Chemical bridges for enhancing hydrogen storage by spillover and methods for forming the same

DOEpatents

Yang, Ralph T.; Li, Yingwei; Qi, Gongshin; Lachawiec, Jr., Anthony J.

2012-12-25

A composition for hydrogen storage includes a source of hydrogen atoms, a receptor, and a chemical bridge formed between the source and the receptor. The chemical bridge is formed from a precursor material. The receptor is adapted to receive hydrogen spillover from the source.

Force Project Technology Presentation to the NRCC

DTIC Science & Technology

2014-02-04

Functional Bridge components Smart Odometer Adv Pretreatment Smart Bridge Multi-functional Gap Crossing Fuel Automated Tracking System Adv...comprehensive matrix of candidate composite material systems and textile reinforcement architectures via modeling/analyses and testing. Product(s...Validated Dynamic Modeling tool based on parametric study using material models to reliably predict the textile mechanics of the hose

Development of Specifications for Engineered Cementitious Composites for Use in Bridge Deck Overlays

DOT National Transportation Integrated Search

2016-02-01

Engineered cementitious composite (ECC) material is a high strength, fiber-reinforced, ductile mortar mixture that can exhibit tensile strains of up to 5%. ECC has a dense matrix, giving the material exceptional durability characteristics. The durabi...

Smart FRP Composite Sandwich Bridge Decks in Cold Regions

DOT National Transportation Integrated Search

2011-07-01

In this study, new and integrated Smart honeycomb Fiber-Reinforced Polymer (S-FRP) : sandwich materials for various transportation construction applications, with particular emphasis : on highway bridge decks in cold regions, were developed and teste...

Smart FRP Composite Sandwich Bridge Decks in Cold Regions

DOT National Transportation Integrated Search

2011-07-01

In this study, new and integrated Smart honeycomb Fiber-Reinforced Polymer (S-FRP) sandwich materials for various transportation construction applications, with particular emphasis on highway bridge decks in cold regions, were developed and tested. T...

Retrofit of the Louisa-Fort Gay Bridge using CFRP laminates.

DOT National Transportation Integrated Search

2007-06-01

This report details the processes pertaining to the repair and strengthening of the Louisa-Fort Gay Bridge, Lawrence County, KY, using advanced composite materials. Site inspections revealed flexural cracks in the reinforced concrete girders of the c...

Demonstration and Validation of a Composite Grid Reinforcement System for Bridge Decks

DTIC Science & Technology

2016-09-01

Abstract The Department of Defense (DoD) maintains a large array of road net- works that include vehicular bridges. Moving people, materials, and equip...tion. The application of corrosion-resistant technology can extend the ser- vice life of bridges and reduce maintenance costs. This DoD Corrosion... maintenance and capital costs for steel reinforcement. Maintaining serviceable bridges is essential to providing access to the facilities on the

Materials science. Materials that couple sensing, actuation, computation, and communication.

PubMed

McEvoy, M A; Correll, N

2015-03-20

Tightly integrating sensing, actuation, and computation into composites could enable a new generation of truly smart material systems that can change their appearance and shape autonomously. Applications for such materials include airfoils that change their aerodynamic profile, vehicles with camouflage abilities, bridges that detect and repair damage, or robotic skins and prosthetics with a realistic sense of touch. Although integrating sensors and actuators into composites is becoming increasingly common, the opportunities afforded by embedded computation have only been marginally explored. Here, the key challenge is the gap between the continuous physics of materials and the discrete mathematics of computation. Bridging this gap requires a fundamental understanding of the constituents of such robotic materials and the distributed algorithms and controls that make these structures smart. Copyright © 2015, American Association for the Advancement of Science.

Performance enhancement of bridge bracing under service and extreme loads.

DOT National Transportation Integrated Search

2010-12-01

The purpose of this study was to develop and demonstrate the concept of retrofitting bridge brace elements with fiber reinforced composites in order to provide restraint against buckling. The advanced materials consisted of a combination of fiber rei...

Experimental evaluation and design of unfilled and concrete-filled FRP composite piles : Task 4B : material & construction specifications : final report.

DOT National Transportation Integrated Search

2015-07-01

The overall goal of this project is the experimental evaluation and design of unfilled and concrete-filled FRP composite piles for load-bearing in bridges. This report covers Task 4B, Materials and Construction Specifications. : This technical report...

Long-term behavior of GFRP reinforced panels after eight years of field exposure.

DOT National Transportation Integrated Search

2014-06-01

Since 1998, Missouri S&T/University of Missouri-Rolla investigators have been involved in more than 25 bridge repairs and/or new : bridge construction involving composite materials. To date, many of these projects have demonstrated reliable field per...

Printing nature: Unraveling the role of nacre's mineral bridges.

PubMed

Gu, Grace X; Libonati, Flavia; Wettermark, Susan D; Buehler, Markus J

2017-12-01

Creating materials with strength and toughness has been a long-sought goal. Conventional engineering materials often face a trade-off between strength and toughness, prompting researchers seeking to overcome these limitations to explore more sophisticated materials, such as composites. This paradigm shift in material design is spurred by nature, which exhibits a plethora of heterogeneous materials that offer outstanding material properties, and many natural materials are widely regarded as examples of high-performing hybrid materials. A classic example is nacre, also known as mother-of-pearl, which boasts a combination of high stiffness, strength, and fracture toughness. Various microstructural features contribute to the toughness of nacre, including mineral bridges (MBs), nano-asperities, and waviness of the constituent platelets. Recent research in biomimicry suggests that MBs contribute to the high strength and toughness observed in nacre and nacre-inspired materials. However, previous work in this area did not allow for complete control over the length scale of the bridges and had limitations on the volume fraction of mineral content. In this work, we present a systematic investigation elucidating the effects of structural parameters, such as volume fraction of mineral phase and density of MBs, on the mechanical response of nacre-inspired additive manufactured composites. Our results demonstrate that it is possible to tune the composite properties by tuning sizes and content of structural features (e.g. MBs and mineral content) in a heterogeneous material. Looking forward, this systematic approach enables materials-by-design of complex architectures to tackle demanding engineering challenges in the future. Copyright © 2017 Elsevier Ltd. All rights reserved.

Evaluation of wearing surface materials for FRP bridge decks : final report.

DOT National Transportation Integrated Search

2005-07-01

The wearing surface on many fiber reinforced polymer (FRP) composite bridge decks have cracked or delaminated after only a short time in service. Consequently, a set of tests were conducted on four wearing surface products in order to select the mate...

A review of the success and failure characteristics of resin-bonded bridges.

PubMed

Miettinen, M; Millar, B J

2013-07-01

This literature review was designed to assess and compare the success rates and modes of failure of metal-framed, fibre-reinforced composite and all-ceramic resin-bonded bridges. A Medline search (Ovid), supplemented by hand searching, was conducted to identify prospective and retrospective cohort studies on different resin-bonded bridges within the last 16 years. A total of 49 studies met the pre-set inclusion criteria. Success rates of 25 studies on metal-framed, 17 studies on fibre-reinforced composite and 7 studies on all-ceramic resin-bonded bridges were analysed and characteristics of failures were identified. The analysis of the studies indicated an estimation of annual failure rates per year to be 4.6% (±1.3%, 95% CI) for metal-framed, 4.1% (±2.1%, 95% CI) for fibre-reinforced and 11.7% (±1.8%, 95% CI) for all-ceramic resin-bonded bridges. The most frequent complications were: debonding for metal-framed, resin-bonded bridges (93% of all failures); delamination of the composite veneering material for the fibre-reinforced bridges (41%) and fracture of the framework for the all-ceramic bridges (57%). All types of resin-bonded bridges provide an effective short- to medium-term option, with all-ceramic performing least well and having the least favourable mode of failure. The methods of failures were different for different bridges with metal frameworks performing the best over time.

Methodology to Estimate the Quantity, Composition, and ...

EPA Pesticide Factsheets

This report, Methodology to Estimate the Quantity, Composition and Management of Construction and Demolition Debris in the US, was developed to expand access to data on CDD in the US and to support research on CDD and sustainable materials management. Since past US EPA CDD estimates have been limited to building-related CDD, a goal in the development of this methodology was to use data originating from CDD facilities and contractors to better capture the current picture of total CDD management, including materials from roads, bridges and infrastructure. This report, Methodology to Estimate the Quantity, Composition and Management of Construction and Demolition Debris in the US, was developed to expand access to data on CDD in the US and to support research on CDD and sustainable materials management. Since past US EPA CDD estimates have been limited to building-related CDD, a goal in the development of this methodology was to use data originating from CDD facilities and contractors to better capture the current picture of total CDD management, including materials from roads, bridges and infrastructure.

Long-term monitoring of mechanical properties of FRP repair materials.

DOT National Transportation Integrated Search

2013-07-01

Fiber- reinforced polymer composites (FRP) are an attractive repair option for existing concrete structures. : CDOT has used this material on some projects, in particular the repair of the Castlewood Canyon Bridge in : 2003. Further use of the materi...

Fermentation based carbon nanotube multifunctional bionic composites

NASA Astrophysics Data System (ADS)

Valentini, Luca; Bon, Silvia Bittolo; Signetti, Stefano; Tripathi, Manoj; Iacob, Erica; Pugno, Nicola M.

2016-06-01

The exploitation of the processes used by microorganisms to digest nutrients for their growth can be a viable method for the formation of a wide range of so called biogenic materials that have unique properties that are not produced by abiotic processes. Here we produced living hybrid materials by giving to unicellular organisms the nutrient to grow. Based on bread fermentation, a bionic composite made of carbon nanotubes (CNTs) and a single-cell fungi, the Saccharomyces cerevisiae yeast extract, was prepared by fermentation of such microorganisms at room temperature. Scanning electron microscopy analysis suggests that the CNTs were internalized by the cell after fermentation bridging the cells. Tensile tests on dried composite films have been rationalized in terms of a CNT cell bridging mechanism where the strongly enhanced strength of the composite is governed by the adhesion energy between the bridging carbon nanotubes and the matrix. The addition of CNTs also significantly improved the electrical conductivity along with a higher photoconductive activity. The proposed process could lead to the development of more complex and interactive structures programmed to self-assemble into specific patterns, such as those on strain or light sensors that could sense damage or convert light stimulus in an electrical signal.

Fermentation based carbon nanotube multifunctional bionic composites

PubMed Central

Valentini, Luca; Bon, Silvia Bittolo; Signetti, Stefano; Tripathi, Manoj; Iacob, Erica; Pugno, Nicola M.

2016-01-01

The exploitation of the processes used by microorganisms to digest nutrients for their growth can be a viable method for the formation of a wide range of so called biogenic materials that have unique properties that are not produced by abiotic processes. Here we produced living hybrid materials by giving to unicellular organisms the nutrient to grow. Based on bread fermentation, a bionic composite made of carbon nanotubes (CNTs) and a single-cell fungi, the Saccharomyces cerevisiae yeast extract, was prepared by fermentation of such microorganisms at room temperature. Scanning electron microscopy analysis suggests that the CNTs were internalized by the cell after fermentation bridging the cells. Tensile tests on dried composite films have been rationalized in terms of a CNT cell bridging mechanism where the strongly enhanced strength of the composite is governed by the adhesion energy between the bridging carbon nanotubes and the matrix. The addition of CNTs also significantly improved the electrical conductivity along with a higher photoconductive activity. The proposed process could lead to the development of more complex and interactive structures programmed to self-assemble into specific patterns, such as those on strain or light sensors that could sense damage or convert light stimulus in an electrical signal. PMID:27279425

Ductile-Phase-Toughened Tungsten for Plasma-Facing Materials

NASA Astrophysics Data System (ADS)

Cunningham, Kevin Hawkins

A variety of processing approaches were employed to fabricate ductile-phase-toughened (DPT) tungsten (W) composites. Mechanical testing and analytical modeling were used to guide composite development. This work provides a basis for further development of W composites to be used in structural divertor components of future fusion reactors. W wire was tested in tension, showing significant ductility and strength. Coatings of copper (Cu) or tungsten carbide (WC) were applied to the W wire via electrodeposition and carburization, respectively. Composites were fabricated using spark plasma sintering (SPS) to consolidate W powders together with each type of coated W wire. DPT behavior, e.g. crack arrest and crack bridging, was not observed in three-point bend testing of the sintered composites. A laminate was fabricated by hot pressing W and Cu foils together with W wires, and subsequently tested in tension. This laminate was bonded via hot pressing to thick W plate as a reinforcing layer, and the composite was tested in three-point bending. Crack arrest was observed along with some fiber pullout, but significant transverse cracking in the W plate confounded further fracture toughness analysis. The fracture toughness of thin W plate was measured in three-point bending. W plates were brazed with Cu foils to form a laminate. Crack arrest and crack bridging were observed in three-point bend tests of the laminate, and fracture resistance curves were successfully calculated for this DPT composite. An analytical model of crack bridging was developed using the basis described by Chao in previous work by the group. The model uses the specimen geometry, matrix properties, and the stress-displacement function of a ductile reinforcement ("bridging law") to calculate the fracture resistance curve (R-curve) and load-displacement curve (P-D curve) for any test specimen geometry. The code was also implemented to estimate the bridging law of an arbitrary composite using R-curve data. Finally, a parametric study was performed to quantitatively determine the necessary mechanical properties of useful toughening reinforcements for a DPT W composite. The analytical model has a broad applicability for any DPT material.

Model for the Effect of Fiber Bridging on the Fracture Resistance of Reinforced-Carbon-Carbon

NASA Technical Reports Server (NTRS)

Chan, Kwai S.; Lee, Yi-Der; Hudak, Stephen J., Jr.

2009-01-01

A micromechanical methodology has been developed for analyzing fiber bridging and resistance-curve behavior in reinforced-carbon-carbon (RCC) panels with a three-dimensional (3D) composite architecture and a silicon carbide (SiC) surface coating. The methodology involves treating fiber bridging traction on the crack surfaces in terms of a weight function approach and a bridging law that relates the bridging stress to the crack opening displacement. A procedure has been developed to deduce material constants in the bridging law from the linear portion of the K-resistance curve. This report contains information on the application of procedures and outcomes.

Application of the bridged crack model for evaluation of materials repairing and self-healing

NASA Astrophysics Data System (ADS)

Perelmuter, M.

2017-12-01

The bridged crack model is used for analysis of repairing and self-healing of cracked structures. Material repairing is treated as insertions of external ligaments into cracks or placement of the reinforcing patches over cracks. Bonds destruction and regeneration at the crack bridged zone is evaluated by the thermo-fluctuation kinetic theory. The healing time is dependent on the chemical reaction rate of the healing agent, the crack size and the external loads. The decreasing of the stress intensity factors is used as the measure of the repairing and healing effects. The mathematical background of the problem solution is based on the methods of the singular integral-differential equations. The model can be used for the evaluation of composite materials durability.

Rewaterproofing Chemical For Use With Silicones

NASA Technical Reports Server (NTRS)

Hill, William L.; Mitchell, Shirley M.; Massey, Howard S.

1990-01-01

Agent restores impermeability without degrading silicone adhesives and substructures. Dimethylethoxysilane (DMES) found to rewaterproof tiles and composite panels internally without harming materials that underlie them. Replaces hexamethyldisilazane (HMDS) as postmission rewaterproofing agent for tiles of thermal-protection system on Space Shuttle. Much of original waterproofing lost during rigors of launch and reentry. Potential terrestrial application includes composite materials in such structures as bridges and submarines.

Bioceramic/poly (glycolic)-poly (lactic acid) composite induces mineralized barrier after direct capping of rat tooth pulp tissue.

PubMed

Gala-Garcia, Alfonso; Teixeira, Karina Imaculada Rosa; Wykrota, Francisco Henrique Lana; Sinisterra, Rubén Dario; Cortés, Maria Esperanza

2010-01-01

The aim of this study was to observe the histopathological pulp response following direct pulp capping of mechanically exposed teeth in rats with a composite of beta-tricalcium phosphate-hydroxyapatite bioceramic (BC) and poly (glycolic)-poly (lactic acid) (PLGA) material or a calcium hydroxide [Ca(OH)2] material, compared to BC alone and a negative control of water. Pulp of the maxillary molars was exposed, followed by capping with the experimental material. The pulpal tissue response was assessed post-operatively at 1, 7, 14 and 30 d, followed by histological analysis. The Ca(OH)2 group exhibited severe acute inflammatory cell infiltration at day 14. However after 30 d, a new hard tissue with macro porous obliteration of the pulp chamber and a characteristic necrotic area had appeared. BC and Ca(OH)2 capping were associated with moderate inflammation and dentinal bridge similar. Meanwhile, in the BC/PLGA composite group, there was moderate inflammatory infiltrate and formation of a dense and complete dentinal bridge. In conclusion, the BC/PLGA composite material showed a large zone of tertiary dentin, and effectively reorganized the dentin-pulp complex.

Mechanical and fracture behavior of veneer-framework composites for all-ceramic dental bridges.

PubMed

Studart, André R; Filser, Frank; Kocher, Peter; Lüthy, Heinz; Gauckler, Ludwig J

2007-01-01

High-strength ceramics are required in dental posterior restorations in order to withstand the excessive tensile stresses that occur during mastication. The aim of this study was to investigate the fracture behavior and the fast-fracture mechanical strength of three veneer-framework composites (Empress 2/IPS Eris, TZP/Cercon S and Inceram-Zirconia/Vita VM7) for all-ceramic dental bridges. The load bearing capacity of the veneer-framework composites were evaluated using a bending mechanical apparatus. The stress distribution through the rectangular-shaped layered samples was assessed using simple beam calculations and used to estimate the fracture strength of the veneer layer. Optical microscopy of fractured specimens was employed to determine the origin of cracks and the fracture mode. Under fast fracture conditions, cracks were observed to initiate on, or close to, the veneer outer surface and propagate towards the inner framework material. Crack deflection occurred at the veneer-framework interface of composites containing a tough framework material (TZP/Cercon S and Inceram-Zirconia/Vita VM7), as opposed to the straight propagation observed in the case of weaker frameworks (Empress 2/IPS Eris). The mechanical strength of dental composites containing a weak framework (K(IC)<3 MPam(1/2)) is ultimately determined by the low fracture strength of the veneer layer, since no crack arresting occurs at the veneer-framework interface. Therefore, high-toughness ceramics (K(IC)>5 MPam(1/2)) should be used as framework materials of posterior all-ceramic bridges, so that cracks propagating from the veneer layer do not lead to a premature failure of the prosthesis.

Bridge-in-a-Backpack(TM). Task 2 : reduction of costs through design modifications and optimization.

DOT National Transportation Integrated Search

2011-09-01

The cost effective use of FRP composites in infrastructure requires the efficient use of the : composite materials in the design. Previous work during the development phase and : demonstration phase illustrated the need to refine the design methods f...

Sequentially bridged graphene sheets with high strength, toughness, and electrical conductivity

PubMed Central

Wan, Sijie; Li, Yuchen; Mu, Jiuke; Aliev, Ali E.; Fang, Shaoli; Kotov, Nicholas A.; Jiang, Lei; Cheng, Qunfeng; Baughman, Ray H.

2018-01-01

We here show that infiltrated bridging agents can convert inexpensively fabricated graphene platelet sheets into high-performance materials, thereby avoiding the need for a polymer matrix. Two types of bridging agents were investigated for interconnecting graphene sheets, which attach to sheets by either π–π bonding or covalent bonding. When applied alone, the π–π bonding agent is most effective. However, successive application of the optimized ratio of π–π bonding and covalent bonding agents provides graphene sheets with the highest strength, toughness, fatigue resistance, electrical conductivity, electromagnetic interference shielding efficiency, and resistance to ultrasonic dissolution. Raman spectroscopy measurements of stress transfer to graphene platelets allow us to decipher the mechanisms of property improvement. In addition, the degree of orientation of graphene platelets increases with increasing effectiveness of the bonding agents, and the interlayer spacing increases. Compared with other materials that are strong in all directions within a sheet, the realized tensile strength (945 MPa) of the resin-free graphene platelet sheets was higher than for carbon nanotube or graphene platelet composites, and comparable to that of commercially available carbon fiber composites. The toughness of these composites, containing the combination of π–π bonding and covalent bonding, was much higher than for these other materials having high strengths for all in-plane directions, thereby opening the path to materials design of layered nanocomposites using multiple types of quantitatively engineered chemical bonds between nanoscale building blocks. PMID:29735659

Elastic, viscoelastic and viscoplastic contributions to compliance during deformation under stress in prosthodontic temporization materials.

PubMed

Vaidyanathan, Tritala K; Vaidyanathan, Jayalakshmi; Arghavani, David

2016-12-01

Purpose: The goal of this investigation was to characterize the compliance properties in selected polymers used for temporary (provisional crown and bridge) applications. Method: Polymethyl methacrylate (PMMA)- and polyethyl methacrylate (PEMA)-based JET and TRIM II were investigated along with two bisacryl composite resins (LUXATEMP and PROTEMP 3 GARANT). Rectangular samples of the resins were subjected to creep-recovery tests in a dynamic mechanical analyzer at and near the oral temperature (27 °C, 37 °C and 47 °C). The instantaneous (elastic), and time-dependent viscoelastic, and viscoplastic compliance profiles of the materials were determined and analyzed as a function of materials and temperature. Results: Highly significant ( p = 0.0001) differences among means of elastic, viscoelastic and viscoplastic compliance values were found as a function of materials. TRIM II showed an order of magnitude higher viscoplastic deformation than the other three materials (LUXATEMP, PROTEMP 3 GARANT and JET). Conclusions: The results indicate that PEMA is susceptible to significantly greater elastic, viscoelastic, and more importantly to viscoplastic compliant behavior compared with bisacryl composite and PMMA provisional crown and bridge materials. This indicates high-dimensional instability and poor stiffness and resiliency in PEMA appliances vis-à-vis those of PMMA and bisacryl composites.

Design Optimization of Hybrid FRP/RC Bridge

NASA Astrophysics Data System (ADS)

Papapetrou, Vasileios S.; Tamijani, Ali Y.; Brown, Jeff; Kim, Daewon

2018-04-01

The hybrid bridge consists of a Reinforced Concrete (RC) slab supported by U-shaped Fiber Reinforced Polymer (FRP) girders. Previous studies on similar hybrid bridges constructed in the United States and Europe seem to substantiate these hybrid designs for lightweight, high strength, and durable highway bridge construction. In the current study, computational and optimization analyses were carried out to investigate six composite material systems consisting of E-glass and carbon fibers. Optimization constraints are determined by stress, deflection and manufacturing requirements. Finite Element Analysis (FEA) and optimization software were utilized, and a framework was developed to run the complete analyses in an automated fashion. Prior to that, FEA validation of previous studies on similar U-shaped FRP girders that were constructed in Poland and Texas is presented. A finer optimization analysis is performed for the case of the Texas hybrid bridge. The optimization outcome of the hybrid FRP/RC bridge shows the appropriate composite material selection and cross-section geometry that satisfies all the applicable Limit States (LS) and, at the same time, results in the lightest design. Critical limit states show that shear stress criteria determine the optimum design for bridge spans less than 15.24 m and deflection criteria controls for longer spans. Increased side wall thickness can reduce maximum observed shear stresses, but leads to a high weight penalty. A taller cross-section and a thicker girder base can efficiently lower the observed deflections and normal stresses. Finally, substantial weight savings can be achieved by the optimization framework if base and side-wall thickness are treated as independent variables.

A laboratory and field study of composite piles for bridge substructures

DOT National Transportation Integrated Search

2006-03-01

The most commonly used pile materials are steel, concrete, and wood. These materials can degrade, and the degradation rate can be relatively rapid in harsh marine environments. It has been estimated that the U.S. spends over $1 billion annually for r...

Steel selection for UBC steel bridge

NASA Astrophysics Data System (ADS)

Liu, Haoyu

2018-03-01

This report conducts a material selection of different types of steel for UBC Steel Bridge Team. I am a third-year material engineering student, so the result from this material selection can only be taken into consideration but not fully adopted. As part of my academic journey, it is possible for technical mistakes in this material selection process. The mechanic properties are the most effective category of properties, making it necessary to be justified from the steel bridge design and chosen in accordance with the objective of the team. An introduction for currently-used steel properties and the expected steel properties is provided. The examination focus on how different alloy compositions of steel changes its properties. The properties of the steel are examined in three main aspects: hardness, strength, and toughness. The results suggest that more nickel, manganese, and chromium in the steel provide better steel for the team to use. Further research is needed if a more precise material selection is required.

Self-repair of cracks in brittle material systems

NASA Astrophysics Data System (ADS)

Dry, Carolyn M.

2016-04-01

One of the most effective uses for self repair is in material systems that crack because the cracks can allow the repair chemical to flow into the crack damage sites in all three dimensions. In order for the repair chemical to stay in the damage site and flow along to all the crack and repair there must be enough chemical to fill the entire crack. The repair chemical must be designed appropriately for the particular crack size and total volume of cracks. In each of the three examples of self repair in crackable brittle systems, the viscosity and chemical makeup and volume of the repair chemicals used is different for each system. Further the chemical delivery system has to be designed for each application also. Test results from self repair of three brittle systems are discussed. In "Self Repair of Concrete Bridges and Infrastructure" two chemicals were used due to different placements in bridges to repair different types of cracks- surface shrinkage and shear cracks, In "Airplane Wings and Fuselage, in Graphite" the composite has very different properties than the concrete bridges. In the graphite for airplane components the chemical also had to survive the high processing temperatures. In this composite the cracks were so definite and deep and thin that the repair chemical could flow easily and repair in all layers of the composite. In "Ceramic/Composite Demonstrating Self Repair" the self repair system not only repaired the broken ceramic but also rebounded the composite to the ceramic layer

Creep and shrinkage effects on integral abutment bridges

NASA Astrophysics Data System (ADS)

Munuswamy, Sivakumar

Integral abutment bridges provide bridge engineers an economical design alternative to traditional bridges with expansion joints owing to the benefits, arising from elimination of expensive joints installation and reduced maintenance cost. The superstructure for integral abutment bridges is cast integrally with abutments. Time-dependent effects of creep, shrinkage of concrete, relaxation of prestressing steel, temperature gradient, restraints provided by abutment foundation and backfill and statical indeterminacy of the structure introduce time-dependent variations in the redundant forces. An analytical model and numerical procedure to predict instantaneous linear behavior and non-linear time dependent long-term behavior of continuous composite superstructure are developed in which the redundant forces in the integral abutment bridges are derived considering the time-dependent effects. The redistributions of moments due to time-dependent effects have been considered in the analysis. The analysis includes nonlinearity due to cracking of the concrete, as well as the time-dependent deformations. American Concrete Institute (ACI) and American Association of State Highway and Transportation Officials (AASHTO) models for creep and shrinkage are considered in modeling the time dependent material behavior. The variations in the material property of the cross-section corresponding to the constituent materials are incorporated and age-adjusted effective modulus method with relaxation procedure is followed to include the creep behavior of concrete. The partial restraint provided by the abutment-pile-soil system is modeled using discrete spring stiffness as translational and rotational degrees of freedom. Numerical simulation of the behavior is carried out on continuous composite integral abutment bridges and the deformations and stresses due to time-dependent effects due to typical sustained loads are computed. The results from the analytical model are compared with the published laboratory experimental and field data. The behavior of the laterally loaded piles supporting the integral abutments is evaluated and presented in terms of the lateral deflection, bending moment, shear force and stress along the pile depth.

PRELIMINARY PROGRESS IN THE DEVELOPMENT OF DUCTILE-PHASE TOUGHENED TUNGSTEN FOR PLASMA-FACING MATERIALS: DUAL-PHASE FINITE ELEMENT DAMAGE MODELS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Henager, Charles H.; Nguyen, Ba Nghiep; Kurtz, Richard J.

The objective of this study is to develop a finite element continuum damage model suitable for modeling deformation, cracking, and crack bridging for W-Cu, W-Ni-Fe, and other ductile phase toughened W-composites, or more generally, any multi-phase composite structure where two or more phases undergo cooperative deformation in a composite system.

A Progressive Damage Methodology for Residual Strength Predictions of Notched Composite Panels

NASA Technical Reports Server (NTRS)

Coats, Timothy W.; Harris, Charles E.

1998-01-01

The translaminate fracture behavior of carbon/epoxy structural laminates with through-penetration notches was investigated to develop a residual strength prediction methodology for composite structures. An experimental characterization of several composite materials systems revealed a fracture resistance behavior that was very similar to the R-curve behavior exhibited by ductile metals. Fractographic examinations led to the postulate that the damage growth resistance was primarily due to fractured fibers in the principal load-carrying plies being bridged by intact fibers of the adjacent plies. The load transfer associated with this bridging mechanism suggests that a progressive damage analysis methodology will be appropriate for predicting the residual strength of laminates with through-penetration notches. A progressive damage methodology developed by the authors was used to predict the initiation and growth of matrix cracks and fiber fracture. Most of the residual strength predictions for different panel widths, notch lengths, and material systems were within about 10% of the experimental failure loads.

Histological evaluation of direct pulp capping with all-in-one adhesives in rat teeth.

PubMed

Shinkai, Koichi; Taira, Yoshihisa; Kawashima, Satoki; Suzuki, Shiro; Suzuki, Masaya

2017-05-31

The aim of this study was to histologically evaluate direct pulp capping using different all-in-one adhesives in rat teeth. Five all-in-one adhesives and a control material (MTA) were used. Each material was applied on the exposed pulp, and each cavity was subsequently restored with the resin composite. Rats were sacrificed 14 days after the surgical procedure. Serial stained sections were histologically evaluated for examining pulp tissue disorganization (PTD), inflammatory cell infiltration (ICI), dentin bridge formation (DBF), and bacterial penetration (BP). We found that rat pulps, which were direct capped with all-in-one adhesives, showed various degrees of PTD, ICI, and DBF depending on the material, and that there were no complete dentin bridges. In contrast, rat pulps capped with MTA showed no PTD and ICI, and there were complete dentin bridges in all, but one specimen. No BP was observed in any specimen.

RECENT PROGRESS IN THE FABRICATION AND CHARACTERIZATION OF DUCTILE-PHASE-TOUGHENED TUNGSTEN LAMINATES FOR PLASMA-FACING MATERIALS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cunningham, Kevin; Odette, G Robert; Fields, Kirk A.

2015-09-23

A promising approach to increasing the fracture toughness of W-alloys is ductile-phase toughening (DPT). A ductile phase reinforcement in a brittle matrix increases toughness primarily by crack bridging. A W-Cu laminate was fabricated and the properties of the constituent metals were characterized along with those for the composite. Development of a design model for large-scale crack bridging continued.

Implementation of thermal residual stresses in the analysis of fiber bridged matrix crack growth in titanium matrix composites

NASA Technical Reports Server (NTRS)

Bakuckas, John G., Jr.; Johnson, W. Steven

1994-01-01

In this research, thermal residual stresses were incorporated in an analysis of fiber-bridged matrix cracks in unidirectional and cross-ply titanium matrix composites (TMC) containing center holes or center notches. Two TMC were investigated, namely, SCS-6/Timelal-21S laminates. Experimentally, matrix crack initiation and growth were monitored during tension-tension fatigue tests conducted at room temperature and at an elevated temperature of 200 C. Analytically, thermal residual stresses were included in a fiber bridging (FB) model. The local R-ratio and stress-intensity factor in the matrix due to thermal and mechanical loadings were calculated and used to evaluate the matrix crack growth behavior in the two materials studied. The frictional shear stress term, tau, assumed in this model was used as a curve-fitting parameter to matrix crack growth data. The scatter band in the values of tau used to fit the matrix crack growth data was significantly reduced when thermal residual stresses were included in the fiber bridging analysis. For a given material system, lay-up and temperature, a single value of tau was sufficient to analyze the crack growth data. It was revealed in this study that thermal residual stresses are an important factor overlooked in the original FB models.

Toughening mechanisms in laminated composites: A biomimetic study in mollusk shells

NASA Astrophysics Data System (ADS)

Kamat, Shekhar Shripad

2000-10-01

Mollusk shells can be described as structural biocomposite materials composed of a mineral (aragonite) and a continuous, albeit minor, organic (protein) component. The conch shell, Strombus Gigas, has intermediate strength and high fracture toughness. The high fracture toughness is a result of enhanced energy dissipation during crack propagation due to delamination, crack bridging, frictional sliding etc. A theoretical and experimental study was conducted on the crack bridging mechanisms operative in the shell. Four-point bend tests were conducted. Acoustic emission and post-mortem dye penetrants were used to characterize the crack propagation, together with conventional fractography. A two layer composite configuration is seen in the shells, with the tough and weak layers having a toughness ratio of ˜4 (Ktough = 2.2MPam1/2). This toughness ratio is a requisite for multiple cracking in the weak layer. A theoretical shear lag analysis of the crack bridging phenomena in the tough layer is shown to lead to a bridging law for the crack wake of the form of p = betau1/2 (p is the bridging traction for a crack opening u, with beta, being a constant of proportionality). Finite element analysis yielded a value of beta = 630 Nmm-5/2 and ucritical = 5 mum for the bridging law parameters. In a nonlinear fracture mechanics phenomenology, these values are relevant material parameters, rather than a critical stress intensity factor. The work of fracture for unnotched specimens is three orders of magnitude higher than mineral aragonite, and is demonstrated numerically incorporating the toughening mechanisms in the shell. Similar structural adaptations have been observed and studied in the red abalone shell, haliotis rufescens and the spines of the sea urchin, Heterocentrotus trigonarius. The toughening mechanisms seen in these shells give insight into structural design needs of brittle matrix composites (BMC) as well as conventional structural ceramics.

Semiconductor bridge, SCB, ignition studies of Al/CuO thermite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bickes, R.W. Jr.; Wackerbarth, D.E.; Mohler, J.H.

1997-04-01

The authors briefly summarize semiconductor bridge operation and review their ignition studies of Al/CuO thermite as a function of the capacitor discharge unit (CDU) firing set capacitance, charge holder material and morphology of the CuO. Ignition thresholds were obtained using a brass charge holder and a non-conducting fiber-glass-epoxy composite material, G10. At - 18 C and a charge voltage of 50V, the capacitance thresholds were 30.1 {mu}F and 2.0 {mu}F respectively. They also present new data on electrostatic discharge (ESD) and radio frequency (RF) vulnerability tests.

Development of a nondestructive evaluation method for FRP bridge decks

NASA Astrophysics Data System (ADS)

Brown, Jeff; Fox, Terra

2010-05-01

Open steel grids are typically used on bridges to minimize the weight of the bridge deck and wearing surface. These grids, however, require frequent maintenance and exhibit other durability concerns related to fatigue cracking and corrosion. Bridge decks constructed from composite materials, such as a Fiber-reinforced Polymer (FRP), are strong and lightweight; they also offer improved rideability, reduced noise levels, less maintenance, and are relatively easy to install compared to steel grids. This research is aimed at developing an inspection protocol for FRP bridge decks using Infrared thermography. The finite element method was used to simulate the heat transfer process and determine optimal heating and data acquisition parameters that will be used to inspect FRP bridge decks in the field. It was demonstrated that thermal imaging could successfully identify features of the FRP bridge deck to depths of 1.7 cm using a phase analysis process.

Fracture and fatigue analysis of functionally graded and homogeneous materials using singular integral equation approach

NASA Astrophysics Data System (ADS)

Zhao, Huaqing

There are two major objectives of this thesis work. One is to study theoretically the fracture and fatigue behavior of both homogeneous and functionally graded materials, with or without crack bridging. The other is to further develop the singular integral equation approach in solving mixed boundary value problems. The newly developed functionally graded materials (FGMs) have attracted considerable research interests as candidate materials for structural applications ranging from aerospace to automobile to manufacturing. From the mechanics viewpoint, the unique feature of FGMs is that their resistance to deformation, fracture and damage varies spatially. In order to guide the microstructure selection and the design and performance assessment of components made of functionally graded materials, in this thesis work, a series of theoretical studies has been carried out on the mode I stress intensity factors and crack opening displacements for FGMs with different combinations of geometry and material under various loading conditions, including: (1) a functionally graded layer under uniform strain, far field pure bending and far field axial loading, (2) a functionally graded coating on an infinite substrate under uniform strain, and (3) a functionally graded coating on a finite substrate under uniform strain, far field pure bending and far field axial loading. In solving crack problems in homogeneous and non-homogeneous materials, a very powerful singular integral equation (SEE) method has been developed since 1960s by Erdogan and associates to solve mixed boundary value problems. However, some of the kernel functions developed earlier are incomplete and possibly erroneous. In this thesis work, mode I fracture problems in a homogeneous strip are reformulated and accurate singular Cauchy type kernels are derived. Very good convergence rates and consistency with standard data are achieved. Other kernel functions are subsequently developed for mode I fracture in functionally graded materials. This work provides a solid foundation for further applications of the singular integral equation approach to fracture and fatigue problems in advanced composites. The concept of crack bridging is a unifying theory for fracture at various length scales, from atomic cleavage to rupture of concrete structures. However, most of the previous studies are limited to small scale bridging analyses although large scale bridging conditions prevail in engineering materials. In this work, a large scale bridging analysis is included within the framework of singular integral equation approach. This allows us to study fracture, fatigue and toughening mechanisms in advanced materials with crack bridging. As an example, the fatigue crack growth of grain bridging ceramics is studied. With the advent of composite materials technology, more complex material microstructures are being introduced, and more mechanics issues such as inhomogeneity and nonlinearity come into play. Improved mathematical and numerical tools need to be developed to allow theoretical modeling of these materials. This thesis work is an attempt to meet these challenges by making contributions to both micromechanics modeling and applied mathematics. It sets the stage for further investigations of a wide range of problems in the deformation and fracture of advanced engineering materials.

A Design Tool for Robust Composite Structures

DTIC Science & Technology

2010-06-01

a a UNIVERSITY OF ^?CAiVI BRIDGE FINAL REPORT A Design Tool for Robust Composite Structures Frank Zok Materials Department University of ...organic fibers, especially Dyneema®. The principal objectives of the present study were to ascertain the fundamental mechanical properties of Dyneema...composites increases by a factor of 2 and the ductility by almost a factor of 3 over the strain rate range 10-3 s-1 to 104 s- 1. One consequence is

Studies on silicon NMR characterization and kinetic modeling of the structural evolution of siloxane-based materials and their applications in drug delivery and adsorption

NASA Astrophysics Data System (ADS)

Ambati, Jyothirmai

This dissertation presents studies of the synthetic processes and applications of siloxane-based materials. Kinetic investigations of bridged organoalkoxysilanes that are precursors to organic-inorganic hybrid polysilsesquioxanes are a primary focus. Quick gelation despite extensive cyclization is found during the polymerization of bridged silane precursors except for silanes with certain short bridges. This work is an attempt to characterize and understand some of the distinct features of bridged silanes using experimental characterization, kinetic modeling and simulation. In addition to this, the dissertation shows how the properties of siloxane-materials can be engineered for drug delivery and adsorption. The phase behavior of polymerizing mixtures is first investigated to identify the solutions that favor kinetic characterization. Microphase separation is found to cause gradual loss of NMR signal for certain initial compositions. Distortionless Enhancement by Polarization Transfer 29Si NMR is employed to identify the products of polymerization of some short-bridged silanes under no signal loss conditions. This technique requires knowing indirect 29Si-1H scalar coupling constants which sometimes cannot be measured due to second-order effects. However, the B3LYP density functional method with 6-31G basis set is found to predict accurate 29Si- 1H coupling constants of organoalkoxysilanes and siloxanes. The scalar coupling constants thus estimated are employed to resolve non-trivial coupled NMR spectra and quantitative kinetic modeling is performed using the DEPT Si NMR transients. In order to investigate the role of the organic bridging group, the structural evolution of bridged and non-bridged silanes are compared using Monte Carlo simulations. Kinetic and simulation models suggest that cyclization plays a key role right from the onset of polymerization for bridged silanes even more than in non-bridged silanes. The simulations indicate that the carbosiloxane rings formed from short-bridged precursors slow down but do not prevent gelation. The tuning of siloxane-based materials for adsorption technologies are also discussed here. In the first example, antioxidant enzyme loading is investigated as a means to reduce oxidative stress generated by silica nanoparticle drug carriers. Materials are engineered for promising enzyme loading and protection from proteolysis. Second, the potential of copper sulfate impregnation to enhance adsorption of ammonia by silica is explored by molecular simulation. KEYWORDS: Sol-gel Polymerization, Kinetic Investigation, Si NMR, Bridged Silanes, DFT Calculations.

Issues related to durability and protection affecting the acceptance and use of engineered wood composites in Europe

Treesearch

Mark Hughes; Jerrold E. Winandy

2007-01-01

Engineered wood composites (EWC) offer significant potential in applications in the built environment, ranging from domestic dwellings to bridges and public buildings. Nevertheless, EWCs, which include products such as glulam, laminated veneer lumber, oriented stand-board, and plywood enjoy a relatively small market share of total wood-based material production and...

The viability and performance characterization of nano scale energetic materials on a semiconductor bridge (SCB)

NASA Astrophysics Data System (ADS)

Strohm, Gianna Sophia

The move from conventional energetic composites to nano scale energetic mixtures (nano energetics) has shown dramatic improvement in energy release rate and sensitivity to ignition. A possible application of nano energetics is on a semiconductor bridge (SCB). An SCB typically requires a tenth of the energy input as compared to a bridge wire design with the same no-fire and is capable of igniting in tens of microseconds. For very low energy applications, SCBs can be manufactured to extremely small sizes and it is necessary to find materials with particle sizes that are even smaller to function. Reactive particles of comparable size to the bridge can lead to problems with ignition reliability for small bridges. Nano-energetic composites and the use of SCBs have been significantly studied individually, however, the process of combining nano energetics with an SCB has not been investigated extensively and is the focus of this work. Goals of this study are to determine if nano energetics can be used with SCBs to further reduce the minimum energy required and improve reliability. The performance of nano-scale aluminum (nAl) and bismuth oxide (Bi2O3) with nitrocellulose (NC), Fluorel(TM) FC 2175 (chemically equivalent to VitonRTM) and Glycidyl Azide Polymer (GAP) as binders where quantified initially using the SenTest(TM) algorithm at three weight fractions (5, 7, and 9%) of binder. The threshold energy was calculated and compared to previous data using conventional materials such as zirconium potassium chlorate (ZPC), mercuric 5-Nitrotetrazol (DXN-1) and titanium sub-hydride potassium per-chlorate (TSPP). It was found that even though there where only slight differences in performance between the binders with nAl/Bi2O 3 at any of the three binder weight fractions, the results show that these nano energetic materials require about half of the threshold energy compared to conventional materials using an SCB with an 84x42 mum bridge. Binder limit testing was conducted to find the critical limit of binder when the output of the SCB declines. The binder was evaluated at 13, 17 and 20% and it was found that the limit amount of binder falls between 17 and 20% by weight of material. Scaling of the SCB bridge was evaluated using a 36x15 mum bridge size and tested using 5, 7 and 9% nAl/Bi2O 3 FC 2175 slurry, creating a functioning SCB compared to previous no-ignition results using TSPP. It was also postulated that the compaction of a secondary material onto the SCB would alter the SCB output during testing. It was found that increased energy values where required for both the 5 and 7% binder amounts and no change was seen at the 9% level.

Sustainability of transportation structures using composite materials to support trade and growth.

DOT National Transportation Integrated Search

2014-06-01

Corrosion-induced deterioration of steel rebar is one of the main reasons for repair and rehabilitation programs : for conventional steel-reinforced concrete bridge decks. According to the National Association of Corrosion Engineers : (NACE), of all ...

Composite materials for rail transit systems

NASA Technical Reports Server (NTRS)

Griffin, O. Hayden, Jr.; Guerdal, Zafer; Herakovich, Carl T.

1987-01-01

The potential is explored for using composite materials in urban mass transit systems. The emphasis was to identify specific advantages of composite materials in order to determine their actual and potential usage for carbody and guideway structure applications. The literature was reviewed, contacts were made with major domestic system operators, designers, and builders, and an analysis was made of potential composite application to railcar construction. Composites were found to be in use throughout the transit industry, usually in secondary or auxiliary applications such as car interior and nonstructural exterior panels. More recently, considerable activity has been initiated in the area of using composites in the load bearing elements of civil engineering structures such as highway bridges. It is believed that new and improved manufacturing refinements in pultrusion and filament winding will permit the production of beam sections which can be used in guideway structures. The inherent corrosion resistance and low maintenance characteristics of composites should result in lowered maintenance costs over a prolonged life of the structure.

Experimental and Analytical Seismic Studies of a Four-Span Bridge System with Innovative Materials

NASA Astrophysics Data System (ADS)

Cruz Noguez, Carlos Alonso

As part of a multi-university project utilizing the NSF Network for Earthquake Engineering Simulation (NEES), a quarter-scale model of a four-span bridge incorporating plastic hinges with different advanced materials was tested to failure on the three shake table system at the University of Nevada, Reno (UNR). The bridge was the second test model in a series of three 4-span bridges, with the first model being a conventional reinforced-concrete (RC) structure. The purpose of incorporating advanced materials was to improve the seismic performance of the bridge with respect to two damage indicators: (1) column damage and (2) permanent deformations. The goals of the study presented in this document were to (1) evaluate the seismic performance of a 4-span bridge system incorporating SMA/ECC and built-in rubber pad plastic hinges as well as post-tensioned piers, (2) quantify the relative merit of these advanced materials and details compared to each other and to conventional reinforced concrete plastic hinges, (3) determine the influence of abutment-superstructure interaction on the response, (4) examine the ability of available elaborate analytical modeling techniques to model the performance of advanced materials and details, and (5) conduct an extensive parametric study of different variations of the bridge model to study several important issues in bridge earthquake engineering. The bridge model included six columns, each pair of which utilized a different advanced detail at bottom plastic hinges: shape memory alloys (SMA), special engineered cementitious composites (ECC), elastomeric pads embedded into columns, and post-tensioning tendons. The design of the columns, location of the bents, and selection of the loading protocol were based on pre-test analyses conducted using computer program OpenSees. The bridge model was subjected to two-horizontal components of simulated earthquake records of the 1994 Northridge earthquake. Over 340 channels of data were collected. The test results showed the effectiveness of the advanced materials in reducing damage and permanent displacements. The damage was minimal in plastic hinges with SMA/ECC and those with built-in elastomeric pads. Conventional RC plastic hinges were severely damaged due to spalling of concrete and rupture of the longitudinal and transverse reinforcement. Extensive post-test analytical studies were conducted and it was determined that a computational model of the bridge that included bridge-abutment interaction using OpenSees was able to provide satisfactory estimations of key structural parameters such as superstructure displacements and base shears. The analytical model was also used to conduct parametric studies on single-column and bridge-system response under near-fault ground motions. The effects of vertical excitations and transverse shear-keys at the bridge abutments on the superstructure displacement and column drifts were also explored.

Ultra-high performance concrete : a state-of-the-art report for the bridge community.

DOT National Transportation Integrated Search

2013-06-01

"The term Ultra-High Performance Concrete (UHPC) refers to a relatively new class of advanced cementitious : composite materials whose mechanical and durability properties far surpass those of conventional concrete. This : class of concrete has been ...

Soft-Templating Synthesis of Mesoporous Silica-Based Materials for Environmental Applications

NASA Astrophysics Data System (ADS)

Gunathilake, Chamila Asanka

Dissertation research is mainly focus on: 1) the development of mesoporous silica materials with organic pendant and bridging groups (isocyanurate, amidoxime, benzene) and incorporated metal (aluminum, zirconium, calcium, and magnesium) species for high temperature carbon dioxide (CO2) sorption, 2) phosphorous-hydroxy functionalized mesoporous silica materials for water treatment, and 3) amidoxime-modified ordered mesoporous silica materials for uranium sorption under seawater conditions. The goal is to design composite materials for environmental applications with desired porosity, surface area, and functionality by selecting proper metal oxide precursors, organosilanes, tetraethylorthosilicate, (TEOS), and block copolymer templates and by adjusting synthesis conditions. The first part of dissertation presents experimental studies on the merge of aluminum, zirconium, calcium, and magnesium oxides with mesoporous silica materials containing organic pendant (amidoxime) and bridging groups (isocyanurate, benzene) to obtain composite sorbents for CO2 sorption at ambient (0-25 °C) and elevated (60-120 °C) temperatures. These studies indicate that the aforementioned composite sorbents are fairly good for CO2 capture at 25 °C via physisorption mechanism and show a remarkably high affinity toward CO2 chemisorption at 60-120 °C. The second part of dissertation is devoted to silica-based materials with organic functionalities for removal of heavy metal ions such as lead from contaminated water and for recovery of metal ions such as uranium from seawater. First, ordered mesoporous organosilica (OMO) materials with diethylphosphatoethyl and hydroxyphosphatoethyl surface groups were examined for Pb2+ adsorption and showed unprecedented adsorption capacities up to 272 mg/g and 202 mg/g, respectively However, the amidoxime-modified OMO materials were explored for uranium extraction under seawater conditions and showed remarkable capacities reaching 57 mg of uranium per gram of adsorbent.

Multifunctional Characteristics of Carbon Nanotube (CNT) Yarn Composites

NASA Technical Reports Server (NTRS)

Hernandez, Corey D.; Zhang, Mei; Fang, Shaoli; Baughman, Ray H.; Gates, Thomas S.; Kahng, Seun K.

2006-01-01

By forming composite structures with Carbon Nanotube (CNT) yarns we achieve materials capable of measuring strain and composite structures with increased mechanical strength. The CNT yarns used are of the 2-ply and 4-ply variety with the yarns having diameters of about 15-30 micrometers. The strain sensing characteristics of the yarns are investigated on test beams with the yarns arranged in a bridge configuration. Additionally, the strain sensing properties are also investigated on yarns embedded on the surface of a flexible membrane. Initial mechanical strength tests also show an increase in the modulus of elasticity of the composite materials while incurring a weight penalty of less than one-percent. Also presented are initial temperature characterizations of the yarns.

Development of load and resistance factor design for FRP strengthening of reinforced concrete bridges.

DOT National Transportation Integrated Search

2006-05-01

Externally bonded fiber reinforced polymer (FRP) composites are an increasingly adopted technology for the renewal of existing concrete structures. In order to encourage the further use of these materials, a design code is needed that considers the i...

Superstretchable Nacre-Mimetic Graphene/Poly(vinyl alcohol) Composite Film Based on Interfacial Architectural Engineering.

PubMed

Zhao, Nifang; Yang, Miao; Zhao, Qian; Gao, Weiwei; Xie, Tao; Bai, Hao

2017-05-23

Through designing hierarchical structures, particularly optimizing the chemical and architectural interactions at its inorganic/organic interface, nacre has achieved an excellent combination of contradictory mechanical properties such as strength and toughness, which is highly demanded yet difficult to achieve by most synthetic materials. Most techniques applied to develop nacre-mimetic composites have been focused on mimicking the "brick-and-mortar" structure, but the interfacial architectural features, especially the asperities and mineral bridges of "bricks", have been rarely concerned, which are of equal importance for enhancing mechanical properties of nacre. Here, we used a modified bidirectional freezing method followed by uniaxial pressing and chemical reduction to assemble a nacre-mimetic graphene/poly(vinyl alcohol) composite film, with both asperities and bridges introduced in addition to the lamellar layers to mimic the interfacial architectural interactions found in nacre. As such, we have developed a composite film that is not only strong (up to ∼150.9 MPa), but also tough (up to ∼8.50 MJ/m 3 ), and highly stretchable (up to ∼10.44%), difficult to obtain by other methods. This was all achieved by only interfacial architectural engineering within the traditional "brick-and-mortar" structure, without introducing a third component or employing chemical cross-linker as in some other nacre-mimetic systems. More importantly, we believe that the design principles and processing strategies reported here can also be applied to other material systems to develop strong and stretchable materials.

High-performance multilayer composite membranes with mussel-inspired polydopamine as a versatile molecular bridge for CO2 separation.

PubMed

Li, Panyuan; Wang, Zhi; Li, Wen; Liu, Yanni; Wang, Jixiao; Wang, Shichang

2015-07-22

It is desirable to develop high-performance composite membranes for efficient CO2 separation in CO2 capture process. Introduction of a highly permeable polydimethylsiloxane (PDMS) intermediate layer between a selective layer and a porous support has been considered as a simple but efficient way to enhance gas permeance while maintaining high gas selectivity, because the introduced intermediate layer could benefit the formation of an ultrathin defect-free selective layer owing to the circumvention of pore penetration phenomenon. However, the selection of selective layer materials is unfavorably restricted because of the low surface energy of PDMS. Various highly hydrophilic membrane materials such as amino group-rich polyvinylamine (PVAm), a representative facilitated transport membrane material for CO2 separation, could not be facilely coated over the surface of the hydrophobic PDMS intermediate layer uniformly. Inspired by the hydrophilic nature and strong adhesive ability of polydopamine (PDA), PDA was therefore selected as a versatile molecular bridge between hydrophobic PDMS and hydrophilic PVAm. The PDA coating endows a highly compatible interface between both components with a large surface energy difference via multiple-site cooperative interactions. The resulting multilayer composite membrane with a thin facilitated transport PVAm selective layer exhibits a notably enhanced CO2 permeance (1887 GPU) combined with a slightly improved CO2/N2 selectivity (83), as well as superior structural stability. Similarly, the multilayer composite membrane with a hydrophilic CO2-philic Pebax 1657 selective layer was also developed for enhanced CO2 separation performance.

Single-Phase Concentrated Solid-Solution Alloys: Bridging Intrinsic Transport Properties and Irradiation Resistance

DOE PAGES

Jin, Ke; Bei, Hongbin

2018-04-30

Single-phase concentrated solid-solution alloys (SP-CSAs), including high entropy alloys (HEAs), are compositionally complex but structurally simple, and provide a playground of tailoring material properties through modifying their compositional complexity. The recent progress in understanding the compositional effects on the energy and mass transport properties in a series of face-centered-cubic SP-CSAs is the focus of this review. Relatively low electrical and thermal conductivities, as well as small separations between the interstitial and vacancy migration barriers have been generally observed, but largely depend on the alloying constituents. We further discuss the impact of such intrinsic transport properties on their irradiation response; themore » linkage to the delayed damage accumulation, slow defect aggregation, and suppressed irradiation induced swelling and segregation has been presented. We emphasize that the number of alloying elements may not be a critical factor on both transport properties and the defect behaviors under ion irradiations. Furthermore, the recent findings have stimulated novel concepts in the design of new radiation-tolerant materials, but further studies are demanded to enable predictive models that can quantitatively bridge the transport properties to the radiation damage.« less

Single-Phase Concentrated Solid-Solution Alloys: Bridging Intrinsic Transport Properties and Irradiation Resistance

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jin, Ke; Bei, Hongbin

Single-phase concentrated solid-solution alloys (SP-CSAs), including high entropy alloys (HEAs), are compositionally complex but structurally simple, and provide a playground of tailoring material properties through modifying their compositional complexity. The recent progress in understanding the compositional effects on the energy and mass transport properties in a series of face-centered-cubic SP-CSAs is the focus of this review. Relatively low electrical and thermal conductivities, as well as small separations between the interstitial and vacancy migration barriers have been generally observed, but largely depend on the alloying constituents. We further discuss the impact of such intrinsic transport properties on their irradiation response; themore » linkage to the delayed damage accumulation, slow defect aggregation, and suppressed irradiation induced swelling and segregation has been presented. We emphasize that the number of alloying elements may not be a critical factor on both transport properties and the defect behaviors under ion irradiations. Furthermore, the recent findings have stimulated novel concepts in the design of new radiation-tolerant materials, but further studies are demanded to enable predictive models that can quantitatively bridge the transport properties to the radiation damage.« less

Boron nitride nanotube reinforced hydroxyapatite composite: mechanical and tribological performance and in-vitro biocompatibility to osteoblasts.

