Non-metallic Systems Research Articles

Recent Progress in Visible-Light Photoredox-Catalyzed Intermolecular 1,2-Difunctionalization of Double Bonds via an ATRA-Type Mechanism.

Radical difunctionalizations of alkenes constitute an efficient method for the construction of complex organic molecules. This synopsis focuses on visible-light catalysis, a recent and very promising technological refinement of this class of transformations. Examples taken from the literature illustrate the use of a variety of (metallic or nonmetallic) systems, which allow us to leverage the energy of readily available visible-light radiation to efficiently create some of the most commonly looked for types of bonds (C-X, C-O, C-N, and C-C) under mild conditions and starting from unsaturated substrates.

Nonlocal energy-optimized kernel: Recovering second-order exchange in the homogeneous electron gas

In order to remedy some of the shortcomings of the random phase approximation (RPA) within adiabatic connection fluctuation-dissipation (ACFD) density functional theory, we introduce a short-ranged, exchange-like kernel that is one-electron self-correlation free and exact for two-electron systems in the high-density limit. By tuning a free parameter in our model to recover an exact limit of the homogeneous electron gas correlation energy, we obtain a nonlocal, energy-optimized kernel that reduces the errors of RPA for both homogeneous and inhomogeneous solids. Using wave-vector symmetrization for the kernel, we also implement RPA renormalized perturbation theory for extended systems, and demonstrate its capability to describe the dominant correlation effects with a low-order expansion in both metallic and nonmetallic systems. The comparison of ACFD structural properties with experiment is also shown to be limited by the choice of norm-conserving pseudopotential.

Germanium–vacancy color center in isotopically enriched diamonds synthesized at high pressures

We report on the high-pressure synthesis of novel nano- and microcrystalline diamonds with germanium–vacancy (Ge–V) color centers emitting at 602 nm. The synthesis was carried out in non-metallic growth systems C–H–Ge and C–H–O–Ge enriched with germanium and carbon isotopes. We demonstrate germanium and carbon isotope shifts in the fine structure of the luminescence, which allows us to unambiguously associate the center with the germanium impurity entering into the diamond lattice. We show that there are two ground-state energy levels with the separation of 0.7 meV and two excited-state levels separated by 4.6 meV in the electronic structure of the center and suggest a split-vacancy structure of this center. High-intensity and narrow-line emission of high-pressure synthesized small diamonds with Ge–V centers makes them promising candidates for single-photon emitters.

These Pipes Have Passed

This article discusses need for introducing new standards for developing efficient piping systems. A barrier to wider adoption of the material has been the absence of non-metallic piping standards that could serve as a common language for manufacturers, fabricators, designers, and other stakeholders. The development of the new standards also reflects the growing international role of ASME standards. The intent of ASME NM-1 is to set engineering requirements for safe design and construction of thermoplastic piping installations. The ASMI NM-2 is expected to address pipe and piping components which are produced as standard products, as well as custom products designed for specific applications. The ASME NM-3 Standard intends to provide greater uniformity, consistency, and transparency for the identification and establishment of physical properties and allowable stress values for materials in non-metallic piping systems. The standards for thermoplastic and fiberglass reinforced plastic piping systems are being developed to fill the unmet need for comprehensive documents in these areas.

Simple bond-order-type interatomic potential for an intermixed Fe-Cr-C system of metallic and covalent bondings in heat-resistant ferritic steels

It is known that M23C6(M = Cr/Fe) behavior in heat-resistant ferritic steels affects the strength of the material at high temperature. The ability to garner direct information regarding the atomic motion using classical molecular dynamics simulations is useful for investigating the M23C6 behavior in heat-resistant ferritic steels. For such classical molecular dynamics calculations, a suitable interatomic potential is needed. To satisfy this requirement, an empirical bond-order-type interatomic potential for Fe-Cr-C systems was developed because the three main elements to simulate the M23C6 behavior in heat-resistant ferritic steels are Fe, Cr, and C. The angular-dependent term, which applies only in non-metallic systems, was determined based on the similarity between a Finnis-Sinclair-type embedded-atom-method interatomic potential and a Tersoff-type bond-order potential. The potential parameters were determined such that the material properties of Fe-Cr-C systems were reproduced. These properties include the energy and lattice constants of 89 crystal structures; the elastic constants of four realistic precipitates; the bulk moduli of B1, B2, and B3 crystals; the surface energies of B1 and B2 crystals; and the defect-formation energies and atomic configurations of 66 Fe-Cr-C complexes. Most of these material properties were found to be reproduced by our proposed empirical bond-order potentials. The formation energies and lattice constants of randomly mixed Fe-Cr alloys calculated using the interatomic potentials were comparable to those obtained through experiments and first-principles calculations. Furthermore, the energies and structures of interfaces between Cr carbide and α-Fe as predicted through first-principles calculations were well reproduced using these interatomic potentials.

