bluuebunny/crossref_metadata_2025_split huggingface dataset:
Models for the Strength of Ductile Matrix Composites
Authors: Bao Gang , Genna Francesco , Hutchinson John W. , Mcmeeking Robert M. 
Published: March 2011

AbstractNumerical results have been obtained for the plastic flow of a metal matrix composite material reinforced by rigid spheres, cylinders and ellipsoids. Aligned geometries have been investigated and 2-d and 3-d cellular calculations carried out using the finite element method. The relative effect of particulates, disks and needles used as reinforcements are compared. Needles in aligned arrangements are found to produce the greatest strengthening. Additional results are presented from plane strain slip line solutions. Such results provide insight into the relative importance to strength of the reinforcement end regions versus the narrow side ligaments.
Particle-Reinforced Nb-26at%Ti-48at%Al Composites
Authors: Aikin R. M. , Mccubbin P. E. , Christodoulou L. 
Published: March 2011

AbstractComposites based on Nb-26at%Ti-48at%Al have been produced in situ by the XDTM process with nitride and silicide particulates, boride whiskers, and carbide plates. The alloy microstructure is a two-phase matrix of γ (TiAl) and σ (Nb2Al) with a uniform distribution of the ceramic phase. The room and elevated temperature strength of these alloys have been investigated and the role that the nondeforming particles play on the deformation of the two-phase γ-σ matrix will be discussed.
Feasibility Study of Intermetallic Composites
Authors: Shah D. M. , Anton D. L. , Musson C. W. 
Published: March 2011

AbstractThe feasibility of developing high-temperature intermetallic composites for use as gas turbine engine components is assessed for a wide range of high temperature intermetallic matrices including aluminides, silicides, Laves and Sigma phases along with Al2O3, SiC, TiC, Si3N4 and Y2O3 as well as ductile refractory metals as either reinforcing phases or coatings. Preliminary evaluations of fabricability and observations of matrix/reinforcing phase compatibility are presented and discussed in terms of various factors, including interstitial impurities, equilibrium phase relationships, kinetics, and physical and mechanical properties of both matrix and reinforcing phases.
High Temperature Oxidation of Ni3Al Composites
Authors: Tortorelli P. F. , DeVan J. H. , McKamey C. G. , Howell M. 
Published: March 2011

AbstractAs part of an effort to develop oxidation-resistant metal matrix composites, the influence of reinforcement materials on the oxidation of Ni3Al was studied. Thermogravimetric measurements and microstructural analyses were used to determine the 800°C oxidation behavior of Ni3Al and composites based on this material. The presence of fiber (Al2O3)- or particle (TiN or TiC)- reinforcement material in the Ni3Al increased susceptibility to oxidation as measured by the amount of reacted material, rate constants, and/or extent of internal attack. The orientation of fibers with respect to the free surfaces was found to affect the oxidation behavior by providing, in certain cases, reactive paths along the fiber-matrix interface that led to significant internal penetration. The results suggest that the choice of reinforcement material and the method of materials processing will be important considerations in the design of oxidation-resistant Ni3Al composites. However, ways to minimize the detrimental influence of the reinforcement material on oxidation resistance often conflict with requirements for obtaining attractive mechanical and physical properties of the composite.
Compatibility of Potential Reinforcing Ceramics with Ni and Fe Aluminides
Authors: Moser J. A. , Aindow M. , Clark W. A. T. , Drapert S. , Fraser H. L. 
Published: March 2011

AbstractThe compatibility of candidate ceramic reinforcement materials with intermetallic matrices for high temperature composite systems has been evaluated. Powders of FeAl and NiAl were mixed with ceramic powders and consolidated by hot isostatic pressing and subsequent heat treatment. The microstructures of these composites and the nature of the ceramic/matrix interfaces were assessed using a wide variety of electron-beam techniques. The system FeAl/TiB2 was found to be particularly promising. The matrix appears to be bonded to the ceramic particles, which may be the result of diffusion of Fe into the ceramic. The particles stabilized in a previously unreported monoclinic crystal structure, rather than the equilibrium hexagonal form exhibited by the binary compound.
Reactive Synthesis of NbAl3 Matrix Composites
Authors: Lu L. , Kim Y. S. , Gokhale A. B. , Abbaschian R. 
Published: March 2011

