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1

The strength characteristics of aluminum honeycomb sandwich panels  

Microsoft Academic Search

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

Jeom Kee Paik; Anil K Thayamballi; Gyu Sung Kim

1999-01-01

2

Prospects of pulse phase thermography for finding disbonds in CFRP-sandwich parts with aluminum honeycomb cores compared to ultrasonic  

NASA Astrophysics Data System (ADS)

This work shows the prospects of pulse phase thermography (PPT) compared to ultrasonic testing when applied to carbon fiber reinforced polymer (CFRP) sandwich parts with aluminum honeycomb cores. Measurements were carried out on full-scale components with flaws like disbonds, septum disbonds, staggers and displaced cores, where the last two are not literally flaws, but nevertheless regions of interest. The effect of the measurement time and the feasibility of extrapolating temperature decays were evaluated. Phase images, gathered with PPT, are compared with ultrasonic Cscan images to show the capability of PPT for quality assurance purposes. Finally, the saving on inspection time when using pulse phase thermography instead of ultrasonic testing is considered.

Gruber, J.; Stotter, B.; Mayr, G.; Hendorfer, G.

2013-01-01

3

An experimental investigation of aluminum honeycomb as an energy absorber  

E-print Network

honeycomb core using a smaller area under compression than the enfire specimen. It was the primary objec- tive to determine what percentage of the crushing load was carried by the shear of the cell walls. Since the guaranteed crush strength... the nominal density of 6 . 18 pounds per cubi f t. Th h' c oo . e t ickness of the core (see Plate 1 for dimensions) for all specimens was 6 inches. Plate 1. Aluminum Honeycomb Nomenclature T is the thickness or cell depth L is the ribbon direction W...

Bland, William Joseph

2012-06-07

4

Evaluating bending fatigue strength of aluminum honeycomb sandwich beams using local parameters  

Microsoft Academic Search

This study analyzed the four-point bending fatigue strengths of aluminum honeycomb sandwich beams with cores of various relative densities. The debonding of the adhesive between the face sheet and the core was identified to be the major failure mode. Several global parameters and local parameters were considered to evaluate the fatigue life of the studied sandwich structures. The finite element

Yi-Ming Jen; Li-Yen Chang

2008-01-01

5

The Impulse Response of Extruded Corrugated Core Aluminum Sandwich Structures  

E-print Network

#12;Abstract Stainless steel sandwich structures with honeycomb cellular cores have demonstratedThe Impulse Response of Extruded Corrugated Core Aluminum Sandwich Structures A Thesis Presented sandwich structures from a 6061-T6 aluminum alloy. The core relative density was 25% and was strongly

Wadley, Haydn

6

Development of graphite/polyimide honeycomb core materials  

NASA Technical Reports Server (NTRS)

Honeycomb panel constructions consisting entirely of graphite/polyimide composites were developed and evaluated. Graphite/polyimide composites, were used in the honeycomb core webs and in pre-cured sandwich skins. Polyimide adhesives were also developed and evaluated for use in skin-core bonding. The purpose of this program was to develop light weight sandwich constructions for high temperature applications which could provide comparable shear strength and stiffness to metallic honeycomb constructions.

Stone, R. H.

1978-01-01

7

Characterizing Facesheet/Core Disbonding in Honeycomb Core Sandwich Structure  

NASA Technical Reports Server (NTRS)

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

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

2013-01-01

8

Evaluation of Ceramic Honeycomb Core Compression Behavior at Room Temperature  

NASA Technical Reports Server (NTRS)

Room temperature flatwise compression tests were conducted on two varieties of ceramic honeycomb core specimens that have potential for high-temperature structural applications. One set of specimens was fabricated using strips of a commercially-available thin-gage "ceramic paper" sheet molded into a hexagonal core configuration. The other set was fabricated by machining honeycomb core directly from a commercially available rigid insulation tile material. This paper summarizes the results from these tests.

Bird, Richard K.; Lapointe, Thomas S.

2013-01-01

9

Characterization of Thermal and Mechanical Impact on Aluminum Honeycomb Structures  

NASA Technical Reports Server (NTRS)

This study supports NASA Kennedy Space Center's research in the area of intelligent thermal management systems and multifunctional thermal systems. This project addresses the evaluation of the mechanical and thermal properties of metallic cellular solid (MCS) materials; those that are lightweight; high strength, tunable, multifunctional and affordable. A portion of the work includes understanding the mechanical properties of honeycomb structured cellular solids upon impact testing under ambient, water-immersed, liquid nitrogen-cooled, and liquid nitrogen-immersed conditions. Additionally, this study will address characterization techniques of the aluminum honeycomb's ability to resist multiple high-rate loadings or impacts in varying environmental conditions, using various techniques for the quantitative and qualitative determination for commercial applicability.

Robinson, Christen M.

2013-01-01

10

Effect of the amount of adhesive on the bending fatigue strength of adhesively bonded aluminum honeycomb sandwich beams  

Microsoft Academic Search

The effect of the amount of adhesive for bonding face sheets and cores on the bending fatigue strength of aluminum honeycomb sandwich beams was analyzed. It was experimentally proved that the fatigue strength increases as increasing the amount of adhesive. Furthermore, the applied loading parameter is not correlated with the fatigue life data of all studied specimens with various amounts

Yi-Ming Jen; Chih-Wei Ko; Hong-Bin Lin

2009-01-01

11

Finite Element Development and Specifications of a Patched, Recessed Nomex Core Honeycomb Panel for Increased Sound Transmission Loss  

NASA Technical Reports Server (NTRS)

This informal report summarizes the development and the design specifications of a recessed nomex core honeycomb panel in fulfillment of the deliverable in Task Order 13RBE, Revision 10, Subtask 17. The honeycomb panel, with 0.020-inch thick aluminum face sheets, has 0.016-inch thick aluminum patches applied to twenty-five, 6 by 6 inch, quarter inch thick recessed cores. A 10 dB higher transmission loss over the frequency range 250 - 1000 Hz was predicted by a MSC/NASTRAN finite element model when compared with the transmission loss of the base nomex core honeycomb panel. The static displacement, due to a unit force applied at either the core or recessed core area, was of the same order of magnitude as the static displacement of the base honeycomb panel when exposed to the same unit force. The mass of the new honeycomb design is 5.1% more than the base honeycomb panel. A physical model was constructed and is being tested.

Grosveld, Ferdinand W.

2007-01-01

12

Static and Fatigue Behaviour of Hexagonal Honeycomb Cores under In-plane Shear Loads  

NASA Astrophysics Data System (ADS)

Due to their high specific strength and high specific stiffness properties the use of honeycomb panels is particularly attractive in spacecraft structures. However, the harsh environment produced during the launch of a satellite can subject the honeycomb cores of these sandwich structures to severe quasi-static and dynamic loads, potentially leading to static or early fatigue failures. Knowledge of the static and fatigue behavior of these honeycomb cores is thus a key requirement when considering their use in spacecraft structural applications. This paper presents the findings of an experimental test campaign carried out to investigate the static and fatigue behaviors of aluminum hexagonal honeycomb cores subject to in-plane shear loads. The investigation involved carrying out both static and fatigue tests using the single block shear test method. These results are also discussed in relation to the observed damage and failure modes which have been reported for the statically tested specimens and for the fatigue tested specimens at various stages of fatigue life. As well as conducting tests for the more conventional principal cell orientations (L and W), results are also presented for tests carried out at intermediate orientations to investigate the variation of core shear strength with loading orientation. The results are further investigated using explicit non-linear finite element analysis to model the buckling failure mechanisms of the tested cores.

Bianchi, Gabriel; Aglietti, Guglielmo S.; Richardson, Guy

2012-04-01

13

Heat Transfer in Adhesively Bonded Honeycomb Core Panels  

NASA Technical Reports Server (NTRS)

The Swann and Pittman semi-empirical relationship has been used as a standard in aerospace industry to predict the effective thermal conductivity of honeycomb core panels. Recent measurements of the effective thermal conductivity of an adhesively bonded titanium honeycomb core panel using three different techniques, two steady-state and one transient radiant step heating method, at four laboratories varied significantly from each other and from the Swann and Pittman predictions. Average differences between the measurements and the predictions varied between 17 and 61% in the temperature range of 300 to 500 K. In order to determine the correct values of the effective thermal conductivity and determine which set of the measurements or predictions were most accurate, the combined radiation and conduction heat transfer in the honeycomb core panel was modeled using a finite volume numerical formulation. The transient radiant step heating measurements provided the best agreement with the numerical results. It was found that a modification of the Swann and Pittman semi-empirical relationship which incorporated the facesheets and adhesive layers in the thermal model provided satisfactory results. Finally, a parametric study was conducted to investigate the influence of adhesive thickness and thermal conductivity on the overall heat transfer through the panel.

Daryabeigi, Kamran

2001-01-01

14

Moisture ingression in honeycomb core sandwich panels  

Microsoft Academic Search

Moisture ingression was studied in several composite sandwich panels, in which hydration was applied over a large surface\\u000a area at the panel edges. Significant moisture ingression occurred in panels with cores of Korex (based on a substrate of a\\u000a fiber pulp paper) and HRP (consisting of a woven-glass-fiber substrate with a polymer coating) of different density. Ingression\\u000a was more rapid

D. Cise; R. S. Lakes

1997-01-01

15

Impact Damage of Partially Foam-filled Co-injected Honeycomb Core Sandwich Composites  

Microsoft Academic Search

The present study considers filling of honeycomb type cores with foam to produce sandwich constructions. The potential benefits of this approach are enhancement of damage resistance, and ability to process honeycomb type sandwich structures through cost-effective vacuum assisted resin transfer molding (VARTM). As weight penalty is incurred in complete filling of honeycomb cells with foam, an alternative approach to reduce

Uday K Vaidya; C. Ulven; S. Pillay; H. Ricks

2003-01-01

16

MANUFACTURE OF ARBITRARY CROSS-SECTION COMPOSITE HONEYCOMB CORES BASED ON ORIGAMI TECHNIQUES  

E-print Network

components, lightweight, rigid, and strong honeycomb sandwich panels are required. In recent years, the useMANUFACTURE OF ARBITRARY CROSS-SECTION COMPOSITE HONEYCOMB CORES BASED ON ORIGAMI TECHNIQUES Kazuya accuracy, composite honeycombs, which can reduce weight and have low thermal expansion, are in increasing

Pellegrino, Sergio

17

Structural analysis of the adhesive bond in a honeycomb core sandwich panel  

Microsoft Academic Search

Detailed finite element models are used to examine the effect of the adhesive joint between the honeycomb core and the face sheets on the load transfer and static response of sandwich panels. The square-cell honeycomb core panels considered have simply supported edges and are subjected to static uniform pressure loading. The sandwich core, face sheets and adhesive joint are modeled

W. Scott Burton; A. K. Noor

1997-01-01

18

Performance of metallic honeycomb-core sandwich beams under shock loading  

E-print Network

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

Hutchinson, John W.

19

PARAMETER IDENTIFICATION FOR ALUMINUM HONEYCOMB SANDWICH PANELS BASED ON ORTHOTROPIC TIMOSHENKO BEAM THEORY  

Microsoft Academic Search

The present paper deals with parameter identification of aluminum honeycomb sandwich panels with the assumption that they can be treated as orthotropic continua. Elastic constants and modal damping ratios are considered as the identified parameters, and the basic equations of Timoshenko beam theory are employed in this paper. The numerical identification problem of minimizing the errors between the experimental and

T. Saito; R. D. Parbery; S. Okuno; S. Kawano

1997-01-01

20

A Model for Simulating the Response of Aluminum Honeycomb Structure to Transverse Loading  

NASA Technical Reports Server (NTRS)

A 1-dimensional material model was developed for simulating the transverse (thickness-direction) loading and unloading response of aluminum honeycomb structure. The model was implemented as a user-defined material subroutine (UMAT) in the commercial finite element analysis code, ABAQUS(Registered TradeMark)/Standard. The UMAT has been applied to analyses for simulating quasi-static indentation tests on aluminum honeycomb-based sandwich plates. Comparison of analysis results with data from these experiments shows overall good agreement. Specifically, analyses of quasi-static indentation tests yielded accurate global specimen responses. Predicted residual indentation was also in reasonable agreement with measured values. Overall, this simple model does not involve a significant computational burden, which makes it more tractable to simulate other damage mechanisms in the same analysis.

Ratcliffe, James G.; Czabaj, Michael W.; Jackson, Wade C.

2012-01-01

21

Prospects and limitations of digital Shearography and Active Thermography in finding and rating flaws in CFRP sandwich parts with honeycomb core  

NASA Astrophysics Data System (ADS)

This work shows the prospects and limitations of the non-destructive testing methods Digital Shearography and Active Thermography when applied to CFRP sandwich parts with honeycomb cores. Two specimens with different core materials (aluminum, NOMEX) and artificial flaws such as delaminations, disbonds and inclusions of foreign material, are tested with Digital Shearography and Pulse Thermography including Pulse Phase Thermography. Both methods provide a good ability for finding and rating the flaws.

Gruber, J.; Mayr, G.; Hendorfer, G.

2012-05-01

22

Quiet Honeycomb Panels  

NASA Technical Reports Server (NTRS)

Sandwich honeycomb composite panels are lightweight and strong, and, therefore, provide a reasonable alternative to the aluminum ring frame/stringer architecture currently used for most aircraft airframes. The drawback to honeycomb panels is that they radiate noise into the aircraft cabin veil- efficiently provoking the need for additional sound treatment which adds weight and reduces the material's cost advantage. A series of honeycomb panels was made -hick incorporated different design strategies aimed at reducing the honeycomb panels' radiation efficiency while at the same time maintaining their strength. The majority of the designs were centered around the concept of creating areas of reduced stiffness in the panel by adding voids and recesses to the core. The effort culminated with a reinforced/recessed panel which had 6 dB higher transmission loss than the baseline solid core panel while maintaining comparable strength.

Palumbo, Daniel L.; Klos, Jacob

2010-01-01

23

Segmented Aluminum Honeycomb Characteristics in T-Direction, Dynamic Crush Environments  

SciTech Connect

Thirteen segmented aluminum honeycomb samples (5 in. diameter and 1.5 in. height) have been crushed in an experimental configuration that uses a drop table impact machine. The 38.0 pcf bulk density samples are a unique segmented geometry that allows the samples to be crushed while maintaining a constant cross-sectional area. A crush weight of 175 lb was used to determine the rate sensitivity of the honeycomb's highest strength orientation, T-direction, in a dynamic environment of {approx}50 fps impact velocity. Experiments were conducted for two honeycomb manufacturers and at two temperatures, ambient and +165 F. Independent measurements of the crush force were made with a custom load cell and a force derived from acceleration measurements on the drop table using the Sum of Weighted Accelerations Technique with a Calibrated Force (SWAT-CAL). Normalized stress-strain curves for all thirteen experiments are included and have excellent repeatability. These data are strictly valid for material characteristics in the T orientation because the cross-sectional area of the honeycomb did not change during the crush. The dynamic crush data have a consistent increase in crush strength of {approximately}7--19% as compared to quasi-static data and suggest that dynamic performance may be inferred from static tests. An uncertainty analysis estimates the error in these data is {+-} 11%.

BATEMAN,VESTA I.; BROWN,FREDERICK A.; NUSSER,MICHAEL A.; SWANSON,LLOYD H.

2000-08-23

24

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

NASA Astrophysics Data System (ADS)

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

Mathias, Adam Dustin

25

Vibration and sound radiation of sandwich beams with honeycomb truss core  

Microsoft Academic Search

The vibrations of and the sound radiation from sandwich beams with truss core are analyzed. The structure of the core is composed of a sequence of identical unit cells repeating along the beam length and across the core thickness. Each cell is composed of beam elements assembled to form a frame structure. Layouts with the typical honeycomb pattern arranged through

M. Ruzzene

2004-01-01

26

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

NASA Technical Reports Server (NTRS)

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

Nettles, Alan T.; Ratcliffe, James G.

2006-01-01

27

Torsion of honeycomb FRP sandwich beams with a sinusoidal core configuration  

Microsoft Academic Search

A combined analytical, numerical and experimental investigation of honeycomb fiber-reinforced polymer (HFRP) sandwich beam samples subjected to torsion loads is conducted. The sandwich panel considered in this study has unique sinusoidal core geometry in the plane extending vertically between face laminates, and it has been used primarily as decking systems in highway bridges. Using a homogenization process and mechanics of

Julio F. Davalos; Pizhong Qiao; Vinod Ramayanam; Luyang Shan; Justin Robinson

2009-01-01

28

An investigation of the skin\\/core bond in honeycomb sandwich structures using statistical experimentation techniques  

Microsoft Academic Search

Experimental design has been used to investigate the effect of processing parameters on the peel strength of Nomex honeycomb core\\/carbon fibre-epoxy prepreg skin sandwich panels, manufactured by vacuum bagging. The four processing parameters considered were: (i) consolidation pressure; (ii) temperature cure cycle; (iii) temperature ramp rate and (iv) vacuum pressure application time. Each parameter was considered at three levels. It

S. M. Grove; E. Popham; M. E. Miles

2006-01-01

29

Optical properties of solid core honeycomb photonic crystal fiber with different doping levels  

Microsoft Academic Search

Group velocity dispersion (GVD) and effective mode area (Aeff) of solid core honeycomb cladding photonic crystal fiber (PCF) with different up\\/down doping levels are investigated theoretically. Both total internal reflection (TIR) and photonic bandgap (PBG) guiding mechanisms are shown to be available in this fiber structure with gradual change of the doping level. It is noted that the previously overlooked

Guangyu Xu; Wei Zhang; Yidong Huang; Jiangde Peng

2006-01-01

30

Moisture Ingression In Honeycomb Core Sandwich Panels: Directional Aspects  

NASA Technical Reports Server (NTRS)

Moisture ingression was studied in several composite sandwich panels.No observable ingression was found in a panel with HRP core of density 0.13 g/cc (8.0 lb/ft'). Significant moisture ingression occurred in a panel with Korex 3.0-lb core with density 0,048 g/cc, (3.0 lb/cu ft). It was as faster in the Y-axis (core ribbon) direction, per unit distance than in other directions.

Cise, D. M.; Lakes, R. S.

1997-01-01

31

Thermal behavior of a titanium honeycomb-core sandwich panel  

NASA Technical Reports Server (NTRS)

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.

Ko, William L.; Jackson, Raymond H.

1991-01-01

32

Comparison of structural behavior of superplastically formed/diffusion-bonded sandwich structures and honeycomb core sandwich structures  

NASA Technical Reports Server (NTRS)

A superplasticity formed/diffusion-bonded (SPF/DB) orthogonally corrugated core sandwich structure is discussed and its structural behavior is compared to that of a conventional honeycomb core sandwich structure. The stiffness and buckling characteristics of the two types of sandwich structures are compared under conditions of equal structural density. It is shown that under certain conditions, the SPF/DB orthogonally corrugated core sandwich structure is slightly more efficient than the optimum honeycomb core (square-cell core) sandwich structure. However, under different conditions, this effect can be reversed.

Ko, W. L.

1980-01-01

33

Sound Transmission through a Cylindrical Sandwich Shell with Honeycomb Core  

NASA Technical Reports Server (NTRS)

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

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

1996-01-01

34

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

NASA Technical Reports Server (NTRS)

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

McQuigg, Thomas D.

2011-01-01

35

Buckling tests of three 4.6 meter diameter aluminum honeycomb sandwich conical shells loaded under external pressure  

NASA Technical Reports Server (NTRS)

Three aluminum honeycomb sandwich conical shells with a 120 apex angle and a 4.6-m (15.0-ft) base diameter were loaded to failure by a uniform external pressure. The cones differed from one another only in the thickness of their respective face sheets. Test specimen details, test procedure, and test results are discussed. Both buckling and prebuckling data are compared with appropriate theoretical predictions, and good agreement was obtained between test and theory. Extensive imperfection measurements were made and reported on the three cones in the as fabricated condition.

Anderson, J. K.; Davis, R. C.

1975-01-01

36

Elevated-Temperature Tests Under Static and Aerodynamic Conditions on Honeycomb-Core Sandwich Panels  

NASA Technical Reports Server (NTRS)

Stainless-steel honeycomb-core sandwich panels which differed primarily in skin thicknesses were tested at elevated temperatures under static and aerodynamic conditions. The results of these tests were evaluated to determine the insulating effectiveness and structural integrity of the panels. The static radiant-heating tests were performed in front of a quartz-tube radiant heater at panel skin temperatures up to 1,5000 F. The aerodynamic tests were made in a Mach 1.4 heated blowdown wind tunnel. The tunnel temperature was augmented by additional heat supplied by a radiant heater which raised the panel surface temperature above 8000 F during air flow. Static radiant-heating tests of 2 minutes duration showed that all the panels protected the load-carrying structure about equally well. Thin-skin panels showed an advantage for this short-time test over thick-skin panels from a standpoint of weight against insulation. Permanent inelastic strains in the form of local buckles over each cell of the honeycomb core caused an increase in surface roughness. During the aero- dynamic tests all of the panels survived with little or no damage, and panel flutter did not occur.

Groen, Joseph M.; Johnson, Aldie E., Jr.

1959-01-01

37

Honeycomb-laminate composite structure  

NASA Technical Reports Server (NTRS)

A honeycomb-laminate composite structure was comprised of: (1) a cellular core of a polyquinoxaline foam in a honeycomb structure, and (2) a layer of a noncombustible fibrous material impregnated with a polyimide resin laminated on the cellular core. A process for producing the honeycomb-laminate composite structure and articles containing the honeycomb-laminate composite structure is described.

Gilwee, W. J., Jr.; Parker, J. A. (inventors)

1977-01-01

38

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

NASA Technical Reports Server (NTRS)

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

Rinker, Martin; Krueger, Ronald; Ratcliffe, James

2013-01-01

39

Optical properties of solid core honeycomb photonic crystal fiber with different doping levels  

NASA Astrophysics Data System (ADS)

Group velocity dispersion (GVD) and effective mode area (Aeff) of solid core honeycomb cladding photonic crystal fiber (PCF) with different up/down doping levels are investigated theoretically. Both total internal reflection (TIR) and photonic bandgap (PBG) guiding mechanisms are shown to be available in this fiber structure with gradual change of the doping level. It is noted that the previously overlooked TIR guiding design with up-doping could acquire improved nonlinear property compared with PBG mechanism in short normalized wavelength region. On the other hand, the total GVD is shown to be dominated by waveguide dispersion corresponding to the fiber structure. Numerical results show that HPCF can achieve small Aeff with low air-fill fraction, and doping level in HPCF provides an additional way to change GVD excepting structure parameters. Special cases are given to demonstrate the potential of HPCF in combining design of Aeff and GVD, aiming at applications such as Raman amplification and dispersion compensation around 1550nm.

Xu, Guangyu; Zhang, Wei; Huang, Yidong; Peng, Jiangde

2006-01-01

40

The soft impact of composite sandwich beams with a square-honeycomb core B.P. Russell, T. Liu, N.A. Fleck, V.S. Deshpande*  

E-print Network

The soft impact of composite sandwich beams with a square-honeycomb core B.P. Russell, T. Liu, N that the sandwich beams outperformed both monolithic composite beams and steel sandwich beams with a square-honeycomb-clamped monolithic beams and sandwich beams of equal areal mass have been measured by loading the beams at mid

Fleck, Norman A.

41

Mechanics and Applications of Pressure Adaptive Honeycomb  

E-print Network

.2.2 Longitudinal Compression-Tension Test 141 5.2.3 Lateral Compression-Tension Test 142 vii 5.3 Multi-Cell Rigid-Member Pressurized Honeycomb 144 5.4 Multi-Cell Pressurized Aluminum Honeycomb 148 5.5 Wind Tunnel Experiment with Pressure adaptive Flap 158 6....1 Aluminum Honeycomb Test Results 170 6.2 Single-Cell Rigid-Member Pressurized Honeycomb 172 6.3 Multi-Cell Rigid-Member Pressurized Honeycomb 177 6.4 Validation of Constant assumption 183 6.5 Multi-Cell Pressurized Aluminum Honeycomb 184 6.6 Pressure...

Vos, Roelof

2009-07-31

42

Buckling Analysis of a Honeycomb-Core Composite Cylinder with Initial Geometric Imperfections  

NASA Technical Reports Server (NTRS)

Thin-walled cylindrical shell structures often have buckling as the critical failure mode, and the buckling of such structures can be very sensitive to small geometric imperfections. The buckling analyses of an 8-ft-diameter, 10-ft-long honeycomb-core composite cylinder loaded in pure axial compression is discussed in this document. Two loading configurations are considered configuration 1 uses simple end conditions, and configuration 2 includes additional structure that may more closely approximate experimental loading conditions. Linear eigenvalue buckling analyses and nonlinear analyses with and without initial geometric imperfections were performed on both configurations. The initial imperfections were introduced in the shell by applying a radial load at the midlength of the cylinder to form a single inward dimple. The critical bifurcation buckling loads are predicted to be 924,190 lb and 924,020 lb for configurations 1 and 2, respectively. Nonlinear critical buckling loads of 918,750 lb and 954,900 lb were predicted for geometrically perfect configurations 1 and 2, respectively. Lower-bound critical buckling loads for configurations 1 and 2 with radial perturbations were found to be 33% and 36% lower, respectively, than the unperturbed critical loads. The inclusion of the load introduction cylinders in configuration 2 increased the maximum bending-boundary-layer rotation up to 11%.

Cha, Gene; Schultz, Marc R.

2013-01-01

43

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

E-print Network

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

44

SIMULATION OF THE DAMAGE TOLERANCE BEHAVIOUR OF CFRP\\/HONEYCOMB SANDWICH BASED ON MEASURED PROPERTIES OF THE RESIN IMPREGNATED CORE PAPER  

Microsoft Academic Search

Structural sandwich is widely used as a lightweight design solution for load-carrying components. In aircraft structures particularly sandwich using carbon fibre reinforced plastics (CFRP) as face sheets and non-metallic honeycombs as core material is applied due to features such as high strength-to-weight and stiffness-to-weight ratios as well as excellent fatigue behaviour. Owing to the rather weak core material, sandwich is

F. Hähnel; K. Wolf

45

Failure mode maps for honeycomb sandwich panels  

Microsoft Academic Search

Failure modes for sandwich beams of GFRP laminate skins and Nomex honeycomb core are investigated. Theoretical models using honeycomb mechanics and classical beam theory are described. A failure mode map for loading under 3-point bending is constructed, showing the dependence of failure mode and load on the ratio of skin thickness to span length and honeycomb relative density. Beam specimens

A. Petras; M. P. F. Sutcliffe

1999-01-01

46

Air guiding with honeycomb photonic bandgap fiber  

Microsoft Academic Search

We notice that honeycomb cladding was overlooked for air-guiding photonic bandgap fiber design. Air-silica honeycomb cladding is shown in this letter to be able to guide light in a slightly large-sized hollow core, with a reasonably wide bandwidth (?200 nm). Noncircular air-hole shape is also explored for air-guiding honeycomb fiber design.

M. Yan; P. Shum

2005-01-01

47

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

Microsoft Academic Search

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

1991-01-01

48

Influence of skin\\/core debonding on free vibration behavior of foam and honeycomb cored sandwich plates  

Microsoft Academic Search

The dynamic behavior of partially delaminated at the skin\\/core interface sandwich plates with flexible cores is studied. The commercial finite element code ABAQUS is used to calculate natural frequencies and mode shapes of the sandwich plates containing a debonding zone. The influence of the debonding size, debonding location and types of debonding on the modal parameters of damaged sandwich plates

Vyacheslav N. Burlayenko; Tomasz Sadowski

2010-01-01

49

Sound insulation improvement using honeycomb sandwich panels  

Microsoft Academic Search

Research results on acoustic treatment technology of honeycomb material to improve noise transmission loss characteristics of light-weight panels are presented in this paper. A prediction model has been presented to describe the transmission loss of the honeycomb panels based on the knowledge of their structural modal parameters. A series of test specimens with aluminum sheets, and fiber reinforced concrete sheets

Huang Wen-chao; Ng Chung-fai

1998-01-01

50

Honeycomb vs. Foam: Evaluating Potential Upgrades to ISS Module Shielding  

NASA Technical Reports Server (NTRS)

The presence of honeycomb cells in a dual-wall structure is advantageous for mechanical performance and low weight in spacecraft primary structures but detrimental for shielding against impact of micrometeoroid and orbital debris particles (MMOD). The presence of honeycomb cell walls acts to restrict the expansion of projectile and bumper fragments, resulting in the impact of a more concentrated (and thus lethal) fragment cloud upon the shield rear wall. The Multipurpose Laboratory Module (MLM) is a Russian research module scheduled for launch and ISS assembly in 2011 (currently under review). Baseline shielding of the MLM is expected to be predominantly similar to that of the existing Functional Energy Block (FGB), utilizing a baseline triple wall configuration with honeycomb sandwich panels for the dual bumpers and a thick monolithic aluminum pressure wall. The MLM module is to be docked to the nadir port of the Zvezda service module and, as such, is subject to higher debris flux than the FGB module (which is aligned along the ISS flight vector). Without upgrades to inherited shielding, the MLM penetration risk is expected to be significantly higher than that of the FGB module. Open-cell foam represents a promising alternative to honeycomb as a sandwich panel core material in spacecraft primary structures as it provides comparable mechanical performance with a minimal increase in weight while avoiding structural features (i.e. channeling cells) detrimental to MMOD shielding performance. In this study, the effect of replacing honeycomb sandwich panel structures with metallic open-cell foam structures on MMOD shielding performance is assessed for an MLM-representative configuration. A number of hypervelocity impact tests have been performed on both the baseline honeycomb configuration and upgraded foam configuration, and differences in target damage, failure limits, and derived ballistic limit equations are discussed.

Ryan, Shannon J.; Christiansen, Eric L.

2009-01-01

51

The structural behavior of a graphite-polymide honeycomb sandwich panel with quasi-isotropic face sheets and an orthotropic core  

NASA Technical Reports Server (NTRS)

The results of a series of tests of graphite-polyimide honeycomb sandwich panels are presented. The panels were 1.22 m long, 0.508 m wide, and approximately 13.3 m thick. The face sheets were a T-300/PMR-15 fabric in a quasi-isotropic layup and were 0.279 mm thick. The core was Hexcel HRH 327-3/16 - 4.0 glass reinforced polyimide honeycomb, 12.7 mm thick. Three panels were used in the test: one was cut into smaller pieces for testing as beam, compression, and shear specimens; a second panel was used for plate bending tests; the third panel was used for in-plane stability tests. Presented are the experimental results of four point bending tests, short block compression tests, core transverse shear modulus, three point bending tests, vibration tests, plate bending tests, and panel stability tests. The results of the first three tests are used to predict the results of some of the other tests. The predictions and experimental results are compared, and the agreement is quite good.

Hyer, M. W.; Hagaman, J. A.

1979-01-01

52

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

NASA Astrophysics Data System (ADS)

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

Song, Fei

53

Probability of Detection Study on Impact Damage to Honeycomb Composite Structure using Thermographic Inspection  

NASA Technical Reports Server (NTRS)

A probability of detection study was performed for the detection of impact damage using flash heating infrared thermography on a full scale honeycomb composite structure. The honeycomb structure was an intertank structure from a previous NASA technology demonstration program. The intertank was fabricated from IM7/8552 carbon fiber/epoxy facesheets and aluminum honeycomb core. The intertank was impacted in multiple locations with a range of impact energies utilizing a spherical indenter. In a single blind study, the intertank was inspected with thermography before and after impact damage was incurred. Following thermographic inspection several impact sites were sectioned from the intertank and cross-sectioned for microscopic comparisons of NDE detection and actual damage incurred. The study concluded that thermographic inspection was a good method of detecting delamination damage incurred by impact. The 90/95 confidence level on the probability of detection was close to the impact energy that delaminations were first observed through cross-sectional analysis.

Hodge, Andrew J.; Walker, James L., II

2008-01-01

54

Perforation of honeycomb sandwich plates by projectiles  

Microsoft Academic Search

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

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

2000-01-01

55

Honeycomb network  

NSDL National Science Digital Library

Issue Date: 31-Jan-2005 Description: Simulation Software: Glotzer Group Code Simulation Method: Monte Carlo A system of 360 patchy particle nano building blocks was simulated at a concentration of 0.56 particles/surface area, starting from a disordered state then quenched to a temperature of 0.8. The building blocks have the following patch locations and patterning: 3 patches uniformly spaced on a sphere. The system was run for ~50e6 until arriving at the final structure (Honeycomb). Simulation Model: United Atom with Kern-Frenkel like potential

Joydeep, Mukherjee

2005-01-31

56

A preliminary report on the effect of elevated temperature exposure on the mechanical properties of titanium-alloy honeycomb-core sandwich panels.  

NASA Technical Reports Server (NTRS)

A study has been initiated to determine the effects of elevated-temperature exposure on the room-temperature mechanical properties of titanium honeycomb-core sandwich panels fabricated by brazing or spot diffusion bonding. Only flatwise tensile properties following exposure have been determined to date. Preliminary results indicate very little change in the flatwise tensile strength of sandwich panels fabricated by spot diffusion bonding following exposures of 10,000 hr at 600 and 800 F and 1000 hr at 1000 F. Titanium panels fabricated by using a Ti-Zr-Be braze alloy are susceptible to oxidation at elevated temperature and experience flatwise tensile strength degradation after continuous exposures of 7500 hr at 600 F, 1000 hr at 800 F, and less than 100 hr at 1000 F. It is possible that the exposure life of the brazed panels may be substantially increased if the panel edges are sealed to prevent oxidation of the braze alloy.

Bales, T. T.; Cain, R. L.

1971-01-01

57

Aluminum foams produced by liquid-state processes  

Microsoft Academic Search

Lightweight cellular materials can be used in the construction of composite plates, shells and tubes with high structural efficiency. Metallic sandwich construction with integrally bonded face-sheet\\/foam core configurations offer a cost-efficient alternative to conventional skin-stringer and honeycomb core components. The potential effectiveness of such constructions is dependent on the properties and performance of the core materials. In this study, aluminum

A. E. Simone; L. J. Gibson

1998-01-01

58

Nonlinear acoustics and honeycomb materials  

NASA Astrophysics Data System (ADS)

The scope of research activity that Bruce Thompson embraced was very large. In this talk three different research topics that the author shared with Bruce are reviewed. They represent Bruce's introduction to NDE and include nonlinear acoustics, nondestructive measurements of adhesive bond strengths in honeycomb panels, and studies of flexural wave dispersion in honeycomb materials. In the first of these, four harmonics of a 30 Mhz finite amplitude wave were measured for both fused silica and aluminum single crystals with varying lengths and amounts of cold work using a capacity microphone with heterodyne receiver with a flat frequency response from 30 to 250 Mhz. The results for fused silica with no dislocation structure could be described by a model due to Fubini, originally developed for gases, that depends upon only the second and third order elastic constants and not the fourth and higher order constants. The same was not true for the aluminum with dislocation structures. These results raised some questions about models for harmonic generation in materials with dislocations. In the second topic, experiments were made to determine the adhesive bond strengths of honeycomb panels using the vibrational response of the panels (Chladni figures). The results showed that both the damping characteristics of panel vibrations as a whole and velocity of propagation of elastic waves that travel along the surface and sample the bondline can be correlated with destructively determined bond strengths. Finally, the phase velocity of flexural waves traveling along a 1-inch honeycomb sandwich panel was determined from 170 Hz to 50 Khz, ranging from 2.2×104 cm/sec at the low end to 1.18×105 cm/sec at 40 Khz. The dispersion arises from the finite thickness of the panel and agreed with the results of continuum models for the honeycomb. Above 40 Khz, this was not the case. The paper concludes with a tribute to Bruce for his many wonderful contributions and lessons beyond his technical legacy for all of us.

Thompson, D. O.

2012-05-01

59

Vibroacoustics and damping analysis of negative Poisson's ratio honeycombs  

Microsoft Academic Search

In this paper a novel class of core material for sandwich structures is analyzed from an analytical and numerical point of view. Honeycombs with re-entrant cell geometry present negative in-plane Poisson's ratio coefficients, with an increase of bending stiffness compared to the one of hexagonal honeycomb cores. Due to the orthotropic mechanical properties of this kind of core material it

Fabrizio Scarpa; Geoffrey R. Tomlinson

1998-01-01

60

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

E-print Network

, sandwich panels traditionally made from foam and honeycomb cores with close-cells [9] cannot accom- modateSandwich-walled cylindrical shells with lightweight metallic lattice truss cores and carbon fiber manufactured sandwich-walled cylindrical shells with aluminum pyramidal truss core of constant curvature

Vaziri, Ashkan

61

Hypervelocity Impact Evaluation of Metal Foam Core Sandwich Structures  

NASA Technical Reports Server (NTRS)

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.

Yasensky, John; Christiansen, Eric L.

2007-01-01

62

Hybrid processing of thick skins for honeycomb sandwich structures  

Microsoft Academic Search

Carbon–epoxy prepregs are generally used to form the skins of honeycomb sandwich structures used in aerospace or racing yachts. For some applications, it is desirable to increase the thickness of the skins. In order to achieve an ideal core pressure level during cure for maximal skin–core bonding, the issue of air extraction from the honeycomb cells through the skin during

S. Sequeira Tavares; Y. Roulin; V. Michaud; J.-A. E. Månson

2011-01-01

63

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

E-print Network

: Received 25 February 2013 Received in revised form 6 May 2013 Accepted 30 May 2013 Available online 20 June panels made from Al 6061-T6. The panels were subjected to impact tests using hard steel spheres over,16] on extruded 6061-T6 aluminum sandwich panels with a strong triangular corrugated core [17] have shown

Wadley, Haydn

64

International Journal of Impact Engineering 35 (2008) 10631074 Mechanical response of metallic honeycomb sandwich panel structures  

E-print Network

honeycomb sandwich panel structures to high-intensity dynamic loading Kumar P. Dharmasenaa,Ã?, Haydn N many of the phenomenological details of the core deformation behavior. The honeycomb sandwich panels Explosive tests were performed in air to study the dynamic mechanical response of square honeycomb core

Hutchinson, John W.

65

Numerical Simulation On Dynamic Indentation Behavior of Sandwich Plates With Aluminum Foam Cores  

NASA Astrophysics Data System (ADS)

Dynamic indentation behavior of sandwich plates with aluminum alloy skins and aluminum foam cores has been simulated by using LS-DYNA. The simulation results were compared with the experimental data in each specimen group for validating the effectiveness and reliability of the FEM model. The numerical simulation results were discussed and several typical failure modes were summarized. An evaluation approach of energy-absorbing ability was proposed based on the deformation mechanism of the sandwich plates. The energy-absorbing ability varied with different structural geometry parameters of sandwich plates was evaluated, which revealed that the energy-absorbing ability of sandwich plates was sensitive to structural geometry parameters.

Zhang, H.; Huang, X. Q.; Tang, L. Q.

2010-05-01

66

A novel method of testing the shear strength of thick honeycomb composites  

NASA Technical Reports Server (NTRS)

Sandwich composites of aluminum and glass/phenolic honeycomb core were tested for shear strength before and after impact damage. The assessment of shear strength was performed in two ways; by four point bend testing of sandwich beams and by a novel double lap shear (DLS) test. This testing technique was developed so smaller specimens could be used, thus making the use of common lab scale fabrication and testing possible. The two techniques yielded similar data. The DLS test gave slightly lower shear strength values of the two methods but were closer to the supplier's values for shear strength.

Hodge, A. J.; Nettles, A. T.

1991-01-01

67

Advanced radiator concepts utilizing honeycomb panel heat pipes (stainless steel)  

NASA Technical Reports Server (NTRS)

The feasibility of fabricating and processing moderate temperature range heat pipes in a low mass honeycomb sandwich panel configuration for highly efficient radiator fins for the NASA space station was investigated. A variety of honeycomb panel facesheet and core-ribbon wick concepts were evaluated within constraints dictated by existing manufacturing technology and equipment. Concepts evaluated include: type of material, material and panel thicknesses, wick type and manufacturability, liquid and vapor communication among honeycomb cells, and liquid flow return from condenser to evaporator facesheet areas. In addition, the overall performance of the honeycomb panel heat pipe was evaluated analytically.

Fleischman, G. L.; Tanzer, H. J.

1985-01-01

68

The use of 1,2-epoxyhexane as a passivating agent for core-shell aluminum nanoparticles with very high active aluminum content  

NASA Astrophysics Data System (ADS)

Aluminum nanoparticles synthesized by titanium (IV) isopropoxide-initiated decomposition of alane have been passivated and capped using oligomerization of 1,2-epoxyhexane. Preliminary synthetic protocols with this capping agent, where the nanoparticle formation reaction and passivation processes were both conducted at ambient temperatures, had resulted in nanoparticles that were highly unstable and that either oxidized rapidly upon exposure to air or were pyrophoric. Use of 1,2-epoxydodecane, on the other hand, had produced stable nanoparticles that were successfully characterized and reported. A modification of the procedure whereby the epoxyhexane passivation process is carried out at 85 °C for 30 min, has afforded surprisingly stable aluminum nanoparticles. Powder X-ray analysis and transmission electron microscopy reveal nanoparticle diameters on the order of 30 nm with 19 nm crystalline aluminum cores. The passivation process yields an extraordinarily high active aluminum (Al0) content of 83%, with degradation of the core to 52% active aluminum after 9 days exposure in a dry air chamber. Differential scanning calorimetry coupled with thermogravimetric analysis reveals distinct cap combustion and metal ignition exotherms, though they are not as well-defined as those found with their epoxydodecane-capped congener. With the additional observation of a metal melting endotherm, it is suggested that while carrying out the passivation process at an elevated temperature affords a higher degree of kinetic stabilization of the aluminum core, the passivation shell is inhomogeneous, possibly as a result of the polydisperse nature of the oligomerized epoxyhexane.

Jelliss, Paul A.; Buckner, Steven W.; Chung, Stephen W.; Patel, Ashish; Guliants, Elena A.; Bunker, Christopher E.

