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1

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

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, the authors 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. The authors have investigated sandwich construction panels that employ cores of polystyrene, polyvinyl chloride (PVC) and polyurethane foams as well as conventional aluminum and cardboard honeycombs. The authors investigations have involved fabricating 0.5 x 0.6-m (20 x 24-inch) spherical-contour panels and testing their optical properties and environmental durability. The authors have also performed preliminary cost and performance studies. Evaluations included optical testing with the SunLab 2f and VSHOT tools both before and after exposures to environmental chamber testing. The results showed that sandwich mirror panels are potentially very accurate. However, long-term degradation due to creep was evident in all of the foam core facets. The aluminum honeycomb core facets were accurate and durable. In this paper, the design principles that guided the investigations, estimates of cost, and the results of the experimental investigations are presented.

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

1999-07-01

3

sandwich structure  

NASA Astrophysics Data System (ADS)

This study investigates the extent to which the TiO2/graphene/TiO2 sandwich structure improves the performance of dye-sensitized solar cells (DSSCs) over that of DSSCs with the traditional structure. Studies have demonstrated that the TiO2/graphene/TiO2 sandwich structure effectively enhances the open circuit voltage ( V oc), short-circuit current density ( J sc), and photoelectrical conversion efficiency ( ?) of DSSCs. The enhanced performance of DSSCs with the sandwich structure can be attributed to an increase in electron transport efficiency and in the absorption of light in the visible range. The DSSC with the sandwich structure in this study exhibited a V oc of 0.6 V, a high J sc of 11.22 mA cm-2, a fill factor (FF) of 0.58, and a calculated ? of 3.93%, which is 60% higher than that of a DSSC with the traditional structure.

Chen, Lung-Chien; Hsu, Chih-Hung; Chan, Po-Shun; Zhang, Xiuyu; Huang, Cing-Jhih

2014-08-01

4

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

NASA Technical Reports Server (NTRS)

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.

1993-01-01

5

Fabrication and characterization of microscale sandwich beams  

E-print Network

with cell diameters and wall widths down to 150 and 15 m, respectively, and having both metallic and polymer/metal structurally efficient, lightweight microscale beams and panels. I. INTRODUCTION Sandwich construction and affordability, however, have prompted investigations of alternative sandwich constructions based on lightweight

Kenis, Paul J. A.

6

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

7

DRAFT: Generalizing Ham Sandwich Cuts to Equitable Subdivisions  

E-print Network

DRAFT: Generalizing Ham Sandwich Cuts to Equitable Subdivisions Sergei Bespamyatnikh David Abstract We prove a generalization of famous Ham Sandwich Theorem for the plane. Given gn red points and gm is equivalent to the Ham Sandwich Theorem in the plane. We also present an efficient algorithm for constructing

Bespamyatnikh, Sergei

8

Tuna Salad Sandwiches Ingredients  

E-print Network

Tuna Salad Sandwiches Ingredients: 12 ounces tuna in water, canned 3 tablespoons pickle relish 1/8 teaspoon ground pepper 1/3 cup fat-free mayonnaise 12 whole wheat bread slices Directions 1. Combine tuna

Liskiewicz, Maciej

9

"If They're the Customer, I'm the Meat in the Sandwich": An Exploration of Tertiary Teachers' Metaphorical Constructions of Teaching  

ERIC Educational Resources Information Center

Metaphors are a primary influence on the way we perceive and construct our world; they are also a way of revealing beliefs and attitudes that might otherwise be difficult to identify. Furthermore, metaphor has been found to be an effective way of shifting people's beliefs, attitudes and behaviour. This paper details the findings of a pilot…

Emerson, Lisa; Mansvelt, Juliana

2014-01-01

10

SPECIALTY SANDWICHES ADDITIONS & SIDES  

E-print Network

, Italian Squash, Red Bell Peppers, Red Onion, and Tomatoes, topped with Feta Cheese, Candied Pecans with Spinach and Mushrooms, topped with Spinach, Roasted Red Bell Pepper, Grilled Onions, and a Smokey Aioli CUP BOWL CUP OF SOUP & SALAD299 419 519 CHILI MARINATED PORK SANDWICH...799 Avocado, Pepper Jack

Mills, Allen P.

11

Salads, Sandwiches and Desserts.  

ERIC Educational Resources Information Center

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

Marine Corps Inst., Washington, DC.

12

The LANL Sandwich Test  

Microsoft Academic Search

The Sandwich Test is a recently developed slab-variant of the copper cylinder test which, like its predecessor, is used for obtaining high explosive (HE) product equation-of-state information. A primary motivation of slab geometry is that the liner bends without stretching, making it less prone to breaking at large expansions than for cylindrical geometry. This allows a wider choice of liner

L. G. Hill

2001-01-01

13

Wet-sand impulse loading of metallic plates and corrugated core sandwich panels J.J. Rimoli a  

E-print Network

Wet-sand impulse loading of metallic plates and corrugated core sandwich panels J.J. Rimoli a , B 2011 Available online 30 May 2011 Keywords: Sandwich panels Blast loading Impulse mitigation a b s t r from impulsive loading. The performance and advantages of sandwich panel construction have been

Wadley, Haydn

14

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

15

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

16

Smooth sandwich gravitational waves  

E-print Network

Gravitational waves which are smooth and contain two asymptotically flat regions are constructed from the homogeneous pp-waves vacuum solution. Motion of free test particles is calculated explicitly and the limit to an impulsive wave is also considered.

J. Podolsky

1998-05-28

17

GEODESIC HAM-SANDWICH CUTS Prosenjit Bose  

E-print Network

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

Hurtado, Ferran

18

Geodesic Ham-Sandwich Cuts Prosenjit Bose  

E-print Network

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

Iacono, John

19

Thermal-Diode Sandwich Panel  

NASA Technical Reports Server (NTRS)

Thermal diode sandwich panel transfers heat in one direction, but when heat load reversed, switches off and acts as thermal insulator. Proposed to control temperature in spacecraft and in supersonic missiles to protect internal electronics. In combination with conventional heat pipes, used in solar panels and other heat-sensitive systems.

Basiulis, A.

1986-01-01

20

Tuna Apple Salad Sandwiches Ingredients  

E-print Network

Tuna Apple Salad Sandwiches Ingredients: 6 1/2 ounces tuna in water, canned 1 stalk celery 1 apple Directions 1. Open tuna and squeeze out liquid. Put in a mixing bowl and break up with a fork. 2. Wash celery pieces. 3. Add celery and apple to tuna. Stir well. 4. Add mayonnaise and lemon juice. Stir well. 5

Liskiewicz, Maciej

21

Wire and Packing Tape Sandwiches  

ERIC Educational Resources Information Center

In this article, the author describes how students can combine craft wire with clear packing tape to create a two-dimensional design that can be bent and twisted to create a three-dimensional form. Students sandwich wire designs between two layers of tape. (Contains 1 online resource.)

Rabinowitz, Sandy

2009-01-01

22

Development of biobased sandwich structures for mass transit application  

NASA Astrophysics Data System (ADS)

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

Munusamy, Sethu Raaj

23

A general small-deflection theory for flat sandwich plates  

NASA Technical Reports Server (NTRS)

A small-deflection theory is developed for the elastic behavior of orthotropic flat plates in which deflections due to shear are taken into account. In this theory, which covers all types of flat sandwich construction, a plate is characterized by seven physical constants (five stiffnesses and two Poisson ratios) of which six are independent. Both the energy expression and the differential equations are developed. Boundary conditions corresponding to simply supported, clamped, and elastically restrained edges are considered.

Libove, Charles; Batdorf, S B

1948-01-01

24

High Strain Rate Response of Sandwich Composites with Nanophased Cores  

Microsoft Academic Search

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

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

2005-01-01

25

GEODESIC HAM-SANDWICH CUTS Prosenjit Bose  

E-print Network

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

Morin, Pat

26

Compressive strength after blast of sandwich composite materials.  

PubMed

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

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

2014-05-13

27

Metal-induced B-H bond activation: reactions between half-sandwich Ir and Rh complexes with carboranylthioamide.  

PubMed

Novel half-sandwich metal (Ir, Rh) complexes constructed from carboranylthioamide ligands containing an unexpected metal-boron bond were synthesized and characterized. The strong base n-butyllithium is demonstrated to be necessary in the reaction process. PMID:25492590

Xu, Bin; Wang, Yin-Ping; Yao, Zi-Jian; Jin, Guo-Xin

2014-12-23

28

Composite Sandwich Technologies Lighten Components  

NASA Technical Reports Server (NTRS)

Leveraging its private resources with several Small Business Innovation Research (SBIR) contracts with both NASA and the U.S. Department of Defense, WebCore Technologies LLC, of Miamisburg, Ohio, developed a fiber-reinforced foam sandwich panel it calls TYCOR that can be used for a wide variety of industrial and consumer applications. Testing at Glenn Research Center?s Ballistic Impact Facility demonstrated that the technology was able to exhibit excellent damage localization and stiffness during impact. The patented and trademarked material has found use in many demanding applications, including marine, ground transportation, mobile shelters, bridges, and most notably, wind turbines.

2010-01-01

29

Facesheet Wrinkling in Sandwich Structures  

NASA Technical Reports Server (NTRS)

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

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

1999-01-01

30

A numerical study of periodic sandwich propellants with oxygenated binders  

NASA Astrophysics Data System (ADS)

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

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

2003-06-01

31

Development and Evaluation of Stitched Sandwich Panels  

NASA Technical Reports Server (NTRS)

This study explored the feasibility and potential benefits provided by the addition of through-the-thickness reinforcement to sandwich structures. Through-the-thickness stitching is proposed to increase the interlaminar strength and damage tolerance of composite sandwich structures. A low-cost, out-of-autoclave processing method was developed to produce composite sandwich panels with carbon fiber face sheets, a closed-cell foam core, and through-the-thickness Kevlar stitching. The sandwich panels were stitched in a dry preform state, vacuum bagged, and infiltrated using Vacuum Assisted Resin Transfer Molding (VARTM) processing. For comparison purposes, unstitched sandwich panels were produced using the same materials and manufacturing methodology. Test panels were produced initially at the University of Utah and later at NASA Langley Research Center. Four types of mechanical tests were performed: flexural testing, flatwise tensile testing, core shear testing, and edgewise compression testing. Drop-weight impact testing followed by specimen sectioning was performed to characterize the damage resistance of stitched sandwich panels. Compression after impact (CAI) testing was performed to evaluate the damage tolerance of the sandwich panels. Results show significant increases in the flexural stiffness and strength, out-of-plane tensile strength, core shear strength, edgewise compression strength, and compression-after-impact strength of stitched sandwich structures.

Stanley, Larry E.; Adams, Daniel O.; Reeder, James R. (Technical Monitor)

2001-01-01

32

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

33

Sound transmission loss of composite sandwich panels  

NASA Astrophysics Data System (ADS)

Light composite sandwich panels are increasingly used in automobiles, ships and aircraft, because of the advantages they offer of high strength-to-weight ratios. However, the acoustical properties of these light and stiff structures can be less desirable than those of equivalent metal panels. These undesirable properties can lead to high interior noise levels. A number of researchers have studied the acoustical properties of honeycomb and foam sandwich panels. Not much work, however, has been carried out on foam-filled honeycomb sandwich panels. In this dissertation, governing equations for the forced vibration of asymmetric sandwich panels are developed. An analytical expression for modal densities of symmetric sandwich panels is derived from a sixth-order governing equation. A boundary element analysis model for the sound transmission loss of symmetric sandwich panels is proposed. Measurements of the modal density, total loss factor, radiation loss factor, and sound transmission loss of foam-filled honeycomb sandwich panels with different configurations and thicknesses are presented. Comparisons between the predicted sound transmission loss values obtained from wave impedance analysis, statistical energy analysis, boundary element analysis, and experimental values are presented. The wave impedance analysis model provides accurate predictions of sound transmission loss for the thin foam-filled honeycomb sandwich panels at frequencies above their first resonance frequencies. The predictions from the statistical energy analysis model are in better agreement with the experimental transmission loss values of the sandwich panels when the measured radiation loss factor values near coincidence are used instead of the theoretical values for single-layer panels. The proposed boundary element analysis model provides more accurate predictions of sound transmission loss for the thick foam-filled honeycomb sandwich panels than either the wave impedance analysis model or the statistical energy analysis model.

Zhou, Ran

34

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

35

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

2012-07-11

36

Precast concrete sandwich panels subjected to impact loading  

NASA Astrophysics Data System (ADS)

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

Runge, Matthew W.

37

Shear lag in truss core sandwich beams  

E-print Network

An experimental study was conducted to investigate the possible influence of shear lag in the discrepancy between the theoretical and measured stiffness of truss core sandwich beams. In previous studies, the measured values ...

Roberts, Ryan (Ryan M.)

2005-01-01

38

Genetic analysis of membrane protein topology by a sandwich gene fusion approach.  

PubMed Central

We describe a cloning vector that allows the construction of phoA sandwich fusions in which mature alkaline phosphatase is inserted into target proteins. In contrast to previous fusions obtained using the TnphoA transposon, the entire amino acid sequence of the target protein is present in the fusion product. We have constructed a series of sandwich fusions of alkaline phosphatase to the multispanning cytoplasmic membrane protein MalF. Despite the fact that the alkaline phosphatase was tethered to MalF at both its N and its C terminus, the enzyme exhibited high activity when it was fused to a periplasmic domain of the membrane protein. Cells harboring an alkaline phosphatase sandwich fusion to the end of the first membrane-spanning segment of MalF exhibited both MalF and alkaline phosphatase activity. When alkaline phosphatase was inserted into a cytoplasmic domain of MalF, its specific activity was very low. Our results suggest that the alkaline phosphatase activity of phoA sandwich fusions provides a more sensitive monitor than previous methods of the cellular localization of the domain of the target protein to which the enzyme is fused. Thus, the sandwich fusion approach can give a more accurate picture of membrane protein topology. Images PMID:2170984

Ehrmann, M; Boyd, D; Beckwith, J

1990-01-01

39

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

40

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

41

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

NASA Technical Reports Server (NTRS)

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.

1983-01-01

42

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

NASA Technical Reports Server (NTRS)

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.

1983-01-01

43

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

NASA Technical Reports Server (NTRS)

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

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

2004-01-01

44

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

NASA Technical Reports Server (NTRS)

A sandwich construction, composed of hybrid carbon-glass fiber-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 of up to about two years in the extreme case. Moisture absorption and strength characteristics, as related to time of exposure to hygrothermal conditions, were evaluated for the sandwich specimens and their constituents (skins and foam). After different exposure periods, low-velocity impact damage was inflicted on most sandwich specimens and damage characteristics were related to impact energy. Eventually, the residual compressive strengths of the damaged (and undamaged) beams were determined flexurally. Test results show that exposure to hygrothermal conditions leads to significant strength reductions for foam specimens and open-edge sandwich panels, compared with reference specimens stored at room temperature. In the case of skin specimens and for beams prepared from encapsulated sanwich panels that had previously been exposed to hygrothermal conditions, moisture absorption was found to improve strength as related to the reference case. The beneficial effect of moisture on skin performance was, however, limited to moisture contents below 1% (at 50 C and lower temperatures). Above this moisture level and at higher temperatures, strength degradation of the skin seems to prevail.

Ishai, Ori; Hiel, Clement; Luft, Michael

1995-01-01

45

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

NASA Technical Reports Server (NTRS)

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

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

2004-01-01

46

Sandwiched Rényi divergence satisfies data processing inequality  

SciTech Connect

Sandwiched (quantum) ?-Rényi divergence has been recently defined in the independent works of Wilde et al. [“Strong converse for the classical capacity of entanglement-breaking channels,” preprint http://arxiv.org/abs/arXiv:1306.1586 (2013)] and Müller-Lennert et al. [“On quantum Rényi entropies: a new definition, some properties and several conjectures,” preprint http://arxiv.org/abs/arXiv:1306.3142v1 (2013)]. This new quantum divergence has already found applications in quantum information theory. Here we further investigate properties of this new quantum divergence. In particular, we show that sandwiched ?-Rényi divergence satisfies the data processing inequality for all values of ? > 1. Moreover we prove that ?-Holevo information, a variant of Holevo information defined in terms of sandwiched ?-Rényi divergence, is super-additive. Our results are based on Hölder's inequality, the Riesz-Thorin theorem and ideas from the theory of complex interpolation. We also employ Sion's minimax theorem.

Beigi, Salman [School of Mathematics, Institute for Research in Fundamental Sciences (IPM), P.O. Box 19395-5746, Tehran (Iran, Islamic Republic of)] [School of Mathematics, Institute for Research in Fundamental Sciences (IPM), P.O. Box 19395-5746, Tehran (Iran, Islamic Republic of)

2013-12-15

47

Heat pipes cool probe and sandwich panel  

NASA Technical Reports Server (NTRS)

Two concepts integrate heat-pipe technology. Probe with heat-pipe cooled jacket is self-contained, passive, and has no moving parts, unlike conventional air and water cooled probes. It is used in hostile, high temperature environments like wind tunnels and powerplants or on high-speed research and hypersonic cruise vehicles. Heat-pipe sandwich panel combines structural efficiency of sandwich with thermal efficiency of heat-pipe. It is used to eliminate thermal gradients and stresses, minimize thermal distortions, and transfer heat from one face of panel to other.

Camarda, C. J.; Couch, L. M.; Kelly, H. N.

1981-01-01

48

Nonlinear dynamic analysis of sandwich panels  

NASA Technical Reports Server (NTRS)

Two analytical techniques applicable to large deflection dynamic response calculations for pressure loaded composite sandwich panels are demonstrated. One technique utilizes finite element modeling with a single equivalent layer representing the face sheets and core. The other technique utilizes the modal analysis computer code DEPROP which was recently modified to include transverse shear deformation in a core layer. The example problem consists of a simply supported rectangular sandwich panel. Included are comparisons of linear and nonlinear static response calculations, in addition to dynamic response calculations.

Lush, A. M.

1984-01-01

49

Mechanical behavior of dip-brazed aluminum sandwich panels  

E-print Network

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

Hohmann, Brian P. (Brian Patrick)

2007-01-01

50

Insert Design and Manufacturing for Foam-Core Composite Sandwich Structures  

NASA Astrophysics Data System (ADS)

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

Lares, Alan

51

THE BORSUK-ULAM AND HAM SANDWICH THEOREMS BRIAN LIBGOBER  

E-print Network

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

May, J. Peter

52

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.

1993-01-01

53

Blast resistance of prismatic sandwich structures  

Microsoft Academic Search

Metallic sandwich panels have emerged as candidate blast resistant structures that can be tailored to contain damage from impulsive loads of the type typically generated by explosives. When such panels are impulsively loaded, the stresses imposed by the core on the front face, as well as those transmitted through the core, govern the response metrics: especially the center displacement, the

Enrico Ferri

2009-01-01

54

Sound transmission loss of composite sandwich panels  

Microsoft Academic Search

Light composite sandwich panels are increasingly used in automobiles, ships and aircraft, because of the advantages they offer of high strength-to-weight ratios. However, the acoustical properties of these light and stiff structures can be less desirable than those of equivalent metal panels. These undesirable properties can lead to high interior noise levels. A number of researchers have studied the acoustical

Ran Zhou

2009-01-01

55

Feedback Sandwiches Affect Perceptions but Not Performance  

ERIC Educational Resources Information Center

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

Parkes, Jay; Abercrombie, Sara; McCarty, Teresita

2013-01-01

56

Optimal design of sandwich cylindrical shells  

NASA Astrophysics Data System (ADS)

A solution of multicriterion optimization of a sandwich cylindrical shell under axial compression and external pressure is presented. A model is formulated by adopting the objectives of minimum weight and minimum reciprocal bending rigidity of the shell. The set of constraints contains 9 or 11 constraints. The best optimal solution is obtained with the aid of the preference functions.

Ostwald, Marian

57

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

2013-03-28

58

Sound Transmission through a Cylindrical Sandwich Shell with Honeycomb Core  

NASA Technical Reports Server (NTRS)

Sound transmission through an infinite cylindrical sandwich shell is studied in the context of the transmission of airborne sound into aircraft interiors. The cylindrical shell is immersed in fluid media and excited by an oblique incident plane sound wave. The internal and external fluids are different and there is uniform airflow in the external fluid medium. An explicit expression of transmission loss is derived in terms of modal impedance of the fluids and the shell. The results show the effects of (a) the incident angles of the plane wave; (b) the flight conditions of Mach number and altitude of the aircraft; (c) the ratios between the core thickness and the total thickness of the shell; and (d) the structural loss factors on the transmission loss. Comparisons of the transmission loss are made among different shell constructions and different shell theories.

Tang, Yvette Y.; Robinson, Jay H.; Silcox, Richard J.

1996-01-01

59

Damping Analysis of a New Sandwich Structure  

E-print Network

Abstract—The aim of the paper is to determine the most important features of damping in the case of an advanced sandwich composite structure starting from the dampings, dynamic Young moduli and Poisson ratio for every lamina. The structure features two carbon/epoxy skins reinforced with twill weave fabric and an expanded polystyrene (EPS) core. At the damping analysis of fibre reinforced composite materials, a so called concept of complex moduli will be used in which the elastic constants will be replaced through their viscoelastic correspondences. The mechanical modeling is based on the correspondence principle of linear viscoelastic theory. Testing scheme allows specimens to be put in one side fixed connection and subjected at bending oscillations in normal conditions: 23°C, 50 % relative air humidity. Dampings, rigidities and compliances of the composite structure are computed. Index Terms—polymer matrix composites, sandwich, core, damping.

Horatiu Teodorescu-draghicescu; Sorin Vlase; Dorin Rosu; Ramona Purcarea; Violeta Munteanu

60

Thermographic Inspection of Metallic Honeycomb Sandwich Structures  

NASA Technical Reports Server (NTRS)

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

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

1998-01-01

61

Learning About Ratios: A Sandwich Study  

NSDL National Science Digital Library

This lesson introduces students to the concept of ratio through a hands-on, delicious experiment. After an introductory activity where students identify the ratio of girls to boys in a group of 10 selected students, they create six different peanut butter and jelly sandwiches with different ingredient ratios to find which is the tastiest. Students then plan their own similar experiment using other concoctions which can be expressed in ratios.

Weinberg, Sheryl

1999-01-16

62

Testing Falling Peanut Butter Sandwich Myth  

NSDL National Science Digital Library

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

Twin Cities Public Television, Inc.

2006-01-01

63

BMI Sandwich Wing Box Analysis and Test  

NASA Technical Reports Server (NTRS)

A composite sandwich single bay wing box test article was developed by Northrop Grumman and tested recently at NASA Langley Research Center. The objectives for the wing box development effort were to provide a demonstration article for manufacturing scale up of structural concepts related to a high speed transport wing, and to validate the structural performance of the design. The box concept consisted of highly loaded composite sandwich wing skins, with moderately loaded composite sandwich spars. The dimensions of the box were chosen to represent a single bay of the main wing box, with a spar spacing of 30 inches, height of 20 inches constant depth, and length of 64 inches. The bismaleimide facesheet laminates and titanium honeycomb core chosen for this task are high temperature materials able to sustain a 300F service temperature. The completed test article is shown in Figure 1. The tests at NASA Langley demonstrated the structures ability to sustain axial tension and compression loads in excess of 20,000 lb/in, and to maintain integrity in the thermal environment. Test procedures, analysis failure predictions, and test results are presented.

Palm, Tod; Mahler, Mary; Shah, Chandu; Rouse, Marshall; Bush, Harold; Wu, Chauncey; Small, William J.

2000-01-01

64

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

NASA Technical Reports Server (NTRS)

By using the Rayleigh-Ritz method of minimizing the total potential energy of a structural system, combined load (mechanical or thermal load) buckling equations are established for orthotropic rectangular sandwich panels supported under four different edge conditions. Two-dimensional buckling interaction curves and three dimensional buckling interaction surfaces are constructed for high-temperature honeycomb-core sandwich panels supported under four different edge conditions. The interaction surfaces provide easy comparison of the panel buckling strengths and the domains of symmetrical and antisymmetrical buckling associated with the different edge conditions. Thermal buckling curves of the sandwich panels also are presented. The thermal buckling conditions for the cases with and without thermal moments were found to be identical for the small deformation theory. In sandwich panels, the effect of transverse shear is quite large, and by neglecting the transverse shear effect, the buckling loads could be overpredicted considerably. Clamping of the edges could greatly increase buckling strength more in compression than in shear.

Ko, William L.

1993-01-01

65

Numerical simulation of the progressive collapse of polymer composite sandwich beams under static loading  

Microsoft Academic Search

Experimental results are given for the progressive collapse of polymer composite sandwich beams with construction typical of high performance marine vehicles. The skins consist of a unidirectional glass epoxy pre-preg (SP Systems SE84) laid up in a crossply form. The core is made from either Divinycell H100 (100kgm?3) or H200 (200kgm?3) foam. A two-dimensional numerical simulation of the progressive collapse

R. A. W Mines; A Alias

2002-01-01

66

Flexural behavior of a hybrid FRP and lightweight concrete sandwich bridge deck  

Microsoft Academic Search

This paper presents a new concept for a lightweight hybrid-FRP bridge deck. The sandwich construction consists of three layers: a fiber-reinforced polymer composite (FRP) sheet with T-upstands for the tensile skin, lightweight concrete (LC) for the core and a thin layer of ultra high performance reinforced concrete (UHPFRC) as a compression skin. Mechanical tests on eight hybrid beams were performed

Thomas Keller; Erika Schaumann; Till Vallée

2007-01-01

67

The growth of a c-axis highly oriented sandwiched TiO2 film with superhydrophilic properties without UV irradiation on SnO:F substrate  

Microsoft Academic Search

A c-axis highly oriented sandwiched film composed of single-crystalline rutile TiO2 on SnO:F (FTO) substrate was fabricated by a simple hydrothermal technique. The sandwich structure of the TiO2 film was found to be constructed by two layers of TiO2 nanorods, which grew towards both directions of the bulk solution and the substrate, respectively. One TiO2 nanoparticle interlayer between them acted

Yangang Han; Gang Wu; Mang Wang; Hongzheng Chen

2009-01-01

68

A Study for the Characteristic Changes Under the Repeated Thermal Exposure in the Process of Repairing Aircraft Sandwich Structures  

Microsoft Academic Search

Delamination can be observed in the sound areas during and\\/or after a couple times exposure to the elevated curing temperature due to the repeated repair condition. This study was conducted for checking the degree of degradation of properties of the cured parts and delamination between skin prepreg and honeycomb core. Specimens with glass honeycomb sandwich construction and glass\\/epoxy prepreg were

Yun Hae Kim; Joong Won Han; Don Won Kim; Byung Keun Choi; R. Murakami

2003-01-01

69

Optimization of composite sandwich cover panels subjected to compressive loadings  

NASA Technical Reports Server (NTRS)

An analysis and design method is presented for the design of composite sandwich cover panels that includes transverse shear effects and damage tolerance considerations. This method is incorporated into an optimization program called SANDOP (SANDwich OPtimization). SANDOP is used in the present study to design optimized composite sandwich cover panels for transport aircraft wing applications as a demonstration of its capabilities. The results of this design study indicate that optimized composite sandwich cover panels have approximately the same structural efficiency as stiffened composite cover panels designed to identical constraints. Results indicate that inplane stiffness requirements have a large effect on the weight of these composite sandwich cover panels at higher load levels. Increasing the maximum allowable strain and the upper percentage limit of the 0 degree and plus or minus 45 degree plies can yield significant weight savings. The results show that the structural efficiency of these optimized composite sandwich cover panels is relatively insensitive to changes in core density.

Cruz, Juan R.

1991-01-01

70

ELECTROCATALYTIC AND ANTIBACTERIAL APPLICATIONS OF SANDWICH TYPE POLYOXOMETALATES .  

E-print Network

??The primary goal of this dissertation is to study the structure-property relationship of sandwich type polyoxometalates and to employ these versatile molecules in electrocatalytic applications… (more)

Sankarraj, Anand

2008-01-01

71

Buckling Analysis of Debonded Sandwich Panel Under Compression  

NASA Technical Reports Server (NTRS)

A sandwich panel with initial through-the-width debonds is analyzed to study the buckling of its faceskin when subject to an in-plane compressive load. The debonded faceskin is modeled as a beam on a Winkler elastic foundation in which the springs of the elastic foundation represent the sandwich foam. The Rayleigh-Ritz and finite-difference methods are used to predict the critical buckling load for various debond lengths and stiffnesses of the sandwich foam. The accuracy of the methods is assessed with a plane-strain finite-element analysis. Results indicate that the elastic foundation approach underpredicts buckling loads for sandwich panels with isotropic foam cores.

Sleight, David W.; Wang, John T.

1995-01-01

72

CFRP sandwiched facesheets inspected by pulsed thermography  

NASA Astrophysics Data System (ADS)

Carbon fiber reinforced polymer (CFRP) has been always used in aerospace, Sandwiched structures composed by a honeycomb core between two multi-layer CFRP facesheets are very common on aerospace parts. As to the application of the CFRP sandwiched facesheets is extended, The demand for quality control of CFRP sandwiched composites is increasing, Infrared thermography is one of several non-destructive testing techniques which can be used for defect detection in aircraft materials such as carbon-fibre-reinforced composites. Infrared thermography can be potentially useful, as it is quick, real time, non-contact and can examine over a relatively large area in one inspection procedure. The technique is based on heating the sample surface with different heat sources and monitoring the surface temperature of the sample with an IR camera, any abnormal behavior of the surface temperature distribution indicates the subsurface defect. This kind of structure is normally affected by anomalies such as delaminations, disbonding, water ingressing to the core. in this paper, several different kinds of defects which are of various size and depth below the test surface are planted in the CFRP composites, the Teflon inserts between the plies in the facesheet represents the delaminations, the Teflon inserts between the inner facesheet and adhensive or between adhensive and core are simulated disbonding in the composites, they are all tested by pulsed thermography, meanwhile, these samples are also inspected by ultrasonic testing, compare with each characteristic and the results got by these two different methods, it shows that pulsed thermography is an effective nondestructive technique for inspecting CFRP composites.

Li, Huijuan; Huo, Yan; Cai, Liangxu; Huang, Zhenhua

2010-10-01

73

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

74

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

75

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

NASA Technical Reports Server (NTRS)

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 922 K (1200 F). 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.

1982-01-01

76

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

NASA Technical Reports Server (NTRS)

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.

1983-01-01

77

Modeling of Sandwich Sheets with Metallic Foam  

SciTech Connect

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

2011-08-22

78

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

79

Finite Element Modeling of the Buckling Response of Sandwich Panels  

NASA Technical Reports Server (NTRS)

A comparative study of different modeling approaches for predicting sandwich panel buckling response is described. The study considers sandwich panels with anisotropic face sheets and a very thick core. Results from conventional analytical solutions for sandwich panel overall buckling and face-sheet-wrinkling type modes are compared with solutions obtained using different finite element modeling approaches. Finite element solutions are obtained using layered shell element models, with and without transverse shear flexibility, layered shell/solid element models, with shell elements for the face sheets and solid elements for the core, and sandwich models using a recently developed specialty sandwich element. Convergence characteristics of the shell/solid and sandwich element modeling approaches with respect to in-plane and through-the-thickness discretization, are demonstrated. Results of the study indicate that the specialty sandwich element provides an accurate and effective modeling approach for predicting both overall and localized sandwich panel buckling response. Furthermore, results indicate that anisotropy of the face sheets, along with the ratio of principle elastic moduli, affect the buckling response and these effects may not be represented accurately by analytical solutions. Modeling recommendations are also provided.

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

2002-01-01

80

Indentation study of foam core sandwich composite panels  

Microsoft Academic Search

Due to their high stiffness and strength to weight ratios, composite sandwich structures have proven their usefulness in a large number of applications in various technical fields, especially in aeronautics, automotive and civil engineering. One of the main drawbacks of sandwich structures is the loss of load caring capacity due to indentation damages. The purpose of the present work is

V. Rizov; A. Shipsha; D. Zenkert

2005-01-01

81

Structural performance of metallic sandwich beams with hollow truss cores  

E-print Network

of sandwich beams with hollow truss lattice cores made from a ductile stainless steel. The trusses the temperature distribution and increasing the average tem- perature difference at the interface between core relative density. The present study explores the structural characteristics of metallic sandwich

Wadley, Haydn

82

Ruthenium Half-Sandwich Complexes as Protein Kinase Inhibitors: An  

E-print Network

Ruthenium Half-Sandwich Complexes as Protein Kinase Inhibitors: An N-Succinimidyl Ester for Rapid@sas.upenn.edu Received August 22, 2006 ABSTRACT Cyclopentadienyl half-sandwich ruthenium complexes have been demonstrated-chelating pyridocarbazole ligand, whereas the carbohydrate is replaced by a ruthenium fragment. The crystal structures

Meggers, Eric

83

Numerical analysis of impact-damaged sandwich composites  

Microsoft Academic Search

Sandwich structures are used in a wide variety of structural applications due to their relative advantages over other conventional structural materials in terms of improved stability, weight savings, and ease of manufacture and repair. Foreign object impact damage in sandwich composites can result in localized damage to the facings, core, and core-facing interface. Such damage may result in drastic reductions

Youngkeun Hwang

2003-01-01

84

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

2014-04-01

85

A Sandwich Interface Dynamo: Linear Dynamo Waves in the Sun  

Microsoft Academic Search

The existence of the solar tachocline inferred from helioseismology leads to the concept of an interface dynamo. The tachocline, where the strong toroidal magnetic field is generated and stored, is sandwiched between and magnetically coupled to the radiative interior and the overlying convection zone. We investigate a linear sandwich interface dynamo in Cartesian geometry. The dynamo model consists of four

K. Zhang; X. Liao; G. Schubert

2004-01-01

86

An effective design procedure for A-Sandwich radome  

Microsoft Academic Search

This paper proposes a simple design equation for A-sandwich radome design. Operating frequency and transmittance are input parameters for the design equation. For a given design specifications to achieve appropriate performance with A-sandwich radome, tedious calculations must be carried out to extract key material and structural parameters. This letter shows that when material constant and thickness of skin of radome

Kyung-Won Lee; Yeong-Chul Chung; Ic-Pyo Hong; Jong-Gwan Yook

2010-01-01

87

Stability design of honeycomb sandwich radome with asymmetric shape  

Microsoft Academic Search

The die radome, which is made of honeycomb sandwich structure, should be entirely refitted, for a big electronic observation facility is being fixed at the head section of an aircraft. In this work, the stability design of honeycomb sandwich radome is investigated. Initially, a local buckling failure is observed in the refitted radome during the preliminary calculation. Then design improvements

P. Y. Wang; F. S. Wang; Y. P. Dong; Z. F. Yue

2011-01-01

88

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

89

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

NASA Astrophysics Data System (ADS)

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

Chachra, Ricky

90

Compressive Strength of Stainless-Steel Sandwiches at Elevated Temperatures  

NASA Technical Reports Server (NTRS)

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

Mathauser, Eldon E.; Pride, Richard A.

1959-01-01

91

Structural properties of superplastically formed/diffusion-bonded orthogonally corrugated core sandwich plates  

NASA Technical Reports Server (NTRS)

This paper describes a new superplastically formed/diffusion-bonded (SPF/DB) orthogonally corrugated sandwich structure, and presents formulae and the associated plots for evaluating the effective elastic constants for the core of this new sandwich structure. Comparison of structural properties of this new sandwich structure with the conventional honeycomb core sandwich structure was made under the condition of equal sandwich density. It was found that the SPF/DB orthogonally corrugated sandwich core has higher transverse shear stiffness than the conventional honeycomb sandwich core. However, the former has lower stiffness in the sandwich core thickness direction than the latter.

Ko, W. L.

1980-01-01

92

Vibration and formability characteristics of aluminum-polymer sandwich materials  

NASA Astrophysics Data System (ADS)

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

Somayajulu, Thamma S. V.

93

Blast resistance of prismatic sandwich structures  

NASA Astrophysics Data System (ADS)

Metallic sandwich panels have emerged as candidate blast resistant structures that can be tailored to contain damage from impulsive loads of the type typically generated by explosives. When such panels are impulsively loaded, the stresses imposed by the core on the front face, as well as those transmitted through the core, govern the response metrics: especially the center displacement, the resistance to tearing and the loads transmitted to the supports. Prismatic cores such as I-, X-, Y- and Z- cores differ from other cores, such as foams and trusses, in that they do not exhibit constant dynamic crush strength, enabling collapse to occur in a controlled manner. Establishing relationships between core topology crushing response and panel performance is one of the major goals of this research. For this purpose a gas gun instrumented with high speed photography and direct impact Hopkinson pressure bar was built and used to perform laboratory scale high-speed impact tests. Samples of representative prismatic core unit cells were manufactured and tested in compression at axial velocities ranging from quasi-static to 200m/s. The dynamic strength and deformation (buckling) were measured and used to calibrate the imperfections in a finite element model. The model was then used to validate a constitutive model that can be used to predict the blast resistance of prismatic sandwich structures. This research identifies a simple dual level dynamic strength as a common response in metallic prismatic cores. This is due to the dominant effect of plastic shock generated by dynamic loading. Furthermore, it justifies the use of a simple dynamic axial compression test for calibration of the dynamic strength of the core. An analytical model that accounts for the shock effects in a homogenized core and embodies the dual-level dynamic strength is presented. It is shown to capture the experimental observations and simulated results with acceptable fidelity. This model provides the basis for a constitutive model that can be used to understand the response of sandwich plates subject to impulsive loads.

Ferri, Enrico

94

Impact damage in aircraft composite sandwich panels  

NASA Astrophysics Data System (ADS)

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

Mordasky, Matthew D.

95

Seismic load tests on reinforced concrete beam-column sandwich joints with strengthening measures  

NASA Astrophysics Data System (ADS)

Reinforced concrete high-rise buildings with high strength concrete (HSC) column and normal strength concrete (NSC) floor are popular nowadays. For these structures, it is ineffective to construct beam-column joint with high strength concrete. So beam-column joints with normal strength concrete attract abundant attention and are strongly recommended in china recent years. In this paper, we refer to this type of joints as sandwich joints. In order to improve seismic behavior of sandwich joints with high stress, strengthening measures including addition of vertical dowels, addition of diagonal bars, and enhancement of joint constraint were proposed to apply to engineering practice recent years. In this paper, 6 full scale sandwich joint specimens were test under cyclic load to investigate the validity of strengthening measures. Tested specimens were consist of 1 specimen with additional vertical dowels, 2 specimens with additional diagonal bars, and 1 specimen with additional lateral beams, compared with 2 specimens without strengthening measures. Integrated seismic performances of these specimens were studied, such as load resistance behavior, deflection performance, ductility, energy dissipation behavior, beam bars anchorage capacity and so on. Based on the experimental results, the effect and mechanical behavior of strengthening measures were analyzed.

Yang, Zhi-Hong; Li, Ying-Min; Liu, Jian-Wei

2009-12-01

96

Seismic load tests on reinforced concrete beam-column sandwich joints with strengthening measures  

NASA Astrophysics Data System (ADS)

Reinforced concrete high-rise buildings with high strength concrete (HSC) column and normal strength concrete (NSC) floor are popular nowadays. For these structures, it is ineffective to construct beam-column joint with high strength concrete. So beam-column joints with normal strength concrete attract abundant attention and are strongly recommended in china recent years. In this paper, we refer to this type of joints as sandwich joints. In order to improve seismic behavior of sandwich joints with high stress, strengthening measures including addition of vertical dowels, addition of diagonal bars, and enhancement of joint constraint were proposed to apply to engineering practice recent years. In this paper, 6 full scale sandwich joint specimens were test under cyclic load to investigate the validity of strengthening measures. Tested specimens were consist of 1 specimen with additional vertical dowels, 2 specimens with additional diagonal bars, and 1 specimen with additional lateral beams, compared with 2 specimens without strengthening measures. Integrated seismic performances of these specimens were studied, such as load resistance behavior, deflection performance, ductility, energy dissipation behavior, beam bars anchorage capacity and so on. Based on the experimental results, the effect and mechanical behavior of strengthening measures were analyzed.

