Science.gov

Sample records for reinforced steel matrix

  1. Enhanced tensile, hardness and wear behaviors of pure aluminum matrix reinforced with steel chips via powder metallurgy technique

    NASA Astrophysics Data System (ADS)

    Mahmoud Emara, Mohamed

    2017-04-01

    The mechanical properties and wear behavior of aluminum matrix reinforced with steel machining chips was investigated. Pure aluminum was reinforced with 5, 7.5, and 10 wt% steel chips with an average size of 100 μm using powder metallurgy technique. Aluminum reinforced with 5 and 10 Wt.% SiC particles were manufactured for comparison. The investigation showed clear evidence that the addition of steel machining chips resulted in significantly low porosity levels in the aluminum matrix composites compared with the use of SiC as reinforcement. The mechanical properties (tensile and hardness) as well as the wear resistance were also observed to improve with the use of the steel machining chips as reinforcement. The results demonstrate the capability of steel machining chips to act as efficient reinforcing material and a reliable cost effective candidate in the development of aluminum matrix composites.

  2. Heat treatment response of TiC-reinforced steel matrix composite

    NASA Astrophysics Data System (ADS)

    Kim, Seong Hoon; Kim, Dae Ha; Hwang, Keum-Cheol; Lee, Sang-Bok; Lee, Sang-Kwan; Hong, Hyun Uk; Suh, Dong-Woo

    2016-09-01

    A particulate TiC-reinforced SKD11 steel matrix composite is fabricated by using a pressure infiltration casting, achieving a homogeneous distribution of the particles with 60 vol%. The retained austenite fraction in the composite matrix is approximately 19% after quenching from the austenitization temperature of 1010 °C, which is larger than 13% in as-quenched condition of unreinforced SKD11. A combined analysis on the austenite lattice parameter using XRD profiles and first-principle calculation suggests the increase of carbon content in the steel matrix possibly by partial dissolution of TiC during casting. The change of carbon content and prior austenite grain size reasonably accounts for the increase of retained austenite fraction in the composite matrix. In the austenitizing temperatures ranging from 950 °C to 1040 °C, the retained austenite fraction in the composite matrix in as-quenched condition increases more rapidly than that of unreinforced SKD11 with the increase of austenitization temperature, while the hardness of the composite is less sensitive to the austenitization temperature. This suggests that it is advantageous to conduct the austenitization at a temperature below 1010 °C, which is typical practice of austenitization of the unreinforced SKD11, because the retention of austenite is effectively suppressed while minimizing the loss of hardness.

  3. Microstructural study and densification analysis of hot work tool steel matrix composites reinforced with TiB{sub 2} particles

    SciTech Connect

    Fedrizzi, A.; Pellizzari, M.; Zadra, M.; Marin, E.

    2013-12-15

    Hot work tool steels are characterized by good toughness and high hot hardness but are less wear resistant than other tooling materials, such as high speed steel. Metal matrix composites show improved tribological behavior, but not much work has been done in the field of hot work tool steels. In this paper TiB{sub 2}-reinforced hot work tool steel matrix composites were produced by spark plasma sintering (SPS). Mechanical alloying (MA) was proposed as a suited process to improve the composite microstructure. Density measurements and microstructure confirmed that MA promotes sintering and produces a fine and homogeneous dispersion of reinforcing particles. X-ray diffraction patterns of the sintered composites highlighted the formation of equilibrium Fe{sub 2}B and TiC, as predicted by thermodynamic calculations using Thermo-Calc® software. Scanning electron microscopy as well as scanning Kelvin probe force microscopy highlighted the reaction of the steel matrix with TiB{sub 2} particles, showing the formation of a reaction layer at the TiB{sub 2}-steel interface. Phase investigations pointed out that TiB{sub 2} is not chemically stable in steel matrix because of the presence of carbon even during short time SPS. - Highlights: • TiB{sub 2} reinforced steel matrix composites were produced by spark plasma sintering. • TiB{sub 2} was successfully dispersed in the steel matrix by mechanical alloying. • Steel and TiB{sub 2} react during sintering forming equilibrium Fe{sub 2}B and TiC. • The new phases were investigated by means of AFM, Volta potential and XRD analyses.

  4. Rehabilitation of notch damaged steel beam using a carbon fiber reinforced multiphase-matrix composite

    SciTech Connect

    Zhou, HongYu; Attard, Dr. Thomas L.; Wang, Yanli; Wang, Jy-An John; Ren, Fei

    2013-01-01

    The retrofit of notch damaged steel beams is investigated via the experimental testing of nine wide-flange steel beam specimens and finite element simulation. Three notch configurations representing various damage levels were identified, and the beam specimens were retrofitted using CFRP laminates and a recently developed polymeric matrix composite - CarbonFlex - that exhibits superior energy dissipation and ductility properties, where the peak-load deflections were between 49.4% and 65.2% higher using the CarbonFlex-retrofitted beams. The results are attributed to the substantially higher damage tolerance capability of CarbonFlex than conventional CFRP. Finite element models were developed to investigate the damage processes and strain/ stress distributions near the notch tips. The numerical results match closely with the experimentally determined load-deflection curves and the strain fields obtained by the digital imaging correlations (DIC) system. Both experimental and numerical results clearly indicate the effectiveness of CarbonFlex, as a candidate retrofitting material, to retrofit damaged steel structures. Lastly, the micro-mechanisms by which CarbonFlex could sufficiently sustain a significant amount of the peak strength at large displacement ductility values are discussed with the aid of scanning electron microscopy (SEM) pictures.

  5. Friction behavior of ceramic fiber-reinforced aluminum metal-matrix composites against a 440C steel counterface

    NASA Astrophysics Data System (ADS)

    Prasad, S. V.; Mecklenburg, K. R.

    1993-04-01

    The friction behavior of short ceramic fiber-reinforced aluminum MMCs against a steel counterface is investigated. The friction coefficients between metallographically polished surfaces of kaowool and saffil fiber-reinforced aluminum MMCs and 44 C steel counterface varied between 0.4 and 0.6. The friction traces were rough with characteristic stick-slip behavior. Transfer of aluminum to steel counterface was observed in all cases. The friction coefficients dropped to below 0.2 when the MMC surface was etched; the stick-slip behavior disappeared. The increase in normal load, the friction coefficients of etched MMC surfaces increased progressively with sliding distance and the rough stick-slip type behavior reappeared. The transition from smooth to rough friction behavior was not observed for the etched surface of the MMC reinforced with 17 percent kaowool fibers even at a normal load of 0.7 N; aluminum transfer to steel was not detected in this case. The results demonstrate the feasibility of producing kaowool and saffil-fiber-reinforced aluminum MMCs by a squeeze infiltration route.

  6. Part I. Corrosion studies of continuous alumina fiber reinforced aluminum-matrix composites. Part II. Galvanic corrosion between continuous alumina fiber reinforced aluminum-matrix composites and 4340 steel

    NASA Astrophysics Data System (ADS)

    Zhu, Jun

    Part I. The corrosion performance of continuous alumina fiber reinforced aluminum-matrix composites (CF-AMCs) was investigated in both the laboratory and field environments by comparing them with their respective monolithic matrix alloys, i.e., pure Al, A1-2wt%Cu T6, and Al 6061 T6. The corrosion initiation sites were identified by monitoring the changes in the surface morphology. Corrosion current densities and pH profiles at localized corrosion sites were measured using the scanning-vibrating electrode technique and the scanning ion-selective electrode technique, respectively. The corrosion damage of the materials immersed in various electrolytes, as well as those exposed in a humidity chamber and outdoor environments, was evaluated. Potentiodynamic polarization behavior was also studied. The corrosion initiation for the composites in 3.15 wt% NaCl occurred primarily around the Fe-rich intermetallic particles, which preferentially existed around the fiber/matrix interface on the composites. The corrosion initiation sites were also caused by physical damage (e.g., localized deformation) to the composite surface. At localized corrosion sites, the buildup of acidity was enhanced by the formation of micro-crevices resulting from fibers left in relief as the matrix corroded. The composites that were tested in exposure experiments exhibited higher corrosion rates than their monolithic alloys. The composites and their monolithic alloys were subjected to pitting corrosion when anodically polarized in the 3.15 wt% NaCl, while they passivated when anodically polarized in 0.5 M Na2SO4. The experimental results indicated that the composites exhibited inferior corrosion resistance compared to their monolithic matrix alloys. Part II. Galvanic corrosion studies were conducted on CF-AMCs coupled to 4340 steel since CF-AMCs have low density and excellent mechanical properties and are being considered as potential jacketing materials for reinforcing steel gun barrels. Coupled and

  7. Bond characteristics of steel fiber and deformed reinforcing steel bar embedded in steel fiber reinforced self-compacting concrete (SFRSCC)

    NASA Astrophysics Data System (ADS)

    Aslani, Farhad; Nejadi, Shami

    2012-09-01

    Steel fiber reinforced self-compacting concrete (SFRSCC) is a relatively new composite material which congregates the benefits of the self-compacting concrete (SCC) technology with the profits derived from the fiber addition to a brittle cementitious matrix. Steel fibers improve many of the properties of SCC elements including tensile strength, ductility, toughness, energy absorption capacity, fracture toughness and cracking. Although the available research regarding the influence of steel fibers on the properties of SFRSCC is limited, this paper investigates the bond characteristics between steel fiber and SCC firstly. Based on the available experimental results, the current analytical steel fiber pullout model (Dubey 1999) is modified by considering the different SCC properties and different fiber types (smooth, hooked) and inclination. In order to take into account the effect of fiber inclination in the pullout model, apparent shear strengths (τ (app)) and slip coefficient (β) are incorporated to express the variation of pullout peak load and the augmentation of peak slip as the inclined angle increases. These variables are expressed as functions of the inclined angle (ϕ). Furthurmore, steel-concrete composite floors, reinforced concrete floors supported by columns or walls and floors on an elastic foundations belong to the category of structural elements in which the conventional steel reinforcement can be partially replaced by the use of steel fibers. When discussing deformation capacity of structural elements or civil engineering structures manufactured using SFRSCC, one must be able to describe thoroughly both the behavior of the concrete matrix reinforced with steel fibers and the interaction between this composite matrix and discrete steel reinforcement of the conventional type. However, even though the knowledge on bond behavior is essential for evaluating the overall behavior of structural components containing reinforcement and steel fibers

  8. Bond characteristics of steel fiber and deformed reinforcing steel bar embedded in steel fiber reinforced self-compacting concrete (SFRSCC)

    NASA Astrophysics Data System (ADS)

    Aslani, Farhad; Nejadi, Shami

    2012-09-01

    Steel fiber reinforced self-compacting concrete (SFRSCC) is a relatively new composite material which congregates the benefits of the self-compacting concrete (SCC) technology with the profits derived from the fiber addition to a brittle cementitious matrix. Steel fibers improve many of the properties of SCC elements including tensile strength, ductility, toughness, energy absorption capacity, fracture toughness and cracking. Although the available research regarding the influence of steel fibers on the properties of SFRSCC is limited, this paper investigates the bond characteristics between steel fiber and SCC firstly. Based on the available experimental results, the current analytical steel fiber pullout model (Dubey 1999) is modified by considering the different SCC properties and different fiber types (smooth, hooked) and inclination. In order to take into account the effect of fiber inclination in the pullout model, apparent shear strengths ( τ ( app)) and slip coefficient ( β) are incorporated to express the variation of pullout peak load and the augmentation of peak slip as the inclined angle increases. These variables are expressed as functions of the inclined angle ( ϕ). Furthurmore, steel-concrete composite floors, reinforced concrete floors supported by columns or walls and floors on an elastic foundations belong to the category of structural elements in which the conventional steel reinforcement can be partially replaced by the use of steel fibers. When discussing deformation capacity of structural elements or civil engineering structures manufactured using SFRSCC, one must be able to describe thoroughly both the behavior of the concrete matrix reinforced with steel fibers and the interaction between this composite matrix and discrete steel reinforcement of the conventional type. However, even though the knowledge on bond behavior is essential for evaluating the overall behavior of structural components containing reinforcement and steel fibers

  9. TiC-reinforced cast Cr steels

    NASA Astrophysics Data System (ADS)

    Doğan, Ö. N.; Hawk, J. A.; Schrems, K. K.

    2006-06-01

    A new class of materials, namely TiC-reinforced cast chromium (Cr) steels, was developed for applications requiring high abrasion resistance and good fracture toughness. The research approach was to modify the carbide structure of commercial AISI 440C steel for better fracture resistance while maintaining the already high abrasion resistance. The new alloys contained 12Cr, 2.5-4.5Ti, and 1-1.5C (wt.%) and were melted in a vacuum induction furnace. Their microstructure was composed primarily of a martensitic matrix with a dispersion of TiC precipitates. Modification of TiC morphology was accomplished through changing the cooling rate during solidification. Wear rates of the TiC-reinforced Cr steels were comparable to that of AISI 440C steel, but the impact resistance was much improved.

  10. TiC reinforced cast Cr steels

    SciTech Connect

    Dogan, O.N.; Hawk, J.A.; Schrems, K.K.

    2006-06-01

    A new class of materials, namely TiC-reinforced cast chromium (Cr) steels, was developed for applications requiring high abrasion resistance and good fracture toughness. The research approach was to modify the carbide structure of commercial AISI 440C steel for better fracture resistance while maintaining the already high abrasion resistance. The new alloys contained 12Cr, 2.5–4.5Ti, and 1–1.5C (wt.%) and were melted in a vacuum induction furnace. Their microstructure was composed primarily of a martensitic matrix with a dispersion of TiC precipitates. Modification of TiC morphology was accomplished through changing the cooling rate during solidification. Wear rates of the TiC-reinforced Cr steels were comparable to that of AISI 440C steel, but the impact resistance was much improved.

  11. Microstructure of arc brazed and diffusion bonded joints of stainless steel and SiC reinforced aluminum matrix composite

    NASA Astrophysics Data System (ADS)

    Elßner, M.; Weis, S.; Grund, T.; Wagner, G.; Habisch, S.; Mayr, P.

    2016-03-01

    Joint interfaces of aluminum and stainless steel often exhibit intermetallics of Al-Fe, which limit the joint strength. In order to reduce these brittle phases in joints of aluminum matrix composites (AMC) and stainless steel, diffusion bonding and arc brazing are used. Due to the absence of a liquid phase, diffusion welding can reduce the formation of these critical in- termetallics. For this joining technique, the influence of surface treatments and adjusted time- temperature-surface-pressure-regimes is investigated. On the other hand, arc brazing offers the advantage to combine a localized heat input with the application of a low melting filler and was conducted using the system Al-Ag-Cu. Results of the joining tests using both approaches are described and discussed with regard to the microstructure of the joints and the interfaces.

  12. TiC reinforced cast chromium steels

    SciTech Connect

    Dogan, Omer N.; Rawers, James C.; Hawk, Jeffrey A.; Schrems, Karol K.

    2003-11-01

    A series of new titanium carbide reinforced cast chromium steels were developed for wear applications. Objective of the program was to enhance wear resistant alloys and, if possible, improve mechanical properties. The new steels which were melted in a vacuum induction furnace contained 12 Cr, 3-5 Ti, 1-2 C in weight percent. Alloying with Ti changed the precipitate microstructure from Cr carbide to TiC dispersed in a martensitic matrix. Yield strength and impact resistance improved with Ti alloying. Wear rates of the cast Cr/TiC steels, (determined from high- and low-stress abrasion tests, erosion test, and scratch tests) were generally lower than both the as-cast and heat-treated AISI type 440°C steel and were often further reduced by increasing the Ti alloy concentration. The exceptions were the erosion test for which all materials had similar wear rate.

  13. Influence of fiber interconnections on the thermomechanical behavior of metal matrix composites consisting of Zn-Al alloy reinforced with steel fibers

    SciTech Connect

    Tao, L.; Delannay, F.

    1998-11-20

    Interconnected fiber networks presenting transverse isotropic symmetry with variable fiber interconnectivity were prepared by sintering assemblies of low carbon steel fibers. The strength and stiffness of these fiber preforms was found to increase very much when increasing sintering temperature or sintering time. Squeeze cast composites were prepared by infiltrating these preforms with alloy ZA8. Creep tests and tensile tests were carried out at 150 C. Both the creep strength and the back-flow strains at unloading drastically increase with increasing preform sintering temperature or time. Also thermal expansion is much affected by fiber interconnectivity. Especially, during cooling, the matrix dilatation strains brought about by thermal mismatches increase with increasing fiber interconnectivity. These results demonstrate that plastic and viscoplastic behaviors of network reinforced composites depend on the mechanical properties of the network as a whole.

  14. Processing of Hybrid Structures Consisting of Al-Based Metal Matrix Composites (MMCs) With Metallic Reinforcement of Steel or Titanium

    DTIC Science & Technology

    2013-09-01

    titanium - and steel-based metals, high specific stiffness, high specific strength , tailorable coefficient of thermal...to titanium and steel- based metals, high specific stiffuess, high specific strength , tailorable coefficient of thermal expansion (CTE), and high ...hollow, periodic cellular structures are of interest due to their very high stiffness to weight ratio and high damage tolerance (e.g., very high

  15. Corrosion control of steel-reinforced concrete

    NASA Astrophysics Data System (ADS)

    Chung, D. D. L.

    2000-10-01

    The methods and materials for corrosion control of steel-reinforced concrete are reviewed. The methods are steel surface treatment, the use of admixtures in concrete, surface coating on concrete, and cathodic protection.

  16. Wear of Cast Chromium Steels With TiC Reinforcement

    SciTech Connect

    Dogan,O.N.; Hawk, J.A.; Tylczak, J.H.

    2001-10-01

    Wear resistance of a series of new titanium carbide reinforced cast chromium steels was investigated under various wear conditions. The steels which were melted in a vacuum induction furnace contained 12 Cr, 3-5 Ti, 1-2 C in weight percent. Microstructure of these materials was characterized using scanning electron microscopy, light optical microscopy, and X-ray diffraction. Microstructure of steels consisted of TiC phase dispersed in a martensitic matrix. High-stress and low-stress abrasion tests, and an erosion test, were utilized to understand the wear behavior of these materials under different environments. The steels were tested in as-cast and heat treated conditions. Wear rates of the cast Cr/TiC steels were compared to those of an AISI type 440C steel and P/M composites reinforced with TiC.

  17. Sapphire reinforced alumina matrix composites

    NASA Technical Reports Server (NTRS)

    Jaskowiak, Martha H.; Setlock, John A.

    1994-01-01

    Unidirectionally reinforced A1203 matrix composites have been fabricated by hot pressing. Approximately 30 volume % of either coated or uncoated sapphire fiber was used as reinforcement. Unstabilized ZrO2 was applied as the fiber coating. Composite mechanical behavior was analyzed both after fabrication and after additional heat treatment. The results of composite tensile tests were correlated with fiber-matrix interfacial shear strengths determined from fiber push-out tests. Substantially higher strength and greater fiber pull-out were observed for the coated fiber composites for all processing conditions studied. The coated fiber composites retained up to 95% and 87% of their as-fabricated strength when heat treated at 14000C for 8 or 24 hours, respectively. Electron microscopy analysis of the fracture surfaces revealed extensive fiber pull-out both before and after heat treatment.

  18. Steel - Structural, reinforcing; Pressure vessel, railway

    SciTech Connect

    Not Available

    1986-01-01

    This book contains specifications for structural steel used in various constructions; concrete reinforcement; plate and forgings for boilers and pressure vesseles; rails, axles, wheels and other accessories for railway service.

  19. Steel-SiC Metal Matrix Composite Development

    SciTech Connect

    Smith, Don D.

    2005-07-17

    The goal of this project is to develop a method for fabricating SiC-reinforced high-strength steel. We are developing a metal-matrix composite (MMC) in which SiC fibers are be embedded within a metal matrix of steel, with adequate interfacial bonding to deliver the full benefit of the tensile strength of the SiC fibers in the composite.

  20. Investigation of Mechanical Properties of Steel Fibre- Reinforced Concrete

    NASA Astrophysics Data System (ADS)

    Ryabchikov, A.; Tamme, V.; Laurson, M.

    2015-11-01

    Steel fibre-reinforced concrete (SFRC) is widely used in the structural elements of buildings: industrial floors, slabs, walls, foundation, etc. When a load is applied to a fibre- reinforced composite consisting of a low-modulus matrix reinforced with high-strength, high- modulus fibres, the plastic flow of the matrix under stress transfers the load to the fibre; this results in high-strength, high-modulus material which determines the stiffness and stress of the composite. In this study the equivalent flexural strength, equivalent flexural ratio Re,3 and the compressing strength of SFRC are investigated. Notched test specimens with five different dosages of steel fibres (20, 25, 30, 35, 40 kg/m3) were prepared using industrial concrete. Determination of flexural tension strength was carried out according to the EU norm EVS-EN 14651:2005+A1:2007. The equivalent flexural strength and subsequent equivalent flexural ratio Re,3 of SFRC with a dosage of 20, 25, 30, 35 kg/m3 similar to their average values and with a dosage of 40 kg/m3 were 31% higher than their average values. The compressive strength of the steel fibre-reinforced concrete was slightly higher compared to plain concrete, except specimens with the dosage of 40 kg/m3 where the increase was 30%.

  1. Diamond-Reinforced Matrix Composites

    DTIC Science & Technology

    1993-05-10

    stainless steel retorts and evacuated to a level 17 of -40 mTorr. Samples were HIPped to full density at 600"C at 18 30 Ksi for 30 minutes. These...composite bulk 12 materials and composite coatings) having high strength and 13 stiffness. These articles can be used, for example, in dental 14 materials...fabricated using standard powder metallurgy 8 techniques. The materials used to synthesize the DRCs were -230 9 mesh , 1100 aluminum powder and 30 jim

  2. Producing Durable Continuously Reinforced Concrete Pavement using Glass-ceramic Coated Reinforcing Steel

    DTIC Science & Technology

    2010-02-01

    BUILDING STRONG® Producing Durable Continuously Reinforced Concrete Pavement using Glass- ceramic Coated Reinforcing Steel Principal Investigator... ceramic Coated Reinforcing Steel 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d. PROJECT NUMBER 5e. TASK NUMBER...Vitreous- Ceramic Coating  Ease of Application to Reinforcement Steel  Bond Strength and Corrosion-Resistance  Field Demonstration Program  Testing in

  3. Corrosion inhibition of reinforcing steel by using acrylic latex

    SciTech Connect

    Wang, S.X.; Lin, W.W.; Ceng, S.A.; Zhang, J.Q.

    1998-05-01

    Acrylic latex was introduced into steel-reinforcing steel concrete as concrete admixtures or rebar coatings in order to prevent corrosion of steel reinforcements. The results showed that applying the latex by both methods took effect in different ways, while the latter was more noticeable. The corrosion prevention mechanism and the surface state of the steel rebar were also explored, based on which suggestions for enhancing the corrosion-resistant ability were made.

  4. A review on the cords & plies reinforcement of elastomeric polymer matrix

    NASA Astrophysics Data System (ADS)

    Mahmood, S. S.; Husin, H.; Mat-Shayuti, M. S.; Hassan, Z.

    2016-06-01

    Steel, polyester, nylon and rayon are the main materials of cords & plies that have been reinforced in the natural rubber to produce quality tyres but there is few research reported on cord and plies reinforcement in silicone rubber. Taking the innovation of tyres as inspiration, this review's first objective is to compile the comprehensive studies about the cords & plies reinforcement in elastomeric polymer matrix. The second objective is to gather information about silicone rubber that has a high potential as a matrix phase for cords and plies reinforcement. All the tests and findings are gathered and compiled in sections namely processing preparation, curing, physical and mechanical properties, and adhesion between cords-polymer.

  5. On matrix cracking in fiber reinforced ceramics

    NASA Astrophysics Data System (ADS)

    Chiang, Yih-Cheng; Wang, A. S. D.; Chou, Tsu-Wei

    1993-07-01

    THISPAPER addresses critical stress at the propagation of a fiber-bridged matrix crack of arbitrary length in fiber-reinforced brittle matrix composites. The formulation of the problem follows the approach adopted earlier by Marshall, Cox and Evans, but a new shear-lag model that accounts for the matrix shear deformation above the slipping region is used here to derive the relationship between the crack opening displacement and the crack surface closure traction. The inclusion of the matrix shear deformation above the slipping region significantly affects the calculated crack tip stress intensity factor and the prediction of the critical stress at the propagation of the crack. Illustrative examples are cited using three available composite systems of SiC-borosilicate, C-borosilicate and Nicalon-lithium-aluminosilicate (LAS).

  6. Research on graphite reinforced glass matrix composites

    NASA Technical Reports Server (NTRS)

    Bacon, J. F.; Prewo, K. M.

    1977-01-01

    The results of research for the origination of graphite-fiber reinforced glass matrix composites are presented. The method selected to form the composites consisted of pulling the graphite fiber through a slurry containing powdered glass, winding up the graphite fiber and the glass it picks up on a drum, drying, cutting into segments, loading the tape segment into a graphite die, and hot pressing. During the course of the work, composites were made with a variety of graphite fibers in a glass matrix.

  7. Research on graphite reinforced glass matrix composites

    NASA Technical Reports Server (NTRS)

    Prewo, K. M.; Thompson, E. R.

    1980-01-01

    High levels of mechanical performance in tension, flexure, fatigue, and creep loading situations of graphite fiber reinforced glass matrix composites are discussed. At test temperatures of up to 813 K it was found that the major limiting factor was the oxidative instability of the reinforcing graphite fibers. Particular points to note include the following: (1) a wide variety of graphite fibers were found to be comparable with the glass matrix composite fabrication process; (2) choice of fiber, to a large extent, controlled resultant composite performance; (3) composite fatigue performance was found to be excellent at both 300 K and 703 K; (4) composite creep and stress rupture at temperatures of up to 813 K was limited by the oxidative stability of the fiber; (5) exceptionally low values of composite thermal expansion coefficient were attributable to the dimensional stability of both matrix and fiber; and (6) component fabricability was demonstrated through the hot pressing of hot sections and brazing using glass and metal joining phases.

  8. Application of nanoindentation testing to study of the interfacial transition zone in steel fiber reinforced mortar

    SciTech Connect

    Wang Xiaohui Jacobsen, Stefan; He Jianying; Zhang Zhiliang; Lee, Siaw Foon; Lein, Hilde Lea

    2009-08-15

    The characteristics of the profiles of elastic modulus and hardness of the steel fiber-matrix and fiber-matrix-aggregate interfacial zones in steel fiber reinforced mortars have been investigated by using nanoindentation and Scanning Electron Microscopy (SEM), where two sets of parameters, i.e. water/binder ratio and content of silica fume were considered. Different interfacial bond conditions in the interfacial transition zones (ITZ) are discussed. For sample without silica fume, efficient interfacial bonds across the steel fiber-matrix and fiber-matrix-aggregate interfaces are shown in low water/binder ratio mortar; while in high water/binder ratio mortar, due to the discontinuous bleeding voids underneath the fiber, the fiber-matrix bond is not very good. On the other hand, for sample with silica fume, the addition of 10% silica fume leads to no distinct presence of weak ITZ in the steel fiber-matrix interface; but the effect of the silica fume on the steel fiber-matrix-aggregate interfacial zone is not obvious due to voids in the vicinity of steel fiber.

  9. 61. photographer unknown November 1935 STEEL REINFORCING FOR APRON, SOUTH ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    61. photographer unknown November 1935 STEEL REINFORCING FOR APRON, SOUTH HALF OF MAIN DAM. OUTLINE OF SPILLWAY PAINTED ON INSIDE OF COFFERDAM. - Bonneville Project, Bonneville Dam, Columbia River, Bonneville, Multnomah County, OR

  10. 62. photographer unknown undated ERECTING FORMS, PLACING REINFORCING STEEL, AND ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    62. photographer unknown undated ERECTING FORMS, PLACING REINFORCING STEEL, AND CONCRETING DRAFT PIER OF POWERHOUSE. - Bonneville Project, Powerhouse No.1, Spanning Bradford Slough, from Bradford Island, Bonneville, Multnomah County, OR

  11. Bond characteristics of reinforcing steel embedded in geopolymer concrete

    NASA Astrophysics Data System (ADS)

    Kathirvel, Parthiban; Thangavelu, Manju; Gopalan, Rashmi; Raja Mohan Kaliyaperumal, Saravana

    2017-07-01

    The force transferring between reinforcing steel and the surrounding concrete in reinforced concrete is influenced by several factors. Whereas, the study on bond behaviour of geopolymer concrete (GPC) is lagging. In this paper, an experimental attempt has been made to evaluate the geopolymer concrete bond with reinforcing steel of different diameter and embedded length using standard pull out test. The geopolymer concrete is made of ground granulated blast furnace slag (GGBFS) as geopolymer source material (GSM). The tests were conducted to evaluate the development of bond between steel and concrete of grade M40 and M50 with 12 and 16 mm diameter reinforcing steel for geopolymer and cement concrete mixes and to develop a relation between bond strength and compressive strength. From the experimental results, it has been observed that the bond strength of the geopolymer concrete mixes was more compared to the cement concrete mixes and increases with the reduction in the diameter of the bar.

  12. 5. GENERAL PLAN OF STRUCTURAL AND REINFORCING STEEL, PIERS AND ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    5. GENERAL PLAN OF STRUCTURAL AND REINFORCING STEEL, PIERS AND DETAILS FOR SWIMMING POOL Drawing 103-21 - Glen Echo Park, Crystal Swimming Pool, 7300 McArthur Boulevard, Glen Echo, Montgomery County, MD

  13. Characterization and design of steel fiber reinforced shotcrete in tunnelling

    SciTech Connect

    Casanova, P.A.; Rossi, P.C.

    1995-12-31

    A design procedure of steel fiber reinforced shotcrete tunnel linings is proposed. It is based on the analysis of a cracked section. The tensile behavior of shotcrete after cracking is obtained by a uniaxial tension test on cored notched samples. As for usual reinforced concrete structures an interaction diagram (moment-axial load) is determined.

  14. Damage tolerance in discontinuously reinforced metal-matrix composites

    SciTech Connect

    Rack, H.J.; Ratnaparkhi, P.

    1988-11-01

    Properly designed discontinuously-reinforced MMCs have been projected by linear-elastic fracture mechanics to be competitive, on both cost and performance bases, with cross-plied graphite-reinforced polymer-matrix composites and continuously-reinforced MMCs. With respect to the latter, discontinuously-reinforced MMCs achieve considerable advantages in virtue of their lower-cost reinforcements and their fabricability by standard metal-working practices. Discontinuously reinforced MMC billets can also be produced through powder-blending and direct-spraying techniques. SiC short fibers, whiskers, and particulates are typical of the discontinuous reinforcements used in 2124 and 6061 aluminum matrices. 18 references.

  15. Fiber reinforced thermoplastic resin matrix composites

    NASA Technical Reports Server (NTRS)

    Jones, Robert J. (Inventor); Chang, Glenn E. C. (Inventor)

    1989-01-01

    Polyimide polymer composites having a combination of enhanced thermal and mechanical properties even when subjected to service temperatures as high as 700.degree. F. are described. They comprise (a) from 10 to 50 parts by weight of a thermoplastic polyimide resin prepared from 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane and (b) from 90 to 50 parts by weight of continuous reinforcing fibers, the total of (a) and (b) being 100 parts by weight. Composites based on polyimide resin formed from 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane and pyromellitic dianhydride and continuous carbon fibers retained at least about 50% of their room temperature shear strength after exposure to 700.degree. F. for a period of 16 hours in flowing air. Preferably, the thermoplastic polyimide resin is formed in situ in the composite material by thermal imidization of a corresponding amide-acid polymer prepared from 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane. It is also preferred to initially size the continuous reinforcing fibers with up to about one percent by weight of an amide-acid polymer prepared from 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane. In this way imidization at a suitable elevated temperature results in the in-situ formation of a substantially homogeneous thermoplastic matrix of the polyimide resin tightly and intimately bonded to the continuous fibers. The resultant composites tend to have optimum thermo-mechanical properties.

  16. Solidification of particle-reinforced metal-matrix composites

    NASA Astrophysics Data System (ADS)

    Hanumanth, G. S.; Irons, G. A.

    1996-08-01

    The solidification behavior of ceramic particle-reinforced metal-matrix composites (MMCs) is different from that of the bare matrix, not only because of the presence of the ceramic particles, but also due to their redistribution in the melt that results in nonhomogeneous thermophysical properties. The MMCs comprised of 10-to 15-μm SiC particles of varying volume fractions, dispersed uniformly in a modified aluminum A356 alloy by the melt stirring technique, were solidified unidirectionally in a thermocouple-instrumented cylindrical steel mold. The cooling rates were continually monitored by measuring temperatures at different depths in the melt, and the solidified MMCs were sectioned into disks and chemically analyzed for SiC volume fraction. The results point out that the cooling rate increased with increasing volume fraction of SiC particles. A small increase in the bulk SiC volume fraction of the cast MMC was observed due to particle settling during solidification. A one-dimensional enthalpy model of MMC solidification was formulated, wherein particle settling occurring in the solidifying matrix was coupled to the enthalpy equation by means of the Richardson-Zaki hindered settling correlation. A comparative study of simulations with experiments suggested that the thermal response of SiC particles used in this study was similar to that of single crystals, and their presence increased the effective thermal conductivity of the composite.

  17. Aluminum-Alloy-Matrix/Alumina-Reinforcement Composites

    NASA Technical Reports Server (NTRS)

    Kashalikar, Uday; Rozenoyer, Boris

    2004-01-01

    Isotropic composites of aluminum-alloy matrices reinforced with particulate alumina have been developed as lightweight, high-specific-strength, less-expensive alternatives to nickel-base and ferrous superalloys. These composites feature a specific gravity of about 3.45 grams per cubic centimeter and specific strengths of about 200 MPa/(grams per cubic centimeter). The room-temperature tensile strength is 100 ksi (689 MPa) and stiffness is 30 Msi (206 GPa). At 500 F (260 C), these composites have shown 80 percent retention in strength and 95 percent retention in stiffness. These materials also have excellent fatigue tolerance and tribological properties. They can be fabricated in net (or nearly net) sizes and shapes to make housings, pistons, valves, and ducts in turbomachinery, and to make structural components of such diverse systems as diesel engines, automotive brake systems, and power-generation, mining, and oil-drilling equipment. Separately, incorporation of these metal matrix composites within aluminum gravity castings for localized reinforcement has been demonstrated. A composite part of this type can be fabricated in a pressure infiltration casting process. The process begins with the placement of a mold with alumina particulate preform of net or nearly net size and shape in a crucible in a vacuum furnace. A charge of the alloy is placed in the crucible with the preform. The interior of the furnace is evacuated, then the furnace heaters are turned on to heat the alloy above its liquidus temperature. Next, the interior of the furnace is filled with argon gas at a pressure about 900 psi (approximately equal to 6.2 MPa) to force the molten alloy to infiltrate the preform. Once infiltrated, the entire contents of the crucible can be allowed to cool in place, and the composite part recovered from the mold.

  18. Graphite fiber reinforced glass matrix composites for aerospace applications

    NASA Technical Reports Server (NTRS)

    Prewo, K. M.; Bacon, J. F.; Dicus, D. L.

    1979-01-01

    The graphite fiber reinforced glass matrix composite system is described. Although this composite is not yet a mature material, it possesses low density, attractive mechanical properties at elevated temperatures, and good environmental stability. Properties are reported for a borosilicate glass matrix unidirectionally reinforced with 60 volume percent HMS graphite fiber. The flexural strength and fatigue characteristics at room and elevated temperature, resistance to thermal cycling and continuous high temperature oxidation, and thermal expansion characteristics of the composite are reported. The properties of this new composite are compared to those of advanced resin and metal matrix composites showing that graphite fiber reinforced glass matrix composites are attractive for aerospace applications.

  19. Graphite fiber reinforced glass matrix composites for aerospace applications

    NASA Technical Reports Server (NTRS)

    Prewo, K. M.; Bacon, J. F.; Dicus, D. L.

    1979-01-01

    The graphite fiber reinforced glass matrix composite system is described. Although this composite is not yet a mature material, it possesses low density, attractive mechanical properties at elevated temperatures, and good environmental stability. Properties are reported for a borosilicate glass matrix unidirectionally reinforced with 60 volume percent HMS graphite fiber. The flexural strength and fatigue characteristics at room and elevated temperature, resistance to thermal cycling and continuous high temperature oxidation, and thermal expansion characteristics of the composite are reported. The properties of this new composite are compared to those of advanced resin and metal matrix composites showing that graphite fiber reinforced glass matrix composites are attractive for aerospace applications.

  20. Reinforcement stresses during deformation of sphere- and particulate-reinforced Al-matrix composites

    SciTech Connect

    Justice, I.; Poza, P.; Martinez, J.L.; Llorca, J.

    1996-02-01

    Recent experimental results showed that reinforcement fracture is very often the dominant damage mechanism during ambient temperature deformation of discontinuously reinforced Al-matrix composites (DRAC). The reinforcements are broken by cracks perpendicular to the loading axis, and the fraction of broken reinforcements increases during plastic deformation as the load transferred from the matrix to the ceramic particulates increases. This process continues until a criteria fraction of broken reinforcements is reached, and then fracture takes place suddenly by a ductile mechanism involving localized necking of the intervoid matrix. The rate of reinforcement fracture depends on the strength of the ceramic reinforcements and on the stresses acting on them, and the modeling of the processes of damage accumulation in DRAC requires the knowledge of both. In particular, the stresses acting on the reinforcements during monotonic tensile deformation are a function of the applied strain, of the matrix and reinforcement properties, and of the volume fraction and shape of the ceramic reinforcements. A parametrical study is presented in this article of the influence of these factors on the stress acting on the reinforcements. The numerical results covered the whole range of matrix strengths which are typical in DRAC and were fitted to simple analytical expressions to facilitate their use by other researchers.

  1. Research on Graphite Reinforced Glass Matrix Composites

    NASA Technical Reports Server (NTRS)

    Bacon, J. F.; Prewo, K. M.

    1977-01-01

    This report contains the results obtained in the first twelve months of research under NASA Langley Contract NAS1-14346 for the origination of graphite-fiber reinforced glass matrix composites. Included in the report is a summary of the research by other investigators in this area. The method selected to form the composites consisted of pulling the graphite fiber through a slurry containing powdered glass, winding up the graphite fiber and the glass it picks up on a drum, drying, cutting into segments, loading the tape segment into a graphite die, and hot pressing. During the course of the work, composites were made with a variety of graphite fibers in a C.G.W. 7740 (Pyrex) glass matrix. The graphite fibers used included Hercules HMS, Hercules HTS, Thornel 300S, and Celanese DG-102 and, of these, the Hercules HMS and Celanese DG-102 graphite fibers in C.G.W. 7740 gave the most interesting but widely different results. Hercules HMS fiber in C.G.W. 7740 glass (Pyrex) showed an average four-point flexural strength of 848 MPa or 127,300 psi. As the test temperature was raised from room temperature to 560 C in argon or vacuum, the strength was higher by 50 percent. However, in air, similar tests at 560 C gave a severe loss in strength. These composites also have good thermal cycle properties in argon or vacuum, greatly increased toughness compared to glass, and no loss in strength in a 100 cycle fatigue test. Celanese DG-102 fiber in C.G.W. 7740 glass (Pyrex) had a much lower flexural strength but did not suffer any loss in this strength when samples were heated to 560 C in air for 4 hrs.

  2. 78 FR 55755 - Steel Concrete Reinforcing Bar From Mexico and Turkey; Institution of Antidumping and...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-09-11

    ... From the Federal Register Online via the Government Publishing Office INTERNATIONAL TRADE COMMISSION Steel Concrete Reinforcing Bar From Mexico and Turkey; Institution of Antidumping and... from Mexico and Turkey of steel concrete reinforcing bar, primarily provided for in subheadings...

  3. Nanoscale Reinforced, Polymer Derived Ceramic Matrix Coatings

    SciTech Connect

    Rajendra Bordia

    2009-07-31

    The goal of this project was to explore and develop a novel class of nanoscale reinforced ceramic coatings for high temperature (600-1000 C) corrosion protection of metallic components in a coal-fired environment. It was focused on developing coatings that are easy to process and low cost. The approach was to use high-yield preceramic polymers loaded with nano-size fillers. The complex interplay of the particles in the polymer, their role in controlling shrinkage and phase evolution during thermal treatment, resulting densification and microstructural evolution, mechanical properties and effectiveness as corrosion protection coatings were investigated. Fe-and Ni-based alloys currently used in coal-fired environments do not possess the requisite corrosion and oxidation resistance for next generation of advanced power systems. One example of this is the power plants that use ultra supercritical steam as the working fluid. The increase in thermal efficiency of the plant and decrease in pollutant emissions are only possible by changing the properties of steam from supercritical to ultra supercritical. However, the conditions, 650 C and 34.5 MPa, are too severe and result in higher rate of corrosion due to higher metal temperatures. Coating the metallic components with ceramics that are resistant to corrosion, oxidation and erosion, is an economical and immediate solution to this problem. Good high temperature corrosion protection ceramic coatings for metallic structures must have a set of properties that are difficult to achieve using established processing techniques. The required properties include ease of coating complex shapes, low processing temperatures, thermal expansion match with metallic structures and good mechanical and chemical properties. Nanoscale reinforced composite coatings in which the matrix is derived from preceramic polymers have the potential to meet these requirements. The research was focused on developing suitable material systems and

  4. Monitoring corrosion of steel bars in reinforced concrete structures.

    PubMed

    Verma, Sanjeev Kumar; Bhadauria, Sudhir Singh; Akhtar, Saleem

    2014-01-01

    Corrosion of steel bars embedded in reinforced concrete (RC) structures reduces the service life and durability of structures causing early failure of structure, which costs significantly for inspection and maintenance of deteriorating structures. Hence, monitoring of reinforcement corrosion is of significant importance for preventing premature failure of structures. This paper attempts to present the importance of monitoring reinforcement corrosion and describes the different methods for evaluating the corrosion state of RC structures, especially hal-cell potential (HCP) method. This paper also presents few techniques to protect concrete from corrosion.

  5. Monitoring Corrosion of Steel Bars in Reinforced Concrete Structures

    PubMed Central

    Verma, Sanjeev Kumar; Bhadauria, Sudhir Singh; Akhtar, Saleem

    2014-01-01

    Corrosion of steel bars embedded in reinforced concrete (RC) structures reduces the service life and durability of structures causing early failure of structure, which costs significantly for inspection and maintenance of deteriorating structures. Hence, monitoring of reinforcement corrosion is of significant importance for preventing premature failure of structures. This paper attempts to present the importance of monitoring reinforcement corrosion and describes the different methods for evaluating the corrosion state of RC structures, especially hal-cell potential (HCP) method. This paper also presents few techniques to protect concrete from corrosion. PMID:24558346

  6. 76 FR 48802 - Certain Steel Concrete Reinforcing Bars From Turkey; Notice of Amended Final Results of...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-08-09

    ... International Trade Administration Certain Steel Concrete Reinforcing Bars From Turkey; Notice of Amended Final... antidumping duty order on certain steel concrete reinforcing bars (rebar) from Turkey. See Certain Steel Concrete Reinforcing Bars From Turkey; Final Results of Antidumping Duty Administrative Review...

  7. 78 FR 60831 - Steel Concrete Reinforcing Bar From Turkey: Initiation of Countervailing Duty Investigation

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-10-02

    ... International Trade Administration Steel Concrete Reinforcing Bar From Turkey: Initiation of Countervailing Duty... (``CVD'') petition \\1\\ concerning imports of steel concrete reinforcing bar (``rebar'') from the Republic... Countervailing Duties on Imports of Steel Concrete Reinforcing Bar from the Republic of Turkey, dated September...

  8. 78 FR 60827 - Steel Concrete Reinforcing Bar From Mexico and Turkey: Initiation of Antidumping Duty Investigations

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-10-02

    ... International Trade Administration Steel Concrete Reinforcing Bar From Mexico and Turkey: Initiation of... imports of steel concrete reinforcing bar (``rebar'') from Mexico and Turkey filed in proper form on... Duties on Steel Concrete Reinforcing Bar from Mexico and Turkey and the Imposition of...

  9. VIEW OF EAST GUN EMPLACEMENT. NOTE THE STEEL REINFORCING RODS ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    VIEW OF EAST GUN EMPLACEMENT. NOTE THE STEEL REINFORCING RODS PROTRUDING FROM THE BROKEN TOP OF THE RETAINING WALL. VIEW FACING NORTHEAST - U.S. Naval Base, Pearl Harbor, Ford Island 5-Inch Antiaircraft Battery, East Gun Emplacement, Ford Island, Pearl City, Honolulu County, HI

  10. RETENTION BASIN. ERECTING REINFORCING STEEL FOR CONCRETE DECK. STACK RISES ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    RETENTION BASIN. ERECTING REINFORCING STEEL FOR CONCRETE DECK. STACK RISES AT TOP LEFT. CAMERA FACES WEST. INL NEGATIVE NO. 2581. Unknown Photographer, 6/18/1951 - Idaho National Engineering Laboratory, Test Reactor Area, Materials & Engineering Test Reactors, Scoville, Butte County, ID

  11. Carbon Fiber Reinforced Glass Matrix Composites for Space Based Applications.

    DTIC Science & Technology

    1987-08-31

    Nardone , "Carbon Fiber Reinforced Glass Matrix Composites for Space Based Applications", Office of Naval Research Contract N00014-85-C-0332, Report R86... Nardone and K M. Prewo, "Tensile Performance of Carbon Fiber Reinforced Glass", J. Mater. Sci. accepted for publication, 1987. 27. R. F. Cooper and K

  12. Research on graphite reinforced glass matrix composites

    NASA Technical Reports Server (NTRS)

    Bacon, J. F.; Prewo, K. M.; Thompson, E. R.

    1978-01-01

    A composite that can be used at temperatures up to 875 K with mechanical properties equal or superior to graphite fiber reinforced epoxy composites is presented. The composite system consist of graphite fiber, uniaxially or biaxially, reinforced borosilicate glass. The mechanical and thermal properties of such a graphite fiber reinforced glass composite are described, and the system is shown to offer promise as a high performance structural material. Specific properties that were measured were: a modified borosilicate glass uniaxially reinforced by Hercules HMS graphite fiber has a three-point flexural strength of 1030 MPa, a four-point flexural strength of 964 MPa, an elastic modulus of 199 GPa and a failure strain of 0.0052. The preparation and properties of similar composites with Hercules HTS, Celanese DG-102, Thornel 300 and Thornel Pitch graphite fibers are also described.

  13. CP systems for steel reinforced concrete bridges

    SciTech Connect

    Bullard, Sophie J.; Cramer, Stephen D.; Covino, Bernard S., Jr.; Holcomb, Gordon R.; Ziomek-Moroz, Margaret; Soltesz, Steven M.

    2004-01-01

    Thermal-sprayed zinc anodes are used for cathodic protection (CP) systems in Oregon?s reinforced concrete coastal bridges to prevent chloride-induced corrosion damage. Thermal-sprayed zinc performs well as an ICCP anode but the service life of the zinc anode is directly related to the average current density used to operate the systems. Oregon Department of Transportation (DOT) is investigating ways of monitoring the rebar corrosion in reinforced concrete bridges to identify conditions when protection of the rebar is needed. This approach reflects the fact that external protection may not be needed for all environmental conditions, leading Oregon DOT to examine the use of intermittent, galvanic, and constant voltage cathodic protection systems. Results from these types of systems are reported.

  14. Fatigue in selectively fiber-reinforced titanium matrix composites

    NASA Astrophysics Data System (ADS)

    Ramamurty, U.

    1999-08-01

    Many applications of the Ti alloy matrix composites (TMCs) reinforced with SiC fibers are expected to use the selective reinforcement concept in order to optimize the processing and increase the cost-effectiveness. In this work, unnotched fatigue behavior of a Ti-6Al-4V matrix selectively reinforced with SCS-6 SiC fibers has been examined. Experiments have been conducted on two different model panels. Results show that the fatigue life of the selectively reinforced composites is far inferior to that of the all-TMC panel. The fatigue life decreases with the decreasing effective fiber volume fraction. Suppression of multiple matrix cracking in the selectively reinforced panels was identified as the reason for their lack of fatigue resistance. Fatigue endurance limit as a function of the clad thickness was calculated using the modified Smith-Watson-Topper (SWT) parameter and the effective fiber volume fraction approach. The regime over which multiple matrix cracking occurs is identified using the bridging fiber fracture criterion. A fatigue failure map for the selectively reinforced TMCs is constructed on the basis of the observed damage mechanisms. Possible applications of such maps are discussed.

  15. 10. View of Riverside Bridge with Steel Reinforcing Rods in ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    10. View of Riverside Bridge with Steel Reinforcing Rods in Place and with 'Tower for Concrete' in the Background. The function of the 'tower for concrete' is uncertain, but may have to do with the transport of concrete from the point of mixing to the point of use (suggestion by NDOT Bridge Section personnel, February 1990). Original snapshot taken July, 1920. - Riverside Bridge, Spanning Truckee River at Booth Street, Reno, Washoe County, NV

  16. Fatigue testing of reinforced-concrete steel bars

    NASA Astrophysics Data System (ADS)

    Maropoulos, S.; Fasnakis, D.; Voulgaraki, Ch; Papanikolaou, S.; Maropoulos, A.; Antonatos, A.

    2016-11-01

    A number of low-cycle fatigue tests were conducted on reinforced-concrete steel bars of various diameters to study their behaviour under axial loading according to EN 10080 and EN 1421-3. Scanning electron microscopy was used to study the specimen fracture surfaces. The problems faced during testing are presented and a specimen preparation method is described that will aid researchers on fatigue testing to obtain accurate test results and save on material and time.

  17. Mechanical Properties of Particulate Reinforced Aluminium Alloy Matrix Composite

    SciTech Connect

    Sayuti, M.; Sulaiman, S.; Baharudin, B. T. H. T.; Arifin, M. K. A.; Suraya, S.; Vijayaram, T. R.

    2011-01-17

    This paper discusses the mechanical properties of Titanium Carbide (TiC) particulate reinforced aluminium-silicon alloy matrix composite. TiC particulate reinforced LM6 alloy matrix composites were fabricated by carbon dioxide sand molding process with different particulate weight fraction. Tensile strength, hardness and microstructure studies were conducted to determine the maximum load, tensile strength, modulus of elasticity and fracture surface analysis have been performed to characterize the morphological aspects of the test samples after tensile testing. Hardness values are measured for the TiC reinforced LM6 alloy composites and it has been found that it gradually increases with increased addition of the reinforcement phase. The tensile strength of the composites increased with the increase percentage of TiC particulate.

  18. Mechanical Properties of Particulate Reinforced Aluminium Alloy Matrix Composite

    NASA Astrophysics Data System (ADS)

    Sayuti, M.; Sulaiman, S.; Baharudin, B. T. H. T.; Arifin, M. K. A.; Suraya, S.; Vijayaram, T. R.

    2011-01-01

    This paper discusses the mechanical properties of Titanium Carbide (TiC) particulate reinforced aluminium-silicon alloy matrix composite. TiC particulate reinforced LM6 alloy matrix composites were fabricated by carbon dioxide sand molding process with different particulate weight fraction. Tensile strength, hardness and microstructure studies were conducted to determine the maximum load, tensile strength, modulus of elasticity and fracture surface analysis have been performed to characterize the morphological aspects of the test samples after tensile testing. Hardness values are measured for the TiC reinforced LM6 alloy composites and it has been found that it gradually increases with increased addition of the reinforcement phase. The tensile strength of the composites increased with the increase percentage of TiC particulate.

  19. 78 FR 68090 - Steel Concrete Reinforcing Bar from Mexico and Turkey

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-11-13

    ... COMMISSION Steel Concrete Reinforcing Bar from Mexico and Turkey Determinations On the basis of the record \\1... injured by reason of imports from Mexico and Turkey of steel concrete reinforcing bar, provided for in... alleged to be sold in the United States at less than fair value (LTFV), and by imports of steel...

  20. 78 FR 73838 - Steel Concrete Reinforcing Bar From Turkey: Postponement of Preliminary Determination in the...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-12-09

    ... International Trade Administration Steel Concrete Reinforcing Bar From Turkey: Postponement of Preliminary... Department of Commerce (the Department) initiated a countervailing duty investigation on steel concrete... December 16, 2013.\\3\\ \\1\\ See Steel Concrete Reinforcing Bar from Turkey: Initiation of Countervailing...

  1. 77 FR 71631 - Steel Concrete Reinforcing Bar From Belarus, China, Indonesia, Latvia, Moldova, Poland, and...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-12-03

    ... COMMISSION Steel Concrete Reinforcing Bar From Belarus, China, Indonesia, Latvia, Moldova, Poland, and Ukraine; Scheduling of Full Five-Year Reviews Concerning the Antidumping Duty Orders on Steel Concrete...) to determine whether revocation of the antidumping duty orders on steel concrete reinforcing bar...

  2. Performance of Straight Steel Fibres Reinforced Alkali Activated Concrete

    NASA Astrophysics Data System (ADS)

    Faris, Meor Ahmad; Bakri Abdullah, Mohd Mustafa Al; Nizar Ismail, Khairul; Muniandy, Ratnasamy; Putra Jaya, Ramadhansyah

    2016-06-01

    This paper focus on the performance of alkali activated concrete produced by using fly ash activated by sodium silicate and sodium hydroxide solutions. These alkali activated concrete were reinforced with straight steel fibres with different weight percentage starting from 0 % up to 5 %. Chemical composition of raw material in the production alkali activated concrete which is fly ash was first identified by using X-ray fluorescence. Results reveal there have an effect of straight steel fibres inclusion to the alkali activated concrete. Highest compressive strength of alkali activated concrete which is 67.72 MPa was obtained when 3 % of straight fibres were added. As well as flexural strength, highest flexural strength which is 6.78 MPa was obtained at 3 % of straight steel fibres inclusions.

  3. 77 FR 64127 - Steel Concrete Reinforcing Bar From Belarus, China, Indonesia, Latvia, Moldova, Poland, and...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-10-18

    ... COMMISSION Steel Concrete Reinforcing Bar From Belarus, China, Indonesia, Latvia, Moldova, Poland, and... determine whether revocation of the antidumping duty orders on steel concrete reinforcing bar from Belarus... concrete reinforcing bar from Latvia and Moldova. The Commission found that the respondent interested...

  4. Mechanical Properties of Continuous Fiber Reinforced Zirconium Diboride Matrix Composites

    NASA Technical Reports Server (NTRS)

    Stuffle, Kevin; Creegan, Peter; Nowell, Steven; Bull, Jeffrey D.; Rasky, Daniel J. (Technical Monitor)

    1995-01-01

    Continuous fiber reinforced zirconium diboride matrix composites, SCS-9a-(RBSiCZrB2)matrix, are being developed for leading edge, rocket nozzle and turbine engine applications. Recently, the composite materials have been characterized for tensile properties to 1250 C, the highest temperature tested. The tensile properties are fiber dominated as the matrix is microcracked on fabrication, but favorable failure characteristic are observed. Compression and shear mechanical testing results will be reported if completed. The effects of fiber volume fraction and matrix density on mechanical properties will be discussed. The target applications of the materials will be discussed. Specific testing being performed towards qualification for these applications will be included.

  5. Mechanical Properties of Continuous Fiber Reinforced Zirconium Diboride Matrix Composites

    NASA Technical Reports Server (NTRS)

    Stuffle, Kevin; Creegan, Peter; Nowell, Steven; Bull, Jeffrey D.; Rasky, Daniel J. (Technical Monitor)

    1995-01-01

    Continuous fiber reinforced zirconium diboride matrix composites, SCS-9a-(RBSiCZrB2)matrix, are being developed for leading edge, rocket nozzle and turbine engine applications. Recently, the composite materials have been characterized for tensile properties to 1250 C, the highest temperature tested. The tensile properties are fiber dominated as the matrix is microcracked on fabrication, but favorable failure characteristic are observed. Compression and shear mechanical testing results will be reported if completed. The effects of fiber volume fraction and matrix density on mechanical properties will be discussed. The target applications of the materials will be discussed. Specific testing being performed towards qualification for these applications will be included.

  6. Fibre reinforced CMC with polymer/filler derived matrix

    SciTech Connect

    Suttor, D.; Erny, T.; Greil, P.

    1995-09-01

    A ceramic matrix for carbon fibre reinforced ceramic matrix composites (CMC) has been developed from polysiloxane/boron mixtures. Complex geometries can be realized by using processing technologies of fibre reinforced polymer composites. Upon pyrolysis the polymer/filler mixture is converted into a ceramic matrix consisting of SiC, B{sub 4}C, BN and a Si-O-C-(N) glass, without reacting with the carbon fibre. Due to the large volume increase of the reactive boron filler upon nitridation (+142 vol%) no multiple reinfiltration of the structure is necessary in order to achieve a dense matrix. Thermodynamic modelling of the pyrolysis is a useful tool to estimate the qualitative and quantitative phase composition as a function of polymer, filler and gas atmospheres.

  7. Plastic matrix composites with continuous fiber reinforcement

    SciTech Connect

    1991-09-19

    Most plastic resins are not suitable for structural applications. Although many resins are extremely tough, most lack strength, stiffness, and deform under load with time. By mixing strong, stiff, fibrous materials into the plastic matrix, a variety of structural composite materials can be formed. The properties of these composites can be tailored by fiber selection, orientation, and other factors to suit specific applications. The advantages and disadvantages of fiberglass, carbon-graphite, aramid (Kevlar 49), and boron fibers are summarized.

  8. Fracture criteria for discontinuously reinforced metal matrix composites

    NASA Technical Reports Server (NTRS)

    Rack, H. J.; Goree, J. G.; Albritton, J.; Ratnaparkhi, P.

    1988-01-01

    Summarized is the progress achieved during the period September 16, 1987 to August 15, l988 on NASA Grant NAG1-724, Fracture Criteria for Discontinuously Reinforced Metal Matrix Composites. Appended are copies of three manuscripts prepared under NASA funding during the performance period.

  9. Fracture criteria for discontinuously reinforced metal matrix composites

    NASA Technical Reports Server (NTRS)

    Rack, H. J.; Goree, J. G.; Albritton, J.; Ratnarparkhi, P.

    1988-01-01

    The effect of sample configuration on the details of initial crack propagation in discontinuously whisker reinforced aluminum metal matrix composites was investigated. Care was taken to allow direct comparison of fracture toughness values utilizing differing sample configurations and orientations, holding all materials variables constant, e.g., extrusion ration, heat treatment, and chemistry.

  10. Acoustic Nondestructive Testing and Measurement of Tension for Steel Reinforcing Members: Part 1-Theory

    DTIC Science & Technology

    2014-09-01

    structural steel reinforcing members. In large concrete structures such as locks and dams, the corrosion of tensioned steel components can lead to...loss of tension and consequent severe problems such as cracking of the concrete or fracturing of the steel. The theory and application address the...problem of determining tension in concrete - embedded pre- and post-tensioned steel reinforcement rods. BACKGROUND: Many concrete structures contain

  11. Research on graphite reinforced glass matrix composites

    NASA Technical Reports Server (NTRS)

    Prewo, K. M.; Thompson, E. R.

    1981-01-01

    A broad group of fibers and matrices were combined to create a wide range of composite properties. Primary material fabrication procedures were developed which readily permit the fabrication of flat plate and shaped composites. Composite mechanical properties were measured under a wide range of test conditions. Tensile, flexure mechanical fatigue, thermal fatigue, fracture toughness, and fatigue crack growth resistance were evaluated. Selected fiber-matrix combinations were shown to maintain their strength at up to 1300 K when tested in an inert atmosphere. Composite high temperature mechanical properties were shown to be limited primarily by the oxidation resistance of the graphite fibers. Composite thermal dimensional stability was measured and found to be excellent.

  12. Glass matrix composites. I - Graphite fiber reinforced glass

    NASA Technical Reports Server (NTRS)

    Prewo, K. M.; Bacon, J. F.

    1978-01-01

    An experimental program is described in which graphite fibers of Hercules HMS and HTS, Thornel 300, and Celanese DG-12 were used to reinforce, both uniaxially and biaxially, borosilicate pyrex glass. Composite flexural strength distribution, strength as a function of test temperature, fracture toughness and oxidative stability were determined and shown to be primarily a function of fiber type and the quality of fiber-matrix bond formed during composite fabrication. It is demonstrated that the graphite fiber reinforced glass system offers unique possibilities as a high performance structural material.

  13. Simulation of Damage Evolution in Discontinously Reinforced Metal Matrix Composites

    SciTech Connect

    Biner, S.B.; Hu, Shenyang Y.

    2009-08-01

    First, a phase-field model for elastic-plastic solids obeying von Mises yield criterion will be described. Then, this phase-field model will be extended to simulate the damage evolution due to nucleation and growth of voids in ductile matrix for discontinuously reinforced composites. The role of reinforcement morphology and the modulus effects leading to final failure all included in the simulations in an effort to make a parametric investigation. The advantages and disadvantages of such phase-field modeling approach in comparison to well established other continuum methods will be elucidated.

  14. Effect of Steel Fibres Distribution on Impact Resistance Performance of Steel Fibre Reinforced Concrete (SFRC)

    NASA Astrophysics Data System (ADS)

    Che Muda, Zakaria; Liyana Mohd Kamal, Nur; Syamsir, Agusril; Shao Yang, Chen; Beddu, Salmia; Nasharuddin Mustapha, Kamal; Thiruchelvam, Sivadass; Usman, Fathoni; Itam, Zarina; Ashraful Alam, Md; Birima, Ahmed H.; Zaroog, O. S.

    2016-03-01

    This paper investigate the effect of the mesh distribution on the impact performance of steel fibre reinforced concrete (SFRC) for the concrete slab of 300mm × 300mm size reinforced with varied thickness and fraction volume subjected to low impact projectile test. A self-fabricated drop-weight impact test rig with a steel ball weight of 1.236 kg drop at 0.57 m height has been used in this research work. The objective of this research is to study the effect of the mesh distribution on the impact resistance SFRC for various slab thickness and fraction volume. Random fibre distribution is the more effective than the top and bottom fibre distribution in terms of absorption of impact energy, crack resistance, the ability to control crack formation and propagation against impact energy.

  15. Fabrication of Fiber-Reinforced Celsian Matrix Composites

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.; Setlock, John A.

    2000-01-01

    A method has been developed for the fabrication of small diameter, multifilament tow fiber reinforced ceramic matrix composites. Its application has been successfully demonstrated for the Hi-Nicalon/celsian system. Strong and tough celsian matrix composites, reinforced with BN/SiC-coated Hi-Nicalon fibers, have been fabricated by infiltrating the fiber tows with the matrix slurry, winding the tows on a drum, cutting and stacking of the prepreg tapes in the desired orientation, and hot pressing. The monoclinic celsian phase in the matrix was produced in situ, during hot pressing, from the 0.75BaO-0.25SrO-Al2O3-2SiO2 mixed precursor synthesized by solid state reaction from metal oxides. Hot pressing resulted in almost fully dense fiber-reinforced composites. The unidirectional composites having approx. 42 vol% of fibers exhibited graceful failure with extensive fiber pullout in three-point bend tests at room temperature. Values of yield stress and strain were 435 +/- 35 MPa and 0.27 +/- 0.01 percent, respectively, and ultimate strengths of 900 +/- 60 MPa were observed. The Young's modulus of the composites was measured to be 165 +/- 5 GPa.

  16. Characterization of bond in steel-fiber-reinforced cementitious composites under tensile loads

    SciTech Connect

    Namur, G.G.

    1989-01-01

    Investigated was bonding in steel fiber reinforced cementitious composites, like fiber-reinforced mortar. The study was basically analytical, consisting primarily of two analytical models that predict the bond shear stress distribution at the interface between the fibers and the matrix, as well as the normal tensile distributions in the fibers and the matrix. The two models were, however, based on separate assumptions. While the first model assumed a known bond shear stress versus slip relationship at the interface between the fibers and the surrounding matrix, the second model was based on a mechanism of force transfer between the fibers and the matrix, hence circumventing the rather complex task of determining the relationship between the bond stress and the slip for the given type of fiber and matrix. Some applications to this second model, such as the bond modulus, the debonding stress, the length of the debonded zone were also investigated. A theoretical study of the pull-out process of steel fibers in cementitious matrices is included. The problem consisted of relating an idealized bond shear stress versus slip relationship to a pull-out curve. The derivation as based on the assumption that this relationship is linearly elastic-perfectly frictional, and then extended to the case of a fiction decaying linearly with the slip. The problem was subdivided into two components: a primal problem, whereby the pull-out curve is predicted from an assumed bond shear stress-slip relationship, and the dual problem, in which an experimentally obtained pull-out curve was used to predict the interfacial constitutive model, namely the bond-slip curve. Model application was illustrated by three examples of pull-out tests. The pull-out curves obtained in the laboratory, which featured the pull-out force versus the end slip of the pull-out fiber, were used to predict bond shear stress-slip relationships.

  17. Mechanical Behaviour of Alumina Silicon Carbide Reinforced Particulate Reinforced Metal Matrix Composite

    NASA Astrophysics Data System (ADS)

    Raghu Ram, K. S.; Sweanney Bandi, Sharon Rose; Sivarama Krishna, Ch.

    2017-08-01

    The present study was aimed at evaluating the effect of hardness and impact strength of Aluminum Al2O3SiC particulate reinforced Composites. These AMCs with multiple reinforcement (hybrid MMCs) are finding increased applications in aerospace, automobile, space, underwater and transportation applications. An effort is made to enhance the Hardness, flexural strength and Impact properties of AMCs by reinforcing Aluminum matrix with Varying Proportion of small particles of Al2O3SiC by stir casting method. Aluminum alloy matrix varying proportions of Al2O3SiC particulates were fabricated. The microstructure, hardness and impact strength properties of the fabricated AMCs were analyzed. The optical microstructure study revealed the homogeneous dispersion of Al2O3SiC particles in the matrix. Based on the results obtained from the Hardness and Impact of the metal matrix composites it is observed that, the hardness and impact strength increases with increase in the amount of reinforcement content.

  18. Steel reinforcement corrosion detection with coaxial cable sensors

    NASA Astrophysics Data System (ADS)

    Muchaidze, Iana; Pommerenke, David; Chen, Genda

    2011-04-01

    Corrosion processes in the steel reinforced structures can result in structural deficiency and with time create a threat to human lives. Millions of dollars are lost each year because of corrosion. According to the U. S. Federal Highway Administration (FHWA) the average annual cost of corrosion in the infrastructure sector by the end of 2002 was estimated to be $22.6 billion. Timely remediation/retrofit and effective maintenance can extend the structure's live span for much less expense. Thus the considerable effort should be done to deploy corrosion monitoring techniques to have realistic information on the location and the severity of damage. Nowadays commercially available techniques for corrosion monitoring require costly equipment and certain interpretational skills. In addition, none of them is designed for the real time quality assessment. In this study the crack sensor developed at Missouri University of Science and Technology is proposed as a distributed sensor for real time corrosion monitoring. Implementation of this technology may ease the pressure on the bridge owners restrained with the federal budget by allowing the timely remediation with the minimal financial and labor expenses. The sensor is instrumented in such a way that the location of any discontinuity developed along its length can be easily detected. When the sensor is placed in immediate vicinity to the steel reinforcement it is subjected to the same chemical process as the steel reinforcement. And corrosion pitting is expected to develop on the sensor exactly at the same location as in the rebar. Thus it is expected to be an effective tool for active corrosion zones detection within reinforced concrete (RC) members. A series of laboratory tests were conducted to validate the effectiveness of the proposed methodology. Nine sensors were manufactured and placed in the artificially created corrosive environment and observed over the time. To induce accelerated corrosion 3% and 5% Na

  19. 7 CFR 1755.702 - Copper coated steel reinforced (CCSR) aerial service wire.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 11 2014-01-01 2014-01-01 false Copper coated steel reinforced (CCSR) aerial service wire. 1755.702 Section 1755.702 Agriculture Regulations of the Department of Agriculture (Continued..., ACCEPTABLE MATERIALS, AND STANDARD CONTRACT FORMS § 1755.702 Copper coated steel reinforced (CCSR)...

