Science.gov

Sample records for sandwich construction

  1. Sandwich construction

    NASA Astrophysics Data System (ADS)

    Marshall, A.

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

  2. Standard test method for edgewise compressive strength of flat sandwich constructions

    SciTech Connect

    Not Available

    1980-01-01

    This method covers determination of the compressive properties of flat structural sandwich constructions in a direction parallel to the plane of the sheet of sandwich. Significance of the edgewise compressive strength of flat sandwich constructions, apparatus, dimensions, number and preparation of specimens, conditioning, procedure and reporting are discussed.

  3. Damage Tolerance of Resin Transfer Molded Composite Sandwich Constructions

    DTIC Science & Technology

    1999-05-01

    cost manufacturing techniques to produce panels included; resin transfer molding ( RTM ), vacuum assisted resin infusion/transfer molding ( VARTM ), co...analysis conducted revealed that in terms of failure characteristics, the RTM / VARTM processed sandwich composites yielded similar performance as those...injection VARTM and vacuum assisted compression molding (VACM). Detailed experimental impact studies were performed under three scenarios low velocity

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

    SciTech Connect

    Keeton, J.R.

    1980-03-01

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

  5. A nano-sandwich construct built with graphene nanosheets and carbon nanotubes enhances mechanical properties of hydroxyapatite–polyetheretherketone scaffolds

    PubMed Central

    Feng, Pei; Peng, Shuping; Wu, Ping; Gao, Chengde; Huang, Wei; Deng, Youwen; Xiao, Tao; Shuai, Cijun

    2016-01-01

    A nano-sandwich construct was built by combining two-dimensional graphene nanosheets (GNSs) and one-dimensional carbon nanotubes (CNTs) to improve the mechanical properties of hydroxyapatite–polyetheretherketone (HAP–PEEK) scaffolds for bone tissue engineering. In this nano-sandwich construct, the long tubular CNTs penetrated the interlayers of graphene and prevented their aggregation, increasing the effective contact area between the construct and matrix. The combination of GNSs and CNTs in a weight ratio of 2:8 facilitated the dispersion of each other and provided a synergetic effect in enhancing the mechanical properties. The compressive strength and modulus of the scaffolds were increased by 63.58% and 56.54% at this time compared with those of HAP–PEEK scaffolds, respectively. The carbon-based fillers, pulling out and bridging, were also clearly observed in the matrix. Moreover, the dangling of CNTs and their entangling with GNSs further reinforced the mechanical properties. Furthermore, apatite layer formed on the scaffold surface after immersing in simulated body fluid, and the cells attached and spread well on the surface of the scaffolds and displayed good viability, proliferation, and differentiation. These evidence indicate that the HAP–PEEK scaffolds enhanced by GNSs and CNTs are a promising alternative for bone tissue engineering. PMID:27555770

  6. Direct construction of an open-sandwich enzyme immunoassay for one-step noncompetitive detection of thyroid hormone T4.

    PubMed

    Islam, Kamrun Nahar; Ihara, Masaki; Dong, Jinhua; Kasagi, Noriyuki; Mori, Toshihiro; Ueda, Hiroshi

    2011-02-01

    To establish a sensitive noncompetitive immunoassay for thyroxine (T4), we attempted to isolate anti-T4 antibodies from a phage display library based on a phagemid pDong1 ( Dong et al. Anal. Biochem.2009, 36, 386 ), which was designed to enable open-sandwich enzyme-linked immunosorbent assay (OS-ELISA) after selection on immobilized antigen. After the Fab-displaying phage library made from the splenocytes of T4-KLH immunized mice was subjected to biopanning on T4-BSA, two T4-specific clones were obtained. When they were assayed by indirect competitive ELISA, both clones showed low IC(50) (5-13 ng/mL), indicating their high affinity to T4. When they were used for OS-ELISA that detects antigen-dependency of the interaction between variable domains V(H) and V(L), a clone successfully detected 1 ng/mL of T4 with a working range superior to that of competitive IA. OS-ELISA was also performed with maltose binding protein (MBP)-fused V(H)/V(L) of this clone, which showed a detection limit less than 0.1 ng/mL T4. Moreover, the assay showed cross-reactivity with T3 similar to that of competitive ELISA, and also gave a reasonable total serum T4 concentration (90 ng/mL) from ethanol-extracted sample serum using the recombinant proteins. This is the first direct construction of an OS-ELISA system bypassing hybridoma, which will be applicable to the detection of many other small molecule antigens.

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

    PubMed

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

    2012-09-03

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

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

    PubMed

    Wang, Xiaohong; Sui, Shaochun

    2011-06-01

    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 β1, 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.

  9. Three-dimensional tin dioxide/carbon composite constructed by hollow nanospheres with quasi-sandwich structures as improved anode materials for lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Tian, Qinghua; Tian, Yang; Zhang, Zhengxi; Yang, Li; Hirano, Shin-ichi

    2016-02-01

    Tin dioxide (SnO2)-based materials have been considered to be promisingly alternative advanced anode materials for lithium-ion batteries and thus attracted wide attention. So far, the research focus of SnO2-based anode materials is to search and develop effective strategies for overcoming the obstacles, such as rapid capacity fading and poor rate capability, which seriously impede the practical application of SnO2-based electrodes. Herein, we have successfully combined nanoscale SnO2 with 3-dimensional carbon (C) conductivity framework to form a 3-dimensional unparalleled SnO2/C composite constructed by closely interconnected hollow nanospheres with quasi-sandwich structures. When evaluated as anode materials for lithium-ion batteries, the as-prepared SnO2/C composite exhibits improved cycling performance and high rate capability, delivering a high capacity of 576.6 mAh g-1 at 200 mA g-1 even after 500 cycles, and a capacity of 411.7 mAh g-1 even at 5 A g-1 during rate test. The unparalleled 3-dimensional architecture should be responsible for the good electrochemical performance.

  10. Simulation of Prestressed Concrete Sandwich Panels Subjected to Blast Loads (Preprint)

    DTIC Science & Technology

    2010-02-01

    insulated concrete sandwich wall panels through ultimate capacity. The experimental program used for model development and validation involved...This paper discusses simulation methodology used to analyze static and dynamic behavior of foam insulated concrete sandwich wall panels through... wall construction, the sandwich panel, is comprised of two concrete wythes separated by a layer of foam insulation. The concrete wythes can be

  11. THE SANDWICH CONJECTURE,

    DTIC Science & Technology

    The ’Sandwich Conjecture’ (SC) was originally formulated by Wheeler and his coworkers. In the course of several years both the original author(s...If the SC were to hold, one would hope that the metric field can be quantized by Feynman integral methods. Quite apart from its bearing on

  12. Salads, Sandwiches and Desserts.

    ERIC Educational Resources Information Center

    Marine Corps Inst., Washington, DC.

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

  13. "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

    Emerson, Lisa; Mansvelt, Juliana

    2014-01-01

    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 study…

  14. Structural Analysis of Sandwich Foam Panels

    SciTech Connect

    Kosny, Jan; Huo, X. Sharon

    2010-04-01

    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.

  15. Terahertz radiation from Josephson sandwiches

    NASA Astrophysics Data System (ADS)

    Malishevskii, A. S.; Silin, V. P.; Uryupin, S. A.; Uspenskii, S. G.

    2010-08-01

    Basic results are presented from a study of the Cerenkov emission of electromagnetic waves by solitary vortices and Swihart waves moving in a long Josephson sandwich embedded in a dielectric. The energy fluxes of the electromagnetic field along a long sandwich are examined. The magnitudes of the fluxes are compared over a wide range of frequencies and wave numbers of surface waves in the sandwich.

  16. Facesheet Delamination of Composite Sandwich Materials at Cryogenic Temperatures

    NASA Technical Reports Server (NTRS)

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

    2003-01-01

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

  17. On the dynamic stability of multilayer sandwich plates

    NASA Technical Reports Server (NTRS)

    Salama, A. M.; Chen, J. C.

    1973-01-01

    Study of the dynamic stability of plates which are constructed of several alternating soft and hard layers and are subjected to time-dependent periodic in-plane loads. A theory that accounts for all of these effects is presented for multilayer sandwich plates. The plate thickness consists of (k - 1) orthotropic soft core layers sandwiched between k hard isotropic membrane layers, each of which may have a different thickness and elastic properties. It is assumed that the core layers carry only the transverse shear stresses, while the hard membrane layers carry the in-plane normal and shear stresses. The complementary variational principle for dynamics is used to derive the governing differential equations and the necessary boundary conditions for the dynamic stability of the sandwich plate. The equations governing the vibration of the plate and those governing its static stability are deduced from the more general equations for dynamic stability.

  18. Wire and Packing Tape Sandwiches

    ERIC Educational Resources Information Center

    Rabinowitz, Sandy

    2009-01-01

    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.)

  19. Thermal-Diode Sandwich Panel

    NASA Technical Reports Server (NTRS)

    Basiulis, A.

    1986-01-01

    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.

  20. High temperature structural sandwich panels

    NASA Astrophysics Data System (ADS)

    Papakonstantinou, Christos G.

    High strength composites are being used for making lightweight structural panels that are being employed in aerospace, naval and automotive structures. Recently, there is renewed interest in use of these panels. The major problem of most commercial available sandwich panels is the fire resistance. A recently developed inorganic matrix is investigated for use in cases where fire and high temperature resistance are necessary. The focus of this dissertation is the development of a fireproof composite structural system. Sandwich panels made with polysialate matrices have an excellent potential for use in applications where exposure to high temperatures or fire is a concern. Commercial available sandwich panels will soften and lose nearly all of their compressive strength temperatures lower than 400°C. This dissertation consists of the state of the art, the experimental investigation and the analytical modeling. The state of the art covers the performance of existing high temperature composites, sandwich panels and reinforced concrete beams strengthened with Fiber Reinforced Polymers (FRP). The experimental part consists of four major components: (i) Development of a fireproof syntactic foam with maximum specific strength, (ii) Development of a lightweight syntactic foam based on polystyrene spheres, (iii) Development of the composite system for the skins. The variables are the skin thickness, modulus of elasticity of skin and high temperature resistance, and (iv) Experimental evaluation of the flexural behavior of sandwich panels. Analytical modeling consists of a model for the flexural behavior of lightweight sandwich panels, and a model for deflection calculations of reinforced concrete beams strengthened with FRP subjected to fatigue loading. The experimental and analytical results show that sandwich panels made with polysialate matrices and ceramic spheres do not lose their load bearing capability during severe fire exposure, where temperatures reach several

  1. A general small-deflection theory for flat sandwich plates

    NASA Technical Reports Server (NTRS)

    Libove, Charles; Batdorf, S B

    1948-01-01

    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.

  2. Radially sandwiched cylindrical piezoelectric transducer

    NASA Astrophysics Data System (ADS)

    Lin, Shuyu; Fu, Zhiqiang; Zhang, Xiaoli; Wang, Yong; Hu, Jing

    2013-01-01

    A new type of radially sandwiched piezoelectric short cylindrical transducer is developed and its radial vibration is studied. The transducer is composed of a solid metal disk, a radially polarized piezoelectric ceramic short tube and a metal tube. The radial vibrations of the solid metal disk, the radially polarized piezoelectric tube and the metal tube are analyzed and their electromechanical equivalent circuits are introduced. Based on the mechanical boundary conditions among the metal disk, the piezoelectric tube and the metal tube, a three-port electromechanical equivalent circuit for the radially sandwiched transducer is obtained and the frequency equation is given. The theoretical relationship of the resonance and anti-resonance frequencies and the effective electromechanical coupling coefficient with the geometrical dimensions is analyzed. The radial vibration of the sandwiched transducer is simulated by using two different numerical methods. It is shown that the analytical resonance and anti-resonance frequencies are in good agreement with the numerically simulated results. The transducer is expected to be used in piezoelectric resonators, actuators and ultrasonic radiators in ultrasonic and underwater sound applications.

  3. Compressive strength after blast of sandwich composite materials

    PubMed Central

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

    2014-01-01

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

  4. Compressive strength after blast of sandwich composite materials.

    PubMed

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

    2014-05-13

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

  5. Composite Sandwich Technologies Lighten Components

    NASA Technical Reports Server (NTRS)

    2010-01-01

    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.

  6. Facesheet Wrinkling in Sandwich Structures

    NASA Technical Reports Server (NTRS)

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

    1999-01-01

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

  7. Applications of thin-film sandwich crystallization platforms

    SciTech Connect

    Axford, Danny Aller, Pierre; Sanchez-Weatherby, Juan; Sandy, James

    2016-03-24

    Crystallization via sandwiches of thin polymer films is presented and discussed. Examples are shown of protein crystallization in, and data collection from, solutions sandwiched between thin polymer films using vapour-diffusion and batch methods. The crystallization platform is optimal for both visualization and in situ data collection, with the need for traditional harvesting being eliminated. In wells constructed from the thinnest plastic and with a minimum of aqueous liquid, flash-cooling to 100 K is possible without significant ice formation and without any degradation in crystal quality. The approach is simple; it utilizes low-cost consumables but yields high-quality data with minimal sample intervention and, with the very low levels of background X-ray scatter that are observed, is optimal for microcrystals.

  8. Construction

    DTIC Science & Technology

    2002-01-01

    Harbor Deepening Project, Jacksonville, FL Palm Valley Bridge Project, Jacksonville, FL Rotary Club of San Juan, San Juan, PR Tren Urbano Subway...David. What is nanotechnology? What are its implications for construction?, Foresight/CRISP Workshop on Nanotechnology, Royal Society of Arts

  9. Construction

    DTIC Science & Technology

    2002-01-01

    San Juan, PR Tren Urbano Subway Project, San Juan, PR U.S. Army South, San Juan, PR U.S. Coast Guard Housing Project, San Juan, PR U.S. Coast Guard...construction?, Foresight/CRISP Workshop on Nanotechnology, Royal Society of Arts . Cheltenham, England: 2001, p.5. 56 Concrete Proposals, Economist, July 24

  10. Development and Evaluation of Stitched Sandwich Panels

    NASA Technical Reports Server (NTRS)

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

    2001-01-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

  12. An h-p Finite Element Vibration Analysis of Open Conical Sandwich Panels and Conical Sandwich Frusta

    NASA Astrophysics Data System (ADS)

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

    1999-09-01

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

  13. Aptamer-based sandwich-type biosensors.

    PubMed

    Seo, Ho Bin; Gu, Man Bock

    2017-01-01

    Sandwich-type biosensor platforms have drawn lots of attentions due to its superior features, compared to other platforms, in terms of its stable and reproducible responses and easy enhancement in the detection sensitivity. The sandwich-type assays can be developed by utilizing a pair of receptors, which bind to the different sites of the same target. In this mini-review paper, the sandwich-type biosensors using either pairs of aptamers or aptamer-antibody pairs are reviewed in terms of its targets and platforms, the schematic designs, and their analytical performance.

  14. Precast concrete sandwich panels subjected to impact loading

    NASA Astrophysics Data System (ADS)

    Runge, Matthew W.

    Precast concrete sandwich panels are a relatively new product in the construction industry. The design of these panels incorporates properties that allow for great resilience against temperature fluctuation as well as the very rapid and precise construction of facilities. The concrete sandwich panels investigated in this study represent the second generation of an ongoing research and development project. This second generation of panels have been engineered to construct midsized commercial buildings up to three stories in height as well as residential dwellings. The panels consist of a double-tee structural wythe, a foam core and a fascia wythe, joined by shear connectors. Structures constructed from these panels may be subjected to extreme loading including the effects of seismic and blast loading in addition to wind. The aim of this work was to investigate the behaviour of this particular sandwich panel when subjected to structural impact events. The experimental program consisted of fourteen concrete sandwich panels, five of which were considered full-sized specimens (2700 mm X 1200mm X 270 mm) and nine half-sized specimens (2700mm X 600mm X 270 mm) The panels were subjected to impact loads from a pendulum impact hammer where the total energy applied to the panels was varied by changing the mass of the hammer. The applied loads, displacements, accelerations, and strains at the mid-span of the panel as well as the reaction point forces were monitored during the impact. The behaviour of the panels was determined primarily from the experimental results. The applied loads at low energy levels that caused little to no residual deflection as well as the applied loads at high energy levels that represent catastrophic events and thus caused immediate failure were determined from an impact on the structural and the fascia wythes. Applied loads at intermediate energy levels representing extreme events were also used to determine whether or not the panels could withstand

  15. Asymmetric MoS2 /Graphene/Metal Sandwiches: Preparation, Characterization, and Application.

    PubMed

    Toth, Peter S; Velický, Matĕj; Bissett, Mark A; Slater, Thomas J A; Savjani, Nicky; Rabiu, Aminu K; Rakowski, Alexander M; Brent, Jack R; Haigh, Sarah J; O'Brien, Paul; Dryfe, Robert A W

    2016-10-01

    The polarizable organic/water interface is used to construct MoS2 /graphene nanocomposites, and various asymmetrically dual-decorated graphene sandwiches are synthesized. High-resolution transmission electron microscopy and 3D electron tomography confirm their structure. These dual-decorated graphene-based hybrids show excellent hydrogen evolution activity and promising capacitance performance.

  16. Experimental study of acoustical characteristics of honeycomb sandwich structures

    NASA Astrophysics Data System (ADS)

    Peters, Portia Renee

    Loss factor measurements were performed on sandwich panels to determine the effects of different skin and core materials on the acoustical properties. Results revealed inserting a viscoelastic material in the core's mid-plane resulted in the highest loss factor. Panels constructed with carbon-fiber skins exhibited larger loss factors than glass-fiber skins. Panels designed to achieve subsonic wave speed did not show a significant increase in loss factor above the coincidence frequency. The para-aramid core had a larger loss factor value than the meta-aramid core. Acoustic absorption coefficients were measured for honeycomb sandwiches designed to incorporate multiple sound-absorbing devices, including Helmholtz resonators and porous absorbers. The structures consisted of conventional honeycomb cores filled with closed-cell polyurethane foams of various densities and covered with perforated composite facesheets. Honeycomb cores filled with higher density foam resulted in higher absorption coefficients over the frequency range of 50 -- 1250 Hz. However, this trend was not observed at frequencies greater than 1250 Hz, where the honeycomb filled with the highest density foam yielded the lowest absorption coefficient among samples with foam-filled cores. The energy-recycling semi-active vibration suppression method (ERSA) was employed to determine the relationship between vibration suppression and acoustic damping for a honeycomb sandwich panel. Results indicated the ERSA method simultaneously reduced the sound transmitted through the panel and the panel vibration. The largest reduction in sound transmitted through the panel was 14.3% when the vibrations of the panel were reduced by 7.3%. The influence of different design parameters, such as core density, core material, and cell size on wave speeds of honeycomb sandwich structures was experimentally analyzed. Bending and shear wave speeds were measured and related to the transmission loss performance for various material

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

    NASA Astrophysics Data System (ADS)

    Song, Fei

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

  18. Transient Thermal Testing and Analysis of a Thermally Insulating Structural Sandwich Panel

    NASA Technical Reports Server (NTRS)

    Blosser, Max L.; Daryabeigi, Kamran; Bird, Richard K.; Knutson, Jeffrey R.

    2015-01-01

    A core configuration was devised for a thermally insulating structural sandwich panel. Two titanium prototype panels were constructed to illustrate the proposed sandwich panel geometry. The core of one of the titanium panels was filled with Saffil(trademark) alumina fibrous insulation and the panel was tested in a series of transient thermal tests. Finite element analysis was used to predict the thermal response of the panel using one- and two-dimensional models. Excellent agreement was obtained between predicted and measured temperature histories.

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

    NASA Technical Reports Server (NTRS)

    Camarda, C. J.; Basiulis, A.

    1983-01-01

    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.

  20. Experimental investigation of fiberglass sandwich composite bending behaviour after severe aging condition

    NASA Astrophysics Data System (ADS)

    Gambaro, Carla; Lertora, Enrico; Mandolfino, Chiara

    2016-10-01

    Fiber Reinforced Polymer (FRP) sandwich panels are increasing their application as structural and non-structural components in all kinds of construction. By varying the material and thickness of core and face sheets, it is possible to obtain sandwich structures with different properties and performance. In particular, their advantages as lightweight and high mechanical properties make them extremely suitable for the transport industry. One of the most critical aspects regarding composite materials for engineering application is their performance after hygrothermal aging. The panels used in this study are composed of low density core, made by thermosetting resin foam with microspheres and glass fibers rolled until obtaining the required thickness, and two face sheets of the same material but realized in high density. In this study, the authors focused on the bending behaviour of this kind of sandwich panel, as received and after severe aging cycles.

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

    NASA Technical Reports Server (NTRS)

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

    2004-01-01

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

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

    SciTech Connect

    Camarda, C.J.; Basiulis, A.

    1983-08-01

    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.

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

    NASA Technical Reports Server (NTRS)

    Ko, William L.

    1994-01-01

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

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

    NASA Technical Reports Server (NTRS)

    Camarda, C. J.; Basiulis, A.

    1983-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

    Ishai, Ori; Hiel, Clement; Luft, Michael

    1995-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

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

    2004-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Lares, Alan

    Sandwich structures have been used in the aerospace industry for many years. The high strength to weight ratios that are possible with sandwich constructions makes them desirable for airframe applications. While sandwich structures are effective at handling distributed loads such as aerodynamic forces, they are prone to damage from concentrated loads at joints or due to impact. This is due to the relatively thin face-sheets and soft core materials typically found in sandwich structures. Carleton University's Uninhabited Aerial Vehicle (UAV) Project Team has designed and manufactured a UAV (GeoSury II Prototype) which features an all composite sandwich structure fuselage structure. The purpose of the aircraft is to conduct geomagnetic surveys. The GeoSury II Prototype serves as the test bed for many areas of research in advancing UAV technologies. Those areas of research include: low cost composite materials manufacturing, geomagnetic data acquisition, obstacle detection, autonomous operations and magnetic signature control. In this thesis work a methodology for designing and manufacturing inserts for foam-core sandwich structures was developed. The results of this research work enables a designer wishing to design a foam-core sandwich airframe structure, a means of quickly manufacturing optimized inserts for the safe introduction of discrete loads into the airframe. The previous GeoSury II Prototype insert designs (v.1 & v.2) were performance tested to establish a benchmark with which to compare future insert designs. Several designs and materials were considered for the new v.3 inserts. A plug and sleeve design was selected, due to its ability to effectively transfer the required loads to the sandwich structure. The insert material was chosen to be epoxy, reinforced with chopped carbon fibre. This material was chosen for its combination of strength, low mass and also compatibility with the face-sheet material. The v.3 insert assembly is 60% lighter than the

  8. Supersonic flutter of composite sandwich panels

    NASA Astrophysics Data System (ADS)

    Shiau, Le-Chung

    1992-12-01

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

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

    NASA Technical Reports Server (NTRS)

    Jegley, D.

    1993-01-01

    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.

  10. Wave propagation in metamaterial lattice sandwich plates

    NASA Astrophysics Data System (ADS)

    Fang, Xin; Wen, Jihong; Yin, Jianfei; Yu, Dianlong

    2016-04-01

    This paper designed a special acoustic metamaterial 3D Kagome lattice sandwich plate. Dispersion properties and vibration responses of both traditional plate and metamaterial plate are investigated based on FEA methods. The traditional plate does not have low-frequency complete bandgaps, but the metamaterial plate has low-frequency complete bandgap (at 620Hz) coming from the symmetrical local cantilever resonators. The bandgap frequency is approximate to the first-order natural frequency of the oscillator. Complex wave modes are analyzed. The dispersion curves of longitudinal waves exist in the flexural bandgap. The dispersion properties demonstrate the metamaterial design is advantageous to suppress the low-frequency flexural wave propagation in lattice sandwich plate. The flexural vibrations near the bandgap are also suppressed efficiently. The longitudinal excitation stimulates mainly longitudinal waves and lots of low-frequency flexural vibration modes are avoided. Furthermore, the free edge effects in metamaterial plate provide new method for damping optimizations. The influences of damping on vibrations of the metamaterial sandwich plate are studied. Damping has global influence on the wave propagation; stronger damping will induce more vibration attenuation. The results enlighten us damping and metamaterial design approaches can be unite in the sandwich plates to suppress the wave propagations.

  11. Understanding Successful Sandwich Placements: A Bourdieusian Approach

    ERIC Educational Resources Information Center

    Clark, Martyn; Zukas, Miriam

    2016-01-01

    Sandwich placements and other integrated work and study schemes are increasingly advocated as a key means by which universities can promote students' employability. However, there is little understanding of how successful placements work in terms of facilitating learning and development. Drawing on three longitudinal case studies of students who…

  12. Noise transmission by viscoelastic sandwich panels

    NASA Technical Reports Server (NTRS)

    Vaicaitis, R.

    1977-01-01

    An analytical study on low frequency noise transmission into rectangular enclosures by viscoelastic sandwich panels is presented. Soft compressible cores with dilatational modes and hard incompressible cores with dilatational modes neglected are considered as limiting cases of core stiffness. It is reported that these panels can effect significant noise reduction.

  13. Feedback Sandwiches Affect Perceptions but Not Performance

    ERIC Educational Resources Information Center

    Parkes, Jay; Abercrombie, Sara; McCarty, Teresita

    2013-01-01

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

  14. Piezoactuation of sandwich plates with viscoelastic cores

    NASA Astrophysics Data System (ADS)

    Wang, Gang; Wereley, Norman M.

    1999-06-01

    Experimental and analytical validations of a Galerkin analysis of sandwich plates is presented in this paper. The 3-layered sandwich plate specimen consists of isotropic face-plates with surface bonded piezo-electric patch actuators, and a viscoelastic core. The experimental validation is conducted by testing sandwiched plates that are 67.31 cm (26.5') long, 52.07 cm (20.5') wide and nominally 0.16 cm (1/16') thick. The analysis includes the membrane and transverse energies in the face plates, and shear energies in the core. The shear modulus of the dissipative core is assumed to be complex and variant with frequency and temperature. The Golla-Hughes-McTavish (GHM) method is used to account for the frequency dependent properties of the viscoelastic core. Experiments have been conducted on sandwich plates with aluminum face-plates under clamped boundary conditions to validate the model for isotropic face-plates. Symmetric and asymmetric sandwiches have been tested. The maximum error in damped natural frequency predictions obtained via the assumed modes solutions is less than 11%. Analytical studies on the influence of the number of assumed modes in the Galerkin approximation, and the temperature variation, have been conducted. Error in the first plate bending mode is 112% when only a single in-plane mode is used; error reduces to 3.95% as the number of in-plane modes is increased to 25 in each of the in-plane directions. The study on the temperature influence shows that every plate mode has a corresponding temperature, wherein the loss factor is maximized.

  15. Sound Transmission through a Cylindrical Sandwich Shell with Honeycomb Core

    NASA Technical Reports Server (NTRS)

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

    1996-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

    Ko, William L.

    1993-01-01

    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.

  17. Thermographic Inspection of Metallic Honeycomb Sandwich Structures

    NASA Technical Reports Server (NTRS)

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

    1998-01-01

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

  18. Ultrasonic Spectroscopy of Stainless Steel Sandwich Panels

    NASA Technical Reports Server (NTRS)

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

    2003-01-01

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

  19. Buckling optimisation of sandwich cylindrical panels

    NASA Astrophysics Data System (ADS)

    Abouhamzeh, M.; Sadighi, M.

    2016-06-01

    In this paper, the buckling load optimisation is performed on sandwich cylindrical panels. A finite element program is developed in MATLAB to solve the governing differential equations of the global buckling of the structure. In order to find the optimal solution, the genetic algorithm Toolbox in MATLAB is implemented. Verifications are made for both the buckling finite element code and also the results from the genetic algorithm by comparisons to the results available in literature. Sandwich cylindrical panels are optimised for the buckling strength with isotropic or orthotropic cores with different boundary conditions. Results are presented in terms of stacking sequence of fibers in the face sheets and core to face sheet thickness ratio.

  20. Damage Tolerance Characterisitics of Composite Sandwich Structures

    DTIC Science & Technology

    2000-02-01

    and very simplified modelling Unit of the EH-101 helicopter is made of a composite skeleton of the damage introduced by impact; second, the evaluation...the delamination boundary. The Multi Point Constraint If the delamination growth data from the teflon strip element of NASTRAN is used for modelling ...component level. These kinds of tests are composite sandwich structures used by the helicopter industry, carried out not only to verify load paths and

  1. Self-healing sandwich composite structures

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

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

  2. BMI Sandwich Wing Box Analysis and Test

    NASA Technical Reports Server (NTRS)

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

    2000-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

    Nettles, Alan T.; Ratcliffe, James G.

    2006-01-01

    Composite sandwich structures will be used in many future applications in aerospace, marine and offshore industries due to the fact that the strength and stiffness to mass ratios surpass any other structural type. Sandwich structure also offers advantages over traditional stiffened panels such as ease of manufacturing and repair. During the last three decades, sandwich structure has been used extensively for secondary structure in aircraft (fuselage floors, rudders and radome structure). Sandwich structure is also used as primary structure in rotorcraft, the most common example being the trailing edge of rotor blades. As with other types of composite construction, sandwich structure exhibits several types of failure mode such as facesheet wrinkling, core crushing and sandwich buckling. Facesheet/core debonding has also been observed in the marine and aerospace industry. During this failure mode, peel stresses applied to an existing facesheet/core debond or an interface low in toughness, results in the facesheet being peeled from the core material, possibly leading to a significant loss in structural integrity of the sandwich panel. In an incident during a test on a liquid hydrogen fuel tank of the X-33 prototype vehicle, the outer graphite/epoxy facesheet and honeycomb core became debonded from the inner facesheet along significant areas, leading to failure of the tank. As a consequence of the accident; significant efforts were made to characterize the toughness of the facesheet/core bond. Currently, the only standardized method available for assessing the quality of the facesheet/core interface is the climbing drum peel test (ASTM D1781). During this test a sandwich beam is removed from a panel and the lip of one of the facesheets is attached to a drum, as shown in Fig. 1. The drum is then rotated along the sandwich beam, causing the facesheet to peel from the core. This method has two major drawbacks. First, it is not possible to obtain quantitative fracture data

  4. Buckling Analysis of Debonded Sandwich Panel Under Compression

    NASA Technical Reports Server (NTRS)

    Sleight, David W.; Wang, John T.

    1995-01-01

    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.

  5. A double-sandwich ELISA for identification of monoclonal antibodies suitable for sandwich immunoassays

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The sandwich immunoassay (sIA) is an invaluable technique for concentrating, detecting, and quantifying target antigens. The two critical components required are a capture antibody and a detection antibody, each binding a different epitope on the target antigen. The specific antibodies incorporated...

  6. Development of the LANL sandwich test.

    SciTech Connect

    Hill, L. G.

    2001-01-01

    The Sandwich test is slab-variant of the ubiquitous copper cylinder test, and is used to obtain high explosive product equation-of-state information in the same manner as its predecessor. The motivation for slab geometry is (1) better high-pressure resolution, and (2) the ability to accommodate initial temperature extremes for solid explosive samples. The present design allows initial temperatures from -55 C to 75 C. The pros and cons of the two geometries we discussed, followed by a description of the mechanical design and instrumentation. gample data for several ambient PBX 9501 tests demonstrates excellent data quality and repeatability.

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

    NASA Technical Reports Server (NTRS)

    Basiulis, A.; Camarda, C. J.

    1983-01-01

    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.

  8. Modeling of Sandwich Sheets with Metallic Foam

    SciTech Connect

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

    2011-08-22

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

  9. Sandwich Cylinder Technology for Cryogenic Tank

    NASA Astrophysics Data System (ADS)

    Rambaud, Wladimir; Lukowiak, Denis; Damas, Alain; Michelot, David; Jousset, Frederic; Mercier, Antoine; Bouilly, Thibault; Leudiere, Vincent

    2014-06-01

    In the frame of the Research and Technology activities, CNES Launcher Directorate and EuroCryospace performed studies on cryogenic tank.Since 2009/2010, we realized analyses and tests on a promising technology for cryogenic tank submitted to high compressive loads. Indeed, the "Sandwich cylinder" (metallic shell, insulating core, composite shell) is a way to improve performance and costs with respect to classical structure. This concept presents specific stiffness behavior (advantageous stiffness/mass ratio) higher than an aluminum alloy structure and scalable thermal behavior.The relevancy of the Sandwich concept was first evaluated by calculation in comparison with 3 other cylinder architectures and then this R&T project was conducted from elementary characterizations to a buckling test of a representative demonstrator.The paper provides an overview of the different steps of the project and the main results obtained. Potential benefits for Ariane 6 launcher are also presented.The concept is submitted to ECSP patent and so, numerical values will not be present in the paper.

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

    ERIC Educational Resources Information Center

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

    1973-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2002-01-01

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

  12. Cherenkov radiation by Josephson vortex travelling in the long sandwich

    NASA Astrophysics Data System (ADS)

    Malishevskii, A. S.; Silin, V. P.; Uryupin, S. A.; Uspenskii, S. G.

    2009-03-01

    Vortex motion in the long Josephson sandwich embedded in dielectric media is described. It is shown that vortices traveling with velocities greater than the speed of light in the dielectric generate electromagnetic waves. Appearance of radiation is due to Cherenkov phenomenon. Radiation appearing at rather high vortex velocities has high enough frequencies. For typical sandwiches radiation frequencies fall on THz domain.

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

    NASA Technical Reports Server (NTRS)

    Mathauser, Eldon E.; Pride, Richard A.

    1959-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Chachra, Ricky

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

  15. Impact damage in aircraft composite sandwich panels

    NASA Astrophysics Data System (ADS)

    Mordasky, Matthew D.

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

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

    NASA Astrophysics Data System (ADS)

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

    2001-02-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2014-01-01

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

  18. An enriched 1D finite element for the buckling analysis of sandwich beam-columns

    NASA Astrophysics Data System (ADS)

    Sad Saoud, Kahina; Le Grognec, Philippe

    2016-06-01

    Sandwich constructions have been widely used during the last few decades in various practical applications, especially thanks to the attractive compromise between a lightweight and high mechanical properties. Nevertheless, despite the advances achieved to date, buckling still remains a major failure mode for sandwich materials which often fatally leads to collapse. Recently, one of the authors derived closed-form analytical solutions for the buckling analysis of sandwich beam-columns under compression or pure bending. These solutions are based on a specific hybrid formulation where the faces are represented by Euler-Bernoulli beams and the core layer is described as a 2D continuous medium. When considering more complex loadings or non-trivial boundary conditions, closed-form solutions are no more available and one must resort to numerical models. Instead of using a 2D computationally expensive model, the present paper aims at developing an original enriched beam finite element. It is based on the previous analytical formulation, insofar as the skin layers are modeled by Timoshenko beams whereas the displacement fields in the core layer are described by means of hyperbolic functions, in accordance with the modal displacement fields obtained analytically. By using this 1D finite element, linearized buckling analyses are performed for various loading cases, whose results are confronted to either analytical or numerical reference solutions, for validation purposes.

  19. "Inverse Sandwich" Complexes of Perhalogenated Cyclohexasilane

    SciTech Connect

    Dai, Xuliang; Shulz, Douglas; Braun, Christopher; Ugrinov, Angel; and Boudjouk, Philip

    2010-04-20

    Perhalogenated cyclohexasilanes, Si6X12 (X = Cl, Br), were prepared by reaction of Si6H12 with molecular chlorine or bromine in cold (-89 °C) dichloromethane. Single-crystal structural determination by X-ray analysis shows that the six silicon atoms comprising Si6Br12 adopt a chair conformation in the solid state. The addition of p-tolunitrile to Si6X12 (X = Cl, Br) leads to the rapid formation of colorless precipitates. Si6Br12 3 2(p-CH3C6H4CN) adopts an 'inverse sandwich' structure where the N atoms of the p-tolunitrile molecules are μ6 bonded and are located above and below the planar hexagonal Si6 ring. In conclusion, Si6X12 (X = Cl, Br) was synthesized by molecular halogenation of Si6H12 in high yield and good purity. Perhalogenated cyclohexasilanes react with p-tolunitrile to give 'inverse sandwich' adducts 3 and 4 with a planar Si6 ring upon coordination. Our future reports will detail dianionic adducts based on tetra-n-butylammonium halides as well as a monoanionic adamantyl azide adduct of Si6Cl12. It is straightforward to conceptualize the utility of Si6X12 ∙ Ln chemistry in molecular assembly of silicon-based clusters/tubes/wires. Thereby, we proffer that this constitutes a new landscape in Si chemistry.

  20. Evaluation of Analysis Techniques for Fluted-Core Sandwich Cylinders

    NASA Technical Reports Server (NTRS)

    Lovejoy, Andrew E.; Schultz, Marc R.

    2012-01-01

    Buckling-critical launch-vehicle structures require structural concepts that have high bending stiffness and low mass. Fluted-core, also known as truss-core, sandwich construction is one such concept. In an effort to identify an analysis method appropriate for the preliminary design of fluted-core cylinders, the current paper presents and compares results from several analysis techniques applied to a specific composite fluted-core test article. The analysis techniques are evaluated in terms of their ease of use and for their appropriateness at certain stages throughout a design analysis cycle (DAC). Current analysis techniques that provide accurate determination of the global buckling load are not readily applicable early in the DAC, such as during preliminary design, because they are too costly to run. An analytical approach that neglects transverse-shear deformation is easily applied during preliminary design, but the lack of transverse-shear deformation results in global buckling load predictions that are significantly higher than those from more detailed analysis methods. The current state of the art is either too complex to be applied for preliminary design, or is incapable of the accuracy required to determine global buckling loads for fluted-core cylinders. Therefore, it is necessary to develop an analytical method for calculating global buckling loads of fluted-core cylinders that includes transverse-shear deformations, and that can be easily incorporated in preliminary design.

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

    NASA Astrophysics Data System (ADS)

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

    2010-03-01

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

  2. Conjoined Cochlear Models:. the Twamp and the Sandwich

    NASA Astrophysics Data System (ADS)

    Hubbard, Allyn

    2009-02-01

    A new model of the cochlea is created by joining parts of the traveling-wave amplifier (TWAMP) and the Sandwich models. The lossy, untuned traveling-wave line of the TWAMP is retained, but the TWAMP's tuned traveling-wave line is replaced by the Sandwich's traveling-wave line that represents the reticular lamina (RL) and scala tympani. The model combines stereocilliary forces, which act between the tectorial membrane (TM) and RL, with somatic outer hair cell forces that power the Sandwich.

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

    NASA Technical Reports Server (NTRS)

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

    1980-01-01

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

  4. Wave propagation in sandwich panels with a poroelastic core.

    PubMed

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

    2014-05-01

    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.

  5. Measuring Moisture Levels in Graphite Epoxy Composite Sandwich Structures

    NASA Technical Reports Server (NTRS)

    Nurge, Mark; Youngquist, Robert; Starr, Stanley

    2011-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2009-08-01

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

  7. Effects of bonding stiffness on thermal stresses in sandwich panels

    NASA Astrophysics Data System (ADS)

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

    1992-10-01

    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.

  8. A consistent large deflection theory of composite sandwich shells

    NASA Astrophysics Data System (ADS)

    Zhu, Jinfu

    1993-05-01

    Composite sandwich shells are important structures in aeronautical and astronautical industry. The theory, especially nonlinear theory, of them is still required to be advanced so as to meet the demand of engineering application. With Lagrangian description, the consistent Green strain tensor, the compatibility equations and the second Piola-Kirchhoff stress tensor of the composite sandwich shells are obtained. Based on these results and several assumptions, the constitutive equations relating the stress resultants to the strains, the strain energy density and the potential energy functional are further developed. In terms of minimum potential energy principle, the equilibrium equations and associated boundary conditions are obtained, which are consistent with the first order approximation under the conditions of small strain accompanied with moderate/small rotation. In terms of the structural features of the shallow composite sandwich shells, the equations obtained are further processed approximately and Donnel-type equations for the shallow composite sandwich shells are obtained.

  9. Ferrocene and Half Sandwich Complexes as Catalysts with Iron Participation

    NASA Astrophysics Data System (ADS)

    Peters, René; Fischer, Daniel F.; Jautze, Sascha

    The unique and readily tunable electronic and spatial characteristics of ferrocenes have been widely exploited in the field of asymmetric catalysis. The ferrocene moiety is not just an innocent steric element to create a three-dimensional chiral catalyst environment. Instead, the Fe center can influence the catalytic process by electronic interaction with the catalytic site, if the latter is directly connected to the sandwich core. Of increasing importance are also half sandwich complexes in which Fe is acting as a mild Lewis acid. Like ferrocene, half sandwich complexes are often relatively robust and readily accessible. This chapter highlights recent applications of ferrocene and half sandwich complexes in which the Fe center is essential for catalytic applications.

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

    NASA Astrophysics Data System (ADS)

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

    2014-04-01

    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.

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

    PubMed Central

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

    2014-01-01

    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

  12. Enhanced antibacterial activity of silver nanoparticles/halloysite nanotubes/graphene nanocomposites with sandwich-like structure.

    PubMed

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

    2014-04-11

    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 possess enhanced antibacterial ability against E. coli and S. aureus compared with individual silver nanoparticles, rGO nanosheets or their nanocomposites.

  13. Modified Mode-I Cracked Sandwich Beam (CSB) Fracture Test

    NASA Technical Reports Server (NTRS)

    Smith, S. A.; Shivakumar, K. N.

    2001-01-01

    Five composite sandwich panels were fabricated using vacuum assisted resin transfer molding (VARTM). Four of these panels had E-glass/vinylester facesheets and one had carbon/epoxy facesheets. The sandwich panels had different density PVC foam cores. The four E-glass panels had core densities of 80, 100, 130, 200 kg/cu m. The sandwich with carbon/epoxy 3 facesheets had a core with density of 100 kg/cu m. Fracture tests were conducted using a modified Cracked Sandwich Beam (CSB) test configuration. Load displacement curves were obtained for loading and unloading of the specimens during crack growth. Various increments of crack growth were monitored. Critical Strain Energy Release Rates (SERR) were determined from the tests using the area method. The critical values of SERR can be considered the fracture toughness of the sandwich material. The fracture toughness ranged 367 J/sq m to 1350 J/sq m over the range of core densities. These results are compared to the Mode-I fracture toughness of the PVC foam core materials and values obtained for foam-cored sandwiches using the TSD specimen. Finite-element analyses (FEA) were performed for the test configuration and Strain Energy Release Rates were calculated using the Virtual Crack Closure Technique (VCCT). The SERR values determined from the FEA were scaled to the fracture loads, or critical loads, obtained from the modified CSB tests. These critical loads were in close agreement with the test values.

  14. Optimization of composite sandwich cover panels subjected to compressive loadings

    NASA Technical Reports Server (NTRS)

    Cruz, Juan R.

    1991-01-01

    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.).

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

    PubMed

    Harrison, Alexandra M

    2014-04-01

    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.

  16. Numerically simulating the sandwich plate system structures

    NASA Astrophysics Data System (ADS)

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

    2010-09-01

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

  17. Hypervelocity impact response of honeycomb sandwich panels

    NASA Astrophysics Data System (ADS)

    Schonberg, William; Schäfer, Frank; Putzar, Robin

    2010-02-01

    Man-made orbital poses a serious threat to spacecraft that are launched to operate in Earth orbit because it can strike such spacecraft at very high velocities and consequently damage mission-critical systems. This paper describes the findings of a study whose objective was to develop a system of empirical equations that can be used to predict the trajectories and spread of the debris clouds that exit the rear facesheet following a high speed perforating impact of a honeycomb sandwich panel (HC/SP). These equations are based on a database containing the results of nearly 400 tests from 13 previously published papers and reports. Overall the correlation coefficient values for the various regression equations obtained are fairly reasonable, and range from near 60% to well above 90%. This indicates that the chosen forms of the equations are a good fit to the data, and that they are capable of picking up most of the variations in the data that result from changes in test conditions. These equations can now be used to estimate the amount of mass in a debris cloud if an HC/SP is perforated by a high speed impact, where this mass will travel, and what spacecraft components will be impacted by it. This information can then be fed into a risk assessment code to calculate the probability of spacecraft failure under a prescribed set of impact conditions.