Yang, Zhi-hong; Li, Ying-min; Liu, Jian-wei

2010-03-01

97

Formability of Aluminum 5182-Polypropylene Sandwich Sheet for Automotive Application  

NASA Astrophysics Data System (ADS)

The AA5182/polypropylene/AA5182 (AA/PP/AA) sandwich sheet is the material fabricated by adhering two aluminum skins to one polypropylene core. When it has the same flexural rigidity as a steel sheet, it is 65% lighter than the steel sheet and 30% lighter than an aluminum alloy sheet. Therefore, it is notified exclusively as good substitutive materials for a steel body to improve the fuel efficiency. Through AA/PP/AA sandwich sheet, however, it has relatively lower formability than that of the steel sheet for automotive application. In this study, we developed formability evaluation techniques in order to apply AA/PP/AA sandwich sheet for an automotive parts. For this purpose, newly adopting formability evaluations (using limit dome height and plane strain test) were carried out in order to secure the fundamental data for the measurement of sheet metal forming and the establishment of optimum forming conditions of the sandwich sheet. The results showed that there were in good agreements between the old formability evaluation method and the new one which was more simplified than that of the old one. From the results of these formability evaluations, the formability of sandwich sheet was higher than that of aluminum alloy sheet alone which was the skin component for the sandwich sheet. In addition, it was found that sandwich sheet could reduce the weight and could have the same flexural rigidity simultaneously when it was compared to the automotive steel sheet.

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

98

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

99

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

ERIC Educational Resources Information Center

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

Roberts, Tim S.

2004-01-01

100

Debonding detection of honeycomb sandwich structures using frequency response functions  

NASA Astrophysics Data System (ADS)

A vibration-based non-destructive evaluation (NDE) method is proposed to determine the location and size of debonding in honeycomb sandwich beams. Although most of the existing vibration-based NDE methods need many measurement points, the method proposed here only utilizes the frequency response function (FRF) measured at one point. A parameterized damaged Timoshenko beam model is developed with the method of reverberation-ray matrix (MRRM) for the first time, and combined with the genetic algorithm (GA) to inverse the damage parameters from the measured FRF. The detection of a honeycomb sandwich beam can be divided into two steps: (1) identifying the equivalent elastic moduli and other parameters of the intact sandwich beam. (2) Identifying the debonding location and size of the damaged sandwich beam with the predetermined parameters. It is demonstrated experimentally that the method can inverse damage parameters with acceptable precision.

Zhu, Kaige; Chen, Mingji; Lu, Qiuhai; Wang, Bo; Fang, Daining

2014-10-01

101

Effects of bonding stiffness on thermal stresses in sandwich panels  

NASA Astrophysics Data System (ADS)

Sandwich panels made of thin skins and a lightweight core expand and/or bow when subjected to temperature changes. The significance of induced thermal stresses in the panels depends on material properties. The effects of bonding layers on these stresses were not investigated in available works on the structural analysis of sandwich panels. This paper presents elasticity solutions for thermal stresses in sandwich panels with interlayer slip. The effects of finite bonding stiffnesses on the structural behavior of the panels are investigated. The numerical results show that the bonding stiffness, up to a certain level, has a strong effect on panel structural response. The answer to what constitutes perfect bonding is best answered in terms of the ratio of the core stiffness to the bonding stiffness. A heat chamber is designed and used to test sandwich specimens under different temperature changes. The experimental values for normal stresses in the skins are in good agreement with the present theory.

Hussein, R.; Fazio, P.; Ha, K.

1992-10-01

102

Magnetorheological elastomer-based smart sandwich beams with nonconductive skins  

Microsoft Academic Search

The field-dependent dynamic flexural rigidity of a simply supported sandwich beam with a soft core composed of a magnetorheological elastomer (MRE) part and non-MRE parts is studied in this paper. The skins of the sandwich beam are nonconductive such that there are no magnetoelastic loads applied to the skins during vibration. The orientation of the chain-like structures inside the MRE

G. Y. Zhou; Q. Wang

2005-01-01

103

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

104

Gold nanoparticles based sandwich electrochemical immunosensor.  

PubMed

In this report we have used gold nanoparticles (AuNPs) to covalently attach an antibody (Ab(1)) using a spacer arm. The AuNPs/Ab(1) modified gold electrode was used for a sandwich electrochemical immunoassay. The detection was done using cyclic voltammetry and impedance measurements using Horse Radish Peroxidase (HRP) as enzyme label on secondary antibody (Ab(2)) and 3,3', 5,5'-tertramethyl benzidine (TMB) as an electroactive dye. The cyclic voltammetric experiments showed three clear peaks at potentials 154 mV, -33 mV and -156 mV. There was an increase in the both anodic and cathodic current values for the peak at potential -33 mV, when H2O2 was added and the other peaks observed at potential 154 mV and -156 mV resulted due to the oxidation and reduction of TMB. The detection limit of this electrode was 2 ng/mL or 10 pg/5 microL of the analyte. The electrochemical impedance spectroscopy studies demonstrate that the formation of antigen-antibody complexes increases the series resistance and thus confirms the assembly on the electrode. This study showed that AuNPs was efficient in preserving the activity and orientation of the antibody and it can form a major platform in many clinical immunoassays. PMID:20171869

Ahirwal, Gautham Kumar; Mitra, Chanchal K

2010-05-15

105

Dynamic characterization of a laminated composite magnetorheological fluid sandwich plate  

NASA Astrophysics Data System (ADS)

This study investigates the dynamic properties of a laminated composite magnetorheological (MR) fluid sandwich plate. The governing differential equations of motion of a sandwich plate embedding a MR fluid layer as the core layer and laminated composite plates as the face layers are presented in a finite element formulation. The validity of the developed finite element formulation is demonstrated by comparing the results in terms of the natural frequencies derived from the present finite element formulation with those in the available literature. Various parametric studies are also performed to investigate the effect of a magnetic field on the variation of the natural frequencies and loss factors of the MR fluid composite sandwich plate under various boundary conditions. Furthermore, the effect of the thickness of the MR fluid layer and the ply orientation of the composite face layers on the variation of the natural frequencies and loss factors are studied. The free vibration mode shapes under various boundary conditions of a MR fluid laminated composite sandwich plate are also presented. The forced vibration response of a MR fluid composite plate is investigated to study the dynamic response of the sandwich plate under harmonic force excitations in various magnetic fields. The study suggests that the natural frequency increases with increasing magnetic field, irrespective of the boundary conditions. The reduction in peak deflection at each mode under a harmonic excitation force with variation of the applied magnetic field shows the effectiveness of the MR fluid layer in reducing the vibration amplitude of the composite sandwich plate.

Manoharan, R.; Vasudevan, R.; Jeevanantham, A. K.

2014-02-01

106

The sandwich model: the 'music and dance' of therapeutic action.  

PubMed

My premise is that a 'layered' approach is necessary to understand the process of exchanges that result in therapeutic change. I imagine these processes occurring in three layers - although the number of domains in which change is taking place is actually infinite - such as in a sandwich. The top layer, or top slice of bread of the sandwich, represents a broad view of the change process; it is non-linear and includes the feature of uncertainty, a general principle of dynamic systems theory. The middle layer, or the meat of the sandwich, is explained by theories that are immediately and clinically useful to a therapist, such as psychoanalytic theories. These are primarily linear theories and use language and symbols to 'tell a story of what happened'. The bottom layer, or bottom slice of bread of the sandwich, is the micro-process; this layer includes the moment-to-moment patterns of coordinated rhythms that both communicate meaning and provide the essential scaffold for all higher-level change processes. The micro-process also requires a non-linear theory to make sense of its variability and emergent properties. Taking a bite out of the sandwich will include a 'polysemic bundle of communicative behaviors' (Harrison and Tronick, 2011). I will illustrate the 'sandwich model' with the clinical case of the analytic treatment of a 5 year-old boy. PMID:24354856

Harrison, Alexandra M

2014-04-01

107

Optimization of composite sandwich cover panels subjected to compressive loadings  

NASA Technical Reports Server (NTRS)

An analysis and design method is presented for the design of composite sandwich cover panels that include the transverse shear effects and damage tolerance considerations. This method is incorporated into a sandwich optimization computer program entitled SANDOP. As a demonstration of its capabilities, SANDOP is used in the present study to design optimized composite sandwich cover panels for for transport aircraft wing applications. The results of this design study indicate that optimized composite sandwich cover panels have approximately the same structural efficiency as stiffened composite cover panels designed to satisfy individual constraints. The results also indicate that inplane stiffness requirements have a large effect on the weight of these composite sandwich cover panels at higher load levels. Increasing the maximum allowable strain and the upper percentage limit of the 0 degree and +/- 45 degree plies can yield significant weight savings. The results show that the structural efficiency of these optimized composite sandwich cover panels is relatively insensitive to changes in core density. Thus, core density should be chosen by criteria other than minimum weight (e.g., damage tolerance, ease of manufacture, etc.).

Cruz, Juan R.

1991-01-01

108

Enhanced Antibacterial Activity of Silver Nanoparticles/Halloysite Nanotubes/Graphene Nanocomposites with Sandwich-Like Structure  

NASA Astrophysics Data System (ADS)

A sandwich-like antibacterial reagent (Ag/HNTs/rGO) was constructed through the direct growth of silver nanoparticles on the surface graphene-based HNTs nanosheets. Herein, various nanomaterials were combined by adhesion effect of DOPA after self-polymerization. Ag/HNTs/rGO posses enhanced antibacterial ability against E. coli and S. aureus compared with individual silver nanoparticles, rGO nanosheets or their nanocomposites.

Yu, Liang; Zhang, Yatao; Zhang, Bing; Liu, Jindun

2014-04-01

109

Enhanced Antibacterial Activity of Silver Nanoparticles/Halloysite Nanotubes/Graphene Nanocomposites with Sandwich-Like Structure  

PubMed Central

A sandwich-like antibacterial reagent (Ag/HNTs/rGO) was constructed through the direct growth of silver nanoparticles on the surface graphene-based HNTs nanosheets. Herein, various nanomaterials were combined by adhesion effect of DOPA after self-polymerization. Ag/HNTs/rGO posses enhanced antibacterial ability against E. coli and S. aureus compared with individual silver nanoparticles, rGO nanosheets or their nanocomposites. PMID:24722502

Yu, Liang; Zhang, Yatao; Zhang, Bing; Liu, Jindun

2014-01-01

110

Formation and electronic structures of organoeuropium sandwich nanowires.  

PubMed

Organoeuropium sandwich clusters, comprising europium (Eu) and 1,3,5,7-cyclooctatetraene (COT) (Eu(n)(COT)(m)), were produced in the gas phase using a laser vaporization synthesis method. Photoionization mass spectra revealed an exclusive Eu(n)(COT)(m) formation with three compositions: m = n + 1, m = n, and m = n - 1, which, we propose, correspond to full-sandwich, half-sandwich, and inverted-sandwich structures, respectively. The charge distributions, metal-ligand bonding characteristics, and electronic structures of the clusters were comprehensively investigated by photoionization measurements of Eu(n)(COT)(m) neutrals and by photoelectron spectroscopy of Eu(n)(COT)(m)(-) and isoelectronic Ba(n)(COT)(m)(-) anions. The results confirmed that (1) highly ionic metal-ligand bonding is formed between Eu(2+) and COT(2-) within the sandwich structure (at the termini, ionic forms are Eu(+) and COT(-)) and (2) size dependence of orbital energy can be explained by the Coulombic interaction of simple point charge models between the detaching electrons and dipoles/quadrupoles. When the terminus of the sandwich clusters is Eu(2+), COT(2-), or Eu(0), the orbital energy of the electron detachment channel at the opposite terminus strongly depends on the cluster size. In this case, the molecular stack behaves as a one-dimensionally aligned dipole; otherwise, it behaves as a quadrupole, and the relationship between cluster size and electron detachment energy is much weaker. The study also reports on the 4f orbital energy in Eu ions and the formation mechanism of organoeuropium sandwich nanowires up to 12 nm in length. The nanowires are formed by successive charge transfer at the terminal part, Eu(+) and COT(-), which reduces the ionization energy and increases the electron affinity, respectively. PMID:24725191

Hosoya, Natsuki; Takegami, Ryuta; Suzumura, Jun-ichi; Yada, Keizo; Miyajima, Ken; Mitsui, Masaaki; Knickelbein, Mark B; Yabushita, Satoshi; Nakajima, Atsushi

2014-09-18

111

Numerical analysis of impact-damaged sandwich composites  

NASA Astrophysics Data System (ADS)

Sandwich structures are used in a wide variety of structural applications due to their relative advantages over other conventional structural materials in terms of improved stability, weight savings, and ease of manufacture and repair. Foreign object impact damage in sandwich composites can result in localized damage to the facings, core, and core-facing interface. Such damage may result in drastic reductions in composite strength, elastic moduli, and durability and damage tolerance characteristics. In this study, physically-motivated numerical models have been developed for predicting the residual strength of impact-damaged sandwich composites comprised of woven-fabric graphite-epoxy facesheets and Nomex honeycomb cores subjected to compression-after-impact loading. Results from non-destructive inspection and destructive sectioning of damaged sandwich panels were used to establish initial conditions for damage (residual facesheet indentation, core crush dimension, etc.) in the numerical analysis. Honeycomb core crush test results were used to establish the nonlinear constitutive behavior for the Nomex core. The influence of initial facesheet property degradation and progressive loss of facesheet structural integrity on the residual strength of impact-damaged sandwich panels was examined. The influence of damage of various types and sizes, specimen geometry, support boundary conditions, and variable material properties on the estimated residual strength is discussed. Facesheet strains from material and geometric nonlinear finite element analyses correlated relatively well with experimentally determined values. Moreover, numerical predictions of residual strength are consistent with experimental observations. Using a methodology similar to that presented in this work, it may be possible to develop robust residual strength estimates for complex sandwich composite structural components with varying levels of in-service damage. Such studies may facilitate sandwich panel design by providing insight into relationships between material configuration and damage progression that lead to improved damage tolerance characteristics.

Hwang, Youngkeun

112

Impact damage analysis of balsawood sandwich composite materials  

NASA Astrophysics Data System (ADS)

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

Abdalslam, Suof Omran

113

Composite panels based on woven sandwich-fabric preforms  

NASA Astrophysics Data System (ADS)

A new type of sandwich material was investigated, based on woven sandwich-fabric preforms. Because of the integrally woven nature of the sandwich-fabric the skin-core debonding resistance of panels and structures based on the preform is very high. As the sandwich-fabrics are produced by a large scale textile weaving process (velvet weaving or distance weaving) and already a preform of a sandwich is available, the cost of the final panel or structure can potentially stay limited. Most attention in this work is focussed on the mechanical performance of sandwich-fabric panels. The high skin-core debonding resistance was verified and also indications were found of a good damage tolerance. Both unfoamed and foamed panels were evaluated and compared with existing sandwich panels. Microstructural parameters investigated for unfoamed cores are pile length, pile density, woven pile angles, degree of pile stretching, tilt angles of the piles induced during panel production and resin content and distribution. For foamed panels it is especially the foam density which has an important influence. There appears to be a synergistic effect between piles and foam in the sandwich core, leading to very acceptable mechanical properties. For panels for (semi) structural applications, foaming is almost indispensable once the panel thickness is higher than about 15 mm. To understand the behaviour of foamed panels, attention was paid to the modelling of the mechanics of pure foam. The foam microstructure was modelled with the model of an anisotropic tetrakaidecahedron. The mechanical properties of unfoamed panels were modelled with the help of finite elements. A detailed geometrical description of the core layout was made which was incorporated into a preprocessing program for a finite element code. Attention is paid to the production of panels based on the woven preforms. A newly developed Adhesive Foil Stretching process was investigated. Also the foaming of panels was studied. A lot of attention was paid to a special application in the field of structural damping, where sandwich-fabric panels could be used as spacer in a constrained layer application. The vibrations and damping were modelled with the help of finite elements.

van Vuure, Aart Willem

114

Sound Transmission through Two Concentric Cylindrical Sandwich Shells  

NASA Technical Reports Server (NTRS)

This paper solves the problem of sound transmission through a system of two infinite concentric cylindrical sandwich shells. The shells are surrounded by external and internal fluid media and there is fluid (air) in the annular space between them. An oblique plane sound wave is incident upon the surface of the outer shell. A uniform flow is moving with a constant velocity in the external fluid medium. Classical thin shell theory is applied to the inner shell and first-order shear deformation theory is applied to the outer shell. A closed form for transmission loss is derived based on modal analysis. Investigations have been made for the impedance of both shells and the transmission loss through the shells from the exterior into the interior. Results are compared for double sandwich shells and single sandwich shells. This study shows that: (1) the impedance of the inner shell is much smaller than that of the outer shell so that the transmission loss is almost the same in both the annular space and the interior cavity of the shells; (2) the two concentric sandwich shells can produce an appreciable increase of transmission loss over single sandwich shells especially in the high frequency range; and (3) design guidelines may be derived with respect to the noise reduction requirement and the pressure in the annular space at a mid-frequency range.

Tang, Yvette Y.; Silcox, Richard J.; Robinson, Jay H.

1996-01-01

115

Actively cooled plate fin sandwich structural panels for hypersonic aircraft  

NASA Technical Reports Server (NTRS)

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

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

1979-01-01

116

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

117

Wave propagation in sandwich panels with a poroelastic core.  

PubMed

Wave propagation in sandwich panels with a poroelastic core, which is modeled by Biot's theory, is investigated using the waveguide finite element method. A waveguide poroelastic element is developed based on a displacement-pressure weak form. The dispersion curves of the sandwich panel are first identified as propagating or evanescent waves by varying the damping in the panel, and wave characteristics are analyzed by examining their motions. The energy distributions are calculated to identify the dominant motions. Simplified analytical models are also devised to show the main physics of the corresponding waves. This wave propagation analysis provides insight into the vibro-acoustic behavior of sandwich panels lined with elastic porous materials. PMID:24815252

Liu, Hao; Finnveden, Svante; Barbagallo, Mathias; Arteaga, Ines Lopez

2014-05-01

118

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

119

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.

120

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

E-print Network

sandwich structures were fabricated by shrink-fitting precision-ground prisms of alumina (CoorsTek grade AD 995) with triangular, trapezoidal or rectangular cross-sections into the voids of extruded sandwich

Wadley, Haydn

121

PHOTOVOLTAIC PROPERTIES OF METAL-MEROCYANINE-TiO2 SANDWICH CELLS  

E-print Network

photovoltaic- mode 1- 11 . It typically involves sandwiching a thin (Photovoltaic Properties of Metal-Merocyanine-Ti0 2 Sandwich Cells By Terje'Asbjorn Skotheim Abstract Photocurrent generation in thin

Skotheim, Terje Asbjorn

2011-01-01

122

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

123

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

NASA Technical Reports Server (NTRS)

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

McGowan, David M.; Ambur, Damodar R.

1997-01-01

124

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

E-print Network

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

125

Response of metallic pyramidal lattice core sandwich panels to high intensity impulsive loading in air  

E-print Network

Response of metallic pyramidal lattice core sandwich panels to high intensity impulsive loading blast Fluidestructure interaction Pyramidal core Sandwich panels a b s t r a c t Small scale explosive loading of sandwich panels with low relative density pyramidal lattice cores has been used to study

Hutchinson, John W.

126

Detection of entrapped moisture in honeycomb sandwich structures  

NASA Technical Reports Server (NTRS)

Thermal neutron moisture detection system detects entrapped moisture in intercellular areas of bonded honeycomb sandwich structures. A radium/beryllium fast neutron source bombards a specimen. The emitted thermal neutrons from the target nucleus are detected and counted by a boron trifluoride thermal neutron detector.

Hallmark, W. B.

1967-01-01

127

Gourmet Sandwiches Flying Cow Club $5.50  

E-print Network

Gourmet Sandwiches Flying Cow Club $5.50 Turkey, ham bacon, lettuce, tomatoes, onions, cheese, mayo Salad $5.00 Albacore tuna, lettuce, tomatoes, pickles & onions on sliced whole wheat bread. Calories 600, tomatoes, pickles, red sliced onions, onions, black olives & mushrooms in a tortilla Calories 327, Fat 13 g

Oklahoma, University of

128

STUDIO SULLA PROPAGAZIONE DI CRICCHE IN PANNELLI SANDWICH (AL NOMEX)  

Microsoft Academic Search

Sommario In questo lavoro viene analizzato il comportamento Damage Tolerant di un pannello a costruzione sandwich in Alluminio-Nomex utilizzato per fusoliere di elicotteri e soggetto a carico di taglio. Il provino è stato testato in una cornice dedicata per trasmettere un carico pulsante di puro taglio. Una cricca artificiale è stata realizzata al centro del pannello su una delle pelli

M. Giglio; A. Manes

129

Damage assessment and damage tolerance of FRP sandwich structures  

Microsoft Academic Search

A review is made of approaches to the assessment of production defects and in-service damage for sandwich structures having fibre reinforced polymer (FRP) face sheets. Particular attention is paid to the following aspects: • The range of defect and damage types that may have to be considered. • Relevant defect and damage models and the failure mechanisms these take account

Brian Hayman

130

Damage Tolerance of Sandwich Plates with Debonded Face Sheets  

NASA Technical Reports Server (NTRS)

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

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

1998-01-01

131

In vivo chondrogenesis in collagen sponge sandwiched by perichondrium  

Microsoft Academic Search

In order to increase the cartilage synthesis of the perichondrium, we combined auricular perichondrium with a collagen sponge as a template (perichondrium-sandwiched collagen sponge) and implanted the assembly as an autograft into the back of rabbits. Microscopic examination revealed that cartilaginous tissue was produced in the collagen sponge and chondrosynthesis was accelerated in the collagen sponge implants in comparison with

Kazuya Matsuda; Naoko Nagasawa; Shigehiko Suzuki; Nobuhiko Isshiki; Yoshito Ikada

1996-01-01

132

Methods for Assessing Honeycomb Sandwich Panel Wrinkling Failures  

NASA Technical Reports Server (NTRS)

Efficient closed-form methods for predicting the facesheet wrinkling failure mode in sandwich panels are assessed. Comparisons were made with finite element model predictions for facesheet wrinkling, and a validated closed-form method was implemented in the HyperSizer structure sizing software.

Zalewski, Bart F.; Dial, William B.; Bednarcyk, Brett A.

2012-01-01

133

Damage Tolerance of Sandwich Plates With Debonded Face Sheets  

NASA Technical Reports Server (NTRS)

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

Sankar, Bhavani V.

2001-01-01

134

Load characteristics of high power sandwich piezoelectric ultrasonic transducers  

Microsoft Academic Search

Based on the equivalent circuit theory, the load characteristics of high power piezoelectric ultrasonic sandwich transducers are studied. Two types of loads are studied. One is liquid load as in ultrasonic cleaning, and the other is solid load as in ultrasonic drilling and machining. The effect of load and structure of the transducer on the resonance frequency of the transducer

Lin Shuyu

2005-01-01

135

Load characteristics of high power sandwich piezoelectric ultrasonic transducers.  

PubMed

Based on the equivalent circuit theory, the load characteristics of high power piezoelectric ultrasonic sandwich transducers are studied. Two types of loads are studied. One is liquid load as in ultrasonic cleaning, and the other is solid load as in ultrasonic drilling and machining. The effect of load and structure of the transducer on the resonance frequency of the transducer is analyzed. It is shown that the effect of load on the resonance frequency of sandwich transducers with different structures is different. For liquid load as in ultrasonic cleaning, the effect of the load on the resonance frequency of the sandwich transducer with symmetrical structure is the largest. It is the smallest for the transducer with its displacement node in the back metal cylinder. For solid load as in ultrasonic drilling and machining, the effect of the load on the resonance frequency of the sandwich transducer with its displacement node in the front metal cylinder is the largest. It is also the smallest for the transducer with its displacement node in the back metal cylinder. On the other hand, for some applications, such as ultrasonic drilling, when the lateral dimension of the tool is much less than that of the transducer, its effect on the resonance frequency of the transducer is small. The conclusions are useful in designing vibrating systems for different ultrasonic applications. PMID:15737387

Shuyu, Lin

2005-03-01

136

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

137

The Impulse Response of Extruded Corrugated Core Aluminum Sandwich Structures  

E-print Network

The Impulse Response of Extruded Corrugated Core Aluminum Sandwich Structures A Thesis Presented of distributed impulse loads. However, under the highest intensity loading conditions, nodal failure bonded to the facesheet. The ability of this structure to mitigate distributed and localized impulsive

Wadley, Haydn

138

Modelling of lightweight sandwich shear diaphragms for dynamic analyses  

Microsoft Academic Search

A procedure interpreting the behaviour of screwed lightweight sandwich shear walls is presented in this paper. The study is part of a general research project aimed at the development of a suitable methodology of analysis, which should allow the effect of cladding panels on the structural response of steel frames to be properly accounted for. Firstly, the monotonic behaviour of

Gianfranco De Matteis; Raffaele Landolfo

2000-01-01

139

Stiff, Strong Splice For A Composite Sandwich Structure  

NASA Technical Reports Server (NTRS)

New type of splice for composite sandwich structure reduces peak shear stress in structure. Layers of alternating fiber orientation interposed between thin ears in adhesive joint. Developed for structural joint in spar of helicopter rotor blade, increases precision of control over thickness of adhesive at joint. Joint easy to make, requires no additional pieces, and adds little weight.

Schmaling, D.

1991-01-01

140

Composite Cocured Modular Eggcrate-Core Sandwich Structure  

NASA Technical Reports Server (NTRS)

Lightweight composite-material (e.g., graphite fiber/epoxy matrix) cocured sandwich panels with eggcratelike cores developed for use as principal components of optical benches and other structures that support precise optical instruments. Structures offer greater thermal and mechanical stability. Advantages include easier fabrication and better mechanical properties.

Magurany, Charles J.

1995-01-01

141

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

142

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

NASA Technical Reports Server (NTRS)

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.

1993-01-01

143

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

NASA Technical Reports Server (NTRS)

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

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

1989-01-01

144

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

NASA Technical Reports Server (NTRS)

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

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

1979-01-01

145

Bismaleimide resins for flame resistant honeycomb sandwich panels  

NASA Technical Reports Server (NTRS)

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

Stenzenberger, H. D.

1978-01-01

146

Laparoscopic Mesh Splenopexy (Sandwich Technique) for Wandering Spleen  

PubMed Central

Background: Wandering spleen is a rare clinical condition caused by incomplete fusion of the 4 primary splenic ligaments, allowing the spleen to be mobile within the abdomen, predisposing to splenic torsion along the vascular pedicle leading to splenomegaly and infarction, often diagnosed in an emergency setting. Methods: The wandering spleen diagnosis was achieved by ultrasound in our case. We successfully treated the patient with laparoscopic splenopexy because the size was almost normal, and no infarction or evidence of hypersplenism was present. We used the sandwich technique in which 2 meshes sandwich the spleen. Results: This technique was found to be highly satisfactory as a treatment for wandering spleen. The patient was discharged on the third postoperative day with no intra-operative or postoperative complications. Conclusion: Laparoscopy usually confirms the diagnosis.Recommended surgical procedures are splenopexy or splenectomy. Splenopexy is feasible, less invasive, and does not diminish splenic function. PMID:17761090

Palanivelu, Chinnusamy; Senthilkumar, Rangaswamy; Parthasarathi, Ramakrishnan; Kavalakat, Alfie J.

2007-01-01

147

Metal/dielectric/metal sandwich film for broadband reflection reduction  

PubMed Central

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

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

2013-01-01

148

Development of lightweight graphite/polyimide sandwich panels.  

NASA Technical Reports Server (NTRS)

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

Poesch, J. G.

1972-01-01

149

Superconducting critical currents in Nb-Cu-Nb sandwiches  

Microsoft Academic Search

A preparation method is presented for Nb-Cu-Nb sandwiches for proximity-effect measurements with a large junction area of about 150×150 µm and intermediate Cu layers of thicknesses between 0.2 and 1.5 µm. The thickness of the Nb layers is about 150 µm. These samples are used to study the dependence of the superconducting critical currentIc through the Cu layer as a

Hartwig Schlüter; Herbert C. Freyhardt

1985-01-01

150

Size Effect on Fracture of Composite and Sandwich Structures  

Microsoft Academic Search

\\u000a The objective of this article is to review the work performed on the scaling and size effect in the failure of composites,\\u000a foams and laminate—foam sandwiches. These materials exhibit quasibrittle behavior which is characterized by a fracture process\\u000a zone that is not negligible compared to the characteristic size of the structure. The mean size effect is found to be essentially

Emmanuel E. Gdoutos; Zden?k P. Bažant

2009-01-01

151

Astronaut Edwin Aldrin makes sandwich in zero gravity conditions  

NASA Technical Reports Server (NTRS)

Astronaut Edwin E. Aldrin Jr., Apollo 11 lunar module pilot, makes a sandwich in zero gravity conditions in this color reproduction taken from at TV transmission from the Apollo 11 spacecraft during its transearth journey home from the moon. When this picture was made, Apollo 11 was approximately 157,000 nautical miles from earth, traveling at a speed of about 4,300 feet per second.

1969-01-01

152

Structural behavior of FRP sandwich panels for bridge decks  

Microsoft Academic Search

This paper presents the analytical and experimental investigations performed to evaluate the structural behavior of Fiber-Reinforced\\u000a Polymer (FRP) Honeycomb Sandwich Panels (HCSPs) used for bridge decks. The analytical investigation includes modeling FRP\\u000a HCSPs using three Finite Element Models (FEM) and a simplified I-beam model. Comparing analysis results of the four models\\u000a against experimental data from literature indicated that the simplified

George Morcous; Yong Cho; Adel El-Safty; Genmiao Chen

2010-01-01

153

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

154

Making Three-Layer Solid Electrolyte/Electrode Sandwiches  

NASA Technical Reports Server (NTRS)

Tape-casting-and-sintering process joins two ceramic materials having widely different sintering temperatures into integral sandwich structure. Layers retain their identities, without migration of constituents. Used to make three-layer structure composed of outer porous layers of strontium-doped lanthanum manganite and inner dense layer of yttria-stabilized zirconia. Structures used to make electrolytic and fuels cells with solid electrolytes for use at high temperatures. Other potential applications include oxygen pumps and oxygen sensors.

Schroeder, James E.

1991-01-01

155

Size Effect on Fracture of Composite and Sandwich Structures  

NASA Astrophysics Data System (ADS)

The objective of this article is to review the work performed on the scaling and size effect in the failure of composites, foams and laminate—foam sandwiches. These materials exhibit quasibrittle behavior which is characterized by a fracture process zone that is not negligible compared to the characteristic size of the structure. The mean size effect is found to be essentially deterministic, caused by energy release due to stress redistribution. The chapter consists of six sections:After introduction, the second section deals with the size effect on the nominal strength of notched specimens of fiber composite laminates under tension. In the third section, the size effect of fiber—composite laminates on flexural strength is studied. The fourth section studies the effect of structure size on the nominal strength of fiber—polymer composites failing by propagation of a kink band with fiber microbuckling. The fifth section deals with the size effect of fracture of closed-cell polymeric foams. The sixth section analyzes the size effect on the compressive strength of sandwich panels subjected to double eccentric axial load and failing by propagation of a softening fracturing kink band. Finally, the seventh section shows that skin imperfections, considered to be proportional to the first eigenmode of wrinkling, lead to strong size dependence of the nominal strength of sandwich structures failing by skin wrinkling.

Gdoutos, Emmanuel E.; Bažant, Zden?k P.

156

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.

157

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

NASA Technical Reports Server (NTRS)

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

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

2004-01-01

158

The development and evaluation of advanced Kevlar sandwich structure for application to rotorcraft airframes  

NASA Astrophysics Data System (ADS)

The results of an evaluation of DuPont Kevlar-based material systems in sandwich structure designed for rotorcraft primary airframe structure are presented in this report. The focus of this work has been to evaluate the durability and compression strength of thin-gage Kevlar sandwich panels and investigate means of improvement. It was found that sandwich panels made with Kevlar 149 fibers can be as strong as Kevlar 49 structures but have reduced compression stiffness properties at typical operating strain levels. Thermal cycling was found to affect permeability but not strength in thin facesheet sandwich structure. Any increased permeability can be prevented with the use of an interleaf or surfacing plies. The surfacing plies investigated also had a beneficial effect on sandwich strength due to their stabilizing effect on the facesheet in compression. Finally, a previously developed model was used to analyze the residual strength of a sandwich panel after impact damage.

Minguet, Pierre; Llorente, Steven; Fay, Russell

1991-05-01

159

Vibrational analysis of rectangular sandwich plates resting on some elastic point supports  

SciTech Connect

An approximate solution of forced-vibration for rectangular sandwich plate resting on some elastic point supports is presented. The sandwich plate has thin, anisotropic composite laminated faces and a thick orthotropic core. The simplified sandwich plate model is used in the analysis. The governing equation of elastically point supported rectangular sandwich plate is obtained by using the Lagrange equation. The steady state response solution to a sinusoidally varying point force is also derived. The response curves of rectangular sandwich plates having CFRP laminated faces and aluminum honeycomb core is calculated. Application examples illustrate the effects of laminate lay-up of face sheets, core material properties and core thickness ratio on the vibration characteristics of rectangular sandwich plate.

Ichinomiya, Osamu; Maruyama, Koichi; Sekine, Kouji [Hokkaido Inst. of Tech., Sapporo (Japan). Dept. of Mechanical engineering

1995-11-01

160

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

161

Analysis of Vibrations and Energy Flows in Sandwich Plates Bearing Concentrated Masses and Spring-Like Inclusions in Heavy Fluid-Loading Conditions  

NASA Astrophysics Data System (ADS)

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 a compressible fluid which is bounded opposite to a plate side by a rigid baffle. The dispersion equation for a fluid-loaded sandwich plate is derived. The wave numbers (complex, pure real and pure imaginary) and relevant normal modes (both the travelling and the evanescent ones) are obtained. Their dependence on the parameter of a fluid's depth is studied. Then the Green matrix is constructed analytically as a linear combination of normal modes to describe the response of a plate and an acoustic medium to the point loading by a force or a moment. Continuity conditions at the loaded cross-section of a plate and in a fluid are formulated. Attention is focused at the selection of roots of the dispersion relation for the formulation of the continuity condition for a fluid at the loaded cross-section. The convergence rate of an approximate solution based on the modal composition of the Green matrix is estimated. The parametric study of the “structural” and the “fluid” energy flows in a fluid-loaded sandwich plate without inclusions is performed for various excitation conditions. Then the Green matrix method is applied to analyze the influence of a pair of identical inclusions on localization of vibrations (modal trapping) and energy flows. Conditions of localization of flexural waves at these inhomogeneities are explored.

SOROKIN, S. V.

2002-05-01

162

Stable high-order molecular sandwiches: Hydrocarbon polyanion pairs with multiple lithium ions inside and out  

SciTech Connect

Stable ten-component sandwich compounds have been characterized in which four lithium ions reside between two tetraanions derived from corannulene or its alkyl-substituted derivatives and four additional lithium ions decorate the exterior. In tetrahydrofuran solution, the four lithium ions inside the sandwich can exchange environments with the four external lithium atoms, but the two tetraanion decks of the sandwich never separate from one another on the time scale of nuclear magnetic resonance. Theoretical calculations point to a [open quotes]stacked bowl[close quotes] conformation and a low energy barrier for synchronous double inversion of the tetraanion bowls in the solvated sandwich compounds.

Ayalon, A.; Rabinovitz, M. (Hebrew Univ. of Jerusalem (Israel)); Sygula, A.; Rabideau, P.W. (Louisiana State Univ., Baton Rouge, LA (United States)); Cheng, P.C.; Scott, L.T. (Boston College, Chestnut Hill, MA (United States))

1994-08-19

163

Fiber-Reinforced-Foam (FRF) Core Composite Sandwich Panel Concept for Advanced Composites Technologi  

NASA Technical Reports Server (NTRS)

Fiber-Reinforced-Foam (FRF) Core Composite Sandwich Panel Concept for Advanced Composites Technologies Project - Preliminary Manufacturing Demonstration Articles for Ares V Payload Shroud Barrel Acreage Structure

2010-01-01

164

Serologic properties of the triple antibody-sandwich-lymphocyte-agglutination assay (TASLA).  

PubMed

Detailed studies concerning the serologic properties of the triple antibody-sandwich-lymphocyte-agglutination (TASLA) assay are described herin. The technique is a sensitive one based on sandwiching three layers of antibody onto the target cell. Two different test systems were utilized which included xeno- and allogeneic models. In the xenogeneic test system, rabbit-anti-DA lymphocyte xenosera served as the primary antibody sandwich layer. Goat-anti-rabbit and swine-anti-goat IgG served as the secondary and tertiary antibody sandwich layers, respectively. In the rat allogeneic test system, LEW-anti-BN rat lymphocyte allosera served as the primary antibody layer. Rabbit-anti-rat and goat-anti-rabbit IgG served as the secondary and tertiary antibody sandwich layers, respectively. Several different experiments were run with varying numbers of antibody sandwich layers, and differing concentrations within each layer. The lymphocyte agglutination reaction was then evaluated by regression analysis. Regardless of the number or concentration of antibody sandwich layers, it was found that the reaction could be functionally defined mathematically, by regression analysis. A secondary or tertiary antibody sandwich layer increased assay sensitivity. The level of lymphocyte agglutination was found to be both a linear function of the number of antibody sandwich layers and the concentration of each utilized. In addition, the serological properties of the TASLA assay were extended to the rat allogeneic test system and was again functionally defined mathematically by regression analysis. PMID:2657072

Hewitt, C W; Black, K S; Henson, L E; Dowdy, S F; Philospe, B; Martin, D C

1989-01-01

165

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

NASA Technical Reports Server (NTRS)

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

Bush, H. G.

1975-01-01

166

Low Velocity Blunt Impact on Lightweight Composite Sandwich Panels  

NASA Astrophysics Data System (ADS)

There is an increased desire to incorporate more composite sandwich structures into modern aircrafts. Because in-service aircrafts routinely experience impact damage during maintenance due to ground vehicle collision, dropped equipment, or foreign object damage (FOD) impact, it is necessary to understand their impact characteristics, particularly when blunt impact sources create internal damage with little or no external visibility. The objective of this investigation is to explore damage formation in lightweight composite sandwich panels due to low-velocity impacts of variable tip radius and energy level. The correlation between barely visible external dent formation and internal core damage was explored as a function of impact tip radius. A pendulum impactor was used to impact composite sandwich panels having honeycomb core while held in a 165 mm square window fixture. The panels were impacted by hardened steel tips with radii of 12.7, 25.4, 50.8, and 76.2 mm at energy levels ranging from 2 to 14 J. Experimental data showed little dependence of external dent depth on tip radius at very low energies of 2 to 6 J, and thus, there was also little variation in visibility due to tip radius. Four modes of internal core damage were identified. Internal damage span and depth were dependent on impact tip radius. Damage depth was also radius-dependent, but stabilized at constant depth independent of kinetic energy. Internal damage span increased with increasing impact energy, but not with increasing tip radius, suggesting a relationship between maximum damage tip radius with core density/size.

Chan, Monica Kar

167

Built-in diagnostics for sandwich structures under extreme temperatures  

NASA Astrophysics Data System (ADS)

In order to maximize the survivability and signal sensitivity of sensors exposed to extreme temperature, piezoelectric ceramics were selected for use as transducers and sensors. An efficient manufacturing technique was developed to install these sensors within a cell of the honeycomb core. This technique doesn't modify the traditional manufacturing technique of the sandwich structures. Instead, the sensor and the wire layer are inserted before closing the sandwich for final curing. The materials used for the sensor and the wire layer were both tested at cryogenic temperature to ensure their survivability. The active sensing technique uses one built-in piezoelectric transducer to generate propagating waves to be received by the neighboring piezoelectric sensors. The difference in sensor measurements before and after the presence of damage provides information about the location and size of the damage. Due to strong wave attenuation in honeycomb core structures, the signal changes greatly when the damage is located in the direct path between a transducer and a sensor as opposed to very little when off the direct path. Based on these observations, a simple detection algorithm was developed which calculates the relative scatter energy for every path to obtain an image of the damage location and uses the time-domain signals to decipher which paths propagate through the damage and thereby evaluate its extent. This damage detection was validated on a composite sandwich panel with a square array of surface mounted sensors. The effect of sensor density on the size of undetectable damage was also studied for different sensor patterns repeated over a large-scale structure. Using a genetic algorithm called differential evolution, the location of the sensors was optimized to minimize the furthest distance from a diagnostic path. Signal attenuation is a key parameter in the selection of the best sensor pattern for a given structure.