  20. 7 CFR 1755.702 - Copper coated steel reinforced (CCSR) aerial service wire.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 11 2011-01-01 2011-01-01 false Copper coated steel reinforced (CCSR) aerial service wire. 1755.702 Section 1755.702 Agriculture Regulations of the Department of Agriculture (Continued..., ACCEPTABLE MATERIALS, AND STANDARD CONTRACT FORMS § 1755.702 Copper coated steel reinforced (CCSR)...

  1. 7 CFR 1755.702 - Copper coated steel reinforced (CCSR) aerial service wire.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 11 2013-01-01 2013-01-01 false Copper coated steel reinforced (CCSR) aerial service wire. 1755.702 Section 1755.702 Agriculture Regulations of the Department of Agriculture (Continued..., ACCEPTABLE MATERIALS, AND STANDARD CONTRACT FORMS § 1755.702 Copper coated steel reinforced (CCSR)...

  2. 7 CFR 1755.702 - Copper coated steel reinforced (CCSR) aerial service wire.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 11 2010-01-01 2010-01-01 false Copper coated steel reinforced (CCSR) aerial service wire. 1755.702 Section 1755.702 Agriculture Regulations of the Department of Agriculture (Continued..., ACCEPTABLE MATERIALS, AND STANDARD CONTRACT FORMS § 1755.702 Copper coated steel reinforced (CCSR)...

  3. 7 CFR 1755.702 - Copper coated steel reinforced (CCSR) aerial service wire.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 11 2012-01-01 2012-01-01 false Copper coated steel reinforced (CCSR) aerial service wire. 1755.702 Section 1755.702 Agriculture Regulations of the Department of Agriculture (Continued..., ACCEPTABLE MATERIALS, AND STANDARD CONTRACT FORMS § 1755.702 Copper coated steel reinforced (CCSR)...

  4. Method of making metal matrix composites reinforced with ceramic particulates

    DOEpatents

    Cornie, James A.; Kattamis, Theodoulos; Chambers, Brent V.; Bond, Bruce E.; Varela, Raul H.

    1989-01-01

    Composite materials and methods for making such materials are disclosed in which dispersed ceramic particles are at chemical equilibrium with a base metal matrix, thereby permitting such materials to be remelted and subsequently cast or otherwise processed to form net weight parts and other finished (or semi-finished) articles while maintaining the microstructure and mechanical properties (e.g. wear resistance or hardness) of the original composite. The composite materials of the present invention are composed of ceramic particles in a base metal matrix. The ceramics are preferably carbides of titanium, zirconium, tungsten, molybdenum or other refractory metals. The base metal can be iron, nickel, cobalt, chromium or other high temperature metal and alloys thereof. For ferrous matrices, alloys suitable for use as the base metal include cast iron, carbon steels, stainless steels and iron-based superalloys.

  5. Method of making metal matrix composites reinforced with ceramic particulates

    DOEpatents

    Cornie, J.A.; Kattamis, T.; Chambers, B.V.; Bond, B.E.; Varela, R.H.

    1989-08-01

    Composite materials and methods for making such materials are disclosed in which dispersed ceramic particles are at chemical equilibrium with a base metal matrix, thereby permitting such materials to be remelted and subsequently cast or otherwise processed to form net weight parts and other finished (or semi-finished) articles while maintaining the microstructure and mechanical properties (e.g. wear resistance or hardness) of the original composite. The composite materials of the present invention are composed of ceramic particles in a base metal matrix. The ceramics are preferably carbides of titanium, zirconium, tungsten, molybdenum or other refractory metals. The base metal can be iron, nickel, cobalt, chromium or other high temperature metal and alloys thereof. For ferrous matrices, alloys suitable for use as the base metal include cast iron, carbon steels, stainless steels and iron-based superalloys. 2 figs.

  6. Ductility of a continuous fiber reinforced aluminum matrix composite

    NASA Technical Reports Server (NTRS)

    Jansson, S.; Leckie, Frederick A.

    1991-01-01

    The transverse properties of an aluminum alloy metal matrix composite reinforced by continuous alumina fibers have been investigated. The composite is subjected to both mechanical and cyclic thermal loading. The ductility can vary by an order of magnitude according to the operating conditions. For high mechanical and low thermal loading the ductility is small, for low mechanical and high thermal loading the ductility is an order of magnitude higher. Experiments on a beam in bending confirm that the ductility is strongly dependent on the loading conditions. The observations suggest a means of utilizing the inherent ductility of the matrix.

  7. Ceramic fiber reinforced glass-ceramic matrix composite

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P. (Inventor)

    1993-01-01

    A slurry of BSAS glass powders is cast into tapes which are cut to predetermined sizes. Mats of continuous chemical vapor deposition (CVD)-SiC fibers are alternately stacked with these matrix tapes. This tape-mat stack is warm-pressed to produce a 'green' composite which is heated to burn out organic constituents. The remaining interim material is then hot-pressed to form a BSAS glass-ceramic fiber-reinforced composite.

  8. Interfacial studies in fiber-reinforced thermoplastic-matrix composites

    SciTech Connect

    Brady, R.L.

    1989-01-01

    The major theme of this dissertation is structure/property relationships in fiber-reinforced thermoplastic-matrix composites. Effort has been focused on the interface: interfacial crystallization and fiber/matrix adhesion. Included are investigations on interfacial nucleation and morphology, measurement of fiber/matrix adhesion, effects of interfacial adsorption and crystallization on fiber/matrix adhesion, and composites reinforced with thermotropic liquid crystal copolyester fibers. Crystallization of a copolyester and polybutylene terephthalate with glass, carbon, or aramid fibers has been studied with regard to interfacial morphology. Techniques employed included hot-stage optical microscopy and differential scanning calorimetry. Nucleation by the fibers was found to be a general phenomenon. Morphology could be varied by changing the cooling rate. In order to better monitor fiber /matrix adhesion, a buckled plate test has been developed. The test measures transverse toughness as the parameter characterizing interfacial adhesion in unidirectional, continuous-fiber composites. The test is simple to perform yet has advantages over other interfacial evaluation techniques. The buckled plate test was found to be a sensitive measure of fiber/matrix adhesion. The buckled plate test has been used along with the transverse tensile test to examine how interfacial adsorption and crystallization affect fiber/matrix adhesion in polycarbonate/carbon fiber composites. Adsorption was found to be of primary importance in developing adhesion, while crystallization is a secondary effect. The toughness data have been fit successfully for annealing time and temperature dependence. The dependence of adsorption and transverse toughness on matrix molecular weight was found to be large, with higher molecular weights adsorbing more effectively.

  9. Cathodic protection of steel reinforced concrete facilitated by using carbon fiber reinforced mortar or concrete

    SciTech Connect

    Hou, J.; Chung, D.D.L.

    1997-05-01

    Due to the decrease in volume electrical resistivity associated with carbon fiber addition (0.35 vol.%) to concrete (embedding steel rebar), concrete containing carbon fibers and silica fume reduced by 18% the driving voltage required for cathodic protection compared to plain concrete, and by 28% compared to concrete with silica fume. Due to the decrease in resistivity associated with carbon fiber addition (1.1 vol.%) to mortar, overlay (embedding titanium wires for electrical contacts to steel reinforced concrete) in the form of mortar containing carbon fibers and latex reduced by the 10% the driving voltage required for cathodic protection, compared to plain mortar overlay. In spite of the low resistivity of mortar overlay with carbon fibers, cathodic protection required multiple metal electrical contacts embedded in the mortar at a spacing of 11 cm or less.

  10. Fatigue damage criteria - Matrix, fibers and interfaces of continuous fiber reinforced metal matrix composites

    NASA Technical Reports Server (NTRS)

    Johnson, W. S.

    1988-01-01

    Continuous fiber reinforced metal matrix composites (MMC) are projected for use in high temperature, stiffness critical parts that will be subjected to cyclic loadings. Depending on the relative fatigue behavior of the fiber and matrix, and the interface properties, the failure modes of MMC can be grouped into four catagories: (1) matrix dominated, (2) fiber dominated, (3) self-similar damage growth, and (4) fiber/matrix interfacial failures. These four types of damage are discussed and illustrated by examples. The emphasis is on the fatigue of unnotched laminates.

  11. Acoustic Nondestructive Testing and Measurement of Tension for Steel Reinforcing Members: Part 2 - Field Testing

    DTIC Science & Technology

    2014-09-01

    BACKGROUND: Many reinforced concrete structures contain embedded pre- and post- tensioned steel members that are subject to corrosion and fracturing...Tension for Steel Reinforcing Members Part 2 – Field Testing by Michael K. McInerney PURPOSE: This Coastal and Hydraulics Engineering Technical...Specifically, the technology application addresses the problem of determining tension in concrete -embedded pre- and post-tensioned reinforcement rods

  12. The Use of Vitreous Enamel Coatings to Improve Bonding and Reduce Corrosion in Concrete Reinforcing Steel

    DTIC Science & Technology

    2009-02-01

    concrete apart • All normal reinforced concrete (cast-in-place and precast ) may have a short service life due to corrosion U S A r m y E n g i n e e...the Army, the Nation The Use of Vitreous Enamel Coatings to Improve Bonding and Reduce Corrosion in Concrete Reinforcing Steel Sean W. Morefield1...TITLE AND SUBTITLE The Use of Vitreous Enamel Coatings to Improve Bonding and Reduce Corrosion in Concrete Reinforcing Steel 5a. CONTRACT NUMBER

  13. Hypervelocity Impacts into Stainless-Steel Tubes Armored with Reinforced Beryllium

    DTIC Science & Technology

    1966-08-01

    INTO STAINLESS-STEEL TUBES ARMORED WITH REINFORCED BERYLLIUM) by A. R. McMillan General Motors Corporation James tk. Diedrich and Nestor Clough k Lewis...STAINLESS-STEEL TUBES ARMORED WITH REINFORCED BERYLLIUM By A. R. McMillan ɝi- General Motors Corporation -Defense Research Laboratories Santa Barbara...TUBES ARMORED WITH REINFORCED BERYLLIUM by A.R. McMilIan General Motors Corporation Defense Research Laboratories Santa Barbara, California James H

  14. 75 FR 7562 - Certain Steel Concrete Reinforcing Bars From Turkey: Notice of Court Decision Not in Harmony With...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-02-22

    ... International Trade Administration Certain Steel Concrete Reinforcing Bars From Turkey: Notice of Court Decision... certain steel concrete reinforcing bars (rebar) from Turkey covering the period of review (POR) of April 1, 2003, through March 31, 2004. See Certain Steel Concrete Reinforcing Bars From Turkey; Final...

  15. 75 FR 22552 - Certain Steel Concrete Reinforcing Bars from Turkey; Notice of Amended Final Results Pursuant to...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-04-29

    ... International Trade Administration Certain Steel Concrete Reinforcing Bars from Turkey; Notice of Amended Final... Department) in the 2003-2004 administrative review of certain steel concrete of reinforcing bars (rebar) from...) of April 1, 2003, through March 31, 2004. See Certain Steel Concrete Reinforcing Bars From...

  16. 75 FR 47260 - Certain Steel Concrete Reinforcing Bars from Turkey: Notice of Amended Final Results Pursuant to...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-08-05

    ... International Trade Administration (A-489-807) Certain Steel Concrete Reinforcing Bars from Turkey: Notice of...) in the 2005-2006 administrative review of certain steel concrete reinforcing bars (rebar) from Turkey..., through March 31, 2006. See Certain Steel Concrete Reinforcing Bars From Turkey; Final Results of...

  17. 77 FR 39254 - Steel Concrete Reinforcing Bar From Belarus, China, Indonesia, Latvia, Moldova, Poland, and...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-07-02

    ... Ukraine; Institution of Five-Year Reviews Concerning the Antidumping Duty Orders on Steel Concrete... determine whether revocation of the antidumping duty orders on steel concrete reinforcing bar from Belarus..., 2001, the Department of Commerce (``Commerce'') issued antidumping duty orders on imports of steel...

  18. 78 FR 41079 - Steel Concrete Reinforcing Bar From Belarus, China, Indonesia, Latvia, Moldova, Poland, and Ukraine

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-07-09

    ... COMMISSION Steel Concrete Reinforcing Bar From Belarus, China, Indonesia, Latvia, Moldova, Poland, and... Tariff Act of 1930 (19 U.S.C. 1675(c)), that revocation of the antidumping duty orders on steel concrete... views of the Commission are contained in USITC Publication 4409 (July 2013), entitled Steel...

  19. 78 FR 43858 - Steel Concrete Reinforcing Bars From Belarus, Indonesia, Latvia, Moldova, Poland, the People's...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-07-22

    ...] Steel Concrete Reinforcing Bars From Belarus, Indonesia, Latvia, Moldova, Poland, the People's Republic... Department of Commerce (``Department'') that revocation of the antidumping duty orders \\1\\ on steel concrete... of the continuation of the antidumping duty orders. \\1\\ See Antidumping Duty Orders: Steel...

  20. Thermomechanical fatigue cracking in fiber reinforced metal-matrix composites

    NASA Astrophysics Data System (ADS)

    Bao, G.; McMeeking, R. M.

    1995-09-01

    A theoretical model is developed for thermomechanical fatigue cracking in fiber reinforced metal-matrix composites. Interfacial debonding is assumed to occur readily, allowing fibers to slide relative to the matrix resisted by a uniform shear stress. The fibers therefore bridge any matrix crack which develops. The crack bridging traction law is obtained, including the effect of thermal expansion mismatch between the fiber and the matrix and a temperature dependence of the frictional shear stress. Any combination of thermal and mechanical cycling is considered as long as the slip zone along the fiber increases in length monotonically during each increment of cycling. However, for clarity, the results are presented in terms of in-phase and out-of-phase cycling of the thermal and mechanical loads at the same frequency. For each case, the stress distributions in the bridging zone as well as the stress intensity factors at the crack tip are computed for relevant regimes of the thermal and mechanical loading conditions. Predictions are made of the matrix fatigue crack growth under combined thermal and mechanical loading conditions. It is found that when the thermal expansion coefficient of the fiber is less than that of the matrix, a significant increase in the crack growth rate results in out-of-phase thermomechanical fatigue. On the other hand, there is decreased tendency for fibers to fail in this case. For in-phase thermomechanical fatigue, the crack growth rate is reduced but the stress in the fiber is larger than that due to mechanical loading alone, resulting in an increased tendency for fiber failure. The implications for life prediction for fiber reinforced metal-matrix composites are discussed.

  1. Tungsten fiber reinforced copper matrix composites: A review

    NASA Technical Reports Server (NTRS)

    Mcdanels, David L.

    1989-01-01

    Tungsten fiber reinforced copper matrix (W/Cu) composites have served as an ideal model system with which to analyze the properties of metal matrix composites. A series of research programs were conducted to investigate the stress-strain behavior of W/Cu composites; the effect of fiber content on the strength, modulus, and conductivity of W/Cu composites; and the effect of alloying elements on the behavior of tungsten wire and of W/Cu composites. Later programs investigated the stress-rupture, creep, and impact behavior of these composites at elevated temperatures. Analysis of the results of these programs as allows prediction of the effects of fiber properties, matrix properties, and fiber content on the properties of W/Cu composites. These analyses form the basis for the rule-of-mixtures prediction of composite properties which was universally adopted as the criteria for measuring composite efficiency. In addition, the analyses allows extrapolation of potential properties of other metal matrix composites and are used to select candidate fibers and matrices for development of tungsten fiber reinforced superalloy composite materials for high temperature aircraft and rocket engine turbine applications. The W/Cu composite efforts are summarized, some of the results obtained are described, and an update is provided on more recent work using W/Cu composites as high strength, high thermal conductivity composite materials for high heat flux, elevated temperature applications.

  2. Shear degradation in fiber reinforced laminates due to matrix damage

    NASA Astrophysics Data System (ADS)

    Salavatian, Mohammedmahdi

    The objective of this study was to develop and implement a shear modulus degradation model to improve the failure analysis of the fiber reinforced composite structures. Matrix damage, involving transverse and shear cracks, is a common failure mode for composite structures, yet little is known concerning their interaction. To understand the material behavior after matrix failure, the nonlinear response of the composite laminate was studied using pressure vessels made from a [+/-o] bias orientation, which tend to exhibit a matrix dominated failure. The result of this work showed laminate matrix hardening in shear and softening in the transverse direction. A modified Iosipescu coupon was proposed to study the evolution of shear and transverse damage and their mutual effects. The proposed method showed good agreement with tubular results and has advantages of simplified specimen fabrication using standard test fixtures. The proposed method was extended by introducing a novel experimental technique to study the shear degradation model under biaxial loading. Experimental results of the transverse modulus reduction were in good agreement with material degradation models, while the predicted shear modulus reduction was higher than experiment. The discrepancy between available models and observations was due to the presence of a traction between the crack surfaces. Accordingly, a closed form solution was proposed for the shear stress-strain field of a cracked laminate by replacing the cracks with cohesive zones. The constitutive equations of the crack laminate were derived including the effects of internal tractions and transverse stress on the shear modulus. The proposed analytical model was shown to be the most comprehensive model for shear modulus degradation reduction of the fiber reinforced laminates. A numerical implementation of the shear degradation model was done using continuum damage mechanics. Through this work it was shown the common assumption of a linear

  3. Matrix cracking of fiber-reinforced ceramic composites in shear

    NASA Astrophysics Data System (ADS)

    Rajan, Varun P.; Zok, Frank W.

    2014-12-01

    The mechanics of cracking in fiber-reinforced ceramic matrix composites (CMCs) under general loadings remains incomplete. The present paper addresses one outstanding aspect of this problem: the development of matrix cracks in unidirectional plies under shear loading. To this end, we develop a model based on potential energy differences upstream and downstream of a fully bridged steady-state matrix crack. Through a combination of analytical solutions and finite element simulations of the constituent stresses before and after cracking, we identify the dominant stress components that drive crack growth. We show that, when the axial slip lengths are much larger than the fiber diameter and when interfacial slip precedes cracking, the shear stresses in the constituents are largely unaffected by the presence of the crack; the changes that do occur are confined to a 'core' region within a distance of about one fiber diameter from the crack plane. Instead, the driving force for crack growth derives mainly from the axial stresses-tensile in the fibers and compressive in the matrix-that arise upon cracking. These stresses are well-approximated by solutions based on shear-lag analysis. Combining these solutions with the governing equation for crack growth yields an analytical estimate of the critical shear stress for matrix cracking. An analogous approach is used in deriving the critical stresses needed for matrix cracking under arbitrary in-plane loadings. The applicability of these results to cross-ply CMC laminates is briefly discussed.

  4. Load carrying capacity of RCC beams by replacing steel reinforcement bars with shape memory alloy bars

    NASA Astrophysics Data System (ADS)

    Bajoria, Kamal M.; Kaduskar, Shreya S.

    2016-04-01

    In this paper the structural behavior of reinforced concrete (RC) beams with smart rebars under two point loading system has been numerically studied, using Finite Element Method. The material used in this study is Super-elastic Shape Memory Alloys (SE SMAs) which contains nickel and titanium. In this study, different quantities of steel and SMA rebars have been used for reinforcement and the behavior of these models under two point bending loading system is studied. A comparison of load carrying capacity for the model between steel reinforced concrete beam and the beam reinforced with S.M.A and steel are performed. The results show that RC beams reinforced with combination of shape memory alloy and steel show better performance.

  5. Evaluating cover depth of steel fiber reinforced concrete using impact-echo testing

    NASA Astrophysics Data System (ADS)

    Lin, Yu-Feng

    2014-04-01

    The purpose of this research is to estimate of the cover depth of steel fiber reinforced concrete using the impact-echo testing. In order to evaluate the security of the construction, usually need to estimate the cover depth of the reinforced concrete. At present, the examination technique of the cover depth of the reinforced concrete without the steel fiber is mainly applied in the magnetic and electrical methods, its rapid detection and good results. But the research of the reactive powder concrete be gradually progress, with the steel fiber concrete structure will be increased, if should still operate the examination with the magnetic and electrical methods, theoretically the steel fiber will have the interference to its electromagnetism field. Therefore, this research designs four kinds of reinforced concrete plate that include different steel fiber contents, to evaluate test results of estimate of the cover depth of the reinforcing bar. The results showed that: estimate of the cover depth of steel fiber reinforced concrete reinforcing bar using the impact-echo testing, the variety of the steel fiber content does not have much influence, the test measurement error within ± 10%, and the most important source of uncertainty is the velocity of concrete.

  6. A micromorphic model for steel fiber reinforced concrete.

    PubMed

    Oliver, J; Mora, D F; Huespe, A E; Weyler, R

    2012-10-15

    A new formulation to model the mechanical behavior of high performance fiber reinforced cement composites with arbitrarily oriented short fibers is presented. The formulation can be considered as a two scale approach, in which the macroscopic model, at the structural level, takes into account the mesostructural phenomenon associated with the fiber-matrix interface bond/slip process. This phenomenon is contemplated by including, in the macroscopic description, a micromorphic field representing the relative fiber-cement displacement. Then, the theoretical framework, from which the governing equations of the problem are derived, can be assimilated to a specific case of the material multifield theory. The balance equation derived for this model, connecting the micro stresses with the micromorphic forces, has a physical meaning related with the fiber-matrix bond slip mechanism. Differently to previous procedures in the literature, addressed to model fiber reinforced composites, where this equation has been added as an additional independent ingredient of the methodology, in the present approach it arises as a natural result derived from the multifield theory. Every component of the composite is defined with a specific free energy and constitutive relation. The mixture theory is adopted to define the overall free energy of the composite, which is assumed to be homogeneously constituted, in the sense that every infinitesimal volume is occupied by all the components in a proportion given by the corresponding volume fraction. The numerical model is assessed by means of a selected set of experiments that prove the viability of the present approach.

  7. Mechanical Behavior of Stainless Steel Fiber-Reinforced Composites Exposed to Accelerated Corrosion

    PubMed Central

    O’Brien, Caitlin; McBride, Amanda; E. Zaghi, Arash; Burke, Kelly A.; Hill, Alex

    2017-01-01

    Recent advancements in metal fibers have introduced a promising new type of stainless steel fiber with high stiffness, high failure strain, and a thickness < 100 μm (<0.00394 in.) that can be utilized in a steel fiber-reinforced polymer. However, stainless steel is known to be susceptible to pitting corrosion. The main goal of this study is to compare the impact of corrosion on the mechanical properties of steel fiber-reinforced composites with those of conventional types of stainless steel. By providing experimental evidences, this study may promote the application of steel fiber-reinforced composite as a viable alternative to conventional metals. Samples of steel fiber-reinforced polymer and four different types of stainless steel were subjected to 144 and 288 h of corrosion in ferric chloride solution to simulate accelerated corrosion conditions. The weight losses due to corrosion were recorded. The corroded and control samples were tested under monotonic tensile loading to measure the ultimate stresses and strains. The effect of corrosion on the mechanical properties of the different materials was evaluated. The digital image correlation (DIC) technique was used to investigate the failure mechanism of the corrosion-damaged specimens. Overall, steel fiber-reinforced composites had the greatest corrosion resistance. PMID:28773132

  8. Mechanical Behavior of Stainless Steel Fiber-Reinforced Composites Exposed to Accelerated Corrosion.

    PubMed

    O'Brien, Caitlin; McBride, Amanda; E Zaghi, Arash; Burke, Kelly A; Hill, Alex

    2017-07-08

    Recent advancements in metal fibers have introduced a promising new type of stainless steel fiber with high stiffness, high failure strain, and a thickness < 100 μm (<0.00394 in.) that can be utilized in a steel fiber-reinforced polymer. However, stainless steel is known to be susceptible to pitting corrosion. The main goal of this study is to compare the impact of corrosion on the mechanical properties of steel fiber-reinforced composites with those of conventional types of stainless steel. By providing experimental evidences, this study may promote the application of steel fiber-reinforced composite as a viable alternative to conventional metals. Samples of steel fiber-reinforced polymer and four different types of stainless steel were subjected to 144 and 288 h of corrosion in ferric chloride solution to simulate accelerated corrosion conditions. The weight losses due to corrosion were recorded. The corroded and control samples were tested under monotonic tensile loading to measure the ultimate stresses and strains. The effect of corrosion on the mechanical properties of the different materials was evaluated. The digital image correlation (DIC) technique was used to investigate the failure mechanism of the corrosion-damaged specimens. Overall, steel fiber-reinforced composites had the greatest corrosion resistance.

  9. Effect of matrix on the dry friction coefficient of unidirectional fiber-reinforced composite

    NASA Astrophysics Data System (ADS)

    Vettegren, V. I.; Savitskii, A. V.; Lyashkov, A. I.; Mamalimov, R. I.

    2008-10-01

    The coefficients of dry rest (μ0) and sliding (μ s ) friction on a polished disk made of quenched steel have been measured for various polymer matrices and fibers and for a composite unidirectionally reinforced with poly(amidobenzimidazole) (PABI) fibers. It is established that μ0 > μ s for matrices and fibers with glass transition temperatures T g below room temperature T R , otherwise μ0 ≈ μ s . This effect is explained by a sharp growth in the plasticity of polymers at T g , which leads to an increase in the polymer-steel contact area. For a composite with T g > T R , the dry friction coefficients obey the relation μ0 ≈ μ s ≈ μ e / C, where μ e is the coefficients of sliding friction of PABI fibers and C is their concentration. For T g < T R (plastic matrix), the friction coefficients of the composite and matrix are close because the latter cannot hold the fiber ends during friction. As a result, they are bent and aligned along the matrix surface or embedded in the surface layer.

  10. Design guidelines for steel-reinforced polymer concrete using resins based on recycled PET

    SciTech Connect

    Rebeiz, K.S.; Fowler, D.W.

    1996-10-01

    Very little research has been done on the structural behavior of steel-reinforced polymer concrete (PC). In all the previous studies, it was generally assumed that the structural behavior of reinforced PC is similar to the structural behavior of reinforced portland cement concrete because both are composite materials consisting of a binder and inorganic aggregates. However, the design equations developed for steel-reinforced portland cement concrete yield very conservative results when applied to reinforced PC. The objective of this paper is to recommend simple, yet effective design guidelines in shear and flexure for steel-reinforced PC. The recommended design procedures are mostly based on test results performed on PC beams using resins based on recycled poly(ethyleneterephthalate), PET, plastic waste (the PET waste is mainly recovered from used beverage bottles). Previous studies have shown that polyester resins based on recycled PET can produce very good quality PC at a potentially lower cost.

  11. Bending Mechanical Behavior of Polyester Matrix Reinforced with Fique Fiber

    NASA Astrophysics Data System (ADS)

    Altoé, Giulio Rodrigues; Netto, Pedro Amoy; Barcelos, Mariana; Gomes, André; Margem, Frederico Muylaert; Monteiro, Sergio Neves

    Environmentally correct composites, made from natural fibers, are among the most investigated and applied today. In this paper, we investigate the mechanical behavior of polyester matrix composites reinforced with continuous fique fibers, through bending tensile tests. Specimens containing 0, 10, 20 and 30% in volume of fique fiber were aligned along the entire length of a mold to create plates of these composites, those plates were cut following the ASTM standard to obtained bending tests specimens. The test was conducted in a Instron Machine and the fractured specimens were analyzed by SEM, the results showed the increase in the materials tensile properties with the increase of fiber amount.

  12. Flexural Strength and Toughness of Austenitic Stainless Steel Reinforced High-Cr White Cast Iron Composite

    NASA Astrophysics Data System (ADS)

    Sallam, H. E. M.; Abd El-Aziz, Kh.; Abd El-Raouf, H.; Elbanna, E. M.

    2013-12-01

    Flexural behavior of high-Cr white cast iron (WCI) reinforced with different shapes, i.e., I- and T-sections, and volume fractions of austenitic stainless steel (310 SS) were examined under three-point bending test. The dimensions of casted beams used for bending test were (50 × 100 × 500 mm3). Carbon and alloying elements diffusion enhanced the metallurgical bond across the interface of casted beams. Carbon diffusion from high-Cr WCI into 310 SS resulted in the formation of Cr-carbides in 310 SS near the interface and Ni diffusion from 310 SS into high-Cr WCI led to the formation of austenite within a network of M7C3 eutectic carbides in high-Cr WCI near the interface. Inserting 310 SS plates into high-Cr WCI beams resulted in a significant improvement in their toughness. All specimens of this metal matrix composite failed in a ductile mode with higher plastic deformation prior to failure. The high-Cr WCI specimen reinforced with I-section of 310 SS revealed higher toughness compared to that with T-section at the same volume fraction. The presence of the upper flange increased the reinforcement efficiency for delaying the crack growth.

  13. Creep behavior of tungsten fiber reinforced niobium metal matrix composites

    NASA Technical Reports Server (NTRS)

    Grobstein, Toni L.

    1992-01-01

    Tungsten fiber reinforced niobium metal matrix composites were evaluated for use in space nuclear power conversion systems. The composite panels were fabricated using the arc-spray monotape technique at the NASA Lewis Research Center. The creep behavior of W/Nb composite material was determined at 1400 and 1500 K in vacuum over a wide range of applied loads. The time to reach 1 percent strain, the time to rupture, and the minimum creep rate were measured. The W/Nb composites exceeded the properties of monolithic niobium alloys significantly even when compared creep strength also was evaluated. Kirkendall void formation was observed at the fiber/matrix interface; the void distribution differed depending the fiber orientation relative to the stress axis. A relationship was found between the fiber orientation and the creep strength.

  14. Creep behavior of tungsten fiber reinforced niobium metal matrix composites

    NASA Technical Reports Server (NTRS)

    Grobstein, T. L.

    1989-01-01

    Tungsten fiber reinforced niobium metal matrix composites were evaluated for use in space nuclear power conversion systems. The composite panels were fabricated using the arc-spray monotape technique at the NASA Lewis Research Center. The creep behavior of W/Nb composite material was determined at 1400 and 1500 K in vacuum over a wide range of applied loads. The time to reach 1 percent strain, the time to rupture, and the minimum creep rate were measured. The W/Nb composites exceeded the properties of monolithic niobium alloys significantly even when compared on a strength to density basis. The effect of fiber orientation on the creep strength also was evaluated. Kirkendall void formation was observed at the fiber/matrix interface; the void distribution differed depending on the fiber orientation relative to the stress axis. A relationship was found between the fiber orientation and the creep strength.

  15. Carbide-reinforced metal matrix composite by direct metal deposition

    NASA Astrophysics Data System (ADS)

    Novichenko, D.; Thivillon, L.; Bertrand, Ph.; Smurov, I.

    Direct metal deposition (DMD) is an automated 3D laser cladding technology with co-axial powder injection for industrial applications. The actual objective is to demonstrate the possibility to produce metal matrix composite objects in a single-step process. Powders of Fe-based alloy (16NCD13) and titanium carbide (TiC) are premixed before cladding. Volume content of the carbide-reinforced phase is varied. Relationships between the main laser cladding parameters and the geometry of the built-up objects (single track, 2D coating) are discussed. On the base of parametric study, a laser cladding process map for the deposition of individual tracks was established. Microstructure and composition of the laser-fabricated metal matrix composite objects are examined. Two different types of structures: (a) with the presence of undissolved and (b) precipitated titanium carbides are observed. Mechanism of formation of diverse precipitated titanium carbides is studied.

  16. Electrical behavior of carbon whisker reinforced elastomer matrix composites

    SciTech Connect

    Chellappa, V.; Chiou, Z.W.; Jang, B.Z.

    1994-12-31

    The electrical and mechanical properties of carbon whisker reinforced thermoplastic elastomer composites were investigated. The reinforcement whisker was made by a catalytic chemical vapor deposition (CCVD) process and the polymer matrix was from a thermoplastic elastomer (TPE, a butadiene-styrene block co-polymer). The electrical resistivity ({rho}) of the CCVD carbon whisker-elastomer composites can be varied by uniaxial deformation (10{sup 1}-10{sup 8}{Omega}-cm) and by changing the temperature (10{sup 1}-10{sup 5}{Omega}-cm). The temperature-resistivity studies indicate, that the resistivity of these composites depend on the physical property of the elastomer. The {rho} vs 1/T curves exhibit two distinct slopes intersected at the T{sub g} of the elastomer (-50{degrees}C). Further uniaxial deformation studies at room temperature (20{degrees}C) demonstrated that the resistivity increased exponentially with the deformation. The dependence of resistivity (or conductivity) of the composites with respect to deformation and temperature was explained on the basis of electron tunnelling induced conduction. CCVD carbon whiskers can be used as a reinforcement (filler) for the elastomer and can also make them electrically conductive.

  17. Use of steel fibres recovered from waste tyres as reinforcement in concrete: pull-out behaviour, compressive and flexural strength.

    PubMed

    Aiello, M A; Leuzzi, F; Centonze, G; Maffezzoli, A

    2009-06-01

    The increasing amount of waste tyres worldwide makes the disposition of tyres a relevant problem to be solved. In the last years over three million tons of waste tyres were generated in the EU states [ETRA, 2006. Tyre Technology International - Trends in Tyre Recycling. http://www.etra-eu.org]; most of them were disposed into landfills. Since the European Union Landfill Directive (EU Landfill, 1999) aims to significantly reduce the landfill disposal of waste tyres, the development of new markets for the tyres becomes fundamental. Recently some research has been devoted to the use of granulated rubber and steel fibres recovered from waste tyres in concrete. In particular, the concrete obtained by adding recycled steel fibres evidenced a satisfactory improvement of the fragile matrix, mostly in terms of toughness and post-cracking behaviour. As a consequence RSFRC (recycled steel fibres reinforced concrete) appears a promising candidate for both structural and non-structural applications. Within this context a research project was undertaken at the University of Salento (Italy) aiming to investigate the mechanical behaviour of concrete reinforced with RSF (recycled steel fibres) recovered from waste tyres by a mechanical process. In the present paper results obtained by the experimental work performed up to now are reported. In order to evaluate the concrete-fibres bond characteristics and to determine the critical fibre length, pull-out tests were initially carried out. Furthermore compressive strength of concrete was evaluated for different volume ratios of added RSF and flexural tests were performed to analyze the post-cracking behaviour of RSFRC. For comparison purposes, samples reinforced with industrial steel fibres (ISF) were also considered. Satisfactory results were obtained regarding the bond between recycled steel fibres and concrete; on the other hand compressive strength of concrete seems unaffected by the presence of fibres despite their irregular

  18. Test study on the impact damage performance of stainless steel reinforced concrete

    NASA Astrophysics Data System (ADS)

    Zhang, Guoxue; Xu, Shixiang

    2017-04-01

    In this study, in order to research the damage performance of stainless steel reinforced concrete under the action of repeated horizontal impact, an ultra-high drop hammer impact tester system was used for impact tests on ordinary reinforced concrete bridge piers and stainless steel reinforced concrete bridge piers with equal longitudinal bar diameter. In addition, ultrasonic waves were adopted for damage testing. The results show that, after each impact, the elastic modulus of the specimen was decreased. With the improvement of impact energy, the damage degrees of the two groups of specimens were also increased. Under the same impact energy, the damage degrees of the stainless steel reinforced concrete bridge pier specimens were lower than those of the ordinary reinforced concrete bridge pier specimens with equal longitudinal bar diameters.

  19. Rapid Prototyping of Continuous Fiber Reinforced Ceramic Matrix Composites

    NASA Technical Reports Server (NTRS)

    Vaidyanathan, R.; Green, C.; Phillips, T.; Cipriani, R.; Yarlagadda, S.; Gillespie, J. W., Jr.; Effinger, M.; Cooper, K. C.

    2003-01-01

    For ceramics to be used as structural components in high temperature applications, their fracture toughness is improved by embedding continuous ceramic fibers. Ceramic matrix composite (CMC) materials allow increasing the overall operating temperature, raising the temperature safety margins, avoiding the need for cooling, and improving the damping capacity, while reducing the weight at the same time. They also need to be reliable and available in large quantities as well. In this paper, an innovative rapid prototyping technique to fabricate continuous fiber reinforced ceramic matrix composites is described. The process is simple, robust and will be widely applicable to a number of high temperature material systems. This technique was originally developed at the University of Delaware Center for Composite Materials (UD-CCM) for rapid fabrication of polymer matrix composites by a technique called automated tow placement or ATP. The results of mechanical properties and microstructural characterization are presented, together with examples of complex shapes and parts. It is believed that the process will be able to create complex shaped parts at an order of magnitude lower cost than current chemical vapor infiltration (CVI) and polymer impregnation and pyrolysis (PIP) processes.

  20. Rapid Prototyping of Continuous Fiber Reinforced Ceramic Matrix Composites

    NASA Technical Reports Server (NTRS)

    Vaidyanathan, R.; Green, C.; Phillips, T.; Cipriani, R.; Yarlagadda, S.; Gillespie, J.; Effinger, M.; Cooper, K. C.; Gordon, Gail (Technical Monitor)

    2002-01-01

    For ceramics to be used as structural components in high temperature applications, their fracture toughness is improved by embedding continuous ceramic fibers. Ceramic matrix composite (CMC) materials allow increasing the overall operating temperature, raising the temperature safety margins, avoiding the need for cooling, and improving the damping capacity, while reducing the weight at the same time. They also need to be reliable and available in large quantities as well. In this paper, an innovative rapid prototyping technique to fabricate continuous fiber reinforced ceramic matrix composites is described. The process is simple, robust and will be widely applicable to a number of high temperature material systems. This technique was originally developed at the University of Delaware Center for Composite Materials (UD-CCM) for rapid fabrication of polymer matrix composites by a technique called automated tow placement or ATP. The results of mechanical properties and microstructural characterization are presented, together with examples of complex shapes and parts. It is believed that the process will be able to create complex shaped parts at an order of magnitude lower cost than current CVI and PIP processes.

  1. Dual-nanoparticulate-reinforced aluminum matrix composite materials

    NASA Astrophysics Data System (ADS)

    Kwon, Hansang; Cho, Seungchan; Leparoux, Marc; Kawasaki, Akira

    2012-06-01

    Aluminum (Al) matrix composite materials reinforced with carbon nanotubes (CNT) and silicon carbide nanoparticles (nano-SiC) were fabricated by mechanical ball milling, followed by hot-pressing. Nano-SiC was used as an active mixing agent for dispersing the CNTs in the Al powder. The hardness of the produced composites was dramatically increased, up to eight times higher than bulk pure Al, by increasing the amount of nano-SiC particles. A small quantity of aluminum carbide (Al4C3) was observed by TEM analysis and quantified using x-ray diffraction. The composite with the highest hardness values contained some nanosized Al4C3. Along with the CNT and the nano-SiC, Al4C3 also seemed to play a role in the enhanced hardness of the composites. The high energy milling process seems to lead to a homogeneous dispersion of the high aspect ratio CNTs, and of the nearly spherical nano-SiC particles in the Al matrix. This powder metallurgical approach could also be applied to other nanoreinforced composites, such as ceramics or complex matrix materials.

  2. Strength and Fracture Behavior of a Particle-Reinforced Transformation-Toughened Trip Steel/ZrO2 Composite

    NASA Astrophysics Data System (ADS)

    Eckner, R.; Krampf, M.; Segel, C.; Krüger, L.

    2016-01-01

    A newly developed particle-reinforced composite based on a high-alloy metastable CrMnNi TRIP steel was investigated concerning its fracture toughness behavior. The particle reinforcement was done using 10 vol.% of metastable MgO-partially-stabilized ZrO 2 (Mg-PSZ), which has the capability of a stress-induced transformation from the tetragonal to the monoclinic phase. Moreover, the alloying concept of the steel matrix enables a strain-induced transformation from the metastable γ-austenite phase to the α'-martensite phase leading to an increase in strength and ductility. Both effects in combination are intended to dissipate energy and increase the fracture toughness of the composite material (R-curve behavior). To evaluate the mechanical performance of the composite, tensile and fracture mechanics tests according to ISO 12135 were performed, followed by microstructural investigations. The fracture process was analyzed in an in situ tensile test with simultaneous recording of SEM micrographs and subsequent optical analysis of deformation. The results obtained show that the toughness of the composite is primarily determined by the presence of reinforcement particles. The low interfacial strength between the steel and ceramic associated with small interparticle spaces leads to an accelerated fracture process and a low overall toughness. This behavior is amplified as soon as particle clusters are formed during processing.

  3. Mechanics of Matrix Cracking in Brittle-Matrix Fibre-Reinforced Composites

    NASA Astrophysics Data System (ADS)

    McCartney, L. N.

    1987-02-01

    Energy-balance calculations for a continuum model of cracking in a uniaxially fibre-reinforced composite having a brittle matrix are presented. It is assumed that the fibres are strong enough to remain intact when the matrix cracks across the entire cross section of the composite. By equating the energy availability for the cracking of continuum and discrete fibre models it is shown how the crack boundary condition relating fibre stress to crack opening must be selected. It is confirmed that the Griffith fracture criterion is valid for matrix cracking in composites. By considering the energy balance of long cracks it is shown that the limiting value of the stress intensity factor is independent of crack length and that it predicts a matrix-cracking strain that is consistent with the known result. An improved numerical method is described for solving a crack problem arising from the study of the cracking of brittle-matrix composites. Numerical results of high accuracy are obtained, which show how the cracking stress is related to the size of a pre-existing defect. Of special significance is the prediction of the correct threshold stress (i.e. matrix-cracking stress) below which matrix cracking is impossible no matter how large the pre-existing defect.

  4. Optimization of Al Matrix Reinforced with B4C Particles

    NASA Astrophysics Data System (ADS)

    Shabani, Mohsen Ostad; Mazahery, Ali

    2013-02-01

    In the current study, abrasive wear resistance and mechanical properties of A356 composite reinforced with B4C particulates were investigated. A center particle swarm optimization algorithm (CenterPSO) is proposed to predict the optimal process conditions in fabrication of aluminum matrix composites. Unlike other ordinary particles, the center particle has no explicit velocity and is set to the center of the swarm at every iteration. Other aspects of the center particle are the same as that of the ordinary particle, such as fitness evaluation and competition for the best particle of the swarm. Because the center of the swarm is a promising position, the center particle generally gets good fitness value. More importantly, due to frequent appearance as the best particle of swarm, it often attracts other particles and guides the search direction of the whole swarm.

  5. Flexural analysis of palm fiber reinforced hybrid polymer matrix composite

    NASA Astrophysics Data System (ADS)

    Venkatachalam, G.; Gautham Shankar, A.; Raghav, Dasarath; Santhosh Kiran, R.; Mahesh, Bhargav; Kumar, Krishna

    2015-07-01

    Uncertainty in availability of fossil fuels in the future and global warming increased the need for more environment friendly materials. In this work, an attempt is made to fabricate a hybrid polymer matrix composite. The blend is a mixture of General Purpose Resin and Cashew Nut Shell Liquid, a natural resin extracted from cashew plant. Palm fiber, which has high strength, is used as reinforcement material. The fiber is treated with alkali (NaOH) solution to increase its strength and adhesiveness. Parametric study of flexure strength is carried out by varying alkali concentration, duration of alkali treatment and fiber volume. Taguchi L9 Orthogonal array is followed in the design of experiments procedure for simplification. With the help of ANOVA technique, regression equations are obtained which gives the level of influence of each parameter on the flexure strength of the composite.

  6. Creep Forming of Carbon-Reinforced Ceramic-Matrix Composites

    NASA Technical Reports Server (NTRS)

    Vaughn, Wallace L.; Scotti, Stephan J.; Ashe, Melissa P.; Connolly, Liz

    2007-01-01

    A set of lecture slides describes an investigation of creep forming as a means of imparting desired curvatures to initially flat stock plates of carbon-reinforced ceramic-matrix composite (C-CMC) materials. The investigation is apparently part of a continuing effort to develop improved means of applying small CCMC repair patches to reinforced carbon-carbon leading edges of aerospace vehicles (e.g., space shuttles) prior to re-entry into the atmosphere of the Earth. According to one of the slides, creep forming would be an intermediate step in a process that would yield a fully densified, finished C-CMC part having a desired size and shape (the other steps would include preliminary machining, finish machining, densification by chemical vapor infiltration, and final coating). The investigation included experiments in which C-CMC disks were creep-formed by heating them to unspecified high temperatures for time intervals of the order of 1 hour while they were clamped into single- and double-curvature graphite molds. The creep-formed disks were coated with an oxidation- protection material, then subjected to arc-jet tests, in which the disks exhibited no deterioration after exposure to high-temperature test conditions lasting 490 seconds.

  7. 221-U Facility concrete and reinforcing steel evaluations specification for the canyon disposition initiative (CDI)

    SciTech Connect

    Baxter, J.T.

    1998-05-28

    This describes a test program to establish the in-situ material properties of the reinforced concrete in Building 221-U for comparison to the original design specifications. Field sampling and laboratory testing of concrete and reinforcing steel structural materials in Building 221-U for design verification will be undertaken. Forty seven samples are to be taken from radiologically clean exterior walls of the canyon. Laboratory testing program includes unconfined compressive strength of concrete cores, tensile strength of reinforcing steel, and petrographic examinations of concrete cores taken from walls below existing grade.

  8. Evaluation of passivation method and corrosion inhibitors for steel-reinforced concrete structures

    NASA Astrophysics Data System (ADS)

    Brown, Richard; Lee, K. Wayne; Cao, Yong

    1999-02-01

    Corrosion of reinforcing steel due to the ingression of chloride ions from deicing salt and/or seawater has been a major cause of the deterioration of reinforced concrete structures. Typically reinforcing steel is protected from corrosion by the formation of passive film because of highly alkaline concrete environment. The film can be damaged with the introduction of chloride ions to concrete, then corrosion occurs. There are mainly three approaches to tackle this problem, i.e., protective coating, cathodic protection and corrosion inhibitors.

  9. Graphite fiber reinforced thermoplastic glass matrix composites for use at 1000 F

    NASA Technical Reports Server (NTRS)

    Prewo, K. M.; Minford, E. J.

    1985-01-01

    The fabrication and properties of the graphite fiber reinforced glass matrix composite system are described. By reinforcing borosilicate glass with graphite fibers it has been possible to develop a composite whose properties can be compared favorably with resin matrix counterparts. Both high elastic modulus and strength can be obtained and maintained to temperatures of approximately 600 C. In addition, composite dimensional stability is superior to resin or metal matrix systems due to the low thermal expansion behavior of the glass matrix.

  10. Behavior of Concrete Panels Reinforced with Synthetic Fibers, Mild Steel, and GFRP Composites Subjected to Blasts

    SciTech Connect

    C. P. Pantelides; T. T. Garfield; W. D. Richins; T. K. Larson; J. E. Blakeley

    2012-03-01

    The paper presents experimental data generated for calibrating finite element models to predict the performance of reinforced concrete panels with a wide range of construction details under blast loading. The specimens were 1.2 m square panels constructed using Normal Weight Concrete (NWC) or Fiber Reinforced Concrete (FRC). FRC consisted of macro-synthetic fibers dispersed in NWC. Five types of panels were tested: NWC panels with steel bars; FRC panels without additional reinforcement; FRC panels with steel bars; NWC panels with glass fiber reinforced polymer (GFRP) bars; and NWC panels reinforced with steel bars and external GFRP laminates on both faces. Each panel type was constructed with three thicknesses: 152 mm, 254 mm, and 356 mm. FRC panels with steel bars had the best performance for new construction. NWC panels reinforced with steel bars and external GFRP laminates on both faces had the best performance for strengthening or rehabilitation of existing structures. The performance of NWC panels with GFRP bars was strongly influenced by the bar spacing. The behavior of the panels is classified in terms of damage using immediate occupancy, life safety, and near collapse performance levels. Preliminary dynamic simulations are compared to the experimental results.

  11. Behavior of Concrete Panels Reinforced with Synthetic Fibers, Mild Steel, and GFRP Composites Subjected to Blasts

    SciTech Connect

    C. P. Pantelides; T. T. Garfield; W. D. Richins; T. K. Larson; J. E. Blakeley

    2012-03-01

    The paper presents experimental data generated for calibrating finite element models to predict the performance of reinforced concrete panels with a wide range of construction details under blast loading. The specimens were 1.2 m square panels constructed using Normal Weight Concrete (NWC) or Fiber Reinforced Concrete (FRC). FRC consisted of macro-synthetic fibers dispersed in NWC. Five types of panels were tested: NWC panels with steel bars; FRC panels without additional reinforcement; FRC panels with steel bars; NWC panels with glass fiber reinforced polymer (GFRP) bars; and NWC panels reinforced with steel bars and external GFRP laminates on both faces. Each panel type was constructed with three thicknesses: 152 mm, 254 mm, and 356 mm. FRC panels with steel bars had the best performance for new construction. NWC panels reinforced with steel bars and external GFRP laminates on both faces had the best performance for strengthening or rehabilitation of existing structures. The performance of NWC panels with GFRP bars was strongly influenced by the bar spacing. The behavior of the panels is classified in terms of damage using immediate occupancy, life safety, and near collapse performance levels. Preliminary dynamic simulations are compared to the experimental results.

  12. Failure Characterization of a Fiber Reinforced Ceramic Matrix Composite with Circular Holes

    DTIC Science & Technology

    1991-12-01

    cyanoacrylate glue , one at the side of the hole (on the axis normal to the load direction) and one centered 0.9 cm from the center of the hole, midway between the...such as FormicaT), concrete reinforced with steel rods, and steel-belted tires. Even in nature, wood is a composite material, with cellulose fibers bound

  13. Nondestructive inspection of corrosion and delamination at the concrete-steel reinforcement interface

    NASA Astrophysics Data System (ADS)

    Miller, Tri Huu

    The proposed study explores the feasibility of detecting and quantifying corrosion and delamination (physical separation) at the interface between reinforcing steel bars and concrete using ultrasonic guided waves. The problem of corrosion of the reinforcing steel in structures has increased significantly in recent years. The emergence of this type of concrete deterioration, which was first observed in marine structures and chemical manufacturing plants, coincided with the increased applications of deicing salts (sodium and calcium chlorides) to roads and bridges during winter months in those states where ice and snow are of major concern. Concrete is strengthened by the inclusion of the reinforcement steel such as deformed or corrugated steel bars. Bonding between the two materials plays a vital role in maximizing performance capacity of the structural members. Durability of the structure is of concern when it is exposed to aggressive environments. Corrosion of reinforcing steel has led to premature deterioration of many concrete members before their design life is attained. It is therefore, important to be able to detect and measure the level of corrosion in reinforcing steel or delamination at the interface. The development and implementation of damage detection strategies, and the continuous health assessment of concrete structures then become a matter of utmost importance. The ultimate goal of this research is to develop a nondestructive testing technique to quantify the amount of corrosion in the reinforcing steel. The guided mechanical wave approach has been explored towards the development of such methodology. The use of an embedded ultrasonic network for monitoring corrosion in real structures is feasible due to its simplicity. The ultrasonic waves, specifically cylindrical guided waves can p ropagate a long distance along the reinforcing steel bars and are found to be sensitive to the interface conditions between steel bars and concrete. Ultrasonic

  14. Shock Interaction Studies on Glass Fibre Reinforced Epoxy Matrix Composites

    NASA Astrophysics Data System (ADS)

    Reddy, K. P. J.; Jagadeesh, G.; Jayaram, V.; Reddy, B. Harinath; Madhu, V.; Reddy, C. Jaya Rami

    Glass fibre reinforced polymer matrix composites are being extensively used for structural applications both in civil and defense sectors, owing to their high specific strength, stiffness and good energy absorbing capability. Understanding the dynamic response of these composites on shock loading is very essential for effective design of structures resistant to blast loads. In the present study, E- glass/epoxy composite laminate has been fabricated and evaluated for their mechanical properties such as tensile strength, flexural strength and inter laminar shear strength (ILSS). Further, dynamic response of E-glass laminates is presently studied by shock loading. When E-glass composite subjected to peak shock reflected pressure of 7.2 MPa and estimated temperature of about 14000 K for short duration, it underwent surface discolorations and charring of epoxy matrix. Post test analysis of the composite sample was carried out to study the damage analysis using Scanning Electron Microscope (SEM), changes in thermal properties of composites using Dynamic Mechanical Analyzer (DMA) and Thermo-Gravimetric Analyzer (TGA). The results of these investigations are discussed in this paper.

  15. Elasto-plastic analysis of interface layers for fiber reinforced metal matrix composites

    NASA Technical Reports Server (NTRS)

    Doghri, I.; Leckie, F. A.

    1991-01-01

    The mismatch in coefficients of thermal expansion (CTE) of fiber and matrix in metal matrix composites reinforced with ceramic fibers induces high thermal stresses in the matrix. Elasto-plastic analyses - with different degrees of simplification and modelization - show that an interface layer with a sufficiently high CTE can reduce the tensile hoop stress in the matrix substantially.

  16. [Study of an optical fiber grating sensor for monitoring corrosion of reinforcing steel].

    PubMed

    Li, Jun; Wu, Jin; Gao, Jun-qi

    2010-01-01

    Based on the principle of the fiber Bragg grating strain sensor as well as the volume expansion of the reinforcing steel due to corrosion, an optical fiber grating sensor for monitoring corrosion of reinforcing steel and the method of temperature compensation were studied in the present paper. The sensor construction is that one Bragg grating is stuck on the inner center of two bars against each other, and the reinforcement volume as well as the diameter will expand due to corrosion. Based upon sensing mechanism, monitoring will be carried out by transforming the diameter increase to the fiber strain, and as a result the degree and rate of reinforcement corrosion can be obtained. The principle of corrosion monitoring is that the strain induced by corrosion and temperature fluctuation is measured by a reinforcing steel fiber grating sensor. At the same time, the strain induced by temperature fluctuation is also measured by an individual stainless fiber grating sensor. Therefore by two independent fiber grating sensors, the volume changed by corrosion can be separated. By the concrete encapsulating and embedding method of FBG corrosion sensor, the degree of corrosion of reinforcing reinforcement will be measured directly, which is not affected by corrosion factors and can be used in the early corrosion monitoring of reinforcement in concrete structures. Finally the relationship between corrosion rate and shift in center wavelength was calibrated by experiment.

  17. Arrangement for connecting a fiber-reinforced plastic pipe to a stainless steel flange

    DOEpatents

    Allais, Arnaud; Hoffmann, Ernst

    2008-02-05

    Arrangement for connecting a fiber-reinforced plastic pipe (18) to a stainless steel flange (12, 16), in which the end of the fiber-reinforced plastic pipe (18) is accommodated in a ring-shaped groove (12a, 16a) in the flange (12, 16), the groove conforming to the dimensions of the fiber-reinforced plastic pipe (18), where the gap remaining between the end of the fiber-reinforced plastic pipe (18) and the ring-shaped groove (12a, 16a) is filled with a sealant (19).

  18. Evaluation of the Technical-Economic Potential of Particle- Reinforced Aluminum Matrix Composites and Electrochemical Machining

    NASA Astrophysics Data System (ADS)

    Schubert, A.; Götze, U.; Hackert-Oschätzchen, M.; Lehnert, N.; Herold, F.; Meichsner, G.; Schmidt, A.

    2016-03-01

    Compared to conventional cutting, the processing of materials by electrochemical machining offers some technical advantages like high surface quality, no thermal or mechanical impact on the work piece and preservation of the microstructure of the work piece material. From the economic point of view, the possibility of process parallelization and the absence of any process-related tool wear are mentionable advantages of electrochemical machining. In this study, based on experimental results, it will be evaluated to what extent the electrochemical machining is technically and economically suitable for the finish-machining of particle- reinforced aluminum matrix composites (AMCs). Initial studies showed that electrochemical machining - in contrast to other machining processes - has the potential to fulfil demanding requirements regarding precision and surface quality of products or components especially when applied to AMCs. In addition, the investigations show that processing of AMCs by electrochemical machining requires less energy than the electrochemical machining of stainless steel. Therefore, an evaluation of electrochemically machined AMCs - compared to stainless steel - from a technical and an economic perspective will be presented in this paper. The results show the potential of electro-chemically machined AMCs and contribute to the enhancement of instruments for technical-economic evaluations as well as a comprehensive innovation control.

  19. Wear Performance of A356 Matrix Composites Reinforced with Different Types of Reinforcing Particles

    NASA Astrophysics Data System (ADS)

    Akbari, Mostafa; Shojaeefard, Mohammad Hasan; Asadi, Parviz; Khalkhali, Abolfazl

    2017-09-01

    To improve the wear resistance of Al-Si alloys, different types of reinforcing particles such as SiC, TiC, ZrO2, and B4C were used to produce matrix composites by friction stir processing (FSP). First, microstructural properties of different locations of stir zone (SZ) in the FSPed specimens such as advancing side, retreating side, shoulder-affected area, and pin-affected area were investigated. The results demonstrate that Si particles size is not the same in different SZ subdomains. SEM investigation was performed in order to investigate the particles distribution in different areas of the SZ as well as bonding quality between particles and metal matrix. Hardness and wear tests were carried out to determine mechanical and wear properties of the composites. The pin-on-disk wear tests were performed at room temperature, with the normal applied loads of 5, 10, and 20 N and sliding speed of 1 and 2 m/s. All fabricated composites show higher resistance in wear than A356 alloy. Wear test results show, by increasing the normal load and sliding velocity, the wear loss weight of all composites increased gradually.

  20. Reuse of EAF Slag as Reinforcing Filler for Polypropylene Matrix Composites

    NASA Astrophysics Data System (ADS)

    Cornacchia, G.; Agnelli, S.; Gelfi, M.; Ramorino, G.; Roberti, R.

    2015-06-01

    Electric-arc furnace (EAF) slag, the by-product of steel fabricated at the EAF, is in most cases still sent to dumps, with serious environmental consequences. This work shows an innovative, economically convenient application for EAF slag: its use as reinforcing filler for polypropylene. Composites based on polypropylene containing 10-40 wt.% of EAF slag particles were prepared by melt compounding followed by injection molding. A physical-chemical analysis of the EAF slag was performed to determine microstructural features and main component phases. Leaching tests demonstrated that, although EAF slag can release small amounts of toxic elements, such as heavy metals, incorporating such material into the polymeric matrix immobilizes the heavy metals inside that matrix. The mechanical characterization of the polymer-based composites was performed. Incorporating EAF slag particles raises the Young's modulus and the tensile strength at yield, whereas elongation at break and the impact strength of the polymer-based composite are significantly reduced only when large amounts of filler are added, i.e., 30% or more.

  1. Shear Behavior Models of Steel Fiber Reinforced Concrete Beams Modifying Softened Truss Model Approaches

    PubMed Central

    Hwang, Jin-Ha; Lee, Deuck Hang; Ju, Hyunjin; Kim, Kang Su; Seo, Soo-Yeon; Kang, Joo-Won

    2013-01-01

    Recognizing that steel fibers can supplement the brittle tensile characteristics of concrete, many studies have been conducted on the shear performance of steel fiber reinforced concrete (SFRC) members. However, previous studies were mostly focused on the shear strength and proposed empirical shear strength equations based on their experimental results. Thus, this study attempts to estimate the strains and stresses in steel fibers by considering the detailed characteristics of steel fibers in SFRC members, from which more accurate estimation on the shear behavior and strength of SFRC members is possible, and the failure mode of steel fibers can be also identified. Four shear behavior models for SFRC members have been proposed, which have been modified from the softened truss models for reinforced concrete members, and they can estimate the contribution of steel fibers to the total shear strength of the SFRC member. The performances of all the models proposed in this study were also evaluated by a large number of test results. The contribution of steel fibers to the shear strength varied from 5% to 50% according to their amount, and the most optimized volume fraction of steel fibers was estimated as 1%–1.5%, in terms of shear performance. PMID:28788364

  2. Shear Behavior Models of Steel Fiber Reinforced Concrete Beams Modifying Softened Truss Model Approaches.

    PubMed

    Hwang, Jin-Ha; Lee, Deuck Hang; Ju, Hyunjin; Kim, Kang Su; Seo, Soo-Yeon; Kang, Joo-Won

    2013-10-23

    Recognizing that steel fibers can supplement the brittle tensile characteristics of concrete, many studies have been conducted on the shear performance of steel fiber reinforced concrete (SFRC) members. However, previous studies were mostly focused on the shear strength and proposed empirical shear strength equations based on their experimental results. Thus, this study attempts to estimate the strains and stresses in steel fibers by considering the detailed characteristics of steel fibers in SFRC members, from which more accurate estimation on the shear behavior and strength of SFRC members is possible, and the failure mode of steel fibers can be also identified. Four shear behavior models for SFRC members have been proposed, which have been modified from the softened truss models for reinforced concrete members, and they can estimate the contribution of steel fibers to the total shear strength of the SFRC member. The performances of all the models proposed in this study were also evaluated by a large number of test results. The contribution of steel fibers to the shear strength varied from 5% to 50% according to their amount, and the most optimized volume fraction of steel fibers was estimated as 1%-1.5%, in terms of shear performance.

  3. Reactive Silicate Coatings for Protecting and Bonding Reinforcing Steel in Cement-Based Composites

    DTIC Science & Technology

    2008-12-01

    Bentur, Diamond and Mindess , 1985; Wei, Mandel and Said, 1986; Horne, Richardson and Brydson, 2007). Most research have concluded that the...around a steel fiber. (after Bentur, Diamond and Mindess , 1985.) The ITZ is typically on the order of 100µm in thickness and the exact...International, West Conshohocken, PA. Bentur, A. Diamond, S. and Mindess , S., 1985: Cracking Processes in Steel Fibre Reinforced Cement Pastes

  4. A&M. TAN607. Construction detail showing structural steel framework with reinforcing ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    A&M. TAN-607. Construction detail showing structural steel framework with reinforcing steel in place prior to pouring concrete for biparting doors between hot shop and special equipment service (SES) room. Facing north. Hot shop to left, SES room to right. slot for north half of door shows at upper left of view. Date: May 21, 1954. INEEL negative no. 10548 - Idaho National Engineering Laboratory, Test Area North, Scoville, Butte County, ID

  5. Mechanical evaluation of hip cement spacer reinforcement with stainless steel Kirschner wires, titanium and carbon rods, and stainless steel mesh.

    PubMed

    Kaku, Nobuhiro; Tabata, Tomonori; Tsumura, Hiroshi

    2015-04-01

    In two-stage treatments for infections after total hip arthroplasty, antibiotic-loaded cement spacers help treat the infection by antibiotic elution and prevent contraction. However, such spacers are weak and may fracture while awaiting replacement, impairing functionality. We evaluated whether a Kirschner wire (K-wire) mounted into the spacer reinforced its strength along with the effects of the reinforcing material, position, and intensity. Spacers without reinforcing materials constituted the control group. As reinforcing materials, stainless steel K-wires (diameters 3 and 6 mm), titanium alloy and carbon fibers (diameter 3.175 mm), and stainless steel meshes (inner and outer diameters, 6 and 9 mm, respectively) were inserted into the spacer mold before filling with cement. The spacers complied with ISO 7206-4; a compressive load was applied using a testing machine with a velocity of 25.4 mm/min, and the maximum load was recorded. We used 1-3 K-wires positioned on the medial side, lateral side, neck only, and stem only and tested 3 specimens for each condition. The control group withstood the highest load. Stainless steel was the strongest material; 3-mm K-wires in the neck and lateral side withstood a higher load. The computed tomography (CT) imaging revealed a cavity between the K-wires and cement. When K-wires were inserted along the whole length, despite cement fractures, continuity was maintained because of the reinforcing materials. It is difficult to improve the reinforcing strength of spacers using K-wires; however, K-wires prevented dislocation of cement spacer fragments, which can help prevent contraction and facilitate spacer removal during replacement.

  6. Application of headed studs in steel fiber reinforced cementitious composite slab of steel beam-column connection

    NASA Astrophysics Data System (ADS)

    Yao, Cui; Nakashima, Masayoshi

    2012-03-01

    Steel fiber reinforced cementitous composites (SFRCC) is a promising material with high strength in both compression and tension compared with normal concrete. The ductility is also greatly improved because of 6% volume portion of straight steel fibers. A steel beam-column connection with Steel fiber reinforced cementitous composites (SFRCC) slab diaphragms is proposed to overcome the damage caused by the weld. The push-out test results suggested that the application of SFRCC promises larger shear forces transferred through headed studs allocated in a small area in the slab. Finite element models were developed to simulate the behavior of headed studs. The failure mechanism of the grouped arrangement is further discussed based on a series of parametric analysis. In the proposed connection, the SFRCC slab is designed as an exterior diaphragm to transfer the beam flange load to the column face. The headed studs are densely arranged on the beam flange to connect the SFRCC slab diaphragms and steel beams. The seismic performance and failure mechanism of the SFRCC slab diaphragm beam-column connection were investigated based on the cyclic loading test. Beam hinge mechanism was achieved at the end of the SFRCC slab diaphragm by using sufficient studs and appropriate rebars in the SFRCC slab.

  7. Experimental and analytical behavior of strengthened reinforced concrete columns with steel angles and strips

    NASA Astrophysics Data System (ADS)

    Khalifa, Essam S.; Al-Tersawy, Sherif H.

    2014-06-01

    The need of strengthening reinforced concrete columns, due to loss of strength and/or stiffness, is an essential requirement due to variation of the loads and environmental conditions applied on these columns. Steel jackets around the reinforced concrete (RC) columns are usually made by means of steel plates covering all over the column surface area. For the value of engineering purposes, another technique was developed using steel angles at the corners of the RC columns connected with discrete steel strips. In this paper, an experimental program is designed to evaluate the improvement in load-carrying capacity, stiffness and ductility of strengthened RC columns, concomitant with steel angles and strips. Despite of prevailing a substantially increased loading capacity and strength a pronounced enhancement in ductility and stiffness has been reported. A need for experimental test results with low value of concrete strength to mimic the local old-age structures condition that required strengthening in local countries. Seven columns specimens are tested to evaluate the strength improvement provided by steel strengthening of columns. The method of strengthened steel angles with strips is compared with another strengthening technique. This technique includes connected and unconnected steel-casing specimens. The observed experimental results describe load-shortening curves, horizontal strains in stirrups and steel strips, as well as description of failure mode. The extra-confinement pressure, due to existence of steel cage, of the strengthened RC column can be also observed from experimental results. The code provisions that predict the load-carrying capacity of the strengthened RC composite column has a discrepancy in the results. For this reason, an analytical model is developed in this paper to compare the code limit with experimental observed results. The proposed model accounts for the composite action for concrete confinement and enhancement of the local buckling

  8. Microstructure and mechanical behavior of metallic glass fiber-reinforced Al alloy matrix composites.

    PubMed

    Wang, Z; Georgarakis, K; Nakayama, K S; Li, Y; Tsarkov, A A; Xie, G; Dudina, D; Louzguine-Luzgin, D V; Yavari, A R

    2016-04-12

    Metallic glass-reinforced metal matrix composites are an emerging class of composite materials. The metallic nature and the high mechanical strength of the reinforcing phase offers unique possibilities for improving the engineering performance of composites. Understanding the structure at the amorphous/crystalline interfaces and the deformation behavior of these composites is of vital importance for their further development and potential application. In the present work, Zr-based metallic glass fibers have been introduced in Al7075 alloy (Al-Zn-Mg-Cu) matrices using spark plasma sintering (SPS) producing composites with low porosity. The addition of metallic glass reinforcements in the Al-based matrix significantly improves the mechanical behavior of the composites in compression. High-resolution TEM observations at the interface reveal the formation of a thin interdiffusion layer able to provide good bonding between the reinforcing phase and the Al-based matrix. The deformation behavior of the composites was studied, indicating that local plastic deformation occurred in the matrix near the glassy reinforcements followed by the initiation and propagation of cracks mainly through the matrix. The reinforcing phase is seen to inhibit the plastic deformation and retard the crack propagation. The findings offer new insights into the mechanical behavior of metal matrix composites reinforced with metallic glasses.

