Kei Yamamoto

Purdue University School of Materials Engineering
Project Title: Microstructure Studies of Carbon-Carbon Composite Materials
Advisor: Prof. Alex King

Introduction

Carbon-carbon composites are made up of crystalline (graphitic) carbon fibers embedded in an amorphous carbon matrix. They have a very high melting point, low coefficient of thermal expansion, a great thermal shock resistance and they keep all these properties at temperatures of over 2000oC. They are used for a wide variety of applications, including brake friction materials for aircraft and for racing cars. Four aircraft brakes manufactured in different ways will be studied.

Project Objectives

  • Develop techniques of microstructural inspection that are appropriate for this material system.
  • Determine volume fraction of fiber, amorphous material and porosity.
  • Study crystallinity of fibrous material

Approach

  • Examine porosity and fiber alignment using the optical microscope
  • Perform microtomy on specimen to prepare it for transmitted light microscopy
  • Study the crystal structure of the specimens using X-Ray diffraction
  • Examine the fiber surface using the scanning electron microscope
  • Examine the amorphous carbon using the scanning electron microscope

Findings

  • Amorphous carbon matrix and carbon fibers are not well bound together, thus matrix is not providing any benefits to the structure
  • Crystallinity of the carbon fibers varies considerably between specimens
  • Carbon was only deposited on the surface in one of the specimens: amorphous carbon nucleation is found only very rarely on the fiber surfaces in this specimen.

Figure 1: Carbon fibers (magnification of 1500X).
Figure 2: Carbon fibers (magnification of 2000X).

Final Presentation