Blaise, Eric

168

Deformation and fracture of impulsively loaded sandwich panels  

NASA Astrophysics Data System (ADS)

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

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

2013-02-01

169

Optimized analysis of geometry parameters for honeycomb sandwich mirror  

NASA Astrophysics Data System (ADS)

The relationship of geometry parameters, specific stiffness, surface figure and natural frequency was investigated based on modified Gibson theory, sandwich theory, Hoff theory and vibration theory. By theoretical analysis and finite element method, we demonstrated the geometric parameters had non-linear influence on dimensionless specific stiffness in different directions with the honeycomb core was equivalent as modified solid material. Approximate expressions of deformation, natural frequency and geometric parameters were obtained. The results showed the optimal solidity ratio and face plate thickness ratio were in the range of 0.03 ~ 0.1 and 0.02 ~0.05, respectively.

Chen, Xiao'an; Cheng, Yuntao; Zeng, Qingna; Liu, Hong; Fang, Jingzhong; Rao, Changhui

2014-07-01

170

Sandwich Hologram Interferometry For Determination Of Sacroiliac Joint Movements  

NASA Astrophysics Data System (ADS)

Investigations were carried out on embalmed and fresh specimens of human pelvisis with preserved lumbar spines, hip joints and all the ligaments. Specimens were tested under static vertical loading by pulsed laser interferometry. The deformations and behaviour of particular pelvic parts were interpreted by providing computer interferogram models. Results indicate rotation and tilting of the sacrum in the dorso-ventral direction and small but significant movements in the cranio-caudal direction. Sandwich holography proved to be the only applicable method when there is a combination of translation and tilt in the range of 200 ?m to 1.5 mm.

Vukicevic, S.; Vinter, I.; Vukicevic, D.

1983-12-01

171

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. PMID:16049097

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

2005-01-01

172

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

173

The growth of a c-axis highly oriented sandwiched TiO2 film with superhydrophilic properties without UV irradiation on SnO:F substrate.  

PubMed

A c-axis highly oriented sandwiched film composed of single-crystalline rutile TiO(2) on SnO:F (FTO) substrate was fabricated by a simple hydrothermal technique. The sandwich structure of the TiO(2) film was found to be constructed by two layers of TiO(2) nanorods, which grew towards both directions of the bulk solution and the substrate, respectively. One TiO(2) nanoparticle interlayer between them acted as the 'seed' layer. The length and the density of the TiO(2) nanoarrays could be tuned by varying the experimental parameters such as temperature and time. The resultant TiO(2) films showed a specific superhydrophilicity without any prior UV irradiation, which can be kept for a long period of time. PMID:19451682

Han, Yangang; Wu, Gang; Wang, Mang; Chen, Hongzheng

2009-06-10

174

The growth of a c-axis highly oriented sandwiched TiO2 film with superhydrophilic properties without UV irradiation on SnO:F substrate  

NASA Astrophysics Data System (ADS)

A c-axis highly oriented sandwiched film composed of single-crystalline rutile TiO2 on SnO:F (FTO) substrate was fabricated by a simple hydrothermal technique. The sandwich structure of the TiO2 film was found to be constructed by two layers of TiO2 nanorods, which grew towards both directions of the bulk solution and the substrate, respectively. One TiO2 nanoparticle interlayer between them acted as the 'seed' layer. The length and the density of the TiO2 nanoarrays could be tuned by varying the experimental parameters such as temperature and time. The resultant TiO2 films showed a specific superhydrophilicity without any prior UV irradiation, which can be kept for a long period of time.

Han, Yangang; Wu, Gang; Wang, Mang; Chen, Hongzheng

2009-06-01

175

Vibration analysis and design optimization of viscoelastic sandwich cylindrical shell  

NASA Astrophysics Data System (ADS)

Damping properties of viscoelastic sandwich structure can be improved by changing some parameters such as thickness of the layers, distribution of partial treatments, slippage between layers at the interfaces, cutting and its distribution at the top and core layers. Since the optimization problem may result in a thick core layer, for achieving more accuracy a new higher-order Taylor's expansion of transverse and in-plane displacement fields is developed for the core layer of sandwich cylindrical shell in which the displacement fields at the core layer are compatibly described in terms of the displacement fields at the elastic faces. The presented model includes fewer parameters than the previously developed models and therefore decreases the number of degree of freedom in the finite element modeling. The transverse normal stress in the core layer is also considered. The formulations are developed to consider the slippage between layers at the interfaces. Finally, by combining the finite element method and the optimization algorithms based on the genetic algorithm and sequential quadratic programming technique, a design optimization methodology has been formulated to maximize the damping characteristics using the optimal number and location of cuts and partial treatments with optimal thicknesses of top and core layers.

Mohammadi, Farough; Sedaghati, Ramin

2012-06-01

176

Stabilizing graphene-based organometallic sandwich structures through defect engineering  

NASA Astrophysics Data System (ADS)

In this theoretical work, we propose a chemical route to creating stable benzene-transition metal-graphene sandwich structures. The binding energy of the transition metal to graphene is enhanced through adsorption at appropriate defects, immobilizing the metal onto the graphene web. Capping the metal with a benzene ring further stabilizes the structure. The stability and the magnetic properties of these composite structures vary for different defects such as vacancies and nitrogen substitutionals in graphene. The proposed complexes have high cohesive energies and are either metallic or are small-band-gap semiconductors. Several of the proposed structures also have large spin polarization energies that make them suitable for use as nanomagnets in ambient conditions. This work also sheds light on the experimental results in the field where the sandwich structures may have been successfully created. We show that defect engineering is a viable option for creating designer, graphene-based structures that may play an important role in fields as diverse as spintronics, nanoelectronics, hydrogen storage, and catalysis.

Dev, Pratibha; Reinecke, Thomas L.

2015-01-01

177

Impact Delamination and Fracture in Aluminum/Acrylic Sandwich Plates  

NASA Technical Reports Server (NTRS)

Impact-induced delamination and fracture in 6061-T6 aluminum/cast acrylic sandwich plates adhered by epoxy were generated in an instrumented drop-weight impact machine. Although only a small dent was produced on the aluminum side when a hemispherical penetrator tup was dropped onto it from a couple of inches, a large ring of delamination at the interface was observed. The delamination damage was often accompanied by severe shattering in the acrylic substratum. Damage patterns in the acrylic layer include radial and ring cracks and, together with delamination at the interface, may cause peeling-off of acrylic material from the sandwich plate. Theory of stress-wave propagation can be used to explain these damage patterns. The impact tests were conducted at various temperatures. The results also show clearly that temperature effect is very important in impact damage. For pure cast acrylic nil-ductile transition (NDT) occurs between 185-195 F. Excessive impact energy was dissipated into fracture energy when tested at temperature below this range or through plastic deformation when tested at temperature above the NDT temperature. Results from this study will be used as baseline data for studying fiber-metal laminates, such as GLARE and ARALL for advanced aeronautical and astronautical applications.

Liaw, Benjamin; Zeichner, Glenn; Liu, Yanxiong; Bowles, Kenneth J. (Technical Monitor)

2000-01-01

178

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

NASA Technical Reports Server (NTRS)

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

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

2000-01-01

179

Half-Sandwich Iridium- and Rhodium-based Organometallic Architectures: Rational Design, Synthesis, Characterization, and Applications.  

PubMed

Conspectus Over the last two decades, researchers have focused on the design and synthesis of supramolecular coordination complexes, which contain discrete functional structures with particular shapes and sizes, and are similar to classic metal-organic frameworks. Chemists can regulate many of these systems by judiciously choosing the metal centers and their adjoining ligands. These resulting complexes have unusual properties and therefore many applications, including molecular recognition, supramolecular catalysis, and some applications as nanomaterials. In addition, researchers have extensively developed synthetic methodologies for the construction of discrete self-assemblies. One of the most important challenges for scientists in this area is to be able to synthesize target structures that can be controlled in both length and width. For this reason, it is important that we understand the factors leading to special shapes and sizes of such architectures, especially how starting building blocks and functional ligands affect the final conformations and cavity sizes of the resulting assemblies. Towards this goal, we have developed a wide range of different organometallic architectures by rationally designing metal-containing precursors and organic ligands. In this Account, we present our recent work, focusing on half-sandwich iridium- and rhodium-based organometallic assemblies that we obtained through rational design. We discuss their synthesis, structures, and applications for the encapsulation of guests and enzyme-mimicking catalysis. We first describe a series of self-assembled organometallic metallarectangles and metallacages, which we constructed from preorganized dinuclear half-sandwich molecular clips and suitable pyridyl ligands. We extended this strategy to tune the size of the obtained rectangles, creating large cavities by introduction of larger molecular clips. The cavity was found to exhibit selective and reversible CH2Cl2 adsorption properties while retaining single crystallinity. By using suitable molecular clips, we found we could use a number of metallacycles as organometallic templates to direct photochemical [2 + 2] cycloaddition reactions, even in the solid state. Due to their chemical stability and potential applications in catalytic reactions, researchers are giving significant attention to complexes with cyclometalated backbones. We also highlight our efforts to develop efficient approaches to utilize cyclometalated building blocks for the formation of organometallic assemblies. By incorporation of imine ligands or benzoic acids, bipyridine linking subunits, and half-sandwich iridium or rhodium fragments, we built up a series of cationic and neutral metallacycles through cyclometalation-driven self-assembly. In addition, we have developed an efficient route to carborane-based metallacycles, involving the exploitation of metal-induced B-H activation. The method can provide prism-like metallacages, which are efficient hosts for the recognition of planar aromatic guests. This effort provides an incentive to generate new building blocks for the construction of organometallic assemblies. Taken together, our results may lead to a promising future for the design of complicated enzyme-mimetic-catalyzed systems. PMID:25419985

Han, Ying-Feng; Jin, Guo-Xin

2014-12-16

180

The dynamic response of clamped rectangular Y-frame and corrugated core sandwich plates  

E-print Network

the response of sandwich beams with a corrugated core . These studies reveal that geometrical imperfections and1 The dynamic response of clamped rectangular Y-frame and corrugated core sandwich plates V. Rubino identical face-sheets and either Y-frame or corrugated cores. The resistance to shock loading is quantified

Fleck, Norman A.

181

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

E-print Network

Dynamic Ham-Sandwich Cuts in the Plane Timothy G. Abbott Michael A. Burr Timothy M. Chan§ Erik D Seyboth¶ Vincent Yeung Abstract We design efficient data structures for dynamically maintaining a ham-sandwich cut of two point sets in the plane subject to insertions and deletions of points in either set. A ham

182

CO-gas-induced resistance switching in SnO 2\\/ultrathin Pt sandwich structure  

Microsoft Academic Search

A novel sandwich structure based on an insulating metal oxide top layer and an ultrathin metal bottom layer is proposed. The experiments are carried out on a model structure consisting of thin films of Pt and SnO2. A resistance switching effect induced by CO gas is obtained in these sandwich structures. The effect is proved to originate from the properties

A. Galdikas; A. Mironas; D. Senulienå; A. Šetkus

1996-01-01

183

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

184

arXiv:1108.5604v2 The asymmetric sandwich theorem  

E-print Network

arXiv:1108.5604v2 [math.FA] 22 Sep 2011 The asymmetric sandwich theorem S. Simons Department the asymmetric sandwich theorem, a generalization of the Hahn{Banach theorem. As applications, we derive various generalizations of the Fenchel duality theorem. Most of the results are about aÃ?ne functions de#12;ned on convex

Simons, Stephen

185

Thermal response of a flat heat pipe sandwich structure to a localized heat flux  

Microsoft Academic Search

The temperature distribution across a flat heat pipe sandwich structure, subjected to an intense localized thermal flux has been investigated both experimentally and computationally. The aluminum sandwich structure consisted of a pair of aluminum alloy face sheets, a truncated square honeycomb (cruciform) core, a nickel metal foam wick and distilled water as the working fluid. Heat was applied via a

G. Carbajal; C. B. Sobhan; G. P. Peterson; D. T. Queheillalt; H. N. G. Wadley

2006-01-01

186

Bondline strength evaluation of cocure\\/precured honeycomb sandwich structures under aircraft hygro and repair environments  

Microsoft Academic Search

Effects of moisture accumulated into the adhesively bonded composite structures on their bondline mechanical strengths are investigated through a series of comparative experiments. Those composite structures include a honeycomb sandwich structures fabricated by the cocure and the precure processes. Mass of moisture accumulated into the closed cells of the honeycomb sandwich panel specimens has been calculated. A pressure due to

Heung Soap Choi; Yong Hoon Jang

2010-01-01

187

Dynamic analysis of magnetorheological elastomer-based sandwich beam with conductive skins under various boundary conditions  

Microsoft Academic Search

The dynamic analysis of a three-layered symmetric sandwich beam with magnetorheological elastomer (MRE) embedded viscoelastic core and conductive skins subjected to a periodic axial load have been carried out under various boundary conditions. As the skins of the sandwich beam are conductive, magnetic loads are applied to the skins during vibration. Due to the field-dependent shear modulus of MRE material,

B. Nayak; S. K. Dwivedy; K. S. R. K. Murthy

2011-01-01

188

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

E-print Network

1 Sandwich and Interdigitated Finger Electrode Ferroelectric Nano Film Capacitors: A Comparison of epitaxial nano ferroelectric thin film capacitors with various electrode configurations. The capacitor polarization in a sandwich type capacitor, stabilized via compressive in-plane misfit, always forms

Yanikoglu, Berrin

189

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

PubMed Central

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

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

2012-01-01

190

Natural cork agglomerate employed as an environmentally friendly solution for quiet sandwich composites.  

PubMed

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

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

2012-01-01

191

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

192

A Novel Sandwich Electrochemical Immunosensor Based on the DNA-Derived Magnetic Nanochain Probes for Alpha-Fetoprotein.  

PubMed

One novel electrochemical immunosensor was constructed by immobilizing capture antibody of alpha-fetoprotein (AFP Ab(1)) on a nafion/nanogold-particle modified glassy carbon electrode. With a sandwich immunoassay, one DNA-derived magnetic nanoprobe, simplified as DNA/(ZMPs-HRP-AFP Ab(2))(n), was employed for the detection of AFP. The fabricated procedure of the proposed biosensor was characterized by cyclic voltammetry and electrochemical impedance spectroscopy. The performance and factors influencing the performance of the biosensor were also evaluated. Under optimal conditions, the developed biosensor exhibited a well-defined electrochemical behavior toward the reduction of AFP ranging from 0.01 to 200?ng/mL with a detection limit of 4?pg/mL (S/N = 3). The biosensor was applied to the determination of AFP in serum with satisfactory results. It is important to note that the sandwich nanochainmodified electro-immunosensor provided an alternative substrate for the immobilization of other tumor markers. PMID:22013390

Gan, Ning; Jia, Liyong; Zheng, Lei

2011-01-01

193

A Novel Sandwich Electrochemical Immunosensor Based on the DNA-Derived Magnetic Nanochain Probes for Alpha-Fetoprotein  

PubMed Central

One novel electrochemical immunosensor was constructed by immobilizing capture antibody of alpha-fetoprotein (AFP Ab1) on a nafion/nanogold-particle modified glassy carbon electrode. With a sandwich immunoassay, one DNA-derived magnetic nanoprobe, simplified as DNA/(ZMPs—HRP-AFP Ab2)n, was employed for the detection of AFP. The fabricated procedure of the proposed biosensor was characterized by cyclic voltammetry and electrochemical impedance spectroscopy. The performance and factors influencing the performance of the biosensor were also evaluated. Under optimal conditions, the developed biosensor exhibited a well-defined electrochemical behavior toward the reduction of AFP ranging from 0.01 to 200?ng/mL with a detection limit of 4?pg/mL (S/N = 3). The biosensor was applied to the determination of AFP in serum with satisfactory results. It is important to note that the sandwich nanochainmodified electro-immunosensor provided an alternative substrate for the immobilization of other tumor markers. PMID:22013390

Gan, Ning; Jia, Liyong; Zheng, Lei

2011-01-01

194

Small bending and stretching of sandwich-type shells  

NASA Technical Reports Server (NTRS)

A theory has been developed for small bending and stretching of sandwich-type shells. This theory is an extension of the known theory of homogeneous thin elastic shells. It was found that two effects are important in the present problem, which are not normally of importance in the theory of curved shells: (1) the effect of transverse shear deformation and (2) the effect of transverse normal stress deformation. The first of these two effects has been known to be of importance in the theory of plates and beams. The second effect was found to occur in a manner which is typical for shells and has no counterpart in flat-plate theory. The general results of this report have been applied to the solution of problems concerning flat plates, circular rings, circular cylindrical shells, and spherical shells. In each case numerical examples have been given, illustrating the magnitude of the effects of transverse shear and normal stress deformation.

Reissner, Eric

1950-01-01

195

Large magnetoresistance at room temperature in semiconducting polymer sandwich devices  

NASA Astrophysics Data System (ADS)

We report on the discovery of a large, room temperature magnetoresistance (MR) effect in polyfluorene sandwich devices in weak magnetic fields. We characterize this effect and discuss its dependence on field direction, voltage, temperature, film thickness, electrode materials, and (unintentional) impurity concentration. Negative MR is usually observed, but positive MR can also be achieved under high applied electric fields. The MR effect reaches up to 10% at fields of 10 mT at room temperature. The effect shows only a weak temperature dependence and is independent of the sign and direction of the magnetic field. We find that the effect is related to the hole current in the devices. To the best of our knowledge, the discovered effect is not adequately described by any of the MR mechanisms known to date.

Francis, T. L.; Mermer, Ö.; Veeraraghavan, G.; Wohlgenannt, M.

2004-11-01

196

Briot-Bouquet differential superordinations and sandwich theorems  

NASA Astrophysics Data System (ADS)

Briot-Bouquet differential subordinations play a prominent role in the theory of differential subordinations. In this article we consider the dual problem of Briot-Bouquet differential superordinations. Let [beta] and [gamma] be complex numbers, and let [Omega] be any set in the complex plane C. The function p analytic in the unit disk U is said to be a solution of the Briot-Bouquet differential superordination if The authors determine properties of functions p satisfying this differential superordination and also some generalized versions of it. In addition, for sets [Omega]1 and [Omega]2 in the complex plane the authors determine properties of functions p satisfying a Briot-Bouquet sandwich of the form Generalizations of this result are also considered.

Miller, Sanford S.; Mocanu, Petru T.

2007-05-01

197

Room Temperature and Elevated Temperature Composite Sandwich Joint Testing  

NASA Technical Reports Server (NTRS)

Testing of composite sandwich joint elements has been completed to verify the strength capacity of joints designed to carry specified running loads representative of a high speed civil transport wing. Static tension testing at both room and an elevated temperature of 350 F and fatigue testing at room temperature were conducted to determine strength capacity, fatigue life, and failure modes. Static tension test results yielded failure loads above the design loads for the room temperature tests, confirming the ability of the joint concepts tested to carry their design loads. However, strength reductions as large as 30% were observed at the elevated test temperature, where all failure loads were below the room temperature design loads for the specific joint designs tested. Fatigue testing resulted in lower than predicted fatigue lives.

Walker, Sandra P.

1998-01-01

198

Predicting The Compression Strength Of Impact-Damaged Sandwich Panels  

NASA Technical Reports Server (NTRS)

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

Ratcliffe, James; Jackson, Wade; Schaff, Jeffery

1990-01-01

199

Diffusion bonding of titanium-titanium aluminide-alumina sandwich  

SciTech Connect

Diffusion bonding of a metallic-intermetallic-ceramic sandwich is of interest for potential armor applications. Low cost titanium, titanium diboride reinforced titanium aluminide (Ti-48at.%Al), and aluminum oxide are diffusion bonded in a vacuum furnace between 1,000 C and 1,400 C. Metallographic examination of the prior bonding interface showed excellent metallurgical coupling between the Ti-48at.%Al composite and the low cost Ti. A series of microstructures representative of phases consistent with a hypothetical Ti-Al-B phase diagram is visible. The alumina-Ti-48at.%Al interfacial bond is achieved through penetration of titanium-aluminum phases into the existing alumina porosity. A detailed microstructural analysis identifying mechanisms of interfacial bonding will be presented for each interfacial zone.

Wickman, H.A.; Chin, E.S.C. [Army Research Lab., Watertown, MA (United States); Biederman, R.R. [Worcester Polytechnic Inst., MA (United States)

1995-12-31

200

Detection of bound residues in soils by sandwich-immunoassay  

SciTech Connect

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

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

1995-12-31

201

Microbiological investigation of an antibacterial sandwich layer system.  

PubMed

To allow medical application of an artificial bladder made of biocompatible polyurethane, a long-term stable antibacterial coating is required. Alone, the artificial bladder exhibits no defense against microorganisms. Silver coating provides long-term antibacterial protection by the continuous release of silver ions into aqueous solutions. To control and to prolong the rate of silver ion release, the deposited silver film has to be protected by an inert film of biocompatible polyparylene by means of chemical vapor deposition. In this study, an antibacterial artificial bladder surface was developed by the formation of a sandwich structure consisting of silver and a biocompatible polymer (polyparylene) as a diffusion barrier. Specifically, this study analyzed the correlation between polyparylene thickness and silver release to determine optimal concentrations to combat common bacteria in vitro. The release of silver from sandwich structures was investigated in vitro by testing different thicknesses of polyparylene (0, 190, 540, and 1000 nm) as a diffusion barrier. The best result was demonstrated with a thickness of 190 nm of polyparylene, which yielded a silver dispense rate of 650?pg/(cm(2)?min), which would yield bacteriozidal concentrations above 30??g/l in the bladder volume. The authors confirmed the antibacterial effect in vitro against common urinary tract infection pathogens, namely, Escherichia coli and Staphylococcus cohnii. Inhibition of bacterial growth could be detected within 8 h. A diffusion assay with spherical silver spots showed concentric zones free of bacterial growth. Our results suggest the possible utility of silver-polyparylene coatings as antibacterial agents. PMID:25280843

Heidari Zare, Hamideh; Sudhop, Stefanie; Schamberger, Florian; Franz, Gerhard

2014-09-01

202

Probabilistic Structural Evaluation of Uncertainties in Radiator Sandwich Panel Design  

NASA Technical Reports Server (NTRS)

The Jupiter Icy Moons Orbiter (JIMO) Space System is part of the NASA's Prometheus Program. As part of the JIMO engineering team at NASA Glenn Research Center, the structural design of the JIMO Heat Rejection Subsystem (HRS) is evaluated. An initial goal of this study was to perform sensitivity analyses to determine the relative importance of the input variables on the structural responses of the radiator panel. The desire was to let the sensitivity analysis information identify the important parameters. The probabilistic analysis methods illustrated here support this objective. The probabilistic structural performance evaluation of a HRS radiator sandwich panel was performed. The radiator panel structural performance was assessed in the presence of uncertainties in the loading, fabrication process variables, and material properties. The stress and displacement contours of the deterministic structural analysis at mean probability was performed and results presented. It is followed by a probabilistic evaluation to determine the effect of the primitive variables on the radiator panel structural performance. Based on uncertainties in material properties, structural geometry and loading, the results of the displacement and stress analysis are used as an input file for the probabilistic analysis of the panel. The sensitivity of the structural responses, such as maximum displacement and maximum tensile and compressive stresses of the facesheet in x and y directions and maximum VonMises stresses of the tube, to the loading and design variables is determined under the boundary condition where all edges of the radiator panel are pinned. Based on this study, design critical material and geometric parameters of the considered sandwich panel are identified.

Kuguoglu, Latife; Ludwiczak, Damian

2006-01-01

203

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

NASA Technical Reports Server (NTRS)

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

Ko, William L.; Jackson, Raymond H.

1991-01-01

204

Open-sandwich immunoassay for sensitive and broad-range detection of a shellfish toxin gonyautoxin.  

PubMed

At present, the analytical method for paralytic shellfish poisoning (PSP) toxins in shellfish is the mouse bioassay (MBA), which is an official method of the Association of Analytical Communities (AOAC [8]). However, the low sensitivity and concerns over the number of live animals required for testing have been cited as the major reason for seeking its replacement. In this report, we employed an open-sandwich immunoassay (OS-IA) to detect gonyautoxin (GTX2/3), a kind of PSP toxins. OS-IA, which utilizes the antigen-induced enhancement of antibody VH/VL interaction, can measure a small molecule antigen in a noncompetitive format. Hence it has a wider working range and shorter measurement time. We isolated anti-GTX2/3 antibody gene from a hybridoma GT-13A by screening a Fab-displaying phage library. Then the vectors for OS-IA were constructed, and examined for antigen concentration-dependency of the VH/VL interaction by OS-ELISA. As a result, in each case, signal intensity increases notably in a wide concentration range (0.1 to >1000 ng mL(-1)) of free GTX2/3, which was enough to cover its regulation value (80 ?g 100 g(-1)) in many countries. So OS-IA will be widely applicable to detect PSP toxins in shellfish meats and in drinking water. PMID:23953213

Hara, Yuko; Dong, Jinhua; Ueda, Hiroshi

2013-09-01

205

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

NASA Technical Reports Server (NTRS)

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

McGowan, David M.; Ambur, Damodar R.

1997-01-01

206

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

NASA Technical Reports Server (NTRS)

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

Ko, W. L.

1980-01-01

207

Modeling Blast and High-Velocity Impact of Composite Sandwich Panels  

NASA Astrophysics Data System (ADS)

Analytical models for predicting the deformation and failure of composite sandwich panels subjected to blast and projectile impact loading are presented in this paper. The analytical predictions of the transient deformations and damage initiation in the composite sandwich panels were compared with finite element solutions using ABAQUS Explicit. For the blast model, the predicted transient deformation of the sandwich panel was within 7%of FEA results, while the predicted damage initiation using Hashin's composite failure criteria was about 15%higher than FEA results in most cases. For the high velocity impact model, the predicted transient deformations were within 20%of FEA results.

Fatt, Michelle S. Hoo; Palla, Leelaprasad; Sirivolu, Dushyanth

208

The Pleural Sandwich Sign in Two Cases of Primary Pleural Lymphoma  

PubMed Central

The sandwich sign is used to describe mesenteric lymphoma in which mesenteric vessels and fat are enveloped by enlarged mesenteric lymph nodes. We present two cases of primary pleural lymphoma demonstrating the "pleural sandwich sign". Contrast-enhanced computed tomography showed conglomerated parietal pleural and extrapleural masses encasing the intercostal arteries. Histopathological examinations confirmed low grade marginal zone B-cell lymphoma in an 80-year-old man and diffuse large B-cell lymphoma in a 68-year-old man. The pleural sandwich sign may suggest the diagnosis of primary pleural lymphoma. PMID:25598693

Lee, Myungjae; Ryu, Yon Ju; Cho, Min-Sun

2015-01-01

209

Unequal Faces Effect on Fracture of Composite Sandwich Beam with Flexible Core  

NASA Astrophysics Data System (ADS)

Sandwich panel higher order theory (SPHOT) which estimates core compression and face stresses is used to predict damage modes of a sandwich beam with unequal faces. It is shown that sandwich panel classical theory (SPCT) which is based on investigating of behavior of the structure with considering core shear stress in simply supported boundary conditions and neglecting shear modulus of core can not predict the failure load in the case of unequal faces when core yielding is happened. Comparing the results obtained by SPHOT, SPCT and available experimental ones shows that the higher order theory is a suitable approach to predict failure loads in this case for different damage modes.

Sadighi, Mojtaba; Saadati, Mahdi

2010-04-01

210

A comparative study of the impact properties of sandwich materials with different cores  

NASA Astrophysics Data System (ADS)

Sandwich panels are made of two high strength skins bonded to either side of a light weight core and are used in applications where high stiffness combined with low structural weight is required. The purpose of this paper is to compare the mechanical response of several sandwich panels whose core materials are different. Sandwich panels with glass fibre-reinforced polymer face sheets were used, combined with five different cores; polystyrene foam, polypropylene honeycomb, two different density Balsa wood and Cork. All specimens were subjected to low velocity impact and their structural response (Force-displacement curves) were compared to quasistatic response of the panel tested using an hemispherical indenter.

Ramakrishnan, K. R.; Shankar, K.; Viot, P.; Guerard, S.

2012-08-01

211

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

212

Response of Honeycomb Core Sandwich Panel with Minimum Gage GFRP Face-Sheets to Compression Loading After Impact  

NASA Technical Reports Server (NTRS)

A compression after impact study has been conducted to determine the residual strength of three sandwich panel constructions with two types of thin glass fiber reinforced polymer face-sheets and two hexagonal honeycomb Nomex core densities. Impact testing is conducted to first determine the characteristics of damage resulting from various impact energy levels. Two modes of failure are found during compression after impact tests with the density of the core precipitating the failure mode present for a given specimen. A finite element analysis is presented for prediction of the residual compressive strength of the impacted specimens. The analysis includes progressive damage modeling in the face-sheets. Preliminary analysis results were similar to the experimental results; however, a higher fidelity core material model is expected to improve the correlation.

McQuigg, Thomas D.; Kapania, Rakesh K.; Scotti, Stephen J.; Walker, Sandra P.

2011-01-01

213

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

NASA Technical Reports Server (NTRS)

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

Baker, Donald J.; Rogers, Charles

1996-01-01

214

Polarization selectivity of two-layer grating sandwiched between two fused-silica substrates  

NASA Astrophysics Data System (ADS)

The polarization selectivity is described based on the two-layer grating sandwiched between two fused-silica substrates. The polarization-selective grating can diffract TE polarization with high efficiency and split TM polarization with good uniformity. With the novel structure, the grating can have high efficiency of sandwiched grating and wideband property of two-layer grating. The modal method is applied to analyze the grating, which corresponds well with the results of rigorous coupled-wave analysis. The physical analysis can give the good guideline to optimize the polarization-selective sandwiched two-layer grating effectively. Such a polarization-selective grating can also have merits of high efficiency for TE polarization and wide angular bandwidth for TM polarization based on the two-layer grating sandwiched between two fused-silica substrate. It is easy to clean and protect the grating surface compared with the surface-relief grating.

Wang, Bo; Shu, Wenhao; Li, Wenhua; Chen, Li; Lei, Liang; Zhou, Jinyun

2015-01-01

215

Your Deli Sandwich May Come with A Side of Listeria, Study Finds  

MedlinePLUS

... Deli Sandwich May Come With a Side of Listeria, Study Finds Nearly 1 in 10 samples from ... February 11, 2015 Related MedlinePlus Pages Foodborne Illness Listeria Infections WEDNESDAY, Feb. 11, 2015 (HealthDay News) -- The ...

216

A sandwich substrate for ultrasensitive and label-free SERS spectroscopic detection of folic acid / methotrexate.  

PubMed

A highly sensitive surface enhanced Raman scattering (SERS) substrate with particle-film sandwich geometry has been developed for the label free detection of folic acid (FA) and methotrexate (MTX). In this sandwich structure, the bottom layer is composed of a copper foil decorated with silver nanoparticles synthesized by the galvanic displacement reaction, and top layer is constituted by silver nanoparticles. The FA and MTX molecules are sandwiched between the silver nanoparticles decorated copper film and the silver nanoparticles. The plasmonic coupling between the two layers of the sandwich structure greatly enhances the SERS spectra of FA and MTX. SERS activity of the substrate was studied and optimized by adjusting the time of galvanic displacement reaction. The SERS spectra of the FA and MTX showed the minimum detection concentration of 100 pM. The identification of methotrexate and folic acid analogs was also carried out by SERS spectra analysis. PMID:24850231

Yang, Jing; Tan, Xuebin; Shih, Wei-Chuan; Cheng, Mark Ming-Cheng

2014-10-01

217

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

Microsoft Academic Search

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

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

218

Size effect on strength of laminate-foam sandwich plates: Finite element analysis with interface fracture  

Microsoft Academic Search

Recent three-point bend tests of size effect on the strength of geometrically scaled sandwich beams of three types – with no notches, and with notches at the upper or lower skin–foam interface, which were previously evaluated using simplified sandwich beam theory and equivalent linear elastic fracture mechanics, are now reanalyzed more accurately by finite elements. Zero-thickness interface elements with a

Ferhun C. Caner; Zden?k P. Bažant

2009-01-01

219

All-optical pulse switching and shaping by a nonlinear sandwich  

SciTech Connect

We demonstrate a simple model system comprised of a thin nonlinear layer sandwiched between two glass plates. This double Nonlinear Interface allows the investigation of both the transmitted and reflected beams for all-optical switching. Various potential applications of this Nonlinear Sandwich based on its intensity-dependent reflectivity and transmissivity are discussed. Focus is given to energy limiting, prepulse suppression, pulse shortening, and shaping. Experimental results show feasibility of these applications. 7 refs., 6 figs.

Strobl, K.; Golub, I.

1991-01-01

220

A numerical model for bird strike of aluminium foam-based sandwich panels  

Microsoft Academic Search

Experimental bird-strike tests have been carried out on double sandwich panels made from AlSi7Mg0.5 aluminium foam core and aluminium AA2024 T3 cover plates. The bird-strike velocity varied from 140 to 190m\\/s. The test specimens were instrumented with strain gauges in the impacted area to measure the local strains of the rear sandwich plate. A numerical model of this problem has

A. G. Hanssen; Y. Girard; L. Olovsson; T. Berstad; M. Langseth

2006-01-01

221

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

222

Calculation of sandwich plates with polymer composite skins under conditions of high humidity  

NASA Astrophysics Data System (ADS)

An engineering method is presented for estimating the temperature gradients, moisture concentration gradients, and changes in stresses and deflections induced by these gradients in sandwich plates with heat-insulation coatings under conditions of high ambient temperatures and humidity. In particular, attention is given to ambient conditions that vary slowly in time, simulating typical airport storage conditions. Results of calculations are presented for sandwich panels with load-bearing layers of a carbon composite and an organic fiber composite.

Mishulin, I. B.

223

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

224

Finite element studies on field-dependent rigidities of sandwich beams with magnetorheological elastomer cores  

Microsoft Academic Search

Sandwich beams with magnetorheological elastomer (MRE) cores exhibit field-dependent dynamic rigidities due to the field-dependent shear modulus of the MRE cores. Such structures have great potential as regards developing stiffness-controllable devices which respond to control signals within milliseconds. The purpose of this paper is to investigate the effect of structural parameters on the field-dependent rigidities of single-layer sandwich beams with

G Y Zhou; K C Lin; Q Wang

2006-01-01

225

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

Microsoft Academic Search

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

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

2010-01-01

226

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

227

Characterizing Facesheet/Core Disbonding in Honeycomb Core Sandwich Structure  

NASA Technical Reports Server (NTRS)

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

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

2013-01-01

228

''Sandwich'' treatment for diospyrobezoar intestinal obstruction: A case report.  

PubMed

Intestinal obstruction is a common clinical entity encountered in surgical practice. The objective of this report is to corroborate an atypical scenario of intestinal obstruction in a Chinese patient and to focus on the diagnosis and treatment. A 27-year-old male presented with a history of gastric pain combined with nausea and abdominal distension that had been present for 5 d. The presence of a foreign body was detected by computed tomography and observed as an abnormal density within the stomach. A diospyrobezoar was revealed during gastroscopy, the extraction of which was prevented due to its size and firmness. An endoscopic holmium laser joined with a snare was used to fragment the obstruction, which was followed by management with a conservative "sandwich" treatment strategy involving intestinal decompression with an ileus tube and Coca-Cola lavage between endoscopic lithotripsy fragmentation procedures. This strategy resulted in the successful removal of the diospyrobezoar along with multiple small bowel obstructions. The patient was discharged after abatement of symptoms. The case presented here demonstrates the implementation of a conservative, yet successful, treatment as an alternative to conventional surgical removal of intestinal obstructions. PMID:25561823

Zheng, Yi-Xiong; Prasoon, Pankaj; Chen, Yan; Hu, Liang; Chen, Li

2014-12-28

229

Sandwiched structural panel having a bi-directional core structure  

NASA Technical Reports Server (NTRS)

A structural panel assembly has a bi-directional core structure sandwiched between and secured to a pair of outer side wall members. The core structure is formed from first and second perpendicular series of elongated strip members having crenelated configurations. The strip members in the first series thereof are transversely interwoven with the strip members in the second series thereof in a manner such that crest portions of the strip members in the first series overlie and oppose trough portions of the strip members in the second series, and trough portions of the strip members in the first series underlie and oppose crest portions of the strip members in the second series. The crest portions of all of the strip members lie generally in a first plane and are secured to the inner side of one of the panel assembly outer side walls, and the trough portions of all of the strip members lie generally in a second plane and are secured to the inner side of the other panel assembly outer side wall.

Weddendorf, Bruce (Inventor)

1995-01-01

230

''Sandwich'' treatment for diospyrobezoar intestinal obstruction: A case report  

PubMed Central

Intestinal obstruction is a common clinical entity encountered in surgical practice. The objective of this report is to corroborate an atypical scenario of intestinal obstruction in a Chinese patient and to focus on the diagnosis and treatment. A 27-year-old male presented with a history of gastric pain combined with nausea and abdominal distension that had been present for 5 d. The presence of a foreign body was detected by computed tomography and observed as an abnormal density within the stomach. A diospyrobezoar was revealed during gastroscopy, the extraction of which was prevented due to its size and firmness. An endoscopic holmium laser joined with a snare was used to fragment the obstruction, which was followed by management with a conservative “sandwich” treatment strategy involving intestinal decompression with an ileus tube and Coca-Cola lavage between endoscopic lithotripsy fragmentation procedures. This strategy resulted in the successful removal of the diospyrobezoar along with multiple small bowel obstructions. The patient was discharged after abatement of symptoms. The case presented here demonstrates the implementation of a conservative, yet successful, treatment as an alternative to conventional surgical removal of intestinal obstructions.

Zheng, Yi-Xiong; Prasoon, Pankaj; Chen, Yan; Hu, Liang; Chen, Li

2014-01-01

231

First Recorded Eruption of Mount Belinda Volcano, South Sandwich Islands  

NASA Astrophysics Data System (ADS)

The MODVOLC satellite monitoring system at the University of Hawaii Manoa has revealed the first recorded eruption of Mount Belinda volcano, on Montagu Island in the remote South Sandwich Islands. Here we present some initial qualitative observations gleaned from the relatively limited amount of satellite imagery available throughout the eruption, including MODIS, Landsat 7 ETM+ and ASTER data. The eruption started some time between September 12 and October 20, 2001, with low-level ash effusion. In January 2002 a Landsat 7 ETM+ image indicated possible collapse structures in the surface of the continuous ice cover within the caldera, suggesting some degree of subglacial volcanism. By May 2002, a broad area of lava or ash was observed close to the subaerial erupting centre, and activity subsequently increased to its highest observed levels in August 2002. Observations in February and March 2003, from a British Antarctic Survey ship and an aircraft of the British Royal Navy, provided the first visual confirmation of the eruption. Minor thermal anomalies continued to be observed in MODIS imagery throughout August 2003, indicating a prolonged low-level eruption or the establishment of a persistent summit lake possibly similar to that believed to occupy the summit crater (Mount Michael) on nearby Saunders Island. A dynamic lava lake on Saunders Island was first reported in 2001 and remains active.

Smellie, J.; Patrick, M.; Harris, A.; Garbeil, H.; Pilger, E.

2003-12-01

232

Sandwich module prototype progress for space solar power  

NASA Astrophysics Data System (ADS)

Space solar power (SSP) has been broadly defined as the collection of solar energy in space and its wireless transmission for use on earth. This approach 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 (MSC) 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. While prototypes of such modules have been designed and developed previously by several groups, none have been subjected to the challenging conditions inherent to the space environment and the possible solar concentration levels in which an array of modules might be required to operate. The research described herein details our team's efforts in the development of photovoltaic arrays, power electronics, microwave conversion electronics, and antennas for microwave-based "sandwich" module prototypes. The implementation status and testing results of the prototypes are reviewed.

Jaffe, Paul; Hodkin, Jason; Harrington, Forest; Person, Clark; Nurnberger, Michael; Nguyen, Bang; LaCava, Susie; Scheiman, Dave; Stewart, Grant; Han, Andrew; Hettwer, Ethan; Rhoades, Daniel

2014-02-01

233

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

NASA Technical Reports Server (NTRS)

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

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

2006-01-01

234

Mechanical properties characterization of composite sandwich materials intended for space antenna applications  

NASA Technical Reports Server (NTRS)

The composite materials proposed for use in the Advanced Communications Technology Satellite (ACTS) program contains a new, high modulus graphite fiber as the reinforcement. A study was conducted to measure certain mechanical properties of the new fiber-reinforced material as well as of a composite-faced aluminum honeycomb sandwich structure. Properties were measured at -157, 22, and 121 C. Complete characterization of this material was not intended. Longitudinal tensile, picture-frame shear, short-beam shear, and flexural tests were performed on specimens of the composite face-sheet materials. Unidirectional, cross-plied, and quasi-isotropic fiber composite ply layup designs were fabricated and tested. These designs had been studied by using NASA's Integrated Composite Analyzer (ICAN) computer program. Flexural tests were conducted on (+/- 60/0 deg) sub s composite-faced sandwich structure material. Resistance strain gages were used to measure strains in the tensile, picture-frame, and sandwich flexural tests. The sandwich flexural strength was limited by the core strength at 157 and 22 c. The adhesive bond strength was the limiting factor at 121 C. Adhesive mechanical properties are reflected in sandwich structure flexural properties when the span-to-depth ratio is great enough to allow a significant shear effect on the load-deflection behavior of the sandwich beam. Most measured properties agreed satisfactorily with the properties predicted by ICAN.