PubMed

Lahiri, Debrupa; Singh, Virendra; Benaduce, Ana Paula; Seal, Sudipta; Kos, Lidia; Agarwal, Arvind

2011-01-01

This study proposes boron nitride nanotube (BNNT) reinforced hydroxyapatite (HA) as a novel composite material for orthopedic implant applications. The spark plasma sintered (SPS) composite structure shows higher density compared to HA. Minimal lattice mismatch between HA and BNNT leads to coherent bonding and strong interface. HA-4 wt% BNNT composite offers excellent mechanical properties-120% increment in elastic modulus, 129% higher hardness and 86% more fracture toughness, as compared to HA. Improvements in the hardness and fracture toughness are related to grain refinement and crack bridging by BNNTs. HA-BNNT composite also shows 75% improvement in the wear resistance. The wear morphology suggests localized plastic deformation supported by the sliding of outer walls of BNNT. Osteoblast proliferation and cell viability show no adverse effect of BNNT addition. HA-BNNT composite is, thus, envisioned as a potential material for stronger orthopedic implants. Copyright © 2010 Elsevier Ltd. All rights reserved.

Tuning the mechanical properties of glass fiber-reinforced bismaleimide–triazine resin composites by constructing a flexible bridge at the interface

PubMed Central

Zeng, Xiaoliang; Yu, Shuhui; Lai, Maobai; Sun, Rong; Wong, Ching-Ping

2013-01-01

We demonstrate a new method that can simultaneously improve the strength and toughness of the glass fiber-reinforced bismaleimide–triazine (BT) resin composites by using polyethylene glycol (PEG) to construct a flexible bridge at the interface. The mechanical properties, including the elongation, ultimate tensile stress, Young’s modulus, toughness and dynamical mechanical properties were studied as a function of the length of PEG molecular chain. It was found that the PEG molecule acts as a bridge to link BT resin and glass fiber through covalent and non-covalent bondings, respectively, resulting in improved interfacial bonding. The incorporation of PEG produces an increase in elongation, ultimate tensile stress and toughness. The Young’s modulus and Tg were slightly reduced when the length of the PEG molecular chain was high. The elongation of the PEG-modified glass fiber-reinforced composites containing 5 wt% PEG-8000 increased by 67.1%, the ultimate tensile stress by 17.9% and the toughness by 78.2% compared to the unmodified one. This approach provides an efficient way to develop substrate material with improved strength and toughness for integrated circuit packaging applications. PMID:27877621

A Progressive Damage Methodology for Residual Strength Predictions of Center-Crack Tension Composite Panels

NASA Technical Reports Server (NTRS)

Coats, Timothy William

1996-01-01

An investigation of translaminate fracture and a progressive damage methodology was conducted to evaluate and develop a residual strength prediction capability for laminated composites with through penetration notches. This is relevant to the damage tolerance of an aircraft fuselage that might suffer an in-flight accident such as an uncontained engine failure. An experimental characterization of several composite materials systems revealed an R-curve type of behavior. Fractographic examinations led to the postulate that this crack growth resistance could be due to fiber bridging, defined here as fractured fibers of one ply bridged by intact fibers of an adjacent ply. The progressive damage methodology is currently capable of predicting the initiation and growth of matrix cracks and fiber fracture. Using two difference fiber failure criteria, residual strength was predicted for different size panel widths and notch lengths. A ply discount fiber failure criterion yielded extremely conservative results while an elastic-perfectly plastic fiber failure criterion showed that the fiber bridging concept is valid for predicting residual strength for tensile dominated failure loads. Furthermore, the R-curves predicted by the model using the elastic-perfectly plastic fiber criterion compared very well with the experimental R-curves.

ASTM and VAMAS activities in titanium matrix composites test methods development

NASA Technical Reports Server (NTRS)

Johnson, W. S.; Harmon, D. M.; Bartolotta, P. A.; Russ, S. M.

1994-01-01

Titanium matrix composites (TMC's) are being considered for a number of aerospace applications ranging from high performance engine components to airframe structures in areas that require high stiffness to weight ratios at temperatures up to 400 C. TMC's exhibit unique mechanical behavior due to fiber-matrix interface failures, matrix cracks bridged by fibers, thermo-viscoplastic behavior of the matrix at elevated temperatures, and the development of significant thermal residual stresses in the composite due to fabrication. Standard testing methodology must be developed to reflect the uniqueness of this type of material systems. The purpose of this paper is to review the current activities in ASTM and Versailles Project on Advanced Materials and Standards (VAMAS) that are directed toward the development of standard test methodology for titanium matrix composites.

Local-based damage detection of cyclically loaded bridge piers using wireless sensing units

NASA Astrophysics Data System (ADS)

Hou, Tsung-Chin; Lynch, Jerome P.; Parra-Montesinos, Gustavo

2005-05-01

Concrete bridge piers are a common structural element employed in the design of bridges and elevated roadways. In order to ensure adequate behavior under earthquake-induced displacements, extensive reinforcement detailing in the form of closely spaced ties or spirals is necessary, leading to congestion problems and difficulties during concrete casting. Further, costly repairs are often necessary in bridge piers after a major earthquake which in some cases involve the total or partial shutdown of the bridge. In order to increase the damage tolerance while relaxing the transverse reinforcement requirements of bridge piers, the use of high-performance fiber reinforced cementitious composites (HPFRCC) in earthquake-resistant bridge piers is explored. HPFRCCs are a relatively new class of cementitious material for civil structures with tensile strain-hardening behavior and high damage tolerance. To monitor the behavior of this new class of material in the field, low-cost wireless monitoring technologies will be adopted to provide HPFRCC structural elements the capability to accurately monitor their performance and health. In particular, the computational core of a wireless sensing unit can be harnessed to screen HPFRCC components for damage in real-time. A seismic damage index initially proposed for flexure dominated reinforced concrete elements is modified to serve as an algorithmic tool for the rapid assessment of damage (due to flexure and shear) in HPFRCC bridge piers subjected to large shear reversals. Traditional and non-traditional sensor strategies of an HPFRCC bridge pier are proposed to optimize the correlation between the proposed damage index model and the damage observed in a circular pier test specimen. Damage index models are shown to be a sufficiently accurate rough measure of the degree of local-area damage that can then be wirelessly communicated to bridge officials.

Environmental Factors Affecting the Strength Characteristics of Modified Resin Mortars

NASA Astrophysics Data System (ADS)

Debska, Bernardeta; Licholai, Lech

2017-12-01

Resin concretes are composites in which a cement binder has been completely replaced by a synthetic resin. These materials are a good choice for the construction industry, especially in solutions requiring high strength, fast curing and durability. Polymer mortars are mainly used for the manufacture of industrial floors and prefabricated products such as tanks for aggressive chemicals, sewage pipes, or road and bridge drainage systems, as well as for the repair of damaged concrete structures. In all these applications, the strength and high chemical resistance of the applied material solutions are of key importance. It is particularly crucial to obtain information on how resin composites behave when exposed to aggressive agents over extended periods of time. It is also very important to use waste materials in order to obtain resin composites, as these activities are very well inscribed in the idea of environmental protection and meet the criteria of sustainable construction. The mortars described in this article meet the above principles. The article presents how the compressive strength of glycolyzate-modified epoxy mortars, obtained with the use of poly(ethylene terephthalate), changes after they are immersed in 10% sodium chloride solution. Sodium chloride solution was chosen due to the prospective applicability of the tested composites as repair materials used for e.g. bridges or overpasses that are exposed to this salt solution in wintertime. Changes in the properties of the composite samples were monitored over the period of one year. Statistical analysis of the test results was carried out with the use of Statistica programme. The module available in the mentioned program called Nonparametric Statistics - Comparing multiple independent samples made it possible to check the monitoring times during which the compressive strength values differed significantly. The obtained results allowed for determining the equation of the function approximating the course of changes in mortar properties. The designated parameters of regression equations can be used to project the properties of composites.

Periodically microstructured composite films made by electric- and magnetic-directed colloidal assembly

PubMed Central

Demirörs, Ahmet Faik; Courty, Diana; Libanori, Rafael; Studart, André R.

2016-01-01

Living organisms often combine soft and hard anisotropic building blocks to fabricate composite materials with complex microstructures and outstanding mechanical properties. An optimum design and assembly of the anisotropic components reinforces the material in specific directions and sites to best accommodate multidirectional external loads. Here, we fabricate composite films with periodic modulation of the soft–hard microstructure by simultaneously using electric and magnetic fields. We exploit forefront directed-assembly approaches to realize highly demanded material microstructural designs and showcase a unique example of how one can bridge colloidal sciences and composite technology to fabricate next-generation advanced structural materials. In the proof-of-concept experiments, electric fields are used to dictate the position of the anisotropic particles through dielectrophoresis, whereas a rotating magnetic field is used to control the orientation of the particles. By using such unprecedented control over the colloidal assembly process, we managed to fabricate ordered composite microstructures with up to 2.3-fold enhancement in wear resistance and unusual site-specific hardness that can be locally modulated by a factor of up to 2.5. PMID:27071113

The effects of temperature on fiber composite bridge decks.

DOT National Transportation Integrated Search

2009-01-01

In this study the fiber composite bridge decks were subjected to thermal gradients to obtain the temperature difference between the top and bottom surface of the decks and to determine the thermal properties of the deck. The fiber composite bridge de...

Experimental evaluation and design of unfilled and concrete-filled FRP composite piles, task 2 - FRP composite pile driving at the Richmond-Dresden bridge over the Kennebec River.

DOT National Transportation Integrated Search

2014-01-01

The overall goal of this project is the experimental evaluation and design of unfilled and concrete-filled FRP : composite piles for load-bearing in bridges. This report covers Task 2, FRP Composite Pile Driving at the : Richmond-Dresden Bridge over ...

Effect of Data Reduction and Fiber-Bridging on Mode I Delamination Characterization of Unidirectional Composites

NASA Technical Reports Server (NTRS)

Murri, Gretchen B.

2011-01-01

Reliable delamination characterization data for laminated composites are needed for input in analytical models of structures to predict delamination onset and growth. The double-cantilevered beam (DCB) specimen is used to measure fracture toughness, GIc, and strain energy release rate, GImax, for delamination onset and growth in laminated composites under mode I loading. The current study was conducted as part of an ASTM Round Robin activity to evaluate a proposed testing standard for Mode I fatigue delamination propagation. Static and fatigue tests were conducted on specimens of IM7/977-3 and G40-800/5276-1 graphite/epoxies, and S2/5216 glass/epoxy DCB specimens to evaluate the draft standard "Standard Test Method for Mode I Fatigue Delamination Propagation of Unidirectional Fiber-Reinforced Polymer Matrix Composites." Static results were used to generate a delamination resistance curve, GIR, for each material, which was used to determine the effects of fiber-bridging on the delamination growth data. All three materials were tested in fatigue at a cyclic GImax level equal to 90% of the fracture toughness, GIc, to determine the delamination growth rate. Two different data reduction methods, a 2-point and a 7-point fit, were used and the resulting Paris Law equations were compared. Growth rate results were normalized by the delamination resistance curve for each material and compared to the nonnormalized results. Paris Law exponents were found to decrease by 5.4% to 46.2% due to normalizing the growth data. Additional specimens of the IM7/977-3 material were tested at 3 lower cyclic GImax levels to compare the effect of loading level on delamination growth rates. The IM7/977-3 tests were also used to determine the delamination threshold curve for that material. The results show that tests at a range of loading levels are necessary to describe the complete delamination behavior of this material.

The weak interfaces within tough natural composites: experiments on three types of nacre.

PubMed

Khayer Dastjerdi, Ahmad; Rabiei, Reza; Barthelat, Francois

2013-03-01

Mineralization is a typical strategy used in natural materials to achieve high stiffness and hardness for structural functions such as skeletal support, protection or predation. High mineral content generally leads to brittleness, yet natural materials such as bone, mollusk shells or glass sponge achieve relatively high toughness considering the weakness of their constituents through intricate microstructures. In particular, nanometers thick organic interfaces organized in micro-architectures play a key role in providing toughness by various processes including crack deflection, crack bridging or energy dissipation. While these interfaces are critical in these materials, their composition, structure and mechanics is often poorly understood. In this work we focus on nacre, one of the most impressive hard biological materials in terms of toughness. We performed interfacial fracture tests on chevron notched nacre samples from three different species: red abalone, top shell and pearl oyster. We found that the intrinsic toughness of the interfaces is indeed found to be extremely low, in the order of the toughness of the mineral inclusions themselves. Such low toughness is required for the cracks to follow the interfaces, and to deflect and circumvent the mineral tablets. This result highlights the efficacy of toughening mechanisms in natural materials, turning low-toughness inclusions and interfaces into high-performance composites. We found that top shell nacre displayed the highest interfacial toughness, because of higher surface roughness and a more resilient organic material, and also through extrinsic toughening mechanisms including crack deflection, crack bridging and process zone. In the context of biomimetics, the main implication of this finding is that the interface in nacre-like composite does not need to be tough; the extensibility or ductility of the interfaces may be more important than their strength and toughness to produce toughness at the macroscale. Copyright © 2012 Elsevier Ltd. All rights reserved.

Implementation and non-destructive evaluation of composite structural shapes in the Tom's Creek Bridge.

DOT National Transportation Integrated Search

2000-01-01

A bridge rehabilitation utilizing a hybrid fiber reinforced polymeric composite has been completed in Blacksburg, Virginia. This project involved replacing the superstructure in the Tom's Creek Bridge, a rural short-span traffic bridge with a timber ...

Unprecedented simultaneous enhancement in damage tolerance and fatigue resistance of zirconia/Ta composites

NASA Astrophysics Data System (ADS)

Smirnov, A.; Beltrán, J. I.; Rodriguez-Suarez, T.; Pecharromán, C.; Muñoz, M. C.; Moya, J. S.; Bartolomé, J. F.

2017-03-01

Dense (>98 th%) and homogeneous ceramic/metal composites were obtained by spark plasma sintering (SPS) using ZrO2 and lamellar metallic powders of tantalum or niobium (20 vol.%) as starting materials. The present study has demonstrated the unique and unpredicted simultaneous enhancement in toughness and strength with very high flaw tolerance of zirconia/Ta composites. In addition to their excellent static mechanical properties, these composites also have exceptional resistance to fatigue loading. It has been shown that the major contributions to toughening are the resulting crack bridging and plastic deformation of the metallic particles, together with crack deflection and interfacial debonding, which is compatible with the coexistence in the composite of both, strong and weak ceramic/metal interfaces, in agreement with predictions of ab-initio calculations. Therefore, these materials are promising candidates for designing damage tolerance components for aerospace industry, cutting and drilling tools, biomedical implants, among many others.

Unprecedented simultaneous enhancement in damage tolerance and fatigue resistance of zirconia/Ta composites

PubMed Central

Smirnov, A.; Beltrán, J. I.; Rodriguez-Suarez, T.; Pecharromán, C.; Muñoz, M. C.; Moya, J. S.; Bartolomé, J. F.

2017-01-01

Dense (>98 th%) and homogeneous ceramic/metal composites were obtained by spark plasma sintering (SPS) using ZrO2 and lamellar metallic powders of tantalum or niobium (20 vol.%) as starting materials. The present study has demonstrated the unique and unpredicted simultaneous enhancement in toughness and strength with very high flaw tolerance of zirconia/Ta composites. In addition to their excellent static mechanical properties, these composites also have exceptional resistance to fatigue loading. It has been shown that the major contributions to toughening are the resulting crack bridging and plastic deformation of the metallic particles, together with crack deflection and interfacial debonding, which is compatible with the coexistence in the composite of both, strong and weak ceramic/metal interfaces, in agreement with predictions of ab-initio calculations. Therefore, these materials are promising candidates for designing damage tolerance components for aerospace industry, cutting and drilling tools, biomedical implants, among many others. PMID:28322343

Comparative Evaluation of Flexural Strength of Provisional Crown and Bridge Materials-An Invitro Study

PubMed Central

Garg, Sandeep

2016-01-01

Introduction Provisional restorations serve a key role as a functional and esthetic try-in for the design of the final prosthesis. During selection of materials for this restoration, clinicians must consider physical properties, ease of handling, cost and patient satisfaction and approval. Aim To evaluate and compare the flexural strength of provisional crown and bridge materials available commercially. Materials and Methods This in-vitro study was done to compare the flexural strength of six temporary crown and bridge materials available commercially at 24 hours, 8 days and after repair. Three poly methyl methacrylate based materials (DPI, SC10 and Trulon) and three bis-acrylic based composite resins (Protemp, Cooltemp and Luxatemp) were selected. A total of 72 specimens of dimensions 64mm×10mm×2.5mm were prepared from these materials (12 from each material) and divided into two groups (n=36). Specimens were stored in artificial saliva and were fractured after 24 hours and 8 days using Universal Testing Machine. The fractured samples from the 8 days study were then subjected to repair. A uniform space of 2mm and a 450 bevel was maintained for all the repaired samples for better distribution of forces. Flexural strength of these repaired samples was recorded using the same machine. Results were recorded and statistically analysed by one-way Anova and Post hoc tests. Result: Results revealed that there was decrease in flexural strength for all the materials tested from 24 hours to 8 days, though flexural strength between poly methyl methacrylate and bis-acrylic resins was similar at 24 hours and 8 days time interval. A substantial decrease was noticed in the strength of bis-acrylic composite resins after repair. Conclusion From the current study it can be suggested that though there is decrease in flexural strength for all the materials from 24 hours to 8 days, both can be used to fabricate the provisional restorations. However, in the event of a fracture of a bis-acrylic provisional restoration, it may be more advantageous to make a new provisional restoration than to repair the fractured one. PMID:27656568

Damage development in titanium metal matrix composites subjected to cyclic loading

NASA Technical Reports Server (NTRS)

Johnson, W. S.

1992-01-01

Several layups of SCS-6/Ti-15-3 composites were investigated. Fatigue tests were conducted and analyzed for both notched and unnotched specimens at room temperature and elevated temperatures. Thermo-mechanical fatigue results were analyzed. Test results indicated that the stress in the 0 degree fibers is the controlling factor in fatigue life. The static and fatigue strength of these materials is shown to be strongly 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 materials without breaking fibers. Fiber bridging models were applied to characterize the crack growth behavior. The matrix cracks are shown to significantly reduce the residual strength of notched composites. The notch strength of these composites was accurately predicted using a micromechanics based methodology.

Damage development in titanium metal-matrix composites subjected to cyclic loading

NASA Technical Reports Server (NTRS)

Johnson, W. S.

1993-01-01

Several layups of SCS-6/Ti-15-3 composites were investigated. Fatigue tests were conducted and analyzed for both notched and unnotched specimens at room temperature and elevated temperatures. Thermo-mechanical fatigue results were analyzed. Test results indicated that the stress in the 0 degree fibers is the controlling factor in fatigue life. The static and fatigue strength of these materials is shown to be strongly 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 materials without breaking fibers. Fiber bridging models were applied to characterize the crack growth behavior. The matrix cracks are shown to significantly reduce the residual strength of notched composites. The notch strength of these composites was accurately predicted using a micromechanics based methodology.

Environmental durability of polymer concrete

DOE Office of Scientific and Technical Information (OSTI.GOV)

Palmese, G.R.; Chawalwala, A.J.

1996-12-31

Over the past two decades, polymer concrete has increasingly been used for a number of applications including piping, machine bases, chemically resistant flooring, and bridge overlays. Currently, the use of polymer concrete as a wear surface for polymeric composite bridge decks is being investigated. Polymer concrete is a particulate composite comprised of mineral aggregate bound by a polymeric matrix. Such materials possess significantly higher mechanical properties than Portland cement concrete. However, the mechanical characteristics and environmental durability of polymer concrete are influenced by a number of factors. Among these are the selection of aggregate and resin, surface treatment, and curemore » conditions. In this work the influence of matrix selection and cure history on the environmental durability of polymer concrete was investigated. Particular attention was given to the effects of water on composite properties and to the mechanisms by which degradation occurs. The basalt-based polymer concrete systems investigated were susceptible to attack by water. Furthermore, results suggest that property loss associated with water exposure was primarily a result of interfacial weakening.« less

Interfacial Micromechanics in Fibrous Composites: Design, Evaluation, and Models

PubMed Central

Lei, Zhenkun; Li, Xuan; Qin, Fuyong; Qiu, Wei

2014-01-01

Recent advances of interfacial micromechanics in fiber reinforced composites using micro-Raman spectroscopy are given. The faced mechanical problems for interface design in fibrous composites are elaborated from three optimization ways: material, interface, and computation. Some reasons are depicted that the interfacial evaluation methods are difficult to guarantee the integrity, repeatability, and consistency. Micro-Raman study on the fiber interface failure behavior and the main interface mechanical problems in fibrous composites are summarized, including interfacial stress transfer, strength criterion of interface debonding and failure, fiber bridging, frictional slip, slip transition, and friction reloading. The theoretical models of above interface mechanical problems are given. PMID:24977189

Research and development of weathering resistant bridge steel of Shougang

NASA Astrophysics Data System (ADS)

Yang, Yongda; Wang, Yanfeng; Huang, Leqing; Di, Guobiao; Ma, Changwen; Ma, Qingshen

2017-09-01

To introduce the composition design and mechanical properties and microstructure of the weathering bridge steel which would be used for bridge of Guanting reservoir. We adopt cyclic immersion corrosion test to study corrosion resistance difference of weathering bridge steel and common bridge steel. At the same corrosion time, the weight loss and corrosion rate of weathering bridge steel are lower than the common bridge steel's. Testing phase composition of rust layer by X-ray diffraction, two kinds of test steel's rust layer is mainly composed of Goethite and Fe3O4 and Fe2O3. At the same corrosion time, the percentage composition of goethite in rust layer of weathering bridge steel are significantly higher than common bridge steel's, the higher goethite content is, the compacter rust layer structure is. The compact rust layer would prevent the water and air passing the rust layer, and then preventing the further corrosion reaction, improving the corrosion resistance performance of weathering bridge steel.

A study of fiber volume fraction effects in notched unidirectional SCS-6/Ti-15V-3Cr-3Al-3Sn composite. Ph.D. Thesis Final Report

NASA Technical Reports Server (NTRS)

Covey, Steven J.

1993-01-01

Notched unidirectional SCS-6/Ti-15-3 composite of three different fiber volume fractions (vf = 0.15, 0.37, and 0.41) was investigated for various room temperature microstructural and material properties including: fatigue crack initiation, fatigue crack growth, and fracture toughness. While the matrix hardness is similar for all fiber volume fractions, the fiber/matrix interfacial shear strength and matrix residual stress increases with fiber volume fraction. The composite fatigue crack initiation stress is shown to be matrix controlled and occurs when the net maximum matrix stress approaches the endurance limit stress of the matrix. A model is presented which includes residual stresses and presents the composite initiation stress as a function of fiber volume fraction. This model predicts a maximum composite initiation stress at vf approximately 0.15 which agrees with the experimental data. The applied composite stress levels were increased as necessary for continued crack growth. The applied Delta(K) values at crack arrest increase with fiber volume fraction by an amount better approximated using an energy based formulation rather than when scaled linear with modulus. After crack arrest, the crack growth rate exponents for vf37 and vf41 were much lower and toughness much higher, when compared to the unreinforced matrix, because of the bridged region which parades with the propagating fatigue crack. However, the vf15 material exhibited a higher crack growth rate exponent and lower toughness than the unreinforced matrix because once the bridged fibers nearest the crack mouth broke, the stress redistribution broke all bridged fibers, leaving an unbridged crack. Degraded, unbridged behavior is modeled using the residual stress state in the matrix ahead of the crack tip. Plastic zone sizes were directly measured using a metallographic technique and allow prediction of an effective matrix stress intensity which agrees with the fiber pressure model if residual stresses are considered. The sophisticated macro/micro finite element models of the 0.15 and 0.37 fiber volume fractions presented show good agreement with experimental data and the fiber pressure model when an estimated effective fiber/matrix debond length is used.

Connecticut permanent long-term bridge monitoring network, volume 3 : monitoring of a multi-steel girder composite bridge - I-91 SB over the Mattabesset River in Cromwell (bridge #3078).

DOT National Transportation Integrated Search

2014-08-01

This report describes the instrumentation and data acquisition for a multi-girder, composite steel bridge in Connecticut. The : computer-based remote monitoring system was developed to collect information on the girder bending strains. The monitoring...

Processing and mechanical properties of metal-ceramic composites with controlled microstructure formed by reactive metal penetration

NASA Astrophysics Data System (ADS)

Ellerby, Donald Thomas

1999-12-01

Compared to monolithic ceramics, metal-reinforced ceramic composites offer the potential for improved toughness and reliability in ceramic materials. As such, there is significant scientific and commercial interest in the microstructure and properties of metal-ceramic composites. Considerable work has been conducted on modeling the toughening behavior of metal reinforcements in ceramics; however, there has been limited application and testing of these concepts on real systems. Composites formed by newly developed reactive processes now offer the flexibility to systematically control metal-ceramic composite microstructure, and to test some of the property models that have been proposed for these materials. In this work, the effects of metal-ceramic composite microstructure on resistance curve (R-curve) behavior, strength, and reliability were systematically investigated. Al/Al2O3 composites were formed by reactive metal penetration (RMP) of aluminum metal into aluminosilicate ceramic preforms. Processing techniques were developed to control the metal content, metal composition, and metal ligament size in the resultant composite microstructure. Quantitative stereology and microscopy were used to characterize the composite microstructures, and then the influence of microstructure on strength, toughness, R-curve behavior, and reliability, was investigated. To identify the strength limiting flaws in the composite microstructure, fractography was used to determine the failure origins. Additionally, the crack bridging tractions produced by the metal ligaments in metal-ceramic composites formed by the RMP process were modeled. Due to relatively large flaws and low bridging stresses in RMP composites, no dependence of reliability on R-curve behavior was observed. The inherent flaws formed during reactive processing appear to limit the strength and reliability of composites formed by the RMP process. This investigation has established a clear relationship between processing, microstructure, and properties in metal-ceramic composites formed by the RMP process. RMP composite properties are determined by the metal-ceramic composite microstructure (e.g., metal content and ligament size), which can be systematically varied by processing. Furthermore, relative to the ceramic preforms used to make the composites, metal-ceramic composites formed by RMP generally have improved properties and combinations of properties that make them more desirable for advanced engineering applications.

Full-Scale Testing of Thermoplastic Composite I-Beams for Bridges

DTIC Science & Technology

2017-06-01

ER D C/ CE RL T R- 17 -1 8 ACSIM Technology Standards Group Full-Scale Testing of Thermoplastic Composite I-Beams for Bridges Co ns tr...default. ACSIM Technology Standards Group ERDC/CERL TR-17-18 June 2017 Full-Scale Testing of Thermoplastic Composite I-Beams for Bridges Ghassan... tests were con- ducted on commercially available, thermoplastic polymer composite I- beams at U.S. Army Corps of Engineers, Engineer Research and

DOE Office of Scientific and Technical Information (OSTI.GOV)

Martz, Joseph Christopher; Spearing, Dane Robert; Labouriau, Andrea

Microclad is a composite material consisting of a thin copper coating applied on a single side over a Kapton substrate. Kapton is the commercial designator for polyimide supplied by DuPont. Microclad is a key material in detonator manufacture and function. Detonators which utilize Microclad function when a large current applied through a thin bridge etched into the copper produces a plasma, accelerating a Kapton flyer into an explosive (PETN) pellet. The geometry and properties of the Microclad are a critical element of this process.

Culvert rehabilitation & invert lining using fiber reinforced polymer (FRP) composites.

DOT National Transportation Integrated Search

2010-06-01

As part of the state of Maine bridge funding initiative, MaineDOT has partnered with the University of : Maines AEWC Advanced Structures and Composite Center and the Maine composites industry to : incorporate composite technologies into bridge con...

Connecticut permanent long-term bridge monitoring network, volume 4 : monitoring of curved steel box-girder composite bridge - I-84 EB Flyover to I-91 NB in Hartford (bridge #5868).

DOT National Transportation Integrated Search

2014-08-01

This report describes the instrumentation and data acquisition for a continuous curved steel box-girder composite bridge in : Connecticut. The computer-based remote monitoring system was installed in 2001, with accelerometers, tilt meters and : tempe...

[Preparation of polyacrylonitrile/natural sand composite materials and analysis of adsorption properties of Pb(II) on it by FAAS].

PubMed

Abduwayit, Medine; Nurulla, Ismayil; Abliz, Shawket

2015-02-01

Surfaces of natural sand particles were modified with (3-chloropropyl) trichlorosilane, so that bridging groups were introduced on the surfaces of natural sand particles; By grafting polyacrylonitrile onto the modified surfaces of the natural sand particles, a novelpolyacrylonitrile/natural sand composite material was prepared from the acrylonitrile, the azobisisobutyronitrile, the divinylbenzene and the modified natural sand particles, which are as functional monomer, initiator, either skeleton monomer or cross-linking agent and carrier respectively; the composite materials were characterized by using infrared spectroscopy and scanning electron microscopy; On the FTIR spectrum, the main characteristic peaks of various functional groups including nitrile, benzene ring, and silicon hydroxyl, which were from functional monomer, cross-linking agent and carrier respectively, were observed. On the SEM, two different cross section morphologies having different density which were from acrylonitrile and modified sand particles were observed; This proved that the polyacrylonitrile was decorated on modified sand particles during our preparation process. After preparing the composite materials, micro-column of separation and preconcentration was prepared using the composite materials as filler; the adsorption of some toxic heavy metal ions onto the composite materials was observed by flame atomic absorption spectrometry (FAAS); The results show that the adsorption of Pb2+ onto the composite materials was more stronger than the absorption of other toxic heavy metal ions, therefore, in this paper, the adsorption of Pb2+ onto the composite materials was mainly studied, at room temperature, when pH and flow rate of solution were 5. 4 and 4 mL x min(-1) respectively, the trace Pb(II) ions could be quantitatively adsorbed onto the composite materials; the maximum adsorption capacity of Pb(II) on the composite materials can reach 62.9 mg x g(-1). The column was eluted by 0.5 mol x L(-1) HCl and recovery of Pb(II) was more than 96%.

Load Distribution Factors for Composite Multicell Box Girder Bridges

NASA Astrophysics Data System (ADS)

Tiwari, Sanjay; Bhargava, Pradeep

2017-12-01

Cellular steel section composite with a concrete deck is one of the most suitable superstructures in resisting torsional and warping effects induced by highway loading. This type of structure has inherently created new design problems for engineers in estimating its load distribution when subjected to moving vehicles. Indian Codes of Practice does not provide any specific guidelines for the design of straight composite concrete deck-steel multi-cell bridges. To meet the practical requirements arising during the design process, a simple design method is needed for straight composite multi-cell bridges in the form of load distribution factors for moment and shear. This work presents load distribution characteristics of straight composite multi-cell box girder bridges under IRC trains of loads.

Coupled Chiral Structure in Graphene-Based Film for Ultrahigh Thermal Conductivity in Both In-Plane and Through-Plane Directions.

PubMed

Meng, Xin; Pan, Hui; Zhu, Chengling; Chen, Zhixin; Lu, Tao; Xu, Da; Li, Yao; Zhu, Shenmin

2018-06-21

The development of high-performance thermal management materials to dissipate excessive heat both in plane and through plane is of special interest to maintain efficient operation and prolong the life of electronic devices. Herein, we designed and constructed a graphene-based composite film, which contains chiral liquid crystals (cellulose nanocrystals, CNCs) inside graphene oxide (GO). The composite film was prepared by annealing and compacting of self-assembled GO-CNC, which contains chiral smectic liquid crystal structures. The helical arranged nanorods of carbonized CNC act as in-plane connections, which bridge neighboring graphene sheets. More interestingly, the chiral structures also act as through-plane connections, which bridge the upper and lower graphene layers. As a result, the graphene-based composite film shows extraordinary thermal conductivity, in both in-plane (1820.4 W m -1 K -1 ) and through-plane (4.596 W m -1 K -1 ) directions. As a thermal management material, the heat dissipation and transportation behaviors of the composite film were investigated using a self-heating system and the results showed that the real-time temperature of the heater covered with the film was 44.5 °C lower than a naked heater. The prepared film shows a much higher efficiency of heat transportation than the commonly used thermal conductive Cu foil. Additionally, this graphene-based composite film exhibits excellent mechanical strength of 31.6 MPa and an electrical conductivity of 667.4 S cm -1 . The strategy reported here may open a new avenue to the development of high-performance thermal management films.

Damage-Resistant Composites Using Electrospun Nanofibers: A Multiscale Analysis of the Toughening Mechanisms.

PubMed

Daelemans, Lode; van der Heijden, Sam; De Baere, Ives; Rahier, Hubert; Van Paepegem, Wim; De Clerck, Karen

2016-05-11

Today, fiber-reinforced polymer composites are a standard material in applications where a high stiffness and strength are required at minimal weight, such as aerospace structures, ultralight vehicles, or even flywheels for highly efficient power storage systems. Although fiber-reinforced polymer composites show many advantages compared to other materials, delamination between reinforcing plies remains a major problem limiting further breakthrough. Traditional solutions that have been proposed to toughen the interlaminar region between reinforcing plies have already reached their limit or have important disadvantages such as a high cost or the need for adapted production processes. Recently, electrospun nanofibers have been suggested as a more viable interlaminar toughening method. Although the expected benefits are numerous, the research on composite laminates enhanced with electrospun nanofibrous veils is still very limited. The work that has been done so far is almost exclusively focused on interlaminar fracture toughness tests with different kinds of nanofibers, where typically a trial and error approach has been used. A thorough understanding of the micromechanical fracture mechanisms and the parameters to obtain toughened composites has not been reported as of yet, but it is crucial to advance the research and design highly damage-resistant composites. This article provides such insight by analyzing the nanofiber toughening effect on three different levels for several nanofiber types. Only by combining the results from different levels, a thorough understanding can be obtained. These levels correspond to the hierarchical nature of a composite: the laminate, the interlaminar region, and the matrix resin. It is found that each level corresponds to certain mechanisms that result in a toughening effect. The bridging of microcracks by electrospun nanofibers is the main toughening mechanism resulting in damage resistance. Nevertheless, the way in which the nanofiber bridging mechanism expresses itself is different for each scale and dependent on parameters linked to a certain scale. The multiscale analysis of the toughening mechanisms reported in this paper is therefore crucial for understanding the behavior of nanofiber toughened composites, and as such allows for designing novel, damage-resistant, nanofiber-toughened materials.

Research notes : modeling a composite reinforced bridge.

DOT National Transportation Integrated Search

2001-06-01

In 1998, Oregon Department of Transportation (ODOT) used fiber reinforced polymer (FRP) composites to strengthen the historic Horsetail Falls Bridge. Because this was the first experience with FRP composites, research was conducted to verify that the...

Structural properties of TiO2 nanomaterials

NASA Astrophysics Data System (ADS)

Kusior, Anna; Banas, Joanna; Trenczek-Zajac, Anita; Zubrzycka, Paulina; Micek-Ilnicka, Anna; Radecka, Marta

2018-04-01

The surface of solids is characterized by active, energy-rich sites that determine physicochemical interaction with gaseous and liquid media and possible applications in photocatalysis. The behavior of materials in such processes is related to their form and amount of various species, especially water and forms of oxygen adsorbed on the surface. The preparation of materials with controlled morphology, which includes modifications of the size, geometry, and composition, is currently an important way of optimizing properties, as many of them depend on not only the size and phase composition, but also on shape. Hydroxylated centers on the surface, which can be treated as trapping sites, are particularly significant. Water adsorbed on the surface bridging hydroxyl groups can distinctly modulate the properties of the surface of titania. The saturation of the surface with hydroxyl groups may improve the photocatalytic properties. TiO2 nanomaterials were obtained via different methods. SEM and TEM analysis were performed to study the morphology. The analysis of XRD and Raman data revealed a phase composition of obtained materials. To examine the surface properties, FTIR absorption spectra of TiO2 nanomaterials were recorded. The photocatalytic activity of titanium dioxide nanoparticles was investigated through the decomposition of methylene blue. It was demonstrated that each surface modification affects the amount of adsorbed hydroxyl groups. The different contributions of the two species to the ν(H2O) FTIR bands for different nanostructures result from the preparation conditions. It was noted that pre-adsorbed water (the surface-bridging hydroxyl) might significantly modulate the surface properties of the material. The increase in hydroxyl group density on the titanium dioxide surface enhances the effectiveness of the photocatalytic processes. It was demonstrated that flower-like titania obtained via hydrothermal synthesis exhibits the weakest catalytic activity, in contrast to the typical spherical TiO2.

Preparation and Thermal Properties of Molecular-Bridged Expanded Graphite/Polyethylene Glycol Composite Phase Change Materials for Building Energy Conservation.

PubMed

Zhang, Dong; Chen, Meizhu; Liu, Quantao; Wan, Jiuming; Hu, Jinxuan

2018-05-16

Using phase change materials (PCMs) in building envelopes became a reliable method to improve indoor comfort and reduce buildings' energy consumption. This research developed molecular-bridged expanded graphite (EG)/polyethylene glycol (PEG) composite PCMs (m-EPs) to conserve energy in buildings. The m-EPs were prepared through a vacuum absorption technique, and a titanate coupling agent was used to build a molecular bridge between EG and PEG. SEM, mercury intrusion porosimetry (MIP), the leakage test, microcalorimetry, X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FT-IR) were conducted to characterize the morphology, pore structure, absorbability, and modifying effects of the m-EPs. The phase change temperature, latent heat, thermal stability, and thermal conductivity of the m-EPs were determined by a differential scanning calorimeter (DSC), TGA, and a thermal constants analyzer. Results showed that the maximum mass ratio of PEG to EG without leakage was 1:7, and a stable connection was established in the m-EPs after modification. Compared with the unmodified EPs, the supercooling degree of the m-EPs reduced by about 3 °C, but the latent heats and initial decomposition temperatures increased by approximately 10% and 20 °C, respectively, which indicated an improvement in the thermal energy storage efficiency. The thermal conductivities of the m-EPs were 10 times higher than those of the pristine PEGs, which ensured a rapid responding to building temperature fluctuations.

Preparation and Thermal Properties of Molecular-Bridged Expanded Graphite/Polyethylene Glycol Composite Phase Change Materials for Building Energy Conservation

PubMed Central

Zhang, Dong; Chen, Meizhu; Liu, Quantao; Hu, Jinxuan

2018-01-01

Using phase change materials (PCMs) in building envelopes became a reliable method to improve indoor comfort and reduce buildings’ energy consumption. This research developed molecular-bridged expanded graphite (EG)/polyethylene glycol (PEG) composite PCMs (m-EPs) to conserve energy in buildings. The m-EPs were prepared through a vacuum absorption technique, and a titanate coupling agent was used to build a molecular bridge between EG and PEG. SEM, mercury intrusion porosimetry (MIP), the leakage test, microcalorimetry, X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FT-IR) were conducted to characterize the morphology, pore structure, absorbability, and modifying effects of the m-EPs. The phase change temperature, latent heat, thermal stability, and thermal conductivity of the m-EPs were determined by a differential scanning calorimeter (DSC), TGA, and a thermal constants analyzer. Results showed that the maximum mass ratio of PEG to EG without leakage was 1:7, and a stable connection was established in the m-EPs after modification. Compared with the unmodified EPs, the supercooling degree of the m-EPs reduced by about 3 °C, but the latent heats and initial decomposition temperatures increased by approximately 10% and 20 °C, respectively, which indicated an improvement in the thermal energy storage efficiency. The thermal conductivities of the m-EPs were 10 times higher than those of the pristine PEGs, which ensured a rapid responding to building temperature fluctuations. PMID:29772728

Evaluation of SPE and GCR Radiation Effects in Inflatable, Space Suit and Composite Habitat Materials Project

NASA Technical Reports Server (NTRS)

Waller, Jess M.; Nichols, Charles

2016-01-01

The radiation resistance of polymeric and composite materials to space radiation is currently based on irradiating materials with Co-60 gamma-radiation to the equivalent total ionizing dose (TID) expected during mission. This is an approximation since gamma-radiation is not truly representative of the particle species; namely, Solar Particle Event (SPE) protons and Galactic Cosmic Ray (GCR) nucleons, encountered in space. In general, the SPE and GCR particle energies are much higher than Co-60 gamma-ray photons, and since the particles have mass, there is a displacement effect due to nuclear collisions between the particle species and the target material. This effort specifically bridges the gap between estimated service lifetimes based on decades old Co-60 gamma-radiation data, and newer assessments of what the service lifetimes actually are based on irradiation with particle species that are more representative of the space radiation environment.

Modeling of crack bridging in a unidirectional metal matrix composite

NASA Technical Reports Server (NTRS)

Ghosn, Louis J.; Kantzos, Pete; Telesman, Jack

1991-01-01

The effective fatigue crack driving force and crack opening profiles were determined analytically for fatigue tested unidirectional composite specimens exhibiting fiber bridging. The crack closure pressure due to bridging was modeled using two approaches; the fiber pressure model and the shear lag model. For both closure models, the Bueckner weight function method and the finite element method were used to calculate crack opening displacements and the crack driving force. The predicted near crack tip opening profile agreed well with the experimentally measured profiles for single edge notch SCS-6/Ti-15-3 metal matrix composite specimens. The numerically determined effective crack driving force, Delta K(sup eff), was calculated using both models to correlate the measure crack growth rate in the composite. The calculated Delta K(sup eff) from both models accounted for the crack bridging by showing a good agreement between the measured fatigue crack growth rates of the bridged composite and that of unreinforced, unbridged titanium matrix alloy specimens.

Modeling of crack bridging in a unidirectional metal matrix composite

NASA Technical Reports Server (NTRS)

Ghosn, Louis J.; Kantzos, Pete; Telesman, Jack

1992-01-01

The effective fatigue crack driving force and crack opening profiles were determined analytically for fatigue tested unidirectional composite specimens exhibiting fiber bridging. The crack closure pressure due to bridging was modeled using two approaches: the fiber pressure model and the shear lag model. For both closure models, the Bueckner weight function method and the finite element method were used to calculate crack opening displacements and the crack driving force. The predicted near crack tip opening profile agreed well with the experimentally measured profiles for single edge notch SCS-6/Ti-15-3 metal matrix composite specimens. The numerically determined effective crack driving force, Delta K(eff), was calculated using both models to correlate the measure crack growth rate in the composite. The calculated Delta K(eff) from both models accounted for the crack bridging by showing a good agreement between the measured fatigue crack growth rates of the bridged composite and that of unreinforced, unbridged titanium matrix alloy specimens.

Testing of full-size reinforced concrete beams strengthened with FRP composites : experimental results and design methods verification

DOT National Transportation Integrated Search

2000-06-01

In 1997, a load rating of an historic reinforced concrete bridge in Oregon, Horsetail Creek Bridge, indicated substandard shear and moment capacities of the beams. As a result, the Bridge was strengthened with fiber reinforced : polymer composites as...

[MoS4]2- Cluster Bridges in Co-Fe Layered Double Hydroxides for Mercury Uptake from S-Hg Mixed Flue Gas.

PubMed

Xu, Haomiao; Yuan, Yong; Liao, Yong; Xie, Jiangkun; Qu, Zan; Shangguan, Wenfeng; Yan, Naiqiang

2017-09-05

[MoS 4 ] 2- clusters were bridged between CoFe layered double hydroxide (LDH) layers using the ion-exchange method. [MoS 4 ] 2- /CoFe-LDH showed excellent Hg 0 removal performance under low and high concentrations of SO 2 , highlighting the potential for such material in S-Hg mixed flue gas purification. The maximum mercury capacity was as high as 16.39 mg/g. The structure and physical-chemical properties of [MoS 4 ] 2- /CoFe-LDH composites were characterized with FT-IR, XRD, TEM&SEM, XPS, and H 2 -TPR. [MoS 4 ] 2- clusters intercalated into the CoFe-LDH layered sheets; then, we enlarged the layer-to-layer spacing (from 0.622 to 0.880 nm) and enlarged the surface area (from 41.4 m 2 /g to 112.1 m 2 /g) of the composite. During the adsorption process, the interlayer [MoS 4 ] 2- cluster was the primary active site for mercury uptake. The adsorbed mercury existed as HgS on the material surface. The absence of active oxygen results in a composite with high sulfur resistance. Due to its high efficiency and SO 2 resistance, [MoS 4 ] 2- /CoFe-LDH is a promising adsorbent for mercury uptake from S-Hg mixed flue gas.

Out of the Toolbox: Toddlers Differentiate Wobbly and Wooden Handrails

ERIC Educational Resources Information Center

Berger, Sarah E.; Adolph, Karen E.; Lobo, Sharon A.

2005-01-01

This study examined whether 16-month-old walking infants take the material composition of a handrail into account when assessing its effectiveness as a tool to augment balance. Infants were encouraged to cross from one platform to another via bridges of various widths (10, 20, 40cm) with either a wobbly (foam or latex) or a wooden handrail…

Testing of full-size reinforced concrete beams strengthened with FRP composites : experimental results and design methods verification(appendices)

DOT National Transportation Integrated Search

2000-06-01

In 1997, a load rating of an historic reinforced concrete bridge in Oregon, Horsetail Creek Bridge, indicated substandard shear and moment capacities of the beams. As a result, the Bridge was strengthened with fiber reinforced polymer composites as a...

In vitro validation of a shape-optimized fiber-reinforced dental bridge.

PubMed

Chen, YungChung; Li, Haiyan; Fok, Alex

2011-12-01

To improve its mechanical performance, structural optimization had been used in a previous study to obtain an alternative design for a 3-unit inlay-retained fiber-reinforced composite (FRC) dental bridge. In that study, an optimized layout of the FRC substructure had been proposed to minimize stresses in the veneering composite and interfacial stresses between the composite and substructure. The current work aimed to validate in vitro the improved fracture resistance of the optimized design. All samples for the 3-unit inlay-retained FRC dental bridge were made with glass-fibers (FibreKor) as the substructure, surrounded by a veneering composite (GC Gradia). Two different FRC substructure designs were prepared: a conventional (n=20) and an optimized design (n=21). The conventional design was a straight beam linking one proximal box to the other, while the optimized design was a curved beam following the lower outline of the pontic. All samples were loaded to 400N on a universal test machine (MTS 810) with a loading speed of 0.2mm/min. During loading, the force and displacement were recorded. Meanwhile, a two-channel acoustic emission (AE) system was used to monitor the development of cracks during loading. The load-displacement curves of the two groups displayed significant differences. For the conventional design, there were numerous drops in load corresponding to local damage of the sample. For the optimized design, the load curves were much smoother. Cracks were clearly visible on the surface of the conventional group only, and the directions of those cracks were perpendicular to those of the most tensile stresses. Results from the more sensitive AE measurement also showed that the optimized design had, on average, fewer cracking events: 38 versus 2969 in the conventional design. The much lower number of AE events and smoother load-displacement curves indicated that the optimized FRC bridge design had a higher fracture resistance. It is expected that the optimized design will significantly improve the clinical performance of FRC bridges. Copyright © 2011 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Bridge toughening in fiber-reinforced composites: A three-dimensional discrete fiber model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hu, K.X.; Huang, Y.; Chandra, A.

1995-07-01

The fracture behavior of unidirectionally fiber-reinforced composites is the principal focus of this paper. The model proposed here is three-dimensional and accounts for the effects of local fiber-crack interactions on spatial variations of crack tip behavior. The model also consistently accounts for the effect of composite anisotropy by embedding a penny-shaped crack in an orthotropic composite medium. Three factors are identified that influence the reductions of stress intensity factors (SIFS) due to fiber bridging: a dimensionless configuration constant, a fiber distribution pattern, and a fiber volume fraction. The model reveals that the fiber distribution pattern does not alter the spatialmore » mean of the SIFS, although it does affect the oscillational amplitude. The dimensionless configuration constant determines the extent of the bridging effect and provides guidance regarding possible avenues for enhancing bridge toughening. The design curve of SIFs (retarded by fiber bridging) vs the fiber volume fraction shows that the isotropic and orthotropic solutions differ just slightly from each other. However, the energy release rate obtained by an isotropic analysis (widely claimed to be the equivalent of SIFs in bridging models) could, significantly underestimate the bridging effect.« less

Development and characterization of powder metallurgically produced discontinuous tungsten fiber reinforced tungsten composites

NASA Astrophysics Data System (ADS)

Mao, Y.; Coenen, J. W.; Riesch, J.; Sistla, S.; Almanstötter, J.; Jasper, B.; Terra, A.; Höschen, T.; Gietl, H.; Bram, M.; Gonzalez-Julian, J.; Linsmeier, Ch; Broeckmann, C.

2017-12-01

In future fusion reactors, tungsten is the prime candidate material for the plasma facing components. Nevertheless, tungsten is prone to develop cracks due to its intrinsic brittleness—a major concern under the extreme conditions of fusion environment. To overcome this drawback, tungsten fiber reinforced tungsten (Wf/W) composites are being developed. These composite materials rely on an extrinsic toughing principle, similar to those in ceramic matrix composite, using internal energy dissipation mechanisms, such as crack bridging and fiber pull-out, during crack propagation. This can help Wf/W to facilitate a pseudo-ductile behavior and allows an elevated damage resilience compared to pure W. For pseudo-ductility mechanisms to occur, the interface between the fiber and matrix is crucial. Recent developments in the area of powder-metallurgical Wf/W are presented. Two consolidation methods are compared. Field assisted sintering technology and hot isostatic pressing are chosen to manufacture the Wf/W composites. Initial mechanical tests and microstructural analyses are performed on the Wf/W composites with a 30% fiber volume fraction. The samples produced by both processes can give pseudo-ductile behavior at room temperature.

A Special Material or a New State of Matter: A Review and Reconsideration of the Aerogel

PubMed Central

Du, Ai; Zhou, Bin; Zhang, Zhihua; Shen, Jun

2013-01-01

The ultrahighly nanoporous aerogel is recognized as a state of matter rather than as a functional material, because of its qualitative differences in bulk properties, transitional density and enthalpy between liquid and gas, and diverse chemical compositions. In this review, the characteristics, classification, history and preparation of the aerogel were introduced. More attention was paid to the sol-gel method for preparing different kinds of aerogels, given its important role on bridging the synthetic parameters with the properties. At last, preparation of a novel single-component aerogel, design of a composite aerogel and industrial application of the aerogel were regarded as the research tendency of the aerogel state in the near future. PMID:28809350

Evaluation of high temperature superconductive thermal bridges for space borne cryogenic detectors

NASA Technical Reports Server (NTRS)

Scott, Elaine P.

1996-01-01

Infrared sensor satellites are used to monitor the conditions in the earth's upper atmosphere. In these systems, the electronic links connecting the cryogenically cooled infrared detectors to the significantly warmer amplification electronics act as thermal bridges and, consequently, the mission lifetimes of the satellites are limited due to cryogenic evaporation. High-temperature superconductor (HTS) materials have been proposed by researchers at the National Aeronautics and Space Administration Langley's Research Center (NASA-LaRC) as an alternative to the currently used manganin wires for electrical connection. The potential for using HTS films as thermal bridges has provided the motivation for the design and the analysis of a spaceflight experiment to evaluate the performance of this superconductive technology in the space environment. The initial efforts were focused on the preliminary design of the experimental system which allows for the quantitative comparison of superconductive leads with manganin leads, and on the thermal conduction modeling of the proposed system. Most of the HTS materials were indicated to be potential replacements for the manganin wires. In the continuation of this multi-year research, the objectives of this study were to evaluate the sources of heat transfer on the thermal bridges that have been neglected in the preliminary conductive model and then to develop a methodology for the estimation of the thermal conductivities of the HTS thermal bridges in space. The Joule heating created by the electrical current through the manganin wires was incorporated as a volumetric heat source into the manganin conductive model. The radiative heat source on the HTS thermal bridges was determined by performing a separate radiant interchange analysis within a high-T(sub c) superconductor housing area. Both heat sources indicated no significant contribution on the cryogenic heat load, which validates the results obtained in the preliminary conduction model. A methodology was presented for the estimation of the thermal conductivities of the individual HTS thermal bridge materials and the effective thermal conductivities of the composite HTS thermal bridges as functions of temperature. This methodology included a sensitivity analysis and the demonstration of the estimation procedure using simulated data with added random errors. The thermal conductivities could not be estimated as functions of temperature; thus the effective thermal conductivities of the HTS thermal bridges were analyzed as constants.

A multiscale MD-FE model of diffusion in composite media with internal surface interaction based on numerical homogenization procedure.

PubMed

Kojic, M; Milosevic, M; Kojic, N; Kim, K; Ferrari, M; Ziemys, A

2014-02-01

Mass transport by diffusion within composite materials may depend not only on internal microstructural geometry, but also on the chemical interactions between the transported substance and the material of the microstructure. Retrospectively, there is a gap in methods and theory to connect material microstructure properties with macroscale continuum diffusion characteristics. Here we present a new hierarchical multiscale model for diffusion within composite materials that couples material microstructural geometry and interactions between diffusing particles and the material matrix. This model, which bridges molecular dynamics (MD) and the finite element (FE) method, is employed to construct a continuum diffusion model based on a novel numerical homogenization procedure. The procedure is general and robust for evaluating constitutive material parameters of the continuum model. These parameters include the traditional bulk diffusion coefficients and, additionally, the distances from the solid surface accounting for surface interaction effects. We implemented our models to glucose diffusion through the following two geometrical/material configurations: tightly packed silica nanospheres, and a complex fibrous structure surrounding nanospheres. Then, rhodamine 6G diffusion analysis through an aga-rose gel network was performed, followed by a model validation using our experimental results. The microstructural model, numerical homogenization and continuum model offer a new platform for modeling and predicting mass diffusion through complex biological environment and within composite materials that are used in a wide range of applications, like drug delivery and nanoporous catalysts.

A multiscale MD–FE model of diffusion in composite media with internal surface interaction based on numerical homogenization procedure

PubMed Central

Kojic, M.; Milosevic, M.; Kojic, N.; Kim, K.; Ferrari, M.; Ziemys, A.