Theory of universal incoherent metallic transport

In an incoherent metal, transport is controlled by the collective diffusion of energy and charge rather than by quasiparticle or momentum relaxation. We explore the possibility of a universal bound $D \gtrsim \hbar v_F^2/(k_B T)$ on the underlying diffusion constants in an incoherent metal. Such a bound is loosely motivated by results from holographic duality, the uncertainty principle and from measurements of diffusion in strongly interacting non-metallic systems. Metals close to saturating this bound are shown to have a linear in temperature resistivity with an underlying dissipative timescale matching that recently deduced from experimental data on a wide range of metals. This bound may be responsible for the ubiquitous appearance of high temperature regimes in metals with $T$-linear resistivity, motivating direct probes of diffusive processes and measurements of charge susceptibilities.

Hierarchically Organized Structures of Hardened Composition in Metal and Cement System

It is shown how action of the directed laser radiation leads to formation of column educations in cement MgO system – MgO – H3BO3 – H2O. Are considered from feature of structurization in the metal and nonmetallic systems hardening by cooling and hardening of fusions from positions of ap-plication of ideology of hierarchical structures.

Pre-selective screening for matrix elements in linear-scaling exact exchange calculations

We present a simple but accurate preselection method based on Schwarz integral estimates to determine the significant elements of the exact exchange matrix before its evaluation, thus providing an asymptotical linear-scaling behavior for non-metallic systems. Our screening procedure proves to be highly suitable for exchange matrix calculations on massively parallel computing architectures, such as graphical processing units, for which we present a first linear-scaling exchange matrix evaluation algorithm.

Domain‐Averaged Exchange‐Correlation Energies as a Physical Underpinning for Chemical Graphs

A novel solution to the problem of assigning a molecular graph to a collection of nuclei (i.e. how to draw a molecular structure) is presented. Molecules are universally understood as a set of nuclei linked by bonds, but establishing which nuclei are bonded and which are not is still an empirical matter. Our approach borrows techniques from quantum chemical topology, which showed for the first time the construction of chemical graphs from wave functions, shifting the focus on energetics. This new focus resolves issues surrounding previous topological analyses, in which domain-averaged exchange-correlation energies (V(xc)), quantities defined in real space between each possible atom pair, hold the key. Exponential decay of V(xc) in non-metallic systems as the intercenter distance increases guarantees a well-defined hierarchy for all possible V(xc) values in a molecule. Herein, we show that extracting the set of atom pairs that display the largest V(xc) values in the hierarchy is equivalent to retrieving the molecular graph itself. Notably, domain-averaged exchange-correlation energies are transferable, and they can be used to calculate bond strengths. Fine-grained details resulted to be related to simple stereoelectronic effects. These ideas are demonstrated in a set of simple pilot molecules.

Decay Properties of Spectral Projectors with Applications to Electronic Structure

Motivated by applications in quantum chemistry and solid state physics, we apply general results from approximation theory and matrix analysis to the study of the decay properties of spectral projectors associated with large and sparse Hermitian matrices. Our theory leads to a rigorous proof of the exponential off-diagonal decay (``nearsightedness'') for the density matrix of gapped systems at zero electronic temperature in both orthogonal and nonorthogonal representations, thus providing a firm theoretical basis for the possibility of linear scaling methods in electronic structure calculations for nonmetallic systems. We further discuss the case of density matrices for metallic systems at positive electronic temperature. A few other possible applications are also discussed.

