Science.gov

Sample records for sandwich construction

  1. Sandwich Construction Solar Structural Facets

    SciTech Connect

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

    1998-12-22

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

  2. Concrete sandwich construction for energy conservation

    NASA Astrophysics Data System (ADS)

    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.

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

    SciTech Connect

    Manning, J.A.; Crosky, A.G.; Bandyopadhyay, S.

    1993-12-31

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

  4. 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

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

    PubMed

    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. Effect of temperature on composite sandwich structures subjected to low velocity impact. [aircraft construction materials

    NASA Technical Reports Server (NTRS)

    Sharma, A. V.

    1980-01-01

    The effect of low velocity projectile impact on sandwich-type structural components was investigated. The materials used in the fabrication of the impact surface were graphite-, Kevlar-, and boron-fibers with appropriate epoxy matrices. The testing of the specimens was performed at moderately low- and high-temperatures as well as at room temperature to assess the impact-initiated strength degradation of the laminates. Eleven laminates with different stacking sequences, orientations, and thicknesses were tested. The low energy projectile impact is considered to simulate the damage caused by runway debris, the dropping of the hand tools during servicing, etc., on the secondary aircraft structures fabricated with the composite materials. The results show the preload and the impact energy combinations necessary to cause catastrophic failure in the laminates tested. A set of faired curves indicating the failure thresholds is shown separately for the tension-and compression-loaded laminates. The specific-strengths and -modulii for the various laminates tested are also given.

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

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

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

  8. Construction of tetranuclear metallacycles based on half-sandwich Ir, Rh fragments and pyridyl-substituted ligands with different coordinate vectors.

    PubMed

    Fan, Qi-Jia; Zhang, Wen-Ying; Lin, Yue-Jian; Jin, Guo-Xin

    2016-03-21

    A series of organometallic macrocycles have been constructed by two-step reactions of [Cp*M(μ-Cl)Cl]2 (M = Ir, Rh), firstly with AgOTf to abstract chloride ions and then with simple pyridyl-substituted ligands-pyridyldipyrromethene (HL(1)), pyridin-4-yl (1H-pyrrol-2-yl)methanone (HL(2)) and pyridine-4-carbohydrazide (HL(3))-resulting in the formation of the tetranuclear 32-membered metallacycles [(Cp*Ir)(L(1))]4(OTf)4 (2a) and [(Cp*Rh)(L(1))]4(OTf)4 (2b), and the 28-membered metallacycles [(Cp*Ir)(L(2))]4 (OTf)4 (3a), [(Cp*Rh)(L(2))]4(OTf)4 (3b), [(Cp*Ir)(L(3))]4(OTf)4 (4a) and [(Cp*Rh)(L(3))]4(OTf)4 (4b). Four target complexes were characterised by single crystal X-ray analyses, revealing that these metallacycles, constructed from half-sandwich metal corners and pyridyl-substituted linkers, form large ring structures. The observed variation in the metallacyclic geometries was explained on the basis of the structural flexibility of the corner fragments, subtle changes in coordination geometries, and changes in the orientation of the coordinate vectors in the given ligands, as well as different dihedral angles between the two binding fragments in the nonplanar ligands. PMID:26845526

  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. 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…

  11. "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…

  12. 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.

  13. 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.

  14. 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.

  15. Survey Of The State Of The Art Composites And Sandwich Structures

    NASA Astrophysics Data System (ADS)

    Cornel, Bucur; Ana Maria, Bucur

    2015-09-01

    The objective of the work is to present some researches regarding composits. The aim is motivated by the new materials such as composites and structural concepts, sandwich construction that have resulted in lighter structural designs with superior performance. There are presented and discussed the types of matrix materials, sandwich construction, failure modes in sandwich structures and design considerations. It is not possible to cover every aspect of this vast subject. The purpose here is to impart the basic knowledge so that the people involved in the structural repairs will have better understanding of the processes.

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

    NASA Astrophysics Data System (ADS)

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

    2010-01-01

    Prediction of mechanical performance of sandwich constructions is a difficult task due to the complex nonlinear and inelastic behavior of the constituent materials. This study tries to utilize an analytical model to estimate the mechanical performance of sandwich structure based on the mechanical properties of the constituents. To this end, the mechanical properties of the core and skin materials were examined separately. The mechanical behavior and deformation mechanism of Ni alloy foam structures have been studied using uniaxial compression testing. The mechanical properties of alloy 625 coating were determined using tensile testing. The flexural rigidity of sandwich structures were calculated using experimentally obtained elastic moduli of the alloy 625 coating and Ni alloy foam. The model was also used to calculate the flexural rigidity of sandwich samples with different skin thicknesses. This study also investigates the effect of post fabrication heat treatment on the mechanical performance of the sandwich structures.

  17. Bending Stiffness of Multiwall Sandwich

    NASA Technical Reports Server (NTRS)

    Blosser, M. L.

    1983-01-01

    An analytical and experimental study was carried out to understand the extensional and flexural behavior of multiwall sandwich, a metallic insulation composed of alternate layers of flat and dimpled foil. The multiwall sandwich was structurally analyzed by using several simplifying assumptions combined with a finite element analysis. The simplifying assumptions made in this analysis were evaluated by bending and tensile tests. Test results validate the assumption that flat sheets in compression do not significantly contribute to the flexural stiffness of multiwall sandwich for the multiwall geometry tested. However, calculations show that thicker flat sheets may contribute significantly to bending stiffness and cannot be ignored. Results of this analytical approach compare well with test data; both show that the extensional stiffness of the dimpled sheet in he 0 deg direction is about 30 percent of that for a flat sheet, and that in the 45 deg direction, it is about 10 percent. The analytical and experimental multiwall bending stiffness showed good agreement for the particular geometry tested.

  18. Cytomegalovirus in urine: detection of viral DNA by sandwich hybridization.

    PubMed

    Virtanen, M; Syvänen, A C; Oram, J; Söderlund, H; Ranki, M

    1984-12-01

    A cytomegalovirus (CMV)-specific sandwich hybridization test was constructed by using two adjacent BamHI DNA fragments of CMV DNA as reagents. The fragments were cloned into two different vectors. One of the recombinants was attached to the filter, and the other was the labeled probe. When present in the sample, CMV DNA mediated labeling of the filter by hybridizing to both the filter-bound DNA and the probe. The sandwich hybridization test was applied for the detection of CMV DNA from urine. DNA was released from virus by 2% Sarkosyl, concentrated by 2-butanol extraction and isopropanol precipitation, denatured, and finally subjected to the sandwich hybridization test. As a result, 70 to 90% of the original viral DNA could be recovered and demonstrated by the quantitative hybridization reaction. Urine could be stored at room temperature in Sarkosyl for at least 2 days without affecting the detectability of CMV. The clinical applicability of the test was evaluated by studying urine samples from four infants excreting CMV. Sandwich hybridization demonstrated the presence of CMV DNA in all of the specimens. These contained originally 10(5) to 10(8) CMV DNA molecules per ml. PMID:6097598

  19. Development of biobased sandwich structures for mass transit application

    NASA Astrophysics Data System (ADS)

    Munusamy, Sethu Raaj

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

  20. 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.

  1. Compressive strength after blast of sandwich composite materials.

    PubMed

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

    2014-05-13

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

  2. 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

  3. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2005-03-01

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

  5. Vibration damping using four-layer sandwich

    NASA Astrophysics Data System (ADS)

    Yadav, Binod P.

    2008-11-01

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

  6. Sound transmission loss of composite sandwich panels

    NASA Astrophysics Data System (ADS)

    Zhou, Ran

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

  7. Graphene-antenna sandwich photodetector.

    PubMed

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

    2012-07-11

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

  8. 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.

  9. Open-die forging of structurally porous sandwich panels

    SciTech Connect

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

    1999-10-01

    Structurally porous metal sandwich panels consisting of dense face sheets and porous cores of controlled relative density can be manufactured by trapping inert gas during hot isostatic pressing and modifying its distribution via subsequent thermomechanical forming. A plane-strain solution for analyzing the open-die forging of such a plastically compressible sandwich panel is developed. An effective yield potential for the face sheet/core sandwich is constructed from the Mises yield criterion for the rigid-plastic face sheet and Doraivelu et al's density-dependent yield function for the compressible core. This effective constitutive response is used in a classical slab analysis of open-die forging. The analysis predicts the upsetting force and the distributions of pressure, core relative density, and average stresses within both the face sheet and the core. During upsetting, a zone of fully constrained material (i.e., with zero lateral strain) is predicted to occur at the center of the workpiece, and this densifies first. A densification front then advances laterally from the panel center toward the outer edges. The nonuniform densification complicates the use of forging for the production of components requiring a uniform density core.

