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Competencies Required for the Design and Implementation of Manufacturing Systems for Advanced Composite Structures

Description: The problem with which this investigation is concerned is that of identifying and prioritizing the competencies required to design and implement manufacturing systems for advanced composite structures. The classical Delphi procedure is the research method used for the conduct of this study. A five-member advisory board developed a list of seventeen categories under which the competencies would reside. In the first-round questionnaire, the seventeen categories were presented to a Delphi panel of experts who provided up to five competencies required in each category. The first-round returns provided two new categories and 973 competency statements. Duplications were eliminated and 366 competency statements remained in nineteen categories. The second, third, and fourth rounds were a reiterative rating process. The panel was asked to rate the items in the questionnaire based on their relative importance to the intent of the study. The importance rating scale included "very important," "important," "slightly important," and "unimportant." The means and interquartile ranges were calculated for each statement and provided as feedback in the successive round. Kendall's coefficient of concordance W for tied ranks was used to validate the panel consensus. The W was significant at the .01 level for each of the three rounds where rating was performed. The data were presented in rank order within categories by importance level. Eighteen percent of the competency statements were rated "very important," 77 percent "important, and 5 percent "slightly important." No statements were rated "unimportant" by the panel. It was concluded that, as indicated by the 19 categories and 366 competencies, the scope of the requirements for designing and implementing manufacturing systems for advanced composite structures represent a broad range of knowledge and skill requirements. The breadth of the range of the requirements indicated the need for the development of areas of specialization within the subject field to adequately ...
Date: May 1986
Creator: Lange, Robert Douglas
Partner: UNT Libraries

Fabrication and Properties of Hot-Pressed Molybdenum Disilicide

Description: Report presenting an investigation of hot-pressed molbdenum disilicide bodies produced by industrial processes at a temperature of 2950 degrees and a pressure of 3000 pounds per square inch. Results regarding the short-time tensile strength, stress-rupture data, compression strength, air-corrosion resistance, hardness, coefficient of linear thermal expansion, thermal conductivity, and density are provided.
Date: May 26, 1950
Creator: Long, Roger A.
Partner: UNT Libraries Government Documents Department

On the Permeability of Porous Materials

Description: Note presenting an investigation of the effects on porous-material permeability characteristics of the absolute pressure level, choking of the flow, bending the material, and other factors. Experiments showed permeability characteristics to be appreciably affected by absolute pressure level, flow choking, and thickness of the material. Results regarding testing with wire cloth and sintered metal are provided.
Date: January 1956
Creator: Yates, E. Carson, Jr.
Partner: UNT Libraries Government Documents Department

Solid Lubrication Mechanisms in Laser Deposited Nickel-titanium-carbon Metal Matrix Composites

Description: A Ni/TiC/C metal matrix composite (MMC) has been processed using the laser engineered net shaping (LENS) process from commercially available powders with a Ni-3Ti-20C (atomic %) composition. This processing route produces the in-situ formation of homogeneously distributed eutectic and primary titanium carbide and graphite precipitates throughout the Ni matrix. The composite exhibits promising tribological properties when tested in dry sliding conditions with a low steady state coefficient of friction (CoF) of ~0.1 and lower wear rates in comparison to LENS deposited pure Ni. The as deposited and tribologically worn composite has been characterized using Auger electron spectroscopy, scanning electron microscopy (SEM), X-ray diffraction, high resolution transmission electron microscopy (HRTEM) with energy dispersive spectroscopy (EDS), dual beam focused ion beam SEM (FIB/SEM) serial sectioning and Vickers micro-hardness testing. The evolution of subsurface stress states and precipitate motion during repeated sliding contact has been investigated using finite element analysis (FEA). The results of FIB/SEM serial sectioning, HRTEM, and Auger electron spectroscopy in conjunction with FEA simulations reveal that the improved tribological behavior is due to the in-situ formation of a low interfacial shear strength amorphous carbon tribofilm that is extruded to the surface via refined Ni grain boundaries.
Date: December 2012
Creator: Mogonye, Jon-Erik
Partner: UNT Libraries

Accuracy and Efficiency in Computational Chemistry: The Correlation Consistent Composite Approach