  9. Microstructure and mechanical behavior of metallic glass fiber-reinforced Al alloy matrix composites

    NASA Astrophysics Data System (ADS)

    Wang, Z.; Georgarakis, K.; Nakayama, K. S.; Li, Y.; Tsarkov, A. A.; Xie, G.; Dudina, D.; Louzguine-Luzgin, D. V.; Yavari, A. R.

    2016-04-01

    Metallic glass-reinforced metal matrix composites are an emerging class of composite materials. The metallic nature and the high mechanical strength of the reinforcing phase offers unique possibilities for improving the engineering performance of composites. Understanding the structure at the amorphous/crystalline interfaces and the deformation behavior of these composites is of vital importance for their further development and potential application. In the present work, Zr-based metallic glass fibers have been introduced in Al7075 alloy (Al-Zn-Mg-Cu) matrices using spark plasma sintering (SPS) producing composites with low porosity. The addition of metallic glass reinforcements in the Al-based matrix significantly improves the mechanical behavior of the composites in compression. High-resolution TEM observations at the interface reveal the formation of a thin interdiffusion layer able to provide good bonding between the reinforcing phase and the Al-based matrix. The deformation behavior of the composites was studied, indicating that local plastic deformation occurred in the matrix near the glassy reinforcements followed by the initiation and propagation of cracks mainly through the matrix. The reinforcing phase is seen to inhibit the plastic deformation and retard the crack propagation. The findings offer new insights into the mechanical behavior of metal matrix composites reinforced with metallic glasses.

  10. Microstructure and mechanical behavior of metallic glass fiber-reinforced Al alloy matrix composites

    PubMed Central

    Wang, Z.; Georgarakis, K.; Nakayama, K. S.; Li, Y.; Tsarkov, A. A.; Xie, G.; Dudina, D.; Louzguine-Luzgin, D. V.; Yavari, A. R.

    2016-01-01

    Metallic glass-reinforced metal matrix composites are an emerging class of composite materials. The metallic nature and the high mechanical strength of the reinforcing phase offers unique possibilities for improving the engineering performance of composites. Understanding the structure at the amorphous/crystalline interfaces and the deformation behavior of these composites is of vital importance for their further development and potential application. In the present work, Zr-based metallic glass fibers have been introduced in Al7075 alloy (Al-Zn-Mg-Cu) matrices using spark plasma sintering (SPS) producing composites with low porosity. The addition of metallic glass reinforcements in the Al-based matrix significantly improves the mechanical behavior of the composites in compression. High-resolution TEM observations at the interface reveal the formation of a thin interdiffusion layer able to provide good bonding between the reinforcing phase and the Al-based matrix. The deformation behavior of the composites was studied, indicating that local plastic deformation occurred in the matrix near the glassy reinforcements followed by the initiation and propagation of cracks mainly through the matrix. The reinforcing phase is seen to inhibit the plastic deformation and retard the crack propagation. The findings offer new insights into the mechanical behavior of metal matrix composites reinforced with metallic glasses. PMID:27067824

  11. The Impact of Corrosion on the Mechanical Behavior of Welded Splices of Reinforcing Steel S400 and B500c

    NASA Astrophysics Data System (ADS)

    Apostolopoulos, Ch. Alk.; Michalopoulos, D.; Dimitrov, L.

    2008-02-01

    The reinforcing steel, used in concrete structures, when corroded causes reduction of the strength properties and especially drastic reduction of ductility. Steel corrosion constitutes an important factor of progressive devaluation of its mechanical properties and serious reduction of the integrity of structures. The problem becomes more evident specifically for structures near coastal areas where salt corrosion is predominant. Reinforced concrete columns and beams are quite often extended by welding new steel reinforcement to the already corroded existing steel. In the present article the impact of corrosion on the mechanical properties of welded splices of reinforcing Steel S400 and B500c is examined. An experimental investigation was conducted and tensile and compressive results are presented for welded precorroded S400 and noncorroded B500c steel splices. The mechanical behavior of welded splices in tension are different in compression and depend strongly on the level of corrosion of the S400 bars.

  12. Corrosion resistance and development length of steel reinforcement with cementitious coatings

    NASA Astrophysics Data System (ADS)

    Pei, Xiaofei

    This research program focused on the corrosion resistance and development length of reinforcing steel coated with Cementitious Capillary Crystalline Waterproofing (CCCW) materials. The first part of this research program involved using the half-cell potential method to evaluate the corrosion resistance of CCCW coating materials. One hundred and two steel bars were embedded in concrete cylinders and monitored. In total, 64 steel reinforcing bars were coated with CCCW prior to embedment, 16 mortar cylinders were externally coated with CCCW, and 22 control (uncoated) samples were tested. All the samples were immersed in a 3.5% concentration chloride solution for a period of one year. Three coating types were studied: CCCW-B, CCCW-B+ C and CCCW-C+D. The test results showed that the CCCW coating materials delayed the corrosion activity to varying degrees. In particular, CCCW-C+D applied on the reinforcing steel surface dramatically delayed the corrosion activity when compared to the control samples. After being exposed to the chloride solution for a period of one year, no sign of corrosion was observed for the cylinders where the concrete surface was coated. The second part of this research evaluated the bond strength and development length of reinforcing steel coated with two types of CCCW coating materials (CCCW-B+C and CCCW-C+D) using a modified pull-out test method. A self-reacting inverted T-shaped beam was designed to avoid compression in the concrete surrounding the reinforcing steel. Steel reinforcing bars were embedded along the web portion of the T-beam with various embedded lengths and were staggered side by side. In total, six T-beams were fabricated and each beam contained 8 samples. Both short-term (7 days) and long-term (3 months) effects of water curing were evaluated. The reinforcing steel bars coated with CCCW-B+C demonstrated a higher bond strength than did samples coated with CCCW-C+D. However, the bond strengths of samples with coating materials

  13. Matrix cracking initiation stress in fiber-reinforced ceramic matrix composites

    NASA Astrophysics Data System (ADS)

    Kangutkar, Pramod Balkrishna

    1991-05-01

    One of the important design parameters in CMC's in the Matrix Cracking Initiation Stress (MCIS) which corresponds to the stress at which first matrix cracks are observed. Above the MCIS, the fibers will be exposed to the oxidizing environment which may degrade the mechanical property of the fibers and thus of the composite. In this thesis a systematic study to explore the effects of matrix toughness and inherent strength, fiber diameter, stiffness and volume fraction, temperature and interfacial bonding on the MCIS was carried out. Composites were fabricated using three different matrices--borosilicate glass, aluminosilicate glass and polycrystalline zirconium silicate (or zircon), and two different reinforcing fibers--an SiC monofilament (140 micron diameter) and an SiC yarn (16 micron diameter). In-situ observations during 3-point bend test inside the SEM indicate that matrix cracking is a local phenomenon and occurs first in the matrix between widest spaced fibers. In all composites the MCIS was found to increase with fiber additions and scaled with the monolithic strength. The relative increase in MCIS over the monolithic strength with fiber volume fraction, however, was found to depend strongly on the a(sub 0)/S ratio, where a(sub 0) is the inherent unreinforced matrix flaw size and S is the inter-fiber spacing. For small ratios, the effect of fiber additions on enhancing MCIS are minimal. As the ratio approaches unity, the role of the fibers in constraining the inherent flaw increases, thereby increasing the MCIS. Thermal residual stresses were also seen to play an important role in determining the MCIS; systems with compressive residual stresses in the matrix show higher MCIS at room temperature than at a higher temperature. In systems such as the 7740/Nicalon, which had negligible thermal stresses, MCIS showed minimal changes on testing at 520 C. Several theoretical models were reviewed and the predictions were compared to the experimental results. It was

  14. Quantitative analysis of the microstructure of interfaces in steel reinforced concrete

    SciTech Connect

    Horne, A.T.; Richardson, I.G. Brydson, R.M.D.

    2007-12-15

    This article reports the results of a backscattered electron imaging study of the microstructure of the steel- and aggregate-cement paste interfaces in concrete containing 9 mm ribbed reinforcing bars. The water to cement (w/c) ratio, hydration age, steel orientation, and surface finish were varied. For vertically cast bars, there was more calcium hydroxide (CH) and porosity and less unreacted cement at both the steel- and aggregate-cement paste interfaces when compared to the bulk cement paste. As the hydration age increased, the porosity near the interfaces decreased, and the CH increased with more CH close to the steel than to the aggregate. Horizontal bars had more porosity and less CH under them than above. An increase in the w/c ratio produced interfaces of higher porosity and lower levels of CH. Wire-brush cleaned bars had higher levels of CH at the steel-cement paste interface at 365 days when compared to uncleaned bars.

  15. Predicting Mechanical Properties of Metal Matrix Syntactic Foams Reinforced with Ceramic Spheres

    DTIC Science & Technology

    2012-01-01

    reinforced with Al2O3 spheres of various sizes, size ranges, and wall thickness to sphere diameter ratios show good agreement. Introduction Metal matrix...treatments reinforced with Al2O3 spheres of various sizes, size ranges, and wall thickness to sphere diameter ratios show good agreement. 15. SUBJECT...longitudinally and not laterally (i.e. no barreling: ) until all hollow reinforcements are crushed. Assuming the wall thickness of the hollow

  16. Cost effective production techniques for continuous fiber reinforced ceramic matrix composites

    SciTech Connect

    Vogel, W.D.; Spelz, U.

    1995-09-01

    Cost effective techniques for fabrication of continuous fibre reinforced ceramic matrix composites like filament winding, prepreg technique and resin transfer moulding are reported. The advantages and disadvantages of the three different manufacture routes are given and examples are shown.

  17. Practical experience of steel fiber reinforced wet shotcrete in large underground construction projects

    SciTech Connect

    Garshol, K.

    1995-12-31

    The paper discusses advantages of SFRS (steel fiber reinforced shotcrete) in underground construction projects, including trends in rock support design; quality and durability of wet mix shotcrete; advantages in safety and working environment and the technical properties of SFRS. Key data from cases illustrate the above. Cost and time factors are highlighted.

  18. Mechanical Behavior of Steel Fiber-Reinforced Concrete Beams Bonded with External Carbon Fiber Sheets.

    PubMed

    Gribniak, Viktor; Tamulenas, Vytautas; Ng, Pui-Lam; Arnautov, Aleksandr K; Gudonis, Eugenijus; Misiunaite, Ieva

    2017-06-17

    This study investigates the mechanical behavior of steel fiber-reinforced concrete (SFRC) beams internally reinforced with steel bars and externally bonded with carbon fiber-reinforced polymer (CFRP) sheets fixed by adhesive and hybrid jointing techniques. In particular, attention is paid to the load resistance and failure modes of composite beams. The steel fibers were used to avoiding the rip-off failure of the concrete cover. The CFRP sheets were fixed to the concrete surface by epoxy adhesive as well as combined with various configurations of small-diameter steel pins for mechanical fastening to form a hybrid connection. Such hybrid jointing techniques were found to be particularly advantageous in avoiding brittle debonding failure, by promoting progressive failure within the hybrid joints. The use of CFRP sheets was also effective in suppressing the localization of the discrete cracks. The development of the crack pattern was monitored using the digital image correlation method. As revealed from the image analyses, with an appropriate layout of the steel pins, brittle failure of the concrete-carbon fiber interface could be effectively prevented. Inverse analysis of the moment-curvature diagrams was conducted, and it was found that a simplified tension-stiffening model with a constant residual stress level at 90% of the strength of the SFRC is adequate for numerically simulating the deformation behavior of beams up to the debonding of the CFRP sheets.

  19. Mechanical Behavior of Steel Fiber-Reinforced Concrete Beams Bonded with External Carbon Fiber Sheets

    PubMed Central

    Gribniak, Viktor; Tamulenas, Vytautas; Ng, Pui-Lam; Arnautov, Aleksandr K.; Gudonis, Eugenijus; Misiunaite, Ieva

    2017-01-01

    This study investigates the mechanical behavior of steel fiber-reinforced concrete (SFRC) beams internally reinforced with steel bars and externally bonded with carbon fiber-reinforced polymer (CFRP) sheets fixed by adhesive and hybrid jointing techniques. In particular, attention is paid to the load resistance and failure modes of composite beams. The steel fibers were used to avoiding the rip-off failure of the concrete cover. The CFRP sheets were fixed to the concrete surface by epoxy adhesive as well as combined with various configurations of small-diameter steel pins for mechanical fastening to form a hybrid connection. Such hybrid jointing techniques were found to be particularly advantageous in avoiding brittle debonding failure, by promoting progressive failure within the hybrid joints. The use of CFRP sheets was also effective in suppressing the localization of the discrete cracks. The development of the crack pattern was monitored using the digital image correlation method. As revealed from the image analyses, with an appropriate layout of the steel pins, brittle failure of the concrete-carbon fiber interface could be effectively prevented. Inverse analysis of the moment-curvature diagrams was conducted, and it was found that a simplified tension-stiffening model with a constant residual stress level at 90% of the strength of the SFRC is adequate for numerically simulating the deformation behavior of beams up to the debonding of the CFRP sheets. PMID:28773024

  20. Corrosion monitoring of reinforcing steel in concrete by electrochemical sensors

    NASA Astrophysics Data System (ADS)

    Qiao, Guofu; Hong, Yi; Ou, Jinping

    2010-04-01

    Health degradation by corrosion of steel in civil engineering, especially in rough environment, is a persistent problem. Structural health monitoring (SHM) techniques can lead to improved estimates of structural safety and serviceability. A novel all solid state-current confined corrosion sensor has been developed to provide the platform for corrosion monitoring of the steel bar in concrete beam by electrochemical method. Finite element method has been used to certify the current confined effect of the sensor. The sensors have been used in concrete beams to monitor the corrosion of the steel bar. Also, half-cell potential of the beam has obtained. The results shows that the corrosion sensor can effectively confine the current in the fixed area which is 45mm×π×Dsteel bar and the monitoring results of the corrosion sensor are accurate.

  1. Prospects of increasing the strength of aluminum by reinforcing it with stainless steel wire (a review)

    NASA Technical Reports Server (NTRS)

    Botvina, L. R.; Ivanova, V. S.; Kopev, I. M.

    1982-01-01

    The theoretical and experimental strength of aluminum reinforced with stainless steel wire is analyzed. Various methods of producing the composite material and it's static and cyclical strengths are considered. The reinforcement of aluminum with stainless steel wire was accomplished from the perspective of increasing the specific strength of aluminum and it's alloys, increasing the strength of the material with respect to high and low temperatures, as well as increasing the cyclical strength. The production of the composite aluminum-stainless steel wire material with approximated or calculated strengthening is possible by any of the considered methods. The selection of the proper production technology depends on precise details and conditions of application of the material.

  2. Internal impedance of steel-reinforced helically stranded conductors at commercial frequency

    NASA Astrophysics Data System (ADS)

    Merkushev, A. G.; Elagin, I. A.

    2015-04-01

    An original simplified mathematical model is proposed that describes the distribution of a harmonic electromagnetic field at a commercial frequency in steel-reinforced high-voltage cables with helically stranded single-layer winding. In the framework of the idealized physical concepts on which the proposed model is based, stranded conductors are treated as an anisotropic conducting layer. It is shown that taking into account the helical twist of conductors leads to the appearance of an axial magnetic field, the presence of which can significantly influence the level of ac losses. The model has been used to calculate the dependence of the internal impedance on the magnetic permeability of the steel core for commercial AS-70 grade steel-reinforced stranded aluminum cable. The results are compared to those obtained using a hollow cylinder model and full-scale numerical calculations using the finite element method.

  3. Comparative investigation of corrosion resistance of steel reinforcement in alinite and Portland cement mortars

    SciTech Connect

    Kostogloudis, G.C.; Kalogridis, D.; Ftikos, C.; Malami, C.; Georgali, B.; Kaloidas, V.

    1998-07-01

    The corrosion resistance of steel-reinforced mortar specimens made from alinite cement was investigated using ordinary Portland cement (OPC) specimens as reference. The specimens were prepared and exposed in three different environments: continuous exposure in tap water, interrupted exposure in tap water, and interrupted exposure in 3.5% NaCl solution. The steel weight loss and the half cell potential were measured vs. exposure time, up to the age of 12 months. Pore solution extraction and analysis and porosity determination were also performed. In continuous exposure in tap water, alinite cement provided adequate protection against corrosion. In interrupted exposure in tap water, a higher corrosion was observed for alinite cement compared to OPC. In the case of interrupted exposure in 3.5% NaCl solution, the simultaneous action of free chlorides and oxygen resulted in the depassivation of steel reinforcing bars in alinite and Portland cement mortars, and led to severe corrosion effect.

  4. Natural Corrosion Inhibitors for Steel Reinforcement in Concrete — a Review

    NASA Astrophysics Data System (ADS)

    Raja, Pandian Bothi; Ghoreishiamiri, Seyedmojtaba; Ismail, Mohammad

    2015-04-01

    Reinforced concrete is one of the widely used construction materials for bridges, buildings, platforms and tunnels. Though reinforced concrete is capable of withstanding a large range of severe environments including marine, industrial and alpine conditions, there are still a large number of failures in concrete structures for many reasons. Either carbonation or chloride attack is the main culprit which is due to depassivation of reinforced steel and subsequently leads to rapid steel corrosion. Among many corrosion prevention measures, application of corrosion inhibitors play a vital role in metal protection. Numerous range of corrosion inhibitors were reported for concrete protection that were also used commercially in industries. This review summarizes the application of natural products as corrosion inhibitors for concrete protection and also scrutinizes various factors influencing its applicability.

  5. Co-extrusion of Discontinuously, Non-centric Steel-reinforced Aluminum

    SciTech Connect

    Foydl, A.; Haase, M.; Khalifa, N. Ben; Tekkaya, A. E.

    2011-05-04

    The process of manufacturing discontinuously non-centric steel reinforced aluminum by means of co-extrusion has been examined. By this process semi-finished reinforced profiles can be fabricated for further treatment through forging techniques. Therefore, steel reinforcement elements consisting of E295GC were inserted into conventional aluminum billets and co-extruded into two different solid profiles; a rectangle one by an extrusion ratio of 10.1:1 and a round one by 4.8:1. The used aluminum alloy is EN AW-6060. The billet temperature as well as the ram speed were varied to investigate their influence on the position of the reinforcement elements inside the strand. The measurement was done by a video measurement system, called Optomess A250, after milling off the strand. The distances between the elements in longitudinal direction were nearly constant, apart from the rear part of the strand. The same was observed for the distance of the steel elements to the profile edge. This due to the inhomogeneous material flow in the transverse weld, related to the billet-to-billet extrusion. The rotation of the reinforcement elements occurs because the elements flow nearby the shear zone. Further, micrographs were made to investigate the embedding situation and the grain size distribution. The embedding of the reinforcement elements were good in the solid round profile, but in the rectangle profile were found some kind of air pocket. The grain size of the aluminum alloy close to the steel elements is much smaller than in the other parts of the solid round profile.

  6. Method of making carbon fiber-carbon matrix reinforced ceramic composites

    NASA Technical Reports Server (NTRS)

    Williams, Brian (Inventor); Benander, Robert (Inventor)

    2007-01-01

    A method of making a carbon fiber-carbon matrix reinforced ceramic composite wherein the result is a carbon fiber-carbon matrix reinforcement is embedded within a ceramic matrix. The ceramic matrix does not penetrate into the carbon fiber-carbon matrix reinforcement to any significant degree. The carbide matrix is a formed in situ solid carbide of at least one metal having a melting point above about 1850 degrees centigrade. At least when the composite is intended to operate between approximately 1500 and 2000 degrees centigrade for extended periods of time the solid carbide with the embedded reinforcement is formed first by reaction infiltration. Molten silicon is then diffused into the carbide. The molten silicon diffuses preferentially into the carbide matrix but not to any significant degree into the carbon-carbon reinforcement. Where the composite is intended to operate between approximately 2000 and 2700 degrees centigrade for extended periods of time such diffusion of molten silicon into the carbide is optional and generally preferred, but not essential.

  7. Characterization of a carbon fiber reinforced polymer repair system for structurally deficient steel piping

    NASA Astrophysics Data System (ADS)

    Wilson, Jeffrey M.

    This Dissertation investigates a carbon fiber reinforced polymer repair system for structurally deficient steel piping. Numerous techniques exist for the repair of high-pressure steel piping. One repair technology that is widely gaining acceptance is composite over-wraps. Thermal analytical evaluations of the epoxy matrix material produced glass transition temperature results, a cure kinetic model, and a workability chart. These results indicate a maximum glass transition temperature of 80°C (176°F) when cured in ambient conditions. Post-curing the epoxy, however, resulted in higher glass-transition temperatures. The accuracy of cure kinetic model presented is temperature dependent; its accuracy improves with increased cure temperatures. Cathodic disbondment evaluations of the composite over-wrap show the epoxy does not breakdown when subjected to a constant voltage of -1.5V and the epoxy does not allow corrosion to form under the wrap from permeation. Combustion analysis of the composite over-wrap system revealed the epoxy is flammable when in direct contact with fire. To prevent combustion, an intumescent coating was developed to be applied on the composite over-wrap. Results indicate that damaged pipes repaired with the carbon fiber composite over-wrap withstand substantially higher static pressures and exhibit better fatigue characteristics than pipes lacking repair. For loss up to 80 percent of the original pipe wall thickness, the composite over-wrap achieved failure pressures above the pipe's specified minimum yield stress during monotonic evaluations and reached the pipe's practical fatigue limit during cyclical pressure testing. Numerous repairs were made to circular, thru-wall defects and monotonic pressure tests revealed containment up to the pipe's specified minimum yield strength for small diameter defects. The energy release rate of the composite over-wrap/steel interface was obtained from these full-scale, leaking pipe evaluations and results

  8. Synthesis and Characterization of TiB2 Reinforced Aluminium Matrix Composites: A Review

    NASA Astrophysics Data System (ADS)

    Kumar, Narendra; Gautam, Gaurav; Gautam, Rakesh Kumar; Mohan, Anita; Mohan, Sunil

    2016-10-01

    Aluminium-matrix composites (AMCs) are developed to meet the demands of light weight high performance materials in aerospace, automotive, marine and other applications. The properties of AMCs can be tailored suitably by combinations of matrix, reinforcement and processing route. AMCs are one of the most attractive alternatives for the manufacturing of light weight and high strength parts due to their low density and high specific strength. There are various techniques for preparing the AMCs with different reinforcement particles. In AMCs, the reinforcements are usually in the form of metal oxides, carbides, borides, nitrides and their combination. Among the various reinforcements titanium di-boride (TiB2) is of much interest due to its excellent stiffness, hardness, and wear resistance. This paper attempts to provide an overview to explore the possibilities of synthesizing titanium di-boride reinforced AMCs with different techniques. The mechanical and tribological properties of these composites have been emphasized to project these as tribo-materials.

  9. Stainless and Galvanized Steel, Hydrophobic Admixture and Flexible Polymer-Cement Coating Compared in Increasing Durability of Reinforced Concrete Structures

    NASA Astrophysics Data System (ADS)

    Tittarelli, Francesca; Giosuè, Chiara; Mobili, Alessandra

    2017-08-01

    The use of stainless or galvanized steel reinforcements, a hydrophobic admixture or a flexible polymer-cement coating were compared as methods to improve the corrosion resistance of sound or cracked reinforced concrete specimens exposed to chloride rich solutions. The results show that in full immersion condition, negligible corrosion rates were detected in all cracked specimens, except those treated with the flexible polymer-cement mortar as preventive method against corrosion and the hydrophobic concrete specimens. High corrosion rates were measured in all cracked specimens exposed to wet-dry cycles, except for those reinforced with stainless steel, those treated with the flexible polymer-cement coating as restorative method against reinforcement corrosion and for hydrophobic concrete specimens reinforced with galvanized steel reinforcements.

  10. Development of hybrid polypropylene-steel fiber-reinforced concrete

    SciTech Connect

    Qian, C.X.; Stroeven, P.

    2000-01-01

    This research first investigates the optimization of fiber size, fiber content, and fly ash content in hybrid polypropylene-steel fiber concrete with low fiber content based on general mechanical properties. The research results show that a certain content of fine particles such as fly ash is necessary to evenly disperse fibers. The different sizes of steel fibers contributed to different mechanical properties, at least to a different degree. Additions of a small fiber type had a significant influence on the compressive strength, but the splitting tensile strength was only slightly affected. A large fiber type gave rise to opposite mechanical effects, which were further fortified by optimization of the aspect ratio. There is a synergy effect in the hybrid fibers system. The fracture properties and the dynamic properties will be further investigated for the hybrid fibers concrete with good general mechanical properties.

  11. Ceramic fiber-reinforced monoclinic celsian phase glass-ceramic matrix composite material

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P. (Inventor); Dicarlo, James A. (Inventor)

    1994-01-01

    A hyridopolysilazane-derived ceramic fiber reinforced monoclinic celsian phase barium aluminum silicate glass-ceramic matrix composite material is prepared by ball-milling an aqueous slurry of BAS glass powder and fine monoclinic celsian seeds. The fibers improve the mechanical strength and fracture toughness and with the matrix provide superior dielectric properties.

  12. Fracture Analysis of Particulate Reinforced Metal Matrix Composites

    NASA Technical Reports Server (NTRS)

    Min, James B.; Cornie, James A.

    2013-01-01

    A fracture analysis of highly loaded particulate reinforced composites was performed using laser moire interferometry to measure the displacements within the plastic zone at the tip of an advancing crack. Ten castings were made of five different particulate reinforcement-aluminum alloy combinations. Each casting included net-shape specimens which were used for the evaluation of fracture toughness, tensile properties, and flexure properties resulting in an extensive materials properties data. Measured fracture toughness range from 14.1 MPa for an alumina reinforced 356 aluminum alloy to 23.9 MPa for a silicon carbide reinforced 2214 aluminum alloy. For the combination of these K(sub Ic) values and the measured tensile strengths, the compact tension specimens were too thin to yield true plane strain K(sub Ic) values. All materials exhibited brittle behavior characterized by very small tensile ductility suggesting that successful application of these materials requires that the design stresses be below the elastic limit. Probabilistic design principles similar to those used with ceramics are recommended when using these materials. Such principles would include the use of experimentally determined design allowables. In the absence of thorough testing, a design allowable stress of 60 percent of the measured ultimate tensile stress is recommended.

  13. Assessment of Steel Reinforcement Corrosion State by Parameters of Potentiodynamic Diagrams

    NASA Astrophysics Data System (ADS)

    Krajči, Ľudovít; Jerga, Ján

    2015-12-01

    The environment of the steel reinforcement has a significant impact on the durability and service life of a concrete structure. It is not only the presence of aggressive substances from the environment, but also the own composition of concrete mixture. The use of new types of cements, additives and admixtures must be preceded by verification, if they themselves shall not initiate the corrosion. There is a need for closer physical expression of the parameters of the potentiodynamic diagrams allowing reliable assessment of the influence of the surrounding environment on electrochemical behaviour of reinforcement. The analysis of zero retardation limits of potentiodynamic curves is presented.

  14. Vertical impedance measurements on concrete bridge decks for assessing susceptibility of reinforcing steel to corrosion.

    PubMed

    Bartholomew, Paul D; Guthrie, W Spencer; Mazzeo, Brian A

    2012-08-01

    Corrosion is a pressing problem for aging concrete infrastructure, especially bridge decks. Because of its sensitivity to factors that affect corrosion of reinforcing steel in concrete, resistivity is an important structural health indicator for reinforced concrete structures. In this research, an instrument was developed to measure vertical impedance on concrete bridge decks. Measurements of vertical impedance on slabs prepared in the laboratory, on slabs removed from decommissioned bridge decks, and on an in-service bridge deck in the field demonstrate the utility of the new apparatus.

  15. Vertical impedance measurements on concrete bridge decks for assessing susceptibility of reinforcing steel to corrosion

    NASA Astrophysics Data System (ADS)

    Bartholomew, Paul D.; Guthrie, W. Spencer; Mazzeo, Brian A.

    2012-08-01

    Corrosion is a pressing problem for aging concrete infrastructure, especially bridge decks. Because of its sensitivity to factors that affect corrosion of reinforcing steel in concrete, resistivity is an important structural health indicator for reinforced concrete structures. In this research, an instrument was developed to measure vertical impedance on concrete bridge decks. Measurements of vertical impedance on slabs prepared in the laboratory, on slabs removed from decommissioned bridge decks, and on an in-service bridge deck in the field demonstrate the utility of the new apparatus.

  16. Buckling of steel cylinders containing circular cutouts reinforced according to the area-replacement method

    SciTech Connect

    Dove, R.C.; Bennett, J.G.; Butler, T.A.

    1982-01-01

    The effect of the use of the area replacement method (ARM) for reinforcing circular penetrations in cylindrical steel shells has been studied both experimentally and analyticaly. How this type of reinforcement affects the buckling strength of a shell subjected to uniform axial compression is the specific area of investigation. In shells that are of such a quality that the penetration reduces the buckling strength, the use of the ARM will increase the bucking strength of the shell. In any case, the conservative knockdown factors suggested for buckling design by the American Society of Mechanical Engineer's (ASME) Boiler and Pressure Vessel Code should ensure an adequate margin to failure under this loading condition.

  17. Mesoscale Characterization of Fracture Properties of Steel Fiber-Reinforced Concrete Using a Lattice-Particle Model.

    PubMed

    Montero-Chacón, Francisco; Cifuentes, Héctor; Medina, Fernando

    2017-02-21

    This work presents a lattice-particle model for the analysis of steel fiber-reinforced concrete (SFRC). In this approach, fibers are explicitly modeled and connected to the concrete matrix lattice via interface elements. The interface behavior was calibrated by means of pullout tests and a range for the bond properties is proposed. The model was validated with analytical and experimental results under uniaxial tension and compression, demonstrating the ability of the model to correctly describe the effect of fiber volume fraction and distribution on fracture properties of SFRC. The lattice-particle model was integrated into a hierarchical homogenization-based scheme in which macroscopic material parameters are obtained from mesoscale simulations. Moreover, a representative volume element (RVE) analysis was carried out and the results shows that such an RVE does exist in the post-peak regime and until localization takes place. Finally, the multiscale upscaling strategy was successfully validated with three-point bending tests.

  18. Mesoscale Characterization of Fracture Properties of Steel Fiber-Reinforced Concrete Using a Lattice–Particle Model

    PubMed Central

    Montero-Chacón, Francisco; Cifuentes, Héctor; Medina, Fernando

    2017-01-01

    This work presents a lattice–particle model for the analysis of steel fiber-reinforced concrete (SFRC). In this approach, fibers are explicitly modeled and connected to the concrete matrix lattice via interface elements. The interface behavior was calibrated by means of pullout tests and a range for the bond properties is proposed. The model was validated with analytical and experimental results under uniaxial tension and compression, demonstrating the ability of the model to correctly describe the effect of fiber volume fraction and distribution on fracture properties of SFRC. The lattice–particle model was integrated into a hierarchical homogenization-based scheme in which macroscopic material parameters are obtained from mesoscale simulations. Moreover, a representative volume element (RVE) analysis was carried out and the results shows that such an RVE does exist in the post-peak regime and until localization takes place. Finally, the multiscale upscaling strategy was successfully validated with three-point bending tests. PMID:28772568

  19. Intermittent cathodic protection for steel reinforced concrete bridges

    SciTech Connect

    Bullard, Sophie J.; Ziomek-Moroz, Margaret; Cramer, Stephen D.; Covino, Bernard S., Jr.; Holcomb, Gordon R.; Russell, James H.; Soltesz, S.M.

    2002-01-01

    Thermal-sprayed zinc anodes are used for impressed current cathodic protection (ICCP) systems on Oregon's reinforced concrete coastal bridges to prevent chloride-induced corrosion damage. Thermal-sprayed zinc performs well as an ICCP anode but the service life of the zinc anode is directly related to the average current density used to operate the systems. After a ICCP system is turned off, the rebar in the concrete remains passive and protected for a period of time. Intermittent operation of CP systems is possible when continuous corrosion rate monitoring is used to identify conditions when the CP system needs to be turned on to reestablish protection conditions for the rebar. This approach applies CP protection only when needed and reflects the fact that external protection may not be needed for a range of environmental conditions. In doing so, intermittent CP would lower the average current necessary to protect rebar, increase the anode service life, and reduce the lifetime costs for protecting reinforced concrete bridges.

  20. Effect of Thickness and Fibre Volume Fraction on Impact Resistance of Steel Fibre Reinforced Concrete (SFRC)

    NASA Astrophysics Data System (ADS)

    Che Muda, Zakaria; Usman, Fathoni; Syamsir, Agusril; Shao Yang, Chen; Nasharuddin Mustapha, Kamal; Beddu, Salmia; Thiruchelvam, Sivadass; Liyana Mohd Kamal, Nur; Ashraful Alam, Md; Birima, Ahmed H.; Itam, Zarina; Zaroog, O. S.

    2016-03-01

    This paper investigate the effect of the thickness and fibre volume fraction (VF) on the impact performance of steel fibre reinforced concrete (SFRC) for the concrete slab of 300mm × 300mm size reinforced subjected to low impact projectile test. A self-fabricated drop-weight impact test rig with a steel ball weight of 1.236 kg drop at 0.57 m height has been used in this research work. The objective of this research is to study the relationship of impact resistance SFRC against slab thickness and volume fraction. There is a good linear correlation between impact resistances of SFRC against slab thickness. However the impact resistance of SFRC against percentage of volume fraction exhibit a non-linear relationship.

  1. Fatigue of continuous fiber reinforced titanium matrix composites

    NASA Technical Reports Server (NTRS)

    Johnson, W. S.

    1991-01-01

    Several lay-ups of SCS-6/Ti-15-3 composites were investigated. Static and fatigue tests were conducted for both notched and unnotched specimens at room and elevated temperatures. Test results indicated that the stress in the 0 fibers is the controlling factor in fatigue life. The static and fatigue strength of these materials is shown to be dependent on the level of residual stresses and the fiber/ matrix interfacial strength. Fatigue tests of notched specimens showed that cracks can initiate and grow many fiber spacings in the matrix material without breaking fibers. These matrix cracks can significantly reduce the residual strength of notched composite.

  2. Extraordinary synergy in the mechanical properties of polymer matrix composites reinforced with 2 nanocarbons.

    PubMed

    Prasad, K Eswar; Das, Barun; Maitra, Urmimala; Ramamurty, Upadrasta; Rao, C N R

    2009-08-11

    One of the applications of nanomaterials is as reinforcements in composites, wherein small additions of nanomaterials lead to large enhancements in mechanical properties. There have been extensive studies in the literature on composites where a polymer matrix is reinforced by a single nanomaterial such as carbon nanotubes. In this article, we examine the significant synergistic effects observed when 2 different types of nanocarbons are incorporated in a polymer matrix. Thus, binary combinations of nanodiamond, few-layer graphene, and single-walled nanotubes have been used to reinforce polyvinyl alcohol. The mechanical properties of the resulting composites, evaluated by the nanoindentation technique, show extraordinary synergy, improving the stiffness and hardness by as much as 400% compared to those obtained with single nanocarbon reinforcements. These results suggest a way of designing advanced materials with extraordinary mechanical properties by incorporating small amounts of 2 nanomaterials such as graphene plus nanodiamond or nanodiamond plus carbon nanotube.

  3. Extraordinary synergy in the mechanical properties of polymer matrix composites reinforced with 2 nanocarbons

    PubMed Central

    Prasad, K. Eswar; Das, Barun; Maitra, Urmimala; Ramamurty, Upadrasta; Rao, C. N. R.

    2009-01-01

    One of the applications of nanomaterials is as reinforcements in composites, wherein small additions of nanomaterials lead to large enhancements in mechanical properties. There have been extensive studies in the literature on composites where a polymer matrix is reinforced by a single nanomaterial such as carbon nanotubes. In this article, we examine the significant synergistic effects observed when 2 different types of nanocarbons are incorporated in a polymer matrix. Thus, binary combinations of nanodiamond, few-layer graphene, and single-walled nanotubes have been used to reinforce polyvinyl alcohol. The mechanical properties of the resulting composites, evaluated by the nanoindentation technique, show extraordinary synergy, improving the stiffness and hardness by as much as 400% compared to those obtained with single nanocarbon reinforcements. These results suggest a way of designing advanced materials with extraordinary mechanical properties by incorporating small amounts of 2 nanomaterials such as graphene plus nanodiamond or nanodiamond plus carbon nanotube. PMID:19651605

  4. Studies on natural fiber reinforced polymer matrix composites

    NASA Astrophysics Data System (ADS)

    Patel, R. H.; Kapatel, P. M.; Machchhar, A. D.; Kapatel, Y. A.

    2016-05-01

    Natural fiber reinforced composites show increasing importance in day to days applications because of their low cost, lightweight, easy availability, non-toxicity, biodegradability and environment friendly nature. But these fibers are hydrophilic in nature. Thus they have very low reactivity and poor compatibility with polymers. To overcome these limitations chemical modifications of the fibers have been carried out. Therefore, in the present work jute fibers have chemically modified by treating with sodium hydroxide (NaOH) solutions. These treated jute fibers have been used to fabricate jute fiber reinforced epoxy composites. Mechanical properties like tensile strength, flexural strength and impact strength have been found out. Alkali treated composites show better properties compare to untreated composites.

  5. Interface Characterization in Fiber-Reinforced Polymer-Matrix Composites

    NASA Astrophysics Data System (ADS)

    Naya, F.; Molina-Aldareguía, J. M.; Lopes, C. S.; González, C.; LLorca, J.

    2017-01-01

    A novel methodology is presented and applied to measure the shear interface strength of fiber-reinforced polymers. The strategy is based in fiber push-in tests carried out on the central fiber of highly-packed fiber clusters with hexagonal symmetry, and it is supported by a detailed finite element analysis of the push-in test to account for the influence of hygrothermal residual stresses, fiber constraint and fiber anisotropy on the interface strength. Examples of application are presented to determine the shear interface strength in carbon and glass fiber composites reinforced with either thermoset or thermoplastic matrices. In addition, the influence of the environment (either dry or wet conditions) on the interface strength in C/epoxy composites is demonstrated.

  6. Carbon Fiber Reinforced Glass Matrix Composites for Satellite Applications

    DTIC Science & Technology

    1992-06-01

    graphite basal planes. On the other hand, a high elastic modulus fiber derived from a mesophase pitch precursor, such as P-100, has a radial...and B. V. Perov. Elsevier Science Publishers B. V., Amsterdam, 1985. 2. B. Rand, "Carbon Fibres from Mesophase Pitch " pp. 495-575 in ibid.. 3. W. K...HMU fiber and the other reinforced with pitch -based fiber (P- 100 or FT700), will be described and compared with respect to various features of the

  7. Mechanisms controlling fatigue damage development in continuous fiber reinforced metal matrix composites

    NASA Technical Reports Server (NTRS)

    Johnson, W. S.

    1989-01-01

    Damage in continuous fiber reinforced metal matrix composite materials can be quite complex since there are a number of different constituents (fiber, matrix, and the fiber/matrix interface) that can fail. Multidirectional lay-ups have an even greater number of possible damage orientations and mechanisms. Based on the simplifying assumption of equivalent constituent strain states in the absence of damage, a strain based failure criteria may be applied to determine when and where initial damage will occur. Based on the relative strain to fatigue failure of the fiber and matrix, the possible damage mechanisms of an MMC can be grouped into three categories: (1) matrix dominated, (2) fiber dominated, and (3) self-similar damage growth. A fourth type of damage development, fiber/matrix interface failure, is dependent on the relative strength of the fiber/matrix interface and the matrix yield strength. These four types of damage are discussed and illustrated by examples.

  8. Effect of fiber reinforcements on thermo-oxidative stability and mechanical properties of polymer matrix composites

    NASA Technical Reports Server (NTRS)

    Bowles, Kenneth J.

    1991-01-01

    A number of studies have investigated the thermo-oxidative behavior of polymer matrix composites. Two significant observations have been made from these research efforts: (1) fiber reinforcement has a significant effect on composite thermal stability; and (2) geometric effects must be considered when evaluating thermal aging data. A compilation of some results from these studies is presented, and this information shows the influence of the reinforcement fibers on the oxidative degradation of various polymer matrix composites. The polyimide PMR-15 was the matrix material that was used in these studies. The control composite material was reinforced with Celion 6000 graphite fiber. T-40R graphite fibers, along with some very stable ceramic fibers were selected as reinforcing fibers because of their high thermal stability. The ceramic fibers were Nicalon (silicon carbide) and Nextel 312 (alumina-silica-boron oxide). The mechanical properties of the two graphite fiber composites were significantly different, probably owing to variations in interfacial bonding between the fibers and the polyimide matrix. The Celion 6000/PMR-15 bond is very tight but the T-40/PMR-15 bond is less tight. Three oxidation mechanisms were observed: (1) the preferential oxidation of the Celion 6000 fiber ends at cut surfaces, leaving a surface of matrix material with holes where the fiber ends were originally situated; (2) preferential oxidation of the composite matrix; and (3) interfacial degradation by oxidation. The latter two mechanisms were also observed on fiber end cut surfaces. The fiber and interface attacks appeared to initiate interfiber cracking along these surfaces.

  9. Reinforcement Size Dependence of Load Bearing Capacity in Ultrafine-Grained Metal Matrix Composites

    NASA Astrophysics Data System (ADS)

    Yang, Hanry; Jiang, Lin; Balog, Martin; Krizik, Peter; Schoenung, Julie M.

    2017-09-01

    The length-scale effects on the load bearing capacity of reinforcement particles in an ultrafine-grained metal matrix composite (MMC) were studied, paying particular attention to the nanoscale effects. We observed that the nanoparticles provide the MMCs with a higher strength but a lower stiffness compared to equivalent materials reinforced with submicron particles. The reduction in stiffness is attributed to ineffective load transfer of the local stresses to the small and equiaxed nanoparticles.

  10. Reinforcement Size Dependence of Load Bearing Capacity in Ultrafine-Grained Metal Matrix Composites

    NASA Astrophysics Data System (ADS)

    Yang, Hanry; Jiang, Lin; Balog, Martin; Krizik, Peter; Schoenung, Julie M.

    2017-07-01

    The length-scale effects on the load bearing capacity of reinforcement particles in an ultrafine-grained metal matrix composite (MMC) were studied, paying particular attention to the nanoscale effects. We observed that the nanoparticles provide the MMCs with a higher strength but a lower stiffness compared to equivalent materials reinforced with submicron particles. The reduction in stiffness is attributed to ineffective load transfer of the local stresses to the small and equiaxed nanoparticles.

  11. Effects of manufacturing techniques on the flexural behavior of steel fiber-reinforced concrete

    SciTech Connect

    Toutanji, H.; Bayasi, Z.

    1998-01-01

    This paper presents experimental research investigating the effects of manufacturing techniques on the mechanical properties of steel fiber-reinforced concrete. Both the effects of curing environments and that of testing direction relative to casting direction on the mechanical properties of fiber-reinforced concrete are reported. Specimens were cured in three different environmental conditions: steam, moisture, and air. Results show that steam curing, as compared to moisture curing, does not enhance the flexural strength of steel fibrous concrete but does reduce flexural toughness. As expected, air curing shows detrimental effects on all aspects of the test results, as compared to steam and moisture curing. The flexural behavior of steel fiber-reinforced concrete is strongly affected by testing direction. When testing direction is perpendicular to casting direction, specimens exhibit reductions in both flexural strength and toughness compared to the case when testing and casting directions are parallel. The effect of testing direction relative to casting direction on flexural strength and toughness increases with increasing the flowability (workability) of the fibrous mixture, which encourages fiber settlement during placement.

  12. Seismic performance of steel reinforced ultra high-strength concrete composite frame joints

    NASA Astrophysics Data System (ADS)

    Yan, Changwang; Jia, Jinqing

    2010-09-01

    To investigate the seismic performance of a composite frame comprised of steel reinforced ultra high-strength concrete (SRUHSC) columns and steel reinforced concrete (SRC) beams, six interior frame joint specimens were designed and tested under low cyclically lateral load. The effects of the axial load ratio and volumetric stirrup ratio were studied on the characteristics of the frame joint performance including crack pattern, failure mode, ductility, energy dissipation capacity, strength degradation and rigidity degradation. It was found that all joint specimens behaved in a ductile manner with flexural-shear failure in the joint core region while plastic hinges appeared at the beam ends. The ductility and energy absorption capacity of joints increased as the axial load ratio decreased and the volumetric stirrup ratio increased. The displacement ductility coefficient and equivalent damping coefficient of the joints fell between the corresponding coefficients of the steel reinforced concrete (SRC) frame joint and RC frame joint. The axial load ratio and volumetric stirrup ratio have less influence on the strength degradation and more influence on the stiffness degradation. The stiffness of the joint degrades more significantly for a low volumetric stirrup ratio and high axial load ratio. The characteristics obtained from the SRUHSC composite frame joint specimens with better seismic performance may be a useful reference in future engineering applications.

  13. Method of producing a ceramic fiber-reinforced glass-ceramic matrix composite

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P. (Inventor)

    1994-01-01

    A fiber-reinforced composite composed of a BaO-Al2O3-2SiO2 (BAS) glass ceramic matrix is reinforced with CVD silicon carbide continuous fibers. A slurry of BAS glass powders is prepared and celsian seeds are added during ball melting. The slurry is cast into tapes which are cut to the proper size. Continuous CVD-SiC fibers are formed into mats of the desired size. The matrix tapes and the fiber mats are alternately stacked in the proper orientation. This tape-mat stack is warm pressed to produce a 'green' composite. The 'green' composite is then heated to an elevated temperature to burn out organic constituents. The remaining interim material is then hot pressed to form a silicon carbide fiber-reinforced celsian (BAS) glass-ceramic matrix composite which may be machined to size.

  14. Short-term microdamageability of a fibrous composite with physically nonlinear matrix and microdamaged reinforcement

    NASA Astrophysics Data System (ADS)

    Khoroshun, L. P.; Shikula, E. N.

    2006-02-01

    A structural theory of short-term microdamage is proposed for a fibrous composite with physically nonlinear matrix and microdamaged reinforcement. The theory is based on the stochastic elasticity equations of a fibrous composite with porous fibers. Microvolumes of the fiber material are damaged in accordance with the Huber-Mises failure criterion. A balance equation for damaged microvolumes in the reinforcement is derived. This equation together with the equations relating macrostresses and macrostrains of a fibrous composite with porous reinforcement and physically nonlinear matrix constitute a closed-form system. This system describes the coupled processes of physically nonlinear deformation and microdamage that occur in different components of the composite. Algorithms are proposed for computing the dependences of microdamage on macrostrains and macrostresses on macrostrains. Uniaxial tension curves are plotted for a fibrous composite with a linearly hardening matrix

  15. Synthesis and Characterization of Multi Wall Carbon Nanotubes (MWCNT) Reinforced Sintered Magnesium Matrix Composites

    NASA Astrophysics Data System (ADS)

    Vijaya Bhaskar, S.; Rajmohan, T.; Palanikumar, K.; Bharath Ganesh Kumar, B.

    2016-04-01

    Metal matrix composites (MMCs) reinforced with ceramic nano particles (less than 100 nm), termed as metal matrix nano composites (MMNCs), can overcome those disadvantages associated with the conventional MMCs. MMCs containing carbon nanotubes are being developed and projected for diverse applications in various fields of engineering like automotive, avionic, electronic and bio-medical sectors. The present investigation deals with the synthesis and characterization of hybrid magnesium matrix reinforced with various different wt% (0-0.45) of multi wall carbon nano tubes (MWCNT) and micro SiC particles prepared through powder metallurgy route. Microstructure and mechanical properties such as micro hardness and density of the composites were examined. Microstructure of MMNCs have been investigated by scanning electron microscope, X-ray diffraction and energy dispersive X-ray spectroscopy (EDS) for better observation of dispersion of reinforcement. The results indicated that the increase in wt% of MWCNT improves the mechanical properties of the composite.

  16. PERFORMANCE OF RC AND FRC WALL PANELS REINFORCED WITH MILD STEEL AND GFRP COMPOSITES IN BLAST EVENTS

    SciTech Connect

    Timothy Garfield; William D. Richins; Thomas K. Larson; Chris P. Pantelides; James E. Blakeley

    2011-06-01

    The structural integrity of reinforced concrete structures in blast events is important for critical facilities. This paper presents experimental data generated for calibrating detailed finite element models that predict the performance of reinforced concrete wall panels with a wide range of construction details under blast loading. The test specimens were 1.2 m square wall panels constructed using Normal Weight Concrete (NWC) or Fiber Reinforced Concrete (FRC). FRC consists of macro-synthetic fibers dispersed in NWC. Five types of panels were tested: NWC panels with steel bar reinforcement (Type A); FRC panels without additional reinforcement (Type B); FRC panels with steel bar reinforcement (Type C); NWC panels with glass fiber reinforced polymer (GFRP) bar reinforcement (Type D); and NWC panels reinforced with steel bar reinforcement and external bidirectional GFRP overlays on both faces (Type E). An additional three Type C panels were used as control specimens (CON). Each panel type was constructed with three thicknesses: 152 mm, 254 mm, and 356 mm. The panels were instrumented with strain gauges, and accelerometers; in addition, pressure sensors and high speed videos were employed during the blast events. Panel types C and E had the best performance, whereas panel type B did not perform well. Preliminary dynamic simulations show crack patterns similar to the experimental results.

  17. High Strength Concrete Columns under Axial Compression Load: Hybrid Confinement Efficiency of High Strength Transverse Reinforcement and Steel Fibers.

    PubMed

    Perceka, Wisena; Liao, Wen-Cheng; Wang, Yo-de

    2016-04-01

    Addition of steel fibers to high strength concrete (HSC) improves its post-peak behavior and energy absorbing capability, which can be described well in term of toughness. This paper attempts to obtain both analytically and experimentally the efficiency of steel fibers in HSC columns with hybrid confinement of transverse reinforcement and steel fibers. Toughness ratio (TR) to quantify the confinement efficiency of HSC columns with hybrid confinement is proposed through a regression analysis by involving sixty-nine TRs of HSC without steel fibers and twenty-seven TRs of HSC with hybrid of transverse reinforcement and steel fibers. The proposed TR equation was further verified by compression tests of seventeen HSC columns conducted in this study, where twelve specimens were reinforced by high strength rebars in longitudinal and transverse directions. The results show that the efficiency of steel fibers in concrete depends on transverse reinforcement spacing, where the steel fibers are more effective if the spacing transverse reinforcement becomes larger in the range of 0.25-1 effective depth of the section column. Furthermore, the axial load-strain curves were developed by employing finite element software (OpenSees) for simulating the response of the structural system. Comparisons between numerical and experimental axial load-strain curves were carried out.

  18. High Strength Concrete Columns under Axial Compression Load: Hybrid Confinement Efficiency of High Strength Transverse Reinforcement and Steel Fibers

    PubMed Central

    Perceka, Wisena; Liao, Wen-Cheng; Wang, Yo-de

    2016-01-01

    Addition of steel fibers to high strength concrete (HSC) improves its post-peak behavior and energy absorbing capability, which can be described well in term of toughness. This paper attempts to obtain both analytically and experimentally the efficiency of steel fibers in HSC columns with hybrid confinement of transverse reinforcement and steel fibers. Toughness ratio (TR) to quantify the confinement efficiency of HSC columns with hybrid confinement is proposed through a regression analysis by involving sixty-nine TRs of HSC without steel fibers and twenty-seven TRs of HSC with hybrid of transverse reinforcement and steel fibers. The proposed TR equation was further verified by compression tests of seventeen HSC columns conducted in this study, where twelve specimens were reinforced by high strength rebars in longitudinal and transverse directions. The results show that the efficiency of steel fibers in concrete depends on transverse reinforcement spacing, where the steel fibers are more effective if the spacing transverse reinforcement becomes larger in the range of 0.25–1 effective depth of the section column. Furthermore, the axial load–strain curves were developed by employing finite element software (OpenSees) for simulating the response of the structural system. Comparisons between numerical and experimental axial load–strain curves were carried out. PMID:28773391

  19. Synergistic Effects of Temperature and Oxidation on Matrix Cracking in Fiber-Reinforced Ceramic-Matrix Composites

    NASA Astrophysics Data System (ADS)

    Longbiao, Li

    2017-06-01

    In this paper, the synergistic effects of temperatrue and oxidation on matrix cracking in fiber-reinforced ceramic-matrix composites (CMCs) has been investigated using energy balance approach. The shear-lag model cooperated with damage models, i.e., the interface oxidation model, interface debonding model, fiber strength degradation model and fiber failure model, has been adopted to analyze microstress field in the composite. The relationships between matrix cracking stress, interface debonding and slipping, fiber fracture, oxidation temperatures and time have been established. The effects of fiber volume fraction, interface properties, fiber strength and oxidation temperatures on the evolution of matrix cracking stress versus oxidation time have been analyzed. The matrix cracking stresses of C/SiC composite with strong and weak interface bonding after unstressed oxidation at an elevated temperature of 700 °C in air condition have been predicted for different oxidation time.

  20. Synergistic Effects of Temperature and Oxidation on Matrix Cracking in Fiber-Reinforced Ceramic-Matrix Composites

    NASA Astrophysics Data System (ADS)

    Longbiao, Li

    2016-10-01

    In this paper, the synergistic effects of temperatrue and oxidation on matrix cracking in fiber-reinforced ceramic-matrix composites (CMCs) has been investigated using energy balance approach. The shear-lag model cooperated with damage models, i.e., the interface oxidation model, interface debonding model, fiber strength degradation model and fiber failure model, has been adopted to analyze microstress field in the composite. The relationships between matrix cracking stress, interface debonding and slipping, fiber fracture, oxidation temperatures and time have been established. The effects of fiber volume fraction, interface properties, fiber strength and oxidation temperatures on the evolution of matrix cracking stress versus oxidation time have been analyzed. The matrix cracking stresses of C/SiC composite with strong and weak interface bonding after unstressed oxidation at an elevated temperature of 700 °C in air condition have been predicted for different oxidation time.

  1. Carbon Fiber Reinforced Glass Matrix Composites for Structural Space Based Applications

    DTIC Science & Technology

    1989-07-31

    1988) 2745-2752. 2 R89-917704-1 10. V. C. Nardone and K. M. Prewo, "Tensile Performance of Carbon-Fibre-Reinforced Glass," J. Mater. Sci., 23 (1988...168-180. 11. K. M. Prewo and V. C. Nardone , "Carbon Fiber Reinforced Glass Matrix Composites for Space Based Applications," UTRC Report R86-917161-1...Mater. Sci., 23 (1988) 2745-2752. 11. V. C. Nardone and K. M. Prewo, "Tensile Performance of Carbon-Fibre-Reinforced Glass," J. Mater. Sci., 23 (1988

  2. Research on construction technology of shaped steel reinforced concrete beam and column

    NASA Astrophysics Data System (ADS)

    Zhu, Shan; Zhang, Zimeng; Liu, Lengjing; Bu, Fangming

    2017-04-01

    The Shaped Steel Reinforced Concrete structures are increasingly used in large-span or irregularly shaped public buildings. In the actual construction, cross-operation of steel structures and concrete is more frequent. Traditional construction method causes a lot of quality problems easily like installation deviation of beam and column, improper treatment of steel at the joints of beams and columns, and unevenness of concrete surface. If you can not take timely measures to deal with or prevent, it will inevitably have a great impact on the reliability of the structure, and also delay the construction schedule. This paper makes related research about the quality issues, proposes corresponding solutions and provides a complete set of construction technology processes. At last, through engineering case, we analyze the economic and social benefits.

  3. An Experimental Study on Strengthening of Reinforced Concrete Flexural Members using Steel Wire Mesh

    NASA Astrophysics Data System (ADS)

    Al Saadi, Hamza Salim Mohammed; Mohandas, Hoby P.; Namasivayam, Aravind

    2017-01-01

    One of the major challenges and contemporary research in the field of structural engineering is strengthening of existing structural elements using readily available materials in the market. Several investigations were conducted on strengthening of various structural components using traditional and advanced materials. Many researchers tried to enhance the reinforced concrete (RC) beams strength using steel plate, Glass and Carbon Fibre Reinforced Polymers (GFRP & CFRP). For the reason that high weight to the strength ratio and compatibility in strength between FRP composites and steel bars, steel plates and GFRP and CFRP composites are not used for strengthening works practically. Hence, in this present work the suitability of using wire mesh for the purpose of strengthening the RC flexural members is studied by conducting experimental works. New technique of strengthening system using wire mesh with a view to improve sectional properties and subsequently flexural strength of RC beams is adopted in this work. The results for experimental and theoretical analysis were compared and found that good correlation exists between them. The experimental results indicate that RC beams strengthened with steel wire mesh are easy technique for strengthening of existing flexural members.

  4. A penny-shaped crack in a filament reinforced matrix. 1: The filament model

    NASA Technical Reports Server (NTRS)

    Erdogan, F.; Pacella, A. H.

    1973-01-01

    The electrostatic problem of a penny-shaped crack in an elastic matrix which reinforced by filaments or fibers perpendicular to the plane of the crack was studied. The elastic filament model was developed for application to evaluation studies of the stress intensity factor along the periphery of the crack, the stresses in the filaments or fibers, and the interface shear between the matrix and the filaments or fibers. The requirements expected of the model are a sufficiently accurate representation of the filament and applicability to the interaction problems involving a cracked elastic continuum with multi-filament reinforcements. The technique for developing the model and numerical examples of it are shown.

  5. Thermo-oxidative stability studies of PMR-15 polymer matrix composites reinforced with various fibers

    NASA Technical Reports Server (NTRS)

    Bowles, Kenneth J.

    1990-01-01

    An experimental study was conducted to measure the thermo-oxidative stability of PMR-15 polymer matrix composites reinforced with various fibers and to observe differences in the way they degrade in air. The fibers that were studied included graphite and the thermally stable Nicalon and Nextel ceramic fibers. Weight loss rates for the different composites were assessed as a function of mechanical properties, specimen geometry, fiber sizing, and interfacial bond strength. Differences were observed in rates of weight loss, matrix cracking, geometry dependency, and fiber-sizing effects. It was shown that Celion 6000 fiber-reinforced composites do not exhibit a straight-line Arrhenius relationship at temperatures above 316 C.

  6. Brillouin corrosion expansion sensors for steel reinforced concrete structures using a fiber optic coil winding method.

    PubMed

    Zhao, Xuefeng; Gong, Peng; Qiao, Guofu; Lu, Jie; Lv, Xingjun; Ou, Jinping

    2011-01-01

    In this paper, a novel kind of method to monitor corrosion expansion of steel rebars in steel reinforced concrete structures named fiber optic coil winding method is proposed, discussed and tested. It is based on the fiber optical Brillouin sensing technique. Firstly, a strain calibration experiment is designed and conducted to obtain the strain coefficient of single mode fiber optics. Results have shown that there is a good linear relationship between Brillouin frequency and applied strain. Then, three kinds of novel fiber optical Brillouin corrosion expansion sensors with different fiber optic coil winding packaging schemes are designed. Sensors were embedded into concrete specimens to monitor expansion strain caused by steel rebar corrosion, and their performance was studied in a designed electrochemical corrosion acceleration experiment. Experimental results have shown that expansion strain along the fiber optic coil winding area can be detected and measured by the three kinds of sensors with different measurement range during development the corrosion. With the assumption of uniform corrosion, diameters of corrosion steel rebars were obtained using calculated average strains. A maximum expansion strain of 6,738 με was monitored. Furthermore, the uniform corrosion analysis model was established and the evaluation formula to evaluate mass loss rate of steel rebar under a given corrosion rust expansion rate was derived. The research has shown that three kinds of Brillouin sensors can be used to monitor the steel rebar corrosion expansion of reinforced concrete structures with good sensitivity, accuracy and monitoring range, and can be applied to monitor different levels of corrosion. By means of this kind of monitoring technique, quantitative corrosion expansion monitoring can be carried out, with the virtues of long durability, real-time monitoring and quasi-distribution monitoring.

  7. Brillouin Corrosion Expansion Sensors for Steel Reinforced Concrete Structures Using a Fiber Optic Coil Winding Method

    PubMed Central

    Zhao, Xuefeng; Gong, Peng; Qiao, Guofu; Lu, Jie; Lv, Xingjun; Ou, Jinping

    2011-01-01

    In this paper, a novel kind of method to monitor corrosion expansion of steel rebars in steel reinforced concrete structures named fiber optic coil winding method is proposed, discussed and tested. It is based on the fiber optical Brillouin sensing technique. Firstly, a strain calibration experiment is designed and conducted to obtain the strain coefficient of single mode fiber optics. Results have shown that there is a good linear relationship between Brillouin frequency and applied strain. Then, three kinds of novel fiber optical Brillouin corrosion expansion sensors with different fiber optic coil winding packaging schemes are designed. Sensors were embedded into concrete specimens to monitor expansion strain caused by steel rebar corrosion, and their performance was studied in a designed electrochemical corrosion acceleration experiment. Experimental results have shown that expansion strain along the fiber optic coil winding area can be detected and measured by the three kinds of sensors with different measurement range during development the corrosion. With the assumption of uniform corrosion, diameters of corrosion steel rebars were obtained using calculated average strains. A maximum expansion strain of 6,738 με was monitored. Furthermore, the uniform corrosion analysis model was established and the evaluation formula to evaluate mass loss rate of steel rebar under a given corrosion rust expansion rate was derived. The research has shown that three kinds of Brillouin sensors can be used to monitor the steel rebar corrosion expansion of reinforced concrete structures with good sensitivity, accuracy and monitoring range, and can be applied to monitor different levels of corrosion. By means of this kind of monitoring technique, quantitative corrosion expansion monitoring can be carried out, with the virtues of long durability, real-time monitoring and quasi-distribution monitoring. PMID:22346672

  8. Thermal shock of fiber reinforced ceramic matrix composites

    NASA Technical Reports Server (NTRS)

    Eckel, Andrew J.; Gyekenyesi, John P.; Herbell, Thomas P.; Generazio, Edward R.

    1991-01-01

    Monolithic silicon carbide and silicon nitride and a Nicalon fiber reinforced silicon carbide composite were subjected to severe thermal shock conditions via impingement of a hydrogen-oxygen flame. Surface heating rates of 1000 C/sec to 2500 C/sec were generated. The performance of the monolithic reference materials are compared and contrasted to the significantly greater thermal shock resistance of the composite. Ultrasonic and radiographic NDE techniques were used to evaluate the integrity of the composite subsequent to thermal shock. Tensile tests were performed to determine the residual tensile strength and modulus. Physical property changes are discussed as a function of number and severity of thermal shock cycles.

  9. Role of interfacial and matrix creep during thermal cycling of continuous fiber reinforced metal-matrix composites

    SciTech Connect

    Dutta, I.

    2000-03-14

    A uni-dimensional micro-mechanical model for thermal cycling of continuous fiber reinforced metal-matrix composites is developed. The model treats the fiber and matrix as thermo-elastic and thermo-elasto-plastic-creeping solids, respectively, and allows the operation of multiple matrix creep mechanisms at various stages of deformation through the use of unified creep laws. It also incorporates the effect of interfacial sliding by an interface-diffusion-controlled diffusional creep mechanism proposed earlier (Funn and Dutta, Acta mater., 1999, 47, 149). The results of thermal cycling simulations based on a graphite fiber reinforced pure aluminum-matrix composite were compared with experimental data on a P100 graphite-6061 Al composite. The model successfully captured all the important features of the observed heating/cooling rate dependence, strain hysteresis, residual permanent strain at the end of a cycle, as well as both intrusion and protrusion of the fiber-ends relative to the matrix at the completion of cycling. The analysis showed that the dominant deformation mechanism operative in the matrix changes continually during thermal cycling due to continuous stress and temperature revision. Based on these results, a framework for the construction of a transient deformation mechanism map for thermal excursions of continuous fiber composites is proposed.

  10. Hardness and wear resistance of carbon nanotube reinforced aluminum-copper matrix composites.

    PubMed

    Nam, Dong Hoon; Kim, Jae Hwang; Cha, Seung Il; Jung, Seung Il; Lee, Jong Kook; Park, Hoon Mo; Park, Hyun Dal; Hong, Hyung

    2014-12-01

    Recently, carbon nanotubes (CNTs) have been attracted to reinforcement of composite materials due to their extraordinary mechanical, thermal and electrical properties. Many researchers have attempted to develop CNT reinforced metal composites with various fabrication methods and have shown possibilities for structural and functional applications. Among them, CNT reinforced Al matrix composites have become very attractive due to their huge structural application in industry. In this study, CNT reinforced Al-Cu matrix composites with a microstructure of homogeneous dispersion of CNTs in the Al-Cu matrix are investigated. The CNT/Al-Cu composites are fabricated by mixing of CNT/Cu composite powders and Al powders by high energy ball mill process followed by hot extrusion process. The hardness and wear resistance of the CNT/Al-Cu composites are enhanced by 1.4 and 3 times, respectively, compared to those values for the Al-Cu matrix. This remarkable enhancement mainly originates from the homogeneous dispersion of CNTs in Al-Cu matrix and self-lubricant effect of CNTs.

  11. Effect of Fiber Poisson Contraction on Matrix Multicracking Evolution of Fiber-Reinforced Ceramic-Matrix Composites

    NASA Astrophysics Data System (ADS)

    Longbiao, Li

    2015-12-01

    An analytical methodology has been developed to investigate the effect of fiber Poisson contraction on matrix multicracking evolution of fiber-reinforced ceramic-matrix composites (CMCs). The modified shear-lag model incorporated with the Coulomb friction law is adopted to solve the stress distribution in the interface slip region and intact region of the damaged composite. The critical matrix strain energy criterion which presupposes the existence of an ultimate or critical strain energy limit beyond which the matrix fails has been adopted to describe matrix multicracking of CMCs. As more energy is placed into the composite, matrix fractures and the interface debonding occurs to dissipate the extra energy. The interface debonded length under the process of matrix multicracking is obtained by treating the interface debonding as a particular crack propagation problem along the fiber/matrix interface. The effects of the interfacial frictional coefficient, fiber Poisson ratio, fiber volume fraction, interface debonded energy and cycle number on the interface debonding and matrix multicracking evolution have been analyzed. The theoretical results are compared with experimental data of unidirectional SiC/CAS, SiC/CAS-II and SiC/Borosilicate composites.

  12. Evaluation of several micromechanics models for discontinuously reinforced metal matrix composites

    NASA Technical Reports Server (NTRS)

    Johnson, W. Steven; Birt, M. J.

