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1

Sandwich construction  

NASA Astrophysics Data System (ADS)

A form of composites known as structural sandwich construction is presented in terms of materials used, design details for solving edging and attachment problems, and charts of design material analysis. Sandwich construction is used in nearly all commercial airliners and helicopters, and military air and space vehicles, and it is shown that this method can stiffen a structure without causing a weight increase. The facing material can be made of 2024 or 7075 aluminum alloy, titanium, or stainless steel, and the core material can be wood or foam. The properties of paper honeycomb and various aluminum alloy honeycombs are presented. Factors pertaining to adhesive materials are discussed, including products given off during cure, bonding pressure, and adaptability. Design requirements and manufacturing specifications are resolved using numerous suggestions.

Marshall, A.

2

Sandwich Construction Solar Structural Facets  

SciTech Connect

Silver/glass mirrors have excellent optical properties but need a method of support in order to be used in concentrating solar thermal systems. In collaboration with the Cummins dish/Stirling development program, they started investigating sandwich construction as a way to integrate silver/glass mirrors into solar optical elements. In sandwich construction, membranes such as sheet metal or plastic are bonded to the front and back of a core (like a sandwich). For solar optical elements, a glass mirror is bonded to one of the membranes. This type of construction has the advantages of a high strength-to-weight ratio, and reasonable material and manufacturing cost. The inherent stiffness of sandwich construction mirror panels also facilitates large panels. This can have cost advantages for both the amount of hardware required as well as reduced installation and alignment costs. In addition, by incorporating the panels into the support structure reductions in the amount of structural support required are potentially possible.

Diver, R. B.; Grossman, J.W.

1998-12-22

3

Sandwich Construction Solar Structural Facets  

Microsoft Academic Search

Silver\\/glass mirrors have excellent optical properties but need a method of support in order to be used in concentrating solar thermal systems. In collaboration with the Cummins dish\\/Stirling development program, they started investigating sandwich construction as a way to integrate silver\\/glass mirrors into solar optical elements. In sandwich construction, membranes such as sheet metal or plastic are bonded to the

R. B. Diver; J. W. Grossman

1998-01-01

4

Concrete sandwich construction for energy conservation  

NASA Astrophysics Data System (ADS)

An abbreviated research study on use of shrinkage-compensating expansive concrete in sandwich-type wall and roof panels containing insulation at mid-thickness is described. The use of expansive concrete is shown to be a technically viable concept for eliminating shrinkage cracking, thus preventing moisture penetration which can reduce insulation effectiveness, cause deterioration of the insulating material, and accelerate steel corrosion. Embeddable resistance strain gages proved to be reliable for measuring expansion and subsequent shrinkage of the experimental panels. As a result of this study, a comprehensive research program is proposed for experimental verification of design and field control measures that will permit the use of shrinkage-compensating cement mortars in sandwich panel construction.

Keeton, J. R.

1980-03-01

5

Environmental Evaluation of Polyurethane Foam Core Sandwich Panel Construction.  

National Technical Information Service (NTIS)

An environmental evaluation of a sandwich panel bearing wall system for use in one of the Operation Breakthrough housing systems is described. Two samples of polyurethane foam core sandwich construction and four full size wall panels were evaluated. The s...

J. R. Shaver L. W. Masters T. W. Reichard J. H. Pielert

1972-01-01

6

Method of Making an Offset Corrugated Sandwich Construction.  

National Technical Information Service (NTIS)

A method for making an offset corrugated core sandwich construction is disclosed. Mandrels of preestablished form and size are arranged into a pattern in a confined area. After covering the mandrels with a release film, strips of pliable, uncured composit...

H. Ray L. W. Gause

1993-01-01

7

Standard method of tension test of flat sandwich constructions in flatwise plane  

SciTech Connect

This method covers the determination of the strength in tension, flatwise, of the core, or of the bond between core and facings, of an assembled sandwich panel. The test consists of subjecting a sandwich construction to tensile load normal to the plane of the sandwich, such loads being transmitted to the sandwich through thick loading blocks bonded to the sandwich facings.

Not Available

1980-01-01

8

Impulsive Loading of Cellular Media in Sandwich Construction  

Microsoft Academic Search

Motivated by recent efforts to mitigate blast loading using energy-absorbing materials, this paper investigates the uniaxial crushing of cellular media in sandwich construction under impulsive pressure loading. The cellular core is modeled using a rigid, perfectly-plastic, locking idealization, as in previous studies, and the front and back faces are modeled as rigid, with pressure loading applied to the front face

Joseph A. Main; George A. Gazonas

2006-01-01

9

Impulsive loading of cellular media in sandwich construction  

Microsoft Academic Search

Motivated by recent efforts to mitigate blast loading using energy absorbing materials, this paper investigates the uniaxial crushing of cellular media in sandwich construction under impulsive pressure loading. The cellular core material is modeled using a rigid, perfectly-plastic, locking idealization, as in previous studies, and the front and back faces are modeled as perfectly rigid. Pressure loading is applied to

Joseph Main; George Gazonas

2005-01-01

10

Impulsive Loading of Cellular Media in Sandwich Construction  

NASA Astrophysics Data System (ADS)

Motivated by recent efforts to mitigate blast loading using energy-absorbing materials, this paper investigates the uniaxial crushing of cellular media in sandwich construction under impulsive pressure loading. The cellular core is modeled using a rigid, perfectly-plastic, locking idealization, as in previous studies, and the front and back faces are modeled as rigid, with pressure loading applied to the front face and the back face unrestrained. Predictions of this analytical model show excellent agreement with explicit finite element computations, and the model is used to investigate the influence of the mass distribution between the core and the faces. Increasing the mass fraction in the front face is found to increase the impulse required for complete crushing of the cellular core but also to produce undesirable increases in back-face accelerations. Optimal mass distributions are investigated by maximizing the impulse capacity while limiting the back-face accelerations to a specified level.

Main, Joseph A.; Gazonas, George A.

2006-07-01

11

Impulsive loading of cellular media in sandwich construction  

NASA Astrophysics Data System (ADS)

Motivated by recent efforts to mitigate blast loading using energy absorbing materials, this paper investigates the uniaxial crushing of cellular media in sandwich construction under impulsive pressure loading. The cellular core material is modeled using a rigid, perfectly-plastic, locking idealization, as in previous studies, and the front and back faces are modeled as perfectly rigid. Pressure loading is applied to the front face with the back face unrestrained, and two forms of pressure input are considered: a triangular pulse and an idealized impulse of zero duration. The equation of motion for this system, which generalizes previous results for a fixed back face, is derived in nondimensional form in terms of a single coordinate representing the remaining mass fraction of uncompressed core material. Predictions of this analytical model show excellent agreement with computational simulations using the explicit finite element code LS-DYNA. This analytical model is used to investigate the influence of the relative distribution of mass among the core and the front and back faces, with the total mass held constant. An optimal mass distribution is obtained by maximizing the total impulse that can be absorbed, while limiting the back-face accelerations to a specified level.

Main, Joseph; Gazonas, George

2005-07-01

12

Experimental Modal Analysis of a Sandwich Construction, Glass Reinforced Plastic Composite Deck Panel.  

National Technical Information Service (NTIS)

This report details the experimental modal analysis of a 20-ft by 6-ft sandwich construction glass reinforced plastic panel. The panel includes four compliant foundations, which are designed to be equipment supports. The analysis reveals that below the fu...

C. P. Ratcliffe

1996-01-01

13

Three-dimensional parasitics cancellation in EMI filters with Power Sandwich construction  

Microsoft Academic Search

This paper exploits the three-dimensional (3D) parasitics cancellation techniques for EMI filters in Power Sandwich integrated construction. A Power Sandwich filter employs surface mount technology (SMT) compatible x-dimensional (x-dim) components which have the same height and double sided SMT electrical terminations. Thereby a 3D spatial components placement platform is provided. The 3D techniques which aim to canceling\\/reducing both mutual and

Xun Gong; J. A. Ferreira

2011-01-01

14

Study of heat and moisture transport for concrete sandwich panel wall construction  

Microsoft Academic Search

This paper presents a mathematical model for simulation of transient heat and moisture transfer in concrete sandwich panel wall constructions with variable outdoor temperature and humidity as boundary conditions. The objective is to evaluate the possibility of diminishing moisture content in constructions in order to reduce deterioration risks. Some control strategies involving installation of heating cables in the air gap

XS Lü; T Lu; V Penttala; T Lehtinen

2004-01-01

15

Deformation of sandwich panels in cylindrical bending by point forces. 1. Analytical construction  

Microsoft Academic Search

A refined model for bending of a three-layered panel with a soft filler is proposed. The modified model permits us to consider\\u000a the asymmetry of elastic properties and thickness of the outer layer relative to the middle plane of the panel in a composite\\u000a sandwich structure. In constructing the deformation mechanism, a heterogeneous kinematic model was adopted, which, in contrast

V. A. Polyakov

1996-01-01

16

Concrete sandwich construction for energy conservation. Final report, October 1975-September 1978  

SciTech Connect

An abbreviated research study on use of shrinkage-compensating expansive concrete in sandwich-type wall and roof panels containing insulation at mid-thickness is described. The use of expansive concrete is shown to be a technically viable concept for eliminating shrinkage cracking, thus preventing moisture penetration which can reduce insulation effectiveness, cause deterioration of the insulating material, and accelerate steel corrosion. Embeddable resistance strain gages proved to be reliable for measuring expansion and subsequent shrinkage of the experimental panels. As a result of this study, a comprehensive research program is proposed for experimental verification of design and field control measures that will permit the use of shrinkage-compensating cement mortars in sandwich panel construction.

Keeton, J.R.

1980-03-01

17

Optimum design of a lightweight mirror using aluminum foam or honeycomb sandwich construction: a case study for the GLAS telescope  

NASA Astrophysics Data System (ADS)

A simple closed form solution was derived for the optimum weight design of a cylindrical sandwich mirror for a given self-weight deflection and mirror radius. This optimum solution is based on the generalized deflection equation for an axisymmetrically supported thick circular plate. This two parameter equation of deflection captures the deflection of the plate caused by bending and transverse shear. The solution yields the optimum facesheet thickness, core thickness, and core density. The derived optimum solution was used in a case stud for the GLAS (Geoscience Laser Altimeter System) primary mirror. This Beryllium mirror is manufactured with an open back isogrid pattern. The objective of this study is to determine a lightweight mirror design using Aluminum sandwich construction that can meet the performances of the current mirror and reduce fabrication costs. With the optimum solution several first order approximations using Aluminum honeycomb or foam core were determined. The performance, 1 g deflection, and wave front error of these designs was determined from Finite Element Analysis. The results conclude that sandwich construction outperforms the isogrid design by significant margins on both weight and distortion if the same material is used. Because of its superior specific stiffness the Beryllium isogrid design still marginally outperforms the optimum Aluminum sandwich design. However, the Aluminum sandwich design should provide significant advantages on cost and ease of fabrication over Beryllium isogrid designs.

Conkey, Shelly B.; Lee, Chiachung; Chaykovsky, Stephen P.; Content, David A.; Morrell, Armando; Budinoff, Jason G.

2000-10-01

18

Effect of Construction Method on the Fire Behavior of Sandwich Panels with Expanded Polystyrene Cores in Room Fire Tests  

Microsoft Academic Search

Room fire tests are conducted, according to the ISO 9705 or ISO 13784-1 protocols, on steel-skinned sandwich panels with expanded polystyrene (EPS) cores. The thickness of the panel cores, grade of EPS, and construction methods of fixing the panels are varied. During the fire tests, the temperature profiles within the panels are measured to determine the onset of EPS melting

Gregory J. Griffin; Ashley D. Bicknell; Glenn P. Bradbury; Nathan White

2006-01-01

19

A study on composite honeycomb sandwich panel structure  

Microsoft Academic Search

Honeycomb sandwich structure combines high flexural rigidity and bending strength with low weight. Sandwich construction plays an increasing role in industry, and sandwich structural designing is an available method for sandwich structures. However, the absence of the design variable is the principal problem of composite sandwich construction. In this paper, the structure and mechanical properties of honeycomb sandwich panels are

Meifeng He; Wenbin Hu

2008-01-01

20

Honeycomb core material for sandwich construction - with common hexagonal walls bonded by thermoplastic resin and free walls carrying layer of resin and masking agent  

Microsoft Academic Search

Abstract:of NL 8902116 (A) \\u000aIn a honeycomb core material for a sandwich construction, the common hexagonal walls are bonded together by a thermoplastic resin, and the free hexagonal walls carry a layer of the same resin and also a masking agent. - A number of plates of raw material are given strips of glue, are laid on one another, and

1991-01-01

21

Performance of sandwich plates with truss cores  

Microsoft Academic Search

Sandwich plates with truss cores fashioned from straight struts have distinct advantages relative to other constructions, including those with honeycomb cores. In addition to opportunities afforded by their open architecture, the truss core sandwich plates meet or exceed the load carrying capacity of other competitive constructions. The weight of truss core sandwich plates subject to a crushing stress and arbitrary

Nathan Wicks; John W. Hutchinson

2004-01-01

22

Characterization of a PLGA sandwiched cell\\/fibrin tubular construct and induction of the adipose derived stem cells into smooth muscle cells  

Microsoft Academic Search

A poly(dl-lactic-co-glycolic acid) (PLGA) sandwiched adipose derived stem cell (ADSC)\\/fibrin tubular construct, fabricated using a step-by-step mold\\/extraction method, was characterized in this work. The ADSCs were also induced into smooth-muscle-like cells using growth factors such as hepatocyte growth factor (HGF), platelet-derived growth factor BB (PDGF-BB), transforming growth factor ?1 (TGF?1), and basic fibroblast growth factor (b-FGF). Compared with the non-induced

Xiaohong Wang; Antti A. Mäkitie; Kaija-Stiina Paloheimo; Jukka Tuomi; Markku Paloheimo; Shaochun Sui; Qiqing Zhang

2011-01-01

23

Rare sandwich-type polyoxomolybdates constructed from Di-/tetra-nuclear transition-metal clusters and trivacant keggin germanomolybdate fragments.  

PubMed

Two types of rare sandwich-type germanomolybdates [Na(12)(H(2)O)(36)][Cu(2)(beta-Y-GeMo(9)O(33))(2)].3H(2)O (1), [N(CH(3))(4)](4) [Na(6)(H(2)O)(24)][Cr(2)(beta-Y-GeMo(9)O(33))(2)].7H(2)O (2), and [Na(11)(H(2)O)(25)]H[M(4)(H(2)O)(2)(alpha-B-GeMo(9)O(34))(2)].6H(2)O (M = Ni(II) for 3, M = Mn(II) for 4 and M = Co(II) for 5) have been synthesized and characterized by elemental analyses, ICP spectra, IR spectroscopy, UV spectroscopy, thermogravimetry (TG) analyses (for 1-3), X-ray photoelectron spectroscopy (XPS) (for 1 and 3), X-ray powder diffraction (XRPD) (for 1 and 3) and single-crystal X-ray diffraction. To our knowledge, 1-5 represent the first sandwich-type germanomolybdates containing both {beta-Y-GeMo(9)O(33)}/{alpha-B-GeMo(9)O(34)} fragments and transition-metal clusters. Interestingly, 1 and 2 display the rare dinuclear transition-metal substituted sandwich-type structures with unusual trivacant {beta-Y-GeMo(9)O(33)} germanomolybdate units whereas 3-5 exhibit the first tetranuclear transition-metal substituted sandwich-type structures with familiar trivacant {alpha-B-GeMo(9)O(34)} germanomolybdate units. Surface photovoltage spectroscopy (SPS) and electric field induced surface photovoltage spectroscopy (EFISPS) measurements reveal that 1 and 3 bear the behavior of the n-type semiconductor. Magnetic measurements indicate 1 and 3 demonstrate antiferromagnetic exchange interactions and ferromagnetic exchange interactions, respectively. PMID:19769384

Li, Suzhi; Zhao, Junwei; Ma, Pengtao; Du, Juan; Niu, Jingyang; Wang, Jingping

2009-10-19

24

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

NASA Astrophysics Data System (ADS)

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.

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

1993-07-01

25

Characteristics of joining inserts for composite sandwich panels  

Microsoft Academic Search

Composite sandwich constructions are widely employed in various light weight structures, because composite sandwich panels have high specific stiffness and high specific bending strength compared to solid panels. Since sandwich panels are basically unsuited to carry localized loads, the sandwich structure should provide joining inserts to transfer the localized loads to other structures.In this work, the load transfer characteristics of

Byoung Jung Kim; Dai Gil Lee

2008-01-01

26

Selective construction of Pd2Pt and PdPt2 triangles in a sandwich framework: carbocyclic ligands as scaffolds for a mixed-metal system.  

PubMed

Sandwich time! The mixed-metal triangular-trinuclear sandwich complexes of Pd(2)Pt and PdPt(2) were selectively synthesized. The Pd(2)Pt and PdPt(2) triangles in a cycloheptatrienyl sandwich framework were identified by (31)P?NMR analyses of the tris-triphenylphosphine complexes (see scheme). PMID:22714664

Murahashi, Tetsuro; Usui, Kentaro; Tachibana, Yuki; Kimura, Seita; Ogoshi, Sensuke

2012-06-19

27

Constructing sandwich-type rare earth double-decker complexes with N-confused porphyrinato and phthalocyaninato ligands.  

PubMed

Reaction of the half-sandwich complexes M(III)(Pc)(acac) (M = La, Eu, Y, Lu; Pc = phthalocyaninate; acac = acetylacetonate) with the metal-free N-confused 5,10,15,20-tetrakis[(4-tert-butyl)phenyl]porphyrin (H(2)NTBPP) or its N2-position methylated analogue H(CH(3))NTBPP in refluxing 1,2,4-trichlorobenzene (TCB) led to the isolation of M(III)(Pc)(HNTBPP) (M = La, Eu, Y, Lu) or Y(III)(Pc)[(CH(3))NTBPP] in 8-15% yield. These represent the first examples of sandwich-type rare earth complexes with N-confused porphyrinato ligands. The complexes were characterized with various spectroscopic methods and elemental analysis. The molecular structures of four of these double-decker complexes were also determined by single-crystal X-ray diffraction analysis. In each of these complexes, the metal center is octa-coordinated by four isoindole nitrogen atoms of the Pc ligand, three pyrrole nitrogen atoms, and the inverted pyrrole carbon atom of the HNTBPP or (CH(3))NTBPP ligand, forming a distorted coordination square antiprism. For Eu(III)(Pc)(HNTBPP), the two macrocyclic rings are further bound to a CH(3)OH molecule through two hydrogen bonds formed between the hydroxyl group of CH(3)OH and an aza nitrogen atom of the Pc ring or the inverted pyrrole nitrogen atom of the HNTBPP ring, respectively. The location of the acidic proton at the inverted pyrrole nitrogen atom (N2) of the protonated double-deckers was revealed by (1)H NMR spectroscopy. PMID:22906488

Cao, Wei; Wang, Hailong; Wang, Xin; Lee, Hung Kay; Ng, Dennis K P; Jiang, Jianzhuang

2012-08-20

28

Construction of a specific and sensitive sandwich enzyme immunoassay for 20 kDa human growth hormone  

Microsoft Academic Search

Twenty kilodalton human growth hormone (20K-hGH) is a naturally occurring isoform lacking amino acid residues 32–46 of 22K-hGH. Due to this structural similarity to 22K-hGH, no one has constructed a specific and sensitive assay system for 20K-hGH, which can be used for measuring physiological concentration of this isoform in the circulation. To construct such a specific assay system, we have

Yoshihide Hashimoto; Ichiro Ikeda; Miwa Ikeda; Yuka Takahashi; Masaharu Hosaka; Hiroshi Uchida; Naoko Kono; Hideo Fukui; Tadashi Makino; Masaru Honjo

1998-01-01

29

Gas Gun Impact Analysis on Adhesives in Sandwich Composite Panels  

Microsoft Academic Search

\\u000a As the application of composite sandwich panels is ever increasing, there is an increasing interest in the impact damage that\\u000a occurs on these sandwich panels. Since these composite sandwich panels are constructed in various manners, analysis on different\\u000a panel construction practices is of interest. Specifically, when a sandwich composite is cured, a film adhesive or just the\\u000a prepreg resin system

Matthew Mordasky; Weinong Chen

30

Pulsatile culture of a poly(DL-lactic-co-glycolic acid) sandwiched cell/hydrogel construct fabricated using a step-by-step mold/extraction method.  

PubMed

To overcome the weak mechanical properties of cell/hydrogel composites, a poly(DL-lactic-co-glycolic acid) sandwiched adipose-derived stem cell (ADSC)/fibrin construct was fabricated using a step-by-step mold/extraction method to generate the middle smooth muscle layer of natural blood vessels. A pulse bioreactor with an adjustable 0-0.2 MPa pressure, 0-7% pulse amplitude, and 0-80 times/min pulse frequency was developed to mimic the liquid movement in the natural blood vessels. This new type of pulse bioreactor is sterilizable and dismantles easily. A comparative study was conducted with static and dynamic in vitro cultures. Exogenous growth factors, such as hepatocyte growth factor, platelet-derived growth factor BB, transforming growth factor ?1, and basic fibroblast growth factor were used as additives in the culture medium for inducing the ADSCs into smooth muscle cells. The dynamic training, integrated with the growth factor, induced the transformation of ADSCs into smooth muscle-like cells with regular arrangement. This strategy shows promise of being widely used in tissue engineering and complex organ manufacturing. PMID:21671960

Wang, Xiaohong; Sui, Shaochun

2011-06-01

31

Advances in the Structural Modeling of Elastic Sandwich Panels  

Microsoft Academic Search

The area of sandwich construction has been an active field of research for more than five decades. During this period, a large number of mathematical models for structural sandwich panels has been provided, ranging from the early sandwich membrane models to more sophisticated recent approaches. Especially during the past decade, the increasing demand for high-performance, lightweight structures has stimulated a

JÖRG HOHE; LIVIU LIBRESCU

2004-01-01

32

The strength characteristics of aluminum honeycomb sandwich panels  

Microsoft Academic Search

Aluminum sandwich construction has been recognized as a promising concept for structural design of lightweight transportation systems such as aircraft, high-speed trains and fast ships. The aim of the present study is to investigate the strength characteristics of aluminum sandwich panels with aluminum honeycomb core theoretically and experimentally. A series of strength tests are carried out on aluminum honeycomb-cored sandwich

Jeom Kee Paik; Anil K Thayamballi; Gyu Sung Kim

1999-01-01

33

Design recommendations for sandwich panels  

Microsoft Academic Search

Professor Davies and L. Heselius summarize a major piece of work by CIB W56, which it is hoped will have immediate practical application; in particular, the importance of possible durability problems in structural sandwich panels used in building construction which had not previously been recognized. The research background to the proposals will be described in a companion paper.

J. M. Davies; L. Heselius

1993-01-01

34

Structural Analysis of Sandwich Foam Panels  

Microsoft Academic Search

The Sandwich Panel Technologies including Structural Insulated Panels (SIPs) can be used to replace the conventional wooden-frame construction method. The main purpose of this Cooperative Research and Development Agreement (CRADA) between UT-Battelle, LLC and SGI Venture, Inc. was to design a novel high R-value type of metal sandwich panelized technology. This CRADA project report presents design concept discussion and numerical

Jan Kosny; X. Sharon Huo

2010-01-01

35

Impact analysis of fiber reinforced polymer honeycomb composite sandwich beams  

Microsoft Academic Search

Large scale fiber reinforced polymer (FRP) composite structures have been used in highway bridge and building construction. Recent applications have demonstrated that FRP honeycomb sandwich panels can be effectively and economically applied for both new construction and rehabilitation and replacement of existing structures. This paper is concerned with impact analysis of an as-manufactured FRP honeycomb sandwich system with sinusoidal core

Pizhong Qiao; Mijia Yang

2007-01-01

36

Composite sandwich panel design  

Microsoft Academic Search

Development of damage-tolerant and fail-safe designs for composite-sandwich panel which is the primary aircraft structures poses a formidable challenge due to the many potential failure modes and lack of structural redundancy in sandwich designs. This challenge has inspired researchers to develop a way to predict facesheet tension rupture or compression failure of impact-damaged composite sandwich panels, and are working on

Steven G. Russell; Weichuan Lin; Han-Pin Kan; Ravi B. Deo

1995-01-01

37

Three-dimensional elasticity solution for sandwich panels with a functionally graded core  

Microsoft Academic Search

Sandwich panels are used in a variety of engineering applications including aircraft, construction and transportation. Due to the mismatch of stiffness properties between the face sheets and the core, sandwich panels are susceptible to delamination, which is a major problem in sandwich construction. To increase the resistance of such panels to delamination, the concept of a functionally graded material (FGM)

M. Kashtalyan; M. Menshykova

2009-01-01

38

Composite sandwich panel design  

NASA Astrophysics Data System (ADS)

Development of damage-tolerant and fail-safe designs for composite-sandwich panel which is the primary aircraft structures poses a formidable challenge due to the many potential failure modes and lack of structural redundancy in sandwich designs. This challenge has inspired researchers to develop a way to predict facesheet tension rupture or compression failure of impact-damaged composite sandwich panels, and are working on a process to predict facesheet local buckling failures at impact sites. Research has also produced a design methodology for sizing tear straps to fail-safe residual strength levels.

Russell, Steven G.; Lin, Weichuan; Kan, Han-Pin; Deo, Ravi B.

1995-04-01

39

Continuously Produced Paper Honeycomb Sandwich Panels for Furniture Applications  

Microsoft Academic Search

Today mechanical requirements and weight targets demand a lightweight sandwich design in many application areas. The potential of honeycomb sandwich construction in furniture applications is, like in many other application areas mainly determined by the production cost of cores and panels. In the last decade the traditional honeycomb production processes for low cost paper honeycomb cores have been optimised towards

J. Pflug; B. Vangrimde; I. Verpoest; D. Vandepitte

40

Advanced robust design optimization of FRP sandwich floor panels  

Microsoft Academic Search

FRP composite is now being used in the construction of main structural elements, such as the FRP sandwich panel for flooring system and bridges. The objective of this research is to use multi-objective optimization and robust design techniques to minimize the weight of the FRP sandwich floor panel design as well as maximizing the natural frequency. An Australian manufactures has

Z. K. Awad; F. Gonzalez; T. Aravinthan

2010-01-01

41

Minimum Weight Structural Sandwich.  

National Technical Information Service (NTIS)

Presents theoretical analyses for determination of dimensions of structural sandwich of minimum weight that will have certain stiffness and load-carrying capabilities. Includes a brief discussion of the resultant minimum weight configurations.

E. W. Kuenzi

1965-01-01

42

High-order free vibration of sandwich panels with a flexible core  

Microsoft Academic Search

Free vibration analysis of sandwich panels with a flexible core based on the high-order sandwich panel theory approach is presented. The mathematical formulation uses the Hamilton principle and includes derivation of the governing equations along with the appropriate boundary conditions. The formulation embodies a rigorous approach for the free vibration analysis of sandwich plates with a general construction, having high-order

Y. Frostig; O. T. Thomsen

2004-01-01

43

Failure mode maps for honeycomb sandwich panels  

Microsoft Academic Search

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 is constructed, showing the dependence of failure mode and load on the ratio of skin thickness to span length and honeycomb relative density. Beam specimens

A. Petras; M. P. F. Sutcliffe

1999-01-01

44

Force protection using composite sandwich structures  

Microsoft Academic Search

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

R. L. Sierakowski; M. L. Hughes

2006-01-01

45

Development of carbon-carbon sandwich panels  

NASA Astrophysics Data System (ADS)

The Electrostatic Gravity Gradiometer (EGG) is the main payload of the Gravity field and steady state Ocean Circulation Explorer (GOCE) mission, which has the objectives of producing models of the Earth's gravity field and geoid with high resolution and accuracy. The EGG allows measuring the components of the gravity gradient tensor by means of a set of accelerometers. To meet the outstanding measurement requirements, the EGG structure must provide high dimensional stability under the expected environmental conditions. Carbon-Carbon technology has been selected for the construction of the sandwich panels, which support the accelerometers and their electronics, as well as the thermal control unit. This technology in fact offers good thermo-elastic characteristics, low sensitivity to moisture (only for organic assembly), high panel stiffness-to-mass ratio. Due to the lack of heritage for large-size sandwich structures, a dedicated evaluation and qualification program has been established for the demonstration of the suitability of the sandwich and associated manufacturing processes to the GOCE applications. Following the evaluation of candidate materials and associated bonding techniques, a preferred baseline has been selected that is undergoing qualification testing. A safe two-steps manufacturing process of the sandwich panels has been adopted: C/C face-sheets and honeycomb cores are procured from Hitco Carbon Composites Inc, USA, and their assembly is performed by Alcatel Space through organic bonding, to obtain the final sandwich structure. The results of the evaluation and of the first qualification tests are presented in the paper.

Panin, Fabio; Lutz-Nivet, Martine; Lemaire, Hugues

2003-09-01

46

Graphene veils and sandwiches.  

PubMed

We report a new and highly versatile approach to artificial layered materials synthesis which borrows concepts of molecular beam epitaxy, self-assembly, and graphite intercalation compounds. It readily yields stacks of graphene (or other two-dimensional sheets) separated by virtually any kind of "guest" species. The new material can be "sandwich like", for which the guest species are relatively closely spaced and form a near-continuous inner layer of the sandwich, or "veil like", where the guest species are widely separated, with each guest individually draped within a close-fitting, protective yet atomically thin graphene net or veil. The veils and sandwiches can be intermixed and used as a two-dimensional platform to control the movements and chemical interactions of guest species. PMID:21770385

Yuk, Jong Min; Kim, Kwanpyo; Alemán, Benjamín; Regan, William; Ryu, Ji Hoon; Park, Jungwon; Ercius, Peter; Lee, Hyuck Mo; Alivisatos, A Paul; Crommie, Michael F; Lee, Jeong Yong; Zettl, Alex

2011-07-25

47

Process for producing sandwich mouldings  

Microsoft Academic Search

A process is described for producing sandwich molding comprised of the sequential introduction into a mold a first material capable of forming the surface layer or skin of the sandwich molding followed by a second material capable of forming the core of the sandwich molding. After filling the mold, an oscillating pressure is applied to the material in the mold

Peter Stewart Allan; Michael John Bevis

1986-01-01

48

Fire hazard assessment on polyurethane sandwich panels for temporary accommodation units  

Microsoft Academic Search

Fire hazard assessment on sandwich panels used for constructing temporary accommodation units (TAUs) is discussed. The requirements imposed by the three responsible local government departments, i.e. Buildings Department, Fire Services Department and Labour Department, are outlined. A typical sandwich panel used for constructing TAUs was assessed by a cone calorimeter. Four radiative heat fluxes of 20, 25, 50 and 65

W. K. Chow

2004-01-01

49

Process for producing sandwich mouldings  

NASA Astrophysics Data System (ADS)

A process is described for producing sandwich molding comprised of the sequential introduction into a mold a first material capable of forming the surface layer or skin of the sandwich molding followed by a second material capable of forming the core of the sandwich molding. After filling the mold, an oscillating pressure is applied to the material in the mold at least during the initial cooling of the melt and concurrently therewith additional thermoplastic material is introduced into the mold.

Allan, Peter Stewart; Bevis, Michael John

1986-08-01

50

Structural Analysis of Sandwich Foam Panels  

SciTech Connect

The Sandwich Panel Technologies including Structural Insulated Panels (SIPs) can be used to replace the conventional wooden-frame construction method. The main purpose of this Cooperative Research and Development Agreement (CRADA) between UT-Battelle, LLC and SGI Venture, Inc. was to design a novel high R-value type of metal sandwich panelized technology. This CRADA project report presents design concept discussion and numerical analysis results from thermal performance study of this new building envelope system. The main objective of this work was to develop a basic concept of a new generation of wall panel technologies which will have R-value over R-20 will use thermal mass to improve energy performance in cooling dominated climates and will be 100% termite resistant. The main advantages of using sandwich panels are as follows: (1) better energy saving structural panels with high and uniform overall wall R-value across the elevation that could not be achieved in traditional walls; and (2) reducing the use of raw materials or need for virgin lumber. For better utilization of these Sandwich panels, engineers need to have a thorough understanding of the actual performance of the panels and system. Detailed analysis and study on the capacities and deformation of individual panels and its assembly have to be performed to achieve that goal. The major project activity was to conduct structural analysis of the stresses, strains, load capacities, and deformations of individual sandwich components under various load cases. The analysis simulated the actual loading conditions of the regular residential building and used actual material properties of the steel facings and foam.

Kosny, Jan [ORNL; Huo, X. Sharon [Tennessee Technological University

2010-04-01

51

Noise transmission through nonlinear sandwich panels  

NASA Astrophysics Data System (ADS)

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.

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

1983-04-01

52

Resonances of sandwiched optical antenna  

Microsoft Academic Search

We calculate the resonant properties of the sandwiched triangle and bowtie antennas using finite difference time domain technique and compare with one-layer structures. The sandwiched antennas possess two tunable resonances corresponding to the symmetric and antisymmetric modes for dipole excitation, which can be understood by the hybridization of the plasmons supported by the two golden layers of the antennas. We

Lisheng Wang; Jiasen Zhang; Xiaofei Wu; Jing Yang; Qihuang Gong

2008-01-01

53

Assessment of the delamination hazard of the core face sheet bond in structural sandwich panels  

Microsoft Academic Search

Delamination of the adhesive bond between face sheets and cellular core of structural sandwich panels is a major problem in sandwich construction. Due to incompatibilities in the modes of deformation associated with the face sheets and the cellular core, stress concentrations and singularities can occur even in absence of cracks. These stress concentrations are assumed to govern the onset of

Jörg Hohe; Wilfried Becker

2001-01-01

54

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

Microsoft Academic Search

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.

Joseph F. Rakow

2005-01-01

55

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

Microsoft Academic Search

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.

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

2010-01-01

56

On the crushing response of composite sandwich panels subjected to edgewise compression: experimental  

Microsoft Academic Search

In the present work the compressive properties, collapse modes and crushing characteristics of various types of composite sandwich panels were investigated in a series of edgewise compression tests. The tested sandwich panels were constructed trying four types of polymer foam core (more specifically PMI foam, two grades of linear PVC foam and polyurethane foam) and two types of FRP faceplate

A. G. Mamalis; D. E. Manolakos; M. B. Ioannidis; D. P. Papapostolou

2005-01-01

57

Experimental study on the flexural behavior of structural insulated sandwich timber panels  

Microsoft Academic Search

A series of flexural test and creep tests were conducted on 53 OSB structural insulated sandwich timber panels to predict their behavior when subjected to gravity loading when used in residential and low rise nonresidential buildings. The experiments were designed and performed to test full-scale panels for roof and floor residential construction. The structural adequacy of the developed sandwich panel

Aleem Shahzad Butt

2008-01-01

58

Numerical modeling and analysis of the damage characteristics of a honeycomb core within a sandwich panel  

Microsoft Academic Search

Sandwich panels increasingly replace metallic components in the aerospace industry. The sandwich panel configuration that is being considered in this research project is composed of carbon fiber composite facesheets encasing a honeycomb core. The honeycomb core is made from a fibrous sheet of material constructed into hexagonal cells. The core is relatively compliant compared to the composite facesheet, but together

Brandon M Wilkins

2009-01-01

59

Radiant heating tests of several liquid metal heat-pipe sandwich panels  

Microsoft Academic Search

Integral heat-pipe sandwich panels, which synergistically combine the thermal efficiency of heat pipes and the structural efficiency of honeycomb sandwich construction, were conceived as a means of alleviating thermal stress problems in the Langley Scramjet Engine. Test panels which utilized two different wickable honeycomb cores, facesheets with screen mesh sintered to the internal surfaces, and a liquid metal working fluid

C. J. Camarda; A. Basiulis

1983-01-01

60

Design, fabrication and test of liquid metal heat-pipe sandwich panels  

Microsoft Academic Search

Integral heat-pipe sandwich panels, which synergistically combine the thermal efficiency of heat pipes and the structural efficiency of honeycomb sandwich panel construction, were fabricated and tested. The designs utilize two different wickable honeycomb cores, facesheets with screen mesh sintered to the internal surfaces, and potassium or sodium as the working fluid. Panels were tested by radiant heating, and the results

A. Basiulis; C. J. Camarda

1983-01-01

61

Experimental and numerical evaluation of the mechanical behaviour of GFRP sandwich panels  

Microsoft Academic Search

This work deals with the analysis of the mechanical behaviour of a class of sandwich structures widely employed in marine constructions, constituted by fiber-glass laminate skins over PVC foam or polyester mat cores. In detail, a systematic experimental study and numerical simulations have shown that the theoretical prediction of the strength and the actual failure mechanism of these sandwich structures

A. Russo; B. Zuccarello

2007-01-01

62

Sonic resonance in a sandwiched electrorheological panel  

NASA Astrophysics Data System (ADS)

We have studied the sound transmission properties of a flexible sandwiched electrorheological (ER) panel. It shows that, at a frequency range of 80-150 Hz, the sound pressure level spectrum exhibits a resonant peak. The resonant peak makes a shift to high frequency and the phase of the transmitted wave changes with an increase of the applied electric field. A vibration-radiation model is set up to simulate the sound radiating process and verifies a resonant effect in the ER panel in qualitative agreement with experiments. The tunable resonance effect in the ER panel would be useful in constructing tunable phononic crystals and other acoustic devices.