Bowles, Kenneth J.; Vannucci, Raymond D.

1989-01-01

235

Mechanical properties characterization of composite sandwich materials intended for space antenna applications  

NASA Technical Reports Server (NTRS)

The composite materials proposed for use in the Advanced Communications Technology Satellite (ACTS) Program contains a new, high modulus graphite fiber as the reinforcement. A study was conducted to measure certain mechanical properties of the new fiber-reinforced material as well as of a composite-faced aluminum honeycomb sandwich structure. Properties were measured at -157, 22, and 121 C. Complete characterization of this material was not intended. Longitudinal tensile, picture-frame shear, short-beam shear, and flexural tests were performed on specimens of the composite face-sheet materials. Unidirectional, cross-plied, and quasi-isotropic fiber composite ply layup designs were fabricated and tested. These designs had been studied by using NASA's Integrated Composite Analyzer (ICAN) computer program. Flexural tests were conducted on (+/- 60/0 deg) sub s composite-faced sandwich structure material. Resistance strain gages were used to measure strains in the tensile, picture-frame, and sandwich flexural tests. The sandwich flexural strength was limited by the core strength at -157 and 22 C. The adhesive bond strength was the limiting factor at 121 C. Adhesive mechanical properties are reflected in sandwich structure flexural properties when the span-to-depth ratio is great enough to allow a significant shear effect on the load-deflection behavior of the sandwich beam. Most measured properties agreed satisfactorily with the properties predicted by ICAN.

Bowles, Kenneth J.; Vannucci, Raymond D.

1986-01-01

236

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

237

A quantitative exposure model simulating human norovirus transmission during preparation of deli sandwiches.  

PubMed

Human noroviruses (HuNoVs) are a major cause of food borne gastroenteritis worldwide. They are often transmitted via infected and shedding food handlers manipulating foods such as deli sandwiches. The presented study aimed to simulate HuNoV transmission during the preparation of deli sandwiches in a sandwich bar. A quantitative exposure model was developed by combining the GoldSim® and @Risk® software packages. Input data were collected from scientific literature and from a two week observational study performed at two sandwich bars. The model included three food handlers working during a three hour shift on a shared working surface where deli sandwiches are prepared. The model consisted of three components. The first component simulated the preparation of the deli sandwiches and contained the HuNoV reservoirs, locations within the model allowing the accumulation of NoV and the working of intervention measures. The second component covered the contamination sources being (1) the initial HuNoV contaminated lettuce used on the sandwiches and (2) HuNoV originating from a shedding food handler. The third component included four possible intervention measures to reduce HuNoV transmission: hand and surface disinfection during preparation of the sandwiches, hand gloving and hand washing after a restroom visit. A single HuNoV shedding food handler could cause mean levels of 43±18, 81±37 and 18±7 HuNoV particles present on the deli sandwiches, hands and working surfaces, respectively. Introduction of contaminated lettuce as the only source of HuNoV resulted in the presence of 6.4±0.8 and 4.3±0.4 HuNoV on the food and hand reservoirs. The inclusion of hand and surface disinfection and hand gloving as a single intervention measure was not effective in the model as only marginal reductions of HuNoV levels were noticeable in the different reservoirs. High compliance of hand washing after a restroom visit did reduce HuNoV presence substantially on all reservoirs. The model showed that good handling practices such as washing hands after a restroom visit, hand gloving, hand disinfection and surface disinfection in deli sandwich bars were an effective way to prevent HuNoV contamination of the prepared foods, but it also demonstrated that further research is needed to ensure a better assessment of the risk of HuNoV transmission during preparation of foods. PMID:25544470

Stals, Ambroos; Jacxsens, Liesbeth; Baert, Leen; Van Coillie, Els; Uyttendaele, Mieke

2015-03-01

238

A novel manifold-manifold distance index applied to looseness state assessment of viscoelastic sandwich structures  

NASA Astrophysics Data System (ADS)

Viscoelastic sandwich structures (VSS) are widely used in mechanical equipment; their state assessment is necessary to detect structural states and to keep equipment running with high reliability. This paper proposes a novel manifold-manifold distance-based assessment (M2DBA) method for assessing the looseness state in VSSs. In the M2DBA method, a manifold-manifold distance is viewed as a health index. To design the index, response signals from the structure are firstly acquired by condition monitoring technology and a Hankel matrix is constructed by using the response signals to describe state patterns of the VSS. Thereafter, a subspace analysis method, that is, principal component analysis (PCA), is performed to extract the condition subspace hidden in the Hankel matrix. From the subspace, pattern changes in dynamic structural properties are characterized. Further, a Grassmann manifold (GM) is formed by organizing a set of subspaces. The manifold is mapped to a reproducing kernel Hilbert space (RKHS), where support vector data description (SVDD) is used to model the manifold as a hypersphere. Finally, a health index is defined as the cosine of the angle between the hypersphere centers corresponding to the structural baseline state and the looseness state. The defined health index contains similarity information existing in the two structural states, so structural looseness states can be effectively identified. Moreover, the health index is derived by analysis of the global properties of subspace sets, which is different from traditional subspace analysis methods. The effectiveness of the health index for state assessment is validated by test data collected from a VSS subjected to different degrees of looseness. The results show that the health index is a very effective metric for detecting the occurrence and extension of structural looseness. Comparison results indicate that the defined index outperforms some existing state-of-the-art ones.

Sun, Chuang; Zhang, Zhousuo; Guo, Ting; Luo, Xue; Qu, Jinxiu; Zhang, Chenxuan; Cheng, Wei; Li, Bing

2014-06-01

239

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

240

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

241

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

242

Hypervelocity Impact Performance of Open Cell Foam Core Sandwich Panel Structures  

NASA Technical Reports Server (NTRS)

Metallic foams are a relatively new class of materials with low density and novel physical, mechanical, thermal, electrical and acoustic properties. Although incompletely characterized, they offer comparable mechanical performance to traditional spacecraft structural materials (i.e. honeycomb sandwich panels) without detrimental through-thickness channeling cells. There are two competing types of metallic foams: open cell and closed cell. Open cell foams are considered the more promising technology due to their lower weight and higher degree of homogeneity. Leading micrometeoroid and orbital debris shields (MMOD) incorporate thin plates separated by a void space (i.e. Whipple shield). Inclusion of intermediate fabric layers, or multiple bumper plates have led to significant performance enhancements, yet these shields require additional non-ballistic mass for installation (fasteners, supports, etc.) that can consume up to 35% of the total shield weight [1]. Structural panels, such as open cell foam core sandwich panels, that are also capable of providing sufficient MMOD protection, represent a significant potential for increased efficiency in hypervelocity impact shielding from a systems perspective through a reduction in required non-ballistic mass. In this paper, the results of an extensive impact test program on aluminum foam core sandwich panels are reported. The effect of pore density, and core thickness on shielding performance have been evaluated over impact velocities ranging from 2.2 - 9.3 km/s at various angles. A number of additional tests on alternate sandwich panel configurations of comparable-weight have also been performed, including aluminum honeycomb sandwich panels (see Figure 1), Nomex honeycomb core sandwich panels, and 3D aluminum honeycomb sandwich panels. A total of 70 hypervelocity impact tests are reported, from which an empirical ballistic limit equation (BLE) has been derived. The BLE is in the standard form suitable for implementation in risk analysis software, and includes the effect of panel thickness, core density, and facesheet material properties. A comparison between the shielding performance of foam core sandwich panel structures and common MMOD shielding configurations is made for both conservative (additional 35% non-ballistic mass) and optimistic (additional mass equal to 30% of bumper mass) considerations. Suggestions to improve the shielding performance of foam core sandwich panels are made, including the use of outer mesh layers, intermediate fabric/composite layers, and varying pore density.

Ryan, Shannon; Christiansen, Eric; Lear, Dana

2009-01-01

243

Carbon sandwich preparation preserves quality of two-dimensional crystals for cryo-electron microscopy  

PubMed Central

Received 7 June 2013; accepted 21 June 2013Abstract Electron crystallography is an important method for determining the structure of membrane proteins. In this paper, we show the impact of a carbon sandwich preparation on the preservation of crystalline sample quality, using characteristic examples of two-dimensional (2D) crystals from gastric H+,K+-ATPase and their analyzed images. Compared with the ordinary single carbon support film preparation, the carbon sandwich preparation dramatically enhanced the resolution of images from flat sheet 2D crystals. As water evaporation is restricted in the carbon-sandwiched specimen, the improvement could be due to the strong protective effect of the retained water against drastic changes in the environment surrounding the specimen, such as dehydration and increased salt concentrations. This protective effect by the carbon sandwich technique helped to maintain the inherent and therefore best crystal conditions for analysis. Together with its strong compensation effect for the image shift due to beam-induced specimen charging, the carbon sandwich technique is a powerful method for preserving crystals of membrane proteins with larger hydrophilic regions, such as H+,K+-ATPase, and thus constitutes an efficient and high-quality method for collecting data for the structural analysis of these types of membrane proteins by electron crystallography. PMID:23883606

Yang, Fan; Abe, Kazuhiro; Tani, Kazutoshi; Fujiyoshi, Yoshinori

2013-01-01

244

Compression After Impact Testing of Sandwich Structures Using the Four Point Bend Test  

NASA Technical Reports Server (NTRS)

For many composite laminated structures, the design is driven by data obtained from Compression after Impact (CAI) testing. There currently is no standard for CAI testing of sandwich structures although there is one for solid laminates of a certain thickness and lay-up configuration. Most sandwich CAI testing has followed the basic technique of this standard where the loaded ends are precision machined and placed between two platens and compressed until failure. If little or no damage is present during the compression tests, the loaded ends may need to be potted to prevent end brooming. By putting a sandwich beam in a four point bend configuration, the region between the inner supports is put under a compressive load and a sandwich laminate with damage can be tested in this manner without the need for precision machining. Also, specimens with no damage can be taken to failure so direct comparisons between damaged and undamaged strength can be made. Data is presented that demonstrates the four point bend CAI test and is compared with end loaded compression tests of the same sandwich structure.

Nettles, Alan T.; Gregory, Elizabeth; Jackson, Justin; Kenworthy, Devon

2008-01-01

245

Feasibility of active sandwich detectors for single-shot dual-energy imaging  

NASA Astrophysics Data System (ADS)

We revisit the doubly-layered sandwich detector configuration for single-shot dual-energy x-ray imaging. In order to understand its proper operation, we investigated the contrast-to-noise performance in terms of the x-ray beam setup using the Monte Carlo methods. Using a pair of active photodiode arrays coupled to phosphor screens, we have built a sandwich detector. For better spectral separation between the projection images obtained from the front and rear detectors during a single x-ray exposure, we inserted a copper sheet between two detectors. We have successfully obtained soft tissue- and bone-enhanced images for a postmortem mouse with the developed sandwich detector using weighted logarithmic subtraction, and the image quality was comparable to those achieved by the conventional kVp-switching technique. Although some problems to be mitigated for the optimal and practical use, for example, the scatter effect and image registration, are still left, the performance of the sandwich detector for single-shot dual-energy x-ray imaging is promising. We expect that the active sandwich detector will provide motion-artifact-free dual-energy images with a reasonable image quality.

Yun, Seungman; Han, Jong Chul; Kim, Dong Woon; Youn, Hanbean; Kim, Ho Kyung; Tanguay, Jesse; Cunningham, Ian A.

2014-03-01

246

Dynamic analysis of magnetorheological elastomer-based sandwich beam with conductive skins under various boundary conditions  

NASA Astrophysics Data System (ADS)

The dynamic analysis of a three-layered symmetric sandwich beam with magnetorheological elastomer (MRE) embedded viscoelastic core and conductive skins subjected to a periodic axial load have been carried out under various boundary conditions. As the skins of the sandwich beam are conductive, magnetic loads are applied to the skins during vibration. Due to the field-dependent shear modulus of MRE material, the stiffness of the MRE embedded sandwich beam can be changed by the application of magnetic fields. Using extended Hamilton's principle along with generalized Galarkin's method the governing equation of motion has been derived. The free vibration analysis of the system has been carried out and the results are compared with the published experimental and analytical results which are found to be in good agreement. The parametric instability regions of the sandwich beam have been determined for various boundary conditions. Here, recently developed magnetorheological elastomer based on natural rubber containing iron particles and carbon blacks have been used. The effects of magnetic field, length of MRE patch, core thickness, percentage of iron particles and carbon blacks on the regions of parametric instability for first three modes of vibration have been studied. These results have been compared with the parametric instability regions of the sandwich beam with fully viscoelastic core to show the passive and active vibration reduction of these structures using MRE and magnetic field. Also, the results are compared with those obtained using higher order theory.

Nayak, B.; Dwivedy, S. K.; Murthy, K. S. R. K.

2011-04-01

247

Construction Technologies.  

ERIC Educational Resources Information Center

This document contains materials developed for and about the construction technologies tech prep program of the South-Western City Schools in Ohio. Part 1 begins with a map of the program, which begins with a construction technologies program in grades 11 and 12 that leads to entry-level employment or one of five 2-year programs at a community…

Columbus State Community Coll., OH.

248

Tests of graphite/polyimide sandwich panels in uniaxial edgewise compression  

NASA Technical Reports Server (NTRS)

The local and general buckling behavior of graphite/polyimide sandwich panels simply supported along all four edges and loaded in uniaxial edgewise compression were investigated. Material properties of sandwich panel constituents (adhesive and facings) were determined from flatwise tension and sandwich beam flexure tests. Buckling specimens were 30.5 by 33 cm, had quasi-isotropic, symmetric facings, and a glass/polyimide honeycomb core. Core thicknesses were varied and three panels of each thickness were tested at room temperature to investigate failure modes and corresponding buckling loads. Specimens 0.635 cm thick failed by overall buckling at loads close to the analytically predicted buckling load; all other panels failed by face wrinkling. Results of the wrinkling tests indicated that several buckling formulas were unconservative and therefore not suitable for design purposes; a recommended wrinkling equation is presented.

Camarda, C. J.

1980-01-01

249

A Higher-Order Bending Theory for Laminated Composite and Sandwich Beams  

NASA Technical Reports Server (NTRS)

A higher-order bending theory is derived for laminated composite and sandwich beams. This is accomplished by assuming a special form for the axial and transverse displacement expansions. An independent expansion is also assumed for the transverse normal stress. Appropriate shear correction factors based on energy considerations are used to adjust the shear stiffness. A set of transverse normal correction factors is introduced, leading to significant improvements in the transverse normal strain and stress for laminated composite and sandwich beams. A closed-form solution to the cylindrical elasticity solutions for a wide range of beam aspect ratios and commonly used material systems. Accurate shear stresses for a wide range of laminates, including the challenging unsymmetric composite and sandwich laminates, are obtained using an original corrected integration scheme. For application of the theory to a wider range of problems, guidelines for finite element approximations are presented.

Cook, Geoffrey M.

1997-01-01

250

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

251

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

252

Three-dimensional solutions for thermomechanical stresses in sandwich panels and shells  

NASA Technical Reports Server (NTRS)

Analytic three-dimensional thermoelasticity solutions are presented for static problems of simply supported sandwich panels and cylindrical shells subjected to mechanical and thermal loads. The panels and shells have laminated composite face sheets of arbitrary thickness separated by a core. Each of the individual layers of the face sheets and the core is modeled as a three-dimensional continuum. Analytic first-order sensitivity coefficients are evaluated to assess the sensitivity of the responses to variations in material parameters of the face sheets and the core, as well as to variations in the curvatures and thicknesses of the sandwich and face sheets. Also, the strain energy associated with various stress components in the face sheets and core are calculated and compared. The information obtained in the present study can aid the development and assessment of two-dimensional models for sandwich structures and illuminate the role of particular material parameters in an equivalent model for the core.

Burton, W. Scott; Noor, Ahmed K.

1995-01-01

253

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

254

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

255

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

2008-03-13

256

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

2013-05-01

257

Construction crane  

NSDL National Science Digital Library

People who operate construction cranes carrying heavy loads must be coordinated. The load on the crane must not injure any workers or anyone else near the site. They must be careful to maneuver heavy loads around buildings without hitting them.

N/A N/A (None; )

2007-07-25

258

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

259

Space Construction  

NASA Technical Reports Server (NTRS)

The purpose was to present to the aerospace community an in-depth review of Experimental Assembly of Structures on EVA (EASE)/Assembly Concept for Construction of Erectable Space Structures (ACCESS) space flight experiments and to present the status of activities regarding future space flight experiments and accompanying technology developments that will demonstrate the capability of on-orbit construction required for the Space Station.

Hagaman, Jane A. (editor)

1987-01-01

260

Worldwide construction  

SciTech Connect

The paper lists major construction projects in worldwide processing and pipelining, showing capacities, contractors, estimated costs, and time of construction. The lists are divided into refineries, petrochemical plants, sulfur recovery units, gas processing plants, pipelines, and related fuel facilities. This last classification includes cogeneration plants, coal liquefaction and gasification plants, biomass power plants, geothermal power plants, integrated coal gasification combined-cycle power plants, and a coal briquetting plant.

Williamson, M.

1994-10-17

261

Analyses for Debonding of Stitched Composite Sandwich Structures Using Improved Constitutive Models  

NASA Technical Reports Server (NTRS)

A fracture mechanics analysis based on strain energy release rates is used to study the effect of stitching in bonded sandwich beam configurations. Finite elements are used to model the configurations. The stitches were modeled as discrete nonlinear spring elements with a compliance determined by experiment. The constitutive models were developed using the results of flatwise tension tests from sandwich material rather than monolithic material. The analyses show that increasing stitch stiffness, stitch density and debond length decrease strain energy release rates for a fixed applied load.

Glaessgen, E. H.; Sleight, D. W.; Krishnamurthy, T.; Raju, I. S.

2001-01-01

262

Impact damage detection in sandwich composite structures using Lamb waves and laser vibrometry  

NASA Astrophysics Data System (ADS)

This experimental study explores the feasibility of impact damage detection in composite sandwich structures using Lamb wave excitation and signals acquired with a laser Doppler vibrometer. Energy maps are computed from the transient velocity wave fields and used to highlight defect areas in impacted coupons of foam core and honeycomb core sandwich materials. The technique performs well for the detection of barely visible damage in this type of material, and is shown to be robust in the presence of wave reverberation. Defect extent information is not always readily retrieved from the obtained defect signatures, which depend on the wave - defect interaction mechanisms.

Lamboul, B.; Passilly, B.; Roche, J.-M.; Osmont, D.

2013-01-01

263

FaceSheet Push-off Tests to Determine Composite Sandwich Toughness at Cryogenic Temperatures  

NASA Technical Reports Server (NTRS)

A new novel test method, associated analysis, and experimental procedures are developed to investigate the toughness of the facesheet-to-core interface of a sandwich material at cryogenic temperatures. The test method is designed to simulate the failure mode associated with facesheet debonding from high levels of gas pressure in the sandwich core. The effects of specimen orientation are considered, and the results of toughness measurements are presented. Comparisons are made between room and liquid nitrogen (-196 C) test temperatures. It was determined that the test method is insensitive to specimen facesheet orientation and strain energy release rate increases with a decrease in the test temperature.

Gates, Thomas S.; Herring, Helen M.

2001-01-01

264

Cherenkov radiation of a Josephson vortex moving in a sandwich embedded in a dielectric medium  

SciTech Connect

A motion of a Josephson vortex in a long sandwich embedded in a dielectric medium is described. If the velocity of the vortex is greater than the velocity of light in the dielectric, terahertz-band Cherenkov radiation is generated and emitted from the lateral surface of the sandwich. The radiation loss power is determined. In the case when radiation loss is compensated for by the energy gain due to transport current, a relation between the current and the velocity of the vortex is obtained.

Malishevskii, A. S., E-mail: malish@lebedev.ru; Silin, V. P.; Uryupin, S. A.; Uspenskii, S. G. [Russian Academy of Sciences, Lebedev Physical Institute (Russian Federation)

2008-08-15

265

A {3,2}-Order Bending Theory for Laminated Composite and Sandwich Beams  

NASA Technical Reports Server (NTRS)

A higher-order bending theory is derived for laminated composite and sandwich beams thus extending the recent {1,2}-order theory to include third-order axial effect without introducing additional kinematic variables. The present theory is of order {3,2} and includes both transverse shear and transverse normal deformations. A closed-form solution to the cylindrical bending problem is derived and compared with the corresponding exact elasticity solution. The numerical comparisons are focused on the most challenging material systems and beam aspect ratios which include moderate-to-thick unsymmetric composite and sandwich laminates. Advantages and limitations of the theory are discussed.

Cook, Geoffrey M.; Tessler, Alexander

1998-01-01

266

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

267

The low velocity impact response of sandwich beams with a corrugated core or a Y-frame core  

E-print Network

1 The low velocity impact response of sandwich beams with a corrugated core or a Y-frame core L. St sandwich beams with corrugated and Y-frame cores have been measured in a drop-weight apparatus at 5 ms-1-statically. Moreover, the corrugated and Y-frame core beams had similar performances. Three-dimensional finite element

Fleck, Norman A.

268

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

E-print Network

theory, Higher-order Models, Sandwich panels, Homogenization, Periodic plates, Folded cores, Chevron-Gradient homogenization scheme and apply it to a sandwich panel including the chevron pattern. It turns out that the shear to a broad variety of configurations. The present work is dedicated to the chevron pattern (Figure A.1) which

Paris-Sud XI, Université de

269

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

270

Structure and characterization of zero- to two-dimensional compounds built up of the sandwich-type clusters and transition-metal linkers  

SciTech Connect

Five new heteropolyoxotungstates K{sub 2}Na{sub 2}Mn{sub 2}(H{sub 2}O){sub 12}[Mn{sub 2}(H{sub 2}O){sub 10}Mn{sub 4}(H{sub 2}O){sub 2}(XW{sub 9}O{sub 34}){sub 2}].18H{sub 2}O (X=Ge, 1; X=Si, 2), Na{sub 4}[Mn{sub 4}(H{sub 2}O){sub 18}Mn{sub 4}(H{sub 2}O){sub 2}(XW{sub 9}O{sub 34}){sub 2}].22H{sub 2}O (X=Ge, 3; X=Si, 4) and K{sub 3}Na{sub 5}[Mn{sub 2}(H{sub 2}O){sub 6}Mn{sub 4}(H{sub 2}O){sub 2}(SiW{sub 9}O{sub 34}){sub 2}].23.5H{sub 2}O (5) have been obtained by the routine synthetic reactions in aqueous solution. In 1 and 2, two isolated Mn{sup 2+} ions are covalently linked to the sandwich-type polyoxoanions [Mn{sub 4}(H{sub 2}O){sub 2}(B-{alpha}-XW{sub 9}O{sub 34}){sub 2}]{sup 12-} (X=Ge or Si) by two {mu}{sub 2}-oxygen atoms resulting in the disupporting sandwich-type polyoxometalates (POMs). Compounds 3 and 4 are built from the disupporting sandwich-type polyoxoanions 1 and 2, linked by additional four Mn{sup 2+} ions to construct a 1D ladder-like chain-like structure, which is rarely observed in the POM chemistry. Compound 5 represents the first example of the 2D structure consisting of the sandwich-type polyoxoanion [Mn{sub 4}(H{sub 2}O){sub 2}(SiW{sub 9}O{sub 34}){sub 2}]{sup 12-} and the binuclear {l_brace}Mn{sub 2}(H{sub 2}O){sub 6}{r_brace}{sup 4+} group. The magnetic studies of compounds 1, 4 and 5 indicate that the antiferromagnetic interactions are predominant in the three compounds between Mn(II) metal ions. - Graphical abstract: Five new compounds, from zero- to two-dimensional built up of the sandwich-type clusters and transition-metal linkers, have been obtained by the routine synthetic reactions in aqueous solution. This polyoxoanion framework architecture represents the first example of the 2D structure consisting of the sandwich-type polyoxoanion [Mn{sub 4}(H{sub 2}O){sub 2}(SiW{sub 9}O{sub 34}){sub 2}]{sup 12-} and the binuclear {l_brace}Mn{sub 2}(H{sub 2}O){sub 6}{r_brace}{sup 4+} group. Display Omitted.

Zhang Zhiming; Yao Shuang [Key Laboratory of Polyoxometalate Science of Ministry of Education, Department of Chemistry, Northeast Normal University, Renmin Street No. 5268, Changchun, Jinlin 130024 (China); Wang Enbo [Key Laboratory of Polyoxometalate Science of Ministry of Education, Department of Chemistry, Northeast Normal University, Renmin Street No. 5268, Changchun, Jinlin 130024 (China)], E-mail: wangenbo@public.cc.jl.cn; Qin Chao; Qi Yanfei [Key Laboratory of Polyoxometalate Science of Ministry of Education, Department of Chemistry, Northeast Normal University, Renmin Street No. 5268, Changchun, Jinlin 130024 (China); Li Yangguang [Key Laboratory of Polyoxometalate Science of Ministry of Education, Department of Chemistry, Northeast Normal University, Renmin Street No. 5268, Changchun, Jinlin 130024 (China); Universite Bordeaux 1, CNRS, Centre de Recherche Paul Pascal (CRPP)-UPR 8641, 115 avenue du Dr. A. Schweitzer, 33600 Pessac (France)], E-mail: Liyg658@nenu.edu.cn; Clerac, Rodolphe [Universite Bordeaux 1, CNRS, Centre de Recherche Paul Pascal (CRPP)-UPR 8641, 115 avenue du Dr. A. Schweitzer, 33600 Pessac (France)

2008-04-15

271

Structural and impact behaviour of an innovative low-cost sandwich panel  

Microsoft Academic Search

The classic sandwich structure consists of two thin and stiff face sheets and a thick, lightweight and stiff enough material in between. Although this structure seems optimal, in practice the large differences between the structural properties of the materials in contact create many problems. Moreover, the cost of the existing core materials is very high, pushing towards the selection of

A. G. Mamalis; K. N. Spentzas; D. E. Manolakos; N. Pantelelis; M. Ioannidis

2008-01-01

272

Ferrocene analogues of sandwich B12·Cr·B12: a theoretical study.  

PubMed

The bowl B(12) 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(B(12))(2) (D(3d)) have been investigated by using density functional theory. It is found that the sandwich Cr(B(12))(2) (D(3d)) is a stable complex with large binding energy (-5.93 eV) and HOMO-LUMO gap (2.37 eV), as well as Fe(C(5)H(5))(2) and Cr(C(6)H(6))(2), following the 18-electron principle. The detailed molecular orbitals and aromaticity analyses indicate that the sandwich compound Cr(B(12))(2) (D(3d)) is electronically very stable. The natural bond orbital analysis suggests that spd-? interaction plays an important role in the sandwich compounds. PMID:23320677

Yuan, Yuan; Cheng, Longjiu

2013-01-14

273

Indentation of Foam-Based Polymer Composite Sandwich Beams and Panels Under Static Loading  

NASA Astrophysics Data System (ADS)

Foam core composite sandwich structures are highly susceptible to damage when subjected to localized loading. Therefore, thorough study of the role of factors such as face sheet thickness, indentor diameter value, and crosshead displacement rate in indentation events is important. The objective of the present work is to investigate experimentally and numerically the influence of these factors on the nonlinear static indentation behavior of sandwich beams and panels consisting of glass fiber/resin face sheets and PVC (polyvinylchloride) foam core. Static indentation tests are carried out on sandwich composite beam and panel specimens using steel cylindrical and spherical indentors, respectively. Numerical models are developed for simulating the mechanical response of sandwich structures subjected to localized indentation beyond the limit of elastic deformation in the foam core. In this relation, the *CRUSHABLE FOAM and the *CRUSHABLE FOAM HARDENING options in the ABAQUS finite element program system are used. The numerical analysis results demonstrate good agreement with experimental data. It is found that increasing the face sheet thickness and indentor diameter value leads to increase in the load (for a given displacement). It is shown also that the indentation behavior does not exhibit sensitivity to crosshead displacement rate over the conditions considered in the present work.

Rizov, V.

2009-06-01

274

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

E-print Network

and prototyping of low-density carbon fiber sandwich panel cores based on laser beam cutting (LBC). Using LCB by Elsevier Ltd. All rights reserved. Keywords: Composite; Lattice structure; Laser beam cutting; Mechanical (2012) 5322­5334 #12;corrugated core with large, flat upper and lower bonding surfaces. This method

Vaziri, Ashkan

275

Curettage and reconstruction by the sandwich technique for giant cell tumours around the knee.  

PubMed

PURPOSE. To evaluate outcomes of 36 patients who underwent curettage, use of phenol, and reconstruction using the sandwich technique for giant cell tumour (GCT) of bone around the knee. METHODS. 22 women and 14 men aged 19 to 46 (mean, 29.6) years underwent intralesional curettage, use of phenol, and reconstruction using the sandwich technique for GCT of the proximal tibia (n=23) or distal femur (n=13). Two of the cases were recurrences. Two, 18, and 16 tumours were classified as grade I, grade II, and grade III, respectively. Five of the grade III tumours were associated with an extra-articular pathological fracture. Patients underwent intralesional curettage, use of phenol, and reconstruction with allograft, gel foam, and cement (the sandwich technique). Pathological fractures were fixed with plates. Functional outcome was evaluated using the Musculoskeletal Tumor Society (MSTS) score. RESULTS. The mean follow-up period was 5 (2.5-11) years. The mean MSTS score was 27.7 out of 30 (standard deviation, 3; range, 16-30). One patient with a grade III tumour in the proximal tibia had a recurrence detected elsewhere after 3 years. Her MSTS score at 2 years was 26. No patient had malignant transformation. CONCLUSION. Intralesional curettage, use of phenol, and reconstruction with allograft, gel foam, and cement (the sandwich technique) for GCT of bone achieved good functional outcome and a low recurrence rate. PMID:25550017

Saibaba, B; Chouhan, D K; Kumar, V; Dhillon, M S; Rajoli, S R

2014-12-01

276

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

E-print Network

of transport (automotive, aero- nautics, shipbuilding and railroads) or civil engineering. NeverthelessOn the computation of interface stresses by finite elements for sandwich materials Vincent Manet ´Ecole des Mines de Saint-Etienne, Material and Mechanical Department, 158, cours Fauriel, 42023 Saint

Paris-Sud XI, Université de

277

Modal analysis and acoustic transmission through offset-core honeycomb sandwich panels  

NASA Astrophysics Data System (ADS)

The work presented in this thesis is motivated by an earlier research that showed that double, offset-core honeycomb sandwich panels increased thermal resistance and, hence, decreased heat transfer through the panels. This result lead to the hypothesis that these panels could be used for acoustic insulation. Using commercial finite element modeling software, COMSOL Multiphysics, the acoustical properties, specifically the transmission loss across a variety of offset-core honeycomb sandwich panels, is studied for the case of a plane acoustic wave impacting the panel at normal incidence. The transmission loss results are compared with those of single-core honeycomb panels with the same cell sizes. The fundamental frequencies of the panels are also computed in an attempt to better understand the vibrational modes of these particular sandwich-structured panels. To ensure that the finite element analysis software is adequate for the task at hand, two relevant benchmark problems are solved and compared with theory. Results from these benchmark results compared well to those obtained from theory. Transmission loss results from the offset-core honeycomb sandwich panels show increased transmission loss, especially for large cell honeycombs when compared to single-core honeycomb panels.

Mathias, Adam Dustin

278

Ultra-Lightweight Nanocomposite Foams and Sandwich Structures for Space Structure Applications  

NASA Technical Reports Server (NTRS)

Microcellular nanocomposite foams and sandwich structures have been created to have excellent electrical conductivity and radiation-resistant properties using a new method that does not involve or release any toxicity. The nanocomposite structures have been scaled up in size to 12 X 12 in. (30 X 30 cm) for components fabrication. These sandwich materials were fabricated mainly from PE, CNF, and carbon fibers. Test results indicate that they have very good compression and compression-after-impact properties, excellent electrical conductivity, and superior space environment durability. Compression tests show that 1000 ESH (equivalent Sun hours) of UV exposure has no effect on the structural properties of the sandwich structures. The structures are considerably lighter than aluminum alloy (= 36 percent lighter), which translates to 36 percent weight savings of the electronic enclosure and its housing. The good mechanical properties of the materials may enable the electronic housing to be fabricated with a thinner structure that further reduces the weight. There was no difficulty in machining the sandwich specimens into electronic enclosure housing.

Tan, Seng

2012-01-01

279

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

280

Non Destructive Testing of sandwich composites: adhesion defects evaluation; Experimental and Finite  

E-print Network

Non Destructive Testing of sandwich composites: adhesion defects evaluation; Experimental and the glue film, or by suppression of glue on small area (before curing process). The A0 Lamb mode an aluminium honeycomb by bonding. However an intensive load or cycle loading can induce debonding

Paris-Sud XI, Université de

281

Sandwiches come with the following: Mayo or mustard, lettuce, tomatoes, red onions, pickles, pepperoncinis, salt & pepper.  

E-print Network

COLD TOGO'S WAY Sandwiches come with the following: Mayo or mustard, lettuce, tomatoes, red onions & SWEETS SALADS & SALAD WRAPS FAVORITES BBQ Ranch Chicken - Chicken, BBQ sauce, red onions, tomatoes, carrots, red cabbage, wontons and sesame seeds, lettuce, green onions and Italian parsley, Asian dressing

de Lijser, Peter

282

Appearance of ``Fragile'' Fermi Liquids in Finite-Width Mott Insulators Sandwiched between Metallic Leads  

E-print Network

temperatures, the Mott insulator develops a thermal excitation induced (one electron) density of states (DOSAppearance of ``Fragile'' Fermi Liquids in Finite-Width Mott Insulators Sandwiched between Metallic that the normal-metal proximity effect could force any finite number of Mott-insulating ``barrier'' planes

Freericks, Jim

283

Optimum stacking sequence design of composite sandwich panel using genetic algorithms  

NASA Astrophysics Data System (ADS)

Composite sandwich structures recently gained preference for various structural components over conventional metals and simple composite laminates in the aerospace industries. For most widely used composite sandwich structures, the optimization problems only requires the determination of the best stacking sequence and the number of laminae with different fiber orientations. Genetic algorithm optimization technique based on Darwin's theory of survival of the fittest and evolution is most suitable for solving such optimization problems. The present research work focuses on the stacking sequence optimization of composite sandwich panels with laminated face-sheets for both critical buckling load maximization and thickness minimization problems, subjected to bi-axial compressive loading. In the previous studies, only balanced and even-numbered simple composite laminate panels have been investigated ignoring the effects of bending-twisting coupling terms. The current work broadens the application of genetic algorithms to more complex composite sandwich panels with balanced, unbalanced, even and odd-numbered face-sheet laminates including the effects of bending-twisting coupling terms.

Bir, Amarpreet Singh

284

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

NASA Technical Reports Server (NTRS)

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 panels have been evaluated with internal pressure loads that generate biaxial tension loading conditions. Design limit load and design ultimate load tests have been performed on both panels. One of the sandwich panels was tested with the middle frame removed to demonstrate the suitability of this two-frame design for supporting the prescribed biaxial loading conditions with twice the initial frame spacing of 20 inches. A damage tolerance study was conducted on the two-frame panel by cutting a notch in the panel that originates at the edge of a cutout and extends in the panel hoop direction through the window-belt area. This panel with a notch was tested in a combined-load condition to demonstrate the structural damage tolerance at the design limit load condition. Both the sandwich panel designs successfully satisfied all desired load requirements in the experimental part of the study, and experimental results from the two-frame panel with and without damage are fully explained by the analytical results. The results of this study suggest that there is potential for using sandwich structural concepts with greater than the usual 20-in. wide frame spacing to further reduce aircraft fuselage structural weight.

Rouse, Marshall; Ambur, Damodar R.; Dopker, Bernard; Shah, Bharat

1998-01-01

285

Experimental investigation of graphite/polyimide sandwich panels in edgewise compression. M.S. Thesis  

NASA Technical Reports Server (NTRS)

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 determined from flatwise tension and sandwich beam flexure tests. An adhesive bond study resulted in the selection of a suitable cure cycle for FM 34 polyimide film adhesive and, a bonding technique using a liquid cell edge version of that adhesive resulted in considerable mass savings. Tensile and compressive material properties of the facings, quasiisotropic, symmetric, laminates (0, +45,90,-45)s of Celion/PMR-15, were determined at 116, R.T., and 589 K (-250, R.T., and 600 F) usng the sandwich beam flexure test method. Results indicate the Gr/PI is a usable structural material for short term use at temperatures as high as 589 K (600 F). Buckling specimens were 1006.5 sq cm. 156 sq in., had quasiisotropic symmetric facings (0, + or - 45,90)s and a glass/polyimide honeycomb core (HRH-327-3/8-4).

Camarda, C. J.

1980-01-01

286

The forced vibration of a three-layer, damped sandwich beam with arbitrary boundary conditions  

Microsoft Academic Search

The sixth-order differential equation of motion is derived in terms of the transverse displacement, w, for a three-layer sandwich beam with a viscoelastic core. Mathematical expressions in terms of w are found for a variety of beam boundary conditions. The solution of the differential equation by the method of Di Taranto is shown to yield a special class of complex,

D. J. Mead; S. Markus

1969-01-01

287

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

288

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

289

Response surface characterization of the mechanical behavior of impact-damaged sandwich composites  

Microsoft Academic Search

In this research, Response Surface Methodology (RSM) is employed to characterize the influence of material configuration on the damage tolerance and residual strength characteristics of sandwich composites. Test specimens used were comprised of carbon-epoxy woven fabric facesheets, and Nomex honeycomb cores. The ranges of the material configuration used are typical of those employed in aircraft applications. A series of carefully

Issam K. Samarah; Gamal S. Weheba; Thomas E. Lacy

2006-01-01

290

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

291

Modelling of low-energy\\/low-velocity impact on Nomex honeycomb sandwich structures with metallic skins  

Microsoft Academic Search

In the aircraft industry, manufacturers have to decide quickly whether an impacted sandwich needs repairing or not. Certain computation tools exist at present but they are very time-consuming and they also fail to perfectly model the physical phenomena involved in an impact. In a previous publication, the authors demonstrated the possibility of representing the Nomex™ honeycomb core by a grid

B. Castanié; C. Bouveta; Y. Aminanda; J.-J. Barrau; P. Thevenet

2008-01-01

292

A SERS-based sandwich assay for ultrasensitive and selective detection of Alzheimer's tau protein.  

PubMed

In this study, a simple and highly selective homogeneous sandwich assay was developed for fast and ultrasensitive detection of the tau protein using a combination of monoclonal antitau functionalized hybrid magnetic nanoparticles and polyclonal antitau immobilized gold nanoparticles as the recognition and surface-enhanced Raman scattering (SERS) component, respectively. The magnetic silica particles were first coated with poly(2-hydroxyethyl methacrylate) via surface-mediated reversible addition-fragmentation chain transfer (RAFT) polymerization and then biofunctionalized with monoclonal antitau, which are both specific for tau and can be collected via a simple magnet. After separating tau from the sample matrix, they were sandwiched with the SERS substrate composed of polyclonal antitau and 5,5-dithiobis(2-dinitrobenzoic acid) on gold nanoparticles. The correlation between the tau concentration and SERS signal was found to be linear within the range of 25 fM to 500 nM. The limit of detection for the sandwich assay is less than 25 fM. Moreover, the sandwich assay was also evaluated for investigating the tau specificity on bovine serum albumin and immunoglobulin G. PMID:23885927

Zengin, Adem; Tamer, Ugur; Caykara, Tuncer

2013-09-01

293

Performance of metallic honeycomb-core sandwich beams under shock loading  

E-print Network

; received in revised form 16 June 2005 Available online 26 August 2005 Abstract Stainless steel square-duration impulses using a shock simulation technique involving high-speed impact of Al foam projectiles associated with nearby explosions, the sandwich beams exhibit smaller displacements than the solid beams

Hutchinson, John W.