2013-09-01

69

Impact analysis of fiber reinforced polymer honeycomb composite sandwich beams  

Microsoft Academic Search

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

Pizhong Qiao; Mijia Yang

2007-01-01

70

Identification of honeycomb sandwich properties by high-resolution modal analysis  

E-print Network

Identification of honeycomb sandwich properties by high-resolution modal analysis M. R´ebillat X and core materials of honeycomb sandwich. All the elastic coefficients and loss-factors that matter the problem of the identification of elastic and damping properties of sandwich panels [1, 2]. The honeycomb

Paris-Sud XI, Université de

71

A comparative investigation for the nondestructive testing of honeycomb structures by holographic interferometry and infrared thermography  

Microsoft Academic Search

The nondestructive testing (NDT) of honeycomb sandwich structures has been the subject of several studies. Classical techniques such as ultrasound testing and x-rays are commonly used to inspect these structures. Holographic interferometry (HI) and infrared thermography (IT) have shown to be interesting alternatives. Holography has been successfully used to detect debonding between the skin and the honeycomb core on honeycomb

S. Sfarra; C. Ibarra-Castanedo; N. P. Avdelidis; M. Genest; L. Bouchagier; D. Kourousis; A. Tsimogiannis; A. Anastassopoulous; A. Bendada; X. Maldague; D. Ambrosini; D. Paoletti

2010-01-01

72

Nde of Bonded Aluminum Components on Aircraft Structures  

NASA Astrophysics Data System (ADS)

Bonded aluminum structures have been commonly used on aircraft for many years, and many of these applications include flight control surfaces. These bonded structures can be made up of aluminum face sheets adhesively bonded to a central honeycomb core, or they could also be composed of machined components that are bonded in a tongue-in-groove type manner called Grid-Lock. Nondestructive Inspection (NDI) methods of bonded aluminum structures usually involve the detection of skin-to-core disbonds, core buckling and damage caused by impacts. In the case of Grid-Lock, NDI techniques are focused on the detection of failures in the tongue-in-groove adhesive joint. Three nondestructive inspection methods were applied to honeycomb sandwich structures and Grid-Lock panels. The three methods were computer aided tap test (CATT), air-coupled ultrasonic testing (ACUT), and mechanical impedance analysis (MIA). The honeycomb structures tested consisted of structural panels and flight control surfaces from various aircraft. The Grid-Lock samples tested are laboratory specimens that simulate various defects. Experimental results and comparisons from each of these methods and samples will be presented.

Barnard, Daniel J.; Hsu, David K.; Foreman, Cory; Wendt, Scott; Kreitinger, Nicholas A.; Steffes, Gary J.

2008-02-01

73

MODAL DENSITY OF COMPOSITE HONEYCOMB SANDWICH PANELS  

Microsoft Academic Search

Honeycomb sandwich panels with composite face sheets are widely used in spacecraft applications. It is necessary to obtain the modal density of such panels to study their behaviour under acoustic excitation. The governing differential equation, with consideration of the shear flexibility of the core, is derived. From this equation the expression for the modal density is derived. Experimental results for

K. Renji; P. S. Nair; S. Narayanan

1996-01-01

74

Honeycomb vs. Foam: Evaluating a Potential Upgrade to ISS Module Shielding for Micrometeoroids and Orbital Debris  

NASA Technical Reports Server (NTRS)

The presence of a honeycomb core in a multi-wall shielding configuration for protection against micrometeoroid and orbital debris (MMOD) particle impacts at hypervelocity is generally considered to be detrimental as the cell walls act to restrict fragment cloud expansion, creating a more concentrated load on the shield rear wall. However, mission requirements often prevent the inclusion of a dedicated MMOD shield, and as such, structural honeycomb sandwich panels are amongst the most prevalent shield types. Open cell metallic foams are a relatively new material with novel mechanical and thermal properties that have shown promising results in preliminary hypervelocity impact shielding evaluations. In this study, an ISS-representative MMOD shielding configuration has been modified to evaluate the potential performance enhancement gained through the substitution of honeycomb for open cell foam. The baseline shielding configuration consists of a double mesh outer layer, two honeycomb sandwich panels, and an aluminum rear wall. In the modified configuration the two honeycomb cores are replaced by open-cell foam. To compensate for the heavier core material, facesheets have been removed from the second sandwich panel in the modified configuration. A total of 19 tests on the double layer honeycomb and double layer foam configurations are reported. For comparable mechanical and thermal performance, the foam modifications were shown to provide a 15% improvement in critical projectile diameter at low velocities (i.e. 3 km/s) and a 3% increase at high velocities (i.e. 7 km/s) for normal impact. With increasing obliquity, the performance enhancement was predicted to increase, up to a 29% improvement at 60 (low velocity). Ballistic limit equations have been developed for the new configuration, and consider the mass of each individual shield component in order to maintain validity in the event of minor configuration modifications. Previously identified weaknesses of open cell foams for hypervelocity impact shielding such as large projectile diameters, low velocities, and high degrees of impact obliquity have all been investigated, and found to be negligible for the double-layer configuration.

Ryan, Shannon; Hedman, Troy; Christiansen, Eric L.

2009-01-01

75

Aluminum and copper plasmonics for enhancing internal quantum efficiency of core-shell and core-multishell nanowire photoelectrodes  

NASA Astrophysics Data System (ADS)

One of the critical challenges for achieving solar-to-hydrogen efficiency greater than 10% (100 W/m2), especially in metal oxide photoelectrodes, is the poor internal quantum efficiency arising from high, bulk and surface, recombination and insufficient light absorption. Plasmonic light harvesting has emerged as a promising strategy to address this challenge. However, most designs are photocatalyst specific and employ precious metals, making large scale applications infeasible. We present metal-photocatalyst core-shell and semiconductor-metal-photocatalyst coremultishell nanowires as a novel class of multi-functional plasmonic photoelectrodes. By combining the optical resonances with the localized surface plasmon resonance within the proposed structures, we achieve extreme light absorption in the visible range within ultrathin photocatalyst layers. Such enhanced absorption ensures that the photocharges are preferentially generated very close to the photocatalyst-electrolyte interface and can effectively drive the reaction forward, thereby improving the internal quantum efficiency. Specifically, for nanowires in an aqueous electrolyte, we demonstrate the effectiveness of aluminum and copper to confine light and establish them as plasmonic alternatives to precious metal counterparts such as silver and gold therefore enabling cheap and scalable plasmonics. Further, we probe the absorption as a function of the permittivity of the electrolyte and show that the absorption in such nanowires is large even for high permittivity electrolytes. Hematite and copper(I) oxide have been chosen as the test materials to validate the generality of this approach. Notably, for hematite, we show that aluminum is more effective than copper, while for a broadband absorber such as copper(I) oxide, we show that both aluminum and copper are equally effective for plasmonic light harvesting.

Ramadurgam, Sarath; Yang, Chen

2014-09-01

76

The Definition of Quality of Honeycomb Structures  

NASA Astrophysics Data System (ADS)

In the represented report the comprehensive approach to quality inspection of honeycomb structures is considered and substantiated to provide their high structural characteristics. The structures are intended for manufacturing micro satellite solar arrays. The investigated structures involve two skins of composite materials by a thickness from 0,1 to 0,3 mm and a filler by hexagonal honeycomb cells of aluminum alloy. It may be glued in a variety of ways: with a film glue or a glue deposited on end faces of cells. Variants and possibilities of nondestructive methods for quality inspection - holographic interferometer and infrared testing ones - are considered for various materials of skins and used glues. The various methods of loading the constructions is appreciated in order to get the required sensitivity of nondestructive besting methods. To provide the required structural properties in addition to the nondestructive testing the application of mechanical tests of honeycomb structure samples is substantiated. The kinds of mechanical tests are described and the results are given. The indicated approach provides the asked level of characteristics for honeycomb structures.

Sitalo, V. G.; Tykhyy, V. G.; Primakov, V. D.

2002-01-01

77

Effects of Processing Parameters on the Fabrication of Copper Cladding Aluminum Rods by Horizontal Core-Filling Continuous Casting  

NASA Astrophysics Data System (ADS)

Copper cladding aluminum (CCA) rods with a diameter of 30 mm and a sheath thickness of 3 mm were fabricated by horizontal core-filling continuous casting (HCFC) technology. The effects of key processing parameters, such as the length of the mandrel tube of composite mold, aluminum casting temperature, flux of the secondary cooling water, and mean withdrawing speed were optimized based on some quality criteria, including the uniformity of the sheath thickness, integrality of the rods, and thickness of the interface. The causes of internal flaws formation of CCA rods were also discussed. The results showed that the continuity of the liquid aluminum core-filling process and the interface reaction control between solid copper and liquid aluminum were two key problems that strongly affected the stability of the casting process and the product quality. Our research indicated that for the CCA rod with the previously mentioned size, the optimal length of mandrel tube was 210 mm. A shorter mandrel tube allowed of easier erosion at the interface, which led to a nonuniform sheath thickness. Conversely, it tended to result in a discontinuous filling process of liquid aluminum, which causes shrinkage or cold shuts. The optimal casting temperatures of copper and aluminum were 1503 K (1230 °C) and 1043 K to 1123 K (770 °C to 850 °C), respectively. When the casting temperature of aluminum was below 1043 K (770 °C), the casting process would be discontinuous, resulting in shrinkages or cold shuts. Nevertheless, when the casting temperature of aluminum was higher than 1123 K (850 °C), a severe interface reaction between solid copper and liquid aluminum would occur. The proper flux of the secondary cooling water and the mean withdrawing speed were determined as 600 to 800 L/h and 60 to 87 mm/min, respectively. In the previously mentioned proper ranges of processing parameters, the interfacial shear strengths of CCA rods were 40.5 to 67.9 MPa.

Su, Ya-Jun; Liu, Xin-Hua; Huang, Hai-You; Wu, Chun-Jing; Liu, Xue-Feng; Xie, Jian-Xin

2011-02-01

78

Extruded ceramic honeycomb and method  

DOEpatents

Extruded low-expansion ceramic honeycombs comprising beta-spodumene solid solution as the principal crystal phase and with less than 7 weight percent of included mullite are produced by compounding an extrusion batch comprising a lithium aluminosilicate glass powder and a clay additive, extruding a green honeycomb body from the batch, and drying and firing the green extruded cellular honeycomb to crystallize the glass and clay into a low-expansion spodumene ceramic honeycomb body.

Day, J. Paul (Big Flats, NY)

1995-04-04

79

Optimization of a metal honeycomb sandwich beam-bar subjected to torsion and bending  

Microsoft Academic Search

In this paper, we analyze a metal honeycomb sandwich beam\\/torsion bar subjected to combined loading conditions. The cell wall arrangement of the honeycomb core is addressed in the context of maximizing resistance to either bending, torsion, or combined bending and torsion for given dimensions, face sheet thicknesses and core relative density. It is found that the relative contributions of the

A.-J. Wang; D. L. McDowell

2003-01-01

80

Thermal Inspection of Composite Honeycomb Structures  

NASA Technical Reports Server (NTRS)

Composite honeycomb structures continue to be widely used in aerospace applications due to their low weight and high strength advantages. Developing nondestructive evaluation (NDE) inspection methods are essential for their safe performance. Pulsed thermography is a commonly used technique for composite honeycomb structure inspections due to its large area and rapid inspection capability. Pulsed thermography is shown to be sensitive for detection of face sheet impact damage and face sheet to core disbond. Data processing techniques, using principal component analysis to improve the defect contrast, are presented. In addition, limitations to the thermal detection of the core are investigated. Other NDE techniques, such as computed tomography X-ray and ultrasound, are used for comparison to the thermography results.

Zalameda, Joseph N.; Parker, F. Raymond

2014-01-01

81

Indentation failure behavior of honeycomb sandwich panels  

Microsoft Academic Search

The failure behavior of simply supported honeycomb sandwich panels subjected to indentation loading on the top skin has been studied. A plate-on-elastic-foundation approach based on distributed load and panel-specific considerations (finite thickness and transverse shear) is developed to analyze the panel stress distribution. Panels with various glass-fibre\\/epoxy skins and aramid cores are analyzed by using this approach together with the

Shaw M. Lee; Thomas K. Tsotsis

2000-01-01

82

Effect of debonding on natural frequencies and frequency response functions of honeycomb sandwich beams  

Microsoft Academic Search

The natural frequencies of honeycomb sandwich beams having debonding or delamination embedded between the face-layer laminates and the honeycomb core are studied herein. A theoretical analysis of the effect of the extent of debonding on the flexural stiffness and on the natural frequency is compared with experimental observations. In this analysis the free vibration of the delaminated sandwich beams is

Hyeung-Yun Kim; Woonbong Hwang

2002-01-01

83

Heat Shielding Characteristics and Thermostructural Performance of a Superalloy Honeycomb Sandwich Thermal Protection System (TPS)  

NASA Technical Reports Server (NTRS)

Heat-transfer, thermal bending, and mechanical buckling analyses have been performed on a superalloy "honeycomb" thermal protection system (TPS) for future hypersonic flight vehicles. The studies focus on the effect of honeycomb cell geometry on the TPS heat-shielding performance, honeycomb cell wall buckling characteristics, and the effect of boundary conditions on the TPS thermal bending behavior. The results of the study show that the heat-shielding performance of a TPS panel is very sensitive to change in honeycomb core depth, but insensitive to change in honeycomb cell cross-sectional shape. The thermal deformations and thermal stresses in the TPS panel are found to be very sensitive to the edge support conditions. Slight corrugation of the honeycomb cell walls can greatly increase their buckling strength.

Ko, William L.

2004-01-01

84

Damping of honeycomb sandwich beams  

Microsoft Academic Search

An experimental investigation was carried out on the damping behaviour of laminated honeycomb cantilever beams with fine solder balls enclosed in the cells as dampers. Attenuation was achieved through the exchange of momentum between the balls and the beam. The effect of the mass ratio (i.e. the number of balls to be enclosed in each honeycomb cell) was studied by

B Wang; M Yang

2000-01-01

85

Flight service evaluation of two aluminum-brazed titanium spoilers  

NASA Technical Reports Server (NTRS)

The long-term service evaluation of two aluminum-brazed titanium (ABTi) honeycomb flight spoilers was concluded. The two spoilers had about 7.5 years of commercial flight experience on All Nippon Airways Model 737 aircraft. All Nippon Airways was selected because Japan has one of the most severe marine-industrial environments in the world. The results indicated that both flight spoilers still had the same load-carrying capability as when they were originally installed. No direct evidence of any corrosion was observed on either spoiler. Another significant accomplishment of this effort was the development of a braze design for efficiently distributing point loads from the fittings and skin into the honeycomb core.

Boyer, R. R.

1984-01-01

86

Bismaleimide resins for flame resistant honeycomb sandwich panels  

NASA Technical Reports Server (NTRS)

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

Stenzenberger, H. D.

1978-01-01

87

Optimized Non-Obstructive Particle Damping (NOPD) Treatment for Composite Honeycomb Structures  

NASA Technical Reports Server (NTRS)

Non-Obstructive Particle Damping (NOPD) technology is a passive vibration damping approach whereby metallic or non-metallic particles in spherical or irregular shapes, of heavy or light consistency, and even liquid particles are placed inside cavities or attached to structures by an appropriate means at strategic locations, to absorb vibration energy. The objective of the work described herein is the development of a design optimization procedure and discussion of test results for such a NOPD treatment on honeycomb (HC) composite structures, based on finite element modeling (FEM) analyses, optimization and tests. Modeling and predictions were performed and tests were carried out to correlate the test data with the FEM. The optimization procedure consisted of defining a global objective function, using finite difference methods, to determine the optimal values of the design variables through quadratic linear programming. The optimization process was carried out by targeting the highest dynamic displacements of several vibration modes of the structure and finding an optimal treatment configuration that will minimize them. An optimal design was thus derived and laboratory tests were conducted to evaluate its performance under different vibration environments. Three honeycomb composite beams, with Nomex core and aluminum face sheets, empty (untreated), uniformly treated with NOPD, and optimally treated with NOPD, according to the analytically predicted optimal design configuration, were tested in the laboratory. It is shown that the beam with optimal treatment has the lowest response amplitude. Described below are results of modal vibration tests and FEM analyses from predictions of the modal characteristics of honeycomb beams under zero, 50% uniform treatment and an optimal NOPD treatment design configuration and verification with test data.

Panossian, H.

2008-01-01

88

A comparative investigation for the nondestructive testing of honeycomb structures by holographic interferometry and infrared thermography  

NASA Astrophysics Data System (ADS)

The nondestructive testing (NDT) of honeycomb sandwich structures has been the subject of several studies. Classical techniques such as ultrasound testing and x-rays are commonly used to inspect these structures. Holographic interferometry (HI) and infrared thermography (IT) have shown to be interesting alternatives. Holography has been successfully used to detect debonding between the skin and the honeycomb core on honeycomb panels under a controlled environment. Active thermography has proven to effectively identify the most common types of defects (water ingress, debonding, crushed core, surface impacts) normally present in aeronautical honeycomb parts while inspecting large surfaces in a fast manner. This is very attractive for both the inspection during the manufacturing process and for in situ regular NDT assessment. A comparative experimental investigation is discussed herein to evaluate the performance of HI and IT for the NDT on a honeycomb panel with fabricated defects. The main advantages and limitations of both techniques are enumerated and discussed.

Sfarra, S.; Ibarra-Castanedo, C.; Avdelidis, N. P.; Genest, M.; Bouchagier, L.; Kourousis, D.; Tsimogiannis, A.; Anastassopoulous, A.; Bendada, A.; Maldague, X.; Ambrosini, D.; Paoletti, D.

2010-03-01

89

Finite Element Development of Honeycomb Panel Configurations with Improved Transmission Loss  

NASA Technical Reports Server (NTRS)

The higher stiffness-to-mass ratio of a honeycomb panel compared to a homogeneous panel results in a lower acoustic critical frequency. Above the critical frequency the panel flexural wave speed is acoustically fast and the structure becomes a more efficient radiator with associated lower sound transmission loss. Finite element models of honeycomb sandwich structures are presented featuring areas where the core is removed from the radiating face sheet disrupting the supersonic flexural and shear wave speeds that exist in the baseline honeycomb panel. These modified honeycomb panel structures exhibit improved transmission loss for a pre-defined diffuse field sound excitation. The models were validated by the sound transmission loss of honeycomb panels measured in the Structural Acoustic Loads and Transmission (SALT) facility at the NASA Langley Research Center. A honeycomb core panel configuration is presented exhibiting a transmission loss improvement of 3-11 dB compared to a honeycomb baseline panel over a frequency range from 170 Hz to 1000 Hz. The improved transmission loss panel configuration had a 5.1% increase in mass over the baseline honeycomb panel, and approximately twice the deflection when excited by a static force.

Grosveld, Ferdinand W.; Palumbo, Daniel L.; Klos, Jacob; Castle, William D.

2006-01-01

90

Honeycomb Weathering of Limestone Formations  

USGS Multimedia Gallery

Honeycomb weathering of sandstone located on the shores of Puget Sound occurs when expanding salt crystals break fragments of rock, creating a small hole that becomes larger as the process repeats itself over time....

2010-08-16

91

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

Microsoft Academic Search

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

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

1996-01-01

92

Investigation of honeycomb structure using pulse infrared thermography method  

NASA Astrophysics Data System (ADS)

To reduce weight and improve strength in the aerospace industry, composite structure has gained popularity as a replacement for conventional materials and structures, such as adhesive bonding and honeycomb structure. Honeycomb structures composed by a honeycomb core between two facesheets are very common on aerospace parts. However, the adhesive bonding process is more susceptible to quality variations during manufacturing than traditional joining methods. With the large increase in the use of composite materials and honeycomb structures, the need for high speed, large area inspection for fracture critical, sub-surface defects in aircraft, missiles and marine composites led to broad acceptance of infrared based NDT methods. Infrared thermography is one of several non-destructive testing techniques which can be used for defect detection in aircraft materials. 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. In this paper, two kinds of defects which are of various size, shape and location below the test surface are planted in the honeycomb structure, they are all tested by pulsed thermography, analyze the thermal sequence and intensity graph got by this methods, it shows that pulsed thermography is an effective nondestructive technique for inspecting disbonding defect, can distinguish the location and the dimension of the defect exactly.

Li, Huijuan

2010-11-01

93

Method of fabricating lightweight honeycomb structures  

NASA Technical Reports Server (NTRS)

A process is disclosed for fabricating lightweight honeycomb type structures out of material such as silicon carbide (SiC) and silicon (S). The lightweight structure consists of a core to define the shape and size of the structure. The core is coated with an appropriate deposit such as SiC or Si to give the lightweight structure strength and stiffness and for bonding the lightweight structure to another surface. The core is fabricated from extremely thin ribs of appropriately stiff and strong material such as graphite. First, a graphite core consisting of an outer hexagonal cell with six inner triangular cells is constructed from the graphite ribs. The graphite core may be placed on the back-up side of a SiC faceplate and then coated with SiC to produce a monolithic structure without the use of any bonding agent. Cores and methods for the fabrication thereof in which the six inner triangular cells are further divided into a plurality of cells are also disclosed.

Goela, Jitendra S. (Inventor); Pickering, Michael (Inventor); Taylor, Raymond L. (Inventor)

1992-01-01

94

The actuated performance of multi-layer piezoelectric actuator in active vibration control of honeycomb sandwich panel  

Microsoft Academic Search

This paper discusses the use of the multi-layer piezoelectric actuator (MPA) in the active vibration control of the honeycomb sandwich panel (HSP). A literature overview of the available works is first presented. And the main motivation using the MPA in the AVC of HSP is discussed. Then, the honeycomb core is in advance treated as an orthotropic plate. The governing

Yajun Luo; Shilin Xie; Xinong Zhang

2008-01-01

95

Liquid ingress recognition in honeycomb structure by pulsed thermography  

NASA Astrophysics Data System (ADS)

Pulsed thermography has been proven to be a fast and effective method to detect fluid ingress in aircraft honeycomb structure; however, water and hydraulic oil may have similar appearance in the thermal image sequence. It is meaningful to identify what kind of liquid ingress it is for aircraft maintenance. In this study, honeycomb specimens with glass fiber and aluminum skin are injected different kinds of liquids: water and oil. Pulsed thermography is adopted; a recognition method is proposed to first get the reference curve by linear fitting the beginning of the logarithmic curve, and then an algorithm based on the thermal contrast between liquid and reference is used to recognize what kind of fluid it is by calculating their thermal properties. It is verified with the results of theory and the finite element simulation.

Chen, Dapeng; Zeng, Zhi; Tao, Ning; Zhang, Cunlin; Zhang, Zheng

2013-05-01

96

Millimeter Wave Holographical Inspection of Honeycomb Composites  

NASA Technical Reports Server (NTRS)

Multi-layered composite structures manufactured with honeycomb, foam or balsa wood cores are finding increasing utility in a variety of aerospace, transportation, and infrastructure applications. Due to the low conductivity and inhomogeneity associated with these composites standard nondestructive testing (NDT) methods are not always capable of inspecting their interior for various defects caused during the manufacturing process or as a result of in-service loading. On the contrary, microwave and millimeter wave NDT methods are well-suited for inspecting these structures since signals at these frequencies readily penetrate through these structures and reflect from different interior boundaries revealing the presence of a wide range of defects such as disbond, delamination, moisture and oil intrusion, impact damage, etc. Millimeter wave frequency spectrum spans 30 GHz - 300 GHz with corresponding wavelengths of 10 - 1 mm. Due to the inherent short wavelengths at these frequencies, one can produce high spatial resolution images of these composites either using real-antenna focused or synthetic-aperture focused methods. In addition, incorporation of swept-frequency in the latter method (i.e., holography) results in high-resolution three-dimensional images. This paper presents the basic steps behind producing such images at millimeter wave frequencies and the results of two honeycomb composite panels are demonstrated at Q-band (33-50 GHz). In addition, these results are compared to previous results using X-ray computed tomography.

Case, J. T.; Kharkovsky, S.; Zoughi, R.; Stefes, G.; Hepburn, Frank L.; Hepburn, Frank L.

2007-01-01

97

Millimeter Wave Holographical Inspection of Honeycomb Composites  

NASA Astrophysics Data System (ADS)

Multi-layered composite structures manufactured with honeycomb, foam, or balsa wood cores are finding increasing utility in a variety of aerospace, transportation, and infrastructure applications. Due to the low conductivity and inhomogeneity associated with these composites, standard nondestructive testing (NDT) methods are not always capable of inspecting their interior for various defects caused during the manufacturing process or as a result of in-service loading. On the contrary, microwave and millimeter wave NDT methods are well-suited for inspecting these structures since signals at these frequencies readily penetrate through these structures and reflect from different interior boundaries revealing the presence of a wide range of defects such as isband, delamination, moisture and oil intrusion, impact damage, etc. Millimeter wave frequency spectrum spans 30 GHz-300 GHz with corresponding wavelengths of 10-1 mm. Due to the inherent short wavelengths at these frequencies, one can produce high spatial resolution images of these composites either using real-antenna focused or synthetic-aperture focused methods. In addition, incorporation of swept-frequency in the latter method (i.e., holography) results in high-resolution three-dimensional images. This paper presents the basic steps behind producing such images at millimeter wave frequencies and the results of two honeycomb composite panels are demonstrated at Q-band (33-50 GHz). In addition, these results are compared to previous results using X-ray computed tomography.

Case, J. T.; Kharkovsky, S.; Zoughi, R.; Steffes, G.; Hepburn, F. L.

2008-02-01

98

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

Microsoft Academic Search

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

Yanfei He; Rongzhou Gong

2009-01-01

99

Cellular Metal Truss Core Sandwich Structures**  

E-print Network

rigidity. Honeycomb core sandwich structures are the current state-of-the-art choice for weight sensitiveCellular Metal Truss Core Sandwich Structures** By David J. Sypeck* and Haydn N. G. Wadley 1. Introduction Cellular metals have attracted interest as alternatives to honeycomb when used as the cores

Wadley, Haydn

100

Design data for brazed Rene 41 honeycomb sandwich  

NASA Technical Reports Server (NTRS)

Strength data, creep data and residual strength data after cyclic thermal exposure were obtained at temperatures from 78 K to 1144 K (-320 F to 1600 F). The influences of face thickness, core depth, core gage, cell size and thermal/stress exposure conditions on the mechanical design properties were investigated. A braze alloy and process was developed that is adequate to fully develop the strength of the honeycomb core while simultaneously solution treating and aging the Rene 41 fact sheets. New test procedures and test specimen configurations were developed to avoid excessive thermal stresses during cyclic thermal exposure.

Hepler, A. K.; Arnquist, J.; Koetje, E. L.; Esposito, J. J.; Lindsay, V. E. J.; Swegle, A. R.

1981-01-01

101

Quasi-static and impact tests of honeycomb  

NASA Astrophysics Data System (ADS)

In this paper the quasi-static and instrumented compression impact testing of two kinds of aluminum-alloy honeycomb are reported. Those two types of honeycomb called Hard (H) and Soft (S) were tested. The specimens in cubical form of dimensions 60 mm × 60 mm × 120 mm were made with and without the front aluminum alloy plates (thickness 1.0 mm) cemented to the specimen two faces. The tests have been performed along the largest dimension that is 120 mm, which is parallel to the aluminum sheet profiles forming the honeycomb. A wide range of compression velocities from the quasi-static rate (V0 = 10 mm/min) to the highest impact velocity V6 = 120 m/s were applied. The total number of velocities applied, including the quasi-static loading, was six. Several series of tests were performed. The first two were carried out with the flat-ended strikers of specific masses, which were adequate to each impact velocity. In order to obtain an adequate displacement of crushing the condition of constant kinetic energy of a striker was assumed. In addition, conical strikers were applied with the cone angle 120circ. Application of the direct impact arrangement along with properly instrumented 9m long Hopkinson bar of Nylon with diameter 80 mm enabled for a wave dispersion analysis to be applied. The crushing force versus time could be exactly determined at the specimen-bar interface by application of an inverse technique along with the theory of visco-elastic wave propagation.

Gary, G.; Klepaczko, J. R.

2006-08-01

102

Honeycomb vs. foam: Evaluating potential upgrades to ISS module shielding  

NASA Astrophysics Data System (ADS)

A series of 19 hypervelocity impact tests have been performed on ISS-representative structure walls to evaluate the effect on micrometeoroid and orbital debris (MMOD) protective capability caused by replacing honeycomb sandwich panel cores with metallic open-cell foam. In the experiments, secondary impacts on individual foam ligaments were found to raise the thermal state of projectile and bumper fragments, inducing break-up and melt at lower impact velocities than the baseline honeycomb configuration. A ballistic limit equation is derived for the foam-modified configuration, and in comparison with the honeycomb baseline a performance increase of 3-15% at normal incidence was predicted. With increasing impact obliquity, the enhancement in protective capability provided by modification is predicted to further increase. Reduction in penetration and failure risk posed by MMOD impacts is achieved by the foam-modified configuration without a significant decrease in mechanical or thermal performance, and with no additional weight. As such, it is considered a promising upgrade to MMOD shielding on ISS modules, which incorporate honeycomb sandwich panels and are yet to fly.

Ryan, S.; Hedman, T.; Christiansen, E. L.

2010-10-01

103

Materials Science and Engineering A 472 (2008) 242250 Shear behavior of aluminum lattice truss sandwich panel structures  

E-print Network

and more than 40% stiffer and stronger than flexible honeycombs used for the cores of curved sandwich honeycomb structures when configured as the core of a sandwich panel. These lattice sandwich structures and corrosion concerns associated with the use of traditional closed cell honeycomb sandwich panels [22

Wadley, Haydn

104

Elastic wave propagation in hexagonal honeycomb sandwich composite by using piezoelectric actuators/sensors  

NASA Astrophysics Data System (ADS)

Honeycomb composite structures have been widely used in aerospace and aeronautic industries due to their unique characteristics. Due to the complex nature of honeycomb composite with the celled core, structural health monitoring (SHM) of honeycomb composite panels inherently imposes many challenges, which requires a detailed knowledge of dynamic elastic responses of such complex structures in a broad frequency domain. This paper gives numerical and experimental analyses of elastic wave propagation phenomena in sandwich panels with a honeycomb core, especially when the frequency domain of interest is relative high. Numerical simulation based on the Finite Element (FE) method is first performed to investigate wave generation and reception using piezoelectric actuators/sensors. The effectiveness of homogenized core model is discussed, compared with the dynamic responses based on honeycomb celled core model. The reliability of the simulated wave will be verified with the experimental results. Specific attention will be paid on core effects on group wave velocity. This research will establish a solid theoretical foundation for the future study of the structural health monitoring in the composites.

Huang, G. L.; Song, F.; Kim, J.

2009-03-01

105

Honeycomb Sandwich Material Modeling for Dynamic Simulations of Aircraft Interior Components  

Microsoft Academic Search

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

S. Heimbs; P. Middendorf; M. Maier

106

Study on the cell size effect of steady state thermal performance of metallic honeycomb sandwich panels  

NASA Astrophysics Data System (ADS)

In this paper, numerical study is performed to reveal the influences of the cell size on the steady state thermal performance of hexagonal metallic honeycomb sandwich panel, by using the semi-empirical Swann and Pittman formula and the Finite Element Method (FEM), respectively. Based on the same material volume of honeycomb core, two types of hexagonal honeycomb core, i.e., size variation of core cell with a constant core height and height variation of core with a constant side length of hexagonal cell, are considered to establish the panel's thermal analysis model, which including the conduction and radiation coupling. Comparisons between the temperature distribution results from both methods show that FEM can reveal the size effect of the honeycomb cell on the thermal performances of sandwich panel while the Swann and Pittman formula can not. At the same time, numerical results show that for the core with constant height, the panel thermal performance analyzed by FEM has a tendency of being close to the results obtained from Swann and Pittman formula as the core cell size decreases; whereas, if the hexagonal cell with constant side length is concerned, the greater the core height, the worse the thermal conductive performance of sandwich panel. Besides, analyses based on both methods also show that the temperature distribution of the lower surface of panel becomes gradually uniform when the wall thickness of hexagonal cell decreases.

Lai, Yu-dong; Sun, Shi-ping

2011-11-01

107

Theoretical design and analysis of a honeycomb panel sandwich structure loaded in pure bending  

Microsoft Academic Search

This paper discusses the theoretical and quantitative design and analysis of a honeycomb panel sandwich structure. The initial design is based on specific requirements that the panel must achieve prior to failure under load. Materials to be used for the facing and core are selected based on the given requirements. With the materials chosen, the facing sheets and core are

Gaetano G. Galletti; Christine Vinquist; Omar S. Es-Said

2008-01-01

108

The role of the resin fillet in the delamination of honeycomb sandwich structures  

Microsoft Academic Search

In this study, the mechanism of peel fracture (or core\\/skin delamination) in honeycomb-core sandwich panels was investigated, and the role of resin fillets on energy absorption was elucidated. Fillet deformation and fracture were shown to control the delamination resistance of sandwich panels, to a great extent. In fact the area fraction of fillets on the fracture surface proved to be

Ryo Okada; M. T Kortschot

2002-01-01

109

Study on the cell size effect of steady state thermal performance of metallic honeycomb sandwich panels  

NASA Astrophysics Data System (ADS)

In this paper, numerical study is performed to reveal the influences of the cell size on the steady state thermal performance of hexagonal metallic honeycomb sandwich panel, by using the semi-empirical Swann and Pittman formula and the Finite Element Method (FEM), respectively. Based on the same material volume of honeycomb core, two types of hexagonal honeycomb core, i.e., size variation of core cell with a constant core height and height variation of core with a constant side length of hexagonal cell, are considered to establish the panel's thermal analysis model, which including the conduction and radiation coupling. Comparisons between the temperature distribution results from both methods show that FEM can reveal the size effect of the honeycomb cell on the thermal performances of sandwich panel while the Swann and Pittman formula can not. At the same time, numerical results show that for the core with constant height, the panel thermal performance analyzed by FEM has a tendency of being close to the results obtained from Swann and Pittman formula as the core cell size decreases; whereas, if the hexagonal cell with constant side length is concerned, the greater the core height, the worse the thermal conductive performance of sandwich panel. Besides, analyses based on both methods also show that the temperature distribution of the lower surface of panel becomes gradually uniform when the wall thickness of hexagonal cell decreases.

Lai, Yu-dong; Sun, Shi-ping

2012-04-01

110

Load-dependent Optimization of Honeycombs for Sandwich Components - New Possibilities by Using Additive Layer Manufacturing  

NASA Astrophysics Data System (ADS)

Due to their feasible geometric complexity, additive layer manufacturing (ALM) processes show a highpotential for the production of lightweight components.Therefore, ALM processes enable the realization of bionic-designedcomponents like honeycombs, which are optimized depending upon load and outer boundary conditions.This optimization is based on a closed-loop, three-steps methodology: At first, each honeycomb is conformed to the surface of the part. Secondly, the structure is optimizedfor lightweight design.It is possible to achieve a homogeneous stress distribution in the part by varying the wall thickness, honeycombdiameter and the amount of honeycombs, depending on the subjected stresses and strains. At last, the functional components like threads or bearing carriers are integrated directly into the honeycomb core.Using all these steps as an iterative process, it is possible to reduce the mass of sandwich components about 50 percent compared to conventional approaches.

Riss, Fabian; Schilp, Johannes; Reinhart, Gunther

111

Multiple debondings' detection in honeycomb sandwich structures using multi-frequency elastic guided waves  

NASA Astrophysics Data System (ADS)

Due to the complex nature of sandwich structures, damage detection in honeycomb sandwich structures inherently imposes many challenges. In this study, leaky guided wave properties generated by piezoelectric wafer actuators/sensors in honeycomb sandwich structures are first simulated by the finite element method. In the numerical model, the detailed honeycomb core geometry is considered. Differential features due to presence of debonding are determined through an appropriate damage index analysis of the signals at the normal and debonded conditions. The image of the debonding is formed by using a probability analysis of the leaky guided wave at each frequency. The final image of the structure can be fused from multi-frequency leaky guided waves. A new method for multi-debonding detection is proposed. Based on the analysis, information about the debondings in the honeycomb sandwich structures can be quantitatively characterized.

Song, F.; Huang, G. L.; Kim, J. H.; Haran, S.

2010-03-01

112

Core polarization for the electric quadrupole moment of neutron-rich aluminum isotopes  

SciTech Connect

The core polarization effects for the electric quadrupole moments of the neutron-rich {sup 31}Al, {sup 33}Al, and {sup 35}Al isotopes in the vicinity of the island of inversion are investigated by means of the microscopic particle-vibration coupling model in which the Skyrme Hartee-Fock-Bogoliubov and quasiparticle random-phase approximations are used to calculate the single-quasiparticle wave functions and the excitation modes. It is found that the polarization charge for the proton 1d{sub 5/2} hole state in {sup 33}Al is quite sensitive to coupling to the neutrons in the pf-shell associated with the pairing correlations and that the polarization charge in {sup 35}Al becomes larger due to the stronger collectivity of the low-lying quadrupole vibrational mode in the neighboring {sup 36}Si nucleus.

Yoshida, Kenichi [RIKEN Nishina Center for Accelerator-Based Science, Wako, Saitama 351-0198 (Japan)

2009-05-15

113

Structural Physics of Bee Honeycomb  

NASA Astrophysics Data System (ADS)

Honeybee combs have aroused interest in the ability of honeybees to form regular hexagonal geometric constructs since ancient times. Here we use a real space technique based on the pair distribution function (PDF) and radial distribution function (RDF), and a reciprocal space method utilizing the Debye-Waller Factor (DWF) to quantify the order for a range of honeycombs made by Apis mellifera. The PDFs and RDFs are fit with a series of Gaussian curves. We characterize the order in the honeycomb using a real space order parameter, OP3, to describe the order in the combs and a two-dimensional Fourier transform from which a Debye-Waller order parameter, u, is derived. Both OP3 and u take values from [0, 1] where the value one represents perfect order. The analyzed combs have values of OP3 from 0.33 to 0.60 and values of u from 0.83 to 0.98. RDF fits of honeycomb histograms show that naturally made comb can be crystalline in a 2D ordered structural sense, yet is more `liquid-like' than cells made on `foundation' wax. We show that with the assistance of man-made foundation wax, honeybees can manufacture highly ordered arrays of hexagonal cells.

Kaatz, Forrest; Bultheel, Adhemar; Egami, Takeshi

2008-03-01

114

Constraints on formation processes of two coarse-grained calcium- aluminum-rich inclusions: A study of mantles, islands and cores  

Microsoft Academic Search

Many coarese-grained calcium- aluminum-rich inclusions (CAIs) contain features that are inconsistent with equilibrium liquid crystallization models of origin. Spinel-free islands (SFIs) in spinel-rich cores of Type B CAIs are examples of such features. One model previously proposed for the origin of Allende 5241, a Type B1 CAI containing SFIs, involves the capture and assimilation of xenoliths by a liquid droplet

Gregory P. Meeker

1995-01-01

115

Fabrication and development of several heat pipe honeycomb sandwich panel concepts. [airframe integrated scramjet engine  

NASA Technical Reports Server (NTRS)

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

Tanzer, H. J.

1982-01-01

116

Fabrication and development of several heat pipe honeycomb sandwich panel concepts. Final report  

SciTech Connect

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

Tanzer, H.J.

1982-06-01

117

Hypervelocity Impact Performance of Open Cell Foam Core Sandwich Panel Structures  

NASA Technical Reports Server (NTRS)

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

Ryan, Shannon; Christiansen, Eric; Lear, Dana

2009-01-01

118

Design of composite hollow-core panels  

SciTech Connect

A design method is proposed to describe the static behavior of hollow-core panels under flexure. These panels are made of diagonal stiffeners placed between two faces with a composite material (carbon-epoxy). The hollow-core panels and the design method were both developed by the ENPC for the making of structural components having a high stiffness/weight ratio. An analytical model based on a periodic media homogenization method was developed to obtain the constitutive law of the equivalent homogeneous panel. The accuracy of this model was assessed by comparing the calculated deflections with those of another 3D finite element model. An optimization method, based on the Euler equations, was further developed to provide the minimum weight for a given deflection. The faces and the stiffeners thicknesses were set as variables for the optimization process. With the partnership of the SNCF (the French railroads company), this method was applied to the design of the intermediate floor of the two-levels cabins for the TGV trains (high speed trains). The deflection of the aluminum honeycomb core sandwich floor already used by the SNCF was computed and, afterwards, the optimization method was used to find a hollow-core floor having the same deflection but a minimum weight. The results of the optimization clearly indicate that it is possible to reduce the aluminum TGV floor weight to one third.

Philippe, M.H.; Naciri, T.; Ehrlacher, A. [CERAM-ENPC, Noisy-le-Grand (France)

1996-11-01

119

Optimized analysis of geometry parameters for honeycomb sandwich mirror  

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

120

The Soudan 2 honeycomb calorimeter  

SciTech Connect

Soudan 2 is an 1100-ton honeycomb tracking calorimeter which is being constructed to search for nucleon decay. The detector consists of finely segmented iron instrumented with long drift tubes, and records three spatial coordinates and dE/dx for every gas crossing. Excellent event reconstruction capability, particle identification and muon sign and direction determination give superior rejection of the neutrino background to nucleon decay in many modes. The first 620 tons of Soudan 2 are now in steady operation, with completion planned for 1992. Detector performance has been studied using cosmic ray tracks and a charged test beam calibration. Results on detector performance and detector response are described in this paper. 2 refs. , 11 figs.

Garcia-Garcia, C.

1990-12-01

121

Honeycomb Mirrors for Large Telescopes  

NASA Astrophysics Data System (ADS)

This chapter deals with the design, fabrication, and use of the borosilicateglass honeycomb mirrors which are being produced at the University ofArizona's Steward Observatory Mirror Laboratory. These mirrors are a coretechnology for the whole telescope, and a number of telescopes are nowoperational using these primary mirrors. The mirrors contribute to the telescopedesign because of their light weight, their high stiffness, and their shortthermal time constant. The light weight of the primary mirrors helps to keepthe weight of the entire telescope low and to maximize the structuralperformance. The ability to circulate air through the glass honeycombstructure allows control of local seeing in the telescope environment. Thehoneycomb sandwich is formed by spin casting borosilicate glass into aceramic fiber mold. The Mirror Lab has previously produced three 3.5-mmirrors, three 6.5-m mirrors, and two 8.4-m mirrors which are now operatingsuccessfully in telescopes. Results are highlighted from these telescopes withemphasis on the Large Binocular Telescope with two 8.4 m primaries.Excellent results have been obtained with adaptive secondary mirrorsin combination with the honeycomb primary mirrors. Two additional6.5-m mirrors and two additional 8.4-m mirrors have also been cast andare in various stages of production for other projects including the firstoff-axis segment for the future Giant Magellan Telescope. An additional keytechnology for large telescopes is the ability to fabricate high-precision primaryoptics with short focal lengths in order to keep the telescope structure andenclosure compact. The stressed lap allows efficient polishing of thesefast conic surfaces by actively adjusting its shape as it strokes across themirror.