Tang, Hong; Luo, Chunrong; Zhao, Xiaopeng

2005-07-01

63

Study of Structurally Efficient Graphite-Thermoplastic Trapezoidal-Corrugation Sandwich and Semi-Sandwich Panels.  

National Technical Information Service (NTIS)

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 be...

D. C. Jegley

1993-01-01

64

Fatigue performance of sandwich beams with a pyramidal core  

Microsoft Academic Search

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.

F. Côté; N. A. Fleck; V. S. Deshpande

2007-01-01

65

Mechanical behaviour of cellular core for structural sandwich panels  

Microsoft Academic Search

This paper deals with the analysis of the mechanical properties of the core materials for sandwich panels. In this work, the core is firstly a honeycomb and secondly tubular structure. This kind of core materials are extensively used, notably in automotive construction (structural components, load floors...). For this study, three approaches are developed: a finite element analysis, an analytical study

F. Meraghni; F. Desrumaux; M. L. Benzeggagh

1999-01-01

66

Impact damage on sandwich panels and multi-layer insulation  

Microsoft Academic Search

Most spacecraft rely intensively on sandwich construction for external structures with multi layer thermal insulation where appropriate. Experience gained in ESA with various spacecraft (ROSETTA, METOP, ATV,…) covers a substantial range of materials and configurations. In this work, the applicability of simple damage equations (e.g. those presently used for single or Whipple shield ballistic limits) to more complex configurations (e.g.

Michel Lambert; Frank K. Schäfer; Tobias Geyer

2001-01-01

67

Singular stress fields in cellular cores for structural sandwich panels  

Microsoft Academic Search

The present study is concerned with the singularity of the stress fields in the cell walls of hexagonal honeycomb cores used in sandwich construction. The stress singularity under consideration occurs at the intersections of the cell walls at the core face sheet interface due to incompatibilities in the modes of deformation associated with the unconstrained cellular core and the face

Jörg Hohe; Wilfried Becker; Sanjib Goswami

2001-01-01

68

Timing resolution of 'Shisk-Kebab' lead scintillator sandwich calorimeters.  

National Technical Information Service (NTIS)

We have constructed lead scintillator sandwich calorimeters with 1/4 (chi)(sub o) sampling frequency and total thickness (approximately)16(chi)(sub o). The 4 mm thick scintillator plates are read out by wavelength shifter fibers 1 mm in diameter which pas...

E. Kistenev S. White Y. Pischalnikov Y. Protopopov V. Rykalin

1992-01-01

69

Cellular Truss Core Sandwich Structures  

Microsoft Academic Search

Sandwich structures with open cell truss cores are a relatively new class of multifunctional material systems that can be made using affordable deformation, assembly and joining processes. A variety of cellular core architectures have recently been made from wrought metal alloys using inexpensive textile and perforated sheet methods. Here, the design, fabrication and properties for these types of structures is

David J. Sypeck

2005-01-01

70

On Sandwiched Magnetic Bearing Design  

Microsoft Academic Search

This paper presents an innovative design for magnetic poles used in active magnetic bearings (AMBs). The proposed hybrid sandwiched magnetic pole design not only practically reduces the bearing size, but also dramatically diminishes its cost. The magnetic force to counterbalance the gravity of the rotor is provided by the embedded permanent magnets (PMs), while the electromagnetic bearing is merely used

Nan-Chyuan Tsai; Sheng-Liang Hsu

2007-01-01

71

High temperature structural sandwich panels  

NASA Astrophysics Data System (ADS)

High strength composites are being used for making lightweight structural panels that are being employed in aerospace, naval and automotive structures. Recently, there is renewed interest in use of these panels. The major problem of most commercial available sandwich panels is the fire resistance. A recently developed inorganic matrix is investigated for use in cases where fire and high temperature resistance are necessary. The focus of this dissertation is the development of a fireproof composite structural system. Sandwich panels made with polysialate matrices have an excellent potential for use in applications where exposure to high temperatures or fire is a concern. Commercial available sandwich panels will soften and lose nearly all of their compressive strength temperatures lower than 400°C. This dissertation consists of the state of the art, the experimental investigation and the analytical modeling. The state of the art covers the performance of existing high temperature composites, sandwich panels and reinforced concrete beams strengthened with Fiber Reinforced Polymers (FRP). The experimental part consists of four major components: (i) Development of a fireproof syntactic foam with maximum specific strength, (ii) Development of a lightweight syntactic foam based on polystyrene spheres, (iii) Development of the composite system for the skins. The variables are the skin thickness, modulus of elasticity of skin and high temperature resistance, and (iv) Experimental evaluation of the flexural behavior of sandwich panels. Analytical modeling consists of a model for the flexural behavior of lightweight sandwich panels, and a model for deflection calculations of reinforced concrete beams strengthened with FRP subjected to fatigue loading. The experimental and analytical results show that sandwich panels made with polysialate matrices and ceramic spheres do not lose their load bearing capability during severe fire exposure, where temperatures reach several hundred degrees Centigrade. Hence the material has excellent potential for various types of applications. The analytical predictions from both models provide reasonably accurate results. Glass, AR-glass, carbon and Nicalon tows and carbon fabrics could be successfully used as skin reinforcements increasing the flexural stiffness and strength of the core. No occurrence of fiber delamination was observed.

Papakonstantinou, Christos G.

72

A computational methodology to select the best material combinations and optimally design composite sandwich panels for minimum cost  

Microsoft Academic Search

A procedure to select the best material combination and optimally design sandwich laminates with fibre reinforced skins and low density cores for minimum cost is described. Sandwich constructions generally provide improved stiffness\\/mass ratios and provide more tailoring opportunities than monolithics, and thus greater chance of satisfying design constraints. The objective of the optimisation is to minimise the laminate cost by

Mark Walker; Ryan Smith

2002-01-01

73

Fundamentals of Composite Sandwich Panels  

NSDL National Science Digital Library

This laboratory exercise will help instructors explain the particulars of designing composite sandwich panels, which are used in a variety of applications like surfboards, wake boards and corrugated cardboard. The experiment is explained step by step; this document will serve as a framework for instructors and may be downloaded in PDF format. The exercise would be appropriate for grades 4 through 12. It should take anywhere from one to three hours to complete.

Flinn, Brian D.

2012-11-09

74

Experimental Analysis of Foam Sandwich Panels with Projection Moiré  

Microsoft Academic Search

\\u000a The use of polymeric and metallic foam sandwich panels in naval, aerospace, railway and automotive constructions is rapidly\\u000a growing in the recent years because of technological improvements in manufacturing processes. However, it is still difficult\\u000a to establish a direct relationship between the mechanical properties possessed by the panel and the specific manufacturing\\u000a process. Mechanisms behind panel deformation, crack growth, fracture

A. Boccaccio; C. Casavola; L. Lamberti; C. Pappalettere

75

LOW VELOCITY PERFORATION BEHAVIOUR OF POLYMER COMPOSITE SANDWICH PANELS  

Microsoft Academic Search

The paper describes low-velocity impact tests on square panels made from two polymer composite sandwich constructions, namely woven glass vinyl ester skins with Coremat core and woven glass epoxy pre-preg skins with honeycomb core. The impact velocity was up to 8ms-1 with an impact mass of up to 30kg giving a maximum impact energy of 882J. This maximum energy gives

R. A. W. Mines; C. M. Worrall; A. G. Gibson

1998-01-01

76

Impact response of integrated hollow core sandwich composite panels  

Microsoft Academic Search

This paper deals with an innovative integrated hollow (space) E-glass\\/epoxy core sandwich composite construction that possesses several multi-functional benefits in addition to the providing lightweight and bending stiffness advantages. In comparison with traditional foam and honeycomb cores, the integrated space core provides a means to route wires\\/rods, embed electronic assemblies, and store fuel and fire-retardant foam, among other conceivable benefits.

U. K Vaidya; M. V Hosur; D Earl; S Jeelani

2000-01-01

77

From sandwich and triple-decker to organometallic polymers  

Microsoft Academic Search

Several types of organometallic polymers with different backbones are known. Our approach for the construction of metal-containing polymers uses the ability of Lewis-acidic boron heterocycles to interact antifacially with metals. The boron heterocycle 2,3-dihydro-1,3-diborole not only allows the formation of sandwich and triple-decker complexes but also the stacking of metal complex fragments to oligodecker and polydecker compounds. This account reviews

Walter Siebert

1991-01-01

78

Evaluation of the Flexural Rigidity of Sandwich Structures Using Experimentally Obtained Mechanical Properties of the Constituents  

Microsoft Academic Search

Prediction of mechanical performance of sandwich constructions is a difficult task due to the complex nonlinear and inelastic\\u000a behavior of the constituent materials. This study tries to utilize an analytical model to estimate the mechanical performance\\u000a of sandwich structure based on the mechanical properties of the constituents. To this end, the mechanical properties of the\\u000a core and skin materials were

F. Azarmi; T. W. Coyle; J. Mostaghimi

2010-01-01

79

Buckling of Sandwich Composites; Effects of Core–Skin Debonding and Core Density  

Microsoft Academic Search

Foam–core sandwich composites have been fabricated using innovative co-injection resin infusion technique and tested under in-plane compression. The sandwich construction consisted of Klegcell foam as core materials and S2-glass\\/vinyl ester composites as face sheets. Tests were conducted with various foam densities and also with implanted delamination between the core and the face sheet. The intent was to investigate the effect

Hassan Mahfuz; Syful Islam; Mrinal Saha; Leif Carlsson; Shaik Jeelani

2005-01-01

80

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

Microsoft Academic Search

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

William L. Ko

1994-01-01

81

DURABILITY OF GFRP RODS, LAMINATES, AND SANDWICH PANELS SUBJECTED TO VARIOUS ENVIRONMENTAL CONDITIONING  

Microsoft Academic Search

This paper outlines the performance of glass fiber-reinforced polymeric (GFRP) materials subjected to various environmental conditioning. The study is performed in conjunction with the construction of one bridge using FRP-reinforced concrete panels and three bridges using GFRP sandwich panels. GFRP rods utilizing a urethane-modified vinyl ester resin and GFRP laminates and sandwich panels utilizing an isophthalic polyester resin were subjected

Danielle K. Stone; Daniel Koenigsfeld; John Myers; Antonio Nanni

82

Long-term hygrothermal effects on damage tolerance of hybrid composite sandwich panels  

Microsoft Academic Search

A sandwich construction, composed of hybrid carbon-glass fibre-reinforced plastic skins and a syntactic foam core, was selected as the design concept for a wind tunnel compressor blade application, where high damage tolerance and durability are of major importance. Beam specimens were prepared from open-edge and encapsulated sandwich panels which had previously been immersed in water at different temperatures for periods

Ori Ishai; Clement Hiel; Michael Luft

1995-01-01

83

Strength evaluations of sinusoidal core for FRP sandwich bridge deck panels  

Microsoft Academic Search

Fiber-reinforced polymer (FRP) sandwich deck panels with sinusoidal core geometry have shown to be successful both in new construction and the rehabilitation of existing bridge decks. This paper is focused on an experimental study of the strength evaluations of a honeycomb sandwich core under out-of-plane compression and transverse shear. The sinusoidal core is made of E-glass Chopped Strand Mat (ChSM)

An Chen; Julio F. Davalos

2010-01-01

84

MECHANICAL AND THERMAL BUCKLING ANALYSIS OF SANDWICH PANELS UNDER DIFFERENT EDGE CONDITIONS  

Microsoft Academic Search

D,# By using the Rayleigh-Ritz method of minimizing the total DQz, DQ_ potential energy of a structural system, combined load (me- chanical or thermal load) buckling equations are established for orthotropic rectangular sandwich panels supported under four different edge conditions. Two-dimensional buckling in- teraction curves and three-dimensional buckling interaction surfaces are constructed for high-temperature honeycomb- core sandwich panels supported under

William L. Ko

85

Buckling of sandwich panels with a flexible core—high-order theory  

Microsoft Academic Search

The buckling behavior of sandwich panels with a core that is flexible in the out-of-plane direction, also denoted as “soft” core including high-order effects, is presented. The buckling analysis consists of the formulation of the linear and the nonlinear governing equations along with the boundary conditions. The sandwich panel construction is general and consists of two skin-panels, metallic or composite

Y. Frostig

1998-01-01

86

Stability Tests of Sandwich Composite Elastica Arches  

Microsoft Academic Search

A novel sandwich elastica arch is made by buckling its individual layers into shape, and then laminating them in place. One single-layer arch and four prototype sandwich composite arches with aluminum skins and discrete cores of balsa or oak wood were tested. Sandwich composite section resulted in a significant increase in the strength-to-weight ratio of the arch. The spacing of

Amde M. Amde; Amir Mirmiran; David Nelsen

2002-01-01

87

Flexural properties of grooved perforation sandwich composites  

Microsoft Academic Search

Selecting H-60 PVC foam, four-axis E-glass non-woven fabric and vinyl resin, a type of innovative reinforced sandwich composite\\u000a as grooved perforation sandwich (GPS) were fabricated by VIMP. The interfacial structure between the face and core of the\\u000a sandwich is innovative because of the acuminate grooves in both sides of foam core and the holes perforated along core’s height.\\u000a The fabrication

Hai Fang; Weiqing Liu; Weidong Lu; Li Wan

2010-01-01

88

Impact-damaged graphite-thermoplastic trapezoidal-corrugation sandwich and semi-sandwich panels  

Microsoft Academic Search

The results of a study of the effects of impact damage on compression-loaded trapezoidal-corrugation sandwich and semi-sandwich graphite-thermoplastic panels are presented. 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 in this study. Panels were designed, fabricated and tested. The panels were

D. Jegley

1993-01-01

89

Nonlinear analysis of a curved sandwich beam joined with a straight sandwich beam  

Microsoft Academic Search

The buckling behaviour of straight sandwich beams joined with curved sandwich beams loaded in pure bending is investigated using two different models. One is based on a high order sandwich beam theory and the other model is based on finite element analysis. The analyses are applied to a numerical example and the results are compared with experimental results.

Anders Lyckegaard; Ole Thybo Thomsen

2005-01-01

90

Advanced robust design optimization of FRP sandwich floor panels  

NASA Astrophysics Data System (ADS)

FRP composite is now being used in the construction of main structural elements, such as the FRP sandwich panel for flooring system and bridges. The objective of this research is to use multi-objective optimization and robust design techniques to minimize the weight of the FRP sandwich floor panel design as well as maximizing the natural frequency. An Australian manufactures has invented a new FRP composite panel suitable for civil engineering constructions. This research work aims to develop an optimal design of structural fibre composite sandwich floor panel by coupling a Finite Element FE and robust design optimization method. The design variables are the skin plies thickness and the core thickness as a robust variable. Results indicate that there is a trade-off between the objectives. The robust design technique is used then to select a set of candidate geometry, which has a high natural frequency, low weight and low standard deviation. The design simulation was formulated by depending on the EUROCOMP standard design constraints.

Awad, Z. K.; Gonzalez, F.; Aravinthan, T.

2010-06-01

91

Buckling of Sandwich Composites; Effects of Core-Skin Debonding and Core Density  

NASA Astrophysics Data System (ADS)

Foam-core sandwich composites have been fabricated using innovative co-injection resin infusion technique and tested under in-plane compression. The sandwich construction consisted of Klegcell foam as core materials and S2-glass/vinyl ester composites as face sheets. Tests were conducted with various foam densities and also with implanted delamination between the core and the face sheet. The intent was to investigate the effect of core density, and the effect of core-skin debonds on the overall buckling behavior of the sandwich. Analytical and finite element calculations were also performed to augment the experimental observations. It has been observed that core density has direct influence on the global buckling of the sandwich panel, while embedded delamination seem to have minimal effect on both global as well as local buckling. Detailed description of the experimental work, finite element modeling and analytical calculations are presented in this paper.

Mahfuz, Hassan; Islam, Syful; Saha, Mrinal; Carlsson, Leif; Jeelani, Shaik

2005-03-01

92

Metal sandwich plates optimized for pressure impulses  

Microsoft Academic Search

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

John W. Hutchinson; Zhenyu Xue

2005-01-01

93

A multifunctional heat pipe sandwich panel structure  

Microsoft Academic Search

A multifunctional sandwich panel combining efficient structural load support and thermal management characteristics has been designed and experimentally assessed. The concept is based upon a truncated, square honeycomb sandwich structure. In closed cell honeycomb structures, the transport of heat from one face to the other occurs by a combination of conduction through the webs and convection\\/radiation within the cells. Here,

Douglas T. Queheillalt; Gerardo Carbajal; G. P. Peterson; Haydn N. G. Wadley

2008-01-01

94

Vibration damping using four-layer sandwich  

NASA Astrophysics Data System (ADS)

This paper discusses vibration damping using four-layer sandwich beam. The present work deals with the analysis of vibration of the primary system having a mass and rubber spring mounted on a four-layer viscoelastic simply supported symmetrically arranged sandwich beam. The equation of motion of a general four-layer with alternate elastic layer and viscoelastic layer simply supported sandwich beam is first derived using the method of equilibrium of forces and beam theory. The above differential equation has been solved for harmonically force excited sandwich beam by applying suitable boundary conditions to get the impedance of the sandwich beam. This impedance is then combined with the impedance of the primary system to obtain the expression for the response of harmonically excited mass and then the expression for transmissibility is obtained. The effectiveness of geometrical and physical parameters in minimizing response and transmissibility for central mounting of the primary system is evaluated.

Yadav, Binod P.

2008-11-01

95

Graphene-antenna sandwich photodetector.  

PubMed

Nanoscale antennas sandwiched between two graphene monolayers yield a photodetector that efficiently converts visible and near-infrared photons into electrons with an 800% enhancement of the photocurrent relative to the antennaless graphene device. The antenna contributes to the photocurrent in two ways: by the transfer of hot electrons generated in the antenna structure upon plasmon decay, as well as by direct plasmon-enhanced excitation of intrinsic graphene electrons due to the antenna near field. This results in a graphene-based photodetector achieving up to 20% internal quantum efficiency in the visible and near-infrared regions of the spectrum. This device can serve as a model for merging the light-harvesting characteristics of optical frequency antennas with the highly attractive transport properties of graphene in new optoelectronic devices. PMID:22703522

Fang, Zheyu; Liu, Zheng; Wang, Yumin; Ajayan, Pulickel M; Nordlander, Peter; Halas, Naomi J

2012-06-19

96

Microleakage in the sandwich technique.  

PubMed

This study assessed the microleakage and if it was possible to reproduce the success that is seen in the oral cavity with properly placed "sandwich" restorations. Simulated Class V erosion lesions were prepared in extracted human molar teeth and restored using a Type III glass ionomer lining cement mixed mechanically at a high powder:liquid ratio of 3:1 or greater with resin composite laminated to it leaving cement exposed at the gingival margin. To update the technique for modern materials a dual cure glass ionomer lining cement was placed in a second series with resin composite laminated to it completely covering the gingival margin. The restorations were stored in water for two weeks before temperature cycled and immersed in dye. The results showed minimal leakage relative to most other published studies and that most leakage was related to the setting shrinkage of the resin composite. PMID:1290608

Mount, G J; Papageorgiou, A; Makinson, O F

1992-08-01

97

Optimization of nonhomogeneous facesheets in composite sandwich plates  

NASA Astrophysics Data System (ADS)

Minimum weight design is an important criterion in aircraft and spacecraft because it allows either an increased pay-load or higher performance. As a result, the use of composite sandwich panels has grown due to their light weight and high rigidity. In order to further increase the efficiency of these structures, designers have used different materials in different shapes in the facesheets and in the core. One of the most recent innovations has been the use of a uniform net of carbon fibre/epoxy as the facesheets. In the present study, the optimal design of sandwich plates with heterogeneous, facesheets is treated. The plate mass is minimized, considering the first natural frequency and certain failure loads as constraints. Weight reduction is obtained by defining a nonuniform distribution of composite material in the facesheets. Initially, the facesheets are assumed to be constructed of composite strips in a regular pattern. During the optimization process, both the widths of the strips and the spacing between them are varied to decrease the amount of material used. Such a design is conceptually straightforward to manufacture and, therefore, would lead to improved performance with little cost penalty. In order to solve this problem, it is first necessary to develop a computer code to determine the natural frequencies and the stresses in these plates. The bending and vibration problems for sandwich plates with heterogeneous facesheets are solved using the Ritz Method in conjunction with the assumptions formulated by Reissner for sandwich plates. Since the sandwich plate considered in this study has facesheets constructed of nets and the computer code was developed to analyse laminates with heterogeneous continuous layers, it was necessary to use a procedure to approximate the nonuniform net as a smoothed orthotropic heterogeneous continuum. The smoothing process is accomplished using the theory of homogenisation and the material coefficients were calculated using the Finite Element Method. Two approaches were considered to define the design variables of the problem: an independent design approach, in which the facesheets are discretized into regions with uniform design parameters; and a reduced basis formulation, in which the design is specified by a linear combination of orthogonal basis functions. This study solved the problem proposed. It has been demonstrated that variation in density is important and can lead to significant design improvement. Across of the face of the optimally designed plate, the density varies by a factor of 9. Also, the problems solved showed that the mass of the facesheets can be reduced up to 50%.

Kataoka Filho, Mario

98

Local effects in the vicinity of inserts in sandwich panels  

Microsoft Academic Search

The paper considers local bending effects induced in the vicinity of inserts in sandwich panels. Such local bending effects are associated with an increase of bending stresses in the sandwich faces and normal and shear stresses in the sandwich core. An earlier developed analytic model [Proceedings of the Sixth International Conference on Sandwich Structures (ICSS-6) (2002) 551] is adapted for

Elena Bozhevolnaya; Anders Lyckegaard; Ole. t. Thomsen; Vitaly Skvortsov

2004-01-01

99

Investigation of Advanced Lightweight Sandwich Structural Concept.  

National Technical Information Service (NTIS)

Although the sandwich panels fabricated of honeycomb core bonded between two face-sheets are very weight-efficient, their application causes many problems such as moisture retention, extensive corrosion, ineffective edge seals, unbonding of face-sheets, a...

H. Ray

1993-01-01

100

Thermonuclear Effects on Sandwich-Type Structures.  

National Technical Information Service (NTIS)

Presence of internal cell pressure during thermal nuclear pulse exposure in honeycomb sandwich structures has been demonstrated. The source of this cell pressure has been shown to be a combination of component outgassing, and the effects of heating a seal...

C. Sparling J. Schibler

1977-01-01

101

Thermal Buckling of Composite Sandwich Plates  

Microsoft Academic Search

By considering that the total transverse displacement of a sandwich plate is the sum of the displacement due to bending of the plate and that due to shear deformation of the core, a 36-degree-of-freedom, high precision, higher-order triangular plate element was developed for the thermal buckling analysis of a rectangular composite sandwich plate. Numerical results show that the buckling mode

Le-Chung Shiau; Shih-Yao Kuo

2004-01-01

102

Analysis of Sandwich Plates of Arbitrary Shape  

Microsoft Academic Search

A linear, static bending analysis of truss-core sandwich plates for arbitrary shape and boundary conditions is presented. The three-dimensional truss-core sandwich plate is idealized as an equivalent two-dimensional structurally orthotropic thick plate continuum. This analysis is based on the small deflection, first-order shear deformation theory of composite plates, which utilizes the Reissner–Mindlin plate theory. The behavior of the plate is

L. V. Kurpa; E. S. Ventsel

2005-01-01

103

Failure Modes of Composite Sandwich Beams  

Microsoft Academic Search

\\u000a The overall performance of sandwich structures depends in general on the properties of the facesheets, the core, the adhesive\\u000a bonding the core to the skins, as well as geometrical dimensions. Sandwich beams under general bending, shear and in-plane\\u000a loading display various failure modes. Their initiation, propagation and interaction depend on the constituent material properties,\\u000a geometry, and type of loading. Failure

Isaac M. Daniel; Emmanuel E. Gdoutos

2009-01-01

104

Equivalent single-layer theory for a complete stress field in sandwich panels under arbitrarily distributed loading  

Microsoft Academic Search

In single-layer theory, the displacement components represent the weighted-average through the thickness of the sandwich panel. Although discrete-layer theories are more representative of sandwich construction than the single-layer theories, they suffer from an excessive number of field variables in proportion to the number of layers. In this study, utilizing Reissner’s definitions for kinematics of thick plates, the displacement components at

A. Barut; E. Madenci; T. Anderson; A. Tessler

2002-01-01

105

Experimental study of acoustical characteristics of honeycomb sandwich structures  

NASA Astrophysics Data System (ADS)

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.

Peters, Portia Renee

106

Experimental study of acoustical behavior of flat honeycomb sandwich panel  

NASA Astrophysics Data System (ADS)

Honeycomb (HC) sandwich composites have lightweight and excellent mechanical properties, but have poor acoustic properties. This work was done to improve the acoustical performance of HC sandwich composites used in airplane floors. Transmission loss (TL) is one of the metrics used to assess acoustical performance of HC sandwiches and requires a TL suite. A small-scale sound transmission loss (TL) test facility was designed, constructed and qualified to conduct the experiments. TL measurements were made using the sound intensity technique based on ASTM. The small-scale facility was qualified between 315 Hz and 10 KHz, and the results of test panels were compared to results from two full-scale accredited labs. TL measured at the small-scale facility yielded reliable, relative comparisons for flat, HC panels. HC panel bending waves are characterized by three frequency regimes---total panel bending, core shear, and individual skin bending---that are controlled by panel geometry, panel mass and elastic properties of the core and the skins. Superior TL performance can be achieved by designing HC panels with significantly subsonic shear wave speed that delays the onset of coincidence frequency. The influence of different commercial HC sandwich design parameters, such as core density, core material, cell size, and cell structure, on TL was investigated. Frequency responses of TL for these panels were inferior. Supersonic core shear wave speed was identified as the reason for inferior acoustic performance. So three classes of panels with different core shear wave speeds---subsonic, transonic, and supersonic---were fabricated and compared for TL. Panels with subsonic and transonic core shear wave speeds showed improved acoustic performance than their supersonic counterparts. Also, optimization studies on panels with subsonic wave speeds showed that the mechanical performance of subsonic and transonic panel designs is generally low, but can be improved when accompanied by weight increase. Comparison of TL performance was made between panels with honeycomb cores made of p-aramid and m-aramid. The stiffer p-aramid HC cores improved the TL above coincidence frequency compared to m-aramid cores. The reason for improved TL at higher frequencies was the lowering of modal density for p-aramid HC cores. Lightweight noise control treatments for honeycomb sandwich panels were explored by adding a gas barrier layer to the panel on the incident side. (Abstract shortened by UMI.)

Rajaram, Shankar

107

Damage Characterisation in FRP Sandwich Beams using a Wavelet Based Multifractal Approach  

Microsoft Academic Search

Fibre reinforced plastic (FRP) sandwich composite materials are widely used in the construction of many structures.' However internal defects can occur, which jf not identified early on, can lead to rapid structural degradation. This paper describes an approach that uses the structure's vibration response to identifY these defects as their occurrence would alter the singUlarity properties of the vibration response.

T. A. DAWOOD; R. A. SHENOI; S. M. VERES; M. SAHIN; M. J. GUNNING

108

Structural performance of near-optimal sandwich panels with corrugated cores  

Microsoft Academic Search

An experimental and computational study of the bending response of steel sandwich panels with corrugated cores in both transverse and longitudinal loading orientations has been performed. Panel designs were chosen on the basis of failure mechanism maps, constructed using analytic models for failure initiation. The assessment affirms that the ana- lytic models provide accurate predictions when failure initiation is controlled

L. Valdevit; Z. Wei; C. Mercer; F. W. Zok; A. G. Evans

2005-01-01

109

HIGH-PERFORMANCE, LOW-COST INFUSION CORES FOR STRUCTURAL SANDWICH PANELS  

Microsoft Academic Search

An innovative new variety of TYCOR? Fiber-Reinforced Composite (FRC) core has been developed for composite sandwich construction. The new FRC core is characterized by a tubular fiber architecture produced by winding structural fiber over foam strips. Dry fiber and foam preforms are used in infusion molding processes to produce a fiber reinforced composite core structure with high stiffness and strength.

Frederick Stoll; Scott Campbell; Stephen Day; Michael Sheppard

110

The Effects of Various Design Parameters on the Free Vibration of Doubly Curved Composite Sandwich Panels  

Microsoft Academic Search

Sandwich panels have a very high stiffness to weight ratio, which makes them particularly useful in the aerospace industry where carbon fibre reinforced plastics and lightweight honeycomb cores are being used in the construction of floor panels, fairings and intake barrel panels. In the latter case, the geometry of the panels can be considered doubly curved. This paper presents an

P. R. Cunningham; R. G. White; G. S. Aglietti

2000-01-01

111

Bending Response of Sandwich Panels with Graded Core: 3D Elasticity Analysis  

Microsoft Academic Search

Sandwich panels are used in a wide variety of applications including aircraft, aerospace, naval\\/marine, construction, and transportation industries where strong stiff and light structures are required. Due to the mismatch of properties between the face sheets and the core, stress concentrations can occur at these interfaces, often leading to delamination, which is a major concern. One solution to this problem

B. Woodward; M. Kashtalyan

2010-01-01

112

THE EFFECTS OF VARIOUS DESIGN PARAMETERS ON THE FREE VIBRATION OF DOUBLY CURVED COMPOSITE SANDWICH PANELS  

Microsoft Academic Search

Sandwich panels have a very high stiffness to weight ratio, which makes them particularly useful in the aerospace industry where carbon fibre reinforced plastics and lightweight honeycomb cores are being used in the construction of floor panels, fairings and intake barrel panels. In the latter case, the geometry of the panels can be considered doubly curved. This paper presents an

P. R. CUNNINGHAM; R. G. WHITE; G. S. AGLIETTI

2000-01-01

113

Structural performance of near-optimal sandwich panels with corrugated cores  

Microsoft Academic Search

An experimental and computational study of the bending response of steel sandwich panels with corrugated cores in both transverse and longitudinal loading orientations has been performed. Panel designs were chosen on the basis of failure mechanism maps, constructed using analytic models for failure initiation. The assessment affirms that the analytic models provide accurate predictions when failure initiation is controlled by

L. Valdevit; Z. Wei; C. Mercer; F. W. Zok; A. G. Evans

2006-01-01

114

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

Microsoft Academic Search

Results are presented from an experimental and analytical study of a sandwich fuselage keel panelwith and without damage. The fuselage keel panel is constructed of graphite-epoxy skins bonded to ahoneycomb core, and is representative of a highly loaded fuselage keel structure. The face sheets of thepanel contain several terminated or dropped plies along the length of the panel. The results

David M. McGowan; Damodar R. Ambur

1997-01-01

115

Piezoelectrically-induced guided wave propagation for health monitoring of honeycomb sandwich structures  

NASA Astrophysics Data System (ADS)

Honeycomb sandwich structures have been widely used in marine and aerospace applications due to their high strength/stiffness-to-weight ratio. However, an excessive load or repeated loading in the core tends to induce debonding along the skin-core interface, threatening the integrity and safety of the whole structure. This dissertation focuses on development of guided wave strategies for health monitoring of honeycomb sandwich structures, based on a piezoelectric actuator/sensor network. The honeycomb sandwich panels, which are composed of aluminum alloy (T6061) skins and hexagonal-celled Nomex core, are specifically considered in the study. First, elastic wave propagation mechanism in honeycomb sandwich structures is numerically and experimentally investigated, based on a piezoelectric actuator/sensor system. Influences of cell geometry parameters upon wave propagation are also discussed. Some wave propagation characteristics, such as wave group velocity dispersion relation and mode tuning capabilities, in the honeycomb composite panels are experimentally characterized. Secondly, effects of skin-core debonding upon the leaky guided wave propagation in honeycomb sandwich structures are studied by the finite element simulation. An appropriate signal difference coefficient is defined to represent the differential features caused by debonding. By means of probability analysis of differential features of transmitted guided waves and the image fusion, the final image of the structure is constructed with improved detection precision. A multilevel sensor network strategy is proposed to detect multiple debondings in the honeycomb sandwich structure. Thirdly, an analytical model considering coupled piezo-elastodynamics is developed to quantitatively describe dynamic load transfer between a surface-bonded piezoelectric wafer actuator and a prestressed plate. The finite element method is used to evaluate the accuracy of the analytical prediction. Effects of prestresses on the characteristics of guided wave generation and propagation, such as time-of-flight, amplitude and wave tuning properties of guided wave modes, are analyzed, based on the developed model. Finally, to overcome the limitations of conventional guided wave methods, a baseline-free detection technique by using nonlinear acoustics is developed for debonding identification in honeycomb sandwich structures. The finite element analysis is performed to understand effects of the interaction of two debonded interfaces upon dynamic behavior of the sandwich structure. Specific experimental study is also conducted on the honeycomb sandwich panel to validate the concept. This dissertation study aims to broaden the scope of existing guided wave methods for debonding detection in honeycomb sandwich structures, and provide some insights for health monitoring of in-service structures.

Song, Fei

116

Fatigue studies of polyurethane sandwich structures  

NASA Astrophysics Data System (ADS)

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.

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

2004-10-01

117

Radiant heating tests of several liquid-metal heat-pipe sandwich panels  

NASA Astrophysics Data System (ADS)

Integral heat-pipe sandwich panels, which synergistically combine the thermal efficiency of heat pipes and the structural efficiency of honeycomb sandwich construction, were conceived as a means of alleviating thermal stress problems in the Langley Scramjet Engine. Test panels which utilized two different wickable honeycomb cores, facesheets with screen mesh sintered to the internal surfaces, and a liquid metal working fluid (either sodium or potassium) were tested by radiant heating at various heat-load levels. The heat-pipe panels reduced maximum temperature differences by 31 percent with sodium working fluid and 45 percent with potassium working fluid. Results indicate that a heat-pipe sandwich panel is a potential, simple solution to the engine thermal stress problem. Other interesting applications of the concept include: cold plates for electronic component and circuit card cooling, radiators for large space platforms, low-distortion large area structures (e.g., space antennas) and laser mirrors.

Camarda, C. J.; Basiulis, A.

1984-02-01

118

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

NASA Astrophysics Data System (ADS)

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.

Ko, William L.

1994-04-01

119

Radiant heating tests of several liquid metal heat-pipe sandwich panels  

SciTech Connect

Integral heat pipe sandwich panels, which synergistically combine the thermal efficiency of heat pipes and the structural efficiency of honeycomb sandwich construction, were conceived as a means of alleviating thermal stress problems in the Langley Scramjet Engine. Test panels which utilized two different wickable honeycomb cores, facesheets with screen mesh sintered to the internal surfaces, and a liquid metal working fluid (either sodium or potassium) were tested by radiant heating at various heat load levels. The heat pipe panels reduced maximum temperature differences by 31 percent with sodium working fluid and 45 percent with potassium working fluid. Results indicate that a heat pipe sandwich panel is a potential, simple solution to the engine thermal stress problem. Other interesting applications of the concept include: cold plates for electronic component and circuit card cooling, radiators for large space platforms, low distortion large area structures (e.g., space antennas) and laser mirrors.

Camarda, C.J.; Basiulis, A.

1983-08-01

120

High Strain Rate Response of Sandwich Composites with Nanophased Cores  

NASA Astrophysics Data System (ADS)

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.

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

2005-05-01

121

Damage Tolerance of Naval Sandwich Panels  

NASA Astrophysics Data System (ADS)

This paper is a review of activities concerning various damage tolerance modelling and testing aspects of sandwich panels for typical Naval applications. It starts with a review of testing methods for primarily core materials and how to extract properties and data required for damage tolerance assessment. Next some typical damage types are defined and how they are modelled with the aim of predicting their effect on load bearing capacity. The paper then describes in brief how such models can used in the context of providing a systematic damage assessment scheme for composite sandwich ship structures.

Zenkert, Dan

122

A h-p Finite Element Vibration Analysis of Open Conical Sandwich Panels and Conical Sandwich Frusta  

NASA Astrophysics Data System (ADS)

The vibration study of a general three-layer conical sandwich panel based on the h-p version of the finite element method is presented in this paper. No restriction is placed on the degree of curvature of the shell, thereby relaxing the strictures associated with shallow shell theory. The methodology incorporates a new set of trigonometric functions to provide the element p -enrichment, and elements may be joined together to model either open conical panels, or complete conical frusta (circumferentially connected, but open at each end). The full range of classical boundary conditions, which includes free, clamped, simply supported and shear diaphragm edges, may be applied in any combination to open and closed panels, thereby facilitating the study of a wide range of conical sandwich shells. The convergence properties of this element have been established for different combinations of the h - and p -parameters, thereby assuring its integrity for more general use. Since very little work has been reported on the vibration characteristic of either circumferentially closed or open conical sandwich panels, the main thrust of this work has been to present and validate an efficient modelling technique, rather than to perform numerous parameter and/or sensitivity studies. To this end, some new results are presented and subsequently validated using a commercially available finite element package. It is shown that for results of comparable accuracy, models constructed using the h-p formulation require significantly fewer degrees of freedom than those assembled using the commercial package. Some preliminary experimental results are also included for completeness.