    1990-01-01

    A systematic experimental evaluation of whisker and particulate reinforced aluminum matrix composites was conducted to assess the variation in tensile properties with reinforcement type, volume fraction, and specimen thickness. Each material was evaluated in three thicknesses, 1.8, 3.18, and 6.35 mm, to determine the size, distribution, and orientation of the reinforcements. This information was used to evaluate several micromechanical models that predict composite moduli. The longitudinal and transverse moduli were predicted for reinforced aluminum. The Paul model, the Cox model and the Halpin-Tsai model were evaluated. The Paul model gave a good upper bound prediction for the particulate reinforced composites but under predicted whisker reinforced composite moduli. The Cox model gave good moduli predictions for the whisker reinforcement, but was too low for the particulate. The Halpin-Tsai model gave good results for both whisker and particulate reinforced composites. An approach using a trigonometric projection of whisker length to predict the fiber contribution to the modulus in the longitudinal and transverse directions was compared to the more conventional lamination theory approach.

  13. Nanofiber reinforcement of a geopolymer matrix for improved composite materials mechanical performance

    NASA Astrophysics Data System (ADS)

    Rahman, AKM Samsur

    Geopolymers have the potential to cross the process performance gap between polymer matrix and ceramic matrix composites (CMC), enabling high temperature capable composites that are manufactured at relatively low temperatures. Unfortunately, the inherently low toughness of these geopolymers limits the performance of the resulting fiber reinforced geopolymer matrix composites. Toughness improvements in composites can be addressed through the adjustments in the fiber/matrix interfacial strength and through the improvements in the inherent toughness of the constituent materials. This study investigates the potential to improve the inherent toughness of the geopolymer matrix material through the addition of nanofillers, by considering physical dimensions, mechanical properties, reinforcing capability and interfacial bond strength effects. A process optimization study was first undertaken to develop the ability to produce consistent, neat geopolymer samples, a critical precursor to producing nano-filled geopolymer for toughness evaluation. After that, single edge notched bend beam fracture toughness and un-notched beam flexural strength were evaluated for silicon carbide, alumina and carbon nanofillers reinforced geopolymer samples treated at various temperatures in reactive and inert environments. Toughness results of silicon carbide and carbon nanofillers reinforced geopolymers suggested that with the improved baseline properties, high aspect ratio nanofillers with high interfacial bond strength are the most capable in further improving the toughness of geopolymers. Among the high aspect ratio nanofillers i.e. nanofibers, 2vol% silicon carbide whicker (SCW) showed the highest improvement in fracture toughness and flexural strength of ~164% & ~185%, respectively. After heat treatment at 650 °C, SCW reinforcement was found to be effective, with little reduction in the performance, while the performance of alumina nanofiber (ANF) reinforced geopolymer significantly

  14. Application of ceramic fibers to the manufacture of reinforced metal-matrix composites

    SciTech Connect

    Wielage, B.; Rahm, J.; Steinhaeuser, S.

    1995-12-31

    The application of the thermal spraying process is a new way to produce carbon fiber or Tyranno fiber reinforced aluminum matrix composites. Spreaded fiber rovings are enveloped in the matrix material with wire flame spraying. The advantage of the thermal spraying process is based in the low times for contacting between the fibers and the liquid matrix material. Chemical reactions on the interface fiber/matrix, which are caused by the decreasing of the fiber tensile strength, can be excluded. The thermal sprayed prepregs can be compressed to MMC by hot pressing process. This longfiber reinforced composites are used to increase f.e. casted components of motors. The aim of this research is the estimation of possibilities to applicate the wire flame spray process for prepreg manufacturing.

  15. A compliant, high failure strain, fibre-reinforced glass-matrix composite

    NASA Technical Reports Server (NTRS)

    Prewo, K. M.

    1982-01-01

    A glass-matrix composite reinforced by discontinuous graphite fibers was produced by hot pressing glass-powder-impregnated two-dimensional arrays of in-plane randomly oriented graphite fibers held together by approximately 5-10% by weight of organic binder (generally polyester). The composite tensile behavior is characterized by a highly nonlinear stress-strain curve which differs markedly from that of either unreinforced glass or a similarly reinforced epoxy-matrix composite. By virtue of this nonlinearity, the composite is able to redistribute applied stresses to achieve a high load-carrying capacity. The fibrous microstructure and the low fiber-matrix bond provide a mechanism for achieving high fracture toughness and unusually high compliance. For a 96%-silica-matrix composite, the strength is retained to over 1000 C.

  16. A compliant, high failure strain, fibre-reinforced glass-matrix composite

    NASA Technical Reports Server (NTRS)

    Prewo, K. M.

    1982-01-01

    A glass-matrix composite reinforced by discontinuous graphite fibers was produced by hot pressing glass-powder-impregnated two-dimensional arrays of in-plane randomly oriented graphite fibers held together by approximately 5-10% by weight of organic binder (generally polyester). The composite tensile behavior is characterized by a highly nonlinear stress-strain curve which differs markedly from that of either unreinforced glass or a similarly reinforced epoxy-matrix composite. By virtue of this nonlinearity, the composite is able to redistribute applied stresses to achieve a high load-carrying capacity. The fibrous microstructure and the low fiber-matrix bond provide a mechanism for achieving high fracture toughness and unusually high compliance. For a 96%-silica-matrix composite, the strength is retained to over 1000 C.

  17. The Application of Magneto Inductive Sensors for Non-Destructive Testing of Steel Reinforcing Bars Embedded Within Pre-Stressed and Reinforced Concrete

    SciTech Connect

    Benitez, D. S.; Quek, S.; Gaydecki, P.; Torres, V.; Fernandes, B.

    2006-03-06

    This paper demonstrates the feasibility of using solid-state magneto-inductive probes for detecting and imaging of steel reinforcing bars embedded within pre-stressed and reinforced concrete. Changes in the inductance of the sensor material are directly proportional to the strength of the measured magnetic field parallel to the sensor. Experimental results obtained by scanning steel bars specimens are presented. General performance characteristics and sensor output limitations are investigated by using different orientations, sensing distance, excitation intensity, bar sizes and geometries.

  18. Recycling of ceramic particulate reinforced aluminium metal matrix composites

    SciTech Connect

    Sharma, S.C.; Murthy, C.S.C.; Kamath, R.; Vinai Babu, B.R.; Satish, B.M.; Girish, B.M.

    1995-12-31

    The aluminum matrix composites with ceramic dispersoids can be separated by the density difference concept. In the proposed work, composite scrap is recycled using an oil fired furnace. The scrap is melted in the furnace and temperature is maintained below 740 degree centigrade. Because of the density difference the lighter dispersoids will float and heavier dispersoids will settle down. The clean melt is separated be removing the floating and settled dispersoids, and then filtering using ceramic filters.

  19. Fiber optic pH sensor for early detection of danger of corrosion in steel-reinforced concrete structures

    NASA Astrophysics Data System (ADS)

    Dantan, Nathalie; Habel, Wolfgang R.; Wolfbeis, Otto S.

    2005-05-01

    Corrosion in steel-reinforced concrete structures is a critical issue. Corrosion appears if the pH value of the concrete matrix decreases due to deterioration of the calcium hydroxide layer on the steel surface. At present, several reliable systems for determination of chemical parameters in aggressive environments are available on the market, but can not be used for long-term monitoring of pH in concrete structures. This paper describes the development of a fiber optic chemical sensor for this purpose. Particular attention is paid to the requirements on such a sensing system. Usually applied methods of fiber optical chemical sensing were investigated and compared by using several pH-sensitive materials. Based on these results, a functional pH sensor has been configured. It shows good response behavior and works under strongly alkaline conditions for one year. Therefore, it represents a promising sensor type for in-situ long-term monitoring in concrete structures. Further work is in progress to test such sensors on-site under real application conditions, e.g. in ground anchors.

  20. Prestressing effect of cold-drawn short NiTi SMA fibres in steel reinforced mortar beams

    NASA Astrophysics Data System (ADS)

    Choi, Eunsoo; Kim, Dong Joo; Hwang, Jin-Ha; Kim, Woo Jin

    2016-08-01

    This study investigated the prestressing effect of cold-drawn short NiTi shape memory alloy (SMA) fibres in steel reinforced mortar beams. The SMA fibres were mixed with 1.5% volume content in a mortar matrix with the compressive strength of 50 MPa. The SMA fibres had an average length of 34 mm, and they were manufactured with a dog-bone shape: the diameters of the end- and middle-parts were 1.024 and 1.0 mm, respectively. Twenty mortar beams with the dimensions of 40 mm × 40 mm × 160 mm (B × H × L) were prepared. Two types of tests were conducted. One was to investigate the prestressing effect of the SMA fibres, and the beams with the SMA fibres were heated at the bottom. The other was to assess the bending behaviour of the beams prestressed by the SMA fibres. The SMA fibres induced upward deflection and cracking at the top surface by heating at the bottom; thus, they achieved an obvious prestressing effect. The beams that were prestressed by the SMA fibres did not show a significant difference in bending behaviour from that of the SMA fibre reinforced beams that were not subjected to heating. Stress analysis of the beams indicated that the prestressing effect decreased in relation to the cooling temperature.

  1. Development and mechanical characterization of carbon-fiber-reinforced cement composites and mechanical properties and structural applications of steel-fiber-reinforced concrete. (Volumes I and II)

    SciTech Connect

    Bayasi, M.Z.

    1989-01-01

    Based on a comprehensive experimental study on carbon fiber reinforced cement composites incorporating the Ashland's industrial grade carbon fiber reinforced cement composites incorporating the Ashland's inductrial grade carbon fibers (Carboflex), the optimum mix variables and processing techniques were decided. The types and proportions of different mix constituents, the fiber lengths and volume fractions, and the mixing and curing procedures which produce desirable fresh mix properties and superior hardened material performance were decided. A comprehensive experimental data set on the performance characteristics of carbon fiber reinforced cement was also generated. The research was performed in three phases: (1) Establishment of the mixing procedure and mix proportions for achieving desirable fresh mix characteristics; (2) Assessment of the trends in the effects of different mix variables on the strength of air cured specimens and further optimization of the mix proportions for achieving superior strength characteristics in addition to the desirable fresh mix workability; and (3) Optimization of the curing condition and full mechanical characterization for carbon fiber reinforced cement composites with some optimum values of fiber length and volume fraction. A comprehensive investigation was performed on the material properties and structural applications of steel fiber reinforced concrete. In studies on the application of steel fiber reinforced concrete a load bearing structural elements, the effects of steel fibers on improving the strength and ductility of concrete footings under bearing pressure, and enhancing bond between deformed bars and concrete were investigated.

  2. Seamless metal-clad fiber-reinforced organic matrix composite structures and process for their manufacture

    NASA Technical Reports Server (NTRS)

    Bluck, Raymond M. (Inventor); Bush, Harold G. (Inventor); Johnson, Robert R. (Inventor)

    1990-01-01

    A metallic outer sleeve is provided which is capable of enveloping a hollow metallic inner member having continuous reinforcing fibers attached to the distal end thereof. The inner member is then introduced into outer sleeve until inner member is completely enveloped by outer sleeve. A liquid matrix member is then injected into space between inner member and outer sleeve. A pressurized heat transfer medium is flowed through the inside of inner member, thereby forming a fiber reinforced matrix composite material. The wall thicknesses of both inner member and outer sleeve are then reduced to the appropriate size by chemical etching, to adjust the thermal expansion coefficient of the metal-clad composite structure to the desired value. thereby forming a fiber reinforced matrix composite material. The wall thicknesses of both inner member and outer sleeve are then reduced to the appropriate size by chemical etching, to adjust the thermal expansion coefficient of the metal-clad composite structure to the desired value. The novelty of this invention resides in the development of a efficient method of producing seamless metal clad fiber reinforced organic matrix composite structures.

  3. Experimental Study on the Strength Characteristics and Water Permeability of Hybrid Steel Fibre Reinforced Concrete.

    PubMed

    Singh, M P; Singh, S P; Singh, A P

    2014-01-01

    Results of an investigation conducted to study the effect of fibre hybridization on the strength characteristics such as compressive strength, split tensile strength, and water permeability of steel fibre reinforced concrete (SFRC) are presented. Steel fibres of different lengths, that is, 12.5 mm, 25 mm, and 50 mm, having constant diameter of 0.6 mm, were systematically combined in different mix proportions to obtain mono, binary, and ternary combinations at each of 0.5%, 1.0%, and 1.5% fibre volume fraction. A concrete mix containing no fibres was also cast for reference purpose. A total number of 1440 cube specimens of size 100∗100∗100 mm were tested, 480 each for compressive strength, split tensile strength, and water permeability at 7, 28, 90, and 120 days of curing. It has been observed from the results of this investigation that a fibre combination of 33% 12.5 mm + 33% 25 mm + 33% 50 mm long fibres can be adjudged as the most appropriate combination to be employed in hybrid steel fibre reinforced concrete (HySFRC) for optimum performance in terms of compressive strength, split tensile strength and water permeability requirements taken together.

  4. Experimental Study on the Strength Characteristics and Water Permeability of Hybrid Steel Fibre Reinforced Concrete

    PubMed Central

    Singh, M. P.; Singh, S. P.; Singh, A. P.

    2014-01-01

    Results of an investigation conducted to study the effect of fibre hybridization on the strength characteristics such as compressive strength, split tensile strength, and water permeability of steel fibre reinforced concrete (SFRC) are presented. Steel fibres of different lengths, that is, 12.5 mm, 25 mm, and 50 mm, having constant diameter of 0.6 mm, were systematically combined in different mix proportions to obtain mono, binary, and ternary combinations at each of 0.5%, 1.0%, and 1.5% fibre volume fraction. A concrete mix containing no fibres was also cast for reference purpose. A total number of 1440 cube specimens of size 100∗100∗100 mm were tested, 480 each for compressive strength, split tensile strength, and water permeability at 7, 28, 90, and 120 days of curing. It has been observed from the results of this investigation that a fibre combination of 33% 12.5 mm + 33% 25 mm + 33% 50 mm long fibres can be adjudged as the most appropriate combination to be employed in hybrid steel fibre reinforced concrete (HySFRC) for optimum performance in terms of compressive strength, split tensile strength and water permeability requirements taken together. PMID:27379298

  5. Nonlinear Lamb waves for fatigue damage identification in FRP-reinforced steel plates.

    PubMed

    Wang, Yikuan; Guan, Ruiqi; Lu, Ye

    2017-09-01

    A nonlinear Lamb-wave-based method for fatigue crack detection in steel plates with and without carbon fibre reinforcement polymer (CFRP) reinforcement is presented in this study. Both numerical simulation and experimental evaluation were performed for Lamb wave propagation and its interaction with a fatigue crack on these two steel plate types. With the generation of the second harmonic, the damage-induced wave nonlinearities were identified by surface-bonded piezoelectric sensors. Numerical simulation revealed that the damage-induced wave component at the second harmonic was slightly affected by the existence of CFRP laminate, although the total wave energy was decreased because of wave leakage into the CFRP laminate. Due to unavoidable nonlinearity from the experimental environments, it was impractical to directly extract the time-of-flight of the second harmonic for locating the crack. To this end, the correlation coefficient of benchmark and signal with damage at double frequency in the time domain was calculated, based on which an imaging method was introduced to locate the fatigue crack in steel plates with and without CFRP laminates. Copyright © 2017 Elsevier B.V. All rights reserved.

  6. Compressive Behavior of Fiber-Reinforced Concrete with End-Hooked Steel Fibers

    PubMed Central

    Lee, Seong-Cheol; Oh, Joung-Hwan; Cho, Jae-Yeol

    2015-01-01

    In this paper, the compressive behavior of fiber-reinforced concrete with end-hooked steel fibers has been investigated through a uniaxial compression test in which the variables were concrete compressive strength, fiber volumetric ratio, and fiber aspect ratio (length to diameter). In order to minimize the effect of specimen size on fiber distribution, 48 cylinder specimens 150 mm in diameter and 300 mm in height were prepared and then subjected to uniaxial compression. From the test results, it was shown that steel fiber-reinforced concrete (SFRC) specimens exhibited ductile behavior after reaching their compressive strength. It was also shown that the strain at the compressive strength generally increased along with an increase in the fiber volumetric ratio and fiber aspect ratio, while the elastic modulus decreased. With consideration for the effect of steel fibers, a model for the stress–strain relationship of SFRC under compression is proposed here. Simple formulae to predict the strain at the compressive strength and the elastic modulus of SFRC were developed as well. The proposed model and formulae will be useful for realistic predictions of the structural behavior of SFRC members or structures. PMID:28788011

  7. Compressive Behavior of Fiber-Reinforced Concrete with End-Hooked Steel Fibers.

    PubMed

    Lee, Seong-Cheol; Oh, Joung-Hwan; Cho, Jae-Yeol

    2015-03-27

    In this paper, the compressive behavior of fiber-reinforced concrete with end-hooked steel fibers has been investigated through a uniaxial compression test in which the variables were concrete compressive strength, fiber volumetric ratio, and fiber aspect ratio (length to diameter). In order to minimize the effect of specimen size on fiber distribution, 48 cylinder specimens 150 mm in diameter and 300 mm in height were prepared and then subjected to uniaxial compression. From the test results, it was shown that steel fiber-reinforced concrete (SFRC) specimens exhibited ductile behavior after reaching their compressive strength. It was also shown that the strain at the compressive strength generally increased along with an increase in the fiber volumetric ratio and fiber aspect ratio, while the elastic modulus decreased. With consideration for the effect of steel fibers, a model for the stress-strain relationship of SFRC under compression is proposed here. Simple formulae to predict the strain at the compressive strength and the elastic modulus of SFRC were developed as well. The proposed model and formulae will be useful for realistic predictions of the structural behavior of SFRC members or structures.

  8. Performance of epoxy-coated reinforced steel in the deck of the Perley Bridge

    SciTech Connect

    Covino, Bernard S., Jr.; Cramer, Stephen D.; Holcomb, Gordon R.; Russell, James H.; Bullard, Sophie J.; Dahlin, Cheryl L.; Tinnea, J.S.

    2001-01-01

    The Perley Bridge spanned the Ottawa River between the Canadian provinces of Ontario and Quebec from 1931 to 1999. Epoxy-coated steel reinforcing bar (ECR) was used in 1979 in an effort to extend the service life of span 17. Patches were needed to repair corrosion of the west lane as little as 7 to 11 years later. No patches were needed for the east lane which had twice the cover concrete of the west lane. Examinations showed that the original concrete in both lanes and the patch concrete in the west lane were of good quality. Epoxy adhesion to the steel reinforcing bar was good to fair over much of the reinforcing bar, but poor to failed in isolated areas. Analytical scanning electron microscopy (ASEM) identified voids, rust, cracked epoxy, and cracked concrete at some ECR locations. Chloride profiling of the concrete in both lanes, coupled with the corrosion threshold level of chloride, indicated that the time required for corrosion to cause visible damage of the deck was 6.2 years for the west lane and 18.9 years for the east lane.

  9. Comparative Study on Corrosion Protection of Reinforcing Steel by Using Amino Alcohol and Lithium Nitrite Inhibitors.

    PubMed

    Lee, Han-Seung; Ryu, Hwa-Sung; Park, Won-Jun; Ismail, Mohamed A

    2015-01-14

    In this study, the ability of lithium nitrite and amino alcohol inhibitors to provide corrosion protection to reinforcing steel was investigated. Two types of specimens-reinforcing steel and a reinforced concrete prism that were exposed to chloride ion levels resembling the chloride attack environment-were prepared. An autoclave accelerated corrosion test was then conducted. The variables tested included the chloride-ion concentration and molar ratios of anti-corrosion ingredients in a CaOH₂-saturated aqueous solution that simulated a cement-pore solution. A concentration of 25% was used for the lithium nitrite inhibitor LiNO₂, and an 80% solution of dimethyl ethanolamine ((CH₃)₂NCH₂CH₂OH, hereinafter DMEA) was used for the amino alcohol inhibitor. The test results indicated that the lithium nitrite inhibitor displayed anti-corrosion properties at a molar ratio of inhibitor of ≥0.6; the amino alcohol inhibitor also displayed anti-corrosion properties at molar ratios of inhibitor greater than approximately 0.3.

  10. Comparative Study on Corrosion Protection of Reinforcing Steel by Using Amino Alcohol and Lithium Nitrite Inhibitors

    PubMed Central

    Lee, Han-Seung; Ryu, Hwa-Sung; Park, Won-Jun; Ismail, Mohamed A.

    2015-01-01

    In this study, the ability of lithium nitrite and amino alcohol inhibitors to provide corrosion protection to reinforcing steel was investigated. Two types of specimens—reinforcing steel and a reinforced concrete prism that were exposed to chloride ion levels resembling the chloride attack environment—were prepared. An autoclave accelerated corrosion test was then conducted. The variables tested included the chloride-ion concentration and molar ratios of anti-corrosion ingredients in a CaOH2-saturated aqueous solution that simulated a cement-pore solution. A concentration of 25% was used for the lithium nitrite inhibitor LiNO2, and an 80% solution of dimethyl ethanolamine ((CH3)2NCH2CH2OH, hereinafter DMEA) was used for the amino alcohol inhibitor. The test results indicated that the lithium nitrite inhibitor displayed anti-corrosion properties at a molar ratio of inhibitor of ≥0.6; the amino alcohol inhibitor also displayed anti-corrosion properties at molar ratios of inhibitor greater than approximately 0.3. PMID:28787936

  11. Fabrication and characterization of carbon nanotube reinforced magnesium matrix composites

    NASA Astrophysics Data System (ADS)

    Mindivan, Harun; Efe, Arife; Kosatepe, A. Hadi; Kayali, E. Sabri

    2014-11-01

    In the present investigation, Mg chips are recycled to produce Mg-6 wt.% Al reinforced with 0.5, 1, 2 and 4 wt.% nanosized CNTs by mechanical ball milling, cold pressing and subsequently hot extrusion process without sintering step. The microstructure, mechanical properties and corrosion behavior of Mg/Al without CNT (base alloy) and composites were evaluated. The distribution of CNTs was analyzed using a Scanning Electron Microscopy (SEM) equipped with Energy Dispersive Spectroscopy (EDS) analyzer and a Wavelength Dispersive X-Ray Fluorescence spectrometer (WDXRF). Microstructural analysis revealed that the CNTs on the Mg chips were present throughout the extrusion direction and the uniform distribution of CNTs at the chip surface decreased with increase in the CNT content. The results of the mechanical and corrosion test showed that small addition of CNTs (0.5 wt.%) evidently improved the hardness and corrosion resistance of the composite by comparing with the base alloy, while increase in the CNT weight fraction in the initial mixture resulted in a significant decrease of hardness, compression strength, wear rate and corrosion resistance.

  12. Study of corrosion behavior of high strength low alloy steel reinforcing bars in industrial and marine environments

    SciTech Connect

    Singh, S.K.; Hocking, M.G.; Jha, R.; Chatterjee, A.; Mukherjee, T.

    1996-11-01

    Mild steel reinforcing bars embedded in concrete exposed to marine environment are prone to severe corrosion leading to serious damage to the structures. The various technologies developed and adopted to reduce the corrosion of steel reinforcement, have been discussed in this paper along with a new high strength low alloy (HSLA) steel reinforcing bar. The bare HSLA rebars have been tested extensively along with mild steel rebars for comparative study in saline and sulfurous electrolytes in the laboratory by Potentiodynamic tests as well as in natural marine and industrial environments. The HSLA and mild steel rebars embedded in concrete were also tested in saline water by alternate immersion test and by impressed anodic current methods. The bare HSLA rebars showed 2--3 and 1.5--1.9 times better corrosion resistance to mild steel rebars in laboratory and field exposure tests respectively. The HSLA rebars embedded in concrete and exposed to saline water with impressed anodic current of 200 {micro}A/sq. cm showed 2.5 times better corrosion resistance to mild steel rebars. The XRD analysis of the rust formed on the samples of field exposure tests conducted in marine and industrial environments, clearly showed the formation of compounds which reduce the corrosion rate of steel.

  13. Determination of Material Parameters for Microbuckling Analysis of Fiber Reinforced Polymer Matrix Composites

    NASA Astrophysics Data System (ADS)

    Romanowicz, M.

    2015-05-01

    This research focuses on studying the effect of the constitutive law adopted for a matrix material on the compressive response of a unidirectional fiber reinforced polymer matrix composite. To investigate this effect, a periodic unit cell model of a unidirectional composite with an initial fiber waviness and inelastic behavior of the matrix was used. The sensitivity of the compressive strength to the hydrostatic pressure, the flow rule and the fiber misalignment angle were presented. The model was verified against an analytical solution and experimental data. Results of this study indicate that a micromechanical model with correctly identified material parameters provides a useful alternative to theoretical models and experimentation.

  14. Compressibility of 304 Stainless Steel Powder Metallurgy Materials Reinforced with 304 Short Stainless Steel Fibers.

    PubMed

    Yao, Bibo; Zhou, Zhaoyao; Duan, Liuyang; Xiao, Zhiyu

    2016-03-04

    Powder metallurgy (P/M) technique is usually used for manufacturing porous metal materials. However, some P/M materials are limitedly used in engineering for their performance deficiency. A novel 304 stainless steel P/M material was produced by a solid-state sintering of 304 stainless steel powders and 304 short stainless steel fibers, which were alternately laid in layers according to mass ratio. In this paper, the compressive properties of the P/M materials were characterized by a series of uniaxial compression tests. The effects of fiber content, compaction pressure and high temperature nitriding on compressive properties were investigated. The results indicated that, without nitriding, the samples changed from cuboid to cydariform without damage in the process of compression. The compressive stress was enhanced with increasing fiber content ranging from 0 to 8 wt.%. For compaction pressure from 55 to 75 MPa, greater compaction pressure improved compressive stress. Moreover, high temperature nitriding was able to significantly improve the yield stress, but collapse failure eventually occurred.

  15. Compressibility of 304 Stainless Steel Powder Metallurgy Materials Reinforced with 304 Short Stainless Steel Fibers

    PubMed Central

    Yao, Bibo; Zhou, Zhaoyao; Duan, Liuyang; Xiao, Zhiyu

    2016-01-01

    Powder metallurgy (P/M) technique is usually used for manufacturing porous metal materials. However, some P/M materials are limitedly used in engineering for their performance deficiency. A novel 304 stainless steel P/M material was produced by a solid-state sintering of 304 stainless steel powders and 304 short stainless steel fibers, which were alternately laid in layers according to mass ratio. In this paper, the compressive properties of the P/M materials were characterized by a series of uniaxial compression tests. The effects of fiber content, compaction pressure and high temperature nitriding on compressive properties were investigated. The results indicated that, without nitriding, the samples changed from cuboid to cydariform without damage in the process of compression. The compressive stress was enhanced with increasing fiber content ranging from 0 to 8 wt.%. For compaction pressure from 55 to 75 MPa, greater compaction pressure improved compressive stress. Moreover, high temperature nitriding was able to significantly improve the yield stress, but collapse failure eventually occurred. PMID:28773285

  16. Characterization of Polyester Matrix Reinforced with Banana Fibers Thermal Properties by Photoacoustic Technique

    NASA Astrophysics Data System (ADS)

    de Assis, Foluke S.; Netto, Pedro A.; Margem, Frederico M.; Monteiro, Artur R. P. Junior Sergio N.

    Synthetic fibers are being replaced gradually by natural materials such as lignocellulosic fibers. Compared to synthetic fibers, natural fibers have shown advantages in technical aspects such as environmental and economic. So there is a growing international interest in the use of those fibers. The banana fiber presents significant properties to be studied, but until now few thermal properties on banana fiber as reinforcement of polyester matrix were performed. The present work had as its objective to investigate, by photoacoustic spectroscopy and photothermal techniques the thermal properties of diffusivity, specific heat capacity and conductivity for polyester composites reinforced with banana fibers. In the polyester matrix will be added up to 30% in volume of continuous and aligned banana fibers. These values show that the incorporation of banana fibers in the polyester matrix changes its thermal properties.

  17. Interfacial characterization in carbon nanotube reinforced aluminum matrix composites

    SciTech Connect

    Housaer, F.; Beclin, F.; Touzin, M.; Tingaud, D.; Legris, A.; Addad, A.

    2015-12-15

    In this work, the effects of the sintering parameters, such as temperature and the techniques used (HP and SPS), on CNT/Al composite interfaces are studied. The major role of the native aluminum oxide (Al{sub 2}O{sub 3}) layer covering the aluminum grains is highlighted. It is shown that, for a sintering temperature below 620 °C, the amorphous Al{sub 2}O{sub 3} layer prevents the reaction between aluminum and carbon. For greater sintering temperatures, the breaking of the oxide layer due to its crystallization leads to the formation of aluminum carbide (Al{sub 4}C{sub 3}) by reaction between aluminum and the CNT. The Al{sub 4}C{sub 3} crystals grow perpendicularly to the matrix grain boundaries by thermally activated diffusion of the carbon atoms coming from the CNT. It is also demonstrated that, by limiting the sintering time, which is the case in SPS, it is possible to limit the growth of the Al{sub 4}C{sub 3} crystals and thus to preserve the CNT. - Highlights: • The high reactivity between CNT and Al matrix, resulting Al{sub 4}C{sub 3} formation during the sintering process is highlighted. • We demonstrate, thanks to in-situ TEM observations, that Al{sub 4}C{sub 3} crystals grow into aluminum grains by carbon diffusion. • The native aluminum oxide around the aluminum particles prevents the diffusion of carbon into the aluminum grains. • We show that the protective layer can be broken because of its crystallization, leading to the formation of Al{sub 4}C{sub 3}. • SPS, by limiting the sintering duration, is an interesting way for preparing CNT/Al composites without carbide formation.

  18. Hybrid Effect Evaluation of Steel Fiber and Carbon Fiber on the Performance of the Fiber Reinforced Concrete

    PubMed Central

    Song, Weimin; Yin, Jian

    2016-01-01

    Fiber reinforcement is an important method to enhance the performance of concrete. In this study, the compressive test and impact test were conducted, and then the hybrid effect between steel fiber (SF) and carbon fiber (CF) was evaluated by employing the hybrid effect index. Compressive toughness and impact toughness of steel fiber reinforced concrete (SFRC), carbon fiber reinforced concrete (CFRC) and hybrid fiber reinforced concrete (HFRC) were explored at steel fiber volume fraction 0.5%, 1%, 1.5% and carbon fiber 0.1%, 0.2%, 0.3%. Results showed that the addition of steel fiber and carbon fiber can increase the compressive strength. SF, CF and the hybridization between them could increase the compressive toughness significantly. The impact test results showed that as the volume of fiber increased, the impact number of the first visible crack and the ultimate failure also increased. The improvement of toughness mainly lay in improving the crack resistance after the first crack. Based on the test results, the positive hybrid effect of steel fiber and carbon fiber existed in hybrid fiber reinforced concrete. The relationship between the compressive toughness and impact toughness was also explored. PMID:28773824

  19. Hybrid Effect Evaluation of Steel Fiber and Carbon Fiber on the Performance of the Fiber Reinforced Concrete.

    PubMed

    Song, Weimin; Yin, Jian

    2016-08-18

    Fiber reinforcement is an important method to enhance the performance of concrete. In this study, the compressive test and impact test were conducted, and then the hybrid effect between steel fiber (SF) and carbon fiber (CF) was evaluated by employing the hybrid effect index. Compressive toughness and impact toughness of steel fiber reinforced concrete (SFRC), carbon fiber reinforced concrete (CFRC) and hybrid fiber reinforced concrete (HFRC) were explored at steel fiber volume fraction 0.5%, 1%, 1.5% and carbon fiber 0.1%, 0.2%, 0.3%. Results showed that the addition of steel fiber and carbon fiber can increase the compressive strength. SF, CF and the hybridization between them could increase the compressive toughness significantly. The impact test results showed that as the volume of fiber increased, the impact number of the first visible crack and the ultimate failure also increased. The improvement of toughness mainly lay in improving the crack resistance after the first crack. Based on the test results, the positive hybrid effect of steel fiber and carbon fiber existed in hybrid fiber reinforced concrete. The relationship between the compressive toughness and impact toughness was also explored.

  20. Fabrication of fibre reinforced nickel aluminide matrix composites by reactive processing

    SciTech Connect

    Downing, M.; Horsfall, I.

    1994-12-31

    This paper describes the fabrication by reactive processing of short, and continuous, alumina fibre reinforced nickel aluminide matrix composites. The fibre is introduced into the aluminide system to increase toughness and high temperature strength. The short fibre reinforced nickel aluminide is formed by squeeze casting a porous preform containing nickel powder and SAFFIL fibre with an aluminium or aluminium alloy melt. The continuous fibre reinforced nickel aluminide is formed by squeeze casting a jig containing nickel coated ALMAX fibre. The short fibre reinforced composite (containing 10% and 20% volume fibre) reacted during infiltration with an aluminium melt to form a single phase intermetallic. Using an aluminium-copper melt the intermetallic formation was inhibited and a multi-phase composite was obtained. A preliminary study into reactive processing of this system by utilising a hot isostatic pressing (HIP) cycle is presented. HIP was required to prevent the formation of porosity due to an imbalance in the diffusive mobility of the various components. It was found that HIP was only effective on canned samples, the preferred encapsulation material being glass. The continuous fibre reinforced composite did not react to an intermetallic phase when infiltrated with an aluminum melt. Use of an aluminum-copper melt resulted in partial nickel-melt reaction producing various nickel-aluminum (-copper) phases. HIP was then used to form a two phase intermetallic matrix with no evidence of fibre damage.

  1. Comparison of rates of general corrosion and maximum pitting penetration on concrete embedded steel reinforcement

    SciTech Connect

    Gonzalez, J.A.; Feliu, S. ); Andrade, C.; Alonso, C. )

    1995-02-01

    Local attack of reinforcement is observed usually in chloride-contaminated concrete. When mechanical weakening of the concrete structure is affected by the bar section loss in the places where corrosion is intensified, the maximum penetration of the deepest pits happens to be a very relevant datum. In this work average corrosion values are compared with maximum pit depth values. Using natural corrosion tests and accelerated tests, it has been found that the maximum penetration of localized attack on steel embedded in concrete containing chlorides is equivalent to about four to eight times the average general penetration.

  2. Design of reinforcement welding machine within steel framework for marine engineering

    NASA Astrophysics Data System (ADS)

    Wang, Gang; Wu, Jin

    2017-04-01

    In this project, a design scheme that reinforcement welding machine is added within the steel framework is proposed according to the double-side welding technology for box-beam structure in marine engineering. Then the design and development of circuit and transmission mechanism for new welding equipment are completed as well with one sample machine being made. Moreover, the trial running is finished finally. Main technical parameters of the equipment are: the working stroke: ≥1500mm, the welding speed: 8˜15cm/min and the welding sheet thickness: ≥20mm.

  3. Hi-Nicalon Fiber-Reinforced Celsian Matrix Composites: Influence of Interface Modification

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.; Eldridge, Jeffrey I.

    1998-01-01

    Unidirectional celsian matrix composites having 42-45 vol % of uncoated or BN-SIC coated Hi-Nicalon fibers were tested in three-point bend at room temperature. The uncoated fiber-reinforced composites showed catastrophic failure with strength of 210 35 MPa and a flat fracture surface. In contrast, composites reinforced with coated fibers exhibited graceful failure with extensive fiber pullout. Values of first matrix cracking stress and strain were 435 +/- 35 MPa and 0.27 +/- 0.01%, respectively, with ultimate strength as high as 960 MPa. The elastic Young modulus of the uncoated and coated fiber-reinforced composites were 184 +/- 4 GPa and 165 +/- 5 GPa, respectively. Fiber push-through tests and microscopic examination indicated no chemical reaction at the uncoated or coated fiber-matrix interface. The low strength of composite with uncoated fibers is due to degradation of the fiber strength from mechanical damage during processing. Because both the coated- and uncoated-fiber-reinforced composites exhibited weak interfaces, the beneficial effect of the BN-SIC dual layer is primarily the protection of fibers from mechanical damage during processing.

  4. Statistical variations in impact resistance of steel fiber-reinforced concrete subjected to drop weight test

    SciTech Connect

    Nataraja, M.C.; Dhang, N.; Gupta, A.P.

    1999-07-01

    The variation in impact resistance of steel fiber-reinforced concrete and plain concrete as determined from a drop weight test is reported. The observed coefficients of variation are about 57 and 46% for first-crack resistance and the ultimate resistance in the case of fiber concrete and the corresponding values for plain concrete are 54 and 51%, respectively. The goodness-of-fit test indicated poor fitness of the impact-resistance test results produced in this study to normal distribution at 95% level of confidence for both fiber-reinforced and plain concrete. However, the percentage increase in number of blows from first crack to failure for both fiber-reinforced concrete and as well as plain concrete fit to normal distribution as indicated by the goodness-of-fit test. The coefficient of variation in percentage increase in the number of blows beyond first crack for fiber-reinforced concrete and plain concrete is 51.9 and 43.1%, respectively. Minimum number of tests required to reliably measure the properties of the material can be suggested based on the observed levels of variation.

  5. LONG-TERM EFFECTS OF WASTE SOLUTIONS ON CONCRETE AND REINFORCING STEEL

    SciTech Connect

    DANIEL JI; START DC; KAAR PH

    1983-05-28

    This report has been prepared for the In Situ Waste Disposal Program Tank Assessment Task (WG-11) as part of an investigation to evaluate the long-term performance of waste storage tanks at the Hanford Site. This report, prepared by the Portland Cement Association, presents the results of four years of concrete degradation studies which exposed concrete and reinforcing steel, under load and at 180 F, to simulated double-shell slurry, simulated salt cake solution, and a control solution. Exposure length varied from 3 months to 36 months. In all cases, examination of the concrete and reinforcing steel at the end of the exposure indicated there was no attack, i.e., no evidence of rusting, cracking, disruption of mill scale or loss of strength. Radioactive waste resulting from the chemical processing of reactor fuel for recovery of special nuclear materials (primarily plutonium), has been accumulating at the Hanford Site since 1944. The defense waste is currently being stored in underground waste tanks and in capsules stored in water basins. Current U.S. Department of Energy (DOE) strategy is to emphasize development and implementation of technology for removal, solidification, and final disposition of defense waste at the Savannah River Site first, then at the Hanford Site. Final disposal of waste in tanks at Hanford is expected to consist of in-place stabilization of most tanks. Selected tank wastes may be retrieved. Disposal operations will be carried out during the next several decades. Consequently, defense waste will remain in the existing underground tanks at Hanford for at least several decades. To ensure the safe storage of the waste, the waste storage tanks are being evaluated for continued service as part of the DOE Waste Tank Evaluation Program (AR-005-10-02-G). Technical studies and laboratory tests have been conducted to determine the effect of the stored waste's chemicals and temperature on the reinforced concrete. Waste solutions, which can be

  6. CermeTi® discontinuously reinforced Ti-matrix composites: Manufacturing, properties, and applications

    NASA Astrophysics Data System (ADS)

    Abkowitz, Stanley; Abkowitz, Susan M.; Fisher, Harvey; Schwartz, Patricia J.

    2004-05-01

    Advanced powder-metallurgy technology has led to the development of the CermeTi® family of titanium metalmatrix composites. Reinforcing the titanium alloy matrix with titanium carbide or titanium boride particles results in superior properties. These discontinuously reinforced titanium composites have excellent room- and elevated-temperature properties and are exceptionally wear resistant. High quality, near-net shape CermeTi composite components are being produced commercially and are being evaluated for potential applications in military vehicles, commercial automotive engines, sporting goods, industrial tooling, and biomedical devices.

  7. Thermo-oxidative stability studies of PMR-15 polymer matrix composites reinforced with various continuous fibers

    NASA Technical Reports Server (NTRS)

    Bowles, Kenneth J.

    1990-01-01

    An experimental study was conducted to measure the thermooxidative stability of PMR-15 composites reinforced with various fibers and to observe differences in the way they degrade in air. The fibers studied include graphite and the thermally stable Nicalon and Nextel ceramic fibers. Weight-loss rates for the different composites were assessed as a function of mechanical properties, specimen geometry, fiber sizing, and interfacial bond strength. Differences were observed in rates of weight loss, matrix cracking, geometry dependency, and fiber sizing effects. It was shown that Celion 6000 fiber-reinforced composites do not exhibit a straight-line Arrhenius relationship at temperatures above 316 C.

  8. Thermo-oxidative stability studies of PMR-15 polymer matrix composites reinforced with various continuous fibers

    NASA Technical Reports Server (NTRS)

    Bowles, Kenneth J.

    1990-01-01

    An experimental study was conducted to measure the thermooxidative stability of PMR-15 composites reinforced with various fibers and to observe differences in the way they degrade in air. The fibers studied include graphite and the thermally stable Nicalon and Nextel ceramic fibers. Weight-loss rates for the different composites were assessed as a function of mechanical properties, specimen geometry, fiber sizing, and interfacial bond strength. Differences were observed in rates of weight loss, matrix cracking, geometry dependency, and fiber sizing effects. It was shown that Celion 6000 fiber-reinforced composites do not exhibit a straight-line Arrhenius relationship at temperatures above 316 C.

  9. Niobium Carbide-Reinforced Al Matrix Composites Produced by High-Energy Ball Milling

    NASA Astrophysics Data System (ADS)

    Travessa, Dilermando Nagle; Silva, Marina Judice; Cardoso, Kátia Regina

    2017-06-01

    Aluminum and its alloys are key materials for the transportation industry as they contribute to the development of lightweight structures. The dispersion of hard ceramic particles in the Al soft matrix can lead to a substantial strengthening effect, resulting in composite materials exhibiting interesting mechanical properties and inspiring their technological use in sectors like the automotive and aerospace industries. Powder metallurgy techniques are attractive to design metal matrix composites, achieving a homogeneous distribution of the reinforcement into the metal matrix. In this work, pure aluminum has been reinforced with particles of niobium carbide (NbC), an extremely hard and stable refractory ceramic. Its use as a reinforcing phase in metal matrix composites has not been deeply explored. Composite powders produced after different milling times, with 10 and 20 vol pct of NbC were produced by high-energy ball milling and characterized by scanning electron microscopy and by X-ray diffraction to establish a relationship between the milling time and size, morphology, and distribution of the particles in the composite powder. Subsequently, an Al/10 pct NbC composite powder was hot extruded into cylindrical bars. The strength of the obtained composite bars is comparable to the commercial high-strength, aeronautical-grade aluminum alloys.

  10. Finite element analysis of stress transfer mechanism from matrix to the fiber in SWCN reinforced nanocomposites

    NASA Astrophysics Data System (ADS)

    Günay, E.

    2017-02-01

    This study defined as micromechanical finite element (FE) approach examining the stress transfer mechanism in single-walled carbon nanotube (SWCN) reinforced composites. In the modeling, 3D unit-cell method was evaluated. Carbon nanotube reinforced composites were modeled as three layers which comprises CNT, interface and matrix material. Firstly; matrix, fiber and interfacial materials all together considered as three layered cylindrical nanocomposite. Secondly, the cylindrical matrix material was assumed to be isotropic and also considered as a continuous medium. Then, fiber material was represented with zigzag type SWCNs. Finally, SWCN was combined with the elastic medium by using springs with different constants. In the FE modeling of SWCN reinforced composite model springs were modeled by using ANSYS spring damper element COMBIN14. The developed interfacial van der Waals interaction effects between the continuous matrix layer and the carbon nanotube fiber layer were simulated by applying these various spring stiffness values. In this study, the layered composite cylindrical FE model was presented as the equivalent mechanical properties of SWCN structures in terms of Young's modulus. The obtained results and literature values were presented and discussed. Figures, 16, 17, and 18 of the original article PDF file, as supplied to AIP Publishing, were affected by a PDF-processing error. Consequently, a solid diamond symbol appeared instead of a Greek tau on the y axis labels for these three figures. This article was updated on 17 March 2017 to correct the PDF-processing error, with the scientific content remaining unchanged.

  11. Microstructural evolution in WC-Co cermet reinforced - A17075 metal matrix composites by stir casting

    NASA Astrophysics Data System (ADS)

    Gopal Krishna, U. B.; Ranganatha, P.; Auradi, V.; Mahendra Kumar, S.; Vasudeva, B.

    2016-09-01

    Aluminium metal matrix composites (AMMCs) are preferred because of their enhanced properties like high strength to weight ratio, stiffness and wear resistance. In the present work, an attempt is made to develop cermet (WC-Co) reinforced with Al7075 metal matrix composite by stir casting technique. WC-Co cermet is reduced to an average size of 10μm through ball milling using Alumina as grinding media. Ball milled WC-Co Cermet in an amount of 6 wt. % is used as reinforcement in Al7075 matrix. Microstructural characterization of the prepared composites is carried out using SEM/EDX and XRD studies. X-ray diffraction studies have revealed the peaks corresponding to α-Al, WC, Co and minor Al5W phases. SEM/EDX characterization revealed the uniform distribution of cermet in Al matrix. Further studies also revealed that, addition of WC-Co cermet to Al7075 matrix has resulted in improvement in hardness and Densities of Al7075 matrix.

  12. Process for the preparation of fiber-reinforced ceramic matrix composites

    SciTech Connect

    Haller, W.; Deshmukh, U.V.

    1993-06-22

    A process for the preparation of a fiber-reinforced ceramic matrix composite comprised of monofilament fibers having a continuous uniform coating of a ceramic matrix material is described comprising the steps of: (a) coating at least one monofilament fiber by drawing the fiber through a filament guide immersed in a slurry comprised of a ceramic matrix material in an amount sufficient to form a continuous uniform coating on the surface of the fiber and an ultraviolet curing agent in an amount sufficient to bind the continuous uniform coating of ceramic matrix material to the fiber upon curing with ultraviolet radiation; (b) rapidly curing the coating before breakup of the coating slurry on the fiber by exposure to ultraviolet radiation; (c) heat treating at least one coated and cured monofilament fiber to decompose the ultraviolet curing agent and sinter the ceramic material to form a compact; and (d) densifying the compact to produce a fiber-reinforced ceramic matrix composite comprised of at least one monofilament fiber having a continuous uniform coating of a ceramic matrix material.

  13. A simple model to predict the effect of volume fraction, diameter, and length of fibres on strength of fibre reinforced brittle matrix composites

    NASA Astrophysics Data System (ADS)

    Kundu, T.; Jang, H. S.; Cha, Y. H.; Desai, C. S.

    2000-06-01

    A simplified model is presented to predict the strength variations of brittle matrix composites, reinforced by steel fibres, with the variations of fibre parameters - length, diameter and volume fraction. This model predicts that its tensile and flexural strength increase non-linearly with the fibre volume fraction. It also predicts that similar non-linear behaviour should be observed with the reduction of the fibre diameter when other parameters are kept constant. The experimental results support both these theoretical predictions. It is also explained why an increase in the fibre length does not always significantly increase the fracture toughness. The objective of this paper is not to explain and understand in great detail the science of all phenomena responsible for the strength increase of fibre reinforced brittle matrix composites, but to provide a simple engineering explanation as to why its strength increases with the fibre addition, and how this increase can be quantitatively related to the variations in fibre parameters - fibre volume fraction, fibre length and diameter. These simplifying steps are needed to provide a tool that the practicing engineers can use to predict the brittle matrix strength variation with the fibre parameters. In the area of geomechanics, the results presented here can be used to assess and predict the behaviour of fibre-reinforced earth.

  14. The surgical treatment of reinforced steel bar injury penetrating the skull base and maxilla-mandibular area.

    PubMed

    Wang, Yanliang; Pan, Lini; Xu, Hui

    2014-11-01

    Penetrating injuries with reinforced screwed steel bar in the skull base represent a unique challenge for oral maxillofacial surgeons. Management of these injuries is complicated by associated injuries and the proximity to vital neurovascular structures. A 35-year-old man was admitted to our hospital because of injury due to a downward fall upon a reinforced steel rod. Radiologic studies of the skull base revealed that the steel bar traversed the temporomandibular space between the left cervical spine and the mastoid process to the space between the inner side of the left mandibular ramus and the maxilla. We performed osteotomy of the left mastoid process tip and the left mandibular ramus to take out the steel bar from the maxilla and repaired the left mandible with internal fixation. Appropriate preoperative planning, including three-dimensional computed tomographic images, is integral in the surgical approach for the safe removal of such objects.

  15. Dynamic Effects in Elastothermodynamic Damping of Hollow Particle Reinforced Metal-Matrix Composites

    NASA Astrophysics Data System (ADS)

    Srivastava, Sunil Kumar; Mishra, Bhanu Kumar

    2016-06-01

    The Metal-Matrix Composites (MMCs) containing hollow spherical reinforcements are under active development for the applications such as space structures, submarine hulls etc. where weight is of critical importance. When these materials are subjected to a time varying strain field, energy is dissipated because of the thermoelastic effect (Elastothermodynamic Damping or ETD). The quasi-static ETD analysis for the MMCs containing hollow spherical particles has been reported in literature. The entropic approach, which is better suited for composite materials with perfect or imperfect interfaces, is used for the analysis. In the present work, the effect of inertia forces is carried out on ETD of hollow particle-reinforced MMCs. For given particle volume fractions (V p ), the inertia forces are found to be more significant at higher value of thermal parameter (Ω T1) (alternatively, frequency of vibration if reinforcement radius is fixed), large cavity volume fraction (V h ) and low value of the parameter B1.

  16. Dynamic Effects in Elastothermodynamic Damping of Hollow Particle Reinforced Metal-Matrix Composites

    NASA Astrophysics Data System (ADS)

    Srivastava, Sunil Kumar; Mishra, Bhanu Kumar

    2017-04-01

    The Metal-Matrix Composites (MMCs) containing hollow spherical reinforcements are under active development for the applications such as space structures, submarine hulls etc. where weight is of critical importance. When these materials are subjected to a time varying strain field, energy is dissipated because of the thermoelastic effect (Elastothermodynamic Damping or ETD). The quasi-static ETD analysis for the MMCs containing hollow spherical particles has been reported in literature. The entropic approach, which is better suited for composite materials with perfect or imperfect interfaces, is used for the analysis. In the present work, the effect of inertia forces is carried out on ETD of hollow particle-reinforced MMCs. For given particle volume fractions ( V p ), the inertia forces are found to be more significant at higher value of thermal parameter (Ω T1) (alternatively, frequency of vibration if reinforcement radius is fixed), large cavity volume fraction ( V h ) and low value of the parameter B1.

  17. Processing and characterization of continuous fiber-reinforced glass and glass-ceramic matrix composites

    SciTech Connect

    Wang, Shaio-Wen.

    1990-01-01

    An investigation of the processing and mechanical behavior, particularly damage evolution and failure mechanisms, of continuous fiber reinforced glass and glass-ceramic composites was conducted. The processing effort utilized a slurry infiltration/hot pressing technique to fabricate carbon fiber reinforced borosilicate glass and Nicalon SiC fiber reinforced borosilicate glass composites. A slurry infiltration prepregging setup was designed and successfully operated. Processing parameters including slurry composition, binder burnout cycle and hot pressing schedule were systematically studied and optimized. Mechanical behavior studies were conducted on Nicalon SiC/Calcium Aluminosilicate (CAS) composites. The nature and the strength of the fiber/matrix interface was first characterized using a variety of fiber indentation test methods and transmission electron microscopy.

  18. Inductively coupled corrosion potential sensor for steel reinforced concrete with time domain gating interrogation

    NASA Astrophysics Data System (ADS)

    Thomson, D. J.; Perveen, K.; Bridges, G. E.; Bhadra, S.

    2012-04-01

    Corrosion is a major problem for civil infrastructure and is one of the leading factors in infrastructure deterioration. Techniques such as half-cell potential can be used to periodically monitor corrosion, but can be difficult to reliably interpret. Wired systems have large installation cost and long-term reliability issues due to wire corrosion. In this paper an embedded inductively coupled coil sensor able to monitor the corrosion potential of reinforcement steel in concrete is presented. The sensor is based on a coil resonator whose resonant frequency changes due to the corrosion potential being applied across a parallel varactor diode. The corrosion potential can be monitored externally using an inductively coupled coil. An accelerated corrosion test shows that it can measure corrosion potentials with a resolution of less than 10 mV. This sensor will detect corrosion at the initiation stage before observable corrosion has taken place. The wireless sensor is passive and simple in design, making it an inexpensive, battery less option for long-term monitoring of the corrosion potential of reinforcing steel.

  19. Multi-Scale CNT-Based Reinforcing Polymer Matrix Composites for Lightweight Structures

    NASA Technical Reports Server (NTRS)

    Eberly, Daniel; Ou, Runqing; Karcz, Adam; Skandan, Ganesh; Mather, Patrick; Rodriguez, Erika

    2013-01-01

    Reinforcing critical areas in carbon polymer matrix composites (PMCs), also known as fiber reinforced composites (FRCs), is advantageous for structural durability. Since carbon nanotubes (CNTs) have extremely high tensile strength, they can be used as a functional additive to enhance the mechanical properties of FRCs. However, CNTs are not readily dispersible in the polymer matrix, which leads to lower than theoretically predicted improvement in mechanical, thermal, and electrical properties of CNT composites. The inability to align CNTs in a polymer matrix is also a known issue. The feasibility of incorporating aligned CNTs into an FRC was demonstrated using a novel, yet commercially viable nanofiber approach, termed NRMs (nanofiber-reinforcing mats). The NRM concept of reinforcement allows for a convenient and safe means of incorporating CNTs into FRC structural components specifically where they are needed during the fabrication process. NRMs, fabricated through a novel and scalable process, were incorporated into FRC test panels using layup and vacuum bagging techniques, where alternating layers of the NRM and carbon prepreg were used to form the reinforced FRC structure. Control FRC test panel coupons were also fabricated in the same manner, but comprised of only carbon prepreg. The FRC coupons were machined to size and tested for flexural, tensile, and compression properties. This effort demonstrated that FRC structures can be fabricated using the NRM concept, with an increased average load at break during flexural testing versus that of the control. The NASA applications for the developed technologies are for lightweight structures for in-space and launch vehicles. In addition, the developed technologies would find use in NASA aerospace applications such as rockets, aircraft, aircraft/spacecraft propulsion systems, and supporting facilities. The reinforcing aspect of the technology will allow for more efficient joining of fiber composite parts, thus offering

  20. Orientation factor and number of fibers at failure plane in ring-type steel fiber reinforced concrete

    SciTech Connect

    Lee, C.; Kim, H.

    2010-05-15

    Considering the probabilistic distributions of fibers in ring-type steel fiber reinforced concrete, the orientation factor and the number of ring-type steel fibers crossing the failure plane were theoretically derived as a function of fiber geometry, specimen dimensions, and fiber volume fraction. A total number of 24 specimens were tested incorporating different fiber types, specimen geometry, and fiber volume fractions of 0.2% and 0.4%: 5 beams and 5 panels containing straight steel fibers; and 6 beams and 8 panels containing ring-type steel fibers. Measurements were made to assess the number of fibers at fractured surfaces of steel fiber reinforced concrete. The developed theoretical expressions reasonably predicted the orientation factor and the number of ring-type steel fibers at failure plane: the average and the standard deviation for the ratios of the test to theory were 1.03 and 0.26, respectively. Theoretical investigations and comparisons were made for the values of orientation factor and the number of fibers at failure plane for straight steel fibers and ring-type steel fibers.

  1. Vertical impedance measurements of concrete bridge deck cover condition without a direct electrical connection to the reinforcing steel

    NASA Astrophysics Data System (ADS)

    Mazzeo, Brian A.; Baxter, Jared; Barton, Jeffrey; Guthrie, W. Spencer

    2017-02-01

    Vertical impedance measurements provide significant quantitative information about the ability of concrete cover to slow the penetration of chloride ions that can corrode steel reinforcement in a bridge deck. The primary limitations preventing the widespread adoption of vertical impedance for assessment of concrete bridge decks are (1) the necessity to have a direct electrical connection to the embedded steel reinforcement and (2) the low speeds of data acquisition. This work presents solutions to both limitations. A method using a large-area electrode as a reference electrode for vertical impedance testing is validated using both simulations and measurements in the field.

  2. Laminate behavior for SiC fiber-reinforced reaction-bonded silicon nitride matrix composites

    NASA Technical Reports Server (NTRS)

    Bhatt, Ramakrishna T.; Phillips, Ronald E.

    1990-01-01

    The room temperature mechanical properties of SiC fiber reinforced reaction-bonded silicon nitride matrix composite laminates (SiC/RBSN) have been measured. The laminates contained approx 30 volume fraction of aligned 142-micron diameter SiC fiber in a porous RBSN matrix. Three types of laminate studied were unidirectional: (1) (0) sub 8, (2) (10) sub 8, and (3) (45) sub 8, and (90) sub 8; cross plied laminates (0 sub 2/90 sub 2); and angle plied laminates: (+45 sub 2/-45 sub 2). Each laminate contained eight fiber plies. Results of the unidirectionally reinforced composites tested at various angles to the reinforcement direction indicate large anisotropy in in-plane properties. In addition, strength properties of these composites along the fiber direction were independent of specimen gage length and were unaffected by notches normal to the fiber direction. Splitting parallel to the fiber at the notch tip appears to be the dominant crack blunting mechanism responsible for notch insensitive behavior of these composites. In-plane properties of the composites can be improved by 2-D laminate construction. Mechanical property results for (0 sub 2/90 sub 2) sub s and (+45/-45 sub 2) sub s laminates showed that their matrix failure strains were similar to that for (0) sub 8 laminates, but their primary elastic moduli, matrix cracking strengths, and ultimate composite strengths were lower. The elastic properties of unidirectional, cross-ply, and angle-ply composites can be predicted from modified constitutive equations and laminate theory. Further improvements in laminate properties may be achieved by reducing the matrix porosity and by optimizing the bond strength between the SiC fiber and RBSN matrix.

  3. Laminate behavior for SiC fiber-reinforced reaction-bonded silicon nitride matrix composites

    NASA Technical Reports Server (NTRS)

    Rhatt, R. T.; Phillips, R. E.

    1988-01-01

    The room temperature mechanical properties of SiC fiber reinforced reaction-bonded silicon nitride matrix composite laminates (SiC/RBSN) have been measured. The laminates contained approx 30 volume fraction of aligned 142-micron diameter SiC fiber in a porous RBSN matrix. Three types of laminate studied were unidirectional: (1) (0) sub 8, (2) (10) sub 8, and (3) (45) sub 8, and (90) sub 8; cross plied laminates (0 sub 2/90 sub 2); and angle plied laminates: (+45 sub 2/-45 sub 2). Each laminate contained eight fiber plies. Results of the unidirectionally reinforced composites tested at various angles to the reinforcement direction indicate large anisotropy in in-plane properties. In addition, strength properties of these composites along the fiber direction were independent of specimen gage length and were unaffected by notches normal to the fiber direction. Splitting parallel to the fiber at the notch tip appears to be the dominant crack blunting mechanism responsible for notch insensitive behavior of these composites. In-plane properties of the composites can be improved by 2-D laminate construction. Mechanical property results for (0 sub 2/90 sub 2)sub s and (+45/-45 sub 2) sub s laminates showed that their matrix failure strains were similar to that for (0) sub 8 laminates, but their primary elastic moduli, matrix cracking strengths, and ultimate composite strengths were lower. The elastic properties of unidirectional, cross-ply, and angle-ply composites can be predicted from modified constitutive equations and laminate theory. Further improvements in laminate properties may be achieved by reducing the matrix porosity and by optimizing the bond strength between the SiC fiber and RBSN matrix.

  4. Evaluation of tensile strength of hybrid fiber (jute/gongura) reinforced hybrid polymer matrix composites

    NASA Astrophysics Data System (ADS)

    Venkatachalam, G.; Gautham Shankar, A.; Vijay, Kumar V.; Chandan, Byral R.; Prabaharan, G. P.; Raghav, Dasarath

    2015-07-01

    The polymer matrix composites attract many industrial applications due to its light weight, less cost and easy for manufacturing. In this paper, an attempt is made to prepare and study of the tensile strength of hybrid (two natural) fibers reinforced hybrid (Natural + Synthetic) polymer matrix composites. The samples were prepared with hybrid reinforcement consists of two different fibers such as jute and Gongura and hybrid polymer consists of polyester and cashew nut shell resins. The hybrid composites tensile strength is evaluated to study the influence of various fiber parameters on mechanical strength. The parameters considered here are the duration of fiber treatment, the concentration of alkali in fiber treatment and nature of fiber content in the composites.

  5. Reinforcing mechanisms of starch nanocrystals in a nonvulcanized natural rubber matrix.

    PubMed

    Mélé, Patrice; Angellier-Coussy, Hélène; Molina-Boisseau, Sonia; Dufresne, Alain

    2011-05-09

    A phenomenological modeling approach was developed to try to understand the reinforcing mechanism of starch nanocrystals in a nonvulcanized natural rubber matrix. Natural rubber was not cross-linked to maintain the biodegradability of the biosourced materials. Nonlinear dynamic mechanical experiments highlighted the significant reinforcing effect of starch nanocrystals and the presence of the Mullins and Payne effects. Two models were used to predict the Payne effect considering that either filler-filler (Kraus model) or matrix-filler (Maier and Göritz model) interactions are preponderant. The use of the Maier and Goritz model demonstrated that phenomena of adsorption and desorption of NR chains on the filler surface governed nonlinear viscoelastic properties, even if the formation of a percolating network for filler contents >6.7 vol % was evidenced by the Kraus model.

  6. Izod Impact Test in Epoxi Matrix Composites Reinforced with Hemp Fiber

    NASA Astrophysics Data System (ADS)

    Rohen, Lázaro A.; Margem, Frederico M.; Neves, Anna C. C.; Monteiro, Sérgio N.; Gomes, Maycon A.; de Castro, Rafael G.; Maurício, F. V. Carlos; de Paula, Fernanda

    Synthetic fiber has been gradually replaced by natural fiber, such as lignocellulosic fiber. In comparison with synthetic fiber, natural fiber has shown economic and environmental advantages. The natural fiber presents interfacial characteristics with polymeric matrices that favor a high impact energy absorption by the composite structure. However, until now little has been evaluated about the hemp fiber incorporated in polymeric matrices. This study has the purpose of evaluate the impact resistance of this kind of epoxy matrix composite reinforced with different percentages of hemp fibers. The impact resistance has substantially increased the relative amount of hemp fiber incorporated as reinforcement in the composite. This performance was associated with the difficulty of rupture imposed by the fibers resulting from the interaction of hemp fiber / epoxy matrix that helps absorb the impact energy.

  7. Short-fibre and particulate-reinforced metal-matrix composites

    SciTech Connect

    Harris, S.J.

    1989-08-01

    Short fibres, whiskers or particles of ceramic materials, e.g. silicon carbide and alumina, when dispersed in a more or less random manner in a metallic matrix can promote increases in stiffness and strength at ambient and elevated temperatures without imposing a weight penalty. The paper considers the available routes for the fabrication of such composites, e.g. by squeeze casting, spray forming, powder technologies and hot working etc. Influences of type and amount of reinforcement, matrix alloy selection and processing route on strength, creep and fatigue resistance are discussed. Comparisons are made with conventional metals and alloys, and polymers and metals reinforced with continuous fibres. Attention is drawn to the behaviour of these materials under compressive loading as well as to their thermal expansion and conductivity. The majority of the matrices considered are aluminium-based.

  8. In situ measurement of the reinforcement modulus in a metal matrix composite by acoustic microscopy

    SciTech Connect

    Canumalla, S.; Gordon, G.A.; Pangborn, R.N.

    1995-12-31

    The mechanical properties of metal-matrix composites have been observed to be a strong function of the content of non-fiber inclusions. Shot particles, with the nominal composition of the reinforcement, have been found to crack prematurely, thus representing prefer-red failure initiation sites under mechanical and thermal fatigue of discontinuous, alumina-silicate fiber reinforced aluminum matrix composites. To better understand the differences between the responses of the shot and fibers to loading, the Young`s modulus of the shot is measured and compared to that of the fibers. Scanning acoustic microscopy is used to nondestructively measure the modulus of the shot in situ, and the fiber modulus is obtained from the previously measured composite response. The shot, with a modulus of 131.5 GPa, has a Young`s modulus that is approximately 40% lower than that of the fibers. The influence of this on the composite response will be discussed.

  9. Tribological properties of metal-matrix composite materials reinforced by superelastic hard carbon particles

    NASA Astrophysics Data System (ADS)

    Ushakova, I. N.; Drozdova, E. I.; Chernogorova, O. P.; Blinov, V. M.; Ekimov, E. A.

    2016-05-01

    Metal-matrix composite materials (CMs) are synthesized from a mixture of a metal powder (Ti, Fe, Co, Ni, Cu, Al-based alloy) and fullerenes (10 wt %). The thermobaric synthesis conditions (700-1000°C, 5-8 GPa) ensure the collapse of fullerene molecules and their transformation into superelastic carbon phase particles with an indentation hardness H IT = 10-37 GPa, an elastic modulus E IT = 60-260 GPa, and an elastic recovery of >80% upon indentation. After reinforcing by superelastic hard carbon, the friction coefficient of CM decreases by a factor of 2-4 as compared to the friction coefficient of the matrix metal, and the abrasive wear resistance increases by a factor of 4-200. Superelastic hard carbon particles are a unique reinforcing material for an increase in the wear resistance and a simultaneous decrease in the friction coefficient of CM.

  10. The mechanical properties measurement of multiwall carbon nanotube reinforced nanocrystalline aluminum matrix composite

    SciTech Connect

    Sharma, Manjula Pal, Hemant; Sharma, Vimal

    2015-05-15

    Nanocrystalline aluminum matrix composite containing carbon nanotubes were fabricated using physical mixing method followed by cold pressing. The microstructure of the composite has been investigated using X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy techniques. These studies revealed that the carbon nanotubes were homogeneously dispersed throughout the metal matrix. The consolidated samples were pressureless sintered in inert atmosphere to further actuate a strong interface between carbon nanotubes and aluminum matrix. The nanoindentation tests carried out on considered samples showed that with the addition of 0.5 wt% carbon nanotubes, the hardness and elastic modulus of the aluminum matrix increased by 21.2 % and 2 % repectively. The scratch tests revealed a decrease in the friction coefficient of the carbon nanotubes reinforced composite due to the presence of lubricating interfacial layer. The prepared composites were promising entities to be used in the field of sporting goods, construction materials and automobile industries.

  11. Strong and Tough Hi-Nicalon Fiber-Reinforced Celsian Matrix Composites

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.

    1997-01-01

    Strong, tough and almost fully dense Hi-Nicalon/BN/SiC fiber reinforced celsian matrix composites have been fabricated by impregnation of the fiber tows with the matrix slurry, winding on a drum, stacking the prepreg tapes in the desired orientation, and hot pressing. The monoclinic celsian phase in the matrix was produced in situ, during hot pressing, from a mixed oxide precursor. The unidirectional composites having approx. 42 volume percent of fibers exhibited graceful failure with extensive fiber pullout in three-point bend tests at room temperature. Values of first matrix cracking stress and strain were 435 +/- 35 MPa and 0.27 +/- 0.01 %, respectively, and ultimate strengths of 900 +/- 60 MPa were observed. The Young's modulus of the composites was 165 +/- 5 GPa.

  12. Characterization of SiC (SCS-6) Fiber Reinforced Reaction-Formed Silicon Carbide Matrix Composites

    NASA Technical Reports Server (NTRS)

    Singh, Mrityunjay; Dickerson, Robert M.

    1995-01-01

    Silicon carbide (SCS-6) fiber reinforced-reaction formed silicon carbide matrix composites were fabricated using NASA's reaction forming process. Silicon-2 at a percent of niobium alloy was used as an infiltrant instead of pure silicon to reduce the amount of free silicon in the matrix after reaction forming. The matrix primarily consists of silicon carbide with a bi-modal grain size distribution. Minority phases dispersed within the matrix are niobium disilicide (NbSi2), carbon and silicon. Fiber push-out tests on these composites determined a debond stress of approx. 67 MPa and a frictional stress of approx. 60 MPa. A typical four point flexural strength of the composite is 297 MPa (43.1 KSi). This composite shows tough behavior through fiber pull out.

