Paper number 576

DENSIFICATION OF C/C COMPOSITES USING PULSED CHEMICAL VAPOR INFILTRATION

Donald W. Radford and Roger A. Ross

Composite Materials, Manufacture and Structures Laboratory Mechanical Engineering Colorado State University Fort Collins, Colorado, USA 80523-1374

Summary

Pulsed chemical vapor infiltration, PCVI, is a modification to traditional CVI that has been suggested to reduce internal porosity while also decreasing manufacturing time and costs. The basic difference between these processes is a cyclic interruption in the precursor gas flow into, and out of, the furnace during processing. To test this prediction, a CVD reactor has been modified to allow low frequency pulsing, and carbon fiber preforms have been infiltrated under various pulsing conditions. Specimens are evaluated using quantitative optical microscopy to map the amount of deposition within the preform at varying depths. The primary results observed include a significant increase in the rate of deposition near the preform surface for specimens densified using pulsed flow and improved deposition with time throughout the thickness for these same specimens. Further, the additional amount of deposition that PCVI provides, along with reduced amounts of gas used, increases the gas utilization efficiency of the process.

Keywords

CVI, carbon/carbon, pulsed mode deposition, precursor gas efficiency.