Bardell, N. S.; Langley, R. S.; Dunsdon, J. M.; Aglietti, G. S.

1999-09-01

123

Blast Impact on Aluminum Foam Composite Sandwich Panels  

Microsoft Academic Search

Sandwich aluminum foam structures are being considered for energy absorption applications, crashworthiness, protection of transformer housings, and structural safety. Blast loading is one such phenomenon that is a potential threat to such structures. This study examines LS-DYNA modeling for aluminum foam sandwich composites subjected to blast loads. The sandwich composite was designed using polymer composite facesheets and aluminum foam as

Rajan Sriram; Uday K. Vaidya

124

Impact Study of Sandwich Composite Structures with Delamination  

Microsoft Academic Search

Finite element analyses were conducted to analyze the dynamic response of an unbalanced sandwich beam, a balanced sandwich beam, and a balanced sandwich plate subject to a low energy impact. In particular, strain versus time history, failure location and mode, and the influence of an existing delamination crack on the failure were investigated. It was found that, in the presence

Y. W. Kwon; G. W. Wojcik

1998-01-01

125

Experimental study of acoustical behavior of flat honeycomb sandwich panel  

Microsoft Academic Search

Honeycomb (HC) sandwich composites have lightweight and excellent mechanical properties, but have poor acoustic properties. This work was done to improve the acoustical performance of HC sandwich composites used in airplane floors. Transmission loss (TL) is one of the metrics used to assess acoustical performance of HC sandwiches and requires a TL suite. A small-scale sound transmission loss (TL) test

Shankar Rajaram

2005-01-01

126

Manufacturing of three dimensional sandwich parts by direct thermoforming  

Microsoft Academic Search

Sandwich panels have been used extensively in the transportation industry. However, as geometric complexities increase, the manufacturing techniques require longer cycle times and significantly increased labour. Press forming of initially flat thermoplastic sandwich panels is a new cost-effective way of obtaining a complex part in a one-step process. Nonetheless, the heterogeneous nature of the sandwich panels requires accurate control of

O Rozant; P.-E Bourban; J.-A. E Månson

2001-01-01

127

Experimental study on mechanical properties of aircraft honeycomb sandwich structures  

Microsoft Academic Search

Mechanical behaviour of sandwich panels under different conditions have been exprimentally studied in this research to increase the knowledge of aircraft sandwich panel structures and facilitate design criteria for aircraft structures. Tests were concentrated on the honeycomb sandwich structures under different loads including flexural, insert shear, flat wise tension and compression loads. Furthermore, effect of core density and face material

A. A. Zakeri; H. Talebi Mazraehshahi

2010-01-01

128

Laser Welding of Metallic Sandwich Structures (Norsial) Soudage Laser de Structures Sandwich Metalliques Norsial.  

National Technical Information Service (NTIS)

Manufacturing of Norsial (trademark) sandwich structures is described. An electrical resistance welding process whereby metal sheet is welded to a corrugated center, or stacks of corrugated sheet, is outlined. In order to cut production costs, introductio...

Maroute

1981-01-01

129

Impact-damaged graphite-thermoplastic trapezoidal-corrugation sandwich and semi-sandwich panels  

NASA Astrophysics Data System (ADS)

The results of a study of the effects of impact damage on compression-loaded trapezoidal-corrugation sandwich and semi-sandwich graphite-thermoplastic panels are presented. 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 in this study. Panels were designed, fabricated and tested. The panels were made using the manufacturing process of thermoforming, a less-commonly used technique for fabricating composite parts. Experimental results for unimpacted control panels and panels subjected to impact damage prior to loading are presented. Little work can be found in the literature about these configurations of thermoformed panels.

Jegley, D.

130

Sandwich targets for heavy-ion experiments  

SciTech Connect

Techniques for producing sandwich targets such as Gd + Pb are described. Better contact between the materials is sometimes assured by evaporating one material onto the other rather than by rolling the two together. Experimental data using both types of targets will be shown.

Thomas, G.E.

1982-01-01

131

Damping Analysis of Sandwich Composite Materials  

Microsoft Academic Search

The article presents an analysis of the damping of sandwich composites, made of PVC foam cores and laminated skins. Damping parameters are investigated using beam test specimens and an impulse technique. Damping modeling is developed using a finite element analysis which evaluated the different energies dissipated in the material directions of the core and the layers of the skins. The

Mustapha Assarar; Abderrahim El Mahi; Jean-Marie Berthelot

2009-01-01

132

Noise transmission through nonlinear sandwich panels  

Microsoft Academic Search

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

R. Vaicaitis; H.-K. Hong

1983-01-01

133

Mechanical properties of fibrous core sandwich panels  

Microsoft Academic Search

Fibrous core sandwich panels are thin, lightweight structures with face sheets separated by an irregular arrangement of independent fibres; the fibres have a random angle of fibre inclination and a range of initial curvatures. These panels have small thickness so that they can be pressed into 3D curvature in a forming operation. This paper analyses the effects of core morphology

Daowu Zhou; W. J. Stronge

2005-01-01

134

Perforation of honeycomb sandwich plates by projectiles  

Microsoft Academic Search

An analytical solution for the ballistic limit of a honeycomb plate subjected to normal impact by blunt and spherical projectiles is presented. The solution involves a three-stage, perforation process that results in complete perforation of the sandwich. Stages 1–3 describe perforation of the top facesheet, honeycomb core, and bottom facesheet, respectively. Residual velocities in Stages 1 and 2 are found

M. S. Hoo Fatt; K. S. Park

2000-01-01

135

Volcanic Action in the Sandwich Islands  

Microsoft Academic Search

IN your notice of my book, ``The Hawaiian Archipelago,'' (vol. xi. p. 322), you allude to the statement that volcanic action on the Sandwich Islands ``has died out from west to east.'' It has also died out in a southerly direction, through nearly four degrees of latitude. In the pit of Hale-mau-mau within the crater of Kilauea, on January 30,

Isabella L. Bird

1875-01-01

136

Effects of the aromatic substitution pattern in cation-? sandwich complexes.  

PubMed

A computational study investigating the effects of the aromatic substitution pattern on the structure and binding energies of cation-? sandwich complexes is reported. The correlation between the binding energies (Ebind) and Hammett substituent constants is approximately the same as what is observed for cation-? half-sandwich complexes. For cation-? sandwich complexes where both aromatics contain substituents the issue of relative conformation is a possible factor in the strength of the binding; however, the work presented here shows the Ebind values are approximately the same regardless of the relative conformation of the two substituted aromatics. Finally, recent computational work has shown conflicting results on whether cation-? sandwich Ebind values (Ebind,S) are approximately equal to twice the respective half-sandwich Ebind values (Ebind,HS), or if cation-? sandwich Ebind,S values are less than double the respective half-sandwich Ebind,HS values. The work presented here shows that for cation-? sandwich complexes involving substituted aromatics the Ebind,S values are less than twice the respective half-sandwich Ebind,HS values, and this is termed nonadditive. The extent to which the cation-? sandwich complexes investigated here are nonadditive is greater for B3LYP calculated values than for MP2 calculated values and for sandwich complexes with electron-donating substituents than those with electron-withdrawing groups. PMID:23452189

Wireduaah, Selina; Parker, Trent M; Lewis, Michael

2013-03-19

137

Timing resolution of ``Shisk-Kebab`` lead scintillator sandwich calorimeters  

SciTech Connect

We have constructed lead scintillator sandwich calorimeters with 1/4 {chi}{sub o} sampling frequency and total thickness {approximately}16{chi}{sub o}. The 4 mm thick scintillator plates are read out by wavelength shifter fibers 1 mm in diameter which pass through holes penetrating the plates on a .95 cm {times} .95 cm grid (Shish-Kebab geometry). We tested these modules in the A2 test beam at Brookhaven using low energy electrons and hadrons. Results are here presented on electron energy and time-of-flight resolution obtained with various combinations of scintillators and wavelength shifters. We also describe results on e/{pi} separation obtained with a new technique for the longitudinal segmentation.

Kistenev, E.; White, S. [Brookhaven National Lab., Upton, NY (United States); Pischalnikov, Y.; Protopopov, Y.; Rykalin, V. [Institut Fiziki Vysokikh Ehnergij, Protvino (Russian Federation)

1992-12-31

138

Timing resolution of Shisk-Kebab'' lead scintillator sandwich calorimeters  

SciTech Connect

We have constructed lead scintillator sandwich calorimeters with 1/4 [chi][sub o] sampling frequency and total thickness [approximately]16[chi][sub o]. The 4 mm thick scintillator plates are read out by wavelength shifter fibers 1 mm in diameter which pass through holes penetrating the plates on a .95 cm [times] .95 cm grid (Shish-Kebab geometry). We tested these modules in the A2 test beam at Brookhaven using low energy electrons and hadrons. Results are here presented on electron energy and time-of-flight resolution obtained with various combinations of scintillators and wavelength shifters. We also describe results on e/[pi] separation obtained with a new technique for the longitudinal segmentation.

Kistenev, E.; White, S. (Brookhaven National Lab., Upton, NY (United States)); Pischalnikov, Y.; Protopopov, Y.; Rykalin, V. (Institut Fiziki Vysokikh Ehnergij, Protvino (Russian Federation))

1992-01-01

139

Nonlinear Dynamic Finite Element Analysis of Thick Transversely Flexible Sandwich Panel on Elastic Foundation with Account of Damage Progression in Time. Part 2. 3D Analysis and Time Integration  

Microsoft Academic Search

A plate theory for a thick transversely compressible sandwich plate with composite laminated face sheets is constructed using the simplified assumptions earlier described in Part 1. An algorithm, which takes account of damage progression in dynamic problems, is incorporated into the computational scheme based on the geometrically nonlinear formulation and applied to failure analysis of a sandwich plate under ground

V. Y. Perel

2005-01-01

140

Impact perforation of sandwich panels with Coremat®  

Microsoft Academic Search

Analytical solutions for the quasi-static and low-velocity perforation of sandwich panels with woven roving E-glass\\/vinyl ester facesheets and Coremat were derived. A multi-stage perforation process involving delamination, debonding, core shear fracture and facesheet fracture was used to predict the quasi-static failure load and ballistic resistance of the panel. The high core-crushing resistance and damping of the Coremat resulted in rupture

Michelle S. Hoo Fatt; Dushyanth Sirivolu

2009-01-01

141

Core material types for sandwich structures  

NASA Astrophysics Data System (ADS)

Sandwich structures, which are composed of a thick core between two thin faces, are commonly used in many engineering applications because they combine high stiffness and strength with low weight. Depending on the application of a particular sandwich structure, various types of cores can be used. Cores with various two-dimensional patterns were studied in this thesis program. The mechanical characteristics of three types of core with isotropic patterns--triangular, hexagonal, and starcell--were studied as related to applications in sandwich structures. The Young's modulus, shear modulus, and Poisson's ratio were calculated for the three core types in the direction normal to the faces. The compressive buckling strength and shear buckling strength were calculated for the three core types by modeling each cell wall of a core as a plate under compressive or shear load. To verify this model, tests were conducted on scaled specimens to measure the compressive buckling strength of each core. The flexibilities of the three cores were also studied. Compliances for the three cores were measured using biaxial flexural tests. Tests were performed on each core types in which the deflection of a circular core sample loaded at its center was measured. The three isotropic core patterns exhibited distinct characteristics. In the direction normal to the faces, all three cores had the same stiffness. However, the triangular core had lower compressive and shear buckling strengths than the other two core types. The starcell core exhibited high flexibility compared to the other cores, indicating a potential for application in curved sandwich structures.

Kim, Beomkeun

1998-09-01

142

Ion irradiation induced hollow and sandwiched nanoparticles  

SciTech Connect

We report on the fabrication of hollow and sandwiched nanoparticles by ion irradiation. Ag nanoparticles embedded in silica were irradiated by N{sup +}, Si{sup +}, Ar{sup +}, and Cu{sup +} ions at 300 keV to a fluence of 5x10{sup 16} ions/cm{sup 2}, by Cu{sup +} ions at varying energies from 110 to 500 keV to a fluence of 5x10{sup 16} ions/cm{sup 2}, and by Cu{sup +} ions at 400 keV to fluences varied from 1x10{sup 16} to 1x10{sup 17} ions/cm{sup 2}. The size of the irradiation-induced nanovoids increases with increasing ion mass and energy. The formation of nanovoids depends on the electronic and nuclear energy loss of the irradiation ions. The formation of irradiation-induced sandwiched nanoparticles is because of the capture of knocked-out Ag atoms from nanoshells by nanovoids. The size of the inner nanoparticles within the sandwiched structure increases with increasing fluence.

Ren Feng; Cai Guangxu; Xiao Xiangheng; Fan Lixia; Liu Chang; Fu Dejun; Wang Jianbo; Jiang Changzhong [Key Laboratory of Acoustic and Photonic Materials and Devices of Ministry of Education, Wuhan University, Wuhan 430072 (China) and Department of Physics, Wuhan University, Wuhan 430072 (China)

2008-04-15

143

Full-scale testing and progressive damage modeling of sandwich composite aircraft fuselage structure  

Microsoft Academic Search

A comprehensive experimental and computational investigation was conducted to characterize the fracture behavior and structural response of large sandwich composite aircraft fuselage panels containing artificial damage in the form of holes and notches. Full-scale tests were conducted where panels were subjected to quasi-static combined pressure, hoop, and axial loading up to failure. The panels were constructed using plain-weave carbon\\/epoxy prepreg

Frank A. Leone Jr.

2010-01-01

144

Glass fiber-reinforced polymer\\/steel hybrid honeycomb sandwich concept for bridge deck applications  

Microsoft Academic Search

Glass fiber-reinforced polymer (GFRP) materials possess inherently high strength-to-weight ratios, but their elastic moduli are low relative to civil engineering (CE) construction materials. As a result, serviceability issues are what govern GFRP material design in the CE bridge industry. Therefore, the study objective was to increase the stiffness of a commercial GFRP honeycomb sandwich panel through the inclusion of steel

Nicolas J Lombardi

2008-01-01

145

On the performance of higher order theories for transient dynamic analysis of sandwich and composite beams  

Microsoft Academic Search

Higher-order shear-deformable refined theories, based on isoparametric elements, are adopted for transient dynamic analysis of symmetric and unsymmetric sandwich and composite beam constructions. These shear-correction coefficient free theories model cross sectional warping using nonlinear variation of inplane displacements across the depth. They also incorporate transverse shear stress in the formulation. A special lumping scheme is employed for the evaluation of

S. R. Marur; T. Kant

1997-01-01

146

Web crippling strength of a steel sandwich panel with V-shaped webs  

Microsoft Academic Search

Steel sandwich panels with V-shaped web flutes (V-core panels) serve the structural functions of a proposed energy-efficient roof system for residential construction. Due to its intended use as a flexural member spanning between a ridge beam and a structural wall, and required slender webs for weight considerations, web crippling under end one-flange loading is a critical strength limit state for

Taichiro Okazaki; Brian J. Siljenberg; Carol K. Shield; Susan C. Mantell

2009-01-01

147

THERMOELASTIC TRIANGULAR SANDWICH ELEMENT FOR THE COMPLETE STRESS FIELD BASED ON A SINGLE-LAYER THEORY  

Microsoft Academic Search

the context of linear and non-linear finite element anal- ysis, can be found in Refs. (2)-(5). Although the FSDT provides acceptable mid-plane displacements, as well as in-plane stress components, it fails to capture the accurate behavior of transverse stresses, especially when analyzing sandwich constructions, which may have extremely different mechanical and thermal prop- erties. This study presents a new triangular

M. Das; A. Barut; E. Madenci; D. R. Ambur

148

Damage-Tolerance Characteristics of Composite Fuselage Sandwich Structures With Thick Facesheets  

Microsoft Academic Search

Damage tolerance characteristics and results from experimental and analytical studies of acomposite fuselage keel sandwich structure subjected to low-speed impact damage and discrete-sourcedamage are presented. The test specimens are constructed from graphite-epoxy skins bonded to ahoneycomb core, and they are representative of a highly loaded fuselage keel structure. Results ofcompression-after-impact (CAI) and notch-length sensitivity studies of 5-in.-wide by 10-in-longspecimens are...

David M. McGowan; Damodar R. Ambur

1997-01-01

149

A comparative evaluation of crashworthy composite sandwich structures  

Microsoft Academic Search

This paper describes an experimental evaluation of the energy absorption properties of a series of novel designs for cost-effective crashworthy composite sandwich structures. All the designs are based on the concept of the “tied-core” sandwich, i.e. the use of additional core reinforcements that act to tie the opposing facings of a sandwich together, thus preventing catastrophic failure under edgewise loading.

G. Pitarresi; J. J. Carruthers; A. M. Robinson; G. Torre; J. M. Kenny; S. Ingleton; O. Velecela; M. S. Found

2007-01-01

150

Free and forced vibration of simply supported, orthotropic sandwich panel  

Microsoft Academic Search

A three-dimensional (3-D) sandwich panel, which is characterized by two thin flat sheets and a core sandwiched between them, is a relatively complex structure. The degree of complexity depends on the type of core used. Despite the complexity, the dynamic flexural behavior of a 3-D, thin-walled sandwich panel may be represented by the response of an equivalent two-dimensional (2-D), homogeneous,

Tat-Seng Lok; Qian-Hua Cheng

2001-01-01

151

Dynamic crushing of sandwich panels with prismatic lattice cores  

Microsoft Academic Search

The dynamic out-of-plane compressive response of stainless steel corrugated and Y-frame sandwich cores have been investigated for impact velocities ranging from quasi-static to 200ms?1. Laboratory-scale sandwich cores of relative density 2.5% were manufactured and the stresses on the front and rear faces of the dynamically compressed sandwich cores were measured using a direct impact Kolsky bar. Direct observational evidence is

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

2007-01-01

152

Compressive Failure of Sandwich Beams with Debonded Face-Sheets  

Microsoft Academic Search

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 bagging process. The face-sheet and the sandwich beam were cocured. 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

John L. Avery; Bhavani V. Sankar

2000-01-01

153

Elastic-plastic deformation of sandwich rod on elastic basis  

Microsoft Academic Search

Sandwich composite material possesses advantages of both light weight and high strength. Although the mechanical behaviors\\u000a of sandwich composite material with the influence of single external environment have been intensively studied, little work\\u000a has been done in the study of mechanical property, in view of the nonlinear behavior of sandwich composites in the complicated\\u000a external environments. In this paper, the

Yu Gu

2008-01-01

154

Thickness Vibrations of Sandwich Plates and Beams and Delamination Detection  

Microsoft Academic Search

In multi-hull marine vehicles assembled by FRP sandwich composite materials, problems with delamination and skin\\/core debonding are reported. An early damage warning (EDW) system for delamination detection in marine vessels based on measurements of bending vibrations in sandwich structures are under development.Related to this EDW system development, this paper presents a theory for qualitative determination of thickness vibrations in sandwich

Alf Egil Jensen; Fridtjov Irgens

1999-01-01

155

COMPRESSIVE STRENGTH OF STAINLESS-STEEL SANDWICHES AT ELEVATED TEMPERATURES  

Microsoft Academic Search

Experimental results are presented from crippling tests of specimens in ; the temperature range from 80 to 1,200 deg F. The specimens included resistance-; welded 177 PH stainless-steel sandwiches with single-corrugated cores, type 301 ; stainless-steel sandwiches with doublecorrugated cores, and brazed 17-7 PH ; stainless-steel sandwiches with honeycomb cores. The experimental strengths are ; compared with predicted buckling and

E. E. Mathauser; R. A. Pride

1959-01-01

156

Impact and Blast Resistance of Sandwich Plates  

NASA Astrophysics Data System (ADS)

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.

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

157

AN h– p FINITE ELEMENT VIBRATION ANALYSIS OF OPEN CONICAL SANDWICH PANELS AND CONICAL SANDWICH FRUSTA  

Microsoft Academic Search

The vibration study of a general three-layer conical sandwich panel based on theh –p version of the finite element method is presented in this paper. No restriction is placed on the degree of curvature of the shell, thereby relaxing the strictures associated with shallow shell theory. The methodology incorporates a new set of trigonometric functions to provide the element p

N. S BARDELL; R. S LANGLEY; J. M DUNSDON; G. S AGLIETTI

1999-01-01

158

Variety of interlayer coupling in sandwiches  

NASA Astrophysics Data System (ADS)

The possible mechanisms of magnetic interlayer coupling in sandwiches has been analyzed on the basis of experimental data of coercive force, domain structure and microstructure of Fe15Co20Ni65/Cr/Fe15Co20Ni65 and Fe19Ni81/Cr/Fe19Ni81 films. By means of theoretical estimations we have shown that with increasing Cr interlayer thickness (L) the exchange interlayer coupling changes into a magnetostatic interaction which is due to either the interface roughness or the magnetization ripple for different L.

Vas'kovskij, V. O.; Savin, P. A.; Lepalovskij, V. N.

1998-06-01

159

Puncture black hole initial data in the conformal thin-sandwich formalism  

NASA Astrophysics Data System (ADS)

We revisit the construction of puncture black hole initial data in the conformal thin-sandwich (CTS) decomposition of Einstein's constraint equations. It has been shown previously that this approach cannot yield quasiequilibrium wormhole data, which connect two asymptotically flat spatial infinities. This argument does not apply to trumpet data, which connect the spatial infinity in one universe with the future timelike infinity of another. As a numerical demonstration, we present results for a single boosted trumpet-puncture black hole, constructed in the original version of the CTS formalism.

Baumgarte, Thomas W.

2011-11-01

160

Manufacturing and tribological properties of sandwich materials with chemically bonded PTFE-PA 66 and PA 66\\/GF  

Microsoft Academic Search

The sandwich molding process for the production of multi-component shaped parts is gaining increasing importance. With this procedure different materials, such as functional and construction materials, can be combined to form composite construction parts with good load-bearing characteristics.The investigations were performed with a pure PA 66 and 4 different modified PTFE-PA 66 compounds with a PA 66 injection type matrix.

R. Franke; I. Haase; D. Lehmann; B. Hupfer; A. Janke

2007-01-01

161

Thermally stable memory devices using graphene flakes sandwiched polymethyl methacrylate polymer layers  

NASA Astrophysics Data System (ADS)

Fabrication and characterization of graphene flakes sandwiched polymethyl methacrylate (PMMA) hybrid bistable devices (HBD) is reported in this paper. Graphene flakes (GFs) sandwiched polymer layers were prepared through a simple solution process. The fabricated memory devices have exhibited remarkable electrical bistable behavior even at 150°C. Bistable memory behavior of the fabricated devices have been described on the basis of current-voltage characteristics. Reasonably good ON/OFF current ratio (˜103) and retention property have been obtained from the constructed memory devices. The device showed excellent stability up to 105 switching cycles without any degradation both in ON and OFF states. The results obtained have indicated that the HBD fabricated by embedding graphene flakes in an insulating polymer matrix have potential applications in organic nonvolatile flash memory devices.

Valanarasu, S.; Kathalingam, A.; Senthilkumar, V.; Kannan, V.; Rhee, J. K.

2012-12-01

162

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

NASA Astrophysics Data System (ADS)

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.

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

2007-02-01

163

Design, fabrication and test of liquid metal heat-pipe sandwich panels  

NASA Astrophysics Data System (ADS)

Integral heat-pipe sandwich panels, which synergistically combine the thermal efficiency of heat pipes and the structural efficiency of honeycomb sandwich panel construction, were fabricated and tested. The designs utilize two different wickable honeycomb cores, facesheets with screen mesh sintered to the internal surfaces, and potassium or sodium as the working fluid. Panels were tested by radiant heating, and the results indicate successful heat pipe operation at temperatures of approximately 922K (1200F). These panels, in addition to solving potential thermal stress problems in an Airframe-Integrated Scramjet Engine, have potential applications as cold plates for electronic component cooling, as radiators for space platforms, and as low distortion, large area structures.

Basiulis, A.; Camarda, C. J.

1983-04-01

164

Modeling of Sandwich Sheets with Metallic Foam  

NASA Astrophysics Data System (ADS)

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.

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

2011-08-01

165

Compression properties of fire-damaged polymer sandwich composites  

Microsoft Academic Search

The effect of fire-induced damage on the edgewise compression properties of polymer sandwich composites is investigated. Fire tests were performed using a cone calorimeter on sandwich composites with high or low flammability. The highly flammable composite had a poly(vinyl chloride) foam core, while the flame resistant composite had a phenolic foam core. The residual edgewise compression properties of the burnt

A. P. Mouritz; C. P. Gardiner

2002-01-01

166

Practical Instruction in Tissue Culture and Cytogenetics for Sandwich Students.  

ERIC Educational Resources Information Center

|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)|

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

1973-01-01

167

High-frequency vibrations of sandwich plates and delamination detection  

Microsoft Academic Search

In multi-hull marine vehicles assembled by FRP sandwich composite materials problems with delamination and skin\\/core debonding are reported. High frequency vibrations in foam core sandwich materials are investigated to see if it was possible to apply them, together with bending vibrations, in an early damage warning system for delamination detection in marine vessels. This manuscript presents a theory for high

Alf E. Jensen; Fridtjov Irgens

1998-01-01

168

A Numerical Investigation of Fractured Sandwich Composites under Flexural Loading  

Microsoft Academic Search

Finite element analyses have been carried out for fractured sandwich composites loaded in flexure. Core skin debonds parallel to the beam axis are considered at different distances from the upper skin interface. Static non-linear elastic two-dimensional finite element analyses of cracked sandwich beams are accounted for the evaluation of stress intensity factors at the crack tips.

Efstathios E. Theotokoglou; Ioannis I. Tourlomousis

2009-01-01

169

Wave propagation in and sound transmission through sandwich plates  

Microsoft Academic Search

Some dynamical and acoustical properties of sandwich plates are investigated. The types of sandwich elements discussed are three-layered plates with a thick lightweight core, with thin and comparatively stiff laminates bonded to each side of the core. In the model derived it is assumed that the laminates and core are isotropic. The laminates are treated as thin plates, whereas the

A. C. Nilsson

1990-01-01

170

VIBRATIONS OF SANDWICH PLATES WITH CONCENTRATED MASSES AND SPRINGLIKE INCLUSIONS  

Microsoft Academic Search

Linear dynamics of a sandwich beam (a plate of sandwich composition in one-dimensional cylindrical bending) bearing concentrated masses and supported by springs is described in the framework of the sixth order theory of multilayered plates. Analysis of the influence of a single inclusion and of a pair of identical inclusion upon vibrations of an infinitely long beam is performed by

S. V. Sorokin; N. Peake

2000-01-01

171

On the mechanical effect of stitch addition in sandwich panel  

Microsoft Academic Search

Monolithic stitched composite materials successfully inspired the addition of transverse reinforcements in the case of sandwich structures. Indeed, the gains are undeniable in term of ultimate stress and of modulus regarding the principal mechanical tests practiced on sandwich (bending, shearing and compression). These bonds reduce the impact of the inter-laminar shearing which tends to break the connection between the core

B. Lascoup; Z. Aboura; K. Khellil; M. Benzeggagh

2006-01-01

172

Material characteristics of 3-D FRP sandwich panels  

Microsoft Academic Search

This paper presents an innovative 3-D fiber reinforced polymer (FRP), panels designed to overcome delamination problems typically encountered in traditional sandwich panels. The sandwich panels consist of GFRP laminates and foam core. The top and bottom consist of GFRP plates connected together with through-thickness fibers to achieve the composite action. The fundamental material characteristics of the panel in tension, compression,

Engin M. Reis; Sami H. Rizkalla

2008-01-01

173

Free vibration and stability analysis of stiffened sandwich plates  

Microsoft Academic Search

Description is given of the development of a B-spline finite strip method for predicting the natural frequencies of vibration and the buckling stresses of rectangular sandwich panels. Each panel comprises a flat sandwich main plate which is reinforced by a number of longitudinal compact plate stiffeners attached to the faceplates. The core of the main plate is represented as a

W. X Yuan; D. J Dawe

2004-01-01

174

Nonlinear Flexural Deflection of Thermoplastic Foam Core Sandwich Beam  

Microsoft Academic Search

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

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

2002-01-01

175

Characterization of Wood-Polypropylene Composite Sandwich System  

Microsoft Academic Search

A new wood-polypropylene composite sandwich was made by bonding unidirectional continuous glass fiber reinforced polypropylene (UCGPP) composite to oak wood using a thermoplastic tie layer. In order to evaluate the practical utility of wood-composite sandwich systems, the effects of moisture changes in both continuous and cyclic manner were investigated by monitoring the modulus change. Dynamic mechanical analysis (DMA) of neat

Ganesan Kumar; Karthik Ramani

2000-01-01

176

High Velocity Impact Response of Composite Lattice Core Sandwich Structures  

NASA Astrophysics Data System (ADS)

In this research, carbon fiber reinforced polymer (CFRP) composite sandwich structures with pyramidal lattice core subjected to high velocity impact ranging from 180 to 2,000 m/s have been investigated by experimental and numerical methods. Experiments using a two-stage light gas gun are conducted to investigate the impact process and to validate the finite element (FE) model. The energy absorption efficiency (EAE) in carbon fiber composite sandwich panels is compared with that of 304 stainless-steel and aluminum alloy lattice core sandwich structures. In a specific impact energy range, energy absorption efficiency in carbon fiber composite sandwich panels is higher than that of 304 stainless-steel sandwich panels and aluminum alloy sandwich panels owing to the big density of metal materials. Therefore, in addition to the multi-functional applications, carbon fiber composite sandwich panels have a potential advantage to substitute the metal sandwich panels as high velocity impact resistance structures under a specific impact energy range.

Wang, Bing; Zhang, Guoqi; Wang, Shixun; Ma, Li; Wu, Linzhi

2013-10-01

177

Structural behaviour of eccentrically loaded precast sandwich panels  

Microsoft Academic Search

Results of an experimental investigation to study the ultimate strength behaviour of precast concrete sandwich panels (PCSP) with steel truss shear connectors are reported. Six full-scale sandwich panels with variable slenderness ratio were cast and tested under eccentric loads. Deflection characteristics, variations of strains across the insulation layer, strains in shear connectors, crack appearance and propagation under increasing load were

A. Benayoune; A. Aziz A. Samad; D. N. Trikha; A. Abdullah Abang Ali; A. A. Ashrabov

2006-01-01

178

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

NASA Astrophysics Data System (ADS)

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 facings onto a lightweight core. However, the lack of fire resistance of the polymers used for the fabrication remains a very important problem. The research presented in this dissertation deals with an inorganic matrix (Geopolymer) that can be used to manufacture laminate composites and sandwich panels that are resistant up to 1000°C. This dissertation deals with the influence of fiber type on the mechanical behavior and the fire response of hybrid composites and sandwich structures manufactured using this resin. The results are categorized into the following distinct studies. (i) High strength carbon fibers were combined with low cost E-glass fibers to obtain hybrid laminate composites that are both economical and strong. The E-glass fabrics were used as a core while the carbon fibers were placed on the tension face and on both tension and compression faces. (ii) Structural sandwich beams were developed by laminating various types of reinforcement onto the tension and compression faces of balsa wood cores. The flexural behavior of the beams was then analyzed and compared to beams reinforced with organic composite. The effect of core density was evaluated using oak beams reinforced with inorganic composite. (iii) To measure the fire response, balsa wood sandwich panels were manufactured using a thin layer of a fire-resistant paste to serve for fire protection. Seventeen sandwich panels were fabricated and tested to measure the heat release rates and smoke-generating characteristics. The results indicate that Geopolymer can be effectively used to fabricate both high strength composite plates and sandwich panels. A 2 mm thick coating of fireproofing on balsa wood is sufficient to satisfy FAA fire requirements.

Giancaspro, James William

179

Identification and enumeration of Microcystis using a sandwich hybridization assay.  

PubMed

Based on sequence analyses of phycocyanin intergenic spacers (PC-IGS) from Microcystis, Anabaena, Aphanizomenon, and Planktothrix (Oscillatoria) strains, a genus-specific probe pair TF/TR was designed, and a sandwich hybridization assay was established to quantitatively detect Microcystis. Through BLAST and cyanobacterial culture tests, TF/TR was demonstrated to be specific for Microcystis. A calibration curve for the sandwich hybridization assay was established, and the lowest detected concentration was 100 cell/ml. Laboratory and field samples were analyzed with both sandwich hybridization assay and microscopy. The biotic and abiotic components of the samples were of little disturbance to the sandwich hybridization assay. The results showed no distinct difference between the two methods. In this study, a sandwich hybridization assay was established to detect Microcystis, providing an alternative to traditional microscopic, morphology-based methods. PMID:22538645

Zhu, Jing Ping; Li, Xian; Du, Shi

2012-04-27

180

Mechanical behavior of a ceramic sandwich composite system  

SciTech Connect

The mechanical behavior of a ceramic sandwich composite system was investigated. The system was comprised of a low density, cellular Al2O3 core, bonded to dense Al2O3 faceplates. Tensile faceplate stresses during flexure were determined for a variety of face thickness and core densities, using a strain gage technique. For most composites, the data agreed well with simple sandwich theory. For composites with relatively thick faces and low modulus cores, however, localized bending caused higher than expected face stresses beneath the load point. These stresses were predicted using a refined model. The strain gage data were also used to measure sandwich stiffness, which were well predicted by conventional sandwich theory when localized face bending was not prevalent. The structures were linear elastic to failure, through the failure was noncatastrophic. For the sandwich geometries studied, failure initiated exclusively in the core. 6 refs.

Van Voorhees, E.J.; Green, D.J. (Pennsylvania State University, University Park (United States))

1992-01-01

181

Analysis and design of sandwich plates with inserts—a high-order sandwich plate theory approach  

Microsoft Academic Search

Sandwich structures are very susceptible to failure due to local stress concentrations induced in areas of load introduction, supports, geometrical and material discontinuities. These local stress concentrations are caused by localised bending effects, where the individual face sheets tend to bend about their own middle surface rather than about the middle surface of the sandwich. This paper deals with such

O. T. Thomsen; W. Rits

1998-01-01

182

Peanut Butter Cracker Sandwich Manufacturing Module  

NSDL National Science Digital Library

For many engineers, their first position after obtaining a B.S. degree is in manufacturing. Job titles like process engineer, product engineer, and quality engineer are common and are directly involved in manufacturing. Most engineering curricula do not cover manufacturing concepts. A student may not even have an opportunity through electives to study manufacturing since smaller engineering colleges rarely have a department of Manufacturing Engineering.A module on peanut butter cracker manufacturing was developed for the Introduction to Engineering course taken by most engineering students in their freshman year. The objective for the students is to design, build and then run a process to manufacture peanut butter cracker sandwiches. The culminating activity is a pilot production run where the students are assigned human operators for their process. The goal for the students is to make a profit during the pilot production run. Material costs, labor costs, quality specifications and selling price all determine whether or not the process was successful. The module includes activities where the students perform calculations and use Excel graphs to determine the process time required to make a profit, the impact of the number of operators on production, the interplay between fixed and variable costs, and the effect of yield on their profit. Students are required to write operating procedures and order supplies based on predictions of the quantity of sandwiches they will produce. Students also learn about quality control and process control, the cost of automation, development costs, and challenges in training operators. After more than two weeks of preparation, the students have 10 minutes to train their operators, and then the operators run the process for 10 minutes. After production day, the students write a report that includes an analysis of their production performance and suggested process modifications. Overall, the module provides a fun and informative introduction to some fundamental manufacturing concepts.The module learning objectives, section descriptions and handouts are included.

2009-08-05

183

Fe3O4 nanoparticles-enhanced SPR sensing for ultrasensitive sandwich bio-assay.  

PubMed

Magnetic nanoparticles (MNPs) have been receiving increasing attention because of its great potentials in bioseparation. However, the separation products are difficult to be detected by general method due to their extremely small size. Here, we demonstrate that MNPs can greatly enhance the signal of surface plasmon resonance spectroscopy (SPR). Features of MNPs-aptamer conjugates as a powerful amplification reagent for ultrasensitive immunoassay are reported in this work for the first time. In order to evaluate the sensing ability of MNPs-aptamer conjugates as an amplification reagent, a sandwich SPR sensor is constructed by using thrombin as model analyte. Thrombin, captured by immobilized anti-thrombin aptamer on SPR gold film, is sensitively detected by SPR spectroscopy with a lowest detection limit of 0.017 nM after MNPs-aptamer conjugates is used as amplification reagent. At the same time, the excellent selectivity of the present biosensor is also confirmed by using three kinds of proteins (BSA, human IgM and human IgE) as controls. These results confirm that MNPs is a powerful sandwich element and an excellent amplification reagent for SPR based sandwich immunoassay and SPR has a great potential for the detection of MNPs-based bioseparation products. PMID:21482283

Wang, Jianlong; Zhu, Zanzan; Munir, Ahsan; Zhou, H Susan

2011-02-19

184

The Effects of Various Design Parameters on the Free Vibration of Doubly Curved Composite Sandwich Panels  

NASA Astrophysics Data System (ADS)

Sandwich panels have a very high stiffness to weight ratio, which makes them particularly useful in the aerospace industry where carbon fibre reinforced plastics and lightweight honeycomb cores are being used in the construction of floor panels, fairings and intake barrel panels. In the latter case, the geometry of the panels can be considered doubly curved. This paper presents an introduction to an ongoing study investigating the dynamic response prediction of acoustically excited composite sandwich panels which have double curvature. The final objective is to assess and hopefully produce an up to date set of acoustic fatigue design guidelines for this type of structure. The free vibration of doubly curved composite honeycomb sandwich panels is investigated here, both experimentally and theoretically, the latter using a commerically available finite element package. The design and manufacture of three test panels is covered before presenting experimental results for the natural frequencies of vibration with freely supported boundary conditions. Once validated against the experimental results, the theoretical investigation is extended to study the effects of changing radii of curvature, orthotropic properties of the core, and ply orientation on the natural frequencies of vibration of rectangular panels with various boundary conditions. The results from the parameter studies show curve veering, particularly when studying the effect of changing radii and ply orientation, however, it is not clear whether this phenomenon is due to the approximation method used or occurs in the physical system.

