Sandwich Panels H.N.G. Wadleya,*

    E-print Network

    Hutchinson, John W.

    the stand-off distance between the test charge and panel surfaces. The sandwich panels suffered global Structural Impact Laboratory (SIMLab), Centre for Research-based Innovation (CRI) and Department by approximately 30%. Square, edge clamped sandwich panels and solid plates of equal mass per unit area were

  4. The fatigue strength of sandwich beams with an aluminium alloy foam core

    Microsoft Academic Search

    A.-M. Harte; N. A. Fleck; M. F. Ashby

    2001-01-01

    Sandwich beams with aluminium face sheets and an aluminium alloy foam core are tested in cyclic four point bend, and S–N fatigue curves are determined for the failure modes of face fatigue, core shear and core indentation. The operative failure mode is dictated by the relative fatigue strength of face sheets to core, and upon the geometry of the sandwich

  5. Functional grading of metal foam cores for yield-limited lightweight sandwich beams

    Microsoft Academic Search

    Yves Conde; Arnaud Pollien; Andreas Mortensen

    2006-01-01

    We show that grading the porosity in a bent metal skin\\/metal foam core sandwich can generate significant weight savings in yield-limited design when, and only when, there is a gradient in the applied moment along the sandwich beam.

  6. The impulsive response of sandwich beams: Analytical and numerical investigation of regimes of behaviour

    Microsoft Academic Search

    M. T. Tilbrook; V. S. Deshpande; N. A. Fleck

    2006-01-01

    An analytical model is developed to classify the impulsive response of sandwich beams based on the relative time-scales of core compression and the bending\\/stretching response of the sandwich beam. It is shown that an overlap in time scales leads to a coupled response and to the possibility of an enhanced shock resistance. Four regimes of behaviour are defined: decoupled responses

  7. Non-linear indentation behavior of foam core sandwich composite materials—A 2D approach

    Microsoft Academic Search

    Victor Iliev Rizov

    2006-01-01

    Light weight high performance sandwich composite materials have been used more and more frequently in various load bearing applications in recent decades. However, sandwich materials with thin composite face sheets and a low density foam core are notoriously sensitive to failure by localized external loads. These loads induce significant local deflections of the loaded face sheet into the core of

  8. Influence of imperfections on the performance of metal foam core sandwich panels

    Microsoft Academic Search

    H. Bart-Smith; J. W. Hutchinson; N. A. Fleck; A. G. Evans

    2002-01-01

    Sandwich panels and beams are used in bending and compression dominated components. The retention of their load capacity in the presence of imperfections is a central consideration. To address this issue, sandwich beams with metallic foam cores have been tested in four-point bending following the introduction of imperfections, created by impressing the face sheets. Limit load expressions for face yielding,

  9. Fatigue of foam core sandwich beams—2: effect of initial damage

    Microsoft Academic Search

    M. Burman; D. Zenkert

    1997-01-01

    This paper addresses the influence of sub-surface core damage in sandwich beams subjected to fatigue loading. Using results from static and fatigue tests of undamaged beams a model for the prediction of the fatigue life of damaged beams are proposed. Sandwich beams subjected to transverse loading inducing a shear stress field in the core material with two typical sub-surface damages,

  10. Analysis of Sandwich Shells with Metallic Foam Cores based on the Uniaxial Tensile Test

    Microsoft Academic Search

    H. Mata; A. Santos; A. A. Fernandes; R. A. F. Valente; M. P. L. Parente; R. Natal Jorge

    2011-01-01

    On this work, the authors present the development and evaluation of an innovative system able to perform reliable panels of sandwich sheets with metallic foam cores for industrial applications, especially in automotive and aeronautical industries. This work is divided into two parts; in the first part the mathematical model used to describe the behavior of sandwich shells with metal cores

  11. Elastica of sandwich panels with a transversely flexible core—A high-order theory approach

    Microsoft Academic Search

    Yeoshua Frostig

    2009-01-01

    The elastica behavior of an extensional sandwich panel with a “soft” core when subjected to in-plane compressive loads is presented and it is compared with the response of its extensional equivalent single layer (ESL) with shear deformations model. The field equations along with the appropriate boundary conditions for the sandwich and the ESL panels have been derived through a variational

  12. The Effect of Load and Geometry on the Failure Modes of Sandwich Beams

    Microsoft Academic Search

    M. S. Konsta-Gdoutos; E. E. Gdoutos

    2005-01-01

    Facing compressive failure, facing wrinkling and core shear failure are the most commonly encountered failure modes in sandwich beams with facings made of composite materials. The occurrence and sequence of these failure modes depends on the geometrical dimensions, the form of loading and type of support of the beam. In this paper the above three failure modes in sandwich beams

  13. Natural Cork Agglomerate Employed as an Environmentally Friendly Solution for Quiet Sandwich Composites

    PubMed Central

    Sargianis, James; Kim, Hyung-ick; Suhr, Jonghwan

    2012-01-01

    Carbon fiber-synthetic foam core sandwich composites are widely used for many structural applications due to their superior mechanical performance and low weight. Unfortunately these structures typically have very poor acoustic performance. There is increasingly growing demand in mitigating this noise issue in sandwich composite structures. This study shows that marrying carbon fiber composites with natural cork in a sandwich structure provides a synergistic effect yielding a noise-free sandwich composite structure without the sacrifice of mechanical performance or weight. Moreover the cork-core sandwich composites boast a 250% improvement in damping performance, providing increased durability and lifetime operation. Additionally as the world seeks environmentally friendly materials, the harvesting of cork is a natural, renewable process which reduces subsequent carbon footprints. Such a transition from synthetic foam cores to natural cork cores could provide unprecedented improvements in acoustic and vibrational performance in applications such as aircraft cabins or wind turbine blades. PMID:22574250

  14. High renewable content sandwich structures based on flax-basalt hybrids and biobased epoxy polymers

    NASA Astrophysics Data System (ADS)

    Colomina, S.; Boronat, T.; Fenollar, O.; Sánchez-Nacher, L.; Balart, R.

    2014-05-01

    In the last years, a growing interest in the development of high environmental efficiency materials has been detected and this situation is more accentuated in the field of polymers and polymer composites. In this work, green composite sandwich structures with high renewable content have been developed with core cork materials. The base resin for composites was a biobased epoxy resin derived from epoxidized vegetable oils. Hybrid basalt-flax fabrics have been used as reinforcements for composites and the influence of the stacking sequence has been evaluated in order to optimize the appropriate laminate structure for the sandwich bases. Core cork materials with different thickness have been used to evaluate performance of sandwich structures thus leading to high renewable content composite sandwich structures. Results show that position of basalt fabrics plays a key role in flexural fracture of sandwich structures due to differences in stiffness between flax and basalt fibers.

  15. Identification of elastic and damping properties of sandwich structures based on high resolution modal analysis of point

    E-print Network

    Paris-Sud XI, Université de

    Identification of elastic and damping properties of sandwich structures based on high resolution properties of the skin and core materials of sandwich structures having heterogeneous cores. All the elastic to the numerical modes of large sandwich panels (lx,y/h 80). The chosen generic model for the visco

  16. Buckling of cylindrical sandwich shells with metal foam cores J.W. Hutchinson a,*, M.Y. He b

    E-print Network

    Hutchinson, John W.

    Buckling of cylindrical sandwich shells with metal foam cores J.W. Hutchinson a,*, M.Y. He b 93106, USA Received 10 November 1999 Abstract Buckling of cylindrical sandwich shells subject to axial of the core are all considered. The range of the structural load index is identi®ed for which the sandwich

  17. Sandwich and Interdigitated Finger Electrode Ferroelectric Nano Film Capacitors: A Comparison of the Effect of Electrostatic Boundary

    E-print Network

    Yanikoglu, Berrin

    1 Sandwich and Interdigitated Finger Electrode Ferroelectric Nano Film Capacitors: A Comparison geometries studied are parallel plate, or so called sandwich type electrodes and the interdigitated finger and asymmetrically distributed defects compared to a classical sandwich type nano film. An out of plane remanent

  18. Geometrically-exact sandwich shells: The static case L. Vu-Quoc *, H. Deng, X.G. Tan

    E-print Network

    Vu-Quoc, Loc

    Geometrically-exact sandwich shells: The static case L. Vu-Quoc *, H. Deng, X.G. Tan Department of geometrically-exact sandwich shells undergoing large deformation. The layer directors at a point for the ®nite rotations of the directors. We present extensive numerical ex- amples, including sandwich shells

  19. Homogenization of thick periodic plates: application of the Bending-Gradient plate theory to a folded core sandwich panel

    E-print Network

    Paris-Sud XI, Université de

    to a folded core sandwich panel A. Leb´ee, K. Sab* Universit´e Paris-Est, Laboratoire Navier ( ´Ecole des to a sandwich panel including a folded core in order to estimate its shear forces stiffness (Leb´ee and Sab-Gradient homogenization scheme and apply it to a sandwich panel including the chevron pattern. It turns out that the shear

  20. arXiv:1108.5604v2[math.FA]22Sep2011 The asymmetric sandwich theorem

    E-print Network

    Simons, Stephen

    arXiv:1108.5604v2[math.FA]22Sep2011 The asymmetric sandwich theorem S. Simons Department the asymmetric sandwich theorem, a generalization of the Hahn­Banach theorem. As applications, we derive various situations. The main results of Section 2 are the asymmetric sandwich theorem of Theorem 4 and the sublevel

  1. Open-Die Forging of Structurally Porous Sandwich Panels D.M. ELZEY and H.N.G. WADLEY

    E-print Network

    Wadley, Haydn

    Open-Die Forging of Structurally Porous Sandwich Panels D.M. ELZEY and H.N.G. WADLEY Structurally porous metal sandwich panels consisting of dense face sheets and porous cores of controlled relative-die forging of such a plastically compressible sandwich panel is developed. An effective yield potential

  2. 2156 IEEE TRANSACTIONS ON AUTOMATIC CONTROL, VOL. 55, NO. 9, SEPTEMBER 2010 Stabilization of a Class of Sandwich

    E-print Network

    of a Class of Sandwich Systems Via State Feedback Xu Wang, Anton A. Stoorvogel, Ali Saberi, Håvard Fjær Grip for a class of sandwich systems, consisting of two linear systems connected in cascade via a saturation sub- ject to input saturation. The methodologies can be further extended to mul- tilayer sandwich

  3. Simulation of the Creep Expansion of Porous Sandwich RAVI VANCHEESWARAN, DOUGLAS T. QUEHEILLALT, DANA M. ELZEY, and HAYDN

    E-print Network

    Wadley, Haydn

    Simulation of the Creep Expansion of Porous Sandwich Structures RAVI VANCHEESWARAN, DOUGLAS T. QUEHEILLALT, DANA M. ELZEY, and HAYDN N.G. WADLEY Recently developed sandwich structures consist of a porous metal core sandwiched between two fully dense face sheets. These structures are produced by pressurizing

  4. Published: Journal of Sandwich Structures and Materials,16, 22-41 (2014) (doi:10.1177/1099636213502980) Corresponding author

    E-print Network

    Nairn, John A.

    2014-01-01

    (Easterling et al., 1982). Balsa is a common core material for sandwich composites used in boats, wind turbine for cores of sandwich composites Meisam Shir Mohammadi and John A Nairn Wood Science & Engineering, Oregon for sandwich composites, this paper presents a detailed study of the fracture properties of balsa

  5. A Study of Indentation Energy in Three Points Bending of Sandwich beams with Composite Laminated Faces and Foam Core

    Microsoft Academic Search

    M. Sadighi; M. Saadati

    This paper deals with analysis of flexural stiffness, indentation and their energies in three point loading of sandwich beams with composite faces from Eglass\\/epoxy and cores from Polyurethane or PVC. Energy is consumed in three stages of indentation in laminated beam, indentation of sandwich beam and bending of sandwich beam. Theory of elasticity is chosen to present equations for indentation

  6. Investigation of failure mechanisms in GFRP sandwich structures with face sheet wrinkle defects used for wind turbine blades

    Microsoft Academic Search

    Martin Leong; Lars C. T. Overgaard; Ole T. Thomsen; Erik Lund; Isaac M. Daniel

    Wrinkle defects can be formed during the production of wind turbine blades consisting of composite monolithic and sandwich laminates. Earlier studies have shown that the in-plane compressive strength of a sandwich panel with wrinkle defects may decrease dramatically. This study focuses on the failure modes of sandwich specimens consisting of thick GFRP face sheets with a wrinkle defect and a

  7. Mechanical behavior of sandwich panels with hollow AlSi tubes core construction Jian Xiong a

    E-print Network

    Vaziri, Ashkan

    ­Si alloy tubes were fabricated using precision casting and were bonded to the face sheets using an epoxy panels have been traditionally made of stochastic cores such as aluminum alloy foams [6,7] or micro tubes and was used to form the casting cav- ities in the sand mold. The Al­Si alloy was melted in the f

  8. Electromagnetic tunneling in a sandwich structure containing single negative media.

    PubMed

    Feng, Tuanhui; Li, Yunhui; Jiang, Haitao; Sun, Yong; He, Li; Li, Hongqiang; Zhang, Yewen; Shi, Yunlong; Chen, Hong

    2009-02-01

    In this paper, the electromagnetic (EM) tunneling phenomenon in a sandwich structure consisting of an mu-negative (MNG) medium, air, and an epsilon-negative (ENG) medium is investigated by means of the transfer-matrix method and microwave experiments. Both results demonstrate that by properly choosing parameters, EM waves can efficiently tunnel through a long distance over several hundreds times the length of the device. Unlike in the ENG-MNG slabs, the electric and the magnetic field of the tunneling mode is interestingly separated and localized at the interface of MNG-air and ENG-air, respectively. Therefore, this structure may be important for potential applications in wireless information and energy transmission, for its high efficiency, security, and health. PMID:19391857

  9. FMR studies of single permalloy layers sandwiched by Au

    NASA Astrophysics Data System (ADS)

    Hurdequint, H.

    2007-03-01

    Results of FMR studies performed at X-band on two series of thin permalloy (Py) layers sandwiched by Au are reported and analyzed. These two series are characterized by an Au layer thickness of 12 and 6 nm, respectively. The FMR results are compared to the ones obtained for a series of (Py/Al 2O 3) control films. A strong interfacial increase of the intrinsic damping is revealed. The spin-orbit perpendicular anisotropy field is also dominated by the metallic interface contribution. Remarkable phenomena evidenced in the angular variation of the FMR spectrum may be well understood in terms of the theoretical description we have developed of the observable signal in a bimetallic (ferro/normal) film.

  10. Detection of bound residues in soils by sandwich-immunoassay

    SciTech Connect

    Dosch, M.; Weller, M.G.; Niessner, R. [Technical Univ. of Munich (Germany). Institute of Hydrochemistry

    1995-12-31

    Immunoassays are useful analytical instruments for the detection of many environmental compounds. This method was not introduced for the detection of non-extractable compounds in soil. So-called ``bound residues`` consist of a soil component, e.g. humic acids and an irreversibly bound pollutant. Because of the complexity of those macromolecules conventional analytical methods in general do not work. Enzyme immunoassays, in contrast, seem to have a large potential for applications and further developments in this field. The use of antibodies with high affinity to the analytes makes a selective detection of environmental pollutants possible. With the development of an enzyme-labeled sandwich-immunoassay polycyclic aromatic hydrocarbons (PAHs) irreversibly bound to humic acids were determined for the first time.

  11. Length scale interactions in the folding of sandwich structures

    NASA Astrophysics Data System (ADS)

    Hunt, G. W.; Wadee, M. A.; Ord, A.

    2001-06-01

    Compressed sandwich structures, comprising thin stiff faces separated by a thick layer of a soft-core material exhibit behaviour analogous to the geological phenomenon of parasitic folding in multi-layered media. Earlier cross-fertilization of ideas from structural mechanics into structural geology is extended, by considering the interactions of folding on two different length scales — overall buckling comprising a single half wave over the length of the structure, combined with short wavelength local wrinkling of a single face or layer. A new theory for such interactions is briefly presented and reviewed in the geological context. In the present problem, we see folding on different length scales at the same moment in time, implying a coupling of the instabilities associated with overall and local bucking.

