Advanced Engineering Materials

Cover image for Advanced Engineering Materials

December, 2002

Volume 4, Issue 12

Pages 895–951

    1. Contents: Adv. Eng. Mater. 12/2002 (pages 895–897)

      Article first published online: 12 DEC 2002 | DOI: 10.1002/adem.200290000

    2. Design, Fabrication, and Application of Thermostructural Composites (TSC) like C/C, C/SiC, and SiC/SiC Composites (pages 903–912)

      F. Christin

      Article first published online: 12 DEC 2002 | DOI: 10.1002/adem.200290001

      The main features of thermostructural composites (TSCs) are their highly specific mechanical properties, high thermal conductivity, excellent behavior to thermal shocks; endurance to very high temperature, and easy fabrication. In this paper, the design, fabrication, and application of ceramic matrix composites are reviewed with special emphasis on applications for solid rocket propulsion, liquid rocket propulsion, brake yields, and jet engines.

    3. Gel-Extrusion: A New Continuous Forming Technique (pages 913–915)

      A.J. Millán, I. Santacruz, A.J. Sánchez-Herencia, M.I. Nieto and R. Moreno

      Article first published online: 12 DEC 2002 | DOI: 10.1002/adem.200290002

      In recent years a variety of direct shaping methods has been developed for the near-net shaping of ceramic powders. The main aim in developing these methods is to provide a simple route for manufacturing bulk complex-shaped bodies with increased green resistance in order to reduce or avoid final machining, which is the most expensive step in the fabrication process. This communication reports a novel processing route for the continuous manufacture of ceramic and/or metal hollow or solid bodies based on the extrusion of aqueous suspensions that contain a small amount (< 1 wt.-%) of a gelling additive that gelates on passing through a refrigerated die.

    4. Thermal Stability of Hydroxyapatite Whiskers Prepared by Homogenous Precipitation (pages 916–919)

      H. Zhang, Y. Yan, Y. Wang and S. Li

      Article first published online: 12 DEC 2002 | DOI: 10.1002/adem.200290003

      Hydroxyapatite (HA) whiskers prepared by homogenous precipitation method were heat treated in air. The phase composition of HA whiskers and their microstructure were investigated before and after the heat treatment using XRD, FT-IR, SEM, and TG-DSC techniques. It was revealed that the HA whiskers obtained were morphologically stable at elevated temperatures below 1200°C. A phase transition of the HA whiskers took place obviously at about 1200°C. The thermal stability of HA whiskers was related to the chemical composition and crystallinity. They could be used as reinforcement materials in dense HA ceramics and porous HA ceramics.

    5. Graded EB-PVD-Thermal Barrier Coatings Produced by Powder Evaporation (pages 919–922)

      E. Lugscheider, K. Bobzin, A. Etzkorn, G. Syrakas and C.W. Siry

      Article first published online: 12 DEC 2002 | DOI: 10.1002/adem.200290004

      Gas turbines in aircraft operation are very often equipped with EB-PVD coated first stage blades. EB-PVD coatings provide a thermal barrier between the hot gas stream and the cooled metal part of the blade. To enhance the erosion resistant behavior of the TBC, in this work a graded transition from zirconia as TBC to alumina as erosion protective coating was investigated.

    6. In-Flight Reactions of Metallic Particles during Thermal Spraying (pages 922–924)

      L. Zhao, C. Herbst-Dederichs and E. Lugscheider

      Article first published online: 12 DEC 2002 | DOI: 10.1002/adem.200290005

      During thermal spraying of metal materials reactions between the spray materials and the gaseous species from plasma gas, atomization gas or surrounding atmosphere occur. Some reactions like nitriding during reactive spraying are designed to improve coating properties, while other reactions like oxidation during atmospheric plasma spraying of stainless steels impair the coating properties. In this study, the reaction of titanium particles in-flight during reactive plasma spraying and the reaction of the 316 L stainless steel in-flight during HVOF spraying were investigated. It was found that the melting degree of the powders was essentially important for the reactions in-flight. The convection movement within a molten particle significantly accelerated the reactions.

    7. Reaction Bonded Composite Foams (pages 925–927)

      J. Luyten, J. Cooymans and A. De Wilde

      Article first published online: 12 DEC 2002 | DOI: 10.1002/adem.200290006

      Conventional ceramic foams suffer from weak thermo-mechanical properties. Therefore, the authors developed reaction bonded composite foams. These materials are characterized by high mechanical strength due to their fine grained microstructure. By a right choice of the composition, high thermal shock properties can also be obtained. Firstly mullite with additions of ZrO2 is considered. Depending on the structural requirements of the application, a certain processing route can be chosen: the polyurethane sponge technique, gel casting or the hollow sphere method. In this contribution, the current state of this study, indicating that this Reaction Bonded manufacturing route is a feasible method for manufacturing composite ceramic foams is discussed.

    8. Stiffness and Thermal Expansion of Short Fiber Composites with Fully Aligned Fibers (pages 927–931)

      A. Gusev, H.R. Lusti and P.J. Hine

      Article first published online: 12 DEC 2002 | DOI: 10.1002/adem.200290007

      Predicting the overall, effective properties of short fiber composites with fully aligned fibers from the properties of the individual phases and the composite’s morphology has attracted a great deal of attention during the last decades. In this work, the authors focus on the overall elastic constants and use the finite-element-based numerical procedure developed by them to assess the adequacy of two of the most widely used micromechanics-based models.

    9. Orientation Averaging for Stiffness and Thermal Expansion of Short Fiber Composites (pages 931–933)

      A. Gusev, M. Heggli, H.R. Lusti and P.J. Hine

      Article first published online: 12 DEC 2002 | DOI: 10.1002/adem.200290008

      It is fairly common in practice that during injection moulding, the mold filling process results in non-uniform fiber orientation distributions in the final injection molded short fiber reinforced composite part. It would be very attractive to employ an orientation averaging scheme to form predictions for the design of short fiber reinforced composite parts. Here, the authors use a finite-element-based numerical procedure developed by themselves and, for the first time, directly predict the stiffness and thermal expansion of several hundred multi-fiber computer models with a variety of different predefined fiber orientation states.

    10. Actuator Classification and Selection—The Development of a Database (pages 933–940)

      M. Zupan, M.F. Ashby and N.A. Fleck

      Article first published online: 12 DEC 2002 | DOI: 10.1002/adem.200290009

      Actuators are controllable work-producing devices. A strategy for selecting actuators to meet specified design requirements is described here. A number of considerations enter: the type and characteristics of the actuator, the nature of the power-source (the “fuel”) that is required to drive it, and the possible need of an interface between the two to convert the energy into a form that the actuator can accept. The strategy is demonstrated by software that includes a database for some 220 actuators drawn from 18 families, and an advanced selection engine. Case studies are used to illustrate its use.

    11. Annual Index: Author Index 2002 (pages 941–942)

      Article first published online: 12 DEC 2002 | DOI: 10.1002/adem.200290010

    12. Annual Index: Subject Index 2002 (pages 943–951)

      Article first published online: 12 DEC 2002 | DOI: 10.1002/adem.200290011