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Sample records for qualified kevlar composite

  1. Testing of Full Scale Flight Qualified Kevlar Composite Overwrapped Pressure Vessels

    NASA Technical Reports Server (NTRS)

    Greene, Nathanael; Saulsberry, Regor; Yoder, Tommy; Forsyth, Brad; Thesken, John; Phoenix, Leigh

    2007-01-01

    Many decades ago NASA identified a need for low-mass pressure vessels for carrying various fluids aboard rockets, spacecraft, and satellites. A pressure vessel design known as the composite overwrapped pressure vessel (COPV) was identified to provide a weight savings over traditional single-material pressure vessels typically made of metal and this technology has been in use for space flight applications since the 1970's. A typical vessel design consisted of a thin liner material, typically a metal, overwrapped with a continuous fiber yarn impregnated with epoxy. Most designs were such that the overwrapped fiber would carry a majority of load at normal operating pressures. The weight advantage for a COPV versus a traditional singlematerial pressure vessel contributed to widespread use of COPVs by NASA, the military, and industry. This technology is currently used for personal breathing supply storage, fuel storage for auto and mass transport vehicles and for various space flight and aircraft applications. The NASA Engineering and Safety Center (NESC) was recently asked to review the operation of Kevlar 2 and carbon COPVs to ensure they are safely operated on NASA space flight vehicles. A request was made to evaluate the life remaining on the Kevlar COPVs used on the Space Shuttle for helium and nitrogen storage. This paper provides a review of Kevlar COPV testing relevant to the NESC assessment. Also discussed are some key findings, observations, and recommendations that may be applicable to the COPV user community. Questions raised during the investigations have revealed the need for testing to better understand the stress rupture life and age life of COPVs. The focus of this paper is to describe burst testing of Kevlar COPVs that has been completed as a part of an the effort to evaluate the effects of ageing and shelf life on full scale COPVs. The test articles evaluated in this discussion had a diameter of 22 inches for S/N 014 and 40 inches for S/N 011. The

  2. Kevlar reinforced neoprene composites

    NASA Technical Reports Server (NTRS)

    Penn, B. G.; Daniels, J. G.; White, W. T.; Thompson, L. M.; Clemons, L. M.

    1985-01-01

    Kevlar/neoprene composites were prepared by two techniques. One method involved the fabrication of a composite from a rubber prepreg prepared by coating Kevlar with viscous neoprene solution and then allowing the solvent to evaporate (solution impregnation technique). The second method involved heating a stack of Kevlar/neoprene sheets at a temperature sufficient to cause polymer flow (melt flow technique). There was no significant difference in the breaking strength and percent elongation for samples obtained by the two methods; however the shear strength obtained for samples fabricated by the solution impregnation technique (275 psi) was significantly higher than that found for the melt flow fabricated samples (110 psi).

  3. Kevlar reinforced neoprene composites

    NASA Technical Reports Server (NTRS)

    Penn, B. G.; Daniels, J. G.; White, W. T.; Thompson, L. M.; Clemons, L. M.

    1985-01-01

    Kevlar/neoprene composites were prepared by two techniques. One method involved the fabrication of a composite from a rubber prepreg prepared by coating Kevlar with viscous neoprene solution and then allowing the solvent to evaporate (solution impregnation technique). The second method involved heating a stack of Kevlar/neoprene sheets at a temperature sufficient to cause polymer flow (melt flow technique). There was no significant difference in the breaking strength and percent elongation for samples obtained by the two methods; however the shear strength obtained for samples fabricated by the solution impregnation technique (275 psi) was significantly higher than that found for the melt flow fabricated samples (110 psi).

  4. Kevlar reinforced neoprene composites

    SciTech Connect

    Penn, B.G.; Daniels, J.G.; White, W.T.; Thompson, L.M.; Clemons, L.M.

    1985-04-01

    Kevlar/neoprene composites were prepared by two techniques. One method involved the fabrication of a composite from a rubber prepreg prepared by coating kevlar with viscous neoprene solution and then allowing the solvent to evaporate (solution impregnation technique). The second method involved heating a stack of kevlar/neoprene sheets at a temperature sufficient to cause polymer flow (melt flow technique). There was no significant difference in the breaking strength and percent elongation for samples obtained by the two methods; however the shear strength obtained for samples fabricated by the solution impregnation technique (275 psi) was significantly higher than that found for the melt flow fabricated samples (110 psi). 1 reference, 2 tables.

  5. Kevlar and carbon composites compared

    SciTech Connect

    Demmler, A.W.

    1985-02-01

    Characteristics of advanced composites are investigated. The fibers considered are Kevlar and carbon. The greatest advantage of composites over metals is emphasized, and lies in their permitting designers to obtain properties in exactly the locations desired. Kevlar replaced S-glass on the Trident 2 missile, saving 800 lbs. and adding 800 miles to its range. Military aircraft builders find that advanced carbon composites more often than not win out over Kevlar.

  6. Compressive response of Kevlar/epoxy composites

    SciTech Connect

    Yeh, J.R.; Teply, J.L.

    1988-03-01

    A mathematical model is developed from the principle of minimum potential energy to determine the longitudinal compressive response of unidirectional fiber composites. A theoretical study based on this model is conducted to assess the influence of local fiber misalignment and the nonlinear shear deformation of the matrix. Numerical results are compared with experiments to verify this study; it appears that the predicted compressive response coincides well with experimental results. It is also shown that the compressive strength of Kevlar/epoxy is dominated by local shear failure. 12 references.

  7. Aging and quality assurance of Kevlar 49-epoxy composites

    SciTech Connect

    Morgan, R.J.

    1981-05-15

    The aging of Kevlar 49-epoxy composites under the service environment conditions expected by ESA will be insignificant to the best of our knowledge at this time. However, certain precautions in materials acceptance criteria and composite fabrication should be followed.

  8. The stab resistant properties of Kevlar/STF composites

    NASA Astrophysics Data System (ADS)

    Zhao, Jinhua; Cao, Hailin; Li, Xia; Wan, Junxi; Wang, Kun; Zhang, Jinfeng

    2012-04-01

    A colloidal shear thickening fluid (STF) was prepared by dispersing submicron silica particles in Polyethylene glycol 200(PEG200) with ball-milling technique. Kevlar/STF composites were fabricated by soaking Kevlar in the solution of STF diluted by ethanol. The rheological behavior of the fluid with various concentrations and the effect of dilution ratio on stab resistant properties of Kevlar/STF composites were studied. The result shows that the initial viscosity and the highest viscosity of the fluid increase as the weight fraction of SiO2 increasing with the weight fraction ranging from 50% to 60%, while the critical shear rate decrease as the weight fraction increasing. The fluid has notable shear thickening behavior at SiO2 weight fraction of 59%. Two solutions with 1:0.5 and 1:1weight ratio of STF:ethanol were used to fabricate Kevlar/STF composites. It is found that the composites fabricated by solution with dilution ratio 1:1 show better stab resistant properties. The Kevlar/STF composites exhibit better stab resistant properties than the neat Kevlar with the same areal density.

  9. The stab resistant properties of Kevlar/STF composites

    NASA Astrophysics Data System (ADS)

    Zhao, Jinhua; Cao, Hailin; Li, Xia; Wan, Junxi; Wang, Kun; Zhang, Jinfeng

    2011-11-01

    A colloidal shear thickening fluid (STF) was prepared by dispersing submicron silica particles in Polyethylene glycol 200(PEG200) with ball-milling technique. Kevlar/STF composites were fabricated by soaking Kevlar in the solution of STF diluted by ethanol. The rheological behavior of the fluid with various concentrations and the effect of dilution ratio on stab resistant properties of Kevlar/STF composites were studied. The result shows that the initial viscosity and the highest viscosity of the fluid increase as the weight fraction of SiO2 increasing with the weight fraction ranging from 50% to 60%, while the critical shear rate decrease as the weight fraction increasing. The fluid has notable shear thickening behavior at SiO2 weight fraction of 59%. Two solutions with 1:0.5 and 1:1weight ratio of STF:ethanol were used to fabricate Kevlar/STF composites. It is found that the composites fabricated by solution with dilution ratio 1:1 show better stab resistant properties. The Kevlar/STF composites exhibit better stab resistant properties than the neat Kevlar with the same areal density.

  10. Failure modes and durability of Kevlar/epoxy composites

    SciTech Connect

    Morgan, R.J.; Mones, E.T.; Steele, W.J.; Deutscher, S.B.

    1980-06-04

    The fracture topographies of Kevlar 49/epoxy composite strands and multilayer composites in the form of pressure vessels are discussed in terms of the microscopic deformation and failure processes of the composites. The effect of resin ductility and fiber-matrix interfacial bond strength on mechanisms of fiber damage are considered. The failure of the Kevlar 49 fibers by a splitting process and the parameters, such as fiber fibrillation and macromolecular chain scission, that control such a process, are discussed in relation to fiber and composite performance.

  11. Failure modes and durability of kevlar/epoxy composites

    SciTech Connect

    Morgan, R.J.; Mones, E.T.; Steele, W.J.; Deutscher, S.B.

    1981-04-01

    The fracture topographies of Kevlar 49/epoxy composite strands and multilayer composites in the form of pressure vessels are discussed in terms of the microscopic deformation and failure processes of the composites. The effect of resin ductility and fiber-matrix interfacial bond strength on mechanisms of fiber damage are considered. The failure of the Kevlar 49 fibers by a splitting process and the parameters, such as fiber fibrillation and macromolecular chain scission, that control such a process are discussed in relation to fiber and composite performance.

  12. Condition Assessment of Kevlar Composite Materials Using Raman Spectroscopy

    NASA Technical Reports Server (NTRS)

    Washer, Glenn; Brooks, Thomas; Saulsberry, Regor

    2007-01-01

    This viewgraph presentation includes the following main concepts. Goal: To evaluate Raman spectroscopy as a potential NDE tool for the detection of stress rupture in Kevlar. Objective: Test a series of strand samples that have been aged under various conditions and evaluate differences and trends in the Raman response. Hypothesis: Reduction in strength associated with stress rupture may manifest from changes in the polymer at a molecular level. If so, than these changes may effect the vibrational characteristics of the material, and consequently the Raman spectra produced from the material. Problem Statement: Kevlar composite over-wrapped pressure vessels (COPVs) on the space shuttles are greater than 25 years old. Stress rupture phenomena is not well understood for COPVs. Other COPVs are planned for hydrogen-fueled vehicles using Carbon composite material. Raman spectroscopy is being explored as an non-destructive evaluation (NDE) technique to predict the onset of stress rupture in Kevlar composite materials. Test aged Kevlar strands to discover trends in the Raman response. Strength reduction in Kevlar polymer will manifest itself on the Raman spectra. Conclusions: Raman spectroscopy has shown relative changes in the intensity and FWHM of the 1613 cm(exp -1) peak. Reduction in relative intensity for creep, fleet leader, and SIM specimens compared to the virgin strands. Increase in FWHM has been observed for the creep and fleet leader specimens compared to the virgin strands. Changes in the Raman spectra may result from redistributing loads within the material due to the disruption of hydrogen bonding between crystallites or defects in the crystallites from aging the Kevlar strands. Peak shifting has not been observed to date. Analysis is ongoing. Stress measurements may provide a tool in the short term.

  13. Interlocked fabric and laminated fabric Kevlar 49/epoxy composites

    SciTech Connect

    Guess, T.R.; Reedy, E.D. Jr.

    1988-01-01

    The mechanical behavior of a novel interlocked fabric reinforced Kevlar 49/epoxy composite has been measured and compared to those of a laminated Kevlar 49 fabric composite (which served as a reference material). Both composites were 5.0 mm thick, contained the same 50% in-plane fiber volume fraction and were fabricated in a similar manner using the same Dow DER 332 epoxy, Jeffamine T403-hardened resin system. The reference material (Material 1) was reinforced with seven plies of Dupont style 1033 Kevlar 49 fabric. A photomicrograph of a section polished parallel to one of the fiber directions is shown. The interlocked fabric was designed and woven for Sandia National Laboratories by Albany International Research Co., Dedham, MA. The main design criterion was to duplicate a sewn through-the-thickness fabric used in preliminary studies. The interlocked fabric composite (Material 2) contains roughly 4% by volume of through-the-thickness fiber reinforcement for the purpose of improving interlaminar strength. A photomicrograph of a section showing the warp-aligned binder yarns interlocking the six fabric plies together is shown. 2 refs., 8 figs.

  14. Debonding characteristics of adhesively bonded woven Kevlar composites

    NASA Technical Reports Server (NTRS)

    Mall, S.; Johnson, W. S.

    1988-01-01

    The fatigue damage mechanism of an adhesively bonded joint between fabric reinforced composite adherends was investigated with cracked-lap-shear specimens. Two bonded systems were studied: fabric Kevlar 49/5208 epoxy adherends bonded together with either EC 3445 or FM-300 adhesive. For each bonded system, two specimen geometries were tested. In all specimens tested, fatigue damage occurred in the form of cyclic debonding; however, the woven Kevlar specimens gave significantly slower debond growth rates and higher fracture toughness than previously found in the nonwoven adherend specimens. The surfaces for the woven adherends were not smooth; rather, they had regular crests (high spots) and troughs (low spots) due to the weave pattern. Radiographs of the specimens and examination of their failure surfaces revealed that fiber bridging occurred between the crests of the two adherends in the debonded region. The observed improvements in debond growth resistance and static fracture toughness are attributed to this bridging.

  15. Prediction of long-term failure in Kevlar 49 composites

    SciTech Connect

    Gerstle, F.P. Jr.

    1982-01-01

    Creep rupture data in Kevlar 49 epoxy usually exhibit considerable scatter: the coefficient of variation (CV) about the mean failure time at a given stress exceeds 100%. Quasi-static strength data, in contrast, shows little scatter: <4% CV for pressure vessels and <10% for impregnated strands. In this paper analysis of existing creep rupture data on Kevlar epoxy vessels at four storage pressures has produced an interesting and useful result. It was found that a significant portion of the scatter in failure times for pressure vessels is due to spool-to-spool variation in the eight spools of Kevlar fibers used to wind the vessels. The order rank of mean times to failure was consistent over a pressure range from 3400 to 4300 psi, 68 to 86% of short term burst. Also, the coefficient of variation about the mean failure time for each spool was less than that for the total sample. The statistical inference that the sample is nonhomogeneous was supported by a nonparametric check using the Kruskal-Wallis test, and by a parametric analysis of variance. The order rank found in long-term tests did not unequivocally agree with static strength ranks; several spool sets were distinctly high or low. The implication is that, while static strengths are not valid predictors of long-term behavior, short term creep rupture tests at high stress definitely are. The material difference which causes the spool-to-spool variations has not yet been identified for all eight spools. However, it appears that Kevlar behavior at lower pressures may be predicted through the use of curves fitted to the data for each spool. A power law relating failure time to pressure, t = t/sub 0/(p/p/sub 0/)/sup m/, was found to fit the data reasonably well. The implication is that, both in composite vessel design and in creep rupture experiments, the pressure (or stress) level be carefully controlled.

  16. Flight service evaluation of Kevlar-49/epoxy composite panels in wide-bodied commercial transport aircraft

    NASA Technical Reports Server (NTRS)

    Stone, R. H.

    1977-01-01

    Kevlar-49 fairing panels, installed as flight service components on three L-1011s, were inspected after three years' service, and found to be performing satisfactorily. There are six Kevlar-49 panels on each aircraft, including sandwich and solid laminate wing-body panels, and 150 C service aft engine fairings. The service history to date indicates that Kevlar-49 epoxy composite materials have satisfactory service characteristics for use in aircraft secondary structure.

  17. Thermoviscoelastic characterization and predictions of Kevlar/epoxy composite laminates

    SciTech Connect

    Gramoll, K.C.

    1988-01-01

    This study consisted of two main parts, the thermoviscoelastic characterization of Kevlar 49/Fiberite 7714A epoxy composite lamina and the development of a numerical procedure to predict the viscoelastic response of any general laminate constructed from the same material. The four orthotropic material properties, S{sub 11}, S{sub 12}, S{sub 22}, and S{sub 66}, were characterized by 20-minute static creep tests on unidirectional ((0){sub s}, (10){sub s}, and (90){sub 16}) lamina specimens. A new numerical procedure to predict long-term laminate properties from lamina properties (obtained experimentally) was developed. Numerical instabilities and time constraints associated with viscoelastic numerical techniques were discussed and solved. The numerical procedure was incorporated into a user-friendly microcomputer program called Viscoelastic Composite Analysis Program (VCAP), which is available for IBM PC type computers. The program was designed for ease of use and includes graphics, menus, help messages, etc. The final phase of the study involved testing actual laminates constructed from the characterized material, Kevlar/epoxy, at various temperature and load levels for 4 to 5 weeks.

  18. Thermoviscoelastic characterization and prediction of Kevlar/epoxy composite laminates

    NASA Technical Reports Server (NTRS)

    Gramoll, K. C.; Dillard, D. A.; Brinson, H. F.

    1990-01-01

    The thermoviscoelastic characterization of Kevlar 49/Fiberite 7714A epoxy composite lamina and the development of a numerical procedure to predict the viscoelastic response of any general laminate constructed from the same material were studied. The four orthotropic material properties, S sub 11, S sub 12, S sub 22, and S sub 66, were characterized by 20 minute static creep tests on unidirectional (0) sub 8, (10) sub 8, and (90) sub 16 lamina specimens. The Time-Temperature Superposition-Principle (TTSP) was used successfully to accelerate the characterization process. A nonlinear constitutive model was developed to describe the stress dependent viscoelastic response for each of the material properties. A numerical procedure to predict long term laminate properties from lamina properties (obtained experimentally) was developed. Numerical instabilities and time constraints associated with viscoelastic numerical techniques were discussed and solved. The numerical procedure was incorporated into a user friendly microcomputer program called Viscoelastic Composite Analysis Program (VCAP), which is available for IBM PC type computers. The program was designed for ease of use. The final phase involved testing actual laminates constructed from the characterized material, Kevlar/epoxy, at various temperatures and load level for 4 to 5 weeks. These results were compared with the VCAP program predictions to verify the testing procedure and to check the numerical procedure used in the program. The actual tests and predictions agreed for all test cases which included 1, 2, 3, and 4 fiber direction laminates.

  19. Use of titanate coupling agents in Kevlar (trade name)/phenolic composites

    SciTech Connect

    Menon, N.; Blum, F.D.; Dharani, L.R.

    1994-04-02

    Surface modification of Kevlar(R) fibers with titanate coupling agents for improved adhesion of the fiber and resin in Kevlar(R)/phenolic composites has been attempted to explore the possibility of enhancement in adhesion and bulk properties of composites for friction materials. Titanate coupling agents were used and flexural properties of the Kevlar(R)-fiber reinforced composites determined. A study of different amounts of the coupling agents at the fiber-matrix interface suggested that 2% by weight of fiber was the optimum amount, in terms of improvement in flexural properties. The composite samples with the coupling agents, showed an increase in flexural strength, over the untreated samples with the maximum increase being approx. 18% over the control. Water absorption studies were conducted on Kevlar(R)/phenolic composites treated with organotitanates to determine the effectiveness of these coupling agents in improving resistance to moisture attack. The treated Kevlar(R)/phenolic composite samples exhibited greater resistance to moisture-ingress over the untreated samples. The control samples showed a decrease of 17% in flexural strength. The largest decrease in strength was 14% for the treated samples containing coupling agent tetrakis(2-ethylhexyl)titanate (TYZOR TOT). Recovery in strength on reconditioning, was also greater for treated samples over control. A recovery in strength of ca. 94% was seen for some treated samples. Coupling agents, Composites, Kevlar, Interfaces, Mechanical properties.

  20. Flight service evaluation of Kevlar-49 epoxy composite panels in wide-bodied commercial transport aircraft

    NASA Technical Reports Server (NTRS)

    Stone, R. H.

    1982-01-01

    Kevlar-49 fairing panels, installed as flight service components on three l-1011's, were inspected after 8 years service. The fairings had accumulated a total of 62,000 hours, with one ship set having 20,850 hours service. Kevlar-49 components were found to be performing satisfactorily in service with no major problems. The only defects noted were minor impact damage, a few minor disbonds and a minor degree of fastener hole fraying and elongation. The service history to date indicates that Kevlar-49 epoxy composite materials have satisfactory service characteristics for use in aircraft secondary structures.

  1. Aging results for PRD 49 III/epoxy and Kevlar 49/epoxy composite pressure vessels

    NASA Technical Reports Server (NTRS)

    Hamstad, M. A.

    1983-01-01

    Kevlar 49/epoxy composite is growing in use as a structural material because of its high strength-to-weight ratio. Currently, it is used for the Trident rocket motor case and for various pressure vessels on the Space Shuttle. In 1979, the initial results for aging of filament-wound cylindrical pressure vessels which were manufactured with preproduction Kevlar 49 (Hamstad, 1979) were published. This preproduction fiber was called PRD 49 III. This report updates the continuing study to 10-year data and also presents 7.5-year data for spherical pressure vessels wound with production Kevlar 49. For completeness, this report will again describe the specimens of the original study with PRD 49 as well as specimens for the new study with Kevlar 49.

  2. Flight service evaluation of Kevlar-49 epoxy composite panels in wide-bodies commercial transport aircraft

    NASA Technical Reports Server (NTRS)

    Stone, R. H.

    1983-01-01

    Kevlar-49 fairing panels, installed as flight service components on three L-1011s, were inspected after 9 years of service. There are six Kevlar-49 panels on each aircraft: a left hand and right hand set of a wing body sandwich fairing; a solid laminate under wing fillet panel; and a 422 K (300 F) service aft engine fairing. The fairings have accumulated a total of 70,000 hours, with one ship set having over 24,000 hours service. The Kevlar-49 components were found to be performing satisfactorily in service with no major problems, or any condition requiring corrective action. The only defects noted were minor impact damage, a few minor disbonds and a minor degree of fastener hole fraying and elongation. These are for the most part comparable to damage noted on fiberglass fairings. The service history to date indicates that Kevlar-49 epoxy composite materials have satisfactory service characteristics for use in aircraft secondary structure.

  3. Investigation on the Crack Behaviour in Kevlar 49 Based Composite Materials using Extended Finite Element Method for Aerospace Applications

    NASA Astrophysics Data System (ADS)

    Handa, Danish; Sekhar Dondapati, Raja; Kumar, Abhinav

    2017-08-01

    Ductile to brittle transition (DTBT) is extensively observed in materials under cryogenic temperatures, thereby observing brittle failure due to the non-resistance of crack propagation. Owing to its outstanding mechanical and thermal properties, Kevlar 49 composites are widely used in aerospace applications under cryogenic temperatures. Therefore, in this paper, involving the assumption of linear elastic fracture mechanics (LEFM), mechanical characterization of Kevlar 49 composite is done using Extended Finite Element Method (X-FEM) technique in Abaqus/CAE software. Further, the failure of Kevlar 49 composites due to the propagation of crack at room temperature and the cryogenic temperature is investigated. Stress, strain and strain energy density as a function of the width of the Kevlar specimen is predicted, indicates that Kevlar 49 composites are suitable for use under cryogenic temperatures.

  4. Surface grafting of Kevlar fibers for improved interfacial properties of fiber-reinforced composites

    SciTech Connect

    Ravichandran, Vasudha.

    1991-01-01

    Matrix-specific chemical modification of the Kevlar fiber surfaces was carried out with the aim of enhancing adhesion, through covalent bonding, to selected thermoset matrix resins such as vinyl ester, unsaturated polyester and epoxy. A two-step grafting method, involving initial metalation followed by subsequent substitution, was used to graft vinyl and epoxy terminated groups onto Kevlar fiber surfaces. The physical changes in fiber surface were characterized by scanning-electron microscopy and surface area measurement and the chemical changes due to grafting were measured by contact angle measurement and neutron activation analysis; high concentrations of double bonds and epoxy groups were measured. The change in interfacial sear strength due to the surface grafting was measured by means of a single fiber pull out test. The results show a nearly twofold increase in the interfacial shear strength due to vinyl terminated grafts in the case of Kevlar/vinyl ester and Kevlar/polyester composites. Kevlar fibers containing the epoxy functionality on the surface had enhanced adhesion to epoxy matrix resin.

  5. Interfacial shear stress distribution in model composites. I - A Kevlar 49 fibre in an epoxy matrix

    SciTech Connect

    Jahankhani, H.; Galiotis, C. )

    1991-05-01

    The technique of Laser Raman Spectroscopy has been applied in the study of aramid fibers, such as Kevlar 49, and aramid/epoxy interfaces. A linear relationship has been found between Raman frequencies and strain upon loading a single Kevlar 49 filament in air. Model composites of single Kevlar 49 fibers embedded in epoxy resins have been fabricated and subjected to various degrees of mechanical deformation. The transfer lengths for reinforcement have been measured at various levels of applied tensile load and the dependence of transfer length upon applied matrix strain has been established. Finally, by balancing the tensile and the shear forces acting along the interface, the interfacial shear stress (ISS) distribution along the embedded fiber was obtained. 52 refs.

  6. Contribution of thermal stresses to the failure of Kevlar fabric composites

    SciTech Connect

    Deteresa, S.J.; Nicolais, L.

    1988-06-01

    The effect of temperature changes on the compressive characteristics of Kevlar 49-epoxy composites were investigated. Using published data on the elastic properties of Kevlar 49 fiber and a typical epoxy matrix and the equation for the thermal expansion coefficient (TEC) developed by Schapery (1968) and Nairn (1985) for isotropic and transversely isotropic fibers, respectively, the temperature change required to cause compressive failure of the fiber was calculated for various volume fractions; it was found that, for typical unidirectional composites, thermally induced compressive failure of Kevlar fibers is of little concern. However, a temperature reduction places the curved fiber in the fabric-reinforced composite in axial compression, adding to the bending strain in the fiber. The combination of thermal stresses and external compressive loads that are below ultimate values by themselves can cause local compresive failure of the fiber. In addition, the kink bands formed as a result of compressive failure of Kevlar fiber are expected to cause debonding between fiber and matrix, and thus are also potential sites for crack initiation. 14 references.

  7. Hygrothermal expansion of Kevlar 49/epoxy and S2-glass/epoxy composites

    SciTech Connect

    Lo, S.Y.; Hahn, H.T.

    1982-11-01

    Ply failure occurred during preconditioning at 75/sup 0/C of (0/90)/sub 2S/ S2-glass/epoxy and Kevlar 49/epoxy laminates. Wet specimens showed different thermal expansion beavior near and above the glass transition temperature. Various available theories can be used to predict the thermal expansion coefficients. Stress analysis showed that the compressive normal stress at the interface in Kevlar 49/epoxy after cure is very small compared with those in other composites. Significant and rapid changes in the transverse coefficient of thermal expansion occurs in the T/sub g/ region. The two-phase diffusion model is a good representation of the diffusion behavior. Desorption process reveals a higher diffusion coefficient than absorption. S2-glass/epoxy was found to be unstable under the conditions applied, with cracking and losses during desorption. Maximum moisture contents were approx. 0.31% at 75/sup 0/C/75% RH and approx. 0.412% at 75/sup 0/C/water. The composite swelled transversely up to about 0.11 and 0.16%. Kevlar 49/epoxy was more stable than S2-glass/epoxy; max moisture contents were approx. 2.47% at 75/sup 0/C/75% RH and approx. 5.5% at 75/sup 0/C/water. The composite swelled transversely up to 1.0 and 2.23%. Results indicate that Kevlar 49 fibers swell radially. Relation between swelling strain and moisture content undergoes hysteresis during moisture cycling. Relation between swelling strain and moisture concentration is fairly linear for S2-glass/epoxy, Kevlar 49/epoxy and AS 3501/5 graphite/epoxy and only weakly depends on the material system. The equilibrium moisture content in (+-45)/sub 2S/ laminate is higher than in unidirectional lamina. The equilibrium thickness swelling strain can be predicted by laminated plate theory.

  8. Fabrication of T142 Tank Track Pads for Evaluation of a Rubber-Kevlar Composite Compound

    DTIC Science & Technology

    1982-06-01

    TO RUBBER ADHESION Since the 1930’s, resorcinol-formaldehyde- latex (RFL) provide a solution to these problems. compositions have been used as primary...fully developed with highly saturated rubbers such as butyl or ROYALENE® (EPDM) A-3 ...PERIOD COVERED Fabrication of T142 Tank Track Pads for Evaluation of a Rubber -Kevlar Composite FINAL Compound S. PERFORMING ORG. REPORT NUMBER 7. AUTHOR

  9. Flight service evaluation of Kevlar-49 epoxy composite panels in wide-bodied commercial transport aircraft

    NASA Technical Reports Server (NTRS)

    Stone, R. H.

    1984-01-01

    Kevlar-49 fairing panels, installed as flight service components on three L-1011s, were inspected after 10 years of service. There are six Kevlar-49 panels on each aircraft: a left-hand and right-hand set of a wing-body sandwich fairing; a solid laminate under-wing fillet panel; and a 422 K (300 F) service aft engine fairing. The three L-1011s include one each in service with Eastern, Air Canada, and TWA. The fairings have accumulated a total of 79,568 hours, with one ship set having nearly 28,000 hours service. The inspections were conducted at the airlines' major maintenance bases with the participation of Lockheed Engineering. The Kevlar-49 components were found to be performing satisfactorily in service with no major problems, or any condition requiring corrective action. The only defects noted were minor impact damage, a few minor disbonds and a minor degree of fastener hole fraying and elongation. These are for the most part comparable to damage noted on fiberglass fairings. The service history obtained in this program indicates that Kevlar-49 epoxy composite materials have satisfactory service characteristics for use in aircraft secondary structure.

  10. Railgun Application for High Energy Impact Testing of Nano-Reinforced Kevlar-Based Composite Materials

    NASA Astrophysics Data System (ADS)

    Micheli, D.; Vricella, A.; Pastore, R.; Morles, R. B.; Marchetti, M.

    2013-08-01

    An advanced electromagnetic accelerator, called railgun, has been assembled and tuned in order to perform high energy impact test on layered structures. Different types of layered composite materials have been manufactured and characterized in terms of energy absorbing capability upon impact of metallic bullets fired at high velocity. The composite materials under testing are manufactured by integrating several layers of Kevlar fabric and carbon fiber ply within a polymeric matrix reinforced by carbon nanotubes at 1% of weight percentage. The experimental results show that the railgun-device is a good candidate to perform impact testing of materials in the space debris energy range, and that carbon nanotubes may enhance, when suitably coupled to the composite's matrix, the excellent antiballistic properties of the Kevlar fabrics.

  11. Modes of deformation and failure of Kevlar 49 fibers and composites

    SciTech Connect

    Pruneda, C.O.; Morgan, R.J.; Kong, F.M.; Hodson, J.A.; Kershaw, R.P.; Casey, A.W.

    1983-12-05

    Fracture-topography and stress-optical-microscopy are utilized to study the deformation and failure modes of Kevlar 49 fibers and their epoxy composites. Fracture topographies of bare yarns, composite strands, and pressure vessels reveal Kevlar 49 fibers fail in tension by axially splitting 20 to 50 times their diameter D (20 to 50D) along their lengths. This type of fiber failure involves shear-induced microvoid growth throughout the fiber which occurs principally along the fiber axis, followed by macroscopic crack propagation through such microscopic crack propagation through such microvoids. Fiber splitting in the fracture of single filaments is < 5D because of the absence of external shear stresses. The topographies observed in fractured single filaments are described in terms of longitudinal and transverse fiber crack propagation paths in the fiber skin and core. Hydrolytically-degraded Kevlar 49 fibers exhibit lower fiber split lengths in composites. There is a correlation between the percentage of fibers that exhibit transverse failure without splitting and the composite strength. Stress-optical-microscopy studies of the deformation and failure processes of simple composite laminates are reported as a function of laminate geometry, temperature, and fiber surface treatment.

  12. Effect of chemical treatment of Kevlar fibers on mechanical interfacial properties of composites.

    PubMed

    Park, Soo-Jin; Seo, Min-Kang; Ma, Tae-Jun; Lee, Douk-Rae

    2002-08-01

    In this work, the effects of chemical treatment on Kevlar 29 fibers have been studied in a composite system. The surface characteristics of Kevlar 29 fibers were characterized by pH, acid-base value, X-ray photoelectron spectroscopy (XPS), and FT-IR. The mechanical interfacial properties of the final composites were studied by interlaminar shear strength (ILSS), critical stress intensity factor (K(IC)), and specific fracture energy (G(IC)). Also, impact properties of the composites were investigated in the context of differentiating between initiation and propagation energies and ductile index (DI) along with maximum force and total energy. As a result, it was found that chemical treatment with phosphoric acid solution significantly affected the degree of adhesion at interfaces between fibers and resin matrix, resulting in improved mechanical interfacial strength in the composites. This was probably due to the presence of chemical polar groups on Kevlar surfaces, leading to an increment of interfacial binding force between fibers and matrix in a composite system.

  13. Environmental effects on mechanical properties of a Kevlar 49/epoxy composite

    SciTech Connect

    Hahn, H.T.; Chin, W.K.

    1980-01-01

    The purpose of this program was to determine the mechanical properties of a Kevlar 49/epoxy composite in a simulated flywheel service environment. The composite was filament-wound using an epoxy formulated at Lawrence Livermore National Laboratory (LLNL). The temperature and vacuum chosen were 75/sup 0/C and approx. 7 x 10/sup -3/ torr, respectively. Specimens were preconditioned in the test environment for periods of 1 to 5 months before mechanical tests. The simulated service environment of 75/sup 0/C in vacuum was found to have little effect on static and fatigue properties. While the elevated temperature of 75/sup 0/C was not deleterious, the lack of air could be beneficial because it eliminates the possibility of oxidation. Thus, the elevated temperature of 75/sup 0/C is no deterrent to the application of the present Kevlar 49/epoxy in flywheels.

  14. Pyrolysis responses of kevlar/epoxy composite materials on laser irradiating

    NASA Astrophysics Data System (ADS)

    Liu, Wei-ping; Wei, Cheng-hua; Zhou, Meng-lian; Ma, Zhi-liang; Song, Ming-ying; Wu, Li-xiong

    2017-05-01

    The pyrolysis responses of kevlar/epoxy composite materials are valuable to study in a case of high temperature rising rate for its widely application. Distinguishing from the Thermal Gravimetric Analysis method, an apparatus is built to research the pyrolysis responses of kevlar/epoxy composite materials irradiated by laser in order to offer a high temperature rising rate of the sample. By deploying the apparatus, a near real-time gas pressure response can be obtained. The sample mass is weighted before laser irradiating and after an experiment finished. Then, the gas products molecular weight and the sample mass loss evolution are derived. It is found that the pressure and mass of the gas products increase with the laser power if it is less than 240W, while the molecular weight varies inversely. The variation tendency is confusing while the laser power is bigger than 240W. It needs more deeper investigations to bring it to light.

  15. Fracture toughness of Kevlar 29/poly(methyl methacrylate) composite materials for surgical implantations.

    PubMed

    Pourdeyhimi, B; Robinson, H H; Schwartz, P; Wagner, H D

    1986-01-01

    A study of the fracture behaviour of Kevlar 29 reinforced dental cement is undertaken using both linear elastic and nonlinear elastic fracture mechanics techniques. Results from both approaches--of which the nonlinear elastic is believed to be more appropriate--indicate that a reinforcing effect is obtained for the fracture toughness even at very low fibre content. The flexural strength and modulus are apparently not improved, however, by the incorporation of Kevlar 29 fibres in the PMMA cement, probably because of the presence of voids, the poor fibre/matrix interfacial bonding and unsatisfying cement mixing practice. When compared to other PMMA composite cements, the present system appears to be probably more effective than carbon/PMMA, for example, in terms of fracture toughness. More experimental and analytical work is needed so as to optimize the mechanical properties with respect to structural parameters and cement preparation technique.

  16. Dynamic small angle x-ray scattering study of stressed Kevlar 49 epoxy composites

    SciTech Connect

    Lee, J.S.; Fellers, J.F.; Tang, M.Y.; Lin, J.S.

    1985-01-01

    The highly crosslinked epoxy resins gave rise to isotropic scattering patterns and applying tensile stresses resulted in very little scattering changes. The dynamic scattering studies on the epoxy resins indicate the failure process as a catastrophic dynamic process with fractures initiating from surface or internal flaws. The crack propagates across the whole sample in a very short time to complete failure. The Kevlar fibers are microporous giving rise to equatorially elongated anisotropic scattering patterns. These microvoids can be partially filled by liquid epoxy. Based on comparisons of the volume fraction of the microvoids obtained by SAXS absolute intensity measurements and by the density measurements, two sizes of microvoids are present in the Kevlar 49 fibers - one in the range of 10 to 20 nm and the other much larger. Applying tensile stresses results in an increase in the scattering intensities and in the volume fraction of smaller microvoids. The average radius of gyration of these microvoids remained constant, and hence the number of these smaller microvoids must have increased in order to account for increased scattering intensities. It is thus concluded that the failure of Kevlar 49 fibers is accompanied by the increase in number of smaller microvoids and the enlargement of the larger microvoids along the fiber axis direction. The reinforced epoxy composites of low volume fraction unidirectional Kevlar 49 fiber gave rise to anisotropic scattering patterns perpendicular to the fiber axis direction, and it is believed this scattering is due to voids within the fibers and voids entrapped along the fiber matrix interface during processing. The dynamic scattering studies on the composites indicate the failure as a catastrophic dynamic process, fracture initiating in the epoxy matrix and the fibers not being able to carry the load, thus failing catastrophically as well. The failure is thus instantaneous once incipient failure occurs.

  17. Tensile and fatigue strength properties of Kevlar 29 aramid/epoxy unidirectional composites

    SciTech Connect

    Zweben, C.

    1981-07-22

    Static and fatigue tensile strength properties of filament wound undirectional Kevlar 29/epoxy, typical of filament wound material used in flywheel rotors, were studied. Machining techniques were developed to minimize fiber fuzzing on edges. The static modulus, normalized to 70% fiber volume fraction is 8.87 x 10/sup 6/ psi. The major Poisson's ratio is 0.37. The static composite tensile strength, normalized to 70% fiber volume fraction is 200 x 10/sup 3/ psi, corresponding to a fiber stress at failure of 286 x 10/sup 3/ psi, which is good for materials having a very high fiber volume fraction. The S-N curve for R = 0.7 was found to be quite flat. Although the techniques used in this program had previously been employed successfully to study the fatigue behavior of Kevlar 29/epoxy and Kevlar 49/epoxy unidirectional materials, we were unable to overcome the persistent problem of cohesive material failure in the tab regions. The apparent reason for this is the very low interlaminar shear strength of the filament wound material. 16 figures.

  18. Kevlar/PMR-15 polyimide matrix composite for a complex shaped DC-9 drag reduction fairing

    NASA Technical Reports Server (NTRS)

    Kawai, R. T.; Mccarthy, R. F.; Willer, M. S.; Hrach, F. J.

    1982-01-01

    The Aircraft Energy Efficiency (ACEE) Program was established by NASA to improve the fuel efficiency of commercial transport aircraft and thereby to reduce the amount of fuel consumed by the air transportation industry. One of the final items developed by the program is an improved fairing which is the aft closure for the thrust reverser actuators on the JT8D nacelles on DC-9 aircraft. The reduced-drag fairing uses, in the interest of weight savings, an advanced composite construction. The composite material contains Kevlar 49 fibers in a PMR-15 matrix. Attention is given to the aerodynamic configuration, the material system, and aspects of fabrication development.

  19. Vacuum infusion manufacturing and experimental characterization of Kevlar/epoxy composites

    NASA Astrophysics Data System (ADS)

    Ricciardi, M. R.; Giordano, M.; Langella, A.; Nele, L.; Antonucci, V.

    2014-05-01

    Epoxy/Kevlar composites have been manufactured by conventional Vacuum Infusion process and the Pulse Infusion technique. Pulse Infusion allows to control the pressure of the vacuum bag on the dry fiber reinforcement by using a proper designed pressure distributor that induces a pulsed transverse action and promotes the through thickness resin flow. The realized composite panel have been mechanically characterized by performing tensile and short beam shear tests according with the ASTM D3039 and ASTM D2344/D 2344M standard respectively in order to investigate the effect of Pulse Infusion on the tensile strength and ILSS.

  20. Kevlar/PMR-15 polyimide matrix composite for a complex shaped DC-9 drag reduction fairing

    NASA Technical Reports Server (NTRS)

    Kawai, R. T.; Mccarthy, R. F.; Willer, M. S.; Hrach, F. J.

    1982-01-01

    The Aircraft Energy Efficiency (ACEE) Program was established by NASA to improve the fuel efficiency of commercial transport aircraft and thereby to reduce the amount of fuel consumed by the air transportation industry. One of the final items developed by the program is an improved fairing which is the aft closure for the thrust reverser actuators on the JT8D nacelles on DC-9 aircraft. The reduced-drag fairing uses, in the interest of weight savings, an advanced composite construction. The composite material contains Kevlar 49 fibers in a PMR-15 matrix. Attention is given to the aerodynamic configuration, the material system, and aspects of fabrication development.

  1. Vacuum infusion manufacturing and experimental characterization of Kevlar/epoxy composites

    SciTech Connect

    Ricciardi, M. R.; Giordano, M.; Antonucci, V.; Langella, A.; Nele, L.

    2014-05-15

    Epoxy/Kevlar composites have been manufactured by conventional Vacuum Infusion process and the Pulse Infusion technique. Pulse Infusion allows to control the pressure of the vacuum bag on the dry fiber reinforcement by using a proper designed pressure distributor that induces a pulsed transverse action and promotes the through thickness resin flow. The realized composite panel have been mechanically characterized by performing tensile and short beam shear tests according with the ASTM D3039 and ASTM D2344/D 2344M standard respectively in order to investigate the effect of Pulse Infusion on the tensile strength and ILSS.

  2. The Influence of impact on Composite Armour System Kevlar-29/polyester-Al2O3

    NASA Astrophysics Data System (ADS)

    Ramadhan, A. A.; Abu Talib, A. R.; Mohd Rafie, A. S.; Zahari, R.

    2012-09-01

    An experimental investigation of high velocity impact responses of composite laminated plates using a helium gas gun has been presented in this paper. The aim of this study was to develop the novel composite structure that meets the specific requirements of ballistic resistance which used for body protections, vehicles and other applications. Thus the high velocity impact tests were performed on composite Kevlar-29 fiber/polyester resin with alumina powder (Al2O3). The impact test was conducted by using a cylindrical steel projectile of 7.62mm diameter at a velocity range of 160-400 m/s. The results (shown in this work) are in terms of varying plate thickness and the amount of energy absorbed by the laminated plates meanwhile we obtained that the 12mm thickness of composite plate suitable for impact loading up to 200m/s impact velocity. Therefore this composite structure (it is used to reduce the amount of Kevlar) considered most economical armoure products. We used the ANSYS AUTODYN 3D- v.12 software for our simulations. The results have been obtained a4.1% maximum errors with experimental work of energy absorption.

  3. Ballistic performance of a Kevlar-29 woven fibre composite under varied temperatures

    NASA Astrophysics Data System (ADS)

    Soykasap, O.; Colakoglu, M.

    2010-05-01

    Armours are usually manufactured from polymer matrix composites and used for both military and non-military purposes in different seasons, climates, and regions. The mechanical properties of the composites depend on temperature, which also affects their ballistic characteristics. The armour is used to absorb the kinetic energy of a projectile without any major injury to a person. Therefore, besides a high strength and lightness, a high damping capacity is required to absorb the impact energy transferred by the projectile. The ballistic properties of a Kevlar 29/polyvinyl butyral composite are investigated under varied temperatures in this study. The elastic modulus of the composite is determined from the natural frequency of composite specimens at different temperatures by using a damping monitoring method. Then, the backside deformation of composite plates is analysed experimentally and numerically employing the finite-element program Abaqus. The experimental and numeric results obtained are in good agreement.

  4. The Layer of Kevlar Angle-interlock Woven Fabric Effect on the Tensile Properties of Composite Materials

    NASA Astrophysics Data System (ADS)

    Xie, Wan-Chen; Guo, Xu-Yi; Yan, Tao; Zhang, Shang-Yong

    2017-09-01

    This article is based on the structure of three-dimensional angle-interlock longitudinal.The 3-layer, 5-layer, 7-layer and 9-layer of angle-interlock 3D fabrics are woven on sample weaving machine respectively with the 1500D Kevlar fiber twist filament produced by United States DuPont. At the same time, Kevlar plain weave fabric is woven, and three, five, seven and nine layers’ fabric are to be compared. In the process of VARTM composite technology, epoxy resin is matrix material, acetone is diluent, triethylene tetramine is curing agent and the five different fabrics are the reinforced materials respectively. Finally, eight different three-dimensional woven fabric composites were prepared. In this paper, the tensile properties of eight kinds of three-dimensional woven fabric composites were tested respectively.Finally, it is concluded that the five-layer angle-interlock woven fabric prepared by Kevlar fiber shows the best tensile property.

  5. Thermal response of radiantly heated Kevlar and graphite/epoxy composites

    SciTech Connect

    Fanucci, J.P.

    1987-02-01

    The response of Kevlar and graphite/epoxy composites subjected to simulated nuclear or laser thermal loads was measured. A solar furnace was used to radiantly heat samples at flux rates of up to 55 cal/sq cm per sec and total fluences of approximately 100 cal/sq cm. An iterative numerical technique was used to estimate the thermophysical properties of the materials by matching observed temperature-time histories with analytical predictions. Comparison of results obtained during this program with previously published data suggests that free stream velocity, which affects smoke blockage and char layer removal, is a critical design parameter. 8 references.

  6. Statistical analysis of Kevlar 49/epoxy composite stress-rupture data

    SciTech Connect

    Glaser, R.E.

    1983-09-01

    Statistical analyses are presented for LLNL stress-rupture data sets involving kevlar 49/epoxy strands and NASA Kevlar 49/epoxy spherical pressure vessels subjected to sustained loading. Raw data, summarized inferences, and figures are included.