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

    NASA Astrophysics Data System (ADS)

    Azarmi, Fardad

    There has been a great deal of interest in the development of sandwich structures as viable engineering constructions. It is due to their unique structural, physical, and mechanical characteristics such as light weight, high strength to weight ratio, high bending stiffness, excellent thermal and acoustical insulation. Although the service temperature for most applications of sandwich structures is low, the outstanding properties make sandwich constructions attractive for use in high temperature service conditions as well. The overall performance of sandwich constructions depends on the material properties of skin and core, and their geometrical characteristics. An investigation of the characteristics of sandwich structures suitable for high temperature application is presented. The objective of the investigation was to develop a process for producing sandwich structures by depositing alloy 625 skins on Ni foam cores using air plasma spraying (APS), and to characterize the structure and mechanical behavior of the constituents and the sandwich structure. The experimental investigation consisted of optimization of deposition process parameters, microstructural and mechanical characterization of sandwich constituents and testing of mechanical performance of sandwich structures under flexural loading conditions. The responses of the as-received foam, as-sprayed coating, and as-fabricated sandwich structure to heat treatment were investigated. Available analytical models and numerical simulations linking the mechanical properties of the Ni alloy foam, the alloy 625 coating, and the sandwich structure to their physical properties and microstructures were compared with the results of mechanical testing to understand the behavior of the sandwich structure in terms of the properties of the constituents. An empirical model was developed to predict deposition parameters which simultaneously minimize the oxide content and the porosity in the alloy 625 coating. The optimum

  11. 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.

  12. 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

  13. 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

  14. 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

  15. Sandwich Panels Evaluated With Ultrasonic Spectroscopy

    NASA Technical Reports Server (NTRS)

    Cosgriff, Laura M.

    2004-01-01

    Enhanced, lightweight material systems, such as 17-4PH stainless steel sandwich panels are being developed for use as fan blades and fan containment systems for next-generation engines. The bond strength between the core and face sheets is critical in maintaining the structural integrity of the sandwich structure. To improve the inspection and production of these systems, researchers at the NASA Glenn Research Center are using nondestructive evaluation (NDE) techniques, such as ultrasonic spectroscopy, to evaluate the brazing quality between the face plates and the metallic foam core. The capabilities and limitations of a swept-frequency approach to ultrasonic spectroscopy were evaluated with respect to these sandwich structures. This report discusses results from three regions of a sandwich panel representing different levels of brazing quality between the outer face plates and a metallic foam core. Each region was investigated with ultrasonic spectroscopy. Then, on the basis of the NDE results, three shear specimens sectioned from the sandwich panel to contain each of these regions were mechanically tested.

  16. Fatigue studies of polyurethane sandwich structures

    NASA Astrophysics Data System (ADS)

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

    2004-10-01

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

  17. Impact resistance of composite laminated sandwich plates

    NASA Astrophysics Data System (ADS)

    Kim, Chun-Gon; Jun, Eui-Jin

    1992-01-01

    Investigated are the effects of face layup sequence and core density of a sandwich plate on the impact delamination area of the laminated facesheet. The sandwich plate is made of graphite/epoxy faces and Nomex honeycomb core. The size and shape of delamination due to impact at each interply location have been measured by the room temperature deply technique. The shape of the interply delamination under impact is, in general, found to be two-lobed. The shape exhibits very peculiar regularity under various experimental conditions. The quantitative measurement of delamination size has shown that the face layup with small relative orientation between adjacent plies and high density core are desirable in sandwich plates to reduce the impact delamination.

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

    NASA Technical Reports Server (NTRS)

    Ko, William L.

    1994-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2004-01-01

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

  20. 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.

  1. 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.

  2. Symplectic analysis of dynamic properties of hexagonal honeycomb sandwich tubes with plateau borders

    NASA Astrophysics Data System (ADS)

    Zhang, Kai; Deng, Zichen; Meng, Junmiao; Xu, Xiaojian; Wang, Yan

    2015-09-01

    A new type of hexagonal honeycomb sandwich tube with plateau borders are introduced in this work and the Symplectic analysis with its high computational efficiency and high accuracy is applied to obtain the structural dynamic properties. The effects of material distribution (β) and relative density (ρbar) on the dynamic properties of the structure are also studied. Based on the definition of the elastic constants and the homogenization method, the independent elastic constants are obtained. By introducing dual variables and applying the variational principle, the canonical equations of Hamiltonian system are constructed. The precise integration method and extended Wittrick-Williams algorithm are adopted to solve the canonical equations. The dispersion relations of sandwich tubes are obtained, and the effects of material distribution and relative density on the normalized frequencies of the sandwich tubes are investigated. The proposed homogenization method is verified by comparing with other researchers' works. Dispersion relations of the sandwich tubes are obtained. The material distribution parameter and the relative density have significant effects on the dynamic properties of the structures. This work expects to offer new opportunities for the optimal design of metallic honeycomb sandwich tubes and future applications in the engineering sector.

  3. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2005-05-01

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

  5. 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

  6. Sandwich targets for heavy-ion experiments

    SciTech Connect

    Thomas, G.E.

    1982-01-01

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

  7. Career Counseling for the Sandwich Generation.

    ERIC Educational Resources Information Center

    Byrd, Virginia

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

  8. 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.

  9. Engineering Sandwich Courses in British Technological Universities

    ERIC Educational Resources Information Center

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

    1971-01-01

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

  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. 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…

  12. 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…

  13. 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.

  14. Lightweight Aluminum Mirrors Using Foam Core Sandwich Construction

    NASA Technical Reports Server (NTRS)

    Content, D.; Lyons, J., III; Budinoff, J.

    1999-01-01

    The possible use of all aluminum mirrors made from thin faceplates supported by aluminum foam is explored from an optomechanical design and fabrication perspective. Foam mirrors can be relatively cheaply and easily made using conventional foam fabrication and diamond turning; such a mirror recently flew for the first time on the Stardust mission. The proposed structural concept is highly weight efficient and should not be prone to quilting. The weight and structural stability of such mirrors is presented, along with plans underway at GSFC for developing this concept.

  15. Applications of thin-film sandwich crystallization platforms

    PubMed Central

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

    2016-01-01

    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. PMID:27050266

  16. Applications of thin-film sandwich crystallization platforms.

    PubMed

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

    2016-04-01

    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. PMID:27050266

  17. 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.

  18. 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.

  19. 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.

  20. Fiber Composite Sandwich Thermostructural Behavior: Computational Simulation

    NASA Technical Reports Server (NTRS)

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

    1986-01-01

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

  1. 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.

  2. Establishment of swine interleukin-6 sandwich ELISA.

    PubMed

    Nuntaprasert, A; Mori, Y; Tsukiyama-Kohara, K; Kai, C

    2005-03-01

    We established a sandwich enzyme-linked immunosorbent assay (ELISA) for swine interleukin-6 (SwIL-6), which was applied for detection of SwIL-6 in vitro and in vivo. Anti-SwIL-6 rabbit- and goat-polyclonal antibodies, and monoclonal antibody (mAb) were prepared, conforming that all of the antibodies were reactive with recombinant SwIL-6 by Western blotting and indirect ELISA. A sandwich ELISA was developed using the mAb as a capture antibody and biotinylated goat-polyclonal antibody as a detection antibody. The detection limit of the sandwich ELISA for rSwIL-6 was 49pg/ml and did not show cross-reactivity with swine IL-1b, IL-4, IL-8, IL-18, IL-12, and IFN-g. Using the ELISA, SwIL-6 was detected in culture medium of the monocytes stimulated with PHA-P and PMA, and the plasma or the bronchoalveolar lavage fluid (BALF) of pigs experimentally infected with Actinobacillus pleuropneumoniae or Mycoplasma hyopneumoniae. This ELISA for SwIL-6 may be useful for understanding the role of this cytokine in various swine diseases. PMID:15582688

  3. 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.