  13. Characterization of SiC Fiber (SCS-6) Reinforced-Reaction-Formed Silicon Carbide Matrix Composites

    NASA Technical Reports Server (NTRS)

    Singh, M.; Dickerson, R. M.

    1996-01-01

    Silicon carbide fiber (SCS-6) reinforced-reaction-formed silicon carbide matrix composites were fabricated using a reaction-forming process. Silicon-2 at.% niobium alloy was used as an infiltrant instead of pure silicon to reduce the amount of free silicon in the matrix after reaction forming. The matrix primarily consists of silicon carbide with a bimodal grain size distribution. Minority phases dispersed within the matrix are niobium disilicide (NbSi2), carbon, and silicon. Fiber pushout tests on these composites determined a debond stress of approximately 67 MPa and a frictional stress of approximately 60 MPa. A typical four-point flexural strength of the composite is 297 MPa (43.1 KSi). This composite shows tough behavior through fiber pullout.

  14. The mechanical properties measurement of multiwall carbon nanotube reinforced nanocrystalline aluminum matrix composite

    NASA Astrophysics Data System (ADS)

    Sharma, Manjula; Pal, Hemant; Sharma, Vimal

    2015-05-01

    Nanocrystalline aluminum matrix composite containing carbon nanotubes were fabricated using physical mixing method followed by cold pressing. The microstructure of the composite has been investigated using X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy techniques. These studies revealed that the carbon nanotubes were homogeneously dispersed throughout the metal matrix. The consolidated samples were pressureless sintered in inert atmosphere to further actuate a strong interface between carbon nanotubes and aluminum matrix. The nanoindentation tests carried out on considered samples showed that with the addition of 0.5 wt% carbon nanotubes, the hardness and elastic modulus of the aluminum matrix increased by 21.2 % and 2 % repectively. The scratch tests revealed a decrease in the friction coefficient of the carbon nanotubes reinforced composite due to the presence of lubricating interfacial layer. The prepared composites were promising entities to be used in the field of sporting goods, construction materials and automobile industries.

  15. SiC reinforced-MoSi sub 2 based matrix composites

    SciTech Connect

    Petrovic, J.J.; Honnell, R.E.

    1990-01-01

    SiC reinforced-MoSi{sub 2} based matrix composites possess very significant potential as high temperature structural materials for temperatures above 1200{degree}C in oxidizing environments, due to their combination of oxidation resistance, thermodynamic stability, machinability, elevated temperature ductility and strength, and ability to alloy the MoSi{sub 2} matrix with other silicides. The fabrication, microstructures, oxidation, and mechanical properties of these materials are described, and their current properties are compared to high temperature metals and structural ceramics. 22 refs., 5 figs., 2 tabs.

  16. Thermal expansion of multiwall carbon nanotube reinforced nanocrystalline silver matrix composite

    SciTech Connect

    Sharma, Manjula Sharma, Vimal; Pal, Hemant

    2014-04-24

    Multiwall carbon nanotube reinforced silver matrix composite was fabricated by novel molecular level mixing method, which involves nucleation of Ag ions inside carbon nanotube dispersion at the molecular level. As a result the carbon nanotubes get embedded within the powder rather than on the surfaces. Micro structural characterization by X- ray diffraction and scanning electron microscopy reveals that the nanotubes are homogeneously dispersed and anchored within the matrix. The thermal expansion of the composite with the multiwall nanotube content (0, 1.5 vol%) were investigated and it is found that coefficient of thermal expansion decreases with the addition of multiwall nanotube content and reduce to about 63% to that of pure Ag.

  17. Mechanical Behavior of Sapphire Reinforced Alumina Matrix Composites at Elevated Temperatures

    NASA Technical Reports Server (NTRS)

    Jaskowiak, Martha H.; Eldridge, Jeffrey I.; Setlock, John A.; Gyekenyesi, John Z.

    1997-01-01

    Zirconia coated sapphire reinforced alumina matrix composites have been tested both after heat treatment to 1400 C and at temperatures ranging from 800 C to 1200 C in. air. Interfacial shear stress has also been measured with fiber pushout tests performed in air at room temperature, 800 C and 1OOO C. Matrix crack spacing was measured for the tensile tested composites and used to estimate interfacial shear stress up to 1200 C. Electron microscopy was used to determine the source of fiber fracture and to study interfacial failure within the composite.

  18. Silicon carbide fiber reinforced strontium aluminosilicate glass-ceramic matrix composite

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam (Inventor)

    1992-01-01

    A SrO-Al2O3 - 2SrO2 (SAS) glass ceramic matrix is reinforced with CVD SiC continuous fibers. This material is prepared by casting a slurry of SAS glass powder into tapes. Mats of continuous CVD-SiC fibers are alternately stacked with the matrix tapes. This tape-mat stack is warm-pressed to produce a 'green' composite. Organic constituents are burned out of the 'green' composite, and the remaining interim material is hot pressed.

  19. Method of producing a silicon carbide fiber reinforced strontium aluminosilicate glass-ceramic matrix composite

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P. (Inventor)

    1995-01-01

    A SrO-Al2O3-2SrO2 (SAS) glass ceramic matrix is reinforced with CVD SiC continuous fibers. This material is prepared by casting a slurry of SAS glass powder into tapes. Mats of continuous CVD-SiC fibers are alternately stacked with the matrix tapes. This tape-mat stack is warm-pressed to produce a 'green' composite. Organic constituents are burned out of the 'green' composite, and the remaining interim material is hot pressed.

  20. The oxidative stability of carbon fibre reinforced glass-matrix composites

    NASA Technical Reports Server (NTRS)

    Prewo, K. M.; Batt, J. A.

    1988-01-01

    The environmental stability of carbon fibre reinforced glass-matrix composites is assessed. Loss of composite strength due to oxidative exposure at elevated temperatures under no load, static load and cyclic fatigue as well as due to thermal cycling are all examined. It is determined that strength loss is gradual and predictable based on the oxidation of carbon fibres. The glass matrix was not found to prevent this degradation but simply to limit it to a gradual process progressing from the composite surfaces inward.

  1. The oxidative stability of carbon fibre reinforced glass-matrix composites

    NASA Technical Reports Server (NTRS)

    Prewo, K. M.; Batt, J. A.

    1988-01-01

    The environmental stability of carbon fibre reinforced glass-matrix composites is assessed. Loss of composite strength due to oxidative exposure at elevated temperatures under no load, static load and cyclic fatigue as well as due to thermal cycling are all examined. It is determined that strength loss is gradual and predictable based on the oxidation of carbon fibres. The glass matrix was not found to prevent this degradation but simply to limit it to a gradual process progressing from the composite surfaces inward.

  2. Effect of fiber shape on mechanical behavior of composite with elastoplastic matrix and SMA reinforcement.

    PubMed

    Zhu, Yuping; Dui, Guansuo

    2009-10-01

    In this paper, an equivalent three-phase micromechanical model of composite with an elasto- plastic matrix and shape memory alloy (SMA) reinforcement is developed. Compared with the traditional two-phase method, the interaction among the austenitic phase, the martensite phase and the matrix phase is considered. During applications of the model, the predicted curve shows good agreement with the experimental result. Most attention is given to the effect of fiber shape on the overall response of the composite and the residual stress. It is helpful to design an intelligent composite.

  3. The role of rapid solidification processing in the fabrication of fiber reinforced metal matrix composites

    NASA Technical Reports Server (NTRS)

    Locci, Ivan E.; Noebe, Ronald D.

    1989-01-01

    Advanced composite processing techniques for fiber reinforced metal matrix composites require the flexibility to meet several widespread objectives. The development of uniquely desired matrix microstructures and uniformly arrayed fiber spacing with sufficient bonding between fiber and matrix to transmit load between them without degradation to the fiber or matrix are the minimum requirements necessary of any fabrication process. For most applications these criteria can be met by fabricating composite monotapes which are then consolidated into composite panels or more complicated components such as fiber reinforced turbine blades. Regardless of the end component, composite monotapes are the building blocks from which near net shape composite structures can be formed. The most common methods for forming composite monotapes are the powder cloth, foil/fiber, plasma spray, and arc spray processes. These practices, however, employ rapid solidification techniques in processing of the composite matrix phase. Consequently, rapid solidification processes play a vital and yet generally overlooked role in composite fabrication. The future potential of rapid solidification processing is discussed.

  4. Ultrasonic velocity technique for monitoring property changes in fiber-reinforced ceramic matrix composites

    NASA Technical Reports Server (NTRS)

    Kautz, Harold E.; Bhatt, Ramakrishna T.

    1991-01-01

    A technique for measuring ultrasonic velocity was used to monitor changes that occur during processing and heat treatment of a SiC/RBSM composite. Results indicated that correlations exist between the ultrasonic velocity data and elastic modulus and interfacial shear strength data determined from mechanical tests. The ultrasonic velocity data can differentiate strength. The advantages and potential of this nondestructive evaluation method for fiber reinforced ceramic matrix composite applications are discussed.

  5. Corrosion of steel members strengthenened with carbon fiber reinforced polymer sheets

    NASA Astrophysics Data System (ADS)

    Bumadian, Ibrahim

    Due to many years of service at several cases of exposure at various environments there are many of steel bridges which are in need of rehabilitation. The infrastructure needs upgrading, repair or maintenance, and also strengthening, but by using an alternative as retrofits methods. The alternative retrofit method, which used fiber reinforced polymer (FRP) composite materials which their strength materials comes largely from the fiber such as carbon, glass, and aramid fiber. Of the most important materials used in the rehabilitation of infrastructure is a composite material newly developed in bonded externally carbon fiber and polymer (CFRP) sheets, which has achieved remarkable success in the rehabilitation and upgrading of structural members. This technique has many disadvantages one of them is galvanic corrosion. This study presents the effect of galvanic corrosion on the interfacial strength between carbon fiber reinforced polymer (CFRP) sheets and a steel substrate. A total of 35 double-lap joint specimens and 19 beams specimens are prepared and exposed to an aggressive service environment in conjunction with an electrical potential method accelerating corrosion damage. Six test categories are planned at a typical exposure interval of 12 hours, including five specimens per category for double-lap joint specimens. And six test categories are planned at a typical exposure interval of 12 hours, including three specimens per category for Beam section specimens. In addition one beam section specimen is control. The degree of corrosion is measured. Fourier transform infrared (FTIR) reflectance spectroscopy has been used to monitor and confirm the proposed corrosion mechanisms on the surface of CFRP. In this study we are using FTIR-spectroscopic measurement systems in the mid infrared (MIR) wavelength region (4000 - 400) cm-1 to monitor characteristic spectral features. Upon completion of corrosion processes, all specimens are monotonically loaded until failure

  6. Strengthening of beam - column joint with steel fibre reinforced concrete under seismic loading

    NASA Astrophysics Data System (ADS)

    Prasanna, K.; Ramasubramani, R.; Anandh, K. S.; Saisabarish; Krupaker Maddu, Vijay

    2017-07-01

    Earthquakes not only kill the human beings but the structures too. Considering this above fact, there is a necessity to take care of the beam column joint region in a structure. Under seismic excitation, the bar segment joint district is subjected to even and the vertical shear force extents are normally commonly greater than those in the adjoining bits of the structural segments. In the event that the joint is not precisely nitty gritty, the shaft segment joint may end up plainly frail. To keep this, an adequate control ought to be given in the joint area. The seismic examination and outline technique ought to be utilised as a part of the plan of the building structures and their segments ought to be recommended in the segment. The building structures incorporate finish sidelong and vertical drive opposing frameworks fit for giving satisfactory quality. Stiffness and the vitality dissemination ability to withstand the outline ground movements inside the recommended furthest reaches of twisting and quality request. The plan ground movements are accepted to happen along any even headings of a building structure. This work focuses on behaviour of M20 concrete in beam-column joint subjected to seismic loading, by using steel fibre (1.5%). The specimens detailed as per IS: 456-2000 and IS: 13920-1993 were casted and tested under cyclic and reverse cyclic loading. The parameters analysed were ductility, energy dissipation, load v/s displacement curve, beam-column reinforcement strain and crack pattern. From the experimental investigation, it is found that the fibre reinforced beam-column joint with fibre (1.50% of steel fibre) performs better ductility, load carrying capacity, energy dissipation and strength by 10% more than conventional reinforced beam-column joint.

  7. Mechanical Properties of Reinforcing Steel and Fatigue Behavior in Corrosive Environment

    NASA Astrophysics Data System (ADS)

    Apostolopoulos, Ch. Alk.; Michalopoulos, D.

    2007-10-01

    Corrosion of reinforcing steel has a great impact on the mass reduction and high- and low-cycle fatigue. An experimental study showed that the mass loss, the fatigue limit and the life expectancy were reduced by approximately 1.50-3.00%, 20-40%, and 55-75%, respectively, according to the level of corrosion. Low-cycle strain controlled fatigue testing under ±1% and ±2.5% constant amplitude strain, indicated that the corroded steel bars exhibit gradual reduction in available energy, number of cycles to failure and the load-bearing ability. Formation of pits and notches took place on the corroded steel surface and stress concentration points were developed which are highly localized at imperfections and especially at the rib bases. The fatigue limit was reduced considerably since the existence of ribs and the formation of pits and notches combined with the mass loss led to reduction of the exterior hard layer of martensite and drastic drop in the energy density of the corroded specimens. Antiseismic design that does not take into account the maximum and cumulative plastic deformation demands and the strain history that a structure will suffer under severe ground motion could lead to unpredictable performance.

  8. Effect of reinforcement type and porosity on strength of metal matrix composite

    NASA Astrophysics Data System (ADS)

    Kulkarni, S. G.; Lal, Achchhe; Menghani, J. V.

    2016-05-01

    In the present work, experimental investigation and the numerical analysis are carried out for strength analysis of A356 alloy matrix composites reinforced with alumina, fly ash and hybrid particle composites. The combined strengthening effect of load bearing, Hall-Petch, Orowan, coefficient of thermal expansion mismatch and elastic modulus mismatch is studied for predicting accurate uniaxial stress-strain behavior of A356 based alloy matrix composite. The unit cell micromechanical approach and nine noded isoparametric finite element analysis (FEA) is used to investigate the yield failure load by considering material defect of porosity as fabrication errors in particulate composite. The Ramberg-Osgood approach is considered for the linear and nonlinear relationship between stress and strain of A356 based metal matrix composites containing different amounts of fly ash and alumina reinforcing particles. A numerical analysis of material porosity on the stress strain behavior of the composite is performed. The literature and experimental results exhibit the validity of this model and confirm the importance of the fly ash as the cheapest and low density reinforcement obtained as a waste by product in thermal power plants.

  9. Development of High Performance Magnesium Matrix Nanocomposites Using Nano-SiC Particulates as Reinforcement

    NASA Astrophysics Data System (ADS)

    Shen, M. J.; Ying, W. F.; Wang, X. J.; Zhang, M. F.; Wu, K.

    2015-10-01

    In the present study, magnesium-based composites with three different volume percentages of nano-sized SiC particulates (SiCp) reinforcement were fabricated using a simple and inexpensive technique followed by hot extrusion. Microstructural characterization of the materials revealed uniform distribution of nano-size SiCp and obvious grain refinement. The tensile test result indicates a remarkable improvement on the strength for the as-extruded SiCp/AZ31B nanocomposite, while the elongation to fracture was decreased by comparing with the AZ31B alloy. Although, compared with the as-extruded AZ31B alloy, the ductility of the SiCp-reinforced AZ31B nanocomposite is decreased, but the ductility of the present SiCp-reinforced AZ31B nanocomposite is far higher than that of the conventional micron or submicron SiCp-reinforced magnesium matrix composites. It is concluded that, compared with the larger sized (micron or submicron) particles, the addition of nano SiCp in the AZ31B alloy resulted in the best combination of the strength and ductility. An attempt is made in the present study to correlate the effect of presence of nano-SiCp as reinforcement and its increasing amount with the microstructural and mechanical properties of magnesium.

  10. Effect of confining pressure due to external jacket of steel plate or shape memory alloy wire on bond behavior between concrete and steel reinforcing bars.

    PubMed

    Choi, Eunsoo; Kim, Dongkyun; Park, Kyoungsoo

    2014-12-01

    For external jackets of reinforced concrete columns, shape memory alloy (SMA) wires are easy to install, and they provide active and passive confining pressure; steel plates, on the other hand, only provide passive confining pressure, and their installation on concrete is not convenient because of the requirement of a special device. To investigate how SMA wires distinctly impact bond behavior compared with steel plates, this study conducted push-out bond tests of steel reinforcing bars embedded in concrete confined by SMA wires or steel plates. For this purpose, concrete cylinders were prepared with dimensions of 100 mm x 200 mm, and D-22 reinforcing bars were embedded at the center of the concrete cylinders. External jackets of 1.0 mm and 1.5 mm thickness steel plates were used to wrap the concrete cylinders. Additionally, NiTiNb SMA wire with a diameter of 1.0 mm was wound around the concrete cylinders. Slip of the reinforcing bars due to pushing force was measured by using a displacement transducer, while the circumferential deformation of specimens was obtained by using an extensometer. The circumferential deformation was used to calculate the circumferential strains of the specimens. This study assessed the radial confining pressure due to the external jackets on the reinforcing bars at bond strength from bond stress-slip curves and bond stress-circumferential strain curves. Then, the effects of the radial confining pressure on the bond behavior of concrete are investigated, and an equation is suggested to estimate bond strength using the radial confining pressure. Finally, this study focused on how active confining pressure due to recovery stress of the SMA wires influences bond behavior.

  11. Fiber reinforced concrete: Characterization of flexural toughness and some studies on fiber-matrix bond-slip interaction

    NASA Astrophysics Data System (ADS)

    Dubey, Ashish

    One major problem associated with the testing of fiber reinforced concrete specimens under flexural loading is that the measured post-cracking response is severely affected by the stiffness of the testing machine. As a consequence, misleading results are obtained when such a flexural response is used for the characterization of composite toughness. An assessment of a new toughness characterization technique termed the Residual Strength Test Method (RSTM) has been made. In this technique, a stable narrow crack is first created in the specimen by applying a flexural load in parallel with a steel plate under controlled conditions. The plate is then removed, and the specimen is tested in a routine manner in flexure to obtain the post-crack load versus displacement response. Flexural response for a variety of fiber reinforced cementitious composites obtained using the Residual Strength Test Method has been found to correlate very well with those obtained with relatively stiffer test configurations such as closed-loop test machines. The Residual Strength Test Method is found to be effective in differentiating between different fiber types, fiber lengths, fiber configurations, fiber volume fractions, fiber geometries and fiber moduli. In particular, the technique has been found to be extremely useful for testing cement-based composites containing fibers at very low dosages (<0.5% by volume). An analytical model based on shear lag theory is introduced to study the problem of fiber pullout in fiber reinforced composites. The proposed model eliminates limitations of many earlier models and captures essential features of pullout process, including progressive interfacial debonding, Poisson's effect, and variation in interfacial properties during the fiber pullout process. Interfacial debonding is modeled using an interfacial shear strength criterion. Influence of normal contact stress at the fiber-matrix interface is considered using shrink-fit theory, and the interfacial

  12. Feasibility of Steel Fiber-Reinforced Rubberized Concrete in Cold Regions for High Volume Intersections

    NASA Astrophysics Data System (ADS)

    Abou Eid, Mahear A.

    There are many challenges faced with the use of Portland Cement Concrete (PCC) in cold regions, but with the inclusion of new technologies such as steel fibers and recycled tire crumb rubber efficient construction may be possible. Research was conducted on a modified concrete material that included both steel fibers and crumb rubber. The composite material was called Steel Fiber-Reinforced Rubberized Concrete (SFRRC). The objective of this investigation was to provide evidence showing that SFRRC can reduce tire rutting compared to asphaltic pavement. In addition, the research showed that the SFRRC could withstand freeze-thaw cycles and increase service life of roadways. Several tests were performed to determine the characteristics of the material. Freeze-thaw testing was performed to determine compressive strength loss and visual deterioration of the material. Wheel tracker rut testing was performed both with the standard steel wheel and with a modified studded rubber tire to determine plastic deformation and rut resistance. An experimental test slab was cast in place on a public approach to observe the construction procedures, the effects of studded tire wear and the frost actions in cold region conditions. Based on freeze-thaw and wheel tracker test results and observations of the experimental test slab, the SFRRC material shows viability in cold regions for resisting freeze-thaw actions. The freeze-thaw testing resulted in increased compressive strength after 300 freeze-thaw cycles and very low deterioration of material compared to standard PCC. The wheel tracker testing resulted in very low plastic deformation and minor material rutting with use of the studded rubber tire. The test slab showed very minor surface wear, no freeze-thaw cracking and no rutting after one winter of use. It is recommended that further testing of the material be conducted by means of a large-scale trial section. This would provide information with respect to cost analysis and

  13. Spray-Formed Stainless Steel Matrix Composites with Co-Injected Carbide Particles

    NASA Astrophysics Data System (ADS)

    Cui, Chengsong; Schulz, Alwin; Uhlenwinkel, Volker; Zoch, Hans-Werner

    2011-08-01

    In order to develop new types of wear-resistant and corrosion-resistant materials, TiC and VC particles were injected into martensitic stainless steel X46Cr13 during spray forming, respectively. The microstructures of the spray-formed steel matrix composites under different processing conditions were investigated. The mechanisms of interactions between the injected particles and the matrix materials during spray forming and their effects on the microstructures of the composites were discussed and clarified based on experimental and theoretical investigations. The current results show that the injected particles may penetrate into the metallic droplets or adhere to the surface of the droplets and, therefore, are incorporated into the deposits to form metal matrix composites. Substantial heat transfer from superheated metallic melts to the room temperature carbide particles takes place as they are incorporated into the matrix material. The matrix steel solidifies in the vicinity of the carbides due to their chilling effect, and thus, the carbides may be engulfed in the matrix or pushed to the grain boundaries by the solidification fronts. TiC particles essentially retain their shape and size in the steel composites, while VC particles dissolve at least partially in the matrix and reprecipitate or form new phases in the final solidification and cooling stage. The porosity in the deposits increases with the gas to melt ratio (GMR) and the powder to melt ratio (PMR) by increasing atomizing gas pressure and powder feeding rate. Carbide type also affects the porosity of the deposits, because different thermodynamic properties of carbides change the heat dissipation and local solidification behavior of the mixture of matrix material and dissolved carbides. Moreover, the microstructure of the matrix material X46Cr13 is refined considerably with increasing GMR and PMR.

  14. Sliding Wear Behavior of TiC-Reinforced Cu-4 wt.% Ni Matrix Composites

    NASA Astrophysics Data System (ADS)

    Jha, Pushkar; Gautam, R. K.; Tyagi, Rajnesh; Kumar, Devendra

    2016-10-01

    The present investigation explores the effect of TiC content on the sliding wear properties of Cu-4 wt.% Ni matrix composites. Cu-4 wt.% Ni - x wt.% TiC ( x = 0, 2, 4 and 8 wt.%) metal matrix composites were developed by powder metallurgy route. Their friction and wear was studied under dry sliding at different loads of 5, 7.5 and 10 N and constant sliding speed of 2 m/s using a pin-on-disk machine. The metallographic observations showed an almost uniform distribution of TiC particles in the matrix. Hardness of the composites increased with increasing TiC content (up to 4 wt.%). Friction and wear results of TiC-reinforced composites show better wear resistance than unreinforced matrix alloy. However, the optimum wear resistance was observed for 4 wt.% TiC-reinforced composites. Worn surfaces of specimens indicated the abrasion as the primary mechanism of wear in all the materials investigated in the study. The observed behavior has been explained on the basis of (1) the hardness which results in a decrease in real area of contact in composites containing TiC particles and (2) the formation of a transfer layer of wear debris on the surface of the composites which protects underlying substrate by inhibiting metal-metal contact.

  15. Residual stresses in shape memory alloy fiber reinforced aluminium matrix composite

    NASA Astrophysics Data System (ADS)

    Tsz Loong, Tang; Jamian, Saifulnizan; Ismail, Al Emran; Nur, Nik Hisyammudin Muhd; Watanabe, Yoshimi

    2017-01-01

    Process-induced residual stress in shape memory alloy (SMA) fiber reinforced aluminum (Al) matrix composite was simulated by ANSYS APDL. The manufacturing process of the composite named as NiTi/Al is start with loading and unloading process of nickel titanium (NiTi) wire as SMA to generate a residual plastic strain. Then, this plastic deformed NiTi wire would be embedded into Al to become a composite. Lastly, the composite is heated form 289 K to 363 K and then cooled back to 300 K. Residual stress is generated in composite because of shape memory effect of NiTi and mismatch of thermal coefficient between NiTi wire and Al matrix of composite. ANSYS APDL has been used to simulate the distribution of residual stress and strain in this process. A sensitivity test has been done to determine the optimum number of nodes and elements used. Hence, the number of nodes and elements used are 15680 and 13680, respectively. Furthermore, the distribution of residual stress and strain of nickel fiber reinforced aluminium matrix composite (Ni/Al) and titanium fiber reinforced aluminium matrix composite (Ti/Al) under same simulation process also has been simulated by ANSYS APDL as comparison to NiTi/Al. The simulation results show that compressive residual stress is generated on Al matrix of Ni/Al, Ti/Al and NiTi/Al during heating and cooling process. Besides that, they also have similar trend of residual stress distribution but difference in term of value. For Ni/Al and Ti/Al, they are 0.4% difference on their maximum compressive residual stress at 363K. At same circumstance, NiTi/Al has higher residual stress value which is about 425% higher than Ni/Al and Ti/Al composite. This implies that shape memory effect of NiTi fiber reinforced in composite able to generated higher compressive residual stress in Al matrix, hence able to enhance tensile property of the composite.

  16. German guidelines for steel fiber reinforced shotcrete in tunnels with special consideration of design and statical aspects

    SciTech Connect

    Schmidt-Schleicher, H.

    1995-12-31

    Steel fiber reinforced concrete can undoubtedly absorb tensile forces. The utilization of this characteristic for the design and specifications of support structures for underground tunnels is regulated by the new Guidelines from the German Concrete Association. Recommendations are given in these guidelines for construction design and for construction itself. The required tests for classification, suitability and quality monitoring are presented.

  17. Microstructure and wear characteristics of si particulate reinforced al matrix composites

    NASA Astrophysics Data System (ADS)

    Song, Suk-Jin; Kim, Do-Hyang; Kim, Jun-Su

    1997-08-01

    In order to obtain a homogeneous distribution of fine Si particles in aluminium matrix and thus to improve the adaptability of Al-Si alloy for aerospace and automobile applications, Si particulate reinforced aluminium matrix composites have been processed by using powder metallurgy method. The Si pariticulates with 20-40 μm size and Al alloy powders were mixed, degassed and extruded at 350°C or 400°C depending on the composition of the matrix alloy. The microstructural characteristics of the composites such as interfacial stability at high temperatures have been investigated by various experimental techniques. Wear properties of the composites were investigated by using a pin-on-disk type wear tester. The results were compared with these obtained from the conventionally cast hypereutectic Al-Si alloys and discussed in terms of the observed microstructural characteristics and physical properties such as hardness and tensile properties.

  18. A Brief Research Review for Improvement Methods the Wettability between Ceramic Reinforcement Particulate and Aluminium Matrix Composites

    NASA Astrophysics Data System (ADS)

    Razzaq, Alaa Mohammed; Majid, Dayang Laila Abang Abdul; Ishak, M. R.; B, Uday M.

    2017-05-01

    The development of new methods for addition fine ceramic powders to Al aluminium alloy melts, which would lead to more uniform distribution and effective incorporation of the reinforcement particles into the aluminium matrix alloy. Recently the materials engineering research has moved to composite materials from monolithic, adapting to the global need for lightweight, low cost, quality, and high performance advanced materials. Among the different methods, stir casting is one of the simplest ways of making aluminium matrix composites. However, it suffers from poor distribution and combination of the reinforcement ceramic particles in the metal matrix. These problems become significantly effect to reduce reinforcement size, more agglomeration and tendency with less wettability for the ceramic particles in the melt process. Many researchers have carried out different studies on the wettability between the metal matrix and dispersion phase, which includes added wettability agents, fluxes, preheating the reinforcement particles, coating the reinforcement particles, and use composting techniques. The enhancement of wettability of ceramic particles by the molten matrix alloy and the reinforcement particles distribution improvement in the solidified matrix is the main objective for many studies that will be discussed in this paper.

  19. Space environmental effects on LDEF low Earth orbit exposed graphite reinforced polymer matrix composites

    NASA Technical Reports Server (NTRS)

    George, Pete

    1992-01-01

    The Long Duration Exposure Facility (LDEF) was deployed on April 7, 1984 in low earth orbit (LEO) at an altitude of 482 kilometers. On board experiments experienced the harsh LEO environment including atomic oxygen (AO), ultraviolet radiation (UV), and thermal cycling. During the 5.8 year mission, the LDEF orbit decayed to 340 kilometers where significantly higher AO concentrations exist. LDEF was retrieved on January 12, 1990 from this orbit. One experiment on board LDEF was M0003, Space Effects on Spacecraft Materials. As a subset of M0003 nearly 500 samples of polymer, metal, and glass matrix composites were flown as the Advanced Composites Experiment M0003-10. The Advanced Composites Experiment is a joint effort between government and industry with the Aerospace Corporation serving as the experiment integrator. A portion of the graphite reinforced polymer matrix composites were furnished by the Boeing Defense and Space Group, Seattle, Washington. Test results and discussions for the Boeing portion of M0003-10 are presented. Experiment and specimen location on the LDEF are presented along with a quantitative summary of the pertinent exposure conditions. Matrix materials selected for the test were epoxy, polysulfone, and polyimide. These composite materials were selected due to their suitability for high performance structural capability in spacecraft applications. Graphite reinforced polymer matrix composites offer higher strength to weight ratios along with excellent dimensional stability. The Boeing space exposed and corresponding ground control composite specimens were subjected to post flight mechanical, chemical, and physical testing in order to determine any changes in critical properties and performance characteristics. Among the more significant findings are the erosive effect of atomic oxygen on leading edge exposed specimens and microcracking in non-unidirectionally reinforced flight specimens.

  20. Dislocation fiber interactions in short fiber reinforced metal matrix composites during creep and during thermal cycling

    SciTech Connect

    Eggeler, G.F.; Earthman, J.C.

    1997-12-22

    Short fiber reinforced metal matrix composites (SFR MMCs) are attractive engineering materials because they exhibit increased strength and wear resistance as compared to the fiber free matrix materials. For example, an aluminum alloy containing 15 volume percent of Al{sub 2}O{sub 3} fibers with average dimensions of 200 {micro}m length and 3 {micro}m diameter exhibits an improved creep strength with respect to the fiber free matrix. In addition to extended periods of isothermal and static creep loading high temperature components are subjected to temperature changes which are associated with thermal stresses. Thermal cycles can be due to start up and shut down events and can also be a consequence of anisothermal operating conditions. In short fiber reinforced aluminum alloys, in the stress and temperature range of interest, dislocation creep governs the deformation behavior of the MMC`s metallic matrix. It is therefore interesting to discuss the role of dislocations during creep and during thermal cycling of SFR MMCs. In the present paper the authors describe some basic dislocation mechanisms near the fiber/matrix-interface (FMI) of SFR MMCs. They first consider dislocation structures which are associated with the processing of SFR MMCs. Then dislocation processes which are associated with (1) static isothermal creep and (2) thermal cycling are discussed. Common and distinct features of the associated dislocation structures in the matrix zone near the FMI are highlighted. The authors then use the insight they have gained to qualitatively understand the role of dislocations in the macroscopic response of a SFR MMC under more complex load profiles.

  1. Micromechanics Fatigue Damage Analysis Modeling for Fabric Reinforced Ceramic Matrix Composites

    NASA Technical Reports Server (NTRS)

    Min, J. B.; Xue, D.; Shi, Y.

    2013-01-01

    A micromechanics analysis modeling method was developed to analyze the damage progression and fatigue failure of fabric reinforced composite structures, especially for the brittle ceramic matrix material composites. A repeating unit cell concept of fabric reinforced composites was used to represent the global composite structure. The thermal and mechanical properties of the repeating unit cell were considered as the same as those of the global composite structure. The three-phase micromechanics, the shear-lag, and the continuum fracture mechanics models were integrated with a statistical model in the repeating unit cell to predict the progressive damages and fatigue life of the composite structures. The global structure failure was defined as the loss of loading capability of the repeating unit cell, which depends on the stiffness reduction due to material slice failures and nonlinear material properties in the repeating unit cell. The present methodology is demonstrated with the analysis results evaluated through the experimental test performed with carbon fiber reinforced silicon carbide matrix plain weave composite specimens.

  2. Flexural properties of glass fiber reinforced composite with multiphase biopolymer matrix.

    PubMed

    Väkiparta, M; Yli-Urpo, A; Vallittu, P K

    2004-01-01

    The aim of this study was to evaluate flexural properties of glass fiber-reinforced composites with a multiphase biopolymer matrix. Continuous unidirectional E-glass fibers were preimpregnated with a novel biopolymer of poly(hydroxyproline) amide and ester. The preimpregnated fibers were then further impregnated in a co-monomer system of Bis-GMA-TEGDMA, which formed semi-interpenetrating polymer networks (semi-IPN) with the preimpregnated polymer. After light initiated polymerization of the monomer system, rectangular shaped bar specimens (n = 4) were tested by the three-point bending test. The control material was a fiber-reinforced composite with a Bis-GMA-TEDGMA-matrix only. The mean flexural strength of poly(hydroxyproline) amide preimpregnated fiber composite was higher than that of the control (FS = 888 vs. 805 MPa). The poly(hydroxyproline) ester preimpregnated fibers resulted in lower strength (FS = 541 MPa). The results of this study suggest that preimpregnation of glass fibers with poly(hydroxyproline) amide and the use of such fibers in fiber-reinforced composites with IPN polymer matrices, can reach relatively high mechanical properties.

  3. Modelling of steel fiber-reinforced concrete under multi-axial loads

    SciTech Connect

    Swaddiwudhipong, Somsak . E-mail: cvesomsa@nus.edu.sg; Seow, Puay Eng Constance

    2006-07-15

    Fifty-four plain concrete and steel fiber-reinforced concrete (SFRC) plate specimens containing 0.5%, 1.0% and 1.5% of hooked fibers were tested under biaxial compression. The experimental results obtained were used to verify a failure surface developed earlier by the authors for SFRC under multi-axial loads. An equation has also been proposed in this study to predict the strain at failure for SFRC under multi-axial loads, {epsilon} {sub ci}. The proposed failure criterion and equation to predict {epsilon} {sub ci} were incorporated into a constitutive model in a well-established finite-element software, ABAQUS. Experiments of SFRC plate specimens under multi-axial loads and beams under two-point load were modeled to illustrate the application of the failure surface to SFRC under varying load conditions. Good agreement between analytical and experimental results is observed.

  4. Pseudo-dynamic tests on masonry residential buildings seismically retrofitted by precast steel reinforced concrete walls

    NASA Astrophysics Data System (ADS)

    Li, Wenfeng; Wang, Tao; Chen, Xi; Zhong, Xiang; Pan, Peng

    2017-07-01

    A retrofitting technology using precast steel reinforced concrete (PSRC) panels is developed to improve the seismic performance of old masonry buildings. The PSRC panels are built up as an external PSRC wall system surrounding the existing masonry building. The PSRC walls are well connected to the existing masonry building, which provides enough confinement to effectively improve the ductility, strength, and stiffenss of old masonry structures. The PSRC panels are prefabricated in a factory, significantly reducing the situ work and associated construction time. To demonstrate the feasibility and mechanical effectivenss of the proposed retrofitting system, a full-scale five-story specimen was constructed. The retrofitting process was completed within five weeks with very limited indoor operation. The specimen was then tested in the lateral direction, which could potentially suffer sigifnicant damage in a large earthquake. The technical feasibility, construction workability, and seismic performance were thoroughly demonstrated by a full-scale specimen construction and pseudo-dynamic tests.

  5. Autopsy results of epoxy coated reinforcing steels embedded in test slabs

    SciTech Connect

    Lee, S.K.; Hartt, W.H.

    1998-12-31

    This paper addresses preliminary results of an on-going research project, which is to investigate performance of epoxy coated reinforcing steels (ECRs) exposed to a laboratory testing environment The ECRs acquired from six sources were embedded in 76 chloride contaminated test slabs (two ECRs per slab, in most cases) and connected to bottom mat of {number_sign}5 black rebar. After they were exposed to different environments, some of the slabs were autopsied at three different times (10 months to 3.5 years). According to the autopsy results in terms of degree of coating disbondment, corrosion state at the substrate and macrocell current, it was observed that ECR performance ranged from excellent to poor and key factor was the density and size of coating defects which were initially present or developed during exposure.

  6. Deformation micromechanics of all-cellulose nanocomposites: comparing matrix and reinforcing components.

    PubMed

    Pullawan, Tanittha; Wilkinson, Arthur N; Zhang, Lina N; Eichhorn, Stephen J

    2014-01-16

    All-cellulose nanocomposites, comprising two different forms of cellulose nanowhiskers dispersed in two different matrix systems, are produced. Acid hydrolysis of both tunicate (T-CNWs) and cotton cellulose (CNWs) is carried out to produce the nanowhiskers. These nanowhiskers are then dispersed in a cellulose matrix material, produced using two dissolution methods; namely lithium chloride/N,N-dimethyl acetamide (LiCl/DMAc) and sodium hydroxide/urea (NaOH/urea). Crystallinity of both nanocomposite systems increases with the addition of nanowhiskers up to a volume fraction of 15 v/v%, after which a plateau is reached. Stress-transfer mechanisms, between the matrix and the nanowhiskers in both of these nanocomposites are reported. This is achieved by following both the mechanical deformation of the materials, and by following the molecular deformation of both the nanowhiskers and matrix phases using Raman spectroscopy. In order to carry out the latter of these analyses, two spectral peaks are used which correspond to different crystal allomorphs; cellulose-I for the nanowhiskers and cellulose-II for the matrix. It is shown that composites comprising a LiCl/DMAc based matrix perform better than NaOH/urea based systems, the T-CNWs provide better reinforcement than CNWs and that an optimum loading of nanowhiskers (at 15 v/v%) is required to obtain maximum tensile strength and modulus.

  7. Fatigue testing and damage development in continuous fiber reinforced metal matrix composites

    NASA Technical Reports Server (NTRS)

    Johnson, W. S.

    1989-01-01

    A general overview of the fatigue behavior of metal matrix composites (MMC) is presented. The first objective is to present experimental procedures and techniques for conducting a meaningful fatigue test to detect and quantify fatigue damage in MMC. These techniques include interpretation of stress-strain responses, acid etching of the matrix, edge replicas of the specimen under load, radiography, and micrographs of the failure surfaces. In addition, the paper will show how stiffness loss in continuous fiber reinforced metal matrix composites can be a useful parameter for detecting fatigue damage initiation and accumulation. Second, numerous examples of how fatigue damage can initiate and grow in various MMC are given. Depending on the relative fatigue behavior of the fiber and matrix, and the interface properties, the failure modes of MMC can be grouped into four categories: (1) matrix dominated, (2) fiber dominated, (3) self-similar damage growth, and (4) fiber/matrix interfacial failures. These four types of damage will be discussed and illustrated by examples with the emphasis on the fatigue of unnotched laminates.

  8. Fatigue testing and damage development in continuous fiber reinforced metal matrix composites

    NASA Technical Reports Server (NTRS)

    Johnson, W. S.

    1988-01-01

    A general overview of the fatigue behavior of metal matrix composites (MMC) is presented. The first objective is to present experimental procedures and techniques for conducting a meaningful fatigue test to detect and quantify fatigue damage in MMC. These techniques include interpretation of stress-strain responses, acid etching of the matrix, edge replicas of the specimen under load, radiography, and micrographs of the failure surfaces. In addition, the paper will show how stiffness loss in continuous fiber reinforced metal matrix composites can be a useful parameter for detecting fatigue damage initiation and accumulation. Second, numerous examples of how fatigue damage can initiate and grow in various MMC are given. Depending on the relative fatigue behavior of the fiber and matrix, and the interface properties, the failure modes of MMC can be grouped into four categories: (1) matrix dominated, (2) fiber dominated, (3) self-similar damage growth, and (4) fiber/matrix interfacial failures. These four types of damage will be discussed and illustrated by examples with the emphasis on the fatigue of unnotched laminates.

  9. Modeling of stress/strain behavior of fiber-reinforced ceramic matrix composites including stress redistribution

    NASA Technical Reports Server (NTRS)

    Mital, Subodh K.; Murthy, Pappu L. N.; Chamis, Christos C.

    1994-01-01

    A computational simulation procedure is presented for nonlinear analyses which incorporates microstress redistribution due to progressive fracture in ceramic matrix composites. This procedure facilitates an accurate simulation of the stress-strain behavior of ceramic matrix composites up to failure. The nonlinearity in the material behavior is accounted for at the constituent (fiber/matrix/interphase) level. This computational procedure is a part of recent upgrades to CEMCAN (Ceramic Matrix Composite Analyzer) computer code. The fiber substructuring technique in CEMCAN is used to monitor the damage initiation and progression as the load increases. The room-temperature tensile stress-strain curves for SiC fiber reinforced reaction-bonded silicon nitride (RBSN) matrix unidirectional and angle-ply laminates are simulated and compared with experimentally observed stress-strain behavior. Comparison between the predicted stress/strain behavior and experimental stress/strain curves is good. Collectively the results demonstrate that CEMCAN computer code provides the user with an effective computational tool to simulate the behavior of ceramic matrix composites.

  10. Mechanical Properties of Aluminum Matrix Composite Reinforced by Carbothermally Reduced of Fly Ash

    NASA Astrophysics Data System (ADS)

    Jamasri, Wildan, M. W.; Sulardjaka, Kusnanto

    2011-01-01

    The addition of fly ash into aluminum as reinforcement can potentially reduce the production cost and density of aluminum. However, mechanical properties of aluminum matrix composite reinforced by fly ash (MMC ALFA) have some limitations due to the characteristic of fly ash. In this study, a carbothermal reduction process of fly ash and activated carbon powder with particle size <32 μm was performed prior to produce MMC ALFA. The process was carried out in a furnace at 1300° C in vacuum condition under argon flow. Synthesis product was analyzed by XRD with Cu-Kα radiation. From XRD analysis, it shows that the synthesis process can produce SiC powder. The synthesis product was subsequently used as reinforcement particle. Aluminum powder was mixed with 5, 10 and 15% of the synthesized powder, and then uni-axially compacted at pressure of 300 MPa. The compacted product was sintered for 2 hours in argon atmosphere at temperature variation of 550 and 600° C. Flexural strength, hardness and density of MMC ALFA's product were respectively evaluated using a four point bending test method based on ASTM C1161 standard, Brinell hardness scale and Archimedes method. The result of this study shows that the increase of weight of reinforcement can significantly increase the hardness and flexural strength of MMCs. The highest hardness and flexural strength of the MMC product are 300 kg/mm2 and 107.5 MPa, respectively.

  11. Strengthening behavior of chopped multi-walled carbon nanotube reinforced aluminum matrix composites

    SciTech Connect

    Shin, S.E.; Bae, D.H.

    2013-09-15

    Strengthening behavior of the aluminum composites reinforced with chopped multi-walled carbon nanotubes (MWCNTs) or aluminum carbide formed during annealing at 500 °C has been investigated. The composites were fabricated by hot-rolling the powders which were ball-milled under various conditions. During the early annealing process, aluminum atoms can cluster inside the tube due to the diffusional flow of aluminum atoms into the tube, providing an increase of the strength of the composite. Further annealing induces the formation of the aluminum carbide phase, leading to an overall drop in the strength of the composites. While the strength of the composites can be evaluated according to the rule of mixture, a particle spacing effect can be additionally imparted on the strength of the composites reinforced with the chopped MWCNTs or the corresponding carbides since the reinforcing agents are smaller than the submicron matrix grains. - Highlights: • Strengthening behavior of chopped CNT reinforced Al-based composites is investigated. • Chopped CNTs have influenced the strength and microstructures of the composites. • Chopped CNTs are created under Ar- 3% H2 atmosphere during mechanical milling. • Strength can be evaluated by the rule of the mixture and a particle spacing effect.

  12. Mechanical Properties of Aluminum Matrix Composite Reinforced by Carbothermally Reduced of Fly Ash

    SciTech Connect

    Jamasri; Wildan, M. W.; Sulardjaka; Kusnanto

    2011-01-17

    The addition of fly ash into aluminum as reinforcement can potentially reduce the production cost and density of aluminum. However, mechanical properties of aluminum matrix composite reinforced by fly ash (MMC ALFA) have some limitations due to the characteristic of fly ash. In this study, a carbothermal reduction process of fly ash and activated carbon powder with particle size <32 {mu}m was performed prior to produce MMC ALFA.The process was carried out in a furnace at 1300 deg. C in vacuum condition under argon flow. Synthesis product was analyzed by XRD with Cu-K{sub {alpha}} radiation. From XRD analysis, it shows that the synthesis process can produce SiC powder. The synthesis product was subsequently used as reinforcement particle. Aluminum powder was mixed with 5, 10 and 15% of the synthesized powder, and then uni-axially compacted at pressure of 300 MPa. The compacted product was sintered for 2 hours in argon atmosphere at temperature variation of 550 and 600 deg. C. Flexural strength, hardness and density of MMC ALFA's product were respectively evaluated using a four point bending test method based on ASTM C1161 standard, Brinell hardness scale and Archimedes method. The result of this study shows that the increase of weight of reinforcement can significantly increase the hardness and flexural strength of MMCs. The highest hardness and flexural strength of the MMC product are 300 kg/mm{sup 2} and 107.5 MPa, respectively.

  13. RC beams shear-strengthened with fabric-reinforced-cementitious-matrix (FRCM) composite

    NASA Astrophysics Data System (ADS)

    Loreto, Giovanni; Babaeidarabad, Saman; Leardini, Lorenzo; Nanni, Antonio

    2015-12-01

    The interest in retrofit/rehabilitation of existing concrete structures has increased due to degradation and/or introduction of more stringent design requirements. Among the externally-bonded strengthening systems fiber-reinforced polymers is the most widely known technology. Despite its effectiveness as a material system, the presence of an organic binder has some drawbacks that could be addressed by using in its place a cementitious binder as in fabric-reinforced cementitious matrix (FRCM) systems. The purpose of this paper is to evaluate the behavior of reinforced concrete (RC) beams strengthened in shear with U-wraps made of FRCM. An extensive experimental program was undertaken in order to understand and characterize this composite when used as a strengthening system. The laboratory results demonstrate the technical viability of FRCM for shear strengthening of RC beams. Based on the experimental and analytical results, FRCM increases shear strength but not proportionally to the number of fabric plies installed. On the other hand, FRCM failure modes are related with a high consistency to the amount of external reinforcement applied. Design considerations based on the algorithms proposed by ACI guidelines are also provided.

  14. Specimen Preparation for Metal Matrix Composites with a High Volume Fraction of Reinforcing Particles for EBSD Analysis

    NASA Astrophysics Data System (ADS)

    Smirnov, A. S.; Belozerov, G. A.; Smirnova, E. O.; Konovalov, A. V.; Shveikin, V. P.; Muizemnek, O. Yu.

    2016-07-01

    The paper deals with a procedure of preparing a specimen surface for the EBSD analysis of a metal matrix composite (MMC) with a high volume fraction of reinforcing particles. Unlike standard procedures of preparing a specimen surface for the EBSD analysis, the proposed procedure is iterative with consecutive application of mechanical and electrochemical polishing. This procedure significantly improves the results of an indexed MMC matrix in comparison with the standard procedure of specimen preparation. The procedure was verified on a MMC with pure aluminum (99.8% Al) as the matrix, SiC particles being used as reinforcing elements. The average size of the SiC particles is 14 μm, and their volume fraction amounts to 50% of the total volume of the composite. It has been experimentally found that, for making the EBSD analysis of a material matrix near reinforcing particles, the difference in height between the particles and the matrix should not exceed 2 µm.

  15. Matrix free fiber reinforced polymeric composites via high-temperature high-pressure sintering

    NASA Astrophysics Data System (ADS)

    Xu, Tao

    2004-11-01

    A novel manufacturing process called high-temperature high-pressure sintering was studied and explored. Solid fiber reinforced composites are produced by consolidating and compacting layers of polymeric fabrics near their melting temperature under high pressure. There is no need to use an additional matrix as a bonding material. Partial melting and recrystallization of the fibers effectively fuse the material together. The product is called a "matrix free" fiber reinforced composite and essentially a one-polymer composite in which the fiber and the matrix have the same chemical composition. Since the matrix is eliminated in the process, it is possible to achieve a high fiber volume fraction and light weight composite. Interfacial adhesion between fibers and matrix is very good due to the molecular continuity throughout the system and the material is thermally shapeable. Plain woven Spectra RTM cloth made of SpectraRTM fiber was used to comprehensively study the process. The intrinsic properties of the material demonstrate that matrix free SpectraRTM fiber reinforced composites have the potential to make ballistic shields such as body armor and helmets. The properties and structure of the original fiber and the cloth were carefully examined. Optimization of the processing conditions started with the probing of sintering temperatures by Differential Scanning Calorimetry. Coupled with the information from structural, morphological and mechanical investigations on the samples sintered at different processing conditions, the optimal processing windows were determined to ensure that the outstanding original properties of the fibers translate into high ballistic performance of the composites. Matrix free SpectraRTM composites exhibit excellent ballistic resistance in the V50 tests conducted by the US Army. In the research, process-structure-property relationship is established and correlations between various properties and structures are understood. Thorough knowledge is

  16. Recent advances in understanding the reinforcing ability and mechanism of carbon nanotubes in ceramic matrix composites

    PubMed Central

    Estili, Mehdi; Sakka, Yoshio

    2014-01-01

    Since the discovery of carbon nanotubes (CNTs), commonly referred to as ultimate reinforcement, the main purpose for fabricating CNT–ceramic matrix composites has been mainly to improve the fracture toughness and strength of the ceramic matrix materials. However, there have been many studies reporting marginal improvements or even the degradation of mechanical properties. On the other hand, those studies claiming noticeable toughening measured using indentation, which is an indirect/unreliable characterization method, have not demonstrated the responsible mechanisms applicable to the nanoscale, flexible CNTs; instead, those studies proposed those classical methods applicable to microscale fiber/whisker reinforced ceramics without showing any convincing evidence of load transfer to the CNTs. Therefore, the ability of CNTs to directly improve the macroscopic mechanical properties of structural ceramics has been strongly questioned and debated in the last ten years. In order to properly discuss the reinforcing ability (and possible mechanisms) of CNTs in a ceramic host material, there are three fundamental questions to our knowledge at both the nanoscale and macroscale levels that need to be addressed: (1) does the intrinsic load-bearing ability of CNTs change when embedded in a ceramic host matrix?; (2) when there is an intimate atomic-level interface without any chemical reaction with the matrix, could one expect any load transfer to the CNTs along with effective load bearing by them during crack propagation?; and (3) considering their nanometer-scale dimensions, flexibility and radial softness, are the CNTs able to improve the mechanical properties of the host ceramic matrix at the macroscale when individually, intimately and uniformly dispersed? If so, how? Also, what is the effect of CNT concentration in such a defect-free composite system? Here, we briefly review the recent studies addressing the above fundamental questions. In particular, we discuss the new

  17. Recent advances in understanding the reinforcing ability and mechanism of carbon nanotubes in ceramic matrix composites.

    PubMed

    Estili, Mehdi; Sakka, Yoshio

    2014-12-01

    Since the discovery of carbon nanotubes (CNTs), commonly referred to as ultimate reinforcement, the main purpose for fabricating CNT-ceramic matrix composites has been mainly to improve the fracture toughness and strength of the ceramic matrix materials. However, there have been many studies reporting marginal improvements or even the degradation of mechanical properties. On the other hand, those studies claiming noticeable toughening measured using indentation, which is an indirect/unreliable characterization method, have not demonstrated the responsible mechanisms applicable to the nanoscale, flexible CNTs; instead, those studies proposed those classical methods applicable to microscale fiber/whisker reinforced ceramics without showing any convincing evidence of load transfer to the CNTs. Therefore, the ability of CNTs to directly improve the macroscopic mechanical properties of structural ceramics has been strongly questioned and debated in the last ten years. In order to properly discuss the reinforcing ability (and possible mechanisms) of CNTs in a ceramic host material, there are three fundamental questions to our knowledge at both the nanoscale and macroscale levels that need to be addressed: (1) does the intrinsic load-bearing ability of CNTs change when embedded in a ceramic host matrix?; (2) when there is an intimate atomic-level interface without any chemical reaction with the matrix, could one expect any load transfer to the CNTs along with effective load bearing by them during crack propagation?; and (3) considering their nanometer-scale dimensions, flexibility and radial softness, are the CNTs able to improve the mechanical properties of the host ceramic matrix at the macroscale when individually, intimately and uniformly dispersed? If so, how? Also, what is the effect of CNT concentration in such a defect-free composite system? Here, we briefly review the recent studies addressing the above fundamental questions. In particular, we discuss the new

  18. Recent advances in understanding the reinforcing ability and mechanism of carbon nanotubes in ceramic matrix composites

    NASA Astrophysics Data System (ADS)

    Estili, Mehdi; Sakka, Yoshio

    2014-12-01

    Since the discovery of carbon nanotubes (CNTs), commonly referred to as ultimate reinforcement, the main purpose for fabricating CNT-ceramic matrix composites has been mainly to improve the fracture toughness and strength of the ceramic matrix materials. However, there have been many studies reporting marginal improvements or even the degradation of mechanical properties. On the other hand, those studies claiming noticeable toughening measured using indentation, which is an indirect/unreliable characterization method, have not demonstrated the responsible mechanisms applicable to the nanoscale, flexible CNTs; instead, those studies proposed those classical methods applicable to microscale fiber/whisker reinforced ceramics without showing any convincing evidence of load transfer to the CNTs. Therefore, the ability of CNTs to directly improve the macroscopic mechanical properties of structural ceramics has been strongly questioned and debated in the last ten years. In order to properly discuss the reinforcing ability (and possible mechanisms) of CNTs in a ceramic host material, there are three fundamental questions to our knowledge at both the nanoscale and macroscale levels that need to be addressed: (1) does the intrinsic load-bearing ability of CNTs change when embedded in a ceramic host matrix?; (2) when there is an intimate atomic-level interface without any chemical reaction with the matrix, could one expect any load transfer to the CNTs along with effective load bearing by them during crack propagation?; and (3) considering their nanometer-scale dimensions, flexibility and radial softness, are the CNTs able to improve the mechanical properties of the host ceramic matrix at the macroscale when individually, intimately and uniformly dispersed? If so, how? Also, what is the effect of CNT concentration in such a defect-free composite system? Here, we briefly review the recent studies addressing the above fundamental questions. In particular, we discuss the new

  19. Prediction of transverse fatigue behavior of unidirectionally reinforced metal matrix composites

    SciTech Connect

    John, R.; Buchanan, D.J.; Larsen, J.M.

    1998-11-03

    Unidirectionally reinforced metal matrix composites (MMC) are targeted for use in many aerospace applications which require high specific strength and stiffness at elevated temperatures. Such applications include blings and disks. The primary weakness of a component made of unidirectionally reinforced MMC is its susceptibility to transverse loads. The strength of the component in the transverse direction is significantly lower than that in the longitudinal direction under monotonic, sustained and fatigue loading conditions. Hence, replacement of monolithic components with MMC components requires that the transverse strength of the MMC should be predicted accurately. This paper discusses the applicability of a net-section based model to predict the fatigue behavior of [909] MMC under transverse loading.

  20. Reinforced Si3N4 matrix composites formed by the directed metal oxidation process

    SciTech Connect

    Johnson, W.B.

    1992-10-01

    Results of an exploratory study in which the DIMOX directed metal oxidation process was used to form reinforced Si3N4 matrix composites are reported. The study focused on C-fiber reinforcement, which is satisfactory for low-to-moderate temperature applications, including some aerospace and turbine engine applications. It is noted, however, that whenever C-fibers are used at high temperatures in an oxidizing environment, the oxidation resistance of the resulting composites must be addressed. The need for investigating more stable fibers, such as SiC, is emphasized. The approach offers the potential to produce lightweight materials with high room temperature and elevated temperature strength as well as the net or near-net shape capability. 15 refs.

  1. Model of brittle matrix composite toughening based on discrete fiber reinforcement

    NASA Technical Reports Server (NTRS)

    Rubinstein, Asher A.

    1992-01-01

    An analytical approach for the analysis of the effectiveness of fiber reinforcement in brittle matrix composites is presented. The analytical method allows consideration of discrete fiber distribution and examination of the development of crack growth parameters on microscale. The problem associated with the bridging zone development is addressed here; therefore, the bridging zone is considered to be smaller than the main preexisting crack, and the small scale approach is used. The mechanics of the reinforcement is accurately accounted for in the process zone of a growing crack. Closed form solutions characterizing the initial failure process are presented for linear and nonlinear force - fiber pullout displacement relationships. The implicit exact solution for the extended bridging zone is presented as well.

  2. The Performance Analysis of Distributed Brillouin Corrosion Sensors for Steel Reinforced Concrete Structures

    PubMed Central

    Wei, Heming; Zhao, Xuefeng; Kong, Xianglong; Zhang, Pinglei; Cui, Yanjun; Sun, Changsen

    2014-01-01

    The Brillouin optical time-domain analysis (BOTDA)-based optical fiber method has been proposed to measure strain variations caused by corrosion expansion. Spatial resolutions of 1 m can be achieved with this kind of Brillouin sensor for detecting the distributed strain. However, when the sensing fiber is wound around the steel rebar in a number of circles in a range of several meters, this spatial resolution still has limitations for corrosion monitoring. Here, we employed a low-coherent fiber-optic strain sensor (LCFS) to survey the performance of Brillouin sensors based on the fact that the deformation measured by the LCFS equals the integral of the strains obtained from Brillouin sensors. An electrochemical accelerated corrosion experiment was carried out and the corrosion expansion was monitored by both BOTDA and the LCFS. Results demonstrated that the BOTDA can only measure the expansion strain of about 1,000 με, which was generated by the 18 mm steel rebar corrosion, but, the LCFS had high sensitivity from the beginning of corrosion to the destruction of the structure, and no obvious difference in expansion speed was observed during the acceleration stage of the corrosion developed in the reinforced concrete (RC) specimens. These results proved that the BOTDA method could only be employed to monitor the corrosion inside the structure in the early stage. PMID:24379048

  3. Experimental Study on Mechanical Property of Steel Reinforced Concrete L-Shaped Short Columns

    NASA Astrophysics Data System (ADS)

    Li, Zhe; Qin, Hao; Dang, Hui; Li, Hui; Zhang, Jian-Shan

    The horizontal press performance of column is deteriorated because of its special-shaped section. Moreover, because the antiseismic performance of column is worse, special-shaped column is only used in regions where seismic intensity is lower. So the main problem is to enhance the ductility and shear capacity. This test study on mechanical performance has been carried out through 14 SRCLSSC and 2 RCLSSC. The study focuses on the impacts of test axial load ratio (nt), hooped reinforcement ratio (ρv), shear span ratio (λ) and steel ratio (ρss) on the shear strength and the antiseismic performance of SRCLSSC. It can be concluded that the shear strength of SRCLSSC is increasing with the increasing of nt and ρss, but the degree of increasing is small when nt is a certainty value, and that the shear strength of SRCLSSC is decreasing with increasing of λ The shear resistance formula of L-shaped column is derived through tests, the calculated results are in correspondence with those of the tests. It also can be concluded that the hysteretic loops of the SRCLSSC are full and the hysteretic behaviors are improved; the displacement ductility is increasing with increasing of ρv and ρss, but decreasing with the increasing of nt; the degree of variety in high axial load ratio is larger than that in low axial load ratio. If steel bars are added, the shear strength and displacement ductility of SRCLSSC are increased in a large degree.

  4. The performance analysis of distributed Brillouin corrosion sensors for steel reinforced concrete structures.

    PubMed

    Wei, Heming; Zhao, Xuefeng; Kong, Xianglong; Zhang, Pinglei; Cui, Yanjun; Sun, Changsen

    2013-12-27

    The Brillouin optical time-domain analysis (BOTDA)-based optical fiber method has been proposed to measure strain variations caused by corrosion expansion. Spatial resolutions of 1 m can be achieved with this kind of Brillouin sensor for detecting the distributed strain. However, when the sensing fiber is wound around the steel rebar in a number of circles in a range of several meters, this spatial resolution still has limitations for corrosion monitoring. Here, we employed a low-coherent fiber-optic strain sensor (LCFS) to survey the performance of Brillouin sensors based on the fact that the deformation measured by the LCFS equals the integral of the strains obtained from Brillouin sensors. An electrochemical accelerated corrosion experiment was carried out and the corrosion expansion was monitored by both BOTDA and the LCFS. Results demonstrated that the BOTDA can only measure the expansion strain of about 1,000 με, which was generated by the 18 mm steel rebar corrosion, but, the LCFS had high sensitivity from the beginning of corrosion to the destruction of the structure, and no obvious difference in expansion speed was observed during the acceleration stage of the corrosion developed in the reinforced concrete (RC) specimens. These results proved that the BOTDA method could only be employed to monitor the corrosion inside the structure in the early stage.

  5. Self-immunity microcapsules for corrosion protection of steel bar in reinforced concrete

    NASA Astrophysics Data System (ADS)

    Wang, Yanshuai; Fang, Guohao; Ding, Weijian; Han, Ningxu; Xing, Feng; Dong, Biqin

    2015-12-01

    A novel microcapsule-based self-immunity system for reinforced concrete is proposed. Its feasibility for hindering the corrosion of steel rebar by means of lifting the threshold value of [Cl-]/[OH-] is discussed. Precisely controlled release behavior enables corrosion protection in the case of depassivation. The release process is characterized over a designated range of pH values, and its release characteristics of the microcapsules, triggered by decreasing pH value, are captured by observing that the core crystals are released when exposed to a signal (stimulus). The aim of corrosion protection of steel bar is achieved through the constantly-stabilized passive film, and its stability is promoted using continuous calcium hydroxide released from the microcapsule, restoring alkaline conditions. The test results exhibited that the release process of the microcapsules is a function of time. Moreover, the release rate of core materials could interact with environmental pH value, in which the release rate is found to increase remarkably with decreasing pH value, but is inhibited by high pH levels.

  6. Corrosion Assessment of Steel Bars Used in Reinforced Concrete Structures by Means of Eddy Current Testing.

    PubMed

    de Alcantara, Naasson P; da Silva, Felipe M; Guimarães, Mateus T; Pereira, Matheus D

    2015-12-24

    This paper presents a theoretical and experimental study on the use of Eddy Current Testing (ECT) to evaluate corrosion processes in steel bars used in reinforced concrete structures. The paper presents the mathematical basis of the ECT sensor built by the authors; followed by a finite element analysis. The results obtained in the simulations are compared with those obtained in experimental tests performed by the authors. Effective resistances and inductances; voltage drops and phase angles of wound coil are calculated using both; simulated and experimental data; and demonstrate a strong correlation. The production of samples of corroded steel bars; by using an impressed current technique is also presented. The authors performed experimental tests in the laboratory using handmade sensors; and the corroded samples. In the tests four gauges; with five levels of loss-of-mass references for each one were used. The results are analyzed in the light of the loss-of-mass and show a strong linear behavior for the analyzed parameters. The conclusions emphasize the feasibility of the proposed technique and highlight opportunities for future works.

  7. Effect of Waste Plastic Shreds on Bond Resistance between Concrete and Steel Reinforcement

    NASA Astrophysics Data System (ADS)

    Osifala, K. B.; Salau, M. A.; Adeniyi, A. A.

    2015-11-01

    This paper investigates the effect of waste plastic shreds on steel-concrete bond. Forty RILEM test specimens with 16mm and 20mm diameter high-yield reinforcing bars were cast and tested. Fifteen specimens with 16mm and 20mm each were cast with the addition of waste plastic shreds at varying percentages of 1%, 1.5% and 2%; another ten RILEM specimens with 16mm and 20mm diameter bars at 0% of waste plastic shreds were cast as reference. Nine 150mm cubes, with three taken from each batch of various percentages of waste plastic shreds, were used to monitor the concrete strength. From the test results and analysis, the compressive strength of concrete was found to reduce with increased percentages of waste plastic shreds, while the waste plastic shreds material was found not to improve the bond resistance between concrete and steel. However, though lower than normal concrete, there was an increase in the bond resistance with increase in the percent of plastic shreds. The bond resistance of 16mm was also found to be higher than that of 20mm in all the specimens tested.

  8. Self-immunity microcapsules for corrosion protection of steel bar in reinforced concrete.

    PubMed

    Wang, Yanshuai; Fang, Guohao; Ding, Weijian; Han, Ningxu; Xing, Feng; Dong, Biqin

    2015-12-17

    A novel microcapsule-based self-immunity system for reinforced concrete is proposed. Its feasibility for hindering the corrosion of steel rebar by means of lifting the threshold value of [Cl(-)]/[OH(-)] is discussed. Precisely controlled release behavior enables corrosion protection in the case of depassivation. The release process is characterized over a designated range of pH values, and its release characteristics of the microcapsules, triggered by decreasing pH value, are captured by observing that the core crystals are released when exposed to a signal (stimulus). The aim of corrosion protection of steel bar is achieved through the constantly-stabilized passive film, and its stability is promoted using continuous calcium hydroxide released from the microcapsule, restoring alkaline conditions. The test results exhibited that the release process of the microcapsules is a function of time. Moreover, the release rate of core materials could interact with environmental pH value, in which the release rate is found to increase remarkably with decreasing pH value, but is inhibited by high pH levels.

  9. Self-immunity microcapsules for corrosion protection of steel bar in reinforced concrete

    PubMed Central

    Wang, Yanshuai; Fang, Guohao; Ding, Weijian; Han, Ningxu; Xing, Feng; Dong, Biqin

    2015-01-01

    A novel microcapsule-based self-immunity system for reinforced concrete is proposed. Its feasibility for hindering the corrosion of steel rebar by means of lifting the threshold value of [Cl−]/[OH−] is discussed. Precisely controlled release behavior enables corrosion protection in the case of depassivation. The release process is characterized over a designated range of pH values, and its release characteristics of the microcapsules, triggered by decreasing pH value, are captured by observing that the core crystals are released when exposed to a signal (stimulus). The aim of corrosion protection of steel bar is achieved through the constantly-stabilized passive film, and its stability is promoted using continuous calcium hydroxide released from the microcapsule, restoring alkaline conditions. The test results exhibited that the release process of the microcapsules is a function of time. Moreover, the release rate of core materials could interact with environmental pH value, in which the release rate is found to increase remarkably with decreasing pH value, but is inhibited by high pH levels. PMID:26673425

  10. Research on the mechanical properties of a glass fiber reinforced polymer-steel combined truss structure.

    PubMed

    Liu, Pengfei; Zhao, Qilin; Li, Fei; Liu, Jinchun; Chen, Haosen

    2014-01-01

    An assembled plane truss structure used for vehicle loading is designed and manufactured. In the truss, the glass fiber reinforced polymer (GFRP) tube and the steel joint are connected by a new technology featuring a pretightened tooth connection. The detailed description for the rod and node design is introduced in this paper, and a typical truss panel is fabricated. Under natural conditions, the short-term load test and long-term mechanical performance test for one year are performed to analyze its performance and conduct a comparative analysis for a reasonable FEM model. The study shows that the design and fabrication for the node of an assembled truss panel are convenient, safe, and reliable; because of the creep control design of the rods, not only does the short-term structural stiffness meet the design requirement but also the long-term creep deformation tends towards stability. In addition, no significant change is found in the elastic modules, so this structure can be applied in actual engineering. Although the safety factor for the strength of the composite rods is very large, it has a lightweight advantage over the steel truss for the low density of GFRP. In the FEM model, simplifying the node as a hinge connection relatively conforms to the actual status.