  12. Predicting The Compression Strength Of Impact-Damaged Sandwich Panels

    NASA Technical Reports Server (NTRS)

    Ratcliffe, James; Jackson, Wade; Schaff, Jeffery

    1990-01-01

    The objective of this work was to develop a technique for predicting the residual compression strength of sandwich panels containing impact damage in one facesheet. The technique was tailored to predict the strength of specimens that exhibit a failure mode involving the formation of kink bands at locations of peak strain in the region of impact damage. Under continued compression loading, the kink bands propagate in a stable manner perpendicular to the applied load. When a critical kink-band length is reached, growth becomes unstable corresponding to panel failure. The analysis follows in two sections. The first section calculates the far-field stress required for stable kink-band growth and the second calculates that required for unstable growth. The residual strength prediction is made when the stress for stable growth becomes equal to that for unstable kink-band growth. Initial comparisons between analysis and experiment show good agreement.

  13. Novel electrochemical dual-aptamer-based sandwich biosensor using molybdenum disulfide/carbon aerogel composites and Au nanoparticles for signal amplification.

    PubMed

    Fang, Lin-Xia; Huang, Ke-Jing; Liu, Yang

    2015-09-15

    A new electrochemical aptamer biosensor for the platelet-derived growth factor BB (PDGF-BB) detection has been developed based on the signal amplification of MoS2/carbon aerogel composites (MoS2/CA) and sandwich assay. A facile hydrothermal route assisted by l-cysteine was applied to synthesize CA incorporated flower-like MoS2 with the large surface active sites and good conductivity. The electrochemical aptasensor was constructed by sandwiching the PDGF-BB between a glassy carbon electrode modified with thiol-terminated PDGF-BB aptamer-1 (Apt1)/gold nanoparticles (AuNPs)/MoS2/CA and the AuNPs with thiol-terminated PDGF-BB aptamer-2 (Apt2) and 6-ferrocenyl hexanethiol (Fc). Fc-AuNPs-Apt2 acted as tracer and AuNPs/MoS2/CA were utilized as the biosensor platform to immobilize a large amount of capture aptamers, owing to their layered structure and high surface-to-volume ratio. Based on the sandwich format, a dual signal amplification strategy had been successfully developed with a wide linear response in the range of 0.001-10nM and a limit of detection of 0.3pM. The developed assay demonstrated good selectivity and high sensitivity, indicating potential applications in bioanalysis and biomedicine. PMID:25909336

  14. Combined compressive and shear buckling analysis of hypersonic aircraft structural sandwich panels

    NASA Technical Reports Server (NTRS)

    Ko, William L.; Jackson, Raymond H.

    1991-01-01

    The combined-load (compression and shear) buckling equations were established for orthotropic sandwich panels by using the Rayleigh-Ritz method to minimize the panel total potential energy. The resulting combined-load buckling equations were used to generate buckling interaction curves for super-plastically-formed/diffusion-bonded titanium truss-core sandwich panels and titanium honeycomb-core sandwich panels having the same specific weight. The relative combined-load buckling strengths of these two types of sandwich panels are compared with consideration of their sandwich orientations. For square and nearly square panels of both types, the combined load always induces symmetric buckling. As the panel aspect ratios increase, antisymmetric buckling will show up when the loading is shear-dominated combined loading. The square panel (either type) has the highest combined buckling strength, but the combined load buckling strength drops sharply as the panel aspect ratio increases. For square panels, the truss-core sandwich panel has higher compression-dominated combined load buckling strength. However, for shear dominated loading, the square honeycomb-core sandwich panel has higher shear-dominated combined load buckling strength.

  15. Combined compressive and shear buckling analysis of hypersonic aircraft sandwich panels

    NASA Technical Reports Server (NTRS)

    Ko, William L.; Jackson, Raymond H.

    1992-01-01

    The combined-load (compression and shear) buckling equations were established for orthotropic sandwich panels by using the Rayleigh-Ritz method to minimize the panel total potential energy. The resulting combined-load buckling equations were used to generate buckling interaction curves for super-plastically-formed/diffusion-bonded titanium truss-core sandwich panels and titanium honeycomb-core sandwich panels having the same specific weight. The relative combined-load buckling strengths of these two types of sandwich panels are compared with consideration of their sandwich orientations. For square and nearly square panels of both types, the combined load always induces symmetric buckling. As the panel aspect ratios increase, antisymmetric buckling will show up when the loading is shear-dominated combined loading. The square panel (either type) has the highest combined buckling strength, but the combined load buckling strength drops sharply as the panel aspect ratio increases. For square panels, the truss-core sandwich panel has higher compression-dominated load buckling strength. However, for shear dominated loading, the square honeycomb-core sandwich panel has higher shear-dominated combined load buckling strength.

  16. Effect of gamma irradiation on Listeria monocytogenes in frozen, artificially contaminated sandwiches.

    PubMed

    Clardy, S; Foley, D M; Caporaso, F; Calicchia, M L; Prakash, A

    2002-11-01

    Gamma irradiation has been shown to effectively control L monocytogenes in uncooked meats but has not been extensively studied in ready-to-eat foods. The presence of Listeria in ready-to-eat foods is often due to postprocess contamination by organisms in the food-manufacturing environment. Because gamma irradiation is applied after products are packaged, the treated foods are protected from environmental recontamination. Currently, a petition to allow gamma irradiation of ready-to-eat foods is under review by the Food and Drug Administration. This study was conducted to determine if gamma irradiation could be used to control L. monocytogenes in ready-to-eat sandwiches. Ham and cheese sandwiches were contaminated with L. monocytogenes, frozen at -40 degrees C, and exposed to gamma irradiation. Following irradiation, sandwiches were assayed for L. monocytogenes. A triangle test was performed to determine if irradiated and nonirradiated sandwiches differed in sensory quality. We found that the D10-values ranged from 0.71 to 0.81 kGy and that a 5-log reduction would require irradiation with 3.5 to 4.0 kGy. The results of a 39-day storage study of sandwiches inoculated with 10(7) CFU of L monocytogenes per g indicated that counts for nonirradiated sandwiches remained fairly constant. Counts for sandwiches treated with 3.9 kGy decreased by 5 log units initially and then decreased further during storage at 4 degrees C. Sensory panelists could distinguish between irradiated and nonirradiated sandwiches but were divided on whether irradiation adversely affected sandwich quality. Our results suggest that manufacturers of ready-to-eat foods could use gamma irradiation to control L. monocytogenes and improve the safety of their products. PMID:12430695

  17. Damage-Tolerance Characteristics of Composite Fuselage Sandwich Structures with Thick Facesheets

    NASA Technical Reports Server (NTRS)

    McGowan, David M.; Ambur, Damodar R.

    1997-01-01

    Damage tolerance characteristics and results from experimental and analytical studies of a composite fuselage keel sandwich structure subjected to low-speed impact damage and discrete-source damage are presented. The test specimens are constructed from graphite-epoxy skins borided to a honeycomb core, and they are representative of a highly loaded fuselage keel structure. Results of compression-after-impact (CAI) and notch-length sensitivity studies of 5-in.-wide by 10-in.long specimens are presented. A correlation between low-speed-impact dent depth, the associated damage area, and residual strength for different impact-energy levels is described; and a comparison of the strength for undamaged and damaged specimens with different notch-length-to-specimen-width ratios is presented. Surface strains in the facesheets of the undamaged specimens as well as surface strains that illustrate the load redistribution around the notch sites in the notched specimens are presented and compared with results from finite element analyses. Reductions in strength of as much as 53.1 percent for the impacted specimens and 64.7 percent for the notched specimens are observed.

  18. Sandwiched confinement of quantum dots in graphene matrix for efficient electron transfer and photocurrent production.

    PubMed

    Zhu, Nan; Zheng, Kaibo; Karki, Khadga J; Abdellah, Mohamed; Zhu, Qiushi; Carlson, Stefan; Haase, Dörthe; Žídek, Karel; Ulstrup, Jens; Canton, Sophie E; Pullerits, Tõnu; Chi, Qijin

    2015-01-01

    Quantum dots (QDs) and graphene are both promising materials for the development of new-generation optoelectronic devices. Towards this end, synergic assembly of these two building blocks is a key step but remains a challenge. Here, we show a one-step strategy for organizing QDs in a graphene matrix via interfacial self-assembly, leading to the formation of sandwiched hybrid QD-graphene nanofilms. We have explored structural features, electron transfer kinetics and photocurrent generation capacity of such hybrid nanofilms using a wide variety of advanced techniques. Graphene nanosheets interlink QDs and significantly improve electronic coupling, resulting in fast electron transfer from photoexcited QDs to graphene with a rate constant of 1.3?×?10(9) s(-1). Efficient electron transfer dramatically enhances photocurrent generation in a liquid-junction QD-sensitized solar cell where the hybrid nanofilm acts as a photoanode. We thereby demonstrate a cost-effective method to construct large-area QD-graphene hybrid nanofilms with straightforward scale-up potential for optoelectronic applications. PMID:25996307

  19. Elastic constants for superplastically formed/diffusion-bonded corrugated sandwich core

    NASA Technical Reports Server (NTRS)

    Ko, W. L.

    1980-01-01

    Formulas and associated graphs for evaluating the effective elastic constants for a superplastically formed/diffusion bonded (SPF/DB) corrugated sandwich core, are presented. A comparison of structural stiffnesses of the sandwich core and a honeycomb core under conditions of equal sandwich core density was made. The stiffness in the thickness direction of the optimum SPF/DB corrugated core (that is, triangular truss core) is lower than that of the honeycomb core, and that the former has higher transverse shear stiffness than the latter.

  20. Analysis and Tests of Reinforced Carbon-Epoxy/Foam-Core Sandwich Panels with Cutouts

    NASA Technical Reports Server (NTRS)

    Baker, Donald J.; Rogers, Charles

    1996-01-01

    The results of a study of a low-cost structurally efficient minimum-gage shear-panel design that can be used in light helicopters are presented. The shear-panel design is based on an integrally stiffened syntactic-foam stabilized-skin with an all-bias-ply tape construction for stabilized-skin concept with an all-bias-ply tape construction for the skins. This sandwich concept is an economical way to increase the panel bending stiffness weight penalty. The panels considered in the study were designed to be buckling resistant up to 100 lbs/in. of shear load and to have an ultimate strength of 300 lbs/in. The panel concept uses unidirectional carbon-epoxy tape on a syntactic adhesive as a stiffener that is co-cured with the skin and is an effective concept for improving panel buckling strength. The panel concept also uses pultruded carbon-epoxy rods embedded in a syntactic adhesive and over-wrapped with a bias-ply carbon-epoxy tape to form a reinforcing beam which is an effective method for redistributing load around rectangular cutout. The buckling strength of the reinforced panels is 83 to 90 percent of the predicted buckling strength based on a linear buckling analysis. The maximum experimental deflection exceeds the maximum deflection predicted by a nonlinear analysis by approximately one panel thickness. The failure strength of the reinforced panels was two and a half to seven times of the buckling strength. This efficient shear-panel design concept exceeds the required ultimate strength requirement of 300 lbs/in by more than 100 percent.

  1. ANALYSES OF DEFORMATION IN VISCOELASTIC SANDWICH COMPOSITES SUBJECT TO MOISTURE DIFFUSION 

    E-print Network

    Joshi, Nikhil P.

    2010-01-16

    . For example extreme temperature changes and humid environmental conditions can significantly degrade the stiffness and strength of the polymer foam core. This study analyzes the effect of moisture diffusion on the deformation of viscoelastic sandwich...

  2. An investigation on low velocity impact response of multilayer sandwich composite structures.

    PubMed

    Jedari Salami, S; Sadighi, M; Shakeri, M; Moeinfar, M

    2013-01-01

    The effects of adding an extra layer within a sandwich panel and two different core types in top and bottom cores on low velocity impact loadings are studied experimentally in this paper. The panel includes polymer composite laminated sheets for faces and the internal laminated sheet called extra layer sheet, and two types of crushable foams are selected as the core material. Low velocity impact tests were carried out by drop hammer testing machine to the clamped multilayer sandwich panels with expanded polypropylene (EPP) and polyurethane rigid (PUR) in the top and bottom cores. Local displacement of the top core, contact force and deflection of the sandwich panel were obtained for different locations of the internal sheet; meanwhile the EPP and PUR were used in the top and bottom cores alternatively. It was found that the core material type has made significant role in improving the sandwich panel's behavior compared with the effect of extra layer location. PMID:24453804

  3. An Investigation on Low Velocity Impact Response of Multilayer Sandwich Composite Structures

    PubMed Central

    Jedari Salami, S.; Sadighi, M.; Shakeri, M.; Moeinfar, M.

    2013-01-01

    The effects of adding an extra layer within a sandwich panel and two different core types in top and bottom cores on low velocity impact loadings are studied experimentally in this paper. The panel includes polymer composite laminated sheets for faces and the internal laminated sheet called extra layer sheet, and two types of crushable foams are selected as the core material. Low velocity impact tests were carried out by drop hammer testing machine to the clamped multilayer sandwich panels with expanded polypropylene (EPP) and polyurethane rigid (PUR) in the top and bottom cores. Local displacement of the top core, contact force and deflection of the sandwich panel were obtained for different locations of the internal sheet; meanwhile the EPP and PUR were used in the top and bottom cores alternatively. It was found that the core material type has made significant role in improving the sandwich panel's behavior compared with the effect of extra layer location. PMID:24453804

  4. Temperature Effects on the Impact Behavior of Fiberglass and Fiberglass/Kevlar Sandwich Composites

    NASA Astrophysics Data System (ADS)

    Halvorsen, Aaron; Salehi-Khojn, Amin; Mahinfalah, Mohammad; Nakhaei-Jazar, Reza

    2006-11-01

    Impact tests were performed on sandwich composites with Fiberglass and Fiberglass/Kevlar face sheets subjected to varied temperatures. A number of specimens were tested at -50 to 120 °C temperature range and at 20, 30, and 45 J low velocity energy levels. Impact properties of the sandwich composites that were evaluated include maximum normal and shear stresses, maximum energy absorption, non-dimensional parameters (AEMP, PI, and RD), and compression after impact strength. Composite specimens tested have a urethane foam filled honeycomb center sandwiched between a variation of four layered Fiberglass and Kevlar/Fiberglass face sheets in a thermoset polymer epoxy matrix. Results showed that the impact performance of these sandwich composites changed over the range of temperature considered and with the addition of a Kevlar layer.