Free Vibrations of Composite Base Plates Stiffened by Two Adhesively Bonded Plate Strips

I N THE last decade or so, advanced composites (and advanced metal alloys) are being increasingly used in flight-vehicle and hydrodynamic-vehicle primary and secondary structures and systems [1,2]. Nowadays, 40–50% of the structural systems of advancedfighter aircraft (such as the SuperHornet F/A-18) and other newest air-superiority fighter aircraft are made of various kinds of advanced composites [2]. Similarly, the so-called advanced composite (and/or advanced metal alloy) stiffened-plate or panel systems with various configurations and geometries have been extensively employed in lightweight, high-strength airand space-vehicle primary structural systems and subsystems [3–5]. A good example for their application in aircraft structures is the wing-cover plates or panels with multistiffeners [3–5]. Additionally, they can be used in bonded repair of metallic and nonmetallic (or composite) aircraft structures and systems [6,7]. These stiffened systems are also used in lightweight, high-speed, hydrodynamic, and marine vehicle structures. Another important application for the aforementioned bonded and stiffened systems is in some civil (and/or military) ground vehicle structures and substructures as well as in other areas of advanced engineering and technology. Generally speaking, the advanced composite (and/or advanced metal alloy) stiffened systemsmay easily be categorized (or grouped) in four main groups, as shown in Fig. 1. The group II systems can further be organized in terms of the subgroups of group II, which are also given in Fig. 1. Finally, subgroup II.1 systems are divided into several classes based on the number of the bonded stiffened-plate strips, as seen in Fig. 2. The subject matter of the present study is, therefore, the free flexural (or bending) vibrations of the subgroup II.1 and class 2 type of the bonded and stiffened system of Fig. 2 (see also Fig. 3). In spite of their general practical importance in advanced engineering and high-tech applications, there are a relatively small number of studies available in worldwide open scientific and engineering literature. For instance, in the case of the free vibrations of subgroup II.1 systems with bonded stiffened-plate strips, the number of published research studies is more or less limited. In this connection, one may mention some recent investigations by Baker et al. [6,7] aswell as byYuceoglu andOzerciyes [8–14]. In the case of the dynamics of the bonded joints, there exists a relatively large number of papers. Some important studies can be found in [15–23] and more recently in [10,24–31]. In passing, one can mention some investigations on group I and subgroup 1 systems given in Yuceoglu et al. [32–34]. As mentioned before, the subgroup II.1 and class 1 (of group II) case has been investigated in some detail by Yuceoglu and Ozerciyes [8–14]. However, to the best knowledge of the present authors, the subgroup II.1 and class 2 and the subgroup II.1 and class 3, etc., case studies (see also Fig. 2) are not available in the open scientific and engineering literature or related journals. Therefore, on the basis of the aforementioned brief review, the main objectives of the present investigations are the theoretical analysis of and the general method of solution and the numerical results (consistent with the theoretical analysis) of the free-bending vibrations response of composite Mindlin plates or panels stiffened by two adhesively bonded plate strips. This means that the Presented as Paper 2009-2375 at the 50th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference and Exhibit, PalmSprings, CA, 4–7May 2009; received1October 2011; revision received 13 November 2011; accepted for publication 14 November 2011. Copyright © 2011 by Jaber Javanshir, Touraj Farsadi, andUmurYuceoglu. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. Copies of this paper may be made for personal or internal use, on condition that the copier pay the $10.00 per-copy fee to the Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923; include the code 0021-8669/12 and $10.00 in correspondence with the CCC. ∗Graduate Student, Department of Aerospace Engineering. Professor, Department of Aerospace Engineering. JOURNAL OF AIRCRAFT Vol. 49, No. 4, July–August 2012

Observation of weak temperature dependence of spin diffusion length in highly-doped Si by using a non-local 3-terminal method

We conduct an experimental investigation of temperature dependence of spin diffusion length in highly doped n-type silicon by using a non-local 3-terminal method. Whereas an effect of spin drift is not negligible in non-metallic systems, it is not fully conclusive how the spin drift affects spin transport properties in highly doped Si in a non-local 3-terminal method. Here, we report on temperature dependence of spin diffusion length in the Si, and it is clarified that the spin transport is less affected by an external electric field.

Non-metallic pipe systems for use in oil and gas

This paper relates to the expanding use of non-metallic materials in piping for the transport of oilfield fluids, onshore and offshore. Qualification processes for thermoplastic and composite pipework all involve long term stress rupture tests to establish a relationship between pressure and time to failure. These qualification tests are needed to account for particular long term failure process that occur in non-metallics, and are essential to the successful application of these materials. Uses of both thermoplastics and composites in several types of pipework are discussed. These include fibreglass pipe, spoolable thermosets, reinforced thermoplastic pipe, flexible risers, rigid risers and, finally, repair and rehabilitation.

ChemInform Abstract: Ferromagnetism in Semiconductors and Oxides. Prospects from a Ten Years′ Perspective

AbstractReview: 109 refs.