  11. Research on the Mechanical Properties of a Glass Fiber Reinforced Polymer-Steel Combined Truss Structure

    PubMed Central

    Liu, Pengfei; Zhao, Qilin; Li, Fei; Liu, Jinchun; Chen, Haosen

    2014-01-01

    An assembled plane truss structure used for vehicle loading is designed and manufactured. In the truss, the glass fiber reinforced polymer (GFRP) tube and the steel joint are connected by a new technology featuring a pretightened tooth connection. The detailed description for the rod and node design is introduced in this paper, and a typical truss panel is fabricated. Under natural conditions, the short-term load test and long-term mechanical performance test for one year are performed to analyze its performance and conduct a comparative analysis for a reasonable FEM model. The study shows that the design and fabrication for the node of an assembled truss panel are convenient, safe, and reliable; because of the creep control design of the rods, not only does the short-term structural stiffness meet the design requirement but also the long-term creep deformation tends towards stability. In addition, no significant change is found in the elastic modules, so this structure can be applied in actual engineering. Although the safety factor for the strength of the composite rods is very large, it has a lightweight advantage over the steel truss for the low density of GFRP. In the FEM model, simplifying the node as a hinge connection relatively conforms to the actual status. PMID:25247203

  12. Corrosion Assessment of Steel Bars Used in Reinforced Concrete Structures by Means of Eddy Current Testing

    PubMed Central

    de Alcantara, Naasson P.; da Silva, Felipe M.; Guimarães, Mateus T.; Pereira, Matheus D.

    2015-01-01

    This paper presents a theoretical and experimental study on the use of Eddy Current Testing (ECT) to evaluate corrosion processes in steel bars used in reinforced concrete structures. The paper presents the mathematical basis of the ECT sensor built by the authors; followed by a finite element analysis. The results obtained in the simulations are compared with those obtained in experimental tests performed by the authors. Effective resistances and inductances; voltage drops and phase angles of wound coil are calculated using both; simulated and experimental data; and demonstrate a strong correlation. The production of samples of corroded steel bars; by using an impressed current technique is also presented. The authors performed experimental tests in the laboratory using handmade sensors; and the corroded samples. In the tests four gauges; with five levels of loss-of-mass references for each one were used. The results are analyzed in the light of the loss-of-mass and show a strong linear behavior for the analyzed parameters. The conclusions emphasize the feasibility of the proposed technique and highlight opportunities for future works. PMID:26712754

  13. Hysteretic behavior of special shaped columns composed of steel and reinforced concrete (SRC)

    NASA Astrophysics Data System (ADS)

    Chen, Zongping; Xu, Jinjun; Xue, Jianyang

    2015-06-01

    This paper describes a series of experimental investigations on seventeen specimens of steel reinforced concrete special shaped (SRCSS) columns under low cyclic reversed loading using parallel crosshead equipment. Nine T-shaped SRC columns, four L-shaped SRC columns and four +-shaped SRC columns were tested to examine the effects of shape steel configuration, loading angle, axial compressive ratio and shear-span ratio on the behavior (strength, stiffness, energy dissipation, ductility, etc.) of SRCSS column specimens. The failure modes and hysteretic performance of all the specimens were obtained in the tests. Test results demonstrate that the shear-span ratio is the main parameter affecting the failure modes of SRCSS columns. The specimens with small shear-span ratio are prone to shear failure, and the primary failure planes in SRCSS columns are parallel to the loading direction. As a result, there is a symmetry between positive and negative loading directions in the hysteretic curves of the SRCSS columns. The majority of displacement ductility coefficients for all the specimens are over 3.0, so that the SRCSS columns demonstrate a better deformation capacity. In addition, the equivalent viscous damping coefficients of all the specimens are greater than 0.2, indicating that the seismic behavior of SRCSS columns is adequate. Finally, the superposition theory was used to calculate the limits of axial compressive ratio for the specimens, and it is found that the test axial compressive ratio is close to or smaller than the calculated axial compressive ratio limit.

  14. Crashworthiness characteristics of a carbon fiber reinforced dual-phase epoxy–polyurea hybrid matrix composite

    DOE PAGES

    Zhou, Hongyu; Attard, Thomas L.; Dhiradhamvit, Kittinan; ...

    2014-11-07

    In this paper, the crashworthiness characteristics of rectangular tubes made from a Carbon-fiber reinforced Hybrid-Polymeric Matrix (CHMC) composite were investigated using quasi-static and impact crush tests. The hybrid matrix formulation of the CHMC was created by combining an epoxy-based thermosetting polymer with a lightly crosslinked polyurea elastomer at various cure-time intervals and volumetric ratios. The load–displacement responses of both CHMC and carbon-fiber reinforced epoxy (CF/epoxy) specimens were obtained under various crushing speeds; and crashworthiness parameters, such as the average crushing force and specific energy absorption (SEA), were calculated using subsequent load–displacement relationships. The CHMC maintained a high level of structuralmore » integrity and post-crush performance, relative to traditional CF/epoxy. The influence of the curing time and volumetric ratios of the polyurea/epoxy dual-hybridized matrix system on the crashworthiness parameters was also investigated. The results reveal that the load carrying capacity and total energy absorption tend to increase with greater polyurea thickness and lower elapsed reaction curing time of the epoxy although this is typically a function of the loading rate. In conclusion, the mechanism by which the CHMC provides increased damage tolerance was also investigated using scanning electron microscopy (SEM).« less

  15. Crashworthiness characteristics of a carbon fiber reinforced dual-phase epoxy–polyurea hybrid matrix composite

    SciTech Connect

    Zhou, Hongyu; Attard, Thomas L.; Dhiradhamvit, Kittinan; Wang, Yanli; Erdman, Donald

    2014-11-07

    In this paper, the crashworthiness characteristics of rectangular tubes made from a Carbon-fiber reinforced Hybrid-Polymeric Matrix (CHMC) composite were investigated using quasi-static and impact crush tests. The hybrid matrix formulation of the CHMC was created by combining an epoxy-based thermosetting polymer with a lightly crosslinked polyurea elastomer at various cure-time intervals and volumetric ratios. The load–displacement responses of both CHMC and carbon-fiber reinforced epoxy (CF/epoxy) specimens were obtained under various crushing speeds; and crashworthiness parameters, such as the average crushing force and specific energy absorption (SEA), were calculated using subsequent load–displacement relationships. The CHMC maintained a high level of structural integrity and post-crush performance, relative to traditional CF/epoxy. The influence of the curing time and volumetric ratios of the polyurea/epoxy dual-hybridized matrix system on the crashworthiness parameters was also investigated. The results reveal that the load carrying capacity and total energy absorption tend to increase with greater polyurea thickness and lower elapsed reaction curing time of the epoxy although this is typically a function of the loading rate. In conclusion, the mechanism by which the CHMC provides increased damage tolerance was also investigated using scanning electron microscopy (SEM).

  16. Reinforced Pulsed Laser-Deposited Hydroxyapatite Coating on 316 Stainless Steel

    NASA Astrophysics Data System (ADS)

    Bajpai, Shubhra; Gupta, Ankur; Pradhan, Siddhartha Kumar; Mandal, Tapendu; Balani, Kantesh

    2014-10-01

    Hydroxyapatite (HA) is a widely used bioceramic known for its chemical similarity with that of bone and teeth (Ca/P ratio of 1.67). But, owing to its extreme brittleness, α-Al2O3 is reinforced with HA and processed as a coating via pulsed laser deposition (PLD). Reinforcement of α-Al2O3 (50 wt.%) in HA via PLD on 316L steel substrate has shown modulus increase by 4% and hardness increase by 78%, and an improved adhesion strength of 14.2 N (improvement by 118%). Micro-scratching has shown an increase in the coefficient-of-friction from 0.05 (pure HA) to 0.17 (with 50 wt.% Al2O3) with enhancement in the crack propagation resistance (CPR) up to 4.5 times. Strong adherence of PLD HA-Al2O3 coatings (~4.5 times than that of HA coating) is attributed to efficient release of stored tensile strain energy (~17 × 10-3 J/m2) in HA-Al2O3 composites, making it a potential damage-tolerant bone-replacement surface coating.

  17. Numerical Study on Section Constitutive Relations of Members Reinforced by Steel-BFRP Composite Bars

    NASA Astrophysics Data System (ADS)

    Xiao, Tongliang; Qiu, Hongxing

    2017-06-01

    Steel-Basalt FRP Composite Bar (S-BFCB) is a new kind of substitute material for longitudinal reinforcement, with high elastic modulus, stable post-yield stiffness and excellent corrosive resistance. Based on mechanical properties of S-BFCB and the plane cross-section assumption, the moment-curvature curves of beam and column members are simulated. Some parameters such as equivalent rebar ratio, postyeild stiffness, concrete strength and axial compression ratio of column were discussed. Results show that the constitutive relation of the cross section is similar with RC member in elastic and cracking stages, while different in post-yield stage. With the increase of postyeild stiffness ratio of composite bar, the ultimate bearing capacity of component improved observably, member may turn out over-reinforced phenomenon, concrete crushing may appear before the fibersarefractured. The effect of concrete strength increase in lower postyeild stiffness ratio is not obvious than in higher. The increase of axial compression ratio has actively influence on bearing capacity of column, but decreases on the ductility.

  18. Analysis of stress-strain, fracture and ductility behavior of aluminum matrix composites containing discontinuous silicon carbide reinforcement

    NASA Technical Reports Server (NTRS)

    Mcdanels, D. L.

    1984-01-01

    Mechanical properties and stress-strain behavior for several types of commercially fabricated aluminum matrix composites, containing up to 40 vol % discontinuous SiC whisker, nodule, or particulate reinforcement were evaluated. It was found that the elastic modulus of the composites was isotropic, to be independent of type of reinforcement, and to be controlled solely by the volume percentage of SiC reinforcement present. The yield/tensile strengths and ductility were controlled primarily by the matrix alloy and temper condition. Ductility decreased with increasing reinforcement content, however, the fracture strains observed were higher than those reported in the literature for this type of composite. This increase in fracture strain is attributed to cleaner matrix powder and increased mechanical working during fabrication. Conventional aluminum and titanium structural alloys were compared and have shown that the properties of these low cost, lightweight composites have good potential for application to aerospace structures.

  19. Effects of matrix porosity on the mechanical properties of fiber-reinforced oxide composites

    NASA Astrophysics Data System (ADS)

    Mattoni, Michael Anthony

    Damage tolerance in fiber-reinforced ceramic matrix composites can be achieved through weak bonding between fibers and matrix by the use of fine-scale porosity within the matrix. The effects of matrix porosity on the mechanical properties of porous-matrix, oxide composites are investigated. Porosity is systematically varied through impregnation and pyrolysis of a ceramic precursor solution, and mechanical tests are performed to identify the role of the matrix in both fiber- and matrix-dominated loadings. Two families of composites are examined in this study. The first family possesses a non-uniform porosity distribution due to precursor segregation during drying. Mechanical testing demonstrates a loss of damage tolerance and tensile strength along the fiber direction as the porosity is reduced. Concurrently some improvements in interlaminar shear strength are observed. Building upon this investigation, segregation is eliminated in subsequent studies through use of a gelation step following precursor impregnation. In this family, moderate additions of precursor-derived alumina to the matrix improve the in-plane shear and tensile strength. Concurrently, a significant increase in notch sensitivity is observed. Two theoretical frameworks are developed for the notched strength of ceramic matrix composites. The first considers composites that exhibit rising fracture resistance and is based upon established concepts of crack stability under stress-controlled loadings. The form of the resistance curve assumes that the crack tip inelastic zone is small in relation to the geometric and bridging length scales, making this framework applicable to relatively dense porous matrix composites. The results reveal salient trends in strength with notch length and specimen geometry. An assessment of the theory is made through comparison with experimental measurements. The second framework developed for notch-sensitivity explicitly accounts for large-scale inelasticity, allowing

  20. Modeling the Tensile Strength of Carbon Fiber - Reinforced Ceramic - Matrix Composites Under Multiple Fatigue Loading

    NASA Astrophysics Data System (ADS)

    Li, Longbiao

    2016-06-01

    An analytical method has been developed to investigate the effect of interface wear on the tensile strength of carbon fiber - reinforced ceramic - matrix composites (CMCs) under multiple fatigue loading. The Budiansky - Hutchinson - Evans shear - lag model was used to describe the micro stress field of the damaged composite considering fibers failure and the difference existed in the new and original interface debonded region. The statistical matrix multicracking model and fracture mechanics interface debonding criterion were used to determine the matrix crack spacing and interface debonded length. The interface shear stress degradation model and fibers strength degradation model have been adopted to analyze the interface wear effect on the tensile strength of the composite subjected to multiple fatigue loading. Under tensile loading, the fibers failure probabilities were determined by combining the interface wear model and fibers failure model based on the assumption that the fiber strength is subjected to two - parameter Weibull distribution and the loads carried by broken and intact fibers satisfy the Global Load Sharing criterion. The composite can no longer support the applied load when the total loads supported by broken and intact fibers approach its maximum value. The conditions of a single matrix crack and matrix multicrackings for tensile strength corresponding to multiple fatigue peak stress levels and different cycle number have been analyzed.

  1. Thermal expansion of selected graphite reinforced polyimide-, epoxy-, and glass-matrix composite

    NASA Technical Reports Server (NTRS)

    Tompkins, S. S.

    1985-01-01

    The thermal expansion of three epoxy-matrix composites, a polyimide-matrix composite and a borosilicate glass-matrix composite, each reinforced with continuous carbon fibers, has been measured and compared. The expansion of a composite with a rubber toughened epoxy-matrix and P75S carbon fibers was very different from the expansion of two different single phase epoxy-matrix composites with P75S fibers although all three had the same stacking sequence. Reasonable agreement was obtained between measured thermal-expansion data and results from classical laminate theory. The thermal expansion of a material may change markedly as a result of thermal cycling. Microdamage, induced by 250 cycles between -156 C and 121 C in the graphite/polyimide laminate, caused a 53 percent decrease in the coefficient of thermal expansion. The thermal expansion of the graphite/glass laminate was not changed by 100 thermal cycles from -129 C to 38 C; however, a residual strain of about 10 x 10 to the minus 6 power was measured for the laminate tested.

  2. Matrix density effects on the mechanical properties of SiC fiber-reinforced silicon nitride matrix properties

    NASA Technical Reports Server (NTRS)

    Bhatt, Ramakrishna T.; Kiser, Lames D.

    1990-01-01

    The room temperature mechanical properties were measured for SiC fiber reinforced reaction-bonded silicon nitride composites (SiC/RBSN) of different densities. The composites consisted of approx. 30 vol percent uniaxially aligned 142 micron diameter SiC fibers (Textron SCS-6) in a reaction-bonded Si3N4 matrix. The composite density was varied by changing the consolidation pressure during RBSN processing and by hot isostatically pressing the SiC/RBSN composites. Results indicate that as the consolidation pressure was increased from 27 to 138 MPa, the average pore size of the nitrided composites decreased from 0.04 to 0.02 microns and the composite density increased from 2.07 to 2.45 gm/cc. Nonetheless, these improvements resulted in only small increases in the first matrix cracking stress, primary elastic modulus, and ultimate tensile strength values of the composites. In contrast, HIP consolidation of SiC/RBSN resulted in a fully dense material whose first matrix cracking stress and elastic modulus were approx. 15 and 50 percent higher, respectively, and ultimate tensile strength values were approx. 40 percent lower than those for unHIPed SiC/RBSN composites. The modulus behavior for all specimens can be explained by simple rule-of-mixture theory. Also, the loss in ultimate strength for the HIPed composites appears to be related to a degradation in fiber strength at the HIP temperature. However, the density effect on matrix fracture strength was much less than would be expected based on typical monolithic Si3N4 behavior, suggesting that composite theory is indeed operating. Possible practical implications of these observations are discussed.

  3. Matrix density effects on the mechanical properties of SiC fiber-reinforced silicon nitride matrix properties

    NASA Technical Reports Server (NTRS)

    Bhatt, Ramakrishna T.; Kiser, Lames D.

    1990-01-01

    The room temperature mechanical properties were measured for SiC fiber reinforced reaction-bonded silicon nitride composites (SiC/RBSN) of different densities. The composites consisted of approx. 30 vol percent uniaxially aligned 142 micron diameter SiC fibers (Textron SCS-6) in a reaction-bonded Si3N4 matrix. The composite density was varied by changing the consolidation pressure during RBSN processing and by hot isostatically pressing the SiC/RBSN composites. Results indicate that as the consolidation pressure was increased from 27 to 138 MPa, the average pore size of the nitrided composites decreased from 0.04 to 0.02 microns and the composite density increased from 2.07 to 2.45 gm/cc. Nonetheless, these improvements resulted in only small increases in the first matrix cracking stress, primary elastic modulus, and ultimate tensile strength values of the composites. In contrast, HIP consolidation of SiC/RBSN resulted in a fully dense material whose first matrix cracking stress and elastic modulus were approx. 15 and 50 percent higher, respectively, and ultimate tensile strength values were approx. 40 percent lower than those for unHIPed SiC/RBSN composites. The modulus behavior for all specimens can be explained by simple rule-of-mixture theory. Also, the loss in ultimate strength for the HIPed composites appears to be related to a degradation in fiber strength at the HIP temperature. However, the density effect on matrix fracture strength was much less than would be expected based on typical monolithic Si3N4 behavior, suggesting that composite theory is indeed operating. Possible practical implications of these observations are discussed.

  4. Porosity characterization of fiber-reinforced ceramic matrix composite using synchrotron X-ray computed tomography

    NASA Astrophysics Data System (ADS)

    Zou, C.; Marrow, T. J.; Reinhard, C.; Li, B.; Zhang, C.; Wang, S.

    2016-03-01

    The pore structure and porosity of a continuous fiber reinforced ceramic matrix composite has been characterized using high-resolution synchrotron X-ray computed tomography (XCT). Segmentation of the reconstructed tomograph images reveals different types of pores within the composite, the inter-fiber bundle open pores displaying a "node-bond" geometry, and the intra-fiber bundle isolated micropores showing a piping shape. The 3D morphology of the pores is resolved and each pore is labeled. The quantitative filtering of the pores measures a total porosity 8.9% for the composite, amid which there is about 7.1~ 9.3% closed micropores.

  5. Corrosive effect of carbon-fibre reinforced plastic on stainless-steel screws during implantation into man.

    PubMed

    Tayton, K

    1983-01-01

    The corrosion of stainless-steel screws used to fix carbon-fibre reinforced plastic (CFRP) plates to human fractures was compared with the corrosion on similar screws used to fix stainless-steel AO plates. Corrosive changes were noted in both sets of screws with similar frequency and severity; however, the stainless-steel plates were 'in situ' almost twice as long as the CFRP ones, showing that the corrosive changes occurred more rapidly on screws in contact with CFRP. Nevertheless, over the implantation time necessary for bone healing, corrosion was very mild and there is no clinical contra-indication to the use of stainless-steel and CFRP together in this particular application.

  6. Wear and corrosion of metal-matrix (stainless steel or NiTi)-TiC coatings

    NASA Astrophysics Data System (ADS)

    Fernandez, Javier; Isalgue, Antonio; Cinca, Nuria; Dosta, Sergi; Ventayol, Judith

    Different spraying technologies (plasma and High Velocity Oxi-Fuel) have been use to obtain TiC - stainless steel or NiTi matrix coatings. The starting feedstock powders have been obtained by SHS technology. After crushing and sieving, the fraction of particles between 20 and 63 μ m, have been selected for thermal spray. The obtained coatings have been characterized by XRD and SEM-EDS to observe the surface and cross section. The coatings adhesion, wear (ball-on-disk and rubber wheel tests) and electrochemical corrosion test have been carried out. Results show that the plasma sprayed coatings with NiTi have better adhesion than the stainless steel matrix coatings. However, the opposite happens for HVOF coatings. NiTi matrix coatings exhibit higher wear resistance both for plasma and HVOF spraying processes.

  7. Influence of oxide reinforcement materials on high-temperatue oxidation resistance of Ni sub 3 A1 matrix composites

    SciTech Connect

    Tortorelli, P.F.; DeVan, J.H.; McKamey, C.G.; Howell, M.

    1990-01-01

    The oxidation resistance of Ni{sub 3}Al-based metal matrix composites was studied in high-temperature air under isothermal and thermal cycling conditions as a function of the composition and form of oxide reinforcement material. The incorporation of oxide fibers Al{sub 2}O{sub 3}, HfO{sub 2}, or Al{sub 2}O{sub 3}--ZrO{sub 2} or particles into the Ni{sub 3}Al matrix led to oxidation rates significantly greater than that for the monolithic aluminide. The increase in susceptibility was primarily due to internal oxidation along the fiber- (or particle-) matrix interfaces and depended on the type of reinforcement material and its deposition in the matrix. 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 Ni{sub 3}Al composites. 10 refs, 4 figs.

  8. Mechanical behavior of fiber reinforced SiC/RBSN ceramic matrix composites: Theory and experiment

    NASA Technical Reports Server (NTRS)

    Chulya, Abhisak; Gyekenyesi, John P.; Bhatt, Ramakrishna T.

    1991-01-01

    The mechanical behavior of continuous fiber reinforced SiC/RBSN (Reaction Bonded Silicon Nitride) composites with various fiber contents is evaluated. Both catastrophic and noncatastrophic failures are observed in tensile specimens. Damage and failure mechanisms are identified via in-situ monitoring using NDE (nondestructive evaluation) techniques through the loading history. Effects of fiber/matrix interface debonding (splitting) parallel to fibers are discussed. Statistical failure behavior of fibers is also observed, especially when the interface is weak. Micromechanical models incorporating residual stresses to calculate the critical matrix cracking strength, ultimate strength, and work of pull-out are reviewed and used to predict composite response. For selected test problems, experimental measurements are compared to analytical predictions.

  9. Thermal expansion of selected graphite-reinforced polyimide-, epoxy-, and glass-matrix composites

    NASA Technical Reports Server (NTRS)

    Tompkins, S. S.

    1987-01-01

    The thermal expansion of continuous carbon-fiber reinforced composites with epoxy-, polyimide-, and borosilicate glass-matrices has been measured and compared. The expansion of a rubber-toughened epoxy-matrix/P75S carbon-fiber composite was very different from the expansion of two different single-phase epoxy-matrix/P75S composites, although all three had the same stacking sequence. Reasonable agreement was obtained between measured thermal expansion data and results from classical laminate theory. Microdamage in the graphite/polyimide laminate, induced by 250 cycles between -156 and 121 C, caused a 53 percent decrease in the coefficient of thermal expansion. The thermal expansion of the graphite/glass laminate was not changed after 100 thermal cycles from -129 to 38 C; however, a residual strain of about 10 x 10 to the -6 was observed for the laminate tested.

  10. Recrystallization in SiC particulate reinforced 6061 aluminium metal matrix composites following low strain deformation

    SciTech Connect

    Yu, D.; Munroe, P.R.; Bandyopadhyay, S. . School of Materials Science and Engineering); Mouritz, A.P. . Materials Research Lab.)

    1994-04-01

    Aluminum metal matrix composites (MMC) are envisaged as candidate materials for the aerospace and automotive industries because of their low density, high stiffness, and strength. While the studies have examined the recrystallization behavior of MMCs deformed by large amounts of cold work, little work has been done on the behavior of the matrix microstructure during annealing following lower amounts (i.e.< 10% reduction) of deformation. The work presented in this paper examines the effect of small amounts of deformation in compression on the recovery and recrystallization behavior of MMCs, in two aluminium-based composites (6xxx series) reinforced with either 3 [mu]m or 20 [mu]m diameter SiC particulates.

  11. Evolution of In-Situ Generated Reinforcement Precipitates in Metal Matrix Composites

    NASA Technical Reports Server (NTRS)

    Sen, S.; Kar, S. K.; Catalina, A. V.; Stefanescu, D. M.; Dhindaw, B. K.

    2004-01-01

    Due to certain inherent advantages, in-situ production of Metal Matrix Composites (MMCs) have received considerable attention in the recent past. ln-situ techniques typically involve a chemical reaction that results in precipitation of a ceramic reinforcement phase. The size and spatial distribution of these precipitates ultimately determine the mechanical properties of these MMCs. In this paper we will investigate the validity of using classical growth laws and analytical expressions to describe the interaction between a precipitate and a solid-liquid interface (SLI) to predict the size and spatial evolution of the in-situ generated precipitates. Measurements made on size and distribution of Tic precipitates in a Ni&I matrix will be presented to test the validity of such an approach.

  12. Vacuum brazing of high volume fraction SiC particles reinforced aluminum matrix composites

    NASA Astrophysics Data System (ADS)

    Cheng, Dongfeng; Niu, Jitai; Gao, Zeng; Wang, Peng

    2015-03-01

    This experiment chooses A356 aluminum matrix composites containing 55% SiC particle reinforcing phase as the parent metal and Al-Si-Cu-Zn-Ni alloy metal as the filler metal. The brazing process is carried out in vacuum brazing furnace at the temperature of 550°C and 560°C for 3 min, respectively. The interfacial microstructures and fracture surfaces are investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy spectrum analysis (EDS). The result shows that adequacy of element diffusion are superior when brazing at 560°C, because of higher activity and liquidity. Dislocations and twins are observed at the interface between filler and composite due to the different expansion coefficient of the aluminum alloy matrix and SiC particles. The fracture analysis shows that the brittle fracture mainly located at interface of filler and composites.

  13. Thermal expansion of selected graphite-reinforced polyimide-, epoxy-, and glass-matrix composites

    NASA Technical Reports Server (NTRS)

    Tompkins, S. S.

    1987-01-01

    The thermal expansion of continuous carbon-fiber reinforced composites with epoxy-, polyimide-, and borosilicate glass-matrices has been measured and compared. The expansion of a rubber-toughened epoxy-matrix/P75S carbon-fiber composite was very different from the expansion of two different single-phase epoxy-matrix/P75S composites, although all three had the same stacking sequence. Reasonable agreement was obtained between measured thermal expansion data and results from classical laminate theory. Microdamage in the graphite/polyimide laminate, induced by 250 cycles between -156 and 121 C, caused a 53 percent decrease in the coefficient of thermal expansion. The thermal expansion of the graphite/glass laminate was not changed after 100 thermal cycles from -129 to 38 C; however, a residual strain of about 10 x 10 to the -6 was observed for the laminate tested.

  14. An analytical model for particulate reinforced composites (PRCs) taking account of particle debonding and matrix cracking

    NASA Astrophysics Data System (ADS)

    Jiang, Yunpeng

    2016-10-01

    In this work, a simple micromechanics-based model was developed to describe the overall stress-strain relations of particulate reinforced composites (PRCs), taking into account both particle debonding and matrix cracking damage. Based on the secant homogenization frame, the effective compliance tensor could be firstly given for the perfect composites without any damage. The progressive interface debonding damage is controlled by a Weibull probability function, and then the volume fraction of detached particles is involved in the equivalent compliance tensor to account for the impact of particle debonding. The matrix cracking was introduced in the present model to embody the stress softening stage in the deformation of PRCs. The analytical model was firstly verified by comparing with the corresponding experiment, and then parameter analyses were conducted. This modeling will shed some light on optimizing the microstructures in effectively improving the mechanical behaviors of PRCs.

  15. Evolution of In-Situ Generated Reinforcement Precipitates in Metal Matrix Composites

    NASA Technical Reports Server (NTRS)

    Sen, S.; Kar, S. K.; Catalina, A. V.; Stefanescu, D. M.; Dhindaw, B. K.

    2004-01-01

    Due to certain inherent advantages, in-situ production of Metal Matrix Composites (MMCs) have received considerable attention in the recent past. ln-situ techniques typically involve a chemical reaction that results in precipitation of a ceramic reinforcement phase. The size and spatial distribution of these precipitates ultimately determine the mechanical properties of these MMCs. In this paper we will investigate the validity of using classical growth laws and analytical expressions to describe the interaction between a precipitate and a solid-liquid interface (SLI) to predict the size and spatial evolution of the in-situ generated precipitates. Measurements made on size and distribution of Tic precipitates in a Ni&I matrix will be presented to test the validity of such an approach.

  16. Aluminum Metal Matrix Composites

    SciTech Connect

    Hunt, Warren; Herling, Darrell R.

    2004-02-01

    Metal matrix composites comprise a relatively wide range of materials defined by the metal matrix, reinforcement type, and reinforcement geometry. In the area of the matrix, most metallic systems have been explored for use in metal matrix composites, including Al, Be, Mg, Ti, Fe, Ni, Co, and Ag. By far, the largest usage is in aluminum matrix composites. From a reinforcement perspective, the materials used are typically ceramics since they provide a very desirable combination of stiffness, strength, and relatively low density. Candidate reinforcement materials include SiC, Al2O3, B4C, TiC, TiB2, graphite, and a number of other ceramics. In addition, there has been work on metallic materials as reinforcements, notably W and steel fibers. The morphology of the reinforcement material is another variable of importance in metal matrix composites. The three major classes of reinforcement morphology are continuous fiber, chopped fiber or whisker, and particulate. Typically, the selection of the reinforcement morphology is determined by the desired property/cost combination. Generally, continuous fiber reinforced MMCs provide the highest properties in the direction of the fiber orientation but are the most expensive. Chopped fiber and whisker reinforced materials can produce significant property improvements in the plane or direction of their orientation, at somewhat lower cost. Particulates provide a comparatively more moderate but isotropic increase in properties and are typically available at the lowest cost. By adding to the three variables of metallic matrix, reinforcement material, and reinforcement morphology the further options of reinforcement volume fraction, orientation, and matrix alloy composition and heat treatment, it is apparent that there is a very wide range of available material combinations and resultant properties. This paper will focus on how MMCs have been applied in specific application areas.

  17. Damage evolution in uniaxial silicon carbide fiber-reinforced titanium matrix composites

    NASA Astrophysics Data System (ADS)

    Hanan, Jay Clarke

    Fiber fractures initiate damage zones ultimately determining the strength and lifetime of metal matrix composites (MMCs). The evolution of damage in a MMC comprising a row of unidirectional SiC fibers (32 vol.%) surrounded by a Ti matrix was examined using X-ray microdiffraction (gym beam size) and macrodiffraction (mm beam size). A comparison of high-energy X-ray diffraction (XRD) techniques including a powerful two-dimensional XRD method capable of obtaining powder averaged strains from a small number of grains is presented (HEmuXRD2). Using macrodiffraction, the bulk residual strain in the composite was determined against a true strain-free reference. In addition, the bulk in situ response of both the fiber reinforcement and the matrix to tensile stress was observed and compared to a three-dimensional finite element model. Using microdiffraction, multiple strain maps including both phases were collected in situ before, during, and after the application of tensile stress, providing an unprecedented detailed picture of the micromechanical behavior in the laminate metal matrix composite. Finally, the elastic axial strains were compared to predictions from a modified shear lag model, which unlike other shear lag models, considers the elastic response of both constituents. The strains showed excellent correlation with the model. The results confirmed, for the first time, both the need and validity of this new model specifically developed for large scale multifracture and damage evolution simulations of metal matrix composites. The results also provided unprecedented insight for the model, revealing the necessity of incorporating such factors as plasticity of the matrix, residual stress in the composite, and selection of the load sharing parameter. The irradiation of a small number of grains provided strain measurements comparable to a continuum mechanical state in the material. Along the fiber axes, thermal residual stresses of 740 MPa (fibers) and +350 MPa (matrix

  18. Assessment of high performance concrete containing fly ash and calcium nitrite based corrosion inhibitor as a mean to prevent the corrosion of reinforcing steel

    NASA Astrophysics Data System (ADS)

    Montes-García, P.; Jiménez-Quero, V.; López-Calvo, H.

    2015-01-01

    This research analyses the effectiveness of the water-to-cement ratio (w/c), fly ash and a calcium nitrite based corrosion inhibitor to prevent the corrosion of reinforcing steel embedded in high performance concrete. The interactive effect between the inhibitor and fly ash was evaluated because the occurrence of a negative effect when both ingredients are added together in a concrete mixture has been reported. All the concrete mixtures studied in this investigation had 8.2% of silica fume. Twenty seven prismatic concrete specimens were fabricated with dimensions of 55 × 230 × 300 mm each containing two steel rods embedded for the purpose of corrosion monitoring. The specimens were exposed to a simulated marine environment with two daily cycles of wetting and drying for one year. To evaluate the deterioration of the specimens corrosion potentials and linear polarization resistance tests were carried out. The results indicate that the use of a low w/c, the addition of fly ash and the addition of the corrosion inhibitor contributed to the reduction of the corrosion of steel in the concrete specimens. The results further suggest that the combination of fly ash and corrosion inhibitor does not promote the deterioration of the concrete matrix.

  19. Influence of thermal residual stress on behaviour of metal matrix composites reinforced with particles

    NASA Astrophysics Data System (ADS)

    Guzmán, R. E.; Hernández Arroyo, E.

    2016-02-01

    The properties of a metallic matrix composites materials (MMC's) reinforced with particles can be affected by different events occurring within the material in a manufacturing process. The existence of residual stresses resulting from the manufacturing process of these materials (MMC's) can markedly differentiate the curves obtained in tensile tests obtained from compression tests. One of the themes developed in this work is the influence of residual stresses on the mechanical behaviour of these materials. The objective of this research work presented is numerically estimate the thermal residual stresses using a unit cell model for the Mg ZC71 alloy reinforced with SiC particles with volume fraction of 12% (hot-forging technology). The MMC's microstructure is represented as a three dimensional prismatic cube-shaped with a cylindrical reinforcing particle located in the centre of the prism. These cell models are widely used in predicting stress/strain behaviour of MMC's materials, in this analysis the uniaxial stress/strain response of the composite can be obtained through the calculation using the commercial finite-element code.

  20. Process for the manufacture of seamless metal-clad fiber-reinforced organic matrix composite structures

    NASA Technical Reports Server (NTRS)

    Bluck, Raymond M. (Inventor); Bush, Harold G. (Inventor); Johnson, Robert R. (Inventor)

    1991-01-01

    A process for producing seamless metal-clad composite structures includes providing a hollow, metallic inner member and an outer sleeve to surround the inner member and define an inner space therebetween. A plurality of continuous reinforcing fibers is attached to the distal end of the outside diameter of the inner member, and the inner member is then introduced, distal end first, into one end of the outer sleeve. The inner member is then moved, distal end first, into the outer sleeve until the inner member is completely enveloped by the outer sleeve. A liquid matrix material is then injected into the space containing the reinforcing fibers between the inner member and the outer sleeve. Next a pressurized heat transfer medium is passed through the inner member to cure the liquid matrix material. Finally, the wall thickness of both the inner member and the outer sleeve are reduced to desired dimensions by chemical etching, which adjusts the thermal expansion coefficient of the metal-clad composite structure to a desired value.

  1. Processing and Material Characterization of Continuous Basalt Fiber Reinforced Ceramic Matrix Composites Using Polymer Derived Ceramics.

    NASA Technical Reports Server (NTRS)

    Cox, Sarah B.

    2014-01-01

    The need for high performance vehicles in the aerospace industry requires materials which can withstand high loads and high temperatures. New developments in launch pads and infrastructure must also be made to handle this intense environment with lightweight, reusable, structural materials. By using more functional materials, better performance can be seen in the launch environment, and launch vehicle designs which have not been previously used can be considered. The development of high temperature structural composite materials has been very limited due to the high cost of the materials and the processing needed. Polymer matrix composites can be used for temperatures up to 260C. Ceramics can take much higher temperatures, but they are difficult to produce and form in bulk volumes. Polymer Derived Ceramics (PDCs) begin as a polymer matrix, allowing a shape to be formed and cured and then to be pyrolized in order to obtain a ceramic with the associated thermal and mechanical properties. The use of basalt in structural and high temperature applications has been under development for over 50 years, yet there has been little published research on the incorporation of basalt fibers as a reinforcement in the composites. In this study, continuous basalt fiber reinforced PDCs have been fabricated and tested for the applicability of this composite system as a high temperature structural composite material. The oxyacetylene torch testing and three point bend testing have been performed on test panels and the test results are presented.

  2. Jet Electrochemical Machining of Particle Reinforced Aluminum Matrix Composites with Different Neutral Electrolytes

    NASA Astrophysics Data System (ADS)

    Hackert-Oschätzchen, M.; Lehnert, N.; Martin, A.; Schubert, A.

    2016-03-01

    Conventional mechanical machining of particle reinforced aluminum matrix composites (AMCs) is challenging because the hard ceramic particles in the soft aluminum matrix lead to an increased tool wear. Furthermore, the mechanical and thermal impact during conventional machining affects the microstructure of the AMCs. Electrochemical machining (ECM) is an alternative method to machine AMCs. Based on anodic dissolution, ECM has a slight influence on the work piece material structure and is independent of material strength and hardness. So the microstructure of the work piece remains unaffected. One method of ECM is electrochemical machining with continuous electrolytic free jet (Jet-ECM). Hereby the electrochemical removal is localized by the geometry of the electrolyte jet. By moving the electrolyte jet micro-structures and microgeometries can be generated quickly and flexibly in metallic parts [1]. Another advantage of Jet-ECM is the low consumption of electrolyte which allows an easy and inexpensive change of electrolyte for investigations with different types of electrolyte. In this study AMCs reinforced with different amounts of SiC-particles are machined with two pH-neutral electrolytes using Jet-ECM. The results provide information about the suitability of the selected electrolytes for the machining of AMCs. In addition, the influence of the particle content on the electrochemical removal result will be evaluated.

  3. Carbon Nanotube-Reinforced Aluminum Matrix Composites Produced by High-Energy Ball Milling

    NASA Astrophysics Data System (ADS)

    Travessa, Dilermando N.; da Rocha, Geovana V. B.; Cardoso, Kátia R.; Lieblich, Marcela

    2017-05-01

    Although multiwall carbon nanotubes (MWCNT) are promising materials to strengthen lightweight aluminum matrix composites, their dispersion into the metallic matrix is challenge. In the present work, MWCNT were dispersed into age-hardenable AA6061 aluminum alloy by high-energy ball milling and the blend was subsequently hot-extruded. The composite bars obtained were heat-treated by solution heat treatment at 520 °C and artificially aged at 177 °C for 8 h, in order to reach the T6 temper. Special attention was given to the integrity of the MWCNT along the entire composite production. The microstructure of the obtained bars was evaluated by optical and scanning electron microscopy, and the mechanical properties were evaluated by Vickers microhardness tests. Raman spectroscopy, x-ray diffraction and transmission electron microscopy were employed to evaluate the structural integrity of MWCNT. It was found that milling time is critical to reach a proper dispersion of the reinforcing phase. The composite hardness increased up to 67% with the dispersion of 2% in weight of MWCNT, when comparing with un-reinforced bars produced by similar route. However, age hardening was not observed in composite bars after heat treatment. It was also found that MWCNT continuously degraded along the process, being partially converted into Al4C3 in the final composite.

  4. Cyclotriphosphazene and TiO2 reinforced nanocomposite coated on mild steel plates for antibacterial and corrosion resistance applications

    NASA Astrophysics Data System (ADS)

    Krishnadevi, Krishnamoorthy; Selvaraj, Vaithilingam

    2016-03-01

    The mild steel surface has been modified to impart anticorrosion and antibacterial properties through a dip coating method followed by thermal curing of a mixture containing amine terminated cyclotriphosphazene and functionalized titanium dioxide nanoparticles reinforced benzoxazine based cyanate ester composite (ATCP/FTiO2/Bz-CE). The corrosion resistance behavior of coating material has been investigated by electrochemical and antibacterial studies by disc diffusion method. The nanocomposites coated mild steels have displayed a good chemical stability over long immersion in a corrosive environment. The protection efficiency has found to be high for ATCP/FTiO2/Bz-CE composites, which can be used in microelectronics and marine applications.

  5. Micromechanical Modeling for Tensile Behaviour of Carbon Fiber - Reinforced Ceramic - Matrix Composites

    NASA Astrophysics Data System (ADS)

    Longbiao, Li

    2015-12-01

    The stress-strain curves of fiber - reinforced ceramic - matrix composites (CMCs) exhibit obvious non-linear behaviour under tensile loading. The occurrence of multiple damage mechanisms, i.e., matrix multicracking, fiber/matrix interface debonding and fibers fracture, is the mainly reason for the non-linear characteristic. The micromechanics approach has been developed to predict the tensile stress-strain curves of unidirectional, cross-ply and woven CMCs. The shear-lag model was used to describe the micro stress field of the damaged composite. The damage models were used to determine the evolution of micro damage parameters, i.e., matrix crack spacing, interface debonded length and broken fibers fraction. By combining the shear-lag model with damage models and considering the effect of transverse multicracking in the 90° plies or transverse yarns in cross-ply or woven CMCs, the tensile stress-strain curves of unidirectional, cross-ply, 2D and 2.5D woven CMCs have been predicted. The results agreed with experimental data.

  6. A first look at erosion of continuous-fiber reinforced ceramic-matrix composites

    SciTech Connect

    Karasek, K.R.; Gonczy, S.T.; Kupperman, J.B.; Zamirowski, E.J.; Goretta, K.C.; Routbort, J.L.

    1991-12-01

    We report the initial results of a study of solid-particle erosion of Nicalon{trademark} Sic reinforced carbon-modified-silica-glass composites. SiC abrasives with diameters between 42 to 390{mu}m were used with impact angles of 30{degrees} and 90{degrees}, and velocities ranged 30 to 80 m/s. Fibers were parallel to the surface in all cases. Woven-fiber composites exhibited the same erosive behavior as uniaxial composites. Interfacial chemistry was controlled, and the comparison between composites which exhibit low-strength-brittle and high-strength-fibrous fractures under flexure conditions showed no significant difference in erosion resistance. This result and SEM data indicate that most of the fracture occurs within the matrix and/or at the fiber-matrix interface. We have found in previous work that polymer-matrix composites (with fibers parallel to the surface) are more susceptible to erosion damage than the matrix polymer. This also appears to be the case for the ceramic composites.

  7. A first look at erosion of continuous-fiber reinforced ceramic-matrix composites

    SciTech Connect

    Karasek, K.R.; Gonczy, S.T. ); Kupperman, J.B.; Zamirowski, E.J.; Goretta, K.C.; Routbort, J.L. )

    1991-12-01

    We report the initial results of a study of solid-particle erosion of Nicalon{trademark} Sic reinforced carbon-modified-silica-glass composites. SiC abrasives with diameters between 42 to 390{mu}m were used with impact angles of 30{degrees} and 90{degrees}, and velocities ranged 30 to 80 m/s. Fibers were parallel to the surface in all cases. Woven-fiber composites exhibited the same erosive behavior as uniaxial composites. Interfacial chemistry was controlled, and the comparison between composites which exhibit low-strength-brittle and high-strength-fibrous fractures under flexure conditions showed no significant difference in erosion resistance. This result and SEM data indicate that most of the fracture occurs within the matrix and/or at the fiber-matrix interface. We have found in previous work that polymer-matrix composites (with fibers parallel to the surface) are more susceptible to erosion damage than the matrix polymer. This also appears to be the case for the ceramic composites.

  8. The effect of temperature and moisture on electrical resistance, strain sensitivity and crack sensitivity of steel fiber reinforced smart cement composite

    NASA Astrophysics Data System (ADS)

    Teomete, Egemen

    2016-07-01

    Earthquakes, material degradations and other environmental factors necessitate structural health monitoring (SHM). Metal foil strain gages used for SHM have low durability and low sensitivity. These factors motivated researchers to work on cement based strain sensors. In this study, the effects of temperature and moisture on electrical resistance, compressive and tensile strain gage factors (strain sensitivity) and crack sensitivity were determined for steel fiber reinforced cement based composite. A rapid increase of electrical resistance at 200 °C was observed due to damage occurring between cement paste, aggregates and steel fibers. The moisture—electrical resistance relationship was investigated. The specimens taken out of the cure were saturated with water and had a moisture content of 9.49%. The minimum electrical resistance was obtained at 9% moisture at which fiber-fiber and fiber-matrix contact was maximum and the water in micro voids was acting as an electrolyte, conducting electrons. The variation of compressive and tensile strain gage factors (strain sensitivities) and crack sensitivity were investigated by conducting compression, split tensile and notched bending tests with different moisture contents. The highest gage factor for the compression test was obtained at optimal moisture content, at which electrical resistance was minimum. The tensile strain gage factor for split tensile test and crack sensitivity increased by decreasing moisture content. The mechanisms between moisture content, electrical resistance, gage factors and crack sensitivity were elucidated. The relations of moisture content with electrical resistance, gage factors and crack sensitivities have been presented for the first time in this study for steel fiber reinforced cement based composites. The results are important for the development of self sensing cement based smart materials.

  9. Friction and wear of hydroxyapatite reinforced high density polyethylene against the stainless steel counterface.

    PubMed

    Wang, M; Chandrasekaran, M; Bonfield, W

    2002-06-01

    Hydroxyapatite (HA) reinforced high density polyethylene (HDPE) was invented as a biomaterial for skeletal applications. In this investigation, tribological properties (e.g. wear rate and coefficient of friction) of unfilled HDPE and HA/HDPE composites were evaluated against the duplex stainless steel in dry and lubricated conditions, with distilled water or aqueous solutions of proteins (egg albumen or glucose) being lubricants. Wear tests were conducted in a custom-built test rig for HDPE and HA/HDPE containing up to 40 vol % of HA. It was found that HA/HDPE composites had lower coefficients of friction than unfilled HDPE under certain conditions. HA/HDPE also exhibited less severe fatigue failure marks than HDPE. The degradation and fatigue failure of HDPE due to the presence of proteins were severe for low speed wear testing (100 rpm) as compared to high speed wear testing (200 rpm). This was due possibly to the high shear rate at the contact which could remove any degraded film instantaneously at high sliding speed, while with a low sliding speed the build-up of a degraded layer of protein could occur. The degraded protein layer would stay at the contact for a longer time and mechanical activation would induce adverse reactions, weakening the surface layer of HDPE. Both egg albumen and glucose were found to be corrosive to steel and adversely reactive for HDPE and HA/HDPE composites. The wear modes observed were similar to that of ultra-high molecular weight polyethylene. Specimens tested with egg albumen also displayed higher wear rates, which was again attributed to corrosion accelerated wear.

  10. Characterization of Corrosion on Outdoor-Exposed Aluminum Metal-Matrix Composites as a Function of Reinforcement Specie and Volume Fraction

    DTIC Science & Technology

    2008-02-01

    Characterization of Corrosion on Outdoor-Exposed Aluminum Metal-Matrix Composites as a Function of Reinforcement Specie and Volume Fraction...Exposed Aluminum Metal-Matrix Composites as a Function of Reinforcement Specie and Volume Fraction Ralph P. I. Adler and Daniel J. Snoha...4. TITLE AND SUBTITLE Characterization of Corrosion on Outdoor-Exposed Aluminum Metal-Matrix Composites as a Function of Reinforcement Specie and

  11. Erosion and corrosion resistance of laser cladded AISI 420 stainless steel reinforced with VC

    NASA Astrophysics Data System (ADS)

    Zhang, Zhe; Yu, Ting; Kovacevic, Radovan

    2017-07-01

    Metal Matrix Composites (MMC) fabricated by the laser cladding process have been widely applied as protective coatings in industries to improve the wear, erosion, and corrosion resistance of components and prolong their service life. In this study, the AISI 420/VC metal matrix composites with different weight percentage (0 wt.%-40 wt.%) of Vanadium Carbide (VC) were fabricated on a mild steel A36 by a high power direct diode laser. An induction heater was used to preheat the substrate in order to avoid cracks during the cladding process. The effect of carbide content on the microstructure, elements distribution, phases, and microhardness was investigated in detail. The erosion resistance of the coatings was tested by using the abrasive waterjet (AWJ) cutting machine. The corrosion resistance of the coatings was studied utilizing potentiodynamic polarization. The results showed that the surface roughness and crack susceptibility of the laser cladded layer were increased with the increase in VC fraction. The volume fraction of the precipitated carbides was increased with the increase in the VC content. The phases of the coating without VC consisted of martensite and austenite. New phases such as precipitated VC, V8C7, M7C3, and M23C6 were formed when the primary VC was added. The microhardness of the clads was increased with the increase in VC. The erosion resistance of the cladded layer was improved after the introduction of VC. The erosion resistance was increased with the increase in the VC content. No obvious improvement of erosion resistance was observed when the VC fraction was above 30 wt.%. The corrosion resistance of the clads was decreased with the increase in the VC content, demonstrating the negative effect of VC on the corrosion resistance of AISI 420 stainless steel

  12. Experimental Investigation of the Capacity of Steel Fibers to Ensure the Structural Integrity of Reinforced Concrete Specimens Coated with CFRP Sheets

    NASA Astrophysics Data System (ADS)

    Gribniak, V.; Arnautov, A. K.; Norkus, A.; Tamulenas, V.; Gudonis, E.; Sokolov, A.

    2016-07-01

    The capacity of steel fibers to ensure the structural integrity of reinforced concrete specimens coated with CFRP sheets was investigated. Test data for four ties and eight beams reinforced with steel or glass-FRP bars are presented. Experiments showed that the fibers significantly increased the cracking resistance and altered the failure character from the splitting of concrete to the debonding of the external sheets, which noticeably increased the load-carrying capacity of the strengthened specimens.

  13. Effect of matrix toughness and grain morphology on fracture of steels

    NASA Astrophysics Data System (ADS)

    Atapek, Ş. H.; Gümüş, S.; Polat, Ş.

    2013-03-01

    The microstructure and fracture surfaces of steel X42 (type 09G2S) and of an experimental bainitic steel (0.23% C, 0.18% Mn, 0.04% Ni, 2.35% Co, 1.40% Cr, 0.50% Mo, 0.08% Nb, 0.08%V, 0.02% Ti) are studied after quenching and tempering. The influence of the toughness of the matrix on the fracture behavior of the steels is determined. It is shown that the fracture toughness changes depending on the tempering temperature, and the nucleation and propagation of cracks depends on the presence of secondary phases and on the morphology of the grain structure.

  14. Retrofit of hollow concrete masonry infilled steel frames using glass fiber reinforced plastic laminates

    NASA Astrophysics Data System (ADS)

    Hakam, Zeyad Hamed-Ramzy

    2000-11-01

    This study focuses on the retrofit of hollow concrete masonry infilled steel frames subjected to in-plane lateral loads using glass fiber reinforced plastic (GFRP) laminates that are epoxy-bonded to the exterior faces of the infill walls. An extensive experimental investigation using one-third scale modeling was conducted and consisted of two phases. In the first phase, 64 assemblages, half of which were retrofitted, were tested under various combined in-plane loading conditions similar to those which different regions of a typical infill wall are subjected to. In the second phase, one bare and four masonry-infilled steel frames representative of a typical single-story, single-bay panel were tested under diagonal loading to study the overall behavior and the infill-frame interaction. The relative infill-to-frame stiffness was varied as a test parameter by using two different steel frame sections. The laminates altered the failure modes of the masonry assemblages and reduced the variability and anisotropic nature of the masonry. For the prisms which failed due to shear and/or mortar joint slip, significant strength increases were observed. For those exhibiting compression failure modes, a marginal increase in strength resulted. Retrofitting the infilled frames resulted in an average increase in initial stiffness of two-fold compared to the unretrofitted infilled frames, and seemed independent of the relative infill-to-frame stiffness. However, the increase in the load-carrying capacity of the retrofitted frames compared to the unretrofitted counterparts was higher for those with the larger relative infill-to-frame stiffness parameter. Unlike the unretrofitted infill walls, the retrofitted panels demonstrated almost identical failure modes that were characterized as "strictly comer crushing" in the vicinity of the loaded comers whereas no signs of distress were evident throughout the remainder of the infill. The laminates also maintained the structural integrity of

  15. A penny-shaped crack in a filament-reinforced matrix. I - The filament model. II - The crack problem

    NASA Technical Reports Server (NTRS)

    Erdogan, F.; Pacella, A. H.

    1974-01-01

    The study deals with the elastostatic problem of a penny-shaped crack in an elastic matrix which is reinforced by filaments or fibers perpendicular to the plane of the crack. An elastic filament model is first developed, followed by consideration of the application of the model to the penny-shaped crack problem in which the filaments of finite length are asymmetrically distributed around the crack. Since the primary interest is in the application of the results to studies relating to the fracture of fiber or filament-reinforced composites and reinforced concrete, the main emphasis of the study is on the evaluation of the stress intensity factor along the periphery of the crack, the stresses in the filaments or fibers, and the interface shear between the matrix and the filaments or fibers. Using the filament model developed, the elastostatic interaction problem between a penny-shaped crack and a slender inclusion or filament in an elastic matrix is formulated.

  16. The influence of reinforcement size on the microstructure and mechanical behavior of a nanostructured aluminum-based metal matrix composite

    NASA Astrophysics Data System (ADS)

    Behm, Nathan Adam

    With increased availability and growing commercial applications, aluminum-based metal matrix composites show promise as high specific strength structural materials. Before they can be implemented however, they require thorough characterization and testing. A novel nanostructured aluminum-based metal matrix composite (MMC) was characterized through a combination of microstructural analysis and mechanical testing. Two composites were studied, an aluminum MMC reinforced with 50 nm boron carbide, (B4C) and an aluminum MMC reinforced with 500 nm boron carbide. Transmission electron microscopy (TEM) analysis revealed an ultra-fine grained matrix with grains on the order of 100--300 nm. The quasi-static and dynamic response of the composites was compared with the behavior of the unreinforced aluminum alloy, and it was found that the reinforcement resulted in a 30% improvement in strength. The decrease in the reinforcement size from 500 to 50 nm activated an additional strengthening mechanism, which further improved the strength of the MMC reinforced with the 50 nm B4C. Dynamic compression tests were performed at elevated temperatures up 400°C on the composites, and it was found that they exhibited impressive strengths considering the thermal softening prevalent in aluminum. The reinforcement size was found to play an important role in the strain softening exhibited at elevated temperature, fracture mechanism, and composite strength. Models to describe the composite behavior are presented.

  17. Dynamic tensile deformation behavior of Zr-based amorphous alloy matrix composites reinforced with tungsten or tantalum fibers

    NASA Astrophysics Data System (ADS)

    Lee, Hyungsoo; Kim, Gyeong Su; Jeon, Changwoo; Sohn, Seok Su; Lee, Sang-Bok; Lee, Sang-Kwan; Kim, Hyoung Seop; Lee, Sunghak

    2016-07-01

    Zr-based amorphous alloy matrix composites reinforced with tungsten (W) or tantalum (Ta) continuous fibers were fabricated by liquid pressing process. Their dynamic tensile properties were investigated in relation with microstructures and deformation mechanisms by using a split Hopkinson tension bar. The dynamic tensile test results indicated that the maximum strength of the W-fiber-reinforced composite (757 MPa) was much lower than the quasi-statically measured strength, whereas the Ta-fiber-reinforced composite showed very high maximum strength (2129 MPa). In the W-fiber-reinforced composite, the fracture abruptly occurred in perpendicular to the tensile direction because W fibers did not play a role in blocking cracks propagated from the amorphous matrix, thereby resulting in abrupt fracture within elastic range and consequent low tensile strength. The very high dynamic tensile strength of the Ta-fiber-reinforced composite could be explained by the presence of ductile Ta fibers in terms of mechanisms such as (1) interrupted propagation of cracks initiated in the amorphous matrix, (2) formation of lots of cracks in the amorphous matrix, and (3) sharing of loads and severe deformation (necking) of Ta fibers in cracked regions.

  18. A Unified Model for the Prediction of Yield Strength in Particulate-Reinforced Metal Matrix Nanocomposites

    PubMed Central

    Mirza, F. A.; Chen, D. L.

    2015-01-01

    Lightweighting in the transportation industry is today recognized as one of the most important strategies to improve fuel efficiency and reduce anthropogenic climate-changing, environment-damaging, and human death-causing emissions. However, the structural applications of lightweight alloys are often limited by some inherent deficiencies such as low stiffness, high wear rate and inferior strength. These properties could be effectively enhanced by the addition of stronger and stiffer reinforcements, especially nano-sized particles, into metal matrix to form composites. In most cases three common strengthening mechanisms (load-bearing effect, mismatch of coefficients of thermal expansion, and Orowan strengthening) have been considered to predict the yield strength of metal matrix nanocomposites (MMNCs). This study was aimed at developing a unified model by taking into account the matrix grain size and porosity (which is unavoidable in the materials processing such as casting and powder metallurgy) in the prediction of the yield strength of MMNCs. The Zener pinning effect of grain boundaries by the nano-sized particles has also been integrated. The model was validated using the experimental data of magnesium- and titanium-based nanocomposites containing different types of nano-sized particles (namely, Al2O3, Y2O3, and carbon nanotubes). The predicted results were observed to be in good agreement with the experimental data reported in the literature. PMID:28793496

  19. A Unified Model for the Prediction of Yield Strength in Particulate-Reinforced Metal Matrix Nanocomposites.

    PubMed

    Mirza, F A; Chen, D L

    2015-08-10

    Lightweighting in the transportation industry is today recognized as one of the most important strategies to improve fuel efficiency and reduce anthropogenic climate-changing, environment-damaging, and human death-causing emissions. However, the structural applications of lightweight alloys are often limited by some inherent deficiencies such as low stiffness, high wear rate and inferior strength. These properties could be effectively enhanced by the addition of stronger and stiffer reinforcements, especially nano-sized particles, into metal matrix to form composites. In most cases three common strengthening mechanisms (load-bearing effect, mismatch of coefficients of thermal expansion, and Orowan strengthening) have been considered to predict the yield strength of metal matrix nanocomposites (MMNCs). This study was aimed at developing a unified model by taking into account the matrix grain size and porosity (which is unavoidable in the materials processing such as casting and powder metallurgy) in the prediction of the yield strength of MMNCs. The Zener pinning effect of grain boundaries by the nano-sized particles has also been integrated. The model was validated using the experimental data of magnesium- and titanium-based nanocomposites containing different types of nano-sized particles (namely, Al₂O₃, Y₂O₃, and carbon nanotubes). The predicted results were observed to be in good agreement with the experimental data reported in the literature.

  20. Probabilistic lifetime assessment of marine reinforced concrete with steel corrosion and cover cracking

    NASA Astrophysics Data System (ADS)

    Lu, Chun-Hua; Jin, Wei-Liang; Liu, Rong-Gui

    2011-06-01

    In order to study the durability behavior of marine reinforced concrete structure suffering from chloride attack, the structural service life is assumed to be divided into three critical stages, which can be characterized by steel corrosion and cover cracking. For each stage, a calculated model used to predict the lifetime is developed. Based on the definition of durability limit state, a probabilistic lifetime model and its time-dependent reliability analytical method are proposed considering the random natures of influencing factors. Then, the probabilistic lifetime prediction models are applied to a bridge pier located in the Hangzhou Bay with Monte Carlo simulation. It is found that the time to corrosion initiation t 0 follows a lognormal distribution, while that the time from corrosion initiation to cover cracking t 1 and the time for crack to develop from hairline crack to a limit crack width t 2 can be described by Weibull distributions. With the permitted failure probability of 5.0%, it is also observed that the structural durability lifetime mainly depends on the durability life t 0 and that the percentage of participation of the life t 0 to the total service life grows from 61.5% to 83.6% when the cover thickness increases from 40 mm to 80 mm. Therefore, for any part of the marine RC bridge, the lifetime predictions and maintenance efforts should also be directed toward controlling the stage of corrosion initiation induced by chloride ion.

  1. Measurement and simulation of millimeter wave scattering cross-sections from steel-reinforced concrete

    NASA Astrophysics Data System (ADS)

    Hassan, A. M.; Martys, N. S.; Garboczi, E. J.; McMichael, R. D.; Stiles, M. D.; Plusquellic, D. F.; Stutzman, P. E.; Wang, S.; Provenzano, V.; Surek, J. T.; Novotny, D. R.; Coder, J. B.; Janezic, M. D.; Kim, S.

    2014-02-01

    Some iron oxide corrosion products exhibit antiferromagnetic magnetic resonances (AFMR) at frequencies on the order of 100 GHz at ambient temperatures. AFMR can be detected in laboratory conditions, which serves as the basis for a new non-destructive spectroscopic method for detecting early corrosion. When attempting to measure the steel corrosion in reinforced concrete in the field, rebar geometry must be taken into account. Experiments and numerical simulations have been developed at frequencies near 100 GHz to sort out these effects. The experimental setup involves a vector network analyzer with converter heads to up-convert the output frequency, which is then connected to a horn antenna followed by a 7.5 cm diameter polymer lens to focus the waves on the sample. Two sets of samples were studied: uniform cylindrical rods and rebar corrosion samples broken out of concrete with different kinds of coatings. Electromagnetic scattering from uniform rods were calculated numerically using classical modal expansion. A finite-element electromagnetic solver was used to model more complex rebar geometry and non-uniform corrosion layers. Experimental and numerical data were compared to help quantify and understand the anticipated effect of local geometrical features on AFMR measurements.

  2. Corrosion Behavior of Steel Reinforcement in Concrete with Recycled Aggregates, Fly Ash and Spent Cracking Catalyst

    PubMed Central

    Gurdián, Hebé; García-Alcocel, Eva; Baeza-Brotons, Francisco; Garcés, Pedro; Zornoza, Emilio

    2014-01-01

    The main strategy to reduce the environmental impact of the concrete industry is to reuse the waste materials. This research has considered the combination of cement replacement by industrial by-products, and natural coarse aggregate substitution by recycled aggregate. The aim is to evaluate the behavior of concretes with a reduced impact on the environment by replacing a 50% of cement by industrial by-products (15% of spent fluid catalytic cracking catalyst and 35% of fly ash) and a 100% of natural coarse aggregate by recycled aggregate. The concretes prepared according to these considerations have been tested in terms of mechanical strengths and the protection offered against steel reinforcement corrosion under carbonation attack and chloride-contaminated environments. The proposed concrete combinations reduced the mechanical performance of concretes in terms of elastic modulus, compressive strength, and flexural strength. In addition, an increase in open porosity due to the presence of recycled aggregate was observed, which is coherent with the changes observed in mechanical tests. Regarding corrosion tests, no significant differences were observed in the case of the resistance of these types of concretes under a natural chloride attack. In the case of carbonation attack, although all concretes did not stand the highly aggressive conditions, those concretes with cement replacement behaved worse than Portland cement concretes. PMID:28788613

  3. Bond Behavior of Historical Clay Bricks Strengthened with Steel Reinforced Polymers (SRP)

    PubMed Central

    Grande, Ernesto; Imbimbo, Maura; Sacco, Elio

    2011-01-01

    In the strengthening interventions of past and historical masonry constructions, the non-standardized manufacture processes, the ageing and the damage of masonry units, could significantly affect the properties of the surfaces where strengthening materials are applied. This aspect requires particular care in evaluating the performance of externally bonded strengthening layers, especially with reference to the detachment mechanism. The bond response of old masonries could be very different from that occurring in new masonry units which are the ones generally considered in most of the bond tests available in technical literature. The aim of the present paper is the study of the bond behavior of historical clay bricks strengthened with steel reinforced polymers (SRP) materials. In particular, the results of an experimental study concerning new manufactured clay bricks and old bricks extracted from different historical masonry buildings are presented. The obtained results, particularly in terms of bond resistance, detachment mechanism and strain distributions, are discussed for the purpose of analyzing the peculiarities of the historical bricks in comparison with new manufactured ones. Some considerations on the efficacy of the theoretical formulations of the recent Italian code are also carried out.

  4. Erosion Characteristics of Nanoparticle-Reinforced Polyurethane Coatings on Stainless Steel Substrate

    NASA Astrophysics Data System (ADS)

    Syamsundar, C.; Chatterjee, Dhiman; Kamaraj, M.; Maiti, A. K.

    2015-04-01

    Hydropower generation from the Himalayan rivers in India faces challenge in the form of silt-laden water which can erode the turbine blades and reduce turbine life. To address this issue, polyurethane coatings reinforced with boron carbide (B4C) or silicon carbide (SiC) nanoparticles on 16Cr-5Ni martensitic stainless steel substrate were used in the present investigation to improve erosion wear resistance in silt erosion conditions. Slurry erosive wear tests were carried out based on ASTM G-73 protocol at various test conditions of impact velocity, impingement angle, and erodent particle size as well as slurry concentrations as determined by the implementation of Taguchi design of experiments. Analysis of variance studies of erosion rate indicated that nanoparticle content in PU material is the single most important parameter, and interaction of impact velocity and impingement angle was also proved to be significant. The coatings with B4C nanoparticles had higher wear resistances than those with SiC nanoparticles due to higher hardness of the former. An interesting finding from the results is that there is an optimum amount of nanoparticles at which mass removal is the minimum. This observation has been explained in terms of surface characteristics of coatings as brought out by a combination of measurements including SEM images as well as roughness measurement.

  5. Numerical analysis on seismic behavior of reinforced concrete beam to concrete filled steel tubular column connections with ring-beam

    NASA Astrophysics Data System (ADS)

    Zhao, Yi.; Xu, Li. Hua.

    2016-06-01

    This paper presents numerical study of the seismic behavior of reinforced concrete beam to concrete filled steel tube column connections with ring-beam. The material stress-strain relations, element type and boundary condition are selected, which are consistent with actual situation. Then the seismic behavior of this type of joint are researched by ABAQUS, and finite element analyses are conducted under cyclic loading. Its parameters are discussed including thickness of steel tubular column wall, sectional dimension of the ring-beam and strength of the core concrete. The results show that the ultimate capacity of the connections is improved with sectional dimension of the ring-beam increased. In the meanwhile, the influence on skeleton curve of the joints is slight of which included thickness of steel tubular column wall and strength of the core concrete.

  6. Numerical analysis on seismic behavior of reinforced concrete beam to concrete filled steel tubular column connections with ring-beam

    SciTech Connect

    Zhao, Yi.; Xu, Li. Hua.

    2016-06-08

    This paper presents numerical study of the seismic behavior of reinforced concrete beam to concrete filled steel tube column connections with ring-beam. The material stress-strain relations, element type and boundary condition are selected, which are consistent with actual situation. Then the seismic behavior of this type of joint are researched by ABAQUS, and finite element analyses are conducted under cyclic loading. Its parameters are discussed including thickness of steel tubular column wall, sectional dimension of the ring-beam and strength of the core concrete. The results show that the ultimate capacity of the connections is improved with sectional dimension of the ring-beam increased. In the meanwhile, the influence on skeleton curve of the joints is slight of which included thickness of steel tubular column wall and strength of the core concrete.