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

    NASA Astrophysics Data System (ADS)

    Hause, Terry John

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

  19. A novel method of measuring leaf epidermis and mesophyll stiffness shows the ubiquitous nature of the sandwich structure of leaf laminas in broad-leaved angiosperm species

    PubMed Central

    Onoda, Yusuke; Schieving, Feike; Anten, Niels P. R.

    2015-01-01

    Plant leaves commonly exhibit a thin, flat structure that facilitates a high light interception per unit mass, but may increase risks of mechanical failure when subjected to gravity, wind and herbivory as well as other stresses. Leaf laminas are composed of thin epidermis layers and thicker intervening mesophyll layers, which resemble a composite material, i.e. sandwich structure, used in engineering constructions (e.g. airplane wings) where high bending stiffness with minimum weight is important. Yet, to what extent leaf laminas are mechanically designed and behave as a sandwich structure remains unclear. To resolve this issue, we developed and applied a novel method to estimate stiffness of epidermis- and mesophyll layers without separating the layers. Across a phylogenetically diverse range of 36 angiosperm species, the estimated Young’s moduli (a measure of stiffness) of mesophyll layers were much lower than those of the epidermis layers, indicating that leaf laminas behaved similarly to efficient sandwich structures. The stiffness of epidermis layers was higher in evergreen species than in deciduous species, and strongly associated with cuticle thickness. The ubiquitous nature of sandwich structures in leaves across studied species suggests that the sandwich structure has evolutionary advantages as it enables leaves to be simultaneously thin and flat, efficiently capturing light and maintaining mechanical stability under various stresses. PMID:25675956

  20. Impact damage analysis of balsawood sandwich composite materials

    NASA Astrophysics Data System (ADS)

    Abdalslam, Suof Omran

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

  1. Composite panels based on woven sandwich-fabric preforms

    NASA Astrophysics Data System (ADS)

    van Vuure, Aart Willem

    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

  2. Sound Transmission through Two Concentric Cylindrical Sandwich Shells

    NASA Technical Reports Server (NTRS)

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

    1996-01-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2010-07-01

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

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

    PubMed

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

    2009-09-17

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

  5. Study on voids of epoxy matrix composites sandwich structure parts

    NASA Astrophysics Data System (ADS)

    He, Simin; Wen, Youyi; Yu, Wenjun; Liu, Hong; Yue, Cheng; Bao, Jing

    2017-03-01

    Void is the most common tiny defect of composite materials. Porosity is closely related to composite structure property. The voids forming behaviour in the composites sandwich structural parts with the carbon fiber reinforced epoxy resin skins was researched by adjusting the manufacturing process parameters. The composites laminate with different porosities were prepared with the different process parameter. The ultrasonic non-destructive measurement method for the porosity was developed and verified through microscopic examination. The analysis results show that compaction pressure during the manufacturing process had influence on the porosity in the laminate area. Increasing the compaction pressure and compaction time will reduce the porosity of the laminates. The bond-line between honeycomb core and carbon fiber reinforced epoxy resin skins were also analyzed through microscopic examination. The mechanical properties of sandwich structure composites were studied. The optimization process parameters and porosity ultrasonic measurement method for composites sandwich structure have been applied to the production of the composite parts.

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

    NASA Technical Reports Server (NTRS)

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

    1979-01-01

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

  7. Microtomography with sandwich detectors for small-animal bone imaging

    NASA Astrophysics Data System (ADS)

    Kim, S. H.; Kim, D. W.; Kim, D.; Youn, H.; Cho, S.; Kim, H. K.

    2016-10-01

    An x-ray radiographic system consisting of two detectors in tandem, or a sandwich detector, can produce dual-energy image from a single-shot exposure. Subtraction of two images obtained from the two detectors can produce a sharper image through an unsharp masking effect if the two images are formed at different spatial resolutions. This is indeed possible by incorporating different thicknesses of x-ray conversion layers in the detectors. In this study, we have developed a microtomography system with a sandwich detector in pursuit of high-resolution bone-enhanced small-animal imaging. The results show that the bone-enhanced images reconstructed from the dual-energy projection data provide higher visibility of bone details than the conventionally reconstructed images. The microtomography with the single-shot dual-energy sandwich detector will be useful for the high-resolution bone-enhanced small-animal imaging.

  8. Free vibration Analysis of Sandwich Plates with cutout

    NASA Astrophysics Data System (ADS)

    Mishra, N.; Basa, B.; Sarangi, S. K.

    2016-09-01

    This paper presents the free vibration analysis of sandwich plates with cutouts. Cutouts are inevitable in structural applications and the presence of these cutouts in the structures greatly influences their dynamic characteristics. A finite element model has been developed here using the ANSYS 15.0 software to study the free vibration characteristics of sandwich plates in the presence of cutouts. Shell 281 element, an 8-noded element with six degrees of freedom suited for analyzing thin to moderately thick structures is considered in the development of the model. Block Lanczose method is adopted to extract the mode shapes to obtain the natural frequency corresponding to free vibration of the plate. The effects of parametric variation on the natural frequency of the sandwich plates with cutout are studied and results are presented.

  9. Vibration analysis and optimization of sandwich composite with curvilinear fibers

    NASA Astrophysics Data System (ADS)

    Honda, S.; Narita, Y.

    2016-09-01

    The present paper develops a shell element based on the refined zigzag theory (RZT) and applies it to the vibration analysis and optimization problem of the composite sandwich plate composed of CFRP skins and soft-cores. The RZT accepts large differences in layer stiffness, and requires less calculation effort than the layer-wise or three-dimensional theories. Numerical results revealed that the present method predicts vibration characteristics of composite sandwich plates with soft-core accurately. Then, shapes of reinforcing fibers in CFRP composite skins are optimized to maximize fundamental frequencies. As an optimizer, the particle swarm optimization (PSO) approach is employed since curvilinear fiber shapes are defined by continuous design variables. Obtained results showed that the composite sandwich with optimum curvilinear fiber shapes indicates higher fundamental frequencies compared with straight fibers.

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

    PubMed

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

    2013-03-01

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

  11. Approaches to Design and Evaluation of Sandwich Composites

    NASA Technical Reports Server (NTRS)

    Shivakumar, Kunigal; Raju, I. S. (Technical Monitor); Ambur, D. (Technical Monitor)

    2001-01-01

    This report describes research during the period June 15, 1997 to October 31, 2000. This grant yielded a low cast manufacturing of composite sandwich structures technology and characterization interfacial and subinterfacial cracks in foam core sandwich panels. The manufacturing technology is called the vacuum assisted resin transfer (VARTM). The VARTM is suitable for processing composite materials both at ambient and elevated temperatures and of unlimited component size. This technology has been successfully transferred to a small business fiber preform manufacturing company 3TEX located in Cary, North Carolina. The grant also supported one Ph.D, one M.S and a number of under graduate students, and nine publications and Presentations.

  12. The extended high-order sandwich panel theory

    NASA Astrophysics Data System (ADS)

    Phan, Catherine N.

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

  13. Methods for Using Durable Adhesively Bonded Joints for Sandwich Structures

    NASA Technical Reports Server (NTRS)

    Smeltzer, Stanley S., III (Inventor); Lundgren, Eric C. (Inventor)

    2016-01-01

    Systems, methods, and apparatus for increasing durability of adhesively bonded joints in a sandwich structure. Such systems, methods, and apparatus includes an first face sheet and an second face sheet as well as an insert structure, the insert structure having a first insert face sheet, a second insert face sheet, and an insert core material. In addition, sandwich core material is arranged between the first face sheet and the second face sheet. A primary bondline may be coupled to the face sheet(s) and the splice. Further, systems, methods, and apparatus of the present disclosure advantageously reduce the load, provide a redundant path, reduce structural fatigue, and/or increase fatigue life.

  14. Comparisons of SHM Sensor Models with Empirical Test Data for Sandwich Composite Structures

    DTIC Science & Technology

    2011-09-01

    propagation in a honeycomb sandwich panel was done by Metis Design Inc. in collaboration with ARC NASA . The sandwich panel fabricated for this test...structures. Sandwich type composites are being studied for use in NASAs new heavy lift launch vehicle and flaw detection is crucial for safety and for...and at the Marshall Space Flight Center to examine acoustic wave propagating and the ability to detect intrinsic faults in sandwich type composite

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

    SciTech Connect

    Horvath, J.

    1993-09-16

    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.

  16. Buckling Design and Imperfection Sensitivity of Sandwich Composite Launch-Vehicle Shell Structures

    NASA Technical Reports Server (NTRS)

    Schultz, Marc R.; Sleight, David W.; Myers, David E.; Waters, W. Allen, Jr.; Chunchu, Prasad B.; Lovejoy, Andrew W.; Hilburger, Mark W.

    2016-01-01

    Composite materials are increasingly being considered and used for launch-vehicle structures. For shell structures, such as interstages, skirts, and shrouds, honeycomb-core sandwich composites are often selected for their structural efficiency. Therefore, it is becoming increasingly important to understand the structural response, including buckling, of sandwich composite shell structures. Additionally, small geometric imperfections can significantly influence the buckling response, including considerably reducing the buckling load, of shell structures. Thus, both the response of the theoretically perfect structure and the buckling imperfection sensitivity must be considered during the design of such structures. To address the latter, empirically derived design factors, called buckling knockdown factors (KDFs), were developed by NASA in the 1960s to account for this buckling imperfection sensitivity during design. However, most of the test-article designs used in the development of these recommendations are not relevant to modern launch-vehicle constructions and material systems, and in particular, no composite test articles were considered. Herein, a two-part study on composite sandwich shells to (1) examine the relationship between the buckling knockdown factor and the areal mass of optimized designs, and (2) to interrogate the imperfection sensitivity of those optimized designs is presented. Four structures from recent NASA launch-vehicle development activities are considered. First, designs optimized for both strength and stability were generated for each of these structures using design optimization software and a range of buckling knockdown factors; it was found that the designed areal masses varied by between 6.1% and 19.6% over knockdown factors ranging from 0.6 to 0.9. Next, the buckling imperfection sensitivity of the optimized designs is explored using nonlinear finite-element analysis and the as-measured shape of a large-scale composite cylindrical

  17. Lamb wave dispersion in a PZT/metal/PZT sandwich plate with imperfect interface

    NASA Astrophysics Data System (ADS)

    Kurt, Ilkay; Akbarov, Surkay D.; Sezer, Semih

    2016-07-01

    The Lamb wave dispersion in a PZT/Metal/PZT sandwich plate is investigated by employing the exact linear equations of electro-elastic waves in piezoelectric materials within the scope of the plane-strain state. It is assumed that at the interfaces between the piezoelectric face layers and metal core layer, shear-spring and normal-spring type imperfect conditions are satisfied. The degree of this imperfectness is estimated through the corresponding shear-spring and normal-spring type parameters which appear in the contact condition characterizing the transverse and normal displacements' discontinuity. The corresponding dispersion equation is derived, and as a result of the numerical solution to this equation, the dispersion curves are constructed for the first and second lowest modes in the cases where the material of the face layers is PZT and the material of the middle layer is Steel (St). Consequently, for the PZT/St/PZT sandwich plate, the study of the influence of the problem parameters such as the piezoelectric and dielectric constants, layer thickness ratios, non-dimensional shear-spring, and normal-spring type parameters, is carried out. In particular, it is established that the imperfectness of the contact between the layers of the plate causes a decrease in the values of the wave propagation velocity.

  18. State estimation of a compound non-smooth sandwich system with backlash and dead zone

    NASA Astrophysics Data System (ADS)

    Zhou, Zupeng; Tan, Yonghong; Xie, Yangqiu; Dong, Ruili

    2017-01-01

    In this paper, a novel switching non-smooth observer is proposed to deal with the state estimation of compound non-smooth sandwich system with backlash and dead zone. Based on the characteristic of the system, two separate non-smooth state-space functions are constructed to describe the input-output relationships of backlash. Then, a Luenberger-type non-smooth observer is developed based on the two separate non-smooth state-space functions and the backlash and dead zone input output functions. The observer can switch among the different operating zones automatically in terms of the change of real operation conditions. The observability of the system has been analyzed and the convergence of the switching compound non-smooth observer has been verified. Finally motor servo hydraulic systems which can be represented as a compound non-smooth sandwich system have been studied as an application case. The comparisons between the proposed non-smooth scheme and the conventional method are illustrated. It is demonstrated that the proposed non-smooth approach can achieve much better performance in the aspects of state estimation accuracy and state estimation convergence speed than the conventional one.

  19. Sandwich-like graphene/polypyrrole/layered double hydroxide nanowires for high-performance supercapacitors

    NASA Astrophysics Data System (ADS)

    Li, Xuejin; Zhang, Yu; Xing, Wei; Li, Li; Xue, Qingzhong; Yan, Zifeng

    2016-11-01

    Electrode design in nanoscale is considered to be ultra-important to construct a superb capacitor. Herein, a sandwich-like composite was made by combining graphene/polypyrrole (GPPY) with nickel-aluminum layered double hydroxide nanowires (NiAl-NWs) via a facile hydrothermal method. This sandwich-like architecture is promising in energy storage applications due to three unique features: (1) the conductive GPPY substrate not only effectively prevents the layered double hydroxides species from aggregating, but also considerably facilitates the electron transmission; (2) the ultrathin NiAl-NWs ensure a maximum exposure of active Ni2+, which can improve the efficiency of rapid redox reactions even at high current densities; (3) the sufficient space between anisotropic NiAl-NWs can accommodate a large volume change of the nanowires to avoid their collapse or distortion during the reduplicative redox reactions. Keeping all these unique features in mind, when the as-prepared composite was applied to supercapacitors, it presented an enhanced capacitive performance in terms of high specific capacitance (845 F g-1), excellent rate performance (67% retained at 30 A g-1), remarkable cyclic stability (92% maintained after 5000 cycles) and large energy density (40.1 Wh·Kg-1). This accomplishment in the present work inspires an innovative strategy of nanoscale electrode design for high-rate performance supercapacitor electrodes containing pseuducapacitive metal oxide.

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

    NASA Technical Reports Server (NTRS)

    McGowan, David M.; Ambur, Damodar R.

    1997-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Yan, Jiaxue

    Honeycomb structures are widely used in many areas for their material characteristics such as high strength-to-weight ratio, stiffness-to-weight, sound transmission, and other properties. Honeycomb structures are generally constructed from periodically spaced tessellations of unit cells. It can be shown that the effective stiffness and mass properties of honeycomb are controlled by the local geometry and wall thickness of the particular unit cells used. Of particular interest are regular hexagonal (6-sided) honeycomb unit cell geometries which exhibit positive effective Poisson's ratio, and modified 6-sided auxetic honeycomb unit cells with Poisson's ratio which is effectively negative; a property not found in natural materials. One important honeycomb meta-structure is sandwich composites designed with a honeycomb core bonded between two panel layers. By changing the geometry of the repetitive unit cell, and overall depth and material properties of the honeycomb core, sandwich panels with different vibration and acoustic properties can be designed to shift resonant frequencies and improve intensity and Sound Transmission Loss (STL). In the present work, a honeycomb finite element model based on beam elements is programmed in MATLAB and verified with the commercial finite element software ABAQUS for frequency extraction and direct frequency response analysis. The MATLAB program was used to study the vibration and acoustic properties of different kinds of honeycomb sandwich panels undergoing in-plane loading with different incident pressure wave angles and frequency. Results for the root mean square intensity IRMS based on normal velocity on the transmitted side of the panel measure vibration magnitude are reported for frequencies between 0 and 1000 Hz. The relationship between the sound transmission loss computed with ABAQUS and the inverse of the intensity of surface velocity is established. In the present work it is demonstrated that the general trend between the

  2. Low-Velocity Impact on Composite Sandwich Plates

    DTIC Science & Technology

    1996-07-01

    plate and correct for this error. 3.4 One- and Two-Degree of Freedom Models A single degree of freedom system (figure 3-3a) was used by Caprino et al...Composite Materials, Vol. 26, No. 10: 1523-1535 (1992). 211) Caprino , G., and Teti, R. "Impact and post-impact behavior of foam core sandwich

  3. Fluid Structure Interaction Effect on Sandwich Composite Structures

    DTIC Science & Technology

    2011-09-01

    14. SUBJECT TERMS Fluid Structure Interaction, FSI, composite, balsa, low velocity impact, sandwich composites, VARTM , Vacuum Assisted Resin Transfer...11 1. Vacuum Assisted Resin Transfer Molding ( VARTM ) ...................11 2. Procedure...required equipment for VARTM composite production. ..............10 Figure 4. VARTM Lay-up (From [8

  4. Damage Tolerance of Sandwich Plates With Debonded Face Sheets

    NASA Technical Reports Server (NTRS)

    Sankar, Bhavani V.

    2001-01-01

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

  5. Modular container assembled from fiber reinforced thermoplastic sandwich panels

    DOEpatents

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

    2007-12-25

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

  6. Star cell type core configuration for structural sandwich materials

    DOEpatents

    Christensen, Richard M.

    1995-01-01

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

  7. Flexural Strength of Functionally Graded Nanotube Reinforced Sandwich Spherical Panel

    NASA Astrophysics Data System (ADS)

    Mahapatra, Trupti R.; Mehar, Kulmani; Panda, Subrata K.; Dewangan, S.; Dash, Sushmita

    2017-02-01

    The flexural behaviour of the functionally graded sandwich spherical panel under uniform thermal environment has been investigated in the present work. The face sheets of the sandwich structure are made by the functionally graded carbon nanotube reinforced material and the core face is made by the isotropic and homogeneous material. The material properties of both the fiber and matrix are assumed to be temperature dependent. The sandwich panel model is developed in the framework of the first order shear deformation theory and the governing equation of motion is derived using the variational principle. For the discretization purpose a suitable shell element has been employed from the ANSYS library and the responses are computed using a parametric design language (APDL) coding. The performance and accuracy of the developed model has been established through the convergence and validation by comparing the obtained results with previously published results. Finally, the influence of different geometrical parameters and material properties on the flexural behaviour of the sandwich spherical panel in thermal environment has been investigated through various numerical illustrations and discussed in details.

  8. Hepatocytes in collagen sandwich: evidence for transcriptional and translational regulation

    PubMed Central

    1992-01-01

    The influence of extracellular matrix configuration on the tissue- specific function of cultured hepatocytes was investigated. Adult rat hepatocytes sandwiched between two layers of collagen gel were compared to cells cultured on a single layer of collagen gel for differences in the total RNA content, the level of albumin-specific mRNA, the rate of albumin gene transcription, and the rate of albumin mRNA translation. Adult hepatocytes in the sandwich system maintained the level of albumin mRNA similar to that found in the normal liver for at least six weeks, whereas the level of albumin mRNA declined rapidly in the single gel system. After one week of culture, hepatocytes in the single gel system could be induced to recover the high level of albumin mRNA and albumin production when a second layer of collagen gel was overlaid at that time. Furthermore, sandwiched hepatocytes maintained significantly higher transcriptional activity compared to cells in the single gel system. In addition to transcriptional control, the ultimate rate of albumin production was shown to depend on the rate of translation, which increased with culture time and reached a plateau in one to two weeks. This increase in translational activity over time in culture was observed in both the sandwich and the single gel systems and, thus, appeared to be independent of the configuration of extracellular matrix. PMID:1734019

  9. Damage Tolerance of Sandwich Plates with Debonded Face Sheets

    NASA Technical Reports Server (NTRS)

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

    1998-01-01

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

  10. Detection of entrapped moisture in honeycomb sandwich structures

    NASA Technical Reports Server (NTRS)

    Hallmark, W. B.

    1967-01-01

    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.

  11. Composite Cocured Modular Eggcrate-Core Sandwich Structure

    NASA Technical Reports Server (NTRS)

    Magurany, Charles J.

    1995-01-01

    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.

  12. Structural Response of Marine Sandwich Panels to Uniform Pressure Loading

    DTIC Science & Technology

    1990-06-01

    PROPERTIES OF SANDWICH PANEL FACES ............. 110 4 .2. P A N E L T E ST S...10 5 Figure 3-57: Comparison of Panel Lower Face Strain Rates During Static P ressu re T est...C yclic P ressure T est ................................................................................... 106 Figure 3-59: Comparison of Panel Lower

  13. Dielectrophoretic behaviours of microdroplet sandwiched between LN substrates

    PubMed Central

    Chen, Lipin; Li, Shaobei; Fan, Bolin; Yan, Wenbo; Wang, Donghui; Shi, Lihong; Chen, Hongjian; Ban, Dechao; Sun, Shihao

    2016-01-01

    We demonstrate a sandwich configuration for microfluidic manipulation in LiNbO3 platform based on photovoltaic effect, and the behaviours of dielectric microdroplet under this sandwich configuration are investigated. It is found that the microdroplet can generate in the form of liquid bridge inside the LiNbO3-based sandwich structure under the governing dielectrophoretic force, and the dynamic process of microdroplet generation highly depends on the substrate combinations. Dynamic features found for different combinations are explained by the different electrostatic field distribution basing on the finite-element simulation results. Moreover, the electrostatic field required by the microdroplet generation is estimated through meniscus evolution and it is found in good agreement with the simulated electrostatic field inside the sandwich gap. Several kinds of microdroplet manipulations are attempted in this work. We suggest that the local dielectrophoretic force acting on the microdroplet depends on the distribution of the accumulated irradiation dosage. Without using any additional pumping or jetting actuator, the microdroplet can be step-moved, deformed or patterned by the inconsecutive dot-irradiation scheme, as well as elastically stretched out and back or smoothly guided in a designed pass by the consecutive line-irradiation scheme. PMID:27383027

  14. Dielectrophoretic behaviours of microdroplet sandwiched between LN substrates

    NASA Astrophysics Data System (ADS)

    Chen, Lipin; Li, Shaobei; Fan, Bolin; Yan, Wenbo; Wang, Donghui; Shi, Lihong; Chen, Hongjian; Ban, Dechao; Sun, Shihao

    2016-07-01

    We demonstrate a sandwich configuration for microfluidic manipulation in LiNbO3 platform based on photovoltaic effect, and the behaviours of dielectric microdroplet under this sandwich configuration are investigated. It is found that the microdroplet can generate in the form of liquid bridge inside the LiNbO3-based sandwich structure under the governing dielectrophoretic force, and the dynamic process of microdroplet generation highly depends on the substrate combinations. Dynamic features found for different combinations are explained by the different electrostatic field distribution basing on the finite-element simulation results. Moreover, the electrostatic field required by the microdroplet generation is estimated through meniscus evolution and it is found in good agreement with the simulated electrostatic field inside the sandwich gap. Several kinds of microdroplet manipulations are attempted in this work. We suggest that the local dielectrophoretic force acting on the microdroplet depends on the distribution of the accumulated irradiation dosage. Without using any additional pumping or jetting actuator, the microdroplet can be step-moved, deformed or patterned by the inconsecutive dot-irradiation scheme, as well as elastically stretched out and back or smoothly guided in a designed pass by the consecutive line-irradiation scheme.

  15. Methods for Assessing Honeycomb Sandwich Panel Wrinkling Failures

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

    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.

  16. Damage tolerance of a composite sandwich with interleaved foam core

    NASA Technical Reports Server (NTRS)

    Ishai, Ori; Hiel, Clement

    1992-01-01

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

  17. Stiff, Strong Splice For A Composite Sandwich Structure

    NASA Technical Reports Server (NTRS)

    Schmaling, D.

    1991-01-01

    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.

  18. Mechanical Behavior of CFRP Lattice Core Sandwich Bolted Corner Joints

    NASA Astrophysics Data System (ADS)

    Zhu, Xiaolei; Liu, Yang; Wang, Yana; Lu, Xiaofeng; Zhu, Lingxue

    2017-02-01

    The lattice core sandwich structures have drawn more attention for the integration of load capacity and multifunctional applications. However, the connection of carbon fibers reinforced polymer composite (CFRP) lattice core sandwich structure hinders its application. In this paper, a typical connection of two lattice core sandwich panels, named as corner joint or L-joint, was investigated by experiment and finite element method (FEM). The mechanical behavior and failure mode of the corner joints were discussed. The results showed that the main deformation pattern and failure mode of the lattice core sandwich bolted corner joints structure were the deformation of metal connector and indentation of the face sheet in the bolt holes. The metal connectors played an important role in bolted corner joints structure. In order to save the calculation resource, a continuum model of pyramid lattice core was used to replace the exact structure. The computation results were consistent with experiment, and the maximum error was 19%. The FEM demonstrated the deflection process of the bolted corner joints structure visually. So the simplified FEM can be used for further analysis of the bolted corner joints structure in engineering.

  19. [Molecular cloning, prokaryotic expression and double-antibody sandwich ELISA development of 17β-hsd10 in mouse].

    PubMed

    Liu, Chuanzhi; Niu, Yingying; Chen, Yuan'an; Wu, Cheng; Yu, Yuanhua

    2014-11-01

    We expressed 17-hydroxysteroid dehydrogenase10 (17β-hsd10) recombinant protein, prepared anti-17β- hsd10 polyclonal antibodies and established sandwich enzyme linked immunosorbent assay (ELISA) test for detection of 17β-hsd10. RT-PCR was used to get the gene of 17β-hsd10 of mouse liver, and a prokaryotic protein expression system pET 15b-17β-hsd10/Escherichia coli BL21 (DE3) which induced with isopropyl-1-thio-β-galactopyranoside (IPTG) for recombinant protein expression was constructed subsequently. The target protein purified using His-Binding-resin column was used to immunize BALB/c mice and rabbits, serum total IgGs from immunized animals were purified by ammonium sulfate precipitation method. We established a Double-antibody Sandwich enzyme linked immunosorbent assay about 17β-hsd10 using the two antibodies we prepared. We got the concentration of 1.5 mg/mL of 17β-hsd10 protein with molecular weight of 29.5 kDa, and polyclonal antibodies from mouse and rabbit with the tite 1.25 x 10(4) and 2.5 x 10(4) respectively. The concentration of 0.1 g/mL of 17β-hsd10 can be detected by the Double-antibody Sandwich ELISA we established, and the assay was sensitive and specific. It can be widely used in clinical and experimental study.

  20. High-performance ultraviolet photodetectors based on solution-grown ZnS nanobelts sandwiched between graphene layers

    PubMed Central

    Kim, Yeonho; Kim, Sang Jin; Cho, Sung-Pyo; Hong, Byung Hee; Jang, Du-Jeon

    2015-01-01

    Ultraviolet (UV) light photodetectors constructed from solely inorganic semiconductors still remain unsatisfactory because of their low electrical performances. To overcome this limitation, the hybridization is one of the key approaches that have been recently adopted to enhance the photocurrent. High-performance UV photodetectors showing stable on-off switching and excellent spectral selectivity have been fabricated based on the hybrid structure of solution-grown ZnS nanobelts and CVD-grown graphene. Sandwiched structures and multilayer stacking strategies have been applied to expand effective junction between graphene and photoactive ZnS nanobelts. A multiply sandwich-structured photodetector of graphene/ZnS has shown a photocurrent of 0.115 mA under illumination of 1.2 mWcm−2 in air at a bias of 1.0 V, which is higher 107 times than literature values. The multiple-sandwich structure of UV-light sensors with graphene having high conductivity, flexibility, and impermeability is suggested to be beneficial for the facile fabrication of UV photodetectors with extremely efficient performances. PMID:26197784

  1. Elastic stability of superplastically formed/diffusion-bonded orthogonally corrugated core sandwich plates

    NASA Technical Reports Server (NTRS)

    Ko, W. L.

    1980-01-01

    The paper concerns the elastic buckling behavior of a newly developed superplastically formed/diffusion-bonded (SPF/DB) orthogonally corrugated core sandwich plate. Uniaxial buckling loads were calculated for this type of sandwich plate with simply supported edges by using orthotropic sandwich plate theory. The buckling behavior of this sandwich plate was then compared with that of an SPF/DB unidirectionally corrugated core sandwich plate under conditions of equal structural density. It was found that the buckling load for the former was considerably higher than that of the latter.

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

    NASA Technical Reports Server (NTRS)

    Ko, William L.; Jackson, Raymond H.

    1993-01-01

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

  3. A novel self-assembled sandwich nanomedicine for NIR-responsive release of NO.

    PubMed

    Fan, Jing; He, Nongyue; He, Qianjun; Liu, Yi; Ma, Ying; Fu, Xiao; Liu, Yijing; Huang, Peng; Chen, Xiaoyuan

    2015-12-21

    A novel sandwich nanomedicine (GO-BNN6) for near-infrared (NIR) light responsive release of nitric oxide (NO) has been constructed by self-assembly of graphene oxide (GO) nanosheets and a NO donor BNN6 through the π-π stacking interaction. The GO-BNN6 nanomedicine has an extraordinarily high drug loading capacity (1.2 mg BNN6 per mg GO), good thermal stability, and high NIR responsiveness. The NO release from GO-BNN6 can be easily triggered and effectively controlled by adjusting the switching, irradiation time and power density of NIR laser. The intracellular NIR-responsive release of NO from the GO-BNN6 nanomedicine causes a remarkable anti-cancer effect.

  4. Novel self-assembled sandwich nanomedicine for NIR-responsive release of NO

    PubMed Central

    Fan, Jing; He, Qianjun; Liu, Yi; Ma, Ying; Fu, Xiao; Liu, Yijing; Huang, Peng; He, Nongyue; Chen, Xiaoyuan

    2015-01-01

    A novel sandwich nanomedicine (GO-BNN6) for near-infrared (NIR) light responsive release of nitric oxide (NO) has been constructed by self-assembling of graphene oxide (GO) nanosheets and a NO donor BNN6 through the π-π stacking interaction. GO-BNN6 nanomedicine has an extraordinarily high drug loading capacity (1.2 mg BNN6 per mg GO), good thermal stability, and high NIR responsiveness. The NO release from GO-BNN6 can be easily triggered and effectively controlled by adjusting the switching, irradiation time and power density of NIR laser. The intracellular NIR-responsive release of NO from GO-BNN6 nanomedicine causes a remarkable anti-cancer effect. PMID:26568270

  5. Analyses of sandwich beams and plates with viscoelastic cores

    NASA Astrophysics Data System (ADS)

    Wang, Gang

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

  6. A novel self-assembled sandwich nanomedicine for NIR-responsive release of NO

    NASA Astrophysics Data System (ADS)

    Fan, Jing; He, Nongyue; He, Qianjun; Liu, Yi; Ma, Ying; Fu, Xiao; Liu, Yijing; Huang, Peng; Chen, Xiaoyuan

    2015-11-01

    A novel sandwich nanomedicine (GO-BNN6) for near-infrared (NIR) light responsive release of nitric oxide (NO) has been constructed by self-assembly of graphene oxide (GO) nanosheets and a NO donor BNN6 through the π-π stacking interaction. The GO-BNN6 nanomedicine has an extraordinarily high drug loading capacity (1.2 mg BNN6 per mg GO), good thermal stability, and high NIR responsiveness. The NO release from GO-BNN6 can be easily triggered and effectively controlled by adjusting the switching, irradiation time and power density of NIR laser. The intracellular NIR-responsive release of NO from the GO-BNN6 nanomedicine causes a remarkable anti-cancer effect.A novel sandwich nanomedicine (GO-BNN6) for near-infrared (NIR) light responsive release of nitric oxide (NO) has been constructed by self-assembly of graphene oxide (GO) nanosheets and a NO donor BNN6 through the π-π stacking interaction. The GO-BNN6 nanomedicine has an extraordinarily high drug loading capacity (1.2 mg BNN6 per mg GO), good thermal stability, and high NIR responsiveness. The NO release from GO-BNN6 can be easily triggered and effectively controlled by adjusting the switching, irradiation time and power density of NIR laser. The intracellular NIR-responsive release of NO from the GO-BNN6 nanomedicine causes a remarkable anti-cancer effect. Electronic supplementary information (ESI) available: NMR and MS data of BNN6, stability of GO-BNN6, NIR-responsibility comparison of BNN6 and GO-BNN6, and NMR spectrum of RBSP. See DOI: 10.1039/c5nr06630a

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

    NASA Technical Reports Server (NTRS)

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

    1979-01-01

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

  8. Fatigue and impact properties of metal honeycomb sandwich panel

    NASA Astrophysics Data System (ADS)

    Zou, Guang ping; Lu, Jie; Liang, Jun; Chang, Zhong liang

    2008-11-01

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

  9. Development of lightweight graphite/polyimide sandwich panels.

    NASA Technical Reports Server (NTRS)

    Poesch, J. G.

    1972-01-01

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

  10. Star cell type core configuration for structural sandwich materials

    DOEpatents

    Christensen, R.M.

    1995-08-01

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

  11. Graphene Sandwiched Mesostructured Li-Ion Battery Electrodes.

    PubMed

    Liu, Jinyun; Zheng, Qiye; Goodman, Matthew D; Zhu, Haoyue; Kim, Jinwoo; Krueger, Neil A; Ning, Hailong; Huang, Xingjiu; Liu, Jinhuai; Terrones, Mauricio; Braun, Paul V

    2016-09-01

    A deterministic graphene-sandwiched Li-ion battery electrode consisting of an integrated 3D mesostructure of electrochemically active materials and graphene is presented. As demonstrations, electrodes with active nanomaterials that coat (V2 O5 @graphene@V2 O5 cathode) or are coated by (graphene@Si@graphene anode) graphene are fabricated. These electrodes exhibit high capacities and ultralong cycle lives (the cathode can be cycled over 2000 times with minimal capacity fade).

  12. Pulled from all sides: The sandwich generation at work.

    PubMed

    O'Sullivan, Ann

    2015-01-01

    Employees who are members of the "sandwich generation", those who are raising children and assisting older adult family members, are a population at risk for issues related to physical and emotional health, balancing work and family responsibilities, and taking care of themselves. This commentary examines their situation and challenges, some of the potential negative effects of these compounded stressors, and recommends strategies that employers, families, and the individuals themselves can use to create a sustainable work/caregiving situation.

  13. Making Three-Layer Solid Electrolyte/Electrode Sandwiches

    NASA Technical Reports Server (NTRS)

    Schroeder, James E.

    1991-01-01

    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.

  14. Design of highly damage-tolerant sandwich panels

    NASA Astrophysics Data System (ADS)

    Hiel, Clement; Ishai, Ori

    The effects of different fabrication procedures to increase the damage tolerance of sandwich panels were studied. Baseline panels consisted of a 25.4 mm premolded core, surfaced with 177 C cure film adhesive and carbon-bismaleimide prepreg which were subsequently cocured onto the core. It was found that panels with a prefabricated skin, which was subsequently bonded onto the core with room temperature cure adhesive, showed greatly increased damage tolerance.

  15. Composite Sandwich Structures for Shock Mitigation and Energy Absorption

    DTIC Science & Technology

    2016-06-28

    examined. In the second or continuation grant period (July 2014 to Apri I 20 16), the research was extended to address the behavior of composite sandwich...understand the crush behavior and hysteresis of PVC foams. MAJOR ACCOMPLISHMENTS The following sections summarizes research findings , and are...numerical damping in ABAQUS 2 Expl icit, and that only the initial transient behavior up to the first peak deflection and/or core strain shou ld

  16. Sandwiched Rényi divergence satisfies data processing inequality

    NASA Astrophysics Data System (ADS)

    Beigi, Salman

    2013-12-01

    Sandwiched (quantum) α-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 arXiv:1306.1586 (2013)] and Müller-Lennert et al. ["On quantum Rényi entropies: a new definition, some properties and several conjectures," preprint 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 α-Rényi divergence satisfies the data processing inequality for all values of α > 1. Moreover we prove that α-Holevo information, a variant of Holevo information defined in terms of sandwiched α-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.

  17. Novel MRE/CFRP sandwich structures for adaptive vibration control

    NASA Astrophysics Data System (ADS)

    Kozlowska, J.; Boczkowska, A.; Czulak, A.; Przybyszewski, B.; Holeczek, K.; Stanik, R.; Gude, M.

    2016-03-01

    The aim of this work was the development of sandwich structures formed by embedding magnetorheological elastomers (MRE) between constrained layers of carbon fibre-reinforced plastic (CFRP) laminates. The MREs were obtained by mechanical stirring of a reactive mixture of substrates with carbonyl-iron particles, followed by orienting the particles into chains under an external magnetic field. Samples with particle volume fractions of 11.5% and 33% were examined. The CFRP/MRE sandwich structures were obtained by compressing MREs samples between two CFRP laminates composed. The used A.S.SET resin was in powder form and the curing process was carried out during pressing with MRE. The microstructure of the manufactured sandwich beams was inspected using SEM. Moreover, the rheological and damping properties of the examined materials with and without a magnetic field were experimentally investigated. In addition, the free vibration responses of the adaptive three-layered MR beams were studied at different fixed magnetic field levels. The free vibration tests revealed that an applied non-homogeneous magnetic field causes a shift in natural frequency values and a reduction in the vibration amplitudes of the CFRP/MRE adaptive beams. The reduction in vibration amplitude was attributed mainly to the stiffening effect of the MRE core and only a minor contribution was made by the enhanced damping capacity, which was evidenced by the variation in damping ratio values.

  18. Size Effects in Impact Damage of Composite Sandwich Panels

    NASA Technical Reports Server (NTRS)

    Dobyns, Alan; Jackson, Wade

    2003-01-01

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

  19. Sandwiched Rényi divergence satisfies data processing inequality

    SciTech Connect

    Beigi, Salman

    2013-12-15

    Sandwiched (quantum) α-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 α-Rényi divergence satisfies the data processing inequality for all values of α > 1. Moreover we prove that α-Holevo information, a variant of Holevo information defined in terms of sandwiched α-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.

  20. Hypervelocity Impact Evaluation of Metal Foam Core Sandwich Structures

    NASA Technical Reports Server (NTRS)

    Yasensky, John; Christiansen, Eric L.

    2007-01-01

    A series of hypervelocity impact (HVI) tests were conducted by the NASA Johnson Space Center (JSC) Hypervelocity Impact Technology Facility (HITF) [1], building 267 (Houston, Texas) between January 2003 and December 2005 to test the HVI performance of metal foams, as compared to the metal honeycomb panels currently in service. The HITF testing was conducted at the NASA JSC White Sands Testing Facility (WSTF) at Las Cruces, New Mexico. Eric L. Christiansen, Ph.D., and NASA Lead for Micro-Meteoroid Orbital Debris (MMOD) Protection requested these hypervelocity impact tests as part of shielding research conducted for the JSC Center Director Discretionary Fund (CDDF) project. The structure tested is a metal foam sandwich structure; a metal foam core between two metal facesheets. Aluminum and Titanium metals were tested for foam sandwich and honeycomb sandwich structures. Aluminum honeycomb core material is currently used in Orbiter Vehicle (OV) radiator panels and in other places in space structures. It has many desirable characteristics and performs well by many measures, especially when normalized by density. Aluminum honeycomb does not perform well in Hypervelocity Impact (HVI) Testing. This is a concern, as honeycomb panels are often exposed to space environments, and take on the role of Micrometeoroid / Orbital Debris (MMOD) shielding. Therefore, information on possible replacement core materials which perform adequately in all necessary functions of the material would be useful. In this report, HVI data is gathered for these two core materials in certain configurations and compared to gain understanding of the metal foam HVI performance.

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

    NASA Technical Reports Server (NTRS)

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

    2004-01-01

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

  2. General stability analysis of composite sandwich plates under thermal load

    NASA Astrophysics Data System (ADS)

    Abdallah, Shaher A.

    In structures subjected to high temperature change such as high-speed aircraft the panels are stressed more significantly under thermal loading than mechanical loading. This can produce instability within the structure; therefore, the thermal loading may become the primary factor in the design of the structure. For example, buckling and facesheet wrinkling are two major failure modes of the composite sandwich plates subjected to various loadings. The goal of this dissertation is to study the stability analysis of composite sandwich plates due to buckling and wrinkling subjected to thermal loading. The primary objective is to find out the critical failure mode and the associated critical temperature change causing it. For thermal buckling and wrinkling analysis, the critical temperature change Delta Tcr, is of more interest than the critical thermal load. In this study, two different approaches of the stability problem of the composite sandwich plate subjected to thermally induced load are developed. In the first approach, the wrinkling analysis and buckling analysis are performed separately to evaluate their associated critical wrinkling and buckling temperature changes. For the face-wrinkling problem, two different models, the linear decaying Hoff model and exponential decaying Chen model are employed. The global buckling analysis is based on the energy method. The second approach is based on the unified theory of Benson and Mayers. In such an approach, the critical temperature change for both the global buckling and face wrinkling can be evaluated simultaneously. A potential energy based variation principle has been applied to formulate the problem. The Lagrange multipliers are used to satisfy the face-core continuity conditions. The buckling and wrinkling can be analyzed and calculated simultaneously. Therefore, the critical wrinkling temperature and the critical buckling temperature are found in a single analysis. The critical buckling and wrinkling stresses

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

    NASA Astrophysics Data System (ADS)

    Rakow, Joseph F.

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

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

    SciTech Connect

    Ichinomiya, Osamu; Maruyama, Koichi; Sekine, Kouji

    1995-11-01

    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.

  5. Synthesis and characterization of a 1D chain-like Cu{sub 6} substituted sandwich-type phosphotungstate with pendant dinuclear Cu–azido complexes

    SciTech Connect

    Li, Yan-Ying; Zhao, Jun-Wei; Wei, Qi; Yang, Bai-Feng; Yang, Guo-Yu

    2014-02-15

    A novel Cu–azido complex modified hexa-Cu{sup II} substituted sandwich-type phosphotungstate [Cu(en){sub 2}]([Cu{sub 2}(en){sub 2}(μ-1,1-N{sub 3}){sub 2}(H{sub 2}O)]{sub 2}[Cu{sub 6}(en){sub 2}(H{sub 2}O){sub 2}(B-α-PW{sub 9}O{sub 34}){sub 2}])·6H{sub 2}O (1) (en=ethylene-diamine) has been prepared under hydrothermal conditions and structurally characterized by elemental analyses, IR spectra, powder X-ray diffraction (PXRD) and single-crystal X-ray diffraction. 1 displays a beautiful 1-D chain architecture constructed from sandwich-type [Cu{sub 2}(en){sub 2}(μ-1,1-N{sub 3}){sub 2}(H{sub 2}O)]{sub 2}[Cu{sub 6}(en){sub 2}(H{sub 2}O){sub 2}(B-α-PW{sub 9}O{sub 34}){sub 2}]{sup 2−} units and [Cu(en){sub 2}]{sup 2+} linkers. To our knowledge, 1 represents the first hexa-Cu{sup II} sandwiched phosphotungstate with supporting Cu–azido complexes. - Graphical abstract: The first hexa-Cu{sup II} sandwiched phosphotungstate with supporting Cu–azido complexes has been prepared and characterized. Display Omitted - Highlights: • Hexa-copper-substituted phosphotungstate. • Cu–azido complexes modified hexa-Cu{sup II} substituted sandwich-type polyoxometalate. • 1-D chain architecture built by hexa-copper-substituted polyoxotungstate units.

