Science.gov

Sample records for advanced composite shear

  1. Development of a metal-clad advanced composite shear web design concept

    NASA Technical Reports Server (NTRS)

    Laakso, J. H.

    1974-01-01

    An advanced composite web concept was developed for potential application to the Space Shuttle Orbiter main engine thrust structure. The program consisted of design synthesis, analysis, detail design, element testing, and large scale component testing. A concept was sought that offered significant weight saving by the use of Boron/Epoxy (B/E) reinforced titanium plate structure. The desired concept was one that was practical and that utilized metal to efficiently improve structural reliability. The resulting development of a unique titanium-clad B/E shear web design concept is described. Three large scale components were fabricated and tested to demonstrate the performance of the concept: a titanium-clad plus or minus 45 deg B/E web laminate stiffened with vertical B/E reinforced aluminum stiffeners.

  2. Effects of specimen configuration and fiber orientation on in-plane shear testing methods for advanced composite panels

    NASA Astrophysics Data System (ADS)

    Iwai, H.; Uemura, M.

    The mechanical in-plane shear testing method for unidirectional CFRP panels has not yet been authorized internationally because of its difficulty in obtaining the uniform shear stress field. A revised picture-frame fixture was proposed earlier to obtain the essential in-plane shear properties along fibers, but the specimen configuration included curved corners which exhibit stress concentration. In the present paper, an attempt is offered to simplify the specimen configuration in order to obtain more uniform shear stress distribution than seen in the previous specimens used in the picture frame fixture. Furthermore, a proposal is offered where the fiber direction is changed perpendicularly in rail shear methods. The experiments on unidirectional CFRP specimens together with the numerical FEM analyses were carried out in order to verify the advantages of such revisions by which the higher true shear strengths were obtained without stress concentration.

  3. Repeated buckling of composite shear panels

    NASA Technical Reports Server (NTRS)

    Singer, Josef; Weller, Tanchum

    1990-01-01

    Failures in service of aerospace structures and research at the Technion Aircraft Structures Laboratory have revealed that repeatedly buckled stiffened shear panels might be susceptible to premature fatigue failures. Extensive experimental and analytical studies have been performed at Technion on repeated buckling, far in excess of initial buckling, for both metal and composite shear panels with focus on the influence of the surrounding structure. The core of the experimental investigation consisted of repeated buckling and postbuckling tests on Wagner beams in a three-point loading system under realistic test conditions. The effects of varying sizes of stiffeners, of the magnitude of initial buckling loads, of the panel aspect ratio and of the cyclic shearing force, V sub cyc, were studied. The cyclic to critical shear buckling ratios, (V sub cyc/V sub cr) were on the high side, as needed for efficient panel design, yet all within possible flight envelopes. The experiments were supplemented by analytical and numerical analyses. For the metal shear panels the test and numerical results were synthesized into prediction formulas, which relate the life of the metal shear panels to two cyclic load parameters. The composite shear panels studied were hybrid beams with graphite/epoxy webs bonded to aluminum alloy frames. The test results demonstrated that composite panels were less fatigue sensitive than comparable metal ones, and that repeated buckling, even when causing extensive damage, did not reduce the residual strength by more than 20 percent. All the composite panels sustained the specified fatigue life of 250,000 cycles. The effect of local unstiffened holes on the durability of repeatedly buckled shear panels was studied for one series of the metal panels. Tests on 2024 T3 aluminum panels with relatively small unstiffened holes in the center of the panels demonstrated premature fatigue failure, compared to panels without holes. Preliminary tests on two graphite

  4. Advanced composites for windmills

    NASA Astrophysics Data System (ADS)

    Bourquardez, G.

    A development status assessment is conducted for advanced composite construction techniques for windmill blade structures which, as in the case of composite helicopter rotors, promise greater reliability, longer service life, superior performance, and lower costs. Composites in wind turbine applications must bear aerodynamic, inertial and gravitational loads in complex interaction cycles. Attention is given to large Darrieus-type vertical axis windmills, to which composite construction methods may offer highly effective pitch-control mechanisms, especially in the 'umbrella' configuration.

  5. Advanced composites X

    SciTech Connect

    1994-12-31

    In the past ten years, high volume, high performance applications of advanced composites in transportation have grown substantially. The 10th annual ASM/ESD Advanced Composites Conference and Exposition presents the latest developments in composite applications and technologies with over 70 papers presented. The conference is organized in tracks covering body, chassis, powertrain and infrastructure applications, material sciences, manufacturing processes and recycling. Polymer composite and metal matrix composite technologies are included throughout. Body sessions feature adhesive bonding, analysis and test methods and crash energy absorption. The Chassis sessions showcase polymer and metal composite applications. The Powertrain/Propulsion track includes emerging materials as well as design and processing case studies. The Materials Science track features papers on new materials, their performance and theoretical treatment. Manufacturing Processes sessions cover process, modelling, fiber preforming and emerging manufacturing methods. The Infrastructure and Recycling track includes a panel discussion of infrastructure applications and technical papers on the recycling of polymer composites and nondestructive testing.

  6. Evaluation of a metal shear web selectively reinforced with filamentary composites for space shuttle application

    NASA Technical Reports Server (NTRS)

    Laakso, J. H.; Straayer, J. W.

    1974-01-01

    A final program summary is reported for test and evaluation activities that were conducted for space shuttle web selection. Large scale advanced composite shear web components were tested and analyzed to evaluate application of advanced composite shear web construction to a space shuttle orbiter thrust structure. The shear web design concept consisted of a titanium-clad + or - 45 deg boron/epoxy web laminate stiffened with vertical boron-epoxy reinforced aluminum stiffeners and logitudinal aluminum stiffening. The design concept was evaluated to be efficient and practical for the application that was studied. Because of the effects of buckling deflections, a requirement is identified for shear buckling resistant design to maximize the efficiency of highly-loaded advanced composite shear webs.

  7. [Advanced Composites Technology Initiatives

    NASA Technical Reports Server (NTRS)

    Julian, Mark R.

    2002-01-01

    This final report closes out the W02 NASA Grant #NCC5-646. The FY02 grant for advanced technology initiatives through the Advanced Composites Technology Institute in Bridgeport, WV, at the Robert C. Byrd Institute (RCBI) Bridgeport Manufacturing Technology Center, is complete; all funding has been expended. RCBI continued to expand access to technology; develop and implement a workforce-training curriculum; improve material development; and provide prototyping and demonstrations of new and advanced composites technologies for West Virginia composites firms. The FY 02 efforts supported workforce development, technical training and the HST development effort of a super-lightweight composite carrier prototype and expanded the existing technical capabilities of the growing aerospace industry across West Virginia to provide additional support for NASA missions. Additionally, the Composites Technology and Training Center was awarded IS0 9001 - 2000 certification and Cleanroom Class 1000 certification during this report period.

  8. Analysis of shear test method for composite laminates

    NASA Technical Reports Server (NTRS)

    Bergner, H. W., Jr.; Davis, J. G., Jr.; Herakovich, C. T.

    1977-01-01

    An elastic plane stress finite element analysis of the stress distributions in four flat test specimens for in-plane shear response of composite materials subjected to mechanical or thermal loads is presented. The shear test specimens investigated include: slotted coupon, cross beam, losipescu, and rail shear. Results are presented in the form of normalized shear contour plots for all three in-plane stess components. It is shown that the cross beam, losipescu, and rail shear specimens have stress distributions which are more than adequate for determining linear shear behavior of composite materials. Laminate properties, core effects, and fixture configurations are among the factors which were found to influence the stress distributions.

  9. Advanced composites technology program

    NASA Technical Reports Server (NTRS)

    Davis, John G., Jr.

    1993-01-01

    This paper provides a brief overview of the NASA Advanced Composites Technology (ACT) Program. Critical technology issues that must be addressed and solved to develop composite primary structures for transport aircraft are delineated. The program schedule and milestones are included. Work completed in the first 3 years of the program indicates the potential for achieving composite structures that weigh less and are cost effective relative to conventional aluminum structure. Selected technical accomplishments are noted. Readers who are seeking more in-depth technical information should study the other papers included in these proceedings.

  10. Iosipescu shear properties of graphite fabric/epoxy composite laminates

    NASA Technical Reports Server (NTRS)

    Walrath, D. E.; Adams, D. F.

    1985-01-01

    The Iosipescu shear test method is used to measure the in-plane and interlaminar shear properties of four T300 graphite fabric/934 epoxy composite materials. Different weave geometries tested include an Oxford weave, a 5-harness satin weave, an 8-harness satin weave, and a plain weave with auxiliary warp yarns. Both orthogonal and quasi-isotropic layup laminates were tested. In-plane and interlaminar shear properties are obtained for laminates of all four fabric types. Overall, little difference in shear properties attributable to the fabric weave pattern is observed. The auxiliary warp material is significantly weaker and less stiff in interlaminar shear parallel to its fill direction. A conventional strain gage extensometer is modified to measure shear strains for use with the Iosipescu shear test. While preliminary results are encouraging, several design iterations failed to produce a reliable shear transducer prototype. Strain gages are still the most reliable shear strain transducers for use with this test method.

  11. Advanced composites in Japan

    NASA Technical Reports Server (NTRS)

    Diefendorf, R. Judd; Hillig, William G.; Grisaffe, Salvatore J.; Pipes, R. Byron; Perepezko, John H.; Sheehan, James E.

    1994-01-01

    The JTEC Panel on Advanced Composites surveyed the status and future directions of Japanese high-performance ceramic and carbon fibers and their composites in metal, intermetallic, ceramic, and carbon matrices. Because of a strong carbon and fiber industry, Japan is the leader in carbon fiber technology. Japan has initiated an oxidation-resistant carbon/carbon composite program. With its outstanding technical base in carbon technology, Japan should be able to match present technology in the U.S. and introduce lower-cost manufacturing methods. However, the panel did not see any innovative approaches to oxidation protection. Ceramic and especially intermetallic matrix composites were not yet receiving much attention at the time of the panel's visit. There was a high level of monolithic ceramic research and development activity. High temperature monolithic intermetallic research was just starting, but notable products in titanium aluminides had already appeared. Matrixless ceramic composites was one novel approach noted. Technologies for high temperature composites fabrication existed, but large numbers of panels or parts had not been produced. The Japanese have selected aerospace as an important future industry. Because materials are an enabling technology for a strong aerospace industry, Japan initiated an ambitious long-term program to develop high temperature composites. Although just starting, its progress should be closely monitored in the U.S.

  12. Advanced composite fuselage technology

    NASA Technical Reports Server (NTRS)

    Ilcewicz, Larry B.; Smith, Peter J.; Horton, Ray E.

    1993-01-01

    Boeing's ATCAS program has completed its third year and continues to progress towards a goal to demonstrate composite fuselage technology with cost and weight advantages over aluminum. Work on this program is performed by an integrated team that includes several groups within The Boeing Company, industrial and university subcontractors, and technical support from NASA. During the course of the program, the ATCAS team has continued to perform a critical review of composite developments by recognizing advances in metal fuselage technology. Despite recent material, structural design, and manufacturing advancements for metals, polymeric matrix composite designs studied in ATCAS still project significant cost and weight advantages for future applications. A critical path to demonstrating technology readiness for composite transport fuselage structures was created to summarize ATCAS tasks for Phases A, B, and C. This includes a global schedule and list of technical issues which will be addressed throughout the course of studies. Work performed in ATCAS since the last ACT conference is also summarized. Most activities relate to crown quadrant manufacturing scaleup and performance verification. The former was highlighted by fabricating a curved, 7 ft. by 10 ft. panel, with cocured hat-stiffeners and cobonded J-frames. In building to this scale, process developments were achieved for tow-placed skins, drape formed stiffeners, braided/RTM frames, and panel cure tooling. Over 700 tests and supporting analyses have been performed for crown material and design evaluation, including structural tests that demonstrated limit load requirements for severed stiffener/skin failsafe damage conditions. Analysis of tests for tow-placed hybrid laminates with large damage indicates a tensile fracture toughness that is higher than that observed for advanced aluminum alloys. Additional recent ATCAS achievements include crown supporting technology, keel quadrant design evaluation, and

  13. Novel shear mechanism in nanolayered composites

    SciTech Connect

    Mara, Nathan; Bhattacharyya, Dhriti; Hirth, John P; Dickerson, Patricia O; Misra, Amit

    2009-01-01

    Recent studies have shown that two-phase nanocomposite materials with semicoherent interfaces exhibit enhanced strength, deformability, and radiation damage resistance. The remarkable behavior exhibited by these materials has been attributed to the atomistic structure of the bi-metal interface that results in interfaces with low shear strength and hence, strong barriers for slip transmission due to dislocation core spreading along the weak interfaces. In this work, the low interfacial shear strength of Cu/Nb nanoscale multilayers dictates a new mechanism for shear banding and strain softening during micropillar compression. Previous work investigating shear band formation in nanocrystalline materials has shown a connection between insufficient strain hardening and the onset of shear banding in Fe and Fe-10% Cu, but has also shown that hardening does not necessarily offset shear banding in Pd nanomaterials. Therefore, the mechanisms behind shear localization in nanocrystalline materials are not completely understood. Our findings, supported by molecular dynamics simulations, provide insight on the design of nanocomposites with tailored interface structures and geometry to obtain a combination of high strength and deformability. High strength is derived from the ability of the interfaces to trap dislocations through relative ease of interfacial shear, while deformability can be maximized by controlling the effects of loading geometry on shear band formation.

  14. Shear induced electrical behaviour of conductive polymer composites

    NASA Astrophysics Data System (ADS)

    Starý, Zdeněk; Krückel, Johannes; Schubert, Dirk W.

    2013-04-01

    The time-dependent electrical resistance of polymethylmethacrylate containing carbon black was measured under oscillatory shear in the molten state. The electrical signal was oscillating exactly at the doubled frequency of the oscillatory shear deformation. Moreover, the experimental results gave a hint to the development of conductive structures in polymer melts under shear deformation. It was shown that the flow induced destruction of conductive paths dominates over the flow induced build-up in the beginning of the shear deformations. However, for longer times both competitive effects reach a dynamic equilibrium and only the thermally induced build-up of pathways influences the changes in the composite resistance during the shear. Furthermore, the oscillating electrical response depends clearly on the deformation amplitude applied. A simple physical model describing the behaviour of conductive pathways under shear deformation was derived and utilized for the description of the experimental data.

  15. Elastic shear moduli of brittle matrix composites with interfacial debonding

    SciTech Connect

    Yuan, F.G.; Pagano, N.J.

    1994-12-31

    Elastic shear moduli of brittle matrix composites with interfacial debonding are studied. Compatibility displacement boundary conditions between representative volume elements are imposed through finite element analyses. Comparisons of the moduli between the full RVE model and quarter cell model are made. Parametric studies assessing the effect of the debonding, the shear moduli ratios in the constituents and the fiber volume fractions on the composite shear moduli are also presented. Results show that the commonly used quarter cell model overestimate the moduli. The disparity increases as the rigidity of the fibers or fiber volume fraction increases.

  16. Advanced composite materials and processes

    NASA Technical Reports Server (NTRS)

    Baucom, Robert M.

    1991-01-01

    Composites are generally defined as two or more individual materials, which, when combined into a single material system, results in improved physical and/or mechanical properties. The freedom of choice of the starting components for composites allows the generation of materials that can be specifically tailored to meet a variety of applications. Advanced composites are described as a combination of high strength fibers and high performance polymer matrix materials. These advanced materials are required to permit future aircraft and spacecraft to perform in extended environments. Advanced composite precursor materials, processes for conversion of these materials to structures, and selected applications for composites are reviewed.

  17. Simplified Shear Solution for Determination of the Shear Stress Distribution in a Composite Panel from the Applied Shear Resultant

    NASA Technical Reports Server (NTRS)

    Bednarcyk, Brett A.; Aboudi, Jacob; Yarrington, Phillip W.; Collier, Craig S.

    2008-01-01

    The simplified shear solution method is presented for approximating the through-thickness shear stress distribution within a composite laminate or panel based on laminated beam theory. The method does not consider the solution of a particular boundary value problem; rather it requires only knowledge of the global shear loading, geometry, and material properties of the laminate or panel. It is thus analogous to lamination theory in that ply level stresses can be efficiently determined from global load resultants (as determined, for instance, by finite element analysis) at a given location in a structure and used to evaluate the margin of safety on a ply by ply basis. The simplified shear solution stress distribution is zero at free surfaces, continuous at ply boundaries, and integrates to the applied shear load. Comparisons to existing theories are made for a variety of laminates, and design examples are provided illustrating the use of the method for determining through-thickness shear stress margins in several types of composite panels and in the context of a finite element structural analysis.

  18. Longitudinal interfacial shearing of a unidirectional fiber composite

    SciTech Connect

    Yang, M.; Kurth, R.E.

    1995-12-31

    In this work, longitudinal interfacial shearing of a unidirectional fiber composite which sustains slippage at the interface between fiber and matrix is analyzed. Based on the experimental work on the fiber pull-out, the interface between the fiber and the matrix can be divided as three regions, depending on the longitudinal shear stress. These three regions are the bonded region, frictional slip regions, and the free-friction slid region. The problem is formulated as a nonlinear system of singular integral equations and solved numerically. It has been shown that when the longitudinal shear stress is less than a critical value, the fiber and the matrix can be assumed to be bonded perfectly. When the longitudinal shear stress is greater than this critical value, the slippage at the interface between the fiber and the interface takes place. From the recent fiber pull-out test, the phenomena of fiber frictional slip followed by free slide has been observed and analyzed. Thus, there are three stages for the deformation of interfacial shearing of a unidirectional fiber composite under longitudinal shearing. The first stage occurs when the applied longitudinal shear stress is less than the critical value corresponding to the onset of slippage. In the second stage, the interface is divided into two regions, namely, the bonded region and the frictional slip region in which the shear stress is either assumed to be constant or governed by a friction law. The third stage occurs when the longitudinal shear stress is greater than the critical value corresponding to free sliding or when the friction limit is exceeded. In the third stage, the interface between the fiber and the matrix can be divided into three regions, depending on the longitudinal shear stress. These three regions are the bonded region, the frictional slip regions, and the free-friction slide region in which the shear stress is neglected.

  19. Evaluation of a metal shear web selectively reinforced with filamentary composites for space shuttle application. Phase 3 Summary report: Shear web component testing and analysis

    NASA Technical Reports Server (NTRS)

    Laakso, J. H.; Straayer, J. W.

    1973-01-01

    Three large scale advanced composite shear web components were tested and analyzed to evaluate application of the design concept to a space shuttle orbiter thrust structure. The shear web design concept consisted of a titanium-clad + or - 45 deg boron/epoxy web laminate stiffened with vertical boron/epoxy reinforced aluminum stiffeners. The design concept was evaluated to be efficient and practical for the application that was studied. Because of the effects of buckling deflections, a requirement is identified for shear buckling resistant design to maximize the efficiency of highly-loaded advanced composite shear webs. An approximate analysis of prebuckling deflections is presented and computer-aided design results, which consider prebuckling deformations, indicate that the design concept offers a theoretical weight saving of 31 percent relative to all metal construction. Recommendations are made for design concept options and analytical methods that are appropriate for production hardware.

  20. Advanced technology composite aircraft structures

    NASA Technical Reports Server (NTRS)

    Ilcewicz, Larry B.; Walker, Thomas H.

    1991-01-01

    Work performed during the 25th month on NAS1-18889, Advanced Technology Composite Aircraft Structures, is summarized. The main objective of this program is to develop an integrated technology and demonstrate a confidence level that permits the cost- and weight-effective use of advanced composite materials in primary structures of future aircraft with the emphasis on pressurized fuselages. The period from 1-31 May 1991 is covered.

  1. Advances in Composites Technology

    NASA Technical Reports Server (NTRS)

    Tenney, D. R.; Dexter, H. B.

    1985-01-01

    A significant level of research is currently focused on the development of tough resins and high strain fibers in an effort to gain improved damage tolerance. Moderate success has been achieved with the development of new resins such as PEEK and additional improvements look promising with new thermoplastic resins. Development of innovative material forms such as 2-D and 3-D woven fabrics and braided structural subelements is also expected to improve damage tolerance and durability of composite hardware. The new thrust in composites is to develop low cost manufacturing and design concepts to lower the cost of composite hardware. Processes being examined include automated material placement, filament winding, pultrusion, and thermoforming. The factory of the future will likely incorporate extensive automation in all aspects of manufacturing composite components.

  2. Dynamic characteristics of piezoelectric shear deformable composite plates

    NASA Astrophysics Data System (ADS)

    Kolar, Ramesh

    2004-07-01

    Layered composites have attracted attention for their high specific stiffness, high specific strength, and application specific tailoring of their properties. It is also recognized that layered composites are prone to delamination failure in addition to other failure modes. Consideration of transverse shear on the deformation behavior of the composites is an important aspect in the study of delamination mode failure of such plates. In this paper, we consider the effects of including the transverse shear deformation on the vibration characteristics of layered piezoelectric composites. The formulation is based on the Raleigh-Ritz method using the beam characteristic functions. MATLAB based symbollic math tool box is used in evaluating th eintegrals resulting from the Raleigh Ritz approach. Various commonly occuring boundary conditions are discussed. Results are provided showing the effects of the shear deformation on the dynamics of layered laminated composites. The effects of laminate thickness, fiber orientation, and the plate aspect ratios on the free vibration characteristics of the composite laminates are given to demonstrate the methodology described.

  3. Simple torsion test for shear moduli determination of orthotropic composites

    NASA Technical Reports Server (NTRS)

    Sumsion, H. T.; Rajapakse, Y. D. S.

    1978-01-01

    The shear moduli G13 and G23 for two different composites (AS/3501 and T300/5209) of uniaxial and cross-ply fiber orientations were determined by torsion testing of flat specimens of rectangular cross section. Torsion tests were run under controlled angle of twist in an electro-hydraulic servo-controlled test system. Both laser and potentiometer methods of measuring the angle of twist were used. The in-plane shear modulus was calculated with a formula for transversally isotropic materials and a formula for orthotropic materials, while the out-of-plane shear modulus was calculated from the orthotropic material formula. Neither the uniaxial nor the angle-ply composite materials studied were transversely isotropic. The degree of anisotropy for the angle-ply materials was several times greater than that of the uniaxial composites. For specimens of uniaxial fiber orientation, the in-plane shear moduli could be calculated to a good approximation by using the isotropic formula and test machine deflection data.

  4. Composite Interlaminar Shear Fracture Toughness, G(sub 2c): Shear Measurement of Sheer Myth?

    NASA Technical Reports Server (NTRS)

    OBrien, T. Kevin

    1997-01-01

    The concept of G2c as a measure of the interlaminar shear fracture toughness of a composite material is critically examined. In particular, it is argued that the apparent G2c as typically measured is inconsistent with the original definition of shear fracture. It is shown that interlaminar shear failure actually consists of tension failures in the resin rich layers between plies followed by the coalescence of ligaments created by these failures and not the sliding of two planes relative to one another that is assumed in fracture mechanics theory. Several strain energy release rate solutions are reviewed for delamination in composite laminates and structural components where failures have been experimentally documented. Failures typically occur at a location where the mode 1 component accounts for at least one half of the total G at failure. Hence, it is the mode I and mixed-mode interlaminar fracture toughness data that will be most useful in predicting delamination failure in composite components in service. Although apparent G2c measurements may prove useful for completeness of generating mixed-mode criteria, the accuracy of these measurements may have very little influence on the prediction of mixed-mode failures in most structural components.

  5. Simple torsion test for shear moduli determination of orthotropic composites

    NASA Technical Reports Server (NTRS)

    Sumsion, H. T.; Rajapakse, Y. D. S.

    1978-01-01

    By means of torsion tests performed on test specimens of the same material having a minimum of two different cross sections (flat sheet of different widths), the effective in-plane (G13) and out-of-plane (G23) shear moduli were determined for two composite materials of uniaxial and angleply fiber orientations. Test specimens were 16 plies (nominal 2 mm) thick, 100 mm in length, and in widths of 6.3, 9.5, 12.5, and 15.8 mm. Torsion tests were run under controlled deflection (constant angle of twist) using an electrohydraulic servocontrolled test system. In-plane and out-of-plane shear moduli were calculated from an equation derived in the theory of elasticity which relates applied torque, the torsional angle of twist, the specimen width/thickness ratio, and the ratio of the two shear moduli G13/G23. Results demonstrate that torsional shear moduli, G23 as well as G13, can be determined by simple torsion tests of flat specimens of rectangular cross section. Neither the uniaxial nor angleply composite material were transversely isotropic.

  6. ISAAC Advanced Composites Research Testbed

    NASA Technical Reports Server (NTRS)

    Wu, K. Chauncey; Stewart, Brian K.; Martin, Robert A.

    2014-01-01

    The NASA Langley Research Center is acquiring a state-of-art composites fabrication capability to support the Center's advanced research and technology mission. The system introduced in this paper is named ISAAC (Integrated Structural Assembly of Advanced Composites). The initial operational capability of ISAAC is automated fiber placement, built around a commercial system from Electroimpact, Inc. that consists of a multi-degree of freedom robot platform, a tool changer mechanism, and a purpose-built fiber placement end effector. Examples are presented of the advanced materials, structures, structural concepts, fabrication processes and technology development that may be enabled using the ISAAC system. The fiber placement end effector may be used directly or with appropriate modifications for these studies, or other end effectors with different capabilities may either be bought or developed with NASA's partners in industry and academia.

  7. Short beam shear tests of polymeric laminates and unidirectional composites

    NASA Technical Reports Server (NTRS)

    Stinchcomb, W. W.; Henneke, E. G.

    1980-01-01

    The application of advanced composite materials in aerospace, ground transportation, and sporting industries are discussed. Failure theories for the design and mechanical behavior of composite materials are emphasized. Methods for detecting specific types of flaws are outlined. The effect of detected flaws on mechanical properties such as stiffness, strength, fatigue lifetime, or residual strength is described.

  8. An interlaminar shear stress continuity theory for both thin and thick composite laminates

    NASA Astrophysics Data System (ADS)

    Lu, Xianqiang; Liu, Dahsin

    1992-09-01

    The interlaminar shear stress plays a very important role in the damage of composite laminates. With higher interlaminar shear stress, delamination can easily occur on the composite interface. In order to calculate the interlaminar shear stress, a laminate theory, which accounts for both the interlaminar shear stress continuity and the transverse shear deformation, was presented in this study. Verification of the theory was performed by comparing the present theory with Pagano's elasticity analysis. It was found that the present theory was able to give excellent results for both stresses and displacements. More importantly, the interlaminar shear stress can be presented directly from the constitutive equations instead of being recovered from the equilibrium equations.

  9. Interlaminar shear fracture toughness and fatigue thresholds for composite materials

    NASA Technical Reports Server (NTRS)

    O'Brien, T. Kevin; Murri, Gretchen B.; Salpekar, Satish A.

    1989-01-01

    Static and cyclic end notched flexure tests were conducted on a graphite epoxy, a glass epoxy, and graphite thermoplastic to determine their interlaminar shear fracture toughness and fatigue thresholds for delamination in terms of limiting values of the mode II strain energy release rate, G-II, for delamination growth. The influence of precracking and data reduction schemes are discussed. Finite element analysis indicated that the beam theory calculation for G-II with the transverse shear contribution included was reasonably accurate over the entire range of crack lengths. Cyclic loading significantly reduced the critical G-II for delamination. A threshold value of the maximum cyclic G-II below which no delamination occurred after one million cycles was identified for each material. Also, residual static toughness tests were conducted on glass epoxy specimens that had undergone one million cycles without delamination. A linear mixed-mode delamination criteria was used to characterize the static toughness of several composite materials; however, a total G threshold criterion appears to characterize the fatigue delamination durability of composite materials with a wide range of static toughness.

  10. Interlaminar shear fracture toughness and fatigue thresholds for composite materials

    NASA Technical Reports Server (NTRS)

    Obrien, T. Kevin; Murri, Gretchen B.; Salpekar, Satish A.

    1987-01-01

    Static and cyclic end notched flexure tests were conducted on a graphite epoxy, a glass epoxy, and graphite thermoplastic to determine their interlaminar shear fracture toughness and fatigue thresholds for delamination in terms of limiting values of the mode II strain energy release rate, G-II, for delamination growth. The influence of precracking and data reduction schemes are discussed. Finite element analysis indicated that the beam theory calculation for G-II with the transverse shear contribution included was reasonably accurate over the entire range of crack lengths. Cyclic loading significantly reduced the critical G-II for delamination. A threshold value of the maximum cyclic G-II below which no delamination occurred after one million cycles was identified for each material. Also, residual static toughness tests were conducted on glass epoxy specimens that had undergone one million cycles without delamination. A linear mixed-mode delamination criteria was used to characterize the static toughness of several composite materials; however, a total G threshold criterion appears to characterize the fatigue delamination durability of composite materials with a wide range of static toughness.

  11. Fabrication and evaluation of advanced titanium and composite structural panels

    NASA Technical Reports Server (NTRS)

    Bales, T. T.; Hoffman, E. L.; Payne, L.; Carter, A. L.

    1976-01-01

    Advanced manufacturing methods for titanium and composite material structures are being developed and evaluated. The focus for the manufacturing effort is the fabrication of full-scale structural panels which replace an existing shear panel on the upper wing surface of the NASA YF-12 aircraft. The program involves design, fabrication, ground testing, and Mach 3 flight service of full-scale structural panels and laboratory testing of representative structural element specimens.

  12. Shear bond strength of indirect composite material to monolithic zirconia

    PubMed Central

    2016-01-01

    PURPOSE This study aimed to evaluate the effect of surface treatments on bond strength of indirect composite material (Tescera Indirect Composite System) to monolithic zirconia (inCoris TZI). MATERIALS AND METHODS Partially stabilized monolithic zirconia blocks were cut into with 2.0 mm thickness. Sintered zirconia specimens were divided into different surface treatment groups: no treatment (control), sandblasting, glaze layer & hydrofluoric acid application, and sandblasting + glaze layer & hydrofluoric acid application. The indirect composite material was applied to the surface of the monolithic zirconia specimens. Shear bond strength value of each specimen was evaluated after thermocycling. The fractured surface of each specimen was examined with a stereomicroscope and a scanning electron microscope to assess the failure types. The data were analyzed using one-way analysis of variance (ANOVA) and Tukey LSD tests (α=.05). RESULTS Bond strength was significantly lower in untreated specimens than in sandblasted specimens (P<.05). No difference between the glaze layer and hydrofluoric acid application treated groups were observed. However, bond strength for these groups were significantly higher as compared with the other two groups (P<.05). CONCLUSION Combined use of glaze layer & hydrofluoric acid application and silanization are reliable for strong and durable bonding between indirect composite material and monolithic zirconia. PMID:27555895

  13. A biaxial method for inplane shear testing. [shear strain in composite materials

    NASA Technical Reports Server (NTRS)

    Bush, H. G.; Weller, T.

    1978-01-01

    A biaxial method for performing inplane shear tests of materials using a shear frame is described. Aluminum plate and sandwich specimens were used to characterize the uniformity of shear strain imparted by the biaxial method of loading as opposed to the uniaxial method. The inplane stiffening effect of aluminum honeycomb core was determined. Test results for (+ or - 45) graphite-epoxy laminate are presented. Some theoretical considerations of subjecting an anisotropic material to a uniform shear deformation are discussed.

  14. Advanced Technology Composite Fuselage - Manufacturing

    NASA Technical Reports Server (NTRS)

    Wilden, K. S.; Harris, C. G.; Flynn, B. W.; Gessel, M. G.; Scholz, D. B.; Stawski, S.; Winston, V.

    1997-01-01

    The goal of Boeing's Advanced Technology Composite Aircraft Structures (ATCAS) program is to develop the technology required for cost-and weight-efficient use of composite materials in transport fuselage structure. Carbon fiber reinforced epoxy was chosen for fuselage skins and stiffening elements, and for passenger and cargo floor structures. The automated fiber placement (AFP) process was selected for fabrication of stringer-stiffened and sandwich skin panels. Circumferential and window frames were braided and resin transfer molded (RTM'd). Pultrusion was selected for fabrication of floor beams and constant-section stiffening elements. Drape forming was chosen for stringers and other stiffening elements cocured to skin structures. Significant process development efforts included AFP, braiding, RTM, autoclave cure, and core blanket fabrication for both sandwich and stiffened-skin structure. Outer-mold-line and inner-mold-line tooling was developed for sandwich structures and stiffened-skin structure. The effect of design details, process control and tool design on repeatable, dimensionally stable, structure for low cost barrel assembly was assessed. Subcomponent panels representative of crown, keel, and side quadrant panels were fabricated to assess scale-up effects and manufacturing anomalies for full-scale structures. Manufacturing database including time studies, part quality, and manufacturing plans were generated to support the development of designs and analytical models to access cost, structural performance, and dimensional tolerance.

  15. Compositional evolution of high-temperature sheared lherzolite PHN 1611

    SciTech Connect

    Smith, D. ); Griffin, W.L.; Ryan, C.G. )

    1993-02-01

    The evolution of fertile' mantle has been studied by proton microprobe (PIXE) analysis of minerals of a high-temperature sheared xenolith from the Thaba Putsoa kimerlite in Lesotho, southern Africa. Analyzed elements include Ni, Cu, Zn, Ga, Sr, Y, and Zr. Garnets are homogeneous in Ni and Zn but have rims enriched relative to cores in Zr and Y. Compositions of olivine neoblasts define intergranular gradients of Fe, Zn, and Ni; Fe-rich olivine is relatively Zn-rich but Ni-poore. Although individual clinopyroxene grains are nearly homogeneous, clinopyroxene associated with Fe-rich olivine is relatively Fe- and Zn-rich but Sr- and Cr-poor. The trace-element abundances and compositional gradients constrain the processes of periodotite enrichment and the thermal history. Enrichment of Zr, Y, and Fe in garnet rims documents infiltration of a silica-undersaturated melt. The Fe-rich olivine compositions and the Zn and Fe gradients establish that the xenolith was sampled from near a melt conduit. Mechanical mixing of inhomogeneous peridotite and melt infiltration may have been concurrent. Because garnets appear homogeneous in Ni, mantle temperature changes affecting PHN 1611 occurred before or over a longer period than the melt infiltration. Measured and calculated abundances of many incompatible trace elements in the rock are similar to those proposed for primitive mantle. Calculated chondrite-normalized abundances of Sr, Ti, Zr, and Y are like those of appropriate REE. Enrichment processes in PHN 1611 proceeded at unusually high recorded temperature and in the apparent absence of minor phases common in lower-temperature metasomatized rocks, but similar processes may be common. In particular, mechanical mixing near mantle dikes may frequently occur. These enrichment mechanisms may produce xenolith compositions that resemble some proposed for primitive mantle but that have different implications for mantle evolution. 61 refs., 7 figs., 2 tabs.

  16. Analysis and design of advanced composite bounded joints

    NASA Technical Reports Server (NTRS)

    Hart-Smith, L. J.

    1974-01-01

    Advances in the analysis of adhesive-bonded joints are presented with particular emphasis on advanced composite structures. The joints analyzed are of double-lap, single-lap, scarf, stepped-lap and tapered-lap configurations. Tensile, compressive, and in-plane shear loads are covered. In addition to the usual geometric variables, the theory accounts for the strength increases attributable to adhesive plasticity (in terms of the elastic-plastic adhesive model) and the joint strength reductions imposed by imbalances between the adherends. The solutions are largely closed-form analytical results, employing iterative solutions on a digital computer for the more complicated joint configurations. In assessing the joint efficiency, three potential failure modes are considered. These are adherend failure outside the joint, adhesive failure in shear, and adherend interlaminar tension failure (or adhesive failure in peel). Each mode is governed by a distinct mathematical analysis and each prevails throughout different ranges of geometric sizes and proportions.

  17. Interlaminar shear properties of graphite fiber, high-performance resin composites

    NASA Technical Reports Server (NTRS)

    Needles, H. L.; Kourtides, D. A.; Fish, R. H.; Varma, D. S.

    1983-01-01

    Short beam testing was used to determine the shear properties of laminates consisting of T-300 and Celion 3000 and 6000 graphite fibers, in epoxy, hot melt and solvent bismaleimide, polyimide and polystyrylpyridine (PSP). Epoxy, composites showed the highest interlaminar shear strength, with values for all other resins being substantially lower. The dependence of interlaminar shear properties on the fiber-resin interfacial bond and on resin wetting characteristics and mechanical properties is investigated, and it is determined that the lower shear strength of the tested composites, by comparison with epoxy resin matrix composites, is due to their correspondingly lower interfacial bond strengths. An investigation of the effect of the wettability of carbon fiber tow on shear strength shows wetting variations among resins that are too small to account for the large shear strength property differences observed.

  18. A novel method of testing the shear strength of thick honeycomb composites

    NASA Technical Reports Server (NTRS)

    Hodge, A. J.; Nettles, A. T.

    1991-01-01

    Sandwich composites of aluminum and glass/phenolic honeycomb core were tested for shear strength before and after impact damage. The assessment of shear strength was performed in two ways; by four point bend testing of sandwich beams and by a novel double lap shear (DLS) test. This testing technique was developed so smaller specimens could be used, thus making the use of common lab scale fabrication and testing possible. The two techniques yielded similar data. The DLS test gave slightly lower shear strength values of the two methods but were closer to the supplier's values for shear strength.

  19. A comparison of three popular test methods for determining the shear modulus of composite materials

    NASA Technical Reports Server (NTRS)

    Ho, Henjen; Tsai, Ming-Yi; Morton, John; Farley, Gary L.

    1991-01-01

    Three popular shear tests (the 10 degree off-axis, the plus or minus 45 degree tensile, and the Iosipescu specimen tested in the modified Wyoming fixture) for shear modulus measurement are evaluated for a graphite-epoxy composite material system. A comparison of the shear stress-strain response for each test method is made using conventional strain gage instrumentation and moire interferometry. The uniformity and purity of the strain fields in the test sections of the specimens are discussed, and the shear responses obtained from each test technique are presented and compared. For accurate measurement of shear modulus, the 90 degree Iosipescu specimen is recommended.

  20. Exploring the piezoelectric performance of PZT particulate-epoxy composites loaded in shear

    NASA Astrophysics Data System (ADS)

    Van Loock, F.; Deutz, D. B.; van der Zwaag, S.; Groen, W. A.

    2016-08-01

    The active and passive piezoelectric response of lead zirconium titanate (PZT)-epoxy particulate composites loaded in shear is studied using analytical models, a finite element model and by experiments. The response is compared to that of the same composites when loaded in simple tension. Analogously to bulk PZT, particulate PZT-polymer composites loaded in shear show higher piezoelectric charge coefficient (d 15) and energy density figure of merit (FOM15) values compared to simple tension (d 33) and (FOM33). This outcome demonstrates the as-yet barely explored potential of piezoelectric particulate composites for optimal strain energy harvesting when activated in shear.

  1. Comparative evaluation of shear bond strength and nanoleakage of conventional and self-adhering flowable composites to primary teeth dentin

    PubMed Central

    Sachdeva, Priyanka; Goswami, Mousumi; Singh, Darrel

    2016-01-01

    Background: The latest advancement in adhesive dentistry is the development of self adhering flowable composite resin which incorporates the self-etch adhesion technology to eliminate the steps of etching, rinsing, priming and bonding. Few studies have addressed resin bonding to primary teeth. Aim: The aim of this study was to compare the shear bond strength and nanoleakage of conventional and self adhering flowable composites to primary teeth dentin. Settings and Design: This study was conducted in the Department of Pedodontics and Preventive Dentistry, I.T.S Dental College, Hospital and Research Centre, Greater Noida; in association with the Department of Mechanical Engineering, I.T.S Engineering College, Greater Noida; and the Advanced Instrumentation Research Facility (AIRF), Jawaharlal Nehru University, New Delhi. Materials and Methods: Sixty of the ninety primary teeth were evaluated for shear bond strength and thirty for nanoleakage. The samples were divided into three groups; Group I – Dyad Flow (Kerr), Group II – Fusio Liquid Dentin (Pentron Clinical Technologies) and Group III – G-aenial Universal Flo (GC). Shear bond strength was determined using a universal testing machine. Nanoleakage pattern was observed under scanning electron microscope. Results: The shear bond strength of conventional flowable composite was significantly greater than self adhering flowable composite (p<0.05). Nanoleakage scores of both conventional and self adhering flowable composites were comparable. Conclusions: Self adhering flowable composites combine properties of composites and self etch adhesives, eliminating the need for separate bond application that simplifies direct restorative procedure. The evolution of self adhering materials could open new horizons for pediatric dentistry.

  2. Environmental effects on advanced composites

    NASA Technical Reports Server (NTRS)

    Unnam, J.; Houska, C. R.; Naidu, S. V. N.

    1979-01-01

    The development of titanium matrix composites for elevated temperature applications was investigated. General solutions for treating diffusion in multiphase multicomponent systems were studied. Graphite polyimide composites were characterized with respect to mechanical property degradation by moisture.

  3. An evaluation of the +/-45 deg tensile test for the determination of the in-plane shear strength of composite materials

    NASA Technical Reports Server (NTRS)

    Kellas, S.; Morton, J.; Jackson, K. E.

    1991-01-01

    The applicability of the +/-45 deg tensile test for the determination of the in-plane shear strength of advanced composite laminates is studied. The assumptions used for the development of the shear strength formulas were examined, and factors such as the specimen geometry and stacking sequence were assessed experimentally. It was found that the strength of symmetric and balanced +/-45 deg laminates depends primarily upon the specimen thickness rather than the specimen width. These findings have important implications for the +/-45 deg tensile test which is recommended by several organizations for the determination of the in-plane shear stress/strain response and the shear strength of continuous fiber reinforced composites. Modifications to the recommended practices for specimen selection and shear strength determination are suggested.

  4. The Iosipescu shear test method as used for testing polymers and composite materials

    NASA Technical Reports Server (NTRS)

    Adams, Donald F.

    1990-01-01

    This paper describes a shear test method for polymers and composite materials, based on the Iosipescu (1967) shear test which was originally developed for use with homogeneous isotropic metals. Special attention is given to the loading fixture for the test, the standard specimen design and shear stress measurements. The range of the test applications is indicated. The method is in the final stages of being accepted as an ASTM standard.

  5. Shear bond strength of composite resin to amalgam: an experiment in vitro using different bonding systems.

    PubMed

    Hadavi, F; Hey, J H; Ambrose, E R

    1991-01-01

    The shear bond strength between amalgam and composite resin with and without the use of adhesive systems was evaluated. It was found that the application of Cover-Up II or Prisma Universal Bond prior to placement of composite resin enhanced the shear bond strength between amalgam and composite resin more than five times; and a shear strength of 4.34 and 4.30 MPa was measured respectively. Acid-etching of the roughened amalgam surface prior to application of Prisma Universal Bond decreased the bond strength by nearly 45%. PMID:1784535

  6. Thermoelastic bending analysis of laminated composite plates according to various shear deformation theories

    NASA Astrophysics Data System (ADS)

    Sayyad, Atteshamuddin Shamshuddin; Shinde, Bharati Machhindra; Ghugal, Yuwaraj Marotrao

    2014-11-01

    This study presents the thermoelastic analysis of laminated composite plates subjected to sinusoidal thermal load linearly varying across the thickness. Analytical solutions for thermal displacements and stresses are investigated by using a unified plate theory which includes different functions in terms of thickness coordinate to represent the effect of shear deformation. The theory presented is variationally consistent, does not require shear correction factor, and gives rise to transverse shear stress variation such that the transverse shear stresses vary parabolically across the thickness satisfying shear stress free surface conditions. Governing equations of equilibrium and associated boundary conditions of the theory are obtained using the principle of virtual work. The Navier solution for simply supported laminated composite plates has been developed. Numerical results are presented to demonstrate the thermal response of the laminated composite plates.

  7. Advanced composite vertical stabilizer for DC-10 transport aircraft

    NASA Technical Reports Server (NTRS)

    Stephens, C. O.

    1979-01-01

    Structural design, tooling, fabrication, and test activities are reported for a program to develop an advanced composite vertical stabilizer (CVS) for the DC 10 Commercial Transport Aircraft. Structural design details are described and the status of structural and weight analyses are reported. A structural weight reduction of 21.7% is currently predicted. Test results are discussed for sine wave stiffened shear webs containing representative of the CVS spar webs and for lightning current transfer and tests on a panel representative of the CVS skins.

  8. Custom Machines Advance Composite Manufacturing

    NASA Technical Reports Server (NTRS)

    2012-01-01

    Here is a brief list of materials that NASA will not be using to construct spacecraft: wood, adobe, fiberglass, bone. While it might be obvious why these materials would not make for safe space travel, they do share a common characteristic with materials that may well be the future foundation of spacecraft design: They all are composites. Formed of two or more unlike materials - such as cellulose and lignin in the case of wood, or glass fibers and plastic resin in the case of fiberglass-composites provide enhanced mechanical and physical properties through the combination of their constituent materials. For this reason, composites are used in everything from buildings, bathtubs, and countertops to boats, racecars, and sports equipment. NASA continually works to develop new materials to enable future space missions - lighter, less expensive materials that can still withstand the extreme demands of space travel. Composites such as carbon fiber materials offer promising solutions in this regard, providing strength and stiffness comparable to metals like aluminum but with less weight, allowing for benefits like better fuel efficiency and simpler propulsion system design. Composites can also be made fatigue tolerant and thermally stable - useful in space where temperatures can swing hundreds of degrees. NASA has recently explored the use of composites for aerospace applications through projects like the Composite Crew Module (CCM), a composite-constructed version of the aluminum-lithium Multipurpose Crew Capsule. The CCM was designed to give NASA engineers a chance to gain valuable experience developing and testing composite aerospace structures.

  9. Performance Properties of Graphite Reinforced Composites with Advanced Resin Matrices

    NASA Technical Reports Server (NTRS)

    Kourtides, Demetrius A.

    1980-01-01

    This article looks at the effect of different resin matrices on thermal and mechanical properties of graphite composites, and relates the thermal and flammability properties to the anaerobic char yield of the resins. The processing parameters of graphite composites utilizing graphite fabric and epoxy or other advanced resins as matrices are presented. Thermoset resin matrices studied were: aminecured polyfunctional glycidyl aminetype epoxy (baseline), phenolicnovolac resin based on condensation of dihydroxymethyl-xylene and phenol cured with hexamine, two types of polydismaleimide resins, phenolic resin, and benzyl resin. The thermoplastic matrices studied were polyethersulfone and polyphenylenesulfone. Properties evaluated in the study included anaerobic char yield, limiting oxygen index, smoke evolution, moisture absorption, and mechanical properties at elevated temperatures including tensile, compressive, and short-beam shear strengths. Generally, it was determined that graphite composites with the highest char yield exhibited optimum fire-resistant properties.

  10. Research priorities for advanced fibrous composites

    NASA Technical Reports Server (NTRS)

    Baumann, K. J.; Swedlow, J. L.

    1981-01-01

    Priorities for research in advanced laminated fibrous composite materials are presented. Supporting evidence is presented in two bodies, including a general literature survey and a survey of aerospace composite hardware and service experience. Both surveys were undertaken during 1977-1979. Specific results and conclusions indicate that a significant portion of contemporary published research diverges from recommended priorites.

  11. The correlation of ultrasonic attenuation and shear strength in graphite-polyimide composites

    NASA Technical Reports Server (NTRS)

    Hayford, D. T.; Henneke, E. G., II; Stinchcomb, W. W.

    1977-01-01

    The buffer rod technique for measuring attenuation in thin specimens is modified here to apply to specimens having intermediate thicknesses and high attenuation. The described procedure, which requires only one accessible surface of the material, was used to determine the initial attenuation values of ultrasonic waves in short beam shear specimens of graphite-polyimide composite material. It is shown that there is good correlation between the initial attenuation values and the shear strengths of the specimens determined by the standard short beam shear test method. The modified ultrasonic buffer block technique offers much potential for service as a quantitative, nondestructive, quality assurance test for composite materials.

  12. Shear Characteristics of Hybrid Composites with Non-Woven Carbon Tissue

    NASA Astrophysics Data System (ADS)

    Lee, Seung-Hwan; Noguchi, Hiroshi

    Mechanical shear characteristics of hybrid composites with non-woven carbon tissue (NWCT) are investigated under uni-axial static tensile loadings. In-plane characteristics were studied on [±45]3S angle-ply CFRP laminates and [+45/-45/+45/-45/+45/-45]S angle-ply hybrid laminates. Here, the symbol “/” means that the NWCT is located at an interface between CFRP layers. A new estimation method was proposed for the stiffness of hybrid composites. Chord shear modulus and 0.2%-offset shear strength of hybrid laminates were compared with those of CFRP laminates. Results estimated with the new method were compared with results of experiments and an ordinary rule of mixtures, and then the validity was confirmed. The hybrid angle-ply laminate seems to be effective to improve the shear characteristics. The damage and failure mechanisms of the hybrid composites were discussed through observation results with an optical microscope.

  13. An Evaluation of the Iosipescu Specimen for Composite Materials Shear Property Measurement. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Ho, Henjen

    1991-01-01

    A detailed evaluation of the suitability of the Iosipescu specimen tested in the modified Wyoming fixture is presented. An experimental investigation using conventional strain gage instrumentation and moire interferometry is performed. A finite element analysis of the Iosipescu shear test for unidirectional and cross-ply composites is used to assess the uniformity of the shear stress field in the vicinity of the notch, and demonstrate the effect of the nonuniform stress field upon the strain gage measurements used for the determination of composite shear moduli. From the test results for graphite-epoxy laminates, it is shown that the proximity of the load introduction point to the test section greatly influences the individual gage readings for certain fiber orientations but the effect upon shear modulus measurement is relatively unimportant. A numerical study of the load contact effect shows the sensitivity of some fiber configurations to the specimen/fixture contact mechanism and may account for the variations in the measured shear moduli. A comparison of the strain gage readings from one surface of a specimen with corresponding data from moire interferometry on the opposite face documented an extreme sensitivity of some fiber orientations to eccentric loading which induced twisting and yielded spurious shear stress-strain curves. In the numerical analysis, it is shown that the Iosipescu specimens for different fiber orientations have to be modeled differently in order to closely approximate the true loading conditions. Correction factors are needed to allow for the nonuniformity of the strain field and the use of the average shear stress in the shear modulus evaluation. The correction factors, which are determined for the region occupied by the strain gage rosette, are found to be dependent upon the material orthotropic ratio and the finite element models. Based upon the experimental and numerical results, recommendations for improving the reliability and

  14. A comparative evaluation of in-plane shear test methods for laminated graphite-epoxy composites

    NASA Technical Reports Server (NTRS)

    Morton, John; Ho, Henjen

    1992-01-01

    The objectives were to evaluate popular shear test methods for various forms of graphite-epoxy composite materials and to determine the shear response of graphite-epoxy composites with various forms of fiber architecture. Numerical and full-field experimental stress analyses were performed on four shear test configurations for unidirectional and bidirectional graphite-epoxy laminates to assess the uniformity and purity of the shear stress (strain) fields produced in the specimen test section and to determine the material in-plane shear modulus and shear response. The test methods were the 10 deg off-axis, the +/- 45 deg tension, the Iosipescu V-notch, and a compact U-notch specimen. Specimens were prepared from AS4/3501-6 graphite-epoxy panels, instrumented with conventional strain gage rosettes and with a cross-line moire grating, and loaded in a convenient testing machine. The shear responses obtained for each test method and the two methods of specimen instrumentation were compared. In a second phase of the program the shear responses obtained from Iosipescu V-notch beam specimens were determined for woven fabric geometries of different weave and fiber architectures. Again the responses of specimens obtained from strain gage rosettes and moire interferometry were compared. Additional experiments were performed on a bidirectional cruciform specimen which was also instrumented with strain gages and a moire grating.

  15. A simple higher order shear deformation theory for mechanical behavior of laminated composite plates

    NASA Astrophysics Data System (ADS)

    Adim, Belkacem; Daouadji, Tahar Hassaine; Rabahi, Aberezak

    2016-06-01

    In the present study, the static, buckling, and free vibration of laminated composite plates is examined using a refined shear deformation theory and developed for a bending analysis of orthotropic laminated composite plates. These models take into account the parabolic distribution of transverse shear stresses and satisfy the condition of zero shear stresses on the top and bottom surfaces of the plates. The most interesting feature of this theory is that it allows for parabolic distributions of transverse shear stresses across the plate thickness and satisfies the conditions of zero shear stresses at the top and bottom surfaces of the plate without using shear correction factors. The number of independent unknowns in the present theory is four, as against five in other shear deformation theories. In the analysis, the equation of motion for simply supported thick laminated rectangular plates is obtained through the use of Hamilton's principle. The accuracy of the analysis presented is demonstrated by comparing the results with solutions derived from other higher order models and with data found in the literature. It can be concluded that the proposed theory is accurate and simple in solving the static, the buckling, and free vibration behaviors of laminated composite plates.

  16. A simple higher order shear deformation theory for mechanical behavior of laminated composite plates

    NASA Astrophysics Data System (ADS)

    Adim, Belkacem; Daouadji, Tahar Hassaine; Rabahi, Aberezak

    2016-05-01

    In the present study, the static, buckling, and free vibration of laminated composite plates is examined using a refined shear deformation theory and developed for a bending analysis of orthotropic laminated composite plates. These models take into account the parabolic distribution of transverse shear stresses and satisfy the condition of zero shear stresses on the top and bottom surfaces of the plates. The most interesting feature of this theory is that it allows for parabolic distributions of transverse shear stresses across the plate thickness and satisfies the conditions of zero shear stresses at the top and bottom surfaces of the plate without using shear correction factors. The number of independent unknowns in the present theory is four, as against five in other shear deformation theories. In the analysis, the equation of motion for simply supported thick laminated rectangular plates is obtained through the use of Hamilton's principle. The accuracy of the analysis presented is demonstrated by comparing the results with solutions derived from other higher order models and with data found in the literature. It can be concluded that the proposed theory is accurate and simple in solving the static, the buckling, and free vibration behaviors of laminated composite plates.

  17. Advanced textile structural composites -- status and outlook

    SciTech Connect

    Arendts, F.J.; Drechsler, K.; Brandt, J.

    1993-12-31

    Composites with 3D woven, braided or knitted fiber reinforcement offer a high potential for the cost-effective manufacturing of structures featuring an interesting mechanical performance, for example with regard to damage tolerance or energy absorption capability. In this paper, the properties of various textile structural composites with regard to stiffness, strength, damage tolerance, energy absorption capability as well as the respective manufacturing processes (RTM or thermoplastic hybrid-yarn technique) are presented in comparison to conventional ud tape based composites. The influence of the fiber architecture on the mechanical performance (tensile stiffness and strength, compression strength, interlaminar shear strength, compression strength after impact, fracture mechanical properties, through-penetration resistance) of monolithic and composite sandwich structures has been evaluated in an experimental study. It has been shown that composites involving new 3D weavings with minimum fiber crimp can compete with tape-based laminates as far as stiffness and strength are concerned. Using knittings makes it possible to manufacture composites having superior through-penetration resistance. The specific feature of the 3D braiding process is the ability to produce complex shaped structures having a high degree of freedom with regard to fiber geometry. Finally, the application of various textile structural composites will be presented on the basis of three demonstrator components (automotive engine mount, aircraft leading edge and motor cycle helmet), and the potential for further developments will be discussed.

  18. Crack Growth Mechanisms under Anti-Plane Shear in Composite Laminates

    NASA Astrophysics Data System (ADS)

    Horner, Allison Lynne

    The research conducted for this dissertation focuses on determining the mechanisms associated with crack growth in polymer matrix composite laminates subjected to anti-plane shear (mode III) loading. For mode III split-beam test methods were proposed, and initial evaluations were conducted. A single test method was selected for further evaluation. Using this test method, it was determined that the apparent mode III delamination toughness, GIIIc , depended on geometry, which indicated a true material property was not being measured. Transverse sectioning and optical microscopy revealed an array of transverse matrix cracks, or echelon cracks, oriented at approximately 45° and intersecting the plane of the delamination. Subsequent investigations found the echelon array formed prior to the onset of planar delamination advance and that growth of the planar delamination is always coupled to echelon array formation in these specimens. The evolution of the fracture surfaces formed by the echelon array and planar delamination were studied, and it was found that the development was similar to crack growth in homogenous materials subjected to mode III or mixed mode I-III loading, although the composite laminate architecture constrained the fracture surface development differently than homogenous materials. It was also found that, for split-beam specimens such as those used herein, applying an anti-plane shear load results in twisting of the specimen's uncracked region which gives rise to a mixed-mode I-III load condition. This twisting has been related to the apparent mode III toughness as well as the orientation of the transverse matrix cracks. A finite element model was then developed to study the mechanisms of initial echelon array formation. From this, it is shown that an echelon array will develop, but will become self-limiting prior to the onset of planar delamination growth.

  19. Advanced composite airframe program: Today's technology

    NASA Technical Reports Server (NTRS)

    Good, Danny E.; Mazza, L. Thomas

    1988-01-01

    The Advanced Composite Airframe Program (ACAP) was undertaken to demonstrate the advantages of the application of advanced composite materials and structural design concepts to the airframe structure on helicopters designed to stringent military requirements. The primary goals of the program were the reduction of airframe production costs and airframe weight by 17 and 22 percent respectively. The ACAP effort consisted of a preliminary design phase, detail design, and design support testing, full-scale fabrication, laboratory testing, and a ground/flight test demonstration. Since the completion of the flight test demonstration programs follow-on efforts were initiated to more fully evaluate a variety of military characteristics of the composite airframe structures developed under the original ACAP advanced development contracts. An overview of the ACAP program is provided and some of the design features, design support testing, manufacturing approaches, and the results of the flight test evaluation, as well as, an overview of Militarization Test and Evaluation efforts are described.

  20. Evaluation of interlaminar shear strength of a unidirectional carbon/epoxy laminated composite under impact loading

    NASA Astrophysics Data System (ADS)

    Yokoyama, T.; Nakai, K.

    2006-08-01

    The interlaminar shear strength (ILSS) of a unidirectional carbon/epoxy (T700/2521) laminated composite under impact loading is determined using the conventional split Hopkinson pressure bar. Double-notch shear (DNS) specimens with lateral constraint from a supporting jig are used in the static and impact interlaminar compressive shear tests. Short-beam shear specimens are also used under static 3-point bending. Numerical stress analyses are performed to determine the shear stress and normal stress distributions on the expected failure plane in the DNS specimen using the MSC/NASTRAN package. The effect of deformation rate on the ILSS and failure mode is investigated. It is observed that the ILSS is independent of the deformation rate up to nearly 1.5m/s (dotγ ≈ 780/s). The validity of the test results is confirmed by microscopic examinations of both static and impact failure surfaces for the DNS specimens.

  1. Characterization of compressive and short beam shear strength of bamboo opened cell foam core sandwich composites

    NASA Astrophysics Data System (ADS)

    Setyawan, Paryanto Dwi; Sugiman, Saputra, Yudhi

    2016-03-01

    The paper presents the compressive and the short beam shear strength of a sandwich composite with opened cell foam made of bamboo fiber as the core and plywood as the skins. The core thickness was varied from 10 mm to 40 mm keeping the volume fraction of fiber constant. Several test s were carried out including the core density, flatwise compressive and the short beam shear testing in three point bending. The results show that the density of bamboo opened cell foam is comparable with commercial plastic foam, such as polyurethane foam. The compressive strength tends to increase linearly with increasing the core thickness. The short beam shear failure load of the sandwich composite increases with the increase of core thickness, however on the contrary, the short beam shear strength which tends to sharply decrease from the thickness of 10 mm to 30 mm and then becomes flat.

  2. Fiber pushout and interfacial shear in metal-matrix composites

    NASA Technical Reports Server (NTRS)

    Koss, Donald A.; Hellmann, John R.; Kallas, M. N.

    1993-01-01

    Recent thin-slice pushout tests have suggested that MMC matrix-fiber interface failure processes depend not only on such intrinsic factors as bond strength and toughness, and matrix plasticity, but such extrinsic factors as specimen configuration, thermally-induced residual stresses, and the mechanics associated with a given test. After detailing the contrasts in fiber-pullout and fiber-pushout mechanics, attention is given to selected aspects of thin-slice fiber pushout behavior illustrative of the physical nature of interfacial shear response and its dependence on both intrinsic and extrinsic factors.

  3. Large strain variable stiffness composites for shear deformations with applications to morphing aircraft skins

    NASA Astrophysics Data System (ADS)

    McKnight, G. P.; Henry, C. P.

    2008-03-01

    Morphing or reconfigurable structures potentially allow for previously unattainable vehicle performance by permitting several optimized structures to be achieved using a single platform. The key to enabling this technology in applications such as aircraft wings, nozzles, and control surfaces, are new engineered materials which can achieve the necessary deformations but limit losses in parasitic actuation mass and structural efficiency (stiffness/weight). These materials should exhibit precise control of deformation properties and provide high stiffness when exercised through large deformations. In this work, we build upon previous efforts in segmented reinforcement variable stiffness composites employing shape memory polymers to create prototype hybrid composite materials that combine the benefits of cellular materials with those of discontinuous reinforcement composites. These composites help overcome two key challenges for shearing wing skins: the resistance to out of plane buckling from actuation induced shear deformation, and resistance to membrane deflections resulting from distributed aerodynamic pressure loading. We designed, fabricated, and tested composite materials intended for shear deformation and address out of plane deflections in variable area wing skins. Our designs are based on the kinematic engineering of reinforcement platelets such that desired microstructural kinematics is achieved through prescribed boundary conditions. We achieve this kinematic control by etching sheets of metallic reinforcement into regular patterns of platelets and connecting ligaments. This kinematic engineering allows optimization of materials properties for a known deformation pathway. We use mechanical analysis and full field photogrammetry to relate local scale kinematics and strains to global deformations for both axial tension loading and shear loading with a pinned-diamond type fixture. The Poisson ratio of the kinematically engineered composite is ~3x higher than

  4. Advanced composite stabilizer for Boeing 737 aircraft

    NASA Technical Reports Server (NTRS)

    1978-01-01

    Activities related to development of an advanced composites stabilizer for the Boeing 737 commercial transport are reported. Activities include discussion of criteria and objectives, design loads, the fatigue spectrum definition to be used for all spectrum fatigue testing, fatigue analysis, manufacturing producibility studies, the ancillary test program, quality assurance, and manufacturing development.

  5. Advanced composite elevator for Boeing 727 aircraft

    NASA Technical Reports Server (NTRS)

    1978-01-01

    Detail design activities are reported for a program to develop an advanced composites elevator for the Boeing 727 commercial transport. Design activities include discussion and results of the ancillary test programs, sustaining efforts, weight status, manufacturing producibility studies, quality assurance development, and production status.

  6. ISAAC - A Testbed for Advanced Composites Research

    NASA Technical Reports Server (NTRS)

    Wu, K. Chauncey; Stewart, Brian K.; Martin, Robert A.

    2014-01-01

    The NASA Langley Research Center is acquiring a state-of-art composites fabrication environment to support the Center's research and technology development mission. This overall system described in this paper is named ISAAC, or Integrated Structural Assembly of Advanced Composites. ISAAC's initial operational capability is a commercial robotic automated fiber placement system from Electroimpact, Inc. that consists of a multi-degree of freedom commercial robot platform, a tool changer mechanism, and a specialized automated fiber placement end effector. Examples are presented of how development of advanced composite materials, structures, fabrication processes and technology are enabled by utilizing the fiber placement end effector directly or with appropriate modifications. Alternatively, end effectors with different capabilities may either be bought or developed with NASA's partners in industry and academia.

  7. Iosipescu shear characterization of polymeric and metal matrix composites

    SciTech Connect

    Pindera, M.J.; Ifju, P.; Post, D. Virginia Polytechnic Institute and State Univ., Blacksburg )

    1990-03-01

    The paper outlines the results of an experimental/analytical investigation of deformation and stress fields in the test section of graphite/epoxy and boron/aluminum Iosipescu specimens using high-resolution moire interferometry and finite-element analysis. Very good correlation between experiment and analysis is demonstrated for the graphite/epoxy specimens. This, in turn, justifies the use of correction factors employed in the previous investigations to eliminate differences in the initial shear moduli obtained from 0-deg and 90-deg Iosipescu specimens. The significant discrepancies observed in the case of boron/aluminum specimens are attributed to localized yielding at the notch tips caused by the clamping action, the associated in-plane bending effects and changing boundary conditions due to slippage in the grips. 9 refs.

  8. A Shear Deformable Shell Element for Laminated Composites

    NASA Technical Reports Server (NTRS)

    Chao, W. C.; Reddy, J. N.

    1984-01-01

    A three-dimensional element based on the total Lagrangian description of the motion of a layered anisotropic composite medium is developed, validated, and used to analyze layered composite shells. The element contains the following features: geometric nonlinearity, dynamic (transient) behavior, and arbitrary lamination scheme and lamina properties. Numerical results of nonlinear bending, natural vibration, and transient response are presented to illustrate the capabilities of the element.

  9. Evaluation of a metal shear web selectively reinforced with filamentary composites for space shuttle application. Phase 1 summary report: Shear web design development

    NASA Technical Reports Server (NTRS)

    Laakso, J. H.; Zimmerman, D. K.

    1972-01-01

    An advanced composite shear web design concept was developed for the Space Shuttle orbiter main engine thrust beam structure. Various web concepts were synthesized by a computer-aided adaptive random search procedure. A practical concept is identified having a titanium-clad + or - 45 deg boron/epoxy web plate with vertical boron/epoxy reinforced aluminum stiffeners. The boron-epoxy laminate contributes to the strength and stiffness efficiency of the basic web section. The titanium-cladding functions to protect the polymeric laminate parts from damaging environments and is chem-milled to provide reinforcement in selected areas. Detailed design drawings are presented for both boron/epoxy reinforced and all-metal shear webs. The weight saving offered is 24% relative to all-metal construction at an attractive cost per pound of weight saved, based on the detailed designs. Small scale element tests substantiate the boron/epoxy reinforced design details in critical areas. The results show that the titanium-cladding reliably reinforces the web laminate in critical edge load transfer and stiffener fastener hole areas.

  10. Interfacial Shear Strength of Cast and Directionally Solidified Nial-Sapphire Fiber Composites

    NASA Technical Reports Server (NTRS)

    Tewari, S. N.; Asthana, R.; Noebe, R. D.

    1993-01-01

    The feasibility of fabricating intermetallic NiAl-sapphire fiber composites by casting and zone directional solidification has been examined. The fiber-matrix interfacial shear strengths measured using a fiber push-out technique in both cast and directionally solidified composites are greater than the strengths reported for composites fabricated by powder cloth process using organic binders. Microscopic examination of fibers extracted from cast, directionally solidified (DS), and thermally cycled composites, and the high values of interfacial shear strengths suggest that the fiber-matrix interface does not degrade due to casting and directional solidification. Sapphire fibers do not pin grain boundaries during directional solidification, suggesting that this technique can be used to fabricate sapphire fiber reinforced NiAl composites with single crystal matrices.