  7. Mechanical Characterization of High-Performance Steel-Fiber Reinforced Cement Composites with Self-Healing Effect

    PubMed Central

    Kim, Dong Joo; Kang, Seok Hee; Ahn, Tae-Ho

    2014-01-01

    The crack self-healing behavior of high-performance steel-fiber reinforced cement composites (HPSFRCs) was investigated. High-strength deformed steel fibers were employed in a high strength mortar with very fine silica sand to decreasing the crack width by generating higher interfacial bond strength. The width of micro-cracks, strongly affected by the type of fiber and sand, clearly produced the effects on the self-healing behavior. The use of fine silica sand in HPSFRCs with high strength deformed steel fibers successfully led to rapid healing owing to very fine cracks with width less than 20 μm. The use of very fine silica sand instead of normal sand produced 17%–19% higher tensile strength and 51%–58% smaller width of micro-cracks. PMID:28788471

  8. The Non-Destructive Test of Steel Corrosion in Reinforced Concrete Bridges Using a Micro-Magnetic Sensor

    PubMed Central

    Zhang, Hong; Liao, Leng; Zhao, Ruiqiang; Zhou, Jianting; Yang, Mao; Xia, Runchuan

    2016-01-01

    This paper presents a non-destructive test method for steel corrosion in reinforced concrete bridges by using a 3-dimensional digital micro-magnetic sensor to detect and analyze the self-magnetic field leakage from corroded reinforced concrete. The setup of the magnetic scanning device and the measurement mode of the micro-magnetic sensor are introduced. The numerical analysis model is also built based on the linear magnetic charge theory. Compared to the self-magnetic field leakage data obtained from magnetic sensor-based measurement and numerical calculation, it is shown that the curves of tangential magnetic field at different lift-off height all intersect near the edge of the steel corrosion zone. The result indicates that the intersection of magnetic field curves can be used to detect and evaluate the range of the inner steel corrosion in engineering structures. The findings of this work propose a new and effective non-destructive test method for steel corrosion, and therefore enlarge the application of the micro-magnetic sensor. PMID:27608029

  9. The Non-Destructive Test of Steel Corrosion in Reinforced Concrete Bridges Using a Micro-Magnetic Sensor.

    PubMed

    Zhang, Hong; Liao, Leng; Zhao, Ruiqiang; Zhou, Jianting; Yang, Mao; Xia, Runchuan

    2016-09-06

    This paper presents a non-destructive test method for steel corrosion in reinforced concrete bridges by using a 3-dimensional digital micro-magnetic sensor to detect and analyze the self-magnetic field leakage from corroded reinforced concrete. The setup of the magnetic scanning device and the measurement mode of the micro-magnetic sensor are introduced. The numerical analysis model is also built based on the linear magnetic charge theory. Compared to the self-magnetic field leakage data obtained from magnetic sensor-based measurement and numerical calculation, it is shown that the curves of tangential magnetic field at different lift-off height all intersect near the edge of the steel corrosion zone. The result indicates that the intersection of magnetic field curves can be used to detect and evaluate the range of the inner steel corrosion in engineering structures. The findings of this work propose a new and effective non-destructive test method for steel corrosion, and therefore enlarge the application of the micro-magnetic sensor.

  10. Effect of particle concentration on the structure and tribological properties of submicron particle SiC reinforced Ni metal matrix composite (MMC) coatings produced by electrodeposition

    NASA Astrophysics Data System (ADS)

    Gül, H.; Kılıç, F.; Uysal, M.; Aslan, S.; Alp, A.; Akbulut, H.

    2012-03-01

    In the present work, a nickel sulfate bath containing SiC submicron particles between 100 and 1000 nm was used as the plating electrolyte. The aim of this work is to obtain Ni-SiC metal matrix composites (MMCs) reinforced with submicron particles on steel surfaces with high hardness and wear resistance for using in anti-wear applications such as dies, tools and working parts for automobiles and vehicles. The influence of the SiC content in the electrolyte on particle distribution, microhardness and wear resistance of nano-composite coatings was studied. During the electroplating process, the proper stirring speed was also determined for sub-micron SiC deposition with Ni matrix. The Ni films were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. The depositions were controlled to obtain a specific thickness (between 50 and 200 μm) and volume fraction of the particles in the matrix (between 0.02 and 0.10). The hardness of the coatings was measured to be 280-571 HV depending on the particle volume in the Ni matrix. The tribological behaviors of the electrodeposited SiC nanocomposite coatings sliding against an M50 steel ball (Ø 10 mm) were examined on a tribometer. All the friction and wear tests were performed without lubrication at room temperature and in the ambient air (with a relative humidity of 55-65%). The results showed that the wear resistance of the nanocomposites was approximately 2-2.2 times more than those of unreinforced Ni.

  11. Mechanical behavior of a continuous fiber reinforced aluminum matrix composite subjected to transverse and thermal loading

    NASA Technical Reports Server (NTRS)

    Jansson, S.; Leckie, F. A.

    1991-01-01

    The transverse properties of an aluminum alloy metal matrix composite reinforced by continuous alumina fibers were investigated. The composite is subjected to both mechanical and cyclic thermal loading. The results of an experimental program indicate that the shakedown concept of structural mechanics provides a means of describing the material behavior. When the loading conditions are within the shakedown region, the material finally responds in an elastic manner after initial plastic response, and for loading conditions outside the shakedown region, the material exhibits a rapid incremental plastic strain accumulation. The failure strain varies by an order of magnitude according to the operating conditions. Hence, for high mechanical and low thermal loading, the failure strains is small; for low mechanical and high thermal loading, the failure strain is large.

  12. Graphene-reinforced aluminum matrix composites prepared by spark plasma sintering

    NASA Astrophysics Data System (ADS)

    Tian, Wen-ming; Li, Song-mei; Wang, Bo; Chen, Xin; Liu, Jian-hua; Yu, Mei

    2016-06-01

    Graphene-reinforced 7055 aluminum alloy composites with different contents of graphene were prepared by spark plasma sintering (SPS). The structure and mechanical properties of the composites were investigated. Testing results show that the hardness, compressive strength, and yield strength of the composites are improved with the addition of 1wt% graphene. A clean, strong interface is formed between the metal matrix and graphene via metallurgical bonding on atomic scale. Harmful aluminum carbide (Al4C3) is not formed during SPS processing. Further addition of graphene (above 1wt%) results in the deterioration in mechanical properties of the composites. The agglomeration of graphene plates is exacerbated with increasing graphene content, which is the main reason for this deterioration.

  13. Solidification of SiC/Al fiber-reinforced metal matrix composites

    SciTech Connect

    Ho, S.; Saigal, A. . Dept. of Mechanical Engineering)

    1994-08-01

    In recent years there has been considerable interest in the development and improvement of near net shape manufacturing processes for the fabrication of metal matrix composites (MMCs). Among the techniques available today, the solidification processing technique, including a casting process, provides the most direct route to a finished shape and stands out as potentially simple and economical. In the present study, the solidification of fiber-reinforced composites was investigated by means of the finite element method (FEM). The finite element formulation of general heat conduction equations is typically done by Galerkin's method, which is one of the weighted residual methods. Numerical results from FEM are compared with analytical solutions for the phase change problems. The interface between the solid and liquid phases and the temperature distribution in the composite are analyzed as a function of volume fraction of fibers. ABAQUS, a general purpose commercially available finite element code, was used in this study.

  14. A study of the composition and microstructure of aluminum matrix composites reinforced with alumina fibers

    NASA Astrophysics Data System (ADS)

    Zolotova, D.; Serpova, V.; Prokofiev, M.; Rabinskiy, L.; Shavnev, A.

    2016-04-01

    This article presents the results of a study of the microstructure and the composition of aluminum-based metal matrix composites (MMC) reinforced with continuous alumina fibers. An Al-Mg-Cu alloy similar to that of AA 2024 was used. X-ray diffraction and X-ray fluorescence analyses were used for investigation of a probable volume fraction of a spinel phase in MMC. Scanning electron microscopy and an X-ray microanalysis were used to study a change of the elemental composition of the composites microstructure on the polished cross sections. The constant mass fractions of magnesium (0.65 wt. %) and copper (1.25 wt. %) were found in the interphase area within radius of 1 μm around fibers.

  15. Acoustic emission during fatigue crack propagation in SiC particle reinforced Al matrix composites

    SciTech Connect

    Niklas, A.; Froyen, L.; Wevers, M.; Delaey, L.

    1995-12-01

    The acoustic emission (AE) behavior during fatigue propagation in aluminum 6061 and aluminum 6061 matrix composites containing 5, 10, and 20 wt pct SiC particle reinforcement was investigated under tension-tension fatigue loading. The purpose of this investigation was to monitor fatigue crack propagation by the AE technique and to identify the source(s) of AE. Most of the AEs detected were observed at the top of the load cycles. The cumulative number of AE events was found to correspond closely to the fatigue crack growth and to increase with increasing SiC content. Fractographic studies revealed an increasing number of fractured particles and to a lesser extent decohered particles on the fatigue fracture surface as the crack propagation rate (e.g., {Delta}K) or the SiC content was increased.

  16. Anodization Mechanism on SiC Nanoparticle Reinforced Al Matrix Composites Produced by Power Metallurgy

    PubMed Central

    Ferreira, Sonia C.; Conde, Ana; Arenas, María A.; Rocha, Luis A.; Velhinho, Alexandre

    2014-01-01

    Specimens of aluminum-based composites reinforced by silicon carbide nanoparticles (Al/SiCnp) produced by powder metallurgy (PM) were anodized under voltage control in tartaric-sulfuric acid (TSA). In this work, the influence of the amount of SiCnp on the film growth during anodizing was investigated. The current density versus time response and the morphology of the porous alumina film formed at the composite surface are compared to those concerning a commercial aluminum alloy (AA1050) anodized under the same conditions. The processing method of the aluminum alloys influences the efficiency of the anodizing process, leading to a lower thicknesses for the unreinforced Al-PM alloy regarding the AA1050. The current density versus time response is strongly dependent on the amount of SiCnp. The current peaks and the steady-state current density recorded at each voltage step increases with the SiCnp volume fraction due to the oxidation of the SiCnp. The formation mechanism of the anodic film on Al/SiCnp composites is different from that occurring in AA1050, partly due the heterogeneous distribution of the reinforcement particles in the metallic matrix, but also to the entrapment of SiCnp in the anodic film. PMID:28788295

  17. Anodization Mechanism on SiC Nanoparticle Reinforced Al Matrix Composites Produced by Power Metallurgy.

    PubMed

    Ferreira, Sonia C; Conde, Ana; Arenas, María A; Rocha, Luis A; Velhinho, Alexandre

    2014-12-19

    Specimens of aluminum-based composites reinforced by silicon carbide nanoparticles (Al/SiCnp) produced by powder metallurgy (PM) were anodized under voltage control in tartaric-sulfuric acid (TSA). In this work, the influence of the amount of SiCnp on the film growth during anodizing was investigated. The current density versus time response and the morphology of the porous alumina film formed at the composite surface are compared to those concerning a commercial aluminum alloy (AA1050) anodized under the same conditions. The processing method of the aluminum alloys influences the efficiency of the anodizing process, leading to a lower thicknesses for the unreinforced Al-PM alloy regarding the AA1050. The current density versus time response is strongly dependent on the amount of SiCnp. The current peaks and the steady-state current density recorded at each voltage step increases with the SiCnp volume fraction due to the oxidation of the SiCnp. The formation mechanism of the anodic film on Al/SiCnp composites is different from that occurring in AA1050, partly due the heterogeneous distribution of the reinforcement particles in the metallic matrix, but also to the entrapment of SiCnp in the anodic film.

  18. Fabrication Of Carbon-Boron Reinforced Dry Polymer Matrix Composite Tape

    NASA Technical Reports Server (NTRS)

    Belvin, Harry L.; Cano, Roberto J.; Treasure, Monte; Shahood, Thomas W.

    1999-01-01

    Future generation aerospace vehicles will require specialized hybrid material forms for component structure fabrication. For this reason, high temperature composite prepregs in both dry and wet forms are being developed at NASA Langley Research Center (LaRC). In an attempt to improve compressive properties of carbon fiber reinforced composites, a hybrid carbon-boron tape was developed and used to fabricate composite laminates which were subsequently cut into flexural and compression specimens and tested. The hybrid material, given the designation HYCARB, was fabricated by modifying a previously developed process for the manufacture of dry polymer matrix composite (PMC) tape at LaRC. In this work, boron fibers were processed with IM7/LaRC(TradeMark)IAX poly(amide acid) solution-coated prepreg to form a dry hybrid tape for Automated Tow Placement (ATP). Boron fibers were encapsulated between two (2) layers of reduced volatile, low fiber areal weight poly(amide acid) solution-coated prepreg. The hybrid prepreg was then fully imidized and consolidated into a dry tape suitable for ATP. The fabrication of a hybrid boron material form for tow placement aids in the reduction of the overall manufacturing cost of boron reinforced composites, while realizing the improved compression strengths. Composite specimens were press-molded from the hybrid material and exhibited excellent mechanical properties.

  19. Comprehensive properties of a novel fiber reinforced composite with a UEDMA-based resin matrix.

    PubMed

    Zhang, Meng; Matinlinna, Jukka Pekka; Botelho, Michael George; Säilynoja, Eija Sinikka

    2014-07-01

    The traditional fiber reinforced composite (FRC) contains bisphenol A glycidyl methacrylate (bis-GMA) in the resin matrix, which is thought to have some disadvantages. This research aimed at replacing bis-GMA with another monomer-urethane dimethacrylate (UEDMA), with the desired properties for dental use still retained. Four groups were prepared with light-curing (n = 30), one Control group with a bis-GMA-based resin matrix and three experimental groups with UEDMA-based matrices (Exper 1, Exper 2 and Exper 3 with a varying UEDMA weight percentage). Specimens were stored in dry conditions for 24 h or in deionized water for 1, 3, 6 or 12 months prior to the tests. Water sorption (n = 6), Vicker's hardness (n = 6) and flexural properties (n = 6) after each storage time were investigated. Scanning electron microscopy (SEM) images were taken at the fracture sites after 3-point bending. All the results were statistically analyzed (α = 0.05). The Exper 1 group exhibited the lowest weight increase after water storage among the experimental groups. As for dry conditions, 1- and 6-month storage, different resin matrix compositions made no significant difference to hardness, while for 3- and 12-month storage, "Control" possessed the highest hardness. The Control group's strength and modulus, Exper 1 and Exper 2's modulus were stable during water storage. Compared to other experimental groups, Exper 1 had the highest strength and modulus values with most of the storage times. SEM images showed relatively good adhesion between the fiber and the matrix. With all the tested properties considered, the Exper 1 group had superior performance among all the three experimental groups.

  20. The Mechanics of Creep Deformation in Polymer Derived Continuous Fiber-Reinforced Ceramic Matrix Composites

    SciTech Connect

    Lara-Curzio, E.

    2001-01-30

    The objective of this Cooperative Research and Development Agreement between Lockheed Martin Energy Research Corporation and Dow Corning Corporation was to study the effects of temperature, stress, fiber type and fiber architecture on the time-dependent deformation and stress-rupture behavior of polymer-derived ceramic matrix composites developed by the Dow Corning Corporation. Materials reinforced with CG-Nicalon{trademark}, Hi-Nicalon{trademark} and Sylramic{reg_sign} fibers were evaluated under fast fracture, stress-relaxation, and stress-rupture conditions at temperatures between 700 C and 1400 C in ambient air and for stresses between 50 and 200 MPa. Some of the stress-rupture tests conducted as part of this program are among the longest-duration experiments ever conducted with these materials. The possibility of using accelerated test techniques to evaluate the very-long term stress-rupture/creep behavior of these materials was investigated by means of stress-relaxation experiments. However it was found that because these materials exhibit non-linear stress-strain behavior at stresses larger than the matrix cracking stress and because of environmentally-induced changes in the micro and mesostructure of the material, particularly at elevated temperatures, this approach is impractical. However, the results of stress-relaxation experiments will be useful to predict the behavior of these materials in applications where stresses are thermally-induced and therefore driven by strains (e.g., when components are subjected to thermal gradients). The evolution of the microstructure of the fibers, matrix and fiber-matrix interface was studied as a function of stress and temperature, using analytical electron microscopy. The results from these analyses were essential to understand the relationships between environment, stress, temperature and processing on the microstructure and properties of these materials.

  1. Adhesive properties of bonded orthodontic retainers to enamel: stainless steel wire vs fiber-reinforced composites.

    PubMed

    Foek, Dave Lie Sam; Ozcan, Mutlu; Krebs, Eliza; Sandham, Andrew

    2009-10-01

    The objectives of this study were to compare the bond strength of a stainless steel orthodontic wire vs various fiber-reinforced composites (FRC) used as orthodontic retainers on enamel, analyze the failure types after debonding, and investigate the influence of different application procedures of stainless steel wires on bond strength. Caries-free, intact human mandibular incisors (N = 80, n = 10 per group) were selected and randomly distributed into 8 groups. After etching with 37% H3PO4 for 30 s, rinsing and drying, bonding agent (Stick Resin) was applied and light polymerized. Then one of the following FRC materials was applied on the flowable composite (Stick Flow) using standard molds: group 1: Angelus Fibrex Ribbon; group 2: DentaPreg Splint; group 3: ever-Stick Ortho; group 4: Ribbond. In group 5, Quad Cat Wire was applied in the same manner as in FRC groups. In group 6, after applying bonding agent (Stick Resin), Quad Cat Wire was placed directly on the tooth surface and covered with Stick Flow composite. In group 7, after bonding agent (Heliobond) was applied, Quad Cat Wire was placed directly on the tooth surface and covered with Tetric Flow composite. In group 8, after applying bonding agent (Heliobond) and polymerization, Tetric Flow composite was applied, not polymerized, and Quad Cat Wire was placed and covered with Tetric Flow again. Specimens were thermocycled for 6000 cycles between 5 degrees C and 55 degrees C and loaded in a universal testing machine under shear stress (crosshead speed: 1 mm/min) until debonding occurred. The failure sites were examined under an optical light microscope. Data were analyzed using one-way ANOVA and the Tukey-Kramer adjustment test (alpha = 0.05). Significant differences were found between the groups (p = 0.0011) (ANOVA). Bond strength results did not significantly differ either between the FRC groups (groups 1 to 4) (6.1 +/- 2.5 to 8.4 +/- 3.7 MPa) (p > 0.05) or the wire groups (groups 5 to 8) (10.6 +/- 3.8 to 14

  2. Mechanics of interfaces in fiber reinforced SiC/RBSN ceramic matrix composites. [reaction bonded silicon nitride

    NASA Technical Reports Server (NTRS)

    Chulya, Abhisak; Gyekenyesi, John P.

    1991-01-01

    The mechanical behavior of continuous fiber reinforced SiC/RBSN composites with strong and weak interface characteristics is evaluated. Both catastrophic and noncatastrophic failures are observed in tensile specimens. Effects of fiber/matrix interface debonding (splitting) parallel to the fibers are discussed. Micromechanical models incorporating residual stresses to calculate the critical matrix cracking strength, ultimate strength and work of pull-out are reviewed and used to predict composite response. Experimental results are compared to analytical predictions.

  3. Effects of Interface Modification on Mechanical Behavior of Hi-Nicalon Fiber-Reinforced Celsian Matrix Composites

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.; Eldridge, Jeffrey I.

    1997-01-01

    Unidirectional celsian matrix composites having approx. 42 volume percent of uncoated or BN/SiC-coated Hi-Nicalon fibers were tested in three-point bend at room temperature. The uncoated fiber-reinforced composites showed catastrophic failure with strength of 210 +/- 35 MPa and a flat fracture surface. In contrast, composites reinforced with BN/SiC-coated fibers exhibited graceful failure with extensive fiber pullout. Values of first matrix cracking stress and strain were 435 +/- 35 MPa and 0.27 +/- 0.01 %, respectively, with ultimate strength as high as 960 MPa. The elastic Young's modulus of the uncoated and BN/SiC-coated fiber-reinforced composites were measured as 184 q 4 GPa and 165 +/- 5 GPa, respectively. Fiber push-through tests and microscopic examination indicated no chemical reaction at the uncoated or coated fiber-matrix interface. The low strength of the uncoated fiber-reinforced composite is probably due to degradation of the fibers from mechanical surface damage during processing. Because both the coated and uncoated fiber reinforced composites exhibited weak interfaces, the beneficial effect of the BN-SiC dual layer is primarily the protection of fibers from mechanical damage during processing.

  4. The effect of matrix microstructure and reinforcement shape on the creep deformation of near-{gamma} titanium aluminide composites

    SciTech Connect

    Kampe, S.L.; Christodoulou, J.; Feng, C.R.; Michel, D.J.; Christodoulou, L.

    1998-05-01

    The influences of composite matrix microstructure, reinforcement shape, and processing methodology have been evaluated for a series of near-gamma (Ti{sub 3}Al + TiAl) titanium aluminide matrix composites evaluated in tension and tensile-creep at 800 C. Specifically, heat treatments were imposed to evolve either fully-equiaxed or fully-lamellar composite matrices containing either dispersed particulate or high-aspect-ratio short-fiber boride reinforcement. The results indicate that the highest creep rates are associated with composites containing particulate reinforcement in equiaxed matrices, whereas the lowest rates were obtained for short-fiber reinforcement in lamellar matrices. The mechanisms controlling creep deformation are observed to rely only on the morphology and details of the matrix microstructure and are independent of the type and shape of the reinforcing phase. The enhanced work hardening tendencies of the lamellar microstructure is shown to improve creep resistance as manifested by a reduced steady state creep rate as well as prolonging primary creep to higher values of accumulated strain.

  5. Effect of Size, Content and Shape of Reinforcements on the Behavior of Metal Matrix Composites (MMCs) Under Tension

    NASA Astrophysics Data System (ADS)

    Paknia, A.; Pramanik, A.; Dixit, A. R.; Chattopadhyaya, S.

    2016-10-01

    The objective of this research was to investigate the mechanical behavior of metal matrix composites (MMCs) 6061 aluminum, reinforced with silicon carbide particles, under unidirectional tensile loading by finite element analysis. The effects of particle's shape, size and content on the tensile properties of the composites were studied and compared with each other. In addition, stress and strain distributions and possible particle fracture or debonding were investigated. It was found that, among different shapes, a certain shape of reinforcement particle provided better tensile properties for MMCs and, within each shape category, composites with smaller particle size and higher particle content (20%) also showed better properties. It was also found that when the reinforcement content was 10%, the effects of shape and size of the particles were negligible. Not only interfacial length between the reinforcement and matrix materials, but also state of matrix material, due to the presence of the reinforcement particles, affected the stiffness of the MMCs. In almost all of the cases, except for MMCs with triangular particles, when the stress increased, with the increase in the applied positive displacement, the stress distributions remained unchanged.

  6. Abrasive Wear Behavior of In Situ TiC Reinforced with Al-4.5%Cu Matrix

    NASA Astrophysics Data System (ADS)

    Kumar, Anand; Jha, P. K.; Mahapatra, M. M.

    2014-03-01

    The present work deals with the investigation on weight loss and coefficient of friction of TiC reinforced Al-4.5%Cu in situ metal matrix composites. Experiments were conducted using pin-on-disc apparatus against abrasive paper by varying the applied load, sliding distance, and weight percentage of TiC. The results indicated significant improvement in the mechanical properties and wear resistance of experimental composites as compared to the parent metal matrix. The percentage of porosity though increased with increasing TiC reinforcement. The variation of weight loss of composites increased linearly with increasing applied load and sliding distance, whereas decreased with increasing weight percentage of TiC reinforcement. The coefficient of friction decreased linearly with increasing applied load and TiC reinforcement. SEM micrographs of worn surfaces show a well compacted transfer layer of wear debris along with wear track over the sliding surface. Grooves, delamination, and crack propagation were also observed in all test samples. The effective depth of penetration and size of debris was seen to reduce with increasing wt.% of TiC reinforcement in metal matrix.

  7. Titanium carbide nanoparticles reinforcing nickel matrix for improving nanohardness and fretting wear properties in wet conditions

    NASA Astrophysics Data System (ADS)

    Dănăilă, Eliza; Benea, Lidia; Caron, Nadège; Raquet, Olivier

    2016-09-01

    In this study Ni/nano-TiC functional composite coatings were produced by electro-codeposition of TiC nanoparticles (50 nm mean diameter) with nickel on 304L stainless steel support. Coatings were obtained from a Watts classical solution in which TiC nanoparticles were added. The surface morphology, chemical composition, structure, roughness and thickness, were evaluated in relation to the effect of TiC nanoparticles incorporation into Ni matrix. It was found that incorporation of TiC nanoparticles into the nickel matrix produces morphological changes in the deposit and increases the roughness. The fretting wear behavior in wet conditions of the obtained coatings was evaluated on a ball-on-plate configuration. To evaluate the wet fretting wear (tribocorrosion) behavior the open circuit potential was measured before, during and after the fretting tests at room temperature in the solution that simulates the primary water circuit of Pressurized Water Reactors. The results show that Ni/nano-TiC composite coatings exhibited a low friction coefficient, high nanohardness and fretting wear resistance in wet conditions compared with pure Ni coatings.

  8. Effect of surface modification on carbon fiber and its reinforced phenolic matrix composite

    NASA Astrophysics Data System (ADS)

    Yuan, Hua; Wang, Chengguo; Zhang, Shan; Lin, Xue

    2012-10-01

    In this work, polyacrylonitrile (PAN)-based carbon fiber were chemically modified with H2SO4, KClO3 and silane coupling agent (γ-aminopropyltriethoxysilane, APS), and carbon fiber reinforced phenolic matrix composites were prepared. The structural and surface characteristics of the carbon fiber were investigated by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), laser Raman scattering (LRS) and Fourier transform infrared spectroscopy (FTIR). Single fiber mechanical properties, specific surface area, composite impact properties and interfacial shear strength (ILSS) were researched to indicate the effects of surface modification on fibers and the interaction between modified fiber surface and phenolic matrix. The results showed that carbon fiber surface modification by oxidation and APS can strengthen fiber surface chemical activity and enlarge the fiber surface area as well as its roughness. When carbon fiber (CF) is oxidized treatment, the oxygen content as well as the O/C ratio will be obviously increased. Oxygen functional groups increase with oxidation time increasing. Carbon fiber treated with APS will make Csbnd Osbnd R content increase and Osbnd Cdbnd O content decrease due to surface reaction. Proper treatment of carbon fiber with acid and silane coupling agent prove an effective way to increase the interfacial adhesion and improve the mechanical and outdoor performance of the resulting fiber/resin composites.

  9. A novel Al matrix composite reinforced by nano-AlNp network

    PubMed Central

    Ma, X.; Zhao, Y. F.; Tian, W. J.; Qian, Z.; Chen, H. W.; Wu, Y. Y.; Liu, X. F.

    2016-01-01

    In pursuit of lightweighting of automobiles and low emission of transportation, the efforts to develop high-strength, heat-resistant and fatigue-resistant Al alloys and/or composites have been ongoing. Here we report a novel Al matrix composite with ultrahigh strength reinforced by a three dimensional network of nano-AlN particles for the first time. The in-situ synthesized AlN particles are connected by twinning bonding chains and built up a three dimensional network strengthening Al matrix enormously like the skeleton to human body. The composite containing 16.4wt.% AlN particles shows excellent properties: the ultimate tensile strengths can be up to 518MPa at room temperature and 190MPa at 350 °C. This peculiar performance results from the novel spatial distribution of nano-scale AlN particles. Our findings in this work would help to develop a potential candidate for high-performance heat resistance light-metal based materials. PMID:27721417

  10. Dry Sliding Wear Behaviour of Flyash Reinforced ZA-27 Alloy Based Metal Matrix Composites

    NASA Astrophysics Data System (ADS)

    Sharma, S. C.; Krishna, M.; Bhattacharyya, D.

    In the present investigation, an attempt has been made to evaluate the wear rate of ZA-27 alloy composites reinforced with fly ash particles from 1 to 3 wt% in steps of 1 wt%. The compo-casting method has been used to fabricate the composites using Raichur fly ash of average size 3-5 microns. The wear specimens are tested under dry conditions using a pin-on-disc sliding wear testing machine with wear loads of 20-120 N in steps of 20 N, and the sliding distances in the range of 0.5 km to 2.5 km. The results indicate that the wear rate of the composites is less than that of the matrix alloy and it further decreases with the increase in fly ash content. However, the material loss in terms of wear rate and wear volume increases with the increase in load and sliding distance, both in the cases of composites and the matrix alloy. An increase in the applied load increases the wear severity by changing the wear mechanism from abrasion to particle-cracking induced delamination wear. It is found that with the increase in fly ash content, the wear resistance increases monotonically. The observations have been explained using scanning electron microscope (SEM) analysis of the worn surfaces of the composites.

  11. A novel Al matrix composite reinforced by nano-AlNp network.

    PubMed

    Ma, X; Zhao, Y F; Tian, W J; Qian, Z; Chen, H W; Wu, Y Y; Liu, X F

    2016-10-10

    In pursuit of lightweighting of automobiles and low emission of transportation, the efforts to develop high-strength, heat-resistant and fatigue-resistant Al alloys and/or composites have been ongoing. Here we report a novel Al matrix composite with ultrahigh strength reinforced by a three dimensional network of nano-AlN particles for the first time. The in-situ synthesized AlN particles are connected by twinning bonding chains and built up a three dimensional network strengthening Al matrix enormously like the skeleton to human body. The composite containing 16.4wt.% AlN particles shows excellent properties: the ultimate tensile strengths can be up to 518MPa at room temperature and 190MPa at 350 °C. This peculiar performance results from the novel spatial distribution of nano-scale AlN particles. Our findings in this work would help to develop a potential candidate for high-performance heat resistance light-metal based materials.

  12. A novel Al matrix composite reinforced by nano-AlNp network

    NASA Astrophysics Data System (ADS)

    Ma, X.; Zhao, Y. F.; Tian, W. J.; Qian, Z.; Chen, H. W.; Wu, Y. Y.; Liu, X. F.

    2016-10-01

    In pursuit of lightweighting of automobiles and low emission of transportation, the efforts to develop high-strength, heat-resistant and fatigue-resistant Al alloys and/or composites have been ongoing. Here we report a novel Al matrix composite with ultrahigh strength reinforced by a three dimensional network of nano-AlN particles for the first time. The in-situ synthesized AlN particles are connected by twinning bonding chains and built up a three dimensional network strengthening Al matrix enormously like the skeleton to human body. The composite containing 16.4wt.% AlN particles shows excellent properties: the ultimate tensile strengths can be up to 518MPa at room temperature and 190MPa at 350 °C. This peculiar performance results from the novel spatial distribution of nano-scale AlN particles. Our findings in this work would help to develop a potential candidate for high-performance heat resistance light-metal based materials.

  13. An evaluation of fiber-reinforced titanium matrix composites for advanced high-temperature aerospace applications

    NASA Astrophysics Data System (ADS)

    Larsen, James M.; Russ, Stephan M.; Jones, J. W.

    1995-12-01

    The current capabilities of continuous silicon-carbide fiber-reinforced titanium matrix composites (TMCs) are reviewed with respect to application needs and compared to the capabilities of conventional high-temperature monolithic alloys and aluminides. In particular, the properties of a firstgeneration titanium aluminide composite, SCS-6/Ti-24Al-11Nb, and a second-generation metastable beta alloy composite, SCS-6/TIMETAL 21S, are compared with the nickel-base superalloy IN100, the high-temperature titanium alloy Ti-1100, and a relatively new titanium aluminide alloy. Emphasis is given to life-limiting cyclic and monotonie properties and to the influence of time-dependent deformation and environmental effects on these properties. The composite materials offer a wide range of performance capabilities, depending on laminate architecture. In many instances, unidirectional composites exhibit outstanding properties, although the same materials loaded transverse to the fiber direction typically exhibit very poor properties, primarily due to the weak fiber/matrix interface. Depending on the specific mechanical property under consideration, composite cross-ply laminates often show no improvement over the capability of conventional monolithic materials. Thus, it is essential that these composite materials be tailored to achieve a balance of properties suitable to the specific application needs if these materials are to be attractive candidates to replace more conventional materials.

  14. An evaluation of fiber-reinforced titanium matrix composites for advanced high-temperature aerospace applications

    SciTech Connect

    Larsen, J.M.; Russ, S.M.; Jones, J.W.

    1995-12-01

    The current capabilities of continuous silicon-carbide fiber-reinforced titanium matrix composites (TMCs) are reviewed with respect to application needs and compared to the capabilities of conventional high-temperature monolithic alloys and aluminides. In particular, the properties of a first-generation titanium aluminide composite, SCS-6/Ti-24Al-11Nb, and a second-generation metastable beta alloy composite, SCS-6/TIMETAL 21S, are compared with the nickel-base superalloy IN100, the high-temperature titanium alloy Ti-1100, and a relatively new titanium aluminide alloy. Emphasis is given to life-limiting cyclic and monotonic properties and to the influence of time-dependent deformation and environmental effects on these properties. The composite materials offer a wide range of performance capabilities, depending on laminate architecture. In many instances, unidirectional composites exhibit outstanding properties, although the same materials loaded transverse to the fiber direction typically exhibit very poor properties, primarily due to the weak fiber/matrix interface. Depending on the specific mechanical property under consideration, composite cross-ply laminates often show no improvement over the capability of conventional monolithic materials. Thus, it is essential that these composite materials be tailored to achieve a balance of properties suitable to the specific application needs if these materials are to be attractive candidates to replace more conventional materials.

  15. Titanate nanotubes for reinforcement of a poly(ethylene oxide)/chitosan polymer matrix

    NASA Astrophysics Data System (ADS)

    Porras, R.; Bavykin, D. V.; Zekonyte, J.; Walsh, F. C.; Wood, R. J.

    2016-05-01

    Soft polyethylene oxide (PEO)/chitosan mixtures, reinforced with hard titanate nanotubes (TiNTs) by co-precipitation from aqueous solution, have been used to produce compact coatings by the ‘drop-cast’ method, using water soluble PEO polymer and stable, aqueous colloidal solutions of TiNTs. The effects of the nanotube concentration and their length on the hardness and modulus of the prepared composite have been studied using nanoindentation and nanoscratch techniques. The uniformity of TiNT dispersion within the polymer matrix has been studied using transmission electron microscopy (TEM). A remarkable increase in hardness and reduced Young’s modulus of the composites, compared to pure polymer blends, has been observed at a TiNT concentration of 25 wt %. The short (up to 30 min) ultrasound treatment of aqueous solutions containing polymers and a colloidal TiNT mixture prior to drop casting has resulted in some improvements in both hardness and reduced Young’s modulus of dry composite films, probably due to a better dispersion of ceramic nanotubes within the matrix. However, further (more than 1 h) treatment of the mixture with ultrasound resulted in a deterioration of the mechanical properties of the composite accompanied by a shortening of the nanotubes, as observed by the TEM.

  16. Using Goals, Feedback, Reinforcement, and a Performance Matrix to Improve Customer Service in a Large Department Store

    ERIC Educational Resources Information Center

    Eikenhout, Nelson; Austin, John

    2005-01-01

    This study employed an ABAC and multiple baseline design to evaluate the effects of (B) feedback and (C) a package of feedback, goalsetting, and reinforcement (supervisor praise and an area-wide celebration as managed through a performance matrix, on a total of 14 various customer service behaviors for a total of 115 employees at a large…

  17. Using Goals, Feedback, Reinforcement, and a Performance Matrix to Improve Customer Service in a Large Department Store

    ERIC Educational Resources Information Center

    Eikenhout, Nelson; Austin, John

    2005-01-01

    This study employed an ABAC and multiple baseline design to evaluate the effects of (B) feedback and (C) a package of feedback, goalsetting, and reinforcement (supervisor praise and an area-wide celebration as managed through a performance matrix, on a total of 14 various customer service behaviors for a total of 115 employees at a large…

  18. Properties of Graphite Fiber Reinforced Copper Matrix Composites for Space Power Applications

    NASA Technical Reports Server (NTRS)

    Ellis, David L.

    1992-01-01

    The thermal and mechanical properties of pitch-based graphite fiber reinforced copper matrix (Gr/Cu) composites usable for space applications such as radiator fins were investigated. Thermal conductivity was measured as a function of fiber volume fraction and architecture. Results showed for unidirectional P-100 Gr/Cu composites, the longitudinal thermal conductivity was nearly independent of fiber volume fraction. Transverse thermal conductivities (perpendicular to the fibers) were strongly affected by the fiber volume fraction with higher volume fractions resulting in lower thermal conductivities. The effect of architecture on thermal conductivity followed the cosine squared law for simple architectures. Insufficient data are available currently to model more complex architectures, but adding fibers in the direction of the heat flow increases the thermal conductivity as low conductivity plies are supplemented by high conductivity plies. Thermal expansion tests were conducted on the Gr fibers and Gr/Cu composites. The results show a considerable thermal expansion mismatch between the fibers and the Cu matrix. The longitudinal thermal expansion showed a strong dependence on the architecture of the Gr/Cu composites. The composites also show a thermal expansion hysteresis. The hysteresis was eliminated by an engineered interface. Mechanical testing concentrated on the dynamic modulus and strength of the composites. The dynamic modulus of the Gr/Cu composites was 305 GPa up to 400 C, a value equivalent to Be. The strengths of the composites were less than expected, but this is attributed to the poor bond across the interface between the Gr fibers and Cu matrix. Testing of composites with an engineered interface is expected to yield strengths nearer the values predicted by the rule of mixtures.

  19. Dynamic behaviors of various volume rate steel-fiber reinforced reactive powder concrete after high temperature burnt

    NASA Astrophysics Data System (ADS)

    Pang, Baojun; Wang, Liwen; Yang, Zhenqi; Chi, Runqiang

    2009-06-01

    Dynamic strain-stress curves of reactive powder concrete under high strain rate (10/s-100/s) were determined by improved split Hopkinson pressure bar (SHPB) system. A plumbum pulse shaper was used to ensure the symmetrical stress in the specimens before fracture and avoid the fluctuation of test data due to input shaky stress pulse. A time modified method was induced for data processing in order to get accurate SHPB results. The results of experiment showed after high temperature burnt, different volume rate (0.0%, 0.5%, 1.0%, 1.5%) steel-fiber reinforced reactive power concrete had the same changing tendency of residual mechanics behaviors, e.g. after 400 centigrade burnt, the residual compression strength was about 70% of material strength without burnt under 100/s. After 800 centigrade burnt, the compression strength is about 30% under 100/s while the deformation ability increased. At meanwhile, steel fiber had improved the mechanism of reinforcing effect and toughening effect of concrete material after burnt. With increasing of steel fiber volume rate, dynamic residual behavior of samples was improved. Microcosmic characteristics and energy absorption were induced for explaining the experiment results.

  20. Superior reinforcement effect of TEMPO-oxidized cellulose nanofibrils in polystyrene matrix: optical, thermal, and mechanical studies.

    PubMed

    Fujisawa, Shuji; Ikeuchi, Tomoyasu; Takeuchi, Miyuki; Saito, Tsuguyuki; Isogai, Akira

    2012-07-09

    Polystyrene (PS) composites reinforced with 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidized cellulose nanofibrils (TOCNs) with various weight ratios were fabricated by casting and vacuum-drying mixtures of PS/N,N-dimethylformamide (DMF) solution and TOCN/DMF dispersion. TOCNs of 3 to 4 nm width were dispersed homogeneously at the individual nanofibril level in the PS matrix, such that the TOCN/PS nanocomposite films exhibited high optical transparencies and their tensile strengths, elastic moduli, and thermal dimensional stabilities increased with increasing TOCN content. Dynamic mechanical analysis showed that the storage modulus of the TOCN/PS films increased significantly with TOCN content above the glass-transition temperature of PS by the formation of an interfibrillar network structure of TOCNs in the PS matrix, based on percolation theory. The outstanding and effective polymer reinforcement by TOCNs results from their high aspect ratio, high crystallinity, and nanodispersibility in the PS matrix.

  1. Mechanical Properties and Fracture Behavior of Electroless Ni-Plated Short Carbon Fiber Reinforced Geopolymer Matrix Composites

    NASA Astrophysics Data System (ADS)

    Lin, Tiesong; Jia, Dechang

    Electroless Ni-plated short carbon fiber reinforced geopolymer matrix composites with various carbon fiber/matrix interface coating thicknesses have been successfully fabricated. The influences of coating thickness on the mechanical properties and fracture behavior have been investigated by three-point bending test and scanning electron microscopy. The flexural strength and Young's modulus of Ni-plated short carbon fiber reinforced geopolymer composites exhibit maximums as the average fiber coating thickness increases, but the work of fracture has a sharp decrease, and the fracture manner changes from ductile to brittle. This is mainly attributed to the fact that the carbon fibers favor breakage rather than pulling-out during loading because of the higher interface bonding strength of fiber/matrix, and pliability of the carbon fibers decreases with the increase of the coating thickness.

  2. Cutting performance and microstructure of high speed steels: Contributions of matrix strengthening and undissolved carbides

    NASA Astrophysics Data System (ADS)

    Karagöz, S.; Fischmeister, H. F.

    1998-01-01

    While it is accepted that both the hot strength of the matrix and the amount of undissolved carbides are important for the cutting performance of high speed steels, the relative weights of their contributions are unknown. In this work, they are separately identified and a model is presented that provides a quantitative prediction of tool life (solely in uninterrupted cutting) on the basis of microstructural and compositional data over a wide range of alloy compositions and cutting speeds. The model seems to describe the individual contributions to tool life well enough to serve as a guide in alloy development. The model has been developed using 13 different steels, spanning the entire range of customary compositions. It is based on the following parameters: volume fractions and compositions of undissolved carbides; precipitates formed during tempering (secondary hardening) and during operation (tertiary precipitates); and, finally, residual solute in the matrix. Tool life is modeled as a linear combination of contributions from the undissolved carbides and from the precipitate population, including a contribution due to the action of Co, and with an additional term due to solute strengthening of the matrix. The weight factors are determined by multiple linear regression analysis. They reflect the relative importance of each contributing factor, and their dependence on cutting speed can be interpreted in terms of the change in operative wear mechanism with tool temperature.

  3. Effect of microstructure (particulate size and volume fraction) and counterface material on the sliding wear resistance of particulate-reinforced aluminum matrix composites

    NASA Astrophysics Data System (ADS)

    Alpas, A. T.; Zhang, J.

    1994-05-01

    The effects of microstructure (namely, particulate volume fraction and particulate size) and the counterface materials on the dry-sliding wear resistance of the aluminum matrix composites 2014A1-SiC and 6061Al-Al2O3 were studied. Experiments were performed within a load range of 0.9 to 350 N at a constant sliding velocity of 0.2 ms-1. Two types of counterface materials, SAE 52100 bearing steel and mullite, were used. At low loads, where particles act as loadbearing constituents, the wear resistance of the 2014A1 reinforced with 15.8 µm diameter SiC was superior to that of the alloy with the same volume fraction of SiC but with 2.4 µm diameter. The wear rates of the composites worn against a steel slider were lower compared with those worn against a mullite slider because of the formation of iron-rich layers that act as in situ solid lubricants in the former case. With increasing the applied load, SiC and A12O3 particles fractured and the wear rates of the composites increased to levels comparable to those of unreinforced matrix alloys. The transition to this regime was delayed to higher loads in the composites with a higher volume percentage of particles. Concurrent with particle fracture, large strains and strain gradients were generated within the aluminum layers adjacent to contact surfaces. This led to the subsurface crack growth and delamination. Because the particles and interfaces provided preferential sites for subsurface crack initiation and growth and because of the propensity of the broken particles to act as third-body abrasive elements at the contact surfaces, no improvement of the wear resistance was observed in the composites in this regime relative to unreinforced aluminum alloys. A second transition, to severe wear, occurred at higher loads when the contact surface temperature exceeded a critical value. The transition loads (and temperatures) were higher in the composites. The alloys with higher volume fraction of reinforcement provided better

  4. Fracture and cyclic-fatigue behavior of ductile phase reinforced brittle matrix laminated composites: Effect of laminate orientation and reinforcement layer thickness

    NASA Astrophysics Data System (ADS)

    Bloyer, Donald Ray, Jr.

    The fracture and cyclic fatigue properties of ductile phase reinforced brittle matrix laminated composites have been investigated through the examination of the effect of layer orientation and reinforcement layer thickness on niobium metal reinforced Nbsb3Al intermetallic laminates. Two laminate orientations, the crack arrester and crack divider, were prepared with layer thickness combinations of 50 mum Nb/200 mum Nbsb3Al, 125 mum Nb/500 mum Nbsb3Al, and 250 mum Nb/1000 mum Nbsb3A1. This gave a nominally constant reinforcement volume fraction of 0.2. The fracture and resistance-curve behavior of these laminates has been compared with similarly reinforced in situ particulate and microlaminate composites. The high aspect ratio of the Nb laminates led to improved toughness in the Nbsb3Al matrix by a factor of 10-20. Laminate orientation had a small effect on crack growth resistance, and properties were optimal in the arrester as compared to the divider orientation. In addition, thicker Nb layers yielded improved fracture toughness. The high fracture toughness observed in these laminates resulted from large crack tip shielding zones formed by bridging Nb layers in the crack wake. These zones were of sufficient size that large scale bridging conditions generally dominated. R-curve modeling using weight function methods allowed simple approximations of the bridging traction functions which were then used to make small scale bridging predictions of the steady state toughness for each laminate. Promising fatigue crack growth resistance properties were observed for the Nb/Nbsb3Al laminates evaluated under cyclic loading conditions. The laminates provided significantly better fatigue resistance than both Nbsb3Al and Nb/Nbsb3Al particulate composites. For a given composite layer thickness, the arrester orientation showed improved cyclic crack growth resistance as compared to divider orientation. The enhanced fatigue behavior of these composites resulted from extrinsic

  5. Corrosion resistance of enamel coating modified by calcium silicate and sand particle for steel reinforcement in concrete

    NASA Astrophysics Data System (ADS)

    Tang, Fujian

    Porcelain enamel has stable chemical property in harsh environments such as high temperature, acid and alkaline, and it can also chemically react with substrate reinforcing steel resulting in improved adherence strength. In this study, the corrosion resistances of enamel coating modified by calcium silicate and sand particles, which are designed for improved bond strength with surrounding concrete, were investigated in 3.5 wt% NaCl solution. It consists of two papers that describe the results of the study. The first paper investigates the corrosion behavior of enamel coating modified by calcium silicate applied to reinforcing steel bar in 3.5 wt% NaCl solution by OCP, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization. The coatings include a pure enamel, a mixed enamel that consists of 50% pure enamel and 50% calcium silicate by weight, and a double enamel that has an inner pure enamel layer and an outer mixed enamel layer. Electrochemical tests demonstrates that both pure and double enamel coatings can significantly improve corrosion resistance, while the mixed enamel coating offers very little protection due to connected channels. The second paper is focused on the electrochemical characteristics of enamel coating modified by sand particle applied to reinforcing steel bar in 3.5 wt% NaCl solution by EIS. Six percentages by weight are considered including 5%, 10%, 20%, 30%, 50%, and 70%. Results reveal that addition of sand particle does not affect its corrosion resistance significantly. Most of the sand particles can wet very well with enamel body, while some have a weak zone which is induced during the cooling stage due to different coefficient of thermal expansion. Therefore, quality control of sand particle is the key factor to improve its corrosion resistance.

  6. Matrix Dominated Failure of Fiber-Reinforced Composite Laminates Under Static and Dynamic Loading

    NASA Astrophysics Data System (ADS)

    Schaefer, Joseph Daniel

    Hierarchical material systems provide the unique opportunity to connect material knowledge to solving specific design challenges. Representing the quickest growing class of hierarchical materials in use, fiber-reinforced polymer composites (FRPCs) offer superior strength and stiffness-to-weight ratios, damage tolerance, and decreasing production costs compared to metals and alloys. However, the implementation of FRPCs has historically been fraught with inadequate knowledge of the material failure behavior due to incomplete verification of recent computational constitutive models and improper (or non-existent) experimental validation, which has severely slowed creation and development. Noted by the recent Materials Genome Initiative and the Worldwide Failure Exercise, current state of the art qualification programs endure a 20 year gap between material conceptualization and implementation due to the lack of effective partnership between computational coding (simulation) and experimental characterization. Qualification processes are primarily experiment driven; the anisotropic nature of composites predisposes matrix-dominant properties to be sensitive to strain rate, which necessitates extensive testing. To decrease the qualification time, a framework that practically combines theoretical prediction of material failure with limited experimental validation is required. In this work, the Northwestern Failure Theory (NU Theory) for composite lamina is presented as the theoretical basis from which the failure of unidirectional and multidirectional composite laminates is investigated. From an initial experimental characterization of basic lamina properties, the NU Theory is employed to predict the matrix-dependent failure of composites under any state of biaxial stress from quasi-static to 1000 s-1 strain rates. It was found that the number of experiments required to characterize the strain-rate-dependent failure of a new composite material was reduced by an order of

  7. Characterization and modeling of three-dimensional self-healing shape memory alloy-reinforced metal-matrix composites

    SciTech Connect

    Zhu, Pingping; Cui, Zhiwei; Kesler, Michael S.; Newman, John A.; Manuel, Michele V.; Wright, M. Clara; Brinson, L. Catherine

    2016-09-10

    In this paper, three-dimensional metal-matrix composites (MMCs) reinforced by shape memory alloy (SMA) wires are modeled and simulated, by adopting an SMA constitutive model accounting for elastic deformation, phase transformation and plastic behavior. A modeling method to create composites with pre-strained SMA wires is also proposed to improve the self-healing ability. Experimental validation is provided with a composite under three-point bending. This modeling method is applied in a series of finite element simulations to investigate the self-healing effects in pre-cracked composites, especially the role of the SMA reinforcement, the softening property of the matrix, and the effect of pre-strain in the SMA. The results demonstrate that SMA reinforcements provide stronger shape recovery ability than other, non-transforming materials. The softening property of the metallic matrix and the pre-strain in SMA are also beneficial to help crack closure and healing. This modeling approach can serve as an efficient tool to design SMA-reinforced MMCs with optimal self-healing properties that have potential applications in components needing a high level of reliability.

  8. Expansion and hydrodynamic properties of cellulose-stainless steel powder composite matrix for expanded bed adsorption.

    PubMed

    Lin, Dong-Qiang; Miao, Zhi-Jun; Yao, Shan-Jing

    2006-02-24

    For better understanding the influences of solid phase properties on the performance of the expanded bed, the expansion and hydrodynamic properties of cellulose-stainless steel powder composite matrix with a series of densities was investigated and analyzed in an expanded bed. Two kinds of matrix particle diameter fractions, the small one (60-125 microm) and the large (125-300 microm), were used in the present work. In general, the expansion factors decreased obviously with the increase of matrix density. A linear relation between the mean density of matrix and superficial velocity at expansion factor of 2.5 was found for same series of matrices. The Richardson-Zaki equation could correlate the bed expansion and operation fluid velocity for all matrices tested. The theoretical prediction of correlation parameters (the terminal settling velocity U(t) and expansion index n) was improved with the modification of equations in the literature. The residence time distributions were investigated to characterize the hydrodynamic property in expanded bed. Compared with three evaluation factors (the height equivalent of theoretical plate, Bo number and axial distribution coefficient D(ax)), the results indicated that D(ax) is the best parameter to analyze the bed stability of expanded bed under various operation conditions and matrix properties. In addition, it was found that fluid velocity is the most essential factor to influence the hydrodynamic properties in the bed. A linear relation between the D(ax) and superficial fluid velocity for all matrices tested was established.

  9. Field Trial of impressed current, sacrificial anode, constant voltage and intermittent cathodic protection on a steel reinforced coastal bridge

    SciTech Connect

    Bullard, S.J.; Covino, B.S., Jr.; Williamson, K.M.; Holcomb, G.R.; Ziomek-Moroz, M.; Eden, D.A.; Cryer, C.B.; Tran, H.

    2007-03-01

    Equipment has been designed and installed for a field trial being conducted on a coastal reinforced concrete bridge with a newly installed cathodic protection (CP) system. The purpose of the field trial is to determine the optimum form of intermittent CP for protecting coastal bridges. The forms of CP that were considered for the field trial are: (1) impressed current CP as the control; (2) currentinterrupted ICCP; (3) corrosion rate monitoring device controlled ICCP; (4) constant voltage CP; and (5) sacrificial anode CP. Once the test is initiated, the performance of these four forms of CP on a coastal RC bridge and their effectiveness in providing protection to reinforcing steel will be is compared with that achieved by present Oregon Department of Transportation ICCP practices. Details are presented on the set up of the experiment and the logic used to control CP intermittently. The field trial is scheduled to be started early 2007.

  10. Fracture analysis of a high-strength concrete and a high-strength steel-fiber-reinforced concrete

    NASA Astrophysics Data System (ADS)

    Ferreira, L. E. T.

    2007-09-01

    This paper addresses the use of R-curves to study the fracture behavior of high-strength concrete and steel-fiber-reinforced concrete subjected to crack ing in a three-point bending configuration. The R-curves are modeled through an effective approach based on the equations of linear-elastic fracture mechanics (LEFM), which relates the applied load to the fundamental displacements of notched-through beams loaded monotonically. It is initially shown that, for quasi-brittle materials, the R-curves responses can be evaluated in a quasi-analytical way, using the load-crack mouth opening, the load-load line displacement, or exclusively the displacement responses obtained experimentally. Afterward, the methodology is used to obtain the fracture responses of high-strength and fiber-reinforced concretes, up to the final stages of rupture.

  11. Calculating the Resistance of Lateral Manganin Gauges in a Steel Matrix

    SciTech Connect

    Harris, E. J.; Winter, R. E.

    2006-07-28

    High resolution computer simulations of manganin gauges mounted to measure lateral stresses in a steel matrix subject to nominally 1-D shock have been run using the AWE Eulerian code Shamrock. The components of the stress and strain in each of the cells in the manganin element have been obtained from the code. Piezoresistive and plastic strain coefficients derived by previous workers have been used to compute the resistivity of each cell in the gauge and, ultimately, the total resistance change of the gauge. The predicted resistance changes are compared with existing experimental data.

  12. Behaviour and Analysis of Steel and Macro-Synthetic Fibre Reinforced Concrete Subjected to Reversed Cyclic Loading: A Pilot Investigation

    NASA Astrophysics Data System (ADS)

    Carnovale, David Joseph

    The benefits of fibre reinforced concrete (FRC) have been thoroughly investigated. Much of this work has focussed on steel FRC subjected to monotonic loads. Data on the structural behaviour of macro-synthetic FRC or FRC under cyclic loads is scarce. A pilot investigation on the shear behaviour of macro-synthetic FRC and on the behaviour of FRC under reversed cyclic in-plane shear loading was carried out. Five in-plane shear panel tests were performed. The parameters under study were the fibre material type (steel or macrosynthetic) and loading protocol. Additionally, a number of compression, direct tension, and flexural tests were performed to determine the material properties of the concretes for comparison. The material response of 2.0% by volume of macro-synthetic FRC matched closely with 1.0% steel FRC. Finally, building upon an existing steel FRC model, a model for macro-synthetic FRC in tension was proposed and a short verification study was undertaken.

  13. Corrosion detection of steel reinforced concrete using combined carbon fiber and fiber Bragg grating active thermal probe

    NASA Astrophysics Data System (ADS)

    Li, Weijie; Ho, Siu Chun Michael; Song, Gangbing

    2016-04-01

    Steel reinforcement corrosion is one of the dominant causes for structural deterioration for reinforced concrete structures. This paper presents a novel corrosion detection technique using an active thermal probe. The technique takes advantage of the fact that corrosion products have poor thermal conductivity, which will impede heat propagation generated from the active thermal probe. At the same time, the active thermal probe records the temperature response. The presence of corrosion products can thus be detected by analyzing the temperature response after the injection of heat at the reinforcement-concrete interface. The feasibility of the proposed technique was firstly analyzed through analytical modeling and finite element simulation. The active thermal probe consisted of carbon fiber strands to generate heat and a fiber optic Bragg grating (FBG) temperature sensor. Carbon fiber strands are used due to their corrosion resistance. Wet-dry cycle accelerated corrosion experiments were performed to study the effect of corrosion products on the temperature response of the reinforced concrete sample. Results suggest a high correlation between corrosion severity and magnitude of the temperature response. The technique has the merits of high accuracy, high efficiency in measurement and excellent embeddability.

  14. The erosion performance of particle reinforced metal matrix composite coatings produced by co-deposition cold gas dynamic spraying

    NASA Astrophysics Data System (ADS)

    Peat, Tom; Galloway, Alexander; Toumpis, Athanasios; McNutt, Philip; Iqbal, Naveed

    2017-02-01

    This work reports on the erosion performance of three particle reinforced metal matrix composite coatings, co-deposited with an aluminium binder via cold-gas dynamic spraying. The deposition of ceramic particles is difficult to achieve with typical cold spray techniques due to the absence of particle deformation. This issue has been overcome in the present study by simultaneously spraying the reinforcing particles with a ductile metallic binder which has led to an increased level of ceramic/cermet particles deposited on the substrate with thick (>400 μm) coatings produced. The aim of this investigation was to evaluate the erosion performance of the co-deposited coatings within a slurry environment. The study also incorporated standard metallographic characterisation techniques to evaluate the distribution of reinforcing particles within the aluminium matrix. All coatings exhibited poorer erosion performance than the uncoated material, both in terms of volume loss and mass loss. The Al2O3 reinforced coating sustained the greatest amount of damage following exposure to the slurry and recorded the greatest volume loss (approx. 2.8 mm3) out of all of the examined coatings. Despite the poor erosion performance, the WC-CoCr reinforced coating demonstrated a considerable hardness increase over the as-received AA5083 (approx. 400%) and also exhibited the smallest free space length between adjacent particles. The findings of this study reveal that the removal of the AA5083 matrix by the impinging silicon carbide particles acts as the primary wear mechanism leading to the degradation of the coating. Analysis of the wear scar has demonstrated that the damage to the soft matrix alloy takes the form of ploughing and scoring which subsequently exposes carbide/oxide particles to the impinging slurry.

  15. Strain measurement in a concrete beam by use of the Brillouin-scattering-based distributed fiber sensor with single-mode fibers embedded in glass fiber reinforced polymer rods and bonded to steel reinforcing bars.

    PubMed

    Zeng, Xiaodong; Bao, Xiaoyi; Chhoa, Chia Yee; Bremner, Theodore W; Brown, Anthony W; DeMerchant, Michael D; Ferrier, Graham; Kalamkarov, Alexander L; Georgiades, Anastasis V

    2002-08-20

    The strain measurement of a 1.65-m reinforced concrete beam by use of a distributed fiber strain sensor with a 50-cm spatial resolution and 5-cm readout resolution is reported. The strain-measurement accuracy is +/-15 microepsilon (microm/m) according to the system calibration in the laboratory environment with non-uniform-distributed strain and +/-5 microepsilon with uniform strain distribution. The strain distribution has been measured for one-point and two-point loading patterns for optical fibers embedded in pultruded glass fiber reinforced polymer (GFRP) rods and those bonded to steel reinforcing bars. In the one-point loading case, the strain deviations are +/-7 and +/-15 microepsilon for fibers embedded in the GFRP rods and fibers bonded to steel reinforcing bars, respectively, whereas the strain deviation is +/-20 microepsilon for the two-point loading case.

  16. The effect of matrix microstructure on the tensile and fatigue behavior of SiC particle-reinforced 2080 Al matrix composites

    SciTech Connect

    Chawla, N.; Habel, U.; Shen, Y.L.; Andres, C.; Jones, J.W.; Allison, J.E.

    2000-02-01

    The effect of matrix microstructure on the stress-controlled fatigue behavior of a 2080 Al alloy reinforced with 30 pct SiC particles was investigated. A thermomechanical heat treatment (T8) produced a fine and homogeneous distribution of S{prime} precipitates, while a thermal heat treatment (T6) resulted in coarser and inhomogeneously distributed S{prime} precipitates. The cyclic and monotonic strength, as well as the cyclic stress-strain response, were found to be significantly affected by the microstructure of the matrix. Because of the finer and more-closely spaced precipitates, the composite given the T8 treatment exhibited higher yield strengths than the T6 materials. Despite its lower yield strength, the T6 matrix composite exhibited higher fatigue resistance than the T8 matrix composite. The cyclic deformation behavior of the composites is compared to monotonic deformation behavior and is explained in terms of microstructural instabilities that cause cyclic hardening or softening. The effect of precipitate spacing and size has a significant effect on fatigue behavior and is discussed. The interactive role of matrix strength and SiC reinforcement on stress within rogue inclusions was quantified using a finite-element analysis (FEA) unit-cell model.

  17. Self-healing of damage in fibre-reinforced polymer-matrix composites.

    PubMed

    Hayes, S A; Zhang, W; Branthwaite, M; Jones, F R

    2007-04-22

    Self-healing resin systems have been discussed for over a decade and four different technologies had been proposed. However, little work on their application as composite matrices has been published although this was one of the stated aims of the earliest work in the field. This paper reports on the optimization of a solid-state self-healing resin system and its subsequent use as a matrix for high volume fraction glass fibre-reinforced composites. The resin system was optimized using Charpy impact testing and repeated healing, while the efficiency of healing in composites was determined by analysing the growth of delaminations following repeated impacts with or without a healing cycle. To act as a reference, a non-healing resin system was subjected to the same treatments and the results are compared with the healable system. The optimized resin system displays a healing efficiency of 65% after the first healing cycle, dropping to 35 and 30% after the second and third healing cycles, respectively. Correction for any healability due to further curing showed that approximately 50% healing efficiency could be achieved with the bisphenol A-based epoxy resin containing 7.5% of polybisphenol-A-co-epichlorohydrin. The composite, on the other hand, displays a healing efficiency of approximately 30%. It is therefore clear that the solid-state self-healing system is capable of healing transverse cracks and delaminations in a composite, but that more work is needed to optimize matrix healing within a composite and to develop a methodology for assessing recovery in performance.

  18. Strain measurement in concrete structure using distributed fiber optic sensing based on Brillouin scattering with single-mode fibers embedded in glass fiber reinforcing vinyl ester rod and bonded to steel reinforcing bars

    NASA Astrophysics Data System (ADS)

    Chhoa, Cia Y.; Bao, Xiaoyi; Bremner, Theodore W.; Brown, Anthony W.; DeMerchant, Michael D.; Kalamkarov, Alexander L.; Georgiades, Anastasis V.

    2001-08-01

    The strain distribution in a 1.65m long reinforced concrete beam was measured using the distributed fiber optic sensing system developed by Dr. Bao's Fiber Optic Group at the University of New Brunswick (UNB) with center point and two point loading pattern. A spatial resolution of 0.5m was used. Past experience has shown that the bare optical fiber is too fragile to act as a sensor in a reinforced concrete structure. Therefore, in this experiment, two methods of protecting the fibers were incorporated into the concrete beam to increase the fibers' resistance to mechanical damages and prevent chemical reaction from occurring between the fibers and the concrete. The fibers were either embedded in pultruded glass fiber reinforced vinyl ester (GFRP) rods or bonded to the steel reinforcing bars with an epoxy adhesive. The strain at midspan of the beam as measured by the distributed sensing system was compared with the readings of electrical resistance strain (ERS) and mechanical strain (MS) gauges. The experimental results showed that the pultruded GFRP rods effectively protected the fibers, but the strain readings from the GFRP rods did not agree with the strain measurement of the ERS on the steel reinforcing bars due to the possible slippage of the rods in the concrete. However, the fiber bonded to steel reinforcing bars produced more accurate results and confirmed the potential of this technology to accurately measure strain in a reinforced concrete structure. As expected, the fiber with direct contact to the concrete and steel reinforcing bar, can effectively measured the strain under center point or two point loading.

  19. Microstructure and microwave absorption properties of MWCNTs reinforced magnesium matrix composites fabriccated by FSP

    NASA Astrophysics Data System (ADS)

    Chen, Yu-hua; Mao, Yu-qing; Xie, Ji-lin; Zhan, Zi-lin; Yu, Liang

    2017-01-01

    Multiwall carbon nanotubes (MWCNTs) reinforced magnesium matrix (MWCNTs/Mg) composites were successfully fabricated by friction stir processing (FSP). Microstructure and microwave-absorption properties of WCNTs/Mg composites are studied. The results show that with increasing the MWCNTs content to 7.1% in volume fraction, the agglomeration of MWCNTs is found in the WCNTs/Mg composites. The addition of MWCNTs has little effect on microwave-absorption properties. With increasing the frequency from 2 GHz to 18 GHz, the microwave absorption of the composites decreases. Compared with the absorption loss of the MWCNTs, the reflection loss of base material takes the most part of the loss of the microwave, and the increase of the reflection loss can promote electromagnetic shielding properties of the composites. Moreover, the electromagnetic shielding properties of the composites are less than -85 dB in the lower frequency range from 0.1 MHz to 3 GHz. With increasing the content of MWCNTs, the electrical conductivity of the composites is decreased, and the electromagnetic shielding properties is slightly enhanced.

  20. Mechanical properties of waste paper/jute fabric reinforced polyester resin matrix hybrid composites.

    PubMed

    Das, Sekhar

    2017-09-15

    Hybrid composites were prepared with jute fabric and un-shredded newspaper in polyester resin matrix. The experiment was designed 1:2 weights ratio jute and unshredded newspaper to have 42 (w/w)% fibre content hybrid composites and two different sequences jute/paper/jute and paper/jute/paper of waste newspaper and jute fabric arrangement. Reinforcing material is characterized by chemically, X-ray diffraction methods, Fourier transform infrared spectroscopy and tensile testing. The tensile, flexural and interlaminar shear strength and fracture surface morphology of composites were evaluated and compared. It was found that tensile and flexural properties of the hybrid composite are higher than that of pure paper-based composite but less than pure woven jute composite. The hybridization effect of woven jute fabric and layering pattern effect on mechanical properties of newspaper/woven jute fabric hybrid composites were studied. The test results of composites were analyzed by one-way ANOVA (α=0.05), it showed significant differences among the groups. Copyright © 2017 Elsevier Ltd. All rights reserved.

  1. Fracture behavior of reinforced aluminum alloy matrix composites using thermal imaging tools

    NASA Astrophysics Data System (ADS)

    Avdelidis, N. P.; Exarchos, D.; Vazquez, P.; Ibarra-Castanedo, C.; Sfarra, S.; Maldague, X. P. V.; Matikas, T. E.

    2016-05-01

    In this work the influence of the microstructure at the vicinity of the interface on the fracture behavior of particulate-reinforced aluminum alloy matrix composites (Al/SiCp composites) is studied by using thermographic tools. In particular, infrared thermography was used to monitor the plane crack propagation behavior of the materials. The deformation of solid materials is almost always accompanied by heat release. When the material becomes deformed or is damaged and fractured, a part of the energy necessary to initiate and propagate the damage is transformed in an irreversible way into heat. The thermal camera detects the heat wave, generated by the thermo-mechanical coupling and the intrinsic dissipated energy during mechanical loading of the sample. By using an adapted detector, thermography records the two dimensional "temperature" field as it results from the infrared radiation emitted by the object. The principal advantage of infrared thermography is its noncontact, non-destructive character. This methodology is being applied to characterise the fracture behavior of the particulate composites. Infrared thermography is being used to monitor the plane crack propagation behavior of such materials. Furthermore, an innovative approach to use microscopic measurements using IR microscopic lenses was attempted, in order to enable smaller features (in the micro scale) to be imaged with accuracy and assurance.

  2. Detection and Inspection of Steel Bars in Reinforced Concrete Structures Using Active Infrared Thermography with Microwave Excitation and Eddy Current Sensors.

