Design And Study On The Properties Of Hybrid Fabric Reinforced Polymer Composites Ablator

Large area ablators used in high heat flux coupled with strong flow erosion environment require advanced properties, such as lightweight, high heat insulation, resistance to flow erosion, and so on. To meet these requirements, the thermal and flow erosion resistance properties of the Kynol phenolic/barium- phenolic(P/PR), poly(p-phenylene benzobisoxazole)/PR(PBO/PR) and quartz/PR(Q/PR) composites with low densities were investigated, respectively. Based on the investigation, two hybrid fabric reinforced plastics(HFRP) of phenolic-quartz/phenolic resin and PBO-quartz/phenolic resin were designed, and the properties of the HFRP in high heat flux and strong flow erosion environment were studied in this paper.Mechanical properties the composites with different char degrees were measured. Mass loss of the composites were investigated through the oxyacetylene ablation test platform which provided a high thermal environment. The resistances to flow erosion of the composites were studied by the exhaust plume ablative test of small liquid motor(EPSLM) which simulated aerodynamic force accompanied by aerodynamic heating effects. Evolution of the properties and main failure reasons of P/PR, PBO/PR and Q/PR composites in the high heat flux coupled with strong flow-erosion environments were obtained. Hybrid effects of the phenolic- quartz/phenolic and PBO-quartz/phenolic HFRP were discussed, and effects of fiber mass ratio, resin types and organic fiber types on the properties of HFRP were also investigated. The results showed that:(1) P/PR, PBO/PR and Q/PR composite specimens with densities of 1.21g/cm3, 1.37g/cm3 and 1.45g/cm3, respectively, had much mass loss and bad damage in EPSLM. The main reason for the failure of the P/PR composites was that carbonaceous residues in the char layer were divided by cracks and poor connection between the char layer and the pyrolysis layer in the ablation. While the main reason for the failure of the PBO/PR composites was that the specimens had delaminated when the resin matrix was highly pyrolyzed and the char layer was also expanded and delaminated. And failure of the Q/PR composites was due to the delamination in ablation.(2) Densities of the phenolic-quartz/phenolic resin HFRP specimens with high resistance to heat-flow erosion were no bigger than 1.4 g/cm3. The hybrid effects of the phenolic-quartz/phenolic resin HFRP were due to the facts that the carbonaceous residues were formed by the Kynol phenolic fibers and the phenolic resin in the high thermal environment, and they could react with each other and formed an integrative char layer. The presence of the Kynol phenolic fiber enriched of the char sources and improved its microstructure. The quartz fiber can also react with the carbonaceous residues and enhanced the connection between the char layer and the main body of the specimens. The synergistic effects of the Kynol phenolic fiber, phenolic resin matrix and quartz fiber in high thermal conditions increased the mechanical properties of the char layer, enhanced the integrity and stability of the microstructure of the char layer, improved the combination of char layers in P/PR composite and the delamination in Q/PR composites in ablation. So the resistance to heat-flow erosion of the P-Q/PR composites had been improved significantly.(3) The PBO-Q/PR HFRP with fiber volume fraction(Vf) of 45% had higher resistance to heat-flow erosion. The hybrid effects of the PBO-Q/PR HFRP can be summarized that the carbonaceous residues formed by the PBO fibers had high resistance to heat-flow erosion, which enriched sources of the char and improved its microstructure, while the presence of the quartz fiber improved interface strength of the PBO-Q/PR HFRP. In ablation, the quartz fiber could react with the carbonaceous residues formed by the PBO fibers, due to the combination of char layer and the main body of the specimens a stable microstructure of the char layer was formed to protect internal material from the heat-flow.(4) Synergistic reaction degree among the components of the HFRP composites directly affected the mechanical properties and microstructure of the char layer, and the resistance to heat-flow of the composites. P-Q/PR HFRP had the best comprehensive performance among P-Q/PR HFRP with different mass ratio of fibers.(5) Among P-Q/BPR、P-Q/PR and P-Q/BZ HFRP composites with different resin matrixes, the char layer formed in P-Q/PR composites had better mechanical properties and integrity of microstructure, and the resistance to heat-flow of P-Q/PR was also good. All these because that the PR resin matrix had wide temperature range of pyrolysis, synchronous pyrolysis with Kynol fiber and higher char yield.(6) Density of the Kynol phenolic fiber is smaller than that of the PBO fiber and the interface strength of the Kynol phenolic fibers and the phenolic resin was better than that of the PBO fibers and the phenolic resin. So the P-Q/PR composites have advantages in decreasing the density and improving the heat insulation properties of the composites.