Description: One of the central concerns of computational chemistry is that of efficiency (i.e. the development of methodologies which will yield increased accuracy of prediction without requiring additional computational resources – RAM, disk space, computing time). Though the equations of quantum mechanics are known, the solutions to these equations often require a great deal of computing power. This dissertation primarily concerns the theme of improved computational efficiency (i.e. the achievement of greater accuracy with reduced computational cost). Improvements in the efficiency of computational chemistry are explored first in terms of the correlation consistent composite approach (ccCA). The ccCA methodology was modified and this enhanced ccCA methodology was tested against the diverse G3/05 set of 454 energetic properties. As computational efficiency improves, molecules of increasing size may be studied and this dissertation explored the issues (differential correlation and size extensivity effects) associated with obtaining chemically accurate (within 1 kcal mol-1) enthalpies of formation for hydrocarbon molecules of escalating size. Two applied projects are also described; these projects concerned the theoretical prediction of a novel rare gas compound, FKrOH, and the mechanism of human glutathione synthetase’s (hGS) negative cooperativity. The final work examined the prospect for the parameterization of the modified embedded atom method (MEAM) potential using first principles calculations of dimer and trimer energies of nickel and carbon systems. This method of parameterization holds promise for increasing the accuracy of simulations for bulk properties within the field of materials science.
Date: August 2011
Creator: Wilson, Brent R.
Partner: UNT Libraries

Handbook of Structural Stability Part 2: Buckling of Composite Elements

Description: "The local buckling of stiffener sections and the buckling of plates with sturdy stiffeners are reviewed, and the results are summarized in charts and tables. Numerical values of buckling coefficients are presented for longitudinally compressed stiffener sections of various shapes, for stiffened plates loaded in longitudinal compression and in shear, and for stiffened cylinders loaded in torsion. Although the data presented consist primarily of elastic-buckling coefficients, the effects of plasticity are discussed for a few special cases" (p. 1).
Date: July 1957
Creator: Becker, Herbert
Partner: UNT Libraries Government Documents Department

New, higher-order, elasticity-based micromechanics model

Description: The formulation for a new homogenization theory is presented. The theory utilizes a higher-order, elasticity-based cell analysis of a periodic array of unit cells. The unit cell is discretized into subregions or subcells. The displacement field within each subcell is approximated by an (truncated) eigenfunction function expansion of up to fifth order. The governing equations are developed by satisfying the pointwise governing equations of geometrically linear continuum mechanics exactly up through the given order of the subcell displacement fields. The specified governing equations are valid for any type of constitutive model used to describe the behavior of the material in a subcell. The fifth order theory is subsequently reduced to a third order theory. The appropriate reduction of the fifth and third order theories to the first order theory (which corresponds to a variant of the original method of cells (MOC) (Aboudi, 1991) theory) is outlined. The 3D ECM theory correctly reduces to the 2D ECM theory microstructures and the exact 1D theory for bilaminated structures. Comparison of the predicted bulk and local responses with published results indicates that the theory accurately predicts both types of responses. Furthermore, it is shown that the higher order fields introduced coupling effects between the local fields that can result in substantial changes in the predicted bulk inelastic response of a composite.
Date: January 1, 2003
Creator: Williams, T. O. (Todd O.)
Partner: UNT Libraries Government Documents Department

Waste Materials from Tetra Pak Packages as Reinforcement of Polymer Concrete

Description: This article discusses how compressive and flexural strength and modulus of elasticity decrease gradually, when either Tetra Pak particle concentration or particle size is increased.
Date: September 28, 2015
Creator: Martínez-López, Miguel; Martínez-Barrera, Gonzalo; Barrera-Díaz, Carlos; Ureña-Núñez, Fernando & Brostow, Witold, 1934-
Partner: UNT College of Engineering

Thermochemistry Investigations Via the Correlation Consistent Composite Approach

Description: Since the development of the correlation consistent composite approach (ccCA) in 2006, ccCA has been shown to be applicable across the periodic table, producing, on average, energetic properties (e.g., ionization potentials, electron affinities, enthalpies of formation, bond dissociation energies) within 1 kcal/mol for main group compounds. This dissertation utilizes ccCA in the investigation of several chemical systems including nitrogen-containing compounds, sulfur-containing compounds, and carbon dioxide complexes. The prediction and calculation of energetic properties (e.g., enthalpies of formation and interaction energies) of the chemical systems investigated within this dissertation has led to suggestions of novel insensitive highly energetic nitrogen-containing compounds, defined reaction mechanisms for sulfur compounds allowing for increased accuracy compared to experimental enthalpies of formation, and a quantitative structure activity relationship for altering the affinity of CO2 with substituted amine compounds. Additionally, a study is presented on the convergence of correlation energy and optimal domain criteria for local Møller–Plesset theory (LMP2).
Date: December 2012
Creator: Jorgensen, Kameron R.
Partner: UNT Libraries