Cunningham, P. R.; White, R. G.; Aglietti, G. S.

2000-02-01

185

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

PubMed Central

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.

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

2013-01-01

186

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

NASA Astrophysics Data System (ADS)

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. .

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

2001-02-01

187

White polarization sandwiches: optical elements with non-orthogonal eigenpolarizations  

NASA Astrophysics Data System (ADS)

Optical elements with non-orthogonal eigenpolarizations have complex anisotropic properties, which are not yet well understood. As an example of such elements, we studied theoretically the class of white polarization sandwiches. Light passing successively through two identical white sandwiches preserves its polarization state, so that, following the terminology of Berry and Dennis, white polarization sandwiches can be regarded as non-trivial square roots of unity. This paper presents a general Jones matrix of white polarization sandwiches and discusses its spectral properties. It further discusses a way to synthesize white sandwiches. Our analysis shows that a general white polarization sandwich has complex anisotropic properties comprising all four basic anisotropy mechanisms: linear and circular dichroism and linear and circular birefringence. Several simple examples of synthesized white sandwiches show, however, that the form, orientation and rotation direction of their eigenpolarization ellipses can be easily controlled by changing a single parameter of the constituent elements. The results could contribute to understanding the properties of optical elements with non-orthogonal eigenpolarizations and, more generally, elements with anisotropic absorption.

Sydoruk, O.; Savenkov, S. N.

2010-03-01

188

Development and Mechanical Behavior of FML/Aluminium Foam Sandwiches  

NASA Astrophysics Data System (ADS)

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.

Ba?türk, S. B.; Tano?lu, M.

2013-10-01

189

Development and Mechanical Behavior of FML/Aluminium Foam Sandwiches  

NASA Astrophysics Data System (ADS)

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.

Ba?türk, S. B.; Tano?lu, M.

2012-12-01

190

The Bending Strength, Internal Bonding and Thickness Swelling of a Five Layer Sandwiched Bamboo Particleboard  

NASA Astrophysics Data System (ADS)

The demand for wood based material is increasing but the supply is decreasing. Therefore the price of these raw materials has increased. Bamboo provides an economically feasible alternative raw material for the wood based industry. Its properties are comparable to wood. It is also compatible with the existing processing technology. Bamboo is in abundance, easy to propagate and of short maturation period. Bamboo provides a cheaper alternative resource for the wood based industry. The development of new structural components from bamboo will widen its area of application from handicrafts to furniture and building components. In this study, five layer sandwiched bamboo particleboard were manufactured. The sandwiched Bamboo PB consists of a bamboo PB core, oil palm middle veneers and thin meranti surface veneers. The physical and mechanical properties of the bamboo sandwiched particleboards were tested in accordance to the BS-EN 317:1993 [1] and BS-EN 310:1993 [2], respectively. All the samples passed the standards. The modulus of elasticity was about 352% higher than the value specified in the BS standard, BS-EN 312-4:1996 [3]. The Internal bonding was about 23% higher than the general requirements specified in the standard. On the other hand, the thickness swelling was about 6% lower than the standard. No glue line failure was observed in the strength tests. Critical failures in the IB tests were observed in the particleboards. Tension failures were observed in the surface veneers in the bending tests. The five layer sandwiched bamboo particleboard can be used for light weight construction such as furniture, and wall and door panels in buildings.

Jamaludin, M. A.; Bahari, S. A.; Nordin, K.; Soh, T. F. T.

2010-03-01

191

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

PubMed

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. Biotechnol. Bioeng. 2013;110: 3048-3058. © 2013 Wiley Periodicals, Inc. PMID:23744752

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

2013-06-27

192

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

Microsoft Academic Search

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

Senthil S. Vel; Vincent Caccese; Huyue Zhao

2005-01-01

193

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

Microsoft Academic Search

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

W. L. Ko; R. H. Jackson

1993-01-01

194

Fabrication of Lightweight Composite Sandwich by Granular Mold.  

National Technical Information Service (NTIS)

Although the sandwich panels fabricated of honeycomb core bonded between two face-sheets are very weight-efficient, their application causes many problems such as moisture retention, extensive corrosion, ineffective edge seals, unbonding of face-sheets, a...

H. Ray

1993-01-01

195

Bis(Phthalocyaninato) Lanthanide Sandwich Compounds Exhibiting Mixed Valence Ligands.  

National Technical Information Service (NTIS)

Bis(phthalocyaninato) lanthanide sandwich compounds have been synthesized for ytterbium and thulium. Low temperature magnetic susceptibility data suggest a strong antiferromagnetic interaction between the lanthanide f-electrons and the phythalocyaninato l...

K. D. Kepler K. L. Trojan M. L. Kirk W. E. Hatfield

1990-01-01

196

Structural Testing and Analysis of Honeycomb Sandwich Composite Fuselage Panels.  

National Technical Information Service (NTIS)

This study investigated the damage tolerance characteristics and failure mechanisms of six honeycomb sandwich composite fuselage panels subjected to quasi-static pressurization and axial loading using the Full-Scale Aircraft Structural Test Evaluation and...

C. Davies F. A. Leone J. G. Bakuckas P. Shyprykevich

2008-01-01

197

Damage Tolerance Evaluation of Sandwich Composite Fuselage Panels - Analysis.  

National Technical Information Service (NTIS)

This study investigated the capability of current analytical methods to model the behavior of fuselage-type composite sandwich panels with large damage. This was accomplished by comparing analytical results to test data obtained from a previous study. In ...

J. S. Tomblin K. S. Raju

2010-01-01

198

Interface examination using 'sandwich' analog of matrix and reinforcement  

NASA Astrophysics Data System (ADS)

To examine factors influencing the reinforcement/matrix interface, a 'sandwich' analog of reinforcement and matrix has been prepared. Silicon carbide wafers were made from a polycarbosilane system to resemble polycarbosilane-derived silicon carbide fibers (Nicalon TM). The wafers were encapsulated between lithium aluminosilicate (LAS). After processing in a manner similar to that for silicon carbide/LAS composites, the 'sandwich' was examined using electron microscopy and X-ray diffraction. In order to examine its influence on the interface, an attempt was made to induce crystallization of the LAS at the silicon carbide/LAS interface from a polymer-derived coating of zirconia on the silicon carbide wafer. Preliminary examination of the LAS 'sandwich' of the coated wafer does not show the predicted interface crystallization. Further study of the coated reinforcement/matrix 'sandwich' system is in progress. The observations from this approach will be applied in the preparation and testing of actual composites.

Ludwick, Adriane G.; Ibrahim, Taleb H.; Phadtare, Hanmantrao; Walker, Ralph; Sands, Randall R.; Pontelandolfo, Matthew

1992-08-01

199

On the Elastic Buckling and Bending of Sandwich Plates.  

National Technical Information Service (NTIS)

A governing differential equation for the buckling and bending of sandwich plates with orthotropic cores is derived from a system of differential equations which is developed by means of a variational theorem. Solution of this resultant equation may be re...

S. Cheng N. Al-Rubayi

1966-01-01

200

Buckling of Cylindrical Sandwich Panels with Laminated Faces.  

National Technical Information Service (NTIS)

General stability of a cylindrically curved sandwich panel with laminated composite face sheets is considered. The analysis accounts for axial compression, edgewise shear, or combined loadings. A mathematical model is formulated, based upon a linear poten...

R. A. Brockman

1977-01-01

201

Interface surface behaviour in the upsetting of sandwich metal sheets  

Microsoft Academic Search

The expansion of the contact surface is a typical problem in welding by the pressure technique. The present work is concerned with some aspects of the strain state of the metal during the plastic deformation of sandwich sheets. Based upon a theoretical model for the plane-strain upsetting of a two-metal sandwich sheet, the non-plane forming of the interface surface in

N. D. Lukaschkin; A. P. Borissow

1996-01-01

202

Collapse of truss core sandwich beams in 3-point bending  

Microsoft Academic Search

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

V. S Deshpande; N. A Fleck

2001-01-01

203

Multi-objective optimization design of radar absorbing sandwich structure  

Microsoft Academic Search

By introducing a dimensionless parameter to couple the two objectives, weight and radar absorbing performance, into a single\\u000a objective function, a multi-objective optimization procedure for the radar absorbing sandwich structure (RASS) with a cellular\\u000a core is proposed. The optimization models considered are one-side clamped sandwich panels with four kinds of cores subject\\u000a to uniformly distributed loads. The average specular reflectivity

Ming-ji Chen; Yong-mao Pei; Dai-ning Fang

2010-01-01

204

Combined shear\\/compression structural testing of asymmetric sandwich structures  

Microsoft Academic Search

Asymmetric sandwich technology can be applied in the design of lightweight, non-pressurized aeronautical structures such as\\u000a those of helicopters. A test rig of asymmetric sandwich structures subjected to compression\\/shear loads was designed, validated,\\u000a and set up. It conforms to the standard certification procedure for composite aeronautical structures set out in the “test\\u000a pyramid”, a multiscale approach. The static tests until

B. Castanié; J. J. Barrau; J. P. Jaouen; S. Rivallant

2004-01-01

205

Flexural fatigue characteristics of sandwich structures at different loading frequencies  

Microsoft Academic Search

The effects of frequency on the fatigue behavior of S2 glass fiber–vinylester reinforced sandwich composites with two different PVC cores have been investigated. Flexural fatigue tests were performed on sandwich beams with core densities of 130 and 260 kg\\/m3 at frequencies of 3 and 15 Hz, at a stress ratio, R=0.1 and at four different load levels viz. 90%, 85%,

K. Kanny; H. Mahfuz

2005-01-01

206

Open-die forging of structurally porous sandwich panels  

Microsoft Academic Search

Structurally porous metal sandwich panels consisting of dense face sheets and porous cores of controlled relative density\\u000a can be manufactured by trapping inert gas during hot isostatic pressing and modifying its distribution via subsequent thermomechanical forming. A plane-strain solution for analyzing the open-die forging of such a plastically compressible\\u000a sandwich panel is developed. An effective yield potential for the face

D. M. Elzey; H. N. G. Wadley

1999-01-01

207

Nonlinear bending of simply supported rectangular sandwich plates  

Microsoft Academic Search

In this paper, fundamental equations and boundary conditions of the nonlinear bending theory for a rectangular sandwich plate\\u000a with a soft core are derived by means of the method of calculus of variations. Then the nonlinear bending for a simply supported\\u000a rectangular sandwich plate under the uniform lateral load is investigated by use of the perturbation method and a quite

Liu Ren-huai; Chen Zhen-qiang

1993-01-01

208

Impact response of sandwich plates with a pyramidal lattice core  

Microsoft Academic Search

The ballistic performance edge clamped 304 stainless-steel sandwich panels has been measured by impacting the plates at mid-span with a spherical steel projectile whose impact velocity ranged from 250 to 1300ms?1. The sandwich plates comprised two identical face sheets and a pyramidal truss core: the diameter of the impacting spherical projectile was approximately half the 25mm truss core cell size.

Christian J. Yungwirth; Haydn N. G. Wadley; John H. O’Connor; Alan J. Zakraysek; Vikram S. Deshpande

2008-01-01

209

Impact Testing on Composites Laminates and Sandwich Panels  

Microsoft Academic Search

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

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

1996-01-01

210

High-performance sandwich panels made from braided tubes  

Microsoft Academic Search

A light weight, high-performance sandwich panel was developed using thin walled braided tubes as the core material. The panels have certain specific advantages over conventional honeycomb sandwich panels including superior skin-core bonding, integral conduit systems and self-draining thereby avoiding moisture accumulation. A short manufacturing process leads to a cost effective product. The technology of the tube production is not material-specific,

D. J. Williams; F. Ajibade

1988-01-01

211

Organometallic half-sandwich iridium anticancer complexes.  

PubMed

The low-spin 5d(6) Ir(III) organometallic half-sandwich complexes [(?(5)-Cp(x))Ir(XY)Cl](0/+), Cp(x) = Cp*, tetramethyl(phenyl)cyclopentadienyl (Cp(xph)), or tetramethyl(biphenyl)cyclopentadienyl (Cp(xbiph)), XY = 1,10-phenanthroline (4-6), 2,2'-bipyridine (7-9), ethylenediamine (10 and 11), or picolinate (12-14), hydrolyze rapidly. Complexes with N,N-chelating ligands readily form adducts with 9-ethylguanine but not 9-ethyladenine; picolinate complexes bind to both purines. Cytotoxic potency toward A2780 human ovarian cancer cells increases with phenyl substitution on Cp*: Cp(xbiph) > Cp(xph) > Cp*; Cp(xbiph) complexes 6 and 9 have submicromolar activity. Guanine residues are preferential binding sites for 4-6 on plasmid DNA. Hydrophobicity (log P), cell and nucleus accumulation of Ir correlate with cytotoxicity, 6 > 5 > 4; they distribute similarly within cells. The ability to displace DNA intercalator ethidium bromide from DNA correlates with cytotoxicity and viscosity of Ir-DNA adducts. The hydrophobicity and intercalative ability of Cp(xph) and Cp(xbiph) make a major contribution to the anticancer potency of their Ir(III) complexes. PMID:21443199

Liu, Zhe; Habtemariam, Abraha; Pizarro, Ana M; Fletcher, Sally A; Kisova, Anna; Vrana, Oldrich; Salassa, Luca; Bruijnincx, Pieter C A; Clarkson, Guy J; Brabec, Viktor; Sadler, Peter J

2011-03-28

212

Numerically simulating the sandwich plate system structures  

NASA Astrophysics Data System (ADS)

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.

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

2010-09-01

213

Sandwich module testing for space solar power  

NASA Astrophysics Data System (ADS)

Solar power satellites have been envisioned as a means to provide electricity for terrestrial use. The approach entails collection of solar energy in space and its wireless transmission to the earth. This potentially gives the benefit of provision of baseload power while avoiding the losses due to the day/night cycle and tropospheric effects that are associated with terrestrial solar power. Proponents have contended that the implementation of such systems could offer energy security, environmental, and technological advantages to those who would undertake their development. Among recent implementations commonly proposed for SSP, the Modular Symmetrical Concentrator and other modular concepts have received considerable attention. Each employs an array of modules for performing conversion of concentrated sunlight into microwaves or laser beams for transmission to earth. The research described herein details efforts in the development and testing of photovoltaic arrays, power electronics, microwave conversion electronics, and antennas for 2.45 GHz microwave-based “ sandwich” module prototypes. Prototypes were designed, fabricated, and subjected to the challenging conditions inherent in the space environment, including the solar concentration levels in which an array of modules might be required to operate.

Jaffe, Paul

214

Ionic liquids of cationic sandwich complexes.  

PubMed

Simple cationic sandwich complexes that contained alkyl- or halogen substituents provided ionic liquids (ILs) with the bis(perfluoroalkanesulfonyl)imide anion. Ferrocenium- and cobaltocenium ILs [M(C(5)H(4)R(1))(C(5)H(4)R(2))][Tf(2)N] (M=Fe, Co) and arene-ferrocenium ILs [Fe(C(5)H(4)R(1))(C(6)H(5)R(2))][Tf(2)N] were prepared and their physical properties were investigated. A detailed comparison of their thermal properties revealed the effects of molecular symmetry and substituents on their melting points. Their viscosity increased on increasing the length of the substituent on the cation and the perfluoroalkyl chain length on the anion. Upon cooling, ILs with low viscosities exhibited crystallization, whereas those with higher viscosities tended to exhibit glass transitions. Most of these salts showed phase transitions in the solid state. A magnetic-switching phenomenon was observed for the paramagnetic ferrocenium IL, which was associated with a liquid/solid transformation, based on the magnetic anisotropy of the ferrocenium cation. (57)Fe Mössbauer spectroscopy was applied to [Fe(C(5)H(4)nBu)(2)][Tf(2)N] to investigate the vibrational behavior of the iron atom in the crystal and glassy states of the ferrocenium IL. PMID:22517602

Inagaki, Takashi; Mochida, Tomoyuki; Takahashi, Masashi; Kanadani, Chikahide; Saito, Toshiaki; Kuwahara, Daisuke

2012-04-19

215

?-Cyclodextrin cuprate sandwich-type complexes.  

PubMed

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

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

2013-02-22

216

Foam core materials for structural sandwich panels  

SciTech Connect

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.

Huang Jongshin.

1991-01-01

217

Design of a sandwich-mode amperometric biosensor for detection of PML\\/RAR? fusion gene using locked nucleic acids on gold electrode  

Microsoft Academic Search

In this study, a novel DNA electrochemical probe (locked nucleic acid, LNA) was designed and involved in constructing an electrochemical DNA biosensor for detection of promyelocytic leukemia\\/retinoic acid receptor alpha (PML\\/RAR?) fusion gene in acute promyelocytic leukemia for the first time. This biosensor was based on a ‘sandwich’ sensing mode, which involved a pair of LNA probes (capture probe immobilized

Kun Wang; Zhouliang Sun; Meijuan Feng; Ailin Liu; Shuyu Yang; Yuanzhong Chen; Xinhua Lin

2011-01-01

218

Thermomechanical postbuckling of geometrically imperfect anisotropic flat and doubly curved sandwich panels  

NASA Astrophysics Data System (ADS)

Sandwich structures constitute basic components of advanced supersonic/hypersonic flight and launch vehicles. These advanced flight vehicles operate in hostile environments consisting of high temperature, moisture, and pressure fields. As a result, these structures are exposed to large lateral pressures, large compressive edge loads, and high temperature gradients which can create large stresses and strains within the structure and can produce the instability of the structure. This creates the need for a better understanding of the behavior of these structures under these complex loading conditions. Moreover, a better understanding of the load carrying capacity of sandwich structures constitutes an essential step towards a more rational design and exploitation of these constructions. In order to address these issues, a comprehensive geometrically non-linear theory of doubly curved sandwich structures constructed of anisotropic laminated face sheets with an orthotropic core under various loadings for simply supported edge conditions is developed. The effects of the radii of curvature, initial geometric imperfections, pressure, uniaxial compressive edge loads, biaxial edge loading consisting of compressive/tensile edge loads, end thermal loads will be analyzed. The effect of the structural tailoring of the facesheets upon the load carrying capacity of the structure under these various loading conditions are analyzed. In addition, the movability/immovability of the unloaded edges and the end-shortening are examined. To pursue this study, two different formulations of the theory are developed. One of these formulations is referred to as the mixed formulation, while the second formulation is referred to as the displacement formulation. Several results are presented encompassing buckling, postbuckling, and stress/strain analysis in conjunction with the application of the structural tailoring technique. The great effects of this technique are explored. Moreover, comparisons with the available theoretical and experimental results are presented and good agreements are reported.

Hause, Terry John

219

Experimental investigation of local bending effects in the vicinity of a junction between a straight sandwich beam and a curved sandwich beam  

Microsoft Academic Search

The junction between a curved and a straight sandwich beam is investigated experimentally using electronic speckle pattern interferometry. This technique facilitates a whole field measurement of the displacements through the thickness of the sandwich beam. The experimental results are compared with results obtained using a high order sandwich theory model. The results generally show good agreement within the accuracy of

Anders Lyckegaard; Elena Bozhevolnaya; Ole Thybo Thomsen

2004-01-01

220

Self-assembled hetero-bimetallic sandwich with Ag-Ag bridging using a flexible two-arm ferrocene amide linker  

NASA Astrophysics Data System (ADS)

The tetradentate ferrocenyl sandwich molecule N,N?-bis(di-2-pyridylamine)-1,1?-ferrocenedicarboxamine (bdpfa) has been designed and synthesized as an organometallic ligand in order to construct hetero-bimetallic architectures. By combining the flexibility from the arm-like molecule bdpfa with AgI ions, a novel complex [Ag2(bdpfa)](ClO4)2·(H2O)2 (1) was obtained. Single crystal X-ray analysis has revealed that complex 1 forms a hetero-trinuclear sandwich-type complex with Ag-Ag bridging. Furthermore, the preliminary electrochemical properties of the ligand and complex were investigated.

Ni, Jia; Wei, Kai-Ju; Chen, Yao-Wen; Liu, Yangzhong

2012-03-01

221

Feasibility study of a SiC sandwich neutron spectrometer  

NASA Astrophysics Data System (ADS)

Semiconductor sandwich neutron spectrometers are suitable for in-pile measurements of fast reactor spectra thanks to their compact and relatively simple design. We have assembled and tested a sandwich neutron spectrometer based on 4H-silicon carbide (4H-SiC) Schottky diodes. The SiC diodes detect neutrons via neutron-induced charged particles (tritons and alpha particles) produced by 6Li(n,?)3H reaction. 6LiF neutron converter layers are deposited on the front surface of Schottky diodes by magnetron sputtering. The responses of SiC diodes to charged particles were investigated with an 241Am alpha source. A sandwich neutron spectrometer was assembled with two SiC Schottky diodes selected based on the charged-particle-response experimental results. The low-energy neutron response of the sandwich spectrometer was measured in the neutron field of the Chinese Fast Burst Reactor-II (CFBR-II). Spectra of alpha particles and tritons from 6Li(n,?)3H reaction were obtained with two well-resolved peaks. The energy resolution of the sum spectrum was 8.8%. The primary experimental results confirmed the 4H-SiC sandwich neutron spectrometer's feasibility.

Wu, Jian; Lei, Jiarong; Jiang, Yong; Chen, Yu; Rong, Ru; Zou, Dehui; Fan, Xiaoqiang; Chen, Gang; Li, Li; Bai, Song

2013-04-01

222

Impact Response of Laminate Metal Honeycomb Sandwich Structure  

NASA Astrophysics Data System (ADS)

The ARMOR TPS is one of important candidate structure of RLV. It will be the best selection for all kinds of RLV. So the ARMOR thermal protection system will be used in aviation and spaceflight field more and more widely. ARMOR TPS panel is above the whole ARMOR TPS, and the metal honeycomb sandwich structure is the surface of the ARMOR TPS panel. So the metal honeycomb sandwich structure plays an important role in the ARMOR TPS, while it bears the flight dynamic pressure and stands against the flight dynamic calefaction and impact load. The metal honeycomb sandwich structure is made of upper faceplate, lower faceplate and honeycomb core. In the course of the reusable launch vehicle working, it is possible that the space chips impact its outer surface. The main problem is what impact the metal honeycomb sandwich structure can stand and how many times it can stand. In the high speed impact experiment we choose different quality and velocity to simulate real space environment. This paper will analyze the mechanics behaviour of metal honeycomb sandwich structure in the course of impact, then we make sure the limit impact load and get the effect of impact flaw.

He, Xiaodong; Kong, Xianghao; Shi, Liping

2009-06-01

223

Examination of Sandwich-Type Multidegree-of-Freedom Spherical Ultrasonic Motor  

NASA Astrophysics Data System (ADS)

A sandwich-type multidegree-of-freedom (MDOF) spherical ultrasonic motor (SUSM) is newly proposed. The motor consists of a spherical rotor and two stator vibrators holding the rotor. This structure has both a rotor support and a preload mechanism. The stator excites five vibration modes, and the rotor can rotate on three axes. An experiment of a torque composition of two stators was carried out. The contact surface between the rotor and the stators forms a spherical surface. Moreover, a displacement magnification mechanism, which was used in the former model to rotate on the Z-axis, is no longer necessary. Hence the stator is simpler in construction than the former model. In this paper, we describe the construction and the operating principle of the MDOF ultrasonic motor, modal analysis results for the stator, and some measurement results from trial manufacturing. The miniaturization of the motor and increase in torque were successfully realized.

Bo Lu,; Manabu Aoyagi,; Takehiro Takano,; Hideki Tamura,

2010-07-01

224

Stability of functionally graded shape memory alloy sandwich panels  

NASA Astrophysics Data System (ADS)

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 fibers across the panel is nonuniform, i.e. the spacing, which is minimum at the centerline, gradually increases with the approach to the edges (sinusoidal distribution). The effectiveness of SMA fibers increases with temperature due to larger tensile recovery stresses. The example of stability of sandwich panels considered in the paper illustrates that functionally graded SMA composites may present significant advantages in engineering design.

Birman, Victor

1997-06-01

225

Response of fiber reinforced sandwich structures subjected to explosive loading  

SciTech Connect

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.

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

226

Sandwich-type polymer nanofiber structure of poly(furfuryl alcohol): an effective template for ordered porous films.  

PubMed

A brand new sandwich-type poly(furfuryl alcohol) (PFA) nanostructure as well as ordered PFA nanofiber arrays has been successfully obtained through a novel two-step polymerization method by using a porous alumina membrane as the template. This novel structure is made up of ordered PFA nanopillars supported by two PFA films on the top and bottom. The thickness of the PFA films on both sides could be adjusted from several micrometers to tens of micrometers, and the flexibility of the membrane could be controlled in a certain range. This sandwich-type polymer nanostructure can be used as an effective template for constructing other ordered porous films resembling the structure of the parent alumina membrane, and in this study, ordered porous titania membrane has been successfully obtained. Theoretically, many other novel porous (or meso- and macro-mixed porous) materials could be synthesized through this novel template. PMID:19702291

Gao, Feng; Lu, Qingyi; Pang, Huan; Komarneni, Sridhar

2009-09-17

227

Structural Performance of Eco-Core Sandwich Panels  

NASA Astrophysics Data System (ADS)

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.

Shivakumar, Kunigal; Chen, Huanchun

228

Successful mouse hepatocyte culture with sandwich collagen gel formation  

PubMed Central

Purpose Primary mammalian hepatocytes largely retain their liver-specific functions when they are freshly derived from donors. However, long-term cultures of functional hepatocytes are difficult to establish. To increase the longevity and maintain the differentiated functions of hepatocytes in primary culture, cells can be cultured in a sandwich configuration of collagen. In such a configuration, hepatocytes can be cultured for longer periods compared with cultures on single layers of collagen. However, research regarding mouse hepatocytes in sandwich culture is lacking. Methods Primary mouse hepatocytes were sandwiched between two layers of collagen to maintain the stability of their liver-specific functions. After gelation, 2 mL of hepatocyte culture medium was applied. Results After 24 hours, 5, 10 days of culture, the collagen gel sandwich maintained the cellular border and numbers of bile canaliculi more efficiently than a single collagen coating in both high and low density culture dishes. Reverse transcription-polymerase chain reaction analysis of alpha-1-antitrypsin (AAT), hepatocyte nuclear factor 4 alpha (HNF4A), alphafetoprotein, albumin, tryptophan oxygenase (TO), the tyrosine aminotransferase gene, glucose-6-phosphatase, glyceraldehyde-3-phosphate dehydrogenase for mouse primary hepatocytes cultured on collagen coated dishes and collagen gels showed superior hepatocyte-related gene expression in cells grown using the collagen gel sandwich culture system. AAT, HNF4A, albumin, TO were found to be expressed in mouse hepatocytes cultured on collagen gels for 5 and 10 days. In contrast, mouse hepatocytes grown on collagen-coated dishes did not express these genes after 5 and 10 days of culture. Conclusion The collagen gel sandwich method is suitable for primary culture system of adult mouse hepatocytes.

Choi, Hyun Jung

2013-01-01

229

Heat transfer characteristics of insulated concrete sandwich panel walls: Draft report  

SciTech Connect

Tests were conducted to evaluate thermal performance of three insulated concrete sandwich panel walls. Heat transfer through the walls was measured for steady-state and dynamic temperature conditions. The objective of the test program was to investigate effects of ties connecting wall layers on thermal properties of insulated sandwich panel walls. The three walls tested were similar except for the type of connectors joining the insulation and concrete layers. Each wall consisted of 2-in. (50-mm) of extruded polystyrene insulation board sandwiched between two 3-in. (75-mm) normal weight concrete layers. The first wall, a control wall, contained no ties. Layers of the second wall were connected using stainless steel ties and anchors. Layers of the third wall were connected using high-tensile fiberglass-composite ties. Walls were tested in the calibrated hot box facility (ASTM Designation: C976) at Construction Technology Laboratories, Inc. (CTL). Steady-state tests were used to measure thermal resistance (R/sub T/) and thermal transmittance (U). A comparison of results from steady-state tests on the control wall and the wall with stainless steel connectors showed that stainless steel connectors reduced wall thermal resistance by 7%. A comparison of results from steady-state tests on the control wall and the wall with high-tensile fiberglass-composite ties showed that the ties did not reduce wall thermal resistance. Dynamic calibrated hot box tests provided a measure of thermal response under selected temperature ranges. Heat storage capacities of the walls delayed heat flows through specimens. Average thermal lag values ranged from 5 to 6 hours for the three walls.

Van Geem, M.G.; Shirley, S.T.

1987-05-01

230

Interdiffusion and magnetism in Cu/Ni/Cu sandwiches  

NASA Astrophysics Data System (ADS)

Results are presented for the magnetic-moment distribution in a (111) sandwich consisting originally of three perfect layers of nickel bounded on each side by a semi-infinite copper crystal, for different degrees of interdiffusion. The approach used is a combination of the recently developed layer Korringa-Kohn-Rostoker method, with the multiple-scattering spin-polarized version of the coherent-potential approximation. When applied to bulk homogeneous CuxNi1-x, it yields average and Ni moments in excellent agreement with experiment. The sandwich geometry is found to favor magnetism at Ni concentrations far below the bulk critical value.

Crampin, S.; Monnier, R.; Schulthess, T.; Schadler, G. H.; Vvedensky, D. D.

1992-01-01

231

The extended high-order sandwich panel theory  

NASA Astrophysics Data System (ADS)

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.

Phan, Catherine N.

232

Antibiotic sandwich patch for ventricular septal defect complicated by endocarditis.  

PubMed

Infective endocarditis in patients with ventricular septal defects can prove life threatening due to acute heart failure or septic embolization. Persistent postoperative risk is bacterial colonization of prosthetic material. We designed the Antibiotic Sandwich Patch to reduce this risk, using a double layer of autologous pericardium containing antibiotic powder. Five patients were managed with this technique for closure of ventricular septal defects complicated by acute infective endocarditis. No colonization of the patches occurred after a median follow up of 1.5 years. This technique reduced the risk of bacterial colonization of the antibiotic sandwich patch, offering an additional surgical option. PMID:21718885

Lo Rito, Mauro; Leon-Wyss, Juan; Veras, Oscar; Vides, Ivan; Najera, Cesar; Castañeda, Aldo R

2011-07-01

233

Experimental Investigation of Graphite/Polyimide Sandwich Panels in Edgewise Compression.  

National Technical Information Service (NTIS)

The local and general buckling of graphite/polyimide sandwich panels simply supported along all four edges and loaded in uniaxial edgewise compression is investigated. Material properties of sandwich panel constituents (adhesive and facings) were determin...

C. J. Camarda

1974-01-01

234

Encapsulating magnetic nanoparticles in sandwich-like coupled graphene sheets and beyond.  

PubMed

The first syntheses of a series of novel graphene-based materials, nanoparticle-encapsulated sandwich-like coupled graphene sheets and pure sandwich-like coupled graphene sheets, are reported. PMID:23224219

Zhang, Huijuan; Bai, Yuanjuan; Feng, Yangyang; Li, Xiao; Wang, Yu

2013-03-21

235

Gravity sag of sandwich panel assemblies as applied to precision cathode strip chamber structural design  

SciTech Connect

The relationship between gravity sag of a precision cathode strip chamber and its sandwich panel structural design is explored parametrically. An algorithm for estimating the dominant component of gravity sag is defined. Graphs of normalized gravity sag as a function of gap frame width and material, sandwich core edge filler width and material, panel skin thickness, gap height, and support location are calculated using the gravity sag algorithm. The structural importance of the sandwich-to-sandwich ``gap frame`` connection is explained.

Horvath, J. [Lawrence Livermore National Lab., CA (United States)

1993-09-16

236

Enhanced Faraday rotation of a thick magneto-optical metal sandwiched between two dielectric photonic crystals  

NASA Astrophysics Data System (ADS)

We present a thick magneto-optical metal sandwiched between two dielectric magnetophotonic crystals of enhancing Faraday rotation effect. It is found that the transmission and Faraday rotation effect can simultaneously be enhanced when impedance and phase matching conditions are satisfied in the sandwiched. Moreover, the Faraday rotation of a double peak and a single peak is studied in sandwiched structure, respectively.

Dong, Lijuan; Liu, Lixiang; Liu, Yanhong; Shi, Yunlong

2013-08-01

237

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

Microsoft Academic Search

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

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

2003-01-01

238

Impact testing and simulation of composite sandwich structures for civil transportation  

Microsoft Academic Search

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

L Torre; J. M Kenny

2000-01-01

239

A study on material damping of 0° laminated composite sandwich cantilever beams with a viscoelastic layer  

Microsoft Academic Search

The damping behavior of a 0° laminated sandwich composite beam inserted with a viscoelastic layer is investigated. A quantitative analysis of damping in the sandwich laminated composite beam has been conducted through the theoretical method. Results showed that the viscoelastic core thickness in the sandwich beam and the length of the beam have a great effect on the damping loss

Jong Hee Yim; Shee Yong Cho; Yun Jong Seo; Bor Z. Jang

2003-01-01

240

Experimental investigation and design of sandwich panels subject to local buckling effects  

Microsoft Academic Search

The use of sandwich panels in Australia has increased significantly in recent years due to their widespread structural applications in building systems. Structural sandwich panels generally used in Australia comprise of polystyrene foam core and thinner and high strength steel faces. The fully profiled sandwich panels, when subjected to axial compression and\\/or bending effects, are susceptible to local buckling failures.

Narayan Pokharel; Mahen Mahendran

2003-01-01

241

An analytical model for composite sandwich panels with honeycomb core subjected to high-velocity impact  

Microsoft Academic Search

In this paper, an analytical model for perforation of composite sandwich panels with honeycomb core subjected to high-velocity impact has been developed. The sandwich panel consists of a aluminum honeycomb core sandwiched between two thin composite skins. The solution involves a three-stage, perforation process including perforation of the front composite skin, honeycomb core, and bottom composite skin. The strain and

S. Feli; M. H. Namdari Pour

242

Impact damage processes in composite sheet and sandwich honeycomb materials  

Microsoft Academic Search

The research interest of this study is the impact toughness of different lightweight sandwich panels and composite sheet materials. This is as to the degrees of damage inflicted on the contact surface, through-thickness and rear surface of the materials when subjected to different impacts. For this study, specimens were prepared from sheet moulding compound (SMC), glass mat thermoplastic (GMT) and

J. P. Dear; H. Lee; S. A. Brown

2005-01-01

243

Vibration of a sandwich plate strip of linearly varying thickness  

Microsoft Academic Search

Free transverse vibration of a sandwich plate strip having a core of linearly varying thickness and symmetrical faces of constant thickness is considered. The materials of the core and the faces are assumed to be linearly elastic and isotropic. The effects of transverse shear deformation and rotary inertia are included in the core as well as in the faces. The

A. P. Gupta; R. R. Bhargava

1993-01-01

244

Compressive behavior of sandwich panels and laminates with damage  

Microsoft Academic Search

A wrinkling model for sandwich panels in compression is developed with the assumption of an isotropic elastic core. Stresses for the three wrinkling cases coupled with global buckling are expressed by a unified expression. It is shown that the stresses in all three cases are identical for short wavelength wrinkling and can be expressed by a single simplified analytical expression,

Kangmin Niu

1998-01-01

245

Wave Propagation in Sandwich Plates with Periodic Auxetic Core  

Microsoft Academic Search

The wave propagation in and the vibration of sandwich plates with cellular core are analyzed and controlled. Negative Poisson’s ratio (auxetic) core materials of different geometry placed periodically in the plate introduce the proper impedance mismatch necessary to obstruct the propagation of waves over specified frequency bands (stop bands) and in particular directions. The location and the extension of the

Massimo Ruzzene; Luca Mazzarella; Panagiotis Tsopelas; Fabrizio Scarpa

2002-01-01

246

Transient wave propagation in a viscoelastic sandwich plate  

Microsoft Academic Search

Summary This paper examines the propagation of coupled P and S waves in a three layer sandwich plate consisting of a viscoelastic core bounded by identical elastic outer layers. The waves are initiated by an impulsive normal line load applied to the upper surface of the plate. The response of the top surface is computed for various values of the

D. Nkemzi; W. A. Green

1994-01-01

247

Drug metabolism in hepatocyte sandwich cultures of rats and humans  

Microsoft Academic Search

Adult hepatocytes from rat and man were maintained for 2 weeks between two gel layers in a sandwich configuration to study the influence of this culture technique on the preservation of basal activities of xenobiotic-metabolizing phase I and phase II enzymes. The response of these enzyme activities to an enzyme inducer was investigated using rifampicin (RIF). Basal levels of cytochrome

A Kern; A Bader; R Pichlmayr; K.-F Sewing

1997-01-01

248

Development of Multispectral Sandwich-Type IR Windows.  