  5. A Quasi-Exact Dynamic Finite Element for Free Vibration Analysis of Sandwich Beams

    Microsoft Academic Search

    Seyed M. Hashemi; Ernest J. Adique

    2010-01-01

    A Dynamic Finite Element (DFE) model for the vibration analysis of three-layered sandwich beams is presented. The governing\\u000a differential equations of motion of the sandwich beam for the general case, when the properties of each layer are dissimilar,\\u000a are exploited. Displacement fields are imposed such that the face layers follow the Rayleigh beam assumptions, while the core\\u000a is governed by

  6. Development of application technique of aluminum sandwich sheets for automotive hood

    Microsoft Academic Search

    Kee Joo Kim; Meung Ho Rhee; Byung-Ik Choi; Cheol-Woong Kim; Chang-Won Sung; Chang-Pyung Han; Ki-Weon Kang; Si-Tae Won

    2009-01-01

    Objective of this study was to develop basic techniques in order to apply aluminum sandwich sheets for an automotive hood\\u000a part. The aluminum sandwich sheet is the material fabricated by adhering two aluminum skins to one polypropylene core. When\\u000a it has the same bending stiffness as a steel sheet, it is 65% lighter than the steel sheet and 30% lighter

  7. Low velocity impact of combination Kevlar\\/carbon fiber sandwich composites

    Microsoft Academic Search

    Jeremy Gustin; Aaran Joneson; Mohammad Mahinfalah; James Stone

    2005-01-01

    Impact, compression after impact, and tensile stiffness properties of carbon fiber and Kevlar combination sandwich composites were investigated in this study. The different samples consisted of impact-side facesheets having different combinations of carbon fiber\\/Kevlar and carbon fiber\\/hybrid. The bottom facesheets remained entirely carbon fiber to maintain the high overall flexural stiffness of the sandwich composite. The focus of this research

  8. Fabrication and transport characterization of Graphene\\/Hexagonal Boron Nitride sandwich structures

    Microsoft Academic Search

    Jian-Hao Chen; Kwanpyo Kim; Will Regan; William Gannett; Kris Erickson; Michael Rousseas; Alex Zettl

    2011-01-01

    High quality, large size hexagonal Boron Nitride (h-BN) thin films and single layer graphene were grown on metal substrates via the chemical vapor deposition method (CVD) and transferred to form Graphene\\/h-BN sandwich structures. High resolution transmission microscopy (TEM) was performed on Graphene and h-BN, confirming highly-ordered crystalline structures of both. The electronic transport properties of various sandwich configurations were investigated

  9. Numerical modeling of impact-damaged sandwich composites subjected to compression-after-impact loading

    Microsoft Academic Search

    Thomas E. Lacy; Youngkeun Hwang

    2003-01-01

    Semi-empirical numerical models are developed for predicting the residual strength of impact-damaged sandwich composites comprised of woven fabric carbon epoxy facesheets and Nomex honeycomb cores subjected to compression-after-impact loading. Results from non-destructive inspection and destructive sectioning of damaged sandwich panels are used to establish initial conditions for damage (residual facesheet indentation, core crush dimensions, etc.) in the numerical analyses. Honeycomb

  10. Finite element analysis of low-velocity impact on composite sandwich plates

    Microsoft Academic Search

    A. N. Palazotto; E. J. Herup; L. N. B. Gummadi

    2000-01-01

    The response of composite sandwich plates to low-velocity impact is predicted by a displacement-based, plate bending, finite element algorithm. Fifth order Hermitian interpolation allows three-dimensional equilibrium integration for transverse stress calculations to be carried out symbolically on the interpolation functions so that transverse stresses within the elements are expressed directly in terms of nodal quantities. Nomex honeycomb sandwich core is

  11. An investigation of SDOF models for large mass impact on sandwich composites

    Microsoft Academic Search

    Todd A. Anderson

    2005-01-01

    This paper describes an investigation of single-degree-of-freedom models for large mass impact on composite sandwich laminates. The stiffness parameters of the models are derived from the results of three-dimensional quasi-static contact analyses of a rigid sphere indenting a multi-layer sandwich laminate. Energy dissipating elements are incorporated into the models to account for material damage. The validity of the models is

  12. Preparation and microwave absorption properties of foam-based honeycomb sandwich structures

    Microsoft Academic Search

    Yanfei He; Rongzhou Gong

    2009-01-01

    Radar-absorbing structures having foam-based honeycomb sandwich structures (FBHSS) were fabricated through a conventional foaming technique. Conductive fillers such as carbonyl iron\\/nickel fibers (CINF) and magnetic metal micropowder (MMP) were added to polyurethane foams so as to efficiently increase the absorbing capacity of FBHSS. A honeycomb sandwich structure, which was made of composite face sheets and foam cores, was used as

  13. Finite element analysis of Carbon composite sandwich material with agglomerated Cork core

    Microsoft Academic Search

    S. Sathis Kumar; M. Milwich; B. L. Deopura; H. Plank

    2011-01-01

    Composite sandwich structures were developed for the hydrofoil sail boat hull using biaxial carbon fabric\\/epoxy composite facing and agglomerated cork core. These ultra-light weight structures were tested through four point bending tests to characterize their flexural behavior. The material exhibited an initial linear elastic behavior followed by non-linear elastic-plastic behavior. Finite element analysis of the sandwich beams was performed to

  14. Dynamic response of composite sandwich plates subjected to time-dependent pressure pulses

    Microsoft Academic Search

    Zafer Kazanci

    2011-01-01

    The dynamic response of orthotropic sandwich composite plates impacted by time-dependent external blast pulses is studied by use of numerical techniques. The theory is based on classical sandwich plate theory including the large deformation effects, such as geometric non-linearities, in-plane stiffness and inertias, and shear deformation. The equations of motion for the plate are derived by the use of the

  15. Effects of Ni buffer layer on giant magnetoresistance in Co\\/Cu\\/Co sandwich

    Microsoft Academic Search

    Tie Li; Hong-Lie Shen; Qin-Wo Shen; Shi-Chang Zou; Koichi Tsukamoto; Mamoru Okutomi

    2001-01-01

    In order to increase the sensitivity of Co\\/Cu\\/Co sandwiches, different thickness Ni layers were used as buffer layer. It was found that in the Co 55Å\\/Cu 35Å\\/Co 55Å sandwiches with different thickness Ni buffer layers, MR ratios between 3.5% and 5.6% could be obtained, and the coercive forces were about 12Oe. Hence, the maximum field sensitivity could be enhanced to

  16. Sandwich ELISA Microarrays: Generating Reliable and Reproducible Assays for High-Throughput Screens

    SciTech Connect

    Gonzalez, Rachel M.; Varnum, Susan M.; Zangar, Richard C.

    2009-05-11

    The sandwich ELISA microarray is a powerful screening tool in biomarker discovery and validation due to its ability to simultaneously probe for multiple proteins in a miniaturized assay. The technical challenges of generating and processing the arrays are numerous. However, careful attention to possible pitfalls in the development of your antibody microarray assay can overcome these challenges. In this chapter, we describe in detail the steps that are involved in generating a reliable and reproducible sandwich ELISA microarray assay.

  17. Modelling of composite sandwich structures with honeycomb core subjected to high-velocity impact

    Microsoft Academic Search

    Brenda L. Buitrago; Carlos Santiuste; Sonia Sánchez-Sáez; Enrique Barbero; Carlos Navarro

    2010-01-01

    In this study the perforation of composite sandwich structures subjected to high-velocity impact was analysed. Sandwich panels with carbon\\/epoxy skins and an aluminium honeycomb core were modelled by a three-dimensional finite element model implemented in ABAQUS\\/Explicit. The model was validated with experimental tests by comparing numerical and experimental residual velocity, ballistic limit, and contact time. By this model the influence

  18. The Effects of Air and Underwater Blast on Composite Sandwich Panels and Tubular Laminate Structures

    Microsoft Academic Search

    H. Arora; P. A. Hooper; J. P. Dear

    The resistance of glass-fibre reinforced polymer (GFRP) sandwich panels and laminate tubes to blast in air and underwater\\u000a environments has been studied. Procedures for monitoring the structural response of such materials during blast events have\\u000a been devised. High-speed photography was employed during the air-blast loading of GFRP sandwich panels, in conjunction with\\u000a digital image correlation (DIC), to monitor the deformation

  19. Fatigue crack growth and life prediction of foam core sandwich composites under flexural loading

    Microsoft Academic Search

    Nitin Kulkarni; Hassan Mahfuz; Shaik Jeelani; Leif A. Carlsson

    2003-01-01

    Fatigue crack growth of foam core sandwich beams loaded in flexure has been investigated. Sandwich panels were manufactured using an innovative co-injection resin transfer molding process. S2-glass fiber with epoxy resins was used as face sheets over a PVC foam core. Testing was performed in a three-point flexure mode utilizing a newly designed fixture such that the localized indentation damage

  20. Evaluation of durability and strength of stitched foam-cored sandwich structures

    Microsoft Academic Search

    Jae Hoon Kim; Young Shin Lee; Byoung Jun Park; Duck Hoi Kim

    1999-01-01

    The static and fatigue characteristics of polyurethane foam-cored sandwich structures are investigated. Three types of specimens with glass fabric faces and polyurethane foam core are used; non-stitched, stitched and stiffened sandwich specimens. The bending strength of the stitched specimen is improved by 50% compared with the non-stitched specimen, and the stiffened specimen is over 10 times stronger than the non-stitched

  1. The structural response of clamped sandwich beams subjected to impact loading

    Microsoft Academic Search

    Zhihua Wang; Lin Jing; Jianguo Ning; Longmao Zhao

    2011-01-01

    The structural response of dynamically loaded monolithic and sandwich beams made of aluminum skins with different cores is determined by loading the end-clamped beams at mid-span with metal foam projectiles. The sandwich beams comprise aluminum honeycomb cores and closed-cell aluminum foam cores. Laser displacement transducer was used to measure the permanent transverse deflection of the back face mid-point of the

  2. Experimental investigation of energy-absorption characteristics of components of sandwich structures

    Microsoft Academic Search

    S. Nemat-Nasser; W. J. Kang; J. D. McGee; W.-G. Guo; J. B. Isaacs

    2007-01-01

    Two series of experiments are performed to investigate the dynamic response of various essential components of a class of sandwich structures, under high-rate inertial loads. One consists of dynamic inertia tests and the other involves dynamic impact tests. A split Hopkinson bar apparatus is modified and used for these experiments.First, the energy-absorbing characteristics of the plate material in a sandwich

  3. Tailoring Sandwich Face\\/Core Interfaces for Improved Damage Tolerance—Part I: Finite Element Analysis

    Microsoft Academic Search

    Christian Lundsgaard-Larsen; Christian Berggreen; Leif A. Carlsson

    2010-01-01

    Various modifications of the face\\/core interface in foam core sandwich specimens are examined in a series of two papers. This\\u000a paper constitutes part I and describes the finite element analysis of a sandwich test specimen, i.e. a DCB specimen loaded\\u000a by uneven bending moments (DCB-UBM). Using this test almost any mode-mixity between pure mode I and mode II can be

  4. Deformation and failure mechanism of dynamically loaded sandwich beams with aluminum-foam core

    Microsoft Academic Search

    J. L Yu; X Wang; Z. G Wei; E. H Wang

    2003-01-01

    In this paper the response and failure of dynamically loaded sandwich beams with an aluminum-foam core is investigated experimentally. The dynamic compressive stress–strain curves of the core material, an open-cell aluminum foam, are obtained by an SHPB technique. No strain-rate sensitivity is found. Quasi-static and dynamic bending tests are carried out for sandwich beams made of aluminum skins with an

  5. Experimental investigation on low energy impact behavior of foam cored sandwich composites

    Microsoft Academic Search

    S. H. Yoon; Y. W. Kwon; L. A. Clawson

    1997-01-01

    This study focuses on an experimental investigation of damage tolerance of the foam cored sandwich composite subjected to\\u000a low energy impact. Tests are performed to correlate delamination length with failure loads and loss of damage tolerance of\\u000a the sandwich composite. The impact force history is used to determine momentum imparted to the specimen, the work done on\\u000a the specimen, and

  6. Static and Low Velocity Impact Behavior of Composite Sandwich Panels with an Aluminum Foam Core

    Microsoft Academic Search

    German Reyes

    2008-01-01

    The static and low velocity impact response of aluminum foam based sandwich structures manufactured using thermoplastic composite skins has been studied. The three-point bend (3PB) test geometry was used to evaluate the static properties of the sandwich structures. An examination of the quasi-statically tested specimens revealed failure modes such as indentation, core yielding, and face wrinkling. The low velocity impact

  7. Mechanical degradation of foam-cored sandwich materials exposed to high moisture

    Microsoft Academic Search

    F. Avilés; M. Aguilar-Montero

    2010-01-01

    Sandwich specimens composed of E-glass\\/polyester face sheets bonded to a PVC foam core were exposed to high moisture (95% RH) and immersed in sea-water for extended periods of time. Degradation of mechanical properties of the face sheets, foam core and face\\/core interface were progressively evaluated using flexural testing of the laminates, through-thickness tension of the foam core and interfacial sandwich

  8. Experimental and Numerical Investigation of Free Vibrations of Composite Sandwich Beams with Curvature and Debonds

    Microsoft Academic Search

    B. O. Baba; S. Thoppul; R. F. Gibson

    2011-01-01

    In this paper experimental and numerical results concerning the dynamic response of composite sandwich beams with curvature\\u000a and debonds are reported. Sandwich beams made of carbon\\/epoxy face sheets and polyurethane foam core material were manufactured\\u000a with four different radii of curvature and debonds between the top and bottom interface of face sheet and foam core. Dynamic\\u000a response was obtained using

  9. The dynamic response of sandwich beams with open-cell metal foam cores

    Microsoft Academic Search

    Lin Jing; Zhihua Wang; Jianguo Ning; Longmao Zhao

    2011-01-01

    The deformation and failure modes of dynamically loaded sandwich beams made of aluminum skins with open-cell aluminum foam cores were investigated experimentally. The dynamic compressive stress–strain curves of core materials, open-cell aluminum foam, were obtained using Split Hopkinson Pressure Bar. And then the dynamic impact tests were conducted for sandwich beams with open-cell aluminum foam cores. The photographs showing the

  10. Dynamic buckling of flat and curved sandwich panels with transversely compressible core

    Microsoft Academic Search

    Jörg Hohe; Liviu Librescu; Sang Yong Oh

    2006-01-01

    In the present study, the effect of the transverse compressibility of the core on the transient dynamic response of structural sandwich panels under rapid loading conditions is investigated. The analysis is based on a higher-order sandwich shell theory in an effective multilayer formulation. The model is based on the standard Kirchhoff–Love hypothesis for the face sheets whereas a first\\/second order

  11. Hybrid Progressive Damage Prediction Model for Loaded Marine Sandwich Composite Structures Subjected to a Fire

    Microsoft Academic Search

    James Lua

    2011-01-01

    The risk of fire, and of fire-related structural degradation, represents an ever present challenge to the safe design of marine\\u000a sandwich composite structures. Current state-of-the-art fire analysis and damage assessment tool has ignored the coexistence\\u000a of discrete (delamination) and continuum damage in a sandwich composite structure after a fire exposure. To capture the synergistic\\u000a interaction between the discrete and continuum

  12. Impulsive loading of clamped monolithic and sandwich beams over a central patch

    NASA Astrophysics Data System (ADS)

    Qiu, X.; Deshpande, V. S.; Fleck, N. A.

    2005-05-01

    An analytical model is developed for the response of clamped monolithic and sandwich beams subjected to impulse loading over a central loading patch. A number of topologies of sandwich core are investigated, including the honeycomb core, pyramidal core, prismatic diamond core and metal foam. The various cores are characterised by their dependencies of through-thickness compressive strength and longitudinal tensile strength upon relative density. Closed-form expressions are derived for the deflection of the beam when the ratio r of length of loading patch to the beam span exceeds 0.5. In contrast, an ordinary differential equation needs to be solved numerically for the choice r<0.5. Explicit finite element calculations show that most practical shock loadings can be treated as impulsive and the accuracy of the impulsive analytical predictions is confirmed. The analytical formulae are employed to determine optimal geometries of the sandwich beams that maximise the shock resistance of the beams for a given mass. The optimisation reveals that sandwich beams have a superior shock resistance relative to monolithic beams of the same mass, with the prismatic diamond core sandwich beam providing the best performance. Further, the optimal sandwich beam designs are only mildly sensitive to the length of the loading patch.

  13. Failure Predictions of Out-of-Autoclave Sandwich Joints with Delaminations under Flexure Loads

    NASA Technical Reports Server (NTRS)

    Nordendale, Nikolas; Goyal, Vinay; Lundgren, Eric; Patel, Dhruv; Farrokh, Babak; Jones, Justin; Fischetti, Grace; Segal, Kenneth

    2015-01-01

    An analysis and a test program was conducted to investigate the damage tolerance of composite sandwich joints. The joints contained a single circular delamination between the face-sheet and the doubler. The coupons were fabricated through out-of-autoclave (OOA) processes, a technology NASA is investigating for joining large composite sections. The four-point bend flexure test was used to induce compression loading into the side of the joint where the delamination was placed. The compression side was chosen since it tends to be one of the most critical loads in launch vehicles. Autoclave cure was used to manufacture the composite sandwich sections, while the doubler was co-bonded onto the sandwich face-sheet using an OOA process after sandwich panels were cured. A building block approach was adopted to characterize the mechanical properties of the joint material, including the fracture toughness between the doubler and facesheet. Twelve four-point-bend samples were tested, six in the sandwich core ribbon orientation and six in sandwich core cross-ribbon direction. Analysis predicted failure initiation and propagation at the pre-delaminated location, consistent with experimental observations. A building block approach using fracture analyses methods predicted failure loads in close agreement with tests. This investigation demonstrated a small strength reduction due to a flaw of significant size compared to the width of the sample. Therefore, concerns of bonding an OOA material to an in-autoclave material was mitigated for the geometries, materials, and load configurations considered.