294

Computer program for determination of natural frequencies of closed spherical sandwich shells  

NASA Technical Reports Server (NTRS)

Solutions for the axially symmetric motion of an elastic spherical sandwich shell have been obtained from a theory of shells which includes the effects of transverse shear deformation and rotary inertia. Frequency equations and mode shapes are derived for the full vibrations of a closed spherical shell.

Wilkinson, J. P. D.

1967-01-01

295

Novel hybrid hetero-sandwich architectures via stoichiometric control of host-guest self-organization.  

PubMed

Thiocyanate cadmium and methylviologen hybrid host-guest compounds give two novel multiple sandwich architectures with regular or irregular grids of the anionic layer in the structures as effected by the molar ratios of starting ingredients, and show evidence of charge-transfer to the organic dications. PMID:15010762

Yu, Zhi; Yu, Kui; Lai, Longli; Udachin, Kostantin A; Zhu, Haoguo; Tao, Jianqin; You, Xiaozeng; Ströbele, Markus; Meyer, H-Jürgen; Ripmeester, John A

2004-03-21

296

Damage Detection and Impact Testing on Laminated and Sandwich Composite Panels  

NASA Technical Reports Server (NTRS)

This research investigates health monitoring of sandwich shell composites to determine if the Transmittance Functions (TF) are effective in determining the present of damage. The health monitoring test was conducted on the sandwich plates before and after low velocity impacts using the health monitoring technique given in TFs are a NDE (Nondestructive Evaluation) technique that utilizes the ratios of cross-spectrums to auto-spectrums between two response points on the sandwich composites. The test for transmittance was conducted on the same density foam core throughout the experiment. The test specimens were 17.8 cm by 25.4 cm in dimension. The external sheets (face sheets) were created from graphite/epoxy laminate with dimension of 1.58 mm thick. The polymethacrylide (Rohacell) foam core was 12.7 mm thick. These samples experienced a transformation in the TF that was considered the low velocity impact damage. The low velocity damage was observed in the TFs for the sandwich composites.

Hughes, Derke R.; Craft, William J.; Schulz, Mark J.; Naser, Ahmad S.; Martin, William N.

1998-01-01

297

Identification of honeycomb sandwich properties by high-resolution modal analysis  

E-print Network

Identification of honeycomb sandwich properties by high-resolution modal analysis M. R´ebillat X are estimated experimentally by means of a high-resolution modal analysis technique. An optimisation procedure implementations. The high-resolution modal analysis (HRMA) technique [5] is an alternative to the FT

Paris-Sud XI, Université de

298

Temperature effects on Kevlar\\/hybrid and carbon fiber composite sandwiches under impact loading  

Microsoft Academic Search

This paper presents the results of a research on impacted sandwich composites with Kevlar\\/hybrid and carbon facesheets subjected to different temperatures. Testing was performed to determine bending and core shear stresses, maximum energy absorption, and “absorbing energy and moment parameter” (AEMP), “performance parameter” (PP), and compression strength after impact (CSAI). Specimens were tested at temperature range of ?50°C to 120°C

Amin Salehi-Khojin; Mohammad Mahinfalah; Reza Bashirzadeh; Brian Freeman

2007-01-01

299

Study on the adjustable rigidity of magnetorheological-elastomer-based sandwich beams  

Microsoft Academic Search

Due to the field-dependent shear modulus of magnetorheological elastomer (MRE), the bulk dynamic flexural rigidity of sandwich beams with MRE cores can be adjusted by applied magnetic fields. The maximum relative change of the flexural rigidity adjusted by applied magnetic fields is referred to as magnetic controllability in this research. This paper will address the structural design for enhancing the

G. Y. Zhou; Q. Wang

2006-01-01

300

Multi-frequency excitation of magnetorheological elastomer-based sandwich beam with conductive skins  

Microsoft Academic Search

The present work deals with the dynamic stability of a symmetric sandwich beam with magnetorheological elastomer (MRE) embedded viscoelastic core and conductive skins subjected to time varying axial force and magnetic field. The conductive skins induce magnetic loads and moments under the application of magnetic field during vibration. The MRE part works in shear mode and hence the dynamic properties

B. Nayak; S. K. Dwivedy; K. S. R. K. Murthy

301

Parametric instability regions of a soft and magnetorheological elastomer cored sandwich beam  

Microsoft Academic Search

Present work deals with the study of parametric instability regions of a three-layered, symmetric sandwich beam with conductive skins subjected to periodic axial load. In the core layer, a magnetorheological elastomer (MRE) patch is placed in between two soft viscoelastic patches. The governing equations of motion of the system have been derived, and the parametric instability regions for simple and

S. K. Dwivedy; N. Mahendra; K. C. Sahu

2009-01-01

302

Perforation of sandwich plates with graded hollow sphere cores under impact loading , S.Pattofattoa  

E-print Network

design features for sandwich panels used in aeronautics structures. For example, such panels are used will largely modify the overall response of the designed FGM structures. This paper deals with the behaviour perforation test with a Hopkinson pressure bar) is measured. A significant influence of the property gradient

Paris-Sud XI, Université de

303

An analytical and experimental investigation of sandwich composites subjected to low-velocity impact  

NASA Astrophysics Data System (ADS)

This study involves an experimental and analytical investigation of low-velocity impact phenomenon in sandwich composite structures. The analytical solution of a three-dimensional finite-geometry multi-layer specially orthotropic panel subjected to static and transient transverse loading cases is presented. The governing equations of the static and dynamic formulations are derived from Reissner's functional and solved by enforcing the continuity of traction and displacement components between adjacent layers. For the dynamic loading case, the governing equations are solved by applying Fourier or Laplace transformation in time. Additionally, the static solution is extended to solve the contact problem between the sandwich laminate and a rigid sphere. An iterative method is employed to determine the sphere's unknown contact area and pressure distribution. A failure criterion is then applied to the sandwich laminate's stress and strain field to predict impact damage. The analytical accuracy of the present study is verified through comparisons with finite element models, other analyses, and through experimentation. Low-velocity impact tests were conducted to characterize the type and extent of the damage observed in a variety of sandwich configurations with graphite/epoxy face sheets and foam or honeycomb cores. Correlation of the residual indentation and cross-sectional views of the impacted specimens provides a criterion for the extent of damage. Quasi-static indentation tests are also performed and show excellent agreement when compared with the analytical predictions. Finally, piezoelectric polyvinylidene fluoride (PVF2) film sensors are found to be effective in detecting low-velocity impact.

Anderson, Todd Alan

1999-12-01

304

Development and fabrication of an autoclave molded PES\\/Quartz sandwich radome  

Microsoft Academic Search

A cohesively bonded, thermoplastic composite sandwich radome for a leading edge supersonic aircraft has been built using autoclave processing with PES\\/Quartz prepreg and a PES coated honeycomb core. Processes were developed for solvent removal, thermoplastic laminate consolidation, surface etching to improve adhesion, honeycomb coating and forming, and ultrasound testing of bond integrity. Environmental testing was also conducted to verify the

Leonard E. Stanton; Stephen D. Levin

1993-01-01

305

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

306

An innovative technique for measuring the high strain rate response of sandwich composites  

Microsoft Academic Search

Foam core sandwich composites have been tested under high strain rate (HSR) loading in the thickness direction. An innovative experimental configuration has been designed for this purpose. Conventional split Hopkinson pressure bar (SHPB) technique has been modified by replacing the steel transmitter bar by a polycarbonate bar. This modification resulted in stronger signals from the transmitter bar, which would otherwise

Hassan Mahfuz; Wahid Al Mamun; Anwarul Haque; Sherida Turner; Hisham Mohamed; Shaik Jeelani

2000-01-01

307

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

E-print Network

to pyramidal truss cores F.W. Zok *, S.A. Waltner, Z. Wei, H.J. Rathbun, R.M. McMeeking, A.G. Evans Materials of realizing this objective is presented and demonstrated for panels with pyramidal truss cores. It combines; Pyramidal core; Constitutive law; Clamped bending; Three-point bending 1. Introduction Metallic sandwich

Zok, Frank

308

Metal Foam Analysis: Improving Sandwich Structure Technology for Engine Fan and Propeller Blades  

NASA Technical Reports Server (NTRS)

The Life Prediction Branch of the NASA Glenn Research Center is searching for ways to construct aircraft and rotorcraft engine fan and propeller blades that are lighter and less costly. One possible design is to create a sandwich structure composed of two metal faces sheets and a metal foam core. The face sheets would carry the bending loads and the foam core would have to resist the transverse shear loads. Metal foam is ideal because of its low density and energy absorption capabilities, making the structure lighter, yet still stiff. The material chosen for the face sheets and core was 17-4PH stainless steel, which is easy to make and has appealing mechanical properties. This material can be made inexpensively compared to titanium and polymer matrix composites, the two current fan blade alternatives. Initial tests were performed on design models, including vibration and stress analysis. These tests revealed that the design is competitive with existing designs; however, some problems were apparent that must be addressed before it can be implemented in new technology. The foam did not hold up as well as expected under stress. This could be due to a number of issues, but was most likely a result of a large number of pores within the steel that weakened the structure. The brazing between the face sheets and the foam was also identified as a concern. The braze did not hold up well under shear stress causing the foam to break away from the face sheets. My role in this project was to analyze different options for improving the design. I primarily spent my time examining various foam samples, created with different sintering conditions, to see which exhibited the most favorable characteristics for our purpose. Methods of analysis that I employed included examining strut integrity under a microscope, counting the number of cells per inch, measuring the density, testing the microhardness, and testing the strength under compression. Shear testing will also be done to examine the strengths of different types of brazes.

Fedor, Jessica L.

2004-01-01

309

Thermo-structural optimization of all-metallic prismatic sandwich panels  

NASA Astrophysics Data System (ADS)

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, the panel geometry is analytically optimized for minimum weight under any combination of bending and transverse shear force. For longitudinal loadings (i.e. bending axis parallel to the core corrugation direction), corrugated panels show excellent performance, equivalent to the best concepts available; for transverse loadings (i.e. bending axis perpendicular to the corrugation direction), this goal is achieved with diamond core designs. Failure maps are constructed based on the analytical model to provide easy visualization of the failure modes and allow immediate identification of optimal designs. Such maps are used to design a selected number of experiments, with the three-fold goal of (i) validating the analytical model, (ii) exploring the behavior subsequent to failure initiation (thus assessing the robustness of the chosen designs), and (iii) check the reliability of numerical simulations in capturing limit loads and deformation modes. Good agreement is achieved among analytical, computational and experimental results. In order to assess the active cooling performance of prismatic panels, a scenario is envisioned where a uniform heat flux is impinging on one face, with the rest of the panel being thermally insulated; under these conditions, all the heat flux is transferred to a cooling fluid flowing through the core channels. At any given level of the pressure drop, the panel geometry is optimized for maximum transferred heat flux subject to a temperature constraint on the structure. Although very large optimal core densities emerge (typically an order of magnitude higher than mechanical optima), good thermal performance can be achieved by much lighter structures; in particular, structurally optimized panels often show active cooling performance within a factor two of thermally optimized structures. This is a promising result for the design and fabrication of multi-functional plates.

Valdevit, Lorenzo

310

constructing realization  

E-print Network

Johannes Kepler University Linz SFB \\Numerical and Symbolic Scienti#12;c Computing" A principle for constructing parallel AMG and its realization II Michael Kuhn, Gundolf Haase Johannes Kepler University Linz. Wolfgang, Upper Austria #12; Johannes Kepler University Linz SFB \\Numerical and Symbolic Scienti#12;c

311

Worldwide construction  

SciTech Connect

Tables list major construction projects for refineries, petrochemical plants, sulfur plants, natural gas processing plants, and gas and oil pipelines. Data are compiled by country, company name, project type, added capacity, status of the project, expected completion date, contractor and contract type. Gas processes include LPG recovery, cryogenic separation, turboexpanders, LNG, liquefaction, desulfurization, NGL recovery, dehydration, hydrogen plants, and fractionators.

Radler, M.

1998-04-13

312

Constructive Interaction.  

ERIC Educational Resources Information Center

To identify conditions that make a conversational interaction constructive--in the sense that the participants can find the way toward the success of what they wanted to accomplish--two situations were examined. In one, a professional researcher explained her data to a statistician. In the other, three groups of two people cooperated with each…

Miyake, Naomi

313

Metal Construction  

NASA Technical Reports Server (NTRS)

The future development of aerial navigation is closely connected with the condition of obtaining airplanes of great stability and sufficient strength. Different construction materials such as wood, aluminum, iron, and alloys are examined to determine which materials or combination of materials provides a greater coefficient of safety.

Verduzio, Rodolfo

1922-01-01

314

A novel double antibody sandwich-lateral flow immunoassay for the rapid and simple detection of hepatitis C virus  

PubMed Central

The objective of this study was to screen for antigens of the hepatitis C virus (HCV) to establish a new double antibody sandwich-lateral flow immunoassay (DAS-LFIA) method for testing the presence of anti-HCV antibodies in human serum or plasma. A series of different recombinant HCV proteins in Escherichia coli cells were constructed, expressed, purified and the new DAS-LFIA strip was developed. The sensitivity and specificity of new the DAS-LFIA strip were evaluated by detecting 23 HCV-positive sera, a set of quality control references for anti-HCV detection that contain known amounts of anti-HCV antibodies, and 8 HCV-negative sera. A total of 300 clinical serum samples was examined by both the new DAS-LFIA strip and enzyme-linked immunosorbent assay (ELISA). Data were analyzed using SPSS 11.5 software. The sensitivity and specificity of the new DAS-LFIA strip were 100%. The lowest test line of the HCV DAS-LFIA strips was 2 NCU/ml. Additionally, the concordance between the new DAS-LFIA strip and ELISA methods was 94.33%. In conclusion, our new testing method is rapid, simple, sensitive and specifically detects the presence of anti-HCV antibodies in human serum or plasma. Therefore, it may be used for monitoring HCV. PMID:22960954

XIANG, TINGXIU; JIANG, ZHENG; ZHENG, JIAN; LO, CHAOYU; TSOU, HARRY; REN, GUOSHENG; ZHANG, JUN; HUANG, AILONG; LAI, GUOQI

2012-01-01

315

A Study for the Characteristic Changes Under the Repeated Thermal Exposure in the Process of Repairing Aircraft Sandwich Structures  

NASA Astrophysics Data System (ADS)

Delamination can be observed in the sound areas during and/or after a couple times exposure to the elevated curing temperature due to the repeated repair condition. This study was conducted for checking the degree of degradation of properties of the cured parts and delamination between skin prepreg and honeycomb core. Specimens with glass honeycomb sandwich construction and glass/epoxy prepreg were prepared. The specimens were cured 1 to 5 times at 260°F in an autoclave and each additionally exposed 50, 100 and 150 hours in the 260°F oven. Each specimen was tested for tensile strength, compressive strength, flatwise tensile strength and interlaminar shear strength. To monitor the characteristics of the resin itself, the cured resin was tested using DMA and DSC. As a results, the decrease of Tg value were observed in the specific specimen which is exposed over 50 hrs at 260°F. This means the change or degradative of resin properties is also related to the decrease of flatwise tensile properties. Accordingly, minimal exposure on the curing temperature is recommended for parts in order to prevent the delation and maintain the better condition.

Kim, Yun Hae; Han, Joong Won; Kim, Don Won; Choi, Byung Keun; Murakami, R.

316

Label-free quantification of microRNAs using ligase-assisted sandwich hybridization on a DNA microarray.  

PubMed

MicroRNAs (miRNAs) can be used as biomarkers for cancer and other human diseases; therefore, high-throughput and reliable miRNA-quantification methods are required to exploit these markers for diagnostic testing. In this report, we describe the construction of a platform for miRNA-quantification using ligase-assisted sandwich hybridization (LASH) without miRNA-labeling. T4 DNA ligase was used to compensate for the low affinity between miRNAs and two short complementary DNA probes, and it improved the hybridization yield ?50,000 times. The LASH assay enabled synthesized miR-143 to be quantified at concentrations ranging from 30 fM to 30 pM. The LASH assay could also quantify endogenous miR-143 released from cultured cells as well as some miRNAs in total RNAs derived from blood. Furthermore, multi-color detection enabled us to distinguish between the highly homologous miR-141 and miR-200a. This simple label-free quantification technique is an easy-to-use approach that can be applied to disease diagnosis. PMID:24614340

Ueno, Taro; Funatsu, Takashi

2014-01-01

317

Airship construction  

NASA Technical Reports Server (NTRS)

Forty-four years ago the first successful metal airship was completed and delivered to the United States Navy, the ZMC-2. Between those years and the present, very little effort or serious consideration has been given to the manufacture, design, construction, or economic impact of airships. It is important to retain and exploit the small but continually diminishing pool of airship talent that will expedite the success of the United States in what is now a pioneering venture. The relative simplicity of airship construction, utilizing the tremendous technical advances of the last 44 years, leads to the conclusion that this form of transportation holds great promise for reducing costs of military missions and improving the international competitive position of the United States in commercial applications.

Roda, J.

1975-01-01

318

Construction measurements  

SciTech Connect

This text/reference on construction measurements contains material concerning electronic surveying and remote sensing. New to this edition is coverage of the GPS satellite positioning system, electronic distance measurement (EDM), laser sweep, calculator techniques, radial surveying and tracking, Loran-C, inertial navigation surveying, 3-point resection, computer software, and electronic fieldbooks. It covers the difference of elevation, angle measurements and directions, coordinate surveying and layout, offshore measurements, and random field and office techniques.

Barry, B.A.

1988-01-01

319

Graduate Studies Construction Engineering  

E-print Network

funded by the National Science Foundation (NSF), Construction Industry Institute (CII), Georgia engineering, building construction, and industrial and systems engineering. SELECTED COURSES · ConstructionGraduate Studies Construction Engineering CONSTRUCTION ENGINEERING The construction engineering

Jacobs, Laurence J.

320

Design maps for scaffold constructs in bone regeneration.  

PubMed

In this article, we propose a methodology for the rational design of scaffold constructs in bone-tissue engineering. The construct under investigation is a sandwich structure with an Intramedullary rod (IM), a Biological Sponge (BS) and an External sleeve (ES). The IM rod provides axial resistance, BS facilitates the growth of new bone and ES provides stability to the construct by resisting torsion and bending. We demonstrate that only select combinations of stiffness between IM and ES facilitate the growth of new bone. Perren's interfragmentary strain theory is employed to clearly identify regions favoring bone growth from those favoring the formation of cartilage. Finally, design maps are constructed that clearly identify the combinations facilitating timely bone growth. PMID:23839166

Ranganathan, Shivakumar I; Ferrari, Mauro; Decuzzi, Paolo

2013-12-01

321

Analysis of Thick Sandwich Shells with Embedded Ceramic Tiles  

NASA Technical Reports Server (NTRS)

The Composite Armored Vehicle (CAV) is an advanced technology demonstrator of an all-composite ground combat vehicle. The CAV upper hull is made of a tough light-weight S2-glass/epoxy laminate with embedded ceramic tiles that serve as armor. The tiles are bonded to a rubber mat with a carefully selected, highly viscoelastic adhesive. The integration of armor and structure offers an efficient combination of ballistic protection and structural performance. The analysis of this anisotropic construction, with its inherent discontinuous and periodic nature, however, poses several challenges. The present paper describes a shell-based 'element-layering' technique that properly accounts for these effects and for the concentrated transverse shear flexibility in the rubber mat. One of the most important advantages of the element-layering technique over advanced higher-order elements is that it is based on conventional elements. This advantage allows the models to be portable to other structural analysis codes, a prerequisite in a program that involves the computational facilities of several manufacturers and government laboratories. The element-layering technique was implemented into an auto-layering program that automatically transforms a conventional shell model into a multi-layered model. The effects of tile layer homogenization, tile placement patterns, and tile gap size on the analysis results are described.

Davila, Carlos G.; Smith, C.; Lumban-Tobing, F.

1996-01-01

322

Clay Nanocomposite/Aerogel Sandwich Structures for Cryotanks  

NASA Technical Reports Server (NTRS)

GRC research has led to the development of epoxy-clay nanocomposites with 60-70% lower gas permeability than the base epoxy resin. Filament wound carbon fiber reinforced tanks made with this nanocomposite had a five-fold lower helium leak rate than the corresponding tanks made without clay. More recent work has produced new composites with more than a 100-fold reduction in helium permeability. Use of these advanced, high barrier composites would eliminate the need for a liner in composite cryotanks, thereby simplifying construction and reducing propellant leakage. Aerogels are attractive materials for use as cryotank insulation because of their low density and low thermal conductivity. However, aerogels are fragile and have poor environmental stability, which have limited their use to certain applications in specialized environments (e.g., in certain types of nuclear reactors as Cerenkov radiation detectors, and as thermal insulators aboard space rovers on Mars). New GRC developed polymer crosslinked aerogels (X-Aerogels) retain the low density of conventional aerogels, but they demonstrate a 300-fold increase in their mechanical strength. Currently, our strongest materials combine a density of approx. 0.45 g/cc, a thermal conductivity of approx. 0.04 W/mK and a compressive strength of 185 MPa. Use of these novel aerogels as insulation materials/structural components in combination with the low permeability of epoxy-clay nanocomposites could significantly reduce cryotank weight and improve durability.

Miller, Sandi; Leventis, Nicholas; Johnston, J. Chris; Meador, Michael

2006-01-01

323

TAYLOR, ELLIOTT McDONALD. Two-way Behavior and Fatigue Performance of 3-D GFRP Sandwich Panels.  

E-print Network

Panels. This research presents the two-way bending and fatigue behavior of an innovative 3- D glass fiber element analysis (FEA) which was used to describe the behavior of the 3-D GFRP sandwich panel under

324

Analysis of an Aircraft Honeycomb Sandwich Panel with Circular Face Sheet/Core Disbond Subjected to Ground-Air Pressurization  

NASA Technical Reports Server (NTRS)

The ground-air pressurization of lightweight honeycomb sandwich structures caused by alternating pressure differences between the enclosed air within the honeycomb core and the ambient environment is a well-known and controllable loading condition of aerospace structures. However, initial face sheet/core disbonds intensify the face sheet peeling effect of the internal pressure load significantly and can decrease the reliability of the sandwich structure drastically. Within this paper, a numerical parameter study was carried out to investigate the criticality of initial disbonds in honeycomb sandwich structures under ground-air pressurization. A fracture mechanics approach was used to evaluate the loading at the disbond front. In this case, the strain energy release rate was computed via the Virtual Crack Closure Technique. Special attention was paid to the pressure-deformation coupling which can decrease the pressure load within the disbonded sandwich section significantly when the structure is highly deformed.

Rinker, Martin; Krueger, Ronald; Ratcliffe, James

2013-01-01

325

Polarized white light from LEDs using remote-phosphor layer sandwiched between reflective polarizer and light-recycling dichroic filter.  

PubMed

This study introduces an efficient polarized, white phosphor-converted, light-emitting diode (pc-LED) using a remote phosphor film sandwiched between a reflective polarizer film (RPF) and a short-wavelength pass dichroic filter (SPDF). The on-axis brightness of polarized white light emission of a RPF/SPDF-sandwiched phosphor film over a blue LED, showed greater recovery than that of a conventional unpolarized remote phosphor film over blue LED, due to the recycling effect of yellow light from an SPDF. The relative luminous efficacy of an RPF/SPDF-sandwiched phosphor film was made 1.40 times better by adding an SPDF on the backside of an RPF-capped phosphor film. A polarization ratio of 0.84 was demonstrated for a white LED with an RPF/SPDF-sandwiched phosphor film, in good agreement with the measured results from the RPF-only sample. PMID:24104572

Oh, Ji Hye; Yang, Su Ji; Do, Young Rag

2013-09-01

326

Analysis of a ceramic filled bio-plastic composite sandwich structure  

SciTech Connect

Design and analysis of a ceramic-filled bio-plastic composite sandwich structure is presented. This proposed high-dielectric structure is used as a substrate for patch antennas. A meandered-strip line-fed fractal-shape patch antenna is designed and fabricated on a copper-laminated sandwich-structured substrate. Measurement results of this antenna show 44% and 20% of bandwidths with maximum gains of 3.45 dBi and 5.87 dBi for the lower and upper bands, respectively. The half-power beam widths of 104° and 78° have been observed from the measured radiation pattern at the two resonance frequencies 0.9 GHz and 2.5?GHz.

Habib Ullah, M. [Institute of Space Science (ANGKASA), Universiti Kebangsaan Malaysia, Bangi Selangor 43600 (Malaysia) [Institute of Space Science (ANGKASA), Universiti Kebangsaan Malaysia, Bangi Selangor 43600 (Malaysia); Department of Electrical, Electronic and System Engineering, Universiti Kebangsaan Malaysia, Bangi 43600 (Malaysia); Islam, M. T. [Institute of Space Science (ANGKASA), Universiti Kebangsaan Malaysia, Bangi Selangor 43600 (Malaysia)] [Institute of Space Science (ANGKASA), Universiti Kebangsaan Malaysia, Bangi Selangor 43600 (Malaysia)

2013-11-25

327

Flexural effects of sandwich beam with a plate insert under in-plane bending  

NASA Astrophysics Data System (ADS)

The local stress concentrations in sandwich beam with a plate insert under in-plane bending are concerned in the study. An improved six-step phase shifting method in digital photoelasticity is employed to calculate the whole-field shear stress.The shear load transfer is realized by shear bands which connect the top and bottom sheet faces through adhesively-bonded interfaces. The plate insert plays a role in load transfer in the sandwich structure, and the fact that debonding might occur at more sites of the interfaces may also leads to the failure of the structure. The local stress concentrations at the insert end change with the load under three-point bending loads, while they remain as the initial residual shear stress under four-point bending loads. The local stress concentration effects generated by the plate insert is essentially caused by the mismatch of elastic properties of the core materials and the irrational geometry of the insert.

Zhenkun, Lei; Wei, Qiu; Libo, Deng

2012-07-01

328

Analysis of a ceramic filled bio-plastic composite sandwich structure  

NASA Astrophysics Data System (ADS)

Design and analysis of a ceramic-filled bio-plastic composite sandwich structure is presented. This proposed high-dielectric structure is used as a substrate for patch antennas. A meandered-strip line-fed fractal-shape patch antenna is designed and fabricated on a copper-laminated sandwich-structured substrate. Measurement results of this antenna show 44% and 20% of bandwidths with maximum gains of 3.45 dBi and 5.87 dBi for the lower and upper bands, respectively. The half-power beam widths of 104° and 78° have been observed from the measured radiation pattern at the two resonance frequencies 0.9 GHz and 2.5 GHz.

Habib Ullah, M.; Islam, M. T.

2013-11-01

329

Development of lightweight graphite/polyimide sandwich panels, phases 3, 4 and 5  

NASA Technical Reports Server (NTRS)

Work performed in the last three phases of the program included: (1) face sheet processing; (2) honeycomb core manufacture; (3) face sheet-to-core bonding development; and (4) sandwich panel fabrication and testing. Resin cure studies were a major portion of this effort since processing problems traced to the polyimide matrix resin had to be resolved before quality core and face sheets could be fabricated. Honeycomb core fabrication and testing were conducted by Hexcel Corporation. A total of four graphite/polyimide resin composite cores were fabricated, tested, and reported. Two sandwich panels weighing .48 and .58 lb/sq ft, respectively were designed and fabricated which meet the support structure loads for the shuttle orbiter thermal protection system.

Merlette, J. B.

1972-01-01

330

A Novel Sandwich Needlelike Structure in Annealed P3HT:PCBM Blend Films  

NASA Astrophysics Data System (ADS)

A unique needlelike sandwich structure is observed in the P3HT:PCBM blend films after annealing at 220°C. The real-time observation of a growing needle indicates that the needle exhibits 7 ?m/min longitudinal growth rate and no lateral growth. Both confocal fluorescence and Raman microscopic mapping measurements reveal that these needles have a PCBM core sandwiched between P3HT edges. According to the eutectic nature of P3HT:PCBM nature, when annealing at high temperature (~220°C), the aggregation of PCBM results in recrystallization of P3HT in the PCBM-depleted regions. These results will give clearer understanding of the melting, diffusion, and recrystallization behavior of the organic eutectic system.

Zeng, Xue-Song; Shi, Tong-Fei; Li, Ning; Li, Xin-Hua; Zhao, Yu-Feng; Wang, Wen-Bo; Zhou, Bu-Kang; Duan, Hua-Hua; Wang, Yu-Qi

2014-06-01

331

Microstructure evolution process of Ferro-Aluminum based sandwich composite for electromagnetic shielding.  

PubMed

In this paper, sandwich composite (SWC) with Fe-Al soft magnetic alloy sandwiched between pure iron substrates was proposed and fabricated by hot pressing and diffusion treatment. The microstructure evolution process of the composite was investigated. Fe/Fe2Al5/Fe diffusion couple was obtained at 700 °C and subsequently kept at 900 °C for further isothermal diffusion. During the diffusion reactive process, we confirmed that major FeAl2 and minor Fe4Al13 were produced when Fe2Al5 dissolved. After 10h of diffusion treatment, FeAl and ?-Fe(Al) were the only two intermetallic phases left. Except FeAl2, the thickness of each intermetallic layer held good parabolic relationship with the diffusion annealing time. PMID:24981211

Luo, Zhichao; Zhang, Qiang; Ma, Xiangyu; Wu, Gaohui

2014-09-01

332

High-Fidelity Modeling for Health Monitoring in Honeycomb Sandwich Structures  

NASA Technical Reports Server (NTRS)

High-Fidelity Model of the sandwich composite structure with real geometry is reported. The model includes two composite facesheets, honeycomb core, piezoelectric actuator/sensors, adhesive layers, and the impactor. The novel feature of the model is that it includes modeling of the impact and wave propagation in the structure before and after the impact. Results of modeling of the wave propagation, impact, and damage detection in sandwich honeycomb plates using piezoelectric actuator/sensor scheme are reported. The results of the simulations are compared with the experimental results. It is shown that the model is suitable for analysis of the physics of failure due to the impact and for testing structural health monitoring schemes based on guided wave propagation.

Luchinsky, Dimitry G.; Hafiychuk, Vasyl; Smelyanskiy, Vadim; Tyson, Richard W.; Walker, James L.; Miller, Jimmy L.

2011-01-01

333

Accurate Determination of Tranverse Normal Stresses in Sandwich Panels Subjected to Thermomechanical Loadings  

NASA Technical Reports Server (NTRS)

A two-stage computational procedure is presented for the accurate determination of transverse normal stresses in sandwich panels subjected to thermomechanical loadings. The procedure involves the use of a first-order shear deformation model in the first stage, and an iterational process for successive improvement of the accuracy of the displacement and stress fields in the second stage. The effectiveness of the procedure is demonstrated by means of numerical studies (if thin and moderately thick flat rectangular sandwich panels. Two sets of boundary conditions are considered; namely, one with all edges simply supported. and the other with two opposite edges simply supported and the remaining two clamped. The displacement components and the transverse shear and normal stresses obtained by the proposed computational procedure are found to be in close agreement with the Solutions of the three-dimensional (3-D) continuum models.

Noor, Ahmed K.; Malik, Moinuddin

1999-01-01

334

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

NASA Astrophysics Data System (ADS)

On this work, the authors present the development and evaluation of an innovative system able to perform reliable panels of sandwich sheets with metallic foam cores for industrial applications, especially in automotive and aeronautical industries. This work is divided into two parts; in the first part the mathematical model used to describe the behavior of sandwich shells with metal cores form is presented and some numerical examples are presented. In the second part of this work, the numerical results are validated using the experimental results obtained from the mechanical experiments. Using the isotropic hardening crushable foam constitutive model, available on ABAQUS, a set of different mechanical tests were simulated. The isotropic hardening model available uses a yield surface that is an ellipse centered at the origin in the p-q stress plane. Using this constitutive model, the uniaxial tensile test for this material was simulated, and a comparison with the experimental results was made.

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

2011-05-01

335

Sandwich-structured enzyme membrane reactor for efficient conversion of maltose into isomaltooligosaccharides.  

PubMed

A novel enzyme membrane reactor with sandwich structure has been developed by confining glucosidase between two sheets of ultrafiltration membranes to effectively convert maltose to isomaltooligosaccharides (IMOs). The hydrophilic ultrafiltration membranes, which were prepared by phase inversion method using PES as bulk polymer and Pluronic F127 as both surface modification and pore formation agent, exhibited the desirable enzyme adsorption-resistant property. The scanning electron microscopy (SEM) photographs showed that two sheets of PES/Pluronic F127 membranes were packed tightly and glucosidase was kept in a free state within a nanoscale space. When the weight ratio of Pluronic F127 to PES was 30%, glucosidase could be completely rejected by the membranes. Due to the sandwich structuring of the membrane reactor and the high hydrophilicity of the PES/Pluronic F127 membrane surface, maltose conversion and yield reached 100% and 58% under the optimum experimental conditions (pH 6.0, 50 degrees C), respectively. PMID:20655202

Zhang, Lei; Su, Yanlei; Zheng, Yang; Jiang, Zhongyi; Shi, Jiafu; Zhu, Yuanyuan; Jiang, Yanjun

2010-12-01

336

The Dynamic Characteristics of 3-D Superconducting Actuator Using the Magnetized HTS Bulk by Sandwiched Electromagnets  

NASA Astrophysics Data System (ADS)

The electric device applications of a high temperature superconducting (HTS) bulk, having stable levitation and suspension properties due to their strong flux pinning force, have been proposed and developed. We have been investigating the three-dimensional (3-D) superconducting actuator using HTS bulk to develop a non-contact transportation device. In our previous works, the overshooting of the HTS bulk mover magnetized by 2-D arranged electromagnets were observed. Therefore, the new magnetization method using sandwiched electromagnets was purposed in order to solve the overshooting problems of HTS bulk mover. In this paper, the dynamic stabilities on the rotating and horizontal moving of the HTS bulk mover magnetized by sandwiched electromagnets was investigated experimentally, and the maximum moving displacements and convergence times during the overshooting state were reduced by proposed magnetization method with small magnetizing current.

Nakano, H.; Kim, S. B.; Ozasa, S.; Sawae, M.

337

Indentation of Foam-Based Polymer Composite Sandwich Beams and Panels Under Static Loading  

Microsoft Academic Search

Foam core composite sandwich structures are highly susceptible to damage when subjected to localized loading. Therefore, thorough\\u000a study of the role of factors such as face sheet thickness, indentor diameter value, and crosshead displacement rate in indentation\\u000a events is important. The objective of the present work is to investigate experimentally and numerically the influence of these\\u000a factors on the nonlinear

V. Rizov

2009-01-01

338

Study of Cellular Materials Sandwich Under Dynamic Loading for Bird Strike Application  

Microsoft Academic Search

This paper reports an original inverse perforation tests on foam core sandwich panels under impact loading. The key point\\u000a is the use of an instrumented Hopkinson pressure bar as a perforator and at the same time a measuring device. It aims at a\\u000a high quality piercing force record during the whole perforation process, which is not available in common free-flying

Y. Girard; I. Elnasri; H. Zhao

339

Comparative studies on “sandwich” rolling and flat rolling in processing Ag\\/Bi2223 tapes  

Microsoft Academic Search

The normal rolling method is commonly used for intermediate mechanical deformation in the powder-in-tube process to make Ag-clad Bi-based superconducting tapes. To compare the effects of different reduction processing on the superconducting properties of Ag\\/Bi-2223 tapes, the reduction rate dependence of the critical current densities J c of tapes processed by three methods, including normal rolling, pressing and “sandwich” rolling,

Wu. M. Chen; Y. C. Guo; X. G. Fu; H. K. Liu; S. X. Dou; M. Apperley

2001-01-01

340

Appearance of ``Fragile'' Fermi Liquids in Finite-Width Mott Insulators Sandwiched between Metallic Leads  

Microsoft Academic Search

Using inhomogeneous dynamical mean-field theory, we show that the normal-metal proximity effect could force any finite number of Mott-insulating ``barrier'' planes sandwiched between semi-infinite metallic leads to become ``fragile'' Fermi liquids. They are fully Fermi-liquid-like at T=0, leading to a restoration of lattice periodicity at zero frequency, with a well-defined Fermi surface, and perfect (ballistic) conductivity. However, the Fermi-liquid character

H. Zenia; J. K. Freericks; H. R. Krishnamurthy; Th. Pruschke

2009-01-01

341

Compression After Impact on Honeycomb Core Sandwich Panels with Thin Facesheets, Part 2: Analysis  

NASA Technical Reports Server (NTRS)

A two part research study has been completed on the topic of compression after impact (CAI) of thin facesheet honeycomb core sandwich panels. The research has focused on both experiments and analysis in an effort to establish and validate a new understanding of the damage tolerance of these materials. Part 2, the subject of the current paper, is focused on the analysis, which corresponds to the CAI testings described in Part 1. Of interest, are sandwich panels, with aerospace applications, which consist of very thin, woven S2-fiberglass (with MTM45-1 epoxy) facesheets adhered to a Nomex honeycomb core. Two sets of materials, which were identical with the exception of the density of the honeycomb core, were tested in Part 1. The results highlighted the need for analysis methods which taken into account multiple failure modes. A finite element model (FEM) is developed here, in Part 2. A commercial implementation of the Multicontinuum Failure Theory (MCT) for progressive failure analysis (PFA) in composite laminates, Helius:MCT, is included in this model. The inclusion of PFA in the present model provided a new, unique ability to account for multiple failure modes. In addition, significant impact damage detail is included in the model. A sensitivity study, used to assess the effect of each damage parameter on overall analysis results, is included in an appendix. Analysis results are compared to the experimental results for each of the 32 CAI sandwich panel specimens tested to failure. The failure of each specimen is predicted using the high-fidelity, physicsbased analysis model developed here, and the results highlight key improvements in the understanding of honeycomb core sandwich panel CAI failure. Finally, a parametric study highlights the strength benefits compared to mass penalty for various core densities.

Mcquigg, Thomas D.; Kapania, Rakesh K.; Scotti, Stephen J.; Walker, Sandra P.

2012-01-01

342

Lightweight steel–concrete–steel sandwich system with J-hook connectors  

Microsoft Academic Search

This paper investigates a new concept for designing composite structures comprising a lightweight concrete core sandwiched in between two steel plates which are interconnected by J-hook connectors. Specifically, lightweight concrete (density less than 1450 kg\\/m3) and novel J-hook connectors have been developed for this purpose. The hook connectors are capable of resisting tension and shear, and their uses are not restricted

J. Y. Richard Liew; K. M. A. Sohel

2009-01-01

343

Core Crush Mechanisms and Solutions in the Manufacturing of Sandwich Structures  

Microsoft Academic Search

Core crush is a manufacturing defect occurred during the autoclave curing process of composite honeycomb sandwich structures.\\u000a It usually leads to costly part rejections since the defect is non-repairable. In addition, this problem has posted constraints\\u000a on aircraft engineers by limiting the ranges of core density and core thickness that could be used when designing these types\\u000a of structures. In

H. M. HSIAO; S. M. LEE; R. A. BUYNY

344

Theoretical study of the novel sandwich compound [Au 3 Cl 3 Tr 2 ] 2+  

Microsoft Academic Search

A theoretical study of a sandwich compound with a metal monolayer sheet between two aromatic ligands is presented. A full\\u000a geometry optimization of the [Au3Cl3Tr2]2+ (1) compound, which is a triangular gold(I) monolayer sheet capped by chlorines and bounded to two cycloheptatrienyl (Tr)\\u000a ligands was carried out using perturbation theory at the MP2 computational level and DFT. Compound (1) is

Jesús Muñiz; Luis Enrique Sansores; Ana Martínez; Roberto Salcedo

2008-01-01

345

Between adolescents and aging grandparents: Midlife concerns of adults in the “Sandwich generation”  

Microsoft Academic Search

This study examined whether the midlife transition of men and women in the “sandwich generation” was related to their 15-\\u000a to 19-year-old adolescent's psychosocial development and their relationships with their own aging parents (i.e., the grandparents).\\u000a One hundred eighty-six (186) respondents representing adolescents, mothers, and fathers from 62 families completed questionnaires\\u000a that assessed adolescents' psychological autonomy and involvement in adult-type

Sharon Boland Hamill; Wendy A. Goldberg

1997-01-01

346

Contact transparency inducing low bias negative differential resistance in two capped carbon nanotubes sandwiching ? barrier  

NASA Astrophysics Data System (ADS)

A first-principles study of the transport properties of two capped (5, 5) carbon nanotubes sandwiching ? barrier is reported. Contact transparency at zero bias is obtained. Strong negative differential resistance effect with large peak-to-valley ratio of 1,124 % is present under very low bias, which may promise the potential applications in nano-electronic devices with low power dissipation in the future.

