MOBILITY ENGINEERING Produced by SAE Media Group
MOBILITY ENGINEERING
Magazines
Magazine cover

Current Issue

Archives

Magazine cover

Current Issue

Archives

Magazine cover

Current Issue

Archives

Magazine cover

Current Issue

Archives

Innovations Pertaining to Carbon-Based Materials

Advances in densification, microtubes, and tailoring surface tension have been made.

Some notable innovations in the design and manufacture of carbonbased materials have been made in a continuing program of basic research on carbon- based materials for use in propulsion systems of aircraft and spacecraft. The research has ranged over diverse topics that have included fabrication of carboncarbon composite-material components, protection of carbon against oxidation, microelectromechanical devices, and surface- tension phenomena.

Carbon-carbon composites are the materials of choice in many high-temperature thermostructural applications, including rocket nozzles and exit cones, missile nose tips, and leading edges of hypersonic vehicles. Although these materials are stronger and stiffer than steel, less dense than aluminum, and resistant to thermal shock, they are susceptible to oxidation at temperatures above 450 °C. In addition, they are very costly, principally because fabrication of a reinforced carbon-carbon component includes a densification process in which a carbon matrix is placed among carbon fibers in a preform that has been constructed to have certain mechanical properties. The present innovations, which have emerged from efforts to address some of the issues mentioned above, are summarized as follows:

  • An in situ densification process has been developed. In this process, a carbon- fiber preform is impregnated with molten naphthalene, with some AlCl3 mixed into the naphthalene as a polymerization catalyst. Following in situ polymerization, the polymerimpregnated preform is heated to convert the polymer matrix material to carbon. This process yields a matrix of very high quality at a fraction of the cost and in a fraction of the time required for prior commercial densification processes. The electrical and thermal conductivities of a material produced by this process exceed those of the best commercial composites. In addition, by virtue of the complete penetration of the liquid precursor material into the preform (a key advantage of this process over prior densification processes), the density of a composite made by this process is more nearly uniform than are densities of commercial carbon- carbon composites.
  • Microtube technology — which overlaps with the disciplines of microelectromechanical systems (MEMS) and microfluidics — has emerged as a byproduct of efforts to address the issue of protecting carbon-carbon composites against oxidation. Briefly, microtube technology provides for the fabrication tubes having features as small as fractions of a micron by use of micromachining techniques to form mandrels, coating the mandrels with metallic or nonmetallic materials destined to become the tube walls, then removal (e.g., by etching) of the mandrel materials. The finished tubes can be free-standing or embedded and can have almost any complex threedimensional shapes, including noncircular cross sections and cross sections that vary with axial position (e.g., bellows-like tubes).
  • A method of tailoring the wetting properties of microtubes and other devices having microscopic features has been developed out of recognition that surface tension is a dominant force at microscopic dimensions. This method is an important innovation because surface tension and wetting behavior are major considerations in potential applications for microtubes, which include cooling, separation of materials, venting, and sensing. This method involves understanding the relationship between contact angle and surface tension and tailoring microscopic surface features to exploit this relationship to obtain or prevent wetting or to obtain different degrees of wetting at different locations. For example, through geometric tailoring of surfaces, one could control entrance of a liquid into a capillary, cause multiple fluids to flow in distinct streams through a capillary device, make the surface of an ordinarily non-wetting material surface wetting, or make the surface of an ordinarily wetting material non-wetting.

This work was done by Wesley P. Hoffman of the Air Force Research Laboratory. For more information, download the Technical Support Package (free white paper) at www.defensetechbriefs.com/tsp  under the Materials category. AFRL-0003

Topics:
Coatings, colorants and finishes Coatings, colorants, and finishes Composite materials Cooling Corrosion Fabrication Fibers Manufacturing processes Materials Microelectromechanical devices Polymers Sensors and actuators
This Brief includes a Technical Support Package (TSP).
Document cover
Innovations Pertaining to Carbon-Based Materials

(reference AFRL-0003) is currently available for download from the TSP library.

Don't have an account?

More From SAE Media Group

    Magazine cover
    Defense Tech Briefs Magazine

    This article first appeared in the April, 2007 issue of Defense Tech Briefs Magazine (Vol. 1 No. 2).

    Read more articles from the archives here.

    Overview

    The document is a final report titled "Carbon Materials Research," authored by Wesley P. Hoffman and published by the Air Force Research Laboratory (AFRL). It covers a basic research study conducted from August 2004 to August 2006, focusing on the development and application of carbon materials, particularly in propulsion systems.

    The report begins with an executive summary that outlines the objectives and findings of the research. The primary aim was to explore various aspects of carbon materials, leading to advancements in several key areas. These include the fabrication of carbon-carbon composites, which are essential for high-performance applications due to their strength and thermal resistance. The research also delves into oxidation protection methods for carbon materials, which is critical for enhancing their durability and performance in extreme environments.

    Additionally, the report discusses the development of microelectromechanical systems (MEMs) devices, which are miniature systems that integrate mechanical and electrical components at a microscale. These devices have significant implications for various applications, including sensors and actuators in aerospace and defense technologies.

    The document includes an abstract summarizing the research's scope and findings, followed by a detailed table of contents that outlines the structure of the report. It features sections on journal papers and patents related to the research, indicating the scholarly contributions and intellectual property generated from the study.

    Several appendices provide in-depth insights into specific research topics. For instance, Appendix A discusses the "Near Net-Shaped, Ultra High Melting, Recession-Resistant Zrc/W-Based Rocket Nozzle Liners," which highlights innovative manufacturing techniques. Appendix B focuses on the "Material Science of Carbon," while Appendices C and D explore microstructural studies and fabrication techniques for high-density carbon-carbon composites. Appendix E presents carbonization studies of glassy carbon derived from bis-ortho-diynylarenes (BODA), showcasing the diverse chemical approaches taken in the research.

    The report concludes with a notice regarding the use of government data and a signature page indicating approval for public release. Overall, this document serves as a significant contribution to the field of materials science, particularly in the context of aerospace applications, and is intended for public dissemination to facilitate knowledge exchange in scientific and technical communities.

    Top Stories

    INSIDERDefense

    Feature Image New 3D-Printable Nanocomposite Prevents Overheating in Military Electronics

    Technology ReportSoftware

    Feature Image Talking SDVs and Zonal Architecture with TE Connectivity

    NewsDesign

    Feature Image 2026 Nissan Sentra Review: Putting the Pieces Together

    INSIDERDesign

    Feature Image New Defense Department Program Seeks 300,000 Drones From Industry by 2027

    INSIDERDefense

    Feature Image Anduril Completes First Semi-Autonomous Flight of CCA Prototype

    INSIDERDefense

    Feature Image F-22 Pilot Controls Drone With Tablet

    Webcasts