National Technical Information Service (NTIS)

Composite or sandwich-type multispectral windows up to 4 x 6 inch in size have been fabricated by a Westinghouse-developed technique called optical brazing. Of the numerous cladding, substrate and adhesives tested, the ZnS/ZnSe composite window is now the...

W. E. Kramer R. H. Hopkins G. B. Brandt R. A. Hoffman J. Schruben

1977-01-01

249

Metal sandwich plates subject to intense air shocks  

Microsoft Academic Search

Recent results on fluid–structure interaction for plates subject to high intensity air shocks are employed to assess the performance of all-metal sandwich plates compared to monolithic solid plates of the same material and mass per area. For a planar shock wave striking the plate, the new results enable the structural analysis to be decoupled from an analysis of shock propagation

Ashkan Vaziri; John W. Hutchinson

2007-01-01

250

A comparative studyof impulse-resistant metal sandwich plates  

Microsoft Academic Search

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

Zhenyu Xue; John W. Hutchinson

251

A comparative study of impulse-resistant metal sandwich plates  

Microsoft Academic Search

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

Zhenyu Xue; John W. Hutchinson

2004-01-01

252

Adhesive Bond Failures in Aircraft Honeycomb Sandwich Composites.  

National Technical Information Service (NTIS)

A number of approaches were initiated to improve bond strength and durability of honeycomb core-sandwich structures, some of which are described in the report. The overall objective was to determine why and how these composites fail and then determine wha...

T. R. Walton J. E. Cowling

1970-01-01

253

Damage detection of fiber-reinforced polymer honeycomb sandwich beams  

Microsoft Academic Search

In a framework of developing a structural health monitoring for civil infrastructure, the damage identification procedure based on dynamic response for fiber reinforced polymer (FRP) sandwich composites is evaluated. In this paper, an experimental damage identification procedure based on structural dynamic responses and using smart sensors is conducted. Damage identification is estimated from comparison of dynamic responses of healthy and

Wahyu Lestari; Pizhong Qiao

2005-01-01

254

A Refined Zigzag Beam Theory for Composite and Sandwich Beams  

Microsoft Academic Search

A new refined theory for laminated composite and sandwich beams that contains the kinematics of the Timoshenko Beam Theory as a proper baseline subset is presented. This variationally consistent theory is derived from the virtual work principle and employs a novel piecewise linear zigzag function that provides a more realistic representation of the deformation states of transverse-shear flexible beams than

Alexander Tessler; Marco Di Sciuva; Marco Gherlone

2009-01-01

255

Failure initiation and propagation characteristics of honeycomb sandwich composites  

Microsoft Academic Search

The energy absorbed during the failure of a variety of structural shapes is influenced by material, geometry and the failure mode. Failure initiation and propagation of the honeycomb sandwich under loading involves not only non-linear behavior of the constituent materials, but also complex interactions between various failure mechanisms. Therefore, there is a need for an improved understanding of the material

A. R. Othman; D. C. Barton

2008-01-01

256

Localised formulations for thick ``sandwich'' laminated and composite structures  

Microsoft Academic Search

A ``sandwich'' panel under axial compressive loading is studied over its post-buckling range. Alternative formulations were developed to cover solutions other than the deflection shape given by the classical Rayleigh-Ritz analysis. General elasticity principles are used to derive the total potential energy function in terms of the displacement field. Given a constant modal amplitude displacement field, which is introduced in

L. A. P. S. da Silva; J. M. C. Santos

1998-01-01

257

A Reusable Sandwich Beam Concept for Composite Compression Test  

Microsoft Academic Search

A reusable sandwich beam for compression testing has been developed. Testing was performed to determine the longitudinal compressive modulus and ultimate compressive strength of a Kevlar® \\/glass intermingled hybrid composite. Results using this test method are reported and compared with results obtained using the IITRI test method.

Mark B. Gruber; Johannes L. Overbeeke; Tsu-Wei Chou

1982-01-01

258

Failure mode investigation of sandwich beams with functionally graded core  

Microsoft Academic Search

A failure mode criterion for piece-wise functionally graded sandwich composites is proposed and compared against experimental data. The average peak load for low and high density core configurations at upper region is 138% and 192% higher than the reference group. The proposed failure mode model predicts with accuracy the failure mechanisms. The best performance was obtained by the beam configuration

Antonio F. Ávila

2007-01-01

259

Design of Sandwich Composite Panels with Enhanced Passive Damping  

Microsoft Academic Search

Sandwich composite panels are being used increasingly in transportation vehicles including aircraft, spacecraft, ships, road and rapid transit vehicles. This is because their strength-to-weight ratios are generally superior to those of metals including aluminum and steel. Their structural strength properties are fairly well known. However their fatigue, vibration and acoustic properties are known less. This is a problem since such

John Smith; Ann Brown

260

Damage detection in a sandwich composite beam using wavelet transforms  

Microsoft Academic Search

There is a growing interest in developing non-destructive damage detection methods for damage assessment of composite structures, especially in the aerospace and marine industries. Although damage detection of composite laminates has been widely investigated, little work has been carried out on sandwich composite configurations. A technique using the Lipschitz exponent, which is estimated by wavelet transforms, as a damage sensitive

Tariq A. Dawood; R. A. Shenoi; Sandor M. Veres; Melin Sahin; Mark J. Gunning

2003-01-01

261

Fracture Behaviour of Adhesively Bonded Joints in Sandwich Composite Beams  

Microsoft Academic Search

Adhesive bonding is widely accepted as one of the most efficient and practical techniques for joining fiber-reinforced polymer (FRP) adherends. Additionally, configuration of such adherends with a core material into a sandwich composite produces structural elements with superior flexural stiffness and strength. While several studies have investigated the performance of bonded joints of FRP adherends, investigations into characterization of bonded

Khaled Shahin; Farid Taheri

2009-01-01

262

Damage detection in a sandwich composite beam using wavelet transforms  

Microsoft Academic Search

ABSTRACT There is a growing interest in developing non-destructive damage detection methods for damage assessment of composite structures, especially in the aerospace and marine industries. Although damage detection of composite laminates has been widely investigated, little work has been carried out on sandwich composite configurations. A technique using the Lipschitz exponent, which is estimated by wavelet transforms, as a damage

T. A. Dawood; R. A. Shenoi; S. M. Veres; M. Sahin; M. J Gunning

263

Fabrication and structural performance of periodic cellular metal sandwich structures  

Microsoft Academic Search

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

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

2003-01-01

264

Buckling of cylindrical sandwich shells with metal foam cores  

Microsoft Academic Search

Buckling of cylindrical sandwich shells subject to axial compression is addressed for shells having foamed metal cores. Optimal face sheet thickness, core thickness and core density are obtained which minimize the weight of a geometrically perfect shell with a specified load carrying capacity. Constraints imposed by wrinkling and yielding of the face sheets and yielding of the core are all

J. w. Hutchinson; M. y. He

2000-01-01

265

Damage tolerance of a composite sandwich with interleaved foam core  

NASA Astrophysics Data System (ADS)

A composite sandwich panel consisting of carbon fiber-reinforced plastic (CFRP) skins and a syntactic foam core was selected as an appropriate structural concept for the design of wind tunnel compressor blades. Interleaving of the core with tough interlayers was done to prevent core cracking and to improve damage tolerance of the sandwich. Simply supported sandwich beam specimens were subjected to low-velocity drop-weight impacts as well as high velocity ballistic impacts. The performance of the interleaved core sandwich panels was characterized by localized skin damage and minor cracking of the core. Residual compressive strength (RCS) of the skin, which was derived from flexural test, shows the expected trend of decreasing with increasing size of the damage, impact energy, and velocity. In the case of skin damage, RCS values of around 50 percent of the virgin interleaved reference were obtained at the upper impact energy range. Based on the similarity between low-velocity and ballistic-impact effects, it was concluded that impact energy is the main variable controlling damage and residual strength, where as velocity plays a minor role.

Ishai, Ori; Hiel, Clement

266

Debris Impact on CFRP-AL Honeycomb Sandwich Structure  

NASA Astrophysics Data System (ADS)

In order to do risk assessments of debris impacts on unmanned spacecraft, it is necessary to investigate damage of honeycomb sandwich structures caused by debris impacts. However, the study of the honeycomb sandwich panel with CFRP face sheets has not been sufficiently performed. The purpose of this study is to investigate hypervelocity impact phenomena of CFRP-AL honeycomb sandwich structure. Hypervelocity impact tests were performed with a two-stage light gas gun at University of Padova. Three kinds of CFRP-AL honeycomb sandwich panels which are frequently used as a material of a spacecraft structure were tested. The cell size and the core thickness were varied. Aluminum spheres, 0.8 mm in diameter, were used as projectiles. The tests were performed at a velocity range between 2 and 5 km/sec. After the tests, the projectiles perforated all targets. The perforation holes on the panels were measured, and ultrasonic inspection was performed. The area of the perforation holes of the panel were increased with the impact velocity. The core size of the honeycomb core did not influence the relationship between the hole and the impact velocity. Impacts of the projectile on the foil of honeycomb cell caused heavy damage to a face sheet of the opposite side of the impact surface.

Higashide, Masumi; Nagao, Yosuke; Kibe, Seishiro; Francesconi, Alessandro; Paverin, Daniele

267

Modern sandwich core materials offer new attractive design possibilities  

Microsoft Academic Search

Activities in trying to make the airplane interiors more attractive to passengers increase the demand for complex, three-dimensional sandwich structural parts. The realization of three-dimensional contours often failed in the past, due to a lack of process ability or the enormous production costs caused by the processing of conventional phenolic cores. The new structural foam cores based on thermoplastic polytherimide

Bruno Imhof

1997-01-01

268

Deepdrawing FE-simulations for thermoplastic sandwich structures  

Microsoft Academic Search

In this paper deepdrawing FE analyses are performed on full three-dimensional and geometrically detailed thermoplastic sandwich\\u000a plates with honeycomb cores. Forming analyses with bending in one and two directions are conducted. The importance of the\\u000a out-of-plane core shear strength in these deepdrawing processes is pointed out.

C. Macaluso; D. Vandepitte; I. Verpoest

2008-01-01

269

Modular container assembled from fiber reinforced thermoplastic sandwich panels  

Microsoft Academic Search

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.

Mathew William Donnelly; William Andrew Kasoff; Patrick Carl Mcculloch; Frederick Truman Williams

2007-01-01

270

Modelling of the Indentation Behaviour of Thermoplastic Honeycomb Sandwich Panels  

Microsoft Academic Search

Thermoplastic honeycombs based on polypropylene are one of the latest types of cores used in sand- wich structures. Up to now there have been few experimental and modelling studies on the mechani- cal behaviour of sandwich structures with thermoplastic cores. In this paper, by considering the sim- ilar properties of foams and thermoplastic honeycombs, attempts are made to model the

V. Khalili Moghamir; H. Rahimi; M. H. R. Ghoreishy; A. M. Rezadoust; M. Esfandeh

2008-01-01

271

Modular container assembled from fiber reinforced thermoplastic sandwich panels  

DOEpatents

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.

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

2007-12-25

272

Thermographic investigation of sandwich structure made of composite material  

Microsoft Academic Search

In this paper an experimental procedure, by means of thermographic technique, was set up in order to detect some typical defects, which could be found in composite material sandwich structures. The material thermal response was investigated for different artificially defects inserted in some specimens; every kind of defect was listed. Then the experimental procedure was applied to study a wind-turbine

V. Dattoma; R. Marcuccio; C. Pappalettere; G. M. Smith

2001-01-01

273

Star cell type core configuration for structural sandwich materials  

DOEpatents

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.

Christensen, Richard M. (Danville, CA)

1995-01-01

274

A h-p Finite Element Vibration Analysis of Open Conical Sandwich Panels and Conical Sandwich Frusta  

Microsoft Academic Search

The vibration study of a general three-layer conical sandwich panel based on the h-p version of the finite element method is presented in this paper. No restriction is placed on the degree of curvature of the shell, thereby relaxing the strictures associated with shallow shell theory. The methodology incorporates a new set of trigonometric functions to provide the element p

N. S. Bardell; R. S. Langley; J. M. Dunsdon; G. S. Aglietti

1999-01-01

275

Elastic design of syntactic foamed sandwiches obtained by filling of three-dimensional sandwich-fabric panels  

Microsoft Academic Search

A non-conventional sandwich, made by a fabric panel core filled by a syntactic foam, and by resin-impregnated fiberglass skins, is studied in the elastic range, with the aim of giving guidelines to its minimum weight design. Standard homogenization techniques are employed to compute the elastic moduli of the skins, whereas a specifically developed homogenization method has been used to obtain

Lorenzo Bardella; Francesco Genna

2001-01-01

276

PLLA/Flax Mat/Balsa Bio-Sandwich—Environmental Impact and Simplified Life Cycle Analysis  

NASA Astrophysics Data System (ADS)

In the present paper the environmental impact of biocomposites and bio-sandwich materials production are evaluated, using simplified Life Cycle Analysis (LCA) following the procedure recommended in the ISO 14044 standard. The materials are dimensioned and evaluated by comparing with reference materials, glass mat reinforced unsatured polyester and glass mat/unsatured polyester/balsa sandwich. The results indicate that bio-sandwich materials are very attractive in terms environmental impact. However further improvements in biocomposite and bio-sandwich mechanical strength are necessary if they are to be used in transport application compared to glass/polyester and glass/polyester/balsa sandwich.

Le Duigou, Antoine; Deux, Jean-Marc; Davies, Peter; Baley, Christophe

2012-06-01

277

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

NASA Astrophysics Data System (ADS)

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.

Ko, William L.; Jackson, Raymond H.

278

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

SciTech Connect

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.

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

1993-06-01

279

Sandwich pressurization systems for smoke control  

SciTech Connect

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.

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

1992-11-01

280

Analyses of sandwich beams and plates with viscoelastic cores  

NASA Astrophysics Data System (ADS)

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.

Wang, Gang

281

Method for making titanium aluminide metallic sandwich structures  

US Patent & Trademark Office Database

A method for fabricating of intermetallic titanium aluminide sandwich structures in which blanks of titanium aluminide are bonded to one another, under vacuum in a retort, at selected areas to form a pack, and then, upon removal of the retort, expanded superplastically to form a desired sandwich structure. Bonding of the various preselected areas of the metal blanks is accomplished using elevated temperature gas diffusion bonding techniques. The invention contemplates a first thermal cycle during which the pack is diffusion bonded in an evacuated retort at one temperature within a predetermined range of temperatures, and a second thermal cycle during which subsequent superplastic forming of the pack of bonded blanks, with the retort removed, is carried out. Optionally, during the first thermal cycle, a step of superplastic preforming may be carried out whereby the pack is preformed against arcuate or other shaped forming members.

1992-06-02

282

Metal/dielectric/metal sandwich film for broadband reflection reduction  

NASA Astrophysics Data System (ADS)

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.

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

2013-04-01

283

Fatigue and impact properties of metal honeycomb sandwich panel  

NASA Astrophysics Data System (ADS)

Honeycomb sandwich structures are significant to be used as applied to thermal protection system on reusable launch vehicle. In this paper the fatigue and impact properties of a novel metallic thermal protection material have been investigated and predicted at room temperature. A series of strength tests are carried out to obtain parameters firstly for further experiments. A set of tension-tension stress fatigue tests and impact tests based on split-Hopkinson pressure bar are carried out. Different high strain rate impact experiments are accomplished. The curves of dynamical stress, strain and strain rate are obtained. Also the cell units images after impact are presented. The results show the fatigue properties of honeycomb sandwich panels are comparatively better. And it has the advantages of anti-impact resistance and high, energy absorption capability.

Zou, Guang Ping; Lu, Jie; Liang, Jun; Chang, Zhong Liang

2008-11-01

284

Localised formulations for thick ``sandwich'' laminated and composite structures  

NASA Astrophysics Data System (ADS)

A ``sandwich'' panel under axial compressive loading is studied over its post-buckling range. Alternative formulations were developed to cover solutions other than the deflection shape given by the classical Rayleigh-Ritz analysis. General elasticity principles are used to derive the total potential energy function in terms of the displacement field. Given a constant modal amplitude displacement field, which is introduced in the total potential energy function, the results are discussed having as background models studied earlier. Techniques for the analysis of localized solutions are presented with reference to the study of the beam on nonlinear elastic foundation. The concepts of localization are introduced by using dynamical analogy and the double scale perturbation method and applied to the sandwich panel, to derive the governing amplitude modulation equations. The resulting formulations are discussed using some examples, and by solving analytical and numerically the amplitude differential equations.

da Silva, L. A. P. S.; Santos, J. M. C.

285

Vibration and stability of sandwich beams with elastic bonding  

NASA Astrophysics Data System (ADS)

This paper is a study of the vibration and stability of symmetrical sandwich cantilevers with elastic bonding. The horizontal displacements of the face layer and the core are discontinuous due to the elasticity of the interface bond. The shear traction at the interface is assumed to be proportional to the relative horizontal displacement of the layers. The core layer is subjected to a horizontal (conservative) or tangential (non-conservative) axial force at its free end. It is shown that a symmetrical sandwich beam with elastic bonding has two kinds of vibration modes: i.e., bending modes and longitudinal modes. Numerical results are given for a beam composed of FRP face layers and a syntactic-foam core layer. It is shown that the divergence and the flutter type instability loads, as well as the natural frequency, are affected considerably by the stiffness of the interface bond.

Chonan, S.

1982-12-01

286

Lightweight composites for modular panelized construction  

NASA Astrophysics Data System (ADS)

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).

Vaidya, Amol S.

287

Interdiffusion and magnetism in Cu\\/Ni\\/Cu sandwiches  

Microsoft Academic Search

Results are presented for the magnetic-moment distribution in a (111) sandwich consisting originally of three perfect layers of nickel bounded on each side by a semi-infinite copper crystal, for different degrees of interdiffusion. The approach used is a combination of the recently developed layer Korringa-Kohn-Rostoker method, with the multiple-scattering spin-polarized version of the coherent-potential approximation. When applied to bulk homogeneous

S. Crampin; R. Monnier; T. Schulthess; G. H. Schadler; D. D. Vvedensky

1992-01-01

288

Damping optimization of viscoelastic laminated sandwich composite structures  

Microsoft Academic Search

Recent developments on the optimization of passive damping for vibration reduction in sandwich structures are presented in\\u000a this paper, showing the importance of appropriate finite element models associated with gradient based optimizers for computationally\\u000a efficient damping maximization programs. A new finite element model for anisotropic laminated plate structures with viscoelastic\\u000a core and laminated anisotropic face layers has been formulated, using

A. L. Araújo; P. Martins; C. M. Mota Soares; C. A. Mota Soares; J. Herskovits

2009-01-01

289

Evaluation of Stiffness Terms for Z -cored Sandwich Panels  

Microsoft Academic Search

This paper presents a model for the stiffness terms of composite sandwich panels with structured cores (referred to as ‘z-core’ panels). Truss-cores, corrugated-cores and double-corrugated cores containing a polymeric foam were considered. The\\u000a model was validated, both through finite element simulation and through comparison with the results of experimental three\\u000a point bend tests on panels. A parametric study was performed

D. Zangani; M. Robinson; A. G. Gibson

2007-01-01

290

Development of multispectral sandwich-type IR windows  

Microsoft Academic Search

Composite or sandwich-type multispectral windows up to 4 x 6 inch in size have been fabricated by a Westinghouse-developed technique called optical brazing. Of the numerous cladding, substrate and adhesives tested, the ZnS\\/ZnSe composite window is now the most promising for airborne common aperture systems. Optical path differences in the assembled windows stem mainly from material property variations in the

W. E. Kramer; R. A. Hopkins; G. B. Brandt; R. A. Hoffman; J. Schruben

1977-01-01

291

Fracture and Fatigue Tests and Analysis of Composite Sandwich Structure  

Microsoft Academic Search

A composite sandwich system is investigated in this research. Quasi-static fracture toughness and fatigue crack growth experimental and analytical approaches are the focus. The particular system studied is comprised of a Nomex (aramid fiber) honeycomb core with graphite\\/epoxy facesheets (skins).A modified version of the double cantilever beam (DCB) specimen geometry is used for experimentation. The critical strain energy release rate,

C. Kyle Berkowitz; W. Steven Johnson

2005-01-01

292

A hard ferromagnetic and elastic beam-plate sandwich structure  

Microsoft Academic Search

.  In this paper, the deformation of a composite hard ferromagnetic-elastic beam-plate structure is investigated. A sandwich\\u000a structure, composed of two thin hard ferromagnetic layers, with a linear elastic layer in between, is considered. The deformation\\u000a is due to the self generated magnetic field (magnetostriction). The aim is to assess the interaction forces among the perfectly\\u000a bonded layers, through a consistent

Andrea Nobili; Angelo Marcello Tarantino

2007-01-01

293

Review and assessment of various theories for modeling sandwich composites  

Microsoft Academic Search

In this paper, an attempt has been made to analyze and assess the various kinematics and theories used for the modeling of sandwich composites. Major classes of representative theories such as classical laminate theory (CLT), first-order shear deformation theory (FSDT) and high-order theories (HOTs) as well as Zig-Zag based theory models have been considered and a unified kinematic formulation is

Heng Hu; Salim Belouettar; Michel Potier-Ferry; El Mostafa Daya

2008-01-01

294

Numerical Investigation of Crack Propagation in Sandwich Structures  

Microsoft Academic Search

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

E. E. Theotokoglou

295

Thermoplastic strain of circular sandwich plates on an elastic base  

Microsoft Academic Search

We consider thermomechanical bending of an elastoplastic circular (solid or annular) light-filler sandwich plate resting on\\u000a an elastic base. The hypotheses of broken normal are used to describe the kinematics of the plate stack nonsymmetric along\\u000a the thickness. The base reaction is described by the Winkler model. We obtain the system of equilibrium equations and its\\u000a exact solution in terms

D. V. Leonenko; E. I. Starovoitov

2009-01-01

296

Warp-knit laminates for stampable sandwich preforms  

Microsoft Academic Search

Thermoforming of doubly-curved sandwich components will offer new design possibilities and cost-effective manufacturing routes. However, the occurrence of folds and wrinkles in face sheets is directly linked to the fabric architecture and constitutes a process-limiting factor. Drapability tests have shown that knitted fabrics are less susceptible to wrinkling than woven preforms because their loop structure can more easily accommodate large

O Rozant; P.-E Bourban; J.-A. E Månson

2001-01-01

297

Electromagnetic tunneling in a sandwich structure containing single negative media  

Microsoft Academic Search

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

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

2009-01-01

298

MoSiâ-based sandwich composite made by tape casting  

Microsoft Academic Search

The mechanical properties of a novel laminar composite made by tape casting have been studied. The composite consists of three layers in which an inner core of pure molybdenum disilicide (MoSiâ) is sandwiched between two layers of MoSiâ reinforced with alumina platelets. Monolithic MoSiâ exhibits poor room-temperature strength and a brittle indentation strength response, indicative of the absence of R-curve

Stephane Tuffe; David S. Wilkinson

1995-01-01

299

Star cell type core configuration for structural sandwich materials  

DOEpatents

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.

Christensen, R.M.

1995-08-01

300

Nonlinear Dynamic Finite Element Analysis of Thick Transversly Flexible Sandwich Panel on Elastic Foundation with Account of Damage Progression in Time. Part 1. Three-Dimensional Formulation and Two-Dimensional Plate Theory  

Microsoft Academic Search

In order to construct a plate theory for a thick transversely compressible sandwich plate with composite laminated face sheets, the author makes simplifying assumptions regarding distribution of transverse strain components in the thickness direction. It is assumed that the transverse strains, i.e., exz, eyz, and ezzdo not vary in the thickness direction within the face sheets and the core, but

V. Y. Perel

2005-01-01

301

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

NASA Astrophysics Data System (ADS)

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.

Rakow, Joseph F.

302

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

Microsoft Academic Search

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

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

2009-01-01

303

Minimum-Weight Sandwich Structure Optimum Design Subjected to Torsional Loading  

Microsoft Academic Search

As one of the most valued structural engineering innovations developed by the composites industry, sandwich structures are\\u000a now used extensively in automotive, aerospace and civil infrastructure due to the main advantage of lightweight. This paper\\u000a develops a minimum weight optimization method for sandwich structure subjected to torsion load. The design process are identified\\u000a for a sandwich structure required to meet

Xiang Li; Gangyan Li; Chun H. Wang; Min You

2011-01-01

304

Optimum Design of Composite Sandwich Structures Subjected to Combined Torsion and Bending Loads  

Microsoft Academic Search

This research is motivated by the increase use of composite sandwich structures in a wide range of industries such as automotive,\\u000a aerospace and civil infrastructure. To maximise stiffness at minimum weight, the paper develops a minimum weight optimization\\u000a method for sandwich structure under combined torsion and bending loads. We first extend the minimum-weight design of sandwich\\u000a structures under bending load

Xiang Li; Gangyan Li; Chun H. Wang; Min You

2011-01-01

305

Materials characterisation and crash modelling of composite-aluminium honeycomb sandwich material  

Microsoft Academic Search

Composite sandwich materials are extensively used in aerospace, motorsport and other applications that require low-weight, high-stiffness materials with high strength and energy absorption. In Formula 1 vehicles, composite-aluminium sandwich materials are used for the energy absorbing structures and the protective cell for the driver. Generally, the loading and failure mechanisms in sandwich composite materials are well understood. However, their behaviour

A. K. Pickett; A. J. Lamb; F. Chaudoye

2009-01-01

306

Modelling the vibration of sandwich beams using frequency-dependent parameters  

Microsoft Academic Search

Various types of sandwich beams with foam or honeycomb cores are currently used in the industry, indicating the need for simple methods describing the dynamics of these complex structures. By implementing frequency-dependent parameters, the vibration of sandwich composite beams can be approximated using simple fourth-order beam theory. A higher-order sandwich beam model is utilized in order to obtain estimates of

D. Backström; A. C. Nilsson

2007-01-01

307

Low-velocity impact response of sandwich beams with functionally graded core  

Microsoft Academic Search

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

N. A. Apetre; B. V. Sankar; D. R. Ambur

2006-01-01

308

Development of a satellite structure with the sandwich T-joint  

Microsoft Academic Search

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

Byoung Jung Kim; Dai Gil Lee

2010-01-01

309

A Quasi2d Finite Element Formulation for Static and Dynamic Analysis of Sandwich Beams  

Microsoft Academic Search

Sandwich structures are typical found in designs that require high stiffness to weight ratio. Their use has also been demonstrated\\u000a in the enhancement of acoustic properties, attainment of specific thermal properties, and for mere aesthetics. The classical\\u000a three-layer sandwich structures have a core that is sandwiched between two face-sheets. The inadequacy of the classical assumptions\\u000a in light of the growing

Jean-Jacques R. Boileau Bekuit; Donatus C. D. Oguamanam; Olatunde Damisa

310

Encapsulating magnetic nanoparticles in sandwich-like coupled graphene sheets and beyond  

NASA Astrophysics Data System (ADS)

The first syntheses of a series of novel graphene-based materials, nanoparticle-encapsulated sandwich-like coupled graphene sheets and pure sandwich-like coupled graphene sheets, are reported.The first syntheses of a series of novel graphene-based materials, nanoparticle-encapsulated sandwich-like coupled graphene sheets and pure sandwich-like coupled graphene sheets, are reported. Electronic supplementary information (ESI) available: Experimental details, detailed characterizations of products, and additional electrochemical characterizations of nanocomposites. See DOI: 10.1039/c2nr33008c

Zhang, Huijuan; Bai, Yuanjuan; Feng, Yangyang; Li, Xiao; Wang, Yu

2013-02-01

311

Energy absorption capabilities of composite sandwich panels under blast loads  

NASA Astrophysics Data System (ADS)

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.

Sankar Ray, Tirtha

312

Control of wave propagation in sandwich beams with auxetic core  

NASA Astrophysics Data System (ADS)

The wave propagation in sandwich beams with cellular core is analyzed and controlled. The material properties of cellular cores are highly dependent on the geometry of the cell composing the honeycomb structure. Core materials of different geometry placed periodically along the beam length introduce the proper impedance mismatch necessary to impede the propagation of waves along the beam. A Spectral Finite Element model is developed to describe the wave propagation characteristics and the vibration of the sandwich beam. The model uses dynamic shape functions obtained from the solution of the corresponding distributed parameter model and thus allows for predicting the dynamic behavior of the structure with a significantly reduced number of elements as compared with the conventional FEM. The model is used to derive the transfer matrix of the sandwich beam, which identifies the location of the frequency bands where traveling waves are attenuated. The influence of core geometry and periodicity on the location and extension of these stop bands is assessed through a series of simulations. The effect of the periodicity of the structure is also evaluated by considering the vibration response of a clamped free beam excited by the harmonic motion of the base. The results demonstrate the simplicity and the effectiveness of the proposed treatment whereby the transmission waves and the vibration over specified frequency bands can be significantly reduced without requiring additional passive or active control devices. The unique characteristics of cellular solids therefore can be used to design light-weight composite panels that behave as mechanical filters. The filtering capabilities of such passive composite panels may be easily changed and optimized to reduce their transmissibility over a desired frequency range without compromising the size and the weight of the structure.

Ruzzene, Massimo; Scarpa, Fabrizio

2001-07-01

313

Mathematical Modelling of Shear Effect of Sandwich Beam  

NASA Astrophysics Data System (ADS)

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.

Magnucka-Blandzi, Ewa

2010-09-01

314

A note concerning the Lighthill "sandwich model" of tropical cyclones  

PubMed Central

The basic element of Lighthill's “sandwich model” of tropical cyclones is the existence of “ocean spray,” a layer intermediate between air and sea made up of a cloud of droplets that can be viewed as a “third fluid.” We propose a mathematical model of the flow in the ocean spray based on a semiempirical turbulence theory and demonstrate that the availability of the ocean spray over the waves in the ocean can explain the tremendous acceleration of the wind as a consequence of the reduction of the turbulence intensity by droplets. This explanation complements the thermodynamic arguments proposed by Lighthill.

Barenblatt, G. I.; Chorin, A. J.; Prostokishin, V. M.

2005-01-01

315

Photoconductive properties of zeaxanthin in a sandwich cell  

Microsoft Academic Search

Photoconduction decay in zeaxanthin in a sandwich cell has been measured as a function of applied field and temperature in\\u000a longer time domains (5–35s). The results show that the gap states decrease exponentially with characteristic temperatureT\\u000a \\u000a c\\u000a ?450 K at an applied field of 1·77×103 V\\/cm. When the sample temperature is 293 K,T\\u000a \\u000a c\\u000a is found to be voltage-dependent and

Dilip Ghosh; Prabir Pal; T N Misra

1990-01-01

316

A multi-frequency sandwich type electromagnetic vibration energy harvester  

NASA Astrophysics Data System (ADS)

We proposed a multi-frequency sandwich type vibration energy harvester to widen the effective frequency range of vibration energy harvester. The harvester is composed of three resonant structures with different natural frequencies. The resonant structures are two cantilevers each with bi-layer coils and a plane spring with a magnet. The maximum peak-peak voltages of the three different frequencies are 172 mV, 104 mV, and 112 mV at the frequencies of 235 Hz, 330 Hz, and 430 Hz, respectively. The first maximum voltage is much higher than the others, because the coils in both cantilevers can produce voltages.

Chen, Jingdong; Chen, Di; Yuan, Tao; Chen, Xiang

2012-05-01

317

A sandwich assay for procalcitonin detection for POCT applications  

NASA Astrophysics Data System (ADS)

A plastic biochip was developed for the detection of procalcitonin (PCT) and consists of a polymethylmethacrylate (PMMA) chip shaped in order to achieve several flow microchannels. A sandwich assay using a new antibody pairs is implemented with the capture antibody immobilized on the PMMA surface and the target antibody labelled with a fluorophore. A laser diode excites the fluorescent sensing layer. Thanks to the anisotropy of the fluorescence the emitted light travels along the thickness of the plastic material. The fluorescence coming out from the chip is collected by 1 mm plastic optical fibre and detected with a spectrum analyser.

Baldini, Francesco; Bolzoni, Luca; Giannetti, Ambra; Kess, Melanie; Kraemer, Petra M.; Kremmer, Elisabeth; Porro, Giampiero; Senesi, Folco; Trono, Cosimo

2009-02-01

318

Approximate solutions of equilibrium equations of sandwich circular plate  

NASA Astrophysics Data System (ADS)

The paper is devoted to a sandwich circular plate consisting of two facings and a core with variable mechanical properties. The simply supported plate is compressed in the middle plane. The mathematical and physical model of the plate is formulated, and also the field of displacements. The system of equilibrium equations is derived basing on the principle of the total potential energy. Then the system is approximately solved. Three formulas for an unknown function of displacements are assumed. The solutions (critical loads) are compared and presented in Figures and Tables.

Magnucka-Blandzi, Ewa; Wittenbeck, Leszek

2013-10-01

319

Fatigue and fracture of foam cores used in sandwich composites  

NASA Astrophysics Data System (ADS)

This study focused on the fracture and fatigue crack growth behavior in polyvinylchloride (PVC) and polyethersulfone (PES) foams. A new sandwich double cantilever beam (DCB) test specimen was implemented. Elastic foundation and finite element analysis and experimental testing confirmed that the DCB specimen is appropriate for static and cyclic crack propagation testing of soft polymer foams. A comprehensive experimental mechanical analysis was conducted on PVC foams of densities ranging from 45 to 100 kg/m3 and PES foams of densities ranging from 60 to 130 kg/m3. An in-situ scanning electron microscope study on miniature foam fracture specimens showed that crack propagation in the PVC foam was inter-cellular and in the PES foam, failure occurred predominately by extensional failure of vertical cell edges. Sandwich DCB specimens were loaded cyclically as well. For the PVC foams, the crack growth rates were substantially influence by the density. For the PES foams, there was no clear indication about the influence of foam density on the crack growth rate.

Saenz, Elio

320

Perforation of aluminium foam core sandwich panels under impact loading  

NASA Astrophysics Data System (ADS)

This paper reports an original inverse perforation tests on foam core sandwich panels under impact loading. The key point is the use of an instrumented Hopkinson pressure bar as a perforator and at the same time a measuring device. It aims at a high quality piercing force record during the whole perforation process, which is a lack of common free-flying projectile - target testing schemes. This new testing arrangement allows for the measurement of piercing force-displacement curves under quasi-static and impact loadings of sandwich samples, which is made of 40?mm AlSi7Mg0.5 Cymat foam cores and 0.8?mm thick 2024 T3 aluminium sheet as top and bottom skins. Compared with quasi-static top skin peak loads (the maximal load before the perforation of top skins) obtained under same geometric and clamping conditions and even in the case that the used foam core (Cymat) and aluminium skin sheet are known and have been confirmed rate insensitive, a significant enhancement under impact loading (25%) of the top skin peak load is found.

Elnasri, I.; Zhao, H.; Girard, Y.