  7. Design and Analysis of Drive Shaft using Kevlar/Epoxy and Glass/Epoxy as a Composite Material

    NASA Astrophysics Data System (ADS)

    Karthikeyan, P.; Gobinath, R.; Kumar, L. Ajith; Jenish, D. Xavier

    2017-05-01

    In automobile industry drive shaft is one of the most important components to transmit power form the engine to rear wheel through the differential gear. Generally steel drive shaft is used in automobile industry, nowadays they are more interested to replace steel drive shaft with that of composite drive shaft. The overall objective of this paper is to analyze the composite drive shaft using to find out the best replacement for conventional steel drive shaft. The uses of advanced composite materials such as Kevlar, Graphite, Carbon and Glass with proper resins ware resulted in remarkable achievements in automobile industry because of its greater specific strength and specific modulus, improved fatigue and corrosion resistances and reduction in energy requirements due to reduction in weight as compared to steel shaft. This paper is to presents, the modeling and analysis of drive shaft using Kevlar/Epoxy and Glass/Epoxy as a composite material and to find best replacement for conventional steel drive shafts with an Kevlar/epoxy or Glass/Epoxy resin composite drive shaft. Modeling is done using CATIA software and Analysis is carried out by using ANSYS 10.0 software for easy understanding. The composite drive shaft reduces the weight by 81.67 % for Kevlar/Epoxy and 72.66% for Glass/Epoxy when compared with conventional steel drive shaft.

  8. Multi-response parametric optimization in drilling of bamboo/Kevlar fiber reinforced sandwich composite

    NASA Astrophysics Data System (ADS)

    Singh, Thingujam Jackson; Samanta, Sutanu

    2016-09-01

    In the present work an attempt was made towards parametric optimization of drilling bamboo/Kevlar K29 fiber reinforced sandwich composite to minimize the delamination occurred during the drilling process and also to maximize the tensile strength of the drilled composite. The spindle speed and the feed rate of the drilling operation are taken as the input parameters. The influence of these parameters on delamination and tensile strength of the drilled composite studied and analysed using Taguchi GRA and ANOVA technique. The results show that both the response parameters i.e. delamination and tensile strength are more influenced by feed rate than spindle speed. The percentage contribution of feed rate and spindle speed on response parameters are 13.88% and 81.74% respectively.

  9. Considerations for acoustic emission monitoring of spherical Kevlar/epoxy composite pressure vessels

    NASA Technical Reports Server (NTRS)

    Hamstad, M. A.; Patterson, R. G.

    1977-01-01

    We are continuing to research the applications of acoustic emission testing for predicting burst pressure of filament-wound Kevlar 49/epoxy pressure vessels. This study has focused on three specific areas. The first area involves development of an experimental technique and the proper instrumentation to measure the energy given off by the acoustic emission transducer per acoustic emission burst. The second area concerns the design of a test fixture in which to mount the composite vessel so that the acoustic emission transducers are held against the outer surface of the composite. Included in this study area is the calibration of the entire test setup including couplant, transducer, electronics, and the instrument measuring the energy per burst. In the third and final area of this study, we consider the number, location, and sensitivity of the acoustic emission transducers used for proof testing composite pressure vessels.

  10. Molecular Composites from the Phase Separation at Low Temperatures of Kevlar and Diaminophenylindane Polyimide in Sulfuric Acid

    DTIC Science & Technology

    1988-09-30

    Pat. Appl. 902525, (1978). 2. Jackson, C. L., Samulski, E. T. and Shaw, M. T., "Foams from Rod-like Molecules", ACS PMSE Division Proceeding, Vol. 57...107 (1987). 3. Alonso, M. A. and Shaw, M. T., "Isotropic Kevlar and PBA (poly 1.4 benzamide) Reinforcements from Composites", ACS PMSE Toronto, Canada

  11. Tissue biocompatibility of kevlar aramid fibers and polymethylmethacrylate, composites in rabbits.

    PubMed

    Henderson, J D; Mullarky, R H; Ryan, D E

    1987-01-01

    Two groups of female NZW rabbits were implanted in the paravertebral muscles with aramid (du Pont Kevlar aramid 49) fibers and aramid-polymethylmethacrylate (PMMA) composites for 14 and 28 days. Rabbits were killed at these times periods, necropsies performed, sites scored for gross tissue response, and tissue specimens containing the implants removed for histopathological evaluation. A mild fibrous tissue reaction was observed around all implants containing aramid fiber similar to that observed around the silicone control implant. Some foreign body giant cells were also present adjacent to the fibers. An intense necrotic inflammatory reaction was present around the positive control material (PVC Y-78). The tissue response to implantation of aramid fiber and fiber-PMMA composites indicates that aramid is a biocompatible material.

  12. An investigation of the compressive strength of Kevlar 49/epoxy composites

    NASA Technical Reports Server (NTRS)

    Kulkarni, S. V.; Rosen, B. W.; Rice, J. S.

    1975-01-01

    Tests were performed to evaluate the effect of a wide range of variables including matrix properties, interface properties, fiber prestressing, secondary reinforcement, and others on the ultimate compressive strength of Kevlar 49/epoxy composites. Scanning electron microscopy is used to assess the resulting failure surfaces. In addition, a theoretical study is conducted to determine the influence of fiber anisotropy and lack of perfect bond between fiber and matrix on the shear mode microbuckling. The experimental evaluation of the effect of various constituent and process characteristics on the behavior of these unidirectional composites in compression did not reveal any substantial increase in strength. However, theoretical evaluations indicate that the high degree of fiber anisotropy results in a significant drop in the predicted stress level for internal instability. Scanning electron microscope data analysis suggests that internal fiber failure and smooth surface debonding could be responsible for the measured low compressive strengths.

  13. Effects of Weave Styles and Crimp Gradients on Damage Tolerance and Energy-Absorption Capacities of Woven Kevlar/Epoxy Composites

    DTIC Science & Technology

    2015-09-01

    Capacities of Woven Kevlar/Epoxy Composites Paul V. Cavallaro Ranges, Engineering, and Analysis Department NEWPORT Naval Undersea Warfare Center Division...Rhode Island and his students for their assistance with the experiments. Special thanks are also given to JPS Composite Materials Inc. for providing...the Kevlar woven fabrics and technical data and to Core Composites Inc. for fabricating the composite laminates. Reviewed and Approved: 1

  14. Composite Bombcase Program: Static tests on Kevlar/epoxy and graphite/epoxy plates and rings

    SciTech Connect

    Guess, T.R.

    1986-10-01

    An experimental study supporting the Composite Bombcase Program is described. The purpose of the study was to generate mechanical properties and structural response data on composite plates and cylinders. This data base is now available to assist in the evaluation of composite materials for bombcase applications. Two composites, Kevlar 49/epoxy and IM6 graphite/epoxy, were chosen for testing. The mechanical properties from flat unidirectional specimens were used to predict the elastic response of thick quasi-isotropic laminates in four-point bending and the elastic response of 18.0 inch diameter quasi-isotropic rings to diametral compressive loading. Good agreement between theoretical and experimental values of elastic response was obtained for both geometries. Load-deflection and load-strain curves in the elastic, post-yield, and failure regions were obtained for composite and aluminum rings. Delamination between plies was the principal failure mode in the QI composite plate and ring specimens. Even with many delaminations at large deflections, composite rings continued to carry load and retain some structural integrity.

  15. Mechanical properties of hybrid (medium modulus graphite, Thornel P-55 Kevlar/Epoxy) composites

    SciTech Connect

    Raghava, R.S.; Peters, S.T.

    1987-01-01

    This paper treats the mechanical behavior of hybrid (Thornel P-55-Kevlar/Epoxy) composites under ambient conditions and under hostile environments. Interply (core/shell) and intraply tubes (5.75'' I.D.) were filament wound and NOL rings were machined from them. Apparently modulus and apparent strength were measured using the split D (ASTM D2290) test. The influence of boiling water exposure (2 hrs and 24 hrs) on short beam shear strength, apparent modulus, and apparent strength was also evaluated at room temperature and the fracture toughness for above configurations was measured at room temperature. Scanning electron microscopy was used to examine failure modes. 6 references, 4 figures, 3 tables.

  16. Use of Acoustic Emission to Monitor Progressive Damage Accumulation in Kevlar (R) 49 Composites

    NASA Technical Reports Server (NTRS)

    Waller, Jess M.; Saulsberry, Regor L.; Andrade, Eduardo

    2009-01-01

    Acoustic emission (AE) data acquired during intermittent load hold tensile testing of epoxy impregnated Kevlar(Registeres TradeMark) 49 (K/Ep) composite strands were analyzed to monitor progressive damage during the approach to tensile failure. Insight into the progressive damage of K/Ep strands was gained by monitoring AE event rate and energy. Source location based on energy attenuation and arrival time data was used to discern between significant AE attributable to microstructural damage and spurious AE attributable to noise. One of the significant findings was the observation of increasing violation of the Kaiser effect (Felicity ratio < 1.0) with damage accumulation. The efficacy of three different intermittent load hold stress schedules that allowed the Felicity ratio to be determined analytically is discussed.

  17. Effect of ultraviolet light on mechanical properties of Kevlar 49 composites

    SciTech Connect

    Larsson, F.

    1986-01-01

    The relationship betwen specimen thickness and tensile strength in Kevlar 49 composites following exposure to ultraviolet light is investigated. Specimens of 0.13, 0.25, and 0.50 mm thickness molded from one, two, and four layers of Fiberdux 914k-49-5 prepreg are exposed to ultraviolet light in a Spectrotest apparatus, which has a low pressure xenon burner with a spectral range of 0.29-0.60 microns, for 500 and 1000 hours. The tensile stiffness and tensile strength data reveal that the ultraviolet light caused a decrease in the tensile strength and tensile retention of the 0.13 mm (1 ply) specimen; however, the 0.25 mm (2 plies) and 0.50 mm (4 plies) specimens, and the initial tensile elastic modulus for each specimen are unaffected by the exposure.

  18. Hybrid composite laminates reinforced with Kevlar/carbon/glass woven fabrics for ballistic impact testing.

    PubMed

    Randjbaran, Elias; Zahari, Rizal; Jalil, Nawal Aswan Abdul; Majid, Dayang Laila Abang Abdul

    2014-01-01

    Current study reported a facile method to investigate the effects of stacking sequence layers of hybrid composite materials on ballistic energy absorption by running the ballistic test at the high velocity ballistic impact conditions. The velocity and absorbed energy were accordingly calculated as well. The specimens were fabricated from Kevlar, carbon, and glass woven fabrics and resin and were experimentally investigated under impact conditions. All the specimens possessed equal mass, shape, and density; nevertheless, the layers were ordered in different stacking sequence. After running the ballistic test at the same conditions, the final velocities of the cylindrical AISI 4340 Steel pellet showed how much energy was absorbed by the samples. The energy absorption of each sample through the ballistic impact was calculated; accordingly, the proper ballistic impact resistance materials could be found by conducting the test. This paper can be further studied in order to characterise the material properties for the different layers.

  19. Hybrid Composite Laminates Reinforced with Kevlar/Carbon/Glass Woven Fabrics for Ballistic Impact Testing

    PubMed Central

    Randjbaran, Elias; Zahari, Rizal; Abdul Jalil, Nawal Aswan; Abang Abdul Majid, Dayang Laila

    2014-01-01

    Current study reported a facile method to investigate the effects of stacking sequence layers of hybrid composite materials on ballistic energy absorption by running the ballistic test at the high velocity ballistic impact conditions. The velocity and absorbed energy were accordingly calculated as well. The specimens were fabricated from Kevlar, carbon, and glass woven fabrics and resin and were experimentally investigated under impact conditions. All the specimens possessed equal mass, shape, and density; nevertheless, the layers were ordered in different stacking sequence. After running the ballistic test at the same conditions, the final velocities of the cylindrical AISI 4340 Steel pellet showed how much energy was absorbed by the samples. The energy absorption of each sample through the ballistic impact was calculated; accordingly, the proper ballistic impact resistance materials could be found by conducting the test. This paper can be further studied in order to characterise the material properties for the different layers. PMID:24955400

  20. Flight service evaluation of kevlar-49 epoxy composite panels in wide-bodied commercial transport aircraft: Flight service report

    NASA Technical Reports Server (NTRS)

    Stone, R. H.

    1981-01-01

    Kevlar-49 fairing panels, installed as flight service components on three L-1011s, were inspected after 7 years service. There are six Kevlar-49 panels on each aircraft: a left hand and right hand set of a wing-body sandwich fairing; a slid laminate under-wing fillet panel; and a 422 K service aft engine fairing. The three L-1011s include one each in service with Eastern, Air Canada, and TWA. The fairings have accumulated a total of 52,500 hours, with one ship set having 17.700 hours service. The inspections were conducted at the airlines' major maintenance bases with the participation of Lockheed Engineering. The Kevlar-49 components were found to be performing satisfactorily in service with no major problems or any condition requiring corrective action. The only defects noted were minor impact damage and a minor degree of fastener hole fraying and elongation. These are for the most part comparable to damage noted on fiberglass fairings. The service history to date indicates that Kevlar-49 epoxy composite materials have satisfactory service characteristics for use in aircraft secondary structure.

  1. In-Situ NDE Characterization of Kevlar and Carbon Composite Micromechanics for Improved COPV Health Monitoring

    NASA Technical Reports Server (NTRS)

    Waller, Jess M.; Saulsberry, Regor L.

    2009-01-01

    This project is a subtask of a multi-center project to advance the state-of-the-art by developing NDE techniques that are capable of evaluating stress rupture (SR) degradation in Kevlar/epoxy (K/Ep) composite overwrapped pressure vessels (COPVs), and damage progression in carbon/epoxy (C/Ep) COPVs. In this subtask, acoustic emission (AE) data acquired during intermittent load hold tensile testing of K/Ep and C/Ep composite tow materials-of-construction used in COPV fabrication were analyzed to monitor progressive damage during the approach to tensile failure. Insight into the progressive damage of composite tow was gained by monitoring AE event rate, energy, source location, and frequency. Source location based on arrival time data was used to discern between significant AE attributable to microstructural damage and spurious AE attributable to background and grip noise. One of the significant findings was the observation of increasing violation of the Kaiser effect (Felicity ratio < 1.0) with damage accumulation.

  2. Influence of weave structures on the tribological properties of hybrid Kevlar/PTFE fabric composites

    NASA Astrophysics Data System (ADS)

    Gu, Dapeng; Yang, Yulin; Qi, Xiaowen; Deng, Wei; Shi, Lei

    2012-09-01

    The existing research of the woven fabric self-lubricating liner mainly focus on the tribological performance improvements and the service life raised by changing different fiber type combinations, adding additive modification, and performing fiber surface modification. As fabric composites, the weave structures play an important role in the mechanical and tribological performances of the liners. However, hardly any literature is available on the friction and wear behavior of such composites with different weave structures. In this paper, three weave structures (plain, twill 1/3 and satin 8/5) of hybrid Kevlar/PTFE fabric composites are selected and pin-on-flat linear reciprocating wear studies are done on a CETR tester under different pressures and different frequencies. The relationship between the tensile strength and the wear performance are studied. The morphologies of the worn surfaces under the typical test conditions are analyzed by means of scanning electron microscopy (SEM). The analysis results show that at 10 MPa, satin 8/5 performs the best in friction-reduction and antiwear performance, and plain is the worst. At 30 MPa, however, the antiwear performance is reversed and satin 8/5 does not even complete the 2 h wear test at 16 Hz. There is no clear evidence proving that the tensile strength has an influence on the wear performance. So the different tribological performance of the three weave structures of fabric composites may be attributed to the different PTFE proportions in the fabric surface and the different wear mechanisms. The fabric composites are divided into three regions: the lubrication region, the reinforced region and the bonding region. The major mechanisms are fatigue wear and the shear effects of the friction force in the lubrication region. In the reinforced region fiber-matrix de-bonding and fiber breakage are involved. The proposed research proposes a regional wear model and further indicates the wear process and the wear mechanism

  3. Flight service evaluation of Kevlar-49 epoxy composite panels in wide-bodied commercial transport aircraft

    NASA Technical Reports Server (NTRS)

    Stone, R. H.

    1980-01-01

    Kevlar-49 fairing panels, installed as flight service components on three L-1011s, were inspected after 6 years' service. The Kevlar-49 components were found to be performing satisfactorily in service with no major problems, or any condition requiring corrective action. The only defects noted were minor impact damage, and a minor degree of fastener hole fraying and elongation. These are for the most part comparable to damage noted on fiberglass fairings.

  4. Experimental and analytical study of high velocity impact on Kevlar/Epoxy composite plates

    NASA Astrophysics Data System (ADS)

    Sikarwar, Rahul; Velmurugan, Raman; Madhu, Velmuri

    2012-12-01

    In the present study, impact behavior of Kevlar/Epoxy composite plates has been carried out experimentally by considering different thicknesses and lay-up sequences and compared with analytical results. The effect of thickness, lay-up sequence on energy absorbing capacity has been studied for high velocity impact. Four lay-up sequences and four thickness values have been considered. Initial velocities and residual velocities are measured experimentally to calculate the energy absorbing capacity of laminates. Residual velocity of projectile and energy absorbed by laminates are calculated analytically. The results obtained from analytical study are found to be in good agreement with experimental results. It is observed from the study that 0/90 lay-up sequence is most effective for impact resistance. Delamination area is maximum on the back side of the plate for all thickness values and lay-up sequences. The delamination area on the back is maximum for 0/90/45/-45 laminates compared to other lay-up sequences.

  5. Experimental and analytical study of high velocity impact on Kevlar/Epoxy composite plates

    NASA Astrophysics Data System (ADS)

    Sikarwar, Rahul S.; Velmurugan, Raman; Madhu, Velmuri

    2012-12-01

    In the present study, impact behavior of Kevlar/Epoxy composite plates has been carried out experimentally by considering different thicknesses and lay-up sequences and compared with analytical results. The effect of thickness, lay-up sequence on energy absorbing capacity has been studied for high velocity impact. Four lay-up sequences and four thickness values have been considered. Initial velocities and residual velocities are measured experimentally to calculate the energy absorbing capacity of laminates. Residual velocity of projectile and energy absorbed by laminates are calculated analytically. The results obtained from analytical study are found to be in good agreement with experimental results. It is observed from the study that 0/90 lay-up sequence is most effective for impact resistance. Delamination area is maximum on the back side of the plate for all thickness values and lay-up sequences. The delamination area on the back is maximum for 0/90/45/-45 laminates compared to other lay-up sequences.

  6. Improvement of interfacial adhesion and nondestructive damage evaluation for plasma-treated PBO and Kevlar fibers/epoxy composites using micromechanical techniques and surface wettability.

    PubMed

    Park, Joung-Man; Kim, Dae-Sik; Kim, Sung-Ryong

    2003-08-15

    Comparison of interfacial properties and microfailure mechanisms of oxygen-plasma treated poly(p-phenylene-2,6-benzobisoxazole (PBO, Zylon) and poly(p-phenylene terephthalamide) (PPTA, Kevlar) fibers/epoxy composites were investigated using a micromechanical technique and nondestructive acoustic emission (AE). The interfacial shear strength (IFSS) and work of adhesion, Wa, of PBO or Kevlar fiber/epoxy composites increased with oxygen-plasma treatment, due to induced hydrogen and covalent bondings at their interface. Plasma-treated Kevlar fiber showed the maximum critical surface tension and polar term, whereas the untreated PBO fiber showed the minimum values. The work of adhesion and the polar term were proportional to the IFSS directly for both PBO and Kevlar fibers. The microfibril fracture pattern of two plasma-treated fibers appeared obviously. Unlike in slow cooling, in rapid cooling, case kink band and kicking in PBO fiber appeared, whereas buckling in the Kevlar fiber was observed mainly due to compressive and residual stresses. Based on the propagation of microfibril failure toward the core region, the number of AE events for plasma-treated PBO and Kevlar fibers increased significantly compared to the untreated case. The results of nondestructive AE were consistent with microfailure modes.

  7. Stressed Kevlar strand test

    SciTech Connect

    Golopol, H.; Clarkson, J.; Moore, R.; Hetherington, N.

    1981-09-10

    Kevlar is a polyaramid fiber used in fiber composites. In order to characterize this material, we determined the effect of time, temperature, and chemical environment on the strength retention of stressed Kevlar strands. In this work, we applied a stress load of 20% of the ultimate tensile strength (UTS). Strands were hung with a suitable weight in a closed container. Each container was then provided with its own heater and chemical environment. No significant loss of strength retention was found on these stressed strands. 4 figures, 5 tables.

  8. Flight service evaluation of Kevlar-49 epoxy composite panels in wide-bodied commercial transport aircraft

    NASA Technical Reports Server (NTRS)

    Stone, R. H.

    1979-01-01

    Kevlar-49 fairing panels, installed as flight service components on three L-1011s, were inspected after five years' service. There are six Kevlar-49 panels on each aircraft: a left-hand and right-hand set of a wing-body sandwich fairing; a solid laminate under-wing fillet panel; and a 150 C (300 F) service aft engine fairing. The fairings have accumulated a total of 40,534 hours, with one ship set having 16,091 hours service as of Feb. 11, 1979. The Kevlar-49 components were found to be performing satisfactorily in service with no major problems, or any condition requiring corrective action. The only defects noted were minor impact damage, and a minor degree of fastener hole fraying and elongation. These are for the most part comparable to damage noted on fiberglass fairings.

  9. Flight service evaluation of Kevlar-49 epoxy composite panels in wide-bodied commercial transport aircraft

    NASA Technical Reports Server (NTRS)

    Stone, R. H.

    1978-01-01

    Kevlar-49 fairing panels, installed as flight service components on three L-1011s, were inspected after four years' service, and found to be performing satisfactorily. The Kevlar-49 components were all found to be performing satisfactorily in service with no major problems, or any condition requiring corrective action. The only defects noted were minor impact damage, and a minor degree of fastener hole fraying and elongation. These are for the most part comparable to damage noted on fiberglass fairings. A concurrent investigation was conducted on Kevlar-49/epoxy coupons exposed to an outdoor environment over a three year period at various locations providing a variety of climatic conditions. Weight changes and retention of mechanical properties were determined after one and three years exposure. A net weight loss occurred due to ultraviolet effects on the unpainted specimens. Mechanical property retentions were satisfactory with most specimens retaining well over 80% of their original value.

  10. Evaluation of Acoustic Emission NDE of Kevlar Composite Over Wrapped Pressure Vessels

    NASA Technical Reports Server (NTRS)

    Horne, Michael R.; Madaras, Eric I.

    2008-01-01

    Pressurization and failure tests of small Kevlar/epoxy COPV bottles were conducted during 2006 and 2007 by Texas Research Institute Austin, Inc., at TRI facilities. This is a report of the analysis of the Acoustic Emission (AE) data collected during those tests. Results of some of the tests indicate a possibility that AE can be used to track the stress-rupture degradation of COPV vessels.

  11. Characterization of Kevlar Using Raman Spectroscopy

    NASA Technical Reports Server (NTRS)

    Washer, Glenn; Brooks, Thomas; Saulsberry, Regor

    2007-01-01

    This paper explores the characterization of Kevlar composite materials using Raman spectroscopy. The goal of the research is to develop and understand the Raman spectrum of Kevlar materials to provide a foundation for the development of nondestructive evaluation (NDE) technologies based on the interaction of laser light with the polymer Kevlar. The paper discusses the fundamental aspects of experimental characterization of the spectrum of Kevlar, including the effects of incident wavelength, polarization and laser power. The effects of environmental exposure of Kevlar materials on certain characteristics of its Raman spectrum are explored, as well as the effects of applied stress. This data may provide a foundation for the development of NDE technologies intended to detect the in-situ deterioration of Kevlar materials used for engineering applications that can later be extended to other materials such as carbon fiber composites.

  12. Evaluation of Material Models within LS-DYNA(Registered TradeMark) for a Kevlar/Epoxy Composite Honeycomb

    NASA Technical Reports Server (NTRS)

    Polanco, Michael A.; Kellas, Sotiris; Jackson, Karen

    2009-01-01

    The performance of material models to simulate a novel composite honeycomb Deployable Energy Absorber (DEA) was evaluated using the nonlinear explicit dynamic finite element code LS-DYNA(Registered TradeMark). Prototypes of the DEA concept were manufactured using a Kevlar/Epoxy composite material in which the fibers are oriented at +/-45 degrees with respect to the loading axis. The development of the DEA has included laboratory tests at subcomponent and component levels such as three-point bend testing of single hexagonal cells, dynamic crush testing of single multi-cell components, and impact testing of a full-scale fuselage section fitted with a system of DEA components onto multi-terrain environments. Due to the thin nature of the cell walls, the DEA was modeled using shell elements. In an attempt to simulate the dynamic response of the DEA, it was first represented using *MAT_LAMINATED_COMPOSITE_FABRIC, or *MAT_58, in LS-DYNA. Values for each parameter within the material model were generated such that an in-plane isotropic configuration for the DEA material was assumed. Analytical predictions showed that the load-deflection behavior of a single-cell during three-point bending was within the range of test data, but predicted the DEA crush response to be very stiff. In addition, a *MAT_PIECEWISE_LINEAR_PLASTICITY, or *MAT_24, material model in LS-DYNA was developed, which represented the Kevlar/Epoxy composite as an isotropic elastic-plastic material with input from +/-45 degrees tensile coupon data. The predicted crush response matched that of the test and localized folding patterns of the DEA were captured under compression, but the model failed to predict the single-cell three-point bending response.

  13. Investigation of Rapidly Deployable Plastic Foam Systems. Volume II. Nonlinear Deformation and Local Buckling of Kevlar Fabric/Polyurethane Foam Composites

    DTIC Science & Technology

    1979-10-01

    fab:il was Kevlar 49*. The aramids have a very high explosion, iviternal temperature was noted to be at modulus of elasticity and high tensile...POLYURETHANE FOAM COMPOSITES and corrosion-resistant properties. Advancement of the fast-foaming technology of high polymers for structural...lightweight, deployed into a desired structural geometry within a high -strength composites has generated significant few seconds. interest in their

  14. Experimental determinations of the eigenmodes for composite bars made with carbon and Kevlar-carbon fibers

    NASA Astrophysics Data System (ADS)

    Miriţoiu, C. M.; Stănescu, M. M.; Burada, C. O.; Bolcu, D.; Roşca, V.

    2015-11-01

    For modal identification, the single-point excitation method has been widely used in modal tests and it consists in applying a force in a given point and recording the vibratory structure response in all interest points, including the excitation point. There will be presented the experimental recordings for the studied bars (with Kevlar-carbon or carbon fibers), the frequency response function in Cartesian and polar coordinates. By using the frequency response functions we determine the eigenparameters for each bar. We present the final panel of the eigenmodes (with the damping factors, eigenfrequencies and critical damping) for each considered bar. Using the eigenfrequency of the first determined eigenmode, the bars stiffness has been determined. The presented bars can be used in practical engineering for: car or bus body parts, planes body parts, bullet-proof vests, reinforcements for sandwich beams, and so on.

  15. Flight service evaluation of Kevlar-49/epoxy composite panels in wide-bodied commercial transport aircraft

    NASA Technical Reports Server (NTRS)

    Stone, R. H.

    1975-01-01

    Kevlar-49 fairing panels were inspected and found to be performing satisfactorily after two years flight service on an Eastern and an Air Canada L-1011. Six panels are on each aircraft including sandwich and solid laminate wing-body panels, and 300 F service aft engine fairings. Some of the panels were removed from the aircraft to permit inspection of inner surfaces and fastener hole conditions. Minor defects such as surface cracks due to impact damage, small delaminated areas, elongation and fraying of fastener holes, were noted. None of these defects were considered serious enough to warrant corrective action in the opinion of airline personnel. The defects are typical for the most part of defects noted on similar fiberglass parts.

  16. Kevlar fiber-epoxy adhesion and its effect on composite mechanical and fracture properties by plasma and chemical treatment

    SciTech Connect

    Shyu, S.S.; Wu, S.R.; Sheu, G.S.

    1996-12-31

    Kevlar 49 fibers were surface modified by gas (ammonia, oxygen, and water vapor) plasmas etching and chlorosulfonation and subsequent reaction with some reagents (glycine, deionized water, ethylenediamine, and 1-butanol) to improve the adhesion to epoxy resin. After these treatments, the changes in fiber topography, chemical compositions of the fiber surfaces and the surface functional groups introduced to the surface of fibers were identified by SEM XPS and static SIMS. Interlaminar shear strength (ILSS) and T-peel strength between the fiber and epoxy resin were markedly improved by gas plasma and chlorosulfonation (0.1% and 0.25% ClSO{sub 3}H at 30 s). However, it is clear from the similar G{sub IC} values of the treated and untreated fiber composites that the fiber/matrix interfacial bond strength is only a minor contributor to G{sub IC}. SEM was also used to study the surface topography of the fracture surfaces of composites in T-peel test.

  17. Etude comparative sur la propagation de l'endommagement apres impact des composites carbone/epoxy renforces par piquage au fil Kevlar et titane-nickel

    NASA Astrophysics Data System (ADS)

    Vachon, Pierre-Luc

    Composite laminates have strong in-plane mechanical properties, but they are generally weaker through their thickness. This specificity makes the laminates prone to delamination, particularly under low-velocity impact loads. Consequently numerous research efforts have been dedicated to developing interlaminar reinforcing methods, such as transverse stitching. The present project proposes the use of the stitching technique combined with a special stitching thread made of superelastic TiNi alloy. This technology is intended to improve the delamination toughness in composite laminates loaded in bending. In the first part of this study a numerical model was developed for analyzing composite structures. The 3-D finite element model was built with the ANSYS commercial software using 20-node solid and 8-node shell elements. The progressive damage modeling technique was used, allowing the prediction of delamination propagation in a laminate submitted to various loading modes. The model was validated for a plate under quasi-static traction load, and it was then used to simulate three-point bending tests. Secondly, carbon/epoxy composite panels were fabricated, with each panel containing unstitched and stitched specimens. Two different materials were used for the stitching thread: superelastic TiNi wires and Kevlar threads as a reference. Some stitched specimens were cut in slices in order to make some observations of the internal stitch using an optical microscope. Standardized low-velocity impact tests and compression after impact tests were carried out on stitched and unstitched specimens (ASTM D7136 and D7137). The Kevlar reinforcements have shown great performance in reducing the delaminated zone after impact, as well as in improving the residual compression strength. The TiNi reinforcements provided encouraging results during the impact tests, though being less effective than the Kevlar threads. During the compression after impact tests, only a slight difference could

  18. Composite Stress Rupture NDE Research and Development Project (Kevlar[R] and Carbon)

    NASA Technical Reports Server (NTRS)

    Saulsberry, Regor

    2010-01-01

    The objective was to develop and demonstrate nondestructive evaluation (NDE) techniques capable of assessing stress rupture related strength degradation for carbon composite pressure vessels, either in a structural health monitoring (SHM) or periodic inspection mode.

  19. Biomimetic Hybridization of Kevlar into Silk Fibroin: Nanofibrous Strategy for Improved Mechanic Properties of Flexible Composites and Filtration Membranes.

    PubMed

    Lv, Lili; Han, Xiangsheng; Zong, Lu; Li, Mingjie; You, Jun; Wu, Xiaochen; Li, Chaoxu

    2017-08-22

    Silk, one of the strongest natural biopolymers, was hybridized with Kevlar, one of the strongest synthetic polymers, through a biomimetic nanofibrous strategy. Regenerated silk materials have outstanding properties in transparency, biocompatibility, biodegradability and sustainability, and promising applications as diverse as in pharmaceutics, electronics, photonic devices and membranes. To compete with super mechanic properties of their natural counterpart, regenerated silk materials have been hybridized with inorganic fillers such as graphene and carbon nanotubes, but frequently lose essential mechanic flexibility. Inspired by the nanofibrous strategy of natural biomaterials (e.g., silk fibers, hemp and byssal threads of mussels) for fantastic mechanic properties, Kevlar was integrated in regenerated silk materials by combining nanometric fibrillation with proper hydrothermal treatments. The resultant hybrid films showed an ultimate stress and Young's modulus two times as high as those of pure regenerated SF films. This is not only because of the reinforcing effect of Kevlar nanofibrils, but also because of the increasing content of silk β-sheets. When introducing Kevlar nanofibrils into the membranes of silk nanofibrils assembled by regenerated silk fibroin, the improved mechanic properties further enabled potential applications as pressure-driven nanofiltration membranes and flexible substrates of electronic devices.

  20. Power generation from base excitation of a Kevlar composite beam with ZnO nanowires

    NASA Astrophysics Data System (ADS)

    Malakooti, Mohammad H.; Hwang, Hyun-Sik; Sodano, Henry A.

    2015-04-01

    One-dimensional nanostructures such as nanowires, nanorods, and nanotubes with piezoelectric properties have gained interest in the fabrication of small scale power harvesting systems. However, the practical applications of the nanoscale materials in structures with true mechanical strengths have not yet been demonstrated. In this paper, piezoelectric ZnO nanowires are integrated into the fiber reinforced polymer composites serving as an active phase to convert the induced strain energy from ambient vibration into electrical energy. Arrays of ZnO nanowires are grown vertically aligned on aramid fibers through a low-cost hydrothermal process. The modified fabrics with ZnO nanowires whiskers are then placed between two carbon fabrics as the top and the bottom electrodes. Finally, vacuum resin transfer molding technique is utilized to fabricate these multiscale composites. The fabricated composites are subjected to a base excitation using a shaker to generate charge due to the direct piezoelectric effect of ZnO nanowires. Measuring the generated potential difference between the two electrodes showed the energy harvesting application of these multiscale composites in addition to their superior mechanical properties. These results propose a new generation of power harvesting systems with enhanced mechanical properties.

  1. Low cost tooling material and process for graphite and Kevlar composites

    NASA Technical Reports Server (NTRS)

    Childs, William I.

    1987-01-01

    An Extruded Sheet Tooling Compound (ESTC) was developed for use in quickly building low cost molds for fabricating composites. The ESTC is a very highly mineral-filled resin system formed into a 6 mm thick sheet. The sheet is laid on the pattern, vacuum (bag) is applied to remove air from the pattern surface, and the assembly is heat cured. The formed ESTC is then backed and/or framed and ready for use. The cured ESTC exhibits low coefficient of thermal expansion and maintains strength at temperatures of 180 to 200 C. Tools were made and used successfully for: Compression molding of high strength epoxy sheet molding compound, stamping of aluminum, resin transfer molding of polyester, and liquid resin molding of polyester. Several variations of ESTC can be made for specific requirements. Higher thermal conductivity can be achieved by using an aluminum particle filler. Room temperature gel is possible to allow use of foam patterns.

  2. Statistics for the time-dependent failure of Kevlar-49/epoxy composites: micromechanical modeling and data interpretation

    SciTech Connect

    Phoenix, S.L.; Wu, E.M.

    1983-03-01

    This paper presents some new data on the strength and stress-rupture of Kevlar-49 fibers, fiber/epoxy strands and pressure vessels, and consolidated data obtained at LLNL over the past 10 years. This data are interpreted by using recent theoretical results from a micromechanical model of the statistical failure process, thereby gaining understanding of the roles of the epoxy matrix and ultraviolet radiation on long term lifetime.

  3. Kevlar 49/Epoxy COPV Aging Evaluation

    NASA Technical Reports Server (NTRS)

    Sutter, James K.; Salem, Jonathan L.; Thesken, John C.; Russell, Richard W.; Littell, Justin; Ruggeri, Charles; Leifeste, Mark R.

    2008-01-01

    NASA initiated an effort to determine if the aging of Kevlar 49/Epoxy composite overwrapped pressure vessels (COPV) affected their performance. This study briefly reviews the history and certification of composite pressure vessels employed on NASA Orbiters. Tests to evaluate overwrap tensile strength changes compared 30 year old samples from Orbiter vessels to new Kevlar/Epoxy pressure vessel materials. Other tests include transverse compression and thermal analyses (glass transition and moduli). Results from these tests do not indicate a noticeable effect due to aging of the overwrap materials.

  4. Kevlar Cable Development Program.

    DTIC Science & Technology

    1978-01-01

    projects. The principal focus of this program was to develop Kevlar as a strength member in general cable and rope applications, including other aspects such as terminations, electrical conductors and user experience .

  5. In-Situ Nondestructive Evaluation of Kevlar(Registered Trademark)and Carbon Fiber Reinforced Composite Micromechanics for Improved Composite Overwrapped Pressure Vessel Health Monitoring

    NASA Technical Reports Server (NTRS)

    Waller, Jess; Saulsberry, Regor

    2012-01-01

    NASA has been faced with recertification and life extension issues for epoxy-impregnated Kevlar 49 (K/Ep) and carbon (C/Ep) composite overwrapped pressure vessels (COPVs) used in various systems on the Space Shuttle and International Space Station, respectively. Each COPV has varying criticality, damage and repair histories, time at pressure, and pressure cycles. COPVs are of particular concern due to the insidious and catastrophic burst-before-leak failure mode caused by stress rupture (SR) of the composite overwrap. SR life has been defined [1] as the minimum time during which the composite maintains structural integrity considering the combined effects of stress level(s), time at stress level(s), and associated environment. SR has none of the features of predictability associated with metal pressure vessels, such as crack geometry, growth rate and size, or other features that lend themselves to nondestructive evaluation (NDE). In essence, the variability or surprise factor associated with SR cannot be eliminated. C/Ep COPVs are also susceptible to impact damage that can lead to reduced burst pressure even when the amount of damage to the COPV is below the visual detection threshold [2], thus necessitating implementation of a mechanical damage control plan [1]. Last, COPVs can also fail prematurely due to material or design noncompliance. In each case (SR, impact or noncompliance), out-of-family behavior is expected leading to a higher probability of failure at a given stress, hence, greater uncertainty in performance. For these reasons, NASA has been actively engaged in research to develop NDE methods that can be used during post-manufacture qualification, in-service inspection, and in-situ structural health monitoring. Acoustic emission (AE) is one of the more promising NDE techniques for detecting and monitoring, in real-time, the strain energy release and corresponding stress-wave propagation produced by actively growing flaws and defects in composite

  6. Microwave-synthesized freestanding iron-carbon nanotubes on polyester composites of woven Kevlar fibre and silver nanoparticle-decorated graphene

    NASA Astrophysics Data System (ADS)

    Hazarika, Ankita; Deka, Biplab K.; Kim, Doyoung; Kong, Kyungil; Park, Young-Bin; Park, Hyung Wook

    2017-01-01

    We synthesized Ag nanoparticle-decorated multilayered graphene nanosheets (Ag-graphene) from graphite nanoplatelets and silver nitrate through 90–100 s of microwave exposure, without the use of any mineral acids or harsh reducing agents. Fe nanoparticle-decorated carbon nanotubes (Fe-CNTs) were grown on polypyrrole (PPy) deposited on woven Kevlar fibre (WKF), using ferrocene as a catalyst, under microwave irradiation. Fe-CNTs grown on WKF and Ag-graphene dispersed in polyester resin (PES) were combined to fabricate Ag-graphene/Fe-CNT/PPy-coated WKF/PES composites by vacuum-assisted resin transfer moulding. The combined effect of Fe-CNTs and Ag-graphene in the resulting composites resulted in a remarkable enhancement of tensile properties (a 192.56% increase in strength and 100.64% increase in modulus) as well as impact resistance (a 116.33% increase). The electrical conductivity significantly increased for Ag-graphene/Fe-CNT/PPy-coated WKF/PES composites. The effectiveness of electromagnetic interference shielding, which relies strongly on the Ag-graphene content in the composites, was 25 times higher in Ag-graphene/Fe-CNT/PPy-coated WKF/PES than in neat WKF/PES composites. The current work offers a novel route for fabricating highly promising, cost effective WKF/PES composites through microwave-assisted synthesis of Fe-CNTs and Ag-graphene.

  7. Microwave-synthesized freestanding iron-carbon nanotubes on polyester composites of woven Kevlar fibre and silver nanoparticle-decorated graphene.

    PubMed

    Hazarika, Ankita; Deka, Biplab K; Kim, DoYoung; Kong, Kyungil; Park, Young-Bin; Park, Hyung Wook

    2017-01-11

    We synthesized Ag nanoparticle-decorated multilayered graphene nanosheets (Ag-graphene) from graphite nanoplatelets and silver nitrate through 90-100 s of microwave exposure, without the use of any mineral acids or harsh reducing agents. Fe nanoparticle-decorated carbon nanotubes (Fe-CNTs) were grown on polypyrrole (PPy) deposited on woven Kevlar fibre (WKF), using ferrocene as a catalyst, under microwave irradiation. Fe-CNTs grown on WKF and Ag-graphene dispersed in polyester resin (PES) were combined to fabricate Ag-graphene/Fe-CNT/PPy-coated WKF/PES composites by vacuum-assisted resin transfer moulding. The combined effect of Fe-CNTs and Ag-graphene in the resulting composites resulted in a remarkable enhancement of tensile properties (a 192.56% increase in strength and 100.64% increase in modulus) as well as impact resistance (a 116.33% increase). The electrical conductivity significantly increased for Ag-graphene/Fe-CNT/PPy-coated WKF/PES composites. The effectiveness of electromagnetic interference shielding, which relies strongly on the Ag-graphene content in the composites, was 25 times higher in Ag-graphene/Fe-CNT/PPy-coated WKF/PES than in neat WKF/PES composites. The current work offers a novel route for fabricating highly promising, cost effective WKF/PES composites through microwave-assisted synthesis of Fe-CNTs and Ag-graphene.

  8. Microwave-synthesized freestanding iron-carbon nanotubes on polyester composites of woven Kevlar fibre and silver nanoparticle-decorated graphene

    PubMed Central

    Hazarika, Ankita; Deka, Biplab K.; Kim, DoYoung; Kong, Kyungil; Park, Young-Bin; Park, Hyung Wook

    2017-01-01

    We synthesized Ag nanoparticle-decorated multilayered graphene nanosheets (Ag-graphene) from graphite nanoplatelets and silver nitrate through 90–100 s of microwave exposure, without the use of any mineral acids or harsh reducing agents. Fe nanoparticle-decorated carbon nanotubes (Fe-CNTs) were grown on polypyrrole (PPy) deposited on woven Kevlar fibre (WKF), using ferrocene as a catalyst, under microwave irradiation. Fe-CNTs grown on WKF and Ag-graphene dispersed in polyester resin (PES) were combined to fabricate Ag-graphene/Fe-CNT/PPy-coated WKF/PES composites by vacuum-assisted resin transfer moulding. The combined effect of Fe-CNTs and Ag-graphene in the resulting composites resulted in a remarkable enhancement of tensile properties (a 192.56% increase in strength and 100.64% increase in modulus) as well as impact resistance (a 116.33% increase). The electrical conductivity significantly increased for Ag-graphene/Fe-CNT/PPy-coated WKF/PES composites. The effectiveness of electromagnetic interference shielding, which relies strongly on the Ag-graphene content in the composites, was 25 times higher in Ag-graphene/Fe-CNT/PPy-coated WKF/PES than in neat WKF/PES composites. The current work offers a novel route for fabricating highly promising, cost effective WKF/PES composites through microwave-assisted synthesis of Fe-CNTs and Ag-graphene. PMID:28074877

  9. Fabrication and Synthesis of Highly Ordered Nickel Cobalt Sulfide Nanowire-Grown Woven Kevlar Fiber/Reduced Graphene Oxide/Polyester Composites.

    PubMed

    Hazarika, Ankita; Deka, Biplab K; Kim, DoYoung; Roh, Hyung Doh; Park, Young-Bin; Park, Hyung Wook

    2017-10-06

    Well-aligned NiCo2S4 nanowires, synthesized hydrothermally on the surface of woven Kevlar fiber (WKF), were used to fabricate composites with reduced graphene oxide (rGO) dispersed in polyester resin (PES) by means of vacuum-assisted resin transfer molding. The NiCo2S4 nanowires were synthesized with three precursor concentrations. Nanowire growth was characterized using scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. Hierarchical and high growth density of the nanowires led to exceptional mechanical properties of the composites. Compared with bare WKF/PES, the tensile strength and absorbed impact energy were enhanced by 96.2% and 92.3%, respectively, for WKF/NiCo2S4/rGO (1.5%)/PES. The synergistic effect of NiCo2S4 nanowires and rGO in the fabricated composites improved the electrical conductivity of insulating WKF/PES composites, reducing the resistance to ∼10(3) Ω. Joule heating performance depended strongly on the precursor concentration of the nanowires and the presence of rGO in the composite. A maximum surface temperature of 163 °C was obtained under low-voltage (5 V) application. The Joule heating performance of the composites was demonstrated in a surface deicing experiment; we observed that 17 g of ice melted from the surface of the composite in 14 min under an applied voltage of 5 V at -28 °C. The excellent performance of WKF/NiCo2S4/rGO/PES composites shows great potential for aerospace structural applications requiring outstanding mechanical properties and Joule heating capability for deicing of surfaces.

  10. Multi-Length Scale-Enriched Continuum-Level Material Model for Kevlar®-Fiber-Reinforced Polymer-Matrix Composites

    NASA Astrophysics Data System (ADS)

    Grujicic, M.; Pandurangan, B.; Snipes, J. S.; Yen, C.-F.; Cheeseman, B. A.

    2013-03-01

    Fiber-reinforced polymer matrix composite materials display quite complex deformation and failure behavior under ballistic/blast impact loading conditions. This complexity is generally attributed to a number of factors such as (a) hierarchical/multi-length scale architecture of the material microstructure; (b) nonlinear, rate-dependent and often pressure-sensitive mechanical response; and (c) the interplay of various intrinsic phenomena and processes such as fiber twisting, interfiber friction/sliding, etc. Material models currently employed in the computational engineering analyses of ballistic/blast impact protective structures made of this type of material do not generally include many of the aforementioned aspects of the material dynamic behavior. Consequently, discrepancies are often observed between computational predictions and their experimental counterparts. To address this problem, the results of an extensive set of molecular-level computational analyses regarding the role of various microstructural/morphological defects on the Kevlar® fiber mechanical properties are used to upgrade one of the existing continuum-level material models for fiber-reinforced composites. The results obtained show that the response of the material is significantly affected as a result of the incorporation of microstructural effects both under quasi-static simple mechanical testing condition and under dynamic ballistic-impact conditions.