  4. Sandwich-like layer-by-layer assembly of gold nanoparticles with tunable SERS properties.

    PubMed

    Liu, Zhicheng; Bai, Lu; Zhao, Guizhe; Liu, Yaqing

    2016-01-01

    Sandwich-like layer-by-layer thin films consisting of polyelectrolytes and gold nanoparticles were utilized to construct surface-enhanced Raman scattering (SERS) substrates with tunable SERS properties. It is found that both the size of the nanoparticles in the layers and the interlayer distance significantly influence the SERS performance of the multilayered thin film. These simple, low-cost, easily processable and controllable SERS substrates have a promising future in the field of molecular sensing. PMID:27547620

  5. Sandwich-like layer-by-layer assembly of gold nanoparticles with tunable SERS properties

    PubMed Central

    Bai, Lu; Zhao, Guizhe

    2016-01-01

    Summary Sandwich-like layer-by-layer thin films consisting of polyelectrolytes and gold nanoparticles were utilized to construct surface-enhanced Raman scattering (SERS) substrates with tunable SERS properties. It is found that both the size of the nanoparticles in the layers and the interlayer distance significantly influence the SERS performance of the multilayered thin film. These simple, low-cost, easily processable and controllable SERS substrates have a promising future in the field of molecular sensing. PMID:27547620

  6. Buckling and structural efficiency of sandwich-blade stiffened composite compression panels

    NASA Technical Reports Server (NTRS)

    Stein, M.; Williams, J. G.

    1978-01-01

    The minimum mass structural efficiency curve was determined for sandwich blade stiffened composite compression panels subjected to buckling and strength constraints. High structural efficiencies are attainable for this type of construction. A method of analysis is presented for the buckling of panels of this configuration which shows that buckling of such panels is strongly dependent on the through-the-thickness transverse shearing of the stiffener. Experimental results are presented and compared with theory.

  7. 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

  8. 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.

  9. Impact and Blast Resistance of Sandwich Plates

    NASA Astrophysics Data System (ADS)

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

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

  10. CFRP sandwiched facesheets inspected by pulsed thermography

    NASA Astrophysics Data System (ADS)

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

    2010-10-01

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

  11. 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.

  12. 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...

  13. Modeling of Sandwich Sheets with Metallic Foam

    NASA Astrophysics Data System (ADS)

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

    2011-08-01

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

  14. 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.

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

    PubMed Central

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

    2015-01-01

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

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

    PubMed

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

    2015-01-01

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

  17. Deflections of anisotropic sandwich beams with variable face sheets and core thicknesses

    NASA Technical Reports Server (NTRS)

    Lu, Chu-Ho

    1994-01-01

    A sandwich construction consists of a low-density core material with high strength face sheets bounded to the top and bottom surfaces. The construction has been widely used in the aerospace and marine industries due to its outstanding characteristics such as noise absorption, weight minimization, heat insulation, and better bending stiffness. In sandwich structures used in high-performance aircraft, the face sheets are often made of fiber-reinforced composite materials and the core is made of honeycomb. The structures may also have variable thickness so as to satisfy aerodynamic requirements. In the stress analysis, the constant-thickness face sheets are usually considered as membrane and the core is assumed to be inextensible but deformable in the thickness direction. The static behavior of variable-thickness, isotropic and homogeneous sandwich beams was successfully studied by employing a constant-thickness theory but allowing stiffnesses to vary in accordance with local thickness variations. It has been recently found in a refined theory that the analyses based on the constant thickness theory locally can lead to significant errors in structural responses if the sandwich beam is thickness-tapered and the cores are deformable in transverse shear. The errors arise mainly from two factors: (1) the transverse shear components of the membrane forces in the face sheets alter the transverse shears carried by the core; and (2) the face-sheet membrane strains arise from transverse shear deformation of the core. In practice the variable thickness may not only exist in core but also in face sheets. The thickness-variations may even be a type of step function. In this case the transverse shear stress in the face sheets and bending stress in the core should be taken into account in the refined theory mentioned. In the present study, energy principles are employed in deriving governing equations for general bending of anisotropic sandwich beams with variable thickness in both

  18. 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.

  19. 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)

  20. High Velocity Impact Response of Composite Lattice Core Sandwich Structures

    NASA Astrophysics Data System (ADS)

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

    2014-04-01

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

  1. Chiral hexagonal cellular sandwich structure: a vibro-acoustic assessment

    NASA Astrophysics Data System (ADS)

    Lew, Tze L.; Spadoni, Alessandro; Scarpa, Fabrizio; Ruzzene, Massimo

    2005-05-01

    In this work we describe the vibroacoustic behavior of a novel concept of core for sandwich structures featuring auxetic characteristics, enhanced shear stiffness and compressive strength compared to classical cellular cores in sandwich components for sandwich applications. The out-plane properties and density values are described in terms of geometric parameters of the honeycomb unit cells. Opposite to classical honeycomb cellular applications, the hexagonal chiral structure presents a noncentresymemetric configuration, i.e., a "mirror" symmetrical topology. The derived mechanical properties are used to assess the modal behaviour and modal densities of sandwich plate elements with chiral and standard cellular cores. The analytical findings are backed up by structural tests on chiral honeycomb plates and sandwich beams.

  2. 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.

  3. 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.

  4. 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

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

    NASA Astrophysics Data System (ADS)

    Somayajulu, Thamma S. V.

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

  6. Nanoparticle organization in sandwiched polymer brushes.

    PubMed

    Curk, Tine; Martinez-Veracoechea, Francisco J; Frenkel, Daan; Dobnikar, Jure

    2014-05-14

    The organization of nanoparticles inside grafted polymer layers is governed by the interplay of polymer-induced entropic interactions and the action of externally applied fields. Earlier work had shown that strong external forces can drive the formation of colloidal structures in polymer brushes. Here we show that external fields are not essential to obtain such colloidal patterns: we report Monte Carlo and molecular dynamics simulations that demonstrate that ordered structures can be achieved by compressing a "sandwich" of two grafted polymer layers, or by squeezing a coated nanotube, with nanoparticles in between. We show that the pattern formation can be efficiently controlled by the applied pressure, while the characteristic length-scale, that is, the typical width of the patterns, is sensitive to the length of the polymers. Based on the results of the simulations, we derive an approximate equation of state for nanosandwiches. PMID:24707901

  7. "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.

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

    NASA Astrophysics Data System (ADS)

    Baştürk, S. B.; Tanoğlu, M.

    2013-10-01

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

  9. Optimization of Sandwich Composites Fuselages Under Flight Loads

    NASA Astrophysics Data System (ADS)

    Yuan, Chongxin; Bergsma, Otto; Koussios, Sotiris; Zu, Lei; Beukers, Adriaan

    2012-02-01

    The sandwich composites fuselages appear to be a promising choice for the future aircrafts because of their structural efficiency and functional integration advantages. However, the design of sandwich composites is more complex than other structures because of many involved variables. In this paper, the fuselage is designed as a sandwich composites cylinder, and its structural optimization using the finite element method (FEM) is outlined to obtain the minimum weight. The constraints include structural stability and the composites failure criteria. In order to get a verification baseline for the FEM analysis, the stability of sandwich structures is studied and the optimal design is performed based on the analytical formulae. Then, the predicted buckling loads and the optimization results obtained from a FEM model are compared with that from the analytical formulas, and a good agreement is achieved. A detailed parametric optimal design for the sandwich composites cylinder is conducted. The optimization method used here includes two steps: the minimization of the layer thickness followed by tailoring of the fiber orientation. The factors comprise layer number, fiber orientation, core thickness, frame dimension and spacing. Results show that the two-step optimization is an effective method for the sandwich composites and the foam sandwich cylinder with core thickness of 5 mm and frame pitch of 0.5 m exhibits the minimum weight.

  10. Formability of Aluminum 5182-Polypropylene Sandwich Sheet for Automotive Application

    NASA Astrophysics Data System (ADS)

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

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

  11. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2000-02-01

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

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. Thermal behavior of a titanium honeycomb-core sandwich panel

    NASA Technical Reports Server (NTRS)

    Ko, William L.; Jackson, Raymond H.

    1991-01-01

    Finite element thermal stress analysis was performed on a rectangular titanium honecomb-core sandwich panel which is subjected to thermal load with a temperature gradient across its depth. The distributions of normal stresses in the face sheets and the face-sheet/sandwich-core interfacial shear stresses are presented. The thermal buckling of the heated face sheet was analyzed by assuming the face sheet to be resting on an elastic foundation representing the sandwich core. Thermal buckling curves and thermal buckling load surface are presented for setting the limit for temperature gradient across the panel depth.