2014-01-01

Mass transport by diffusion within composite materials may depend not only on internal microstructural geometry, but also on the chemical interactions between the transported substance and the material of the microstructure. Retrospectively, there is a gap in methods and theory to connect material microstructure properties with macroscale continuum diffusion characteristics. Here we present a new hierarchical multiscale model for diffusion within composite materials that couples material microstructural geometry and interactions between diffusing particles and the material matrix. This model, which bridges molecular dynamics (MD) and the finite element (FE) method, is employed to construct a continuum diffusion model based on a novel numerical homogenization procedure. The procedure is general and robust for evaluating constitutive material parameters of the continuum model. These parameters include the traditional bulk diffusion coefficients and, additionally, the distances from the solid surface accounting for surface interaction effects. We implemented our models to glucose diffusion through the following two geometrical/material configurations: tightly packed silica nanospheres, and a complex fibrous structure surrounding nanospheres. Then, rhodamine 6G diffusion analysis through an aga-rose gel network was performed, followed by a model validation using our experimental results. The microstructural model, numerical homogenization and continuum model offer a new platform for modeling and predicting mass diffusion through complex biological environment and within composite materials that are used in a wide range of applications, like drug delivery and nanoporous catalysts. PMID:24578582

Use of composite materials, health monitoring and self-healing concepts to refurbish our civil and military infrastructure.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Roach, Dennis Patrick; Delong, Waylon Anthony; White, Scott

An unavoidable by-product of a metallic structure's use is the appearance of crack, corrosion, erosion and other flaws. Economic barriers to the replacement of these structures have created an aging civil and military infrastructure and placed even greater demands on efficient and safe repair and inspection methods. As a result of Homeland Security issues and these aging infrastructure concerns, increased attention has been focused on the rapid repair and preemptive reinforcement of structures such as buildings and bridges. This Laboratory Directed Research and Development (LDRD) program established the viability of using bonded composite patches to repair metallic structures. High modulusmore » fiber-reinforced polymer (FRP) material may be used in lieu of mechanically fastened metallic patches or welds to reinforce or repair damaged structures. Their use produces a wide array of engineering and economic advantages. Current techniques for strengthening steel structures have several drawbacks including requiring heavy equipment for installation, poor fatigue performance, and the need for ongoing maintenance due to continued corrosion attack or crack growth. The use of bonded composite doublers has the potential to correct the difficulties associated with current repair techniques and the ability to be applied where there are currently no rehabilitation options. Applications include such diverse structures as: buildings, bridges, railroad cars, trucks and other heavy machinery, steel power and communication towers, pipelines, factories, mining equipment, ships, tanks and other military vehicles. This LDRD also proved the concept of a living infrastructure by developing custom sensors and self-healing chemistry and linking this technology with the application of advanced composite materials. Structural Health Monitoring (SHM) systems and mountable, miniature sensors were designed to continuously or periodically assess structural integrity. Such systems are able to detect incipient damage before catastrophic failure occurs. The ease of monitoring an entire network of distributed sensors means that structural health assessments can occur more often, allowing operators to be even more vigilant with respect to flaw onset. In addition, the realization of smart structures, through the use of in-situ sensors, allows condition-based maintenance to be substituted for conventional time-based maintenance practices. The sensitivity and reliability of a series of sensor systems was quantified in laboratory and real-world environments. Finally, self healing methods for composite materials were evolved--using resin modules that are released in response to the onset of delaminations--so that these components can provide a living infrastructure with minimal need for human intervention. This program consisted of four related research elements: (1) design, installation, and performance assessment of composite repairs, (2) in-situ sensors for real-time health monitoring, (3) self healing of in-service damage in a repair, and (4) numerical modeling. Deployment of FRP materials and bonded joints requires proper design, suitable surface preparation methods, and adequate surveillance to ensure structural integrity. By encompassing all 'cradle-to-grave' tasks --including design, analysis, installation, durability, flaw containment, and inspection--this program is designed to firmly establish the capabilities of composite doubler repairs and introduce technology to incorporate self-monitoring and self-healing (living structures) methodologies. A proof-of-concept repair was completed on a steel highway bridge in order to demonstrate the potential of composite doubler technology for critical infrastructure use.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kornreich, Drew E; Vaidya, Rajendra U; Ammerman, Curtt N

Integrated Computational Materials Engineering (ICME) is a novel overarching approach to bridge length and time scales in computational materials science and engineering. This approach integrates all elements of multi-scale modeling (including various empirical and science-based models) with materials informatics to provide users the opportunity to tailor material selections based on stringent application needs. Typically, materials engineering has focused on structural requirements (stress, strain, modulus, fracture toughness etc.) while multi-scale modeling has been science focused (mechanical threshold strength model, grain-size models, solid-solution strengthening models etc.). Materials informatics (mechanical property inventories) on the other hand, is extensively data focused. All of thesemore » elements are combined within the framework of ICME to create architecture for the development, selection and design new composite materials for challenging environments. We propose development of the foundations for applying ICME to composite materials development for nuclear and high-radiation environments (including nuclear-fusion energy reactors, nuclear-fission reactors, and accelerators). We expect to combine all elements of current material models (including thermo-mechanical and finite-element models) into the ICME framework. This will be accomplished through the use of a various mathematical modeling constructs. These constructs will allow the integration of constituent models, which in tum would allow us to use the adaptive strengths of using a combinatorial scheme (fabrication and computational) for creating new composite materials. A sample problem where these concepts are used is provided in this summary.« less

Design protocols and analytical strategies that incorporate structural reliability models

NASA Technical Reports Server (NTRS)

Duffy, Stephen F.

1995-01-01

In spite of great improvements in accuracy through the use of computers, design methods, which can be equally critical in establishing the commercial success of a material, have been treated as afterthoughts. Early investment in design and development technologies can easily reduce manufacturing costs later in the product cycle. To avoid lengthy product development times for ceramic composites, funding agencies for materials research must commit resources to support design and development technologies early in the material life cycle. These technologies need not focus on designing the material, rather, the technology must focus on designing with the material, i. e., developing methods to design components fabricated from the new material. Thus a basic tenet that motivated this research effort is that a persistent need exists for improvements in the analysis of components fabricated from CMC material systems. From an aerospace design engineer's perspective the new generation of ceramic composites offers a significant potential for raising the thrust/weight ratio and reducing NOx emissions of gas turbine engines. Continuous ceramic fiber composites exhibit an increase in work of fracture, which allows for 'graceful' rather than catastrophic failure. When loaded in the fiber direction, these composites retain substantial strength capacity beyond the initiation of transverse matrix cracking despite the fact that neither of its constituents would exhibit such behavior if tested alone. As additional load is applied beyond first matrix cracking, the matrix tends to break in a series of cracks bridged by the ceramic fibers. Thus any additional load is born increasingly by the fibers until the ultimate strength of the composite is reached. Establishing design protocols that enable the engineer to analyze and predict this type of behavior in ceramic composites was the general goal of this project.

Design protocols and analytical strategies that incorporate structural reliability models

NASA Astrophysics Data System (ADS)

Duffy, Stephen F.

1995-08-01

In spite of great improvements in accuracy through the use of computers, design methods, which can be equally critical in establishing the commercial success of a material, have been treated as afterthoughts. Early investment in design and development technologies can easily reduce manufacturing costs later in the product cycle. To avoid lengthy product development times for ceramic composites, funding agencies for materials research must commit resources to support design and development technologies early in the material life cycle. These technologies need not focus on designing the material, rather, the technology must focus on designing with the material, i. e., developing methods to design components fabricated from the new material. Thus a basic tenet that motivated this research effort is that a persistent need exists for improvements in the analysis of components fabricated from CMC material systems. From an aerospace design engineer's perspective the new generation of ceramic composites offers a significant potential for raising the thrust/weight ratio and reducing NOx emissions of gas turbine engines. Continuous ceramic fiber composites exhibit an increase in work of fracture, which allows for 'graceful' rather than catastrophic failure. When loaded in the fiber direction, these composites retain substantial strength capacity beyond the initiation of transverse matrix cracking despite the fact that neither of its constituents would exhibit such behavior if tested alone. As additional load is applied beyond first matrix cracking, the matrix tends to break in a series of cracks bridged by the ceramic fibers. Thus any additional load is born increasingly by the fibers until the ultimate strength of the composite is reached. Establishing design protocols that enable the engineer to analyze and predict this type of behavior in ceramic composites was the general goal of this project.

Hierarchical composites of polyaniline-graphene nanoribbons-carbon nanotubes as electrode materials in all-solid-state supercapacitors.

PubMed

Liu, Mingkai; Miao, Yue-E; Zhang, Chao; Tjiu, Weng Weei; Yang, Zhibin; Peng, Huisheng; Liu, Tianxi

2013-08-21

A three dimensional (3D) polyaniline (PANI)-graphene nanoribbon (GNR)-carbon nanotube (CNT) composite, PANI-GNR-CNT, has been prepared via in situ polymerization of an aniline monomer on the surface of a GNR-CNT hybrid. Here, the 3D GNR-CNT hybrid has been conveniently prepared by partially unzipping the pristine multi-walled CNTs, while the residual CNTs act as "bridges" connecting different GNRs. The morphology and structure of the resulting hybrid materials have been characterized using transmission electron microscopy (TEM), scanning electron microscopy (SEM), Raman spectroscopy and X-ray diffraction (XRD). Electrochemical tests reveal that the hierarchical PANI-GNR-CNT composite based on the two-electrode cell possesses much higher specific capacitance (890 F g(-1)) than the GNR-CNT hybrid (195 F g(-1)) and neat PANI (283 F g(-1)) at a discharge current density of 0.5 A g(-1). At the same time, the PANI-GNR-CNT composite displays good cycling stability with a retention ratio of 89% after 1000 cycles, suggesting that this novel PANI-GNR-CNT composite is a promising candidate for energy storage applications.

Hierarchical composites of polyaniline-graphene nanoribbons-carbon nanotubes as electrode materials in all-solid-state supercapacitors

NASA Astrophysics Data System (ADS)

Liu, Mingkai; Miao, Yue-E.; Zhang, Chao; Tjiu, Weng Weei; Yang, Zhibin; Peng, Huisheng; Liu, Tianxi

2013-07-01

A three dimensional (3D) polyaniline (PANI)-graphene nanoribbon (GNR)-carbon nanotube (CNT) composite, PANI-GNR-CNT, has been prepared via in situ polymerization of an aniline monomer on the surface of a GNR-CNT hybrid. Here, the 3D GNR-CNT hybrid has been conveniently prepared by partially unzipping the pristine multi-walled CNTs, while the residual CNTs act as ``bridges'' connecting different GNRs. The morphology and structure of the resulting hybrid materials have been characterized using transmission electron microscopy (TEM), scanning electron microscopy (SEM), Raman spectroscopy and X-ray diffraction (XRD). Electrochemical tests reveal that the hierarchical PANI-GNR-CNT composite based on the two-electrode cell possesses much higher specific capacitance (890 F g-1) than the GNR-CNT hybrid (195 F g-1) and neat PANI (283 F g-1) at a discharge current density of 0.5 A g-1. At the same time, the PANI-GNR-CNT composite displays good cycling stability with a retention ratio of 89% after 1000 cycles, suggesting that this novel PANI-GNR-CNT composite is a promising candidate for energy storage applications.

Ceramic composites: A review of toughening mechanisms and demonstration of micropillar compression for interface property extraction

DOE PAGES

Kabel, Joey; Hosemann, Peter; Zayachuk, Yevhen; ...

2018-01-24

We present that ceramic fiber–matrix composites (CFMCs) are exciting materials for engineering applications in extreme environments. By integrating ceramic fibers within a ceramic matrix, CFMCs allow an intrinsically brittle material to exhibit sufficient structural toughness for use in gas turbines and nuclear reactors. Chemical stability under high temperature and irradiation coupled with high specific strength make these materials unique and increasingly popular in extreme settings. This paper first offers a review of the importance and growing body of research on fiber–matrix interfaces as they relate to composite toughening mechanisms. Second, micropillar compression is explored experimentally as a high-fidelity method formore » extracting interface properties compared with traditional fiber push-out testing. Three significant interface properties that govern composite toughening were extracted. For a 50-nm-pyrolytic carbon interface, the following were observed: a fracture energy release rate of ~2.5 J/m 2, an internal friction coefficient of 0.25 ± 0.04, and a debond shear strength of 266 ± 24 MPa. Lastly, this research supports micromechanical evaluations as a unique bridge between theoretical physics models for microcrack propagation and empirically driven finite element models for bulk CFMCs.« less

X ray attenuation measurements for high-temperature materials characterization and in-situ monitoring of damage accumulation. Ph.D. Thesis - Cleveland State Univ., 1991

NASA Technical Reports Server (NTRS)

Baaklini, George Y.

1992-01-01

The scope of this dissertation is to develop and apply x ray attenuation measurement systems that are capable of: (1) characterizing density variations in high-temperature materials, e.g., monolithic ceramics, ceramic and intermetallic matrix composites, and (2) noninvasively monitoring damage accumulation and failure sequences in ceramic matrix composites under room temperature tensile testing. This dissertation results in the development of: (1) a point scan digital radiography system, and (2) an in-situ x ray material testing system. Radiographic evaluation before, during, and after loading shows the effect of preexisting volume flaws on the fracture behavior of composites. Results show that x ray film radiography can monitor damage accumulation during tensile loading. Matrix cracking, fiber matrix debonding, fiber bridging, and fiber pullout are imaged throughout the tensile loading of the specimens. Further in-situ radiography is found to be a practical technique for estimating interfacial shear strength between the silicon carbide fibers and the reaction bonded silicon nitride matrix. It is concluded that pretest, in-situ, and post test x ray imaging can provide for greater understanding of ceramic matrix composite mechanical behavior.

Ceramic composites: A review of toughening mechanisms and demonstration of micropillar compression for interface property extraction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kabel, Joey; Hosemann, Peter; Zayachuk, Yevhen

We present that ceramic fiber–matrix composites (CFMCs) are exciting materials for engineering applications in extreme environments. By integrating ceramic fibers within a ceramic matrix, CFMCs allow an intrinsically brittle material to exhibit sufficient structural toughness for use in gas turbines and nuclear reactors. Chemical stability under high temperature and irradiation coupled with high specific strength make these materials unique and increasingly popular in extreme settings. This paper first offers a review of the importance and growing body of research on fiber–matrix interfaces as they relate to composite toughening mechanisms. Second, micropillar compression is explored experimentally as a high-fidelity method formore » extracting interface properties compared with traditional fiber push-out testing. Three significant interface properties that govern composite toughening were extracted. For a 50-nm-pyrolytic carbon interface, the following were observed: a fracture energy release rate of ~2.5 J/m 2, an internal friction coefficient of 0.25 ± 0.04, and a debond shear strength of 266 ± 24 MPa. Lastly, this research supports micromechanical evaluations as a unique bridge between theoretical physics models for microcrack propagation and empirically driven finite element models for bulk CFMCs.« less

76 FR 55160 - Annual Materials Report on New Bridge Construction and Bridge Rehabilitation

Federal Register 2010, 2011, 2012, 2013, 2014

2011-09-06

... DEPARTMENT OF TRANSPORTATION Federal Highway Administration Annual Materials Report on New Bridge Construction and Bridge Rehabilitation AGENCY: Federal Highway Administration (FHWA), DOT. ACTION: Notice... for Users (SAFETEA-LU) (Pub. L. 109-59; 119 Stat. 1144) continued the highway bridge program to enable...

77 FR 53251 - Annual Materials Report on New Bridge Construction and Bridge Rehabilitation

Federal Register 2010, 2011, 2012, 2013, 2014

2012-08-31

... DEPARTMENT OF TRANSPORTATION Federal Highway Administration Annual Materials Report on New Bridge Construction and Bridge Rehabilitation AGENCY: Federal Highway Administration (FHWA), DOT. ACTION: Notice... for Users (SAFETEA-LU) (Pub. L. 109-59; 119 Stat. 1144) continued the highway bridge program to enable...

75 FR 62181 - Annual Materials Report on New Bridge Construction and Bridge Rehabilitation

Federal Register 2010, 2011, 2012, 2013, 2014

2010-10-07

... DEPARTMENT OF TRANSPORTATION Federal Highway Administration Annual Materials Report on New Bridge Construction and Bridge Rehabilitation AGENCY: Federal Highway Administration (FHWA), DOT. ACTION: Notice... for Users (SAFETEA-LU) (Pub. L. 109-59; 119 Stat. 1144) continued the highway bridge program to enable...

DUCTILE-PHASE TOUGHENED TUNGSTEN FOR PLASMA-FACING MATERIALS IN FUSION REACTORS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Henager, Charles H.; Setyawan, Wahyu; Roosendaal, Timothy J.

2017-05-01

Tungsten (W) and W-alloys are the leading candidates for plasma-facing components in nuclear fusion reactor designs because of their high melting point, strength retention at high temperatures, high thermal conductivity, and low sputtering yield. However, tungsten is brittle and does not exhibit the required fracture toughness for licensing in nuclear applications. A promising approach to increasing fracture toughness of W-alloys is by ductile-phase toughening (DPT). In this method, a ductile phase is included in a brittle matrix to prevent on inhibit crack propagation by crack blunting, crack bridging, crack deflection, and crack branching. Model examples of DPT tungsten are exploredmore » in this study, including W-Cu and W-Ni-Fe powder product composites. Three-point and four-point notched and/or pre-cracked bend samples were tested at several strain rates and temperatures to help understand deformation, cracking, and toughening in these materials. Data from these tests are used for developing and calibrating crack-bridging models. Finite element damage mechanics models are introduced as a modeling method that appears to capture the complexity of crack growth in these materials.« less

A novel abutment construction technique for rapid bridge construction : controlled low strength Materials (CLSM) with full-height concrete panels.

DOT National Transportation Integrated Search

2012-01-01

One of the major obstacles facing rapid bridge construction for typical span type bridges is the time required to construct bridge abutments and foundations. This can be remedied by using the controlled low strength materials (CLSM) bridge abutment. ...

Evaluation of the composite wing girder bridge at Bear Creek.

DOT National Transportation Integrated Search

1984-11-01

This report documents the construction monitoring and subsequent field testing : to evaluate the performance of an innovative nloose-fit" composite post-tensioned : concrete wing girder bridge constructed over Bear Creek, south of Austin, Texas. : Th...

Multi-scale simulations of apatite-collagen composites: from molecules to materials

NASA Astrophysics Data System (ADS)

Zahn, Dirk

2017-03-01

We review scale-bridging simulation studies for the exploration of atomicto-meso scale processes that account for the unique structure and mechanic properties of apatite-protein composites. As the atomic structure and composition of such complex biocomposites only partially is known, the first part (i) of our modelling studies is dedicated to realistic crystal nucleation scenarios of inorganic-organic composites. Starting from the association of single ions, recent insights range from the mechanisms of motif formation, ripening reactions and the self-organization of nanocrystals, including their interplay with growth-controlling molecular moieties. On this basis, (ii) reliable building rules for unprejudiced scale-up models can be derived to model bulk materials. This is exemplified for (enamel-like) apatite-protein composites, encompassing up to 106 atom models to provide a realistic account of the 10 nm length scale, whilst model coarsening is used to reach μm length scales. On this basis, a series of deformation and fracture simulation studies were performed and helped to rationalize biocomposite hardness, plasticity, toughness, self-healing and fracture mechanisms. Complementing experimental work, these modelling studies provide particularly detailed insights into the relation of hierarchical composite structure and favorable mechanical properties.

The Peculiarities of Structure Formation and Properties of Zirconia-Based Nanocomposites with Addition of Al2O3 and NiO

NASA Astrophysics Data System (ADS)

Danilenko, I.; Lasko, G.; Brykhanova, I.; Burkhovetski, V.; Ahkhozov, L.

2017-02-01

The present study is devoted to the problem of enhancing fracture toughness of ZrO2 ceramic materials through the formation of composite structure by addition of Al2O3 and NiO particles. In this paper, we analyzed the general and distinguished features of microstructure of both composite materials and its effect on fracture toughness of materials. In this paper, we used the XRD, SEM, and EDS methods for determination of granulometric, phase, and chemical composition of sintered materials. The peculiarities of dependence of fracture toughness values from dopant concentration and changing the Y3+ amount in zirconia grains allow us to assume that at least two mechanisms can affect the fracture toughness of ZrO2 ceramics. Crack bridging/deflection processes with the "transformation toughening" affect the K1C values depending on the dopant concentration. Crack deflection mechanism affects the K1C values when the dopant concentrations are low, and transformation toughening affects the K1C values when the dopant concentrations begin to have an impact on microstructure reorganization-redistribution of Y3+ ions and formation of Y3+-depleted grains with high ability to phase transformation.

Tool for analysis of early age transverse cracking of composite bridge decks.

DOT National Transportation Integrated Search

2011-08-29

"Executive Summary: Computational methods and associated software were developed : to compute stresses in HP concrete composite bridge decks due to temperature, shrinkage, and : vehicle loading. The structural analysis program uses a layered finite e...

Retrofit of existing reinforced concrete bridges with fiber reinforced polymer composites

DOT National Transportation Integrated Search

2001-12-01

A two-part research was focused on examining various issues related to the use of fiber reinforced polymer (FRP) composites for strengthening of existing reinforced concrete bridges. A summary of each phase is presented separately.

19 CFR 123.18 - Equipment and materials for constructing bridges or tunnels between the United States and Canada...

Code of Federal Regulations, 2011 CFR

2011-04-01

... 19 Customs Duties 1 2011-04-01 2011-04-01 false Equipment and materials for constructing bridges... WITH CANADA AND MEXICO International Traffic § 123.18 Equipment and materials for constructing bridges.... Equipment for use in construction of bridges or tunnels between the United States and Canada or Mexico shall...

19 CFR 123.18 - Equipment and materials for constructing bridges or tunnels between the United States and Canada...

Code of Federal Regulations, 2010 CFR

2010-04-01

... 19 Customs Duties 1 2010-04-01 2010-04-01 false Equipment and materials for constructing bridges... bridges or tunnels between the United States and Canada or Mexico. (a) Admission of equipment and materials. Equipment for use in construction of bridges or tunnels between the United States and Canada or...

Superhydrophobic engineered cementitious composites for highway bridge applications : technology transfer and implementation.

DOT National Transportation Integrated Search

2013-09-01

The strength and durability of highway bridges are two of the key components in maintaining a : high level of freight transportation capacity on the nations highways. Superhydrophobic : engineered cementitious composite (SECC) is a new advanced con...

Quality control and in-service inspection technology for hybrid-composite girder bridges.

DOT National Transportation Integrated Search

2014-08-01

This report describes efforts to develop quality control tools and in-service inspection technologies for the fabrication and construction of Hybrid Composite Beams (HCBs). HCBs are a new bridge technology currently being evaluated by the Missouri De...

Bridge-in-a-Backpack(TM). Task 4 : monitoring and load rating.

DOT National Transportation Integrated Search

2015-01-01

Five bridges were constructed utilizing UMaines hybrid composite arch technology as part of the Maine : Department of Transportations Composites Initiative. Three were constructed in 2010, one in 2011 and the final : one in 2012. The designs fo...

FHWA study tour for advanced composites in bridges in Europe and Japan

DOT National Transportation Integrated Search

1997-10-01

Under the Federal Highway Administration's (FHWA) International Technology Scanning Program, a team of 13 U.S. bridge engineers and advanced composite experts from Federal and State transportation agencies, academia, and industry conducted a 2-week s...

Evaluation of the composition of the binder bridges in matrix granules prepared with a small-scale high-shear granulator.

PubMed

Bajdik, János; Baki, Gabriella; Szent-Királlyi, Zsuzsanna; Knop, Klaus; Kleinebudde, Peter; Pintye-Hódi, Klára

2008-11-04

The aim of this work was to evaluate the binder bridges which can form in hydrophilic matrix granules prepared with a small-scale high-shear granulator. Matrices contained hydroxypropyl methylcellulose (HPMC) as a matrix-forming agent, together with lactose monohydrate and microcrystalline cellulose as filler. Water was used as granulating liquid. A 2(4) full factorial design was used to evaluate the effects of the operational parameters (impeller speed, chopper speed, dosing speed and wet massing time) on the granulation process. The temperature of the sample increased relevantly during the preparation in the small-scale apparatus. The same setup induced different temperature increases for different amounts of powder. This alteration enhances the solubility of lactose and decreases that of HPMC, and thus the quantities of the dissolved components can vary. Accordingly, changes in composition of the binder bridge can occur. Since exact determination of the dissolution of these materials during granulation is difficult, the consequences of the changes in solubility were examined. Differential scanning calorimetry (DSC), thermomechanical analysis (TMA) and X-ray diffraction (XRD) measurements were made to evaluate the films prepared from liquids with different ratios of soluble materials. The DSC and XRD measurements confirmed that the lactose lost its crystalline state in the film. The TMA tests revealed that increase of the quantity of lactose in the film decreased the glass transition temperature of the film; this may be attributed to the interaction of the additives. At a lactose content of 37.5%, a second glass transition appeared. This phenomenon may be indicative of a separate amorphous lactose phase.

NPSNET: Dynamic Terrain and Cultured Feature Depiction

DTIC Science & Technology

1992-09-01

defaults. bridge(terrain *ptr, vertex pos, bridge mattype bmat ); This constructor takes only the pointer to the underlying terrain, a placement, and a...material to use for construction. bridge(terrain *ptr, vertex pos, bridge-mattype bmat , float dir); This constructor takes a terrain pointer, a...placement position, a material to use, and a direction to run. bridge(terrain *ptr, vertex pos, bridge-mattype bmat , float dir, float width, float height

Evaluation of high performance pavement and bridge deck wearing surface repair materials.

DOT National Transportation Integrated Search

2016-08-01

This project provided for a laboratory and field testing of several high performance repair materials for : pavements and concrete bridge decks. The main purpose was to provide ODOT with materials and procedures : to shorten road and bridge closures....

Learning from Natural Nacre: Constructing Layered Polymer Composites with High Thermal Conductivity.

PubMed

Pan, Guiran; Yao, Yimin; Zeng, Xiaoliang; Sun, Jiajia; Hu, Jiantao; Sun, Rong; Xu, Jian-Bin; Wong, Ching-Ping

2017-09-27

Inspired by the microstructures of naturally layered and highly oriented materials, such as natural nacre, we report a thermally conductive polymer composite that consists of epoxy resin and Al 2 O 3 platelets deposited with silver nanoparticles (AgNPs). Owing to their unique two-dimensional structure, Al 2 O 3 platelets are stacked together via a hot-pressing technique, resulting in a brick-and-mortar structure, which is similar to the one of natural nacre. Moreover, the AgNPs deposited on the surfaces of the Al 2 O 3 platelets act as bridges that link the adjacent Al 2 O 3 platelets due to the reduced melting point of the AgNPs. As a result, the polymer composite with 50 wt % filler achieves a maximum thermal conductivity of 6.71 W m -1 K -1 . In addition, the small addition of AgNPs (0.6 wt %) minimally affects the electrical insulation of the composites. Our bioinspired approach will find uses in the design and fabrication of thermally conductive materials for thermal management in modern electronics.

Rotator Cuff Repair with a Tendon-Fibrocartilage-Bone Composite Bridging Patch

PubMed Central

Ji, Xiaoxi; Chen, Qingshan; Thoreson, Andrew R.; Qu, Jin; An, Kai-Nan; Amadio, Peter C.; Steinmann, Scott P.; Zhao, Chunfeng

2015-01-01

Background To compare the mechanical performance of a rotator cuff repaired with a novel tendon-fibrocartilage-bone composite bridging patch vs the traditional Mason-Allen repair in an in vitro canine model. Methods Twenty shoulders and 10 bridging patches from patellar tendon were harvested. The patches were trimmed and sliced into 2 layers. An infraspinatus tendon tear was created in each shoulder. Modified Mason-Allen sutures were used to repair the infraspinatus tendon to the greater tuberosity, with or without the bridging patch (bridging patch group and controls, respectively). Shoulders were loaded to failure under displacement control at a rate of 0.5mm/sec. Findings The ultimate tensile load was significantly higher in the bridging patch group than control (mean [SD], 365.46 [36.45] vs 272.79 [48.88] N; P<.001). Stiffness at the greater tuberosity repair site and the patch-infraspinatus tendon repair site was significantly higher than the control repair site (93.96 [27.72] vs 42.62 [17.48] N/mm P<.001; 65.94 [24.51] vs 42.62 [17.48] N/mm P=.02, respectively). Interpretation The tendon-fibrocartilage-bone composite bridging patch achieved higher ultimate tensile load and stiffness at the patch–greater tuberosity repair site compared with traditional repair in a canine model. This composite tissue transforms the traditional tendon-to-bone healing interface (with dissimilar tissues) into a pair of bone-to-bone and tendon-to-tendon interfaces, which may improve healing quality and reduce retear rate. PMID:26190097

Rotator cuff repair with a tendon-fibrocartilage-bone composite bridging patch.

PubMed

Ji, Xiaoxi; Chen, Qingshan; Thoreson, Andrew R; Qu, Jin; An, Kai-Nan; Amadio, Peter C; Steinmann, Scott P; Zhao, Chunfeng

2015-11-01

To compare the mechanical performance of a rotator cuff repaired with a novel tendon-fibrocartilage-bone composite bridging patch vs the traditional Mason-Allen repair in an in vitro canine model. Twenty shoulders and 10 bridging patches from patellar tendon were harvested. The patches were trimmed and sliced into 2 layers. An infraspinatus tendon tear was created in each shoulder. Modified Mason-Allen sutures were used to repair the infraspinatus tendon to the greater tuberosity, with or without the bridging patch (bridging patch group and controls, respectively). Shoulders were loaded to failure under displacement control at a rate of 0.5mm/s. The ultimate tensile load was significantly higher in the bridging patch group than control (mean [SD], 365.46 [36.45] vs 272.79 [48.88] N; P<.001). Stiffness at the greater tuberosity repair site and the patch-infraspinatus tendon repair site was significantly higher than the control repair site (93.96 [27.72] vs 42.62 [17.48] N/mm P<.001; 65.94 [24.51] vs 42.62 [17.48] N/mm P=.02, respectively). The tendon-fibrocartilage-bone composite bridging patch achieved higher ultimate tensile load and stiffness at the patch-greater tuberosity repair site compared with traditional repair in a canine model. This composite tissue transforms the traditional tendon-to-bone healing interface (with dissimilar tissues) into a pair of bone-to-bone and tendon-to-tendon interfaces, which may improve healing quality and reduce retear rate. Copyright © 2015 Elsevier Ltd. All rights reserved.

Investigation of early timber–concrete composite bridges in the United States

Treesearch

James P. Wacker; Alfredo Dias; Travis K. Hosteng

2017-01-01

The use of timber–concrete composite (TCC) bridges in the United States dates back to circa 1925. Two different TCC systems were constructed during this early period. The first system included a longitudinal nail-laminated deck composite with a concrete deck top layer. The second system included sawn timber stringers supporting a concrete deck top layer. Records...

Demonstration of Corrosion-Resistant Hybrid Composite Bridge Beams for Structural Applications

DTIC Science & Technology

2016-09-01

result of corrosion of the steel support structures or the reinforcing bar in the concrete. The application of corrosion-resistant technology can...demonstrated and validated a corrosion-resistant hybrid-composite beam (HCB) for the reconstruction of a one span of a traditional steel and...concrete bridge at Fort Knox, Kentucky. The HCBs were installed on half of the bridge, and conventional steel beams were installed on the other half

Acoustic emission monitoring of CFRP cables for cable-stayed bridges

NASA Astrophysics Data System (ADS)

Rizzo, Piervincenzo; Lanza di Scalea, Francesco

2001-08-01

The advantages of fiber-reinforced polymer (FRP) composite include excellent corrosion resistance, high specific strength and stiffness, as well as outstanding fatigue behavior. The University of California San Diego's I- 5/Gilman Advanced Technology Bridge Project will help demonstrating the use of such materials in civil infrastructures. This paper presents an acoustic emission (AE) study performed during laboratory proof tests of carbon fiber-reinforced polymer stay-cables of possible use in the I-5/Gilman bridge. Three types of cables, both braided and single strand, were tested to failure at lengths ranging from 5500 mm to 5870 mm. AE allowed to monitor damage initiation and progression in the test pieces more accurately than the conventional load versus displacement curve. All of the cables exhibited acoustic activities revealing some degree of damage well before reaching final collapse, which is expected in FRP's. It was also shown that such cables are excellent acoustic waveguides exhibiting very low acoustic attenuation, which makes them an ideal application for an AE-based health monitoring approach.

Lithium conductivity in glasses of the Li2O-Al2O3-SiO2 system.

PubMed

Ross, Sebastian; Welsch, Anna-Maria; Behrens, Harald

2015-01-07

To improve the understanding of Li-dynamics in oxide glasses, i.e. the effect of [AlO4](-) tetrahedra and non-bridging oxygens on the potential landscape, electrical conductivity of seven fully polymerized and partly depolymerized lithium aluminosilicate glasses was investigated using impedance spectroscopy (IS). Lithium is the only mobile particle in these materials. Data derived from IS, i.e. activation energies, pre-exponential factors and diffusivities for lithium, are interpreted in light of Raman spectroscopic analyses of local structures in order to identify building units, which are crucial for lithium dynamics and migration. In polymerized glasses (compositional join LiAlSiO4-LiAlSi4O10) the direct current (DC) electrical conductivity continuously increases with increasing lithium content while lithium diffusivity is not affected by the Al/Si ratio in the glasses. Hence, the increase in electrical conductivity can be solely assigned to lithium concentration in the glasses. An excess of Li with respect to Al, i.e. the introduction of non-bridging oxygen into the network, causes a decrease in lithium mobility in the glasses. Activation energies in polymerized glasses (66 to 70 kJ mol(-1)) are significantly lower than those in depolymerized networks (76 to 78 kJ mol(-1)) while pre-exponential factors are nearly constant across all compositions. Comparison of the data with results for lithium silicates from the literature indicates a minimum in lithium diffusivity for glasses containing both aluminium tetrahedra and non-bridging oxygens. The findings allow a prediction of DC conductivity for a large variety of lithium aluminosilicate glass compositions.

Micromechanics of fatigue in woven and stitched composites

NASA Technical Reports Server (NTRS)

Cox, B. N.; Dadkhah, M. S.; Inman, R. V.; Mitchell, M. R.; Morris, W. L.; Schroeder, S.

1991-01-01

The goal is to determine how microstructural factors, especially the architecture of microstructural factors, control fatigue damage in 3D reinforced polymer composites. Test materials were fabricated from various preforms, including stitched quasi-isotropic laminates, and through-the-thickness angle interlock, layer-to-layer angle interlock, and through-the-thickness stitching effect weaves. Preforms were impregnated with a tough resin by a special vacuum infiltration method. Most tests are being performed in uniaxial compression/compression loading. In all cases to date, failure has occurred not by delamination, but by shear failure, which occurs suddenly rather than by gradual macroscopic crack growth. Some theoretical aspects of bridging are also examined.

Interlaminar fracture of random short-fiber SMC composite

NASA Technical Reports Server (NTRS)

Wang, S. S.; Suemasu, H.; Zahlan, N. M.

1984-01-01

In the experimental phase of the present study of the interlaminar fracture behavior of a randomly oriented short fiber sheet molding compound (SMC) composite, the double cantilever beam fracture test is used to evaluate the mode I interlaminar fracture toughness of different composite thicknesses. In the analytical phase of this work, a geometrically nonlinear analysis is introduced in order to account for large deflections and nonlinear load deflection curves in the evaluation of interlaminar fracture toughness. For the SMC-R50 material studied, interlaminar toughness is an order of magnitude higher than that of unreinforced neat resin, due to unusual damage mechanisms ahead of the crack tip, together with significant fiber bridging across crack surfaces. Composite thickness effects on interlaminar fracture are noted to be appreciable, and a detailed discussion is given on the influence of SMC microstructure.

Semiconductor bridge (SCB) detonator

DOEpatents

Bickes, Jr., Robert W.; Grubelich, Mark C.

1999-01-01

The present invention is a low-energy detonator for high-density secondary-explosive materials initiated by a semiconductor bridge igniter that comprises a pair of electrically conductive lands connected by a semiconductor bridge. The semiconductor bridge is in operational or direct contact with the explosive material, whereby current flowing through the semiconductor bridge causes initiation of the explosive material. Header wires connected to the electrically-conductive lands and electrical feed-throughs of the header posts of explosive devices, are substantially coaxial to the direction of current flow through the SCB, i.e., substantially coaxial to the SCB length.

Advanced bridge safety initiative : live load testing and load rating of the Evans Brook Bridge (#5506) and the Hastings Bridge (#5507) in Batchelders Grant, Maine.

DOT National Transportation Integrated Search

2014-01-01

The Advanced Structures and Composites Center at the University of Maine (UMaine) performed live load testing : and rating factor analysis for two bridges (No. 5506 and No. 5507) in Batchelders Grant, Maine. The bridge load : rating performed by cons...

Adhesive strength of paint-on resins to crown and bridge composites.

PubMed

Kanie, Takahito; Arikawa, Hiroyuki; Fujii, Koichi; Ban, Seiji

2004-12-01

This paper examined the adhesive strength of paint-on resin to crown and bridge composites after soaking in water and thermal-cycling. Three shades of paint-on resin were coated on three kinds of crown and bridge composite under four surface treatment conditions (a combination of sandblaster and pretreatment liquid). These specimens were soaked in water at 37 degrees C for 1 day, 1 month, and 1 year, and at 4 degrees C and 60 degrees C alternatively for 1-minute periods for 10,000 cycles by thermal-cycling machine. The adhesive strengths were obtained by shear test. There were no significant differences among the adhesive strengths of three shades of paint-on resin to three composites after storage (p > 0.05). The adhesive strengths to composites with sandblasting showed higher values than those without it (p < 0.01).

Field testing of the Wolf Creek curved girder bridge : part I : vibration tests.

DOT National Transportation Integrated Search

2009-01-01

The Wolf Creek Bridge is a curved, multi-girder three span steel composite bridge located south of Narrows, Virginia, that was completed in 2006. A finite element model of the bridge revealed that pier flexibility may be important in modeling the bri...

Field testing of the Wolf Creek curved girder bridge : part II : strain measurements.

DOT National Transportation Integrated Search

2009-01-01

The Wolf Creek Bridge is a curved, multi-girder three span steel composite bridge located south of Narrows, Virginia, that was completed in 2006. A finite element (FE) model of the bridge revealed that pier flexibility may be important in modeling th...

Implementation project: strengthening of a bridge near Hondo, Texas using post-installed shear connectors.

DOT National Transportation Integrated Search

2009-03-01

This project was an implementation of research conducted under TxDOT Research Project 0-4124 on the use : of post-installed shear connectors to develop composite action in existing non-composite steel bridge girder : systems. In this implementation s...

Use of microfasteners to produce damage tolerant composite structures

PubMed Central

Hallett, Stephen R.

2016-01-01

The paper concerns the mechanical performance of continuous fibre/thermosetting polymer matrix composites reinforced in the through-thickness direction with fibrous or metallic rods or threads in order to mitigate against low delamination resistance. Specific illustrations of the effects of microfasteners in reducing delamination crack growth are made for Z-pinned and tufted composites. Response to loading in such ‘structured materials’ is subject to multiple parameters defining their in-plane and out-of-plane properties. Single microfastener mechanical tests are well suited to establish the crack bridging laws under a range of loading modes, from simple delamination crack opening to shear, and provide the basis for predicting the corresponding response of microfastener arrays, within a given material environment. The fundamental experiments on microfasteners can be used to derive analytical expressions to describe the crack bridging behaviour in a general sense, to cover all possible loadings. These expressions can be built into cohesive element constitutive laws in a finite-element framework for modelling the effects of microfastener arrays on the out-of-plane mechanical response of reinforced structural elements, including the effects of known manufacturing imperfections. Such predictive behaviour can then be used to assess structural integrity under complex loading, as part of the component design process. This article is part of the themed issue ‘Multiscale modelling of the structural integrity of composite materials’. PMID:27242299

Preservation treatment for wood bridge application

Treesearch

Jake Bigelow; Stan Lebow; Carol A. Clausen; Lowell Greimann; Terry J. Wipf

2009-01-01

Timber can often be a cost-effective construction material for new bridges. The durability of the bridge greatly depends on proper attention to construction details and fabrication, as well as proper preservative treatment before, during, and after construction. Material repair and replacement costs for bridges are a considerable expense for highway agencies. To...

Review on antibacterial characteristics of bridge engineering biomaterials.

PubMed

Zhao, Qing-Qing; Chen, Meng-Yao; He, Rui-Lin; Zhang, Zhong-Feng; Ashraf, Muhammad Aqeel

2016-01-01

This review summarizes the research on timber construction materials used in bridge construction. It focuses on the application of antiseptic treatments and the use of timber engineering materials in decks and bridges. This review also provides an overview on the future research and prospects of engineered timber materials.

Determination and reoxidation of the disulfide bridges of a squash-type trypsin inhibitor from Sechium edule seeds.

PubMed

Faça, Vitor M; Pereira, Sandra R; Laure, Hélen J; Greene, Lewis J

2004-07-01

The determination of the disulfide pairings of SETI-II, a trypsin inhibitor isolated from Sechium edule, is described herein. The inhibitor contains 31 amino acid residues per mol, 6 of which are cysteine. Forty-five nmol (160 microg) of SETI-II was hydrolyzed with 20 microg thermolysin for 48 hr at 45 degrees C, and peptides were separated by reverse phase high performance liquid chromatography (RP-HPLC). The major products were identified by amino acid composition, Edman degradation, and on the basis of the sequence of the inhibitor. The disulfide bridge pairings and (yields) are: Cys1-Cys4 (79%), Cys2-Cys5 (21%) and Cys3-Cys6 (43%). When the reduced inhibitor was reoxidized with glutathione reduced form (GSH)/glutathione oxidized form (GSSG) at pH 8.5 for 3 hr, full activity was recovered. These data show that disulfide bridge pairing and oxidation can be determined at nanomole levels and that sensitive and quantitative Edman degradation can eliminate the final time- and material-consuming step of disulfide determinations by eliminating the need to purify and cleave each peptide containing a disulfide bridge.

Long term monitoring of carbon composite strands in the Penobscot-Narrows bridge.

DOT National Transportation Integrated Search

2015-06-01

The Penobscot-Narrows Bridge was constructed between May 2003 and December 2006. The bridge is a cable-stayed design with twin pylons and a 2,120-foot span. This cable-stayed bridge features a cradle stay system that : allows for each cable strand in...

Nanoporous metal organic frameworks as hybrid polymer-metal composites for drug delivery and biomedical applications.

PubMed

Beg, Sarwar; Rahman, Mahfoozur; Jain, Atul; Saini, Sumant; Midoux, Patrick; Pichon, Chantal; Ahmad, Farhan Jalees; Akhter, Sohail

2017-04-01

Metal organic frameworks (MOFs), porous hybrid polymer-metal composites at the nanoscale, are recent innovations in the field of chemistry; they are novel polymeric materials with diverse biomedical applications. MOFs are nanoporous materials, consisting of metal ions linked together by organic bridging ligands. The unique physical and chemical characteristics of MOFs have attracted wider attention from the scientific community, exploring their utility in the field of material science, biology, nanotechnology and drug delivery. The practical feasibility of MOFs is possible owing to their abilities for biodegradability, excellent porosity, high loading capacity, ease of surface modification, among others. In this regard, this review provides an account of various types of MOFs, their physiochemical characteristics and use in diverse disciplines of biomedical sciences - with special emphasis on drug delivery and theranostics. Moreover, this review also highlights the stability and toxicity issues of MOFs, along with their market potential for biomedical applications. Copyright © 2016 Elsevier Ltd. All rights reserved.

Design and evaluation of steel bridges with double composite action

DOT National Transportation Integrated Search

2010-02-01

This report presents findings from a cooperative USF/URS/FDOT research study undertaken to develop design rules for : double composite steel bridges. In the study, a 48 ft long, 16 ft wide, 4 ft. 10 in. deep trapezoidal HPS 70W box section : desig...

49 CFR 237.131 - Design.

Code of Federal Regulations, 2010 CFR

2010-10-01

... modification which materially modifies the capacity of a bridge or the stresses in any primary load-carrying... materially modify the capacity of a bridge or the stresses in any primary load-carrying component of a bridge...

49 CFR 237.131 - Design.

Code of Federal Regulations, 2012 CFR

2012-10-01

... modification which materially modifies the capacity of a bridge or the stresses in any primary load-carrying... materially modify the capacity of a bridge or the stresses in any primary load-carrying component of a bridge...

Monitoring system of arch bridge for safety network management

NASA Astrophysics Data System (ADS)

Joo, Bong Chul; Yoo, Young Jun; Lee, Chin Hyung; Park, Ki Tae; Hwang, Yoon Koog

2010-03-01

Korea has constructed the safety management network monitoring test systems for the civil infrastructure since 2006 which includes airport structure, irrigation structure, railroad structure, road structure, and underground structure. Bridges among the road structure include the various superstructure types which are Steel box girder bridge, suspension bridge, PSC-box-girder bridge, and arch bridge. This paper shows the process of constructing the real-time monitoring system for the arch bridge and the measured result by the system. The arch type among various superstructure types has not only the structural efficiency but the visual beauty, because the arch type superstructure makes full use of the feature of curve. The main measuring points of arch bridges composited by curved members make a difference to compare with the system of girder bridges composited by straight members. This paper also shows the method to construct the monitoring system that considers the characteristic of the arch bridge. The system now includes strain gauges and thermometers, and it will include various sensor types such as CCTV, accelerometers and so on additionally. For the long term and accuracy monitoring, the latest optical sensors and equipments are applied to the system.

Dependence of cell adhesion on extracellular matrix materials formed on pore bridge boundaries by nanopore opening and closing geometry.

PubMed

Kim, Sueon; Han, Dong Yeol; Chen, Zhenzhong; Lee, Won Gu

2018-04-30

In this study, we report experimental results for characterization of the growth and formation of pore bridge materials that modified the adhesion structures of cells cultured on nanomembranes with opening and closing geometry. To perform the proof-of-concept experiments, we fabricated two types of anodized alumina oxide substrates with single-sided opening (i.e., one side open, but closed at the other side) and double-sided opening (i.e., both sides open). In our experiment, we compared the densities of pores formed and of bridge materials which differently act as connective proteins depending on the size of pores. The results show that the pore opening geometry can be used to promote the net contact force between pores, resulting in the growth and formation of pore bridge materials before and after cell culture. The results also imply that the bridge materials can be used to attract the structural protrusion of filopodia that can promote the adhesion of cell-to-cell and cell-to-pore bridge. It is observed that the shape and size of cellular structures of filopodia depend on the presence of pore bridge materials. Overall, this observation brought us a significant clue that cells cultured on nanopore substrates would change the adhesion property depending on not only the formation of nanopores formed on the surface of topological substrates, but also that of pore bridge materials by its morphological growth.

Semiconductor bridge (SCB) detonator

DOEpatents

Bickes, R.W. Jr.; Grubelich, M.C.

1999-01-19

The present invention is a low-energy detonator for high-density secondary-explosive materials initiated by a semiconductor bridge (SCB) igniter that comprises a pair of electrically conductive lands connected by a semiconductor bridge. The semiconductor bridge is in operational or direct contact with the explosive material, whereby current flowing through the semiconductor bridge causes initiation of the explosive material. Header wires connected to the electrically-conductive lands and electrical feed-throughs of the header posts of explosive devices, are substantially coaxial to the direction of current flow through the SCB, i.e., substantially coaxial to the SCB length. 3 figs.

Oriented Polyaniline Nanowire Arrays Grown on Dendrimer (PAMAM) Functionalized Multiwalled Carbon Nanotubes as Supercapacitor Electrode Materials.

PubMed

Jin, Lin; Jiang, Yu; Zhang, Mengjie; Li, Honglong; Xiao, Linghan; Li, Ming; Ao, Yuhui

2018-04-19

At present, PANI/MWNT composites have been paid more attention as promising electrode materials in supercapacitors. Yet some shortcomings still limit the widely application of PANI/MWNT electrolytes. In this work, in order to improve capacitance ability and long-term stability of electrode, a multi-amino dendrimer (PAMAM) had been covalently linked onto multi-walled carbon nanotubes (MWNT) as a bridge to facilitating covalent graft of polyaniline (PANI), affording P-MWNT/PANI electrode composites for supercapacitor. Surprisingly, ordered arrays of PANI nanowires on MWNT (setaria-like morphology) had been observed by scanning electron microscopy (SEM). Electrochemical properties of P-MWNT/PANI electrode had been characterized by cyclic voltammetry (CV) and galvanostatic charge-discharge technique. The specific capacitance and long cycle life of P-MWNT-PANI electrode material were both much higher than MWNT/PANI. These interesting results indicate that multi-amino dendrimer, PAMAM, covalently linked on MWNT provides more reaction sites for in-situ polymerization of ordered PANI, which could efficiently shorten the ion diffusion length in electrolytes and lead to making fully use of conducting materials.

Composite Action in Prestressed NU I-Girder Bridge Deck Systems Constructed with Bond Breakers to Facilitate Deck Removal

DOT National Transportation Integrated Search

2017-11-01

Results are reported from tests of small-scale push-off and large-scale composite NU I-girder specimens conducted to establish an interface connection detail that (1) Facilitates in-situ removal of the bridge deck without damaging prestressed girders...

29 CFR 1926.754 - Structural steel assembly.

Code of Federal Regulations, 2013 CFR

2013-07-01

... connectors on composite floors, roofs and bridge decks. When shear connectors are used in construction of composite floors, roofs and bridge decks, employees shall lay out and install the shear connectors after the... requirements of paragraph (e)(3)(i) of this section. (4) Decking gaps around columns. Wire mesh, exterior...

29 CFR 1926.754 - Structural steel assembly.

Code of Federal Regulations, 2012 CFR

2012-07-01

... connectors on composite floors, roofs and bridge decks. When shear connectors are used in construction of composite floors, roofs and bridge decks, employees shall lay out and install the shear connectors after the... requirements of paragraph (e)(3)(i) of this section. (4) Decking gaps around columns. Wire mesh, exterior...

29 CFR 1926.754 - Structural steel assembly.

Code of Federal Regulations, 2014 CFR

2014-07-01

... connectors on composite floors, roofs and bridge decks. When shear connectors are used in construction of composite floors, roofs and bridge decks, employees shall lay out and install the shear connectors after the... requirements of paragraph (e)(3)(i) of this section. (4) Decking gaps around columns. Wire mesh, exterior...

Composite Action in Prestressed NU I-Girder Bridge Deck Systems Constructed with Bond Breakers to Facilitate Deck Removal : Technical Summary

DOT National Transportation Integrated Search

2017-11-01

Results are reported from tests of small-scale push-off and large-scale composite NU I-girder specimens conducted to establish an interface connection detail that (1) Facilitates in-situ removal of the bridge deck without damaging prestressed girders...

3 D Network-Structured Crumpled Graphene/Carbon Nanotube/Polyaniline Composites for Supercapacitors.

PubMed

Jo, Eun H; Jang, Hee D; Chang, Hankwon; Kim, Sun K; Choi, Ji-Hyuk; Lee, Chong M

2017-05-22

Crumpled graphene (CGR) is considered a promising supercapacitor material to achieve high power and energy density because it could overcome the disadvantages of 2 D GR sheets such as aggregation during the electrode fabrication process, reduction of the available surface area, and limitation of the electron and ion transport. Even though CGR shows good results, carbon materials are limited in terms of their capacitance performance. Here, we report highly enhanced supercapacitor materials by fabricating a 3 D composite containing CGR, carbon nanotubes (CNTs), and polyaniline (PANI). The CNTs increased the basal spacing and bridged the defects for electron transfer between the GR sheets in CGR. PANI can enhance the rate of conduction of electrons and offer high pseudocapacitance originating from its redox reactions. The synergistic effect of the CNTs and PANI may also result in a higher electrochemical capacitance and better stability than each individual component as electrode materials for supercapacitors in a two-electrode system. More importantly, the performance of the supercapacitors can be further enhanced by employing 2 D GR as the binder for the composite electrodes, resulting in specific capacitance of 456 F g -1 , rate capability of 89 %, and cyclic stability of 97 % after 1000 cycles. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Response of No-Name Creek FRP Bridge to Local Weather

DOT National Transportation Integrated Search

2012-09-01

Since 1996, over 30 Fiber Reinforced Polymer (FRP) composite bridges have been installed in the United States. Bridge : locations are in Kansas, Missouri, New York, Iowa, Colorado, West Virginia, Ohio, California, Idaho, Washington, Pennsylvania, : I...

Automated analysis of long-term bridge behavior and health using a cyber-enabled wireless monitoring system

NASA Astrophysics Data System (ADS)

O'Connor, Sean M.; Zhang, Yilan; Lynch, Jerome; Ettouney, Mohammed; van der Linden, Gwen

2014-04-01

A worthy goal for the structural health monitoring field is the creation of a scalable monitoring system architecture that abstracts many of the system details (e.g., sensors, data) from the structure owner with the aim of providing "actionable" information that aids in their decision making process. While a broad array of sensor technologies have emerged, the ability for sensing systems to generate large amounts of data have far outpaced advances in data management and processing. To reverse this trend, this study explores the creation of a cyber-enabled wireless SHM system for highway bridges. The system is designed from the top down by considering the damage mechanisms of concern to bridge owners and then tailoring the sensing and decision support system around those concerns. The enabling element of the proposed system is a powerful data repository system termed SenStore. SenStore is designed to combine sensor data with bridge meta-data (e.g., geometric configuration, material properties, maintenance history, sensor locations, sensor types, inspection history). A wireless sensor network deployed to a bridge autonomously streams its measurement data to SenStore via a 3G cellular connection for storage. SenStore securely exposes the bridge meta- and sensor data to software clients that can process the data to extract information relevant to the decision making process of the bridge owner. To validate the proposed cyber-enable SHM system, the system is implemented on the Telegraph Road Bridge (Monroe, MI). The Telegraph Road Bridge is a traditional steel girder-concrete deck composite bridge located along a heavily travelled corridor in the Detroit metropolitan area. A permanent wireless sensor network has been installed to measure bridge accelerations, strains and temperatures. System identification and damage detection algorithms are created to automatically mine bridge response data stored in SenStore over an 18-month period. Tools like Gaussian Process (GP) regression are used to predict changes in the bridge behavior as a function of environmental parameters. Based on these analyses, pertinent behavioral information relevant to bridge management is autonomously extracted.

Design of a biomimetic self-healing superalloy composite

NASA Astrophysics Data System (ADS)

Files, Bradley Steven

1997-10-01

Use of systems engineering concepts to design technologically advanced materials has allowed ambitious goals of self-healing alloys to be realized. Shape memory alloy reinforcements are embedded in an alloy matrix to demonstrate concepts of stable crack growth and matrix crack closure. Computer methods are used to design thermodynamically compatible iron-based alloys using bio-inspired concepts of crack bridging and self-healing. Feasibility of crack closure and stable crack growth is shown in a prototype system with a Sn-Bi matrix and TiNi fibers. Design of Fe-Ni-Co-Ti-Al alloys using thermodynamic models to determine stabilities and phase equilibria allows for a methodical system designing compatible multicomponent alloys for composite systems. Final alloy computations for this project led to the alloy Fe-27.6Ni-18.2Co-4.1Ti-1.6Al as a compatible shape memory a with a 650sp°C 90 minute heat treatment leading to martensite and austenite start temperatures (Msbs and Asbs) near room temperature. Thin slices of this alloy were able to fully recover at least 5% strain upon unloading heating. Composites made from the designed shape memory alloy and a compatible Fe-based B2 matrix were used to test self-healing concepts in the superalloy system. Diffusion couple experiments verified thermodynamic compatibility between matrix and reinforcement alloys at the solution treatment temperature of 1100sp°C. Concepts of stable crack growth and crack bridging were demonstrated in the composite, leading to enhanced toughness of the brittle matrix. However, healing behavior in this system was limited by intergranular fracture of the reinforcement alloy. It is believed that use of rapidly solidified powders could eliminate intergranular fracture, leading to greatly enhanced properties of toughening and healing. Crack clamping and stable crack growth were achieved in a feasibility study using a Sn-Bi matrix reinforced with TiNi fibers. Tensile specimens with less than 1% fibers showed an ability upon heating to recover over 80% of the plastic deformation induced during a tensile test. Further straining proved that stable crack growth can be realized in this system due to crack bridging of the shape memory fibers. Macroscopic cracks were clamped shut after heating of the material above the TiNi reversion temperature.