  11. Detonation nanodiamonds for doping Kevlar.

    PubMed

    Comet, Marc; Pichot, Vincent; Siegert, Benny; Britz, Fabienne; Spitzer, Denis

    2010-07-01

    This paper reports on the first attempt to enclose diamond nanoparticles--produced by detonation--into a Kevlar matrix. A nanocomposite material (40 wt% diamond) was prepared by precipitation from an acidic solution of Kevlar containing dispersed nanodiamonds. In this material, the diamond nanoparticles (Ø = 4 nm) are entirely wrapped in a Kevlar layer about 1 nm thick. In order to understand the interactions between the nanodiamond surface and the polymer, the oxygenated surface functional groups of nanodiamond were identified and titrated by Boehm's method which revealed the exclusive presence of carboxyl groups (0.85 sites per nm2). The hydrogen interactions between these groups and the amide groups of Kevlar destroy the "rod-like" structure and the classical three-dimensional organization of this polymer. The distortion of Kevlar macromolecules allows the wrapping of nanodiamonds and leads to submicrometric assemblies, giving a cauliflower structure reminding a fractal object. Due to this structure, the macroscopic hardness of Kevlar doped by nanodiamonds (1.03 GPa) is smaller than the one of pure Kevlar (2.31 GPa). To our knowledge, this result is the first illustration of the change of the mechanical properties induced by doping the Kevlar with nanoparticles.

  12. Lightweight engine containment. [Kevlar shielding

    NASA Technical Reports Server (NTRS)

    Weaver, A. T.

    1977-01-01

    Kevlar fabric styles and weaves were studied, as well as methods of application for advanced gas turbine engines. The Kevlar material was subjected to high speed impacts by simple projectiles fired from a rifle, as well as more complex shapes such as fan blades released from gas turbine rotors in a spin pit. Just contained data was developed for a variety of weave and/or application techniques, and a comparative containment weight efficiency was established for Kevlar containment applications. The data generated during these tests is being incorporated into an analytical design system so that blade containment trade-off studies between Kevlar and metal case engine structures can be made. Laboratory tests and engine environment tests were performed to determine the survivability of Kevlar in a gas turbine environment.

  13. Aging studies of Kevlar 49 fibers

    SciTech Connect

    Morgan, R.J.; Pruneda, C.O.; Kong, F.M.

    1983-11-01

    The aging mechanisms in service environment of Kevlar 49 fibers, E.I. duPont, (poly(p-phenylene)terephthalamide) are reviewed. The principal aging mechanisms considered are (i) u.v.-, (ii) hydrolytic- and (iii) stress-induced macromolecular chain scission and microvoid growth. U.V.-induced strength degradation can be significant as a result of photo-oxidative and photodegradative radical formation but in Kevlar 49-epoxy composites only the exterior yarn layer is deteriorated. Hydrolytic chain scission of the amide linkage and corresponding fiber strength deterioration is considered in terms of R.H., time, temperature and stress level. The rates of hydrolytic degradation at 100% R.H. in the 100 to 200/sup 0/C range are reported. The estimated rates of fiber degradation in various service environment conditions are also reported and shown not to be serious. The stress-induced aging of Kevlar 49 fibers is considered in terms of the growth and coalescence of inherent microvoids along the fiber axis together with the generation of new microvoids. (These growth processes involve no detectable macromolecular chain scission or deterioration in fiber strength.) At a critical microvoid volume fraction catastrophic failure occurs by interconnection of such voids.

  14. Moisture dependence of positron lifetime in Kevlar-49

    NASA Technical Reports Server (NTRS)

    Singh, Jag J.; Holt, William H.; Mock, Willis, Jr.

    1984-01-01

    Because of filamentary character of Kevlar-49 aramid fibers, there is some concern about the moisture uptake and its effect on plastic composites reinforced with Kevlar-49 fibers. As part of continuing studies of positron lifetime in polymers, we have measured positron lifetime spectra in Kevlar-49 fibers as a function of their moisture content. The long lifetime component intensities are rather low, being only of the order of 2-3 percent. The measured values of long component lifetimes at various moisture levels in the specimens are as follows: 2072 +/- 173 ps (dry); 2013 +/- 193 ps (20.7 percent saturation); 1665 +/- 85 ps (25.7 percent saturation); 1745 +/- 257 ps (32.1 percent saturation); and 1772 +/- 217 ps (100 percent saturation). It is apparent that the long component lifetime at first decreases and then increases as the specimen moisture content increases. These results have been compared with those inferred from Epon-815 and Epon-815/K-49 composite data.

  15. Robust Tensioned Kevlar Suspension Design

    NASA Technical Reports Server (NTRS)

    Young, Joseph B.; Naylor, Bret J.; Holmes, Warren A.

    2012-01-01

    One common but challenging problem in cryogenic engineering is to produce a mount that has excellent thermal isolation but is also rigid. Such mounts can be achieved by suspending the load from a network of fibers or strings held in tension. Kevlar fibers are often used for this purpose owing to their high strength and low thermal conductivity. A suite of compact design elements has been developed to improve the reliability of suspension systems made of Kevlar.

  16. Kevlar/PMR-15 reduced drag DC-9 reverser stang fairing

    NASA Technical Reports Server (NTRS)

    Kawai, R. T.

    1982-01-01

    A reduced drag fairing for the afterbody enclosing the thrust reverser actuators on the DC-9 has been developed with Kevlar-49/PMR-15 advanced composite material. The improved fairing reduces airplane drag 1% compared to the production baseline. Use of composites reduces weight 40% compared to an equivalent metal fairing. The Kevlar-49/PMR-15 advanced composite is an organic matrix material system that can be used at temperatures up to 500 F.

  17. Kevlar: Transitioning Helix from Research to Practice

    DTIC Science & Technology

    2015-04-01

    protective transformations are applied to application binaries before they are deployed. Salient features of Kevlar include applying high- entropy ...variety of classes. Kevlar uses novel, fine-grained, high- entropy diversification transformations to prevent an attacker from successfully exploiting...Kevlar include applying high- entropy randomization techniques, automated program repairs, leveraging highly-optimized virtual machine technology, and in

  18. Fabrication of a Kevlar liner assembly

    SciTech Connect

    Schloman, A.H.

    1980-07-01

    Several liner assemblies were fabricated with Kevlar 49 and epoxy using various wet layup and prepreg processes. A production process, using prepreg material, was developed for fabricating the liner and a wet layup molding process was used to fabricate the Kevlar hat-shaped tunnels. Fabrication of the tunnels using Kevlar prepreg with an autoclave curving process was evaluated.

  19. Investigation of Kevlar fabric-based materials for use with inflatable structures

    NASA Technical Reports Server (NTRS)

    Niccum, R. J.; Munson, J. B.; Rueter, L. L.

    1977-01-01

    Design, manufacture and testing of laminated and coated composite materials incorporating a structural matrix of Kevlar are reported. The practicality of using Kevlar in aerostat materials is demonstrated, and data are provided on practical weaves, lamination and coating particulars, rigidity, strength, weight, elastic coefficients, abrasion resistance, crease effects, peel strength, blocking tendencies, helium permeability, and fabrication techniques. Properties of the Kevlar-based materials are compared with conventional Dacron-reinforced counterparts. A comprehensive test and qualification program is discussed, and considerable quantitative biaxial tensile and shear test data are provided.

  20. Laser machining of graphite-, Kevlar- and glass-reinforced epoxy

    NASA Astrophysics Data System (ADS)

    Mukherjee, K.; Khan, P. A. A.; Cherif, M.

    1990-12-01

    Laser machining of graphite-, Kevlar- and glass-fiber reinforced epoxy composites were investigated with particular emphasis on laser parameters, cutting speed, quality of cut, gas emission and thermal damage. A computer numerically controlled CNC stage and a 2.8 KW, RF excited, carbon dioxide laser were used for the study. It is shown that glass and Kevlar reinforced composites can be successfully machined by a high-energy laser process. However, because of the large thermal anisotropy of the graphite fibers along with the high ablation temperature of graphite, thermal processing of graphite/epoxy composite is presently not achievable. The role of thermal anisotropy in laser machining is discussed and a mathematical model for the evaluation of the longitudinal versus transverse thermal conductivity has been developed. Effects of cover gas on the volatile emissions were studied and results are presented. Results of a preliminary investigation of mechanical properties of laser machined samples are also reported.

  1. Ultrasonic analysis of Kevlar-epoxy filament wound structures

    SciTech Connect

    Brosey, W.D.

    1985-07-16

    Composite structures are often desirable for their strength and weight characteristics. Since composites are not as well characterized mechanically as metallic or ceramic structures, much work has been performed at the Oak Ridge Y-12 Plant to obtain that characterization and to develop methods of determining the mechanical properties of a composite nondestructively. Most of the work to date has been performed on nonenclosed structures. One notable exception has been the holographic evaluation of spherical Kevlar-epoxy composite pressure vessels. Several promising nondestructive evaluation techniques have been used to locate flaws and predict the integrity of the composite. Several of these include thermography, Moire interferometry, ultrasonic stress wave factor, ultrasonic C-scan image enhancement, radiography, and nuclear magnetic resonance. As a first step in this transfer and development of NDE techniques, known defects were placed within spherical Kevlar-epoxy, filament-wound test specimens to determine the extent to which they could be detected. These defects included Teflon shim-simulated delaminations, macrosphere-simulated voids, dry-band sets, variable tension, Kevlar 29 fiber instead of the higher strength Kevlar 40 fiber, and an alternate high-void-content winding pattern. Ultrasonic waveform analysis was performed in both the time and frequency domains to determine the detectability and locatability of structural flaws within the composite. Preparation has been made at Virginia Polytechnic Institute and State University and at the University of Delaware, to examine the specimens using various NDE techniques. This work is a compilation of interim project reports in partial fulfillment of the contracts between Virginia Polytechnic Institute and State University, the University of Delaware, and Y-12 Plant.

  2. Ultrasonic analysis of Kevlar-epoxy filament wound structures

    NASA Astrophysics Data System (ADS)

    Brosey, W. D.

    1985-07-01

    Composite structures are often desirable for their strength and weight characteristics. Since composites are not as well characterized mechanically as metallic or ceramic structures, much work has been performed at the Oak Ridge Y-12 Plant to obtain that characterization and to develop methods of determining the mechanical properties of a composite nondestructively. Most of the work to date has been performed on nonenclosed structures. One notable exception has been the holographic evaluation of spherical Kevlar-epoxy composite pressure vessels. Several promising nondestructive evaluation techniques have been used to locate flaws and predict the integrity of the composite. Several of these include thermography, Moire interferometry, ultrasonic stress wave factor, ultrasonic C-scan image enhancement, radiography, and nuclear magnetic resonance. As a first step in this transfer and development of NDE techniques, known defects were placed within spherical Kevlar-epoxy, filament-wound test specimens to determine the extent to which they could be detected. These defects included Teflon shim-simulated delaminations, macrosphere-simulated voids, dry-band sets, variable tension, Kevlar 29 fiber instead of the higher strength Kevlar 40 fiber, and an alternate high-void-content winding pattern. Ultrasonic waveform analysis was performed in both the time and frequency domains to determine the detectability and locatability of structural flaws within the composite. Preparation has been made at Virginia Polytechnic Institute and State University and at the University of Delaware, to examine the specimens using various NDE techniques. This work is a compilation of interim project reports in partial fulfillment of the contracts between Virginia Polytechnic Institute and State University, the University of Delaware, and Y-12 Plant.

  3. Investigation of Kevlar fabric based materials for use with inflatable structures

    NASA Technical Reports Server (NTRS)

    Niccum, R. J.; Munson, J. B.

    1974-01-01

    Design, manufacture and testing of laminated and coated composite materials incorporating a structural matrix of Kevlar are reported in detail. The practicality of using Kevlar in aerostat materials is demonstrated and data are provided on practical weaves, lamination and coating particulars, rigidity, strength, weight, elastic coefficients, abrasion resistance, crease effects, peel strength, blocking tendencies, helium permeability, and fabrication techniques. Properties of the Kevlar based materials are compared with conventional, Dacron reinforced counterparts. A comprehensive test and qualification program is discussed and quantitative biaxial tensile and shear test data are provided. The investigation shows that single ply laminates of Kevlar and plastic films offer significant strength to weight improvements, are less permeable than two ply coated materials, but have a lower flex life.

  4. Robustness Improvement of ARA Kevlar Holddown Restraint Cables

    NASA Astrophysics Data System (ADS)

    Bongers, E.; Koning, J.; Konink, T.

    2013-09-01

    Dutch Space has developed a Hold Down and Release System based on Kevlar Restraint cables and Thermal Knife release in the early nineties of the previous century. The system has been qualified for application in the company's solar array families ARA and FRED for GEO, LEO, MEO and scientific deep space missions comprising solar panel stacks ranging from 2 to 6 panels. Beside solar arrays, derivatives of the HDRS have been used for antenna, cooler and experiment cover hold down and release. Over 500 HDRS units have performed with 100% success in space.Today's missions do not differ much in nominal conditions but more extreme failure modes are specified resulting in more extreme temperatures. The restraint cables, which are exposed directly to these limits of the thermal environment, have been upgraded to cope with the new requirements. An extended life time acceleration test program has been defined and executed to demonstrate their robustness.The qualified upper temperature of the system, the most critical one concerning loads, has been increased from 105°C to 125°C.The paper will describe problems experienced at high temperatures, the new design, supporting engineering tests, the measurement of tension distribution in the cables with Raman spectroscopy, and the accelerated test program and its results.Kevlar cables according to this new design are now baseline for solar arrays of the ESA programs Sentinel- 1, Sentinel-2, Galileo FOC, EarthCARE and Aeolus.

  5. Development of failure criterion for Kevlar-epoxy fabric laminates

    NASA Technical Reports Server (NTRS)

    Tennyson, R. C.; Elliott, W. G.

    1984-01-01

    The development of the tensor polynomial failure criterion for composite laminate analysis is discussed. In particular, emphasis is given to the fabrication and testing of Kevlar-49 fabric (Style 285)/Narmco 5208 Epoxy. The quadratic-failure criterion with F(12)=0 provides accurate estimates of failure stresses for the Kevlar/Epoxy investigated. The cubic failure criterion was re-cast into an operationally easier form, providing the engineer with design curves that can be applied to laminates fabricated from unidirectional prepregs. In the form presented no interaction strength tests are required, although recourse to the quadratic model and the principal strength parameters is necessary. However, insufficient test data exists at present to generalize this approach for all undirectional prepregs and its use must be restricted to the generic materials investigated to-date.

  6. Development of Kevlar parachute webbings

    SciTech Connect

    Ericksen, R.H.

    1991-01-01

    This paper describes the development of Kevlar webbings for parachute applications. Evaluation of existing webbings and a study of the effects of filling yarn denier and pick count on tensile and joint strength provided data for fabric design. Measurements of warp crimp as a function of filling denier and pick count demonstrated the relationship between warp crimp and strength. One newly developed webbing had higher strength efficiency and another had higher joint efficiency than comparable existing webbings. Both new webbings had overall efficiencies over 5% higher than values for existing webbings. 10 refs., 4 figs., 2 tabs.

  7. Ultrasonic analysis of Kevlar-epoxy filament wound spherical test specimens

    SciTech Connect

    Brosey, W.D.

    1984-12-06

    Increased use of composite materials in enclosed geometries such as cylindrical, spherical, or conical shapes has led to the desire to transfer and further develop the most promising nondestructive evaluation (NDE) techniques used on nonenclosed geometries to enclosed geometries. Known defects were placed within spherical Kevlar-epoxy filament wound test specimens to determine the extent to which they could be detected. These defects included Teflon shim-simulated delaminations, macrosphere-simulated voids, dry-band sets, variable tension, Kevlar 29 fiber, and an alternate high void content winding pattern. Ultrasonic C-scan analysis of Kevlar-epoxy filament wound spheres was performed to determine detectability of normal winding patterns and implanted flaw conditions in the composite using this technique. Ultrasonic waveform analysis was performed in both the time and frequency domains to determine the detectability and locatability of structural flaws within the composite.

  8. Impurities in Kevlar 49 fibers

    SciTech Connect

    Pruneda, C.O.; Morgan, R.J.; Lim, R.; Gregory, L.J.; Fischer, J.W.

    1984-12-11

    The impurities in Kevlar 49 fibers (poly(p-phenylene terephthalamide)PPTA) are reported and discussed in terms of the fiber fabrication processes. These impurities were monitored by inductively coupled plasma emission and optical emission spectroscopy. The principal impurities Na/sub 2/SO/sub 4/ and total S were analyzed chemically. From these chemical analyses together with C, N, H elemental analyses we show that there are 1.5 wt % impurities present in Kevlar 49 fibers of which approx. 50% are in the form of Na/sub 2/SO/sub 4/ and the remainder probably in the form of benzene sulfonic -SO/sub 3/H PPTA side groups. There are 3 of these acid groups per each PPTA macromolecule. Organic impurities, such as terephthalic acid are discussed in the light of degradation studies of PPTA-H/sub 2/SO/sub 4/ spinning dopes. Electron microprobe x-ray spectroscopy and laser-induced damage studies were utilized to investigate the distribution of impurities through the fiber cross-section. The distribution of impurities throughout the fiber are determined by the fiber fabrication processes and are discussed at the microscopic and molecular level. The defects caused by these impurities and their effect on the deformation and failure modes are also considered. 22 references, 3 tables.

  9. The mechanical response of woven Kevlar fabric

    SciTech Connect

    Warren, W.E.

    1991-01-01

    Woven Kevlar fabrics exhibit a number of beneficial mechanical properties which include strength, flexibility, and relatively low density. The desire to engineer or design Kevlar fabrics for specific applications has stimulated interest in the development of theoretical models which relate their effective mechanical properties to specific aspects of the fabric morphology and microstructure. In this work the author provides a theoretical investigation of the large deformation elastic response of a plane woven Kevlar fabric and compares these theoretical results with experimental data obtained from uniaxially loaded Kevlar fabrics. The theoretical analysis assumes the woven fabric to be a regular network of orthogonal interlaced yarns and the individual yarns are modeled as extensible elastica, thus coupling stretching and bending effects at the outset. This comparison of experiment with theory indicates that the deformation of woven fabric can be quite accurately predicted by modeling the individual yarns as extensible elastica. 2 refs., 1 fig.

  10. Experimental analysis of graphene nanocomposite on Kevlar

    NASA Astrophysics Data System (ADS)

    Manigandan, S.; Gunasekar, P.; Nithya, S.; Durga Revanth, G.; Anudeep, A. V. S. C.

    2017-08-01

    Graphene nanocomposite is a two dimensional structure which has intense role in material science. This paper investigates the topological property of the graphene nanocomposite doped in Kevlar fiber by direct mixing process. The Kevlar fiber by direct mixing process. The Kevlar fiber taken as the specimen which is fabricated by vacuum bag moulding process. Epoxy used as resin and HY951 as hardener. Three different specimens are fabricated based on the percentage of graphene nanocomposite 2%, 5%, 10% and 20% respectively. We witnessed the strength of the Kevlar fiber is increased when it is treated with nanocomposite. The percentage of the nanocomposite increase the strength of the fiber is increased. However as the nanocomposite beyond 5% the strength of fiber is dropped. In addition, we also seen the interfacial property of the fiber is dropped when the nanocomposite is added beyond threshold limit.

  11. Prestressed concrete using KEVLAR reinforced tendons

    SciTech Connect

    Dolan, C.W.

    1989-01-01

    KEVLAR is a high strength, high modulus synthetic fiber manufactured by the E.I. DuPont de Nemours Company. The fiber is resistant to chloride and alkali attack. The resistance is enhanced when the fibers are assembled into a resin matrix and fabricated as rods. These properties suggest that KEVLAR reinforced rods may be a substitute for high strength steel prestress tendons in certain applications such as bridge decks and parking structures. This dissertation presents the background, theoretical development, and experimental investigations of KEVLAR reinforced rod strength, anchorage, fabrication and performance in prestressed concrete structures. The study concludes that KEVLAR has significant potential for these prestressed concrete applications. However, the reliability of the long term anchorage of the KEVLAR reinforced rods must be improved before production applications are undertaken. KEVLAR has a low shear strength compared to its tensile capacity. The anchorage of KEVLAR reinforced rods is sensitive to the shear forces generated in the anchorage assembly. Finite element analyses, using interface elements to simulate the addition of a mold release agent in a conic anchor, predict the behavior of resin socketed anchors. Test results confirm that mold release agents reduce the anchor shear stresses and suggest that moderate strength resins may be used in the anchor. KEVLAR is nearly linearly elastic to failure, yet ductility of a structure is an important design concern. Prestressed concrete beam tests using both bonded and unbonded tendons demonstrated that ductile structural behavior is obtained. Methods of predicting the strength and deflection behavior of the prestressed beams are presented and the theoretical predictions are compared to the experimental results. The overall correlation between predicted and theoretical results is satisfactory.

  12. Structure-property-processing relationships in Kevlar fibers

    SciTech Connect

    Lacks, D.J.

    1996-12-31

    Molecular simulations are carried out to elucidate the differences in the properties of the commercial fibers Kevlar 29, Kevlar 49 and Kevlar 149, which are manufactured under different processing conditions, and are composed of poly(p-phenylene teraphthalamide) (PPTA). In going from Kevlar 29 to Kevlar 49 to Kevlar 149, the axial Young`s modulus increases significantly and the torsion modulus decreases significantly, while the compressive strength stays roughly the same. Previous investigators have shown that the increase in the Young`s modulus arises from increased axial orientation. The present paper addresses the torsion modulus and compressive strength of the fibers.

  13. Room-temperature transverse compressive creep of thick Kevlar fabric/ epoxy laminates

    SciTech Connect

    Ericksen, R.H.; Guess, T.R.

    1980-01-01

    Creep and recovery of thick Kevlar 49/epoxy composites were investigated in transverse compressive loading at room temperature. Cylindrical samples with void contents of 4 and 14 percent were tested along with those of unreinforced resin. The composites exhibited logarithmic creep. Creep rates were 2 times higher over the entire stress range for the high porosity composites. At a stress of 87 MPa the resin creep curve was similar to that of the composites. At higher stresses, the resin crept faster and exhibited more strain. It is proposed that axial compressive creep of the cylindrical composite specimens is governed by Poisson induced strains leading to tensile loading of the reinforcing fibers. Axial initial strain and creep rate data for the composite were converted to radial data using measured values of Poisson ratio. These values of composite specimen radial creep rate were in good agreement with tensile creep data of Kevlar 49 fibers.

  14. Multi-Length Scale-Enriched Continuum-Level Material Model for Kevlar (registered trademark)-Fiber-Reinforced Polymer-Matrix Composites

    DTIC Science & Technology

    2013-03-01

    Derivation of the Materials Constitutive Relations for Carbon Nanotube Reinforced Poly-Vinyl-Ester-Epoxy Based Composites, J. Mater. Sci., 2007, 42, p...within the yarns , fiber/matrix de-bonding, diffuse delamination/interlam- ina separation, etc.) as well as discrete damage modes (e.g., transverse...fabric. Specifically, details of yarn weaving and crimping, yarn cross-section change, and yarn sliding at the warp- yarn /weft- yarn cross-over points are

  15. The Kevlar-walled anechoic wind tunnel

    NASA Astrophysics Data System (ADS)

    Devenport, William J.; Burdisso, Ricardo A.; Borgoltz, Aurelien; Ravetta, Patricio A.; Barone, Matthew F.; Brown, Kenneth A.; Morton, Michael A.

    2013-08-01

    The aerodynamic and acoustic performance of an anechoic wind tunnel test section with walls made from thin Kevlar cloth have been measured and analyzed. The Kevlar test section offers some advantages over a conventional free-jet arrangement. The cloth contains the bulk of the flow but permits the transmission of sound with little loss. The containment results in smaller far-field aerodynamic corrections meaning that larger models can be tested at higher Reynolds numbers. The containment also eliminates the need for a jet catcher and allows for a much longer test section. Model-generated noise is thus more easily separated from facility background using beamforming. Measurements and analysis of acoustic and aerodynamic corrections for a Kevlar-walled test section are presented and discussed, along with benchmark trailing edge noise measurements.

  16. Hydrolytic degradation of Kevlar 49 fibers

    SciTech Connect

    Morgan, R.J.; Pruneda, C.O.; Butler, N.; Kong, F.M.; Caley, L.; Moore, R.L.

    1983-12-05

    The hydrolytic degradation of Kevlar 49 fibers and the principal parameters that control this degradation are presented. Hydrolytic chain scission of the amide linkage and corresponding fiber strength deterioration are considered in terms of RH, time, temperature and stress level. The rates of hydrolytic degradation at 100% RH in the 100 to 200/sup 0/C range are reported. The estimated rates of fiber degradation in various service environment conditions are also reported and shown not to be serious. The impurities present in Kevlar 49 fibers and their effect on hydrolytic degradation are also discussed. In addition, the aging of Kevlar 49 fibers as a result of exposure to uv and stress are reviewed.

  17. Use of LS-DYNA(Registered TradeMark) to Assess the Energy Absorption Performance of a Shell-Based Kevlar(TradeMark)/Epoxy Composite Honeycomb

    NASA Technical Reports Server (NTRS)

    Polanco, Michael

    2010-01-01

    The forward and vertical impact stability of a composite honeycomb Deployable Energy Absorber (DEA) was evaluated during a full-scale crash test of an MD-500 helicopter at NASA Langley?s Landing and Impact Research Facility. The lower skin of the helicopter was retrofitted with DEA components to protect the airframe subfloor upon impact and to mitigate loads transmitted to Anthropomorphic Test Device (ATD) occupants. To facilitate the design of the DEA for this test, an analytical study was conducted using LS-DYNA(Registered TradeMark) to evaluate the performance of a shell-based DEA incorporating different angular cell orientations as well as simultaneous vertical and forward impact conditions. By conducting this study, guidance was provided in obtaining an optimum design for the DEA that would dissipate the kinetic energy of the airframe while maintaining forward and vertical impact stability.

  18. Surface characterization of Kevlar fibers by FT-IR spectroscopy

    SciTech Connect

    Chatzi, E.G.

    1987-01-01

    The Kevlar-49 aramid fiber offers considerable potential for utilization in high-performance composite materials. However, it has poor adhesion to the polymer matrix resin. In order to improve the adhesion the surface of the fiber was characterized by using two nondestructive Fourier transform infrared (FT-IR) techniques. It was shown that the polymer chains in the skin are oriented parallel to the surface, while in the core they are almost radially oriented. This orientation as well as the fact that the functional groups are intermolecularly hydrogen-bonded might limit their availability for reacting with the polymer matrix. The author also characterized the water absorbed in both the skin and the core of the fiber and found the existence of three types of water: (a) weakly hydrogen-bonded between one NH and one carbonyl group, (b) between two carbonyl groups and (c) liquid-like water clustered in microvoids and other sites inside the fibers. It was also found that 30% of the NH groups of the Kevlar-49 fiber are accessible for deuterium exchange. These groups on one hand are available for reactions that would improve the adhesion, but on the other hand can hydrogen-bond with water, which would be detrimental for the mechanical properties of the composite.

  19. Ultrasonic NDE of Kevlar-epoxy filament wound spherical pressure vessels

    SciTech Connect

    Blake, R.A.; Steiner, K.V.

    1985-10-01

    The nondestructive evaluation of Kevlar-epoxy filament wound spherical composite pressure vessels is performed through the use of a six axis rotatorially articulated robotic manipulator. Ultrasonic pulse-echo techniques are employed to form C-scan images based upon amplitude and attenuation data gathered by a 68000 based microcomputer system. The data are imaged in planar and three dimensional forms and are further enhanced and analyzed through image processing techniques specifically developed for the analysis of complex composite structures. 25 figs.

  20. Bound water in Kevlar 49 fibers

    SciTech Connect

    Garza, R.G.; Pruneda, C.O.; Morgan, R.J.

    1981-04-01

    From elemental analyses, thermogravimetric-mass spectroscopy studies and re-evaluation of previous water diffusion studies in Kevlar 49 fibers it is concluded that these fibers can contain two types of sorbed moisture. The fibers can absorb up to approx. 6 wt % loosely bound water with an activation energy for outgassing by desorption of 6 kcal/mole. This loosely bound water is a direct result of the presence of Na/sub 2/SO/sub 4/ impurities and the perturbations they induce on the packing of the rod-like poly (p-phenylene terephthalamide) macromolecules. Kevlar 49 fibers also inherently contain up to 30 wt % additional water which is tightly bound within the crystal lattice. This water exhibits an activation energy for outgassing by diffusion of approx. 40 kcal/mole and is only evolved from the fiber in significant quantities at t > 350/sup 0/C over a period of hours.

  1. Fabrication of Graphene on Kevlar Supercapacitor Electrodes

    DTIC Science & Technology

    2011-05-01

    electrode was nickel foil and (3) the reference electrode was a Ag/AgCl pellet electrode...3 3.4 Characterization of graphene-coated Kevlar fibers The reduced GO electrodes were wrapped with nickel (Ni) wire to make electrical contact...peaks from the copper metal present in the metallization, which was deposited onto these fibers using an electroless plating process. A larger

  2. Kevlar support for thermal isolation at low temperatures

    NASA Technical Reports Server (NTRS)

    Roach, Pat R.

    1992-01-01

    A cryogenic support is developed that rigidly attaches two U-shaped aluminum beams to each other with strands of Kevlar. The Kevlar creates a very strong and stiff coupling between the beams while allowing only very minor heat flow between them. Measurements at room temperature and at 77 K confirm the stiffness and strength of the support.

  3. Carbon nanotube and graphene nanoribbon-coated conductive Kevlar fibers.

    PubMed

    Xiang, Changsheng; Lu, Wei; Zhu, Yu; Sun, Zhengzong; Yan, Zheng; Hwang, Chi-Chau; Tour, James M

    2012-01-01

    Conductive carbon material-coated Kevlar fibers were fabricated through layer-by-layer spray coating. Polyurethane was used as the interlayer between the Kevlar fiber and carbon materials to bind the carbon materials to the Kevlar fiber. Strongly adhering single-walled carbon nanotube coatings yielded a durable conductivity of 65 S/cm without significant mechanical degradation. In addition, the properties remained stable after bending or water washing cycles. The coated fibers were analyzed using scanning electron microcopy and a knot test. The as-produced fiber had a knot efficiency of 23%, which is more than four times higher than that of carbon fibers. The spray-coating of graphene nanoribbons onto Kevlar fibers was also investigated. These flexible coated-Kevlar fibers have the potential to be used for conductive wires in wearable electronics and battery-heated armors.

  4. Bending response of Kevlar 49/epoxy beams and rings

    SciTech Connect

    Reedy, E.D. Jr.; Guess, T.R.

    1988-01-01

    Kevlar 49/epoxy laminates often exhibit substantial material nonlinearity when subjected to bending. A unidirectionally reinforced Kevlar 49 lamina is nearly linear elastic to failure in tension, however, in fiber-directed compression, it responds in a perfectly plastic-like manner once a compressive strength of roughly 20% of its tensile ultimate strength is exceeded. This combined linear tensile/nonlinear compressive behavior is the source of Kevlar 49/epoxy's flexural nonlinearity. Since Kevlar 49 reinforced laminates can often carry bending loads well above those needed to cause initial compressive yield, it is desirable to be able to predict the post-yield flexural response. In this presentation, analyses that utilize a simple idealization of compressive yielding are described and calculated results for Kevlar 49 reinforced beams and rings are compared with available data. 2 refs., 3 figs.

  5. Lifetimes statistics for single Kevlar 49 aramid filaments in creep-rupture at elevated temperatures

    SciTech Connect

    Wu, H.F.

    1987-01-01

    Kevlar 49 fibrous composites are routinely fabricated to have strengths above 1.5 GPa(200 ksi), but in many applications one would like to sustain such stresses for long time periods, sometimes at elevated temperatures. Thus the temperature dependence of the creep-rupture process in the fibers is of interest. Experimental data are presented for the lifetime of single Kevlar 49 filaments under constant stress at elevated temperatures. The goal of this research was to fully characterize the statistical strength and lifetime behavior of single filaments in order to separate fiber effects from fiber/matrix interactions in the creep-rupture lifetime of Kevlar 49/epoxy composites as described for example in Phoenix and Wu (1983). First we conducted experiments to determine distributions for the strength of filaments from the two distinct spools as a function of temperature. As expected, the data could generally be fitted by a two-parameter Weibull distribution. Lifetime experiments at 80 and 130/sup 0/C were conducted at several stress levels chosen as suitable fractions of the Weibull scale parameter for short-term strength for that temperature. The lifetime data were well modelled by a two-parameter Weibull distribution with large variability.

  6. Evaluation of filament-wound Kevlar-49/epoxy fatigue properties. Final report

    SciTech Connect

    Not Available

    1980-06-03

    This study was conducted by AiResearch Manufacturing of California for LLL to investigate the long-term properties of Kevlar-49/epoxy composite in a fatigue and elevated temperature environment to provide additional information on the material properties of Kevlar-49/epoxy for use in the design of composite flywheel energy storage units. Testing showed that Kevlar-49 has the unusual property of increasing tensile modulus of elasticity under fatigue loading conditions. The change in modulus was shown to be a function of temperature, induced stress level, and number of fatigue cycles. The average modulus before cycling was 13.28 x 10/sup 6/ psi at ambient temperature versus 11.96 x 10/sup 6/ psi at 150/sup 0/F. Creep or residual strain after 100,000 cycles was 4.1 x 10/sup -4/ in/in (ambient) and 11.7 x 10/sup -4/ in/in (150/sup 0/F) at 140 ksi maximum stress level. At 190 ksi temperature did not show any effects on creep, which was measured to be approximately 28 x 10/sup -4/ in/in. The ultimate strength of 150/sup 0/F rings was 249,000 psi compared to 262,000 psi for ambient temperature.

  7. Thick-wall Kevlar 49/Epoxy pressure vessels

    SciTech Connect

    Guess, T.R.

    1984-01-01

    The feasibility of thick-wall composite vessels for very high pressure applications is demonstrated. Prototype vessels, in both spherical and cylindrical geometries, were designed, fabricated and burst tested. It is shown that experimental burst pressures are in excellent agreement with predicted values for burst pressures up to 60 ksi. Each unit consisted of a thin, seamless, copper liner with stainless steel fill stems and a filament-wound Kevlar 49/epoxy outer shell. Analysis of vessel performance accounted for liner thickness and yield strengths, composite thickness, mechanical properties and fiber volume fraction, and stress concentrations caused by the fill stem. Spherical vessels of three different sizes (inside diameters of 2.15 inches, 4.0 inches and 5.3 inches) with either 30 ksi or 60 ksi design burst pressure are discussed. Also, cylindrical vessels with identical liners but of two different composite thicknesses are described. These vessels achieved 50 ksi and 57 ksi burst pressures, respectively. In addition to the design considerations alluded to throughout the paper, the stress state in a thin metal liner during cyclic loading and the life prediction of composite vessels under sustained loading are discussed.

  8. Residual stiffness and strength of Kevlar/epoxy laminates impulsively loaded to 7. 9 ktaps

    SciTech Connect

    Guess, T.R.

    1987-11-01

    An experimental investigation of impulse-damaged composites is described. The purpose was to assess material property degradation in Kevlar/epoxy composites that had been subjected to impulse loads up to about 7.9 ktaps. These impulse loads produced intense short-duration compressive stress waves in flat composite panels. In most tests 25% to 45% of the initial composite thickness was delaminated (spalled) and removed from the back surface of the target. Optical inspection of residual target material did not reveal any matrix microcracking or delaminations away from the immediate vicinity of the spall surface of 0.125 and 0.25 inch thick targets; the 0.5 inch thick targets had some tensile stress induced delaminations. Specimens cut from residual targets and from as-fabricated materials were tested in tension, compression, four-point bend and three-point bend. There was basically no difference between the stress-strain responses of residual, impacted composite and as-fabricated composite samples. The load carrying capacity of the residual, impacted composites was reduced in proportion to the thickness of the material removed by spallation. Predictions of composite elastic properties were in good agreement with experimental values. Combined evidence of optical inspection and experimental results suggests that intense compression stresses did not significantly degrade the basic lamina properties of the Kevlar/epoxy composites investigated. 12 refs., 7 figs., 7 tabs.

  9. An experimental and theoretical study of the bending behavior of Kevlar 49/epoxy beams and rings

    SciTech Connect

    Guess, T.R.; Reedy, E.D. Jr.

    1987-01-01

    The basic lamina properties were determined by testing unidirectionally reinforced specimens in tension and compression. Results indicate that unidirectional Kevlar 49/epoxy composites manifest nearly linear elastic response in tension and yield-like behavior in fiber-directed compression. The measured compressive yield strength is roughly 20% of the tensile ultimate strength. We also tested 3.2 and 12.7 mm thick, quasi-isotropic beams in tension, compression, short beam shear, and four-point bending, and 457 mm diameter, 12.7 mm thick, quasi-isotropic rings in diametral compression. All specimens were fully instrumented with strain gages to provide a detailed record of their deformation. As anticipated, the flexural response of laminated Kevlar 49/epoxy beams and rings exhibit nonlinearity. For this reason, a material model which includes compressive yield behavior was examined. In this model, a Kevlar 49 lamina is assumed to respond in a linear elastic manner to all loads except compression in the fiber direction. In fiber-directed compression, it is assumed to behave in an elastic-perfectly plastic manner. Laminate response is determined from the postulated lamina behavior in a manner analogous to that used in classical laminated plate theory. This constitutive model was used in conjunction with the ABAQUS finite element code to analyze the tested specimens. Comparison of predicted results with experimental data corroborates the model's ability to reproduce much of the observed nonlinear behavior.

  10. Multiscale modeling of interwoven Kevlar fibers based on random walk to predict yarn structural response

    NASA Astrophysics Data System (ADS)

    Recchia, Stephen

    Kevlar is the most common high-end plastic filament yarn used in body armor, tire reinforcement, and wear resistant applications. Kevlar is a trade name for an aramid fiber. These are fibers in which the chain molecules are highly oriented along the fiber axis, so the strength of the chemical bond can be exploited. The bulk material is extruded into filaments that are bound together into yarn, which may be chorded with other materials as in car tires, woven into a fabric, or layered in an epoxy to make composite panels. The high tensile strength to low weight ratio makes this material ideal for designs that decrease weight and inertia, such as automobile tires, body panels, and body armor. For designs that use Kevlar, increasing the strength, or tenacity, to weight ratio would improve performance or reduce cost of all products that are based on this material. This thesis computationally and experimentally investigates the tenacity and stiffness of Kevlar yarns with varying twist ratios. The test boundary conditions were replicated with a geometrically accurate finite element model, resulting in a customized code that can reproduce tortuous filaments in a yarn was developed. The solid model geometry capturing filament tortuosity was implemented through a random walk method of axial geometry creation. A finite element analysis successfully recreated the yarn strength and stiffness dependency observed during the tests. The physics applied in the finite element model was reproduced in an analytical equation that was able to predict the failure strength and strain dependency of twist ratio. The analytical solution can be employed to optimize yarn design for high strength applications.

  11. [Research on structure of MC-nylon 6/aramid composites by spectroanalysis method].

    PubMed

    Wang, Can-Yao; Zheng, Yu-Ying

    2008-01-01

    The Kevlar fiber, treated with toluene-2,4-diisocyanate and caprolactam, was used to reinforce MC nylon 6. XPS showed the change in chemical components and spectra after fiber was treated. IR showed that the spectra of Kevlar fiber and MC-nylon 6 were incorporated purely when they were mixed, while the treated Kevlar fiber provided the activation in the ring-opening polymerization of caprolactam, and the amide groups of graft chains could form strong hydrogen bonds with matrix. These graft chains and hydrogen bonds would contribute to improving interfacial bonding between MC-nylon 6 and Kevlar fiber. XRD indicated that the induction of Kevlar fiber had no effect on the cryastalline style of MC-nylon 6 obviously, however, the crystals had better seasonal structure. The crystals of MC-nylon 6/Kevlar fiber composites were more perfect than that of MC-nylon 6/Kevlar untreated fiber composites with the same amount of Kevlar fiber. The increase of Kevlar fiber contributed to forming perfect a spherulite when the mass concentration of Kevlar fiber was less than 2%, however, the more the Kevlar fiber, the less the content of a spherulite when the mass concentration of Kevlar fiber was more than 2%.

  12. Dispersion in fiber lifetime under load. [Kevlar

    SciTech Connect

    Cook, R.

    1985-11-13

    The best Gaussian fit for the distribution of the static strength of Kevlar strands is given by G(s) = (2..pi..a)/sup -1/2/exp(-(s-)/sup 2//2a), where a = ..sigma..(s/sub i/ - )/sup 2//N = 0.290 and s is the strength of sample i. The distribution of breaking times span nearly three decades with the time for breakage of the first 50% of the fibers only about 15% of the time required for breakage of all of the fibers. More important from the reliability viewpoint is the short time failure; 9% of the sample had failed in less than 10% of the time for 50% to fail. The ability to understand and predict this very non-Gaussian distribution from the Gaussian distribution of static strengths is what this paper is concerned with.

  13. The behavior of Kevlar fibers under environmental-stress conditions

    NASA Astrophysics Data System (ADS)

    Perry, Mark Charles

    There are a myriad of mechanisms by which polymers can degrade and fail. It is therefore important to understand the physical mechanics, chemistry, their interactions, and kinetics. This pursuit becomes more than just "academic" because these mechanisms might just change with service conditions (i.e. environment and loading). If one does not understand these processes from the molecular to macroscopic scale it would be exceedingly difficult to gain information from accelerated testing because the mechanisms just might change from one condition to another. The purpose of this study was to probe these processes on scales ranging from molecular to macroscopic in environmental stress conditions. This study reports the results of environmental-stress degradation of Kevlar 49 fibers. The environmental agent of focus was the ubiquitous air pollutant complex NOsb{x}. Other materials and environments were investigated to a lesser extent for purposes of comparison. Mechanical property (i.e., short-term strength, modulus, and creep lifetime) degradation was examined using single fiber, yarn, and epoxy coated yarn (composite) specimens under environmental-stress conditions. Optical and scanning electron microscopes were employed to examine and compare the appearance of fracture features resulting from the various testing conditions. Atomic force microscopy augmented these studies with detailed topographical mappings and measures of the fracture surface frictional and modulus properties. Molecular processes (i.e., chain scission and other mechanical-chemical reactions) were probed by measures of changes in viscosity average molecular weight and the infrared spectra. It was demonstrated that environmental-stress degradation effects do occur in the Kevlar-NOsb{x} gas system. Strength decay in environmentally exposed unloaded fibers was demonstrated and a synergistic response in creep reduced fiber lifetimes by three orders of magnitude at moderate loadings. That is to say, the

  14. Experimental Measurement and Computational Simulation of the Strains on a Single Yarn in a Kevlar Fabric During Stretching

    DTIC Science & Technology

    2010-06-01

    displacement and strain time histories matched reasonably well with the experimental data. 15. SUBJECT TERMS Photogrammetry strain measurements optical...and textile composites. For instance, Lomov et al. (1, 2) studied the in-plane deformation of yarns in a fabric that underwent shearing using two...sensitivity of the friction coefficient between yarns under a static stretching condition. 2. Experimental Method We used a 5x5 plain- weave Kevlar

  15. Cytotoxicity and mutagenicity of Kevlar: an in vitro evaluation.

    PubMed

    Wening, J V; Marquardt, H; Katzer, A; Jungbluth, K H; Marquardt, H

    1995-03-01

    Toxicity and mutagenicity of Kevlar 49 (PPPT; poly-para-phenylene-terephthalamide) was tested in six strains of Salmonella typhimurium (Ames test; TA97, TA98, TA100, TA102, TA1535, TA1537) with and without an external metabolic activation system (S9), as well as in a mammalian cell mutagenesis assay using V79 Chinese hamster cells. For the Ames test, liquid preincubation, which is considered particularly sensitive, was used. The cells were incubated for 24 h at a temperature of 37 degrees C either directly with Kevlar49 or with ethanol- or chloroform-extracted Kevlar49. The experiments were performed at least twice. The Ames test with six different Salmonella typhimurium strains featuring either base pair substitution or frameshift mutations revealed no cytotoxic or mutagenic activity of Kevlar49. In the mammalian cell mutagenesis assay, using 8-azaguanine (AG) as a selective agent, Kevlar49 was also devoid of cytotoxic or mutagenic activity. Both tests have to be regarded as an initial exploratory screening due to the chosen testing conditions and should be supplemented by tests at different temperatures.

  16. Metallization of Kevlar fibers with gold.

    PubMed

    Little, Brian K; Li, Yunfeng; Cammarata, V; Broughton, R; Mills, G

    2011-06-01

    Electrochemical gold plating processes were examined for the metallization of Kevlar yarn. Conventional Sn(2+)/Pd(2+) surface activation coupled with electroless Ni deposition rendered the fibers conductive enough to serve as cathodes for electrochemical plating. The resulting coatings were quantified gravimetrically and characterized via adhesion tests together with XRD, SEM, TEM; the coatings effect on fiber strength was also probed. XRD data showed that metallic Pd formed during surface activation whereas amorphous phases and trace amounts of pure Ni metal were plated via the electroless process. Electrodeposition in a thiosulfate bath was the most efficient Au coating process as compared with the analogous electroless procedure, and with electroplating using a commercial cyanide method. Strongly adhering coatings resulted upon metallization with three consecutive electrodepositions, which produced conductive fibers able to sustain power outputs in the range of 1 W. On the other hand, metallization affected the tensile strength of the fiber and defects present in the metal deposits make questionable the effectiveness of the coatings as protective barriers.

  17. Tendon cell outgrowth rates and morphology associated with kevlar-49.

    PubMed

    Zimmerman, M; Gordon, K E

    1988-12-01

    A rat tendon cell model was used to evaluate the in vitro biocompatibility of kevlar-49. The cell response to kevlar was compared to carbon AS-4 and nylon sutures. Three trials were run and cell growth rates were statistically similar for all the materials tested. A separate experiment was conducted in which the same fiber materials were placed in the same Petri dish. Again, the rates were similar for each material. Finally, the cells were observed with a scanning electron microscope, and the three classic cell morphologies associated with this tendon cell model were observed. Also, cellular attachment to the fiber and cellular encapsulation of the fiber were identical for the three materials tested. Kevlar-49 proved to be comparable to carbon AS4 and nylon sutures in terms of cellular response and cell outgrowth rates.