  18. 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.

  19. 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.

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

    ERIC Educational Resources Information Center

    Roberts, Tim S.

    2004-01-01

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

  1. Forced vibration of a shear thickening fluid sandwich beam

    NASA Astrophysics Data System (ADS)

    Wei, Minghai; Hu, Gang; Jin, Lu; Lin, Kun; Zou, Dujian

    2016-05-01

    The forced vibration of a sandwich beam integrating a shear thickening fluid (STF) core and with conductive skins subjected to a periodic excitation was investigated theoretically in this study. The rheological properties of the STF material including viscosity, plasticity, and elasticity may be changed under the periodic vibration, and hence they were considered. The governing equation of motion was derived based on the complex stiffness method and some key parameters were derived based on the Timoshenko beam theory. Effects of the excitation frequency, the excitation amplitude, the excitation location, and the skin/core thickness ratio on the nature frequency of the sandwich beam were investigated. It was found that the STF core has a significant effect on the dynamic property of the sandwich beam. Based on the findings, integrating the STF core in a sandwich beam can reduce the vibration of the beam.

  2. 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.

  3. Foam core materials for structural sandwich panels

    SciTech Connect

    Huang Jongshin.

    1991-01-01

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

  4. Tungsten Biscorroles: New Chiral Sandwich Compounds.

    PubMed

    Alemayehu, Abraham B; Vazquez-Lima, Hugo; Gagnon, Kevin J; Ghosh, Abhik

    2016-05-10

    The oxidative metalation method, involving the interaction of free-base meso-triarylcorroles and W(CO)6 in refluxing decalin, led to a set of three tungsten(VI) biscorroles, the first homoleptic sandwich compounds involving corroles. Single-crystal X-ray structures of two of the complexes revealed square-antiprismatic coordination and strongly domed corroles with long W-N distances of 2.15-2.22 Å and a substantial displacement of ∼1.17 Å of the metal relative to the mean N4 planes of the ligands. The structures correspond to approximate C2 symmetry and are thus chiral. DFT calculations strongly indicate that the enantiomers are configurationally stable and hence amenable to chiral resolution. Their other notable properties include a strongly blueshifted Soret band at (357±2) nm, a relatively intense π→W(dz2 ) near-IR feature at (781±3) nm, and a low electrochemical HOMO-LUMO gap of approximately 1.3 V. The results obtained herein suggest that metallobiscorroles may emerge as a new class of inherently chiral chromophores with novel optical and electrochemical properties. PMID:27059004

  5. 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.

  6. 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.

  7. A novel biosensor for bovine serum albumin based on fluorescent self-assembled sandwich bilayers.

    PubMed

    Sun, Xiangying; Liu, Bin; He, Fei

    2009-01-01

    Fluorescent dyes butyl rhodamine B were assembled via a DL-cystenine intermediate onto quartz wafers whose surface had first adsorbed gold nanoparticles. Hence self-assembled sandwich bilayers with nanocomposite structure were constructed which can be used as a biosensor for bovine serum albumin. The biosensor-based self-assembled monolayers (SAMs) are regenerable and have high sensitivity, five orders of magnitude higher than that of bulk solution phase sensing. The effects of existing forms of dyes on the fluorescence spectra of bilayers in the presence of bovine serum albumin were investigated. PMID:18785615

  8. 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.).

  9. 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.

  10. 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. PMID:24354856

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

    NASA Technical Reports Server (NTRS)

    Jegley, Dawn C.

    1993-01-01

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

  12. 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.

  13. 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

  14. Numerical analysis of impact-damaged sandwich composites

    NASA Astrophysics Data System (ADS)

    Hwang, Youngkeun

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

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

    ERIC Educational Resources Information Center

    McLernon, Tim; Hughes, David

    2004-01-01

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

  16. 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

  17. 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

  18. In situ processing methods for composite fuselage sandwich structures

    NASA Technical Reports Server (NTRS)

    Saatchi, Hossein; Durako, Bill; Reynolds, Dick; Dost, Ernest; Willden, Kurtis

    1993-01-01

    Conventional sandwich structure fabrication methods are labor intensive and high in cost. A low cost method is needed to produce lightweight sandwich structures. Sundstrand has developed a series of in situ composite fabrication methods in which the raw materials (skin and core materials) are placed in a closed mold, and the component is produced in one heating cycle. Internal pressure is generated by chemical agents during the thermal cycles, which consolidates the skins and produces the foam core. The finished part is a net-shape composite sandwich structure with skins and a foamed core. The in situ process reduces cost by eliminating several secondary operations that are used in conventional fabrication methods. Further, a strong molecular bond is produced between the core and skin, which eliminates adhesive bonding and prevents a weak bond section in the sandwich structure. In this investigation, we evaluated the feasibility of the in situ process using thermoset materials currently under consideration for commercial airplane fuselage applications, such as keel sections. The materials used were Hercules 855340 toughened epoxy resin in both liquid and powder forms, and 3M Scotchply PR500 resin, manufactured by 3M Corporation, in powder form. We successfully foamed these resins and produced experimental panels with AS-4/855340 Hercules prepreg skins. Chopped fibers were added to the core to increase performance of the foam. Mechanical property testing on these panels showed properties competitive with other foams. Additional experiments are required to optimize the in situ foam core sandwiches for specific properties and applications.

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

    PubMed

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

    2015-01-01

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

  20. 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.

  1. Self-assembled half-sandwich polyhedral cages via flexible Schiff-base ligands: an unusual macrocycle-to-cage conversion.

    PubMed

    Liu, Jing-Jing; Lin, Yue-Jian; Li, Zhen-Hua; Jin, Guo-Xin

    2016-09-21

    An edge-directed strategy was adopted to construct highly ordered polyhedral structures using flexible functions. Half-sandwich M6(L1)4 octahedral and M8(L2)4 cubic cages have been assembled by flexible Schiff-base ligands upon coordination to Cp*Rh(iii) organometallic acceptors. In particular, the rearrangement from a Rh(iii)-based half-sandwich M2(HL1)2 macrocycle to M6(L1)4 cage was found to occur in a solution. PMID:27491394

  2. 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. PMID:24815252

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

    SciTech Connect

    Perotti, Luigi E.; El Sayed, Tamer; Deiterding, Ralf; Ortiz, Michael

    2011-01-01

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

  4. 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.

  5. Sandwich enzyme-linked immunosorbent assay for naringin.

    PubMed

    Qu, Huihua; Wang, Xueqian; Qu, Baoping; Kong, Hui; Zhang, Yue; Shan, Wenchao; Cheng, Jinjun; Wang, Qingguo; Zhao, Yan

    2016-01-15

    Among the currently used immunoassay techniques, sandwich ELISA exhibits higher specificity, lower cross-reactivity, and a wider working range compared to the corresponding competitive assays. However, it is difficult to obtain a pair of antibodies that can simultaneously bind to two epitopes of a molecule with a molecular weight of less than 1000 Da. Naringin (Nar) is a flavonoid with a molecular mass of 580 Da. The main aim of this study was to develop a sandwich ELISA for detecting Nar. Two hybridomas secreting anti-Nar monoclonal antibodies (mAbs) were produced by fusing splenocytes from a mouse immunised against Nar-bovine serum albumin (BSA) conjugated with a hypoxanthine-aminopterin-thymidine (HAT)-sensitive mouse myeloma cell line; a sandwich ELISA for detecting Nar was developed using these two well-characterised anti-Nar mAbs. The performance of the sandwich assay was further evaluated by limit of detection (LOD), limit of quantification (LOQ), recovery, and interference analyses. A dose-response curve to Nar was obtained with an LOD of 6.78 ng mL(-1) and an LOQ of 13.47 ng mL(-1). The inter-assay and intra-assay coefficients of variation were 4.32% and 7.48%, respectively. The recovery rate of Nar from concentrated Fructus aurantii granules was 83.63%. A high correlation was obtained between HPLC and sandwich ELISA. These results demonstrate that the sandwich ELISA method has higher specificity for Nar than indirect competitive ELISA. PMID:26709308

  6. 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

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

    2015-05-01

    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

  7. 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

  8. 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.

  9. 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.