  14. An Analysis of Nondestructive Evaluation Techniques for Polymer Matrix Composite Sandwich Materials

    NASA Technical Reports Server (NTRS)

    Cosgriff, Laura M.; Roberts, Gary D.; Binienda, Wieslaw K.; Zheng, Diahua; Averbeck, Timothy; Roth, Donald J.; Jeanneau, Philippe

    2006-01-01

    Structural sandwich materials composed of triaxially braided polymer matrix composite material face sheets sandwiching a foam core are being utilized for applications including aerospace components and recreational equipment. Since full scale components are being made from these sandwich materials, it is necessary to develop proper inspection practices for their manufacture and in-field use. Specifically, nondestructive evaluation (NDE) techniques need to be investigated for analysis of components made from these materials. Hockey blades made from sandwich materials and a flat sandwich sample were examined with multiple NDE techniques including thermographic, radiographic, and shearographic methods to investigate damage induced in the blades and flat panel components. Hockey blades used during actual play and a flat polymer matrix composite sandwich sample with damage inserted into the foam core were investigated with each technique. NDE images from the samples were presented and discussed. Structural elements within each blade were observed with radiographic imaging. Damaged regions and some structural elements of the hockey blades were identified with thermographic imaging. Structural elements, damaged regions, and other material variations were detected in the hockey blades with shearography. Each technique s advantages and disadvantages were considered in making recommendations for inspection of components made from these types of materials.

  15. Characterizing Facesheet/Core Disbonding in Honeycomb Core Sandwich Structure

    NASA Technical Reports Server (NTRS)

    Rinker, Martin; Ratcliffe, James G.; Adams, Daniel O.; Krueger, Ronald

    2013-01-01

    Results are presented from an experimental investigation into facesheet core disbonding in carbon fiber reinforced plastic/Nomex honeycomb sandwich structures using a Single Cantilever Beam test. Specimens with three, six and twelve-ply facesheets were tested. Specimens with different honeycomb cores consisting of four different cell sizes were also tested, in addition to specimens with three different widths. Three different data reduction methods were employed for computing apparent fracture toughness values from the test data, namely an area method, a compliance calibration technique and a modified beam theory method. The compliance calibration and modified beam theory approaches yielded comparable apparent fracture toughness values, which were generally lower than those computed using the area method. Disbonding in the three-ply facesheet specimens took place at the facesheet/core interface and yielded the lowest apparent fracture toughness values. Disbonding in the six and twelve-ply facesheet specimens took place within the core, near to the facesheet/core interface. Specimen width was not found to have a significant effect on apparent fracture toughness. The amount of scatter in the apparent fracture toughness data was found to increase with honeycomb core cell size.

  16. Flow-through amperometric immunosensor: fast 'sandwich' scheme immunoassay.

    PubMed

    Ghindilis, A L; Krishnan, R; Atanasov, P; Wilkins, E

    1997-01-01

    A flow-through immunosensor based on a high-surface-area carbon immunoelectrode has been developed. Dispersed carbon material serves as a carrier for immobilized antibodies and at the same time as an electrode material. The 'sandwich' scheme of immunoassay has been used. Iodine formed as a result of the enzymatic oxidation of iodide by a peroxidase label has been detected amperometrically. The immunosensor consists of a disposable sensing element (immunocolumn) containing dispersed carbon material with immobilized antibodies which also acts as a working electrode. A current collector connects the working electrode to the measuring device. The electrochemical detection time of the peroxidase-labeled immuno-complex does not exceed several minutes. The overall time of analysis including flowing of analyte, flowing of antigen, washing and detection stages is as low as 22 min. This technique allows fast determination of rabbit IgG (used as a model analyte) with a low detection limit in the picomolar range and also the determination of human IgM in blood plasma with a low detection limit in the nanomolar range. PMID:9228733

  17. Simulations of backgate sandwich nanowire MOSFETs with improved device performance

    NASA Astrophysics Data System (ADS)

    Hengliang, Zhao; Huilong, Zhu; Jian, Zhong; Xiaolong, Ma; Xing, Wei; Chao, Zhao; Dapeng, Chen; Tianchun, Ye

    2014-10-01

    We propose a novel backgate sandwich nanowire MOSFET (SNFET), which offers the advantages of ETSOI (dynamic backgate voltage controllability) and nanowire FETs (good short channel effect). A backgate is used for threshold voltage (Vt) control of the SNFET. Compared with a backgate FinFET with a punch-through stop layer (PTSL), the SNFET possesses improved device performance. 3D device simulations indicate that the SNFET has a three times larger overdrive current, a ~75% smaller off leakage current, and reduced subthreshold swing (SS) and DIBL than those of a backgate FinFET when the nanowire (NW) and the fin are of equal width. A new process flow to fabricate the backgate SNFET is also proposed in this work. Our analytical model suggests that Vt control by the backgate can be attributed to the capacitances formed by the frontgate, NW, and backgate. The SNFET devices are compatible with the latest state-of-the-art high-k/metal gate CMOS technology with the unique capability of independent backgate control for nFETs and pFETs, which is promising for sub-22 nm scaling down.

  18. Refined Zigzag Theory for Laminated Composite and Sandwich Plates

    NASA Technical Reports Server (NTRS)

    Tessler, Alexander; DiSciuva, Marco; Gherlone, Marco

    2009-01-01

    A refined zigzag theory is presented for laminated-composite and sandwich plates that includes the kinematics of first-order shear deformation theory as its baseline. The theory is variationally consistent and is derived from the virtual work principle. Novel piecewise-linear zigzag functions that provide a more realistic representation of the deformation states of transverse-shear-flexible plates than other similar theories are used. The formulation does not enforce full continuity of the transverse shear stresses across the plate s thickness, yet is robust. Transverse-shear correction factors are not required to yield accurate results. The theory is devoid of the shortcomings inherent in the previous zigzag theories including shear-force inconsistency and difficulties in simulating clamped boundary conditions, which have greatly limited the accuracy of these theories. This new theory requires only C(sup 0)-continuous kinematic approximations and is perfectly suited for developing computationally efficient finite elements. The theory should be useful for obtaining relatively efficient, accurate estimates of structural response needed to design high-performance load-bearing aerospace structures.

  19. Shear mode energy harvesting of piezoelectric sandwich beam

    NASA Astrophysics Data System (ADS)

    Malakooti, Mohammad H.; Sodano, Henry A.

    2013-04-01

    Piezoelectric materials due to their high electromechanical coupling properties are good candidates for energy harvesting applications by transforming mechanical energy to electrical power. The piezoelectric coupling coefficient of each material is dependent on its operating mode and higher coupling coefficient means higher efficiency in energy harvesting. In most of the piezoelectric materials, the d15 piezoelectric strain coefficient is the highest coefficient compared to the d33 and d31 coefficients. However complicated fabrication and evaluation of energy harvesting devices operating in the shear mode has slow down the research in this area. The shear piezoelectric effect can be induced during the steady state response of a thick cantilever composite beam due to the effect of shear force through the thickness. Here, a model based on the Timoshenko beam theory is developed to estimate the electric power output in a cantilever beam with a piezoelectric core subjected to the base excitation. The governing electromechanical equations as well as the output voltage and power frequency responses are derived for the piezoelectric sandwich beam. This model is applicable to different geometries and piezoelectric compositions in order to design an optimal shear energy harvester. At the end, the performance of this type of shear energy harvesters is compared to the typical cantilever bimorph energy harvesting beams with the same piezoelectric volume.

  20. First Recorded Eruption of Mount Belinda Volcano, South Sandwich Islands

    NASA Astrophysics Data System (ADS)

    Smellie, J.; Patrick, M.; Harris, A.; Garbeil, H.; Pilger, E.

    2003-12-01

    The MODVOLC satellite monitoring system at the University of Hawaii Manoa has revealed the first recorded eruption of Mount Belinda volcano, on Montagu Island in the remote South Sandwich Islands. Here we present some initial qualitative observations gleaned from the relatively limited amount of satellite imagery available throughout the eruption, including MODIS, Landsat 7 ETM+ and ASTER data. The eruption started some time between September 12 and October 20, 2001, with low-level ash effusion. In January 2002 a Landsat 7 ETM+ image indicated possible collapse structures in the surface of the continuous ice cover within the caldera, suggesting some degree of subglacial volcanism. By May 2002, a broad area of lava or ash was observed close to the subaerial erupting centre, and activity subsequently increased to its highest observed levels in August 2002. Observations in February and March 2003, from a British Antarctic Survey ship and an aircraft of the British Royal Navy, provided the first visual confirmation of the eruption. Minor thermal anomalies continued to be observed in MODIS imagery throughout August 2003, indicating a prolonged low-level eruption or the establishment of a persistent summit lake possibly similar to that believed to occupy the summit crater (Mount Michael) on nearby Saunders Island. A dynamic lava lake on Saunders Island was first reported in 2001 and remains active.

  1. A quantitative exposure model simulating human norovirus transmission during preparation of deli sandwiches.

    PubMed

    Stals, Ambroos; Jacxsens, Liesbeth; Baert, Leen; Van Coillie, Els; Uyttendaele, Mieke

    2015-03-01

    Human noroviruses (HuNoVs) are a major cause of food borne gastroenteritis worldwide. They are often transmitted via infected and shedding food handlers manipulating foods such as deli sandwiches. The presented study aimed to simulate HuNoV transmission during the preparation of deli sandwiches in a sandwich bar. A quantitative exposure model was developed by combining the GoldSim® and @Risk® software packages. Input data were collected from scientific literature and from a two week observational study performed at two sandwich bars. The model included three food handlers working during a three hour shift on a shared working surface where deli sandwiches are prepared. The model consisted of three components. The first component simulated the preparation of the deli sandwiches and contained the HuNoV reservoirs, locations within the model allowing the accumulation of NoV and the working of intervention measures. The second component covered the contamination sources being (1) the initial HuNoV contaminated lettuce used on the sandwiches and (2) HuNoV originating from a shedding food handler. The third component included four possible intervention measures to reduce HuNoV transmission: hand and surface disinfection during preparation of the sandwiches, hand gloving and hand washing after a restroom visit. A single HuNoV shedding food handler could cause mean levels of 43±18, 81±37 and 18±7 HuNoV particles present on the deli sandwiches, hands and working surfaces, respectively. Introduction of contaminated lettuce as the only source of HuNoV resulted in the presence of 6.4±0.8 and 4.3±0.4 HuNoV on the food and hand reservoirs. The inclusion of hand and surface disinfection and hand gloving as a single intervention measure was not effective in the model as only marginal reductions of HuNoV levels were noticeable in the different reservoirs. High compliance of hand washing after a restroom visit did reduce HuNoV presence substantially on all reservoirs. The model showed that good handling practices such as washing hands after a restroom visit, hand gloving, hand disinfection and surface disinfection in deli sandwich bars were an effective way to prevent HuNoV contamination of the prepared foods, but it also demonstrated that further research is needed to ensure a better assessment of the risk of HuNoV transmission during preparation of foods. PMID:25544470

  2. Construction aggregates

    USGS Publications Warehouse

    Tepordei, V.V.

    1995-01-01

    Part of the 1994 Industrial Minerals Review. The production, consumption, and applications of construction aggregates are reviewed. In 1994, the production of construction aggregates, which includes crushed stone and construction sand and gravel combined, increased 7.7 percent to 2.14 Gt compared with the previous year. These record production levels are mostly a result of funding for highway construction work provided by the Intermodal Surface Transportation Efficiency Act of 1991. Demand is expected to increase for construction aggregates in 1995.

  3. CCCG 2008, Montreal, Quebec, August 1315, 2008 Generalized Ham-Sandwich Cuts for Well Separated Point Sets

    E-print Network

    Steiger, William

    CCCG 2008, Montr´eal, Qu´ebec, August 13­15, 2008 Generalized Ham-Sandwich Cuts for Well Separated of h, and h is a "generalized ham-sandwich cut". We give a discrete analogue for a set S of n points are also necessary. 1 Introduction. Given d sets S1, S2, ..., Sd Rd , a ham-sandwich cut is a hyperplane h

  4. Buckling analysis of curved composite sandwich panels subjected to inplane loadings

    NASA Technical Reports Server (NTRS)

    Cruz, Juan R.

    1993-01-01

    Composite sandwich structures are being considered for primary structure in aircraft such as subsonic and high speed civil transports. The response of sandwich structures must be understood and predictable to use such structures effectively. Buckling is one of the most important response mechanisms of sandwich structures. A simple buckling analysis is derived for sandwich structures. This analysis is limited to flat, rectangular sandwich panels loaded by uniaxial compression (N(sub x)) and having simply supported edges. In most aerospace applications, however, the structure's geometry, boundary conditions, and loading are usually very complex. Thus, a general capability for analyzing the buckling behavior of sandwich structures is needed. The present paper describes and evaluates an improved buckling analysis for cylindrically curved composite sandwich panels. This analysis includes orthotropic facesheets and first-order transverse shearing effects. Both simple support and clamped boundary conditions are also included in the analysis. The panels can be subjected to linearly varying normal loads N(sub x) and N(sub y) in addition to a constant shear load N(sub xy). The analysis is based on the modified Donnell's equations for shallow shells. The governing equations are solved by direct application of Galerkin's method. The accuracy of the present analysis is verified by comparing results with those obtained from finite element analysis for a variety of geometries, loads, and boundary conditions. The limitations of the present analysis are investigated, in particular those related to the shallow shell assumptions in the governing equations. Finally, the computational efficiency of the present analysis is considered.

  5. Experimental investigation on sandwich structure ring-type ultrasonic motor.

    PubMed

    Peng, Taijiang; Shi, Hongyan; Liang, Xiong; Luo, Feng; Wu, Xiaoyu

    2015-02-01

    This paper presents a manufacture method for a sandwich structure Ultrasonic Motor (USM) and experiment. Two pieces of rotor clamped on a stator, and a stainless steel disk-spring is bonded on the hollow rotor disk to provide the press by a nut assembled on the shaft. The stator is made of a double-side Printed-Circuit Board (PCB) which is sawed out the ring in the center and connected on the board with three legs. On each side of the ring surface, there are electrodes connected at the same position via through hole. The three layer drive circuit for sine, cosine, and ground signal is connected on the board through each leg. There are many piezoelectric components (PZT) bonded between two electrodes and fill soldering tin on each electrode. Then PZT is welded on PCB by reflow soldering. Finally, rub the gibbous soldering tin down to the position of PZT surface makes sure the surface contacts with rotor evenly. The welding process can also be completed by Surface Mounted Technology (SMT). A prototype motor is manufactured by this method. Two B03 model shapes of the stator are obtained by the finite element analysis and the optimal frequency of the motor is 56.375 kHz measured by impedance instrument. The theoretical analysis is conducted for the relationship between the revolving speed of the USM and thickness of stator ring, number of the travelling waves, PZT amplitude, frequency and the other parameters. The experiment result shows that the maximum revolving speed is 116 RPM and the maximum torque is 25 N mm, when the actuate voltage is 200 VAC. PMID:25213313

  6. Hymenaea courbaril Marine construction, heavy construction,

    E-print Network

    FSC Jatoba Hymenaea courbaril Marine construction, heavy construction, light construction, interior construction, furniture FSC Pine Pinus spp. Marine construction, heavy construction, light construction, interior construction, panel products, furniture FSC Larch Larix spp. (European Larch, Larix decidua

  7. A Study on Flexural Properties of Sandwich Structures with Fiber/Metal Laminate Face Sheets

    NASA Astrophysics Data System (ADS)

    Dariushi, S.; Sadighi, M.