  18. The effect of configuration on strength, durability, and handle of Kevlar fabric-based materials

    NASA Technical Reports Server (NTRS)

    Reuter, L. L.; Munson, J. B.

    1977-01-01

    Five Kevlar based laminates and three Kevlar based coated materials were designed, hand made, and tested against comparative conventional Dacron based materials for strength, peel, tear, puncture, creases, and handle. Emphasis was placed on evaluating geometric orientation of constituents, use of elastomeric film in place of high modulus films, and the use of flying thread loom bias reinforcement of Kevlar yarns. Whereas, the performance of the Kevlar laminates was severely degraded by crease effects, significant gains in overall performance factors were shown for the coated Kevlar materials.

  19. The large deformation elastic response of woven Kevlar fabric

    SciTech Connect

    Warren, W.E.

    1991-01-01

    The large deformation elastic response of a plane woven Kevlar fabric is investigated analytically and experimentally. The analysis assumes the undeformed geometry to be a sequence of interlaced arcs of circles which reverse at each yarn midpoint, ad each yarn is modeled as an extensible elastical subject to certain compatibility conditions. Deflection-force relations for the fabric are determined in terms of the initial weave geometry and the elastic properties of the individual yarns. The theoretical results agree well with the results of experiments performed on a fabric woven from 400 denier Kevlar yarns under conditions of uniaxial loading in both warp and fill directions. 13 refs., 4 figs.

  20. Novel nanocomposite Kevlar fabric membranes: Fabrication characterization, and performance in oil/water separation

    NASA Astrophysics Data System (ADS)

    Karimnezhad, Hanieh; Rajabi, Laleh; Salehi, Ehsan; Derakhshan, Ali Ashraf; Azimi, Sara

    2014-02-01

    Nanocomposite membranes with hydrophilic surface were fabricated for separation of oil (n-hexane) from oil/water emulsion. Three different nanomaterials namely, para-aminobenzoate alumoxane (PAB-A), boehmite-epoxide and polycitrate alumoxane (PC-A) were coated on the Kevlar fabric (support), according to a three-step dip-coating protocol. FTIR, SEM, TEM, UV/vis spectrophotometer, and wettability analyses were used to characterize the composite membranes. The three coating layers interacted chemically with one another and also physically with the Kevlar fabric. Water uptake measurements indicated that the membrane is a hydrophilic one. SEM and TEM analyses showed the smooth surface of the composite membrane and three-dimensional dendrimeric hyper-branched structure of (PC-A), respectively. A dead-end filtration setup was applied to test the membranes performance under natural gravity force. Effect of pH as an important variable affecting separation process was investigated with the neutral pH provided the optimum condition for the separation. Oil rejection and permeate fluxes were also monitored. The optimum flux and rejection obtained, were 7392 (Lm-2 h-1) and 89.06% at pH 7, respectively. Fouling occurred as a gel layer on the membrane surface. The deposited oil droplets on the surface of the membrane were successfully washed away with satisfactory permeate flux recovery (FRR = 88.88% at neutral pH), using hot distilled water and acidic solution as eluents.

  1. Development of a Continuum Damage Mechanics Material Model of a Graphite-Kevlar(Registered Trademark) Hybrid Fabric for Simulating the Impact Response of Energy Absorbing Kevlar(Registered Trademark) Hybrid Fabric for Simulating the Impact Response of Energy Absorbing

    NASA Technical Reports Server (NTRS)

    Jackson, Karen E.; Fasanella, Edwin L.; Littell, Justin D.

    2017-01-01

    This paper describes the development of input properties for a continuum damage mechanics based material model, Mat 58, within LS-DYNA(Registered Trademark) to simulate the response of a graphite-Kevlar(Registered Trademark) hybrid plain weave fabric. A limited set of material characterization tests were performed on the hybrid graphite-Kevlar(Registered Trademark) fabric. Simple finite element models were executed in LS-DYNA(Registered Trademark) to simulate the material characterization tests and to verify the Mat 58 material model. Once verified, the Mat 58 model was used in finite element models of two composite energy absorbers: a conical-shaped design, designated the "conusoid," fabricated of four layers of hybrid graphite-Kevlar(Registered Trademark) fabric; and, a sinusoidal-shaped foam sandwich design, designated the "sinusoid," fabricated of the same hybrid fabric face sheets with a foam core. Dynamic crush tests were performed on components of the two energy absorbers, which were designed to limit average vertical accelerations to 25- to 40-g, to minimize peak crush loads, and to generate relatively long crush stroke values under dynamic loading conditions. Finite element models of the two energy absorbers utilized the Mat 58 model that had been verified through material characterization testing. Excellent predictions of the dynamic crushing response were obtained.

  2. What's new in intraperitoneal test on Kevlar (asbestos substitute)?

    PubMed

    Brinkmann, O A; Müller, K M

    1989-09-01

    The intraperitoneal test is a suitable experimental method for studying the different patterns of morphological reaction to foreign body substances of various kinds and concentrations as well as their transport within and elimination from the organism, Kevlar fibres are synthetic aromatic polyamid (aramid) fibres which, investigated by means of the intraperitoneal test in Wistar rats, show distinct pathogenetic reaction patterns: 1. In the early stage after application, the formation of multinucleated giant cells with phagocytosis of the amber-coloured Kevlar fibres, and an inflammatory reaction are foremost features. 2. The typical feature of the second stage is the development of granulomas with central necrosis indicating the cytotoxic nature of Kevlar fibres. 3. The third stage is dominated by the mesenchymal activation with capsular structures of collagenous fibres. Besides granulomatous foci, a slight submesothelial fibrosis is observed. 4. Fragments of Kevlar fibres are drained through lymphatic pathways and stored in lymph nodes where they lead to inflammatory reactions. 5. The reactive granulomatous changes in the greater omentum of rats are accompanied by proliferative mesothelial changes which, in one cases, even led to the development of a multilocular mesothelioma.

  3. Fiber composite materials technology development

    SciTech Connect

    Chiao, T.T.

    1980-10-23

    The FY1980 technical accomplishments from the Lawrence Livermore National laboratory (LLNL) for the Fiber Composite Materials Technology Development Task fo the MEST project are summarized. The task is divided into three areas: Engineering data base for flywheel design (Washington University will report this part separately), new materials evaluation, and time-dependent behavior of Kevlar composite strands. An epoxy matrix was formulated which can be used in composites for 120/sup 0/C service with good processing and mechanical properties. Preliminary results on the time-dependent properties of the Kevlar 49/epoxy strands indicate: Fatigue loading, as compared to sustained loading, drastically reduces the lifetime of a Kevlar composie; the more the number of on-off load cycles, the less the lifetime; and dynamic fatigue of the Kevlar composite can not be predicted by current damage theories such as Miner's Rule.

  4. Pulmonary response to inhaled Kevlar aramid synthetic fibers in rats.

    PubMed

    Lee, K P; Kelly, D P; Kennedy, G L

    1983-11-01

    Groups of male rats were exposed to specially prepared ultrafine Kevlar pulp fibers (du Pont's registered trademark for certain aramid fibers) at atmospheric concentrations of either 0.1, 0.5, 3.0, or 18 mg/m3 for 2 weeks. Rats were killed at 0 and 2 weeks and 3 and 6 months postexposure (PE) except the rats exposed to 18 mg/m3, which were killed 0, 4, and 14 days and 1, 3, and 6 months PE. Another group of male rats was exposed to 18 mg/m3 (respirable dust approximately 2.5 mg/m3) of commercial Kevlar fibers for 2 weeks and were killed at 0 and 2 weeks and 3 and 6 months PE. Inhaled ultrafine Kevlar fibers were mostly phagocytized by alveolar macrophages (dust cells) in the alveolar ducts and adjoining alveoli after exposure to either 0.1 or 0.5 micrograms/m3. Most dust cells had disappeared and lungs showed a normal appearance throughout 6 months PE. The pulmonary response almost satisfied the biological criteria for a nuisance dust. Rats exposed to 3 mg/m3 ultrafine Kevlar fibers revealed occasional patchy thickening of alveolar ducts with dust cells and inflammatory cells but with no collagen fibers deposited throughout 6 months PE. After exposure to 18 mg/m3 ultrafine Kevlar, the respiratory bronchioles, alveolar ducts, and adjoining alveoli showed granulomatous lesions with dust cells by 2 weeks PE. The granulomatous lesions converted to patchy fibrotic thickening with dust cells after 1 month PE. The fibrotic lesions were markedly reduced in cellularity, size, and numbers from 3 to 6 months PE but revealed networks of reticulum fibers with slight collagen fiber deposition.

  5. Kevlar Vest Protection Against Blast Overpressure Brain Injury: Systemic Contributions to Injury Etiology

    DTIC Science & Technology

    2014-11-01

    Award Number: W81XWH-08-2-0017 TITLE: " Kevlar Vest Protection Against Blast Overpressure Brain Injury: Systemic Contributions to Injury Etiology...TITLE AND SUBTITLE 5a. CONTRACT NUMBER “ Kevlar Vest Protection Against Blast Overpressure Brain Injury: Systemic Contributions to Injury Etiology...traumatic brain injury (bTBI) is largely undefined. Along with reducing mortality, in preliminary experiments Kevlar vests significantly protected

  6. Feasibility of Kevlar 49/PMR-15 polyimide for high temperature applications

    NASA Technical Reports Server (NTRS)

    Hanson, M. P.

    1980-01-01

    Kevlar 49 aramid organic fiber reinforced PMR-15 polyimide laminates were characterized to determine the applicability of the material to high temperature aerospace structures. Kevlar 49/3501-6 epoxy laminates were fabricated and characterized for comparison with the Kevlar 49/PMR-15 polyimide material. Flexural strengths and moduli and interlaminar shear strengths were determined from 75 to 600 F for the PMR-15 and from 75 to 450 F for the Kevlar 49/3501-6 epoxy material. The study also included the effects of hydrothermal and long-term elevated temperature exposures on the flexural strengths and moduli and the interlaminar shear strengths.

  7. Feasibility of Kevlar 49/PMR-15 Polyimide for High Temperature Applications

    NASA Technical Reports Server (NTRS)

    Hanson, M. P.

    1980-01-01

    Kevlar 49 aramid organic fiber reinforced PMR-15 polyimide laminates were characterized to determine the applicability of the material to high temperature aerospace structures. Kevlar 49/3501-6 epoxy laminates were fabricated and characterized for comparison with the Kevlar 49/PMR-15 polyimide material. Flexural strengths and moduli and interlaminar shear strengths were determined from 75 F to 600 F for the PMR-15 and from 75 F to 450 F for the Kevlar/3501-6 epoxy material. The effects of hydrothermal and long-term elevated temperature exposures on the flexural strengths and moduli and the interlaminar shear strengths were also studied.

  8. A comparison of wire- and Kevlar-reinforced provisional restorations.

    PubMed

    Powell, D B; Nicholls, J I; Yuodelis, R A; Strygler, H

    1994-01-01

    Stainless steel wire 0.036 inch in diameter was compared with Kevlar 49 polyaramid fiber as a means of reinforcing a four-unit posterior provisional fixed restoration with 2 pontics. Three reinforcement patterns for wire and two for Kevlar 49 were evaluated and compared with the control, which was an unreinforced provisional restoration. A central tensile load was placed on the cemented provisional restoration and the variables were measured: (1) the initial stiffness; (2) the load at initial fracture; and (3) the unit toughness, or the energy stored in the beam at a point where the load had undergone a 1.0-mm deflection. Statistical analysis showed (1) the bent wire configuration had a significantly higher initial stiffness (P < or = .05), (2) there was no difference between designs for load at initial fracture, and (3) the bent wire had a significantly higher unit toughness value (P < or = .05).

  9. [Surface grafting modification and stabilization of Kevlar fiber].

    PubMed

    Zheng, Yu-ying; Fu, Ming-lian; Wang, Can-yao; Wang, Liang-en

    2005-11-01

    Chemical disposal was used to bring the activity group onto the surface of Kevlar fiber for the purpose of surface grafting modification. The interfacial constitution of the grafting of toluene-2,4-diisocyanate (TDI) onto Kevlar fiber was determined by Fourier transform infrared spectroscopy. In the mean time, hexyl-lactam stabilization and poly-glycol (400, PEG) stabilization on the grafted product were also studied. The effects of different nTDI:nPEG ratios on the production's interfacial constitution was analysed. It is concluded that the stabilization took place on the surface. The intensity of the bands relented at about 3300 cm(-1) and was reinforced at about 1700-1720 cm(-1) when the ratio of nTDI:nPEG = 1:3, but when the ratio is 1:1 and 1:2, the bands at about 3 300 and 1700-1720 cm(-1) are almost the same.

  10. Materials and Design Criteria for Kevlar-29 Ribbon Parachutes

    DTIC Science & Technology

    1982-04-01

    independent of dynamic pressure and, in most cases , test item configuration. A notable exception to the configurational independence are test items IH-8...I AFWAL-TR-81-31 38 MATERIALS AND DESIGN CRITERIA FOR KEVLAR-29 RIBBON PARACHUTES William R. Pinnell Crew Escape and Subsystems Branch Vehicle...nations. This tehr:ical report hlis beer. reviewea and is approved for publication. ILLIA4 R. PINNELL R. HAkLEY WAVK•R Project Engineer/Scientist Group

  11. Analysis methods for Kevlar shield response to rotor fragments

    NASA Technical Reports Server (NTRS)

    Gerstle, J. H.

    1977-01-01

    Several empirical and analytical approaches to rotor burst shield sizing are compared and principal differences in metal and fabric dynamic behavior are discussed. The application of transient structural response computer programs to predict Kevlar containment limits is described. For preliminary shield sizing, present analytical methods are useful if insufficient test data for empirical modeling are available. To provide other information useful for engineering design, analytical methods require further developments in material characterization, failure criteria, loads definition, and post-impact fragment trajectory prediction.

  12. The Rupture Behaviour Of Woven Fabrics Containing Kevlar Fibres

    NASA Astrophysics Data System (ADS)

    Mao, N.; Qu, J.; Darley, M.; Lingard, S.

    2012-07-01

    Woven fabrics containing high performance fibres are frequently used in spacecraft structures and the rupture behaviour of these fabrics heavily influences the performance of its final products. However, the initiation and propagation of a ruptured fracture in the woven fabrics is not clear and the interpretation of the results from different tear testing methods varies. Currently there is a lack of knowledge about both the characteristics of tear propagation woven fabrics containing high performance fibres such as Kevlar and the influence of the fabric structural parameters on the rupture behaviour of the fabrics; this knowledge gap creates difficulties for the engineering design and selection of suitable fabric materials to meet specific requirements in each application case involving such woven fabrics. In this paper, the tear propagations in a polyurethane-coated woven fabric containing Kevlar fibres based on two different tear testing standards are examined; the mechanism of tear propagation in woven fabrics and the influences of tear testing design on the interpretation of the results from different tear testing methods are discussed. It is expected that the results will guide both the engineering design of Kevlar woven fabric structures and the evaluation of the fabric performance.

  13. Investigation of woven composites as potential cryogenic tank materials

    NASA Astrophysics Data System (ADS)

    Islam, Md. S.; Melendez-Soto, E.; Castellanos, A. G.; Prabhakar, P.

    2015-12-01

    In this paper, carbon fiber and Kevlar® fiber woven composites were investigated as potential cryogenic tank materials for storing liquid fuel in spacecraft or rocket. Towards that end, both carbon and Kevlar® fiber composites were manufactured and tested with and without cryogenic exposure. The focus was on the investigation of the influence of initial cryogenic exposure on the degradation of the composite. Tensile, flexural and inter laminar shear strength (ILSS) tests were conducted, which indicate that Kevlar® and carbon textile composites are potential candidates for use under cryogenic exposure.

  14. Ultrasonic girth weld evaluation for aluminum substrate of spherical Kevlar-epoxy test specimens

    SciTech Connect

    Brosey, W.D.; Dews, T.W.

    1984-08-28

    An ultrasonic weld inspection has been developed for the girth weld of the aluminum substrate for a Kevlar-epoxy filament wound test specimen. The filament wound spheres are test coupons in a study to evaluate NDE techniques on a composite material with enclosed geometry. The girth weld of the aluminum substrate has been examined to ensure the weld is not a weak point in the coupon in which failure will initiate. Analog and B-scan data are combined to determine the presence of lack of penetration, suckback, protrusion, or porosity in the weld. The data are calibrated with a standard and then plotted as analog, B-scan, or color contour data as a function of angular position around the weld.

  15. Strain Measurement during Stress Rupture of Composite Over-Wrapped Pressure Vessel with Fiber Bragg Gratings Sensors

    NASA Technical Reports Server (NTRS)

    Banks, Curtis E.; Grant, Joseph; Russell, Sam; Arnett, Shawn

    2008-01-01

    Fiber optic Bragg gratings were used to measure strain fields during Stress Rupture (SSM) test of Kevlar Composite Over-Wrapped Pressure Vessels (COPV). The sensors were embedded under the over-wrapped attached to the liner released from the Kevlar and attached to the Kevlar released from the liner. Additional sensors (foil gages and fiber bragg gratings) were surface mounted on the COPY liner.

  16. Strain measurement during stress rupture of composite over-wrapped pressure vessel with fiber Bragg gratings sensors

    NASA Astrophysics Data System (ADS)

    Banks, Curtis E.; Grant, Joseph; Russell, Sam; Arnett, Shawn

    2008-03-01

    Fiber optic Bragg gratings were used to measure strain fields during Stress Rupture (SSM) test of Kevlar Composite Over-Wrapped Pressure Vessels (COPVs). The sensors were embedded under the over-wrapped attached to the liner released from the Kevlar and attached to the Kevlar released from the liner. Additional sensors (foil gages and fiber bragg gratings) were surface mounted on the COPV liner.

  17. Composite Materials

    NASA Technical Reports Server (NTRS)

    1985-01-01

    Composites are lighter and stronger than metals. Aramid fibers like Kevlar and Nomex were developed by DuPont Corporation and can be combined in a honeycomb structure which can give an airplane a light, tough structure. Composites can be molded into many aerodynamic shapes eliminating rivets and fasteners. Langley Research Center has tested composites for both aerospace and non-aerospace applications. They are also used in boat hulls, military shelters, etc.

  18. Composites review

    NASA Technical Reports Server (NTRS)

    Hordonneau, A.

    1987-01-01

    The properties and applications of composite materials are reviewed. Glass, carbon, Kevlar, ceramic, whisker, and metal fibers are discussed along with polyester, epoxy, polyimide, Peek, carbon, ceramic, and metal matrices. The quantitative distribution of high technology fiber in various applications is given. The role of aerospace industry in the development and promotion of composite utilization is discussed. Consumption trends indicate a rapid development of the composite market.

  19. Experimental analysis of Kevlar modification for TRUPACT-I puncture panels. [Drop tests; radiant heat tests

    SciTech Connect

    Longenbaugh, R.S.; Joseph, B.J.

    1987-05-01

    The Kevlar Test Services was initiated to determine the maximum failure force and the energy-absorbing capability of puncture panels consisting of 16, 20, and 24 layers of 3000-denier 4 x 4 basket weave Kevlar-29, bonded to a 3.41 mm 304 annealed stainless steel puncture plate. Results of these tests were compared to the TRUPACT-1 Unit-0 drop test results to determine if the existing puncture panel configuration of TRUPACT-1 could be reduced. The data indicate for 24 layers of Kevlar, the panels failed at loads greater than those recorded in the TRUPACT-1, Unit 0 tests. Energy absorbed by the 24-layer Kevlar panels was 53% greater than that measured in the TRUPACT-1, Unit 0 test. Thermal performance of 20-layer Kevlar panels was measured in a conservative test environment and exceeded the design specifications.

  20. Intricacies of Using Kevlar and Thermal Knives in a Deployable Release System: Issues and Solutions

    NASA Technical Reports Server (NTRS)

    Stewart, Alphonso C.; Hair, Jason H.; Broduer, Steve (Technical Monitor)

    2002-01-01

    The utilization of Kevlar cord and thermal knives in a deployable release system produces a number of issues that must be addressed in the design of the system. This paper proposes design considerations that minimize the major issues, thermal knife failure, Kevlar cord relaxation, and the measurement of the cord tension. Design practices can minimize the potential for thermal knife laminate and element damage that result in failure of the knife. A process for in-situ inspection of the knife with resistance, rather than continuity, checks and 10x zoom optical imaging can detect damaged knives. Tests allow the characterization of the behavior of the particular Kevlar cord in use and the development of specific pre-stretching techniques and initial tension values needed to meet requirements. A new method can accurately measure the tension of the Kevlar cord using a guitar tuner, because more conventional methods do not apply to arimid cords such as Kevlar.

  1. Intricacies of Using Kevlar Cord and Thermal Knives in a Deployable Release System: Issues and Solutions

    NASA Technical Reports Server (NTRS)

    Stewart, Alphonso; Hair, Jason H.

    2002-01-01

    The utilization of Kevlar cord and thermal knives in a deployable release system produces a number of issues that must be addressed in the design of the system. This paper proposes design considerations that minimize the major issues, thermal knife failure, Kevlar cord relaxation, and the measurement of the cord tension. Design practices can minimize the potential for thermal knife laminate and element damage that result in failure of the knife. A process for in-situ inspection of the knife with resistance, rather than continuity, checks and 10x zoom optical imaging can detect damaged knives. Tests allow the characterization of the behavior of the particular Kevlar cord in use and the development of specific prestretching techniques and initial tension values needed to meet requirements. A new method can accurately measure the tension of the Kevlar cord using a guitar tuner, because more conventional methods do not apply to arimid cords such as Kevlar.

  2. Intricacies of Using Kevlar Cord and Thermal Knives in a Deployable Release System: Issues and Solutions

    NASA Astrophysics Data System (ADS)

    Stewart, Alphonso; Hair, Jason H.

    2002-04-01

    The utilization of Kevlar cord and thermal knives in a deployable release system produces a number of issues that must be addressed in the design of the system. This paper proposes design considerations that minimize the major issues, thermal knife failure, Kevlar cord relaxation, and the measurement of the cord tension. Design practices can minimize the potential for thermal knife laminate and element damage that result in failure of the knife. A process for in-situ inspection of the knife with resistance, rather than continuity, checks and 10x zoom optical imaging can detect damaged knives. Tests allow the characterization of the behavior of the particular Kevlar cord in use and the development of specific prestretching techniques and initial tension values needed to meet requirements. A new method can accurately measure the tension of the Kevlar cord using a guitar tuner, because more conventional methods do not apply to arimid cords such as Kevlar.

  3. Mechanical behavior of silica nanoparticle-impregnated Kevlar fabrics

    NASA Astrophysics Data System (ADS)

    Dong, Zhaoxu

    Plain woven Kevlar fabrics are widely used as body protection materials. The present study investigated the impact performance of five styles of Kevlar fabrics K310, K706, K720, K745 and K779 from Hexcel. The fabrics are different in many aspects, i.e., weight per square meter, yarn counts, yarn size, Kevlar fiber type, friction and breaking strength. Silica nanoparticles were impregnated into the fabric to enhance the ballistic impact performance. The fabric impregnated with nanoparticles exhibit significant enhancement in impact performance over their neat counterparts. Fabrics experience large deformation under impact. More or less yarn pull-out was observed on all the fabrics. The in-plane yarn pull-out force has good correlation to the impact performance: fabrics with higher pull-out force performed better in impact tests. A two-dimensional finite element model was proposed to simulate the single yarn pull-out procedure and predict the maximum pull-out force. The most important fabric features are included in this model: yarn count, yarn size, fabric thickness, yarn waviness, fiber modulus, fiber diameter and coefficients of friction et al. The numerical results show good agreement with the experimentally measured pull-out forces. To understand the impact process, a constitutive model was developed to characterize the nonlinear anisotropic properties of the fabric in large deformation. The nanoparticles largely increase the shear stiffness, while only slightly affect the tension behavior along warp and weft yarn directions. This constitutive model was incorporated in the commercial FEA software ABAQUS through the user-defined material subroutine and used to simulate deformations with various loads. Finally the out-of-plane yarn pull-out force was predicted from the in-plane yarn pull-out results using finite element method and the proposed constitutive model.

  4. Quality-assurance tests of five Y-12 Kevlar-49 spools used to fabricate strands and reliability specimens for stress-rupture tests

    SciTech Connect

    Caley, L.E.; Ambalal, P.K.; Carley, J.F.; Ford, T.S.; Moore, R.L.; Noecker, D.J.; Ross, M.E.; Sherry, R.J.; Yoshiyama, J.M.

    1984-05-07

    An important component of the composite reliability program is the assurance of quality of Kevlar 49, 380-denier yarn and epoxy-impregnated yarn. This yarn, which is used in the fabrication of W-82 components from Kevlar 49/epoxy composites, is also formed into test specimens for long-term, stress-rupture studies and reliability studies. The QA work covered in this report encompasses preparation of impregnated-yarn specimens, examination of the yarn itself and individual fibers therefrom, tensile testing of bare and impregnated yarns and heat-degraded yarns. The yarn samples were all drawn from spools of 380-denier Kevlar 49 shipped to LLNL from Y-12. The resin matrix is an amine-hardened epoxy with low viscosity and long pot life, intended for filament winding. The components are Dow epoxy resin (DER) 332 and Jeffamine T-403 triamine hardener. The stoichiometric combining ratio, which we used in our work, is 100 parts by weight resin to 44 parts hardener. Quality-assurance testing not only verifies that the yarns actually meet the manufacturer's specifications, but also provides data on the relationships between fiber characteristics and the lifetime reliability of fabricated items.

  5. Electron-beam-induced fracture of Kevlar single fibers

    SciTech Connect

    Dickinson, J.T.; Jensen, L.C.; Klakken, M.L.

    1986-05-01

    We examine the unique situation involving the exposure of polymers to both electron bombardment and mechanical stress. Under certain conditions, crack formation, crack growth, and fracture can occur due to this combination of stimuli. These studies relate to the performance of a number of materials under hostile environments such as space, plasma, and propulsion systems. In this paper we present our initial measurements on the response of single Kevlar fibers loaded in tension to bombardment by 3-keV electrons. We present evidence that the resulting electron-beam-induced fracture is due to bond breaking.

  6. A Kinematic, Kevlar(registered) Suspension System for an ADR

    NASA Technical Reports Server (NTRS)

    Voellmer, George M.; Jackson, Michael L.; Shirron, Peter J.; Tuttle, James G.

    2003-01-01

    The High Resolution Airborne Wideband Camera (HAWC) and the Submillimeter And Far Infrared Experiment (SAFIRE) will use identical Adiabatic Demagnetization Refrigerators (ADR) to cool their bolometer detectors to 200mK and 100mK, respectively. In order to minimize thermal loads on the salt pill, a Kevlar@ suspension system is used to hold it in place. An innovative, kinematic suspension system is presented. The suspension system is unique in that it consists or two parts that can be assembled and tensioned offline, and later bolted onto the salt pill. The resulting assembly constrains each degree of freedom only once, yielding a kinematic, tensile structure.

  7. Analog data compression for Versatile Experimental Kevlar Array (VEKA) telemetry

    NASA Astrophysics Data System (ADS)

    Gholson, N. H.; Harris, P.

    1981-08-01

    The feasibility of amplitude data compression has been explored with respect to the Versatile Experimental Kevlar Array (VEKA) analog multiplexed telemetry of acoustic data. A Fourier transform approach has been developed to quantify the potential benefits and penalties associated with a particular invertible compression function. Analysis was performed using sinusoidal signals and white noise. Results of the analysis indicate that substantial gains in dynamic range can be achieved with tolerable sacrifices in telemetry system linearity. Specific examples for a particular telemetry system illustrate an increase in dynamic range from 80dB to approximately 120dB.

  8. Kinetics for the degradation of nylon and Kevlar parachute materials

    SciTech Connect

    Auerbach, I.

    1986-01-01

    The degradation of nylon 66 and Kevlar 29 yarns at elevated temperatures and over a broad range of humidities was studied and a rate relationship developed which models the degradation and permits computation of rate constants. The degradation rates are slow initially due to the presence of an inhibitor but increase rapidly as the inhibitor is depleted. The effect of relative humidity (RH) can be very large especially at values in the 100% range. An exponential relationship exists for nylon between the rate constant and RH. Kinetic parameters were evaluated and the rate constants at 25/sup 0/C calculated. These values showed that the tensile strength of nylon 66 will remain at a safe level over a 25-year period if the humidity is maintained at the 10% range or less. Kevlar 29 is more resistant and can tolerate humidity levels in the range of 90% or less. Degradation is governed by thermal-oxidative and moisture induced mechanisms. At the very high humidities the moisture induced degradation predominates. A relationship is developed which predicts the degradation rate over a very broad range of temperatures and humidities.

  9. Ground exposure of composite materials for helicopters

    NASA Technical Reports Server (NTRS)

    Baker, D. J.

    1984-01-01

    Residual strength results are presented on four composite material systems that were exposed for three years at locations on the North American Continent. The exposure locations are near the areas where Bell Model 206L Helicopters, that are in a NSA/U.S. Army sponsored flight service program, are flying in daily commercial service. The composite systems are: (1) Kevlar-49 fabric/F-185 epoxy; (2) Kevlar-49 fabric/LRF-277 epoxy; (3) Kevlar-49 fabric/CE-306 epoxy; and (4) T-300 Graphite/E-788 epoxy. All material systems exhibited good strength retention in compression and short beam shear. The Kevlar-49/LRF-277 epoxy retained 88 to 93 percent of the baseline strength while the other material systems exceeded 95 percent of baseline strength. Residual tensile strength of all materials did not show a significant reduction. The available moisture absorption data is also presented.

  10. Radiation exposure reduction by use of Kevlar cassettes in the neonatal nursery

    SciTech Connect

    Herman, M.W.; Mak, H.K.; Lachman, R.S.

    1987-05-01

    A study was performed to determine whether the use of Kevlar cassettes in the neonatal intensive care nursery would reduce radiation exposure to patients. The radiation dose to the neonates was measured by using thermoluminescent dosimeters. In addition, the attenuation of the Kevlar cassettes and the sensitivity of the film-screen combination were compared with the previously used system. The greatest radiation reduction using a mobile X-ray unit was 27%; based on sensitivity measurements, the theoretical reduction averaged 38%. The reduction in radiation exposure resulted from reduced attenuation by the Kevlar cassette.

  11. Radiation exposure reduction by use of Kevlar cassettes in the neonatal nursery.

    PubMed

    Herman, M W; Mak, H K; Lachman, R S

    1987-05-01

    A study was performed to determine whether the use of Kevlar cassettes in the neonatal intensive care nursery would reduce radiation exposure to patients. The radiation dose to the neonates was measured by using thermoluminescent dosimeters. In addition, the attenuation of the Kevlar cassettes and the sensitivity of the film-screen combination were compared with the previously used system. The greatest radiation reduction using a mobile X-ray unit was 27%; based on sensitivity measurements, the theoretical reduction averaged 38%. The reduction in radiation exposure resulted from reduced attenuation by the Kevlar cassette.

  12. QF monitoring. [Qualifying Facilities

    SciTech Connect

    Greenwald, S. ); Hoffman, B. )

    1991-10-01

    This article examines the effects on project financing of independent power projects of the California Public Utilities Commission decision to grant authority to California utilities to monitor and enforce compliance with the Federal Energy Regulatory Commission Qualifying Facility standards. The topics of the article include monitoring proposals, monitoring guidelines, the effects of monitoring, minimizing status loss and monitoring requirements.

  13. Kevlar based nanofibrous particles as robust, effective and recyclable absorbents for water purification.

    PubMed

    Nie, Chuanxiong; Peng, Zihang; Yang, Ye; Cheng, Chong; Ma, Lang; Zhao, Changsheng

    2016-11-15

    Developing robust and recyclable absorbents for water purification is of great demand to control water pollution and to provide sustainable water resources. Herein, for the first time, we reported the fabrication of Kevlar nanofiber (KNF) based composite particles for water purification. Both the KNF and KNF-carbon nanotube composite particles can be produced in large-scale by automatic injection of casting solution into ethanol. The resulted nanofibrous particles showed high adsorption capacities towards various pollutants, including metal ions, phenylic compounds and various dyes. Meanwhile, the adsorption process towards dyes was found to fit well with the pseudo-second-order model, while the adsorption speed was controlled by intraparticle diffusion. Furthermore, the adsorption capacities of the nanofibrous particles could be easily recovered by washing with ethanol. In general, the KNF based particles integrate the advantages of easy production, robust and effective adsorption performances, as well as good recyclability, which can be used as robust absorbents to remove toxic molecules and forward the application of absorbents in water purification.

  14. An experimental study of the effects of water repellant treatment on the acoustic properties of Kevlar

    NASA Technical Reports Server (NTRS)

    Smith, C. D.; Parrott, T. L.

    1978-01-01

    The treatment consisted of immersing samples of Kevlar in a solution of distilled water and Zepel. The samples were then drained, dried in a circulating over, and cured. Flow resistance tests showed approximately one percent decrease in flow resistance of the samples. Also there was a density increase of about three percent. It was found that the treatment caused a change in the texture of the samples. There were significant changes in the acoustic properties of the treated Kevlar over the frequency range 0.5 to 3.5 kHz. In general it was found that the propagation constant and characteristic impedance increased with increasing frequency. The real and imaginary components of the propagation constant for the treated Kevlar exhibited a decrease of 8 to 12 percent relative to that for the untreated Kevlar at the higher frequencies. The magnitude of the reactance component of the characteristic impedance decreased by about 40 percent at the higher frequencies.

  15. Study of insoluble crystals derived from solutions of Kevlar 49 in sulfuric acid

    SciTech Connect

    Butler, N.L.

    1984-05-21

    The object of the study was to isolate and obtain x-ray diffraction analysis of the insoluble crystals which have been observed in Kevlar 49/H/sub 2/SO/sub 4/ dope. These insoluble crystals had previously been reported to be Kevlar single crystals after analysis by optical microscopy. A more detailed analysis does not support this conclusion. Additional optical microscopy coupled with FTIR and elemental analysis for C, H and N, has shown that these insoluble crystals are in fact terephthalic acid which is a decomposition product of the acid hydrolysis of Kevlar. A model compound study of sulfuric-acid hydrolysis of aromatic amide was carried out in order to better understand the sulfuric-acid-hydrolysis of Kevlar.

  16. The development and evaluation of advanced Kevlar sandwich structure for application to rotorcraft airframes

    NASA Astrophysics Data System (ADS)

    Minguet, Pierre; Llorente, Steven; Fay, Russell

    1991-05-01

    The results of an evaluation of DuPont Kevlar-based material systems in sandwich structure designed for rotorcraft primary airframe structure are presented in this report. The focus of this work has been to evaluate the durability and compression strength of thin-gage Kevlar sandwich panels and investigate means of improvement. It was found that sandwich panels made with Kevlar 149 fibers can be as strong as Kevlar 49 structures but have reduced compression stiffness properties at typical operating strain levels. Thermal cycling was found to affect permeability but not strength in thin facesheet sandwich structure. Any increased permeability can be prevented with the use of an interleaf or surfacing plies. The surfacing plies investigated also had a beneficial effect on sandwich strength due to their stabilizing effect on the facesheet in compression. Finally, a previously developed model was used to analyze the residual strength of a sandwich panel after impact damage.

  17. Development of an alternating flat to tubular Kevlar parachute tape

    SciTech Connect

    Ericksen, R.H.; Koch, R.

    1989-01-01

    An alternating flat to tubular Kevlar tape was developed to replace braided suspension lines and woven tape radials on the new crew escape module parachute system for the F-111 aircraft. Weaves were developed which had high strength efficiency and low weight throughout the flat, tubular, and transition sections. A tubular section strength of 535 lbs at a weight of 0.044 oz/yd was achieved. This reduces suspension line weight by 8% compared with that of the most efficient braid which has a strength of 470 lbs and weighs 0.048 oz/yd. Length measuring procedures for production control and inspection were developed. Using these procedures it was possible to produce alternating weave fabric with less than 1% variation in length in the tubular sections. 3 refs., 4 figs., 3 tabs.

  18. Fracto-emission from single fibres of Kevlar

    NASA Technical Reports Server (NTRS)

    Dickinson, J. T.; Jahan-Latibari, A.; Jensen, L. C.

    1985-01-01

    Fracto-emission (FE) is the emission of particles (e.g. electrons, ions and photons) during and following fracture. In this paper, we present data on electron emission (EE) and positive ion emission (PIE) from the tensile fracture of Kevlar single fibers. The fibers were initially fractured in pure tension, where a stranded form of fracture was observed, often with multiple peaks spread over several hundred microseconds. The loading condition was then changed by stretching and breaking the fibers over a dull metal edge. With this change in the loading, different forms of fracture were observed, each with distinctive forms of emission curves. When fracture was accompanied by extensive fibril formation, total emission was high and both EE and PIE decay times were long relative to fractures in which little fibril formation occurred. The results of this study suggest that FE has some applicability as a tool for the detection of fracture mechanisms of single fibers.

  19. Fracto-emission from single fibres of Kevlar

    NASA Technical Reports Server (NTRS)

    Dickinson, J. T.; Jahan-Latibari, A.; Jensen, L. C.

    1985-01-01

    Fracto-emission (FE) is the emission of particles (e.g. electrons, ions and photons) during and following fracture. In this paper, we present data on electron emission (EE) and positive ion emission (PIE) from the tensile fracture of Kevlar single fibers. The fibers were initially fractured in pure tension, where a stranded form of fracture was observed, often with multiple peaks spread over several hundred microseconds. The loading condition was then changed by stretching and breaking the fibers over a dull metal edge. With this change in the loading, different forms of fracture were observed, each with distinctive forms of emission curves. When fracture was accompanied by extensive fibril formation, total emission was high and both EE and PIE decay times were long relative to fractures in which little fibril formation occurred. The results of this study suggest that FE has some applicability as a tool for the detection of fracture mechanisms of single fibers.

  20. Direct Functionalization of Kevlar (registered trademark) with Copolymers Containing Sulfonyl Nitrene

    DTIC Science & Technology

    2016-01-01

    pyrenemethylamine solution; (d) Kevlar coated with pPFPA-co-SSAz that has undergone post- polymerization modification with 1-pyrenemethylamine. Polymer ...distribution is unlimited. 13. SUPPLEMENTARY NOTES Reprint of article published in the peer-reviewed journal Polymer Chemistry: 2015 March; 6:3090-7...covalent grafting of a wide variety of common commercial polymers to Kevlar. Also, by using reactive ester copolymers, an avenue for the attachment

  1. In-line Kevlar filters for microfiltration of transuranic-containing liquid streams.

    PubMed

    Gonzales, G J; Beddingfield, D H; Lieberman, J L; Curtis, J M; Ficklin, A C

    1992-06-01

    The Department of Energy Rocky Flats Plant has numerous ongoing efforts to minimize the generation of residue and waste and to improve safety and health. Spent polypropylene liquid filters held for plutonium recovery, known as "residue," or as transuranic mixed waste contribute to storage capacity problems and create radiation safety and health considerations. An in-line process-liquid filter made of Kevlar polymer fiber has been evaluated for its potential to: (1) minimize filter residue, (2) recover economically viable quantities of plutonium, (3) minimize liquid storage tank and process-stream radioactivity, and (4) reduce potential personnel radiation exposure associated with these sources. Kevlar filters were rated to less than or equal to 1 mu nominal filtration and are capable of reducing undissolved plutonium particles to more than 10 times below the economic discard limit, however produced high back-pressures and are not yet acid resistant. Kevlar filters performed independent of loaded particles serving as a sieve. Polypropylene filters removed molybdenum particles at efficiencies equal to Kevlar filters only after loading molybdenum during recirculation events. Kevlars' high-efficiency microfiltration of process-liquid streams for the removal of actinides has the potential to reduce personnel radiation exposure by a factor of 6 or greater, while simultaneously achieving a reduction in the generation of filter residue and waste by a factor of 7. Insoluble plutonium may be recoverable from Kevlar filters by incineration.

  2. Hot Billet Surface Qualifier

    SciTech Connect

    Tzyy-Shuh Chang

    2007-04-30

    OG Technologies, Inc. (OGT), developed a prototype of a Hot Billet Surface Qualifier (“Qualifier”) based on OGT’s patented HotEye™ technology and other proprietary imaging and computing technologies. The Qualifier demonstrated its ability of imaging the cast billets in line with high definition pictures, pictures capable of supporting the detection of surface anomalies on the billets. The detection will add the ability to simplify the subsequent process and to correct the surface quality issues in a much more timely and efficient manner. This is challenging due to the continuous casting environment, in which corrosive water, temperature, vibration, humidity, EMI and other unbearable factors exist. Each installation has the potential of 249,000 MMBTU in energy savings per year. This represents a cost reduction, reduced emissions, reduced water usage and reduced mill scale.

  3. Application of Raman Spectroscopy for Nondestructive Evaluation of Composite Materials

    NASA Technical Reports Server (NTRS)

    Washer, Glenn A.; Brooks, Thomas M. B.; Saulsberry, Regor

    2007-01-01

    This paper will present an overview of efforts to investigate the application of Raman spectroscopy for the characterization of Kevlar materials. Raman spectroscopy is a laser technique that is sensitive to molecular interactions in materials such as Kevlar, graphite and carbon used in composite materials. The overall goal of this research reported here is to evaluate Raman spectroscopy as a potential nondestructive evaluation (NDE) tool for the detection of stress rupture in Kevlar composite over-wrapped pressure vessels (COPVs). Characterization of the Raman spectra of Kevlar yarn and strands will be presented and compared with analytical models provided in the literature. Results of testing to investigate the effects of creep and high-temperature aging on the Raman spectra will be presented.

  4. Why does Kevlar decompose, while Nomex does not, when treated with aqueous chlorine solutions?

    PubMed

    Akdag, Akin; Kocer, Hasan B; Worley, S D; Broughton, R M; Webb, T R; Bray, Travis H

    2007-05-24

    Kevlar and Nomex are high-performance polymers which have wide varieties of applications in daily life. Recently, they have been proposed to be biocidal materials when reacted with household bleach (sodium hypochlorite solution) because they contain amide moieties which can be chlorinated to generate biocidal N-halamine functional groups. Although Nomex can be chlorinated without any significant decomposition, Kevlar decomposes under the same chlorination conditions. In this study, two mimics for each of the polymers were synthesized to simulate the carboxylate and diaminophenylene components of the materials. It was found that the p-diaminophenylene component of the Kevlar mimic is oxidized to a quinone-type structure upon treatment with hypochlorous acid, which then decomposes. However, such a mechanism for the Nomex mimic is not possible. In this paper, based upon these observations, a plausible answer will be provided to the title question.

  5. Fracture resistance of Kevlar-reinforced poly(methyl methacrylate) resin: a preliminary study.

    PubMed

    Berrong, J M; Weed, R M; Young, J M

    1990-01-01

    The reinforcing effect of Kevlar fibers incorporated in processed poly(methyl methacrylate) resin samples was studied using 0% (controls), 0.5%, 1%, and 2% by weight of the added fibers. The samples were subjected to impact testing to determine fracture resistance, and sample groups were statistically compared using an ANOVA. Each reinforced sample had significantly greater fracture resistance (P less than 0.05) than the control, and no difference was found either within or between control groups. The use of reinforcing Kevlar fibers appears to enhance the fracture resistance of acrylic resin denture base materials.

  6. Long term elongation of Kevlar-49 single fiber at low temperature

    NASA Astrophysics Data System (ADS)

    Bersani, A.; Canonica, L.; Cariello, M.; Cereseto, R.; Di Domizio, S.; Pallavicini, M.

    2013-02-01

    We have measured the rate of elongation of a loaded Kevlar-49 fiber as a function of time at 4.2 K. The result puts a worst case upper limit of 0.028% in the elongation rate ΔL/L for a 0.5 mm diameter fiber kept under a constant tension of 2.7 kg for 8 months. A value that is probably closer to reality is actually 0.004%. This result proves that Kevlar-49 can be safely used in cryogenic applications in which high mechanical stability under stress is required.

  7. Mechanical tensile testing of titanium 15-3-3-3 and Kevlar 49 at cryogenic temperatures

    NASA Astrophysics Data System (ADS)

    James, B. L.; Martinez, R. M.; Shirron, P.; Tuttle, J.; Galassi, N. M.; McGuinness, D. S.; Puckett, D.; Francis, J. J.; Flom, Y.

    2012-06-01

    Titanium 15-3-3-3 and Kevlar 49 are highly desired materials for structural components in cryogenic applications due to their low thermal conductivity at low temperatures. Previous tests have indicated that titanium 15-3-3-3 becomes increasingly brittle as the temperature decreases. Furthermore, little is known regarding the mechanical properties of Kevlar 49 at low temperatures, most specifically its Young's modulus. This testing investigates the mechanical properties of both materials at cryogenic temperatures through cryogenic mechanical tensile testing to failure. The elongation, ultimate tensile strength, yield strength, and break strength of both materials are provided and analyzed here.

  8. Comparison of methods for predicting fiber stresses in a cracked Kevlar/epoxy monolayer

    SciTech Connect

    Reedy, E.D. Jr.

    1984-01-01

    Shear-lag and 3-D finite element predictions for the fiber stresses in a cracked Kevlar 49/epoxy monolayer are compared. Results are given for a 5-fiber wide monolayer containing a single broken fiber. Both methods of analysis are found to predict nearly the same fiber stress distribution along the crack-tip fiber when the monolayer is fully elastic. Results for highly loaded monolayers with extensive matrix yielding are not in quite as good agreement, but even then the predicted stress distributions are within 5%. These calculations show that a shear-lag analysis is accurate even though the Kevlar 49 fiber is highly anisotropic.

  9. Laser cutting of Kevlar laminates and thermal stress formed at cutting sections

    NASA Astrophysics Data System (ADS)

    Yilbas, B. S.; Akhtar, S. S.