Hill, John; Martin, Hubert; Angel, Roger

122

Dynamic and quasi-static deformation of aluminium honeycomb sandwich panel in three point bending  

Microsoft Academic Search

In this research, the dynamic and quasi-static deformations of aluminium honeycomb sandwich panels in three point bending were investigated experimentally. The load, the deflection of a loading point and the strain response of the rear surface plate at various locations were measured. A peak load caused by local plastic buckling of the cores just under the loading point appeared in

H. Kobayashi; M. Daimaruya; Y. Takaya

2003-01-01

123

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

Microsoft Academic Search

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

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

2008-01-01

124

Mechanical response of metallic honeycomb sandwich panel structures to high-intensity dynamic loading  

Microsoft Academic Search

Explosive tests were performed in air to study the dynamic mechanical response of square honeycomb core sandwich panels made from a super-austenitic stainless steel alloy. Tests were conducted at three levels of impulse load on the sandwich panels and solid plates with the same areal density. Impulse was varied by changing the charge weight of the explosive at a constant

Kumar P. Dharmasena; Haydn N. G. Wadley; Zhenyu Xue; John W. Hutchinson

2008-01-01

125

Strength reduction behavior of honeycomb sandwich structure subjected to low-velocity impact  

Microsoft Academic Search

The paper deals with the effect of constituent materials on impact damage and strength reduction of a sandwich structure, composed of laminated facesheets and Nomex® honeycomb core. Low-velocity impact tests were performed and damage was inspected by scanning acoustic microscopy. In addition, static tests were conducted under flexural loading. The damage behavior is characterized through the energy absorbed during impact.

Ki-Weon Kang; Heung Seob Kim; Man Sig Kim; Jung-Kyu Kim

2008-01-01

126

Constraints on formation processes of two coarse-grained calcium- aluminum-rich inclusions: a study of mantles, islands and cores  

USGS Publications Warehouse

Many coarse-grained calcium- aluminum-rich inclusions (CAIs) contain features that are inconsistent with equilibrium liquid crystallization models of origin. Spinel-free islands (SFIs) in spinel-rich cores of Type B CAIs are examples of such features. One model previously proposed for the origin of Allende 5241, a Type B1 CAI containing SFIs, involves the capture and assimilation of xenoliths by a liquid droplet in the solar nebula (El Goresy et al, 1985; MacPherson et al 1989). This study reports new textural and chemical zoning data from 5241 and identifies previously unrecognized chemical zoning patterns in the melilite mantle and in a SFI. -from Author

Meeker, G.P.

1995-01-01

127

Comparison of experimental and theoretical turbulence reduction characteristics for screens, honeycomb, and honeycomb-screen combinations  

NASA Technical Reports Server (NTRS)

Turbulence reduction research using screens, honeycomb, and combinations thereof was conducted in a half-scale model of a portion of the Langley 8-foot transonic pressure tunnel. It was found that screens alone reduce axial turbulence more than lateral turbulence; whereas, honeycomb alone reduces laterial turbulence more than axial turbulence. Because of this difference, the physical mechanism for decreasing turbulence for screens and honeycomb must be completely different. It is concluded that honeycomb with a downstream screen is an excellent combination for reducing turbulences.

Scheiman, J.

1981-01-01

128

Ceramic honeycomb structures and the method thereof  

NASA Technical Reports Server (NTRS)

The subject invention pertains to a method of producing an improved composite-composite honeycomb structure for aircraft or aerospace use. Specifically, the subject invention relates to a method for the production of a lightweight ceramic-ceramic composite honeycomb structure, which method comprises: (1) pyrolyzing a loosely woven fabric/binder having a honeycomb shape and having a high char yield and geometric integrity after pyrolysis at between about 700 and 1,100 C; (2) substantially evenly depositing at least one layer of ceramic material on the pyrolyzed fabric/binder of step (1); (3) recovering the coated ceramic honeycomb structure; (4) removing the pyrolyzed fabric/binder of the structure of step (3) by slow pyrolysis at between 700 and 1000 C in between about a 2 to 5% by volume oxygen atmosphere for between about 0.5 and 5 hr.; and (5) substantially evenly depositing on and within the rigid hollow honeycomb structure at least one additional layer of the same or a different ceramic material by chemical vapor deposition and chemical vapor infiltration. The honeycomb shaped ceramic articles have enhanced physical properties and are useful in aircraft and aerospace uses.

Riccitiello, Salvatore R. (inventor); Cagliostro, Domenick E. (inventor)

1987-01-01

129

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

Microsoft Academic Search

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

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

2009-01-01

130

Perturbative approach to an exactly solved problem: Kitaev honeycomb model  

NASA Astrophysics Data System (ADS)

We analyze the gapped phase of the Kitaev honeycomb model perturbatively in the isolated-dimer limit. Our analysis is based on the continuous unitary transformations method, which allows one to compute the spectrum as well as matrix elements of operators between eigenstates at high order. The starting point of our study consists of an exact mapping of the original honeycomb spin system onto a square-lattice model involving an effective spin and a hard-core boson. We then derive the low-energy effective Hamiltonian up to order 10 which is found to describe an interacting-anyon system, contrary to the order 4 result which predicts a free theory. These results give the ground-state energy in any vortex sector and thus also the vortex gap, which is relevant for experiments. Furthermore, we show that the elementary excitations are emerging free fermions composed of a hard-core boson with an attached spin- and phase-operator string. We also focus on observables and compute, in particular, the spin-spin correlation functions. We show that they admit a multiplaquette expansion that we derive up to order 6. Finally, we study the creation and manipulation of anyons with local operators, show that they also create fermions, and discuss the relevance of our findings for experiments in optical lattices.

Vidal, Julien; Schmidt, Kai Phillip; Dusuel, Sébastien

2008-12-01

131

An elastic analysis of a honeycomb structure with negative Poisson’s ratio  

NASA Astrophysics Data System (ADS)

This paper presents a novel honeycomb structure that exhibits a negative Poisson’s ratio (NPR). In contrast to other NPR honeycomb structures studied in the past, the new structure can be easily fabricated using conventional technology and materials on a large scale of production with a low cost. The geometry of the structure is first described, and then an elastic analysis based on standard beam theory is carried out to establish the relation of its Young’s modulus with relevant geometrical parameters and material properties. The effects of the geometrical parameters in non-dimensional forms on the Young’s modulus of the structure are discussed. The compressive tests were performed on samples of the structure made with the same aluminum alloy but with different geometrical parameters to verify the theoretical analysis. The results obtained from both the theoretical calculations and experiments show that the proposed NPR honeycomb structure has a very obvious NPR behavior. Moreover, its elastic modulus is significantly affected by its geometrical parameters, and can be optimized for specific applications through the design and control of honeycomb geometry parameters.

Zhang, Z. K.; Hu, H.; Xu, B. G.

2013-08-01

132

Design and fabrication of a radiative actively cooled honeycomb sandwich structural panel for a hypersonic aircraft  

NASA Technical Reports Server (NTRS)

The panel assembly consisted of an external thermal protection system (metallic heat shields and insulation blankets) and an aluminum honeycomb structure. The structure was cooled to temperature 442K (300 F) by circulating a 60/40 mass solution of ethylene glycol and water through dee shaped coolant tubes nested in the honeycomb and adhesively bonded to the outer skin. Rene'41 heat shields were designed to sustain 5000 cycles of a uniform pressure of + or - 6.89kPa (+ or - 1.0 psi) and aerodynamic heating conditions equivalent to 136 kW sq m (12 Btu sq ft sec) to a 422K (300 F) surface temperature. High temperature flexible insulation blankets were encased in stainless steel foil to protect them from moisture and other potential contaminates. The aluminum actively cooled honeycomb sandwich structural panel was designed to sustain 5000 cycles of cyclic in-plane loading of + or - 210 kN/m (+ or - 1200 lbf/in.) combined with a uniform panel pressure of + or - 6.89 kPa (?1.0 psi).

Ellis, D. A.; Pagel, L. L.; Schaeffer, D. M.

1978-01-01

133

Thermographic nondestructive testing (TNDT) of honeycomb composite structural parts of Atlas space launch vehicles  

SciTech Connect

Thermography is a means of recording the patterns of heat emission from a surface. Thermographic nondestructive testing (TNDT) uses this technology to detect sub-surface defects. Generally, a heat pulse is applied to a surface that is thermographically monitored. If a sub-surface defect exists that locally reduces or improves the thermal properties of the material, the surface thermal pattern will be perturbed over the defect. TNDT has been used successfully on a wide variety of composite laminates, filament-wound structures, sandwich structures, and foam-insulated cryogenic tanks. Both real structures with real delamination and impact damage, as well as test panels with simulated delaminations, face sheet disbonds, and interply implants have been tested. For some of these applications, TNDT is the best technique. The thrust structure at the aft end of the Atlas space launch vehicle is a composite sandwich comprised of aluminum honeycomb core with fiberglass/phenolic face sheets. The surface area of this structure is approximately 600 ft{sup 2}. In 1992, General Dynamics Space Systems Division (GDSS) began using TNDT for quality verification of these complex composite parts. TNDT has been used on these parts during manufacture and assembly, and on the launch pad at Cape Canaveral. The NDT technique previously used on these parts, since their design in 1957, was ``coin tap.`` Compared to this method, TNDT provides a greatly improved inspection in less time and at a lower cost. A heat gun with a diffuser attachment is used to heat the inspection area while the area is monitored thermographically. TNDT is a rapid, remote, non-contact, highly portable, real-time scanning technique that can provide a well-documented video record of subsurface structural details including facesheet disbonds and skin delaminations. A specification and test procedure has been written, equipment has been procured, and personnel have been trained and certified.

Burleigh, D.D.; Kuhns, D.R.; Cowell, S.D.; Engel, J.E. [General Dynamics Space Systems Division, San Diego, CA (United States)

1994-12-31

134

A comparison of experimental and theoretical turbulence reduction from screens, honeycomb and honeycomb-screen combinations  

NASA Technical Reports Server (NTRS)

A 1/2-scale model of a portion of the NASA Langley 8-foot transonic pressure tunnel was used to conduct some turbulence reduction research. The experimental results are correlated with various theories. Screens alone reduce axial turbulence more than the lateral turbulence; whereas, honeycomb alone reduce lateral turbulence more than axial turbulence. Because of this difference, the physical mechanism for decreasing turbulence for screens and honeycomb must be completely different. Honeycomb with a downstream screen is an excellent combination for reducing turbulence.

Scheiman, J.; Brooks, J. D.

1980-01-01

135

Method and apparatus for extruding large honeycombs  

DOEpatents

Extrusion die apparatus and an extrusion method for extruding large-cross-section honeycomb structures from plasticized ceramic batch materials are described, the apparatus comprising a die having a support rod connected to its central portion, the support rod being anchored to support means upstream of the die. The support rod and support means act to limit die distortion during extrusion, reducing die strain and stress to levels permitting large honeycomb extrusion without die failure. Dies of optimal thickness are disclosed which reduce the maximum stresses exerted on the die during extrusion.

Kragle, Harry A. (Corning, NY); Lambert, David W. (Corning, NY); Lipp, G. Daniel (Painted Post, NY)

1996-09-03

136

Impact behavior and energy absorption of paper honeycomb sandwich panels  

Microsoft Academic Search

Dynamic cushioning tests were conducted by free drop and shock absorption principle. The effect of paper honeycomb structure factors on the impact behavior was analyzed. Results of many experiments show that the dynamic impact curve of paper honeycomb sandwich panel is concave and upward; the thickness and length of honeycomb cell-wall have a great effect on its cushioning properties; increasing

Dongmei Wang

2009-01-01

137

PT-symmetry in honeycomb photonic lattices  

SciTech Connect

We apply gain and loss to honeycomb photonic lattices and show that the dispersion relation is identical to tachyons--particles with imaginary mass that travel faster than the speed of light. This is accompanied by -symmetry breaking in this structure. We further show that the -symmetry can be restored by deforming the lattice.

Szameit, Alexander; Rechtsman, Mikael C.; Bahat-Treidel, Omri; Segev, Mordechai [Physics Department and Solid State Institute, Technion, 32000 Haifa (Israel)

2011-08-15

138

Mechanics and applications of pressure adaptive honeycomb  

Microsoft Academic Search

A novel adaptive aerostructure is presented that relies on certified aerospace materials and can therefore be applied in conventional passenger aircraft. This structure consists of a honeycomb material which' cells extend over a significant length perpendicular to the plane of the cells. Each of the cells contains an inelastic pouch (or bladder) that forms a circular tube when the cell

Roelof Vos

2009-01-01

139

Classification of triangular and honeycomb cellular automata  

NASA Astrophysics Data System (ADS)

Cellular automata on a two-dimensional triangular and honeycomb lattice are classified according to their fixed points and periods. The results are compared with other lattices in one of three dimensions. We also compare the totalistic rules for all mentioned lattices.

Gerling, R. W.

1990-01-01

140

Calculating Transport Of Moisture Through Honeycomb Panels  

NASA Technical Reports Server (NTRS)

Diffusion equations solved for steady-state and transient conditions. HUMID is computer program for predicting moisture gradients and internal bursting pressure in composite honeycomb-sandwich panels. Designed to monitor ebb and flow of moisture in Space Shuttle Orbiter payload bay doors, but applicable for general use. Written in FORTRAN.

Martin, R. T.; Zigrang, D. J.

1987-01-01

141

Honeycomb Betavoltaic Battery for Space Applications  

Microsoft Academic Search

Radioisotopic batteries offer advantages relative to conventional chemical batteries for applications requiring a long lifetime with minimum maintenance. Thus, thermoelectric type cells fueled with Pu have been used extensively on NASA space missions. The design for a small beta battery using nickel-63 (Ni-63) and a vacuum direct collection method is described here. A honeycomb nickel wire structure is employed to

Jin R. Lee; Ben Ulmen; George H. Miley

2008-01-01

142

Honeycomb Geometry: Applied Mathematics in Nature.  

ERIC Educational Resources Information Center

Study and exploration of the hexagonal shapes found in honeycombs is suggested as an interesting topic for geometry classes. Students learn that the hexagonal pattern maximizes the enclosed region and minimizes the wax needed for construction, while satisfying the bees' cell-size constraint. (MNS)

Roberts, William J.

1984-01-01

143

Viscoelastic Analysis of Sandwich Beams Having Aluminum and Fiber-reinforced Polymer Skins with a Polystyrene Foam Core  

E-print Network

Sandwich beams are composite systems having high stiffness-to-weight and strength-to-weight ratios and are used as light weight load bearing components. The use of thin, strong skin sheets adhered to thicker, lightweight core materials has allowed...

Roberts-Tompkins, Altramese L.

2010-07-14

144

Tensile mechanical properties of metal honeycomb sandwich structure with interface connection defects  

NASA Astrophysics Data System (ADS)

Thermal protection system is one of the key technologies of reusable launch vehicle (RLV). The ARMOR TPS is one of important candidate structure of RLV. ARMOR TPS has many advantages, for example: fixing easily, longer life, good properties, short time of maintenance and service. In comparison with traditional TPS, the ARMOR TPS will be the best selection for all kinds of RLV. So the ARMOR thermal protection system will be used in aviation and spaceflight field more and more widely because of its much better performance. ARMOR TPS panel is above the whole ARMOR TPS, and the metal honeycomb sandwich structure is the surface of the ARMOR TPS panel. So the metal honeycomb sandwich structure plays an important role in the ARMOR TPS, while it bears the flight dynamic pressure and stands against the flight dynamic calefaction. Because the active environment of metal honeycomb sandwich structure is very formidable, it can produce interface connection defects which can exist in the process of manufacture as well. Tensile mechanical properties of the metallic honeycomb sandwich structure with defects are analyzed to obtain damage tolerance of the structure. The effect of shape, dimension and location of defects on the tensile mechanical properties is conducted by experimental study. Then finite element analysis is performed to validate the experimental results. Haynes214 which is a kind of super alloy materials with high performances is chosen as both face sheet and core in this paper.

He, Xiaodong; Kong, Xianghao

2010-04-01

145

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

Microsoft Academic Search

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

Eric J Herup; Anthony N Palazotto

1998-01-01

146

Effective elastic characteristics of honeycomb sandwich composite shells made of generally orthotropic materials  

Microsoft Academic Search

This paper works on the analytical development of the method of two-scale asymptotic homogenization. The technique is used to determine the effective elastic stiffnesses of hexagonal honeycomb-cored structural sandwich composite shells made of generally orthotropic materials. Orthotropy of the constituent materials leads to much more complex unit-cell problems and is considered in the present paper for the first time. At

Gobinda C. Saha; Alexander L. Kalamkarov; Anastasis V. Georgiades

2007-01-01

147

The low velocity impact response of an aluminium honeycomb sandwich structure  

Microsoft Academic Search

The low velocity impact response of two aluminium honeycomb sandwich structures has been investigated by conducting drop-weight impact tests using an instrumented falling-weight impact tower. Initially, the rate-sensitivity of the glass fibre reinforced\\/epoxy skins and aluminium core was investigated through a series of flexure, shear and indentation tests. Here, it was found that the flexural modulus of the composite skins

W. J. Cantwell

2003-01-01

148

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

NASA Technical Reports Server (NTRS)

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

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

1978-01-01

149

Zero-energy states and fragmentation of spin in the easy-plane antiferromagnet on a honeycomb lattice  

E-print Network

The core of the vortex in the Neel order parameter for an easy-plane antiferromagnet on honeycomb lattice is demonstrated to bind two zero-energy states. Remarkably, a single electron occupying this mid-gap band has its spin fragmented between the two sublattices: Whereas it yields a vanishing total magnetization it shows a finite Neel order, orthogonal to the one of the assumed background. The requisite easy-plane anisotropy may be introduced by a magnetic field parallel to the graphene layer, for example. The results are relevant for spin-1/2 fermions on graphene's or optical honeycomb lattice, in the strongly interacting regime.

Igor F. Herbut

2007-04-18

150

Thermographic Inspection of Metallic Honeycomb Sandwich Structures  

NASA Technical Reports Server (NTRS)

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

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

1998-01-01

151

Engineering polar discontinuities in honeycomb lattices  

NASA Astrophysics Data System (ADS)

Unprecedented and fascinating phenomena have been recently observed at oxide interfaces between centrosymmetric cubic materials, where polar discontinuities can give rise to polarization charges and electric fields that drive a metal–insulator transition and the appearance of a two-dimensional electron gas. Lower-dimensional analogues are possible, and honeycomb lattices offer a fertile playground, thanks to their versatility and the extensive ongoing experimental efforts in graphene and related materials. Here we suggest different realistic pathways to engineer polar discontinuities in honeycomb lattices and support these suggestions with extensive first-principles calculations. Several approaches are discussed, based on (i) nanoribbons, where a polar discontinuity against the vacuum emerges, and (ii) functionalizations, where covalent ligands are used to engineer polar discontinuities by selective or total functionalization of the parent systems. All the cases considered have the potential to deliver innovative applications in ultra-thin and flexible solar-energy devices and in micro- and nano-electronics.

Gibertini, Marco; Pizzi, Giovanni; Marzari, Nicola

2014-10-01

152

Engineering polar discontinuities in honeycomb lattices.  

PubMed

Unprecedented and fascinating phenomena have been recently observed at oxide interfaces between centrosymmetric cubic materials, where polar discontinuities can give rise to polarization charges and electric fields that drive a metal-insulator transition and the appearance of a two-dimensional electron gas. Lower-dimensional analogues are possible, and honeycomb lattices offer a fertile playground, thanks to their versatility and the extensive ongoing experimental efforts in graphene and related materials. Here we suggest different realistic pathways to engineer polar discontinuities in honeycomb lattices and support these suggestions with extensive first-principles calculations. Several approaches are discussed, based on (i) nanoribbons, where a polar discontinuity against the vacuum emerges, and (ii) functionalizations, where covalent ligands are used to engineer polar discontinuities by selective or total functionalization of the parent systems. All the cases considered have the potential to deliver innovative applications in ultra-thin and flexible solar-energy devices and in micro- and nano-electronics. PMID:25300521

Gibertini, Marco; Pizzi, Giovanni; Marzari, Nicola

2014-01-01

153

Radiated Sound Power from a Curved Honeycomb Panel  

NASA Technical Reports Server (NTRS)

The validation of finite element and boundary element model for the vibro-acoustic response of a curved honeycomb core composite aircraft panel is completed. The finite element and boundary element models were previously validated separately. This validation process was hampered significantly by the method in which the panel was installed in the test facility. The fixture used was made primarily of fiberboard and the panel was held in a groove in the fiberboard by a compression fitting made of plastic tubing. The validated model is intended to be used to evaluate noise reduction concepts from both an experimental and analytic basis simultaneously. An initial parametric study of the influence of core thickness on the radiated sound power from this panel, using this numerical model was subsequently conducted. This study was significantly influenced by the presence of strong boundary condition effects but indicated that the radiated sound power from this panel was insensitive to core thickness primarily due to the offsetting effects of added mass and added stiffness in the frequency range investigated.

Robinson, Jay H.; Buehrle, Ralph D.; Klos, Jacob; Grosveld, Ferdinand W.

2003-01-01

154

Forced convection in metallic honeycomb structures  

Microsoft Academic Search

The heat transfer and pressure drop characteristics of sandwiched metallic honeycomb structures, with one face-sheet heated by constant heat flux and cooled by forced air convection, have been investigated both experimentally and numerically. Six test samples, made of two materials with different thermal conductivities (16.2W\\/(mK) for stainless steel and 401W\\/(mK) for pure copper), were evaluated. The effect of cell shapes

T. Wen; J. Tian; T. J. Lu; D. T. Queheillalt; H. N. G. Wadley

2006-01-01

155

Collapse mechanism maps for the hollow pyramidal core of a sandwich panel under transverse shear  

E-print Network

alternatives to prismatic (corrugated) and honeycomb structures when configured as the core of a sandwich panel concerns associated with the use of traditional closed cell honeycomb sandwich panels (Blitzer, 1997Collapse mechanism maps for the hollow pyramidal core of a sandwich panel under transverse shear S

Fleck, Norman A.

156

Titanium honeycomb acoustic lining structural and thermal test report. [for acoustic tailpipe for JT8D engine  

NASA Technical Reports Server (NTRS)

The results are presented of static, fatigue and thermal testing of titanium honeycomb acoustic panels representing the acoustic tailpipe for the Pratt and Whitney Aircraft JT8D Refan engine which is being studied for use on the Boeing 727-200 airplane. Test specimens represented the engine and tailpipe flange joints, the rail to which the thrust reverser is attached and shear specimens of the tailpipe honeycomb. Specimens were made in four different batches with variations in configuration, materials and processes in each. Static strength of all test specimens exceeded the design ultimate load requirements. Fatigue test results confirmed that aluminum brazed titanium, as used in the Refan tailpipe design, meets the fatigue durability objectives. Quality of welding was found to be critical to life, with substandard welding failing prematurely, whereas welding within the process specification exceeded the panel skin life. Initial fatigue testing used short grip length bolts which failed prematurely. These were replaced with longer bolts and subsequent testing demonstrated the required life. Thermal tests indicate that perforated skin acoustic honeycomb has approximately twice the heat transfer of solid skin honeycomb.

Joynes, D.; Balut, J. P.

1974-01-01

157

High-Fidelity Modeling for Health Monitoring in Honeycomb Sandwich Structures  

NASA Technical Reports Server (NTRS)

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

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

2011-01-01

158

Epitaxial graphene on SiC(0001): more than just honeycombs.  

PubMed

Using scanning tunneling microscopy with Fe-coated W tips and first-principles calculations, we show that the interface of epitaxial graphene/SiC(0001) is a warped graphene layer with hexagon-pentagon-heptagon (H(5,6,7)) defects that break the honeycomb symmetry, thereby inducing a gap and states below E(F near the K point. Although the next graphene layer assumes the perfect honeycomb lattice, its interaction with the warped layer modifies )the dispersion about the Dirac point. These results explain recent angle-resolved photoemission and carbon core-level shift data and solve the long-standing problem of the interfacial structure of epitaxial graphene on SiC(0001). PMID:20868110

Qi, Y; Rhim, S H; Sun, G F; Weinert, M; Li, L

2010-08-20

159

SOUND TRANSMISSION THROUGH A CYLINDRICAL SANDWICH SHELL WITH HONEYCOMB CORE  

Microsoft Academic Search

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

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

1996-01-01

160

Calculation of the elastic properties of a triangular cell core for lightweight composite mirrors  

NASA Astrophysics Data System (ADS)

The use of composite materials in the fabrication of optical telescope mirrors offers many advantages over conventional methods, including lightweight, portability and the potential for lower manufacturing costs. In the construction of the substrate for these mirrors, sandwich construction offers the advantage of even lower weight and higher stiffness. Generally, an aluminum or Nomex honeycomb core is used in composite applications requiring sandwich construction. However, the use of a composite core offers the potential for increased stiffness and strength, low thermal distortion compatible with that of the facesheets, the absence of galvanic corrosion and the ability to readily modify the core properties. In order to design, analyze and optimize these mirrors, knowledge of the mechanical properties of the core is essential. In this paper, the mechanical properties of a composite triangular cell core (often referred to as isogrid) are determined using finite element analysis of a representative unit cell. The core studied offers many advantages over conventional cores including increased thermal and dimensional stability, as well as low weight. Results are provided for the engineering elastic moduli of cores made of high stiffness composite material as a function of the ply layup and cell size. Finally, in order to illustrate the use of these properties in a typical application, a 1.4-m diameter composite mirror is analyzed using the finite element method, and the resulting stiffness and natural frequencies are presented.

Penado, F. Ernesto; Clark, James H., III; Walton, Joshua P.; Romeo, Robert C.; Martin, Robert N.

2007-09-01

161

Experimental study on mechanical properties of aircraft honeycomb sandwich structures  

NASA Astrophysics Data System (ADS)

Mechanical behaviour of sandwich panels under different conditions have been exprimentally studied in this research to increase the knowledge of aircraft sandwich panel structures and facilitate design criteria for aircraft structures. Tests were concentrated on the honeycomb sandwich structures under different loads including flexural, insert shear, flat wise tension and compression loads. Furthermore, effect of core density and face material on mechanical behavior of different samples were investigated and compared with analytical and FEM method. Effects of skin thickness on strength of honycomb sandwhich panels under shear pull out and moments have also been considerd in this study. According to this investigation, insert strength and flexural test under different load conditions is strongly affected by face thickness, but compression and tearoff (falt wise tensile) properties of a sandwich panel depends on core material. The study concludes that the correlation between experimental results and the analytical predictions will enable the designer to predict the mechanical behaviour and strength of a sandwich beam; however, applied formula may lead engineers to unreliable results for shear modulus.

Zakeri, A. A.; Talebi Mazraehshahi, H.

2010-06-01

162

COMPRESSIVE STRENGTH TO WEIGHT RATIO OPTIMIZATION OF COMPOSITE HONEYCOMB THROUGH ADDITION OF INTERNAL REINFORCEMENTS.  

E-print Network

??This work focuses on the compressive strength to weight ratio optimization of reinforced composite honeycomb materials for sandwich panel construction. Currently, metallic honeycomb has densities… (more)

Rudd, Jeffrey Roy

2006-01-01

163

Magnetic Edge Anisotropy in Graphenelike Honeycomb Crystals  

NASA Astrophysics Data System (ADS)

The independent predictions of edge ferromagnetism and the quantum spin Hall phase in graphene have inspired the quest of other two-dimensional honeycomb systems, such as silicene, germanene, stanene, iridates, and organometallic lattices, as well as artificial superlattices, all of them with electronic properties analogous to those of graphene, but a larger spin-orbit coupling. Here, we study the interplay of ferromagnetic order and spin-orbit interactions at the zigzag edges of these graphenelike systems. We find an in-plane magnetic anisotropy that opens a gap in the otherwise conducting edge channels that should result in large changes of electronic properties upon rotation of the magnetization.

Lado, J. L.; Fernández-Rossier, J.

2014-07-01

164

Photovoltaic Berry curvature in the honeycomb lattice  

E-print Network

Abstract. Photovoltaic Hall effect — the Hall effect induced by intense, circularly-polarized light in the absence of static magnetic fields — has been proposed in Phys. Rev. B 79, 081406R (2009) for graphene where a massless Dirac dispersion is realized. The photovoltaic Berry curvature (a nonequilibrium extension of the standard Berry curvature) is the key quantity to understand this effect, which appears in the Kubo formula extended to Hall transport in the presence of strong AC field backgrounds. Here we elaborate the properties of the photovoltaic curvature such as the frequency and field strength dependence in the honeycomb lattice. 1.

Takashi Oka; Hideo Aoki

165

Optimal Fractal-Like Hierarchical Honeycombs  

NASA Astrophysics Data System (ADS)

Hexagonal honeycomb structures are known for their high strength and low weight. We construct a new class of fractal-appearing cellular metamaterials by replacing each three-edge vertex of a base hexagonal network with a smaller hexagon and iterating this process. The mechanical properties of the structure after different orders of the iteration are optimized. We find that the optimal structure (with highest in-plane stiffness for a given weight ratio) is self-similar but requires higher order hierarchy as the density vanishes. These results offer insights into how incorporating hierarchy in the material structure can create low-density metamaterials with desired properties and function.

Oftadeh, Ramin; Haghpanah, Babak; Vella, Dominic; Boudaoud, Arezki; Vaziri, Ashkan

2014-09-01

166

Investigation on the square cell honeycomb structures under axial loading  

Microsoft Academic Search

To investigate into the collapse of a sandwich panel or beam with a square cell honeycomb, the novel plate model and beam model are developed according to the cross-sectional symmetry of the cell. The treble series solution of buckling mode is presented, and the formulas of critical compressive stress on skins are derived. The honeycomb sandwich panels are classified as

Sen Liang; H. L. Chen

2006-01-01

167

A study on composite honeycomb sandwich panel structure  

Microsoft Academic Search

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

Meifeng He; Wenbin Hu

2008-01-01

168

Assessment of semi-impregnated fabrics in honeycomb sandwich structures  

Microsoft Academic Search

Semi-impregnated fabrics, or semipregs, are fabrics alternating dry and resin impregnated areas along the fibre bed surface. Due to their increased initial through thickness permeability to gas flow, these could constitute an alternative to prepreg in the skins of vacuum-bagged honeycomb sandwich structures, reducing the pressure in the honeycomb. The semipreg through thickness air permeability before cure is measured and

S. Sequeira Tavares; V. Michaud; J.-A. E. Månson

2010-01-01

169

Clean Electrical-Discharge Machining Of Delicate Honeycomb  

NASA Technical Reports Server (NTRS)

Precise recesses in fragile metal honeycomb blocks formed in special electrical-discharge machining process. Special tooling used, and recesses bored with workpiece in nonstandard alignment. Cutting electrode advances into workpiece along x axis to form pocket of rectangular cross section. Deionized water flows from fitting, along honeycomb tubes of workpiece, to electrode/workpiece interface.

Johnson, Clarence S.

1993-01-01

170

A Monitoring Project for Performance Evaluation of Transparent Honeycomb Insulation  

Microsoft Academic Search

To evaluate the performance of Transparent Honeycomb Insulation (THI), a monitoring program was carried out at Saint Helens (UK). The Northwest and Southeast facades of an existing terraced house were clad with honeycomb transparent insulation. Various heating and energy flow variables were monitored within this Transparently Insulated House (TIH) and in an adjoining Non-insulated House (NIH), which was a mirror

Javed A. Chattha; S. I. Gilani

2005-01-01

171

Hexagonal honeycomb foams Foams out of mechanical equilibrium  

E-print Network

's honeycomb Unit cell Princen's honeycomb late 1970s through 1980s, plus several reviews AB C D AB C D A D B C: constraint eqn film midpt: fixed film midpt: fixed film midpt: prescribed motion Quasistatic mechanical equilibrium configuration given vertex locations for unit cell Vertex = Fermat-Steiner point Films meet at 2 3

Cox, Simon

172

Local feedback control of light honeycomb panels.  

PubMed

This paper summarizes theoretical and experimental work on the feedback control of sound radiation from honeycomb panels using piezoceramic actuators. It is motivated by the problem of sound transmission in aircraft, specifically the active control of trim panels. Trim panels are generally honeycomb structures designed to meet the design requirement of low weight and high stiffness. They are resiliently mounted to the fuselage for the passive reduction of noise transmission. Local coupling of the closely spaced sensor and actuator was observed experimentally and modeled using a single degree of freedom system. The effect of the local coupling was to roll off the response between the actuator and sensor at high frequencies, so that a feedback control system can have high gain margins. Unfortunately, only relatively poor global performance is then achieved because of localization of reduction around the actuator. This localization prompts the investigation of a multichannel active control system. Globalized reduction was predicted using a model of 12-channel direct velocity feedback control. The multichannel system, however, does not appear to yield a significant improvement in the performance because of decreased gain margin. PMID:17297778

Hong, Chinsuk; Elliott, Stephen J

2007-01-01

173

Aluminum Hydroxide  

MedlinePLUS

Aluminum hydroxide is used for the relief of heartburn, sour stomach, and peptic ulcer pain and to ... Aluminum hydroxide comes as a capsule, a tablet, and an oral liquid and suspension. The dose and ...

174

Steps toward 8 m honeycomb mirror blanks. II - Experiments with waffleplate and honeycomb casting  

NASA Technical Reports Server (NTRS)

A technique for fabricating large low-cost light-weight borosilicate-glass mirrors for ground and space-based astronomy is described. This technique involves the remelting of glass into complex molds for vacuum-formed ceramic fiber and is used to cast in one piece either waffleplate or full honeycomb sandwich blanks. The construction of molds and the cycle for melting and annealing are described in detail. A 1.1-m square blank with a 22.4-cm-thick face and 1.6-cm ribs, 15-cm deep on 15-cm squares, has been cast, and a 1.8-m circular blank of full honeycomb construction is scheduled for production. The casting of blanks of up to 8-m in diameter is anticipated, with densities of 200 kg/sq m (like that of the ST mirror) being typical of casting.

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

1983-01-01

175

Fabrication and evaluation of a novel cathode-supported honeycomb SOFC stack  

Microsoft Academic Search

A novel solid oxide fuel cell (SOFC) stack based on a cathode-supported honeycomb SOFC single unit, capable of generating high volumetric power density, was fabricated. Facile connection of the honeycomb single units is achieved using a metal interconnect with a gastight conductive paste. The honeycomb single unit is designed to use the outer honeycomb face and the anode layer on

Toshiaki Yamaguchi; Sota Shimizu; Toshio Suzuki; Yoshinobu Fujishiro; Masanobu Awano

2009-01-01

176

Height Fluctuations in the Honeycomb Dimer Model  

NASA Astrophysics Data System (ADS)

We study a model of random surfaces arising in the dimer model on the honeycomb lattice. For a fixed “wire frame” boundary condition, as the lattice spacing ? ? 0, Cohn, Kenyon and Propp [3] showed the almost sure convergence of a random surface to a non-random limit shape ?0. In [12], Okounkov and the author showed how to parametrize the limit shapes in terms of analytic functions, in particular constructing a natural conformal structure on them. We show here that when ?0 has no facets, for a family of boundary conditions approximating the wire frame, the large-scale surface fluctuations (height fluctuations) about ?0 converge as ? ? 0 to a Gaussian free field for the above conformal structure. We also show that the local statistics of the fluctuations near a given point x are, as conjectured in [3], given by the unique ergodic Gibbs measure (on plane configurations) whose slope is the slope of the tangent plane of ?0 at x.

Kenyon, Richard

2008-08-01

177

Thermochemical response of honeycomb sandwich panels  

NASA Technical Reports Server (NTRS)

A simple study aimed at predicting the thermochemical response of honeycomb sandwich panels is presented. The overall thermal conductivity coefficient for the panel is obtained through a consideration of the convective gas movement within the cell spaces. The earlier correlations of Catton and Edwards are used. The analytical solution for the one-dimensional approximation is quoted from an earlier study. In comparison with three data points obtained at JPL at heat fluxes of 2.5, 5 and 8 W/sq cm, the char penetration depth is well predicted, especially when the debonding of the face sheet is considered. Re-radiation of incident heat flux from the debonded face sheet plays an important role in this model.

Ramohalli, K.

1983-01-01

178

Simulation of the honeycomb construction process  

NASA Astrophysics Data System (ADS)

The construction process of the honeycomb by bees is an astonishing process. The original structure which the bees built is nothing more than a lot of rough cylinders. But keeping the beeswax semi-flow for a certain time, those rough structures become perfect hexahedral columns. A modified, simplified particle method was used here to simulate the semi-flow state of the material. Although the parameters used here were still rather subjective, the simulation still could demonstrate some behavior of that sort of material like beeswax. And the method that the bees used to build their honey comb, could be an efficient method to imitate when we are trying to manufacture cellular materials.

Yuanzhang, Zhang

2010-06-01

179

Honeycomb Betavoltaic Battery for Space Applications  

NASA Astrophysics Data System (ADS)

Radioisotopic batteries offer advantages relative to conventional chemical batteries for applications requiring a long lifetime with minimum maintenance. Thus, thermoelectric type cells fueled with Pu have been used extensively on NASA space missions. The design for a small beta battery using nickel-63 (Ni-63) and a vacuum direct collection method is described here. A honeycomb nickel wire structure is employed to achieve bi-directional direct collection by seeding Ni-63 onto honeycomb shaped wires that will provide structural support as well. The battery design is intended to power low power electronics and distribute power needs in space probes as well as space colonies. Ni-63 is chosen as the source emitter because it has a long half-life and ease of manufacturing. The use of vacuum is especially well mated to space use; hence, vacuum insulation is employed to gain a higher efficiency than prior beta batteries with a dielectric insulator. A unique voltage down-converter is incorporated to efficiently reduce the inherent output voltage from 17.4 kV to ~17.4 V. This converter operates like a ``reverse'' Marx circuit where capacitor charging occurs in series but the discharge is in parallel. The reference battery module described here is about 100 cm×100 cm×218 cm and has a power of ~10 W with a conversion efficiency of ~15.8%. These modules can be stacked for higher powers and are very attractive for various applications in space colonization due to their long life (half-life for Ni-63~100 yrs) and low maintenance.

Lee, Jin R.; Ulmen, Ben; Miley, George H.

2008-01-01

180

Modeling the Axial Mechanical Response of Amorphous Fe45Ni45Mo7B3 Honeycombs  

NASA Astrophysics Data System (ADS)

The high yield strength and elastic modulus of metallic glasses suggests they could perform an important role in structural applications. To produce materials with a high strength-to-weight ratio and excellent mechanical energy absorption, it is advantageous to form amorphous alloys as cellular solids. Using the elastic properties of slip cast amorphous Fe45Ni45Mo7B3 ribbons, a metallic glass honeycomb was manufactured with a unique manufacturing approach. First, prototypes were manufactured with a porosity of 97 pct, a cell wall thickness of 0.03 mm, and a cell size of 3 mm. Experimentally measured mechanical properties were reasonably similar to analytical models. This suggests that a three-times improvement in the yield strength along the out-of-plane direction is achievable when compared with crystalline aluminum honeycombs. An analytical model was developed to predict the relative density and the compressive stress ( ? {3/ * }) in the out-of-plane ( X 3) direction of the "teardrop" cellular structure. The predictions are validated by initial experimental results and compare well with existing analytical models for hexagonal cellular materials.

Jayakumar, Balaji; Hanan, Jay C.

2012-08-01

181

Nuclear design analysis of square-lattice honeycomb space nuclear rocket engine  

SciTech Connect

The square-lattice honeycomb reactor is designed based on a cylindrical core that is determined to have critical diameter and length of 0.50 m and 0.50 c, respectively. A 0.10-cm thick radial graphite reflector, in addition to a 0.20-m thick axial graphite reflector are used to reduce neutron leakage from the reactor. The core is fueled with solid solution of 93% enriched (U, Zr, Nb)C, which is one of several ternary uranium carbides that are considered for this concept. The fuel is to be fabricated as 2 mm grooved (U, Zr, Nb)C wafers. The fuel wafers are used to form square-lattice honeycomb fuel assemblies, 0.10 m in length with 30% cross-sectional flow area. Five fuel assemblies are stacked up axially to form the reactor core. Based on the 30% void fraction, the width of the square flow channel is about 1.3 mm. The hydrogen propellant is passed through these flow channels and removes the heat from the reactor core. To perform nuclear design analysis, a series of neutron transport and diffusion codes are used. The preliminary results are obtained using a simple four-group cross-section model. To optimize the nuclear design, the fuel densities are varied for each assembly. Tantalum, hafnium and tungsten are considered and used as a replacement for niobium in fuel material to provide water submersion sub-criticality for the reactor. Axial and radial neutron flux and power density distributions are calculated for the core. Results of the neutronic analysis indicate that the core has a relatively fast spectrum. From the results of the thermal hydraulic analyses, eight axial temperature zones are chosen for the calculation of group average cross-sections. An iterative process is conducted to couple the neutronic calculations with the thermal hydraulics calculations. Results of the nuclear design analysis indicate that a compact core can be designed based on ternary uranium carbide square-lattice honeycomb fuel. This design provides a relatively high thrust to weight ratio.

Widargo, Reza; Anghaie, Samim [Innovative Nuclear Space Power and Propulsion Institute, University of Florida, 202 NSC, Gainesville, Florida 32611-8300 (United States)

1999-01-22

182

Optimal Fractal-Like Hierarchical Honeycombs Ramin Oftadeh,1  

E-print Network

.e., zeroth) to fourth order hierarchical honeycombs fabricated using 3D printing. The physical thickness of the structures is constant, tn � 2 mm, because of the limitations of the 3D printing. To maintain the structure

Vaziri, Ashkan

183

Thermal hydraulic design analysis of ternary carbide fueled square-lattice honeycomb nuclear rocket engine  

NASA Astrophysics Data System (ADS)

A computational analysis is conducted to determine the optimum thermal-hydraulic design parameters for a square-lattice honeycomb nuclear rocket engine core that will incorporate ternary carbide based uranium fuels. Recent studies at the Innovative Nuclear Space Power and Propulsion Institute (INSPI) have demonstrated the feasibility of processing solid solution, ternary carbide fuels such as (U, Zr, Nb)C, (U, Zr, Ta)C, (U, Zr, Hf)C and (U, Zr, W)C. The square-lattice honeycomb design provides high strength and is amenable to the processing complexities of these ultrahigh temperature fuels. A parametric analysis is conducted to examine how core geometry, fuel thickness and the propellant flow area effect the thermal performance of the nuclear rocket engine. The principal variables include core size (length and diameter) and fuel element dimensions. The optimum core configuration requires a balance between high specific impulse and thrust level performance, and maintaining the temperature and strength limits of the fuel. A nuclear rocket engine simulation code is developed and used to examine the system performance as well as the performance of the main reactor core components. The system simulation code was originally developed for analysis of NERVA-Derivative and Pratt & Whitney XNR-2000 nuclear thermal rockets. The code is modified and adopted to the square-lattice geometry of the new fuel design. Thrust levels ranging from 44,500 to 222,400 N (10,000 to 50,000 lbf) are considered. The average hydrogen exit temperature is kept at 2800 K, which is well below the melting point of these fuels. For a nozzle area ratio of 300 and a thrust chamber pressure of 4.8 Mpa (700 psi), the specific impulse is 930 s. Hydrogen temperature and pressure distributions in the core and the fuel maximum temperatures are calculated.