  10. Toughness of composite steel-concrete structure of sandwich system

    SciTech Connect

    Iwata, Setsuo; Hattori, Yoichi

    1994-12-31

    Offshore structure should have a high degree of structural safety not only under normal conditions but also extreme conditions even under collision loadings. The authors carried out both experimental and theoretical investigations on the toughness of the sandwich composite structures. Experiments were carried out for the two-dimensional models of composite structures under pure bending and combined shear and bending as well. A nonlinear analysis was developed to predict the toughness of sandwich beam under pure bending. In the analysis the material nonlinearity of both concrete and steel plate were taken into consideration. The analysis were found to be very close to the experimental results.

  11. 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.

  12. 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.

  13. 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.

  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. Dielectrophoretic behaviours of microdroplet sandwiched between LN substrates.

    PubMed

    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

  16. 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

  17. Pulsed terahertz inspection of non-conducting sandwich composites

    NASA Astrophysics Data System (ADS)

    Lopato, P.; Chady, T.

    2013-01-01

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

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. High-frequency vibrations of sandwich plates and delamination detection

    NASA Astrophysics Data System (ADS)

    Jensen, Alf E.; Irgens, Fridtjov

    1998-06-01

    In multi-hull marine vehicles assembled by FRP sandwich composite materials problems with delamination and skin/core debonding are reported. High frequency vibrations in foam core sandwich materials are investigated to see if it was possible to apply them, together with bending vibrations, in an early damage warning system for delamination detection in marine vessels. This manuscript presents a theory for high frequency vibration in sandwich plates and beams. The core is modeled as a two parameter foundation with shearing interaction effects as well as normal stress effects in the core included. The skins are modeled as ordinary plates or beams on a foundation. Expressions for both anti-symmetric and symmetric modes are given. In addition to the theoretical development, experiments with a simply supported sandwich beam, using a TV-Holography technic, were performed and good accordance between theory and experiments were achieved. The results indicates that disappearance of symmetric modes may be used a parameter for delamination detection. The anti-symmetric modes may be interchangeable with higher bending modes by an early damage warning system. To avoid this, the theory presented may be applied to determine the anti-symmetric frequency values in forehand.

  3. 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.

  4. Debris Impact on CFRP-AL Honeycomb Sandwich Structure

    NASA Astrophysics Data System (ADS)

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

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

  5. 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.

  6. 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.

  7. Comparative Study of Permeatal Sandwich Tympanoplasty and Postaural Underlay Technique

    PubMed Central

    Nagpure, Prakash Shankarrao; Yadav, Manish; Chavan, Sushil

    2016-01-01

    Introduction Tympanoplasty is the most common operation performed by an Otolaryngologist right from the period of residency. During the last hundred years various modifications in this surgical technique have come up because of continued efforts made by otologists all over the world to achieve the best surgical outcome. Aim To compare the graft take up and complications associated with the Permeatal Sandwich Tympanoplasty performed with the use of Otoendoscope and traditional Postaural Underlay technique of Tympanoplasty from 1st September 2014 to 30th August 2015. Materials and Methods Patients attending the ENT OPD, suffering from Chronic Suppurative Otitis Media (CSOM) were selected on the basis of type of perforation and their workup was done to assess the candidature for tympanoplasty. Results A total of 100 patients were included in the study and the overall graft take was 92.3% in cases of Permeatal Sandwich technique as compared to 64.58% in the case of postaural underlay technique, with a majority of the failures in the large central perforation group rendering a p = 0.021 for patients operated for Large perforations, p = 0.036 for moderate perforations and p = 0.476 for small perforations. The overall p = 0.000649 which is highly significant. On comparing the complications there were only 2 cases in Permeatal Sandwich Technique compared to 25 cases in Postaural Underlay technique rendering a highly significant p-value 0f 0.000000348. There was a difference in hearing improvement with majority of the cases improving to the range of 16-25 dB in Permeatal Sandwich technique compared to 26-45 dB in Postaural Underlay technique. Conclusion Permeatal Sandwich technique produce much better results when compared with Postaural approach in terms of graft take up, complications and hearing improvement. PMID:27190842

  8. 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

  9. 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.

  10. 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

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

    PubMed

    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 10(7) 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

  12. 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.

  13. 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

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

    PubMed Central

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

    2013-01-01

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

  15. Vibration Characteristics of Partially Covered Double-Sandwich Cantilever Beam

    NASA Technical Reports Server (NTRS)

    Chen, Qinghua; Levy, Cesar

    1996-01-01

    The differential equations of motion together with the boundary conditions for a partially covered, double-sandwich cantilever beam are derived. Bending and extension, rotational and longitudinal inertia of damping layers, and shear deformation and rotational and longitudinal inertia of the constraining layers and the primary beam are included in the equations. The theory is applicable for long as well as short, soft, or stiff damping layer, double-sandwich beams. Also, the effects of different parameters on the system loss factor and resonance frequency are discussed. Differences are found to exist with the previous beam model (called the Euler beam model) when the damping layers are stiff, when the thickness of the damping layer is large compared to the primary-beam thickness, and in the case of higher modes of vibration.

  16. 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.

  17. 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.

  18. Bismaleimide resins for flame resistant honeycomb sandwich panels

    NASA Technical Reports Server (NTRS)

    Stenzenberger, H. D.

    1978-01-01

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

  19. 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

  20. Impact energy absorption of sandwich plates with crushable core

    SciTech Connect

    Wierzbicki, T.; Fatt, M.H.; Alvarez, A.L.

    1995-12-31

    The objective of this paper is to derive a closed-form solution for deformations, resisting forces, and energy absorption of a metal honeycomb with face plating subjected to localize static and dynamic loads. Two load cases are considered: a quasi-static indentation by a circular punch and dynamic impact by a cylindrical projectile with a velocity in the range of 20 {divided_by} 40 m/sec. The present analysis is building-up on the earlier solution obtained by one of the authors in which the crash resistance of a bare honeycomb was predicted from a known geometry of the cell and material properties. The face plating increases crush resistance of the honeycomb by spreading deformation outside the loading area and invoking considerable membrane action in the plate. Each of the above contributions is quantified and is shown that the resisting force and the radial extent of deformation are increasing functions of punch displacement. The present analytical predictions are compared with measurements taken on seven impact tests on sandwich plates, reported by Goldsmith and Sackman. A correlation of final plate deflections under the projectile was very good for lower impact velocities (less that 6.3% error) and good for higher impact velocities (between 2.08% and 8.9% error). This exceeds the accuracy of a purely numerical solution presented. Three mechanisms limiting the energy absorbed by a sandwich plate are identified: densification of the honeycomb, punch-through shear of the facing plates, and reaching deformation of the outer boundary of the sandwich plate. The present theory provides the necessary background information for optimum designing of sandwich plates against impact loads.

  1. 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. PMID:25248534

  2. 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.

  3. 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.

  4. 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.

  5. Coulomb blockade phenomena in ultrathin Langmuir-Blodgett sandwich junctions

    NASA Astrophysics Data System (ADS)

    Burghard, M.; Mueller-Schwanneke, C.; Philipp, G.; Roth, S.

    1999-04-01

    Electrical junctions were fabricated in sandwich configuration from Langmuir-Blodgett (LB) films of two types of material, 0953-8984/11/14/015/img1-conjugated, peripherally substituted ring systems or a 0953-8984/11/14/015/img2-bonded polymer. The sandwich junctions consisted of four to ten monolayers between two micro-structured gold electrodes, corresponding to a nominal film thickness between about 8 and 20 nm. At liquid helium temperature, the current (I)/voltage (V) characteristics generally exhibited smooth exponential behaviour or irregular steps. However, for a small fraction of the LB sandwiches comprising a 0953-8984/11/14/015/img1-conjugated or 0953-8984/11/14/015/img2-bonded compound, regular staircases were observed. It was possible to fit such 0953-8984/11/14/015/img5 characteristics with curves calculated on the basis of a Coulomb blockade model. These results are accounted for by the presence of nanometre-sized gold particles formed upon evaporation of the top electrode. Single electron tunnelling is assumed to proceed through double tunnel barrier junctions consisting of a gold island asymmetrically located between the top and bottom electrode.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. Data characterizing compressive properties of Al/Al2O3 syntactic foam core metal matrix sandwich.