2006-08-01

321

THE RESISTANCE OF METALLIC SANDWICH BEAMS WITH LATTICE CORES TO UNDERWATER SHOCK LOADING  

Microsoft Academic Search

Analytical models for the dynamic response of sandwich beams to an under-water shock are developed. The relative performance of the clamped beams is sensitive to the choice of the core topology of the beams. It is found that lattice cores with high through-thickness and longitudinal strength outperform metallic foam cores. It is concluded that sandwich panels have high potential as

Norman A. Fleck

322

Numerical analysis of adhesively bonded T-joints with structural sandwiches and study of design parameters  

Microsoft Academic Search

Adhesively bonded T-joints are extensively used in assembling sandwich structures. The advantage of adhesive bonded joints over bolted or riveted joints is that the use of fastener holes in mechanical joints inherently results in micro and local damages to the composite laminate during their fabrication. One type of adhesive joint in such structures is the T-joint between sandwich panels. The

S. M. R. Khalili; A. Ghaznavi

2011-01-01

323

Higher-order impact modeling of sandwich structures with flexible core  

Microsoft Academic Search

In this study, a higher-order impact model is presented to simulate the response of a soft-core sandwich beam subjected to a foreign object impact. A free vibration problem of sandwich beams is first solved, and the results are validated by comparing with numerical finite element modeling results of ABAQUS and the solution by Frostig and Baruch [Frostig, Y., Baruch, M.,

Mijia Yang; Pizhong Qiao

2005-01-01

324

BENDING AND FORCED VIBRATION RESPONSE OF A CLAMPED ORTHOTROPIC THICK PLATE AND SANDWICH PANEL  

Microsoft Academic Search

A closed-form solution for the forced response of an orthotropic thick plate and sandwich panel has been developed and is presented in this paper. The paper outlines the methodology and develops the formulation to enable the solution to be derived. A novel truss-core sandwich panel is introduced and a method is outlined in which the panel is represented as an

T. S. LOK; Q. H. CHENG

2001-01-01

325

Bending and Forced Vibration Response of a Clamped Orthotropic Thick Plate and Sandwich Panel  

Microsoft Academic Search

A closed-form solution for the forced response of an orthotropic thick plate and sandwich panel has been developed and is presented in this paper. The paper outlines the methodology and develops the formulation to enable the solution to be derived. A novel truss-core sandwich panel is introduced and a method is outlined in which the panel is represented as an

T. S. Lok; Q. H. Cheng

2001-01-01

326

Dynamic response of anisotropic sandwich flat panels to underwater and in-air explosions  

Microsoft Academic Search

The problem of the dynamic response of flat rectangular sandwich panels subjected to underwater and in-air explosions is analyzed. The study is carried out in the framework of a geometrically non-linear model of sandwich structures featuring anisotropic laminated face sheets and an orthotropic core, in conjunction with the unsteady pressure generated by an explosion. Effects of the core and of

Liviu Librescu; Sang-Yong Oh; Joerg Hohe

2006-01-01

327

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

Microsoft Academic Search

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

Victor Iliev Rizov

2006-01-01

328

Effect of sea environment on interfacial delamination behavior of polymeric sandwich structures  

Microsoft Academic Search

Sandwich structures are utilized in naval craft and thereby are exposed to sea water environment and temperature fluctuations over extended periods. The sandwich layup consists of a closed cell polymeric foam layer placed between thin carbon or glass fiber reinforced polymeric composite facings. Attention in this paper is focused on sea water effects on the interfacial mechanical response between foam

Akawut Siriruk; Dayakar Penumadu; Y. Jack Weitsman

2009-01-01

329

Polymeric foams and sandwich composites: Material properties, environmental effects, and shear-lag modeling  

Microsoft Academic Search

Marine composite sandwich structural materials, comprising of low density PVC foam core and carbon fiber reinforced vinyl ester based resin composite facings, are studied for associated degradation in mechanical behavior caused by sea water. This paper presents experimental and analytical results concerning the properties and response of closed cell polymeric foams (PVC H100) and their sandwich composites. Data regarding the

Akawut Siriruk; Y. Jack Weitsman; Dayakar Penumadu

2009-01-01

330

Comparison of an Established Antibody Sandwich Method with an Inhibition Method of Histoplasma capsulatum Antigen Detection  

Microsoft Academic Search

The Histoplasma antigen immunoassay utilizes an antibody sandwich method that provides a rapid and reliable means of diagnosing the more severe forms of histoplasmosis. Inhibition assays have been developed for antigen detection and offer at least one potential advantage, namely, reduced antibody requirements. We have developed an inhibition assay using the polyclonal antibody employed in our standard sandwich assay. Urine

TODD O. GARRINGER; L. JOSEPH WHEAT; EDWARD J. BRIZENDINE

2000-01-01

331

Honeycomb Sandwich Material Modeling for Dynamic Simulations of Aircraft Interior Components  

Microsoft Academic Search

An approach for modeling sandwich structures with a Nomex ® honeycomb core and phenolic composite faces in the commercial finite element code LS-DYNA with solid elements for the core and shell elements for the thin faces is presented, which accounts for the major sandwich failure modes. Extensive material testing was conducted to determine the parameters for the composite face material

S. Heimbs; P. Middendorf; M. Maier

332

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

Microsoft Academic Search

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

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

333

Experimental Combustion Studies of Two-Dimensional Ammonium Perchlorate-Binder Sandwiches  

Microsoft Academic Search

In order to obtain information essential to the future success of analytical modeling of solid propellant combustion, an experimental investigation was conducted using the quench combustion of two-dimensional propellant sandwiches prepared with AP oxidizer and four conventional propellant binders—polysulfide (PS), polyurethane (PU), polybutadiene acrylic acid (PBAA), and carboxy terminated polybutadiene (CTPB). Propellant sandwiches, prepared with both single crystal sheets and

A. MICHAEL VARNEY; WARREN C. STRAHLE

1971-01-01

334

FRACTURE TOUGHNESS OF SKIN\\/CORE INTERFACES IN SANDWICH MATERIALS UNDER MIXED MODE LOADINGS  

Microsoft Academic Search

Defects in sandwich structures are often inevitable and can originate both from manufacture and use. An important defect type is debonding, i.e. areas with weak or no adhesion between skin and core. In a sandwich structure debondings can arise in production when an area between skin and core has not been wetted properly resulting in a lack of adhesion. In

Christian Lundsgaard-Larsen; Rasmus C. Østergaard; Bent F. Sørensen; Christian Berggreen

335

Detection of Fasciola hepatica antigen in cattle faeces by a monoclonal antibody-based sandwich immunoassay  

Microsoft Academic Search

A monoclonal antibody-based sandwich immunoassay (mAb sandwich ELISA) was developed for the detection of Fasciola hepatica antigen in the faeces of cattle. The assay was applied to samples from 100 cattle infected with F hepatica, 56 animals with parasitologically proven infections of other parasites and 100 uninfected animals. F hepatica antigen was detected in all the faecal samples from animals

B. E Duménigo; A. M Espino; C. M Finlay

1996-01-01

336

Three-Point Flexural Behaviour of GFRP Sandwich Composites: A Failure Map  

Microsoft Academic Search

In this work, the failure mechanisms of GFRP\\/PVC foam core sandwich structures subjected to three-point bending are analysed. By varying the skin thickness (t) and the span length between supports (l), experimental tests were carried out in order to find the relationship between the geometrical configuration of the sandwiches and the failure mechanism. By plotting failure mechanism on a graph

A. Valenza; V. Fiore; L. Calabrese

2010-01-01

337

A procedure to embed fibre Bragg grating strain sensors into GFRP sandwich structures  

Microsoft Academic Search

Embedding FBG strain sensors within a GFRP sandwich composite material allows early detection of internal defects. However, the sensors need to survive the manufacturing process to provide this capability. Vacuum infusion is commonly used to manufacture GFRP sandwich composite materials but, it needs to be modified to accommodate the embedding process. A stage by stage procedure is demonstrated here to

T. A. Dawood; R. A. Shenoi; M. Sahin

2007-01-01

338

Heat transfer characteristics of insulated concrete sandwich panel walls: Draft report  

Microsoft Academic Search

Tests were conducted to evaluate thermal performance of three insulated concrete sandwich panel walls. Heat transfer through the walls was measured for steady-state and dynamic temperature conditions. The objective of the test program was to investigate effects of ties connecting wall layers on thermal properties of insulated sandwich panel walls. The three walls tested were similar except for the type

M. G. Van Geem; S. T. Shirley

1987-01-01

339

Finite element modelling of the crushing response of composite sandwich panels with FRP tubular reinforcements  

Microsoft Academic Search

The crushing response and the crash energy absorption characteristics of composite sandwich panels with internal fibre reinforced plastic (FRP) tubular reinforcements were investigated in the numerical simulation works described here using the LS-DYNA3D finite element code. Several models were developed in order to simulate a series of compressive tests performed at the National Technical University of Athens using composite sandwich

A. G. Mamalis; D. E. Manolakos; M. B. Ioannidis; D. P. Papapostolou

2006-01-01

340

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

Microsoft Academic Search

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,

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

2002-01-01

341

An investigation of lightly profiled sandwich panels subject to local buckling and flexural wrinkling effects  

Microsoft Academic Search

Sandwich panels exhibit various types of failure modes depending on the steel face used. For the flat and lightly profiled sandwich panels, flexural wrinkling is an extremely important design criterion as the behaviour of these panels is governed mainly by flexural wrinkling. However, in the lightly profiled panels, when the depth or spacing of the ribs increases, flat plate buckling

Narayan Pokharel; Mahen Mahendran

2005-01-01

342

Experimental investigation of strain rate effects on the crushing characteristics of composite sandwich panels  

Microsoft Academic Search

In the present work, the influence of strain rate on the collapse modes, the crushing mechanisms and the energy absorption characteristics of four types of composite sandwich panels was investigated in a series of impact and static in-plane tests. The tested sandwich specimens were formed combining two types of glass fibre reinforced plastic (FRP) faceplate laminates with three types of

A. G. Mamalis; D. P. Papapostolou

2010-01-01

343

Benthic infaunal communities across the Weddell Sea Basin and South Sandwich Slope, Antarctica  

Microsoft Academic Search

The present study represents the first quantitative investigation of deep-sea benthic infauna in Antarctica. Box cores and multicores were used to collect sediment from 12 stations across the slope and abyssal basin of the Weddell Sea and the slope off the South Sandwich Islands, including sites in the South Sandwich Trench (6300m). The multicore was a more efficient sampler than

James A. Blake; Bhavani E. Narayanaswamy

2004-01-01

344

Benthic infaunal communities across the Weddell Sea Basin and South Sandwich Slope, Antarctica  

Microsoft Academic Search

The present study represents the first quantitative investigation of deep-sea benthic infauna in Antarctica. Box cores and multicores were used to collect sediment from 12 stations across the slope and abyssal basin of the Weddell Sea and the slope off the South Sandwich Islands, including sites in the South Sandwich Trench (6300 m). The multicore was a more efficient sampler

James A. Blake; Bhavani E. Narayanaswamy

2004-01-01

345

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

Microsoft Academic Search

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

W. L. Ko; R. H. Jackson

1991-01-01

346

Analysis of wave propagation in sandwich beams with parametric stiffness modulations  

Microsoft Academic Search

Propagation of flexural and shear waves in an unbounded sandwich beam is considered. This beam is thought of as a ‘unit width strip’, which is cut from an unbounded sandwich plate in the direction of propagation of a plane flexural or shear wave. The skin plies of such a plate (or, in effect, a beam) are made of a homogeneous

S. V. Sorokin; S. V. Grishina

2004-01-01

347

Dynamic properties of sandwich structures with integrated shear-thickening fluids  

Microsoft Academic Search

The integration of shear-thickening fluids (STFs) into composite structures has been investigated with the aim of tuning part stiffness and damping capacity under dynamic deformation. Results from oscillatory rheological measurements for a STF based on concentrated fused silica in polypropylene glycol were correlated with results from vibrating beam tests on model sandwich structures containing layers of the same STF sandwiched

C. Fischer; S. A. Braun; P.-E. Bourban; V. Michaud; C. J. G. Plummer; J.-A. E. Månson

2006-01-01

348

The response of clamped sandwich plates with metallic foam cores to simulated blast loading  

Microsoft Academic Search

The dynamic responses of clamped circular monolithic and sandwich plates of equal areal mass have been measured by loading the plates at mid-span with metal foam projectiles. The sandwich plates comprise AISI 304 stainless steel face sheets and aluminium alloy metal foam cores. The resistance to shock loading is quantified by the permanent transverse deflection at mid-span of the plates

D. D. Radford; G. J. McShane; V. S. Deshpande; N. A. Fleck

2006-01-01

349

Evaluation of a Composite Sandwich Fuselage Side Panel With Damage and Subjected to Internal Pressure  

Microsoft Academic Search

The results from an experimental and analytical study of a composite sandwich fuselage side panel for a transport aircraft are presented. The panel has two window cutouts and three frames, and has been evaluated with internal pressure loads that generete biaxial tension loading conditions. Design limit load and design ultimate load tests have been performed on the graphite-epoxy sandwich panel

Marshall Rouse; Damodar R. Ambur; Jerry Bodine; Bernhard Dopker

1997-01-01

350

Low velocity impact response of novel fiber-reinforced aluminum foam sandwich structures  

Microsoft Academic Search

Sandwich structures based on high performance skins are currently finding widespread use in a number of aerospace, marine and automotive applications, where low weight, high strength and high stiffness are important design requirements. Many sandwich structures are based on polymeric foams such as PUR, PEI and PVC and aluminum honeycomb. Currently, most of such structures are manufactured using low curing

G. Reyes Villanueva; W. J. Cantwell

2003-01-01

351

Study of structurally efficient graphite-thermoplastic trapezoidal-corrugation sandwich and semisandwich panels  

Microsoft Academic Search

The structural efficiency of compression-loaded trapezoidal-corrugation sandwich and semisandwich 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 semisandwich 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

Dawn C. Jegley

1994-01-01

352

Modelling component cost in compression moulding of thermoplastic composite and sandwich components  

Microsoft Academic Search

Thermoplastic composite and sandwich materials offer a potential of reducing component weight and improving recyclability while at the same time enhancing process economy through reduced manufacturing cycle time. The economical aspects of compression moulding of three different thermoplastic composite and sandwich material systems are modelled herein and are compared to compression moulding of a thermoset sheet moulding compound and stamping

M. Åkermo; B. T. Åström

2000-01-01

353

An experimental investigation of static and fatigue behaviour of sandwich composite panels joined by fasteners  

Microsoft Academic Search

An experimental investigation has been carried out to estimate the static and fatigue behaviour of specimens made up of steel plates and sandwich composite panels joined together by either blind or mechanical lock fasteners.A preliminary study was carried out in order to analyse the drilling operation of sandwich panels to determine the best values of parameters to use for fastener

Giuseppe Demelio; Katia Genovese; Carmine Pappalettere

2001-01-01

354

Ply drop-off effects in CFRP\\/honeycomb sandwich panels—experimental results  

Microsoft Academic Search

The results of a combined experimental and theoretical investigation of local bending effects induced by ply drop-off in CFRP\\/honeycomb sandwich panels are presented. The objective of the investigation was to validate a simple model for engineering analysis of sandwich panels with tapered face laminates presented in a previous paper. The experimental investigation was conducted by using electronic speckle pattern interferometry

O. T. Thomson; W. Rits; D. C. G. Eaton; O. Dupont; P. Queekers

1996-01-01

355

Minimum-Weight Sandwich Structure Optimum Design Subjected to Torsional Loading  

NASA Astrophysics Data System (ADS)

As one of the most valued structural engineering innovations developed by the composites industry, sandwich structures are now used extensively in automotive, aerospace and civil infrastructure due to the main advantage of lightweight. This paper develops a minimum weight optimization method for sandwich structure subjected to torsion load. The design process are identified for a sandwich structure required to meet the design constraint of torsion stiffness. The optimum solutions show that at optimum design the core weight accounts for 66.7% of the whole sandwich structure. To illustrate the newly developed optimum design solutions, numerical examples are presented for sandwich structures made of either isotropic face skins or orthotropic composite face skins. Agreement between the theoretical analysis and the examples results is good.

Li, Xiang; Li, Gangyan; Wang, Chun H.; You, Min

2012-04-01

356

Vibration analysis of sandwich rectangular plates with magnetorheological elastomer damping treatment  

NASA Astrophysics Data System (ADS)

In this study, the vibration analysis of sandwich rectangular plates with magnetorheological (MR) elastomer damping treatment is presented. The rectangular plate is combined with a magnetorheological elastomer core layer and a constraining layer to improve the vibration behaviors of the sandwich system. The MR material shows variations in the rheological properties when subjected to varying magnetic fields. Additionally, the MR material exhibits a rapid time response and is applicable to structures or devices when a tunable system is required. The magnetorheological elastomer is found to have a significant effect on the vibration characteristics of the sandwich rectangular plate. The modal damper and the natural frequencies for the sandwich plate system are calculated for various magnetic fields and some designed parameters by utilizing the finite element method. The damping effects of the sandwich plate system can be controlled and changed when different magnetic field strengths are applied.

Yeh, Jia-Yi

2013-03-01

357

Parametric instability regions of three-layered soft-cored sandwich beam using higher-order theory  

NASA Astrophysics Data System (ADS)

The purpose of the present work is to study the parametric instability of a three-layered, soft-cored, symmetric sandwich beam subjected to a periodic axial load. Due to soft core, the displacements of the top and bottom skins are different and hence, instead of using the classical theory a higher-order theory is used. Using extended Hamilton's principle and taking beam theory for the skins and a two-dimensional theory for the core, the governing equations of motion and boundary conditions are derived. A generalized Galerkin's method is used to reduce the equations of motion to a set of non-dimensional coupled Mathieu Hill's equations with complex coefficients. The parametric instability regions for simple and combination resonances are investigated for simply supported, clamped guided, clamped free riveted and clamped free end conditions by modified Hsu's method. The influences of shear parameter; the core loss-factor and the ratio of core thickness to skin thickness on the zones of instability have been studied. This general analysis can be applied to sandwich beams with a flexible core and any type of construction. The results are compared with those reported for classical theories.

Dwivedy, S. K.; Sahu, K. C.; Babu, Sk.

2007-07-01

358

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

Microsoft Academic Search

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

M. Sadighi; M. Saadati

359

Vibration Control of Sandwich Beams Using Electro-Rheological Fluids  

NASA Astrophysics Data System (ADS)

Electro-rheological (ER) fluids are a class of smart materials exhibiting significant reversible changes in their rheological and hence mechanical properties under the influence of an applied electric field. Efforts are in progress to embed ER fluids in various structural elements to mitigate vibration problems. The present work is an experimental investigation of the behaviour of a sandwich beam with ER fluid acting as the core material. A starch-silicone-oil-based ER fluid is used in the present study. Significant improvements in the damping properties are achieved in experiments and the damping contributions by viscous and non-viscous forces are estimated by force-state mapping (FSM) technique. With the increase in electric field across the ER fluid from 0 to 2 kV, an increase of 25-50% in equivalent viscous damping is observed. It is observed that as concentration of starch is increased, the ER effect grows stronger but eventually is overcome by applied stresses.

Srikantha Phani, A.; Venkatraman, K.

2003-09-01

360

The terahertz characteristics of a sandwich type microplasma structure  

NASA Astrophysics Data System (ADS)

Recently, major technical advances in developing intense terahertz (THz) sources have provided us with new opportunities to investigate characteristics of a high density microplasma with THz waves. In this paper, a simple sandwich type microplasma model is established. The finite-difference time-domain method using Z-transforms is utilized to simulate the characteristics of reflection, transmission, and absorption of THz waves in this microplasma structure. The effects of both the microplasma width and the permittivity of the outer medium on the propagation are analyzed, and the results show that the THz waves can be greatly influenced and modulated by the structure of the plasma slab and the outer medium. It is demonstrated that such plasma metamaterials exhibit some extraordinary properties in THz frequency range.

Gao, Ruilin; Yuan, Chengxun; Wang, Ying; Zhou, Zhongxiang; Gong, Dewei; Fang, Yuan; Rong, Xianwei

2013-09-01

361

Scaled model measurements of the sandwiched V-antenna  

NASA Astrophysics Data System (ADS)

At frequencies above a few hundred GHz, waveguide mixer blocks become extremely difficult to build, so open structure feeds may be more appropriate. One promising planar antenna structure, which can easily be integrated with SIS junctions, is the sandwiched V-antenna. The antenna is completely enclosed in dielectric by placing it between substrate and superstrate blocks. Using a model scaled to a center frequency of 10 Hz, the beam pattern is investigated as a function of frequency, and its dependence on gaps between the supersubstrates and substrates is measured. It is planned to test the structure at a frequency of 345 GHz and to compare it with waveguide horn antennas for possible use in submillimeter astronomical receivers. The antenna patterns and analysis in this work are substantially more extensive than earlier published results.

Eckart, A.; Harris, A. I.; Wohlleben, R.

1988-06-01

362

Laser pulse induced micropatterning on sandwiched thin films  

NASA Astrophysics Data System (ADS)

We introduce a routine for surface micropatterning. Our samples are sandwiched "ZnS–SiO2/PtOx/ZnS–SiO2" thin films. The driving energy comes from a laser pulse. The sample is initially exposed to the laser pulse. When the laser pulse is switched off, a bubble is formed. The stain inside the bubble generates a stress wave which diffuses radially along the surface. The stress wave induces concentric micropatterns on the surface and the process of micropatterning lasts a considerably long time. Finally, concentric and periodic patterns are formed permanently on the sample surface, and the experimental results also demonstrate that the routine is feasible for surface micropatterning.

Wei, Jingsong; Liu, Qian; Xiao, Mufei

2013-09-01

363

Levator aponeurosis sandwich flap for reconstruction of upper eyelid defect.  

PubMed

A 72-year-old woman suffered from a sebaceous gland carcinoma on her left upper eyelid. The tumour was 13 × 5 mm without metastasis. The tumour was excised with a 5-mm safety margin, resulting in a large, full-thickness defect in which almost all of the tarsal plate, approximately half of the orbicularis oculi muscle, and part of the levator aponeurosis were lost. Reconstruction of the upper eyelid was successfully performed with a levator aponeurosis sandwich flap, upon which the posterior lamella was covered by a free tarsal graft with medial and lateral periosteal flaps, and a skin graft from the contralateral upper eyelid for the anterior lamella. No lagophthalmos was demonstrated after the operation. Six months postoperatively, there was no tumour recurrence, no ocular complications, and good cosmetic results. PMID:22631047

Kang, Hyera; Takahashi, Yasuhiro; Iwaki, Masayoshi; Kakizaki, Hirohiko

2012-05-25

364

A crucial sequence for transglutaminase type 2 extracellular trafficking in renal tubular epithelial cells lies in its N-terminal beta-sandwich domain.  

PubMed

Transglutaminase type 2 (TG2) catalyzes the formation of an ?-(?-glutamyl)-lysine isopeptide bond between adjacent peptides or proteins including those of the extracellular matrix (ECM). Elevated extracellular TG2 leads to accelerated ECM deposition and reduced clearance that underlie tissue scarring and fibrosis. The extracellular trafficking of TG2 is crucial to its role in ECM homeostasis; however, the mechanism by which TG2 escapes the cell is unknown as it has no signal leader peptide and therefore cannot be transported classically. Understanding TG2 transport may highlight novel mechanisms to interfere with the extracellular function of TG2 as isoform-specific TG2 inhibitors remain elusive. Mammalian expression vectors were constructed containing domain deletions of TG2. These were transfected into three kidney tubular epithelial cell lines, and TG2 export was assessed to identify critical domains. Point mutation was then used to highlight specific sequences within the domain required for TG2 export. The removal of ?-sandwich domain prevented all TG2 export. Mutations of Asp(94) and Asp(97) within the N-terminal ?-sandwich domain were identified as crucial for TG2 externalization. These form part of a previously identified fibronectin binding domain ((88)WTATVVDQQDCTLSLQLTT(106)). However, siRNA knockdown of fibronectin failed to affect TG2 export. The sequence (88)WTATVVDQQDCTLSLQLTT(106) within the ?-sandwich domain of TG2 is critical to its export in tubular epithelial cell lines. The extracellular trafficking of TG2 is independent of fibronectin. PMID:21652693

Chou, Che-Yi; Streets, Andrew J; Watson, Philip F; Huang, Linghong; Verderio, Elisabetta A M; Johnson, Timothy S

2011-06-07

365

Transient Dynamic Response and Failure of Sandwich Composite Structures under Impact Loading with Fluid Structure Interaction  

NASA Astrophysics Data System (ADS)

The objective of this study is to examine the Fluid Structure Interaction (FSI) effect on transient dynamic response and failure of sandwich composite structures under impact loading. The primary sandwich composite used in this study consisted of a 6.35 mm balsa core and a multi-ply symmetrical plain weave 6 oz E-glass skin. Both clamped sandwich composite plates and beams were studied using a uniquely designed vertical drop-weight testing machine. There were three impact conditions on which these experiments focused. The first of these conditions was completely dry (or air surrounded) testing. The second condition was completely water submerged. The final condition was also a water submerged test with air support at the backside of the plates. The tests were conducted sequentially, progressing from a low to high drop height to determine the onset and spread of damage to the sandwich composite when impacted with the test machine. The study showed the FSI effect on sandwich composite structures is very critical such that impact force, strain response, and damage size are generally much greater with FSI under the same impact condition. As a result, damage initiates at much lower impact energy conditions with the effect of FSI. Neglecting to account for FSI effects on sandwich composite structures results in very non-conservative analysis and design. Additionally, it was observed that the damage location changed for sandwich composite beams with the effect of FSI.

Kwon, Y. W.; Violette, M. A.; McCrillis, R. D.; Didoszak, J. M.

2012-12-01

366

Conjugated ligands modulated sandwich structures and luminescence properties of lanthanide metal-organic frameworks.  

PubMed

A conjugated ligand, 2-(carboxylic acid)-6-(2-benzimidazolyl) pyridine (Hcbmp), and a series of Lanthanide metal-organic frameworks (MOFs) [Ln(2)(cbmp)(ox)(3)(H(2)O)(2)](2)·2H(3)O(+)·7H(2)O (Ln = Sm (3), Eu (4), and Gd (5), H(2)ox = oxalic acid) have been designed and assembled. To elucidate how the conjugated ligands modulate the structures and luminescence properties, we carried out the structural characterizations and luminescence studies of complexes 3 and 4, and their corresponding oxalate complexes [Ln(ox)(1.5)(H(2)O)(3)]·2H(2)O (Ln = Sm (1) and Eu (2)) were also investigated for comparison. The changes of luminescence behaviors upon dehydration and D(2)O-rehydration processes are presented and discussed in detail. The results indicated that, the cbmp(-) ligands distribute on both sides of the ox(-)-Ln bilayer network to construct a sandwich structure. Moreover, the lowest triplet state of cbmp(-) ligands can match well the energy levels of the Sm(3+) and Eu(3+) cations which allow the preparation of new Ln-MOF materials with enhanced luminescence properties. Meanwhile, the crystallinity of solid states produces more substantial change in the luminescence behaviors than removal or replacement of effective nonradiative relaxers. PMID:21553823

Liu, Tian-Fu; Zhang, Wenjuan; Sun, Wen-Hua; Cao, Rong

2011-05-09

367

Modified Opsite(R) Sandwich for Temporary Abdominal Closure: A Non-Traumatic Experience  

PubMed Central

INTRODUCTION Laparostomy techniques have advanced since the advent of damage control surgery for the critically injured patient. Numerous methods of temporary abdominal closure (TAC) are described in the literature with most reports focusing on trauma. We describe a modified technique for TAC and report its use in a series of critically ill non-trauma patients. PATIENTS AND METHODS Eleven patients under the care of one consultant underwent TAC over a 36-month period. A standardised technique was used in all cases and this is described. Severity of illness at the time of the first laparotomy was assessed using the Portsmouth variant of the Physiological and Operative Severity Score for the enUmeration of Mortality and morbidity (P-POSSUM). RESULTS Nineteen TACs were performed in 11 patients with a variety of serious surgical conditions. In-hospital mortality was zero despite seven of the patients having an individual P-POSSUM predicted mortality in excess of 50%. The laparostomy dressing proved simple in construction, facilitated nursing care and was well-tolerated in the critical care environment. All patients underwent definitive fascial closure during the index admission. CONCLUSIONS Laparostomy is a useful technique outwith the context of trauma. We have demonstrated the utility of the modified Opsite® sandwich vacuum pack for TAC in a series of critically ill patients with a universally favourable outcome. This small study suggests that selective use of TAC may reduce surgical mortality.

Wilde, JM; Loudon, MA

2007-01-01

368

Construction aggregates  

USGS Publications Warehouse

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.

Tepordei, V. V.

1995-01-01

369

Power flow analysis for a floating sandwich raft isolation system using a higher-order theory  

NASA Astrophysics Data System (ADS)

A higher-order sandwich theory is implemented in conjunction with an equivalent mobility-based power flow progressive method to determine power flow for a sandwich configured floating raft vibration isolation system. The power spectrum changes in whole frequency range effectively when core materials’ properties change. It is also shown that the loss factors of the sandwich configured floating raft influence the power flow transmitted to the foundation effectively in the medium- to high-frequency range and that the resonant peak cannot be avoided by increasing damping only in high-frequency ranges which is not found in floating raft isolation systems with isotropic beams.

Choi, W. J.; Xiong, Y. P.; Shenoi, R. A.

2009-01-01

370

Preservation of Aortic Arch Branches Using Chimney and Sandwich Stent Grafts  

PubMed Central

Purpose: To share our hybrid endovascular experiences using chimney or sandwich stent grafts for acute aortic arch pathologies. Methods: Hybrid procedures for a distal aortic arch aneurysm and an ascending anastomotic aortic aneurysm rupture were reported. Right to left common carotid and left axillar artery bypasses were located. Covered stents were inserted into the inominate artery, with the flow-proximal end located in the ascending (standard chimney) or the descending aortic stent graft (retrograde sandwich). Results: Both cases had no signs of brain ischemia. Aneurysms are decreasing in size. Conclusion: Chimney and sandwich techniques were technically feasible in the complex and acute situations.

Mitsuoka, Hiroshi; Shintani, Tsunehiro; Saito, Takaaki; Norimatsu, Togo; Higashi, Shigeki

2012-01-01

371

Web buckling behavior under in-plane compression and shear loads for web reinforced composite sandwich core  

NASA Astrophysics Data System (ADS)

Sandwich construction is one of the most functional forms of composite structures developed by the composite industry. Due to the increasing demand of web-reinforced core for composite sandwich construction, a research study is needed to investigate the web plate instability under shear, compression, and combined loading. If the web, which is an integral part of the three dimensional web core sandwich structure, happens to be slender with respect to one or two of its spatial dimensions, then buckling phenomena become an issue in that it must be quantified as part of a comprehensive strength model for a fiber reinforced core. In order to understand the thresholds of thickness, web weight, foam type, and whether buckling will occur before material yielding, a thorough investigation needs to be conducted, and buckling design equations need to be developed. Often in conducting a parametric study, a special purpose analysis is preferred over a general purpose analysis code, such as a finite element code, due to the cost and effort usually involved in generating a large number of results. A suitable methodology based on an energy method is presented to solve the stability of symmetrical and specially orthotropic laminated plates on an elastic foundation. Design buckling equations were developed for the web modeled as a laminated plate resting on elastic foundations. The proposed equations allow for parametric studies without limitation regarding foam stiffness, geometric dimensions, or mechanical properties. General behavioral trends of orthotropic and symmetrical anisotropic plates show pronounced contribution of the elastic foundation and fiber orientations on the buckling resistance of the plate. The effects of flexural anisotropy on the buckling behavior of long rectangular plates when subjected to pure shear loading are well represented in the model. The reliability of the buckling equations as a design tool is confirmed by comparison with experimental results. Comparing to predicted values, the experimental plate shear test results range between 15 and 35 percent, depending on the boundary conditions considered. The compression testing yielded conservative results, and as such, can provide a valuable tool for the designer.

Toubia, Elias Anis

372

Left ventricle remodelling by double-patch sandwich technique  

PubMed Central

Background The sandwich double-patch technique was adopted as an alternative method for reconstruction of the left ventricle after excision of postinfarction dysfunctional myocardium to solve technical problems due to the thick edges of the ventricular wall. Methods Over a 5-year period, 12 of 21 patients with postinfarction antero-apical left ventricular aneurysm had thick wall edges after wall excision. It was due to akinetic muscular thick tissue in 6 cases, while in the other 6 with classic fibrous aneurysm, thick edges remained after the cut of the border zone. The ventricular opening was sandwiched between two patches and this is a technique which is currently used for the treatment of the interventricular septum rupture. In our patients the patches are much smaller than the removed aneurysm and they were sutured simply by a single row of single stitches. However, in contrast to interventricular septum rupture where the patches loosen the tension of the tissues, in our patients the patches pull strongly and restrain the walls by fastening their edges and supporting tight stitches. In this way they could narrow the cavity and close the ventricle. Results The resected area varied from 5 × 4 to 8 × 8 cm. Excision was extended into the interventricular septum in 5 patients, thus opening the right ventricle. CABG was performed on all patients but two. Left ventricular volumes and the ejection fraction changed significantly: end-systolic volume 93.5 ± 12.4 to 57.8 ± 8.9 ml, p < 0.001; end-diastolic volume 157.2 ± 16.7 to 115.3 ± 14.9 ml, p < 0.001; ejection fraction 40.3 ± 4.2 to 49.5 ± 5.7%, p < 0.001. All patients did well. One patient suffered from bleeding, which was not from the wall suture, and another had a left arm paresis. The post-operative hospital stay was 5 to 30 days with a mean 10.5 ± 7.5 days/patient. At follow-up, 9 to 60 months mean 34, all patients were symptom-free. NYHA class 2.5 ± 0.8 changed to 1.2 ± 0.4, p < 0.001. Conclusion The double-patch sandwich technique (bi-patch closure) offers some advantages and does not result in increased morbidity and mortality. In the case of excising a left ventricular aneurysm, this technique in no way requires eversion of the edges, felt strips, buttressed and multiple sutures, all of which are needed for longitudinal linear closure. Moreover, it does not require purse string sutures, endocardial scar remnant to secure the patch or folding the excluded non-functional tissue, all of which are needed for endoventricular patch repair.

Tappainer, Ernesto; Fiorani, Vinicio; Pederzolli, Nicola; Manfredi, Jacopo; Nocchi, Andrea; Zogno, Mario

2007-01-01

373

Compressive behavior of sandwich panels and laminates with damage  

NASA Astrophysics Data System (ADS)

A wrinkling model for sandwich panels in compression is developed with the assumption of an isotropic elastic core. Stresses for the three wrinkling cases coupled with global buckling are expressed by a unified expression. It is shown that the stresses in all three cases are identical for short wavelength wrinkling and can be expressed by a single simplified analytical expression, but may differ significantly in moderate and long wavelength wrinkling and for these cases are given by simplified analytical expressions. Based on the conducted analysis limitations of the commonly used Winkler, Pasternak and two-parameter models are discussed. Exact closed form solutions of the buckling load and mode shape are obtained for a face layer debonded locally from the core of a sandwich panel. The effects of length and location of debonds and the end constraints of the face layer on the load carrying capacity are discussed. Interactive effects due to two debonds are also studied. A master curve based on a classical solution is developed by employing the characteristic length normalization and the modification to the usual Winkler foundation constant, and it agrees very well with published results of a finite element analysis. A beam-plate element method for composite sheets is developed for both multiple aligned delaminations and multi-ply parallel delaminations. Our result shows that the buckling load of the beam-plate with multiple aligned delamination is mainly decided by a major delamination. A simple reduced model is suggested to remove overlapping of the secondary delaminated portion. The buckling load is dramatically reduced by multi-ply parallel delaminations due to antisymmetric modes. The classical results of compressive strength in fiber reinforced composites are rederived by using a new generalized Timoshenko beam model. Introducing a "shear hinge" to simulate a kink band and using the method of split rigidities it is shown that not only an initial fiber misalignment but also any misalignment in the loading system can affect the critical stress for kinking. A new mechanism based on shear instability of matrix is proposed for kink band formation and a simple formula is then derived to predict the kink band angle.

Niu, Kangmin

374

[Sandwich-graft myringoplasty: the authors' personal technic and results].  

PubMed

The authors describe the anatomic and functional results obtained with a sandwich myringoplasty technique (MPL) employing an endaural approach. The suggested technique is a modified sandwich MPL by endaural approach with a reduced Shambaugh incision, a systematic profiling of the canal wall bulge and separation of the meatal and tympano-meatal flaps that are maintained pedunculated. The temporal fascia is inserted between the fibrous layer of the tympanic remnant and a single pedunculated tympano-meatal cutaneous flap replaced in the original location. The authors present 72 cases operated between January 1987 and December 1989 for perforations involving up to three quadrants. In 93.1% of the cases a complete and lasting resolution of the perforation was obtained. Of the 5 failures, 4 presented a perforation smaller than the original one. An average (250, 500, 1000 Hz) functional recovery of 14.1 dB was observed compared to an average pre-operatory gap of 21.6 dB. In 25% of the cases, average recovery was greater than 25 dB and in 5 patients a slight worsening with an average difference of -3.3 dB was observed. On the whole, in 41 patients a residual post-operatory gap of only 10 dB was achieved. The anatomical results obtained with the MPL presented are similar to those found in the literature describing the classical overlay technique. However, the cases reported do not present those inconveniences associated to the latter technique (lateralization of the graft and blunting). The anatomic and functional results obtained with the technique discussed are on the whole superior to those described with the underlay and the classical overlay techniques. The Authors believe that this is mainly due to the absence of the gelfoam in the middle ear and to the double contention and vascularization of the temporal fascia graft. By means of the profiling of the canal wall the endaural approach permits a good view of the operating field. Furthermore, it is less traumatic and more acceptable to the patient than the postauricular one that has to be limited to the MPL where there are clinical indications for the exploration of antrum. The personal technique here presented implies, however, a certain presence of epithelial pearls. Their localization is nevertheless facilitated by the absence of blunting, thickening and lateralization of the graft. This allows for an early and easy removal on an out-patient basis. Other inconveniences of the technique are the length of the procedure and a more difficult control of the ossicular chain.(ABSTRACT TRUNCATED AT 400 WORDS) PMID:1414324

Pagnini, P; Scarpini, L; Fanfani, F; Norberti, A

375

Research in the Field of Fiberglassreinforced Sandwich Structure for Airframe Use.  

National Technical Information Service (NTIS)

The research covered in this report involves investigation of the effects of raw materials usage and fabrication process variables on the final strength properties of fiberglass-reinforced plastic (FRP) sandwich structure suitable for use as a primary air...

G. Nordby J. Noyes W. C. Crisman

1964-01-01

376

A variable transverse stiffness sandwich structure using fluidic flexible matrix composites (F2MC)  

NASA Astrophysics Data System (ADS)

Presented in this paper is the development of a novel honeycomb sandwich panel with variable transverse stiffness. In this structure, the traditional sandwich face sheets are replaced by the fluidic flexible matrix composite (F2MC) tube layers developed in recent studies. The F2MC layers, combined with the anisotropic honeycomb core material properties, provide a new sandwich structure with variable stiffness properties for transverse loading. In this research, an analytical model is derived based on Lekhitskii's anisotropic pressurized tube solution and Timoshenko beam theory. Experimental investigations are also conducted to verify the analytical findings. A segmented multiple-F2MC-tube configuration is synthesized to increase the variable stiffness range. The analysis shows that the new honeycomb sandwich structure using F2MC tubes of 10 segments can provide a high/low transverse stiffness ratio of 60. Segmentation and stiffness control can be realized by an embedded valve network, granting a fast response time.

