Process Simulation for Chemical Vapor Infiltrated Composites

The Chemical Vapor Infiltration (CVI) process for the manufacture of ceramic matrix composites (CMC's) has a number of inherent advantages over other methods: benign, low temperature process; stoichiometric matrices; complex shape and large scale production potential. The basic process is also fairly mature, and is practiced by a growing number of material suppliers: DuPont, Amercon, etc. However, the production of reliable, reproducible CVI composites is still very much a "black art", where nuances is furnace conditions have a large impact on outputs and where the need for some kind of CVI process simulation model is readily apparent. Such a model would allow process parameters to be established in advance of the actual run, thereby reducing the need for expensive and time consuming validation runs, and minimizing part rejection rules. This was the goal of the recently completed Air Force "Processing Science for CVI" program. This program went a long way in developing and validating a prototype CVI Process Model. However, there are a number of outstanding issues which must be addressed. The objective of this program is the development of preform, process, property relationships, and their integration into the CVI existing Process Science Model.