AbstractNbA13 matrix composites were synthesized “in-situ” via reactive hot compaction (RHC) of elemental powders. It was found that the simultaneous application of pressure during synthesis was effective in attaining a near-theoretical density matrix at relatively low temperatures and pressures. Using this technique, two types of composites were produced: (1) matrices containing a uniform dispersion of second phase particles (either Nb3Al or Nb2Al with an Nb core or Nb2Al) and (2) matrices reinforced with coated or uncoated ductile Nb filaments. It was found that a limited amount of toughening is obtained using the first approach, while composites containing coated Nb filaments exhibited a significant increase in the ambient temperature fracture toughness. In this paper, various aspects of RHC processing of NbAI3 matrix composites, the effect of initial stoichiometry and powder size on the microstructure, as well as the mechanical behavior of the composites will be discussed.
Solidification Processing Routes to High Aspect Ratio Reinforcements in γ-TiAl
Authors: Valencia J. J. , Löfvander J. P. A. , Rösler J. , Levi C. G. , Mehrabian R. 
Published: March 2011

AbstractAdditions of ∼5%B1 and ∼9%Ta to binary γ-TiAl result in the formation of a monoboride isomorphous with TiB but containing Ta in solid solution. This boride exhibits strongly anisotropic growth from the melt, producing rod-like primary phases which are of potential interest for creep strengthening of the γ matrix. Fibrous borides with aspect ratios larger than ∼20 and volume fractions of ∼0.12 have been produced in arc-melted Ti-48AI-9Ta-4.3B alloys. Creep testing at 1255 K indicates that these “in-situ” composites have much higher creep strength than γ-TiAl, but the contribution of the reinforcements is relatively small compared with the solute-strengthening of the matrix.
Densification Models for Plasma Sprayed Metal Matrix Composite Foils
Authors: Elzey D. M. , Kunze J. M. , Duva J. M. , Wadley H. N. G. 
Published: March 2011

AbstractThe development of a constitutive model describing the deformation response of plasma sprayed metal matrix composite (MMC) foils during hot isostatic pressing (HIP) is described. A representative volume element of the composite is chosen whose constitutive behavior, including inelastic compressibility, is analyzed for the particular case of constrained uniaxial compression. Results of this preliminary model for the case of a SCS–6/Ti–14wt%Al–21wt%Nb intermetallic matrix composite are presented in the form of a density–pressure HIP map.
Testing of Impact Limiters for Transportation Cask Design
Authors: Maji A. K. , Donald S. , Cone K. 
Published: March 2011

Abstract‘Soft Impact Limiters’ such as polyurethane foams and aluminum honeycombs are being studied to assist the Sandia National Lbiatory's Transportation Base Technology Program. The aim of this research is to study the mechanical behavior of these materials, which are being used as impact absorbers in nuclear waste transportation containers.A series of tests were performed along various loading paths using an Instron, servo-controlled, multi-axial loading machine and Soiltest triaxial testing apparatus. Static tests included uniaxial tension, uniaxial compression, triaxial compression, hydrostatic compression and fracture toughness testing. The purpose of using different loading paths was to generate an extensive test data which is being used to develop constitutive models for these materials, under a separate research program.Dynamic tests were conducted at strain rates of 100 strains/sec., to generate experimental data relevant to accident situations. These tests were conducted on an instrumented Charpy impact testing apparatus. Results of these tests were subsequently used to conduct scale-model tests of transportation casks of different industrial designers.Different densities of Polyurethane foams, aluminum honeycombs, and corrugated aluminum honeycombs were tested in different orientations. The paper discusses the experimental program, instrumentation and test results for the nuclear waste transportation industry and other potential applications.
A Comparison of Mechanical Properties and Scaling Law Relationships for Silica Aerogels and their Organic Counterparts
Authors: Pekalaa R. W. , Hrubesh L. W. , Tillotson T. M. , Alviso C. T. , Poco J. F. , LeMay J. D. 
Published: March 2011