  6. Effects of Subzero Temperatures and Sea Water Immersion on Damage Initiation and Growth in Sandwich Composites

    DTIC Science & Technology

    2008-12-10

    single cantilever beam sandwich test. The TSD is perhaps 19 An improved methodology for measuring the interracial toughness of sandwich beams 3...measuring the interracial toughness of sandwich beams 5 Table 4.1. Material properties Glass face Glass face Carbon „ , ,, Loading L...which shows the relationship between reaction forces for an MSCB specimen with 12 ply glass face sheets at different crack lengths. It is observed

  7. Performance and Characterization of Shear Ties for Use in Insulated Precast Concrete Sandwich Wall Panels

    DTIC Science & Technology

    2010-11-01

    AFRL-RX-TY-TP-2010-0082 PERFORMANCE AND CHARACTERIZATION OF SHEAR TIES FOR USE IN INSULATED PRECAST CONCRETE SANDWICH WALL PANELS...of Shear Ties for Use in Insulated Precast Concrete Sandwich Wall Panels (PREPRINT) FA8903-08-D-8768-0002 0909999F GOVT F0 QF101000 #Naito, Clay...PERFORMANCE AND CHARACTERIZATION OF SHEAR TIES FOR USE IN 1 INSULATED PRECAST CONCRETE SANDWICH WALL PANELS 2 Clay Naito1, John Hoemann2, Mark Beacraft3

  8. Lightweight composites for modular panelized construction

    NASA Astrophysics Data System (ADS)

    Vaidya, Amol S.

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

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

    NASA Technical Reports Server (NTRS)

    Bush, H. G.

    1975-01-01

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

  10. Damping Properties of Sandwich Truss Core Structures by Strain Energy Method

    NASA Astrophysics Data System (ADS)

    Wesolowski, M.; Rucevskis, S.; Janeliukstis, R.; Polanski, M.

    2015-11-01

    Sandwich panel structures with stiff face sheets and cellular cores are widely used to support dynamic loads. Combining face sheets made of carbon fibre reinforced plastics (CFRPs) with an aluminium pyramidal truss improves the damping performance of the structure due to viscoelastic character of CRFP composites. To predict the damping characteristics of the pyramidal truss core sandwich panel the strain energy method is adopted. The procedure for evaluating the damping of the sandwich panel was performed using commercial finite element software NASTRAN and MATLAB. Non-contact vibration tests were performed on the real sandwich panels in order to extract the modal characteristics and compare them with the numerical predictions.

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

    NASA Technical Reports Server (NTRS)

    2010-01-01

    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

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

    NASA Astrophysics Data System (ADS)

    Sankar Ray, Tirtha

    As blast threats on military and civilian structures continue to be a significant concern, there remains a need for improved design strategies to increase blast resistance capabilities. The approach to blast resistance proposed here is focused on dissipating the high levels of pressure induced during a blast through maximizing the potential for energy absorption of composite sandwich panels, which are a competitive structural member type due to the inherent energy absorption capabilities of fiber reinforced polymer (FRP) composites. Furthermore, the middle core in the sandwich panels can be designed as a sacrificial layer allowing for a significant amount of deformation or progressive failure to maximize the potential for energy absorption. The research here is aimed at the optimization of composite sandwich panels for blast mitigation via energy absorption mechanisms. The energy absorption mechanisms considered include absorbed strain energy due to inelastic deformation as well as energy dissipation through progressive failure of the core of the sandwich panels. The methods employed in the research consist of a combination of experimentally-validated finite element analysis (FEA) and the derivation and use of a simplified analytical model. The key components of the scope of work then includes: establishment of quantified energy absorption criteria, validation of the selected FE modeling techniques, development of the simplified analytical model, investigation of influential core architectures and geometric parameters, and investigation of influential material properties. For the parameters that are identified as being most-influential, recommended values for these parameters are suggested in conceptual terms that are conducive to designing composite sandwich panels for various blast threats. Based on reviewing the energy response characteristic of the panel under blast loading, a non-dimensional parameter AET/ ET (absorbed energy, AET, normalized by total energy

  13. Low Velocity Blunt Impact on Lightweight Composite Sandwich Panels

    NASA Astrophysics Data System (ADS)

    Chan, Monica Kar

    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.

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

    NASA Technical Reports Server (NTRS)

    Nettles, A. T.

    2006-01-01

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

  15. Optimization of the curing process of a sandwich panel

    NASA Astrophysics Data System (ADS)

    Phyo Maung, Pyi; Tatarnikov, O.; Malysheva, G.

    2016-10-01

    This study presented finite element modelling and experimental measurements of temperatures during the autoclave curing of the T-50 aircraft wing sandwich panel. This panel consists of upper and lower carbon fibre based laminates and an aluminium foil honeycomb. The finite element modelling was performed using the Femap-Nastran product. During processing, the temperature at various points on the surface of the panel was measured using the thermocouples. The finite element method simulated the thermal conditions and determined the temperatures in the different parts of the panel for a full cycle of the curing process. A comparison of the calculated and experimental data shows that their difference does not exceed 6%.

  16. Deformation and fracture of impulsively loaded sandwich panels

    NASA Astrophysics Data System (ADS)

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

    2013-02-01

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

  17. A Flow SPR Immunosensor Based on a Sandwich Direct Method

    PubMed Central

    Tomassetti, Mauro; Conta, Giorgia; Campanella, Luigi; Favero, Gabriele; Sanzò, Gabriella; Mazzei, Franco; Antiochia, Riccarda

    2016-01-01

    In this study, we report the development of an SPR (Surface Plasmon Resonance) immunosensor for the detection of ampicillin, operating under flow conditions. SPR sensors based on both direct (with the immobilization of the antibody) and competitive (with the immobilization of the antigen) methods did not allow the detection of ampicillin. Therefore, a sandwich-based sensor was developed which showed a good linear response towards ampicillin between 10−3 and 10−1 M, a measurement time of ≤20 min and a high selectivity both towards β-lactam antibiotics and antibiotics of different classes. PMID:27187486

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

    PubMed

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

    2015-09-01

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

  19. Devices, systems, and methods for conducting sandwich assays using sedimentation

    SciTech Connect

    Schaff, Ulrich Y; Sommer, Gregory J; Singh, Anup K; Hatch, Anson V

    2015-02-03

    Embodiments of the present invention are directed toward devices, systems, and method for conducting sandwich assays using sedimentation. In one example, a method includes generating complexes on a plurality of beads in a fluid sample, individual ones of the complexes comprising a capture agent, a target analyte, and a labeling agent. The plurality of beads including the complexes may be transported through a density media, wherein the density media has a density lower than a density of the beads and higher than a density of the fluid sample, and wherein the transporting occurs, at least in part, by sedimentation. Signal may be detected from the labeling agents of the complexes.

  20. Sandwich Hologram Interferometry For Determination Of Sacroiliac Joint Movements

    NASA Astrophysics Data System (ADS)

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

    1983-12-01

    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 μm to 1.5 mm.

  1. Longitudinal and transverse bending by a cylindrical shape of the sandwich plate stiffened in the end sections by rigid bodies

    NASA Astrophysics Data System (ADS)

    Badriev, I. B.; Makarov, M. V.; Paimuhin, V. N.

    2016-11-01

    We study the problems of deformation mechanics of sandwich constructions with taking into account the interaction with the contour reinforcing rods. To derive the basic equations of equilibrium, static boundary conditions for the shell and reinforcing rods, as well as conditions of the kinematic conjugation the carrier layers with a core, the carrier layers and a core with reinforcing rods we use a generalized variational Lagrange principle. We reduce the boundary value problem on the to the integral-algebraic system of Volterra equations of the second kind. To approximate the obtained integral equations of Volterra type a collocation method with Gaussian nodes and a method for constructing the integrating matrices are proposed. For the numerical realization of the proposed methods we have developed a software package. Numerical calculations were performed. Analyze the results of numerical experiments is carried out.

  2. Automated fringe analysis in diffusivity measurements by sandwich holography

    NASA Astrophysics Data System (ADS)

    Paoletti, Domenica; Schirripa Spagnolo, Giuseppe; Laurenti, Lucio; Ponticiello, Antonio

    1992-09-01

    An image processing system to analyze interference patterns, related to the measurement of diffusion coefficient of liquid binary mixtures by sandwich holography, is proposed. Basic image processing tools are used and a specific software has been developed to perform an automated analysis of interferometric data. An example of application of this electrooptical method to the measurement of the diffusion coefficient of LiBr is reported. On propose un système de traitement d'images pour analyser des modèles d'interférence par rapport à la mesure du coefficient de diffusion des mélanges liquides binaires, obtenue suivant la technique de l'holographie sandwich. Les appareils et les outils utilisés sont standard tandis que le logiciel spécifique pour l'analyse automatique des données interférométriques acquises a été développé ad hoc. Un exemple d'application de cette méthode électro-optique a regardé la mesure du coefficient de diffusion du LiBr.

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

    NASA Technical Reports Server (NTRS)

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

    2000-01-01

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

  4. Plasmonic nanomesh sandwiches for ultrathin film silicon solar cells

    NASA Astrophysics Data System (ADS)

    Gao, Tongchuan; Wang, Baomin; Leu, Paul W.

    2017-02-01

    We theoretically investigate the strategy of integrating metal nanoparticles (NPs)/nanomeshes (NMs) into the top and/or bottom of crystalline silicon (c-Si) thin film solar cells for light trapping and enhanced carrier collection. C-Si thin films exhibit absorption resonances corresponding to Fabry-Pérot modes. Frontside metal NPs enhance absorption by additionally coupling light into localized surface plasmon resonances and c-Si waveguide modes, while a frontside metal NM increases absorption by coupling light into surface plasmon polaritons and c-Si waveguide modes. The frontside metal NM also functions as a flexible top electrode, which may replace conventional brittle transparent conductive oxide thin films. The backside metal NM exhibits enhanced absorption due to the coupling of light into c-Si waveguide modes and the cavity modes within the holes of metal NM. We illustrate how the optimal metal NM sandwich, consisting of NMs on both sides of a 300 nm thick c-Si with an appropriate antireflection coating (ARC), achieves a 72.9% enhancement in short-circuit current density compared with that of a 300 nm thick c-Si thin film solar cell with 100 nm thick Si3N4 ARC and 300 nm thick Ag back reflector. The current generation in the metal NM sandwich is more in the center of the thin film such that there should be less surface recombination. The uniform current generation throughout the film results in less overall recombination.

  5. First record of a banded Sandwich Tern (Thalasseus sandvicensis) moving from England to the United States

    USGS Publications Warehouse

    Spendelow, Jeffrey A.

    2015-01-01

    A Sandwich Tern (Thalasseus sandvicensis sandvicensis) banded as a chick in 2002 at Coquet Island off the northeast coast of Great Britain was observed at two locations on Cape Cod, Massachusetts, USA, in August and September 2013. This is the first record of a banded Sandwich Tern from the United Kingdom being observed in the United States.

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

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

    PubMed

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

    2012-01-01

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

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

    PubMed Central

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

    2012-01-01

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

  9. Computed tomography with single-shot dual-energy sandwich detectors

    NASA Astrophysics Data System (ADS)

    Kim, Seung Ho; Youn, Hanbean; Kim, Daecheon; Kim, Dong Woon; Jeon, Hosang; Kim, Ho Kyung

    2016-03-01

    Single-shot dual-energy sandwich detector can produce sharp images because of subtraction of images from two sub-detector layers, which have different thick x-ray converters, of the sandwich detector. Inspired by this observation, the authors have developed a microtomography system with the sandwich detector in pursuit of high-resolution bone-enhanced small-animal imaging. The preliminary results show that the bone-enhanced images reconstructed with the subtracted projection data are better in visibility of bone details than the conventionally reconstructed images. In addition, the bone-enhanced images obtained from the sandwich detector are relatively immune to the artifacts caused by photon starvation. The microtomography with the single-shot dual-energy sandwich detector will be useful for the high-resolution bone imaging.

  10. Ocean Engineering Studies Compiled 1991. Volume 8. Pressure Hulls - Cellular Sandwich Construction

    DTIC Science & Technology

    1991-01-01

    rigid (less thanO.010-in. Although the internal mounting problem may radial deflection under maximum operational be solved by the use of proper mounting...joints, and hand- like local stiffeners, increasing the rigidity of hole openings and covers. Considerable thought the shell. Since radial shell...ference in radial deflections at various points ful shell design. Very rigid shells will need on the shell, the originally smooth vehicle en- some

  11. Small bending and stretching of sandwich-type shells

    NASA Technical Reports Server (NTRS)

    Reissner, Eric

    1950-01-01

    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.

  12. Vibration Control of Sandwich Beams Using Electro-Rheological Fluids

    NASA Astrophysics Data System (ADS)

    Srikantha Phani, A.; Venkatraman, K.

    2003-09-01

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

  13. Tailoring the Acoustic Properties of Truss-Core Sandwich Structure

    NASA Astrophysics Data System (ADS)

    Lee, Richard

    Undesirable cabin noise has an adverse physiological effect on passengers and crews in an aircraft. In order to reduce the noise level, a passive approach using a truss-core sandwich (TCS) panel as a sound insulator is proposed. Design guidelines and analysis methodologies were developed in order to explore the vibro-acoustic characteristics of TCS structure. Its sound isolation properties can be thereby assessed. Theoretical analyses show that the transmission-loss and sound radiation properties of a TCS structure can be represented by the root-mean-square velocity of its surface, and a beam structure analysis is sufficient to reveal many of the important aspects of TCS panel design. Using finite element analysis, a sensitivity study was performed to create design guidelines for TCS structures. Transmission-loss experiments show that the analytical and numerical analyses correctly predict the trend of TCS structure's vibro-acoustic performance.

  14. Prediction of the ballistic limit of an aluminium sandwich panel

    NASA Astrophysics Data System (ADS)

    Campbell, J.; De Vuyst, T.; Vignjevic, R.; Hughes, K.

    2016-08-01

    This paper presents research on modelling the impact of a 150g projectile on a 35mm thick aluminium sandwich panel. The objective of the work is a predictive modelling capability for the ballistic limit of the panel. A predictive modelling capability supports the design of capture and deorbit missions for large items of space debris such as satellites and rocket upper stages. A detailed explicit finite element model was built using the LSDYNA software and results were compared with experimental data for the projectile exit velocity to establish key parameters. The primary parameters influencing the model behaviour were the strength and failure of the aluminium face sheets and the friction between projectile and panel. The model results showed good agreement with experimental results for ogive nose projectiles, but overestimated the exit velocity for flat nose projectiles.

  15. Diffusion bonding of titanium-titanium aluminide-alumina sandwich

    SciTech Connect

    Wickman, H.A.; Chin, E.S.C.; Biederman, R.R.

    1995-12-31

    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.

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

    NASA Astrophysics Data System (ADS)

    Dosch, M.; Weller, Michael G.; Niessner, Reinhard

    1995-10-01

    Immunoassays are useful analytical instruments for the detection of many environmental compounds. This method is now 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.

  17. A sandwich structured SiO(2)/cytochrome c/SiO(2) on a boron-doped diamond film electrode as an electrochemical nitrite biosensor.

    PubMed

    Geng, Rong; Zhao, Guohua; Liu, Meichuan; Li, Mingfang

    2008-06-01

    A novel sandwich structured SiO(2) gel/cytochrome c (Cyt c)/SiO(2) gel was designed and constructed on conductive boron-doped diamond (BDD) film substrate. A SiO(2) gel membrane was first in situ deposited on the pretreated positive charged H-terminated BDD electrode with a simple and artful surface vapor sol-gel method. Cyt c was subsequently immobilized onto the SiO(2) membranes by electrostatic attraction, followed by another SiO(2) gel layer in situ depositing on it. The SiO(2) interlayer was conceived to play an important role in the resultant sandwich structured SiO(2)/Cyt c/SiO(2)/BDD electrode as a selective "semi-open" medium, which guaranteed the immobilized Cyt c to maintain high stability and perform good electrochemistry and biocatalysis responses. The bioactivity of Cyt c was well protected and the immobilized biomolecule even didn't denature at extremely high or low pH condition. More attractively, Cyt c in the sandwich structured electrode could be further oxidized into highly reactive Cyt c pi-cation by two-step electrochemical oxidation, which could oxidize NO(2)(-) into NO(3)(-) in the solution. A sensitive determination approach of nitrite was accordingly built up based on this biocatalytic oxidative interaction for the first time and a possible mechanism of the interaction was herein proposed.

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

    PubMed

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

    2015-09-15

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

  19. Nondestructive and Strain Testing of Composite Sandwich Panels

    NASA Astrophysics Data System (ADS)

    Goyings, Ryan

    In April 2006, Sikorsky Aircraft received a contract from the United States Marine Corps (USMC) to develop a successor to their CH-53E heavy-lift helicopter. The new designation is the CH-53K "Super Stallion" and provides increased operating capabilities through the use of design revisions that incorporate extensive use of carbon fiber composites and composite sandwich panels. "The CH-53K will have five times the capability at half of the operational cost of the aircraft it's replacing. It will be the most capable helicopter ever produced. With more than twice the combat radius of the CH-53E, the CH-53K uses mature technology to deliver a fully shipboard compatible platform to meet current and future Marine Corps requirements". Upon introduction, it will be the largest rotary wing aircraft in the United States Department of Defense. The USMC will incorporate the CH-53K into the Joint Operations Concept of Full Spectrum Dominance and Sea Power 21 thereby enabling rapid, decisive operations and the early termination of conflict by projecting and sustaining forces to distant anti-access, area-denial environments. Even with an increased lift capability, the CH-53K is a slow moving, low flying helicopter susceptible to damage from small arms fire. There is no field level composite repair capability within any maintained documents published by the Department of Defense. Purdue University has developed a field level rapid repair technique capable of returning strength and integrity to damaged carbon composite structural components. The patch is made from carbon fiber weave that is applied using a field capable Vacuum Assisted Resin Transfer Molding (VARTM). This thesis seeks to validate, using nondestructive testing methods and strain monitoring, the manufacturing, damage, and repair process of composite sandwich panels representative of the CH-53K structural panels.

  20. Probabilistic Structural Evaluation of Uncertainties in Radiator Sandwich Panel Design

    NASA Technical Reports Server (NTRS)

    Kuguoglu, Latife; Ludwiczak, Damian

    2006-01-01

    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.

  1. Microbiological investigation of an antibacterial sandwich layer system.

    PubMed

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

    2014-09-01

    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 μg/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.

  2. Microbiological quality and risk factors related to sandwiches served in bakeries, cafés, and sandwich bars in South Korea.

    PubMed

    Jang, Hong Geun; Kim, Nam Hee; Choi, Young Min; Rhee, Min Suk

    2013-02-01

    The objective of this study was to investigate the microbiological quality of sandwiches produced on site and served in bakeries, cafés, and sandwich bars in South Korea and to determine the major risk factors affecting the sanitation level in each store (n = 1,120). The microbiological quality of the sandwiches was analyzed, and the sanitation level of each store was evaluated as satisfactory or unsatisfactory based on sanitation guidelines. Total coliforms were detected in 906 samples (80.9%), but only 3 samples (0.3%) contained confirmed Escherichia coli contamination. The detection rate was highest for Bacillus cereus (10.0%), followed by Staphylococcus aureus (1.3%) and Salmonella (0.2%). Vibrio parahaemolyticus was not detected in any samples. The microbial contamination level was significantly lower in winter (P < 0.05) and in stores with a higher sanitation grade. Factors related to the microbiological quality of sandwiches were evaluated as the relative risk (RR) of coliform contamination, and the higher risk factors for sandwich contamination were improper holding temperature (RR = 8.75), cross-contamination (RR = 6.30), lack of proper ventilation systems (RR = 6.16), and the absence of clean and/or suitable outer garments (RR = 5.73). Most factors were related to the failure of food handlers to adhere to sanitation guidelines rather than to unsanitary environments. This study provides a comprehensive analysis of the relationship between the microbiological quality of sandwiches served on-site and various risk factors. These results will help researchers establish guidelines for the sanitary management of sandwich shops.

  3. Experimental study of the mechanical behaviour of pin reinforced foam core sandwich materials under shear load

    NASA Astrophysics Data System (ADS)

    Dimassi, M. A.; Brauner, C.; Herrmann, A. S.

    2016-03-01

    Sandwich structures with a lightweight closed cell hard foam core have the potential to be used in primary structures of commercial aircrafts. Compared to honeycomb core sandwich, the closed cell foam core sandwich overcomes the issue of moisture take up and makes the manufacturing of low priced and highly integrated structures possible. However, lightweight foam core sandwich materials are prone to failure by localised external loads like low velocity impacts. Invisible cracks could grow in the foam core and threaten the integrity of the structure. In order to enhance the out-of-plane properties of foam core sandwich structures and to improve the damage tolerance (DT) dry fibre bundles are inserted in the foam core. The pins are infused with resin and co-cured with the dry fabric face sheets in an out-of-autoclave process. This study presents the results obtained from shear tests following DIN 53294-standard, on flat sandwich panels. All panels were manufactured with pin-reinforcement manufactured with the Tied Foam Core Technology (TFC) developed by Airbus. The effects of pin material (CFRP and GFRP) and pin volume fraction on the shear properties of the sandwich structure and the crack propagation were investigated and compared to a not pinned reference. It has been concluded that the pin volume fraction has a remarkable effect on the shear properties and damage tolerance of the observed structure. Increasing the pin volume fraction makes the effect of crack redirection more obvious and conserves the integrity of the structure after crack occurrence.

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

    PubMed Central

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

    2015-01-01

    Quantum dots (QDs) and graphene are both promising materials for the development of new-generation optoelectronic devices. Towards this end, synergic assembly of these two building blocks is a key step but remains a challenge. Here, we show a one-step strategy for organizing QDs in a graphene matrix via interfacial self-assembly, leading to the formation of sandwiched hybrid QD-graphene nanofilms. We have explored structural features, electron transfer kinetics and photocurrent generation capacity of such hybrid nanofilms using a wide variety of advanced techniques. Graphene nanosheets interlink QDs and significantly improve electronic coupling, resulting in fast electron transfer from photoexcited QDs to graphene with a rate constant of 1.3 × 109 s−1. Efficient electron transfer dramatically enhances photocurrent generation in a liquid-junction QD-sensitized solar cell where the hybrid nanofilm acts as a photoanode. We thereby demonstrate a cost-effective method to construct large-area QD-graphene hybrid nanofilms with straightforward scale-up potential for optoelectronic applications. PMID:25996307

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

    PubMed

    Hara, Yuko; Dong, Jinhua; Ueda, Hiroshi

    2013-09-02

    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 μg 100 g(-1)) in many countries. So OS-IA will be widely applicable to detect PSP toxins in shellfish meats and in drinking water.

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

    NASA Technical Reports Server (NTRS)

    McGowan, David M.; Ambur, Damodar R.

    1997-01-01

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

  7. Elastic and plastic buckling of simply supported solid-core sandwich plates in compression

    NASA Technical Reports Server (NTRS)

    Seide, Paul; Stowell, Elbridge Z

    1950-01-01

    A solution is presented for the problem of the compressive buckling of simply supported, flat, rectangular, solid-core sandwich plates stressed either in the elastic range or in the plastic range. Charts for the analysis of long sandwich plates are presented for plates having face materials of 24s-t3 aluminum alloy, 76s-t6 alclad aluminum alloy, and stainless steel. A comparison of computed and experimental buckling stresses of square solid-core sandwich plates indicates fair agreement between theory and experiment.

  8. Design Considerations for Thermally Insulating Structural Sandwich Panels for Hypersonic Vehicles

    NASA Technical Reports Server (NTRS)

    Blosser, Max L.

    2016-01-01

    Simplified thermal/structural sizing equations were derived for the in-plane loading of a thermally insulating structural sandwich panel. Equations were developed for the strain in the inner and outer face sheets of a sandwich subjected to uniaxial mechanical loads and differences in face sheet temperatures. Simple equations describing situations with no viable solution were developed. Key design parameters, material properties, and design principles are identified. A numerical example illustrates using the equations for a preliminary feasibility assessment of various material combinations and an initial sizing for minimum mass of a sandwich panel.

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

    NASA Technical Reports Server (NTRS)

    Ko, W. L.

    1980-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2011-01-01

    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.

  11. Steps toward 8m honeycomb mirror blanks. III - 1.8m honeycomb sandwich blanks cast from borosilicate glass

    NASA Technical Reports Server (NTRS)

    Angel, J. R. P.; Hill, J. M.

    1984-01-01

    The design, fabrication techniques, and equipment used for producing two 1.8-m honeycomb sandwich blanks, eventually leading to production of 8-m blanks, are reported. The procedure employed 85 cast hexagonal tiles at the bottom section, affixed against flotation by SiC bolts. The two plano concave mirrors are 1.83 m thick, weight 500 kg, and are each designed for 19 supports of astatic-lever type. Both blanks are of high quality and with an adequately low bubble content; one is to be figured to high-precision 0.25-arcsecond images, and is to be tested on the Multiple Mirror Telescope. Construction of a spin-casting facility based on the same principle is being planned for test-fabricating spin-cast mirrors on a smaller scale.

  12. Left ventricle remodelling by double-patch sandwich technique

    PubMed Central

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

    2007-01-01

    Background The sandwich double-patch technique was adopted as an alternative method for reconstruction of the left ventricle after excision of postinfarction dysfunctional myocardium to solve technical problems due to the thick edges of the ventricular wall. Methods Over a 5-year period, 12 of 21 patients with postinfarction antero-apical left ventricular aneurysm had thick wall edges after wall excision. It was due to akinetic muscular thick tissue in 6 cases, while in the other 6 with classic fibrous aneurysm, thick edges remained after the cut of the border zone. The ventricular opening was sandwiched between two patches and this is a technique which is currently used for the treatment of the interventricular septum rupture. In our patients the patches are much smaller than the removed aneurysm and they were sutured simply by a single row of single stitches. However, in contrast to interventricular septum rupture where the patches loosen the tension of the tissues, in our patients the patches pull strongly and restrain the walls by fastening their edges and supporting tight stitches. In this way they could narrow the cavity and close the ventricle. Results The resected area varied from 5 × 4 to 8 × 8 cm. Excision was extended into the interventricular septum in 5 patients, thus opening the right ventricle. CABG was performed on all patients but two. Left ventricular volumes and the ejection fraction changed significantly: end-systolic volume 93.5 ± 12.4 to 57.8 ± 8.9 ml, p < 0.001; end-diastolic volume 157.2 ± 16.7 to 115.3 ± 14.9 ml, p < 0.001; ejection fraction 40.3 ± 4.2 to 49.5 ± 5.7%, p < 0.001. All patients did well. One patient suffered from bleeding, which was not from the wall suture, and another had a left arm paresis. The post-operative hospital stay was 5 to 30 days with a mean 10.5 ± 7.5 days/patient. At follow-up, 9 to 60 months mean 34, all patients were symptom-free. NYHA class 2.5 ± 0.8 changed to 1.2 ± 0.4, p < 0.001. Conclusion The

  13. Twistable and bendable actuator: a CNT/polymer sandwich structure driven by thermal gradient.

    PubMed

    Seo, Dong Kyun; Kang, Tae June; Kim, Dae Weon; Kim, Yong Hyup

    2012-02-24

    We demonstrate a novel configuration of an electrothermal actuator (ETA), which is based on a polydimethylsiloxane (PDMS) slab sandwiched by upper and lower active layers of CNT-PDMS composite. When only one active layer of a single sandwich structure ETA is heated and the other is not, there exists a thermal gradient in the direction of the slab thickness, resulting in bending motion toward the unheated side. Moreover, a dual sandwich structure ETA, consisting of two parallel assembled sandwich structures on the same body, has the unique ability to act with a twisting motion as the two ETAs bend in opposite directions. We expect the advent of the bendable and twistable actuator to break new ground in ETAs.

  14. A sandwich-type triple-decker lanthanide complex with mixed phthalocyanine and Schiff base ligands.

    PubMed

    Gao, Feng; Li, Yu-Yang; Liu, Cai-Ming; Li, Yi-Zhi; Zuo, Jing-Lin

    2013-08-21

    A new triple-decker dinuclear sandwich-type dysprosium complex based on both the phthalocyanine ligand and the tetradentate Schiff base ligand was synthesized, which is of interest for synthetic chemistry and also shows single-molecule magnetic behaviour.

  15. Investigation of out of plane compressive strength of 3D printed sandwich composites

    NASA Astrophysics Data System (ADS)

    Dikshit, V.; Yap, Y. L.; Goh, G. D.; Yang, H.; Lim, J. C.; Qi, X.; Yeong, W. Y.; Wei, J.

    2016-07-01

    In this study, the 3D printing technique was utilized to manufacture the sandwich composites. Composite filament fabrication based 3D printer was used to print the face-sheet, and inkjet 3D printer was used to print the sandwich core structure. This work aims to study the compressive failure of the sandwich structure manufactured by using these two manufacturing techniques. Two different types of core structures were investigated with the same type of face-sheet configuration. The core structures were printed using photopolymer, while the face-sheet was made using nylon/glass. The out-of-plane compressive strength of the 3D printed sandwich composite structure has been examined in accordance with ASTM standards C365/C365-M and presented in this paper.

  16. Metal-graphene-metal sandwich contacts for enhanced interface bonding and work function control.

    PubMed

    Gong, Cheng; Hinojos, David; Wang, Weichao; Nijem, Nour; Shan, Bin; Wallace, Robert M; Cho, Kyeongjae; Chabal, Yves J

    2012-06-26

    Only a small fraction of all available metals has been used as electrode materials for carbon-based devices due to metal-graphene interface debonding problems. We report an enhancement of the bonding energy of weakly interacting metals by using a metal-graphene-metal sandwich geometry, without sacrificing the intrinsic π-electron dispersions of graphene that is usually undermined by strong metal-graphene interface hybridization. This sandwich structure further makes it possible to effectively tune the doping of graphene with an appropriate selection of metals. Density functional theory calculations reveal that the strengthening of the interface interaction is ascribed to an enhancement of interface dipole-dipole interactions. Raman scattering studies of metal-graphene-copper sandwiches are used to validate the theoretically predicted tuning of graphene doping through sandwich structures.

  17. Interfacial Crack Arrest in Sandwich Panels with Embedded Crack Stoppers Subjected to Fatigue Loading

    NASA Astrophysics Data System (ADS)

    Martakos, G.; Andreasen, J. H.; Berggreen, C.; Thomsen, O. T.

    2017-02-01

    A novel crack arresting device has been implemented in sandwich panels and tested using a special rig to apply out-of-plane loading on the sandwich panel face-sheets. Fatigue crack propagation was induced in the face-core interface of the sandwich panels which met the crack arrester. The effect of the embedded crack arresters was evaluated in terms of the achieved enhancement of the damage tolerance of the tested sandwich panels. A finite element (FE) model of the experimental setup was used for predicting propagation rates and direction of the crack growth. The FE simulation was based on the adoption of linear fracture mechanics and a fatigue propagation law (i.e. Paris law) to predict the residual fatigue life-time and behaviour of the test specimens. Finally, a comparison between the experimental results and the numerical simulations was made to validate the numerical predictions as well as the overall performance of the crack arresters.

  18. Detection of Penicillinase in Milk by Sandwich ELISA Based Polyclonal and Monoclonal Antibody.

    PubMed

    Zhao, Yinli; Li, Guoxi

    2016-01-01

    A sandwich ELISA has been developed using polyclonal and monoclonal antibody for the determination of penicillinase in milk. For this purpose, specific polyclonal and monoclonal antibodies against penicillinase were generated and characterized. Using penicillinase standards prepared from 1-128 ng/mL, the method indicated that the detection limit of the sandwich ELISA, as measured in an ELISA plate reader, was as low as 0.86 ng/mL of penicillinase. For determine the accuracy, raw milk containing 2, 8, 32, and 64 ng/mL of penicillinase were tested by sandwich ELISA. Recoveries were from 93-97.5%, and the coefficient of variation [CV (%)] were from 5.55-8.38%. For interassay reproducibility, recoveries were from 89.5-95.1%, the coefficient of variation [CV (%)] were from 5.26-9.58%. This sandwich ELISA provides a useful screening method for quantitative detection of penicillinase in milk.

  19. Twistable and bendable actuator: a CNT/polymer sandwich structure driven by thermal gradient

    NASA Astrophysics Data System (ADS)

    Seo, Dong Kyun; Kang, Tae June; Kim, Dae Weon; Hyup Kim, Yong

    2012-02-01

    We demonstrate a novel configuration of an electrothermal actuator (ETA), which is based on a polydimethylsiloxane (PDMS) slab sandwiched by upper and lower active layers of CNT-PDMS composite. When only one active layer of a single sandwich structure ETA is heated and the other is not, there exists a thermal gradient in the direction of the slab thickness, resulting in bending motion toward the unheated side. Moreover, a dual sandwich structure ETA, consisting of two parallel assembled sandwich structures on the same body, has the unique ability to act with a twisting motion as the two ETAs bend in opposite directions. We expect the advent of the bendable and twistable actuator to break new ground in ETAs.

  20. Vibroacoustic optimization of anti-tetrachiral and auxetic hexagonal sandwich panels with gradient geometry

    NASA Astrophysics Data System (ADS)

    Ranjbar, Mostafa; Boldrin, Luca; Scarpa, Fabrizio; Neild, Simon; Patsias, Sophoclis

    2016-05-01

    The work describes the vibroacoustic behavior of anti-tetrachiral and auxetic hexagonal gradient sandwich panels using homogenized finite element models to determine the mechanical properties of the auxetic structures, the natural frequencies and radiated sound power level of sandwich panels made by the auxetic cores. The mechanical properties and the vibroacoustic behavior of auxetic hexagonal sandwich panels are investigated as a benchmark. The radiated sound power level of the structure over the frequency range of 0-1000 Hz is minimized by modifying the core geometry of the gradient auxetic sandwich panels. Several excitation cases are considered. First-order and random optimization methods are used for the minimization of radiated sound power level of the structures. The results of this study present significant insights into the design of auxetic structures with respect to their vibroacoustical properties.

  1. Quantitative surface enhanced Raman scattering detection based on the ``sandwich'' structure substrate

    NASA Astrophysics Data System (ADS)

    Zhang, Junmeng; Qu, Shengchun; Zhang, Lisheng; Tang, Aiwei; Wang, Zhanguo

    2011-08-01

    A sandwich structured substrate was designed for quantitative molecular detection using surface enhanced Raman scattering (SERS), in which the probe molecule was sandwiched between silver nanoparticles (SNPs) and silver nanoarrays. The SNPs was prepared using Lee-Meisel method, and the silver nanoarrays was fabricated on porous anodic aluminum oxide (AAO) using electrodepositing method. The SERS studies show that the sandwich structured substrate exhibits good stability and reproducibility, and the detection sensitivity of Rhodamine 6G (R6G) and Melamine can respectively reach up to 10 -19 M and 10 -9 M, which is improved greatly as compared to other SERS substrates. The improved SERS sensitivity is closely associated with the stronger electromagnetic field enhancement, which stems from localized surface plasmon (LSP) coupling between the two silver nanostructures. Furthermore, the SERS intensity increased almost linearly as the mother concentration increased, which indicates that such a sandwich structure may be used as a good SERS substrate for quantitative analysis.

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

    PubMed Central

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

    2013-01-01

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

  3. Evaluation of Shear Tie Connectors for Use in Insulated Concrete Sandwich Panels

    DTIC Science & Technology

    2009-12-01

    of non-load bearing precast /prestressed or tilt-up concrete sandwich wall panels (WP) are examined. These components are used extensively in modern...prestress wall panels, precast wall panels, tilt-up wall panels, concrete insulted wall systems U U U UU 37 Paul Sheppard Reset i Table of...illustrate this concept, the blast resistances of non-load bearing precast /prestressed or tilt-up concrete sandwich wall panels were examined. These

  4. Precast/Prestressed Concrete Experiments Performance on Non-Load Bearing Sandwich Wall Panels

    DTIC Science & Technology

    2011-01-01

    AFRL-RX-TY-TR-2011-0021 PRECAST /PRESTRESSED CONCRETE EXPERIMENTS PERFORMANCE ON NON-LOAD BEARING SANDWICH WALL PANELS Clay J. Naito...2008 -- 20-NOV-2010 Precast /Prestressed Concrete Experiments Performance on Non-Loadbearing Sandwich Wall Panels FA8903-08-D-8768-0002 99999F GOVT F0...conducted by AFRL and the Portland Cement Association (PCA) on the performance of insulated concrete wall panels. The purpose of the research is to

  5. Design Limits for Precast Concrete Sandwich Walls Subjected to External Explosions (PREPRINT)

    DTIC Science & Technology

    2010-02-01

    AFRL-RX-TY-TP-2010-0013 PREPRINT DESIGN LIMITS FOR PRECAST CONCRETE SANDWICH WALLS SUBJECTED TO EXTERNAL EXPLOSIONS Clay Naito and... Precast Concrete Sandwich Walls Subjected to External Explosions (PREPRINT) FA4819-09-C-0032 62012F 4918 C1 Q103013 *Naito, Clay; *Beacraft, Mark...Structures Congress, 12-14 May 2010, in Orlando FL. The use of precast /prestressed concrete and tilt‐up concrete for exterior walls is common

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

    SciTech Connect

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

    2009-05-11

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

  7. Numerical analysis of sandwich beam with corrugated core under three-point bending

    SciTech Connect

    Wittenbeck, Leszek; Grygorowicz, Magdalena; Paczos, Piotr

    2015-03-10

    The strength problem of sandwich beam with corrugated core under three-point bending is presented.The beam are made of steel and formed by three mutually orthogonal corrugated layers. The finite element analysis (FEA) of the sandwich beam is performed with the use of the FEM system - ABAQUS. The relationship between the applied load and deflection in three-point bending is considered.

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

    NASA Technical Reports Server (NTRS)

    Bowles, Kenneth J.; Vannucci, Raymond D.

    1986-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

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

    2006-01-01

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

  10. Development of a finite element model for the simulation of parabolic impact of sandwich panels

    NASA Astrophysics Data System (ADS)

    Ram Ramakrishnan, Karthik; Guérard, Sandra; Mahéo, Laurent; Shankar, Krishna; Viot, Philippe

    2015-09-01

    Sandwich panels are lightweight structures of two thin high strength facesheets bonded to either side of a thick low density core such as foams and honeycombs. It is necessary to study the impact response of sandwich structures in order to ensure the reliability and safety of these structures. The response of sandwich panels to impact loading is usually studied for impact at normal angle of incidence. In real engineering situations, the structures are more frequently loaded at some oblique angle or with a complex trajectory. It is easy to carry out normal impact tests using devices like the drop tower, but impacts at oblique angles are difficult to characterise experimentally. A tri-dimensional impact device called Hexapod has been developed to experimentally study the impact loading of sandwich plates with a parabolic trajectory. The Hexapod is a modified Gough-Stewart platform that can be moved independently in the six degrees of freedom, corresponding to three translation axes and three rotation axes. In this paper, an approach for modelling the parabolic impact of sandwich structures with thin metallic facesheets and polymer foam core using commercial finite element code LS-DYNA software is presented. The results of the FE model of sandwich panels are compared with experimental data in terms of the time history of vertical and horizontal components of force. A comparison of the strain history obtained from Digital Image Correlation and LS-Dyna model are also presented.

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

    NASA Technical Reports Server (NTRS)

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

    2015-01-01

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

  12. Failure Predictions of Out-of-Autoclave Sandwich Joints with Delaminations Under Flexure Loads

    NASA Technical Reports Server (NTRS)

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

    2015-01-01

    An analysis and a test program was conducted to investigate the damage tolerance of composite sandwich joints. The joints contained a single circular delamination between the face-sheet and the doubler. The coupons were fabricated through out-of-autoclave (OOA) processes, a technology NASA is investigating for joining large composite sections. The four-point bend flexure test was used to induce compression loading into the side of the joint where the delamination was placed. The compression side was chosen since it tends to be one of the most critical loads in launch vehicles. Autoclave cure was used to manufacture the composite sandwich sections, while the doubler was co-bonded onto the sandwich face-sheet using an OOA process after sandwich panels were cured. A building block approach was adopted to characterize the mechanical properties of the joint material, including the fracture toughness between the doubler and face-sheet. Twelve four-point-bend samples were tested, six in the sandwich core ribbon orientation and six in sandwich core cross-ribbon direction. Analysis predicted failure initiation and propagation at the pre-delaminated location, consistent with experimental observations. Fracture analyses methods predicted failure loads in close agreement with tests. This investigation demonstrated a strength reduction of 10 percent due to a flaw of significant size compared to the width of the sample. Therefore, concerns of bonding an OOA material to an in-autoclave material was mitigated for the geometries, materials, and load configurations considered.

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

    NASA Technical Reports Server (NTRS)

    Nordendale, Nikolas A.; Goyal, Vinay K.; Lundgren, Eric C.; Patel, Dhruv N.; Farrokh, Babak; Jones, Justin; Fischetti, Grace; Segal, Kenneth N.

    2015-01-01

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

  14. High Temperature Residual Properties of Carbon Fiber Composite Sandwich Panel with Pyramidal Truss Cores

    NASA Astrophysics Data System (ADS)

    Liu, Jiayi; Zhou, Zhengong; Wu, Linzhi; Ma, Li; Pan, Shidong

    2013-08-01

    A study on the mechanical property degradation of carbon fiber composite sandwich panel with pyramidal truss cores by high temperature exposure is performed. Analytical formulae for the residual bending strength of composite sandwich panel after thermal exposure are presented for possible competing failure modes. The composite sandwich panels were fabricated from unidirectional carbon/epoxy prepreg, and were exposed to different temperatures for different time. The bending properties of the exposed specimens were measured by three-point bending tests. Then the effect of high temperature exposure on the bending properties and damage mechanism were analyzed. The results have shown that the residual bending strength of composite sandwich panels decreased with increasing exposure temperature and time, which was caused by the degradation of the matrix property and fiber-matrix interface property at high temperature. The effect of thermal exposure on failure mode of composite sandwich panel was observed as well. The measured failure loads showed good agreement with the analytical predictions. It is expected that this study can provide useful information on the design and application of carbon fiber composite sandwich panel at high temperature.

  15. Sandwich concept: enhancement for direct absorption measurements by laser-induced deflection (LID) technique

    NASA Astrophysics Data System (ADS)

    Mühlig, Ch.; Bublitz, S.; Paa, W.

    2012-11-01

    The new sandwich concept for absolute photo-thermal absorption measurements using the laser induced deflection (LID) technique is introduced and tested in comparison to the standard LID concept. The sandwich concept's idea is the decoupling of the optical materials for the pump and probe beams by placing a sample of investigation in between two optical (sandwich) plates. The pump beam is guided through the sample whereas the probe beams are deflected within the sandwich plates by the thermal lens that is generated by heat transfer from the irradiated sample. Electrical simulation and laser experiments reveal that using appropriate optical materials for the sandwich plates, the absorption detection limit for photo-thermally insensitive materials can be lowered by up to two orders of magnitude. Another advantage of the sandwich concept, the shrinking of the currently required minimum sample size, was used to investigate the laser induced absorption change in a Nd:YVO4 crystal at 1030nm. It was found that the absorption in Nd:YVO4 lowers due to the laser irradiation but partially recovers during irradiation breaks. Furthermore, absorption spectroscopy has been performed at two LBO crystals in the wavelength range 410...600nm to study the absorption structure around the SHG wavelengths of common high power lasers based on Neodymium doped laser crystals.