    2012-02-01

    Laser cutting of Kevlar laminates is carried out and thermal stress field developed in the cutting region is predicted using the finite element code. Temperature predictions are validated through the thermocouple data. The morphological changes in the cutting section are examined by incorporating optical and scanning electron microscopes. It is found that temperature predictions agree well with the thermocouple data. High values of von Mises stress are observed at the cutting edges and at the mid-thickness of the Kevlar laminate due to thermal compression formed in this region. The laser cut edges are free from whiskers; however, striation formation and some small sideways burning is observed at the kerf edges.

  10. Overview of NASA White Sands Test Facility Composite Overwrapped Pressure Vessel Testing

    NASA Technical Reports Server (NTRS)

    Greene, Nathanael; Saulsberry, Regor; Thesken, John; Phoenix, Leigh

    2006-01-01

    This viewgraph presentation examines the White Sands Test Facility testing of Composite overwrapped pressure vessel (COPV). A COPV is typically a metallic liner overwrapped with a fiber epoxy matrix. There is a weight advantage over the traditional all metal design. The presentation shows pictures of the facilities at White Sands, and then examines some of the testing performed. The tests include fluids compatibility, and Kevlar COPV. Data for the Kevlar tests are given, and an analysis is reviewed. There is also a comparison between Carbon COPVs and the Kevlar COPVs.

  11. Enhanced stab resistance of armor composites with functionalized silica nanoparticles

    NASA Astrophysics Data System (ADS)

    Mahfuz, Hassan; Clements, Floria; Rangari, Vijaya; Dhanak, Vinod; Beamson, Graham

    2009-03-01

    Traditionally shear thickening fluid (STF) reinforced with Kevlar has been used to develop flexible armor. At the core of the STF-Kevlar composites is a mixture of polyethylene glycol (PEG) and silica particles. This mixture is often known as STF and is consisted of approximately 45 wt % PEG and 55 wt % silica. During rheological tests, STF shows instantaneous spike in viscosity above a critical shear rate. Fabrication of STF-Kevlar composites requires preparation of STF, dilution with ethanol, and then impregnation with Kevlar. In the current approach, nanoscale silica particles were dispersed directly into a mixture of PEG and ethanol through a sonic cavitation process. Two types of silica nanoparticles were used in the investigation: 30 nm crystalline silica and 7 nm amorphous silica. The admixture was then reinforced with Kevlar fabric to produce flexible armor composites. In the next step, silica particles are functionalized with a silane coupling agent to enhance bonding between silica and PEG. The performance of the resulting armor composites improved significantly. As evidenced by National Institute of Justice spike tests, the energy required for zero-layer penetration (i.e., no penetration) jumped twofold: from 12 to 25 J cm2/g. The source of this improvement has been traced to the formation of siloxane (Si-O-Si) bonds between silica and PEG and superior coating of Kevlar filaments with particles. Fourier transform infrared, x-ray photoemission spectroscopy, and scanning electron microscopy studies were performed to examine chemical bonds, elemental composition, and particle dispersion responsible for such improvement. In summary, our experiments have demonstrated that functionalization of silica particles followed by direct dispersion into PEG resulted in superior Kevlar composites having much higher spike resistance.

  12. The Protective Effect of Kevlar ® Socks Against Hockey Skate Blade Injuries: A Biomechanical Study

    PubMed Central

    Nauth, Aaron; Aziz, Mina; Tsuji, Matthew; Whelan, Daniel B.; Theodoropoulos, John S.; Zdero, Rad

    2014-01-01

    Objectives: Several recent high profile injuries to elite players in the National Hockey League (NHL) secondary to skate blade lacerations have generated significant interest in these injuries and possible methods to protect against them. These injuries are typically due to direct contact of the skate blade of another player with posterior aspect of the calf resulting in a range of potential injuries to tendons or neurovascular structures. The Achilles tendon is most commonly involved. Kevlar® reinforced socks have recently become available for hockey players to wear and are cited as providing possible protection against such injuries. However, there has been no investigation of the possible protective effects of Kevlar® reinforced socks against skate blade injuries, and it is currently unknown what protective effects, if any, that these socks provide against these injuries. The proposed study sought to address this by conducting a biomechanical investigation of the protective effects of Kevlar® reinforced socks against Achilles tendon injuries in a simulated model of skate blade injury using human cadaver limbs. This novel investigation is the first to address the possible benefits to hockey players of wearing Kevlar® reinforced socks. Methods: Seven matched pairs of human cadaver lower limbs were fitted with a Kevlar ® reinforced sock comprised of 60% Kevlar®/20% Coolmax® polyester/18 % Nylon/12% Spandex (Bauer Elite Performance Skate Sock) on one limb and a standard synthetic sock comprised of 51% polyester/47% nylon/2% spandex (Bauer Premium Performance Skate Sock) on the contralateral limb as a control. Each limb was then mounted on a Materials Testing System (MTS) with the ankle dorsiflexed to 90° and the knee held in full extension using a custom designed jig. Specimens were then impacted with a hockey skate blade directed at the posterior calf, 12 cm above the heel, at an angle of 45° and a speed of 31m/s, to a penetration depth of 4.3 cm, to

  13. Assessment of impact damage in Kevlar{reg_sign}-epoxy, filament-wound spherical test specimens by acoustic emission techniques

    SciTech Connect

    Whittaker, J.W.; Brosey, W.D.; Hamstad, M.A.

    1996-09-26

    The results of a study of the acoustic emission (AE) behavior of impact-damaged, spherical, composite test specimens subjected to thermal cycling and biaxial mechanical loading are presented. Seven Kevlar{reg_sign}-epoxy, filament-wound, spherical composite test specimens were subjected to different levels of impact damage. The seven specimens were a subset of a group of 77 specimens made with simulated fabrication-induced flaws. The specimens were subjected to two or three cycles of elevated temperature and then hydraulically pressurized to failure. The pressurization regime consisted of two cycles to different intermediate levels with a hold at each peak pressure level; a final pressurization to failure followed. The thermal and pressurization cycles were carefully designed to stimulate AE production under defined conditions. Both impacted and nonimpacted specimens produced thermo-AE (the term given to emission stimulated by thermal loading), but impacted specimens produced significantly more. Thermo-AE was produced primarily by damaged composite material. Damaged material produced emission as a function of both rising and falling temperature, but the effect was not repeatable. More seriously damaged specimens produced very large quantities of emission. Emission recorded during the static portion of the hydraulic loading cycles varied with load, time, and degree of damage. Static load AE behavior was quantified using a newly developed concept, the event-rate moment, and various correlations with residual strength were attempted. Correlations between residual strength, long-duration events, and even-rate moments were developed with varying degrees of success.

  14. On the bending response of Kevlar 49/epoxy beams and rings

    SciTech Connect

    Reedy, E.D. Jr.

    1988-05-01

    Kevlar 49/epoxy laminates often exhibit substantial material nonlinearity when subjected to bending. This is a consequence of the yeild-like behavior of a Kevlar 49/epoxy lamina in fiber-directed compression. In this paper, analyses that utilize a simple idealization of compressive yielding are described and calculated results for Kevlar 49 reinforced beams and rings are compared with available data. First, results of a finite element analysis of a thin, unidirectionally reinforced ring subjected to diametral compression are presented. This analysis uses beam elements that incorporate linear tensile and elastic-perfectly plastic compressive behavior. Then a method used to analyze quasi-isotropic beams tested in four-point bending is discussed. This finite element analysis uses a layered shell element with a lamina constitutive model that permits elastic-perfectly plastic response to fiber-directed compression, but otherwise assumes linear elastic behavior. Comparison of calculated and experimental results corroborate the ability of analyses using a simple compressive yield model to account for much of the observed flexural nonlinearity in Kevlar 49/epoxy beams and rings. 6 figs.

  15. Tensile testing of nylon and Kevlar parachute materials under Federal specified temperature and relative humidity conditions

    SciTech Connect

    Botner, W.T.

    1980-01-01

    A small 10-ft x 12-ft temperature and relative humidity controlled room for tensile testing of parachute materials is presented. Tensile tests of nylon and Kevlar parachute materials indicate there is a negligible change in break strength of test samples soaked in the controlled environment vs samples soaked in ambient conditions.

  16. Local Strain Measurement of Kevlar Strand with Fiber Optic Bragg Grating

    NASA Technical Reports Server (NTRS)

    Banks, Curtis E.; Grant, Joseph; Russell, Sam; Arnett, Shawn

    2008-01-01

    1987 DuPont manufactured 4560 denier Kevlar/Epoxy Strands were instrumented with nine and three sensors each. Stress tests were performed at 30,45,60,70 and 80% of ultimate strength with dwell times of 10,000 seconds. FBG showed uneven stress levels which is contrary to conventional observation.

  17. Finite Element Modeling of Fragment Penetration of Thin Structural Composite Laminates

    DTIC Science & Technology

    1991-12-01

    his direction and assistance provided during the program. The following are registered trade names: Kevlar-29, 3M Co., Scotchply, Owens Corning Fiberglass...grains, are used. Composite laminates such as Owens Corning Fiberglass (R) panels, 3M Scotchply 1002 (R) panels and Kevlar-29 (R) reinforced plastic...results [2]: 1. Owens Corning Fiberglass (OCF) Structural Panels. Woven S-2 glass and a typical resin type, contert, sizing, and cure cycle at 220

  18. A New and Innovative Use of the Thermal Knife and Kevlar Cord Components in a Restraint and Release System

    NASA Technical Reports Server (NTRS)

    Stewart, Alphonso; Brodeur, Stephen J. (Technical Monitor)

    2001-01-01

    A Kevlar cord and two thermal knives are key components in the Soar Array Restraint and Release System (SARRS) on the Microwave Anisotropy Probe (MAP) spacecraft at NASA's Goddard Space Flight Center. The SARRS uses a 25-foot (7.62 m) length Kevlar cord that encircles the spacecraft and secures the solar panels in stowed configuration for launch. Once in orbit, one of two redundantly configured thermal knives severs the Kevlar cord and permits the panels to deploy. The purpose of this paper is to present the details of the design, development test results, and the various innovations that were created during the development of this novel use of the thermal knife and Kevlar cord.

  19. A new and innovative use of the thermal knife and Kevlar cord components in a restraint and release system

    NASA Astrophysics Data System (ADS)

    Stewart, Alphonso C.

    2001-09-01

    A Kevlar cord and two thermal knives are key components in the Solar Array Restraint and Release System (SARRS) on the Microwave Anisotropy Probe (MAP) spacecraft at NASA's Goddard Space Flight Center. The SARRS uses a 25-foot (7.62 m) length Kevlar cord that encircles the spacecraft and secures the solar panels in stowed configuration for launch. Once in orbit, one of two redundantly configured thermal knives severs the Kevlar cord and permits the panels to deploy. The purpose of this paper is to present the details of the design, development test results, and the various innovations that were created during the development of this novel use of the thermal knife and Kevlar cord.

  20. 77 FR 39143 - Executive Branch Qualified Trusts

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-07-02

    ... continues to read as follows: Authority: 5 U.S.C. App. (Ethics in Government Act of 1978); 26 U.S.C. 1043... excess of the diversification standards. (c) Hybrid qualified trust. A qualified trust may contain both a... to this arrangement as a hybrid qualified trust. Sec. 2634.407 Certification of qualified trust...

  1. 7 CFR 1786.154 - Qualified Notes.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 12 2011-01-01 2011-01-01 false Qualified Notes. 1786.154 Section 1786.154... Discounted Prepayments on RUS Electric Loans § 1786.154 Qualified Notes. An eligible borrower may prepay Qualified Notes under this subpart at the discounted present value. A Qualified Note is a note evidencing an...

  2. 7 CFR 1786.154 - Qualified Notes.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 12 2013-01-01 2013-01-01 false Qualified Notes. 1786.154 Section 1786.154... Discounted Prepayments on RUS Electric Loans § 1786.154 Qualified Notes. An eligible borrower may prepay Qualified Notes under this subpart at the discounted present value. A Qualified Note is a note evidencing an...

  3. 7 CFR 1786.154 - Qualified Notes.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 12 2014-01-01 2013-01-01 true Qualified Notes. 1786.154 Section 1786.154 Agriculture... Prepayments on RUS Electric Loans § 1786.154 Qualified Notes. An eligible borrower may prepay Qualified Notes under this subpart at the discounted present value. A Qualified Note is a note evidencing an RUS...

  4. 75 FR 27934 - Qualified Nonpersonal Use Vehicles

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-05-19

    ... driver and all passengers of a qualified nonpersonal use vehicle. However, a working condition fringe... Internal Revenue Service 26 CFR Part 1 RIN 1545-BH65 Qualified Nonpersonal Use Vehicles AGENCY: Internal... regulations relating to qualified nonpersonal use vehicles as defined in section 274(i). Qualified...

  5. 20 CFR 302.3 - Qualifying conditions.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 20 Employees' Benefits 1 2014-04-01 2012-04-01 true Qualifying conditions. 302.3 Section 302.3 Employees' Benefits RAILROAD RETIREMENT BOARD REGULATIONS UNDER THE RAILROAD UNEMPLOYMENT INSURANCE ACT QUALIFIED EMPLOYEE § 302.3 Qualifying conditions. (a) Basic requirements. To qualify for benefits...

  6. 20 CFR 302.3 - Qualifying conditions.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 20 Employees' Benefits 1 2012-04-01 2012-04-01 false Qualifying conditions. 302.3 Section 302.3 Employees' Benefits RAILROAD RETIREMENT BOARD REGULATIONS UNDER THE RAILROAD UNEMPLOYMENT INSURANCE ACT QUALIFIED EMPLOYEE § 302.3 Qualifying conditions. (a) Basic requirements. To qualify for benefits...

  7. 20 CFR 302.3 - Qualifying conditions.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 20 Employees' Benefits 1 2013-04-01 2012-04-01 true Qualifying conditions. 302.3 Section 302.3 Employees' Benefits RAILROAD RETIREMENT BOARD REGULATIONS UNDER THE RAILROAD UNEMPLOYMENT INSURANCE ACT QUALIFIED EMPLOYEE § 302.3 Qualifying conditions. (a) Basic requirements. To qualify for benefits...

  8. 20 CFR 302.3 - Qualifying conditions.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 20 Employees' Benefits 1 2010-04-01 2010-04-01 false Qualifying conditions. 302.3 Section 302.3 Employees' Benefits RAILROAD RETIREMENT BOARD REGULATIONS UNDER THE RAILROAD UNEMPLOYMENT INSURANCE ACT QUALIFIED EMPLOYEE § 302.3 Qualifying conditions. (a) Basic requirements. To qualify for benefits with...

  9. A study of the effects of long-term exposure to fuels and fluids on the behavior of advanced composite materials

    NASA Technical Reports Server (NTRS)

    Hendricks, C. L.

    1977-01-01

    The Task 1 (thirty-six-month) and Task 2 (twelve-month) exposure of composite materials to fuel and fluid environments are reported. Narmco T300/5209 (Task 1) shows no significant degradation. Slightly lower mechanical properties were obtained from fuel/water immersion exposure of this material. Kevlar 49/2544 (also Task 1) exhibits significant drop in short-beam shear when exposed to fuel/water immersion. Task 2 materials (T300/5208, Kevlar 49 fabric/5209, and Kevlar 49 fibers) have not shown any significant mechanical property degradation to date.

  10. [Imaging of alloplastic ligament implant. An in vivo and in vitro study exemplified by Kevlar].

    PubMed

    Wening, J V; Katzer, A; Nicolas, V; Hahn, M; Jungbluth, K H; Kratzer A [corrected to Katzer, A

    1994-04-01

    Neither native X-ray nor CT or NMR allow to evaluate intraarticular implantation results of Kevlar -49 directly. In animal trials, the course of an artificial ligament may only be presumed from connective tissue ingrowth. Although soft tissue structure appears much better in NMR than in CT, direct proof of ligament continuity is still impossible. As soon as the connective tissue becomes continuous, it appears clearly and allows indirect evaluation of the prosthesis, as integrity can be judged by its shape like in natural cruciate ligament. Anatomic preparations show that connective tissue fills up the small space between the two cords of a Kevlar -49 two bundle prosthesis eight weeks after implantation, so that imaging systems show only one intraarticular bundle.

  11. [The research on the surfacial modification of organic high-performance Kevlar fiber].

    PubMed

    Zheng, Yu-ying; Fu, Ming-lian; Cai, Wei-long; Wang, Can-yao; Wang, Liang-en

    2004-04-01

    In the paper the authors tried to use chemical disposal to bring the activity mass onto the surface of Kevlar fiber with the purpose of surface graft modification. In the paper the authors used the FTIR spectra to discuss the graft of toluene-2, 4-diisocyanate onto Kevlar fiber. The authors studied and analysed the effect of hydrolytic time on the content of -O-H group of the production, and the effect of hydrolyzation and hexyl-lactam steadily disposing on the graft reaction. The result showed that the content of -O-H group increased after hydrolyzation, it's helpful for the graft reaction, and hexyl-lactam steadily disposing made the graf product more stable. Through the research the authors came to the conclusion that by bringing some activity masses onto the fiber surface the authors can improve the interface of fiber/resin effectively.

  12. Acoustic behavior of a fibrous bulk material. [Kevlar 29 sound absorber

    NASA Technical Reports Server (NTRS)

    Hersh, A. S.; Walker, B.

    1979-01-01

    A semiempirical model is presented describing the acoustic behavior of Kevlar 29, a bulk absorbing material. The model is based on an approximate solution to the one-dimensional equations representing conservation of fluctuating mass, momentum and energy. By treating the material as a momentum sink, theoretical expressions of the material complex propagation constants and characteristic impedance were derived in terms of a single constant. Evaluating the constant at a single frequency for a particular specimen, excellent agreement between prediction and measurement was achieved for a large range of sound frequencies and material porosities and thicknesses. Results show that Kevlar 29 absorbs sound efficiently even at low frequencies. This is explained in terms of a frequency dependent material phase speed.

  13. Smart wearable Kevlar-based safeguarding electronic textile with excellent sensing performance.

    PubMed

    Wang, Sheng; Xuan, Shouhu; Liu, Mei; Bai, Linfeng; Zhang, Shuaishuai; Sang, Min; Jiang, Wanquan; Gong, Xinglong

    2017-03-29

    A novel S-ST/MWCNT/Kevlar-based wearable electronic textile (WET) with enhanced safeguarding performance and force sensing ability was fabricated. Stab resistance performance tests under quasi-static and dynamic conditions show that the maximum resistance force and penetration impact energy for the WET are 18 N and 11.76 J, which represent a 90% and 50% increment with respect to the neat Kevlar, respectively. Dynamic impact resistance tests show that the WET absorbs all the impact energy. The maximum resistance force of the WET is 1052 N, which represents an improvement of about 190% with respect to neat Kevlar. With the incorporation of multi-walled carbon nanotubes (MWCNTs), the WET can achieve a stable electrical conductivity of ∼10(-2) S m(-1), and the conductivity is highly sensitive to external mechanic forces. Notably, the sensing fabric also exhibits an outstanding ability to detect and analyze external forces. In addition, it can be fixed at any position of the human body and exhibits an ideal monitoring performance. Because of its flexibility, high sensitivity to various types of deformations and excellent safeguarding performance, the WET has a strong potential for wearable monitoring devices that simultaneously provide body protection and monitor the movements of the human body under various conditions.

  14. Kevlar photochemical degradation mechanisms. Final report, 1 October 1983-30 April 1986

    SciTech Connect

    Toy, M.S.

    1987-04-01

    The objective of this program was to investigate and determine Kevlar's photochemical degradation mechanisms, rate constants, and activation energies in air. The underlying reason was to understand the oxidative photodegradation processes, which would help to provide service life forecast under the sunlight conditions and to aid effective method development against its photodecomposition. The first significant accomplishment of the project was the new and novel analytical approach, which demonstrated the rate constant and activation energy determinations of Kevlar's photooxidative processes. The 0.2 atm of oxygen-18-labeled environment in a solar chamber simulates the air exposure under sunlight conditions. The technique also allows the radial /sup 18/O distribution measurement from the fiber surface toward the fiber center. The data from the accelerated experimental conditions in the solar chamber in an diatomic /sup 18/O atmosphere are differentiated from the similar ambient daylight exposure effects. The second significant accomplishment was the recognition of a thermal-decomposition pattern of Kevlar in concentrated sulfuric acid at 196 C to give the same two types of decarboxylations: one yields one mole of carbon dioxide per (C/sub 7/H/sub 5/NO) moiety and the other gives two moles of CO/sub 2/ per (C/sub 7/H/sub 5/NO) moiety. The third significant accomplishment was the analytical methodology applied to deduce the four photooxidative processes.

  15. Paralinguistic Qualifiers: Our Many Voices.

    ERIC Educational Resources Information Center

    Poyatos, Fernando

    1991-01-01

    A case is made for the increased study of paralinguistic voice qualifiers, which include variations in breathing, laryngeal, esophageal, pharyngeal, velopharyngeal, lingual, labial, mandibular, articulatory, articulatory tension, and objectual control. It is proposed that attention to these voice qualities has a variety of practical, literary,…

  16. Canada's Highly Qualified Manpower Resources.

    ERIC Educational Resources Information Center

    Atkinson, A. G.; And Others

    The purpose of this report is to assemble basic statistics on highly qualified manpower resources in Canada, especially focusing on scientists and engineers, for the development of policies and research in this field. The economic background contributing to the growth of the white-collar and professional labor force is discussed, and the roles of…

  17. Small Angle X-Ray Scattering of Carbon and Kevlar Fibers Under Load

    NASA Astrophysics Data System (ADS)

    Effler, Lawrence Joseph, Jr.

    Small angle X-ray scattering (SAXS) was used as the primary tool for investigating the microporous structure of Kevlar and mesophase pitch based carbon fibers. The orientation present in the scattering entities was determined by extending Porod's invariant into a pseudo-invariant for one-dimensional data slices. By comparing the pseudo -invariants at different aximuthal angles the extent of the orientation present in the scattering system was determined. The orientation of the microvoids was found to correlate best with the modulus of the carbon fibers. Distance distribution functions were also determined for the fibers. For the carbon fibers the average size of the voids and the breadth of the distribution was found to increase with both fiber modulus and strength. In addition, the distance distribution curves were able to distinguish between fibers spun under different conditions. These results were found to mirror the enhancement of crystalline orientation and the development of graphitic phases in the fibers. Studies were also conducted to determine the response of the microvoids to an applied tensile load. Both Kevlar and the carbon fibers indicated a loss of outer fiber surface, with the most dramatic loss being seen for Kevlar. Experiments were conducted which compared both as received fibers to those which had been strained to failure. Additional experiments were done with the fibers being strained while in the SAXS camera. For the Kevlar fibers the loss of its skin layer was indicated by less anisotropic scattering patterns of the fractured fibers. The dynamic studies indicated that initially void orientation increases accompanied by the formation of newer, smaller voids. However these trends are reversed as the fiber tow approaches and reaches fracture. The loss of the skin region was confirmed by both laser backscattering and optical microscopy. The response of the microvoid phase of Kevlar to loading is interpreted in light of Morgan's chain end model

  18. Composite containment systems for jet engine fan blades

    NASA Technical Reports Server (NTRS)

    Smith, G. T.

    1981-01-01

    The use of composites in fan blade containment systems is investigated and the associated structural benefits of the composite system design are identified. Two basic types of containment structures were investigated. The short finned concept was evaluated using Kevlar/epoxy laminates for fins which were mounted in a 6061 T-6 aluminum ring. The long fin concept was evaluated with Kevlar/epoxy, 6Al4V titanium, and 2024 T-3 aluminum fins. The unfinned configurations consisted of the base-line steel sheet, a circumferentially oriented aluminum honeycomb, and a Kevlar cloth filled ring. Results obtained show that a substantial reduction in the fan blade containment system weight is possible. Minimization of damage within the engine arising from impact interaction between blade debris and the engine structure is also achieved.

  19. Mallow Fiber-Reinforced Epoxy Composites in Multilayered Armor for Personal Ballistic Protection

    NASA Astrophysics Data System (ADS)

    Nascimento, Lucio Fábio Cassiano; Louro, Luis Henrique Leme; Monteiro, Sergio Neves; Lima, Édio Pereira; da Luz, Fernanda Santos

    2017-10-01

    Lighter and less expensive polymer composites reinforced with natural fibers have been investigated as possible components of a multilayered armor system (MAS) for personal protection against high-velocity ammunition. Their ballistic performance was consistently found comparable with that of conventional Kevlar® synthetic aramid fiber. Among the numerous existing natural fibers with the potential for reinforcing polymer composites to replace Kevlar® in MAS, mallow fiber has not been fully investigated. Thus, the objective of this work is to evaluate the ballistic performance of epoxy composites reinforced with 30 vol.% of aligned mallow fibers as a second MAS layer backing a front ceramic plate. The results using high-velocity 7.62 ammunition show a similar indentation to a Kevlar® layer with the same thickness. An impedance matching calculation supports the similar ballistic performance of mallow fiber composite and Kevlar®. Reduced MAS costs associated with the mallow fiber composite are practical advantages over Kevlar®.

  20. Mallow Fiber-Reinforced Epoxy Composites in Multilayered Armor for Personal Ballistic Protection

    NASA Astrophysics Data System (ADS)

    Nascimento, Lucio Fábio Cassiano; Louro, Luis Henrique Leme; Monteiro, Sergio Neves; Lima, Édio Pereira; da Luz, Fernanda Santos

    2017-08-01

    Lighter and less expensive polymer composites reinforced with natural fibers have been investigated as possible components of a multilayered armor system (MAS) for personal protection against high-velocity ammunition. Their ballistic performance was consistently found comparable with that of conventional Kevlar® synthetic aramid fiber. Among the numerous existing natural fibers with the potential for reinforcing polymer composites to replace Kevlar® in MAS, mallow fiber has not been fully investigated. Thus, the objective of this work is to evaluate the ballistic performance of epoxy composites reinforced with 30 vol.% of aligned mallow fibers as a second MAS layer backing a front ceramic plate. The results using high-velocity 7.62 ammunition show a similar indentation to a Kevlar® layer with the same thickness. An impedance matching calculation supports the similar ballistic performance of mallow fiber composite and Kevlar®. Reduced MAS costs associated with the mallow fiber composite are practical advantages over Kevlar®.

  1. 42 CFR 495.204 - Incentive payments to qualifying MA organizations for qualifying MA-EPs and qualifying MA...

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... hospitals for which such qualifying organizations received incentive payments were meaningful EHR users in... of EHR incentive payment due the MA organization. (c) Amount payable to qualifying MA organization... for qualifying MA-affiliated eligible hospitals under the Medicare FFS EHR hospital incentive program...

  2. 42 CFR 495.204 - Incentive payments to qualifying MA organizations for qualifying MA-EPs and qualifying MA...

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... hospitals for which such qualifying organizations received incentive payments were meaningful EHR users in... of EHR incentive payment due the MA organization. (c) Amount payable to qualifying MA organization... for qualifying MA-affiliated eligible hospitals under the Medicare FFS EHR hospital incentive program...

  3. Stress Rupture Life Reliability Measures for Composite Overwrapped Pressure Vessels

    NASA Technical Reports Server (NTRS)

    Murthy, Pappu L. N.; Thesken, John C.; Phoenix, S. Leigh; Grimes-Ledesma, Lorie

    2007-01-01

    Composite Overwrapped Pressure Vessels (COPVs) are often used for storing pressurant gases onboard spacecraft. Kevlar (DuPont), glass, carbon and other more recent fibers have all been used as overwraps. Due to the fact that overwraps are subjected to sustained loads for an extended period during a mission, stress rupture failure is a major concern. It is therefore important to ascertain the reliability of these vessels by analysis, since the testing of each flight design cannot be completed on a practical time scale. The present paper examines specifically a Weibull statistics based stress rupture model and considers the various uncertainties associated with the model parameters. The paper also examines several reliability estimate measures that would be of use for the purpose of recertification and for qualifying flight worthiness of these vessels. Specifically, deterministic values for a point estimate, mean estimate and 90/95 percent confidence estimates of the reliability are all examined for a typical flight quality vessel under constant stress. The mean and the 90/95 percent confidence estimates are computed using Monte-Carlo simulation techniques by assuming distribution statistics of model parameters based also on simulation and on the available data, especially the sample sizes represented in the data. The data for the stress rupture model are obtained from the Lawrence Livermore National Laboratories (LLNL) stress rupture testing program, carried out for the past 35 years. Deterministic as well as probabilistic sensitivities are examined.

  4. 46 CFR 391.5 - Qualified withdrawals.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 8 2014-10-01 2014-10-01 false Qualified withdrawals. 391.5 Section 391.5 Shipping... TAX ASPECTS OF THE CAPITAL CONSTRUCTION FUND § 391.5 Qualified withdrawals. (a) In general. (1) A qualified withdrawal is one made from the fund during the taxable year which is in accordance with...

  5. 46 CFR 391.5 - Qualified withdrawals.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 8 2013-10-01 2013-10-01 false Qualified withdrawals. 391.5 Section 391.5 Shipping... TAX ASPECTS OF THE CAPITAL CONSTRUCTION FUND § 391.5 Qualified withdrawals. (a) In general. (1) A qualified withdrawal is one made from the fund during the taxable year which is in accordance with...

  6. 46 CFR 391.5 - Qualified withdrawals.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 8 2011-10-01 2011-10-01 false Qualified withdrawals. 391.5 Section 391.5 Shipping... TAX ASPECTS OF THE CAPITAL CONSTRUCTION FUND § 391.5 Qualified withdrawals. (a) In general. (1) A qualified withdrawal is one made from the fund during the taxable year which is in accordance with...

  7. 7 CFR 4290.110 - Qualified management.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 15 2014-01-01 2014-01-01 false Qualified management. 4290.110 Section 4290.110... Qualifications for the RBIC Program Organizing A Rbic § 4290.110 Qualified management. An Applicant must show, to the satisfaction of the Secretary, that its current or proposed management team is qualified and...

  8. 7 CFR 4290.110 - Qualified management.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 15 2012-01-01 2012-01-01 false Qualified management. 4290.110 Section 4290.110... Qualifications for the RBIC Program Organizing A Rbic § 4290.110 Qualified management. Link to an amendment..., that its current or proposed management team is qualified and has the knowledge, experience,...

  9. Tribological study of non-asbestos fiber reinforced phenolic composites for braking applications

    SciTech Connect

    Gopal, P.; Dharani, L.R.; Blum, F.D.

    1994-12-31

    A cashew modified phenolic resin was used as the binder to prepare several different nonasbestos fiber reinforced composite friction materials. Friction-wear tests were conducted at various loads, speeds and temperatures on a Chase friction testing machine. The fade and wear characteristics of glass and carbon fiber reinforced friction materials were studied. The wear rates of hybrid composites containing Kevlar{reg_sign} (registered trademark of E.I. duPont de Nemours) pulp were compared to those of control composites without Kevlar{reg_sign} pulp.

  10. Kinematic Kevlar suspension system for the HAWC and SAFIRE ADR salt pills

    NASA Astrophysics Data System (ADS)

    Voellmer, George M.; Jackson, Michael; Shirron, Peter J.; Tuttle, James G.

    2003-03-01

    The High Resolution Airborne Wideband Camera (HAWC) and the Submillimeter And Far Infrared Experiment (SAFIRE) will use identical Adiabatic Demagnetization Refrigerators (ADR) to cool their detectors to 200mK and 100mK, respectively. In order to minimize thermal loads on the salt pill, a Kevlar® suspension system is used to hold it in place. An innovative, kinematic suspension system is presented. The suspension system is unique in that it consists of two parts that can be assembled and tensioned offline, and later bolted onto the salt pill.

  11. Development of dimensionally stable lightweight composite satellite antenna structures

    NASA Astrophysics Data System (ADS)

    Grimaldi, Filippo; Tempesta, Giancarlo; Pastorelli, Fabrizio; Pesciarelli, Sergio; Stonier, Roger A.

    Lightweight, dimensionally-stable advanced composite satellite antennas and their supporting structures have been developed for the Eutelsat-I, Intelsat-VI, Insat-I, Arabsat, and Italsat satellites. Both carbon-fiber and kevlar-49 fabrics are used as the reinforcements for epoxy resin matrices in these antenna structures; a novel system being employed consists of ultrathin prepreg surfaces on a kevlar-49 honeycomb core. Cocuring and semicocuring processes have been devised for the manufacture of such thin-skin honeycomb sandwich designs.

  12. Bayes Analysis and Reliability Implications of Stress-Rupture Testing a Kevlar/Epoxy COPV Using Temperature and Pressure Acceleration

    NASA Technical Reports Server (NTRS)

    Phoenix, S. Leigh; Kezirian, Michael T.; Murthy, Pappu L. N.

    2009-01-01

    Composite Overwrapped Pressure Vessels (COPVs) that have survived a long service time under pressure generally must be recertified before service is extended. Flight certification is dependent on the reliability analysis to quantify the risk of stress rupture failure in existing flight vessels. Full certification of this reliability model would require a statistically significant number of lifetime tests to be performed and is impractical given the cost and limited flight hardware for certification testing purposes. One approach to confirm the reliability model is to perform a stress rupture test on a flight COPV. Currently, testing of such a Kevlar49 (Dupont)/epoxy COPV is nearing completion. The present paper focuses on a Bayesian statistical approach to analyze the possible failure time results of this test and to assess the implications in choosing between possible model parameter values that in the past have had significant uncertainty. The key uncertain parameters in this case are the actual fiber stress ratio at operating pressure, and the Weibull shape parameter for lifetime; the former has been uncertain due to ambiguities in interpreting the original and a duplicate burst test. The latter has been uncertain due to major differences between COPVs in the database and the actual COPVs in service. Any information obtained that clarifies and eliminates uncertainty in these parameters will have a major effect on the predicted reliability of the service COPVs going forward. The key result is that the longer the vessel survives, the more likely the more optimistic stress ratio model is correct. At the time of writing, the resulting effect on predicted future reliability is dramatic, increasing it by about one "nine," that is, reducing the predicted probability of failure by an order of magnitude. However, testing one vessel does not change the uncertainty on the Weibull shape parameter for lifetime since testing several vessels would be necessary.

  13. Bayes Analysis and Reliability Implications of Stress-Rupture Testing a Kevlar/Epoxy COPV using Temperature and Pressure Acceleration

    NASA Technical Reports Server (NTRS)

    Phoenix, S. Leigh; Kezirian, Michael T.; Murthy, Pappu L. N.

    2009-01-01

    Composite Overwrapped Pressure Vessel (COPVs) that have survived a long service time under pressure generally must be recertified before service is extended. Sometimes lifetime testing is performed on an actual COPV in service in an effort to validate the reliability model that is the basis for certifying the continued flight worthiness of its sisters. Currently, testing of such a Kevlar49(registered TradeMark)/epoxy COPV is nearing completion. The present paper focuses on a Bayesian statistical approach to analyze the possible failure time results of this test and to assess the implications in choosing between possible model parameter values that in the past have had significant uncertainty. The key uncertain parameters in this case are the actual fiber stress ratio at operating pressure, and the Weibull shape parameter for lifetime; the former has been uncertain due to ambiguities in interpreting the original and a duplicate burst test. The latter has been uncertain due to major differences between COPVs in the data base and the actual COPVs in service. Any information obtained that clarifies and eliminates uncertainty in these parameters will have a major effect on the predicted reliability of the service COPVs going forward. The key result is that the longer the vessel survives, the more likely the more optimistic stress ratio is correct. At the time of writing, the resulting effect on predicted future reliability is dramatic, increasing it by about one nine , that is, reducing the probability of failure by an order of magnitude. However, testing one vessel does not change the uncertainty on the Weibull shape parameter for lifetime since testing several would be necessary.

  14. ISS qualified thermal carrier equipment

    NASA Astrophysics Data System (ADS)

    Deuser, Mark S.; Vellinger, John C.; Jennings, Wm. M.

    2000-01-01

    Biotechnology is undergoing a period of rapid and sustained growth, a trend which is expected to continue as the general population ages and as new medical treatments and products are conceived. As pharmaceutical and biomedical companies continue to search for improved methods of production and, for answers to basic research questions, they will seek out new avenues of research. Space processing on the International Space Station (ISS) offers such an opportunity! Space is rapidly becoming an industrial laboratory for biotechnology research and processing. Space bioprocessing offers exciting possibilities for developing new pharmaceuticals and medical treatments, which can be used to benefit mankind on Earth. It also represents a new economic frontier for the private sector. For over eight years, the thermal carrier development team at SHOT has been working with government and commercial sector scientists who are conducting microgravity experiments that require thermal control. SHOT realized several years ago that the hardware currently being used for microgravity thermal control was becoming obsolete. It is likely that the government, academic, and industrial bioscience community members could utilize SHOT's hardware as a replacement to their current microgravity thermal carrier equipment. Moreover, SHOT is aware of several international scientists interested in utilizing our space qualified thermal carrier. SHOT's economic financing concept could be extremely beneficial to the international participant, while providing a source of geographic return for their particular region. Beginning in 2000, flight qualified thermal carriers are expected to be available to both the private and government sectors. .

  15. Comparison of impact strength of acrylic resin reinforced with kevlar and polyethylene fibres.

    PubMed

    Kamath, G; Bhargava, K

    2002-01-01

    The present study was done to evaluate the impact strengths of heat-activated acrylic resins reinforced with Kevlar fibres, polyethylene fibres and unreinforced heat activated acrylic resin. Each of three groups had 25 specimens. Brass rods of uniform length of 40 mm and diameter of 8 mm were used to prepare the moulds. A combination of long fibres (40 mm length) and short fibres (6 mm length) were used. The total amount of fibres incorporated was limited to 2% by weight of the resin matrix. Short and long fibres of equal weight were incorporated. The short fibres were mixed with polymer and monomer and packed into the mould, while, the long axis of the specimen, perpendicular to the applied force. The specimens were then processed. Impact strength testing was done on Hounsfield's impact testing machine. Kevlar fibre reinforced heat activated acrylic resin specimens recorded higher mean impact strength of 0.8464 Joules, while polyethylene fibres reinforced heat activated acrylic resin recorded mean impact strength of 0.7596 joules. The unreinforced heat activated acrylic resin recorded mean impact strength of 0.3440 Joules.

  16. Ballistic Impact Response of Kevlar 49 and Zylon under Conditions Representing Jet Engine Fan Containment

    NASA Technical Reports Server (NTRS)

    Pereira, J. Michael; Revilock, Duane M.

    2007-01-01

    A ballistic impact test program was conducted to provide validation data for the development of numerical models of blade out events in fabric containment systems. The impact response of two different fiber materials - Kevlar 49 (E.I. DuPont Nemours and Company) and Zylon AS (Toyobo Co., Ltd.) was studied by firing metal projectiles into dry woven fabric specimens using a gas gun. The shape, mass, orientation and velocity of the projectile were varied and recorded. In most cases the tests were designed such that the projectile would perforate the specimen, allowing measurement of the energy absorbed by the fabric. The results for both Zylon and Kevlar presented here represent a useful set of data for the purposes of establishing and validating numerical models for predicting the response of fabrics under conditions simulating those of a jet engine blade release situation. In addition some useful empirical observations were made regarding the effects of projectile orientation and the relative performance of the different materials.

  17. Measurements on radiation shielding efficacy of Polyethylene and Kevlar in the ISS (Columbus)

    PubMed Central

    Di Fino, L.; Larosa, M.; Zaconte, V.; Casolino, M.; Picozza, P.; Narici, L.

    2014-01-01

    The study and optimization of material effectiveness as radiation shield is a mandatory step toward human space exploration. Passive radiation shielding is one of the most important element in the entire radiation countermeasures package. Crewmembers will never experience direct exposure to space radiation; they will be either inside some shelter (the spacecraft, a ‘base’) or in an EVA (Extra Vehicular Activity) suit. Understanding the radiation shielding features of materials is therefore an important step toward an optimization of shelters and suits construction in the quest for an integrated solution for radiation countermeasures. Materials are usually tested for their radiation shielding effectiveness first with Monte Carlo simulations, then on ground, using particle accelerators and a number of specific ions known to be abundant in space, and finally in space. Highly hydrogenated materials perform best as radiation shields. Polyethylene is right now seen as the material that merges a high level of hydrogenation, an easiness of handling and machining as well as an affordable cost, and it is often referred as a sort of ‘standard’ to which compare other materials' effectiveness. Kevlar has recently shown very interesting radiation shielding properties, and it is also known to have important characteristics toward debris shielding, and can be used, for example, in space suits. We have measured in the ISS the effectiveness of polyethylene and kevlar using three detectors of the ALTEA system [ 1– 3] from 8 June 2012 to 13 November 2012, in Express Rack 3 in Columbus. These active detectors are able to provide the radiation quality parameters in any orbital region; being identical, they are also suitable to be used in parallel (one for the unshielded baseline, two measuring radiation with two different amounts of the same material: 5 and 10 g/cm2). A strong similarity of the shielding behavior between polyethylene and kevlar is documented. We measured

  18. Plastic matrix composites with continuous fiber reinforcement

    SciTech Connect

    1991-09-19

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

  19. Mechanical property characterization of intraply hybrid composites

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.; Lark, R. F.; Sinclair, J. H.

    1979-01-01

    An investigation was conducted to characterize the mechanical properties of intraply hybrids made from graphite fiber/epoxy matrix (primary composites) hybridized with varying amounts of secondary composites made from S-glass or Kevlar 49 fibers. The tests were conducted using thin laminates having the same thickness. The specimens for these tests were instrumented with strain gages to determine stress-strain behavior. Significant results are included.

  20. Scanning-electron-microscopy study of argon-plasma-treated and untreated peel-test Kevlar 49/epoxy laminates

    SciTech Connect

    Ingraham, J.A.; Walton, J.; Pruneda, C.O.; Morgan, R.J.

    1982-10-01

    It is concluded that a 200-watt RF argon plasma treatment of Kevlar fibers for four minutes increases the fiber/epoxy interfacial bonding. However, as a consequence of this increase in fiber-matrix bonding, the fiber is readily fibrillated during laminate deformation and failure.

  1. Kevlar® as a Potential Accident Radiation Dosimeter for First Responders, Law Enforcement and Military Personnel.

    PubMed

    Romanyukha, Alexander; Trompier, François; Benevides, Luis A

    2016-08-01

    Today the armed forces and law enforcement personnel wear body armor, helmets, and flak jackets composed substantially of Kevlar® fiber to prevent bodily injury or death resulting from physical, ballistic, stab, and slash attacks. Therefore, there is a high probability that during a radiation accident or its aftermath, the Kevlar®-composed body armor will be irradiated. Preliminary study with samples of Kevlar® foundation fabric obtained from body armor used by the U.S. Marine Corps has shown that all samples evaluated demonstrated an EPR signal, and this signal increased with radiation dose. Based on these results, the authors predict that, with individual calibration, exposure at dose above 1 Gy can be reliably detected in Kevlar® samples obtained from body armor. As a result of these measurements, a post-event reconstruction of exposure dose can be obtained by taking various samples throughout the armor body and helmet worn by the same irradiated individual. The doses can be used to create a whole-body dose map that would be of vital importance in a case of a partial body or heterogeneous exposure.

  2. Clinical, biomechanical and morphological assessment of anterior cruciate ligament Kevlar®-based artificial prosthesis in rabbit model.

    PubMed

    de la Garza-Castro, Santiago; González-Rivera, Carlos E; Vílchez-Cavazos, Félix; Morales-Avalos, Rodolfo; Barrera-Flores, Francisco J; Elizondo-Omaña, Rodrigo E; Soto-Dominguez, Adolfo; Acosta-Olivo, Carlos; Mendoza-Lemus, Oscar F

    2017-07-27

    The aim of this study was to evaluate the clinical, biomechanical and morphological characteristics of a Kevlar®-based prosthetic ligament as a synthetic graft of the anterior cruciate ligament (ACL) in an experimental animal model in rabbits. A total of 27 knees of rabbits randomly divided into 3 groups (control, ACL excision and ACL replacement with a Kevlar® prosthesis) were analyzed using clinical, biomechanical and morphological tests at 6, 12 and 18 weeks postprocedure. The mean displacement in mechanical testing was 0.73 ± 0.06 mm, 1.58 ± 0.19 mm and 0.94 ± 0.20 mm for the control, ACL excision and ACL replacement with synthetic prosthesis groups, respectively. The results showed an improvement in the stability of the knee with the use of the Kevlar® synthetic prosthesis in the biomechanical testing (p<0.05) compared with rabbits that underwent ACL excision, in addition to displacements that were larger but comparable to that in the control group (p>0.05), between the replacement group and the control group. The histological study revealed a good morphological adaptation of the synthetic material to the knee. This study proposes a new animal model for the placement and evaluation of Kevlar®-based synthetic ACL implants. The studied prosthesis showed promising behavior in the clinical and biomechanical tests and in the histological analysis. This study lays the foundation for further basic and clinical studies of artificial ACL prostheses using this material.

  3. Ultrasonic NDE for composite materials using embedded fiber-optic interferometric sensors

    NASA Astrophysics Data System (ADS)

    Liu, Kexing; Ferguson, Suzanne M.; Davis, Andrew; McEwen, Keith; Measures, Raymond M.

    1991-04-01

    An interferometric fiber optic sensor using ordinary single-mode fibers is developed to detect elastic strain waves for nondestructive evaluation of composite materials. This fiber sensor has been embedded in both graphite/epoxy and Kevlar/epoxy composite specimens. Applications of the sensor for detection of acoustic emission and laser generated ultrasound are presented. Limitations of the sensor are also discussed.

  4. A Logic for Qualified Syllogisms

    NASA Astrophysics Data System (ADS)

    Schwartz, Daniel G.

    In various works, L.A. Zadeh has introduced fuzzy quantifiers, fuzzy usuality modifiers, and fuzzy likelihood modifiers. This paper provides these notions with a unified semantics and uses this to define a formal logic capable of expressing and validating arguments such as 'Most birds can fly; Tweety is a bird; therefore, it is likely that Tweety can fly'. In effect, these are classical Aristotelean syllogisms that have been "qualified" through the use of fuzzy quantifiers. It is briefly outlined how these, together with some likelihood combination rules, can be used to address some well-known problems in the theory of nonmonotonic reasoning. The work is aimed at future applications in expert systems and robotics, including both hardware and software agents.