  11. Prebuckling and Postbuckling Response of Tailored Composite Stiffened Panels with Axial-Shear Coupling

    NASA Technical Reports Server (NTRS)

    Young, Richard D.; Hyer, Michael W.; Starnes, James H., Jr.

    2000-01-01

    Results of a numerical parametric study of the prebuckling and postbuckling response of tailored composite stiffened panels with axial-shear coupling are presented. In the stiffened panels, axial-shear stiffness coupling is created by rotating the stiffener orientation and tailoring the skin laminate anisotropy. The panels are loaded in axial compression and the effects of stiffener orientation and skin anisotropy on the panel stiffness, buckling parameters, and axial-shear coupling response are described. Results are obtained from a nonlinear general shell finite element analysis computer code. The prebuckling and postbuckling responses can be affected by both the stiffener orientation and skin laminate anisotropy, and the effects are different and load dependent. The results help identify different mechanisms for axial-shear coupling, and show that a load-dependent structural response can be controlled by selecting appropriate stiffener and skin parameters.

  12. Structural Aspects of Railway Truss Bridges Affecting Transverse Shear Forces in Steel-Concrete Composite Decks

    NASA Astrophysics Data System (ADS)

    Siekierski, Wojciech

    2015-03-01

    At the steel-concrete interface, the horizontal shear forces that are transverse to cross beams occur due to joint action of the steel-concrete composite deck and the truss girders. Numerical analysis showed that values of the forces are big in comparison to the longitudinal shear forces. In both cases extreme force values occur near side edges of a slab. The paper studies possibilities of reduction of these shear forces by structural alterations of the following: rigidity of a concrete slab, arrangement of a wind bracing, arrangement of concrete slab expansion joints. An existing railway truss bridge span has been analysed. Numerical analysis shows that it is possible to reduce the values of shear forces transverse to cross beams. It may reach 20% near the side edges of slabs and 23% in the centre of slab width.

  13. Automotive applications for advanced composite materials

    NASA Technical Reports Server (NTRS)

    Deutsch, G. C.

    1978-01-01

    A description is presented of nonaerospace applications for advanced composite materials with special emphasis on the automotive applications. The automotive industry has to satisfy exacting requirements to reduce the average fuel consumption of cars. A feasible approach to accomplish this involves the development of composites cars with a total weight of 2400 pounds and a fuel consumption of 33 miles per gallon. In connection with this possibility, the automotive companies have started to look seriously at composite materials. The aerospace industry has over the past decade accumulated a considerable data base on composite materials and this is being made available to the nonaerospace sector. However, the automotive companies will place prime emphasis on low cost resins which lend themselves to rapid fabrication techniques.

  14. An Experimental and Analytical Evaluation of a Biaxial Test for Determining Shear Properties of Composite Materials

    NASA Technical Reports Server (NTRS)

    Kennedy, John M.; Barnett, Terry R.

    1988-01-01

    The results of an experimental and analytical investigation of a biaxial tension/compression test for determining shear properties of composite materials are reported. Using finite element models of isotropic and orthotropic laminates, a specimen geometry was optimized. A kinematic fixture was designed to introduce an equal and opposite pair of forces into a specimen with a one inch square test section. Aluminum and several composite laminates with the optimized geometry and a configuration with large stress gradients were tested in the fixture. The specimens were instrumented with strain gages in the center of the test section for shear stiffness measurements. Pure shear strain was measured. The results from the experiments correlated well with finite element results. Failure of the specimens occurred through the center of the test section and appeared to have initiated at the high stress points. The results lead to the conclusion that the optimized specimen is suitable for determining shear modulus for composite materials. Further revisions to the specimen geometry are necessary if the method is to give shear strength data.

  15. Shear deformable versus classical theories for nonlinear vibrations of rectangular isotropic and laminated composite plates

    NASA Astrophysics Data System (ADS)

    Amabili, M.; Farhadi, S.

    2009-02-01

    In the present study, (i) the classical Von Kárman theory, (ii) the first-order shear deformation theory and (iii) the higher-order (third-order) shear deformation theory are compared for studying the nonlinear forced vibrations of isotropic and laminate composite rectangular plates. In particular, the harmonic response in the frequency neighborhood of the fundamental mode of rectangular plates is investigated and the response curves computed by using the three different theories are compared. The boundary conditions of the plates are simply supported with immovable edges. Geometric imperfections are taken into account. Calculations for isotropic and laminated composite plates are presented and results are discussed. For isotropic plates, the frequency-response curves for large-amplitude vibrations obtained by using the three theories are almost coincident. For laminated composite plates, differences arise for relatively thick plates (ratio between the thickness and the edge equal to 0.1), while for thin plates (ratio between the thickness and the edge equal to 0.01), no difference is obtained. For all cases, the first-order shear deformation (with shear correction factor √{3}/2) and the higher-order shear deformation theories give practically coincident results and differences are observed with respect to the classical Von Kárman theory.

  16. Electrically Percolating Clusters in Sheared Carbon Nanotube Composites

    NASA Astrophysics Data System (ADS)

    Migler, Kalman; Moon, Doyoung; Obrzut, Jan; Douglas, Jack; Lam, Thomas; Sharma, Renu; Liddle, Alex James

    2013-03-01

    The electrical conductivity of polymer nanotube composites can be dramatically modified by processing flows and subsequent annealing. The mechanism is widely believed to be nanotube structural rearrangements that occur during flow and alter the percolating pathways. We seek to directly visualize these flow-induced three-dimensional percolating clusters through three-dimensional confocal microscopy and image analysis.

  17. Relationship between voids and interlaminar shear strength of polymer matrix composites

    NASA Technical Reports Server (NTRS)

    Bowles, Kenneth J.; Frimpong, Stephen

    1991-01-01

    The effect of voids on the interlaminar shear strength of a polyimide matrix composite system is described. The AS4 graphite/PMR-15 composite was chosen for study because this system can be readily processed by using the standard specified cure cycle to produce void-free composites and because preliminary work in this study had shown that the processing parameters of this resin matrix system can be altered to produce cured composites of varying void contents. Thirty-eight 12-ply unidirectional composite panels were fabricated for this study. A significant range of void contents (0 to 10 percent) was produced. The panels were mapped, ultrasonically inspected, and sectioned into interlaminar shear, flexure, and fiber content specimens. The density of each specimen was measured and interlaminar shear and flexure strength measurements were then made. The fiber content was measured last. The results of these tests were evaluated by using ultrasonic results, photomicrographs, statistical methods, theoretical relationships derived by other investigators, and comparison of the test data with the Integrated Composite Analyzer (ICAN) computer program developed at the Lewis Research Center for predicting composite ply properties. The testing is described in as much detail as possible in order to help others make realistic comparisons.

  18. The effect of dentin primer on the shear bond strength between composite resin and enamel.

    PubMed

    Hadavi, F; Hey, J H; Ambrose, E R; Louie, P W; Shinkewski, D J

    1993-01-01

    The purpose of this study was to determine the effect of accidental dentin primer contact with etched enamel on shear bond strength of composite resin to enamel. Four dentin bonding systems were included in this study: GLUMA Dentin Bond, Scotchbond, and Prisma Universal Bond 2 and 3. Eighty extracted human permanent anterior teeth were used and divided in eight test groups. The vestibular surfaces were ground and acid etched. For each dentin bonding system 10 samples were treated with dentin primer prior to placement of resin. Shear bond testing showed that enamel contact with dentin primer in the above two systems decreased the shear bond strength between composite and enamel by 31 to 44%. PMID:8337183

  19. Compressive and shear buckling analysis of metal matrix composite sandwich panels under different thermal environments

    NASA Technical Reports Server (NTRS)

    Ko, William L.; Jackson, Raymond H.

    1993-01-01

    Combined inplane compressive and shear buckling analysis was conducted on flat rectangular sandwich panels using the Raleigh-Ritz minimum energy method with a consideration of transverse shear effect of the sandwich core. The sandwich panels were fabricated with titanium honeycomb core and laminated metal matrix composite face sheets. The results show that slightly slender (along unidirectional compressive loading axis) rectangular sandwich panels have the most desirable stiffness-to-weight ratios for aerospace structural applications; the degradation of buckling strength of sandwich panels with rising temperature is faster in shear than in compression; and the fiber orientation of the face sheets for optimum combined-load buckling strength of sandwich panels is a strong function of both loading condition and panel aspect ratio. Under the same specific weight and panel aspect ratio, a sandwich panel with metal matrix composite face sheets has much higher buckling strength than one having monolithic face sheets.

  20. Second NASA Advanced Composites Technology Conference

    NASA Technical Reports Server (NTRS)

    Davis, John G., Jr. (Compiler); Bohon, Herman L. (Compiler)

    1992-01-01

    The conference papers are presented. The Advanced Composite Technology (ACT) Program is a major multi-year research initiative to achieve a national goal of technology readiness before the end of the decade. Conference papers recorded results of research in the ACT Program in the specific areas of automated fiber placement, resin transfer molding, textile preforms, and stitching as these processes influence design, performance, and cost of composites in aircraft structures. These papers will also be included in the Ninth Conference Proceedings to be published by the Federal Aviation Administration as a separate document.

  1. NASA Thermographic Inspection of Advanced Composite Materials

    NASA Technical Reports Server (NTRS)

    Cramer, K. Elliott

    2004-01-01

    As the use of advanced composite materials continues to increase in the aerospace community, the need for a quantitative, rapid, in situ inspection technology has become a critical concern throughout the industry. In many applications it is necessary to monitor changes in these materials over an extended period of time to determine the effects of various load conditions. Additionally, the detection and characterization of defects such as delaminations, is of great concern. This paper will present the application of infrared thermography to characterize various composite materials and show the advantages of different heat source types. Finally, various analysis methodologies used for quantitative material property characterization will be discussed.

  2. Advanced fiber placement of composite fuselage structures

    NASA Technical Reports Server (NTRS)

    Anderson, Robert L.; Grant, Carroll G.

    1991-01-01

    The Hercules/NASA Advanced Composite Technology (ACT) program will demonstrate the low cost potential of the automated fiber placement process. The Hercules fiber placement machine was developed for cost effective production of composite aircraft structures. The process uses a low cost prepreg tow material form and achieves equivalent laminate properties to structures fabricated with prepreg tape layup. Fiber placement demonstrations planned for the Hercules/NASA program include fabrication of stiffened test panels which represent crown, keel, and window belt segments of a typical transport aircraft fuselage.

  3. Normal and shear impact of layered composite with a crack - Dynamic stress intensification

    NASA Technical Reports Server (NTRS)

    Sih, G. C.; Chen, E. P.

    1980-01-01

    The dynamic response of a layered composite under normal and shear impact is analyzed by assuming that the composite contains an initial flaw in the matrix material. One of the objectives was to develop an analytical method for determining dynamic stress solutions which should lead to a numerical method which utilizes Fourier transform for the space variable and Laplace transform for the time variable. The time-dependent angle loading is separated into two parts: a symmetric and a skew-symmetric with reference to the crack plane. By superposition, the transient boundary conditions consist of applying normal and shear tractions to a crack embedded in a layered composite; one phase of the composite could represent the fiber while the other could be the matrix. Mathematically, these conditions reduce the problem to a system of dual integral equations solved in the transform plane for the transform of the dynamic stress-intensity factor.

  4. Advanced composite elevator for Boeing 727 aircraft

    NASA Technical Reports Server (NTRS)

    1979-01-01

    Detail design activities are reported for a program to develop an advanced composites elevator for the Boeing 727 commercial transport. Design activities include discussion of the full scale ground test and flight test activities, the ancillary test programs, sustaining efforts, weight status, and the production status. Prior to flight testing of the advanced composites elevator, ground, flight flutter, and stability and control test plans were reviewed and approved by the FAA. Both the ground test and the flight test were conducted according to the approved plan, and were witnessed by the FAA. Three and one half shipsets have now been fabricated without any significant difficulty being encountered. Two elevator system shipsets were weighed, and results validated the 26% predicted weight reduction. The program is on schedule.

  5. Incremental layer shear bond strength of low-shrinkage resin composites under different bonding conditions.

    PubMed

    Al Musa, A H; Al Nahedh, H N A

    2014-01-01

    The purpose of this study was to determine the incremental shear bond strength of a silorane-based composite (Filtek Silorane) repaired with silorane or a methacrylate-based composite (Filtek Z250) under various aging conditions. Also, the incremental bond strength of the silorane-based composite was compared with that of another low-shrinkage methacrylate-based composite (Aelite LS Posterior) under fresh and aged conditions, with and without the use of an adhesive resin between successive layers. The two brands of low-shrinkage composites were compared with a microhybrid, Filtek Z250, which served as the control. Substrate discs were fabricated and second layers were adhered to them immediately, after two weeks of aging, or after four weeks of aging and with and without an adhesive resin. Shear bond strengths were measured and failure modes were evaluated. The incremental bond strength of silorane to the silorane-based composite was not significantly different from that of the methacrylate-based composite. However, repairing a silorane-based composite with a methacrylate-based composite significantly reduced the bond strength. Aelite showed a lower incremental bond strength than Z250 and silorane, but the use of an adhesive significantly improved the bond strength. The absence of an oxygen-inhibited layer did not affect the bond strength of the consecutive layers of the silorane-based composite. PMID:24807812

  6. Advanced powder metallurgy aluminum alloys and composites

    NASA Technical Reports Server (NTRS)

    Lisagor, W. B.; Stein, B. A.

    1982-01-01

    The differences between powder and ingot metallurgy processing of aluminum alloys are outlined. The potential payoff in the use of advanced powder metallurgy (PM) aluminum alloys in future transport aircraft is indicated. The national program to bring this technology to commercial fruition and the NASA Langley Research Center role in this program are briefly outlined. Some initial results of research in 2000-series PM alloys and composites that highlight the property improvements possible are given.

  7. The plane strain shear fracture of the advanced high strength steels

    SciTech Connect

    Sun, Li

    2013-12-16

    The “shear fracture” which occurs at the high-curvature die radii in the sheet metal forming has been reported to remarkably limit the application of the advanced high strength steels (AHSS) in the automobile industry. However, this unusual fracture behavior generally cannot be predicted by the traditional forming limit diagram (FLD). In this research, a new experimental system was developed in order to simulate the shear fracture, especially at the plane strain state which is the most common state in the auto-industry and difficult to achieve in the lab due to sample size. Furthermore, the system has the capability to operate in a strain rate range from quasi-static state to the industrial forming state. One kinds of AHSS, Quenching-Partitioning (QP) steels have been performed in this test and the results show that the limiting fracture strain is related to the bending ratio and strain rate. The experimental data support that deformation-induced heating is an important cause of “shear fracture” phenomena for AHSS: a deformation-induced quasi-heating caused by smaller bending ratio and high strain rate produce a smaller limiting plane strain and lead a “shear fracture” in the component.

  8. Micromechanical Modeling Efforts for Advanced Composites

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Over the past two decades, NASA Lewis Research Center's in-house efforts in analytical modeling for advanced composites have yielded several computational predictive tools. These are, in general, based on simplified micromechanics equations. During the last 3 years, our efforts have been directed primarily toward developing prediction tools for high temperature ceramic matrix composite (CMC's) materials. These materials are being considered for High Speed Research program applications, specifically for combustor liners. In comparison to conventional materials, CMC's offer several advantages: high specific stiffness and strength, and higher toughness and nonbrittle failure in comparison to monolithic ceramics, as well as environmental stability and wear resistance for both roomtemperature and elevated-temperature applications. Under the sponsorship of the High Temperature Engine Materials Program (HITEMP), CMC analytical modeling has resulted in the computational tool Ceramic Matrix Composites Analyzer (CEMCAN).

  9. Development of advanced composite ceramic tool material

    SciTech Connect

    Huang Chuanzhen; Ai Xing

    1996-08-01

    An advanced ceramic cutting tool material has been developed by means of silicon carbide whisker (SiCw) reinforcement and silicon carbide particle (SiCp) dispersion. The material has the advantage of high bending strength and fracture toughness. Compared with the mechanical properties of Al{sub 2}O{sub 3}/SiCp(AP), Al{sub 2}O{sub 3}/SiCw(JX-1), and Al{sub 2}O{sub 3}/SiCp/SiCw(JX-2-I), it confirms that JX-2-I composites have obvious additive effects of both reinforcing and toughening. The reinforcing and toughening mechanisms of JX-2-I composites were studied based on the analysis of thermal expansion mismatch and the observation of microstructure. The cutting performance of JX-2-I composites was investigated primarily.

  10. Reinforcement of metals with advanced filamentary composites

    NASA Technical Reports Server (NTRS)

    Herakovich, C. T.; Davis, J. G.; Dexter, H. B.

    1974-01-01

    This paper reviews some recent applications of the concept of reinforcing metal structures with advanced filamentary composites, and presents some results of an experimental investigation of the tensile behavior of aluminum and titanium reinforced with unidirectional boron/epoxy. Results are given for tubular and flat specimens, bonded at either room temperature or elevated temperature. The composite reinforced metals showed increased stiffness over the all-metal counterpart, as predicted by the rule of mixtures, and the results were independent of specimen geometry. The tensile strength of the born/epoxy reinforced metals is shown to be a function of the geometry of the test specimen and the method of bonding the composite to the metal.

  11. Thermo-Oxidative Stability of Graphite/PMR-15 Composites: Effect of Fiber Surface Modification on Composite Shear Properties

    NASA Technical Reports Server (NTRS)

    Madhukar, Madhu S.; Bowles, Kenneth J.; Papadopolous, Demetrios S.

    1994-01-01

    Experiments were conducted to establish a correlation between the weight loss of a polyimide (PMR- 15) matrix and graphite fibers and the in-plane shear properties of their unidirectional composites subjected to different isothermal aging times up to 1000 hr at 316 C. The role of fiber surface treatment on the composite degradation during the thermo-oxidative aging was investigated by using A4 graphite fibers with three surface modifications: untreated (AU-4), surface treated (AS-4), and surface treated and sized with an epoxy-compatible sizing (AS-4G). The weight loss of the matrix fibers, and composites was determined during the aging. The effect of thermal aging was seen in all the fiber samples in terms of weight loss and reduction in fiber diameter. Calculated values of weight loss fluxes for different surfaces of rectangular unidirectional composite plates showed that the largest weight loss occurred at those cut surfaces where fibers were perpendicular to the surface. Consequently, the largest amount of damage was also noted on these cut surfaces. Optical observation of the neat matrix and composite plates subjected to different aging times revealed that the degradation (such as matrix microcracking and void growth) occurred in a thin surface layer near the specimen edges. The in-plane shear modulus of the composites was unaffected by the fiber surface treatment and the thermal aging. The shear strength of the composites with the untreated fibers was the lowest and it decreased with aging. A fracture surface examination of the composites with untreated fibers suggested that the weak interface allowed the oxidation reaction to proceed along the interface and thus expose the inner material to further oxidation. The results indicated that the fiber-matrix interface affected the composite degradation process during its thermal aging and that the the weak interface accelerated the composite degradation.

  12. Advanced composite combustor structural concepts program

    NASA Technical Reports Server (NTRS)

    Sattar, M. A.; Lohmann, R. P.

    1984-01-01

    An analytical study was conducted to assess the feasibility of and benefits derived from the use of high temperature composite materials in aircraft turbine engine combustor liners. The study included a survey and screening of the properties of three candidate composite materials including tungsten reinforced superalloys, carbon-carbon and silicon carbide (SiC) fibers reinforcing a ceramic matrix of lithium aluminosilicate (LAS). The SiC-LAS material was selected as offering the greatest near term potential primarily on the basis of high temperature capability. A limited experimental investigation was conducted to quantify some of the more critical mechanical properties of the SiC-LAS composite having a multidirection 0/45/-45/90 deg fiber orientation favored for the combustor linear application. Rigorous cyclic thermal tests demonstrated that SiC-LAS was extremely resistant to the thermal fatigue mechanisms that usually limit the life of metallic combustor liners. A thermal design study led to the definition of a composite liner concept that incorporated film cooled SiC-LAS shingles mounted on a Hastelloy X shell. With coolant fluxes consistent with the most advanced metallic liner technology, the calculated hot surface temperatures of the shingles were within the apparent near term capability of the material. Structural analyses indicated that the stresses in the composite panels were low, primarily because of the low coefficient of expansion of the material and it was concluded that the dominant failure mode of the liner would be an as yet unidentified deterioration of the composite from prolonged exposure to high temperature. An economic study, based on a medium thrust size commercial aircraft engine, indicated that the SiC-LAS combustor liner would weigh 22.8N (11.27 lb) less and cost less to manufacture than advanced metallic liner concepts intended for use in the late 1980's.

  13. Shear-flexible finite-element models of laminated composite plates and shells

    NASA Technical Reports Server (NTRS)

    Noor, A. K.; Mathers, M. D.

    1975-01-01

    Several finite-element models are applied to the linear static, stability, and vibration analysis of laminated composite plates and shells. The study is based on linear shallow-shell theory, with the effects of shear deformation, anisotropic material behavior, and bending-extensional coupling included. Both stiffness (displacement) and mixed finite-element models are considered. Discussion is focused on the effects of shear deformation and anisotropic material behavior on the accuracy and convergence of different finite-element models. Numerical studies are presented which show the effects of increasing the order of the approximating polynomials, adding internal degrees of freedom, and using derivatives of generalized displacements as nodal parameters.

  14. Aeroelastic response of composite rotor blades considering transverse shear and structural damping

    NASA Astrophysics Data System (ADS)

    Jung, Sung Nam; Kim, Seung Jo

    1994-04-01

    The effects of transverse shear deformations and structural damping on the flutter phenomena of a composite rotor blade in hover have been investigated using the finite element method. First-order shear deformation theory with rotary inertia effects and a damped element model of composite laminates are employed for the structural formulation. A quasisteady aerodynamic theory with a dynamic inflow model is used. Torsion-related out-of-plane warping and noncirculatory aerodynamic components are also incorporated in the formulation. Using these structural and aerodynamic tools, several numerical studies are carried out, first to validate the current approach and second to show the effects of transverse shear deformations and structural damping on the aeroelstic stability of a composite rotor as a function of fiber orientation. The predictions derived by the frequency analysis of this model are found to be more accurate than those given by an alternative approach compared with experimental data. It is shown that the transverse shear flexibility tends to lower the frequency of the rotor, and generally has a destabilizing effect on the lag mode and a stabilizing effect on the flap mode. It is also presented that the magnitude of structural damping can be controlled by changing ply orientation angle.

  15. Propagation of shear elastic and electromagnetic waves in one dimensional piezoelectric and piezomagnetic composites.

    PubMed

    Shi, P; Chen, C Q; Zou, W N

    2015-01-01

    Coupled shear (SH) elastic and electromagnetic (EM) waves propagating oblique to a one dimensional periodic piezoelectric and piezomagnetic composite are investigated using the transfer matrix method. Closed-form expression of the dispersion relations is derived. We find that the band structures of the periodic composite show simultaneously the features of phononic and photonic crystals. Strong interaction between the elastic and EM waves near the center of the Brillouin zone (i.e., phonon-polariton) is revealed. It is shown the elastic branch of the band structures is more sensitive to the piezoelectric effect while the phonon-polariton is more sensitive to the piezomagnetic effect of the composite. PMID:25200701

  16. Evaluation of Transverse Thermal Stresses in Composite Plates Based on First-Order Shear Deformation Theory

    NASA Technical Reports Server (NTRS)

    Rolfes, R.; Noor, A. K.; Sparr, H.

    1998-01-01

    A postprocessing procedure is presented for the evaluation of the transverse thermal stresses in laminated plates. The analytical formulation is based on the first-order shear deformation theory and the plate is discretized by using a single-field displacement finite element model. The procedure is based on neglecting the derivatives of the in-plane forces and the twisting moments, as well as the mixed derivatives of the bending moments, with respect to the in-plane coordinates. The calculated transverse shear stiffnesses reflect the actual stacking sequence of the composite plate. The distributions of the transverse stresses through-the-thickness are evaluated by using only the transverse shear forces and the thermal effects resulting from the finite element analysis. The procedure is implemented into a postprocessing routine which can be easily incorporated into existing commercial finite element codes. Numerical results are presented for four- and ten-layer cross-ply laminates subjected to mechanical and thermal loads.

  17. A finite element method for shear stresses calculation in composite blade models

    NASA Astrophysics Data System (ADS)

    Paluch, B.

    1991-09-01

    A finite-element method is developed for accurately calculating shear stresses in helicopter blade models, induced by torsion and shearing forces. The method can also be used to compute the equivalent torsional stiffness of the section, their transverse shear coefficient, and the position of their center of torsion. A grid generator method which is a part of the calculation program is also described and used to discretize the sections quickly and to condition the grid data reliably. The finite-element method was validated on a few sections composed of isotropic materials and was then applied to a blade model sections made of composite materials. Good agreement was obtained between the calculated and experimental data.

  18. Bioinspired polydimethylsiloxane-based composites with high shear resistance against wet tissue.

    PubMed

    Fischer, Sarah C L; Levy, Oren; Kroner, Elmar; Hensel, René; Karp, Jeffrey M; Arzt, Eduard

    2016-08-01

    Patterned microstructures represent a potential approach for improving current wound closure strategies. Microstructures can be fabricated by multiple techniques including replica molding of soft polymer-based materials. However, polymeric microstructures often lack the required shear resistance with tissue needed for wound closure. In this work, scalable microstructures made from composites based on polydimethylsiloxane (PDMS) were explored to enhance the shear resistance with wet tissue. To achieve suitable mechanical properties, PDMS was reinforced by incorporation of polyethylene (PE) particles into the pre-polymer and by coating PE particle reinforced substrates with parylene. The reinforced microstructures showed a 6-fold enhancement, the coated structures even a 13-fold enhancement in Young׳s modulus over pure PDMS. Shear tests of mushroom-shaped microstructures (diameter 450µm, length 1mm) against chicken muscle tissue demonstrate first correlations that will be useful for future design of wound closure or stabilization implants. PMID:26849031

  19. Impact of triacylglycerol composition on shear-induced textural changes in highly saturated fats.

    PubMed

    Gregersen, Sandra B; Andersen, Morten D; Hammershøj, Marianne; Wiking, Lars

    2017-01-15

    This study demonstrates a strong interaction between triacylglycerol (TAG) composition and effects of shear rate on the microstructure and texture of fats. Cocoa butter alternatives with similar saturated fat content, but different major TAGs (PPO-, PSO-, SSO-, POP- and SOS-rich blends) were evaluated. Results show how shear can create a harder texture in fat blends based on symmetric monounsaturated TAGs (up to ∼200%), primarily due to reduction in crystal size, whereas shear has little effect on hardness of asymmetric monounsaturated TAGs. Such differences could not be ascribed to differences in the degree of supercooling, but was found to be a consequence of differences in the crystallisation behaviour of different TAGs. The fractal dimension was evaluated by dimensional detrended fluctuation analysis and Fourier transformation of microscopy images. However, the concept of fractal patterns was found to be insufficient to describe microstructural changes of fat blends with high solid fat content. PMID:27542496

  20. Shear bond strength of new self-adhesive flowable composite resins.

    PubMed

    Wajdowicz, Michael N; Vandewalle, Kraig S; Means, Mark T

    2012-01-01

    Recently, new self-adhesive flowable composite resin systems have been introduced to the market. These new composite resin systems reportedly bond to dentin and enamel without the application of an adhesive bonding agent. The purpose of this study was to evaluate the shear bond strength to enamel of two new self-adhesive flowable composites with and without the use of an etch-and-rinse bonding agent. The new self-adhesive flowable composites had significantly lower bond strengths to enamel compared to a traditional adhesively bonded flowable composite. Both self-adhesive flowable composites had a significant increase in bond strength to enamel with the use of a phosphoric acid-etch and adhesive bonding agent. PMID:22414513

  1. Advanced composites wing study program, volume 2

    NASA Technical Reports Server (NTRS)

    Harvey, S. T.; Michaelson, G. L.

    1978-01-01

    The study on utilization of advanced composites in commercial aircraft wing structures was conducted as a part of the NASA Aircraft Energy Efficiency Program to establish, by the mid-1980s, the technology for the design of a subsonic commercial transport aircraft leading to a 40% fuel savings. The study objective was to develop a plan to define the effort needed to support a production commitment for the extensive use of composite materials in wings of new generation aircraft that will enter service in the 1985-1990 time period. Identification and analysis of what was needed to meet the above plan requirements resulted in a program plan consisting of three key development areas: (1) technology development; (2) production capability development; and (3) integration and validation by designing, building, and testing major development hardware.

  2. Creep rupture behavior of unidirectional advanced composites

    NASA Technical Reports Server (NTRS)

    Yeow, Y. T.

    1980-01-01

    A 'material modeling' methodology for predicting the creep rupture behavior of unidirectional advanced composites is proposed. In this approach the parameters (obtained from short-term tests) required to make the predictions are the three principal creep compliance master curves and their corresponding quasi-static strengths tested at room temperature (22 C). Using these parameters in conjunction with a failure criterion, creep rupture envelopes can be generated for any combination of in-plane loading conditions and ambient temperature. The analysis was validated experimentally for one composite system, the T300/934 graphite-epoxy system. This was done by performing short-term creep tests (to generate the principal creep compliance master curves with the time-temperature superposition principle) and relatively long-term creep rupture tensile tests of off-axis specimens at 180 C. Good to reasonable agreement between experimental and analytical results is observed.

  3. Estimate Interface Shear Stress of Woven Ceramic Matrix Composites from Hysteresis Loops

    NASA Astrophysics Data System (ADS)

    Li, Longbiao; Song, Yingdong

    2013-12-01

    An approach to estimate the fiber/matrix interface shear stress of woven ceramic matrix composites during fatigue loading has been developed in this paper. Based on the analysis of the microstructure, the woven ceramic matrix composites were divided into four elements of 0o warp yarns, 90o weft yarns, matrix outside of the yarns and the open porosity. When matrix cracking and fiber/matrix interface debonding occur upon first loading to the peak stress, it is assumed that fiber slipping relative to matrix in the interface debonded region of the 0o warp yarns is the mainly reason for the occurrence of the hysteresis loops of woven ceramic matrix composiets during unloading and subsequent reloading. The unloading interface reverse slip length and reloading interface new slip length are determined by the interface slip mechanisms. The hysteresis loops of three different cases have been derived. The hysteresis loss energy for the strain energy lost per volume during corresponding cycle is formulated in terms of the fiber/matrix interface shear stress. By comparing the experimental hysteresis loss energy with the computational values, the fiber/matrix interface shear stress of woven ceramic matrix composites corresponding to different cycles can then be derived. The theoretical results have been compared with experimental data of two different woven ceramic composites.

  4. Novel Composites for Wing and Fuselage Applications: Speedy Nonlinear Analysis of Postbuckled Panels in Shear (SNAPPS)

    NASA Technical Reports Server (NTRS)

    Sharp, Dave; Sobel, Larry

    1997-01-01

    A simple and rapid analysis method, consisting of a number of modular, 'strength-of-materials-type' models, is presented for predicting the nonlinear response and stiffener separation of postbuckled, flat, composite, shear panels. The analysis determines the maximum principal tensile stress in the skin surface layer under to toe. Failure is said to occur when this stress reaches the mean transverse tensile strength of the layer. The analysis methodology consists of a number of closed-form equations that can easily be used in a 'hand analysis. For expediency, they have been programmed into a preliminary design code called SNAPPS (Speedy Nonlinear Analysis of Postbuckled Panels in Shear), which rapidly predicts postbuckling response of the panel for each value of the applied shear load. SNAPPS response and failure predictions were found to agree well with test results for three panels with widely different geometries, laminates and stiffnesses. Design guidelines are given for increasing the load-carrying capacity of stiffened, composite shear panels.

  5. In-plane and Interlaminar Shear Strength of a Unidirectional Hi-nicalon Fiber-reinforced Celsian Matrix Composite

    NASA Technical Reports Server (NTRS)

    Uenal, O.; Bansal, N. P.

    2000-01-01

    In-plane and interlaminar shear strength of a unidirectional SiC fiber-reinforced (BaSr)Al2Si2O8 celsian composite were measured by the double-notch shear test method between room temperature and 1200 C. The interlaminar shear strength was lower than the in-plane shear strength at all temperatures. Stress analysis, using finite element modeling, indicated that shear stress concentration was not responsible for the observed difference in strength. Instead, the difference in layer architecture and thus, the favorable alignment of fiber-rich layers with the shear plane in the interlaminar specimens appears to be the reason for the low strength of this composite. A rapid decrease in strength was observed with temperature due to softening of the glassy phase in the material.

  6. Ten Deg Off-Axis Test for Shear Properties in Fiber Composites

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.; Sinclair, J. H.

    1977-01-01

    A combined theoretical and experimental investigation was conducted to assess the suitability of the 10 deg off-axis tensile test specimen for the intralaminar shear characterization of unidirectional composites. Composite mechanics, a combined-stress failure criterion, and a finite variation across the specimen width and the relative stress and strain magnitudes at the 10 deg plane. Strain gages were used to measure the strain variation across the specimen width at specimen midlength and near the end tabs. Specimens from Mod-I/epoxy, T-300/epoxy, and S-glass/epoxy were used in the experimental program. It was found that the 10 deg off-axis tensile test specimen is suitable for intralaminar shear characterization, and it is recommended that it should be considered as a possible standard test specimen for such a characterization.

  7. 10-deg off-axis test for shear properties in fiber composites

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.; Sinclair, J. H.

    1977-01-01

    A combined theoretical and experimental investigation was conducted to assess the suitability of the 10-deg off-axis tensile test specimen for the intralaminar shear characterization of unidirectional composites. Composite mechanics, a combined-stress failure criterion, and a finite-element analysis were used to determine theoretically the stress-strain variation across the specimen width and the relative stress and strain magnitudes at the 10-deg plane. Strain gages were employed to measure the strain variation across the specimen width at specimen midlength and near the end tabs. Specimens from Mod-I/epoxy, T-300/epoxy, and S-glass/epoxy were used in the experimental program. It was found that the 10-deg off-axis tensile test specimen is suitable for intralaminar shear characterization, and it is recommended that it should be considered as a possible standard test specimen for such a characterization.

  8. Ten deg off-axis tensile test for intralaminar shear characterization of fiber composites

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.; Sinclair, J. H.

    1976-01-01

    A combined theoretical and experimental investigation was conducted to assess the suitability of the 10 deg off-axis tensile test specimen for the intralaminar shear characterization of unidirectional composites. Composite mechanics, a combined-stress failure criterion, and a finite element analysis were used to determine theoretically the stress-strain variation across the specimen width and the relative stress and strain magnitudes at the 10 deg plane. Strain gages were used to measure the strain variation across the specimen width at specimen midlength and near the end tabs. Specimens from Mod-I/epoxy, T-300/epoxy, and S-glass/epoxy were used in the experimental program. It was found that the 10 deg off-axis tensile test specimen is suitable for intralaminar shear characterization and it is recommended that it should be considered as a possible standard test specimen for such a characterization.

  9. Bayesian decision and mixture models for AE monitoring of steel-concrete composite shear walls

    NASA Astrophysics Data System (ADS)

    Farhidzadeh, Alireza; Epackachi, Siamak; Salamone, Salvatore; Whittaker, Andrew S.

    2015-11-01

    This paper presents an approach based on an acoustic emission technique for the health monitoring of steel-concrete (SC) composite shear walls. SC composite walls consist of plain (unreinforced) concrete sandwiched between steel faceplates. Although the use of SC system construction has been studied extensively for nearly 20 years, little-to-no attention has been devoted to the development of structural health monitoring techniques for the inspection of damage of the concrete behind the steel plates. In this work an unsupervised pattern recognition algorithm based on probability theory is proposed to assess the soundness of the concrete infill, and eventually provide a diagnosis of the SC wall’s health. The approach is validated through an experimental study on a large-scale SC shear wall subjected to a displacement controlled reversed cyclic loading.

  10. Effect of surface treatment on micro shear bond strength of two indirect composites

    PubMed Central

    Moezizadeh, Maryam; Ansari, Zahra Jaberi; Fard, Fatemeh Matin

    2012-01-01

    Aim: To determine the effect of surface treatment on micro shear bond strength of two indirect composites. Materials and Methods: Blocks of 2 × 7 × 20 mm dimensions were made from two kinds of resin composites, Gradia and Signum plus. Samples were subjected to secondary curing to complete polymerization. They were divided into five groups: control without any preparation, second group sandblasted with aluminum oxide, third, fourth and fifth groups were lased under a beam of 0.5, 1 and 2 W respectively. Panavia resin cement was placed on the composite blocks using tygon tubes and cured and micro shear bond strength was measured. One sample of each group was observed under electronic microscope. Data was analyzed by two-way ANOVA and Tukey's multiple comparison tests. Results: For Gradia composite, the sandblasted group showed highest strength (25.7±2.9 MPa) followed by the laser beam of 1 W group (with 23.6± 2.8 MPa). In Signum composite, the laser beam of 1 W (21.4±4.2 MPa) showed the highest strength followed by the sandblasted group (with 19.4±3.2 MPa). Conclusion: Surface treatments using sandblast and laser beam of 1W power along with silane are two effective methods to increase the bond strength of composites. PMID:22876007

  11. Bond slip detection of concrete-encased composite structure using shear wave based active sensing approach

    NASA Astrophysics Data System (ADS)

    Zeng, Lei; Parvasi, Seyed Mohammad; Kong, Qingzhao; Huo, Linsheng; Lim, Ing; Li, Mo; Song, Gangbing

    2015-12-01

    Concrete-encased composite structure exhibits improved strength, ductility and fire resistance compared to traditional reinforced concrete, by incorporating the advantages of both steel and concrete materials. A major drawback of this type of structure is the bond slip introduced between steel and concrete, which directly reduces the load capacity of the structure. In this paper, an active sensing approach using shear waves to provide monitoring and early warning of the development of bond slip in the concrete-encased composite structure is proposed. A specimen of concrete-encased composite structure was investigated. In this active sensing approach, shear mode smart aggregates (SAs) embedded in the concrete act as actuators and generate desired shear stress waves. Distributed piezoceramic transducers installed in the cavities of steel plates act as sensors and detect the wave response from shear mode SAs. Bond slip acts as a form of stress relief and attenuates the wave propagation energy. Experimental results from the time domain analysis clearly indicate that the amplitudes of received signal by lead zirconate titanate sensors decreased when bond slip occurred. In addition, a wavelet packet-based analysis was developed to compute the received signal energy values, which can be used to determine the initiation and development of bond slip in concrete-encased composite structure. In order to establish the validity of the proposed method, a 3D finite element analysis of the concrete-steel bond model is further performed with the aid of the commercial finite element package, Abaqus, and the numerical results are compared with the results obtained in experimental study.

  12. Shear bond strength of composite resin to titanium according to various surface treatments

    PubMed Central

    Lee, Seung-Yun; Yang, Hong-So; Park, Sang-Won; Park, Ha-Ok; Lim, Hyun-Pil

    2009-01-01

    STATEMENT OF PROBLEM When veneering composite resin-metal restoration is prepared, the fact that bond strength between Ti and composite resin is relatively weak should be considered. PURPOSE The purpose of this study is to evaluate the shear bond strength between the veneering composite resin and commercial pure (CP) Ti / Ti-6Al-4V alloy according to the method of surface treatment. MATERIAL AND METHODS The disks were cast by two types of metal. Their surfaces were treated by sandblasting, metal conditioner, TiN coating and silicoating respectively. After surface treatment, the disks were veneered by composite resin (Tescera™, Bisco, USA) which is 5 mm in diameter and 3 mm in thickness. The specimens were stored in water at 25℃ for 24 hours, and then evaluated for their shear bond strength by universal testing machine (STM-5®, United Calibration, USA). These values were statistically analyzed. RESULTS 1. All methods of surface treatment were used in this study satisfied the requirements of ISO 10477 which is the standard of polymer-based crown and bridge materials. 2. The metal conditioner treated group showed the highest value in shear bond strength of CP Ti, silicoated group, TiN coated group, sandblasted group, in following order. 3. The silicoated group showed the highest value in shear bond strength of Ti-6Al-4V alloy, metal conditioner treated group, sandblasted group, TiN coated group, in following order. CONCLUSION Within the limitations of this study, all methods of surface treatment used in this study are clinically available. PMID:21165258

  13. Investigation of interfacial shear strength in SiC/Si3N4 composites

    NASA Technical Reports Server (NTRS)

    Eldridge, J. I.; Bhatt, R. T.; Kiser, J. D.

    1991-01-01

    A fiber push-out technique was used to determine fiber/matrix interfacial shear strength (ISS) for silicon carbide fiber reinforced reaction-bonded silicon nitride (SiC/RBSN) composites in the as-fabricated condition and after consolidation by hot isostatic pressing (HIPing). In situ video microscopy and acoustic emission detection greatly aided the interpretation of push-out load/displacement curves.

  14. Shear strain mediated magneto-electric effects in composites of piezoelectric lanthanum gallium silicate or tantalate and ferromagnetic alloys

    SciTech Connect

    Sreenivasulu, G.; Piskulich, E.; Srinivasan, G.; Qu, P.; Qu, Hongwei; Petrov, V. M.; Fetisov, Y. K.; Nosov, A. P.

    2014-07-21

    Shear strain mediated magneto-electric (ME) coupling is studied in composites of piezoelectric Y-cut lanthanum gallium silicate (LGS) or tantalate (LGT) and ferromagnetic Fe-Co-V alloys. It is shown that extensional strain does not result in ME effects in these layered composites. Under shear strain generated by an ac and dc bias magnetic fields along the length and width of the sample, respectively, strong ME coupling is measured at low-frequencies and at mechanical resonance. A model is discussed for the ME effects. These composites of Y-cut piezoelectrics and ferromagnetic alloys are of importance for shear strain based magnetic field sensors.

  15. Shear strain mediated magneto-electric effects in composites of piezoelectric lanthanum gallium silicate or tantalate and ferromagnetic alloys

    NASA Astrophysics Data System (ADS)

    Sreenivasulu, G.; Qu, P.; Piskulich, E.; Petrov, V. M.; Fetisov, Y. K.; Nosov, A. P.; Qu, Hongwei; Srinivasan, G.

    2014-07-01

    Shear strain mediated magneto-electric (ME) coupling is studied in composites of piezoelectric Y-cut lanthanum gallium silicate (LGS) or tantalate (LGT) and ferromagnetic Fe-Co-V alloys. It is shown that extensional strain does not result in ME effects in these layered composites. Under shear strain generated by an ac and dc bias magnetic fields along the length and width of the sample, respectively, strong ME coupling is measured at low-frequencies and at mechanical resonance. A model is discussed for the ME effects. These composites of Y-cut piezoelectrics and ferromagnetic alloys are of importance for shear strain based magnetic field sensors.

  16. Fiber-Reinforced-Foam (FRF) Core Composite Sandwich Panel Concept for Advanced Composites Technologi

    NASA Technical Reports Server (NTRS)

    2010-01-01

    Fiber-Reinforced-Foam (FRF) Core Composite Sandwich Panel Concept for Advanced Composites Technologies Project - Preliminary Manufacturing Demonstration Articles for Ares V Payload Shroud Barrel Acreage Structure

  17. Effect of different surface treatments on the shear bond strength of nanofilled composite repairs.

    PubMed

    Ahmadizenouz, Ghazaleh; Esmaeili, Behnaz; Taghvaei, Arnica; Jamali, Zahra; Jafari, Toloo; Amiri Daneshvar, Farshid; Khafri, Soraya

    2016-01-01

    Background. Repairing aged composite resin is a challenging process. Many surface treatment options have been proposed to this end. This study evaluated the effect of different surface treatments on the shear bond strength (SBS) of nano-filled composite resin repairs. Methods. Seventy-five cylindrical specimens of a Filtek Z350XT composite resin were fabricated and stored in 37°C distilled water for 24 hours. After thermocycling, the specimens were divided into 5 groups according to the following surface treatments: no treatment (group 1); air abrasion with 50-μm aluminum oxide particles (group 2); irradiation with Er:YAG laser beams (group 3); roughening with coarse-grit diamond bur + 35% phosphoric acid (group 4); and etching with 9% hydrofluoric acid for 120 s (group 5). Another group of Filtek Z350XT composite resin samples (4×6 mm) was fabricated for the measurement of cohesive strength (group 6). A silane coupling agent and an adhesive system were applied after each surface treatment. The specimens were restored with the same composite resin and thermocycled again. A shearing force was applied to the interface in a universal testing machine. Data were analyzed using one-way ANOVA and post hoc Tukey tests (P < 0.05). Results. One-way ANOVA indicated significant differences between the groups (P < 0.05). SBS of controls was significantly lower than the other groups; differences between groups 2, 3, 4, 5 and 6 were not significant. Surface treatment with diamond bur + 35% phosphoric acid resulted in the highest bond strength. Conclusion. All the surface treatments used in this study improved the shear bond strength of nanofilled composite resin used. PMID:27092209

  18. Effect of different surface treatments on the shear bond strength of nanofilled composite repairs

    PubMed Central

    Ahmadizenouz, Ghazaleh; Esmaeili, Behnaz; Taghvaei, Arnica; Jamali, Zahra; Jafari, Toloo; Amiri Daneshvar, Farshid; Khafri, Soraya

    2016-01-01

    Background. Repairing aged composite resin is a challenging process. Many surface treatment options have been proposed to this end. This study evaluated the effect of different surface treatments on the shear bond strength (SBS) of nano-filled composite resin repairs. Methods. Seventy-five cylindrical specimens of a Filtek Z350XT composite resin were fabricated and stored in 37°C distilled water for 24 hours. After thermocycling, the specimens were divided into 5 groups according to the following surface treatments: no treatment (group 1); air abrasion with 50-μm aluminum oxide particles (group 2); irradiation with Er:YAG laser beams (group 3); roughening with coarse-grit diamond bur + 35% phosphoric acid (group 4); and etching with 9% hydrofluoric acid for 120 s (group 5). Another group of Filtek Z350XT composite resin samples (4×6 mm) was fabricated for the measurement of cohesive strength (group 6). A silane coupling agent and an adhesive system were applied after each surface treatment. The specimens were restored with the same composite resin and thermocycled again. A shearing force was applied to the interface in a universal testing machine. Data were analyzed using one-way ANOVA and post hoc Tukey tests (P < 0.05). Results. One-way ANOVA indicated significant differences between the groups (P < 0.05). SBS of controls was significantly lower than the other groups; differences between groups 2, 3, 4, 5 and 6 were not significant. Surface treatment with diamond bur + 35% phosphoric acid resulted in the highest bond strength. Conclusion. All the surface treatments used in this study improved the shear bond strength of nanofilled composite resin used. PMID:27092209

  19. Life Limiting Behavior in Interlaminar Shear of Continuous Fiber-Reinforced Ceramic Matrix Composites at Elevated Temperatures

    NASA Technical Reports Server (NTRS)

    Choi, Sung R.; Calomino, Anthony M.; Bansal, Narottam P.; Verrilli, Michael J.

    2006-01-01

    Interlaminar shear strength of four different fiber-reinforced ceramic matrix composites was determined with doublenotch shear test specimens as a function of test rate at elevated temperatures ranging from 1100 to 1316 C in air. Life limiting behavior, represented as interlaminar shear strength degradation with decreasing test rate, was significant for 2-D crossplied SiC/MAS-5 and 2-D plain-woven C/SiC composites, but insignificant for 2-D plain-woven SiC/SiC and 2-D woven Sylramic (Dow Corning, Midland, Michigan) SiC/SiC composites. A phenomenological, power-law delayed failure model was proposed to account for and to quantify the rate dependency of interlaminar shear strength of the composites. Additional stress rupture testing in interlaminar shear was conducted at elevated temperatures to validate the proposed model. The model was in good agreement with SiC/MAS-5 and C/SiC composites, but in poor to reasonable agreement with Sylramic SiC/SiC. Constant shear stress-rate testing was proposed as a possible means of life prediction testing methodology for ceramic matrix composites subjected to interlaminar shear at elevated temperatures when short lifetimes are expected.

  20. Advanced composites for large Navy spacecraft

    NASA Technical Reports Server (NTRS)

    Davis, William E.

    1986-01-01

    An overview is given of work conducted on contract for the Naval Sea Systems Command. The objective of this contract was to provide direction for the development of high modulus graphite reinforced metal matrix composites. These advanced materials can have a significant effect on the performance of a spacecraft before, during and after an evasive maneuver. The work conducted on this program was organized into seven technical tasks. Task 1 was development of a generic Navy spacecraft model. Finite element models of candidate structural designs were developed. In Task 2, the finite-element model(s) of the structure were used to conduct analytical assessments involving conventional materials, resin matrix composites and metal matrix composites (MMC). In Task 3 and 4, MMC material design, fabrication and evaluation was conducted. This consisted of generating material designs and developing a data base for a broad range of graphite reinforced MMC materials. All material was procured according to specifications which set material quality and material property standards. In Task 5, a set of evasive maneuvering requirements were derived and used in Task 6 to conduct analytical simulations. These analytical simulations used current SOA material properties and projected material properties to provide an indication of key payoffs for material development. In Task 7, a set of material development recommendations was generated.

  1. Influence of Compression and Shear on the Strength of Composite Laminates with Z-Pinned Reinforcement

    NASA Technical Reports Server (NTRS)

    O'Brien, T. Kevin; Krueger, Ronald

    2005-01-01

    The influence of compression and shear loads on the strength of composite laminates with z-pins is evaluated parametrically using a 2D Finite Element Code (FLASH) based on Cosserat couple stress theory. Meshes were generated for three unique combinations of z-pin diameter and density. A laminated plate theory analysis was performed on several layups to determine the bi-axial stresses in the zero degree plies. These stresses, in turn, were used to determine the magnitude of the relative load steps prescribed in the FLASH analyses. Results indicated that increasing pin density was more detrimental to in-plane compression strength than increasing pin diameter. Compression strengths of lamina without z-pins agreed well with a closed form expression derived by Budiansky and Fleck. FLASH results for lamina with z-pins were consistent with the closed form results, and FLASH results without z-pins, if the initial fiber waviness due to z-pin insertion was added to the fiber waviness in the material to yield a total misalignment. Addition of 10% shear to the compression loading significantly reduced the lamina strength compared to pure compression loading. Addition of 50% shear to the compression indicated shear yielding rather than kink band formation as the likely failure mode. Two different stiffener reinforced skin configurations with z-pins, one quaiisotropic and one orthotropic, were also analyzed. Six unique loading cases ranging from pure compression to compression plus 50% shear were analyzed assuming material fiber waviness misalignment angles of 0, 1, and 2 degrees. Compression strength decreased with increased shear loading for both configurations, with the quasi-isotropic configuration yielding lower strengths than the orthotropic configuration.

  2. Influence of Compression and Shear on the Strength of Composite Laminates With Z-Pinned Reinforcement

    NASA Technical Reports Server (NTRS)

    OBrien, T. Kevin; Krueger, Ronald

    2005-01-01

    The influence of compression and shear loads on the strength of composite laminates with z-pins is evaluated parametrically using a 2D Finite Element Code (FLASH) based on Cosserat couple stress theory. Meshes were generated for three unique combinations of z-pin diameter and density. A laminated plate theory analysis was performed on several layups to determine the bi-axial stresses in the zero degree plies. These stresses, in turn, were used to determine the magnitude of the relative load steps prescribed in the FLASH analyses. Results indicated that increasing pin density was more detrimental to in-plane compression strength than increasing pin diameter. Compression strengths of lamina without z-pins agreed well with a closed form expression derived by Budiansky and Fleck. FLASH results for lamina with z-pins were consistent with the closed form results, and FLASH results without z-pins, if the initial fiber waviness due to z-pin insertion was added to the fiber waviness in the material to yield a total misalignment. Addition of 10% shear to the compression loading significantly reduced the lamina strength compared to pure compression loading. Addition of 50% shear to the compression indicated shear yielding rather than kink band formation as the likely failure mode. Two different stiffener reinforced skin configurations with z-pins, one quasi-isotropic and one orthotropic, were also analyzed. Six unique loading cases ranging from pure compression to compression plus 50% shear were analyzed assuming material fiber waviness misalignment angles of 0, 1, and 2 degrees. Compression strength decreased with increased shear loading for both configurations, with the quasi-isotropic configuration yielding lower strengths than the orthotropic configuration.

  3. Influence of Compression and Shear on the Strength of Composite Laminates with Z-Pinned Reinforcement

    NASA Technical Reports Server (NTRS)

    O'Brien, T. Kevin; Krueger, Ronald

    2005-01-01

    The influence of compression and shear loads on the strength of composite laminates with z-pins is evaluated parametrically using a 2D Finite Element Code (FLASH). Meshes were generated for three unique combinations of z-pin diameter and density. A laminated plate theory analysis was performed on several layups to determine the bi-axial stresses in the zero degree plies. These stresses, in turn, were used to determine the magnitude of the relative load steps prescribed in the FLASH analyses. Results indicated that increasing pin density was more detrimental to in-plane compression strength than increasing pin diameter. FLASH results for lamina with z-pins were consistent with the closed form results, and FLASH results without z-pins, if the initial fiber waviness due to z-pin insertion was added to the fiber waviness in the material to yield a total misalignment. Addition of 10% shear to the compression loading significantly reduced the lamina strength compared to pure compression loading. Addition of 50% shear to the compression indicated shear yielding rather than kink band formation as the likely failure mode. Two different stiffener reinforced skin configurations with z-pins, one quasi-isotropic and one orthotropic, were also analyzed. Six unique loading cases ranging from pure compression to compression plus 50% shear were analyzed assuming material fiber waviness misalignment angles of 0, 1, and 2 degrees. Compression strength decreased with increased shear loading for both configurations, with the quasi-isotropic configuration yielding lower strengths than the orthotropic configuration.

  4. Shear Bond Strength of the Repair Composite Resin to Zirconia Ceramic by Different Surface Treatment

    PubMed Central

    Arami, Sakineh; Hasani Tabatabaei, Masoumeh; Namdar, Fatemeh; Safavi, Nassimeh; Chiniforush, Nasim

    2014-01-01

    Introduction: The purpose of this study is the evaluation of the amount of surface roughness (Ra) of Zirconia Ceramic following different surface treatments as well as the assessment of its shear bond strength to composite resin. Methods: 40 sintered zirconia ceramic block samples were randomly divided in 4 groups of 10 and underwent the following surface treatments: a) Control group without treatment b) Air abrasion with Al2O3 particles (50um) c) Er:YAG laser with 2W power for 10s d) Nd:YAG laser with 1.5W power for 2min Then the mean surface roughness (Ra) was evaluated by profilometer. In the next step, Alloy primer was used on a section of 9mm2 on the samples following the manufacturer’s instructions. After that Clearfil AP-X composite resin in cylinder shape with an internal diameter and height of 3mm were cured on the sections mentioned. At the end, all samples were tested to assess the shear bond strength by the Universal Testing Machine at a speed of 0.5mm/min until fracture occurred. The mean shear bond strengths were calculated and statistically analyzed by One Way ANOVA. Results: ANOVA analysis showed that roughness (Ra) was significantly different between the groups (P≤0.05). Ra was higher in the Nd:YAG group compared to the other groups (P≤0.05). The lower Ra was related to the control group. Air abrasion group showed highest amounts of shear bond strength and Nd:YAG laser group demonstrated lower amounts of shear bond strength (P≤0.05). Conclusion: Various surface treatments are differently effective on bond strength. Air abrasion is the most effective method to condition zirconia ceramic surfaces. PMID:25653817

  5. Inclusion of transverse shear deformation in the exact buckling and vibration analysis of composite plate assemblies

    NASA Technical Reports Server (NTRS)

    Anderson, Melvin S.; Kennedy, David

    1993-01-01

    The problem considered is the development of the necessary plate stiffnesses for use in the general purpose program VICONOPT for buckling and vibration of composite plate assemblies. The required stiffnesses include the effects of transverse shear deformation and are for sinusoidal response along the plate length as required in VICONOPT. The method is based on the exact solution of the plate differential equations for a composite laminate having fully populated A, B, and D stiffness matrices which leads to an ordinary differential equation of tenth order.

  6. Shear bond strength evaluation of resin composite bonded to GIC using three different adhesives.

    PubMed

    Gopikrishna, V; Abarajithan, M; Krithikadatta, J; Kandaswamy, D

    2009-01-01

    The current study evaluated the bonding ability of composite to glass ionomer cement (GIC) using three different bonding systems. One hundred samples of composites bonded to GIC were prepared and divided into five groups. In Group A, the composite was bonded to GIC after the initial setting of the GIC being employed as a total-etch adhesive. In Group B, the self-etch primer was employed to bond composite to GIC before the initial setting of the GIC. In Group C, the self-etch primer was employed to bond composite to the GIC after the initial setting of the GIC. In Group D, the GIC-based adhesive was employed to bond composite to the GIC before the initial setting of the GIC. In Group E, the GIC-based adhesive was employed to bond composite to the GIC after the initial setting of the GIC. Shear bond strength analysis was performed at a crosshead speed of 0.5 mm/minute. The results were tabulated and the statistical analysis was performed with one-way ANOVA; the Tukey's test showed that the bond strength of composite to GIC was significantly higher for the self-etch primer group employed on unset GIC and the GIC-based adhesive group employed on the set GIC for bonding composite to GIC. PMID:19678453

  7. Numerical analysis and parametric studies of the buckling of composite orthotropic compression and shear panels

    NASA Technical Reports Server (NTRS)

    Housner, J. M.; Stein, M.

    1975-01-01

    A computer program is presented which was developed for the combined compression and shear of stiffened variable thickness orthotropic composite panels on discrete springs: boundary conditions are general and include elastic boundary restraints. Buckling solutions are obtained by using a newly developed trigonometric finite difference procedure which improves the solution convergence rate over conventional finite difference methods. The classical general shear buckling results which exist only for simply supported panels over a limited range of orthotropic properties, were extended to the complete range of these properties for simply supported panels and, in addition, to the complete range of orthotropic properties for clamped panels. The program was also applied to parametric studies which examine the effect of filament orientation upon the buckling of graphite-epoxy panels. These studies included an examination of the filament orientations which yield maximum shear or compressive buckling strength for panels having all four edges simply supported or clamped over a wide range of aspect ratios. Panels with such orientations had higher buckling loads than comparable, equal weight, thin skinned aluminum panels. Also included among the parameter studies were examinations of combined axial compression and shear buckling and examinations of panels with rotational elastic edge restraints.

  8. Shear Pressed Aligned Carbon Nanotubes and their use as Composite and Adhesive Interlayers

    NASA Astrophysics Data System (ADS)

    Stahl, James Joseph, III

    The following studies utilize shearing force to consolidate and re-orient multi-walled carbon nanotubes (MWCNT) into a shear pressed sheet (SPS) preform. Carbon nanotube (CNT) array growth and shear pressing angle are studied to improve the quality of SPSs. Heat assisted vacuum infusion is used to form a nano-composite from the SPS preform, and mechanical properties are characterized and compared between non-functionalized and functionalized nano-composite tensile specimens. A novel functionalization technique is applied which rinses SPSs with an acidic wet chemical oxidation treatment of H2SO4 and KMnO4 in order to add sidewall carboxyl groups to the CNTs. This is shown to impart hydrophilicity to the SPS and improves composite modulus by 62%, strain-to-failure 42% and failure stress 113%. Composite laminates and joints are vulnerable to shearing forces which cause delamination in the former and failure in the latter. Damage is initiated and propagated at defects and free edges often due to high peel stress, which is much higher than the shear stress and functions as a tensile opening of the joint just as in Mode I delamination failure of laminate composites. In order to resist failure it is necessary to improve the strain-to-failure of the interphase where a crack propagates without sacrificing strength or modulus of the material, thus toughening the material without impacting the rigidity of the composite. Due to the similarity between peel stress/strain and Mode I delamination, the initiation fracture toughness of a double cantilever beam (DCB) test should provide a good indication of peel toughness at a joint free edge. Many studies have explored the possibility of improving Mode I fracture toughness (G IC) of a composite through locally incorporating a tough material into the interlaminar interphase; this material is termed an interleaf. Common interleaf categories are toughened adhesive, disperse particle, disperse fiber, short fiber nonwoven, and continuous

  9. Advanced Technology Composite Fuselage-Structural Performance

    NASA Technical Reports Server (NTRS)

    Walker, T. H.; Minguet, P. J.; Flynn, B. W.; Carbery, D. J.; Swanson, G. D.; Ilcewicz, L. B.

    1997-01-01

    Boeing is studying the technologies associated with the application of composite materials to commercial transport fuselage structure under the NASA-sponsored contracts for Advanced Technology Composite Aircraft Structures (ATCAS) and Materials Development Omnibus Contract (MDOC). This report addresses the program activities related to structural performance of the selected concepts, including both the design development and subsequent detailed evaluation. Design criteria were developed to ensure compliance with regulatory requirements and typical company objectives. Accurate analysis methods were selected and/or developed where practical, and conservative approaches were used where significant approximations were necessary. Design sizing activities supported subsequent development by providing representative design configurations for structural evaluation and by identifying the critical performance issues. Significant program efforts were directed towards assessing structural performance predictive capability. The structural database collected to perform this assessment was intimately linked to the manufacturing scale-up activities to ensure inclusion of manufacturing-induced performance traits. Mechanical tests were conducted to support the development and critical evaluation of analysis methods addressing internal loads, stability, ultimate strength, attachment and splice strength, and damage tolerance. Unresolved aspects of these performance issues were identified as part of the assessments, providing direction for future development.

  10. Advanced Technology Composite Fuselage - Materials and Processes

    NASA Technical Reports Server (NTRS)

    Scholz, D. B.; Dost, E. F.; Flynn, B. W.; Ilcewicz, L. B.; Nelson, K. M.; Sawicki, A. J.; Walker, T. H.; Lakes, R. S.

    1997-01-01

    The goal of Boeing's Advanced Technology Composite Aircraft Structures (ATCAS) program was to develop the technology required for cost and weight efficient use of composite materials in transport fuselage structure. This contractor report describes results of material and process selection, development, and characterization activities. Carbon fiber reinforced epoxy was chosen for fuselage skins and stiffening elements and for passenger and cargo floor structures. The automated fiber placement (AFP) process was selected for fabrication of monolithic and sandwich skin panels. Circumferential frames and window frames were braided and resin transfer molded (RTM'd). Pultrusion was selected for fabrication of floor beams and constant section stiffening elements. Drape forming was chosen for stringers and other stiffening elements. Significant development efforts were expended on the AFP, braiding, and RTM processes. Sandwich core materials and core edge close-out design concepts were evaluated. Autoclave cure processes were developed for stiffened skin and sandwich structures. The stiffness, strength, notch sensitivity, and bearing/bypass properties of fiber-placed skin materials and braided/RTM'd circumferential frame materials were characterized. The strength and durability of cocured and cobonded joints were evaluated. Impact damage resistance of stiffened skin and sandwich structures typical of fuselage panels was investigated. Fluid penetration and migration mechanisms for sandwich panels were studied.

  11. Advanced Technology Composite Fuselage: Program Overview

    NASA Technical Reports Server (NTRS)

    Ilcewicz, L. B.; Smith, P. J.; Hanson, C. T.; Walker, T. H.; Metschan, S. L.; Mabson, G. E.; Wilden, K. S.; Flynn, B. W.; Scholz, D. B.; Polland, D. R.; Fredrikson, H. G.; Olson, J. T.; Backman, B. F.

    1997-01-01

    The Advanced Technology Composite Aircraft Structures (ATCAS) program has studied transport fuselage structure with a large potential reduction in the total direct operating costs for wide-body commercial transports. The baseline fuselage section was divided into four 'quadrants', crown, keel, and sides, gaining the manufacturing cost advantage possible with larger panels. Key processes found to have savings potential include (1) skins laminated by automatic fiber placement, (2) braided frames using resin transfer molding, and (3) panel bond technology that minimized mechanical fastening. The cost and weight of the baseline fuselage barrel was updated to complete Phase B of the program. An assessment of the former, which included labor, material, and tooling costs, was performed with the help of design cost models. Crown, keel, and side quadrant cost distributions illustrate the importance of panel design configuration, area, and other structural details. Composite sandwich panel designs were found to have the greatest cost savings potential for most quadrants. Key technical findings are summarized as an introduction to the other contractor reports documenting Phase A and B work completed in functional areas. The current program status in resolving critical technical issues is also highlighted.

  12. Shear Bond Strength of Repaired Composites Using Surface Treatments and Repair Materials: An In vitro Study

    PubMed Central

    Hemadri, M; Saritha, G; Rajasekhar, V; Pachlag, K Amit; Purushotham, R; Reddy, Veera Kishore Kumar

    2014-01-01

    Background: Enhancement of bond strength between new and old composite usually requires increased surface roughness of old composite to promote mechanical interlocking and subsequent coating with bonding agents to improve surface wetting and chemical bonding. So this study was carried out to evaluate and compare the effects of different surface treatments and repair materials on the shear bond strength (SBS) of composite repairs The mode of failure of repaired composites whether cohesive or adhesive was also evaluated. Materials and Methods: The substrates for 60 composite specimens were fabricated and aged with water treatment and subjected to various surface treatments. The surface treatment regimens used in the study were: No surface treatment, abraded with diamond bur, air abraded (sandblasted) with 50 µ aluminum oxide particles. Specimens were then repaired with fresh composite using either Clearfil™ repair or all-bond two adhesive systems. Specimens were water stored, thermocycled and tested for SBS using universal testing machine. Fractured specimens were then examined under stereomicroscope to determine the mode of failure. Results: It was clearly showed that surface roughening of the aged composite substrate with air abrasion, followed by the application of Clearfil™ repair adhesive system (Group IIIa) yielded the highest repair bond strength (32.3 ± 2.2 MPa). Conclusion: Surface treatment with air abrasion followed by bonding with Clearfil™ repair adhesive system can be attempted clinically for the repair of composite restorations. PMID:25628478

  13. 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.

  14. Response of Damaged and Undamaged Tailored Extension-Shear-Coupled Composite Panels

    NASA Technical Reports Server (NTRS)

    Baker, Donald J.

    2008-01-01

    The results of an analytical and experimental investigation of the response of composite I-stiffener panels with extension-shear coupling are presented. This tailored concept, when used in the panel cover skins of a tiltrotor aircraft wing has the potential for increasing the aeroelastic stability margins and improving the aircraft productivity. The extension-shear coupling is achieved by using unbalanced plus or minus 45 deg. plies in the skin. Experimental and STAGS analysis results are compared for eight I-stiffener panel specimens. The results indicate that the tailored concept would be feasible to use in the wing skin of a tiltrotor aircraft. Evaluation of specimens impacted at an energy level of 500 in.-lbs indicate a minimal loss in stiffness and less than 30 percent loss in strength. Evaluation of specimens with severed center stiffener and adjacent skin indicated a strength loss in excess of 60 percent.

  15. Studies of noise transmission in advanced composite material structures

    NASA Technical Reports Server (NTRS)

    Roussos, L. A.; Mcgary, M. C.; Powell, C. A.

    1983-01-01

    Noise characteristics of advanced composite material fuselages were discussed from the standpoints of applicable research programs and noise transmission theory. Experimental verification of the theory was also included.