  16. Measuring Hsp72 (HSPA1A) by indirect sandwich ELISA.

    PubMed

    Ireland, H Elyse; Williams, John H H

    2011-01-01

    The enzyme-linked immunosorbent assay (ELISA) is an immunological technique which is used to determine the presence or quantity of an antigen within a sample. ELISAs rely on the use of at least one antibody (Ab) specific for the antigen being measured. This antibody is covalently linked to an enzyme which is detected through the use of an enzymatic substrate, which can be colorimetric, fluorogenic, or chemiluminescent. The ELISA for Hsp72 described here is a typical indirect sandwich ELISA, which can be used for measuring Hsp72 from cellular/tissue extracts, tissue culture supernatant, and serum. Typically, a 96-well ELISA plate is coated with a specific antibody which captures Hsp72 from the sample, and another antibody specific for a different Hsp72 epitope is used to detect Hsp72. An enzyme-labelled species-specific antibody conjugate is then applied which is consequently detected using a colorimetric enzyme substrate. The quantity of Hsp72 present in the samples is interpolated using a standard curve of known amounts of pure Hsp72.

  17. Piezoelectric performance of fluor polymer sandwiches with different void structures

    NASA Astrophysics Data System (ADS)

    Lou, Kexing; Zhang, Xiaoqing; Xia, Zhongfu

    2012-06-01

    Film sandwiches, consisting of two outer layers of fluoroethylenepropylene and one middle layer of patterned porous polytetrafluoroethylene, were prepared by patterning and fusion bonding. Contact charging was conducted to render the films piezoelectric. The critical voltage to trigger air breakdown in the inner voids in the fabricated films was investigated. The piezoelectric d 33 coefficients were measured employing the quasistatic method and dielectric resonance spectrum. The results show that the critical voltage for air breakdown in the inner voids is associated with the void microstructure of the films. For the films with patterning factors of 0%, 25% and 44%, the critical values are 300, 230 and 230 kV/cm, respectively. With an increase in the patterning factor, both the piezoelectric d 33 coefficients determined from the dielectric resonance spectra and those determined from quasistatic measurements increase, which might be due to a decrease in Young's modulus for the films. The nonlinearity of d 33 becomes increasingly obvious as the patterning factor increases.

  18. Dispersion of Lamb waves in a honeycomb composite sandwich panel.

    PubMed

    Baid, Harsh; Schaal, Christoph; Samajder, Himadri; Mal, Ajit

    2015-02-01

    Composite materials are increasingly being used in advanced aircraft and aerospace structures. Despite their many advantages, composites are often susceptible to hidden damages that may occur during manufacturing and/or service of the structure. Therefore, safe operation of composite structures requires careful monitoring of the initiation and growth of such defects. Ultrasonic methods using guided waves offer a reliable and cost effective method for defects monitoring in advanced structures due to their long propagation range and their sensitivity to defects in their propagation path. In this paper, some of the useful properties of guided Lamb type waves are investigated, using analytical, numerical and experimental methods, in an effort to provide the knowledge base required for the development of viable structural health monitoring systems for composite structures. The laboratory experiments involve a pitch-catch method in which a pair of movable transducers is placed on the outside surface of the structure for generating and recording the wave signals. The specific cases considered include an aluminum plate, a woven composite laminate and an aluminum honeycomb sandwich panel. The agreement between experimental, numerical and theoretical results are shown to be excellent in certain frequency ranges, providing a guidance for the design of effective inspection systems.

  19. Sandwich module prototype progress for space solar power

    NASA Astrophysics Data System (ADS)

    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

    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.

  20. An extraterrestrial sandwich: The perils of food in space.

    PubMed

    Levi, Jane

    2010-03-01

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

  1. Theoretical limitations of quantification for noncompetitive sandwich immunoassays.

    PubMed

    Woolley, Christine F; Hayes, Mark A; Mahanti, Prasun; Douglass Gilman, S; Taylor, Tom

    2015-11-01

    Immunoassays exploit the highly selective interaction between antibodies and antigens to provide a vital method for biomolecule detection at low concentrations. Developers and practitioners of immunoassays have long known that non-specific binding often restricts immunoassay limits of quantification (LOQs). Aside from non-specific binding, most efforts by analytical chemists to reduce the LOQ for these techniques have focused on improving the signal amplification methods and minimizing the limitations of the detection system. However, with detection technology now capable of sensing single-fluorescence molecules, this approach is unlikely to lead to dramatic improvements in the future. Here, fundamental interactions based on the law of mass action are analytically connected to signal generation, replacing the four- and five-parameter fittings commercially used to approximate sigmoidal immunoassay curves and allowing quantitative consideration of non-specific binding and statistical limitations in order to understand the ultimate detection capabilities of immunoassays. The restrictions imposed on limits of quantification by instrumental noise, non-specific binding, and counting statistics are discussed based on equilibrium relations for a sandwich immunoassay. Understanding the maximal capabilities of immunoassays for each of these regimes can greatly assist in the development and evaluation of immunoassay platforms. While many studies suggest that single molecule detection is possible through immunoassay techniques, here, it is demonstrated that the fundamental limit of quantification (precision of 10 % or better) for an immunoassay is approximately 131 molecules and this limit is based on fundamental and unavoidable statistical limitations.

  2. Sensitive detection of estrogenic mycotoxin zearalenone by open sandwich immunoassay.

    PubMed

    Suzuki, Tatsuya; Munakata, Yuriko; Morita, Kazuki; Shinoda, Tatsuya; Ueda, Hiroshi

    2007-01-01

    Zearalenone (ZEA) is an estrogenic mycotoxin produced by Fusarium sp., and its production on corn and small grains during storage has been of considerable concern. For sensitive ZEA detection, we applied an open sandwich (OS) immunoassay that can noncompetitively detect monovalent antigens utilizing an antigen-induced enhancement of the V(H)/V(L) interaction. We cloned the V(H) and V(L) cDNAs of anti-ZEA mAb to a split-Fv phagemid pKST2, and firstly both V(H) and V(L) fragments were displayed on M13 phage p9 and p7, respectively, using an amber suppressor, TG-1, as a host. The split-Fv phage showed specific binding to immobilized ZEA, which was well inhibited by free ZEA. Then, the V(H)/V(L) interaction and its antigen-dependency were analyzed using a non-suppressor HB2151 as a host to produce V(H)-displaying phage and his/myc-tagged soluble V(L) in the culture supernatant. By capturing V(L) with an anti-myc or -his antibody and probing bound V(H)-phage, ZEA was successfully detected with a superior detection limit as well as a wider working range than those of a competitive assay. Also, essentially the same results were reproduced with purified V(H)-alkaline phosphatase and MBP-V(L) fusion proteins.

  3. Refined Zigzag Theory for Laminated Composite and Sandwich Plates

    NASA Technical Reports Server (NTRS)

    Tessler, Alexander; DiSciuva, Marco; Gherlone, Marco

    2009-01-01

    A refined zigzag theory is presented for laminated-composite and sandwich plates that includes the kinematics of first-order shear deformation theory as its baseline. The theory is variationally consistent and is derived from the virtual work principle. Novel piecewise-linear zigzag functions that provide a more realistic representation of the deformation states of transverse-shear-flexible plates than other similar theories are used. The formulation does not enforce full continuity of the transverse shear stresses across the plate s thickness, yet is robust. Transverse-shear correction factors are not required to yield accurate results. The theory is devoid of the shortcomings inherent in the previous zigzag theories including shear-force inconsistency and difficulties in simulating clamped boundary conditions, which have greatly limited the accuracy of these theories. This new theory requires only C(sup 0)-continuous kinematic approximations and is perfectly suited for developing computationally efficient finite elements. The theory should be useful for obtaining relatively efficient, accurate estimates of structural response needed to design high-performance load-bearing aerospace structures.

  4. Parametric results for heat transfer across honeycomb sandwich panels

    NASA Technical Reports Server (NTRS)

    Ramohalli, K.; Sahakian, J.

    1981-01-01

    The problem of heat transfer across honeycomb sandwich panels is theoretically investigated. The basic objective is to predict the rear surface temperature as a function of time when the front surface is exposed to a prescribed heat flux; the faces are bounded by planar sheets so that the air circulation in the honeycomb cells is bounded and contained. The influence of the air circulation on convective heat transfer is explicitly included. Drawing upon previous investigators' results that indicated various relations for the Nusselt numbers vs Rayleigh numbers in different regimes of the aspect ratio (defined as the ratio of the cell height to cell width), parametric calculations are performed to predict the rear surface temperatures. Chemical degradation of the material, especially the glue holding the face material on the end, is important but has not yet been included. The results indicate that decreasing the cell width, increasing the cell wall thickness and increasing the cell height all have beneficial effects upon the heat transfer; i.e., all of these variations reduce rear surface temperature for a given time for a prescribed heat flux on the front surface.

  5. GAMBE: multipurpose sandwich detector for neutrons and photons

    NASA Astrophysics Data System (ADS)

    Ahmed, A.; Burdin, S.; Casse, G.; van Zalinge, H.; Powel, S.; Rees, J.; Smith, A.; Tsurin, I.

    2016-10-01

    Detectors made with semiconductors such as silicon can be efficiently used for detecting and imaging neutrons when coated with suitable materials. They detect the charged reaction products resulting from the interaction of thermal neutrons with materials with high capture cross section like 10B, 6Li, and 6LiF. This work describes the performance of a thermal neutron detector system, GAMBE, which is based on silicon sensors and a layer of neutron-sensitive material, such as a lithium fluoride film or a lithium-6 foil, in a sandwich configuration. This arrangement has a total detection efficiency of 4 +/- 2 %, 7 +/- 1 %, and12 +/- 1 % for 7 μm 6LiF film, 40 μm and 70 μm 6Li foil respectively. Also, it enhances the rejection of fake hits using a simple coincidence method. The coincidence that defines a true neutron hit is the simultaneous signal recorded by the two sensors facing the conversion layer (or foil). These coincidences provide a very good method for rejecting the spurious hits coming from gamma-rays, which are usually present in the neutron field under measurement. The GAMBE system yields a rejection factor at the level of 108 allowing very pure neutron detection in high gamma background conditions. However, the price to pay is a reduction of the detection efficiency of 1 +/- 1 % or 0:9 +/- 0:3 % for 7 μm 6LiF film and 40 μm 6Li foil respectively.

  6. Sandwiched structural panel having a bi-directional core structure

    NASA Technical Reports Server (NTRS)

    Weddendorf, Bruce (Inventor)

    1995-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

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

    2013-01-01

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

  8. Constructed Wetlands

    EPA Pesticide Factsheets

    these systems can improve water quality, engineers and scientists construct systems that replicate the functions of natural wetlands. Constructed wetlands are treatment systems that use natural processes

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

    NASA Astrophysics Data System (ADS)

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

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

  10. The sandwich technique for repair of pectus carinatum and excavatum/carinatum complex

    PubMed Central

    Kim, Kyung Soo

    2016-01-01

    Background Simple external compression of pectus carinatum seems to have its limitations, particularly the repair of asymmetric pectus carinatum or excavatum/carinatum complex. We devised the sandwich technique (press-molding) to remodel the entire chest wall. The purpose of this study is to introduce the sandwich technique and appraise the early results. Methods Between January 2007 and January 2016, 523 consecutive patients with pectus carinatum and its variants were analyzed retrospectively. No patients were excluded during the study period. The sandwich 1 and 2 techniques using the internal and external pectus bars were for pectus carinatum repair. Modified techniques using the external string and the internal bar were to treat the lower costal flare (the flare-buster) and focal protuberances (the magic string) in pectus excavatum repair. Statistical analyses were carried out using paired and unpaired t-test or Wilcoxon signed rank tests. Results The sandwich repair with the external and internal bars was applied to 58 pectus carinatum patients: seven symmetric (12.1%), 14 asymmetric (24.1%), and 37 carinatum-excavatum complex (63.8%). After pectus excavatum repair, 426 patients had the flare-buster and 39 patients received the magic string. The sandwich 1 technique achieved near-complete resolution of carinatum in 52 patients (86.2%). The sandwich 2 technique accomplished almost symmetric configuration with no residual carinatum in all six cases. Conclusions The sandwich technique using the external and internal bars seems to be effective in treating asymmetric pectus carinatum and complex excavatum/carinatum deformities. The flare-buster and the magic string effectively relieve the costal flare and focal protuberances in pectus excavatum repair. PMID:27747176

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

    NASA Astrophysics Data System (ADS)

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

    2014-06-01

    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.

  12. Experimental investigation on sandwich structure ring-type ultrasonic motor.

    PubMed

    Peng, Taijiang; Shi, Hongyan; Liang, Xiong; Luo, Feng; Wu, Xiaoyu

    2015-02-01

    This paper presents a manufacture method for a sandwich structure Ultrasonic Motor (USM) and experiment. Two pieces of rotor clamped on a stator, and a stainless steel disk-spring is bonded on the hollow rotor disk to provide the press by a nut assembled on the shaft. The stator is made of a double-side Printed-Circuit Board (PCB) which is sawed out the ring in the center and connected on the board with three legs. On each side of the ring surface, there are electrodes connected at the same position via through hole. The three layer drive circuit for sine, cosine, and ground signal is connected on the board through each leg. There are many piezoelectric components (PZT) bonded between two electrodes and fill soldering tin on each electrode. Then PZT is welded on PCB by reflow soldering. Finally, rub the gibbous soldering tin down to the position of PZT surface makes sure the surface contacts with rotor evenly. The welding process can also be completed by Surface Mounted Technology (SMT). A prototype motor is manufactured by this method. Two B03 model shapes of the stator are obtained by the finite element analysis and the optimal frequency of the motor is 56.375 kHz measured by impedance instrument. The theoretical analysis is conducted for the relationship between the revolving speed of the USM and thickness of stator ring, number of the travelling waves, PZT amplitude, frequency and the other parameters. The experiment result shows that the maximum revolving speed is 116 RPM and the maximum torque is 25 N mm, when the actuate voltage is 200 VAC.

  13. A Refined Zigzag Beam Theory for Composite and Sandwich Beams

    NASA Technical Reports Server (NTRS)

    Tessler, Alexander; Sciuva, Marco Di; Gherlone, Marco

    2009-01-01

    A new refined theory for laminated composite and sandwich beams that contains the kinematics of the Timoshenko Beam Theory as a proper baseline subset is presented. This variationally consistent theory is derived from the virtual work principle and employs a novel piecewise linear zigzag function that provides a more realistic representation of the deformation states of transverse-shear flexible beams than other similar theories. This new zigzag function is unique in that it vanishes at the top and bottom bounding surfaces of a beam. The formulation does not enforce continuity of the transverse shear stress across the beam s cross-section, yet is robust. Two major shortcomings that are inherent in the previous zigzag theories, shear-force inconsistency and difficulties in simulating clamped boundary conditions, and that have greatly limited the utility of these previous theories are discussed in detail. An approach that has successfully resolved these shortcomings is presented herein. Exact solutions for simply supported and cantilevered beams subjected to static loads are derived and the improved modelling capability of the new zigzag beam theory is demonstrated. In particular, extensive results for thick beams with highly heterogeneous material lay-ups are discussed and compared with corresponding results obtained from elasticity solutions, two other zigzag theories, and high-fidelity finite element analyses. Comparisons with the baseline Timoshenko Beam Theory are also presented. The comparisons clearly show the improved accuracy of the new, refined zigzag theory presented herein over similar existing theories. This new theory can be readily extended to plate and shell structures, and should be useful for obtaining relatively low-cost, accurate estimates of structural response needed to design an important class of high-performance aerospace structures.

  14. Construction aggregates

    USGS Publications Warehouse

    Tepordei, V.V.

    1995-01-01

    Part of the 1994 Industrial Minerals Review. The production, consumption, and applications of construction aggregates are reviewed. In 1994, the production of construction aggregates, which includes crushed stone and construction sand and gravel combined, increased 7.7 percent to 2.14 Gt compared with the previous year. These record production levels are mostly a result of funding for highway construction work provided by the Intermodal Surface Transportation Efficiency Act of 1991. Demand is expected to increase for construction aggregates in 1995.

  15. Hypervelocity Impact Performance of Open Cell Foam Core Sandwich Panel Structures

    NASA Technical Reports Server (NTRS)

    Ryan, Shannon; Christiansen, Eric; Lear, Dana

    2009-01-01

    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

  16. Applications of Composite Materials in Helicopter Construction (Les Applications des Materiaux Composite dans la Construction des Helicopteres),

    DTIC Science & Technology

    1983-11-21

    developments. Besides the weight savings obtained by the use of composite materials, it is appropriate to stress the reliability, the resistance to corrosion...molding Assembly by gluing and "ultrasonic" welding or resistance welding Price Ratio 1 4 2 Advantages No risk of corrosion Weight slightly Weight...all-composite cabin floor in place of the metal sandwich construction of DAUPHIN N. Bending strength Shear resistance Better ball impact strength

  17. Viewpoints of working sandwich generation women and occupational therapists on role balance strategies.

    PubMed

    Evans, Kiah L; Girdler, Sonya J; Falkmer, Torbjorn; Richmond, Janet E; Wagman, Petra; Millsteed, Jeannine; Falkmer, Marita

    2016-11-04

    Occupational therapists need to be cognizant of evidence-based role balance advice and strategies that women with multigenerational caring responsibilities can implement independently or with minimal assistance, as role balance may not be the primary goal during many encounters with this population. Hence, this study aimed to identify the viewpoints on the most helpful role balance strategies for working sandwich generation women, both from their own perspectives and from the perspective of occupational therapists. This was achieved through a Q methodology study, where 54 statements were based on findings from interviews, sandwich generation literature and occupational therapy literature. In total, 31 working sandwich generation women and 42 occupational therapists completed the Q sort through either online or paper administration. The data were analysed using factor analysis with varimax rotation and were interpreted through collaboration with experts in the field. The findings revealed similarities between working sandwich generation women and occupational therapists, particularly in terms of advocating strategies related to sleep, rest and seeking practical assistance from support networks. Differences were also present, with working sandwich generation women viewpoints tending to emphasize strategies related to coping with a busy lifestyle attending to multiple responsibilities. In contrast, occupational therapy viewpoints prioritized strategies related to the occupational therapy process, such as goal setting, activity focused interventions, monitoring progress and facilitating sustainable outcomes.

  18. Comparison of manufacturing of lightweight corrugated sheet sandwiches by hydroforming and incremental sheet forming

    NASA Astrophysics Data System (ADS)

    Maqbool, Fawad; Elze, Lars; Seidlitz, Holger; Bambach, Markus

    2016-10-01

    Sandwich materials made from corrugated sheet metal provide excellent mechanical properties for lightweight design without using filler material. The increased mechanical properties of these sandwich materials are achieved by the 3-D geometry of the corrugated sheet and the hardening due to pre-forming. In the present study, manufacturing of corrugated sheet metal consisting of hexagonal bulge patterns through hydroforming and incremental forming is analyzed. Double layered corrugated sheet metal sandwiches with hexagonal patterns of free-form bulge geometries are investigated through finite element analysis for the maximum increase in stiffness over the normal flat sheets. The analysis shows that a bending stiffness increase of up to 13 times over flat sheet of the same mass is attainable by corrugated sandwiches. Further, it is proved for these types of corrugation sandwiches that stiffness increases by increasing the height of the corrugation bulge but that hydroforming poses restrictions with respect to bulge height, since it is limited by forming force and formability of the material. Incremental sheet metal forming can be used to produce sheets with a hexagonal bulge pattern with increased height. Hence, a higher increase in stiffness as compared to hydroforming is possible but at the expense of process speed.

  19. Thermostructural Behavior of a Hypersonic Aircraft Sandwich Panel Subjected to Heating on One Side

    NASA Technical Reports Server (NTRS)

    Ko, William L.

    1997-01-01

    Thermostructural analysis was performed on a heated titanium honeycomb-core sandwich panel. The sandwich panel was supported at its four edges with spar-like substructures that acted as heat sinks, which are generally not considered in the classical analysis. One side of the panel was heated to high temperature to simulate aerodynamic heating during hypersonic flight. Two types of surface heating were considered: (1) flat-temperature profile, which ignores the effect of edge heat sinks, and (2) dome-shaped-temperature profile, which approximates the actual surface temperature distribution associated with the existence of edge heat sinks. The finite-element method was used to calculate the deformation field and thermal stress distributions in the face sheets and core of the sandwich panel. The detailed thermal stress distributions in the sandwich panel are presented, and critical stress regions are identified. The study shows how the magnitudes of those critical stresses and their locations change with different heating and edge conditions. This technical report presents comprehensive, three-dimensional graphical displays of thermal stress distributions in every part of a titanium honeycomb-core sandwich panel subjected to hypersonic heating on one side. The plots offer quick visualization of the structural response of the panel and are very useful for hot structures designers to identify the critical stress regions.

  20. Network architecture design of an agile sensing system with sandwich wireless sensor nodes

    NASA Astrophysics Data System (ADS)

    Dorvash, S.; Li, X.; Pakzad, S.; Cheng, L.

    2012-04-01

    Wireless sensor network (WSN) is recently emerged as a powerful tool in the structural health monitoring (SHM). Due to the limitations of wireless channel capacity and the heavy data traffic, the control on the network is usually not real time. On the other hand, many SHM applications require quick response when unexpected events, such as earthquake, happen. Realizing the need to have an agile monitoring system, an approach, called sandwich node, was proposed. Sandwich is a design of complex sensor node where two Imote2 nodes are connected with each other to enhance the capabilities of the sensing units. The extra channel and processing power, added into the nodes, enable agile responses of the sensing network, particularly in interrupting the network and altering the undergoing tasks for burst events. This paper presents the design of a testbed for examination of the performance of wireless sandwich nodes in a network. The designed elements of the network are the software architecture of remote and local nodes, and the triggering strategies for coordinating the sensing units. The performance of the designed network is evaluated through its implementation in a monitoring test in the laboratory. For both original Imote2 and the sandwich node, the response time is estimated. The results show that the sandwich node is an efficient solution to the collision issue in existing interrupt approaches and the latency in dense wireless sensor networks.

  1. Evaluation of modal-based damage detection techniques for composite aircraft sandwich structures

    NASA Astrophysics Data System (ADS)

    Oliver, J. A.; Kosmatka, J. B.

    2005-05-01

    Composite sandwich structures are important as structural components in modern lightweight aircraft, but are susceptible to catastrophic failure without obvious forewarning. Internal damage, such as disbonding between skin and core, is detrimental to the structures' strength and integrity and thus must be detected before reaching critical levels. However, highly directional low density cores, such as Nomex honeycomb, make the task of damage detection and health monitoring difficult. One possible method for detecting damage in composite sandwich structures, which seems to have received very little research attention, is analysis of global modal parameters. This study will investigate the viability of modal analysis techniques for detecting skin-core disbonds in carbon fiber-Nomex honeycomb sandwich panels through laboratory testing. A series of carbon fiber prepreg and Nomex honeycomb sandwich panels-representative of structural components used in lightweight composite airframes-were fabricated by means of autoclave co-cure. All panels were of equal dimensions and two were made with predetermined sizes of disbonded areas, created by substituting areas of Teflon release film in place of epoxy film adhesive during the cure. A laser vibrometer was used to capture frequency response functions (FRF) of all panels, and then real and imaginary FRFs at different locations on each plate and operating shapes for each plate were compared. Preliminary results suggest that vibration-based techniques hold promise for damage detection of composite sandwich structures.

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

    NASA Astrophysics Data System (ADS)

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

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

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

    NASA Technical Reports Server (NTRS)

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

    2008-01-01

    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.

  4. Designing novel thin film polycrystalline solar cells for high efficiency: sandwich CIGS and heterojunction perovskite

    NASA Astrophysics Data System (ADS)

    Wang, Tianyue; Chen, Jiewei; Wu, Gaoxiang; Song, Dandan; Li, Meicheng

    2017-01-01

    Heterojunction and sandwich architectures are two new-type structures with great potential for solar cells. Specifically, the heterojunction structure possesses the advantages of efficient charge separation but suffers from band offset and large interface recombination; the sandwich configuration is favorable for transferring carriers but requires complex fabrication process. Here, we have designed two thin-film polycrystalline solar cells with novel structures: sandwich CIGS and heterojunction perovskite, referring to the advantages of the architectures of sandwich perovskite (standard) and heterojunction CIGS (standard) solar cells, respectively. A reliable simulation software wxAMPS is used to investigate their inherent characteristics with variation of the thickness and doping density of absorber layer. The results reveal that sandwich CIGS solar cell is able to exhibit an optimized efficiency of 20.7%, which is much higher than the standard heterojunction CIGS structure (18.48%). The heterojunction perovskite solar cell can be more efficient employing thick and doped perovskite films (16.9%) than these typically utilizing thin and weak-doping/intrinsic perovskite films (9.6%). This concept of structure modulation proves to be useful and can be applicable for other solar cells. Project supported by the National High-Tech R&D Program of China (No. 2015AA034601), the National Natural Science Foundation of China (Nos. 91333122, 61204064, 51202067, 51372082, 51402106, 11504107), the Ph.D. Programs Foundation of Ministry of Education of China (Nos. 20120036120006, 20130036110012), the Par-Eu Scholars Program, and the Fundamental Research Funds for the Central Universities.

  5. The Use of Sprint Interface Element Delamination Simulation of Sandwich Composite Beam

    NASA Astrophysics Data System (ADS)

    Xu, Geng; Yan, Renjun

    2016-12-01

    Sandwich composite beams have been more and more used in various industries because of their excellent mechanical properties. However, the mismatched performance between face sheet and foam core always lead to such as cracks and damages in the core or face/core interface during the processes of manufacturing or service. Delamination damage at the adhesive interface is the most dangerous and could be one main source that the mechanical capability of the structure is serous degenerated. In this paper, a simple and natural model to evaluate the stiffness of the spring interface elements, which is based on the physics and the geometry of the adhesive layers, is proposed. In order to validate the model, cantilever beam bending test were conducted for marine sandwich composite I-beam. A good comparison has been found between predictions and experimental results, and results indicate that the spring interface element can provide an efficient model for the delamination simulation of sandwich composite structures.

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

    PubMed

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

    2004-05-01

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

  7. Study of sandwiched three-port transmission grating with a connection layer under normal incidence

    NASA Astrophysics Data System (ADS)

    Li, Hongtao; Wang, Bo

    2016-09-01

    A sandwiched three-port transmission grating with a connection layer under normal incidence is shown. The sandwiched dielectric grating can mainly diffract the identical energies in the ±1st orders and the zeroth diffraction order based on optimized grating parameters by employing rigorous coupled-wave analysis (RCWA) for TE and TM polarizations. On account of optimized parameters, efficiencies more than 32.5% in each diffraction order for two polarizations can be gained under normal incidence. A simplified modal method is used to describe the mechanism of beam propagation and analyze diffraction behavior clearly in the grating. Most importantly, diffraction efficiencies numerically obtained by using RCWA can be in agreement with the rough theoretical analysis on account of the simplified modal method. Therefore, the connection-layer-based sandwiched three-port grating is significant for the further practical manufacture.

  8. Influence of residual stresses on the tensile strength of composite-metal sandwich laminates

    NASA Technical Reports Server (NTRS)

    Herakovich, C. T.; Wong, D. M.

    1977-01-01

    The tensile strength of boron-epoxy/aluminum sandwich laminates is discussed relative to the residual thermal stresses generated by curing and bonding at elevated temperatures. It is shown that the sandwich laminates investigated exhibit three dinstinct modes of failure, depending upon the fiber orientation of the composite. Sandwich laminates with moderate to high percentage of 0-deg fibers exhibit early failures initiated by edge effect; laminates with moderate to high percentage of 90-deg fibers fail according to a first-ply failure criterion; laminates with moderate to high percentages of plus or minus 45 deg plies fail at strains equal to or greater than the failure strain of the corresponding all-composite laminate.

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

    NASA Astrophysics Data System (ADS)

    Chen, Chunlin; Peters, Kara; Li, Yulong

    2013-02-01

    A self-healing capability specifically targeted for sandwich composite laminates based on interfacial layers with built-in vascular networks is presented. The self-healing occurs at the facesheet-core interface through an additional interfacial layer to seal facesheet cracks and rebond facesheet-core regions. The efficacy of introducing the self-healing system at the facesheet-core interface is evaluated through four-point bend and edgewise compression testing of representative foam core sandwich composite specimens with impact induced damage. The self-healing interfacial layer partially restored the specific initial stiffness, doubling the residual initial stiffness as compared to the control specimen after the impact event. The restoration of the ultimate specific skin strength was less successful. The results also highlight the critical challenge in self-healing of sandwich composites, which is to rebond facesheets which have separated from the core material.

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

    NASA Astrophysics Data System (ADS)

    Zhang, Lulu; Jiang, Changlong; Zhang, Zhongping

    2013-04-01

    Analytical techniques based on surface-enhanced Raman scattering (SERS) suffer from a lack of reproducibility and reliability, thus hampering their practical applications. Herein, we have developed a SERS-active substrate based on a graphene oxide embedded sandwich nanostructure for ultrasensitive Raman signal readout. By using this novel Au@Ag NPs/GO/Au@Ag NPs sandwich nanostructure as a SERS substrate, the Raman signals of analytes were dramatically enhanced due to having plenty of hot spots on their surfaces and the unique structure of the graphene oxide sheets. These features make the sandwich nanostructured film an ideal SERS substrate to improve the sensitivity, reproducibility and reliability of the Raman readout. The sandwich nanostructure film can be applied to detect rhodamine-6G (R6G) with an enhancement factor (EF) of ~7.0 × 107 and the pesticide thiram in commercial grape juice with a detection limit of as low as 0.1 μM (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

  11. Simultaneous determination of iron (II) and ascorbic acid in pharmaceuticas based on flow sandwich technique.

    PubMed

    Vakh, Christina; Freze, Elena; Pochivalov, Alexsey; Evdokimova, Ekaterina; Kamencev, Mihail; Moskvin, Leonid; Bulatov, Andrey

    2015-01-01

    The simple and easy performed flow system based on sandwich technique has been developed for the simultaneous separate determination of iron (II) and ascorbic acid in pharmaceuticals. The implementation of sandwich technique assumed the injection of sample solution between two selective reagents and allowed the carrying out in reaction coil two chemical reactions simultaneously: iron (II) with 1,10-phenanthroline and ascorbic acid with sodium 2,6-dichlorophenolindophenol. For achieving of excellent repeatability and considerable reagent saving the various parameters such as flow rate, sample and reagent volumes, reaction coil length were also optimized. The limits of detection (LODs) obtained by using the developed flow sandwich-type approach were 0.2 mg L(-1) for iron (II) and 0.7 mg L(-1) for ascorbic acid. The suggested approach was validated according to the following parameters: linearity and sensitivity, precision, recoveries and accuracy. The sampling frequency was 41 h(-1).

  12. Influence of Stacking Sequence on the Impact and Postimpact Bending Behavior of Hybrid Sandwich Composites

    NASA Astrophysics Data System (ADS)

    Özen, M.

    2017-01-01

    A new hybrid sandwich structure was developed by using carbon, e-glass, and s-glass fabrics as reinforcement materials, an epoxy resin as the matrix material for face sheets, and a PVC foam as the core material. Six different configurations were prepared. Sandwich composites plates with different stacking sequences were subjected to low-speed impacts will energies of 7.5, 15, and 22.5 J. Their impact response is analyzed and reported in terms of the peak load as a function of impact energy. After impact tests, 3-point bending tests were conducted to determine the bending behavior of the sandwich composites after impacts in terms of their flexural strength. The results obtained showed that the use of carbon fabrics in the face sheets increased the peak loads for all the impact energies considered. The presence of carbon fibers in skin regions increased the flexural strength of the composites, but e-glass fibers decreased this strength.

  13. Coupled Néel domain wall motion in sandwiched perpendicular magnetic anisotropy nanowires.

    PubMed

    Purnama, I; Kerk, I S; Lim, G J; Lew, W S

    2015-03-04

    The operating performance of a domain wall-based magnetic device relies on the controlled motion of the domain walls within the ferromagnetic nanowires. Here, we report on the dynamics of coupled Néel domain wall in perpendicular magnetic anisotropy (PMA) nanowires via micromagnetic simulations. The coupled Néel domain wall is obtained in a sandwich structure, where two PMA nanowires that are separated by an insulating layer are stacked vertically. Under the application of high current density, we found that the Walker breakdown phenomenon is suppressed in the sandwich structure. Consequently, the coupled Néel domain wall of the sandwich structure is able to move faster as compared to individual domain walls in a single PMA nanowire.

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

    NASA Technical Reports Server (NTRS)

    Cook, Geoffrey M.

    1997-01-01

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

  15. Low-Velocity Impact Response of Sandwich Beams with Functionally Graded Core

    NASA Technical Reports Server (NTRS)

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

    2006-01-01

    The problem of low-speed impact of a one-dimensional sandwich panel by a rigid cylindrical projectile is considered. The core of the sandwich panel is functionally graded such that the density, and hence its stiffness, vary through the thickness. The problem is a combination of static contact problem and dynamic response of the sandwich panel obtained via a simple nonlinear spring-mass model (quasi-static approximation). The variation of core Young's modulus is represented by a polynomial in the thickness coordinate, but the Poisson's ratio is kept constant. The two-dimensional elasticity equations for the plane sandwich structure are solved using a combination of Fourier series and Galerkin method. The contact problem is solved using the assumed contact stress distribution method. For the impact problem we used a simple dynamic model based on quasi-static behavior of the panel - the sandwich beam was modeled as a combination of two springs, a linear spring to account for the global deflection and a nonlinear spring to represent the local indentation effects. Results indicate that the contact stiffness of thc beam with graded core Increases causing the contact stresses and other stress components in the vicinity of contact to increase. However, the values of maximum strains corresponding to the maximum impact load arc reduced considerably due to grading of thc core properties. For a better comparison, the thickness of the functionally graded cores was chosen such that the flexural stiffness was equal to that of a beam with homogeneous core. The results indicate that functionally graded cores can be used effectively to mitigate or completely prevent impact damage in sandwich composites.

  16. Electrochemical construction

    DOEpatents

    Einstein, Harry; Grimes, Patrick G.

    1983-08-23

    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.

  17. Microstructure of the combustion zone: Thin-binder AP-polymer sandwiches

    NASA Technical Reports Server (NTRS)

    Price, E. W.; Panyam, R. R.; Sigman, R. K.

    1980-01-01

    Experimental results are summarized for systematic quench-burning tests on ammonium perchlorate-HC binder sandwiches with binder thicknesses in the range 10 - 150 microns. Tests included three binders (polysulfide, polybutadiene-acrylonitrile, and hydroxy terminated polybutadiene), and pressures from 1.4 to 14 MPa. In addition, deflagration limits were determined in terms of binder thickness and pressure. Results are discussed in terms of a qualitative theory of sandwich burning consolidated from various sources. Some aspects of the observed results are explained only speculatively.

  18. Equivalent material modelling of sandwich beams, evanescent solutions and damping investigations

    NASA Astrophysics Data System (ADS)

    de Rijk, Sophie; Nijman, Eugene

    2016-11-01

    A novel method for representing the transverse vibrations of sandwich beams as equivalent Timoshenko beams is developed. Special attention is given to damping modelling together with the evanescent parts of the solutions to assert applicability of the approach to any boundary conditions. Shear stiffness is evaluated based on current knowledge. The latter is then used to update the reference theory for vibrations in sandwich beams. Analytical case studies are presented to show the performance and limitations of the method and compared with experimental data.

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

    SciTech Connect

    Malishevskii, A. S. Silin, V. P.; Uryupin, S. A.; Uspenskii, S. G.

    2008-08-15

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

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

    NASA Technical Reports Server (NTRS)

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

    2001-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Malishevskii, A. S.; Silin, V. P.; Uryupin, S. A.; Uspenskii, S. G.

    2008-08-01

    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.

  2. Systems, Apparatuses, and Methods for Using Durable Adhesively Bonded Joints for Sandwich Structures

    NASA Technical Reports Server (NTRS)

    Smeltzer, III, Stanley S. (Inventor); Lundgren, Eric C. (Inventor)

    2014-01-01

    Systems, methods, and apparatus for increasing durability of adhesively bonded joints in a sandwich structure. Such systems, methods, and apparatus includes an first face sheet and an second face sheet as well as an insert structure, the insert structure having a first insert face sheet, a second insert face sheet, and an insert core material. In addition, sandwich core material is arranged between the first face sheet and the second face sheet. A primary bondline may be coupled to the face sheet(s) and the splice. Further, systems, methods, and apparatus of the present disclosure advantageously reduce the load, provide a redundant path, reduce structural fatigue, and/or increase fatigue life.

  3. Durable and Efficient PTFE Sandwiched SPEEK Membrane for Vanadium Flow Batteries.

    PubMed

    Yu, Lihong; Xi, Jingyu

    2016-09-14

    To overcome the poor cycling stability of sulfonated poly(ether ether ketone) (SPEEK) membrane in vanadium flow batteries (VFB), we demonstrate a facile and effective sandwich design by using hydrophilic porous poly(tetrafluoroethylene) (PTFE) films as a stress protective and electrolyte buffer layer for SPEEK membrane. VFB based on this novel sandwich PTFE/SPEEK/PTFE membrane exhibits super long-life properties, which can steadily run (98.5% of Coulombic efficiency and 85.0% of energy efficiency @ 80 mA cm(-2)) with 2.0 M vanadium electrolyte for more than 1000 cycles. This simple and powerful strategy may also be applied to other nonfluoride membranes.

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

    NASA Technical Reports Server (NTRS)

    Gates, Thomas S.; Herring, Helen M.

    2001-01-01

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

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

    NASA Technical Reports Server (NTRS)

    Cook, Geoffrey M.; Tessler, Alexander

    1998-01-01

    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.

  6. Photo-induced currents in the sandwich metal-ferroelectric-metal structure

    NASA Astrophysics Data System (ADS)

    Ivanov, V.; Karpets, Yu; Perkov, Yu

    2017-01-01

    It was described the photoelectric effect in thin sandwich metal-ferroelectric-metal system. The effect was observed in doped lithium niobate crystals with two electrodes of different metals. The effect is observed only in doped lithium niobate crystals and has a maximum for concentrations of impurities of iron around 0.3 % weight. This paper proposed thermal model of the investigated phenomena resulting from field contact potential difference on the borders of section of metal-ferroelectric material. The results obtained can be used to develop radiation receivers, as well as in the interpretation of experimental results on studying the properties of sandwiched metal-ferroelectric-metal structure.

  7. Sandwich consumption by adults in the U.S., What We Eat in America, NHANES 2009-2012

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Although sandwiches are a staple of the American diet, little is known about their consumption and their contributions to dietary intakes of energy, nutrients, and food components. In this report, the definition of “sandwich” includes not only sandwiches represented in the dietary data by a single ...

  8. Fabrication of a 2014Al-SiC/2014Al Sandwich Structure Composite with Good Tensile Strength and Ductility

    NASA Astrophysics Data System (ADS)

    Zhu, Xian; Zhao, Yu-Guang; Wang, Hui-Yuan; Wang, Zhi-Guo; Wu, Min; Pei, Chang-hao; Chen, Chao; Jiang, Qi-Chuan

    2016-11-01

    A sandwich structure laminate composed of a ductile 2014Al inter-layer and two nanoscale SiC reinforced 2014Al (SiC/2014Al) composite outer layers was successfully fabricated through the combination of powder metallurgy and hot rolling. The ductile 2014Al inter-layer effectively improved the processability of the sandwiched laminates. Tensile test revealed that the yield strength and ultimate tensile strength of the sandwiched laminate were 287 and 470 MPa, respectively, compared with 235 and 425 MPa for monolithic 2014Al. The good performance of the sandwiched laminate results from the strong bonding between the SiC/2014Al composites layer and the ductile 2014Al layer. Thus, the sandwich structure with a composite surface and ductile core is effective for increasing the strength and toughness of composite laminates.

  9. Finite Element Simulation and Assessment of Single-Degree-of-Freedom Prediction Methodology for Insulated Concrete Sandwich Panels Subjected to Blast Loads

    DTIC Science & Technology

    2011-02-01

    tests referenced in this report. 2.3. Precast /Prestressed Sandwich Wall Panels The typical configuration of concrete sandwich wall panels is two...Sandwich Wall Panels,” Journal of the Precast /Prestressed Concrete Institute, 42 (2). PCI Industry Handbook Committee (2004). PCI Design Handbook...the Composite Behavior of Precast Concrete Sandwich Wall Panels,” PCI Journal, Precast /Prestressed Concrete Institute, Vol. 48, No. 2, March-April

  10. STS-43 Pilot Baker eats a sandwich on OV-104's forward flight deck

    NASA Technical Reports Server (NTRS)

    1991-01-01

    STS-43 Pilot Michael A. Baker, seated at the forward flight deck pilots station controls, eats a freefloating peanut butter and jelly sandwich while holding a carrot. Surrounding Baker on Atlantis', Orbiter Vehicle (OV) 104's, flight deck are procedural checklists, control panels, and windows. A lemonade drink bag is velcroed to overhead panel O9.

  11. The Sandwich Generation Diner: Development of a Web-Based Health Intervention for Intergenerational Caregivers

    PubMed Central

    George, Nika; MacDougall, Megan

    2016-01-01

    Background Women are disproportionately likely to assist aging family members; approximately 53 million in the United States are involved with the health care of aging parents, in-laws, or other relatives. The busy schedules of “sandwich generation” women who care for older relatives require accessible and flexible health education, including Web-based approaches. Objective This paper describes the development and implementation of a Web-based health education intervention, The Sandwich Generation Diner, as a tool for intergenerational caregivers of older adults with physical and cognitive impairments. Methods We used Bartholomew’s Intervention Mapping (IM) process to develop our theory-based health education program. Bandura’s (1997) self-efficacy theory provided the overarching theoretical model. Results The Sandwich Generation Diner website features four modules that address specific health care concerns. Our research involves randomly assigning caregiver participants to one of two experimental conditions that are identical in the type of information provided, but vary significantly in the presentation. In addition to structured Web-based assessments, specific website usage data are recorded. Conclusions The Sandwich Generation Diner was developed to address some of the informational and self-efficacy needs of intergenerational female caregivers. The next step is to demonstrate that this intervention is: (1) attractive and effective with families assisting older adults, and (2) feasible to embed within routine home health services for older adults. PMID:27269632

  12. Morphing nacelle inlet lip with pneumatic actuators and a flexible nano composite sandwich panel

    NASA Astrophysics Data System (ADS)

    Gulsine Ozdemir, Nazli; Scarpa, Fabrizio; Craciun, Monica; Remillat, Chrystel; Lira, Cristian; Jagessur, Yogesh; Da Rocha-Schmidt, Luiz

    2015-12-01

    We present a hybrid pneumatic/flexible sandwich structure with thermoplastic (TP) nanocomposite skins to enable the morphing of a nacelle inlet lip. The design consists of pneumatic inflatables as actuators and a flexible sandwich panel that morphs under variable pressure combinations to adapt different flight conditions and save fuel. The sandwich panel forms the outer layer of the nacelle inlet lip. It is lightweight, compliant and impact resistant with no discontinuities, and consists of graphene-doped thermoplastic polyurethane (G/TPU) skins that are supported by an aluminium Flex-core honeycomb in the middle, with near zero in-plane Poisson’s ratio behaviour. A test rig for a reduced-scale demonstrator was designed and built to test the prototype of morphing nacelle with custom-made pneumatic actuators. The output force and the deflections of the experimental demonstrator are verified with the internal pressures of the actuators varying from 0 to 0.41 MPa. The results show the feasibility and promise of the hybrid inflatable/nanocomposite sandwich panel for morphing nacelle airframes.