  5. Energy-absorption capability and scalability of square cross section composite tube specimens

    NASA Technical Reports Server (NTRS)

    Farley, Gary L.

    1987-01-01

    Static crushing tests were conducted on graphite/epoxy and Kevlar/epoxy square cross section tubes to study the influence of specimen geometry on the energy-absorption capability and scalability of composite materials. The tube inside width-to-wall thickness (W/t) ratio was determined to significantly affect the energy-absorption capability of composite materials. As W/t ratio decreases, the energy-absorption capability increases nonlinearly. The energy-absorption capability of Kevlar epoxy tubes was found to be geometrically scalable, but the energy-absorption capability of graphite/epoxy tubes was not geometrically scalable.

  6. 42 CFR 435.116 - Qualified pregnant women and children who are not qualified family members.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 42 Public Health 4 2010-10-01 2010-10-01 false Qualified pregnant women and children who are not... Categorically Needy Mandatory Coverage of Pregnant Women, Children Under 8, and Newborn Children § 435.116 Qualified pregnant women and children who are not qualified family members. (a) The agency must...

  7. 42 CFR 435.116 - Qualified pregnant women and children who are not qualified family members.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 42 Public Health 4 2011-10-01 2011-10-01 false Qualified pregnant women and children who are not... Categorically Needy Mandatory Coverage of Pregnant Women, Children Under 8, and Newborn Children § 435.116 Qualified pregnant women and children who are not qualified family members. (a) The agency must provide...

  8. 30 CFR 795.10 - Qualified laboratories.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 30 Mineral Resources 3 2012-07-01 2012-07-01 false Qualified laboratories. 795.10 Section 795.10... laboratories. (a) Basic qualifications. To be designated a qualified laboratory, a firm shall demonstrate that... necessary field samples and making hydrologic field measurements and analytical laboratory determinations...

  9. 7 CFR 802.1 - Qualified laboratories.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 7 2012-01-01 2012-01-01 false Qualified laboratories. 802.1 Section 802.1... REQUIREMENTS FOR GRAIN WEIGHING EQUIPMENT AND RELATED GRAIN HANDLING SYSTEMS § 802.1 Qualified laboratories. (a) Metrology laboratories. (1) Any State metrology laboratory currently approved by the NBS...

  10. 30 CFR 795.10 - Qualified laboratories.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 30 Mineral Resources 3 2013-07-01 2013-07-01 false Qualified laboratories. 795.10 Section 795.10... laboratories. (a) Basic qualifications. To be designated a qualified laboratory, a firm shall demonstrate that... necessary field samples and making hydrologic field measurements and analytical laboratory determinations...

  11. 7 CFR 802.1 - Qualified laboratories.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 7 2014-01-01 2014-01-01 false Qualified laboratories. 802.1 Section 802.1... REQUIREMENTS FOR GRAIN WEIGHING EQUIPMENT AND RELATED GRAIN HANDLING SYSTEMS § 802.1 Qualified laboratories. (a) Metrology laboratories. (1) Any State metrology laboratory currently approved by the NBS...

  12. 30 CFR 795.10 - Qualified laboratories.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 30 Mineral Resources 3 2014-07-01 2014-07-01 false Qualified laboratories. 795.10 Section 795.10... laboratories. (a) Basic qualifications. To be designated a qualified laboratory, a firm shall demonstrate that... necessary field samples and making hydrologic field measurements and analytical laboratory determinations...

  13. 7 CFR 802.1 - Qualified laboratories.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 7 2013-01-01 2013-01-01 false Qualified laboratories. 802.1 Section 802.1... REQUIREMENTS FOR GRAIN WEIGHING EQUIPMENT AND RELATED GRAIN HANDLING SYSTEMS § 802.1 Qualified laboratories. (a) Metrology laboratories. (1) Any State metrology laboratory currently approved by the NBS...

  14. 7 CFR 802.1 - Qualified laboratories.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 7 2011-01-01 2011-01-01 false Qualified laboratories. 802.1 Section 802.1... REQUIREMENTS FOR GRAIN WEIGHING EQUIPMENT AND RELATED GRAIN HANDLING SYSTEMS § 802.1 Qualified laboratories. (a) Metrology laboratories. (1) Any State metrology laboratory currently approved by the NBS...

  15. 30 CFR 795.10 - Qualified laboratories.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 3 2011-07-01 2011-07-01 false Qualified laboratories. 795.10 Section 795.10... laboratories. (a) Basic qualifications. To be designated a qualified laboratory, a firm shall demonstrate that... necessary field samples and making hydrologic field measurements and analytical laboratory determinations...

  16. 46 CFR 390.9 - Qualified withdrawals.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 8 2010-10-01 2010-10-01 false Qualified withdrawals. 390.9 Section 390.9 Shipping MARITIME ADMINISTRATION, DEPARTMENT OF TRANSPORTATION REGULATIONS UNDER PUBLIC LAW 91-469 CAPITAL CONSTRUCTION FUND § 390.9 Qualified withdrawals. (a) In general—(1) Defined. In accordance with 46 U.S.C....

  17. 46 CFR 391.5 - Qualified withdrawals.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 8 2010-10-01 2010-10-01 false Qualified withdrawals. 391.5 Section 391.5 Shipping MARITIME ADMINISTRATION, DEPARTMENT OF TRANSPORTATION REGULATIONS UNDER PUBLIC LAW 91-469 FEDERAL INCOME TAX ASPECTS OF THE CAPITAL CONSTRUCTION FUND § 391.5 Qualified withdrawals. (a) In general. (1)...

  18. In Every Core Class, a Qualified Teacher...

    ERIC Educational Resources Information Center

    Keller, Bess

    2006-01-01

    This article reports the teacher-quality plans of putting a highly qualified teacher in every core class which were due to the Education Department in July 7. In the plans, states are required to describe which groups of teachers are not yet highly qualified according to the federal standard, how they would help--and prod--districts to use only…

  19. 12 CFR 1808.200 - Qualified Issuers.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 12 Banks and Banking 10 2014-01-01 2014-01-01 false Qualified Issuers. 1808.200 Section 1808.200 Banks and Banking COMMUNITY DEVELOPMENT FINANCIAL INSTITUTIONS FUND, DEPARTMENT OF THE TREASURY COMMUNITY DEVELOPMENT FINANCIAL INSTITUTIONS BOND GUARANTEE PROGRAM Eligibility § 1808.200 Qualified Issuers...

  20. 13 CFR 108.110 - Qualified management.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 13 Business Credit and Assistance 1 2012-01-01 2012-01-01 false Qualified management. 108.110... management. An Applicant must show, to the satisfaction of SBA, that its current or proposed management team is qualified and has the knowledge, experience, and capability in Community Development Finance...

  1. Eddy Current COPV Overwrap and Liner Thickness Measurement System and Data Analysis for 40-Inch Kevlar COPVs SN002 and SN027

    NASA Technical Reports Server (NTRS)

    Wincheski, Russell A.

    2008-01-01

    As part of the health assessment of flight spare 40in diameter Kevlar composite overwrapped pressure vessels (COPVs) SN002 and SN027 an eddy current characterization of the composite and liner thickness change during pressurization was requested under WSTF-TP-1085-07.A, "Space Shuttle Orbiter Main Propulsion System P/N MC282-0082-0101 S/N 002 and Orbital Maneuvering System P/N MC282-0082-001 S/N 027 COPV Health Assessment." The through the thickness strains have been determined to be an important parameter in the analysis of the reliability and likelihood of stress rupture failure. Eddy current techniques provide a means to measure these thicknesses changes based upon the change in impedance of an eddy current sensor mounted on the exterior of the vessel. Careful probe and technique design have resulted in the capability to independently measure the liner and overwrap thickness changes to better than +/- 0.0005 in. at each sensor location. Descriptions of the inspection system and test results are discussed.

  2. Thermoplastic polymides and composites therefrom

    NASA Technical Reports Server (NTRS)

    Harris, Frank W. (Inventor)

    1994-01-01

    A new class polyimide and polyimide precursors based on diaryl oxyalkylene diamines, such as 1,3-bis[4-aminophenoxy]-2,2-dimethyl propane, a process for their preparation and their use as the continuous phase for the manufacture of composites and composite laminates reinforced by reinforcing agents such as carbon fibers, Kevlar.TM., and other similar high strength reinforcing agents. The polyimides and molecular composites obtained from the diamines according to the invention show thermoplastic properties, excellent flex fatigue and fracture resistance, and excellent thermal and oxidative stability.

  3. Strength of Kevlar narrow fabrics as influenced by folding and compression in the presence of moisture

    SciTech Connect

    Ericksen, R.H.

    1986-08-01

    The tensile strength of dry Kevlar narrow fabrics was investigated as a function of moisture present during folding and compression. Fabric samples were exposed to 96% relative humidity, or soaked in water prior to compression; or moisture was introduced while the samples were compressed. The fabrics exhibited a 10 to 30% tensile strength loss after wet compression relative to data for samples compressed dry. Similar tests on nylon did not show this effect. Warp yarns removed from fabrics compressed with moisture present exhibited nominally the same strength as those obtained from fabrics compressed dry or from uncompressed fabrics. These results are consistent with test data from a parachute that had been exposed to moisture and with packing difficulties encountered under high humidity environments.

  4. Stress transfer of a Kevlar 49 fiber pullout test studied by micro-Raman spectroscopy.

    PubMed

    Lei, Zhenkun; Wang, Quan; Qiu, Wei

    2013-06-01

    The interfacial stress transfer behavior of a Kevlar 49 aramid fiber-epoxy matrix was studied with fiber pullout tests, the fibers of which were stretched by a homemade microloading device. Raman spectra on the embedded fiber were recorded by micro-Raman spectroscopy, under different strain levels. Then, the fiber axial stress was obtained by the relationship between the stress and Raman shift of the aramid fiber. Experimental results revealed that the fiber axial stress increased significantly with the load. The shear stress concentration occurred at the fiber entry to the epoxy resin. Thus, interfacial friction stages exist in the debonded fiber segment, and the interfacial friction shear stress is constant within one stage. The experimental results are consistent with the theoretical model predictions.

  5. Fiber-Level Modeling of Dynamic Strength of Kevlar® KM2 Ballistic Fabric

    NASA Astrophysics Data System (ADS)

    Grujicic, M.; Hariharan, A.; Pandurangan, B.; Yen, C.-F.; Cheeseman, B. A.; Wang, Y.; Miao, Y.; Zheng, J. Q.

    2012-07-01

    In recent years, modeling of the high-performance ballistic fabric has gradually shifted from the continuum and yarn length scales to the sub-yarn length scale which enabled establishment of the relationships between the fabric penetration resistance and various fiber-level phenomena such as fiber-fiber friction, fiber twist, transverse properties of the fibers, and the stochastic nature of fiber strength. In general, these sub-yarn modeling schemes involve special numerical techniques (e.g., digital-element method) and customized computational codes. This status of the sub-yarn fabric-modeling methods and tools makes them not readily available to wider academic and industrial research communities. In the present work, an attempt is made to use conventional finite-element methods and tools in order to carry out sub-yarn numerical analysis of the penetration resistance of Kevlar® KM2 ballistic fabric. The goal was to demonstrate that results could be obtained which are comparable to their digital-element method = based counterparts. Specifically, a series of transient nonlinear dynamics finite-element analyses was carried out in order to investigate the role of the following two important sub-yarn phenomena on the penetration resistance of Kevlar® KM2 fabric: (a) fiber transverse properties including nonlinear elastic and plastic response and (b) fiber-fiber friction within the context of stochastically distributed fiber axial strength. It is generally found that the results obtained are consistent with their digital-element method-based counterparts.

  6. Flight service evaluation of composite helicopter components

    NASA Technical Reports Server (NTRS)

    Rich, M. J.; Lowry, D. W.

    1982-01-01

    This first interim report presents the technical background for including environmental effects in the design of helicopter composite structures, and test results after approximately two year field exposure of components and panels. Composite structural components were removed from Sikorsky S-76 helicopters commercially operated in the Gulf Coast region of Louisiana. Fatigue tests were conducted for a graphite/epoxy tail rotor spar and static test for a graphite/epoxy and Kevlar/epoxy stabilizer. Graphite/epoxy and Kevlar/epoxy panels are being exposed to the outdoor environment in Stratford, Connecticut and West Palm Beach, Florida. For this reporting period the two year panels were returned, moisture measurements taken, and strength tests conducted. Results are compared with initial type certificate strengths for components and with initial laboratory coupon tests for the exposed panels. Comparisons are also presented with predicted and measured moisture contents.

  7. Preliminary results of the effects of sewing, packing and parachute deployment on material strength. [Kevlar and nylon

    SciTech Connect

    Ericksen, R.H.; Pepper, W.B.; Whinery, L.D.

    1984-01-01

    Ribbon parachute fabrics were tested during development and production of a 24 ft parachute, and after 2.5 years ambient exposure at several storage sites. The effects of sewing, packing, and parachute deployment on material strength were obtained in the 1000 lb Kevlar ribbon after moisture exposure during packing, and when packed parachutes absorbed moisture or were thermal cycled. Individual yarn samples from the low strength ribbons exhibited little change in strength indicating that the material itself had not degraded. Factors leading to the change in ribbon strength are discussed. Considering all materials, there have been no indications to date of any uncontrollable changes in material strength that would limit the use of Kevlar in parachute applications.

  8. A novel Ag catalyzation process using swelling impregnation method for electroless Ni deposition on Kevlar® fiber

    NASA Astrophysics Data System (ADS)

    Pang, Hongwei; Bai, Ruicheng; Shao, Qinsi; Gao, Yufang; Li, Aijun; Tang, Zhiyong

    2015-12-01

    A novel Ag catalyzation process using swelling impregnation pretreatment method was developed for electroless nickel (EN) deposition on Kevlar fiber. Firstly, the fiber was immersed into an aqueous dimethylsulfoxide (DMSO) solution of silver nitrate to impart silver nitrate into the inner part of the fiber near the surface. Subsequently silver nitrate was reduced to metal silver nanoparticles on the fiber surface by treatment with aqueous solution of sodium borohydride. After electroless plating, a dense and homogeneous nickel coating was obtained on the fiber surface. The silver nanoparticles formed at the fiber surface functioned as a catalyst for electroless deposition as well as an anchor for the plated layer. The study also revealed that the incorporation of surfactant sodium dodecyl sulfate (SDS) in electroless nickel plating bath can enhance the adhesion strength of EN layer with the fiber surface and minimize the surface roughness of the EN coating. The Ni plated Kevlar fiber possessed excellent corrosion resistance and high tensile strength.

  9. Flight Qualified Micro Sun Sensor

    NASA Technical Reports Server (NTRS)

    Liebe, Carl Christian; Mobasser, Sohrab; Wrigley, Chris; Schroeder, Jeffrey; Bae, Youngsam; Naegle, James; Katanyoutanant, Sunant; Jerebets, Sergei; Schatzel, Donald; Lee, Choonsup

    2007-01-01

    A prototype small, lightweight micro Sun sensor (MSS) has been flight qualified as part of the attitude-determination system of a spacecraft or for Mars surface operations. The MSS has previously been reported at a very early stage of development in NASA Tech Briefs, Vol. 28, No. 1 (January 2004). An MSS is essentially a miniature multiple-pinhole electronic camera combined with digital processing electronics that functions analogously to a sundial. A micromachined mask containing a number of microscopic pinholes is mounted in front of an active-pixel sensor (APS). Electronic circuits for controlling the operation of the APS, readout from the pixel photodetectors, and analog-to-digital conversion are all integrated onto the same chip along with the APS. The digital processing includes computation of the centroids of the pinhole Sun images on the APS. The spacecraft computer has the task of converting the Sun centroids into Sun angles utilizing a calibration polynomial. The micromachined mask comprises a 500-micron-thick silicon wafer, onto which is deposited a 57-nm-thick chromium adhesion- promotion layer followed by a 200-nm-thick gold light-absorption layer. The pinholes, 50 microns in diameter, are formed in the gold layer by photolithography. The chromium layer is thin enough to be penetrable by an amount of Sunlight adequate to form measurable pinhole images. A spacer frame between the mask and the APS maintains a gap of .1 mm between the pinhole plane and the photodetector plane of the APS. To minimize data volume, mass, and power consumption, the digital processing of the APS readouts takes place in a single field-programmable gate array (FPGA). The particular FPGA is a radiation- tolerant unit that contains .32,000 gates. No external memory is used so the FPGA calculates the centroids in real time as pixels are read off the APS with minimal internal memory. To enable the MSS to fit into a small package, the APS, the FPGA, and other components are mounted

  10. Radiographic layer counter for composites. Final technical report, Jun 87-Feb 88

    SciTech Connect

    Larsen, R.E.

    1991-06-01

    The Army helmet is a composite of layers of resin-bonded Kevlar. Inadvertent omission of layers or undetected shifting of layers during molding processes can reduce the effective number of fibers in some helmet areas and impair their strength properties. A nondestructive method of 100% testing of the helmets, more effective than random sampling by ballistic testing, is needed. This six-month study evaluated the feasibility of using relatively low-energy radioisotopes to gauge the uniformity of Kelvar helmets. The potential for constructing a portable detection unit was also assessed. A laboratory radiometric test system was used to evaluate resin-bonded Kevlar samples, as well as actual Army helmets from current suppliers. It was found that the radiometric test system has the capacity to reflect the general condition of fabricated Kevlar helmets.

  11. 7 CFR 1150.109 - Qualified program.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... AGREEMENTS AND ORDERS; MILK), DEPARTMENT OF AGRICULTURE DAIRY PROMOTION PROGRAM Dairy Promotion and Research..., research or nutrition education program which is certified as a qualified program pursuant to § 1150.153....

  12. 7 CFR 1150.109 - Qualified program.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... AGREEMENTS AND ORDERS; MILK), DEPARTMENT OF AGRICULTURE DAIRY PROMOTION PROGRAM Dairy Promotion and Research..., research or nutrition education program which is certified as a qualified program pursuant to § 1150.153....

  13. 7 CFR 1150.109 - Qualified program.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... Agreements and Orders; Milk), DEPARTMENT OF AGRICULTURE DAIRY PROMOTION PROGRAM Dairy Promotion and Research..., research or nutrition education program which is certified as a qualified program pursuant to § 1150.153....

  14. [Research on the modification of Kevlar fiber by polypropylene glycol and cis-2-butene-1,4-diol].

    PubMed

    Zheng, Yu-ying; Wang, Can-yao; Fu, Ming-lian; Cai, Wei-long; Wang, Liang-en

    2005-03-01

    The mechanism of the modification of Kevlar fiber by polypropylene glycol(PPG) and cis-2-butene-1, 4-diol was studied in the paper, the authors learned the esterification of toluene-2, 4-diisocyanate (TDI) onto Kevlar fiber by infrared spectrum. In the mean time, the infrared spectrograms of the productions which steadily disposed by PPG and butendiol were analysed respectively, the result showed that the intensity of the bands was reinforced at about 1700-1720 cm(-1) after the samples were steadily disposed, that is to say, the group of --NCO has been stabilized into --NHCO group, the effect of steady disposal was obvious; but the disposal effect of butendiol was apparently better than PPG's at the same condition. Finally, the authors compared the influence of different mol rates between TDI and butendiol on the productions. Based onthe consequence, excessive butendiol would prevent the Kevlar fiber from farther reaction, therefore, the mol rate between TDI and butendiol should approach 1:1.

  15. Elevated Temperature Ballistic Impact Testing of PBO and Kevlar Fabrics for Application in Supersonic Jet Engine Fan Containment Systems

    NASA Technical Reports Server (NTRS)

    Pereira, J. Michael; Roberts Gary D.; Revilock, Duane M., Jr.

    1997-01-01

    Ballistic impact tests were conducted on fabric made from both Poly(phenylene benzobizoxazole) (PBO) and Kevlar 29 which were selected to be similar in weave pattern, areal density, and fiber denier. The projectiles were 2.54-cm- (1-in.-) long aluminum cylinders with a diameter of 1.27 cm (0.5 in.). The fabric specimens were clamped on four sides in a 30.5-cm- (12-in.-) square frame. Tests on PBO were conducted at room temperature and at 260 C (500 F). A number of PBO specimens were aged in air at 204 and 260 C (400 and 500 F) before impact testing. Kevlar specimens were tested only at room temperature and with no aging. The PBO absorbed significantly more energy than the Kevlar at both room and elevated temperatures. However, after aging at temperatures of 204 C (400 F) and above, the PBO fabric lost almost all of its energy absorbing ability. It was concluded that PBO fabric is not a feasible candidate for fan containment system applications in supersonic jet engines where operating temperatures exceed this level.

  16. Chiral braided and woven composites: design, fabrication, and electromagnetic characterization

    NASA Astrophysics Data System (ADS)

    Wheeland, Sara; Bayatpur, Farhad; Amirkhizi, Alireza V.; Nemat-Nasser, Sia

    2011-04-01

    This work presents a new chiral composite composed of copper wires braided with Kevlar and nylon to form conductive coils integrated among structural fiber. To create a fabric, these braids were woven with plain Kevlar fiber. This yielded a composite with all coils possessing the same handedness, producing a chiral material. The electromagnetic response of this fabric was first simulated using a finite element full-wave simulation. For the electromagnetic measurement, the sample was placed between two lens-horn antennas connected to a Vector Network Analyzer. The frequency response of the sample was scanned between 5.5 and 8GHz. The measured scattering parameters were then compared to those of the simulated model. The measured parameters agreed well with the simulation results, showing a considerable chirality within the measured frequency band. The new composite combines the strength and durability of traditional composites with an electromagnetic design to create a multifunctional material.

  17. Community Characteristics and Qualified Health Plan Selection during the First Open Enrollment Period.

    PubMed

    Boudreaux, Michel; Blewett, Lynn A; Fried, Brett; Hempstead, Katherine; Karaca-Mandic, Pinar

    2017-06-01

    To examine state and community factors that contributed to geographic variation in qualified health plan selection during the first open enrollment period. Administrative data on qualified health plan selections at the ZIP code area merged with survey estimates from the American Community Survey. Descriptive and regression analyses. Data were generated by healthcare.gov and from a household survey. Thirty-one percent of the variation in qualified health plan selection ratios resulted from between-state differences, and the rest was driven by local area differences. Education, language, age, gender, and the ethnic composition of communities contributed to disparate levels of plan selection. Medicaid expansion states had a qualified health plan selection ratio that was 4.4 points lower than non-Medicaid expansion states, controlling for covariates. Our results suggest community-level differences in the intensity or receptiveness to outreach and enrollment activities during the first open enrollment period. © Health Research and Educational Trust.

  18. Examining the Relationship Between Ballistic and Structural Properties of Lightweight Thermoplastic Unidirectional Composite Laminates

    DTIC Science & Technology

    2011-08-01

    Kevlar KM2® Style 705 PVB phenolic woven aramid composite was included. A developmental unidirectional thermoplastic aramid fiber, Honeywell... discovery and development of the ARL X Hybrid architecture, which consists of 1) the balance of architecture in the panel being 75% [0°/90°] and 25

  19. Fracto-emission from graphite/epoxy composites

    NASA Technical Reports Server (NTRS)

    Dickinson, J. T.

    1983-01-01

    Fracto-emission (FE) is the emission of particles and photons during and following crack propagation. Electrons (EE), positive ions (PIE), and excited and ground state neutrals (NE) were observed. Results of a number of experiments involving principally graphite/epoxy composites and Kevlar single fibers are presented. The physical processes responsible for EE and PIE are discussed as well as FE from fiber- and particulate-reinforced composites.

  20. Pulmonary cellular effects in rats following aerosol exposures to ultrafine Kevlar aramid fibrils: evidence for biodegradability of inhaled fibrils.

    PubMed

    Warheit, D B; Kellar, K A; Hartsky, M A

    1992-10-01

    Previous chronic inhalation studies have shown that high concentrations of Kevlar fibrils produced fibrosis and cystic keratinizing tumors in rats following 2-year inhalation exposures. The current studies were undertaken to evaluate mechanisms and to assess the toxicity of inhaled Kevlar fibrils relative to other reference materials. Rats were exposed to ultrafine Kevlar fibers (fibrils) for 3 or 5 days at concentrations ranging from 600-1300 fibers/cc (gravimetric concentrations ranging from 2-13 mg/m3). A complete characterization of the fiber aerosol and dose was carried out. These measurements included gravimetric concentrations, mass median aerodynamic diameter, fiber number, and count median lengths and diameters of the aerosol. Following exposures, cells and fluids from groups of sham- and fiber-exposed animals were recovered by bronchoalveolar lavage (BAL). Alkaline phosphatase, lactate dehydrogenase (LDH), protein, and N-acetyl glucosaminidase (NAG) values were measured in BAL fluids at several time points postexposure. Alveolar macrophages were cultured and studied for morphology, chemotaxis, and phagocytosis by scanning electron microscopy. The lungs of additional exposed animals were processed for deposition, cell labeling, retained dose, and lung clearance studies, as well as fiber dimensions (from digested lung tissue), histopathology, and transmission electron microscopy. Five-day exposures to Kevlar fibrils elicited a transient granulocytic inflammatory response with concomitant increases in BAL fluid levels of alkaline phosphatase, NAG, LDH, and protein. Unlike the data from silica and asbestos exposures where inflammation persisted, biochemical parameters returned to control levels at time intervals between 1 week and 1 month postexposure. Macrophage function in Kevlar-exposed alveolar macrophages was not significantly different from sham controls at any time period. Cell labeling studies were carried out immediately after exposure, as well as 1

  1. 30 CFR 75.155 - Qualified hoisting engineer; qualifications.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...-hoisting engineer; or (2) If a State has no program for qualifying persons as electric-hoisting engineers... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Qualified hoisting engineer; qualifications. 75... Persons § 75.155 Qualified hoisting engineer; qualifications. (a)(1) A person is a qualified hoisting...

  2. 30 CFR 75.155 - Qualified hoisting engineer; qualifications.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...-hoisting engineer; or (2) If a State has no program for qualifying persons as electric-hoisting engineers... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Qualified hoisting engineer; qualifications. 75... Persons § 75.155 Qualified hoisting engineer; qualifications. (a)(1) A person is a qualified hoisting...

  3. 30 CFR 75.155 - Qualified hoisting engineer; qualifications.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...-hoisting engineer; or (2) If a State has no program for qualifying persons as electric-hoisting engineers... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Qualified hoisting engineer; qualifications. 75... Persons § 75.155 Qualified hoisting engineer; qualifications. (a)(1) A person is a qualified hoisting...

  4. 30 CFR 75.155 - Qualified hoisting engineer; qualifications.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...-hoisting engineer; or (2) If a State has no program for qualifying persons as electric-hoisting engineers... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Qualified hoisting engineer; qualifications. 75... Persons § 75.155 Qualified hoisting engineer; qualifications. (a)(1) A person is a qualified hoisting...

  5. 30 CFR 75.155 - Qualified hoisting engineer; qualifications.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...-hoisting engineer; or (2) If a State has no program for qualifying persons as electric-hoisting engineers... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Qualified hoisting engineer; qualifications. 75... Persons § 75.155 Qualified hoisting engineer; qualifications. (a)(1) A person is a qualified hoisting...

  6. 7 CFR 701.110 - Qualifying minimum cost of restoration.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 7 2011-01-01 2011-01-01 false Qualifying minimum cost of restoration. 701.110... Conservation Program § 701.110 Qualifying minimum cost of restoration. (a) To qualify for assistance under... Deputy Administrator shall establish the minimum qualifying cost of restoration. Each affected State may...

  7. 5 CFR 847.202 - Definition of qualifying move.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 5 Administrative Personnel 2 2010-01-01 2010-01-01 false Definition of qualifying move. 847.202... FUND INSTRUMENTALITIES Elections To Continue Retirement Coverage After a Qualifying Move § 847.202 Definition of qualifying move. (a) A qualifying move occurring on or after December 28, 2001, that...

  8. 5 CFR 847.202 - Definition of qualifying move.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 5 Administrative Personnel 2 2011-01-01 2011-01-01 false Definition of qualifying move. 847.202... FUND INSTRUMENTALITIES Elections To Continue Retirement Coverage After a Qualifying Move § 847.202 Definition of qualifying move. (a) A qualifying move occurring on or after December 28, 2001, that...

  9. 5 CFR 847.202 - Definition of qualifying move.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 5 Administrative Personnel 2 2013-01-01 2013-01-01 false Definition of qualifying move. 847.202... FUND INSTRUMENTALITIES Elections To Continue Retirement Coverage After a Qualifying Move § 847.202 Definition of qualifying move. (a) A qualifying move occurring on or after December 28, 2001, that...

  10. 5 CFR 847.202 - Definition of qualifying move.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 5 Administrative Personnel 2 2012-01-01 2012-01-01 false Definition of qualifying move. 847.202... FUND INSTRUMENTALITIES Elections To Continue Retirement Coverage After a Qualifying Move § 847.202 Definition of qualifying move. (a) A qualifying move occurring on or after December 28, 2001, that...

  11. 5 CFR 847.202 - Definition of qualifying move.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 5 Administrative Personnel 2 2014-01-01 2014-01-01 false Definition of qualifying move. 847.202... FUND INSTRUMENTALITIES Elections To Continue Retirement Coverage After a Qualifying Move § 847.202 Definition of qualifying move. (a) A qualifying move occurring on or after December 28, 2001, that...

  12. 12 CFR 1806.201 - Measuring and reporting Qualified Activities.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 12 Banks and Banking 7 2011-01-01 2011-01-01 false Measuring and reporting Qualified Activities..., DEPARTMENT OF THE TREASURY BANK ENTERPRISE AWARD PROGRAM Awards § 1806.201 Measuring and reporting Qualified... applicable BEA NOFA for current limitations on Qualified Activities. (e) Measuring the Value of Qualified...

  13. 42 CFR 436.120 - Qualified pregnant women and children who are not qualified family members.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 42 Public Health 4 2010-10-01 2010-10-01 false Qualified pregnant women and children who are not... women and children who are not qualified family members. (a) The Medicaid agency must provide Medicaid to a pregnant woman whose pregnancy has been medically verified and who— (1) Would be eligible for...

  14. 42 CFR 436.120 - Qualified pregnant women and children who are not qualified family members.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 42 Public Health 4 2011-10-01 2011-10-01 false Qualified pregnant women and children who are not... women and children who are not qualified family members. (a) The Medicaid agency must provide Medicaid to a pregnant woman whose pregnancy has been medically verified and who— (1) Would be eligible for an...

  15. 42 CFR 436.120 - Qualified pregnant women and children who are not qualified family members.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 42 Public Health 4 2014-10-01 2014-10-01 false Qualified pregnant women and children who are not... women and children who are not qualified family members. (a) The Medicaid agency must provide Medicaid to a pregnant woman whose pregnancy has been medically verified and who— (1) Would be eligible for...

  16. 42 CFR 436.120 - Qualified pregnant women and children who are not qualified family members.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 42 Public Health 4 2012-10-01 2012-10-01 false Qualified pregnant women and children who are not... women and children who are not qualified family members. (a) The Medicaid agency must provide Medicaid to a pregnant woman whose pregnancy has been medically verified and who— (1) Would be eligible for...

  17. 42 CFR 436.120 - Qualified pregnant women and children who are not qualified family members.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 42 Public Health 4 2013-10-01 2013-10-01 false Qualified pregnant women and children who are not... women and children who are not qualified family members. (a) The Medicaid agency must provide Medicaid to a pregnant woman whose pregnancy has been medically verified and who— (1) Would be eligible for...

  18. Evaluation of Thin Kevlar-Epoxy Fabric Panels Subjected to Shear Loading

    SciTech Connect

    Baker, D.J.

    1996-04-01

    The results of an analytical and experimental investigation of 4-ply Kevlar-49-epoxy panels loaded by in-plane shear are presented. Approximately one-half of the panels are thin-core sandwich panels and the other panels are solid-laminate panels. Selected panels were impacted with an aluminum sphere at a velocity of either 150 or 220 ft/sec. The strength of panels impacted at 150 ft/sec was not reduced when compared to the strength of the undamaged panels, but the strength of panels impacted at 220 ft/sec was reduced by 27 to 40 percent. Results are presented for panels that were cyclically loaded from a load less than the buckling load to a load in the postbuckling load range. The thin-core sandwich panels had a lower fatigue life than the solid panels. The residual strength of the solid and sandwich panels cycled more than one million cycles exceeded the baseline undamaged panel strengths. The effect of hysteresis in the response of the sandwich panels is not significant. Results of a nonlinear finite element analysis conducted for each panel design are presented.

  19. Time-Dependent Behavior of High-Strength Kevlar and Vectran Webbing

    NASA Technical Reports Server (NTRS)

    Jones, Thomas C.; Doggett, William R.

    2014-01-01

    High-strength Kevlar and Vectran webbings are currently being used by both NASA and industry as the primary load-bearing structure in inflatable space habitation modules. The time-dependent behavior of high-strength webbing architectures is a vital area of research that is providing critical material data to guide a more robust design process for this class of structures. This paper details the results of a series of time-dependent tests on 1-inch wide webbing including an initial set of comparative tests between specimens that underwent realtime and accelerated creep at 65 and 70% of their ultimate tensile strength. Variability in the ultimate tensile strength of the webbings is investigated and compared with variability in the creep life response. Additional testing studied the effects of load and displacement rate, specimen length and the time-dependent effects of preconditioning the webbings. The creep test facilities, instrumentation and test procedures are also detailed. The accelerated creep tests display consistently longer times to failure than their real-time counterparts; however, several factors were identified that may contribute to the observed disparity. Test setup and instrumentation, grip type, loading scheme, thermal environment and accelerated test postprocessing along with material variability are among these factors. Their effects are discussed and future work is detailed for the exploration and elimination of some of these factors in order to achieve a higher fidelity comparison.

  20. High temperature testing of TRUPACT-I materials: Kevlar, honeycomb, rigid polyurethane foam

    SciTech Connect

    Hudson, M.L.

    1985-12-01

    When the Transuranic Package Transporter Model-I (TRUPACT-I) failed to afford sufficient containment after a 35-minute JP-4 fueled open-pool fire, component tests were conducted, in conjunction with analyses, to guide and assess the redesign of TRUPACT-I. Since materials which change phase or combust are difficult to numerically analyze, the component tests determined the behavior of these materials in TRUPACT-I. The component tests approximated the behavior of Kevlar (registered trademark of DuPont), metal honeycomb, and rigid polyurethane foam, as they appear in TRUPACT-I, in an open-pool fire environment. Six series of tests were performed at Sandia's Radiant Heat Facility and one test at the wind-shielded fire test facility (LAARC Chimney). Each test facility was controlled to yield temperatures or heat fluxes equivalent to those measured in the TRUPACT-I, Unit 0, open-pool fire. This extensive series of component tests (34 runs total) provided information on the high-temperature behavior of unique materials which was not previously available or otherwise attainable. The component tests were a timely and cost-effective means of providing the data for the TRUPACT-I redesign.

  1. Evaluation of Thin Kevlar-Epoxy Fabric Panels Subjected to Shear Loading

    NASA Technical Reports Server (NTRS)

    Baker, Donald J.

    1996-01-01

    The results of an analytical and experimental investigation of 4-ply Kevlar-49-epoxy panels loaded by in-plane shear are presented. Approximately one-half of the panels are thin-core sandwich panels and the other panels are solid-laminate panels. Selected panels were impacted with an aluminum sphere at a velocity of either 150 or 220 ft/sec. The strength of panels impacted at 150 ft/sec was not reduced when compared to the strength of the undamaged panels, but the strength of panels impacted at 220 ft/sec was reduced by 27 to 40 percent. Results are presented for panels that were cyclically loaded from a load less than the buckling load to a load in the postbuckling load range. The thin-core sandwich panels had a lower fatigue life than the solid panels. The residual strength of the solid and sandwich panels cycled more than one million cycles exceeded the baseline undamaged panel strengths. The effect of hysteresis in the response of the sandwich panels is not significant. Results of a nonlinear finite element analysis conducted for each panel design are presented.

  2. The development of studying flexible pipe bend reinforced by Kevlar fibers

    NASA Astrophysics Data System (ADS)

    Shuai, Chang-Geng; He, Lin; Lu, Zhi-Qiang

    2003-12-01

    The flexible pipe bend can not only reduce the structural vibration and fluid noise in pipeline, but also realize the flexible connection of a horizontal line and a vertical line and compensate the displacement of three dimensions produced by the shock or vibration of pipeline in the special situations. Up to now, little attention has been paid to study the flexible pipe bend applied in the pipeline of medium or high pressure, because no appropriate framework materials can be used to reinforce it which must endure the burst pressure higher than 10 MPa. The investigation shows that it is possible to produce the flexible pipe bend of medium or high pressure if such fibers with high performance as Kevlar fibers are used to be its reinforced materials. However, its structural designing theory, manufacturing technology and measuring techniques aren’t yet perfect and systematic, which leads to the instability of the performance of products. Furthermore, few references about its research can be seen. Therefore, it is necessary to systematically and thoroughly develop the structural designing theory, manufacture technology and measuring techniques of flexible pipe bend.

  3. 26 CFR 1.30-1 - Definition of qualified electric vehicle and recapture of credit for qualified electric vehicle.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 26 Internal Revenue 1 2011-04-01 2009-04-01 true Definition of qualified electric vehicle and recapture of credit for qualified electric vehicle. 1.30-1 Section 1.30-1 Internal Revenue INTERNAL REVENUE... qualified electric vehicle and recapture of credit for qualified electric vehicle. (a) Definition...

  4. 26 CFR 1.30-1 - Definition of qualified electric vehicle and recapture of credit for qualified electric vehicle.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 26 Internal Revenue 1 2014-04-01 2013-04-01 true Definition of qualified electric vehicle and recapture of credit for qualified electric vehicle. 1.30-1 Section 1.30-1 Internal Revenue INTERNAL REVENUE... qualified electric vehicle and recapture of credit for qualified electric vehicle. (a) Definition...

  5. 26 CFR 1.30-1 - Definition of qualified electric vehicle and recapture of credit for qualified electric vehicle.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 26 Internal Revenue 1 2010-04-01 2010-04-01 true Definition of qualified electric vehicle and recapture of credit for qualified electric vehicle. 1.30-1 Section 1.30-1 Internal Revenue INTERNAL REVENUE... qualified electric vehicle and recapture of credit for qualified electric vehicle. (a) Definition...

  6. 26 CFR 1.30-1 - Definition of qualified electric vehicle and recapture of credit for qualified electric vehicle.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 26 Internal Revenue 1 2013-04-01 2013-04-01 false Definition of qualified electric vehicle and recapture of credit for qualified electric vehicle. 1.30-1 Section 1.30-1 Internal Revenue INTERNAL REVENUE... qualified electric vehicle and recapture of credit for qualified electric vehicle. (a) Definition...

  7. 26 CFR 1.30-1 - Definition of qualified electric vehicle and recapture of credit for qualified electric vehicle.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 26 Internal Revenue 1 2012-04-01 2012-04-01 false Definition of qualified electric vehicle and recapture of credit for qualified electric vehicle. 1.30-1 Section 1.30-1 Internal Revenue INTERNAL REVENUE... qualified electric vehicle and recapture of credit for qualified electric vehicle. (a) Definition...

  8. 26 CFR 1.401(a)-1 - Post-ERISA qualified plans and qualified trusts; in general.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 26 Internal Revenue 5 2013-04-01 2013-04-01 false Post-ERISA qualified plans and qualified trusts..., Stock Bonus Plans, Etc. § 1.401(a)-1 Post-ERISA qualified plans and qualified trusts; in general. (a...-406) (“ERISA”). (2) (b) Requirements for pension plans—(1) Definitely determinable benefits. (i)...

  9. 26 CFR 1.401(a)-1 - Post-ERISA qualified plans and qualified trusts; in general.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 26 Internal Revenue 5 2012-04-01 2011-04-01 true Post-ERISA qualified plans and qualified trusts..., Stock Bonus Plans, Etc. § 1.401(a)-1 Post-ERISA qualified plans and qualified trusts; in general. (a...-406) (“ERISA”). (2) (b) Requirements for pension plans—(1) Definitely determinable benefits. (i)...

  10. 26 CFR 1.401(a)-1 - Post-ERISA qualified plans and qualified trusts; in general.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 26 Internal Revenue 5 2011-04-01 2011-04-01 false Post-ERISA qualified plans and qualified trusts..., Stock Bonus Plans, Etc. § 1.401(a)-1 Post-ERISA qualified plans and qualified trusts; in general. (a...-406) (“ERISA”). (2) (b) Requirements for pension plans—(1) Definitely determinable benefits. (i)...

  11. 26 CFR 1.401(a)-1 - Post-ERISA qualified plans and qualified trusts; in general.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 26 Internal Revenue 5 2014-04-01 2014-04-01 false Post-ERISA qualified plans and qualified trusts..., Stock Bonus Plans, Etc. § 1.401(a)-1 Post-ERISA qualified plans and qualified trusts; in general. (a...-406) (“ERISA”). (2) (b) Requirements for pension plans—(1) Definitely determinable benefits. (i)...

  12. Material Issues in Space Shuttle Composite Overwrapped Pressure Vessels

    NASA Technical Reports Server (NTRS)

    Sutter, James K.; Jensen, Brian J.; Gates, Thomas S.; Morgan, Roger J.; Thesken, John C.; Phoenix, S. Leigh

    2006-01-01

    Composite Overwrapped Pressure Vessels (COPV) store gases used in four subsystems for NASA's Space Shuttle Fleet. While there are 24 COPV on each Orbiter ranging in size from 19-40", stress rupture failure of a pressurized Orbiter COPV on the ground or in flight is a catastrophic hazard and would likely lead to significant damage/loss of vehicle and/or life and is categorized as a Crit 1 failure. These vessels were manufactured during the late 1970's and into the early 1980's using Titanium liners, Kevlar 49 fiber, epoxy matrix resin, and polyurethane coating. The COPVs are pressurized periodically to 3-5ksi and therefore experience significant strain in the composite overwrap. Similar composite vessels were developed in a variety of DOE Programs (primarily at Lawrence Livermore National Laboratories or LLNL), as well as for NASA Space Shuttle Fleet Leader COPV program. The NASA Engineering Safety Center (NESC) formed an Independent Technical Assessment (ITA) team whose primary focus was to investigate whether or not enough composite life remained in the Shuttle COPV in order to provide a strategic rationale for continued COPV use aboard the Space Shuttle Fleet with the existing 25-year-old vessels. Several material science issues were examined and will be discussed in this presentation including morphological changes to Kevlar 49 fiber under stress, manufacturing changes in Kevlar 49 and their effect on morphology and tensile strength, epoxy resin strain, composite creep, degradation of polyurethane coatings, and Titanium yield characteristics.

  13. Firefighting and Emergency Response Study of Advanced Composites Aircraft. Objective 4: Post Fire Decontamination of Personal Protection Equipment

    DTIC Science & Technology

    2011-11-01

    graphite-Kevlar, glass-graphite, and boron -graphite hybrid composites. The results were inconclusive regarding threats to electronic equipment.[1...cause lung irritation effects. More serious effects such as cancer were not demonstrated.[10] Whitehead et al. investigated acute lung injury (ALI

  14. Development and Standardization of the Air Force Officer Qualifying Test Form M.

    ERIC Educational Resources Information Center

    Miller, Robert E.

    Air Force Officer Qualifying Test (AFOQT) Form M was constructed as a replacement for AFOQT Form L in Fiscal Year 1974. The new form serves the same purposes as its predecessor and possesses basically the same characteristics. It yields Pilot, Navigator-Technical, Officer Quality, Verbal, and Quantitative composite scores. Three sets of conversion…

  15. 7 CFR 3431.15 - Qualifying loans.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... SERVICE, DEPARTMENT OF AGRICULTURE VETERINARY MEDICINE LOAN REPAYMENT PROGRAM Administration of the Veterinary Medicine Loan Repayment Program § 3431.15 Qualifying loans. (a) General. Loan repayments provided... accredited college of veterinary medicine resulting in a degree of Doctor of Veterinary Medicine, or...

  16. 30 CFR 795.10 - Qualified laboratories.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...) Meets applicable Federal or State safety and health requirements; (4) Has analytical, monitoring and... acceptable hydrologic, geologic, or analytical methods in accordance with the requirements of §§ 780.21, 780... identified at the time a determination is made that a firm is qualified and they meet requirements specified...

  17. Profitability of Qualified-Labour-Power Production

    ERIC Educational Resources Information Center

    Baldino, Roberto Ribeiro; Cabral, Tânia Cristina Baptista

    2015-01-01

    In Baldino and Cabral (2013) we introduced the concept of qualified labour-power as the commodity produced by the school system. In the present article we outline a quantitative model to evaluate the profit rate of educational programmes. We compare a medical school programme with a teacher education programme at a public university in Brazil,…

  18. 34 CFR 303.22 - Qualified.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... REHABILITATIVE SERVICES, DEPARTMENT OF EDUCATION EARLY INTERVENTION PROGRAM FOR INFANTS AND TODDLERS WITH... intervention services. (Authority: 20 U.S.C. 1432(4)) Note: These regulations contain the following provisions relating to a State's responsibility to ensure that personnel are qualified to provide early intervention...

  19. 40 CFR 1400.12 - Qualified researchers.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 32 2010-07-01 2010-07-01 false Qualified researchers. 1400.12 Section 1400.12 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY AND DEPARTMENT OF JUSTICE ACCIDENTAL RELEASE PREVENTION REQUIREMENTS; RISK MANAGEMENT PROGRAMS UNDER THE CLEAN AIR ACT SECTION 112(r)(7...

  20. 14 CFR 314.6 - Qualifying dislocation.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 4 2010-01-01 2010-01-01 false Qualifying dislocation. 314.6 Section 314.6 Aeronautics and Space OFFICE OF THE SECRETARY, DEPARTMENT OF TRANSPORTATION (AVIATION PROCEEDINGS) PROCEDURAL... provided by the Airline Deregulation Act of 1978. ...