AbstractAerogels are a unique type of ultrafine cell size, low density foam. Traditional aerogels are inorganic, but the synthesis of organic aerogels has also been reported. In all cases, solution chemistry can be used to tailor the structure and properties of the resultant aerogels. This study examines the microstructural dependence of the compressive mechanical properties of silica, resorcinol-formaldehyde, carbon, and melamine-formaldehyde aerogels.
Mechanical Structure-Property Relationships of Microcellular, Low Density Foams.
Authors: Lemay James D. 
Published: March 2011

AbstractHigh energy physics applications at the Department of Energy National Laboratories require unique low-density foams of demanding homogeneity specifications (cell sizes on the order of 10 μm or smaller). These delicate and fragile foams are machined and shaped into specimens to exacting tolerances. In this work, the mechanical properties of a variety of these low density microcellular foams are reported as functions of foam density and morphology.
The Porosity Dependence of Mechanical and other Properties of Materials
Authors: Rice Roy W. , Grace W. R. 
Published: March 2011

AbstractThough the volume fraction (or %) porosity is commonly used as the exclusive porosity variable to describe the porosity dependence of physical properties, it is not sufficient. The average minimum solid area, i.e., of the bond or sintered area between sintering particles, or the minimum web or strut cross-sections is the most appropriate second porosity parameter. Pore shape-stress concentration effects have, at best, limited direct effect on mechanical properties, but generally correlate with minimum solid area effects. Methods of combining effects of different types of porosity within the same body are important and result in quite reasonable descriptions of mechanical properties across a broad range of porosities.
Thermal Shock Behavior of Open Cell Ceramic Foams
Authors: Orenstein Robert M. , Green David J. , Segall Albert E. 
Published: March 2011

AbstractSpecimens of heated alumina foams were thermally shocked by immersion in water or oil. Two distinct temperature profiles were found to exist during liquid quenching: a macroscopic gradient due to heating of the fluid during infiltration into the foam and a microscopic gradient across each individual strut. Thermal stresses were calculated using a semi-empirical, finite element model. The peak thermal stresses were coupled with the two-parameter Weibull distribution of the strut strengths to calculate the probability of crack extension on a strut for eight cellular geometries. Experimentally, the thermal shock resistance increased with increasing relative density and increasing cell size. The predicted critical temperature differences were in fair agreement with measured values.
Multiaxial Failure Criteria for Cellular Materials
Authors: Triantafillou T. C. , Gibson L. J. 
Published: March 2011

AbstractCellular materials are increasingly used in engineering. Proper design requires an understanding of the response of the materials to stress; and, in real engineering design, the stress state is often a complex one. In this paper we model the elastic buckling, plastic yield, and brittle fracture of cellular solids under multiaxial stresses to develop equations describing their failure surfaces. Comparison of the analysis with data shows that the models describe the main features of the multiaxial behavior of foams well.
Oxynitride Glass Reinforced Cement Composites
Authors: Leatherman Gary. L. , El-Korchi Tahar , Holmes Thomas M. , Katz R. Nathan 
Published: March 2011

AbstractGlass fiber reinforced composites made with an oxynitride analogue of alkali resistant glass were tested in tension after accelerated aging. The results were compared to composites made from oxide alkali resistant glass. The strength of the oxynitride glass reinforced composites was almost double that of the oxide glass based material. The results are related to the improved properties of oxynitride glass over oxide glass. In particular previous work has shown that surface chemistry of the oxynitride glass inhibits the formation of a strong bond between fiber and matrix. The difference in surface chemistry was examined by measuring the contact angle of aqueous solutions with respect to nitrogen content of the glass.
Effect of Aging on Interfacial Properties of Glass Fiber Reinforced Concrete
Authors: Shah S. P , Li Z. , Mobasher B. 
Published: March 2011

AbstractThis paper explores the behavior of the interface of glass fiber and cementitious matrix under the effect of aging. Pull-out tests of multiple alkali resistant glass fiber strands embedded in portland cement paste matrix were conducted. Four different curing regimes of 3 and 14 days normal curing, in addition to 3 and 7 days accelerated aging were employed. A recently developed method of characterizing interfacial properties was used to identify and evaluate the important parameters at interface. The experimental data are presented on the parameter of shear stiffness of a fiber-matrix boundary layer, the shear bond strength, the frictional bond strength and the specific surface energy as a function of fiber embedded length. It was observed that aging had a larger effect on the stiffness of the interface, the shear bond strength and the specific surface energy than on the frictional bond.
Durability of FRC-Materials
Authors: Larsen Erik Stoklund , Krenchel Herbert 
Published: March 2011