  13. Dynamic toughness of composite steel-concrete structure of sandwich system

    SciTech Connect

    Iwata, Setsuo; Hattori, Yoichi

    1995-12-31

    Offshore structures should have a high degree of structural safety even under extreme environmental loadings. The authors have studied a composite steel-concrete structure of sandwich system for the strength members of huge offshore structures, where concrete is placed between steel plates. In the previous paper, the authors carried out both experimental and theoretical investigations into the strength of the composite structure. It was clarified that the composite structure has various excellent properties: the ultimate load-bearing capacity of the composite structure is very high and it can absorb a great deal of energy until failure under any type of loading conditions. In the present paper, the authors carried out both experimental and theoretical investigations into the dynamic toughness of the sandwich composite structures. Experiments were carried out using the two dimensional models of composite structure under high speed loading. A nonlinear analysis was developed to predict the toughness of sandwich beam under dynamic load. In the analysis, the material non linearities of both concrete and steel with strain rate. The nonlinear analysis accurately represented the behavior and toughness of the sandwich beam structure.

  14. Teacher Professional Development through Sandwich Programmes and Absenteeism in Basic Schools in Ghana

    ERIC Educational Resources Information Center

    Tamanja, Emmanuel Makabu J.

    2016-01-01

    Continuous professional development of teachers plays a crucial role in improving learning outcomes in schools. This study investigated how teaching time is lost when teachers absent themselves to participate in sandwich programmes to upgrade themselves in the University of Education, Winneba (UEW) in Ghana. Using a survey of 475 teachers pursuing…

  15. Enhanced thermal stability of functionally graded sandwich cylindrical shells by shape memory alloys

    NASA Astrophysics Data System (ADS)

    Asadi, H.; Akbarzadeh, A. H.; Chen, Z. T.; Aghdam, M. M.

    2015-04-01

    The present paper deals with the nonlinear thermal instability of geometrically imperfect sandwich cylindrical shells under uniform heating. The sandwich shells are made of a shape memory alloy (SMA)-fiber-reinforced composite and functionally graded (FG) face sheets (FG/SMA/FG). The Brinson phenomenological model is used to express the constitutive characteristics of SMA fibers. The governing equations are established within the framework of the third-order shear deformation shell theory by taking into account the von Karman geometrical nonlinearity and initial imperfection. The material properties of constituents are assumed to be temperature dependent. The Galerkin technique is utilized to derive expressions of the bifurcation points and bifurcation paths of the sandwich cylindrical shells. Using the developed closed-form solutions, extensive numerical results are presented to provide an insight into the influence of the SMA fiber volume fraction, SMA pre-strain, core thickness, non-homogeneity index, geometrical imperfection, geometry parameters of sandwich shells and temperature dependency of materials on the stability of shells. The results reveal that proper application of SMA fibers postpones the thermal bifurcation point and dramatically decreases thermal post-buckling deflection. Moreover, the induced tensile recovery stress of SMA fibers could also stabilize the geometrically imperfect shells during the inverse martensite phase transformation.

  16. Dynamic response of clamped corrugated sandwich plates subjected to underwater impulsive loads

    NASA Astrophysics Data System (ADS)

    Huang, Wei; Zhang, Wei; Ye, Nan; Li, Dacheng

    2017-01-01

    Corrugated sandwich plates are widely used in marine industry because such plates have high strength-to-weight ratios and blast resistance. The laboratory-scaled fluid-structure interaction experiments are performed to demonstrate the shock resistance of corrugated sandwich plates by quantifying the permanent transverse deflection at mid-span of the plates as a function of impulsive loadings per areal mass. Sandwich structures with 6mm-thick 3003 H18 aluminum corrugated core and 5A06 face sheets subjected to underwater impulsive loadings are studied experimentally in this paper. The dynamic deformations of plates are captured with the the 3D digital imaging correlation method (DIC). The results affirm the peak deflection during the processes of dynamic deformation and the residual maximum deflection for post-mortem plates show a linear trend with the impulses per areal mass, and show sensitivity to the change of impulses. Inhomogeneous deformation for corrugated sandwich plates are show uneven rather than the perfect parabolic shapes reported in previous studies. With the increasing of intensities for impulsive loadings, the failure modes can be observed more complicated from the initial plastic deformation to debonding and crack. This paper provides valid data to quantify the peak deflection, residual deflection and failure modes as functions of impulses and geometric parameters in the future work.

  17. Aligned carbon nanotubes sandwiched in epitaxial NbC film for enhanced superconductivity.

    PubMed

    Zhang, Yingying; Ronning, Filip; Gofryk, Krzysztof; Mara, Nathan A; Haberkorn, Nestor; Zou, Guifu; Wang, Haiyan; Lee, Joon H; Bauer, Eve; McCleskey, Thomas M; Burell, Anthony K; Civale, Leonardo; Zhu, Y T; Jia, Quanxi

    2012-04-07

    Highly aligned carbon nanotube (CNT) ribbons were sandwiched in epitaxial superconducting NbC films by a chemical solution deposition method. The incorporation of aligned long CNTs into NbC film enhances the normal-state conductivity and improves the superconducting properties of the assembly.

  18. Extremely low-frequency Lamb wave band gaps in a sandwich phononic crystal thin plate

    NASA Astrophysics Data System (ADS)

    Shen, Li; Wu, Jiu Hui; Liu, Zhangyi; Fu, Gang

    2015-11-01

    In this paper, a kind of sandwich phononic crystal (PC) plate with silicon rubber scatterers embedded in polymethyl methacrylate (PMMA) matrix is proposed to demonstrate its low-frequency Lamb wave band gap (BG) characteristics. The dispersion relationship and the displacement vector fields of the basic slab modes and the locally resonant modes are investigated to show the BG formation mechanism. The anti-symmetric Lamb wave BG is further studied due to its important function in reducing vibration. The analysis on the BG characteristics of the PC through changing their geometrical parameters is performed. By optimizing the structure, a sandwich PC plate with a thickness of only 3 mm and a lower boundary (as low as 23.9 Hz) of the first anti-symmetric BG is designed. Finally, sound insulation experiment on a sandwich PC plate with the thickness of only 2.5 mm is conducted, showing satisfactory noise reduction effect in the frequency range of the anti-symmetric Lamb BG. Therefore, this kind of sandwich PC plate has potential applications in controlling vibration and noise in low-frequency ranges.

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

    NASA Astrophysics Data System (ADS)

    Mathias, Adam Dustin

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2005-01-01

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

  1. Phonons transmission by thin films sandwiched between two similar fcc structures

    NASA Astrophysics Data System (ADS)

    Belkacemi, Ghania; Bourahla, Boualem

    2015-09-01

    An analytical and numerical formalism are developed to study the influence of the sandwiched atomic films on the vibration properties and phonon transmission modes in fcc waveguides. The model system consists of two identical semi-infinite fcc leads joined by ultrathin atomic films in between. The matching technique is applied to calculate the local Green's functions for the irreducible set of sites that constitute the inhomogeneous domain. Numerical results are presented for the reflection/transmission, total phonon transmittance and localized vibration states in considered fcc lattices. The results show that vibrational properties of the sandwich materials are strongly dependent on the scattering frequency, the thickness of the insured films, incidence angles and elastic boundary conditions. We note that some of the fluctuations, observed in the vibration spectra, are related to Fano resonances, they are due to the coherent coupling between travelling phonons and the localized vibration modes in the neighborhood of the nanojunction domains. The number of localized modes which interact with the propagating modes of the continuum is proportional to the number of the sandwiched Slabs in the interfacial zone. The results give also the effect of the sandwiched ultrathin films on elastic waves propagation by atomic interfaces in fcc lattices.

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

    NASA Astrophysics Data System (ADS)

    Rizov, V.

    2009-06-01

    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.

  3. ACTIV: Sandwich Detector Activity from In-Pile Slowing-Down Spectra Experiment

    SciTech Connect

    2013-08-01

    ACTIV calculates the activities of a sandwich detector, to be used for in-pile measurements in slowing-down spectra below a few keV. The effect of scattering with energy degradation in the filter and in the detectors has been included to a first approximation.

  4. Sandwich-type tetrakis(phthalocyaninato) dysprosium-cadmium quadruple-decker SMM.

    PubMed

    Wang, Hailong; Qian, Kang; Wang, Kang; Bian, Yongzhong; Jiang, Jianzhuang; Gao, Song

    2011-09-14

    Homoleptic tetrakis[2,3,9,10,16,17,23,24-octa(butyloxy)phthalocyaninato] dysprosium-cadmium quadruple-decker complex 1 was isolated in relatively good yield of 43% from a simple one-pot reaction. This compound represents the first sandwich-type tetrakis(phthalocyaninato) rare earth-cadmium quadruple-decker SMM that has been structurally characterized.

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

    NASA Technical Reports Server (NTRS)

    Tan, Seng

    2012-01-01

    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.

  6. Distinctive electrical properties in sandwich-structured Al2O3/low density polyethylene nanocomposites

    NASA Astrophysics Data System (ADS)

    Wang, Si-Jiao; Zha, Jun-Wei; Li, Wei-Kang; Dang, Zhi-Min

    2016-02-01

    The sandwich-structured Al2O3/low density polyethylene (Al2O3/LDPE) nanocomposite dielectrics consisting of layer-by-layer with different concentration Al2O3 loading were prepared by melt-blending and following hot pressing method. The space charge distribution from pulsed electro-acoustic method and breakdown strength of the nanocomposites were investigated. Compared with the single-layer Al2O3/LDPE nanocomposites, the sandwich-structured nanocomposites remarkably suppressed the space charge accumulation and presented higher breakdown strength. The charges in the sandwich-structured nanocomposites decayed much faster than that in the single-layer nanocomposites, which was attributed to an effective electric field caused by the formation of the interfacial space charges. The energy depth of shallow and deep traps was estimated as 0.73 eV and 1.17 eV in the sandwich-structured nanocomposites, respectively, according to the thermal excitation theoretical model we proposed. This work provides an attractive strategy of design and fabrication of polymer nanocomposites with excellent space charge suppression.

  7. A high-throughput, precipitating colorimetric sandwich ELISA microarray for shiga toxins

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Shiga toxins 1 and 2 (Stx1 and Stx2) from Shiga toxin-producing E. coli (STEC) bacteria were simultaneously detected with a newly developed, high-throughput antibody microarray platform. The proteinaceous toxins were immobilized and sandwiched between biorecognition elements (monoclonal antibodies)...

  8. Comparison of Retention Rates Using Traditional, Drill Sandwich, and Incremental Rehearsal Flash Card Methods.

    ERIC Educational Resources Information Center

    MacQuarrie, Lara L.; Tucker, James A.; Burns, Matthew K.; Hartman, Brian

    2002-01-01

    Research has demonstrated increased retention from drill, but the data regarding drill format are inconsistent. Two commonly used models, Drill Sandwich (DS) and Incremental Rehearsal (IR), were compared to each other and to a traditional flashcard method. The IR model consistently led to significantly more words retained than the traditional or…

  9. Photocatalytic perfermance of sandwich-like BiVO4 sheets by microwave assisted synthesis

    NASA Astrophysics Data System (ADS)

    Liu, Suqin; Tang, Huiling; Zhou, Huan; Dai, Gaopeng; Wang, Wanqiang

    2017-01-01

    Sandwich-like BiVO4 sheets were successfully synthesized in an aqueous solution containing bismuth nitrate, ammonium metavanadate and polyethylene glycol with a molecular weight of 10,000 (PEG-10000) using a facile microwave-assisted method. The as-prepared samples were characterized by scanning electron microscopy, N2 adsorption-desorption, X-ray diffraction, X-ray photoelectron spectroscopy (XPS), and UV-vis diffuse reflectance spectroscopy. The results show that the presence of PEG-10000 plays a critical role in the formation of BiVO4 sheets, and Ostwald ripening is the primary driving force for the formation of sandwich-like structures. The sandwich-like BiVO4 sheets exhibit a high activity for the degradation of methyl orange under visible light irradiation (λ ≥ 420 nm). The enhancement of photocatalytic activity of sandwich-like BiVO4 sheets can be attributed to its large surface area over the irregular BiVO4 particles.

  10. Qualitative and quantitative detection of T7 bacteriophages using paper based sandwich ELISA.

    PubMed

    Khan, Mohidus Samad; Pande, Tripti; van de Ven, Theo G M

    2015-08-01

    Viruses cause many infectious diseases and consequently epidemic health threats. Paper based diagnostics and filters can offer attractive options for detecting and deactivating pathogens. However, due to their infectious characteristics, virus detection using paper diagnostics is more challenging compared to the detection of bacteria, enzymes, DNA or antigens. The major objective of this study was to prepare reliable, degradable and low cost paper diagnostics to detect viruses, without using sophisticated optical or microfluidic analytical instruments. T7 bacteriophage was used as a model virus. A paper based sandwich ELISA technique was developed to detect and quantify the T7 phages in solution. The paper based sandwich ELISA detected T7 phage concentrations as low as 100 pfu/mL to as high as 10(9) pfu/mL. The compatibility of paper based sandwich ELISA with the conventional titre count was tested using T7 phage solutions of unknown concentrations. The paper based sandwich ELISA technique is faster and economical compared to the traditional detection techniques. Therefore, with proper calibration and right reagents, and by following the biosafety regulations, the paper based technique can be said to be compatible and economical to the sophisticated laboratory diagnostic techniques applied to detect pathogenic viruses and other microorganisms.

  11. The Association between Membership in the Sandwich Generation and Health Behaviors: A Longitudinal Study

    ERIC Educational Resources Information Center

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

    2010-01-01

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

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

    NASA Technical Reports Server (NTRS)

    Camarda, C. J.

    1980-01-01

    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).

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

    NASA Technical Reports Server (NTRS)

    Wilkinson, J. P. D.

    1967-01-01

    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.

  14. Analysis and Testing of a Tapered End Connection for Laser Welded Steel Sandwich Panels

    DTIC Science & Technology

    2009-08-15

    reduced distortion lessens or eliminates the need for straightening and rework . Cost-effective, and weight efficient designs are the result. As with...Structural Engineering Vol 67, pp. 159-166. 26. Vel, S.S., Caccese, V., Zhao.,H, 2005, Elastic coupling effects in tapered sandwich panels with laminated

  15. Solid state sandwich concept: Designs, considerations and issues. [solar power satellite transmission

    NASA Technical Reports Server (NTRS)

    Maynard, O. E.

    1980-01-01

    Progress in analysis and design of solid state approaches to the solar power satellite microwave power transmission system is reviewed with special emphasis on the Sandwich concept and the issues of maintenance of low junction temperatures for amplifiers to assure acceptable lifetime. Ten specific issues or considerations are discussed and their resolution or status is presented.

  16. Job Burnout and Couple Burnout in Dual-Earner Couples in the Sandwiched Generation

    ERIC Educational Resources Information Center

    Pines, Ayala Malach; Neal, Margaret B.; Hammer, Leslie B.; Icekson, Tamar

    2011-01-01

    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…

  17. Gender Analysis of Sandwich Admissions: A Case Study of South-South Nigeria

    ERIC Educational Resources Information Center

    Imakpokpomwan, Monday Imuetinyan; Adeyemi, J. K.

    2016-01-01

    Even though university institutions produce high level manpower for the various sectors of the economy Nigeria had none until 1948. In its desire to increase the spread of university education, Ashby Commission recommended a dual mode delivery especially to accommodate the workers quest for upgrade of their qualification. Sandwich is the part-time…

  18. Proximate and mineral content of fast foods. Pizzas, Mexican-American-style foods, and submarine sandwiches.

    PubMed

    Appledorf, H; Kelly, L S

    1979-01-01

    Pizzas, Mexican-American style foods, and submarine sandwiches were analyzed for proximate and mineral composition, and the nutrients compared with the Recommended Dietary Allowances for teen-agers. Fast foods can be a source of considerable nutrition. More nutritional analyses of fast foods are warranted and should be encouraged.

  19. Construction aggregates

    USGS Publications Warehouse

    Tepordei, V.V.

    1996-01-01

    Part of the Annual Commodities Review 1995. Production of construction aggregates such as crushed stone and construction sand and gravel showed a marginal increase in 1995. Most of the 1995 increases were due to funding for highway construction work. The major areas of concern to the industry included issues relating to wetlands classification and the classification of crystalline silica as a probable human carcinogen. Despite this, an increase in demand is anticipated for 1996.

  20. Survival of Salmonella in Cookie and Cracker Sandwiches Containing Inoculated, Low-Water Activity Fillings.

    PubMed

    Beuchat, Larry R; Mann, David A

    2015-10-01

    A study was done to determine the rate of inactivation of Salmonella in cookie and cracker snack sandwiches. Two cookie bases (chocolate and vanilla) and cheese crackers, along with high-sugar chocolate and peanut butter-based crème cookie fillings and peanut butter- and cheese-based cracker fillings, were obtained from commercial sources. Fillings and sandwiches containing fillings that had been dry- or wet-inoculated with Salmonella were stored at 25°C for 1, 6, 21, 35, 70, 112, and 182 days (6 months). At initial populations of 3.4 and 3.6 log CFU/g of cookie sandwiches containing chocolate crème and peanut butter crème fillings, respectively, Salmonella survived for at least 182 days; initially at 0.36 log CFU/g, the pathogen survived for at least 35 and 70 days. Initially at 2.9 and 3.4 log CFU/g of cracker sandwiches containing peanut butter- and cheese-based fillings, respectively, Salmonella survived for at least 182 and 112 days; initially at 0.53 log CFU/g, the pathogen survived for at least 6 and 35 days. Inactivation of Salmonella was more rapid in wet-inoculated peanut butter crème cookie filling than in dry-inoculated filling but was less affected by type of inoculum in peanut butter-based cracker filling. Chocolate cookie base (water activity [aw] 0.39) and chocolate crème filling (aw 0.30) components of sandwiches equilibrated to aw 0.38 within 15 days at 25°C; vanilla cookie base (aw 0.21) and peanut butter-based crème filling (aw 0.27) equilibrated to aw 0.24 between 50 and 80 days. Cheese cracker (aw 0.14) and peanut butter-based filling (aw 0.31) or cheese-based filling (aw 0.33) components of sandwiches equilibrated to aw 0.33 in 80 days. The ability of Salmonella to survive for at least 182 days in fillings of cookie and cracker sandwiches demonstrates a need to assure that filling ingredients do not contain the pathogen and that contamination does not occur during manufacture.

  1. Behavior of sandwich panels subjected to bending fatigue, axial compression loading and in-plane bending

    NASA Astrophysics Data System (ADS)

    Mathieson, Haley Aaron

    This thesis investigates experimentally and analytically the structural performance of sandwich panels composed of glass fibre reinforced polymer (GFRP) skins and a soft polyurethane foam core, with or without thin GFRP ribs connecting skins. The study includes three main components: (a) out-of-plane bending fatigue, (b) axial compression loading, and (c) in-plane bending of sandwich beams. Fatigue studies included 28 specimens and looked into establishing service life (S-N) curves of sandwich panels without ribs, governed by soft core shear failure and also ribbed panels governed by failure at the rib-skin junction. Additionally, the study compared fatigue life curves of sandwich panels loaded under fully reversed bending conditions (R=-1) with panels cyclically loaded in one direction only (R=0) and established the stiffness degradation characteristics throughout their fatigue life. Mathematical models expressing fatigue life and stiffness degradation curves were calibrated and expanded forms for various loading ratios were developed. Approximate fatigue thresholds of 37% and 23% were determined for non-ribbed panels loaded at R=0 and -1, respectively. Digital imaging techniques showed significant shear contribution significantly (90%) to deflections if no ribs used. Axial loading work included 51 specimens and examined the behavior of panels of various lengths (slenderness ratios), skin thicknesses, and also panels of similar length with various rib configurations. Observed failure modes governing were global buckling, skin wrinkling or skin crushing. In-plane bending involved testing 18 sandwich beams of various shear span-to-depth ratios and skin thicknesses, which failed by skin wrinkling at the compression side. The analytical modeling components of axially loaded panels include; a simple design-oriented analytical failure model and a robust non-linear model capable of predicting the full load-displacement response of axially loaded slender sandwich panels

  2. Constructive Fun.

    ERIC Educational Resources Information Center

    Simanek, Donald E.

    1994-01-01

    Compares and reviews currently available brands of steel construction sets that are useful to physics teachers for building demonstrations, prototypes of mechanisms, robotics, and remote control devices. (ZWH)

  3. Thermo-structural optimization of all-metallic prismatic sandwich panels

    NASA Astrophysics Data System (ADS)

    Valdevit, Lorenzo

    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

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

    NASA Technical Reports Server (NTRS)

    Fedor, Jessica L.

    2004-01-01

    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

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

    NASA Astrophysics Data System (ADS)

    Leone, Frank A., Jr.

    A comprehensive experimental and computational investigation was conducted to characterize the fracture behavior and structural response of large sandwich composite aircraft fuselage panels containing artificial damage in the form of holes and notches. Full-scale tests were conducted where panels were subjected to quasi-static combined pressure, hoop, and axial loading up to failure. The panels were constructed using plain-weave carbon/epoxy prepreg face sheets and a Nomex honeycomb core. Panel deformation and notch tip damage development were monitored during the tests using several techniques, including optical observations, strain gages, digital image correlation (DIC), acoustic emission (AE), and frequency response (FR). Additional pretest and posttest inspections were performed via thermography, computer-aided tap tests, ultrasound, x-radiography, and scanning electron microscopy. The framework to simulate damage progression and to predict residual strength through use of the finite element (FE) method was developed. The DIC provided local and full-field strain fields corresponding to changes in the state-of-damage and identified the strain components driving damage progression. AE was monitored during loading of all panels and data analysis methodologies were developed to enable real-time determination of damage initiation, progression, and severity in large composite structures. The FR technique has been developed, evaluating its potential as a real-time nondestructive inspection technique applicable to large composite structures. Due to the large disparity in scale between the fuselage panels and the artificial damage, a global/local analysis was performed. The global FE models fully represented the specific geometries, composite lay-ups, and loading mechanisms of the full-scale tests. A progressive damage model was implemented in the local FE models, allowing the gradual failure of elements in the vicinity of the artificial damage. A set of modifications

  6. (Porphyrinato)bis(phthalocyaninato)dilanthanide(III) complexes presenting a sandwich triple-decker-like structure

    SciTech Connect

    Moussavi, M.; De Cian, A.; Fischer, J.; Weiss, R.

    1986-06-18

    Bis(phthalocyaninato)lanthanide(III) derivatives presenting a sandwich-type structure have been known for many years. These complexes are still intensively studied due to their semi-conductor and electrochromic properties. The synthesis and properties of bis(porphyrinato) and tris(porphyrinato)lanthanide(III) derivatives have also been reported. X-ray structural studies have shown that bis(porphyrinato) complexes have geometries that are similar to those displayed by the LnPc/sub 2/ complexes (Ln = lanthanide; Pc = phthalocyanine) whereas the tris(porphyrinato) derivatives present structures in which two lanthanide(III) metal cations are sandwiched between three macrocyclic rings in triple-decker-like geometry. Structural, magnetic, and spectroscopic properties of the green form of lutetium(III) bis(phthalocyanate) have shown that this complex is in a nonprotonated, one-electron-oxidized ligand form, Ln (Pc/sup 2 -/) (Pc..pi..). In such a molecule, the unpaired spin could be either located on one phthalocyanine ring or delocalized over both rings. In order to force the localization of the unpaired spin on one ring, the authors have tried to synthesize a dissymmetric mixed-ligand, porphyrin (Por) phthalocyanine (Pc), lanthanide sandwich Ln(Por)(Pc). However, under the conditions used, the authors obtained dilanthanide sandwich-triple-decker-like complexes. (Por(Ln)Pc(Ln)Pc) in which the two metal cations are sandwiched between three macrocyclic rings. They report the synthesis and spectral properties of such derivatives obtained with Ln = Nd(III), Eu(III), and Gd(III) and with meso-tetrakis(4-methoxyphenyl) porphyrin (H/sub 2/T(4-OCH/sub 3/)PP) and phthalocyanine (H/sub 2/Pc). The X-ray structure of the neodymim complex is also reported.

  7. Design & construction.

    PubMed

    Souhrada, L

    1991-02-20

    The deepening recession hasn't slowed hospital construction activity--at least not yet. While experts say health care executives should expect fewer large projects within the next two years, as the result of unpredictable sources of capital and increasing censure of hospital capital spending, for the moment hospital projects are helping to shelter some design and construction firms from the recession's fallout.

  8. Sandwich-Cultured Hepatocytes as a Tool to Study Drug Disposition and Drug-Induced Liver Injury

    PubMed Central

    YANG, KYUNGHEE; GUO, CEN; WOODHEAD, JEFFREY L; CLAIRE, ROBERT LST.; WATKINS, PAUL B; SILER, SCOTT Q; HOWELL, BRETT A; BROUWER, KIM LR

    2016-01-01

    Sandwich-cultured hepatocytes (SCH) are metabolically competent and have proper localization of basolateral and canalicular transporters with functional bile networks. Therefore, this cellular model is a unique tool that can be used to estimate biliary excretion of compounds. SCH have been used widely to assess hepatobiliary disposition of endogenous and exogenous compounds and metabolites. Mechanistic modeling based on SCH data enables estimation of metabolic and transporter-mediated clearances, which can be employed to construct physiologically-based pharmacokinetic models for prediction of drug disposition and drug-drug interactions in humans. In addition to pharmacokinetic studies, SCH also have been employed to study cytotoxicity and perturbation of biological processes by drugs and hepatically-generated metabolites. Human SCH can provide mechanistic insights underlying clinical drug-induced liver injury (DILI). In addition, data generated in SCH can be integrated into systems pharmacology models to predict potential DILI in humans. In this review, applications of SCH in studying hepatobiliary drug disposition and bile acid-mediated DILI are discussed. An example is presented to show how data generated in the SCH model was used to establish a quantitative relationship between intracellular bile acids and cytotoxicity, and how this information was incorporated into a systems pharmacology model for DILI prediction. PMID:26869411

  9. Sandwich-Cultured Hepatocytes as a Tool to Study Drug Disposition and Drug-Induced Liver Injury.

    PubMed

    Yang, Kyunghee; Guo, Cen; Woodhead, Jeffrey L; St Claire, Robert L; Watkins, Paul B; Siler, Scott Q; Howell, Brett A; Brouwer, Kim L R

    2016-02-01

    Sandwich-cultured hepatocytes (SCH) are metabolically competent and have proper localization of basolateral and canalicular transporters with functional bile networks. Therefore, this cellular model is a unique tool that can be used to estimate biliary excretion of compounds. SCH have been used widely to assess hepatobiliary disposition of endogenous and exogenous compounds and metabolites. Mechanistic modeling based on SCH data enables estimation of metabolic and transporter-mediated clearances, which can be used to construct physiologically based pharmacokinetic models for prediction of drug disposition and drug-drug interactions in humans. In addition to pharmacokinetic studies, SCH also have been used to study cytotoxicity and perturbation of biological processes by drugs and hepatically generated metabolites. Human SCH can provide mechanistic insights underlying clinical drug-induced liver injury (DILI). In addition, data generated in SCH can be integrated into systems pharmacology models to predict potential DILI in humans. In this review, applications of SCH in studying hepatobiliary drug disposition and bile acid-mediated DILI are discussed. An example is presented to show how data generated in the SCH model were used to establish a quantitative relationship between intracellular bile acids and cytotoxicity, and how this information was incorporated into a systems pharmacology model for DILI prediction.

  10. Sandwiched assembly of ZnO nanowires between graphene layers for a self-powered and fast responsive ultraviolet photodetector

    NASA Astrophysics Data System (ADS)

    Deka Boruah, Buddha; Mukherjee, Anwesha; Misra, Abha

    2016-03-01

    A heterostructure of graphene and zinc oxide (ZnO) nanowires (NWs) is fabricated by sandwiching an array of ZnO NWs between two graphene layers for an ultraviolet (UV) photodetector. This unique structure allows NWs to be in direct contact with the graphene layers, minimizing the effect of the substrate or metal electrodes. In this device, graphene layers act as highly conducting electrodes with a high mobility of the generated charge carriers. An excellent sensitivity is demonstrated towards UV illumination, with a reversible photoresponse even for a short period of UV illumination. Response and recovery times of a few milliseconds demonstrated a much faster photoresponse than most of the conventional ZnO nanostructure-based photodetectors. It is shown that the generation of a built-in electric field between the interface of graphene and ZnO NWs effectively contributes to the separation of photogenerated electron-hole pairs for photocurrent generation without applying any external bias. Upon application of external bias voltage, the electric field further increases the drift velocity of photogenerated electrons by reducing the charge recombination rates, and results in an enhancement of the photocurrent. Therefore, the graphene-based heterostructure (G/ZnO NW/G) opens avenues to constructing a novel heterostructure with a combination of two functionally dissimilar materials.

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

    PubMed

    Xiang, Tingxiu; Jiang, Zheng; Zheng, Jian; Lo, Chaoyu; Tsou, Harry; Ren, Guosheng; Zhang, Jun; Huang, Ailong; Lai, Guoqi

    2012-11-01

    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.

  12. Theory of Moderately Large Deflections of Sandwich Shells Having a Transversely Soft Core and Reinforced Along Their Contour

    NASA Astrophysics Data System (ADS)

    Paimushin, V. N.

    2017-03-01

    Variants of sandwich structural elements in the form of plates and shells with a transversely soft core are analyzed. Their outer, load-carrying layers are reinforced along their outer contour with elastic bars to ensure the transfer of loads to the layers during their interaction with other structural elements. For such structures, at small strains and moderate displacements, a refined geometrically nonlinear a theory is constructed that allows one to describe their subcritical deformation and reveal all possible buckling modes (cophasal, antiphasal, mixed flexural, mixed shear-flexural, and arbitrary modes including all the listed ones) of the load-carrying layers and the reinforcing elements (flexural, shear-flexural, and pure shear ones at various subcritical stressstrain states). This theory is based on considering the interaction forces of outer layers with the core and of the layers and core with the reinforcing bars as unknowns. To derive the basic equations of static equilibrium, boundary conditions for the shell and stiffening bars, the conditions of kinematic conjunction of outer layers with the core and of the outer layers and core with the reinforcing bars, and the generalized Lagrange variational principle proposed earlier are utilized. The theory suggested differs from all known variants by a high degree of accuracy and maningfulness at a minimum number of unknown two-dimensional functions for the shells, one-dimensional functions for the reinforcing bars, and one and two-dimensional contact forces of interaction between structural elements.

  13. An unusual zinc substrate-induced self-construction route to various hierarchical architectures of hydrated tungsten oxide.

    PubMed

    Ma, De-Kun; Jiang, Jing-Lu; Huang, Jia-Rui; Yang, Dong-Peng; Cai, Ping; Zhang, Li-Jie; Huang, Shao-Ming

    2010-07-07

    A novel active zinc substrate-induced sequential self-construction method is presented for the fabrication of hydrated WO(3) hierarchical octahedrons, flakes, lanterns, and arresting sandwiched double-layer nanorods arrays architectures for the first time. Photocatalytic activity and gas sensing properties of the as-obtained various WO(3).0.33H(2)O architectures were studied as well.

  14. From Dispersed Microspheres to Interconnected Nanospheres: Carbon-Sandwiched Monolayered MoS2 as High-Performance Anode of Li-Ion Batteries.

    PubMed

    Shao, Jie; Qu, Qunting; Wan, Zhongming; Gao, Tian; Zuo, Zhichen; Zheng, Honghe

    2015-10-21

    Hierarchical structured carbon@MoS2 (C@MoS2) microspheres and nanospheres composed of carbon-sandwiched monolayered MoS2 building blocks are synthesized through a facile one-pot polyvinylpyrrolidone (PVP) micelle-assisted hydrothermal route. The dimension and carbon content of C@MoS2 spheres are effectively controlled by singly adjusting the concentration of PVP, which plays the dual functions of soft-template and carbon source. As the anode materials of Li-ion batteries, C@MoS2 nanospheres present considerably higher capacity, better rate behavior and cycling stability than C@MoS2 microspheres. The reasons are attributed to the unique interconnected nanospherical morphology and the internal hierarchical construction of C@MoS2 nanospheres with expanded MoS2/carbon interlayer spacing.

  15. Constructing Phylogenies.

    ERIC Educational Resources Information Center

    Bilardello, Nicholas; Valdes, Linda

    1998-01-01

    Introduces a method for constructing phylogenies using molecular traits and elementary graph theory. Discusses analyzing molecular data and using weighted graphs, minimum-weight spanning trees, and rooted cube phylogenies to display the data. (DDR)

  16. Construction Administration.

    ERIC Educational Resources Information Center

    Barley, John McKim, II

    1986-01-01

    Successful completion of a construction project requires the efforts of a team composed of the owner, architect, and contractor. A preconstruction conference can clarify the roles of the team as specified in the design contract. (MLF)

  17. Construction aggregates

    USGS Publications Warehouse

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

    2007-01-01

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

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

    PubMed

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

    2013-09-09

    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.

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

    NASA Technical Reports Server (NTRS)

    Rinker, Martin; Krueger, Ronald; Ratcliffe, James

    2013-01-01

    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.

  20. Fabrication of anti-protein-fouling poly(ethylene glycol) microfluidic chip electrophoresis by sandwich photolithography.

    PubMed

    Cong, Hailin; Xu, Xiaodan; Yu, Bing; Liu, Huwei; Yuan, Hua

    2016-07-01

    Microfluidic chip electrophoresis (MCE) is a powerful separation tool for biomacromolecule analysis. However, adsorption of biomacromolecules, particularly proteins onto microfluidic channels severely degrades the separation performance of MCE. In this paper, an anti-protein-fouling MCE was fabricated using a novel sandwich photolithography of poly(ethylene glycol) (PEG) prepolymers. Photopatterned microchannel with a minimum resolution of 10 μm was achieved. After equipped with a conventional online electrochemical detector, the device enabled baseline separation of bovine serum albumin, lysozyme (Lys), and cytochrome c (Cyt-c) in 53 s under a voltage of 200 V. Compared with a traditional polydimethylsiloxane MCE made by soft lithography, the PEG MCE made by the sandwich photolithography not only eliminated the need of a master mold and the additional modification process of the microchannel but also showed excellent anti-protein-fouling properties for protein separation.

  1. Analysis of a ceramic filled bio-plastic composite sandwich structure

    SciTech Connect

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

    2013-11-25

    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.

  2. Torsional guided wave-based debonding detection in honeycomb sandwich beams

    NASA Astrophysics Data System (ADS)

    Zhu, Kaige; Qing, Xinlin P.; Liu, Bin

    2016-11-01

    Debonding is one of the most dangerous damages in honeycomb sandwich structures, which causes stiffness reduction and is invisible from the surface. Guided wave-based non-destructive evaluation is a promising approach with high sensitivity and high efficiency for debonding detection. A torsional guided wave method is proposed to inspect debonding damage in honeycomb sandwich beams, which is proved to be better in damage location for the beams in the paper than the flexural wave used before. The honeycomb heterogeneity effect on the interaction between guided waves and debonding are first investigated by finite element methods. Then the ability of torsional waves to determine debonding locations and sizes is discussed in detail. Finally, in order to verify the proposed method, experiments are carried out to inspect debonding damage with two sizes.

  3. Graphene-sandwiched silicon structures for greatly enhanced unpolarized light absorption

    NASA Astrophysics Data System (ADS)

    Shi, Kaifeng; Haque, Riaz R.; Mao, Ling-Feng; Lu, Zhaolin

    2015-03-01

    Based on the attenuated total reflection configuration, a multi-layer graphene (MLG) sandwiched silicon structure is proposed for greatly enhancing light absorption over a broad spectral range (1000-2000 nm). At specific incident angles, the electric field in the sandwiched graphene can be simultaneously enhanced for both transverse electric (TE) and transverse magnetic (TM) polarized light. Numerical analysis and finite-difference time-domain simulation demonstrate over 80% and 70% light absorption for TE- and TM-polarized light, respectively. Owing to the unique optical properties of graphene, the absorption of any photon by graphene may give rise to an electron-hole pair. Thus, the greatly enhanced absorption of unpolarized, broadband light may find significant applications in future photovoltaic devices. However, the excess energy carried by the electron-hole pair can dissipate within a sub-picosecond due to the ultra-fast intraband carrier relaxation, which is the challenge for photovoltaic application and will also be discussed.

  4. A Finite Element Analysis for Predicting the Residual Compressive Strength of Impact-Damaged Sandwich Panels

    NASA Technical Reports Server (NTRS)

    Ratcliffe, James G.; Jackson, Wade C.

    2008-01-01

    A simple analysis method has been developed for predicting the residual compressive strength of impact-damaged sandwich panels. The method is tailored for honeycomb core-based sandwich specimens that exhibit an indentation growth failure mode under axial compressive loading, which is driven largely by the crushing behavior of the core material. The analysis method is in the form of a finite element model, where the impact-damaged facesheet is represented using shell elements and the core material is represented using spring elements, aligned in the thickness direction of the core. The nonlinear crush response of the core material used in the analysis is based on data from flatwise compression tests. A comparison with a previous analysis method and some experimental data shows good agreement with results from this new approach.

  5. A Finite Element Analysis for Predicting the Residual Compression Strength of Impact-Damaged Sandwich Panels

    NASA Technical Reports Server (NTRS)

    Ratcliffe, James G.; Jackson, Wade C.

    2008-01-01

    A simple analysis method has been developed for predicting the residual compression strength of impact-damaged sandwich panels. The method is tailored for honeycomb core-based sandwich specimens that exhibit an indentation growth failure mode under axial compression loading, which is driven largely by the crushing behavior of the core material. The analysis method is in the form of a finite element model, where the impact-damaged facesheet is represented using shell elements and the core material is represented using spring elements, aligned in the thickness direction of the core. The nonlinear crush response of the core material used in the analysis is based on data from flatwise compression tests. A comparison with a previous analysis method and some experimental data shows good agreement with results from this new approach.

  6. Physical properties of mononuclear organoeuropium sandwich complexes ligated by cyclooctatetraene and bis(trimethylsilyl)cyclooctatetraene

    NASA Astrophysics Data System (ADS)

    Tsuji, Takashi; Fukazawa, Suguru; Sugiyama, Rion; Kawasaki, Kenshiro; Iwasa, Takeshi; Tsunoyama, Hironori; Tokitoh, Norihiro; Nakajima, Atsushi

    2014-03-01

    Mononuclear organoeuropium sandwich complexes were synthesized from ligands of 1,3,5,7-cyclooctatetraene (COT) and 1,4- and 1,6-bis(trimethylsilyl)-cyclooctatetraenes (COT″) in a liquid ammonia of europium (Eu) and lithium (Li). Elemental analyses revealed the chemical compositions as [(DME)Li]2Eu(COT)2 (1) and [(DME)Li]2Eu(COT″)2 (2). Vibrational analyses and magnetic measurements revealed a ligand-Eu-ligand sandwich structure. The Eu2+ ions induce paramagnetic behaviors at 6-300 K. Although UV-irradiated 1 and 2 emit light of similar color, the quantum yields of their toluene solution widely differ (2.4% and 21%, respectively). The effects of the trimethylsilyl group are evaluated from quantum chemical calculations.

  7. A finite element model for sandwich viscoelastic beams: Experimental and numerical assessment

    NASA Astrophysics Data System (ADS)

    Barbosa, F. S.; Farage, M. C. R.

    2008-10-01

    Among the passive control systems for attenuation of vibrations in structures, those that use viscoelastic materials as a damping core in laminated-plate-like components are focused herein. In the present work an assessment of a time-domain formulation for numerical modelling of viscoelastic materials is made. This formulation, which is called Golla-Hughes method (GHM), is based on a second-order time-domain realization of Laplace-domain motion equations. The GHM parameters used in the characterization of a viscoelastic material are experimentally determined and a sandwich GHM-based finite element model is presented and validated through numerical comparisons with classic formulation results. Finally, a time-domain simulation of an experimentally tested sandwich beam is carried out.

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

    NASA Technical Reports Server (NTRS)

    Merlette, J. B.

    1972-01-01

    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.

  9. A Novel Counter Sheet-flow Sandwich Cell Culture Device for Mammalian Cell Growth in Space

    NASA Astrophysics Data System (ADS)

    Sun, Shujin; Gao, Yuxin; Shu, Nanjiang; Tang, Zemei; Tao, Zulai; Long, Mian

    2008-08-01

    Cell culture and growth in space is crucial to understand the cellular responses under microgravity. The effects of microgravity were coupled with such environment restrictions as medium perfusion, in which the underlying mechanism has been poorly understood. In the present work, a customer-made counter sheet-flow sandwich cell culture device was developed upon a biomechanical concept from fish gill breathing. The sandwich culture unit consists of two side chambers where the medium flow is counter-directional, a central chamber where the cells are cultured, and two porous polycarbonate membranes between side and central chambers. Flow dynamics analysis revealed the symmetrical velocity profile and uniform low shear rate distribution of flowing medium inside the central culture chamber, which promotes sufficient mass transport and nutrient supply for mammalian cell growth. An on-orbit experiment performed on a recovery satellite was used to validate the availability of the device.

  10. The Accuracy of the ABAQUS FE Numerical Modeling for Sandwich Beams with Foam Core

    NASA Astrophysics Data System (ADS)

    Papakaliatakis, G. E.; Karavagelas, N.

    2009-08-01

    The foam of the sandwich core is a compressible material and in ABAQUS FEA is modelled using the crushable foam model. There are crushable foam models with volumetric hardening and with isotropic hardening in ABAQUS standard analysis and the same models for the ABAQUS explicit analysis, for isotropic compressible materials. Also, the Hill's plasticity model for general anisotropic incompressible solids, is available in ABAQUS. All the above modelling cases were performed for sandwich beams with composite faces and PVC foam cores. The specimens were subjected to three-point bending, under quasi-static loading, using the experimental load-deflection curves to compare with ABAQUS FEA predictions. The best modelling case is suggested.

  11. Enhancement of Fluorescence-Based Sandwich Immunoassay Using Multilayered Microplates Modified with Plasma-Polymerized Films.

    PubMed

    Yano, Kazuyoshi; Iwasaki, Akira

    2016-12-25

    A functional modification of the surface of a 96-well microplate coupled with a thin layer deposition technique is demonstrated for enhanced fluorescence-based sandwich immunoassays. The plasma polymerization technique enabling the deposition of organic thin films was employed for the modification of the well surface of a microplate. A silver layer and a plasma-polymerized film were consecutively deposited on the microplate as a metal mirror and the optical interference layer, respectively. When Cy3-labeled antibody was applied to the wells of the resulting multilayered microplate without any immobilization step, greatly enhanced fluorescence was observed compared with that obtained with the unmodified one. The same effect could be also exhibited for an immunoassay targeting antigen directly adsorbed on the multilayered microplate. Furthermore, a sandwich immunoassay for the detection of interleukin 2 (IL-2) was performed with the multilayered microplates, resulting in specific and 88-fold-enhanced fluorescence detection.

  12. Characterization of compressive and short beam shear strength of bamboo opened cell foam core sandwich composites

    NASA Astrophysics Data System (ADS)

    Setyawan, Paryanto Dwi; Sugiman, Saputra, Yudhi

    2016-03-01

    The paper presents the compressive and the short beam shear strength of a sandwich composite with opened cell foam made of bamboo fiber as the core and plywood as the skins. The core thickness was varied from 10 mm to 40 mm keeping the volume fraction of fiber constant. Several test s were carried out including the core density, flatwise compressive and the short beam shear testing in three point bending. The results show that the density of bamboo opened cell foam is comparable with commercial plastic foam, such as polyurethane foam. The compressive strength tends to increase linearly with increasing the core thickness. The short beam shear failure load of the sandwich composite increases with the increase of core thickness, however on the contrary, the short beam shear strength which tends to sharply decrease from the thickness of 10 mm to 30 mm and then becomes flat.