On flaw tolerance of nacre: a theoretical study

PubMed Central

Shao, Yue; Zhao, Hong-Ping; Feng, Xi-Qiao

2014-01-01

As a natural composite, nacre has an elegant staggered ‘brick-and-mortar’ microstructure consisting of mineral platelets glued by organic macromolecules, which endows the material with superior mechanical properties to achieve its biological functions. In this paper, a microstructure-based crack-bridging model is employed to investigate how the strength of nacre is affected by pre-existing structural defects. Our analysis demonstrates that owing to its special microstructure and the toughening effect of platelets, nacre has a superior flaw-tolerance feature. The maximal crack size that does not evidently reduce the tensile strength of nacre is up to tens of micrometres, about three orders higher than that of pure aragonite. Through dimensional analysis, a non-dimensional parameter is proposed to quantify the flaw-tolerance ability of nacreous materials in a wide range of structural parameters. This study provides us some inspirations for optimal design of advanced biomimetic composites. PMID:24402917

Response of No-Name Creek FRP Bridge to Local Weather : Technical Summary

DOT National Transportation Integrated Search

2012-09-01

Since 1996, over 30 Fiber Reinforced Polymer (FRP) composite bridges have been installed in the United States. Bridge locations are in Kansas, Missouri, New York, Iowa, Colorado, West Virginia, Ohio, California, Idaho, Washington, Pennsylvania, Illin...

Response of No-Name Creek FRP Bridge to Local Weather : Technical Summary

DOT National Transportation Integrated Search

2012-09-01

Since 1996, over 30 Fiber Reinforced Polymer (FRP) composite bridges have been installed : in the United States. Bridge locations are in Kansas, Missouri, New York, Iowa, Colorado, West : Virginia, Ohio, California, Idaho, Washington, Pennsylvania, I...

Top-lateral bracing systems for trapezoidal steel box-girder bridges.

DOT National Transportation Integrated Search

2005-08-01

Trapezoidal steel box girders are becoming increasingly popular as a bridge system due to their torsional efficiency and aesthetic appearance. These bridge systems utilize one or more trapezoidal steel girders with a cast-in-place composite concrete ...

Modeling Ductile-Phase Toughened Tungsten for Plasma-Facing Materials: Progress in Damage Finite Element Analysis of the Tungsten-Copper Bend Bar Tests

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nguyen, Ba Nghiep; Henager, Charles H.; Kurtz, Richard J.

The objective of this study is to investigate the deformation behavior of ductile phase toughened W-composites such as W-Cu and W-Ni-Fe by means of a multiscale finite element model that involves a microstructural dual-phase model where the constituent phases (i.e., W, Cu, Ni-Fe) are finely discretized and are described by a continuum damage model. Such a model is suitable for modeling deformation, cracking, and crack bridging for W-Cu, W-Ni-Fe, and other ductile phase toughened W-composites, or more generally, any multi-phase composite structure where two or more phases undergo cooperative deformation in a composite system. Our current work focuses on simulatingmore » the response and damage development of the W-Cu specimen subjected to three-point bending.« less

Fiber reinforced polymer bridge decks : [technical summary].

DOT National Transportation Integrated Search

2011-01-01

A number of researchers have addressed the use of Fiber Reinforced Polymer (FRP) deck as a replacement solution for deteriorated bridge decks made of traditional materials. The use of new, advanced materials such as FRP is advantageous when the bridg...

Simple model of cable-stayed bridge deck subjected to static wind loading

NASA Astrophysics Data System (ADS)

Kang, Yi-Lung; Wang, Yang Cheng

1997-05-01

Cable-stayed bridges have been known since 18th century with aesthetics design. The structural system and the structural behavior are significantly different from those of continuous bridges. Compared to continuous bridge, cable- stayed bridges have more flexure bridge deck than those of continuous bridges.On the other hand, cable-stayed bridges have less stiffness to resist wind loading especially for lateral loads. The first considering of bridge engineering is safety. In 1940's, Tacoma Narrows Suspension Bridge destroyed by wind loading is a good example even though it is not a cable-stayed bridge. After the bridge was destroyed, a lot of research articles have been published regarding cable supported bridge subjected to wind loading. In recent days, high strength materials have been served. The bridge engineers use the advantages to expand the span length of cable-stayed bridges. Due to the span length increased and the use of high strength materials, cable- stayed bridges have more significant nonlinear behavior subjected to wind loading. In this paper, a slice bridge deck of cable-stayed bridge connected to internal support cables is considered. The deck has been considered to be subjected to lateral static wind loading. Since cables can not take compressive force, the deck has strongly nonlinear behavior even though the materials are linear elastic. Several primary load combinations have ben considered in this paper such as the bridge deck supposed to be moved horizontally without rotation or the bridge deck supposed to be moved horizontally with rotational deformation. The mathematical formulas and the numerical solutions are found and represented in graphical forms. The results can be provided to bridge designers and researchers for further study of this type of structure subjected to wind loading.

Microfluidic device and methods for focusing fluid streams using electroosmotically induced pressures

DOEpatents

Jacobson, Stephen C.; Ramsey, J. Michael

2010-06-01

A microfabricated device employing a bridging membrane and methods for electrokinetic transport of a liquid phase biological or chemical material using the same are described. The bridging membrane is deployed in or adjacent to a microchannel and permits either electric current flow or the transport of gas species, while inhibiting the bulk flow of material. The use of bridging membranes in accordance with this invention is applicable to electrokinetically inducing fluid flow to confine a selected material in a region of a microchannel that is not influenced by an electric field. Other structures for inducing fluid flow in accordance with this invention include nanochannel bridging membranes and alternating current fluid pumping devices. Applications of the bridging membranes according to this invention include the separation of species from a sample material, valving of fluids in a microchannel network, mixing of different materials in a microchannel, and the pumping of fluids.

Insights into Silicate and Oxide Melt Structure from Amorphous, Non-Glass-Forming Materials

NASA Astrophysics Data System (ADS)

Stebbins, J. F.

2015-12-01

Many silicate and oxide liquids of interest in the Earth sciences and in technology cannot readily be quenched to glasses, either because of low silica contents (and hence low viscosity at the melting point and accompanying liquid 'fragility') or because of liquid-liquid unmixing at high temperature. Although in-situ, high temperature structural tools have been in use for decades and are rapidly developing, many methods are still most informative for glass samples quenched to ambient pressure and temperature, e.g. high-resolution solid-state NMR. Amorphous oxides, including alumina and silicate compositions, have widespread technological applications. These are generally deposited by a variety of high-energy sputtering methods, as films of thicknesses of 10's to 100's of nm. Using Al-27, Si-29, and O-17 NMR, we have recently shown that for such films, very similar short-range structure is seen in materials made by very different kinetic pathways, such as sol-gel synthesis vs. ion-beam sputtering. This path-independent structure suggests that these materials pass through transient equilibrium states during their formation, probably that of deeply supercooled liquids just above glass transition temperatures. In the HfO2-SiO2 and ZrO2-SiO2 systems, for example, samples have well-resolved O-17 NMR spectra, allowing quantitation of O sites with only Hf(Zr) neighbors (so-called "free" oxide ions), with mixed Hf(Zr) and Si neighbors, and Si only. The observed oxygen speciation agrees well with a simple thermodynamic model of one of the most fundamental equilibria in silicate systems, namely the reaction of bridging (Si-O-Si) and "free" (e.g. OHf3 and OHf4) oxide ions to produce "non-bridging" oxygens (e.g. Si-OHf2). This new approach to sampling such structural equilibria in compositions far outside the range of normal glass-forming liquids may provide new insights into more geological compositions as well, as well as in more general models of silicate melt chemistry.

Strain monitoring for horsetail falls and sylvan bridges

DOT National Transportation Integrated Search

2002-05-01

Fiber optic sensors were installed on two reinforced concrete bridges that had been strengthened with fiber reinforced polymer composites. The primary objective for one of the bridges was to provide strain data to verify a computer model for the brid...

Connecticut permanent long-term bridge monitoring network, volume 6 : monitoring of a continuous plate girder bridge with load restrictions - Route 15 over the Housatonic River in Stratford (Bridge #761).

DOT National Transportation Integrated Search

2014-08-01

This report describes the instrumentation and data acquisition system for monitoring of a continuous span steel plate : girder bridge with a composite concrete deck located on a limited access highway. The monitoring system was : developed and instal...

Cellulose-hemicellulose interaction in wood secondary cell-wall

NASA Astrophysics Data System (ADS)

Zhang, Ning; Li, Shi; Xiong, Liming; Hong, Yu; Chen, Youping

2015-12-01

The wood cell wall features a tough and relatively rigid fiber reinforced composite structure. It acts as a pressure vessel, offering protection against mechanical stress. Cellulose microfibrils, hemicellulose and amorphous lignin are the three major components of wood. The structure of secondary cell wall could be imagined as the same as reinforced concrete, in which cellulose microfibrils acts as reinforcing steel bar and hemicellulose-lignin matrices act as the concrete. Therefore, the interface between cellulose and hemicellulose/lignin plays a significant role in determine the mechanical behavior of wood secondary cell wall. To this end, we present a molecular dynamics (MD) simulation study attempting to quantify the strength of the interface between cellulose microfibrils and hemicellulose. Since hemicellulose binds with adjacent cellulose microfibrils in various patterns, the atomistic models of hemicellulose-cellulose composites with three typical binding modes, i.e. bridge, loop and random binding modes are constructed. The effect of the shape of hemicellulose chain on the strength of hemicellulose-cellulose composites under shear loadings is investigated. The contact area as well as hydrogen bonds between cellulose and hemicellulose, together with the covalent bonds in backbone of hemicellulose chain are found to be the controlling parameters which determine the strength of the interfaces in the composite system. For the bridge binding model, the effect of shear loading direction on the strength of the cellulose material is also studied. The obtained results suggest that the shear strength of wood-inspired engineering composites can be optimized through maximizing the formations of the contributing hydrogen bonds between cellulose and hemicellulose.

Performance evaluation of concrete bridge decks reinforced with MMFX and SSC rebars.

DOT National Transportation Integrated Search

2006-01-01

This report investigates the performance of bridge decks reinforced with stainless steel clad (SSC) and micro-composite multistructural formable steel (MMFX) rebars. The two-span Galloway Road Bridge on route CR5218 over North Elkhorn Creek in Scott ...

Rapid replacement of Tangier Island bridges including lightweight and durable fiber-reinforced polymer deck systems.

DOT National Transportation Integrated Search

2009-01-01

Fiber-reinforced polymer (FRP) composite cellular deck systems were used as new bridge decks on two replacement bridges on Tangier Island, Virginia. The most important characteristics of this application were reduced self-weight and increased durabil...

Environmental, mechanical and life-cycle cost analysis of bridge columns.

DOT National Transportation Integrated Search

2014-08-01

Corrosion of RC bridge element is one of the major deterioration distresses in US Highway Bridges. FRP composites jackets can be : the economic and effective corrosion repair in future, though its practices and field installation as a means of corros...

Manning's roughness coefficient for buried composite arch bridges.

DOT National Transportation Integrated Search

2014-08-01

This report includes fulfillment of Task 9 of a multi-task contract to further enhance concrete filled FRP tubes, or : the Bridge in a Backpack. Task 9 investigates the interaction of water flow under the bridge with the tubes and : decking and recom...

Behaviour study of thick laminated composites: Experimentation and finite element analyses

NASA Astrophysics Data System (ADS)

Duchaine, Francois

In today's industries, it is common practice to utilize composite materials in very large and thick structures like bridge decks, high pressure vessels, wind turbine blades and aircraft parts to mention a few. Composite materials are highly favoured due to their physical characteristics: low weight, low cost, adaptable mechanical properties, high specific strength and stiffness. The use of composite materials for large structures has however raised several concerns in the prediction of the behaviour of thick laminated composite parts. A lack of knowledge and experience in the use of composite materials during the design, sizing and manufacturing of thick composite parts can lead to catastrophic events. In this thesis, it was supposed that the elastic material properties may vary with the laminate thickness. In order to measure the influence of the thickness on nine orthotropic elastic material properties (E1, E2, E3, nu12, nu 13, nu23, G12, G13 and G23), three categories of thickness have been defined using a comparison between the classical lamination theory (CLT), different beam theories and a numerical 3D solid finite element analysis (FEA) model. The defined categories are: thin laminates for thicknesses below 6 mm (0.236"), moderately thick laminates for thicknesses up to 16 mm (0.630") and thick laminates for thicknesses above 16 mm (0.630"). For three different thicknesses (thin -- 1.5 mm, moderately thick -- 10 mm and thick -- 20 mm), the influence of the thickness on the orthotropic elastic material properties of unidirectional (UD) fibreglass/epoxy laminates has been measured. A torsion test on rectangular bar is also proposed to measure the influence of the thickness on G13 and G23. The nine elastic material properties, in function of the thickness, have been used in CLT and 3D solid FEA model in order to predict the axial Young's modulus and Poisson's ratios of cross-ply and quasi-isotropic laminates. Experimental results have also been obtained for those laminates. The analysis of test results with CLT and FEA showed that the variation of elastic material properties with the thickness is not significant for in-plane problems. On the other hand, a substantial influence has been highlighted on UD elastic material properties driven by the matrix like E 2, E3, nu13 and G12. .

Nonlinear fracture of concrete and ceramics

NASA Technical Reports Server (NTRS)

Kobayashi, Albert S.; Du, Jia-Ji; Hawkins, Niel M.; Bradt, Richard C.

1989-01-01

The nonlinear fracture process zones in an impacted unnotched concrete bend specimen, a prenotched ceramic bend specimen, and an unnotched ceramic/ceramic composite bend specimen were estimated through hybrid experimental numerical analysis. Aggregate bridging in concrete, particulate bridging in ceramics, and fiber bridging in ceramic/ceramic composite are modeled by Barenblatt-type cohesive zones which are incorporated into the finite-element models of the bend specimens. Both generation and propagation analyses are used to estimate the distribution of crack closure stresses in the nonlinear fracture process zones. The finite-element models are then used to simulate fracture tests consisting of rapid crack propagation in an impacted concrete bend specimen, and stable crack growth and strain softening in a ceramic and ceramic/ceramic composite bend specimens.

Innovative Structural Materials and Sections with Strain Hardening Cementitious Composites

NASA Astrophysics Data System (ADS)

Dey, Vikram

The motivation of this work is based on development of new construction products with strain hardening cementitious composites (SHCC) geared towards sustainable residential applications. The proposed research has three main objectives: automation of existing manufacturing systems for SHCC laminates; multi-level characterization of mechanical properties of fiber, matrix, interface and composites phases using servo-hydraulic and digital image correlation techniques. Structural behavior of these systems were predicted using ductility based design procedures using classical laminate theory and structural mechanics. SHCC sections are made up of thin sections of matrix with Portland cement based binder and fine aggregates impregnating continuous one-dimensional fibers in individual or bundle form or two/three dimensional woven, bonded or knitted textiles. Traditional fiber reinforced concrete (FRC) use random dispersed chopped fibers in the matrix at a low volume fractions, typically 1-2% to avoid to avoid fiber agglomeration and balling. In conventional FRC, fracture localization occurs immediately after the first crack, resulting in only minor improvement in toughness and tensile strength. However in SHCC systems, distribution of cracking throughout the specimen is facilitated by the fiber bridging mechanism. Influence of material properties of yarn, composition, geometry and weave patterns of textile in the behavior of laminated SHCC skin composites were investigated. Contribution of the cementitious matrix in the early age and long-term performance of laminated composites was studied with supplementary cementitious materials such as fly ash, silica fume, and wollastonite. A closed form model with classical laminate theory and ply discount method, coupled with a damage evolution model was utilized to simulate the non-linear tensile response of these composite materials. A constitutive material model developed earlier in the group was utilized to characterize and correlate the behavior of these structural composites under uniaxial tension and flexural loading responses. Development and use of analytical models enables optimal design for application of these materials in structural applications. Another area of immediate focus is the development of new construction products from SHCC laminates such as angles, channels, hat sections, closed sections with optimized cross sections. Sandwich composites with stress skin-cellular core concept were also developed to utilize strength and ductility of fabric reinforced skin in addition to thickness, ductility, and thermal benefits of cellular core materials. The proposed structurally efficient and durable sections promise to compete with wood and light gage steel based sections for lightweight construction and panel application.

Continuity diaphragm for skewed continuous span precast prestressed concrete girder bridges : technical summary report.

DOT National Transportation Integrated Search

2004-03-01

Most highway bridges are built as cast-in-place : reinforced concrete slabs and prestressed concrete : girders. The shear connectors on the top of the girders : assure composite action between the slabs and : girders. The design guidelines for bridge...

Advanced bridge safety initiative : investigation of floor beam performance in three steel through-truss bridges - task 7.

DOT National Transportation Integrated Search

2014-08-01

The Advanced Structures and Composites Center at the University of Maine (UMaine) performed live load testing : and rating adjustment factor analysis for three truss bridges. The Maine Department of Transportation (DOT) : indicated that the floor bea...

Bridge-in-a-Backpack(TM) task 5: guidelines for quality assurance.

DOT National Transportation Integrated Search

2016-03-01

This report includes fulfillment of Task 5 of a multi-task contract to further enhance concrete filled FRP tubes, or : the Bridge in a Backpack. Task 6 provides guidelines for quality assurance. : The Bridge-in-a-Backpack or hybrid composite arch ...

Process of changing the refractive index of a composite containing a polymer and a compound having large dipole moment and polarizability and applications thereof

NASA Technical Reports Server (NTRS)

Peyghambarian, Nasser (Inventor); Hendrickx, Eric (Inventor); Volodin, Boris (Inventor); Marder, Seth R. (Inventor); Kippelen, Bernard (Inventor)

2000-01-01

Fused ring bridge, ring locked dyes that form thermally stable photorfractive compositions. The fused ring bridge structures are .pi.-conjugated bonds in benzene-, naphthalene- or anthracene-derived fused ring systems that connect donor and acceptor groups. The donor and acceptor groups contribute to a high molecular dipole moment and linear polarizability anisotropy. The polarization characteristics of the dye molecules are stabilized since the bonds in the fused ring bridge are not susceptible to rotation, reducing the opportunity for photoisomerization. The dyes are compatible with polymeric compositions, including thermoplastics. The dyes are electrically neutral but have charge transport, electronic and orientational properties such that upon illumination of a composition containing the dye, the dye facilitates refractive index modulation and a photorefractive effect that can be utilized advantageously in numerous applications such as in optical quality devices and biological imaging.

Long-term bridge performance high priority bridge performance issues.

DOT National Transportation Integrated Search

2014-10-01

Bridge performance is a multifaceted issue involving performance of materials and protective systems, : performance of individual components of the bridge, and performance of the structural system as a whole. The : Long-Term Bridge Performance (LTBP)...

Comparative analysis of three different methods for monitoring the use of green bridges by wildlife.

PubMed

Gužvica, Goran; Bošnjak, Ivana; Bielen, Ana; Babić, Danijel; Radanović-Gužvica, Biserka; Šver, Lidija

2014-01-01

Green bridges are used to decrease highly negative impact of roads/highways on wildlife populations and their effectiveness is evaluated by various monitoring methods. Based on the 3-year monitoring of four Croatian green bridges, we compared the effectiveness of three indirect monitoring methods: track-pads, camera traps and active infrared (IR) trail monitoring system. The ability of the methods to detect different species and to give good estimation of number of animal crossings was analyzed. The accuracy of species detection by track-pad method was influenced by granulometric composition of track-pad material, with the best results obtained with higher percentage of silt and clay. We compared the species composition determined by track-pad and camera trap methods and found that monitoring by tracks underestimated the ratio of small canids, while camera traps underestimated the ratio of roe deer. Regarding total number of recorder events, active IR detectors recorded from 11 to 19 times more events then camera traps and app. 80% of them were not caused by animal crossings. Camera trap method underestimated the real number of total events. Therefore, an algorithm for filtration of the IR dataset was developed for approximation of the real number of crossings. Presented results are valuable for future monitoring of wildlife crossings in Croatia and elsewhere, since advantages and disadvantages of used monitoring methods are shown. In conclusion, different methods should be chosen/combined depending on the aims of the particular monitoring study.

U.S. Geological Survey - Virginia Department of Transportation: Bridge scour pilot study

USGS Publications Warehouse

Austin, Samuel H.

2018-02-27

BackgroundCost effective and safe highway bridge designs are required to ensure the long-term sustainability of Virginia’s road systems. The streamflows that, over time, scour streambed sediments from bridge piers inherently affect bridge safety and design costs. To ensure safety, bridge design must anticipate streambed scour at bridge piers over the lifespan of a bridge. Until recently Federal Highway Administration (FHWA) guidance provided only for scour estimates of granular, noncohesive, highly erosive material yielding overestimates of scour potential in instances when streambed materials offer some resistance to scour. This study seeks to estimate stream power and streambed scour for these more resistive sites, with bridge piers potentially established in cohesive soil or erodible rock. This new knowledge may provide significant construction cost savings while ensuring design and construction of safe highway bridges.

RECENT PROGRESS OF CRACK BRIDGING MODELING OF DUCTILE-PHASE-TOUGHENED W-CU COMPOSITES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Setyawan, Wahyu; Henager, Charles H.; Wagner, Karla B.

2015-04-16

A crack bridging model using calculated Cu stress-strain curves has been developed to study the toughening of W-Cu composites. A strengthening factor and necking parameters have been added to the model for the ductile-phase bridges to incorporate constraint effects at small bridge sizes. Parametric studies are performed to investigate the effect of these parameters. The calculated maximum applied stress intensity, aKmax, to induce a 1-mm stable crack is compared to the experimental stress intensity at peak load, Kpeak. Without bridge necking, increasing the strengthening factor improves the agreement between aKmax and Kpeak when plotted vs. logarithm of the displacement rate.more » Improvement can also be achieved by allowing necking with a larger failure strain. While the slope is better matched with this latter approach, the calculated value of aKmax is significantly larger than Kpeak.« less

Smart FRP Composite Sandwich Bridge Decks in Cold Regions

DOT National Transportation Integrated Search

2011-07-01

What if every time a bridge on a lonely road got icy, it automatically notified the local DOT to begin ice-control safety measures? What if a bridge could tell someone : every time an overloaded truck hit the decking, or when the trusses under it beg...

Influence of fly ash, slag cement and specimen curing on shrinkage of bridge deck concrete.

DOT National Transportation Integrated Search

2014-12-01

Cracks occur in bridge decks due to restrained shrinkage of concrete materials. Concrete materials shrink as : cementitious materials hydrate and as water that is not chemically bonded to cementitious materials : migrates from the high humid environm...

Critical stresses for extension of filament-bridged matrix cracks in ceramic-matrix composites: An assessment with a model composite with tailored interfaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Danchaivijit, S.; Shetty, D.K.; Eldridge, J.

Matrix cracking was studied in a model unidirectional composite of SiC filaments in an epoxy-bonded alumina matrix. The residual clamping stress on the filaments due to the shrinkage of the epoxy was moderated with the addition of the alumina filler, and the filament surface was coated with a releasing agent to produce unbonded frictional interfaces. Uniaxial tension specimens with controlled through-cracks with bridging filaments were fabricated by a two-step casting technique. Critical stresses for extension of the filament-bridged cracks of various lengths were measured in uniaxial tension using a high-sensitivity extensometer. The measured crack-length dependence of the critical stress wasmore » in good agreement with the prediction of a stress-intensity analysis that employed a new force-displacement law for the bridging filaments. The analysis required independent experimental evaluation of the matrix fracture toughness, the interfacial sliding friction stress, and the residual tension in the matrix. The matrix-cracking stress for the test specimens without the deliberately introduced cracks was significantly higher than the steady-state cracking stress measured for the long, filament-bridged cracks.« less

Tungsten bridge for the low energy ignition of explosive and energetic materials

DOEpatents

Benson, David A.; Bickes, Jr., Robert W.; Blewer, Robert S.

1990-01-01

A tungsten bridge device for the low energy ignition of explosive and energetic materials is disclosed. The device is fabricated on a silicon-on-sapphire substrate which has an insulating bridge element defined therein using standard integrated circuit fabrication techniques. Then, a thin layer of tungsten is selectively deposited on the silicon bridge layer using chemical vapor deposition techniques. Finally, conductive lands are deposited on each end of the tungsten bridge layer to form the device. It has been found that this device exhibits substantially shorter ignition times than standard metal bridges and foil igniting devices. In addition, substantially less energy is required to cause ignition of the tungsten bridge device of the present invention than is required for common metal bridges and foil devices used for the same purpose.

Microscale solid-state thermal diodes enabling ambient temperature thermal circuits for energy applications.

PubMed

Wang, Song; Cottrill, Anton L; Kunai, Yuichiro; Toland, Aubrey R; Liu, Pingwei; Wang, Wen-Jun; Strano, Michael S

2017-05-24

Thermal diodes, or devices that transport thermal energy asymmetrically, analogous to electrical diodes, hold promise for thermal energy harvesting and conservation, as well as for phononics or information processing. The junction of a phase change material and phase invariant material can form a thermal diode; however, there are limited constituent materials available for a given target temperature, particularly near ambient. In this work, we demonstrate that a micro and nanoporous polystyrene foam can house a paraffin-based phase change material, fused to PMMA, to produce mechanically robust, solid-state thermal diodes capable of ambient operation with Young's moduli larger than 11.5 MPa and 55.2 MPa above and below the melting transition point, respectively. Moreover, the composites show significant changes in thermal conductivity above and below the melting point of the constituent paraffin and rectification that is well-described by our previous theory and the Maxwell-Eucken model. Maximum thermal rectifications range from 1.18 to 1.34. We show that such devices perform reliably enough to operate in thermal diode bridges, dynamic thermal circuits capable of transforming oscillating temperature inputs into single polarity temperature differences - analogous to an electrical diode bridge with widespread implications for transient thermal energy harvesting and conservation. Overall, our approach yields mechanically robust, solid-state thermal diodes capable of engineering design from a mathematical model of phase change and thermal transport, with implications for energy harvesting.

Using Genre to Bridge Research, Professional Writing, and Public Writing at University of North Dakota: A Program Profile

ERIC Educational Resources Information Center

Basgier, Christopher

2017-01-01

To illustrate how genre pedagogy and public writing pedagogy can inform one another, this program profile describes the second-semester composition course at University of North Dakota, ENGL 130: College Composition II: Writing for Public Audiences. In this course, genre works as a rhetorical bridge across an interlinked sequence of research,…

Evaluation of the in-service performance of the Tom's Creek Bridge fiber-reinforced polymer superstructure.

DOT National Transportation Integrated Search

2003-01-01

The Tom's Creek Bridge is a small-scale demonstration project involving the use of fiber-reinforced polymer (FRP) composite girders as the main load carrying members. It is a simply supported, short-span bridge located along Tom's Creek Road in Black...

Methods for forming small-volume electrical contacts and material manipulations with fluid microchannels

DOEpatents

Jacobson, Stephen C [Knoxville, TN; Ramsey, J Michael [Knoxville, TN; Culbertson, Christopher T [Oak Ridge, TN; Whitten, William B [Lancing, TN; Foote, Robert S [Oak Ridge, TN

2011-12-27

A microfabricated device employing a bridging membrane and methods for electrokinetic transport of a liquid phase biological or chemical material using the same are described. The bridging membrane is deployed in or adjacent to a microchannel and permits either ionic current flow or the transport of gas species, while inhibiting the bulk flow of material. The use of bridging membranes in accordance with this invention is applicable to a variety of processes, including electrokinetically induced pressure flow in a region of a microchannel that is not influenced by an electric field, sample concentration enhancement and injection, as well as improving the analysis of materials where it is desired to eliminate electrophoretic bias. Other applications of the bridging membranes according to this invention include the separation of species from a sample material, valving of fluids in a microchannel network, mixing of different materials in a microchannel, and the pumping of fluids.

Methods for forming small-volume electrical contacts and material manipulations with fluidic microchannels

DOEpatents

Jacobson, Stephen C [Knoxville, TN; Ramsey, J Michael [Knoxville, TN; Culbertson, Christopher T [Oak Ridge, TN; Whitten, William B [Lancing, TN; Foote, Robert S [Oak Ridge, TN

2011-04-26

A microfabricated device employing a bridging membrane and methods for electrokinetic transport of a liquid phase biological or chemical material using the same are described. The bridging membrane is deployed in or adjacent to a microchannel and permits either ionic current flow or the transport of gas species, while inhibiting the bulk flow of material. The use of bridging membranes in accordance with this invention is applicable to a variety of processes, including electrokinetically induced pressure flow in a region of a microehannel that is not influenced by an electric field, sample concentration enhancement and injection, as well as improving the analysis of materials where it is desired to eliminate electrophoretic bias. Other applications of the bridging membranes according to this invention include the separation of species from a sample material, valving of fluids in a microchannel network, mixing of different materials in a microchannel, and the pumping of fluids.

Methods for forming small-volume electrical contacts and material manipulations with fluidic microchannels

DOEpatents

Jacobson, Stephen C [Knoxville, TN; Ramsey, J Michael [Knoxville, TN; Culbertson, Christopher T [Oak Ridge, TN; Whitten, William B [Lancing, TN; Foote, Robert S [Oak Ridge, TN

2011-03-22

A microfabricated device employing a bridging membrane and methods for electrokinetic transport of a liquid phase biological or chemical material using the same are described. The bridging membrane is deployed in or adjacent to a microchannel and permits either ionic current flow or the transport of gas species, while inhibiting the bulk flow of material. The use of bridging membranes in accordance with this invention is applicable to a variety of processes, including electrokinetically induced pressure flow in a region of a microchannel that is not influenced by an electric field, sample concentration enhancement and injection, as well as improving the analysis of materials where it is desired to eliminate electrophoretic bias. Other applications of the bridging membranes according to this invention include the separation of species from a sample material, valving of fluids in a microchannel network, mixing of different materials in a microchannel, and the pumping of fluids.

Methods for forming small-volume electrical contacts and material manipulations with fluidic microchannels

DOEpatents

Jacobson, Stephen C.; Ramsey, J. Michael

2007-11-20

A microfabricated device employing a bridging membrane and methods for electrokinetic transport of a liquid phase biological or chemical material using the same are described. The bridging membrane is deployed in or adjacent to a microchannel and permits either ionic current flow or the transport of gas species, while inhibiting the bulk flow of material. The use of bridging membranes in accordance with this invention is applicable to a variety of processes, including electrokinetically induced pressure flow in a region of a microchannel that is not influenced by an electric field, sample concentration enhancement and injection, as well as improving the analysis of materials where it is desired to eliminate electrophoretic bias. Other applications of the bridging membranes according to this invention include the separation of species from a sample material, valving of fluids in a microchannel network, mixing of different materials in a microchannel, and the pumping of fluids.

Methods for forming small-volume electrical contacts and material manipulations with fluidic microchannels

DOEpatents

Jacobson, Stephen C.; Ramsey, J. Michael; Culbertson, Christopher T.; Whitten, William B.; Foote, Robert S.

2004-02-03

A microfabricated device employing a bridging membrane and methods for electrokinetic transport of a liquid phase biological or chemical material using the same are described. The bridging membrane is deployed in or adjacent to a microchannel and permits either ionic current flow or the transport of gas species, while inhibiting the bulk flow of material. The use of bridging membranes in accordance with this invention is applicable to a variety of processes, including electrokinetically induced pressure flow in a region of a microchannel that is not influenced by an electric field, sample concentration enhancement and injection, as well as improving the analysis of materials where it is desired to eliminate electrophoretic bias. Other applications of the bridging membranes according to this invention include the separation of species from a sample material, valving of fluids in a microchannel network, mixing of different materials in a microchannel, and the pumping of fluids.

Cyclic Fiber Push-In Test Monitors Evolution of Interfacial Behavior in Ceramic Matrix Composites

NASA Technical Reports Server (NTRS)

Eldridge, Jeffrey I.

1998-01-01

SiC fiber-reinforced ceramic matrix composites are being developed for high-temperature advanced jet engine applications. Obtaining a strong, tough composite material depends critically on optimizing the mechanical coupling between the reinforcing fibers and the surrounding matrix material. This has usually been accomplished by applying a thin C or BN coating onto the surface of the reinforcing fibers. The performance of these fiber coatings, however, may degrade under cyclic loading conditions or exposure to different environments. Degradation of the coating-controlled interfacial behavior will strongly affect the useful service lifetime of the composite material. Cyclic fiber push-in testing was applied to monitor the evolution of fiber sliding behavior in both C- and BN-coated small-diameter (15-mm) SiC-fiber-reinforced ceramic matrix composites. The cyclic fiber push-in tests were performed using a desktop fiber push-out apparatus. At the beginning of each test, the fiber to be tested was aligned underneath a 10- mm-diameter diamond punch; then, the applied load was cycled between selected maximum and minimum loads. From the measured response, the fiber sliding distance and frictional sliding stresses were determined for each cycle. Tests were performed in both room air and nitrogen. Cyclic fiber push-in tests of C-coated, SiC-fiber-reinforced SiC showed progressive increases in fiber sliding distances along with decreases in frictional sliding stresses for continued cycling in room air. This rapid degradation in interfacial response was not observed for cycling in nitrogen, indicating that moisture exposure had a large effect in immediately lowering the frictional sliding stresses of C-coated fibers. These results indicate that matrix cracks bridged by C-coated fibers will not be stable, but will rapidly grow in moisture-containing environments. In contrast, cyclic fiber push-in tests of both BN-coated, SiC-fiber-reinforced SiC and BNcoated, SiC-fiber-reinforced barium strontium aluminosilicate showed no significant changes in fiber sliding behavior with continued short-term cycling in either room air or nitrogen. Although the composites with BN-coated fibers showed stable short-term cycling behavior in both environments, long-term (several-week) exposure of debonded fibers to room air resulted in dramatically increased fiber sliding distances and decreased frictional sliding stresses. These results indicate that although matrix cracks bridged by BNcoated fibers will show short-term stability, such cracks will show substantial growth with long-term exposure to moisture-containing environments. Newly formulated BN coatings, with higher moisture resistance, will be tested in the near future.

Bioinspired Catecholic Primers for Rigid and Ductile Dental Resin Composites.

PubMed

Shin, Eeseul; Ju, Sung Won; An, Larry; Ahn, Eungjin; Ahn, Jin-Soo; Kim, Byeong-Su; Ahn, B Kollbe

2018-01-17

In the construction of dental restorative polymer composite materials, surface priming on mineral fillers is essential to improve the mechanical performance of the composites. Here we present bioinspired catechol-functionalized primers for a tougher dental resin composite containing glass fillers. The catecholic primers with different polymerizable end groups were designed and then coated on glass surfaces using a simple drop-casting or dip-coating process. The surface binding ability and possible cross-linking (coupling or chemical bridging between the glass substrate and the dental resin) of the catecholic bifunctional primers were evaluated using atomic force microscopy, contact angle measurements, and the knife shear bonding test and compared to a state-of-the-art silane-based coupling agent. Various mechanical tests including shrinkage and compression tests of the dental resin composites were also conducted. Compression tests of the composites containing the catecholic primed fillers exhibited enhanced mechanical properties, owing to the bidentate hydrogen bonding of catechol moieties to the oxide mineral surface. Furthermore, the superior biocompatibility of the primed surface was confirmed via cell attachment assay, thus providing applicability of catecholic primers for practical dental and biomedical applications.

Matrix cracking with irregular fracture fronts as observed in fiber reinforced ceramic composites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hu, K.X.; Yeh, C.P.; Wyatt, K.W.

1998-01-01

As a result of matrix cracking in fiber reinforced composites, fracture planforms assume a wide variation of profiles due to the fact that fiber bridging strongly affects the behavior of local crack fronts. This observation raises the question on the legitimacy of commonly used penny-shaped crack solutions when applied to fiber reinforced composites. Accordingly, investigation of the effects of fracture front profiles on mechanical responses is the thrust of this paper. The authors start with the solution of a penny-shaped crack in a unidirectional, fiber reinforced composite, which demonstrates necessity of considering wavy fracture fronts in fiber reinforced composites. Amore » theoretical framework for fiber reinforced composites with irregular fracture fronts due to matrix cracking is then established via a micromechanics model. The difference between small crack-size matrix cracking and large crack-size matrix cracking is investigated in detail. It is shown that the bridging effect is insignificant when matrix crack size is small and solution of effective property are obtained using Mori-Tanaka`s method by treating cracks and reinforcing fibers as distinct, but interacting phases. When the crack size becomes large, the bridging effects has to be taken into consideration. With bridging tractions obtained in consistency with the micromechanics solution, and corresponding crack energy backed out, the effective properties are obtained through a modification of standard Mori-Tanaka`s treatment of multiphase composites. Analytical solutions show that the generalization of a crack density of a penny-shaped planform is insufficient in describing the effective responses of fiber-reinforced composites with matrix cracking. Approximate solutions that account for the effects of the irregularity of crack planforms are given in closed forms for several irregular crack planforms, including cracks of cross rectangle, polygon and rhombus.« less

Two-photon or higher-order absorbing optical materials and methods of use

NASA Technical Reports Server (NTRS)

Marder, Seth (Inventor); Perry, Joseph (Inventor)

2012-01-01

Compositions capable of simultaneous two-photon absorption and higher order absorptivities are provided. Compounds having a donor-pi-donor or acceptor-pi-acceptor structure are of particular interest, where the donor is an electron donating group, acceptor is an electron accepting group, and pi is a pi bridge linking the donor and/or acceptor groups. The pi bridge may additionally be substituted with electron donating or withdrawing groups to alter the absorptive wavelength of the structure. Also disclosed are methods of generating an excited state of such compounds through optical stimulation with light using simultaneous absorption of photons of energies individually insufficient to achieve an excited state of the compound, but capable of doing so upon simultaneous absorption of two or more such photons. Applications employing such methods are also provided, including controlled polymerization achieved through focusing of the light source(s) used.

Tungsten bridge for the low energy ignition of explosive and energetic materials

DOEpatents

Benson, D.A.; Bickes, R.W. Jr.; Blewer, R.S.

1990-12-11

A tungsten bridge device for the low energy ignition of explosive and energetic materials is disclosed. The device is fabricated on a silicon-on-sapphire substrate which has an insulating bridge element defined therein using standard integrated circuit fabrication techniques. Then, a thin layer of tungsten is selectively deposited on the silicon bridge layer using chemical vapor deposition techniques. Finally, conductive lands are deposited on each end of the tungsten bridge layer to form the device. It has been found that this device exhibits substantially shorter ignition times than standard metal bridges and foil igniting devices. In addition, substantially less energy is required to cause ignition of the tungsten bridge device of the present invention than is required for common metal bridges and foil devices used for the same purpose. 2 figs.

Synthesis, mechanical properties, and in vitro biocompatibility with osteoblasts of calcium silicate-reduced graphene oxide composites.

PubMed

Mehrali, Mehdi; Moghaddam, Ehsan; Shirazi, Seyed Farid Seyed; Baradaran, Saeid; Mehrali, Mohammad; Latibari, Sara Tahan; Metselaar, Hendrik Simon Cornelis; Kadri, Nahrizul Adib; Zandi, Keivan; Osman, Noor Azuan Abu

2014-03-26

Calcium silicate (CaSiO3, CS) ceramics are promising bioactive materials for bone tissue engineering, particularly for bone repair. However, the low toughness of CS limits its application in load-bearing conditions. Recent findings indicating the promising biocompatibility of graphene imply that graphene can be used as an additive to improve the mechanical properties of composites. Here, we report a simple method for the synthesis of calcium silicate/reduced graphene oxide (CS/rGO) composites using a hydrothermal approach followed by hot isostatic pressing (HIP). Adding rGO to pure CS increased the hardness of the material by ∼40%, the elastic modulus by ∼52%, and the fracture toughness by ∼123%. Different toughening mechanisms were observed including crack bridging, crack branching, crack deflection, and rGO pull-out, thus increasing the resistance to crack propagation and leading to a considerable improvement in the fracture toughness of the composites. The formation of bone-like apatite on a range of CS/rGO composites with rGO weight percentages ranging from 0 to 1.5 has been investigated in simulated body fluid (SBF). The presence of a bone-like apatite layer on the composite surface after soaking in SBF was demonstrated by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). The biocompatibility of the CS/rGO composites was characterized using methyl thiazole tetrazolium (MTT) assays in vitro. The cell adhesion results showed that human osteoblast cells (hFOB) can adhere to and develop on the CS/rGO composites. In addition, the proliferation rate and alkaline phosphatase (ALP) activity of cells on the CS/rGO composites were improved compared with the pure CS ceramics. These results suggest that calcium silicate/reduced graphene oxide composites are promising materials for biomedical applications.

Design Protocols and Analytical Strategies that Incorporate Structural Reliability Models

NASA Technical Reports Server (NTRS)

Duffy, Stephen F.

1997-01-01

Ceramic matrix composites (CMC) and intermetallic materials (e.g., single crystal nickel aluminide) are high performance materials that exhibit attractive mechanical, thermal and chemical properties. These materials are critically important in advancing certain performance aspects of gas turbine engines. From an aerospace engineer's perspective the new generation of ceramic composites and intermetallics offers a significant potential for raising the thrust/weight ratio and reducing NO(x) emissions of gas turbine engines. These aspects have increased interest in utilizing these materials in the hot sections of turbine engines. However, as these materials evolve and their performance characteristics improve a persistent need exists for state-of-the-art analytical methods that predict the response of components fabricated from CMC and intermetallic material systems. This need provided the motivation for the technology developed under this research effort. Continuous ceramic fiber composites exhibit an increase in work of fracture, which allows for "graceful" rather than catastrophic failure. When loaded in the fiber direction, these composites retain substantial strength capacity beyond the initiation of transverse matrix cracking despite the fact that neither of its constituents would exhibit such behavior if tested alone. As additional load is applied beyond first matrix cracking, the matrix tends to break in a series of cracks bridged by the ceramic fibers. Any additional load is born increasingly by the fibers until the ultimate strength of the composite is reached. Thus modeling efforts supported under this research effort have focused on predicting this sort of behavior. For single crystal intermetallics the issues that motivated the technology development involved questions relating to material behavior and component design. Thus the research effort supported by this grant had to determine the statistical nature and source of fracture in a high strength, NiAl single crystal turbine blade material; map a simplistic failure strength envelope of the material; develop a statistically based reliability computer algorithm, verify the reliability model and computer algorithm, and model stator vanes for rig tests. Thus establishing design protocols that enable the engineer to analyze and predict the mechanical behavior of ceramic composites and intermetallics would mitigate the prototype (trial and error) approach currently used by the engineering community. The primary objective of the research effort supported by this short term grant is the continued creation of enabling technologies for the macroanalysis of components fabricated from ceramic composites and intermetallic material systems. The creation of enabling technologies aids in shortening the product development cycle of components fabricated from the new high technology materials.

Design Protocols and Analytical Strategies that Incorporate Structural Reliability Models

NASA Technical Reports Server (NTRS)

Duffy, Stephen F.

1997-01-01

Ceramic matrix composites (CMC) and intermetallic materials (e.g., single crystal nickel aluminide) are high performance materials that exhibit attractive mechanical, thermal, and chemical properties. These materials are critically important in advancing certain performance aspects of gas turbine engines. From an aerospace engineers perspective the new generation of ceramic composites and intermetallics offers a significant potential for raising the thrust/weight ratio and reducing NO(sub x) emissions of gas turbine engines. These aspects have increased interest in utilizing these materials in the hot sections of turbine engines. However, as these materials evolve and their performance characteristics improve a persistent need exists for state-of-the-art analytical methods that predict the response of components fabricated from CMC and intermetallic material systems. This need provided the motivation for the technology developed under this research effort. Continuous ceramic fiber composites exhibit an increase in work of fracture, which allows for 'graceful' rather than catastrophic failure. When loaded in the fiber direction these composites retain substantial strength capacity beyond the initiation of transverse matrix cracking despite the fact that neither of its constituents would exhibit such behavior if tested alone. As additional load is applied beyond first matrix cracking, the matrix tends to break in a series of cracks bridged by the ceramic fibers. Any additional load is born increasingly by the fibers until the ultimate strength of the composite is reached. Thus modeling efforts supported under this research effort have focused on predicting this sort of behavior. For single crystal intermetallics the issues that motivated the technology development involved questions relating to material behavior and component design. Thus the research effort supported by this grant had to determine the statistical nature and source of fracture in a high strength, NiAl single crystal turbine blade material; map a simplistic future strength envelope of the material; develop a statistically based reliability computer algorithm; verify the reliability model and computer algorithm-, and model stator vanes for rig tests. Thus establishing design protocols that enable the engineer to analyze and predict the mechanical behavior of ceramic composites and intermetallics would mitigate the prototype (trial and error) approach currently used by the engineering community. The primary objective of the research effort supported by this short term grant is the continued creation of enabling technologies for the macro-analysis of components fabricated from ceramic composites and intermetallic material systems. The creation of enabling technologies aids in shortening the product development cycle of components fabricated from the new high technology materials.

Three-unit bridge construction in anterior single-pontic areas using a metal-free restorative.

PubMed

Narcisi, E M

1999-02-01

A new glass-ceramic material, IPS Empress 2, is revolutionizing esthetic restorative dentistry by allowing metal-free, three-unit bridge construction in anterior and premolar single-pontic areas. The case discussed in this article illustrates the material's application in the dual-arch restoration of a young woman with congenitally missing teeth. The material was used as an alternative to single-tooth implant restorations to place two maxillary three-unit bridges, one mandibular three-unit bridge, and two mandibular porcelain veneers. IPS Empress 2 provides an esthetic alternative to porcelain-fused-to-metal restorations by facilitating attractive, functional tooth restoration.

GOOD HEALTH AND THE BRIDGING OF STRUCTURAL HOLES

PubMed Central

Cornwell, Benjamin

2009-01-01

Bridges that span structural holes are often explained in terms of the entrepreneurial personalities or rational motivations of brokers, or structural processes that lead to the intersection of social foci. I argue that the existence and use of bridges in interpersonal networks also depends on individuals’ health. Poor health may make it more difficult to withstand the pressures and to execute some of the common tasks associated with bridging (e.g., brokerage). I examine this possibility using egocentric network data on over 2,500 older adults drawn from the recent National Social Life, Health, and Aging Project (NSHAP). Multivariate regression analyses show that both cognitive and functional health are significantly positively associated with bridging, net of sociodemographic and life-course controls. The relationship between functional (kinesthetic) health and bridging appears to be partially mediated by network composition, as older adults who have poorer functional health also tend to have networks that are richer in strong ties. Several potential mediation mechanisms are discussed. Cognitive function remains significantly associated with bridging net of network composition, suggesting that the inherent challenges of maintaining bridging positions may be more difficult to cope with for those who have cognitive impairments than for those who have functional impairments such as limited mobility. An alternative explanation is that cognitively impaired individuals have more difficulty recognizing (and thus strategically using) bridges in their networks. Theoretical implications and possibilities for future research are discussed. PMID:20046998

Implementation project : strengthening a continuous steel girder bridge in Lakeport, Texas with post-installed shear connectors : Phase 1 : bridge strengthening design and load testing.

DOT National Transportation Integrated Search

2017-03-01

In Implementation Project 5-6719, a non-composite continuous steel girder bridge located in Lakeport, Texas will be strengthened using techniques developed in TxDOT Research Project 0-6719. This strengthening technique involves the use of post-instal...

Bio-derived three-dimensional hierarchical carbon-graphene-TiO2 as electrode for supercapacitors.

PubMed

Jiang, Lili; Ren, Zhifeng; Chen, Shuo; Zhang, Qinyong; Lu, Xiong; Zhang, Hongping; Wan, Guojiang

2018-03-13

This paper reports a novel loofah-derived hierarchical scaffold to obtain three-dimensional biocarbon-graphene-TiO 2 (BC-G-TiO 2 ) composite materials as electrodes for supercapacitors. The loofah scaffold was first loaded with G and TiO 2 by immersing, squeezing, and loosening into the mixed solution of graphene oxide and titania, and then carbonized at 900 °C to form the BC-G-TiO 2 composite. The synergistic effects of the naturally hierarchical biocarbon structure, graphene, and TiO 2 nanoparticles on the electrochemical properties are analyzed. The biocarbon provides a high interconnection and an easy accessibility surface for the electrolyte. Graphene bridged the BC and TiO 2 nanoparticles, improved the conductivity of the BC-G-TiO 2 composite, and increased the electron transfer efficiency. TiO 2 nanoparticles also contributed to the pesudocapacitance and electrochemical stability.

Apollo 16 - Impact melt sheets, contrasting nature of the Cayley plains and Descartes mountains, and geologic history

NASA Technical Reports Server (NTRS)

Mckinley, J. P.; Taylor, G. J.; Keil, K.; Ma, M.-S.; Schmitt, R. A.

1984-01-01

Apollo 16 stations four and five rake samples have been examined petrographically and by electron microprobe and INAA. Lithologic abundances support the idea (Korontev, 1981) that the variation of soil composition at Apollo 16 results from mixing between a component represented by station five and components much like either the dimict breccias or feldspathic fragmental breccias in composition. Pyroxene, olivine, and coexisting plagioclase compositions from within the anorthosite portions of dimict breccias bridge the gap between the Mg-rich and ferroan anorthosite fields. Analyses from associated cumulate and granulitic clasts indicate that they are the source of the intermediate material. Dimict breccias formed about 3.92 b.y. ago, the nectaris event occurred 3.84-3.92 b.y. ago, and the Cayley plains were deposited as a result of the Imbrium event sometime later than 3.84 b.y.

Three-dimensional Finite Element Modelling of Composite Slabs for High Speed Rails

NASA Astrophysics Data System (ADS)

Mlilo, Nhlanganiso; Kaewunruen, Sakdirat

2017-12-01

Currently precast steel-concrete composite slabs are being considered on railway bridges as a viable alternative replacement for timber sleepers. However, due to their nature and the loading conditions, their behaviour is often complex. Present knowledge of the behaviour of precast steel-concrete composite slabs subjected to rail loading is limited. FEA is an important tool used to simulate real life behaviour and is widely accepted in many disciples of engineering as an alternative to experimental test methods, which are often costly and time consuming. This paper seeks to detail FEM of precast steel-concrete slabs subjected to standard in-service loading in high-speed rail with focus on the importance of accurately defining material properties, element type, mesh size, contacts, interactions and boundary conditions that will give results representative of real life behaviour. Initial finite element model show very good results, confirming the accuracy of the modelling procedure

Performance of Nanotube-Based Ceramic Composites: Modeling and Experiment

NASA Technical Reports Server (NTRS)

Curtin, W. A.; Sheldon, B. W.; Xu, J.

2004-01-01

The excellent mechanical properties of carbon-nanotubes are driving research into the creation of new strong, tough nanocomposite systems. In this program, our initial work presented the first evidence of toughening mechanisms operating in carbon-nanotube- reinforced ceramic composites using a highly-ordered array of parallel multiwall carbon-nanotubes (CNTs) in an alumina matrix. Nanoindentation introduced controlled cracks and the damage was examined by SEM. These nanocomposites exhibit the three hallmarks of toughening in micron-scale fiber composites: crack deflection at the CNT/matrix interface; crack bridging by CNTs; and CNT pullout on the fracture surfaces. Furthermore, for certain geometries a new mechanism of nanotube collapse in shear bands was found, suggesting that these materials can have multiaxial damage tolerance. The quantitative indentation data and computational models were used to determine the multiwall CNT axial Young's modulus as 200-570 GPa, depending on the nanotube geometry and quality.

Fatigue crack growth in unidirectional metal matrix composite

NASA Technical Reports Server (NTRS)

Ghosn, Louis J.; Telesman, Jack; Kantzos, Peter

1990-01-01

The weight function method was used to determine the effective stress intensity factor and the crack opening profile for a fatigue tested composite which exhibited fiber bridging. The bridging mechanism was modeled using two approaches; the crack closure approach and the shear lag approach. The numerically determined stress intensity factor values from both methods were compared and correlated with the experimentally obtained crack growth rates for SiC/Ti-15-3 (0)(sub 8) oriented composites. The near crack tip opening profile was also determined for both methods and compared with the experimentally obtained measurements.

49 CFR 1242.15 - Roadway, tunnels and subways, bridges and culverts, ties, rails, other track material, ballast...

Code of Federal Regulations, 2010 CFR

2010-10-01

... 49 Transportation 9 2010-10-01 2010-10-01 false Roadway, tunnels and subways, bridges and culverts, ties, rails, other track material, ballast, track laying and surfacing, and road property damaged... RAILROADS 1 Operating Expenses-Way and Structures § 1242.15 Roadway, tunnels and subways, bridges and...

Hierarchical analysis of bridge decision makers : the role of new technology adoption in the timber bridge market : special project fiscal year 1992

DOT National Transportation Integrated Search

1995-08-01

Bridge design engineers and local highway officials make bridge replacement decisions across the : United States. The Analytical Hierarchy Process was used to characterize the bridge material selection : decision of these individuals. State Departmen...

Growth Kinetics of Magnesio-Aluminate Spinel in Al/Mg Lamellar Composite Interface

NASA Astrophysics Data System (ADS)

Fouad, Yasser; Rabeeh, Bakr Mohamed

The synthesis of Mg-Al2O3 double layered interface is introduced via the application of hot isostatic pressing, HIPing, in Al-Mg foils. Polycrystalline spinel layers are grown experimentally at the interfacial contacts between Al-Mg foils. The growth behavior of the spinel layers along with the kinetic parameters characterizing interface motion and long-range diffusion is established. Low melting depressant (LMD), Zn, and alloying element segregation tends to form micro laminated and/or Nano structure interphase in a lamellar composite solid state processing. Nano composite ceramic interphase materials offer interesting mechanical properties not achievable in other materials, such as superplastic flow and metal-like machinability. Microstructural characterization, mechanical characterization is also established via optical microscopy scanning electron microscopy, energy dispersive X-ray spectroscopy and tensile testing. Chemical and mechanical bonding via inter diffusion processing with alloy segregation are dominant for interphase kinetics. Mechanical characterization with interfacial shear strength is also introduced. HIPing processing is successfully applied on 6082 Al-alloy and AZ31 magnesium alloy for either particulate or micro-laminated interfacial composite processing. The interphase kinetic established through localized micro plasticity, metal flow, alloy segregation and delocalized Al oxide and Mg oxide. The kinetic of interface/interphase induce new nontraditional crack mitigation a long with new bridging and toughening mechanisms.

Development of a high capacity bubble domain memory element and related epitaxial garnet materials for application in spacecraft data recorders. Item 2: The optimization of material-device parameters for application in bubble domain memory elements for spacecraft data recorders

NASA Technical Reports Server (NTRS)

Besser, P. J.

1976-01-01

Bubble domain materials and devices are discussed. One of the materials development goals was a materials system suitable for operation of 16 micrometer period bubble domain devices at 150 kHz over the temperature range -10 C to +60 C. Several material compositions and hard bubble suppression techniques were characterized and the most promising candidates were evaluated in device structures. The technique of pulsed laser stroboscopic microscopy was used to characterize bubble dynamic properties and device performance at 150 kHz. Techniques for large area LPE film growth were developed as a separate task. Device studies included detector optimization, passive replicator design and test and on-chip bridge evaluation. As a technology demonstration an 8 chip memory cell was designed, tested and delivered. The memory elements used in the cell were 10 kilobit serial registers.

Graphene/fly ash geopolymeric composites as self-sensing structural materials

NASA Astrophysics Data System (ADS)

Saafi, Mohamed; Tang, Leung; Fung, Jason; Rahman, Mahbubur; Sillars, Fiona; Liggat, John; Zhou, Xiangming

2014-06-01

The reduction of graphene oxide during the processing of fly ash-based geopolymers offers a completely new way of developing low-cost multifunctional materials with significantly improved mechanical and electrical properties for civil engineering applications such as bridges, buildings and roads. In this paper, we present for the first time the self-sensing capabilities of fly ash-based geopolymeric composites containing in situ reduced graphene oxide (rGO). Geopolymeric composites with rGO concentrations of 0.0, 0.1 and 0.35% by weight were prepared and their morphology and conductivity were determined. The piezoresistive effect of the rGO-geopolymeric composites was also determined under tension and compression. The Fourier transform infrared spectroscopy (FTIR) results indicate that the rGO sheets can easily be reduced during synthesis of geopolymers due to the effect of the alkaline solution on the functional groups of GO. The scanning electron microscope (SEM) images showed that the majority of pores and voids within the geopolymers were significantly reduced due to the addition of rGO. The rGO increased the electrical conductivity of the fly ash-based rGO-geopolymeric composites from 0.77 S m-1 at 0.0 wt% to 2.38 S m-1 at 0.35 wt%. The rGO also increased the gauge factor by as much as 112% and 103% for samples subjected to tension and compression, respectively.