AbstractAsbestos cement was the first type of FRC-material that was ever made. It consisted of neat, hardened Portland cement reinforced with asbestos fibres (Vt - 7 vol-%). The most outstanding and valuable property of a high quality asbestos cement was the highly improved durability of this composite material in comparison to what would have been the case, if no fibres had been added or the fibre reinforcement of this extremely brittle matrix had been carried out incorrectly.This paper describes an analysis of the variation in time of the fracture energy, GF, of different types of FRC-material exposed to various climatic conditions.The following types of fibres were examined: steel fibre, ar-glass fibre, synthetic fibre (polypropylene) and natural fibre (sisal fibre and paper pulp cellulose).The climatic exposure conditions were natural out-door weathering or laboratory tests in a special weather-o-meter. Three test series were carried out at the Danish Building Research Institute. The results from these tests have been compared to results from five test series taken from the literature (ar-glass-, steel-, polypropylen-, sisal-fibres and neat concrete).It is concluded that natural and glass fibres are losing strength and ductility in a cementitious matrix. This results in a drastically reduced fracture energy of the composite material over the years. In the worst cases practically no fibre effect is left after some ten years of normal out-door exposure.For the best types of fibres examined (steel fibre, high tenacity, high bond polypropylene and combinations of these two types) the ductility and fracture energy of the composites are increasing significantly even after very long time of exposure.
Fibrous Concrete - Sensitivity of Workability to Percentage and Type of Fibre
Authors: Debicki G. , Bouchekouk M. , Clastres P. , Hamelin P. 
Published: March 2011

AbstractWorkability is measured with the LCL consistometer. The device is an open rectangular mould with an external vibrator and a removable vertical partition dividing it into two compartments. When the partition is removed, the vibrator is triggered at the same time as a chronometer. The time, t, that the concrete takes to flow to a reference line is measured.For a matrix with a given composition (mortar and concrete), we study how workability varies when the percentage of fibres increases. The curves thus obtained take the form Ln(t)= A + B %. We show that the value of coefficient A is linked to the matrix composition while coefficient B is especially sensitive to the type of fibre used and to the gravel -fibre interaction.Mortar and concrete compositions reinforced by fibres of very different types with different lengths and geometries (rods or ribbons) are tested and are used to validate the proposed model. The types of fibres studied are: glass fibres coated with thermoplastic, PVC fibres, steel fibres and amorphous cast iron fibres. The results can be used to optimize the geometry of very different types of fibres and thus obtain a better workability.
Noninvasive Diagnosis of Toughening Mechanisms in Fiber Reinforced Concrete
Authors: Maji A. K. , Wang J. L. 
Published: March 2011

AbstractVarious physical phenomena are involved in the fracture process of steel fiber reinforced concrete (SFRC). Although pullout of the fiber has been the most intensively investigated parameter in studying the micromechanics of these materials, other mechanisms could be dominant, depending on the nature of the loading and the fiber orientations. Pullout tests were conducted on isolated fibers embedded in a mortar matrix with different orientations to the direction of loading.The specimens were loaded in the chamber of a scanning electron microscope (SEM), and on an optical table with instrumentation for Laser holographic interferometry (HI). The relative contribution of the various mechanisms, such as: fiber debonding and pullout, mortar crushing, friction at comers, and plastic energy dissipation on the fibers were evaluated. When the specimens were tested in the SEM, it was observed that compressive failure with crushing of the mortar is an important physical phenomenon, in addition to plastic bending of the fiber. HI studies also indicated the crushing of mortar prior to interface debonding.The relative amounts of energy dissipated by the various mechanisms were evaluated using experimental observations and analytical approximations. The importance of the different mechanisms at progressive stages of fiber pullout was estimated.
Micro-Mechanical Modeling of the Pull-Out Behavior of Corrugated Wiredrawn Steel Fibers from Cementitious Matrices.
Authors: Chanvillard Gilles , Aitcin Pierre-Claude 
Published: March 2011