    PubMed

    Szymanik, Barbara; Frankowski, Paweł Karol; Chady, Tomasz; John Chelliah, Cyril Robinson Azariah

    2016-02-16

    The purpose of this paper is to present a multi-sensor approach to the detection and inspection of steel bars in reinforced concrete structures. In connection with our past experience related to non-destructive testing of different materials, we propose using two potentially effective methods: active infrared thermography with microwave excitation and the eddy current technique. In this article active infrared thermography with microwave excitation is analyzed both by numerical modeling and experiments. This method, based on thermal imaging, due to its characteriatics should be considered as a preliminary method for the assessment of relatively shallowly located steel bar reinforcements. The eddy current technique, on the other hand, allows for more detailed evaluation and detection of deeply located rebars. In this paper a series of measurement results, together with the initial identification of certain features of steel reinforcement bars will be presented.

  3. Detection and Inspection of Steel Bars in Reinforced Concrete Structures Using Active Infrared Thermography with Microwave Excitation and Eddy Current Sensors

    PubMed Central

    Szymanik, Barbara; Frankowski, Paweł Karol; Chady, Tomasz; John Chelliah, Cyril Robinson Azariah

    2016-01-01

    The purpose of this paper is to present a multi-sensor approach to the detection and inspection of steel bars in reinforced concrete structures. In connection with our past experience related to non-destructive testing of different materials, we propose using two potentially effective methods: active infrared thermography with microwave excitation and the eddy current technique. In this article active infrared thermography with microwave excitation is analyzed both by numerical modeling and experiments. This method, based on thermal imaging, due to its characteriatics should be considered as a preliminary method for the assessment of relatively shallowly located steel bar reinforcements. The eddy current technique, on the other hand, allows for more detailed evaluation and detection of deeply located rebars. In this paper a series of measurement results, together with the initial identification of certain features of steel reinforcement bars will be presented. PMID:26891305

  4. Effect of Matrix Multicracking on the Hysteresis Loops of Carbon-Fiber-Reinforced Cross-Ply Ceramic-Matrix Composites

    NASA Astrophysics Data System (ADS)

    Li, L. B.

    2017-01-01

    The effect of matrix multicracking on the stress-strain hysteresis loops of cross-ply C/SiC ceramic-matrix composites (CMCs) under cyclic loading/unloading was investigated. When matrix multicracking and fiber/matrix interface debonding occur in the 0° plies, fiber slipping relative to the matrix in the debonded region of interface is the mainly reason for occurrence of the loops. The interfacial slip lengths, i.e., the debonded lengths of interface are determined, with consideration of matrix multicracking in the 90° and 0° plies, by using the fracture mechanics approach. The effects of peak stress, fiber volume content, fiber/matrix interfacial shear stress, and number of cycles on the hysteresis loops are analyzed. The stress-strain hysteresis loops of cross-ply C/SiC composites corresponding to different peak stresses and numbers of cycles are predicted.

  5. Comparing energy use and environmental emissions of reinforced wood doors and steel doors

    Treesearch

    Lynn Knight; Melissa Huff; Janet I. Stockhausen; Robert J. Ross

    2005-01-01

    The USDA Forest Service Forest Products Laboratory has patented a technology that incorporates fiberglass-reinforced wood into the structure of wood doors and other wood building products. The process of reinforcing wood doors with epoxy and fiberglass increases the strength and durability of the product. Also, it allows the use of low-value, small-diameter wood which...

  6. Hot Extrusion of A356 Aluminum Metal Matrix Composite with Carbon Nanotube/Al2O3 Hybrid Reinforcement

    NASA Astrophysics Data System (ADS)

    Kim, H. H.; Babu, J. S. S.; Kang, C. G.

    2014-05-01

    Over the years, the attention of material scientists and engineers has shifted from conventional composite materials to nanocomposite materials for the development of light weight and high-performance devices. Since the discovery of carbon nanotubes (CNTs), many researchers have tried to fabricate metal matrix composites (MMCs) with CNT reinforcements. However, CNTs exhibit low dispersibility in metal melts owing to their poor wettability and large surface-to-volume ratio. The use of an array of short fibers or hybrid reinforcements in a preform could overcome this problem and enhance the dispersion of CNTs in the matrix. In this study, multi-walled CNT/Al2O3 preform-based aluminum hybrid composites were fabricated using the infiltration method. Then, the composites were extruded to evaluate changes in its mechanical properties. In addition, the dispersion of reinforcements was investigated using a hardness test. The required extrusion pressure of hybrid MMCs increased as the Al2O3/CNT fraction increased. The deformation resistance of hybrid material was over two times that of the original A356 aluminum alloy material due to strengthening by the Al2O3/CNTs reinforcements. In addition, an unusual trend was detected; primary transition was induced by the hybrid reinforcements, as can be observed in the pressure-displacement curve. Increasing temperature of the material can help increase formability. In particular, temperatures under 623 K (350 °C) and over-incorporating reinforcements (Al2O3 20 pct, CNTs 3 pct) are not recommended owing to a significant increase in the brittleness of the hybrid material.

  7. Tensile Properties of Nano AL2O3 Particulate-Reinforced Aluminum Matrix Composites by Mechanical Alloying and Hot Extrusion

    NASA Astrophysics Data System (ADS)

    Mehdinia, M.; Jenabali Jahromi, S. A.

    The powder of the micro Al and variant volume fractions of nano Al2O3 were milled by a high energy planetary ball-mill. By milling, a homogenous distribution of nano Al2O3 particles in the metal matrix were developed. Then the milled powder was cold compressed and sintered at 545°C for one hr. The mold and the sintered sample hold in a furnace until the temperature reached 545°C. Then the hot 27mm diameter sample was extruded to 6mm diameter. From the extruded specimens, tensile, hardness and microstructure of the prepared specimens were determined. By these tests the effect of milling time, the percent of nano-particles and the microstructure were evaluated. The hardness and tensile behaviors of aluminum matrix composites reinforced with nano Al2O3 particulate have been found to increase remarkably with the volume fraction of the reinforcement.

  8. Approach to In- Situ Producing Reinforcing Phase Within an Active-Transient Liquid Phase Bond Seam for Aluminum Matrix Composite

    NASA Astrophysics Data System (ADS)

    Zhang, Guifeng; Liao, Xianjin; Chen, Bo; Zhang, Linjie; Zhang, Jianxun

    2015-06-01

    To optimize the braze composition design route for aluminum matrix composite, the feasibility of in situ producing reinforcing phase within the transient liquid phase bond seam matrix, by adding active melting point increaser (MPI, e.g., Ti) together with general melting point depressant (MPD, e.g., Cu) into the interlayer, was demonstrated. For SiC p /A356 composite, by comparing the wettability, joint microstructure, joint shear strength, and fracture path for the developed Al-19Cu-1Ti, Al-19Cu, Al-33Cu-1Ti, Al-33Cu (wt pct), and commercial Cu foils as interlayer, the feasibility of in situ producing reinforcing phase within the bond seam by adding Ti was demonstrated. Especially for Al-19Cu-1Ti active braze, small and dispersed ternary aluminide of Al-Si-Ti phase was obtained within the bond seam as in situ reinforcement, leading to a favorable fracture path within SiC p /A356, not along the initial interface or within the bond seam. For the formation mechanism of the in situ reinforcing phase of MPI-containing intermetallic compound within the bond seam, a model of repeating concentration-precipitation-termination-engulfment during isothermal solidification is proposed.

  9. Corrosion of Continuous Fiber Reinforced Aluminum Metal Matrix Composites (CF-AMCs)

    NASA Astrophysics Data System (ADS)

    Tiwari, Shruti

    The first objective of this research is to study the atmospheric corrosion behavior of continuous reinforced aluminum matrix composites (CF-AMCs). The materials used for this research were alumina (Al2O3) and nickel (Ni) coated carbon (C) fibers reinforced AMCs. The major focus is to identify the correlation between atmospheric parameters and the corrosion rates of CF-AMCs in the multitude of microclimates and environments in Hawai'i. The micro-structures of CF-AMCs were obtained to correlate the microstructures with their corrosion performances. Also electrochemical polarization experiments were conducted in the laboratory to explain the corrosion mechanism of CF-AMCs. In addition, CF-AMCs were exposed to seven different test sites for three exposure periods. The various climatic conditions like temperature (T), relative humidity (RH), rainfall (RF), time of wetness (TOW), chloride (Cl- ) and sulfate (SO42-) deposition rate, and pH were monitored for three exposure period. Likewise, mass losses of CF-AMCs at each test site for three exposure periods were determined. The microstructure of the CF-AMCS showed that Al/C/50f MMCs contained a Ni-rich phase in the matrix, indicating that the Ni coating on the C fiber dissolved in the matrix. The intermetallic phases obtained in Al-2wt% Cu/Al 2O3/50f-T6 MMC and Al-2wt%-T6 monolith were rich in Cu and Fe. The intermetallic phases obtained in Al 7075/Al2O3/50f-T6 MMC and Al 7075-T6 monolith also contained traces of Mg, Zn, Ni, and Si. Electrochemical polarization experiment indicated that the Al/Al 2O3/50f Al-2wt% Cu/Al2O3/50f-T6 and Al 7075/Al2O3/50f-T6 MMC showed similar corrosion trends as their respective monoliths pure Al, Al-2wt%-T6 and Al 7075-T6 in both aerated and deaerated condition. Al2O3 fiber, being an insulator, did not have a great effect on the polarization behavior of the composites. Al/C/50f MMCs corroded at a much faster rate as compared to pure Al monolith due to the galvanic effect between C and Al

  10. Lifetime Response of a Hi-Nicalon Fiber-Reinforced Melt-Infiltrated SiC Matrix Composites

    SciTech Connect

    Becher, P.F.; Lin, H.T.; Singh, M.

    1999-04-25

    Lifetime studies in four-point flexure were performed on a Hi-NicalonTM fiber-reinforced SiC matrix composite over a temperature range of 700 degrees to 1150 degrees C in air. The composite consisted of ~40 vol. % Hi-NicalonTM fiber (8-harness weave) with a 0.5 Mu-m BN fiber coating and a melt-infiltration SiC matrix wand was tested with as-machined surfaces. Lifetime results indicated that the composite exhibited a stress-dependent lifetime at stress levels above an apparent fatigue limit, similar to the trend observed in CG-NicalonTM fiber reinforced CVI SiC matrix composites. At less than or equal to 950 degrees C, the lifetimes of Hi-Nicalon/MI SiC composites decreased with increasing applied stress level and test temperature. However, the lifetimes were extended as test temperature increased from 950 degees to 1150 degrees C as a result of surface crack sealing due to glass formation by the oxidation of Mi SiC matrix. The lifetime governing processes were, in general, attributed to the progressive oxidation of BN fiber coating and formation of glassy phase, which formed a strong bond between fiber and matrix, resulting in embrittlement of the composite with time.

  11. Understanding the interdiffusion behavior and determining the long term stability of tungsten fiber reinforced niobium-base matrix composite systems

    NASA Technical Reports Server (NTRS)

    Tien, John K.

    1990-01-01

    The long term interdiffusional stability of tungsten fiber reinforced niobium alloy composites is addressed. The matrix alloy that is most promising for use as a high temperature structural material for reliable long-term space power generation is Nb1Zr. As an ancillary project to this program, efforts were made to assess the nature and kinetics of interphase reaction between selected beryllide intermetallics and nickel and iron aluminides.

  12. Multi-Length Scale-Enriched Continuum-Level Material Model for Kevlar-Fiber-Reinforced Polymer-Matrix Composites

    DTIC Science & Technology

    2012-08-03

    Angstadt, Y.-P. Sun, and K.L. Koudela, Micro-Mechanics Based Derivation of the Materials Constitutive Relations for Carbon Nanotube Reinforced Poly-Vinyl...intralamina and interlamina damage mechanisms (e.g., fiber breakage within the yarns , fiber/matrix de-bonding, diffuse delamination/interlam- ina separation...a closer look is given to the architecture of the woven fabric. Specifically, details of yarn weaving and crimping, yarn cross-section change, and

  13. Thermal diffusivity of Al-Mg based metallic matrix composite reinforced with Al2O3 ceramic particles

    NASA Astrophysics Data System (ADS)

    Cruz-Orea, A.; Morales, J. E.; Saavedra S, R.; Carrasco, C.

    2010-03-01

    Thermal diffusivities of Al-Mg based metallic matrix composite reinforced with ceramic particles of Al2O3 are reported in this article. The samples were produced by rheocasting and the studied operational condition in this case is the shear rate: 800, 1400 and 2000 rpm. Additionally, the AlMg base alloy was tested. Measurements of thermal diffusivity were performed at room temperature by using photoacoustic technique.

  14. Fiber-Reinforced Concrete For Hardened Shelter Construction

    DTIC Science & Technology

    1993-02-01

    not limited to, steel, nylon, polypropylene, carbon, glass , and steel fiber - mat matrices. Based on this literature review, areas where research is...reinforce concrete in a wide range of areas, from large size tanks such as swimming pools to roofing system tiles and shingles . 3. Polymeric Fibers ...Page 1 Steel Mat Fiber Matrix Used In Test Beam Types MI And M2 ................ 12 2 Test Beam Cross-Sections. Test Phases I And H

  15. Unveiling the Semicoherent Interface with Definite Orientation Relationships between Reinforcements and Matrix in Novel Al3BC/Al Composites.

    PubMed

    Zhao, Yongfeng; Qian, Zhao; Ma, Xia; Chen, Houwen; Gao, Tong; Wu, Yuying; Liu, Xiangfa

    2016-10-05

    High-strength lightweight Al-based composites are promising materials for a wide range of applications. To provide high performance, a strong bonding interface for effective load transfer from the matrix to the reinforcement is essential. In this work, the novel Al3BC reinforced Al composites have been in situ fabricated through a liquid-solid reaction method and the bonding interface between Al3BC and Al matrix has been unveiled. The HRTEM characterizations on the Al3BC/Al interface verify it to be a semicoherent bonding structure with definite orientation relationships: (0001)Al3BC//(11̅1)Al;[112̅0]Al3BC//[011]Al. Periodic arrays of geometrical misfit dislocations are also observed along the interface at each (0001)Al3BC plane or every five (11̅1)Al planes. This kind of interface between the reinforcement and the matrix is strong enough for effective load transfer, which would lead to the evidently improved strength and stiffness of the introduced new Al3BC/Al composites.

  16. Use of GIS for the development of digital structural integrity maps of high risk areas in Cyprus due to corrosion of steel reinforcement

    NASA Astrophysics Data System (ADS)

    Christofe, Andreas; Neocleous, Kyriacos; Themistocleous, Kyriacos; Agapiou, Athos; Hadjimitsis, Diofantos G.

    2013-08-01

    Concrete reinforced with steel rebars remains one of the most widely used construction materials. Despite its good mechanical performance and expected service life of at least 50 years, reinforced concrete is subjected to corrosion of the steel rebars which normally leads to concrete spalling, deterioration of the reinforced concrete's (RC) mechanical properties and eventual reduction of the structural load capacity. In Cyprus, especially in coastal regions where almost 60% of the population resides, many structural problems have been identified in RC structures, which are caused by the severe corrosion of steel rebars. Most RC, located in coastal areas, show signs of corrosion within the first 15-20 years of their service life and this affects their structural integrity and reliability, especially against seismic loading. This paper presents the research undertaken as part of the `STEELCOR' project which aims to extensively evaluate the steel corrosion of RC buildings in coastal areas of Cyprus and conduct a risk assessment relating to steel corrosion. GIS are utilized in conjunction with non-destructive testing of corroded RC structures to develop a digital structural integrity map of Cyprus which shows the areas with high risk of steel corrosion of RC buildings.

  17. Improvement of Wear Resistance in Alumina Matrix Composites Reinforced with Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Kim, Sung Wan; Chung, Won Sub; Sohn, Kee-Sun; Son, Chang-Young; Lee, Sunghak

    2010-02-01

    Alumina matrix composites reinforced with carbon nanotubes (CNTs) fabricated by CNT purification, mixing, compaction, and sintering processes, and the effects of the CNT addition on wear resistance were investigated in relation to the relative density, hardness, and fracture toughness. Wear resistance and fracture toughness were measured by the dry sliding wear test method and the indentation fracture test method, respectively. Zero to ~3 vol pct of CNTs were homogeneously distributed in the composites, although some pores existed. The wear resistance and fracture toughness increased with an increasing CNT fraction, but the composite specimen containing 3.0 vol pct of CNTs hardly showed an increase over the specimen containing 2.25 vol pct of CNTs. Observations of worn surfaces revealed that the wear mechanism involved both the abrasive and delamination wear modes in the specimens containing 0 to ~0.75 vol pct of CNTs, whereas the surface was worn largely in an abrasive wear mode in the specimens containing 1.5 to ~3.0 vol pct of CNTs. This was because CNTs helped to change the delamination wear mode to the abrasive wear mode by preventing crack initiation and propagation at alumina grains. The fracture toughness increase provided beneficial effects in the resistance to crack initiation and propagation, the reduction in delamination wear on the worn surface, and the consequent improvement in wear resistance. Because the effect of the porosity increase due to the CNT addition unfavorably affected the improvement of wear resistance and fracture toughness in the specimen containing 3.0 vol pct of CNTs, the appropriate level of CNT fraction was 1.5 to ~2.25 vol pct.

  18. Mechanical characterization of copper coated carbon nanotubes reinforced aluminum matrix composites

    SciTech Connect

    Maqbool, Adnan; Hussain, M. Asif; Khalid, F. Ahmad; Bakhsh, Nabi; Hussain, Ali; Kim, Myong Ho

    2013-12-15

    In this investigation, carbon nanotube (CNT) reinforced aluminum composites were prepared by the molecular-level mixing process using copper coated CNTs. The mixing of CNTs was accomplished by ultrasonic mixing and ball milling. Electroless Cu-coated CNTs were used to enhance the interfacial bonding between CNTs and aluminum. Scanning electron microscope analysis revealed the homogenous dispersion of Cu-coated CNTs in the composite samples compared with the uncoated CNTs. The samples were pressureless sintered under vacuum followed by hot rolling to promote the uniform microstructure and dispersion of CNTs. In 1.0 wt.% uncoated and Cu-coated CNT/Al composites, compared to pure Al, the microhardness increased by 44% and 103%, respectively. As compared to the pure Al, for 1.0 wt.% uncoated CNT/Al composite, increase in yield strength and ultimate tensile strength was estimated about 58% and 62%, respectively. However, in case of 1.0 wt.% Cu-coated CNT/Al composite, yield strength and ultimate tensile strength were increased significantly about 121% and 107%, respectively. - Graphical Abstract: Copper coated CNTs were synthesized by the electroless plating process. Optimizing the plating bath to (1:1) by wt CNTs with Cu, thickness of Cu-coated CNTs has been reduced to 100 nm. Cu-coated CNTs developed the stronger interfacial bonding with the Al matrix which resulted in the efficient transfer of load. Highlights: • Copper coated CNTs were synthesized by the electroless plating process. • Thickness of Cu-coated CNTs has been reduced to 100 nm by optimized plating bath. • In 1.0 wt.% Cu-coated CNT/Al composite, microhardness increased by 103%. • Cu-coated CNTs transfer load efficiently with stronger interfacial bonding. • In 1.0 wt.% Cu-coated CNT/Al composite, Y.S and UTS increased by 126% and 105%.

  19. Synthesis of Carbon Nanotube-Reinforced Al2024 Matrix Nanocomposite Using Flake Powder Metallurgy Method

    NASA Astrophysics Data System (ADS)

    Rikhtegar, F.; Shabestari, S. G.; Saghafian, H.

    2016-12-01

    In current work, the flake powder metallurgy method was applied to achieve the uniform dispersion of carbon nanotubes (CNTs) within the Al2024 powder. For this purpose, the flake morphology of Al2024 powder with suitable diameter-to-thickness ratio ( D/ t = 85) was obtained after ball milling for 4 hours at 250 rpm and ball-to-powder ratio = 10. Then, the surface of matrix was modified by a hydrophilic polymer [polyvinyl alcohol (PVA)] to obtain the sufficient -OH group on its surface. Additionally, the refluxing of CNTs in nitric acid was performed at 393 K (120 °C) for 6 hours to functionalize the reinforcement by -COOH agent. After preparation of initial materials, the Al2024-1.5 wt pct CNTs suspension was stirred in a slurry at pH 3 until the color was changed in steady state from ink-like to transparent at pH 5. The hydrogen bonding was formed between the -OH groups of PVA coated Al2024 and -COOH groups of functionalized MWCNTs during the mixing step. Also, the temporary polarity could be considered between H+ and {{{C}}_{12}}{{{H}}_{25}}{{SO}}_4^ - ions on the surface of constituents, which led to improvement in the CNT distribution due to the changing of suspension pH. Consequently, the homogenous dispersion of CNTs in Al2024 flaky powders resulted in a chemical reaction of constituents without any destructive effects of mechanical forces. The morphological changes of Al2024 powders were studied by scanning electron microscopy (SEM), and surface treatments were evaluated by Fourier transform infrared and Raman spectroscopies. The dispersion of nanocomposite powder was investigated through field emission SEM. Also, X-ray diffraction analysis was used to investigate the initial Al2024 powder and formed phases after the ball milling process.

  20. Metal matrix composite structures

    SciTech Connect

    Krivov, G.A.; Beletsky, V.M.; Gribkov, A.N.

    1993-12-31

    High strength-weight properties, stiffness and fatigue resistance characteristics together with low sensitivity to stress concentration make metal matrix composites (MMC) rather promising for their use in structures. Metal matrix composites consist of a matrix (aluminum, magnesium, titanium and their alloys are the most frequently used) and reinforcers (carbon and boron fibers, high-strength steel wire, silicon carbide whiskers, etc.). This work considers various types of MMC and their applications in structures. The methods of structure production from metal matrix CM of aluminum-boron system with the help of machining, deformation, part joining by welding and riveting are given.

  1. Finite element analysis of bridge steel pedestal anchor bolts in reinforced concrete

    NASA Astrophysics Data System (ADS)

    Logan Hancock, B.; Hite Head, Monique

    2009-10-01

    Steel pedestals are short, column-like structures currently being used to elevate highway bridges to reduce the risk of collisions with over-height vehicles. Previous full-scale experimental research has been done to examine the efficacy of these steel pedestals and their components under quasi-static loading to evaluate any added instability in the event of an earthquake. As part of the Undergraduate Summer Research Grant (USRG) program at Texas A&M University, this specific project was focused on observing the behavior of the post-installed steel pedestal anchor bolts under applied shear and tensile loading using the finite element (FE) software Abaqus. The results from some of the preliminary analyses are compared to theoretical anchorage calculations with the aim of producing a benchmark for future steel pedestal anchor bolt embedment design. Future research improvements regarding FE modeling and structural design suggestions are proposed as well.

  2. Fiber phase transformation and matrix plastic flow in a room temperature tensile strained NiTi shape memory alloy fiber reinforced 6082 aluminum matrix composite

    SciTech Connect

    Armstrong, W.D.; Lorentzen, T.

    1997-05-01

    Macroscopic tensile and in-situ neutron diffraction measurements are reported from a 20.5 volume percent, 50.7 at% Ni-Ti fiber reinforced 6082-T6 aluminum matrix composite subjected to a room temperature, 4% tensile elongation. The austenite B2(110) diffraction intensity was essentially stable until approximately 0.9% strain, beyond which, the austenite B2(110) diffraction intensity strongly decreased with increasing tensile strain. The martensite M(001) diffraction intensity strongly increased from a zero intensity intercept at approximately 2.3% strain to the conclusion of tensile straining. This report concludes that the initial decrease in austenite B2(11) diffraction intensity locates the initiation of stress induced transformations in the NiTi reinforcement, furthermore this feature corresponds with an elevated yield point region in the macroscopic tensile results. Therefore, it appears that the elevated yield point region is caused by a temporary inhibition of fiber stress induced transformations.

  3. Effect of Reinforcement Using Stainless Steel Mesh, Glass Fibers, and Polyethylene on the Impact Strength of Heat Cure Denture Base Resin - An In Vitro Study

    PubMed Central

    Murthy, H B Mallikarjuna; Shaik, Sharaz; Sachdeva, Harleen; Khare, Sumit; Haralur, Satheesh B; Roopa, K T

    2015-01-01

    Background: The impact strength of denture base resin is of great concern and many approaches have been made to strengthen acrylic resin dentures. The objective of this study was to compare the impact strength of the denture base resin with and without reinforcement and to evaluate the impact strength of denture base resin when reinforced with stainless steel mesh, glass fiber, and polyethylene fibers in the woven form. Materials and Methods: The specimens (maxillary denture bases) were fabricated using a standard polyvinylsiloxane mold with conventional heat cured polymethyl methacrylate resin. The specimens were divided into four groups (n = 10). Group I specimens or control group were not reinforced. Group II specimens were reinforced with stainless steel mesh and Group III and Group IV specimens were reinforced with three percent by weight of glass fibers and polyethylene fibers in weave form respectively. All the specimens were immersed in water for 1-week before testing. The impact strength was measured with falling weight impact testing machine. One-way analysis of variance and Tukey’s post-hoc test were used for statistical analysis. Results: Highest impact strength values were exhibited by the specimens reinforced with polyethylene fibers followed by glass fibers, stainless steel mesh, and control group. Conclusions: Reinforcement of maxillary complete dentures showed a significant increase in impact strength when compared to unreinforced dentures. Polyethylene fibers exhibit better impact strength followed by glass fibers and stainless steel mesh. By using pre-impregnated glass and polyethylene fibers in woven form (prepregs) the impact strength of the denture bases can be increased effectively. PMID:26124604

  4. Mechanical Properties of SiC, Al2O3 Reinforced Aluminium 6061-T6 Hybrid Matrix Composite

    NASA Astrophysics Data System (ADS)

    Murugan, S. Senthil; Jegan, V.; Velmurugan, M.

    2017-06-01

    This paper contains the investigation of tensile, compression and impact characterization of SiC, Al2O3 reinforced Aluminium 6061-T6 matrix hybrid composite. Hybrid matrix composite fabrication was done by stir casting method. An attempt has been made by keeping Al2O3 percentage (7%) constant and increasing SiC percentage (10, 15, and 20%). After fabricating, the samples were prepared and tested to find out the various mechanical properties like tensile, compressive, and impact strength of the developed composites of different weight % of silicon carbide and Alumina in Aluminium alloy. The main objective of the study is to compare the values obtained and choose the best composition of the hybrid matrix composite from the mechanical properties point of view.

  5. In Situ Synthesis Aluminum Borate Whiskers Reinforced TiB2 Matrix Composites for Application in Aluminum Reduction Cells

    NASA Astrophysics Data System (ADS)

    Zhang, Gang; Yang, Jianhong

    2013-11-01

    The TiB2 matrix ceramics reinforced by aluminum borate whiskers (Al18B4O33 w) had been prepared by the pressureless sintering method. The mechanical properties and densification behavior of the TiB2 matrix ceramics were investigated. The results showed that Al18B4O33 w was in situ synthesized by the reaction of boehmite (AlOOH) and TiB2 powders during the sintering process. Increasing the sintering temperature had benefited for densification of the TiB2 matrix ceramics. Al18B4O33 w could increase the flexural strength and Vicker's hardness. It is obtained that the maximum value Vicker's hardness with 1.81 GPa and flexural strength with 82 MPa for samples sintered at 1600°C.

  6. On the effect of pre-straining on the fatigue behavior of a particulate-reinforced metal-matrix composite

    SciTech Connect

    Beyer, G.; Biermann, H.; Mughrabi, H.

    1997-04-15

    Since the development of the Duralcan melt-stirring process, particulate-reinforced metal-matrix composites (MMCs) can be produced in sufficient amounts and at low enough cost to meet industrial demands. Aluminium-alloy based MMCs with Al{sub 2}O{sub 3} particulate reinforcement fabricated by casting processes have already been applied as engine components and other automotive parts, mainly because of their high strength and stiffness and their superior wear resistance. Another property of great interest and practical importance is the fatigue behavior of MMCs which has been studied repeatedly in the past. A particular aspect which has not been investigated so far is the influence of pre-straining on the fatigue properties. In view of the possibility of pre-straining during the finishing process, its effect on the fatigue behavior is of interest. Here the authors report results on the fatigue behavior of a ceramic-particle reinforced MMC obtained in the framework of a more extended study. In an earlier publication, quantitative data on the stress-dependence of the Young`s modulus in tension and compression were reported. The present paper deals with the influence of pre-straining on the fatigue properties and on the fatigue life of the aluminium-matrix composite AA6061-Al{sub 2}O{sub 3}-15p-T6. The mechanical tests were supplemented by microstructural investigations, using in particular optical, scanning (SEM) and transmission electron microscopy (TEM).

  7. Tribological Wear Behaviour and Hardness Measurement of SiC, Al2O3 Reinforced Al. Matrix Hybrid Composite

    NASA Astrophysics Data System (ADS)

    Subramanian, Senthil Murugan; Vijayan, Jegan; Muthaiah, Velmurugan

    2017-01-01

    In the present study, Aluminium Matrix Hybrid Composite (AMHC) of 6061-T6 alloy reinforced with silicon carbide (SiC) particulate and further addition of aluminium oxide (Al2O3) particulate was fabricated by stir casting process. The wear resistance and frictional properties of that AMHC were studied by performing dry sliding wear test using a pin on disk wear tester. The experiments were conducted at a constant sliding velocity of 1.57 m/s and sliding distance of 1800 m under loading conditions of 10 and 20 N. Further tests were also carried out by keeping Al2O3 percentage (7%) constant and increasing the SiC percentage (10, 15, and 20%). The results show that the reinforcement of the metal matrix with SiC and Al2O3 reduces the wear rate range and also indicate that the wear of the test specimen increases with the increasing load and sliding distance. The coefficient of friction increases with load and increasing volume content of reinforcement. The worn surfaces were examined by scanning electron microscope to study the wear mechanism. By using wear mechanism analysis, the wear surfaces and wear properties of AMHC were determined.

  8. Tribological Wear Behaviour and Hardness Measurement of SiC, Al2O3 Reinforced Al. Matrix Hybrid Composite

    NASA Astrophysics Data System (ADS)

    Subramanian, Senthil Murugan; Vijayan, Jegan; Muthaiah, Velmurugan

    2017-10-01

    In the present study, Aluminium Matrix Hybrid Composite (AMHC) of 6061-T6 alloy reinforced with silicon carbide (SiC) particulate and further addition of aluminium oxide (Al2O3) particulate was fabricated by stir casting process. The wear resistance and frictional properties of that AMHC were studied by performing dry sliding wear test using a pin on disk wear tester. The experiments were conducted at a constant sliding velocity of 1.57 m/s and sliding distance of 1800 m under loading conditions of 10 and 20 N. Further tests were also carried out by keeping Al2O3 percentage (7%) constant and increasing the SiC percentage (10, 15, and 20%). The results show that the reinforcement of the metal matrix with SiC and Al2O3 reduces the wear rate range and also indicate that the wear of the test specimen increases with the increasing load and sliding distance. The coefficient of friction increases with load and increasing volume content of reinforcement. The worn surfaces were examined by scanning electron microscope to study the wear mechanism. By using wear mechanism analysis, the wear surfaces and wear properties of AMHC were determined.

  9. Galvanic interaction between carbon fiber reinforced plastic (CFRP) composites and steel in chloride contaminated concretes

    SciTech Connect

    Torres-Acosta, A.A.; Sagues, A.A.; Sen, R.

    1998-12-31

    Experiments were performed to determine the possible extent of galvanic corrosion when CFRP and steel are in contact in chloride contaminated concrete. Three concrete environments (water-to-cement (w/c) ratio of 0.41) at relative humidities (RH) of {approx}60%, {approx}80% and {approx}95%, and 14 kg/m{sup 3} chloride were investigated. The CFRP composite potential reached between {minus}180 and {minus}590 mV (vsCSE) when it was in contact with steel at these environments. Results showed significant galvanic action in the 80% RH chloride contaminated concrete (nominal steel current densities as high as 0.3 {micro}A/cm{sup 2}).

  10. Fundamental Studies of Low Velocity Impact Resistance of Graphite Fiber Reinforced Polymer Matrix Composites. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Bowles, K. J.

    1985-01-01

    A study was conducted to relate the impact resistance of graphite fiber reinforced composites with matrix properties through gaining an understanding of the basic mechanics involved in the deformation and fracture process, and the effect of the polymer matrix structure on these mechanisms. It was found that the resin matrix structure influences the composite impact resistance in at least two ways. The integration of flexibilizers into the polymer chain structure tends to reduce the T sub g and the mechanical properties of the polymer. The reduction in the mechanical properties of the matrix does not enhance the composite impact resistance because it allows matrix controlled failure to initiate impact damage. It was found that when the instrumented dropweight impact tester is used as a means for assessing resin toughness, the resin toughness is enhanced by the ability of the clamped specimen to deflect enough to produce sufficient membrane action to support a significant amount of the load. The results of this study indicate that crossplied composite impact resistance is very much dependent on the matrix mechanical properties.

  11. Modeling the Effect of Oxidation on Tensile Strength of Carbon Fiber-Reinforced Ceramic-Matrix Composites

    NASA Astrophysics Data System (ADS)

    Longbiao, Li

    2015-12-01

    An analytical method has been developed to investigate the effect of oxidation on the tensile strength of carbon fiber - reinforced ceramic - matrix composites (CMCs). The Budiansky - Hutchinson - Evans shear - lag model was used to describe the micro stress field of the damaged composite considering fibers failure. The statistical matrix multicracking model and fracture mechanics interface debonding criterion were used to determine the matrix crack spacing and interface debonded length. The fiber strength degradation model and oxidation region propagation model have been adopted to analyze the oxidation effect on tensile strength of the composite, which is controlled by diffusion of oxygen gas through matrix cracks. Under tensile loading, the fibers failure probabilities were determined by combining oxidation model and fiber statistical failure model based on the assumption that fiber strength is subjected to two-parameter Weibull distribution and the loads carried by broken and intact fibers statisfy the global load sharing criterion. The composite can no longer support the applied load when the total loads supported by broken and intact fibers approach its maximum value. The conditions of a single matrix crack and matrix multicrackings for tensile strength considering oxidation time and temperature have been analyzed.

  12. Laser surface forming of AlCoCrCuFeNi particle reinforced AZ91D matrix composites

    NASA Astrophysics Data System (ADS)

    Meng, Guanghui; Yue, T. M.; Lin, Xin; Yang, Haiou; Xie, Hui; Ding, Xu

    2015-07-01

    Traditionally, the laser melt injection (LMI) technique can only be used for forming ceramic particles reinforced metal matrix composites (MMCs) for enhancing surface properties of lightweight engineering materials. In this research, the LMI method was employed to form metal particles reinforced MMCs on AZ91D instead. This was viable because of the unique properties of the AlCoCrCuFeNi high-entropy alloy (HEA) metal particles used. The large difference in melting point between the HEA and the substrate material (AZ91D), and the limited reaction and the lack of fusion between the HEA and Mg have made it possible that a metal particles reinforced AZ91D composite material was produced. The reason of limited reaction was considered mainly due to the relatively high mixing enthalpy between the HEA constituent elements and Mg. Although there was some melting occurred at the particles surface with some solute segregation found in the vicinity close to the surface, intermetallic compounds were not observed. With regard to the wear resistance of the MMCs, it was found that when the volume fraction of the reinforcement phase, i.e. the HEA particles, reached about 0.4, the wear volume loss of the coating was only one-seventh of that of the substrate material.

  13. The effect of recycled concrete aggregate properties on the bond strength between RCA concrete and steel reinforcement

    SciTech Connect

    Butler, L. West, J.S.; Tighe, S.L.

    2011-10-15

    The purpose of this study was to investigate the influence that replacing natural coarse aggregate with recycled concrete aggregate (RCA) has on concrete bond strength with reinforcing steel. Two sources of RCA were used along with one natural aggregate source. Numerous aggregate properties were measured for all aggregate sources. Two types of concrete mixture proportions were developed replacing 100% of the natural aggregate with RCA. The first type maintained the same water-cement ratios while the second type was designed to achieve the same compressive strengths. Beam-end specimens were tested to determine the relative bond strength of RCA and natural aggregate concrete. On average, natural aggregate concrete specimens had bond strengths that were 9 to 19% higher than the equivalent RCA specimens. Bond strength and the aggregate crushing value seemed to correlate well for all concrete types.

  14. New Insights in the Long-Term Atmospheric Corrosion Mechanisms of Low Alloy Steel Reinforcements of Cultural Heritage Buildings

    PubMed Central

    Bouchar, Marie; Dillmann, Philippe; Neff, Delphine

    2017-01-01

    Reinforcing clamps made of low alloy steel from the Metz cathedral and corroded outdoors during 500 years were studied by OM, FESEM/EDS, and micro-Raman spectroscopy. The corrosion product layer is constituted of a dual structure. The outer layer is mainly constituted of goethite and lepidocrocite embedding exogenous elements such as Ca and P. The inner layer is mainly constituted of ferrihydrite. The behaviour of the inner layer under conditions simulating the wetting stage of the RH wet/dry atmospheric corrosion cycle was observed by in situ micro-Raman spectroscopy. The disappearance of ferrihydrite near the metal/oxide interface strongly suggests a mechanism of reductive dissolution caused by the oxidation of the metallic substrate and was observed for the first time in situ on an archaeological system. PMID:28773030

  15. New Insights in the Long-Term Atmospheric Corrosion Mechanisms of Low Alloy Steel Reinforcements of Cultural Heritage Buildings.

    PubMed

    Bouchar, Marie; Dillmann, Philippe; Neff, Delphine

    2017-06-19

    Reinforcing clamps made of low alloy steel from the Metz cathedral and corroded outdoors during 500 years were studied by OM, FESEM/EDS, and micro-Raman spectroscopy. The corrosion product layer is constituted of a dual structure. The outer layer is mainly constituted of goethite and lepidocrocite embedding exogenous elements such as Ca and P. The inner layer is mainly constituted of ferrihydrite. The behaviour of the inner layer under conditions simulating the wetting stage of the RH wet/dry atmospheric corrosion cycle was observed by in situ micro-Raman spectroscopy. The disappearance of ferrihydrite near the metal/oxide interface strongly suggests a mechanism of reductive dissolution caused by the oxidation of the metallic substrate and was observed for the first time in situ on an archaeological system.

  16. Nondestructive Evaluation of Advanced Fiber Reinforced Polymer Matrix Composites: A Technology Assessment

    NASA Technical Reports Server (NTRS)

    Yolken, H. Thomas; Matzkanin, George A.

    2009-01-01

    Because of their increasing utilization in structural applications, the nondestructive evaluation (NDE) of advanced fiber reinforced polymer composites continues to receive considerable research and development attention. Due to the heterogeneous nature of composites, the form of defects is often very different from a metal and fracture mechanisms are more complex. The purpose of this report is to provide an overview and technology assessment of the current state-of-the-art with respect to NDE of advanced fiber reinforced polymer composites.

  17. Processing of a fiber-reinforced transparent glass matrix composite and study of micromechanics of load transfer from matrix to fiber using micro-fluorescence spectroscopy

    NASA Astrophysics Data System (ADS)

    Banerjee, Debangshu

    The brittleness of monolithic ceramic materials can be overcome by reinforcing them with high strength, high modulus ceramic fibers. These ceramic matrix composites exhibit improved strength, toughness, and work of fracture. Successful design of a ceramic matrix composite (CMC) depends on two factors: proper choice of fiber, matrix, and interface material, and understanding the mechanics of fracture. The conventional techniques for measuring stress and strain at a local level in CMCs are based on indirect experiments and analytical models. In recent years a couple of optical techniques have been explored for non- contact and direct evaluation of the stress and strain in materials, such as laser Raman spectroscopy and fluorescence spectroscopy. In order to employ spectroscopy to study stress in a composite, a transparent matrix was needed. In this study a SiC fiber reinforced transparent glass matrix composite was developed. A tape casting, binder burnout, and sintering route was adopted to achieve the optimum transparency with proper fiber alignment and interfacial properties. Sapphire fibers were used to act as probe to generate fluorescence signals for measuring stress. A fugitive carbon coating was developed to act as a weak interface for the sapphire fiber, which otherwise, forms a strong bond with the matrix. A fixture was designed to apply stress on the composite specimen, in situ, under the microscope of the spectrometer. Using fluorescence spectroscopy, the micromechanics of load transfer from matrix to fibers were studied. Studies were conducted on both strongly and weakly bonded fibers, as well as on single fiber, and multi fiber situations. Residual stresses arising from thermal expansion mismatch have been mapped along the fiber length with resolution in microns. Residual axial stress was found to follow a shear lag profile along the fiber length. A finite residual axial stress was detected at the fiber ends. Correction of the measured stress for sample

  18. Electrospun Yarn Reinforced NanoHA Composite Matrix as a Potential Bone Substitute for Enhanced Regeneration of Segmental Defects.

    PubMed

    Anitha, A; Joseph, John; Menon, Deepthy; Nair, Shantikumar V; Nair, Manitha B

    2017-04-01

    Nanohydroxyapatite (nanoHA) is a well-established synthetic bone substitute with excellent osteoconduction and osteointegration. However, brittleness coupled with slow degradation curtails its load-bearing and bone regeneration potential, respectively. To address these limitations, nanoHA composite matrix reinforced with electrospun fibrous yarns was fabricated and tested in vitro and in vivo. Different weight percentages (5, 10, 15 wt%) and varying lengths (short and continuous) of poly(l-lactic acid) yarns were randomly dispersed in a gelatinous matrix containing nanoHA. This significantly improved the compressive strength as well as work of fracture, especially for continuous yarns at high weight percentages (10 and 15 wt%). Incorporation of yarns did not adversely affect the pore size (50-350 μm) or porosity of the scaffolds as well as the in vitro cellular response. Finally, when tested in a critical-sized femoral segmental defect in rat, the nanocomposite scaffolds induced osteoblast cell infiltration at 2 months that subsequently underwent increased mature lamellar bone formation at 4 months, in both the mid and peripheral defect regions. Histomorphometric analysis demonstrated that new bone formation and biomaterial degradation were significantly enhanced in the composite scaffold when compared to commercially available HA. Overall, the composite matrix reinforced with electrospun yarns proved to be a potential bone substitute having an appropriate balance between mechanical strength, porosity, biodegradation, and bone regeneration ability.

  19. Impressed-current cathodic protection of steel-reinforced concrete pilings: Protection criteria and the threshold for hydrogen embrittlement

    SciTech Connect

    Enos, D.G.; Williams, A.J. Jr.; Scully, J.R.; Clemena, G.G.

    1998-05-01

    Safe cathodic protection (CP) limits for prestressing steel in concrete and the adequacy of CP using established criteria were evaluated in regard to hydrogen embrittlement (HE). Impressed-current CP was applied to laboratory scale pilings at current densities from 0.1 {micro}A/cm{sup 2} to 3.0 {micro}A/cm{sup 2} via a skirt anode located at the waterline. Adequate CP was achieved at positions 25 cm (9.8 in.) above to 50 cm (19.7 in.) below the waterline, according to the 100-mV depolarization criterion, at an apparent applied current density of 0.33 {micro}A/cm{sup 2}. However, the {minus}780 mV{sub SCE} criterion was not met for currents as high as 1.33 {micro}A/cm{sup 2} for these positions. Hydrogen production, absorption, and permeation in steel first was observed via embedded hydrogen sensors 50 cm and 25 cm above the water line at an applied current density of 0.33 {micro}A/cm{sup 2}. Observation of hydrogen production verified concerns that the local oxygen concentration might be depleted readily at modest CP levels and that local pH levels may be below 12.5. Experimentation demonstrated that steel crevice corrosion was initiated readily within chloride (Cl{sup {minus}})-contaminated concrete prior to CP application and that this corrosion was accompanied by acidification of the local environment to pH {le} 6 as a result of ferrous ion (Fe{sup 2+}) hydrolysis. The mobile subsurface hydrogen concentration present within the steel reinforcement was determined for each applied cathodic current density. Although hydrogen production and uptake occurred at current densities as low as 0.33 {micro}A/cm{sup 2}, the critical hydrogen concentration for embrittlement (i.e., 2 {times} 10{sup {minus}7} mol H/cm{sup 3}, as determined in prior research for bluntly notched prestressing steel) was not exceeded at area averaged current densities <1.33 {micro}A/cm{sup 2}.

  20. On Porosity Formation in Metal Matrix Composites Made with Dual-Scale Fiber Reinforcements Using Pressure Infiltration Process

    NASA Astrophysics Data System (ADS)

    Etemadi, Reihaneh; Pillai, Krishna M.; Rohatgi, Pradeep K.; Hamidi, Sajad Ahmad

    2015-05-01

    This is the first such study on porosity formation phenomena observed in dual-scale fiber preforms during the synthesis of metal matrix composites (MMCs) using the gas pressure infiltration process. In this paper, different mechanisms of porosity formation during pressure infiltration of Al-Si alloys into Nextel™ 3D-woven ceramic fabric reinforcements (a dual-porosity or dual-scale porous medium) are studied. The effect of processing conditions on porosity content of the ceramic fabric infiltrated by the alloys through the gas PIP (PIP stands for "Pressure Infiltration Process" in which liquid metal is injected under pressure into a mold packed with reinforcing fibers.) is investigated. Relative density (RD), defined as the ratio of the actual MMC density and the density obtained at ideal 100 pct saturation of the preform, was used to quantify the overall porosity. Increasing the infiltration temperature led to an increase in RD due to reduced viscosity of liquid metal and enhanced wettability leading to improved feedability of the liquid metal. Similarly, increasing the infiltration pressure led to enhanced penetration of fiber tows and resulted in higher RD and reduced porosity. For the first time, the modified Capillary number ( Ca*), which is found to predict formation of porosity in polymer matrix composites quite well, is employed to study porosity in MMCs made using PIP. It is observed that in the high Ca* regime which is common in PIP, the overall porosity shows a strong downward trend with increasing Ca*. In addition, the effect of matrix shrinkage on porosity content of the samples is studied through using a zero-shrinkage Al-Si alloy as the matrix; usage of this alloy as the matrix led to a reduction in porosity content.

  1. Crack initiation and propagation behavior of WC particles reinforced Fe-based metal matrix composite produced by laser melting deposition

    NASA Astrophysics Data System (ADS)

    Wang, Jiandong; Li, Liqun; Tao, Wang

    2016-08-01

    It is generally believed that cracks in metal matrix composites (MMC) parts manufacturing are crucial to the reliable material properties, especially for the reinforcement particles with high volume fraction. In this paper, WC particles (WCp) reinforced Fe-based metal matrix composites (WCp/Fe) were manufactured by laser melting deposition (LMD) technology to investigate the characteristics of cracks formation. The section morphology of composites were analyzed by optical microscope (OM), and microstructure of WCp, matrix and interface were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM), in order to study the crack initiation and propagation behavior under different laser process conditions. The temperature of materials during the laser melting deposition was detected by the infrared thermometer. The results showed that the cracks often appeared after five layers laser deposition in this experiment. The cracks crossed through WC particles rather than the interface, so the strength of interface obtained by the LMD was relatively large. When the thermal stress induced by high temperature gradient during LMD and the coefficient of thermal expansion mismatch between WC and matrix was larger than yield strength of WC, the cracks would initiate inside WC particle. Cracks mostly propagated along the eutectic phases whose brittleness was very large. The obtained thin interface was beneficial to transmitting the stress from particle to matrix. The influence of volume fraction of particles, laser power and scanning speed on cracks were investigated. This paper investigated the influence of WC particles size on cracks systematically, and the smallest size of cracked WC in different laser processing parameters was also researched.

  2. The long term effects of cathodic protection on corroding, pre-stressed concrete structures: Hydrogen embrittlement of the reinforcing steel

    NASA Astrophysics Data System (ADS)

    Enos, David George

    Assessment of the effect of cathodic protection on a chloride contaminated bridge pile involves the definition of the hydrogen embrittlement behavior of the pearlitic reinforcement combined with quantification of the local (i.e., at the steel/concrete interface) chemical and electrochemical conditions, both prior to and throughout the application of cathodic protection. The hydrogen embrittlement behavior of the reinforcement was assessed through a combination of Devanathan/Stachurski permeation experiments to quantify subsurface hydrogen concentrations, CsbH, as a function of the applied hydrogen overpotential, eta, and crack initiation tests for bluntly notched and fatigue pre-cracked tensile specimens employing elastic-plastic finite element analysis and linear elastic fracture mechanics, respectively. A threshold mobile lattice hydrogen concentration for embrittlement of 2×10sp{-7} mol/cmsp3 was established for bluntly notched and fatigue pre-cracked specimens. Crack initiation occurred by the formation of shear cracks oriented at an angle approaching 45sp° from the tensile axis, as proposed by Miller and Smith (Miller, 1970), in regions where both the longitudinal and shear stresses were maximized (i.e., near the notch root). These Miller cracks then triggered longitudinal splitting which continued until fast fracture of the remaining ligament occurred. Instrumented laboratory scale piles were constructed and partially immersed in ASTM artificial ocean water. With time, localized corrosion (crevicing) was initiated along the reinforcement, and was accompanied by an acidic shift in the pH of the occluded environment due to ferrous ion hydrolysis. Cathodic protection current densities from -0.1 muA/cmsp2 to -3.0 muA/cmsp2 were applied via a skirt anode located at the waterline. Current densities as low as 0.66 muA/cmsp2 were sufficient to deplete the dissolved oxygen concentration at the steel/concrete interface and result in the observance of hydrogen

  3. Fatigue damage growth mechanisms in continuous fiber reinforced titanium matrix composites

    NASA Technical Reports Server (NTRS)

    Johnson, W. S.; Naik, R. A.; Pollock, W. D.

    1990-01-01

    The role of fiber/matrix interface strength, residual thermal stresses, and fiber and matrix properties on fatigue damage accumulation in continuous fiber metal matrix composites (MMC) is discussed. Results from titanium matrix silicon carbide fiber composites is the primary topic of discussion. Results were obtained from both notched and unnotched specimens at room and elevated temperatures. The stress in the 0 deg fibers was identified as the controlling factor in fatigue life. Fatigue of the notched specimens indicated that cracks can grow in the matrix materials without breaking fibers.

  4. Fatigue damage growth mechanisms in continuous fiber reinforced titanium matrix composites

    NASA Technical Reports Server (NTRS)

    Johnson, W. S.; Naik, R. A.; Pollock, W. D.

    1990-01-01

    The role of fiber/matrix interface strength, residual thermal stresses, and fiber and matrix properties on fatigue damage accumulation in continuous fiber metal matrix composites (MMC) will be discussed. Results from titanium matrix/silicon-carbide fiber composites will be the primary topic of discussion. Results have been obtained from both notched and unnotched specimens at room and elevated temperatures. The stress in the 0 deg fibers has been indentified as the controlling factor in fatigue life. Fatigue of the notched specimens indicated that cracks can grow many fiber spacings in the matrix materials without breaking fibers.

  5. Microstructure and compression strength of novel TRIP-steel/Mg-PSZ composites

    NASA Astrophysics Data System (ADS)

    Biermann, H.; Aneziris, C. G.; Kolbe, A.; Martin, U.; Müller, A.; Schärfl, W.; Herrmann, M.

    2010-07-01

    A novel steel-based composite material, composed of metastable austenitic stainless steel as matrix and up to 15 % zirconia as reinforcement, is processed by two powder metallurgy routes. The matrix exhibits the so-called TRIP-effect (TRIP: TRansformation-Induced Plasticity) and shows a deformation-induced formation of martensite. Compression tests of rod samples processed by cold isostatic pressing show increased strength compared to the non-reinforced steel matrix up to 20 % strain. Three-point bending tests show, however, reduced ductility for high zirconia contents. Filigree honeycomb structures were produced by a novel extrusion technique with extraordinary high values of specific energy absorption.

  6. Applicability of ultrasonic testing for the determination of volume fraction of particulates in alumina-reinforced aluminum matrix composites

    SciTech Connect

    Fang, C.K.; Fang, R.L.; Weng, W.P.; Chuang, T.H.

    1999-10-01

    An ultrasonic testing technique was employed to determine the volume fraction of alumina particulate reinforcement in 6061 aluminum matrix composites. this study was performed on various composites with Al{sub 2}O{sub 3} nominal volume fractions of 10, 15, and 20%. For comparison, other techniques were employed as well, including the Archimedes method, metallographic image analysis, X-ray diffraction, and acid dissolution. Observations indicated that ultrasonic testing and acid dissolution methods are more reliable than the other techniques, while ultrasonic testing is faster than the acid dissolution method.

  7. The correlation of low-velocity impact resistance of graphite-fiber-reinforced composites with matrix properties

    NASA Technical Reports Server (NTRS)

    Bowles, K. J.

    1986-01-01

    Summarized are basic studies that were conducted to correlate the impact resistance of graphite-fiber-reinforced composites with polymer matrix properties. Three crosslinked epoxy resins and a linear polysulfone were selected as composite matrices. As a group, these resins possess a significantly large range of mechanical properties. The mechanical properties of the resins and their respective composites were measured. Neat resin specimens and unidirectional and crossply composite specimens were impact tested with an instrumented dropweight tester. Impact resistances of the specimens were assessed on the basis of loading capability, energy absorption, and extent of damage.

  8. Field assisted sintering of refractory carbide ceramics and fiber reinforced ceramic matrix composites

    NASA Astrophysics Data System (ADS)

    Gephart, Sean

    materials. While FAST sintered materials showed higher average values, in general they also showed consistently larger variation in the scattered data and consequently larger standard deviation for the resulting material properties. In addition, dynamic impact testing (V50 test) was conducted on the resulting materials and it was determined that there was no discernable correlation between observed mechanical properties of the ceramic materials and the resulting dynamic testing. Another study was conducted on the sintering of SiC and carbon fiber reinforced SiC ceramic matrix composites (CMC) using FAST. There has been much interest recently in fabricating high strength, low porosity SiC CMC.s for high temperature structural applications, but the current methods of production, namely chemical vapor infiltration (CVI), melt infiltration (MI), and polymer infiltration and pyrolysis (PIP), are considered time consuming and involve material related shortcomings associated with their respective methodologies. In this study, SiC CMC.s were produced using the 25 ton laboratory unit with a target sample size of 40 mm diameter and 3 mm thickness, as well as on the larger 250 ton industrial FAST system targeting a sample size of 101.6 x 101.6 x 3 mm3 to investigate issues associated with scaling. Several sintering conditions were explored including: pressure of 35-65 MPa, temperature of 1700-1900°C, and heating rates between 50-400°C/min. The SiC fibers used in this study were coated using chemical vapor deposition (CVD) with boron nitride (BN) and pyrolytic carbon to act as a barrier layer and preserve the integrity of the fibers during sintering. Then the barrier coating was coated by an outer layer of SiC to enhance the bonding between the fibers and the SiC matrix. Microstructures of the sintered samples were examined by FE-SEM. Mechanical properties including flexural strength-deflection and stress-strain were characterized using 4-point bend testing. Tensile testing was

  9. Non-linear finite element-based material constitutive law for zero slump steel fiber reinforced concrete pipe structures

    NASA Astrophysics Data System (ADS)

    Mikhaylova, Alena

    This study presents a comprehensive investigation of performance and behavior of steel-fiber reinforced concrete pipes (SFRCP). The main goal of this study is to develop the material constitutive model for steel fiber reinforced concrete used in dry-cast application. To accomplish this goal a range of pipe sizes varying from 15 in. (400 mm) to 48 in. (1200 mm) in diameter and fiber content of 0.17%, 0.25%, 0.33%, 0.5%, 0.67% and 83% by volume were produced. The pipes were tested in three-edge bearing condition to obtain the load-deformation response and overall performance of the pipe. The pipes were also subjected to hydrostatic joint and joint shear tests to evaluate the performance of the fiber-pipe joints for water tightness and under differential displacements, respectively. In addition, testing on hardened concrete was performed to obtain the basic mechanical material properties. High variation in the test results for material testing was identified as a part of experimental investigation. A three-dimensional non-linear finite element model of the pipe under the three edge bearing condition was developed to identify the constitutive material relations of fiber-concrete composite. A constitutive model of concrete implementing the concrete plasticity and continuum fracture mechanics was considered for defining the complex non-linear behavior of fiber-concrete. Three main concrete damage algorithms were examined: concrete brittle cracking, concrete damaged plasticity with adaptive meshing technique and concrete damaged plasticity with visco-plastic regularization. The latter was identified as the most robust and efficient to model the post-cracking behavior of fiber reinforced concrete and was used in the subsequent studies. The tension stiffening material constitutive law for composite concrete was determined by converging the FEM solution of load-deformation response with the results of experimental testing. This was achieved by iteratively modifying the non

  10. Effect of Elevated Temperature on Mechanical Assets of Metakaolin Base Steel Fiber Reinforced Concrete

    NASA Astrophysics Data System (ADS)

    Vijay Anand, M.; Ibrahim, Azmi; Patil, Anand A.; Muthu, K. U.

    2017-06-01

    The fact of vast usage of concrete leads to important problems regarding its design and preparation of eco-friendly to obtain an economic cost of the product on varieties of time periods. Conventional ordinary Portland concrete may not able to meet its functional requisites as it found inconsistency in high temperature. The exposing of concrete structure to elevated temperature may be in case of rocket launching space ships, nuclear power plants. In this experiment, to enhance the high temperature resistance, pozzolanic materials and steel fibres are added to preserve the strength characteristics of concrete structure. In this analysis, the pozzolanic admixture MK is used as partial replacement of cementatious materials. The volume fraction of steel fibre is varied 0.25%, 0.5%, 0.75% and 1% by preserving MK as stationary for 10% replacement of cement. The strength parameters of concrete such as compressive strength, split tensile strength and flexural strength are studied.

  11. Using electroless nickel to coat reinforcing steel in chloride contaminated concrete

    SciTech Connect

    Sanchez, M.A.; Parra, L.A.; Perez, O.A.; Rincon, O. de

    1998-12-31

    This work is a study of the behavior of steel rebar coated by electroless nickel in chloride-contaminated concrete. The steel rebars were coated in an electroless nickel bath for 1, 2 and 3 hours. They were then subjected to heat treatment at 400 C for periods of 1, 2 and 3 hours. The nickel-coated rebars were embedded in concrete samples with NaCl concentrations at 0.00; 0.10; 0.15 and 0.20 %, based on concrete weight. Their behavior was evaluated by measurement of potentials, polarization resistance, potentiodynamic polarization curves, electrical resistance and visual inspection. Corrosion rates were less than 0.01 {micro}A/cm{sup 2} after 40 months` testing.

  12. Performance and Characterization of Geopolymer Concrete Reinforced with Short Steel Fiber

    NASA Astrophysics Data System (ADS)

    Abdullah, M. M. A. B.; Faris, M. A.; Tahir, M. F. M.; Kadir, A. A.; Sandu, A. V.; Mat Isa, N. A. A.; Corbu, O.

    2017-06-01

    In the recent years, geopolymer concrete are reporting as the greener construction technology compared to conventional concrete that made up of ordinary Portland cement. Geopolymer concrete is an innovative construction material that utilized fly ash as one of waste material in coal combustion industry as a replacement for ordinary Portland cement in concrete. The uses of fly ash could reduce the carbon dioxide emission to the atmosphere, redundant of fly ash waste and costs compared to ordinary Portland cement concrete. However, the plain geopolymer concrete suffers from numerous drawbacks such as brittleness and low durability. Thus, in this study the addition of steel fiber is introduced in plain geopolymer concrete to improve its mechanical properties especially in compressive and flexural strength. Characterization of raw materials also determined by using chemical composition analysis. Short type of steel fiber is added to the mix in weight percent of 1 wt%, 3 wt%, 5 wt% and 7 wt% with fixed molarity of sodium hydroxide of 12M and solid to liquid ratio as 2.0. The addition of steel fiber showed the excellent improvement in the mechanical properties of geopolymer concrete that are determined by various methods available in the literature and compared with each other.

  13. Processing, compatibility and oxidation of diboride-reinforced oxide matrix composites for ultrahigh-temperature applications

    SciTech Connect

    Abada, A.

    1990-01-01

    Promising results for the development of a ceramic/ceramic composite to be used for structural applications in the ultra high temperature range (1650 to 1850 C) were obtained for alumina reinforced with titanium or zirconium diboride coated with molybdenum disilicide. Calculations of the compatibility and stability of oxide matrices with the diborides in vacuum showed positive energies of formation, indicating suitability of reinforcement of alumina under vacuum conditions. Stability and chemical compatibility of the particulate and ternary composites in their as hot pressed states and following their vacuum and air oxidation treatment were characterized.

  14. Mechanical characterization and modeling of non-linear deformation and fracture of a fiber reinforced metal matrix composite

    NASA Technical Reports Server (NTRS)

    Jansson, S.

    1991-01-01

    The nonlinear anisotropic mechanical behavior of an aluminum alloy metal matrix composite reinforced with continuous alumina fibers was determined experimentally. The mechanical behavior of the composite were modeled by assuming that the composite has a periodical microstructure. The resulting unit cell problem was solved with the finite element method. Excellent agreement was found between theoretically predicted and measured stress-strain responses for various tensile and shear loadings. The stress-strain responses for transverse and inplane shear were found to be identical and this will provide a simplification of the constitutive equations for the composite. The composite has a very low ductility in transverse tension and a limited ductility in transverse shear that was correlated to high hydrostatic stresses that develop in the matrix. The shape of the initial yield surface was calculated and good agreement was found between the calculated shape and the experimentally determined shape.

  15. Creep and Stress-strain Behavior After Creep from Sic Fiber Reinforced, Melt-infiltrated Sic Matrix Composites

    NASA Technical Reports Server (NTRS)

    Morscher, Gregory N.; Pujar, Vijay

    2004-01-01

    Silicon carbide fiber (Hi-Nicalon Type S, Nippon Carbon) reinforced silicon carbide matrix composites containing melt-infiltrated Si were subjected to creep at 1315 C for a number of different stress conditions, This study is aimed at understanding the time-dependent creep behavior of CMCs for desired use-conditions, and also more importantly, how the stress-strain response changes as a result of the time-temperature-stress history of the crept material. For the specimens that did not rupture, fast fracture experiments were performed at 1315 C or at room temperature immediately following tensile creep. In many cases, the stress-strain response and the resulting matrix cracking stress of the composite change due to stress-redistribution between composite constituents during tensile creep. The paper will discuss these results and its implications on applications of these materials for turbine engine components.

  16. Mechanical behavior of fiber reinforced SiC/RBSN ceramic matrix composites - Theory and experiment. [Reaction Bonded Silicon Nitride

    NASA Technical Reports Server (NTRS)

    Chulya, Abhisak; Gyekenyesi, John P.; Bhatt, Ramakrishna T.

    1991-01-01

    The mechanical behavior of continuous fiber reinforced SiC/RBSN (Reaction Bonded Silicon Nitride) composites with various fiber contents is evaluated. Both catastrophic and noncatastrophic failures are observed in tensile specimens. Damage and failure mechanisms are identified via in-situ monitoring using NDE (nondestructive evaluation) techniques throughout the loading history. Effects of fiber/matrix interface debonding (splitting) parallel to fibers are discussed. Statistical failure behavior of fibers is also observed, especially when the interface is weak. Micromechanical models incorproating residual stresses to calculate the critical matrix cracking strength, ultimate strength, and work of pull-out are reviewed and used to predict composite response. For selected test problems, experimental measurements are compared to analytical predictions.

  17. Development and analysis of three-dimensionally reinforced cellular matrix composites

    NASA Astrophysics Data System (ADS)

    Xu, Wei

    2000-10-01

    The objective of this research was to develop a new class of lightweight three-dimensional textile reinforced cellular matrix composite (3-D CMC) materials using a high-pressure foaming method. The scope of the research includes fabrication, experimental evaluation and mathematical modeling of the new composite materials. Principles of thermodynamics and transport phenomena involved in the cell nucleation and bubble growth in plastics using gas blowing agents were reviewed. The determinative factors for the foaming process were the foaming pressure, surface tension, viscous and inertial resistance forces. Foaming of epoxy resins by pressure quenching were carried out using a high-pressure vessel with a digital temperature controller and nitrogen gas as the blowing agent, at 100°C and 28--110.5 bar. The cure time was 2--2.5 hr., well before the time of gel point, 293 min., determined by means of dynamic mechanical spectroscopy. It was found that the foam density decreased monotonously and the average bubble radius slightly decreased, while the cell density increased, with the increasing foaming pressure. Cure time of 2 and 2.5 hours have no influence on the foam density, but have opposite influences on the bubble radius and cell density. Samples of 3-D woven carbon CMC materials were fabricated using the high-pressure foaming apparatus at a foaming pressure of 60 bar as the epoxy resin cured for 1.5--2 hr. at 100°C. Photomicrographs of cross-sections of the samples revealed that the epoxy resins in the epoxy pockets of the 3-D CMC samples were removed during foaming. Average density was found 1.009 g/cm 3 for TM samples and 1.076 g/cm3 for TS samples, corresponding to weight reduction of 36.92% and 28.37%, respectively, as compared with the 3-D RMC material, where TM and TS samples used 3-D woven carbon preforms of different weaving parameters. Tensile test, 3-point bending and high velocity projectile impact test were conducted to evaluate the mechanical

  18. Reduction of thermal stresses in continuous fiber reinforced metal matrix composites with interface layers

    NASA Technical Reports Server (NTRS)

    Jansson, S.; Leckie, F. A.

    1992-01-01

    The potential of using interface layer to reduce thermal stresses in the matrix of composites with a mismatch in coefficients of thermal expansion of fiber and matrix has been investigated. It was found that compliant layers, with properties of readily available materials, do not have the potential to reduce thermal stresses significantly. However, interface layers with high coefficient of thermal expansion can compensate for the mismatch and reduce thermal stresses in the matrix significantly.

  19. Reduction of thermal stresses in continuous fiber reinforced metal matrix composites with interface layers

    NASA Technical Reports Server (NTRS)

    Jansson, S.; Leckie, F. A.

    1990-01-01

    The potential of using an interface layer to reduce thermal stresses in the matrix of composites with a mismatch in coefficients of thermal expansion of fiber and matrix was investigated. It was found that compliant layers, with properties of readily available materials, do not have the potential to reduce thermal stresses significantly. However, interface layers with high coefficient of thermal expansion can compensate for the mismatch and reduce thermal stresses in the matrix significantly.

  20. Microstructural evolution and micromechanical modeling of the mechanical behavior of a ceramic particle-reinforced metal-matrix composite

    SciTech Connect

    Christman, T.A.

    1989-01-01

    The objective was to develop a thorough understanding of the precipitation characteristics and mechanical behavior of a 2124 Al-SiC Aluminum alloy reinforced with 13.2 volume% SiC whiskers. Microstructural development of the 2124 Al-SiC composite subject to controlled and systematic aging treatments was investigated. The results indicate that the matrix of the composite material has a much greater dislocation density than the control alloy. The increased dislocation density facilitates the nucleation of the strengthening precipitates whereby the incubation time for precipitate nucleation and the time to reach peak hardness in the matrix of the composite are significantly reduced. Theoretical analysis of dislocation generation due to thermal contraction mismatch and of the punching of dislocations at whisker ends are examined in the context of microstructural development. An experimental and theoretical investigation into the uniaxial: stress-strain response of the 2124 Al-SiC whisker composite system was undertaken where the effects of accelerated aging of the matrix of the composite were incorporated into the modeling of deformation behavior. The 0.2% offset yield strength was found to be independent of aging state, whereas the strain to failure was found to decrease monotonically with an increase in aging time for the composite. A self consistent approximation was formulated and was found to provide the most accurate predictions for the elastic response of the composite. A finite-element unit-cell model was used to predict the plastic response of the composite material. The effects of SiC reinforcement and matrix aging treatment on crack growth under quasi-static and fatigue loading were also investigated. The composite exhibits a fatigue threshold value which is about twice that of the control alloy.