    2013-10-01

    In this work, a new family of sandwich structures with fiber metal laminate (FML) faces is investigated. FMLs have benefits over both metal and fiber reinforced composites. To investigate the bending properties of sandwich beams with FML faces and compare with similar sandwich beams with fibrous composite faces, 6 groups of specimen with different layer arrangements were made and tested. Results show that FML faces have good resistance against transverse local loads and minimize stress concentration and local deformations of skin and core under the loading tip. In addition, FML faces have a good integrity even after plateau region of foam cores and prevent from catastrophic failures, which cannot be seen in fibrous composite faces. Also, FML faces are lighter than metal faces and have better connection with foam cores. Sandwich beams with FML faces have a larger elastic region because of simultaneous deformation of top and bottom faces and larger failure strain thanks to good durability of FMLs. A geometrical nonlinear classical theory is used to predict force-deflection behavior. In this model an explicit formula between symmetrical sandwich beams deflections and applied force which can be useful for designers, is derived. Good agreement is obtained between the analytical predictions and experimental results. Also, analytical results are compared with small deformation solution in a parametric study, and the effects of geometric parameters on difference between linear and nonlinear results are discussed.

  8. Evaluation of modal-based damage detection techniques for composite aircraft sandwich structures

    NASA Astrophysics Data System (ADS)

    Oliver, J. A.; Kosmatka, J. B.

    2005-05-01

    Composite sandwich structures are important as structural components in modern lightweight aircraft, but are susceptible to catastrophic failure without obvious forewarning. Internal damage, such as disbonding between skin and core, is detrimental to the structures' strength and integrity and thus must be detected before reaching critical levels. However, highly directional low density cores, such as Nomex honeycomb, make the task of damage detection and health monitoring difficult. One possible method for detecting damage in composite sandwich structures, which seems to have received very little research attention, is analysis of global modal parameters. This study will investigate the viability of modal analysis techniques for detecting skin-core disbonds in carbon fiber-Nomex honeycomb sandwich panels through laboratory testing. A series of carbon fiber prepreg and Nomex honeycomb sandwich panels-representative of structural components used in lightweight composite airframes-were fabricated by means of autoclave co-cure. All panels were of equal dimensions and two were made with predetermined sizes of disbonded areas, created by substituting areas of Teflon release film in place of epoxy film adhesive during the cure. A laser vibrometer was used to capture frequency response functions (FRF) of all panels, and then real and imaginary FRFs at different locations on each plate and operating shapes for each plate were compared. Preliminary results suggest that vibration-based techniques hold promise for damage detection of composite sandwich structures.

  9. Thermostructural Behavior of a Hypersonic Aircraft Sandwich Panel Subjected to Heating on One Side

    NASA Technical Reports Server (NTRS)

    Ko, William L.

    1997-01-01

    Thermostructural analysis was performed on a heated titanium honeycomb-core sandwich panel. The sandwich panel was supported at its four edges with spar-like substructures that acted as heat sinks, which are generally not considered in the classical analysis. One side of the panel was heated to high temperature to simulate aerodynamic heating during hypersonic flight. Two types of surface heating were considered: (1) flat-temperature profile, which ignores the effect of edge heat sinks, and (2) dome-shaped-temperature profile, which approximates the actual surface temperature distribution associated with the existence of edge heat sinks. The finite-element method was used to calculate the deformation field and thermal stress distributions in the face sheets and core of the sandwich panel. The detailed thermal stress distributions in the sandwich panel are presented, and critical stress regions are identified. The study shows how the magnitudes of those critical stresses and their locations change with different heating and edge conditions. This technical report presents comprehensive, three-dimensional graphical displays of thermal stress distributions in every part of a titanium honeycomb-core sandwich panel subjected to hypersonic heating on one side. The plots offer quick visualization of the structural response of the panel and are very useful for hot structures designers to identify the critical stress regions.

  10. Constructive Mathematics.

    ERIC Educational Resources Information Center

    Calder, Allan

    1979-01-01

    Discusses the question of whether mathematics is discovered or invented. An approach known as constructive mathematics and based on the belief that mathematics can have real meaning if its concepts can be constructed by the human mind is presented. (HM)

  11. Non-explosive simulated blast loading of composite sandwich beams

    E-print Network

    Chen, Antony C.

    2010-01-01

    Composites were first used immediately after World War II in the construction of small personnel boats.composites over traditional materials such as steel and aluminum has been found to drastically reduce the structural weight of the boat

  12. Can a combination of the conformal thin-sandwich and puncture methods yield binary black hole solutions in quasi-equilibrium?

    E-print Network

    Mark D. Hannam; Charles R. Evans; Gregory B. Cook; Thomas W. Baumgarte

    2003-06-06

    We consider combining two important methods for constructing quasi-equilibrium initial data for binary black holes: the conformal thin-sandwich formalism and the puncture method. The former seeks to enforce stationarity in the conformal three-metric and the latter attempts to avoid internal boundaries, like minimal surfaces or apparent horizons. We show that these two methods make partially conflicting requirements on the boundary conditions that determine the time slices. In particular, it does not seem possible to construct slices that are quasi-stationary and avoid physical singularities and simultaneously are connected by an everywhere positive lapse function, a condition which must obtain if internal boundaries are to be avoided. Some relaxation of these conflicting requirements may yield a soluble system, but some of the advantages that were sought in combining these approaches will be lost.

  13. Initial data for binary black holes in quasi-circular orbit: The conformal thin-sandwich puncture method

    NASA Astrophysics Data System (ADS)

    Hannam, Mark D.

    Numerical relativists have been trying to simulate astrophysically realistic binary black hole collisions for over fifteen years. It is believed that prior to collision the two black holes will be in a slowly decaying circular orbit. Any simulation begins with initial data, but it is not clear whether the orbits represented by current initial data for very close black holes are quasi-stable or even quasi-circular. To construct initial data we must make choices for freely-specifiable quantities and choose boundary conditions. All of these choices should be compatible with the physical system we wish to describe. The physical significance of the freely-specifiable data in York's conformal thin-sandwich (CTS) decomposition is clearer than in previous decompositions of the initial value equations of general relativity. The CTS system has already been used to construct data for quasi-equilibrium binary black hole configurations. These implementations used excision methods, which require boundary conditions on the excision surface. An alternative method that avoids inner boundary conditions is Brandt and Brugmann's puncture method. I combine the CTS decomposition and the puncture method. I show that this method is numerically feasible, but that it may not be possible to identify which of the resulting data sets represent binary black holes in quasi-circular orbits. I also consider two methods for locating quasi-circular orbits, the effective-potential and mass-comparison methods. I find that both methods agree when applied to CTT puncture initial data sets.

  14. Simultaneous determination of iron (II) and ascorbic acid in pharmaceuticas based on flow sandwich technique.

    PubMed

    Vakh, Christina; Freze, Elena; Pochivalov, Alexsey; Evdokimova, Ekaterina; Kamencev, Mihail; Moskvin, Leonid; Bulatov, Andrey

    2015-01-01

    The simple and easy performed flow system based on sandwich technique has been developed for the simultaneous separate determination of iron (II) and ascorbic acid in pharmaceuticals. The implementation of sandwich technique assumed the injection of sample solution between two selective reagents and allowed the carrying out in reaction coil two chemical reactions simultaneously: iron (II) with 1,10-phenanthroline and ascorbic acid with sodium 2,6-dichlorophenolindophenol. For achieving of excellent repeatability and considerable reagent saving the various parameters such as flow rate, sample and reagent volumes, reaction coil length were also optimized. The limits of detection (LODs) obtained by using the developed flow sandwich-type approach were 0.2mgL(-1) for iron (II) and 0.7mgL(-1) for ascorbic acid. The suggested approach was validated according to the following parameters: linearity and sensitivity, precision, recoveries and accuracy. The sampling frequency was 41h(-1). PMID:25862995

  15. Penetration and perforation of composite sandwich panels by hemispherical and conical projectiles

    SciTech Connect

    Reddy, T.Y.; Wen, H.M.; Reid, S.R.; Soden, P.D. [Univ. of Manchester Inst. of Science and Technology (United Kingdom). Applied Mechanics Div.

    1998-05-01

    The results of penetration and perforation tests carried out on composite sandwich panels with GRP skins and PVC foam cores using hemispherical-ended and conical-nosed indenters/projectiles under quasi-static, drop-weight, and ballistic impact conditions, with impact velocities up to 305 m/s, are described. Load-displacement characteristics under quasi-static loading are presented and the ballistic limits as well as perforation energies are determined. A classification of the sandwich panel responses based on the panel thickness-to-projectile diameter ratio is deduced. General empirical formulas that predict the dynamic perforation energies for fiber-reinforced plastic (FRP) laminates and composite sandwich panels loaded by hemispherical-ended projectiles are derived. The empirical equations correlate well with available experimental data. It is shown that, to a first approximation, the formulas obtained for hemispherical-ended projectiles are also applicable to conical-nosed projectiles.

  16. A Higher-Order Bending Theory for Laminated Composite and Sandwich Beams

    NASA Technical Reports Server (NTRS)

    Cook, Geoffrey M.

    1997-01-01

    A higher-order bending theory is derived for laminated composite and sandwich beams. This is accomplished by assuming a special form for the axial and transverse displacement expansions. An independent expansion is also assumed for the transverse normal stress. Appropriate shear correction factors based on energy considerations are used to adjust the shear stiffness. A set of transverse normal correction factors is introduced, leading to significant improvements in the transverse normal strain and stress for laminated composite and sandwich beams. A closed-form solution to the cylindrical elasticity solutions for a wide range of beam aspect ratios and commonly used material systems. Accurate shear stresses for a wide range of laminates, including the challenging unsymmetric composite and sandwich laminates, are obtained using an original corrected integration scheme. For application of the theory to a wider range of problems, guidelines for finite element approximations are presented.

  17. Tests of graphite/polyimide sandwich panels in uniaxial edgewise compression

    NASA Technical Reports Server (NTRS)

    Camarda, C. J.

    1980-01-01

    The local and general buckling behavior of graphite/polyimide sandwich panels simply supported along all four edges and loaded in uniaxial edgewise compression were investigated. Material properties of sandwich panel constituents (adhesive and facings) were determined from flatwise tension and sandwich beam flexure tests. Buckling specimens were 30.5 by 33 cm, had quasi-isotropic, symmetric facings, and a glass/polyimide honeycomb core. Core thicknesses were varied and three panels of each thickness were tested at room temperature to investigate failure modes and corresponding buckling loads. Specimens 0.635 cm thick failed by overall buckling at loads close to the analytically predicted buckling load; all other panels failed by face wrinkling. Results of the wrinkling tests indicated that several buckling formulas were unconservative and therefore not suitable for design purposes; a recommended wrinkling equation is presented.

  18. Improving the extinction ratio by a novel sandwiched two-layer grating polarizer

    NASA Astrophysics Data System (ADS)

    Wang, Bo; Li, Hongtao; Shu, Wenhao; Chen, Li; Lei, Liang; Zhou, Jinyun

    2015-05-01

    The high efficiency and the wideband properties are not easy to be obtained by the conventional binary grating-based polarizer. Although the grating polarizer was demonstrated in experiments, the performance should be improved further to meet the practical applications. A novel sandwiched two-layer grating polarizer is presented to improve the efficiency and the bandwidth. Such a polarizer can have advantages of high efficiency of the sandwiched grating and wide bandwidth of the two-layer grating. The grating depths of two layers are optimized for the special duty cycle of 0.3 and the given period. The diffraction efficiency and the incident bandwidth of the novel grating polarizer are improved greatly compared with the conventional simple grating and the sandwiched single-layer grating. Moreover, high extinction ratio can be shown in both two orders and the moderate fabrication tolerance should be good guideline for practical applications.

  19. Penetration Depth of Closed-Cell Aluminum Foam Sandwich Structures under Low Velocity Impact

    NASA Astrophysics Data System (ADS)

    Chen, Yu-Liang; Chen, Hong-Chang

    In this paper, the response of closed-cell aluminum foam sandwich structures under low velocity impact of an ogival-ended mild steel projectile was studied. An analytical model was proposed to predict the penetration depth as well as residual velocity based on the dynamic cavity expansion theory and the Poncelet resistance formula using in the closed-cell aluminum foam sandwich panel. A high-pressure air gun was employed to execute penetration depth tests. Two tests had been done and the results were measured, those are, the residual velocity of the first layer (aluminum plate) and the penetration depth of the sandwich panel. Simultaneously, the finite element analysis software LS-DYNA was utilized for describing the penetrating process of steel projectiles normal impact. It was found that both residual velocity and penetration depth showed nonlinear variation against impact velocity, also the analytical results showed acceptable deviation with those from tests and FEM simulations during specific impact velocities.

  20. Self-healing sandwich structures incorporating an interfacial layer with vascular network

    NASA Astrophysics Data System (ADS)

    Chen, Chunlin; Peters, Kara; Li, Yulong

    2013-02-01

    A self-healing capability specifically targeted for sandwich composite laminates based on interfacial layers with built-in vascular networks is presented. The self-healing occurs at the facesheet-core interface through an additional interfacial layer to seal facesheet cracks and rebond facesheet-core regions. The efficacy of introducing the self-healing system at the facesheet-core interface is evaluated through four-point bend and edgewise compression testing of representative foam core sandwich composite specimens with impact induced damage. The self-healing interfacial layer partially restored the specific initial stiffness, doubling the residual initial stiffness as compared to the control specimen after the impact event. The restoration of the ultimate specific skin strength was less successful. The results also highlight the critical challenge in self-healing of sandwich composites, which is to rebond facesheets which have separated from the core material.

  1. Graphene oxide embedded sandwich nanostructures for enhanced Raman readout and their applications in pesticide monitoring.

    PubMed

    Zhang, Lulu; Jiang, Changlong; Zhang, Zhongping

    2013-05-01

    Analytical techniques based on surface-enhanced Raman scattering (SERS) suffer from a lack of reproducibility and reliability, thus hampering their practical applications. Herein, we have developed a SERS-active substrate based on a graphene oxide embedded sandwich nanostructure for ultrasensitive Raman signal readout. By using this novel Au@Ag NPs/GO/Au@Ag NPs sandwich nanostructure as a SERS substrate, the Raman signals of analytes were dramatically enhanced due to having plenty of hot spots on their surfaces and the unique structure of the graphene oxide sheets. These features make the sandwich nanostructured film an ideal SERS substrate to improve the sensitivity, reproducibility and reliability of the Raman readout. The sandwich nanostructure film can be applied to detect rhodamine-6G (R6G) with an enhancement factor (EF) of ?7.0 × 10(7) and the pesticide thiram in commercial grape juice with a detection limit of as low as 0.1 ?M (0.03 ppm), which is much lower than the maximal residue limit (MRL) of 7 ppm in fruit prescribed by the U.S. Environmental Protection Agency (EPA). The GO embedded sandwich nanostructure also has the ability to selectively detect dithiocarbamate compounds over other types of agricultural chemical. Furthermore, spiked tests show that the sandwich nanostructure can be used to monitor thiram in natural lake water and commercial grape juice without further treatment. In addition, the GO enhanced Raman spectroscopic technique offers potential practical applications for the on-site monitoring and assessment of pesticide residues in agricultural products and environments. PMID:23535912

  2. Low-Velocity Impact Response of Sandwich Beams with Functionally Graded Core

    NASA Technical Reports Server (NTRS)

    Apetre, N. A.; Sankar, B. V.; Ambur, D. R.

    2006-01-01

    The problem of low-speed impact of a one-dimensional sandwich panel by a rigid cylindrical projectile is considered. The core of the sandwich panel is functionally graded such that the density, and hence its stiffness, vary through the thickness. The problem is a combination of static contact problem and dynamic response of the sandwich panel obtained via a simple nonlinear spring-mass model (quasi-static approximation). The variation of core Young's modulus is represented by a polynomial in the thickness coordinate, but the Poisson's ratio is kept constant. The two-dimensional elasticity equations for the plane sandwich structure are solved using a combination of Fourier series and Galerkin method. The contact problem is solved using the assumed contact stress distribution method. For the impact problem we used a simple dynamic model based on quasi-static behavior of the panel - the sandwich beam was modeled as a combination of two springs, a linear spring to account for the global deflection and a nonlinear spring to represent the local indentation effects. Results indicate that the contact stiffness of thc beam with graded core Increases causing the contact stresses and other stress components in the vicinity of contact to increase. However, the values of maximum strains corresponding to the maximum impact load arc reduced considerably due to grading of thc core properties. For a better comparison, the thickness of the functionally graded cores was chosen such that the flexural stiffness was equal to that of a beam with homogeneous core. The results indicate that functionally graded cores can be used effectively to mitigate or completely prevent impact damage in sandwich composites.