Min, Y.; Fang, J. H.; Zhong, C. G.; Dong, Z. C.; Li, J. F.; Yao, K. L.; Zhou, L. P.

2015-01-01

347

Low-velocity impact damage initiation in graphite\\/epoxy\\/Nomex honeycomb-sandwich plates  

Microsoft Academic Search

Low-velocity impact and static indentation tests on sandwich plates composed of 4- to 48-ply graphite\\/epoxy cross-ply laminate facesheets and Nomex honeycomb cores have been performed to characterize damage initiation as a function of facesheet thickness and loading rate. Force histories during low-velocity impact are measured by using an instrumented impactor and integrated to produce energy histories. Energy histories are shown

Eric J Herup; Anthony N Palazotto

1998-01-01

348

The quasi-static and dynamic responses of metallic sandwich structures  

E-print Network

waterway tankers with a Y-frame single hull structure. Adapted from Graaf et al. (2004) and Vredeveldt and Roeters (2004). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 3.1 (a) Unit cell of the hollow pyramidal lattice. (b) Top view... of mid-span roller displacement ?/L. All images are showing a side view of the beam. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115 5.9 FE predictions of the quasi-static and 5 m/s responses of simply sup- ported and clamped sandwich beams...

St-Pierre, Luc

2012-06-12

349

FEM analysis of dynamic flexural behaviour of composite sandwich beams with foam core  

Microsoft Academic Search

The dynamic flexural behaviour of sandwich beams, with composite face-sheets and a foam core, was analysed by developing a 3D finite-element model. To model the core behaviour, a crushable foam model was used. The Hou criteria were used to predict the failure of the face-sheets. Dynamic bending tests were performed to validate the numerical model. The comparison between numerical and

Inés Ivañez; Carlos Santiuste; Sonia Sanchez-Saez

2010-01-01

350

Numerical modelling of foam-cored sandwich plates under high-velocity impact  

Microsoft Academic Search

This paper studies the high-velocity impact response of sandwich plates, with E-glass fibre\\/polyester face-sheets and foam core, using finite-element models developed in ABAQUS\\/explicit code. The failure of the face-sheets was predicted by implementing Hou failure criteria and a procedure to degrade material properties in a user subroutine (VUMAT). The foam core was modelled as a crushable foam material. The numerical

I. Ivañez; C. Santiuste; E. Barbero; S. Sanchez-Saez

2011-01-01

351

Development and fabrication of an autoclave molded PES/Quartz sandwich radome  

NASA Astrophysics Data System (ADS)

A cohesively bonded, thermoplastic composite sandwich radome for a leading edge supersonic aircraft has been built using autoclave processing with PES/Quartz prepreg and a PES coated honeycomb core. Processes were developed for solvent removal, thermoplastic laminate consolidation, surface etching to improve adhesion, honeycomb coating and forming, and ultrasound testing of bond integrity. Environmental testing was also conducted to verify the structural integrity of the radome for its intended application.

Stanton, Leonard E.; Levin, Stephen D.

1993-04-01

352

IOURNAL OF MATHEMATICAL ANALYSIS AND APPLICATIONS 146, 53-71 (1990) Sandwich Theorem and Supportability for  

E-print Network

the following result. (2) The continuous sandwich theorem is valid if E is a separable Frechet space, C, D is a Frechet space and there exist closed convex sets C, c C, D, c D having 0 E (C, - D,)', and weakly Bore1 of pseudo-complete convex sets in a Frechet space is fairly large-in particular it contains as a proper

Noll, Dominikus

353

Localized Effects across Core Junctions in Sandwich Beams Subjected to In-Plane and Out-of-Plane Loading  

NASA Astrophysics Data System (ADS)

The paper concerns local effects that occur across junctions between different cores in sandwich beams subjected to in-plane and out-of-plane loads. These local effects display themselves by a significant rise of the bending normal stresses in the faces of the sandwich near the core junctions. At the same time, an elevation of the transverse normal and shear stresses in the adjacent core parts is observed.

Bozhevolnaya, Elena; Lyckegaard, Anders; Thomsen, Ole Thybo

2005-05-01

354

Sandwich ELISA for detecting urinary Survivin in bladder cancer  

PubMed Central

Objective Survivin as a tumor marker in the diagnosis of bladder cancer has not been completely confirmed yet and there are few reports about using Survivin enzyme-linked immunosorbent assay (ELISA) kit to detect the urine of bladder cancer patients. This study aimed to develop a Survivin ELISA and validate its value in the detection of bladder cancer. Methods Through square matrix titration, different combinations of coating antibody and detecting antibody, a Survivin ELISA was constructed. This assay was evaluated according to intra-assay precision, inter-assay precision and minimum detectable dose (MDD). Survivin levels were detected and analyzed in 102 bladder cancer patients and 102 healthy people by established ELISA. Then cutoff value was defined according to the analysis of receiver operating characteristic (ROC) curve. The sensitivity and specificity of detection were calculated on the basis of cutoff value to diagnose bladder cancer patients. Furthermore, the value of Survivin expression detected by ELISA among different clinicopathological characteristics of patients was also compared. Results Through optimization of different conditions, intra-assay precision was 8.39%, inter-assay precision 8.57% and MDD 0.0625 ng/mL in this assay. When the optical density at 450 nm (OD450) was 0.09, it could get the optimized diagnostic cutoff value. According to this value, the sensitivity and specificity of diagnosis in bladder cancer patients were 70.6% and 89.2%, respectively. The associations between patients’ clinical variables and OD450 were not significant except tumor numbers in patients. Conclusions This experiment has preliminarily developed a Survivin ELISA and confirmed Survivin as a biomarker which owned a practical and significant value in the diagnosis of bladder cancer. PMID:23997523

Li, Xuefeng; Wang, Yaming; Xu, Jianjun

2013-01-01

355

Monoclonal antibody-based sandwich ELISA for the detection of staphylococcal enterotoxin A.  

PubMed

A sensitive and specific monoclonal antibody-based sandwich enzyme-linked immunosorbent assay (ELISA) was established and validated for the detection of staphylococcal enterotoxin A (SEA). After routine fusion and selection, 10 monoclonal antibodies showed high affinity for SEA. An optimal pair for sandwich ELISA was selected by pairwise interaction analysis. After optimization, the limit of detection (LOD) and linear dynamic range of the method were established, and were found to be 0.0282 ng/mL and 0.06-2 ng/mL, respectively. The recovery in pure milk ranged from 82.67% to 111.95% and the intra- and inter-assay coefficients of variation ranged from 3.16% to 6.05% and from 5.16% to 10.79%, respectively. Cross-reactivity with staphylococcal enterotoxin B (SEB), staphylococcal enterotoxin C (SEC), staphylococcal enterotoxin D (SED), and staphylococcal enterotoxin E (SEE) in this method were insignificant. These results indicate that the sandwich ELISA method developed in our study is effective for routine identification of SEA in food samples. PMID:23603865

Kuang, Hua; Wang, Wenbing; Xu, Liguang; Ma, Wei; Liu, Liqiang; Wang, Libing; Xu, Chuanlai

2013-04-01

356

Computation of linear transmittance of thermal bridges in precast concrete sandwich panels  

NASA Astrophysics Data System (ADS)

Precast concrete lightened sandwich panels are widely used building elements. They are made by two concrete wythes separated by a layer of lightweight material: the central layer is inhomogeneous due to the presence of concrete ribs which tie the external wythe and act as thermal bridges. Computation of thermal transmittance of sandwich panels is clearly described in European Standards, but in many cases it requires numerical simulations to determine the linear transmittance ? associated with lightweight material-concrete interfaces in the inhomogeneous layer. Although simple, these simulations represent a critical issue for many panel manufacturers and they would much rather prefer correlations to compute ?. In this work we present a correlation based on an artificial neural network (ANN) to estimate linear trasmittauce values for current Italian sandwich panel production. Five input parameters are considered: rib width, lightweight material conductivity, and thickness of the three panel layers. To obtain the data which are necessary to train and test the ANN, a fast and accurate Spectral Element Method is used to solve Laplace equation in the neighborhood of a rib. 5460 ? values are collected which ensure an accurate network response.

Luscietti, Davide; Gervasio, Paola; Lezzi, Adriano M.

2014-11-01

357

Non-destructive inspection of drilled holes in reinforced honeycomb sandwich panels using active thermography  

NASA Astrophysics Data System (ADS)

The aerospace industry is in constant need of ever-more efficient inspection methods for quality control. Product inspection is also essential to maintain the safe operation of aircraft components designed to perform for decades. This paper proposes a method for non-destructive inspection of drilled holes in reinforced honeycomb sandwich panels. Honeycomb sandwich panels are extensively employed in the aerospace industry due to their high strength and stiffness to weight ratios. In order to attach additional structures to them, panels are reinforced by filling honeycomb cells and drilling holes into the reinforced areas. The proposed procedure is designed to detect the position of the holes within the reinforced area and to provide a robust measurement of the distance between each hole and the boundary of the reinforced area. The result is a fast, safe and clean inspection method for drilled holes in reinforced honeycomb sandwich panels that can be used to robustly assess a possible displacement of the hole from the center of the reinforced area, which could have serious consequences. The proposed method is based on active infrared thermography, and uses state of the art methods for infrared image processing, including signal-to-nose ratio enhancement, hole detection and segmentation. Tests and comparison with X-ray inspections indicate that the proposed system meets production needs.

Usamentiaga, R.; Venegas, P.; Guerediaga, J.; Vega, L.; López, I.

2012-11-01

358

Experimental study on the seismic performance of new sandwich masonry walls  

NASA Astrophysics Data System (ADS)

Sandwich masonry walls are widely used as energy-saving panels since the interlayer between the outer leaves can act as an insulation layer. New types of sandwich walls are continually being introduced in research and applications, and due to their unique bond patterns, experimental studies have been performed to investigate their mechanical properties, especially with regard to their seismic performance. In this study, three new types of sandwich masonry wall have been designed, and cyclic lateral loading tests were carried out on five specimens. The results showed that the specimens failed mainly due to slippage along the bottom cracks or the development of diagonal cracks, and the failure patterns were considerably influenced by the aspect ratio. Analysis was undertaken on the seismic response of the new walls, which included ductility, stiffness degradation and energy dissipation capacity, and no obvious difference was observed between the seismic performance of the new walls and traditional walls. Comparisons were made between the experimental results and the calculated results of the shear capacity. It is concluded that the formulas in the two Chinese codes (GB 50011 and GB 50003) are suitable for the calculation of the shear capacity for the new types of walls, and the formula in GB 50011 tends to be more conservative.

Xiao, Jianzhuang; Pu, Jie; Hu, Yongzhong

2013-03-01

359

Hypervelocity Impact Performance of Open Cell Foam Core Sandwich Panel Structures  

NASA Technical Reports Server (NTRS)

Open cell metallic foam core sandwich panel structures are of interest for application in spacecraft micrometeoroid and orbital debris shields due to their novel form and advantageous structural and thermal performance. Repeated shocking as a result of secondary impacts upon individual foam ligaments during the penetration process acts to raise the thermal state of impacting projectiles ; resulting in fragmentation, melting, and vaporization at lower velocities than with traditional shielding configurations (e.g. Whipple shield). In order to characterize the protective capability of these structures, an extensive experimental campaign was performed by the Johnson Space Center Hypervelocity Impact Technology Facility, the results of which are reported in this paper. Although not capable of competing against the protection levels achievable with leading heavy shields in use on modern high-risk vehicles (i.e. International Space Station modules), metallic foam core sandwich panels are shown to provide a substantial improvement over comparable structural panels and traditional low weight shielding alternatives such as honeycomb sandwich panels and metallic Whipple shields. A ballistic limit equation, generalized in terms of panel geometry, is derived and presented in a form suitable for application in risk assessment codes.

Ryan, S.; Ordonez, E.; Christiansen, E. L.; Lear, D. M.

2010-01-01

360

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

NASA Technical Reports Server (NTRS)

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 generate biaxial tension loading conditions. Design limit load and design ultimate load tests have been performed on the graphite-epoxy sandwich panel with the middle frame removed to demonstrate the suitability of this two-frame design for supporting the prescribed biaxial loading conditions with twice the initial frame spacing of 20 inches. The two-frame panel was damaged by cutting a notch that originates at the edge of a cutout and extends in the panel hoop direction through the window-belt area. This panel with a notch was tested in a combined-load condition to demonstrate the structural damage tolerance at the design limit load condition. The two panel configurations successfully satisfied all design load requirements in the experimental part of the study, and the three-frame and two-frame panel responses are fully explained by the analysis results. The results of this study suggest that there is potential for using sandwich structural concepts with greater than the usual 20-in.-wide frame spacing to further reduce aircraft fuselage structural weight.

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

1997-01-01

361

Sound Transmission Loss Through a Corrugated-Core Sandwich Panel with Integrated Acoustic Resonators  

NASA Technical Reports Server (NTRS)

The goal of this study is to better understand the effect of structurally integrated resonators on the transmission loss of a sandwich panel. The sandwich panel has facesheets over a corrugated core, which creates long aligned chambers that run parallel to the facesheets. When ports are introduced through the facesheet, the long chambers within the core can be used as low-frequency acoustic resonators. By integrating the resonators within the structure they contribute to the static load bearing capability of the panel while also attenuating noise. An analytical model of a panel with embedded resonators is derived and compared with numerical simulations. Predictions show that acoustic resonators can significantly improve the transmission loss of the sandwich panel around the natural frequency of the resonators. In one configuration with 0.813 m long internal chambers, the diffuse field transmission loss is improved by more than 22 dB around 104 Hz. The benefit is achieved with no added mass or volume relative to the baseline structure. The embedded resonators are effective because they radiate sound out-of-phase with the structure. This results in destructive interference, which leads to less transmitted sound power.

Schiller, Noah H.; Allen, Albert R.; Zalewski, Bart F; Beck, Benjamin S.

2014-01-01

362

Design of Fiber Reinforced Foam Sandwich Panels for Large Ares V Structural Applications  

NASA Technical Reports Server (NTRS)

The preliminary design of three major structural components within NASA's Ares V heavy lift vehicle using a novel fiber reinforced foam composite sandwich panel concept is presented. The Ares V payload shroud, interstage, and core intertank are designed for minimum mass using this panel concept, which consists of integral composite webs separated by structural foam between two composite facesheets. The HyperSizer structural sizing software, in conjunction with NASTRAN finite element analyses, is used. However, since HyperSizer does not currently include a panel concept for fiber reinforced foam, the sizing was performed using two separate approaches. In the first, the panel core is treated as an effective (homogenized) material, whose properties are provided by the vendor. In the second approach, the panel is treated as a blade stiffened sandwich panel, with the mass of the foam added after completion of the panel sizing. Details of the sizing for each of the three Ares V components are given, and it is demonstrated that the two panel sizing approaches are in reasonable agreement for thinner panel designs, but as the panel thickness increases, the blade stiffened sandwich panel approach yields heavier panel designs. This is due to the effects of local buckling, which are not considered in the effective core property approach.

Bednarcyk, Brett A.; Arnold, Steven M.; Hopkins, Dale A.

2010-01-01

363

Experimental investigation of graphite/polyimide sandwich panels in edgewise compression  

NASA Technical Reports Server (NTRS)

The local and general buckling behavior of graphite/polyimide sandwich panels simply supported along all four edges and loaded in uniaxial edgewise compression was investigated. Material properties of adhesive and facings were determined from flatwise tension and sandwich beam flexure tests. Tensile and compressive material properties of the facings were determined at 116, R.T., and 589 K (-250, R.T., and 600 F) using the sandwich beam flexure test method. Results indicate that Gr/PI is a usable structural material for short term use at temperatures as high as 589 K (600 F). Buckling specimens were 30.5 X 33.0 cm (12 x 13 in.), had quasi-isotropic symmetric facings and a glass/polyimide honeycomb core. Core thicknesses varied and three panels of each thickness were tested in edgewise compression at room temperature to investigate failure modes and corresponding buckling formulas. Specimens 0.635 cm (0.25 in.) thick failed by overall buckling at loads close to the analytically predicted buckling load; all other panels failed by face wrinkling. Results of the winkling tests indicate that several buckling formulas were unconservative and therefore not suitable for design purposes; recommended wrinkling equations are presented.

Camarda, C. J.

1980-01-01

364

Sandwich-type polyoxotungstate hybrids decorated by nickel-aromatic amine complexes  

SciTech Connect

Three new sandwich-type polyoxotungstates (POTs) decorated by nickel-2,2'-bpy complexes [{l_brace}Ni(2,2'-bpy){sub 2}(H{sub 2}O){r_brace}{sub 2}{l_brace}Ni(2,2'-bpy){r_brace}{sub 2} {l_brace}Ni{sub 4}(H{sub 2}O){sub 2}(B-alpha-XW{sub 9}O{sub 34}){sub 2}{r_brace}]{sup n-} (X=P{sup V}, n=4 for 1; X=As{sup V}, n=4 for 2; X=Ge{sup IV}, n=4 for 3) (2,2'-bpy=2,2'-bipyridine) were successfully synthesized under hydrothermal conditions and structurally characterized by elemental analyses, IR spectroscopy, single-crystal X-ray diffraction, and magnetic properties. Single-crystal structural analyses indicate that 1 and 2 are isostructural and both crystallize in the monoclinic space group C2/c, whereas 3 belongs to the triclinic space group P1-bar. To our knowledge, 1, 2 and 3 represent rare examples of the organic-inorganic hybrid sandwich-type polyoxometalates functionalized by multiple nickel-aromatic amine complexes. Magnetic measurements of 1 exhibit the presence of ferromagnetic interactions within the rhombic tetranuclear-Ni{sup II} cluster. - Graphical abstract: Three new sandwich-type polyoxotungstates (POTs) decorated by nickel-2,2'-bpy complexes were successfully synthesized under hydrothermal conditions and structurally characterized.

Ma Pengtao; Zhao Junwei [Institute of Molecular and Crystal Engineering, College of Chemistry and Chemical Engineering, Henan University, Kaifeng 475004 (China); Wang Jingping, E-mail: jpwang@henu.edu.c [Institute of Molecular and Crystal Engineering, College of Chemistry and Chemical Engineering, Henan University, Kaifeng 475004 (China); Shen Yue [Institute of Molecular and Crystal Engineering, College of Chemistry and Chemical Engineering, Henan University, Kaifeng 475004 (China); Niu Jingyang, E-mail: jyniu@henu.edu.c [Institute of Molecular and Crystal Engineering, College of Chemistry and Chemical Engineering, Henan University, Kaifeng 475004 (China)

2010-01-15

365

A Sandwich ELISA for Adducts of Polycyclic Aromatic Hydrocarbons with Human Serum Albumin1  

PubMed Central

Adducts of benzo[?]pyrene-diolepoxide (BPDE)2 with blood nucleophiles have been used as biomarkers of exposure to polycyclic aromatic hydrocarbons (PAHs). The most popular such assay is a competitive ELISA which employs monoclonal antibody 8E11 to detect benzo[?]pyrene tetrols following hydrolysis of BPDE adducts from lymphocyte DNA or human serum albumin (HSA). Here we use 8E11 as the capture antibody in a sandwich ELISA to detect BPDE-HSA adducts directly in 1 mg samples of HSA or 20 ?L of serum/plasma. The assay employs an anti-HSA antibody for detection, which is amplified by an avidin/biotinylated horseradish peroxidase complex. The sandwich ELISA has advantages of specificity and simplicity and is about 10 times more sensitive than the competitive ELISA. To validate the assay, HSA samples were assayed from three populations with known high (coke-oven workers), medium (steel-factory control workers), and low (volunteer subjects) PAH exposures (n = 30). The respective geometric mean levels of BPDE-HSA adducts, i.e., 67.8, 14.7 and 1.93 ng/mg HSA (1,010, 220 and 28.9 fmol BPDE equivalents/mg HSA), were significantly different (p < 0.05). The sandwich ELISA will be useful for screening PAH exposures in large epidemiologic studies and can be extended to other adducts for which capture antibodies are available. PMID:20083082

Chung, Ming Kei; Riby, Jacques; Li, He; Iavarone, Anthony T.; Williams, Evan R.; Zheng, Yuxin; Rappaport, Stephen M.

2010-01-01

366

Process Factors and Edgewise Compressive Properties of Scarf-repaired Honeycomb Sandwich Structures  

NASA Astrophysics Data System (ADS)

Bonded repairs were conducted on flat and edge-closed composite sandwich panels that had undergone different levels of initial damage, and edgewise compression behaviors of repaired panel were tested. Experimental results indicate that these repair techniques can restore the compression performance of damaged panels effectively. The repaired specimens recovered an average of over 83 % of their strength. A k-sample Anderson-Darling test was used to analyze the influence of various parameters, including curing temperature, curing pressure, and repair configurations. After a thorough comparison, it was concluded that a high-temperature, high-pressure treatment can improve the mechanical performance of repaired panels, but the improvement is closely related to the structural complexity of the repaired region. A double-side repair scheme could be used to prevent the degradation of mechanical performance caused by the additional bending moment. The conclusions drawn in the present study provide further insight into the mechanical performance of repaired sandwich panels under edgewise compressive loads. These data facilitate the improved design methodology on bonded repair of composite sandwich structures.

Liu, Sui; Guan, Zhidong; Guo, Xia; Sun, Kai; Kong, Jiaoyue; Yan, Dongxiu

2014-10-01

367

Finite element based stability-constrained weight minimization of sandwich composite ducts for airship applications  

NASA Astrophysics Data System (ADS)

High Altitude Long Endurance (HALE) airships are platform of interest due to their persistent observation and persistent communication capabilities. A novel HALE airship design configuration incorporates a composite sandwich propulsive hull duct between the front and the back of the hull for significant drag reduction via blown wake effects. The sandwich composite shell duct is subjected to hull pressure on its outer walls and flow suction on its inner walls which result in in-plane wall compressive stress, which may cause duct buckling. An approach based upon finite element stability analysis combined with a ply layup and foam thickness determination weight minimization search algorithm is utilized. Its goal is to achieve an optimized solution for the configuration of the sandwich composite as a solution to a constrained minimum weight design problem, for which the shell duct remains stable with a prescribed margin of safety under prescribed loading. The stability analysis methodology is first verified by comparing published analytical results for a number of simple cylindrical shell configurations with FEM counterpart solutions obtained using the commercially available code ABAQUS. Results show that the approach is effective in identifying minimum weight composite duct configurations for a number of representative combinations of duct geometry, composite material and foam properties, and propulsive duct applied pressure loading.

Khode, Urmi B.

368

Using a silver-enhanced microarray sandwich structure to improve SERS sensitivity for protein detection.  

PubMed

A simple and sensitive method, based on surface-enhanced Raman scattering (SERS), for immunoassay and label-free protein detection is reported. A series of bowl-shaped silver cavity arrays were fabricated by electrodeposition using a self-assembled polystyrene spheres template. The reflection spectra of these cavity arrays were recorded as a function of film thickness, and then correlated with SERS enhancement using sodium thiophenolate as the probe molecule. The results reveal that SERS enhancement can be maximized when the frequency of both the incident laser and the Raman scattering approach the frequency of the localized surface plasmon resonance. The optimized array was then used as the bottom layer of a silver nanoparticle-protein-bowl-shaped silver cavity array sandwich. The second layer of silver was introduced by the interactions between the proteins in the middle layer of the sandwich architecture and silver nanoparticles. Human IgG bound to the surface of this microcavity array can retain its recognition function. With the Raman reporter molecules labeled on the antibody, a detection limit down to 0.1 ng mL(-1) for human IgG is easily achieved. Furthermore, the SERS spectra of label-free proteins (catalase, cytochrome C, avidin and lysozyme) from the assembled sandwich have excellent reproducibility and high quality. The results reveal that the proposed approach has potential for use in qualitative and quantitative detection of biomolecules. PMID:24577570

Gu, Xuefang; Yan, Yuerong; Jiang, Guoqing; Adkins, Jason; Shi, Jian; Jiang, Guomin; Tian, Shu

2014-03-01

369

Failure Maps for Rectangular 17-4PH Stainless Steel Sandwiched Foam Panels  

NASA Technical Reports Server (NTRS)

A new and innovative concept is proposed for designing lightweight fan blades for aircraft engines using commercially available 17-4PH precipitation hardened stainless steel. Rotating fan blades in aircraft engines experience a complex loading state consisting of combinations of centrifugal, distributed pressure and torsional loads. Theoretical failure plastic collapse maps, showing plots of the foam relative density versus face sheet thickness, t, normalized by the fan blade span length, L, have been generated for rectangular 17-4PH sandwiched foam panels under these three loading modes assuming three failure plastic collapse modes. These maps show that the 17-4PH sandwiched foam panels can fail by either the yielding of the face sheets, yielding of the foam core or wrinkling of the face sheets depending on foam relative density, the magnitude of t/L and the loading mode. The design envelop of a generic fan blade is superimposed on the maps to provide valuable insights on the probable failure modes in a sandwiched foam fan blade.

Raj, S. V.; Ghosn, L. J.

2007-01-01

370

Development of monoclonal antibody-based sandwich ELISA for detection of dextran.  

PubMed

Dextran as anti-nutritional factor is usually a result of bacteria activity and has associated serial problems during the process stream in the sugar industry and in medical therapy. A sensitive method is expected to detect dextran quantitatively. Here we generated four monoclonal antibodies (MAbs) against dextran using dextran T40 conjugated with bovine serum albumin (BSA) as immunogen in our lab following hybridoma protocol. Through pairwise, an MAb named D24 was determined to be conjugated with horseradish peroxidase (HRP) and was used in the establishment of a sensitive sandwich enzyme-linked immunosorbent assay (ELISA) method for determination of dextran, in which MAb D9 was chosen as a capture antibody. The detection limit and working scope of the developed sandwich ELISA method were 3.9 ng/mL and 7.8-500 ng/mL with a correlation coefficient of 0.9909. In addition, the cross-reaction assay demonstrated that the method possessed high specificity with no significant cross-reaction with dextran-related substances, and the recovery rate ranged from 96.35 to 102.00%, with coefficient of variation ranging from 1.58 to 6.94%. These results indicated that we developed a detection system of MAb-based sandwich ELISA to measure dextran and this system should be a potential tool to determine dextran levels. PMID:25358002

Wang, Sheng-Yu; Li, Zhe; Wang, Xian-Jiang; Lv, Sha; Yang, Yun; Zeng, Lian-Qiang; Luo, Fang-Hong; Yan, Jiang-Hua; Liang, Da-Feng

2014-10-01

371

Mathematical Modeling of a Rectangular Sandwich Plate with a Non-Homogeneous Core  

NASA Astrophysics Data System (ADS)

Subject of the paper is a simply supported rectangular sandwich plate. The plate is compressed in plane. It is assumed that the plate under consideration is symmetrical in build and consists of two isotropic facings and core. Middle plane of the plate is its symmetry plane. The core is made of metal foam with properties vary across its thickness. The porous-cellular metal as a core of three layered plate is of continuous structure, while its mechanical properties are isotropic. Dimensionless coefficients are introduced to compensate for this. The field of displacements and geometric relationships are assumed. This non-linear hypothesis is generalization of the classical hypotheses, in particular, the broken-line hypothesis. The principle of stationarity of the total potential energy of the compressed sandwich plate are used and a system of differential equations are formulated. This system is approximately solved. The forms of unknown functions are assumed, which satisfy boundary conditions for supports of the plate. Critical loads for a family of sandwich plates are numerically determined. Results of the calculation are shown in figures.

Magnucka-Blandzi, Ewa

2007-09-01

372

The dynamic mechanical properties study on the sandwich panel of different thickness steel plate-foam aluminum core  

NASA Astrophysics Data System (ADS)

The foam aluminum belongs to multi-cell materials, and it has good mechanical performance, such as large deformation capacity and good energy absorption, and usually used as core material of sandwich panel, now it is widely used in automotive, aviation, aerospace and other fields, particularly suitable for various anti-collision structure and buffer structure. In this article, based on an engineering background, the INSTRON4505 electronic universal testing machine and split Hopkinson pressure bar (SHPB) were used for testing the static and dynamic mechanical properties of sandwich panel with different thickness steel plate- foam aluminum core, from the results we can see that the steel plate thickness has big influence on the stress-strain curve of the sandwich panel, and also takes the sandwich panel with 1mm steel panel to study the material strain rate dependence which under different high shock wave stress loaded, the results show that the sandwich panel is strain rate dependence material. And also, in order to get good waveforms in the SHPB experiment, the waveform shaped technique is used in the dynamic experiments, and the study of this paper will good to sandwich panel used in the engineering.

Chang, Zhongliang; Zou, Guangping; Zhao, Weiling; Xia, Peixiu

2010-03-01

373

The dynamic mechanical properties study on the sandwich panel of different thickness steel plate-foam aluminum core  

NASA Astrophysics Data System (ADS)

The foam aluminum belongs to multi-cell materials, and it has good mechanical performance, such as large deformation capacity and good energy absorption, and usually used as core material of sandwich panel, now it is widely used in automotive, aviation, aerospace and other fields, particularly suitable for various anti-collision structure and buffer structure. In this article, based on an engineering background, the INSTRON4505 electronic universal testing machine and split Hopkinson pressure bar (SHPB) were used for testing the static and dynamic mechanical properties of sandwich panel with different thickness steel plate- foam aluminum core, from the results we can see that the steel plate thickness has big influence on the stress-strain curve of the sandwich panel, and also takes the sandwich panel with 1mm steel panel to study the material strain rate dependence which under different high shock wave stress loaded, the results show that the sandwich panel is strain rate dependence material. And also, in order to get good waveforms in the SHPB experiment, the waveform shaped technique is used in the dynamic experiments, and the study of this paper will good to sandwich panel used in the engineering.

Chang, Zhongliang; Zou, Guangping; Zhao, Weiling; Xia, Peixiu

2009-12-01

374

Open-Mode Debonding Analysis of Curved Sandwich Panels Subjected to Heating and Cryogenic Cooling on Opposite Faces  

NASA Technical Reports Server (NTRS)

Increasing use of curved sandwich panels as aerospace structure components makes it vital to fully understand their thermostructural behavior and identify key factors affecting the open-mode debonding failure. Open-mode debonding analysis is performed on a family of curved honeycomb-core sandwich panels with different radii of curvature. The curved sandwich panels are either simply supported or clamped, and are subjected to uniform heating on the convex side and uniform cryogenic cooling on the concave side. The finite-element method was used to study the effects of panel curvature and boundary condition on the open-mode stress (radial tensile stress) and displacement fields in the curved sandwich panels. The critical stress point, where potential debonding failure could initiate, was found to be at the midspan (or outer span) of the inner bonding interface between the sandwich core and face sheet on the concave side, depending on the boundary condition and panel curvature. Open-mode stress increases with increasing panel curvature, reaching a maximum value at certain high curvature, and then decreases slightly as the panel curvature continues to increase and approach that of quarter circle. Changing the boundary condition from simply supported to clamped reduces the magnitudes of open-mode stresses and the associated sandwich core depth stretching.

Ko, William L.

1999-01-01

375

Development of an innovative sandwich common bulkhead for cryogenic upper stage propellant tank  

NASA Astrophysics Data System (ADS)

In the frame of the Future Launcher Preparatory Program (FLPP) investigating advancing technologies for the Next Generation of Launchers (NGL) a number of novel key technologies are presently under development for significantly improving vehicle performance in terms of payload capacity and mission versatility. As a respective ESA guided technology development program, Cryogenic Upper Stage Technologies (CUST) has been launched within FLPP that hosts among others the development of a common bulkhead to separate liquid hydrogen from the liquid oxygen compartment. In this context, MT Aerospace proposed an advanced sandwich design concept which is currently in the development phase reaching for TRL4 under MT Aerospace responsibility. Key components of this sandwich common bulkhead are a specific core material, situated in-between two thin aluminum face sheets, and an innovative thermal decoupling element at the equatorial region. The combination of these elements provides excellent thermal insulation capabilities and mechanical performance at a minimum weight, since mechanical and thermal functions are merged in the same component. This improvement is expressed by substantial performance figures of the proposed concept that include high resistance against reverse pressure, an optimized heat leak and minimized mass, involving the sandwich dome structure and the adjacent interface rings. The development of single sub-technologies, all contributing to maturate the sandwich common bulkhead towards the desired technology readiness level (TRL), is described in the context of the given design constraints as well as technical, functional and programmatic requirements, issued from the stage level. This includes the thermal and mechanical characterization of core materials, manufacturing issues as well as non-destructive testing and the thermal and structural analyses and dimensioning of the complete common bulkhead system. Dedicated TRL assessments in the Ariane 5 Mid-life Evolution (A5-ME) program track the progress of these technology developments and analyze their applicability in time for A5-ME. In order to approximate A5-ME concerned preconditions, activities are initiated aiming at harmonization of the available specifications. Hence, a look-out towards a further technology step approaching TRL6 in a subsequent phase is given, briefly addressing topics of full scale manufacture and appropriate thermo-mechanical testing of an entire sandwich common bulkhead.

Szelinski, B.; Lange, H.; Röttger, C.; Sacher, H.; Weiland, S.; Zell, D.

2012-12-01

376

phenogram construction  

NSDL National Science Digital Library

Prior to this exercise, I introduce some fundamental concepts regarding systematics and phylogenetic reconstruction. I do it early in the semester because I like to have the students thinking about these things while we are discussing the major fossil groups later in the semester. The exercise is simple: students construct a phenogram using a collection of objects â could be fossils, or toy animals, or whatever. I use about ten things. At first, students think it'll be easy. They soon realize how difficult it is to identify characters that group some taxa but exclude others. Obviously, the particular taxa you choose can make the exercise more or less difficult. I should also mention that I require the students to produce a dendrogram with strictly dichotomous branching. I explicitly refer to it as a phenogram because I allow students to use whatever characters they wish, and it isn't even necessary that they be able to recognize the organisms. Inevitably, this exercise leads to discussions about the importance of phylogenetically informative characters.

Dan Stephen

377

Vertically-aligned sandwich nanowires enhance the photoelectrochemical reduction of hydrogen peroxide: Hierarchical formation on carbon nanotubes of cadmium sulfide quantum dots and Prussian blue nanocoatings.  

PubMed

We describe a vertically-aligned array of sandwiched nanowires comprising Prussian blue (PB) nanocoating-carbon nanotube (CNT) core-shell structures with CdS particles positioning at the core/shell interface, viz. PB/CdS/CNT. The PB/CdS/CNT electrode thus constructed are noticeable in synchronically harvesting photon-, ionic-, and chemical-energies, respectively, from visible light radiation, K(+) uptaking and releasing, and the reduction of H2O2. In 0.2M K2SO4 aqueous solution, the photoelectrocatalytic reduction of 1.5mM H2O2 at PB/CdS/CNT delivered the current density as high as 1.91mA/cm(2) at reduced overpotential, that is, three times that at the Pt/C. This superb performance is causally linked to the judicious choice of materials and their assembly into defining sandwich nanostructures wherein the three components closely cooperate with each other in the photoelectrocatalytic reduction of H2O2, including photo-induced charge separation in CdS, spontaneous electron injection into PB due to its relatively low Fermi level, and the electrocatalytic reduction of H2O2 by PB via an electrochemical-chemical-electrochemical reaction mechanism. The structural alignment of PB/CdS/CNT ensures the simplest pathway for the mass diffusion and electron shuttle, and a high surface area accessible to the chemical and electrochemical reactions, so as to minimize the concentration- and electrochemical-polarization and thus ensure the fast overall kinetics of the electrode reaction. PMID:25458868

Gong, Kuanping

2014-10-16

378

A cost-effective sandwich electrochemiluminescence immunosensor for ultrasensitive detection of HIV-1 antibody using magnetic molecularly imprinted polymers as capture probes.  

PubMed

In this report, a rapid and cost-effective sandwich electrochemiluminescence (ECL) immunosensor was constructed for the ultrasensitive detection of human immunodeficiency virus type 1 antibody (anti-HIV-1) using magnetic molecularly imprinted polymers (MMIPs) as capture probes by combining surface and epitope imprinting techniques and antigen conjugated with horseradish peroxidase (HRP-HIV-1) as labels. First, 3-aminobenzeneboronic acid (APBA) was used as the functional monomer and cross-linking reagent, which was polymerized on the surface of silicate-coated magnetic iron oxide nanoparticles (Fe3O4@SiO2 NPs) in the presence of human immunoglobulin G (HIgG), as the template exhibiting the same Fc region but different Fab region to anti-HIV-1 after the addition of the initiator, ammonium persulfate. This process resulted in grafting a hydrophilic molecularly imprinted polymer (MIP) film on the Fe3O4@SiO2 NPs. Thus, MMIPs, which could be reused after eluting the template, were used to recognize and enrich ultra-trace levels of anti-HIV-1. Subsequently, a novel sandwich ECL immunosensor was formed through the immunoreaction between MMIPs conjugated with varied concentrations of anti-HIV-1 and HRP-HIV-1. By the catalysis of HRP immobilized onto HRP-HIV-1 on the ECL system of Luminol-H2O2, a linear response range of the anti-HIV-1 dilution ratio (standard positive serum) was achieved from 1:20,000 to 1:50, with a detection limit of 1:60,000 (S/N=3). The developed method provides a low-cost, simple, and sensitive way for the early diagnosis of HIV infected patients. PMID:24280050

Zhou, Jing; Gan, Ning; Li, Tianhua; Hu, Futao; Li, Xing; Wang, Lihong; Zheng, Lei

2014-04-15

379

A contribution to the finite element formulation for the analysis of composite sandwich shells  

NASA Astrophysics Data System (ADS)

The ultimate goal of the present research is to come up with an accurate and efficient analysis approach for composite and sandwich shells, which is simple enough to be capable of implementing into a FE code without significantly affecting its computational efficiency, and at the same time gives good accuracy in predicting the behavior of layered shells. It has to be capable of accurately modeling both overall behavior, and the local distribution of strains and stresses in all layers and all constituents in the composite laminae. Two different approaches are utilized in the attempt to fulfill the final research objective of the present work. First, a homogenization procedure for the FE analysis of sandwich shells is developed. The procedure works on the material constitutive level. A homogenization of the sandwich shell is performed at each call of the corresponding constitutive subroutine. Thus the sandwich nature of the problem is hidden from the main FE program. As a consequence there is no need to develop a new shell element formulation, but instead the available homogeneous shell elements in the utilized FE code can be used for the analysis of sandwich shells. However, the defined homogenization procedure works with first order shear deformable shell elements, which sets a limit to the accuracy with which the transverse distribution of the unknowns is represented. To overcome this, a higher order shear deformable shell element is formulated and implemented into a general nonlinear explicit FE code. Using the differential equilibrium equations and the interlayer requirements, special treatment is developed for the transverse shear, resulting in a continuous, piecewise quartic distribution of the transverse shear stresses through the shell thickness. A similar approach is applied to the transverse normal stresses, which are represented by a continuous piecewise cubic function. The FE implementation is cast into a 4-noded quadrilateral shell element with 9 degrees of freedom per node. Only C0 continuity of the displacement functions is required in the shell plane, which makes the present formulation applicable to the most popular 4-noded bilinear isoparametric shell elements. Expressions are developed for the critical time step oft he explicit time integration for orthotropic homogeneous and layered shells based on the developed third order formulation. Finally, to be able to analyze shells with woven composite layers, two micromechanical models for analysis of woven fabric composites are developed. Both models utilize the representative volume cell approach and divide a representative unit of the woven lamina into sub-cells of homogeneous material. Starting with the average strains in the representative volume cell and based on continuity requirements at the sub-cell interfaces, the strains and stresses in the composite constituents are determined as well as the average stresses in the lamina. Equivalent homogenized material properties are also determined. Their very good accuracy together with the simplicity of formulation makes these models attractive for the nonlinear FE analysis of composite laminates and can be efficiently utilized in explicit and implicit FE codes. The formulations developed within the research provide an efficient analysis approach to layered shells including sandwich shells with composite facings. Furthermore, the developed micromechanical models can be used to determine the stress and strain fields in the composite layer constituents. This would enable important strength and durability phenomena as failure, damage, and property degradation of the constituents to be included into the FE analysis of layered shells.