  1. 27 CFR 479.68 - Qualified manufacturer.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 3 2014-04-01 2014-04-01 false Qualified manufacturer. 479.68 Section 479.68 Alcohol, Tobacco Products, and Firearms BUREAU OF ALCOHOL, TOBACCO, FIREARMS, AND EXPLOSIVES, DEPARTMENT OF JUSTICE FIREARMS AND AMMUNITION MACHINE GUNS, DESTRUCTIVE DEVICES, AND...

  2. 27 CFR 479.68 - Qualified manufacturer.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 3 2012-04-01 2010-04-01 true Qualified manufacturer. 479.68 Section 479.68 Alcohol, Tobacco Products, and Firearms BUREAU OF ALCOHOL, TOBACCO, FIREARMS, AND EXPLOSIVES, DEPARTMENT OF JUSTICE FIREARMS AND AMMUNITION MACHINE GUNS, DESTRUCTIVE DEVICES, AND CERTAIN...

  3. 27 CFR 479.68 - Qualified manufacturer.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 3 2010-04-01 2010-04-01 false Qualified manufacturer. 479.68 Section 479.68 Alcohol, Tobacco Products, and Firearms BUREAU OF ALCOHOL, TOBACCO, FIREARMS, AND EXPLOSIVES, DEPARTMENT OF JUSTICE FIREARMS AND AMMUNITION MACHINE GUNS, DESTRUCTIVE DEVICES, AND...

  4. 27 CFR 479.68 - Qualified manufacturer.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 3 2011-04-01 2010-04-01 true Qualified manufacturer. 479.68 Section 479.68 Alcohol, Tobacco Products, and Firearms BUREAU OF ALCOHOL, TOBACCO, FIREARMS, AND EXPLOSIVES, DEPARTMENT OF JUSTICE FIREARMS AND AMMUNITION MACHINE GUNS, DESTRUCTIVE DEVICES, AND CERTAIN...

  5. 27 CFR 479.68 - Qualified manufacturer.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 3 2013-04-01 2013-04-01 false Qualified manufacturer. 479.68 Section 479.68 Alcohol, Tobacco Products, and Firearms BUREAU OF ALCOHOL, TOBACCO, FIREARMS, AND EXPLOSIVES, DEPARTMENT OF JUSTICE FIREARMS AND AMMUNITION MACHINE GUNS, DESTRUCTIVE DEVICES, AND...

  6. 13 CFR 108.110 - Qualified management.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 13 Business Credit and Assistance 1 2013-01-01 2013-01-01 false Qualified management. 108.110... management. An Applicant must show, to the satisfaction of SBA, that its current or proposed management team... or proposed management team has sufficient qualifications, SBA will consider information provided...

  7. 13 CFR 108.110 - Qualified management.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 13 Business Credit and Assistance 1 2014-01-01 2014-01-01 false Qualified management. 108.110... management. An Applicant must show, to the satisfaction of SBA, that its current or proposed management team... or proposed management team has sufficient qualifications, SBA will consider information provided...

  8. 13 CFR 108.110 - Qualified management.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 13 Business Credit and Assistance 1 2010-01-01 2010-01-01 false Qualified management. 108.110... management. An Applicant must show, to the satisfaction of SBA, that its current or proposed management team... or proposed management team has sufficient qualifications, SBA will consider information provided by...

  9. 24 CFR 236.710 - Qualified tenant.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 24 Housing and Urban Development 2 2011-04-01 2011-04-01 false Qualified tenant. 236.710 Section 236.710 Housing and Urban Development Regulations Relating to Housing and Urban Development (Continued... DEVELOPMENT MORTGAGE AND LOAN INSURANCE PROGRAMS UNDER NATIONAL HOUSING ACT AND OTHER AUTHORITIES...

  10. Profitability of Qualified-Labour-Power Production

    ERIC Educational Resources Information Center

    Baldino, Roberto Ribeiro; Cabral, Tânia Cristina Baptista

    2015-01-01

    In Baldino and Cabral (2013) we introduced the concept of qualified labour-power as the commodity produced by the school system. In the present article we outline a quantitative model to evaluate the profit rate of educational programmes. We compare a medical school programme with a teacher education programme at a public university in Brazil,…

  11. 13 CFR 108.110 - Qualified management.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... Act, the regulations in this part and its business plan. In determining whether an Applicant's current... 13 Business Credit and Assistance 1 2011-01-01 2011-01-01 false Qualified management. 108.110 Section 108.110 Business Credit and Assistance SMALL BUSINESS ADMINISTRATION NEW MARKETS VENTURE...

  12. Hiring a Qualified Interpreter. NETAC Teacher Tipsheet

    ERIC Educational Resources Information Center

    Downs, Sharon; West, John; Mile, Shana Kirksey

    2000-01-01

    Finding good help is difficult enough these days, but trying to hire a qualified sign language interpreter can be especially difficult if you don't know what to look for. This paper provides some ideas that may help in your search. These include such considerations as using an interpreter referral agency versus direct hiring and certification and…

  13. 40 CFR 1400.12 - Qualified researchers.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 33 2014-07-01 2014-07-01 false Qualified researchers. 1400.12 Section 1400.12 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY AND DEPARTMENT OF JUSTICE ACCIDENTAL RELEASE PREVENTION REQUIREMENTS; RISK MANAGEMENT PROGRAMS UNDER THE CLEAN AIR ACT SECTION...

  14. 40 CFR 1400.12 - Qualified researchers.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 34 2013-07-01 2013-07-01 false Qualified researchers. 1400.12 Section 1400.12 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY AND DEPARTMENT OF JUSTICE ACCIDENTAL RELEASE PREVENTION REQUIREMENTS; RISK MANAGEMENT PROGRAMS UNDER THE CLEAN AIR ACT SECTION...

  15. 40 CFR 1400.12 - Qualified researchers.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 33 2011-07-01 2011-07-01 false Qualified researchers. 1400.12 Section 1400.12 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY AND DEPARTMENT OF JUSTICE ACCIDENTAL RELEASE PREVENTION REQUIREMENTS; RISK MANAGEMENT PROGRAMS UNDER THE CLEAN AIR ACT SECTION...

  16. 40 CFR 1400.12 - Qualified researchers.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 34 2012-07-01 2012-07-01 false Qualified researchers. 1400.12 Section 1400.12 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY AND DEPARTMENT OF JUSTICE ACCIDENTAL RELEASE PREVENTION REQUIREMENTS; RISK MANAGEMENT PROGRAMS UNDER THE CLEAN AIR ACT SECTION...

  17. 46 CFR 390.9 - Qualified withdrawals.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 8 2011-10-01 2011-10-01 false Qualified withdrawals. 390.9 Section 390.9 Shipping MARITIME ADMINISTRATION, DEPARTMENT OF TRANSPORTATION REGULATIONS UNDER PUBLIC LAW 91-469 CAPITAL..., including a corporate merger, where the party obtains a proprietary interest in an existing vessel and...

  18. 34 CFR 303.22 - Qualified.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 34 Education 2 2011-07-01 2010-07-01 true Qualified. 303.22 Section 303.22 Education Regulations of the Offices of the Department of Education (Continued) OFFICE OF SPECIAL EDUCATION AND REHABILITATIVE SERVICES, DEPARTMENT OF EDUCATION EARLY INTERVENTION PROGRAM FOR INFANTS AND TODDLERS WITH...

  19. Yarn Pull-Out as a Mechanism for Dissipation of Ballistic Impact Energy in Kevlar KM-2 Fabric, Part 2: Prediction of Ballistic Performance

    DTIC Science & Technology

    2004-05-01

    fabrics made from high-strength fibers, such as Kevlar,* Zylon ,† Armos,‡ and Spectra,§ have been widely used in flexible armors such as ballistic vests...pull-out during low velocity (< 300 m/s) impacts of Zylon fabrics, especially when at least two boundaries were unclamped, when impact occurred near the...Kevlar is a registered trademark of DuPont. † Zylon is a registered trademark of Toyobo. ‡ Armos is a registered trademark of Kamenskvolokno JSC

  20. Determination of the accessibility of N-H groups of Kevlar 49 fibres by photoacoustic FTi. r. spectroscopy

    SciTech Connect

    Chatzi, E.G.; Urban, M.W.; Ishida, H.; Koenig, J.L.

    1986-12-01

    Fourier transform infrared (FTi.r.) photoacoustic spectroscopy in combination with deuterium exchange was used to determine the accessibility of the N-H groups of Kevlar 49 fibres. The spectra were corrected for the dependence of the photoacoustic signal on the frequency and the integrated intensities of the N-H and N-D stretching bands were used to calculate the fraction of accessible N-H groups. Exposure of the deuterated fibers to saturated water vapor showed a residual N-D stretching absorption, in agreement with the improved molecular packaging expected after heat treatment at high temperature.

  1. Quantitative orientational analysis of a polymeric material (Kevlar{sup {reg_sign}} fibers) with x-ray microspectroscopy

    SciTech Connect

    Smith, A.P.; Ade, H.

    1996-12-01

    It has previously been shown that x-ray linear dichroism microscopy can be utilized to image and determine orientation in a polymeric material at high spatial resolution. We have now expanded on this technique and extracted quantitative information about the orientation of specific functional groups in a polymeric system from submicron areas. This is accomplished by acquiring and analyzing spectral data sets rather than just images at specific energies. It has allowed us to compare the relative lateral orientation of various grades of Kevlar{sup {reg_sign}} fibers. {copyright} {ital 1996 American Institute of Physics.}

  2. Lung response to ultrafine Kevlar aramid synthetic fibrils following 2-year inhalation exposure in rats.

    PubMed

    Lee, K P; Kelly, D P; O'Neal, F O; Stadler, J C; Kennedy, G L

    1988-07-01

    Four groups of 100 male and 100 female rats were exposed to ultrafine Kevlar fibrils at concentrations of 0, 2.5, 25, and 100 fibrils/cc for 6 hr/day, 5 days/week for 2 years. One group was exposed to 400 fibrils/cc for 1 year and allowed to recover for 1 year. At 2.5 fibrils/cc, the lungs had normal alveolar architecture with a few dust-laden macrophages (dust cell response) in the alveolar airspaces. At 25 fibrils/cc, the lungs showed a dust cell response, slight Type II pneumocyte hyperplasia, alveolar bronchiolarization, and a negligible amount of collagenized fibrosis in the alveolar duct region. At 100 fibrils/cc, the same pulmonary responses were seen as at 25 fibrils/cc. In addition, cystic keratinizing squamous cell carcinoma (CKSCC) was found in 4 female rats, but not in male rats. Female rats had more prominent foamy alveolar macrophages, cholesterol granulomas, and alveolar bronchiolarization. These pulmonary lesions were related to the development of CKSCC. The lung tumors were derived from metaplastic squamous cells in areas of alveolar bronchiolarization. At 400 fibrils/cc following 1 year of recovery, the lung dust content, average fiber length, and the pulmonary lesions were markedly reduced, but slight centriacinar emphysema and minimal collagenized fibrosis were found in the alveolar duct region. One male and 6 female rats developed CKSCC. The lung tumors were a unique type of experimentally induced tumors in the rats and have not been seen as spontaneous tumors in man or animals. Therefore, the relevance of this type of lung tumor to the human situation is minimal.

  3. 33 CFR 155.1026 - Qualified individual and alternate qualified individual.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... must be available on a 24-hour basis. (b) The qualified individual and alternate must— (1) Speak fluent English; (2) Except as set out in paragraph (c) of this section, be located in the United States; (3)...

  4. 33 CFR 155.1026 - Qualified individual and alternate qualified individual.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... must be available on a 24-hour basis. (b) The qualified individual and alternate must— (1) Speak fluent English; (2) Except as set out in paragraph (c) of this section, be located in the United States; (3)...

  5. 33 CFR 155.1026 - Qualified individual and alternate qualified individual.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... must be available on a 24-hour basis. (b) The qualified individual and alternate must— (1) Speak fluent English; (2) Except as set out in paragraph (c) of this section, be located in the United States; (3)...

  6. 33 CFR 155.1026 - Qualified individual and alternate qualified individual.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... must be available on a 24-hour basis. (b) The qualified individual and alternate must— (1) Speak fluent English; (2) Except as set out in paragraph (c) of this section, be located in the United States; (3)...

  7. 33 CFR 155.1026 - Qualified individual and alternate qualified individual.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... must be available on a 24-hour basis. (b) The qualified individual and alternate must— (1) Speak fluent English; (2) Except as set out in paragraph (c) of this section, be located in the United States; (3)...

  8. Composite Overwrapped Pressure Vessel (COPV) Stress Rupture Testing

    NASA Technical Reports Server (NTRS)

    Greene, Nathanael J.; Saulsberry, Regor L.; Leifeste, Mark R.; Yoder, Tommy B.; Keddy, Chris P.; Forth, Scott C.; Russell, Rick W.

    2010-01-01

    This paper reports stress rupture testing of Kevlar(TradeMark) composite overwrapped pressure vessels (COPVs) at NASA White Sands Test Facility. This 6-year test program was part of the larger effort to predict and extend the lifetime of flight vessels. Tests were performed to characterize control parameters for stress rupture testing, and vessel life was predicted by statistical modeling. One highly instrumented 102-cm (40-in.) diameter Kevlar(TradeMark) COPV was tested to failure (burst) as a single-point model verification. Significant data were generated that will enhance development of improved NDE methods and predictive modeling techniques, and thus better address stress rupture and other composite durability concerns that affect pressure vessel safety, reliability and mission assurance.

  9. Composite Overwrapped Pressure Vessel(COPV) Stress Rupture Testing

    NASA Astrophysics Data System (ADS)

    Greene, Nathanael J.; Saulsberry, Regor L.; Leifeste, Mark, R.; Yoder, Tommy B.; Keddy, Chris P.; Forth, Scott C.; Russell, Rick W.

    2010-09-01

    This paper reports stress rupture testing of Kevlar® composite overwrapped pressure vessels(COPVs) at NASA White Sands Test Facility. This 6-year test program was part of the larger effort to predict and extend the lifetime of flight vessels. Tests were performed to characterize control parameters for stress rupture testing, and vessel life was predicted by statistical modeling. One highly instrumented 102-cm(40-in.) diameter Kevlar® COPV was tested to failure(burst) as a single-point model verification. Significant data were generated that will enhance development of improved NDE methods and predictive modeling techniques, and thus better address stress rupture and other composite durability concerns that affect pressure vessel safety, reliability and mission assurance.

  10. Compression failure mechanisms of composite structures

    NASA Technical Reports Server (NTRS)

    Hahn, H. T.; Sohi, M.; Moon, S.

    1986-01-01

    An experimental and analytical study was conducted to delineate the compression failure mechanisms of composite structures. The present report summarizes further results on kink band formation in unidirectional composites. In order to assess the compressive strengths and failure modes of fibers them selves, a fiber bundle was embedded in epoxy casting and tested in compression. A total of six different fibers were used together with two resins of different stiffnesses. The failure of highly anisotropic fibers such as Kevlar 49 and P-75 graphite was due to kinking of fibrils. However, the remaining fibers--T300 and T700 graphite, E-glass, and alumina--failed by localized microbuckling. Compressive strengths of the latter group of fibers were not fully utilized in their respective composite. In addition, acoustic emission monitoring revealed that fiber-matrix debonding did not occur gradually but suddenly at final failure. The kink band formation in unidirectional composites under compression was studied analytically and through microscopy. The material combinations selected include seven graphite/epoxy composites, two graphite/thermoplastic resin composites, one Kevlar 49/epoxy composite and one S-glass/epoxy composite.

  11. The Significance of Defects on the Failure of Fibre Composites,

    DTIC Science & Technology

    1981-12-01

    effects produced by discontinuous and kinked plies in unidirectional carbon fibre reinforced plastic under tension. The mean stress at failure on the...5 to6.5%) void contents on changes in torsional properties of carbon fibre reinforced plastic when exposed at various temperatures to dry or wet...properties of carbon fibre/Kevlar fibre reinforced plastic hybrid composites." RAE Technical Report 76057 (1976)* 15 G. Dorey, D.J. Portsmouth, Private

  12. Design development tests for composite crashworthy helicopter fuselage

    SciTech Connect

    Sen, J.K.; Dremann, C.C.

    1985-10-01

    Design development tests were conducted to investigate the crashworthy characteristics of composite helicopter fuselage subcomponents, and to design helicopter center beam/bulkhead specimens lighter than structural elements of honeycomb sandwich construction. Skinstringer designs of center beams - made of carbon, and hybrids of carbon and Kevlar - were fabricated and tested in axial compression. Crashworthy design parameters of specific energy, operating load and stroke efficiency were investigated. 8 references, 15 figures, 2 tables.

  13. Rapid detection and quantification of impact damage in composite structures

    NASA Technical Reports Server (NTRS)

    Zalameda, Joseph N.; Farley, Gary; Smith, Barry T.

    1991-01-01

    NDE results from thermographic and volumetric ultrasonic techniques are presented to illustrate the multidisciplinary NDE approach to impact-damage detection in such composite structures as are increasingly prevalent in helicopters. Attention is given to both flat-panel and 'y-stiffened' panel specimens; these were fabricated either with kevlar or carbon fiber through-the-thickness reinforcements. While thermal inspection identifies impact damage, volumetric imaging quantifies the impact-generated delaminations through the volume of the structure.

  14. Tests of shielding effectiveness of Kevlar and Nextel onboard the International Space Station and the Foton-M3 capsule.

    PubMed

    Pugliese, M; Bengin, V; Casolino, M; Roca, V; Zanini, A; Durante, M

    2010-08-01

    Radiation assessment and protection in space is the first step in planning future missions to the Moon and Mars, where mission and number of space travelers will increase and the protection of the geomagnetic shielding against the cosmic radiation will be absent. In this framework, the shielding effectiveness of two flexible materials, Kevlar and Nextel, were tested, which are largely used in the construction of spacecrafts. Accelerator-based tests clearly demonstrated that Kevlar is an excellent shield for heavy ions, close to polyethylene, whereas Nextel shows poor shielding characteristics. Measurements on flight performed onboard of the International Space Station and of the Foton-M3 capsule have been carried out with special attention to the neutron component; shielded and unshielded detectors (thermoluminescence dosemeters, bubble detectors) were exposed to a real radiation environment to test the shielding properties of the materials under study. The results indicate no significant effects of shielding, suggesting that thin shields in low-Earth Orbit have little effect on absorbed dose.

  15. Effect of Mesoscale and Multiscale Modeling on the Performance of Kevlar Woven Fabric Subjected to Ballistic Impact: A Numerical Study

    NASA Astrophysics Data System (ADS)

    Jia, Xin; Huang, Zhengxiang; Zu, Xudong; Gu, Xiaohui; Xiao, Qiangqiang

    2013-12-01

    In this study, an optimal finite element model of Kevlar woven fabric that is more computational efficient compared with existing models was developed to simulate ballistic impact onto fabric. Kevlar woven fabric was modeled to yarn level architecture by using the hybrid elements analysis (HEA), which uses solid elements in modeling the yarns at the impact region and uses shell elements in modeling the yarns away from the impact region. Three HEA configurations were constructed, in which the solid element region was set as about one, two, and three times that of the projectile's diameter with impact velocities of 30 m/s (non-perforation case) and 200 m/s (perforation case) to determine the optimal ratio between the solid element region and the shell element region. To further reduce computational time and to maintain the necessary accuracy, three multiscale models were presented also. These multiscale models combine the local region with the yarn level architecture by using the HEA approach and the global region with homogenous level architecture. The effect of the varying ratios of the local and global area on the ballistic performance of fabric was discussed. The deformation and damage mechanisms of fabric were analyzed and compared among numerical models. Simulation results indicate that the multiscale model based on HEA accurately reproduces the baseline results and obviously decreases computational time.

  16. Performances of Kevlar and Polyethylene as radiation shielding on-board the International Space Station in high latitude radiation environment.

    PubMed

    Narici, Livio; Casolino, Marco; Di Fino, Luca; Larosa, Marianna; Picozza, Piergiorgio; Rizzo, Alessandro; Zaconte, Veronica

    2017-05-10

    Passive radiation shielding is a mandatory element in the design of an integrated solution to mitigate the effects of radiation during long deep space voyages for human exploration. Understanding and exploiting the characteristics of materials suitable for radiation shielding in space flights is, therefore, of primary importance. We present here the results of the first space-test on Kevlar and Polyethylene radiation shielding capabilities including direct measurements of the background baseline (no shield). Measurements are performed on-board of the International Space Station (Columbus modulus) during the ALTEA-shield ESA sponsored program. For the first time the shielding capability of such materials has been tested in a radiation environment similar to the deep-space one, thanks to the feature of the ALTEA system, which allows to select only high latitude orbital tracts of the International Space Station. Polyethylene is widely used for radiation shielding in space and therefore it is an excellent benchmark material to be used in comparative investigations. In this work we show that Kevlar has radiation shielding performances comparable to the Polyethylene ones, reaching a dose rate reduction of 32 ± 2% and a dose equivalent rate reduction of 55 ± 4% (for a shield of 10 g/cm(2)).

  17. 24 CFR 236.710 - Qualified tenant.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... Qualified Tenant found in § 236.2 of subpart A (contained in the April 1, 1995 edition of 24 CFR, parts 220... Income, as defined in § 236.2 of subpart A (contained in the April 1, 1995 edition of 24 CFR, parts 220...” in 24 CFR 236.2 (contained in the April 1, 1995 edition of 24 CFR, parts 220 to 499; see the Savings...

  18. 24 CFR 236.710 - Qualified tenant.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... Qualified Tenant found in § 236.2 of subpart A (contained in the April 1, 1995 edition of 24 CFR, parts 220... Income, as defined in § 236.2 of subpart A (contained in the April 1, 1995 edition of 24 CFR, parts 220...” in 24 CFR 236.2 (contained in the April 1, 1995 edition of 24 CFR, parts 220 to 499; see the Savings...

  19. The practical skills of newly qualified nurses.

    PubMed

    Danbjørg, Dorthe Boe; Birkelund, Regner

    2011-02-01

    This paper reports the findings from a study of newly qualified nurses and which subjects the nurses regarded as the most important in order to be able to live up to the requirements of clinical practice, and how they experience their potential for developing practical and moral skills, after the decrease in practical training. A qualitative approach guided the research process and the analysis of the data. The data was collected by participant observation and qualitative interviews with four nurses as informants. The conclusions made in this study are based on the statements and the observations of the newly qualified nurses. Our findings are discussed in relation to the Aristotelian concept and other relevant literature. The main message is that the newly qualified nurses did not feel equipped when they finished their training. This could be interpreted as a direct consequence of the decrease in practical training. Our study also underlines that the way nursing theory is perceived and taught is problematic. The interviews revealed that the nurses think that nursing theories should be applied directly in practice. This misunderstanding is probably also applicable to the teachers of the theories.

  20. Receptivity to Bariatric Surgery in Qualified Patients

    PubMed Central

    Fung, Michael; Wharton, Sean; Macpherson, Alison

    2016-01-01

    Objectives. Bariatric surgery has been shown to be an effective intervention for weight loss and diabetes management. Despite this, many patients qualified for bariatric surgery are not interested in undergoing the procedure. The objective of this study is to determine the factors influencing receptivity to bariatric surgery among those who qualify for the procedure. Methods. Patients attending a publicly funded weight management clinic who qualified for bariatric surgery were asked to complete an elective questionnaire between February 2013 and April 2014. Results. A total of 371 patients (72% female) completed the questionnaire. Only 87 of 371 (23%) participants were interested in bariatric surgery. Individuals interested in bariatric surgery had a higher BMI (48.0 versus 46.2 kg/m2, P = 0.03) and believed that they would lose more weight with surgery (51 versus 44 kg, P = 0.0069). Those who scored highly on past weight loss success and financial concerns were less likely to be interested in bariatric surgery, whereas those who scored highly on high receptivity to surgery and positive social support were more likely to be interested in bariatric surgery. Conclusion. Although participants overestimated the effect of bariatric surgery on weight loss, most were still not interested in bariatric surgery. PMID:27516900

  1. Reliability Considerations for Composite Overwrapped Pressure Vessels on Spacecraft

    NASA Technical Reports Server (NTRS)

    Murthy, Pappu L. N.; Gyekenyesi, John P.; Grimes-Ledesma, Lorie; Phoenix, S. L.

    2007-01-01

    Composite Overwrapped Pressure Vessels (COPVs) are used to store gases under high pressure onboard spacecraft. These are used for a variety of purposes such as propelling liquid fuel etc, Kevlar, glass, Carbon and other more recent fibers have all been in use to overwrap the vessels. COPVs usually have a thin metallic liner with the primary purpose of containing the gases and prevent any leakage. The liner is overwrapped with filament wound composite such as Kevlar, Carbon or Glass fiber. Although the liner is required to perform in the leak before break mode making the failure a relatively benign mode, the overwrap can fail catastrophically under sustained load due to stress rupture. It is this failure mode that is of major concern as the stored energy of such vessels is often great enough ta cause loss of crew and vehicle. The present paper addresses some of the reliability concerns associated specifically with Kevlar Composite Overwrapped Pressure Vessels. The primary focus of the paper is on how reliability of COPV's are established for the purpose of deciding in general their flight worthiness and continued use. Analytical models based on existing design data will be presented showing how to achieve the required reliability metric to the end of a specific period of performance. Uncertainties in the design parameters and how they affect reliability and confidence intervals will be addressed as well. Some trade studies showing how reliability changes with time during a program period will be presented.

  2. 30 CFR 75.153 - Electrical work; qualified person.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Electrical work; qualified person. 75.153....153 Electrical work; qualified person. (a) Except as provided in paragraph (f) of this section, an individual is a qualified person within the meaning of §§ 75.511 and 75.512 to perform electrical work (other...

  3. 30 CFR 77.103 - Electrical work; qualified person.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Electrical work; qualified person. 77.103... SAFETY AND HEALTH MANDATORY SAFETY STANDARDS, SURFACE COAL MINES AND SURFACE WORK AREAS OF UNDERGROUND COAL MINES Qualified and Certified Persons § 77.103 Electrical work; qualified person. (a) Except as...

  4. 30 CFR 77.103 - Electrical work; qualified person.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Electrical work; qualified person. 77.103... SAFETY AND HEALTH MANDATORY SAFETY STANDARDS, SURFACE COAL MINES AND SURFACE WORK AREAS OF UNDERGROUND COAL MINES Qualified and Certified Persons § 77.103 Electrical work; qualified person. (a) Except as...

  5. 30 CFR 75.153 - Electrical work; qualified person.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Electrical work; qualified person. 75.153....153 Electrical work; qualified person. (a) Except as provided in paragraph (f) of this section, an individual is a qualified person within the meaning of §§ 75.511 and 75.512 to perform electrical work (other...

  6. 9 CFR 201.73 - Scale operators to be qualified.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 9 Animals and Animal Products 2 2014-01-01 2014-01-01 false Scale operators to be qualified. 201... ACT Services § 201.73 Scale operators to be qualified. Stockyard owners, market agencies, dealers, packers, and live poultry dealers shall employ qualified persons to operate scales for weighing livestock...

  7. 9 CFR 201.73 - Scale operators to be qualified.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 9 Animals and Animal Products 2 2012-01-01 2012-01-01 false Scale operators to be qualified. 201... ACT Services § 201.73 Scale operators to be qualified. Stockyard owners, market agencies, dealers, packers, and live poultry dealers shall employ qualified persons to operate scales for weighing livestock...

  8. 9 CFR 201.73 - Scale operators to be qualified.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 9 Animals and Animal Products 2 2013-01-01 2013-01-01 false Scale operators to be qualified. 201... ACT Services § 201.73 Scale operators to be qualified. Stockyard owners, market agencies, dealers, packers, and live poultry dealers shall employ qualified persons to operate scales for weighing livestock...

  9. 9 CFR 201.73 - Scale operators to be qualified.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 9 Animals and Animal Products 2 2010-01-01 2010-01-01 false Scale operators to be qualified. 201... ACT Services § 201.73 Scale operators to be qualified. Stockyard owners, market agencies, dealers, packers, and live poultry dealers shall employ qualified persons to operate scales for weighing livestock...

  10. 9 CFR 201.73 - Scale operators to be qualified.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 9 Animals and Animal Products 2 2011-01-01 2011-01-01 false Scale operators to be qualified. 201... ACT Services § 201.73 Scale operators to be qualified. Stockyard owners, market agencies, dealers, packers, and live poultry dealers shall employ qualified persons to operate scales for weighing livestock...

  11. 26 CFR 54.4980B-4 - Qualifying events.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 26 Internal Revenue 17 2014-04-01 2014-04-01 false Qualifying events. 54.4980B-4 Section 54.4980B... EXCISE TAXES (CONTINUED) PENSION EXCISE TAXES § 54.4980B-4 Qualifying events. The determination of what constitutes a qualifying event is addressed in the following questions and answers: Q-1: What is a...

  12. 26 CFR 54.4980B-4 - Qualifying events.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 26 Internal Revenue 17 2011-04-01 2011-04-01 false Qualifying events. 54.4980B-4 Section 54.4980B... EXCISE TAXES (CONTINUED) PENSION EXCISE TAXES § 54.4980B-4 Qualifying events. The determination of what constitutes a qualifying event is addressed in the following questions and answers: Q-1: What is a...

  13. 26 CFR 54.4980B-4 - Qualifying events.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 26 Internal Revenue 17 2012-04-01 2012-04-01 false Qualifying events. 54.4980B-4 Section 54.4980B... EXCISE TAXES (CONTINUED) PENSION EXCISE TAXES § 54.4980B-4 Qualifying events. The determination of what constitutes a qualifying event is addressed in the following questions and answers: Q-1: What is a...

  14. 26 CFR 54.4980B-4 - Qualifying events.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 26 Internal Revenue 17 2013-04-01 2013-04-01 false Qualifying events. 54.4980B-4 Section 54.4980B... EXCISE TAXES (CONTINUED) PENSION EXCISE TAXES § 54.4980B-4 Qualifying events. The determination of what constitutes a qualifying event is addressed in the following questions and answers: Q-1: What is a...

  15. 26 CFR 1.25-3 - Qualified mortgage credit certificate.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 26 Internal Revenue 1 2011-04-01 2009-04-01 true Qualified mortgage credit certificate. 1.25-3... TAXES Changes in Rates During A Taxable Year § 1.25-3 Qualified mortgage credit certificate. (a)-(g)(1... certificates for certain refinancings—(1) In general. If the issuer of a qualified mortgage credit...

  16. 49 CFR 604.7 - Qualified human service organizations.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 49 Transportation 7 2010-10-01 2010-10-01 false Qualified human service organizations. 604.7... ADMINISTRATION, DEPARTMENT OF TRANSPORTATION CHARTER SERVICE Exceptions § 604.7 Qualified human service organizations. (a) A recipient may provide charter service to a qualified human service organization (QHSO)...

  17. 49 CFR 604.7 - Qualified human service organizations.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 49 Transportation 7 2011-10-01 2011-10-01 false Qualified human service organizations. 604.7... ADMINISTRATION, DEPARTMENT OF TRANSPORTATION CHARTER SERVICE Exceptions § 604.7 Qualified human service organizations. (a) A recipient may provide charter service to a qualified human service organization (QHSO)...

  18. 26 CFR 1.884-5 - Qualified resident.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 26 Internal Revenue 9 2010-04-01 2010-04-01 false Qualified resident. 1.884-5 Section 1.884-5...) INCOME TAXES Foreign Corporations § 1.884-5 Qualified resident. (a) Definition of qualified resident. A... country (within the meaning of such treaty) and either— (1) Meets the requirements of paragraphs (b)...

  19. 42 CFR 435.119 - Qualified family members.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 42 Public Health 4 2010-10-01 2010-10-01 false Qualified family members. 435.119 Section 435.119... Family Members § 435.119 Qualified family members. (a) Definition. A qualified family member is any member of a family, including pregnant women and children eligible for Medicaid under § 435.116 of...

  20. 42 CFR 436.121 - Qualified family members.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 42 Public Health 4 2010-10-01 2010-10-01 false Qualified family members. 436.121 Section 436.121... Coverage of the Categorically Needy § 436.121 Qualified family members. (a) Definition. A qualified family member is any member of a family, including pregnant women and children eligible for Medicaid under §...

  1. 30 CFR 77.103 - Electrical work; qualified person.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Electrical work; qualified person. 77.103... COAL MINES Qualified and Certified Persons § 77.103 Electrical work; qualified person. (a) Except as... Subparts F, G, H, I, and J of this Part 77 to perform electrical work (other than work on energized surface...

  2. 30 CFR 75.153 - Electrical work; qualified person.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Electrical work; qualified person. 75.153....153 Electrical work; qualified person. (a) Except as provided in paragraph (f) of this section, an individual is a qualified person within the meaning of §§ 75.511 and 75.512 to perform electrical work (other...

  3. 30 CFR 77.103 - Electrical work; qualified person.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Electrical work; qualified person. 77.103... COAL MINES Qualified and Certified Persons § 77.103 Electrical work; qualified person. (a) Except as... Subparts F, G, H, I, and J of this Part 77 to perform electrical work (other than work on energized surface...

  4. 30 CFR 75.153 - Electrical work; qualified person.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Electrical work; qualified person. 75.153....153 Electrical work; qualified person. (a) Except as provided in paragraph (f) of this section, an individual is a qualified person within the meaning of §§ 75.511 and 75.512 to perform electrical work (other...

  5. 49 CFR 604.7 - Qualified human service organizations.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 49 Transportation 7 2012-10-01 2012-10-01 false Qualified human service organizations. 604.7... ADMINISTRATION, DEPARTMENT OF TRANSPORTATION CHARTER SERVICE Exceptions § 604.7 Qualified human service organizations. (a) A recipient may provide charter service to a qualified human service organization (QHSO) for...

  6. 49 CFR 604.7 - Qualified human service organizations.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 49 Transportation 7 2014-10-01 2014-10-01 false Qualified human service organizations. 604.7... ADMINISTRATION, DEPARTMENT OF TRANSPORTATION CHARTER SERVICE Exceptions § 604.7 Qualified human service organizations. (a) A recipient may provide charter service to a qualified human service organization (QHSO) for...

  7. 49 CFR 604.7 - Qualified human service organizations.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 49 Transportation 7 2013-10-01 2013-10-01 false Qualified human service organizations. 604.7... ADMINISTRATION, DEPARTMENT OF TRANSPORTATION CHARTER SERVICE Exceptions § 604.7 Qualified human service organizations. (a) A recipient may provide charter service to a qualified human service organization (QHSO) for...

  8. 26 CFR 1.884-5 - Qualified resident.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 26 Internal Revenue 9 2011-04-01 2011-04-01 false Qualified resident. 1.884-5 Section 1.884-5 Internal Revenue INTERNAL REVENUE SERVICE, DEPARTMENT OF THE TREASURY (CONTINUED) INCOME TAX (CONTINUED) INCOME TAXES (CONTINUED) Foreign Corporations § 1.884-5 Qualified resident. (a) Definition of qualified resident. A foreign corporation is a...

  9. 46 CFR 4.03-6 - Qualified medical personnel.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 1 2010-10-01 2010-10-01 false Qualified medical personnel. 4.03-6 Section 4.03-6... AND INVESTIGATIONS Definitions § 4.03-6 Qualified medical personnel. The term qualified medical personnel means a physician, physician's assistant, nurse, emergency medical technician, or other...

  10. 12 CFR 621.4 - Audit by qualified public accountant.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 12 Banks and Banking 6 2011-01-01 2011-01-01 false Audit by qualified public accountant. 621.4... REQUIREMENTS General Rules § 621.4 Audit by qualified public accountant. (a) Each institution shall, at least annually, have its financial statements audited by a qualified public accountant in accordance...

  11. 30 CFR 77.103 - Electrical work; qualified person.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Electrical work; qualified person. 77.103... COAL MINES Qualified and Certified Persons § 77.103 Electrical work; qualified person. (a) Except as... Subparts F, G, H, I, and J of this Part 77 to perform electrical work (other than work on energized...

  12. 30 CFR 75.153 - Electrical work; qualified person.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Electrical work; qualified person. 75.153....153 Electrical work; qualified person. (a) Except as provided in paragraph (f) of this section, an individual is a qualified person within the meaning of §§ 75.511 and 75.512 to perform electrical work...

  13. 26 CFR 1.132-9 - Qualified transportation fringes.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... compensation at a specified future date or a fixed amount of qualified transportation fringes to be provided for a specified future period (such as qualified parking to be used during a future calendar month... that is not used for qualified transportation fringes is not refunded to the employee at any...

  14. 26 CFR 1.132-9 - Qualified transportation fringes.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... compensation at a specified future date or a fixed amount of qualified transportation fringes to be provided for a specified future period (such as qualified parking to be used during a future calendar month... that is not used for qualified transportation fringes is not refunded to the employee at any...

  15. 7 CFR 1221.24 - Qualified sorghum producer organization.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 10 2013-01-01 2013-01-01 false Qualified sorghum producer organization. 1221.24... SORGHUM PROMOTION, RESEARCH, AND INFORMATION ORDER Sorghum Promotion, Research, and Information Order Definitions § 1221.24 Qualified sorghum producer organization. Qualified sorghum producer organization means...

  16. 7 CFR 1221.24 - Qualified sorghum producer organization.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 10 2011-01-01 2011-01-01 false Qualified sorghum producer organization. 1221.24... SORGHUM PROMOTION, RESEARCH, AND INFORMATION ORDER Sorghum Promotion, Research, and Information Order Definitions § 1221.24 Qualified sorghum producer organization. Qualified sorghum producer organization means...

  17. 7 CFR 1221.24 - Qualified sorghum producer organization.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 10 2012-01-01 2012-01-01 false Qualified sorghum producer organization. 1221.24... SORGHUM PROMOTION, RESEARCH, AND INFORMATION ORDER Sorghum Promotion, Research, and Information Order Definitions § 1221.24 Qualified sorghum producer organization. Qualified sorghum producer organization means...

  18. 7 CFR 1221.24 - Qualified sorghum producer organization.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 10 2014-01-01 2014-01-01 false Qualified sorghum producer organization. 1221.24... SORGHUM PROMOTION, RESEARCH, AND INFORMATION ORDER Sorghum Promotion, Research, and Information Order Definitions § 1221.24 Qualified sorghum producer organization. Qualified sorghum producer organization means...

  19. 41 CFR 101-29.207 - Qualified products list (QPL).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 41 Public Contracts and Property Management 2 2011-07-01 2007-07-01 true Qualified products list (QPL). 101-29.207 Section 101-29.207 Public Contracts and Property Management Federal Property... PRODUCT DESCRIPTIONS 29.2-Definitions § 101-29.207 Qualified products list (QPL). A qualified products...

  20. 41 CFR 101-29.207 - Qualified products list (QPL).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 41 Public Contracts and Property Management 2 2010-07-01 2010-07-01 true Qualified products list (QPL). 101-29.207 Section 101-29.207 Public Contracts and Property Management Federal Property... PRODUCT DESCRIPTIONS 29.2-Definitions § 101-29.207 Qualified products list (QPL). A qualified products...

  1. 7 CFR 701.210 - Qualifying minimum cost of restoration.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 7 2011-01-01 2011-01-01 false Qualifying minimum cost of restoration. 701.210... Restoration Program § 701.210 Qualifying minimum cost of restoration. (a) FSA will establish the minimum qualifying cost of restoration, which may vary by State or region. (b) An applicant may request a waiver of...

  2. 46 CFR 4.03-6 - Qualified medical personnel.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 1 2012-10-01 2012-10-01 false Qualified medical personnel. 4.03-6 Section 4.03-6... AND INVESTIGATIONS Definitions § 4.03-6 Qualified medical personnel. The term qualified medical personnel means a physician, physician's assistant, nurse, emergency medical technician, or other person...

  3. 11 CFR 9002.11 - Qualified campaign expense.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 11 Federal Elections 1 2010-01-01 2010-01-01 false Qualified campaign expense. 9002.11 Section 9002.11 Federal Elections FEDERAL ELECTION COMMISSION PRESIDENTIAL ELECTION CAMPAIGN FUND: GENERAL ELECTION FINANCING DEFINITIONS § 9002.11 Qualified campaign expense. (a) Qualified campaign expense...

  4. 31 CFR 321.4 - Paying agents previously qualified.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 31 Money and Finance: Treasury 2 2010-07-01 2010-07-01 false Paying agents previously qualified...) Procedures for Qualification § 321.4 Paying agents previously qualified. Institutions qualified as paying agents under previous revisions of this part are authorized to continue to act in that capacity without...

  5. 31 CFR 317.4 - Issuing agents currently qualified.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 31 Money and Finance: Treasury 2 2010-07-01 2010-07-01 false Issuing agents currently qualified... ISSUE OF UNITED STATES SAVINGS BONDS § 317.4 Issuing agents currently qualified. Each organization, qualified as an issuing agent under a trust agreement currently in effect, is authorized to continue to act...

  6. 31 CFR 321.4 - Paying agents previously qualified.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 31 Money and Finance: Treasury 2 2014-07-01 2014-07-01 false Paying agents previously qualified... SHARES) Procedures for Qualification § 321.4 Paying agents previously qualified. Institutions qualified as paying agents under previous revisions of this part are authorized to continue to act in that...

  7. 31 CFR 321.4 - Paying agents previously qualified.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 31 Money and Finance:Treasury 2 2011-07-01 2011-07-01 false Paying agents previously qualified...) Procedures for Qualification § 321.4 Paying agents previously qualified. Institutions qualified as paying agents under previous revisions of this part are authorized to continue to act in that capacity without...

  8. 31 CFR 317.4 - Issuing agents currently qualified.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 31 Money and Finance:Treasury 2 2012-07-01 2012-07-01 false Issuing agents currently qualified... ISSUE OF UNITED STATES SAVINGS BONDS § 317.4 Issuing agents currently qualified. Each organization, qualified as an issuing agent under a trust agreement currently in effect, is authorized to continue to act...

  9. 31 CFR 317.4 - Issuing agents currently qualified.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 31 Money and Finance:Treasury 2 2013-07-01 2013-07-01 false Issuing agents currently qualified... ISSUE OF UNITED STATES SAVINGS BONDS § 317.4 Issuing agents currently qualified. Each organization, qualified as an issuing agent under a trust agreement currently in effect, is authorized to continue to act...

  10. 31 CFR 321.4 - Paying agents previously qualified.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 31 Money and Finance:Treasury 2 2012-07-01 2012-07-01 false Paying agents previously qualified... SHARES) Procedures for Qualification § 321.4 Paying agents previously qualified. Institutions qualified as paying agents under previous revisions of this part are authorized to continue to act in that...

  11. 31 CFR 321.4 - Paying agents previously qualified.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 31 Money and Finance:Treasury 2 2013-07-01 2013-07-01 false Paying agents previously qualified... SHARES) Procedures for Qualification § 321.4 Paying agents previously qualified. Institutions qualified as paying agents under previous revisions of this part are authorized to continue to act in that...

  12. 31 CFR 317.4 - Issuing agents currently qualified.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 31 Money and Finance:Treasury 2 2011-07-01 2011-07-01 false Issuing agents currently qualified... ISSUE OF UNITED STATES SAVINGS BONDS § 317.4 Issuing agents currently qualified. Each organization, qualified as an issuing agent under a trust agreement currently in effect, is authorized to continue to act...

  13. 31 CFR 317.4 - Issuing agents currently qualified.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 31 Money and Finance: Treasury 2 2014-07-01 2014-07-01 false Issuing agents currently qualified... FOR ISSUE OF UNITED STATES SAVINGS BONDS § 317.4 Issuing agents currently qualified. Each organization, qualified as an issuing agent under a trust agreement currently in effect, is authorized to continue to act...

  14. 28 CFR 41.32 - Qualified handicapped person.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 28 Judicial Administration 1 2010-07-01 2010-07-01 false Qualified handicapped person. 41.32..., NONDISCRIMINATION ON THE BASIS OF HANDICAP IN FEDERALLY ASSISTED PROGRAMS Standards for Determining Who Are Handicapped Persons § 41.32 Qualified handicapped person. Qualified handicapped person means: (a) With respect...

  15. 45 CFR 1151.12 - Qualified handicapped person.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 45 Public Welfare 3 2010-10-01 2010-10-01 false Qualified handicapped person. 1151.12 Section 1151... AND THE HUMANITIES NATIONAL ENDOWMENT FOR THE ARTS NONDISCRIMINATION ON THE BASIS OF HANDICAP Standards for Determining Who Are Handicapped Persons § 1151.12 Qualified handicapped person. Qualified...

  16. 42 CFR 436.121 - Qualified family members.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 42 Public Health 4 2011-10-01 2011-10-01 false Qualified family members. 436.121 Section 436.121... Coverage of the Categorically Needy § 436.121 Qualified family members. (a) Definition. A qualified family member is any member of a family, including pregnant women and children eligible for Medicaid under § 436...

  17. 42 CFR 435.119 - Qualified family members.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 42 Public Health 4 2011-10-01 2011-10-01 false Qualified family members. 435.119 Section 435.119... Family Members § 435.119 Qualified family members. (a) Definition. A qualified family member is any member of a family, including pregnant women and children eligible for Medicaid under § 435.116 of this...

  18. 42 CFR 436.121 - Qualified family members.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 42 Public Health 4 2013-10-01 2013-10-01 false Qualified family members. 436.121 Section 436.121... Coverage of the Categorically Needy § 436.121 Qualified family members. (a) Definition. A qualified family member is any member of a family, including pregnant women and children eligible for Medicaid under § 436...

  19. 42 CFR 436.121 - Qualified family members.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 42 Public Health 4 2012-10-01 2012-10-01 false Qualified family members. 436.121 Section 436.121... Coverage of the Categorically Needy § 436.121 Qualified family members. (a) Definition. A qualified family member is any member of a family, including pregnant women and children eligible for Medicaid under § 436...

