Measurement of Mass Transport Properties of Carbon Phenolic Ablator Materials and Their Relationship to Material Behavior in Use Environments
Start Date
1-3-2011 4:15 PM
Description
Several types of anomalous behavior have been observed with phenolic based ablatives in post-fired nozzles, exit cones, and reentry vehicles. Many of these events have been shown to be related to the development of internal gas pressure within the material during use. The development of internal gas pressure is a function of the amount of gas produced within the material and the rate at which that gas is allowed to escape. The former is controlled by the material’s temperature, the kinetics of chemical conversion of the phenolic resin, and possibly the internal gas pressure itself. The latter property of a material is referred to as the material’s permeability and as such is independent of specimen geometry, pressure differential, and properties of the gas being transported. The permeability of carbonized fiber based phenolic composites is a function of material direction, temperature, temperature history, constituent composition, processing, and the stress-strain state of the material. Other variables like the environmental history of the material prior to use may also affect the subsequent development of porosity in the material during use. This paper examine why we think these variables are important in modeling the behavior of phenolic based materials in their use environment.
Measurement of Mass Transport Properties of Carbon Phenolic Ablator Materials and Their Relationship to Material Behavior in Use Environments
Several types of anomalous behavior have been observed with phenolic based ablatives in post-fired nozzles, exit cones, and reentry vehicles. Many of these events have been shown to be related to the development of internal gas pressure within the material during use. The development of internal gas pressure is a function of the amount of gas produced within the material and the rate at which that gas is allowed to escape. The former is controlled by the material’s temperature, the kinetics of chemical conversion of the phenolic resin, and possibly the internal gas pressure itself. The latter property of a material is referred to as the material’s permeability and as such is independent of specimen geometry, pressure differential, and properties of the gas being transported. The permeability of carbonized fiber based phenolic composites is a function of material direction, temperature, temperature history, constituent composition, processing, and the stress-strain state of the material. Other variables like the environmental history of the material prior to use may also affect the subsequent development of porosity in the material during use. This paper examine why we think these variables are important in modeling the behavior of phenolic based materials in their use environment.