    PubMed

    Omar, Mohammed Yaseer; Xiang, Chongchen; Gupta, Nikhil; Strbik, Oliver M; Cho, Kyu

    2015-12-01

    Microstructural observations and compressive property datasets of metal matrix syntactic foam core sandwich composite at quasi-static and high strain rate (HSR) conditions (525-845 s(-1)) are provided. The data supplied in this article includes sample preparation procedure prior to scanning electron and optical microscopy as well as the micrographs. The data used to construct the stress-strain curves and the derived compressive properties of all specimens in both quasi-static and HSR regions are included. Videos of quasi-static compressive failure and that obtained by a high speed image acquisition system during deformation and failure of HSR specimen are also included. PMID:26587558

  11. Data characterizing compressive properties of Al/Al2O3 syntactic foam core metal matrix sandwich

    PubMed Central

    Omar, Mohammed Yaseer; Xiang, Chongchen; Gupta, Nikhil; Strbik, Oliver M.; Cho, Kyu

    2015-01-01

    Microstructural observations and compressive property datasets of metal matrix syntactic foam core sandwich composite at quasi-static and high strain rate (HSR) conditions (525–845 s−1) are provided. The data supplied in this article includes sample preparation procedure prior to scanning electron and optical microscopy as well as the micrographs. The data used to construct the stress–strain curves and the derived compressive properties of all specimens in both quasi-static and HSR regions are included. Videos of quasi-static compressive failure and that obtained by a high speed image acquisition system during deformation and failure of HSR specimen are also included. PMID:26587558

  12. 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

  13. 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.

  14. 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

  15. 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.

  16. 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.

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

    NASA Technical Reports Server (NTRS)

    Ko, William L.; Jackson, Raymond H.

    1991-01-01

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

  18. 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

  19. Hail Ice Impact of Lightweight Composite Sandwich Panels

    NASA Astrophysics Data System (ADS)

    Luong, Sean Dustin

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

  20. 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.

  1. Analysis and Fabrication of Paraboloidal CFRP Sandwich Mirrors

    NASA Astrophysics Data System (ADS)

    Hong, Tayo Steve

    The low areal weight requirements of telescopes in aerospace applications has driven the study on composite mirrors for several years. For example, the primary parabolic mirror in a balloon-borne, Cassegrain telescope required an optical quality better than 30 microns in figure RMS error. A parametric study on composite sandwich mirrors was conducted by using finite element analysis as well as optical analysis. The factors covered the cell sizes, core materials, core thicknesses, face layups, and support configurations. Based on theoretical calculations, many high quality spherical composite sandwich mirrors were generated by using a non-heat curing process. The CFRP faces and Nomex core were chosen as the baseline materials for mirror fabrication due to their high strength and low weight. The proposed replication method applied an interface layer between face and surface coat to eliminate print -through problems. Many important goals have been realized in those mirror samples with optical laser interferometer testing. These include the figure RMS error less than 2 microns and the surface RMS error less than 0.05 micron. The areal weights of the mirror samples are less than 7 kg/m ^2. The thermal stability of these mirrors was observed from the optical results with thermal cycling tests. The proposed 2-meter parabolic composite sandwich mirror, with an areal weight of less than 10 kg/m ^2, would consist of either (0/90/45/ -45) _{rm S} layup faces with an optimal 3^{' '} core or (QC) layup faces with a total core thickness of 5 inches. Both a ring support around the equator and the 18-point Hindle-type support would lead to the best optical quality under both self weight and thermal loading.

  2. 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

  3. Sandwich double gate vertical tunneling field-effect transistor

    NASA Astrophysics Data System (ADS)

    Wang, Ying; Zhang, Wen-hao; Yu, Cheng-hao; Cao, Fei

    2016-05-01

    In this work, a sandwich vertical tunnel field effect transistor (SDG-VTFET) is presented and studied. Since the dominant carrier tunneling of SDG-VFET occurs in a direction that is in line with the gate field, high ON-state current and steep subthreshold slope are observed. Comparisons between SDG-VFET and double gate tunnel field effect transistor are made to clarify advantages of SDG-VTFET. The simulation results of our work show that SDG-VTFET has stronger gate control, steeper subthreshold slope and higher ON-state current. The device plays a promising candidate for future low power circuit applications.

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

    PubMed

    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

  5. 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

  6. Sandwich electrode designed for high performance lithium-ion battery.

    PubMed

    Zhao, Chunsong; Luo, Xi; Chen, Chengmeng; Wu, Hui

    2016-05-01

    We fabricated a sandwich structure Li-ion battery electrode by trapping micron-sized silicon between a copper current collector and a graphene coating. During dynamic electrochemical cycles, the volume change of the silicon can be buffered by the coating through the deformation of soft graphenes. This structure can effectively prevent the silicon particles from escaping from the current collector while keeping the buffered graphene coating integrated and unbroken during deformation. The electrodes could be maintained for 400 cycles at a constant charge capacity of 1000 mA h g(-1). PMID:27117447

  7. 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.

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

    NASA Technical Reports Server (NTRS)

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

    1988-01-01

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

  9. 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.

  10. 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.

  11. 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.

  12. Sandwich electrode designed for high performance lithium-ion battery

    NASA Astrophysics Data System (ADS)

    Zhao, Chunsong; Luo, Xi; Chen, Chengmeng; Wu, Hui

    2016-05-01

    We fabricated a sandwich structure Li-ion battery electrode by trapping micron-sized silicon between a copper current collector and a graphene coating. During dynamic electrochemical cycles, the volume change of the silicon can be buffered by the coating through the deformation of soft graphenes. This structure can effectively prevent the silicon particles from escaping from the current collector while keeping the buffered graphene coating integrated and unbroken during deformation. The electrodes could be maintained for 400 cycles at a constant charge capacity of 1000 mA h g-1.We fabricated a sandwich structure Li-ion battery electrode by trapping micron-sized silicon between a copper current collector and a graphene coating. During dynamic electrochemical cycles, the volume change of the silicon can be buffered by the coating through the deformation of soft graphenes. This structure can effectively prevent the silicon particles from escaping from the current collector while keeping the buffered graphene coating integrated and unbroken during deformation. The electrodes could be maintained for 400 cycles at a constant charge capacity of 1000 mA h g-1. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr09049k

  13. Impact Delamination and Fracture in Aluminum/Acrylic Sandwich Plates

    NASA Technical Reports Server (NTRS)

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

    2000-01-01

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

  14. Mechanical behavior of Kenaf/Epoxy corrugated sandwich structures

    NASA Astrophysics Data System (ADS)

    Bakhori, S.; Hassan, M. Z.; Daud, Y.; Sarip, S.; Rahman, N.; Ismail, Z.; Aziz, S. A.

    2015-12-01

    This study presents the response of kenaf/epoxy corrugated sandwich structure during quasi-static test. Force-displacements curves have been deducted to determine the deformation pattern and collapse behavior of the structure. Kenaf/epoxy sandwich structures skins fabricated by using hand layup technique and the corrugated core were moulded by using steel mould. Different thicknesses of corrugated core web with two sizes of kenaf fibers were used. The corrugated core is then bonded with the skins by using poly-epoxy resin and has been cut into different number of cells. The specimens then tested under tensile and compression at different constant speeds until the specimens fully crushed. Tensile tests data showed the structure can be considered brittle when it breaking point strain, ε less than 0.025. In compression test, the specimens fail due to dominated by stress concentration that initiated by prior cracks. Also, the specimens with more number of cells and thicker core web have higher strength and the ability to absorb higher energy.

  15. Dispersion of guided waves in composite laminates and sandwich panels

    NASA Astrophysics Data System (ADS)

    Schaal, Christoph; Mal, Ajit

    2015-03-01

    In composite structures, damages are often invisible from the surface and can grow to reach a critical size, potentially causing catastrophic failure of the entire structure. Thus safe operation of these 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 structural health monitoring in advanced structures. Guided waves allow for long monitoring ranges and are very sensitive to defects within their propagation path. In this work, the relevant properties of guided Lamb waves for damage detection in composite structures are investigated. An efficient numerical approach is used to determine their dispersion characteristics, and these results are compared to those from laboratory experiments. The experiments are based on a pitch-catch method, in which a pair of movable transducers is placed on one surface of the structure to induce and detect guided Lamb waves. The specific cases considered include an aluminum plate and an aluminum honeycomb sandwich panel with woven composite face sheets. In addition, a disbond of the interface between one of the face sheets and the honeycomb core of the sandwich panel is also considered, and the dispersion characteristics of the two resultant waveguides are determined. Good agreement between numerical and experimental dispersion results is found, and suggestions on the applicability of the pitch-catch system for structural health monitoring are made.