A Macrocyclic Ligand as Receptor and ZnII‐Complex Receptor for Anions in Water: Binding Properties and Crystal Structures

Binding properties of 24,29-dimethyl-6,7,15,16-tetraoxotetracyclo[19.5.5.0(5,8).0(14,17)]-1,4,9,13,18,21,24,29-octaazaenatriaconta-Δ(5,8),Δ(14,17)-diene ligand L towards Zn(II) and anions, such as the halide series and inorganic oxoanions (phosphate (Pi), sulfate, pyrophosphate (PPi), and others), were investigated in aqueous solution; in addition, the Zn(II)/L system was tested as a metal-ion-based receptor for the halide series. Ligand L is a cryptand receptor incorporating two squaramide functions in an over-structured chain that connects two opposite nitrogen atoms of the Me(2)[12]aneN(4) polyaza macrocyclic base. It binds Zn(II) to form mononuclear species in which the metal ion, coordinated by the Me(2)[12]aneN(4) moiety, lodges inside the three-dimensional cavity. Zn(II)-containing species are able to bind chloride and fluoride at the physiologically important pH value of 7.4; the anion is coordinated to the metal center but the squaramide units play the key role in stabilizing the anion through a hydrogen-bonding network; two crystal structures reported here clearly show this aspect. Free L is able to bind fluoride, chloride, bromide, sulfate, Pi, and PPi in aqueous solution. The halides are bound at acidic pH, whereas the oxoanions are bound in a wide range of pH values ranging from acidic to basic. The cryptand cavity, abundant in hydrogen-bonding sites at all pH values, allows excellent selectivity towards Pi to be achieved mainly at physiological pH 7.4. By joining amine and squaramide moieties and using this preorganized topology, it was possible, with preservation of the solubility of the receptor, to achieve a very wide pH range in which oxoanions can be bound. The good selectivity towards Pi allows its discrimination in a manner not easily obtainable with nonmetallic systems in aqueous environment.

A ten-year perspective on dilute magnetic semiconductors and oxides

Over the past ten years, the search for compounds combining the properties of semiconductors and ferromagnets has evolved into an important field of materials science. This endeavour has been fuelled by many demonstrations of remarkable low-temperature functionalities in the ferromagnetic structures (Ga,Mn)As and p-(Cd,Mn)Te, and related compounds, and by the theoretical prediction that magnetically doped, p-type nitride and oxide semiconductors might support ferromagnetism mediated by valence-band holes to above room temperature. Indeed, ferromagnetic signatures persisting at high temperatures have been detected in a number of non-metallic systems, even under conditions in which the presence of spin ordering was not originally anticipated. Here I review recent experimental and theoretical developments, emphasizing that they not only disentangle many controversies and puzzles accumulated over the past decade but also offer new research prospects.

A Commentary on “Diffusion, Mobility and Their Interrelation through Free Energy in Binary Metallic Systems,” L.S. Darken: Trans. AIME, 1948, vol. 175, p. 184ff