A Hierarchical Analysis of Bridge Decision Makers; the Role of New Technology Adoption in the Timber Bridge Market: Special Project Fiscal Year 1992

DOT National Transportation Integrated Search

1995-08-01

Bridge design engineers and local highway officials make bridge replacement decsions across the U.S. The Analytical Hierarchical Process was used to characterize the bridge material selection decisions of these individuals. State Departments of Trans...

Evaluation of Effects of Fire on the I-465 Mainline Bridges : Volume II

DOT National Transportation Integrated Search

2012-06-01

Currently, when a bridge has been involved in a fire loading, DOT and inspectors are called to determine if the bridge is passable to : traffic. Inspectors must close the bridge for an indefinite period of time to take material samples from the bridg...

Ship-bridge collision monitoring system based on flexible quantum tunneling composite with cushioning capability

NASA Astrophysics Data System (ADS)

Zheng, Qiaofeng; Han, Baoguo; Ou, Jinping

2018-07-01

In this paper, a ship-bridge collision monitoring system based on flexible quantum tunneling composite (QTC) with cushioning capability is proposed by investigating the sensing capability and positioning capability of QTC to collisions. QTCs with different rubber matrix and thickness were fabricated, and collision tests between steel ball and QTCs sensors were designed to simulate ship-bridge collision. The results show that QTCs have a sensing range over 50 MPa with stress resolution ranging between 0.017 and 0.13 MPa, enough to achieve the full-time monitoring of ship-bridge collision. The system has instant and repeatable respond to impact load, and can accurately position the collisions. Moreover, QTC can remarkably absorb the kinetic energy during collisions, exhibiting excellent cushioning capability. These findings indicate the proposed ship-bridge collision monitoring system has great potential for application to detecting collision information such as collision occurrence and duration, impact load and collision location, as well as providing basis for citizen evacuation, post-accident damage estimation and rescue strategy.

Tooth brush abrasion of paint-on resins for shade modification of crown and bridge resins.

PubMed

Fujii, Koichi; Ban, Seiji; McCabe, John F

2003-09-01

The purpose of this study was to evaluate the surface roughness and resistance to toothbrush abrasion of three experimental paint-on composite resins developed for the shade modification of crown and bridge resins. The paint-on resins had less filler volume fraction than restorative composites or the crown and bridge resins and consequently were of low viscosity. The maximum surface roughness (Rmax) and the maximum depth loss by abrasion for the paint-on resins following 40,000 cycles of brushing ranged from 2.45 to 4.07 microm and 8.63 to 13.67 microm, respectively. Rmax values were 37.7-67.5% lower than that for the crown and bridge resin subjected to the same test. Wear depth was 19.9-49.4% lower than for the crown and bridge resin. These results suggest that the paint-on resins are expected to have adequate resistance to toothbrush abrasion and may therefore be suitable for clinical use.

Numerical Simulation of Thermal Performance of Glass-Fibre-Reinforced Polymer

NASA Astrophysics Data System (ADS)

Zhao, Yuchao; Jiang, Xu; Zhang, Qilin; Wang, Qi

2017-10-01

Glass-Fibre-Reinforced Polymer (GFRP), as a developing construction material, has a rapidly increasing application in civil engineering especially bridge engineering area these years, mainly used as decorating materials and reinforcing bars for now. Compared with traditional construction material, these kinds of composite material have obvious advantages such as high strength, low density, resistance to corrosion and ease of processing. There are different processing methods to form members, such as pultrusion and resin transfer moulding (RTM) methods, which process into desired shape directly through raw material; meanwhile, GFRP, as a polymer composite, possesses several particular physical and mechanical properties, and the thermal property is one of them. The matrix material, polymer, performs special after heated and endue these composite material a potential hot processing property, but also a poor fire resistance. This paper focuses on thermal performance of GFRP as panels and corresponding researches are conducted. First, dynamic thermomechanical analysis (DMA) experiment is conducted to obtain the glass transition temperature (Tg) of the object GFRP, and the curve of bending elastic modulus with temperature is calculated according to the experimental data. Then compute and estimate the values of other various thermal parameters through DMA experiment and other literatures, and conduct numerical simulation under two condition respectively: (1) the heat transfer process of GFRP panel in which the panel would be heated directly on the surface above Tg, and the hot processing under this temperature field; (2) physical and mechanical performance of GFRP panel under fire condition. Condition (1) is mainly used to guide the development of high temperature processing equipment, and condition (2) indicates that GFRP’s performance under fire is unsatisfactory, measures must be taken when being adopted. Since composite materials’ properties differ from each other and their high temperature parameters can’t be obtained through common methods, some parameters are estimated, the simulation is to guide the actual high temperature experiment, and the parameters will also be adjusted by then.

Monitoring bridge scour using fiber optic sensors.

DOT National Transportation Integrated Search

2015-04-01

The scouring process excavates and carries away materials from the bed and banks of streams, and from : around the piers and abutments of bridges. Scour undermines bridges and may cause bridge failures due to : structural instability. In the last 30 ...

A loading study of older highway bridges in Virginia. Pt. 2, Concrete slab and steel beam bridge in Clarke County.

DOT National Transportation Integrated Search

1976-01-01

A 60-foot non-composite steel beam and concrete deck highway bridge span over the Shenandoah River on Route 7 in Clarke County was tested with a 23-ton, tandem axle test vehicle in July1975. Strain gages were placed near midspan on the lower flanges,...

Strength and stiffness of reinforced yellow-poplar glued-laminated beams

Treesearch

R. Hernandez; R. C. Moody

In bridge applications, it is often necessary to minimize the depth of the bridge structure to provide for the required hydraulic opening or reduce the volume of approach fill. For bridges that utilize structural glued-laminated (glulam) timber beams as stringers, reinforcement using thin strips of pultruded E-glass-fiber-reinforced plastic (GFRP) composites may permit...

Composite action in a steel girder span with precast deck panels : the I-81 bridge over the New River in Radford, Virginia.

DOT National Transportation Integrated Search

2003-01-01

Two parallel bridges carry I-81 north and south over the New River in southwest Virginia, near the city of Radford. The bridges are identical in design and have been in place since 1985. In recent years, a number of maintenance issues have been repor...

Supercapacitors based on 3D network of activated carbon nanowhiskers wrapped-on graphitized electrospun nanofibers

NASA Astrophysics Data System (ADS)

He, Shuijian; Chen, Linlin; Xie, Chencheng; Hu, Huan; Chen, Shuiliang; Hanif, Muddasir; Hou, Haoqing

2013-12-01

Due to their cycling stability and high power density, the supercapacitors bridge the power/energy gap between traditional dielectric capacitors and batteries/fuel cells. Electrode materials are key components for making high performance supercapacitors. An activated carbon nanowhiskers (ACNWs) wrapped-on graphitized electrospun nanofiber (GENF) network (ACNWs/GENFN) with 3D porous structure is prepared as a new type of binder-free electrode material for supercapacitors. The supercapacitor based on the ACNWs/GENFN composite material displays an excellent performance with a specific capacitance of 176.5 F g-1 at current density of 0.5 A g-1, an ultrahigh power density of 252.8 kW kg-1 at current density of 800 A g-1 and an outstanding cycling stability of no capacitance loss after 10,000 charge/discharge cycles.

Improved BN Coatings on SiC Fibers in SiC Matrices

NASA Technical Reports Server (NTRS)

Morscher, Gregory N.; Bhatt, Ramakrishna; Yun, Hee-Mann; DiCarlo, James A.

2004-01-01

Modifications of BN-based coatings that are used as interfacial layers between the fibers and matrices of SiCfiber/SiC-matrix composite materials have been investigated to improve the thermomechanical properties of these materials. Such interfacial coating layers, which are also known as interphases (not to be confused with interphase in the biological sense), contribute to strength and fracture toughness of a fiber/matrix composite material by providing for limited amounts of fiber/matrix debonding and sliding to absorb some of the energy that would otherwise contribute to the propagation of cracks. Heretofore, the debonding and sliding have been of a type called inside debonding because they have taken place predominantly on the inside surfaces of the BN layers that is, at the interfaces between the SiC fibers and the interphases. The modifications cause the debonding and sliding to include more of a type, called outside debonding, that takes place at the outside surfaces of the BN layers that is, at the interfaces between the interphases and the matrix (see figure). One of the expected advantages of outside debonding is that unlike in inside debonding, the interphases would remain on the crack-bridging fibers. The interphases thus remaining should afford additional protection against oxidation at high temperature and should delay undesired fiber/fiber fusion and embrittlement of the composite material. A secondary benefit of outside debonding is that the interphase/matrix interfaces could be made more compliant than are the fiber/interphase interfaces, which necessarily incorporate the roughness of the SiC fibers. By properly engineering BN interphase layers to favor outside debonding, it should be possible, not only to delay embrittlement at intermediate temperatures, but also to reduce the effective interfacial shear strength and increase the failure strain and toughness of the composite material. Two techniques have been proposed and partially experimentally verified as candidate means to promote outside debonding in state-of-the-art SiC/SiC composites.

Composition of corn dry-grind ethanol by-products: DDGS, wet cake, and thin stillage.

PubMed

Kim, Youngmi; Mosier, Nathan S; Hendrickson, Rick; Ezeji, Thaddeus; Blaschek, Hans; Dien, Bruce; Cotta, Michael; Dale, Bruce; Ladisch, Michael R

2008-08-01

DDGS and wet distillers' grains are the major co-products of the dry grind ethanol facilities. As they are mainly used as animal feed, a typical compositional analysis of the DDGS and wet distillers' grains mainly focuses on defining the feedstock's nutritional characteristics. With an increasing demand for fuel ethanol, the DDGS and wet distillers' grains are viewed as a potential bridge feedstock for ethanol production from other cellulosic biomass. The introduction of DDGS or wet distillers' grains as an additional feed to the existing dry grind plants for increased ethanol yield requires a different approach to the compositional analysis of the material. Rather than focusing on its nutritional value, this new approach aims at determining more detailed chemical composition, especially on polymeric sugars such as cellulose, starch and xylan, which release fermentable sugars upon enzymatic hydrolysis. In this paper we present a detailed and complete compositional analysis procedure suggested for DDGS and wet distillers' grains, as well as the resulting compositions completed by three different research groups. Polymeric sugars, crude protein, crude oil and ash contents of DDGS and wet distillers' grains were accurately and reproducibly determined by the compositional analysis procedure described in this paper.

Material Characterization for the Analysis of Skin/Stiffener Separation

NASA Technical Reports Server (NTRS)

Davila, Carlos G.; Leone, Frank A.; Song, Kyongchan; Ratcliffe, James G.; Rose, Cheryl A.

2017-01-01

Test results show that separation failure in co-cured skin/stiffener interfaces is characterized by dense networks of interacting cracks and crack path migrations that are not present in standard characterization tests for delamination. These crack networks result in measurable large-scale and sub-ply-scale R curve toughening mechanisms, such as fiber bridging, crack migration, and crack delving. Consequently, a number of unknown issues exist regarding the level of analysis detail that is required for sufficient predictive fidelity. The objective of the present paper is to examine some of the difficulties associated with modeling separation failure in stiffened composite structures. A procedure to characterize the interfacial material properties is proposed and the use of simplified models based on empirical interface properties is evaluated.

Novel High Efficient Organic Photovoltaic Materials

NASA Technical Reports Server (NTRS)

Sun, Sam; Haliburton, James; Fan, Zben; Taft, Charles; Wang, Yi-Qing; Maaref, Shahin; Mackey, Willie R. (Technical Monitor)

2001-01-01

In man's mission to the outer space or a remote site, the most abundant, renewable, nonpolluting, and unlimited external energy source is light. Photovoltaic (PV) materials can convert light into electrical power. In order to generate appreciable electrical power in space or on the Earth, it is necessary to collect sunlight from large areas due to the low density of sunlight, and this would be very costly using current commercially available inorganic solar cells. Future organic or polymer based solar cells seemed very attractive due to several reasons. These include lightweight, flexible shape, ultra-fast optoelectronic response time (this also makes organic PV materials attractive for developing ultra-fast photo detectors), tunability of energy band-gaps via molecular design, versatile materials synthesis and device fabrication schemes, and much lower cost on large-scale industrial production. It has been predicted that nano-phase separated block copolymer systems containing electron rich donor blocks and electron deficient acceptor blocks will facilitate the charge separation and migration due to improved electronic ultrastructure and morphology in comparison to current polymer composite photovoltaic system. This presentation will describe our recent progress in the design, synthesis and characterization of a novel donor-bridge-acceptor block copolymer system for potential high-efficient organic optoelectronic applications. Specifically, the donor block contains an electron donating alkyloxy derivatized polyphenylenevinylene, the acceptor block contains an electron withdrawing alkyl-sulfone derivatized polyphenylenevinylene, and the bridge block contains an electronically neutral non-conjugated aliphatic hydrocarbon chain. The key synthetic strategy includes the synthesis of each individual block first, then couple the blocks together. While the donor block stabilizes the holes, the acceptor block stabilizes the electrons. The bridge block is designed to hinder the electron-hole recombination. Thus, improved charge separation is expected. In addition, charge migration will also be facilitated due to the expected nano-phase separated and highly ordered block copolymer ultrastructural. The combination of all these factors will result in significant overall enhancement of photovoltaic power conversion efficiency.

The Selection of Bridge Materials Utilizing the Analytical Hierarchy Process

Treesearch

Robert L. Smith; Robert J. Bush; Daniel L. Schmoldt

1997-01-01

Effective decisions on the use of natural resources often require the input of many individuals. Determining how specific criteria affect the selection of materials can lead to better utilization of raw materials. Concrete, steel, and timber represent over 98% of the materials used for bridge construction in the United States. Highway officials must often consider...

Surface development of a brazing alloy during heat treatment-a comparison between UHV and APXPS

NASA Astrophysics Data System (ADS)

Rullik, L.; Johansson, N.; Bertram, F.; Evertsson, J.; Stenqvist, T.; Lundgren, E.

2018-01-01

In an attempt to bridge the pressure gap, APXPS was used to follow the surface development of an aluminum brazing sheet during heating in an ambient oxygen-pressure mimicking the environment of an industrial brazing furnace. The studied aluminum alloy brazing sheet is a composite material consisting of two aluminum alloy standards whose surface is covered with a native aluminum oxide film. To emphasize the necessity of studies of this system in ambient sample environments it is compared to measurements in UHV. Changes in thickness and composition of the surface oxide were followed after heating to 300 °C, 400 °C, and 500 °C. The two sets presented in this paper show that the surface development strongly depends on the environment the sample is heated in.

Reinforcing effect of graphene on the mechanical properties of Al2O3/TiC ceramics

NASA Astrophysics Data System (ADS)

Li, Zuo-li; Zhao, Jun; Sun, Jia-lin; Gong, Feng; Ni, Xiu-ying

2017-12-01

Multilayer graphene (MLG)-reinforced Al2O3/TiC ceramics were fabricated through hot pressing sintering, and the reinforcing effect of MLG on the microstructure and mechanical properties of the composites was investigated by experiment and simulation. The simulation of dynamic crack initiation and propagation was investigated based on the cohesive zone method. The results show that the composite added with 0.2wt% MLG has excellent flexural strength and high fracture toughness. The major reinforcing mechanisms are the synergistic effect by strong and weak bonding interfaces, MLG pull-out, and grain refinement resulting from the addition of MLG. In addition, the aggravating of crack deflection, branching, blunting, and bridging have indispensable contribution to the improvement of the as-designed materials.

Thermally stable molecules with large dipole moments and polarizabilities and applications thereof

NASA Technical Reports Server (NTRS)

Marder, Seth R. (Inventor); Peyghambarian, Nasser (Inventor); Kippelen, Bernard (Inventor); Volodin, Boris (Inventor); Hendrickx, Eric (Inventor)

2002-01-01

Disclosed are fused ring bridge, ring-locked dyes that form thermally stable photorefractive compositions. The fused ring bridge structures are .pi.-conjugated bonds in benzene-, naphthalene- or anthracene-derived fused ring systems that connect donor and acceptor groups. The donor and acceptor groups contribute to a high molecular dipole moment and linear polarizability anisotropy. The polarization characteristics of the dye molecules are stabilized since the bonds in the fused ring bridge are not susceptible to rotation, reducing the opportunity for photoisomerization. The dyes are compatible with polymeric compositions, including thermoplastics. The dyes are electrically neutral but have charge transport, electronic and orientational properties such that upon illumination of a composition containing the dye, the dye facilitates refractive index modulation and a photorefractive effect that can be utilized advantageously in numerous applications such as in optical quality devices and biological imaging.

Monitoring steel bridge renovation using lead isotopic tracing.

PubMed

Salome, Fred; Gulson, Brian; Chiaradia, Massimo; Davis, Jeffrey; Morris, Howard

2017-05-01

Monitoring removal of lead (Pb) paint from steel structures usually involves analysis of environmental samples for total lead and determination of blood Pb levels of employees involved in the Pb paint removal. We used high precision Pb isotopic tracing for a bridge undergoing Pb paint removal to determine if Pb in the environmental and blood samples originated from the bridge paint. The paint system on the bridge consisted of an anti-corrosive red Pb primer top-coated with a Micaceous Iron Oxide (MIO) alkyd. Analysis of the red Pb primer gave uniform isotopic ratios indicative of Pb from the geologically-ancient Broken Hill mines in western New South Wales, Australia. Likewise waste abrasive material, as anticipated, had the same isotopic composition as the paint. The isotopic ratios for other samples lay on 2 separate linear arrays on a 207 Pb/ 204 Pb versus 206 Pb/ 204 Pb diagram, one largely defined by gasoline and the majority of the ambient air data, and the other by data for one sample each of gasoline and ambient air and underwater sediments. Isotopic ratios in background ambient air samples for the project were characteristic of leaded gasoline. Air sampling during paint removal showed a contribution of paint Pb ranging from about 20 to 40%. Isotopic ratios in the blood of 8 employees prior to the commencement of work showed that 6 of these had been previously exposed to the Broken Hill Pb possibly from earlier bridge paint removal projects. One subject appeared to have increased exposure to Pb probably from the paint renovations. Copyright © 2017 Elsevier Ltd. All rights reserved.

Computational investigation of CO adsorbed on Aux, Agx and (AuAg)x nanoclusters (x = 1 - 5, 147) and monometallic Au and Ag low-energy surfaces*

NASA Astrophysics Data System (ADS)

Gould, Anna L.; Catlow, C. Richard A.; Logsdail, Andrew J.

2018-02-01

Density functional theory calculations have been performed to investigate the use of CO as a probe molecule for the determination of the structure and composition of Au, Ag and AuAg nanoparticles. For very small nanoclusters (x = 1 - 5), the CO vibrational frequencies can be directly correlated to CO adsorption strength, whereas larger 147-atom nanoparticles show a strong energetic preference for CO adsorption at a vertex position but the highest wavenumbers are for the bridge positions. We also studied CO adsorption on Au and Ag (100) and (111) surfaces, for a 1 monolayer coverage, which proves to be energetically favourable on atop only and bridge positions for Au (100) and atop for Ag (100); vibrational frequencies of the CO molecules red-shift to lower wavenumbers as a result of increased metal coordination. We conclude that CO vibrational frequencies cannot be solely relied upon in order to obtain accurate compositional analysis, but we do propose that elemental rearrangement in the core@shell nanoclusters, from Ag@Au (or Au@Ag) to an alloy, would result in a shift in the CO vibrational frequencies that indicate changes in the surface composition. Contribution to the Topical Issue "Shaping Nanocatalysts", edited by Francesca Baletto, Roy L. Johnston, Jochen Blumberger and Alex Shluger.Supplementary material in the form of one pdf file available from the Journal web page at http://https://doi.org/10.1140/epjb/e2017-80280-7

Phase change materials handbook

NASA Technical Reports Server (NTRS)

Hale, D. V.; Hoover, M. J.; Oneill, M. J.

1971-01-01

This handbook is intended to provide theory and data needed by the thermal design engineer to bridge the gap between research achievements and actual flight systems, within the limits of the current state of the art of phase change materials (PCM) technology. The relationship between PCM and more conventional thermal control techniques is described and numerous space and terrestrial applications of PCM are discussed. Material properties of the most promising PCMs are provided; the purposes and use of metallic filler materials in PCM composites are presented; and material compatibility considerations relevant to PCM design are included. The engineering considerations of PCM design are described, especially those pertaining to the thermodynamic and heat transfer phenomena peculiar to PCM design. Methods of obtaining data not currently available are presented. The special problems encountered in the space environment are described. Computational tools useful to the designer are discussed. In summary, each aspect of the PCM problem important to the design engineer is covered to the extent allowed by the scope of this effort and the state of the art.

FY82 Posture Report.

DTIC Science & Technology

1982-01-01

illustrate MERADCOM’s missio and continued growth as an independent subordinate Command. MERADCOM- DIVERSIFCATION IN SCIECE AND ENGINEERING COUNETEREIEE...Magnetic Signature Duplicator!1 Pre- staged Ammo Loading System Portable Mine Neutralization SystemN;- . Heavy Assault Bridge Composite Bridge Components

Assessment of dynamic properties and stiffness of composite bridges with pavement defects

NASA Astrophysics Data System (ADS)

Kartopol'tsev, Vladimir; Kartopol'tsev, Andrei; Kolmakov, Boris

2017-01-01

This paper is aimed at assessing the dynamic properties and stiffness of the reinforced concrete roadway slab under live loads that impact composite bridge girders considering pavement defects. A special attention is paid to the reinforced concrete roadway slab as a transfer member of forced oscillations. The test results obtained for bridges with different spans ranging from 24 to 110 m are presented to assess the behavior of the reinforced concrete roadway slab and the dynamic stiffness of bridge span allowed for the pavement defects. Dynamic tests are carried out under controlled and random loads that simulate live load interaction with the span and the pavement with defects. The differential equations are presented for vertical oscillations of spans, pavement defect parameter, Eigen frequency and others. As a result of the experimental research the equation is derived to ascertain the dynamic stiffness of the vehicle-span system.

Characterization of stormwater runoff from bridge decks in eastern Massachusetts, 2014–16

USGS Publications Warehouse

Smith, Kirk P.; Sorenson, Jason R.; Granato, Gregory E.

2018-05-02

The quality of stormwater runoff from bridge decks (hereafter referred to as “bridge-deck runoff”) was characterized in a field study from August 2014 through August 2016 in which concentrations of suspended sediment (SS) and total nutrients were monitored. These new data were collected to supplement existing highway-runoff data collected in Massachusetts which were deficient in bridge-deck runoff concentration data. Monitoring stations were installed at three bridges maintained by the Massachusetts Department of Transportation in eastern Massachusetts (State Route 2A in the city of Boston, Interstate 90 in the town of Weston, and State Route 20 near Quinsigamond Village in the city of Worcester). The bridges had annual average daily traffic volumes from 21,200 to 124,000 vehicles per day; the land use surrounding the monitoring stations was 25 to 67 percent impervious.Automatic-monitoring techniques were used to collect more than 160 flow-proportional composite samples of bridge-deck runoff. Samples were analyzed for concentrations of SS, loss on ignition of suspended solids (LOI), particulate carbon (PC), total phosphorus (TP), total dissolved nitrogen (DN), and particulate nitrogen (PN). The distribution of particle size of SS also was determined for composite samples. Samples of bridge-deck runoff were collected year round during rain, mixed precipitation, and snowmelt runoff and with different dry antecedent periods throughout the 2-year sampling period.At the three bridge-deck-monitoring stations, median concentrations of SS in composite samples of bridge-deck runoff ranged from 1,490 to 2,020 milligrams per liter (mg/L); however, the range of SS in individual composites was vast at 44 to 142,000 mg/L. Median concentrations of SS were similar in composite samples collected from the State Route 2A and Interstate 90 bridge (2,010 and 2,020 mg/L, respectively), and lowest at the State Route 20 bridge (1,490 mg/L). Concentrations of coarse sediment (greater than 0.25 millimeters in diameter) dominated the SS matrix by more than an order of magnitude. Concentrations of LOI and PC in composite samples ranged from 15 to 1,740 mg/L and 6.68 to 1,360 mg/L, respectively, and generally represented less than 10 and 3 percent of the median mass of SS, respectively. Concentrations of TP in composite samples ranged from 0.09 to 7.02 mg/L; median concentrations of TP ranged from 0.505 to 0.69 mg/L and were highest on the bridge on State Route 2A in Boston. Concentrations of total nitrogen (TN) (sum DN and PN) in composite samples were variable (0.36 to 29 mg/L). Median DN (0.64 to 0.90 mg/L) concentrations generally represented about 40 percent of the TN concentration at each bridge and were similar to annual volume-weighted mean concentrations of nitrogen in precipitation in Massachusetts.Nonparametric statistical methods were used to test for differences between sample constituent concentrations among the three bridges. These results indicated that there are no statistically significant differences for concentrations of SS, LOI, PC, and TP among the three bridges (one-way analysis of variance test on rank-transformed data, 95-percent confidence level). Test results for concentrations of TN in composite samples indicated that concentrations of TN collected on State Route 20 near Quinsigamond Village were significantly higher than those concentrations collected on State Route 2A in Boston and Interstate 90 near Weston. Median concentrations of TN were about 93 and 55 percent lower at State Route 2A and at Interstate 90, respectively, compared to the median concentrations of TN at State Route 20.Samples of sediment were collected from five fixed locations on each bridge on three occasions during dry weather to calculate semiquantitative distributions of sediment yields on the bridge surface relative to the monitoring location. Mean yields of bridge-deck sediment during this study for State Route 2A in Boston, Interstate 90 near Weston, and State Route 20 near Quinsigamond Village were 1,500, 250, and 5,700 pounds per curb-mile, respectively. Sediment yields at each sampling location varied widely (26 to 25,000 pounds per curb-mile) but were similar to yields reported elsewhere in Massachusetts and the United States. Yields calculated for each sampling location indicated that the sediment was not evenly distributed across each bridge in this study for plausible reasons such as bridge slope, vehicular tracking, and bridge deterioration.Bridge-deck sediment quality was largely affected by the distribution of sediment particle size. Concentrations of TP in the fine sediment-size fraction (less than 0.0625 millimeter in diameter) of samples of bridge-deck sediment were about 6 times greater than in the coarse size fraction. Concentrations for many total-recoverable metals were 2 to 17 times greater in the fine size fraction compared to concentrations in the coarse size fraction (greater than or equal to 0.25 millimeter in diameter), and concentrations of total-recoverable copper and lead in the fine size fraction were 2 to 65 times higher compared to concentrations in the intermediate (greater than or equal to 0.0625 to 0.25 millimeter in diameter) or the coarse size fraction. However, the proportion of sediment particles less than 0.0625 millimeter in diameter in composite samples of bridge-deck runoff was small (median values range from 4 to 8 percent at each bridge) compared to the larger sediment particle-size mass. As a result, more than 50 percent of the sediment-associated TP, aluminum, chromium, manganese, and nickel was estimated to be associated with the coarse size fraction of the SS load. In contrast, about 95 percent of the estimated sediment-associated copper concentration was associated with the fine size fraction of the SS load.Version 1.0.2 of the Stochastic Empirical Loading and Dilution Model was used to simulate long-term (29–30-year) concentrations and annual yields of SS, TP, and TN in bridge-deck runoff and in discharges from a hypothetical stormwater treatment best-management practice structure. Three methods (traditional statistics, robust statistics, and L-moments) were used to calculate statistics for stochastic simulations because the high variability in measured concentration values during the field study resulted in extreme simulated concentrations. Statistics of each dataset, including the average, standard deviation, and skew of the common (base 10) logarithms, for each of the three bridges, and for a lumped dataset, were calculated and used for simulations; statistics representing the median of statistics calculated for the three bridges also were used for simulations. These median statistics were selected for the interpretive simulations so that the simulations could be used to estimate concentrations and yields from other, unmonitored bridges in Massachusetts. Comparisons of the standard and robust statistics indicated that simulation results with either method would be similar, which indicated that the large variability in simulated results was not caused by a few outliers. Comparison to statistics calculated by the L-moments methods indicated that L-moments do not produce extreme concentrations; however, they also do not produce results that represent the bulk of concentration data.The runoff-quality risk analysis indicated that bridge-deck runoff would exceed discharge standards commonly used for large, advanced wastewater treatment plants, but that commonly used stormwater best-management practices may reduce the percentage of exceedances by one-half. Results of simulations indicated that long-term average yields of TN, TP, and SS may be about 21.4, 6.44, and 40,600 pounds per acre per year, respectively. These yields are about 1.3, 3.4, and 16 times simulated ultra-urban highway yields in Massachusetts; however, simulations indicated that use of a best-management practice structure to treat bridge-deck runoff may reduce discharge yields to about 10, 2.8, and 4,300, pounds per acre per year, respectively.

30 CFR 57.16015 - Work or travel on overhead crane bridges.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Work or travel on overhead crane bridges. 57... MINES Materials Storage and Handling § 57.16015 Work or travel on overhead crane bridges. No person shall work from or travel on the bridge of an overhead crane unless the bridge is provided with...

30 CFR 56.16015 - Work or travel on overhead crane bridges.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Work or travel on overhead crane bridges. 56... Materials Storage and Handling § 56.16015 Work or travel on overhead crane bridges. No person shall work from or travel on the bridge of an overhead crane unless the bridge is provided with substantial...

A Hierarchical Analysis of Bridge Decision Makers ... The Role of New Technology Adoption in the Timber Bridge Market: Special Project

Treesearch

Robert L. Smith; Robert J. Bush; Daniel L. Schmoldt

1995-01-01

Bridge design engineers and local highway officials make bridge replacement decisions across the United States. The Analytical Hierarchy Process was used to characterize the bridge material selection decision of these individuals. State Department of Transportation engineers, private consulting engineers, and local highway officials were personally interviewed in...

30 CFR 57.16015 - Work or travel on overhead crane bridges.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Work or travel on overhead crane bridges. 57... MINES Materials Storage and Handling § 57.16015 Work or travel on overhead crane bridges. No person shall work from or travel on the bridge of an overhead crane unless the bridge is provided with...

30 CFR 56.16015 - Work or travel on overhead crane bridges.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Work or travel on overhead crane bridges. 56... Materials Storage and Handling § 56.16015 Work or travel on overhead crane bridges. No person shall work from or travel on the bridge of an overhead crane unless the bridge is provided with substantial...

A testing platform for durability studies of polymers and fiber-reinforced polymer composites under concurrent hygrothermo-mechanical stimuli.

PubMed

Gomez, Antonio; Pires, Robert; Yambao, Alyssa; La Saponara, Valeria

2014-12-11

The durability of polymers and fiber-reinforced polymer composites under service condition is a critical aspect to be addressed for their robust designs and condition-based maintenance. These materials are adopted in a wide range of engineering applications, from aircraft and ship structures, to bridges, wind turbine blades, biomaterials and biomedical implants. Polymers are viscoelastic materials, and their response may be highly nonlinear and thus make it challenging to predict and monitor their in-service performance. The laboratory-scale testing platform presented herein assists the investigation of the influence of concurrent mechanical loadings and environmental conditions on these materials. The platform was designed to be low-cost and user-friendly. Its chemically resistant materials make the platform adaptable to studies of chemical degradation due to in-service exposure to fluids. An example of experiment was conducted at RT on closed-cell polyurethane foam samples loaded with a weight corresponding to ~50% of their ultimate static and dry load. Results show that the testing apparatus is appropriate for these studies. Results also highlight the larger vulnerability of the polymer under concurrent loading, based on the higher mid-point displacements and lower residual failure loads. Recommendations are made for additional improvements to the testing apparatus.

A Testing Platform for Durability Studies of Polymers and Fiber-reinforced Polymer Composites under Concurrent Hygrothermo-mechanical Stimuli

PubMed Central

Gomez, Antonio; Pires, Robert; Yambao, Alyssa; La Saponara, Valeria

2014-01-01

The durability of polymers and fiber-reinforced polymer composites under service condition is a critical aspect to be addressed for their robust designs and condition-based maintenance. These materials are adopted in a wide range of engineering applications, from aircraft and ship structures, to bridges, wind turbine blades, biomaterials and biomedical implants. Polymers are viscoelastic materials, and their response may be highly nonlinear and thus make it challenging to predict and monitor their in-service performance. The laboratory-scale testing platform presented herein assists the investigation of the influence of concurrent mechanical loadings and environmental conditions on these materials. The platform was designed to be low-cost and user-friendly. Its chemically resistant materials make the platform adaptable to studies of chemical degradation due to in-service exposure to fluids. An example of experiment was conducted at RT on closed-cell polyurethane foam samples loaded with a weight corresponding to ~50% of their ultimate static and dry load. Results show that the testing apparatus is appropriate for these studies. Results also highlight the larger vulnerability of the polymer under concurrent loading, based on the higher mid-point displacements and lower residual failure loads. Recommendations are made for additional improvements to the testing apparatus. PMID:25548950

Polymer-silicon nanosheet composites: bridging the way to optoelectronic applications

NASA Astrophysics Data System (ADS)

Lyuleeva, Alina; Helbich, Tobias; Rieger, Bernhard; Lugli, Paolo

2017-04-01

The fabrication of electronic devices from sensitive, functional, two-dimensional (2D) nanomaterials with anisotropic structural properties has attracted much attention. Many theoretical and experimental studies have been performed; however, such materials have not been used in applications. In this context, the focus has shifted toward the study and synthesis of new materials. Freestanding hydrogen-terminated silicon nanosheets (SiNSs) are a new class of material with outstanding (opto)electronic properties (e.g. photoluminescence at approximately 510 nm) (Nakano 2014 J. Ceram. Soc. Japan 122 748). SiNSs are promising candidates for use in nanoelectronic devices and flexible electronics. Additional reasons for interest in such nanomaterials are their structural anisotropy and the fact that they are made from silicon. Here, we present examples for the application of functionalized SiNS-based composites as active materials for photonic sensors. The implementation of SiNSs in a covalent nanocomposite not only improves their stability but also facilitates subsequent device fabrication. Thus, SiNSs can be used in a straightforward setup preparation procedure. We show that the modification of novel Si-based 2D nanosheets with selected organic components not only opens a new field of photosensitive applications but also improves the processability of these nanosheets (Niu et al 2014 Sci. Rep. 4 4810, Chimene et al 2015 Adv. Mater. 27 7261).

[Effect of investment composition ratio for pure titanium crown and bridge on some mechanical properties of mould].

PubMed

Yang, Se-fei; Wang, You-xu; Guo, Tian-wen; Liu, Hong-chen

2011-11-01

To determine the optimal composition of a self-developing investment material by measuring physical and mechanical properties of mould. L(9) (3(4)) orthogonal design was adopted. One hundred and fifty specimens with the size of 80 mm × 20 mm × 20 mm were prepared to measure the atmospheric temperature bending strength, high temperature bending strength and residual bending strength. Nine specimens with the size of 5 mm diameter 25 mm heigh were prepared to survey the thermal expansion curve from ambient temperature to 1150°C. Strengths were greatly affected by fine powder proportion in refractory and water/powder ratio. When the content of fine powder was 35% and water/powder ratio was 1:7.5, adequate atmospheric temperature strength and high temperature strength could be achieved. Moreover, the residual strength was moderate. The thermal extension curves of specimens in experiment group were almost similar. And the average linear expansion coefficient was (4 ∼ 5) × 10(-6)/°C. The three kinds of bending strength of self-developing investment material are compared with commercialized investment material for titanium casting when water/powder ratio and the content of fine powder are carefully controlled.

Tough and Sustainable Graft Block Copolymer Thermoplastics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Jiuyang; Li, Tuoqi; Mannion, Alexander M.

Fully sustainable poly[HPMC-g-(PMVL-b-PLLA)] graft block copolymer thermoplastics were prepared from hydroxypropyl methylcellulose (HPMC), β-methyl-δ-valerolactone (MVL), and l-lactide (LLA) using a facile two-step sequential addition approach. In these materials, rubbery PMVL functions as a bridge between the semirigid HPMC backbone and the hard PLLA end blocks. This specific arrangement facilitates PLLA crystallization, which induces microphase separation and physical cross-linking. By changing the backbone molar mass or side chain composition, these thermoplastic materials can be easily tailored to access either plastic or elastomeric behavior. Moreover, the graft block architecture can be utilized to overcome the processing limitations inherent to linear block polymers.more » Good control over molar mass and composition enables the deliberate design of HPMC-g-(PMVL-b-PLLA) samples that are incapable of microphase separation in the melt state. These materials are characterized by relatively low zero shear viscosities in the melt state, an indication of easy processability. The simple and scalable synthetic procedure, use of inexpensive and renewable precursors, and exceptional rheological and mechanical properties make HPMC-g-(PMVL-b-PLLA) polymers attractive for a broad range of applications.« less

Field Testing and Load Rating Report for Bridge No. 4, Hybrid Composite Beam Span, at Fort Knox, Kentucky

DTIC Science & Technology

2016-09-01

required load rating (HL-93) and performance criteria for deflection and strain. Results showed the bridge met all design specifications and load...their respective owners. The findings of this report are not to be construed as an official Department of the Army position unless so designated by...composite beams met design specifications and could deliver safe crossing of Heavy Equipment Transport System (HETS-115) vehicles. Their report

49 CFR 1242.15 - Roadway, tunnels and subways, bridges and culverts, ties, rails, other track material, ballast...

Code of Federal Regulations, 2012 CFR

2012-10-01

... 49 Transportation 9 2012-10-01 2012-10-01 false Roadway, tunnels and subways, bridges and culverts, ties, rails, other track material, ballast, track laying and surfacing, and road property damaged... culverts, ties, rails, other track material, ballast, track laying and surfacing, and road property damaged...

49 CFR 1242.15 - Roadway, tunnels and subways, bridges and culverts, ties, rails, other track material, ballast...

Code of Federal Regulations, 2011 CFR

2011-10-01

... 49 Transportation 9 2011-10-01 2011-10-01 false Roadway, tunnels and subways, bridges and culverts, ties, rails, other track material, ballast, track laying and surfacing, and road property damaged... culverts, ties, rails, other track material, ballast, track laying and surfacing, and road property damaged...

49 CFR 1242.15 - Roadway, tunnels and subways, bridges and culverts, ties, rails, other track material, ballast...

Code of Federal Regulations, 2013 CFR

2013-10-01

... 49 Transportation 9 2013-10-01 2013-10-01 false Roadway, tunnels and subways, bridges and culverts, ties, rails, other track material, ballast, track laying and surfacing, and road property damaged... culverts, ties, rails, other track material, ballast, track laying and surfacing, and road property damaged...

49 CFR 1242.15 - Roadway, tunnels and subways, bridges and culverts, ties, rails, other track material, ballast...

Code of Federal Regulations, 2014 CFR

2014-10-01

... 49 Transportation 9 2014-10-01 2014-10-01 false Roadway, tunnels and subways, bridges and culverts, ties, rails, other track material, ballast, track laying and surfacing, and road property damaged... culverts, ties, rails, other track material, ballast, track laying and surfacing, and road property damaged...

Effect of voids in grouted, post-tensioned concrete bridge construction : volume 2--inspection, repair, materials, and risks.

DOT National Transportation Integrated Search

2009-09-01

Post-tensioned (PT) bridges are major structures that carry significant traffic. These bridges are designed and : constructed because they are economical for spanning long distances. In Texas, there are several signature PT : bridges. In the late 199...

Composite Sandwich Technologies Lighten Components

NASA Technical Reports Server (NTRS)

2010-01-01

Leveraging its private resources with several Small Business Innovation Research (SBIR) contracts with both NASA and the U.S. Department of Defense, WebCore Technologies LLC, of Miamisburg, Ohio, developed a fiber-reinforced foam sandwich panel it calls TYCOR that can be used for a wide variety of industrial and consumer applications. Testing at Glenn Research Center?s Ballistic Impact Facility demonstrated that the technology was able to exhibit excellent damage localization and stiffness during impact. The patented and trademarked material has found use in many demanding applications, including marine, ground transportation, mobile shelters, bridges, and most notably, wind turbines.

Performance estimates of a Boeing 747-100 transport mated with an outsize cargo pod

NASA Technical Reports Server (NTRS)

Jernell, L. S.

1980-01-01

The design mission performance of a Boeing 747-100 aircraft mated with an outsize cargo pod was studied. The basic design requirement was the rapid deployment of a combat loaded mobile bridge launcher from a United States east coast staging base to Europe. Weight was minimized by stripping the aircraft of unneeded, quick removal items and by utilizing graphite-epoxy composite materials for most pod components. The mission analysis was based on wind tunnel data and full scale carrier aircraft and engine data. The results are presented in tabular and graphic form.

Bridging a High School Science Fair Experience with First Year Undergraduate Research: Using the E-SPART Analyzer to Determine Electrostatic Charge Properties of Compositionally Varied Rock Dust Particles as Terrestrial Analogues to Mars Materials

NASA Technical Reports Server (NTRS)

Scott, A. G.; Williams, W. J. W.; Mazumder, M. K.; Biris, A.; Srirama, P. K.

2005-01-01

NASA missions to Mars confirm presence of surficial particles, as well as dramatic periods of aeolian reworking. Dust deposition on, or infiltration into, exploration equipment such as spacecraft, robotic explorers, solar panel power supplies, and even spacesuits, can pose significant problems such as diminished power collection, short circuits / discharges, and added weight. We report results conducted initially as a science fair project and a study now part of a first year University undergraduate research experience.

Development and performance evaluation of fiber reinforced polymer bridge.

DOT National Transportation Integrated Search

2014-03-01

Fiber reinforced polymers (FRP) have become more popular construction materials in the last decade due to the reduction of : material costs. The installation and performance evaluation of the first FRP-wrapped balsa wood bridge in Louisiana is descri...

Composites for Exploration Upper Stage

NASA Technical Reports Server (NTRS)

Fikes, J. C.; Jackson, J. R.; Richardson, S. W.; Thomas, A. D.; Mann, T. O.; Miller, S. G.

2016-01-01

The Composites for Exploration Upper Stage (CEUS) was a 3-year, level III project within the Technology Demonstration Missions program of the NASA Space Technology Mission Directorate. Studies have shown that composites provide important programmatic enhancements, including reduced weight to increase capability and accelerated expansion of exploration and science mission objectives. The CEUS project was focused on technologies that best advanced innovation, infusion, and broad applications for the inclusion of composites on future large human-rated launch vehicles and spacecraft. The benefits included near- and far-term opportunities for infusion (NASA, industry/commercial, Department of Defense), demonstrated critical technologies and technically implementable evolvable innovations, and sustained Agency experience. The initial scope of the project was to advance technologies for large composite structures applicable to the Space Launch System (SLS) Exploration Upper Stage (EUS) by focusing on the affordability and technical performance of the EUS forward and aft skirts. The project was tasked to develop and demonstrate critical composite technologies with a focus on full-scale materials, design, manufacturing, and test using NASA in-house capabilities. This would have demonstrated a major advancement in confidence and matured the large-scale composite technology to a Technology Readiness Level 6. This project would, therefore, have bridged the gap for providing composite application to SLS upgrades, enabling future exploration missions.

Approach for establishing approximate load carrying capacity for bridges with unknown material and unknown design properties.

DOT National Transportation Integrated Search

2011-07-01

There are 16 small to medium simple span bridges in Larimer County, Colorado that are currently load rated solely based on visual inspections. Most of these bridges are prestressed concrete bridges. The objective of this project is to load rate these...

Miscellaneous wood structures

Treesearch

Michael A. Ritter; Keith F. Faherty

1999-01-01

This section addresses the design of two types of glulam timber bridges : beam bridges with transverse decks and longitudinal glulam deck (slab) bridges. The material presented in the section is based on the 1992 edition of the AASHTO Standard Specifications for Highway Bridges (AASHTO specifications), including interim specifications through 1993. When specific design...

Toughening by crack bridging in heterogeneous ceramics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Curtin, W.A.

1995-05-01

The toughening of a ceramic by crack bridging is considered, including the heterogeneity caused simply by spatial randomness in the bridge locations. The growth of a single planar crack is investigated numerically by representing the microstructure as an array of discrete springs with heterogeneity in the mechanical properties of each spring. The stresses on each microstructural element are determined, for arbitrary configurations of spring properties and heterogeneity, using a lattice Green function technique. For toughening by (heterogeneous) crack bridging for both elastic and Dugdale bridging mechanisms, the following key physical results are found: (1) growing cracks avoid regions which aremore » efficiently bridged, and do not propagate as self-similar penny cracks; (2) crack growth thus proceeds at lower applied stresses in a heterogeneous material than in an ordered material; (3) very little toughening is evident for moderate amounts of crack growth in many cases; and (4) a different R-curve is found for every particular spatial distribution of bridging elements. These results show that material reliability is determined by both the flaw distribution and the ``toughness`` distribution, or local environment, around each flaw. These results also demonstrate that the ``microstructural`` parameters derived from fitting an R-curve to a continuum model may not have an immediate relationship to the actual microstructure; the parameters are ``effective`` parameters that absorb the effects of the heterogeneity. The conceptual issues illuminated by these conclusions must be fully understood and appreciated to further develop microstructure-property relationships in ceramic materials.« less

Lattice Modeling of Early-Age Behavior of Structural Concrete.

PubMed

Pan, Yaming; Prado, Armando; Porras, Rocío; Hafez, Omar M; Bolander, John E

2017-02-25

The susceptibility of structural concrete to early-age cracking depends on material composition, methods of processing, structural boundary conditions, and a variety of environmental factors. Computational modeling offers a means for identifying primary factors and strategies for reducing cracking potential. Herein, lattice models are shown to be adept at simulating the thermal-hygral-mechanical phenomena that influence early-age cracking. In particular, this paper presents a lattice-based approach that utilizes a model of cementitious materials hydration to control the development of concrete properties, including stiffness, strength, and creep resistance. The approach is validated and used to simulate early-age cracking in concrete bridge decks. Structural configuration plays a key role in determining the magnitude and distribution of stresses caused by volume instabilities of the concrete material. Under restrained conditions, both thermal and hygral effects are found to be primary contributors to cracking potential.

Lattice Modeling of Early-Age Behavior of Structural Concrete

PubMed Central

Pan, Yaming; Prado, Armando; Porras, Rocío; Hafez, Omar M.; Bolander, John E.

2017-01-01

The susceptibility of structural concrete to early-age cracking depends on material composition, methods of processing, structural boundary conditions, and a variety of environmental factors. Computational modeling offers a means for identifying primary factors and strategies for reducing cracking potential. Herein, lattice models are shown to be adept at simulating the thermal-hygral-mechanical phenomena that influence early-age cracking. In particular, this paper presents a lattice-based approach that utilizes a model of cementitious materials hydration to control the development of concrete properties, including stiffness, strength, and creep resistance. The approach is validated and used to simulate early-age cracking in concrete bridge decks. Structural configuration plays a key role in determining the magnitude and distribution of stresses caused by volume instabilities of the concrete material. Under restrained conditions, both thermal and hygral effects are found to be primary contributors to cracking potential. PMID:28772590

Fatigue testing of wood-concrete composite beams.

DOT National Transportation Integrated Search

2013-05-01

Currently, wood-concrete composite structural members are usually applied in building structures. There are a relatively small number (in the low 100s) of known bridge applications involving wood-concrete composites. A problem with using these novel ...

Preparation, characterization and catalyst application of ternary interpenetrating networks of poly 4-methyl vinyl pyridinium hydroxide-SiO{sub 2}-Al{sub 2}O{sub 3}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kalbasi, Roozbeh Javad, E-mail: rkalbasi@iaush.ac.ir; Kolahdoozan, Majid, E-mail: kolahdoozan@iaush.ac.ir; Vanani, Sedigheh Mozafari

2011-08-15

In this work, Al{sub 2}O{sub 3} was mixed with SiO{sub 2} and poly 4-vinylpyridine by the sol-gel method in order to make a composite which is used as a heterogeneous basic catalyst for Knoevenagel condensation reaction. The physical and chemical properties of the composite catalyst were investigated by XRD, FT-IR, TG, BET and SEM techniques. The catalytic performance of each material was determined for the Knoevenagel condensation reaction between carbonyl compound and malononitrile. The reactions were performed in solvent-free conditions and the product was obtained in high yield and purity after a simple work-up. The effects of the amount ofmore » catalyst, amount of monomer for the synthesis of composite and recyclability of the heterogeneous composite were investigated. The composite catalyst used for this synthetically useful transformation showed considerable level of reusability besides very good activity. - Graphical abstract: In this paper, we report the synthesis of poly 4-methyl vinyl pyridinium hydroxide-SiO{sub 2}-Al{sub 2}O{sub 3}. The novelty of this procedure is at easy preparation together with using inexpensive materials. Highlights: > P4MVPH-SiO{sub 2}-Al{sub 2}O{sub 3} composite was prepared as a novel polymer-inorganic hybrid. > The composite was prepared without using any bridged organosilanes compound. > SEM photograph showed that the composite is completely uniform. > P4MVPH-SiO{sub 2}-Al{sub 2}O{sub 3} could behave as a recyclable catalyst for Knoevenagel reaction.« less

Predicting fatigue service life extension of RC bridges with externally bonded CFRP repairs : [project brief].

DOT National Transportation Integrated Search

2015-12-01

Externally bonded carbon fiber reinforced polymer composites (CFRPs) are increasingly used to : repair concrete bridges. CFRP design techniques are a proven approach for enhancing the strength : of existing structures. This project investigated the d...

Use of fiber reinforced polymer composite cable for post-tensioning application : [summary].

DOT National Transportation Integrated Search

2015-05-01

Post-tensioning is a method frequently used in construction of segmental bridges, continuous : I-girder bridges, and piers. It involves using tendons, which are multiple strands, usually : steel, installed through voids formed by ducts either inside ...

Bridge deck cracking and composite action analyses : final report, March 2010.

DOT National Transportation Integrated Search

2010-03-01

According to the American Society of Civil Engineers Report Card (ASCE, 2005), United States infrastructure received a grade point average of "D"(i.e., poor rating) in 2005. Moreover, the National Bridge Inventory (Federal Highway Administration, 200...

Geometry control of long-span continuous girder concrete bridge during construction through finite element model updating

NASA Astrophysics Data System (ADS)

Wu, Jie; Yan, Quan-sheng; Li, Jian; Hu, Min-yi

2016-04-01

In bridge construction, geometry control is critical to ensure that the final constructed bridge has the consistent shape as design. A common method is by predicting the deflections of the bridge during each construction phase through the associated finite element models. Therefore, the cambers of the bridge during different construction phases can be determined beforehand. These finite element models are mostly based on the design drawings and nominal material properties. However, the accuracy of these bridge models can be large due to significant uncertainties of the actual properties of the materials used in construction. Therefore, the predicted cambers may not be accurate to ensure agreement of bridge geometry with design, especially for long-span bridges. In this paper, an improved geometry control method is described, which incorporates finite element (FE) model updating during the construction process based on measured bridge deflections. A method based on the Kriging model and Latin hypercube sampling is proposed to perform the FE model updating due to its simplicity and efficiency. The proposed method has been applied to a long-span continuous girder concrete bridge during its construction. Results show that the method is effective in reducing construction error and ensuring the accuracy of the geometry of the final constructed bridge.

Hydraulic modeling of mussel habitat at a bridge-replacement site, Allegheny River, Pennsylvania, USA

USGS Publications Warehouse

Fulton, John W.; Wagner, Chad R.; Rogers, Megan E.; Zimmerman, Gregory F.

2010-01-01

Based on the statistical targets established, the hydraulic model results suggest that an additional 2428 m2 or a 30-percent increase in suitable mussel habitat could be generated at the replacement-bridge site when compared to the baseline condition associated with the existing bridge at that same location. The study did not address the influences of substrate, acid mine drainage, sediment loads from tributaries, and surface-water/ground-water exchange on mussel habitat. Future studies could include methods for quantifying (1) channel–substrate composition and distribution using tools such as hydroacoustic echosounders specifically designed and calibrated to identify bed composition and mussel populations, (2) surface-water and ground-water interactions, and (3) a high-streamflow event.

Comparison of Load-Bearing Capacities of 3-Unit Fiber-Reinforced Composite Adhesive Bridges with Different Framework Designs.

PubMed

Tacir, Ibrahim H; Dirihan, Roda S; Polat, Zelal Seyfioglu; Salman, Gizem Ön; Vallittu, Pekka; Lassila, Lippo; Ayna, Emrah

2018-06-28

BACKGROUND The aim of this study was to investigate and compare the load-bearing capacities of three-unit direct resin-bonded fiber-reinforced composite fixed dental prosthesis with different framework designs. MATERIAL AND METHODS Sixty mandibular premolar and molar teeth without caries were collected and direct glass fiber-resin fixed FDPs were divided into 6 groups (n=10). Each group was restored via direct technique with different designs. In Group 1, the inlay-retained bridges formed 2 unidirectional FRC frameworks and pontic-reinforced transversal FRC. In Group 2, the inlay-retained bridges were supported by unidirectional lingual and occlusal FRC frameworks. Group 3, had buccal and lingual unidirectional FRC frameworks without the inlay cavities. Group 4 had reinforced inlay cavities and buccal-lingual FRC with unidirectional FRC frameworks. Group 5, had a circular form of fiber reinforcement around cusps in addition to buccal-lingual FRC frameworks. Group 6 had a circular form of fiber reinforcement around cusps with 2 bidirectional FRC frameworks into inlay cavities. All groups were loaded until final fracture using a universal testing machine at a crosshead speed of 1 mm/min. RESULTS Mean values of the groups were determined with ANOVA and Tukey HSD. When all data were evaluated, Group 6 had the highest load-bearing capacities and revealed significant differences from Group 3 and Group 4. Group 6 had the highest strain (p>0.05). When the fracture patterns were investigated, Group 6 had the durability to sustain fracture propagation within the restoration. CONCLUSIONS The efficiency of fiber reinforcement of the restorations alters not only the amount of fiber, but also the design of the restoration with fibers.

21 CFR 872.3770 - Temporary crown and bridge resin.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Temporary crown and bridge resin. 872.3770 Section... (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Prosthetic Devices § 872.3770 Temporary crown and bridge resin. (a) Identification. A temporary crown and bridge resin is a device composed of a material, such as...

21 CFR 872.3770 - Temporary crown and bridge resin.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Temporary crown and bridge resin. 872.3770 Section... (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Prosthetic Devices § 872.3770 Temporary crown and bridge resin. (a) Identification. A temporary crown and bridge resin is a device composed of a material, such as...

Demonstration and Validation of a Lightweight Composite Bridge Deck Technology as an Alternative to Reinforced Concrete

DTIC Science & Technology

2016-08-01

Abstract Cyclic loading and weathering of reinforced concrete bridge decks cause corrosion of reinforcement steel , which leads to cracking, potholes...inforcement steel , on a deteriorated concrete bridge at Redstone Arsenal, AL. A pultruded deck system made by Zellcomp, Inc., was selected for...16 Figure 13. Form for grout haunch fabricated by tack welding steel strips to the top of the girder

Simple analysis of the effect of construction materials on bridge impact factors

DOT National Transportation Integrated Search

1999-06-01

The purpose of this research is to study the influence of different construction materials on the dynamic impact factor of bridges. Initially, introduction of the dynamic impact factor and some evaluation methods are presented. A comparison of the re...