  16. Bisimide amine cured epoxy /IME/ resins and composites. II - Ten-degree off-axis tensile and shear properties of Celion 6000/IME composites

    NASA Technical Reports Server (NTRS)

    Scola, D. A.

    1982-01-01

    Bisimide amines (BIAs), which are presently used as curing agents in a state-of-the-art epoxy resin, are oligomeric and polymeric mixtures. A series of composites consisting of the novel BIA-cured epoxy resin reinforced with Celion 6000 graphite fibers were fabricated and evaluated, and the ten-degree, off-axis uniaxial tensile and shear properties of these composites were determined. The use of the intralaminar shear strain-to-failure was used in the calculation of resin shear strain-to-failure. Study results indicate that several of these novel composite systems exhibit shear strain properties that are superior to those of the control composite system of the present experiments, which employed a sulfone curing agent.

  17. Dependency of Shear Strength on Test Rate in SiC/BSAS Ceramic Matrix Composite at Elevated Temperature

    NASA Technical Reports Server (NTRS)

    Choi, Sung R.; Bansal, Narottam P.; Gyekenyesi, John P.

    2003-01-01

    Both interlaminar and in-plane shear strengths of a unidirectional Hi-Nicalon(TM) fiber-reinforced barium strontium aluminosilicate (SiC/BSAS) composite were determined at 1100 C in air as a function of test rate using double notch shear test specimens. The composite exhibited a significant effect of test rate on shear strength, regardless of orientation which was either in interlaminar or in in-plane direction, resulting in an appreciable shear-strength degradation of about 50 percent as test rate decreased from 3.3 10(exp -1) mm/s to 3.3 10(exp -5) mm/s. The rate dependency of composite's shear strength was very similar to that of ultimate tensile strength at 1100 C observed in a similar composite (2-D SiC/BSAS) in which tensile strength decreased by about 60 percent when test rate varied from the highest (5 MPa/s) to the lowest (0.005 MPa/s). A phenomenological, power-law slow crack growth formulation was proposed and formulated to account for the rate dependency of shear strength of the composite.

  18. Postbuckling analysis of shear deformable composite flat panels taking into account geometrical imperfections

    NASA Technical Reports Server (NTRS)

    Librescu, L.; Stein, M.

    1990-01-01

    The effects of initial geometrical imperfections on the postbuckling response of flat laminated composite panels to uniaxial and biaxial compressive loading are investigated analytically. The derivation of the mathematical model on the basis of first-order transverse shear deformation theory is outlined, and numerical results for perfect and imperfect, single-layer and three-layer square plates with free-free, clamped-clamped, or free-clamped edges are presented in graphs and briefly characterized. The present approach is shown to be more accurate than analyses based on the classical Kirchhoff plate model.

  19. Modeling shear instability and fracture in dynamically deformed Al/W granular composites

    NASA Astrophysics Data System (ADS)

    Olney, Karl; Benson, David; Nesterenko, Vitali F.

    2012-03-01

    Aluminum/Tungsten granular composites are materials which combine high density and strength with bulk distributed fracture of Al matrix into small particles under impact or shock loading. They are processed using cold and hot isostatic pressing of W particles/rods in the matrix of Al powder. Numerical models were used to elucidate the dynamic behavior of these materials under dynamic conditions simulating low velocity high energy impact in drop weight test (10 m/s). It was demonstrated that arrangement of W components and bonding between Al particles dramatically affect the samples shear localization and mode of fracture of the Al matrix in agreement with experiments.

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  1. Shear characterization of unidirectional composites with the off-axis tension test

    NASA Technical Reports Server (NTRS)

    Pindera, M.-J.; Herakovich, C. T.

    1986-01-01

    The influence of end constraints on accurate determination of the intralaminar shear modulus G(12) from an off-axis tension test is examined both analytically and experimentally. The Pagano-Halpin (1968) model is employed to illustrate that, when the effect of end constraints is properly considered, the exact expression for G(12) is obtained. When the effect of end constraints is neglected, expressions for the apparent shear modulus G(12)-asterisk and apparent Young's modulus Exx-asterisk are obtained. Numerical comparison for various off-axis configurations and aspect ratios is carried out using typical material properties for graphite/polyimide unidirectional composites. It is demonstrated that the end-constraint effect influences accurate determination of G(12) more adversely than it affects the laminate Young's modulus E(xx) in the low off-axis range. Experimental results obtained from off-axis tests on unidirectional graphite/polyimide specimens confirm the above. Based on the presented analytical and experimental evidence, the 45-deg off-axis coupon is proposed for the determination of the intralaminar shear modulus G(12).

  2. Advanced tow placement of composite fuselage structure

    NASA Technical Reports Server (NTRS)

    Anderson, Robert L.; Grant, Carroll G.

    1992-01-01

    The Hercules NASA ACT program was established to demonstrate and validate the low cost potential of the automated tow placement process for fabrication of aircraft primary structures. The program is currently being conducted as a cooperative program in collaboration with the Boeing ATCAS Program. The Hercules advanced tow placement process has been in development since 1982 and was developed specifically for composite aircraft structures. The second generation machine, now in operation at Hercules, is a production-ready machine that uses a low cost prepreg tow material form to produce structures with laminate properties equivalent to prepreg tape layup. Current program activities are focused on demonstration of the automated tow placement process for fabrication of subsonic transport aircraft fuselage crown quadrants. We are working with Boeing Commercial Aircraft and Douglas Aircraft during this phase of the program. The Douglas demonstration panels has co-cured skin/stringers, and the Boeing demonstration panel is an intricately bonded part with co-cured skin/stringers and co-bonded frames. Other aircraft structures that were evaluated for the automated tow placement process include engine nacelle components, fuselage pressure bulkheads, and fuselage tail cones. Because of the cylindrical shape of these structures, multiple parts can be fabricated on one two placement tool, thus reducing the cost per pound of the finished part.

  3. Evaluation of shear bond strengths of gingiva-colored composite resin to porcelain, metal and zirconia substrates

    PubMed Central

    An, Hong-Seok; Park, Ji-Man

    2011-01-01

    PURPOSE The purpose of this study is to evaluate and compare the shear bond strength of the gingiva-colored composite resin and the tooth-colored composite resin to porcelain, metal and zirconia. MATERIALS AND METHODS Sixty cylindrical specimens were fabricated and divided into the following 6 groups (Group 1-W: tooth-colored composite bonded to porcelain, Group 1-P: gingiva-colored composite bonded to porcelain, Group 2-W: tooth-colored composite bonded to base metal, Group 2-P: gingiva-colored composite bonded to base metal, Group 3-W: toothcolored composite bonded to zirconia, Group 3-P: gingiva-colored composite bonded to zirconia). The shear bond strength was measured with a universal testing machine after thermocycling and the failure mode was noted. All data were analyzed using the two-way analysis of variance test and the Bonferroni post-hoc test at a significance level of 0.05. RESULTS The mean shear bond strength values in MPa were 12.39, 13.42, 8.78, 7.98, 4.64 and 3.74 for Group 1-W, 1-P, 2-W, 2-P, 3-W and 3-P, respectively. The difference between the two kinds of composite resin was not significant. The shear bond strength of Group 1 was the highest and that of Group 3 was the lowest. The differences among Group 1, 2 and 3 were all significant (P<.05). CONCLUSION The shear bond strength of the gingiva-colored composite was not less than that of the tooth-colored composite. Thus, repairing or fabricating ceramic restorations using the gingiva-colored composite resin can be regarded as a practical method. Especially, the prognosis would be fine when applied on porcelain surfaces. PMID:22053249

  4. Advanced organic composite materials for aircraft structures: Future program

    NASA Technical Reports Server (NTRS)

    1987-01-01

    Revolutionary advances in structural materials have been responsible for revolutionary changes in all fields of engineering. These advances have had and are still having a significant impact on aircraft design and performance. Composites are engineered materials. Their properties are tailored through the use of a mix or blend of different constituents to maximize selected properties of strength and/or stiffness at reduced weights. More than 20 years have passed since the potentials of filamentary composite materials were identified. During the 1970s much lower cost carbon filaments became a reality and gradually designers turned from boron to carbon composites. Despite progress in this field, filamentary composites still have significant unfulfilled potential for increasing aircraft productivity; the rendering of advanced organic composite materials into production aircraft structures was disappointingly slow. Why this is and research and technology development actions that will assist in accelerating the application of advanced organic composites to production aircraft is discussed.

  5. Free Vibration and Bending Behaviour of CNT Reinforced Composite Plate using Different Shear Deformation Theory

    NASA Astrophysics Data System (ADS)

    Mehar, K.; Panda, S. K.

    2016-02-01

    In the present study, the free vibration and the bending behaviour of carbon nanotube reinforced composite plate are computed using three different shear deformation theories under thermal environment. The material properties of carbon nanotube and matrix are assumed to be temperature-dependent, and the extended rule of mixture is used to compute the effectivematerial properties of the composite plate. The convergence and validity of the present modelalso have been checked by computing the wide variety of the numerical example. The applicability of the proposed higher-order models has been highlighted by solving the wide variety of examples for different geometrical and material parameters underelevated thermal environment.The responses are also examined using the simulation model developed in commercial finite element package (ANSYS).

  6. Shear Strength of Single Lap Joint Aluminium-Thermoplastic Natural Rubber (Al-TPNR) Laminated Composite

    NASA Astrophysics Data System (ADS)

    Muzakkar, M. Z.; Ahmad, S.; Yarmo, M. A.; Jalar, A.; Bijarimi, M.

    2013-04-01

    In this work, we studied the effect of surface treatment on the aluminium surface and a coupling agent to improve adhesion between aluminium with organic polymer. Thermoplastic natural rubber (TPNR) matrix was prepared by melt blending of natural rubber (NR), liquid natural rubber (LNR) compatibilizer, linear low density polyethylene (LLDPE) and polyethylene grafted maleic anhydride (PE-g-MAH). The PEgMAH concentration used was varied from 0% - 25%. In addition, the aluminium surface was pre-treated with 3-glycidoxy propyl trimethoxy silane (3-GPS) to enhance the mechanical properties of laminated composite. It was found that the shear strength of single lap joint Al-TPNR laminated composite showing an increasing trend as a function of PE-g-MAH contents for the 3-GPS surface treated aluminium. Moreover, the scanning electron microscope (SEM) revealed that the strength improvement was associated with the chemical state of the compound involved.

  7. Failure Analysis of Discrete Damaged Tailored Extension-Shear-Coupled Stiffened Composite Panels

    NASA Technical Reports Server (NTRS)

    Baker, Donald J.

    2005-01-01

    The results of an analytical and experimental investigation of the failure of composite is tiffener panels with extension-shear coupling are presented. This tailored concept, when used in the cover skins of a tiltrotor aircraft wing has the potential for increasing the aeroelastic stability margins and improving the aircraft productivity. The extension-shear coupling is achieved by using unbalanced 45 plies in the skin. The failure analysis of two tailored panel configurations that have the center stringer and adjacent skin severed is presented. Finite element analysis of the damaged panels was conducted using STAGS (STructural Analysis of General Shells) general purpose finite element program that includes a progressive failure capability for laminated composite structures that is based on point-stress analysis, traditional failure criteria, and ply discounting for material degradation. The progressive failure predicted the path of the failure and maximum load capability. There is less than 12 percent difference between the predicted failure load and experimental failure load. There is a good match of the panel stiffness and strength between the progressive failure analysis and the experimental results. The results indicate that the tailored concept would be feasible to use in the wing skin of a tiltrotor aircraft.

  8. Statistical shear lag model - unraveling the size effect in hierarchical composites.

    PubMed

    Wei, Xiaoding; Filleter, Tobin; Espinosa, Horacio D

    2015-05-01

    Numerous experimental and computational studies have established that the hierarchical structures encountered in natural materials, such as the brick-and-mortar structure observed in sea shells, are essential for achieving defect tolerance. Due to this hierarchy, the mechanical properties of natural materials have a different size dependence compared to that of typical engineered materials. This study aimed to explore size effects on the strength of bio-inspired staggered hierarchical composites and to define the influence of the geometry of constituents in their outstanding defect tolerance capability. A statistical shear lag model is derived by extending the classical shear lag model to account for the statistics of the constituents' strength. A general solution emerges from rigorous mathematical derivations, unifying the various empirical formulations for the fundamental link length used in previous statistical models. The model shows that the staggered arrangement of constituents grants composites a unique size effect on mechanical strength in contrast to homogenous continuous materials. The model is applied to hierarchical yarns consisting of double-walled carbon nanotube bundles to assess its predictive capabilities for novel synthetic materials. Interestingly, the model predicts that yarn gauge length does not significantly influence the yarn strength, in close agreement with experimental observations. PMID:25684701

  9. Shear bond strength of orthodontic brackets to aged resin composite surfaces: effect of surface conditioning.

    PubMed

    Bayram, Mehmet; Yesilyurt, Cemal; Kusgöz, Adem; Ulker, Mustafa; Nur, Metin

    2011-04-01

    The aim of this study was to investigate the effects of surface conditioning protocols on the shear bond strength (SBS) of metal brackets to aged composite resin surfaces in vitro. Ninety composite resin discs, 6 mm in diameter and 2 mm in height, were prepared and treated with an ageing procedure. After ageing, the specimens were randomly assigned to one of the following groups: (1) control with no surface treatment, (2) 38 per cent phosphoric acid gel, (3) 9.6 per cent hydrofluoric acid gel, (4) airborne aluminium trioxide particle abrasion, (5) sodium bicarbonate particle abrasion, and (6) diamond bur. The metal brackets were bonded to composite surfaces by means of an orthodontic adhesive (Transbond XT). All specimens were stored in water for 1 week at 37°C and then thermocycled (1000 cycles, 5-55°C) prior to SBS testing. SBS values and residual adhesive on the composite surface were evaluated. Analysis of variance showed a significant difference (P = 0.000) between the groups. Group 6 had the highest mean SBS (10.61 MPa), followed by group 4 (10.29 MPa). The results of this study suggest that a clinically acceptable bond strength can be achieved by surface conditioning of aged resin composite via the application of hydrofluoric acid, aluminium trioxide particle abrasion, sodium bicarbonate particle abrasion, or a diamond bur. PMID:20660131

  10. A study of void effects on the interlaminar shear strength of unidirectional graphite fiber reinforced composites

    NASA Technical Reports Server (NTRS)

    Bowles, Kenneth J.; Frimpong, Stephen

    1990-01-01

    A study was conducted to evaluate the effect of voids on the interlaminar shear strength (ILSS) of a polyimide matrix composite system. The graphite/PRM-15 composite was chosen for study because of the extensive amount of experience that has been amassed in the processing of this material. Composite densities and fiber contents of more than thirty different laminates were measured along with ILSS. Void contents were calculated and the void geometry and distribution were noted using microscopic techniques such as those used in metallography. It was found that there was a good empirical correlation between ILSS and composite density. The most acceptable relationship between the ILSS and density was found to be a power equation which closely resembles theoretically derived expressions. An increase in scatter in the strength data was observed as the void content increased. In laminates with low void content, the void appears to be more segregated in one area of the laminate. It was found that void free composites could be processed in matched metal die molds at pressures greater than 1.4 and less than 6.9 MPa.

  11. Biofouling of reverse-osmosis membranes under different shear rates during tertiary wastewater desalination: microbial community composition.

    PubMed

    Al Ashhab, Ashraf; Gillor, Osnat; Herzberg, Moshe

    2014-12-15

    We investigated the influence of feed-water shear rate during reverse-osmosis (RO) desalination on biofouling with respect to microbial community composition developed on the membrane surface. The RO membrane biofilm's microbial community profile was elucidated during desalination of tertiary wastewater effluent in a flat-sheet lab-scale system operated under high (555.6 s(-1)), medium (370.4 s(-1)), or low (185.2 s(-1)) shear rates, corresponding to average velocities of 27.8, 18.5, and 9.3 cm s(-1), respectively. Bacterial diversity was highest when medium shear was applied (Shannon-Weaver diversity index H' = 4.30 ± 0.04) compared to RO-membrane biofilm developed under lower and higher shear rates (H' = 3.80 ± 0.26 and H' = 3.42 ± 0.38, respectively). At the medium shear rate, RO-membrane biofilms were dominated by Betaproteobacteria, whereas under lower and higher shear rates, the biofilms were dominated by Alpha- and Gamma- Proteobacteria, and the latter biofilms also contained Deltaproteobacteria. Bacterial abundance on the RO membrane was higher at low and medium shear rates compared to the high shear rate: 8.97 × 10(8) ± 1.03 × 10(3), 4.70 × 10(8) ± 1.70 × 10(3) and 5.72 × 10(6) ± 2.09 × 10(3) copy number per cm(2), respectively. Interestingly, at the high shear rate, the RO-membrane biofilm's bacterial community consisted mainly of populations known to excrete high amounts of extracellular polymeric substances. Our results suggest that the RO-membrane biofilm's community composition, structure and abundance differ in accordance with applied shear rate. These results shed new light on the biofouling phenomenon and are important for further development of antibiofouling strategies for RO membranes. PMID:25262553

  12. Advanced thermoset resins for fire-resistant composites

    NASA Technical Reports Server (NTRS)

    Kourtides, D. A.; Parker, J. A.

    1979-01-01

    The thermal and flammability properties of some thermoset polymers and composites are described. The processing and evaluation of composites fabricated from currently used resins and advanced fire-resistant resins are also described. Laboratory test methodology used to qualify candidate composite materials includes thermochemical characterization of the polymeric compounds and evaluation of the glass reinforced composites for flammability and smoke evolution. The use of these test methods will be discussed in comparing advanced laminating resins and composites consisting of modified epoxies, phenolics and bismaleimide, with conventional baseline materials consisting of epoxy.

  13. Advanced Composite Structures At NASA Langley Research Center

    NASA Technical Reports Server (NTRS)

    Eldred, Lloyd B.

    2015-01-01

    Dr. Eldred's presentation will discuss several NASA efforts to improve and expand the use of composite structures within aerospace vehicles. Topics will include an overview of NASA's Advanced Composites Project (ACP), Space Launch System (SLS) applications, and Langley's ISAAC robotic composites research tool.

  14. In-Plane Shear Testing of Medium and High Modulus Woven Graphite Fiber Reinforced/Polyimide Composites

    NASA Technical Reports Server (NTRS)

    Gentz, M.; Armentrout, D.; Rupnowski, P.; Kumosa, L.; Shin, E.; Sutter, J. K.; Kumosa, M.

    2004-01-01

    Iosipescu shear tests were performed at room temperature and at 316 C (600 F) o woven composites with either M40J or M60J graphite fibers and PMR-II-50 polyimide resin matrix. The composites were tested as supplied and after thermo-cycling, with the thermo-cycled composites being tested under dry and wet conditions. Acoustic emission (AE) was monitored during the room and high temperature Iosipescu experiments. The shear stresses at the maximum loads and the shear stresses at the significant onset of AE were determined for the composites as function of temperature and conditioning. The combined effects of thermo-cycling and moisture on the strength and stiffness properties of the composites were evaluated. It was determined that the room and high temperature shear stresses at the maximum loads were unaffected by conditioning. However, at room temperature the significant onset of AE was affected by conditioning; the thermal conditioned wet specimens showed the highest shear stress at the onset of AE followed by thermal-conditioned and then as received specimens. Also, at igh temperature the significant onset of AE occurred in some specimens after the maximum load due to the viscoelastoplastic nature of the matrix material.

  15. The Comparison of Shear Bond Strength Between Fibre Reinforced Composite Posts with Three Different Composite Core Materials – An In vitro Study

    PubMed Central

    Anche, Sampath; Kakarla, Pranitha; Kadiyala, Krishna Kishore; Sreedevi, B.; Chiramana, Sandeep; Dev J., Ravi Rakesh; Manne, Sanjay Dutt; G., Deepthi

    2014-01-01

    Aim: The aim of this study is to compare the shear bond strength between fiber reinforced composite post with three different composite core materials. Materials and Methods: The materials used for the study were: 30 maxillary central incisors, pre fabricated fiber reinforced composite post (postec plus posts), Multi-core heavy body, Ti-core, Fluoro-core, Etchant gel, Silane coupling agent, Dentin bonding agent, Standardized gutta percha points, Rely-X dual cure composite resin. A total of 30 human maxillary central incisor were selected for this study. They were divided into three groups of 10 specimens each namely A, B and C. Results: The results obtained were analyzed by using one way analysis (ANOVA) and Tukey Honestly Significant Difference and they showed highest mean shear bond strength for group C when compared with group A and group B. There is no significant difference in the shear bond strength values between group A and group B. Conclusion: The teeth restored with multicore HB showed highest shear bond strength. The teeth restored with Fluoro core showed lowest shear bond strength. No statistically significant difference exists between the shear bond strength values between Ti-core and Fluoro-core. PMID:24596784

  16. Quantification of Shear-Relative Asymmetries in Eyewall Slope Using Airborne Doppler Radar Composites

    NASA Astrophysics Data System (ADS)

    Hazelton, A.; Rogers, R.; Hart, R. E.

    2013-12-01

    Recently, it has become apparent that typical methods for analyzing tropical cyclones (TCs), such as track and intensity, are insufficient for evaluating TC structural evolution and numerical model forecasts of that evolution. Many studies have analyzed different metrics related to TC inner-core structure in an attempt to better understand the processes that drive changes in core structure. One important metric related to vertical TC structure is the slope of the eyewall. Hazelton and Hart (2013) discussed azimuthal mean eyewall slope based on radar reflectivity data, and its relationship with TC intensity and core structure. That study also noted significant azimuthal variation in slopes, but did not significantly explore reasons for this variation. Accordingly, in this study, we attempt to quantify the role of vertical wind shear in causing azimuthal variance of slope, using research quality Doppler radar composites from the NOAA Hurricane Research Division (HRD). We analyze the slope of the 20 dBZ surface as in Hazelton and Hart (2013), and also look at azimuthal variation in other measures of eyewall slope, such as the slope of the radius of maximum winds (RMW), which has been analyzed in an azimuthal mean sense by Stern and Nolan (2009), and an angular momentum surface. The shear-relative slopes are quantified by separating the radar data into four quadrants relative to the vertical shear vector: Downshear Left (DSL), Upshear Left (USL), Upshear Right (USR), and Downshear Right (DSR). This follows the method employed in shear-relative analyses of other aspects of TC core structure, such as Rogers et al. (2013) and Reasor et al. (2013). The data suitable for use in this study consist of 36 flights into 15 different TCs (14 Atlantic, 1 Eastern Pacific) between 1997 and 2010. Preliminary results show apparent shear-induced asymmetries in eyewall slope. The slope of the RMW shows an asymmetry due to the tilt of the vortex approximately along the shear vector, with

  17. Core Turbulence and Transport Response to Increasing Toroidal Rotation and Shear in Advanced-Inductive Plasmas

    NASA Astrophysics Data System (ADS)

    McKee, G.; Yan, Z.; Holland, C.; Luce, T.; Petty, C.; Rhodes, T.; Schmitz, L.; Solomon, W.

    2014-10-01

    Multi-scale turbulence properties are altered as core toroidal rotation and ExB shearing rates are systematically varied in relatively high-beta, advanced-inductive H-mode plasmas on DIII-D. The energy confinement time increases by 50% as the toroidal rotation is increased by a factor of 2.5 (to Mo = 0.5), while core turbulence, measured with BES, DBS and PCI, decreases in dimensionlessly matched plasmas (β ~ 2 . 7 ,q95 = 5 . 1). Low-wavenumber (k⊥ρ< 1) density fluctuations obtained with BES near mid-radius exhibit significant amplitude reduction along with a slight reduction in radial correlation length at higher rotation, while fluctuations in the outer region of the plasma, ρ > 0 . 6 , exhibit, but little change in amplitude. Fluctuation measurements and transport behavior will be quantitatively compared with nonlinear simulations. The resulting reduction in confinement will need to be ascertained for low-rotating plasmas such as ITER and FNSF. Work supported by the US DOE under DE-FG02-08ER54999, DE-FG02-07ER54917, DE-FC02-04ER54698, DE-FG02-08ER54984 and DE-AC02-09CH11466.

  18. Design, fabrication and test of graphite/polyimide composite joints and attachments for advanced aerospace vehicles

    NASA Technical Reports Server (NTRS)

    1981-01-01

    The development of several types of graphite/polyimide (GR/PI) bonded and bolted joints is reported. The program consists of two concurrent tasks: (1) design and test of specific built up attachments; and (2) evaluation of standard advanced bonded joint concepts. A data base for the design and analysis of advanced composite joints for use at elevated temperatures (561K (550 deg F)) to design concepts for specific joining applications, and the fundamental parameters controlling the static strength characteristics of such joints are evaluated. Data for design and build GR/PI of lightly loaded flight components for advanced space transportation systems and high speed aircraft are presented. Results for compression and interlaminar shear strengths of Celion 6000/PMR-15 laminates are given. Static discriminator test results for type 3 and type 4 bonded and bolted joints and final joint designs for TASK 1.4 scale up fabrication and testing are presented.

  19. Advanced composite applications for sub-micron biologically derived microstructures

    NASA Technical Reports Server (NTRS)

    Schnur, J. M.; Price, R. R.; Schoen, P. E.; Bonanventura, Joseph; Kirkpatrick, Douglas

    1991-01-01

    A major thrust of advanced material development is in the area of self-assembled ultra-fine particulate based composites (micro-composites). The application of biologically derived, self-assembled microstructures to form advanced composite materials is discussed. Hollow 0.5 micron diameter cylindrical shaped microcylinders self-assemble from diacetylenic lipids. These microstructures have a multiplicity of potential applications in the material sciences. Exploratory development is proceeding in application areas such as controlled release for drug delivery, wound repair, and biofouling as well as composites for electronic and magnetic applications, and high power microwave cathodes.

  20. Exact solutions for coupled free vibrations of tapered shear-flexible thin-walled composite beams

    NASA Astrophysics Data System (ADS)

    Piovan, Marcelo T.; Filipich, Carlos P.; Cortínez, Víctor H.

    2008-09-01

    In this paper, analytical solutions for the free vibration analysis of tapered thin-walled laminated-composite beams with both closed and open cross-sections are developed. The present study is based on a recently developed model that incorporates in a full form the shear flexibility. The model considers shear flexibility due to bending as well as warping related to non-uniform torsion. The theory is briefly reviewed with the aim to present the equilibrium equations, the related boundary conditions and the constitutive equations. The stacking sequences in the panels of the cross-sections are selected in order to behave according to certain elastic coupling features. Typical laminations for a box-beam such as circumferentially uniform stiffness (CUS) or circumferentially asymmetric stiffness (CAS) configurations are adopted. For open cross-sections, special laminations behaving elastically like the CAS and CUS configurations of closed sections are also taken into account. The exact values (i.e. with arbitrary precision) of frequencies are obtained by means of a generalized power series methodology. A recurrence scheme is introduced with the aim to simplify the algebraic manipulation by shrinking the number of unknown variables. A parametric analysis for different taper ratios, slenderness ratios and stacking sequences is performed. Numerical examples are also carried out focusing attention in the validation of the present theory with respect to 2D FEM computational approaches, as well as to serve as quality test and convergence test of former finite elements schemes.

  1. A problem formulation for glideslope tracking in wind shear using advanced robust control techniques

    NASA Technical Reports Server (NTRS)

    Belcastro, Christine M.; Chang, B.-C.; Fischl, Robert

    1992-01-01

    A formulation of the longitudinal glideslope tracking of a transport-class aircraft in severe wind shear and turbulence for application to robust control system design is presented. Mathematical wind shear models are incorporated into the vehicle mathematical model, and wind turbulence is modeled as an input disturbance signal. For this problem formulation, the horizontal and vertical wind shear gradients are treated as real uncertain parameters that vary over an entire wind shear profile. The primary objective is to examine the formulation of this problem into an appropriate design format for use in m-synthesis control system design.

  2. Bioresorbable composite screws manufactured via forging process: pull-out, shear, flexural and degradation characteristics.

    PubMed

    Felfel, R M; Ahmed, I; Parsons, A J; Rudd, C D

    2013-02-01

    Bioresorbable screws have the potential to overcome some of the complications associated with metallic screws currently in use. Removal of metallic screws after bone has healed is a serious issue which can lead to refracture due to the presence of screw holes. Poly lactic acid (PLA), fully 40 mol% P(2)O(5) containing phosphate unidirectional (P40UD) and a mixture of UD and short chopped strand random fibre mats (P40 70%UD/30%RM) composite screws were prepared via forging composite bars. Water uptake and mass loss for the composite screws manufactured increased significantly to ∼1.25% (P=0.0002) and ∼1.1% (P<0.0001), respectively, after 42 days of immersion in PBS at 37 °C. The initial maximum flexural load for P40 UD/RM and P40 UD composite screws was ∼60% (P=0.0047) and ∼100% (P=0.0037) higher than for the PLA screws (∼190 N), whilst the shear load was slightly higher in comparison to PLA (∼2.2 kN). The initial pull-out strengths for the P40 UD/RM and PLA screws were similar whereas that for P40 UD screws was ∼75% higher (P=0.022). Mechanical properties for the composite screws decreased initially after 3 days of immersion and this reduction was ascribed to the degradation of the fibre/matrix interface. After 3 days interval the mechanical properties (flexural, shear and pull-out) maintained their integrity for the duration of the study (at 42 days). This property retention was attributed to the chemical durability of the fibres used and stability of the matrix properties during the degradation process. It was also deemed necessary to enhance the fibre/matrix interface via use of a coupling agent in order to maintain the initial mechanical properties acquired for the required period of time. Lastly, it is also suggested that the degrading reinforcement fibres may have the potential to buffer any acidic products released from the PLA matrix. PMID:23262309

  3. Effect of nanocomposite composition on shear and elongational rheological behavior of PLA/MMT hybrids

    NASA Astrophysics Data System (ADS)

    Garofalo, Emilia; Scarfato, Paola; Di Maio, Luciano; Incarnato, Loredana

    2014-05-01

    The present work focuses on the possibility of conveniently tuning materials in PLA based nanocomposites in order to improve their processability in manufacturing processes where extensional flow is mainly involved. Nanocomposites at a constant silicate loading were produced by melt compounding, using a commercial polylactide grade (PLA 4032D) and two different organo-silicates (Cloisite 30B and Nanofil SE3010). A morphological characterization in solid and molten state, realized by TEM investigations and shear rheological measurements, firstly pointed out the influence of composition on the nanostructure of the hybrid systems. All the samples were then submitted to uniaxial stretching and the rheological response of the different nanocomposites was correlated to the initial nanostructure and the different polymer-clay affinity.

  4. Modeling shear instability and fracture in dynamically deformed Al/W granular composites

    NASA Astrophysics Data System (ADS)

    Olney, Karl; Benson, David; Nesterenko, Vitali

    2011-06-01

    Aluminum/Tungsten granular composites are materials which combine high density and strength with bulk distributed fracture of Al matrix into small particles under impact or shock loading. They are processed using cold and hot isostatic pressing of W particles/rods in the matrix of Al powder. The presentation will describe modeling of these materials under dynamic conditions simulating low velocity high energy impact in drop weight test (10 m/s) and also behavior following impact with velocities up to 1200 m/s. It will be demonstrated that morphology of W component and bonding between Al particles dramatically affects their strength, shear localization and mode of fracture of Al matrix. The support for this project provided by the Office of Naval Research Multidisciplinary University Research Initiative Award N00014-07-1-0740 (Program Officer Dr. Clifford Bedford).

  5. Controlling exfoliation in order to minimize damage during dispersion of long SWCNTs for advanced composites

    PubMed Central

    Yoon, Howon; Yamashita, Motoi; Ata, Seisuke; Futaba, Don N.; Yamada, Takeo; Hata, Kenji

    2014-01-01

    We propose an approach to disperse long single-wall carbon nanotubes (SWCNTs) in a manner that is most suitable for the fabrication of high-performance composites. We compare three general classes of dispersion mechanisms, which encompass 11 different dispersion methods, and we have dispersed long SWCNTs, short multi-wall carbon nanotubes, and short SWCNTs in order to understand the most appropriate dispersion methods for the different types of CNTs. From this study, we have found that the turbulent flow methods, as represented by the Nanomizer and high-pressure jet mill methods, produced unique and superior dispersibility of long SWCNTs, which was advantageous for the fabrication of highly conductive composites. The results were interpreted to imply that the biaxial shearing force caused an exfoliation effect to disperse the long SWCNTs homogeneously while suppressing damage. A conceptual model was developed to explain this dispersion mechanism, which is important for future work on advanced CNT composites. PMID:24469607

  6. Shear test of composite bonded to dentin: Er:YAG laser versus dental handpiece preparations

    NASA Astrophysics Data System (ADS)

    Visuri, Steven R.; Gilbert, Jeremy L.; Walsh, Joseph T., Jr.; Wigdor, Harvey A.

    1995-05-01

    The erbium:YAG laser coupled with a cooling stream of water appears to be an effective means of removing dental hard tissues. However, before the procedure is deemed clinically viable, there are several important issues of safety and efficacy that need to be explored. In this study we investigated the surface that remains following laser ablation of dentin and compared the results to the use of a dental handpiece. Specifically, we studied the effect the laser radiation had on the bonding of composite to dentin. The crowns of extracted human molars were removed revealing the underlying dentin. An additional thickness of material was removed with either a dental handpiece or an Er:YAG laser by raster scanning the samples under a fixed handpiece or laser. Comparable surface roughnesses were achieved. A cylinder of composite was bonded onto the prepared surfaces following the manufacturer's directions. The dentin-composite bond was then shear stressed to failure on a universal testing apparatus and the maximum load recorded. Preliminary results indicated that laser irradiated samples had improved bond strengths. SEM photographs of the surfaces were also taken to compare the two methods of tooth preparation.

  7. Effects of Shear, Defocus, and Wavefront Error on the Theoretical Performance of the Composite Infrared Spectrometer for Cassini

    NASA Technical Reports Server (NTRS)

    Martino, Antonio J.; Hagopian, John G.

    1998-01-01

    The combined effects on performance of shear between the two arms, defocus of die detector, and difference in wavefront between the two arms of a Fourier transform spectrometer using cube corner retroreflectors were investigated. Performance was characterized by the amplitude of the fringe signals coming from a detector as the path-length difference was scanned. A closed-form expression was found for the combined effects of shear and defocus, and it was found that defocus had no effect in the absence of shear. The effect of wavefront error was modeled numerically and assumed to be independent of shear and defocus. Results were compared with measurements made on the breadboard and engineering model of the Composite Infrared Spectrometer for the Cassini mission to Saturn, and good agreement was found.

  8. Overview Shear Strengthening of RC Beams with Externally Bonded FRP Composites

    NASA Astrophysics Data System (ADS)

    Alzoubi, Feras; Zhengliang, Li

    Shear strengthening is required when an RC beam is found deficient in shear, or when its shear capacity falls below its flexural capacity after flexural strengthening. This study presents a state-of-the-art review of existing research on this topic. The research programs conducted to investigate the shear performance and to evaluate the shear capacity of the strengthened beams are reviewed in this paper by details. The research is a good reference for all engineers and researchers in fields of shear strengthening and repair RC beams in building and bridges.

  9. High temperature composites for advanced missile and space transportation systems

    NASA Technical Reports Server (NTRS)

    Mccleskey, S. F.; Cushman, J. B.; Skoumal, D. E.

    1982-01-01

    A study has been conducted to characterize a state-of-the-art graphite/polyimide composite system by determining mechanical and thermophysical properties of selected laminates over a temperature range of -250 F to 600 F. The material studied was Celion 3000/PMR-15. Material property data obtained from testing included tension, compression and shear strengths, and coefficient of thermal expansion. Environmental conditions examined were: as cured/post-cured, isothermal aged at 600 F, thermal cycled from -250 F to 600 F, and moisture conditioned. This study has provided an initial data base on a graphite/polyimide composite system capable of operating in 500/600 F applications.

  10. Mechanics of advanced fiber reinforced lattice composites

    NASA Astrophysics Data System (ADS)

    Fan, Hua-Lin; Zeng, Tao; Fang, Dai-Ning; Yang, Wei

    2010-12-01

    Fiber reinforced lattice composites are light-weight attractive due to their high specific strength and specific stiffness. In the past 10 years, researchers developed three-dimensional (3D) lattice trusses and two-dimensional (2D) lattice grids by various methods including interlacing, weaving, interlocking, filament winding and molding hot-press. The lattice composites have been applied in the fields of radar cross-section reduction, explosive absorption and heat-resistance. In this paper, topologies of the lattice composites, their manufacturing routes, as well as their mechanical and multifunctional applications, were surveyed.

  11. Basic failure mechanisms in advanced composites

    NASA Technical Reports Server (NTRS)

    Mullin, J. V.; Mazzio, V. F.; Mehan, R. L.

    1972-01-01

    Failure mechanisms in carbon-epoxy composites are identified as a basis for more reliable prediction of the performance of these materials. The approach involves both the study of local fracture events in model specimens containing small groups of filaments and fractographic examination of high fiber content engineering composites. Emphasis is placed on the correlation of model specimen observations with gross fracture modes. The effects of fiber surface treatment, resin modification and fiber content are studied and acoustic emission methods are applied. Some effort is devoted to analysis of the failure process in composite/metal specimens.

  12. The Advanced Composition Explorer power subsystem

    SciTech Connect

    Panneton, P.E.; Tarr, J.E.; Goliaszewski, L.T.

    1998-07-01

    The Johns Hopkins University Applied Physics Laboratory, under contract with NASA Goddard Space Flight Center, has designed and launched the Advanced Composition Explorer (ACE) spacecraft. ACE is a scientific observatory housing ten instruments, and is located in a halo orbit about the L1 Sun-Earth libration point. ACE is providing real-time solar wind monitoring and data on elemental and isotopic matter of solar and galactic origin. The ACE Electrical Power Subsystem (EPS) is a fault tolerant, solar powered, shunt regulated, direct energy transfer architecture based on the Midcourse Space Experiment (MSX) EPS. The differences are that MSX used oriented solar arrays with a nickel hydrogen-battery defined bus, while ACE uses fixed solar panels with a regulated bus decoupled from its nickel cadmium (NiCd) battery. Also, magnetometer booms are mounted on two of the four ACE solar panels. The required accuracy of the magnetometers impose severe requirements on the magnetic fields induced by the solar array. Other noteworthy features include a solar cell degradation experiment, in-flight battery reconditioning, a battery requalified to a high vibrational environment, and an adjustable bus voltage setpoint. The four solar panels consist of aluminum honeycomb substrates covered with 15.1% efficient silicon cells. The cells are strung using silver interconnects and are back-wired to reduce magnetic emissions below 0.1nT. Pyrotechnic actuated, spring loaded hinges deploy the panels after spacecraft separation from the Delta II launch vehicle. Solar cell experiments on two of the panels track cell performance degradation at L1, and also distinguish any hydrazine impingement degradation which may be caused by the thrusters. Each solar panel uses a digital shunt box, containing blocking diodes and MOSFETs, for short-circuit control of its 5 solar strings. A power box contains redundant analog MOSFET shunts, the 90% efficient boost regulator, and redundant battery chargers

  13. Basic failure mechanisms in advanced composites

    NASA Technical Reports Server (NTRS)

    Mullin, J. V.; Mazzio, V. F.; Mehan, R. L.

    1971-01-01

    Fundamental failure mechanisms in carbon-epoxy composites were studied for more reliable prediction of the performance of these materials. Single and multiple fiber specimens were tested under tensile loads, and the sequence of failure events was observed. Parameters such as resin crack sensitivity, fiber surface treatment and variations in fibers from batch to batch are being evaluated. The analysis of bulk composite fracture processes using acoustic emission techniques is being studied in order to correlate microscopic observations with bulk composite behavior. Control of the fracture process through matrix and interface modification is being attempted, and study of failure processes in composite/metal specimens is being conducted. Most of the studies involved DEN 438 epoxy novolac as the matrix, but some experiments are now underway using the higher temperature resin ERLA 4617.

  14. Flat tensile specimen design for advanced composites

    NASA Technical Reports Server (NTRS)

    Worthem, Dennis W.

    1990-01-01

    Finite element analyses of flat, reduced gage section tensile specimens with various transition region contours were performed. Within dimensional constraints, such as maximum length, tab region width, gage width, gage length, and minimum tab length, a transition contour radius of 41.9 cm produced the lowest stress values in the specimen transition region. The stresses in the transition region were not sensitive to specimen material properties. The stresses in the tab region were sensitive to specimen composite and/or tab material properties. An evaluation of stresses with different specimen composite and tab material combinations must account for material nonlinearity of both the tab and the specimen composite. Material nonlinearity can either relieve stresses in the composite under the tab or elevate them to cause failure under the tab.

  15. Graphite/Polyimide Composites. [conference on Composites for Advanced Space Transportation Systems

    NASA Technical Reports Server (NTRS)

    Dexter, H. B. (Editor); Davis, J. G., Jr. (Editor)

    1979-01-01

    Technology developed under the Composites for Advanced Space Transportation System Project is reported. Specific topics covered include fabrication, adhesives, test methods, structural integrity, design and analysis, advanced technology developments, high temperature polymer research, and the state of the art of graphite/polyimide composites.

  16. Film in the Advanced Composition Classroom: A Tapestry of Style

    ERIC Educational Resources Information Center

    Durst, Pearce

    2015-01-01

    This article advances film as worthy of rhetorical inquiry and deserving of more sustained attention in the advanced composition classroom. The first section identifies various approaches to the "language" of film, which can be adopted to navigate the technical, rhetorical, and cultural concerns needed to compose informed multimodal…

  17. Advanced composites: Design and application. Proceedings of the meeting of the Mechanical Failures Prevention Group

    NASA Technical Reports Server (NTRS)

    Shives, T. R.; Willard, W. A.

    1979-01-01

    The design and application of advanced composites is discussed with emphasis on aerospace, aircraft, automotive, marine, and industrial applications. Failure modes in advanced composites are also discussed.

  18. Dynamic analysis of composite beam subjected to harmonic moving load based on the third-order shear deformation theory

    NASA Astrophysics Data System (ADS)

    Rezvanil, Mohammad Javad; Kargarnovin, Mohammad Hossein; Younesian, Davood

    2011-12-01

    The response of an infinite Timoshenko beam subjected to a harmonic moving load based on the thirdorder shear deformation theory (TSDT) is studied. The beam is made of laminated composite, and located on a Pasternak viscoelastic foundation. By using the principle of total minimum potential energy, the governing partial differential equations of motion are obtained. The solution is directed to compute the deflection and bending moment distribution along the length of the beam. Also, the effects of two types of composite materials, stiffness and shear layer viscosity coefficients of foundation, velocity and frequency of the moving load over the beam response are studied. In order to demonstrate the accuracy of the present method, the results TSDT are compared with the previously obtained results based on first-order shear deformation theory, with which good agreements are observed.

  19. Effects of large deflection and transverse shear on response of rectangular symmetric composite laminates subjected to acoustic excitation

    NASA Technical Reports Server (NTRS)

    Mei, Chuh; Prasad, C. B.

    1987-01-01

    Nonlinear equations of motion of symmetrically laminated anisotropic plates are derived accounting for von Karman strains. The effect of transverse shear is included in the formulation. Using a single-mode Galerkin procedure, the nonlinear modal equation is obtained. The direct equivalent linearization method is employed for solution of this equation. The response to acoustic excitation of moderately thick composite panels is studied. Further, the effects of transverse shear on large deflection vibration of laminates under random excitation are studied. Mean-square deflections and mean-square inplane stresses are obtained for symmetric graphite-epoxy laminates. Using equilibrium equations and the continuity requirements, the mean-square transverse shear stresses are calculated. The results obtained will be useful in the sonic fatigue design of composite aircraft panels. The analysis is presented in detail for simply supported plates. The analogous equations for a clamped case are also obtained.

  20. Influence of large deflection and transverse shear on random response of rectangular symmetric composite laminates to acoustic loads

    NASA Technical Reports Server (NTRS)

    Mei, Chuh; Prasad, C. B.

    1987-01-01

    Nonlinear equations of motion of symmetrically laminated anisotropic plates are derived accounting for von Karman strains. The effect of transverse shear is included in the formulation and the rotatory inertia effect is ignored. Using a single-mode Galerkin procedure the nonlinear modal equation is obtained. Direct equivalent linearization is employed. The response of acoustic excitation on moderately thick composite panels is studied. Further, the effects of transverse shear on large deflection vibration of laminates under random excitation are studied. Mean-square deflection and mean-square inplane stresses are obtained for some symmetric graphite-epoxy laminates. Using equilibrium equations and the continuity requirements, the mean-square transverse shear stresses are calculated. The results obtained will be useful in the sonic fatigue design of composite aircraft panels. The analysis is presented in detail for simply supported plate. The analogous equations for a clamped case are given in the appendix.

  1. Failure behavior for composite single-bolted joints in double shear tension

    NASA Astrophysics Data System (ADS)

    Tang, Zhanwen; Liu, Hanyang; Yang, Zhiyong; Shi, Hanqiao; Sun, Baogang

    2016-05-01

    In order to improve the reliability and load carrying capacity of composite laminates structures which were lap jointed by bolt, in this paper, the failure strength and failure mode of laminated composite pinned-joints is investigated. To determine the effects of joint geometry and stacking sequence on the bearing strength and damage mode, the multi-scale numerical model combining with the Generalized Method of Cells (GMC) and considering the failure and the damage of constituent materials was created based on the ABAQUS and its user subroutine (USDFLD). A three-dimensional finite element technique was used for the stress analysis. Based on the three-dimensional state of stress of each element, different failure modes were detected by the failure theories of constituent materials, all of which are applied at the fiber, matrix and fiber-matrix interface constituent level. Numerical simulations have been carried out by which edge distance-to-hole diameter ratio, and plate width-to-hole diameter ratio are varied, The composite laminated plates are stacked with the following four different orientations: [+45/-45]2s, [90/+45/-45]s, and [0/90/0]s, the results show that failure mode and bearing strength are closely related to by stacking sequence of plates and geometrical parameters. Finally, the ultimate strength and failure modes of composite bolted joints in static tension double-shear loading conditions are predicted by using the progressive damage method established and the effects of layup and dimension of laminates on the properties of the connection structure were researched in this paper. An excellent agreement is found between data obtained from this study and the experiment.

  2. Trapped rubber processing for advanced composites

    NASA Technical Reports Server (NTRS)

    Marra, P. J.

    1976-01-01

    Trapped rubber processing is a molding technique for composites in which precast silicone rubber is placed within a closed cavity where it thermally expands against the composite's surface supported by the vessel walls. The method has been applied by the Douglas Aircraft Company, under contract to NASA-Langley, to the design and fabrication of 10 DC-10 graphite/epoxy upper aft rudder assemblies. A three-bay development tool form mold die has been designed and manufactured, and tooling parameters have been established. Fabrication procedures include graphite layup, assembly of details in the tool, and a cure cycle. The technique has made it possible for the cocured fabrication of complex primary box structures otherwise impracticable via standard composite material processes.

  3. Evaluation of micro-shear bond strength of resin modified glass-ionomer to composite resins using various bonding systems

    PubMed Central

    Kasraie, Shahin; Shokripour, Mohadese; Safari, Mahin

    2013-01-01

    Aim: The aim was to compare the micro-shear bond strength between composite and resin-modified glass-ionomer (RMGI) by different adhesive systems. Materials and Methods: A total of 16 discs of RMGI with a diameter of 15 mm and a thickness of 2 mm were randomly divided into four groups (n = 4). Four cylinders of composite resin (z250) were bonded to the RMGI discs with Single Bond, Clearfil SE Bond and Clearfil S3 Bond in Groups 1-3, respectively. The fourth group was the control. Samples were tested by a mechanical testing machine with a strain rate of 0.5 mm/min. Failure mode was assessed under a stereo-microscope. Results: The means of micro-shear bond strength values for Groups 1-4 were 14.45, 23.49, 16.23 and 5.46 MPa, respectively. Using a bonding agent significantly increased micro-shear bond strength (P = 0.0001). Conclusion: Micro-shear bond strength of RMGI to composite increased significantly with the use of adhesive resin. The bond strength of RMGI to composite resin could vary depending upon the type of adhesive system used. PMID:24347892

  4. Effect of composite resin contamination with powdered and unpowdered latex gloves on its shear bond strength to bovine dentin.

    PubMed

    Oskoee, S S; Navimipour, E J; Bahari, M; Ajami, A A; Oskoee, P A; Abbasi, N M

    2012-01-01

    The aim of the present study was to evaluate the effect of composite resin contamination with powdered and unpowdered latex gloves on the shear bond strength of etch-and-rinse and two-step self-etch adhesive systems. Standard flat dentin surfaces were prepared on the facial aspect of 120 bovine incisors and randomly assigned into two (n=60) groups: group 1: Single Bond (SB), group 2: Clearfil SE Bond (CSE). Furthermore, each group was randomly subdivided into three (n=20) based on the type of composite contamination (without contamination, contamination with powdered latex gloves, and contamination with unpowdered latex gloves). The adhesives were applied and resin composite bonded to the dentin. After thermocycling, the specimens were subjected to a shear bond strength test. Two-way analysis of variance (ANOVA) and a post hoc Bonferroni test were used for statistical analysis. One-way ANOVA was used to compare shear bond strength values in each group. Statistical significance was set at p < 0.02. Two-way ANOVA showed that the shear bond strength was significantly influenced by the type of composite surface contamination (p=0.001). In the SB group there were no significant differences between different surface treatments (p=0.08). In the CSE group a significant difference was observed between the subgroup without contamination and the subgroup with powdered latex glove contamination (p=0.01); however, no significant differences were observed between the other subgroups. PMID:22433010

  5. Effect of an Extra Hydrophobic Resin Layer on Repair Shear Bond Strength of a Silorane-Based Composite Resin

    PubMed Central

    Mohammadi, Narmin; Bahari, Mahmoud; Kimyai, Soodabeh; Rahbani Nobar, Behnam

    2015-01-01

    Objectives: Composite repair is a minimally invasive and conservative approach. This study aimed to evaluate the effect of an additional hydrophobic resin layer on the repair shear bond strength of a silorane-based composite repaired with silorane or methacrylate-based composite. Materials and Methods: Sixty bar-shaped composite blocks were fabricated and stored in saline for 72 hours. The surface of the samples were roughened by diamond burs and etched with phosphoric acid; then, they were randomly divided into three groups according to the repairing process: Group 1: Silorane composite-silorane bonding agent-silorane composite; group 2: Silorane composite-silorane bonding agent-hydrophobic resin-silorane composite, and group 3: Silorane composite-silorane bonding agent-hydrophobic resin methacrylate-based composite. Repairing composite blocks measured 2.5×2.5×5mm. After repairing, the samples were stored in saline for 24 hours and thermocycled for 1500 cycles. The repair bond strength was measured at a strain rate of 1mm/min. Twenty additional cylindrical composite blocks (diameter: 2.5mm, height: 6mm) were also fabricated for measuring the cohesive strength of silorane-based composite. The data were analyzed using One-way ANOVA and the post hoc Tukey’s test (α=0.05). Results: Cohesive bond strength of silorane composite was significantly higher than the repair bond strengths in other groups (P<0.001). The repair bond strength of group 3 was significantly higher than that of group 1 (P=0.001). Conclusion: Application of an additional hydrophobic resin layer for repair of silorane-based composite with a methacrylate-based composite enhanced the repair shear bond strength. PMID:27559348

  6. Advanced Composition and the Computerized Library.

    ERIC Educational Resources Information Center

    Hult, Christine

    1989-01-01

    Discusses four kinds of computerized access tools: online catalogs; computerized reference; online database searching; and compact disks and read only memory (CD-ROM). Examines how these technologies are changing research. Suggests how research instruction in advanced writing courses can be refocused to include the new technologies. (RS)

  7. Advanced Composition: English as a Second Language.

    ERIC Educational Resources Information Center

    Sarantos, R. L.

    This course is designed for advanced students to enable them to express themselves in writing with native proficiency comparable to North American students of similar educational levels by providing activities specifically geared to the elimination of interfering features of language in the mother tongue. Students learn to produce outlines,…

  8. Aeroelastic behavior of composite helicopter rotor blades with advanced geometry tips

    SciTech Connect

    Friedmann, P.P.; Yuan, K.A.

    1995-12-31

    A new structural and aeroelastic model capable of representing the aeroelastic stability and response of composite helicopter rotor blades with advanced geometry tips is presented. Where it is understood that advanced geometry tips are blade tips having sweep, anhedral and taper in the outboard 10% segment of the blade. The blade is modeled by beam finite elements. A single element is used to represent the swept tip. The nonlinear equations of motion are derived using the Hamilton`s principle and are based on moderate deflection theory. Thus, the nonlinearities are of the geometric type. The important structural blade attributes captured by the model are arbitrary cross-sectional shape, general anisotropic material behavior, transverse shear and out-of-plane warping. The aerodynamic loads are based on quasi-steady Greenberg theory with reverse flow effects, using an implicit formulation. The nonlinear aeroelastic response of the blade is obtained from a fully coupled propulsive trim/aeroelastic response analysis. Aeroelastic stability is obtained from linearizing the equations of motion about the steady state response of the blade and using Floquet theory. Numerical results for the aeroelastic stability and response of a hingeless composite blade with two cell type cross section are presented, together with vibratory hub shears and moments. The influence of ply orientation and tip sweep is clearly illustrated by the results.

  9. The Effect of Fracture Filler Composition on the Parameters of Shear Deformation Regime

    NASA Astrophysics Data System (ADS)

    Pavlov, D.; Ostapchuk, A.; Batuhtin, I.

    2015-12-01

    Geomechanical models of different slip mode nucleation and transformation can be developed basing on laboratory experiments, in which regularities of shear deformation of gouge-filled faults are studied. It's known that the spectrum of possible slip modes is defined by both macroscopic deformation characteristics of the fault and mesoscale structure of fault filler. Small variations of structural parameters of the filler may lead to a radical change of slip mode [1, 2]. This study presents results of laboratory experiments investigating regularities of shear deformation of discontinuities filled with multicomponent granular material. Qualitative correspondence between experimental results and natural phenomena is detected. The experiments were carried out in the classical "slider model" statement. A granite block slides under shear load on a granite substrate. The contact gap between rough surfaces was filled with a discrete material, which simulated the principal slip zone of a fault. The filler components were quartz sand, salt, glass beads, granite crumb, corundum, clay and pyrophyllite. An entire spectrum of possible slip modes was obtained - from stable slip to slow-slip events and to regular stick-slip with various coseismic displacements realized per one act of instability. Mixing several components in different proportions, it became possible to trace the gradual transition from stable slip to regular stick-slip, from slow-slip events to fast-slip events. Depending on specific filler component content, increasing the portion of one of the components may lead to both a linear and a non-linear change of slip event moment (a laboratory equivalent of the seismic moment). For different filler compositions durations of equal-moment events may differ by more than two orders of magnitude. The findings can be very useful for developing geomechnical models of nucleation and transformation of different slip modes observed at natural faults. The work was supported by

  10. Mechanically fastened composite laminates subjected to combined bearing-bypass and shear loading

    NASA Technical Reports Server (NTRS)

    Madenci, Erdogan

    1993-01-01

    Bolts and rivets provide a means of load transfer in the construction of aircraft. However, they give rise to stress concentrations and are often the source and location of static and fatigue failures. Furthermore, fastener holes are prone to cracks during take-off and landing. These cracks present the most common origin of structural failures in aircraft. Therefore, accurate determination of the contact stresses associated with such loaded holes in mechanically fastened joints is essential to reliable strength evaluation and failure prediction. As the laminate is subjected to loading, the contact region, whose extent is not known, develops between the fastener and the hole boundary through this contact region, which consists of slip and no-slip zones due to friction. The presence of the unknown contact stress distribution over the contact region between the pin and the composite laminate, material anisotropy, friction between the pin and the laminate, pin-hole clearance, combined bearing-bypass and shear loading, and finite geometry of the laminate result in a complex non-linear problem. In the case of bearing-bypass loading in compression, this non-linear problem is further complicated by the presence of dual contact regions. Previous research concerning the analysis of mechanical joints subjected to combined bearing-bypass and shear loading is non-existent. In the case of bearing-bypass loading only, except for the study conducted by Naik and Crews (1991), others employed the concept of superposition which is not valid for this non-linear problem. Naik and Crews applied a linear finite element analysis with conditions along the pin-hole contact region specified as displacement constraint equations. The major shortcoming of this method is that the variation of the contract region as a function of the applied load should be known a priori. Also, their analysis is limited to symmetric geometry and material systems, and frictionless boundary conditions. Since the

  11. Determination of the shear buckling load of a large polymer composite I-section using strain and displacement sensors.

    PubMed

    Park, Jin Y; Lee, Jeong Wan

    2012-01-01

    This paper presents a method and procedure of sensing and determining critical shear buckling load and corresponding deformations of a comparably large composite I-section using strain rosettes and displacement sensors. The tested specimen was a pultruded composite beam made of vinyl ester resin, E-glass and carbon fibers. Various coupon tests were performed before the shear buckling test to obtain fundamental material properties of the I-section. In order to sensitively detect shear buckling of the tested I-section, twenty strain rosettes and eight displacement sensors were applied and attached on the web and flange surfaces. An asymmetric four-point bending loading scheme was utilized for the test. The loading scheme resulted a high shear and almost zero moment condition at the center of the web panel. The web shear buckling load was determined after analyzing the obtained test data from strain rosettes and displacement sensors. Finite element analysis was also performed to verify the experimental results and to support the discussed experimental approach. PMID:23443364

  12. Effect of various intraoral repair systems on the shear bond strength of composite resin to zirconia

    PubMed Central

    Han, In-Hae; Kang, Dong-Wan; Chung, Chae-Heon; Choe, Han-Cheol

    2013-01-01

    PURPOSE This study compared the effect of three intraoral repair systems on the bond strength between composite resin and zirconia core. MATERIALS AND METHODS Thirty zirconia specimens were divided into three groups according to the repair method: Group I- CoJet™ Repair System (3M ESPE) [chairside silica coating with 30 µm SiO2 + silanization + adhesive]; Group II- Ceramic Repair System (Ivoclar Vivadent) [etching with 37% phosphoric acid + Zirconia primer + adhesive]; Group III- Signum Zirconia Bond (Heraus) [Signum Zirconia Bond I + Signum Zirconia Bond II]. Composite resin was polymerized on each conditioned specimen. The shear bond strength was tested using a universal testing machine, and fracture sites were examined with FE-SEM. Surface morphology and wettability after surface treatments were examined additionally. The data of bond strengths were statistically analyzed with one-way ANOVA and Tamhane post hoc test (α=.05). RESULTS Increased surface roughness and the highest wettability value were observed in the CoJet sand treated specimens. The specimens treated with 37% phosphoric acid and Signum Zirconia Bond I did not show any improvement of surface irregularity, and the lowest wettability value were found in 37% phosphoric acid treated specimens. There was no significant difference in the bond strengths between Group I (7.80 ± 0.76 MPa) and III (8.98 ± 1.39 MPa). Group II (3.21 ± 0.78 MPa) showed a significant difference from other groups (P<.05). CONCLUSION The use of Intraoral silica coating system and the application of Signum Zirconia Bond are effective for increasing the bond strength of composite resin to zirconia. PMID:24049565

  13. Investigation of the shear thinning behavior of epoxy resins for utilization in vibration assisted liquid composite molding processes

    NASA Astrophysics Data System (ADS)

    Meier, R.; Kirdar, C.; Rudolph, N.; Zaremba, S.; Drechsler, K.

    2014-05-01

    Efficient production and consumption of energy are of greatest importance for contemporary industries and their products. This has led to an increasing application of lightweight materials in general and of Carbon Fiber Reinforced Plastics (CFRP) in particular. However, broader application of CFRP is often limited by high costs and manual labor production processes. These constraints are addressed by Liquid Composite Molding (LCM) processes. In LCM a dry fibrous preform is placed into a cavity and infiltrated mostly by thermoset resins; epoxy resins are wide spread in CFRP applications. One crucial parameter for a fast mold filling is the viscosity of the resin, which is affected by the applied shear rates as well as temperature and curing time. The work presented focuses on the characterization of the shear thinning behavior of epoxy resins. Furthermore, the correlation with the conditions in vibration assisted LCM processes, where additional shear rates are created during manufacture, is discussed. Higher shear rates result from high frequencies and/or high amplitudes of the vibration motions which are created by a vibration engine mounted on the mold. In rheological investigations the shear thinning behavior of a representative epoxy resin is studied by means of rotational and oscillatory experiments. Moreover, possible effects of shear rates on the chemical curing reaction are studied. Here, the time for gelation is measured for different levels of shear rates in a pre-shearing phase. Based on the rheological studies, the beneficial effect of vibration assistance in LCM processes with respect to mold filling can further be predicted and utilized.

  14. Composites for Advanced Space Transportation Systems (CASTS)

    NASA Technical Reports Server (NTRS)

    Davis, J. G., Jr. (Compiler)

    1979-01-01

    A summary is given of the in-house and contract work accomplished under the CASTS Project. In July 1975 the CASTS Project was initiated to develop graphite fiber/polyimide matrix (GR/PI) composite structures with 589K (600 F) operational capability for application to aerospace vehicles. Major tasks include: (1) screening composites and adhesives, (2) developing fabrication procedures and specifications, (3) developing design allowables test methods and data, and (4) design and test of structural elements and construction of an aft body flap for the Space Shuttle Orbiter Vehicle which will be ground tested. Portions of the information are from ongoing research and must be considered preliminary. The CASTS Project is scheduled to be completed in September 1983.

  15. Combustion synthesis of advanced composite materials

    NASA Technical Reports Server (NTRS)

    Moore, John J.

    1993-01-01

    Self-propagating high temperature (combustion) synthesis (SHS), has been investigated as a means of producing both dense and expanded (foamed) ceramic and ceramic-metal composites, ceramic powders and whiskers. Several model exothermic combustion synthesis reactions were used to establish the importance of certain reaction parameters, e.g., stoichiometry, green density, combustion mode, particle size, etc. on the control of the synthesis reaction, product morphology and properties. The use of an in situ liquid infiltration technique and the effect of varying the reactants and their stoichiometry to provide a range of reactant and product species i.e., solids, liquids and gases, with varying physical properties e.g., volatility and thermal conductivity, on the microstructure and morphology of synthesized composite materials is discussed. Conducting the combustion synthesis reaction in a reactive gas environment to take advantage of the synergistic effects of combustion synthesis and vapor phase transport is also examined.

  16. Recent Advances in Composite Damage Mechanics

    NASA Technical Reports Server (NTRS)

    Reifsnider, Ken; Case, Scott; Iyengar, Nirmal

    1996-01-01

    The state of the art and recent developments in the field of composite material damage mechanics are reviewed, with emphasis on damage accumulation. The kinetics of damage accumulation are considered with emphasis on the general accumulation of discrete local damage events such as single or multiple fiber fractures or microcrack formation. The issues addressed include: how to define strength in the presence of widely distributed damage, and how to combine mechanical representations in order to predict the damage tolerance and life of engineering components. It is shown that a damage mechanics approach can be related to the thermodynamics of the damage accumulation processes in composite laminates subjected to mechanical loading and environmental conditions over long periods of time.

  17. Blast protection of infrastructure using advanced composites

    NASA Astrophysics Data System (ADS)

    Brodsky, Evan

    This research was a systematic investigation detailing the energy absorption mechanisms of an E-glass web core composite sandwich panel subjected to an impulse loading applied orthogonal to the facesheet. Key roles of the fiberglass and polyisocyanurate foam material were identified, characterized, and analyzed. A quasi-static test fixture was used to compressively load a unit cell web core specimen machined from the sandwich panel. The web and foam both exhibited non-linear stress-strain responses during axial compressive loading. Through several analyses, the composite web situated in the web core had failed in axial compression. Optimization studies were performed on the sandwich panel unit cell in order to maximize the energy absorption capabilities of the web core. Ultimately, a sandwich panel was designed to optimize the energy dissipation subjected to through-the-thickness compressive loading.

  18. Marine applications for advanced composite materials

    SciTech Connect

    Hihara, L.H.; Bregman, R.; Takahashi, P.K.

    1993-12-31

    Very large floating structures (VLFSs) may one day be essential to the study and utilization of the ocean. Some possible applications for VLFSs are ocean ranching homeports. observatories for ocean research, seabed mineral refineries, energy generation platforms. and waste management facilities. A VLFS that is in the conceptual phase, and may one day be based off the coast of Hawaii, has been named Blue Revolution. Candidate materials for Blue Revolution were identified based on criteria of rigidity, strength, and weight. Priority was given to materials that could be used to construct lightweight VLFSs. Major static forces were considered in this preliminary analysis. The best materials were identified as those having low values of density/modulus ({rho}/E) and density/strength ({rho}/{sigma}). Concrete, metal alloys, organic-matrix composites (OMCs), and metal-matrix composites (MMCs) were evaluated. OMCs and MMCs were generally the best materials based on their very low {rho}/E and {rho}/{sigma} values.

  19. Compositional layering within the large low shear-wave velocity provinces (LLSVPs) in the lower mantle

    NASA Astrophysics Data System (ADS)

    Ballmer, Maxim; Lekic, Vedran; Schumacher, Lina; Ito, Garrett; Thomas, Christine

    2016-04-01

    Seismic tomography reveals two antipodal LLSVPs in the Earth's mantle, each extending from the core-mantle boundary (CMB) up to ~1000 km depth. The LLSVPs are thought to host primordial mantle materials that bear witness of early-Earth processes, and/or subducted basalt that has accumulated in the mantle over billions of years. A compositional distinction between the LLSVPs and the ambient mantle is supported by anti-correlation of bulk-sound and shear-wave velocity (Vs) anomalies as well as abrupt lateral gradients in Vs along LLSVP margins. Both of these observations, however, are mainly restricted to the LLSVP bottom domains (2300~2900 km depth), or hereinafter referred to as "deep distinct domains" (DDD). Seismic sensitivity calculations suggest that DDDs are more likely to be composed of primordial mantle material than of basaltic material. On the other hand, the seismic signature of LLSVP shallow domains (1000~2300 km depth) is consistent with a basaltic composition, though a purely thermal origin cannot be ruled out. Here, we explore the dynamical, seismological, and geochemical implications of the hypothesis that the LLSVPs are compositionally layered with a primordial bottom domain (or DDD) and a basaltic shallow domain. We test this hypothesis using 2D thermochemical mantle-convection models. Depending on the density difference between primordial and basaltic materials, the materials either mix or remain separate as they join to form thermochemical piles in the deep mantle. Separation of both materials within these piles provides an explanation for LLSVP seismic properties, including substantial internal vertical gradients in Vs observed at 400-700 km height above the CMB, as well as out-of-plane reflections on LLSVP sides over a range of depths. Predicted geometry of thermochemical piles is compared to LLSVP and DDD shapes as constrained by seismic cluster analysis. Geodynamic models predict short-lived "secondary" plumelets to rise from LLSVP roofs and

  20. The effects of three different desensitizing agents on the shear bond strength of composite resin bonding agents.

    PubMed

    Zorba, Yahya Orcun; Erdemir, Ali; Ercan, Ertugrul; Eldeniz, Ayce Unverdi; Kalaycioglu, Baris; Ulker, Mustafa

    2010-07-01

    The aim of this study was to evaluate the effects of three desensitizing agents on the shear bond strengths of four different bonding agents used to bond composite resin to dentin. A total of 160 extracted human molars were sectioned parallel to the occlusal plane under water cooling, polished and randomly divided into 4 groups of 40. Each group was treated with a different desensitizing agent (Tooth Mousse, Ultra-EZ, Cervitec Plus), except for an untreated control group. Each group was then randomly subdivided into 4 groups of 10, and a different dentin bonding agent (XP Bond, AdheSE, Adper Prompt L-pop, GBond) was applied to each group in order to bond the specimens to a resin composite (Gradia Direct) built up using a plastic apparatus. A Universal Testing Machine was used to measure the shear bond strength of each specimen. Statistical analysis was performed using one-way ANOVA and Tukey's tests. With the exception of the Control/AdheSE and Ultra-EZ/XP Bond groups, no statistically significant differences were found in the shear bond strength values of the groups tested. These findings suggest that the use of different desensitizing agents does not affect the shear bond strength of various adhesive systems used to bond resin composite to dentin. PMID:20416554

  1. JTEC panel report on advanced composites in Japan

    NASA Technical Reports Server (NTRS)

    Diefendorf, R. J.; Grisaffe, S. J.; Hillig, W. B.; Perepezko, J. H.; Pipes, R. B.; Sheehan, J. E.