AS an undergraduate and graduate student of metallurgy, the subject of diffusion at first appeared to me as being rather empirical when compared with thermodynamics. It wasn’t until the end of the course when multicomponent diffusion was discussed and when Darken’s phenomenological equations were described that I appreciated the fundamental nature of diffusion and how the earlier descriptions of flux were really only special cases of Darken’s description in his classic article. Indeed, now that I teach diffusion and transport myself, I often wonder whether the subject should be introduced through Darken’s equations, which related diffusivity to mobility and activity, rather than through Fick’s First Law. In his classic article titled ‘‘Diffusion, Mobility and Their Interrelation Through Free Energy in Binary Metallic Systems,’’ Dr. Darken presents his phenomenological analysis of diffusion on binary systems. It is divided into two interrelated sections, with the first handling the issue of marker movement and the second handling the effect of nonideality on diffusion. His treatment is general, but he utilizes the then recent experimental work by Smigelskas and Kirkendall, which showed marker movement in the Cu-brass couple as an example for the first part of his analysis. As a basis for his analysis, he separated the diffusive flux from the flux associated with marker movements (gross material flow) and established a Lagrangian reference frame from which both fluxes were observed. Then, by making a critical assumption that gram atomic volume (density) is constant, he developed two equations: v 1⁄4 D2 D1 ð Þ2 @x and D 1⁄4 N1D2 þN2D1: The first expression identifies individual (intrinsic) diffusion coefficients for the two diffusing species and quantitatively links the marker movement to their difference and the concentration gradient at a given location. The significance of the equation is that, assuming that there are two different diffusivities and markers are found to move, it shows how the problem can be treated. The second equation evolves from the first because the homogenization rate is dependent on the two diffusivities, which are linked through the marker movement. It essentially identifies the chemical diffusion coefficient that is measured through the Bolzmann–Matano analysis. The work by Johnson shows that the diffusivity in the 0.5Au–0.5Ag system deviates significantly from what is expected from the ideal tracer diffusivity and is used as a basis for the second part of his analysis. This analysis is, in my opinion, possibly even more general in nature because it only assumes that a drift velocity on atoms results from the force arising from the magnitude of a potential gradient. The resulting equation, D 1⁄4 N1D 2 þN2D 1 1þN2 ln c2 dN2 ; provides the invaluable link that describes how the chemical diffusion coefficient deviates from the ideal (tracer) coefficient, depending on the nature of the thermodynamic solution. Thus, the equation describes a dynamic phenomenon in terms of a thermodynamic state function in an elegant manner and describes how the interactions between the elements (or the enthalpy of mixing) influences diffusion, and how it could lead to uphill diffusion. In practice, this information provides a way to utilize databases and models on thermodynamic solutions to predict diffusion coefficients in non-ideal systems. The beauty of Darken’s analysis lies in that it is devoid of any assumptions of mechanisms or structural aspects of the material. Indeed, at the very onset of his introduction, he exemplifies dissimilar ion mobility in nonmetallic systems, such as Ag2S and FeO, in addition to the classic Cu-Zn system used in the experiments of Smigelskas and Kirkendall. It comes as no surprise that this article published in 1948 still rates as one of the most cited articles in our community. Beyond the elegance and scientific importance of Darken’s article, it is of practical importance to processing and high-temperature performance of more or less all structural multicomponent alloys that contain substitutional alloying elements (e.g., alloyand stainless steels and super-alloys). His treatment also has been extended to ceramics, polymers, metallic melts, and has been used in structurally very different systems, such as the molecular diffusion of CH4 and CF4 in Zeolite, which in effect confirms the generality of Dr. Darken’s elegant analysis. SEETHARAMAN SRIDHAR, POSCO Professor of Materials Science and Engineering, is with Carnegie Mellon University, 5000 Forbes Avenue, Wean Hall 4317, Pittsburgh, PA 15213. Contact e-mail: sridhars@andrew.cmu.edu Article published online February 6, 2010

A Commentary on “Diffusion, Mobility and Their Interrelation through Free Energy in Binary Metallic Systems,” L.S. Darken: Trans. AIME, 1948, vol. 175, p. 184ff