  3. Conformal thin-sandwich puncture initial data for boosted black holes

    SciTech Connect

    Hannam, Mark D.; Cook, Gregory B. [Center for Gravitational Wave Astronomy, University of Texas at Brownsville, 80 Fort Brown, Brownsville, Texas 78520 (United States); Department of Physics, Wake Forest University, Winston-Salem, North Carolina 27109 (United States)

    2005-04-15

    We apply the puncture approach to conformal thin-sandwich black-hole initial data. We solve numerically the conformal thin-sandwich puncture (CTSP) equations for a single black hole with nonzero linear momentum. We show that conformally-flat solutions for a boosted black hole have the same maximum gravitational radiation content as the corresponding Bowen-York solution in the conformal transverse-traceless decomposition. We find that the physical properties of these data are independent of the free slicing parameter.

  4. Cherenkov radiation of a Josephson vortex moving in a sandwich embedded in a dielectric medium

    SciTech Connect

    Malishevskii, A. S., E-mail: malish@lebedev.ru; Silin, V. P.; Uryupin, S. A.; Uspenskii, S. G. [Russian Academy of Sciences, Lebedev Physical Institute (Russian Federation)

    2008-08-15

    A motion of a Josephson vortex in a long sandwich embedded in a dielectric medium is described. If the velocity of the vortex is greater than the velocity of light in the dielectric, terahertz-band Cherenkov radiation is generated and emitted from the lateral surface of the sandwich. The radiation loss power is determined. In the case when radiation loss is compensated for by the energy gain due to transport current, a relation between the current and the velocity of the vortex is obtained.

  5. On core compressibility of sandwich composite panels subjected to intense underwater shock loads

    NASA Astrophysics Data System (ADS)

    Ghoshal, Ritwik; Mitra, Nilanjan

    2014-01-01

    Novel analytical models have been proposed in this study which extends current available fluid-structure interaction (FSI) theories for explosion induced shock loading on monolithic and laminated composite plates to sandwich composite panels, featuring core compression. The proposed models have been asymptotically validated against other FSI existing theories in low pressure range. A qualitative comparative analysis of the proposed models has been made with other existing FSI theories from the viewpoint of energy conservation. Core compression as predicted by the proposed models can be utilized for more economical, robust design of blast resistant sandwich composite structures.

  6. Analyses for Debonding of Stitched Composite Sandwich Structures Using Improved Constitutive Models

    NASA Technical Reports Server (NTRS)

    Glaessgen, E. H.; Sleight, D. W.; Krishnamurthy, T.; Raju, I. S.

    2001-01-01

    A fracture mechanics analysis based on strain energy release rates is used to study the effect of stitching in bonded sandwich beam configurations. Finite elements are used to model the configurations. The stitches were modeled as discrete nonlinear spring elements with a compliance determined by experiment. The constitutive models were developed using the results of flatwise tension tests from sandwich material rather than monolithic material. The analyses show that increasing stitch stiffness, stitch density and debond length decrease strain energy release rates for a fixed applied load.

  7. Enhanced transmittance and fields of a thick metal sandwiched between two dielectric photonic crystals

    NASA Astrophysics Data System (ADS)

    Du, Gui-qiang; Jiang, Hai-tao; Wang, Li; Wang, Zhan-shan; Chen, Hong

    2010-11-01

    We demonstrated that transmittance and field intensities of a thick metal sandwiched between two dielectric photonic crystals (PCs) can be enhanced by more than two orders of magnitude and by nearly 20 times, respectively, compared to a single metal layer with the same thickness. Under the tunneling mechanism, the light can enter the sandwiched structure without reflection and localizes at the two interfaces of the metal film and PCs. This configuration of fields facilitates the reduction of absorption in the metal. Experimental results are in good agreement with simulations.

  8. Impact damage detection in sandwich composite structures using Lamb waves and laser vibrometry

    NASA Astrophysics Data System (ADS)

    Lamboul, B.; Passilly, B.; Roche, J.-M.; Osmont, D.

    2013-01-01

    This experimental study explores the feasibility of impact damage detection in composite sandwich structures using Lamb wave excitation and signals acquired with a laser Doppler vibrometer. Energy maps are computed from the transient velocity wave fields and used to highlight defect areas in impacted coupons of foam core and honeycomb core sandwich materials. The technique performs well for the detection of barely visible damage in this type of material, and is shown to be robust in the presence of wave reverberation. Defect extent information is not always readily retrieved from the obtained defect signatures, which depend on the wave - defect interaction mechanisms.

  9. Conformal thin-sandwich puncture initial data for boosted black holes

    E-print Network

    Mark D. Hannam; Gregory B. Cook

    2005-05-23

    We apply the puncture approach to conformal thin-sandwich black-hole initial data. We solve numerically the conformal thin-sandwich puncture (CTSP) equations for a single black hole with non-zero linear momentum. We show that conformally flat solutions for a boosted black hole have the same maximum gravitational radiation content as the corresponding Bowen-York solution in the conformal transverse-traceless decomposition. We find that the physical properties of these data are independent of the free slicing parameter.

  10. High-performance ultraviolet photodetectors based on ZnO/Au/ZnO sandwich structure

    NASA Astrophysics Data System (ADS)

    Liu, Rusheng; Jiang, Dayong; Zhang, Qingchao; Li, Rui; Duan, Qian; Qin, Jieming; Shen, Xiande; Hou, Jianhua; Zhao, Jianxun; Liang, Qingcheng; Gao, Shang

    2015-06-01

    We developed sandwich ultraviolet photodetectors by a radio frequency magnetron sputtering method. As expected, the performances of the optimized ZnO/Au/ZnO sandwich photodetectors are much better than that of a metal-semiconductor-metal structure through combing high responsivity (enlarged ~60 times) and low dark current (reduced by more than two orders of magnitudes). To investigate the above phenomena, simulations of electric-field intensity distribution in the two structured photodetectors were performed using the ANSYS software. A proposed physical mechanism is used to explain the above results, which agree well with the simulations.

  11. FaceSheet Push-off Tests to Determine Composite Sandwich Toughness at Cryogenic Temperatures

    NASA Technical Reports Server (NTRS)

    Gates, Thomas S.; Herring, Helen M.

    2001-01-01

    A new novel test method, associated analysis, and experimental procedures are developed to investigate the toughness of the facesheet-to-core interface of a sandwich material at cryogenic temperatures. The test method is designed to simulate the failure mode associated with facesheet debonding from high levels of gas pressure in the sandwich core. The effects of specimen orientation are considered, and the results of toughness measurements are presented. Comparisons are made between room and liquid nitrogen (-196 C) test temperatures. It was determined that the test method is insensitive to specimen facesheet orientation and strain energy release rate increases with a decrease in the test temperature.

  12. Impact damage detection in composite chiral sandwich panels using nonlinear vibro-acoustic modulations

    NASA Astrophysics Data System (ADS)

    Klepka, Andrzej; Staszewski, Wieslaw J.; di Maio, Dario; Scarpa, Fabrizio

    2013-08-01

    This paper reports an application of nonlinear acoustics to impact damage detection in a composite chiral sandwich panel. The panel is built from a chiral honeycomb and two composite skins. High-frequency ultrasonic excitation and low-frequency modal excitation were used to observe nonlinear modulations in ultrasonic waves due to structural damage. Low-profile, surface-bonded piezoceramic transducers were used for ultrasonic excitation. Non-contact laser vibrometry was applied for ultrasonic sensing. The work presented focuses on the analysis of the modulation intensities and damage-related nonlinearities. The paper demonstrates that the method can be used for impact damage detection in composite chiral sandwich panels.

  13. The composition of low-degree partial melts of garnet peridotite at 3 GPa by modified iterative sandwich experiments (MISE)

    Microsoft Academic Search

    F. A. Davis; M. M. Hirschmann; M. Humayun

    2009-01-01

    We have determined the composition of the incipient partial melt (F=0%) of garnet peridotite with composition similar to KLB-1 at 3 GPa through piston cylinder experiments using the modified iterative sandwich experiment (MISE) method (Hirschmann and Dasgupta, 2007). Sandwich experiments were performed iteratively, with new melt compositions for subsequent experiments determined by calculation from the bulk mineral\\/melt partition coefficients for

  14. The low velocity impact response of sandwich beams with a corrugated core or a Y-frame core

    E-print Network

    Fleck, Norman A.

    of impact response to (i) velocity, over a wider range of velocities than achievable with the drop-weight are needed in ship hull designs that do not employ a back face. Keywords: Drop-weight test, Sandwich beam sandwich beams with corrugated and Y-frame cores have been measured in a drop-weight apparatus at 5 ms-1

  15. Wet-sand impulse loading of metallic plates and corrugated core sandwich panels J.J. Rimoli a

    E-print Network

    Wadley, Haydn

    Wet-sand impulse loading of metallic plates and corrugated core sandwich panels J.J. Rimoli a , B the mechanical response of edge-clamped sandwich panels subject to the impact of explosively driven wet sand of wet sand placed at different standoff distances. Monolithic plates of the same alloy and mass per unit

  16. Geometrically exact sandwich shells: The dynamic case L. Vu-Quoc *, H. Deng, X.G. Tan

    E-print Network

    Vu-Quoc, Loc

    Geometrically exact sandwich shells: The dynamic case L. Vu-Quoc *, H. Deng, X.G. Tan Department for geometrically exact sandwich shells. Vu-Quoc et al. [19] employ a ®nite element method to solve numerically (2001) 2825±2873 * Corresponding author. Tel.: +1-352-392-6227; fax: +1-352-392-7303. E-mail address: vu

  17. Shock loading response of sandwich panels with 3-D woven E-glass composite skins and stitched foam core

    Microsoft Academic Search

    Srinivasan Arjun Tekalur; Alexander E. Bogdanovich; Arun Shukla

    2008-01-01

    Sandwich composite are used in numerous structural applications, with demonstrated weight savings over conventional metals and solid composite materials. The increasing use of sandwich composites in defense structures, particularly those which may be exposed to shock loading, demands for a thorough understanding of their response to suc highly transient loadings. In order to fully utilize their potential in such extreme

  18. Quantum mechanical design and structures of hexanuclear sandwich complex and its multidecker sandwich clusters (Li6)n([18]annulene)n+1 (n = 1-3).

    PubMed

    Wang, Shu-Jian; Li, Ying; Wu, Di; Wang, Yin-Feng; Li, Zhi-Ru

    2012-09-13

    By means of density functional theory, a hexanuclear sandwich complex [18]annulene-Li6-[18]annulene which consists of a central Li6 hexagon ring and large face-capping ligands, [18]annulene, is designed and investigated. The large interaction energy and HOMO-LUMO gap suggest that this novel charge-separated complex is highly stable and may be experimentally synthesized. In addition, the stability found in the [18]annulene-Li6-[18]annulene complex extends to multidecker sandwich clusters (Li6)n([18]annulene)n+1 (n = 2-3). The energy gain upon addition of a [18]annulene-Li6 unit to (Li6)n-1([18]annulene)n is pretty large (96.97-98.22 kcal/mol), indicating that even larger multideckers will also be very stable. Similar to ferrocene, such a hexanuclear sandwich complex could be considered as a versatile building block to find potential applications in different areas of chemistry, such as nanoscience and material science. PMID:22873344

  19. Construction aggregates

    USGS Publications Warehouse

    Tepordei, V.V.

    1994-01-01

    Part of a special section on industrial minerals in 1993. The 1993 production of construction aggregates increased 6.3 percent over the 1992 figure, to reach 2.01 Gt. This represents the highest estimated annual production of combined crushed stone and construction sand and gravel ever recorded in the U.S. The outlook for construction aggregates and the issues facing the industry are discussed.

  20. Construction aggregates

    USGS Publications Warehouse

    Langer, W.H.; Tepordei, V.V.; Bolen, W.P.

    2000-01-01

    Construction aggregates consist primarily of crushed stone and construction sand and gravel. Total estimated production of construction aggregates increased in 1999 by about 2% to 2.39 Gt (2.64 billion st) compared with 1998. This record production level continued an expansion that began in 1992. By commodities, crushed stone production increased 3.3%, while sand and gravel production increased by about 0.5%.

  1. Construction aggregates

    USGS Publications Warehouse

    Tepordei, V.V.

    1996-01-01

    Part of the Annual Commodities Review 1995. Production of construction aggregates such as crushed stone and construction sand and gravel showed a marginal increase in 1995. Most of the 1995 increases were due to funding for highway construction work. The major areas of concern to the industry included issues relating to wetlands classification and the classification of crystalline silica as a probable human carcinogen. Despite this, an increase in demand is anticipated for 1996.

  2. Composite sandwich structures consisting of fibre-reinforced composite skins and foam cores are widely used in aerospace and marine applications due to

    E-print Network

    Sóbester, András

    Background · Composite sandwich structures consisting of fibre-reinforced composite skins and foam of the elastic property of composite sandwich structures. · To address the paucity of data in assessing and Assessment of Composite Sandwich Structures Xiaoguang Xue ­xx4g10@soton.ac.uk - School of Engineering

  3. Dynamic Ham-Sandwich Cuts of Convex Polygons in the Plane Timothy Abbott Erik D. Demaine Martin L. Demaine Daniel Kane Stefan Langerman y

    E-print Network

    Dynamic Ham-Sandwich Cuts of Convex Polygons in the Plane Timothy Abbott #3; Erik D. Demaine #3 provide an eÆcient data structure for dynami- cally maintaining a ham-sandwich cut of two non- overlapping convex polygons in the plane. Given two non-overlapping convex polygons P 1 and P 2 in the plane, the ham-sandwich

  4. Applied Composite Materials, 2005. 12(3-4): p. 247-261 247 Enhancement of Energy Absorption in Syntactic Foams by Nanoclay Incorporation for Sandwich

    E-print Network

    Gupta, Nikhil

    in Syntactic Foams by Nanoclay Incorporation for Sandwich Core Applications Nikhil Gupta1 and Rahul Maharsia2 testing. Introduction Sandwich structured materials are widely used in structural applications requiring. Several types of light weight polymer composites are being developed for use as sandwich cores

  5. An analytical solution for the large deflections of a slender sandwich beam with a metallic foam core under transverse loading by a flat punch

    Microsoft Academic Search

    Qing Hua Qin; T. J. Wang

    2009-01-01

    The large deflections of slender ultralight sandwich beams with a metallic foam core are studied under transverse loading by a flat punch, in which interaction of bending and stretching induced by large deflections is considered. Firstly, a unified yield criterion for metallic sandwich structures considering the effect of core strength is proposed, which is valid for metallic sandwich cross-sections with

  6. Structure and characterization of zero- to two-dimensional compounds built up of the sandwich-type clusters and transition-metal linkers

    SciTech Connect

    Zhang Zhiming; Yao Shuang [Key Laboratory of Polyoxometalate Science of Ministry of Education, Department of Chemistry, Northeast Normal University, Renmin Street No. 5268, Changchun, Jinlin 130024 (China); Wang Enbo [Key Laboratory of Polyoxometalate Science of Ministry of Education, Department of Chemistry, Northeast Normal University, Renmin Street No. 5268, Changchun, Jinlin 130024 (China)], E-mail: wangenbo@public.cc.jl.cn; Qin Chao; Qi Yanfei [Key Laboratory of Polyoxometalate Science of Ministry of Education, Department of Chemistry, Northeast Normal University, Renmin Street No. 5268, Changchun, Jinlin 130024 (China); Li Yangguang [Key Laboratory of Polyoxometalate Science of Ministry of Education, Department of Chemistry, Northeast Normal University, Renmin Street No. 5268, Changchun, Jinlin 130024 (China); Universite Bordeaux 1, CNRS, Centre de Recherche Paul Pascal (CRPP)-UPR 8641, 115 avenue du Dr. A. Schweitzer, 33600 Pessac (France)], E-mail: Liyg658@nenu.edu.cn; Clerac, Rodolphe [Universite Bordeaux 1, CNRS, Centre de Recherche Paul Pascal (CRPP)-UPR 8641, 115 avenue du Dr. A. Schweitzer, 33600 Pessac (France)