    1991-01-01

    The JTEC Panel on Advanced Composites visited Japan and surveyed the status and future directions of Japanese high performance ceramic and carbon fibers and their composites in metal, intermetallic, ceramic and carbon matrices. The panel's interests included not only what composite systems were chosen, but also how these systems were developed. A strong carbon and fiber industry makes Japan the leader in carbon fiber technology. Japan has initiated an oxidation resistant carbon/carbon composite program. The goals for this program are ambitious, and it is just starting, but its progress should be closely monitored in the United States.

  2. Advances in Computational Stability Analysis of Composite Aerospace Structures

    SciTech Connect

    Degenhardt, R.; Araujo, F. C. de

    2010-09-30

    European aircraft industry demands for reduced development and operating costs. Structural weight reduction by exploitation of structural reserves in composite aerospace structures contributes to this aim, however, it requires accurate and experimentally validated stability analysis of real structures under realistic loading conditions. This paper presents different advances from the area of computational stability analysis of composite aerospace structures which contribute to that field. For stringer stiffened panels main results of the finished EU project COCOMAT are given. It investigated the exploitation of reserves in primary fibre composite fuselage structures through an accurate and reliable simulation of postbuckling and collapse. For unstiffened cylindrical composite shells a proposal for a new design method is presented.

  3. An advanced cone-and-plate reactor for the in vitro-application of shear stress on adherent cells.

    PubMed

    Dreyer, Lutz; Krolitzki, Benjamin; Autschbach, Rüdiger; Vogt, Peter; Welte, Tobias; Ngezahayo, Anaclet; Glasmacher, Birgit

    2011-01-01

    Endothelial cells (ECs) are permanently exposed to the blood flow and the resulting shear stress, its magnitude varying with the EC site in the blood stream. Along with other mechanical stimuli like vessel wall stretching or hydrostatic blood pressure, this shear stress modulates the endothelial cell function, morphology and gene expression. Here, we describe our improved cone-and-plate reactor that applies up to 10 dyn/cm(2) uniform wall shear stress on a defined, ring-shaped region on a culture dish. At the same time, a hydrostatic pressure of up to 195 mmHg can be applied by increasing the atmospheric pressure in the incubator box. Gas composition can be controlled additionally, used for maintaining CO2-homeostasis or inducing hypoxic conditions. For better comparability, six cone-and-plate systems can be used at the same time at different rotational velocities. The effects on cell morphology, cytoskeleton and cell alignment can be monitored during application using a laser scanning microscope. Flow conditions have been studied and a sufficient area of uniform wall shear stress could be shown. To exceed 10 dyn/cm2, we suggest an increase in medium viscosity. PMID:22214709

  4. Ceramic matrix composites -- Advanced high-temperature structural materials

    SciTech Connect

    Lowden, R.A.; Ferber, M.K.; Hellmann, J.R.; Chawla, K.K.; DiPietro, S.G.

    1995-10-01

    This symposium on Ceramic Matrix Composites: Advanced High-Temperature Structural Materials was held at the 1994 MRS Fall Meeting in Boston, Massachusetts on November 28--December 2. The symposium was sponsored by the Department of Energy`s Office of Industrial Technology`s Continuous Fiber Ceramic Composites Program, the Air Force Office of Scientific Research, and NASA Lewis Research Center. Among the competing materials for advanced, high-temperature applications, ceramic matrix composites are leading candidates. The symposium was organized such that papers concerning constituents--fibers and matrices--were presented first, followed by composite processing, modeling of mechanical behavior, and thermomechanical testing. More stable reinforcements are necessary to enhance the performance and life of fiber-reinforced ceramic composites, and to ensure final acceptance of these materials for high-temperature applications. Encouraging results in the areas of polymer-derived SiC fibers and single crystal oxide filaments were given, suggesting composites with improved thermomechanical properties and stability will be realized in the near future. The significance of the fiber-matrix interface in the design and performance of these materials is evident. Numerous mechanical models to relate interface properties to composite behavior, and interpret test methods and data, were enthusiastically discussed. One issue of great concern for any advanced material for use in extreme environments is stability. This theme arose frequently throughout the symposium and was the topic of focus on the final day. Fifty nine papers have been processed separately for inclusion on the data base.

  5. Advanced composite vertical fin for L-1011 aircraft

    NASA Technical Reports Server (NTRS)

    Jackson, A. C.

    1984-01-01

    The structural box of the L-1011 vertical fin was redesigned using advanced composite materials. The box was fabricated and ground tested to verify the structural integrity. This report summarizes the complete program starting with the design and analysis and proceeds through the process development ancillary test program production readiness verification testing, fabrication of the full-scale fin boxes and the full-scale ground testing. The program showed that advanced composites can economically and effectively be used in the design and fabrication of medium primary structures for commercial aircraft. Static-strength variability was demonstrated to be comparable to metal structures and the long term durability of advanced composite components was demonstrated.

  6. An improved shear beam method for the characterization of bonded composite joints

    NASA Technical Reports Server (NTRS)

    Hiel, Clem C.; Brinson, Hal F.

    1989-01-01

    Closed-form analytical solutions, which govern the displacements and stresses in an adhesive shear beam, are discussed. The remarkable precision with which the shear stresses in the adhesive can be predicted forms the basis of the proposed characterization procedure. The shear modulus of the adhesive is obtained by means of a parameter estimation procedure which requires a symbiosis of theoretical and experimental stress analysis.

  7. Process simulation for advanced composites production

    SciTech Connect

    Allendorf, M.D.; Ferko, S.M.; Griffiths, S.

    1997-04-01

    The objective of this project is to improve the efficiency and lower the cost of chemical vapor deposition (CVD) processes used to manufacture advanced ceramics by providing the physical and chemical understanding necessary to optimize and control these processes. Project deliverables include: numerical process models; databases of thermodynamic and kinetic information related to the deposition process; and process sensors and software algorithms that can be used for process control. Target manufacturing techniques include CVD fiber coating technologies (used to deposit interfacial coatings on continuous fiber ceramic preforms), chemical vapor infiltration, thin-film deposition processes used in the glass industry, and coating techniques used to deposit wear-, abrasion-, and corrosion-resistant coatings for use in the pulp and paper, metals processing, and aluminum industries.

  8. Combined Effect of Shear and Fibrous Fillers on Orientation-Induced Crystallization in Discontinuous Aramid Fiber-Isotactic Polypropylene Composites

    SciTech Connect

    Larin,B.; Avila-Orta, C.; Somani, R.; Hsiao, B.; Marom, G.

    2008-01-01

    The shear-induced crystallization behavior in isotactic polypropylene (iPP) composite melt containing short aramid fibers was investigated by means of WAXD (wide-angle X-ray diffraction) and SAXS (small-angle X-ray scattering) techniques using synchrotron radiation. The study was carried out in a post-shear isothermal crystallization mode at temperatures of 140-160 C. Parameters pertaining to the crystallization morphology and kinetics were analyzed, including total crystallinity, orientated crystalline and amorphous fractions, dimensions of the formed shish-kebab structure, as well as induction time and rate of crystallization. The individual contributions of shear and fibers were evaluated and the combined effect was compared. The results clearly indicated that the effect is synergistic rather than additive.

  9. Effects of transverse shear on large deflection random response of symmetric composite laminates with mixed boundary conditions

    NASA Technical Reports Server (NTRS)

    Prasad, C. B.; Mei, Chuh

    1989-01-01

    Nonlinear equations of motion of symmetrically laminated anisotropic plates are derived considering von Karman strains and transverse shear effects. Using a single-mode Galerkin procedure, the nonlinear modal equation is obtained. The direct equivalent linearization method is employed for solution of this equation. The effects of transverse shear on large deflection vibration of laminated plates with mixed boundary support conditions under random excitation are studied. Mean-square deflections and mean-square inplane strains are obtained for symmetric graphite-epoxy laminates. Using equilibrium equations and the continuity requirements, the mean-square transverse shear stresses are calculated. The results obtained will be useful in the sonic fatigue design of composite aircraft panels. The analysis is presented in detail for plates with two opposing edges simply supported and the remaining edges clamped.

  10. Application of advanced shearing techniques to the calibration of autocollimators with small angle generators and investigation of error sources.

    PubMed

    Yandayan, T; Geckeler, R D; Aksulu, M; Akgoz, S A; Ozgur, B

    2016-05-01

    The application of advanced error-separating shearing techniques to the precise calibration of autocollimators with Small Angle Generators (SAGs) was carried out for the first time. The experimental realization was achieved using the High Precision Small Angle Generator (HPSAG) of TUBITAK UME under classical dimensional metrology laboratory environmental conditions. The standard uncertainty value of 5 mas (24.2 nrad) reached by classical calibration method was improved to the level of 1.38 mas (6.7 nrad). Shearing techniques, which offer a unique opportunity to separate the errors of devices without recourse to any external standard, were first adapted by Physikalisch-Technische Bundesanstalt (PTB) to the calibration of autocollimators with angle encoders. It has been demonstrated experimentally in a clean room environment using the primary angle standard of PTB (WMT 220). The application of the technique to a different type of angle measurement system extends the range of the shearing technique further and reveals other advantages. For example, the angular scales of the SAGs are based on linear measurement systems (e.g., capacitive nanosensors for the HPSAG). Therefore, SAGs show different systematic errors when compared to angle encoders. In addition to the error-separation of HPSAG and the autocollimator, detailed investigations on error sources were carried out. Apart from determination of the systematic errors of the capacitive sensor used in the HPSAG, it was also demonstrated that the shearing method enables the unique opportunity to characterize other error sources such as errors due to temperature drift in long term measurements. This proves that the shearing technique is a very powerful method for investigating angle measuring systems, for their improvement, and for specifying precautions to be taken during the measurements. PMID:27250375

  11. Stiffening of short small-size circular composite steel–concrete columns with shear connectors

    PubMed Central

    Younes, Sherif M.; Ramadan, Hazem M.; Mourad, Sherif A.

    2015-01-01

    An experimental program was conducted to investigate the effect of shear connectors’ distribution and method of load application on load–displacement relationship and behavior of thin-walled short concrete-filled steel tube (CFT) columns when subjected to axial load. The study focused on the compressive strength of the CFT columns and the efficiency of the shear stud in distribution of the load between the concrete core and steel tube. The study showed that the use of shear connectors enhanced slightly the axial capacity of CFT columns. It is also shown that shear connectors have a great effect on load distribution between the concrete and steel tubes. PMID:27222757

  12. Stiffening of short small-size circular composite steel-concrete columns with shear connectors.

    PubMed

    Younes, Sherif M; Ramadan, Hazem M; Mourad, Sherif A

    2016-05-01

    An experimental program was conducted to investigate the effect of shear connectors' distribution and method of load application on load-displacement relationship and behavior of thin-walled short concrete-filled steel tube (CFT) columns when subjected to axial load. The study focused on the compressive strength of the CFT columns and the efficiency of the shear stud in distribution of the load between the concrete core and steel tube. The study showed that the use of shear connectors enhanced slightly the axial capacity of CFT columns. It is also shown that shear connectors have a great effect on load distribution between the concrete and steel tubes. PMID:27222757

  13. Vibration and damping of laminated, composite-material plates including thickness-shear effects

    NASA Technical Reports Server (NTRS)

    Bert, C. W.; Siu, C. C.

    1972-01-01

    An analytical investigation of sinusoidally forced vibration of laminated, anisotropic plates including bending-stretching coupling, thickness-shear flexibility, all three types of inertia effects, and material damping is presented. In the analysis the effects of thickness-shear deformation are considered by the use of a shear correction factor K, analogous to that used by Mindlin for homogeneous plates. Two entirely different approaches for calculating the thickness-shear factor for a laminate are presented. Numerical examples indicate that the value of K depends on the layer properties and the stacking sequence of the laminate.

  14. Pore fluid pressure and shear behavior in debris flows of different compositions

    NASA Astrophysics Data System (ADS)

    Kaitna, Roland; Palucis, Marisa; Yohannes, Bereket; Hill, Kimberly; Dietrich, William

    2016-04-01

    Debris flows are mixtures of sediment and water that can have a wide range of different grain size distributions and water contents. The composition of the material is expected to have a strong effect on the development of pore fluid pressures in excess to hydrostatic, which in turn might affect the internal deformation behavior. We present a set of large scale experiments with debris flow mixtures of different compositions in a 4-m diameter rotating drum. Longitudinal profiles of basal fluid pressure and normal stress were measured and a probe to determine fluid pressure at different depths within the flow was developed and tested. Additionally we determined vertical profiles of mean particle velocities in the flow interior by measuring small variations of conductivity of the passing material and calculating the time lag between signals from two independent measurements at a small, known distance apart. Mean values of basal pore fluid pressure range from hydrostatic pressure for gravel-water flows to nearly complete liquefaction for muddy mixtures having a wide grain size distribution. The data indicate that the presence of fines dampens fluctuations of normalized fluid pressure and normal stress and concentrates shear at the base. The mobility of grain-fluid flows is strongly enhanced by a combination of fines in suspension as part of the interstitial fluid and a wide grain size distribution. Excess fluid pressure may arise from fluid displacement by converging grains at the front of the flow and the slow settling of grains through a highly viscous non-Newtonian fluid. Our findings support the need for pore pressure evolution and diffusion equations in debris flow models as they depend on particle size distributions. This study contributes to the understanding of the production of excess fluid pressure in grain fluid mixtures and may guide the development of constitutive models that describe natural events.

  15. Advanced composite polymer electrolyte fuel cell membranes

    SciTech Connect

    Wilson, M.S.; Zawodzinski, T.A.; Gottesfeld, S.; Kolde, J.A.; Bahar, B.

    1995-09-01

    A new type of reinforced composite perfluorinated polymer electrolyte membrane, GORE-SELECT{trademark} (W.L. Gore & Assoc.), is characterized and tested for fuel cell applications. Very thin membranes (5-20 {mu}m thick) are available. The combination of reinforcement and thinness provides high membrane, conductances (80 S/cm{sup 2} for a 12 {mu}m thick membrane at 25{degrees}C) and improved water distribution in the operating fuel cell without sacrificing longevity or durability. In contrast to nonreinforced perfluorinated membranes, the x-y dimensions of the GORE-SELECT membranes are relatively unaffected by the hydration state. This feature may be important from the viewpoints of membrane/electrode interface stability and fuel cell manufacturability.

  16. A study on the compatibility between one-bottle dentin adhesives and composite resins using micro-shear bond strength

    PubMed Central

    2015-01-01

    Objectives This study was performed to determine whether the combined use of one-bottle self-etch adhesives and composite resins from same manufacturers have better bond strengths than combinations of adhesive and resins from different manufacturers. Materials and Methods 25 experimental micro-shear bond test groups were made from combinations of five dentin adhesives and five composite resins with extracted human molars stored in saline for 24 hr. Testing was performed using the wire-loop method and a universal testing machine. Bond strength data was statistically analyzed using two way analysis of variance (ANOVA) and Tukey's post hoc test. Results Two way ANOVA revealed significant differences for the factors of dentin adhesives and composite resins, and significant interaction effect (p < 0.001). All combinations with Xeno V (Dentsply De Trey) and Clearfil S3 Bond (Kuraray Dental) adhesives showed no significant differences in micro-shear bond strength, but other adhesives showed significant differences depending on the composite resin (p < 0.05). Contrary to the other adhesives, Xeno V and BondForce (Tokuyama Dental) had higher bond strengths with the same manufacturer's composite resin than other manufacturer's composite resin. Conclusions Not all combinations of adhesive and composite resin by same manufacturers failed to show significantly higher bond strengths than mixed manufacturer combinations. PMID:25671210

  17. Recent advancement in optical fiber sensing for aerospace composite structures

    NASA Astrophysics Data System (ADS)

    Minakuchi, Shu; Takeda, Nobuo

    2013-12-01

    Optical fiber sensors have attracted considerable attention in health monitoring of aerospace composite structures. This paper briefly reviews our recent advancement mainly in Brillouin-based distributed sensing. Damage detection, life cycle monitoring and shape reconstruction systems applicable to large-scale composite structures are presented, and new technical concepts, "smart crack arrester" and "hierarchical sensing system", are described as well, highlighting the great potential of optical fiber sensors for the structural health monitoring (SHM) field.

  18. Effect of mesh distortion on the accuracy of transverse shear stresses and their sensitivity coefficients in multilayered composites

    NASA Technical Reports Server (NTRS)

    Noor, Ahmed K.; Kim, Yong H.

    1995-01-01

    A study is made of the effect of mesh distortion on the accuracy of transverse shear stresses and their first-order and second-order sensitivity coefficients in multilayered composite panels subjected to mechanical and thermal loads. The panels are discretized by using a two-field degenerate solid element, with the fundamental unknowns consisting of both displacement and strain components, and the displacement components having a linear variation throughout the thickness of the laminate. A two-step computational procedure is used for evaluating the transverse shear stresses. In the first step, the in-plane stresses in the different layers are calculated at the numerical quadrature points for each element. In the second step, the transverse shear stresses are evaluated by using piecewise integration, in the thickness direction, of the three-dimensional equilibrium equations. The same procedure is used for evaluating the sensitivity coefficients of transverse shear stresses. Numerical results are presented showing no noticeable degradation in the accuracy of the in-plane stresses and their sensitivity coefficients with mesh distortion. However, such degradation is observed for the transverse shear stresses and their sensitivity coefficients. The standard of comparison is taken to be the exact solution of the three-dimensional thermoelasticity equations of the panel.

  19. Implementation of Improved Transverse Shear Calculations and Higher Order Laminate Theory Into Strain Rate Dependent Analyses of Polymer Matrix Composites

    NASA Technical Reports Server (NTRS)

    Zhu, Lin-Fa; Kim, Soo; Chattopadhyay, Aditi; Goldberg, Robert K.

    2004-01-01

    A numerical procedure has been developed to investigate the nonlinear and strain rate dependent deformation response of polymer matrix composite laminated plates under high strain rate impact loadings. A recently developed strength of materials based micromechanics model, incorporating a set of nonlinear, strain rate dependent constitutive equations for the polymer matrix, is extended to account for the transverse shear effects during impact. Four different assumptions of transverse shear deformation are investigated in order to improve the developed strain rate dependent micromechanics model. The validities of these assumptions are investigated using numerical and theoretical approaches. A method to determine through the thickness strain and transverse Poisson's ratio of the composite is developed. The revised micromechanics model is then implemented into a higher order laminated plate theory which is modified to include the effects of inelastic strains. Parametric studies are conducted to investigate the mechanical response of composite plates under high strain rate loadings. Results show the transverse shear stresses cannot be neglected in the impact problem. A significant level of strain rate dependency and material nonlinearity is found in the deformation response of representative composite specimens.

  20. Effect of three different antioxidants on the shear bond strength of composite resin to bleached enamel: An in vitro study

    PubMed Central

    Subramonian, Rajalekshmy; Mathai, Vijay; Christaine Angelo, Jeya Balaji Mano; Ravi, Jotish

    2015-01-01

    Objective: The effect of 10% sodium ascorbate, 10% grape seed extract, and 10% pine bark extract on the shear bond strength of composite resin to bleached enamel was evaluated. Materials and Methods: Ninety recently extracted human premolars were divided into six groups of 15 teeth each. Except Group I (negative control), the labial enamel surface of all specimens in the other groups were bleached with 37.5% hydrogen peroxide. After bleaching, Group II specimens were stored in artificial saliva for 3weeks before composite bonding. Immediately following bleaching; Groups III, IV, and V specimens were treated with antioxidants 10% sodium ascorbate, 10% grape seed extract, and 10% pine bark extract, respectively, for 10 min and bonded with composite resin. In Group VI (positive control), the composite bonding was done immediately after bleaching. All specimens were stored in deionized water for 24 h at 37΀C before shear bond strength testing. The data obtained were tabulated and statistically analyzed using analysis of variance (ANOVA) and Duncan's multiple range test. Results: The unbleached teeth showed the highest shear bond strength followed by the bleached teeth treated with the antioxidant 10% pine bark extract. Conclusion: Within the limitations of this study, it was observed that the use of antioxidants effectively reversed the compromised bond strength of bleached enamel. Among the antioxidants, 10% pine bark extract application after bleaching showed better bond strength. PMID:25829695

  1. A Multi-scale Refined Zigzag Theory for Multilayered Composite and Sandwich Plates with Improved Transverse Shear Stresses

    NASA Technical Reports Server (NTRS)

    Iurlaro, Luigi; Gherlone, Marco; Di Sciuva, Marco; Tessler, Alexander

    2013-01-01

    The Refined Zigzag Theory (RZT) enables accurate predictions of the in-plane displacements, strains, and stresses. The transverse shear stresses obtained from constitutive equations are layer-wise constant. Although these transverse shear stresses are generally accurate in the average, layer-wise sense, they are nevertheless discontinuous at layer interfaces, and thus they violate the requisite interlaminar continuity of transverse stresses. Recently, Tessler applied Reissner's mixed variational theorem and RZT kinematic assumptions to derive an accurate and efficient shear-deformation theory for homogeneous, laminated composite, and sandwich beams, called RZT(m), where "m" stands for "mixed". Herein, the RZT(m) for beams is extended to plate analysis, where two alternative assumptions for the transverse shear stresses field are examined: the first follows Tessler's formulation, whereas the second is based on Murakami's polynomial approach. Results for elasto-static simply supported and cantilever plates demonstrate that Tessler's formulation results in a powerful and efficient structural theory that is well-suited for the analysis of multilayered composite and sandwich panels.

  2. Deformation measurements of composite multi-span beam shear specimens by Moire interferometry

    NASA Technical Reports Server (NTRS)

    Post, D.; Czarnek, R.; Joh, D.; Wood, J.

    1984-01-01

    Experimental analyses were performed for determination of in plane deformations and shear strains in unidirectional and quasi-isotropic graphite-epoxy beams. Forty-eight ply beams were subjected to 5 point and 3 point flexure. Whole field measurements were recorded at load levels from about 20% to more than 90% of failure loads. Contour maps of U and W displacement fields were obtained by moire interferometry, using reference gratings of 2400 lines/mm. Clearly defined fringes with fringe orders exceeding 1000 were obtained. Whole field contour maps of shear strains were obtained by a method developed for these tests. Various anomalous effects were detected in the displacement fields. Their analysis indicated excess shear strains in resin rich zones in regions of shear tractions; free edge shear strains in quasi-isotropic specimens in regions of normal stresses; and shear stresses associated with cyclic shear compliances of quasi-isotropic plies in regions of shear tractions. Their contributions could occur independently or in superposition. Qualitative analyses addressed questions of relaxation; influence of contact stress distribution; specimen failure; effect of specimen overhang; nonlinearity; and qualities of 5 and 3 point flexure tests.

  3. Boron/aluminum graphite/resin advanced fiber composite hybrids

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.; Lark, R. F.; Sullivan, T. L.

    1975-01-01

    Fabrication feasibility and potential of an adhesively bonded metal and resin matrix fiber-composite hybrid are determined as an advanced material for aerospace and other structural applications. The results show that using this hybrid concept makes possible a composite design which, when compared with nonhybrid composites, has greater transverse strength, transverse stiffness, and impact resistance with only a small penalty on density and longitudinal properties. The results also show that laminate theory is suitable for predicting the structural response of such hybrids. The sequence of fracture modes indicates that these types of hybrids can be readily designed to meet fail-safe requirements.

  4. Third NASA Advanced Composites Technology Conference, volume 1, part 1

    NASA Technical Reports Server (NTRS)

    Davis, John G., Jr. (Compiler); Bohon, Herman L. (Compiler)

    1993-01-01

    This document is a compilation of papers presented at the Third NASA Advanced Composites Technology (ACT) Conference. The ACT Program is a major multi-year research initiative to achieve a national goal of technology readiness before the end of the decade. Conference papers recorded results of research in the ACT Program in the specific areas of automated fiber placement, resin transfer molding, textile preforms, and stitching as these processes influence design, performance, and cost of composites in aircraft structures. Papers sponsored by the Department of Defense on the Design and Manufacturing of Low Cost Composites (DMLCC) are also included in Volume 2 of this document.

  5. Research priorities and history of advanced composite compression testing

    NASA Technical Reports Server (NTRS)

    Baumann, K. J.

    1981-01-01

    Priorities for standard compression testing research in advanced laminated fibrous composite materials are presented along with a state of the art survey (completed in 1979) including history and commentary on industrial test methods. Historically apparent research priorities and consequent (lack of) progress are supporting evidence for newly derived priorities.

  6. ADVANCED COMPOSITES TECHNOLOGY CASE STUDY AT NASA LANGLEY RESEARCH CENTER

    EPA Science Inventory

    Under the Chesapeake Bay Agreement, NASA-LaRC is a member of the Tidewater Interagency Pollution Prevention Program (TIPPP). t NASA-LaRC, a technique for producing advanced composite materials without the use of solvents has been developed. his assessment was focused on the produ...

  7. Development of Metal Matrix Composites for NASA'S Advanced Propulsion Systems

    NASA Technical Reports Server (NTRS)

    Lee, Jonathan A.

    2000-01-01

    The state-of-the-art development of several aluminum and copper based Metal Matrix Composites (MMC) for NASA's advanced propulsion systems will be presented. The presentation's goal is to provide an overview of NASA-Marshall Space Flight Center's planned and on-going activities in MMC for advanced liquid rocket engines such as the X-33 vehicle's Aerospike and X-34 Fastrac engine. The focus will be on lightweight and environmental compatibility with oxygen and hydrogen of key MMC materials, within each NASA's new propulsion application, that will provide a high payoff for NASA's reusable launch vehicle systems and space access vehicles. Advanced MMC processing techniques such as plasma spray, centrifugal casting, pressure infiltration casting will be discussed. Development of a novel 3D printing method for low cost production of composite preform, and functional gradient MMC to enhanced rocket engine's dimensional stability will be presented.

  8. Effect of low-velocity or ballistic impact damage on the strength of thin composite and aluminum shear panels

    NASA Technical Reports Server (NTRS)

    Farley, G. L.

    1985-01-01

    Impact tests were conducted on shear panels fabricated from 6061-T6 aluminum and from woven fabric prepreg of Du Pont Kevlara fiber/epoxy resin and graphite fiber/epoxy resin. The shear panels consisted of three different composite laminates and one aluminum material configuration. Three panel aspect ratios were evaluated for each material configuration. Composite panels were impacted with a 1.27-cm (0.05-in) diameter aluminum sphere at low velocities of 46 m/sec (150 ft/sec) and 67 m/sec (220 ft/sec). Ballistic impact conditions consisted of a tumbled 0.50-caliber projectile impacting loaded composite and aluminum shear panels. The results of these tests indicate that ballistic threshold load (the lowest load which will result in immediate failure upon penetration by the projectile) varied between 0.44 and 0.61 of the average failure load of undamaged panels. The residual strengths of the panels after ballistic impact varied between 0.55 and 0.75 of the average failure strength of the undamaged panels. The low velocity impacts at 67 m/sec (220 ft/sec) caused a 15 to 20 percent reduction in strength, whereas the impacts at 46 m/sec (150 ft/sec) resulted in negligible strength loss. Good agreement was obtained between the experimental failure strengths and the predicted strength with the point stress failure criterion.

  9. Shear bond strengths of an indirect composite layering material to a tribochemically silica-coated zirconia framework material.

    PubMed

    Iwasaki, Taro; Komine, Futoshi; Fushiki, Ryosuke; Kubochi, Kei; Shinohara, Mitsuyo; Matsumura, Hideo

    2016-01-01

    This study evaluated shear bond strengths of a layering indirect composite material to a zirconia framework material treated with tribochemical silica coating. Zirconia disks were divided into two groups: ZR-PRE (airborne-particle abrasion) and ZR-PLU (tribochemical silica coating). Indirect composite was bonded to zirconia treated with one of the following primers: Clearfil Ceramic Primer (CCP), Clearfil Mega Bond Primer with Clearfil Porcelain Bond Activator (MGP+Act), ESPE-Sil (SIL), Estenia Opaque Primer, MR. Bond, Super-Bond PZ Primer Liquid A with Liquid B (PZA+PZB), and Super-Bond PZ Primer Liquid B (PZB), or no treatment. Shear bond testing was performed at 0 and 20,000 thermocycles. Post-thermocycling shear bond strengths of ZR-PLU were higher than those of ZR-PRE in CCP, MGP+Act, SIL, PZA+PZB, and PZB groups. Application of silane yielded better durable bond strengths of a layering indirect composite material to a tribochemically silica-coated zirconia framework material. PMID:27252003

  10. Mishap risk control for advanced aerospace/composite materials

    NASA Technical Reports Server (NTRS)

    Olson, John M.

    1994-01-01

    Although advanced aerospace materials and advanced composites provide outstanding performance, they also present several unique post-mishap environmental, safety, and health concerns. The purpose of this paper is to provide information on some of the unique hazards and concerns associated with these materials when damaged by fire, explosion, or high-energy impact. Additionally, recommended procedures and precautions are addressed as they pertain to all phases of a composite aircraft mishap response, including fire-fighting, investigation, recovery, clean-up, and guidelines are general in nature and not application-specific. The goal of this project is to provide factual and realistic information which can be used to develop consistent and effective procedures and policies to minimize the potential environmental, safety, and health impacts of a composite aircraft mishap response effort.

  11. Advanced Ceramic Matrix Composites with Multifunctional and Hybrid Structures

    NASA Technical Reports Server (NTRS)

    Singh, Mrityunjay; Morscher, Gregory N.

    2004-01-01

    Ceramic matrix composites are leading candidate materials for a number of applications in aeronautics, space, energy, and nuclear industries. Potential composite applications differ in their requirements for thickness. For example, many space applications such as "nozzle ramps" or "heat exchangers" require very thin (< 1 mm) structures whereas turbine blades would require very thick parts (> or = 1 cm). Little is known about the effect of thickness on stress-strain behavior or the elevated temperature tensile properties controlled by oxidation diffusion. In this study, composites consisting of woven Hi-Nicalon (trademark) fibers a carbon interphase and CVI SiC matrix were fabricated with different numbers of plies and thicknesses. The effect of thickness on matrix crack formation, matrix crack growth and diffusion kinetics will be discussed. In another approach, hybrid fiber-lay up concepts have been utilized to "alloy" desirable properties of different fiber types for mechanical properties, thermal stress management, and oxidation resistance. Such an approach has potential for the C(sub I)-SiC and SiC(sub f)-SiC composite systems. CVI SiC matrix composites with different stacking sequences of woven C fiber (T300) layers and woven SiC fiber (Hi-Nicalon (trademark)) layers were fabricated. The results will be compared to standard C fiber reinforced CVI SiC matrix and Hi-Nicalon reinforced CVI SiC matrix composites. In addition, shear properties of these composites at different temperatures will also be presented. Other design and implementation issues will be discussed along with advantages and benefits of using these materials for various components in high temperature applications.

  12. Interfacial shear behavior of sapphire-reinforced NiAl composites

    NASA Technical Reports Server (NTRS)

    Moose, C. A.; Koss, D. A.; Hellmann, J. R.

    1990-01-01

    The interfacial shear behavior in near-equiatomic NiAl reinforced by sapphire filaments has been examined at room temperature using a fiber pushout test technique. The load-displacement data indicate a large variability in the initial interface failure stress, although reverse push behavior indicates a comparatively constant interfacial sliding friction stress. The observed behavior suggests that the presence of asperities on the fiber surfaces and nonuniformities in fiber diameter require constrained plastic flow within the NiAl matrix in order for interfacial shear to occur. The location, shape, severity, and distribution of fiber asperities as well as the uniformity of fiber diameter are critical to the interfacial shear process.

  13. Longitudinal splitting in epoxy and K-polymer composites - Shear lag analysis including the effect of fiber bridging

    NASA Technical Reports Server (NTRS)

    Nairn, John A.; Liu, Siulie; Chen, Hsichieh; Wedgewood, Alan R.

    1991-01-01

    The shear-lag model used previously by Nairn (1988) to derive a fracture mechanics analysis of longitudinal splitting in double-edge notched unidirectional composites was used to investigate the effect of fibers bridging across the longitudinal split in these composites. Using the new analysis, the longitudinal splitting fracture toughness, G(Lc), was determined for Hercules AS4/3501-6 graphite/epoxy laminates and for K-polymer based laminates containing Magnamite IM-6 as the graphite reinforcing fiber. Results show that the inclusion of the fiber bridging in the fracture analysis significantly affects the reported fracture toughness.

  14. Analyses of Failure Mechanisms and Residual Stresses in Graphite/Polyimide Composites Subjected to Shear Dominated Biaxial Loads

    NASA Technical Reports Server (NTRS)

    Kumosa, M.; Predecki, P. K.; Armentrout, D.; Benedikt, B.; Rupnowski, P.; Gentz, M.; Kumosa, L.; Sutter, J. K.

    2002-01-01

    This research contributes to the understanding of macro- and micro-failure mechanisms in woven fabric polyimide matrix composites based on medium and high modulus graphite fibers tested under biaxial, shear dominated stress conditions over a temperature range of -50 C to 315 C. The goal of this research is also to provide a testing methodology for determining residual stress distributions in unidirectional, cross/ply and fabric graphite/polyimide composites using the concept of embedded metallic inclusions and X-ray diffraction (XRD) measurements.

  15. Ductility of Advanced High-Strength Steel in the Presence of a Sheared Edge

    NASA Astrophysics Data System (ADS)

    Ruggles, Tim; Cluff, Stephen; Miles, Michael; Fullwood, David; Daniels, Craig; Avila, Alex; Chen, Ming

    2016-07-01

    The ductility of dual-phase (DP) 980 and transformation-induced plasticity (TRIP) assisted bainitic ferritic (TBF) 980 steels was studied in the presence of a sheared edge. Specimens were tested in uniaxial tension in a standard test frame as well as in situ in the scanning electron microscope (SEM). Incremental tensile straining was done in the SEM with images taken at each strain increment. Then digital image correlation (DIC) was used to compute the effective strain at the level of the individual phases in the microstructure. Shear banding across multiple phases was seen in strained TBF specimens, while the DP specimens exhibited more of a patchwork strain pattern, with high strains concentrated in ferrite and low strains observed in the martensite. Two-point statistics were applied to the strain data from the DIC work and the corresponding microstructure images to evaluate the effect of phase hardness on localization and fracture. It was observed that the DP 980 material had a greater tendency for localization around hard phases compared to the TBF 980. This at least partially explains the greater ductility of the TBF material, especially in specimens where a sheared edge was present.

  16. Ductility of Advanced High-Strength Steel in the Presence of a Sheared Edge

    NASA Astrophysics Data System (ADS)

    Ruggles, Tim; Cluff, Stephen; Miles, Michael; Fullwood, David; Daniels, Craig; Avila, Alex; Chen, Ming

    2016-05-01

    The ductility of dual-phase (DP) 980 and transformation-induced plasticity (TRIP) assisted bainitic ferritic (TBF) 980 steels was studied in the presence of a sheared edge. Specimens were tested in uniaxial tension in a standard test frame as well as in situ in the scanning electron microscope (SEM). Incremental tensile straining was done in the SEM with images taken at each strain increment. Then digital image correlation (DIC) was used to compute the effective strain at the level of the individual phases in the microstructure. Shear banding across multiple phases was seen in strained TBF specimens, while the DP specimens exhibited more of a patchwork strain pattern, with high strains concentrated in ferrite and low strains observed in the martensite. Two-point statistics were applied to the strain data from the DIC work and the corresponding microstructure images to evaluate the effect of phase hardness on localization and fracture. It was observed that the DP 980 material had a greater tendency for localization around hard phases compared to the TBF 980. This at least partially explains the greater ductility of the TBF material, especially in specimens where a sheared edge was present.

  17. Single-crystal-material-based induced-shear actuation for vibration reduction of helicopters with composite rotor system

    NASA Astrophysics Data System (ADS)

    Pawar, Prashant M.; Jung, Sung Nam

    2008-12-01

    In this study, an assessment is made for the helicopter vibration reduction of composite rotor blades using an active twist control concept. Special focus is given to the feasibility of implementing the benefits of the shear actuation mechanism along with elastic couplings of composite blades for achieving maximum vibration reduction. The governing equations of motion for composite rotor blades with surface bonded piezoceramic actuators are obtained using Hamilton's principle. The equations are then solved for dynamic response using finite element discretization in the spatial and time domains. A time domain unsteady aerodynamic theory with free wake model is used to obtain the airloads. A newly developed single-crystal piezoceramic material is introduced as an actuator material to exploit its superior shear actuation authority. Seven rotor blades with different elastic couplings representing stiffness properties similar to stiff-in-plane rotor blades are used to investigate the hub vibration characteristics. The rotor blades are modeled as a box beam with actuator layers bonded on the outer surface of the top and bottom of the box section. Numerical results show that a notable vibration reduction can be achieved for all the combinations of composite rotor blades. This investigation also brings out the effect of different elastic couplings on various vibration-reduction-related parameters which could be useful for the optimal design of composite helicopter blades.

  18. Methods and Compositions Based on Culturing Microorganisms in Low Sedimental Fluid Shear Conditions

    NASA Technical Reports Server (NTRS)

    Ott, C. Mark; Nickerson, Cheryl A.; Wilson, James W.; Sarker, Shameema; Nauman, Eric A.; Schurr, Michael J.; Nelman-Gonzalez, Mayra A.

    2012-01-01

    The benefits of applying a low sedimental fluid shear environment to manipulate microorganisms were examined. Microorganisms obtained from a low sedimental fluid shear culture, which exhibit modified phenotypic and molecular genetic characteristics, are useful for the development of novel and improved diagnostics, therapeutics, vaccines, and bio-industrial products. Furthermore, application of low sedimental fluid conditions to microorganisms permits identification of molecules uniquely expressed under these conditions, providing a basis for the design of new therapeutic targets.

  19. Comparing the shear bond strength of direct and indirect composite inlays in relation to different surface conditioning and curing techniques

    PubMed Central

    Zorba, Yahya Orcun; Ilday, Nurcan Ozakar; Bayındır, Yusuf Ziya; Demirbuga, Sezer

    2013-01-01

    Objective: The aim of this study was to test the null hypothesis that different surface conditioning (etch and rinse and self-etch) and curing techniques (light cure/dual cure) had no effect on the shear bond strength of direct and indirect composite inlays. Materials and Methods: A total of 112 extracted human molar teeth were horizontally sectioned and randomly divided into two groups according to restoration technique (direct and indirect restorations). Each group was further subdivided into seven subgroups (n = 8) according to bonding agent (etch and rinse adhesives Scotchbond multi-purpose plus, All-Bond 3, Adper Single Bond and Prime Bond NT; and self-etch adhesives Clearfil Liner Bond, Futurabond DC and G bond). Indirect composites were cemented to dentin surfaces using dual-curing luting cement. Shear bond strength of specimens was tested using a Universal Testing Machine. Two samples from each subgroup were evaluated under Scanning electron microscopy to see the failing modes. Data was analyzed using independent sample t-tests and Tukey's tests. Results: Surface conditioning and curing of bonding agents were all found to have significant effects on shear bond strength (P < 0.05) of both direct and indirect composite inlays. With direct restoration, etch and rinse systems and dual-cured bonding agents yielded higher bond strengths than indirect restoration, self-etch systems and light-cured bonding agents. Conclusions: The results of the present study indicated that direct restoration to be a more reliable method than indirect restoration. Although etch and rinse bonding systems showed higher shear bond strength to dentin than self-etch systems, both systems can be safely used for the adhesion of direct as well as indirect restorations. PMID:24932118

  20. Effect of Different Anti-Oxidants on Shear Bond Strength of Composite Resins to Bleached Human Enamel

    PubMed Central

    Saladi, Hari Krishna; Bollu, Indira Priyadarshini; Burla, Devipriya; Ballullaya, Srinidhi Vishnu; Devalla, Srihari; Maroli, Sohani; Jayaprakash, Thumu

    2015-01-01

    Introduction The bond strength of the composite to the bleached enamel plays a very important role in the success and longevity of an aesthetic restoration. Aim The aim of this study was to compare and evaluate the effect of Aloe Vera with 10% Sodium Ascorbate on the Shear bond strength of composite resin to bleached human enamel. Materials and Methods Fifty freshly extracted human maxillary central incisors were selected and divided into 5 groups. Group I and V are unbleached and bleached controls groups respectively. Group II, III, IV served as experimental groups. The labial surfaces of groups II, III, IV, V were treated with 35% Carbamide Peroxide for 30mins. Group II specimens were subjected to delayed composite bonding. Group III and IV specimens were subjected to application of 10% Sodium Ascorbate and leaf extract of Aloe Vera following the Carbamide Peroxide bleaching respectively. Specimens were subjected to shear bond strength using universal testing machine and the results were statistically analysed using ANOVA test. Tukey (HSD) Honest Significant Difference test was used to comparatively analyse statistical differences between the groups. A p-value <0.05 is taken as statistically significant. Results The mean shear bond strength values of Group V showed significantly lower bond strengths than Groups I, II, III, IV (p-value <0.05). There was no statistically significant difference between the shear bond strength values of groups I, II, III, IV. Conclusion Treatment of the bleached enamel surface with Aloe Vera and 10% Sodium Ascorbate provided consistently better bond strength. Aloe Vera may be used as an alternative to 10% Sodium Ascorbate. PMID:26674656

  1. Micromechanical and in situ shear testing of Al–SiC nanolaminate composites in a transmission electron microscope (TEM)

    SciTech Connect

    Mayer, Carl; Li, Nan; Mara, Nathan Allan; Chawla, Nikhilesh

    2014-11-07

    Nanolaminate composites show promise as high strength and toughness materials. Still, due to the limited volume of these materials, micron scale mechanical testing methods must be used to determine the properties of these films. To this end, a novel approach combining a double notch shear testing geometry and compression with a flat punch in a nanoindenter was developed to determine the mechanical properties of these films under shear loading. To further elucidate the failure mechanisms under shear loading, in situ TEM experiments were performed using a double notch geometry cut into the TEM foil. Aluminum layer thicknesses of 50nm and 100nm were used to show the effect of constraint on the deformation. Higher shear strength was observed in the 50 nm sample (690±54 MPa) compared to the 100 nm sample (423±28.7 MPa). Additionally, failure occurred along the Al-SiC interface in the 50 nm sample as opposed to failure within the Al layer in the 100 nm sample.

  2. Micromechanical and in situ shear testing of Al–SiC nanolaminate composites in a transmission electron microscope (TEM)

    DOE PAGESBeta

    Mayer, Carl; Li, Nan; Mara, Nathan Allan; Chawla, Nikhilesh

    2014-11-07

    Nanolaminate composites show promise as high strength and toughness materials. Still, due to the limited volume of these materials, micron scale mechanical testing methods must be used to determine the properties of these films. To this end, a novel approach combining a double notch shear testing geometry and compression with a flat punch in a nanoindenter was developed to determine the mechanical properties of these films under shear loading. To further elucidate the failure mechanisms under shear loading, in situ TEM experiments were performed using a double notch geometry cut into the TEM foil. Aluminum layer thicknesses of 50nm andmore » 100nm were used to show the effect of constraint on the deformation. Higher shear strength was observed in the 50 nm sample (690±54 MPa) compared to the 100 nm sample (423±28.7 MPa). Additionally, failure occurred along the Al-SiC interface in the 50 nm sample as opposed to failure within the Al layer in the 100 nm sample.« less

  3. The effects of neutron irradiation on shear properties of monolayered PyC and multilayered PyC/SiC interfaces of SiC/SiC composites

    NASA Astrophysics Data System (ADS)

    Nozawa, T.; Katoh, Y.; Snead, L. L.

    2007-08-01

    The effect of neutron irradiation on mechanical properties at the fiber/matrix interface of SiC/SiC composites was evaluated. The materials investigated were Hi-Nicalon™ Type-S fiber reinforced chemically vapor infiltrated SiC matrix composites with varied interphases: monolayered pyrolytic carbon (PyC) or multilayered PyC/SiC. The neutron fluence was 7.7 × 10 25 n/m 2 ( E > 0.1 MeV), and the irradiation temperature was 800 °C. Interfacial shear properties were evaluated by the fiber push-out test method. A modified shear-lag model was applied to analyze the interfacial shear parameters. Test results indicate that the interfacial debond shear strength and the interfacial friction stress for the multilayer composites were significantly degraded by irradiation. Nevertheless, the multilayer composites retained sufficient interfacial shear properties so that overall composite strength after neutron irradiation was unaffected. The actual mechanism of interphase property decrease for the multilayer composites is unknown. The interfacial shear properties of the irradiated monolayer composites appear unaffected.

  4. Application of advanced composites to helicopter airframe structures. [CH-53 D materials

    NASA Technical Reports Server (NTRS)

    Rich, M. J.; Ridgley, G. F.; Lowry, D. W.

    1974-01-01

    The present work outlines a study whose objective was to assess the possible use of advanced composite materials to helicopter fuselage structure. The study used the CH-53D as a baseline design for comparison of composite with current conventional construction. Boron/epoxy and graphite/epoxy appeared to be the prime candidate materials for the major portion of the primary structure, while Kevlar-49/epoxy was the prime candidate material for secondary structure. A single-laminate shear-carrying skin combined with stringers and frames in an all-molded construction was considered the most promising concept for the airframe shell construction; foam-stabilized graphite/epoxy stringer was considered the prime concept for stringer construction. Shell construction and assembly concepts are discussed, and comparison of weight and material between current CH-53D airframe and the composite airframe shows that the latter may represent an 18% weight saving. Based on a fleet requirement of 600 vehicles, the operating cost for a fleet of helicopters constructed with the composite material airframe flying 500 hours a year per aircraft over a ten-year service life was calculated, indicating a $337,000 saving per helicopter.

  5. In-Situ Investigation of Advanced Structural Coatings and Composites

    NASA Technical Reports Server (NTRS)

    Ustundag, Ersan

    2003-01-01

    The premise of this project is a comprehensive study that involves the in-situ characterization of advanced coatings and composites by employing both neutron and x-ray diffraction techniques in a complementary manner. The diffraction data would then be interpreted and used in developing or validating advanced micromechanics models with life prediction capability. In the period covered by this report, basic work was conducted to establish the experimental conditions for various specimens and techniques. In addition, equipment was developed that will allow the in-situ studies under a range of conditions (stress, temperature, atmosphere, etc.).

  6. Characterization and development of materials for advanced textile composites

    NASA Technical Reports Server (NTRS)

    Hartness, J. Timothy; Greene, Timothy L.; Taske, Leo E.

    1993-01-01

    Work ongoing under the NASA Langley - Advanced Composite Technology (ACT) program is discussed. The primary emphasis of the work centers around the development and characterization of graphite fiber that has been impregnated with an epoxy powder. Four epoxies have been characterized in towpreg form as to their weaveability and braidability. Initial mechanical properties have been generated on each resin system. These include unidirectional as well as 8-harness satin cloth. Initial 2D and 3D weaving and braiding trials will be reported on as well as initial efforts to develop towpreg suitable for advanced tow placement.

  7. CAD/CAM of braided preforms for advanced composites

    NASA Astrophysics Data System (ADS)

    Yang, Gui; Pastore, Christopher; Tsai, Yung Jia; Soebroto, Heru; Ko, Frank

    A CAD/CAM system for braiding to produce preforms for advanced textile structural composites is presented in this paper. The CAD and CAM systems are illustrated in detail. The CAD system identifies the fiber placement and orientation needed to fabricate a braided structure over a mandrel, for subsequent composite formation. The CAM system uses the design parameters generated by the CAD system to control the braiding machine. Experimental evidence demonstrating the success of combining these two technologies to form a unified CAD/CAM system for the manufacture of braided fabric preforms with complex structural shapes is presented.

  8. Hydrogen bonds, interfacial stiffness moduli, and the interlaminar shear strength of carbon fiber-epoxy matrix composites

    SciTech Connect

    Cantrell, John H.

    2015-03-15

    The chemical treatment of carbon fibers used in carbon fiber-epoxy matrix composites greatly affects the fraction of hydrogen bonds (H-bonds) formed at the fiber-matrix interface. The H-bonds are major contributors to the fiber-matrix interfacial shear strength and play a direct role in the interlaminar shear strength (ILSS) of the composite. The H-bond contributions τ to the ILSS and magnitudes K{sub N} of the fiber-matrix interfacial stiffness moduli of seven carbon fiber-epoxy matrix composites, subjected to different fiber surface treatments, are calculated from the Morse potential for the interactions of hydroxyl and carboxyl acid groups formed on the carbon fiber surfaces with epoxy receptors. The τ calculations range from 7.7 MPa to 18.4 MPa in magnitude, depending on fiber treatment. The K{sub N} calculations fall in the range (2.01 – 4.67) ×10{sup 17} N m{sup −3}. The average ratio K{sub N}/|τ| is calculated to be (2.59 ± 0.043) × 10{sup 10} m{sup −1} for the seven composites, suggesting a nearly linear connection between ILSS and H-bonding at the fiber-matrix interfaces. The linear connection indicates that τ may be assessable nondestructively from measurements of K{sub N} via a technique such as angle beam ultrasonic spectroscopy.

  9. Hydrogen bonds, interfacial stiffness moduli, and the interlaminar shear strength of carbon fiber-epoxy matrix composites

    NASA Astrophysics Data System (ADS)

    Cantrell, John H.

    2015-03-01

    The chemical treatment of carbon fibers used in carbon fiber-epoxy matrix composites greatly affects the fraction of hydrogen bonds (H-bonds) formed at the fiber-matrix interface. The H-bonds are major contributors to the fiber-matrix interfacial shear strength and play a direct role in the interlaminar shear strength (ILSS) of the composite. The H-bond contributions τ to the ILSS and magnitudes KN of the fiber-matrix interfacial stiffness moduli of seven carbon fiber-epoxy matrix composites, subjected to different fiber surface treatments, are calculated from the Morse potential for the interactions of hydroxyl and carboxyl acid groups formed on the carbon fiber surfaces with epoxy receptors. The τ calculations range from 7.7 MPa to 18.4 MPa in magnitude, depending on fiber treatment. The KN calculations fall in the range (2.01 - 4.67) ×1017 N m-3. The average ratio KN/|τ| is calculated to be (2.59 ± 0.043) × 1010 m-1 for the seven composites, suggesting a nearly linear connection between ILSS and H-bonding at the fiber-matrix interfaces. The linear connection indicates that τ may be assessable nondestructively from measurements of KN via a technique such as angle beam ultrasonic spectroscopy.

  10. Fatigue Damage Mechanisms in Advanced Hybrid Titanium Composite Laminates

    NASA Technical Reports Server (NTRS)

    Johnson, W. Steven; Rhymer, Donald W.; St.Clair, Terry L. (Technical Monitor)

    2000-01-01

    Hybrid Titanium Composite Laminates (HTCL) are a type of hybrid composite laminate with promise for high-speed aerospace applications, specifically designed for improved damage tolerance and strength at high-temperature (350 F, 177 C). However, in previous testing, HTCL demonstrated a propensity to excessive delamination at the titanium/PMC interface following titanium cracking. An advanced HTCL has been constructed with an emphasis on strengthening this interface, combining a PETI-5/IM7 PMC with Ti-15-3 foils prepared with an alkaline-perborate surface treatment. This paper discusses how the fatigue capabilities of the "advanced" HTCL compare to the first generation HTCL which was not modified for interface optimization, in both tension-tension (R = 0.1) and tension-compression (R=-0.2). The advanced HTCL under did not demonstrate a significant improvement in fatigue life, in either tension-tension or tension-compression loading. However, the advanced HTCL proved much more damage tolerant. The R = 0.1 tests revealed the advanced HTCL to increase the fatigue life following initial titanium ply damage up to 10X that of the initial HTCL at certain stress levels. The damage progression following the initial ply damage demonstrated the effect of the strengthened PMC/titanium interface. Acetate film replication of the advanced HTCL edges showed a propensity for some fibers in the adjacent PMC layers to fail at the point of titanium crack formation, suppressing delamination at the Ti/PMC interface. The inspection of failure surfaces validated these findings, revealing PMC fibers bonded to the majority of the titanium surfaces. Tension compression fatigue (R = -0.2) demonstrated the same trends in cycles between initial damage and failure, damage progression, and failure surfaces. Moreover, in possessing a higher resistance to delamination, the advanced HTCL did not exhibit buckling following initial titanium ply cracking under compression unlike the initial HTCL.

  11. Effect of Epigallocatechin Gallate on shear bond strength of composite resin to bleached enamel: an in vitro study

    PubMed Central

    Khamverdi, Zahra; Kasraei, Shahin; Ronasi, Negin; Rostami, Shiva

    2013-01-01

    Objectives The aim of this study was to determine the effect of epigallocatechin gallate (EGCG) on the shear bond strength of composite resin to bleached enamel. Materials and Methods Ninety enamel surfaces of maxillary incisors were randomly divided into 9 groups as follows: G1: control (no bleaching); G2: bleaching; G3: bleaching and storage for seven days; G4 - 6: bleaching and application of 600, 800 and 1,000 µmol of EGCG-containing solution for 10 minutes, respectively; G7 - 9: bleaching and application of 600, 800 and 1,000 µmol of EGCG-containing solution for 20 minutes, respectively. The specimens were bleached with 30% hydrogen peroxide gel and a composite resin cylinder was bonded on each specimen using a bonding agent. Shear bond strength of the samples were measured in MPa. Data was analyzed using the two-way ANOVA and Tukey HSD tests (α = 0.05). Results The maximum and minimum mean shear bond strength values were observed in G1 and G2, respectively. Time and concentration of EGCG showed no significant effects on bond strength of the groups (p > 0.05). Multiple comparison of groups did not reveal any significant differences between the groups except for G2 and all the other groups (p < 0.05). Conclusions There is a significant decrease in bond strength of composite resin to enamel immediately after bleaching. A delay of one week before bonding and the use of EGCG increased bond strength of composite resin to bleached enamel. PMID:24303360

  12. High resolution computed tomography of advanced composite and ceramic materials

    NASA Technical Reports Server (NTRS)

    Yancey, R. N.; Klima, S. J.

    1991-01-01

    Advanced composite and ceramic materials are being developed for use in many new defense and commercial applications. In order to achieve the desired mechanical properties of these materials, the structural elements must be carefully analyzed and engineered. A study was conducted to evaluate the use of high resolution computed tomography (CT) as a macrostructural analysis tool for advanced composite and ceramic materials. Several samples were scanned using a laboratory high resolution CT scanner. Samples were also destructively analyzed at the locations of the scans and the nondestructive and destructive results were compared. The study provides useful information outlining the strengths and limitations of this technique and the prospects for further research in this area.

  13. Review on advanced composite materials boring mechanism and tools

    NASA Astrophysics Data System (ADS)

    Shi, Runping; Wang, Chengyong

    2010-12-01

    With the rapid development of aviation and aerospace manufacturing technology, advanced composite materials represented by carbon fibre reinforced plastics (CFRP) and super hybrid composites (fibre/metal plates) are more and more widely applied. The fibres are mainly carbon fibre, boron fibre, Aramid fiber and Sic fibre. The matrixes are resin matrix, metal matrix and ceramic matrix. Advanced composite materials have higher specific strength and higher specific modulus than glass fibre reinforced resin composites of the 1st generation. They are widely used in aviation and aerospace industry due to their high specific strength, high specific modulus, excellent ductility, anticorrosion, heat-insulation, sound-insulation, shock absorption and high&low temperature resistance. They are used for radomes, inlets, airfoils(fuel tank included), flap, aileron, vertical tail, horizontal tail, air brake, skin, baseboards and tails, etc. Its hardness is up to 62~65HRC. The holes are greatly affected by the fibre laminates direction of carbon fibre reinforced composite material due to its anisotropy when drilling in unidirectional laminates. There are burrs, splits at the exit because of stress concentration. Besides there is delamination and the hole is prone to be smaller. Burrs are caused by poor sharpness of cutting edge, delamination, tearing, splitting are caused by the great stress caused by high thrust force. Poorer sharpness of cutting edge leads to lower cutting performance and higher drilling force at the same time. The present research focuses on the interrelation between rotation speed, feed, drill's geometry, drill life, cutting mode, tools material etc. and thrust force. At the same time, holes quantity and holes making difficulty of composites have also increased. It requires high performance drills which won't bring out defects and have long tool life. It has become a trend to develop super hard material tools and tools with special geometry for drilling

  14. Review on advanced composite materials boring mechanism and tools

    NASA Astrophysics Data System (ADS)

    Shi, Runping; Wang, Chengyong

    2011-05-01

    With the rapid development of aviation and aerospace manufacturing technology, advanced composite materials represented by carbon fibre reinforced plastics (CFRP) and super hybrid composites (fibre/metal plates) are more and more widely applied. The fibres are mainly carbon fibre, boron fibre, Aramid fiber and Sic fibre. The matrixes are resin matrix, metal matrix and ceramic matrix. Advanced composite materials have higher specific strength and higher specific modulus than glass fibre reinforced resin composites of the 1st generation. They are widely used in aviation and aerospace industry due to their high specific strength, high specific modulus, excellent ductility, anticorrosion, heat-insulation, sound-insulation, shock absorption and high&low temperature resistance. They are used for radomes, inlets, airfoils(fuel tank included), flap, aileron, vertical tail, horizontal tail, air brake, skin, baseboards and tails, etc. Its hardness is up to 62~65HRC. The holes are greatly affected by the fibre laminates direction of carbon fibre reinforced composite material due to its anisotropy when drilling in unidirectional laminates. There are burrs, splits at the exit because of stress concentration. Besides there is delamination and the hole is prone to be smaller. Burrs are caused by poor sharpness of cutting edge, delamination, tearing, splitting are caused by the great stress caused by high thrust force. Poorer sharpness of cutting edge leads to lower cutting performance and higher drilling force at the same time. The present research focuses on the interrelation between rotation speed, feed, drill's geometry, drill life, cutting mode, tools material etc. and thrust force. At the same time, holes quantity and holes making difficulty of composites have also increased. It requires high performance drills which won't bring out defects and have long tool life. It has become a trend to develop super hard material tools and tools with special geometry for drilling

  15. Effect of Matrix Modification on Interlaminar Shear Strength of Glass Fibre Reinforced Epoxy Composites at Cryogenic Temperature

    NASA Astrophysics Data System (ADS)

    Wu, Zhixiong; Li, Jingwen; Huang, Chuanjun; Li, Laifeng

    In order to investigate the effect of the matrix variability on the interlaminar shear strength (ILSS) of glass fiber reinforced composites at 77K, three kinds of modifiers were employed to diethyl toluene diamine (DETD) cured diglycidyl ether of bisphenol F (DGEBF) epoxy resin system. The woven glass fiber reinforced composites were fabricated by vacuum pressure impregnation (VPI). The ILSS at 77 K was studied and the results indicated that introduction of modifiers used in this study can enhance the ILSS of composite at 77 K. A maximum of 14.87% increase was obtained by addition of 10 wt% IPBE into the epoxy matrix. Furthermore, scanning electron microscopy (SEM) was used to investigate the fracture mechanism and strengthening effect.

  16. Composite transport wing technology development: Design development tests and advanced structural concepts

    NASA Technical Reports Server (NTRS)

    Griffin, Charles F.; Harvill, William E.

    1988-01-01

    Numerous design concepts, materials, and manufacturing methods were investigated for the covers and spars of a transport box wing. Cover panels and spar segments were fabricated and tested to verify the structural integrity of design concepts and fabrication techniques. Compression tests on stiffened panels demonstrated the ability of graphite/epoxy wing upper cover designs to achieve a 35 percent weight savings compared to the aluminum baseline. The impact damage tolerance of the designs and materials used for these panels limits the allowable compression strain and therefore the maximum achievable weight savings. Bending and shear tests on various spar designs verified an average weight savings of 37 percent compared to the aluminum baseline. Impact damage to spar webs did not significantly degrade structural performance. Predictions of spar web shear instability correlated well with measured performance. The structural integrity of spars manufactured by filament winding equalled or exceeded those fabricated by hand lay-up. The information obtained will be applied to the design, fabrication, and test of a full-scale section of a wing box. When completed, the tests on the technology integration box beam will demonstrate the structural integrity of an advanced composite wing design which is 25 percent lighter than the metal baseline.

  17. Composite Structure Modeling and Analysis of Advanced Aircraft Fuselage Concepts

    NASA Technical Reports Server (NTRS)

    Mukhopadhyay, Vivek; Sorokach, Michael R.

    2015-01-01

    NASA Environmentally Responsible Aviation (ERA) project and the Boeing Company are collabrating to advance the unitized damage arresting composite airframe technology with application to the Hybrid-Wing-Body (HWB) aircraft. The testing of a HWB fuselage section with Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS) construction is presently being conducted at NASA Langley. Based on lessons learned from previous HWB structural design studies, improved finite-element models (FEM) of the HWB multi-bay and bulkhead assembly are developed to evaluate the performance of the PRSEUS construction. In order to assess the comparative weight reduction benefits of the PRSEUS technology, conventional cylindrical skin-stringer-frame models of a cylindrical and a double-bubble section fuselage concepts are developed. Stress analysis with design cabin-pressure load and scenario based case studies are conducted for design improvement in each case. Alternate analysis with stitched composite hat-stringers and C-frames are also presented, in addition to the foam-core sandwich frame and pultruded rod-stringer construction. The FEM structural stress, strain and weights are computed and compared for relative weight/strength benefit assessment. The structural analysis and specific weight comparison of these stitched composite advanced aircraft fuselage concepts demonstrated that the pressurized HWB fuselage section assembly can be structurally as efficient as the conventional cylindrical fuselage section with composite stringer-frame and PRSEUS construction, and significantly better than the conventional aluminum construction and the double-bubble section concept.

  18. Design aid for shear strengthening of reinforced concrete T-joints using carbon fiber reinforced plastic composites

    NASA Astrophysics Data System (ADS)

    Gergely, Ioan

    The research presented in the present work focuses on the shear strengthening of beam column joints using carbon fiber composites, a material considered in seismic retrofit in recent years more than any other new material. These composites, or fiber reinforced polymers, offer huge advantages over structural steel reinforced concrete or timber. A few of these advantages are the superior resistance to corrosion, high stiffness to weight and strength to weight ratios, and the ability to control the material's behavior by selecting the orientation of the fibers. The design and field application research on reinforced concrete cap beam-column joints includes analytical investigations using pushover analysis; design of carbon fiber layout, experimental tests and field applications. Several beam column joints have been tested recently with design variables as the type of composite system, fiber orientation and the width of carbon fiber sheets. The surface preparation has been found to be critical for the bond between concrete and composite material, which is the most important factor in joint shear strengthening. The final goal of this thesis is to develop design aids for retrofitting reinforced concrete beam column joints. Two bridge bents were tested on the Interstate-15 corridor. One bent was tested in the as-is condition. Carbon fiber reinforced plastic composite sheets were used to externally reinforce the second bridge bent. By applying the composite, the displacement ductility has been doubled, and the bent overall lateral load capacity has been increased as well. The finite element model (using DRAIN-2DX) was calibrated to model the actual stiffness of the supports. The results were similar to the experimental findings.

  19. Boron/aluminum-graphite/resin advanced fiber composite hybrids

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.; Lark, R. F.; Sullivan, T. L.

    1974-01-01

    An investigation was conducted to determine the fabrication feasibility and to assess the potential of adhesively-bonded metal and resin matrix fiber composite hybrids as an advanced material, for aerospace and other structural applications. The results of fabrication studies and of evaluation of physical and mechanical properties show that using this hybrid concept it is possible to design a composite which, when compared to nonhybrid composites, has improved transverse strength, transverse stiffness, and impact resistance with only a small penalty on density and longitudinal properties. The results also show that laminate theory is suitable for perdicting the structural response of such hybrids. The sequence of fracture modes indicates that these types of hybrids can be readily designed to meet fail-safe requirements.

  20. Third NASA Advanced Composites Technology Conference, volume 1, part 2

    NASA Technical Reports Server (NTRS)

    Davis, John G., Jr. (Compiler); Bohon, Herman L. (Compiler)

    1993-01-01

    This document is a compilation of papers presented at the Third NASA Advanced Composites Technology (ACT) Conference held at Long Beach, California, 8-11 June 1992. The ACT Program is a major multi-year research initiative to achieve a national goal of technology readiness before the end of the decade. Conference papers recorded results of research in the ACT Program in the specific areas of automated fiber placement, resin transfer molding, textile preforms, and stitching as these processes influence design, performance, and cost of composites in aircraft structures. Papers sponsored by the Department of Defense on the Design and Manufacturing of Low Cost Composites (DMLCC) are also included in Volume 2 of this document.

  1. Boron/aluminum-graphite/resin advanced fiber composite hybrids

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.; Lark, R. F.; Sullivan, T. L.

    1974-01-01

    An investigation was conducted to determine the fabrication feasibility and to assess the potential of adhesively-bonded metal and resin matrix fiber composite hybrids as an advanced material, for aerospace and other structural applications. The results of fabrication studies and of evaluation of physical and mechanical properties show that using this hybrid concept it is possible to design a composite which, when compared to nonhybrid composites, has improved transverse strength, transverse stiffness, and impact resistance with only a small penalty on density and longitudinal properties. The results also show that laminate theory is suitable for predicting the structural response of such hybrids. The sequence of fracture modes indicates that these types of hybrids can be readily designed to meet fail-safe requirements.

  2. Composite intermediate case manufacturing scale-up for advanced engines

    NASA Technical Reports Server (NTRS)

    Ecklund, Rowena H.