Furman, Eric M.; Anghaie, Samim

1999-01-01

184

Thermal hydraulic design analysis of ternary carbide fueled square-lattice honeycomb nuclear rocket engine  

SciTech Connect

A computational analysis is conducted to determine the optimum thermal-hydraulic design parameters for a square-lattice honeycomb nuclear rocket engine core that will incorporate ternary carbide based uranium fuels. Recent studies at the Innovative Nuclear Space Power and Propulsion Institute (INSPI) have demonstrated the feasibility of processing solid solution, ternary carbide fuels such as (U, Zr, Nb)C, (U, Zr, Ta)C, (U, Zr, Hf)C and (U, Zr, W)C. The square-lattice honeycomb design provides high strength and is amenable to the processing complexities of these ultrahigh temperature fuels. A parametric analysis is conducted to examine how core geometry, fuel thickness and the propellant flow area effect the thermal performance of the nuclear rocket engine. The principal variables include core size (length and diameter) and fuel element dimensions. The optimum core configuration requires a balance between high specific impulse and thrust level performance, and maintaining the temperature and strength limits of the fuel. A nuclear rocket engine simulation code is developed and used to examine the system performance as well as the performance of the main reactor core components. The system simulation code was originally developed for analysis of NERVA-Derivative and Pratt and Whitney XNR-2000 nuclear thermal rockets. The code is modified and adopted to the square-lattice geometry of the new fuel design. Thrust levels ranging from 44,500 to 222,400 N (10,000 to 50,000 lbf) are considered. The average hydrogen exit temperature is kept at 2800 K, which is well below the melting point of these fuels. For a nozzle area ratio of 300 and a thrust chamber pressure of 4.8 Mpa (700 psi), the specific impulse is 930 s. Hydrogen temperature and pressure distributions in the core and the fuel maximum temperatures are calculated.

Furman, Eric M.; Anghaie, Samim [Innovative Nuclear Space Power and Propulsion Institute, University of Florida, Gainesville, Florida 32611 (United States)

1999-01-22

185

Low Voltage Reversible Electrowetting Exploiting Lubricated Polymer Honeycomb Substrates  

E-print Network

Low-voltage electrowetting-on-dielectric scheme realized with lubricated honeycomb polymer surfaces is reported. Polycarbonate honeycomb reliefs manufactured with the breath-figures self-assembly were impregnated with silicone and castor oils. The onset of the reversible electrowetting for silicone oil impregnated substrates occurred at 35 V, whereas for castor oil impregnated ones it took place at 80 V. The semi-quantitative analysis of electrowetting of impregnated surfaces is proposed.

Edward Bormashenko; Roman Pogreb; Yelena Bormashenko; Roman Grynyov; Oleg Gendelman

2014-06-16

186

Low voltage reversible electrowetting exploiting lubricated polymer honeycomb substrates  

NASA Astrophysics Data System (ADS)

Low-voltage electrowetting-on-dielectric scheme realized with lubricated honeycomb polymer surfaces is reported. Polycarbonate honeycomb reliefs manufactured with the breath-figures self-assembly were impregnated with silicone and castor oils. The onset of the reversible electrowetting for silicone oil impregnated substrates occurred at 35 V, whereas for castor oil impregnated ones it took place at 80 V. The semi-quantitative analysis of electrowetting of impregnated surfaces is proposed.

Bormashenko, Edward; Pogreb, Roman; Bormashenko, Yelena; Grynyov, Roman; Gendelman, Oleg

2014-04-01

187

Structural performance of metallic sandwich beams with hollow truss cores  

E-print Network

; Lightweight structures; Hollow tube core 1. Introduction Metallic sandwich panels with various honeycomb, latStructural performance of metallic sandwich beams with hollow truss cores H.J. Rathbun a , F.W. Zok of sandwich beams with hollow truss lattice cores made from a ductile stainless steel. The trusses

Wadley, Haydn

188

Control of Wave Propagation in Sandwich Beams with Auxetic Core  

Microsoft Academic Search

The wave propagation in sandwich beams with cellular core is analyzed and controlled. The material properties of cellular cores are highly dependent on the geometry of the cell composing the honeycomb structure. Core materials of different geometry placed periodically along the beam length introduce the proper impedance mismatch necessary to impede the propagation of waves along the beam. A theoretical

MASSIMO RUZZENE; FABRIZIO SCARPA

2003-01-01

189

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

NASA Technical Reports Server (NTRS)

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

Ko, W. L.

1980-01-01

190

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

NASA Astrophysics Data System (ADS)

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

He, Yanfei; Gong, Rongzhou

2009-03-01

191

Height fluctuations in the honeycomb dimer model  

E-print Network

We study a model of random surfaces arising in the dimer model on the honeycomb lattice. For a fixed ``wire frame'' boundary condition, as the lattice spacing $\\epsilon\\to0$, Cohn, Kenyon and Propp [CKP] showed the almost sure convergence of a random surface to a non-random limit shape $\\Sigma_0$. In [KO], Okounkov and the author showed how to parametrize the limit shapes in terms of analytic functions, in particular constructing a natural conformal structure on them. We show here that when $\\Sigma_0$ has no facets, for a family of boundary conditions approximating the wire frame, the large-scale surface fluctuations (height fluctuations) about $\\Sigma_0$ converge as $\\epsilon\\to0$ to a Gaussian free field for the above conformal structure. We also show that the local statistics of the fluctuations near a given point $x$ are, as conjectured in [CKP], given by the unique ergodic Gibbs measure (on plane configurations) whose slope is the slope of the tangent plane of $\\Sigma_0$ at $x$.

Richard Kenyon

2004-05-19

192

Development of Rene 41 honeycomb structure as an integral cryogenic tankage/fuselage concept for future space transportation systems  

NASA Technical Reports Server (NTRS)

The status of the structural development of an integral cryogenic-tankage/hot-fuselage concept for future space transportation systems is reviewed. The concept comprises a honeycomb sandwich structure that serves the combined functions of containing the cryogenic fuel, supporting the vehicle loads, and protecting the spacecraft from entry heating. The inner face sheet is exposed to cryogenic temperature of -423 F during boost; the outer face sheet, which is slotted to reduce thermal stress, is exposed to a maximum temperature of 1400 F during a high-altitude gliding entry. Attention is given to the development of a fabrication process for a Rene 41 honeycomb sandwich panel with a core density of less than 1 percent that is consistent with desirable heat treatment processes for high strength.

Shideler, J. L.; Swegle, A. R.; Fields, R. A.

1982-01-01

193

Development of Rene' 41 honeycomb structure as an integral cryogenic tankage/fuselage concept for future space transportation systems  

NASA Technical Reports Server (NTRS)

The status of the structural development of an integral cryogenic-tankage/hot-fuselage concept for future space transportation systems (STS) is discussed. The concept consists of a honeycomb sandwich structure which serves the combined functions of containment of cryogenic fuel, support of vehicle loads, and thermal protection from an entry heating environment. The inner face sheet is exposed to a cryogenic (LH2) temperature of -423 F during boost; and the outer face sheet, which is slotted to reduce thermal stress, is exposed to a maximum temperature of 1400 F during a high altitude, gliding entry. A fabrication process for a Rene' 41 honeycomb sandwich panel with a core density less than 1 percent was developed which is consistent with desirable heat treatment processes for high strength.

Shideler, J. J.; Swegle, A. R.; Fields, R. A.

1982-01-01

194

Transverse Shear Stiffness of a Chevron Folded Core Used in Sandwich Construction  

E-print Network

and that in some cases chevron folded cores are 40% stiffer than honeycomb-like cores. Key words: Sandwich panelsTransverse Shear Stiffness of a Chevron Folded Core Used in Sandwich Construction A. Leb´ee, K. Sab trans- verse shear moduli of a chevron folded core used in sandwich construction are analytically

Boyer, Edmond

195

Underwater blast response of free-standing sandwich plates with metallic lattice cores  

Microsoft Academic Search

The underwater blast response of free-standing sandwich plates with a square honeycomb core and a corrugated core has been measured. The total momentum imparted to the sandwich plate and the degree of core compaction are measured as a function of (i) core strength, (ii) mass of the front face sheet (that is, the wet face) and (iii) time constant of

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

2010-01-01

196

Conic dispersion surfaces for point scatterers on a honeycomb lattice  

E-print Network

We investigate the spectrum and dispersion relation of Schr\\"odinger operator with point scatterers on a triangular lattice and a honeycomb lattice, respectively. We prove that the low-level dispersion surfaces have conic singularities near Dirac points, which are the vertices of the first Brillouin Zone. The existence of such conic dispersion surface plays an important role in various electronic properties of honeycomb-structured materials such as graphene. We then prove that for the honeycomb lattice, the band spectra generated by higher-level dispersion surfaces are all connected so the complete spectrum consists of at most three bands. Numerical simulations for dispersion surfaces with various coupling constant are also presented.

Minjae Lee

2014-02-21

197

Aluminum Analysis.  

ERIC Educational Resources Information Center

Presents three problems based on the price of aluminum designed to encourage students to be cooperative and to use an investigative approach to learning. Students collect and synthesize information, analyze results, and draw conclusions. (AIM)

Sumrall, William J.

1998-01-01

198

Linear and nonlinear traveling edge waves in optical honeycomb lattices  

NASA Astrophysics Data System (ADS)

Traveling unidirectional localized edge states in optical honeycomb lattices are analytically constructed. They are found in honeycomb arrays of helical waveguides designed to induce a periodic pseudomagnetic field varying in the direction of propagation. Conditions on whether a given pseudofield supports a traveling edge mode are discussed; a special case of the pseudofields studied agrees with recent experiments. Interesting classes of dispersion relations are obtained. Envelopes of nonlinear edge modes are described by the classical one-dimensional nonlinear Schrödinger equation along the edge. Nonlinear states termed edge solitons are predicted analytically and are found numerically.

Ablowitz, Mark J.; Curtis, Christopher W.; Ma, Yi-Ping

2014-08-01

199

Validation of a vibration and electric model of honeycomb panels equiped with  

E-print Network

homogeneiza- tion of honeycombs and shell models of piezoelectric patches. These models are validatedValidation of a vibration and electric model of honeycomb panels equiped with piezoelectric patch experimentally. The considered honeycomb is shown to be significantly viscoelastic and local bending effects

Paris-Sud XI, Université de

200

Vacuum Bag Only Prepreg Processing of Honeycomb Sandwich Panels James Kratz  

E-print Network

Vacuum Bag Only Prepreg Processing of Honeycomb Sandwich Panels James Kratz Department. This technique can be very effective for laminates, but extremely lightweight honeycomb structures introduce two to solve the manufacturing problems for honeycomb structures. Biography James Kratz recently defended his

Dawson, Jeff W.

201

Sound transmission loss of damped honeycomb sandwich Portia Peters and Steven Nutt  

E-print Network

Sound transmission loss of damped honeycomb sandwich panels Portia Peters and Steven Nutt Honeycomb be a base for further enhancements in the acoustical behavior of honeycomb sandwich structures. #12; sandwich panels are widely used in aerospace applications because of the high stiffness-to-weight ratios

Southern California, University of

202

Some considerations of the performance of two honeycomb gas path seal material systems  

NASA Technical Reports Server (NTRS)

A standard Hastelloy-X honeycomb material and a pack aluminide coated honeycomb material were evaluated as to their performance as labyrinth seal materials for aircraft gas turbine engines. Consideration from published literature was given to the fluid sealing characteristics of two honeycomb materials in labyrinth seal applications, and their rub characteristics, erosion resistance, and oxidation resistance were evaluated. The increased temperature potential of the coated honeycomb material compared to the uncoated standard could be achieved without compromising the honeycomb material's rub tolerance, although there was some penalty in terms of reduced erosion resistance.

Bill, R. C.; Shiembob, L. T.

1980-01-01

203

Hollow needle used to cut metal honeycomb structures  

NASA Technical Reports Server (NTRS)

Hollow needle tool cuts metal honeycomb structures without damaging adjacent material. The hollow needle combines an electrostatic discharge and a stream of oxygen at a common point to effect rapid, accurate metal cutting. The tool design can be varied to use the hollow needle principle for cutting a variety of shapes.

Gregg, E. A.

1966-01-01

204

Detection of entrapped moisture in honeycomb sandwich structures  

NASA Technical Reports Server (NTRS)

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

Hallmark, W. B.

1967-01-01

205

Adsorption characteristics of water vapor on honeycomb adsorbents  

NASA Astrophysics Data System (ADS)

Recovery of tritium released into working areas in nuclear fusion plants is a key issue of safety. A large volume of air from tritium fuel cycle or vacuum vessel should be processed by air cleanup system (ACS). In ACS, tritium gas is oxidized by catalysts, and then tritiated water vapor is collected by adsorbents. This method can remove tritium effectively, whereas high throughput of air causes high-pressure drop in catalyst and adsorbent beds. In this study, the applicability of honeycomb-type adsorbents, which offers a useful advantage in terms of their low-pressure drop, to ACS was examined, in comparison with conventional pebble-type adsorbent. Honeycomb-type adsorbent causes far less pressure drop than pebble-type adsorbent beds. Adsorption capacity of water vapor on a honeycomb-type adsorbent is slightly lower than that on a pebble-type adsorbent, while adsorption rate of water vapor on honeycomb-type adsorbent is much higher than that of pebble-type adsorbent.

Wajima, Takaaki; Munakata, Kenzo; Takeishi, Toshiharu; Hara, Keisuke; Wada, Kouhei; Katekari, Kenichi; Inoue, Keita; Shinozaki, Yohei; Mochizuki, Kazuhiro; Tanaka, Masahiro; Uda, Tatsuhiko

2011-10-01

206

Homogenizing media containing a highly conductive honeycomb substructure  

E-print Network

Homogenizing media containing a highly conductive honeycomb substructure by Isabelle Gruais and Dan Polisevski Abstract. The present paper deals with the homogenization of the heat conduction which-zone of the vanishing domain. Mathematical Subject Classification (2000). 35B27, 35K57, 76R50. Keywords. homogenization

Boyer, Edmond

207

Pressure adaptive honeycomb: a new adaptive structure for aerospace applications  

Microsoft Academic Search

A new type of adaptive structure is presented that relies on pressurized honeycomb cells that extent a significant length with respect to the plane of the hexagons. By varying the pressure inside each of the cells, the stiffness can be altered. A variable stiffness in combination with an externally applied force field results in a fully embedded pressure adaptive actuator

Roelof Vos; Ron Barrett

2010-01-01

208

Titanium honeycomb structure. [for supersonic aircraft wing structure  

NASA Technical Reports Server (NTRS)

A brazed titanium honeycomb sandwich system for supersonic transport wing cover panels provides the most efficient structure spanwise, chordwise, and loadwise. Flutter testing shows that high wing stiffness is most efficient in a sandwich structure. This structure also provides good thermal insulation if liquid fuel is carried in direct contact with the wing structure in integral fuel tanks.

Davis, R. A.; Elrod, S. D.; Lovell, D. T.

1972-01-01

209

Failure initiation and propagation characteristics of honeycomb sandwich composites  

Microsoft Academic Search

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

A. R. Othman; D. C. Barton

2008-01-01

210

Fatigue analysis of honeycomb-composite sandwich beams  

Microsoft Academic Search

The fatigue behaviour of honeycomb sandwich beams is experimentally investigated through four-point bending tests. Two kinds of specimens, initially undamaged and damaged by interface debonding, have been tested. The fatigue tests results are presented in standard SN diagrams with a best curve fit of the experimental data, while the fatigue limit is evaluated through a stair-case procedure. Two different failure

G. Belingardi; P. Martella; L. Peroni

2007-01-01

211

Failure behaviour of honeycomb sandwich corner joints and inserts  

Microsoft Academic Search

In nearly all sandwich constructions certain types of joints have to be used for assembly, but little is known about their failure behaviour. This paper deals with the investigation of the mechanical behaviour of three different corner joints as a right-angled connection of two sandwich panels and of two different potted inserts as a localised load introduction in Nomex® honeycomb

Sebastian Heimbs; Marc Pein

2009-01-01

212

Homogenized elastic properties of honeycomb sandwich with skin effect  

Microsoft Academic Search

The adaptation of homogenization theory to periodic plates is presented and extended to include transverse shear deformation theory for a honeycomb sandwich. Based on the scaling asymptotic expansions about plate thickness ? for sandwiches with comparable characteristic periodicity ?, the homogenization functions ?, U, and V are formulated implicitly in 3-D elliptical equations corresponding to the modes of transverse shear,

X. Frank Xu; Pizhong Qiao

2002-01-01

213

Leakage loss of air-guiding honeycomb photonic bandgap fiber  

Microsoft Academic Search

We report a new class of air-guiding photonic bandgap fiber using honeycomb air-silica cladding design. Full-vector numerical simulation shows the leakage loss can be as small as 0.06 dB\\/m using eight cladding rings.

M. Yan; P. Shum

2005-01-01

214

Repair of honeycomb panels with welded breakaway studs  

NASA Technical Reports Server (NTRS)

Damaged metallic honeycomb panels can be repaired by drilling holes and welding breakaway studs to both facing sheets. Minimal heat required for welding reduces distortion of highly stressed panels. Repairs can be made without the use of doublers and with greater strength when doublers are used.

Bruce, D. F.

1969-01-01

215

Metal honeycomb to porous wireform substrate diffusion bond evaluation  

NASA Technical Reports Server (NTRS)

Two nondestructive techniques were used to evaluate diffusion bond quality between a metal foil honeycomb and porous wireform substrate. The two techniques, cryographics and acousto-ultrasonics, are complementary in revealing variations of bond integrity and quality in shroud segments from an experimental aircraft turbine engine.

Vary, A.; Moorhead, P. E.; Hull, D. R.

1982-01-01

216

Microstrip base station antenna made of honeycomb composites  

Microsoft Academic Search

This paper describes the advantages of using honeycomb composite technology in the design of cheap, flat-panel base station antennas. To demonstrate this technology, antenna elements with dual polarization for use in the in the 890 to 960 MHz frequency band are designed and manufactured. CAD and CAM techniques are used to achieve the design objectives. The antenna has a strong

P. Kabacik; M. Bialkowski

1998-01-01

217

Soundproof characteristics of finite length orthotropic honeycomb shells  

Microsoft Academic Search

Acoustic radiation emanating from the walls of orthotropic honeycomb shells is studied analytically for the case of axisymmetric acoustic mode transmission within the shell. The shell has a finite vibrating length and is mounted on an infinite rigid baffle in a free field. The problem is studied on the basis of a shell theory in which it is assumed that

S. Chonan

1989-01-01

218

Experimental study of acoustical behavior of flat honeycomb sandwich panel  

Microsoft Academic Search

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

Shankar Rajaram

2005-01-01

219

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

NASA Technical Reports Server (NTRS)

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

Ko, W. L.

1980-01-01

220

Identification of honeycomb sandwich properties by high-resolution modal analysis  

NASA Astrophysics Data System (ADS)

A method is proposed to identify the mechanical properties of the skin and core materials of honeycomb sandwich. All the elastic coefficients and loss-factors that matter in the dynamics of a panel in the thick-plate approximation are identified. To this end, experimental natural modes (i.e. eigenmodes of the damped system) are compared to the numerical modes of a large sandwich panel (lx,y/h ? 80). The chosen generic model for the visco-elastic behaviour of the materials is E (1 + j?). The numerical modes are computed by means of a Rayleigh-Ritz procedure and their dampings are predicted according to the visco-elastic model. The frequencies and dampings of the natural modes of the panel are estimated experimentally by means of a high-resolution modal analysis technique. An optimisation procedure yields the desired coefficients. A sensitivity analysis assess the reliability of the method.

Rebillat, M.; Boutillon, X.

2010-06-01

221

Conversion of aluminum chlorohydrate to aluminum hydroxide  

Microsoft Academic Search

aluminum hydroxide. X-ray, IR, and 27A1 NMR spectroscopic data indicate that aluminum chlorohydrate is composed of a central aluminum in tetrahedral configuration surrounded by 12 aluminums each in octahedral configuration. This highly .charged complex is neutralized by 7 chloride counterions. In contrast, aluminum hydroxide has a polymer-like structure whose basic unit is a ring of six aluminums in octahedral configuration

DIRK L. TEAGARDEN; STANLEY L. HEM

222

Mesoporous aluminum phosphite  

SciTech Connect

High surface area pure mesoporous aluminum-phosphorus oxide-based derivatives have been synthesized through an S{sup +}I{sup -} surfactant-assisted cooperative mechanism by means of a one-pot preparative procedure from aqueous solution and starting from aluminum atrane complexes and phosphoric and/or phosphorous acids. A soft chemical extraction procedure allows opening the pore system of the parent as-prepared materials by exchanging the surfactant without mesostructure collapse. The nature of the pore wall can be modulated from mesoporous aluminum phosphate (ALPO) up to total incorporation of phosphite entities (mesoporous aluminum phosphite), which results in a gradual evolution of the acidic properties of the final materials. While phosphate groups in ALPO act as network building blocks (bridging Al atoms), the phosphite entities become basically attached to the pore surface, what gives practically empty channels. The mesoporous nature of the final materials is confirmed by X-ray diffraction (XRD), transmission electron microscopy (TEM) and N{sub 2} adsorption-desorption isotherms. The materials present regular unimodal pore systems whose order decreases as the phosphite content increases. NMR spectroscopic results confirm the incorporation of oxo-phosphorus entities to the framework of these materials and also provide us useful information concerning the mechanism through which they are formed. - Abstract: TEM image of the mesoporous aluminum phosphite showing the hexagonal disordered pore array that is generated by using surfactant micelles as template. Also a scheme emphasizing the presence of an alumina-rich core and an ALPO-like pore surface is presented.

El Haskouri, Jamal, E-mail: haskouri@uv.e [Institut de Ciencia dels Materials de la Universitat de Valencia (ICMUV), P. O. Box 22085, 46071 Valencia (Spain); Perez-Cabero, Monica; Guillem, Carmen; Latorre, Julio; Beltran, Aurelio; Beltran, Daniel [Institut de Ciencia dels Materials de la Universitat de Valencia (ICMUV), P. O. Box 22085, 46071 Valencia (Spain); Amoros, Pedro, E-mail: pedro.amoros@uv.e [Institut de Ciencia dels Materials de la Universitat de Valencia (ICMUV), P. O. Box 22085, 46071 Valencia (Spain)

2009-08-15

223

EVALUATION OF THE MATERIAL PROPERTIES OF RESIN-IMPREGNATED NOMEX PAPER AS BASIS FOR THE SIMULATION OF THE IMPACT BEHAVIOUR OF HONEYCOMB SANDWICH  

Microsoft Academic Search

Driven by stringent weight saving requirements composite sandwich construction has evolved as one of the basic structural design concepts for load-carrying components of advanced aeroplanes and helicopters. Particularly, sandwich using laminated carbon fibre reinforced plastics (CFRP) as face sheets and NOMEX honeycombs as core material is increasingly used due to features such as high strength-to-weight and stiffness-to-weight ratios as well

Falk Hähnel; Klaus Wolf

224

Chemical interactions of aluminum-citrate solutions with formation minerals  

SciTech Connect

To test the effectiveness of complexing agents for in-depth cross-linking and mobility control in polymer and waterfloods, the transport of aluminum citrate solutions in sandstone and limestone cores was investigated. The study was prompted by experimental observations indicating that cross-linking attempts cause plugging of the inlet end of core sections unless special precautions were observed. The plugging was caused by poor transport of the aluminum citrate solutions, which, in turn, was caused by precipitation of aluminum hydroxide in limestone cores, and of both aluminum and ferric hydroxide in sandstone cores. The formation of these precipitates and the poor transport of the aluminum citrate solution were confirmed experimentally and modeled quantitatively by a geochemical flow simulator. The flow simulator was used then to design injected solutions that would avoid precipitation, generally by raising the injected pH and by using a larger citrate to aluminum ratio. 28 references.

Walsh, M.P.; Rouse, B.A.; Pope, G.A.; Lake, L.W.; Senol, N.N.

1983-01-01

225

Underwater blast response of free-standing sandwich plates with metallic lattice cores  

E-print Network

-standing sandwich plates with a square honeycomb core and a corrugated core has been measured. The total momentumUnderwater blast response of free-standing sandwich plates with metallic lattice cores G.J. Mc 19 May 2010 Accepted 29 May 2010 Available online 12 June 2010 Keywords: Sandwich structures Lattice

Fleck, Norman A.

226

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

E-print Network

Performance of sandwich plates with truss cores Nathan Wicks *, John W. Hutchinson Division in revised form 30 January 2003 Abstract Sandwich plates with truss cores fashioned from straight struts have distinct advantages relative to other con- structions, including those with honeycomb cores. In addition

Hutchinson, John W.

227

Structurally optimized sandwich panels with prismatic cores L. Valdevit a,*, J.W. Hutchinson b  

E-print Network

Structurally optimized sandwich panels with prismatic cores L. Valdevit a,*, J.W. Hutchinson b , A sandwich panels with corrugated and prismatic diamond cores have been analyzed and their behavior compared with panels designed using truss and honeycomb cores. Failure mechanism maps have been devised that account

Hutchinson, John W.

228

Vibration and sound radiation from a sandwich cylindrical shell with prismatic core  

Microsoft Academic Search

The vibration and the sound radiation of cylindrical shells with cellular core is here analyzed. The considered structure is composed of a repeated unit cell and can be classified as a Linear Cellular Alloy (LCA) core. The unit cells are of a tetrahedral configuration, arranged according to a honeycomb lay-out. The considered configuration has previously been proposed for core designs

Sang M. Jeong; Massimo Ruzzene

2004-01-01

229

Layer Anti-Ferromagnetism on Bilayer Honeycomb Lattice  

PubMed Central

Bilayer honeycomb lattice, with inter-layer tunneling energy, has a parabolic dispersion relation, and the inter-layer hopping can cause the charge imbalance between two sublattices. Here, we investigate the metal-insulator and magnetic phase transitions on the strongly correlated bilayer honeycomb lattice by cellular dynamical mean-field theory combined with continuous time quantum Monte Carlo method. The procedures of magnetic spontaneous symmetry breaking on dimer and non-dimer sites are different, causing a novel phase transition between normal anti-ferromagnet and layer anti-ferromagnet. The whole phase diagrams about the magnetism, temperature, interaction and inter-layer hopping are obtained. Finally, we propose an experimental protocol to observe these phenomena in future optical lattice experiments. PMID:24947369

Tao, Hong-Shuai; Chen, Yao-Hua; Lin, Heng-Fu; Liu, Hai-Di; Liu, Wu-Ming

2014-01-01

230

Debonding detection of honeycomb sandwich structures using frequency response functions  

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

231

Spin and the honeycomb lattice: lessons from graphene.  

PubMed

A model of electrons hopping from atom to atom in graphene's honeycomb lattice gives low-energy electronic excitations that obey a relation formally identical to a 2+1 dimensional Dirac equation. Graphene's spin equivalent, "pseudospin," arises from the degeneracy introduced by the honeycomb lattice's two inequivalent atomic sites per unit cell. Previously it has been thought that the usual electron spin and the pseudospin indexing the graphene sublattice state are merely analogues. Here we show that the pseudospin is also a real angular momentum. This identification explains the suppression of electron backscattering in carbon nanotubes and the angular dependence of light absorption by graphene. Furthermore, it demonstrates that half-integer spin like that carried by the quarks and leptons can derive from hidden substructure, not of the particles themselves, but rather of the space in which these particles live. PMID:21469887

Mecklenburg, Matthew; Regan, B C

2011-03-18

232

Fabrication of prepackaged superalloy honeycomb Thermal Protection System (TPS) panels  

NASA Technical Reports Server (NTRS)

High temperature materials were surveyed, and Inconel 617 and titanium were selected for application to a honeycomb TPS configuration designed to withstand 2000 F. The configuration was analyzed both thermally and structurally. Component and full-sized panels were fabricated and tested to obtain data for comparison with analysis. Results verified the panel design. Twenty five panels were delivered to NASA Langley Research Center for additional evaluation.

Blair, W.; Meaney, J. E.; Rosenthal, H. A.

1985-01-01

233

Superelastic NiTi honeycombs: fabrication and experiments  

Microsoft Academic Search

In this paper we demonstrate a new class of superelastic NiTi honeycomb structures. We have developed a novel brazing technique that has allowed us to fabricate Nitinol-based cellular structures with relative densities near 5%. Commercially available nickel-rich Nitinol strips were shape-set into corrugated form, stacked, and bonded at high temperature by exploiting a contact eutectic melting reaction involving pure niobium.

John A. Shaw; David S. Grummon; John Foltz

2007-01-01

234

Low-velocity impact failure of aluminium honeycomb sandwich panels  

Microsoft Academic Search

In this paper, the failure response of aluminium sandwich panels subjected to low-velocity impact is discussed. A three-dimensional geometrically correct finite element model of the honeycomb sandwich plate and a rigid impactor was developed using the commercial software, ABAQUS. This discrete modelling approach enabled further understanding of the parameters affecting the initiation and propagation of impact damage. Strain-hardening behaviour of

C. C. Foo; L. K. Seah; G. B. Chai

2008-01-01

235

Order parameters from image analysis: a honeycomb example  

NASA Astrophysics Data System (ADS)

Honeybee combs have aroused interest in the ability of honeybees to form regular hexagonal geometric constructs since ancient times. Here we use a real space technique based on the pair distribution function (PDF) and radial distribution function (RDF), and a reciprocal space method utilizing the Debye-Waller Factor (DWF) to quantify the order for a range of honeycombs made by Apis mellifera ligustica. The PDFs and RDFs are fit with a series of Gaussian curves. We characterize the order in the honeycomb using a real space order parameter, OP 3 , to describe the order in the combs and a two-dimensional Fourier transform from which a Debye-Waller order parameter, u, is derived. Both OP 3 and u take values from [0, 1] where the value one represents perfect order. The analyzed combs have values of OP 3 from 0.33 to 0.60 and values of u from 0.59 to 0.69. RDF fits of honeycomb histograms show that naturally made comb can be crystalline in a 2D ordered structural sense, yet is more ‘liquid-like’ than cells made on ‘foundation’ wax. We show that with the assistance of man-made foundation wax, honeybees can manufacture highly ordered arrays of hexagonal cells. This is the first description of honeycomb utilizing the Debye-Waller Factor, and provides a complete analysis of the order in comb from a real-space order parameter and a reciprocal space order parameter. It is noted that the techniques used are general in nature and could be applied to any digital photograph of an ordered array.

Kaatz, Forrest H.; Bultheel, Adhemar; Egami, Takeshi

2008-11-01

236

Aluminum chlorohydrate III: Conversion to aluminum hydroxide.  

PubMed

Bayerite, an aluminum hydroxide polymorph, readily forms when the hydroxyl to aluminum ratio of aluminum chlorohydrate is raised to 3 by titration with sodium hydroxide. Dilution of aluminum chlorhydrate solutions with water leads to the formation of gibbsite, another aluminum hydroxide polymorph. The mechanism of conversion in each instance is related to the structure of the Al13O4(OH)24(H2O)7+(12) complex. PMID:7264935

Teagarden, D L; White, J L; Hem, S L

1981-07-01

237

Pressure adaptive honeycomb: a new adaptive structure for aerospace applications  

NASA Astrophysics Data System (ADS)

A new type of adaptive structure is presented that relies on pressurized honeycomb cells that extent a significant length with respect to the plane of the hexagons. By varying the pressure inside each of the cells, the stiffness can be altered. A variable stiffness in combination with an externally applied force field results in a fully embedded pressure adaptive actuator that can yield strains well beyond the state-of-the-art in adaptive materials. The stiffness change as a function of the pressure is modeled by assigning an equivalent material stiffness to the honeycomb walls that accounts for both the inherent material stiffness as the pressure-induced stiffness. A finite element analysis of a beam structure that relies on this model is shown to correlate well to experimental results of a three-point bend test. To demonstrate the concept of embedded pressure adaptive honeycomb, an wind tunnel test article with adaptive flap has been constructed and tested in a low speed wind tunnel. It has been proven that by varying the cell pressure the flap changed its geometry and subsequently altered the lift coefficient.

Vos, Roelof; Barrett, Ron

2010-04-01

238

Water ingress detection in honeycomb sandwich panels by passive infrared thermography using a high-resolution thermal imaging camera  

NASA Astrophysics Data System (ADS)

Water ingress in honeycomb structures is of great concern for the civil and military aerospace industries. Pressure and temperature variations during take-off and landing produce considerable stress on aircraft structures, promoting moisture ingress (by diffusion through fibers or by direct ingress through voids, cracks or unsealed joints) into the core. The presence of water (or other fluids such as kerosene, hydraulic fluid and de-icing agents) in any of its forms (gas vapor, liquid or ice) promotes corrosion, cell breakage, and induce composite layer delaminations and skin disbonds. In this study, testing specimens were produced from unserviceable parts from military aircraft. In order to simulate atmospheric conditions during landing, selected core areas were filled with measured quantities of water and then frozen in a cold chamber. The specimens were then removed from the chamber and monitored for over 20 minutes as they warm up using a cooled high-resolution infrared camera. Results have shown that detection and quantification of water ingress on honeycomb sandwich structures by passive infrared thermography is possible using a HD mid-wave infrared cameras for volumes of water as low as 0.2 ml and from a distance as far as 20 m from the target.

Ibarra-Castanedo, C.; Brault, L.; Marcotte, F.; Genest, M.; Farley, V.; Maldague, X.

2012-06-01

239

Effective electromagnetic properties of honeycomb substrate coated with dielectric or magnetic layer  

NASA Astrophysics Data System (ADS)

Effective electromagnetic properties of aramid honeycomb board coated with a layer of multi-wall carbon nanotube or iron flakes composites were measured with waveguide method from 4 to 12 GHz. It was proved that homogenization theory could predict the effective permittivity or permeability of the honeycomb composites with good accuracy. The coated honeycomb composites of relatively high permittivity and permeability could potentially be used to develop dielectric or magnetic substrate for shielding layer or absorbing structures working at microwave frequencies.

Liu, L.; Fan, C. Z.; Zhu, N. B.; Zhao, Z. Y.; Liu, R. P.

2014-09-01

240

49 CFR 587.15 - Verification of aluminum honeycomb crush strength.  

Code of Federal Regulations, 2013 CFR

...following condition must be met. For the 0.342 MPa (49.6 psi) material, the strength must be equal to or greater than 0.308 MPa (45 psi) but less than or equal to 0.342 MPa (49.6 psi) for all three compression intervals. For the...

2013-10-01

241

49 CFR 587.15 - Verification of aluminum honeycomb crush strength.  

Code of Federal Regulations, 2012 CFR

...following condition must be met. For the 0.342 MPa (49.6 psi) material, the strength must be equal to or greater than 0.308 MPa (45 psi) but less than or equal to 0.342 MPa (49.6 psi) for all three compression intervals. For the...

2012-10-01

242

Commercial application of aluminum honeycomb and foam in load bearing tubular structures  

E-print Network

Small dimension engineering tubular structures subjected to a complex load system are designed like hollow circular shells. For minimum weight design, the ratio between the shell radius and the thickness has to be as large ...

Bartolucci, Stefano, 1976-

2004-01-01

243

Buckling Testing and Analysis of Honeycomb Sandwich Panel Arc Segments of a Full-Scale Fairing Barrel. Part 3; 8-ply Out-of-Autoclave Facesheets  

NASA Technical Reports Server (NTRS)

Four honeycomb sandwich panels, representing 1/16th arc segments of a 10 m diameter barrel section of the heavy lift launch vehicle, were manufactured under the NASA Composites for Exploration program and the NASA Constellation Ares V program. Two configurations were chosen for the panels: 6-ply facesheets with 1.125 in. honeycomb core and 8-ply facesheets with 1.000 in. honeycomb core. Additionally, two separate carbon fiber/epoxy material systems were chosen for the facesheets: inautoclave IM7/977-3 and out-of-autoclave T40-800B/5320-1. Smaller 3- by 5-ft panels were cut from the 1/16th barrel sections. These panels were tested under compressive loading at the NASA Langley Research Center. Furthermore, linear eigenvalue and geometrically nonlinear finite element analyses were performed to predict the compressive response of the 3- by 5-ft panels. This manuscript summarizes the experimental and analytical modeling efforts pertaining to the panel composed of 8-ply, T40-800B/5320-1 facesheets (referred to as Panel C). To improve the robustness of the geometrically nonlinear finite element model, measured surface imperfections were included in the geometry of the model. Both the linear and nonlinear, two-dimensional (2-D) and three-dimensional (3-D), models yield good qualitative and quantitative predictions. Additionally, it was predicted correctly that the panel would fail in buckling prior to failing in strength.

Pineda, Evan J.; Myers, David E.; Kosareo, Daniel N.; Kellas, Sotiris

2014-01-01

244

Finite Element Modeling and Design of Honeycomb Sandwich Panels for Acoustic Performance.  

E-print Network

?? Honeycomb cellular metamaterial structures offer many distinct advantages over homogenous materials because their effective material properties depend on both their constituent material properties and… (more)

Griese, David

2012-01-01

245

Service evaluation of Aluminum-Brazed Titanium (ABTi) jet engine tailpipe extensions. Final report  

SciTech Connect

Aluminum-brazed titanium (ABTi) jet engine tailpipe extensions were evaluated in commercial service over a 3-year period. The purpose of the evaluation was to determine the corrosion resistance of ABTi in acoustic applications (i.e., honeycomb sandwich incorporating a perforated inner skin). The results showed that ABTi does not have acceptable corrosion resistance in acoustic applications under severe operating conditions, but may be acceptable for acoustic applications in less severe environments.

Elrod, S.D.

1982-09-01

246

Service evaluation of Aluminum-Brazed Titanium (ABTi) jet engine tailpipe extensions  

NASA Technical Reports Server (NTRS)

Aluminum-brazed titanium (ABTi) jet engine tailpipe extensions were evaluated in commercial service over a 3-year period. The purpose of the evaluation was to determine the corrosion resistance of ABTi in acoustic applications (i.e., honeycomb sandwich incorporating a perforated inner skin). The results showed that ABTi does not have acceptable corrosion resistance in acoustic applications under severe operating conditions, but may be acceptable for acoustic applications in less severe environments.

Elrod, S. D.

1982-01-01

247

International Journal of Impact Engineering 35 (2008) 920936 Impact response of sandwich plates with a pyramidal lattice core  

E-print Network

), prismatic sandwich cores such as the corrugated and Y-frame cores [7] and various honeycomb cores. The trussInternational Journal of Impact Engineering 35 (2008) 920­936 Impact response of sandwich plates The ballistic performance edge clamped 304 stainless-steel sandwich panels has been measured by impacting

Wadley, Haydn

248

VIBRATION AND ACOUSTIC PROPERTIES OF HONEYCOMB SANDWICH STRUCTURES SUBJECT TO VARIABLE INCIDENT PLANE-WAVE ANGLE PRESSURE LOADS.  

E-print Network

??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… (more)

Yan, Jiaxue

2013-01-01

249

Adhesives and the ATS satellite. [construction of honeycomb panels  

NASA Technical Reports Server (NTRS)

Adhesives in the ATS satellite allow the designers to save weight, simplify design and fabrication and provide thermal and electrical conductivity or resistivity as required. The selections of adhesives are restricted to those few which can pass rigorous outgassing tests in order to avoid contaminating lenses and thermal control surfaces in space. An epoxy adhesive is used to construct the honeycomb panels which constitute most of the satellite's structure. General purpose epoxy adhesives hold doublers and standoffs in place and bond the truss to its fittings. Specialized adhesives include a high temperature resistant polyamide, a flexible polyurethane and filled epoxies which conduct heat or electricity.

Hancock, F. E.

1972-01-01

250

Quarter-Filled Honeycomb Lattice with a Quantized Hall Conductance  

NASA Astrophysics Data System (ADS)

We study a generic two-dimensional hopping model on a honeycomb lattice with strong spin-orbit coupling, without the requirement that the half-filled lattice be a Topological Insulator. For quarter-(or three-quarter) filling, we show that a state with a quantized Hall conductance generically arises in the presence of a Zeeman field of sufficient strength. We discuss the influence of Hubbard interactions and argue that spontaneous ferromagnetism (which breaks time-reversal) will occur, leading to a quantized anomalous Hall effect. G. Murthy, E. Shimshoni, R. Shankar, and H. A. Fertig, arxiv:1108.2010[cond-mat.mes-hall

Shimshoni, Efrat; Murthy, Ganpathy; Shankar, Ramamurti; Fertig, Herbert

2012-02-01

251

Anisotropic frustrated Heisenberg model on the honeycomb lattice  

NASA Astrophysics Data System (ADS)

We investigate the ground-state phase diagram of an anisotropic Heisenberg model on the honeycomb lattice with competing interactions. We use quantum Monte Carlo simulations, as well as linear spin-wave and Ising series expansions, to determine the phase boundaries of the ordered magnetic phases. We find a region without any classical order in the vicinity of a highly frustrated point. Higher-order correlation functions in this region give no signal for long-range valence-bond order. The low-energy spectrum is derived via exact diagonalization to check for topological order on small-size periodic lattices.

Kalz, Ansgar; Arlego, Marcelo; Cabra, Daniel; Honecker, Andreas; Rossini, Gerardo

2012-03-01

252

Water intrusion in thin-skinned composite honeycomb sandwich structures  

NASA Technical Reports Server (NTRS)

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.

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

1988-01-01

253

Stiffness and strength properties for basic sandwich material core types  

SciTech Connect

Three basic core material types for sandwich structure applications are studied. The three two-dimensional pattern types are: honeycomb, triangular cells, and a new configuration involving star type cells. The specific critical properties of stiffness and strength type are identified and studied, both theoretically and experimentally.

Beomkeun, K; Christensen, R M

1999-08-03

254

Properties of a chiral honeycomb with a poisson's ratio of — 1  

Microsoft Academic Search

A theoretical and experimental investigation is conducted of a two-dimensionally chiral honeycomb. The honeycomb exhibits a Poisson's ratio of —1 for deformations in-plane. This Poisson's ratio is maintained over a significant range of strain, in contrast to the variation with strain seen in known negative Poisson's ratio materials.

