Ablative performance of various low-density elastomeric composites

Abstract 5. Date February 1971 6. Performing Organization Code Performing Organization Report No. L-6635 10. Work Unit No. 124-64-03-03 11. Contract or Grant No. 13. Type of Report and Period Covered Technical Note 14. Sponsoring Agency Code Results are presented of an experimental investigation of the performance of low-density (160 to 320 kg/m3) silicone-phenolic and commercial ablative composites. Tests were conducted in air and in a mixture of 72 percent nitrogen and 28 percent carbon dioxide by mass. The ablative performance of the silicone-phenolic composites increased signifi­cantly as the density decreased. Also, the performance of these composites was found to be influenced by stream composition when tested at a cold-wall heating rate of about 0.2 MW/m2, but the stream composition had little effect at a heating rate of about 0.6 MW/m2. The addition of nylon to the silicone-phenolic material improved the ablative performance. Three commercial composites were tested and their ablative performances were compared with those of the silicone-phenolic composites of comparable densities. When the heat of degradation was considered, a commercial composite that incorporated a high volume per­centage of ground cork filler appeared to be superior to the other composites. However, a comparison made on the basis of a more significant parameter, the ablative effectiveness, showed little difference in the ablative performance of the various composites.