Development of an engineered cementitious composite to enhance bridge approach slab durability.

DOT National Transportation Integrated Search

2013-06-01

The strength and durability of highway bridges are two of the key components in maintaining a : high level of freight transportation capacity on the nations highways. : The CFIRE project 04-09 demonstrated the feasibility of a new hybrid engineered...

Enhancement mechanisms of graphene in nano-58S bioactive glass scaffold: mechanical and biological performance.

PubMed

Gao, Chengde; Liu, Tingting; Shuai, Cijun; Peng, Shuping

2014-04-16

Graphene is a novel material and currently popular as an enabler for the next-generation nanocomposites. Here, we report the use of graphene to improve the mechanical properties of nano-58S bioactive glass for bone repair and regeneration. And the composite scaffolds were fabricated by a homemade selective laser sintering system. Qualitative and quantitative analysis demonstrated the successful incorporation of graphene into the scaffold without obvious structural damage and weight loss. The optimum compressive strength and fracture toughness reached 48.65 ± 3.19 MPa and 1.94 ± 0.10 MPa · m(1/2) with graphene content of 0.5 wt%, indicating significant improvements by 105% and 38% respectively. The mechanisms of pull-out, crack bridging, crack deflection and crack tip shielding were found to be responsible for the mechanical enhancement. Simulated body fluid and cell culture tests indicated favorable bioactivity and biocompatibility of the composite scaffold. The results suggest a great potential of graphene/nano-58S composite scaffold for bone tissue engineering applications.

Fractography of composite delamination

NASA Technical Reports Server (NTRS)

1988-01-01

Studies were made of the fractography of mode 2 delamination and the impact damage of carbon fiber reinforced polymer composites. Laminates fractured under mode 2 loading were potted in a clear epoxy polymer, sectioned and polished and examined using transmission and reflection light microscopy. There were only occasional fibers bridging the mode 2 cracks. These cracks were not always visible probably because the crack opening displacement was too small as to be resolved using light microscopy. A study was made of the effect of repetitive impacts on laminates of AS4/3501-6 and IM6/3501-6. Plots of cumulative impact energy vs cumulative absorbed energy exhibited a sharp change in slope which corresponded to the damage area reaching the edges of the specimen. The initial slope was highly reproducible for both composite materials. On the other hand, the intersection point between the two slopes, where the damage area reaches the specimen edges, was highly variable between specimens. This variability is tentatively ascribed to differences in laminate quality.

Effect of molybdenum on gamma ray shielding and structural properties of PbO-B2O3 glasses

NASA Astrophysics Data System (ADS)

Dogra, Mridula; Singh, K. J.; Kaur, Kulwinder

2018-04-01

The present study is aimed at developing new shielding materials for gamma ray shielding applications. Transparent glasses of the composition xMoO3-0.7PbO-(0.3-x)B2O3 where x= 0.03 to 0. 06 (mole fraction) have been prepared by using melt-quenchingtechnique. Gamma ray shielding properties have been evaluated in terms of mass attenuation coefficient and half value layer parameter at photon energies 662 and 1173 keV. These shielding parameters are also compared with standard shielding material`concretes'. It has been found that prepared glass system shows better shielding properties than barite and ordinary concretes proving the possibility of its usage as an alternate to conventional concrete for gamma ray shielding applications. The density, molar volume, X-Ray Diffraction, Fourier Transform InfraRed and Raman studies have been performed to study the structural properties of the glass system. It has been analyzed from FTIR and Raman studies that bridging oxygens increase with the decrease of MoO3 content in the glass composition.

New conceptual design of portable bamboo bridge for emergency purposes

NASA Astrophysics Data System (ADS)

Musthaffa, A. A.; Nor, N. M.; Yusof, M. A.; Yuhazri, M. Y.

2018-02-01

Portable bridges serve as routes for troops during the military operations and the disaster relief operation. Nowadays, bamboo has been regarded as one of the alternative construction materials for building and bridge structures. This paper presents the conceptual design of the portable bridge. Several types of portable bridges and bamboo bridges are reviewed in the current work. The characteristics, capability and method of construction of each bridge are discussed. Finally, the conceptual of the portable bamboo bridge for emergency purposes is presented. The idea of producing portable bridge is proposed in the current work as it is crucial for providing route for communities affected by natural disasters.

Influence of a cellulosic ether carrier on the structure of biphasic calcium phosphate ceramic particles in an injectable composite material.

PubMed

Dupraz, A; Nguyen, T P; Richard, M; Daculsi, G; Passuti, N

1999-04-01

An injectable composite material based on biphasic calcium phosphate (BCP) and a nonionic cellulose ether has been elaborated for use in percutaneous surgery for spine fusion. This paper reports the characterization results of this material by spectroscopic techniques including X-ray diffraction (XRD), infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) fitted with an energy dispersive X-Ray analysis system and high-resolution transmission electron microscopy (HR-TEM). From FTIR and XPS results, it was observed that the adhesion between the polymer and the ceramic might be insured by oxygen bridging developed through an ionic bonding between calcium ions and (C-O) groups of the polymer. Moreover, XPS showed attraction of Ca2+ ions in the polymer matrix, while the ceramic surface was modified in a HPO4(2-) -rich layer. These results suggest a possible dissolution/precipitation process at the interface ceramic/polymer. HR-TEM observations supported this hypothesis, showing a light contrasted fringe at the surface of the ceramic grains in the composite paste. As well, changes in the XRD spectra could indicate a small decrease in the crystal size of the BCP powder through the contact to polymer solution. In addition, SEM observation showed a decrease of the initial BCP granulometry. Aggregates of 80-200 microm seemed to be mostly dissociated in micrograins. The ceramic grains were coated with and bonded between each other by the polymer matrix, which acted as spacer in between the ceramic grains, creating a macroporous-like material structure.

Acoustic emissions (AE) monitoring of large-scale composite bridge components

NASA Astrophysics Data System (ADS)

Velazquez, E.; Klein, D. J.; Robinson, M. J.; Kosmatka, J. B.

2008-03-01

Acoustic Emissions (AE) has been successfully used with composite structures to both locate and give a measure of damage accumulation. The current experimental study uses AE to monitor large-scale composite modular bridge components. The components consist of a carbon/epoxy beam structure as well as a composite to metallic bonded/bolted joint. The bonded joints consist of double lap aluminum splice plates bonded and bolted to carbon/epoxy laminates representing the tension rail of a beam. The AE system is used to monitor the bridge component during failure loading to assess the failure progression and using time of arrival to give insight into the origins of the failures. Also, a feature in the AE data called Cumulative Acoustic Emission counts (CAE) is used to give an estimate of the severity and rate of damage accumulation. For the bolted/bonded joints, the AE data is used to interpret the source and location of damage that induced failure in the joint. These results are used to investigate the use of bolts in conjunction with the bonded joint. A description of each of the components (beam and joint) is given with AE results. A summary of lessons learned for AE testing of large composite structures as well as insight into failure progression and location is presented.

Fully integrated carbon nanotube composite thin film strain sensors on flexible substrates for structural health monitoring

NASA Astrophysics Data System (ADS)

Burton, A. R.; Lynch, J. P.; Kurata, M.; Law, K. H.

2017-09-01

Multifunctional thin film materials have opened many opportunities for novel sensing strategies for structural health monitoring. While past work has established methods of optimizing multifunctional materials to exhibit sensing properties, comparatively less work has focused on their integration into fully functional sensing systems capable of being deployed in the field. This study focuses on the advancement of a scalable fabrication process for the integration of multifunctional thin films into a fully integrated sensing system. This is achieved through the development of an optimized fabrication process that can create a broad range of sensing systems using multifunctional materials. A layer-by-layer deposited multifunctional composite consisting of single walled carbon nanotubes (SWNT) in a polyvinyl alcohol and polysodium-4-styrene sulfonate matrix are incorporated with a lithography process to produce a fully integrated sensing system deposited on a flexible substrate. To illustrate the process, a strain sensing platform consisting of a patterned SWNT-composite thin film as a strain-sensitive element within an amplified Wheatstone bridge sensing circuit is presented. Strain sensing is selected because it presents many of the design and processing challenges that are core to patterning multifunctional thin film materials into sensing systems. Strain sensors fabricated on a flexible polyimide substrate are experimentally tested under cyclic loading using standard four-point bending coupons and a partial-scale steel frame assembly under lateral loading. The study reveals the material process is highly repeatable to produce fully integrated strain sensors with linearity and sensitivity exceeding 0.99 and 5 {{V}}/{ε }, respectively. The thin film strain sensors are robust and are capable of high strain measurements beyond 3000 μ {ε }.

Experimental evaluation and design of unfilled and concrete-filled FRP composite piles, task 3 - FRP composite pile flexural testing.

DOT National Transportation Integrated Search

2014-06-01

The overall goal of this project is the experimental evaluation and design of unfilled and concrete-filled FRP : composite piles for load-bearing in bridges. This report covers Task 3, FRP Composite Pile Flexural Testing. : Hollow and concrete filled...

Experimental evaluation and design of unfilled and concrete-filled FRP composite piles, task 6 - FRP composite pile axial compression testing.

DOT National Transportation Integrated Search

2015-04-01

The overall goal of this project is the experimental evaluation and design of unfilled and concrete-filled FRP : composite piles for load-bearing in bridges. This report covers Task 6, FRP Composite Pile Axial Compression : Testing. : Hollow and conc...

Use of a ground-penetrating radar system to detect pre-and post-flood scour at selected bridge sites in New Hampshire, 1996-98

USGS Publications Warehouse

Olimpio, Joseph R.

2000-01-01

Ground-penetrating radar was used to measure the depth and extent of existing and infilled scour holes and previous scour surfaces at seven bridges in New Hampshire from April 1996 to November 1998. Ground-penetrating-radar survey techniques initially were used by the U.S. Geological Survey to study streambed scour at 30 bridges. Sixteen of the 30 bridges were re-surveyed where floods exceeded a 2-year recurrence interval. A 300-megahertz signal was used in the ground-penetrating radar system that penetrated through depths as great as 20 feet of water and as great as 32 feet of streambed materials. Existing scour-hole dimensions, infilled thickness, previous scour surfaces, and streambed materials were detected using ground-penetrating radar. Depths to riprap materials and pier footings were identified and verified with bridge plans. Post data-collection-processing techniques were applied to assist in the interpretation of the data, and the processed data were displayed and printed as line plots. Processing included distance normalization, migration, and filtering but processing was kept to a minimum and some interference from multiple reflections was left in the record. Of the 16 post-flood bridges, 22 ground-penetrating-radar cross sections at 7 bridges were compared and presented in this report. Existing scour holes were detected during 1996 (pre-flood) data collection in nine cross sections where scour depths ranged from 1 to 3 feet. New scour holes were detected during 1998 (post-flood) data collection in four cross sections where scour depths were as great as 4 feet deep. Infilled scour holes were detected in seven cross sections, where depths of infilling ranged from less than 1 to 4 feet. Depth of infilling by means of steel rod and hammer was difficult to verify in the field because of cobble and boulder streambeds or deep water. Previous scour surfaces in streambed materials were identified in 15 cross sections and the depths to these surfaces ranged from 1 to 10 feet below the streambed. Riprap materials or pier footings were identified in all cross sections. Calculated record depths generally agree with bridge plans. Pier footings were exposed at two bridges and steel pile was exposed at one bridge. Exposures were verified by field observations.

19 CFR 123.18 - Equipment and materials for constructing bridges or tunnels between the United States and Canada...

Code of Federal Regulations, 2014 CFR

2014-04-01

... or tunnels between the United States and Canada or Mexico. 123.18 Section 123.18 Customs Duties U.S... WITH CANADA AND MEXICO International Traffic § 123.18 Equipment and materials for constructing bridges or tunnels between the United States and Canada or Mexico. (a) Admission of equipment and materials...

19 CFR 123.18 - Equipment and materials for constructing bridges or tunnels between the United States and Canada...

Code of Federal Regulations, 2013 CFR

2013-04-01

... or tunnels between the United States and Canada or Mexico. 123.18 Section 123.18 Customs Duties U.S... WITH CANADA AND MEXICO International Traffic § 123.18 Equipment and materials for constructing bridges or tunnels between the United States and Canada or Mexico. (a) Admission of equipment and materials...

19 CFR 123.18 - Equipment and materials for constructing bridges or tunnels between the United States and Canada...

Code of Federal Regulations, 2012 CFR

2012-04-01

... or tunnels between the United States and Canada or Mexico. 123.18 Section 123.18 Customs Duties U.S... WITH CANADA AND MEXICO International Traffic § 123.18 Equipment and materials for constructing bridges or tunnels between the United States and Canada or Mexico. (a) Admission of equipment and materials...

Bridging the Cultural Gap: Ten Steps toward a More Multicultural Youth Library.

ERIC Educational Resources Information Center

Agosto, Denise E.

2001-01-01

Presents ten steps toward a more multicultural youth library to help bridge cultural and linguistic gaps in public and school libraries. Topics include mission statements; physical environment; collection diversity; collaboration; bilingual materials; multicultural materials; community involvement; and appreciating diversity. (LRW)

Reduction of Bridge Deck Cracking through Alternative Material Usage

DOT National Transportation Integrated Search

2017-12-01

ODOT routinely deploys a large number of continuous span structural slab bridges. Despite being designed to strictly satisfy all the relevant AASHTO and ODOT BDM requirements, many such bridge decks show transverse cracks, with widths greater than th...

Long‐Term Monitoring of a Geosynthetic Reinforced Soil Integrated Bridge System (GRS‐IBS)

DOT National Transportation Integrated Search

2017-11-01

The geosynthetic reinforced soil integrated bridge system (GRS-IBS) is an innovative alternative to conventional bridge technology that utilizes closely spaced layers of geosynthetic reinforcement and compacted granular fill material to provide direc...

A general method to improve 3D-printability and inter-layer adhesion in lignin-based composites

DOE PAGES

Nguyen, Ngoc A.; Bowland, Christopher C.; Naskar, Amit K.

2018-05-02

Here, we report the utilization of a melt-stable lignin waste-stream from biorefineries as a renewable feedstock, with acrylonitrile-butadiene rubber and acrylonitrile-butadiene-styrene (ABS) polymer to synthesize a renewable matrix having excellent 3D-printability. While the initial low melt viscosity of the dispersed lignin phase induces local thermo-rheological relaxation facilitating the composite's melt flow, thermal crosslinking in both lignin and rubber phases as well as at the lignin-rubber interface decreases the molecular mobility. Consequently, interfacial diffusion and the resulting adhesion between deposited layers is decreased. However, addition of 10 wt.% of discontinuous carbon fibers (CFs) within the green composites not only significantly enhancesmore » the material performance but also lowers the degree of chemical crosslinking formed in the matrix during melt-phase synthesis. Furthermore, abundant functional groups including hydroxyl (from lignin) and nitrile (from rubber and ABS) allow combinations of hydrogen bonded structures where CFs play a critical bridging role between the deposited layers. As a result, a highly interfused printed structure with 100% improved inter-layer adhesion strength was obtained. This research offers a route toward utilizing lignin for replacement of petroleum-based thermoplastics used in additive manufacturing and methods to enhance printability of the materials with exceptional mechanical performance.« less

A general method to improve 3D-printability and inter-layer adhesion in lignin-based composites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nguyen, Ngoc A.; Bowland, Christopher C.; Naskar, Amit K.

Here, we report the utilization of a melt-stable lignin waste-stream from biorefineries as a renewable feedstock, with acrylonitrile-butadiene rubber and acrylonitrile-butadiene-styrene (ABS) polymer to synthesize a renewable matrix having excellent 3D-printability. While the initial low melt viscosity of the dispersed lignin phase induces local thermo-rheological relaxation facilitating the composite's melt flow, thermal crosslinking in both lignin and rubber phases as well as at the lignin-rubber interface decreases the molecular mobility. Consequently, interfacial diffusion and the resulting adhesion between deposited layers is decreased. However, addition of 10 wt.% of discontinuous carbon fibers (CFs) within the green composites not only significantly enhancesmore » the material performance but also lowers the degree of chemical crosslinking formed in the matrix during melt-phase synthesis. Furthermore, abundant functional groups including hydroxyl (from lignin) and nitrile (from rubber and ABS) allow combinations of hydrogen bonded structures where CFs play a critical bridging role between the deposited layers. As a result, a highly interfused printed structure with 100% improved inter-layer adhesion strength was obtained. This research offers a route toward utilizing lignin for replacement of petroleum-based thermoplastics used in additive manufacturing and methods to enhance printability of the materials with exceptional mechanical performance.« less

Hierarchical Nanostructures of Nitrogen-Doped Porous Carbon Polyhedrons Confined in Carbon Nanosheets for High-Performance Supercapacitors.

PubMed

Zhao, Zhe; Liu, Siliang; Zhu, Jixin; Xu, Jingsan; Li, Le; Huang, Zhaoqi; Zhang, Chao; Liu, Tianxi

2018-05-31

Interconnected close-packed nitrogen-doped porous carbon polyhedrons (NCPs) confined in two-dimensional carbon nanosheets (CNSs) have been prepared through a sustainable one-pot pyrolysis of a simple solid mixture of zeolitic imidazolate framework-8 (ZIF-8) crystals and with organic potassium as the precursors. The hierarchically organized framework of the NCP-CNS composites enables NCPs and CNSs to act as well-defined electrolyte reservoirs and mechanical buffers accommodating large volume expansions of NCPs, respectively. Among the unique composite nanostructures, the NCPs with vast micropores provide electric double-layer capacitances, while the CNSs bridge the individual NCPs to form a conductive pathway with a hierarchical porosity. As a result, the NCP-CNS composites with high electrical integrity and structural stability are used as electrode materials for high-performance supercapacitors, which exhibit excellent electrochemical capacitive characteristics in terms of an outstanding capacitance of 300 F g -1 at 1 A g -1 , large energy density of 20.9 W h kg -1 , and great cycling performance of 100% retention after 6000 cycles. This work therefore presents a one-pot and efficient strategy to prepare an ordered arrangement of ZIF-8-derived porous carbons toward new electrode materials in promising energy storage systems.

Post-tensioned carbon fiber composite cable (CFCC), Little Pond Bridge, Route 302, Fryeburg, Maine.

DOT National Transportation Integrated Search

2013-02-01

Corrosion of reinforcing steel in concrete has been a constant and expensive maintenance problem which : is exacerbated by Maines coastal environment, harsh winters, and the use of chlorides on the roads and : bridges. Carbon fiber products are in...

Plate & tube bridge deck evaluation in the deck test bed of the Troutville, Virginia, weigh station.

DOT National Transportation Integrated Search

2004-01-01

This report addresses the laboratory and field performance of multi-cellular fiber-reinforced polymer (FRP) composite bridge deck systems. We focus specifically on FRP decks produced from adhesively bonded pultrusions where the core of the deck posse...

Strengthening of Route 378 bridge over Wynantskill Creek in New York using FRP laminates

DOT National Transportation Integrated Search

2001-03-01

This report describes application of Fiber-Reinforced Polymer (FRP) composite laminates to strengthen an aging reinforced-concrete T-beam bridge in South Troy, Rensselaer County, New York. Leakage at the end joints of this single-span structure led t...

78 FR 63136 - Drawbridge Operation Regulation; Inner Harbor Navigational Canal, New Orleans, LA

Federal Register 2010, 2011, 2012, 2013, 2014

2013-10-23

... operating schedules so the bridge owner would be able to use the same bridge crew personnel to operate both bridges with little to no effect on navigation through the bridges. DATES: Comments and related material... INFORMATION CONTACT: If you have questions on this proposed rule, call or email the Coast Guard; Mr. Jim...

[Fiber-reinforced composite in fixed prosthodontics].

PubMed

Pilo, R; Abu Rass, Z; Shmidt, A

2010-07-01

Fiber reinforced composite (FRC) is composed of resin matrix and fibers filler. Common types of fibers: polyethylene, carbon and glass. Fibers can be continuous and aligned, discontinuous and aligned, discontinuous and randomly oriented. The architecture of the fibers is unidirectional, woven or braided. The two main types are: dry fibers or impregnated. Inclusion of fibers to resin composite increased its average flexural strength in 100-200 MPa. FRC can be utilized by the dentist in direct approach (splinting, temporary winged bridge) or indirect approach (laboratory made fixed partial denture). Laboratory fixed partial denture (FPD) is made from FRC substructure and Hybrid/Microfill particulate composite veneer. Main indications: interim temporary FPD or FPD in cases of questionable abutment teeth, in aesthetic cases where All Ceram FPD is not feasible. Retention is attained by adhesive cementation to minimally prepared teeth or to conventionally prepared teeth; other options are inlay-onlay bridges or hybrid bridges. Contraindications are: poor hygiene, inability to control humidity, parafunction habits, and more than two pontics. Survival rate of FRC FPD over 5 years is 75%, lower compared to porcelain fused to metal FPD which is 95%. Main reasons for failure are: fracture of framework and delamination of the veneer. Part of the failures is repairable.

SCB initiator

DOEpatents

Bickes Jr., Robert W.; Renlund, Anita M.; Stanton, Philip L.

1994-11-01

A detonator for high explosives initiated by mechanical impact includes a cylindrical barrel, a layer of flyer material mechanically covering the barrel at one end, and a semiconductor bridge ignitor including a pair of electrically conductive pads connected by a semiconductor bridge. The bridge is in operational contact with the layer, whereby ignition of said bridge forces a portion of the layer through the barrel to detonate the explosive. Input means are provided for igniting the semiconductor bridge ignitor.

SCB initiator

DOEpatents

Bickes, Jr., Robert W.; Renlund, Anita M.; Stanton, Philip L.

1994-01-01

A detonator for high explosives initiated by mechanical impact includes a cylindrical barrel, a layer of flyer material mechanically covering the barrel at one end, and a semiconductor bridge ignitor including a pair of electrically conductive pads connected by a semiconductor bridge. The bridge is in operational contact with the layer, whereby ignition of said bridge forces a portion of the layer through the barrel to detonate the explosive. Input means are provided for igniting the semiconductor bridge ignitor.

Field measurements of diaphragm and top lateral members of three trapezoidal composite box girder bridges.

DOT National Transportation Integrated Search

2002-12-01

The results of field tests on three trapezoidal box girder bridges are presented. The study concentrated on the : measurement of the strains in the external and internal diaphragms and the top laterals of the boxes. The strains were : collected when ...

Development and evaluation of an adhesively bonded panel-to-panel joint for a fiber-reinforced polymer bridge deck system.

DOT National Transportation Integrated Search

2007-01-01

A fiber-reinforced polymer (FRP) composite cellular deck system was used to rehabilitate a historical cast iron thru-truss structure (Hawthorne Street Bridge in Covington, Virginia). The most important characteristic of this application is reduction ...

Strength and fatigue of three glass fiber reinforced composite bridge decks with mechanical deck to stringer connections.

DOT National Transportation Integrated Search

2012-02-01

Replacement of the steel grating deck on the lift span of the Morrison Bridge in Portland, OR, will utilize glass : fiber reinforced polymer (FRP) panels to address ongoing maintenance issues of the deteriorated existing deck, improve driver : safety...

Bridge-in-a-Backpack(TM). Task 3 : investigation of durability enhancements relative to abrasion from ice and other sources.

DOT National Transportation Integrated Search

2013-02-01

The arch-shaped concrete filled fiber reinforced polymer tube bridges are being constructed throughout New : England and elsewhere. The composite system durability and maintenance requirements need to be evaluated. For : this study, an asymmetric hyb...

Long-term corrosion protection of bridge elements reinforcing materials in concrete : final report.

DOT National Transportation Integrated Search

2017-09-01

Preventing or mitigating the corrosion of reinforcing steel in bridge decks is a major challenge for state transportation agencies. With agency budgets stretched thinner every year, they must implement strategies to extend the service lives of bridge...

Repairing/strengthening of bridges with post-tensioned FRP materials and performance evaluation.

DOT National Transportation Integrated Search

2015-09-01

One of the challenges that transportation agencies are facing is to keep bridges in good condition during their service life. : Numerous bridges are classified as structurally and/or functionally deficient in the country. In the state of Louisiana, 4...

Fatigue study of a GRP pedestrian bridge : final report.

DOT National Transportation Integrated Search

1986-01-01

Static and cyclic load tests were conducted on a 16-ft long bridge constructed with fiberglass materials. Approximately 1.6 million cycles of loads were applied to the deck to study the fatigue characteristics of the bridge. The location and magnitud...

Fixed partial dentures investigated by optical coherent tomography

NASA Astrophysics Data System (ADS)

Sinescu, Cosmin; Negrutiu, Meda; Todea, Carmen; Hughes, Mike; Tudorache, Florin; Podoleanu, Adrian G.

2008-02-01

Fixed partial prostheses as integral ceramics, integral polymers, metal ceramics or metal polymers bridges, are mainly used in the frontal part of the dental arch (especially the integral bridges). They have to satisfy high stress requirements as well as esthetic. The masticatory stress may induce fractures of the bridges. These may be triggered by initial materials defects or by alterations of the technological process. The fractures of these bridges lead to functional, esthetic and phonetic disturbances which finally render the prosthetic treatment inefficient. The purpose of this study is to evaluate the capability of en-face optical coherence tomography (OCT) in detection and analysis of possible fractures in several integral fixed partial dentures. The materials used were represented by several fixed partial prostheses, integral ceramics, integral polymers, metal ceramics and metal polymers bridges. In order to discover the defects, scanning was performed from incisal, vestibular, oral and cervical directions material defects such as fractures and pores were investigated using OCT. In conclusion, en-face OCT has proven as a valuable non invasive method to investigate fixed partial prostheses before their insertion in the oral cavity.

Morphological aspects of myocardial bridges.

PubMed

Lujinović, Almira; Kulenović, Amela; Kapur, Eldan; Gojak, Refet

2013-11-01

Although some myocardial bridges can be asymptomatic, their presence often causes coronary disease either through direct compression of the "tunnel" segment or through stimulation and accelerated development of atherosclerosis in the segment proximally to the myocardial bridge. The studied material contained 30 human hearts received from the Department of Anatomy. The hearts were preserved 3 to 5 days in 10% formalin solution. Thereafter, the fatty tissue was removed and arterial blood vessels prepared by careful dissection with special reference to the presence of the myocardial bridges. Length and thickness of the bridges were measured by the precise electronic caliper. The angle between the myocardial bridge fibre axis and other axis of the crossed blood vessel was measured by a goniometer. The presence of the bridges was confirmed in 53.33% of the researched material, most frequently (43.33%) above the anterior interventricular branch. The mean length of the bridges was 14.64 ± 9.03 mm and the mean thickness was 1.23 ± 1.32 mm. Myocardial bridge fibres pass over the descending blood vessel at the angle of 10-90 degrees. The results obtained on a limited sample suggest that the muscular index of myocardial bridge is the highest for bridges located on RIA, but that the difference is not significant in relation to bridges located on other branches. The results obtained suggest that bridges located on other branches, not only those on RIA, could have a great contractive power and, consequently, a great compressive force, which would be exerted on the wall of a crossed blood vessel.

Two-photon or higher-order absorbing optical materials and methods of use

NASA Technical Reports Server (NTRS)

Perry, Joseph (Inventor); Marder, Seth (Inventor)

2001-01-01

Compositions capable of simultaneous two-photon absorption and higher order absorptivities are disclosed. Many of these compositions are compounds satisfying the formulae D-.PI.-D, A-.PI.-A, D-A-D and A-D-A, wherein D is an electron donor group, A is an electron acceptor group and .PI. comprises a bridge of .pi.-conjugated bonds connecting the electron donor groups and electron acceptor groups. In A-D-A and D-A-D compounds, the .pi. bridge is substituted with electron donor groups and electron acceptor groups, respectively. Also disclosed are methods that generate an electronically excited state of a compound, including those satisfying one of these formulae. The electronically excited state is achieved in a method that includes irradiating the compound with light. Then, the compound is converted to a multi-photon electronically excited state upon simultaneous absorption of at least two photons of light. The sum of the energies of all of the absorbed photons is greater than or equal to the transition energy from a ground state of the compound to the multi-photon excited state. The energy of each absorbed photon is less than the transition energy between the ground state and the lowest single-photon excited state of the compound is less than the transition energy between the multi-photon excited state and the ground state.

[Preparation and structural analysis of diatomite-supported SPFS flocculant].

PubMed

Zheng, Huai-li; Fang, Hui-li; Jiang, Shao-jie; Yang, Chun; Ma, Jiang-ya; Zhang, Zhao-qing

2011-07-01

In the presetn study, polymerized ferric sulphate (PFS) flocculant was prepared and tested. In the preparation of PFS flocculant, industrial by-product ferrous sulfate heptahydrate (FeSO4.7H2O) was reused as the main material. By composition with diatomite and drying up at certain temperature in vacuum drying oven, solid PFS flocculant was produced. Structural characteristics of the new flocculant product were examined through infrared spectroscopy and scanning electron microscopy (SEM), which showed that by compositing with diatomite, new group bridging emerged in the structure of PFS, which made the bond of groups stronger. In addition, part of the metalic contents in diatomite was polymerized with PFS, the product of which was polymerized ferric complex. Furthermore, the absorbing and agglomerating capacity of the diatomite carrier was significant. Considering the factors listed above, the new solid polymerized ferric sulphate (SPFS) flocculant was characterized with a larger molecule structure and enhanced absorbing, bridging and rolling sweep capacities. Through orthogonal experiment, optimum conditions of synthesis were as follows: the ratio of FeSO4.7H2O/diatomite in weight was 43/1, the reaction time is 1 h and the reaction temperature is 55 degrees C. By wastewater treatment experiment, it was found that the synthetic products showed good flocculation performance in the treatment of domestic sewage, the removal of COD was 80.00% and the removal of turbidity was 99.98%.

Trilateral Design and Test Code for Military Bridging and Gap-Crossing Equipment

DTIC Science & Technology

2005-05-01

Property data should be provided for individual lamina and for the ( laminat - ed) composite . The required lamina properties are identified in...Resistance Welding ....... a Brazing ......................... X Machining ..................... a Chemical Composition : Element... Machining .................. b Chemical Composition : Element % Si .................................. 0.2 max Fe

Learning Bridge: Curricular Integration of Didactic and Experiential Education

PubMed Central

Arendt, Cassandra S.; Cawley, Pauline; Buhler, Amber V.; Elbarbry, Fawzy; Roberts, Sigrid C.

2010-01-01

Objectives To assess the impact of a program to integrate introductory pharmacy practice experiences with pharmaceutical science topics by promoting active learning, self-directed learning skills, and critical-thinking skills. Design The Learning Bridge, a curriculum program, was created to better integrate the material first-year (P1) students learned in pharmaceutical science courses into their introductory pharmacy practice experiences. Four Learning Bridge assignments required students to interact with their preceptors and answer questions relating to the pharmaceutical science material concurrently covered in their didactic courses. Assessment Surveys of students and preceptors were conducted to measure the effectiveness of the Learning Bridge process. Feedback indicated the Learning Bridge promoted students' interaction with their preceptors as well as development of active learning, self-directed learning, and critical-thinking skills. Students also indicated that the Learning Bridge assignments increased their learning, knowledge of drug information, and comprehension of relevant data in package inserts. Conclusion The Learning Bridge process integrated the didactic and experiential components of the curriculum, enhancing student learning in both areas, and offered students educational opportunities to interact more with their preceptors. PMID:20498741

Precast concrete deck panel performance on long span, high traffic volume bridges : final report.

DOT National Transportation Integrated Search

2006-02-01

The NHDOT prohibited the use of partial depth precast deck panels on its long span, high traffic volume bridges until it could investigate if the precast : slabs and the concrete overpour were acting in a composite manner. The NHDOT also wanted to en...

Structural Modification of Sol-Gel Materials through Retro Diels-Alder Reaction

DOE Office of Scientific and Technical Information (OSTI.GOV)

SHALTOUT,RAAFAT M.; LOY,DOUGLAS A.; MCCLAIN,MARK D.

1999-12-08

Hydrolysis and condensation of organically bridged bis-triethoxysilanes, (EtO){sub 3}Si-R-Si(OEt){sub 3}, results in the formation of three dimensional organic/inorganic hybrid networks (Equation 1). Properties of these materials, including porosity, are dependent on the nature of the bridging group, R. Flexible groups (akylene-spacers longer than five carbons in length) polymerize under acidic conditions to give non-porous materials. Rigid groups (such as arylene-, alkynylene-, or alkenylene) form non-porous, microporous, and macroporous gels. In many cases the pore size distributions are quite narrow. One of the motivations for preparing hybrid organic-inorganic materials is to extend the range of properties available with sol-gel systems bymore » incorporating organic groups into the inorganic network. For example, organically modified silica gels arc either prepared by co-polymerizing an organoalkoxysilane with a silica precursor or surface silylating the inorganic gel. This can serve to increase hydrophobicity or to introduce some reactive organic functionality. However, the type and orientation of these organic functionalities is difficult to control. Furthermore, many organoalkoxysilanes can act to inhibitor even prevent gelation, limiting the final density of organic functionalities. We have devised a new route for preparing highly functionalized pores in hybrid materials using bridging groups that are thermally converted into the desired functionalities after the gel has been obtained. In this paper, we present the preparation and characterization of bridged polysilsesquioxanes with Diels-Alder adducts as the bridging groups from the sol-gel polymerization of monomers 2 and 4. The bridging groups are constructed such that the retro Diela-Alder reaction releases the dienes and leaves the dienophiles as integral parts of the network polymers. In the rigid architecture of a xerogel, this loss of organic functionality should liberate sufficient space to modify the overall porosity. Furthermore, the new porosity will be functionalized with the dienophilic olefin bridging group. We also demonstrate that by changing the type of Diels-Alder adduct used as the bridging group, we can change the temperature at which the retro-Diels-Alder reaction will occur.« less

Repairing/strengthening of bridges with post-tensioned FRP materials and performance evaluation : [tech summary].

DOT National Transportation Integrated Search

2015-09-01

One of the challenges that transportation agencies are facing is keeping bridges in good condition during their : service life. Numerous bridges are classi ed as structurally and/or functionally de cient in the country. In the : state of Louisi...

Evaluation of Effects of Fire on the I-465 Mainline Bridges : Volume II [Technical Summary

DOT National Transportation Integrated Search

2012-01-01

Steel bridges are occasionally subjected to fire events : due to accidents or explosions of vehicles containing : flammable materials. Significant bridge fire events have : occurred in the recent past. In order to assist with the investigation : of d...

Voluntary Consensus Organization Standards for Nondestructive Evaluation of Thin-Walled Metallic Liners and Composite Overwraps in Composite Overwrapped Pressure Vessels

NASA Technical Reports Server (NTRS)

Waller, Jess; Saulsberry, Regor

2012-01-01

NASA fracture control requirements outlined in NASA-STD-5009 and NASA-STD-5014 are predicated on the availability and use of sensitive nondestructive evaluation (NDE) methods that can detect and monitor defects, thereby providing data that can be used to predict failure or reduce the risk of failure in fracture critical components. However, in the case of composite materials and components, including composite overwrapped pressure vessels (COPVs), the effect of defects is poorly understood, the NDE methods used to evaluate locate and size defects are typically at lower technical readiness level than analogous NDE methods used for metals, and demonstration studies to verify the probability of detection (POD) are generally lacking or unavailable. These factors together make failure prediction of fracture critical composite materials and components based on size, quantity, or orientation of defects nearly impossible. Also, when inspecting metal liners in as-manufactured COPVs, sensitivity is lost and only the inner surface of the liner is accessible. Also, NDE of COPVs as applied during manufacturing varies significantly from manufacturer to manufacturer and has not yet been standardized. Although requirements exist to perform NDE immediately after manufacturing to establish initial integrity of the parts, procedural detail for NDE of composites is still nonexistent or under development. For example, in practice, only a visual inspection of COPVs is performed during manufacturing and service, leaving in question whether defects of concern, for example, bridging, overwrap winding anomalies, impact damage below visible threshold, out-of-family strain growth, and liner buckling have been adequately detected and monitored. To address these shortcomings, in 2005 the NASA Nondestructive Evaluation Working Group (NNWG) began funding work to develop and adopt standards for nondestructive evaluation of aerospace composites in collaboration with the American Society for Testing and Materials (ASTM) Committee E07 on Nondestructive Testing. Similarly, in 2006 the NASA Engineering and Safety Center (NESC) recommended that nondestructive evaluation methods that can predict composite failure in COPVs should be developed and verified, and integrated into the damage control plan for these vessels

Morphological characterization of dental prostheses interfaces using optical coherence tomography

NASA Astrophysics Data System (ADS)

Sinescu, Cosmin; Negrutiu, Meda L.; Ionita, Ciprian; Marsavina, Liviu; Negru, Radu; Caplescu, Cristiana; Bradu, Adrian; Topala, Florin; Rominu, Roxana O.; Petrescu, Emanuela; Leretter, Marius; Rominu, Mihai; Podoleanu, Adrian G.

2010-03-01

Fixed partial prostheses as integral ceramic, polymers, metal-ceramic or metal-polymers bridges are mainly used in the frontal part of the dental arch (especially the integral bridges). They have to satisfy high stress as well as esthetic requirements. The masticatory stress may induce fractures of the bridges. These may be triggered by initial materials defects or by alterations of the technological process. The fractures of these bridges lead to functional, esthetic and phonetic disturbances which finally render the prosthetic treatment inefficient. Dental interfaces represent one of the most significant aspects in the strength of the dental prostheses under the masticatory load. The purpose of this study is to evaluate the capability of optical coherence tomography (OCT) to characterize the dental prostheses interfaces. The materials used were several fixed partial prostheses integral ceramic, polymers, metal-ceramic and metal-polymers bridges. It is important to produce both C-scans and B-scans of the defects in order to differentiate morphological aspects of the bridge infrastructures. The material defects observed with OCT were investigated with micro-CT in order to prove their existence and positions. In conclusion, it is important to have a non invasive method to investigate dental prostheses interfaces before the insertion of prostheses in the oral cavity.

[Research on the aging of all-ceramics restoration materials].

PubMed

Zhang, Dongjiao; Chen, Xinmin

2011-10-01

All-ceramic crowns and bridges have been widely used for dental restorations owing to their excellent functionality, aesthetics and biocompatibility. However, the premature clinical failure of all-ceramic crowns and bridges may easily occur when they are subjected to the complex environment of oral cavity. In the oral environment, all-ceramic materials are prone to aging. Aging can lead all-ceramic materials to change color, to lower bending strength, and to reduce anti-fracture toughness. There are many factors affecting the aging of the all-ceramic materials, for example, the grain size, the type of stabilizer, the residual stress and the water environment. In order to analyze the aging behavior, to optimize the design of all-ceramic crowns and bridges, and to evaluate the reliability and durability, we review in this paper recent research progress of aging behavior for all-ceramics restoration materials.

From brittle to ductile fracture of bone

NASA Astrophysics Data System (ADS)

Peterlik, Herwig; Roschger, Paul; Klaushofer, Klaus; Fratzl, Peter

2006-01-01

Toughness is crucial to the structural function of bone. Usually, the toughness of a material is not just determined by its composition, but by the ability of its microstructure to dissipate deformation energy without propagation of the crack. Polymers are often able to dissipate energy by viscoplastic flow or the formation of non-connected microcracks. In ceramics, well-known toughening mechanisms are based on crack ligament bridging and crack deflection. Interestingly, all these phenomena were identified in bone, which is a composite of a fibrous polymer (collagen) and ceramic nanoparticles (carbonated hydroxyapatite). Here, we use controlled crack-extension experiments to explain the influence of fibre orientation on steering the various toughening mechanisms. We find that the fracture energy changes by two orders of magnitude depending on the collagen orientation, and the angle between collagen and crack propagation direction is decisive in switching between different toughening mechanisms.

Fundamental analysis of the failure of polymer-based fiber reinforced composites

NASA Technical Reports Server (NTRS)

Kanninen, M. F.; Rybicki, E. F.; Griffith, W. I.; Broek, D.

1975-01-01

A mathematical model predicting the strength of unidirectional fiber reinforced composites containing known flaws and with linear elastic-brittle material behavior was developed. The approach was to imbed a local heterogeneous region surrounding the crack tip into an anisotropic elastic continuum. This (1) permits an explicit analysis of the micromechanical processes involved in the fracture, and (2) remains simple enough to be useful in practical computations. Computations for arbitrary flaw size and orientation under arbitrary applied loads were performed. The mechanical properties were those of graphite epoxy. With the rupture properties arbitrarily varied to test the capabilities of the model to reflect real fracture modes, it was shown that fiber breakage, matrix crazing, crack bridging, matrix-fiber debonding, and axial splitting can all occur during a period of (gradually) increasing load prior to catastrophic failure. The calculations also reveal the sequential nature of the stable crack growth process proceding fracture.

The Effect of Fiber Architecture on Matrix Cracking in Sic/sic Cmc's

NASA Technical Reports Server (NTRS)

Morscher, Gregory N.

2005-01-01

Applications incorporating silicon carbide fiber reinforced silicon carbide matrix composites (CMC's) will require a wide range of fiber architectures in order to fabricate complex shape. The stress-strain response of a given SiC/SiC system for different architectures and orientations will be required in order to design and effectively life-model future components. The mechanism for non-linear stress-strain behavior in CMC's is the formation and propagation of bridged-matrix cracks throughout the composite. A considerable amount of understanding has been achieved for the stress-dependent matrix cracking behavior of SiC fiber reinforced SiC matrix systems containing melt-infiltrated Si. This presentation will outline the effect of 2D and 3D architectures and orientation on stress-dependent matrix-cracking and how this information can be used to model material behavior and serve as the starting point foe mechanistic-based life-models.

Influence of fibre reinforcement on selected mechanical properties of dental composites.

PubMed

Niewczas, Agata M; Zamościńska, Jolanta; Krzyżak, Aneta; Pieniak, Daniel; Walczak, Agata; Bartnik, Grzegorz

2017-01-01

For splinting or designing adhesive bridges, reconstructive composite structures with increased mechanical properties owing to embedded reinforcement fibres are used. The aim of this article was to determine the influence of glass and aramid fibres on the mechanical strength of composites reinforced with these fibres. Two polymer-ceramic microhybrid materials: Boston and Herculite were tested. Three types of reinforcement fibres were used: aramid (Podwiązka) with a single layer weave, a single layer weave glass fibre (FSO) and triple layer weave glass fibre (FSO evo). Tests were conducted in accordance with the requirements of ISO 4049:2009. The following material types were chosen for research: Boston, Boston + Podwiązka, Herculite, Herculite + Podwiązka, Herculite + FSO and Herculite + FSO evo. The scope of research included: flexural strength B, bending modulus of elasticity εB and work to failure of the reinforced composite Wfb. Additionally, microscopic observations of fracture occurring in samples were made. In comparison: the Herculite (97.7 MPa) type with the Herculite + FSO evo (177.5 MPa) type was characterized by the highest strength. Fibre reinforcement resulted in decreasing the elasticity modulus: Herculite + reinforcement (6.86 GPa; 6.33 GPa; 6.11 GPa) in comparison with the Herculite (9.84 GPa) and respectively Boston + reinforcement (10.08 GPa) as compared with the Boston (11.81 GPa). Using glass fibres increases flexural strength of the test composites. Using aramid fibres does not change their strength. The elasticity modulus of the reinforced reconstructive structures decreases after application of either type of fibres. However, their resistance to the crack initiation increases.

Study of the toughening mechanisms in bone and biomimetic hydroxyapatite materials using Raman microprobe spectroscopy.

PubMed

Pezzotti, Giuseppe; Sakakura, Seiji

2003-05-01

A Raman microprobe spectroscopy characterization of microscopic fracture mechanisms is presented for a natural hydroxyapatite material (cortical bovine femur) and two synthetic hydroxyapatite-based materials with biomimetic structures-a hydroxyapatite skeleton interpenetrated with a metallic (silver) or a polymeric (nylon-6) phase. In both the natural and synthetic materials, a conspicuous amount of toughening arose from a microscopic crack-bridging mechanism operated by elasto-plastic stretching of unbroken second-phase ligaments along the crack wake. This mechanism led to a rising R-curve behavior. An additional micromechanism, responsible for stress relaxation at the crack tip, was recognized in the natural bone material and was partly mimicked in the hydroxyapatite/silver composite. This crack-tip mechanism conspicuously enhanced the cortical bone material resistance to fracture initiation. A piezo-spectroscopic technique, based on a microprobe measurement of 980 cm(-1) Raman line of hydroxyapatite, enabled us to quantitatively assess in situ the microscopic stress fields developed during fracture both at the crack tip and along the crack wake. Using the Raman piezo-spectroscopy technique, toughening mechanisms were assessed quantitatively and rationally related to the macroscopic fracture characteristics of hydroxyapatite-based materials. Copyright 2003 Wiley Periodicals, Inc.

Method for melting glass by measurement of non-bridging oxygen

DOEpatents

Jantzen, Carol M.

1992-01-01

A method for making better quality molten glass in a glass melter, the glass having the desired viscosity and, preferably, also the desired resistivity so that the glass melt can be established effectively and the product of the glass melter will have the desired level of quality. The method includes the adjustment of the composition of the glass constituents that are fed into the melter in accordance with certain correlations that reliably predict the viscosity and resistivity from the melter temperature and the melt composition, then heating the ingredients to the melter's operating temperature until they melt and homogenize. The equations include the calculation of a "non-bridging oxygen" term from the numbers of moles of the various ingredients, and then the determination of the viscosity and resistivity from the operating temperature of the melter and the non-bridging oxygen term.

Use of wood in buildings and bridges

Treesearch

Russell C. Moody; Anton TenWolde

1999-01-01

In North America, most housing and commercial structures built prior to the 20th century used wood as the major structural material. The abundant wood resource formed the basic structure for most houses, commercial buildings, bridges, and utility poles. Today, houses and many light commercial and industrial buildings are made using modern wood structural materials....

Cross-bridge kinetics of fast and slow fibres of cat jaw and limb muscles: correlations with myosin subunit composition.

PubMed

Hoh, Joseph F Y; Li, Zhao-Bo; Qin, Han; Hsu, Michael K H; Rossmanith, Gunther H

2007-01-01

Mechanical properties of the jaw-closing muscles of the cat are poorly understood. These muscles are known to differ in myosin and fibre type compositions from limb muscles. This work aims to correlate mechanical properties of single fibres in cat jaw and limb muscles with their myosin subunit compositions. The stiffness minimum frequency, f(min), which reflects isometric cross-bridge kinetics, was measured in Ca(2+)-activated glycerinated fast and slow fibres from cat jaw and limb muscles for temperatures ranging between 15 and 30 degrees C by mechanical perturbation analysis. At 15 degrees C, f(min) was 0.5 Hz for limb-slow fibres, 4-6 Hz for jaw-slow fibres, and 10-13 Hz for limb-fast and jaw-fast fibres. The activation energy for f(min) obtained from the slope of the Arrhenius plot for limb-slow fibres was 30-40% higher than values for the other three types of fibres. SDS-PAGE and western blotting using highly specific antibodies verified that limb-fast fibres contained IIA or IIX myosin heavy chain (MyHC). Jaw-fast fibres expressed masticatory MyHC while both jaw-fast and jaw-slow fibres expressed masticatory myosin light chains (MLCs). The nucleotide sequences of the 3' ends of the slow MyHC cDNAs isolated from cat masseter and soleus cDNA libraries showed identical coding and 3'-untranslated regions, suggesting that jaw-slow and limb-slow fibres express the same slow MyHC gene. We conclude that the isometric cross-bridge cycling kinetics of jaw-fast and limb-fast fibres detected by f(min) are indistinguishable in spite of differences in MyHC and light chain compositions. However, jaw-slow fibres, in which the same slow MyHCs are found in combination with MLCs of the jaw type, show enhanced cross-bridge cycling kinetics and reduced activation energy for cross-bridge detachment.

The effects of anisotropy on the nonlinear behavior of bridged cracks in long strips

NASA Technical Reports Server (NTRS)

Ballarini, R.; Luo, H. A.

1994-01-01

A model which can be used to predict the two-dimensional nonlinear behavior of bridged cracks in orthotropic strips is presented. The results obtained using a singular integral equation formulation which incorporates the anisotropy rigorously show that, although the effects of anisotropy are significant, the nondimensional quantities employed by Cox and Marshall can generate nearly universal results (R-curves, for example) for different levels of relative anisotropy. The role of composite constituent properties in the behavior of bridged cracks is clarified.

Mirror Support

NASA Technical Reports Server (NTRS)

Baron, Richard L. (Inventor)

2013-01-01

Disclosed herein is a method of making a mirror support comprising a composite, the composite comprising a plurality of carbon nanotubes, wherein at least two of the plurality of carbon nanotubes are bonded to each other through a bridging moiety bound to each of the two carbon nanotubes, and a laminate comprising the composite.

An evaluation of two bridge deck overlay systems on the Rte. 85 bridges over the Roanoke River.

DOT National Transportation Integrated Search

1971-01-01

Because of exposed reinforcing steel in some areas of the decks, the interstate route 85 bridges over the Roanoke River were treated with overlays in August 1969. In order to evaluate two different materials on a comparative basis, the Department of ...

Experimental verification of the influence of time-dependent material properties on long-term bridge characteristics.

DOT National Transportation Integrated Search

2006-08-01

Post-tensioned cast-in-place box girder bridges are commonly used in California. Losses in tension in : the steel prestressing tendons used in these bridges occur over time due to creep and shrinkage of : concrete and relaxation of the tendons. The u...

Bridging the Gap: Linking Simulation and Testing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Krajewski, Paul E.; Carsley, John; Stoudt, Mark R.

2012-09-01

The Materials Genome Initiative (MGI) which is a key enabler for the Advanced Manufacturing Partnership, announced in 2011 by U.S. President Barack Obama, was established to accelerate the development and deployment of advanced materials. The MGI is driven by the need to "bridge the gap" between (I) experimental results and computational analysis to enable the rapid development and validation of new mateirals, and (II) the processes required to convert these materials into useable goods.

Separators used in microbial electrochemical technologies: Current status and future prospects.

PubMed

Daud, Siti Mariam; Kim, Byung Hong; Ghasemi, Mostafa; Daud, Wan Ramli Wan

2015-11-01

Microbial electrochemical technologies (METs) are emerging green processes producing useful products from renewable sources without causing environmental pollution and treating wastes. The separator, an important part of METs that greatly affects the latter's performance, is commonly made of Nafion proton exchange membrane (PEM). However, many problems have been identified associated with the Nafion PEM such as high cost of membrane, significant oxygen and substrate crossovers, and transport of cations other than protons protons and biofouling. A variety of materials have been offered as alternative separators such as ion-exchange membranes, salt bridges, glass fibers, composite membranes and porous materials. It has been claimed that low cost porous materials perform better than PEM. These include J-cloth, nylon filter, glass fiber mat, non-woven cloth, earthen pot and ceramics that enable non-ion selective charge transfer. This paper provides an up-to-date review on porous separators and plots directions for future studies. Copyright © 2015 Elsevier Ltd. All rights reserved.

Methods for Detecting Defects in Composite Rehabilitated Concrete Structures : Final Report

DOT National Transportation Integrated Search

2005-04-01

Fiber reinforced polymer (FRP) composites are increasingly being used to rehabilitate under-strength or deteriorating concrete structural elements and to prolong useful service-life of bridge structures. The rehabilitation is conducted through the ex...

Research notes : durability of composite repairs on bridges.

DOT National Transportation Integrated Search

2009-08-01

The research showed that conditions that allow moisture to get under the carbon fiber reinforced polymer composites (CFRP) combined with freeze-thaw were detrimental to durability. In addition, the results showed that the American Concrete Institute ...

Structural Assessment of Externally Strengthened Bridge Deck Panels

NASA Astrophysics Data System (ADS)

Sim, Jongsung; Oh, Hongseob; Meyer, Christian

2006-03-01

Deteriorated concrete bridge decks are strengthened with external bonding technique using either steel plate or various FRPs to enhance the decreased load carrying capacity and serviceability. But the failure characteristics of bridge decks strengthened with various materials can be changed according to mechanical properties of strengthening materials or strengthening scheme as well as the strengthening amount. In this paper, strengthening effect of deck strengthened with carbon fiber sheets, glass fiber sheets or steel plates is compared. And the theoretical load carrying capacity are evaluated using yield line theory and punching shear model properly modified for the strengthened RC member. The panels strengthened with sheet type FRP materials failed more often in a ductile mode, indicating that the failure developed after the rebar yielded.

Characterization of gas tunnel type plasma sprayed hydroxyapatite-nanostructure titania composite coatings

NASA Astrophysics Data System (ADS)

Yugeswaran, S.; Kobayashi, A.; Ucisik, A. Hikmet; Subramanian, B.

2015-08-01

Hydroxyapatite (HA) can be coated onto metal implants as a ceramic biocompatible coating to bridge the growth between implants and human tissue. Meanwhile many efforts have been made to improve the mechanical properties of the HA coatings without affecting its bioactivity. In the present study, nanostructure titania (TiO2) was mixed with HA powder and HA-nanostructure TiO2 composite coatings were produced by gas tunnel type plasma spraying torch under optimized spraying conditions. For this purpose, composition of 10 wt% TiO2 + 90 wt% HA, 20 wt% TiO2 + 80 wt% HA and 30 wt% TiO2 + 70 wt% HA were selected as the feedstock materials. The phase, microstructure and mechanical properties of the coatings were characterized. The obtained results validated that the increase in weight percentage of nanostructure TiO2 in HA coating significantly increased the microhardness, adhesive strength and wear resistance of the coatings. Analysis of the in vitro bioactivity and cytocompatibility of the coatings were done using conventional simulated body fluid (c-SBF) solution and cultured green fluorescent protein (GFP) labeled marrow stromal cells (MSCs) respectively. The bioactivity results revealed that the composite coating has bio-active surface with good cytocompatibility.

Interfacial Materials for Organic Solar Cells: Recent Advances and Perspectives

PubMed Central

Yin, Zhigang; Wei, Jiajun

2016-01-01

Organic solar cells (OSCs) have shown great promise as low‐cost photovoltaic devices for solar energy conversion over the past decade. Interfacial engineering provides a powerful strategy to enhance efficiency and stability of OSCs. With the rapid advances of interface layer materials and active layer materials, power conversion efficiencies (PCEs) of both single‐junction and tandem OSCs have exceeded a landmark value of 10%. This review summarizes the latest advances in interfacial layers for single‐junction and tandem OSCs. Electron or hole transporting materials, including metal oxides, polymers/small‐molecules, metals and metal salts/complexes, carbon‐based materials, organic‐inorganic hybrids/composites, and other emerging materials, are systemically presented as cathode and anode interface layers for high performance OSCs. Meanwhile, incorporating these electron‐transporting and hole‐transporting layer materials as building blocks, a variety of interconnecting layers for conventional or inverted tandem OSCs are comprehensively discussed, along with their functions to bridge the difference between adjacent subcells. By analyzing the structure–property relationships of various interfacial materials, the important design rules for such materials towards high efficiency and stable OSCs are highlighted. Finally, we present a brief summary as well as some perspectives to help researchers understand the current challenges and opportunities in this emerging area of research. PMID:27812480

Boundary condition identification for a grid model by experimental and numerical dynamic analysis

NASA Astrophysics Data System (ADS)

Mao, Qiang; Devitis, John; Mazzotti, Matteo; Bartoli, Ivan; Moon, Franklin; Sjoblom, Kurt; Aktan, Emin

2015-04-01

There is a growing need to characterize unknown foundations and assess substructures in existing bridges. It is becoming an important issue for the serviceability and safety of bridges as well as for the possibility of partial reuse of existing infrastructures. Within this broader contest, this paper investigates the possibility of identifying, locating and quantifying changes of boundary conditions, by leveraging a simply supported grid structure with a composite deck. Multi-reference impact tests are operated for the grid model and modification of one supporting bearing is done by replacing a steel cylindrical roller with a roller of compliant material. Impact based modal analysis provide global modal parameters such as damped natural frequencies, mode shapes and flexibility matrix that are used as indicators of boundary condition changes. An updating process combining a hybrid optimization algorithm and the finite element software suit ABAQUS is presented in this paper. The updated ABAQUS model of the grid that simulates the supporting bearing with springs is used to detect and quantify the change of the boundary conditions.