D. Prall; R. S. Lakes

1997-01-01

255

Local buckling of honeycomb sandwich plates under action of transverse shear forces  

Microsoft Academic Search

We evaluate the critical transverse shear forces for the local buckling of honeycomb sandwich plates subjected to lateral loads. The evaluation is based on the stress field accounting for the stresses on the microscale in the honeycomb's hexagonal cells. These microscale stresses are computed by the two-scale method of homogenization theory for periodic media. The elastic restraints resulting from neighboring

Guangyu Shi; Pin Tong

1994-01-01

256

Modeling and characterization of fiber-reinforced plastic honeycomb sandwich panels for highway bridge applications  

Microsoft Academic Search

Fiber-reinforced plastic (FRP) composite decks have been increasingly used in highway bridge applications, both in new construction and rehabilitation and replacement of existing bridge decks. Recent applications have demonstrated that FRP honeycomb panels can be effectively and economically used for highway bridge deck systems. This paper is concerned with design modeling and experimental characterization of a FRP honeycomb panel with

Julio F Davalos; Pizhong Qiao; X Frank Xu; Justin Robinson; Karl E Barth

2001-01-01

257

Guided wave propagation in honeycomb sandwich structures using a piezoelectric actuator\\/sensor system  

Microsoft Academic Search

Due to the complex nature of such composite structures, an understanding of the guided wave propagation mechanism in honeycomb composite panels with different frequencies inherently imposes many challenges. In this paper, a numerical simulation is first conducted to investigate the wave propagation mechanism in honeycomb sandwich structures using piezoelectric actuators\\/sensors. In contrast to most of the previous work, elastic wave

F. Song; G. L. Huang; K. Hudson

2009-01-01

258

The 2D Hubbard model on the honeycomb lattice Alessandro Giuliani  

E-print Network

relation of its quasi particles, see [6] for an up-to-date description of the state of art. Among the mostThe 2D Hubbard model on the honeycomb lattice Alessandro Giuliani Dipartimento di Matematica the 2D Hubbard model on the honeycomb lattice, as a model for a single layer graphene sheet

Roma "La Sapienza", Università di

259

Considerations for the installation of honeycomb and screens to reduce wind-tunnel turbulence  

NASA Technical Reports Server (NTRS)

Tests were conducted on a half-scale model representing a 0.914-m (3.0-ft) square stream tube of the flow through the fourth corner and settling chamber of the Langley 8-Foot Transonic Pressure Tunnel. The model included the tube cooler 45 degree turning vanes, and the turbulence reduction screens and honeycomb, which were the subject of the tests. Hot-wire measurements of the turbulence reduction for various combinations of screens and honeycomb were made at various duct speeds. Of the four sizes of honeycomb cells tested, none were found to have a superior performance advantage. The effectiveness of screens and honeycomb in reducing turbulence is greatly affected by relatively minor physical damage; therefore, extreme care must be exercised in installing and maintaining honeycomb or screens if the turbulence reduction performance is to be maintained.

Scheiman, J.

1981-01-01

260

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

E-print Network

TEMPERATURE DEPENDENT CREEP EXPANSION OF Ti-6Al-4V LOW DENSITY CORE SANDWICH STRUCTURES Douglas T The application of lightweight, structurally efficient metal based honeycomb structures has been limited for the low cost manufacture of porous metal sandwich structures. These porous cored sandwich structures

Wadley, Haydn

261

Parametric results for heat transfer across honeycomb sandwich panels  

NASA Technical Reports Server (NTRS)

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

Ramohalli, K.; Sahakian, J.

1981-01-01

262

Spin and the Honeycomb Lattice: Lessons from Graphene  

E-print Network

Spin-1/2 particles such as the electron are described by the Dirac equation, which allows for two spin eigenvalues (up or down) and two types of energy eigenvalues (positive or negative, corresponding to the electron and the positron). A model of electrons hopping from atom to atom in graphene's honeycomb lattice gives low-energy electronic excitations that obey a relation formally identical to a 2+1 dimensional Dirac equation. Graphene's spin equivalent, "pseudospin", arises from the degeneracy introduced by the honeycomb lattice's two inequivalent atomic sites per unit cell. Previously it has been thought that the usual electron spin and the pseudospin indexing the graphene sublattice state are merely analogues. Here we show that the pseudospin is also a real angular momentum. This identification explains the suppression of electron backscattering in carbon nanotubes and the angular dependence of light absorption by graphene. Furthermore, it demonstrates that half-integer spin like that carried by the quarks and leptons can derive from hidden substructure, not of the particles themselves, but rather of the space in which these particles live.

Matthew Mecklenburg; B. C. Regan

2010-03-19

263

Netlike knitting of polyelectrolyte multilayers on honeycomb-patterned substrate.  

PubMed

The pH-amplified exponential growth layer-by-layer (LBL) self-assembly process was directly performed on honeycomb-patterned substrate for achievement of "guided patterning" of polyelectrolyte multilayers. Polyethylenimine (PEI) and poly(acrylic acid) (PAA) were used as polyanions, and their pH were carefully tuned to achieve pH-enhanced exponential growth. Guided by underlying hexagonally patterned islandlike poly(dimethylsiloxane) (PDMS) arrays, the diffusive polyelectrolytes rapidly interweaved into linear, multilayered structures distributed along the grooves between the patterned protuberate and formed a regular network of multilayered film with uniform mesh size. Netlike "knitting" of polyelectrolyte multilayers on honeycomb-patterned substrate has been realized by following this procedure. Superhydrophobic surfaces could be readily obtained after several bilayers of LBL assembly (with thermal cross-linking and surface fluorination by chemical vapor deposition), indicating that successful fabrication of functional micro- and nanoscale hierarchical structures can be achieved. Both high- and low-adhesion superhydrophobic surfaces ("petal effect" and "lotus effect") can be obtained with different bilayers of assembly, proving that different levels of nano- to microstructural hierarchy can be realized using this method. Furthermore, we were able to get topographically asymmetric, free-standing, polyelectrolyte multilayer films in the case that we performed more than eight bilayers of assembly. This research reported template-directed LBL patterning assembly for the first time. It provides a beneficial exploration for the surface patterning technique for the LBL assembly process. PMID:20684559

Sun, Wei; Shen, Liyan; Wang, Jiaming; Fu, Ke; Ji, Jian

2010-09-01

264

Discrete breathers in honeycomb Fermi–Pasta–Ulam lattices  

NASA Astrophysics Data System (ADS)

We consider the two-dimensional Fermi–Pasta–Ulam lattice with hexagonal honeycomb symmetry, which is a Hamiltonian system describing the evolution of a scalar-valued quantity subject to nearest neighbour interactions. Using multiple-scale analysis we reduce the governing lattice equations to a nonlinear Schrödinger equation coupled to a second equation for an accompanying slow mode. Two cases in which the latter equation can be solved and so the system decoupled are considered in more detail: firstly, in the case of a symmetric potential, we derive the form of moving breathers. We find an ellipticity criterion for the wavenumbers of the carrier wave, together with asymptotic estimates for the breather energy. The minimum energy threshold depends on the wavenumber of the breather. We find that this threshold is locally maximized by stationary breathers. Secondly, for an asymmetric potential we find stationary breathers, which, even with a quadratic nonlinearity generate no second harmonic component in the breather. Plots of all our findings show clear hexagonal symmetry as we would expect from our lattice structure. Finally, we compare the properties of stationary breathers in the square, triangular and honeycomb lattices.

Wattis, Jonathan AD; James, Lauren M.

2014-08-01

265

The fate of aluminum in Cochnewagan Lake, Monmouth, Maine  

SciTech Connect

Aluminum salts are commonly used to improve lake water quality. The primary goal of this study is to determine the fate of the aluminum in a lake system. In June, 1986, Cochnewagan Lake was treated with aluminum sulfate and sodium aluminate to remove phosphorus from the water. As a result of this treatment, phosphorus concentrations in the lake decreased from about 20[mu]g/1 to about 10[mu]g/1, algal blooms were eliminated and the water clarity improved. Water and sediment samples were taken in the fall of 1992. The water was analyzed for pH, dissolved oxygen, alkalinity, aluminum, and total phosphate. Only trace amounts of aluminum and phosphate were found in the water column. The sediment samples that were recovered by box coring were highly bioturbated and dark brown-gray in color. After the removal of water and total organic matter, the cores showed a color gradation from light red-gray at the surface to dark gray at 8 cm. depth. The lack of aluminum in the water column and the color gradation in the cores indicates that aluminum concentrations in the sediments have increased. SEM-EDX studies will be performed on the cores to verify the presence of aluminum in the sediments.

Talbot, M. (Bates Coll., Lewiston, ME (United States). Geology Dept.)

1993-03-01

266

Directed Self-Assembly of Large Scaffold-free Multicellular Honeycomb Structures  

PubMed Central

A significant challenge to the field of biofabrication is the rapid construction of large three dimensional (3D) living tissues and organs. Multi-cellular spheroids have been used as building blocks. In this paper, we create large multi-cellular honeycomb building blocks using directed self-assembly, whereby cell-to-cell adhesion, in the context of the shape and obstacles of a micromold, drives the formation of a 3D structure. Computer aided design, rapid prototyping and replica molding were used to fabricate honeycomb-shaped micro-molds. Nonadhesive hydrogels cast from these micro-molds were equilibrated in cell culture medium and seeded with two types of mammalian cells. The cells settled into the honeycomb recess, were unable to attach to the nonadhesive hydrogel and so cell-to-cell adhesion drove the self-assembly of a large multicellular honeycomb within 24 hours. Distinct morphological changes occurred to the honeycomb and its cells indicating the presence of significant cell-mediated tension. Unlike the spheroid, whose size is constrained by a critical diffusion distance needed to maintain cell viability, the overall size of the honeycomb is not limited. The rapid production of the honeycomb building unit, with its multiple rings of high density cells and open lumen spaces, offers interesting new possibilities for biofabrication strategies. PMID:21828905

Tejavibulya, Nalin; Youssef, Jacquelyn; Bao, Brian; Ferruccio, Toni-Marie; Morgan, Jeffrey R.

2011-01-01

267

The Morphology and Functions of Articular Chondrocytes on a Honeycomb-Patterned Surface  

PubMed Central

The present study investigated the potential of a novel micropatterned substrate for neocartilage formation. Articular chondrocytes were cultured on poly(?-caprolactone) materials whose surfaces were either flat or honeycomb-patterned. The latter was prepared using a novel self-organization technique, while the former, was prepared by spin-coating. The chondrocytes attached and proliferated on both surfaces. On the honeycomb films, chondrocytes were found at the top surface and encased within the 10??m pores. Meanwhile, chondrocytes on the spin-coated surface flattened out. Accumulation of DNA and keratin sulphate was comparatively higher on the honeycomb films within the first 7 days. At their respective peaks, DNA concentration increased on the honeycomb and flat surfaces by approximately 210% and 400% of their day 1 values, respectively. However, cultures on the flat surface took longer to peak. Extracellular Matrix (ECM) concentrations peaked at 900% and 320% increases for the honeycomb and flat cultures. Type II collagen was upregulated on the honeycomb and flat surfaces by as much as 28% and 25% of their day 1 values, while aggrecan was downregulated with time, by 3.4% and 7.4%. These initial results demonstrate the potential usefulness of honeycomb-based scaffolds during early cultures neocartilage and soft tissue engineering. PMID:24804237

Eniwumide, Joshua O.; Tanaka, Masaru; Nagai, Nobuhiro; Morita, Yuka; de Bruijn, Joost; Yamamoto, Sadaaki; Onodera, Shin; Kondo, Eiji; Yasuda, Kazunori; Shimomura, Masatsugu

2014-01-01

268

Evaluation of Composite Honeycomb Sandwich Panels Under Compressive Loads at Elevated Temperatures  

NASA Technical Reports Server (NTRS)

Fourteen composite honeycomb sandwich panels were tested to failure under compressive loading. The test specimens included panels with both 8 and 24-ply graphite-bismaleimide composite facesheets and both titanium and graphite-polyimide core materials. The panels were designed to have the load introduced through fasteners attached to pairs of steel angles on the ends of the panels to simulate double shear splice joints. The unloaded edges were unconstrained. Test temperatures included room temperature, 250F, and 300F. For the room and 250F temperature tests, the 24-ply specimen failure strains were close to the unnotched allowable strain values and failure loads were well above the design loads. However, failure strains much lower than the unnotched allowable strain values, and failure loads below the design loads were observed with several of the 8-ply specimens. For each individual test temperature, large variations in the failure strains and loads were observed for the 8-ply specimens. Dramatic decreases in the failure strains and loads were observed for the 24-ply specimens as the test temperature was increased from 250F to 300F. All 8-ply specimens appeared to have failed in a facesheet strength failure mode for all test temperatures. The 24-ply specimens displayed appreciably greater amounts of bending prior to failure than the 8-ply specimens, and panel buckling occurred prior to facesheet strength failure for the 24-ply room and 250F temperature tests.

Walker, Sandra P.

1998-01-01

269

Position space formulation for Dirac fermions on honeycomb lattice  

NASA Astrophysics Data System (ADS)

We study how to construct Dirac fermion defined on the honeycomb lattice in position space. Starting from the nearest neighbor interaction in tight binding model, we show that the Hamiltonian is constructed by kinetic term and second derivative term of three flavor Dirac fermions in which one flavor has a mass of cutoff order and the other flavors are massless. In this formulation, the structure of the Dirac point is simplified so that its uniqueness can be easily shown even if we consider the next-to-nearest neighbor interaction. We also show that there is a hidden exact U(1) symmetry (flavor-chiral symmetry) at finite lattice spacing, which protects the masslessness of the Dirac fermion, and discuss the analogy with the staggered fermion formulation.

Hirotsu, Masaki; Onogi, Tetsuya; Shintani, Eigo

2014-08-01

270

Kane-Mele-Hubbard model on the ?-flux honeycomb lattice  

NASA Astrophysics Data System (ADS)

We consider the Kane-Mele-Hubbard model with a magnetic ? flux threading each honeycomb plaquette. The resulting model has remarkably rich physical properties. In each spin sector, the noninteracting band structure is characterized by a total Chern number C =±2. Fine-tuning of the intrinsic spin-orbit coupling ? leads to a quadratic band crossing point associated with a topological phase transition. At this point, quantum Monte Carlo simulations reveal a magnetically ordered phase that extends to weak coupling. Although the spinful model has two Kramers doublets at each edge and is explicitly shown to be a Z2 trivial insulator, the helical edge states are protected at the single-particle level by translation symmetry. Drawing on the bosonized low-energy Hamiltonian, we predict a correlation-induced gap as a result of umklapp scattering for half-filled bands. For strong interactions, this prediction is confirmed by quantum Monte Carlo simulations.

Bercx, Martin; Hohenadler, Martin; Assaad, Fakher F.

2014-08-01

271

Sound Transmission Through a Curved Honeycomb Composite Panel  

NASA Technical Reports Server (NTRS)

Composite structures are often used in aircraft because of the advantages offered by a high strength to weight ratio. However, the acoustical properties of these light and stiff structures can often be less than desirable resulting in high aircraft interior noise levels. In this paper, measurements and predictions of the transmission loss of a curved honeycomb composite panel are presented. The transmission loss predictions are validated by comparisons to measurements. An assessment of the behavior of the panel is made from the dispersion characteristics of transverse waves propagating in the panel. The speed of transverse waves propagating in the panel is found to be sonic or supersonic over the frequency range from 100 to 5000 Hz. The acoustical benefit of reducing the wave speed for transverse vibration is demonstrated.

Klos, Jacob; Robinson, Jay H.; Buehrle, Ralph D.

2003-01-01

272

The 2D Hubbard model on the honeycomb lattice  

E-print Network

We consider the 2D Hubbard model on the honeycomb lattice, as a model for a single layer graphene sheet in the presence of screened Coulomb interactions. At half filling and weak enough coupling, we compute the free energy, the ground state energy and we construct the correlation functions up to zero temperature in terms of convergent series; analiticity is proved by making use of constructive fermionic renormalization group methods. We show that the interaction produces a modification of the Fermi velocity and of the wave function renormalization without changing the asymptotic infrared properties of the model with respect to the unperturbed non-interacting case; this rules out the possibility of superconducting or magnetic instabilities in the ground state. We also prove that the correlations verify a Ward Identity similar to the one for massless Dirac fermions, up to asymptotically negligible corrections and a renormalization of the charge velocity.

Alessandro Giuliani; Vieri Mastropietro

2008-11-12

273

Weyl semimetal from the honeycomb array of topological insulator nanowires  

NASA Astrophysics Data System (ADS)

We introduce a topological semimetal phase with four isolated Weyl nodes in momentum space from a honeycomb arrangement of topological insulator nanowires. This realizes a Weyl semimetal phase in which the topological charge response is absent due to the opposite separation of two pairs of Weyl nodes in the Brillouin zone (BZ). The topological nature of the system manifests itself in the nonzero transverse “valley” current which is proportional to the length of the Weyl nodes' separation vector. In the end, we show that anomalous Hall current can also emerge by considering the Haldane term, i.e., the next-nearest-neighbour inter-wire hopping of the electrons in the presence of a modulating magnetic flux.

Vazifeh, M. M.

2013-06-01

274

Porphyrin-based honeycomb films and their antibacterial activity.  

PubMed

Micrometer-sized porous honeycomb-patterned thin films based on hybrid complexes formed via electrostatic interaction between Mn(III) meso-tetra(4-sulfonatophenyl) porphine chloride (an acid form, {MnTPPS}) and dimethyldioctadecylammonium bromide (DODMABr). The morphology of the microporous thin films can be well regulated by controlling the concentration of MnTPPS-DODMA complexes, DODMABr, and polystyrene (PS), respectively. The formation of the microporous thin films was largely influenced by different solvents. The well-ordered microporous films of MnTPPS-DODMA complexes exhibit a more efficient antibacterial activity under visible light than those of hybrid complexes of nanoparticles modified with DODMABr, implying that well-ordered microporous films containing porphyrin composition can improve photochemical activity and more dominance in applications in biological medicine fields. PMID:24846091

Wang, Yanran; Liu, Yan; Li, Guihua; Hao, Jingcheng

2014-06-10

275

Armchair nanoribbons of silicon and germanium honeycomb structures  

NASA Astrophysics Data System (ADS)

We present a first-principles study of bare and hydrogen passivated armchair nanoribbons of the puckered single layer honeycomb structures of silicon and germanium. Our study includes optimization of atomic structure, stability analysis based on the calculation of phonon dispersions, electronic structure, and the variation in band gap with the width of the ribbon. The band gaps of silicon and germanium nanoribbons exhibit family behavior similar to those of graphene nanoribbons. The edges of bare nanoribbons are sharply reconstructed, which can be eliminated by the hydrogen termination of dangling bonds at the edges. Periodic modulation of the nanoribbon width results in a superlattice structure which can act as a multiple quantum well. Specific electronic states are confined in these wells. Confinement trends are qualitatively explained by including the effects of the interface. In order to investigate wide and long superlattice structures we also performed empirical tight-binding calculations with parameters determined from ab initio calculations.

Cahangirov, S.; Topsakal, M.; Ciraci, S.

2010-05-01

276

Honeycomb: Visual Analysis of Large Scale Social Networks  

NASA Astrophysics Data System (ADS)

The rise in the use of social network sites allows us to collect large amounts of user reported data on social structures and analysis of this data could provide useful insights for many of the social sciences. This analysis is typically the domain of Social Network Analysis, and visualization of these structures often proves invaluable in understanding them. However, currently available visual analysis tools are not very well suited to handle the massive scale of this network data, and often resolve to displaying small ego networks or heavily abstracted networks. In this paper, we present Honeycomb, a visualization tool that is able to deal with much larger scale data (with millions of connections), which we illustrate by using a large scale corporate social networking site as an example. Additionally, we introduce a new probability based network metric to guide users to potentially interesting or anomalous patterns and discuss lessons learned during design and implementation.

van Ham, Frank; Schulz, Hans-Jörg; Dimicco, Joan M.

277

Friction factor data for flat plate tests of smooth and honeycomb surfaces  

E-print Network

And Honeycomb Surfaces. (May 1989) Tae Woong Ha, B.S., Han Yang University in Korea Chair of Advisory Committee: Dr. Dara Childs Friction factors for honeycomb surfaces are measured with a flat plate tester. The flat plate test apparatus is described and a... method is discussed for determining the friction factor experimentally. The friction factor model is developed for the flat plate test based on the Fanno Line Flow. The comparisons of the friction factor are plotted for smooth surface and six-honeycomb...

Ha, Tae Woong

2012-06-07

278

Theoretical Predictions of Freestanding Honeycomb Sheets of Cadmium Chalcogenides  

SciTech Connect

Two-dimensional (2D) nanocrystals of CdX (X = S, Se, Te) typically grown by colloidal synthesis are coated with organic ligands. Recent experimental work on ZnSe showed that the organic ligands can be removed at elevated temperature, giving a freestanding 2D sheet of ZnSe. In this theoretical work, freestanding single- to few-layer sheets of CdX, each possessing a pseudo honeycomb lattice, are considered by cutting along all possible lattice planes of the bulk zinc blende (ZB) and wurtzite (WZ) phases. Using density functional theory, we have systematically studied their geometric structures, energetics, and electronic properties. A strong surface distortion is found to occur for all of the layered sheets, and yet all of the pseudo honeycomb lattices are preserved, giving unique types of surface corrugations and different electronic properties. The energetics, in combination with phonon mode calculations and molecular dynamics simulations, indicate that the syntheses of these freestanding 2D sheets could be selective, with the single- to few-layer WZ110, WZ100, and ZB110 sheets being favored. Through the GW approximation, it is found that all single-layer sheets have large band gaps falling into the ultraviolet range, while thicker sheets in general have reduced band gaps in the visible and ultraviolet range. On the basis of the present work and the experimental studies on freestanding double-layer sheets of ZnSe, we envision that the freestanding 2D layered sheets of CdX predicted herein are potential synthesis targets, which may offer tunable band gaps depending on their structural features including surface corrugations, stacking motifs, and number of layers.

Zhou, Jia [ORNL] [ORNL; Huang, Jingsong [ORNL] [ORNL; Sumpter, Bobby G [ORNL] [ORNL; Kent, Paul R [ORNL] [ORNL; Xie, Yu [ORNL] [ORNL; Terrones Maldonado, Humberto [ORNL] [ORNL; Smith, Sean C [ORNL] [ORNL

2014-01-01

279

Design of metallic textile core sandwich panels F.W. Zok *, H.J. Rathbun, Z. Wei, A.G. Evans  

E-print Network

Design of metallic textile core sandwich panels F.W. Zok *, H.J. Rathbun, Z. Wei, A.G. Evans-5050, USA Received 3 March 2003 Abstract Metallic sandwich panels with textile cores have been analyzed are made with competing concepts, especially honeycomb and truss core systems. It is demonstrated that all

Zok, Frank

280

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

NASA Technical Reports Server (NTRS)

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.

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

1984-01-01

281

Repair of brazed steel honeycomb-sandwich panels with vertical pins only  

NASA Technical Reports Server (NTRS)

Vertical steel tubular pins restore the shear strength of honeycomb panels and improve the quality of the repaired panel. New repair method eliminates diagonal pins. Vertical pins are welded to face sheets, forming ''Vierendeel Truss'' arrangement to transmit shear loads.

Rowe, J.

1970-01-01

282

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

E-print Network

??Includes bibliographical references (p. 207-214).Traditionally, honeycomb sandwich structures are designed in the elastic range, but recent studies on the crushing of sandwich profiles have shown… (more)

Mohr, Dirk, 1976-

2003-01-01

283

A study of the effects of eccentricity on honeycomb annular gas seals  

E-print Network

Results are presented which show the effects of eccentricity on high pressure honeycomb and smooth annular gas seals. The results of the experiments indicate the ability to utilize centered seal solutions for rotordynamic coefficients and seal...

Weatherwax, Mark

2012-06-07

284

Experimental investigation and constitutive modeling of metallic honeycombs in sandwich structures  

E-print Network

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

Mohr, Dirk, 1976-

2003-01-01

285

Aluminum and Young Artists.  

ERIC Educational Resources Information Center

The author suggests a variety of ways in which aluminum and aluminum foil can be used in elementary and junior high art classes: relief drawing and rubbing; printing; repousse; sculpture; mobiles; foil sculpture; and three dimensional design. Sources of aluminum supplies are suggested. (SJL)

Anderson, Thomas

1980-01-01

286

Band Structure Calculations for Two-Dimensional Plasma Photonic Crystals in Honeycomb Lattice Arrangement  

Microsoft Academic Search

We propose an approach originating from plane wave expansion method to calculate band structure for two types of honeycomb lattice two-dimensional plasma photonic crystals. The eigenvalue equations of E-polarization for two types of structures, which depend on the honeycomb lattice realization(plasma rods immersed in dielectric background or vice versa), are derived respectively. A standard linearization technique which solves the general

Xiang-Kun Kong; Shao-Bin Liu; Hai-Feng Zhang; Liang Zhou; Chun-Zao Li

2011-01-01

287

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

Microsoft Academic Search

Radar absorbing materials with metal magnetic micropowder-coated honeycomb sandwich structures are prepared by a spray process. Metal magnetic micropowder is applied as an absorber which maintains a high absorption, and a honeycomb sandwich structure as a supporter enhancing mechanical strength. The microwave absorption properties are measured by a network analyzer system in the frequency range of 2.6-18 GHz. The concentration

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

2007-01-01

288

Controllable growth of aluminum nanorods using physical vapor deposition  

NASA Astrophysics Data System (ADS)

This letter proposes and experimentally demonstrates that oxygen, through action as a surfactant, enables the growth of aluminum nanorods using physical vapor deposition. Based on the mechanism through which oxygen acts, the authors show that the diameter of aluminum nanorods can be controlled from 50 to 500 nm by varying the amount of oxygen present, through modulating the vacuum level, and by varying the substrate temperature. When grown under medium vacuum, the nanorods are in the form of an aluminum metal - aluminum oxide core-shell. The thickness of the oxide shell is ~2 nm as grown and is stable when maintained in ambient for 30 days or annealed in air at 475 K for 1 day. As annealing temperature is increased, the nanorod morphology remains stable while the ratio of oxide shell to metallic core increases, resulting in a fully aluminum oxide nanorod at 1,475 K.

Stagon, Stephen P.; Huang, Hanchen

2014-08-01

289

One-to-One Embedding between Honeycomb Mesh and Petersen-Torus Networks  

PubMed Central

As wireless mobile telecommunication bases organize their structure using a honeycomb-mesh algorithm, there are many studies about parallel processing algorithms like the honeycomb mesh in Wireless Sensor Networks. This paper aims to study the Peterson-Torus graph algorithm in regard to the continuity with honeycomb-mesh algorithm in order to apply the algorithm to sensor networks. Once a new interconnection network is designed, parallel algorithms are developed with huge research costs to use such networks. If the old network is embedded in a newly designed network, a developed algorithm in the old network is reusable in a newly designed network. Petersen-Torus has been designed recently, and the honeycomb mesh has already been designed as a well-known interconnection network. In this paper, we propose a one-to-one embedding algorithm for the honeycomb mesh (HMn) in the Petersen-Torus PT(n,n), and prove that dilation of the algorithm is 5, congestion is 2, and expansion is 5/3. The proposed one-to-one embedding is applied so that processor throughput can be minimized when the honeycomb mesh algorithm runs in the Petersen-Torus. PMID:22319392

Seo, Jung-Hyun; Sim, Hyun; Park, Dae-Heon; Park, Jang-Woo; Lee, Yang-Sun

2011-01-01

290

Effect of honeycomb seals on loss characteristics in shroud cavities of an axial turbine  

NASA Astrophysics Data System (ADS)

The loss in efficiency due to shroud leakage or tip clearance flow accounts for a substantial part of the overall losses in turbomachinery. It is important to identify the leakage loss characteristics in order to optimize turbomachinery. At present, little information is available in the open literature concerning the effect of honeycomb seals on the loss characteristics in shroud cavities of an axial turbine, despite of the widespread use of the honeycomb seals. Therefore, interaction between rotor labyrinth seal leakage flow with and without honeycomb facings and main flow is investigated to provide the loss characteristics of the mixing process of the re-entering leakage flow into the main flow. The effects of honeycomb seals on the flow in shroud cavities and interaction with the main flow are analyzed. An additional study on the impact of subtle shroud cavity exit geometry is also presented. The investigation results indicate that the honeycomb seal affects the over tip leakage flow and reduces mixing losses when compared to the solid labyrinth seal. The leakage flow interactions with the main flow have considerably changed the flow fields in the endwall regions. The proposed research reveals the effects of honeycomb seals on the loss characteristics in shroud cavities and the impact of subtle shroud cavity exit geometry, and it is helpful for the design optimization of turbomachinery.

Gao, Jie; Zheng, Qun; Wang, Zheng

2013-01-01

291

Competing Topological and Kondo Insulator Phases on a Honeycomb Lattice  

NASA Astrophysics Data System (ADS)

We investigate the competition between the spin-orbit interaction of itinerant electrons and their Kondo coupling with local moments densely distributed on the honeycomb lattice. We find that the model at half-filling displays a quantum phase transition between topological and Kondo insulators at a nonzero Kondo coupling. In the Kondo-screened case, tuning the electron concentration can lead to a new topological insulator phase. The results suggest that the heavy-fermion phase diagram contains a new regime with a competition among topological, Kondo-coherent and magnetic states, and that the regime may be especially relevant to Kondo lattice systems with 5d-conduction electrons. Finally, we discuss the implications of our results in the context of the recent experiments on SmB6 implicating the surface states of a topological insulator, as well as the existing experiments on the phase transitions in SmB6 under pressure and in CeNiSn under chemical pressure.

Feng, Xiao-Yong; Dai, Jianhui; Chung, Chung-Hou; Si, Qimiao

2013-07-01

292

Competing topological and Kondo insulator phases on a honeycomb lattice.  

PubMed

We investigate the competition between the spin-orbit interaction of itinerant electrons and their Kondo coupling with local moments densely distributed on the honeycomb lattice. We find that the model at half-filling displays a quantum phase transition between topological and Kondo insulators at a nonzero Kondo coupling. In the Kondo-screened case, tuning the electron concentration can lead to a new topological insulator phase. The results suggest that the heavy-fermion phase diagram contains a new regime with a competition among topological, Kondo-coherent and magnetic states, and that the regime may be especially relevant to Kondo lattice systems with 5d-conduction electrons. Finally, we discuss the implications of our results in the context of the recent experiments on SmB(6) implicating the surface states of a topological insulator, as well as the existing experiments on the phase transitions in SmB(6) under pressure and in CeNiSn under chemical pressure. PMID:23863017

Feng, Xiao-Yong; Dai, Jianhui; Chung, Chung-Hou; Si, Qimiao

2013-07-01

293

Bloch-Zener oscillations in a tunable optical honeycomb lattice  

SciTech Connect

Ultracold gases in optical lattices have proved to be a flexible tool to simulate many different phenomena of solid state physics [1, 2]. Recently, optical lattices with complex geometries have been realized [3, 4, 5, 6, 7], paving the way to simulating more realistic systems. The honeycomb structure has recently become accessible in an optical lattice composed of mutually perpendicular laser beams. This lattice structure exhibits topological features in its band structure – the Dirac points. At these points, two energy bands intersect linearly and the particles behave as relativistic Dirac fermions. In optical lattices, Bloch oscillations [8] resolved both in time and in quasi-momentum space can be directly observed. We make use of such Bloch-Zener oscillations to probe the vanishing energy gap at the Dirac points as well as their position in the band structure. In small band gap regions, we observe Landau-Zener tunneling [7, 9] to the second band and the regions of maximum transfer can be identified with the position of the Dirac points.

Uehlinger, Thomas; Greif, Daniel; Jotzu, Gregor; Esslinger, Tilman [Institute for Quantum Electronics, ETH Zurich, 8093 Zurich (Switzerland); Tarruell, Leticia [Institute for Quantum Electronics, ETH Zurich, 8093 Zurich, Switzerland and LP2N, Universite Bordeaux 1, IOGS, CNRS, 351 cours de la Liberation, 33405 Talence (France)

2013-12-04

294

B. P. Russell V. S. Deshpande  

E-print Network

With a Hierarchical Square Honeycomb Sandwich Core Sandwich panels with aluminum alloy face sheets and a hierarchical direction of the square honeycomb is aligned with the normal of the overall sandwich panel. The cell walls of the honeycomb comprise sandwich plates made from glass fiber/epoxy composite faces and a polymethacrylimide foam

Fleck, Norman A.

295

Aluminum: Recycling of Aluminum Dross/Saltcake  

SciTech Connect

As this NICE3 publication details, the objective of this project is to commercialize the process technology to eliminate all landfill waste associated with black dross and saltcake generated from aluminum recycling in the United States.

Blazek, S.

1999-01-29

296

Heat Shield Employing Cured Thermal Protection Material Blocks Bonded in a Large-Cell Honeycomb Matrix  

NASA Technical Reports Server (NTRS)

A document describes a new way to integrate thermal protection materials on external surfaces of vehicles that experience the severe heating environments of atmospheric entry from space. Cured blocks of thermal protection materials are bonded into a compatible, large-cell honeycomb matrix that can be applied on the external surfaces of the vehicles. The honeycomb matrix cell size, and corresponding thermal protection material block size, is envisioned to be between 1 and 4 in. (.2.5 and 10 cm) on a side, with a depth required to protect the vehicle. The cell wall thickness is thin, between 0.01 and 0.10 in. (.0.025 and 0.25 cm). A key feature is that the honeycomb matrix is attached to the vehicle fs unprotected external surface prior to insertion of the thermal protection material blocks. The attachment integrity of the honeycomb can then be confirmed over the full range of temperature and loads that the vehicle will experience. Another key feature of the innovation is the use of uniform-sized thermal protection material blocks. This feature allows for the mass production of these blocks at a size that is convenient for quality control inspection. The honeycomb that receives the blocks must have cells with a compatible set of internal dimensions. The innovation involves the use of a faceted subsurface under the honeycomb. This provides a predictable surface with perpendicular cell walls for the majority of the blocks. Some cells will have positive tapers to accommodate mitered joints between honeycomb panels on each facet of the subsurface. These tapered cells have dimensions that may fall within the boundaries of the uniform-sized blocks.

Zell, Peter

2012-01-01

297

Differentiation of mesenchymal stem cells into osteoblasts on honeycomb collagen scaffolds.  

PubMed

Tissue engineering using living cells is emerging as an alternative to tissue or organ transplantation. The adult mesenchymal stem cells can be differentiated into multilineage cells, such as adipocytes, chondrocytes, or osteoblasts when cultured with specific growth factors. In the present investigation, we have studied the effect of honeycomb collagen scaffolds for the adhesion, differentiation and proliferation of bone marrow-derived mesenchymal stem cells into osteoblasts. Mesenchymal stem cells were isolated from 6-week old albino rat femur bone marrow, and cultured in alpha-MEM medium without beta-glycerophosphate and dexamethasone. Honeycomb collagen discs were prepared from bovine dermal atelocollagen, cross-linked by UV-irradiation and sterilized by heat. The honeycomb discs were placed on the culture dishes before seeding the stem cells. The cells attached quickly to the honeycomb collagen scaffold, differentiated and proliferated into osteoblasts. The differentiated osteoblasts were characterized by morphological examination and alkaline phosphatase activity. The osteoblasts also synthesized calcium-deficient hydroxyapatite (pseudo-hydroxyapatite) crystals in the culture. The mineralization was confirmed by Von Kossa staining and the crystals were analyzed by X-ray diffraction. Light microscopy and DNA measurements showed that the differentiated osteoblasts multiplied into several layers on the honeycomb collagen scaffold. The results demonstrated that the honeycomb collagen sponge is an excellent scaffold for the differentiation and proliferation of mesenchymal stem cells into osteoblasts. The data further proved that honeycomb collagen is an effective substrate for tissue engineering applications, and is very useful in the advancing field of stem cell technology and cell-based therapy. PMID:16572435

George, Joseph; Kuboki, Yoshinori; Miyata, Teruo

2006-10-20

298

Aluminum/magnesium 3D-Printing rapid prototyping  

US Patent & Trademark Office Database

A 3D Printing Rapid Prototyping process using Al/Mg particles coated with a metal (i.e. copper, nickel, zinc, or tin) that (1) prevents oxidation of the Al/Mg particles, and (2) either alone, or when alloyed with the aluminum or magnesium core metal, melts below the liquidus temperature of the core.

2006-11-28

299

Aspects of aluminum toxicity  

SciTech Connect

Aluminum is the most abundant metal in the earth's crust. The widespread occurrence of aluminum, both in the environment and in foodstuffs, makes it virtually impossible for man to avoid exposure to this metal ion. Attention was first drawn to the potential role of aluminum as a toxic metal over 50 years ago, but was dismissed as a toxic agent as recently as 15 years ago. The accumulation of aluminum, in some patients with chronic renal failure, is associated with the development of toxic phenomena; dialysis encephalopathy, osteomalacic dialysis osteodystrophy, and an anemia. Aluminum accumulation also occurs in patients who are not on dialysis, predominantly infants and children with immature or impaired renal function. Aluminum has also been implicated as a toxic agent in the etiology of Alzheimer's disease, Guamiam amyotrophic lateral sclerosis, and parkinsonism-dementia. 119 references.

Hewitt, C.D.; Savory, J.; Wills, M.R. (Univ. of Virginia Health Sciences Center, Charlottesville (USA))

1990-06-01

300

Porous and Microporous Honeycomb Composites as Potential Boundary-Layer Bleed Materials  

NASA Technical Reports Server (NTRS)

Results of an experimental investigation are presented in which the use of porous and microporous honeycomb composite materials is evaluated as an alternate to perforated solid plates for boundary-layer bleed in supersonic aircraft inlets. The terms "porous" and "microporous," respectively, refer to bleed orifice diameters roughly equal to and much less than the displacement thickness of the approach boundary-layer. A Baseline porous solid plate, two porous honeycomb, and three microporous honeycomb configurations are evaluated. The performance of the plates is characterized by the flow coefficient and relative change in boundary-layer profile parameters across the bleed region. The tests were conducted at Mach numbers of 1.27 and 1.98. The results show the porous honeycomb is not as efficient at removing mass compared to the baseline. The microporous plates were about equal to the baseline with one plate demonstrating a significantly higher efficiency. The microporous plates produced significantly fuller boundary-layer profiles downstream of the bleed region for a given mass flow removal rate than either the baseline or the porous honeycomb plates.

Davis, D. O.; Willis, B. P.; Schoenenberger, M.

1997-01-01

301

Design of functionalized cellulosic honeycomb films: site-specific biomolecule modification via "click chemistry".  

PubMed

Value-added materials from naturally abundant polymers such as cellulose are of significant importance. In particular, cellulosic open-framework structures with controlled chemical functionality of the internal surface have great potential in many biosensor applications. Although various cellulose derivatives can form porous honeycomb structured materials, solubility issues and problems with film formation exist. To address this, we have generated robust cellulosic open-framework structures that can be post-functionalized through site-specific modification. Regioselectively modified amphiphilic cellulose azides, 3-O-azidopropoxypoly(ethylene glycol)-2,6-di-O-thexyldimethylsilyl cellulosics, were synthesized, and honeycomb-patterned films were readily produced by the simple breath figures method. Changing the degree of polymerization (DP) of the pendent ethylene glycol (EG(DP)) groups from 22 to 4 increased the corresponding honeycomb film pore diameters from ~1.2 to ~2.6 ?m, enabling the potential tuning of pore size. Moreover, these novel azido-functionalized honeycomb films were easily functionalized using Cu(I)-catalyzed alkyne-azide [2 + 3] cycloaddition reaction; biotin was "clicked" onto the azide functionalized cellulosic honeycomb films without any effect to the film structure. These results indicate this system may serve as a platform for the design and development of biosensors. PMID:22148461

Xu, William Z; Zhang, Xinyue; Kadla, John F

2012-02-13

302

Papillary Thyroid Carcinoma with Honeycomb-Like Multiple Small Cysts: Characteristic Features on Ultrasonography  

PubMed Central

Background Thyroid nodules with cystic content or mixed sponge-like aspect on ultrasonography and a concordant cytology are strongly predictive of benignity. Objectives We present 8 patients with honeycomb-like papillary thyroid carcinoma with multiple small cysts on ultrasonography. Methods The patients were 6 women and 2 men aged between 30 and 57 years. The tumors of these patients showed honeycomb-like multiple small cysts that were aggregated in some area of the thyroid gland on ultrasonography. Histopathological examination indicated a well-differentiated type of papillary thyroid carcinoma with multiple small cysts and a small solid lesion. The cysts were lined with papillary carcinoma cells, and normal thyroid tissue lay between the cysts. Results There is a peculiar type of papillary thyroid carcinoma that histopathologically shows honeycomb-like multiple small cysts in the thyroid gland. Ultrasonography can be used to identify characteristic features of honeycomb-like multiple small cysts in the thyroid gland in such patients. Conclusions One should be aware of this peculiar type of papillary thyroid carcinoma with honeycomb-like multiple small cysts on ultrasonography, although thyroid nodules with cystic lesions are generally regarded as benign in clinical management. PMID:24783058

Kobayashi, Kaoru; Hirokawa, Mitsuyoshi; Yabuta, Tomonori; Fukushima, Mitsuhiro; Kihara, Minoru; Takamura, Yuuki; Ito, Yasuhiro; Miya, Akihiro; Amino, Nobuyuki; Miyauchi, Akira

2013-01-01

303

Design optimization of sinusoidal glass honeycomb for flat plate solar collectors  

NASA Technical Reports Server (NTRS)

The design of honeycomb made of sinusoidally corrugated glass strips was optimized for use in water-cooled, single-glazed flat plate solar collectors with non-selective black absorbers. Cell diameter (d), cell height (L), and pitch/diameter ratio (P/d) maximizing solar collector performance and cost effectiveness for given cell wall thickness (t sub w) and optical properties of glass were determined from radiative and convective honeycomb characteristics and collector performance all calculated with experimentally validated algorithms. Relative lifetime values were estimated from present materials costs and postulated production methods for corrugated glass honeycomb cover assemblies. A honeycomb with P/d = 1.05, d = 17.4 mm, L = 146 mm and t sub w = 0.15 mm would provide near-optimal performance over the range delta T sub C greater than or equal to 0 C and less than or equal to 80 C and be superior in performance and cost effectiveness to a non-honeycomb collector with a 0.92/0.12 selective black absorber.

Mcmurrin, J. C.; Buchberg, H.

1980-01-01

304

Thermal insulation with paper honeycombs with solar gain  

SciTech Connect

In this contribution the authors describe the concept and the model for the heat flux and the effective U-value of paper honeycombs (PHC) used as efficient and cheap transparent insulation material. With this thermal-insulation-material static U-values of U = 0.25 W/(m{sup 2}K) are obtained due to the very low thermal conduction value {lambda} = 0.04 W/(mK), which is comparable to thermal insulators as PU-foam or mineral wool. Contrary to conventional insulation materials PHC also gathers solar radiation due to its geometry, thereby providing heat flux into the interior of the building. Because the angle of incidence of the sun in wintertime is low, the direct solar radiation is absorbed approximately within the outermost 3 centimeters of the PHC. Even at ambient temperatures below 0 C, this region is warmed up to 60 C. By conduction the heat is brought to the brick wall underneath, which acts as reservoir and gets to temperatures between 15 and 30 C. Calculated across the full heating period, it is shown, that effective U values of 0.14 W/(m{sup 2}K) are reached by using PHC, reducing the brick wall U value by a factor of 3/4. Contrary to other transparent thermal insulation systems, e.g. developed by the Fraunhofer Institute for Solar Energy Systems, this system does not overheat during summertime, because the capillary structure is shielding the solar rays. A Windows based program solves the heat conduction equation with finite element methods.