    2008-04-15

    Five new heteropolyoxotungstates K{sub 2}Na{sub 2}Mn{sub 2}(H{sub 2}O){sub 12}[Mn{sub 2}(H{sub 2}O){sub 10}Mn{sub 4}(H{sub 2}O){sub 2}(XW{sub 9}O{sub 34}){sub 2}].18H{sub 2}O (X=Ge, 1; X=Si, 2), Na{sub 4}[Mn{sub 4}(H{sub 2}O){sub 18}Mn{sub 4}(H{sub 2}O){sub 2}(XW{sub 9}O{sub 34}){sub 2}].22H{sub 2}O (X=Ge, 3; X=Si, 4) and K{sub 3}Na{sub 5}[Mn{sub 2}(H{sub 2}O){sub 6}Mn{sub 4}(H{sub 2}O){sub 2}(SiW{sub 9}O{sub 34}){sub 2}].23.5H{sub 2}O (5) have been obtained by the routine synthetic reactions in aqueous solution. In 1 and 2, two isolated Mn{sup 2+} ions are covalently linked to the sandwich-type polyoxoanions [Mn{sub 4}(H{sub 2}O){sub 2}(B-{alpha}-XW{sub 9}O{sub 34}){sub 2}]{sup 12-} (X=Ge or Si) by two {mu}{sub 2}-oxygen atoms resulting in the disupporting sandwich-type polyoxometalates (POMs). Compounds 3 and 4 are built from the disupporting sandwich-type polyoxoanions 1 and 2, linked by additional four Mn{sup 2+} ions to construct a 1D ladder-like chain-like structure, which is rarely observed in the POM chemistry. Compound 5 represents the first example of the 2D structure consisting of the sandwich-type polyoxoanion [Mn{sub 4}(H{sub 2}O){sub 2}(SiW{sub 9}O{sub 34}){sub 2}]{sup 12-} and the binuclear {l_brace}Mn{sub 2}(H{sub 2}O){sub 6}{r_brace}{sup 4+} group. The magnetic studies of compounds 1, 4 and 5 indicate that the antiferromagnetic interactions are predominant in the three compounds between Mn(II) metal ions. - Graphical abstract: Five new compounds, from zero- to two-dimensional built up of the sandwich-type clusters and transition-metal linkers, have been obtained by the routine synthetic reactions in aqueous solution. This polyoxoanion framework architecture represents the first example of the 2D structure consisting of the sandwich-type polyoxoanion [Mn{sub 4}(H{sub 2}O){sub 2}(SiW{sub 9}O{sub 34}){sub 2}]{sup 12-} and the binuclear {l_brace}Mn{sub 2}(H{sub 2}O){sub 6}{r_brace}{sup 4+} group. Display Omitted.

  7. Worldwide construction

    Microsoft Academic Search

    1994-01-01

    The paper lists major construction projects in worldwide processing and pipelining, showing capacities, contractors, estimated costs, and time of construction. The lists are divided into refineries, petrochemical plants, sulfur recovery units, gas processing plants, pipelines, and related fuel facilities. This last classification includes cogeneration plants, coal liquefaction and gasification plants, biomass power plants, geothermal power plants, integrated coal gasification combined-cycle

  8. Extremely low-frequency Lamb wave band gaps in a sandwich phononic crystal thin plate

    NASA Astrophysics Data System (ADS)

    Shen, Li; Wu, Jiu Hui; Liu, Zhangyi; Fu, Gang

    2015-11-01

    In this paper, a kind of sandwich phononic crystal (PC) plate with silicon rubber scatterers embedded in polymethyl methacrylate (PMMA) matrix is proposed to demonstrate its low-frequency Lamb wave band gap (BG) characteristics. The dispersion relationship and the displacement vector fields of the basic slab modes and the locally resonant modes are investigated to show the BG formation mechanism. The anti-symmetric Lamb wave BG is further studied due to its important function in reducing vibration. The analysis on the BG characteristics of the PC through changing their geometrical parameters is performed. By optimizing the structure, a sandwich PC plate with a thickness of only 3 mm and a lower boundary (as low as 23.9 Hz) of the first anti-symmetric BG is designed. Finally, sound insulation experiment on a sandwich PC plate with the thickness of only 2.5 mm is conducted, showing satisfactory noise reduction effect in the frequency range of the anti-symmetric Lamb BG. Therefore, this kind of sandwich PC plate has potential applications in controlling vibration and noise in low-frequency ranges.

  9. Hepatocyte function and extracellular matrix geometry: long-term culture in a sandwich configuration

    Microsoft Academic Search

    JAMES C. Y. DUNN; MARTIN L. YARMUSH; HANS G. KOEBE; RONALD G. TOMPKINS

    Adult rat hepatocytes cultured in a collagen sandwich system maintained normal morphology and a physiolog- ical rate of albumin secretion for at least 42 days. Hep- atocytes cultured on a single layer of collagen gel essen- tially ceased albumin secretion within I wk but could recover function with the overlay of a second layer of collagen gel. This culture configuration

  10. The Convergence Rate of the Sandwich Algorithm for Approximating Convex Functions

    Microsoft Academic Search

    Günter Rote

    1992-01-01

    The Sandwich algorithm approximates a convex function of one variable over an interval by evaluating the function and its derivative at a sequence of points. The connection of the obtained points is a piecewise linear upper approximation, and the tangents yield a piecewise linear lower approximation. Similarly, a planar convex figure can be approximated by convex polygons. Different versions of

  11. The Math-On-Ed Sandwich: An Innovative Approach to Inservice Education.

    ERIC Educational Resources Information Center

    Damarin, Suzanne K.

    1981-01-01

    An approach to inservice training for teachers of elementary mathematics, designed to meet a set of common problems, is noted. The organization places a mathematics course between two education courses. A sandwich approach to whole number arithmetic is detailed. The method is viewed workable for any mathematics curriculum area. (MP)

  12. Sandwich Placements: Improving the Learning Experience--Part 1 and Part 2.

    ERIC Educational Resources Information Center

    Bourner, Tom; Ellerker, Mary

    1998-01-01

    "Sandwich" education, alternating periods of work experience and coursework, can be managed effectively using an action learning approach. Reflection, group support, vicarious learning, and other outcomes of action learning enable students to integrate the academic and vocational aspects of their experiences. (SK)

  13. Theoretical and experimental investigation of local bending effects in sandwich plates

    Microsoft Academic Search

    O. T. Thomsen

    1995-01-01

    This paper presents the results of a combined theoretical and experimental investigation of local bending effects in a clamped circular foam-cored sandwich plate subjected to a central point load. The theoretical investigation was conducted using an approximate method of local bending analysis, where the basic approach is to consider the deflection of the loaded face as being governed by a

  14. A protocol for characterizing the structural performance of metallic sandwich panels: application to pyramidal truss cores

    Microsoft Academic Search

    F. W. Zok; S. A. Waltner; Z. Wei; H. J. Rathbun; R. M. McMeeking; A. G. Evans

    2004-01-01

    All-metallic sandwich panels with truss and prismatic cores have impending application as ultra-light load bearing panels amenable to simultaneous active cooling and blast resistance. To facilitate application, a protocol for characterizing the structural performance of such panels is needed that can be used for design calculations. An approach capable of realizing this objective is presented and demonstrated for panels with

  15. Learning Outcomes and Assessment Strategies for a Psychology Sandwich Placement Year

    ERIC Educational Resources Information Center

    Reddy, Peter; Hill, Ros

    2002-01-01

    The aim of this action research study was to identify learning outcomes for assessing work-related transferable skills during undergraduate psychology sandwich year placements as part of an ongoing cycle of development of the placement. The merits of assessing such skills are considered in relation to the role of universities in preparing…

  16. On stress concentration in the bending of sandwich beams with transversely flexible core

    Microsoft Academic Search

    Y. Frostig

    1993-01-01

    Stress concentrations in sandwich beams with compressible cores, subjected to bending loading are investigated, and the level of stress concentrations under ordinary bending loads in various regions of the structure, and under some common-practice conditions, is analytically determined. The cases investigated include stress concentration effects for the following conditions: (1) in the vicinity of concentrated loads and supporting zones, (2)

  17. Comparison of Retention Rates Using Traditional, Drill Sandwich, and Incremental Rehearsal Flash Card Methods.

    ERIC Educational Resources Information Center

    MacQuarrie, Lara L.; Tucker, James A.; Burns, Matthew K.; Hartman, Brian

    2002-01-01

    Research has demonstrated increased retention from drill, but the data regarding drill format are inconsistent. Two commonly used models, Drill Sandwich (DS) and Incremental Rehearsal (IR), were compared to each other and to a traditional flashcard method. The IR model consistently led to significantly more words retained than the traditional or…

  18. A high-throughput, precipitating colorimetric sandwich ELISA microarray for shiga toxins

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Shiga toxins 1 and 2 (Stx1 and Stx2) from Shiga toxin-producing E. coli (STEC) bacteria were simultaneously detected with a newly developed, high-throughput antibody microarray platform. The proteinaceous toxins were immobilized and sandwiched between biorecognition elements (monoclonal antibodies)...

  19. Temperature effects on Kevlar\\/hybrid and carbon fiber composite sandwiches under impact loading

    Microsoft Academic Search

    Amin Salehi-Khojin; Mohammad Mahinfalah; Reza Bashirzadeh; Brian Freeman

    2007-01-01

    This paper presents the results of a research on impacted sandwich composites with Kevlar\\/hybrid and carbon facesheets subjected to different temperatures. Testing was performed to determine bending and core shear stresses, maximum energy absorption, and “absorbing energy and moment parameter” (AEMP), “performance parameter” (PP), and compression strength after impact (CSAI). Specimens were tested at temperature range of ?50°C to 120°C

  20. Perforation of sandwich plates with graded hollow sphere cores under impact loading , S.Pattofattoa

    E-print Network

    Paris-Sud XI, Université de

    1 Perforation of sandwich plates with graded hollow sphere cores under impact loading H.B.Zenga , S) are studied. The experiments at 45m/s were performed with an inversed perforation setup using SHPB system available) to better understand the perforation process. With these experimental and numerical tools

  1. Static and fatigue bending behavior of pultruded GFRP sandwich panels with through-thickness fiber insertions

    E-print Network

    Static and fatigue bending behavior of pultruded GFRP sandwich panels with through-thickness fiber to evaluate the static and fatigue characteristics of an innovative 3-D glass fiber reinforced polymer (GFRP to resist one-way bending. The experimental program was conducted in two phases to study the static

  2. Page 1 of 8 PERFORMANCE OF NEW 3D GFRP SANDWICH PANELS WITH

    E-print Network

    @solomoncomposites.com Abstract This paper presents the behavior of a new three-dimensional glass fiber reinforced polymer (3-D material characteristics, including flat-wise compression, skin tension, core shear and one-way bending behavior of 3-D glass FRP (GFRP) composite sandwich panels with through-thickness fiber insertions

  3. Shear and bending performance of carbon fiber composite sandwich panels with pyramidal truss cores

    E-print Network

    Vaziri, Ashkan

    Shear and bending performance of carbon fiber composite sandwich panels with pyramidal truss cores presented for possible competing fail- ure modes. In the experimental part of the study, pyramidal truss: Composites; Pyramidal truss cores; Shear; Bending; Failure mechanisms 1. Introduction Fiber reinforced

  4. A sandwich structured membrane for direct methanol fuel cells operating with neat methanol

    E-print Network

    Zhao, Tianshou

    of consumable electronic devices in re- cent years calls for innovation in portable power sources with high by the hygroscopic SiO2 nanoparticles in the sandwich structured membrane. As a result, such a created water source design, low noise and operating cost, high energy-conversion efficiency and specific energy, ease in fuel

  5. Finite element modelling of low velocity impact of composite sandwich panels

    Microsoft Academic Search

    T Besant; G. A. O Davies; D Hitchings

    2001-01-01

    This paper outlines a finite element procedure for predicting the behaviour under low velocity impact of sandwich panels consisting of brittle composite skins supported by a ductile core. The modelling of the impact requires a dynamic analysis that can also handle non-linearities caused by large deflections, plastic deformation of the core and in-plane degradation of the composite skins. Metal honeycomb,

  6. Compressive Failure of Impacted NCF Composite Sandwich Panels - Characterisation of the Failure Process

    Microsoft Academic Search

    Fredrik Edgren; Leif E. Asp; Peter H. Bull

    2004-01-01

    In the present study, non-crimp fabric (NCF) composite face sheet sandwich panels have been tested in compression after impact (CAI). Damage in the face sheets was characterised by fractography.Compression after impact loaded panels were found to fail by plastic fibre microbuckling (kinking) in the damaged face sheet. Studies of panels for which loading was interrupted prior to failure revealed extensive

  7. Qualitative and quantitative detection of T7 bacteriophages using paper based sandwich ELISA.

    PubMed

    Khan, Mohidus Samad; Pande, Tripti; van de Ven, Theo G M

    2015-08-01

    Viruses cause many infectious diseases and consequently epidemic health threats. Paper based diagnostics and filters can offer attractive options for detecting and deactivating pathogens. However, due to their infectious characteristics, virus detection using paper diagnostics is more challenging compared to the detection of bacteria, enzymes, DNA or antigens. The major objective of this study was to prepare reliable, degradable and low cost paper diagnostics to detect viruses, without using sophisticated optical or microfluidic analytical instruments. T7 bacteriophage was used as a model virus. A paper based sandwich ELISA technique was developed to detect and quantify the T7 phages in solution. The paper based sandwich ELISA detected T7 phage concentrations as low as 100pfu/mL to as high as 10(9)pfu/mL. The compatibility of paper based sandwich ELISA with the conventional titre count was tested using T7 phage solutions of unknown concentrations. The paper based sandwich ELISA technique is faster and economical compared to the traditional detection techniques. Therefore, with proper calibration and right reagents, and by following the biosafety regulations, the paper based technique can be said to be compatible and economical to the sophisticated laboratory diagnostic techniques applied to detect pathogenic viruses and other microorganisms. PMID:26052109

  8. Bioaccumulation of lead and cadmium in the Royal Tern and Sandwich Tern

    Microsoft Academic Search

    Joseph L. Maedgen; Carl S. Hacker; Gene D. Schroder; Francis W. Weir

    1982-01-01

    Lead and cadmium concentrations were measured in eggs and tissues of downy young, prefledgling, and adult Royal and Sandwich Terns collected from Galveston Bay, Texas. These species do not differ significantly in the amount of heavy metals they accumulate; however, they differed from other species of the same trophic level from Galveston Bay in degree and pattern of temporal accumulations

  9. Low-energy impact response of composite and sandwich composite plates with piezoelectric sensory layers

    E-print Network

    Papadopoulos, Evangelos

    , aerospace and every-day life applications, in cases such as a tool drop during repair, a hit by a runaway of composite and sandwich composite plates under low-energy impact is of practical significance in auto- motive stone or the fall of a composite cell-phone case from a table to the floor, where the damage caused may

  10. Detection of coproantigens by sandwich ELISA in sheep experimentally infected with Fasciola gigantica

    Microsoft Academic Search

    S. Endah Estuningsih; S. Widjayanti; G. Adiwinata; D. Piedrafita

    Two monoclonal antibodies to Fasciola gigantica excretory\\/secretory (ES) antigens were used in a sandwich ELISA for the detection of Fasciola antigens in faeces of 9 sheep experimentally infected with 300 metacercariae of F. gigantica. The detection of coproantigens was found in four of the seven sheep within 5 weeks of infection, and within 7 weeks of infection coproantigens were detected

  11. Diagnosis of Echinococcus granulosus infection in dogs by a coproantigen sandwich ELISA

    Microsoft Academic Search

    Prathapan Rema Prathiush; Placid Eugene D'Souza; Ananda K. Javare Gowda

    Echinococcosis is a near-cosmopolitan zoonosis caused by the adult or larval stages of tapeworms belonging to the genus echinococcus . Cystic echinococcosis in food animals is highly prevalent in India in general and in the Karnataka state in particular. A sandwich ELISA was standardized and evaluated in field conditions for coproantigen detection of echinococcus granulosus infection in dogs. Field fecal

  12. 8th International Conference on Sandwich Structures A. J. M. Ferreira (Editor)

    E-print Network

    Fleck, Norman A.