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

    SciTech Connect

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

    2011-05-04

    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.

  14. High-Fidelity Modeling for Health Monitoring in Honeycomb Sandwich Structures

    NASA Technical Reports Server (NTRS)

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

    2011-01-01

    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.

  15. Flutter of a sandwich cylindrical shell supported with annular ribs and loaded with axial forces

    NASA Astrophysics Data System (ADS)

    Bakulin, V. N.; Volkov, E. N.; Nedbaj, A. Ya.

    2015-08-01

    The supersonic flutter of a sandwich cylindrical shell supported from within with annular ribs and loaded with axial forces on the end faces is investigated. The shell motion is described by the equations of the theory of sandwich orthotropic shells. The solution of the equations is sought as a trigonometric series with respect to the axial coordinate. With the help of the Bubnov—Galerkin method, this problem is reduced to the set of algebraic equations for the analysis of the stability of which one uses the Routh—Hurwits criterion. By a numerical example, the effect of the number and the heights of the ribs on the critical velocity of the flow around the shell is shown.

  16. Tensile Properties and Failure Mechanism of 3D Woven Hollow Integrated Sandwich Composites

    NASA Astrophysics Data System (ADS)

    Liu, Chang; Cai, Deng'an; Zhou, Guangming; Lu, Fangzhou

    2017-01-01

    Tensile properties and failure mechanism of 3D woven hollow integrated sandwich composites are investigated experimentally, theoretically and numerically in this paper. Firstly, the tensile properties are obtained by quasi-static tensile tests on the specimens in two principal directions of the sandwich panels, called warp and weft. The experimental results shows that the tensile performances of the warp are better than that of the weft. By observing the broken specimens, it is found that the touch parts between yarns are the main failure regions under tension. Then, a theoretical method is developed to predict the tensile properties. By comparing with the experimental data, the accuracy of the theoretical method is verified. Simultaneously, a finite element model is established to predict the tensile behavior of the composites. The numerical results agree well with the experimental data. Moreover, the simulated progressive damages show that the contact regions in the warp and weft tension are both the initial failure areas.

  17. Vibroacoustic Characterization of Corrugated-Core and Honeycomb-Core Sandwich Panels

    NASA Technical Reports Server (NTRS)

    Allen, Albert; Schiller, Noah

    2016-01-01

    The vibroacoustic characteristics of two candidate launch vehicle fairing structures, corrugated- core and honeycomb-core sandwich designs, were studied. The study of these structures has been motivated by recent risk reduction efforts focused on mitigating high noise levels within the payload bays of large launch vehicles during launch. The corrugated-core sandwich concept is of particular interest as a dual purpose structure due to its ability to harbor resonant noise control systems without appreciably adding mass or taking up additional volume. Specifically, modal information, wavelength dispersion, and damping were determined from a series of vibrometer measurements and subsequent analysis procedures carried out on two test panels. Numerical and analytical modeling techniques were also used to assess assumed material properties and to further illuminate underlying structural dynamic aspects. Results from the tests and analyses described herein may serve as a reference for additional vibroacoustic studies involving these or similar structures.

  18. Electronic aspect and giant magnetoresistance in Co/Cu/Co sandwich structures

    NASA Astrophysics Data System (ADS)

    Diao, Z. T.; Tsunashima, S.; Jimbo, M.; Iwata, S.

    1996-07-01

    We have studied the electronic states in a non-magnetic spacer layer of Co/Cu/Co sandwich layers using the magneto-optical Kerr effect (MOKE) and x-ray photoemission and have found that they are discrete owing to the quantum size effect and appear approximately every 0953-8984/8/27/007/img7. This coincides with the oscillation period of the saturation field. We connect them with the quantum minority-spin interface states near the Fermi level 0953-8984/8/27/007/img8. The magnetoresistance found in these sandwich layers has been calculated on the basis of the quantum size effect transport theory with the requirement that there exist quantum well states within individual layers or groups of layers. The results of the calculation and experiments have been discussed.

  19. Enhancement of Fluorescence-Based Sandwich Immunoassay Using Multilayered Microplates Modified with Plasma-Polymerized Films

    PubMed Central

    Yano, Kazuyoshi; Iwasaki, Akira

    2016-01-01

    A functional modification of the surface of a 96-well microplate coupled with a thin layer deposition technique is demonstrated for enhanced fluorescence-based sandwich immunoassays. The plasma polymerization technique enabling the deposition of organic thin films was employed for the modification of the well surface of a microplate. A silver layer and a plasma-polymerized film were consecutively deposited on the microplate as a metal mirror and the optical interference layer, respectively. When Cy3-labeled antibody was applied to the wells of the resulting multilayered microplate without any immobilization step, greatly enhanced fluorescence was observed compared with that obtained with the unmodified one. The same effect could be also exhibited for an immunoassay targeting antigen directly adsorbed on the multilayered microplate. Furthermore, a sandwich immunoassay for the detection of interleukin 2 (IL-2) was performed with the multilayered microplates, resulting in specific and 88-fold–enhanced fluorescence detection. PMID:28029144

  20. Path integral centroid molecular dynamics simulation of para-hydrogen sandwiched by graphene sheets

    NASA Astrophysics Data System (ADS)

    Minamino, Yuki; Kinugawa, Kenichi

    2016-11-01

    The carbon-hydrogen composite systems of para-hydrogen (p-H2) sandwiched by a couple of graphene sheets have been investigated by means of path integral centroid molecular dynamics simulations at 17 K. It has been shown that sandwiched hydrogen is liquid-like but p-H2 molecules are preferably adsorbed onto the graphene sheets because of attractive graphene-hydrogen interaction. The diffusion coefficient of p-H2 molecules in the direction parallel to the graphene sheets is comparable to that in pure liquid p-H2. There exists a characteristic mode of 140 cm-1 of the p-H2 molecules, attributed to adsorption-binding motion perpendicular to the graphene sheets.

  1. Strong Exchange Coupling Between the Lanthanide Ions and Phthalocyaniato Ligand Radical in Bis(phthalocyaninato)Lanthanide Sandwich Compounds

    DTIC Science & Technology

    1992-07-06

    trstonQeai n Report ~1 ,fero 4. TITLE AND SUBTITLE 5. FUNDING NUMBERS Strong Exchange Coupling Between the Lanthanide Ions and Phthalocyaniato Ligand...Radical in N00014-92-J-1637 Bis(phthalocyaninato) lanthanide Sandwich Compoun s 6. AUTHOR(S) Kathleen L. Trojan, Jonathan L. Kendall, Keith Kepler and...200 words) A series of lanthanide phthalocyanine sandwich compounds with the formula [ (Pc 2")Ln 1 (Pc ’ ) ] have been synthesized and characterized

  2. Infrared spectra of V(n)Bz(n+1) sandwich clusters: a theoretical study of size evolution.

    PubMed

    Wang, Jinlan; Jellinek, Julius

    2005-11-17

    Results of density functional theory computations of infrared (IR) spectra of linear sandwich V(n)Bz(n+1), n = 1-6, complexes are presented. It is shown that the systematic changes in the spectra as a function of the complex size can be categorized and understood in terms of responses of the "parent" modes of the Bz molecule and the VBz complex. The analysis presented should be applicable to a broad class of linear sandwich systems.

  3. Process for Design Optimization of Honeycomb Core Sandwich Panels for Blast Load Mitigation

    DTIC Science & Technology

    2012-12-01

    damage causing potential of the blast impulse. Though metal sandwich panels have been used for a long time in aircraft and other light weight struc...aluminum alloy with bilinear isotropic-hardening elastoplastic material model is used for the foil. Since the yield and ultimate strength of the AL5052...foil are very close, bilinear elastoplastic mate- rial model with very low tangent modulus is a reasonable approximation. The adhesive is modeled as

  4. Observation of a Strongly Enhanced Magnetic Susceptibility of Pd in Au-Pd-Au Sandwiches

    NASA Astrophysics Data System (ADS)

    Brodsky, M. B.; Freeman, A. J.

    1980-07-01

    Exceptionally large increases in the magnetic susceptibility (indicating nearly magnetic ordering) of thin films of Pd sandwiched between thicker Au films have been observed at low temperatures-presumably due to the expansion of the Pd average lattice constant by the Au. The large resultant Stoner factors and the modified paramagnon model of Levin and Valls indicate the possibility of observing p-wave superconductivity in Pd structures with reduced proximity effects.

  5. Defining the Growth/No-Growth Boundary for Listeria monocytogenes in Shelf Stable Pocket Sandwiches

    DTIC Science & Technology

    2008-12-01

    contains 50% of the usual glycerol amount, 50% of the usual tomato paste amount, no vinegar, no brown sugar and bread that contains no glycerol and...product pouch ɘ.30% The second product is a Bacon Cheddar Sandwich in which a precooked bacon product is enrobed into bread . The formulation...factor to consider is the variability of the process. The batch might be non homogeneous mixed, the ratio of filling and bread can vary, the baking

  6. Bacillus shackletonii sp. nov., from volcanic soil on Candlemas Island, South Sandwich archipelago.

    PubMed

    Logan, Niall A; Lebbe, Liesbeth; Verhelst, An; Goris, Johan; Forsyth, Gillian; Rodríguez-Díaz, Marina; Heyndrickx, Marc; De Vos, Paul

    2004-03-01

    A sample of mossy soil taken from the eastern lava flow of northern Candlemas Island, South Sandwich archipelago, yielded six isolates of aerobic, endospore-forming bacteria. Miniaturized routine phenotypic tests and other observations, amplified rDNA restriction analysis and SDS-PAGE analysis suggested that the strains represent a novel taxon. 16S rDNA sequence comparisons support the proposal of a novel species, Bacillus shackletonii sp. nov., the type strain of which is LMG 18435(T) (=CIP 107762(T)).

  7. "Half-sandwich" Yb(III) single-ion magnets with metallacrowns.

    PubMed

    Li, Quan-Wen; Liu, Jun-Liang; Jia, Jian-Hua; Chen, Yan-Cong; Liu, Jiang; Wang, Long-Fei; Tong, Ming-Liang

    2015-06-28

    The first "half-sandwich" Yb(III) single-ion magnets (SIMs) based on [12-MCZn(ii)-4] are reported, in which the central ytterbium ion is coordinated by YbO8 geometry in D4d symmetry. The anisotropic barrier is extracted from the analysis of static, dynamic magnetism and emission spectrum offering an insight into the magneto-optical correlation.

  8. High Strength and Impact Damage Tolerant Syntactic Foam for High Performance Sandwich Structures

    DTIC Science & Technology

    2006-07-25

    it needs additional curing sources, its uniformity is not as good as other curing methods, and its shrinkage is usually high. Summary...Fast Repair of Laminated Beams Using UV Curing Composites ,” Composite Structures, 60(1), pp. 73-81, (2003). 3. S.S. Pang, G. Li, J.E. Helms, and...strength and higher impact tolerant syntactic foam for composite sandwich structures. A unique microstructure was designed and realized through a

  9. An experimental investigation into nonlinear dynamics of a magneto-rheological elastomer sandwich beam

    NASA Astrophysics Data System (ADS)

    Yildirim, Tanju; Ghayesh, Mergen H.; Li, Weihua; Alici, Gursel

    2016-01-01

    An experimental investigation has been carried out on the nonlinear dynamics of a clamped-clamped Magneto-Rheological Elastomer (MRE) sandwich beam with a point mass when subjected to a point excitation. Three sets of experiments have been conducted namely for (i) an aluminium beam, (ii) a MRE sandwich beam in the absence of a magnetic field and (iii) a MRE sandwich beam in the presence of a magnetic field. An electrodynamic shaker was used to excite each system and the corresponding displacement of the point mass was measured: for the third experiment (iii), an array of magnets has been placed at various distances away from the centre of the point mass to investigate the effect of changing stiffness and damping properties on the nonlinear dynamical behaviour. An interesting feature for the third group is the beam point mass displacement was no longer symmetric as the stiffness and damping of the system are increased when moving towards the magnets. Both the first and second groups exhibited distinct nonlinear behaviour; however, for the third group this work shows that for a low magnetic field the sandwich beam exhibits two distinct resonance peaks, one occurring above and the other below the fundamental natural frequency of the transverse motion, with the right one larger. For a larger magnetic field, these peaks even out until the magnetic force was large enough that the hardening-type nonlinear behaviour changes to a softening-type; a significant qualitative change in the nonlinear dynamical behaviour of the system, due to the presence of the magnetic field, was observed.

  10. Blast and Fragment Protective Sandwich Panel Concepts for Stainless Steel Monohull Designs

    DTIC Science & Technology

    2008-10-21

    topologies, accessibility to inner nodes in the panel, scale issues, and safety issues. Evaluation could include round robin testing of full scale...experimental geometry (see Figure 1): where Vb is the impact velocity, / and s are the acoustic impedances of the fluid and of the solid respec- tively, and D...machined to round specimens 305 mm in diameter (see Figure 3). The total thickness of the sandwich panels was 13.97 mm and the relative density of the

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

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

    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.

  12. Sandwich type plasmonic platform for MEF using silver fractals.

    PubMed

    Raut, Sangram L; Rich, Ryan; Shtoyko, Tanya; Bora, Ilkay; Laursen, Bo W; Sørensen, Thomas Just; Borejdo, Julian; Gryczynski, Zygmunt; Gryczynski, Ignacy

    2015-11-14

    In this report, we describe a plasmonic platform with silver fractals for metal enhanced fluorescence (MEF) measurements. When a dye containing surface was brought into contact with silver fractals, a significantly enhanced fluorescence signal from the dye was observed. Fluorescence enhancement was studied with the N-methyl-azadioxatriangulenium chloride salt (Me-ADOTA·Cl) in PVA films made from 0.2% PVA (w/v) solution spin-coated on a clean glass coverslip. The Plasmonic Platforms (PP) were assembled by pressing together silver fractals on one glass slide and a separate glass coverslip spin-coated with a uniform Me-ADOTA·Cl in PVA film. In addition, we also tested ADOTA labeled human serum albumin (HSA) deposited on a glass slide for potential PP bioassay applications. Using the new PP, we could achieve more than a 20-fold fluorescence enhancement (bright spots) accompanied by a decrease in the fluorescence lifetime. The experimental results were used to calculate the extinction (excitation) enhancement factor (GA) and fluorescence radiative rate enhancements factor (GF). No change in emission spectrum was observed for a dye with or without contact with fractals. Our studies indicate that this type of PP can be a convenient approach for constructing assays utilizing metal enhanced fluorescence (MEF) without the need for depositing the material directly on metal structures platforms.

  13. Sandwich type plasmonic platform for MEF using silver fractals

    NASA Astrophysics Data System (ADS)

    Raut, Sangram L.; Rich, Ryan; Shtoyko, Tanya; Bora, Ilkay; Laursen, Bo W.; Sørensen, Thomas Just; Borejdo, Julian; Gryczynski, Zygmunt; Gryczynski, Ignacy

    2015-10-01

    In this report, we describe a plasmonic platform with silver fractals for metal enhanced fluorescence (MEF) measurements. When a dye containing surface was brought into contact with silver fractals, a significantly enhanced fluorescence signal from the dye was observed. Fluorescence enhancement was studied with the N-methyl-azadioxatriangulenium chloride salt (Me-ADOTA.Cl) in PVA films made from 0.2% PVA (w/v) solution spin-coated on a clean glass coverslip. The Plasmonic Platforms (PP) were assembled by pressing together silver fractals on one glass slide and a separate glass coverslip spin-coated with a uniform Me-ADOTA.Cl in PVA film. In addition, we also tested ADOTA labeled human serum albumin (HSA) deposited on a glass slide for potential PP bioassay applications. Using the new PP, we could achieve more than a 20-fold fluorescence enhancement (bright spots) accompanied by a decrease in the fluorescence lifetime. The experimental results were used to calculate the extinction (excitation) enhancement factor (GA) and fluorescence radiative rate enhancements factor (GF). No change in emission spectrum was observed for a dye with or without contact with fractals. Our studies indicate that this type of PP can be a convenient approach for constructing assays utilizing metal enhanced fluorescence (MEF) without the need for depositing the material directly on metal structures platforms.

  14. Analysis of Thick Sandwich Shells with Embedded Ceramic Tiles

    NASA Technical Reports Server (NTRS)

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

    1996-01-01

    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.

  15. Clay Nanocomposite/Aerogel Sandwich Structures for Cryotanks

    NASA Technical Reports Server (NTRS)

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

    2006-01-01

    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.

  16. Modification of the Sandwich Estimator in Generalized Estimating Equations with Correlated Binary Outcomes in Rare Event and Small Sample Settings

    PubMed Central

    Rogers, Paul; Stoner, Julie

    2016-01-01

    Regression models for correlated binary outcomes are commonly fit using a Generalized Estimating Equations (GEE) methodology. GEE uses the Liang and Zeger sandwich estimator to produce unbiased standard error estimators for regression coefficients in large sample settings even when the covariance structure is misspecified. The sandwich estimator performs optimally in balanced designs when the number of participants is large, and there are few repeated measurements. The sandwich estimator is not without drawbacks; its asymptotic properties do not hold in small sample settings. In these situations, the sandwich estimator is biased downwards, underestimating the variances. In this project, a modified form for the sandwich estimator is proposed to correct this deficiency. The performance of this new sandwich estimator is compared to the traditional Liang and Zeger estimator as well as alternative forms proposed by Morel, Pan and Mancl and DeRouen. The performance of each estimator was assessed with 95% coverage probabilities for the regression coefficient estimators using simulated data under various combinations of sample sizes and outcome prevalence values with an Independence (IND), Autoregressive (AR) and Compound Symmetry (CS) correlation structure. This research is motivated by investigations involving rare-event outcomes in aviation data. PMID:26998504

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

    NASA Technical Reports Server (NTRS)

    Ko, William L.

    1999-01-01

    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.

  18. Effect of applied magnetic field on sound transmission loss of MR-based sandwich panels

    NASA Astrophysics Data System (ADS)

    Hemmatian, Masoud; Sedaghati, Ramin

    2017-02-01

    This study aims to investigate the sound transmission loss (STL) capability of sandwich panels treated with Magnetorheological (MR) fluids at low frequencies. An experimental setup has been designed to investigate the effect of the intensity of applied magnetic field on the natural frequencies and STL of a clamped circular panel. It is shown that the fundamental natural frequency of the MR sandwich panel increases in proportion to the applied magnetic field. In addition, the STL of the panel at the resonance frequency increases as the magnetic field is amplified. Furthermore, the classical plate theory and Ritz method have been utilized to develop the governing equations of motion of the finite multilayered circular panels comprising two elastic face sheets and MR fluid core layer. The radiated sound power from the panel is derived using Rayleigh integral as a function of the transverse velocity of the panel which is subsequently used to evaluate the STL. The theoretical study is validated comparing the simulation results with the experimental measurements. Experimental and analytical parametric study have also been conducted to study the effect of the core layers’ thickness on the natural frequency and the STL of sandwich panel.

  19. On the Rigidity in Bending of a Sandwich with Thick CFRP Facings and Thin Soft Core

    NASA Astrophysics Data System (ADS)

    Caprino, G.; Iaccarino, P.; Langella, A.; Lamboglia, A.

    2009-06-01

    Flexure tests in three-point bending were performed in the elastic domain on sandwich specimens whose facings were made of T800H/3900-2 laminates, and the core by a soft rubbery layer. The contribution of the shear and flexural deformations to the overall deflection was varied by varying the slenderness ratio. The rigidities yielded by the load-displacement curve were corrected for the indentation occurring at the points of load introduction, using an experimentally determined calibration curve. Due to the thinness of the sandwich, indentation negligibly affected the precision of the results, with the apparent rigidities differing from the actual ones by less than 2%. By an analytical formula previously developed for sandwich structures, a prediction of the rigidities in flexure was attempted, adopting elastic constants available in the literature. The correlation with the data points was poor, with the theoretical results largely overestimating the actual rigidities. However, the reliability of the closed-form formula was supported by finite element analysis, carried out modelling the facings by 2D plate elements, and the core by 3D brick elements. Through the formula, the core shear modulus was individuated as responsible of the discrepancies observed. Assuming a suitable value for this parameter, both the analytic solution and the finite element models were able to match with accuracy the rigidities measured.

  20. Hypervelocity Impact Performance of Open Cell Foam Core Sandwich Panel Structures

    NASA Technical Reports Server (NTRS)

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

    2010-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

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

    1997-01-01

    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.

  2. A novel sandwich differential capacitive accelerometer with symmetrical double-sided serpentine beam-mass structure

    NASA Astrophysics Data System (ADS)

    Xiao, D. B.; Li, Q. S.; Hou, Z. Q.; Wang, X. H.; Chen, Z. H.; Xia, D. W.; Wu, X. Z.

    2016-02-01

    This paper presents a novel differential capacitive silicon micro-accelerometer with symmetrical double-sided serpentine beam-mass sensing structure and glass-silicon-glass sandwich structure. The symmetrical double-sided serpentine beam-mass sensing structure is fabricated with a novel pre-buried mask fabrication technology, which is convenient for manufacturing multi-layer sensors. The glass-silicon-glass sandwich structure is realized by a double anodic bonding process. To solve the problem of the difficulty of leading out signals from the top and bottom layer simultaneously in the sandwich sensors, a silicon pillar structure is designed that is inherently simple and low-cost. The prototype is fabricated and tested. It has low noise performance (the peak to peak value is 40 μg) and μg-level Allan deviation of bias (2.2 μg in 1 h), experimentally demonstrating the effectiveness of the design and the novel fabrication technology.

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

    NASA Astrophysics Data System (ADS)

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

    2012-11-01

    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.

  4. Lamb wave-based BVID imaging for a curved composite sandwich panel

    NASA Astrophysics Data System (ADS)

    He, Jiaze; Yuan, Fuh-Gwo

    2017-02-01

    Composite sandwich structures, consisting of a low density core sandwiched between two laminated facesheets, have been widely used in various aerospace structures. A new Lamb wave-based imaging condition, which will be referred to as the inverse incident wave energy (IIWE) imaging criterion, is proposed in this paper to resolve the situations where the incident wave energy weakly penetrates into the damaged area in the upper facesheet region. Current imaging conditions by analyzing wavefield reconstructed from laser Doppler vibrometer (LDV) scanning have been proven to be adequate for imaging damage in layered composite laminates. In this research, those current imaging conditions were applied and compared in the composite foam structures for barely visible impact damage (BVID). A piezoelectric wafer was used to excite Lamb waves into the structure and a LDV was used to scan the potential damaged areas in the upper facesheet of the panel. A BVID site in a curved composite sandwich foam aileron was inspected using various wavefield analysis methods and the damage images were compared with C-scan images. A few imaging conditions that are effective for this BVID site are identified when the incident waves have difficulties penetrating into the damaged region.

  5. Modified Class II open sandwich restorations: evaluation of interfacial adaptation and influence of different restorative techniques.

    PubMed

    Andersson-Wenckert, Ingrid E; van Dijken, Jan W V; Hörstedt, Per

    2002-06-01

    The sandwich technique with resin-modified glass ionomer cement (RMGIC) has been proposed to relieve the contraction stresses of direct resin composite (RC) restorations. The aim of this study was to evaluate the interfacial adaptation to enamel and dentin of modified Class II open RMGIC/RC sandwich restorations and the influence of different light curing techniques and matrix bands. Forty box-shaped Class II fillings were placed in vivo in premolars scheduled for extraction after one month. In groups I and II, a metal matrix was used; RC was inserted with horizontal (group I) and diagonal (group II) increments and cured with indirect/direct light. Group III was performed as group II, but a transparent matrix was used. Group IV was as group II, but with a separating liner between RMGIC and RC. Group V was a closed sandwich restoration. Interfacial quality was studied using SEM replica technique. Gap-free interfacial adaptation to enamel was observed for RMGIC in 70%, for RC in 70% and to dentin for RMGIC in 81%, for RC in 56%. No significant differences were seen between the experimental groups. At the cervical margins, RMGIC showed significantly better adaptation to enamel than RC, 74% and 42%, respectively. In conclusion, the investigated restorations showed a high percentage of gap-free interfacial adaptation in vivo. Interfacial adaptation to dentin and to cervical enamel was significantly better for RMGIC than for RC.

  6. Use of the skin sandwich technique to probe the role of the hair follicles in sonophoresis.

    PubMed

    Sarheed, Omar; Frum, Yakov

    2012-02-28

    The human skin sandwich technique was used to explore the effect of brief ultrasound exposure on the transfollicular pathway of absorption. Hydrocortisone was used as a model drug. In order to calculate the permeability coefficient of hydrocortisone, its concentration at saturation in the PBS donor solution was determined. Skin samples were prepared by sandwich technique with total hydration of the epidermal and sandwich membranes. The skin was sonicated for 0 s (control), 30 s or 45 s using a pulsed mode (10% duty cycle) with the spatial and temporal average intensity (SATA) of 3.7 W/cm(2). The transducer was then removed and permeation was allowed to proceed for 52 h. Then the percentage follicular contribution was determined. It was determined that without ultrasound, drug entry into follicles accounted for 46% of total penetration. As the duration of sonication increased, the follicular contribution fell to zero even though total transepidermal flux dramatically increased. This is explained by ultrasound exposure causing sloughing off of the uppermost stratum corneum. This permeabilises the continuous surface but at the same time the disturbed cornceocytes will plug hair follicle orifices.

  7. Use of a compact sandwich specimen to evaluate fracture toughness and interfacial bonding of bone.

    PubMed

    Wang, X; Lankford, J; Agrawal, C M

    1994-01-01

    The objective of the present study was to develop a reliable and statistically valid test to measure the fracture toughness of small specimens of bone, and by extension, prosthetic materials, using a compact sandwich specimen. Samples of bone were sandwiched between holders of a different material and using this specimen configuration a new technique was developed to test the fracture toughness of the bone interlayer. The effects of different specimens sizes and holder materials were investigated empirically. Using finite element analysis a correction factor was determined to account for the finite thickness of the interlayer and the analytical solutions governing the test specimen were accordingly modified. Bulk compact tension specimens of bone were tested for comparison. Both wet and dry bone were evaluated and the fracture surface morphology characterized using scanning electron microscopy. The results indicate no statistically significant differences between the fracture toughness values obtained from the compact tension and sandwich specimens. The application of this technique to the testing of interfacial bonding between bone and biomaterials is discussed.

  8. In-situ observation of nucleated polymer crystallization in polyoxymethylene sandwich composites

    NASA Astrophysics Data System (ADS)

    Slouf, Miroslav; Krejcikova, Sabina; Vackova, Tatana; Kratochvil, Jaroslav; Novak, Libor

    2015-03-01

    We introduce a dynamic sandwich method, which can be used for in-situ observation and quantification of polymer crystallization nucleated by micro/nanoparticles. The method was applied on polyoxymethylene (POM) composites with three nucleating agents: talc micropowder (POM/mTalc), chalk nanopowder (POM/nChalk) and titanate nanotubes (POM/TiNT). The nucleating agents were deposited between polymer films, the resulting sandwich samples were consolidated by thermal treatment, and their microtomed cross-sections were observed during isothermal crystallization by polarized light microscopy. As the intensity of polarized light was shown to be proportional to the relative crystallinity, the PLM results could be fitted to Avrami equation and the nucleating activity of all investigated particles could be quantified by means of Avrami parameters (n, k). The crystallization half-times increased reproducibly in the following order: POM/nChalk < POM/mTalc < POM/TiNT ~ POM. For strong nucleating agents (mTalc, nChalk), the crystallization kinetics corresponded to spontaneous crystallization starting from central nucleating layer, which was verified by computer simulations. The results were also confirmed by DSC. We concluded that the sandwich method is an efficient microscopic technique for detailed evaluation of nucleating activity of arbitrary micro/nanoparticles in polymer systems.

  9. Sandwiched polymer fibre in fibrin matrices for the dictation of endothelial cells undergoing angiogenesis

    NASA Astrophysics Data System (ADS)

    Sukmana, I.; Djuansjah, J. R. P.

    2013-04-01

    We present here a three-dimensional (3D) sandwich system made by poly(ethylene terephthalate) (PET) fibre and fibrin extracellular matrix (ECM) for endothelial cell dictation and angiogenesis guidance. In this three-dimensional system, Human Umbilical Vein Endothelial cells (HUVECs) were firstly cultured for 2 (two) days to cover the PET fibre before sandwiched in two layer fibrin gel containing HUVECs. After 4 (four) days of culture, cel-to-cel connection, tube-like structure and multi-cellular lumen formation were then assessed and validated. Phase contrast and fluorescence imaging using an inverted microscope were used to determine cell-to-cell and cell-ECM interactions. Laser scanning confocal microscopy and histological techniques were used to confirm the development of tube-like structure and multi-cellular lumen formation. This study shows that polymer fibres sandwiched in fibrin gel can be used to dictate endothelial cells undergoing angiogenesis with potential application in cancer and cardiovascular study and tissue engineering vascularisation.

  10. Design and reinforcement: vertically aligned carbon nanotube-based sandwich composites.

    PubMed

    Zeng, You; Ci, Lijie; Carey, Brent J; Vajtai, Robert; Ajayan, Pulickel M

    2010-11-23

    Carbon nanotube (CNT) reinforcement of polymer composites has not yielded optimum results in that the composite properties are typically compromised by poor dispersion and random orientation of CNTs in polymers. Given the short lengths available for nanotubes, opportunities lie in incorporating CNTs with other structural reinforcements such as carbon fibers (CFs) to achieve improvement over existing composite designs. Growth of vertically aligned CNTs (VACNTs) offers new avenues for designing high-performance composites by integrating CFs and nanotubes into layered 3D architectures. To obtain composites with high rigidity and damping, we have designed and fabricated VACNT-based sandwich composites from simply stacking the freestanding VACNTs and CF fabrics and infiltrating with epoxy matrix. Comparing with the CF/epoxy laminates, the VACNT-based sandwich composites exhibit higher flexural rigidity and damping, which is achieved due to the effective integration of the VACNTs as an interfacial layer between the CF stacks. Furthermore, the lighter weight of these VACNT-based sandwich composites offers advantages in aerospace and transportation applications.

  11. Shear Behavior of 3D Woven Hollow Integrated Sandwich Composites: Experimental, Theoretical and Numerical Study

    NASA Astrophysics Data System (ADS)

    Zhou, Guangming; Liu, Chang; Cai, Deng'an; Li, Wenlong; Wang, Xiaopei

    2016-11-01

    An experimental, theoretical and numerical investigation on the shear behavior of 3D woven hollow integrated sandwich composites was presented in this paper. The microstructure of the composites was studied, then the shear modulus and load-deflection curves were obtained by double lap shear tests on the specimens in two principal directions of the sandwich panels, called warp and weft. The experimental results showed that the shear modulus of the warp was higher than that of the weft and the failure occurred in the roots of piles. A finite element model was established to predict the shear behavior of the composites. The simulated results agreed well with the experimental data. Simultaneously, a theoretical method was developed to predict the shear modulus. By comparing with the experimental data, the accuracy of the theoretical method was verified. The influence of structural parameters on shear modulus was also discussed. The higher yarn number, yarn density and dip angle of the piles could all improve the shear modulus of 3D woven hollow integrated sandwich composites at different levels, while the increasing height would decrease the shear modulus.

  12. Sensitive sandwich immunoassay based on single particle mode inductively coupled plasma mass spectrometry detection.

    PubMed

    Liu, Rui; Xing, Zhi; Lv, Yi; Zhang, Sichun; Zhang, Xinrong

    2010-11-15

    A sensitive sandwich type immunoassay has been proposed with the detection by inductively coupled plasma mass spectrometry (ICP-MS) in a single particle mode (time resolved analysis). The signal induced by the flash of ions ((197)Au(+)) due to the ionization of single Au-nanoparticle (Au-NP) label in the plasma torch can be measured by the mass spectrometer. The frequency of the transient signals is proportional to the concentration of Au-NPs labels. Characteristics of the signals obtained from Au-NPs of 20, 45 and 80 nm in diameters were discussed. The analytical figures for the determination of Au-labeled IgG using ICP-MS in conventional integral mode and single particle mode were compared in detail. Rabbit-anti-human IgG was used as a model analyte in the sandwich immunoassay. A detection limit (3 σ) of 0.1 ng mL(-1) was obtained for rabbit-anti-human IgG after immunoreactions, with a linear range of 0.3-10 ng mL(-1) and a RSD of 8.1% (2.0 ng mL(-1)). Finally, the proposed method was successfully applied to spiked rabbit-anti-human IgG samples and rabbit-anti-human serum samples. The method resulted to be a highly sensitive ICP-MS based sandwich type immunoassay.

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

    PubMed

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

    2014-03-01

    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.

  14. Long-range fluorescence quenching by gold nanoparticles in a sandwich immunoassay for cardiac troponin T.

    PubMed

    Mayilo, Sergiy; Kloster, Meike A; Wunderlich, Michael; Lutich, Andrey; Klar, Thomas A; Nichtl, Alfons; Kürzinger, Konrad; Stefani, Fernando D; Feldmann, Jochen

    2009-12-01

    We report the first homogeneous sandwich immunoassay with gold nanoparticles (AuNPs) as fluorescence quenchers. The sandwich assay is designed for the detection of the protein cardiac troponin T (cTnT) by its simultaneous interaction with two different antibodies, one attached to AuNPs and the other labeled with fluorescent dyes. We demonstrate the working principle of the assay and using time-resolved fluorescence spectroscopy, we determine the quenching efficiency of the gold nanoparticles. In spite of the relatively large separation distance between dye molecules and AuNPs, ranging from 3 to 22 nm, the AuNPs quench the fluorescence with efficiencies as high as 95%. A limit of detection of 0.02 nM (0.7 ng/mL) was obtained for cTnT, which is the lowest value reported for a homogeneous sandwich assay for cTnT. These results illustrate the use of metallic nanoparticles as fluorescence quenchers in immunoassays where the large biomolecules involved impose distances for which energy transfer between fluorophores would be inefficient.

  15. Aptamer-Au NPs conjugates-enhanced SPR sensing for the ultrasensitive sandwich immunoassay.

    PubMed

    Wang, Jianlong; Munir, Ahsan; Li, Zhonghong; Zhou, H Susan

    2009-09-15

    The goal of this work is to explore the amplification effect of aptamer-gold nanoparticles (Au NPs) conjugates for ultrasensitive detection of large biomolecules by surface plasmon resonance (SPR). A novel sandwich immunoassay is designed to demonstrate the amplification effect of aptamer-Au NPs conjugates by using human immunoglobulin E (IgE) as model analyte. Human IgE, captured by immobilized goat anti-human IgE on SPR gold film, is sensitively detected by SPR spectroscopy with a lowest detection limit of 1 ng/ml after anti-human IgE aptamer-Au NPs conjugates is used as amplification reagent. Meanwhile, the non-specific adsorption of aptamer-Au NPs conjugates on goat anti-human IgE is confirmed by SPR spectroscopy and then it is minimized by treating aptamer-Au NPs conjugates with 6-mercaptohexan-1-ol (MCH). These results confirm that aptamer-Au NPs conjugates is a powerful sandwich element and an excellent amplification reagent for SPR-based sandwich immunoassay.

  16. Numerical comparison of patch and sandwich piezoelectric transducers for transmitting ultrasonic waves

    NASA Astrophysics Data System (ADS)

    Loveday, Philip W.

    2006-03-01

    Guided wave ultrasonic inspection is becoming an important method of non-destructive testing for long, slender structures such as pipes and rails. Often it is desirable to use transducers that can strongly excite a specific mode of wave propagation in the waveguide. Piezoelectric patch transducers are frequently employed, by researchers, for exciting waves in beam like structures. Sonar systems frequently make use of resonant transducers, such as sandwich transducers, for acoustic wave generation and this principle has been used to excite waves in a rail. This paper compares the two transduction approaches, for launching bending waves in rectangular waveguides, with numerical modeling. The numerical modeling combined a waveguide finite element model, of the waveguide, with conventional three-dimensional piezoelectric finite element models of the transducers. The waveguide finite elements were formulated using a complex exponential to describe the wave propagation along the structure and conventional finite element interpolation over the area of the element. Consequently, only a two-dimensional finite element mesh covering the cross-section of the waveguide is required. The harmonic forced response of the waveguide was used to compute a complex dynamic stiffness matrix which represented the waveguide in the transducer model. The effects of geometrical parameters of patch and sandwich transducers were considered before the comparison was made. It appears that piezoelectric patch transducers offer advantages at low frequencies while sandwich transducers are superior at high frequencies, where resonance can be exploited, at the cost of more complex design.

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

    NASA Technical Reports Server (NTRS)

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

    2007-01-01

    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.

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

    PubMed

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

    2013-04-19

    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.

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

    NASA Technical Reports Server (NTRS)

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

    2010-01-01

    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.

  20. Efficient Design and Analysis of Lightweight Reinforced Core Sandwich and PRSEUS Structures

    NASA Technical Reports Server (NTRS)

    Bednarcyk, Brett A.; Yarrington, Phillip W.; Lucking, Ryan C.; Collier, Craig S.; Ainsworth, James J.; Toubia, Elias A.

    2012-01-01

    Design, analysis, and sizing methods for two novel structural panel concepts have been developed and incorporated into the HyperSizer Structural Sizing Software. Reinforced Core Sandwich (RCS) panels consist of a foam core with reinforcing composite webs connecting composite facesheets. Boeing s Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS) panels use a pultruded unidirectional composite rod to provide axial stiffness along with integrated transverse frames and stitching. Both of these structural concepts are ovencured and have shown great promise applications in lightweight structures, but have suffered from the lack of efficient sizing capabilities similar to those that exist for honeycomb sandwich, foam sandwich, hat stiffened, and other, more traditional concepts. Now, with accurate design methods for RCS and PRSEUS panels available in HyperSizer, these concepts can be traded and used in designs as is done with the more traditional structural concepts. The methods developed to enable sizing of RCS and PRSEUS are outlined, as are results showing the validity and utility of the methods. Applications include several large NASA heavy lift launch vehicle structures.

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

    NASA Technical Reports Server (NTRS)

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

    2014-01-01

    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.

  2. Amniotic Membrane Transplant with a Special Technique (Motowa's Sandwich Technique) in Mooren's Ulcer.

    PubMed

    Al Motowa, Saeed; Al Zobidi, Mohammed

    2015-01-01

    To illustrate amniotic membrane transplant (AMT) with a novel surgical technique ("sandwich technique") for treating patients with malignant Mooren's ulcer. A case report of a patient with bilateral, malignant Mooren's ulcer who had undergone systemic steroid therapy and topical immunosuppresive therapy to stabilize his condition. However, perforation of cornea occurred in one eye. AMT with a new surgical technique ("Motowa's sandwich technique") was performed to treat this case. On the 1(st) day postoperatively, there was no pain, no photophobia, and visual acuity was same as preoperatively. At 4 weeks postoperatively, visual acuity improved in the right eye to 20/160 with pinhole, and there was no fluorescein staining. The right eye was quiet. Amniotic membrane transplant with "Motowa's sandwich technique" resulted in the preservation of the anatomical integrity and progression of disease was halted along with an improved vision. This technique is a novel surgical modality in treating Mooren's ulcer. Further study on a large cohort of patients is required for evidence-based data to verify the outcome of this initial case report.

  3. Experimental investigation of graphite/polyimide sandwich panels in edgewise compression

    NASA Technical Reports Server (NTRS)

    Camarda, C. J.

    1980-01-01

    The local and general buckling behavior of graphite/polyimide sandwich panels simply supported along all four edges and loaded in uniaxial edgewise compression 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.

  4. Sandwich mixer-reactor: influence of the diffusion coefficient and flow rate ratios.

    PubMed

    Abonnenc, Mélanie; Josserand, Jacques; Girault, Hubert H

    2009-02-07

    A sandwich mixer consists of mixing two solutions in a channel, one central laminar flow being sandwiched between two outer flow solutions. The present numerical study considers the convection-diffusion of two reacting species A and B, provided respectively by the two incoming solutions. The simulations show how the diffusion coefficient, flow rate and species concentration ratios influence, via the transversal diffusion length and reaction kinetics, the reaction extent at the end of the sandwich mixer. First, this extent can be enhanced up to 60% if the species with the lowest diffusion coefficient is located in the outer solutions where the flow velocity is small compared to that of the central part (higher residence time). Secondly, decreasing the outer flow rates (to confine the reaction close to the walls) and increasing the local concentration to keep the same flux ratio improve the extent by 300%. Comparison with a bi-lamination passive mixer, with an ideal mixer and an electro-osmotic driven flow mixer is presented. These conclusions are also demonstrated for consecutive reactions, showing an amplification of the effects described above. The results are also presented versus the residence time in the mixer-reactor to show the time window for which the gain is appreciable.

  5. Sizing Single Cantilever Beam Specimens for Characterizing Facesheet/Core Peel Debonding in Sandwich Structure

    NASA Technical Reports Server (NTRS)

    Ratcliffe, James G.

    2010-01-01

    This technical publication details part of an effort focused on the development of a standardized facesheet/core peel debonding test procedure. The purpose of the test is to characterize facesheet/core peel in sandwich structure, accomplished through the measurement of the critical strain energy release rate associated with the debonding process. Following an examination of previously developed tests and a recent evaluation of a selection of these methods, a single cantilever beam (SCB) specimen was identified as being a promising candidate for establishing such a standardized test procedure. The objective of the work described here was to begin development of a protocol for conducting a SCB test that will render the procedure suitable for standardization. To this end, a sizing methodology was developed to ensure appropriate SCB specimen dimensions are selected for a given sandwich system. Application of this method to actual sandwich systems yielded SCB specimen dimensions that would be practical for use. This study resulted in the development of a practical SCB specimen sizing method, which should be well-suited for incorporation into a standardized testing protocol.

  6. A thin-walled polydimethylsiloxane bioreactor for high-density hepatocyte sandwich culture.

    PubMed

    Tan, Guo-Dong Sean; Toh, Guoyang William; Birgersson, Erik; Robens, Jeffrey; van Noort, Danny; Leo, Hwa Liang

    2013-06-01

    In vitro drug testing requires long-term maintenance of hepatocyte liver specific functions. Hepatocytes cultured at a higher seeding density in a sandwich configuration exhibit an increased level of liver specific functions when compared to low density cultures due to the better cell to cell contacts that promote long term maintenance of polarity and liver specific functions. However, culturing hepatocytes at high seeding densities in a standard 24-well plate poses problems in terms of the mass transport of nutrients and oxygen to the cells. In view of this drawback, we have developed a polydimethylsiloxane (PDMS) bioreactor that was able to maintain the long-term liver specific functions of a hepatocyte sandwich culture at a high seeding density. The bioreactor was fabricated with PDMS, an oxygen permeable material, which allowed direct oxygenation and perfusion to take place simultaneously. The mass transport of oxygen and the level of shear stress acting on the cells were analyzed by computational fluid dynamics (CFD). The combination of both direct oxygenation and perfusion has a synergistic effect on the liver specific function of a high density hepatocyte sandwich culture over a period of 9 days.