Hingerl, K.; Baumgartner, G.; Aschauer, H.

1996-12-31

305

Diffusion bonded boron/aluminum spar-shell fan blade  

NASA Technical Reports Server (NTRS)

Design and process development tasks intended to demonstrate composite blade application in large high by-pass ratio turbofan engines are described. Studies on a 3.0 aspect radio space and shell construction fan blade indicate a potential weight savings for a first stage fan rotor of 39% when a hollow titanium spar is employed. An alternate design which featured substantial blade internal volume filled with titanium honeycomb inserts achieved a 14% potential weight savings over the B/M rotor system. This second configuration requires a smaller development effort and entails less risk to translate a design into a successful product. The feasibility of metal joining large subsonic spar and shell fan blades was demonstrated. Initial aluminum alloy screening indicates a distinct preference for AA6061 aluminum alloy for use as a joint material. The simulated airfoil pressings established the necessity of rigid air surfaces when joining materials of different compressive rigidities. The two aluminum alloy matrix choices both were successfully formed into blade shells.

Carlson, C. E. K.; Cutler, J. L.; Fisher, W. J.; Memmott, J. V. W.

1980-01-01

306

Carbothermic Aluminum Production Using Scrap Aluminum As A Coolant  

DOEpatents

A process for producing aluminum metal by carbothermic reduction of alumina ore. Alumina ore is heated in the presence of carbon at an elevated temperature to produce an aluminum metal body contaminated with about 10-30% by wt. aluminum carbide. Aluminum metal or aluminum alloy scrap then is added to bring the temperature to about 900-1000.degree. C. and precipitate out aluminum carbide. The precipitated aluminum carbide is filtered, decanted, or fluxed with salt to form a molten body having reduced aluminum carbide content.

LaCamera, Alfred F. (Trafford, PA)

2002-11-05

307

Shear fatigue strength of a prismatic diamond sandwich core F. Co^te, V.S. Deshpande* and N.A. Fleck  

E-print Network

Shear fatigue strength of a prismatic diamond sandwich core F. Co^te´, V.S. Deshpande* and N; Sandwich panels Metallic micro-architectured materials are under development for multi basic architectures are the truss [2], honeycomb [3] and prismatic core [4]. Their deformation response

Fleck, Norman A.

308

Novel Aharonov-Bohm-like effect: Detectability of the vector potential in a solenoidal configuration with a ferromagnetic core covered by superconducting lead, and surrounded by a thin cylindrical shell of aluminum  

E-print Network

The flux as measured by the Josephson effect in a SQUID-like configuration with a ferromagnetic core inserted into its center, is shown to be sensitive to the vector potential arising from the central ferromagnetic core, even when the core is covered with a superconducting material that prevents any magnetic field lines from ever reaching the perimeter of the SQUID-like configuration. This leads to a macroscopic, Aharonov-Bohm-like effect that is observable in an asymmetric hysteresis loop in the response of the SQUID-like configuration to an externally applied magnetic field.

R. Y. Chiao

2012-06-23

309

Realization of a three-dimensional spin-anisotropic harmonic honeycomb iridate  

NASA Astrophysics Data System (ADS)

Spin and orbital quantum numbers play a key role in the physics of Mott insulators, but in most systems they are connected only indirectly—via the Pauli exclusion principle and the Coulomb interaction. Iridium-based oxides (iridates) introduce strong spin-orbit coupling directly, such that these numbers become entwined together and the Mott physics attains a strong orbital character. In the layered honeycomb iridates this is thought to generate highly spin-anisotropic magnetic interactions, coupling the spin to a given spatial direction of exchange and leading to strongly frustrated magnetism. Here we report a new iridate structure that has the same local connectivity as the layered honeycomb and exhibits striking evidence for highly spin-anisotropic exchange. The basic structural units of this material suggest that a new family of three-dimensional structures could exist, the ‘harmonic honeycomb’ iridates, of which the present compound is the first example.

Modic, K. A.; Smidt, Tess E.; Kimchi, Itamar; Breznay, Nicholas P.; Biffin, Alun; Choi, Sungkyun; Johnson, Roger D.; Coldea, Radu; Watkins-Curry, Pilanda; McCandless, Gregory T.; Chan, Julia Y.; Gandara, Felipe; Islam, Z.; Vishwanath, Ashvin; Shekhter, Arkady; McDonald, Ross D.; Analytis, James G.

2014-06-01

310

Realization of a three-dimensional spin-anisotropic harmonic honeycomb iridate.  

PubMed

Spin and orbital quantum numbers play a key role in the physics of Mott insulators, but in most systems they are connected only indirectly--via the Pauli exclusion principle and the Coulomb interaction. Iridium-based oxides (iridates) introduce strong spin-orbit coupling directly, such that these numbers become entwined together and the Mott physics attains a strong orbital character. In the layered honeycomb iridates this is thought to generate highly spin-anisotropic magnetic interactions, coupling the spin to a given spatial direction of exchange and leading to strongly frustrated magnetism. Here we report a new iridate structure that has the same local connectivity as the layered honeycomb and exhibits striking evidence for highly spin-anisotropic exchange. The basic structural units of this material suggest that a new family of three-dimensional structures could exist, the 'harmonic honeycomb' iridates, of which the present compound is the first example. PMID:24969742

Modic, K A; Smidt, Tess E; Kimchi, Itamar; Breznay, Nicholas P; Biffin, Alun; Choi, Sungkyun; Johnson, Roger D; Coldea, Radu; Watkins-Curry, Pilanda; McCandless, Gregory T; Chan, Julia Y; Gandara, Felipe; Islam, Z; Vishwanath, Ashvin; Shekhter, Arkady; McDonald, Ross D; Analytis, James G

2014-01-01

311

Holes Localized on a Skyrmion in a Doped Antiferromagnet on the Honeycomb Lattice: Symmetry Analysis  

E-print Network

Using the low-energy effective field theory for hole-doped antiferromagnets on the honeycomb lattice, we study the localization of holes on Skyrmions, as a potential mechanism for the preformation of Cooper pairs. In contrast to the square lattice case, for the standard radial profile of the Skyrmion on the honeycomb lattice, only holes residing in one of the two hole pockets can get localized. This differs qualitatively from hole pairs bound by magnon exchange, which is most attractive between holes residing in different momentum space pockets. On the honeycomb lattice, magnon exchange unambiguously leads to $f$-wave pairing, which is also observed experimentally. Using the collective-mode quantization of the Skyrmion, we determine the quantum numbers of the localized hole pairs. Again, $f$-wave symmetry is possible, but other competing pairing symmetries cannot be ruled out.

Vlasii, N D; Jiang, F -J; Wiese, U -J

2014-01-01

312

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

NASA Technical Reports Server (NTRS)

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

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

1972-01-01

313

Optimization and Design of 2d Honeycomb Lattice Photonic Crystal Modulated by Liquid Crystals  

NASA Astrophysics Data System (ADS)

Photonic crystals (PCs) with infiltrating liquid crystals (LCs) have many potential applications because of their ability to continuously modulate the band-gaps. Using the plane-wave expansion method (PWM), we simulate the band-gap distribution of 2D honeycomb lattice PC with different pillar structures (circle, hexagonal and square pillar) and with different filling ratios, considering both when the LC is used as filling pillar material and semiconductors (Si, Ge) are used in the substrate, and when the semiconductors (Si, Ge) are pillar material and the LC is the substrate. Results show that unlike LC-based triangle lattice PC, optimized honeycomb lattice PC has the ability to generate absolute photonic band-gaps for fabricating optical switches. We provide optimization parameters for LC infiltrating honeycomb lattice PC structure based on simulation results and analysis.

Guo, Caihong; Zheng, Jihong; Gui, Kun; Zhang, Menghua; Zhuang, Songlin

2013-12-01

314

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

NASA Astrophysics Data System (ADS)

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

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

2007-10-01

315

Thermal behavior of laboratory models of honeycomb-covered solar ponds  

NASA Astrophysics Data System (ADS)

Laboratory experiments were conducted to provide insight into the technical feasibility of honeycomb-covered solar ponds. Cooling tests using honeycomb panels of various materials and geometries showed that a 5.7-cm-thick one-tier panel insulated as effectively as a 10-cm fiberglass slab. Heating tests demonstrated that a model pond covered with a polycarbonate panel boiled upon 16 hours of continuous exposure to a 150-W spotlight. Analysis of the experimental data indicates positively that honeycomb-covered solar ponds can be expected to perform satisfactorily, and that larger-scale outdoor tests should be conducted to provide a more realistic assessment and a more refined performance estimate.

Lin, E. I. H.

316

Monte Carlo study of degenerate ground states and residual entropy in a frustrated honeycomb lattice Ising model  

E-print Network

Monte Carlo study of degenerate ground states and residual entropy in a frustrated honeycomb a classical fully frustrated honeycomb lattice Ising model using Markov-chain Monte Carlo methods and exact that grows as the number of spins N. Traditional single-spin-flip Monte Carlo methods fail to sample all

De Sterck, Hans

317

Aluminum-Air Battery.  

National Technical Information Service (NTIS)

An investigation of aluminum alloyed with small amounts (less than 0.1%) of In, Ga, and Tl in an aluminum-air battery with 2M NaCl as the electrolyte is reported. The tested laboratory model of the battery with a total weight of about 500 g operated at a ...

A. Despic, D. Drazic, S. Zecevic

1979-01-01

318

Anodizing Aluminum with Frills.  

ERIC Educational Resources Information Center

"Anodizing Aluminum" (previously reported in this journal) describes a vivid/relevant laboratory experience for general chemistry students explaining the anodizing of aluminum in sulfuric acid and constrasting it to electroplating. Additions to this procedure and the experiment in which they are used are discussed. Reactions involved are also…

Doeltz, Anne E.; And Others

1983-01-01

319

Stabilized Aluminum Titanate  

NASA Technical Reports Server (NTRS)

Stable, potentially-inexpensive, cubic crystalline alpha aluminum titanate that shows no phase change to 1,700 K used in heat exchangers. Particular stabilizing species must be selected with careful attention to crystal dimensions and bond angles of alpha and beta phases of aluminum titanate.

Schroeder, J. E.

1985-01-01

320

Is the Aluminum Hypothesis Dead?  

PubMed Central

The Aluminum Hypothesis, the idea that aluminum exposure is involved in the etiology of Alzheimer disease, dates back to a 1965 demonstration that aluminum causes neurofibrillary tangles in the brains of rabbits. Initially the focus of intensive research, the Aluminum Hypothesis has gradually been abandoned by most researchers. Yet, despite this current indifference, the Aluminum Hypothesis continues to attract the attention of a small group of scientists and aluminum continues to be viewed with concern by some of the public. This review article discusses reasons that mainstream science has largely abandoned the Aluminum Hypothesis and explores a possible reason for some in the general public continuing to view aluminum with mistrust. PMID:24806729

2014-01-01

321

Is the Aluminum Hypothesis dead?  

PubMed

The Aluminum Hypothesis, the idea that aluminum exposure is involved in the etiology of Alzheimer disease, dates back to a 1965 demonstration that aluminum causes neurofibrillary tangles in the brains of rabbits. Initially the focus of intensive research, the Aluminum Hypothesis has gradually been abandoned by most researchers. Yet, despite this current indifference, the Aluminum Hypothesis continues to attract the attention of a small group of scientists and aluminum continues to be viewed with concern by some of the public. This review article discusses reasons that mainstream science has largely abandoned the Aluminum Hypothesis and explores a possible reason for some in the general public continuing to view aluminum with mistrust. PMID:24806729

Lidsky, Theodore I

2014-05-01

322

Enhanced Cell Survival and Yield of Rat Small Hepatocytes by Honeycomb-Patterned Films  

NASA Astrophysics Data System (ADS)

Surface designing of substrate to regulate cell adhesion and function in nano and micro scale is a critical issue in biomaterial science. In this study, we describe the fabrication of highly regular patterned porous films (honeycomb-patterned film) formed by a simply casting technique, and the culture of mature hepatocytes and small hepatocytes on the films. The pore size of the honeycomb-patterned films used was 6, 12, and 16 µm. We evaluated the effect of the honeycomb-patterned films on the morphology, cell yield, survival and the differentiated hepatic function (albumin production) of the both hepatocytes. Both hepatocytes attached on the flat films appeared to spread well, showing a typical monolayer morphology. They peeled off from the films at 7 days in culture on the flat films. On the other hand, spreading of the each hepatocytes was restricted on the honeycomb-patterned films at 3 and 7 days in culture. The cell yield and survival of the each hepatocytes increased with increasing culture time. Small hepatocyte on the pore sizes of 16 µm showed the highest cell yield (approximately 3 times). Albumin production of mature hepatocyte on the pore sizes of 16 µm (224.1.3 ±157 ng ml-1 well-1 at 1 day in culture, 369.5 ±222 ng ml-1 well-1 at 3 days in culture) was higher than that of the hepatocytes on the flat films (119.3 ±9.3 ng ml-1 well-1 at 1 day in culture, 262.8 ±47.3 ng ml-1 well-1 at 3 days in culture), although that of small hepatocytes on the honeycomb-patterned films (pore size: 16 µm) was similar on the flat film. These results indicated that both the surface topography and the pore size of the honeycomb-patterned film affected the hepatic metabolic function.

Tsukiyama, Shusaku; Matsushita, Michiaki; Tanaka, Masaru; Tamura, Hitoshi; Todo, Satoru; Yamamoto, Sadaaki; Shimomura, Masatsugu

2008-02-01

323

Experimental study of acoustical characteristics of honeycomb sandwich structures  

Microsoft Academic Search

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

Portia Renee Peters

2009-01-01

324

The aluminum smelting process.  

PubMed

This introduction to the industrial primary aluminum production process presents a short description of the electrolytic reduction technology, the history of aluminum, and the importance of this metal and its production process to modern society. Aluminum's special qualities have enabled advances in technologies coupled with energy and cost savings. Aircraft capabilities have been greatly enhanced, and increases in size and capacity are made possible by advances in aluminum technology. The metal's flexibility for shaping and extruding has led to architectural advances in energy-saving building construction. The high strength-to-weight ratio has meant a substantial reduction in energy consumption for trucks and other vehicles. The aluminum industry is therefore a pivotal one for ecological sustainability and strategic for technological development. PMID:24806722

Kvande, Halvor

2014-05-01

325

Extended in-band and band-gap solutions of the nonlinear honeycomb lattice  

NASA Astrophysics Data System (ADS)

We study the dynamics of extended collective excitations in the pristine honeycomb lattice in the presence of the cubic nonlinearity. We show that not only band-gap excitations but also, stable and quasistable, extended excitations between the two lowest bands of the honeycomb system and labeled as in band exist. We also show that some solutions bifurcate from the saddle points of the Floquet band structure. Among other results, we report the existence of nontrivial stationary solutions even for the Floquet eigenvalue where the Dirac points occur. Numerical findings, in fair agreement with our theoretical predictions, are also reported.

Arévalo, E.; Mejía-Cortés, C.

2014-08-01

326

BCx layers with honeycomb lattices on an NbB2(0001) surface.  

PubMed

At elevated temperatures of 1000-1500 K, carbon (C) atoms that segregated to a surface and mixed with the boron (B) honeycomb lattice resulted in the formation of three different BC(x) layers as the topmost layers of NbB(2)(0001). Two of the layers were commensurate lattices: ?7 × ?7 and ?3 × ?3 structures; the third was incommensurate. The characteristic features of the ?3 × ?3 lattice with a honeycomb structure are discussed on the basis of the experimental data. PMID:22820552

Oshima, Chuhei

2012-08-01

327

Steps toward eight-meter honeycomb mirror blanks. I Rationale and approach  

NASA Technical Reports Server (NTRS)

The best form for 8-m telescope mirrors is discussed. It is concluded that honeycomb sandwich structure can meet the most exacting demand goals for subarcsecond image quality in optical and infrared astronomy. These structures are light, have good stiffness against gravitational and wind loading, and have low thermal inertia. The latter permits them to be operated at the ambient air temperature to avoid local seeing problems. Borosilicate and aluminosilicate glasses are adequate materials for ventilated honeycombs, which do not require low expansion materials.

Angel, J. R. P.; Woolf, N. J.

1984-01-01

328

Experimental investigation of static and thermal-mechanical bending fatigue strength of steel honeycomb sandwich beams  

NASA Astrophysics Data System (ADS)

The aim of this work is to investigate static and thermal-mechanical strength and fatigue behaviors of steel honeycomb sandwich beams through three-point bending. The bending strength limits at different experimental temperatures (room temperature, 200, 300 and 400°C, respectively) are obtained. The bending fatigue behaviors at high temperature are discussed and the fatigue test results are presented in standard S/N diagrams. Meanwhile damage and failure modes are reported and analyzed. Effects of the honeycomb cell orientation (L or W) on the maximum load and on the damage processes are also investigated.

Lu, Jie; Zou, Guang-ping

2010-03-01

329

Clinical biochemistry of aluminum  

SciTech Connect

Aluminum toxicity has been implicated in the pathogenesis of a number of clinical disorders in patients with chronic renal failure on long-term intermittent hemodialysis treatment. The predominant disorders have been those involving either bone (osteomalacic dialysis osteodystrophy) or brain (dialysis encephalopathy). In nonuremic patients, an increased brain aluminum concentration has been implicated as a neurotoxic agent in the pathogenesis of Alzheimer's disease and was associated with experimental neurofibrillary degeneration in animals. The brain aluminum concentrations of patients dying with the syndrome of dialysis encephalopathy (dialysis dementia) are significantly higher than in dialyzed patients without the syndrome and in nondialyzed patients. Two potential sources for the increased tissue content of aluminum in patients on hemodialysis have been proposed: (1) intestinal absorption from aluminum containing phosphate-binding gels, and (2) transfer across the dialysis membrane from aluminum in the water used to prepare the dialysate. These findings, coupled with our everyday exposure to the ubiquitous occurrence of aluminum in nature, have created concerns over the potential toxicity of this metal.

King, S.W.; Savory, J.; Wills, M.R.

1981-05-01

330

Arizona Radio Observatory (ARO) The SMT is the most accurate submillimeter astronomical  

E-print Network

Spaceframe support: Carbon fiber reinforced plastic (CFRP) Tubes with invar steel joints (3040 kg weight). Panels: CFRP skin with aluminum honeycomb sandwich core (110 Kg weight). Subreflector support: CFRP tube: CFRP aluminum honeycomb sandwich. Chopping mechanism: at 80% duty cycle: 10 Hz with 4 arcminute throw

Ziurys, Lucy M.

331

Modeling and Parameters Identification of Dynamic Properties of Paper Honeycomb Panel  

Microsoft Academic Search

According to the quasi-static compression experiment and the creep experiment results, the paper honeycomb panel can be modeled as linear material with viscoelastic property whose relaxation kernel is expressed by a sum of exponentials. A parameter identification procedure is formulated which is based on the Prony method and the free response data of the single degree of freedom system. The

Zhu Dapeng; Zhou Shisheng

2008-01-01

332

Aircraft Metal Skin Repair and Honeycomb Structure Repair; Sheet Metal Work 3: 9857.02.  

ERIC Educational Resources Information Center

The course helps students determine types of repairs, compute repair sizes, and complete the repair through surface protection. Course content includes goals, specific objectives, protection of metals, repairs to metal skin, and honeycomb structure repair. A bibliography and post-test are appended. A prerequisite for this course is mastery of the…

Dade County Public Schools, Miami, FL.

333

[Determining the concentration of coating solution attaching to honeycomb denuder in summer in Tianjin].  

PubMed

The study on determining the concentration of coating solution attaching to honeycomb denuder was conducted, from 1 July to 31 August, 2013, at the roof of Lihua building at Nankai University in Tianjin. The results of experiment showed that the optimized concentration of sodium carbonate coated on the honeycomb denuder was 3%, and the optimized concentration of citric acid was 6%. The contrast sampling results of PM2.5 between honeycomb denuder system and conventional method showed that 86% of the concentration of PM2.5 samples obtained by honeycomb denuder system were less than those obtained by conventional method, the main reasons may include that: (1) the majority of acid/alkaline gases were removed, so they could neither react with the enriched particles on the sampling membrane nor be adsorbed on particles; (2) parts of the particles were captured by the denuder during sampling; (3) the removal of acid/alkaline gases disturbed the state of equilibrium between gas- and particle-phases which may lead to the volatilization of some particles. PMID:25338355

Zhang, Shi-Jian; Ji, Ya-Qin; Zhang, Lei-Bo; Zhao, Xue-Yan; Zhu, Zhen-Yu; Yang, Wen

2014-08-01

334

Tridimensional photographic reconstruction in a study of the pathogenesis of honeycomb lung  

PubMed Central

Tridimensional photographic reconstruction of the lesions found in honeycomb lung in 10 different types of pulmonary disease was made. The pathological picture was characteristic and well defined by tridimensional microscopy and quite independent of the accompanying disease. The lesions responsible for its appearance involved the whole lobular bronchiolar system but were most marked in the terminal and respiratory bronchioli. The changes were fundamentally diffuse, saccular, and cystic bronchiolectasis. Other bronchiolar lesions were found such as changes in direction and mode of division, amputations, and anastomoses between bronchioles and cysts belonging to anatomically independent airways. There was some evidence that the bullous aspects of honeycomb lung were due to multiple valvular arrangements which let the air in but do not let it out. Honeycomb lung was, in the majority of cases, a complication of interstitial pulmonary fibrosis. Honeycombing was usually due to marked changes in the lobular bronchioles caused by the obliteration or rigidity of alveolar ducts and the corresponding alveoli and even by localization of the interstitial fibrosis in the bronchiolar wall. Images PMID:6050292

Pimentel, J. Cortez

1967-01-01

335

Graphene, a sheet of carbon atoms arranged in a honeycomb lattice, possesses many  

E-print Network

Graphene, a sheet of carbon atoms arranged in a honeycomb lattice, possesses many excellent chemical species onto the graphene plane offers an effective route to alter and engineer the properties of graphene. NSF-supported researchers have demonstrated that graphene covered dilutely with covalently bonded

Maroncelli, Mark

336

Heavy-gage bonded honeycomb sandwich as primary load-bearing structure  

NASA Technical Reports Server (NTRS)

Heavy-gage bonded honeycomb sandwich is used as a primary load-bearing structural material in large-diameter boosters. Theoretical investigations based on a small deflection theory for prediction of stress fields and buckling loads, and structural testing were made. This structure is a potential weight saver for compression load-critical components.

1967-01-01

337

Identification of complex crack damage for honeycomb sandwich plate using wavelet analysis and neural networks  

Microsoft Academic Search

In this study, crack damage detection for a honeycomb sandwich plate is studied using the energy spectrum of dynamic response decomposed by wavelet transform and the artificial neural network (NN). The results show that taking the energy spectrum of the decomposed wavelet signals of dynamic responses as the inputs of the NN can simplify the NN design for structural damage

L H Yam; Y J Yan; L Cheng; J S Jiang

2003-01-01

338

Evaluation of the in-service performance behavior of honeycomb composite sandwich structures  

Microsoft Academic Search

When honeycomb composite structures are fabricated for the aerospace industry, they are designed to be closed to their operating environment for the life of the composite structure. However, once in service, this design can break down. Damage can set in motion a chain reaction of events that will ultimately degrade the mechanical integrity of the composite structure. Through thermographic analysis,

J. E. Shafizadeh; J. C. Seferis; E. F. Chesmar; R. Geyer

1999-01-01

339

Evaluation of the in-service performance behavior of honeycomb composite sandwich structures  

SciTech Connect

When honeycomb composite structures are fabricated for the aerospace industry, they are designed to be closed to their operating environment for the life of the composite structure. However, once in service, this design can break down. Damage can set in motion a chain reaction of events that will ultimately degrade the mechanical integrity of the composite structure. Through thermographic analysis, the tendency of honeycomb composite structures to absorb and retain water was investigated, and an attempt was made to quantify the extent of water ingression in the Boeing 767 aircraft. Through thermographic analysis, the exterior honeycomb composite structures were found to contain less than 50 kg of water per plane. On average, over 90% of the water found on an aircraft was contained in five problematic parts, which included the outboard flap wedge, the nose landing gear doors, the main landing gear doors, the fixed upper wing panels, and the escape slide door. Kevlar lamina induced microcracking, skin porosity problems, and cracked potting compound were the root causes of water ingression and migration in these structures. Ultimately, this research will aid in the fundamental understanding and design of future honeycomb composite sandwich structures.

Shafizadeh, J.E.; Seferis, J.C.; Chesmar, E.F.; Geyer, R.

1999-12-01

340

Dynamic response of doubly curved honeycomb sandwich panels to random acoustic excitation. Part 1: Experimental study  

Microsoft Academic Search

A set of four doubly curved, composite honeycomb sandwich panels has been tested with broad band, random acoustic excitation in a progressive wave tube facility. This paper presents the experimental results in the form of dynamic face plate strain measurements taken from various points close to the centre of the panels, on both the inner and outer face plates. The

P. R. Cunningham; R. G. White

2003-01-01

341

EXPERIMENTAL TEST AND FINITE ELEMENT MODELLING OF PEDESTRIAN HEADFORM IMPACT ON HONEYCOMB SANDWICH PANEL  

Microsoft Academic Search

This paper represents a Finite Element model of Cel lbond's aluminium honeycomb sandwich panel and proposes an original technique to develop the mater ial characteristics which realistically simulate a child headform impacting on a sandwich panel. As part of a major study to develop a pedestrian friendly car bonnet design, this investigation has been carried out with the requirement as

M. Asadi; A. C. Vollaire; M. Ashmead; H. Shirvani

342

Non-autoclave processing of honeycomb sandwich structures: Skin through thickness air permeability during cure  

Microsoft Academic Search

In non-autoclave processing of sandwich structures, the pressure level inside the honeycomb becomes a critical process parameter, which depends on the permeability to air of the upper skin. In this work, prepreg and adhesive permeabilities were determined separately and in combination through a falling pressure method. We showed that a range of initial skin through thickness air permeability could be

S. Sequeira Tavares; N. Caillet-Bois; V. Michaud; J.-A. E. Månson

2010-01-01

343

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

Microsoft Academic Search

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

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

1996-01-01

344

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

NASA Astrophysics Data System (ADS)

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

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

2012-11-01

345

Loading, Degradation and Repair of F-111 Bonded Honeycomb Sandwich Panels - Preliminary Study  

Microsoft Academic Search

Many of the fixed and removable panels on the RAAF F-111 aircraft are made up of bonded honeycomb sandwich panels. Experience with the RAAF fleet has shown that a serious problem exists with degradation and damage of these panels. A review of the literature was undertaken to gain an understanding of the extent of this problem. It was found that

S. Whitehead; M. McDonald; R. A. Bartholomeusz

346

Honeycomb Layer of Cobalt(II) Azide Hydrazine Showing Weak Ferromagnetism  

E-print Network

Honeycomb Layer of Cobalt(II) Azide Hydrazine Showing Weak Ferromagnetism Xiu-Teng Wang, ZheVersity, Beijing 100871, People's Republic of China Received August 26, 2007 Using hydrazine (N2H4) as a cobridge the synthesis process. Herein, using hydrazine sulfate (N2H4,H2SO4) as the reducing protective agent,5 we

Gao, Song

347

[Removal of toluene from waste gas by honeycomb adsorption rotor with modified 13X molecular sieves].  

PubMed

The removal of toluene from waste gas by Honeycomb Adsorption Rotor with modified 13X molecular sieves was systematically investigated. The effects of the rotor operating parameters and the feed gas parameters on the adsorption efficiency were clarified. The experimental results indicated that the honeycomb adsorption rotor had a good humidity resistance. The removal efficiency of honeycomb adsorption rotor achieved the maximal value with optimal rotor speed and optimal generation air temperature. Moreover, for an appropriate flow rate ratio the removal efficiency and energy consumption should be taken into account. When the recommended operating parameters were regeneration air temperature of 180 degrees C, rotor speed of 2.8-5 r x h(-1), flow rate ratio of 8-12, the removal efficiency kept over 90% for the toluene gas with concentration of 100 mg x m(-3) and inlet velocity of 2 m x s(-1). The research provided design experience and operating parameters for industrial application of honeycomb adsorption rotor. It showed that lower empty bed velocity, faster rotor speed and higher temperature were necessary to purify organic waste gases of higher concentrations. PMID:24640908

Wang, Jia-De; Zheng, Liang-Wei; Zhu, Run-Ye; Yu, Yun-Feng

2013-12-01

348

Corrosion Inhibitors for Aluminum.  

ERIC Educational Resources Information Center

Describes a simple and reliable test method used to investigate the corrosion-inhibiting effects of various chelating agents on aluminum pigments in aqueous alkaline media. The experiments that are presented require no complicated or expensive electronic equipment. (DDR)

Muller, Bodo

1995-01-01

349

Walnut Hulls Clean Aluminum  

NASA Technical Reports Server (NTRS)

Hulls inflict minimal substrate damage. Walnut hulls found to be best abrasive for cleaning aluminum surfaces prior to painting. Samples blasted with walnut hulls showed no compressive stress of surface.

Colberg, W. R.; Gordon, G. H.; Jackson, C. H.

1984-01-01

350

Advances in aluminum anodizing  

NASA Technical Reports Server (NTRS)

White anodize is applied to aluminum alloy surfaces by specific surface preparation, anodizing, pigmentation, and sealing techniques. The development techniques resulted in alloys, which are used in space vehicles, with good reflectance values and excellent corrosive resistance.

Dale, K. H.

1969-01-01

351

Autonomous bottom-up fabrication of three-dimensional nano/microcellulose honeycomb structures, directed by bacterial nanobuilder.  

PubMed

We investigated the autonomous bottom-up fabrication of three-dimensional honeycomb cellulose structures, using Gluconacetobacter xylinus as a bacterial nanoengine, on cellulose honeycomb templates prepared by casting water-in-oil emulsions on glass substrates (Kasai and Kondo, Macromol. Biosci., 4, 17-21, 2004). The template film had a unique molecular orientation state along the honeycomb frames, but was non-crystalline. When G. xylinus, used as a nanofiber-producing bacterium, was incubated on the honeycomb scaffold in a culture medium, it secreted cellulose nanofibers only on the upper surface of the honeycomb frame. The movement was regulated by a selective interaction between the synthesized nanofiber and the surface of the honeycomb frames of the template. The relationship between directed deposition of synthesized nanofibers and ordered fabrication from the nano- to the micro-scale could provide a novel bottom-up methodology, using bacteria, for the design of three-dimensional honeycomb structures as functional materials with nano/micro hierarchical structures, with low energy consumption. PMID:24799259

Kondo, Tetsuo; Kasai, Wakako

2014-10-01

352

Aluminum-air battery  

Microsoft Academic Search

Aluminum alloyed with small amounts (less than 0.1%) of In, Ga, and Tl in an aluminum air battery with 2M NaCl as the electrolyte is reported. The tested laboratory model of the battery with a total weight of about 500 g operated at a total current of 8 A (j = 30 mA\\/cu cm) and a voltage of about 1

A. R. Despic; D. Drazic; S. Zecevic

1979-01-01

353

Shearography for Non-destructive Inspection with applications to BAT Mask Tile Adhesive Bonding and Specular Surface Honeycomb Panels  

NASA Technical Reports Server (NTRS)

The applicability of shearography techniques for non-destructive evaluation in two unique application areas is examined. In the first application, shearography is used to evaluate the quality of adhesive bonds holding lead tiles to the B.4T gamma ray mask for the NASA Swift program. Using a vibration excitation, the more poorly bonded tiles are readily identifiable in the shearography image. A quantitative analysis is presented that compares the shearography results with a destructive pull test measuring the force at bond failure. The second application is to evaluate the bonding between the skin and core of a honeycomb structure with a specular (mirror-like) surface. In standard shearography techniques, the object under test must have a diffuse surface to generate the speckle patterns in laser light, which are then sheared. A novel configuration using the specular surface as a mirror to image speckles from a diffuser is presented, opening up the use of shearography to a new class of objects that could not have been examined with the traditional approach. This new technique readily identifies large scale bond failures in the panel, demonstrating the validity of this approach.

Lysak, Daniel B.

2003-01-01

354

A biomimetic honeycomb-like scaffold prepared by flow-focusing technology for cartilage regeneration.  

PubMed

A tissue engineering chondrocytes/scaffold construct provides a promise to cartilage regeneration. The architecture of a scaffold such as interconnections, porosities, and pore sizes influences the fates of seeding cells including gene expression, survival, migration, proliferation, and differentiation thus may determine the success of this approach. Scaffolds of highly ordered and uniform structures are desirable to control cellular behaviors. In this study, a newly designed microfluidic device based on flow-focusing geometry was developed to fabricate gelatin scaffolds of ordered pores. In comparison with random foam scaffolds made by the conventional freeze-dried method, honeycomb-like scaffolds exhibit higher swelling ratio, porosity, and comparable compressive strength. In addition, chondrocytes grown in the honeycomb-like scaffolds had good cell viability, survival rate, glycosaminoglycans production, and a better proliferation than ones in freeze-dried scaffolds. Real-time PCR analysis showed that the mRNA expressions of aggrecan and collagen type II were up-regulated when chondrocytes cultured in honeycomb-like scaffolds rather than cells cultured as monolayer fashion. Oppositely, chondrocytes expressed collagen type II as monolayer culture when seeded in freeze-dried scaffolds. Histologic examinations revealed that cells produced proteoglycan and distributed uniformly in honeycomb-like scaffolds. Immunostaining showed protein expression of S-100 and collagen type II but negative for collagen type I and X, which represents the chondrocytes maintained normal phenotype. In conclusion, a highly ordered and honeycomb-like scaffold shows superior performance in cartilage tissue engineering. Biotechnol. Bioeng. 2014;111: 2338-2348. © 2014 Wiley Periodicals, Inc. PMID:24895237

Wang, Chen-Chie; Yang, Kai-Chiang; Lin, Keng-Hui; Wu, Chang-Chin; Liu, Yen-Liang; Lin, Feng-Huei; Chen, Ing-Ho

2014-11-01

355

Turbulence in the Core of a Transpired Channel  

SciTech Connect

Flow in a fully transpired channel is examined using Particle-Image Velocimetry(PIV) to investigate the effect of stream-wise injection length scales on the core flow mean and turbulence properties. Instantaneous velocity fields are captured in a stream-wise - wall-normal plane at four different stream-wise locations (x/h=7,15,25,35) and four different porous surfaces: 3.175-mm, 4.7625-mm, 6.35-mm, 9.525-mm honeycombs. The 3.175-mm and 4.7625-mm honeycombs create smaller fluctuations in the wall-normal injection velocity and result in lower core turbulence. As a result, their mean flow profiles follow the inviscid Culick solution for a considerable distance downstream. The 6.35-mm and 9.525-mm honeycombs create higher wall-normal perturbations which get strongly amplified by the mean strain field resulting in a higher turbulence intensity downstream. As a result, their mean flow profiles deviate significantly from the Culick solution. It is found that the turbulence is profoundly affected by the mean details of the wall boundary conditions. In addition, for the first time, a database of turbulence statistics along with the complete boundary conditions (including the wall dynamic impedance) is provided to completely characterize the flow in a fully transpired channel.

Balamkumar, B J.; Adrian, Ronald J.; Deng, Zhiqun

2005-08-24

356

Interfacial electronic structure of trimethyl-aluminum and water on an In0.20Ga0.80As(001)-4 × 2 surface: A high-resolution core-level photoemission study  

NASA Astrophysics Data System (ADS)

In atomic-layer deposition (ALD), organoaluminum as trimethyl-aluminum (TMA) on a freshly molecular beam epitaxy grown In0.20Ga0.80As(001)-4 × 2 surface has three forms: Al bonding with 1, 2, and 3 methyl groups. The ALD method of using one pulse (0.1 s) of TMA plus one pulse (0.1 s) of water was ineffective in passivating the surface, as demonstrated by the increased intensity of the reacted surface components with high numbers of pulses. The intact TMA was physisorbed on the trough In atoms, while the methyl-deficient precursors are either bridged with two As atoms or on the row-edge As atoms. After the water pulse on the TMA-covered surface, a bond in the bridged As atoms was scissored off to produce the As-Al-CH3 and As-OH, and the physisorbed TMA was unaffected. TMA removed some row In atoms, which allowed the In and Ga atoms in the second layer to form OH bonds after the water exposure. The appearance of the As-OH bonds may cause interfacial defect density (Dit) a peak at the midgap.

Pi, T. W.; Lin, H. Y.; Chiang, T. H.; Liu, Y. T.; Wertheim, G. K.; Kwo, J.; Hong, M.

2013-05-01

357

Aluminum, parathyroid hormone, and osteomalacia  

SciTech Connect

Aluminum exposure in man is unavoidable. The occurrence of dialysis dementia, vitamin D-resistant osteomalacia, and hypochromic microcytic anemia in dialysis patients underscores the potential for aluminum toxicity. Although exposure via dialysate and hyperalimentation leads to significant tissue aluminum accumulation, the ubiquitous occurrence of aluminum and the severe pathology associated with large aluminum burdens suggest that smaller exposures via the gastrointestinal tract and lungs could represent an important, though largely unrecognized, public health problem. It is clear that some aluminum absorption occurs with the ingestion of small amounts of aluminum in the diet and medicines, and even greater aluminum absorption is seen in individuals consuming large amounts of aluminum present in antacids. Aluminum absorption is enhanced in the presence of elevated circulating parathyroid hormone. In addition, elevated PTH leads to the preferential deposition of aluminum in brain and bone. Consequently, PTH is likely to be involved in the pathogenesis of toxicities in those organs. PTH excess also seems to lead to the deposition of aluminum in the parathyroid gland. The in vitro demonstration that aluminum inhibits parathyroid hormone release is consistent with the findings of a euparathyroid state in dialysis patients with aluminum related vitamin D-resistant osteomalacia. Nevertheless, it seems likely that hyperparathyroidism is at least initially involved in the pathogenesis of aluminum neurotoxicity and osteomalacia; the increases in tissue aluminum stores are followed by suppression of parathyroid hormone release, which is required for the evolution of osteomalacia. Impaired renal function is not a prerequisite for increased tissue aluminum burdens, nor for aluminum-related organ toxicity. Consequently, it is likely that these diseases will be observed in populations other than those with chronic renal disease.

Burnatowska-Hledin, M.A.; Kaiser, L.; Mayor, G.H.

1983-01-01

358

Shearography for Non-Destructive Evaluation with Applications to BAT Mask Tile Adhesive Bonding and Specular Surface Honeycomb Panels  

NASA Technical Reports Server (NTRS)

In this report we examine the applicability of shearography techniques for nondestructive inspection and evaluation in two unique application areas. In the first application, shearography is used to evaluate the quality of adhesive bonds holding lead tiles to the BAT gamma ray mask for the NASA Swift program. By exciting the mask with a vibration, the more poorly bonded tiles can be distinguished by their greater displacement response, which is readily identifiable in the shearography image. A quantitative analysis is presented that compares the shearography results with a destructive pull test measuring the force at bond failure. Generally speaking, the results show good agreement. Further investigation would be useful to optimize certain test parameters such as vibration frequency and amplitude. The second application is to evaluate the bonding between the skin and core of a honeycomb structure with a specular (mirror-like) surface. In standard shearography techniques, the object under test must have a diffuse surface to generate the speckle patterns in laser light, which are then sheared. A novel configuration using the specular surface as a mirror to image speckles from a diffuser is presented, opening up the use of shearography to a new class of objects that could not have been examined with the traditional approach. This new technique readily identifies large scale bond failures in the panel, demonstrating the validity of this approach. For the particular panel examined here, some scaling issues should be examined further to resolve the measurement scale down to the very small size of the core cells. In addition, further development should be undertaken to determine the general applicability of the new approach and to establish a firm quantitative foundation.

Lysak, Daniel B.

2003-01-01

359

Application of Wavelet Transform to analyze acceleration signals generated by HVI on thin aluminum plates and all-aluminum honeycomb sandwich panels  

Microsoft Academic Search

Among all possible dangers, hypervelocity impacts on structures produce also a disturbance field, which results from the superimposition of vibrations originating on the impact point and then reflected at the target boundaries. Such disturbance environment is composed by waves of different amplitudes, frequency contents, speeds and directions of propagation. The aim of this paper is to characterize this complex environment,

A. Bettella; A. Francesconi; D. Pavarin; C. Giacomuzzo; F. Angrilli

2008-01-01

360

A comparison of rotordynamic-coefficient predictions for annular honeycomb gas seals using different friction-factor models  

E-print Network

Predictions of rotordynamic-coefficients for annular honeycomb gas seals are compared using different friction-factor models. Analysis shows that the fundamental improvement in predicting the rotordynamic-coefficients accurately is the two...

D'Sousa, Rohan Joseph

2012-06-07

361

A numerical adaptation of self-avoiding walk identities from the honeycomb to other 2D lattices  

NASA Astrophysics Data System (ADS)

Recently, Duminil-Copin and Smirnov proved a long-standing conjecture of Nienhuis that the connective constant of self-avoiding walks (SAWs) on the honeycomb lattice is \\sqrt{2+\\sqrt{2}}. A key identity used in that proof depends on the existence of a parafermionic observable for SAWs on the honeycomb lattice. Despite the absence of a corresponding observable for SAWs on the square and triangular lattices, we show that in the limit of large lattices, some of the consequences observed on the honeycomb lattice persist on other lattices. This permits the accurate estimation, though not an exact evaluation, of certain critical amplitudes, as well as critical points, for these lattices. For the honeycomb lattice, an exact amplitude for loops is proved.

Beaton, Nicholas R.; Guttmann, Anthony J.; Jensen, Iwan

2012-01-01

362

Selective adhesion and controlled activity of yeast cells on honeycomb-patterned polymer films via a microemulsion approach.  

PubMed

Selective adhesion, growth promotion, proliferation inhibition and in situ transformation of Saccharomyces cerevisiae cells have been realized in a limited space of honeycomb-patterned polystyrene films prepared through a microemulsion method. PMID:25376599

Ma, Yingyi; Zhou, Mengcheng; Walter, Shaylyn; Liang, Jing; Chen, Zhijun; Wu, Lixin

2014-11-20

363

ALUMINUM RECLAMATION BY ACIDIC EXTRACTION OF ALUMINUM-ANODIZING SLUDGES  

EPA Science Inventory

Extraction of aluminum-anodizing sludges with sulfuric acid was examined to determine the potential for production of commercial-strength solutions of aluminum sulfate, that is liquid alum. The research established kinetic and stoichiometric relationships and evaluates product qu...

364

Safety evaluation of dietary aluminum.  