    1992-01-01

    This Manufacturing Technology for Propulsion Program developed a process to produce a composite intermediate case for advanced gas turbine engines. The method selected to manufacture this large, complex part uses hard tooling for surfaces in the airflow path and trapped rubber to force the composite against the mold. Subelements were manufactured and tested to verify the selected design, tools, and processes. The most significant subelement produced was a half-scale version of a composite intermediate case. The half-scale subelement maintained the geometry and key dimensions of the full-scale case, allowing relevant process development and structural verification testing to be performed on the subelement before manufacturing the first full-scale case.

  3. Advanced composite combustor structural concepts program. Final Report

    SciTech Connect

    Sattar, M.A.; Lohmann, R.P.

    1984-12-01

    An analytical study was conducted to assess the feasibility of and benefits derived from the use of high temperature composite materials in aircraft turbine engine combustor liners. The study included a survey and screening of the properties of three candidate composite materials including tungsten reinforced superalloys, carbon-carbon and silicon carbide (SiC) fibers reinforcing a ceramic matrix of lithium aluminosilicate (LAS). The SiC-LAS material was selected as offering the greatest near term potential primarily on the basis of high temperature capability. A limited experimental investigation was conducted to quantify some of the more critical mechanical properties of the SiC-LAS composite having a multidirection 0/45/-45/90 deg fiber orientation favored for the combustor linear application. Rigorous cyclic thermal tests demonstrated that SiC-LAS was extremely resistant to the thermal fatigue mechanisms that usually limit the life of metallic combustor liners. A thermal design study led to the definition of a composite liner concept that incorporated film cooled SiC-LAS shingles mounted on a Hastelloy X shell. With coolant fluxes consistent with the most advanced metallic liner technology, the calculated hot surface temperatures of the shingles were within the apparent near term capability of the material. Structural analyses indicated that the stresses in the composite panels were low, primarily because of the low coefficient of expansion of the material and it was concluded that the dominant failure mode of the liner would be an as yet unidentified deterioration of the composite from prolonged exposure to high temperature. An economic study, based on a medium thrust size commercial aircraft engine, indicated that the SiC-LAS combustor liner would weigh 22.8N (11.27 lb) less and cost less to manufacture than advanced metallic liner concepts intended for use in the late 1980's.

  4. Shear Wave Velocity Structure of Southern African Crust: Evidence for Compositional Heterogeneity within Archaean and Proterozoic Terrains

    SciTech Connect

    Kgaswane, E M; Nyblade, A A; Julia, J; Dirks, P H H M; Durrheim, R J; Pasyanos, M E

    2008-11-11

    Crustal structure in southern Africa has been investigated by jointly inverting receiver functions and Rayleigh wave group velocities for 89 broadband seismic stations spanning much of the Precambrian shield of southern Africa. 1-D shear wave velocity profiles obtained from the inversion yield Moho depths that are similar to those reported in previous studies and show considerable variability in the shear wave velocity structure of the lower part of the crust between some terrains. For many of the Archaean and Proterozoic terrains in the shield, S velocities reach 4.0 km/s or higher over a substantial part of the lower crust. However, for most of the Kimberley terrain and adjacent parts of the Kheis Province and Witwatersrand terrain, as well as for the western part of the Tokwe terrain, mean shear wave velocities of {le} 3.9 km/s characterize the lower part of the crust along with slightly ({approx}5 km) thinner crust. These findings indicate that the lower crust across much of the shield has a predominantly mafic composition, except for the southwest portion of the Kaapvaal Craton and western portion of the Zimbabwe Craton, where the lower crust is intermediate-to-felsic in composition. The parts of the Kaapvaal Craton underlain by intermediate-to-felsic lower crust coincide with regions where Ventersdorp rocks have been preserved, and thus we suggest that the intermediate-to-felsic composition of the lower crust and the shallower Moho may have resulted from crustal melting during the Ventersdorp tectonomagmatic event at c. 2.7 Ga and concomitant crustal thinning caused by rifting.

  5. Effect of Er:YAG Laser on Shear Bond Strength of Composite to Enamel and Dentin of Primary Teeth

    PubMed Central

    Bahrololoomi, Zahra; Kabudan, Mona; Gholami, Leila

    2015-01-01

    Objectives: Bond strength of composite resin to enamel and dentin of primary teeth is lower than that to permanent teeth; therefore, it may compromise the adhesive bonding. New methods, such as laser application have been recently introduced for tooth preparation. The purpose of this study was to evaluate the effect of tooth preparation with bur and Er:YAG laser on shear bond strength of composite to enamel and dentin of primary teeth. Materials and Methods: Seventy-five primary molar teeth were collected and 150 specimens were obtained by mesiodistal sectioning of each tooth. In each of the enamel and dentin groups, the teeth were randomly assigned to 3 subgroups with the following preparations: bur preparation + etching (37% H3PO4), laser preparation + etching, and laser preparation without etching. Single Bond adhesive and Z250 composite were applied to all samples. After thermocycling, the shear bond strength testing was preformed using the Instron Testing Machine. Data were analysed using SPSS-17 and two-way ANOVA. Results: The bond strength of enamel specimens was significantly higher than that of dentin specimens, except for the laser-non-etched groups. The enamel and dentin laser-non-etched groups had no significant difference in bond strength. In both enamel and dentin groups, bur preparation + etching yielded the highest bond strength, followed by laser preparation + etching, and the laser preparation without etching yielded the lowest bond strength (P < 0.001). Conclusion: In both enamel and dentin groups, laser preparation caused lower shear bond strength compared to bur preparation. PMID:26622267

  6. Effect of Different Surface Treatments on Repair Micro-shear Bond Strength of Silica- and Zirconia-filled Composite Resins

    PubMed Central

    Joulaei, Mohammad; Bahari, Mahmoud; Ahmadi, Anahid; Savadi Oskoee, Siavash

    2012-01-01

    Background and aims Effect of surface treatments on repair bond strength of aged composite resins might be different due to their dissimilar fillers. The aim was to evaluate the effect of different surface treatments on repair micro-shear bond strength (µSBS) of silica- (Spectrum TPH) and zirconia-filled (Filtek Z250) composite resins. Materials and methods Twenty-seven composite resin blocks were made from each type of composite resin: Z250 and Spectrum TPH. After aging, blocks of each type were randomly divided into three groups according to surface treatments: alloy primer, silane, and only surface roughening. Subsequently, each group was further subdivided into 3 subgroups based on the adhesive system used: Single Bond, Clearfil SE Bond, and Margin Bond. Four composite resin columns were added on each block. After thermocycling, µSBStest were done at cross head speed of 0.5 mm/min. Data was analysed using multifactor ANOVA, one-way ANOVA and a post-hoc Bonferroni tests (α = 0.05). Results Analysis of data showed that the effect of composite resin type was not significant (p > 0.05), but the effects of the type of surface treatment (p = 0.01) and the type of adhesive system (p = 0.01) were significant on repair µSBS. In addition, the cumulative effect of the composite type-surface treatment and the composite type with the type of adhesive system were not statistically significant (p > 0.05). However, the cumulative effects of the adhesive system-surface treatment (p = 0.03) and the composite type-the adhesive system-surface treatments (p = 0.002) were significant. Conclusion Although repair µSBS values of both silica- and zirconia-filled composite resins were similar, use of different combinations of surface treatments and adhesive systems affected their repair µSBS differently. PMID:23277859

  7. An In Vitro Comparative Study of Shear Bond Strength of Composite Resin to Bleached Enamel using Synthetic and Herbal Antioxidants

    PubMed Central

    Suneetha, Ram; Pavithra, S; Thomas, John; Nanga, G Swapna Priya; Shiromany, Aseem; Shivrayan, Amit

    2014-01-01

    Background: The bond strength to bleached enamel is reduced, if adhesive restorations are carried out immediately. So the purpose of this in vitro study was an attempt to regain the lost bond strength, for which, the comparison of shear bond strength of composite resin to bleached enamel was carried out using various antioxidants: 10% Sodium ascorbate, Rosemary extracts, Pedicularis extracts. Materials and Methods: Fifty human extracted single rooted teeth were collected. They were decoronated and coronal portions were embedded in self cure acrylic resin with their buccal surfaces facing upwards. The samples were randomly divided into positive, negative control groups and three experimental groups (n = 10). In positive control group, specimens were not bleached, before bonding procedure. In negative control group, bleaching was done with 10% carbamide peroxide and bonding was carried out immediately. In experimental groups, following antioxidants were used after bleaching: Group A: 10% Sodium ascorbate, Group B: Rosemary extracts, Group C: Pedicularis extracts. Then the bonding procedures were carried out in all the groups and were subjected for shear bond strength analysis. Results: Results clearly showed that groups A and B were effective in reversal of bond strength immediately. Conclusion: 10% sodium ascorbate solution and rosemary extracts were effective in reversal of shear bond strength immediately after bleaching. PMID:25628489

  8. Finite element stress analysis of a notched coupon specimen for in-plane shear behaviour of composites

    NASA Technical Reports Server (NTRS)

    Herakovich, C. T.; Bergner, H. W., Jr.

    1980-01-01

    The results of a linear elastic, plane stress finite element investigation of the stress distribution in a double V-notched coupon specimen are presented for an isotropic material (steel) and five graphite/polyimide laminates: (0), (90), (0/90)s, (plus or minus 45)s and (0/90/plus or minus 45)s. Stress contours, stress profiles, and stress concentration factors are presented for specimens loaded through rigid fixtures. It is shown that the finite element analysis predicts a region of essentially uniform pure shear in the central portion of the specimen for all laminates considered. Stress concentrations vary considerably with laminate configuration. The influences of elastic fixtures and thermal stresses on the stress distribution in (0) laminates are also investigated. The (0) laminate is predicted to exhibit maximum pure shear in the center of the test section for both rigid and elastic fixtures. It is concluded that the specimen is a practicable candidate for use as a composite shear specimen.

  9. Low Activation Joining of SiC/SiC Composites for Fusion Applications: Miniature Torsion Specimen Shear Testing

    SciTech Connect

    Henager, Charles H.; Kurtz, Richard J.; Ventrella, Andrea; Ferraris, Monica

    2011-04-17

    The use of SiC composites in fusion environments likely requires joining of plates using reactive joining or brazing. One promising reactive joining method uses solid-state displacement reactions between Si and TiC to produce Ti3SiC2 + SiC. We continue to explore the processing envelope for this joint for the TITAN collaboration in order to produce optimal joints to undergo irradiation studies in HFIR. The TITAN collaboration has designed miniature torsion joints for preparation, testing, and irradiation in HFIR. PNNL synthesized 40 miniature torsion joints and several were tested for shear strength prior to irradiation testing in HFIR. The resulting tests indicated that (1) joint fixture alignment problems cause joint strengths to be lower than optimal, (2) that non-planar torsion test failures limit the effectiveness of the miniature specimen design, and (3) that several joints that were well aligned had high shear strengths and promising mechanical properties. In summary, we now show conclusively that high joint strengths cause non-planar shear fracture and complicate strength analysis for miniature torsion specimens.

  10. Ultrasonic Welding of Thermoplastic Composite Coupons for Mechanical Characterization of Welded Joints through Single Lap Shear Testing.

    PubMed

    Villegas, Irene F; Palardy, Genevieve

    2016-01-01

    This paper presents a novel straightforward method for ultrasonic welding of thermoplastic-composite coupons in optimum processing conditions. The ultrasonic welding process described in this paper is based on three main pillars. Firstly, flat energy directors are used for preferential heat generation at the joining interface during the welding process. A flat energy director is a neat thermoplastic resin film that is placed between the parts to be joined prior to the welding process and heats up preferentially owing to its lower compressive stiffness relative to the composite substrates. Consequently, flat energy directors provide a simple solution that does not require molding of resin protrusions on the surfaces of the composite substrates, as opposed to ultrasonic welding of unreinforced plastics. Secondly, the process data provided by the ultrasonic welder is used to rapidly define the optimum welding parameters for any thermoplastic composite material combination. Thirdly, displacement control is used in the welding process to ensure consistent quality of the welded joints. According to this method, thermoplastic-composite flat coupons are individually welded in a single lap configuration. Mechanical testing of the welded coupons allows determining the apparent lap shear strength of the joints, which is one of the properties most commonly used to quantify the strength of thermoplastic composite welded joints. PMID:26890931

  11. Shear Bond Strengths of Methacrylate- and Silorane-based Composite Resins to Feldspathic Porcelain using Different Adhesive Systems.

    PubMed

    Mohammadi, Narmin; Shakur Shahabi, Maryam; Kimyai, Soodabeh; Pournagi Azar, Fatemeh; Ebrahimi Chaharom, Mohammad Esmaeel

    2015-01-01

    Background and aims. Use of porcelain as inlays, laminates and metal-ceramic and all-ceramic crowns is common in modern dentistry. The high cost of ceramic restorations, time limitations and difficulty of removing these restorations result in delays in replacing fractured restorations; therefore, their repair is indicated. The aim of the present study was to compare the shear bond strengths of two types of composite resins (methacrylate-based and silorane-based) to porcelain, using three adhesive types. Materials and methods. A total of 156 samples of feldspathic porcelain surfaces were prepared with air-abrasion and randomly divided into 6 groups (n=26). In groups 1-3, Z250 composite resin was used to repair porcelain samples with Ad-per Single Bond 2 (ASB), Clearfil SE Bond (CSB) and Silorane Adhesive (SA) as the bonding systems, afterapplication of silane, respectively. In groups 4-6, the same adhesives were used in the same manner with Filtek Silorane composite resin. Finally, the shear bond strengths of the samples were measured. Two-way ANOVA and post hoc Tukey tests were used to compare bond strengths between the groups with different adhesives at P<0.05. Results. There were significant differences in the mean bond strength values in terms of the adhesive type (P<0.001). In addition, the interactive effect of the adhesive type and composite resin type had no significant effect on bond strength (P=0.602). Conclusion. The results of the present study showed the highest repair bond strength values to porcelain with both composite resin types with the application of SA and ASB. PMID:26697151

  12. Shear Bond Strengths of Methacrylate- and Silorane-based Composite Resins to Feldspathic Porcelain using Different Adhesive Systems

    PubMed Central

    Mohammadi, Narmin; Shakur Shahabi, Maryam; Kimyai, Soodabeh; Pournagi Azar, Fatemeh; Ebrahimi Chaharom, Mohammad Esmaeel

    2015-01-01

    Background and aims. Use of porcelain as inlays, laminates and metal-ceramic and all-ceramic crowns is common in modern dentistry. The high cost of ceramic restorations, time limitations and difficulty of removing these restorations result in delays in replacing fractured restorations; therefore, their repair is indicated. The aim of the present study was to compare the shear bond strengths of two types of composite resins (methacrylate-based and silorane-based) to porcelain, using three adhesive types. Materials and methods. A total of 156 samples of feldspathic porcelain surfaces were prepared with air-abrasion and randomly divided into 6 groups (n=26). In groups 1-3, Z250 composite resin was used to repair porcelain samples with Ad-per Single Bond 2 (ASB), Clearfil SE Bond (CSB) and Silorane Adhesive (SA) as the bonding systems, afterapplication of silane, respectively. In groups 4-6, the same adhesives were used in the same manner with Filtek Silorane composite resin. Finally, the shear bond strengths of the samples were measured. Two-way ANOVA and post hoc Tukey tests were used to compare bond strengths between the groups with different adhesives at P<0.05. Results. There were significant differences in the mean bond strength values in terms of the adhesive type (P<0.001). In addition, the interactive effect of the adhesive type and composite resin type had no significant effect on bond strength (P=0.602). Conclusion. The results of the present study showed the highest repair bond strength values to porcelain with both composite resin types with the application of SA and ASB. PMID:26697151

  13. Advanced composite structures. [metal matrix composites - structural design criteria for spacecraft construction materials

    NASA Technical Reports Server (NTRS)

    1974-01-01

    A monograph is presented which establishes structural design criteria and recommends practices to ensure the design of sound composite structures, including composite-reinforced metal structures. (It does not discuss design criteria for fiber-glass composites and such advanced composite materials as beryllium wire or sapphire whiskers in a matrix material.) Although the criteria were developed for aircraft applications, they are general enough to be applicable to space vehicles and missiles as well. The monograph covers four broad areas: (1) materials, (2) design, (3) fracture control, and (4) design verification. The materials portion deals with such subjects as material system design, material design levels, and material characterization. The design portion includes panel, shell, and joint design, applied loads, internal loads, design factors, reliability, and maintainability. Fracture control includes such items as stress concentrations, service-life philosophy, and the management plan for control of fracture-related aspects of structural design using composite materials. Design verification discusses ways to prove flightworthiness.

  14. Shear bond strength of resin composite bonded with two adhesives: Influence of Er: YAG laser irradiation distance

    PubMed Central

    Shirani, Farzaneh; Birang, Reza; Malekipour, Mohammad Reza; Hourmehr, Zahra; Kazemi, Shantia

    2014-01-01

    Background: Dental surfaces prepared with different Er:YAG laser distance may have different characteristics compared with those prepared with conventional instruments. The aim of this study was to investigate the effect of Er:YAG laser irradiation distance from enamel and dentin surfaces on the shear bond strength of composite with self-etch and etch and rinse bonding systems compared with conventional preparation method. Materials and Methods: Two hundred caries-free human third molars were randomly divided into twenty groups (n = 10). Ten groups were designated for enamel surface (E1-E10) and ten for dentin surface (D1-D10). Er: YAG laser (2940 nm) was used on the E1-E8 (240 mJ, 25 Hz) and D1-D8 (140 mJ, 30 Hz) groups at four different distances of 0.5 (standard), 2, 4 and 11 mm. Control groups (E9, E10, D9 and D10) were ground with medium grit diamond bur. The enamel and dentin specimens were divided into two subgroups that were bonded with either Single Bond or Clearfil SE Bond. Resin composite (Z100) was dispensed on prepared dentin and enamel. The shear bond strengths were tested using a universal testing machine. Data were analyzed by SPSS12 statistical software using three way analysis of variance, Tukey and independent t-test. P < 0.05 was considered as significant. Results: There was a significant difference between enamel and dentin substrates (P < 0.001) and between lased and un-lased groups; the un-lased group had significantly higher bond strength (P < 0.001). Shear bond strength increased significantly with an increase in the laser irradiation distance (P < 0.05) on enamel surfaces (in both bonding agent subgroups) and on dentin surfaces (in the Single Bond subgroup). Conclusion: Laser irradiation decreases shear bond strength. Irradiation distance affects shear bond strength and increasing the distance would decrease the negative effects of laser irradiation. PMID:25540665

  15. Probabilistic Evaluation of Advanced Ceramic Matrix Composite Structures

    NASA Technical Reports Server (NTRS)

    Abumeri, Galib H.; Chamis, Christos C.

    2003-01-01

    The objective of this report is to summarize the deterministic and probabilistic structural evaluation results of two structures made with advanced ceramic composites (CMC): internally pressurized tube and uniformly loaded flange. The deterministic structural evaluation includes stress, displacement, and buckling analyses. It is carried out using the finite element code MHOST, developed for the 3-D inelastic analysis of structures that are made with advanced materials. The probabilistic evaluation is performed using the integrated probabilistic assessment of composite structures computer code IPACS. The affects of uncertainties in primitive variables related to the material, fabrication process, and loadings on the material property and structural response behavior are quantified. The primitive variables considered are: thermo-mechanical properties of fiber and matrix, fiber and void volume ratios, use temperature, and pressure. The probabilistic structural analysis and probabilistic strength results are used by IPACS to perform reliability and risk evaluation of the two structures. The results will show that the sensitivity information obtained for the two composite structures from the computational simulation can be used to alter the design process to meet desired service requirements. In addition to detailed probabilistic analysis of the two structures, the following were performed specifically on the CMC tube: (1) predicted the failure load and the buckling load, (2) performed coupled non-deterministic multi-disciplinary structural analysis, and (3) demonstrated that probabilistic sensitivities can be used to select a reduced set of design variables for optimization.

  16. On fracture phenomena in advanced fiber composite materials.

    NASA Technical Reports Server (NTRS)

    Konish, H. J., Jr.; Swedlow, J. L.; Cruse, T. A.

    1972-01-01

    The extension of linear elastic fracture mechanics (LEFM) from metallic alloys to advanced fiber composite laminates is considered. LEFM is shown to be valid for both isotropic and anisotropic homogeneous continua; the applicability of LEFM to advanced fiber composites is thus dependent on the validity of a homogeneous model of such materials. An experimental program to determine the validity of such a model for graphite/epoxy laminates is reviewed. Such laminates are found to have an apparent fracture toughness, from which it is inferred that a homogeneous material model is valid for the particular specimen geometry and composite laminates considered. Strain energy release rates are calculated from the experimentally determined fracture toughness of the various laminates. These strain energy release rates are found to lie in one of two groups, depending upon whether crack extension required fiber failure or matrix failure. The latter case is further investigated. It is concluded that matrix failure is governed by the tensile stress normal to the crack path.

  17. Orientated Crystallization in Discontinuous Aramid Fiber/isotactic Polypropylene Composites under Shear Flow Conditions

    SciTech Connect

    Larin,B.; Marom, G.; Avila-Orta, C.; Somani, R.Hsiao, B.

    2005-01-01

    Melt blends of short aramid fibers (AF) and isotactic polypropylene (iPP) are subjected to shear at 145 C and the structural evolution and final morphology are examined by in situ synchrotron X-ray scattering/diffraction and high-resolution scanning electron microscopy, respectively. The results indicate that the presence of short AFs significantly enhances the crystallization of iPP. It is argued that shear flow in this system exerts a twofold orientating action, namely, on the bulk iPP molecules and on the short AFs. The resultant crystalline morphology reflects the combined effects of crystallization on orientated iPP molecules to facilitate a shish kebab morphology and at the interface of the aligned fibers, to form transcrystallinity.

  18. A photoelastic investigation of asymmetric four point bend shear test for composite materials

    NASA Technical Reports Server (NTRS)

    Prabhakaran, R.; Sawyer, W.

    1986-01-01

    The shear stress fringe value of orthotropic birefringent model materials is presently used in an asymmetric four-point bend test that employs a notched specimen and is a modification of the Iosipescu test (1967). While in the case of a unidirectionally reinforced glass-polyester model material, shear stress fringe values obtained from 90- and 120-deg (sharp and radiused) notches are reasonably close to the values obtained for an off-axis tensile specimen, no conclusions can be drawn on the influence of the notch parameters, due to the peculiarities of the photoelastic response of the inhomogeneous orthotropic model material. The failure modes nevertheless indicate that a notch radius, and the 120-deg notch angle, reduce the stress concentration. Comparisons are made with finite element results.

  19. Analyses of Failure Mechanisms in Woven Graphite/Polyimide Composites with Medium and High Modulus Graphite Fibers Subjected to In-Plane Shear

    NASA Technical Reports Server (NTRS)

    Kumosa, M.; Armentrout, D.; Rupnowski, P.; Kumosa, L.; Shin, E.; Sutter, J. K.

    2003-01-01

    The application of the Iosipescu shear test for the room and high temperature failure analyses of the woven graphite/polyimide composites with the medium (T-650) and igh (M40J and M60J) modulus graphite fibers is discussed. The M40J/PMR-II-50 and M60J/PMR-II-50 composites were tested as supplied and after thermal conditioning. The effect of temperature and conditioning on the initiation of intralaminar damage and the shear strength of the composites was established.

  20. The Effect of Rheological Parameters on the Ballistic Properties of Shear Thickening Fluid (STF)-Kevlar Composites

    NASA Astrophysics Data System (ADS)

    Wetzel, Eric D.; Lee, Y. S.; Egres, R. G.; Kirkwood, K. M.; Kirkwood, J. E.; Wagner, N. J.

    2004-06-01

    The addition of colloidal shear thickening fluids (STFs) to Kevlar fabrics has been shown to enhance the ballistic penetration resistance of the fabric, under conditions of low velocities and small target sizes. It is believed that this improvement in ballistic properties is related to the resistance of the STF to deformation at high strain rates, since the addition of Newtonian fluids to Kevlar fabric does not improve ballistic performance. However, the precise role of the STF, and its rheological properties, in the ballistic defeat process are not known. In this study, ballistic and rheological experiments are performed to determine the effect of fluid viscosity, particle loadings, and particle size and shape on the behavior of STF-Kevlar composites. These results will be help to determine which rheological parameters are most critical to achieving enhanced composite properties.

  1. Influence of interfacial shear strength on the mechanical properties of SiC fiber reinforced reaction-bonded silicon nitride matrix composites

    NASA Technical Reports Server (NTRS)

    Bhatt, Ramakrishna T.

    1990-01-01

    The influence of fiber/matrix interface microstructure and interfacial shear strength on the mechanical properties of a fiber-reinforced ceramic composite was evaluated. The composite consisted of approximately 30 vol percent uniaxially aligned 142 microns diameter SiC fibers (Textron SCS-6) in a reaction-bonded Si3N4 matrix (SiC/RBSN). The interface microstructure was varied by controlling the composite fabrication conditions and by heat treating the composite in an oxidizing environment. Interfacial shear strength was determined by the matrix crack spacing method. The results of microstructural examination indicate that the carbon-rich coating provided with the as-produced SiC fibers was stable in composites fabricated at 1200 C in a nitrogen or in a nitrogen plus 4 percent hydrogen mixture for 40 hr. However this coating degraded in composites fabricated at 1350 C in N2 + 4 percent H2 for 40 and 72 hr and also in composites heat treated in an oxidizing environment at 600 C for 100 hr after fabrication at 1200 C in a nitrogen. It was determined that degradation occurred by carbon removal which in turn had a strong influence on interfacial shear strength and other mechanical properties. Specifically, as the carbon coating was removed, the composite interfacial shear strength, primary elastic modulus, first matrix cracking stress, and ultimate tensile strength decreased, but the first matrix cracking strain remained nearly the same.

  2. Effect of fabric structure and polymer matrix on flexural strength, interlaminar shear stress, and energy dissipation of glass fiber-reinforced polymer composites

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We report the effect of glass fiber structure and the epoxy polymer system on the flexural strength, interlaminar shear stress (ILSS), and energy absorption properties of glass fiber-reinforced polymer (GFRP) composites. Four different GFRP composites were fabricated from two glass fiber textiles of...

  3. Mechanical Behaviour of Woven Graphite/Polyimide Composites with Medium and High Modulus Graphite Fibers Subjected to Biaxial Shear Dominated Loads

    NASA Technical Reports Server (NTRS)

    Kumose, M.; Gentz, M.; Rupnowski, P.; Armentrout, D.; Kumosa, L.; Shin, E.; Sutter, J. K.

    2003-01-01

    A major limitation of woven fiber/polymer matrix composite systems is the inability of these materials to resist intralaminar and interlaminar damage initiation and propagation under shear-dominated biaxial loading conditions. There are numerous shear test methods for woven fabric composites, each with its own advantages and disadvantages. Two techniques, which show much potential, are the Iosipescu shear and +/- 45 deg tensile tests. In this paper, the application of these two tests for the room and high temperature failure analyses of woven graphite/polyimide composites is briefly evaluated. In particular, visco-elastic micro, meso, and macro-stress distributions in a woven eight harness satin (8HS) T650/PMR-15 composite subjected to these two tests are presented and their effect on the failure process of the composite is evaluated. Subsequently, the application of the Iosipescu tests to the failure analysis of woven composites with medium (T650) and high (M40J and M60J) modulus graphite fibers and PMR-15 and PMR-II-50 polyimide resins is discussed. The composites were tested as-supplied and after thermal conditioning. The effect of temperature and thermal conditioning on the initiation of intralaminar damage and the shear strength of the composites was established.

  4. Investigation of interfacial shear strength in a SiC fibre/Ti-24Al-11Nb composite by a fibre push-out technique

    NASA Technical Reports Server (NTRS)

    Eldridge, J. I.; Brindley, P. K.

    1989-01-01

    A fiber push-out technique applied at several sample thicknesses was used to determine both the debond shear stress and the frictional shear stress at the fiber-matrix interface at room temperautre for a unidirectional SiC fiber-reinforced T-24Al-11Nb (in at. pct) composite prepared by a powder cloth technique. The push-out technique measures the separate contributions of bond strength and friction to the mechanical shear strength at the fiber-matrix interface. It was found that the fiber-matrix bond shear strength of this material is significantly higher than the fiber-matrix frictional shear stress (119.2 and 47.8 MPa, respectively).

  5. 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.

  6. Development of Metal Matrix Composites for NASA's Advanced Propulsion Systems

    NASA Technical Reports Server (NTRS)

    Lee, J.; Elam, S.

    2001-01-01

    The state-of-the-art development of several Metal Matrix Composites (MMC) for NASA's advanced propulsion systems will be presented. The goal is to provide an overview of NASA-Marshall Space Flight Center's on-going activities in MMC components for advanced liquid rocket engines such as the X-33 vehicle's Aerospike engine and X-34's Fastrac engine. The focus will be on lightweight, low cost, and environmental compatibility with oxygen and hydrogen of key MMC materials, within each of NASA's new propulsion application, that will provide a high payoff for NASA's Reusable Launch Vehicles and space access vehicles. In order to fabricate structures from MMC, effective joining methods must be developed to join MMC to the same or to different monolithic alloys. Therefore, a qualitative assessment of MMC's welding and joining techniques will be outlined.

  7. Micromechanical characterization of nonlinear behavior of advanced polymer matrix composites

    NASA Technical Reports Server (NTRS)

    Gates, Thomas S.; Chen, J. L.; Sun, C. T.

    1994-01-01

    Due to the presence of curing stresses and oriented crystalline structures in the matrix of polymer matrix fiber composites, the in situ nonlinear properties of the matrix are expected to be rather different from those of the bulk resin. A plane stress micromechanical model was developed to retrieve the in situ elastic-plastic properties of Narmco 5260 and Amoco 8320 matrices from measured elastic-plastic properties of IM7/5260 and IM7/8320 advance composites. In the micromechanical model, the fiber was assumed to be orthotropically elastic and the matrix to be orthotropic in elastic and plastic properties. The results indicate that both in situ elastic and plastic properties of the matrices are orthotropic.

  8. Ultrasonic and radiographic evaluation of advanced aerospace materials: Ceramic composites

    NASA Technical Reports Server (NTRS)

    Generazio, Edward R.

    1990-01-01

    Two conventional nondestructive evaluation techniques were used to evaluate advanced ceramic composite materials. It was shown that neither ultrasonic C-scan nor radiographic imaging can individually provide sufficient data for an accurate nondestructive evaluation. Both ultrasonic C-scan and conventional radiographic imaging are required for preliminary evaluation of these complex systems. The material variations that were identified by these two techniques are porosity, delaminations, bond quality between laminae, fiber alignment, fiber registration, fiber parallelism, and processing density flaws. The degree of bonding between fiber and matrix cannot be determined by either of these methods. An alternative ultrasonic technique, angular power spectrum scanning (APSS) is recommended for quantification of this interfacial bond.

  9. Advanced composites in sailplane structures: Application and mechanical properties

    NASA Technical Reports Server (NTRS)

    Muser, D.

    1979-01-01

    Advanced Composites in sailplanes mean the use of carbon and aramid fibers in an epoxy matrix. Weight savings were in the range of 8 to 18% in comparison with glass fiber structures. The laminates will be produced by hand-layup techniques and all material tests were done with these materials. These values may be used for calculation of strength and stiffness, as well as for comparison of the materials to get a weight-optimum construction. Proposals for material-optimum construction are mentioned.

  10. Environment enhanced fatigue of advanced aluminum alloys and composites

    NASA Technical Reports Server (NTRS)

    Slavik, Donald C.; Gangloff, Richard P.

    1990-01-01

    The objective is to characterize and understand the environmental fatigue crack propagation behavior of advanced, high stiffness and strength, aluminum alloys and metal matrix composites. Those gases and aqueous electrolytes which are capable of producing atomic hydrogen by reactions on clean crack surfaces are emphasized. Characterizations of the behavior of new materials are sought to provide data for damage tolerant component life prediction. Mechanistic models are sought for crack tip damage processes which are generally applicable to structural aluminum alloys. Such models will enable predictions of cracking behavior outside of the data, metallurgical improvements in material cracking resistance, and insight on hydrogen compatibility.

  11. First NASA Advanced Composites Technology Conference, Part 2

    NASA Technical Reports Server (NTRS)

    Davis, John G., Jr. (Compiler); Bohon, Herman L. (Compiler)

    1991-01-01

    Presented here is a compilation of papers presented at the first NASA Advanced Composites Technology (ACT) Conference held in Seattle, Washington, from 29 Oct. to 1 Nov. 1990. The ACT program is a major new multiyear research initiative to achieve a national goal of technology readiness before the end of the decade. Included are papers on materials development and processing, innovative design concepts, analysis development and validation, cost effective manufacturing methodology, and cost tracking and prediction procedures. Papers on major applications programs approved by the Department of Defense are also included.

  12. Advanced Technology Composite Fuselage - Repair and Damage Assessment Supporting Maintenance

    NASA Technical Reports Server (NTRS)

    Flynn, B. W.; Bodine, J. B.; Dopker, B.; Finn, S. R.; Griess, K. H.; Hanson, C. T.; Harris, C. G.; Nelson, K. M.; Walker, T. H.; Kennedy, T. C.; Nahan, M. F.

    1997-01-01

    Under the NASA-sponsored contracts for Advanced Technology Composite Aircraft Structures (ATCAS) and Materials Development Omnibus Contract (MDOC), Boeing is studying the technologies associated with the application of composite materials to commercial transport fuselage structure. Included in the study is the incorporation of maintainability and repairability requirements of composite primary structure into the design. This contractor report describes activities performed to address maintenance issues in composite fuselage applications. A key aspect of the study was the development of a maintenance philosophy which included consideration of maintenance issues early in the design cycle, multiple repair options, and airline participation in design trades. Fuselage design evaluations considered trade-offs between structural weight, damage resistance/tolerance (repair frequency), and inspection burdens. Analysis methods were developed to assess structural residual strength in the presence of damage, and to evaluate repair design concepts. Repair designs were created with a focus on mechanically fastened concepts for skin/stringer structure and bonded concepts for sandwich structure. Both a large crown (skintstringer) and keel (sandwich) panel were repaired. A compression test of the keel panel indicated the demonstrated repairs recovered ultimate load capability. In conjunction with the design and manufacturing developments, inspection methods were investigated for their potential to evaluate damaged structure and verify the integrity of completed repairs.

  13. Composite Fan Blade Design for Advanced Engine Concepts

    NASA Technical Reports Server (NTRS)

    Abumeri, Galib H.; Kuguoglu, Latife H.; Chamis, Christos C.

    2004-01-01

    The aerodynamic and structural viability of composite fan blades of the revolutionary Exo-Skeletal engine are assessed for an advanced subsonic mission using the NASA EST/BEST computational simulation system. The Exo-Skeletal Engine (ESE) calls for the elimination of the shafts and disks completely from the engine center and the attachment of the rotor blades in spanwise compression to a rotating casing. The fan rotor overall adiabatic efficiency obtained from aerodynamic analysis is estimated at 91.6 percent. The flow is supersonic near the blade leading edge but quickly transitions into a subsonic flow without any turbulent boundary layer separation on the blade. The structural evaluation of the composite fan blade indicates that the blade would buckle at a rotor speed that is 3.5 times the design speed of 2000 rpm. The progressive damage analysis of the composite fan blade shows that ply damage is initiated at a speed of 4870 rpm while blade fracture takes place at 7640 rpm. This paper describes and discusses the results for the composite blade that are obtained from aerodynamic, displacement, stress, buckling, modal, and progressive damage analyses. It will be demonstrated that a computational simulation capability is readily available to evaluate new and revolutionary technology such as the ESE.

  14. 24% Indigenously Prepared Ethylene Diamine Tetra Acetic Acid Compared to Self-Etching Adhesives and their Effect on Shear Bond Strength of Composites in Primary Teeth: An In-vitro Study

    PubMed Central

    Nagar, Priya; Tandil, Yogesh L.; T.P., Chandru; Gupta, Anamika; Kalaria, Devendra; Kumar, Prafful

    2015-01-01

    Background: Over the years, it has been known that 34% phosphoric acid is the benchmark in etchants with the best shear bond strength shown with composites in primary teeth. However, with latest technological advancements and innovations, in order to reduce the number of steps and less damage to the tooth structure, non-rinse conditioner (NRC) & Single-Etch and various other etchants have been tried and tested. These etchants have been found to have shear bond strength comparable to phosphoric acid. In this study, indigenously prepared 24% ethylenediaminetetraacetic acid (EDTA) has been compared with established etchants, as to prove if their shear bond strength was closely related. As it is a well-known fact that EDTA could be less damaging to the enamel during etching and hence can be an alternative for etching of primary teeth. Materials and Methods: For the study 60 caries-free primary molars were used, they were sectioned in the middle, after making area for bonding; the marked area was then etched using different etchants for 30 s. Each of the teeth was then rinsed and bonded with composite resin and thermocycling was done. Shear bond strength testing was done on the composite using Universal Testing Machine. Results: Results of the study showed that phosphoric acid showed the highest bond strength, closely followed by Single Etch (Adper Prompt) and NRC, then by EDTA. Conclusions: About 24% EDTA can be another comparable replacement for phosphoric acid if used with a Single Etch Primer, like Prime and Bond NT on primary teeth. 34% phosphoric acid has the highest bond strength values with composite resin. Single etch followed by NRC has the second and third highest bond strength values, which are comparable to phosphoric acid. PMID:26464540

  15. Experimental, numerical, and analytical studies on the seismic response of steel-plate concrete (SC) composite shear walls

    NASA Astrophysics Data System (ADS)

    Epackachi, Siamak

    The seismic performance of rectangular steel-plate concrete (SC) composite shear walls is assessed for application to buildings and mission-critical infrastructure. The SC walls considered in this study were composed of two steel faceplates and infill concrete. The steel faceplates were connected together and to the infill concrete using tie rods and headed studs, respectively. The research focused on the in-plane behavior of flexure- and flexure-shear-critical SC walls. An experimental program was executed in the NEES laboratory at the University at Buffalo and was followed by numerical and analytical studies. In the experimental program, four large-size specimens were tested under displacement-controlled cyclic loading. The design variables considered in the testing program included wall thickness, reinforcement ratio, and slenderness ratio. The aspect ratio (height-to-length) of the four walls was 1.0. Each SC wall was installed on top of a re-usable foundation block. A bolted baseplate to RC foundation connection was used for all four walls. The walls were identified to be flexure- and flexure-shear critical. The progression of damage in the four walls was identical, namely, cracking and crushing of the infill concrete at the toes of the walls, outward buckling and yielding of the steel faceplates near the base of the wall, and tearing of the faceplates at their junctions with the baseplate. A robust finite element model was developed in LS-DYNA for nonlinear cyclic analysis of the flexure- and flexure-shear-critical SC walls. The DYNA model was validated using the results of the cyclic tests of the four SC walls. The validated and benchmarked models were then used to conduct a parametric study, which investigated the effects of wall aspect ratio, reinforcement ratio, wall thickness, and uniaxial concrete compressive strength on the in-plane response of SC walls. Simplified analytical models, suitable for preliminary analysis and design of SC walls, were

  16. An in vitro evaluation of shear bond strength of silorane and bis-GMA resin-based composite using different curing units

    PubMed Central

    Khosla, Manak; Malhotra, Neeraj; Mala, Kundabala

    2012-01-01

    Aim: To evaluate shear bond strength of silorane and bis-GMA based composite resins using self-etch and total-etch adhesive systems, and compare the effect of Quartz-tungten-halogen (QTH) and Light emitting diode (LED) on the shear bond strength of the experimental materials. Materials and Methods: Flat dentin surfaces were exposed on intact extracted molars and composite resin was built 2 mm in diameter. Teeth were divided randomly into four groups. Groups 1 and 2 were restored with P90 system adhesive and Filtek P90 and cured with QTH and LED units respectively. Groups 3 and 4 were restored with total etch adhesive and Filtek Z100 and cured with QTH and LED units respectively. Specimens were subjected to shear bond strength testing using Instrom Universal testing machine. Results: Data was subjected to one-way analysis of variance. Total-etch groups gave significantly higher shear bond strength values than the self-etch groups. No significant difference in shear bond strength was found between Groups 3 and 4, while Group 1 showed significantly higher values than Group 2. Conclusion: Type of light curing unit is not a significant factor affecting shear bond strength for bis-GMA RBCs using total-etch technique; while for curing silorane resin based composite (RBCs), conventional halogen curing units showed better results. PMID:22876019

  17. Evaluation of a metal shear web selectively reinforced with filamentary composites for space shuttle application. Phase 2: summary report: Shear web component fabrication

    NASA Technical Reports Server (NTRS)

    Laakso, J. H.; Smith, D. D.; Zimmerman, D. K.

    1973-01-01

    The fabrication of two shear web test elements and three large scale shear web test components are reported. In addition, the fabrication of test fixtures for the elements and components is described. The center-loaded beam test fixtures were configured to have a test side and a dummy or permanent side. The test fixtures were fabricated from standard extruded aluminum sections and plates and were designed to be reuseable.

  18. Geometrically nonlinear free vibration of shear deformable piezoelectric carbon nanotube/fiber/polymer multiscale laminated composite plates

    NASA Astrophysics Data System (ADS)

    Rafiee, M.; Liu, X. F.; He, X. Q.; Kitipornchai, S.

    2014-07-01

    The nonlinear free vibration of carbon nanotubes/fiber/polymer composite (CNTFPC) multi-scale plates with surface-bonded piezoelectric actuators is studied in this paper. The governing equations of the piezoelectric nanotubes/fiber/polymer multiscale laminated composite plates are derived based on first-order shear deformation plate theory (FSDT) and von Kármán geometrical nonlinearity. Halpin-Tsai equations and fiber micromechanics are used in hierarchy to predict the bulk material properties of the multiscale composite. The carbon nanotubes are assumed to be uniformly distributed and randomly oriented through the epoxy resin matrix. A perturbation scheme of multiple time scales is employed to determine the nonlinear vibration response and the nonlinear natural frequencies of the plates with immovable simply supported boundary conditions. The effects of the applied constant voltage, plate geometry, volume fraction of fibers and weight percentage of single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs) on the linear and nonlinear natural frequencies of the piezoelectric nanotubes/fiber/polymer multiscale composite plate are investigated through a detailed parametric study.

  19. Vibroacoustic behavior and noise control studies of advanced composite structures

    NASA Astrophysics Data System (ADS)

    Li, Deyu

    The research presented in this thesis is devoted to the problems of sound transmission and noise transmission control for advanced composite payload fairings. There are two advanced composite fairings under study. The first is a tapered, cylindrical advanced grid-stiffened composite fairing, and the second is a cylindrical ChamberCore composite fairing. A fully coupled mathematical model for characterizing noise transmission into a finite elastic cylindrical structure with application to the ChamberCore fairing is developed. It combines advantages of wave radiation principles and structural-acoustic modal interaction, and provides an ideal noise transmission model that can be extended to other finite cylindrical structures. Structural-acoustic dynamic parameters of the two fairings are obtained using a combination of numerical, analytical, and experimental approaches. An in-situ method for experimentally characterizing sound transmission into the fairings called noise reduction spectrum (NRS) is developed based on noise reduction. The regions of interest in the NRS curves are identified and verified during a passive control investigation, where various fill materials are added into wall-chambers of the ChamberCore fairing. Both Helmholtz resonators (HRs) and long T-shaped acoustic resonators (ARs) are also used to successfully control noise transmission into the ChamberCore fairing. In the process, an accurate model for the resonant frequency calculation and design of cylindrical HRs is derived. Further, a novel and more general model for the design of multi-modal, long, T-shaped ARs is developed, including three new end-correction equations that are validated experimentally. The control results show that noise attenuation is significant in the controlled modes, and the control is also observed in some modes that are not targeted, due to acoustic modal coupling via the structure. Helmholtz resonators are found to produce between 2.0 and 7.7 dB increase in NRS in

  20. Exudate protein composition and Warner-Bratzler shear force in broiler breast fillets

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Muscle exudate is often associated with pale color and poor water-holding capacity in broiler breast meat. The relationship between exudate protein composition and breast meat tenderness is unknown. The objective of this study was to determine the relationship between exudate protein composition a...

  1. Ultrasonics transduction in metallic and composite structures for structural health monitoring using extensional and shear horizontal piezoelectric wafer active sensors

    NASA Astrophysics Data System (ADS)

    Abdelrahman, Ayman Kamal

    Structural health monitoring (SHM) is crucial for monitoring structures performance, detecting the initiation of flaws and damages, and predicting structural life span. The dissertation emphasizes on developing analytical and numerical models for ultrasonics transduction between piezoelectric wafer active sensors (PWAS), and metallic and composite structures. The first objective of this research is studying the power and energy transduction between PWAS and structure for the aim of optimizing guided waves mode tuning and PWAS electromechanical (E/M) impedance for power-efficient SHM systems. Analytical models for power and energy were developed based on exact Lamb wave solution with application on multimodal Lamb wave situations that exist at high excitation frequencies and/or relatively thick structures. Experimental validation was conducted using Scanning Laser Doppler Vibrometer. The second objective of this work focuses on shear horizontal (SH) PWAS which are poled in thickness-shear direction (d35 mode). Analytical and finite element predictive models of the E/M impedance of free and bonded SH-PWAS were developed. Next, the wave propagation method has been considered for isotropic materials. Finally, the power and energy of SH waves were analytically modeled and a MATLAB graphical user interface (GUI) was developed for determining phase and group velocities, mode shapes, and energy of SH waves. The third objective focuses on guided wave propagation in composites. The transfer matrix method (TMM) has been used to calculate dispersion curves of guided waves in composites. TMM suffers numerical instability at high frequency-thickness values, especially in multilayered composites. A method of using stiffness matrix method was investigated to overcome instability. A procedure of using combined stiffness transfer matrix method (STMM) was presented and coded in MATLAB. This was followed by a comparative study between commonly used methods for the calculation of

  2. Design synthesis of a boron/epoxy reinforced metal shear web.

    NASA Technical Reports Server (NTRS)

    Laakso, J. H.

    1972-01-01

    An advanced composite shear web design concept has been developed for the Space Shuttle Orbiter main engine thrust beam structure. Various web concepts were synthesized by a computer-aided adaptive random search procedure. A practical concept is identified having a titanium-clad, boron/epoxy plate with vertical boron/epoxy reinforced stiffeners. Baseline composite and titanium shear resistant designs are compared; the composite concept is 28% lighter than the titanium web. Element test results show the metal cladding effectively reinforces critical composite load transfer and fastener hole areas making the composite web concept practical for other shear structure applications.-

  3. Micromechanics Based Design/Analysis Codes for Advanced Composites

    NASA Technical Reports Server (NTRS)

    Mital, Subodh K.; Murthy, Pappu L. N.; Gyekenyesi, John P.

    2002-01-01

    Advanced high temperature Ceramic Matrix Composites (CMC) hold an enormous potential for use in aero and space related applications specifically for propulsion system components. Consequently, this has led to a multitude of research activities pertaining to fabrication, testing and modeling of these materials. The efforts directed at the development of ceramic matrix composites have focused primarily on improving the properties of the constituents as individual phases. It has, however, become increasingly clear that for CMC to be successfully employed in high temperature applications, research and development efforts should also focus on optimizing the synergistic performance of the constituent phases within the as-produced microstructure of the complex shaped CMC part. Despite their attractive features, the introduction of these materials in a wide spectrum of applications has been excruciatingly slow. The reasons are the high costs associated with the manufacturing and a complete experimental testing and characterization of these materials. Often designers/analysts do not have a consistent set of necessary properties and design allowables to be able to confidently design and analyze structural components made from these composites. Furthermore, the anisotropy of these materials accentuates the burden both on the test engineers and the designers by requiring a vastly increased amount of data/characterization compared to conventional materials.

  4. Effect of fiber on shear-induced crystallization of i-PP in UHMWPE/i-PP and Aramid/i-PP fiber composites

    NASA Astrophysics Data System (ADS)

    Avila-Orta, Carlos; Somani, Rajesh; Yang, Ling; Hsiao, Benjamin; Marom, Gad

    2003-03-01

    Shear-induced crystallization of the isotactic polypropylene (i-PP) matrix in fiber composites containing ultra high molecular weight polyethylene (UHMWPE) fibers or Aramid fibers was studied by in-situ synchrotron small-angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS) techniques. The maximum fiber content was 10 wt composite and the shearing conditions included the application of step shear with rate = 60 1/s and duration time = 5 s at 145 ^oC. The development of lamellar structures (by SAXS) and crystal orientation (by WAXS) was strongly affected by the type of fiber present. It was found that Kebab structures were more likely to develop in the presence of UHMWPE fiber than Aramid fiber. In addition, the orientation of i-PP lamellae was greater in the UHMWPE composite than that in the Aramid composite, even though the crystallization rate was similar in both systems. As the UHMWPE phase was non-crystalline at the measurement temperature (145 ^oC), our results suggest that a high degree of molecular interactions between the oriented PE chains and the surrounding iPP chains makes the molten UHMWPE phase an effective nucleating agents for iPP crystallization under shear. The epitaxial effect of Aramid fiber on the crystallization of iPP was not a dominating factor under the shear conditions.

  5. The effects of different surface treatments on the shear bond strength of composite resin to machined titanium

    NASA Astrophysics Data System (ADS)

    Aljadi, Mohammad

    Purpose: The purpose of this study was to evaluate the shear bond strength between machined titanium and composite resin using different surface treatments. Materials and Methods: Titanium (Ti-6Al-4V) specimens were ground with 600 grit SiC paper and randomly divided into 6 groups (n=20/group). Group #1 (Control): samples were sandblasted with 110 microm Al2 O3 for 10 sec. Group #2 (Rocatec): samples were treated with the Rocatec system following the manufacturer's directions but the silanization step was eliminated. Group #3 (Silano Pen): samples were treated with the Silano Pen system. Group #4 (H2SO4 etched): samples were sandblasted with 110 microm Al2O3 for 10 sec and etched with 48% H2SO4 for 60 minutes at 60 oC. Group#5 (acid etching + Rocatec): samples received both treatments as described in Groups 4 and 2, respectively. Group #6 (acid etching + Silano Pen): samples received both treatments as described in Groups 4 and 3, respectively. Composite was bonded to the treated titanium surface, half of the specimens from each group (n=10/group) were subjected to thermocycling, and the samples were tested for shear bond strength in a universal testing machine. Representative samples from each group were evaluated with SEM. Results: Two-way ANOVA revealed that there were significant differences (p < 0.05) in bond strength between the six groups of surface treatment and that thermocycling significantly decreased shear bond strength. There was no significant interaction (p = 0.07) between surface treatment and thermocycling status. With regard to the effect of surface treatment, a Tukey Post Hoc test showed that groups 3 (Silano Pen) and 6 (Silano Pen + H2SO4) showed significantly (p < 0.05) greater bond strengths compared to the rest of the groups. There was no significant difference in the bond strength between the four other groups. Conclusion: 1) Silano Pen is effective in improving the bond strength of titanium to composite resin. 2) The silanization step in

  6. Shear wave velocity structure of the lower crust in southern Africa: Evidence for compositional heterogeneity within Archaean and Proterozoic terrains

    NASA Astrophysics Data System (ADS)

    Kgaswane, Eldridge M.; Nyblade, Andrew A.; Juliã, Jordi; Dirks, Paul H. G. M.; Durrheim, Raymond J.; Pasyanos, Michael E.

    2009-12-01

    The nature of the lower crust across the southern African shield has been investigated by jointly inverting receiver functions and Rayleigh wave group velocities for 89 broadband seismic stations located in Botswana, South Africa and Zimbabwe. For large parts of both Archaean and Proterozoic terrains, the velocity models obtained from the inversions show shear wave velocities ≥4.0 km/s below ˜20-30 km depth, indicating a predominantly mafic lower crust. However, for much of the Kimberley terrain and adjacent parts of the Kheis Province and Witwatersrand terrain in South Africa, as well as for the western part of the Tokwe terrain in Zimbabwe, shear wave velocities of ≤3.9 km/s are found below ˜20-30 km depth, indicating an intermediate-to-felsic lower crust. The areas of intermediate-to-felsic lower crust in South Africa coincide with regions where Ventersdorp rocks have been preserved, suggesting that the more evolved composition of the lower crust may have resulted from crustal reworking and extension during the Ventersdorp tectonomagmatic event at c. 2.7 Ga.

  7. Advanced Constituents and Processes for Ceramic Composite Engine Components

    NASA Technical Reports Server (NTRS)

    Yun, H. M.; DiCarlo, J. A.; Bhatt, R. T.

    2004-01-01

    The successful replacement of metal alloys by ceramic matrix composites (CMC) in hot-section engine components will depend strongly on optimizing the processes and properties of the CMC microstructural constituents so that they can synergistically provide the total CMC system with improved temperature capability and with the key properties required by the components for long-term structural service. This presentation provides the results of recent activities at NASA aimed at developing advanced silicon carbide (Sic) fiber-reinforced hybrid Sic matrix composite systems that can operate under mechanical loading and oxidizing conditions for hundreds of hours at 2400 and 2600 F, temperatures well above current metal capability. These SiC/SiC composite systems are lightweight (-30% metal density) and, in comparison to monolithic ceramics and carbon fiber-reinforced ceramic composites, are able to reliably retain their structural properties for long times under aggressive engine environments. It is shown that the improved temperature capability of the SiC/SiC systems is related first to the NASA development of the Sylramic-iBN Sic fiber, which displays high thermal stability, creep resistance, rupture resistance, and thermal conductivity, and possesses an in-situ grown BN surface layer for added environmental durability. This fiber is simply derived from Sylramic Sic fiber type that is currently produced at ATK COI Ceramics. Further capability is then derived by using chemical vapor infiltration (CVI) to form the initial portion of the hybrid Sic matrix. Because of its high creep resistance and thermal conductivity, the CVI Sic matrix is a required base constituent for all the high temperature SiC/SiC systems. By subsequently thermo- mechanical-treating the CMC preform, which consists of the S ylramic-iBN fibers and CVI Sic matrix, process-related defects in the matrix are removed, further improving matrix and CMC creep resistance and conductivity.

  8. Short-wavelength buckling and shear failures for compression-loaded composite laminates. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Shuart, M. J.

    1985-01-01

    The short-wavelength buckling (or the microbuckling) and the interlaminar and inplane shear failures of multi-directional composite laminates loaded in uniaxial compression are investigated. A laminate model is presented that idealizes each lamina. The fibers in the lamina are modeled as a plate, and the matrix in the lamina is modeled as an elastic foundation. The out-of-plane w displacement for each plate is expressed as a trigonometric series in the half-wavelength of the mode shape for laminate short-wavelength buckling. Nonlinear strain-displacement relations are used. The model is applied to symmetric laminates having linear material behavior. The laminates are loaded in uniform end shortening and are simply supported. A linear analysis is used to determine the laminate stress, strain, and mode shape when short-wavelength buckling occurs. The equations for the laminate compressive stress at short-wavelength buckling are dominated by matrix contributions.

  9. Advances in electromagnetic models for three-dimensional nondestructive evaluation of advanced composites

    NASA Astrophysics Data System (ADS)

    Sabbagh, Harold A.; Murphy, R. Kim; Sabbagh, Elias H.

    2016-02-01

    In past work we have developed a rigorous electromagnetic model and an inversion algorithm for the three-dimensional NDE of advanced composite materials. This approach extends Victor Technologies' work in eddy-current NDE of conventional metals, and allows one to determine in localized regions the fiber-resin ratio in graphite-epoxy, and to determine those anomalies, e.g., delaminations, broken fibers, moisture content, etc., that can be reconstructed by our inversion method. In developing the model, we applied rigorous electromagnetic theory to determine a Green's function for a slab of anisotropic composite material, and then determine the integral relations for the forward and inverse problems using the Green's function. In addition, we have given examples of the solution of forward and inverse problems using these algorithms.

  10. Comparison of Shear Bond Strength of Composite to Stainless Steel Crowns Using Two Mechanical Surface Treatments and Two Bonding Systems

    PubMed Central

    Ghadimi, Sara; Heidari, Alireza

    2016-01-01

    Objectives: This study aimed to compare the shear bond strength (SBS) of composite to stainless steel crowns (SSC) using two mechanical surface treatments (MSTs) and two bonding systems. Materials and Methods: Eighty-four SSCs were divided into six groups of 14; Group1: No MST+Scotchbond Universal adhesive (N+U), Group 2: Surface roughening by a diamond bur+Scotchbond Universal adhesive (R+U), Group 3: Sandblasting+Scotchbond Universal adhesive (S+U), Group 4: No MST+Alloy Primer+Clearfil SE Primer and Bond (N+A), Group 5: Surface roughening by a diamond bur+Alloy Primer+Clearfil SE Primer and Bond (R+A), Group 6: Sandblasting+Alloy Primer+Clearfil SE Primer and Bond (S+A). After MST and bonding procedure, composite cylinders were bonded to the lingual surface of SSCs, then the SBS of composite to SSCs was measured using a universal testing machine following thermocycling. Results: The SBS of groups R+U and S+U was significantly higher than that of group N+U. No significant difference was noted in SBS of groups R+U and S+U. The SBS of group S+A was significantly higher than that of groups N+A and R+A. No significant difference was noted in the SBS of groups N+A and R+A (P>0.05). Conclusions: In Scotchbond Universal adhesive groups, sandblasting and surface roughening by diamond bur significantly increased the SBS of composite to SSCs compared to no MST. In Alloy Primer groups, sandblasting significantly increased the SBS of composite to SSC compared to surface roughening with diamond bur and no MST. PMID:27536330

  11. Advanced composite aileron for L-1011 transport aircraft

    NASA Technical Reports Server (NTRS)

    1978-01-01

    Design and evaluation of alternate concepts for the major subcomponents of the advanced composite aileron (ACA) was completed. From this array of subcomponents, aileron assemblies were formulated and evaluated. Based on these analyses a multirib assembly with graphite tape/syntactic core covers, a graphite tape front spar, and a graphite fabric rib was selected for development. A weight savings of 29.1 percent (40.8 pounds per aileron) is predicted. Engineering cost analyses indicate that the production cost of the ACA will be 7.3 percent less than the current aluminum aileron. Fabrication, machining, and testing of the material evaluation specimens for the resin screening program was completed. The test results lead to the selection of Narmco 5208 resin for the ACA. Other activities completed include: the detailed design of the ACA, construction of a three dimensional finite element model for structural analysis, and formulation of detail plans for material verification and process development.

  12. Advanced composite aileron for L-1011 transport aircraft: Aileron manufacture

    NASA Technical Reports Server (NTRS)

    Dunning, E. G.; Cobbs, W. L.; Legg, R. L.

    1981-01-01

    The fabrication activities of the Advanced Composite Aileron (ACA) program are discussed. These activities included detail fabrication, manufacturing development, assembly, repair and quality assurance. Five ship sets of ailerons were manufactured. The detail fabrication effort of ribs, spar and covers was accomplished on male tools to a common cure cycle. Graphite epoxy tape and fabric and syntactic epoxy materials were utilized in the fabrication. The ribs and spar were net cured and required no post cure trim. Material inconsistencies resulted in manufacturing development of the front spar during the production effort. The assembly effort was accomplished in subassembly and assembly fixtures. The manual drilling system utilized a dagger type drill in a hydraulic feed control hand drill. Coupon testing for each detail was done.

  13. Structural Assessment of Advanced Composite Tow-Steered Shells

    NASA Technical Reports Server (NTRS)

    Wu, K. Chauncey; Stanford, Bret K.; Hrinda, Glenn A.; Wang, Zhuosong; Martin, Robert a.; Kim, H. Alicia

    2013-01-01

    The structural performance of two advanced composite tow-steered shells, manufactured using a fiber placement system, is assessed using both experimental and analytical methods. The fiber orientation angles vary continuously around the shell circumference from 10 degrees on the shell crown and keel, to 45 degrees on the shell sides. The two shells differ in that one shell has the full 24-tow course applied during each pass of the fiber placement system, while the second shell uses the fiber placement system s tow drop/add capability to achieve a more uniform shell wall thickness. The shells are tested in axial compression, and estimates of their prebuckling axial stiffnesses and bifurcation buckling loads are predicted using linear finite element analyses. These preliminary predictions compare well with the test results, with an average agreement of approximately 10 percent.

  14. Advanced Measurements of Silicon Carbide Ceramic Matrix Composites

    SciTech Connect

    Farhad Farzbod; Stephen J. Reese; Zilong Hua; Marat Khafizov; David H. Hurley

    2012-08-01

    Silicon carbide (SiC) is being considered as a fuel cladding material for accident tolerant fuel under the Light Water Reactor Sustainability (LWRS) Program sponsored by the Nuclear Energy Division of the Department of Energy. Silicon carbide has many potential advantages over traditional zirconium based cladding systems. These include high melting point, low susceptibility to corrosion, and low degradation of mechanical properties under neutron irradiation. In addition, ceramic matrix composites (CMCs) made from SiC have high mechanical toughness enabling these materials to withstand thermal and mechanical shock loading. However, many of the fundamental mechanical and thermal properties of SiC CMCs depend strongly on the fabrication process. As a result, extrapolating current materials science databases for these materials to nuclear applications is not possible. The “Advanced Measurements” work package under the LWRS fuels pathway is tasked with the development of measurement techniques that can characterize fundamental thermal and mechanical properties of SiC CMCs. An emphasis is being placed on development of characterization tools that can used for examination of fresh as well as irradiated samples. The work discuss in this report can be divided into two broad categories. The first involves the development of laser ultrasonic techniques to measure the elastic and yield properties and the second involves the development of laser-based techniques to measurement thermal transport properties. Emphasis has been placed on understanding the anisotropic and heterogeneous nature of SiC CMCs in regards to thermal and mechanical properties. The material properties characterized within this work package will be used as validation of advanced materials physics models of SiC CMCs developed under the LWRS fuels pathway. In addition, it is envisioned that similar measurement techniques can be used to provide process control and quality assurance as well as measurement of

  15. Conceptual design study of advanced acoustic-composite nacelles

    NASA Technical Reports Server (NTRS)

    Nordstrom, K. E.; Marsh, A. H.; Sargisson, D. F.

    1975-01-01

    Conceptual studies were conducted to assess the impact of incorporating advanced technologies in the nacelles of a current wide-bodied transport and an advanced technology transport. The improvement possible in the areas of fuel consumption, flyover noise levels, airplane weight, manufacturing costs, and airplane operating cost were evaluated for short and long-duct nacelles. Use of composite structures for acoustic duct linings in the fan inlet and exhaust ducts was considered as well as for other nacelle components. For the wide-bodied transport, the use of a long-duct nacelle with an internal mixer nozzle in the primary exhaust showed significant improvement in installed specific fuel consumption and airplane direct operating costs compared to the current short-duct nacelle. The long-duct mixed-flow nacelle is expected to achieve significant reductions in jet noise during takeoff and in turbo-machinery noise during landing approach. Recommendations were made of the technology development needed to achieve the potential fuel conservation and noise reduction benefits.

  16. Factors Affecting Fiber Design and Selection for Advanced Ceramic Composites

    NASA Technical Reports Server (NTRS)

    DiCarlo, James A.

    1998-01-01

    Structural Ceramic Matrix Composites (CMC) have the potential for application in the hot sections of a variety of advanced propulsion and power systems. It is therefore necessary to have a general understanding of the key properties of CMC and Reinforcing Fibers. This need is complicated by the wide variety of application conditions and structural requirements for which CMC's will be used, and the proprietary concerns of the design engineers. CMC's, to be successful, must display properties which are competitive with the currently used high temperature structural materials: (i.e., Iron and Nickel based superalloys, tough monolithic ceramics, and carbon/carbon composites.) Structural CMC offers several areas of competition: (1) performance, (i.e., strength and strength retention, creep resistance, and thermal conductivity), (2) reliability (i.e., environmental durability, and damage tolerance) and (3) processing (i.e., capability for varying sizes and shapes, and cost effective fabrication). The presentation further discusses, and illustrates with fiber and CMC data the key fiber properties and processes which strongly affect each CMC area of competition. The presentation further discusses the current knowledge of the important factors which control the key fiber properties. A design guidelines for the optimum fiber characteristics is developed, and the currently available fibers are compared against those guidelines.

  17. Atmosphere composition monitor for space station and advanced missions application

    SciTech Connect

    Wynveen, R.A.; Powell, F.T.

    1987-01-01

    Long-term human occupation of extraterrestrial locations may soon become a reality. The National Aeronautics and Space Administration (NASA) has recently completed the definition and preliminary design of the low earth orbit (LEO) space station. They are now currently moving into the detailed design and fabrication phase of this space station and are also beginning to analyze the requirements of several future missions that have been identified. These missions include, for example, Lunar and Mars sorties, outposts, bases, and settlements. A requirement of both the LEO space station and future missions are environmental control and life support systems (ECLSS), which provide a comfortable environment for humans to live and work. The ECLSS consists of several major systems, including atmosphere revitalization system (ARS), atmosphere pressure and composition control system, temperature and humidity control system, water reclamation system, and waste management system. Each of these major systems is broken down into subsystems, assemblies, units, and instruments. Many requirements and design drivers are different for the ECLSS of the LEO space station and the identified advanced missions (e.g., longer mission duration). This paper discusses one of the ARS assemblies, the atmosphere composition monitor assembly (ACMA), being developed for the LEO space station and addresses differences that will exist for the ACMA of future missions.

  18. Steady-state creep of bent reinforced metal-composite plates with consideration of their reduced resistance to transverse shear. 1. Deformation model

    NASA Astrophysics Data System (ADS)

    Yankovskii, A. P.

    2014-05-01

    The problem of deformation of reinforced metal-composite plates is formulated in rectangular Cartesian coordinates using the second version of Timoshenko theory and taking into account the reduced transverse shear resistance of the plates under steady-state creep conditions. A similar model problem of axisymmetric bending of reinforced plates is considered in polar coordinates.

  19. Design, fabrication and test of graphite/polyimide composite joints and attachments for advanced aerospace vehicles

    NASA Technical Reports Server (NTRS)

    Barclay, D. L.

    1980-01-01

    Results of an experimental program to develop several types of graphite/polyimide (GR/PI) bonded and bolted joints for lightly loaded flight components for advanced space transportation systems and high speed aircraft are presented. Tasks accomplished include: a literature survey; design of static discriminator specimens; design allowables testing; fabrication of test panels and specimens; small specimen testing; and standard joint testing. Detail designs of static discriminator specimens for each of the four major attachment types are presented. Test results are given for the following: (1) transverse tension of Celion 3000/PMR-15 laminate; (2) net tension of a laminate for both a loaded and unloaded bolt hole; (3) comparative testing of bonded and co-cured doublers along with pull-off tests of single and double bonded angles; (4) single lap shear tests, transverse tension and coefficient of thermal expansion tests of A7F (LARC-13 amide-imide modified) adhesive; and (5) tension tests of standard single lap, double lap, and symmetric step lap bonded joints. Also, included are results of a finite element analysis of a single lap bonded composite joint.