  16. Experimental and Numerical Analysis of Inserts in Sandwich Structures

    NASA Astrophysics Data System (ADS)

    Bunyawanichakul, P.; Castanie, B.; Barrau, J.-J.

    2005-05-01

    In aeronautics, sandwich structures are widely used for secondary structures like flaps or landing gear doors. In the case of landing gear doors, the junction is made by a local reinforcement called an insert. This insert is made by a resin molded in the Nomex™ sandwich core. Such structures are still designed mainly using test results and the lack of an efficient numerical model remains a problem. The purpose of this study is on the one hand to perform experiments in order to be able to identify the failure modes and on the other hand to propose an efficient numerical model. Pull-out tests with cycling were conducted and 3D displacement measured by optical methods. The potential failure modes are numerous (delamination, local fiber breaking, skin/core debonding, core crushing, core shear buckling, potting failure, etc.). Experiments demonstrated that, for the lower loads, the non-linearity and the hysteresis are mainly due to core shear buckling. From this observation, the nonlinear behavior of the core is identified by a 3 point-bending test. The shear-modulus damage law is then implemented on a non-linear finite element model and an acceptable correlation of the tests is achieved. As a consequence, some improvements of the technology will be proposed, manufactured and tested.

  17. 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

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

    PubMed

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

    2015-07-28

    Two classes of novel tetra-iron substituted sandwich-type arsenotungastates (ATs) with supporting lanthanide (Ln) pendants KNa2 [Ln(H2O)7][Fe4(H2O)10(B-β-AsW9O33)2]·21H2O [Ln = La(III) (1), Pr(III) (2), Nd(III) ()3, Sm(III) (4)] and [Ln(H2O)8]2[Fe4(H2O)8(l-thr)2(B-β-AsW9O33)2]·20H2O [Ln = La(III) (5), Pr(III) ()6, Nd(III) (7), Sm(III) (8), Eu(III) (9), Gd(III) (10), Tb(III) (11), Dy(III) (12), Er(III) (13)] (l-thr = l-threonine) have been synthesized by the hydrothermal reaction of the [As2W19O67(H2O)](14-) precursor with Fe(3+) cations and Ln(3+) cations in the presence of l-thr or l-leucine and l-alanine, and further characterized by elemental analyses, IR spectra and single-crystal X-ray diffraction. Structural analyses indicate that 1-4 display the inorganic 2-D sheet architecture constructed from tetra-iron sandwiched AT [Fe4(H2O)10(B-β-AsW9O33)2](6-) fragments by bridging [Ln(H2O)7](3+) cations whereas the molecular structures of the isostructural 5-13 consist of an organic-inorganic hybrid tetra-iron substituted sandwich-type AT [Fe4(H2O)8(l-thr)2(B-β-AsW9O33)2](6-) fragment and two pendant [Ln(H2O)8](3+) cations. As far as we know, 1-4 represent the rare inorganic 2-D extended ATs based on transition-metal substituted sandwich-type polyoxometalate units and Ln linkers and 5-13 are the first Fe-Ln heterometallic ATs with amino acid ligands. The solid state photoluminescence (PL) measurements of 9 and 11 have been performed at room temperature. The PL emission of 9 is mainly derived from the characteristic (5)D0 → (7)F2 (J = 4-0) transitions of the Eu(III) cations whereas the PL behavior of 11 stems from the common contribution of the (5)D4 → (7)FJ (J = 5-3) transitions of the Tb(III) ions and oxygen-to-metal (O → W) charge-transfer transitions of AT segments. The thermogravimetric (TG) analyses of 1-4 and 6-12 have been investigated. PMID:26066321

  19. Minimum-Weight Sandwich Structure Optimum Design Subjected to Torsional Loading

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

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

  20. PLLA/Flax Mat/Balsa Bio-Sandwich Manufacture and Mechanical Properties

    NASA Astrophysics Data System (ADS)

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

    2011-10-01

    This paper describes the manufacture and mechanical characterization of a sandwich material which is 100% bio-sourced. The flax mat/PLLA facings and balsa core can also be composted at end of service life. Manufacture is by vacuum bag moulding. The optimum moulding time and temperature are a compromise between ensuring good impregnation and avoiding degradation, and holding for 60 min at 180°C was found to be satisfactory. The mechanical properties of the bio-sandwich obtained are compared to those of a traditional glass reinforced polyester balsa sandwich. The flexural strength is 30% lower, as predicted based on the facing properties. Skin/core adhesion is also measured using debonding tests. Crack propagation occurs at the skin/core interface in the traditional sandwich but within the facing in the bio-sandwich. The impregnation of the core in the two materials is examined using X-ray micro-tomography.

  1. 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. PMID:22574250

  2. 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.

  3. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2012-06-01

    This research is motivated by the increase use of composite sandwich structures in a wide range of industries such as automotive, aerospace and civil infrastructure. To maximise stiffness at minimum weight, the paper develops a minimum weight optimization method for sandwich structure under combined torsion and bending loads. We first extend the minimum-weight design of sandwich structures under bending load to the case of torsional deformation and then present optimum solutions for the combined requirements of both bending and torsional stiffness. Three design cases are identified for a sandwich structure required to meet multiple design constraints of torsion and bending stiffness. The optimum solutions for all three cases are derived. To illustrate the newly developed optimum design solutions, numerical examples are presented for sandwich structures made of either isotropic face skins or orthotropic composite face skins.

  5. Vibration analysis of sandwich rectangular plates with magnetorheological elastomer damping treatment

    NASA Astrophysics Data System (ADS)

    Yeh, Jia-Yi

    2013-03-01

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

  6. 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

  7. Static and dynamic response of a sandwich structure under axial compression

    NASA Astrophysics Data System (ADS)

    Ji, Wooseok

    This thesis is concerned with a combined experimental and theoretical investigation of the static and dynamic response of an axially compressed sandwich structure. For the static response problem of sandwich structures, a two-dimensional mechanical model is developed to predict the global and local buckling of a sandwich beam, using classical elasticity. The face sheet and the core are assumed as linear elastic orthotropic continua in a state of planar deformation. General buckling deformation modes (periodic and non-periodic) of the sandwich beam are considered. On the basis of the model developed here, validation and accuracy of several previous theories are discussed for different geometric and material properties of a sandwich beam. The appropriate incremental stress and conjugate incremental finite strain measure for the instability problem of the sandwich beam, and the corresponding constitutive model are addressed. The formulation used in the commercial finite element package is discussed in relation to the formulation adopted in the theoretical derivation. The Dynamic response problem of a sandwich structure subjected to axial impact by a falling mass is also investigated. The dynamic counterpart of the celebrated Euler buckling problem is formulated first and solved by considering the case of a slender column that is impacted by a falling mass. A new notion, that of the time to buckle, "t*" is introduced, which is the corresponding critical quantity analogous to the critical load in static Euler buckling. The dynamic bifurcation buckling analysis is extended to thick sandwich structures using an elastic foundation model. A comprehensive set of impact test results of sandwich columns with various configurations are presented. Failure mechanisms and the temporal history of how a sandwich column responds to axial impact are discussed through the experimental results. The experimental results are compared against analytical dynamic buckling studies and finite

  8. Laser evaporation of metal sandwich layers for improved IC metallization

    NASA Astrophysics Data System (ADS)

    Pielmeier, R.; Bollmann, D.; Haberger, K.

    1990-12-01

    With the further shrink of IC dimensions, metallization becomes the most crucial layer because conductivity and contact resistivity determine the RC constants and thus the speed of the circuits. With our Q-switched Nd:YAG laser we have evaporated different materials (Al, Ti, W, Pt, Au), alloys (Ta-Si) and dielectrics (ZrO 2, Al 2O 3). We also produced sandwich layers (Al-Au, Ti-Al). The layers were investigated with regard to deposition rate, homogeneity, adhesion, step coverage and surface roughness. Deposition rates in the order of 60 nm/min were achieved. At a power of 10 W and a repetition rate of about 5 kHz we could form ohmic contacts to silicon with a good step coverage in the contact.

  9. Bending properties of foamed aluminum panels and sandwiches

    SciTech Connect

    Simancik, F.; Kovacik, J.; Minarikova, N.