Li, Suyi; Lotfi, Amir; Shan, Ying; Wang, K. W.; Rahn, Christopher D.; Bakis, Charles E.

2008-05-01

377

Ferrocene analogues of sandwich B12.Cr.B12: A theoretical study  

NASA Astrophysics Data System (ADS)

The bowl B12 cluster was previously reported to be analogous to benzene and predicted to be one of the best candidates to be new inorganic ligands. The structural stability and electronic properties of a new sandwich compound Cr(B12)2 (D3d) have been investigated by using density functional theory. It is found that the sandwich Cr(B12)2 (D3d) is a stable complex with large binding energy (-5.93 eV) and HOMO-LUMO gap (2.37 eV), as well as Fe(C5H5)2 and Cr(C6H6)2, following the 18-electron principle. The detailed molecular orbitals and aromaticity analyses indicate that the sandwich compound Cr(B12)2 (D3d) is electronically very stable. The natural bond orbital analysis suggests that spd-? interaction plays an important role in the sandwich compounds.

Yuan, Yuan; Cheng, Longjiu

2013-01-01

378

Publix Recalls Sub Sandwiches with Onions Due To Possible Health Risk  

NASA Website

Publix Super Markets is issuing a voluntary recall for custom sub sandwiches that contain onions because they may be adulterated with Listeria monocytogenes. Publix received notification from their supplier, who receives sliced onions from Gills ...

379

Design Parameters for Torsion of Sandwich Strips Having Trapezoidal, Rectangular, and Triangular Cross Sections.  

National Technical Information Service (NTIS)

Solutions for the elastic torsion of sandwich strips having triangular, rectangular, or trapezoidal cross sections are presented analytically in terms of suitable design parameters. Data obtained from resulting expressions are presented in a series of des...

H. M. Montrey E. W. Kuenzi

1972-01-01

380

Development of Beryllium Honeycomb Sandwich Composite for Structural and Other Related Applications.  

National Technical Information Service (NTIS)

The feasibility of fabricating large beryllium honeycomb panels was demonstrated. Both flat and curved sandwich structures were manufactured using practical, braze bonding techniques. The processes developed prove that metallurgically assembled beryllium ...

J. W. Vogan L. A. Grant

1972-01-01

381

Identification of Equivalent Core Elastic Parameters for Sandwich Panels (Application of Nonlinear Optimization Algorithm)  

NASA Astrophysics Data System (ADS)

Composite sandwich panels have been employed in many structural applications. Therefore, it is very important to obtain the dynamical properties of the composite sandwich panels. Also, an inverse analysis method has already been proposed by one of the authors to identify the layer elastic parameters of laminated plates and shells using the FEM eigenvalue analysis and the nonlinear optimization algorithm. The purpose of this study is to improve the already proposed identification method to apply to a sandwich panel and to identify the equivalent core elastic parameters. By applying the experimental modal analysis technique to the sandwich panel, natural frequencies and mode shapes of the panel are obtained. From the obtained natural frequencies and mode shapes, the equivalent core elastic parameters are identified numerically. Furthermore, the usefulness of the improved identification method is clarified.

Hosokawa, Kenji; Takagi, Kohei; Sakata, Toshiyuki

382

Damage Characteristics and Residual Strength of Composite Sandwich Panels Impacted with and Without Compression Loading.  

National Technical Information Service (NTIS)

The results of an experimental study of the impact damage characteristics and residual strength of composite sandwich panels impacted with and without a compression loading are presented. Results of impact damage screening tests conducted to identify the ...

D. M. McGowan D. R. Ambur

1998-01-01

383

Response of Composite Fuselage Sandwich Side Panels Subjected to Internal Pressure and Axial Tension.  

National Technical Information Service (NTIS)

The results from an experimental and analytical study of two composite sandwich fuselage side panels for a transport aircraft are presented. Each panel has two window cutouts and three frames and utilizes a distinctly different structural concept. These p...

B. Dopker B. Shah D. R. Ambur M. Rouse

1998-01-01

384

Mechanical Characterizations of the Dispersion U3Si2-Al Fuel Plate with Sandwich Structure  

NASA Astrophysics Data System (ADS)

This paper is to assess effect of the dispersion U3Si2-Al fuel plate with sandwich structure on its mechanical properties and to assess the quality of this fuel plate by the suitable processing because the optimum performance of fuel plate affects directly the safety and reliability of a power reactor. For this purpose, the mechanical properties of the fuel plate with sandwich structure were described that the relationship between the strength and the sandwich microstructure of dispersion U3Si2-Al fuel plate based on the experimental investigations and the fracture analysis of SEM images. These results shown that it can be improved that the mechanical properties of dispersion U3Si2-Al fuel plate with sandwich structure by the optimizing clad material, U3Si2-Al powder composite contents and process of rolling as well as the optimizing the heat treatment methods.

Wang, Xi-Shu; Xu, Yong

2003-05-01

385

Electrochemical construction  

DOEpatents

An electrochemical cell construction features a novel co-extruded plastic electrode in an interleaved construction with a novel integral separator-spacer. Also featured is a leak and impact resistant construction for preventing the spill of corrosive materials in the event of rupture.

Einstein, Harry (Springfield, NJ); Grimes, Patrick G. (Westfield, NJ)

1983-08-23

386

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

Microsoft Academic Search

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

James Lua

2011-01-01

387

Application of Modal Analysis for Evaluation of the Impact Resistance of Aerospace Sandwich Materials  

Microsoft Academic Search

\\u000a Impact resistance of different types of composite sandwich beams is evaluated by studying vibration response changes (natural\\u000a frequency and damping ratio). This experimental works will help aerospace structural engineer in assess structural integrity\\u000a using classification of impact resistance of various composite sandwich beams (entangled carbon and glass fibers, honeycomb\\u000a and foam cores). Low velocity impacts are done below the BVID

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

388

Characterisation by Inverse Techniques of Elastic, Viscoelastic and Piezoelectric Properties of Anisotropic Sandwich Adaptive Structures  

Microsoft Academic Search

In this article we present recent developments regarding parameter estimation in sandwich structures with viscoelastic frequency\\u000a dependent core and elastic laminated skin layers, with piezoelectric patch sensors and actuators bonded to the exterior surfaces\\u000a of the sandwich. The frequency dependent viscoelastic properties of the core material are modelled using fractional derivative\\u000a models, with unknown parameters that are to be estimated

Aurelio L. Araújo; Cristovao M. Mota Soares; Carlos A. Mota Soares; Jose Herskovits

2010-01-01

389

Optimal design of box-section sandwich beams subject to moving load  

Microsoft Academic Search

Minimum weight designs of sandwich beams subject to moving load are performed as a function of prescribed load index, where\\u000a the stiffness and strength constraints are both considered. The dynamic properties of sandwich beams are detected and validated\\u000a through finite element simulation. Five different topologies are optimized and compared. Numerical results show that the topology\\u000a of a hollow tube with

Xiuhui Hou; Zichen Deng; Jiaxi Zhou

2010-01-01

390

The response of clamped sandwich plates with lattice cores subjected to shock loading  

Microsoft Academic Search

The dynamic response of clamped circular monolithic and sandwich plates of equal areal mass and thickness has been measured by loading the plates at mid-span with metal foam projectiles. The sandwich plates comprise AISI 304 stainless steel face sheets and either AL-6XN stainless steel pyramidal core or AISI 304 stainless steel square-honeycomb lattice core. The resistance to shock loading is

G. J. McShane; D. D. Radford; V. S. Deshpande; N. A. Fleck

2006-01-01

391

Quench collection of nano-aluminium agglomerates from combustion of sandwiches and propellants  

Microsoft Academic Search

An experimental investigation has been carried out to measure the size of nano-aluminium agglomerates emerging from the combustion of nano-aluminized sandwiches and composite solid propellants. Nano-aluminium of median size of 50nm produced in-house by the electrical wire explosion method is used in these samples. Propellants with different sizes of coarse and fine ammonium perchlorate are considered. Surface features of sandwiches

K. Jayaraman; S. R. Chakravarthy; R. Sarathi

2011-01-01

392

The soft impact of composite sandwich beams with a square-honeycomb core  

Microsoft Academic Search

The dynamic response of end-clamped monolithic beams and sandwich beams of equal areal mass have been measured by loading the beams at mid-span with metal foam projectiles to simulate localised blast loading. The sandwich beams were made from carbon fibre laminate and comprised identical face sheets and a square-honeycomb core. The transient deflection of the beams was determined as a

B. P. Russell; T. Liu; N. A. Fleck; V. S. Deshpande

393

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

Microsoft Academic Search

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

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

2003-01-01

394

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

Microsoft Academic Search

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

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

1997-01-01

395

Flexural analysis of balsa core sandwich composite: Failure mechanisms, core grain orientation and padding effect  

Microsoft Academic Search

A comprehensive investigation was undertaken to study failure mechanisms of sandwich composites and their influence on flexural behavior (load-displacement curve). Sandwich composite panels were cured from compression thermoforming of E-glass\\/epoxy skins and a low density balsa wood core. Balsa core grain orientation is found to have major effect on flexural response and failure modes. Flexural behavior, failure mode and its

Avinash S Phadatare

2012-01-01

396

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

Microsoft Academic Search

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

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

2006-01-01

397

A sub-laminates FEM approach for the analysis of sandwich beams with multilayered composite faces  

Microsoft Academic Search

A finite element approach based on the Hermitian ZigZag theory and on the sub-laminates concept is proposed for the static analysis of sandwich structures. The accuracy of the model is evaluated through a set of numerical results about the static response of sandwich beams with composite multilayered faces subjected to different boundary conditions and external loads; a comparison with three-dimensional

M. Degiovanni; M. Gherlone; M. Mattone; M. Di Sciuva

2010-01-01

398

Flexural analysis of balsa core sandwich composite: failure mechanisms, core grain orientation and padding effect  

Microsoft Academic Search

A comprehensive investigation was undertaken to study failure mechanisms of sandwich composites and their influence on flexural behavior (load-displacement curve). Sandwich composite panels were cured from compression thermoforming of E-glass\\/epoxy skins and a low density balsa wood core. Balsa core grain orientation is found to have major effect on flexural response and failure modes. Flexural behavior, failure mode and its

Avinash S Phadatare

2012-01-01

399

Mechanical behaviour of a syntactic foam\\/glass fibre composite sandwich: experimental results  

Microsoft Academic Search

This note presents the main results of an experimental investigation into the mechanical behaviour of a composite sandwich conceived as a lightweight material for naval engineering applications. The sandwich structure is formed by a three-dimensional glass fibre\\/polymer matrix fabric with transverse piles interconnecting the skins; the core is filled with a polymer matrix\\/glass microspheres syntactic foam; additional Glass Fibre Reinforced

Enrico Papa; Egidio Rizzi

2001-01-01

400

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

Microsoft Academic Search

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

Jeremy Gustin; Aaran Joneson; Mohammad Mahinfalah; James Stone

2005-01-01

401

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

Microsoft Academic Search

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

German Reyes

2008-01-01

402

A Monte Carlo Algorithm Simulation of Antiferroelectricity in Sandwich Structural Film  

Microsoft Academic Search

We prepared BaTiO3\\/BiFeO3\\/BaTiO3 sandwich structural film by sol-gel process. Antiferroelectric hysteresis loop was observed in the sandwich structural film. A Monte Carlo simulation based on Ising model using a 100× 100 polarization grid is carried out. Simulating result matches to the experimental result very well and it shows that the antiferroelectricity is originated from the antiferroelectric couple between the different

Yuxia Sun; Hongri Liu

2011-01-01

403

Dynamic Ham-Sandwich Cuts of Convex Polygons in the Plane  

Microsoft Academic Search

We provide an ecient 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 P1 and P2 in the plane, the ham-sandwich cut of P1 and P2 is a line that simultaneously bisects the area (or perimeter or ver- tex count) of both polygons. We provide a

Timothy G. Abbott; Erik D. Demaine; Martin L. Demaine; Daniel Kane; Stefan Langerman; Jelani Nelson; Vincent Yeung

2005-01-01

404

Ply drop-off effects in CFRP\\/honeycomb sandwich panels—theory  

Microsoft Academic Search

This paper introduces a simple method for engineering analysis of ply drop-off induced local bending effects in CFRP\\/honeycomb sandwich panels. The model constituent parts are the base-line face laminate of a CFRP\\/sandwich panel, a dropped sub-laminate, a supporting honeycomb core material, and an adhesive\\/resin layer interfacing the laminates. The interaction between the core material and the face laminates is modelled

O. T. Thomsen; W. Rits; D. C. G. Eaton; S. Brown

1996-01-01

405

An extraterrestrial sandwich: The perils of food in space.  

PubMed

Food was and is an essential component in human space exploration. If it had not proved possible to eat and digest in space, none of the long-term space missions of the last four decades would have been achievable. Every country that has sent an astronaut on a mission has used its national foods as a means of stating both their presence and their identity to their colleagues in the programme and their citizens at home: in space, as on earth, food has provided a means of asserting national culture. From the earliest missions, the US and USSR's differing attitudes to the programme have been reflected in the food provided and the respective administrations' approaches to feeding in space. The contrast between the US focus on space travel and the USSR's focus on space living is highlighted through their attitudes to the often vexed question of what astronauts and cosmonauts should be permitted to eat, illustrated by the corned-beef sandwich incident of 1965. PMID:20138668

Levi, Jane

2010-02-06

406

Windsurf-Board Sandwich Panels Under Static Indentation  

NASA Astrophysics Data System (ADS)

In recent years composite materials have found application in several fields as sport and sea transportation, where the incidence of the cost of materials is not significant compared with the required high mechanical performances. As a matter of fact, in some sports the whole equipment is nowadays realized in composite materials (i.e. windsurf boards, snowboards). The aim of the present work is to evaluate the mechanical performance of some sandwich structures produced by vacuum bagging technology for the windsurf boards production. The behaviour of the structures is tested under static indentation conditions; different fibres materials, for the skins, and different polystyrene foams, for the core, have been taken into account. In particular both the effect of the kind of fibre (glass, carbon and kevlar fibres) and the effect of the polystyrene cells size (and its density) have been investigated. The purpose was to obtain a stiff structure able to bear localized loads. Additionally, the effects induced on the indentation resistance by both the speed and the diameter of pin have been analysed.

Borsellino, C.; Calabrese, L.; di Bella, G.

2008-03-01

407

A conformal thin-sandwich solver for generic initial data  

NASA Astrophysics Data System (ADS)

We will present our recently implemented code for an initial data (ID) solver for general relativity, IDSolve. A 3+1 decomposition breaks the Einstein Equations into two groups: hyperbolic ``evolution equations'' and elliptic ``constraint equations.'' IDSolve aims to provide physically meaningful data that satisfies the constraint equations, which can be used as initial data in numerical evolution. IDSolve uses the Conformal Thin Sandwich (CTS) method and does not assume any symmetries or simplifications of the equations of CTS, unlike most of the currently used ID solvers. Specifically, it does not assume the freely specified conformal spatial metric to be flat. IDSolve uses a parallelized multi-grid (MG) elliptic solver with adaptive mesh refinement (AMR) to solve the CTS equations. Singularities are avoided using a regularization scheme. I will present our results of binary object initial data, for which the generality of our code enables us to set the CTS free data using a superposition of the exactly known single object space-times.

Ramazanoglu, Fethi M.; East, William E.; Pretorius, Frans

2012-03-01

408

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

NASA Astrophysics Data System (ADS)

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.

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

2005-05-01

409

Construction and commissioning of the CALICE analog hadron calorimeter prototype  

Microsoft Academic Search

An analog hadron calorimeter (AHCAL) prototype of 5.3 nuclear interaction lengths thickness has been constructed by members of the CALICE Collaboration. The AHCAL prototype consists of a 38-layer sandwich structure of steel plates and highly-segmented scintillator tiles that are read out by wavelength-shifting fibers coupled to SiPMs. The signal is amplified and shaped with a custom-designed ASIC. A calibration\\/monitoring system

C. Adloff; Y. Karyotakis; J. Repond; A. Brandt; H. Brown; K. De; C. Medina; J. Smith; J. Li; M. Sosebee; A. White; J. Yu; T. Buanes; G. Eigen; Y. Mikami; O. Miller; N. K. Watson; J. A. Wilson; T. Goto; G. Mavromanolakis; M. A. Thomson; D. R. Ward; W. Yan; D. Benchekroun; A. Hoummada; Y. Khoulaki; M. Oreglia; M. Benyamna; C. Cârloganu; P. Gay; J. Ha; G. C. Blazey; D. Chakraborty; A. Dyshkant; K. Francis; D. Hedin; G. Lima; V. Zutshi; V. A. Babkin; S. N. Bazylev; Yu I. Fedotov; V. M. Slepnev; I. A. Tiapkin; S. V. Volgin; J.-Y. Hostachy; L. Morin; N. D'Ascenzo; U. Cornett; D. David; R. Fabbri; G. Falley; N. Feege; K. Gadow; E. Garutti; P. Göttlicher; T. Jung; S. Karstensen; V. Korbel; A.-I. Lucaci-Timoce; B. Lutz; N. Meyer; V. Morgunov; M. Reinecke; S. Schätzel; S. Schmidt; F. Sefkow; P. Smirnov; A. Vargas-Trevino; N. Wattimena; O. Wendt; M. Groll; R.-D. Heuer; S. Richter; J. Samson; A. Kaplan; H.-Ch Schultz-Coulon; W. Shen; A. Tadday; B. Bilki; E. Norbeck; Y. Onel; E. J. Kim; G. Kim; D.-W. Kim; K. Lee; S. C. Lee; K. Kawagoe; Y. Tamura; J. A. Ballin; P. D. Dauncey; A.-M. Magnan; H. Yilmaz; O. Zorba; V. Bartsch; M. Postranecky; M. Warren; M. Wing; M. Faucci Giannelli; M. G. Green; F. Salvatore; R. Kieffer; I. Laktineh; M. C. Fouz; D. S. Bailey; R. J. Barlow; R. J. Thompson; M. Batouritski; O. Dvornikov; Yu Shulhevich; N. Shumeiko; A. Solin; P. Starovoitov; V. Tchekhovski; A. Terletski; B. Bobchenko; M. Chadeeva; M. Danilov; O. Markin; R. Mizuk; E. Novikov; V. Rusinov; E. Tarkovsky; V. Andreev; N. Kirikova; A. Komar; V. Kozlov; Y. Soloviev; A. Terkulov; P. Buzhan; B. Dolgoshein; A. Ilyin; V. Kantserov; V. Kaplin; A. Karakash; E. Popova; S. Smirnov; N. Baranova; E. Boos; L. Gladilin; D. Karmanov; M. Korolev; M. Merkin; A. Savin; A. Voronin; A. Topkar; A. Frey; C. Kiesling; S. Lu; K. Prothmann; K. Seidel; F. Simon; C. Soldner; L. Weuste; B. Bouquet; S. Callier; P. Cornebise; F. Dulucq; J. Fleury; H. Li; G. Martin-Chassard; F. Richard; Ch de la Taille; R. Poeschl; L. Raux; M. Ruan; N. Seguin-Moreau; F. Wicek; M. Anduze; V. Boudry; J.-C. Brient; G. Gaycken; R. Cornat; D. Jeans; P. Mora de Freitas; G. Musat; M. Reinhard; A. Rougé; J.-Ch Vanel; H. Videau; K.-H. Park; J. Zacek; J. Cvach; P. Gallus; M. Havranek; M. Janata; J. Kvasnicka; M. Marcisovsky; I. Polak; J. Popule; L. Tomasek; M. Tomasek; P. Ruzicka; P. Sicho; J. Smolik; V. Vrba; J. Zalesak; Yu Arestov; V. Ammosov; B. Chuiko; V. Gapienko; Y. Gilitski; V. Koreshev; A. Semak; Yu Sviridov; V. Zaets; B. Belhorma; M. Belmir; A. Baird; R. N. Halsall; S. W. Nam; I. H. Park; J. Yang; J.-S. Chai; J.-T. Kim; Y. Kim; J. Kang; Y.-J. Kwon; I. Kim; T. Lee; J. Sung; S. Itoh; K. Kotera; M. Nishiyama; T. Takeshita; S. Weber; C. Zeitnitz

2010-01-01

410

Construction aggregates  

USGS Publications Warehouse

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.

Tepordei, V. V.

1994-01-01

411

Construction aggregates  

USGS Publications Warehouse

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.

Tepordei, V. V.

1996-01-01

412

Construction aggregates  

USGS Publications Warehouse

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%.

Langer, W. H.; Tepordei, V. V.; Bolen, W. P.

2000-01-01

413

Natural and recombinant bovine somatotropin: immunodetection with a sandwich ELISA.  

PubMed

Bovine Somatotropin (bST) is a peptide hormone secreted by the anterior pituitary gland and its recombinant form (rbST) is used for artificially boosting milk yield in cows. Identification of rbST is difficult in that there is little difference from the pituitary bST (pbST). In this work, we further studied the possibility of immunologically discriminating between rbST and pbST. With this purpose, we produced mouse monoclonal antibodies using, as antigen, a peptide mimicking the N-terminus of rbST from Monsanto (rbST-M) conjugated to keyhole limpet haemocyanin (KLH) and polyclonal antibodies in rabbits immunized with the whole bST or rbST-M. Hence, we developed a sandwich ELISA with the obtained antibodies for detection and quantification of bST in serum and compared its performance on the two worldwide commercialized rbSTs: rbST-M and rbST from LG Life Science (rbST-LG). The lowest detection limit of the assay was 0.05 ng/ml for rbST-M, 0.10 ng/ml for rbST-LG and 0.15 ng/ml for pbST. Furthermore, the assay showed the capability to amplify the signal in the presence of rbSTs, recognizing more efficiently rbST-M and rbST-LG than pbST (ECn pbST/ECn rbST: 3 and 1.6 respectively). Its employment for measuring bST levels in sera from bovines administered with rbST LG allowed us to detect exceptional values due to the treatment itself and probably further increased as a consequence of the higher affinity for rbSTs of our monoclonal antibody. PMID:16978434

Castigliego, Lorenzo; Iannone, Giorgio; Grifoni, Goffredo; Rosati, Remo; Gianfaldoni, Daniela; Guidi, Alessandra

2006-09-15

414

6Li foil scintillation sandwich thermal neutron detector  

NASA Astrophysics Data System (ADS)

Increasing needs for neutron detection and limited supply of 3He have led to the need for replacement neutron detection technology. This paper presents the design and initial results for a neutron detector (6Li foil scintillator sandwich) that uses lithium metal foil to detect thermal neutrons. The reaction products, primarily triton, deposit most of their energy in thin scintillator films and create light pulses. Gamma rays can deposit only a small amount of energy in the thin films and so produce only very small light pulses. Lithium is preferable to boron in this application because triton escapes from lithium more easily than does the alpha particle from boron, allowing the use of thicker films and hence greater efficiency. In addition, triton has a higher light output in the scintillator than the boron alpha particle. Lithium metal is preferable to a lithium compound, such as lithium fluoride, because the number of tritons that escape from the metal is greater for the same amount of lithium. Monte Carlo simulations show that good efficiency values can be achieved with reasonably sized detectors, values that are greater than that of comparable 3He systems for portal monitors. In addition, simulations of a neutron coincidence counting concept show high counting efficiency and short die-away time (16 ?s), which imply better performance than that of the high-level neutron coincidence counter (HLNCC)-II. Initial experimental measurements on a prototype detector using alpha particles (having similar light output to the expected tritons) show good light collection and transport properties.

Ianakiev, K. D.; Swinhoe, M. T.; Favalli, A.; Chung, K.; MacArthur, D. W.

2011-10-01

415

FLD determination of AL 3105\\/Polypropylene\\/AL 3105 sandwich sheet using numerical calculation and experimental investigations  

Microsoft Academic Search

Sandwich structures are gaining increase application in aeronautical, marine, automotive and civil engineering. Since such\\u000a sheet can be subjected to stamping processes and their deformation limited by various defects, knowing beforehand the limiting\\u000a amount of deformation is very important. For achieving this goal, sandwich sheet of Al 3105\\/Polymer\\/Al 3105 were prepared\\u000a using thin film hot melt adheres. FLD of sandwich

M. H. Parsa; M. Ettehad; S. Nasher Al Ahkami

2009-01-01

416

Different degree of reduction and sliding phenomenon study for three-dimensional hot rolling with sandwich flat strip  

Microsoft Academic Search

Symmetric rolling of 3D sandwich flat strips with thermal-elastic–plastic coupled model was studied under the assumption of an elastic roller and the condideration of heat transfer. Aluminum–copper sandwich flat strips were used in this study.The numerical model of symmetric rolling for 3D sandwich flat strip with thermal-elastic–plastic coupled model was developed based on the large deformation–large strain theory, the update

Zone-Ching Lin; Tang-Guo Huang

2000-01-01

417

Determination of critical loads for cylindrical sandwich panels of composite materials under two-sided compression and shear  

NASA Astrophysics Data System (ADS)

The problem of determining the critical buckling stress of symmetric and nonsymmetric sandwich panels loaded in two-sided compression and shear is investigated analytically. The governing equation is obtained by solving equations of balance of forces and moments for an element of a sandwich structure in the case of buckling. The solution is based on the general assumptions of the theory of thin shallow shells. The results of the study can be used to optimize the structure of sandwich panels.

Rubina, A. L.; Krashakov, Yu. F.

418

Construction I.  

ERIC Educational Resources Information Center

Construction One is a programed text on building construction being used in the first term in the School of Architecture, Nova Scotia Technical College. Illustrated throughout with diagramatic line drawings, the text is set up with a pretest, specific work assignments in the text, and a comprehensive post-test. The individualized course is…

Eppell, Frank J.

419

Study on the sandwich piezoelectric ceramic ultrasonic transducer in thickness vibration  

NASA Astrophysics Data System (ADS)

A sandwich piezoelectric ceramic ultrasonic transducer in thickness vibration is studied. The transducer consists of front and back metal masses, and coaxially segmented, thickness polarized piezoelectric ceramic thin rings. For this kind of sandwich piezoelectric transducers in thickness vibration, it is required that the lateral dimension of the transducer is sufficiently large compared with its longitudinal dimension so that no lateral displacements in the transducer can occur (laterally clamped). In this paper, the thickness vibration of the piezoelectric ceramic stack consisting of a number of identical piezoelectric ceramic thin rings is analysed and its electro-mechanical equivalent circuit is obtained. The resonance frequency equation for the sandwich piezoelectric ceramic ultrasonic transducer in thickness vibration is derived. Based on the frequency equation, two sandwich piezoelectric ceramic ultrasonic transducers are designed and manufactured, and their resonance frequencies are measured. It is shown that the measured resonance frequencies are in good agreement with the theoretical results. This kind of sandwich piezoelectric ultrasonic transducer is expected to be used in megasonic ultrasonic cleaning and sonochemistry where high power and high frequency ultrasound is needed.

Lin, Shuyu; Tian, Hua

2008-02-01

420

A ballistic limit equation for hypervelocity impacts on composite honeycomb sandwich panel satellite structures  

NASA Astrophysics Data System (ADS)

During a recent experimental test campaign performed in the framework of ESA Contract 16721, the ballistic performance of multiple satellite-representative Carbon Fibre Reinforced Plastic (CFRP)/Aluminium honeycomb sandwich panel structural configurations (GOCE, Radarsat-2, Herschel/Planck, BeppoSax) was investigated using the two-stage light-gas guns at EMI. The experimental results were used to develop and validate a new empirical Ballistic Limit Equation (BLE), which was derived from an existing Whipple-shield BLE. This new BLE provided a good level of accuracy in predicting the ballistic performance of stand-alone sandwich panel structures. Additionally, the equation is capable of predicting the ballistic limit of a thin Al plate located at a standoff behind the sandwich panel structure. This thin plate is the representative of internal satellite systems, e.g. an Al electronic box cover, a wall of a metallic vessel, etc. Good agreement was achieved with both the experimental test campaign results and additional test data from the literature for the vast majority of set-ups investigated. For some experiments, the ballistic limit was conservatively predicted, a result attributed to shortcomings in correctly accounting for the presence of high surface density multi-layer insulation on the outer facesheet. Four existing BLEs commonly applied for application with stand-alone sandwich panels were reviewed using the new impact test data. It was found that a number of these common approaches provided non-conservative predictions for sandwich panels with CFRP facesheets.

Ryan, S.; Schaefer, F.; Destefanis, R.; Lambert, M.

421

A Study on Flexural Properties of Sandwich Structures with Fiber/Metal Laminate Face Sheets  

NASA Astrophysics Data System (ADS)

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.

Dariushi, S.; Sadighi, M.

2013-10-01

422

A Study on Flexural Properties of Sandwich Structures with Fiber/Metal Laminate Face Sheets  

NASA Astrophysics Data System (ADS)

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.

Dariushi, S.; Sadighi, M.

2013-01-01

423

Dynamic response of metal honeycomb sandwich structure under high-speed impact  

NASA Astrophysics Data System (ADS)

The ARMOR TPS is one of important candidate structure of RLV. It will be the best selection for all kinds of RLV. So the ARMOR thermal protection system will be used in aviation and spaceflight field more and more widely. ARMOR TPS panel is above the whole ARMOR TPS, and the metal honeycomb sandwich structure is the surface of the ARMOR TPS panel. So the metal honeycomb sandwich structure plays an important role in the ARMOR TPS, while it bears the flight dynamic pressure and stands against the flight dynamic calefaction and impact load. The metal honeycomb sandwich structure is made of upper faceplate, lower faceplate and honeycomb core. In the course of the reusable launch vehicle working, it is possible that the space chips impact its outer surface. The main problem is what impact the metal honeycomb sandwich structure can stand and how many times it can stand. In the high speed impact experiment we choose different quality and velocity to simulate real space environment. This paper will analyze the mechanics behaviour of metal honeycomb sandwich structure in the course of impact, and then we make sure the limit impact load and get the effect of impact flaw.

He, Xiaodong; Kong, Xianghao; Shi, Liping; Li, Mingwei

2009-12-01

424

Synthesis, structure and fluorescence of a 2-D network tetra-ZnII-substituted sandwich-type Keggin tungstoarsenate: {[Zn(dap)2(H2O)]2[Zn(dap)2]2[Zn4(Hdap)2(B-?-AsW9O34)2]}?4H2O  

NASA Astrophysics Data System (ADS)

A new 2-D network tetra-ZnII-substituted sandwich-type Keggin tungstoarsenate {[Zn(dap)2(H2O)]2[Zn(dap)2]2[Zn4(Hdap)2(B-?-AsW9O34)2]}·4H2O (1) (dap = 1,2-diaminopropane) has been synthesized by combining the conventional aqueous solution method and the hydrothermal method and structurally characterized by elemental analyses, X-ray powder diffraction (XRPD), IR spectrum, thermogravimetric analysis (TGA) and single-crystal X-ray diffraction. Structural analysis shows that 1 displays an interesting 2-D (4,4)-topological network constructed by tetra-ZnII-substituted sandwich-type Keggin tungstoarsenate units and [Zn(dap)2)2+] linkers. To our knowledge, 1 represents the first 2-D network Zn-substituted sandwich-type tungstoarsenate. The fluorescent properties of 1 have also been investigated.

Ma, Xiang; Hua, Jiai; Ma, Pengtao; Yang, Lei; Wang, Jingping; Niu, Jingyang

2013-09-01

425

Construction aggregates  

USGS Publications Warehouse

The estimated production during 2000 of construction aggregates, crushed stone, and construction sand and gravel increased by about 2.6% to 2.7 Gt (3 billion st), compared with 1999. The expansion that started in 1992 continued with record production levels for the ninth consecutive year. By commodity, construction sand and gravel production increased by 4.5% to 1.16 Gt (1.28 billion st), while crushed stone production increased by 1.3% to 1.56 Gt (1.72 billion st).

Bolen, W. P.; Tepordei, V. V.

2001-01-01

426

Construction 2003  

National Technical Information Service (NTIS)

Partial Contents: Portland Cement Concrete Pavements (Use of a Ride Quality Index for Construction Quality Control and Acceptance Specifications); Bituminous Pavements (Application of Infrared Imaging and Ground-Penetrating Radar to Detect Segregation in ...

2003-01-01

427

Construction aggregates  

USGS Publications Warehouse

Construction aggregates, primarily stone, sand and gravel, are recovered from widespread naturally occurring mineral deposits and processed for use primarily in the construction industry. They are mined, crushed, sorted by size and sold loose or combined with portland cement or asphaltic cement to make concrete products to build roads, houses, buildings, and other structures. Much smaller quantities are used in agriculture, cement manufacture, chemical and metallurgical processes, glass production and many other products.

Nelson, T. I.; Bolen, W. P.

2007-01-01

428

Construction aggregates  

USGS Publications Warehouse

Part of a special section on the market performance of industrial minerals in 1992. Production of construction aggregates increased by 4.6 percent in 1992. This increase was due, in part, to the increased funding for transportation and infrastructure projects. The U.S. produced about 1.05 Gt of crushed stone and an estimated 734 Mt of construction sand and gravel in 1992. Demand is expected to increase by about 5 percent in 1993.

Tepordei, V. V.

1993-01-01

429

Tunable and Sizable Band Gap of Single Layer Graphene Sandwiched between Hexagonal Boron Nitride  

NASA Astrophysics Data System (ADS)

It is a big challenge to open a tunable and sizable band gap of single layer graphene without big loss in structural integrity and carrier mobility. By using density functional theory calculations, we show that the band gap of single layer graphene can be opened to 0.16 (without electrical field) and 0.34 eV (with a strong electrical field) when sandwiched between two hexagonal boron nitride single layers in a proper way. The zero-field band gaps are increased by about 50% when many-body effects are included. Ab initio quantum transport simulation of a dual-gated FET out of such a sandwich structure further confirms an electrical field-enhanced transport gap. The tunable and sizeable band gap and structural integrity render this sandwich structure a promising candidate for high-performance single layer graphene field effect transistors.

Zheng, Jiaxin; Qu, Heruge; Liu, Qihang; Qin, Rui; Zhou, Jing; Yu, Dapeng; Gao, Zhengxiang; Lu, Jing; Luo, Guangfu; Nagase, Shigeru; Mei, Wai-Ning

2012-02-01

430

Yttrium polyoxometalates. Synthesis and characterization of a carbonate-encapsulated sandwich-type complex.  

PubMed

Reaction of A-alpha-PW(9)O(34)(9)(-) with YCl(3) in an aqueous Na(2)CO(3) solution produces a dianion-encapsulated A-type sandwich polyoxometalate, (YOH(2))(3)(CO(3))(A-alpha-PW(9)O(34))(2)(11)(-). The X-ray structure of this complex reveals that three Y(III) ions are sandwiched between two A-alpha-PW(9)O(34)(9)(-) moieties and that a carbonate dianion is encapsulated in the same plane as the three Y(III) atoms. The oxygen atoms of the CO(3)(2)(-) are sitting at the midpoints of the sides of the triangle formed by the three Y(III) ions. (31)P and (13)C NMR studies confirm that this complex is significantly more stable than the analogous A-type sandwich polyoxometalates containing divalent metals. PMID:14686830

Fang, Xikui; Anderson, Travis M; Neiwert, Wade A; Hill, Craig L

2003-12-29

431

Self-healing sandwich structures incorporating an interfacial layer with vascular network  

NASA Astrophysics Data System (ADS)

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.

Chen, Chunlin; Peters, Kara; Li, Yulong

2013-02-01

432

Preparation and microwave absorption properties of metal magnetic micropowder-coated honeycomb sandwich structures  

NASA Astrophysics Data System (ADS)

Radar absorbing materials with metal magnetic micropowder-coated honeycomb sandwich structures are prepared by a spray process. Metal magnetic micropowder is applied as an absorber which maintains a high absorption, and a honeycomb sandwich structure as a supporter enhancing mechanical strength. The microwave absorption properties are measured by a network analyzer system in the frequency range of 2.6-18 GHz. The concentration of the MMP and the coating thickness of the absorber affect the attenuation properties, a suitable value of them contributing to a broad bandwidth and high loss. A matching layer is introduced to the honeycomb sandwich structure on top, which allows the incident electromagnetic wave to enter and largely get attenuated through the absorbing system, increasing the microwave absorption.

He, Yanfei; Gong, Rongzhou; Cao, Heng; Wang, Xian; Zheng, Yi

2007-10-01

433

A plastic indentation model for sandwich beams with metallic foam cores  

NASA Astrophysics Data System (ADS)

Light weight high performance sandwich composite structures have been used extensively in various load bearing applications. Experiments have shown that the indentation significantly reduces the load bearing capacity of sandwiched beams. In this paper, the indentation behavior of foam core sandwich beams without considering the globally axial and flexural deformation was analyzed using the principle of virtual velocities. A concisely theoretical solution of loading capacity and denting profile was presented. The denting load was found to be proportional to the square root of the denting depth. A finite element model was established to verify the prediction of the model. The load-indentation curves and the profiles of the dented zone predicted by theoretical model and numerical simulation are in good agreement.