  7. Archetypal sandwich-structured CuO for high performance non-enzymatic sensing of glucose.

    PubMed

    Meher, Sumanta Kumar; Rao, G Ranga

    2013-03-07

    In the quest to enhance the selectivity and sensitivity of novel structured metal oxides for electrochemical non-enzymatic sensing of glucose, we report here a green synthesis of unique sandwich-structured CuO on a large scale under microwave mediated homogeneous precipitation conditions. The physicochemical studies carried out by XRD and BET methods show that the monoclinic CuO formed via thermal decomposition of Cu(2)(OH)(2)CO(3) possesses monomodal channel-type pores with largely improved surface area (~43 m(2) g(-1)) and pore volume (0.163 cm(3) g(-1)). The fascinating surface morphology and pore structure of CuO is formulated due to homogeneous crystallization and microwave induced self assembly during synthesis. The cyclic voltammetry and chronoamperometry studies show diffusion controlled glucose oxidation at ~0.6 V (vs. Ag/AgCl) with extremely high sensitivity of 5342.8 μA mM(-1) cm(-2) and respective detection limit and response time of ~1 μM and ~0.7 s, under a wide dynamic concentration range of glucose. The chronoamperometry measurements demonstrate that the sensitivity of CuO to glucose is unaffected by the absence of dissolved oxygen and presence of poisoning chloride ions in the reaction medium, which essentially implies high poison resistance activity of the sandwich-structured CuO. The sandwich-structured CuO also shows insignificant interference/significant selectivity to glucose, even in the presence of high concentrations of other sugars as well as reducing species. In addition, the sandwich-structured CuO shows excellent reproducibility (relative standard deviation of ~2.4% over ten identically fabricated electrodes) and outstanding long term stability (only ~1.3% loss in sensitivity over a period of one month) during non-enzymatic electrochemical sensing of glucose. The unique microstructure and suitable channel-type pore architecture provide structural stability and maximum accessible electroactive surface for unimpeded mobility of glucose

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

    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

  9. Constructive Criticism.

    ERIC Educational Resources Information Center

    Lieberfeld, Lawrence

    1982-01-01

    Many crucial questions need to be answered before a college embarks on a construction project and makes a substantial financial commitment. Computer modeling techniques can be used to make even complex project feasibility analyses. Available from Peat, Marwick, Mitchell & Co., 345 Park Avenue, New York, NY 10154. (MSE)

  10. Constructing Space

    NASA Astrophysics Data System (ADS)

    Henderson, Austin

    This chapter chronicles the growth of the author's understanding of Media Space through his 20-year experience with coupling spaces, using video. It is a “technology-first” understanding of the construction of space. Key ideas from research studies and practice are presented, and contrasts with other genres of communication are made. The implications for distributed collaboration are explored.

  11. Worldwide construction

    SciTech Connect

    Radler, M.

    1998-04-13

    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.

  12. Abstract Constructions.

    ERIC Educational Resources Information Center

    Pietropola, Anne

    1998-01-01

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

  13. Recyclable Saccharomyces cerevisiae loaded nanofibrous mats with sandwich structure constructing via bio-electrospraying for heavy metal removal.

    PubMed

    Xin, Shangjing; Zeng, Zhaoyang; Zhou, Xue; Luo, Wenjing; Shi, Xiaowen; Wang, Qun; Deng, Hongbing; Du, Yumin

    2017-02-15

    Biosorbents, such as algae and yeast, have been applied in heavy metal adsorption due to their low cost and efficacy. However, they cannot be recycled and reused after direct application, which may cause a secondary pollution. In this study, we used bio-electrospraying technique to immobilize Saccharomyces cerevisiae (a byproduct from food fermentation) onto the surface of poly(ε-caprolactone)/chitosan/rectorite ternary composites based nanofibrous mats. This technique not only combined the advantages of both S. cerevisiae (cheap) and nanofibers (large surface area) in heavy metal removal, but also made biosorbents easy to recollect and reuse. Layer-by-layer structured nanofibrous mats were also fabricated by alternating electrospinning and bio-electrospraying for a couple of times and loaded more S. cerevisiae for enhancing heavy metal biosorption. The morphology of S. cerevisiae loaded nanofibrous mats with different numbers of layers was observed. Biosorption assay was performed on PbNO3 solution under different pH values, contact time, initial concentrations of Pb(2+) and biosorbents weights, at last the elemental composition was measured before and after biosorption. The results showed that S. cerevisiae loaded nanofibrous mats had a biosorption capacity of Pb(2+) up to 238mg/g. Desorption assay indicated that these mats were reusable and maintained high biosorption capacity after three biosorption-desorption cycles.

  14. Alternatives to lumber and plywood in home construction

    SciTech Connect

    Lund, E.

    1993-04-01

    The diminished supply and unstable price of lumber is compelling designers, builders, and developers to explore alternative materials for residential construction. The report discusses several commercially available alternative materials or building systems that may be used in framing and sheathing, including: engineered wood products; laminated fiberboard that can be used for sheathing walls; light-gauge structural steel components for floors, walls and roof systems; foam core structure sandwich panels for walls and roofs; and a variety of concrete and concrete block systems, many of which include insulation material.

  15. Design, Construction and Analysis of a Flat Heat Pipe

    DTIC Science & Technology

    2007-11-02

    fullscale model was to be constructed differently than the subscale model. This was due to Technical Support Department’s acquisition of a new CNC Punch...screens and Monel sheets were cut to the proper dimensions, their size and assigned hole placement were loaded into the CNC Punch-Press machine’s...sheets (3rOmil), and sandwiched in between the sheets. They were then loaded onto the CNC Punch-Press machine and were punched in the appropriate places

  16. Sigma and Pi Interactions of the Pyrrolic Ligand Sandwich-Like Lanthanide Phthalocyanines Determined from Magnetic Susceptibility and Ligand-Field Theory

    DTIC Science & Technology

    1990-06-25

    ACCESSION NO. 11, TITLE (include Security Classification) UNCLASSIFIED: Sigma and Pi Interactions of the Pyrro- lic Ligand Sandwich-Like Lanthanide ...4135007---05 TECHNICAL REPORT NO. 36 Sigma and Pi Interactions of the Pyrrolic Ligand Sandwich-Like Lanthanide Phthalocyanines Determined From Magnetic...Hill Chapel Hill, North Carolina 27599-3290 Sigma and Pi Interactions of the Pyrrolic Ligand Sandwich-Like Lanthanide Phthalocyanines Determined From

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

    PubMed

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

    2014-04-15

    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.

  18. Analysis of propagation characteristics of flexural wave in honeycomb sandwich panel and design of loudspeaker for radiating inclined sound

    NASA Astrophysics Data System (ADS)

    Fujii, Ayaka; Wakatsuki, Naoto; Mizutani, Koichi

    2015-07-01

    A loudspeaker for an auditory guiding system is proposed. This loudspeaker utilizes inclined sound transformed from a flexural wave in a honeycomb sandwich panel. We focused on the fact that the inclined sound propagates extensively with uniform level and direction. Furthermore, sound can be generated without group delay dispersion because the phase velocity of the flexural wave in the sandwich panel becomes constant with increasing frequency. These characteristics can be useful for an auditory guiding system in public spaces since voice-guiding navigation indicates the right direction regardless of position on a pathway. To design the proposed loudspeaker, the behavior of the sandwich panel is predicted using a theoretical equation in which the honeycomb core is assumed as an orthotropic continuum. We calculated the phase velocity dispersion of the flexural wave in the sandwich panel and compared the results obtained using the equation with those of a simulation based on the finite element method and an experiment in order to confirm the applicability of the theoretical equation. It was confirmed that the phase velocities obtained using the theoretical equation and by the simulation were in good agreement with that obtained experimentally. The obtained results suggest that the behavior of the sandwich panel can be predicted using the parameters of the panel. In addition, we designed an optimized honeycomb sandwich panel for radiating inclined sound by calculating the phase velocity characteristics of various panels that have different parameters of core height and cell size using the theoretical equation. Sound radiation from the optimized panel was simulated and compared with that of a homogeneous plate. It was clear that the variance of the radiation angle with varying frequency of the optimized panel was smaller than that of the homogeneous plate. This characteristic of sound radiation with a uniform angle is useful for indicating the destination direction. On

  19. Sandwich-format electrochemiluminescence assay for PDGF-BB using quantum dots-dendrimer nanocomposites as probe.

    PubMed

    Zhang, Jing-Jing; Cao, Jun-Tao; Shi, Gui-Fang; Liu, Yan-Ming; Chen, Yong-Hong; Ren, Shu-Wei

    2015-08-15

    This work describes a novel electrochemiluminescence aptasensor for highly sensitive detection of platelet-derived growth factor BB (PDGF-BB) using aptamer functionalized CdS quantum dots-polyamidoamine as probe (CdS QDs-PAMAM-Apt). CdS QDs-PAMAM nanocomposites were synthesized by one-pot synthesis in methanol. The prepared nanocomposites were linked with the NH2-aptamer 2 (Apt2) of PDGF-BB to form the CdS QDs-PAMAM-Apt2 probe by glutaraldehyde as coupling reagent. For constructing the aptasensor, MWCNTs-chitosan composites and NH2-aptamer 1 (Apt1) with the same base sequence as Apt2 were immobilized on the electrode by the self-assembled method to recognize the target protein PDGF-BB. In the presence of PDGF-BB, the structure of sandwiched format was formed between the Apt1 and the CdS QDs-PAMAM-Apt2 probe, thereby resulting in a proportional increase of ECL emission. Thanks to the efficient and stable ECL emission of CdS QDs-PAMAM dendrimer and the advantage of MWCNTs for accelerating the electron transfer, the highly sensitive detection of PDGF-BB with a detection limit of 0.13pM was achieved. The linear range is from 0.5pM to 1nM. The present protocol was applied to the analysis of PDGF-BB in human serum samples. The recoveries of PDGF-BB in human serum samples are 87.2-113% and RSD values are less than 3.6%.

  20. Multiplexed sandwich immunoassays using flow-injection electrochemiluminescence with designed substrate spatial-resolved technique for detection of tumor markers.

    PubMed

    Zhang, Yan; Liu, Weiyan; Ge, Shenguang; Yan, Mei; Wang, Shaowei; Yu, Jinghua; Li, Nianqiang; Song, Xianrang

    2013-03-15

    Convenient sensor array for simultaneous multi-analyte testing was increasingly needed in clinical diagnosis. A novel electrochemiluminescence (ECL) immunosensor array for the sequential detection of multiple tumor markers was developed by site-selectively immobilizing multiple antigens on different electrodes. Disposable indium tin oxide (ITO) glass array was employed as detection platform. With a sandwich-type immunoassay format, the amount of carbon dots coated silica (SiO(2)@C-dots) labeled antibodies increased with the increment of antigens in the samples. The ECL signal from different immunosensors was collected in turn by a photomultiplier (PMT) with the aid of a home-made potential transformer equiped with a home-made multiplexed-switch. Using carcino embryonic antigen (CEA), prostate specific antigen (PSA) and α-fetoprotein (α-AFP) as model analytes, the proposed immunoassay exhibited excellent precision and sensitivity. For all three analytes, the relative standard deviations (RSDs) for six times detection were lower than 7.1% and the detection limits were in the range of 0.003-0.006 ng mL(-1). The results for real sample analysis demonstrated that the newly constructed immunosensor array provided a rapid, simple, simultaneous multi-analyte immunoassay with high throughput, cost-effective and sufficiently low detection limits for clinical applications. Importantly, the novel individually addressable immunosensor array for multi-analyte immunoassay by introducing the ECL readout mechanism with the aid of the home-made potential transformer and multiplexed-switch could be a useful supplement to commercial assay methods in clinical chemistry.

  1. Airship construction

    NASA Technical Reports Server (NTRS)

    Roda, J.

    1975-01-01

    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.

  2. Construction measurements

    SciTech Connect

    Barry, B.A.

    1988-01-01

    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.

  3. Present-day stress field on the South American slab underneath the Sandwich Plate (Southern Atlantic Ocean)

    NASA Astrophysics Data System (ADS)

    Giner-Robles, J. L.; Pérez-López, R.; Álvarez-Gómez, J. A.; Martínez-Díaz, J. J.; Rodríguez-Pascua, M. A.

    2009-04-01

    This work confirms the present-day principal stress orientation on the South Sandwich Plate (SSP) from the analysis of 331 earthquake focal mechanisms (Harvard catalog, HCMT). Principal stress orientation was deduced from earthquake focal mechanisms, examined by fault population analysis methods. The SSP plate is composed by oceanic crust limits an elliptical trench to the east (South Sandwich Trench), a ridge to the west and transforms faults towards the northern and southern boundaries. Within the trench region, the maximum horizontal shortening direction (SHMAX) rotates in trend in a clockwise direction, from NNE, in the northern boundary, to SSE in the southern boundary. Therefore, and keeping in mind the gradual rotation of SHMAX along the trench, three different areas were defined according to the prevailing focal mechanism type: (1) the North Zone, with SHMAX oriented N060°E and reverse and strike-slip focal mechanisms; (2) the Central Zone, with only reverse focal mechanism and SHMAX striking N080°E; (3) the South Zone, with SHMAX oriented N110°E and reverse and strike-slip focal geometry. Furthermore, the accommodation of the strain field in the Northern Zone of the South Sandwich Plate generates a subduction decoupling of the slab at, approximately, 70 km depth. In contrast, the South Zone slab exhibits a gradual stress and strain magnitude decreasing in depth. Finally, we define a sinistral strike-slip parallel to the southern boundary between the South Sandwich Plate and the Antarctic Plate, the South Sandwich Fault Zone.

  4. Facile conversion of silicon nitride nanobelts into sandwich-like nanosaws II: growth mechanism and optical properties

    NASA Astrophysics Data System (ADS)

    Guo, Gang Feng; He, Mingsheng; Kong, Xiang Yang; Lin, Hong; Li, Jianbao; Fan, Li-Zhen

    2010-02-01

    In a previous paper (G.F. Guo et al., Appl. Phys. A, 2009), the microstructures of sandwich-like nanosaws have been revealed clearly. Here, the growth mechanism and optical properties of Si3N4 sandwich-like nanosaws were further investigated. It is assumed that the growth atmosphere with a large amount of *N (active nitrogen) from the decomposition of NH3 would be the key factor for the formation of sandwich-like nanosaws during the catalyst-assisted pyrolysis of the polymeric precursors. From the characterizations of TEM together with the systematic composition analysis, we found that a large excess of nitrogen element occurred in the central “soldering” region as well as high density defects, which induced the asymmetric growth of nanoteeth on the original nanobelt sidewall, forming into a sandwich-like nanosaw morphology. The unique optical properties of sandwich-like nanosaws could be attributed from the presence of a large amount of nitrogen dangling bond defects in the central “soldering” region, and a new optical band-gap model was proposed for the interpretation of the photoluminescence spectra.

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

    PubMed

    Kanwal, Shamsa; Traore, Zoumama; Su, Xingguang

    2010-12-01

    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.

  6. Free-edge effects in a cylindrical sandwich panel with a flexible core and laminated composite face sheets

    NASA Astrophysics Data System (ADS)

    Afshin, M.; Sadighi, M.; Shakeri, M.

    2010-12-01

    In the present study, the static response of cylindrical sandwich panels with a flexible core is investigated. The face sheets are considered as composite laminates with a cross-ply lay-up and the core as a flexible elastic medium. The flexibility of the low-strength core leads to high stress concentrations in terms of peeling stresses between the face sheets and the core at edges of the sandwich panel. To take into account the compressibility of the core and to determine the free-edge stresses of sandwich structures accurately, the Reddy layerwise theory (LWT) is used in this paper. The paper outlines the mathematical formulation, along with a numerical study, of a cylindrical sandwich panel with two simply supported and two free edges under a transverse load. The formulation includes the derivation of field equations along with boundary conditions. A Levy-type solution procedure is performed to determine the distributions of stresses and strains. In the numerical study, first a comparison is made with results from the commercial finite-element software ANSYS to verify the LWT results. Finally, a parametric study is conducted, and the effect caused by varying different parameters, such as the radii of curvature and the core to face sheet thickness ratio, on the results are investigated. The results obtained demonstrate a good agreement between LWT and FEM solutions and show increasing interlaminar stresses in the free edge of the sandwich panel

  7. Sandwich-Architectured Poly(lactic acid)-Graphene Composite Food Packaging Films.

    PubMed

    Goh, Kunli; Heising, Jenneke K; Yuan, Yang; Karahan, Huseyin E; Wei, Li; Zhai, Shengli; Koh, Jia-Xuan; Htin, Nanda M; Zhang, Feimo; Wang, Rong; Fane, Anthony G; Dekker, Matthijs; Dehghani, Fariba; Chen, Yuan

    2016-04-20

    Biodegradable food packaging promises a more sustainable future. Among the many different biopolymers used, poly(lactic acid) (PLA) possesses the good mechanical property and cost-effectiveness necessary of a biodegradable food packaging. However, PLA food packaging suffers from poor water vapor and oxygen barrier properties compared to many petroleum-derived ones. A key challenge is, therefore, to simultaneously enhance both the water vapor and oxygen barrier properties of the PLA food packaging. To address this issue, we design a sandwich-architectured PLA-graphene composite film, which utilizes an impermeable reduced graphene oxide (rGO) as the core barrier and commercial PLA films as the outer protective encapsulation. The synergy between the barrier and the protective encapsulation results in a significant 87.6% reduction in the water vapor permeability. At the same time, the oxygen permeability is reduced by two orders of magnitude when evaluated under both dry and humid conditions. The excellent barrier properties can be attributed to the compact lamellar microstructure and the hydrophobicity of the rGO core barrier. Mechanistic analysis shows that the large rGO lateral dimension and the small interlayer spacing between the rGO sheets have created an extensive and tortuous diffusion pathway, which is up to 1450-times the thickness of the rGO barrier. In addition, the sandwiched architecture has imbued the PLA-rGO composite film with good processability, which increases the manageability of the film and its competency to be tailored. Simulations using the PLA-rGO composite food packaging film for edible oil and potato chips also exhibit at least eight-fold extension in the shelf life of these oxygen and moisture sensitive food products. Overall, these qualities have demonstrated the high potential of a sandwich-architectured PLA-graphene composite film for food packaging applications.

  8. A novel sandwich-type traveling wave piezoelectric tracked mobile system.

    PubMed

    Wang, Liang; Shu, Chengyou; Zhang, Quan; Jin, Jiamei

    2017-03-01

    In this paper, a novel sandwich-type traveling wave piezoelectric tracked mobile system was proposed, designed, fabricated and experimentally investigated. The proposed system exhibits the advantages of simple structure, high mechanical integration, lack of electromagnetic interference, and lack of lubrication requirement, and hence shows potential application to robotic rovers for planetary exploration. The tracked mobile system is comprised of a sandwich actuating mechanism and a metal track. The actuating mechanism includes a sandwich piezoelectric transducer and two annular parts symmetrically placed at either end of the transducer, while the metal track is tensioned along the outer surfaces of the annular parts. Traveling waves with the same rotational direction are generated in the two annular parts, producing the microscopic elliptical motions of the surface particles on the annular parts. In this situation, if the pre-load is applied properly, the metal track can be driven by friction force to achieve bidirectional movement. At first, the finite element method was adopted to conduct the modal analysis and harmonic response analysis of the actuating mechanism, and the vibration characteristics were measured to confirm the operating principle. Then the optimal driving frequency of the system prototype, namely 35.1kHz, was measured by frequency sensitivity experiments. At last, the mechanical motion characteristics of the prototype were investigated experimentally. The results show that the average motion speeds of the prototype in dual directions were as 72mm/s and 61.5mm/s under the excitation voltage of 500VRMS, respectively. The optimal loading weights of the prototype in bi-directions were 0.32kg and 0.24kg with a maximum speed of 59.5mm/s and 61.67mm/s at the driving voltage of 300VRMS, respectively.

  9. Ligand-induced haptotropic rearrangements in bis(indenyl)zirconium sandwich complexes.

    PubMed

    Bradley, Christopher A; Lobkovsky, Emil; Keresztes, Ivan; Chirik, Paul J

    2005-07-27

    Addition of principally sigma-donating ligands such as THF, chelating diethers, or 1,2-bis(dimethyl)phosphinoethane to eta(9),eta(5)-bis(indenyl)zirconium sandwich complexes, (eta(9)-C(9)H(5)-1,3-R(2))(eta(5)-C(9)H(5)-1,3-R(2))Zr (R = alkyl or silyl), induces haptotropic rearrangement to afford (eta(6)-C(9)H(5)-1,3-R(2))(eta(5)-C(9)H(5)-1,3-R(2))ZrL adducts. Examples where L = THF and DME have been characterized by X-ray diffraction and revealed significant buckling of the eta(6) benzo ring, consistent with reduction of the arene, and highlight the importance of the zirconium(IV) canonical form. For the THF-induced haptotropic rearrangements, the thermodynamic driving force for ring migration has been measured as a function of indenyl substituent and demonstrates silylated sandwiches favor THF coordination and the eta(6),eta(5) bonding motif over their alkylated counterparts. In the case of chelating diethers, measurement of the corresponding equilibrium constants establish more stable eta(6),eta(5) adducts with five- over four-membered chelates and with smaller oxygen and carbon backbone substituents. Kinetic studies on both THF and DME addition to (eta(9)-C(9)H(5)-1,3-(SiMe(3))(2))(eta(5)-C(9)H(5)-1,3-(SiMe(3))(2))Zr established a first-order dependence on the incoming ligand, consistent with a mechanism involving direct attack of the incoming nucleophile on the eta(9),eta(5) sandwich. These results further highlight the ability of the indenyl ligand to smoothly adjust hapticity to meet the electronic requirements of the metal center.

  10. It All Starts with a Sandwich: Identification of Sialidases with Trans-Glycosylation Activity

    PubMed Central

    Nordvang, Rune T.; Nyffenegger, Christian; Holck, Jesper; Jers, Carsten; Sundekilde, Ulrik K.; Meyer, Anne S.; Mikkelsen, Jørn D.

    2016-01-01

    Sialidases (3.2.1.18) may exhibit trans-sialidase activity to catalyze sialylation of lactose if the active site topology is congruent with that of the Trypanosoma cruzi trans-sialidase (EC 2.4.1.-). The present work was undertaken to test the hypothesis that a particular aromatic sandwich structure of two amino acids proximal to the active site of the T. cruzi trans-sialidase infers trans-sialidase activity. On this basis, four enzymes with putative trans-sialidase activity were identified through an iterative alignment from 2909 native sialidases available in GenBank, which were cloned and expressed in Escherichia coli. Of these, one enzyme, SialH, derived from Haemophilus parasuis had an aromatic sandwich structure on the protein surface facing the end of the catalytic site (Phe168; Trp366), and was indeed found to exhibit trans-sialidase activity. SialH catalyzed production of the human milk oligosaccharide 3’-sialyllactose as well as the novel trans-sialylation product 3-sialyllactose using casein glycomacropeptide as sialyl donor and lactose as acceptor. The findings corroborated that Tyr119 and Trp312 in the T. cruzi trans-sialidase are part of an aromatic sandwich structure that confers trans-sialylation activity for lactose sialylation. The in silico identification of trans-glycosidase activity by rational active site topology alignment thus proved to be a quick tool for selecting putative trans-sialidases amongst a large group of glycosyl hydrolases. The approach moreover provided data that help understand structure-function relations of trans-sialidases. PMID:27367145

  11. Laser drilling of nano-pores in sandwiched thin glass membranes.

    PubMed

    Yu, Minrui; Kim, Hyun-Seok; Blick, Robert H

    2009-06-08

    We report on a novel method of using an excimer laser to drill ultra-small pores in borosilicate glass membranes. By introducing a thin layer of liquid between sandwiches of two glass slides, we can shrink the pore size and smoothen the surface on the exit side. We are able to push the minimal exit pore diameter down to 90 nm, well below the laser wavelength of 193 nm. This is achieved with substrates over 150 microm thick. Compared to other methods, this technique is fast, inexpensive, and produces high quality smooth pores.

  12. Computational aspects of crack growth in sandwich plates from reinforced concrete and foam

    NASA Astrophysics Data System (ADS)

    Papakaliatakis, G.; Panoskaltsis, V. P.; Liontas, A.

    2012-12-01

    In this work we study the initiation and propagation of cracks in sandwich plates made from reinforced concrete in the boundaries and from a foam polymeric material in the core. A nonlinear finite element approach is followed. Concrete is modeled as an elastoplastic material with its tensile behavior and damage taken into account. Foam is modeled as a crushable, isotropic compressible material. We analyze slabs with a pre-existing macro crack at the position of the maximum bending moment and we study the macrocrack propagation, as well as the condition under which we have crack arrest.

  13. Application of air-coupled acoustic thermography (ACAT) for inspection of honeycomb sandwich structures

    NASA Astrophysics Data System (ADS)

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

    2009-05-01

    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.

  14. Vibroacoustic Response of a Double-Walled Cylindrical FGM Shell with a Porous Sandwiched Layer

    NASA Astrophysics Data System (ADS)

    Ramezani, H.; Talebitooti, R.

    2015-11-01

    The transmission loss of sound through a cylindrical structure whose walls sandwich a layer of porous material is predicted on the basis of the classical shell theory for shells made of functionally graded materials (FGMs). FGM shells composed of metal and ceramic, with three different distributions (power-law, sigmoid, or exponential) of their volume fractions across the wall thickness, are considered. The porous layer is modeled as a fluid with equivalent properties. The transmission loss through the multilayered structure is obtained analytically in a broad frequency band. To validate the results found, they are compared with some known ones. The effects of variation in the volume fractions of materials are also studied.

  15. Employment of a metal microgrid as a front electrode in a sandwich-structured photodetector.

    PubMed

    Zhang, Junying; Cai, Chao; Pan, Feng; Hao, Weichang; Zhang, Weiwei; Wang, Tianmin

    2009-07-01

    A highly UV-transparent metal microgrid was prepared and employed as the front electrode in a sandwich-structured ultraviolet (UV) photodetector using TiO(2) thin film as the semiconductor layer. The photo-generated charger carriers travel a shorter distance before reaching the electrodes in comparison with a photodetector using large-spaced interdigitated metal electrodes (where distance between fingers is several to tens of micrometers) on the surface of the semiconductor film. This photodetector responds to UV light irradiation, and the photocurrent intensity increases linearly with the irradiation intensity below 0.2 mW/cm(2).

  16. Monolayer graphene saturable absorber with sandwich structure for ultrafast solid-state laser

    NASA Astrophysics Data System (ADS)

    Zhu, Hongtong; Zhao, Lina; Liu, Jie; Xu, Shicai; Cai, Wei; Jiang, Shouzhen; Zheng, Lihe; Su, Liangbi; Xu, Jun

    2016-08-01

    The uniform-quality, large-area, monolayer graphene saturable absorber (SA) with sandwich structure was fabricated, tested, and successfully applied for the generation of diode-pumped Yb:Y2SiO5 mode-locked laser. Without extra negative dispersion elements, the shortest pulse with duration of ˜883 fs was obtained at 1042.6 nm with an output power of ˜1 W. These promising experimental results suggested that the low-cost, high-quality graphene SA could potentially be employed in practical, high-power, ultrafast mode-locking laser systems.

  17. Enhanced performance of dye-sensitized solar cells via plasmonic sandwiched structure

    NASA Astrophysics Data System (ADS)

    Lin, Su-Jien; Lee, Kuang-Che; Wu, Jyun-Lin; Wu, Jun-Yi

    2011-07-01

    The plasmonic structure of sandwiched TiO2/NPs-Ag/TiO2 electrodes was fabricated by sputter technology and sol-gel and spin coating procedure to enhance the performance of dye-sensitized solar cells. The improvement of the incident photon to photocurrent efficiency spectrum corresponding to the strong absorption and damping reflection indicated light trapping of plasmonic structure to elongate the optical pathways of photons. More light trapped close to photocurrent collecting electrode provides better charge-collection and light harvesting efficiencies. As a result of improved dye absorption, about 23% enhancement in photocurrent density has been achieved.

  18. Parameters estimation of sandwich beam model with rigid polyurethane foam core

    NASA Astrophysics Data System (ADS)

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

    2010-02-01

    In this work, the physical parameters of sandwich beams made with the association of hot-rolled steel, Polyurethane rigid foam and High Impact Polystyrene, used for the assembly of household refrigerators and food freezers are estimated using measured and numeric frequency response functions (FRFs). The mathematical models are obtained using the finite element method (FEM) and the Timoshenko beam theory. The 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.

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

    NASA Technical Reports Server (NTRS)

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

    2009-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

    McQuigg, Thomas D.

    2011-01-01

    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.

  1. Search for the radioactivity of 180mTa using an underground HPGe sandwich spectrometer.

    PubMed

    Hult, Mikael; Wieslander, J S Elisabeth; Marissens, Gerd; Gasparro, Joël; Wätjen, Uwe; Misiaszek, Marcin

    2009-05-01

    The radioactivity of (180m)Ta has never been detected. The present attempt to detect it was carried out using a newly developed HPGe sandwich spectrometer installed 500m water equivalent underground in the HADES laboratory. The sample consisted of 6 discs of tantalum of natural isotopic composition with a total mass of 1500 g and a total mass for (180)Ta of 180 mg. The sample was measured for 68 days and the resulting lower bound for the half-life of (180m)Ta was 2.0 x 10(16)y, which is a factor of 2.8 higher than the previous highest value.

  2. Oceanographic, atmospheric and water-quality measurements Sandwich Town Neck Beach, Massachusetts, 2016

    USGS Publications Warehouse

    Sherwood, Christopher R.; Montgomery, Ellyn; Suttles, Steven; Brosnahan, Sandra M.

    2016-01-01

    This web page provides access to oceanographic, atmospheric, and water quality observations near Sandwich Town Neck Beach, Massachusetts. These measurements were made in conjunction with two U.S. Geological Survey (USGS) projects; the Coastal Model Applications and Measurements Project, and the Barrier Island Evolution Research project, both supported by the USGS Coastal and Marine Geology Program. These measurements provide information about waves, tides, and overwash during a winter storm in January 2016; about waves, tides, currents, and water properties between February and May, 2016; and about waves and tides between May and June 2016, during a period that overlaps with offshore bathymetric surveys.

  3. Disentangling interface and bulk contributions to the anisotropic magnetoresistance in Pt/Co/Pt sandwiches

    NASA Astrophysics Data System (ADS)

    Kobs, André; Oepen, Hans Peter

    2016-01-01

    We report on interfacial contributions to the anisotropic magnetoresistance (AMR) in Co layers sandwiched between Pt. Utilizing the Fuchs-Sondheimer formalism interface contributions can be separated from bulklike AMR. We demonstrate that for all-metal systems interfacial AMR is also present when varying the magnetization within the film plane. This interfacial in-plane AMR is two times smaller than the contribution that arises when the magnetization is varied within the plane perpendicular to the current direction. This finding is in contrast to the spin Hall MR found for ferromagnetic insulator/Pt bilayers revealing the existence of different MR effects at the interfaces of Pt with conducting and insulating ferromagnets.

  4. Discussion: "On interactive buckling in a sandwich structure" by C. D. Coman

    NASA Astrophysics Data System (ADS)

    Wadee, M. Ahmer; Yiatros, Stylianos

    2011-02-01

    A recent article by Coman (Z Angew Math Phys 2009) on the response of compression sandwich struts made some claims on the quality of the simplified version of the interactive buckling model presented in Hunt and Wadee (Proc R Soc A 454(1972):1197-1216, 1998). Some of these claims are examined in detail herein; it is concluded that great care must be exercised when performing parametric studies with equations that have been derived from simplifying a mechanical model. This is because the resulting system of equations does not necessarily describe the original mechanical system in full, since the key assumptions necessarily change.

  5. An Experimental Investigation of Sandwich Flat Panels Under Low Velocity Impact.

    DTIC Science & Technology

    1994-12-01

    adhesive also contribute to damage in some cases . xvii AN EXPERIMENTAL INVESTIGATION OF SANDWICH PANELS UNDER LOW VELOCITY IMPACT Introduction 1.1...properties of the adhesive and core were determined from the manufacturers specification. In the case of the core, the curves shown in Figure 2.4 and...In this case , the 90° layer is defined as the two 90* plies in the middle of the lay-up. The upper portion of the core beneath the impact site in the 0

  6. Plasmonic Enhancement of Raman Scattering for Metal-Analyte Sandwich Configuration

    NASA Astrophysics Data System (ADS)

    Kulakovich, O. S.; Shabunya-Klyachkovskaya, E. V.; Matsukovich, A. S.; Trotsiuk, L. L.; Gaponenko, S. V.

    2016-11-01

    The effect of the mutual positions of plasmonic gold fi lms and a layer of analyte (malachite green and mitoxantrone molecules) on surface-enhanced Raman scattering (SERS) was investigated. When the excitation emission in the plasmon resonance region (531 nm and 632.8 nm) was used the SERS intensity of the analyte in a sandwich configuration was up to five times higher compared with the "analyte under gold film" arrangement and up to 60 times higher than for the "analyte on gold fi lm" case.

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

    NASA Technical Reports Server (NTRS)

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

    1978-01-01

    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.

  8. Proton radiography of PBX 9502 detonation shock dynamics confinement sandwich test

    SciTech Connect

    Aslam, Tariq D; Jackson, Scott I; Morris, John S

    2009-01-01

    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.

  9. New sandwich-type lanthanide complexes based on closed-macrocyclic Schiff base and phthalocyanine molecules.

    PubMed

    Gao, Feng; Feng, Xiaowan; Yang, Liu; Chen, Xiaoyu

    2016-04-25

    Two new sandwich-type lanthanide complexes with the general formula [(Pc)2Ln3(L)(OAc)(OCH3)2] (Ln(3+) = Dy(3+) () and Er(3+) ()) were successfully synthesized and structurally characterized based on closed-macrocyclic Schiff base and phthalocyanine molecules. The magnetic properties and structure-property relationship in this multi-decker system were investigated. Interestingly, the corresponding dysprosium complex shows typical single-molecule magnetic behavior with ferromagnetic dipole-dipole interactions and the slow relaxation of magnetization.

  10. Mechanical analysis of confectioning flaw of refractory alloy honeycomb sandwich structure

    NASA Astrophysics Data System (ADS)

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

    2009-03-01

    Thermal protection system is one of the key technology of reusable launch vehicle (RLV). After C/C and ceramic-matrix composite used in space orbiter, one new-typed thermal protection systems (TPS)-ARMOR TPS is coming forth. ARMOR TPS is means adaptable, robust, metallic, operable, reusable TPS. The ARMOR TPS has many advantages, for example: fixing easily, longer life, good properties, short time of maintenance and service. The ARMOR TPS is one of important candidate structure of RLV. ARMOR thermal protection system in foreign countries for reusable launch vehicle is used instead of the traditional ceramic-matrix composite thermal protection system and C/C thermal protection system. Also the constituent feature of ARMOR thermal protection system is much better than the traditional TPS. In comparison with traditional TPS, the ARMOR TPS will be the best selection for all kinds of RLV. So the ARMOR thermal protection system will be used in aviation and spaceflight field more and more widely because of its much better performance. ARMOR TPS panel is above the whole ARMOR TPS, and the metal honeycomb sandwich structure is the surface of the ARMOR TPS panel. So the metal honeycomb sandwich structure plays an important role in the ARMOR TPS, while it bears the flight dynamic pressure and stands against the flight dynamic calefaction. The metal honeycomb sandwich structure is made using the technique of the whole braze welding. In the course of the vacuum high temperature braze welding, its surface will appear concave. The reasons which lead to the shortage are summarized and discussed. The difference of thermal expansion coefficient and pressure between the core and the panels may be the chief reasons. This paper will analyze the mechanics behavior of metal honeycomb sandwich structure in the course of the vacuum high temperature braze welding, then make sure the reasons and get a way to solve it. Haynes214 is a good material of face sheet at present. γ - TiAl and

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

    NASA Technical Reports Server (NTRS)

    Liechti, Kenneth M.; Marton, Balazs

    2000-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

    Hui, David

    1989-01-01

    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.

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

    SciTech Connect

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

    2014-12-15

    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 C{sup 6+}-ion beam with an energy exceeding 10 MeV/nucleon is produced at a laser intensity of 5 × 10{sup 19} W/cm{sup 2}.

  14. Prophylactic vertebroplasty procedure applied with a resorbable bone cement can decrease the fracture risk of sandwich vertebrae: long-term evaluation of clinical outcomes

    PubMed Central

    Jia, Pu; Tang, Hai; Chen, Hao; Bao, Li; Feng, Fei; Yang, He; Li, Jinjun

    2017-01-01

    A sandwich vertebra is formed after multiple osteoporotic vertebral fractures treated by percutaneous vertebroplasty, which has a risk of developing new fractures. The purpose of our study was to (i) investigate the occurrence of new fractures in sandwich vertebra after cement augmentation procedures and to (ii) evaluate the clinical outcomes after prophylactic vertebral reinforcement applied with resorbable bone cement. From June 2011 to 2014, we analysed 55 patients with at least one sandwich vertebrae and treated with percutaneous vertebroplasty. Eighteen patients were treated by prophylactic vertebroplasty with a resorbable bone cement to strengthen the sandwich vertebrae as the prevention group. The others were the non-prevention group. All patients were examined by spinal radiographs within 1 day, 6 months, 12 months, 24 months and thereafter. The incidence of sandwich vertebra is 8.25% (55/667) in our study. Most sandwich vertebrae (69.01%, 49/71) are distributed in the thoracic–lumbar junction. There are 24 sandwich vertebrae (18 patients) and 47 sandwich vertebrae (37 patients) in either prevention group or non-prevention group, respectively. No significant difference is found between age, sex, body mass index, bone mineral density, cement disk leakage, sandwich vertebrae distribution or Cobb angle in the two groups. In the follow-up, 8 out of 37 (21.6%) patients (with eight sandwich vertebrae) developed new fractures in non-prevention’ group, whereas no new fractures were detected in the prevention group. Neither Cobb angle nor vertebral compression rate showed significant change in the prevention group during the follow-up. However, in the non-prevention group, we found that Cobb angle increased and vertebral height lost significantly (P < 0.05). Prophylactic vertebroplasty procedure applied with resorbable bone cement could decrease the rate of new fractures of sandwich vertebrae. PMID:28149529

  15. Face Sheet/Core Disbond Growth in Honeycomb Sandwich Panels Subjected to Ground-Air-Ground Pressurization and In-Plane Loading

    NASA Technical Reports Server (NTRS)

    Chen, Zhi M.; Krueger, Ronald; Rinker, Martin

    2015-01-01

    Typical damage modes in light honeycomb sandwich structures include face sheet/core disbonding and core fracture, both of which can pose a threat to the structural integrity of a component. These damage modes are of particular interest to aviation certification authorities since several in-service occurrences, such as rudder structural failure and other control surface malfunctions, have been attributed to face sheet/core disbonding. Extensive studies have shown that face sheet/core disbonding and core fracture can lead to damage propagation caused by internal pressure changes in the core. The increasing use of composite sandwich construction in aircraft applications makes it vitally important to understand the effect of ground-air-ground (GAG) cycles and conditions such as maneuver and gust loads on face sheet/core disbonding. The objective of the present study was to use a fracture mechanics based approach developed earlier to evaluate the loading at the disbond front caused by ground-air-ground pressurization and in-plane loading. A honeycomb sandwich panel containing a circular disbond at one face sheet/core interface was modeled with three-dimensional (3D) solid finite elements. The disbond was modeled as a discrete discontinuity and the strain energy release rate along the disbond front was computed using the Virtual Crack Closure Technique (VCCT). 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. The commercial finite element analysis software, Abaqus/Standard, was used for the analyses. The recursive pressure-deformation coupling problem was solved by representing the entrapped air in the honeycomb cells as filled cavities in Abaqus/Standard. The results show that disbond size, face sheet thickness and core thickness are important parameters that determine crack tip loading at the disbond front. Further, the pressure

  16. Advances in Joining Techniques Used in Development of SPF/DB Titanium Sandwich Reinforced with Metal Matrices

    NASA Technical Reports Server (NTRS)

    Fischler, J. E.

    1985-01-01

    Three and four-sheet expanded titanium sandwich sheets have been developed at Douglas Aircraft Company, a division of McDonnell Douglas Corporation, under contract to NASA Langley Research Center. In these contracts, spot welding and roll seam welding are used to join the core sheets. These core sheets are expanded to the face sheets and diffusion bonded to form various type cells. The advantages of various cell shapes and the design parameters for optimizing the wing and fuselage concepts are discussed versus the complexity of the spot weld pattern. In addition, metal matrix composites of fibers in an aluminum matrix encapsulated in a titanium sheath are aluminum brazed successfully to the titanium sandwich face sheets. The strength and crack growth rate of the superplastic-formed/diffusion bonded (SPF/DB) titanium sandwich with and without the metal matrix composites are described.

  17. The magnetic and quantum transport properties of benzene-vanadium-borazine mixed sandwich clusters: a new kind of spin filter.

    PubMed

    Yang, Zhi; Liu, Shaoding; Liu, Xuguang; Yang, Yongzhen; Li, Xiuyan; Xiong, Shijie; Xu, Bingshe

    2012-11-07

    Using density functional theory and the non-equilibrium Green's function technique, we performed theoretical investigations on the magnetic and quantum transport properties of benzene-vanadium-borazine mixed organic/inorganic ligand sandwich clusters. The calculated results show that these finite sandwich clusters coupled to Ni electrodes exhibit novel quantum transport properties such as half-metallicity, negative differential resistance and spin-reversal effect, and can be viewed as a new kind of spin filter. However, for the infinite molecular wire, the ground state was identified as a ferromagnetic semiconductor with high stability. These findings suggest that the mixed organic/inorganic ligand sandwich clusters and molecular wires are promising materials for application in molecular electronics and spintronics.

  18. Sound radiation and transmission loss characteristics of a honeycomb sandwich panel with composite facings: Effect of inherent material damping

    NASA Astrophysics Data System (ADS)

    Arunkumar, M. P.; Jagadeesh, M.; Pitchaimani, Jeyaraj; Gangadharan, K. V.; Babu, M. C. Lenin

    2016-11-01

    This paper presents the results of numerical studies carried out on vibro-acoustic and sound transmission loss behaviour of aluminium honeycomb core sandwich panel with fibre reinforced plastic (FRP) facings. Layered structural shell element with equivalent orthotropic elastic properties of core and orthotropic properties of FRP facing layer is used to predict the free and forced vibration characteristics. Followed by this, acoustic response and transmission loss characteristics are obtained using Rayleigh integral. Vibration and acoustic characteristics of FRP sandwich panels are compared with aluminium sandwich panels. The result reveals that FRP panel has better vibro-acoustic and transmission loss characteristics due to high stiffness and inherent material damping associated with them. Resonant amplitudes of the response are fully controlled by modal damping factors calculated based on modal strain energy. It is also demonstrated that FRP panel can be used to replace the aluminium panel without losing acoustic comfort with nearly 40 percent weight reduction.

  19. A novel 3D sandwich structure of hybrid graphite nanosheets and silver nanowires as fillers for improved thermal conductivity

    NASA Astrophysics Data System (ADS)

    Zhuang, Xiao; Zhou, Yongcun; Liu, Feng

    2017-01-01

    We explored a novel 3D sandwich structure of fillers in the polymer matrix to enhance thermal conductivity. A variety of fillers in the polymer matrix play a significant role in the physical properties of the composite. Fillers containing particle and line structures are popular, and enhance the thermal and electrical conductivities. Therefore, filler-based matrix network improves conductivity. We propose a sandwich structure consisting of hybrid graphite nanosheets (two dimensions), and silver nanowires (AgNWs) (one dimension), to create a 3D sandwich structure of polyimide matrix with improved thermal conductivity. Surface treatment of graphite and silver nanowires were conducted to reduce the dielectric constant of the composite. We designed the filler of 20 wt% resulting in a high thermal conductivity of 3.21 W m‑1 K‑1 with 15% C@SiO2 and 5% AgNWs@SiO2 filler loading. The novel combination and structure markedly enhanced the thermal conductivity of the composite.