    1998-12-31

    The foamed panels and sandwiches were prepared by powder metallurgical route using various matrix alloys. The effect of the apparent density, geometry and structure of the foam on its bending stiffness was studied with respect to the results of the four-point-bending. It has been shown that the modulus of elasticity of the foam cannot be related only to its apparent density, because the distribution of the cell-wall material along the thickness of the foamed panel is not uniform. Therefore the real moment of inertia of the foam`s cross-section should be used for the calculation of bending stiffness. This moment can be determined from the square weight of the foamed sample.

  10. Development and Optimization of a Thrombin Sandwich Aptamer Microarray

    PubMed Central

    Meneghello, Anna; Sosic, Alice; Antognoli, Agnese; Cretaio, Erica; Gatto, Barbara

    2012-01-01

    A sandwich microarray employing two distinct aptamers for human thrombin has been optimized for the detection of subnanomolar concentrations of the protein. The aptamer microarray demonstrates high specificity for thrombin, proving that a two-site binding assay with the TBA1 aptamer as capture layer and the TBA2 aptamer as detection layer can ensure great specificity at times and conditions compatible with standard routine analysis of biological samples. Aptamer microarray sensitivity was evaluated directly by fluorescent analysis employing Cy5-labeled TBA2 and indirectly by the use of TBA2-biotin followed by detection with fluorescent streptavidin. Sub-nanomolar LODs were reached in all cases and in the presence of serum, demonstrating that the optimized aptamer microarray can identify thrombin by a low-cost, sensitive and specific method.

  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. Room Temperature and Elevated Temperature Composite Sandwich Joint Testing

    NASA Technical Reports Server (NTRS)

    Walker, Sandra P.

    1998-01-01

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

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

    SciTech Connect

    Dosch, M.; Weller, M.G.; Niessner, R.

    1995-12-31

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

  14. 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.

  15. 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.

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

    PubMed Central

    Gan, Ning; Jia, Liyong; Zheng, Lei

    2011-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

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

    NASA Technical Reports Server (NTRS)

    Ko, William L.; Jackson, Raymond H.

    1991-01-01

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

  19. 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.

  20. 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

  1. 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.

  2. 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. PMID:25909336

  3. Modelling the vibration of sandwich beams using frequency-dependent parameters

    NASA Astrophysics Data System (ADS)

    Backström, D.; Nilsson, A. C.

    2007-03-01

    Various types of sandwich beams with foam or honeycomb cores are currently used in the industry, indicating the need for simple methods describing the dynamics of these complex structures. By implementing frequency-dependent parameters, the vibration of sandwich composite beams can be approximated using simple fourth-order beam theory. A higher-order sandwich beam model is utilized in order to obtain estimates of the frequency-dependent bending stiffness and shear modulus of the equivalent Bernoulli-Euler and Timoshenko models. The resulting predicted eigenfrequencies and transfer accellerance functions are compared to the data obtained from the higher-order model and from measurements.

  4. 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.

  5. Meshless Analysis of Laminated Composite and Sandwich Plates Subjected to Various Types of Loads

    NASA Astrophysics Data System (ADS)

    Singh, Jeeoot; Singh, Sandeep; Shukla, K. K.

    2014-03-01

    The bending analysis of laminated composite and sandwich plates using different radial basis functions and higher-order shear deformation theory is presented. This meshfree technique is insensitive to spatial dimension and considers only a cloud of nodes (centers) for the spatial discretization of both the problem domain and the boundary. Numerical results for simply supported isotropic, symmetric cross-ply composite and sandwich plate are presented. The results are compared with other available results. It is observed that convergence of the polynomial function is faster as compared to other radial basis functions, whereas Gaussian function takes the least solution time. The effect of various types of loadings on sandwich plate is presented.

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

    NASA Astrophysics Data System (ADS)

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

    2012-08-01

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

  7. 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.

  8. 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.

  9. 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.

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

    NASA Technical Reports Server (NTRS)

    Baker, Donald J.; Rogers, Charles

    1996-01-01

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

  11. 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.

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

    PubMed

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

    2013-01-01

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

  13. 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

  14. Aptamer carbon nanodot sandwich used for fluorescent detection of protein.

    PubMed

    Xu, Bailu; Zhao, Chuanqi; Wei, Weili; Ren, Jinsong; Miyoshi, Daisuke; Sugimoto, Naoki; Qu, Xiaogang

    2012-12-01

    Carbon nanodots (C-Dots) have attracted growing interest in recent years due to their low cost, ready scalability, excellent chemical stability, biocompatibility, colloidal stability, and resilience of photoluminescence. They have been employed as novel, ideal fluorescent probes for bio-imaging and smart sensing. In addition, taking advantage of their low-cytotoxicity, C-Dots have potential applications in biochemical and cell biological fields. Herein, we present the first assay with aptamer-functionalized C-Dots as a sensory platform for protein detection. The presence of thrombin can induce the aptamer-modified fluorescent C-Dots to form a sandwich structure with aptamer-functionalized silica nanoparticles through specific protein/aptamer interaction. The assay shows high specificity toward thrombin. A detection limit of 1 nM is obtained, which is significantly improved as compared to that of many previously reported fluorescence-based thrombin detection assays. Using other modified aptamers and antibodies instead of thrombin binding aptamers, this strategy may offer a suitable approach for detection of other proteins in biological, pharmaceutical and nano-mechanical applications. PMID:23050264

  15. 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.

  16. Variable stiffness sandwich panels using electrostatic interlocking core

    NASA Astrophysics Data System (ADS)

    Heath, Callum J. C.; Bond, Ian P.; Potter, Kevin D.

    2016-04-01

    Structural topology has a large impact on the flexural stiffness of a beam structure. Reversible attachment between discrete substructures allows for control of shear stress transfer between structural elements, thus stiffness modulation. Electrostatic adhesion has shown promise for providing a reversible latching mechanism for controllable internal connectivity. Building on previous research, a thin film copper polyimide laminate has been used to incorporate high voltage electrodes to Fibre Reinforced Polymer (FRP) sandwich structures. The level of electrostatic holding force across the electrode interface is key to the achievable level of stiffness modulation. The use of non-flat interlocking core structures can allow for a significant increase in electrode contact area for a given core geometry, thus a greater electrostatic holding force. Interlocking core geometries based on cosine waves can be Computer Numerical Control (CNC) machined from Rohacell IGF 110 Foam core. These Interlocking Core structures could allow for enhanced variable stiffness functionality compared to basic planar electrodes. This novel concept could open up potential new applications for electrostatically induced variable stiffness structures.

  17. Efficient transport of droplet sandwiched between saw-tooth plates.

    PubMed

    Wang, Liya; Wu, Hengan; Wang, Fengchao

    2016-01-15

    The transport of droplet sandwiched between smooth and saw-tooth plates was investigated using molecular dynamics method. The repeated opening and closing of the plates result in sequential stretching and squeezing of the droplet, which provide the driving force. The asymmetrical saw tooth obstructs the backward motion of the droplet, and gives rise to a net forward displacement of the droplet in every opening and closing cycle. This unidirectional motion facilitates the efficient droplet transport, which is referred to as the ratchet-like effect in this work. Our simulations also reveal that the influence of the surface wettability on the droplet transport is different for saw-tooth and smooth plates. Droplet transport efficiency exhibits monotonic decrease with the increase of the solid-liquid interactions for saw-tooth plates. While for smooth plates, unidirectional droplet movement was only observed for certain solid-liquid interactions. Taken together these simulation results and theoretical analysis, we demonstrate that hydrophobic saw-tooth plates can improve the transport efficiency significantly. These findings not only enhance our understanding of the droplet transport from atomistic scale, but also are beneficial to practical applications in designing of micro- and nano-fluidic systems. PMID:26473277

  18. Refined Zigzag Theory for Laminated Composite and Sandwich Plates

    NASA Technical Reports Server (NTRS)

    Tessler, Alexander; DiSciuva, Marco; Gherlone, Marco

    2009-01-01

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

  19. ''Sandwich'' treatment for diospyrobezoar intestinal obstruction: a case report.

    PubMed

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

    2014-12-28

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

  20. 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.

  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. PMID:26342315

  2. Windsurf-Board Sandwich Panels Under Static Indentation

    NASA Astrophysics Data System (ADS)

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

    2008-03-01

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

  3. 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. PMID:25287973

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

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

    NASA Technical Reports Server (NTRS)

    Bowles, Kenneth J.; Vannucci, Raymond D.

    1989-01-01

    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.

  10. 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.