Tanov, Romil Raykov

2000-10-01

380

Socioeconomic and demographic factors modify the association between informal caregiving and health in the Sandwich Generation  

PubMed Central

Background Nearly 50 million Americans provide informal care to an older relative or friend. Many are members of the “sandwich generation”, providing care for elderly parents and children simultaneously. Although evidence suggests that the negative health consequences of caregiving are more severe for sandwiched caregivers, little is known about how these associations vary by sociodemographic factors. Methods We abstracted data from the Behavioral Risk Factor Surveillance System to determine how the association between caregiving and health varies by sociodemographic factors, using ordinal logistic regression with interaction terms and stratification by number of children, income, and race/ethnicity. Results The association between informal caregiving and health varied by membership in the “sandwich generation,” income, and race/ethnicity. This association was significant among subjects with one (OR =?1.13, 95% CI [1.04, 1.24]) and two or more children (OR =?1.17, 95% CI =?1.09, 1.26]), but not in those without children (OR =?1.01, 95% CI [0.97, 1.05]). Associations were strongest in those earning $50,000-$75,000 annually, but these income-dependent associations varied by race/ethnicity. In Whites with two or more children, the strongest associations between caregiving and health occurred in lower income individuals. These trends were not observed for Whites without children. Conclusions Our findings suggest that the added burden of caregiving for both children and elderly relatives may be impacted by income and race/ethnicity. These differences should be considered when developing culturally appropriate interventions to improve caregiver health and maintain this vital component of the US health care system. PMID:24735495

2014-01-01

381

Creep expansion of porous Ti-6Al-4V sandwich structures  

NASA Astrophysics Data System (ADS)

Low-density titanium alloy sandwich structures consisting of a porous core and fully dense face sheets can be produced by consolidating argon gas charged powder compacts followed by not rolling and annealing to expand the gas-filled pores. Little is known about the rate of pore expansion, its dependence upon temperature, and the morphological evolution of the pore shape during expansion. In situ eddy current and laser ultrasonic sensors have been combined with metallographic and texture measurements to measure the relative density, the elastic moduli, and the microstructural evolution of Ti-6Al-4V sandwich panels during the annealing stage of low-density core (LDC) processing. The eddy current data indicated that expansion began during, the heating phase, reached a maximum expansion rate (?) of 2 × 10-5 s-1 at approximately 685 °C, and had almost ceased (? < 1 × 10-6 s-1) after annealing for 4 hours at 920 °C. The elastic moduli were found to decrease with increasing temperature and volume fraction of porosity. The initial (as-rolled) microstructure consisted of a lamellar ? + ? microstructure with an ?-phase lath thickness of 2.0 µm and contained a distribution of oblate-shaped pores with aspect ratios of up to 10. During the expansion process, it recrystallized into an equiaxed ? + ? structure with an ?-phase grain diameter of 7.5 µm with spheroidal pores with aspect ratios of up to 3. The combination of the two sensors was found to enable the in situ determination of both the porous cores relative density and its elastic properties. These are the two material indices that govern the elastic response of a sandwich structure.

Queheillalt, Douglas T.; Wadley, Haydn N. G.; Choi, Bill W.; Schwartz, Daniel S.

2000-01-01

382

Advancing availability of papillary muscle sandwich plasty from functional to organic mitral valve regurgitation.  

PubMed

An original papillary muscle heads approximation procedure, commonly known as a sandwich plasty, has been successfully used for the treatment of functional mitral regurgitation (MR) associated with ischemic cardiomyopathy (ICM) and aortic valve disease (AVD). In this study, we evaluated the availability of this method as the concomitant procedure for the plasty of organic MR in comparison with the operative results in patients with functional MR. Fifty-six patients who underwent sandwich plasty were reviewed, including 45 functional MR (29 ICM and 16 AVD) patients and 11 organic MR patients. The mean age of patients was 67 years. In the organic MR patients, predominant cardiac diseases were solitary MR in six patients and combined valve diseases including aortic valve stenosis in five. Mitral valve changes included prolapse in six patients and moderate cusp thickening with calcification in five. Two heads of the papillary muscle connecting to the choldae of both the anterior and posterior leaflets are fixed with two teflon-pledgeted 3-0 TiCron™ (Covidien, Dublin, Ireland) sutures in order to achieve coaptation of the two leaflets. Prominent MR was observed in a patient with functional MR after surgery, however residual MR was not detected in organic MR patients. The tenting height (coaptation distance) of mitral valve significantly decreased after surgery from 11±1 to 7±2mm in the organic MR patients, which was similar to the results in the functional MR patients (from 12±2 to 7±2 mm). The postoperative mean mitral orifice area in the organic MR patients was 4.3±0.1cm2 without stenosis. Sandwich plasty reduces the distance of choldae connecting to anterior and posterior leaflets and achieves the better coaptation of two leaflets. This procedure is effective in the treatment of both functional and organic MR. PMID:25433409

Ishikawa, Susumu; Mishima, Hideki; Matsunaga, Hiroki; Katayama, Yasushi

2014-11-01

383

Polystyrene microspheres based sandwich immunosensor using CdTe nanoparticles amplification and ultrasensitive flow-injection chemiluminescence detection.  

PubMed

In this paper we propose a specific sandwich immunoassay method for human-immunoglobulin G (HIgG). This immunoassay protocol takes advantage of sandwich binding of primary and secondary antibodies for increased specificity. Polystyrene microspheres (PS) serve as immobilizing support, site for sandwich immunoassay and then subsequently used for chemiluminescence (CL) detections. In this sandwich immunoassay, PS microspheres were modified with the primary anti-HIgG (Ab1) via electrostatic interaction, while CdTe nanoparticles (CdTeNPs) were modified with horseradish peroxidase labeled anti-HIgG (Ab2) via covalent binding. Antigen HIgG (Ag) was specifically captured by the first and secondary antibody and form sandwich immunoassay format. Combination of the remarkable sensitivity of CL method and the use of CdTe NPs as anti-HIgG-HRP carrier for the enzymatic signal amplification, provide a linear response range of HIgG from 0.01 to 300 ng mL(-1) with an extremely low detection limit of 0.3 pg mL(-1). This immunoassay system has many desirable merits including sensitivity, accuracy, and little required instrumentation. The assay results were compared with enzyme-linked immunosorbent assay (ELISA), and showed relatively good reliability. Significantly the new protocol may become quite promising technique for protein immune-detection as well as DNA analysis and other biological analyses. PMID:20801005

Kanwal, Shamsa; Traore, Zoumama; Su, Xingguang

2010-12-01

384

The performance of metallic sandwich panels subject to quasi-static and dynamic loads  

NASA Astrophysics Data System (ADS)

Sandwich panels with cellular metals are multifunctional. They are utilized in ultra-light designs, in heat dissipation and for energy absorption. The benefits are topology-sensitive: that is, the important properties are sensitive to both the geometry of the sandwich panels and the micro-architecture of the cellular cores. Establishing relationships between prismatic core topology and performance is the major goal of this research. To realize this objective, the thesis is in four interrelated parts. In Part I, ultra-light sandwich panels with prismatic cores are optimized for quasi-static load capacity at minimum weight by using elastic analysis and imposing load limits based on yielding and buckling. The optimization is performed in the two principal in-plane directions and jointly for both orientations. The designs emerging from joint optimizations have slightly lower load capacity than those optimized singly, but with the benefit of equal strengths in all in-plane directions. In Part II, the quasi-static load capacity beyond the initial nonlinearity is characterized by means of a full nonlinear analysis that incorporates plastic hardening, post buckling and core/face contact. For corrugated structures, a study of buckling modes and their imperfection sensitivity is performed. For pyramidal truss cores, a constitutive law is utilized instead of 3D fully-meshed simulation. Comparisons between simulation and experiment are used to assess the fidelity of the constitutive law. In Part III, the response to impulsive loads, especially to water blast, is investigated. The characterization is conducted by means of the constitutive law with strain-rate dependence. The law was assessed by comparison with two sets of experiments. Integration of Parts II and III affirms that the constitutive law approach is capable of predicting the overall performance. Finally, in Part IV, a comprehensive study of multilayer corrugated panels is conducted, including quasi-static and dynamic measurements, 3D fully-meshed simulations, calibration of the constitutive law for large-scale simulations and analytic estimates. Such a study enables a thorough understanding of the performance of sandwich panels subject to a variety of loads, thereby providing a template for future research.

Wei, Zhensong

385

High heat flux actively cooled honeycomb sandwich structural panel for a hypersonic aircraft  

NASA Technical Reports Server (NTRS)

The results of a program to design and fabricate an unshielded actively cooled structural panel for a hypersonic aircraft are presented. The design is an all-aluminum honeycomb sandwich with embedded cooling passages soldered to the inside of the outer moldline skin. The overall finding is that an actively cooled structure appears feasible for application on a hypersonic aircraft, but the fabrication process is complex and some material and manufacturing technology developments are required. Results from the program are summarized and supporting details are presented.

Koch, L. C.; Pagel, L. L.

1978-01-01

386

Generation of quasi-monoenergetic carbon ions accelerated parallel to the plane of a sandwich target  

NASA Astrophysics Data System (ADS)

A new ion acceleration scheme, namely, target parallel Coulomb acceleration, is proposed in which a carbon plate sandwiched between gold layers is irradiated with intense linearly polarized laser pulses. The high electrostatic field generated by the gold ions efficiently accelerates the embedded carbon ions parallel to the plane of the target. The ion beam is found to be collimated by the concave-shaped Coulomb potential. As a result, a quasi-monoenergetic and collimated C6+-ion beam with an energy exceeding 10 MeV/nucleon is produced at a laser intensity of 5 × 1019 W/cm2.

Wang, J. W.; Murakami, M.; Weng, S. M.; Xu, H.; Ju, J. J.; Luan, S. X.; Yu, W.

2014-12-01

387

The Effect of Temperature on Faceplate/Core Delamination in Composite/Titanium Sandwich Plates  

NASA Technical Reports Server (NTRS)

A study was made of the delamination behavior of sandwich beams made of titanium core bonded to face-plates that consisted of carbon fiber reinforced polymer composite. Nominally mode I behavior was considered at 23C and 180C, by making use of a specially reinforced double cantilever (DCB) specimens. The toughness of the bond between the faceplate and the core was determined on the basis of a beam on elastic foundation analysis. The specimen compliance, and toughness were all independent of temperature in these relatively short-term experiments. The fracture mechanism showed temperature dependence, due to the hygrothermal sensitivity of the adhesive.

Liechti, Kenneth M.; Marton, Balazs

2000-01-01

388

Airflow-field-induced sandwich-type membrane of block copolymer for selective ion separation.  

PubMed

A simple and effective airflow method to prepare sandwich-type block copolymer films is reported. The films are composed of three layers: vertically oriented nanocylinders align in both upper and bottom layers and irregular nanocylinders exist in the bulk of the film. The vertically oriented nanocylinders in both sides can provide high accessibility to ions and ensures the exchange of chemical species between the membrane and external environment, while the irregularly oriented nanocylinders in the middle part of the film can prolong the pathway of ions transportation and enhance ions selectivity. PMID:24497315

Shan, Feng; Lu, Xuemin; Guan, Junfang; Lu, Qinghua; Feng, Xingliang

2014-04-01

389

Low-energy impact resistance of graphite-epoxy plates and ALS honeycomb sandwich panels  

NASA Technical Reports Server (NTRS)

Low energy impact may be potentially dangerous for many highly optimized stiff structures. Impact by foreign objects such as birds, ice, and runways stones or dropping of tools occur frequently and the resulting damage and stress concentrations may be unacceptable from a designer's standpoint. The barely visible, yet potentially dangerous dents due to impact of foreign objects on the Advanced Launch System (ALS) structure are studied. Of particular interest is the computation of the maximum peak impact force for a given impactor mass and initial velocity. The theoretical impact forces will be compared with the experimental dropweight results for the ALS face sheets alone as well as the ALS honeycomb sandwich panels.

Hui, David

1989-01-01

390

Electrochemical aptamer-based sandwich assays for the detection of explosives.  

PubMed

Electrochemical impedance spectroscopy (EIS) is used to detect 2,4,6-trinitrotoluene (TNT) in a novel sandwiched structure which relies on the specific interactions between (i) primary amine with TNT and (ii) TNT and anti-TNT aptamer. With pure targets, the assay has a sensitivity of 10(-14) M, a dynamic range of 10(-14)-10(-3) M, and employs a small sample volume (25 ?L). The method's sensitivity is comparable to state of the art optical methods with the added advantages of electrochemical detection, which can be easily miniaturized and implemented into a hand-held device. PMID:22519699

Ho, Man Yi; D'Souza, Natasha; Migliorato, Piero

2012-05-15

391

Parameters estimation of sandwich beam model with rigid polyurethane foam core  

NASA Astrophysics Data System (ADS)

In this work, the physical parameters of sandwich beams made with the association of hot-rolled steel, Polyurethane rigid foam and High Impact Polystyrene, used for the assembly of household refrigerators and food freezers are estimated using measured and numeric frequency response functions (FRFs). The mathematical models are obtained using the finite element method (FEM) and the Timoshenko beam theory. The physical parameters are estimated using the amplitude correlation coefficient and genetic algorithm (GA). The experimental data are obtained using the impact hammer and four accelerometers displaced along the sample (cantilevered beam). The parameters estimated are Young's modulus and the loss factor of the Polyurethane rigid foam and the High Impact Polystyrene.

Barbieri, Nilson; Barbieri, Renato; Winikes, Luiz Carlos

2010-02-01

392

Proton radiography of PBX 9502 detonation shock dynamics confinement sandwich test  

SciTech Connect

Recent results utilizing proton radiography (P-Rad) during the detonation of the high explosive PBX 9502 are presented. Specifically, the effects of confinement of the detonation are examined in the LANL detonation confinement sandwich geometry. The resulting detonation velocity and detonation shock shape are measured. In addition, proton radiography allows one to image the reflected shocks through the detonation products. Comparisons are made with detonation shock dynamics (DSD) and reactive flow models for the lead detonation shock and detonation velocity. In addition, predictions of reflected shocks are made with the reactive flow models.

Aslam, Tariq D [Los Alamos National Laboratory; Jackson, Scott I [Los Alamos National Laboratory; Morris, John S [Los Alamos National Laboratory

2009-01-01

393

Numerical Analysis of Thermodynamic Behaviour of Through-Thickness Stitched Sandwich Laminate  

NASA Astrophysics Data System (ADS)

Effects of stitching angle on mechanical properties, thermal protection capability and induced thermal stress of stitched sandwich laminate (SSL) are numerically analyzed by ABAQUS codes. Interest centers on the potential for microcracking in the vicinity of the through-thickness stitches and the skins/foam interfaces. Two numerical models, in-depth heat transfer and thermoelastic deformation, are coupled to yield the transient response of the SSL. Six different stitching angles are considered and the simulation results showed that: the heat conductivity ability of the SSL is improved as the stitching angle increasing, which alters the mechanical behaviour and the thermal stress state of the SSL.

Shigang, Ai; Yiqi, Mao; Yongmao, Pei; Daining, Fang; Liqun, Tang

2013-12-01

394

Application of Air Coupled Acoustic Thermography (ACAT) for Inspection of Honeycomb Sandwich Structures  

NASA Technical Reports Server (NTRS)

The application of a noncontact air coupled acoustic heating technique is investigated for the inspection of advanced honeycomb composite structures. A weakness in the out of plane stiffness of the structure, caused by a delamination or core damage, allows for the coupling of acoustic energy and thus this area will have a higher temperature than the surrounding area. Air coupled acoustic thermography (ACAT) measurements were made on composite sandwich structures with damage and were compared to conventional flash thermography. A vibrating plate model is presented to predict the optimal acoustic source frequency. Improvements to the measurement technique are also discussed.

Winfree, William P.; Zalameda, Joseph N.; Pergantis, Charles; Flanagan, David; Deschepper, Daniel

2009-01-01

395

Thermally stable dynamic piezoelectricity in sandwich films of porous and nonporous amorphous fluoropolymer  

NASA Astrophysics Data System (ADS)

Porous amorphous fluoropolymer films of very low stiffness were produced by a solvent evaporation technique. Corona-charged sandwich films consisting of a porous and a nonporous layer exhibit piezoelectric thickness-extension resonances in their dielectric spectrum, through which the temperature dependence of their dynamic stiffness, coupling factor, and piezoelectric coefficient could be determined. Their strong piezoelectricity with coefficients of up to 600 pC/N at temperatures of at least 120 °C could make these polymer electret films interesting candidates for sensor and actuator applications in elevated temperature environments.

Mellinger, Axel; Wegener, Michael; Wirges, Werner; Gerhard-Multhaupt, Reimund

2001-09-01

396

Effect of temperature on composite sandwich structures subjected to low velocity projectile impact  

NASA Technical Reports Server (NTRS)

An experimental investigation was conducted to study the effect of low velocity projectile impact on graphite/epoxy and Kevlar 49- graphite/epoxy sandwich structural components. Testing was performed at moderately low- and high-temperatures to assess the strength degradation of composites as compared to room temperature values. Low energy projectile impact is considered to simulate the damage caused by runway debris such as small rocks, dropping of hand tools during servicing, etc., on secondary aircraft structures fabricated out of composites. The preload and impact energy necessary to cause catastrophic failure were determined. The residual strength of impact-damaged specimens was also measured.

Sharma, A. V.

1978-01-01

397

Compression After Impact Experiments and Analysis on Honeycomb Core Sandwich Panels with Thin Facesheets  

NASA Technical Reports Server (NTRS)

A better understanding of the effect of impact damage on composite structures is necessary to give the engineer an ability to design safe, efficient structures. Current composite structures suffer severe strength reduction under compressive loading conditions, due to even light damage, such as from low velocity impact. A review is undertaken to access the current state-of-development in the areas of experimental testing, and analysis methods. A set of experiments on honeycomb core sandwich panels, with thin woven fiberglass cloth facesheets, is described, which includes detailed instrumentation and unique observation techniques.

McQuigg, Thomas D.

2011-01-01

398

APPLICATION CONSTRUCTION LEADERSHIP COURSE  

E-print Network

in the construction industry 5) If your GPA . Include experience in construction industry. Recommendation from an Instructor Provide instructorAPPLICATION CONSTRUCTION LEADERSHIP COURSE RECOMMENDATION FORM CON464 Construction Leadership

Stephens, Graeme L.

399

Localised Effects in Sandwich Structures with Internal Core Junctions:Modelling and Experimental Characterisation of Load Response, Failure and Fatigue  

NASA Astrophysics Data System (ADS)

The objective is to provide an overview of the mechanisms which determine the occurrence and severity of localized bending effects in sandwich structures. It is known from analytical and numerical modelling that local effects lead to an increase of the face bending stresses as well as the core shear and transverse normal stresses. The modelling and experimental characterisation of local effects in sandwich structures will be addressed based on the simple and generic case of sandwich structures with internal core junctions under general shear, bending and in-plane loading conditions. The issue of failure and fatigue phenomena induced by the presence of core junctions will be discussed in detail, with the inclusion of recent theoretical and experimental results.

Johannes, Martin; Thomsen, Ole Thybo

400

Redox-induced reversible metal assembly through translocation and reversible ligand coupling in tetranuclear metal sandwich frameworks  

NASA Astrophysics Data System (ADS)

Sandwich structures formed by metal atoms intercalated between sp2-carbon planes can be found either in metal-graphite-based materials or discrete multinuclear sandwich complexes. Their reactivity, and in particular their dynamic behaviour, has recently attracted interest both from a structural and a practical aspect, for example in catalysis. However, progress in this area has been rather slow, and it remains difficult to elucidate their structure and behaviour at the molecular level. Here, we report two sandwich complexes—in which four palladium centres are incorporated between two ?-conjugated ligands—which exhibit two modes of redox-switchable structural changes. In the first complex, the tetrapalladium chain is split by oxidation into two well-separated dipalladium units. This motion is reversed on reduction. In the second complex, reversible carbon-carbon coupling occurs between the ligands during the redox process.

Murahashi, Tetsuro; Shirato, Katsunori; Fukushima, Azusa; Takase, Kohei; Suenobu, Tomoyoshi; Fukuzumi, Shunichi; Ogoshi, Sensuke; Kurosawa, Hideo

2012-01-01

401

Giant Magnetoimpedance Effect in a Sandwiched Structure of as-Quenched FeNiCrSiB Ribbons  

NASA Astrophysics Data System (ADS)

The giant magnetoimpedance (GMI) effect and effective permeability ratio in a QFR/Cu/QFR sandwiched structure are studied, where QFR stands for the as-quenched FeNiCrSiB amorphous ribbon. Remarkable GMI effects are obtained in the QFR/Cu/QFR sandwiched structure without annealing. The maximum values of the longitudinal and transverse GMI ratios at 0.5 MHz are 282% and 408%, respectively. Correspondingly, the maximum effective permeability ratios at 0.5 MHz are 326% and 1013% in longitudinal and transverse field, respectively. These large GMI values are attributed to the high effective permeability of the sample due to the closed alternating current (ac) magnetic flux path in the sandwiched structure, and large permeability variation induced by the magnetic field.

Chen, Wei-Ping; Li, Zhi-Gang; Shao, Xian-Yi; Zhong, Wen-Wu; Li, Qin-Tao; Liu, Yan-Ping

2013-06-01

402

Elevated Temperature, Residual Compressive Strength of Impact-Damaged Sandwich Structure Manufactured Out-of-Autoclave  

NASA Technical Reports Server (NTRS)

Several 1/16th-scale curved sandwich composite panel sections of a 10 m diameter barrel were fabricated to demonstrate the manufacturability of large-scale curved sections using minimum gauge, [+60/-60/0]s, toughened epoxy composite facesheets co-cured with low density (50 kilograms per cubic meters) aluminum honeycomb core. One of these panels was fabricated out of autoclave (OoA) by the vacuum bag oven (VBO) process using Cycom(Registered Trademark) T40-800b/5320-1 prepreg system while another panel with the same lay-up and dimensions was fabricated using the autoclave-cure, toughened epoxy prepreg system Cycom(Registered Trademark) IM7/977-3. The resulting 2.44 m x 2 m curved panels were investigated by non-destructive evaluation (NDE) at NASA Langley Research Center (NASA LaRC) to determine initial fabrication quality and then cut into smaller coupons for elevated temperature wet (ETW) mechanical property characterization. Mechanical property characterization of the sandwich coupons was conducted including edge-wise compression (EWC), and compression-after-impact (CAI) at conditions ranging from 25 C/dry to 150 C/wet. The details and results of this characterization effort are presented in this paper.

Grimsley, Brian W.; Sutter, James K.; Burke, Eric R.; Dixon, Genevieve D.; Gyekenyesi, Thomas G.; Smeltzer, Stanley S.

2012-01-01

403

Bulk-heterojunction organic solar cells sandwiched by solution processed molybdenum oxide and titania nanosheet layers  

NASA Astrophysics Data System (ADS)

The contributions of ultrathin titania nanosheet (TN) crystallites were studied in both an inverted bulk-heterojunction (BHJ) cell in an indium-tin oxide (ITO)/titania nanosheet (TN)/poly(3-hexylthiophene) (P3HT):phenyl-C61-butyric acid methylester (PCBM) active layer/MoOx/Ag multilayered photovoltaic device and a conventional BHJ cell in ITO/MoOx/P3HT:PCBM active layer/TN/Al multilayered photovoltaic device. The insertion of only one or two layers of poly(diallyldimethylammonium chloride) (PDDA) and TN multilayered film prepared by the layer-by-layer deposition technique effectively decreased the leakage current and increased the open circuit voltage (VOC), fill factor (FF), and power conversion efficiency (?). The conventional cell sandwiched between a solution-processed, partially crystallized molybdenum oxide hole-extracting buffer layer and a TN electron extracting buffer layer showed comparable cell performance to a device sandwiched between vacuum-deposited molybdenum oxide and TN layers, whereas the inverted cell with solution-processed molybdenum oxide showed a poorer performance probably owing to the increment in the leakage current across the film. The abnormal S-shaped curves observed in the inverted BHJ cell above VOC disappeared with the use of a polyfluorene-based cationic semiconducting polymer as a substitute for an insulating PDDA film, resulting in the improved cell performance.

Itoh, Eiji; Goto, Yoshinori; Fukuda, Katsutoshi

2014-02-01

404

Sequential chemotherapy and radiotherapy as sandwich therapy for the treatment of high risk endometrial cancer  

PubMed Central

Objective The purpose of this retrospective study was to assess the tolerability and efficacy of sequential chemotherapy and radiotherapy for the treatment of high risk endometrial cancer. Methods We conducted a retrospective study of previously untreated high risk endometrial cancer patients who received sequential chemotherapy and radiotherapy in accordance with the sandwich approach from June 2008 until June 2011. High risk endometrial cancer patients underwent complete surgical staging followed by adjuvant therapy encompassing sequential chemotherapy, radiation therapy and consolidation chemotherapy. Results The study analysis comprised 32 endometrial cancer patients. All subjects were treated with carboplatin and paclitaxel chemotherapy; currently, 186 cycles have been administered and 94% of patients have completed the planned number of cycles. Grade 3 neutropenia developed in 1 (3.1%) patient; there was no incidence of grade 4 neutropenia. Moreover, we observed grade 3 anemia in four (12.5%) patients and grade 4 anemia in one (3.1%) patient. One (3.1%) patient developed grade 3 thrombocytopenia; grade 4 thrombocytopenia was not observed. Five patients exhibited progressive disease, three of whom have since expired; mean progression free survival and follow-up were 17.4 months and 18.9 months, respectively. Conclusion The preliminary results from our study suggest that the sandwich approach to treating high risk endometrial cancer patients is feasible. Hematologic toxicity was well tolerated and non-hematologic toxicity was mild and easily managed. Further study of this novel regimen in a larger patient population with extended follow-up is necessary. PMID:22355463

Abaid, Lisa N.; Rettenmaier, Mark A.; Brown, John V.; Micha, John P.; Mendivil, Alberto A.; Wabe, Marie A.

2012-01-01

405

Development of sandwich-form biosensor to detect Mycobacterium tuberculosis complex in clinical sputum specimens.  

PubMed

Mycobacterium tuberculosis, the causing agent of tuberculosis, comes second only after HIV on the list of infectious agents slaughtering many worldwide. Due to the limitations behind the conventional detection methods, it is therefore critical to develop new sensitive sensing systems capable of quick detection of the infectious agent. In the present study, the surface modified cadmium-telluride quantum dots and gold nanoparticles conjunct with two specific oligonucleotides against early secretory antigenic target 6 were used to develop a sandwich-form fluorescence resonance energy transfer-based biosensor to detect M. tuberculosis complex and differentiate M. tuberculosis and M. bovis Bacille Calmette-Guerin simultaneously. The sensitivity and specificity of the newly developed biosensor were 94.2% and 86.6%, respectively, while the sensitivity and specificity of polymerase chain reaction and nested polymerase chain reaction were considerably lower, 74.2%, 73.3% and 82.8%, 80%, respectively. The detection limits of the sandwich-form fluorescence resonance energy transfer-based biosensor were far lower (10fg) than those of the polymerase chain reaction and nested polymerase chain reaction (100fg). Although the cost of the developed nanobiosensor was slightly higher than those of the polymerase chain reaction-based techniques, its unique advantages in terms of turnaround time, higher sensitivity and specificity, as well as a 10-fold lower detection limit would clearly recommend this test as a more appropriate and cost-effective tool for large scale operations. PMID:25181404

Shojaei, Taha Roodbar; Mohd Salleh, Mohamad Amran; Tabatabaei, Meisam; Ekrami, Alireza; Motallebi, Roya; Rahmani-Cherati, Tavoos; Hajalilou, Abdollah; Jorfi, Raheleh

2014-01-01

406

Evaluation of the sensitivity and fatigue performance of embedded piezopolymer sensor systems in sandwich composite laminates  

NASA Astrophysics Data System (ADS)

It has been claimed that embedding piezoceramic devices as structural diagnostic systems in advanced composite structures may introduce mechanical impedance mismatches that favor the formation of intralaminar defects. This and other factors, such as cost and their high strain sensitivity, have motivated the use of thin-film piezopolymer sensors. In this paper, we examine the performance of sandwich composite panels fitted with embedded piezopolymer sensors. Our experiments examine both how such thin-film sensors perform within a structure and how the inclusion of sensor films affects structural performance. Strain-controlled tests on sandwich panels subjected to three-point bending under wide-ranging static and dynamic strains lead us to conclude that embedding thin piezopolymer films has no marked reduction on the tensile strength for a wide range of strain loading paths and magnitudes, and that the resilience of the embedded sensor is itself satisfactory, even up to the point of structural failure. Comparing baseline data obtained from standard surface-mounted sensors and foil gauges, we note that whereas it is possible to match experimental and theoretical strain sensitivities, key properties—especially the pronounced orthotropic electromechanical factor of such films—must be duly considered before an effective calibration can take place.

Chrysochoidis, N. A.; Gutiérrez, E.

2015-02-01

407

Debonding Stress Concentrations in a Pressurized Lobed Sandwich-Walled Generic Cryogenic Tank  

NASA Technical Reports Server (NTRS)

A finite-element stress analysis has been conducted on a lobed composite sandwich tank subjected to internal pressure and cryogenic cooling. The lobed geometry consists of two obtuse circular walls joined together with a common flat wall. Under internal pressure and cryogenic cooling, this type of lobed tank wall will experience open-mode (a process in which the honeycomb is stretched in the depth direction) and shear stress concentrations at the junctures where curved wall changes into flat wall (known as a curve-flat juncture). Open-mode and shear stress concentrations occur in the honeycomb core at the curve-flat junctures and could cause debonding failure. The levels of contributions from internal pressure and temperature loading to the open-mode and shear debonding failure are compared. The lobed fuel tank with honeycomb sandwich walls has been found to be a structurally unsound geometry because of very low debonding failure strengths. The debonding failure problem could be eliminated if the honeycomb core at the curve-flat juncture is replaced with a solid core.

Ko, William L.

2004-01-01

408

Sandwich-type polyoxotungstate hybrids decorated by nickel-aromatic amine complexes  

NASA Astrophysics Data System (ADS)

Three new sandwich-type polyoxotungstates (POTs) decorated by nickel-2,2'-bpy complexes [{Ni(2,2'-bpy) 2(H 2O)} 2{Ni(2,2'-bpy)} 2 {Ni 4(H 2O) 2(B- ?- XW 9O 34) 2}] n- ( X=P V, n=4 for 1; X=As V, n=4 for 2; X=Ge IV, n=4 for 3) (2,2'-bpy=2,2'-bipyridine) were successfully synthesized under hydrothermal conditions and structurally characterized by elemental analyses, IR spectroscopy, single-crystal X-ray diffraction, and magnetic properties. Single-crystal structural analyses indicate that 1 and 2 are isostructural and both crystallize in the monoclinic space group C2 /c, whereas 3 belongs to the triclinic space group P1¯. To our knowledge, 1, 2 and 3 represent rare examples of the organic-inorganic hybrid sandwich-type polyoxometalates functionalized by multiple nickel-aromatic amine complexes. Magnetic measurements of 1 exhibit the presence of ferromagnetic interactions within the rhombic tetranuclear-Ni II cluster.

Ma, Peng-Tao; Zhao, Jun-Wei; Wang, Jing-Ping; Shen, Yue; Niu, Jing-Yang

2010-01-01

409

Sandwich beam model for free vibration analysis of bilayer graphene nanoribbons with interlayer shear effect  

SciTech Connect

In this study, sandwich beam model (SM) is proposed for free vibration analysis of bilayer graphene nanoribbons (BLGNRs) with interlayer shear effect. This model also takes into account the intralayer (in-plane) stretch of graphene nanoribbons. The molecular dynamics (MD) simulations using the software LAMMPS and Adaptive Intermolecular Reactive Empirical Bond Order (AIREBO) potential are done to validate the accuracy of the sandwich model results. The MD simulation results include the two first frequencies of cantilever BLGNRs with different lengths and two interlayer shear moduli, i.e., 0.25 and 4.6?GPa. These two interlayer shear moduli, 0.25 and 4.6?GPa, can be obtained by sliding a small flake of graphene on a large graphene substrate when the parameter of E-LJ term in AIREBO potential, epsilon-CC, is set to be 2.84 and 45.44?meV, respectively. The SM results for a wide range of bending rigidity values show that the proposed model, i.e., the SM, predicts much better than the previous beam model in which the intralayer stretch is ignored. In addition, it is observed that the model can properly predict the natural frequencies of BLGNRs for various values of the bending rigidity and the interlayer shear modulus.

Nazemnezhad, Reza, E-mail: rnazemnezhad@iust.ac.ir, E-mail: rnazemnezhad@du.ac.ir [School of Mechanical Engineering, Iran University of Science and Technology, Narmak, Tehran (Iran, Islamic Republic of); Shokrollahi, Hassan [School of Mechanical Engineering, Sharif University of Technology, Tehran (Iran, Islamic Republic of); Hosseini-Hashemi, Shahrokh [School of Mechanical Engineering, Iran University of Science and Technology, Narmak, Tehran (Iran, Islamic Republic of); Center of Excellence in Railway Transportation, Iran University of Science and Technology, Narmak, Tehran (Iran, Islamic Republic of)

2014-05-07

410

Research of processing method for infrared image of sandwich structure composite  

NASA Astrophysics Data System (ADS)

Composite sandwich structure has been widely used in aerospace due to its lightweight, high stiffness and strength. Existence of delaminations in the structure reduce the performance of the composites significantly, such flaws can be detected effectively and non-destructively by non-contact pulsed infrared thermography, but the contrast of infrared images of the material is low due to complex structure, so delaminations and sound area are difficult to be differentiated. In this paper, sandwich structure composites with aluminum facesheet and aluminum honeycomb cores are chosen as study objectives, several round-shape and rectangle-shape Teflon inserts with different sizes embedded in specimen, which simulate delaminations in the structure, and the processing method of infrared image is developed. The thermal image is processed through image denoising, image enhancement and feature extraction, and then the sizes of the defects are determined. Refer to the designed sizes, the results show that the accuracy of sizes measured by image processing is more than 90% for the defects bigger than ?10mm , these results demonstrated that detecting accuracy of the structure is higher by infrared image processing.

Huo, Yan; Zhang, Cun-Lin; Hu, Chun-Yu; Li, Chun-Guang

2012-10-01

411

SERS-based direct and sandwich assay methods for mir-21 detection.  

PubMed

In this study, two different assay methods were developed using a surface enhanced Raman scattering (SERS) label for sensitive miR-21 detection. In the first method (direct assay), the miR-21 probe was attached to SERS-labelled, rod-shaped gold nanoparticles and hybridised with the target miR-21, which was previously immobilised onto the gold slide. In the second method (sandwich assay), the target miR-21 was captured by an miR-21 probe immobilised onto the gold slide and hybridised with a second miR-21 probe immobilised on the SERS-labeled, rod-shaped gold nanoparticles. SERS signals of developed assays were obtained via a SERS spectrum of 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB) on the rod-shaped nanoparticles. The calibration curves were plotted to measure the different concentrations of miR-21. The detection limits of the direct and sandwich assays, which last less than 40 min, were found to be 0.36 and 0.85 nM, respectively. The developed SERS-based methods offer rapid, selective, sensitive and easy detection of miR-21, especially compared to conventional PCR-based methods. PMID:24418951

Guven, Burcu; Dudak, Fahriye Ceyda; Boyaci, Ismail Hakki; Tamer, Ugur; Ozsoz, Mehmet

2014-03-01

412

Dynamic Response and Optimal Design of Curved Metallic Sandwich Panels under Blast Loading  

PubMed Central

It is important to understand the effect of curvature on the blast response of curved structures so as to seek the optimal configurations of such structures with improved blast resistance. In this study, the dynamic response and protective performance of a type of curved metallic sandwich panel subjected to air blast loading were examined using LS-DYNA. The numerical methods were validated using experimental data in the literature. The curved panel consisted of an aluminum alloy outer face and a rolled homogeneous armour (RHA) steel inner face in addition to a closed-cell aluminum foam core. The results showed that the configuration of a “soft” outer face and a “hard” inner face worked well for the curved sandwich panel against air blast loading in terms of maximum deflection (MaxD) and energy absorption. The panel curvature was found to have a monotonic effect on the specific energy absorption (SEA) and a nonmonotonic effect on the MaxD of the panel. Based on artificial neural network (ANN) metamodels, multiobjective optimization designs of the panel were carried out. The optimization results revealed the trade-off relationships between the blast-resistant and the lightweight objectives and showed the great use of Pareto front in such design circumstances. PMID:25126606

Yang, Shu; Han, Shou-Hong; Lu, Zhen-Hua

2014-01-01

413

Sandwich transitional metal complexes with tungstobismuthates and 1-methylimidazole ligands: Syntheses, structures and magnetic properties  

NASA Astrophysics Data System (ADS)

Two novel sandwich-type coordination compounds of tungstobismuthate Na 9[{Na(H 2O) 2} 3{Co II(mim)} 3(Bi IIIW VI9O 33) 2]·36H 2O ( 1) and Na 7H 2[{Na(H 2O) 2} 3{Mn II(mim)} 3(Bi IIIW VI9O 33) 2]·21H 2O ( 2) (mim = 1-methylimidazole) have been synthesized in alkaline aqueous solution. Their composition and structures were established by elemental analyses, IR spectra, and single crystal X-ray diffraction. These two complexes consist of two tri-vacant [?-B-Bi IIIW VI9O 33] 9- moieties linked through three Cu II or Mn II and three Na + ions. These Na + cations around the complex anion were bonded with some terminal and bridging oxo atoms from the complex anion and water molecules. In addition to tungstobismuthate ligands, 1-methylimidazoles also coordinate to sandwich transitional metal ions. Magnetic measurement indicates the existence of antiferromagnetic interaction between the trimeric transitional metal ions for 1 and 2.

Liu, Hong; Xu, Lin; Gao, Guanggang; Li, Fengyan; Jiang, Ning

2008-04-01

414

Sensitive, simultaneous quantitation of two unlabeled DNA targets using a magnetic nanoparticle-enzyme sandwich assay.  

PubMed

We report herein the development of a simple, sensitive colorimetric magnetic nanoparticle (MNP)-enzyme-based DNA sandwich assay that is suitable for simultaneous, label-free quantitation of two DNA targets down to 50 fM level. It can also effectively discriminate single-nucleotide polymorphisms (SNPs) in genes associated with human cancers (KRAS codon 12/13 SNPs). This assay uses a pair of specific DNA probes, one being covalently conjugated to an MNP for target capture and the other being linked to an enzyme for signal amplification, to sandwich a DNA target, allowing for convenient magnetic separation and subsequent efficient enzymatic signal amplification for high sensitivity. Careful optimization of the MNP surfaces and assay conditions greatly reduced the background, allowing for sensitive, specific detection of as little as 5 amol (50 fM in 100 ?L) of target DNA. Moreover, this sensor is robust, it can effectively discriminate cancer-specific SNPs against the wild-type noncancer target, and it works efficiently in 10% human serum. Furthermore, this sensor can simultaneously quantitate two different DNA targets by using two pairs of unique capture- and signal-DNA probes specific for each target. This general, simple, and sensitive DNA sensor appears to be well-suited for a wide range of genetics-based biosensing and diagnostic applications. PMID:23971744

Zhang, Yue; Pilapong, Chalermchai; Guo, Yuan; Ling, Zhenlian; Cespedes, Oscar; Quirke, Philip; Zhou, Dejian

2013-10-01

415

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

NASA Astrophysics Data System (ADS)

Radar-absorbing structures having foam-based honeycomb sandwich structures (FBHSS) were fabricated through a conventional foaming technique. Conductive fillers such as carbonyl iron/nickel fibers (CINF) and magnetic metal micropowder (MMP) were added to polyurethane foams so as to efficiently increase the absorbing capacity of FBHSS. A honeycomb sandwich structure, which was made of composite face sheets and foam cores, was used as a supporter to enhance mechanical strength. A matching layer made of nanotitanium powder and hydrogenation acrylonitrile-butadiene rubber composites was used for the face sheet, which allows the incident electromagnetic wave to enter and largely get attenuated through the absorbing system. Polyurethane foams containing CINFs and MMP of which a suitable content contributing to a broad bandwidth and high loss, were used as the core material. The measurement results show reflection loss was less than -10 dB over the frequency range of 3-18 GHz, which has a minimum value of - 26 dB at 14.2 GHz.

He, Yanfei; Gong, Rongzhou

2009-03-01

416

The three-point bending of Y-frame and corrugated core sandwich beams V. Rubino, V.S. Deshpande n  

E-print Network

The three-point bending of Y-frame and corrugated core sandwich beams V. Rubino, V.S. Deshpande n Three-point bending a b s t r a c t Sandwich beams comprising Y-frame and corrugated cores have been of the beams is governed by the indentation of the Y-frame or corrugated core for all beam geometries

Fleck, Norman A.