AS an undergraduate and graduate student of metallurgy, the subject of diffusion at first appeared to me as being rather empirical when compared with thermodynamics. It wasn’t until the end of the course when multicomponent diffusion was discussed and when Darken’s phenomenological equations were described that I appreciated the fundamental nature of diffusion and how the earlier descriptions of flux were really only special cases of Darken’s description in his classic article. Indeed, now that I teach diffusion and transport myself, I often wonder whether the subject should be introduced through Darken’s equations, which related diffusivity to mobility and activity, rather than through Fick’s First Law. In his classic article titled ‘‘Diffusion, Mobility and Their Interrelation Through Free Energy in Binary Metallic Systems,’’ Dr. Darken presents his phenomenological analysis of diffusion on binary systems. It is divided into two interrelated sections, with the first handling the issue of marker movement and the second handling the effect of nonideality on diffusion. His treatment is general, but he utilizes the then recent experimental work by Smigelskas and Kirkendall, which showed marker movement in the Cu-brass couple as an example for the first part of his analysis. As a basis for his analysis, he separated the diffusive flux from the flux associated with marker movements (gross material flow) and established a Lagrangian reference frame from which both fluxes were observed. Then, by making a critical assumption that gram atomic volume (density) is constant, he developed two equations: v 1⁄4 D2 D1 ð Þ2 @x and D 1⁄4 N1D2 þN2D1: The first expression identifies individual (intrinsic) diffusion coefficients for the two diffusing species and quantitatively links the marker movement to their difference and the concentration gradient at a given location. The significance of the equation is that, assuming that there are two different diffusivities and markers are found to move, it shows how the problem can be treated. The second equation evolves from the first because the homogenization rate is dependent on the two diffusivities, which are linked through the marker movement. It essentially identifies the chemical diffusion coefficient that is measured through the Bolzmann–Matano analysis. The work by Johnson shows that the diffusivity in the 0.5Au–0.5Ag system deviates significantly from what is expected from the ideal tracer diffusivity and is used as a basis for the second part of his analysis. This analysis is, in my opinion, possibly even more general in nature because it only assumes that a drift velocity on atoms results from the force arising from the magnitude of a potential gradient. The resulting equation, D 1⁄4 N1D 2 þN2D 1 1þN2 ln c2 dN2 ; provides the invaluable link that describes how the chemical diffusion coefficient deviates from the ideal (tracer) coefficient, depending on the nature of the thermodynamic solution. Thus, the equation describes a dynamic phenomenon in terms of a thermodynamic state function in an elegant manner and describes how the interactions between the elements (or the enthalpy of mixing) influences diffusion, and how it could lead to uphill diffusion. In practice, this information provides a way to utilize databases and models on thermodynamic solutions to predict diffusion coefficients in non-ideal systems. The beauty of Darken’s analysis lies in that it is devoid of any assumptions of mechanisms or structural aspects of the material. Indeed, at the very onset of his introduction, he exemplifies dissimilar ion mobility in nonmetallic systems, such as Ag2S and FeO, in addition to the classic Cu-Zn system used in the experiments of Smigelskas and Kirkendall. It comes as no surprise that this article published in 1948 still rates as one of the most cited articles in our community. Beyond the elegance and scientific importance of Darken’s article, it is of practical importance to processing and high-temperature performance of more or less all structural multicomponent alloys that contain substitutional alloying elements (e.g., alloyand stainless steels and super-alloys). His treatment also has been extended to ceramics, polymers, metallic melts, and has been used in structurally very different systems, such as the molecular diffusion of CH4 and CF4 in Zeolite, which in effect confirms the generality of Dr. Darken’s elegant analysis. SEETHARAMAN SRIDHAR, POSCO Professor of Materials Science and Engineering, is with Carnegie Mellon University, 5000 Forbes Avenue, Wean Hall 4317, Pittsburgh, PA 15213. Contact e-mail: sridhars@andrew.cmu.edu Article published online February 6, 2010

Finite element analysis of weakened roots restored with composite resin and posts

Finite element analysis (FEA) was used to investigate the influence of different post systems on the stress distribution of weakened teeth under oblique-load application. A maxillary central incisor root obtained from a sound tooth was weakened by partial removal of dentin inside the root canal. Seven two-dimensional numerical models, one from the sound tooth and six from the weakened root restored with composite resin and post systems were created as follows - ST: sound tooth; CPC: cast CuAl post and core; SSP: stainless steel post + composite core; GP: fiberglass + composite core; CP: carbon fiber + composite core; ZP: zirconium dioxide post + composite core; TP: titanium post + composite core. The numerical models were considered to be restored with a leucite-reinforced all-ceramic crown and received a 45 masculine occlusal load (10 N) on the lingual surface.All the materials and structures were considered linear elastic, homogeneous, and isotropic, with the exception of fiberglass and carbon fiber posts which assumed orthotropic behavior. The numerical models were plotted and meshed with isoparametric elements, and the results were analyzed using von Mises and Sy stress criteria. When compared with the sound tooth, FEA revealed differences in stress distribution when post systems were used. Among the restored teeth, the use of CPC, SSP, ZP, and TP resulted in higher stress concentration in the post itself when compared to GP and CP. Therefore, results from the FEA images suggested that the use of non-metallic post systems could result in improved mechanical behavior for the weakened restored teeth.

Flexural Strengthening of RC Beams with Prestressed CFRP Sheets: Using Nonmetallic Anchor Systems

This paper presents the flexural behavior of reinforced concrete beams strengthened with prestressed carbon fiber-reinforced polymer (CFRP) sheets using nonmetallic anchor systems. The developed nonmetallic anchor systems replace the permanent steel anchorage. Nine doubly reinforced concrete beams are tested with various types of nonmetallic anchor systems such as nonanchored U-wraps, mechanically anchored U-wraps, and CFRP sheet-anchored U-wraps. The flexural behavior of the tested beams, including detailed failure modes of each nonmetallic anchor system, is investigated. The study shows that the developed nonmetallic anchors are more effective in resisting peeling-off cracks compared to the permanent steel anchors and the beams strengthened with the nonmetallic anchors provide comparable load-carrying capacity with respect to the steel anchored control beam.