    made from an elastic brittle diamond-celled honeycomb, containing a centre-crack. The honeycomb fails, absorbers for solar receivers, supports for space mirrors, and orthopaedic implants for bone repair. Cracks(a) t 45= A B CRACK (b) Fig. 1 (a) Sandwich panel containing a cracked diamond-celled honeycomb

  13. Calibration of an analytical thermal model for an epoxy-based composite sandwich design

    Microsoft Academic Search

    Thomas R. Reinarts; Darrell Davis; Charles I. Stuckey

    2001-01-01

    An epoxy-based sandwich configuration was designed to meet the structural and thermal requirements of a nose cap for the space shuttle solid rocket boosters (SRB's). This project was suspended in late 1999, but the information gathered during this work is unique in the sense that portions of graphite-epoxy layers were modeled at temperatures exceeding their glass transition temperatures. This work

  14. End compression of sandwich columns N.A. Fleck*, I. Sridhar

    E-print Network

    Fleck, Norman A.

    sheets comprising woven glass ®bre Ð epoxy. The columns are subjected to end compression and the strength; accepted 18 July 2001 Abstract Sandwich columns, comprising woven glass ®bre reinforced epoxy face sheets macrobuckling, shear macrobuckling or by face sheet microbuckling, depending upon the material combination

  15. The forced vibration of a three-layer, damped sandwich beam with arbitrary boundary conditions

    Microsoft Academic Search

    D. J. Mead; S. Markus

    1969-01-01

    The sixth-order differential equation of motion is derived in terms of the transverse displacement, w, for a three-layer sandwich beam with a viscoelastic core. Mathematical expressions in terms of w are found for a variety of beam boundary conditions. The solution of the differential equation by the method of Di Taranto is shown to yield a special class of complex,

  16. Impact response of fiber metal laminate sandwich composite structure with polypropylene honeycomb core

    Microsoft Academic Search

    C. Y. Tan

    Fiber metal laminates (FMLs) were used as skin on polypropylene honeycomb core to form a sandwich structure. Impact response was measured by conducting a series of low-velocity impact test. Impact force and the force time history were recorded and analyzed. It was found that the maximum impact load increased up to a threshold value at which it plateaus while the

  17. Deformation and fracture of impulsively loaded sandwich panels H.N.G. Wadley a,n

    E-print Network

    Wadley, Haydn

    and impulse applied by the sand were gradually increased by reducing the stand-off distance between the test 22904, USA b Structural Impact Laboratory (SIMLab), Centre for Research-based Innovation (CRI clamped sandwich panels and solid plates of equal mass per unit area were subjected to localized impulsive

  18. Compression-after-Impact Strength of Sandwich Panels with Core Crushing Damage

    NASA Astrophysics Data System (ADS)

    Shipsha, Andrey; Zenkert, Dan

    2005-05-01

    Compression-after-impact (CAI) strength of foam-cored sandwich panels with composite face sheets is investigated experimentally. The low-velocity impact by a semi-spherical (blunt) projectile is considered, producing a damage mainly in a form of core crushing accompanied by a permanent indentation (residual dent) in the face sheet. Instrumentation of the panels by strain gauges and digital speckle photography analysis are used to study the effect of damage on failure mechanisms in the panel. Residual dent growth inwards toward the mid-plane of a sandwich panel followed by a complete separation of the face sheet is identified as the failure mode. CAI strength of sandwich panels is shown to decrease with increasing impact damage size. Destructive sectioning of sandwich panels is used to characterise damage parameters and morphology for implementation in a finite element model. The finite element model that accounts for relevant details of impact damage morphology is developed and proposed for failure analysis and CAI strength predictions of damaged panels demonstrating a good correlation with experimental results.

  19. Numerical and experimental investigations on the behaviour of the sandwiched tube-type airbag

    Microsoft Academic Search

    Jing Huang; Wen He; Jikuang Yang; Zhihua Zhong

    2009-01-01

    Airbags have been widely used in passenger vehicles to protect occupants from vehicle collisions. Although the airbag is an advanced protective device, it has been continuously improved to minimise occupant injuries for true safety. The current study developed a new sandwiched tube-type airbag (STAB) consisting of two flat layers and a middle layer with a tube-type structure. The objective of

  20. Acoustic emission analysis of full-scale honeycomb sandwich composite curved fuselage panels

    Microsoft Academic Search

    Frank A. Leone Jr.; Didem Ozevin; Valery Godinez; Bao Mosinyi; John G. Bakuckas Jr.; Jonathan Awerbuch; Alan Lau; Tein-Min Tan

    2008-01-01

    Acoustic emission (AE) was monitored in notched full-scale honeycomb sandwich composite curved fuselage panels during loading. The purpose of the study was to evaluate the AE technique as a tool for detecting notch tip damage initiation and evaluating damage severity in such structures. This evaluation was a part of a more general study on the damage tolerance of six honeycomb

  1. An examination of nondestructive evaluation techniques for polymer matrix composite sandwich materials

    NASA Astrophysics Data System (ADS)

    Cosgriff, Laura M.; Roberts, Gary D.; Averbeck, Timothy; Jeanneau, Philippe; Quddus, Michael

    2006-03-01

    Structural sandwich materials composed of triaxially braided polymer matrix composite material face sheets sandwiching a foam core are being utilized for applications including aerospace components and recreational equipment. Since full scale components are being made from these sandwich materials, it is necessary to develop proper inspection practices for their manufacture and in field use. Specifically, nondestructive evaluation (NDE) techniques need to be investigated for analysis of components made from these materials. Hockey blades made from sandwich materials were examined with multiple NDE techniques including thermographic, radiographic, and laser based methods to investigate the manufactured condition of blades and damage induced from play. Hockey blades in an as received condition and damaged blades used in play were investigated with each technique. NDE images from the blades were presented and discussed. Structural elements within each blade were observed with radiographic imaging. Damaged regions and some structural elements of the hockey blades were identified with thermographic imaging. With shearography, structural elements, damaged regions, and other material variations were detected in the hockey blades. Each technique's advantages and disadvantages were considered in making recommendations for inspection of components made from these types of materials.

  2. Parameters estimation of sandwich beam model with rigid polyurethane foam core

    Microsoft Academic Search

    Nilson Barbieri; Renato Barbieri; Luiz Carlos Winikes

    2010-01-01

    In this work, the physical parameters of sandwich beams made with the association of hot-rolled steel, Polyurethane rigid foam and High Impact Polystyrene, used for the assembly of household refrigerators and food freezers are estimated using measured and numeric frequency response functions (FRFs). The mathematical models are obtained using the finite element method (FEM) and the Timoshenko beam theory. The

  3. Effective design of a sandwich beam with a metal foam core

    Microsoft Academic Search

    E. Magnucka-Blandzi; K. Magnucki

    2007-01-01

    The subject of the paper is a simply supported sandwich beam with a metal foam core. Mechanical properties of the core vary through its depth. A nonlinear hypothesis of deformation of a plane cross section of the beam is assumed and described. The elastic potential energy and the work of the load are formulated. The system of differential equations of

  4. Experimental investigation of compression moulding of glass\\/PA12PMI foam core sandwich components

    Microsoft Academic Search

    L. D. McGarva; B. T. Åström

    1999-01-01

    The manufacturing of sandwich components from pre-consolidated glass\\/polyamide 12 faces and polymethacrylimide foam core by compression moulding has been studied. A statistical experiment design was used initially to identify the dominant process parameters in terms of interfacial bond strength, evaluated using the transverse tensile test method. In a subsequent extended study, the influence of face temperature and moulding pressure on

  5. The Accuracy of the ABAQUS FE Numerical Modeling for Sandwich Beams with Foam Core

    Microsoft Academic Search

    G. E. Papakaliatakis; N. Karavagelas

    2009-01-01

    The foam of the sandwich core is a compressible material and in ABAQUS FEA is modelled using the crushable foam model. There are crushable foam models with volumetric hardening and with isotropic hardening in ABAQUS standard analysis and the same models for the ABAQUS explicit analysis, for isotropic compressible materials. Also, the Hill's plasticity model for general anisotropic incompressible solids,

  6. The plastic collapse of sandwich beams with a metallic foam core

    Microsoft Academic Search

    C. Chen; A. M. Harte; N. A. Fleck

    2001-01-01

    Plastic collapse modes of sandwich beams have been investigated experimentally and theoretically for the case of an aluminium alloy foam with cold-worked aluminium face sheets. Plastic collapse is by three competing mechanisms: face yield, indentation and core shear, with the active mechanism depending upon the choice of geometry and material properties. The collapse loads, as predicted by simple upper bound

  7. Failure mode shifts during constant amplitude fatigue loading of GFRP\\/foam core sandwich beams

    Microsoft Academic Search

    Dan Zenkert; Magnus Burman

    2011-01-01

    This paper presents fatigue results for sandwich beams that exhibit a transition in failure mode, from core shear failure to face laminate tensile failure, as function of load amplitude only. The basis of this are fatigue tests of foam cores in shear and tensile tests on composite laminates. These results show that the slopes of the stress–life (S–N) relation are

  8. Low-velocity heavy-mass impact response of slender metal foam core sandwich beam

    Microsoft Academic Search

    Qing Hua Qin; T. J. Wang

    2011-01-01

    The objective of this work is to investigate the dynamic large deflection response of fully clamped metal foam core sandwich beam struck by a low-velocity heavy mass. Analytical solution and ‘bounds’ of dynamic solutions are derived, respectively. Also, finite element analysis is carried out to obtain the numerical solution of the problem. Comparisons of the dynamic, the quasi-static and numerical

  9. Library Services to the Sandwich Generation and Serial Caregivers. ASCLA Changing Horizons Series.

    ERIC Educational Resources Information Center

    Walling, Linda Lucas, Comp.

    This book discusses library services to the "sandwich generation" (i.e., people in late middle age who find themselves caring for their elderly, impaired parents at the same time that their adult children are returning home for economic or other reasons) and "serial caregivers" (i.e., people who, at various periods throughout their lifetimes, find…

  10. Optimum stacking sequence design of composite sandwich panel using genetic algorithms

    NASA Astrophysics Data System (ADS)

    Bir, Amarpreet Singh

    Composite sandwich structures recently gained preference for various structural components over conventional metals and simple composite laminates in the aerospace industries. For most widely used composite sandwich structures, the optimization problems only requires the determination of the best stacking sequence and the number of laminae with different fiber orientations. Genetic algorithm optimization technique based on Darwin's theory of survival of the fittest and evolution is most suitable for solving such optimization problems. The present research work focuses on the stacking sequence optimization of composite sandwich panels with laminated face-sheets for both critical buckling load maximization and thickness minimization problems, subjected to bi-axial compressive loading. In the previous studies, only balanced and even-numbered simple composite laminate panels have been investigated ignoring the effects of bending-twisting coupling terms. The current work broadens the application of genetic algorithms to more complex composite sandwich panels with balanced, unbalanced, even and odd-numbered face-sheet laminates including the effects of bending-twisting coupling terms.

  11. Analysis of Laminated and Sandwich Composite Structures Using Solid-like Shell Elements

    NASA Astrophysics Data System (ADS)

    Kwon, Y. W.

    2013-08-01

    A new solid-like shell element was formulated which is suitable for analysis of laminated and sandwich composite structures. Then, a multiscale analysis technique was implemented to the shell element formulation so that micro-level stresses and strains (i.e. stresses and strains in reinforcing fibers and the binding matrix) in those structures can be computed. The shell element has three displacement degrees of freedom per node like a 3-D solid element. Therefore, the shell elements can be stacked easily on top of one another like 3-D solid elements in order to represent multiple layers through the thickness of laminated and sandwich structures. The effect of a thin resin or adhesive layer in laminated and sandwich composite structures was investigated on both static and the dynamic responses of the structures using the developed shell elements. The study showed an apparent effect of the resin/adhesive layer even though it is very thin. As a result, the present shell element can be used effectively to include those thin layers in finite element analysis models of laminated and sandwich composite structures.

  12. Identification of honeycomb sandwich properties by high-resolution modal analysis

    E-print Network

    Paris-Sud XI, Université de

    Identification of honeycomb sandwich properties by high-resolution modal analysis M. R´ebillat X are estimated experimentally by means of a high-resolution modal analysis technique. An optimisation procedure by comparing simulated and measured characteristics (for example modal dampings Num n vs. XP n and frequencies

  13. Shear cracks in foam core sandwich panels - Nondestructive testing and damage assessment

    Microsoft Academic Search

    Dan Zenkert; Mats Vikstrom; TK O'Brien

    1992-01-01

    Different types of shear cracks in foam core sandwich panels were simulated using various procedures and were examined with a thermal NDT method based on an IR detector, showing that all types of simulated cracks could be satisfactorily detected. The residual strength of cracked panels was estimated, using the finite element method to compute fracture mechanics parameters, and the results

  14. Investigation on the indentation behavior of sandwich beams using crushable and hyperelastic foam cores

    Microsoft Academic Search

    J. Amorim; G. Pitarresi

    2010-01-01

    In this work the indentation behaviour of sandwich beams is studied adopting the classical approach representing the core material as a Winkler-type foundation. It is shown how most of the proposed theories can be derived from a general fourth order linear differential equation expressing the equilibrium of the indented beam skin. Different assumptions on the supporting boundary constraints and materials

  15. Characterization of Flexural Properties of Syntactic Foam Core Sandwich Composites and Effect of Density Variation

    Microsoft Academic Search

    Nikhil Gupta; Eyassu Woldesenbet

    2005-01-01

    Microballoons (hollow particles) of the same outer radius but with five different inner radius values are used to fabricate five types of syntactic foam slabs. These five types of slabs are used as the core material to fabricate sandwich composites. Three- and four-point bending and short beam shear strength tests are carried out to characterize the flexural behavior of syntactic

  16. Experimental and Numerical Study of Interface Crack Propagation in Foam-cored Sandwich Beams

    Microsoft Academic Search

    C. Berggreen; B. C. Simonsen; K. K. Borum

    2007-01-01

    This article deals with the prediction of debonding between core and face sheet in foam-cored sandwich structures. It describes the development, validation, and application of a FEM-based numerical model for the prediction of the propagation of debond damage. The structural mechanics is considered to be geometrically nonlinear while the local fracture mechanics problem is assumed to be linear. The presented

  17. Mechanical properties of chemically-treated hemp fibre reinforced sandwich composites

    Microsoft Academic Search

    M. M. Kabir; H. Wang; K. T. Lau; F. Cardona; T. Aravinthan

    In this study, hemp fabrics were used as reinforcements with polyester resin to form composite skins while short hemp fibres with polyester as a core for making composite sandwich structures. To improve the fibre matrix adhesion properties, alkalisation, silane and acetylation treatments on the fibres surface were carried out. Examinations through fourier transform infrared (FTIR) spectroscopy, scanning electron microscope (SEM),

  18. A nonlinear theory for doubly curved anisotropic sandwich shells with transversely compressible core

    Microsoft Academic Search

    Jörg Hohe; Liviu Librescu

    2003-01-01

    In the present paper, an advanced geometrically nonlinear shell theory of doubly curved structural sandwich panels with transversely compressible core is presented. The model is based on the adoption of the Kirchhoff theory for the face sheets and a second\\/third order power series expansion for the core displacements. The theory accounts for dynamic effects as well as for initial geometric

  19. Collapse mechanisms of sandwich beams with composite faces and a foam core,

    E-print Network

    Fleck, Norman A.

    microbuckling, face wrinkling and indentation. New models of indentation failure are introduced as previousCollapse mechanisms of sandwich beams with composite faces and a foam core, loaded in three with composite faces and polymer foam cores. Failure is by the competing modes of face sheet microbuckling

  20. Mechanical behavior and failure of composite pyramidal truss core sandwich columns

    Microsoft Academic Search

    Jian Xiong; Li Ma; Linzhi Wu; Jiayi Liu; Ashkan Vaziri

    2011-01-01

    A series of analytical and experimental investigations is presented to study the response and failure of pyramidal truss core sandwich panels made of carbon fiber composite under axial compression. In the analytical part of the study, three failure modes: (i) Euler or core shear macro-buckling, (ii) face wrinkling, and (iii) face sheet crushing, were considered and theoretical relationships for predicting