PubMed

Aluminum is a nonessential metal to which humans are frequently exposed. Aluminum in the food supply comes from natural sources, water used in food preparation, food ingredients, and utensils used during food preparations. The amount of aluminum in the diet is small, compared with the amount of aluminum in antacids and some buffered analgesics. The healthy human body has effective barriers (skin, lungs, gastrointestinal tract) to reduce the systemic absorption of aluminum ingested from water, foods, drugs, and air. The small amount of aluminum (<1%) that is systemically absorbed is excreted principally in the urine and, to a lesser extent, in the feces. No reports of dietary aluminum toxicity to healthy individuals exist in the literature. Aluminum can be neurotoxic, when injected directly into the brains of animals and when accidentally introduced into human brains (by dialysis or shrapnel). A study from Canada reports cognitive and other neurological deficits among groups of workers occupationally exposed to dust containing high levels of aluminum. While the precise pathogenic role of aluminum in Alzheimer's disease (AD) remains to be defined, present data do not support a causative role for aluminum in AD. High intake of aluminum from antacid for gastrointestinal ailments has not been reported to cause any adverse effects and has not been correlated with neurotoxicity or AD. Foods and food ingredients are generally the major dietary sources of aluminum in the United States. Cooking in aluminum utensils often results in statistically significant, but relatively small, increases in aluminum content of food. Common aluminum-containing food ingredients are used mainly as preservatives, coloring agents, leavening agents, anticaking agents, etc. Safety evaluation and approval of these ingredients by the Food and Drug Administration indicate that these aluminum-containing compounds are safe for use in foods. PMID:11259180

Soni, M G; White, S M; Flamm, W G; Burdock, G A

2001-02-01

365

Hot\\/Wet Environmental Degradation of Honeycomb Sandwich Structure Representative of F\\/A-18: Flatwise Tension Strength  

Microsoft Academic Search

Aluminium honeycomb structure is widely used in the F\\/A-18 to save weight, however it is susceptible to degradation by water. The US Navy has experienced in-flight failures of honeycomb components such as the rudder which are believed to be due to moisture induced degradation. A long-term (52 week) environmental exposure trial was conducted to determine the effects on the flatwise

T. C. Radtke; A. Charon; R. Vodicka

366

Honeycomb mirrors of borosilicate glass - Current results and plans for 7-8m diameter. [astronomical telescope  

NASA Technical Reports Server (NTRS)

The making of large astronomical mirrors with borosilicate glass honeycomb structure is discussed. Particular attention is given to a single casting technique for making borosilicate honeycomb mirror blanks up to 7 meters in diameter. Current work on the development of this technique involves the casting of blanks 60 cm in diameter which have the full thickness (33 cm), cell size (15 cm), and faceplate thickness (2.5 cm) needed for a 1.8-m mirror.

Angel, J. R. P.; Arganbright, D.; Harmonson, L.; Hill, J. M.; Woolf, N.

1982-01-01

367

A novel isolation curtain to reduce turbine ingress heating and an advanced model for honeycomb labyrinth seals  

Microsoft Academic Search

A combination of 3-D and 2-D computational fluid dynamics (CFD) modeling as well as experimental testing of the labyrinth seal with hexagonal honeycomb cells on the stator wall was performed. For the 3-D and 2-D CFD models, the hexagonal honeycomb structure was modeled using the concept of the baffle (zero-thickness wall) and the simplified 2-D fin, respectively. The 3-D model

Dong Chun Choi

2005-01-01

368

Buckling Testing and Analysis of Honeycomb Sandwich Panel Arc Segments of a Full-Scale Fairing Barrel Part 1: 8-Ply In-Autoclave Facesheets. Part 1; 8-Ply In-Autoclave Facesheets  

NASA Technical Reports Server (NTRS)

Four honeycomb sandwich panels, representing 1/16th arc segments of a 10-m diameter barrel section of the heavy lift launch vehicle, were manufactured under the NASA Composites for Exploration program and the NASA Space Launch Systems program. Two configurations were chosen for the panels: 6-ply facesheets with 1.125 in. honeycomb core and 8-ply facesheets with 1.000 in. honeycomb core. Additionally, two separate carbon fiber/epoxy material systems were chosen for the facesheets: inautoclave IM7/977-3 and out-of-autoclave T40-800b/5320-1. Smaller 3.00- by 5.00-ft panels were cut from the 1/16th barrel sections. These panels were tested under compressive loading at the NASA Langley Research Center. Furthermore, linear eigenvalue and geometrically nonlinear finite element analysis was performed to predict the compressive response of the 3.00- by 5.00-ft panels. This manuscript summarizes the experimental and analytical modeling efforts pertaining to the panel composed of 8-ply, IM7/977-3 facesheets (referred to Panel A). To improve the robustness of the geometrically nonlinear finite element model, measured surface imperfections were included in the geometry of the model. Both the linear and nonlinear models yield good qualitative and quantitative predictions. Additionally, it was predicted correctly that the panel would fail in buckling prior to failing in strength. Furthermore, several imperfection studies were performed to investigate the influence of geometric imperfections, fiber misalignments, and three-dimensional (3 D) effects on the compressive response of the panel.

Myers, David E.; Pineda, Evan J.; Zalewski, Bart F.; Kosareo, Daniel N.; Kellas, Sotiris

2013-01-01

369

Aluminum/Magnesium 3D-Printing Rapid Prototyping.  

National Technical Information Service (NTIS)

A 3D Printing Rapid Prototyping process using Al/Mg particles coated with a metal (i.e. copper, nickel, zinc, or tin) that (1) prevents oxidation of the Al/Mg particles, and (2) either alone, or when alloyed with the aluminum or magnesium core metal, melt...

J. E. Hetzner, W. F. Jandeska

2004-01-01

370

Recycled Aluminum Ornaments  

NSDL National Science Digital Library

This lesson plan from ATEEC will explain the principles of recycling. The activity would be most appropriate for technology studies or high school science classes. In all, it would require 2-5 hours of class time to complete. The purpose of the lesson is to demonstrate how aluminum is recycled. This laboratory activity does require some special equipment including a heat source capable of melting aluminum and an outdoor work area. Extension activities are also provided. The lesson plan is available for download as a PDF; users must create a free, quick login with ATEEC to access the materials.

Wishart, Ray

2013-06-14

371

Regeneration of aluminum hydride  

DOEpatents

The present invention provides methods and materials for the formation of hydrogen storage alanes, AlH.sub.x, where x is greater than 0 and less than or equal to 6 at reduced H.sub.2 pressures and temperatures. The methods rely upon reduction of the change in free energy of the reaction between aluminum and molecular H.sub.2. The change in free energy is reduced by lowering the entropy change during the reaction by providing aluminum in a state of high entropy, by increasing the magnitude of the change in enthalpy of the reaction or combinations thereof.

Graetz, Jason Allan (Mastic, NY); Reilly, James J. (Bellport, NY)

2009-04-21

372

Regeneration of aluminum hydride  

DOEpatents

The present invention provides methods and materials for the formation of hydrogen storage alanes, AlH.sub.x, where x is greater than 0 and less than or equal to 6 at reduced H.sub.2 pressures and temperatures. The methods rely upon reduction of the change in free energy of the reaction between aluminum and molecular H.sub.2. The change in free energy is reduced by lowering the entropy change during the reaction by providing aluminum in a state of high entropy, and by increasing the magnitude of the change in enthalpy of the reaction or combinations thereof.

Graetz, Jason Allan; Reilly, James J; Wegrzyn, James E

2012-09-18

373

Aluminum Hydroxide and Magnesium Hydroxide  

MedlinePLUS

Aluminum Hydroxide, Magnesium Hydroxide are antacids used together to relieve heartburn, acid indigestion, and upset stomach. They ... They combine with stomach acid and neutralize it. Aluminum Hydroxide, Magnesium Hydroxide are available without a prescription. ...

374

Electrical Control of Edge Magnetism in Two-Dimensional Buckled Honeycomb Lattice  

NASA Astrophysics Data System (ADS)

We theoretically study indirect spin coupling strength between two magnetic impurities located on honeycomb Kane—Mele zigzag ribbon (KMZR) with periodic and open boundary (PB and OB). We show that spin interaction J in PB ribbons displays an AFM-FM oscillating behavior with increasing the staggered potential and electron density, and approaches to maximum at the edges. While the spin coupling in OB KMZR shows a trivial smooth AFM coupling with varying staggered potential. Such a novel J(?) behavior is the combining effect of finite size, topological edge states and inversion symmetry breaking induced by the staggered potential. We propose that one could control the edge magnetism electrically in two-dimensional buckled honeycomb materials, e.g., silicence, germanene and stanene.

Bao, Wei-Cheng; Zou, Liang-Jian

2014-09-01

375

Fabrication of honeycomb texture on poly-Si by laser interference and chemical etching  

NASA Astrophysics Data System (ADS)

In this paper, we present a laser-interference method to fabricate honeycomb textures on poly-Si wafer for reflection reduction. When exposed to three interfering pulsed laser beams at 532 nm, the Si surface was periodically melted in accordance with the interference pattern. As a result, concave holes were generated on the surface because the melted material overflowed and condensed at the periphery. Subsequent acid etching revealed uniform and clean honeycomb textures. The texture depth could be controlled by varying the irradiation condition and a minimum reflectance of 10% was obtained. Transmission electron microscopy analysis showed that no irradiation-induced damage remained after etching. This approach can be a cost-effective alternative to lithographic processes for fabricating high-efficiency poly-Si solar cells.

Yang, Bogeum; Lee, Myeongkyu

2013-11-01

376

The critical surface fugacity of self-avoiding walks on a rotated honeycomb lattice  

NASA Astrophysics Data System (ADS)

In a recent paper by Beaton et al, it was proved that a model of self-avoiding walks on the honeycomb lattice, interacting with an impenetrable surface, undergoes an adsorption phase transition when the surface fugacity is 1+\\sqrt{2}. Their proof used a generalization of an identity obtained by Duminil-Copin and Smirnov, and confirmed a conjecture of Batchelor and Yung. We consider a similar model of self-avoiding walk adsorption on the honeycomb lattice, but with the lattice rotated by ?/2. For this model there also exists a conjecture for the critical surface fugacity, made in 1998 by Batchelor, Bennett-Wood and Owczarek. Using similar methods to Beaton et al, we prove that this is indeed the critical fugacity.

Beaton, Nicholas R.

2014-02-01

377

Steps toward 8m honeycomb mirrors. VIII - Design and demonstration of a system of thermal control  

NASA Technical Reports Server (NTRS)

Directed jets of ambient temperature air are proposed for the maintenance of low internal temperature gradients and conformity with ambient temperatures in honeycomb-structure borosilicate glass telescope mirrors. The use of greater airflow on thicker sections, to match cooling rates, and the cooling or heating of the internal, back, and edge surfaces of the mirror at the same rate established by convection on the front surface, have been tested on a full scale glass thermal model of a single honeycomb cell from an 8-m diameter mirror. The internal thermal gradient (less than 0.1 C) and ambient-temperature-change lag (less than 0.24 C) ensure minimum image degradation.

Cheng, A. Y. S.; Angel, J. R. P.

1986-01-01

378

Carbon honeycomb grids for advanced lead-acid batteries. Part I: Proof of concept  

NASA Astrophysics Data System (ADS)

The carbon honeycomb grid is proposed as innovative solution for high energy density lead acid battery. The proof of concept is demonstrated, developing grids suitable for the small capacity, scale of valve-regulated lead acid batteries with 2.5-3 Ah plates. The manufacturing of the grids, includes fast, known and simple processes which can be rescaled for mass production with a minimum, investment costs. The most critical process of green composite carbonisation by heating in inert, atmosphere from 200 to 1000 °C takes about 5 h, guaranteeing the low cost of the grids. An AGM-VRLA, cell with prototype positive plate based on the lead-2% tin electroplated carbon honeycomb grid and, conventional negative plates is cycled demonstrating 191 deep cycles. The impedance spectroscopy, measurements indicate the grid performance remains acceptable despite the evolution of the corrosion, processes during the cycling.

Kirchev, Angel; Kircheva, Nina; Perrin, Marion

2011-10-01

379

Reentrant metallicity in the Hubbard model: the case of honeycomb nanoribbons  

NASA Astrophysics Data System (ADS)

Based on the cluster perturbation solution of the Hubbard Hamiltonian for a 2D honeycomb lattice, we present quasi-particle band structures of nanoribbons at half filling as a function of on-site electron-electron (e-e) repulsion. We show that, at moderate values of e-e interaction, ribbons with armchair-shaped edges exhibit an unexpected semimetallic behavior, recovering the original insulating character only at larger values of U.

Manghi, F.; Petocchi, F.

2014-07-01

380

High-fluorine rhyolite: An eruptive pegmatite magma at the Honeycomb Hills, Utah  

Microsoft Academic Search

The Honeycomb Hills rhyolite dome in western Utah displays chemical and mineralogical features characteristic of a rare-element pegmatite magma. The lavas show extreme enrichments in such trace elements as Rb (<=1960 ppm), Cs (<=78), Li (<=344), Sn (<=33), Be (<=270), and Y (<=156). Phenocrysts (10%-50% by volume) include sanidine (Or66-70), plagioclase (Ab83-92), quartz, biotite approaching fluorsiderophyllite, and fluortopaz, as well

Roger D. Congdon; W. P. Nash

1988-01-01

381

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

Microsoft Academic Search

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

Nicolas J Lombardi

2008-01-01

382

A single EFEMP1 mutation associated with both Malattia Leventinese and Doyne honeycomb retinal dystrophy  

Microsoft Academic Search

Malattia Leventinese (ML) and Doyne honeycomb retinal dystrophy (DHRD) refer to two autosomal dominant diseases characterized by yellow-white deposits known as drusen that accumulate beneath the retinal pigment epithelium (RPE). Both loci were mapped to chromosome 2p16-21 (Refs 5,6) and this genetic interval has been subsequently narrowed. The importance of these diseases is due in large part to their close

Andrew J. Lotery; Elise Héon; Bertrand Piguet; Robyn H. Guymer; Kimberlie Vandenburgh; Pascal Cousin; Darryl Nishimura; Ruth E. Swiderski; Giuliana Silvestri; David A. Mackey; Gregory S. Hageman; Alan C. Bird; Daniel F. Schorderet; Edwin M. Stone; Francis L. Munier; Val C. Sheffield

1999-01-01

383

Fabrication and compressive performance of plain carbon steel honeycomb sandwich panels  

Microsoft Academic Search

Plain carbon steel Q215 honeycomb sandwich panels were manufactured by brazing in a vacuum furnace. Their characteristic parameters, including equivalent density, equivalent elastic modulus, and equivalent compressive strength along out-of-plane (z-direction) and in-plane (x- and y-directions), were derived theoretically and then determined experimentally by an 810 material test system. On the basis of the experimental data, the compressive stress-strain curves

Yu'an Jing; Shiju Guo; Jingtao Han; Yufei Zhang; Weijuan Li

2008-01-01

384

Vibration control of honeycomb sandwich panel using multi-layer piezoelectric actuator  

Microsoft Academic Search

A novel multi-layer piezoelectric actuator (MPA) is developed and used to control the vibration of honeycomb sandwich panel (HSP). The governing equation of the system is derived with the Hamilton principle considering third-order shearing deformation of HSP. The formulation of the actuation force is obtained and indicates the actuation force is a fourth-order polynomial function of the piezoelectric layers number.

Yajun Luo; Shilin Xie; Xinong Zhang

2008-01-01

385

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

Microsoft Academic Search

During a recent experimental test campaign performed in the framework of ESA Contract 16721, the ballistic performance of multiple satellite-representative Carbon Fibre Reinforced Plastic (CFRP)\\/Aluminium honeycomb sandwich panel structural configurations (GOCE, Radarsat-2, Herschel\\/Planck, BeppoSax) was investigated using the two-stage light-gas guns at EMI. The experimental results were used to develop and validate a new empirical Ballistic Limit Equation (BLE), which

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

2008-01-01

386

Evaluation of the in-service performance behavior of honeycomb composite sandwich structures  

Microsoft Academic Search

When honeycomb composite structures are fabricated for the aerospace industry, they are designed to be closed to their operating\\u000a environment for the life of the composite structure. However, once in service, this design can break down. Damage can set\\u000a in motion a chain reaction of events that will ultimately degrade the mechanical integrity of the composite structure. Through\\u000a thermographic analysis,

J. E. Shafizadeh; J. C. Seferis; E. F. Chesmar; R. Geyer

1999-01-01

387

NON-DESTRUCTIVE TESTING OF HONEYCOMB SANDWICH STRUCTURES USING ELASTIC WAVES  

Microsoft Academic Search

A new method for accurately measuring localized phase velocities in reverberant panels in the frequency range 5–50 kHz is applied to the problem of the non-destructive testing of honeycomb sandwich structures. First, a brief description of the elastic and vibration properties of these materials is given. With access to only one side of the panel, the method is shown to

S. Thwaites; N. H. Clark

1995-01-01

388

Critical surface of the Blume-Emery-Griffiths model on the honeycomb lattice  

Microsoft Academic Search

We consider the Blume-Emergy-Griffiths (BEG) model on the honeycomb lattice and obtain a closed-form expression for the critical surface of second-order transitions. The BEG model is first formulated as a three-state vertex model. Using the fact that the BEG critical surface coincides with that of a general three-state vertex model, we construct critical surfaces by forming polynomial combinations of vertex

Leh-Hun Gwa; F. Y. Wu

1991-01-01

389

Carbon honeycomb grids for advanced lead-acid batteries. Part I: Proof of concept  

Microsoft Academic Search

The carbon honeycomb grid is proposed as innovative solution for high energy density lead acid battery. The proof of concept is demonstrated, developing grids suitable for the small capacity, scale of valve-regulated lead acid batteries with 2.5–3Ah plates. The manufacturing of the grids, includes fast, known and simple processes which can be rescaled for mass production with a minimum, investment

Angel Kirchev; Nina Kircheva; Marion Perrin

390

Antiferromagnetic critical point on graphene's honeycomb lattice: A functional renormalization group approach  

E-print Network

Electrons on the half-filled honeycomb lattice are expected to undergo a direct continuous transition from the semimetallic into the antiferromagnetic insulating phase with increase of on-site Hubbard repulsion. We attempt to further quantify the critical behavior at this quantum phase transition by means of functional renormalization group (RG), within an effective Gross-Neveu-Yukawa theory for an SO(3) order parameter ("chiral Heisenberg universality class"). Our calculation yields an estimate of the critical exponents $\

Lukas Janssen; Igor F. Herbut

2014-02-25

391

Affleck-Kennedy-Lieb-Tasaki State on a Honeycomb Lattice is a Universal Quantum Computational Resource  

E-print Network

Universal quantum computation can be achieved by simply performing single-qubit measurements on a highly entangled resource state, such as cluster states. The family of Affleck-Kennedy-Lieb-Tasaki states has recently been intensively explored and shown to provide restricted computation. Here, we show that the two-dimensional Affleck-Kennedy-Lieb-Tasaki state on a honeycomb lattice is a universal resource for measurement-based quantum computation.

Tzu-Chieh Wei; Ian Affleck; Robert Raussendorf

2011-02-24

392

Electrically conductive anodized aluminum coatings  

NASA Technical Reports Server (NTRS)

A process for producing anodized aluminum with enhanced electrical conductivity, comprising anodic oxidation of aluminum alloy substrate, electrolytic deposition of a small amount of metal into the pores of the anodized aluminum, and electrolytic anodic deposition of an electrically conductive oxide, including manganese dioxide, into the pores containing the metal deposit; and the product produced by the process.

Alwitt, Robert S. (Inventor); Liu, Yanming (Inventor)

2001-01-01

393

RECLAMATION OF ALUMINUM FINISHING SLUDGES  

EPA Science Inventory

The research study of the reclamation of aluminum-anodizing sludges was conducted in two sequential phases focused on enhanced dewatering of aluminum-anodizing sludges to produce commercial-strength solutions of aluminum sulfate, i.e., liquid alum. The use of high-pressure (14 to...

394

Self-sustained oscillations in blood flow through a honeycomb capillary network.  

PubMed

Numerical simulations of unsteady blood flow through a honeycomb network originating at multiple inlets and terminating at multiple outlets are presented and discussed under the assumption that blood behaves as a continuum with variable constitution. Unlike a tree network, the honeycomb network exhibits both diverging and converging bifurcations between branching capillary segments. Numerical results based on a finite difference method demonstrate that as in the case of tree networks considered in previous studies, the cell partitioning law at diverging bifurcations is an important parameter in both steady and unsteady flow. Specifically, a steady flow may spontaneously develop self-sustained oscillations at critical conditions by way of a Hopf bifurcation. Contrary to tree-like networks comprised entirely of diverging bifurcations, the critical parameters for instability in honeycomb networks depend weakly on the system size. The blockage of one or more network segments due to the presence of large cells or the occurrence of capillary constriction may cause flow reversal or trigger a transition to unsteady flow. PMID:25142744

Davis, J M; Pozrikidis, C

2014-09-01

395

Photoactive, porous honeycomb films prepared from Rose Bengal-grafted polystyrene.  

PubMed

Honeycomb-structured porous polymer films based on photosensitizer-grafted polystyrene are prepared through the breath figure process. Rose Bengal (RB) photosensitizer is first attached to a well-defined poly(styrene-stat-4-vinylbenzyl chloride) statistical copolymer, synthesized by nitroxide-mediated radical polymerization. The RB grafted poly(styrene-stat-4-vinylbenzyl chloride) (ca. 20,000 g mol(-1) molar mass, 1.2 dispersity) leads to porous polymer films, with a hexagonal pore pattern, while a simple mixture of poly(styrene-stat-4-vinylbenzyl chloride) and the insoluble RB photosensitizer produced unstructured, nonporous films. The RB-grafted honeycomb films, compared with the corresponding nonporous flat films, are more efficient for oxidation of organic molecules via singlet oxygen production at a liquid/solid interface. The oxidations of 1,5-dihydroxynaphthalene to juglone and ?-terpinene to ascaridole are followed in ethanol in the presence of both types of films. Oxidation of the organic molecules is a factor 5 greater with honeycomb compared to the nonporous films. This gain is ascribed to two factors: the specific location of the polar photosensitizer at the film interface and the greater exchange surface, as revealed by fluorescence and scanning electron microscopies. PMID:23855310

Pessoni, Laurence; Lacombe, Sylvie; Billon, Laurent; Brown, Ross; Save, Maud

2013-08-13

396

LiZn2Mo3O8: honeycomb spin liquid in a triangular lattice material?  

NASA Astrophysics Data System (ADS)

LiZn2Mo3O8 is a S=1/2 triangular lattice material in which two-thirds of the spins vanish at 100K, while the remaining spins remain free down to the lowest temperatures. There is no thermodynamic phase transition, and does not appear to be any magnetic order. The experimental proposal is that the triangular lattice decouples into a honeycomb lattice with free spins in the center of each hexagon, however, it is not immediately clear what favors this decompostion. We argue that a set of alternating octahedral rotations can strengthen the bonds of the honeycomb lattice while weakening those to the central spin. Furthermore, if the honeycomb lattice forms a Z2 spin liquid, as proposed for the J1-J2 Heisenberg model, instead of a Néel or valence bond solid state, the central spin can delocalize over the hexagon, further favoring this decomposition, and also stabilizing the spin liquid phase over the Néel and VBS phases. Experimentally, this proposal can be tested by searching for signatures of the octahedral rotations, which may be short range or dynamic, but should result in a q=0 soft phonon mode. The spinon spectrum of the gapped Z2 spin liquid should also have signatures in inelastic neutron scattering. We also discuss possible 3D analogues.

Flint, Rebecca; Lee, Patrick

2013-03-01

397

Experimental demonstration of waveguiding in honeycomb and square-lattice silicon photonic crystal membranes  

NASA Astrophysics Data System (ADS)

Sub-micron waveguides and cavities have been shown to produce the confinement of elastic and optical waves in the same devices in order to benefit from their interaction. It has been shown that square and honeycomb lattices are the most suitable to produce simultaneous photonic and phononic band gaps on suspended silicon slabs. The introduction of line defects on such "phoxonic" (or optomechanical) crystals should lead to an enhanced interaction between confined light and sound. In this work we report on the experimental measurements of light guiding through waveguides created in these kinds of two-dimensional photonic crystal membranes. The dimensions of the fabricated structures are chosen to provide a "phoxonic" bandgap with a photonic gap around 1550 nm. For both kinds of lattice, we observe a high-transmission band when introducing a linear defect, although it is observed for TM polarization in the honeycomb lattice and for TE in the square. Using the plane-wave expansion and the finite element methods we demonstrate that the guided modes are below the light line and, therefore, without additional losses beside fabrication imperfections. Our results lead us to conclude that waveguides implemented in honeycomb and square lattice "phoxonic" crystals are a very suitable platform to observe an enhanced interaction between propagating photons and phonons.

Puerto, Daniel; Griol, Amadeu; Escalante, José Maria; Djafari-Rouhani, Bahram; Pennec, Yan; Laude, Vincent; Beugnot, Jean-Charles; Martínez, Alejandro

2012-06-01

398

Formation and soot combustion of honeycomb-like LaFeO3 microfibers.  

PubMed

The nanocrystalline, honeycomb-like, perovskite LaFeO3 microfibers with a fibre diameter about 1-2 microm and channel sizes about 180-220 nm on the cross-section were prepared by the citrate-gel process. These microfibers were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and Brunauere-Emmette-Teller (BET) method. After calcined at a low temperature of 550 degrees C for 6 hours, the single phase of perovskite LaFeO3 microfibers is formed and the grain size increases from 27 to 38 nm with the calcination temperature increasing from 500 to 650 degrees C. The catalytic activity for soot combustion was analyzed by thermo-gravimetric method (TG), and the LaFeO3 microfibers calcined at 600 degrees C exhibits the highest catalytic activity for soot combustion, with a lowest T50 (393 degrees C) and T90 (434 degrees C). The formation mechanism of the honeycomb-like structure is analyzed and these honeycomb-like microfibers can be used as advanced catalysts, absorbents, filters and microreactors. PMID:24745245

Zou, Lianli; Jing, Maoxiang; Xiang, Jun; Wang, Pan; Shen, Xiangqian

2014-03-01

399

Quantum molecular dynamics simulations of the oxidation of aluminum-cyclopentadienyl clusters  

NASA Astrophysics Data System (ADS)

We report Car-Parrinello molecular dynamics simulations of the oxidation of aluminum-cyclopentadienyl clusters currently being considered as novel fuels or energetic materials. These clusters contain a small aluminum core surrounded by a single organic ligand layer. The aromatic cyclopentadienyl ligands form a very strong bond with surface Al atoms, giving rise to a stable organometallic cluster which crystallizes into a low-symmetry solid-state material. Our calculations of an isolated cluster in oxygen show minimal reaction between the ligand and oxygen molecules at simulation temperatures of 300 and 1000 K. Rather, in all cases O2 diffuses through the ligand barrier, splits into atomic oxygen upon contact with the aluminum, and forms an amorphous aluminum oxide core. Loss of aluminum-ligand units, as expected from bond strength calculations, is not observed except following significant oxidation. We present simple metrics to quantitatively compare the steric barrier of the outer ligands that limits the oxidation process.

Alnemrat, Sufian; Hooper, Joseph P.

2014-05-01

400

Application of Wave Propagation and Vibration-based Structural Health Monitoring Techniques to Friction Stir Welded Plate and Sandwich Honeycomb Panel  

NASA Astrophysics Data System (ADS)

Wave propagation and vibration-based structural health monitoring methodologies are presented to detect, locate and quantify dent/crack, thermal debond, and corrosion damage in a solid aluminum friction stir weld plate and a sandwich honeycomb thermal protection panel. A wave propagation based method can identify small defects because propagating waves typically consist of small wavelengths while a vibration-based scheme is better equipped to quantify damage over wide areas of large structures. Near-real time online diagnostics is achieved by using localized sensing (wave propagation) and distributed sensing (vibration-based) in an active measurement array. Sensor/actuator arrays have been developed to implement these techniques and portable health management systems have been developed based on the combination of damage detection algorithms, active sensing, and graphical user interfaces. Propagating waves are shown to have a heightened sensitivity to damage located at the anti-nodes of a friction stir wed plate forced by low frequency environmental vibrations. Measurement of the input forcing in the vibration-based method is shown to enable damage quantification.

Sundararaman, S.; White, J. R.; Adams, D. E.; Jata, K. V.

2007-03-01

401

Pitting corrosion of aluminum  

Microsoft Academic Search

This review describes the experiments performed during the last few decades which enhance knowledge of the pitting of aluminum. Specifically, metastable and stable pits, pit chemistry and the effect of intermetallics on pitting are discussed. The properties of metastable alloys and inhibition of Al are also discussed.

Z Szklarska-Smialowska

1999-01-01

402

Aluminum Sulfate 18 Hydrate  

ERIC Educational Resources Information Center

A chemical laboratory information profile (CLIP) of the chemical, aluminum sulfate 18 hydrate, is presented. The profile lists physical and harmful properties, exposure limits, reactivity risks, and symptoms of major exposure for the benefit of teachers and students using the chemical in the laboratory.

Young, Jay A.

2004-01-01

403

Mesoporous aluminum phosphite  

NASA Astrophysics Data System (ADS)

High surface area pure mesoporous aluminum-phosphorus oxide-based derivatives have been synthesized through an S +I - surfactant-assisted cooperative mechanism by means of a one-pot preparative procedure from aqueous solution and starting from aluminum atrane complexes and phosphoric and/or phosphorous acids. A soft chemical extraction procedure allows opening the pore system of the parent as-prepared materials by exchanging the surfactant without mesostructure collapse. The nature of the pore wall can be modulated from mesoporous aluminum phosphate (ALPO) up to total incorporation of phosphite entities (mesoporous aluminum phosphite), which results in a gradual evolution of the acidic properties of the final materials. While phosphate groups in ALPO act as network building blocks (bridging Al atoms), the phosphite entities become basically attached to the pore surface, what gives practically empty channels. The mesoporous nature of the final materials is confirmed by X-ray diffraction (XRD), transmission electron microscopy (TEM) and N 2 adsorption-desorption isotherms. The materials present regular unimodal pore systems whose order decreases as the phosphite content increases. NMR spectroscopic results confirm the incorporation of oxo-phosphorus entities to the framework of these materials and also provide us useful information concerning the mechanism through which they are formed.

El Haskouri, Jamal; Pérez-Cabero, Mónica; Guillem, Carmen; Latorre, Julio; Beltrán, Aurelio; Beltrán, Daniel; Amorós, Pedro

2009-08-01

404

Aluminum Corrosion and Turbidity  

SciTech Connect

Aluminum corrosion and turbidity formation in reactors correlate with fuel sheath temperature. To further substantiate this correlation, discharged fuel elements from R-3, P-2 and K-2 cycles were examined for extent of corrosion and evidence of breaking off of the oxide film. This report discusses this study.

Longtin, F.B.

2003-03-10

405

Aluminum battery alloys  

DOEpatents

Aluminum alloys suitable for use as anode structures in electrochemical cells are disclosed. These alloys include iron levels higher than previously felt possible, due to the presence of controlled amounts of manganese, with possible additions of magnesium and controlled amounts of gallium.

Thompson, D.S.; Scott, D.H.

1984-09-28

406

Design Criteria for X-CRV Honeycomb Panels: A Preliminary Study  

NASA Technical Reports Server (NTRS)

The objective of this project is to perform the first step in developing structural design criteria for composite sandwich panels that are to be used in the aeroshell of the crew return vehicle (X-CRV). The preliminary concept includes a simplified method for assessing the allowable strength in the laminate material. Ultimately, it is intended that the design criteria be extended to address the global response of the vehicle. This task will require execution of a test program as outlined in the recommendation section of this report. The aeroshell of the X-CRV is comprised of composite sandwich panels consisting of fiberite face sheets and a phenolic honeycomb core. The function of the crew return vehicle is to enable the safe return of injured or ill crewpersons from space station, the evacuation of crew in case of emergency or the return of crew if an orbiter is not available. A significant objective of the X-CRV project is to demonstrate that this vehicle can be designed, built and operated at lower cost and at a significantly faster development time. Development time can be reduced by driving out issues in both structural design and manufacturing concurrently. This means that structural design and analysis progresses in conjunction with manufacturing and testing. Preliminary tests results on laminate coupons are presented in the report. Based on these results a method for detection material failure in the material is presented. In the long term, extrapolation of coupon data to large scale structures may be inadequate. Test coupons used to develop failure criteria at the material scale are typically small when compared to the overall structure. Their inherent small size indicates that the material failure criteria can be used to predict localized failure of the structure, however, it can not be used to predict failure for all failure modes. Some failure modes occur only when the structure or one of its sub-components are studied as a whole. Conversely, localized failure may not indicate failure of the structure as a whole and the amount of reserve capacity, if any, should be assessed. To develop a complete design criteria experimental studies of the sandwich panel are needed. Only then can a conservative and accurate design criteria be developed. This criteria should include effects of flaws and defects, and environmental factors such as temperature and moisture. Preliminary results presented in this report suggest that a simplified analysis can be used to predict the strength of a laminate. Testing for environmental effects have yet to be included in this work. The so called 'rogue flaw test' appears to be a promising method for assessing the effect of a defect in a laminate. This method fits in quite well with the philosophy of achieving a damage tolerant design.

Caccese, Vincent; Verinder, Irene

1997-01-01

407

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

NASA Astrophysics Data System (ADS)

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

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

2012-08-01

408

Mechanisms of Aluminum Tolerance  

Microsoft Academic Search

\\u000a Aluminum (Al) toxicity limits agricultural productivity over much of the world’s arable land by inhibiting root growth and\\u000a development. Affected plants have difficulty in acquiring adequate water and nutrition from their soil environments and thus\\u000a have stunted shoot development and diminished yield. Al toxicity is due to soil acidity and is largely a natural problem;\\u000a however, it can also result

Owen A. Hoekenga; Jurandir V. Magalhaes

409

Aluminum Carbothermic Technology  

SciTech Connect

This report documents the non-proprietary research and development conducted on the Aluminum Carbothermic Technology (ACT) project from contract inception on July 01, 2000 to termination on December 31, 2004. The objectives of the program were to demonstrate the technical and economic feasibility of a new carbothermic process for producing commercial grade aluminum, designated as the ''Advanced Reactor Process'' (ARP). The scope of the program ranged from fundamental research through small scale laboratory experiments (65 kW power input) to larger scale test modules at up to 1600 kW power input. The tasks included work on four components of the process, Stages 1 and 2 of the reactor, vapor recovery and metal alloy decarbonization; development of computer models; and economic analyses of capital and operating costs. Justification for developing a new, carbothermic route to aluminum production is defined by the potential benefits in reduced energy, lower costs and more favorable environmental characteristics than the conventional Hall-Heroult process presently used by the industry. The estimated metrics for these advantages include energy rates at approximately 10 kWh/kg Al (versus over 13 kWh/kg Al for Hall-Heroult), capital costs as low as $1250 per MTY (versus 4,000 per MTY for Hall-Heroult), operating cost reductions of over 10%, and up to 37% reduction in CO2 emissions for fossil-fuel power plants. Realization of these benefits would be critical to sustaining the US aluminum industries position as a global leader in primary aluminum production. One very attractive incentive for ARP is its perceived ability to cost effectively produce metal over a range of smelter sizes, not feasible for Hall-Heroult plants which must be large, 240,000 TPY or more, to be economical. Lower capacity stand alone carbothermic smelters could be utilized to supply molten metal at fabrication facilities similar to the mini-mill concept employed by the steel industry. Major accomplishments for the program include definition of the system thermo-chemistry, demonstration of reactor stage 1, development of reactor stage 2 critical components in a 500 kW module, experimental determination of the vapor recovery reactor fundamentals, detailed design and installation of an advanced stage 1/vapor recovery reactor, feasibility of efficient separation of Al-C metal alloy product, updated capital and operating cost estimates, and development of computer models for all steps of the Advanced Reactor Process.

Bruno, Marshall J.

2005-03-31

410

Structural design and analysis of a lightweight composite sandwich space radiator panel  

E-print Network

models to validate the predictions of finite element analysis. The optimum dimensions of the sandwich panel are determined and structural and thermal response of the Poco foam is compared with existing aluminum honeycomb core....

Mukundan, Sudharsan

2005-02-17

411

Molecular aspects of aluminum toxicity  

Microsoft Academic Search

The focus in this review is directed to molecular aspects of aluminum toxicity in animal and plant cells. Unique thermodynamic features of Al(lII) ions impart biological specificity which may form the biochemical basis of aluminum interactions with cellular constituents. Current knowledge about aluminum?specific, molecular interactions is rather scanty. Al(III) ions may coordinate with nucleotides or complex to phospholipids resulting in

Alfred Haug; Charles E. Foy

1984-01-01

412

Quasicrystalline particulate reinforced aluminum composite  

SciTech Connect

Particulate reinforced aluminum and aluminum alloy composites are rapidly emerging as new commercial materials for aerospace, automotive, electronic packaging and other high performance applications. However, their low processing ductility and difficulty in recyclability have been the key concern. In this study, two composite systems having the same aluminum alloy matrix, one reinforced with quasicrystals and the other reinforced with the conventional SiC reinforcements were produced with identical processing routes. Their processing characteristics and tensile mechanical properties were compared.

Anderson, I.E.; Biner, S.B.; Sordelet, D.J.; Unal, O.

1997-07-01

413

Critical behavior of self-assembled rigid rods on triangular and honeycomb lattices.  

PubMed

Using Monte Carlo simulations and finite-size scaling analysis, the critical behavior of self-assembled rigid rods on triangular and honeycomb lattices at intermediate density has been studied. The system is composed of monomers with two attractive (sticky) poles that, by decreasing temperature or increasing density, polymerize reversibly into chains with three allowed directions and, at the same time, undergo a continuous isotropic-nematic (IN) transition. The determination of the critical exponents, along with the behavior of Binder cumulants, indicate that the IN transition belongs to the q=1 Potts universality class. PMID:20942550

López, L G; Linares, D H; Ramirez-Pastor, A J

2010-10-01

414

Fermionic Quantum Critical Point of Spinless Fermions on a Honeycomb Lattice  

E-print Network

Spinless fermions on a honeycomb lattice provide a minimal realization of lattice Dirac fermions. Repulsive interactions between nearest neighbors drive a quantum phase transition from a Dirac semimetal to a charge-density-wave state through a fermionic quantum critical point, where the coupling of Ising order parameter to the Dirac fermions at low energy drastically affects the quantum critical behavior. Encouraged by a recently discovery of absence of the fermion sign problem in this model, we study the fermionic quantum critical point using the continuous time quantum Monte Carlo method with worm sampling technique. We estimate the transition point $V/t= 1.356(1)$ with the critical exponents $\

Lei Wang; Philippe Corboz; Matthias Troyer

2014-06-30

415

Honeycomb, square, and kagome vortex lattices in superconducting systems with multiscale intervortex interactions  

NASA Astrophysics Data System (ADS)

The recent proposal of Romero-Isart et al. [Phys. Rev. Lett. 111, 145304 (2013), 10.1103/PhysRevLett.111.145304] to utilize the vortex lattice phases of superconducting materials to prepare a lattice for ultracold-atom-based quantum emulators raises the need to create and control vortex lattices of different symmetries. Here we propose a mechanism by which honeycomb, hexagonal, square, and kagome vortex lattices could be created in superconducting systems with multiscale intervortex interactions. Multiple scales of the intervortex interaction can be created and controlled in layered systems made of different superconducting materials or with differing interlayer spacings.

Meng, Qingyou; Varney, Christopher N.; Fangohr, Hans; Babaev, Egor

2014-07-01

416

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

NASA Technical Reports Server (NTRS)

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

Hui, David

1989-01-01

417

Two- and One-Dimensional Honeycomb Structures of Silicon and Germanium  

NASA Astrophysics Data System (ADS)

First-principles calculations of structure optimization, phonon modes, and finite temperature molecular dynamics predict that silicon and germanium can have stable, two-dimensional, low-buckled, honeycomb structures. Similar to graphene, these puckered structures are ambipolar and their charge carriers can behave like a massless Dirac fermion due to their ? and ?* bands which are crossed linearly at the Fermi level. In addition to these fundamental properties, bare and hydrogen passivated nanoribbons of Si and Ge show remarkable electronic and magnetic properties, which are size and orientation dependent. These properties offer interesting alternatives for the engineering of diverse nanodevices.

Cahangirov, S.; Topsakal, M.; Aktürk, E.; ?ahin, H.; Ciraci, S.

2009-06-01

418

Experimental percolation studies of two-dimensional honeycomb lattice: Li2Mn1-xTixO3.  

PubMed

Li2MnO3 with a S = 3/2 two-dimensional Mn honeycomb lattice has a Neel-type antiferromagnetic transition at TN = 36?K with a broad maximum in magnetic susceptibility at TM = 48?K. We have investigated site percolation effects by replacing Mn with nonmagnetic Ti, and completed a full phase diagram of Li2Mn1-xTixO3 solid solution systems to find that antiferromagnetic transition is continuously suppressed without a clear sign of changes in the Neel-type antiferromagnetic structure. The magnetic ordering eventually disappears at a critical concentration of xc = 0.7. This experimental observation is consistent with percolation theories for a honeycomb lattice when one considers up to 3rd nearest-neighbor interactions. This study highlights the importance of interaction beyond nearest neighbors even for the Mn element with relative localized 3d electrons in the honeycomb lattice. PMID:25001600

Lee, Sanghyun; Park, Junghwan; Kim, Jiyeon; Hong, Kun-Pyo; Song, Youngmi; Park, Je-Geun

2014-07-30

419

Assembly of acid and sintering resistant honeycomb washcoat and catalytically active phase using sols of silica, zirconia, and platinum  

SciTech Connect

Development of high performance honeycomb catalysts containing platinum active phase for gas phase air oxidation of sulfur dioxide is described. Stepwise assembly of these washcoated honeycombs consists of: (1) selection of honeycomb composition (mullite substrate) and cell density based on pressure drop requirements; (2) identification of washcoat slurry composition (silica-precursor sol, silica powder, and surfactants if needed); (3) processing of the washcoat-substrate by dip coating, drying, and calcining; (4) loading of the platinum active phase through a facilitated adsorption technique followed by drying and activation steps; and (5) reactor loading and evaluation. Details of these steps will be presented that include thermal and chemical stability tests. Characterization by transmission electron microscopy of the final Pt/(ZrO{sub 2}-SiO{sub 2}) composite attached to the mullite substrate will be reported.