Method for melting glass by measurement of non-bridging oxygen

DOEpatents

Jantzen, C.M.

1992-04-07

A method is described for making better quality molten glass in a glass melter, the glass having the desired viscosity and, preferably, also the desired resistivity so that the glass melt can be established effectively and the product of the glass melter will have the desired level of quality. The method includes the adjustment of the composition of the glass constituents that are fed into the melter in accordance with certain correlations that reliably predict the viscosity and resistivity from the melter temperature and the melt composition, then heating the ingredients to the melter's operating temperature until they melt and homogenize. The equations include the calculation of a non-bridging oxygen' term from the numbers of moles of the various ingredients, and then the determination of the viscosity and resistivity from the operating temperature of the melter and the non-bridging oxygen term. 4 figs.

Effect of neutron-irradiation on optical properties of SiO2-Na2O-MgO-Al2O3 glasses

NASA Astrophysics Data System (ADS)

Sandhu, Amanpreet Kaur; Singh, Surinder; Pandey, Om Prakash

2009-07-01

Silica based glasses are used as nuclear shielding materials. The effect of radiation on these glasses varies as per the constituents used in these glasses. Glasses of different composition of SiO2-Na2OMgO-Al2O3 were made by melt casting techniques. These glasses were irradiated with neutrons of different fluences. Optical absorption measurements of neutron-irradiated silica based glasses were performed at room temperature (RT) to detect and characterize the induced radiation damage in these materials. The absorption band found for neutron-irradiated glasses are induced by hole type color centers related to non-bridging oxygen ions (NBO) located in different surroundings of glass matrix. Decrease in the transmittance indicates the formation of color-center defects. Values for band gap energy and the width of the energy tail above the mobility gap have been measured before and after irradiation. The band gap energy has been found to decrease with increasing fluence while the Urbach energy shows an increase. The effects of the composition of the glasses on these parameters have been discussed in detail in this paper.

Structural comparison of Ag-Ge-S bulk glasses and thin films

NASA Astrophysics Data System (ADS)

Wang, Fei; Jain, Mukul; Dunn, Porter; de Leo, Carter; Boolchand, Punit

2007-03-01

Ternary glasses of composition (GeS3)1-xAgx (x=0.1 and 0.2) are studied in form of bulk and thin films. Bulk glasses are synthesized and examined in Raman scattering and SEM. Raman scattering results of bulk glasses show that with increasing x, an increasing fraction of the Ag additive enters the base glass as Ag^+ with S^-anions serving to form thiogermanate species with one, two and three non-bridging S^- species. SEM measurements of the bulk glass show the material is intrinsically phase separated. White colored islands are observed distributed in a dark base. The EDS measurements show islands are Ag rich and the base is relatively Ag deficient. The Ag rich islands are expected to be mainly glassy phase Ag2S. Thin films of same compositions are fabricated using thermal evaporation. Films are evaporated following two different procedures to prevent the material from spitting. One method was preheating outgas and the other method was using tungsten mesh wrapped boats. The stoichiometry and molecular structure of films under each procedure are analyzed by Raman scattering and SEM to be compared with bulk glasses.

Effects of Fragmentation and Sea-Level Changes upon Frog Communities of Land-Bridge Islands off the Southeastern Coast of Brazil

PubMed Central

Bittencourt-Silva, Gabriela B.; Silva, Hélio R.

2014-01-01

We investigate the composition of anuran communities of land-bridge islands off the southeastern coast of Brazil. These islands provide natural long-term experiments on the effects of fragmentation in the Brazilian Atlantic Forest (BAF). We hypothesize that Pleistocene sea-level changes, in combination with other abiotic variables such as area and habitat diversity, has affected anuran species richness and community composition on these islands. Data from the literature and collections databases were used to produce species lists for eight land-bridge islands and for the mainland adjacent to the islands. We assess the effects of area, number of breeding habitats and distance to the mainland upon anuran species richness on land-bridge islands. Additionally we use nestedness analysis to quantify the extent to which the species on smaller and less habitat-diverse islands correspond to subsets of those on larger and more diverse ones. We found that area has both direct and indirect effects on anuran species richness on land-bridge islands, irrespective of distance to the mainland. However, on islands with comparable sizes, differences in species richness can be attributed to the number and quality of breeding habitats. Anuran communities on these islands display a nested pattern, possibly caused by selective extinction related to habitat loss. Common lowland pond-breeders were conspicuous by their absence. In the BAF, the conservation of fragments with a high diversity of breeding habitats could compensate for the generally negative effect of small area upon species richness. We suggest that sea-level changes have an important role in shaping composition of anuran species on coastal communities. PMID:25068643

Multi-physics damage sensing in nano-engineered structural composites.

PubMed

de Villoria, Roberto Guzmán; Yamamoto, Namiko; Miravete, Antonio; Wardle, Brian L

2011-05-06

Non-destructive evaluation techniques can offer viable diagnostic and prognostic routes to mitigating failures in engineered structures such as bridges, buildings and vehicles. However, existing techniques have significant drawbacks, including poor spatial resolution and limited in situ capabilities. We report here a novel approach where structural advanced composites containing electrically conductive aligned carbon nanotubes (CNTs) are ohmically heated via simple electrical contacts, and damage is visualized via thermographic imaging. Damage, in the form of cracks and other discontinuities, usefully increases resistance to both electrical and thermal transport in these materials, which enables tomographic full-field damage assessment in many cases. Characteristics of the technique include the ability for real-time measurement of the damage state during loading, low-power operation (e.g. 15 °C rise at 1 W), and beyond state-of-the-art spatial resolution for sensing damage in composites. The enhanced thermographic technique is a novel and practical approach for in situ monitoring to ascertain structural health and to prevent structural failures in engineered structures such as aerospace and automotive vehicles and wind turbine blades, among others.

Enhancement mechanisms of graphene in nano-58S bioactive glass scaffold: mechanical and biological performance

PubMed Central

Gao, Chengde; Liu, Tingting; Shuai, Cijun; Peng, Shuping

2014-01-01

Graphene is a novel material and currently popular as an enabler for the next-generation nanocomposites. Here, we report the use of graphene to improve the mechanical properties of nano-58S bioactive glass for bone repair and regeneration. And the composite scaffolds were fabricated by a homemade selective laser sintering system. Qualitative and quantitative analysis demonstrated the successful incorporation of graphene into the scaffold without obvious structural damage and weight loss. The optimum compressive strength and fracture toughness reached 48.65 ± 3.19 MPa and 1.94 ± 0.10 MPa·m1/2 with graphene content of 0.5 wt%, indicating significant improvements by 105% and 38% respectively. The mechanisms of pull-out, crack bridging, crack deflection and crack tip shielding were found to be responsible for the mechanical enhancement. Simulated body fluid and cell culture tests indicated favorable bioactivity and biocompatibility of the composite scaffold. The results suggest a great potential of graphene/nano-58S composite scaffold for bone tissue engineering applications. PMID:24736662

Multi-physics damage sensing in nano-engineered structural composites

NASA Astrophysics Data System (ADS)

Guzmán de Villoria, Roberto; Yamamoto, Namiko; Miravete, Antonio; Wardle, Brian L.

2011-05-01

Non-destructive evaluation techniques can offer viable diagnostic and prognostic routes to mitigating failures in engineered structures such as bridges, buildings and vehicles. However, existing techniques have significant drawbacks, including poor spatial resolution and limited in situ capabilities. We report here a novel approach where structural advanced composites containing electrically conductive aligned carbon nanotubes (CNTs) are ohmically heated via simple electrical contacts, and damage is visualized via thermographic imaging. Damage, in the form of cracks and other discontinuities, usefully increases resistance to both electrical and thermal transport in these materials, which enables tomographic full-field damage assessment in many cases. Characteristics of the technique include the ability for real-time measurement of the damage state during loading, low-power operation (e.g. 15 °C rise at 1 W), and beyond state-of-the-art spatial resolution for sensing damage in composites. The enhanced thermographic technique is a novel and practical approach for in situ monitoring to ascertain structural health and to prevent structural failures in engineered structures such as aerospace and automotive vehicles and wind turbine blades, among others.

High-temperature transverse fracture toughness of Nicalon-fiber-reinforced CAS-II glass-ceramic matrix composite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kahraman, R.; Mandell, J.F.; Deibert, M.C.

Cracking parallel to the fibers in off-axis plies is usually the initial form of damage in composite laminates. This cracking process has been associated with the (transverse) fracture toughness, defined by the critical strain energy release rate, G{sub Ic}. The measurement of G{sub Ic} provides basic information about the transverse crack resistance. In this study, the utility of the double torsion (DT) test technique to determine G{sub Ic} in a glass-ceramic matrix composite (Nicalon/CAS-II) at temperatures up to 1,000 C has been demonstrated. G{sub Ic} did decrease moderately with increasing temperature (as does the bulk matrix); however, no evidence ofmore » an interphase oxidizing effect on crack growth (parallel to the fibers) could be found. The inevitable misalignment of fibers in the material was not very efficient at bridging the crack in the DT specimens, in contrast to the significant matrix crack interactions with the fibers reported for other geometries such as double cantilever beam and flexure specimens.« less

Perspective: Web-based machine learning models for real-time screening of thermoelectric materials properties

NASA Astrophysics Data System (ADS)

Gaultois, Michael W.; Oliynyk, Anton O.; Mar, Arthur; Sparks, Taylor D.; Mulholland, Gregory J.; Meredig, Bryce

2016-05-01

The experimental search for new thermoelectric materials remains largely confined to a limited set of successful chemical and structural families, such as chalcogenides, skutterudites, and Zintl phases. In principle, computational tools such as density functional theory (DFT) offer the possibility of rationally guiding experimental synthesis efforts toward very different chemistries. However, in practice, predicting thermoelectric properties from first principles remains a challenging endeavor [J. Carrete et al., Phys. Rev. X 4, 011019 (2014)], and experimental researchers generally do not directly use computation to drive their own synthesis efforts. To bridge this practical gap between experimental needs and computational tools, we report an open machine learning-based recommendation engine (http://thermoelectrics.citrination.com) for materials researchers that suggests promising new thermoelectric compositions based on pre-screening about 25 000 known materials and also evaluates the feasibility of user-designed compounds. We show this engine can identify interesting chemistries very different from known thermoelectrics. Specifically, we describe the experimental characterization of one example set of compounds derived from our engine, RE12Co5Bi (RE = Gd, Er), which exhibits surprising thermoelectric performance given its unprecedentedly high loading with metallic d and f block elements and warrants further investigation as a new thermoelectric material platform. We show that our engine predicts this family of materials to have low thermal and high electrical conductivities, but modest Seebeck coefficient, all of which are confirmed experimentally. We note that the engine also predicts materials that may simultaneously optimize all three properties entering into zT; we selected RE12Co5Bi for this study due to its interesting chemical composition and known facile synthesis.

Development and construction of low-cracking high-performance concrete (LC-HPC) bridge decks : free shrinkage, moisture optimization and concrete production : final report.

DOT National Transportation Integrated Search

2009-08-01

The development and evaluation of low-cracking high-performance concrete (LC-HPC) for use in bridge decks : is described based on laboratory test results and experience gained during the construction of 14 bridges. This report : emphasizes the materi...

Development and construction of low-cracking high-performance concrete (LC-HPC) bridge decks : free shrinkage, moisture optimization and concrete production : summary report.

DOT National Transportation Integrated Search

2009-08-01

The development and evaluation of low-cracking high-performance concrete (LC-HPC) for use in bridge decks : is described based on laboratory test results and experience gained during the construction of 14 bridges. This report : emphasizes the materi...

Measuring Nanomaterial Release from Carbon Nanotube Composites: Review of the State of the Science

NASA Astrophysics Data System (ADS)

Harper, Stacey; Wohlleben, Wendel; Doa, Maria; Nowack, Bernd; Clancy, Shaun; Canady, Richard; Maynard, Andrew

2015-05-01

Hazard studies of “as-produced” nanomaterials are increasingly available, yet a critical gap exists in exposure science that may impede safe development of nanomaterials. The gap is that we do not understand what is actually released because nanomaterials can change when released in ways that are not understood. We also generally do not have methods capable of quantitatively measuring what is released to support dose assessment. This review presents a case study of multi-walled carbon nanotubes (MWCNTs) for the measurement challenge to bridge this gap. As the use and value of MWCNTs increases, methods to measure what is released in ways relevant to risk evaluation are critically needed if products containing these materials are to be economically, environmentally, and socially sustainable. This review draws on the input of over 50 experts engaged in a program of workshops and technical report writing to address the release of MWCNTs from nanocomposite materials across their life cycle. The expert analyses reveals that new and sophisticated methods are required to measure and assess MWCNT exposures for realistic exposure scenarios. Furthermore, method requirements vary with the materials and conditions of release across life cycle stages of products. While review shows that the likelihood of significant release of MWCNTs appears to be low for many stages of composite life cycle, measurement methods are needed so that exposures from MWCNT-composites are understood and managed. In addition, there is an immediate need to refocus attention from study of “as-produced” nanomaterials to coordinated research on actual release scenarios.

Inter-wall bridging induced peeling of multi-walled carbon nanotubes during tensile failure in aluminum matrix composites.

PubMed

Chen, Biao; Li, Shufeng; Imai, Hisashi; Umeda, Junko; Takahashi, Makoto; Kondoh, Katsuyoshi

2015-02-01

In situ scanning electron microscopy (SEM) observation of a tensile test was performed to investigate the fracturing behavior of multi-walled carbon nanotubes (MWCNTs) in powder metallurgy Al matrix composites. A multiple peeling phenomenon during MWCNT fracturing was clearly observed. Its formation mechanism and resultant effect on the composite strength were examined. Through transition electron microscopy characterizations, it was observed that defective structures like inter-wall bridges cross-linked adjacent walls of MWCNTs. This structure was helpful to improve the inter-wall bonding conditions, leading to the effective load transfer between walls and resultant peeling behaviors of MWCNTs. These results might provide new understandings of the fracturing mechanisms of carbon nanotube reinforcements for designing high-performance nanocomposites. Copyright © 2014 Elsevier Ltd. All rights reserved.

Concept Development Modular Hybrid Pier (MHP)

DTIC Science & Technology

2000-02-01

rated FRP composite bridge or bridge deck is commercially available from Creative Pultrusions, Kansas Structural Systems, Martin - Marietta , Hardcore...NAVAL FACILITIES ENGINEERING SERVICE CENTER Port Hueneme, California 93043-4370 Contract Report CR 00-001-SHR FINAL REPORT PHASE 1 - CONCEPT...20000301 043 Approved for public release; distribution is unlimited. DTIC QUALITY IMWSOfBD 4 ^^ Printed on recycled paper REPORT DOCUMENTATION PAGE

Development of steel design details and selection criteria for cost effective and innovative steel bridges in Colorado : CDOT study no. 85-00 final report.

DOT National Transportation Integrated Search

2011-07-01

This research focuses on finding a method for creating cost effective and innovative steel bridges in Colorado. The design method that was discovered to create this cost efficiency was designing the beams as simply supported for non-composite dead lo...

Validation of Material Models For Automotive Carbon Fiber Composite Structures Via Physical And Crash Testing (VMM Composites Project)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Coppola, Anthony; Faruque, Omar; Truskin, James F

As automotive fuel economy requirements increase, the push for reducing overall vehicle weight will likely include the consideration of materials that have not previously been part of mainstream vehicle design and manufacturing, including carbon fiber composites. Vehicle manufacturers currently rely on computer-aided engineering (CAE) methods as part of the design and development process, so going forward, the ability to accurately and predictably model carbon fiber composites will be necessary. If composites are to be used for structural components, this need applies to both, crash and quasi-static modeling. This final report covers the results of a five-year, $6.89M, 50% cost-shared researchmore » project between Department of Energy (DOE) and the US Advanced Materials Partnership (USAMP) under Cooperative Agreement DE-EE-0005661 known as “Validation of Material Models for Automotive Carbon Fiber Composite Structures Via Physical and Crash Testing (VMM).” The objective of the VMM Composites Project was to validate and assess the ability of physics-based material models to predict crash performance of automotive primary load-carrying carbon fiber composite structures. Simulation material models that were evaluated included micro-mechanics based meso-scale models developed by the University of Michigan (UM) and micro-plane models by Northwestern University (NWU) under previous collaborations with the DOE and Automotive Composites Consortium/USAMP, as well as five commercial crash codes: LS-DYNA, RADIOSS, VPS/PAM-CRASH, Abaqus, and GENOA-MCQ. CAE predictions obtained from seven organizations were compared with experimental results from quasi-static testing and dynamic crash testing of a thermoset carbon fiber composite front-bumper and crush-can (FBCC) system gathered under multiple loading conditions. This FBCC design was developed to demonstrate progressive crush, virtual simulation, tooling, fabrication, assembly, non-destructive evaluation and crash testing advances in order to assess the correlation of the predicted results to the physical tests. The FBCC was developed to meet a goal of 30-35% mass reduction while aiming for equivalent energy absorption as a steel component for which baseline experimental results were obtained from testing in the same crash modes. The project also evaluated crash performance of thermoplastic composite structures fabricated from commercial prepreg materials and low cost carbon fiber sourced from Oak Ridge National Laboratory. The VMM Project determined that no set of predictions from a CAE supplier were found to be universally accurate among all the six crash modes evaluated. In general, crash modes that were most dependent on the properties of the prepreg were more accurate than those that were dependent on the behavior of the joints. The project found that current CAE modeling methods or best practices for carbon fiber composites have not achieved standardization, and accuracy of CAE is highly reliant on the experience of its users. Coupon tests alone are not sufficient to develop an accurate material model, but it is necessary to bridge the gap between the coupon data and performance of the actual structure with a series of subcomponent level tests. Much of the unreliability of the predictions can be attributed to shortcomings in our ability to mathematically link the effects of manufacturing and material variability into the material models. This is a subject of ongoing research in the industry. The final report is organized by key technical tasks to describe how the validation project developed, modeled and compared crash data obtained on the composite FBCC to the multiple sets of CAE predictions. Highlights of the report include a discussion of the quantitative comparison between predictions and experimental data, as well as an in-depth discussion of remaining technological gaps that exist in the industry, which are intended to spur innovations and improvements in CAE technology.« less

A low-ignition energy, SCB, thermite igniter

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bickes, R.W. Jr.; Grubelich, M.C.; Wackerbarth, D.E.

1996-06-01

The authors describe threshold ignition studies for semiconductor bridge, SCB, ignition of aluminum/copper oxide (Al/CuO) thermite as a function of the capacitor discharge unit (CDU) firing set discharge capacitance, the charge holder material and the morphology of the CuO. All of the tests were carried out with the devices cooled to 0 F ({minus}18 C). They compared ignition thresholds using a brass charge holder and a G10 charge holder; G10 is a non-conducting, fiber-glass-epoxy composite material. They determined that at 50 V on the discharge capacitor, the thresholds were 30.1 {micro}F and 2.0 {micro}F respectively. The tests revealed that differentmore » CuO morphologies affected the function time (interval between start of the firing set current and the output of the thermite device) but did not significantly affect the threshold sensitivity.« less

Improving Sorbents for Glycerol Capture in Biodiesel Refinement

PubMed Central

Johnson, Brandy J.; Melde, Brian J.; Moore, Martin H.; Malanoski, Anthony P.; Taft, Jenna R.

2017-01-01

Biodiesel is produced by transesterification of animal fat, vegetable oil, or waste cooking oil with alcohol. After production costs, the economic viability of biodiesel is dependent on what steps are necessary to remove impurities following synthesis and the effectiveness of quality control analysis. Solid-phase extraction offers a potentially advantageous approach in biodiesel processing applications. Nanoporous scaffolds were investigated for adsorption of glycerol, a side product of biodiesel synthesis that is detrimental to engine combustion when present. Materials were synthesized with varying pore wall composition, including ethane and diethylbenzene bridging groups, and sulfonated to promote hydrogen bonding interactions with glycerol. Materials bearing sulfonate groups throughout the scaffold walls as well as those post-synthetically grafted onto the surfaces show notably superior performance for uptake of glycerol. The sorbents are effective when used in biodiesel mixtures, removing greater than 90% of glycerol from a biodiesel preparation. PMID:28773042

Improving Sorbents for Glycerol Capture in Biodiesel Refinement.

PubMed

Johnson, Brandy J; Melde, Brian J; Moore, Martin H; Malanoski, Anthony P; Taft, Jenna R

2017-06-21

Biodiesel is produced by transesterification of animal fat, vegetable oil, or waste cooking oil with alcohol. After production costs, the economic viability of biodiesel is dependent on what steps are necessary to remove impurities following synthesis and the effectiveness of quality control analysis. Solid-phase extraction offers a potentially advantageous approach in biodiesel processing applications. Nanoporous scaffolds were investigated for adsorption of glycerol, a side product of biodiesel synthesis that is detrimental to engine combustion when present. Materials were synthesized with varying pore wall composition, including ethane and diethylbenzene bridging groups, and sulfonated to promote hydrogen bonding interactions with glycerol. Materials bearing sulfonate groups throughout the scaffold walls as well as those post-synthetically grafted onto the surfaces show notably superior performance for uptake of glycerol. The sorbents are effective when used in biodiesel mixtures, removing greater than 90% of glycerol from a biodiesel preparation.

Hydraulic analysis of the Schoharie Creek bridge

USGS Publications Warehouse

Froehlich, David C.; Trent, Roy E.

1989-01-01

Ten people died on April 5, 1987 as a result of the collapse of two spans of a New York State Thruway bridge into the floodwaters of Schoharie Creek. The cause of the bridge failure was determined to be scour of bed material from under the foundations of piers supporting the bridge. To evaluate the hydraulic conditions that produced the scour, a two-dimensional finite element surface-water flow model was constructed. The model was used to obtain a detailed description of water-surface elevations and depth-averaged velocities within a reach that extends from about 4000 ft downstream of the bridge to about 6000 ft upstream of the bridge.

A novel method of temperature compensation for piezoresistive microcantilever-based sensors.

PubMed

Han, Jianqiang; Wang, Xiaofei; Yan, Tianhong; Li, Yan; Song, Meixuan

2012-03-01

Microcantilever with integrated piezoresistor has been applied to in situ surface stress measurement in the field of biochemical sensors. It is well known that piezoresistive cantilever-based sensors are sensitive to ambient temperature changing due to highly temperature-dependent piezoresistive effect and mismatch in thermal expansion of composite materials. This paper proposes a novel method of temperature drift compensation for microcantilever-based sensors with a piezoresistive full Wheatstone bridge integrated at the clamped ends by subtracting the amplified output voltage of the reference cantilever from the output voltage of the sensing cantilever through a simple temperature compensating circuit. Experiments show that the temperature drift of microcantilever sensors can be significantly reduced by the method.

3D printing of concentrated emulsions into multiphase biocompatible soft materials.

PubMed

Sommer, Marianne R; Alison, Lauriane; Minas, Clara; Tervoort, Elena; Rühs, Patrick A; Studart, André R

2017-03-01

3D printing via direct ink writing (DIW) is a versatile additive manufacturing approach applicable to a variety of materials ranging from ceramics over composites to hydrogels. Due to the mild processing conditions compared to other additive manufacturing methods, DIW enables the incorporation of sensitive compounds such as proteins or drugs into the printed structure. Although emulsified oil-in-water systems are commonly used vehicles for such compounds in biomedical, pharmaceutical, and cosmetic applications, printing of such emulsions into architectured soft materials has not been fully exploited and would open new possibilities for the controlled delivery of sensitive compounds. Here, we 3D print concentrated emulsions into soft materials, whose multiphase architecture allows for site-specific incorporation of both hydrophobic and hydrophilic compounds into the same structure. As a model ink, concentrated emulsions stabilized by chitosan-modified silica nanoparticles are studied, because they are sufficiently stable against coalescence during the centrifugation step needed to create a bridging network of droplets. The resulting ink is ideal for 3D printing as it displays high yield stress, storage modulus and elastic recovery, through the formation of networks of droplets as well as of gelled silica nanoparticles in the presence of chitosan. To demonstrate possible architectures, we print biocompatible soft materials with tunable hierarchical porosity containing an encapsulated hydrophobic compound positioned in specific locations of the structure. The proposed emulsion-based ink system offers great flexibility in terms of 3D shaping and local compositional control, and can potentially help address current challenges involving the delivery of incompatible compounds in biomedical applications.

Food composition databases

USDA-ARS?s Scientific Manuscript database

Food composition is the determination of what is in the foods we eat and is the critical bridge between nutrition, health promotion and disease prevention and food production. Compilation of data into useable databases is essential to the development of dietary guidance for individuals and populat...

Coaxial Lithography

NASA Astrophysics Data System (ADS)

Ozel, Tuncay

The optical and electrical properties of heterogeneous nanowires are profoundly related to their composition and nanoscale architecture. However, the intrinsic constraints of conventional synthetic and lithographic techniques have limited the types of multi-compositional nanowires that can be realized and studied in the laboratory. This thesis focuses on bridging templated electrochemical synthesis and lithography for expanding current synthetic capabilities with respect to materials generality and the ability to tailor two-dimensional growth in the formation of core-shell structures for the rational design and preparation of nanowires with very complex architectures that cannot be made by any other techniques. Chapter 1 introduces plasmonics, templated electrochemical synthesis, and on-wire lithography concepts and their significances within chemistry and materials science. Chapter 2 details a powerful technique for the deposition of metals and semiconductors with nanometer resolution in segment and gap lengths using on-wire lithography, which serves as a new platform to explore plasmon-exciton interactions in the form of long-range optical nanoscale rulers. Chapter 3 highlights an approach for the electrochemical synthesis of solution dispersible core-shell polymeric and inorganic semiconductor nanowires with metallic leads. A photodetector based on a single core-shell semiconductor nanowire is presented to demonstrate the functionality of the nanowires produced using this approach. Chapter 4 describes a new materials general technique, termed coaxial lithography (COAL), bridging templated electrochemical synthesis and lithography for generating coaxial nanowires in a parallel fashion with sub-10 nanometer resolution in both axial and radial dimensions. Combinations of coaxial nanowires composed of metals, metal oxides, metal chalcogenides, conjugated polymers, and a core/shell semiconductor nanowire with an embedded plasmonic nanoring are presented to demonstrate the possibilities afforded by COAL. Chapter 5 addresses the use of COAL for the synthesis of solution dispersible metal nanorings and nanotubes with exceptional architectural tailorability of inner diameter, outer diameter, and length leading to precise spectral control over the resulting plasmonic fields ranging from visible to the near-IR. Chapter 6 is an outlook on templated electrochemical synthesis using coaxial lithography and highlights a few promising applications from nanoparticle assembly to light-matter interactions.

75 FR 54069 - Drawbridge Operation Regulations; Curtis Creek, Baltimore, MD

Federal Register 2010, 2011, 2012, 2013, 2014

2010-09-03

... Baltimore, MD. The requested change would have allowed the bridge to operate from a remote location at the...) 398-6629, e-mail [email protected] . If you have questions on viewing material in the... eliminating the need for a bridge tender by allowing the bridge to be operated from a remote location at the...

Fabrication and calibration of a piezoelectric nanocomposite paint

NASA Astrophysics Data System (ADS)

Osho, Samuel; Wu, Nan; Aramfard, Mohammad; Deng, Chuang; Ojo, Olanrewaju

2018-03-01

A new liquid form piezoelectric nanocomposite paint material is fabricated with possible applications as dynamic strain sensors and/or piezoelectric transducers. The applied coating is in the form of low-cost paint, which is flexible and bonds strongly on a metallic surface after drying out via the solvent-casting method. The nanocomposite is produced by an ultrasonic mixture of varying percentages of zinc oxide (ZnO) nanoparticle water dispersion, poly vinyl acetate glue (PVA) and carbon nanotubes (CNTs). ZnO nanoparticles are used as the piezoelectric sensing elements in a PVA matrix of the paint, while CNTs are introduced as robust bridge of ZnO particles enhancing the piezoelectricity and material properties. Transmission electron microscopy (TEM) images confirmed the linkages of ZnO nanoparticles in the composite by CNTs. Through piezoelectricity calibration, the optimum mixing ratio with the highest piezoelectricity is 78.1 wt% ZnO, 19.5 wt% PVA glue and 2.4 wt% multi-wall carbon nanotubes (MWCNTs). Through nanoindentation tests for the characterization of the mechanical properties of the nano-composite paint, it is found that Young’s modulus and hardness reached a threshold point in the increment in the addition of CNTs to the paint before showing signs of decline. Detailed analysis and explanation of the calibration results and physical phenomenon are provided. The stable paint material is ready to be applied on rough area of engineering structures as sensor and transducer.

49 CFR 236.1021 - Discontinuances, material modifications, and amendments.

Code of Federal Regulations, 2011 CFR

2011-10-01

... such as landslide, burned bridge, high water, high and wide load, or tunnel protection when the unusual... to provide protection against unusual contingencies such as landslide, burned bridges, high water...

49 CFR 236.1021 - Discontinuances, material modifications, and amendments.

Code of Federal Regulations, 2010 CFR

2010-10-01

... such as landslide, burned bridge, high water, high and wide load, or tunnel protection when the unusual... to provide protection against unusual contingencies such as landslide, burned bridges, high water...

Improved bridge joint materials and design details.

DOT National Transportation Integrated Search

2017-06-01

Expansion joints accommodate bridge movements that result from factors such as thermal expansion and contraction, concrete shrinkage, creep effects, live loading, settlement of the foundation and substructure, and environmental stressors. Expansion j...

Key Royale bridge five year evaluation.

DOT National Transportation Integrated Search

2013-06-01

This report describes the design, construction, instrumentation, and five-year evaluation of the Key Royale Bridge substructure. The primary focus was the evaluation of the implementation of highly reactive supplementary cementitious materials (SCM) ...

49 CFR 236.1021 - Discontinuances, material modifications, and amendments.

Code of Federal Regulations, 2013 CFR

2013-10-01

... such as landslide, burned bridge, high water, high and wide load, or tunnel protection when the unusual... to provide protection against unusual contingencies such as landslide, burned bridges, high water...

49 CFR 236.1021 - Discontinuances, material modifications, and amendments.

Code of Federal Regulations, 2014 CFR

2014-10-01

... such as landslide, burned bridge, high water, high and wide load, or tunnel protection when the unusual... to provide protection against unusual contingencies such as landslide, burned bridges, high water...

49 CFR 236.1021 - Discontinuances, material modifications, and amendments.

Code of Federal Regulations, 2012 CFR

2012-10-01

... such as landslide, burned bridge, high water, high and wide load, or tunnel protection when the unusual... to provide protection against unusual contingencies such as landslide, burned bridges, high water...

Material characterization of field-cast connection grouts.

DOT National Transportation Integrated Search

2013-01-01

Accelerated bridge construction methods can help increase safety and minimize the inconveniences to the traveling public. Many new construction methods have been investigated and implemented using prefabricated subassemblies on bridges. These methods...

Westfall fiberglass bridge drain system.

DOT National Transportation Integrated Search

2013-03-01

VTrans Transportation District Administrators have asked the Agencys Structures Section to consider : using nonmetallic materials in bridge drainage systems. Fiberglass is inert to oil, gas, road salt, ice : melting : solutions and many other corr...

Current trends and future perspectives of bone substitute materials - from space holders to innovative biomaterials.

PubMed

Kolk, Andreas; Handschel, Jörg; Drescher, Wolf; Rothamel, Daniel; Kloss, Frank; Blessmann, Marco; Heiland, Max; Wolff, Klaus-Dietrich; Smeets, Ralf

2012-12-01

An autologous bone graft is still the ideal material for the repair of craniofacial defects, but its availability is limited and harvesting can be associated with complications. Bone replacement materials as an alternative have a long history of success. With increasing technological advances the spectrum of grafting materials has broadened to allografts, xenografts, and synthetic materials, providing material specific advantages. A large number of bone-graft substitutes are available including allograft bone preparations such as demineralized bone matrix and calcium-based materials. More and more replacement materials consist of one or more components: an osteoconductive matrix, which supports the ingrowth of new bone; and osteoinductive proteins, which sustain mitogenesis of undifferentiated cells; and osteogenic cells (osteoblasts or osteoblast precursors), which are capable of forming bone in the proper environment. All substitutes can either replace autologous bone or expand an existing amount of autologous bone graft. Because an understanding of the properties of each material enables individual treatment concepts this review presents an overview of the principles of bone replacement, the types of graft materials available, and considers future perspectives. Bone substitutes are undergoing a change from a simple replacement material to an individually created composite biomaterial with osteoinductive properties to enable enhanced defect bridging. Copyright © 2012 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.

Double Super-Exchange in Silicon Quantum Dots Connected by Short-Bridged Networks

NASA Astrophysics Data System (ADS)

Li, Huashan; Wu, Zhigang; Lusk, Mark

2013-03-01

Silicon quantum dots (QDs) with diameters in the range of 1-2 nm are attractive for photovoltaic applications. They absorb photons more readily, transport excitons with greater efficiency, and show greater promise in multiple-exciton generation and hot carrier collection paradigms. However, their high excitonic binding energy makes it difficult to dissociate excitons into separate charge carriers. One possible remedy is to create dot assemblies in which a second material creates a Type-II heterojunction with the dot so that exciton dissociation occurs locally. This talk will focus on such a Type-II heterojunction paradigm in which QDs are connected via covalently bonded, short-bridge molecules. For such interpenetrating networks of dots and molecules, our first principles computational investigation shows that it is possible to rapidly and efficiently separate electrons to QDs and holes to bridge units. The bridge network serves as an efficient mediator of electron superexchange between QDs while the dots themselves play the complimentary role of efficient hole superexchange mediators. Dissociation, photoluminescence and carrier transport rates will be presented for bridge networks of silicon QDs that exhibit such double superexchange. This material is based upon work supported by the Renewable Energy Materials Research Science and Engineering Center (REMRSEC) under Grant No. DMR-0820518 and Golden Energy Computing Organization (GECO).

Stability of aggregates in the environment: role of solid bridging

NASA Astrophysics Data System (ADS)

Seiphoori, A.; Jerolmack, D. J.; Arratia, P. E.

2017-12-01

Colloids in suspension may form larger flocs under favorable conditions, via diffusion- or reaction-limited aggregation. In addition, the process of drying colloidal suspensions drives colloids together via hydrodynamic forces to form aggregates, that may be stable or unstable when subject to re-wetting and transport. Channel banks, shorelines and hillslopes are examples where the periodic wetting and drying results in the aggregation of muds. If aggregates disperse, the mud structure is unstable to subsequent wetting or fluid shear and can easily be detached and transported to rivers and coasts. The effective friction that governs hillslope and channel-bank soil creep rates also depends on the stability of the soil aggregates. Yet, few studies probe the particle-scale assembly or stability of aggregates subject to environmental loads, and the effects of shape or size heterogeneity have not been examined in detail. Here we investigate the formation and stability of aggregates subject to passive re-wetting (by misting) and shearing using a simple Poiseuille flow in a microfluidic device. We study the kinetics of a wide range of silicate colloids of different size and surface charge properties using in situ microscopy and particle tracking. We find that negatively charged silica microspheres are dragged by the retreating edge of an evaporating drop and are resuspended easily on re-wetting, showing that aggregates are unstable. In contrast, a bi-disperse suspension created by the addition of silica nanoparticles forms stable deposits, where nanoparticles bind larger particles by bridging the interparticle space, a mechanism similar to capillary bridging that we refer to as "solid bridging." Although aggregate structure and dynamics of the bi-disperse system changes quantitatively with surface-charge of the nanoparticles, smaller particles always conferred stability on the aggregates. Investigation of other colloids, including asbestos fibers and various clays, reveals that this solid bridging effect is robust across variations in particle shape and material composition. These experiments suggest that natural mud and soil may form more stable aggregates than would naively be expected by considering the charge effects alone, because their inherent size heterogeneity is conducive to solid bridging.

Optimizing Mississippi aggregates for concrete bridge decks.

DOT National Transportation Integrated Search

2012-12-01

AASHTO M 43 Standard Specification for Sizes of Aggregate for Road and Bridge Construction : addresses particle size distribution of material included in various maximum nominal size aggregates. This : particle size distribution requires additi...

Shrinkage and durability study of bridge deck concrete.

DOT National Transportation Integrated Search

2010-12-01

The Mississippi Department of Transportation is incorporating changes to material : specifications and construction procedures for bridge decks in an effort to reduce shrinkage : cracking. These changes are currently being implemented into a limited ...

GFRP reinforced concrete bridge decks

DOT National Transportation Integrated Search

2000-07-01

This report investigates the application of glass fiber reinforced polymer (GFRP) rebars in concrete bridge decks as a potential replacement or supplement to conventional steel rebars. Tests were conducted to determine the material properties of the ...

GFRP reinforced concrete bridge decks.

DOT National Transportation Integrated Search

2000-07-01

This report investigates the application of glass fiber reinforced polymer (GFRP) rebars in concrete bridge decks as a potential replacement or supplement to conventional steel rebars. Tests were conducted to determine the material properties of the ...

Differential temperature integrating diagnostic method and apparatus

DOEpatents

Doss, James D.; McCabe, Charles W.

1976-01-01

A method and device for detecting the presence of breast cancer in women by integrating the temperature difference between the temperature of a normal breast and that of a breast having a malignant tumor. The breast-receiving cups of a brassiere are each provided with thermally conductive material next to the skin, with a thermistor attached to the thermally conductive material in each cup. The thermistors are connected to adjacent arms of a Wheatstone bridge. Unbalance currents in the bridge are integrated with respect to time by means of an electrochemical integrator. In the absence of a tumor, both breasts maintain substantially the same temperature, and the bridge remains balanced. If the tumor is present in one breast, a higher temperature in that breast unbalances the bridge and the electrochemical cells integrate the temperature difference with respect to time.

A methodology to predict damage initiation, damage growth and residual strength in titanium matrix composites

NASA Technical Reports Server (NTRS)

Bakuckas, J. G., Jr.; Johnson, W. S.

1994-01-01

In this research, a methodology to predict damage initiation, damage growth, fatigue life, and residual strength in titanium matrix composites (TMC) is outlined. Emphasis was placed on micromechanics-based engineering approaches. Damage initiation was predicted using a local effective strain approach. A finite element analysis verified the prevailing assumptions made in the formulation of this model. Damage growth, namely, fiber-bridged matrix crack growth, was evaluated using a fiber bridging (FB) model which accounts for thermal residual stresses. This model combines continuum fracture mechanics and micromechanics analyses yielding stress-intensity factor solutions for fiber-bridged matrix cracks. It is assumed in the FB model that fibers in the wake of the matrix crack are idealized as a closure pressure, and an unknown constant frictional shear stress is assumed to act along the debond length of the bridging fibers. This frictional shear stress was used as a curve fitting parameter to the available experimental data. Fatigue life and post-fatigue residual strength were predicted based on the axial stress in the first intact 0 degree fiber calculated using the FB model and a three-dimensional finite element analysis.

Study on Construction Technology of Municipal Road and Bridge Concrete

NASA Astrophysics Data System (ADS)

Tang, Fuyong

2018-03-01

With the continuous development of social economy and the accelerating process of urbanization, municipal road and bridge projects have also shown a trend of rapid development. Municipal road and bridge work can fully reflect the economic and cultural development level of cities and is also an important symbol of urban development. As a basic material of construction, concrete is widely used in engineering construction. This article will analyze the municipal road and bridge concrete construction technology, put forward corresponding measures.

Development of a six-year research needs assessment for timber transportation structures

Treesearch

Terry J. Wipf; Michael A. Ritter; Sheila Rimal Duwadi; Russell C. Moody

1993-01-01

A timber bridge, once a thing of the past, is now becoming a thing of the present. Interest in timber bridges and other transportation structures has been rapidly increasing. Much of this is due to new technologies in design and construction as well as advances in material manufacturing and presevative treatments. Although timber bridges and other transportation...

Simplified Analytical Model for a Queen-Post Covered Timber Bridge

Treesearch

F Fanous; D. Rammer; T. Wipf

2013-01-01

During the 19th century, the economic material to build bridges was timber due to its abundant availability, cost, and ease of construction. Many of the well-known timber bridge types are the Burr arch, Town lattice, Howe, Queen and King type of trusses. This paper summarizes an investigation that was sponsored by the Federal Highway Administration and the USDA Forest...

Long term striping alternatives for bridge decks : final report, January 2009.

DOT National Transportation Integrated Search

2009-01-01

This study evaluated the performance of the following pavement marking materials on Portland cement concrete bridge decks: Waterborne traffic paint: Ennis fast dry waterborne traffic paint; Thermoplastic: Swarcotherm alkyd; Preformed thermoplastic: P...

Research notes : keeping bridges strong and handsome.

DOT National Transportation Integrated Search

1999-07-01

ODOT Research Unit, in collaboration with Oregon State University (OSU), are continuing to study fiber-reinforced polymer (FRP) materials as a cost-effective, structurally sound methodology for upgrading bridges. The decision to use this approach was...

Energy harvesting on highway bridges.

DOT National Transportation Integrated Search

2011-01-01

A concept for harvesting energy from the traffic-induced loadings on a highway bridge using piezoelectric : materials to generate electricity was explored through the prototype stage. A total of sixteen lead-zirconate : titanate (PZT) Type 5A piezoel...

Strategic sensor locations of FPR bridge decks

NASA Astrophysics Data System (ADS)

Wu, Hwai-Chung; Warnemuende, Kraig; Yan, An; Mu, Bin

2003-07-01

Advanced fiber-reinforced polymer composite (FRP) has been increasingly used in bridge deck to replace concrete or steel. A FRP bridge deck can be designed to meet AASHTO HS-25 load requirements. FRP decks have many advantages over the conventional reinforced concrete or steel decks owing to their lightweight, high strength and corrosion resistance. However, such new deck system requires extensive monitoring to ensure its designed performance before its widespread acceptance by the bridge community. For inspection and evaluation purpose, a proper monitoring system consisting of various kinds of sensors installed in the FRP deck is critical. This paper provides a framework for designing an efficient monitoring system. The strategic sensor locations are identified based on the stress analysis of the FRP deck.

Sol-gel derived polymer composites for energy storage and conversion

NASA Astrophysics Data System (ADS)

Han, Kuo

Sol-gel process is a simple chemistry to convert the small precursor molecules into an inorganic polymer, which could be applied to synthesize inorganic materials, modify the interface of materials, bridge the organic and inorganic materials, etc. In this dissertation, novel sol-gel derived composites have been developed for high dielectric breakdown capacitors, low high frequency loss capacitors and flexible piezoelectrics. Numerous efforts have been made in the past decades to improve the energy storage capability of composite materials by incorporating nanometer scale ceramic addictives with high dielectric permittivity into dielectric polymers with high breakdown strength. However, most composites suffer from the low breakdown strength and make the potential gain in energy density small. Here, a new chemical strategy is proposed that, through sol-gel reactions between ceramic precursors and functional groups at the end of the functionalized Poly(vinylidene fluoride -co-chlorotrifluoroethylene) chains, amorphous low permittivity ceramics was in-situ generated in the polymer matrix and cross-linked the polymer chains simultaneously. By carefully tuning precursors, the polymer/precursors feeding ratios, a series of nanocomposites were systematically designed. All the samples are comprehensively characterized and the structure-property correlations are well investigated. The optimal samples exhibit higher breakdown strength than the pristine polymer. The enhanced breakdown strength ascribed to low contrast in permittivity, great dispersion and improved electrical and mechanical properties. This newly developed approach has shown great promise for new composite capacitors. The percolative polymer composites have recently exhibited great potential in energy storage due to their high dielectric permittivities at the neighborhood of the percolation threshold. Yet high energy dissipation and poor voltage endurance of the percolative composites resulted from electrical conduction are still open issues to be addressed before full potential can be realized. Herein we report the percolative composites based on ferroelectric poly(vinylidene fluoride-co-chlorotrifluoroethylene) as the matrix and sol-gel derived SiO2 coated reduced graphene oxide nanosheets as the filler. By capitalizing on the SiO2 surface layers which have high electrical resistivity and breakdown strength, the composites exhibit superior dielectric performance as compared to the respective composites containing bare reduced graphene oxide nanosheet fillers. In addition to greatly reduced dielectric loss, little change in dielectric loss has been observed within medium frequency range (ie. 300 KHz-3 MHz) in the prepared composites even with a filler concentration beyond the percolation threshold, indicating significantly suppressed energy dissipation and the feasibility of using the conductor-insulator composites beyond the percolation threshold. Moreover, remarkable breakdown strength of 80 MV/m at the percolation threshold has been achieved in the composite, which far exceeds those of conventional percolative composites (lower than 0.1 MV/m in most cases) and thus enables the applications of the percolative composites at high electric fields. This work offers a new avenue to the percolative polymer composites exhibiting high permittivity, reduced loss and excellent breakdown strength for electrical energy storage applications. Flexible piezoelectric materials have attracted extensive attention because they can provide a practical way to scavenge energy from the environment and motions. It also provides the possibility to fabricate wearable and self-powered energy generator for powering small electronic devices. In the dissertation a new composite including BTO 3D structure and PDMS has been successfully fabricated using the sol-gel process. The structure, flexibility, dielectric and piezoelectric properties have been well studied. The new material shows a high g33 value of more than 400 mV m/N. Moreover, the durability of this composite has been confirmed by cycle tests even though the BTO structure falls apart into small pieces in the PDMS matrix. The unique morphology of the composite allows the broken piece to connect with each other to generate power under stress. This work also opens a new route toward flexible piezoelectric composites.

Push-out tests and evaluation of FRP perfobond rib shear connectors performance

NASA Astrophysics Data System (ADS)

Kolpasky, Ludvik; Ryjacek, Pavel

2017-09-01

The behavioural characteristics of FRP (fibre-reinforced polymer) perfobond rib shear connector was examined through push-out tests in order to verify the applicability for pedestrian bridge structure. The aim of this study is to determine interaction between high performance concrete slab and handmade FRP plate which represent web of the composite beam. Combination of these modern materials leads to structural system with both great load bearing capacity and also sufficient flexural stiffness of the composite element. Openings cut into the GFRP plate at a variable spacing allow GFRP reinforcement bars to be inserted to act as shear studs. Hand lay-up process can increase suitable properties of FRP for connection by perfobond rib shear connectors. In this study, three push-out tests on fiber-reinforced polymer were performed to investigate their shear behaviour. The results of the push-out tests on FRP perfobond rib shear connector indicates great promise for application in full scale structures.

Electrochemistry of redox-active self-assembled monolayers

PubMed Central

Eckermann, Amanda L.; Feld, Daniel J.; Shaw, Justine A.; Meade, Thomas J.

2010-01-01

Redox-active self-assembled monolayers (SAMs) provide an excellent platform for investigating electron transfer kinetics. Using a well-defined bridge, a redox center can be positioned at a fixed distance from the electrode and electron transfer kinetics probed using a variety of electrochemical techniques. Cyclic voltammetry, AC voltammetry, electrochemical impedance spectroscopy, and chronoamperometry are most commonly used to determine the rate of electron transfer of redox-activated SAMs. A variety of redox species have been attached to SAMs, and include transition metal complexes (e.g., ferrocene, ruthenium pentaammine, osmium bisbipyridine, metal clusters) and organic molecules (e.g., galvinol, C60). SAMs offer an ideal environment to study the outer-sphere interactions of redox species. The composition and integrity of the monolayer and the electrode material influence the electron transfer kinetics and can be investigated using electrochemical methods. Theoretical models have been developed for investigating SAM structure. This review discusses methods and monolayer compositions for electrochemical measurements of redox-active SAMs. PMID:20563297

Nanowired three-dimensional cardiac patches

NASA Astrophysics Data System (ADS)

Dvir, Tal; Timko, Brian P.; Brigham, Mark D.; Naik, Shreesh R.; Karajanagi, Sandeep S.; Levy, Oren; Jin, Hongwei; Parker, Kevin K.; Langer, Robert; Kohane, Daniel S.

2011-11-01

Engineered cardiac patches for treating damaged heart tissues after a heart attack are normally produced by seeding heart cells within three-dimensional porous biomaterial scaffolds. These biomaterials, which are usually made of either biological polymers such as alginate or synthetic polymers such as poly(lactic acid) (PLA), help cells organize into functioning tissues, but poor conductivity of these materials limits the ability of the patch to contract strongly as a unit. Here, we show that incorporating gold nanowires within alginate scaffolds can bridge the electrically resistant pore walls of alginate and improve electrical communication between adjacent cardiac cells. Tissues grown on these composite matrices were thicker and better aligned than those grown on pristine alginate and when electrically stimulated, the cells in these tissues contracted synchronously. Furthermore, higher levels of the proteins involved in muscle contraction and electrical coupling are detected in the composite matrices. It is expected that the integration of conducting nanowires within three-dimensional scaffolds may improve the therapeutic value of current cardiac patches.

Effects of metal binder on the microstructure and mechanical properties of Al2O3-based micro-nanocomposite ceramic tool material

NASA Astrophysics Data System (ADS)

Ni, Xiu-ying; Zhao, Jun; Sun, Jia-lin; Gong, Feng; Li, Zuo-li

2017-07-01

The Al2O3-(W,Ti)C composites with Ni and Mo additions varying from 0vol% to 12vol% were prepared via hot pressing sintering under 30 MPa. The microstructure was investigated via X-ray diffraction (XRD) and scanning electron microscopy (SEM) equipped with energy dispersive spectrometry (EDS). Mechanical properties such as flexural strength, fracture toughness, and Vickers hardness were also measured. Results show that the main phases A12O3 and (W,Ti)C were detected by XRD. Compound MoNi also existed in sintered nanocomposites. The fracture modes of the nanocomposites were both intergranular and transgranular fractures. The plastic deformation of metal particles and crack bridging were the main toughening mechanisms. The maximum flexural strength and fracture toughness were obtained for 9vol% and 12vol% additions of Ni and Mo, respectively. The hardness of the composites reduced gradually with increasing content of metals Ni and Mo.

Organic-inorganic Interface in Nacre: Learning Lessons from Nature

NASA Astrophysics Data System (ADS)

Rahbar, Nima; Askarinejad, Sina

Problem-solving strategies of naturally growing composites such as nacre give us a fantastic vision to design and fabricate tough, stiff while strong composites. To provide the outstanding mechanical functions, nature has evolved complex and effective functionally graded interfaces. Particularly in nacre, organic-inorganic interface in which the proteins behave stiffer and stronger in proximity of calcium carbonate minerals provide an impressive role in structural integrity and mechanical deformation of the natural composite. The well-known shear-lag theory was employed on a simplified two-dimensional unit-cell of the multilayered composite considering the interface properties. The closed-form solutions for the displacements in the elastic components as a function of constituent properties can be used to calculate the effective mechanical properties of composite such as elastic modulus, strength and work-to-failure. The results solve the important mysteries about nacre and emphasize on the role of organic-inorganic interface properties and mineral bridges. Our results show that the properties of proteins in proximity of mineral bridges are also significant. More studies need to be performed on the strategies to enhance the interface properties in manmade composites. NSF Career Award no. 1281264.

Analysis of the Shear Behavior of Stubby Y-Type Perfobond Rib Shear Connectors for a Composite Frame Structure.

PubMed

Kim, Sang-Hyo; Kim, Kun-Soo; Lee, Do-Hoon; Park, Jun-Seung; Han, Oneil

2017-11-22

Shear connectors are used in steel beam-concrete slabs of composite frame and bridge structures to transfer shear force according to design loads. The existing Y-type perfobond rib shear connectors are designed for girder slabs of composite bridges. Therefore, the rib and transverse rebars of the conventional Y-type perfobond rib shear connectors are extremely large for the composite frames of building structures. Thus, this paper proposes stubby Y-type perfobond rib shear connectors, redefining the existing connectors, for composite frames of building structures; these were used to perform push-out tests. These shear connectors have relatively small ribs compared to the conventional Y-type perfobond rib shear connectors. To confirm the shear resistance of these stubby shear connectors, we performed an experiment by using transverse rebars D13 and D16. The results indicate that these shear connectors have suitable shear strength and ductility for application in composite frame structures. The shear strengths obtained using D13 and D16 were not significantly different. However, the ductility of the shear connectors with D16 was 45.1% higher than that of the shear connectors with D13.

Evaluation of the color durability of acrylic resin veneer materials after immersion in common beverages at different time intervals: A spectrophotometric study.

PubMed

Kohli, Shivani; Bhatia, Shekhar

2015-01-01

Proper function, esthetics, and cost are the prime factors to be considered while selecting bridge veneering materials. The purpose of the study is to evaluate color durability of acrylic veneer materials after immersion in common beverages at different time intervals. Spectrophotometer was used for taking color measurements based on the transmission of light through the specimens made of the selected materials which were Tooth moulding powder (DPI) and Acrylux (Ruthinium). Thirty specimens of standardized dimensions were prepared from each material. The specimens were divided into three groups of 10 each. One group of each material was immersed in tea (TajMahal) and another group of each material in cola (Pepsi) as the staining solutions. The remaining group of 10 from each material served as control and was stored in distilled water. Color measurements were obtained pre-immersion, and after 1, 15, and 30 days of immersion. Tooth moulding powder displayed better color durability than Acrylux over the 1 month immersion period in both staining solutions. Tea resulted in more discoloration compared to cola (Pepsi). The difference in the color durability of Acrylux and Tooth moulding powder may be attributed to the differences in the composition of tested resin veneering materials, i.e. their polar properties, which contribute to the absorption of staining solution, and the different brands and the strengths of the solutions.

Self-Consolidating Concrete for Prestressed Bridge Girders

DOT National Transportation Integrated Search

2017-07-01

This document reports the findings of a research project designed to better understand material and structural performance of prestressed bridge girders made with Self-Consolidating Concrete (SCC) from Wisconsin. SCC has high potential to be used for...

Bridges Structural Health Monitoring and Deterioration Detection - Synthesis of Knowledge and Technology

DOT National Transportation Integrated Search

2010-12-01

Bridges are continuously subjected to destructive effects of material aging, widespread corrosion of steel : reinforcing bars in concrete structures, corrosion of steel structures and components, increasing traffic : volume and overloading, or simply...

Investigation of Prefabricated Steel-Truss Bridge Deck System

DOT National Transportation Integrated Search

2017-11-01

Steel truss bridges are an efficient and aesthetic option for highway crossings. Their relatively light weight compared with plate girder systems make them a desirable alternative for both material savings and constructability. A prototype of a welde...

Nano-catalysts: Bridging the gap between homogeneous and heterogeneous catalysis

EPA Science Inventory

Functionalized nanoparticles have emerged as sustainable alternatives to conventional materials, as robust, high-surface-area heterogeneous catalyst supports. We envisioned a catalyst system, which can bridge the homogenous and heterogeneous system. Postsynthetic surface modifica...