Xie, Zhong-You; Yu, Ji-Lin; Zheng, Zhi-Jun

2011-12-01

434

Distortion-free single point imaging of multi-layered composite sandwich panel structures.  

PubMed

The results of a magnetic resonance imaging (MRI) investigation concerning the effects of an aluminum honeycomb sandwich panel on the B1 and B0 fields and on subsequent image quality are presented. Although the sandwich panel structure, representative of an aircraft composite material, distorts B0 and attenuates B1, distortion-free imaging is possible using single point (constant time) imaging techniques. A new expression is derived for the error caused by gradient field distortion due to the heterogeneous magnetic susceptibility within a sample and this error is shown not to cause geometric distortion in the image. The origin of the B0 distortion in the sample under investigation was also examined. The graphite-epoxy 'skin' of the panel is the principal source of the B0 distortion. Successful imaging of these structures sets the stage for the development of methods for detecting moisture ingress and degradation within composite sandwich structures. PMID:15082262

Marble, Andrew E; Mastikhin, Igor V; MacGregor, Rod P; Akl, Mohamad; LaPlante, Gabriel; Colpitts, Bruce G; Lee-Sullivan, Pearl; Balcom, Bruce J

2004-05-01

435

Distortion-free single point imaging of multi-layered composite sandwich panel structures  

NASA Astrophysics Data System (ADS)

The results of a magnetic resonance imaging (MRI) investigation concerning the effects of an aluminum honeycomb sandwich panel on the B1 and B0 fields and on subsequent image quality are presented. Although the sandwich panel structure, representative of an aircraft composite material, distorts B0 and attenuates B1, distortion-free imaging is possible using single point (constant time) imaging techniques. A new expression is derived for the error caused by gradient field distortion due to the heterogeneous magnetic susceptibility within a sample and this error is shown not to cause geometric distortion in the image. The origin of the B0 distortion in the sample under investigation was also examined. The graphite-epoxy `skin' of the panel is the principal source of the B0 distortion. Successful imaging of these structures sets the stage for the development of methods for detecting moisture ingress and degradation within composite sandwich structures.

Marble, Andrew E.; Mastikhin, Igor V.; MacGregor, Rod P.; Akl, Mohamad; Laplante, Gabriel; Colpitts, Bruce G.; Lee-Sullivan, Pearl; Balcom, Bruce J.

2004-05-01

436

Graphene oxide embedded sandwich nanostructures for enhanced Raman readout and their applications in pesticide monitoring  

NASA Astrophysics Data System (ADS)

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 × 107 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.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 × 107 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. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr00631j

Zhang, Lulu; Jiang, Changlong; Zhang, Zhongping

2013-04-01

437

Nonlinear vibration of viscoelastic sandwich beams by the harmonic balance and finite element methods  

NASA Astrophysics Data System (ADS)

This paper deals with geometrically nonlinear vibrations of sandwich beams with viscoelastic materials. For this purpose, a new finite element formulation has been developed, in which a zig-zag model is used to describe the displacement field. The viscoelastic behaviour is handled by using hereditary integrals and their relationships with complex moduli. An efficient solution procedure based on the harmonic balance method is also developed. To demonstrate its abilities, various problems of nonlinear vibrations of sandwich beams are considered. First, the results derived from the proposed approach are compared with those of nonlinear dynamic analyses using direct time integration and to experimental data. Then, the influence of the vibration amplitude on the damping properties of sandwich beams is investigated. The effect of an initial axial strain is also examined.

Jacques, N.; Daya, E. M.; Potier-Ferry, M.

2010-09-01

438

Chromium aromatic hydrocarbon sandwich molecules and the eighteen-electron rule.  

PubMed

Ab initio density functional theory (DFT) calculations are reported for the chromium sandwich structure CrnR2, where n = 7 and R is the aromatic hydrocarbon hexabenzocoronene (C42H18). This system is remarkable in that the structure of the chromium sites strongly resemble those in chromium bis-benzene Cr1(C6H6)2, as judged by geometry and charge density properties. The electron localization function of the sandwich shows a hexagonally arrayed set of V(C, Cr, C) valence basins about each chromium atom with modification due to local site symmetry. This system satisfies an extension of the 18-electron rule to components of a conjugated molecular system. This idea is explored further by examining the electronic and geometric properties of the series CrnR2, where n and R are given by n = 1, benzene C6H6 as reference; n = 2, biphenyl (C6H5)2; n = 3, triphenylene C18H12; n = 3, coronene C24H18; and n = 4, dibenzopyrene C24H14. On the basis of electron counting and ring isolation, all the sandwich structures in this series could satisfy the extension of the 18-electron rule, with the exception of coronene, which was deliberately included. The DFT calculations predict spin-paired ground states for some but not all of the sandwich structures, implying that the Cr-ring interactions at work require understanding at a deeper level. Thus, while sandwiches with n = 1, n = 2, n = 4 and n = 7 have spin paired singlet ground states and appear to satisfy the rule, those with n = 3 (triphenylene, coronene) have antiferromagnetic singlet ground states and do not. This is attributed to nonuniformity in the electronic charge density of the rings of the isolated hydrocarbons and to a reduction of symmetry from D3h to C2v with a concomitant spin-charge density change in the sandwiches. PMID:18211037

Philpott, Michael R; Kawazoe, Yoshiyuki

2008-01-23

439

Graphene oxide embedded sandwich nanostructures for enhanced Raman readout and their applications in pesticide monitoring.  

PubMed

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

Zhang, Lulu; Jiang, Changlong; Zhang, Zhongping

2013-03-27

440

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

Microsoft Academic Search

Quasi-static uniform compression tests and low-velocity concentrated impact tests were conducted to reveal the failure mechanisms and energy absorption capacity of two-layer carbon fiber composite sandwich panels with pyramidal truss cores. Three different volume-fraction cores (i.e., with different relative densities) were fabricated: 1.25%, 1.81%, and 2.27%. Two-layer sandwich panels with identical volume-fraction cores (either 1.25% or 2.27%), and also stepwise

Jian Xiong; Ashkan Vaziri; Li Ma; Jim Papadopoulos; Linzhi Wu

441

Left-handed behavior and low-loss passband in a ferromagnetic sandwich structure  

NASA Astrophysics Data System (ADS)

The electromagnetic properties of a ferromagnetic-dielectric-ferromagnetic sandwich structure were studied by experiment and simulation. In the transmission spectra, an obvious passband emerges in the broad forbidden band of ferromagnetic resonance because the strong coupling of two resonating ferrite slabs excites a propagating mode. The passband has ultralow loss (~-1 dB) due to the feature of surface wave and the bias magnetic field pump. A negative phase evolution of propagating wave occurs in the second slab only based on the magnetic resonance. The ultralow insertion loss of passband and magnetotunability endow the sandwich structure a promising application future.

Xu, Fang; Bai, Yang; Qiao, Lijie; Zhao, Hongjie; Zhou, Ji

2009-09-01

442

Parameter Estimation in Hybrid Active-Passive Laminated Sandwich Composite Structures  

SciTech Connect

In this article we present recent developments regarding parameter estimation in sandwich structures with viscoelastic frequency dependent core and elastic laminated skin layers, with piezoelectric patch sensors and actuators bonded to the exterior surfaces of the sandwich. The frequency dependent viscoelastic properties of the core material are modelled using fractional derivative models, with unknown parameters that are to be estimated by an inverse technique, using experimentally measured natural frequencies and associated modal loss factors. The inverse problem is formulated as a constrained minimization problem, and gradient based optimization techniques are employed. An application case is presented and discussed, focused on identification of viscoelastic frequency dependent core material properties.

Araujo, A. L. [ESTIG-Polytechnic Institute of Braganca, Campus de Sta. Apolonia, Apartado 1134, 5301-857 Braganca (Portugal); Mota Soares, C. M.; Mota Soares, C. A. [IDMEC/IST-Technical University of Lisbon, Av. Rovisco Pais, 1049-001 Lisbon (Portugal); Herskovits, J. [COPPE/UFRJ-Federal University of Rio de Janeiro, Caixa Postal 68503, 21945-970 Rio de Janeiro (Brazil)

2010-05-21

443

Measurement of stress distribution in sandwich beams under four-point bending  

Microsoft Academic Search

The bending-stress distributions through thickness in sandwich-composite beams are different from those obtained by conventional\\u000a composite-beam theory because of the shear effect of the core, especially when the ratio of elastic moduli of face to core\\u000a (k=E\\u000a \\u000a f\\u000a \\/E\\u000a \\u000a c\\u000a ) is large.\\u000a \\u000a Accordingly, the stress distributions in sandwich beams of composite materials with various combinations of face and core

K. Kemmochi; M. Uemura

1980-01-01

444

Giant magnetoresistance of magnetically soft sandwiches: Dependence on temperature and on layer thicknesses  

Microsoft Academic Search

We present comprehensive results on the magnetoresistive properties of spin-valve sandwiches comprising glass\\/M(1)\\/Cu\\/Ni80Fe20\\/Fe50Mn50\\/Cu, where M(1) is a ferromagnetic transition metal or alloy (Co,Ni,Ni80Fe20). We discuss the thermal variation of the magnetoresistance (DeltaR\\/R) and its dependence on the thicknesses of the layers constituting the active part of the spin-value sandwich [i.e., M(1)\\/Cu\\/NiFe]. An almost linear decrease of DeltaR\\/R is observed between

B. Dieny; P. Humbert; V. S. Speriosu; S. Metin; B. A. Gurney; P. Baumgart; H. Lefakis

1992-01-01

445

Optical fiber SPR biosensor with sandwich assay for the detection of prostate specific antigen  

NASA Astrophysics Data System (ADS)

We present a new, sensitive, few mode fiber (FMF) surface plasmon resonance (SPR) biosensor with a sandwich assay for the detection of PSA. The side-polished FMF biosensor does not need a polarizer and a thin high-index overlayer. The optical sensitivity of the SPR sensor was determined as 2.5 × 10-6 RIU. In the SPR PSA sensor, the SPR signals were amplified by a factor of 6 in average over no secondary antibody, using the sandwich assay. The proposed FMF SPR biosensor has great potential for real-time analysis of immune reaction between biomolecules and the advantages of high-sensitivity and label-free detection.

Jang, Hyun Soo; Park, Kwang No; Kang, Chang Duk; Kim, Jun Pyo; Sim, Sang Jun; Lee, Kyung Shik

2009-07-01

446

Investigation of Lanthanide Sandwich Nanoclusters Encapsulated with a Cyclo-Olefin Polymer as a Gas Barrier  

NASA Astrophysics Data System (ADS)

Lanthanide nanoclusters ligated by planar organic molecules have one-dimensional sandwich structures and are air/moisture sensitive. To investigate their optical properties, originating from the lanthanide elements, for novel nanodevices, we preserved the nanoclusters with a cyclo-olefin polymer as a gas barrier. The technique enabled us to conduct various spectroscopic analyses without oxidation of the samples, such as fluorescence microscopy, photoluminescence, and X-ray absorption fine structure determination, thus revealing that lanthanide sandwich nanoclusters containing europium (Eu) atoms exhibit orange fluorescence attributed to divalent Eu2+.

Tsunemi, Eika; Tsuji, Takashi; Fukazawa, Suguru; Tsunoyama, Hironori; Watanabe, Yoshio; Nakajima, Atsushi

2012-03-01

447

COHESIVE MIXED-MODE DAMAGE MODEL APPLIED TO THE SIMULATION OF THE MECHANICAL BEHAVIOUR OF A REPAIRED SANDWICH BEAM  

Microsoft Academic Search

Delamination caused by low velocity impact is one of the most frequent cases of damage in sandwich composite materials. When delamination is present the ability of the material to withstand structural loading is limited (1, 2). In many cases, a local repair of a damaged sandwich structure is preferable over replacement for economical, mechanical and environmental reasons. Bonded repairs are

D. A. Ramantani; R. D. S. G Campilho; A. T. Marques

448

Experimental determination of validated, critical interfacial modes I and II energy release rates in a composite sandwich panel  

Microsoft Academic Search

A validated experimental approach to obtaining critical mode I and mode II energy release rates for interfacial failure in a sandwich composite panel is outlined in this paper. By modifying the geometry of the sandwich structure to align the face sheet-core interface to coincide with the neutral axis, it is possible to obtain critical mode I and mode II energy

Paul Davidson; Anthony M. Waas; Chandra S. Yerramalli

449

Study of Compression-Loaded and Impact-Damaged Structurally Efficient Graphite-Thermoplastic Trapezoidal-Corrugation Sandwich and Semisandwich Panels.  

National Technical Information Service (NTIS)

The structural efficiency of compression-loaded trapezoidal-corrugation sandwich and semisandwich composite panels is studied to determine their weight savings potential. Sandwich panels with two identical face sheets and a trapezoidal corrugated core bet...

D. C. Jegley

1992-01-01

450

Trail Construction  

NSDL National Science Digital Library

In this highly physical outdoor activity, learners construct and compare experimental trail sections to select the best trail-construction technique for their site. As they measure, evaluate and build, they must consider factors including erosion, slope, materials, labor, cost, human effort, and various environmental impacts. The slope measuring component not only involves mathematical problem-solving, but can incorporate measurement of human health performance, since one way of measuring slope in this activity can be having learners check their pulse as they climb a hill. This activity can be well combined with the "Hold a Hill" and "Cardiac Hill" activities from the same resource.

Science, Lawrence H.

1982-01-01

451

Bioadhesive constructs  

US Patent & Trademark Office Database

The invention describes substrates, such as prosthetics, films, nonwovens, meshes, etc. that are treated with a bioadhesive. The bioadhesive includes polymeric substances that have phenyl moieties with at least two hydroxyl groups. The bioadhesive constructs can be used to treat and repair, for example, hernias and damaged tendons.

Lee; Bruce P. (Madison, WI); Vollenweider; Laura (Middleton, WI); Murphy; John L. (Madison, WI); Xu; Fangmin (Middleton, WI); Dalsin; Jeffrey L. (Madison, WI); Virosco; Jeanne (Madison, WI); Lew; William (Mendota Heights, MN); White; Jed (Madison, WI)

2013-02-26

452

Construction Work  

USGS Multimedia Gallery

Construction work taking place at the Theodore Roosevelt National Park in North Dakota. Funding for the road project at Theodore Roosevelt National Park comes from the $170 million appropriated for the Federal Highway Administration to spend on roads in national parks....

2009-07-24

453

Abstract Constructions.  

ERIC Educational Resources Information Center

|Describes a lesson designed to culminate a year of eighth-grade art classes in which students explore elements of design and space by creating 3-D abstract constructions. Outlines the process of using foam board and markers to create various shapes and optical effects. (DSK)|

Pietropola, Anne

1998-01-01

454

Detector construction  

Microsoft Academic Search

Methods for constructing radiation sensitive detectors are described. In one method, distinct layers of optical cement and plastics material are disposed between a semiconductor photodiode and a layer of rare earth phosphor in order to permit the phosphor and the plastics material to be peeled from the optical cement without damaging the photodiode in the event of a problem arising

1981-01-01

455

ANALYSIS OF VIBRATIONS AND ENERGY FLOWS IN SANDWICH PLATES BEARING CONCENTRATED MASSES AND SPRINGLIKE INCLUSIONS IN HEAVY FLUID-LOADING CONDITIONS  

Microsoft Academic Search

Vibrations of and the energy propagation in an infinitely long fluid-loaded sandwich beam (a plate of the sandwich composition in one-dimensional cylindrical bending) bearing concentrated masses and supported by springs are described in the framework of the sixth order theory of multilayered plates coupled with the standard theory of linear acoustics. A sandwich plate is loaded by a layer of

S. V. Sorokin

2002-01-01

456

A protocol for characterizing the structural performance of metallic sandwich panels: application to pyramidal truss cores  

Microsoft Academic Search

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

F. W. Zok; S. A. Waltner; Z. Wei; H. J. Rathbun; R. M. McMeeking; A. G. Evans

2004-01-01

457

Impact characterization of sandwich structures with an integrated orthogrid stiffened syntactic foam core  

Microsoft Academic Search

This paper presents the manufacturing, testing, and modeling of a new composite sandwich structure with a hybrid grid stiffened core. The hybrid core consists of a continuous fiber reinforced polymer orthogrid skeleton that is filled in with light weight syntactic foam in the bays or cells. The grid skeleton was manufactured by a dry weaving process per the pin-guided filament

Guoqiang Li; Venkata Dinesh Muthyala

2008-01-01

458

The association between membership in the sandwich generation and health behaviors: A longitudinal study  

Microsoft Academic Search

The current study examined the association between membership in the sandwich generation, defined as providing care to both children and parents or in-laws, and five health behaviors: checking the food label for health value when buying foods, using a seat belt, choosing foods based on health value, exercising regularly, and cigarette smoking. Participants (N = 4943) were from a longitudinal

Laurie Chassin; Jon T. Macy; Dong-Chul Seo; Clark C. Presson; Steven J. Sherman

2010-01-01

459

The Stability of Simply-Supported Sandwich Panels with Fibre Reinforced Faceplates.  

National Technical Information Service (NTIS)

The research is concerned with the stability under in-plane loading of simply-supported sandwich panels with laminated fibre-reinforced faceplates. Three types of faceplate lay-up are considered and they are referred to as symmetrical, angle-ply and cross...

T. R. A. Pearce

1973-01-01

460

Characterisation of viscoelastic layers in sandwich panels via an inverse technique  

Microsoft Academic Search

A new inverse technique to characterise the nonlinear mechanical properties of viscoelastic core layers in sandwich panels has been developed based on simple vibration tests. The present methodology allows one to preserve the frequency and temperature dependences of the storage and loss moduli of viscoelastic materials for a wide range of frequencies and to perform a structural analysis using high

E. Barkanov; E. Skukis; B. Petitjean

2009-01-01

461

Job Burnout and Couple Burnout in Dual-Earner Couples in the Sandwiched Generation  

ERIC Educational Resources Information Center

|We use existential theory as a framework to explore the levels of and relationship between job and couple burnout reported by dual-earner couples in the "sandwich generation" (i.e., couples caring both for children and aging parents) in a sample of such couples in Israel and the United States. This comparison enables an examination of the…

Pines, Ayala Malach; Neal, Margaret B.; Hammer, Leslie B.; Icekson, Tamar

2011-01-01

462

Calculation of polarization states of transmitted and reflected light from the sandwich structure of photorefractive elements  

Microsoft Academic Search

The states of polarization of the light after reflection and transmission through the sandwich structure of the refractive layers are analyzed. Calculated by Wolter formula, the complex transmission coefficient of multilayer system indicates that the transmitted light, having linear polarization at incidence, is elliptically polarized. The ellipticity and the azimuth of the transmitted light is connected with K and L

Jahja O. Kokaj; Yacob Makdisi; Kuldip Bahtia

1995-01-01

463

Acoustic emission analysis of full-scale honeycomb sandwich composite curved fuselage panels  

Microsoft Academic Search

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

Frank A. Leone Jr.; Didem Ozevin; Valery Godinez; Bao Mosinyi; John G. Bakuckas Jr.; Jonathan Awerbuch; Alan Lau; Tein-Min Tan

2008-01-01

464

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

NASA Astrophysics Data System (ADS)

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 and is generally rather thick and of low density. The task of the core is to separate and stabilize the two facings, transmit shear between the facings and provide most of the shear rigidity. For sandwich panels no stiffeners are needed. Therefore no mass will be lost in stiffeners resulting in a relative high value of mass per unit area of the skin which results in a better TL according to the mass law. Also the core can be made of a material with high insulation properties (acoustic and thermal). The number of discrete stiffeners can then be minimized, since they are only required at places where high concentrated forces have to be introduced (wing, landing gear, etc.) or diverted (from cut-outs). This can reduce the production and maintenance cost. So it can be concluded that the sandwich concept offers great potential for multidisciplinary fuselage design.

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

2005-01-01

465

Uniaxial crushing of sandwich plates under air blast: Influence of mass distribution  

Microsoft Academic Search

Motivated by recent efforts to mitigate blast loading using energy-absorbing materials, this paper uses analytical and computational modeling to investigate the influence of mass distribution on the uniaxial crushing of cellular sandwich plates under air blast loading. In the analytical model, the cellular core is represented using a rigid, perfectly-plastic, locking idealization, as in previous studies, and the front and

Joseph A. Main; George A. Gazonas

2008-01-01

466

The Association between Membership in the Sandwich Generation and Health Behaviors: A Longitudinal Study  

ERIC Educational Resources Information Center

|The current study examined the association between membership in the sandwich generation, defined as providing care to both children and parents or in-laws, and five health behaviors: checking the food label for health value when buying foods, using a seat belt, choosing foods based on health value, exercising regularly, and cigarette smoking.…

Chassin, Laurie; Macy, Jon T.; Seo, Dong-Chul; Presson, Clark C.; Sherman, Steven J.

2010-01-01

467

Static and dynamic analysis of transversely isotropic, moderately thick sandwich beams by analogy  

Microsoft Academic Search

Summary A flexural theory of elastic sandwich beams is derived which renders quite precise results within a wide range of ratios of dimensions, mass densities, and elastic constants of the core and faces. The assumptions of the Timoshenko theory of shear-deformable beams are applied to each of the homogeneous, linear elastic, transversely isotropic layers individually. Core and faces are perfectly

R. Heuer

1992-01-01

468

Shear buckling in foam-filled web core sandwich panels using a Pasternak foundation model  

Microsoft Academic Search

Web core panels, foam-filled sandwich panels with interior webs, are a structurally efficient option for transverse load bearing applications. In web core panels, the interaction between the webs and core material can have a substantial impact on web shear buckling strength and is a key element of lightweight structural design. The present work is an investigation of web buckling behavior

Casey R. Briscoe; Susan C. Mantell; Jane H. Davidson

2010-01-01

469

Numerical and experimental studies on aluminum sandwich plates of variable thickness  

Microsoft Academic Search

The elastic flexural behavior of static deformation and free vibration of sandwich plates of variable thickness is investigated numerically and experimentally. In the analysis, the face plates are treated as Marguerre shells, and the core is assumed to be an antiplane core and to provide resistance to transverse shear and normal stresses only. Displacement continuity conditions are used at the

2006-01-01

470

Control of vibration and wave propagation in sandwich plates with periodic auxetic core  

Microsoft Academic Search

The wave propagation in and the vibration of sandwich plates with cellular core are analyzed and controlled. Negative Poisson's ratio (auxetic) core materials of different geometry placed periodically in the plate introduce the proper impedance mismatch necessary to obstruct the propagation of waves over specified frequency bands (stop bands) and in particular directions. The location and the extension of the

Fabrizio L. Scarpa; Massimo Ruzzene; Luca Mazzarella; Panagiotis Tsopelas

2002-01-01

471

Pointwise impulse (blast) response of a composite sandwich plate including core compressibility effects  

Microsoft Academic Search

This work analyzes the nonlinear impulse response of a composite sandwich plate exposed to a sudden point-wise transverse loading on the top face sheet. The nonlinearity arising from the core compressibility in the thickness direction is modeled and incorporated into the constitutive relations explicitly. As such, one can have a deep insight regarding the stress, strain and displacement profiles into

Renfu Li; George A. Kardomateas; George J. Simitses

2009-01-01

472

Buckling of laminated sandwich plates with soft core based on an improved higher order zigzag theory  

Microsoft Academic Search

An improved higher order zigzag theory is presented and it is applied to study the buckling of laminated sandwich plates. The present theory satisfies the conditions of transverse shear stress continuity at all the layer interfaces including transverse shear stress free conditions at the top and bottom surfaces of the plate. The variation of in-plane displacements through thickness direction is

M. K. Pandit; B. N. Singh; A. H. Sheikh

2008-01-01

473

Defining the Growth/No-Growth Boundary for Listeria monocytogenes in Shelf Stable Pocket Sandwiches.  

National Technical Information Service (NTIS)

Honey Barbecue Beef and Bacon Cheddar pocket sandwiches were formulated such that their pH values and water activity values were much higher than allowable under the product specification, to create an environment that might support the growth of L. monoc...

D. Schaffner H. B. Bruins

2008-01-01

474

Enhancing the resistance of composite sandwich panels to localized forces for civil infrastructure and transportation applications  

Microsoft Academic Search

This paper presents the details of an experimental and numerical study that was conducted to evaluate different methods of increasing the punching resistance of glass fiber reinforced polymer (GFRP) composite sandwich panels with balsa wood cores. A total of four large-scale panels were subjected to concentrated loads in a two-way bending configuration. Different techniques of locally stiffening the panels were

M. Dawood; W. Ballew; J. Seiter

475

Torsional wave dispersion in a finitely pre-strained hollow sandwich circular cylinder  

Microsoft Academic Search

This paper studies torsional wave dispersion in a three-layered (sandwich) hollow cylinder with finite initial strains. The investigations are carried out within the scope of the piecewise homogeneous body model with the use of the three-dimensional linearized theory of elastic waves in initially stressed bodies. The mechanical relations of the materials of the cylinders are described through their harmonic potential.

S. D. Akbarov; T. Kepceler; M. Mert Egilmez

2011-01-01

476

Loading, Degradation and Repair of F-111 Bonded Honeycomb Sandwich Panels - Preliminary Study  

Microsoft Academic Search

Many of the fixed and removable panels on the RAAF F-111 aircraft are made up of bonded honeycomb sandwich panels. Experience with the RAAF fleet has shown that a serious problem exists with degradation and damage of these panels. A review of the literature was undertaken to gain an understanding of the extent of this problem. It was found that

S. Whitehead; M. McDonald; R. A. Bartholomeusz

477

Loading, Degradation and Repair of F-111 Bonded Honeycomb Sandwich Panels - Preliminary Study.  

National Technical Information Service (NTIS)

Many of the fixed and removable panels on the RAAF F-111 aircraft are made up of bonded honeycomb sandwich panels. Experience with the RAAF fleet has shown that a serious problem exists with degradation and damage of these panels. A review of the literatu...

S. Whitehead M. McDonald R. A. Bartholomeusz

2000-01-01

478

A study on diffraction efficiency of an adaptive optical limiter based on nonlinear medium sandwiched structure  

NASA Astrophysics Data System (ADS)

An adaptive optical limiter composed of nonlinear medium sandwiched between phase grating and one piece of slab is discussed under the circumstances of weak lights and intense laser pulses. The effects of refractive indices mismatch between phase grating and nonlinear medium on diffraction efficiency are investigated, which provides guidance for compounding nonlinear medium and evaluating limiting performance.

Wang, H. J.; Yu, Y. B.; Zhao, J. W.; Ji, F. M.; Wang, Y. J.; Yin, Z.

2013-10-01

479

A novel “sandwich” method for observation of the keyhole in deep penetration laser welding  

Microsoft Academic Search

A sandwich method was used to observe the keyhole in deep penetration laser welding, which provided an effective way to analyze both the Fresnel and inverse Bremsstrahlung absorption. In the transparent metal-analog system, different densities of metal vapor, ionized atoms, and free electrons in the keyhole can be simulated by changing the thickness of aluminum films. The research results show

Yi Zhang; Genyu Chen; Haiying Wei; Jun Zhang

2008-01-01

480

Library Services to the Sandwich Generation and Serial Caregivers. ASCLA Changing Horizons Series.  

ERIC Educational Resources Information Center

|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,…

Walling, Linda Lucas, Comp.

481

Nanometric self-assembling peptide layers maintain adult hepatocyte phenotype in sandwich cultures  

Microsoft Academic Search

BACKGROUND: Isolated hepatocytes removed from their microenvironment soon lose their hepatospecific functions when cultured. Normally hepatocytes are commonly maintained under limited culture medium supply as well as scaffold thickness. Thus, the cells are forced into metabolic stress that degenerate liver specific functions. This study aims to improve hepatospecific activity by creating a platform based on classical collagen sandwich cultures. RESULTS:

Jonathan Wu; Núria Marí-Buyé; Teresa Fernández Muiños; Salvador Borrós; Pietro Favia; Carlos E Semino

2010-01-01

482

Vibration control of a sandwich annular plate with an electrorheological fluid core layer  

Microsoft Academic Search

A free vibration analysis of an annular plate with an electrorheological (ER) fluid core and a constraining layer is presented in this study. A discrete finite element method is used to investigate the vibrational characteristics of the sandwich annular plate. The extensional and shear moduli of the ER fluid layer are described by complex quantities. Complex eigenvalues are then found

Jia-Yi Yeh

2007-01-01

483

Multi-scale modelling of sandwich structures using the Arlequin method Part I: Linear modelling  

Microsoft Academic Search

The paper presents an Arlequin based multi-scale method for studying problems related to the mechanical behaviour of sandwich composite structures. Towards this end, different models are mixed and glued to each other. Several coupling operators are tested in order to assess the usefulness of the proposed approach. A new coupling operator is proposed and tested on the different glued Arlequin

Heng Hu; Salim Belouettar; Michel Potier-Ferry; El Mostafa Daya

2008-01-01

484

Lamb waves for the non-destructive inspection of monolithic and sandwich composite beams  

Microsoft Academic Search

The aim of the current study is to develop a cost and time effective inspection strategy for in-service health monitoring of composite structures. An experimental study is presented, that demonstrates the potential of low-frequency Lamb waves being used for the inspection of monolithic and sandwich composite beams. Small and unobtrusive piezoceramic patches are used to generate and capture flexural waves

K. Diamanti; C. Soutis; J. M. Hodgkinson

2005-01-01

485

Treatment of Unsymmetric Adhesively Bonded Composite Sandwich Panels-To-Flange Joints  

Microsoft Academic Search

An analytical solution for the determination of stresses in unsymmetric adhesively bonded joints is presented. The classical sandwich plate theory and an adhesive interface constitutive model are employed for this development. In addition, an analytical solution for the consideration of the effect of fracture in the joints, using the modified crack closure also is developed. Joints with various configurations (symmetrical

F. TAHERI; G. P. ZOU

2004-01-01

486

Characterization of syntactic foams and their sandwich composites: Modeling and experimental approaches  

Microsoft Academic Search

Hollow particle filled polymers known as syntactic foams are lightweight and highly damage tolerant. Syntactic foams are used as core materials in sandwich composites. The use of such materials in aeronautical and space structures make it necessary to understand their characteristics for various environmental and loading conditions. The first part of the present work takes modeling and finite element analysis

Nikhil Gupta

2003-01-01

487

Multi-scale nonlinear modelling of sandwich structures using the Arlequin method  

Microsoft Academic Search

The paper presents a combination of the Arlequin Method (AM) and the Asymptotic Numerical Method (ANM) for studying nonlinear problems related to the mechanical behavior of sandwich composite structures. The Arlequin Method is a multi-scale method in which different models are crossed and glued to each other. The ANM is an alternative method which falls into the category of numerical

Heng Hu; Salim Belouettar; Michel Potier-Ferry; El Mostafa Daya; Ahmed Makradi

2010-01-01

488

A comprehensive assessment of adhesively bonded joints between sandwich composite beams  

Microsoft Academic Search

Assessment of adhesively bonded joints between sandwich composite beams are presented in this thesis in three parts, each is concerned with a distinct aspect of the joint behaviour. In physical order, these include the deformations of the entire joint assembly, the state of stress in the joint overlap region, and the strain energy release at the crack-tip at the end

Khaled Omar Shahin

2008-01-01

489

Deep-water sedimentary environments of the northwestern Weddell Sea and South Sandwich Islands, Antarctica  

Microsoft Academic Search

Two transects have been sampled using short cores (multi and box), seabed photography, video sequences, and sediment profile images across the northwestern Weddell Sea and South Sandwich Forearc, Antarctica. A total of 12 core stations were examined for sediment structure, texture and composition to determine their depositional history. Four of the core stations from the Weddell Continental Slope, Abyssal Plain

John A. Howe; Tracy M. Shimmield; Robert Diaz

2004-01-01

490

Response of pre-cast reinforced composite sandwich panels to axial loading  

Microsoft Academic Search

This paper summarises the results of an experimental and numerical study of precast reinforced composite sandwich panels. Full-scale tests were carried out to determine their axial strength capacity. Load–deformation response, strains variation across the insulation layer, strains in shear connectors, crack appearance and propagation under increasing load were recorded and analysed. A brief review of previous research works undertaken on

A. Benayoune; A. A. A. Samad; A. A. Abang Ali; D. N. Trikha

2007-01-01

491

Parametric study of the post-buckling strength of structural core sandwich panels  

Microsoft Academic Search

Post-buckling strength of simply supported orthotropic corrugated board panels subjected to edge compressive loading has been investigated using geometrically non-linear finite element analysis (FEA). Adjustments of the transverse shear stiffnesses in the FEA were necessary and performed by comparing the critical buckling load calculated by FEA with a closed form solution. The collapse load of the sandwich plate was calculated

T. M. Nordstrand

1995-01-01

492

Resisting Collapse of Steel-faced Sandwich Panel Walls and Ceilings Exposed to Fire  

Microsoft Academic Search

This article deals with the overall structural stability of sandwich panels used as ceilings and fire walls when exposed to fire on one side. Only panels with flat steel faces are considered. Simple mechanisms of instability are described, load actions are quantified, and practical design guidance is given to ensure stability i.e., resistance to overall collapse. The analysis for ceilings

Gordon M. E. Cooke

2008-01-01

493

Influence of Cell Size on the Core Shear Properties of FRP Honeycomb Sandwich Panels  

Microsoft Academic Search

This paper deals with the influence of cell size on the core shear modulus and shear strength of fiber reinforced plastic (FRP) honeycomb core sandwich panels. A relationship between the cell size and core density has been established for the honeycomb core made by matching the mold method. The cell size ranges from 8 to 25 mm, with the cell height

M. D. Antony Arul Prakash; V. L. Jagannatha Guptha; Ramesh S. Sharma; B. Mohan

2011-01-01

494

Static and fatigue bending behavior of pultruded GFRP sandwich panels with through-thickness fiber insertions  

Microsoft Academic Search

This paper presents the findings of a research program that was undertaken to evaluate the static and fatigue characteristics of an innovative 3-D glass fiber reinforced polymer (GFRP) sandwich panel proposed for civil infrastructure and transportation applications. The research consists of analytical modeling verified by experimental results. A rational analytical model is presented and used to evaluate the effective elastic

M. Dawood; E. Taylor; W. Ballew; S. Rizkalla

2010-01-01

495

Influence of Cell Size on the Core Shear Properties of FRP Honeycomb Sandwich Panels  

Microsoft Academic Search

This article deals with the influence of cell size on the core shear modulus and shear strength of fiber-reinforced plastic (FRP) honeycomb core sandwich panels. A relationship between the cell size and core density has been established for the honeycomb core made by matching the mold method. The cell size ranges from 8 to 25 mm, with the cell height kept

M. D. Antony Arul Prakash; V. L. Jagannatha Guptha; Ramesh S. Sharma; B. Mohan

2012-01-01

496

Thermo-structural optimization of all-metallic prismatic sandwich panels  

Microsoft Academic Search

All-metallic sandwich panels with prismatic cores offer tremendous potential for thermostructural applications, due to their exceptional bending response together with the possibility of driving a fluid through their open cores, thus enabling active cooling. This thesis offers a complete thermo-mechanical characterization of prismatic panels with both corrugated and diamond cores, with main emphasis on geometric optimization. For the mechanical study,

Lorenzo Valdevit

2005-01-01

497

Thermomechanical postbuckling of geometrically imperfect anisotropic flat and doubly curved sandwich panels  

Microsoft Academic Search

Sandwich structures constitute basic components of advanced supersonic\\/hypersonic flight and launch vehicles. These advanced flight vehicles operate in hostile environments consisting of high temperature, moisture, and pressure fields. As a result, these structures are exposed to large lateral pressures, large compressive edge loads, and high temperature gradients which can create large stresses and strains within the structure and can produce

Terry John Hause

1998-01-01

498

Boranametallacarboranes. 1. Synthesis and Characterization of (Borane) Cobalt (Carborane) Sandwich Complexes.  

National Technical Information Service (NTIS)

The first known examples of borane-metal-carborane sandwich complexes, in which a metal atom simultaneously occupies vertices in a metallaborane and a metallacarborane framework, have been obtained from reactions of B5H8- or B9H14- ions with CoCl2 in THF,...

L. Borodinsky R. N. Grimes

1981-01-01

499

A sandwich-type triple-decker lanthanide complex with mixed phthalocyanine and Schiff base ligands.  

PubMed

A new triple-decker dinuclear sandwich-type dysprosium complex based on both the phthalocyanine ligand and the tetradentate Schiff base ligand was synthesized, which is of interest for synthetic chemistry and also shows single-molecule magnetic behaviour. PMID:23818021

Gao, Feng; Li, Yu-Yang; Liu, Cai-Ming; Li, Yi-Zhi; Zuo, Jing-Lin

2013-08-21

500

Perforation of aluminium foam core sandwich panels under impact loading—An experimental study  

Microsoft Academic Search

This paper reports an original inverse perforation tests on foam core sandwich panels under impact loading. The key point is the use of an instrumented Hopkinson pressure bar as a perforator and at the same time a measuring device. It aims at a high quality piercing force record during the whole perforation process, which is a weak point of common

H. Zhao; I. Elnasri; Y. Girard

2007-01-01