  20. Role of multiwalled carbon nanotube in interlaminar shear strength of epoxy/glass fiber/multi walled carbon nanotube hybrid composites

    NASA Astrophysics Data System (ADS)

    Srinivasan Chandrasekaran, Vasan Churchill

    2011-12-01

    The motivation of this thesis is to investigate the role of multi-walled carbon nanotube (MWCNT) in enhancing the interlaminar shear strength (ILSS) of hybrid composites. The objective of this thesis is to understand the relationships between processing history, material variability, matrix properties, glass fiber/matrix interface properties and their correlations with interlaminar shear strength of hybrid composites. The interlaminar shear strength (ILSS) of hybrid composites made from glass fiber and multi-walled carbon nanotube (MWCNT) modified epoxy is compared with that for unmodified epoxy/glass fiber composites (control). By combining the techniques of high speed mechanical stirring and ultrasonic agitation, 0.5% MWCNT by weight were dispersed in epoxy to prepare a suspension. Composites were manufactured by both injection double vacuum-assisted resin transfer molding (IDVARTM) and the flow flooding chamber (FFC) methods. Compression shear tests (CST) were conducted on the manufactured samples to determine the ILSS. The effect of processing history and batch-to-batch variability of materials---glass fiber preform, resin and carbon nanotubes---on the ILSS of samples made by both techniques was investigated. Statistical comparison of the measured ILSS values for hybrid composites with the control specimens clearly show that hybrid composites made by the FFC process resulted in significant ILSS enhancement relative to the control and the IDVARTM specimens. After it was established that the FFC process improved the ILSS, the effect of functionalizing the nanotubes was explored. Multi walled carbon nanotubes (MWCNT) were oxidized by acid treatment and heated with triethylene tetra amine (TETA) to obtain amino functionalized MWCNTs (f-MWCNT). Hybrid composites with f-MWCNTs were manufactured using FFC technique and control samples were fabricated using the same E-Glass fiber mat and unmodified epoxy resin subjected to the same processing history. CST results show

  1. Interface shear strength and fracture behaviour of porous glass-fibre-reinforced composite implant and bone model material.

    PubMed

    Nganga, Sara; Ylä-Soininmäki, Anne; Lassila, Lippo V J; Vallittu, Pekka K

    2011-11-01

    Glass-fibre-reinforced composites (FRCs) are under current investigation to serve as durable bone substitute materials in load-bearing orthopaedic implants and bone implants in the head and neck area. The present form of biocompatible FRCs consist of non-woven E-glass-fibre tissues impregnated with varying amounts of a non-resorbable photopolymerisable bifunctional polymer resin with equal portions of both bis-phenyl-A-glycidyl dimethacrylate (BisGMA) and triethyleneglycol dimethacrylate (TEGDMA). FRCs with a total porosity of 10-70 vol% were prepared, more than 90 vol% of which being functional (open pores), and the rest closed. The pore sizes were greater than 100 μm. In the present study, the push-out test was chosen to analyse the shear strength of the interface between mechanically interlocked gypsum and a porous FRC implant structure. Gypsum was used as a substitute material for natural bone. The simulative in vitro experiments revealed a significant rise of push-out forces to the twofold level of 1147 ± 271 N for an increase in total FRC porosity of 43%. Pins, intended to model the initial mechanical implant fixation, did not affect the measured shear strength of the gypsum-FRC interface, but led to slightly more cohesive fracture modes. Fractures always occurred inside the gypsum, it having lower compressive strength than the porous FRC structures. Therefore, the largest loads were restricted by the brittleness of the gypsum. Increases of the FRC implant porosity tended to lead to more cohesive fracture modes and higher interfacial fracture toughness. Statistical differences were confirmed using the Kruskal-Wallis test. The differences between the modelled configuration showing gypsum penetration into all open pores and the real clinical situation with gradual bone ingrowth has to be considered. PMID:22098879

  2. Development of Stitched Composite Structure for Advanced Aircraft

    NASA Technical Reports Server (NTRS)

    Jegley, Dawn; Przekop, Adam; Rouse, Marshall; Lovejoy, Andrew; Velicki, Alex; Linton, Kim; Wu, Hsi-Yung; Baraja, Jaime; Thrash, Patrick; Hoffman, Krishna

    2015-01-01

    NASA has created the Environmentally Responsible Aviation Project to develop technologies which will reduce the impact of aviation on the environment. A critical aspect of this pursuit is the development of a lighter, more robust airframe that will enable the introduction of unconventional aircraft configurations. NASA and The Boeing Company are working together to develop a structural concept that is lightweight and an advancement beyond state-of-the-art composites. The Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS) is an integrally stiffened panel design where elements are stitched together and designed to maintain residual load-carrying capabilities under a variety of damage scenarios. With the PRSEUS concept, through-the-thickness stitches are applied through dry fabric prior to resin infusion, and replace fasteners throughout each integral panel. Through-the-thickness reinforcement at discontinuities, such as along flange edges, has been shown to suppress delamination and turn cracks, which expands the design space and leads to lighter designs. The pultruded rod provides stiffening away from the more vulnerable skin surface and improves bending stiffness. A series of building blocks were evaluated to explore the fundamental assumptions related to the capability and advantages of PRSEUS panels. These building blocks addressed tension, compression, and pressure loading conditions. The emphasis of the development work has been to assess the loading capability, damage arrestment features, repairability, post-buckling behavior, and response of PRSEUS flat panels to out-of plane pressure loading. The results of this building-block program from coupons through an 80%-scale pressure box have demonstrated the viability of a PRSEUS center body for the Hybrid Wing Body (HWB) transport aircraft. This development program shows that the PRSEUS benefits are also applicable to traditional tube-andwing aircraft, those of advanced configurations, and other

  3. Interlaminar shear strength and thermo-mechanical properties of nano-enhanced composite materials under thermal shock

    NASA Astrophysics Data System (ADS)

    Gkikas, G.; Douka, D.-D.; Barkoula, N.-M.; Paipetis, A. S.

    2013-04-01

    The introduction of nanoscaled reinforcement in otherwise conventional fiber reinforced composite materials has opened an exciting new area in composites research. The unique properties of these materials combined with the design versatility of fibrous composites may offer both enhanced mechanical properties and multiple functionalities which has been a focus area of the aerospace technology on the last decades. Due to unique properties of carbon nanofillers such as huge aspect ratio, extremely large specific surface area as well as high electrical and thermal conductivity, Carbon Nanotubes have benn investigated as multifunvtional materials for electrical, thermal and mechanical applications. In this study, MWCNTs were incorporated in a typical epoxy system using a sonicator. The volume of the nanoreinforcement was 0.5 % by weight. Two different levels of sonication amplitude were used, 50% and 100% respectively. After the sonication, the hardener was introduced in the epoxy, and the system was cured according to the recommended cycle. For comparison purposes, specimens from neat epoxy system were prepared. The thermomechanical properties of the materials manufactured were investigated using a Dynamic Mechanical Analyser. The exposed specimens were subjected to thermal shock. Thermal cycles from +30 °C to -30 °C were carried out and each cycle lasted 24 hours. The thermomechanical properties were studied after 30 cycles . Furthermore, the epoxy systems prepared during the first stage of the study were used for the manufacturing of 16 plies quasi isotropic laminates CFRPs. The modified CFRPs were subjected to thermal shock. For comparison reasons unmodified CFRPs were manufactured and subjected to the same conditions. In addition, the interlaminar shear strength of the specimens was studied using 3-point bending tests before and after the thermal shock. The effect of the nanoreinforcement on the environmental degradation is critically assessed.

  4. Design procedures for Strain Hardening Cement Composites (SHCC) and measurement of their shear properties by mechanical and 2-D Digital Image Correlation (DIC) method

    NASA Astrophysics Data System (ADS)

    Aswani, Karan

    The main objective of this study is to investigate the behaviour and applications of strain hardening cement composites (SHCC). Application of SHCC for use in slabs of common configurations was studied and design procedures are prepared by employing yield line theory and integrating it with simplified tri-linear model developed in Arizona State University by Dr. Barzin Mobasher and Dr. Chote Soranakom. Intrinsic material property of moment-curvature response for SHCC was used to derive the relationship between applied load and deflection in a two-step process involving the limit state analysis and kinematically admissible displacements. For application of SHCC in structures such as shear walls, tensile and shear properties are necessary for design. Lot of research has already been done to study the tensile properties and therefore shear property study was undertaken to prepare a design guide. Shear response of textile reinforced concrete was investigated based on picture frame shear test method. The effects of orientation, volume of cement paste per layer, planar cross-section and volume fraction of textiles were investigated. Pultrusion was used for the production of textile reinforced concrete. It is an automated set-up with low equipment cost which provides uniform production and smooth final surface of the TRC. A 3-D optical non-contacting deformation measurement technique of digital image correlation (DIC) was used to conduct the image analysis on the shear samples by means of tracking the displacement field through comparison between the reference image and deformed images. DIC successfully obtained full-field strain distribution, displacement and strain versus time responses, demonstrated the bonding mechanism from perspective of strain field, and gave a relation between shear angle and shear strain.

  5. Effect of endodontic irrigation and dressing procedures on the shear bond strength of composite to coronal dentin.

    PubMed

    Abo-Hamar, Sahar E

    2013-01-01

    This study aimed to evaluate the effects of three sodium hypochlorite (NaOCl)-endodontic irrigation procedures used alone or in combinations with two intermediate dressing materials on bond strengths of two adhesive composite systems to coronal dentin. Surfaces were treated with NaOCl or NaOCl-Glyde-File-Prep (H2O2 and EDTA) with or without chlorhexidine (CHX) as a final rinse. Intermediate dressing materials of calcium hydroxide (Ca(OH)2) and sodium perborate (SP) were combined with surface treatments. Surface treatment groups (n = 10/group) included (1) distilled water (control), (2) 5.25% NaOCl (30 min), (3) NaOCl/Glyde (30 min), (4) NaOCl/Glyde (30 min) + CHX (2 min), (5) NaOCl/Glyde (30 min) + Ca(OH)2 (5 days) + CHX (2 min), and (6) NaOCl/Glyde (30 min) + SP (9 days) + CHX (2 min). For each surface treatment group, dentin shear bond strengths of two different composite systems (Excite/Tetric Flow Chroma, [EX/TFC], and Clearfil Protect Bond/Protect Liner F [PB/PLF]) were evaluated. Median shear bond strengths (EX/TFC, PB/PLF) for each surface treatment group in MPa were (1) 21, 18; (2) 26, 18; (3) 21, 17; (4) 22, 16; (5) 17, 11; and (6) 14, 11, respectively. NaOCl significantly increased the bond strength of EX/TFC (p < 0.05), but did not significantly affect that of PB/PLF. The use of NaOCl/Glyde with CHX did not significantly affect EX/TFC (p > 0.05), whereas it significantly decreased PB/PLF (p < 0.05). Ca(OH)2 and SP significantly decreased the bond strengths of both adhesive systems (p < 0.05). Adhesion to coronal dentin is dependent upon the irrigation regimen and the type of adhesive. PMID:25685402

  6. Effect of endodontic irrigation and dressing procedures on the shear bond strength of composite to coronal dentin

    PubMed Central

    Abo-Hamar, Sahar E.

    2012-01-01

    This study aimed to evaluate the effects of three sodium hypochlorite (NaOCl)-endodontic irrigation procedures used alone or in combinations with two intermediate dressing materials on bond strengths of two adhesive composite systems to coronal dentin. Surfaces were treated with NaOCl or NaOCl–Glyde-File-Prep (H2O2 and EDTA) with or without chlorhexidine (CHX) as a final rinse. Intermediate dressing materials of calcium hydroxide (Ca(OH)2) and sodium perborate (SP) were combined with surface treatments. Surface treatment groups (n = 10/group) included (1) distilled water (control), (2) 5.25% NaOCl (30 min), (3) NaOCl/Glyde (30 min), (4) NaOCl/Glyde (30 min) + CHX (2 min), (5) NaOCl/Glyde (30 min) + Ca(OH)2 (5 days) + CHX (2 min), and (6) NaOCl/Glyde (30 min) + SP (9 days) + CHX (2 min). For each surface treatment group, dentin shear bond strengths of two different composite systems (Excite/Tetric Flow Chroma, [EX/TFC], and Clearfil Protect Bond/Protect Liner F [PB/PLF]) were evaluated. Median shear bond strengths (EX/TFC, PB/PLF) for each surface treatment group in MPa were (1) 21, 18; (2) 26, 18; (3) 21, 17; (4) 22, 16; (5) 17, 11; and (6) 14, 11, respectively. NaOCl significantly increased the bond strength of EX/TFC (p < 0.05), but did not significantly affect that of PB/PLF. The use of NaOCl/Glyde with CHX did not significantly affect EX/TFC (p > 0.05), whereas it significantly decreased PB/PLF (p < 0.05). Ca(OH)2 and SP significantly decreased the bond strengths of both adhesive systems (p < 0.05). Adhesion to coronal dentin is dependent upon the irrigation regimen and the type of adhesive. PMID:25685402

  7. Experimental Classical Flutter Reesults of a Composite Advanced Turboprop Model

    NASA Technical Reports Server (NTRS)

    Mehmed, O.; Kaza, K. R. V.

    1986-01-01

    Experimental results are presented that show the effects of blade pitch angle and number of blades on classical flutter of a composite advanced turboprop (propfan) model. An increase in the number of blades on the rotor or the blade pitch angle is destablizing which shows an aerodynamic coupling or cascade effect between blades. The flutter came in suddenly and all blades vibrated at the same frequency but at different amplitudes and with a common predominant phase angle between consecutive blades. This further indicates aerodynamic coupling between blades. The flutter frequency was between the first two blade normal modes, signifying an aerodynamic coupling between the normal modes. Flutter was observed at all blade pitch angles from small to large angles-of-attack of the blades. A strong blade response occurred, for four blades at the two-per-revolution (2P) frequency, when the rotor speed was near the crossing of the flutter mode frequency and the 2P order line. This is because the damping is low near the flutter condition and the interblade phase angle of the flutter mode and the 2P response are the same.

  8. Imperfection Insensitivity Analyses of Advanced Composite Tow-Steered Shells

    NASA Technical Reports Server (NTRS)

    Wu, K. Chauncey; Farrokh, Babak; Stanford, Bret K.; Weaver, Paul M.

    2016-01-01

    Two advanced composite tow-steered shells, one with tow overlaps and another without overlaps, were previously designed, fabricated and tested in end compression, both without cutouts, and with small and large cutouts. In each case, good agreement was observed between experimental buckling loads and supporting linear bifurcation buckling analyses. However, previous buckling tests and analyses have shown historically poor correlation, perhaps due to the presence of geometric imperfections that serve as failure initiators. For the tow-steered shells, their circumferential variation in axial stiffness may have suppressed this sensitivity to imperfections, leading to the agreement noted between tests and analyses. To investigate this further, a numerical investigation was performed in this study using geometric imperfections measured from both shells. Finite element models of both shells were analyzed first without, and then, with measured imperfections that were then, superposed in different orientations around the shell longitudinal axis. Small variations in both the axial prebuckling stiffness and global buckling load were observed for the range of imperfections studied here, which suggests that the tow steering, and resulting circumferentially varying axial stiffness, may result in the test-analysis correlation observed for these shells.

  9. Advanced Ceramic Matrix Composites (CMCs) for High Temperature Applications

    NASA Technical Reports Server (NTRS)

    Singh, M.

    2005-01-01

    Advanced ceramic matrix composites (CMCs) are enabling materials for a number of demanding applications in aerospace, energy, and nuclear industries. In the aerospace systems, these materials are being considered for applications in hot sections of jet engines such as the combustor liner, vanes, nozzle components, nose cones, leading edges of reentry vehicles, and space propulsion components. Applications in the energy and environmental industries include radiant heater tubes, heat exchangers, heat recuperators, gas and diesel particulate filters, and components for land based turbines for power generation. These materials are also being considered for use in the first wall and blanket components of fusion reactors. In the last few years, a number of CMC components have been developed and successfully tested for various aerospace and ground based applications. However, a number of challenges still remain slowing the wide scale implementation of these materials. They include robust fabrication and manufacturing, assembly and integration, coatings, property modeling and life prediction, design codes and databases, repair and refurbishment, and cost. Fabrication of net and complex shape components with high density and tailorable matrix properties is quite expensive, and even then various desirable properties are not achievable. In this presentation, a number of examples of successful CMC component development and testing will be provided. In addition, critical need for robust manufacturing, joining and assembly technologies in successful implementation of these systems will be discussed.

  10. Advanced Very High Resolution Radiometer Normalized Difference Vegetation Index Composites

    USGS Publications Warehouse

    U.S. Geological Survey

    2005-01-01

    The Advanced Very High Resolution Radiometer (AVHRR) is a broad-band scanner with four to six bands, depending on the model. The AVHRR senses in the visible, near-, middle-, and thermal- infrared portions of the electromagnetic spectrum. This sensor is carried on a series of National Oceanic and Atmospheric Administration (NOAA) Polar Orbiting Environmental Satellites (POES), beginning with the Television InfraRed Observation Satellite (TIROS-N) in 1978. Since 1989, the United States Geological Survey (USGS) Center for Earth Resources Observation and Science (EROS) has been mapping the vegetation condition of the United States and Alaska using satellite information from the AVHRR sensor. The vegetation condition composites, more commonly called greenness maps, are produced every week using the latest information on the growth and condition of the vegetation. One of the most important aspects of USGS greenness mapping is the historical archive of information dating back to 1989. This historical stretch of information has allowed the USGS to determine a 'normal' vegetation condition. As a result, it is possible to compare the current week's vegetation condition with normal vegetation conditions. An above normal condition could indicate wetter or warmer than normal conditions, while a below normal condition could indicate colder or dryer than normal conditions. The interpretation of departure from normal will depend on the season and geography of a region.

  11. A shear deformable theory of laminated composite shallow shell-type panels and their response analysis. I - Free vibration and buckling

    NASA Technical Reports Server (NTRS)

    Librescu, L.; Khdeir, A. A.; Frederick, D.

    1989-01-01

    This paper deals with the substantiation of a shear deformable theory of cross-ply laminated composite shallow shells. While the developed theory preserves all the advantages of the first order transverse shear deformation theory it succeeds in eliminating some of its basic shortcomings. The theory is further employed in the analysis of the eigenvibration and static buckling problems of doubly curved shallow panels. In this context, the state space concept is used in conjunction with the Levy method, allowing one to analyze these problems in a unified manner, for a variety of boundary conditions. Numerical results are presented and some pertinent conclusions are formulated.

  12. Resin transfer molding for advanced composite primary wing and fuselage structures

    NASA Technical Reports Server (NTRS)

    Markus, Alan

    1992-01-01

    The stitching and resin transfer molding (RTM) processes developed at Douglas Aircraft Co. are successfully demonstrating significant cost reductions with good damage tolerance properties. These attributes were identified as critical to application of advanced composite materials to commercial aircraft primary structures. The RTM/stitching developments, cost analyses, and test results are discussed of the NASA Advanced Composites Technology program.

  13. Effect of Surface Treatment with Er;Cr:YSSG, Nd:YAG, and CO2 Lasers on Repair Shear Bond Strength of a Silorane-based Composite Resin

    PubMed Central

    Alizadeh Oskoee, Parnian; Mohammadi, Narmin; Ebrahimi Chaharom, Mohammad Esmaeel; Kimyai, Soodabeh; Pournaghi Azar, Fatemeh; Rikhtegaran, Sahand; Shojaeei, Maryam

    2013-01-01

    Background and aims. The aim of the present study was to compare the effect ofsurface treatment with Er; Cr:YSSG, Nd:YAG, and CO2 lasers on repair shear bond strength of a silorane-based composite resin. Materials and methods. Sixty eight cylindrical samples of a silorane-based composite resin (Filtek Silorane) were pre-pared and randomly divided into 4 groups as follows: group 1: without surface treatment; groups 2, 3 and 4 with surface treatments using Er; Cr:YSSG, Nd:YAG, and CO2 lasers, respectively. A positive control group (group 5) was assigned in order to measure cohesive strength. Repair shear bond strength values were measured and data was analyzed using one-way ANOVA and a post hoc Tukey test at a significance level of α=0.05. Results. There were statistically significant differences in repair shear bond strength values between group 2 and other groups (P < 0.05); and between group 1and groups 3and 4 (P < 0.001); however, there were no significant differences be-tween groups 3 and 4 (P = 0.91). Conclusion. The repair shear bond strength of silorane-based composite resin was acceptable by surface treatment with lasers PMID:23875082

  14. Role of Mechanics of Textile Preform Composites in the NASA Advanced Composites Technology Program

    SciTech Connect

    Harris, C.E.; Poe, C.C. Jr.

    1995-10-01

    The Advanced Composites Technology Program was initiated by NASA as a partnership with the United States aeronautical industry in fiscal year 1989. The broad objective of the Program was to develop the technology to design and manufacture cost-effective and structurally optimized light-weight composite airframe primary structure. Phase A of the Program, 1989-1991, focused on the identification and evaluation of innovative manufacturing technologies and structural concepts. At the end of Phase A, the leading wing and fuselage design concepts were down-selected for further development in Phase B of the Program, 1992-1995. Three major fabrication technologies emerged from Phase A. These three approaches were the stitched dry preform, textile preform, and automated tow placement manufacturing methods. Each method emphasized rapid fiber placement, near net-shape preform fabrication, part count minimization, and matching the technologies to the specific structural configurations and requirements. The objective of Phase B was to continue the evolution of design concepts using the concurrent engineering process, down-select to the leading structural concept, and design, build, and test subscale components. Phase C of the ACT Program, 1995-2002, is a critical element of the NASA Advanced Subsonic Technology Program and has been approved for implementation beginning in 1995. The objective of Phase C is to design, build, and test major components of the airframe to demonstrate the technology readiness for applications in the next generation subsonic commercial transport aircraft. Part of the technology readiness demonstration will include a realistic comparison of manufacturing costs and an increased confidence in the ability to accurately estimate the costs of composite structure. The Program Plan calls for the structural components to be a complete fuselage barrel with a window-belt and a wing box at the wing/fuselage intersection.

  15. Shear bond strength of a new self-adhering flowable composite resin for lithium disilicate-reinforced CAD/CAM ceramic material

    PubMed Central

    Sancakli, Hande Sar; Sancakli, Erkan; Eren, Meltem Mert; Ozel, Sevda; Yucel, Taner; Yildiz, Esra

    2014-01-01

    PURPOSE The purpose of this study was to evaluate and compare the effects of different surface pretreatment techniques on the surface roughness and shear bond strength of a new self-adhering flowable composite resin for use with lithium disilicate-reinforced CAD/CAM ceramic material. MATERIALS AND METHODS A total of one hundred thirty lithium disilicate CAD/CAM ceramic plates with dimensions of 6 mm × 4 mm and 3 mm thick were prepared. Specimens were then assigned into five groups (n=26) as follows: untreated control, coating with 30 µm silica oxide particles (Cojet™ Sand), 9.6% hydrofluoric acid etching, Er:YAG laser irradiation, and grinding with a high-speed fine diamond bur. A self-adhering flowable composite resin (Vertise Flow) was applied onto the pre-treated ceramic plates using the Ultradent shear bond Teflon mold system. Surface roughness was measured by atomic force microscopy. Shear bond strength test were performed using a universal testing machine at a crosshead speed of 1 mm/min. Surface roughness data were analyzed by one-way ANOVA and the Tukey HSD tests. Shear bond strength test values were analyzed by Kruskal-Wallis and Mann-Whitney U tests at α=.05. RESULTS Hydrofluoric acid etching and grinding with high-speed fine diamond bur produced significantly higher surface roughness than the other pretreatment groups (P<.05). Hydrofluoric acid etching and silica coating yielded the highest shear bond strength values (P<.001). CONCLUSION Self-adhering flowable composite resin used as repair composite resin exhibited very low bond strength irrespective of the surface pretreatments used. PMID:25551002

  16. Buckling of Carbon Nanotube-Reinforced Polymer Laminated Composite Materials Subjected to Axial Compression and Shear Loadings

    NASA Technical Reports Server (NTRS)

    Riddick, J. C.; Gates, T. S.; Frankland, S.-J. V.

    2005-01-01

    A multi-scale method to predict the stiffness and stability properties of carbon nanotube-reinforced laminates has been developed. This method is used in the prediction of the buckling behavior of laminated carbon nanotube-polyethylene composites formed by stacking layers of carbon nanotube-reinforced polymer with the nanotube alignment axes of each layer oriented in different directions. Linking of intrinsic, nanoscale-material definitions to finite scale-structural properties is achieved via a hierarchical approach in which the elastic properties of the reinforced layers are predicted by an equivalent continuum modeling technique. Solutions for infinitely long symmetrically laminated nanotube-reinforced laminates with simply-supported or clamped edges subjected to axial compression and shear loadings are presented. The study focuses on the influence of nanotube volume fraction, length, orientation, and functionalization on finite-scale laminate response. Results indicate that for the selected laminate configurations considered in this study, angle-ply laminates composed of aligned, non-functionalized carbon nanotube-reinforced lamina exhibit the greatest buckling resistance with 1% nanotube volume fraction of 450 nm uniformly-distributed carbon nanotubes. In addition, hybrid laminates were considered by varying either the volume fraction or nanotube length through-the-thickness of a quasi-isotropic laminate. The ratio of buckling load-to-nanotube weight percent for the hybrid laminates considered indicate the potential for increasing the buckling efficiency of nanotube-reinforced laminates by optimizing nanotube size and proportion with respect to laminate configuration.

  17. Nondestructive Evaluation of Advanced Fiber Reinforced Polymer Matrix Composites: A Technology Assessment

    NASA Technical Reports Server (NTRS)

    Yolken, H. Thomas; Matzkanin, George A.

    2009-01-01

    Because of their increasing utilization in structural applications, the nondestructive evaluation (NDE) of advanced fiber reinforced polymer composites continues to receive considerable research and development attention. Due to the heterogeneous nature of composites, the form of defects is often very different from a metal and fracture mechanisms are more complex. The purpose of this report is to provide an overview and technology assessment of the current state-of-the-art with respect to NDE of advanced fiber reinforced polymer composites.

  18. Evaluation of bisphenol E cyanate ester for the resin-injection repair of advanced composites

    NASA Astrophysics Data System (ADS)

    Lio, Wilber Yaote

    Polymer matrix composites (PMCs) are susceptible to impacts that often result in microcracks and delaminations that can greatly reduce their mechanical integrity. Current injection repair techniques are limited to low glass transition temperature (Tg) composites due to the temperature and viscosity limitations of current repair resins. Bisphenol E cyanate ester (BECy) has both a high Tg and low prepolymer viscosity that makes it an ideal resin for the injection repair of high temperature PMCs. In addition, alumina nanoparticles have been shown to increase the strengths of some adhesives as well as impart shear thinning properties in suspension; both of which are desirable effects for injection repair. Lap shear tests were performed to evaluate adhesive properties of BECy and BECy-alumina nanocomposites. Effects of substrate, temperature, nanoparticle loading, and moisture were investigated. A resin-injection process was developed and the efficiency of BECy in repairing bismaleimide-carbon fiber composite plates was studied through ultrasonic evaluation and compression-after-impact tests.

  19. Association of Coronary Wall Shear Stress With Atherosclerotic Plaque Burden, Composition, and Distribution in Patients With Coronary Artery Disease

    PubMed Central

    Eshtehardi, Parham; McDaniel, Michael C.; Suo, Jin; Dhawan, Saurabh S.; Timmins, Lucas H.; Binongo, José Nilo G.; Golub, Lucas J.; Corban, Michel T.; Finn, Aloke V.; Oshinski, John N.; Quyyumi, Arshed A.; Giddens, Don P.; Samady, Habib

    2012-01-01

    Background Extremes of wall shear stress (WSS) have been associated with plaque progression and transformation, which has raised interest in the clinical assessment of WSS. We hypothesized that calculated coronary WSS is predicted only partially by luminal geometry and that WSS is related to plaque composition. Methods and Results Twenty‐seven patients with coronary artery disease underwent virtual histology intravascular ultrasound and Doppler velocity measurement for computational fluid dynamics modeling for WSS calculation in each virtual histology intravascular ultrasound segment (N=3581 segments). We assessed the association of WSS with plaque burden and distribution and with plaque composition. WSS remained relatively constant across the lower 3 quartiles of plaque burden (P=0.08) but increased in the highest quartile of plaque burden (P<0.001). Segments distal to lesions or within bifurcations were more likely to have low WSS (P<0.001). However, the majority of segments distal to lesions (80%) and within bifurcations (89%) did not exhibit low WSS. After adjustment for plaque burden, there was a negative association between WSS and percent necrotic core and calcium. For every 10 dynes/cm2 increase in WSS, percent necrotic core decreased by 17% (P=0.01), and percent dense calcium decreased by 17% (P<0.001). There was no significant association between WSS and percent of fibrous or fibrofatty plaque components (P=NS). Conclusions In patients with coronary artery disease: (1) Luminal geometry predicts calculated WSS only partially, which suggests that detailed computational techniques must be used to calculate WSS. (2) Low WSS is associated with plaque necrotic core and calcium, independent of plaque burden, which suggests a link between WSS and coronary plaque phenotype. (J Am Heart Assoc. 2012;1:e002543 doi: 10.1161/JAHA.112.002543.) PMID:23130168

  20. Impact of E × B flow shear on turbulence and resulting power fall-off width in H-mode plasmas in experimental advanced superconducting tokamak

    SciTech Connect

    Yang, Q. Q. Zhong, F. C. E-mail: fczhong@dhu.edu.cn; Jia, M. N.; Xu, G. S. E-mail: fczhong@dhu.edu.cn; Wang, L.; Wang, H. Q.; Chen, R.; Yan, N.; Liu, S. C.; Chen, L.; Li, Y. L.; Liu, J. B.

    2015-06-15

    The power fall-off width in the H-mode scrape-off layer (SOL) in tokamaks shows a strong inverse dependence on the plasma current, which was noticed by both previous multi-machine scaling work [T. Eich et al., Nucl. Fusion 53, 093031 (2013)] and more recent work [L. Wang et al., Nucl. Fusion 54, 114002 (2014)] on the Experimental Advanced Superconducting Tokamak. To understand the underlying physics, probe measurements of three H-mode discharges with different plasma currents have been studied in this work. The results suggest that a higher plasma current is accompanied by a stronger E×B shear and a shorter radial correlation length of turbulence in the SOL, thus resulting in a narrower power fall-off width. A simple model has also been applied to demonstrate the suppression effect of E×B shear on turbulence in the SOL and shows relatively good agreement with the experimental observations.

  1. Flutter study of an advanced composite wing with external stores

    NASA Technical Reports Server (NTRS)

    Cole, Stanley R.; Rivera, Jose A., Jr.; Nagaraja, K. S.

    1987-01-01

    A flutter test using a scaled model of an advanced composite wing for a Navy attack aircraft has been conducted in the NASA Langley Research Center Transonic Dynamics Tunnel. The model was a wall-mounted half-span wing with a semi-span of 6.63 ft. The wing had an aspect ratio of 5.31, taper ratio of 0.312, and quarter-chord sweep of 25 degrees. The model was supported in a manner that simulated the load path in the carry-through structure of the aircraft and the symmetric boundary condition at the fuselage centerline. The model was capable of carrying external stores from three pylon locations on the wing. Flutter tests were conducted for the wing with and without external stores. No flutter was encountered for the clean wing at test conditions which simulated the scaled airplane operating envelope. Flutter boundaries were obtained for several external store configurations. The flutter boundaries for the fuel tanks were nearly Mach number independent (occurring at constant dynamic pressure). To study the aerodynamic effect of the fuel tank stores, pencil stores (slender cylindrical rods) which had the same mass and pitch and yaw inertia as the fuel tanks were tested on the model. These pencil store configurations exhibited a transonic dip in the flutter dynamic pressure, indicating that the aerodynamic effect of the actual fuel tanks on flutter was significant. Several flutter analyses methods were used in an attempt to predict the flutter phenomenon exhibited during the wind-tunnel test. The analysis gave satisfactory predictions of flutter for the pencil store configurations, but unsatisfactory correlation for the actual fuel tank configurations.

  2. Can Suspended Iron-Alloy Droplets Explain the Origin, Composition and Properties of Large Low Shear Velocity Provinces?

    NASA Astrophysics Data System (ADS)

    Zhang, Z.; Dorfman, S. M.; Labidi, J.; Zhang, S.; Manga, M.; Stixrude, L. P.; McDonough, W. F.; Williams, Q. C.

    2014-12-01

    The enigmatic large low shear velocity provinces (LLSVPs) identified by seismic tomography at the base of the Earth's mantle have been proposed to be reservoirs of primordial mantle composition tapped by hot spot volcanism. The LLSVPs are characterized by anomalously low shear wave speed, VS, slightly elevated bulk sound speed, VB, and high density, ρ, in piles as thick as 1000 km above the core-mantle boundary. This combination of properties could be explained by a few percent dense melt, but the solidus of the lower mantle silicate and oxide assemblage may be too high to produce melt over the large extent of these regions. Iron-rich sulfur-bearing alloy may be molten at the conditions of the LLSVPs and ~1-2% of this component could satisfy both constraints on VS and ρ. An Fe alloy phase in the LLSVPs also has the potential to explain geochemical anomalies associated with hot spot volcanism, and its existence can be constrained by geochemical mass balance. Primordial noble gases such as 3He would be preferentially dissolved in Fe-rich melt rather than crystalline silicates. The reconstructed abundances of the moderately siderophile/chalcophile elements S, Cu and Pb in iron-alloy-bearing LLSVPs do not exceed predicted losses from volatilization, though this depends on the S-content of the alloy. The alloy phase would also be expected to incorporate W, and W isotope anomalies associated with hot spots are thus expected to have important implications for the timing of LLSVP formation. We have developed a model, via CIDER-2014, for the origin and properties of LLSVPs incorporating geochemistry, mineral physics, and fluid dynamic constraints on the generation, capture, and thermoelastic properties of Fe-rich melt droplets. The solidification of a basal magma ocean would produce both solid silicates and metallic melt. The bulk of the alloy generated by this process would sink to merge with the core. However, once the density of the remnant liquid exceeds that of the

  3. Aromatic/aliphatic diamine derivatives for advanced compositions and polymers

    NASA Technical Reports Server (NTRS)

    Delozier, Donovan M. (Inventor); Watson, Kent A. (Inventor); Connell, John W. (Inventor); Smith, Jr., Joseph G. (Inventor)

    2010-01-01

    Novel compositions of matter comprise certain derivatives of 9,9-dialkyl fluorene diamine (AFDA). The resultant compositions, whether compositions of matter or monomers that are subsequently incorporated into a polymer, are unique and useful in a variety of applications. Useful applications of AFDA-based material include heavy ion radiation shielding components and components of optical and electronic devices.

  4. Study of The Porosity Occurrence in Composite Materials by Means of Ultrasonic and In-Plane Shear Testing

    NASA Astrophysics Data System (ADS)

    Toscano, Cinzia; Vitiello, Carlo; Caramuta, Pietro

    2010-06-01

    The induced porosity in CFRP specimens, with different staking sequence, has been inspected by means the Pulse-Echo Ultrasonic testing. The specimens with [45°/-45°] staking sequence have also been processed by in-plane shear testing, to study the influence of the porosity on the degradation of interlaminar shear strength.

  5. Research on the exploitation of advanced composite materials to lightly loaded structures

    NASA Technical Reports Server (NTRS)

    Mar, J. W.

    1976-01-01

    The objective was to create a sailplane which could fly in weaker thermals than present day sailplanes (by being lighter) and to fly in stronger thermals than present sailplanes (by carrying more water ballast). The research was to tackle the interaction of advanced composites and the aerodynamic performance, the interaction of fabrication procedures and the advanced composites, and the interaction of advanced composites and the design process. Many pieces of the overall system were investigated but none were carried to the resolution required for engineering application. Nonetheless, interesting and useful results were obtained and are here reported.

  6. Effects of different fluorination routes on aramid fiber surface structures and interlaminar shear strength of its composites

    NASA Astrophysics Data System (ADS)

    Gao, Jie; Dai, Yunyang; Wang, Xu; Huang, Jieyang; Yao, Jin; Yang, Jin; Liu, Xiangyang

    2013-04-01

    Poly-p-phenylene-benzimidazole-terephthalamide (PBIA) fiber was surface modified by direct fluorination under three different routes. The fiber was dried under vacuum to remove physisorbed water trapped on it and then fluorinated by the fluorine and oxygen gases or by the fluorine gas only. Results show that the interlaminar shear strength (ILSS) value of these two kinds of fluorinated fiber reinforced epoxy resin was 43.9 MPa and 51.0 MPa, which was improved about 14.0% and 32.5% compared with that of the virgin fiber (38.5 MPa), respectively. In the third route, the fiber was fluorinated by the fluorine and oxygen gases without removing physisorbed water, and the ILSS value decreased for nearly 31.2%, i.e. from 38.5 MPa to 26.5 MPa. X-ray photoelectron spectroscopy (XPS) showed that oxygen-containing and fluorine-containing chemical groups were introduced onto the fiber surface after fluorination, providing a stronger chemical bonding to polymeric matrices. Scanning electronic microscopy (SEM) indicated that the surface morphology of the fluorinated PBIA fiber varied with the different fluorination routes. A mass of compact micro groove structures was formed by the route that the fiber was dried to remove physisorbed water and then fluorinated with fluorine gas only. And these structures would markedly improve the ILSS of the composites. But, a mass of unstable flake surface structures was formed by the route that the fiber was fluorinated with the fluorine and oxygen gases without removing physisorbed water. And these structures would be the weak interface between the fiber and matrix and decrease the ILSS, even a lot of polar chemical groups were bonded onto the fiber surface as well.

  7. FIBER-TEX 1992: The Sixth Conference on Advanced Engineering Fibers and Textile Structures for Composites

    NASA Technical Reports Server (NTRS)

    Buckley, John D. (Editor)

    1993-01-01

    The FIBER-TEX 1992 proceedings contain the papers presented at the conference held on 27-29 Oct. 1992 at Drexel University. The conference was held to create a forum to encourage an interrelationship of the various disciplines involved in the fabrication of materials, the types of equipment, and the processes used in the production of advanced composite structures. Topics discussed were advanced engineering fibers, textile processes and structures, structural fabric production, mechanics and characteristics of woven composites, and the latest requirements for the use of textiles in the production of composite materials and structures as related to global activities focused on textile structural composites.

  8. Synergistic Effect of Local Endothelial Shear Stress and Systemic Hypercholesterolemia on Coronary Atherosclerotic Plaque Progression and Composition in Pigs

    PubMed Central

    Koskinas, Konstantinos C.; Chatzizisis, Yiannis S.; Papafaklis, Michail I.; Coskun, Ahmet U.; Baker, Aaron B.; Jarolim, Petr; Antoniadis, Antonios; Edelman, Elazer R.; Stone, Peter H.; Feldman, Charles L.

    2014-01-01

    Background Systemic risk factors and local hemodynamic factors both contribute to coronary atherosclerosis, but their possibly synergistic inter-relationship remains unknown. The purpose of this natural history study was to investigate the combined in-vivo effect of varying levels of systemic hypercholesterolemia and local endothelial shear stress (ESS) on subsequent plaque progression and histological composition. Methods Diabetic, hyperlipidemic swine with higher systemic total cholesterol (TC) (n=4) and relatively lower TC levels (n=5) underwent three-vessel intravascular ultrasound (IVUS) at 3–5 consecutive time-points in-vivo. ESS was calculated serially using computational fluid dynamics. 3-D reconstructed coronary arteries were divided into 3mm-long segments (n=595), which were stratified according to higher vs. relatively lower TC and low (<1.2 Pa) vs. higher local ESS (≥1.2 Pa). Arteries were harvested at 9 months, and a subset of segments (n=114) underwent histopathologic analyses. Results Change of plaque volume (ΔPV) by IVUS over time was most pronounced in low-ESS segments from higher-TC animals. Notably, higher-ESS segments from higher-TC animals had greater ΔPV compared to low-ESS segments from lower-TC animals (p<0.001). The time-averaged ESS in segments that resulted in significant plaque increased with increasing TC levels (slope: 0.24 Pa/100mg/dl; r=0.80; p<0.01). At follow-up, low-ESS segments from higher-TC animals had the highest mRNA levels of lipoprotein receptors and inflammatory mediators and, consequently, the greatest lipid accumulation and inflammation. Conclusions This study redefines the principle concept that “low” ESS promotes coronary plaque growth and vulnerability by demonstrating that: (i.) the pro-atherogenic threshold of low ESS is not uniform, but cholesterol-dependent; and (ii.) the atherogenic effects of local low ESS are amplified, and the athero-protective effects of higher ESS may be outweighed, by increasing

  9. Steady-state creep of bent reinforced metal-composite plates with consideration of their reduced resistance to transverse shear 2. Analysis of calculated results

    NASA Astrophysics Data System (ADS)

    Yankovskii, A. P.

    2014-07-01

    Deformation of annular plates with different structures of helical reinforcement is studied. It is demonstrated that the use of the classical theory for calculating steady-state creep for thick reinforced plates subjected to bending leads to underprediction of the compliance of thin-walled metal-composite structures. It is also shown that there are significant shear strain rates in the binder of such plates, which has to be taken into account and which is mainly responsible for creep strain accumulation. Results calculated by two different models, which take into account the composite structure, are compared.

  10. ADVANCED COMPOSITE WIND TURBINE BLADE DESIGN BASED ON DURABILITY AND DAMAGE TOLERANCE

    SciTech Connect

    Galib Abumeri; Frank Abdi

    2012-02-16

    The objective of the program was to demonstrate and verify Certification-by-Analysis (CBA) capability for wind turbine blades made from advanced lightweight composite materials. The approach integrated durability and damage tolerance analysis with robust design and virtual testing capabilities to deliver superior, durable, low weight, low cost, long life, and reliable wind blade design. The GENOA durability and life prediction software suite was be used as the primary simulation tool. First, a micromechanics-based computational approach was used to assess the durability of composite laminates with ply drop features commonly used in wind turbine applications. Ply drops occur in composite joints and closures of wind turbine blades to reduce skin thicknesses along the blade span. They increase localized stress concentration, which may cause premature delamination failure in composite and reduced fatigue service life. Durability and damage tolerance (D&DT) were evaluated utilizing a multi-scale micro-macro progressive failure analysis (PFA) technique. PFA is finite element based and is capable of detecting all stages of material damage including initiation and propagation of delamination. It assesses multiple failure criteria and includes the effects of manufacturing anomalies (i.e., void, fiber waviness). Two different approaches have been used within PFA. The first approach is Virtual Crack Closure Technique (VCCT) PFA while the second one is strength-based. Constituent stiffness and strength properties for glass and carbon based material systems were reverse engineered for use in D&DT evaluation of coupons with ply drops under static loading. Lamina and laminate properties calculated using manufacturing and composite architecture details matched closely published test data. Similarly, resin properties were determined for fatigue life calculation. The simulation not only reproduced static strength and fatigue life as observed in the test, it also showed composite

  11. An Investigation of Some Advanced Skills of Composition.

    ERIC Educational Resources Information Center

    Das, Bikram K.

    1978-01-01

    A study was conducted to investigate: (1) what linguistic and mental abilities are involved in composition; (2) to what extent undergraduate students in India possess these abilities, in English and in their native language; and (3) to what extent these abilities are being taught. The major portion of the paper discusses the nature of composition,…

  12. Advanced SiC composites for fusion applications

    SciTech Connect

    Snead, L.L.; Schwarz, O.J.

    1995-04-01

    This is a short review of the motivation for and progress in the development of ceramic matrix composites for fusion. Chemically vapor infiltrated silicon carbide (SiC) composites have been fabricated from continuous fibers of either SiC or graphite and tested for strength and thermal conductivity. Of significance is the the Hi-Nicalon{trademark} SiC based fiber composite has superior unirradiated properties as compared to the standard Nicalon grade. Based on previous results on the stability of the Hi-Nicalon fiber, this system should prove more resistant to neutron irradiation. A graphite fiber composite has been fabricated with very good mechnical properties and thermal conductivity an order of magnitude higher than typical SiC/SiC composites.

  13. Recent advances in research on carbon nanotube-polymer composites.

    PubMed

    Byrne, Michele T; Gun'ko, Yurii K

    2010-04-18

    Carbon nanotubes (CNTs) demonstrate remarkable electrical, thermal, and mechanical properties, which allow a number of exciting potential applications. In this article, we review the most recent progress in research on the development of CNT-polymer composites, with particular attention to their mechanical and electrical (conductive) properties. Various functionalization and fabrication approaches and their role in the preparation of CNT-polymer composites with improved mechanical and electrical properties are discussed. We tabulate the most recent values of Young's modulus and electrical conductivities for various CNT-polymer composites and compare the effectiveness of different processing techniques. Finally, we give a future outlook for the development of CNT-polymer composites as potential alternative materials for various applications, including flexible electrodes in displays, electronic paper, antistatic coatings, bullet-proof vests, protective clothing, and high-performance composites for aircraft and automotive industries. PMID:20496401

  14. Structural design and stress analysis program for advanced composite filament-wound axisymmetric pressure vessels (COMTANK)

    NASA Technical Reports Server (NTRS)

    Knoell, A. C.

    1972-01-01

    Computer program has been specifically developed to handle, in an efficient and cost effective manner, planar wound pressure vessels fabricated of either boron-epoxy or graphite-epoxy advanced composite materials.

  15. Comparison of shear bond strength of composite resin to enamel surface with laser etching versus acid etching: An in vitro evaluation

    PubMed Central

    Hoshing, Upendra A; Patil, Suvarna; Medha, Ashish; Bandekar, Siddhesh Dattatray

    2014-01-01

    Introduction: The aim of the study is in vitro evaluation of the shear bond strength of composite resin bonded to enamel which is pretreated using acid etchant and Er,Cr:Ysgg. Materials and Methods: 40 extracted human teeth were divided in two groups of 20 each (Groups A and B). In Group A, prepared surface of enamel was etched using 37% phosphoric acid (Scotchbond, 3M). In Group B, enamel was surface treated by a an Er, Cr: YSGG laser system (Waterlase MD, Biolase Technology Inc., San Clemente, CA, USA) operating at a wavelength of 2,780 nm and having a pulse duration of 140-200 microsecond with a repetition rate of 20 Hz and 40 Hz. Bonding agent ((Scotchbond Multipurpose, 3M) was applied over the test areas on 20 samples of Groups A and B each, and light cured. Composite resin (Ceram X duo Nanoceramic restorative, Densply) was applied onto the test areas as a 3 × 3 mm diameter bid, and light cured. The samples were tested for shear bond strength. Results: Mean shear bond strength for acid-etched enamel (26.41 ± 0.66MPa, range 25.155 to 27.150 MPa) was significantly higher (P < 0.01) than for laser-etched enamel (16.23 ± 0.71MPa, range 15.233 to 17.334 MPa). Conclusions: For enamel surface, mean shear bond strength of bonded composite obtained after laser etching were significantly lower than those obtained after acid etching. PMID:25125842

  16. Shear/Defocus Sensitivity of the Mid Infrared Channel (MIR) of the Composite Infrared Spectrometer (CIRS) for the Cassini Mission to Saturn

    NASA Technical Reports Server (NTRS)

    Martino, Anthony J.; Hagopian, John G.; Losch, Patricia; Crooke, Julie

    1998-01-01

    The Composite Infrared Spectrometer (CIRS) of the Cassini mission to Saturn has two interferometers covering the far infrared and mid infrared wavelength region. The mid infrared wavelength interferometer has a focal plane consisting of a germanium focus lens and HgCdTe array. System level calibration of the CIRS Flight Unit indicated a discrepancy between the expected and actual signal levels. Testing on the CIRS breadboard and Engineering Unit indicated that defocus of the germanium lens could significantly reduce the modulation efficiency of the interferometer in the presence of a moderate degree of wavefront shear. Defocus of the lens in the focal plane was of concern because of the temperature dependence of the index of refraction of germanium and our nominal operation temperature of 170 K. The shear/defocus interaction was extensively investigated and correlated to a newly developed analytical model, It was eventually determined that the CIRS instrument was in focus, had no appreciable wavefront shear and was operating near theoretical limits. The shear/defocus effect is however, of considerable interest, since it has not been described in previous literature on interferometers.

  17. “Evaluation of shear bond strength of a composite resin to white mineral trioxide aggregate with three different bonding systems”-An in vitro analysis

    PubMed Central

    Patil, Anand C.

    2016-01-01

    Background Mineral trioxide aggregate (MTA) is a biomaterial that has been investigated for endodontic applications. With the increased use of MTA in pulp capping, pulpotomy, perforation repair, apexification and obturation, the material that would be placed over MTA as a final restoration is an important matter. As composite resins are one of the most widely used final restorative materials, this study was conducted to evaluate the shear bond strength of a composite resin to white mineral trioxide aggregate (WMTA) using three different bonding systems namely the two-step etch and rinse adhesive, the self-etching primer and the All-in-one system. Material and Methods Forty five specimens of white MTA (Angelus) were prepared and randomly divided into three groups of 15 specimens each depending on the bonding systems used respectively. In Group A, a Two-step etch and rinse adhesive or ‘total-etch adhesive’, Adper Single Bond 2 (3M/ESPE) and Filtek Z350 (3M ESPE, St Paul, MN) were placed over WMTA. In group B, a Two-step self-etching primer system, Clearfil SE Bond (Kuraray, Medical Inc) and Filtek Z350 were used. In Group C, an All-in-one system, G Bond (GC corporation, Tokyo, Japan) and Filtek Z350 were used. The shear bond strength was measured for all the specimens. The data obtained was subjected to One way Analysis of Variance (ANOVA) and Scheffe’s post hoc test. Results The results suggested that the Two-step etch and rinse adhesive when used to bond a composite resin to white MTA gave better bond strength values and the All-in-one exhibited the least bond strength values. Conclusions The placement of composite used with a Two-step etch and rinse adhesive over WMTA as a final restoration may be appropriate. Key words:Composite resins, dentin bonding agents, mineral trioxide aggregate, shear bond strength. PMID:27398177

  18. Recent advances in the sensitivity analysis for the thermomechanical postbuckling of composite panels

    NASA Technical Reports Server (NTRS)

    Noor, Ahmed K.

    1995-01-01

    Three recent developments in the sensitivity analysis for thermomechanical postbuckling response of composite panels are reviewed. The three developments are: (1) effective computational procedure for evaluating hierarchical sensitivity coefficients of the various response quantities with respect to the different laminate, layer, and micromechanical characteristics; (2) application of reduction methods to the sensitivity analysis of the postbuckling response; and (3) accurate evaluation of the sensitivity coefficients to transverse shear stresses. Sample numerical results are presented to demonstrate the effectiveness of the computational procedures presented. Some of the future directions for research on sensitivity analysis for the thermomechanical postbuckling response of composite and smart structures are outlined.

  19. Manufacturing Aspects of Advanced Polymer Composites for Automotive Applications

    NASA Astrophysics Data System (ADS)

    Friedrich, Klaus; Almajid, Abdulhakim A.

    2013-04-01

    Composite materials, in most cases fiber reinforced polymers, are nowadays used in many applications in which light weight and high specific modulus and strength are critical issues. The constituents of these materials and their special advantages relative to traditional materials are described in this paper. Further details are outlined regarding the present markets of polymer composites in Europe, and their special application in the automotive industry. In particular, the manufacturing of parts from thermoplastic as well as thermosetting, short and continuous fiber reinforced composites is emphasized.

  20. Advanced composites: Fabrication processes for selected resin matrix materials

    NASA Technical Reports Server (NTRS)

    Welhart, E. K.

    1976-01-01

    This design note is based on present state of the art for epoxy and polyimide matrix composite fabrication technology. Boron/epoxy and polyimide and graphite/epoxy and polyimide structural parts can be successfully fabricated. Fabrication cycles for polyimide matrix composites have been shortened to near epoxy cycle times. Nondestructive testing has proven useful in detecting defects and anomalies in composite structure elements. Fabrication methods and tooling materials are discussed along with the advantages and disadvantages of different tooling materials. Types of honeycomb core, material costs and fabrication methods are shown in table form for comparison. Fabrication limits based on tooling size, pressure capabilities and various machining operations are also discussed.

  1. Advanced composites: Environmental effects on selected resin matrix materials

    NASA Technical Reports Server (NTRS)

    Welhart, E. K.

    1976-01-01

    The effects that expected space flight environment has upon the mechanical properties of epoxy and polyimide matrix composites were analyzed. Environmental phenomena covered water immersion, high temperature aging, humidity, lightning strike, galvanic action, electromagnetic interference, thermal shock, rain and sand erosion, and thermal/vacuum outgassing. The technology state-of-the-art for graphite and boron reinforced epoxy and polyimide matrix materials is summarized to determine the relative merit of using composites in the space shuttle program. Resin matrix composites generally are affected to some degree by natural environmental phenomena with polyimide resin matrix materials less affected than epoxies.

  2. Evaluation of shear bond strength of two resin-based composites and glass ionomer cement to pure tricalcium silicate-based cement (Biodentine®)

    PubMed Central

    CANTEKİN, Kenan; AVCİ, Serap

    2014-01-01

    Objectives Tricalcium silicate is the major constituent phase in mineral trioxide aggregate (MTA). It is thus postulated that pure tricalcium silicate can replace the Portland cement component of MTA. The aim of this study was to evaluate bond strength of methacrylate-based (MB) composites, silorane-based (SB) composites, and glass ionomer cement (GIC) to Biodentine® and mineral trioxide aggregate (MTA). Material and Methods Acrylic blocks (n=90, 2 mm high, 5 mm diameter central hole) were prepared. In 45 of the samples, the holes were fully filled with Biodentine® and in the other 45 samples, the holes were fully filled with MTA. The Biodentine® and the MTA samples were randomly divided into 3 subgroups of 15 specimens each: Group-1: MB composite; Group-2: SB composite; and Group-3: GIC. For the shear bond strength (SBS) test, each block was secured in a universal testing machine. Results The highest (17.7±6.2 MPa) and the lowest (5.8±3.2 MPa) bond strength values were recorded for the MB composite-Biodentine® and the GIC-MTA, respectively. Although the MB composite showed significantly higher bond strength to Biodentine (17.7±6.2) than it did to MTA (8.9±5.7) (p<0.001), the SB composite (SB and MTA=7.4±3.3; SB and Biodentine®=8.0±3,6) and GIC (GIC and MTA=5.8±3.2; GIC and Biodentine=6.7±2.6) showed similar bond strength performance with MTA compared with Biodentine (p=0.73 and p=0.38, respectively). Conclusions The new pure tricalcium-based pulp capping, repair, and endodontic material showed higher shear bond scores compared to MTA when used with the MB composite. PMID:25141202

  3. Bending and Shear Behavior of Pultruded Glass Fiber Reinforced Polymer Composite Beams With Closed and Open Sections

    NASA Astrophysics Data System (ADS)

    Estep, Daniel Douglas

    Several advantages, such as high strength-to-weight ratio, high stiffness, superior corrosion resistance, and high fatigue and impact resistance, among others, make FRPs an attractive alternative to conventional construction materials for use in developing new structures as well as rehabilitating in-service infrastructure. As the number of infrastructure applications using FRPs grows, the need for the development of a uniform Load and Resistance Factor Design (LRFD) approach, including design procedures and examples, has become paramount. Step-by-step design procedures and easy-to-use design formulas are necessary to assure the quality and safety of FRP structural systems by reducing the possibility of design and construction errors. Since 2008, the American Society of Civil Engineers (ASCE), in coordination with the American Composites Manufacturers Association (ACMA), has overseen the development of the Pre-Standard for Load and Resistance Factor Design (LRFD) of Pultruded Fiber Reinforced Polymer (FRP) Structures using probability-based limit states design. The fifth chapter of the pre-standard focuses on the design of members in flexure and shear under different failure modes, where the current failure load prediction models proposed within have been shown to be highly inaccurate based on experimental data and evaluation performed by researchers at the West Virginia University Constructed Facilities Center. A new prediction model for determining the critical flexural load capacity of pultruded GFRP square and rectangular box beams is presented within. This model shows that the type of failure can be related to threshold values of the beam span-to-depth ratio (L/h) and total flange width-to-thickness ratio (bf /t), resulting in three governing modes of failure: local buckling failure in the compression flange (4 ≤ L/h < 6), combined strain failure at the web-flange junction (6 ≤ L/h ≤ 10), and bending failure in the tension flange (10 < L/h ≤ 42

  4. The brittle-viscous-plastic evolution of shear bands in the South Armorican Shear Zone

    NASA Astrophysics Data System (ADS)

    Bukovská, Zita; Jeřábek, Petr; Morales, Luiz F. G.; Lexa, Ondrej; Milke, Ralf

    2014-05-01

    Shear bands are microscale shear zones that obliquely crosscut an existing anisotropy such as a foliation. The resulting S-C fabrics are characterized by angles lower than 45° and the C plane parallel to shear zone boundaries. The S-C fabrics typically occur in granitoids deformed at greenschist facies conditions in the vicinity of major shear zones. Despite their long recognition, mechanical reasons for localization of deformation into shear bands and their evolution is still poorly understood. In this work we focus on microscale characterization of the shear bands in the South Armorican Shear Zone, where the S-C fabrics were first recognized by Berthé et al. (1979). The initiation of shear bands in the right-lateral South Armorican Shear Zone is associated with the occurrence of microcracks crosscutting the recrystallized quartz aggregates that define the S fabric. In more advanced stages of shear band evolution, newly formed dominant K-feldspar, together with plagioclase, muscovite and chlorite occur in the microcracks, and the shear bands start to widen. K-feldspar replaces quartz by progressively bulging into the grain boundaries of recrystallized quartz grains, leading to disintegration of quartz aggregates and formation of fine-grained multiphase matrix mixture. The late stages of shear band development are marked by interconnection of fine-grained white mica into a band that crosscuts the original shear band matrix. In its extremity, the shear band widening may lead to the formation of ultramylonites. With the increasing proportion of shear band matrix from ~1% to ~12%, the angular relationship between S and C fabrics increases from ~30° to ~40°. The matrix phases within shear bands show differences in chemical composition related to distinct evolutionary stages of shear band formation. The chemical evolution is well documented in K-feldspar, where the albite component is highest in porphyroclasts within S fabric, lower in the newly formed grains within

  5. Inspection of composite materials with an advanced ultrasonic flaw detector

    NASA Astrophysics Data System (ADS)

    Yamamoto, W.

    The structures and shapes of the composite material products are described. Methods of ultrasonic wave detection are described. New damage detection equipment for laminate and honeycomb structures is addressed.

  6. Chemical and sulphur isotope compositions of pyrite in the Jaduguda U (-Cu-Fe) deposit, Singhbhum shear zone, eastern India: Implications for sulphide mineralization

    NASA Astrophysics Data System (ADS)

    Pal, Dipak C.; Sarkar, Surajit; Mishra, Biswajit; Sarangi, A. K.

    2011-06-01

    The Jaduguda U (-Cu-Fe) deposit in the Singhbhum shear zone has been the most productive uranium deposit in India. Pyrite occurs as disseminated grains or in sulphide stringers and veins in the ore zone. Veins, both concordant and discordant to the pervasive foliation, are mineralogically either simple comprising pyrite ± chalcopyrite or complex comprising pyrite + chalcopyrite + pentlandite + millerite. Nickel-sulphide minerals, though fairly common in concordant veins, are very rare in the discordant veins. Pyrite in Ni-sulphide association is commonly replaced by pentlandite at the grain boundary or along micro-cracks. Based on concentrations of Co and Ni, pyrite is classified as: type-A - high Co (up to 30800 ppm), no/low Ni; type-B - moderate Co (up to 16500 ppm) and moderate to high Ni (up to 32700 ppm); type-C - no/low Co and high Ni (up to 43000 ppm); type-D - neither Co nor Ni. Textural and compositional data of pyrites suggest that the hydrothermal fluid responsible for pre-/early-shearing mineralization evolved from Co-rich to Ni-rich and the late-/post-shearing fluid was largely depleted in minor elements. Sulphur isotope compositions of pyrite mostly furnish positive values ranging between -0.33 and 12.06‰. Composite samples of pyrites with only type-A compositions and mixed samples of type-A and type-B are consistently positive. However, pyrite with mixed type-A and type-C and pyrite with type-D compositions have negative values but close to 0‰. By integrating minor element and sulphur isotope compositions of pyrite in conjunction with other published data on the Jaduguda deposit, it is proposed that reduced sulphur for the precipitation of most pyrites (type-A, type-B) was likely derived from isotopically heavy modified seawater. However, some later sulphur might be magmatic in origin remobilized from existing sulphides in the mafic volcanic rocks in the shear zone.

  7. Recent advances in bonded composite repair technology for metallic aircraft components

    SciTech Connect

    Baker, A.A.; Chester, R.J.

    1993-12-31

    Advanced fiber composites such as boron/epoxy can be employed as adhesively bonded patches to repair or to reinforce metallic aerospace components. This approach provides many advantages over conventional mechanically fastened metallic patches, including improved fatigue behavior, reduced corrosion and easy conformance to complex aerodynamic contours. Bonded composite repairs have been shown to provide high levels of bond durability under aircraft operating conditions. The recent application of bonded composite repairs to military and civil aircraft is described.

  8. An integrated theory for predicting the hydrothermomechanical response of advanced composite structural components

    NASA Technical Reports Server (NTRS)

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

    1977-01-01

    A theory is developed for predicting the hydrothermomechanical response of advanced composite structural components. The combined hydrothermal effects on the mechanical properties of unidirectional composites loaded along the material axis and off-axis, and of angleplied laminates are also evaluated. The materials investigated consist of neat PR-288 epoxy matrix resin and an AS-type graphite fiber/PR-288 resin unidirectional composite.

  9. Effects of reaction layer on interfacial shear properties and strength of fiber in silicon-carbide (SiC) fiber-reinforced titanium alloy composite

    SciTech Connect

    Kagawa, Yutaka; Masuda, Chitoshi; Fujiwara, Chikara; Fukushima, Akira

    1996-12-31

    The effect of the interfacial thickness of the reaction layer on the interfacial shear properties and the tensile strength of double carbon-coated SCS-6 SiC fiber in Ti-15Mo-5Zr-3Al alloy matrix composite was examined. The major reaction layer thickness, that is, titanium-carbide (TiC) layer thickness, varied with heat-exposure temperature and time, respectively, and the resultant mean thickness of the reaction layer of the composite ranged from 0.4 to 1.7 {micro}m. The critical interfacial toughness, G{sub i}{sup c}, and the mean shear sliding resistance, {tau}{sub s}, were evaluated by the thin specimen pushout technique. Tensile strength of the silicon-carbide (SiC) fiber extracted from the titanium alloy matrix before and after the heat exposure was determined in relationship to the thickness of the reaction layer. The critical interface toughness, G{sub i}{sup c}, for the failure of the root of the reaction layer was {approx}4 J/m{sup 2}, and the average shear sliding resistance of the interface, {tau}{sub s}, was 102 to 118 MPa. The interfacial shear mechanical properties were adequate to prevent failure of the fiber due to the stress concentration caused by cracks that formed first in the reaction layer. The results showed that when the growth of reaction layer was within 1.7 {micro}m, the mean strength of the extracted fiber was unaffected by the existence of the reaction layer because of weak bonding between it and the fiber. However, with the increase of the reaction layer thickness, the strength distribution of the extracted fiber tended to Weibull bimodal distribution.

  10. Investigation of fatigue strength of multilayer advanced fiber composites

    NASA Technical Reports Server (NTRS)

    Thornton, H. R.; Kozik, T. J.

    1974-01-01

    The analytical characterization of a multilayer fiber composite plate (without hole) was accomplished for both static and dynamic loading conditions using the finite difference technique. Thornel 300/5208 composites with and without holes were subjected to static and tensile fatigue testing. Five (5) fiber orientations were submitted to test. Tensile fatigue testing also included three (3) loading conditions and two (2) frequencies. The low-cycle test specimens demonstrated a shorter tensile fatigue life than the high-cycle test specimens. Failure surfaces demonstrated effect of testing conditions. Secondary failure mechanisms, such as: delamination, fiber breakage, and edge fiber delamination were present. Longitudinal delamination between plies also occurred in these specimens.

  11. Resin transfer molding for advanced composite primary aircraft structures

    NASA Technical Reports Server (NTRS)

    Markus, Alan; Palmer, Ray

    1991-01-01

    Resin Transfer Molding (RTM) has been identified by Douglas Aircraft Company (DAC) and industry to be one of the promising processes being developed today which can break the cost barrier of implementing composite primary structures into a commercial aircraft production environment. The RTM process developments and scale-up plans Douglas Aircrart will be conducting under the NASA ACT contract are discussed.

  12. Musical Composition and Creativity in an Advanced Software Environment

    ERIC Educational Resources Information Center

    Reynolds, Nicholas

    2002-01-01

    This paper serves as a brief description of research into the use of professional level music software as a learning tool for creativity and composition by primary school children. The research formed the basis of a Master of Information Technology in Education degree at the University of Melbourne. The paper examines the physical environment, the…

  13. Advanced Nano-Composites for Increased Energy Efficiency

    SciTech Connect

    2009-05-01

    This factsheet describes a research project whose goal is to increase energy efficiency and operating lifetime of wear-intensive industrial components and systems by developing and commercializing a family of ceramic-based monolithic composites that have shown remarkable resistance to wear in laboratory tests.

  14. Reported Usage and Perceived Value of Advanced Placement English Language and Composition Curricular Requirements by High School and College Assessors of the Essay Portion of the English Language and Composition Advanced Placement Exam

    ERIC Educational Resources Information Center

    Holifield-Scott, April

    2011-01-01

    A study was conducted to determine the extent to which high school and college/university Advanced Placement English Language and Composition readers value and implement the curricular requirements of Advanced Placement English Language and Composition. The participants were 158 readers of the 2010 Advanced Placement English Language and…

  15. Advanced Modeling Strategies for the Analysis of Tile-Reinforced Composite Armor

    NASA Technical Reports Server (NTRS)

    Davila, Carlos G.; Chen, Tzi-Kang

    1999-01-01

    A detailed investigation of the deformation mechanisms in tile-reinforced armored components was conducted to develop the most efficient modeling strategies for the structural analysis of large components of the Composite Armored Vehicle. The limitations of conventional finite elements with respect to the analysis of tile-reinforced structures were examined, and two complementary optimal modeling strategies were developed. These strategies are element layering and the use of a tile-adhesive superelement. Element layering is a technique that uses stacks of shear deformable shell elements to obtain the proper transverse shear distributions through the thickness of the laminate. The tile-adhesive superelement consists of a statically condensed substructure model designed to take advantage of periodicity in tile placement patterns to eliminate numerical redundancies in the analysis. Both approaches can be used simultaneously to create unusually efficient models that accurately predict the global response by incorporating the correct local deformation mechanisms.

  16. Effects of Fusion Zone Size and Failure Mode on Peak Load and Energy Absorption of Advanced High Strength Steel Spot Welds under Lap Shear Loading Conditions

    SciTech Connect

    Sun, Xin; Stephens, Elizabeth V.; Khaleel, Mohammad A.