417

Dynamic Ham-Sandwich Cuts of Convex Polygons in the Plane Timothy Abbott Erik D. Demaine Martin L. Demaine Daniel Kane Stefan Langerman y  

E-print Network

Dynamic Ham-Sandwich Cuts of Convex Polygons in the Plane Timothy Abbott #3; Erik D. Demaine #3 provide an eÃ?cient data structure for dynami- cally maintaining a ham-sandwich cut of two non- overlapping convex polygons in the plane. Given two non-overlapping convex polygons P 1 and P 2 in the plane, the ham

418

Compass & Straight Edge Constructions  

NSDL National Science Digital Library

Use compass & straight edge to do basic constructions. Follow the directions to construct a segment bisector. construct midpoint or segment bisector Now, follow the directions to construct a perpendicular line through a point on a line. Construct a perpendicular line through a point on a line Another perpendicular line to construct is one through a point not on a line. Construct a perpendicular line through a point not on the line Now we\\'ve constructed perpendicular lines, let\\'s construct a parallel line. ...

Silotti, Mrs.

2007-06-12

419

Development of a simple, rapid sandwich enzyme immunoassay for the measurement of serum rat LH.  

PubMed

The present study describes the development and validation of a rapid, sensitive, specific and precise enzyme immunoassay (EIA) sandwich suitable for measuring luteinizing hormone (LH) in rat serum. Ninety-six well polystyrene microtiter plates were coated with 100 microliters (250 ng/ml) of a well-characterized monoclonal antibody (518B7, Roser, UC Davis) generated against bovine LH. A polyclonal antiserum raised in rabbits against ovine FSH (G4-215B, Papkoff) was conjugated to sodium periodate-activated horseradish peroxidase (HRP), and used as the second antibody of the sandwich assay. This anti-ovine FSH antiserum cross-reacted more than 200% with rat LH. Standards (r-LH-RP-3, NIADDK, range 0 pg/well to 2.5 ng/well or 100 microliters) diluted in a 3(N-Morpholino) propane sulfonic acid (MOPS) buffer, or serum, were incubated with the solid phase antibody for 2 hours. Plates were washed and the anti-oFSH:HRP (100 microliters) in MOPS buffer was added and incubated a further 2 hours before a second wash and the addition of the substrate (TMB, 3,3',5,5'-tetramethylbenzidine dihydrochloride and H2O2). The least detectable concentration of LH was 16.1 +/- 1.42 pg/ml. The recovery of known concentrations of LH added to several samples was 93.5 +/- 1.70%. Mean intra-assay and inter-assay coefficients of variation (%) were less than 10% (n = 20). The anti-FSH:HRP showed less than 8.0% cross reactivity with rFSH in this LH EIA system. The correlation coefficient (r) of samples analyzed by EIA in parallel with RIA was r = 0.90 (p < 0.001, n = 26). Results showed levels between 105.21 and 633.87 pg/ml. This new LH EIA sandwich offers a stable, rapid, and improved EIA system for the measurement of serum LH concentrations of this species over previously reported methods. PMID:8870107

Illera, J C; Munro, C J; Silvan, G; BonDurant, R H; Illera, M

1996-06-01

420

A sandwich-designed temperature-gradient incubator for studies of microbial temperature responses.  

PubMed

A temperature-gradient incubator (TGI) is described, which produces a thermal gradient over 34 aluminium modules (15x30x5 cm) intersected by 2-mm layers of partly insulating graphite foil (SigraFlex Universal). The new, sandwich-designed TGI has 30 rows of six replicate sample wells for incubation of 28-ml test tubes. An electric plate heats one end of the TGI, and the other end is cooled by thermoelectric Peltier elements in combination with a liquid cooling system. The TGI is equipped with 24 calibrated Pt-100 temperature sensors and insulated by polyurethane plates. A PC-operated SCADA (Supervisory Control And Data Acquisition) software (Genesis 4.20) is applied for temperature control using three advanced control loops. The precision of the TGI temperature measurements was better than +/-0.12 degrees C, and for a 0-40 degrees C gradient, the temperature at the six replicate sample wells varied less than +/-0.04 degrees C. Temperatures measured in incubated water samples closely matched the TGI temperatures, which showed a linear relationship to the sample row number. During operation for 8 days with a gradient of 0-40 degrees C, the temperature at the cold end was stable within +/-0.02 degrees C, while the temperatures at the middle and the warm end were stable within +/-0.08 degrees C (n=2370). Using the new TGI, it was shown that the fine-scale (1 degrees C) temperature dependence of S(o) oxidation rates in agricultural soil (0-29 degrees C) could be described by the Arrhenius relationship. The apparent activation energy (E(a)) for S(o) oxidation was 79 kJ mol(-1), which corresponded to a temperature coefficient (Q(10)) of 3.1. These data demonstrated that oxidation of S(o) in soil is strongly temperature-dependent. In conclusion, the new TGI allowed a detailed study of microbial temperature responses as it produced a precise, stable, and certifiable temperature gradient by the new and combined use of sandwich-design, thermoelectric cooling, and advanced control loops. The sandwich-design alone reduced the disadvantageous thermal gradient over individual sample wells by 56%. PMID:11777580

Elsgaard, Lars; Jørgensen, Leif Wagner

2002-03-01

421

Sandwich-walled cylindrical shells with lightweight metallic lattice truss cores and carbon fiber-reinforced composite face sheets  

E-print Network

Sandwich-walled cylindrical shells with lightweight metallic lattice truss cores and carbon fiber employing an interlocking fabrication technique for the metallic core. The skins were made of carbon-fiber reinforced composites and co-cured with the metallic truss core. Thereafter, we carried out axial compression

Vaziri, Ashkan

422

Sound transmission loss of foam-filled honeycomb sandwich panels using statistical energy analysis and theoretical and measured dynamic properties  

NASA Astrophysics Data System (ADS)

Comparisons between the experimental and predicted sound transmission loss values obtained from statistical energy analysis are presented for two foam-filled honeycomb sandwich panels. Statistical energy analysis (SEA) is a modeling procedure which uses energy flow relationships for the theoretical estimation of the sound transmission through structures in resonant motion. The accuracy of the prediction of the sound transmission loss using SEA greatly depends on accurate estimates of: (1) the modal density, (2) the internal loss factor, and (3) the coupling loss factor parameters of the structures. A theoretical expression for the modal density of sandwich panels is developed from a sixth-order governing equation. Measured modal density estimates of the two foam-filled honeycomb sandwich panels are obtained by using a three-channel spectral method with a spectral mass correction to allow for the mass loading of the impedance head. The effect of mass loading of the accelerometer is corrected in the estimations of both the total loss factor and radiation loss factor of the sandwich panels.

Zhou, Ran; Crocker, Malcolm J.

2010-03-01

423

The Role of Sandwich In-Service Program in Developing Agricultural Science Teachers in Delta State, Nigeria  

ERIC Educational Resources Information Center

This study examined the role of the sandwich in-service educational program of Delta State University, Abraka in developing agricultural science teachers in the state. Data were collected from 895 agricultural science teachers who completed the program between 1989-2004. However, response to the questionnaire was by 391 in-service agricultural…

Ikeoji, Canice N.; Agwubike, Christian C.; Ideh, Victor

2007-01-01

424

DETECTION OF ESCHERICHIA COLI 0157:H7 THROUGH THE FORMATION OF SANDWICHED COMPLEXES WITH IMMUNOMAGNETIC AND FLUORESCENT BEADS  

Technology Transfer Automated Retrieval System (TEKTRAN)

A new fluorescent sandwich method for the detection of Escherichia coli O157:H7 in ground beef was developed. Immunomagnetic beads (IMB) pre-coated with anti-E. coli O157 antibody were used to capture and concentrate E.coli O157:H7 present in ground beef. Streptavidin-coated fluorescent beads (SFB...

425

Elasticity, shell theory and finite element results for the buckling of long sandwich cylindrical shells under external pressure  

Microsoft Academic Search

The buckling of a sandwich cylindrical shell under uniform external hydrostatic pressure is studied in three ways. The simplifying assumption of a long shell is made (or, equivalently, ‘ring’ assumption), in which the buckling modes are assumed to be two-dimensional, i.e. no axial component of the displacement field, and no axial dependence of the radial and hoop displacement components. All

Jea-Hyeong Han; George A. Kardomateas; George J. Simitses

2004-01-01

426

Shear and Flexural Buckling Modes of a Spherical Sandwich Shell in a Centrosymmetric Temperature Field Inhomogeneous across the Thickness  

Microsoft Academic Search

Problems on buckling modes (BMs) are considered for a spherical sandwich shell with thin isotropic external layers and a transversely soft core of arbitrary thickness in a centrosymmetric temperature field inhomogeneous across the shell thickness. For their statement, the two-dimensional equations of the theory of moderate bending of thin Kirchhoff–Love shells are used for the external layers, with regard for

V. N. Paimushin; V. A. Ivanov; S. A. Lukankin; A. A. Bushkov

2004-01-01

427

Ultrathin proton-conducting sandwich membrane with low methanol permeability based on perfluorosulfonic acid polymer and phosphosilicate  

NASA Astrophysics Data System (ADS)

An ultra-thin, free-standing proton-conductive membrane of Nafion®/Phosphosilicate/Nafion® (NPN) with a sandwich structure has been prepared. The NPN membrane of thickness 960 nm shows extremely low methanol permeability of 1 × 10-8 cm2 s-1, and area specific resistance (ASR) smaller than 0.2 ? cm2.

Li, Haibin; Ai, Minghuan; Jiang, Fengjing; Yu, Lijun; Tu, Hengyong; Yu, Qingchun; Wang, Hong

2011-05-01

428

PAPER www.rsc.org/obc | Organic & Biomolecular Chemistry Ruthenium half-sandwich complexes as protein kinase inhibitors  

E-print Network

PAPER www.rsc.org/obc | Organic & Biomolecular Chemistry Ruthenium half-sandwich complexes being to organize the organic ligands in three-dimensional space. As a proof-of-principle study, we have to a Department of Chemistry, University of Pennsylvania, 231 South 34th Street, Philadelphia, PA, 19104, USA. E

Meggers, Eric

429

Exploratory Investigation of Failure Mechanisms in Transition Regions between Solid Laminates and X-cor(registered tm) Truss Sandwich  

NASA Technical Reports Server (NTRS)

Small sub-component specimens consisting of solid laminates at the ends that transition to X-cor(R) truss sandwich in the center, were tested in a combination of three point bending, uni-axial tension, and combined tension and bending. The failure process in the transition region was documented for each loading using digital video and high-resolution cameras. For the 3-point bending tests, most of the deformation occurred in the solid laminate regions on either end of the specimen. Some pin debonding from the skin of the X-cor(R) truss sandwich was observed in the transition region and was accompanied by audible "pings" throughout the loading. Tension loaded specimens failed in the sandwich skin in the middle of the gage length, accompanied by separation of the sandwich core from the back skin and by delamination between the top skin and bottom skin at the transition region. The pinging associated with pin debonding occurred as the load was increased. However, the frequency of the pinging exceeded any visual observations of pin debonding in the video of the transition region. For specimens tested in combined tension and bending, the greatest amount of pinging occurred during initial application of the axial load. High-resolution images in the transition region indicated that the pinging corresponded to pins debonding and buckling due to the through-thickness Poisson contraction of the specimen. This buckling continued to a much smaller extent as the transverse load was applied.

OBrien, T. Kevin; Paris, Isabelle L.

2004-01-01

430

Multi-objective optimization of laser-welded steel sandwich panels for static loads using a genetic algorithm  

E-print Network

Finite element analysis Genetic algorithms Evolutionary optimization a b s t r a c t We present for multiple, conflicting objectives using an integer-coded non-dominated sorting genetic algorithmMulti-objective optimization of laser-welded steel sandwich panels for static loads using a genetic

Vel, Senthil

431

Sandwich nanohybrid of single-walled carbon nanohorns-TiO2-porphyrin for electrocatalysis and amperometric biosensing towards chloramphenicol.  

PubMed

A sandwich nanohybrid of single-walled carbon nanohorn-TiO2-porphyrin was prepared via the dentate binding of TiO2 nanoparticles to carboxylate groups, which showed an excellent electrocatalytic activity towards the reduction of chloramphenicol in neutral media, leading to a highly sensitive and stable amperometric biosensor for chloramphenicol. PMID:19585029

Tu, Wenwen; Lei, Jianping; Ding, Lin; Ju, Huangxian

2009-07-28

432

The Journey of a Sandwich: Computer-Based Laboratory Experiments about the Human Digestive System in High School Biology Teaching  

ERIC Educational Resources Information Center

Teaching high school students about the digestive system can be a challenge for a teacher when s/he wants to overcome rote learning of facts without a deeper understanding of the physiological processes inside the alimentary tract. A series of model experiments illustrating the journey of a sandwich was introduced into teaching high school…

Sorgo, Andrej; Hajdinjak, Zdravka; Briski, Darko

2008-01-01

433

Damage Evolution in Composite Materials and Sandwich Structures Under Impulse Loading  

NASA Astrophysics Data System (ADS)

Damage evolution in composite materials is a rather complex phenomenon. There are numerous failure modes in composite materials stemming from the interaction of the various constituent materials and the particular loading conditions. This thesis is concerned with investigating damage evolution in sandwich structures under repeated transient loading conditions associated with impulse loading due to hull slamming of high-speed marine craft. To fully understand the complex stress interactions, a full field technique to reveal stress or strain is required. Several full field techniques exist but are limited to materials with particular optical properties. A full field technique applicable to most materials is known as thermoelastic stress analysis (TSA) and reveals the variation in sum of principal stresses of a cyclically loaded sample by correlating the stresses to a small temperature change occurring at the loading frequency. Digital image correlation (DIC) is another noncontact full field technique that reveals the deformation field by tracking the motion of subsets of a random speckle pattern during the loading cycles. A novel experimental technique to aid in the study of damage progression that combines TSA and DIC simultaneously utilizing a single infrared camera is presented in this thesis. A technique to reliably perform DIC with an infrared (IR) camera is developed utilizing variable emissivity paint. The thermal data can then be corrected for rigid-body motion and deformation such that each pixel represents the same material point in all frames. TSA is then performed on this corrected data, reducing motion blur and increasing accuracy. This combined method with a single infrared camera has several advantages, including a straightforward experimental setup without the need to correct for geometric effects of two spatially separate cameras. Additionally, there is no need for external lighting in TSA as the measured electromagnetic radiation is emitted by the sample's thermal fields. The particular stress resolution of TSA will depend on properties of the material of interest but the noise floor for the temperature variation is universal to the camera utilized. For the camera system in this thesis, the noise floor was found to be fairly frequency independent with a magnitude of 0.01 °C, giving the minimum measurable stress for 2024 aluminum alloy of 3.6 MPa and for Nylon of 0.84 MPa. The average displacement range found during a static DIC test with IR images was 0.1 pixels. The maximum displacement variation at 1 Hz was 0.018 pixels. The average variation in strain at 1 Hz was 25 microstrain comparable to traditional DIC measurements in the visible optical regime. The combined TSA-DIC method in IR was validated with several benchmark example problems including plate structures with holes, cracks, and bimaterials. The validated technique was applied to foam-core sandwich composite beams under repeated simulated wave slamming loading. There are numerous failure modes in sandwich composite materials and the full field stress and strain from TSA and DIC, respectively, allow for improved failure analysis and prediction. Understanding damage in sandwich structures under impulse loading is a complex open area of research and the combined TSA-DIC method provides further insight into the failure process.

Silva, Michael Lee

434

Theoretical reflective performance of a sandwiched two-layer grating polarizer  

NASA Astrophysics Data System (ADS)

The reflective polarizer is described by a sandwiched two-layer grating with a metal slab. Such a new polarizer is aimed to improve the performance of a reflective grating-based polarizer. The grating is optimized with the usual duty cycle of 0.5, where TE and TM polarizations are reflected in the -1st and the 0th diffraction orders, respectively. With optimized grating parameters, the extinction ratio can reach 45.5 dB and 41.9 dB in two diffraction orders, which are greatly improved compared with the conventional reported surface grating polarizer with the simple structure. Attractive merits of the new design are high efficiency, high extinction ratio, wide incident wavelength bandwidth for TE polarization, and wide angular range for TM polarization. Numerical results are expected to open new opportunities for the design of a grating-based polarizer with the enhanced performance by the complicated grating configuration.

Wang, Bo; Shu, Wenhao; Chen, Li; Lei, Liang; Zhou, Jinyun

2014-11-01

435

Large magnetoresistance at room-temperature in small-molecular-weight organic semiconductor sandwich devices  

NASA Astrophysics Data System (ADS)

We present an extensive study of a large, room temperature magnetoresistance (MR) effect in tris-(8-hydroxyquinoline) aluminum sandwich devices. The effect is similar to that previously discovered in ?-conjugated polymer devices. We characterize this effect and discuss its dependence on magnetic field direction, voltage, temperature, film thickness, and electrode materials. The MR effect reaches almost 10% at fields of 10 mT at room temperature. The effect shows only a weak temperature dependence and is independent of the sign and direction of the magnetic field. Measuring the devices' current-voltage characteristics, we find that the current depends on the voltage through a power-law. We find that the magnetic field changes the prefactor of the power-law. We also studied the effect of the magnetic field on the electroluminescence (MEL) of the devices and analyze the relationship between MR and MEL.

Mermer, Ö.; Veeraraghavan, G.; Francis, T. L.; Wohlgenannt, M.

2005-06-01

436

Theoretical prediction of the damping of a railway wheel with sandwich-type dampers  

NASA Astrophysics Data System (ADS)

This paper presents a procedure for predicting the damping added to a railway wheel when sandwich-type dampers are installed. Although there are different ways to reduce the noise generated by a railway wheel, most devices are based on the mechanism of increasing wheel damping. This is why modal damping ratios are a clear indicator of the efficiency of the damping device and essential when a vibro-acoustic study of a railway wheel is carried out. Based on a number of output variables extracted from the wheel and damper models, the strategy explained herein provides the final damping ratios of the damped wheel. Several different configurations are designed and experimentally tested. Theoretical and experimental results agree adequately, and it is demonstrated that this procedure is a good tool for qualitative comparison between different solutions in the design stages.

Merideno, Inaki; Nieto, Javier; Gil-Negrete, Nere; Giménez Ortiz, José Germán; Landaberea, Aitor; Iartza, Jon

2014-09-01

437

Generation of very high pressure pulses at the surface of a sandwiched piezoelectric material.  

PubMed

New clinical concepts in lithotripsy demand small shock heads. Reducing the size of piezoelectric shock heads will only be possible if the pressure generated at the surface of each transducer can be increased so that the total pressure at the focus remains very high. We propose for the first time to increase the pressure without increasing the transducer voltage by using sandwiched transducers, which are a combination of several stacked transducers. When excited at appropriate time intervals, the pressure waves generated by each one reinforce when they reach the load. This new technique has been successfully tested. A pressure of 2.5 MPa was generated with two stacked, 5 mm-thick 1-3 piezocomposite transducers operating at an excitation voltage of 8 kV. No transducer damage was detected after 10(6) shocks, which corresponds approximately to the treatment of 500 patients. PMID:11106008

Sferruzza, J P; Birer, A; Cathignol, D

2000-11-01

438

Nanoscale quantification of charge injection and transportation process in Si-nanocrystal based sandwiched structure.  

PubMed

Si nanocrystals are formed by using KrF pulsed laser crystallization of an amorphous SiC/ultrathin amorphous Si/amorphous SiC sandwiched structure. Electrons and holes are injected into Si nanocrystals via a biased conductive AFM tip and the carrier decay and transportation behaviours at the nanoscale are studied by joint characterization techniques of Kelvin probe force microscopy (KPFM) and conductive atomic force microscopy (CAFM). Quantification of the surface charge density is realized by solving the Poisson equation based on KPFM measurements. Besides, the asymmetric barrier height for electrons and holes is considered to play a dominant role in controlling the charge retention and transportation characteristics. The methodology developed in this work is promising for studying the charge injection and transportation process in other materials and structures at the nanoscale. PMID:23989206

Xu, Jie; Xu, Jun; Zhang, Pengzhan; Li, Wei; Chen, Kunji

2013-10-21

439

RBFOX and SUP-12 sandwich a G base to cooperatively regulate tissue-specific splicing.  

PubMed

Tissue-specific alternative pre-mRNA splicing is often cooperatively regulated by multiple splicing factors, but the structural basis of cooperative RNA recognition is poorly understood. In Caenorhabditis elegans, ligand binding specificity of fibroblast growth factor receptors (FGFRs) is determined by mutually exclusive alternative splicing of the sole FGFR gene, egl-15. Here we determined the solution structure of a ternary complex of the RNA-recognition motif (RRM) domains from the RBFOX protein ASD-1, SUP-12 and their target RNA from egl-15. The two RRM domains cooperatively interact with the RNA by sandwiching a G base to form the stable complex. Multichromatic fluorescence splicing reporters confirmed the requirement of the G and the juxtaposition of the respective cis elements for effective splicing regulation in vivo. Moreover, we identified a new target for the heterologous complex through an element search, confirming the functional significance of the intermolecular coordination. PMID:25132178

Kuwasako, Kanako; Takahashi, Mari; Unzai, Satoru; Tsuda, Kengo; Yoshikawa, Seiko; He, Fahu; Kobayashi, Naohiro; Güntert, Peter; Shirouzu, Mikako; Ito, Takuhiro; Tanaka, Akiko; Yokoyama, Shigeyuki; Hagiwara, Masatoshi; Kuroyanagi, Hidehito; Muto, Yutaka

2014-09-01

440

Thermal stability tests of CFRP sandwich panels for far infrared astronomy  

NASA Technical Reports Server (NTRS)

An account is given of fabrication methods and low temperature figure tests for CFRP sandwich panels, in order to ascertain their applicability to ultralightweight 3-m aperture primary mirrors for balloon-borne sub-mm and far-IF telescopes that must maintain a 1-2 micron rms surface figure accuracy at -40 to -50 C. Optical figure measurements on the first two of a series of four 0.5-m test panels, replicated to a spherical surface, show a radius-of-curvature change and astigmatism down to -60 C; this approximately follows the composite's theoretical predictions and implies that material and process control is excellent, so that the large scale changes observed can be compensated for.

Hoffmann, W. F.; Helwig, G.; Scheulen, D.

1986-01-01

441

Preliminary weight and costs of sandwich panels to distribute concentrated loads  

NASA Technical Reports Server (NTRS)

Minimum mass honeycomb sandwich panels were sized for transmitting a concentrated load to a uniform reaction through various distances. The form skin gages were fully stressed with a finite element computer code. The panel general stability was evaluated with a buckling computer code labeled STAGS-B. Two skin materials were considered; aluminum and graphite-epoxy. The core was constant thickness aluminum honeycomb. Various panel sizes and load levels were considered. The computer generated data were generalized to allow preliminary least mass panel designs for a wide range of panel sizes and load intensities. An assessment of panel fabrication cost was also conducted. Various comparisons between panel mass, panel size, panel loading, and panel cost are presented in both tabular and graphical form.

Belleman, G.; Mccarty, J. E.

1976-01-01

442

Development of beryllium honeycomb sandwich composite for structural and other related applications  

NASA Technical Reports Server (NTRS)

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 honeycomb panels show decided potential where rigid, lightweight structures are required. Three panels, each 10 square feet in surface area, were fabricated, and radiographically inspected to determine integrity. This examination revealed a 97 percent braze in the final panel. It is believed that ceramic dies for forming and brazing would facilitate the fabrication techniques for higher production rates. Ceramic dies would yield a lower thermal gradient in the panel during the braze cycle. This would eliminate the small amount of face sheet wrinkling present in the panels. Hot forming the various panel components demonstrated efficient manufacturing techniques for scaling up and producing large numbers of hot formed beryllium components and panels. The beryllium honeycomb panel demonstrated very good vibrational loading characteristics under test with desirable damping characteristics.

Vogan, J. W.; Grant, L. A.

1972-01-01

443

Thermodynamic stability and electron structure of polymeric sandwich complexes of porphyrins with different metals  

NASA Astrophysics Data System (ADS)

The thermodynamic stability of different conformers of the polymeric sandwich structures of metalloporphyrins (MeP) is studied by means of quantum chemistry. The possibility of forming stable layered BaP, SrP, ScP, YP, and ZrP structures with shielded and retarded conformation is demonstrated. Shielded conformers are preferable in the case of SrP, BaP, and ScP complexes, while retarded conformers are most advantageous for YP and ZrP complexes. Based on the results from calculating the electron structure of the investigated compounds, we find that SrP and BaP are semiconductors and ScP, YP, and ZrP are electrical conductors

Kuzubov, A. A.; Krasnov, P. O.; Ignatova, N. Yu.; Fedorov, A. S.; Tomilin, F. N.

2012-10-01

444

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

NASA Technical Reports Server (NTRS)

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 impact-energy levels at which damage initiates and at which barely visible impact damage occurs in the impacted facesheet are discussed. Parametric effects studied in these tests include the impactor diameter, dropped-weight versus airgun-launched impactors, and the effect of the location of the impact site with respect to the panel boundaries. Residual strength results of panels tested in compression after impact are presented and compared with results of panels that are subjected to a compressive preload prior to being impacted.

McGowan, David M.; Ambur, Damodar R.

1998-01-01

445

Fabrication and development of several heat pipe honeycomb sandwich panel concepts  

NASA Astrophysics Data System (ADS)

The feasibility of fabricating and processing liquid metal heat pipes in a low mass honeycomb sandwich panel configuration for application on the NASA Langley airframe-integrated Scramjet engine was investigated. A variety of honeycomb panel facesheet and core-ribbon wick concepts was evaluated within constraints dictated by existing manufacturing technology and equipment. The chosen design consists of an all-stainless steel structure, sintered screen facesheets, and two types of core-ribbon; a diffusion bonded wire mesh and a foil-screen composite. Cleaning, fluid charging, processing, and process port sealing techniques were established. The liquid metals potassium, sodium and cesium were used as working fluids. Eleven honeycomb panels 15.24 cm X 15.24 cm X 2.94 cm were delivered to NASA Langley for extensive performance testing and evaluation; nine panels were processed as heat pipes, and two panels were left unprocessed.

Tanzer, H. J.

1982-06-01

446

Self-healing of sandwich structures with a grid stiffened shape memory polymer syntactic foam core  

NASA Astrophysics Data System (ADS)

In this paper, a new sandwich with an orthogrid stiffened shape memory polymer (SMP) based syntactic foam core was proposed, fabricated, programmed, impacted, healed (sealed), and compression tested, for the purposes of healing impact damage repeatedly and almost autonomously. Two prestrain levels (3% and 20%), two impact energy levels (30.0 and 53.3 J), and two recovery (healing) conditions (2D confined and 3D confined) were employed in this paper. Up to seven impact-healing cycles were conducted. Macroscopic and microscopic damage-healing observation and analysis were implemented. Residual strength was evaluated using an anti-buckling compression test fixture. It was found that the healing efficiency was over 100% for almost all the impact-healing cycles; programming using 20% prestrain led to higher residual strength than that with 3% prestrain; 3D confined recovery resulted in higher residual strength than 2D confined recovery; and as the impact energy increased, the healing efficiency slightly decreased.

John, Manu; Li, Guoqiang

2010-07-01

447

An efficient finite element with layerwise mechanics for smart piezoelectric composite and sandwich shallow shells  

NASA Astrophysics Data System (ADS)

In this work, we present a new efficient four-node finite element for shallow multilayered piezoelectric shells, considering layerwise mechanics and electromechanical coupling. The laminate mechanics is based on the zigzag theory that has only seven kinematic degrees of freedom per node. The normal deformation of the piezoelectric layers under the electric field is accounted for without introducing any additional deflection variables. A consistent quadratic variation of the electric potential across the piezoelectric layers with the provision of satisfying the equipotential condition of electroded surfaces is adopted. The performance of the new element is demonstrated for the static response under mechanical and electric potential loads, and for free vibration response of smart shells under different boundary conditions. The predictions are found to be very close to the three dimensional piezoelasticity solutions for hybrid shells made of not only single-material composite substrates, but also sandwich substrates with a soft core for which the equivalent single layer (ESL) theories perform very badly.

Yasin, M. Yaqoob; Kapuria, S.

2014-01-01

448

Double-antibody sandwich enzyme-linked immunosorbent assay for cellobiohydrolase I  

SciTech Connect

A double-antibody sandwich enzyme-linked immunosorbent assay was developed for quantifying cellobiohydrolase I (CBH I) in crude preparations of the cellulase complex from Trichoderma reesei. The other enzymes (endoglucanase and {beta}-glucosidase) in this complex and other ingredients in culture broth did not interfere with this assay. The antibody configuration that resulted in the highest specificity for the assay of CBH I employed a monoclonal antibody to coat wells in polystyrene plates and peroxidase-labeled polyclonal antibody to detect cellobiohydrolase bound to the immobilized monoclonal antibody. Previously, procedures have not been available for the direct assay of CBH I activity in the presence of the other enzymes in the complex, and current indirect procedures are cumbersome and inaccurate. The direct procedure described here is highly specific for CBH I and useful for quantifying this enzyme in the range of 0.1 to 0.8 {mu}g/ml.

Riske, F.J.; Eveleigh, D.E.; MacMillan, J.D. (Rutgers Univ., New Brunswick, NJ (USA))

1990-11-01

449

LSPR biomolecular assay with high sensitivity induced by aptamer-antigen-antibody sandwich complex.  

PubMed

Herein we demonstrate a sensitive approach for protein detection based on peak shifts of localized surface plasmon resonance (LSPR) induced by aptamer-antigen-antibody sandwich structures. The applicability of the proposed method is demonstrated using human ?-thrombin as a model analyte. While the binding of thrombin to its specific receptor, thrombin binding aptamer (TBA) modified on Au nanorods (AuNRs), causes a measurable LSPR shift, a subsequent binding of an anti-thrombin antibody to the captured thrombin can exhibit a nearly 150% amplification in the LSPR response. This enhanced signal essentially leads to an improvement of limit of detection (LOD) by more than one order of magnitude. In addition, the use of TBA as thrombin recognition units makes the biosensor reusable. The feasibility of the proposed method was further exploited by the detection of thrombin in human serum, opening the possibility of a real application for diagnostics and medical investigations. PMID:22099957

Guo, Longhua; Kim, Dong-Hwan

2012-01-15

450

The sandwich cartilage shoe technique for ossicular reconstruction in a case of an unsecure stapes footplate.  

PubMed

This article describes a new surgical method for total ossicular reconstruction in a case of a broken stapes footplate. We developed the technique of the "cartilage shoe sandwich," which consists of two surgical steps. First, the closure of the oval window is achieved by a cartilage shoe without a central perforation. During this surgical intervention, the prearrangement of a secure placement of a total ossicular replacement prosthesis is provided by a second cartilage with a central hole that is plugged with silicone. In a staged procedure, the silicone plug is removed and the ossicular reconstruction can be performed. The audiological results of the first patients show a stable inner ear function with an air-conduction gain of 9 dB. The technique described herein has proven to be safe and reliable in total ossicular reconstruction in the event of an unsecure stapes footplate. PMID:22024850

Bremke, Martin; Hüttenbrink, Karl-Bernd; Beutner, Dirk

2011-09-01

451

WORM ALGORITHM PATH INTEGRAL MONTE CARLO APPLIED TO THE 3He-4He II SANDWICH SYSTEM  

NASA Astrophysics Data System (ADS)

We present a numerical investigation of the thermal and structural properties of the 3He-4He sandwich system adsorbed on a graphite substrate using the worm algorithm path integral Monte Carlo (WAPIMC) method [M. Boninsegni, N. Prokof'ev and B. Svistunov, Phys. Rev. E74, 036701 (2006)]. For this purpose, we have modified a previously written WAPIMC code originally adapted for 4He on graphite, by including the second 3He-component. To describe the fermions, a temperature-dependent statistical potential has been used. This has proven very effective. The WAPIMC calculations have been conducted in the millikelvin temperature regime. However, because of the heavy computations involved, only 30, 40 and 50 mK have been considered for the time being. The pair correlations, Matsubara Green's function, structure factor, and density profiles have been explored at these temperatures.

Al-Oqali, Amer; Sakhel, Asaad R.; Ghassib, Humam B.; Sakhel, Roger R.

2012-12-01

452

The conformal method and the conformal thin-sandwich method are the same  

NASA Astrophysics Data System (ADS)

The conformal method developed in the 1970s and the more recent Lagrangian and Hamiltonian conformal thin-sandwich methods are techniques for finding solutions of the Einstein constraint equations. We show that they are manifestations of a single conformal method: there is a straightforward way to convert back and forth between the parameters for these methods so that the corresponding solutions of the Einstein constraint equations agree. The unifying idea is the need to clearly distinguish tangent and cotangent vectors to the space of conformal classes on a manifold, and we introduce a vocabulary for working with these objects without reference to a particular representative background metric. As a consequence of these conceptual advantages, we demonstrate how to strengthen previous near-CMC (constant mean curvature) existence and non-existence theorems for the original conformal method to include metrics with scalar curvatures that change sign.

Maxwell, David

2014-07-01

453

Fabrication method for cores of structural sandwich materials including star shaped core cells  

DOEpatents

A method for fabricating structural sandwich materials having a core pattern which utilizes star and non-star shaped cells is disclosed. The sheets of material are bonded together or a single folded sheet is used, and bonded or welded at specific locations, into a flat configuration, and are then mechanically pulled or expanded normal to the plane of the sheets which expand to form the cells. This method can be utilized to fabricate other geometric cell arrangements than the star/non-star shaped cells. Four sheets of material (either a pair of bonded sheets or a single folded sheet) are bonded so as to define an area therebetween, which forms the star shaped cell when expanded. 3 figs.

Christensen, R.M.

1997-07-15

454

Fabrication method for cores of structural sandwich materials including star shaped core cells  

DOEpatents

A method for fabricating structural sandwich materials having a core pattern which utilizes star and non-star shaped cells. The sheets of material are bonded together or a single folded sheet is used, and bonded or welded at specific locations, into a flat configuration, and are then mechanically pulled or expanded normal to the plane of the sheets which expand to form the cells. This method can be utilized to fabricate other geometric cell arrangements than the star/non-star shaped cells. Four sheets of material (either a pair of bonded sheets or a single folded sheet) are bonded so as to define an area therebetween, which forms the star shaped cell when expanded.

Christensen, Richard M. (Danville, CA)

1997-01-01

455

Sandwich structure of Pd doped nanostructure TiO2 film as O2 sensor.  

PubMed

In this paper, we investigated the sensing properties of sandwich structure of TiO2/Pd/TiO2 thin films at various operating temperatures and oxygen partial pressures. The nanostructure TiO2 thin films were prepared by the sol-gel method. Various thickness of Pd buried layer was deposited by magnetron sputtering of a pure Pd target. The films were characterized using X-ray diffraction analysis and SEM. It was found that TiO2/Pd/TiO2 thin films have the p-type behavior while the pure TiO2 thin film is n-type semiconductor materials. We found that the structure of TiO2/Pd/TiO2 thin films with 10 s sputtering Pd layer has a better stability at 240 °C. PMID:24089853

Wang, Hairong; Sun, Quantao; Chen, Lei; Zhao, Yulong

2013-09-01

456

Mechanical properties and optical testing of metal honeycomb sandwich panel in MTPS  

NASA Astrophysics Data System (ADS)

Mechanical tests of a Co-based superalloy honeycomb thermal protection system (TPS) panel are finished at room temperature. The lateral tensile limit strength is higher than 59MPa and nearly four multiples of the flatwise compressive strength. Also the modulus in lateral tests are nearly two multiples of the ones under compressive loads. Because of many advantages in application, two optical non-contact methods are introduced in this work to solve different problems of honeycomb sandwich panels. Longitudinal strain of lateral tensile specimens is obtained by digital speckle correlation method (DSCM) and the results of different sub-pixel methods are constrasted. Then the equivalent elastic modulus is calculated further. Electronic speckle shearography pattern interferometry (ESSPI) is presented to obtain the nondestructive results of debonding defects between honeycomb cores and face sheets. Also the size and approximate location are decided real-time. All the results show the two introduced methods are feasible.

Lu, Jie; Zou, Guang ping; Liang, Jun

2008-11-01

457

A sandwiched microarray platform for benchtop cell-based high throughput screening  

PubMed Central

The emergence of combinatorial chemistries and the increased discovery of natural compounds have led to the production of expansive libraries of drug candidates and vast numbers of compounds with potentially interesting biological activities. Despite broad interest in high throughput screening (HTS) across varied fields of biological research, there has not been an increase in accessible HTS technologies. Here, we present a simple microarray sandwich system suitable for screening chemical libraries in cell-based assays at the benchtop. The microarray platform delivers chemical compounds to isolated cell cultures by ‘sandwiching’ chemical-laden arrayed posts with cell-seeded microwells. In this way, an array of sealed cell-based assays was generated without cross-contamination between neighboring assays. After chemical exposure, cell viability was analyzed by fluorescence detection of cell viability indicator assays on a per microwell basis in a standard microarray scanner. We demonstrate the efficacy of the system by generating four hits from toxicology screens towards MCF-7 human breast cancer cells. Three of the hits were identified in a combinatorial screen of a library of natural compounds in combination with verapamil, a P-glycoprotein inhibitor. A fourth hit, 9-methoxy-camptothecin, was identified by screening the natural compound library in the absence of verapamil. The method developed here miniaturizes existing HTS systems and enables the screening of a wide array of individual or combinatorial libraries in a reproducible and scalable manner. We anticipate broad application of such a system as it is amenable to combinatorial drug screening in a simple, robust and portable platform. PMID:20965560

Wu, Jinhui; Wheeldon, Ian; Guo, Yuqi; Lu, Tingli; Du, Yanan; Wang, Ben; He, Jiankang; Hu, Yiqiao; Khademhosseini, Ali

2010-01-01

458

Controlled release of metformin hydrochloride and repaglinide from sandwiched osmotic pump tablet.  

PubMed

The marketed compound tablet of metformin hydrochloride (MH) and repaglinide (RG) exhibits perfect multidrug therapeutic effect of type 2 diabetes. However, due to the short half life of the drugs, the tablet has to be administered 2 to 3 times a day, causing inconvenience to patient and fluctuations of plasma concentration. Here, a sandwiched osmotic pump tablet was developed to deliver the two drugs simultaneously at zero-order rate, in which MH and RG were loaded in different layers separated by a push layer. The osmotic pump tablet was prepared by a combination of three tableting procedure and film coating method. The factors including type and amount of propellant, osmotic active agents, amount of porogenic agent, coating weight, orifice diameter were optimized. The pharmacokinetic study was performed in beagle dogs, and the drug concentration in plasma samples was assayed by HPLC-MS/MS method. Simultaneous, controlled release of MH and RG in the first 12 and 8h was achieved from the optimized formulation. A significantly decreased Cmax, prolonged Tmax and satisfactory bioavailability of the osmotic pump tablet were obtained, and a good in vivo-in vitro correlation of the two drugs was also established. In summary, the sandwiched osmotic pump tablet released the MH and RG simultaneously at zero-order rate, and exhibited significant sustained release effect in vivo and good in vivo-in vitro correlation. The designed controlled release system for MH and RG proposed a promising replacement for the marked compound product in the therapy of type 2 diabetes. PMID:24607209

Qin, Chao; He, Wei; Zhu, Chunli; Wu, Mengmeng; Jin, Zhu; Zhang, Qiang; Wang, Guangji; Yin, Lifang

2014-05-15

459

A Sandwich Electrochemical Immunosensor Using Magnetic DNA Nanoprobes for Carcinoembryonic Antigen  

PubMed Central

A novel magnetic nanoparticle-based electrochemical immunoassay of carcinoembryonic antigen (CEA) was designed as a model using CEA antibody-functionalized magnetic beads [DNA/Fe3O4/ZrO2; Fe3O4 (core)/ZrO2 (shell) nano particles (ZMPs)] as immunosensing probes. To design the immunoassay, the CEA antibody and O-phenylenediamine (OPD) were initially immobilized on a chitosan/nano gold composite membrane on a glassy carbon electrode (GCE/CS-nano Au), which was used for CEA recognition. Then, horseradish peroxidase (HRP)-labeled anti-CEA antibodies (HRP-CEA Ab2) were bound to the surface of the synthesiz