EXTENDED HEATING ABLATION OF CARBON PHENOLIC AND SILICA PHENOLIC

摘要

An analysis was made of experimental and analytical investigations of the ablation of carbon phenolic and silica phenolic composites under extended heating conditions. Specimens of up to 8.75 sq. in. in area and instrumented with indepth thermocouples were characterized under stepwise pulses of either five minutes (2 steps) or up to 1.4 minutes (to 5 steps) in duration using two air arc heaters. The nominal peak heat load was 35,000 Btu/sq ft. Internal and surface temperatures, recession rates, and recession patterns in the residual char were not anomalous for the two step, low shear (to 2.5 lb/sq ft) runs. Charring-ablator theory indepth and surface temperature responses agreed well with experimental results for a carbon phenolic. For the five step condition with a moderate peak shear (30 lb/sq ft) there was cine film evidence of micromechanical surface removal at late times. Micromechanical effects, by difference, were further consistent with theory. Reliable composite properties were found to be necessary to accurately model extended heating ablation. (Author)