    2008-06-01

    This paper examines the effects of fusion zone size on failure modes, static strength and energy absorption of resistance spot welds (RSW) of advanced high strength steels (AHSS) under lap shear loading condition. DP800 and TRIP800 spot welds are considered. The main failure modes for spot welds are nugget pullout and interfacial fracture. Partial interfacial fracture is also observed. Static weld strength tests using lap shear samples were performed on the joint populations with various fusion zone sizes. The resulted peak load and energy absorption levels associated with each failure mode were studied for all the weld populations using statistical data analysis tools. The results in this study show that AHSS spot welds with conventionally required fusion zone size of can not produce nugget pullout mode for both the DP800 and TRIP800 welds under lap shear loading. Moreover, failure mode has strong influence on weld peak load and energy absorption for all the DP800 welds and the TRIP800 small welds: welds failed in pullout mode have statistically higher strength and energy absorption than those failed in interfacial fracture mode. For TRIP800 welds above the critical fusion zone level, the influence of weld failure modes on peak load and energy absorption diminishes. Scatter plots of peak load and energy absorption versus weld fusion zone size were then constructed, and the results indicate that fusion zone size is the most critical factor in weld quality in terms of peak load and energy absorption for both DP800 and TRIP800 spot welds.

  17. Development of Curved-Plate Elements for the Exact Buckling Analysis of Composite Plate Assemblies Including Transverse-Shear Effects

    NASA Technical Reports Server (NTRS)

    McGowan, David M.

    1999-01-01

    The analytical formulation of curved-plate non-linear equilibrium equations including transverse-shear-deformation effects is presented. A unified set of non-linear strains that contains terms from both physical and tensorial strain measures is used. Linearized, perturbed equilibrium equations (stability equations) that describe the response of the plate just after buckling occurs are derived. These equations are then modified to allow the plate reference surface to be located a distance z(sub c) from the centroidal surface. The implementation of the new theory into the VICONOPT exact buckling and vibration analysis and optimum design computer program is described. The terms of the plate stiffness matrix using both classical plate theory (CPT) and first-order shear-deformation plate theory (SDPT) are presented. The effects of in-plane transverse and in-plane shear loads are included in the in-plane stability equations. Numerical results for several example problems with different loading states are presented. Comparisons of analyses using both physical and tensorial strain measures as well as CPT and SDPT are made. The computational effort required by the new analysis is compared to that of the analysis currently in the VICONOPT program. The effects of including terms related to in-plane transverse and in-plane shear loadings in the in-plane stability equations are also examined. Finally, results of a design-optimization study of two different cylindrical shells subject to uniform axial compression are presented.

  18. Advanced composite fiber/metal pressure vessels for aircraft applications

    NASA Astrophysics Data System (ADS)

    Papanicolopoulos, Aleck

    1993-06-01

    Structural Composites Industries has developed, qualified, and delivered a number of high performance carbon epoxy overwrapped/seamless aluminum liner pressure vessels for use in military aircraft where low weight, low cost, high operating pressure and short lead time are the primary considerations. This paper describes product design, development, and qualification for a typical program. The vessel requirements included a munitions insensitivity criterion as evidenced by no fragmentation following impact by a .50 cal tumbling bullet. This was met by the development of a carbon-Spectra hybrid composite overwrap on a thin-walled seamless aluminum liner. The same manufacturing, inspection, and test processes that are used to produce lightweight, thin walled seamless aluminum lined carbon/epoxy overwrapped pressure vessels for satellite and other space applications were used to fabricate this vessel. This report focuses on the results of performance in the qualification testing.

  19. Recent Advances and Developments in Composite Dental Restorative Materials

    PubMed Central

    Cramer, N.B.; Stansbury, J.W.; Bowman, C.N.

    2011-01-01

    Composite dental restorations represent a unique class of biomaterials with severe restrictions on biocompatibility, curing behavior, esthetics, and ultimate material properties. These materials are presently limited by shrinkage and polymerization-induced shrinkage stress, limited toughness, the presence of unreacted monomer that remains following the polymerization, and several other factors. Fortunately, these materials have been the focus of a great deal of research in recent years with the goal of improving restoration performance by changing the initiation system, monomers, and fillers and their coupling agents, and by developing novel polymerization strategies. Here, we review the general characteristics of the polymerization reaction and recent approaches that have been taken to improve composite restorative performance. PMID:20924063

  20. Shear Bond Strength of Acidic Primer, Light-Cure Glass Ionomer, Light-Cure and Self Cure Composite Adhesive Systems - An In Vitro Study

    PubMed Central

    D, Krishnakanth Reddy; V, Kishore M S; Safeena, Safeena

    2013-01-01

    Background: The purpose of this study was to determine shear bond strength and the effect on the bracket/ adhesive failure mode when an acidic primer and other etchants were used to condition the enamel surface before bonding. Materials & Methods: Group I: Brackets bonded with Ultimate cure-on-light Light-cure composite adhesive system. Group II: Brackets bonded with Ortho-one no-mix. Self-cure composite adhesive system. Group III: Brackets bonded with Light-cure glass ionomer adhesive system. Group IV: Brackets bonded with Transbond plus self etching primer. Results: The results of this study indicated that the shear bond strength when using Transbond plus self etching primer showed the highest bond strength Group- IV(8.69 2.54 MPa) followed by Ultimate cure-on-light Group-I (8.62 1.84 MPa), Ortho-one no-mix (Bisco Inc. USA)Group-II (8.07 1.72 MPa), and least bond strength was seen in G.C. Fuji Ortho L.C. Group-III (6.01 1.6) MPa Conclusion: Use of self etching primer saves chairside time and satisfactory high bond strength was obtained. Care should be taken during debonding of ceramic brackets How to cite this article: Reddy K D, Kishore M S V, Safeena S. Shear Bond Strength of Acidic Primer, Light-Cure Glass Ionomer, Light-Cure and Self Cure Composite Adhesive Systems - An In Vitro Study. J Int Oral Health 2013; 5(3):73-78. PMID:24155606

  1. SRM nozzle design breakthroughs with advanced composite materials

    NASA Astrophysics Data System (ADS)

    Berdoyes, Michel

    1993-06-01

    The weight reduction-related performance and cost of the Space Shuttle's Solid Rocket Motor (SRM) units' critical nozzle components are undergoing revolutionary improvements through the use of 3D-woven carbon/carbon and carbon/alumina composite materials. These can be used to fabricate the SRM's nozzle throat nondegradable insulators, thermostructural insulator, and exit cones. Additional developments are noted among nozzle-related structural components for additional rocket propulsion systems, including a three-piece extendible nozzle.

  2. Advanced composite vertical stabilizer for DC-10 transport aircraft

    NASA Technical Reports Server (NTRS)

    Stephens, C. O.

    1978-01-01

    The structural design configuration for the Composite Vertical Stabilizer is described and the structural design, analysis, and weight activities are presented. The status of fabrication and test activities for the development test portion of the program is described. Test results are presented for the skin panels, spar web, spar cap to cover, and laminate properties specimens. Engineering drawings of vertification test panels and root fittings, rudder support specimens, titanium fittings, and rear spar specimen analysis models are included.

  3. Design and fabrication of Rene 41 advanced structural panels. [their performance under axial compression, shear, and bending loads

    NASA Technical Reports Server (NTRS)

    Greene, B. E.; Northrup, R. F.

    1975-01-01

    The efficiency was investigated of curved elements in the design of lightweight structural panels under combined loads of axial compression, inplane shear, and bending. The application is described of technology generated in the initial aluminum program to the design and fabrication of Rene 41 panels for subsequent performance tests at elevated temperature. Optimum designs for two panel configurations are presented. The designs are applicable to hypersonic airplane wing structure, and are designed specifically for testing at elevated temperature in the hypersonic wing test structure located at the NASA Flight Research Center. Fabrication methods developed to produce the Rene panels are described, and test results of smaller structural element specimens are presented to verify the design and fabrication methods used. Predicted strengths of the panels under several proposed elevated temperature test load conditions are presented.

  4. FIBER-TEX 1991: The Fifth Conference on Advanced Engineering Fibers and Textile Structures for Composites

    SciTech Connect

    Buckley, J.D.

    1992-10-01

    This document is a compilation of papers presented at a joint NASA/North Carolina State University/DoD/Clemson University/Drexel University conference on Fibers, Textile Technology, and Composites Structures held at the College of Textiles Building on Centennial Campus of North Carolina State University, Raleigh, North Carolina on October 15-17, 1991. Conference papers presented information on advanced engineering fibers, textile processes and structures, structural fabric production, mechanics and characteristics of woven composites, pultruded composites, and the latest requirements for the use of textiles in the production of composite materials and structures. Separate abstracts have been prepared for papers in this report.

  5. FIBER-TEX 1991: The Fifth Conference on Advanced Engineering Fibers and Textile Structures for Composites

    NASA Technical Reports Server (NTRS)

    Buckley, John D. (Editor)

    1992-01-01

    This document is a compilation of papers presented at a joint NASA/North Carolina State University/DoD/Clemson University/Drexel University conference on Fibers, Textile Technology, and Composites Structures held at the College of Textiles Building on Centennial Campus of North Carolina State University, Raleigh, North Carolina on October 15-17, 1991. Conference papers presented information on advanced engineering fibers, textile processes and structures, structural fabric production, mechanics and characteristics of woven composites, pultruded composites, and the latest requirements for the use of textiles in the production of composite materials and structures.

  6. In-vitro comparison of the effect of different bonding strategies on the micro-shear bond strength of a silorane-based composite resin to dentin

    PubMed Central

    Samimi, Pouran; Alizadeh, Vahid; Fathpour, Kamyar; Mazaheri, Hamid; Mortazavi, Vajihosadat

    2016-01-01

    Background: The current study evaluated the micro-shear bond strengths of a new low-shrinkage composite resin to dentin. Materials and Methods: In this in-vitro study, 70 extracted premolars were assigned to one of seven groups (n = 10): Group 1: OptiBond Solo Plus (Opt; Kerr); Group 2: SE Bond (SE; Kuraray); Group 3: Silorane System Adhesive (SSA; 3M ESPE); Group 4: OptiBond Solo Plus + LS Bond (Opt LS); Group 5: SE Bond + LS Bond (SE LS); Group 6: OptiBond Solo Plus (Opt Po); and Group 7: SE Bond (SE Po). Occlusal dentin was exposed and restored with Filtek LS (3M ESPE) in groups 1 to 5 and Point 4 (Kerr) in groups 6 and 7. After thermocycling (1000 cycles at 5/55΀C), micro-shear bond test was carried out to measure the bond strengths. The results were submitted to analysis of variance and post hoc Tukeytests (P < 0.05). Results: Two-way ANOVA showed no significant differences between the two types of composite resin (P = 0.187), between bonding agents (P = 0.06) and between composite resin and bonding agents (P = 0.894). Because P value of bonding agents was near the significance level, one-way ANOVA was used separately between the two composite groups. This analysis showed significant differences between silorane composite resin groups (P = 0.045) and Tukey test showed a significant difference between Groups 4 and 5 (P = 0.03). Conclusion: The application of total-etch and self-etch methacrylate-based adhesives with and without use of a hydrophobic resin coating resulted in acceptable bond strengths. PMID:27076826

  7. Effect of surface treatments on shear bond strength of resin composite bonded to CAD/CAM resin-ceramic hybrid materials

    PubMed Central

    Güngör, Merve Bankoğlu; Bal, Bilge Turhan; Ünver, Senem; Doğan, Aylin

    2016-01-01

    PURPOSE The purpose of this study was to assess the effect of surface treatments on shear bond strength of resin composite bonded to thermocycled and non-thermocycled CAD/CAM resin-ceramic hybrid materials. MATERIALS AND METHODS 120 specimens (10×10×2 mm) from each material were divided into 12 groups according to different surface treatments in combination with thermal aging procedures. Surface treatment methods were airborne-particle abrasion (abraded with 50 micron alumina particles), dry grinding (grinded with 125 µm grain size bur), and hydrofluoric acid (9%) and silane application. According to the thermocycling procedure, the groups were assigned as non-thermocycled, thermocycled after packing composites, and thermocycled before packing composites. The average surface roughness of the non-thermocycled specimens were measured after surface treatments. After packing composites and thermocycling procedures, shear bond strength (SBS) of the specimens were tested. The results of surface roughness were statistically analyzed by 2-way Analysis of Variance (ANOVA), and SBS results were statistically analyzed by 3-way ANOVA. RESULTS Surface roughness of GC were significantly lower than that of LU and VE (P<.05). The highest surface roughness was observed for dry grinding group, followed by airborne particle abraded group (P<.05). Comparing the materials within the same surface treatment method revealed that untreated surfaces generally showed lower SBS values. The values of untreated LU specimens showed significantly different SBS values compared to those of other surface treatment groups (P<.05). CONCLUSION SBS was affected by surface treatments. Thermocycling did not have any effect on the SBS of the materials except acid and silane applied GC specimens, which were subjected to thermocycling before packing of the composite resin. PMID:27555894

  8. Preparation, Fabrication, and Evaluation of Advanced Polymeric and Composite Materials

    NASA Technical Reports Server (NTRS)

    Orwoll, Robert A.

    1997-01-01

    The thesis titles are given below: physical and mechanical behavior of amorphous poly(arylene ether-co-imidasole)s and poly(arylene ether-co-imidasole) modification epoxies; the requirements of patentability as applied to the chemical arts; fabrication of thermoplastic polymer composite ribbon; blend of reactive diluents with phenylethynyl-terminated arylene ether oligomers; the synthesis, characterization, and application of ether-containing polyimides; the synthesis of reflective and electrically conductive polyimide films via an in-situ self-metalization procedure using silver (I) complexes; the thermal cure of phenylethynyl terminated polyimides and selected model compounds; and the synthesis, characterization, and molecular modeling of cyclic arylene ether oligomers.

  9. Composite magnetostrictive materials for advanced automotive magnetomechanical sensors

    NASA Astrophysics Data System (ADS)

    McCallum, R. W.; Dennis, K. W.; Jiles, D. C.; Snyder, J. E.; Chen, Y. H.

    2001-04-01

    In this paper we present the development of a composite magnetostrictive material for automotive applications. The material is based on cobalt ferrite, CoOṡFe2O3, and contains a small fraction of metallic matrix phase that serves both as a liquid-phase sintering aid during processing and enhances the mechanical properties over those of a simple sintered ferrite ceramic. In addition the metal matrix makes it possible to braze the material, making the assembly of a sensor relatively simple. The material exhibits good sensitivity and should have high corrosion resistance, while at the same time it is low in cost.

  10. Advanced ultrasonic testing of complex shaped composite structures

    NASA Astrophysics Data System (ADS)

    Dolmatov, D.; Zhvyrblya, V.; Filippov, G.; Salchak, Y.; Sedanova, E.

    2016-06-01

    Due to the wide application of composite materials it is necessary to develop unconventional quality control techniques. One of the methods that can be used for this purpose is ultrasonic tomography. In this article an application of a robotic ultrasonic system is considered. Precise positioning of the robotic scanner and path generating are defined as ones of the most important aspects. This study proposes a non-contact calibration method of a robotic ultrasonic system. Path of the scanner requires a 3D model of controlled objects which are created in accordance with the proposed algorithm. The suggested techniques are based on implementation of structured light method.

  11. Advanced refractory metals and composites for extraterrestrial power systems

    NASA Technical Reports Server (NTRS)

    Titran, R. H.; Grobstein, Toni L.

    1990-01-01

    Concepts for future space power systems include nuclear and focused solar heat sources coupled to static and dynamic power-conversion devices; such systems must be designed for service lives as long as 30 years, despite service temperatures of the order of 1600 K. Materials are a critical technology-development factor in such aspects of these systems as reactor fuel containment, environmental protection, power management, and thermal management. Attention is given to the prospective performance of such refractory metals as Nb, W, and Mo alloys, W fiber-reinforced Nb-matrix composites, and HfC precipitate-strengthened W-Re alloys.

  12. Advances in Moire interferometry for thermal response of composites

    NASA Technical Reports Server (NTRS)

    Brooks, E. W., Jr.; Herakovich, C. T.; Post, D.; Hyer, M. W.

    1982-01-01

    An experimental technique for the precise measurement of the thermal response of both sides of a laminated composite coupon specimen uses Moire interferometry with fringe multiplication which yields a sensitivity of 833 nm (32.8 micro in.) per fringe. The reference gratings used are virtual gratings and are formed by partially mirrorized glass prisms in close proximity to the specimen. Results are compared with both results obtained from tests which used Moire interferometry on one side of composite laminates, and with those predicted by classical lamination theory. The technique is shown to be capable of producing the sensitivity and accuracy necessary to measure a wide range of thermal responses and to detect small side to side variations in the measured response. Tests were conducted on four laminate configurations of T300/5208 graphite epoxy over a temperature range of 297 K (75 F) to 422 K (300 F). The technique presented allows for the generation of reference gratings for temperature regimes well outside that used in these tests.

  13. Application of advanced material systems to composite frame elements

    NASA Technical Reports Server (NTRS)

    Llorente, Steven; Minguet, Pierre; Fay, Russell; Medwin, Steven

    1992-01-01

    A three phase program has been conducted to investigate DuPont's Long Discontinuous Fiber (LDF) composites. Additional tests were conducted to compare LDF composites against toughened thermosets and a baseline thermoset system. Results have shown that the LDF AS4/PEKK offers improved interlaminar (flange bending) strength with little reduction in mechanical properties due to the discontinuous nature of the fibers. In the third phase, a series of AS4/PEKK LDF C-section curved frames (representing a typical rotorcraft light frame) were designed, manufactured and tested. Specimen reconsolidation after 'stretch forming' and frame thickness were found to be key factors in this light frame's performance. A finite element model was constructed to correlate frame test results with expected strain levels determined from material property tests. Adequately reconsolidated frames performed well and failed at strain levels at or above baseline thermoset material test strains. Finally a cost study was conducted which has shown that the use of LDF for this frame would result in a significant cost savings, for moderate to large lot sizes compared with the hand lay-up of a thermoset frame.

  14. Innovative fabrication processing of advanced composite materials concepts for primary aircraft structures

    NASA Technical Reports Server (NTRS)

    Kassapoglou, Christos; Dinicola, Al J.; Chou, Jack C.

    1992-01-01

    The autoclave based THERM-X(sub R) process was evaluated by cocuring complex curved panels with frames and stiffeners. The process was shown to result in composite parts of high quality with good compaction at sharp radius regions and corners of intersecting parts. The structural properties of the postbuckled panels fabricated were found to be equivalent to those of conventionally tooled hand laid-up parts. Significant savings in bagging time over conventional tooling were documented. Structural details such as cocured shear ties and embedded stiffener flanges in the skin were found to suppress failure modes such as failure at corners of intersecting members and skin stiffeners separation.

  15. Status of Advanced Stitched Unitized Composite Aircraft Structures

    NASA Technical Reports Server (NTRS)

    Jegley, Dawn C.; Velicki, Alex

    2013-01-01

    NASA has created the Environmentally Responsible Aviation (ERA) Project to explore and document the feasibility, benefits and technical risk of advanced vehicle configurations and enabling technologies that will reduce the impact of aviation on the environment. A critical aspect of this pursuit is the development of a lighter, more robust airframe that will enable the introduction of unconventional aircraft configurations that have higher lift-to-drag ratios, reduced drag, and lower community noise levels. The primary structural concept being developed under the ERA project in the Airframe Technology element is the Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS) concept. This paper describes how researchers at NASA and The Boeing Company are working together to develop fundamental PRSEUS technologies that could someday be implemented on a transport size aircraft with high aspect ratio wings or unconventional shapes such as a hybrid wing body airplane design.

  16. Advanced resin systems and 3D textile preforms for low cost composite structures

    NASA Technical Reports Server (NTRS)

    Shukla, J. G.; Bayha, T. D.

    1993-01-01

    Advanced resin systems and 3D textile preforms are being evaluated at Lockheed Aeronautical Systems Company (LASC) under NASA's Advanced Composites Technology (ACT) Program. This work is aimed towards the development of low-cost, damage-tolerant composite fuselage structures. Resin systems for resin transfer molding and powder epoxy towpreg materials are being evaluated for processability, performance and cost. Three developmental epoxy resin systems for resin transfer molding (RTM) and three resin systems for powder towpregging are being investigated. Various 3D textile preform architectures using advanced weaving and braiding processes are also being evaluated. Trials are being conducted with powdered towpreg, in 2D weaving and 3D braiding processes for their textile processability and their potential for fabrication in 'net shape' fuselage structures. The progress in advanced resin screening and textile preform development is reviewed here.

  17. Determination of critical loads for cylindrical sandwich panels of composite materials under two-sided compression and shear

    NASA Astrophysics Data System (ADS)

    Rubina, A. L.; Krashakov, Yu. F.

    The problem of determining the critical buckling stress of symmetric and nonsymmetric sandwich panels loaded in two-sided compression and shear is investigated analytically. The governing equation is obtained by solving equations of balance of forces and moments for an element of a sandwich structure in the case of buckling. The solution is based on the general assumptions of the theory of thin shallow shells. The results of the study can be used to optimize the structure of sandwich panels.

  18. Damage Prediction Models for Advanced Materials and Composites

    NASA Technical Reports Server (NTRS)

    Xie, Ming; Ahmad, Jalees; Grady, Joseph E. (Technical Monitor)

    2005-01-01

    In the present study, the assessment and evaluation of various acoustic tile designs were conducted using three-dimensional finite element analysis, which included static analysis, thermal analysis and modal analysis of integral and non-integral tile design options. Various benchmark specimens for acoustic tile designs, including CMC integral T-joint and notched CMC plate, were tested in both room and elevated temperature environment. Various candidate ceramic matrix composite materials were used in the numerical modeling and experimental study. The research effort in this program evolved from numerical modeling and concept design to a combined numerical analysis and experimental study. Many subjects associated with the design and performance of the acoustic tile in jet engine exhaust nozzle have been investigated.

  19. Advanced composite aileron for L-1011 transport aircraft, task 1

    NASA Technical Reports Server (NTRS)

    Griffin, C. F.; Fogg, L. D.; Stone, R. L.; Dunning, E. G.

    1978-01-01

    Structural design and maintainability criteria were established and used as a guideline for evaluating a variety of configurations and materials for each of the major subcomponents. From this array of subcomponent designs, several aileron assemblies were formulated and analyzed. The selected design is a multirib configuration with sheet skin covers mechanically fastened to channel section ribs and spars. Qualitative analysis of currently available composite material systems led to the selection of three candidate materials on which comparative structural tests were conducted to measure the effects of environment and impact damage on mechanical property retention. In addition, each system was evaluated for producibility characteristics. From these tests, Thornel 300/5208 unidirectional tape was selected for the front spar and covers, and Thornel 300 fabric/5208 was chosen for the ribs.

  20. Durability Characterization of Advanced Polymeric Composites at Cryogenic Temperatures

    NASA Technical Reports Server (NTRS)

    Gates, T. S.

    2001-01-01

    The next generation of reusable launch vehicles will require technology development in several key areas. Of these key areas, the development of polymeric composite cryogenic fuel tanks promises to present one of the most difficult technical challenges. It is envisioned that a polymer matrix composite (PMC) tank would be a large shell structure capable of containing cryogenic fuels and carrying a range of structural loads. The criteria that will be imposed on such a design include reduced weight, conformal geometry, and impermeability. It is this last criterion, impermeability, that will provide the focus of this paper. The essence of the impermeability criterion is that the tank remains leak free throughout its design lifetime. To address this criterion, one of the first steps is to conduct a complete durability assessment of the PMC materials. At Langley Research Center, a durability assessment of promising new polyimide-based PMCs is underway. This durability program has focused on designing a set of critical laboratory experiments that will determine fundamental material properties under combined thermal-mechanical loading at cryogenic temperatures. The test program provides measurements of lamina and laminate properties, including strength, stiffness, and fracture toughness. The performance of the PMC materials is monitored as a function of exposure conditions and aging time. Residual properties after exposure are measured at cryogenic temperatures and provide quantitative values of residual strength and stiffness. Primary degradation mechanisms and the associated damage modes are measured with both destructive and nondestructive techniques. In addition to mechanical properties, a range of physical properties, such as weight, glass transition, and crack density, are measured and correlated with the test conditions. This paper will report on the progress of this research program and present critical results and illustrative examples of current findings.

  1. Use of advanced composite pipe technology to design seawater systems on open type offshore production platforms

    SciTech Connect

    Lea, R.H.; Griffin, S.A.; Pang, S.S.; Cundy, V.A.

    1993-12-31

    Since the 1950`s composite pipe has been considered a viable alternative to carbon steel, stainless steel and copper-nickel pipe in sea water applications. The most obvious benefit of utilizing composite pipe for offshore applications is its excellent corrosion resistance. Case histories exceeding twenty years have been reported in the Gulf of Mexico. A typical example is a water flood system installed by Exxon in block 16 in 1970. In order to utilize composite piping systems for offshore applications more extensively, design procedures, failure criteria, new advanced pipe design, and fire characteristics have been identified. This information can assist the engineer in working within the guidelines established by major industrial groups and regulatory bodies such as The International Maritime Organization, Health Safety Executive, Norwegian Petroleum Directorate and The American Petroleum Directorate. The results of this program has led to the installation of over 3,660 m of advanced composite pipe on the new Corvette Class coastal destroyer.

  2. Polymer, metal and ceramic matrix composites for advanced aircraft engine applications

    NASA Technical Reports Server (NTRS)

    Mcdanels, D. L.; Serafini, T. T.; Dicarlo, J. A.

    1985-01-01

    Advanced aircraft engine research within NASA Lewis is being focused on propulsion systems for subsonic, supersonic, and hypersonic aircraft. Each of these flight regimes requires different types of engines, but all require advanced materials to meet their goals of performance, thrust-to-weight ratio, and fuel efficiency. The high strength/weight and stiffness/weight properties of resin, metal, and ceramic matrix composites will play an increasingly key role in meeting these performance requirements. At NASA Lewis, research is ongoing to apply graphite/polyimide composites to engine components and to develop polymer matrices with higher operating temperature capabilities. Metal matrix composites, using magnesium, aluminum, titanium, and superalloy matrices, are being developed for application to static and rotating engine components, as well as for space applications, over a broad temperature range. Ceramic matrix composites are also being examined to increase the toughness and reliability of ceramics for application to high-temperature engine structures and components.

  3. Advanced composite structural concepts and material technologies for primary aircraft structures

    NASA Technical Reports Server (NTRS)

    Jackson, Anthony

    1991-01-01

    Structural weight savings using advanced composites have been demonstrated for many years. Most military aircraft today use these materials extensively and Europe has taken the lead in their use in commercial aircraft primary structures. A major inhibiter to the use of advanced composites in the United States is cost. Material costs are high and will remain high relative to aluminum. The key therefore lies in the significant reduction in fabrication and assembly costs. The largest cost in most structures today is assembly. As part of the NASA Advanced Composite Technology Program, Lockheed Aeronautical Systems Company has a contract to explore and develop advanced structural and manufacturing concepts using advanced composites for transport aircraft. Wing and fuselage concepts and related trade studies are discussed. These concepts are intended to lower cost and weight through the use of innovative material forms, processes, structural configurations and minimization of parts. The approach to the trade studies and the downselect to the primary wing and fuselage concepts is detailed. The expectations for the development of these concepts is reviewed.

  4. Advanced thermoplastic composites: An attractive new material for usage in highly loaded vehicle components

    SciTech Connect

    Mehn, R.; Seidl, F.; Peis, R.; Heinzmann, D.; Frei, P.

    1995-10-01

    Beside the lightweight potential and further well known advantages of advanced composite materials, continuous fiber reinforced thermoplastics employed in vehicle structural parts especially offer short manufacturing cycle times and an additional economically viable manufacturing process. Presenting a frame structure concept for two highly loaded vehicle parts, a safety seat and a side door, numerous features concerning the choice of suitable composite materials, design aspects, investigations to develop a thermoforming technique, mature for a series production of vehicle parts, are discussed.

  5. High performance fibers for structurally reliable metal and ceramic composites. [advanced gas turbine engine materials

    NASA Technical Reports Server (NTRS)

    Dicarlo, J. A.

    1984-01-01

    Very few of the commercially available high performance fibers with low densities, high Young's moduli, and high tensile strengths possess all the necessary property requirements for providing either metal matrix composites (MMC) or ceramic matrix composites (CMC) with high structural reliability. These requirements are discussed in general and examples are presented of how these property guidelines are influencing fiber evaluation and improvement studies at NASA aimed at developing structurally reliable MMC and CMC for advanced gas turbine engines.

  6. Advances in the Use of Thermography to Inspect Composite Tanks for Liquid Fuel Propulsion Systems

    NASA Technical Reports Server (NTRS)

    Lansing, Matthew D.; Russell, Samuel S.; Walker, James L.; Jones, Clyde S. (Technical Monitor)

    2001-01-01

    This viewgraph presentation gives an overview of advances in the use of thermography to inspect composite tanks for liquid fuel propulsion systems. Details are given on the thermographic inspection system, thermographic analysis method (includes scan and defect map, method of inspection, and inclusions, ply wrinkle, and delamination defects), graphite composite cryogenic feedline (including method, image map, and deep/shallow inclusions and resin rich area defects), and material degradation nondestructive evaluation.

  7. Advanced glucose biosensing and nano-composite research

    NASA Astrophysics Data System (ADS)

    Uba, Humphreys Douglas I.

    The fascinating and enhanced properties of carbon nanotubes (CNTs) have been of intense interest since their discovery. This is primarily due to their exceptional mechanical , electrical, and thermal properties , as well as their many and varied applications in modern industries such as in fuel cells, sensors, reinforced composites, electromagnetic interference shielding applications, actuators and fabrication of sophisticated nanostructures. During the production of CNTs, there are associated impurities such as metal nanoparticle and carbonaceous impurities. There are different types of CNTs such as single-walled nanotubes (SWNTs), double-walled nanotubes (DWNTs) and multi-walled nanotubes (MWNTs). In this study, XD-grade CNTs (XD) was used. XD is a mixture of SWNTs, DWNTs and MWNTs. The focus of this study was primarily geared toward the purification and application of CNTs. Two generally accepted cycles of purification were followed, purification under oxygen environment and purification under oxygen/argon mixture environment. XD was purified to different extents by oxidation and acid wash. The raw and purified CNTs were compounded into Epikote 862 and Epikure W epoxy resin to prepare composite materials and also in the biosensor studies. The CNTs and composite materials were characterized by means of thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and transimssion electron microscopy (TEM). It was discovered that, excessive purification would not lead to further removal of metal residues; instead, it could result in disruption of the structure and property of CNTs. The use of CNTs as fillers was found to hinder the epoxy curing in general, and the removal of metal impurities seemed to worsen the situation. This would imply that the metal residue might catalyze the epoxy curing to a certain degree while the increased viscosity should be the primary reason for the slowed curing. An electrochemical

  8. Impact of leachate composition on the advanced oxidation treatment.

    PubMed

    Oulego, Paula; Collado, Sergio; Laca, Adriana; Díaz, Mario

    2016-01-01

    Advanced oxidation processes (AOPs) are gaining importance as an alternative to the biological or physicochemical treatments for the management of leachates. In this work, it has been studied the effect of the characteristics of the leachate (content in humic acids, landfill age and degree of stabilization) on the wet oxidation process and final quality of the treated effluent. A high concentration of humic acids in the leachate had a positive effect on the COD removal because this fraction is more easily oxidizable. Additionally, it has been demonstrated that the simultaneous presence of humic acid and the intermediates generated during the oxidation process improved the degradation of this acid, since such intermediates are stronger initiators of free radicals than the humic acid itself. Similar values of COD removals (49% and 51%) and biodegradability indices (0.30 and 0.35) were observed, after 8 h of wet oxidation, for the stabilised leachate (biologically pretreated) and the raw one, respectively. Nevertheless, final colour removal was much higher for the stabilised leachate, achieving values up to 91%, whereas for the raw one only 56% removal was attained for the same reaction time. Besides, wet oxidation treatment was more efficient for the young leachate than for the old one, with final COD conversions of 60% and 37%, respectively. Eventually, a triangular "three-lump" kinetic model, which considered direct oxidation to CO2 and partial oxidation through intermediate compounds, was here proposed. PMID:26517790

  9. Robust Joining and Integration of Advanced Ceramics and Composites: Challenges, Opportunities, and Realities

    NASA Technical Reports Server (NTRS)

    Singh, Mrityunjay

    2006-01-01

    Advanced ceramics and fiber reinforced composites are under active consideration for use in a wide variety of high temperature applications within the aeronautics, space transportation, energy, and nuclear industries. The engineering designs of ceramic and composite components require fabrication and manufacturing of large and complex shaped parts of various thicknesses. In many instances, it is more economical to build up complex shapes by joining simple geometrical shapes. In addition, these components have to be joined or assembled with metallic sub-components. Thus, joining and attachment have been recognized as enabling technologies for successful utilization of ceramic components in various demanding applications. In this presentation, various challenges and opportunities in design, fabrication, and testing of high temperature joints in advanced ceramics and ceramic matrix composites will be presented. Silicon carbide based advanced ceramics and fiber reinforced composites in different shapes and sizes, have been joined using an affordable, robust ceramic joining technology. In addition, some examples of metal-ceramic brazing will also be presented. Microstructure and high temperature mechanical properties of joints in silicon carbide ceramics and composites will be reported. Various joint design philosophies and design issues in joining of ceramics and composites will be discussed.

  10. Properties of fiber composites for advanced flywheel energy storage devices

    SciTech Connect

    DeTeresa, S J; Groves, S E

    2001-01-12

    The performance of commercial high-performance fibers is examined for application to flywheel power supplies. It is shown that actual delivered performance depends on multiple factors such as inherent fiber strength, strength translation and stress-rupture lifetime. Experimental results for recent stress-rupture studies of carbon fibers will be presented and compared with other candidate reinforcement materials. Based on an evaluation of all of the performance factors, it is concluded that carbon fibers are preferred for highest performance and E-glass fibers for lowest cost. The inferior performance of the low-cost E-glass fibers can be improved to some extent by retarding the stress-corrosion of the material due to moisture and practical approaches to mitigating this corrosion are discussed. Many flywheel designs are limited not by fiber failure, but by matrix-dominated failure modes. Unfortunately, very few experimental results for stress-rupture under transverse tensile loading are available. As a consequence, significant efforts are made in flywheel design to avoid generating any transverse tensile stresses. Recent results for stress-rupture of a carbon fiber/epoxy composite under transverse tensile load reveal that these materials are surprisingly durable under the transverse loading condition and that some radial tensile stress could be tolerated in flywheel applications.

  11. Performance and stability of advanced monolithic and fiber reinforced composite candle filters during PCFBC operation

    SciTech Connect

    Alvin, M.A.

    1996-12-31

    Advanced clay bonded silicon carbide, alumina/mullite and CVI-SiC fiber reinforced composite porous ceramic candle filters have been identified for use in pressurized circulating fluidized-bed combustion (PCFBC) systems where operating temperatures approach 870--900 C. In this paper the author will discuss the performance of these filter elements, and explore the response and stability of the advanced filter materials after 540 hours of operation in Foster Wheeler`s PCFBC system in Karhula, Finland. The potential use of the advanced filter materials for extended operating life in high temperature, pressurized, coal-fired process applications will also be addressed.

  12. A study on the utilization of advanced composites in commercial aircraft wing structure

    NASA Technical Reports Server (NTRS)

    Watts, D. J.

    1978-01-01

    A study was conducted to define the technology and data needed to support the introduction of advanced composite materials in the wing structure of future production aircraft. The study accomplished the following: (1) definition of acceptance factors, (2) identification of technology issues, (3) evaluation of six candidate wing structures, (4) evaluation of five program options, (5) definition of a composite wing technology development plan, (6) identification of full-scale tests, (7) estimation of program costs for the total development plan, (8) forecast of future utilization of composites in commercial transport aircraft and (9) identification of critical technologies for timely program planning.

  13. A study on the utilization of advanced composites in commercial aircraft wing structure: Executive summary

    NASA Technical Reports Server (NTRS)

    Watts, D. J.

    1978-01-01

    The overall wing study objectives are to study and plan the effort by commercial transport aircraft manufacturers to accomplish the transition from current conventional materials and practices to extensive use of advanced composites in wings of aircraft that will enter service in the 1985-1990 time period. Specific wing study objectives are to define the technology and data needed to support an aircraft manufacturer's commitment to utilize composites primary wing structure in future production aircraft and to develop plans for a composite wing technology program which will provide the needed technology and data.

  14. Criteria for initiation of delamination in quasi-static punch-shear tests of a carbon-fiber composite material.

    SciTech Connect

    Chin, Eric Brian; English, Shawn Allen; Briggs, Timothy

    2015-09-01

    V arious phenomenological delamination initiation criteria are analyzed in quasi - static punch - shear tests conducted on six different geometries. These six geometries are modeled and analyzed using elastic, large - deformation finite element analysis. Analysis output is post - processed to assess different delamination initiation criteria, and their applicability to each of the geometries. These criteria are compared to test results to assess whether or not they are appropriate based on what occurred in testing. Further, examinations of CT scans and ultrasonic images o f test specimens are conducted in the appendix to determine the sequence of failure in each test geometry.

  15. Variation in Content Coverage by Classroom Composition: An Analysis of Advanced Math Course Content

    ERIC Educational Resources Information Center

    Covay, Elizabeth

    2011-01-01

    Everyone knows that there is racial inequality in achievement returns from advanced math; however, they do not know why black students and white students taking the same level of math courses are not leaving with the same or comparable skill levels. To find out, the author examines variation in course coverage by the racial composition of the…

  16. Study on utilization of advanced composites in fuselage structures of large transports

    NASA Technical Reports Server (NTRS)

    Johnson, R. W.; Thomson, L. W.; Wilson, R. D.

    1985-01-01

    The potential for utilizing advanced composites in fuselage structures of large transports was assessed. Six fuselage design concepts were selected and evaluated in terms of structural performance, weight, and manufacturing development and costs. Two concepts were selected that merit further consideration for composite fuselage application. These concepts are: (1) a full depth honeycomb design with no stringers, and (2) an I section stringer stiffened laminate skin design. Weight reductions due to applying composites to the fuselages of commercial and military transports were calculated. The benefits of applying composites to a fleet of military transports were determined. Significant technology issues pertinent to composite fuselage structures were identified and evaluated. Program plans for resolving the technology issues were developed.

  17. Evaluation of Advanced Composite Structures Technologies for Application to NASA's Vision for Space Exploration

    NASA Technical Reports Server (NTRS)

    Tenney, Darrel R.

    2008-01-01

    AS&M performed a broad assessment survey and study to establish the potential composite materials and structures applications and benefits to the Constellation Program Elements. Trade studies were performed on selected elements to determine the potential weight or performance payoff from use of composites. Weight predictions were made for liquid hydrogen and oxygen tanks, interstage cylindrical shell, lunar surface access module, ascent module liquid methane tank, and lunar surface manipulator. A key part of this study was the evaluation of 88 different composite technologies to establish their criticality to applications for the Constellation Program. The overall outcome of this study shows that composites are viable structural materials which offer from 20% to 40% weight savings for many of the structural components that make up the Major Elements of the Constellation Program. NASA investment in advancing composite technologies for space structural applications is an investment in America's Space Exploration Program.

  18. Vibration of shear deformable rings: Theory and experiment†

    NASA Astrophysics Data System (ADS)

    Gardner, T. G.; Bert, C. W.

    1985-12-01

    A new first-approximation theory is presented for analysis of the in-plane dynamic behavior of shear deformable ring structures. This theory may be applied to curved beams as well as complete rings. Natural frequencies and associated vibrational modes for a complete ring are investigated experimentally using modern instrumentation and experimental techniques. The natural frequencies predicted by the new theory are compared with the new experimental data as well as some previously reported data and predictions from thin-ring theory, various other shear deformable theories, elasticity theory, and various finite element analyses. The present theory includes a description of transverse shear strain which permits satisfaction of the physical requirements of zero shear stress at the inner-and outer-ring surfaces. Transverse shear strain is an important effect when analyzing thick, homogeneous, material rings and even more significant for rings made of composite materials. This theory is an advancement over Bresse-type, shear-correction theories, which utilize a shear correction factor determined in an ad hoc fashion.

  19. Advanced composite structural concepts and materials technologies for primary aircraft structures: Advanced material concepts

    NASA Technical Reports Server (NTRS)

    Lau, Kreisler S. Y.; Landis, Abraham L.; Chow, Andrea W.; Hamlin, Richard D.

    1993-01-01

    To achieve acceptable performance and long-term durability at elevated temperatures (350 to 600 F) for high-speed transport systems, further improvements of the high-performance matrix materials will be necessary to achieve very long-term (60,000-120,000 service hours) retention of mechanical properties and damage tolerance. This report emphasizes isoimide modification as a complementary technique to semi-interpenetrating polymer networks (SIPN's) to achieve greater processibility, better curing dynamics, and possibly enhanced thermo-mechanical properties in composites. A key result is the demonstration of enhanced processibility of isoimide-modified linear and thermo-setting polyimide systems.

  20. Evaluation of Shear Bond Strength of Methacrylate- and Silorane-based Composite Resin Bonded to Resin-Modified Glass-ionomer Containing Micro- and Nano-hydroxyapatite

    PubMed Central

    Sharafeddin, Farahnaz; Moradian, Marzie; Motamedi, Mehran

    2016-01-01

    Statement of the Problem The adhesion of resin-modified glass-ionomer (RMGI) to composite resin has a very important role in the durability of sandwich restorations. Hydroxyapatite is an excellent candidate as a filler material for improving the mechanical properties of glass ionomer cement. Purpose The aim of this study was to assess the effect of adding micro- and nano-hydroxyapatite (HA) powder to RMGI on the shear bond strength (SBS) of nanofilled and silorane-based composite resins bonded to RMGI containing micro- and nano-HA. Materials and Method Sixty cylindrical acrylic blocks containing a hole of 5.5×2.5 mm (diameter × height) were prepared and randomly divided into 6 groups as Group 1 with RMGI (Fuji II LC) plus Adper Single Bond/Z350 composite resin (5.5×3.5 mm diameter × height); Group 2 with RMGI containing 25 wt% of micro-HA plus Adper Single Bond/Z350 composite resin; Group3 with RMGI containing 25 wt% of nano-HA plus Adper Single Bond/Z350 composite resin; Group 4 with RMGI plus P90 System Adhesive/P90 Filtek composite resin (5.5×3.5 mm diameter × height); Group 5 with RMGI containing 25 wt% of micro-HA plus P90 System Adhesive/P90Filtek composite resin; and Group 6 with RMGI containing 25 wt% of nano-HA plus P90 System Adhesive/P90 Filtek composite resin. The specimens were stored in water (37° C, 1 week) and subjected to 1000 thermal cycles (5°C/55°C). SBS test was performed by using a universal testing machine at a crosshead speed of 1 mm/min. Data were analyzed by two-way ANOVA and Tukey test (p< 0.05). Results There were significant differences between groups 1 and 4 (RMGI groups, p= 0.025), and groups 3 and 6 (RMGI+ nano-HA groups, p= 0.012). However, among Z350 and P90 specimens, no statistically significant difference was detected in the SBS values (p= 0.19, p= 0.083, respectively). Conclusion RMGI containing HA can improve the bond strength to methacrylate-based in comparison to silorane-based composite resins. Meanwhile, RMGI

  1. Joining and Assembly of Silicon Carbide-based Advanced Ceramics and Composites for High Temperature Applications

    NASA Technical Reports Server (NTRS)

    Singh, M.

    2004-01-01

    Silicon carbide based advanced ceramics and fiber reinforced composites are under active consideration for use in wide variety of high temperature applications within the aeronautics, space transportation, energy, and nuclear industries. The engineering designs of ceramic and composite component require fabrication and manufacturing of large and complex shaped parts of various thicknesses. In many instances, it is more economical to build up complex shapes by joining simple geometrical shapes. In addition these components have to be joined or assembled with metallic sub-components. Thus, joining and attachment have been recognized as enabling technologies for successful utilization of ceramic components in various demanding applications. In this presentation, various challenges and opportunities in design, fabrication, and testing o high temperature joints in ceramic matrix composites will be presented. Silicon carbide based advanced ceramics (CVD and hot pressed), and C/SiC and SiC/SiC composites, in different shapes and sizes, have been joined using an affordable, robust ceramic joining technology (ARCJoinT). Microstructure and high temperature mechanical properties of joints in silicon carbide ceramics and CVI and melt infiltrated SiC matrix composites will,be reported. Various joint design philosophies and design issues in joining of ceramics and composites well be discussed.

  2. Influence of Cr and W alloying on the fiber-matrix interfacial shear strength in cast and directionally solidified sapphire NiAl composites

    NASA Technical Reports Server (NTRS)

    Asthana, R.; Tiwari, R.; Tewari, S. N.

    1995-01-01

    Sapphire-reinforced NiAl matrix composites with chromium or tungsten as alloying additions were synthesized using casting and zone directional solidification (DS) techniques and characterized by a fiber pushout test as well as by microhardness measurements. The sapphire-NiAl(Cr) specimens exhibited an interlayer of Cr rich eutectic at the fiber-matrix interface and a higher interfacial shear strength compared to unalloyed sapphire-NiAl specimens processed under identical conditions. In contrast, the sapphire-NiAl(W) specimens did not show interfacial excess of tungsten rich phases, although the interfacial shear strength was high and comparable to that of sapphire-NiAl(Cr). The postdebond sliding stress was higher in sapphire-NiAl(Cr) than in sapphire-NiAl(W) due to interface enrichment with chromium particles. The matrix microhardness progressively decreased with increasing distance from the interface in both DS NiAl and NiAl(Cr) specimens. The study highlights the potential of casting and DS techniques to improve the toughness and strength of NiAl by designing dual-phase microstructures in NiAl alloys reinforced with sapphire fibers.

  3. Influence of transverse-shear and large-deformation effects on the low-speed impact response of laminated composite plates

    NASA Technical Reports Server (NTRS)

    Ambur, Damodar R.; Starnes, James H., Jr.; Prasad, Chunchu B.

    1993-01-01

    An analytical procedure is presented for determining the transient response of simply supported, rectangular laminated composite plates subjected to impact loads from airgun-propelled or dropped-weight impactors. A first-order shear-deformation theory is included in the analysis to represent properly any local short-wave-length transient bending response. The impact force is modeled as a locally distributed load with a cosine-cosine distribution. A double Fourier series expansion and the Timoshenko small-increment method are used to determine the contact force, out-of-plane deflections, and in-plane strains and stresses at any plate location due to an impact force at any plate location. The results of experimental and analytical studies are compared for quasi-isotropic laminates. The results indicate that using the appropriate local force distribution for the locally loaded area and including transverse-shear-deformation effects in the laminated plate response analysis are important. The applicability of the present analytical procedure based on small deformation theory is investigated by comparing analytical and experimental results for combinations of quasi-isotropic laminate thicknesses and impact energy levels. The results of this study indicate that large-deformation effects influence the response of both 24- and 32-ply laminated plates, and that a geometrically nonlinear analysis is required for predicting the response accurately.

  4. MIT/Marine Industry Collegium Opportunity Brief: Advanced composites for offshore structures. Held in Cambridge, Massachusetts on October 30-31, 1991

    SciTech Connect

    Moore, J.

    1991-01-01

    Synopses of Presentations: An Overview of Advanced Structural Composites for Offshore Structures; High-Performance Composites for Deepwater Risers; Failure and Damage Mechanisms in Composites; Environmental Degradation of Composites; Composites Manufacturing; Steel-Concrete-Steel Sandwich Composite Construction for Permanently Floating Platforms; High-Strength Cement Composites for Marine Applications; Minimum Weight Design of Foam Core Sandwich Panels; Design of Fiber Reinforced Brittle and Quasi-Brittle Matrix Composites for Marine Applications; Offshore Applications and Requirements for Use of Advanced Composites; Polymer Composites in Structures; Non-Conventional Profiles of Composites for Structural Applications; Composite in Construction Require a Structural Design System; Economic Evaluation of Composites for Offshore Use.

  5. Hydration of marginal basins and compositional variations within the continental lithospheric mantle inferred from a new global model of shear and compressional velocity

    NASA Astrophysics Data System (ADS)

    Tesoniero, Andrea; Auer, Ludwig; Boschi, Lapo; Cammarano, Fabio

    2015-11-01

    We present a new global model of shear and compressional wave speeds for the entire mantle, partly based on the data set employed for the shear velocity model savani. We invert Rayleigh and Love surface waves up to the sixth overtone in combination with major P and S body wave phases. Mineral physics data on the isotropic δlnVS/δlnVP ratio are taken into account in the form of a regularization constraint. The relationship between VP and VS that we observe in the top 300 km of the mantle has important thermochemical implications. Back-arc basins in the Western Pacific are characterized by large VP/VS and not extremely low VS at ˜150 km depth, consistently with presence of water. Most pronounced anomalies are located in the Sea of Japan, in the back-arc region of the Philippine Sea, and in the South China Sea. Our results indicate the effectiveness of slab-related processes to hydrate the mantle and suggest an important role of Pacific plate subduction also for the evolution of the South China Sea. We detect lateral variations in composition within the continental lithospheric mantle. Regions that have been subjected to rifting, collisions, and flood basalt events are underlain by relatively large VP/VS ratio compared to undeformed Precambrian regions, consistently with a lower degree of chemical depletion. Compositional variations are also observed in deep lithosphere. At ˜200 km depth, mantle beneath Australia and African cratons has comparable positive VS anomalies with other continental regions, but VP is ˜1% higher.

  6. Study of mould design and forming process on advanced polymer-matrix composite complex structure

    NASA Astrophysics Data System (ADS)

    Li, S. J.; Zhan, L. H.; Bai, H. M.; Chen, X. P.; Zhou, Y. Q.

    2015-07-01

    Advanced carbon fibre-reinforced polymer-matrix composites are widely applied to aviation manufacturing field due to their outstanding performance. In this paper, the mould design and forming process of the complex composite structure were discussed in detail using the hat stiffened structure as an example. The key issues of the moulddesign were analyzed, and the corresponding solutions were also presented. The crucial control points of the forming process such as the determination of materials and stacking sequence, the temperature and pressure route of the co-curing process were introduced. In order to guarantee the forming quality of the composite hat stiffened structure, a mathematical model about the aperture of rubber mandrel was introduced. The study presented in this paper may provide some actual references for the design and manufacture of the important complex composite structures.

  7. Modeling Creep Effects in Advanced SiC/SiC Composites

    NASA Technical Reports Server (NTRS)

    Lang, Jerry; DiCarlo, James

    2006-01-01

    Because advanced SiC/SiC composites are projected to be used for aerospace components with large thermal gradients at high temperatures, efforts are on-going at NASA Glenn to develop approaches for modeling the anticipated creep behavior of these materials and its subsequent effects on such key composite properties as internal residual stress, proportional limit stress, ultimate tensile strength, and rupture life. Based primarily on in-plane creep data for 2D panels, this presentation describes initial modeling progress at applied composite stresses below matrix cracking for some high performance SiC/SiC composite systems recently developed at NASA. Studies are described to develop creep and rupture models using empirical, mechanical analog, and mechanistic approaches, and to implement them into finite element codes for improved component design and life modeling

  8. Investigation of the relations between resin and advanced composite mechanical properties. Volume 2: Appendices

    NASA Technical Reports Server (NTRS)

    Zimmerman, R. S.; Adams, D. F.; Walrath, D. E.

    1984-01-01

    One untoughened epoxy baseline resin and three toughened epoxy resin systems were evaluated. The Hercules 3502, 2220-1, and 2220-3, and Ciba-Geigy Fibredux 914 resin systems were supplied in the uncured state by NASA-Langley and cast into thin flat specimens and round dogbone specimens. Tensile and torsional shear measurements were performed at three temperatures and two moisture conditions. Coefficients of thermal expansion and moisture expansion were also measured. Extensive scanning electron microscopic examination of fracture surfaces was performed to permit the correlation of observed failure modes with the environmental conditions under which the various specimens were tested. A micromechanics analysis was used to predict the unidirectional composite response under the various test conditions, incorporating the neat resin experimental results as the required input data. The mechanical and physical test results, the scanning electron microscope observations, and the analytical predictions were then correlated.

  9. Investigation of the relations between neat resin and advanced composite mechanical properties. Volume 1: Results

    NASA Technical Reports Server (NTRS)

    Zimmerman, R. S.; Adams, D. F.; Walrath, D. E.

    1984-01-01

    A detailed evaluation of one untoughened epoxy baseline resin and three toughened epoxy resin systems was performed. The Hercules 3502, 2220-1, and 2220-3, and Ciba-Geigy Fibredux 914 resin systems were supplied in the uncured state by NASA-Langley and cast into thin flat specimens and round dogbone specimens. Tensile and torsional shear measurements were performed at three temperatures and two moisture conditions. Coefficients of thermal expansion and moisture expansion were also measured. Extensive scanning electron microscopic examination of fracture surfaces was performed, to permit the correlation of observed failure modes with the environmental conditions under which the various specimens were tested. A micromechanics analysis was used to predict the unidirectional composite response under the various test conditions, using the neat resin experimental results as the required input data. Mechanical and physical test results, the scanning electron microscope observations, and the analytical predictions were then correlated.

  10. Recent advances in lightweight, filament-wound composite pressure vessel technology

    NASA Technical Reports Server (NTRS)

    Lark, R. F.

    1977-01-01

    A review of recent advances is presented for lightweight, high performance composite pressure vessel technology that covers the areas of design concepts, fabrication procedures, applications, and performance of vessels subjected to single cycle burst and cyclic fatigue loading. Filament wound fiber/epoxy composite vessels were made from S glass, graphite, and Kevlar 49 fibers and were equipped with both structural and nonstructural liners. Pressure vessels structural efficiencies were attained which represented weight savings, using different liners, of 40 to 60 percent over all titanium pressure vessels. Significant findings in each area are summarized.

  11. Modeling and response analysis of thin-walled beam structures constructed of advanced composite materials

    SciTech Connect

    Song, O.

    1990-01-01

    Thin-walled beam structures are adopted as structural members in various fields of modern technology including aeronautical/aerospacial, naval, mechanical and civil ones. With the advent of advanced composite material systems, there is a vital need to reformulate the classical theory of thin-walled beams in a wide framework. In this dissertation, the aeroelastic divergence instability of aircraft wings modeled as thin-walled beams as well as the eigenfrequency problem of cantilevered composite thin-walled beams of closed cross-section are considered in the framework of a refined theory incorporating non-classical effects.

  12. Integrated Design for Manufacturing of Braided Preforms for Advanced Composites Part I: 2D Braiding

    NASA Astrophysics Data System (ADS)

    Gao, Yan Tao; Ko, Frank K.; Hu, Hong

    2013-12-01

    This paper presents a 2D braiding design system for advanced textile structural composites was based on dynamic models. A software package to assist in the design of braided preform manufacturing has been developed. The package allows design parameters (machine speeds, fiber volume fraction, tightness factor, etc.) to be easily obtained and the relationships between said parameters to be demonstrated graphically. The fabirc geometry model (FGM) method was adopted to evaluate the mechanical properties of the composites. Experimental evidence demonstrates the success of the use of dynamic models in the design software for the manufacture of braided fabric preforms.

  13. Displaying Composite and Archived Soundings in the Advanced Weather Interactive Processing System

    NASA Technical Reports Server (NTRS)

    Barrett, Joe H., III; Volkmer, Matthew R.; Blottman, Peter F.; Sharp, David W.

    2008-01-01

    This presentation describes work done by the Applied Meteorology Unit (AMU) to add composite soundings to the Advanced Weather Interactive Processing System (AWIPS). This allows National Weather Service (NWS) forecasters to compare the current atmospheric state with climatology. In a previous task, the AMU created composite soundings for four rawinsonde observation stations in Florida, for each of eight flow regimes. The composite soundings were delivered to the NWS Melbourne (MLB) office for display using the NSHARP software program. NWS MLB requested that the AMU make the composite soundings available for display in AWIPS. The AMU first created a procedure to customize AWIPS so composite soundings could be displayed. A unique four-character identifier was created for each of the 32 composite soundings. The AMIU wrote a Tool Command Language/Tool Kit (TclITk) software program to convert the composite soundings from NSHARP to Network Common Data Form (NetCDF) format. The NetCDF files were then displayable by AWIPS.

  14. A shear deformable theory of laminated composite shallow shell-type panels and their response analysis. II - Static response

    NASA Technical Reports Server (NTRS)

    Khdeir, A. A.; Librescu, L.; Frederick, D.

    1989-01-01

    In the second part of this paper, by using the static counterparts of the governing equations derived in Librescu (1989), the static response of shallow composite shell-type panels subjected to a sinusoidal transverse load is investigated. The numerical applications, encompassing a large number of boundary conditions and various lamination schemes, allow one to obtain some conclusions which are formulated in the paper.

  15. Advanced Compositional Analysis of Nanoparticle-polymer Composites Using Direct Fluorescence Imaging.

    PubMed

    Crick, Colin R; Noimark, Sacha; Peveler, William J; Bear, Joseph C; Ivanov, Aleksandar P; Edel, Joshua B; Parkin, Ivan P

    2016-01-01

    The fabrication of polymer-nanoparticle composites is extremely important in the development of many functional materials. Identifying the precise composition of these materials is essential, especially in the design of surface catalysts, where the surface concentration of the active component determines the activity of the material. Antimicrobial materials which utilize nanoparticles are a particular focus of this technology. Recently swell encapsulation has emerged as a technique for inserting antimicrobial nanoparticles into a host polymer matrix. Swell encapsulation provides the advantage of localizing the incorporation to the external surfaces of materials, which act as the active sites of these materials. However, quantification of this nanoparticle uptake is challenging. Previous studies explore the link between antimicrobial activity and surface concentration of the active component, but this is not directly visualized. Here we show a reliable method to monitor the incorporation of nanoparticles into a polymer host matrix via swell encapsulation. We show that the surface concentration of CdSe/ZnS nanoparticles can be accurately visualized through cross-sectional fluorescence imaging. Using this method, we can quantify the uptake of nanoparticles via swell encapsulation and measure the surface concentration of encapsulated particles, which is key in optimizing the activity of functional materials. PMID:27500449

  16. Launch vehicle flight control augmentation using smart materials and advanced composites (CDDF Project 93-05)

    NASA Technical Reports Server (NTRS)

    Barret, C.

    1995-01-01

    The Marshall Space Flight Center has a rich heritage of launch vehicles that have used aerodynamic surfaces for flight stability such as the Saturn vehicles and flight control such as on the Redstone. Recently, due to aft center-of-gravity locations on launch vehicles currently being studied, the need has arisen for the vehicle control augmentation that is provided by these flight controls. Aerodynamic flight control can also reduce engine gimbaling requirements, provide actuator failure protection, enhance crew safety, and increase vehicle reliability, and payload capability. In the Saturn era, NASA went to the Moon with 300 sq ft of aerodynamic surfaces on the Saturn V. Since those days, the wealth of smart materials and advanced composites that have been developed allow for the design of very lightweight, strong, and innovative launch vehicle flight control surfaces. This paper presents an overview of the advanced composites and smart materials that are directly applicable to launch vehicle control surfaces.

  17. The effect of surface treatment with Er: YAG laser on shear bond strength of orthodontic brackets to fiber-reinforced composite

    PubMed Central

    Dehghani, Mahboobe

    2014-01-01

    Objectives: This study aimed to investigate the effect of surface treatment with Er:YAG laser on shear bond strength (SBS) of orthodontic brackets to fiber-reinforced composite (FRC). Study Design: Ninety human premolars were randomly divided into six groups of 15. FRC bars were bonded to the teeth with a flowable composite (FC) and then underwent following treatments. In group 1 no further treatment was performed. In group 2 the FRC surfaces were covered by FC. An Er:YAG laser was employed to treat FRCs in groups 3 ( 200 mJ/10 Hz) and 4 (300 mJ/15 Hz). The FRC strips in groups 5 and 6 were first covered by FC and then irradiated with Er:YAG laser at 200 mJ/10 Hz (group 5) or 300 mJ/15 Hz (group 6). Stainless steel brackets were bonded to FRCs using a light-cure adhesive system. After 24 hours, the samples were tested for SBS and the adhesive remnant index (ARI) scores were determined. Results: There was a significant difference in SBS among the study groups (P <0.001). Pairwise comparisons indicated that SBS was significantly lower in group 1 compared to all other groups (p<0.05) except group 2. Bond strength in group 6 was significantly greater than all the study groups (p<0.05) except group 5. No significant difference was found in ARI scores among the groups. Conclusions: Covering the FRC surface by a layer of flowable composite and then application of Er:YAG laser at 300 mJ/15 Hz could be recommended to increase bond strength of orthodontic attachments to FRC. Key words:Fiber-reinforced composite, orthodontics, Sshear bond strength, laser, Er:YAG, surface treatment, bracket, FRC. PMID:25593660

  18. Influence of Different Power Outputs of Er:YAG Laser on Shear Bond Strength of a Resin Composite to Feldspathic Porcelain

    PubMed Central

    Sadeghi, Mostafa; Davari, Abdolrahim; Abolghasami Mahani, Amin; Hakimi, Hamid

    2015-01-01

    Statement of the Problem Porcelain may fracture or chip if exposed to any traumas and can be repaired by using a resin composite. Purpose This study was aimed to evaluate the influences of Er:YAG laser on shear bond strength (SBS) of resin composite to feldspathic porcelain. Materials and Method Seventy-two porcelain blocks were divided into six groups (n=12): G1: no treatment (control group); G2: 9% hydrofluoric acid (HF); G3-6 were separately irradiated with Er:YAG laser using four energy parameters: 2W, 100mj (G3); 3W, 150mj (G4); 4W, 200mj (G5) and 5W, 250mj (G6), respectively; and 20 Hz frequency in long-pulse mode. After silane treatment, a resin composite rod was bonded to each of the porcelain block. The SBS was measured following storage and thermocycling. Data were analyzed by one-way ANOVA, Tamhane and Chi-Square tests. Results The highest SBS (12.29±3.04 MPa) was obtained with HF (G2). The lowest SBS (2.23±0.60 MPa) was observed in G4, followed by G3 (1.96±0.76 MPa). G6 had a significantly higher SBS (8.00±2.22 MPa) than other laser irradiation groups. Conclusion Although, Er:YAG laser irradiation at 5W, 250mJ/20 Hz was effective in promoting adhesion of resin composite to feldspathic porcelain compared with the control group, it cannot be used as a safe alternative method to HF acid. Laser irradiation with the evaluated parameters in this study does not promote an effective adhesion on porcelain surface to create adequate bond for clinical use. PMID:25759855

  19. The Advanced Composition Explorer is placed atop its Delta II launcher at Pad 17A, CCAS

    NASA Technical Reports Server (NTRS)

    1997-01-01

    The Advanced Composition Explorer (ACE) spacecraft is placed atop its launch vehicle at Launch Complex 17A. Scheduled for launch on a Delta II rocket from Cape Canaveral Air Station on Aug. 24, ACE will study low-energy particles of solar origin and high-energy galactic particles. The collecting power of instruments aboard ACE is 10 to 1,000 times greater than anything previously flown to collect similar data by NASA.

  20. Advanced composite elevator for Boeing 727 aircraft. Volume 1: Technical summary

    NASA Technical Reports Server (NTRS)

    Chovil, D. V.; Harvey, S. T.; Mccarty, J. E.; Desper, O. E.; Jamison, E. S.; Syder, H.

    1981-01-01

    The design, development, analysis, and testing activities and results that were required to produce five and one-half shipsets of advanced composite elevators for Boeing 727 aircraft are summarized. During the preliminary design period, alternative concepts were developed. After selection of the best design, detail design and basic configuration improvements were evaluated. Five and one-half shipsets were manufactured. All program goals (except competitive cost demonstration) were accomplished when our design met or exceeded all requirements, criteria, and objectives.

  1. Stress analysis of advanced attack helicopter composite main rotor blade root end lug

    NASA Technical Reports Server (NTRS)

    Baker, D. J.

    1982-01-01

    Stress analysis of the Advanced Attack Helicopter (AAH) composite main rotor blade root end lug is described. The stress concentration factor determined from a finite element analysis is compared to an empirical value used in the lug design. The analysis and test data indicate that the stress concentration is primarily a function of configuration and independent of the range of material properties typical of Kevlar-49/epoxy and glass epoxy.

  2. High Thermal Conductivity NARloy-Z-Diamond Composite Combustion Chamber Liner For Advanced Rocket Engines

    NASA Technical Reports Server (NTRS)

    Bhat, Biliyar N.; Ellis, David; Singh, Jogender

    2014-01-01

    Advanced high thermal conductivity materials research conducted at NASA Marshall Space Flight Center (MSFC) with state of the art combustion chamber liner material NARloy-Z showed that its thermal conductivity can be increased significantly by adding diamond particles and sintering it at high temperatures. For instance, NARloy-Z containing 40 vol. percent diamond particles, sintered at 975C to full density by using the Field assisted Sintering Technology (FAST) showed 69 percent higher thermal conductivity than baseline NARloy-Z. Furthermore, NARloy-Z-40vol. percent D is 30 percent lighter than NARloy-Z and hence the density normalized thermal conductivity is 140 percent better. These attributes will improve the performance and life of the advanced rocket engines significantly. By one estimate, increased thermal conductivity will directly translate into increased turbopump power up to 2X and increased chamber pressure for improved thrust and ISP, resulting in an expected 20 percent improvement in engine performance. Follow on research is now being conducted to demonstrate the benefits of this high thermal conductivity NARloy-Z-D composite for combustion chamber liner applications in advanced rocket engines. The work consists of a) Optimizing the chemistry and heat treatment for NARloy-Z-D composite, b) Developing design properties (thermal and mechanical) for the optimized NARloy-Z-D, c) Fabrication of net shape subscale combustion chamber liner, and d) Hot fire testing of the liner for performance. FAST is used for consolidating and sintering NARlo-Z-D. The subscale cylindrical liner with built in channels for coolant flow is also fabricated near net shape using the FAST process. The liner will be assembled into a test rig and hot fire tested in the MSFC test facility to determine performance. This paper describes the development of this novel high thermal conductivity NARloy-Z-D composite material, and the advanced net shape technology to fabricate the combustion

  3. Annual Conference on Composites and Advanced Ceramic Materials, 11th, Cocoa Beach, FL, Jan. 18-23, 1987, Proceedings

    SciTech Connect

    Not Available

    1987-08-01

    The present conference on advanced ceramic materials discusses topics in the fields of NDE, coating/joining/tribology techniques, fracture and interface phenomena, whisker- and particulate-reinforced composites, fiber and whisker properties, SiC and Si/sub 3/N/sub 4/, glass/glass-ceramic matrix composites, alumina-matrix composites, ceramic materials for space structures, and SiC- and Si/sub 3/N/sub 4/-matrix composites. Attention is given to ceramic characterization by thermal wave imaging, an advanced ceramic-to-metal joining process, the fracture modes of brittle-matrix unidirectional composites, the oxidation of SiC-containing composites, particulate matter in SiC whiskers, corrosion reactions in SiC ceramics, melt-infiltrated ceramic-matrix composites, environmental effects in toughened ceramics, and a ceramic composite heat exchanger.