Felthouse, T.R. [Monsanto Enviro-Chem Systems, Inc., St.Louis, MO (United States); [Huntsman Specialty Chemicals Corp., St. Louis, MO (United States); Berkel, D.A.; Jost, S.R. [Monsanto Enviro-Chem Systems, Inc., St. Louis, MO (United States)] [and others

1995-12-01

420

First-principles calculations of a robust two-dimensional boron honeycomb sandwiching a triangular molybdenum layer  

NASA Astrophysics Data System (ADS)

A graphenelike two-dimensional boron honeycomb is inherently prohibited due to its empty ? valence band. Based on chemical intuition and first-principles calculations, we design a two-dimensional crystal MoB4 with two graphenelike boron honeycombs sandwiching a triangular molybdenum layer. It has the attractive electronic structure of double Dirac cones near Fermi level with high Fermi velocity, which are contributed by the coupling of Mo d orbitals and B pz orbitals. Such a metal stabilized boron honeycomb system could even have both superconductivity and ferromagnetism through appropriate selection of the metal layer, such as manganese. The unique electronic properties of these two-dimensional systems inspire broad interest in nanoelectronics.

Xie, Sheng-Yi; Li, Xian-Bin; Tian, Wei Quan; Chen, Nian-Ke; Zhang, Xu-Lin; Wang, Yeliang; Zhang, Shengbai; Sun, Hong-Bo

2014-07-01

421

Application of transfer matrix method in heat transfer performance analysis of multi-re-entrant honeycomb structures  

NASA Astrophysics Data System (ADS)

The thermal properties for the multi-re-entrant honeycomb are investigated, where the hexagon and re-entrant topologies are applied for comparison. A compact model was adopted for the local heat transfer rate and pressure drop estimations while the total heat transfer rate was analyzed using the transfer matrix method. A thermal performance index was specified to characterize a good heat exchange medium that can transfer more heat at the expense of lower pressure loss. Numerical results reveal better thermal performances of multi-re-entrant honeycombs over hexagon and re-entrant topologies, attributed to the presence of added base walls. Auxetic effect introduced in multi-re-entrant honeycomb generally provides enhanced out-of-plane thermal conductivity and increased total heat transfer efficiency due to higher surface area density.

Hou, Xiuhui; Deng, Zichen; Yin, Guansheng

2014-12-01

422

Laser welding of aluminum alloys  

SciTech Connect

Recent interest in reducing the weight of automobiles to increase fuel mileage has focused attention on the use of aluminum and associated joining technologies. Laser beam welding is one of the more promising methods for high speed welding of aluminum. Consequently, substantial effort has been expended in attempting to develop a robust laser beam welding process. Early results have not been very consistent in the process requirements but more definitive data has been produced recently. This paper reviews the process parameters needed to obtain consistent laser welds on 5,000 series aluminum alloys and discusses the research necessary to make laser processing of aluminum a reality for automotive applications.

Leong, K.H.; Sabo, K.R.; Sanders, P.G. [Argonne National Lab., IL (United States). Technology Development Div.; Spawr, W.J.

1997-03-01

423

Mineral of the month: aluminum  

USGS Publications Warehouse

Aluminum is the second most abundant metallic element in Earth’s crust after silicon. Even so, it is a comparatively new industrial metal that has been produced in commercial quantities for little more than 100 years. Aluminum is lightweight, ductile, malleable and corrosion resistant, and is a good conductor of heat and electricity. Weighing about one-third as much as steel or copper per unit of volume, aluminum is used more than any other metal except iron. Aluminum can be fabricated into desired forms and shapes by every major metalworking technique to add to its versatility.

Plunkert, Patricia A.

2005-01-01

424

Aluminum-lithium for aerospace  

SciTech Connect

Aluminum-lithium alloys were developed primarily to reduce the weight of aircraft and aerospace structures. Lithium is the lightest metallic element, and each 1% of lithium added to aluminum reduces alloy density by about 3% and increases modulus by about 5%. Though lithium has a solubility limit of 4.2% in aluminum, the amount of lithium ranges between 1 and 3% in commercial alloys. Aluminum-lithium alloys are most often selected for aerospace components because of their low density, high strength, and high specific modulus. However, other applications now exploit their excellent fatigue resistance and cryogenic toughness.

Fielding, P.S.; Wolf, G.J. [Reynolds Metals Co., Richmond, VA (United States)

1996-10-01

425

Landau level spectrum of Bloch electrons in a honeycomb lattice Centre de Recherches sur les Trs Basses Tempratures, CNRS, B.P. 166X, 38042 Grenoble Cedex, France,  

E-print Network

honeycomb network. A comparison of the structure of the edge of the spectrum on square, triangular networks. This connection has been achieved experi- mentally [5] by a direct measurement of the critical1345 Landau level spectrum of Bloch electrons in a honeycomb lattice R. Rammal Centre de Recherches

Paris-Sud XI, Université de

426

A comparison of the static and dynamic characteristics of straight-bore and convergent tapered-bore honeycomb annular gas seals  

E-print Network

Results are presented from tests conducted with straight-bore and convergent tapered-bore honeycomb annular gas seals. The test seals had a 114.3 mm bore with an L/D = 0.75 and a nominal radial clearance of 0.19 mm. The honeycomb cell depth for both...

Dawson, Matthew Peter

2012-06-07

427

Production of aluminum metal by electrolysis of aluminum sulfide  

DOEpatents

Metallic aluminum may be produced by the electrolysis of Al/sub 2/S/sub 3/ at 700 to 800/sup 0/C in a chloride melt composed of one or more alkali metal chlorides, and one or more alkaline earth metal chlorides and/or aluminum chloride to provide improved operating characteristics of the process.

Minh, N.Q.; Loutfy, R.O.; Yao, N.P.

1982-04-01

428

Aluminum monocarbonyl and aluminum isocarbonyl Steve S. Wesolowski,a)  

E-print Network

valence d electrons.2 One particularly useful experimental technique em- ployed in the study of metalAluminum monocarbonyl and aluminum isocarbonyl Steve S. Wesolowski,a) T. Daniel Crawford,b) Justin, configuration interaction, and coupled-cluster levels of theory with large basis sets. At the highest level

Crawford, T. Daniel

429

Characterization of ultradispersed aluminum  

SciTech Connect

Samples of ultradispersed Al were received, which were produced by electrically exploding Al wires in argon. These samples comprised very small particles that were not significantly oxidized and that were stable in air. Particle morphology were studied with SE, micropycnometry, and gas adsorption surface area. Composition were determined using various techniques, as were thermal stability and reaction exotherms. The inexplicable reports of an Al-Ar compound and of an exothermic reaction were not confirmed. The material is a stable, nonoxidized, small-particle, highly reactive form of aluminum that is of interest in energetic materials formulations.

Simpson, R.L.; Maienschein, J.L.; Swansiger, R.W.; Garcia, F.; Darling, D.H.

1994-12-08

430

Aluminum nitride grating couplers.  

PubMed

Grating couplers in sputtered aluminum nitride, a piezoelectric material with low loss in the C band, are demonstrated. Gratings and a waveguide micromachined on a silicon wafer with 600 nm minimum feature size were defined in a single lithography step without partial etching. Silicon dioxide (SiO(2)) was used for cladding layers. Peak coupling efficiency of -6.6 dB and a 1 dB bandwidth of 60 nm have been measured. This demonstration of wire waveguides and wideband grating couplers in a material that also has piezoelectric and elasto-optic properties will enable new functions for integrated photonics and optomechanics. PMID:22695653

Ghosh, Siddhartha; Doerr, Christopher R; Piazza, Gianluca

2012-06-10

431

Thermal transport and fire retardance properties of cellular aluminum alloys  

SciTech Connect

Closed-cell aluminum alloy foams exhibit exceptional resistance to fire. It is unclear why this happens, although the protection imparted by oxide Al{sub 2}O{sub 3} layers has been suggested. This work attempts to uncover the thermal transport processes in metallic foams. The apparent thermal conductivities of two-dimensional foams having a variety of cellular microstructures are first calculated. These include regular honeycombs, Voronoi structures and Johnson-Mehl models. The effects of several types of geometric imperfection--Plateau borders, cell-edge misalignments, fractured cell edges, missing cells, inclusions and cell size variations--are studied by using analytical as well as finite element methods. The focus is on metallic foams where the transport of heat is dominated by solid conduction and thermal radiation; contributions from gaseous conduction and convection are neglected. The coupling of solid conduction with thermal radiation is dealt with by using the method of finite elements. These results are then applied to solve the transient temperature field of a cellular metal plate subjected to a sudden introduction of a high-temperature source of heat such as fire. The factors which dictate the thermal and structural fire retardance of cellular metallic foams are identified.

Lu, T.J.; Chen, C. [Univ. of Cambridge (United Kingdom). Dept. of Engineering] [Univ. of Cambridge (United Kingdom). Dept. of Engineering

1999-03-31

432

21 CFR 172.310 - Aluminum nicotinate.  

Code of Federal Regulations, 2012 CFR

... 3 2012-04-01 2012-04-01 false Aluminum nicotinate. 172.310 Section 172.310 ...Dietary and Nutritional Additives § 172.310 Aluminum nicotinate. Aluminum nicotinate may be safely used as a source of...

2012-04-01

433

75 FR 80527 - Aluminum Extrusions From China  

Federal Register 2010, 2011, 2012, 2013

...Final) and 731-TA-1177 (Final)] Aluminum Extrusions From China AGENCY: United...less-than-fair-value imports from China of aluminum extrusions, primarily provided for in...these investigations is contained in Aluminum Extrusions From the People's...

2010-12-22

434

21 CFR 73.2645 - Aluminum powder.  

Code of Federal Regulations, 2012 CFR

...2012-04-01 2012-04-01 false Aluminum powder. 73.2645 Section 73...CERTIFICATION Cosmetics § 73.2645 Aluminum powder. (a) Identity and specifications. The color additive aluminum powder shall conform in...

2012-04-01

435

21 CFR 73.1645 - Aluminum powder.  

Code of Federal Regulations, 2012 CFR

...2012-04-01 2012-04-01 false Aluminum powder. 73.1645 Section 73.1645...CERTIFICATION Drugs § 73.1645 Aluminum powder. (a) Identity. (1) The color additive aluminum powder shall be composed of finely...

2012-04-01

436

DUBLIN CORE  

EPA Science Inventory

The Dublin Core is a metadata element set intended to facilitate discovery of electronic resources. It was originally conceived for author-generated descriptions of Web resources, and the Dublin Core has attracted broad ranging international and interdisciplinary support. The cha...

437

Vibration and sound radiation from a sandwich cylindrical shell with prismatic core  

NASA Astrophysics Data System (ADS)

The vibration and the sound radiation of cylindrical shells with cellular core is here analyzed. The considered structure is composed of a repeated unit cell and can be classified as a Linear Cellular Alloy (LCA) core. The unit cells are of a tetrahedral configuration, arranged according to a honeycomb lay-out. The considered configuration has previously been proposed for core designs of sandwich beams with superior structural properties. In here, the effects of the core configuration on the structural-acoustic behavior of the considered sandwich shell is investigated through a FE model. The FE model is created with ANSYS, a commercially available Finite Element Analysis (FEA) package. The sensitivity of the shell's dynamic characteristics to changes in the geometric properties of the core is investigated. An optimization problem is formulated to determine the core configuration which minimizes, within a target frequency range, the sound radiation of the shell in an unbounded fluid environment.

Jeong, Sang M.; Ruzzene, Massimo

2004-07-01

438

Selective Adsorption of Sodium Aluminum Fluoride Salts from Molten Aluminum  

SciTech Connect

Aluminum is produced in electrolytic reduction cells where alumina feedstock is dissolved in molten cryolite (sodium aluminum fluoride) along with aluminum and calcium fluorides. The dissolved alumina is then reduced by electrolysis and the molten aluminum separates to the bottom of the cell. The reduction cell is periodically tapped to remove the molten aluminum. During the tapping process, some of the molten electrolyte (commonly referred as “bath” in the aluminum industry) is carried over with the molten aluminum and into the transfer crucible. The carryover of molten bath into the holding furnace can create significant operational problems in aluminum cast houses. Bath carryover can result in several problems. The most troublesome problem is sodium and calcium pickup in magnesium-bearing alloys. Magnesium alloying additions can result in Mg-Na and Mg-Ca exchange reactions with the molten bath, which results in the undesirable pickup of elemental sodium and calcium. This final report presents the findings of a project to evaluate removal of molten bath using a new and novel micro-porous filter media. The theory of selective adsorption or removal is based on interfacial surface energy differences of molten aluminum and bath on the micro-porous filter structure. This report describes the theory of the selective adsorption-filtration process, the development of suitable micro-porous filter media, and the operational results obtained with a micro-porous bed filtration system. The micro-porous filter media was found to very effectively remove molten sodium aluminum fluoride bath by the selective adsorption-filtration mechanism.

Leonard S. Aubrey; Christine A. Boyle; Eddie M. Williams; David H. DeYoung; Dawid D. Smith; Feng Chi

2007-08-16

439

Candidate Quantum Spin Liquid due to Dimensional Reduction of a Two-Dimensional Honeycomb Lattice  

NASA Astrophysics Data System (ADS)

As with quantum spin liquids based on two-dimensional triangular and kagome lattices, the two-dimensional honeycomb lattice with either a strong spin-orbital coupling or a frustrating second-nearest-neighbor coupling is expected to be a source of candidate quantum spin liquids. An ammonium salt [(C3H7)3NH]2[Cu2(C2O4)3](H2O)2.2 containing hexagonal layers of Cu2+ was obtained from solution. No structural transition or long-range magnetic ordering was observed from 290 K to 2 K from single crystal X-ray diffraction, specific heat and susceptibility measurements. The anionic layers are separated by sheets of ammonium and H2O with distance of 3.5 Å and no significant interaction between anionic layers. The two-dimensional honeycomb lattice is constructed from Jahn-Teller distorted Cu2+ and oxalate anions, showing a strong antiferromagnetic interaction between S = 1/2 metal atoms with ? = -120 (1) K. Orbital analysis of the Cu2+ interactions through the oxalate-bridges suggests a stripe mode pattern of coupling with weak ferromagnetic interaction along the b axis, and strong antiferromagnetic interaction along the a axis. Analysis of the magnetic susceptibility shows that it is dominated by a quasi-one-dimensional contribution with spin chains that are at least as well isolated as those of well-known quasi-one-dimensional spin liquids.

Zhang, Bin; Zhang, Yan; Wang, Zheming; Wang, Dongwei; Baker, Peter J.; Pratt, Francis L.; Zhu, Daoben

2014-09-01

440

Electrokinetic desalination using honeycomb carbon nanotubes (HC-CNTs): a conceptual study by molecular simulation.  

PubMed

A new concept of electrokinetic desalination using a CNT honeycomb is presented through molecular dynamics simulation. The preferential translocation of ions towards the outlets near two electrodes was realized by applying an electric field perpendicular to bulk fluid flow in a CNT network, which, in the meantime, generated deionized water flux discharged from the central outlets. The effects of the major factors such as electric field strength, numbers of separation units, diameter of CNT, and ion concentration on the desalination were examined. It was shown that over 95% salt rejection and around 50% fresh water recovery were achieved by the presented module by applying an electric field of 0.8 V nm(-1). CNT diameter, which is critical to ion rejection without the electric field, had a marginal effect on the desalination of this new module when a strong electric field was applied. The desalination was also not sensitive to ion concentration, indicating its excellent workability for a wide range of water salinity, e.g. from brackish water to seawater. A potential of mean force profile revealed a free energy barrier as large as 2.0-6.0 kcal mol(-1) for ions to move opposite to the implemented electrical force. The simulation confirmed the high potential of the CNT honeycomb in water desalination. PMID:25092215

Chen, Qile; Kong, Xian; Li, Jipeng; Lu, Diannan; Liu, Zheng

2014-09-21

441

Functionalization of BN honeycomb structure by adsorption and substitution of foreign atoms  

NASA Astrophysics Data System (ADS)

We carried out first-principles calculations within density-functional theory to investigate the structural, electronic, and magnetic properties of boron-nitride (BN) honeycomb structure functionalized by adatom adsorption, as well as by the substitution of foreign atoms for B and N atoms. For periodic high-density coverage, most of 3d transition metal atoms and some of group 3A, 4A, and 6A elements are adsorbed with significant binding energy and modify the electronic structure of bare BN monolayer. While bare BN monolayer is nonmagnetic, wide band-gap semiconductor, at high coverage of specific adatoms it can achieve magnetic metallic, even half-metallic ground states. At low coverage, the bands associated with adsorbed atoms are flat and the band structure of parent BN is not affected significantly. Therefore, adatoms and substitution of foreign atoms at low coverage are taken to be the representative of impurity atoms yielding localized states in the band gap and resonance states in the band continua. Notably, the substitution of C for B and N yield donorlike and acceptorlike magnetic states in the band gap. Localized impurity states occurring in the gap give rise to interesting properties for electronic and optical application of the single-layer BN honeycomb structure.

Ataca, C.; Ciraci, S.

2010-10-01

442

Featureless and nonfractionalized Mott insulators on the honeycomb lattice at 1/2 site filling  

PubMed Central

Within the Landau paradigm, phases of matter are distinguished by spontaneous symmetry breaking. Implicit here is the assumption that a completely symmetric state exists: a paramagnet. At zero temperature such quantum featureless insulators may be forbidden, triggering either conventional order or topological order with fractionalized excitations. Such is the case for interacting particles when the particle number per unit cell, f, is not an integer. However, can lattice symmetries forbid featureless insulators even at integer f? An especially relevant case is the honeycomb (graphene) lattice—where free spinless fermions at (the two sites per unit cell mean is half-filling per site) are always metallic. Here we present wave functions for bosons, and a related spin-singlet wave function for spinful electrons, on the honeycomb lattice and demonstrate via quantum to classical mappings that they do form featureless Mott insulators. The construction generalizes to symmorphic lattices at integer f in any dimension. Our results explicitly demonstrate that in this case, despite the absence of a noninteracting insulator at the same filling, lack of order at zero temperature does not imply fractionalization.

Kimchi, Itamar; Parameswaran, S. A.; Turner, Ari M.; Wang, Fa; Vishwanath, Ashvin

2013-01-01

443

Effect of geometry and microstructure of honeycomb TCP scaffolds on bone regeneration.  

PubMed

In recent years, artificial biological materials have been commonly used for the treatment of bone tissue defects caused by trauma, tumors, or surgical stress. Although tricalcium phosphate (TCP) is a promising absorbent bone tissue reconstruction biomaterial, it has been reported that its biocompatibility and osteoconductivity depend on its preparation method and sintering temperature. In addition, although it is thought that the microenvironment produced by the extracellular matrix plays an important role in cell growth and differentiation, there have been few studies on how the geometric structure of artificial biological materials affects cells. In the present study, a new honeycomb TCP scaffold containing through-holes with diameters of 300 µm has been developed. The influence of the sintering temperature on the crystal structure and material properties of the honeycomb TCP scaffold was investigated using scanning electron microscopy and X-ray diffraction. Its biocompatibility and osteoconductivity were also evaluated by implantation into experimental animals. It was found that a ?-TCP scaffold sintered at 1200°C exhibited high biocompatibility and osteoconductivity, and when it was loaded with BMP-2, it exhibited both osteoconductivity and osteoinductivity, promoting rapid bone formation in both ectopic and orthotopic areas. It is thus a highly promising bone reconstruction material that is expected to find clinical applications. PMID:24115688

Takabatake, Kiyofumi; Yamachika, Eiki; Tsujigiwa, Hidetsugu; Takeda, Yasushi; Kimura, Mariko; Takagi, Shin; Nagatsuka, Hitoshi; Iida, Seiji

2014-09-01

444

Merging and alignment of Dirac points in a shaken honeycomb optical lattice  

NASA Astrophysics Data System (ADS)

Inspired by the recent creation of a honeycomb optical lattice and the realization of a Mott-insulating state in a square lattice by shaking, we study here the shaken honeycomb optical lattice. For a periodic shaking of the lattice, Floquet theory may be applied to derive a time-independent Hamiltonian. In this effective description, the hopping parameters are renormalized by a Bessel function, which depends on the shaking direction, amplitude, and frequency. Consequently, the hopping parameters can vanish and even change sign, in an anisotropic manner, thus yielding different band structures. Here, we study the merging and the alignment of Dirac points and dimensional crossovers from the two-dimensional system to one-dimensional chains and zero-dimensional dimers. We also consider next-nearest-neighbor hopping, which breaks the particle-hole symmetry and leads to a metallic phase when it becomes dominant over the nearest-neighbor hopping. Furthermore, we include weak repulsive on-site interactions and find the density profiles for different values of the hopping parameters and interactions, both in a homogeneous system and in the presence of a trapping potential. Our results may be experimentally observed by use of momentum-resolved Raman spectroscopy.

Koghee, Selma; Lim, Lih-King; Goerbig, M. O.; Smith, C. Morais

2012-02-01

445

Candidate quantum spin liquid due to dimensional reduction of a two-dimensional honeycomb lattice.  

PubMed

As with quantum spin liquids based on two-dimensional triangular and kagome lattices, the two-dimensional honeycomb lattice with either a strong spin-orbital coupling or a frustrating second-nearest-neighbor coupling is expected to be a source of candidate quantum spin liquids. An ammonium salt [(C3H7)3NH]2[Cu2(C2O4)3](H2O)2.2 containing hexagonal layers of Cu(2+) was obtained from solution. No structural transition or long-range magnetic ordering was observed from 290 K to 2 K from single crystal X-ray diffraction, specific heat and susceptibility measurements. The anionic layers are separated by sheets of ammonium and H2O with distance of 3.5 Å and no significant interaction between anionic layers. The two-dimensional honeycomb lattice is constructed from Jahn-Teller distorted Cu(2+) and oxalate anions, showing a strong antiferromagnetic interaction between S = 1/2 metal atoms with ? = -120 (1) K. Orbital analysis of the Cu(2+) interactions through the oxalate-bridges suggests a stripe mode pattern of coupling with weak ferromagnetic interaction along the b axis, and strong antiferromagnetic interaction along the a axis. Analysis of the magnetic susceptibility shows that it is dominated by a quasi-one-dimensional contribution with spin chains that are at least as well isolated as those of well-known quasi-one-dimensional spin liquids. PMID:25245216

Zhang, Bin; Zhang, Yan; Wang, Zheming; Wang, Dongwei; Baker, Peter J; Pratt, Francis L; Zhu, Daoben

2014-01-01

446

Quantum computational universality of Affleck-Kennedy-Lieb-Tasaki states beyond the honeycomb lattice  

NASA Astrophysics Data System (ADS)

Universal quantum computation can be achieved by simply performing single-spin measurements on a highly entangled resource state, such as cluster states. The family of Affleck-Kennedy-Lieb-Tasaki (AKLT) states has recently been explored; for example, the spin-1 AKLT chain can be used to simulate single-qubit gate operations on a single qubit, and the spin-3/2 two-dimensional AKLT state on the honeycomb lattice can be used as a universal resource. However, it is unclear whether such universality is a coincidence for the specific state or a shared feature in all two-dimensional AKLT states. Here we consider the family of spin-3/2 AKLT states on various trivalent Archimedean lattices and show that in addition to the honeycomb lattice, the spin-3/2 AKLT states on the square octagon (4,82) and the “cross” (4,6,12) lattices are also universal resource, whereas the AKLT state on the “star” (3,122) lattice is likely not due to geometric frustration.

Wei, Tzu-Chieh

2013-12-01

447

Mechanisms and factors affecting chromium oxide particle reduction in iron-chromium honeycombs  

NASA Astrophysics Data System (ADS)

In the production of iron chromium honeycombs, iron oxide and chromium oxide mixtures are reduced by hydrogen at elevated temperatures to produce a metallic alloy. The complete reduction of the iron oxide occurs prior to the reduction of the chromium oxide. The reduction of the chromium oxide particles within the iron matrix is affected by factors that include the diffusion of the reduced chromium away from the chromium oxide particle into the iron matrix, the diffusion of the gaseous reactants and products to and from the chromium oxide particles, and the porosity of the iron matrix, which changes as a result of sintering. The type of heat-treatment used, (isothermal or non-isothermal, i.e., holding at a specific temperature versus using a steadily increasing temperature) plays a vital role in how these factors will affect chromium oxide reduction. Experimental data were used in conjunction with sintering and dissolution models to obtain an understanding of the environment in which the chromium oxide particles reduce as a function of heat-treatment. This understanding will assist in the development of more effective processing steps for the reduction of metallic honeycombs from oxide mixtures.

McIntosh, Monique Sandra

448

Lost-Soap Aluminum Casting.  

ERIC Educational Resources Information Center

Lost-wax casting in sterling silver is a costly experience for the average high school student. However, this jewelry process can be learned at no cost if scrap aluminum is used instead of silver, and soap bars are used instead of wax. This lost-soap aluminum casting process is described. (Author/KC)

Mihalow, Paula

1980-01-01

449

Aluminum frame motors: Environmental testing  

Microsoft Academic Search

The Civil Engineering Laboratory has conducted environmental tests to determine if aluminum frame motors instead of cast iron frame motors would be suitable for use in salt fog environments similar to those experienced at Naval Shore Facilities. The aluminum frame in the salt fog environment had minimal corrosion, indicating it is superior to cast iron for these applications. During the

D. E. Weems

1976-01-01

450

Primary Aluminum Plants Worldwide - 1998  

USGS Publications Warehouse

The 1990 U.S. Bureau of Mines publication, Primary Aluminum Plants Worldwide, has been updated and is now available. The 1998 USGS edition of Primary Aluminum Plants Worldwide is published in two parts. Part I—Detail contains information on individual primary smelter capacity, location, ownership, sources of energy, and other miscellaneous information. Part II—Summary summarizes the capacity data by country

1999-01-01

451

SOME PROPERTIES OF ALUMINUM NITRIDE  

Microsoft Academic Search

ABS>Aluminum nitride crystals in the form of bid-sided prismatic ; needles. up to 0.5 mm in diameter by 30 mm long, and thin plates, 2 to 3 mm in ; diameter, were prepared by vaporization of aluminum in a nitrogen atmosphere at ; temperatures ranging from 1800 to 2000 deg C, and the properties of the crystals ; determined. An

K. M. Taylor; Camille Lenie

1960-01-01

452

Investigation of surface oxides on aluminum alloys by valence band photoemission  

NASA Astrophysics Data System (ADS)

Core level and valence band x-ray photoelectron spectroscopy are used to study the chemical composition of the surface films on aluminum alloys. Certain alloying elements may preferentially migrate to the surface of an alloy, thereby altering the composition and consequently the chemistry of the surface. The behavior of a 6061 aluminum alloy is compared with that of pure aluminum. It is shown that the type of magnesium film formed at the alloy surface can be determined by comparing the valence band spectra of the aluminum alloy surface with that of known magnesium and aluminum compounds. The experimental valence band spectra of these compounds are supported by spectra generated from band structure calculations. The effect of boiling water on the surface film is discussed, with significant differences in surface chemistry being seen for the metal and the alloy. copyright 2002 American Vacuum Society.

Claycomb, Gregory D.; Sherwood, Peter M. A.

2002-07-01

453

NASA-UVA Light Aerospace Alloy and Structure Technology Program Supplement: Aluminum-Based Materials for High Speed Aircraft  

NASA Technical Reports Server (NTRS)

This is the final report of the study "Aluminum-Based Materials for High Speed Aircraft" which had the objectives (1) to identify the most promising aluminum-based materials with respect to major structural use on the HSCT and to further develop those materials and (2) to assess the materials through detailed trade and evaluation studies with respect to their structural efficiency on the HSCT. The research team consisted of ALCOA, Allied-Signal, Boeing, McDonnell Douglas, Reynolds Metals and the University of Virginia. Four classes of aluminum alloys were investigated: (1) I/M 2XXX containing Li and I/M 2XXX without Li, (2) I/M 6XXX, (3) two P/M 2XXX alloys, and (4) two different aluminum-based metal matrix composites (MMC). The I/M alloys were targeted for a Mach 2.0 aircraft and the P/M and MMC alloys were targeted for a Mach 2.4 aircraft. Design studies were conducted using several different concepts including skin/stiffener (baseline), honeycomb sandwich, integrally stiffened and hybrid adaptations (conventionally stiffened thin-sandwich skins). Alloy development included fundamental studies of coarsening behavior, the effect of stress on nucleation and growth of precipitates, and fracture toughness as a function of temperature were an integral part of this program. The details of all phases of the research are described in this final report.

Starke, E. A., Jr.

1997-01-01

454

Thermionic in-core heat pipe design and performance  

NASA Astrophysics Data System (ADS)

The heat pipe cooled thermionic reactor (HPTI) relies on in-core sodium heat pipes to provide a redundant means of cooling the 72 thermionic fuel elements (TFEs) and 36 driver fuel pins which comprise the 40 kWe core assembly. In-core heat pipe cooling was selected for the reactor design to meet the requirements for a system design with the potential to achieve a high survivability level against natural and man-made threats and one that possesses no-mission ending single point failures. A detailed study was performed to determine the potential in-core heat pipe geometries which could be developed for an HPTI concept. Requirements and performance estimates were developed for two in-core heat pipe geometries. Both nominal and faulted operating conditions were evaluated using a two-dimensional thermal model of the core to assess TFE and driver fuel pin temperature profiles. A bow tie in-core heat pipe geometry was selected as the optimum design using a HPTI honeycomb core structure.

Determan, W. R.; Hagelston, G.

1992-01-01

455

24. A CORE WORKER DISPLAYS THE CORE BOX AND CORES ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

24. A CORE WORKER DISPLAYS THE CORE BOX AND CORES FOR A BRASS GATE VALVE BODY MADE ON A CORE BOX, CA. 1950. - Stockham Pipe & Fittings Company, 4000 Tenth Avenue North, Birmingham, Jefferson County, AL

456

First principles pseudopotential calculations on aluminum and aluminum alloys  

SciTech Connect

Recent advances in computational techniques have led to the possibility of performing first principles calculations of the energetics of alloy formation on systems involving several hundred atoms. This includes impurity concentrations in the 1% range as well as realistic models of disordered materials (including liquids), vacancies, and grain boundaries. The new techniques involve the use of soft, fully nonlocal pseudopotentials, iterative diagonalization, and parallel computing algorithms. This approach has been pioneered by Car and Parrinello. Here the authors give a review of recent results using parallel and serial algorithms on metallic systems including liquid aluminum and liquid sodium, and also new results on vacancies in aluminum and on aluminum-magnesium alloys.

Davenport, J.W.; Chetty, N.; Marr, R.B.; Narasimhan, S.; Pasciak, J.E.; Peierls, R.F.; Weinert, M.

1993-12-31

457

Micropatterned culture of HepG2 spheroids using microwell chip with honeycomb-patterned polymer film.  

PubMed

Microwell chip culture is a promising technique for the generation of homogenous spheroids. We investigated the relationship between the structure of the bottom surface of microwell chip and the properties of HepG2 spheroid. We developed a microwell chip, the bottom surface of which consisted of a honeycomb-patterned polymer film (honeycomb film) that had a regular porous structure (HF chip). The chip comprised 270 circular microwells; each microwell was 600 ?m in diameter and 600 ?m in depth. At the center of the honeycomb film, an area, 200 ?m in diameter, was modified with collagen to facilitate cell adhesion. With the exception of the collagen-coated area, the entire microwell was modified with polyethylene glycol to eliminate cell adhesion. HepG2 cells formed uniform spheroids when cultured in the microwells of HF chip. Furthermore, the cells passed through the porous structure of honeycomb film and formed spheroids at its opposite side. The spheroid growth of HepG2 cells cultured in HF chip was greater than that when the cells were culture in a microwell chip, the bottom surface of which was made of poly-methylmethacrylate (PMMA chip). The albumin secretion activity of HepG2 spheroids in HF chip was equal to that in PMMA chip. These results indicate that the microwell bottom with a porous structure enhances the cell growth and maintains well the spheroid function. Thus, HF chip is a promising platform for spheroid cell culture. PMID:24742630

Yamazaki, Hidekazu; Gotou, Shun; Ito, Koju; Kohashi, Souichi; Goto, Yuki; Yoshiura, Yukiko; Sakai, Yusuke; Yabu, Hiroshi; Shimomura, Masatsugu; Nakazawa, Kohji

2014-10-01

458

Critical line of an anisotropic Ising antiferromagnet on square and honeycomb lattices Xian-Zhi Wang and Jai Sam Kim  

E-print Network

Critical line of an anisotropic Ising antiferromagnet on square and honeycomb lattices Xian-784, South Korea Received 20 March 1997 Using the approach that we developed recently, we find the critical the precise knowledge of its thermodynamic properties. Particular interest has focused on its critical

Kim, Jai Sam

459

Amorphous silicon honeycombs as a binder/carbon-free, thin-film Li-ion battery anode.  

PubMed

Amorphous silicon thin films with honeycombed structures have been prepared using a self-assembled monolayer of polystyrene spheres as the template. The as-prepared thin films may serve as a good anode candidate for thin film Li-ion batteries. This approach can be extended to a wide range of coating materials and substrates with controlled periodic structures. PMID:25220144

Zhao, Yu; Peng, Lele; Ding, Yu; Yu, Guihua

2014-09-30

460

The numerical simulation of laser-generated ultrasound to detect the debonding in the honeycomb sandwich board  

NASA Astrophysics Data System (ADS)

Among complex materials, honeycomb sandwich structure has a lot of advantages. However, it is usually found poor bonding or even debonding. Some convenient nondestructive methods should be found to measure the defect efficiently. Laser-generated ultrasound detection is a new nondestructive method with a bright future. Compared with traditional methods, the advantages of non-contact and high resolution in spatial and temporal made it applicable not only in measuring defects with high precision, but also in the characterization of various complex shapes. In this paper, to detect the debonding of the honeycomb sandwich board, the laser-generated ultrasound technology was used. By the use of the finite element method (FEM), a 2D model dealing with laser-generated ultrasound in the honeycomb sandwich board was presented. Take into account of the debonding problem, by adopting the scanned laser source, the propagation of Lamb wave and longitudinal wave were studied. The debonding in the honeycomb sandwich board was assessed though the characteristic of the Lamb wave and longitudinal wave in time domain and frequency domain.

Yuan, Ling; Cui, Yi-ping; Gu, Zhujun; Shen, Zhong-hua; Ni, Xiao-wu

2011-06-01

461

Aerodynamic performance of conventional and advanced design labyrinth seals with solid-smooth abradable, and honeycomb lands. [gas turbine engines  

NASA Technical Reports Server (NTRS)

Labyrinth air seal static and dynamic performance was evaluated using solid, abradable, and honeycomb lands with standard and advanced seal designs. The effects on leakage of land surface roughness, abradable land porosity, rub grooves in abradable lands, and honeycomb land cell size and depth were studied using a standard labyrinth seal. The effects of rotation on the optimum seal knife pitch were also investigated. Selected geometric and aerodynamic parameters for an advanced seal design were evaluated to derive an optimized performance configuration. The rotational energy requirements were also measured to determine the inherent friction and pumping energy absorbed by the various seal knife and land configurations tested in order to properly assess the net seal system performance level. Results indicate that: (1) seal leakage can be significantly affected with honeycomb or abradable lands; (2) rotational energy absorption does not vary significantly with the use of a solid-smooth, an abradable, or a honeycomb land; and (3) optimization of an advanced lab seal design produced a configuration that had leakage 25% below a conventional stepped seal.

Stocker, H. L.; Cox, D. M.; Holle, G. F.

1977-01-01

462

A fault-tolerant data dissemination based on Honeycomb Architecture for Mobile Multi-Sink wireless sensor networks  

Microsoft Academic Search

In mission critical applications of wireless sensor networks (WSNs), multiple sinks can be associated to first responders such as firefighters, but also to unmanned aerial vehicles (UAVs). In such scenarios, data dissemination of events towards mobile sinks should be performed reliably. In this paper we present Honeycomb Architecture which enables data dissemination considering dynamic conditions of multiple sinks and sources.

Aysegul Tuysuz Erman; Arta Dilo; Paul Havinga

2010-01-01

463

Induction of Female-to–male Sex Change in the Honeycomb Grouper (Epinephelus merra) by 11-ketotestosterone Treatments  

Microsoft Academic Search

The honeycomb grouper, Epinephelus merra , is a protogynous hermaphrodite fish. Sex steroid hor- mones play key roles in sex change of this species. A significant drop in endogenous estradiol- 17? ? ? ? (E2) levels alone triggers female-to-male sex change, and the subsequent elevation of 11- ketotestosterone (11KT) levels correlates with the progression of spermatogenesis. To elucidate the role

Ramji Kumar Bhandari; Mohammad Ashraful Alam; Kiyoshi Soyano; Masaru Nakamura

2006-01-01

464

Experimental rotordynamic coefficient results for: (a) a labyrinth seal with and without shunt injection and (b) a honeycomb seal  

E-print Network

been modified by (a) using swirl brakes, and (b) using shunt injection. In some cases, labyrinth seals have been replaced entirely by honeycomb seals. In shunt injection, the gas is taken from the diff-user or discharge volute, and injected...

Soto Azuaje, Elias Antonio

2012-06-07

465

Soft x-ray emission studies of several aluminum alloys  

SciTech Connect

During the first few months of operation of our soft x-ray spectrometer at the NSLS, we have measured the L emission spectrum for three classes of aluminum alloys: dilute aluminum-magnesium alloys to extend the Al-Mg system to the impurity limit; a 50-50 alloy of aluminum-lithium to characterize the band structure of bulk samples of this potential battery electrolite; and the icosahedral and normal Al-Mn alloys to see if the two phases had measurably different density of states which have been predicted. All spectra shown are produced when core holes generated by energetic electrons or photons are filled by radiative transitions from conduction band states. Dipole selection rules govern the transitions. Thus, K spectra provide a measure of the p-symmetic partial density of states (DOS) near the atom. Similarly, L spectra produced by transitions to p-core holes map the s and d symmetric DOS in the vicinity of the atom with the core hole.

Tsang, K.L.; Zhang, C.H.; Callcott, T.A.; Arakawa, E.T.; Ederer, D.L.; Biancaniello, F.; Curelaru, I.

1986-09-23

466

Oxidation of aluminum nanoclusters  

SciTech Connect

The dynamics of oxidation of aluminum nanoclusters (20 nm diameter) is investigated using a parallel molecular dynamics approach based on variable charge interatomic interactions due to Streitz and Mintmire that include both ionic and covalent effects. Simulations are performed for both canonical ensembles for molecular oxygen (O{sub 2}) environments and microcanonical ensembles for molecular (O{sub 2}) and atomic (O{sub 1}) oxygen environments. Structural and dynamic correlations in the oxide region are calculated, as well as the evolution of charges, surface oxide thickness, diffusivities of atoms, and local stresses. In the microcanonical ensemble, the oxidizing reaction becomes explosive in both molecular and atomic oxygen environments due to the enormous energy release associated with Al-O bonding. Local stresses in the oxide scale cause rapid diffusion of aluminum and oxygen atoms. Analyses of the oxide scale reveal significant charge transfer and a variation of local structures from the metal-oxide interface to the oxide-environment interface. In the canonical ensemble, oxide depth grows linearly in time until {approx}30 ps, followed by saturation of oxide depth as a function of time. An amorphous oxide layer of thickness {approx}40 A is formed after 466 ps, in good agreement with experiments. The average mass density in the oxide scale is 75% of the bulk alumina density. Evolution of structural correlation in the oxide is analyzed through radial distribution and bond angles. Through detailed analyses of the trajectories of O atoms and their formation of OAl{sub n} structures, we propose a three-step process of oxidative percolation that explains deceleration of oxide growth in the canonical ensemble.

Campbell, Timothy J. [Collaboratory for Advanced Computing and Simulations, Department of Materials Science and Engineering, Department of Physics and Astronomy, Department of Computer Science, University of Southern California, Los Angeles, California 90089-0242 (United States); Mississippi State University, Stennis Space Center, Mississippi 39529 (United States); Aral, Gurcan; Kalia, Rajiv K.; Nakano, Aiichiro; Vashishta, Priya [Collaboratory for Advanced Computing and Simulations, Department of Materials Science and Engineering, Department of Physics and Astronomy, Department of Computer Science, University of Southern California, Los Angeles, California 90089-0242 (United States); Ogata, Shuji [Graduate School of Engineering, Nagoya Institute of Technology, Nagoya 466-8555 (Japan)

2005-05-15

467

Aluminum: Industry of the future  

SciTech Connect

For over a century, the US aluminum industry has led the global market with advances in technology, product development, and marketing. Industry leaders recognize both the opportunities and challenges they face as they head into the 21st century, and that cooperative R and D is key to their success. In a unique partnership, aluminum industry leaders have teamed with the US Department of Energy`s Office of Industrial Technologies (OIT) to focus on innovative technologies that will help to strengthen the competitive position of the US aluminum industry and, at the same time, further important national goals. This industry-led partnership, the Aluminum Industry of the Future, promotes technologies that optimize the use of energy and materials in operations and reduce wastes and energy-related emissions. Led by The Aluminum Association, industry leaders began by developing a unified vision of future market, business, energy, and environmental goals. Their vision document, Partnerships for the Future, articulates a compelling vision for the next 20 years: to maintain and grow the aluminum industry through the manufacture and sale of competitively priced, socially desirable, and ecologically sustainable products. Continued global leadership in materials markets will require the combined resources of industry, universities, and government laboratories. By developing a unified vision, the aluminum industry has provided a framework for the next step in the Industries of the Future process, the development of a technology roadmap designed to facilitate cooperative R and D.

NONE

1998-11-01

468

Micro Joining of Aluminum Graphite Composites  

E-print Network

-doped Yttrium Aluminum Garnet laser OM Optical Microscopy RSW Resistance Spot Welding SEM Scanning Electron Microscopy UTM Universal Testing Machine YAG Yttrium Aluminum Garnet laser viii TABLE OF CONTENTS...-doped Yttrium Aluminum Garnet laser OM Optical Microscopy RSW Resistance Spot Welding SEM Scanning Electron Microscopy UTM Universal Testing Machine YAG Yttrium Aluminum Garnet laser viii TABLE OF CONTENTS...

Velamati, Manasa

2012-07-16

469

Noise transmission through an acoustically treated and honeycomb stiffened aircraft sidewall  

NASA Technical Reports Server (NTRS)

The noise transmission characteristics of test panels and acoustic treatments representative of an aircraft sidewall are experimentally investigated in the NASA Langley Research Center transmission loss apparatus. The test panels were built to represent a segment sidewall in the propeller plane of a twin-engine, turboprop light aircraft. It is shown that an advanced treatment, which uses honeycomb for structural stiffening of skin panels, has better noise transmission loss characteristics than a conventional treatment. An alternative treatment, using the concept of limp mass and vibration isolation, provides more transmission loss than the advanced treatment for the same total surface mass. Effects on transmission loss of a variety of acoustic treatment materials (acoustic blankets, septa, damping tape, and trim panels) are presented. Damping tape does not provide additional benefit when the other treatment provides a high level of damping. Window units representative of aircraft installations are shown to have low transmission loss relative to a completely treated sidewall.

Grosveld, F. W.; Mixson, J. S.

1984-01-01