  20. The Highly Qualified Physical Education Teacher: Traveling the Professional Pathway

    ERIC Educational Resources Information Center

    Van Volkinburg, Pat; Marston, Rip; Napper-Owen, Gloria

    2008-01-01

    Defining the quantifiable elements of a highly qualified physical education teacher is challenging. For the past two years, a task force of the National Association for Sport and Physical Education (NASPE) has worked on describing characteristics associated with highly qualified physical education teachers. Highly qualified teachers are needed to…

  1. 12 CFR 621.4 - Audit by qualified public accountant.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 12 Banks and Banking 7 2014-01-01 2014-01-01 false Audit by qualified public accountant. 621.4... REQUIREMENTS General Rules § 621.4 Audit by qualified public accountant. (a) Each institution shall, at least annually, have its financial statements audited by a qualified public accountant in accordance with...

  2. 12 CFR 621.4 - Audit by qualified public accountant.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 12 Banks and Banking 7 2013-01-01 2013-01-01 false Audit by qualified public accountant. 621.4... REQUIREMENTS General Rules § 621.4 Audit by qualified public accountant. (a) Each institution shall, at least annually, have its financial statements audited by a qualified public accountant in accordance with...

  3. 12 CFR 621.4 - Audit by qualified public accountant.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 12 Banks and Banking 7 2012-01-01 2012-01-01 false Audit by qualified public accountant. 621.4... REQUIREMENTS General Rules § 621.4 Audit by qualified public accountant. (a) Each institution shall, at least annually, have its financial statements audited by a qualified public accountant in accordance with...

  4. 5 CFR 847.402 - Definition of qualifying move.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 5 Administrative Personnel 2 2011-01-01 2011-01-01 false Definition of qualifying move. 847.402....402 Definition of qualifying move. (a) A qualifying move occurring after December 31, 1965, and before... under CSRS or FERS retroactive to the date of the move must meet all the following criteria: (1)(i)...

  5. 5 CFR 847.402 - Definition of qualifying move.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 5 Administrative Personnel 2 2013-01-01 2013-01-01 false Definition of qualifying move. 847.402....402 Definition of qualifying move. (a) A qualifying move occurring after December 31, 1965, and before... under CSRS or FERS retroactive to the date of the move must meet all the following criteria: (1)(i)...

  6. 5 CFR 847.402 - Definition of qualifying move.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 5 Administrative Personnel 2 2012-01-01 2012-01-01 false Definition of qualifying move. 847.402....402 Definition of qualifying move. (a) A qualifying move occurring after December 31, 1965, and before... under CSRS or FERS retroactive to the date of the move must meet all the following criteria: (1)(i)...

  7. 5 CFR 847.402 - Definition of qualifying move.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 5 Administrative Personnel 2 2014-01-01 2014-01-01 false Definition of qualifying move. 847.402....402 Definition of qualifying move. (a) A qualifying move occurring after December 31, 1965, and before... under CSRS or FERS retroactive to the date of the move must meet all the following criteria: (1)(i)...

  8. 10 CFR 436.32 - Qualified contractors lists.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 10 Energy 3 2010-01-01 2010-01-01 false Qualified contractors lists. 436.32 Section 436.32 Energy... Procedures for Energy Savings Performance Contracting § 436.32 Qualified contractors lists. (a) DOE shall... energy savings performance contracts. (c) DOE may remove a firm from DOE's list of qualified...

  9. 9 CFR 77.36 - Interstate movement from qualified herds.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 9 Animals and Animal Products 1 2010-01-01 2010-01-01 false Interstate movement from qualified... TUBERCULOSIS Captive Cervids § 77.36 Interstate movement from qualified herds. (a) Qualifications. To be... and is classified as a qualified herd. (b) Movement allowed. Except as provided in § 77.23 with regard...

  10. 11 CFR 9032.9 - Qualified campaign expense.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 11 Federal Elections 1 2012-01-01 2012-01-01 false Qualified campaign expense. 9032.9 Section 9032.9 Federal Elections FEDERAL ELECTION COMMISSION PRESIDENTIAL ELECTION CAMPAIGN FUND: PRESIDENTIAL PRIMARY MATCHING FUND DEFINITIONS § 9032.9 Qualified campaign expense. (a) Qualified campaign...

  11. 11 CFR 9032.9 - Qualified campaign expense.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 11 Federal Elections 1 2011-01-01 2011-01-01 false Qualified campaign expense. 9032.9 Section 9032.9 Federal Elections FEDERAL ELECTION COMMISSION PRESIDENTIAL ELECTION CAMPAIGN FUND: PRESIDENTIAL PRIMARY MATCHING FUND DEFINITIONS § 9032.9 Qualified campaign expense. (a) Qualified campaign...

  12. 11 CFR 9032.9 - Qualified campaign expense.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 11 Federal Elections 1 2010-01-01 2010-01-01 false Qualified campaign expense. 9032.9 Section 9032.9 Federal Elections FEDERAL ELECTION COMMISSION PRESIDENTIAL ELECTION CAMPAIGN FUND: PRESIDENTIAL PRIMARY MATCHING FUND DEFINITIONS § 9032.9 Qualified campaign expense. (a) Qualified campaign...

  13. 11 CFR 9032.9 - Qualified campaign expense.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 11 Federal Elections 1 2013-01-01 2012-01-01 true Qualified campaign expense. 9032.9 Section 9032.9 Federal Elections FEDERAL ELECTION COMMISSION PRESIDENTIAL ELECTION CAMPAIGN FUND: PRESIDENTIAL PRIMARY MATCHING FUND DEFINITIONS § 9032.9 Qualified campaign expense. (a) Qualified campaign...

  14. 11 CFR 9032.9 - Qualified campaign expense.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 11 Federal Elections 1 2014-01-01 2014-01-01 false Qualified campaign expense. 9032.9 Section 9032.9 Federal Elections FEDERAL ELECTION COMMISSION PRESIDENTIAL ELECTION CAMPAIGN FUND: PRESIDENTIAL PRIMARY MATCHING FUND DEFINITIONS § 9032.9 Qualified campaign expense. (a) Qualified campaign...

  15. 46 CFR 4.03-6 - Qualified medical personnel.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 1 2011-10-01 2011-10-01 false Qualified medical personnel. 4.03-6 Section 4.03-6... AND INVESTIGATIONS Definitions § 4.03-6 Qualified medical personnel. The term qualified medical personnel means a physician, physician's assistant, nurse, emergency medical technician, or other person...

  16. 26 CFR 1.132-9 - Qualified transportation fringes.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 26 Internal Revenue 2 2011-04-01 2011-04-01 false Qualified transportation fringes. 1.132-9... Qualified transportation fringes. (a) Table of contents. This section contains a list of the questions and answers in § 1.132-9. (1) General rules. Q-1. What is a qualified transportation fringe? Q-2. What is...

  17. 26 CFR 1.132-9 - Qualified transportation fringes.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 26 Internal Revenue 2 2010-04-01 2010-04-01 false Qualified transportation fringes. 1.132-9... Qualified transportation fringes. (a) Table of contents. This section contains a list of the questions and answers in § 1.132-9. (1) General rules. Q-1. What is a qualified transportation fringe? Q-2. What is...

  18. 26 CFR 301.7430-7 - Qualified offers.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... conference. (5) Remains open. A qualified offer must, by its terms, remain open for acceptance by the United... that would have resulted from the acceptance of E's qualified offer is a reduction in that liability of... 26 Internal Revenue 18 2010-04-01 2010-04-01 false Qualified offers. 301.7430-7 Section...

  19. 26 CFR 1.25-3 - Qualified mortgage credit certificate.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 26 Internal Revenue 1 2010-04-01 2010-04-01 true Qualified mortgage credit certificate. 1.25-3... TAXES Changes in Rates During A Taxable Year § 1.25-3 Qualified mortgage credit certificate. (a)-(g)(1... certificates for certain refinancings—(1) In general. If the issuer of a qualified mortgage credit certificate...

  20. 26 CFR 1.1092(c)-1 - Qualified covered calls.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 26 Internal Revenue 11 2010-04-01 2010-04-01 true Qualified covered calls. 1.1092(c)-1 Section 1... (CONTINUED) INCOME TAXES Wash Sales of Stock Or Securities § 1.1092(c)-1 Qualified covered calls. (a) In...), however, writing a qualified covered call option and owning the optioned stock is not treated as...

  1. Infrared thermographic analysis of polymer composites during ballistic impact

    NASA Technical Reports Server (NTRS)

    Hsieh, C. Y.; Nagarajan, S.; Zee, R. H.

    1992-01-01

    An infrared thermographic system was used to measure the surface temperature profile of composite materials under ballistic impact. The heat deposited was calculated based on the temperature profiles. The extent of damage induced in the materials was determined qualitatively from the measured data. The relative contribution of frictional heat to total energy absorption was evaluated, and the effect of the shape of the projectile on the extent of damage and temperature distribution in the composites was examined. The results show that graphite and polyethylene composite are more effective than Kevlar composite in dissipating heat during the ballistic impact penetration process due to their higher thermal conductivity.

  2. Tethers as Debris: Simulating Impacts of Kevlar Tethers on Shuttle Tiles

    NASA Technical Reports Server (NTRS)

    Evans, Steven W.

    2004-01-01

    In a previous paper I examined the effects of impacts of polymer tethers on aluminum plates using the SPHC hydrodynamic code. In this paper I apply tether models to a new target - models of Space Shuttle tiles developed during the STS 107 accident investigation. In this three-dimensional simulation, a short tether fragment strikes a single tile supported on an aluminum backing plate. A tile of the LI-900 material is modeled. Penetration and damage to the tile and the backwall are characterized for three normal impact velocities. The tether is modeled as a bundle of eight 1-mm strands, with the bundle having dimensions 2-mm x 4-mm x 20-cm. The bulk material properties used are those of Kevlar(TradeMark) 49, for which a Mie-Gruneisen multiphase equation of state (eos) is used. In addition, the strength model is applied in a linear sense, such that tensile loads along the strand length are supported, but there is no strength in the lateral directions. Tile models include the various layers making up the tile structure. The outermost layer is a relatively dense borosilicate glass, known as RCG, 0.5-mm thick. The RCG layer is present on the top and four sides of the tile. Below this coating is the bulk of the tile, 1.8- in thick, made of LI-900, a product consisting of rigidized fiberous silica with a density of 9 lWft3. Below the main insulating layer is a bottom layer of the same material that has been treated to increase its density by approximately 69% to improve its strength. This densified layer is bonded to a Strain Isolation Pad (SIP), modeled as a refractory felt fabric. The SIP is bonded to an aluminum 2024 wall 0.1-in thick. The tile and backwall materials use a Me-Gruneisen multiphase eos, with the exception of the SIP felt, which uses a fabric equation of state. Fabrics must be crushed to the full bulk material density before bulk material properties and a Mie-Gruneisen eos are applied. Tether fragment impact speeds of 3,7, and 10 km/s are simulated, with

  3. Analysis of Potential for Titanium Liner Buckling after Proof in a Large Kevlar/Epoxy COPV

    NASA Technical Reports Server (NTRS)

    Phoenix, S. Leigh; Kezirian, Michael T.

    2009-01-01

    We analyze the potential for liner buckling in a 40-in Kevlar49/epoxy overwrapped spherical pressure vessel (COPV) due to long, local depressions or valleys in the titanium liner, which appeared after proof testing (autofrettage). We begin by presenting the geometric characteristics of approximately 20 mil (0.02 in.) deep depressions measured by laser profilometry in several vessels. While such depths were more typical, depths of more than 40 mils (0.02 in.) were seen near the equator in one particular vessel. Such depressions are largely the result of overlap of the edges of overwrap bands (with rectangular cross-section prepreg tows) from the first or second wrap patterns particularly where they start and end. We then discuss the physical mechanisms of formation of the depressions during the autofrettage process in terms of uneven void compaction in the overwrap around the tow overlap lines and the resulting 10-fold increase in through-thickness stiffness of the overwrap. We consider the effects of liner plastic yielding mechanisms in the liner on residual bending moments and interface pressures with the overwrap both at the peak proof pressure (approx.6500 psi) and when reducing the pressure to 0 psi. During depressurization the Bauschinger phenomenon becomes very important whereby extensive yielding in tension reduces the magnitude of the yield threshold in compression by 30 to 40%, compared to the virgin annealed state of the liner titanium. In the absence of a depression, the liner is elastically stable in compression even at liner overwrap interface pressures nominally 6 times the approx. 1000 psi interface pressure that exists at 0 psi. Using a model based on a plate-on-an-elastic-foundation, we develop an extensive analysis of the possible destabilizing effects of a frozen-in valley. The analysis treats the modifying effects of the residual bending moments and interface pressures remaining after the proof hold as well as the Bauschinger effect on the

  4. Additional results on space environmental effects on polymer matrix composites: Experiment A0180

    NASA Technical Reports Server (NTRS)

    Tennyson, R. C.

    1992-01-01

    Additional experimental results on the atomic oxygen erosion of boron, Kevlar, and graphite fiber reinforced epoxy matrix composites are presented. Damage of composite laminates due to micrometeoroid/debris impacts is also examined with particular emphasis on the relationship between damage area and actual hole size due to particle penetration. Special attention is given to one micrometeoroid impact on an aluminum base plate which resulted in ejecta visible on an adjoining vertical flange structure.

  5. Participation in the Qualified Medical Beneficiary Program.

    PubMed

    Neumann, P J; Bernardin, M D; Evans, W N; Bayer, E J

    1995-01-01

    This article has three objectives: to estimate how many eligible elderly beneficiaries are participating in the Qualified Medicare Beneficiary (QMB) program; to determine the characteristics of participating and non participating eligibles; and to identify the most significant barriers to program participation. We used data from the Medicare Current Beneficiary Survey (MCBS) and the Medicare Buy-In file. We found that 41 percent of QMB eligibles are enrolled in the program; participation is higher for poor and less educated beneficiaries, those in poorer health, rural residents, African Americans, and Hispanics. Finally, we found that, in general, eligible beneficiaries are ill informed about the program.

  6. Residual stresses and their effects in composite laminates

    NASA Technical Reports Server (NTRS)

    Hahn, H. T.; Hwang, D. G.

    1983-01-01

    Residual stresses in composite laminates are caused by the anisotropy in expansional properties of constituent unidirectional plies. The effect of these residual stresses on dimensional stability is studied through the warping of unsymmetric (0 sub 4/90 sub 4)sub T graphite/epoxy laminates while their effect on ply failure is analyzed for (0/90)sub 2s Kevlar 49/epoxy laminate. The classical laminated plate theory is used to predict the warping of small and large panels. The change of warping does not indicate a noticeable stress relaxation at 75 C while it is very sensitive to moisture content and hence to environment. A prolonged gellation at the initial cure temperature reduces residual stresses while postcure does not. The matrix/interface cracking in dry (0/90)sub 2s Kevlar 49/epoxy laminate is shown to be the result of the residual stress exceeding the transverse strength.

  7. Residual stresses and their effects in composite laminates

    NASA Technical Reports Server (NTRS)

    Hahn, H. T.; Hwang, D. G.

    1983-01-01

    Residual stresses in composite laminates are caused by the anisotropy in expansional properties of constituent unidirectional plies. The effect of these residual stresses on dimensional stability is studied through the warping of unsymmetric (0 sub 4/90 sub 4)sub T graphite/epoxy laminates while their effect on ply failure is analyzed for (0/90)sub 2s Kevlar 49/epoxy laminate. The classical laminated plate theory is used to predict the warping of small and large panels. The change of warping does not indicate a noticeable stress relaxation at 75 C while it is very sensitive to moisture content and hence to environment. A prolonged gellation at the initial cure temperature reduces residual stresses while postcure does not. The matrix/interface cracking in dry (0/90)sub 2s Kevlar 49/epoxy laminate is shown to be the result of the residual stress exceeding the transverse strength.

  8. Crash energy absorbing composite sub-floor structure

    NASA Technical Reports Server (NTRS)

    Farley, G. L.

    1986-01-01

    Static crushing tests were conducted on four different beam concepts; honeycomb sandwich, sine-wave and two integrally stiffened designs. The sine-wave beams, depending upon specimen geometry, has the highest energy absorption potential of the four concepts evaluated. All beam designs produced a progressive crushing mode similar to tube specimens. The energy absorption capability of sine-wave beam specimens were predictable from results of circular cross section tubes. A comparison of energy absorption capability was made between integrally stiffened beams fabricated from graphite/epoxy, Kevlar-49/epoxy and aluminum. The energy absorption capability of the graphite/epoxy integrally stiffened beams exceeded both the Kevlar-49/epoxy and aluminum integrally stiffened beams. The energy absorption potential of composite structures is between five and ten times that of comparable metallic structure.

  9. Producibility aspects of advanced composites for an L-1011 Aileron

    NASA Technical Reports Server (NTRS)

    Van Hamersveld, J.; Fogg, L. D.

    1976-01-01

    The design of advanced composite aileron suitable for long-term service on transport aircraft includes Kevlar 49 fabric skins on honeycomb sandwich covers, hybrid graphite/Kevlar 49 ribs and spars, and graphite/epoxy fittings. Weight and cost savings of 28 and 20 percent, respectively, are predicted by comparison with the production metallic aileron. The structural integrity of the design has been substantiated by analysis and static tests of subcomponents. The producibility considerations played a key role in the selection of design concepts with potential for low-cost production. Simplicity in fabrication is a major factor in achieving low cost using advanced tooling and manufacturing methods such as net molding to size, draping, forming broadgoods, and cocuring components. A broadgoods dispensing machine capable of handling unidirectional and bidirectional prepreg materials in widths ranging from 12 to 42 inches is used for rapid layup of component kits and covers. Existing large autoclaves, platen presses, and shop facilities are fully exploited.

  10. Space-Qualified Traveling-Wave Tube

    NASA Technical Reports Server (NTRS)

    Wilson, Jeffrey D.; Krawczyk, Richard; Simons, Rainee N.; Williams, Wallace D.; Robbins, Neal R.; Dibb, Daniel R.; Menninger, William L.; Zhai, Xiaoling; Benton, Robert T.

    2010-01-01

    The L-3 Communications Electron Technologies, Inc. Model 999HA traveling-wave tube (TWT), was developed for use as a high-power microwave amplifier for high-rate transmission of data and video signals from deep space to Earth (see figure). The 999HA is a successor to the 999H a non-space qualified TWT described in High-Power, High-Efficiency Ka-Band Traveling-Wave Tube (LEW-17900-1), NASA Tech Briefs, Vol. 31, No. 2 (February 2007), page 32. Operating in the 31.8-to-32.3 GHz frequency band, the 999HA has been shown to generate 252 W of continuous- wave output power at 62 percent overall power efficiency a 75-percent increase in output power over the 999H. The mass of the 999HA is 35 percent less than that of the 999H. Moreover, taking account of the elimination of a Faraday cage that is necessary for operation of the 999H but is obviated by a redesign of high-voltage feed-throughs for the 999HA, the overall reduction in mass becomes 57 percent with an 82 percent reduction in volume. Through a series of rigorous tests, the 999HA has been qualified for operation aboard spacecraft with a lifetime exceeding seven years. Offspring of the 999HA will fly on the Kepler and Lunar Reconnaissance Orbiter missions.

  11. Design prediction for long term stress rupture service of composite pressure vessels

    NASA Technical Reports Server (NTRS)

    Robinson, Ernest Y.

    1992-01-01

    Extensive stress rupture studies on glass composites and Kevlar composites were conducted by the Lawrence Radiation Laboratory beginning in the late 1960's and extending to about 8 years in some cases. Some of the data from these studies published over the years were incomplete or were tainted by spurious failures, such as grip slippage. Updated data sets were defined for both fiberglass and Kevlar composite stand test specimens. These updated data are analyzed in this report by a convenient form of the bivariate Weibull distribution, to establish a consistent set of design prediction charts that may be used as a conservative basis for predicting the stress rupture life of composite pressure vessels. The updated glass composite data exhibit an invariant Weibull modulus with lifetime. The data are analyzed in terms of homologous service load (referenced to the observed median strength). The equations relating life, homologous load, and probability are given, and corresponding design prediction charts are presented. A similar approach is taken for Kevlar composites, where the updated stand data do show a turndown tendency at long life accompanied by a corresponding change (increase) of the Weibull modulus. The turndown characteristic is not present in stress rupture test data of Kevlar pressure vessels. A modification of the stress rupture equations is presented to incorporate a latent, but limited, strength drop, and design prediction charts are presented that incorporate such behavior. The methods presented utilize Cartesian plots of the probability distributions (which are a more natural display for the design engineer), based on median normalized data that are independent of statistical parameters and are readily defined for any set of test data.

  12. Yarn Pull-Out as a Mechanism for Dissipation of Ballistic Impact Energy in Kevlar KM-2 Fabric, Part 1: Quasi-Static Characterization of Yarn Pull-Out

    DTIC Science & Technology

    2004-05-01

    architectures and fiber types, including Kevlar K29, Spectra,* and Zylon .† The study found that the pull-out forces strongly depend on the transverse...during testing. *Spectra is a registered trademark of Honeywell. † Zylon is a registered trademark of...deformations measured by Shockey et al. (2001) for Zylon and Kevlar K29 fabrics. Therefore, yarn stretching does not play an important role in the

  13. Neural network burst pressure prediction in impact damaged Kevlar/epoxy bottles from acoustic emission amplitude data

    SciTech Connect

    Walker, J.L.; Workman, G.L.; Russell, S.S.

    1994-12-31

    Acoustic emission (AE) signal analysis has been used to measure the effect of impact damage on the burst pressure of 5.75 inch diameter filament wound Kevlar/epoxy pressure vessels. A calibrated dead weight drop fixture, featuring both sharp and blunt hemispherical impact tups, generated impact damages with energies up to twenty ft-lb{sub f} in the mid hoop region of each vessel. Burst pressures were obtained by hydrostatically testing twenty-seven damaged and undamaged bottles, eleven of which were filled with inert propellant to simulate a rocket motor. Burst pressure prediction models were developed by correlating the differential AE amplitude distributions, Generated during the first pressure ramp to 25% of the expected burst pressure for the undamaged vessels, to known burst pressures using back propagation neural networks. Independent networks were created for the inert propellant filled vessels and the unfilled vessels using a small subset of each during the training phases. The remaining bottles served as the test sets. The eleven filled vessels had an average prediction error of 5.6%, while the unfilled bottles averaged 5.4%. Both of these results were within the 95% prediction interval, but a portion of the vessel burst pressure errors were greater than the {+-}5% worst case error obtained in previous work. in conclusion, the AE amplitude distribution data collected at low proof loads provided a suitable input for neural network burst pressure prediction in damaged and undamaged Kevlar/epoxy bottles. This included pressure vessels both with and without propellant backing. Work is ongoing to decrease the magnitude of the prediction error through network restructuring.

  14. Effect of Hybridization on Stiffness Properties of Woven Textile Composites

    NASA Astrophysics Data System (ADS)

    Bejan, Liliana; Taranu, Nicolae; Sîrbu, Adriana

    2013-04-01

    The present study focuses on stiffness properties of woven textile reinforced polymeric composites with respect to hybridization, and geometry of reinforcement. The analyzed composites represent combinations of different fibre materials (E-glass, Kevlar 49, carbon HM) in a predetermined fabric geometry (a plane weave embedded in thermosetting polymeric resin) serving controlled properties and required performance. The effects of hybridization on the stiffness properties of woven textile composites have been studied with respect to the fibres materials, the unbalancing degree of fabrics, and the variation of compactness and undulation of yarns. Some undesirable effects in fabric geometry can be overcome by the combined effects of hybridization and compactness.

  15. Simulation of tensile strength of anisotropic fibre-reinforced composites at low temperature

    NASA Astrophysics Data System (ADS)

    Abdelmohsen, H. H.

    This article presents a simulation scheme to predict the effect of fibre anisotropy on composite tensile failure strength at room and low temperatures. The simulation model combines the shear lag equation with the chain of bundles probability model to describe the composite failure behaviour. The effect of fibre anisotropy on thermal stresses developed in composite constituents due to cooling to low temperatures is considered. The failure strength of composites composed of fibres with different degrees of anisotropy is obtained and comparisons are made with experiments. Simulated results for E-glass-, graphite- and Kevlar-epoxy type composites showed close agreement with the experiments.

  16. 49 CFR 109.11 - Assistance of properly qualified personnel.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... MATERIALS SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION HAZARDOUS MATERIALS AND OIL TRANSPORTATION... properly qualified to perform a function that is essential to the agent's exercise of authority under this...

  17. Use of Raman Spectroscopy and Delta Volume Growth from Void Collapse to Assess Overwrap Stress Gradients Compromising the Reliability of Large Kevlar/Epoxy COPVs

    NASA Technical Reports Server (NTRS)

    Kezirian, Michael T.; Phoenix, S. Leigh; Eldridge, Jeffrey I.

    2009-01-01

    Composite Overwrapped Pressure Vessels (COPVs) are frequently used for storing pressurized gases aboard spacecraft and aircraft when weight saving is desirable compared to all-metal versions. Failure mechanisms in fibrous COPVs and variability in lifetime can be very different from their metallic counterparts; in the former, catastrophic stress-rupture can occur with virtually no warning, whereas in latter, a leak before burst design philosophy can be implemented. Qualification and certification typically requires only one burst test on a production sample (possibly after several pressure cycles) and the vessel need only meet a design burst strength (the maximum operating pressure divided by a knockdown factor). Typically there is no requirement to assess variability in burst strength or lifetime, much less determine production and materials processing parameters important to control of such variability. Characterizing such variability and its source is crucial to models for calculating required reliability over a given lifetime (e.g. R = 0.9999 for 15 years). In this paper we present a case study of how lack of control of certain process parameters in COPV manufacturing can result in variations among vessels and between production runs that can greatly increase uncertainty and reduce reliability. The vessels considered are 40-inch ( NASA Glenn Research center, Cleveland, OH, 44135 29,500 in3 ) spherical COPVs with a 0.74 in. thick Kevlar49/epoxy overwrap and with a titanium liner of which 34 were originally produced. Two burst tests were eventually performed that unexpectedly differed by almost 5%, and were 10% lower than anticipated from burst tests on 26-inch sister vessels similar in every detail. A major observation from measurements made during proof testing (autofrettage) of the 40-inch vessels was that permanent volume growth from liner yielding varied by a factor of more than two (150 in3 to 360 in3 ), which suggests large differences in the residual

  18. Characterization of multiaxial warp knit composites

    NASA Technical Reports Server (NTRS)

    Dexter, H. Benson; Hasko, Gregory H.; Cano, Roberto J.

    1991-01-01

    The objectives were to characterize the mechanical behavior and damage tolerance of two multiaxial warp knit fabrics to determine the acceptability of these fabrics for high performance composite applications. The tests performed included compression, tension, open hole compression, compression after impact and compression-compression fatigue. Tests were performed on as-fabricated fabrics and on multi-layer fabrics that were stitched together with either carbon or Kevlar stitching yarn. Results of processing studies for vacuum impregnation with Hercules 3501-6 epoxy resin and pressure impregnation with Dow Tactix 138/H41 epoxy resin and British Petroleum BP E905L epoxy resin are presented.

  19. AZ-2000-IECW and StaMet Black Kapton Options for Solar Probe Plus MAG Sensor MLI Kevlar/Polyimide Shells

    NASA Technical Reports Server (NTRS)

    Choi, Michael K.

    2017-01-01

    AZ-2000-IECW white paint and StaMet black Kapton have been evaluated for the Kevlar/polyimide shells that enclose the Solar Probe Plus Magnetometer (MAG) sensors and multilayer insulation. Flight qualification testing on AZ-2000-IECW painted Kevlar/polyimide laminate was completed at Goddard Space Flight Center. This paint potentially meets all the requirements. However, it has no flight heritage. StaMet is hotter in the sun, and is specular. The results of the MAG thermal balance test show StaMet meets the thermal requirement and heater power budget. The mission prefers to fly StaMet after evaluating the risks of AZ-2000-IECW flaking and glint from StaMet to the Star Trackers.

  20. Composites

    NASA Astrophysics Data System (ADS)

    Taylor, John G.

    The Composites market is arguably the most challenging and profitable market for phenolic resins aside from electronics. The variety of products and processes encountered creates the challenges, and the demand for high performance in critical operations brings value. Phenolic composite materials are rendered into a wide range of components to supply a diverse and fragmented commercial base that includes customers in aerospace (Space Shuttle), aircraft (interiors and brakes), mass transit (interiors), defense (blast protection), marine, mine ducting, off-shore (ducts and grating) and infrastructure (architectural) to name a few. For example, phenolic resin is a critical adhesive in the manufacture of honeycomb sandwich panels. Various solvent and water based resins are described along with resin characteristics and the role of metal ions for enhanced thermal stability of the resin used to coat the honeycomb. Featured new developments include pultrusion of phenolic grating, success in RTM/VARTM fabricated parts, new ballistic developments for military vehicles and high char yield carbon-carbon composites along with many others. Additionally, global regional market resin volumes and sales are presented and compared with other thermosetting resin systems.

  1. Multi-Length Scale-Enriched Continuum-Level Material Model for Kevlar-Fiber-Reinforced Polymer-Matrix Composites

    DTIC Science & Technology

    2012-08-03

    Angstadt, Y.-P. Sun, and K.L. Koudela, Micro-Mechanics Based Derivation of the Materials Constitutive Relations for Carbon Nanotube Reinforced Poly-Vinyl...intralamina and interlamina damage mechanisms (e.g., fiber breakage within the yarns , fiber/matrix de-bonding, diffuse delamination/interlam- ina separation...a closer look is given to the architecture of the woven fabric. Specifically, details of yarn weaving and crimping, yarn cross-section change, and

  2. Characterization of Kevlar 49 fibers by electron paramagnetic resonance. Final report, 20 May 1981-20 June 1982. [Radicals induced by ultraviolet or fracture

    SciTech Connect

    Brown, I.M.; Sandreczki, T.C.

    1982-06-20

    EPR was used to investigate the free radicals created in Kevlar 49 fibers by stress-induced and photo-induced macromolecular chain scissions. Mn/sup +2/ ions were identified from the EPR spectrum of frozen solutions of concentrated sulfuric acid containing Kevlar 49. Other ions present are Cu/sup +2/, and possibly Fe/sup +3/, Cr/sup +3/, and Ti/sup +3/. EPR lineshape anisotropy indicates that some of the metal ions and first coordinate spheres are oriented. The concentration of stress-induced radicals (2 x 10/sup 10/ per filament) suggest that chain scission occurs in more weak planes than are estimated to exist in the fracture surfaces of the fiber core. These radicals are unstable in air and have some aromatic character. Several different types of radicals were obtained following uv irradiations of the Kevlar 49 fibers in vacuum (photodegradative radicals) and in air (photo-oxidative radicals). The photodegradative radicals are identified with primary radicals involved in the photo-Fries rearrangement reaction, secondary radicals formed as a result of a hydrogen atom abstraction by the primary radical, and/or ketyl radicals produced as a result of uv irradiation of the photo-Fries rearrangement product. The photo-oxidative radicals are identified with the uv irradiation products of a peroxide intermediate. Lineshape anisotropy indicates that both radical types are oriented. 31 figures.

  3. Development of Composite Case Salvage Procedures

    DTIC Science & Technology

    1982-04-01

    Roving: Kevlar/UF-328J2 prepreg Kevlar - DC20 coated /UF-3283 prepreg Glass Cloth: 341 glass cloth(3)/UF-3283 Film Adhesive: FM73 (4 ) Steel Mandrels...tests. * Construction: Elevational - FM73 film adhesive steel mandrel, Kevlar/UF-3283 Epoxy Resin Prepreg; 341 glass cloth/UF-3283; and Kevlar coated ...propellant from rocket motors. Cutback of the Thiokol Genie motor is performed primarily to obtain an exact grain length. The machined surface is coated

  4. A (13)C NMR analysis of the effects of electron radiation on graphite/polyetherimide composites

    NASA Technical Reports Server (NTRS)

    Ferguson, Milton W.

    1989-01-01

    Initial investigations have been made into the use of high resolution nuclear magnetic resonance (NMR) for the characterization of radiation effects in graphite and Kevlar fibers, polymers, and the fiber/matrix interface in graphite/polyetherimide composites. Sample preparation techniques were refined. Essential equipment has been procured. A new NMR probe was constructed to increase the proton signal-to-noise ratio. Problem areas have been identified and plans developed to resolve them.

  5. High-performance vessels from an aromatic polyamide fiber/epoxy composite

    NASA Technical Reports Server (NTRS)

    Chiao, T. T.; Hamstad, M. A.

    1975-01-01

    The investigation reported is concerned with the development of a filament-wound, ultralightweight composite vessel for the containment of cryogenic propellants and pressurant gases. The vessels are to be used within an operational temperature range from -253 C to ambient temperature. The fiber used for the process is Kevlar 49. The design and the fabrication of specimens and vessels are discussed along with the results obtained in a testing program.

  6. 26 CFR 1.103A-2 - Qualified mortgage bond.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 26 Internal Revenue 2 2011-04-01 2011-04-01 false Qualified mortgage bond. 1.103A-2 Section 1.103A... mortgage bond. (a)-(j) (k) Information reporting requirement—(1) In general. An issue meets the... requirements of this paragraph apply to qualified veterans' mortgage bonds issued after July 18, 1984, and to...

  7. 77 FR 18651 - Qualifying Urban Areas for the 2010 Census

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-03-27

    ...\\ The Census Bureau delineates urbanized areas \\2\\ and urban clusters \\3\\ primarily on the basis of... provides the list of urbanized areas and urban clusters that qualified based on results of the 2010 Census...'s official announcement of the list of qualifying urbanized areas and urban clusters for...

  8. 42 CFR 436.128 - Coverage for certain qualified aliens.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 42 Public Health 4 2014-10-01 2014-10-01 false Coverage for certain qualified aliens. 436.128... Mandatory Coverage of the Categorically Needy § 436.128 Coverage for certain qualified aliens. The agency... § 440.255(c) of this chapter to those aliens described in § 436.406(c) of this subpart. ...

  9. 42 CFR 436.128 - Coverage for certain qualified aliens.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 42 Public Health 4 2013-10-01 2013-10-01 false Coverage for certain qualified aliens. 436.128... Mandatory Coverage of the Categorically Needy § 436.128 Coverage for certain qualified aliens. The agency... § 440.255(c) of this chapter to those aliens described in § 436.406(c) of this subpart. ...

  10. 42 CFR 436.128 - Coverage for certain qualified aliens.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 42 Public Health 4 2012-10-01 2012-10-01 false Coverage for certain qualified aliens. 436.128... Mandatory Coverage of the Categorically Needy § 436.128 Coverage for certain qualified aliens. The agency... § 440.255(c) of this chapter to those aliens described in § 436.406(c) of this subpart. ...

  11. 49 CFR 599.300 - Requirements for qualifying transactions.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... Requirements for qualifying transactions. (a) In general. To qualify for a credit under the CARS Program, a... history provider evidencing registration for a period of not less than one year immediately prior to the... letters that do not obscure the owner's name, VIN, or other writing as follows: “Junk Automobile,...

  12. 49 CFR 599.300 - Requirements for qualifying transactions.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... Requirements for qualifying transactions. (a) In general. To qualify for a credit under the CARS Program, a... history provider evidencing registration for a period of not less than one year immediately prior to the... letters that do not obscure the owner's name, VIN, or other writing as follows: “Junk Automobile,...

  13. 24 CFR 266.100 - Qualified housing finance agency (HFA).

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 24 Housing and Urban Development 2 2010-04-01 2010-04-01 false Qualified housing finance agency... AUTHORITIES HOUSING FINANCE AGENCY RISK-SHARING PROGRAM FOR INSURED AFFORDABLE MULTIFAMILY PROJECT LOANS Housing Finance Agency Requirements § 266.100 Qualified housing finance agency (HFA). (a) Qualifications...

  14. 7 CFR 1260.181 - Qualified State beef councils.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 10 2010-01-01 2010-01-01 false Qualified State beef councils. 1260.181 Section 1260... SERVICE (MARKETING AGREEMENTS AND ORDERS; MISCELLANEOUS COMMODITIES), DEPARTMENT OF AGRICULTURE BEEF PROMOTION AND RESEARCH Beef Promotion and Research Order Assessments § 1260.181 Qualified State beef...

  15. 42 CFR 417.412 - Qualifying condition: Administration and management.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 42 Public Health 3 2010-10-01 2010-10-01 false Qualifying condition: Administration and management... Qualifying condition: Administration and management. The HMO or CMP must demonstrate that it— (a) Has... agents or management staff or persons with ownership or control interests who have been convicted...

  16. 7 CFR 1450.101 - Qualified biomass conversion facility.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 10 2011-01-01 2011-01-01 false Qualified biomass conversion facility. 1450.101... CORPORATION, DEPARTMENT OF AGRICULTURE LOANS, PURCHASES, AND OTHER OPERATIONS BIOMASS CROP ASSISTANCE PROGRAM (BCAP) Matching Payments § 1450.101 Qualified biomass conversion facility. (a) To be considered a...

  17. 7 CFR 1450.101 - Qualified biomass conversion facility.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 10 2013-01-01 2013-01-01 false Qualified biomass conversion facility. 1450.101... CORPORATION, DEPARTMENT OF AGRICULTURE LOANS, PURCHASES, AND OTHER OPERATIONS BIOMASS CROP ASSISTANCE PROGRAM (BCAP) Matching Payments § 1450.101 Qualified biomass conversion facility. (a) To be considered a...

  18. 7 CFR 1450.101 - Qualified biomass conversion facility.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 10 2014-01-01 2014-01-01 false Qualified biomass conversion facility. 1450.101... CORPORATION, DEPARTMENT OF AGRICULTURE LOANS, PURCHASES, AND OTHER OPERATIONS BIOMASS CROP ASSISTANCE PROGRAM (BCAP) Matching Payments § 1450.101 Qualified biomass conversion facility. (a) To be considered a...

  19. 7 CFR 1450.101 - Qualified biomass conversion facility.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 10 2012-01-01 2012-01-01 false Qualified biomass conversion facility. 1450.101... CORPORATION, DEPARTMENT OF AGRICULTURE LOANS, PURCHASES, AND OTHER OPERATIONS BIOMASS CROP ASSISTANCE PROGRAM (BCAP) Matching Payments § 1450.101 Qualified biomass conversion facility. (a) To be considered a...

  20. 42 CFR 68.9 - What loans qualify for repayment?

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 42 Public Health 1 2013-10-01 2013-10-01 false What loans qualify for repayment? 68.9 Section 68.9 Public Health PUBLIC HEALTH SERVICE, DEPARTMENT OF HEALTH AND HUMAN SERVICES FELLOWSHIPS, INTERNSHIPS, TRAINING NATIONAL INSTITUTES OF HEALTH (NIH) LOAN REPAYMENT PROGRAMS (LRPs) § 68.9 What loans qualify...

  1. 42 CFR 68.9 - What loans qualify for repayment?

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 42 Public Health 1 2014-10-01 2014-10-01 false What loans qualify for repayment? 68.9 Section 68.9 Public Health PUBLIC HEALTH SERVICE, DEPARTMENT OF HEALTH AND HUMAN SERVICES FELLOWSHIPS, INTERNSHIPS, TRAINING NATIONAL INSTITUTES OF HEALTH (NIH) LOAN REPAYMENT PROGRAMS (LRPs) § 68.9 What loans qualify...

  2. 13 CFR 107.130 - Requirement for qualified management.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... qualified management. When applying for a license, you must show, to the satisfaction of SBA, that your current or proposed management is qualified and has the knowledge, experience, and capability necessary... management. 107.130 Section 107.130 Business Credit and Assistance SMALL BUSINESS ADMINISTRATION...

  3. 48 CFR 837.7002 - List of qualified funeral directors.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 48 Federal Acquisition Regulations System 5 2010-10-01 2010-10-01 false List of qualified funeral... SPECIAL CATEGORIES OF CONTRACTING SERVICE CONTRACTING Mortuary Services 837.7002 List of qualified funeral..., a list of funeral directors capable of performing the burial services specified in 837.7003....

  4. 26 CFR 6a.103A-2 - Qualified mortgage bond.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... treated as part of a qualified mortgage bond issue. (b) Definitions and special rules. For purposes of this section and § 6a.103A-1, the following definitions apply: (1) Qualified mortgage bond. The term... bond proceeds. For example, where a mortgagor purchases a building which is so incomplete that...

  5. 26 CFR 6a.103A-2 - Qualified mortgage bond.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... treated as part of a qualified mortgage bond issue. (b) Definitions and special rules. For purposes of this section and § 6a.103A-1, the following definitions apply: (1) Qualified mortgage bond. The term... bond proceeds. For example, where a mortgagor purchases a building which is so incomplete that...

  6. 26 CFR 301.6362-5 - Qualified nonresident tax.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 26 Internal Revenue 18 2012-04-01 2012-04-01 false Qualified nonresident tax. 301.6362-5 Section... AND ADMINISTRATION PROCEDURE AND ADMINISTRATION Seizure of Property for Collection of Taxes § 301.6362-5 Qualified nonresident tax. (a) In general. A tax meets the requirements of section 6362(d)...

  7. 26 CFR 301.6362-5 - Qualified nonresident tax.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 26 Internal Revenue 18 2013-04-01 2013-04-01 false Qualified nonresident tax. 301.6362-5 Section... AND ADMINISTRATION PROCEDURE AND ADMINISTRATION Seizure of Property for Collection of Taxes § 301.6362-5 Qualified nonresident tax. (a) In general. A tax meets the requirements of section 6362(d)...

  8. 7 CFR 1260.115 - Qualified State beef council.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 10 2010-01-01 2010-01-01 false Qualified State beef council. 1260.115 Section 1260... SERVICE (MARKETING AGREEMENTS AND ORDERS; MISCELLANEOUS COMMODITIES), DEPARTMENT OF AGRICULTURE BEEF PROMOTION AND RESEARCH Beef Promotion and Research Order Definitions § 1260.115 Qualified State beef...

  9. 5 CFR 838.1004 - Qualifying court orders.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 5 Administrative Personnel 2 2014-01-01 2014-01-01 false Qualifying court orders. 838.1004 Section... (CONTINUED) COURT ORDERS AFFECTING RETIREMENT BENEFITS Court Orders Affecting Civil Service Retirement Benefits § 838.1004 Qualifying court orders. (a) A former spouse is entitled to a portion of an employee's...

  10. 5 CFR 838.1004 - Qualifying court orders.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 5 Administrative Personnel 2 2013-01-01 2013-01-01 false Qualifying court orders. 838.1004 Section... (CONTINUED) COURT ORDERS AFFECTING RETIREMENT BENEFITS Court Orders Affecting Civil Service Retirement Benefits § 838.1004 Qualifying court orders. (a) A former spouse is entitled to a portion of an employee's...

  11. 20 CFR 404.1018b - Medicare qualified government employment.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 20 Employees' Benefits 2 2014-04-01 2014-04-01 false Medicare qualified government employment. 404... Excluded from Employment § 404.1018b Medicare qualified government employment. (a) General. The work of a Federal, State, or local government employee not otherwise subject to Social Security coverage...

  12. 20 CFR 404.1018b - Medicare qualified government employment.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 20 Employees' Benefits 2 2011-04-01 2011-04-01 false Medicare qualified government employment. 404... Excluded from Employment § 404.1018b Medicare qualified government employment. (a) General. The work of a Federal, State, or local government employee not otherwise subject to Social Security coverage...

  13. 20 CFR 404.1018b - Medicare qualified government employment.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 20 Employees' Benefits 2 2012-04-01 2012-04-01 false Medicare qualified government employment. 404... Excluded from Employment § 404.1018b Medicare qualified government employment. (a) General. The work of a Federal, State, or local government employee not otherwise subject to Social Security coverage...

  14. 42 CFR 436.128 - Coverage for certain qualified aliens.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 42 Public Health 4 2010-10-01 2010-10-01 false Coverage for certain qualified aliens. 436.128... Mandatory Coverage of the Categorically Needy § 436.128 Coverage for certain qualified aliens. The agency... § 440.255(c) of this chapter to those aliens described in § 436.406(c) of this subpart....

  15. 42 CFR 436.128 - Coverage for certain qualified aliens.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 42 Public Health 4 2011-10-01 2011-10-01 false Coverage for certain qualified aliens. 436.128... Mandatory Coverage of the Categorically Needy § 436.128 Coverage for certain qualified aliens. The agency... § 440.255(c) of this chapter to those aliens described in § 436.406(c) of this subpart....

  16. Enhancing the Employability of Newly Qualified Nurses: A Pilot Study

    ERIC Educational Resources Information Center

    Dray, Beattie; Burke, Linda; Hurst, Heather M.; Ferguson, Anne; Marks-Maran, Diane

    2011-01-01

    Vocationally based higher education programmes are meant to prepare people for employment in their chosen fields of study. In nursing, historically, employment after qualifying has been almost assured, with sufficient vacancies available for newly qualified nurses. Recently, however, for a number of reasons, primarily related to economic…

  17. 42 CFR 417.414 - Qualifying condition: Range of services.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... HEALTH CARE PREPAYMENT PLANS Qualifying Conditions for Medicare Contracts § 417.414 Qualifying condition... practice to refer patients to sources outside that geographic area. (3) Exception for hospice care. An HMO or CMP is not required to furnish hospice care as described in part 418 of this chapter. However...

  18. 7 CFR 900.356 - Listing of qualified associations.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 8 2010-01-01 2010-01-01 false Listing of qualified associations. 900.356 Section 900... REGULATIONS Procedure for Determining the Qualification of Cooperative Milk Marketing Associations § 900.356 Listing of qualified associations. A copy of each determination of qualification is furnished to the...

  19. 24 CFR 3286.303 - Responsibilities of qualified trainers.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...-Administered States § 3286.303 Responsibilities of qualified trainers. (a) Curriculum and hours. In providing... program, qualified trainers must adequately address the curriculum and instruction-time requirements... compliance with the applicable curriculum and time requirements under subparts C and D of this part....

  20. 20 CFR 404.1018b - Medicare qualified government employment.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... AND DISABILITY INSURANCE (1950- ) Employment, Wages, Self-Employment, and Self-Employment Income Work Excluded from Employment § 404.1018b Medicare qualified government employment. (a) General. The work of a... 20 Employees' Benefits 2 2013-04-01 2013-04-01 false Medicare qualified government employment. 404...