  20. A sandwiched biological fluorescent probe for the diagnosis of human ovarian tumor based on TiO2 nanoparticles.

    PubMed

    Zhu, Peisi; Huang, Shasheng; Li, Mengyao; Ding, Na; Peng, Bing; Kong, Lingmi; Bo, Yang

    2011-01-01

    In this paper, we report a novel biological fluorescent probe for the diagnosis of human ovarian tumor based on sandwiched TiO(2) nanoparticles. The fluorescence nanoparticles consist of a fluorescent molecule, tetramethyl rhodamine isothiocyanate (TRITC), sandwiched between titanium dioxide (TiO(2)) nanoparticles and nano-gold via reacting with each other. The antibodies HER2, labeled on the surface of the biofluorescence nanoparticles, have granted nanoparticles the privilege of aiming at peculiar tumor antigen. The specificity of antibody-nanoparticles interacting with cells was characterized by Laser Scanning Confocal Microscope. The results showed that these sandwiched nanoparticles were innocuous and stable, and the method offered potential advantages of sensitivity and simplicity due to high combing efficiency between nanoparticles and cells and provided an alternative method for the diagnosis of human ovarian tumor (HOT).

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

    NASA Astrophysics Data System (ADS)

    Johannes, Martin; Thomsen, Ole Thybo

    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.

  2. Comparing the soft x-rays transport in Si and Ge-sandwich targets by measuring transmission flux

    NASA Astrophysics Data System (ADS)

    Zhang, Lu; Li, Liling; Guo, Liang; Jing, Longfei; Lin, Zhiwei; Qing, Bo; Li, Zhichao; Li, Hang; Kuang, Longyu; Zheng, Jianhua; Zhang, Jiyan; Yang, Jiamin; Jiang, Shaoen; Ding, Yongkun

    2017-03-01

    Mid-Z dopant in ablator is very important in point design targets. In this paper, we develop a method to evaluate the soft x-ray transport of doped material with one dimensional planar target. The targets are designed as sandwich, so that the mid-layer is heated by M band, shock and thermal wave. The transmission fluxes from heated targets are measured with band-pass x-ray diodes. The Si and Ge dopants are evaluated with this method. The experimental results show that 1-1.6 keV x-ray transmission flux through Si-sandwich is higher than that through Ge-sandwich all the time. Also, the comparison of opacities shows that the opacity of Si is lower than that of Ge in the range of 1-1.6 keV, which is consistent with the experimental results.

  3. Robust optical properties of sandwiched lateral composition modulation GaInP structure grown by molecular beam epitaxy

    SciTech Connect

    Park, Kwangwook; Kang, Seokjin; Ravindran, Sooraj; Min, Jung-Wook; Hwang, Hyeong-Yong; Jho, Young-Dahl; Lee, Yong Tak

    2016-12-26

    Double-hetero structure lateral composition modulated (LCM) GaInP and sandwiched LCM GaInP having the same active layer thickness were grown and their optical properties were compared. Sandwiched LCM GaInP showed robust optical properties due to periodic potential nature of the LCM structure, and the periodicity was undistorted even for thickness far beyond the critical layer thickness. A thick LCM GaInP structure with undistorted potential that could preserve the properties of native LCM structure was possible by stacking thin LCM GaInP structures interspaced with strain compensating GaInP layers. The sandwiched structure could be beneficial in realizing the LCM structure embedded high efficiency solar cells.

  4. A new surgical management for oro-antral communication: the resorbable guided tissue regeneration membrane--bone substitute sandwich technique.

    PubMed

    Ogunsalu, C

    2005-09-01

    This paper describes a new technique for the closure of oro-antral fistula/communication, in which both hard tissue (bone) and soft tissue closure is achieved. The sandwich technique utilizes a suitable bone grafting material sandwiched between two sheaths of Biogide (a resorbable membrane) for the hard tissue closure of oro-antral communication post traumatic exodontia. The bone grafting material utilized for this case was Bio-oss. The result obtained was excellent with regeneration of sufficient bony tissue to allow placement of an endosseous implant. This sandwich technique is a simple and excellent technique for the closure of oro-antral communication, especially when subsequent placement of endosseous implant is considered without the need of donor site surgery for bone grafting. The otorhinolaryngologists and oral and maxillofacial surgeons should find this technique very useful in the closure of oro-antral fistulae.

  5. PUMP CONSTRUCTION

    DOEpatents

    Strickland, G.; Horn, F.L.; White, H.T.

    1960-09-27

    A pump which utilizes the fluid being pumped through it as its lubricating fluid is described. This is achieved by means of an improved bearing construction in a pump of the enclosed or canned rotor type. At the outlet end of the pump, adjacent to an impeller mechanism, there is a bypass which conveys some of the pumped fluid to a chamber at the inlet end of the pump. After this chamber becomes full, the pumped fluid passes through fixed orifices in the top of the chamber and exerts a thrust on the inlet end of the pump rotor. Lubrication of the rotor shaft is accomplished by passing the pumped fluid through a bypass at the outlet end of the rotor shaft. This bypass conveys Pumped fluid to a cooling means and then to grooves on the surface of the rotor shait, thus lubricating the shaft.

  6. Constructing Knowledge

    NASA Astrophysics Data System (ADS)

    Blanton, Patricia

    2003-02-01

    Schools are expected to lay the foundation upon which knowledge can be built and equip students with the tools necessary to accomplish the construction. The role of the teacher in this building process is crucial to the type of structure the student can build. Whether you call it constructivism, discussion teaching, project-based learning, inquiry learning, or any of the other names given to the instructional strategies being suggested by education researchers, the key is getting students to become active participants in the process. While some students may be able to learn from eloquently delivered lectures and dynamic demonstrations, the majority of students cannot effectively retain and apply ideas communicated in this manner.

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

    NASA Astrophysics Data System (ADS)

    Nazemnezhad, Reza; Shokrollahi, Hassan; Hosseini-Hashemi, Shahrokh

    2014-05-01

    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.

  8. Results of repair of iliac artery aneurysms with the sandwich technique

    PubMed Central

    Shutze, Ryan A.; Oglesby, Wes; Lee, Allen

    2017-01-01

    Patients undergoing endovascular repair (EVAR) of aortoiliac or iliac artery aneurysm may require sacrifice of one or both internal iliac arteries (IIAs). Until Food and Drug Administration–approved commercial grafts became available, endovascular IIA preservation was accomplished using the “sandwich” technique, but limited information is available regarding the results of this method. After obtaining institutional review board approval, we identified patients undergoing IIA preservation with the sandwich technique during EVAR at our institution. The patients have been followed prospectively since being identified to record patency rates and vascular symptoms or events. Twenty-four procedures were performed from 2011 through 2015 to treat iliac artery aneurysms. Fourteen of these procedures were done with concomitant EVAR using different endografts (Gore Excluder 11, Endologix AFX 2, Cook Zenith 1). Five were done to extend a previous EVAR that had developed a type Ib endoleak, 2 for an isolated external iliac artery aneurysm, 3 for an anastomotic aneurysm from a previous aortobiiliac graft, and 2 for isolated iliac aneurysm repair. There were 25 sandwich grafts (unilateral in 19, bilateral in 6). Contralateral embolization was performed in 5 cases. Immediate success rates were high, and patency rates were excellent at intermediate follow-up. Intraoperative type 3 endoleaks were not uncommon but usually resolved postoperatively. Endovascular IIA preservation is feasible with currently available devices using this technique. This procedure is recommended for preservation of the IIA during endovascular treatment of aortoiliac and iliac artery aneurysms when anatomy requires IIA preservation. PMID:28127120

  9. Hydrothermal synthesis and structural characterization of three inorganic organic composite sandwich-type phosphotungstates

    NASA Astrophysics Data System (ADS)

    Zhao, Jun-Wei; Zheng, Shou-Tian; Yang, Guo-Yu

    2007-12-01

    Three inorganic-organic composite sandwich-type phosphotungstates [Ni(tepa)(H 2O)] 4H 2[Ni 4(H 2O) 2( α- B-PW 9O 34) 2]·8H 2O ( 1), (enH 2) 3[Ni 2(H 2O) 10][Ni 4(H 2O) 2( α- B-PW 9O 34) 2]·en·8H 2O ( 2) and (enH 2) 10[Mn 4(H 2O) 2( α- B-PW 9O 34) 2] 2·20H 2O ( 3) (tepa=tetraethylenepentamine and en=ethylenediamine) have been synthesized by the hydrothermal reaction of the trivacant Keggin polyoxoanion [ α- A-PW 9O 34] 9- with Ni 2+ or Mn 2+ ions in the presence of tepa or en and structurally characterized by IR spectra, elemental analysis, thermogravimetric analysis and variable temperature magnetic susceptibility. X-ray crystallographic analyses indicate that they all contain the classical tetra- M sandwiched polyoxoanions [ M4(H 2O) 2( α- B-PW 9O 34) 2] 10- ( M=Ni 2+ or Mn 2+) and nickel-organoamine cations or organoamine cations work as the charge balance ions. The tetra- M clusters in 1, 2 and 3 exhibit the familiar structural type of a β-junction at the sites of metal incorporation. The study of magnetic property of 1 is indicative of a typical ferromagnetic coupling between Ni 2+ cations.

  10. Sandwich Wound Closure Reduces the Risk of Cerebrospinal Fluid Leaks in Posterior Fossa Surgery

    PubMed Central

    Heymanns, Verena; Oseni, Abidemi W.; Alyeldien, Ameer; Maslehaty, Homajoun; Parvin, Richard; Scholz, Martin

    2016-01-01

    Posterior fossa surgery is demanding and hides a significant number of obstacles starting from the approach to the wound closure. The risk of cerebrospinal fluid (CSF) leakage in posterior fossa surgery given in the literature is around 8%. The present study aims to introduce a sandwich closure of the dura in posterior fossa surgery, which reduces significantly the number of CSF leaks (3.8%) in the patients treated in our department. Three hundred and ten patients treated in our hospital in the years 2009-2013 for posterior fossa pathologies were retrospectively evaluated. The dura closure method was as following: lyophilized dura put under the dura and sealed with fibrin glue and sutures, dura adapting stitches, TachoSil® (Takeda Pharma A/S, Roskilde, Denmark), Gelfoam® (Pfizer Inc., New York, NY, USA) and polymethylmethacrylate (osteoclastic craniotomy). The incidence of postsurgical complications associated with the dural closure like CSF leakage, infections, bleeding is evaluated. Only 3.8% of patients developed CSF leakage and only 0.5% needed a second surgery for CSF leakage closure. Two percent had a cerebellar bleeding with no need for re-operation and 3% had a wound infection treated with antibiotics. The sandwich wound closure we are applying for posterior fossa surgery in our patients correlates with a significant reduction of CSF leaks compared to the literature. PMID:27478578

  11. Compression strengths of advanced composites from a novel mini-sandwich beam

    SciTech Connect

    Crasto, A.S.; Kim, R.Y. )

    1991-04-01

    The intrinsic compression strength of advanced composites is difficult to measure, as the results often depend on the loading geometry and test conditions. Slight variations in specimen geometry can result in an eccentricity of the applied load with consequent specimen buckling. Complex test fixtures and specimen geometries have therefore been developed to avoid such premature failure under compressive loading. In spite of this, there is a large variation in reported strengths for some composites (notably those of intermediate-modulus carbon fibers), and failure strains are also significantly lower than those of the individual filaments. To better approximate the intrinsic composite compressive strength, a novel symmetric mini-sandwich beam was designed for testing. The beam has a composite skin (of variable thickness) on both sides of a neat resin core (of same material as the composite matrix). Unidirectional mini-sandwich specimens of AS4 and S-glass fibers in an epoxy matrix and AS4 in a PEEK matrix were tested in direct axial compression and four-point flexure. Failure occurred predominantly in the specimen gage section, at composite stresses and strains substantially higher than observed in corresponding tests on all composite-coupons. This paper discusses the fabrication and testing of these beams and analyzes the resulting compressive data and failure modes.

  12. Three different signal amplification strategies for the impedimetric sandwich detection of thrombin.

    PubMed

    Ocaña, Cristina; del Valle, Manel

    2016-03-17

    In this work, we report a comparative study on three highly specific amplification strategies for the ultrasensitive detection of thrombin with the use of aptamer sandwich protocol. The protocol consisted on the use of a first thrombin aptamer immobilized on the electrode surface, the recognition of thrombin protein, and the reaction with a second biotinylated thrombin aptamer forming the sandwich. Through the exposed biotin end, three variants have been tested to amplify the electrochemical impedance signal. The strategies included (a) silver enhancement treatment, (b) gold enhancement treatment and (c) insoluble product produced by the combination of the enzyme horseradish peroxidase (HRP) and 3-amino-9-ethylcarbazole (AEC). The properties of the sensing surface were probed by electrochemical impedance measurements in the presence of the ferrocyanide/ferricyanide redox marker. Insoluble product strategy and silver enhancement treatment resulted in the lowest detection limit (0.3 pM), while gold enhancement method resulted in the highest reproducibility, 8.8% RSD at the pM thrombin concentration levels. Results of silver and gold enhancement treatment also permitted direct inspection by scanning electron microscopy (SEM).

  13. Plating a Dendrite-Free Lithium Anode with a Polymer/Ceramic/Polymer Sandwich Electrolyte.

    PubMed

    Zhou, Weidong; Wang, Shaofei; Li, Yutao; Xin, Sen; Manthiram, Arumugam; Goodenough, John B

    2016-08-03

    A cross-linked polymer containing pendant molecules attached to the polymer framework is shown to form flexible and low-cost membranes, to be a solid Li(+) electrolyte up to 270 °C, much higher than those based on poly(ethylene oxide), to be wetted by a metallic lithium anode, and to be not decomposed by the metallic anode if the anions of the salt are blocked by a ceramic electrolyte in a polymer/ceramic membrane/polymer sandwich electrolyte (PCPSE). In this sandwich architecture, the double-layer electric field at the Li/polymer interface is reduced due to the blocked salt anion transfer. The polymer layer adheres/wets the lithium metal surface and makes the Li-ion flux at the interface more homogeneous. This structure integrates the advantages of the ceramic and polymer. With the PCPSE, all-solid-state Li/LiFePO4 cells showed a notably high Coulombic efficiency of 99.8-100% over 640 cycles.

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

    SciTech Connect

    Nazemnezhad, Reza E-mail: rnazemnezhad@du.ac.ir; Shokrollahi, Hassan; Hosseini-Hashemi, Shahrokh

    2014-05-07

    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.

  15. Reconstruction of chest wall using a two-layer prolene mesh and bone cement sandwich.

    PubMed

    Aghajanzadeh, Manouchehr; Alavi, Ali; Aghajanzadeh, Gilda; Ebrahimi, Hannan; Jahromi, Sina Khajeh; Massahnia, Sara

    2015-02-01

    Wide surgical resection is the most effective treatment for the vast majority of chest wall tumors. This study evaluated the clinical success of chest wall reconstruction using a Prolene mesh and bone cement prosthetic sandwich. The records of all patients undergoing chest wall resection and reconstruction were reviewed. Surgical indications, the location and size of the chest wall defect, diaphragm resection, pulmonary performance, postoperative complications, and survival of each patient were recorded. From 1998 to 2008, 43 patients (27 male, 16 female; mean age of 48 years) underwent surgery in our department to treat malignant chest wall tumors: chondrosarcoma (23), osteosarcoma (8), spindle cell sarcoma (6), Ewing's sarcoma (2), and others (4). Nine sternectomies and 34 antero-lateral and postero-lateral chest wall resections were performed. Postoperatively, nine patients experienced respiratory complications, and one patient died because of respiratory failure. The overall 4-year survival rate was 60 %. Chest wall reconstruction using a Prolene mesh and bone cement prosthetic sandwich is a safe and effective surgical procedure for major chest wall defects.

  16. Electrochemical sandwich assay for attomole analysis of DNA and RNA from beer spoilage bacteria Lactobacillus brevis.

    PubMed

    Shipovskov, Stepan; Saunders, Aaron M; Nielsen, Jesper S; Hansen, Majken H; Gothelf, Kurt V; Ferapontova, Elena E

    2012-01-01

    Attomole (10(-18)mol) levels of RNA and DNA isolated from beer spoilage bacterial cells Lactobacillus brevis have been detected by the electrochemical sandwich DNA hybridization assay exploiting enzymatic activity of lipase. DNA sequences specific exclusively to L. brevis DNA and RNA were selected and used for probe and target DNA design. The assay employs magnetic beads (MB) modified with a capture DNA sequence and a reporter DNA probe labeled with the enzyme, both made to be highly specific for L. brevis DNA. Lipase-labeled DNAs captured on MBs in the sandwich assay were collected on gold electrodes modified with a ferrocene (Fc)-terminated SAM formed by aliphatic esters. Lipase hydrolysis of the ester bond released a fraction of the Fc redox active groups from the electrode surface, decreasing the electrochemical signal from the surface-confined Fc. The assay, shown to be efficient for analysis of short synthetic DNA sequences, was ineffective with genomic double stranded bacterial DNA, but it allowed down to 16 amole detection of 1563 nts long RNA, isolated from bacterial ribosomes without the need for PCR amplification, and single DNA strands produced from ribosomal RNA. No interference from E. coli RNA was registered. The assay allowed analysis of 400 L. brevis cells isolated from 1L of beer, which fits the "alarm signal" range (from 1 to 100 cells per 100mL).

  17. Characterization of dermal plates from armored catfish Pterygoplichthys pardalis reveals sandwich-like nanocomposite structure.

    PubMed

    Ebenstein, Donna; Calderon, Carlos; Troncoso, Omar P; Torres, Fernando G

    2015-05-01

    Dermal plates from armored catfish are bony structures that cover their body. In this paper we characterized structural, chemical, and nanomechanical properties of the dermal plates from the Amazonian fish Pterygoplichthys pardalis. Analysis of the morphology of the plates using scanning electron microscopy (SEM) revealed that the dermal plates have a sandwich-like structure composed of an inner porous matrix surrounded by two external dense layers. This is different from the plywood-like laminated structure of elasmoid fish scales but similar to the structure of osteoderms found in the dermal armour of some reptiles and mammals. Chemical analysis performed using Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and X-ray diffraction (XRD) results revealed similarities between the composition of P. pardalis plates and the elasmoid fish scales of Arapaima gigas. Reduced moduli of P. pardalis plates measured using nanoindentation were also consistent with reported values for A. gigas scales, but further revealed that the dermal plate is an anisotropic and heterogeneous material, similar to many other fish scales and osteoderms. It is postulated that the sandwich-like structure of the dermal plates provides a lightweight and tough protective layer.

  18. Fabrication of mucoadhesive chitosan coated polyvinylpyrrolidone/cyclodextrin/clotrimazole sandwich patches for oral candidiasis.

    PubMed

    Tonglairoum, Prasopchai; Ngawhirunpat, Tanasait; Rojanarata, Theerasak; Panomsuk, Suwanee; Kaomongkolgit, Ruchadaporn; Opanasopit, Praneet

    2015-11-05

    This study aims to fabricate clotrimazole (CZ)-composite sandwich nanofibers using electrospinning. The CZ-loaded polyvinylpyrrolidone (PVP)/hydroxypropyl-β-cyclodextrin (HPβCD) fiber was coated with chitosan-cysteine (CS-SH)/polyvinyl alcohol (PVA) to increase the mucoadhesive properties and to achieve a sustained release of the drug from the nanofibers. The nanofibers were characterized using scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy and X-ray diffractometry (XRD). The nanofibers mechanical and mucoadhesive properties, drug release, antifungal activity and cytotoxicity were also assessed. The fibers were in the nanoscale with good mucoadhesive properties. The XRPD revealed a molecular dispersion of amorphous CZ in the nanofibers. The initial fast release of CZ from the nanofibers was achieved. Moreover, the sandwich nanofibers coated for longer times resulted in slower release rates compared with the shorter coating times. The CZ-loaded nanofibers killed the Candida significantly faster than the commercial CZ lozenges at 5, 15 and 30 min and were safe for a 2-h incubation. Therefore, these nanofibers may be promising candidates for the treatment of oral candidiasis.

  19. Sandwich node architecture for agile wireless sensor networks for real-time structural health monitoring applications

    NASA Astrophysics Data System (ADS)

    Wang, Zi; Pakzad, Shamim; Cheng, Liang

    2012-04-01

    In recent years, wireless sensor network (WSN), as a powerful tool, has been widely applied to structural health monitoring (SHM) due to its low cost of deployment. Several commercial hardware platforms of wireless sensor networks (WSN) have been developed and used for structural monitoring applications [1,2]. A typical design of a node includes a sensor board and a mote connected to it. Sensing units, analog filters and analog-to-digital converters (ADCs) are integrated on the sensor board and the mote consists of a microcontroller and a wireless transceiver. Generally, there are a set of sensor boards compatible with the same model of mote and the selection of the sensor board depends on the specific applications. A WSN system based on this node lacks the capability of interrupting its scheduled task to start a higher priority task. This shortcoming is rooted in the hardware architecture of the node. The proposed sandwich-node architecture is designed to remedy the shortcomings of the existing one for task preemption. A sandwich node is composed of a sensor board and two motes. The first mote is dedicated to managing the sensor board and processing acquired data. The second mote controls the first mote via commands. A prototype has been implemented using Imote2 and verified by an emulation in which one mote is triggered by a remote base station and then preempts the running task at the other mote for handling an emergency event.

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

    NASA Astrophysics Data System (ADS)

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

    2008-04-01

    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 [α-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.

  1. Material Based Structure Design: Numerical Analysis Thermodynamic Response of Thermal Pyrolytic Graphite /Al Sandwich Composites

    NASA Astrophysics Data System (ADS)

    Wang, Junxia; Yan, Shilin; Yu, Dingshan

    2016-12-01

    Amine-grafted multiwalled carbon nanotubes (MWCNTs) based thermally conductive adhesive (TCA) was studied in the previous paper and applied here in thermal pyrolytic graphite (TPG)/Al radiator due to its high thermal conductivity, toughness and cohesiveness. In this paper, in an attempt to confirm the application of TCA to TPG/Al sandwich radiator, the thermodynamic response in TPG/Al sandwich composites associated with key material properties and structural design was investigated using finite element simulation with commercial available ANSYS software. The induced thermal stress in TCA layer is substantial due to the thermal expansion mismatch between Al plate and TPG. The maximum thermal stress is located near the edge of TCA layer with the von Mises stress value of 4.02 MPa and the shear stress value of 1.66 MPa. The reasonable adjustment of physical-mechanical properties including thermal conductivity, thermal expansion, Young,s modulus and the thickness of TCA layer, Al plate and TPG are beneficial for reducing the temperature of the top surface of the upper skin and their effects on the reduction of thermal structural response in some ways. These findings will highlight the structural optimization of TPG/Al radiator for future application.

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

    PubMed Central

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

    2014-01-01

    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

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

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

    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.

  4. Spin current valve effect in normal metal/magnetic insulator/normal metal sandwiches

    NASA Astrophysics Data System (ADS)

    Li, Junxue; Xu, Yadong; Aldosary, Mohammed; Tang, Chi; Lin, Zhisheng; Zhang, Shufeng; Lake, Roger; Shi, Jing; Shines Collaboration

    Pure spin current is generated in two common ways. One makes use of the spin Hall effect in normal metals (NM), the other utilizes spin waves with the quasi-particle excitations called magnons. A popular material for the latter is yttrium iron garnet (YIG), a magnetic insulator (MI). Here we demonstrate in NM/MI/NM sandwiches that these two types of spin current are interconvertible, which allows transmitting an electrical signal across the MI, predicted as the magnon-mediated current drag phenomenon. We show experimentally that the spin current can be switched ``on'' or ``off'' by controlling the magnetization orientation of MI, analogous to conventional spin valves for spin-polarized charge current. The transmitted current drag signal scales linearly with the driving current without any threshold and follows the power-law Tn with n ranging from 1.5 to 2.5. Our results indicate that the NM/MI/NM sandwich structure can serve as a scalable pure spin current valve device which is an essential ingredient in spintronics. As part of the SHINES, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences under Award # SC0012670.

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

    NASA Astrophysics Data System (ADS)

    Itoh, Eiji; Goto, Yoshinori; Fukuda, Katsutoshi

    2014-02-01

    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 (η). 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.

  6. Open-sandwich enzyme immunoassay for one-step noncompetitive detection of corticosteroid 11-deoxycortisol.

    PubMed

    Ihara, Masaki; Suzuki, Tatsuya; Kobayashi, Norihiro; Goto, Junichi; Ueda, Hiroshi

    2009-10-15

    A noncompetitive immunoassay has the potential for improved sensitivity and working range compared with corresponding competitive assays. However, monovalent antigens with less than 1000 in molecular weight are not susceptible to sandwich assays due to their small size. As a noncompetitive immunoassay that can be performed with a clone of an antibody, an open-sandwich immunoassay (OS-IA) based on the antigen-dependent stabilization of the antibody variable region (V(H) + V(L)) was applied to the quantification of 11-deoxycortisol (11-DC; M(r) 346.5), a corticosteroid serving as a diagnostic index for pituitary-adrenal function, as a model target hapten. By one step OS-IA detection of enzyme-labeled V(H) fragment bound to immobilized V(L) in the presence of sample in microplate wells, 11-DC was measured with a femtomolar detection limit and the working range was wider than that with corresponding competitive assay. In addition, the selectivity against analogues was found almost identical to that of conventional assays. The effect of the mutagenesis of a V(H) residue at the V(H)/V(L) interface to reduce background signal was also shown, implying the wider application of OS-IA in small molecule analyses.

  7. A rapid sandwich immunoassay for human fetuin A using agarose-3-aminopropyltriethoxysilane modified microtiter plate.

    PubMed

    Vashist, Sandeep Kumar; Schneider, E Marion; Luong, John H T

    2015-07-09

    A rapid sandwich immunoassay (IA) with enhanced signal response for human fetuin A (HFA) was developed by modifying the surface of a KOH-treated polystyrene microtiter plate (MTP) with agarose and 3-aminopropyltriethoxysilane (APTES). The agarose-APTES complex binds covalently to the hydroxyl moiety of the MTP plate to serve as a binding platform for bioconjugation of EDC-activated anti-HFA antibody (Ab) via carbodiimide coupling. The one-step kinetics-based sandwich enzyme-linked immunosorbent assay (ELISA) enabled the detection of HFA in 30 min with a limit of detection (LOD) and a linear range of 0.02 ng mL(-1) and 1-243 ng mL(-1), respectively. It detected HFA spiked in diluted human whole blood and serum, and HFA in ethylenediaminetetraacetic acid (EDTA)-plasma of patients with high precision similar to that of conventional ELISA. The anti-HFA Ab-bound agarose-functionalized MTPs retained their functional activity after 6 weeks of storage in 0.1 M PBS, pH 7.4 at 4 °C.

  8. A sandwich immunoassay for detection of Aβ(1-42) based on quantum dots.

    PubMed

    Pi, Jiangli; Long, Yijuan; Huang, Ning; Cheng, Yuan; Zheng, Huzhi

    2016-01-01

    Alzheimer's disease (AD) is the primary cause of dementia over the age of 60, affecting more than 35 million people worldwide. Methods for early diagnosis of AD are critical for the development of effective treatments to combat this debilitating disease. It was confirmed that amyloid-beta peptide 1-42 (Aβ(1-42)) is the biomarker of its early diagnosis. In this work, we present a new sandwich immunoassay method for the detection of Aβ(1-42) based on quantum dot (QDs) nanolabels and magnetic separation. In the presence of Aβ(1-42), QDs linked to magnetic beads (MB) via the formation of immune-sandwich complex and can be removed by a magnetic field. And as a result, fluorescence intensity from QDs in the supernatant decreased. Under the optimized conditions, there is a linear relationship between the fluorescence intensity of supernatant solution and the concentration of Aβ(1-42) from 0.50 to 8.0 nM with a limit detection of 0.2 nM (3σ). This immunoassay was applied to detect Aβ(1-42) in human cerebrospinal fluid (CSF) successfully.

  9. Ultrasensitive and selective homogeneous sandwich immunoassay detection by Surface Enhanced Raman Scattering (SERS).

    PubMed

    Pekdemir, Mustafa Ersin; Ertürkan, Deniz; Külah, Haluk; Boyacı, Ismail H; Ozgen, Canan; Tamer, Uğur

    2012-10-21

    In this report, a simple and highly selective homogeneous sandwich immunoassay was developed for ultrasensitive detection of Staphylococcal Enterotoxin B (SEB) using Surface Enhanced Raman Scattering (SERS). The assay uses polyclonal-antibody functionalized magnetic gold nanorod particles as capture probes for SEB, which can be collected via a simple magnet. After separating SEB from the sample matrix, they are sandwiched by using binding-specific antibody-antigen pairs with the help of gold nanorod particles. Gold nanorod particles are bifunctional by design and contain self-assembled monolayers (SAMs) of a SERS tag molecule (5,5-dithiobis (2-nitrobenzoic acid), DTNB) and carboxylic functionalities of DTNB for coupling with a suitable antibody. The correlation between the SEB concentration and SERS signal was found to be linear within the range of 3 fM to 0.3 μM. The limit of detection for the assay was determined to be 768 aM (ca., 9250 SEB molecules per 20 μL sample volume). The gold heterogeneous assay system for SEB detection was also compared with the same SERS probes and gold-coated surfaces as capture substrates. The developed method was further evaluated for detecting SEB in artificially contaminated milk. Finally, the method was used for investigating the SEB specificity on bovine serum albumin (BSA) and avidin.

  10. Shape and Stress Sensing of Multilayered Composite and Sandwich Structures Using an Inverse Finite Element Method

    NASA Technical Reports Server (NTRS)

    Cerracchio, Priscilla; Gherlone, Marco; Di Sciuva, Marco; Tessler, Alexander

    2013-01-01

    The marked increase in the use of composite and sandwich material systems in aerospace, civil, and marine structures leads to the need for integrated Structural Health Management systems. A key capability to enable such systems is the real-time reconstruction of structural deformations, stresses, and failure criteria that are inferred from in-situ, discrete-location strain measurements. This technology is commonly referred to as shape- and stress-sensing. Presented herein is a computationally efficient shape- and stress-sensing methodology that is ideally suited for applications to laminated composite and sandwich structures. The new approach employs the inverse Finite Element Method (iFEM) as a general framework and the Refined Zigzag Theory (RZT) as the underlying plate theory. A three-node inverse plate finite element is formulated. The element formulation enables robust and efficient modeling of plate structures instrumented with strain sensors that have arbitrary positions. The methodology leads to a set of linear algebraic equations that are solved efficiently for the unknown nodal displacements. These displacements are then used at the finite element level to compute full-field strains, stresses, and failure criteria that are in turn used to assess structural integrity. Numerical results for multilayered, highly heterogeneous laminates demonstrate the unique capability of this new formulation for shape- and stress-sensing.

  11. Compression After Impact on Honeycomb Core Sandwich Panels With Thin Facesheets. Part 1; Experiments

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

    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 one, the subject of the current paper, is focused on the experimental testing. 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 specimens, which were identical with the exception of the density of the honeycomb core, were tested. Static indentation and low velocity impact using a drop tower are used to study damage formation in these materials. A series of highly instrumented CAI tests was then completed. New techniques used to observe CAI response and failure include high speed video photography, as well as digital image correlation (DIC) for full-field deformation measurement. Two CAI failure modes, indentation propagation, and crack propagation, were observed. From the results, it can be concluded that the CAI failure mode of these panels depends solely on the honeycomb core density.

  12. Optimal Design of Litz Wire Coils With Sandwich Structure Wirelessly Powering an Artificial Anal Sphincter System.

    PubMed

    Ke, Lei; Yan, Guozheng; Yan, Sheng; Wang, Zhiwu; Li, Xiaoyang

    2015-07-01

    Transcutaneous energy transfer system (TETS) is widely used to energize implantable biomedical devices. As a key part of the TETS, a pair of applicable coils with low losses, high unloaded Q factor, and strong coupling is required to realize an efficient TETS. This article presents an optimal design methodology of planar litz wire coils sandwiched between two ferrite substrates wirelessly powering a novel mechanical artificial anal sphincter system for treating severe fecal incontinence, with focus on the main parameters of the coils such as the wire diameter, number of turns, geometry, and the properties of the ferrite substrate. The theoretical basis of optimal power transfer efficiency in an inductive link was analyzed. A set of analytical expressions are outlined to calculate the winding resistance of a litz wire coil on ferrite substrate, taking into account eddy-current losses, including conduction losses and induction losses. Expressions that describe the geometrical dimension dependence of self- and mutual inductance are derived. The influence of ferrite substrate relative permeability and dimensions is also considered. We have used this foundation to devise an applicable coil design method that starts with a set of realistic constraints and ends with the optimal coil pair geometries. All theoretical predictions are verified with measurements using different types of fabricated coils. The results indicate that the analysis is useful for optimizing the geometry design of windings and the ferrite substrate in a sandwich structure as part of which, in addition to providing design insight, allows speeding up the system efficiency-optimizing design process.

  13. Semi-active control of a sandwich beam partially filled with magnetorheological elastomer

    NASA Astrophysics Data System (ADS)

    Dyniewicz, Bartłomiej; Bajkowski, Jacek M.; Bajer, Czesław I.

    2015-08-01

    The paper deals with the semi-active control of vibrations of structural elements. Elastomer composites with ferromagnetic particles that act as magnetorheological fluids are used. The damping coefficient and the shear modulus of the elastomer increases when it is exposed to an electro-magnetic field. The control of this process in time allows us to reduce vibrations more effectively than if the elastomer is permanently exposed to a magnetic field. First the analytical solution for the vibrations of a sandwich beam filled with an elastomer is given. Then the control problem is defined and applied to the analytical formula. The numerical solution of the minimization problem results in a periodic, perfectly rectangular control function if free vibrations are considered. Such a temporarily acting magnetic field is more efficient than a constantly acting one. The surplus reaches 20-50% or more, depending on the filling ratio of the elastomer. The resulting control was verified experimentally in the vibrations of a cantilever sandwich beam. The proposed semi-active control can be directly applied to engineering vibrating structural elements, for example helicopter rotors, aircraft wings, pads under machines, and vehicles.

  14. Development of a Multiplex Sandwich Aptamer Microarray for the Detection of VEGF165 and Thrombin

    PubMed Central

    Sosic, Alice; Meneghello, Anna; Antognoli, Agnese; Cretaio, Erica; Gatto, Barbara

    2013-01-01

    In this work we have developed a multiplex microarray system capable of detecting VEGF165 and thrombin. We recently described a Sandwich Aptamer Microarray (SAM) for thrombin detection feasible for use in multiplex microarrays; here we describe a new aptasensor for VEGF165 detection employing Vap7 and VEa5, two DNA aptamers recognizing different sites of the protein. The aptamers were modified to be adapted to the solid phase platform of SAM and their capability to simultaneously recognize VEGF165 by forming a ternary complex was analyzed in solution. Having so defined the best tandem arrangement of modified aptamers, we set up the aptasensor for VEGF165, and finally analyzed the multiplex system with the two aptasensors for the simultaneous detection of VEGF165 and thrombin. The results indicate that each sandwich is specific, even when the two proteins are mixed. The system performance is consistent with the behavior evidenced by the biochemical analysis, which proves to be valuable to drive the evaluation and refinement of aptamers prior to or along the development of a detection platform. Since thrombin upregulates VEGF expression, the simultaneous recognition of these two proteins could be useful in the analysis of biomarkers in pathologies characterized by neo-angiogenesis. PMID:24097233

  15. Sandwich-format 3D printed microfluidic mixers: a flexible platform for multi-probe analysis

    PubMed Central

    Kise, Drew P; Reddish, Michael J; Dyer, R Brian

    2015-01-01

    We report on a microfluidic mixer fabrication platform that increases the versatility and flexibility of mixers for biomolecular applications. A sandwich-format design allows the application of multiple spectroscopic probes to the same mixer. A polymer spacer is ‘sandwiched’ between two transparent windows, creating a closed microfluidic system. The channels of the mixer are defined by regions in the polymer spacer that lack material and therefore the polymer need not be transparent in the spectral region of interest. Suitable window materials such as CaF2 make the device accessible to a wide range of optical probe wavelengths, from the deep UV to the mid-IR. In this study, we use a commercially available 3D printer to print the polymer spacers to apply three different channel designs into the passive, continuous-flow mixer, and integrated them with three different spectroscopic probes. All three spectroscopic probes are applicable to each mixer without further changes. The sandwich-format mixer coupled with cost-effective 3D printed fabrication techniques could increase the applicability and accessibility of microfluidic mixing to intricate kinetic schemes and monitoring chemical synthesis in cases where only one probe technique proves insufficient. PMID:26855478

  16. Analysis of crack propagation in nuclear graphite using three-point bending of sandwiched specimens

    NASA Astrophysics Data System (ADS)

    Shi, Li; Li, Haiyan; Zou, Zhenmin; Fok, Alex S. L.; Marsden, Barry J.; Hodgkins, Andrew; Mummery, Paul M.; Marrow, James

    2008-01-01

    The aim of this paper was to assess the suitability of the sandwiched beam in three-point bending as a technique for determining fracture toughness and R-curve behaviour of nuclear graphite using small beam specimens. Surface displacements of the cracked beam specimen were measured using Electronic Speckle Pattern Interferometry (ESPI) and Image Correlation in order to accurately monitor crack propagation and frictional contact between the test specimen and the sandwiching beams. The results confirmed that solutions based on the simple beam theory could overestimate the fracture toughness of graphite. Finite element analysis using a Continuum Damage Mechanics failure model indicated that both friction and shape of the notch played an important part in providing resistance to crack growth. Inclusion of these factors and the use of more accurate load vs. crack length curves derived from the FE model would provide a satisfactory measure of fracture toughness in small beam specimens under such a loading configuration. The particular graphite tested, IG-110, showed a decrease in fracture toughness with increasing crack length.

  17. Comparison of wear and clinical performance between amalgam, composite and open sandwich restorations: 2-year results.

    PubMed

    Sachdeo, A; Gray, Gordon B; Sulieman, M A; Jagger, Daryll C

    2004-03-01

    There has been some disquiet over the use of mercury containing restorative materials. The most commonly used alternative is composite resin but this has the potential disadvantage associated with wear and marginal leakage, which in turn, has proven to result in secondary caries and sensitivity. To overcome the shortcomings of a directly placed composite restoration, the glass-ionomer/composite open sandwich technique was introduced followed by the subsequent introduction of compomer systems. The aims of this study were to evaluate the wear and clinical performance of a control group of amalgam restorations compared with that of a group of posterior composite resin restorations fillings and a group of compomer/composite open sandwich restorations placed by a single general dental practitioner. The duration of the study was 2 years. One hundred and thirty three (71.4%) patients were successfully recalled and the wear and clinical performance of each restoration after 6, 12 and 24 months was measured, indirectly. There was no statistically significant difference recorded between the groups at 6 months or 1 year (p > 0.05). However, at the end of the 2-year study, there was a significantly lower rate of wear recorded for the control amalgam restorations compared with other two groups (p = 0.033). There was no statistically significant difference in wear recorded between the two groups of tooth-coloured restorations (p > 0.05). With regards to clinical performance of the restorations, occlusal and proximal contacts in each group of restoration remained satisfactory throughout the study.

  18. Effect of the Protein Corona on Antibody-Antigen Binding in Nanoparticle Sandwich Immunoassays.

    PubMed

    de Puig, Helena; Bosch, Irene; Carré-Camps, Marc; Hamad-Schifferli, Kimberly

    2017-01-18

    We investigated the effect of the protein corona on the function of nanoparticle (NP) antibody (Ab) conjugates in dipstick sandwich immunoassays. Ab specific for Zika virus nonstructural protein 1 (NS1) were conjugated to gold NPs, and another anti-NS1 Ab was immobilized onto the nitrocellulose membrane. Sandwich immunoassay formation was influenced by whether the strip was run in corona forming conditions, i.e., in human serum. Strips run in buffer or pure solutions of bovine serum albumin exhibited false positives, but those run in human serum did not. Serum pretreatment of the nitrocellulose also eliminated false positives. Corona formation around the NP-Ab in serum was faster than the immunoassay time scale. Langmuir binding analysis determined how the immobilized Ab affinity for the NP-Ab/NS1 was impacted by corona formation conditions, quantified as an effective dissociation constant, KD(eff). Results show that corona formation mediates the specificity and sensitivity of the antibody-antigen interaction of Zika biomarkers in immunoassays, and plays a critical but beneficial role.

  19. An innovative sandwich ELISA system based on an antibody cocktail for gluten analysis.

    PubMed

    Sorell, L; López, J A; Valdés, I; Alfonso, P; Camafeita, E; Acevedo, B; Chirdo, F; Gavilondo, J; Méndez, E

    1998-11-13

    A cocktail sandwich ELISA based on the employ of two monoclonal antibodies (MAbs) as coating antibodies and a third MAb conjugated to horseradish peroxidase has been developed for the analysis of gluten in foods. Given that each MAb displays a wide specificity spectrum for wheat, barley, rye and oats prolamins, their combination for ELISA ensures a high crossreactivity with most of the potentially toxic gliadin, hordein, secalin and avenin protein family. One of the unprecedented features of the cocktail sandwich ELISA is that it permits for the first time analysis of barley hordeins in foods, which is unattainable using conventional or commercial ELISA kits. Besides, gliadins, hordeins and secalins are recognised to the same extent. The system provides a high detection sensitivity for gliadins, hordeins, secalins and avenins (1.5, 0.05, 0.15 and 12 ng/ml, respectively). The working linear range comprises 3-100 ng/ml with a gliadin detection limit of 1.5 ppm. This limit of detection is even better than that demanded in the latest Codex recommendation, 10 ppm. Cocktail ELISA data were contrasted with those of commercial ELISA kits and confirmed by mass spectrometry, a non-immunological technique which provides evidence for the occurrence of false positive results with the commercial kits.

  20. High-quality sandwiched black phosphorus heterostructure and its quantum oscillations

    NASA Astrophysics Data System (ADS)

    Chen, Xiaolong; Wu, Yingying; Wu, Zefei; Han, Yu; Xu, Shuigang; Wang, Lin; Ye, Weiguang; Han, Tianyi; He, Yuheng; Cai, Yuan; Wang, Ning

    2015-06-01

    Two-dimensional materials such as graphene and transition metal dichalcogenides have attracted great attention because of their rich physics and potential applications in next-generation nanoelectronic devices. The family of two-dimensional materials was recently joined by atomically thin black phosphorus which possesses high theoretical mobility and tunable bandgap structure. However, degradation of properties under atmospheric conditions and high-density charge traps in black phosphorus have largely limited its actual mobility thus hindering its future applications. Here, we report the fabrication of stable sandwiched heterostructures by encapsulating atomically thin black phosphorus between hexagonal boron nitride layers to realize ultra-clean interfaces that allow a high field-effect mobility of ~1,350 cm2V-1 s-1 at room temperature and on-off ratios exceeding 105. At low temperatures, the mobility even reaches ~2,700 cm2V-1 s-1 and quantum oscillations in black phosphorus two-dimensional hole gas are observed at low magnetic fields. Importantly, the sandwiched heterostructures ensure that the quality of black phosphorus remains high under ambient conditions.