Anisotropic fiber alignment in composite structures

Description: High strength material composite structures are formed with oriented fibers to provide controlled anisotropic fibers. Fibers suspended in non-dilute concentrations (e.g., up to 20 volume percent for fibers having an aspect ratio of 20) in a selected medium are oriented by moving an axially spaced array of elements in the direction of desired fiber alignment. The array elements are generally perpendicular to the desired orientation. The suspension medium may also include sphere-like particles where the resulting material is a ceramic.
Date: December 31, 1992
Creator: Graham, A.L.; Mondy, L.A. & Guell, D.C.
Partner: UNT Libraries Government Documents Department

Characterization of three dimensional fiber orientation in short-fiber composites

Description: A mathematical procedure for recovering from image analysis the three dimensional nonsymmetric fiber-orientation distribution in short-fiber composites is proposed. Microphotographs from two orthogonal faces of a composite sample are needed to determine the three dimensional fiber orientation. A simple weighting function is derived to take into account the probability of intercepting fibers at varying inclination angles. The present procedure improves the previous works of other researchers in the following two aspects. First, it can obtain the single-angle fiber-orientation distribution from one micrograph in reference to the normal of the photographed surface. This distribution is often needed in predicting the mechanical and physical properties of short-fiber composites in this direction. Second, no symmetry in fiber-orientation distribution is assumed in the determination of the three dimensional fiber-orientation, which makes the present procedure more practical and versatile.
Date: May 1, 1995
Creator: Zhu, Yuntian T. & Blumenthal, W.R.
Partner: UNT Libraries Government Documents Department

The performance of a composite engine consisting of a reciprocating spark-ignition engine, a blow-down turbine, and a steady-flow turbine

Description: Report presenting an analysis of the performance of a composite engine consisting of a reciprocating spark-ignition engine, two superchargers, a blowdown turbine, and a steady-flow turbine. The performance of the configuration was analyzed in order to determine the suitability and cost of design compromises when the size of turbines and superchargers and all gear ratios are assumed fixed. Results regarding the variable-component system, fixed-component system, and auxiliary-propeller system are provided.
Date: October 1947
Creator: Turner, L. Richard & Noyes, Robert N.
Partner: UNT Libraries Government Documents Department

Handbook of Structural Stability Part 2: Buckling of Composite Elements

Description: "The local buckling of stiffener sections and the buckling of plates with sturdy stiffeners are reviewed, and the results are summarized in charts and tables. Numerical values of buckling coefficients are presented for longitudinally compressed stiffener sections of various shapes, for stiffened plates located in longitudinal compression and in shear, and for stiffened cylinders loaded in torsion. Although the data presented consist primarily of elastic-buckling coefficients, the effects of plasticity are discussed for a few special cases" (p. 1).
Date: July 1957
Creator: Becker, Herbert
Partner: UNT Libraries Government Documents Department

CRADA Final Report for NFE-08-01826: Development and application of processing and processcontrol for nano-composite materials for lithium ion batteries

Description: Oak Ridge National Laboratory and A123 Systems, Inc. collaborated on this project to develop a better understanding, quality control procedures, and safety testing for A123 System’s nanocomposite separator (NCS) technology which is a cell based patented technology and separator. NCS demonstrated excellent performance. x3450 prismatic cells were shown to survive >8000 cycles (1C/2C rate) at room temperature with greater than 80% capacity retention with only NCS present as an alternative to conventional polyolefin. However, for a successful commercialization, the coating conditions required to provide consistent and reliable product had not been optimized and QC techniques for being able to remove defective material before incorporation into a cell had not been developed. The work outlined in this report addresses these latter two points. First, experiments were conducted to understand temperature profiles during the different drying stages of the NCS coating when applied to both anode and cathode. One of the more interesting discoveries of this study was the observation of the large temperature decrease experienced by the wet coating between the end of the infrared (IR) drying stage and the beginning of the exposure to the convection drying oven. This is not a desirable situation as the temperature gradient could have a deleterious effect on coating quality. Based on this and other experimental data a radiative transfer model was developed for IR heating that also included a mass transfer module for drying. This will prove invaluable for battery coating optimization especially where IR drying is being employed. A stress model was also developed that predicts that under certain drying conditions tensile stresses are formed in the coating which could lead to cracking that is sometimes observed after drying is complete. Prediction of under what conditions these stresses form is vital to improving coating quality. In addition to understanding the drying process ...
Date: December 15, 2012
Creator: Daniel, C.; Armstrong, B.; Maxey, C.; Sabau, A.; Wang, H.; Hagans, P. (A123 Systems, Inc.) et al.
Partner: UNT Libraries Government Documents Department