  4. Study of the costs and benefits of composite materials in advanced turbofan engines

    NASA Technical Reports Server (NTRS)

    Steinhagen, C. A.; Stotler, C. L.; Neitzel, R. E.

    1974-01-01

    Composite component designs were developed for a number of applicable engine parts and functions. The cost and weight of each detail component was determined and its effect on the total engine cost to the aircraft manufacturer was ascertained. The economic benefits of engine or nacelle composite or eutectic turbine alloy substitutions was then calculated. Two time periods of engine certification were considered for this investigation, namely 1979 and 1985. Two methods of applying composites to these engines were employed. The first method just considered replacing an existing metal part with a composite part with no other change to the engine. The other method involved major engine redesign so that more efficient composite designs could be employed. Utilization of polymeric composites wherever payoffs were available indicated that a total improvement in Direct Operating Cost (DOC) of 2.82 to 4.64 percent, depending on the engine considered, could be attained. In addition, the percent fuel saving ranged from 1.91 to 3.53 percent. The advantages of using advanced materials in the turbine are more difficult to quantify but could go as high as an improvement in DOC of 2.33 percent and a fuel savings of 2.62 percent. Typically, based on a fleet of one hundred aircraft, a percent savings in DOC represents a savings of four million dollars per year and a percent of fuel savings equals 23,000 cu m (7,000,000 gallons) per year.

  5. Validation of an Advanced Material Model for Simulating the Impact and Shock Response of Composite Materials

    NASA Astrophysics Data System (ADS)

    Clegg, Richard A.; Hayhurst, Colin J.; Nahme, Hartwig

    2002-07-01

    Composite materials are now commonly used as ballistic and hypervelocity protection materials and the demand for simulation of impact on these materials is increasing. A new material model specifically designed for the shock response of anisotropic materials has been developed and implemented in the hydrocode AUTODYN. The model allows for the representation of non-linear shock effects in combination with anisotropic material stiffness and damage. The coupling of the equation of state and anisotropic response is based on the methodology proposed by Anderson et al. [2]. An overview of the coupled formulation is described in order to point out the important assumptions, key innovations and basic theoretical framework. The coupled model was originally developed by Century Dynamics and Fhg-EMI for assessing the hypervelocity impact response of composite satellite protection systems [1]. It was also identified that the developed model should also offer new possibilities and capabilities for modelling modern advanced armour materials. Validation of the advanced composite model is firstly shown via simulations of uniaxial strain flyer plate experiments on aramid and polyethylene fibre composite systems. Finally, practical application of the model as implemented in AUTODYN is demonstrated through the simulation of ballistic and hypervelocity impact events. Comparison with experiment is given where possible.

  6. Study of utilization of advanced composites in fuselage structures of large transports

    NASA Technical Reports Server (NTRS)

    Jackson, A. C.; Campion, M. C.; Pei, G.

    1984-01-01

    The effort required by the transport aircraft manufacturers to support the introduction of advanced composite materials into the fuselage structure of future commercial and military transport aircraft is investigated. Technology issues, potential benefits to military life cycle costs and commercial operating costs, and development plans are examined. The most urgent technology issues defined are impact dynamics, acoustic transmission, pressure containment and damage tolerance, post-buckling, cutouts, and joints and splices. A technology demonstration program is defined and a rough cost and schedule identified. The fabrication and test of a full-scale fuselage barrel section is presented. Commercial and military benefits are identified. Fuselage structure weight savings from use of advanced composites are 16.4 percent for the commercial and 21.8 percent for the military. For the all-composite airplanes the savings are 26 percent and 29 percent, respectively. Commercial/operating costs are reduced by 5 percent for the all-composite airplane and military life cycle costs by 10 percent.

  7. Time-temperature-stress capabilities of composite materials for advanced supersonic technology application, phase 1

    NASA Technical Reports Server (NTRS)

    Kerr, J. R.; Haskins, J. F.

    1980-01-01

    Implementation of metal and resin matrix composites into supersonic vehicle usage is contingent upon accelerating the demonstration of service capacity and design technology. Because of the added material complexity and lack of extensive service data, laboratory replication of the flight service will provide the most rapid method of documenting the airworthiness of advanced composite systems. A program in progress to determine the time temperature stress capabilities of several high temperature composite materials includes thermal aging, environmental aging, fatigue, creep, fracture, and tensile tests as well as real time flight simulation exposure. The program has two parts. The first includes all the material property determinations and aging and simulation exposures up through 10,000 hours. The second continues these tests up to 50,000 cumulative hours. Results are presented of the 10,000 hour phase, which has now been completed.

  8. Advanced leading edge thermal-structure concept. Direct bond reusable surface insulation to a composite structure

    NASA Technical Reports Server (NTRS)

    Riccitiello, S. R.; Figueroa, H.; Coe, C. F.; Kuo, C. P.

    1984-01-01

    An advanced leading-edge concept was analyzed using the space shuttle leading edge system as a reference model. The comparison indicates that a direct-bond system utilizing a high temperature (2700 F) fibrous refractory composite insulation tile bonded to a high temperature (PI/graphite) composite structure can result in a weight savings of up to 800 lb. The concern that tile damage or loss during ascent would result in adverse entry aerodynamics if a leading edge tile system were used is addressed. It was found from experiment that missing tiles (as many as 22) on the leading edge would not significantly affect the basic force-and-moment aerodynamic coefficients. Additionally, this concept affords a degree of redundancy to a thermal protection system in that the base structure (being a composite material) ablates and neither melts nor burns through when subjected to entry heating in the event tiles are actually lost or damaged during ascent.

  9. The Influence of SiC on the Ablation Response of Advanced Refractory Composite Materials

    NASA Technical Reports Server (NTRS)

    Bull, Jeffrey D.; Rasky, Daniel J. (Technical Monitor)

    1994-01-01

    In continuing our studies of advanced refractory composite materials we have recently completed an arc-jet test series of a diverse group of ceramics and ceramic matrix composites. The compositions range from continuous fiber reinforced ceramics to monoliths. Many of these materials contain SiC and one objective of this test series was to identify the influence of SiC oxidation mechanisms on material performance. Hence the arc heater was operated at two conditions; one in which the passive oxidation of SiC would be dominant and the other where the active oxidation of SiC would be dominant. It is shown here that the active oxidation mechanism of SiC does not dominate material performance when it is present at levels equal to or below 20 volume percent.

  10. MRS International Meeting on Advanced Materials, 1st, Tokyo, Japan, June 2, 3, 1988, Proceedings. Volume 4 - Composites corrosion/Coating of advanced materials

    SciTech Connect

    Kimura, Shiushichi; Kobayashi, Akira; Nii, Kazuyoshi; Saito, Yasutoshi; Umekawa, Sokichi.

    1989-01-01

    The present conference on metal-matrix composites (MMCs) and ceramic-matrix composites (CMCs) discusses electrodeposited C/Cu MMCs, the quasi-liquid hot press method for SiC/Al composites, die-cast MMCs for tribological applications, the solidification-processing of monotectic alloy matrix composites, the fracture of SiC whisker-reinforced Al-alloy MMCs, the elastic constants of a graphite/magnesium composite, and an elastoplastic analysis of metal/plastic/metal sandwich plates in three-point bending. Also discussed are the fabrication of diamond particle-dispersed glass composites in space, heat-resistant graphite fiber-reinforced phosphate ceramic CMCs, the high-temperature creep of SiC-reinforced alumina CMCs, flexible carbon fiber-reinforced exfoliated graphite composites, and the application of advanced CMCs to advanced railway systems, the corrosion and oxidation of SiC, Si{sub 3}N{sub 4}, and other structural ceramics, corrosion properties of advanced alloys, and novel coating systems for advanced materials.

  11. Effects of hydrogen peroxide pretreatment and heat activation of silane on the shear bond strength of fiber-reinforced composite posts to resin cement

    PubMed Central

    Shin, Tae-Bong; Lee, Joo-Hee; Ahn, Kang-Min; Kim, Tae-Hyung

    2016-01-01

    PURPOSE To evaluate the effects of hydrogen peroxide pretreatment and heat activation of silane on the shear bond strength of fiber-reinforced composite posts to resin cement. MATERIALS AND METHODS The specimens were prepared to evaluate the bond strength of epoxy resin-based fiber posts (D.T. Light-Post) to dual-curing resin cement (RelyX U200). The specimens were divided into four groups (n=18) according to different surface treatments: group 1, no treatment; group 2, silanization; group 3, silanization after hydrogen peroxide etching; group 4, silanization with warm drying at 80℃ after hydrogen peroxide etching. After storage of the specimens in distilled water at 37℃ for 24 hours, the shear bond strength (in MPa) between the fiber post and resin cement was measured using a universal testing machine. The fractured surface of the fiber post was examined using scanning electron microscopy. Data were analyzed using one-way ANOVA and post-hoc analysis with Tukey's HSD test (α=0.05). RESULTS Silanization of the fiber post (Group 2) significantly increased the bond strength in comparison with the non treated control (Group 1) (P<.05). Heat drying after silanization also significantly increased the bond strength (Group 3 and 4) (P<.05). However, no effect was determined for hydrogen peroxide etching before applying silane agent (Group 2 and 3) (P>.05). CONCLUSION Fiber post silanization and subsequent heat treatment (80℃) with warm air blower can be beneficial in clinical post cementation. However, hydrogen peroxide etching prior to silanization was not effective in this study. PMID:27141252

  12. Reduced toxicity polyester resins and microvascular pre-preg tapes for advanced composites manufacturing

    NASA Astrophysics Data System (ADS)

    Poillucci, Richard

    Advanced composites manufacturing broadly encapsulates topics ranging from matrix chemistries to automated machines that lay-up fiber-reinforced materials. Environmental regulations are stimulating research to reduce matrix resin formulation toxicity. At present, composites fabricated with polyester resins expose workers to the risk of contact with and inhalation of styrene monomer, which is a potential carcinogen, neurotoxin, and respiratory irritant. The first primary goal of this thesis is to reduce the toxicity associated with polyester resins by: (1) identification of potential monomers to replace styrene, (2) determination of monomer solubility within the polyester, and (3) investigation of approaches to rapidly screen a large resin composition parameter space. Monomers are identified based on their ability to react with polyester and their toxicity as determined by the Globally Harmonized System (GHS) and a green screen method. Solubilities were determined by the Hoftyzer -- Van Krevelen method, Hansen solubility parameter database, and experimental mixing of monomers. A combinatorial microfluidic mixing device is designed and tested to obtain distinct resin compositions from two input chemistries. The push for safer materials is complemented by a thrust for multifunctional composites. The second primary goal of this thesis is to design and implement the manufacture of sacrificial fiber materials suitable for use in automated fiber placement of microvascaular multifunctional composites. Two key advancements are required to achieve this goal: (1) development of a roll-to-roll method to place sacrificial fibers onto carbon fiber pre-preg tape; and (2) demonstration of feasible manufacture of microvascular carbon fiber plates with automated fiber placement. An automated method for placing sacrificial fibers onto carbon fiber tapes is designed and a prototype implemented. Carbon fiber tows with manual placement of sacrificial fibers is implemented within an

  13. Shear debonding behavior of a carbon-coated interface in a tungsten fiber-reinforced tungsten matrix composite

    NASA Astrophysics Data System (ADS)

    Du, J.; Höschen, T.; Rasinski, M.; You, J.-H.

    2011-10-01

    One of the crucial issues related to structural application of tungsten for fusion reactor components is its brittleness. To improve tungsten toughness we explored a novel toughening method based on W fiber reinforcement. The idea is to utilize the effective energy dissipation caused by controlled cracking and friction at fiber/matrix interfaces. To realize this, the interfaces need to be engineered by means of adequate coating. In this work we investigated fracture behavior of a carbon-coated (0.6 μm) interface in a single-filament mini-composite using fiber push-out test. The composite was fabricated by CVD process. Mechanical parameters were determined by fitting the related theoretical models with the experimental data. Calibrated fracture energy and debonding strength was 7.4 J/m 2 and 285 MPa, respectively. This fracture energy value satisfied the theoretical criterion of controlled crack deflection. The result of the carbon coating was compared to the case of uncoated interface which exhibited stronger friction.

  14. Advances in Ceramic Matrix Composite Blade Damping Characteristics for Aerospace Turbomachinery Applications

    NASA Technical Reports Server (NTRS)

    Min, James B.; Harris, Donald L.; Ting, J. M.

    2011-01-01

    For advanced aerospace propulsion systems, development of ceramic matrix composite integrally-bladed turbine disk technology is attractive for a number of reasons. The high strength-to-weight ratio of ceramic composites helps to reduce engine weight and the one-piece construction of a blisk will result in fewer parts count, which should translate into reduced operational costs. One shortcoming with blisk construction, however, is that blisks may be prone to high cycle fatigue due to their structural response to high vibration environments. Use of ceramic composites is expected to provide some internal damping to reduce the vibratory stresses encountered due to unsteady flow loads through the bladed turbine regions. A goal of our research was to characterize the vibration viscous damping behavior of C/SiC composites. The vibration damping properties were measured and calculated. Damping appeared to decrease with an increase in the natural frequency. While the critical damping amount of approximately 2% is required for typical aerospace turbomachinery engines, the C/SiC damping at high frequencies was less than 0.2% from our study. The advanced high-performance aerospace propulsion systems almost certainly will require even more damping than what current vehicles require. A purpose of this paper is to review some work on C/SiC vibration damping by the authors for the NASA CMC turbine blisk development program and address an importance of the further investigation of the blade vibration damping characteristics on candidate CMC materials for the NASA s advanced aerospace turbomachinery engine systems.

  15. The Effect of Aloe Vera, Pomegranate Peel, Grape Seed Extract, Green Tea, and Sodium Ascorbate as Antioxidants on the Shear Bond Strength of Composite Resin to Home-bleached Enamel

    PubMed Central

    Sharafeddin, Farahnaz; Farshad, Farnaz

    2015-01-01

    Statement of the Problem Immediate application of bonding agent to home- bleached enamel leads to significant reduction in the shear bond strength of composite resin due to the residual oxygen. Different antioxidant agents may overcome this problem. Purpose This study aimed to assess the effect of different antioxidants on the shear bond strength of composite resin to home-bleached. Materials and Method Sixty extracted intact human incisors were embedded in cylindrical acrylic resin blocks (2.5×1.5 cm), with the coronal portion left out of the block. After bleaching the labial enamel surface with 15% carbamide peroxide, they were randomly divided into 6 groups (n=10). Before performing composite resin restoration by using a cylindrical Teflon mold (5×2 mm), each group was treated with one of the following antioxidants: 10% sodium ascorbate solution, 10% pomegranate peel solution, 10% grape seed extract, 5% green tea extract, and aloe vera leaf gel. One group was left untreated as the control. The shear bond strength of samples was tested under a universal testing machine (ZwickRoell Z020). The shear bond strength data were analyzed by one-way ANOVA and post hoc Tukey tests (p< 0.05). Results No significant difference existed between the control and experimental groups. Moreover, there was no statistically significant difference between the effects of different antioxidants on the shear bond strength of bleached enamel. Conclusion Different antioxidants used in this study had the same effect on the shear bond strength of home-bleached enamel, and none of them caused a statistically significant increase in its value. PMID:26636116

  16. A Study of the Utilization of Advanced Composites in Fuselage Structures of Commercial Aircraft

    NASA Technical Reports Server (NTRS)

    Watts, D. J.; Sumida, P. T.; Bunin, B. L.; Janicki, G. S.; Walker, J. V.; Fox, B. R.

    1985-01-01

    A study was conducted to define the technology and data needed to support the introduction of advanced composites in the future production of fuselage structure in large transport aircraft. Fuselage structures of six candidate airplanes were evaluated for the baseline component. The MD-100 was selected on the basis of its representation of 1990s fuselage structure, an available data base, its impact on the schedule and cost of the development program, and its availability and suitability for flight service evaluation. Acceptance criteria were defined, technology issues were identified, and a composite fuselage technology development plan, including full-scale tests, was identified. The plan was based on composite materials to be available in the mid to late 1980s. Program resources required to develop composite fuselage technology are estimated at a rough order of magnitude to be 877 man-years exclusive of the bird strike and impact dynamic test components. A conceptual composite fuselage was designed, retaining the basic MD-100 structural arrangement for doors, windows, wing, wheel wells, cockpit enclosure, major bulkheads, etc., resulting in a 32 percent weight savings.

  17. Advances in SiC/SiC Composites for Aero-Propulsion

    NASA Technical Reports Server (NTRS)

    DiCarlo, James A.

    2013-01-01

    In the last decade, considerable progress has been made in the development and application of ceramic matrix composites consisting of silicon carbide (SiC) based matrices reinforced by small-diameter continuous-length SiC-based fibers. For example, these SiC/SiC composites are now in the early stages of implementation into hot-section components of civil aero-propulsion gas turbine engines, where in comparison to current metallic components they offer multiple advantages due to their lighter weight and higher temperature structural capability. For current production-ready SiC/SiC, this temperature capability for long time structural applications is 1250 degC, which is better than 1100 degC for the best metallic superalloys. Foreseeing that even higher structural reliability and temperature capability would continue to increase the advantages of SiC/SiC composites, progress in recent years has also been made at NASA toward improving the properties of SiC/SiC composites by optimizing the various constituent materials and geometries within composite microstructures. The primary objective of this chapter is to detail this latter progress, both fundamentally and practically, with particular emphasis on recent advancements in the materials and processes for the fiber, fiber coating, fiber architecture, and matrix, and in the design methods for incorporating these constituents into SiC/SiC microstructures with improved thermo-structural performance.

  18. Joining and Integration of Advanced Carbon-Carbon Composites to Metallic Systems for Thermal Management Applications

    NASA Technical Reports Server (NTRS)

    Singh, M.; Asthana, R.

    2008-01-01

    Recent research and development activities in joining and integration of carbon-carbon (C/C) composites to metals such as Ti and Cu-clad-Mo for thermal management applications are presented with focus on advanced brazing techniques. A wide variety of carbon-carbon composites with CVI and resin-derived matrices were joined to Ti and Cu-clad Mo using a number of active braze alloys. The brazed joints revealed good interfacial bonding, preferential precipitation of active elements (e.g., Ti) at the composite/braze interface. Extensive braze penetration of the inter-fiber channels in the CVI C/C composites was observed. The chemical and thermomechanical compatibility between C/C and metals at elevated temperatures is assessed. The role of residual stresses and thermal conduction in brazed C/C joints is discussed. Theoretical predictions of the effective thermal resistance suggest that composite-to-metal brazed joints may be promising for lightweight thermal management applications.

  19. NiAl-Base Composite Containing High Volume Fraction of AIN Particulate for Advanced Engines

    NASA Technical Reports Server (NTRS)

    Hebsur, Mohan G.; Whittenberger, J. D.; Lowell, C. E.; Garg, A.

    1995-01-01

    Cryomilling of prealloyed NiAl containing 53 at. % AJ was carried out to achieve high nitrogen levels. The consolidation of cryomilled powder by extrusion or hot pressing/ hot isostatic pressing resulted in a fully dense NiAl-base composite containing 30 vol. % of inhomogeneously distributed, nanosized AIN particulate. The NiAl-30AIN composite exhibited the highest compression yield strengths at all temperatures between 300 and 1300 K as compared with other compositions of NiAl-AIN composite. The NiAl-30AIN specimens tested under compressive creep loading between 1300 and 1500 K also exhibited the highest creep resistance with very little surface oxidation indicating also their superior elevated temperature oxidation resistance. In the high stress exponent regime, the strength is proportional to the square root of the AIN content and in the low stress exponent regime, the influence of AIN content on strength appears to be less dramatic. The specific creep strength of this material at 1300 K is superior to a first generation Ni-base single crystal superalloy. The improvements in elevated temperature creep strength and oxidation resistance have been achieved without sacrificing the room temperature fracture toughness of the NiAl-base material. Based on its attractive combination of properties, the NiAl-30AIN composite is a potential candidate for advanced engine applications,

  20. Full-scale testing, production and cost analysis data for the advanced composite stabilizer for Boeing 737 aircraft, volume 2

    NASA Technical Reports Server (NTRS)

    Aniversario, R. B.; Harvey, S. T.; Mccarty, J. E.; Parson, J. T.; Peterson, D. C.; Pritchett, L. D.; Wilson, D. R.; Wogulis, E. R.

    1982-01-01

    The development, testing, production activities, and associated costs that were required to produce five-and-one-half advanced-composite stabilizer shipsets for Boeing 737 aircraft are defined and discussed.

  1. Badhwar-O'Neil 2007 Galactic Cosmic Ray (GCR) Model Using Advanced Composition Explorer (ACE) Measurements for Solar Cycle 23

    NASA Technical Reports Server (NTRS)

    ONeill, P. M.

    2007-01-01

    Advanced Composition Explorer (ACE) satellite measurements of the galactic cosmic ray flux and correlation with the Climax Neutron Monitor count over Solar Cycle 23 are used to update the Badhwar O'Neill Galactic Cosmic Ray (GCR) model.

  2. Advanced carbon materials/olivine LiFePO4 composites cathode for lithium ion batteries

    NASA Astrophysics Data System (ADS)

    Gong, Chunli; Xue, Zhigang; Wen, Sheng; Ye, Yunsheng; Xie, Xiaolin

    2016-06-01

    In the past two decades, LiFePO4 has undoubtly become a competitive candidate for the cathode material of the next-generation LIBs due to its abundant resources, low toxicity and excellent thermal stability, etc. However, the poor electronic conductivity as well as low lithium ion diffusion rate are the two major drawbacks for the commercial applications of LiFePO4 especially in the power energy field. The introduction of highly graphitized advanced carbon materials, which also possess high electronic conductivity, superior specific surface area and excellent structural stability, into LiFePO4 offers a better way to resolve the issue of limited rate performance caused by the two obstacles when compared with traditional carbon materials. In this review, we focus on advanced carbon materials such as one-dimensional (1D) carbon (carbon nanotubes and carbon fibers), two-dimensional (2D) carbon (graphene, graphene oxide and reduced graphene oxide) and three-dimensional (3D) carbon (carbon nanotubes array and 3D graphene skeleton), modified LiFePO4 for high power lithium ion batteries. The preparation strategies, structure, and electrochemical performance of advanced carbon/LiFePO4 composite are summarized and discussed in detail. The problems encountered in its application and the future development of this composite are also discussed.

  3. Small-Angle X-Ray Scattering on the ChemMatCARS Beamline at the Advanced Photon Source: A Study of Shear-Induced Crystallisation in Polypropylene

    SciTech Connect

    Sutton, D.; Hanley, T.; Knott, R.; Cookson, D.

    2008-09-08

    The first ever time-resolved small-angle X-ray scattering (SAXS) data from the undulator 15-ID-D beamline (ChemMatCARS) are presented. A 1.3 {angstrom} (9.54 keV) X-ray beam was selected to study the structure development in a polypropylene sample during shear-induced crystallization. A Linkam CSS450 shear cell provided the temperature and shear control. The polypropylene was first melted and then quenched to the crystallization temperature, where a step shear was applied. The SAXS data were collected using a Bruker 6000 CCD detector, which provided images of excellent resolution. The SAXS images (with 180{sup o} rotational symmetry) indicated that the polypropylene crystallizes with a high degree of anisotropy, and the lamellae are oriented perpendicular to the flow direction.

  4. Time-temperature-stress capabilities of composite materials for advanced supersonic technology application

    NASA Technical Reports Server (NTRS)

    Kerr, James R.; Haskins, James F.

    1987-01-01

    Advanced composites will play a key role in the development of the technology for the design and fabrication of future supersonic vehicles. However, incorporating the material into vehicle usage is contingent on accelerating the demonstration of service capacity and design technology. Because of the added material complexity and lack of extensive data, laboratory replication of the flight service will provide the most rapid method to document the airworthiness of advanced composite systems. Consequently, a laboratory program was conducted to determine the time-temperature-stress capabilities of several high temperature composites. Tests included were thermal aging, environmental aging, fatigue, creep, fracture, tensile, and real-time flight simulation exposure. The program had two phases. The first included all the material property determinations and aging and simulation exposures up through 10,000 hours. The second continued these tests up to 50,000 cumulative hours. This report presents the results of the Phase 1 baseline and 10,000-hr aging and flight simulation studies, the Phase 2 50,000-hr aging studies, and the Phase 2 flight simulation tests, some of which extended to almost 40,000 hours.

  5. Titanium and advanced composite structures for a supersonic cruise arrow wing configuration

    NASA Technical Reports Server (NTRS)

    Turner, M. J.; Hoy, J. M.

    1976-01-01

    Structural design studies were made, based on current technology and on an estimate of technology to be available in the mid 1980's, to assess the relative merits of structural concepts and materials for an advanced arrow wing configuration cruising at Mach 2.7. Preliminary studies were made to insure compliance of the configuration with general design criteria, integrate the propulsion system with the airframe, and define an efficient structural arrangement. Material and concept selection, detailed structural analysis, structural design and airplane mass analysis were completed based on current technology. Based on estimated future technology, structural sizing for strength and a preliminary assessment of the flutter of a strength designed composite structure were completed. An advanced computerized structural design system was used, in conjunction with a relatively complex finite element model, for detailed analysis and sizing of structural members.

  6. Validation of an Advanced Material Model for Simulating the Impact and Shock Response of Composite Materials

    NASA Astrophysics Data System (ADS)

    Clegg, Richard A.; Hayhurst, Colin J.; Nahme, Hartwig

    2001-06-01

    Validation of an advanced continuum based numerical model for the simulation of the shock response of composite materials during high rate transient dynamic loading is described. The constitutive model, implemented in AUTODYN-2D and 3D, allows for the representation of non-linear shock effects in combination with orthotropic stiffness and damage. Simulations of uniaxial flyer plate experiments on aramid and polyethylene fibre composite systems are presented and compared with experiment. The continuum model is shown to reproduce well the experimental VISAR velocity traces at the rear surface of the targets. Finally, practical application of the model as implemented in AUTODYN is demonstrated through the simulation of ballistic and hypervelocity impact events. Comparison with experiment is given where possible.

  7. Advanced Composites: Mechanical Properties and Hardware Programs for Selected Resin Matrix Materials. [considering space shuttle applications

    NASA Technical Reports Server (NTRS)

    Welhart, E. K.

    1976-01-01

    This design note presents typical mechanical properties tabulated from industrial and governmental agencies' test programs. All data are correlated to specific products and all of the best known products are presented. The data include six epoxies, eight polyimides and one polyquinoxaline matrix material. Bron and graphite are the fiber reinforcements. Included are forty-two summaries of advanced (resin matrix) composite programs in existence in the United States. It is concluded that the selection of appropriate matrices, the geometric manner in which the fibers are incorporated in the matrix and the durability of the bond between fiber and matrix establish the end properties of the composite material and the performance of the fabricated structure.

  8. Recent advances in lightweight, filament-wound composite pressure vessel technology

    NASA Technical Reports Server (NTRS)

    Lark, R. F.

    1977-01-01

    A review of recent advances is presented for lightweight, high-performance composite pressure vessel technology that covers the areas of design concepts, fabrication procedures, applications, and performance of vessels subjected to single-cycle burst and cyclic fatigue loading. Filament-wound fiber/epoxy composite vessels were made from S-glass, graphite, and Kevlar 49 fibers and were equipped with both structural and nonstructural liners. Pressure vessel structural efficiencies were attained which represented weight savings, using different liners, of 40 to 60 percent over all-titanium pressure vessels. Significant findings in each area are summarized including data from current NASA-Lewis Research Center contractual and in-house programs.

  9. Study on utilization of advanced composites in commercial aircraft wing structures. Volume 1: Executive summary

    NASA Technical Reports Server (NTRS)

    Sakata, I. F.; Ostrom, R. B.; Cardinale, S. V.

    1978-01-01

    The effort required by commercial transport manufacturers to accomplish the transition from current construction materials and practices to extensive use of composites in aircraft wings was investigated. The engineering and manufacturing disciplines which normally participate in the design, development, and production of an aircraft were employed to ensure that all of the factors that would enter a decision to commit to production of a composite wing structure were addressed. A conceptual design of an advanced technology reduced energy aircraft provided the framework for identifying and investigating unique design aspects. A plan development effort defined the essential technology needs and formulated approaches for effecting the required wing development. The wing development program plans, resource needs, and recommendations are summarized.

  10. An eddy-current model for three-dimensional nondestructive evaluation of advanced composites

    NASA Astrophysics Data System (ADS)

    Sabbagh, Harold A.; Murphy, R. Kim; Sabbagh, Elias H.

    2015-03-01

    We have developed a rigorous electromagnetic model and an inversion algorithm for the three-dimensional NDE of advanced composite materials. This approach extends Victor Technologies' work in eddy-current NDE of conventional metals, and allows one to determine in localized regions the fiber-resin ratio in graphite-epoxy, and to determine those anomalies, e.g., delaminations, broken fibers, moisture content, etc., that can be reconstructed by our inversion method. In developing the model, we apply rigorous electromagnetic theory to determine a Green's function for a slab of anisotropic composite material, and then determine the integral relations for the forward and inverse problems using the Green's function. We will give examples of the solution of forward problems using this model.

  11. Environment enhanced fatigue of advanced aluminum alloys and metal matrix composites

    NASA Technical Reports Server (NTRS)

    Slavik, Donald C.; Gangloff, Richard P.

    1991-01-01

    The environmental fatigue crack propagation behavior of advanced Al-Li-Cu based alloys and metal matrix composites is being characterized. Aqueous NaCl and water vapor, which produce atomic hydrogen by reactions on clean crack surfaces, are emphasized. The effects of environment sensitive crack closure, stress ratio, and precipitate microstructure are assessed. Mechanistic models are sought for intrinsic crack tip damage processes to enable predictions of cracking behavior outside of the data, metallurgical improvements in material cracking resistance, and insight on hydrogen compatibility.

  12. APL workers install CRIS on the Advanced Composition Explorer (ACE) in SAEF-2

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Workers from the Johns Hopkins University's Applied Physics Laboratory (APL) install the Cosmic Ray Isotope Spectrometer (CRIS) on the Advanced Composition Explorer (ACE) spacecraft in KSC's Spacecraft Assembly and Encapsulation Facility-2 (SAEF-2). From left, are Al Sadilek, Marcos Gonzalez and Cliff Willey. CRIS is one of nine instruments on ACE, which will investigate the origin and evolution of solar phenomenon, the formation of the solar corona, solar flares and the acceleration of the solar wind. ACE was developed for NASA by the APL. The spacecraft is scheduled to be launched Aug. 21 aboard a two-stage Delta II 7920-8 rocket from Space Launch Complex 17, Pad A.

  13. Techniques for measurement of the thermal expansion of advanced composite materials

    NASA Technical Reports Server (NTRS)

    Tompkins, Stephen S.

    1989-01-01

    Techniques available to measure small thermal displacements in flat laminates and structural tubular elements of advanced composite materials are described. Emphasis is placed on laser interferometry and the laser interferometric dilatometer system used at the National Aeronautics and Space Administration (NASA) Langley Research Center. Thermal expansion data are presented for graphite-fiber reinforced 6061 and 2024 aluminum laminates and for graphite fiber reinforced AZ91 C and QH21 A magnesium laminates before and after processing to minimize or eliminate thermal strain hysteresis. Data are also presented on the effects of reinforcement volume content on thermal expansion of silicon-carbide whisker and particulate reinforced aluminum.

  14. Development of damped metal-matrix composites for advanced structural applications. Technical report

    SciTech Connect

    Updike, C.A.; Bhagat, R.B.

    1990-04-01

    The development of damped metal matrix composite structures for advanced applications has been investigated by the use of two different approaches: (1) the development of metal matrix composites with high intrinsic damping compared to that of the matrix material, and (2) the development of coated metal matrix composites with high structural damping compared to that of the composite substrates. The two different approaches are analyzed in terms of their potential for improved damping and feasibility for structural applications. Damping was measured by the transverse vibration of free-free beams using the bandwidth technique by a laser vibrometer under ambient conditions. The damping measurements were made over a wide range of frequencies (.7 kHz to 25.6 kHz) at low strain amplitudes (10 to the -10 power to 10 to the -7 power). Materials investigated for their tensile stiffness, strength, and damping performance include mechanically alloyed (MA) Aluminum-Magnesium, SiC(p)/Aluminum-Copper (MA), SiC(p)/AL, AL2O3(p)/AL, SiC(W)/AL, planar random Gr/AL, unidirectional Gr/AL and unidirectional SiC(Nicalon)/AL composites. The effects of coatings of high damping metals (nitinol and incramute) on 6061-T6 AL and AL2O3(p)/AL substrates have also been studied. The AL-Mg (MA), SiC(p)/AL (MA), SiC(W)/AL and th AL2O3(p)/AL composites show no significant improvement in damping compared with that of the 6061-T6 AL.

  15. Assessment of the Shear Bond Strength between Nanofilled Composite Bonded to Glass-ionomer Cement Using Self-etch Adhesive with Different pHs and Total-Etch Adhesive

    PubMed Central

    Sharafeddin, Farahnaz; Choobineh, Mohammad Mehdi

    2016-01-01

    Statement of the Problem In the sandwich technique, the undesirable bond between the composite resin and glass-ionomer cement (GIc) is one of the most important factors which lead to the failure of restoration. Total-etch and self-etch adhesives may improve the bond strength based on their pH. Purpose The purpose of this study was to evaluate the shear bond strength between the nanofilled composite resin and GIc using different adhesives. Materials and Method In this experimental study, 40 specimens (6×6mm) in 4 groups (n=10) were prepared in acrylic mold. Each specimen contained conventional GI ChemFil Superior with a height of 3mm, bonded to Z350 composite resin with a height measured 3mm. In order to bond the composite to the GI, the following adhesives were used, respectively: A: mild Clearfil SE Bond self-etch (pH=2), B: intermediate OptiBond self-etch (pH=1.4), C: strong Adper Prompt L-Pop (pH=1), and D: Adper Single Bond 2 total-etch (pH=7.2). The shear bond strength was measured by using universal testing machine with a crosshead speed of 1mm/min. One-way ANOVA and Tukey’s test were used to analyze the data (p< 0.05). Results The shear bond strength in group A was significantly higher than group B (p= 0.002), C (p< 0.001), and D (p< 0.001). Moreover, the shear bond strength of groups A and B (self-etch) was significantly different from group D (total-etch) (p< 0.001); and C (self-etch) with D (p= 0.024). Conclusion The results of this study showed that applying the mild self-etch adhesive between the composite and the GIc results in stronger shear bond strength compared to intermediate and strong self-etch adhesives. Moreover, the self-etch adhesive increased the shear bond strength between composite resin and GIc more significantly than total-etch adhesive. PMID:26966701

  16. Carbon fibers: Thermochemical recovery from advanced composite materials and activation to an adsorbent

    NASA Astrophysics Data System (ADS)

    Staley, Todd Andrew

    This research addresses an expanding waste disposal problem brought about by the increasing use of advanced composite materials, and the lack of technically and environmentally viable recycling methods for these materials. A thermochemical treatment process was developed and optimized for the recycling of advanced composite materials. Counter-current gasification was employed for the treatment of carbon fiber reinforced-epoxy resin composite wastes. These materials were treated, allowing the reclamation of the material's valuable components. As expected in gasification, the organic portion of the waste was thermochemically converted to a combustible gas with small amounts of organic compounds that were identified by GC/MS. These compounds were expected based on data in the literature. The composites contain 70% fiber reinforcement, and gasification yielded approximately 70% recovered fibers, representing nearly complete recovery of fibers from the waste. Through SEM and mechanical testing, the recovered carbon fibers were found to be structurally and mechanically intact, and amenable to re-use in a variety of applications, some of which were identified and tested. In addition, an application was developed for the carbon fiber component of the waste, as an activated carbon fiber adsorbent for the treatment of wastewaters. This novel class of adsorbent was found to have adsorption rates, for various organic molecules, up to a factor of ten times those of commercial granular activated carbon, and adsorption capacities similar to conventional activated carbons. Overall, the research addresses an existing environmental waste problem, employing a thermochemical technique to recycle and reclaim the waste. Components of the reclaimed waste material are then employed, after further modification, to address other existing and potential environmental waste problems.

  17. Review of status and potential of tungsten-wire: Superalloy composites for advanced gas turbine engine blades

    NASA Technical Reports Server (NTRS)

    Signorelli, R. A.

    1972-01-01

    The current status of development of refractory-wire-superalloy composites and the potential for their application to turbine blades in land-based power generation and advanced aircraft engines are reviewed. The data indicate that refractory-wire-superalloy composites have application as turbine blades at temperatures of 2200 F and above.

  18. Robust Joining and Integration Technologies for Advanced Metallic, Ceramic, and Composite Systems

    NASA Technical Reports Server (NTRS)

    Singh, M.; Shpargel, Tarah; Morscher, Gregory N.; Halbig, Michael H.; Asthana, Rajiv

    2006-01-01

    Robust integration and assembly technologies are critical for the successful implementation of advanced metallic, ceramic, carbon-carbon, and ceramic matrix composite components in a wide variety of aerospace, space exploration, and ground based systems. Typically, the operating temperature of these components varies from few hundred to few thousand Kelvin with different working times (few minutes to years). The wide ranging system performance requirements necessitate the use of different integration technologies which includes adhesive bonding, low temperature soldering, active metal brazing, diffusion bonding, ARCJoinT, and ultra high temperature joining technologies. In this presentation, a number of joining examples and test results will be provided related to the adhesive bonding and active metal brazing of titanium to C/C composites, diffusion bonding of silicon carbide to silicon carbide using titanium interlayer, titanium and hastelloy brazing to silicon carbide matrix composites, and ARCJoinT joining of SiC ceramics and SiC matrix composites. Various issues in the joining of metal-ceramic systems including thermal expansion mismatch and resulting residual stresses generated during joining will be discussed. In addition, joint design and testing issues for a wide variety of joints will be presented.

  19. A hybrid method for damage detection and quantification in advanced X-COR composite structures

    NASA Astrophysics Data System (ADS)

    Neerukatti, Rajesh Kumar; Rajadas, Abhishek; Borkowski, Luke; Chattopadhyay, Aditi; Huff, Daniel W.

    2016-04-01

    Advanced composite structures, such as foam core carbon fiber reinforced polymer composites, are increasingly being used in applications which require high strength, high in-plane and flexural stiffness, and low weight. However, the presence of in situ damage due to manufacturing defects and/or service conditions can complicate the failure mechanisms and compromise their strength and reliability. In this paper, the capability of detecting damages such as delaminations and foam-core separations in X-COR composite structures using non-destructive evaluation (NDE) and structural health monitoring (SHM) techniques is investigated. Two NDE techniques, flash thermography and low frequency ultrasonics, were used to detect and quantify the damage size and locations. Macro fiber composites (MFCs) were used as actuators and sensors to study the interaction of Lamb waves with delaminations and foam-core separations. The results indicate that both flash thermography and low frequency ultrasonics were capable of detecting damage in X-COR sandwich structures, although low frequency ultrasonic methods were capable of detecting through thickness damages more accurately than flash thermography. It was also observed that the presence of foam-core separations significantly changes the wave behavior when compared to delamination, which complicates the use of wave based SHM techniques. Further, a wave propagation model was developed to model the wave interaction with damages at different locations on the X-COR sandwich plate.

  20. Advances in Composite Reflectors: From X-Ray to Radio Wave Astronomy

    NASA Astrophysics Data System (ADS)

    Connell, S. J.; Abusafieh, A. A.; Mehle, G. V.; Sheikh, D. A.; Giles, D. C.

    2000-12-01

    In recent years, Composite Optics, Inc. (COI) has made significant advances in the use of graphite fiber reinforced composite (GFRC) materials for astronomical instrument applications. The inherent low density, high stiffness, and thermal stability makes GFRC a natural candidate for many astronomy applications. In order to reap these inherent benefits in astronomical applications, basic research has focused on material and process improvement. This has been accompanied by the design, fabrication, and test of several prototype reflectors that cover a broad wavelength spectrum of astronomical interests. The results of, and applications for, these efforts are summarized in the following list. X-Ray Carrier Shell: Innovative composite process yields accuracy and moisture stability. Demonstrated by vacuum optical test of 6" Wolter-I shell. Applicable to Con-X, etc. Lightweight Mirror Substrate for Visible Astronomy: Composite/glass hybrid design. Areal density < 15 kg/m2. Demonstrated by cryo-optical test (to 35K) of 1.6m NMSD mirror. Applicable to NGST, etc. Polishable Composite Facesheet: Glass-like coating applied to composite. Polishable by conventional methods. Multiple six-inch substrates polished to 20 angstroms. Technology will enable future 5 kg/m2 visible to UV optics. 10 kg/m2 Submillimeter Reflector: Apertures to 5m possible with economical, all-composite mirror design, diffraction limited at 80 microns. Demonstrated with cryo-optical test (to 70K) of FIRST 2-meter prototype mirror. Applicable to FIRST and other IR astronomy. Large, Ultra-Stable Optical Support Structure: Uniform and near-zero CTE over broad dimensions. Demonstrated with cryo-optical test of 2-meter FIRST prototype. Applicable to NGST, SIM, LISSA. Ground Based Radio Telescope Reflector: Low-cost, accurate, stable, durable all-composite design for support structure & reflective surface. Demonstrated via fab & test of 3m adjustable and 5m static prototypes. Applicable to LMT, ALMA, etc. These

  1. Apparatus for shearing spent nuclear fuel assemblies

    DOEpatents

    Weil, Bradley S.; Metz, III, Curtis F.

    1980-01-01

    A method and apparatus are described for shearing spent nuclear fuel assemblies of the type comprising an array of fuel pins disposed within an outer metal shell or shroud. A spent fuel assembly is first compacted in a known manner and then incrementally sheared using fixed and movable shear blades having matched laterally projecting teeth which slidably intermesh to provide the desired shearing action. Incremental advancement of the fuel assembly after each shear cycle is limited to a distance corresponding to the lateral projection of the teeth to ensure fuel assembly breakup into small uniform segments which are amenable to remote chemical processing.

  2. Improve the performance of coated cemented hip stem through the advanced composite materials.

    PubMed

    Hedia, H S; Fouda, N

    2015-01-01

    Design of hip joint implant using functionally graded material (FGM) (advanced composite material) has been used before through few researches. It gives great results regarding the stress distribution along the implant and bone interfaces. However, coating of orthopaedic implants has been widely investigated through many researches. The effect of using advanced composite stem material, which mean by functionally graded stem material, in the total hip replacement coated with the most common coated materials has not been studied yet. Therefore, this study investigates the effect of utilizing these two concepts together; FGM and coating, in designing new stem material. It is concluded that the optimal FGM cemented stem is consisting from titanium at the upper stem layers graded to collagen at a lower stem layers. This optimal graded stem coated with hydroxyapatite found to reduce stress shielding by 57% compared to homogenous titanium stem coated with hydroxyapatite. However, the optimal functionally graded stem coated with collagen reduced the stress shielding by 51% compared to homogenous titanium stem coated with collagen. PMID:26407117

  3. Flight service evaluation of an advanced composite empennage component on commercial transport aircraft

    NASA Technical Reports Server (NTRS)

    1976-01-01

    The development and flight evaluation of an advanced composite empennage component is presented. The recommended concept for the covers is graphite-epoxy hats bonded to a graphite-epoxy skin. The hat flare-out has been eliminated, instead the hat is continuous into the joint. The recommended concept for the spars is graphite-epoxy caps and a hybrid of Kevlar-49 and graphite-epoxy in the spar web. The spar cap, spar web stiffeners for attaching the ribs, and intermediate stiffeners are planned to be fabricated as a unit. Access hole in the web will be reinforced with a donut type, zero degree graphite-epoxy wound reinforcement. The miniwich design concept in the upper three ribs originally proposed is changed to a graphite-epoxy stiffened solid laminate design concept. The recommended configuration for the lower seven ribs remains as graphite-epoxy caps with aluminum cruciform diagonals. The indicated weight saving for the current advanced composite vertical fin configuration is 20.2% including a 24 lb growth allowance. The project production cost saving is approximately 1% based on a cumulative average of 250 aircraft and including only material, production labor, and quality assurance costs.

  4. Advances in SiC/SiC Composites for Aerospace Applications

    NASA Technical Reports Server (NTRS)

    DiCarlo, James A.

    2006-01-01

    In recent years, supported by a variety of materials development programs, NASA Glenn Research Center has significantly increased the thermostructural capability of SiC/SiC composite materials for high-temperature aerospace applications. These state-of-the-art advances have occurred in every key constituent of the composite: fiber, fiber coating, matrix, and environmental barrier coating, as well as processes for forming the fiber architectures needed for complex-shaped components such as turbine vanes for gas turbine engines. This presentation will briefly elaborate on the nature of these advances in terms of performance data and underlying mechanisms. Based on a list of first-order property goals for typical high-temperature applications, key data from a variety of laboratory tests are presented which demonstrate that the NASA-developed constituent materials and processes do indeed result in SiC/SiC systems with the desired thermal and structural capabilities. Remaining process and microstructural issues for further property enhancement are discussed, as well as on-going approaches at NASA to solve these issues. NASA efforts to develop physics-based property models that can be used not only for component design and life modeling, but also for constituent material and process improvement will also be discussed.

  5. Study of advanced composite structural design concepts for an arrow wing supersonic cruise configuration, task 3

    NASA Technical Reports Server (NTRS)

    1978-01-01

    A structural design study was conducted to assess the relative merits of structural concepts using advanced composite materials for an advanced supersonic aircraft cruising at Mach 2.7. The configuration and structural arrangement developed during Task I and II of the study, was used as the baseline configuration. Allowable stresses and strains were established for boron and advanced graphite fibers based on projected fiber properties available in the next decade. Structural concepts were designed and analyzed using graphite polyimide and boron polyimide, applied to stiffened panels and conventional sandwich panels. The conventional sandwich panels were selected as the structural concept to be used on the wing structure. The upper and lower surface panels of the Task I arrow wing were redesigned using high-strength graphite polyimide sandwich panels over the titanium spars and ribs. The ATLAS computer system was used as the basis for stress analysis and resizing the surface panels using the loads from the Task II study, without adjustment for change in aeroelastic deformation. The flutter analysis indicated a decrease in the flutter speed compared to the baseline titanium wing design. The flutter analysis indicated a decrease in the flutter speed compared to the baseline titanium wing design. The flutter speed was increased to that of the titanium wing, with a weight penalty less than that of the metallic airplane.

  6. Extension-torsion coupling behavior of advanced composite tilt-rotor blades

    NASA Technical Reports Server (NTRS)

    Kosmatka, J. B.

    1989-01-01

    An analytic model was developed to study the extension-bend-twist coupling behavior of an advanced composite helicopter or tilt-rotor blade. The outer surface of the blade is defined by rotating an arbitrary cross section about an initial twist axis. The cross section can be nonhomogeneous and composed of generally anisotropic materials. The model is developed based upon a three dimensional elasticity approach that is recast as a coupled two-dimensional boundary value problem defined in a curvilinear coordinate system. Displacement solutions are written in terms of known functions that represent extension, bending, and twisting and unknown functions for local cross section deformations. The unknown local deformation functions are determined by applying the principle of minimum potential energy to the discretized two-dimensional cross section. This is an application of the Ritz method, where the trial function family is the displacement field associated with a finite element (8-node isoparametric quadrilaterals) representation of the section. A computer program was written where the cross section is discretized into 8-node quadrilateral subregions. Initially the program was verified using previously published results (both three-dimensional elasticity and technical beam theory) for pretwisted isotropic bars with an elliptical cross section. In addition, solid and thin-wall multi-cell NACA-0012 airfoil sections were analyzed to illustrate the pronounced effects that pretwist, initial twist axis location, and spar location has on coupled behavior. Currently, a series of advanced composite airfoils are being modeled in order to assess how the use of laminated composite materials interacts with pretwist to alter the coupling behavior of the blade. These studies will investigate the use of different ply angle orientations and the use of symmetric versus unsymmetric laminates.

  7. Mechanical properties of advanced SiC/SiC composites after neutron irradiation

    NASA Astrophysics Data System (ADS)

    Ozawa, K.; Nozawa, T.; Katoh, Y.; Hinoki, T.; Kohyama, A.

    2007-08-01

    The effect of neutron irradiation on tensile properties in advanced 2D-SiC/SiC composites was evaluated. The composites used were composed of a SiC matrix obtained by the forced-flow chemical vapor infiltration (FCVI) process and either Tyranno™-SA Grade-3 or Hi-Nicalon™ Type-S fibers with single-layered PyC coating as the interphase. Neutron irradiation fluence and temperature were 3.1 × 10 25 n/m 2 ( E > 0.1 MeV) and 1.2 × 10 26 n/m 2 at 740-750 °C. Tensile properties were evaluated by cyclic tensile test, and hysteresis loop analysis was applied in order to evaluate interfacial properties. Both composites exhibited excellent irradiation resistance in ultimate and proportional limit tensile stresses. From the hysteresis loop analysis, the level of interfacial sliding stress decreased significantly after irradiation to 1.5 × 10 26 n/m 2 at 750 °C.

  8. Plasma-modified graphene nanoplatelets and multiwalled carbon nanotubes as fillers for advanced rubber composites

    NASA Astrophysics Data System (ADS)

    Sicinski, M.; Gozdek, T.; Bielinski, D. M.; Szymanowski, H.; Kleczewska, J.; Piatkowska, A.

    2015-07-01

    In modern rubber industry, there still is a room for new fillers, which can improve the mechanical properties of the composites, or introduce a new function to the material. Modern fillers like carbon nanotubes or graphene nanoplatelets (GnP), are increasingly applied in advanced polymer composites technology. However, it might be hard to obtain a well dispersed system for such systems. The polymer matrix often exhibits higher surface free energy (SFE) level with the filler, which can cause problems with polymer-filler interphase adhesion. Filler particles are not wet properly by the polymer, and thus are easier to agglomerate. As a consequence, improvement in the mechanical properties is lower than expected. In this work, multi-walled carbon nanotubes (MWCNT) and GnP surface were modified with low-temperature plasma. Attempts were made to graft some functionalizing species on plasma-activated filler surface. The analysis of virgin and modified fillers’ SFE was carried out. MWCNT and GnP rubber composites were produced, and ultimately, their morphology and mechanical properties were studied.

  9. More than meets the eye in bacterial cellulose: biosynthesis, bioprocessing, and applications in advanced fiber composites.

    PubMed

    Lee, Koon-Yang; Buldum, Gizem; Mantalaris, Athanasios; Bismarck, Alexander

    2014-01-01

    Bacterial cellulose (BC) nanofibers are one of the stiffest organic materials produced by nature. It consists of pure cellulose without the impurities that are commonly found in plant-based cellulose. This review discusses the metabolic pathways of cellulose-producing bacteria and the genetic pathways of Acetobacter xylinum. The fermentative production of BC and the bioprocess parameters for the cultivation of bacteria are also discussed. The influence of the composition of the culture medium, pH, temperature, and oxygen content on the morphology and yield of BC are reviewed. In addition, the progress made to date on the genetic modification of bacteria to increase the yield of BC and the large-scale production of BC using various bioreactors, namely static and agitated cultures, stirred tank, airlift, aerosol, rotary, and membrane reactors, is reviewed. The challenges in commercial scale production of BC are thoroughly discussed and the efficiency of various bioreactors is compared. In terms of the application of BC, particular emphasis is placed on the utilization of BC in advanced fiber composites to manufacture the next generation truly green, sustainable and renewable hierarchical composites. PMID:23897676

  10. Structural Framework for Flight: NASA's Role in Development of Advanced Composite Materials for Aircraft and Space Structures

    NASA Technical Reports Server (NTRS)

    Tenney, Darrel R.; Davis, John G., Jr.; Johnston, Norman J.; Pipes, R. Byron; McGuire, Jack F.

    2011-01-01

    This serves as a source of collated information on Composite Research over the past four decades at NASA Langley Research Center, and is a key reference for readers wishing to grasp the underlying principles and challenges associated with developing and applying advanced composite materials to new aerospace vehicle concepts. Second, it identifies the major obstacles encountered in developing and applying composites on advanced flight vehicles, as well as lessons learned in overcoming these obstacles. Third, it points out current barriers and challenges to further application of composites on future vehicles. This is extremely valuable for steering research in the future, when new breakthroughs in materials or processing science may eliminate/minimize some of the barriers that have traditionally blocked the expanded application of composite to new structural or revolutionary vehicle concepts. Finally, a review of past work and identification of future challenges will hopefully inspire new research opportunities and development of revolutionary materials and structural concepts to revolutionize future flight vehicles.

  11. Effect of light activation mode on the incompatibility between one-bottle adhesives and light-cured composites: an in vitro shear bond strength study.

    PubMed

    Shafiei, Fereshteh; Saffarpour, Aida; Safarpoor, Ida; Moradmand, Masoud; Alavi, Ali Asghar

    2009-01-01

    This study examined the effect of different light activation modes for light-cured resin-based composites on the shear bond strength to dentin of two one-bottle adhesives with differing acidity. In this experimental study, a flat middle dentin surface was prepared on 110 extracted sound molars using a 600-grit polish paper. The teeth were then randomly divided into 10 equal groups (n = 11). One-Step Plus (OS) and Prime & Bond NT (P&B NT) were used according to the manufacturer's instruction with their respective composite (Aelite, Spectrum TPH) applied and cured using five different light-activation modes: 1. Conventional (CO): 600 mW/cm2 (40 seconds) 2. Soft-Start I (SSI): 100 mW/cm2 (10 seconds) 600 mW/cm2 (30 seconds) 3. Soft-Start II (SSII): 200 mW/cm2 (10 seconds), 600 mW/cm2 (30 seconds) 4. Pulse-Delay I (PDI): 100 mW/cm2 (3 seconds), 3-minute delay, 600 mW/cm2 (37 seconds) 5. Pulse-Delay II (PDII): 200 mW/cm2 (3 seconds), 3-minute delay, 600 mW/cm2 (37 seconds) After 24 hours storage in distilled water at room temperature, a shear bond strength (SBS) test was performed using an Instron machine at 1 mm/minute and the results were recorded in MPa. Statistical analysis included two-way ANOVA and Tukey HSD (p < 0.05). The highest SBS (MPa) was shown in the OS conventional group (19.62 +/- 2.21) and the lowest SBS was shown in P&B NT, PDII (5.93 +/- 1.79). In each group of five curing modes, the mean SBS for P&B NT was significantly lower than OS: conventional mode--P&B NT (17.27 +/- 1.98) vs OS (19.62 +/- 2.21); SSI-P&B NT (10.84 +/- 2.82) vs OS (13.09 +/- 1.24); SSII - P&B NT (14.78 +/- 1.63) vs OS (18.79 +/- 1.57); PDI-P&B NT (5.93 +/- 1.79) vs OS (11.97 +/- 2.59) and PDII-P&B NT (11.82 +/- 1.24) vs OS (16.00 +/- 1.62) (p < 0.001 for all comparisons). For each of the adhesives, the ranking of SBS was as follows: CO > SSII > PDII > SSI > PDI, with the two-paired comparisons of curing modes being significantly different (p < 0.05). The results of the current

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

    PubMed

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

    2008-11-01

    The aim of this work was to evaluate the binder bridges which can form in hydrophilic matrix granules prepared with a small-scale high-shear granulator. Matrices contained hydroxypropyl methylcellulose (HPMC) as a matrix-forming agent, together with lactose monohydrate and microcrystalline cellulose as filler. Water was used as granulating liquid. A 2(4) full factorial design was used to evaluate the effects of the operational parameters (impeller speed, chopper speed, dosing speed and wet massing time) on the granulation process. The temperature of the sample increased relevantly during the preparation in the small-scale apparatus. The same setup induced different temperature increases for different amounts of powder. This alteration enhances the solubility of lactose and decreases that of HPMC, and thus the quantities of the dissolved components can vary. Accordingly, changes in composition of the binder bridge can occur. Since exact determination of the dissolution of these materials during granulation is difficult, the consequences of the changes in solubility were examined. Differential scanning calorimetry (DSC), thermomechanical analysis (TMA) and X-ray diffraction (XRD) measurements were made to evaluate the films prepared from liquids with different ratios of soluble materials. The DSC and XRD measurements confirmed that the lactose lost its crystalline state in the film. The TMA tests revealed that increase of the quantity of lactose in the film decreased the glass transition temperature of the film; this may be attributed to the interaction of the additives. At a lactose content of 37.5%, a second glass transition appeared. This phenomenon may be indicative of a separate amorphous lactose phase. PMID:18774256

  13. The effect of various sandblasting conditions on surface changes of dental zirconia and shear bond strength between zirconia core and indirect composite resin

    PubMed Central

    Su, Naichuan; Yue, Li; Liao, Yunmao; Liu, Wenjia; Zhang, Hai; Li, Xin

    2015-01-01

    PURPOSE To measure the surface loss of dental restorative zirconia and the short-term bond strength between an indirect composite resin (ICR) and zirconia ceramic after various sandblasting processes. MATERIALS AND METHODS Three hundred zirconia bars were randomly divided into 25 groups according to the type of sandblasting performed with pressures of 0.1, 0.2, 0.4 and 0.6 MPa, sandblasting times of 7, 14 and 21 seconds, and alumina powder sizes of 50 and 110 µm. The control group did not receive sandblasting. The volume loss and height loss on zirconia surface after sandblasting and the shear bond strength (SBS) between the sandblasted zirconia and ICR after 24-h immersion were measured for each group using multivariate analysis of variance (ANOVA) and Least Significance Difference (LSD) test (α=.05). After sandblasting, the failure modes of the ICR/zirconia surfaces were observed using scanning electron microscopy. RESULTS The volume loss and height loss were increased with higher sandblasting pressure and longer sandblasting treatment, but they decreased with larger powder size. SBS was significantly increased by increasing the sandblasting time from 7 seconds to 14 seconds and from 14 seconds to 21 seconds, as well as increasing the size of alumina powder from 50 µm to 110 µm. SBS was significantly increased from 0.1 MPa to 0.2 MPa according to the size of alumina powder. However, the SBSs were not significantly different with the sandblasting pressure of 0.2, 0.4 and 0.6 MPa. The possibilities of the combination of both adhesive failure and cohesive failure within the ICR were higher with the increases in bonding strength. CONCLUSION Based on the findings of this study, sandblasting with alumina particles at 0.2 MPa, 21 seconds and the powder size of 110 µm is recommended for dental applications to improve the bonding between zirconia core and ICR. PMID:26140173

  14. Advanced SiC/SiC Ceramic Composites For Gas-Turbine Engine Components

    NASA Technical Reports Server (NTRS)

    Yun, H. M.; DiCarlo, J. A.; Easler, T. E.

    2004-01-01

    NASA Glenn Research Center (GRC) is developing a variety of advanced SiC/SiC ceramic composite (ASC) systems that allow these materials to operate for hundreds of hours under stress in air at temperatures approaching 2700 F. These SiC/SiC composite systems are lightweight (approximately 30% metal density) and, in comparison to monolithic ceramics and carbon fiber-reinforced ceramic composites, are able to reliably retain their structural properties for long times under aggressive gas-turbine engine environments. The key for the ASC systems is related first to the NASA development of the Sylramic-iBN Sic fiber, which displays higher thermal stability than any other SiC- based ceramic fibers and possesses an in-situ grown BN surface layer for higher environmental durability. This fiber is simply derived from Sylramic Sic fiber type that is currently produced at ATK COI Ceramics (COIC). Further capability is then derived by using chemical vapor infiltration (CVI) and/or polymer infiltration and pyrolysis (PIP) to form a Sic-based matrix with high creep and rupture resistance as well as high thermal conductivity. The objectives of this study were (1) to optimize the constituents and processing parameters for a Sylramic-iBN fiber reinforced ceramic composite system in which the Sic-based matrix is formed at COIC almost entirely by PIP (full PIP approach), (2) to evaluate the properties of this system in comparison to other 2700 F Sylramic-iBN systems in which the matrix is formed by full CVI and CVI + PIP, and (3) to examine the pros and cons of the full PIP approach for fabricating hot-section engine components. A key goal is the development of a composite system with low porosity, thereby providing high modulus, high matrix cracking strength, high interlaminar strength, and high thermal conductivity, a major property requirement for engine components that will experience high thermal gradients during service. Other key composite property goals are demonstration at

  15. Shear Bond Strength of Superficial, Intermediate and Deep Dentin In Vitro with Recent Generation Self-etching Primers and Single Nano Composite Resin

    PubMed Central

    Singh, Kulshrest; Naik, Rajaram; Hegde, Srinidhi; Damda, Aftab

    2015-01-01

    Background: This in vitro study is intended to compare the shear bond strength of recent self-etching primers to superficial, intermediate, and deep dentin levels. Materials and Methods: All teeth were sectioned at various levels and grouped randomly into two experimental groups and two control groups having three subgroups. The experimental groups consisted of two different dentin bonding system. The positive control group consisted of All Bond 2 and the negative control group was without the bonding agent. Finally, the specimens were subjected to shear bond strength study under Instron machine. The maximum shear bond strengths were noted at the time of fracture. The results were statistically analyzed. Results: Comparing the shear bond strength values, All Bond 2 (Group III) demonstrated fairly higher bond strength values at different levels of dentin. Generally comparing All Bond 2 with the other two experimental groups revealed highly significant statistical results. Conclusion: In the present investigation with the fourth generation, higher mean shear bond strength values were recorded compared with the self-etching primers. When intermediate dentin shear bond strength was compared with deep dentin shear bond strength statistically significant results were found with Clearfil Liner Bond 2V, All Bond 2 and the negative control. There was a statistically significant difference in shear bond strength values both with self-etching primers and control groups (fourth generation bonding system and without bonding system) at superficial, intermediate, and deep dentin. There was a significant fall in bond strength values as one reaches deeper levels of dentin from superficial to intermediate to deep. PMID:26225101

  16. An in vitro evaluation of the effect of sandblasting and laser surface treatment on the shear bond strength of a composite resin to the facial surface of primary anterior stainless steel crowns

    PubMed Central

    Nandlal, Bhojraj

    2015-01-01

    Objectives: The present study was conducted to evaluate the optimal method of enhancing the bond strength of a composite resin to the facial surface of the primary anterior stainless steel crowns using various surface treatments namely Nd: YAG laser surface treatment, sandblasting , alloy primer application and no surface treatment. Study Design: The study sample consisted of 60 primary anterior stainless steel crowns (UnitekTM size R 4), with 15 samples randomly divided into the 4 study groups, embedded in acrylic blocks. The facial surface of these surface treated crowns was utilized as the bonding surface to which 2.5mm diameter composite resin cylinders were bonded for the evaluation of the shear bond strength. Shear bond strength measurements were made using a universal testing machine utilizing a shearing blade (jig).The mode of failure at composite-metal interface was determined using a Stereomicroscope at 10 X magnification. Results: The mean bond strength values obtained for surface treatment of Nd: YAG laser surface treated, Sandblasting ,Alloy Primer and No surface treatments were 17.01±.92 , 13.18 ± .73, 7.46 ± .70 and 7.33 ± .77 MPa respectively. The obtained bond strength values were subjected to a one way ANOVA and a Scheffe’s post-hoc comparison test. The results of the present study indicated that Laser surface treatment of the facial surface of the crowns enhanced the bond strength of the composite resin significantly compared to the other groups. Conclusions: Nd: YAG laser surface treatment produced an excellent surface roughness and obtained the highest shear bond strength values suggestive for recommendation as an optimal surface treatment to be used to enhance the resin-metal bond at the interface of the composite resin and the facial surface of primary anterior stainless steel crowns for the purpose of chairside veneering. Key words:Nd: YAG laser treatment, Sandblasting, Primary anterior stainless steel crown, Chairside veneering

  17. On the Use of Accelerated Test Methods for Characterization of Advanced Composite Materials

    NASA Technical Reports Server (NTRS)

    Gates, Thomas S.

    2003-01-01

    A rational approach to the problem of accelerated testing for material characterization of advanced polymer matrix composites is discussed. The experimental and analytical methods provided should be viewed as a set of tools useful in the screening of material systems for long-term engineering properties in aerospace applications. Consideration is given to long-term exposure in extreme environments that include elevated temperature, reduced temperature, moisture, oxygen, and mechanical load. Analytical formulations useful for predictive models that are based on the principles of time-based superposition are presented. The need for reproducible mechanisms, indicator properties, and real-time data are outlined as well as the methodologies for determining specific aging mechanisms.

  18. Study of advanced composite structural design concepts for an arrow wing supersonic cruise configuration

    NASA Technical Reports Server (NTRS)

    Turner, M. J.; Grande, D. L.

    1978-01-01

    Based on estimated graphite and boron fiber properties, allowable stresses and strains were established for advanced composite materials. Stiffened panel and conventional sandwich panel concepts were designed and analyzed, using graphite/polyimide and boron/polyimide materials. The conventional sandwich panel was elected as the structural concept for the modified wing structure. Upper and lower surface panels of the arrow wing structure were then redesigned, using high strength graphite/polyimide sandwich panels, retaining the titanium spars and ribs from the prior study. The ATLAS integrated analysis and design system was used for stress analysis and automated resizing of surface panels. Flutter analysis of the hybrid structure showed a significant decrease in flutter speed relative to the titanium wing design. The flutter speed was increased to that of the titanium design by selective increase in laminate thickness and by using graphite fibers with properties intermediate between high strength and high modulus values.

  19. Experimental method for determination of bending and torsional rigidities of advanced composite laminates

    SciTech Connect

    Maeda, Takenori

    1995-11-01

    This paper presents an experimental method for the determination of the bending and torsional rigidities of advanced fiber composite laminates with the aid of laser holographic interferometry. The proposed method consists of a four-point bending test and a resonance test. The bending rigidity ratio (D{sub 12}/D{sub 22}) can be determined from the fringe patterns of the four-point bending test. The bending rigidities (D{sub 11} and D{sub 22}) and the torsional rigidity (D{sub 66}) are calculated from the natural frequencies of cantilever plates of the resonance test. The test specimens are carbon/epoxy cross-ply laminates. The adequacy of the experimental method is confirmed by comparing the measured rigidities with the theoretical values obtained from classical lamination theory (CLT) by using the measured tensile properties. The results show that the present method can be used to evaluate the rigidities of orthotropic laminates with reasonably good accuracy.

  20. Advanced Cosmic-ray Composition Experiment for Space Station: ISS accommodation study

    SciTech Connect

    Wefel, John P.

    1999-01-22

    ACCESS--Advanced Cosmic-ray Composition Experiment for Space Station--was selected as a new Mission Concept under NRA 96-OSS-03, with the goal of combining calorimeter and transition radiation techniques to provide measurements of cosmic rays from Hydrogen through Nickel up to energies approaching the 'knee' in the cosmic ray all particle spectrum, plus providing measurements of the Z>28 (Ultra-Heavy) nuclei at all energies. An instrument to perform such an investigation is undergoing an ISS/STS Accommodation Study at JSC. The instrument concept, the mission plan, and the accommodation issues for an ISS attached payload which include, in part, the carrier, ISS Site, thermal control, power, data and operations are described and the current status of these issues, for an ACCESS Mission, is summarized.