Designing added functions in engineered cementitious composites

NASA Astrophysics Data System (ADS)

Yang, En-Hua

In this dissertation, a new and systematic material design approach is developed for ECC with added functions through material microstructures linkage to composite macroscopic behavior. The thesis research embodies theoretical development by building on previous ECC micromechanical models, and experimental investigations into three specific new versions of ECC with added functions aimed at addressing societal demands of our built infrastructure. Specifically, the theoretical study includes three important ECC modeling elements: Steady-state crack propagation analyses and simulation, predictive accuracy of the fiber bridging constitutive model, and development of the rate-dependent strain-hardening criteria. The first element establishes the steady-state cracking criterion as a fundamental requirement for multiple cracking behavior in brittle matrix composites. The second element improves the accuracy of crack-width prediction in ECC. The third element establishes the micromechanics basis for impact-resistant ECC design. Three new ECCs with added functions were developed and experimentally verified in this thesis research through the enhanced theoretical framework. A green ECC incorporating a large volume of industrial waste was demonstrated to possess reduced crack width and drying shrinkage. The self-healing ECC designed with tight crack width was demonstrated to recover transport and mechanical properties after microcrack damage when exposed to wet and dry cycles. The impact-resistant ECC was demonstrated to retain tensile ductility with increased strength under moderately high strain-rate loading. These new versions of ECC with added functions are expected to contribute greatly to enhancing the sustainability, durability, and safety of civil infrastructure built with ECC. This research establishes the effectiveness of micromechanics-based design and material ingredient tailoring for ECC with added new attributes but without losing its basic tensile ductile characteristics.

Vertically oriented graphene bridging active-layer/current-collector interface for ultrahigh rate supercapacitors.

PubMed

Bo, Zheng; Zhu, Weiguang; Ma, Wei; Wen, Zhenhai; Shuai, Xiaorui; Chen, Junhong; Yan, Jianhua; Wang, Zhihua; Cen, Kefa; Feng, Xinliang

2013-10-25

Dense networks of graphene nanosheets standing vertically on a current collector can work as numerous electrically conductive bridges to facilitate charge transport and mitigate the constriction/spreading resistance at the interface between the active material and the current collector. The vertically oriented graphene-bridged supercapacitors present excellent rate and power capabilities. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The Collapse of the I-35W Bridge in Minneapolis

ERIC Educational Resources Information Center

Feldman, Bernard J.

2010-01-01

On Wednesday, Aug. 1, 2007, at 6:05 p.m. (during evening rush hour), the I-35W bridge across the Mississippi River in Minneapolis collapsed, killing 13 people and injuring 145. At the time of the collapse, repair work was in progress on the deck of the bridge, resulting in an additional 287 tons of construction material and equipment being on the…

Study on safety level of RC beam bridges under earthquake

NASA Astrophysics Data System (ADS)

Zhao, Jun; Lin, Junqi; Liu, Jinlong; Li, Jia

2017-08-01

This study considers uncertainties in material strengths and the modeling which have important effects on structural resistance force based on reliability theory. After analyzing the destruction mechanism of a RC bridge, structural functions and the reliability were given, then the safety level of the piers of a reinforced concrete continuous girder bridge with stochastic structural parameters against earthquake was analyzed. Using response surface method to calculate the failure probabilities of bridge piers under high-level earthquake, their seismic reliability for different damage states within the design reference period were calculated applying two-stage design, which describes seismic safety level of the built bridges to some extent.

Experimental evaluation and design of unfilled and concrete-filled FRP composite piles : Task 4A : design specifications.

DOT National Transportation Integrated Search

2015-08-01

The overall goal of this project is the experimental evaluation and design of unfilled and concrete-filled FRP composite piles for load-bearing in bridges. This report covers Task 4A, Design Specifications. : Structural design specifications are base...

Carbon nanofibers grafted on activated carbon as an electrode in high-power supercapacitors.

PubMed

Gryglewicz, Grażyna; Śliwak, Agata; Béguin, François

2013-08-01

A hybrid electrode material for high-power supercapacitors was fabricated by grafting carbon nanofibers (CNFs) onto the surface of powdered activated carbon (AC) through catalytic chemical vapor deposition (CCVD). A uniform thin layer of disentangled CNFs with a herringbone structure was deposited on the carbon surface through the decomposition of propane at 450 °C over an AC-supported nickel catalyst. CNF coating was controlled by the reaction time and the nickel content. The superior CNF/AC composite displays excellent electrochemical performance in a 0.5 mol L(-1) solution of K2 SO4 due to its unique structure. At a high scan rate (100 mV s(-1) ) and current loading (20 A g(-1) ), the capacitance values were three- and fourfold higher than those for classical AC/carbon black composites. Owing to this feature, a high energy of 10 Wh kg(-1) was obtained over a wide power range in neutral medium at a voltage of 0.8 V. The significant enhancement of charge propagation is attributed to the presence of herringbone CNFs, which facilitate the diffusion of ions in the electrode and play the role of electronic bridges between AC particles. An in situ coating of AC with short CNFs (below 200 nm) is a very attractive method for producing the next generation of carbon composite materials with a high power performance in supercapacitors working in neutral medium. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Inclined Fiber Pullout from a Cementitious Matrix: A Numerical Study

PubMed Central

Zhang, Hui; Yu, Rena C.

2016-01-01

It is well known that fibers improve the performance of cementitious composites by acting as bridging ligaments in cracks. Such bridging behavior is often studied through fiber pullout tests. The relation between the pullout force vs. slip end displacement is characteristic of the fiber-matrix interface. However, such a relation varies significantly with the fiber inclination angle. In the current work, we establish a numerical model to simulate the entire pullout process by explicitly representing the fiber, matrix and the interface for arbitrary fiber orientations. Cohesive elements endorsed with mixed-mode fracture capacities are implemented to represent the bond-slip behavior at the interface. Contact elements with Coulomb’s friction are placed at the interface to simulate frictional contact. The bond-slip behavior is first calibrated through pull-out curves for fibers aligned with the loading direction, then validated against experimental results for steel fibers oriented at 30∘ and 60∘. Parametric studies are then performed to explore the influences of both material properties (fiber yield strength, matrix tensile strength, interfacial bond) and geometric factors (fiber diameter, embedment length and inclination angle) on the overall pullout behavior, in particular on the maximum pullout load. The proposed methodology provides the necessary pull-out curves for a fiber oriented at a given angle for multi-scale models to study fracture in fiber-reinforced cementitious materials. The novelty lies in its capacity to capture the entire pullout process for a fiber with an arbitrary inclination angle. PMID:28773921

Inclined Fiber Pullout from a Cementitious Matrix: A Numerical Study.

PubMed

Zhang, Hui; Yu, Rena C

2016-09-26

It is well known that fibers improve the performance of cementitious composites by acting as bridging ligaments in cracks. Such bridging behavior is often studied through fiber pullout tests. The relation between the pullout force vs. slip end displacement is characteristic of the fiber-matrix interface. However, such a relation varies significantly with the fiber inclination angle. In the current work, we establish a numerical model to simulate the entire pullout process by explicitly representing the fiber, matrix and the interface for arbitrary fiber orientations. Cohesive elements endorsed with mixed-mode fracture capacities are implemented to represent the bond-slip behavior at the interface. Contact elements with Coulomb's friction are placed at the interface to simulate frictional contact. The bond-slip behavior is first calibrated through pull-out curves for fibers aligned with the loading direction, then validated against experimental results for steel fibers oriented at 30 ∘ and 60 ∘ . Parametric studies are then performed to explore the influences of both material properties (fiber yield strength, matrix tensile strength, interfacial bond) and geometric factors (fiber diameter, embedment length and inclination angle) on the overall pullout behavior, in particular on the maximum pullout load. The proposed methodology provides the necessary pull-out curves for a fiber oriented at a given angle for multi-scale models to study fracture in fiber-reinforced cementitious materials. The novelty lies in its capacity to capture the entire pullout process for a fiber with an arbitrary inclination angle.

Recent approaches for bridging the pressure gap in photoelectron microspectroscopy

PubMed Central

Kolmakov, Andrei; Gregoratti, Luca; Kiskinova, Maya; Günther, Sebastian

2016-01-01

Ambient-pressure photoelectron spectroscopy (APPES) and microscopy are at the frontier of modern chemical analysis at liquid-gas, solid-liquid and solid-gas interfaces, bridging science and engineering of functional materials. Complementing the current state-of-the art of the instruments, we survey in this short review several alternative APPES approaches, developed recently in the scanning photoelectron microscope (SPEM) at the Elettra laboratory. In particular, we report on experimental setups for dynamic near-ambient pressure environment, using pulsed-gas injection in the vicinity of samples or reaction cells with very small apertures, allowing for experiments without introducing additional differential pumping stages. The major part of the review is dedicated to the construction and performance of novel environmental cells using ultrathin electron-transparent but molecularly impermeable membranes to isolate the gas or liquid ambient from the electron detector operating in ultra-high vacuum (UHV). We demonstrate that two dimensional materials, such as graphene and derivatives, are mechanically robust to withstand atmospheric - UHV pressure differences and are sufficiently transparent for the photoelectrons emitted from samples immersed in the liquid or gaseous media. There are many unique opportunities for APPES using X-rays over a wide energy range. We show representative results that illustrate the potential of these ‘ambient-pressure’ approaches. Combined with the ca 100 nm lateral resolution of SPEM, they can overcome the pressure gap challenges and address the evolution of chemical composition and electronic structure at surface and interfaces under realistic operation conditions with unprecedented lateral and spectral resolution. PMID:28008215

Use of lightweight concrete for reducing cracks in bridge decks.

DOT National Transportation Integrated Search

2016-04-01

Cracks in bridge decks can be due to many factors related to environmental effects, chemical reactions, and structural : loads. Careful selection of materials and mixture proportions can minimize cracking to some degree. To reduce cracking, : shrinka...

Evaluating scour at bridges.

DOT National Transportation Integrated Search

1995-11-01

This document is the third of HEC 18, i.e., presents the state of knowledge and practice for the design, : evaluation, and inspection of bridges for scour. It contains updated material not included in the second : edition dated April 1993. This docum...

Repair methods for prestressed girder bridges.

DOT National Transportation Integrated Search

2009-04-30

It is common practice that aging and structurally damaged prestressed concrete bridge members are taken out of service and replaced. : This, however, is not an efficient use of materials and resources since the member can often be repaired in situ. T...

78 FR 13747 - Safety Advisory 2013-01; Passing Stop Signals Protecting Movable Bridges

Federal Register 2010, 2011, 2012, 2013, 2014

2013-02-28

... 82 freight cars, including 51 hazardous materials tank cars, derailed seven cars while crossing a... bridge to close using the key pad on the locomotive radio. Through the use of a programmable logic...

New LowP bridge overlays performing well in St. Louis area.

DOT National Transportation Integrated Search

2010-01-01

Closing bridge decks for rehabilitation is an inconvenience for Missouri motorists. MoDOT is aggressively pursuing alternate materials to speed up this process to provide a smooth pavement with minimal traffic interruptions. Unfortunately, many mater...

In-house fabrication of precast concrete bridge slabs.

DOT National Transportation Integrated Search

1976-01-01

Information is reported on the labor, equipment, material, and cost required for seven bridge maintenance situations in which state forces widened or replaced an existing short span structure. Precast concrete slabs were installed at three of the loc...

Visual inspection & capacity assessment of earthquake damaged reinforced concrete bridge elements.

DOT National Transportation Integrated Search

2008-11-01

The overarching objective of this project was to produce standard procedures and associated training materials, for the conduct of post-earthquake visual inspection and capacity assessment of damaged reinforced concrete (RC) bridges where the procedu...

Determining the Environmental Benefits of Ultra High Performance Concrete as a Bridge Construction Material

NASA Astrophysics Data System (ADS)

Lande Larsen, Ingrid; Granseth Aasbakken, Ida; O'Born, Reyn; Vertes, Katalin; Terje Thorstensen, Rein

2017-10-01

Ultra High Performance Concrete (UHPC) is a material that is attracting attention in the construction industry due to the high mechanical strength and durability, leading to structures having low maintenance requirements. The production of UHPC, however, has generally higher environmental impact than normal strength concrete due to the increased demand of cement required in the concrete mix. What is still not sufficiently investigated, is if the longer lifetime, slimmer construction and lower maintenance requirements lead to a net environmental benefit compared to standard concrete bridge design. This study utilizes life cycle assessment (LCA) to determine the lifetime impacts of two comparable highway crossing footbridges spanning 40 meters, designed respectively with UHPC and normal strength concrete. The results of the study show that UHPC is an effective material for reducing lifetime emissions from construction and maintenance of long lasting infrastructure, as the UHPC design outperforms the normal strength concrete bridge in most impact categories.

Application of fiber bridging models to fatigue crack growth in unidirectional titanium matrix composites

NASA Technical Reports Server (NTRS)

Bakuckas, J. G., Jr.; Johnson, W. S.

1992-01-01

Several fiber bridging models were reviewed and applied to study the matrix fatigue crack growth behavior in center notched (0)(sub 8) SCS-6/Ti-15-3 and (0)(sub 4) SCS-6/Ti-6Al-4V laminates. Observations revealed that fatigue damage consisted primarily of matrix cracks and fiber matrix interfacial failure in the (0)(sub 8) SCS-6/Ti-15-3 laminates. Fiber-matrix interface failure included fracture of the brittle reaction zone and cracking between the two carbon rich fiber coatings. Intact fibers in the wake of the matrix cracks reduce the stress intensity factor range. Thus, an applied stress intensity factor range is inappropriate to characterize matrix crack growth behavior. Fiber bridging models were used to determine the matrix stress intensity factor range in titanium metal matrix composites. In these models, the fibers in the wake of the crack are idealized as a closure pressure. An unknown constant frictional shear stress is assumed to act along the debond or slip length of the bridging fibers. The frictional shear stress was used as a curve fitting parameter to available data (crack growth data, crack opening displacement data, and debond length data). Large variations in the frictional shear stress required to fit the experimental data indicate that the fiber bridging models in their present form lack predictive capabilities. However, these models provide an efficient and relatively simple engineering method for conducting parametric studies of the matrix growth behavior based on constituent properties.

Making data matter: Voxel printing for the digital fabrication of data across scales and domains.

PubMed

Bader, Christoph; Kolb, Dominik; Weaver, James C; Sharma, Sunanda; Hosny, Ahmed; Costa, João; Oxman, Neri

2018-05-01

We present a multimaterial voxel-printing method that enables the physical visualization of data sets commonly associated with scientific imaging. Leveraging voxel-based control of multimaterial three-dimensional (3D) printing, our method enables additive manufacturing of discontinuous data types such as point cloud data, curve and graph data, image-based data, and volumetric data. By converting data sets into dithered material deposition descriptions, through modifications to rasterization processes, we demonstrate that data sets frequently visualized on screen can be converted into physical, materially heterogeneous objects. Our approach alleviates the need to postprocess data sets to boundary representations, preventing alteration of data and loss of information in the produced physicalizations. Therefore, it bridges the gap between digital information representation and physical material composition. We evaluate the visual characteristics and features of our method, assess its relevance and applicability in the production of physical visualizations, and detail the conversion of data sets for multimaterial 3D printing. We conclude with exemplary 3D-printed data sets produced by our method pointing toward potential applications across scales, disciplines, and problem domains.

Fiber-reinforced composite analysis using optical coherence tomography after mechanical and thermal cycling

NASA Astrophysics Data System (ADS)

Kyotoku, B. B. C.; Braz, A. K. S.; Braz, R.; Gomes, A. S. L.

2007-02-01

Fiber-reinforced composites are new materials which have been used for a variety of dental applications, including tooth splinting, replacement of missing teeth, treatment of dental emergencies, reinforcement of resin provisional fixed prosthodontic restorations, orthodontic retention, and other clinical applications. Different fiber types are available, but little clinical information has been disseminated. The traditional microscopy investigation, most commonly used to study this material, is a destructive technique, which requires specimen sectioning and are essentially surface measurements. On the basis of these considerations, the aim of this research is to analyze the interior of a dental sample reinforced with fiber after a mechanical and thermal cycling to emulate oral conditions using optical coherence tomography (OCT). The device we are using is a home built Fourier domain OCT working at 800 nm with 6 μm resolution. The results are compared with microscopy images to validate OCT as a working method. In long term, fractures allow bacterial invasion provoking plaque and calculus formation that can cause caries and periodontal disease. Therefore, non invasive imaging of the bridge fiber enables the possibility of periodic clinical evaluation to ensure the patient health. Furthermore, OCT images can provide a powerful method for quantitative analysis of crack propagation, and can potentially be used for in vivo assessment.

Carbon nanotube-based bioceramic grafts for electrotherapy of bone.

PubMed

Mata, D; Horovistiz, A L; Branco, I; Ferro, M; Ferreira, N M; Belmonte, M; Lopes, M A; Silva, R F; Oliveira, F J

2014-01-01

Bone complexity demands the engineering of new scaffolding solutions for its reconstructive surgery. Emerging bone grafts should offer not only mechanical support but also functional properties to explore innovative bone therapies. Following this, ceramic bone grafts of Glass/hydroxyapatite (HA) reinforced with conductive carbon nanotubes (CNTs) - CNT/Glass/HA - were prepared for bone electrotherapy purposes. Computer-aided 3D microstructural reconstructions and TEM analysis of CNT/Glass/HA composites provided details on the CNT 3D network and further correlation to their functional properties. CNTs are arranged as sub-micrometric sized ropes bridging homogenously distributed ellipsoid-shaped agglomerates. This arrangement yielded composites with a percolation threshold of pc=1.5vol.%. At 4.4vol.% of CNTs, thermal and electrical conductivities of 1.5W·m(-1)·K(-1) and 55S·m(-1), respectively, were obtained, matching relevant requisites in electrical stimulation protocols. While the former avoids bone damaging from Joule's heat generation, the latter might allow the confinement of external electrical fields through the conductive material if used for in vivo electrical stimulation. Moreover, the electrically conductive bone grafts have better mechanical properties than those of the natural cortical bone. Overall, these highly conductive materials with controlled size CNT agglomerates might accelerate bone bonding and maximize the delivery of electrical stimulation during electrotherapy practices. © 2013.

Modeling fatigue crack growth in cross ply titanium matrix composites

NASA Technical Reports Server (NTRS)

Bakuckas, J. G., Jr.; Johnson, W. S.

1993-01-01

In this study, the fatigue crack growth behavior of fiber bridging matrix cracks in cross-ply SCS-6/Ti-15-3 and SCS-6/Timetal-21S laminates containing center holes was investigated. Experimental observations revealed that matrix cracking was far more extensive and wide spread in the SCS-6/Ti-15-3 laminates compared to that in the SCS-6/Timetal-21S laminates. In addition, the fatigue life of the SCS-6/Ti-15-3 laminates was significantly longer than that of the SCS-6/Timetal-21S laminates. The matrix cracking observed in both material systems was analyzed using a fiber bridging (FB) model which was formulated using the boundary correction factors and weight functions for center hole specimen configurations. A frictional shear stress is assumed in the FB model and was used as a curve fitting parameter to model matrix crack growth data. The higher frictional shear stresses calculated in the SCS-6/Timetal-21S laminates resulted in lower stress intensity factors in the matrix and higher axial stresses in the fibers compared to those in the SCS-6/Ti-15-3 laminates at the same applied stress levels.

Chapter 4. Cytomechanics of hair basics of the mechanical stability.

PubMed

Popescu, Crisan; Höcker, Hartwig

2009-01-01

Hair is a complex "cornified" multicellular tissue composed of cuticle and cortex cells mechanically acting as a whole. The cuticle cells overlap and cortex cells interdigitate, all cells being composed of different morphological elements and separated by the cell membrane complex (CMC). The CMC and the morphological elements of the cortex cells, the macrofibrils, composed of microfibrils or intermediate filaments (IFs), and the intermacrofibrillar and intermicrofibrillar cement or the amorphous matrix material determine the mechanical properties of hair. The IFs consist of alpha-keratin molecules being arranged in a sophisticated way of two parallel monomers and antiparallel and shifted dimers rationalized by the amino acid composition and sequence. The mechanical properties of hair result from mechanical interlocking effects, hydrophobic effects, hydrogen bridges, Coulombic interactions, and (covalent) isodipeptide and, in particular, disulfide bridges on a molecular level. The mechanical models applied to hair are based on a simple two-component system, the microfibril/matrix structure. An important regime of the stress-strain curve is the transition of the molecules of the microfibrils from the alpha-helical to the beta-sheet structure. Due to the longitudinal orientation of the IF molecules the longitudinal swelling of the fibers in water is negligible, the radial swelling, however, is substantial.

Proposed framework for thermomechanical life modeling of metal matrix composites

NASA Technical Reports Server (NTRS)

Halford, Gary R.; Lerch, Bradley A.; Saltsman, James F.

1993-01-01

The framework of a mechanics of materials model is proposed for thermomechanical fatigue (TMF) life prediction of unidirectional, continuous-fiber metal matrix composites (MMC's). Axially loaded MMC test samples are analyzed as structural components whose fatigue lives are governed by local stress-strain conditions resulting from combined interactions of the matrix, interfacial layer, and fiber constituents. The metallic matrix is identified as the vehicle for tracking fatigue crack initiation and propagation. The proposed framework has three major elements. First, TMF flow and failure characteristics of in situ matrix material are approximated from tests of unreinforced matrix material, and matrix TMF life prediction equations are numerically calibrated. The macrocrack initiation fatigue life of the matrix material is divided into microcrack initiation and microcrack propagation phases. Second, the influencing factors created by the presence of fibers and interfaces are analyzed, characterized, and documented in equation form. Some of the influences act on the microcrack initiation portion of the matrix fatigue life, others on the microcrack propagation life, while some affect both. Influencing factors include coefficient of thermal expansion mismatch strains, residual (mean) stresses, multiaxial stress states, off-axis fibers, internal stress concentrations, multiple initiation sites, nonuniform fiber spacing, fiber debonding, interfacial layers and cracking, fractured fibers, fiber deflections of crack fronts, fiber bridging of matrix cracks, and internal oxidation along internal interfaces. Equations exist for some, but not all, of the currently identified influencing factors. The third element is the inclusion of overriding influences such as maximum tensile strain limits of brittle fibers that could cause local fractures and ensuing catastrophic failure of surrounding matrix material. Some experimental data exist for assessing the plausibility of the proposed framework.

Experimental evaluation and design of unfilled and concrete-filled FRP composite piles : Task 7 : final report : thesis.

DOT National Transportation Integrated Search

2015-05-01

The overall goal of this project is the experimental evaluation and design of unfilled and concrete-filled FRP composite piles for load-bearing in bridges. This report covers Task 7, Final Report - Thesis. : This final report covers Tasks 1, 2, 3, 5 ...

Experimental evaluation and design of unfilled and concrete-filled FRP composite piles : Task 5 : laminate durability testing : final report.

DOT National Transportation Integrated Search

2015-05-01

The overall goal of this project is the experimental evaluation and design of unfilled and concrete-filled FRP composite piles for load-bearing in bridges. This report covers Task 5, Laminate Durability Testing. : Mechanical properties of the FRP mat...

Experimental evaluation and design of unfilled and concrete-filled FRP composite piles, task 1 - mechanical properties of FRP piles.

DOT National Transportation Integrated Search

2014-10-01

The overall goal of this project is the experimental evaluation and design of unfilled and concrete-filled FRP : composite piles for load-bearing in bridges. This report covers Task 1, Mechanical Properties of FRP Piles. : Mechanical and geotechnic...

Bridge Frost Prediction by Heat and Mass Transfer Methods

NASA Astrophysics Data System (ADS)

Greenfield, Tina M.; Takle, Eugene S.

2006-03-01

Frost on roadways and bridges can present hazardous conditions to motorists, particularly when it occurs in patches or on bridges when adjacent roadways are clear of frost. To minimize materials costs, vehicle corrosion, and negative environmental impacts, frost-suppression chemicals should be applied only when, where, and in the appropriate amounts needed to maintain roadways in a safe condition for motorists. Accurate forecasts of frost onset times, frost intensity, and frost disappearance (e.g., melting or sublimation) are needed to help roadway maintenance personnel decide when, where, and how much frost-suppression chemical to use. A finite-difference algorithm (BridgeT) has been developed that simulates vertical heat transfer in a bridge based on evolving meteorological conditions at its top and bottom as supplied by a weather forecast model. BridgeT simulates bridge temperatures at numerous points within the bridge (including its upper and lower surface) at each time step of the weather forecast model and calculates volume per unit area (i.e., depth) of deposited, melted, or sublimed frost. This model produces forecasts of bridge surface temperature, frost depth, and bridge condition (i.e., dry, wet, icy/snowy). Bridge frost predictions and bridge surface temperature are compared with observed and measured values to assess BridgeT's skill in forecasting bridge frost and associated conditions.

Spark plasma sintering of silicon carbide, multi-walled carbon nanotube and graphene reinforced zirconium diboride ceramic composite

NASA Astrophysics Data System (ADS)

Balaraman Yadhukulakrishnan, Govindaraajan

Scope and Method of Study: Space vehicles re-entering the earth's atmosphere experience very high temperatures due to aerodynamic heating. Ultra-high temperature ceramics (UHTC) with melting point higher than 3200°C are promising materials for thermal protection systems of such space vehicles re-entering the earth's atmosphere. Among several UHTC systems ZrB2 based ceramic composites are particularly important for thermal protection systems due to their better mechanical and thermoelectric properties and high oxidation resistance. In this study spark plasma sintering of SiC, carbon nanotubes (CNT) and graphene nano platelets (GNP) reinforced ZrB2 ultra-high temperature ceramic matrix composites is reported. Findings and Conclusions: Systematic investigations on the effect of reinforcement type (SiC, CNTs and GNP) and content (10-40 vol.% SiC, 2-6 vol.% CNTs and 2-6 vol.% GNP) on densification behavior, microstructure development, and mechanical properties (microhardness, bi-axial flexural strength, and indentation fracture toughness) are reported. With the similar SPS parameters near-full densification (>99% relative density) was achieved with 10-40 vol.% SiC, 4-6 vol.% CNT reinforced composites. Highly dense composites were obtained in 4-6 vol.% GNP reinforced composites. The SiC, CNT and GNP reinforcement improved the indentation fracture toughness of the composites through a range of toughening mechanisms, including particle shearing, crack deflection at the particle-matrix interface, and grain pull-outs for ZrB2-SiC composites, CNT pull-outs and crack deflection in ZrB2-CNT composites and crack deflection, crack bridging and GNP sheet pull-out for ZrB2 -GNP composites.

Salt-bridge networks within globular and disordered proteins: characterizing trends for designable interactions.

PubMed

Basu, Sankar; Mukharjee, Debasish

2017-07-01

There has been considerable debate about the contribution of salt bridges to the stabilization of protein folds, in spite of their participation in crucial protein functions. Salt bridges appear to contribute to the activity-stability trade-off within proteins by bringing high-entropy charged amino acids into close contacts during the course of their functions. The current study analyzes the modes of association of salt bridges (in terms of networks) within globular proteins and at protein-protein interfaces. While the most common and trivial type of salt bridge is the isolated salt bridge, bifurcated salt bridge appears to be a distinct salt-bridge motif having a special topology and geometry. Bifurcated salt bridges are found ubiquitously in proteins and interprotein complexes. Interesting and attractive examples presenting different modes of interaction are highlighted. Bifurcated salt bridges appear to function as molecular clips that are used to stitch together large surface contours at interacting protein interfaces. The present work also emphasizes the key role of salt-bridge-mediated interactions in the partial folding of proteins containing long stretches of disordered regions. Salt-bridge-mediated interactions seem to be pivotal to the promotion of "disorder-to-order" transitions in small disordered protein fragments and their stabilization upon binding. The results obtained in this work should help to guide efforts to elucidate the modus operandi of these partially disordered proteins, and to conceptualize how these proteins manage to maintain the required amount of disorder even in their bound forms. This work could also potentially facilitate explorations of geometrically specific designable salt bridges through the characterization of composite salt-bridge networks. Graphical abstract ᅟ.

Mechanical properties of Al/Al[sub 2]O[sub 3] and Cu/Al[sub 2]O[sub 3] composites with interpenetrating networks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Knechtel, M.; Prielipp, H.; Claussen, N.

The rising fracture resistance with crack length in metal-toughened ceramics due to ductile bridging has been discussed from some selected microstructures and metal-ceramic combinations. An intriguing feature of these composites is the influence of interfacial fracture strength. Strong interfacial bonding leads to high geometrical constraint for the metal and high degree of triaxial tension in the metal ligament, thereby increasing the uniaxial yield strength by a factor of 5--7. This in turn increases the closure stress of the metal ligament, but ultimately limits the total plastic dissipation in the ductile reinforcement. The intent of this paper is to provide somemore » insight on the influence of metal ligament size on both fracture toughness and fracture strength. The materials chosen are Al/Al[sub 2]O[sub 3] and Cu/Al[sub 2]O[sub 3] composites, both prepared by gas-pressure metal-infiltration of porous alumina preforms. SEM observations of fracture surfaces in conjunction with preliminary TEM and PEELS investigations of the metal-ceramic interfaces are used to explain the trends in mechanical property data.« less

A new inorganic-organic composite coagulant, consisting of polyferric sulphate (PFS) and polyacrylamide (PAA).

PubMed

Moussas, P A; Zouboulis, A I

2009-08-01

Currently, research is focused on the synthesis of new composite coagulants, which are constituted of both inorganic and organic materials. In this paper, the development of relevant reagents was investigated, by combining the inorganic pre-polymerised iron-based coagulant Polyferric Sulphate (PFS) with an organic, non-ionic polymer (Polyacrylamide, PAA) under different PAA/Fe (mg/l) and OH/Fe molar ratios. Moreover, the new reagents were characterised in terms of typical properties, stability and morphological analysis (XRD, FTIR, SEM). Their coagulation performance, when treating low or high turbid kaolin-humic acid suspensions, was also investigated, whereas the applied coagulation mechanisms were discussed by using the Photometric Dispersion Analysis (PDA) analysis. The results show that the new coagulation reagents present improved properties, including increased effective polymer species concentration, and they exhibit very good stability. The respective tests using PDA confirmed that the predominant coagulation mechanism of PFS-PAA is the bridge formation mechanism. Coagulation experiments in low or high turbid kaolin-humic acid suspensions reveal that the novel composite reagent PFS-PAA exhibits better coagulation performance, when compared with simple PFS, in terms of zeta-potential reduction, turbidity and organic matter removal and residual iron concentration.

Fabrication and Characteristics of Al/PTFE Multilayers and Application in Micro-initiator

NASA Astrophysics Data System (ADS)

Zhang, Yuxin; Jiang, Hongchuan; Zhao, Xiaohui; Zhang, Wanli; Li, Yanrong

2017-12-01

In this paper, a micro-initiator was designed and fabricated by integrating Al/PTFE multilayers with a Cu film bridge. The regularity layer structure and interface composition of Al/PTFE multilayers was analysed by transmission electron microscope and X-ray photoelectron spectroscopy, respectively. The heat release reaction in Al/PTFE multilayers can be triggered with reaction temperature of 430 °C, and the overall heat of reaction is 3192 J/g. Al/PTFE multilayers with bilayer thickness of 200 nm was alternately deposited on a Cu film bridge to improve the electric explosion performances. Compared to Cu film bridge, the Al/PTFE/Cu integrated film bridge exhibits improved performances with longer explosion duration time, more violent explosion phenomenon and larger quantities of ejected product particles.

Agar-based bridges as biocompatible candidates to provide guide cues in spinal cord injury repair.

PubMed

Martín-López, Eduardo; Darder, Margarita; Ruiz-Hitzky, Eduardo; Nieto Sampedro, Manuel

2013-01-01

Spinal bridge implants are strategic to provide growth surfaces for axonal regeneration after spinal cord injuries. The design of an appropriate substrate, one that is suitable for implantation, must involve careful testing of the biomaterial properties both in vitro and in vivo. The goal of this work was to test the structure, stability and biological response after spinal bridges implantation of several biopolymers, composed of mixtures of agar (AG), as structural matrix scaffold, with κ-carrageenan (Kc), gelatin (G), xanthan gum (Xn) and polysulfone (PS). Biopolymer structures were studied by environmental scanning electron microscopy, whereas the stability of gels was analyzed by in vitro degradation and swelling tests. The biocompatibility of these materials and their ability to promote cell growth and axonal regeneration were studied by implantation of spinal bridges containing empty linear channels in an acute rat spinal cord transection model at thoracic level (T8). All gel mixtures gave rise to porous structures and they were stables to degradation, excepting the AG+G mixture. Spinal bridges constructed from all mixtures were implanted during a month in adult rats. After this time a low host reaction occurred to all bridge materials as well as neurite and cell ingrowths through the empty channels. Neurites within the bridges were mostly peripheral sensory fibers such as those positive for CGRP, whereas there was a lack of regeneration of central axons crossing from the spinal tissue to bridges. Many of these neurites established closed contacts with non-myelin Schwann cells. The histological analysis revealed a high accumulation of collagen fibers within the channels. Unexpected was the apparent loss of channels linearity which affected the growth of neurites and cells, indicating the need for additional regeneration strategies and vertebrae bridge fixing.

First Investigation of Microbial Community Composition in the Bridge (Gadeok Channel) between the Jinhae-Masan Bay and the South Sea of Korea

NASA Astrophysics Data System (ADS)

Lee, Jiyoung; Lim, Jae-Hyun; Park, Junhyung; Youn, Seok-Hyun; Oh, Hyun-Ju; Kim, Ju-Hyoung; Kim, Myung Kyum; Cho, Hyeyoun; Yoon, Joo-Eun; Kim, Soyeon; Markkandan, Kesavan; Park, Ki-Tae; Kim, Il-Nam

2018-02-01

Microbial community composition varies based on seasonal dynamics (summer: strongly stratified water column; autumn: weakly stratified water column; winter: vertically homogeneous water column) and vertical distributions (surface, middle, and bottom depths) in the Gadeok Channel, which is the primary passage to exchange waters and materials between the Jinhae-Masan Bay and the South Sea waters. The microbial community composition was analyzed from June to December 2016 using 16S rRNA gene sequencing. The community was dominated by the phyla Proteobacteria (45%), Bacteroidetes (18%), Cyanobacteria (15%), Verrucomicrobia (6%), and Actinobacteria (6%). Alphaproteobacteria (29%) was the most abundant microbial class, followed by Flavobacteria (15%) and Gammaproteobacteria (15%) in all samples. The composition of the microbial communities was found to vary vertically and seasonally. The orders Flavobacteriales and Stramenopiles showed opposing seasonal patterns; Flavobacteriales was more abundant in August and December while Stramenopiles showed high abundance in June and October at all depths. The genus Synechococcus reached extremely high abundance (14%) in the June surface water column, but was much less abundant in December water columns. Clustering analysis showed that there was a difference in the microbial community composition pattern between the strongly stratified season and well-mixed season. These results indicate that the seasonal dynamics of physicochemical and hydrologic conditions throughout the water column are important parameters in shaping the microbial community composition in the Gadeok Channel.

Blast and Impact Resistant Composite Structures for Navy Ships

DTIC Science & Technology

2013-03-15

Navy cargo ships, Air Force tactical shelters, Air Force runway matting, vehicular bridge decks, railcar floors and wind turbine blades. The US Army...bridge decks, railcar floors and wind turbine blades. NAVY RELEVANCE Producing stronger, safer and more cost-effective platforms for the new generation...floors and wind turbine blades. 32 NAVY RELEVANCE Producing stronger, safer and more cost-effective platforms for the new generation naval ships

Development of micro-electromechanical system (MEMS) cochlear biomodel

NASA Astrophysics Data System (ADS)

Ngelayang, Thailis Bounya Anak; Latif, Rhonira

2015-05-01

Human cochlear is undeniably one of the most amazing organs in human body. The functional mechanism is very unique in terms of its ability to convert the sound waves in the form of mechanical vibrations into the electrical nerve impulses. It is known that the normal human auditory system can perceive the audible frequency range between 20 Hz to 20 kHz. Scientists have conducted several researches trying to build the artificial basilar membrane in the human cochlea (cochlear biomodel). Micro-electromechanical system (MEMS) is one of the potential inventions that have the ability to mimic the active behavior of the basilar membrane. In this paper, an array of MEMS bridge beams that are mechanically sensitive to the perceived audible frequency has been proposed. An array of bridge bridge beams with 0.5 µm thickness and length varying from 200 µm to 2000 µm have been designed operate within the audible frequency range. In the bridge beams design, aluminium (Al), copper (Cu), tantalum (Ta) and platinum (Pt) have considered as the material for the bridge beam structure. From the finite element (FE) and lumped element (LE) models of the MEMS bridge beams, platinum has been found to be the best material for the cochlear biomodel design, closely mimicking the basilar membrane.

Development of micro-electromechanical system (MEMS) cochlear biomodel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ngelayang, Thailis Bounya Anak; Latif, Rhonira

Human cochlear is undeniably one of the most amazing organs in human body. The functional mechanism is very unique in terms of its ability to convert the sound waves in the form of mechanical vibrations into the electrical nerve impulses. It is known that the normal human auditory system can perceive the audible frequency range between 20 Hz to 20 kHz. Scientists have conducted several researches trying to build the artificial basilar membrane in the human cochlea (cochlear biomodel). Micro-electromechanical system (MEMS) is one of the potential inventions that have the ability to mimic the active behavior of the basilar membrane. Inmore » this paper, an array of MEMS bridge beams that are mechanically sensitive to the perceived audible frequency has been proposed. An array of bridge bridge beams with 0.5 µm thickness and length varying from 200 µm to 2000 µm have been designed operate within the audible frequency range. In the bridge beams design, aluminium (Al), copper (Cu), tantalum (Ta) and platinum (Pt) have considered as the material for the bridge beam structure. From the finite element (FE) and lumped element (LE) models of the MEMS bridge beams, platinum has been found to be the best material for the cochlear biomodel design, closely mimicking the basilar membrane.« less

A literature survey on industrialized bridge construction.

DOT National Transportation Integrated Search

1972-01-01

The purpose of this survey was to aid the writer in understanding and retaining material in preparation for a project on the industrialization of bridge construction. However, it was believed that the results of the survey would be informative to oth...

Self-consolidating concrete for prestressed applications - phase II : bridge construction and in-place performance.

DOT National Transportation Integrated Search

2015-04-01

Prior to statewide acceptance of self-consolidating concrete (SCC) in precast, prestressed bridge member : production, the Alabama Department of Transportation sponsored an investigation of the material to be : performed by the Auburn University High...

Expansion joint noise reduction on the new Tacoma Narrows Bridge.

DOT National Transportation Integrated Search

2011-12-01

"Washington State Department of Transportation (WSDOT) responded to citizen complaints about expansion joint noise on the new Tacoma Narrows Bridge (TNB) by installing new wall coated in noise absorptive materials. The goal of the project was to redu...

Simultaneous life extension and crack monitoring of fatigue-damaged steel members using multifunctional carbon nanotube based composites

NASA Astrophysics Data System (ADS)

Ahmed, Shafique; Schumacher, Thomas; Thostenson, Erik T.; McConnell, Jennifer

2017-04-01

Steel structures including bridges are susceptible to cracking, particularly due to fatigue-sensitive details found in older designs. Therefore, one of the major challenges to keep those steel bridges in service is to rehabilitate existing and potential fatigue damage. There are several conventional approaches to extend the fatigue-life of damaged steel members, e.g., drilling a crack stop-hole to reduce the stress concentration at the crack tip as well as welding and bolting of steel plates or adhesive-bonding of fiber-reinforced polymers (FRP) to reduce the overall stresses. Improvement in material properties of FRP and adhesives make them a viable candidate to apply for extending the fatigue-life of steel members. However, drawbacks include the potential for debonding of the adhesive layer and/or interfaces between adhesive and adherents as well as difficulty in monitoring fatigue crack growth after rehabilitation. In this research, a holistic approach is proposed and evaluated for simultaneous extension of fatigue-life and monitoring by integrating a carbon nanotube (CNT)-based sensing layer with an adhesively-bonded FRP reinforcement. CNT-based sensing layers have a nerve-like electric resistance network, which enables distributed sensing capabilities to monitor stress levels, crack growth, and damage progression. Using laboratory-scale experiments, the simultaneous fatigue-life extension and crack monitoring capability of multifunctional CNT-based composites was evaluated. This paper introduces the fundamental concept of integrated fatigue-rehabilitation and monitoring of steel members, presents a laboratory-scale experiment to demonstrate the feasibility and effectiveness, and discusses challenges for implementation in real structures.

Disulfide-Bridged (Mo3S11) Cluster Polymer: Molecular Dynamics and Application as Electrode Material for a Rechargeable Magnesium Battery.

PubMed

Truong, Quang Duc; Kempaiah Devaraju, Murukanahally; Nguyen, Duc N; Gambe, Yoshiyuki; Nayuki, Keiichiro; Sasaki, Yoshikazu; Tran, Phong D; Honma, Itaru

2016-09-14

Exploring novel electrode materials is critical for the development of a next-generation rechargeable magnesium battery with high volumetric capacity. Here, we showed that a distinct amorphous molybdenum sulfide, being a coordination polymer of disulfide-bridged (Mo3S11) clusters, has great potential as a rechargeable magnesium battery cathode. This material provided good reversible capacity, attributed to its unique structure with high flexibility and capability of deformation upon Mg insertion. Free-terminal disulfide moiety may act as the active site for reversible insertion and extraction of magnesium.

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 occurs to measure their residual capacity. A relationship between the level of galvanic corrosion and the failure characteristics of steel-composite interface is established.

Comparison of Flexural Strength of Different CAD/CAM PMMA-Based Polymers.

PubMed

Alp, Gülce; Murat, Sema; Yilmaz, Burak

2018-01-28

To compare the flexural strength of different computer-aided design/computer-aided manufacturing (CAD/CAM) poly(methyl methacrylate)-based (PMMA) polymers and conventional interim resin materials after thermocycling. Rectangular-shaped specimens (n = 15, for each material) (25 × 2 × 2 mm 3 ) were fabricated from 3 CAD/CAM PMMA-based polymers (Telio CAD [T]; M-PM-Disc [M]; Polident-PMMA [P]), 1 bis-acrylate composite resin (Protemp 4 [PT]), and 1 conventional PMMA (ArtConcept Artegral Dentine [C]) according to ISO 10477:2004 Standards (Dentistry-Polymer-Based Crown and Bridge Materials). The specimens were subjected to 10,000 thermocycles (5 to 55°C). Three-point flexural strength of the specimens was tested in a universal testing machine at a 1.0 mm/min crosshead speed, and the flexural strength data (σ) were calculated (MPa). The flexural strength values were statistically analyzed using 1-way ANOVA, and Tukey HSD post-hoc test for multiple comparisons (α = 0.05). Flexural strength values ranged between 66.1 ± 13.1 and 131.9 ± 19.8 MPa. There were significant differences among the flexural strengths of tested materials, except for between T and P CAD/CAM PMMA-based polymers (p > 0.05). CAD/CAM PMMA-based polymer M had the highest flexural strength and conventional PMMA had the lowest (p < 0.05). CAD/CAM PMMA-based T and P polymers had significantly higher flexural strength than the bis-acrylate composite resin (p < 0.05), and conventional PMMA (p < 0.0001), and significantly lower flexural strength compared to CAD/CAM PMMA-based M (p < 0.05). The flexural strength of CAD/CAM PMMA-based polymers was greater than the flexural strength of bis-acrylate composite resin, which had a greater flexural strength compared to conventional PMMA resin. © 2018 by the American College of Prosthodontists.

The Status and Prospect of Research into Protective Structures of Bridge Piers against Rockfall Impact

NASA Astrophysics Data System (ADS)

Gao, Liang; Zhang, Shan; Zhang, Junfa; Wu, Xiangnan

2017-06-01

Rockfall impact on bridge piers threats severely the mountain bridge structures of lifeline engineering. Intended for mountain bridge pier protection against rockfall impact, the paper conducted comprehensive reviews on the research status of impact effects, anti-collision structure, impact response to rockfall, and protective design at home and abroad, and proposed a new-type protective structure against rockfall impact. In addition, the paper carried out deep studies on such key scientific issues as impact effect calculation, protective materials against rockfall impact, damage mechanism of protective units, and parameter optimization on the system of protective structures against rockfall impact as well, aiming to strength disaster prevention of mountain bridge structures.

THERMAL CONDUCTIVITY ANALYSIS OF GASES

DOEpatents

Clark, W.J.

1949-06-01

This patent describes apparatus for the quantitative analysis of a gaseous mixture at subatmospheric pressure by measurement of its thermal conductivity. A heated wire forms one leg of a bridge circuit, while the gas under test is passed about the wire at a constant rate. The bridge unbalance will be a measure of the change in composition of the gas, if compensation is made for the effect due to gas pressure change. The apparatus provides a voltage varying with fluctuations of pressure in series with the indicating device placed across the bridge, to counterbalance the voltage change caused by fluctuations in the pressure of the gaseous mixture.

Models and Materials: Bridging Art and Science in the Secondary Curriculum

NASA Astrophysics Data System (ADS)

Pak, D.; Cavazos, L.

2006-12-01

Creating and sustaining student engagement in science is one challenge facing secondary teachers. The visual arts provide an alternative means of communicating scientific concepts to students who may not respond to traditional formats or identify themselves as interested in science. We have initiated a three-year teacher professional development program at U C Santa Barbara focused on bridging art and science in secondary curricula, to engage students underrepresented in science majors, including girls, English language learners and non-traditional learners. The three-year format provides the teams of teachers with the time and resources necessary to create innovative learning experiences for students that will enhance their understanding of both art and science content. Models and Materials brings together ten secondary art and science teachers from six Santa Barbara County schools. Of the five participating science teachers, three teach Earth Science and two teach Life Science. Art and science teachers from each school are teamed and challenged with the task of creating integrated curriculum projects that bring visual art concepts to the science classroom and science concepts to the art classroom. Models and Materials were selected as unifying themes; understanding the concept of models, their development and limitations, is a prominent goal in the California State Science and Art Standards. Similarly, the relationship between composition, structure and properties of materials is important to both art and science learning. The program began with a 2-week institute designed to highlight the natural links between art and science through presentations and activities by both artists and scientists, to inspire teachers to develop new ways to present models in their classrooms, and for the teacher teams to brainstorm ideas for curriculum projects. During the current school year, teachers will begin to integrate science and art and the themes of modeling and materials into their classrooms. Initial results indicate that the participating teachers developed a clearer understanding of the uses and limitations of models the classroom, better understanding of materials science, and strong initial ideas for integrated curricula.

Reverse engineering of mandible and prosthetic framework: Effect of titanium implants in conjunction with titanium milled full arch bridge prostheses on the biomechanics of the mandible.

PubMed

De Santis, Roberto; Gloria, Antonio; Russo, Teresa; D'Amora, Ugo; Varriale, Angelo; Veltri, Mario; Balleri, Piero; Mollica, Francesco; Riccitiello, Francesco; Ambrosio, Luigi

2014-12-18

This study aimed at investigating the effects of titanium implants and different configurations of full-arch prostheses on the biomechanics of edentulous mandibles. Reverse engineered, composite, anisotropic, edentulous mandibles made of a poly(methylmethacrylate) core and a glass fibre reinforced outer shell were rapid prototyped and instrumented with strain gauges. Brånemark implants RP platforms in conjunction with titanium Procera one-piece or two-piece bridges were used to simulate oral rehabilitations. A lateral load through the gonion regions was used to test the biomechanical effects of the rehabilitations. In addition, strains due to misfit of the one-piece titanium bridge were compared to those produced by one-piece cast gold bridges. Milled titanium bridges had a better fit than cast gold bridges. The stress distribution in mandibular bone rehabilitated with a one-piece bridge was more perturbed than that observed with a two-piece bridge. In particular the former induced a stress concentration and stress shielding in the molar and symphysis regions, while for the latter design these stresses were strongly reduced. In conclusion, prosthetic frameworks changed the biomechanics of the mandible as a result of both their design and manufacturing technology. Copyright © 2014 Elsevier Ltd. All rights reserved.

Analysis of resonance mechanism and conditions of train bridge system

NASA Astrophysics Data System (ADS)

Xia, H.; Zhang, N.; Guo, W. W.

2006-11-01

In this paper, the resonance mechanism and conditions of train-bridge system are investigated through theoretical derivations, numerical simulations and experimental data analyses. The resonant responses of the bridge induced by moving trains are classified into three types according to different resonance mechanisms: the first is related to the periodical actions of moving load series of the vertical weights, lateral centrifugal and wind forces of vehicles; the second is induced by the loading rate of moving load series of vehicles; the third is owing to the periodically loading of the swing forces of the train vehicles excited by track irregularities and wheel hunting movements. The vehicle resonance is induced by the periodical action of regular arrangement of bridge spans and their deflections. The resonant conditions are proposed and the corresponding resonant train speeds are determined. The application scopes of resonance conditions are discussed. The resonance of the train-bridge system is affected by the span, total length, lateral and vertical stiffness of the bridge, the compositions of the train, and the axle arrangements and natural frequencies of the vehicles. The resonant train speeds for some bridges are estimated and are compared with the critical train speeds obtained from the dynamic simulation of train-bridge interaction model or from the field measurements.

Development of high-performance concrete mixtures for durable bridge decks in Montana using locally available materials.

DOT National Transportation Integrated Search

2005-03-01

"The Montana Department of Transportation (MDT) is performing research to develop a cost-effective, indigenous highperformance : concrete (HPC) for use in bridge deck applications. The investigation was divided into two tasks: 1) : identification of ...

Design and evaluation of a single-span bridge using ultra-high performance concrete.

DOT National Transportation Integrated Search

2009-09-01

"Research presented herein describes an application of a newly developed material called Ultra-High Performance Concrete (UHPC) to a : single-span bridge. The two primary objectives of this research were to develop a shear design procedure for possib...

Design and evaluation of a single-span bridge using ultra-high performance concrete.

DOT National Transportation Integrated Search

2009-09-01

Research presented herein describes an application of a newly developed material called Ultra-High Performance Concrete (UHPC) to a : single-span bridge. The two primary objectives of this research were to develop a shear design procedure for possibl...

Implementation of a pilot continuous monitoring system : Iowa Falls Arch Bridge : [tech transfer summary].

DOT National Transportation Integrated Search

2015-06-01

As part of designing, constructing, and maintaining the bridge infrastructure in : Iowa, the Iowa Department of Transportation (DOT) has, in recent years, focused : efforts on investigating the use of new high-performance materials, new design : conc...

Microfabrication of hierarchical structures for engineered mechanical materials

NASA Astrophysics Data System (ADS)

Vera Canudas, Marc

Materials found in nature present, in some cases, unique properties from their constituents that are of great interest in engineered materials for applications ranging from structural materials for the construction of bridges, canals and buildings to the fabrication of new lightweight composites for airplane and automotive bodies, to protective thin film coatings, amongst other fields. Research in the growing field of biomimetic materials indicates that the micro-architectures present in natural materials are critical to their macroscopic mechanical properties. A better understanding of the effect that structure and hierarchy across scales have on the material properties will enable engineered materials with enhanced properties. At the moment, very few theoretical models predict mechanical properties of simple materials based on their microstructures. Moreover these models are based on observations from complex biological systems. One way to overcome this challenge is through the use of microfabrication techniques to design and fabricate simple materials, more appropriate for the study of hierarchical organizations and microstructured materials. Arrays of structures with controlled geometry and dimension can be designed and fabricated at different length scales, ranging from a few hundred nanometers to centimeters, in order to mimic similar systems found in nature. In this thesis, materials have been fabricated in order to gain fundamental insight into the complex hierarchical materials found in nature and to engineer novel materials with enhanced mechanical properties. The materials fabricated here were mechanically characterized and compared to simple mechanics models to describe their behavior with the goal of applying the knowledge acquired to the design and synthesis of future engineered materials with novel properties.

[Biocompatibility of crown and bridge materials. 1. Substances in contact with dentin].

PubMed

Klotzer, W T

1989-11-01

It is mandatory that the materials and drugs used in restorative dentistry be free from side effects resulting in potential tooth loss or irreversible damage to vital dental tissues. Up to now there have been no reliable in vitro methods available for the evaluation of pulp reactions. Since numerous different materials and drugs are successively applied to prepared dentine, pulp reactions are caused by cumulative action, and the causative factors, except for extremely toxic substances, cannot be revealed by clinical and/or posttreatment studies alone. At present, the evaluation of pulp reactions must still rely on histologic studies using human or animal teeth. Reports on pulp reactions to materials and drugs are reviewed. Few dependable figures have been reported on pulp reactions to dentinal medication, "sterilization", disinfectants and on the biologic response to and effectiveness of varnishes, liners, desensitizing agents, smear-layer removers, etc. Resins and composite materials seem to provoke acute reactions, mainly by the heat generated during setting, and chronic reactions due to the stimulation of bacterial growth. Except for glass ionomer cements, most of the publications show a high degree of agreement on the tissue reactions to luting agents. Regarding dentine bonding agents, however, it has not been possible to draw any conclusions, so far.

Development of a liquefaction hazard screening tool for caltrans bridge sites

USGS Publications Warehouse

Knudsen, K.-L.; Bott, J.D.J.; Woods, M.O.; McGuire, T.L.

2009-01-01

We have developed a liquefaction hazard screening tool for the California Department of Transportation (Caltrans) that is being used to evaluate the liquefaction hazard to approximately 13,000 bridge sites in California. Because of the large number of bridge sites to be evaluated, we developed a tool that makes use of parameters not typically considered in site-specific liquefaction investigations. We assessed geologic, topographic, seismic hazard, and subsurface conditions at about 100 sites of past liquefaction in California. Among the parameters we found common to many of these sites are: (a) low elevations, (b) proximity to a water body, and (c) presence of geologically youthful deposits or artificial fill materials. The nature of the study necessitated the use of readily available data, preferably datasets that are consistent across the state. The screening tool we provided to Caltrans makes use of the following parameters: (1) proximity to a water body, (2) whether the bridge crosses a water body, (3) the age of site geologic materials and the environment in which the materials were deposited, as discerned from available digital geologic maps, (4) probabilistic shaking estimates, (5) the site elevation, (6) information from available liquefaction hazard maps [covering the 9-county San Francisco Bay Area and Ventura County] and California Geological Survey (CGS) Zones of Required Investigation. For bridge sites at which subsurface boring data were available (from CGS' existing database), we calculated Displacement Potential Index values using a methodology developed by Allison Faris and Jiaer Wu. Caltrans' staff will use this hazard-screening tool, along with other tools focused on bridges and foundations, to prioritize site-specific investigations. ?? 2009 ASCE.

Room temperature metastable monoclinic phase in BaTiO3 crystals

NASA Astrophysics Data System (ADS)

Lummen, Tom; Wang, Jianjun; Holt, Martin; Kumar, Amit; Vlahos, Eftihia; Denev, Sava; Chen, Long-Qing; Gopalan, Venkatraman

2011-03-01

Low-symmetry monoclinic phases in ferroelectric materials are of considerable interest, due to their associated enhanced electromechanical coupling. Such phases have been found in Pb-based perovskite solid solutions such as lead zirconate titanate (PZT), where they form structural bridges between the rhombohedral and tetragonal ground states in compositional space. In this work, we directly image such a monoclinic phase in BaTi O3 crystals at room-temperature, using optical second harmonic generation, Raman, and X-ray microscopic imaging techniques. Phase-field modeling indicates that ferroelectric domain microstructures in BaTi O3 induce local inhomogeneous stresses in the crystals, which can effectively trap the transient intermediate monoclinic structure that occurs across the thermal orthorhombic-tetragonal phase boundary. The induced metastable monoclinic domains are ferroelectrically soft, being easily moved by electric fields as low as 0.5 kV cm-1 . Stabilizing such intermediate low-symmetry phases could very well lead to Pb-free materials with enhanced piezoelectric properties.