AbstractThe pull-out behavior of non-straight steel fibers cannot always be analyzed solely in terms of bonding. Rather, it is necessary to take into account the mechanical anchorage provided by the fiber geometry.It is shown in this paper, that in the case of non-straight steel fibers a strong interaction exists between bonding and anchorage. A micro-mechanical model, based on the dissipation of energy during slipping of the fiber is proposed. In this model, bonding is included on the basis of the Coulomb friction law, without reference to a bond-slip law; mechanical anchorage is modelled from plastic deformation of the fiber.With this model, it is possible to evaluate the significance of some physical parameters such as the water/cement ratio of the matrix, the fiber's geometry and the steel properties. Moreover, this model provides a rational basis for the optimization of the fiber-cementitious matrix interaction from an energy point of view.
Fracture of Sifcon Under Combined Tensile and Shearlike Loading
Authors: Van Mier J. G. M. 
Published: March 2011

AbstractIn a series of preliminary experiments, the shear stiffness degradation and ’shear’ failure mechanisms of pre-cracked Slurry Infiltrated Fiber CONcrete (SIFCON) were studied. The specimens were first subjected to axial tension (in displacement control), whereafter a lateral shear was applied over the crack band. Variables in the investigation were the direction of loading with regard to the main fiber direction, and the axial crack opening before shearing. The degradation of shear stiffness resembles that of normal concrete at low crack openings, but seems governed by fiber action at larger crack openings. At low crack openings, shear failure was observed in the sense of an array of inclined tensile microcracks. At larger crack openings, inclined cracks developed through coalescence of preexisting tensile cracks.
Tensile Testing of Fiber Reinforced Cementitious Composites
Authors: El-Korchi Tahar , Toutanji Houssam , Katz R. Nathan , Leatherman Gary L. , Lucas Harald , Demers Cornelia 
Published: March 2011

AbstractA novel approach in tensile testing of cementitious composites using the ASCERA® hydraulic tensile tester is described. The test specimens are cylindrical bars. Steel pistons are adhesively bonded on either end of the specimens and inserted in a pressure chamber. The pressure is increased until the specimen is pulled apart by the hydraulic pressure exerted on the pistons.Advantages of this method are: large volume under load, self-alignment to minimize externally applied bending moments, and determination of the rupture stress exactly at the fracture initiation point.Glass reinforced cementitious composites were tested. Results are discussed with respect to curing time and fiber volume fraction. The tensile strength values obtained by hydraulic testing are compared to values obtained by traditional uniaxial tensile strength tests. A biaxial model is adopted to verify the results.
Fiber Reinforced Alkali Activated Blended Cement Materials
Authors: Silsbee M. R. , Wolfe-Confer D. , Roy D. M. 
Published: March 2011

AbstractRecently there has been renewed interest in the use of alkali activation to increase the rate of strength development in blended cements. The objective of this study was to examine the advantages-disadvantages of using alkali activated blended cement materials with fiber reinforcing. There are advantages of the rapid set for certain applications.
Toughening of MDF - OPC Composites
Authors: Park C. K. , Silsbee M. R. , Roy D. M. 
Published: March 2011

AbstractMacro-Defect-Free (MDF) materials are cement-polymer composites exhibiting high flexural strengths and high toughness (for cement based systems). The incorporation of fibers into MDF composites has been found to offer the possibility of increasing both the ultimate flexural strength and toughness of MDF materials prepared using an ordinary portland cement-polyacrylamide matrix.This paper examined the effect of fiber type and fine particles as a packing filler on the resulting mechanical properties. The incorporation of non-traditional materials (for MDF) into the MDF matrix is also discussed.
Carbon Fiber Reinforced Cement and Mortar
Authors: Linton J. R. , Berneburg P. L. , Gartner E. M. , Bentur A. 
Published: March 2011

AbstractAlthough carbon fibers have high tensile strengths and are chemically inert, their application in cementitious composites is limited due to their brittleness. An image analysis technique employed to determine the length distribution of the reinforcing fibers before and after mixing in cement paste and mortar matrices indicates that substantial fiber breakage occurs during mixing. In paste mixtures, the average fiber length after mixing remains above the critical fiber length, but in mortar mixes the average fiber length falls below the critical fiber length resulting in no significant enhancement of composite flexural properties.