Preparation And Properties Of Qyartz Fiber Reinforced Low Density Phenolic Composites

Since the twenty-first Century,the great powerful countries of the world have put forward large scale exploration plans for the moon,Mars and distant planets,and set off a wave of deep space exploration.The thermal protection materials has been put forward higher requirements for the aerodynamic shape keeping capability,lightweight,efficient heat protection and long service capability the deep space exploration vehicleIn this paper,in view of the long service requirements of a new type of light ablative heat resistant material,the deficiency of the traditional light quartz fiber reinforced low density phenolic compound has been further studied and improved on the basis of the research group,and the phenolic aerogels are modified by MTMS and DDS as the matrix phase.In this paper,aiming at the light,heat insulation,low enthalpy and long service requirements for the aero craft in a specific thermal environment,the shortcomings of the traditional light quartz fiber / modified phenolic composites are further studied and improved on the base of the research group.The phenolic aerogels are modified by by MTMS and DDS as the matrix phase,the new type of integrated ultra-light weight quartz fiber reinforced low density phenolic composites(NQF/Si-PR composite material)is prepared with the enhance-ment of quartz fiber preform.For the silane modified phenolic aerogels,three-dimensional quartz fiber preform and NQF/Si-PR composites were made,the material system design,microstructure control and performance evaluation were carried out.Furthermore,the structural evolution,physical and chemical properties of NQF/Si-PR composites after pyrolysis and carbonization were studied.The silane modified phenol formaldehyde aerogel was successfully prepared by sol-gel polymerization,solvent replacement and atmospheric pressure drying by using phenolic resin of THC800,HMTA as catalyst,EG as solvent and pore forming agent,MTMS and DDS as precursor solution.The three-dimensional network structure of the Si-PR aerogels are composed of nanoscale gel particles and the gel particles and pores in the network structure are continuous respectively.The addition of silane Modifier makes the gel particle size of PR aerogels grading,differentiating the smaller size nanoparticles,improving the aerogel pore size distribution and pore structure,and improving the specific surface area of the aerogel material.The high bond energy energetic groups such as Si-O-C and Si-O-Si functional groups were successfully introduced into the long chain structure of phenolic aerogels,which effectively improved the thermal stability of phenolic aerogels.The rigid quartz fiber preform(NQF)was prepared by pre impregnation,drying and curing process by using the continuous fiber needling felt as reinforcing material with the 5%,10%,15% and 20% concentration of phenolic resin respectively.The NQF was prepared by pre-impregnation,drying and curing process.The NQF/Si-PR aerogel composites were synthesized by vacuum assisted impregnation and sol-gel polymerization with the three-dimensional continuous quartz fiber preform as the strengthening phase and Si-PR aerogel as the impregnated phase and the base.The experimental results show that the mechanical properties of the fiber preform and aerogel composites are all improved with the increase of the concentration of phenolic adhesives,in other words,the bonding process of the preform can significantly affect the ultimate mechanical properties of the composites.The NQF/Si-PR aerogel composites were treated at RT?,400?,600?,800?,1000? and 1200? respectively.The results show that with the increase of heat treatment temperature,the carbonization degree of phenolic aldehyde gradually increases,the micropore size increases gradually,the pore volume increases,and the specific surface area decreases.In chemical state,with the increase of heat treatment temperature,the chemical bonds such as methylene(-CH2-),C-H bond on aromatic ring and C-H bond occur in turn,and the internal crosslinking structure of the material is destroyed gradually,and small molecules such as CH4,H2,phenol and so on are released,and the degree of carbonization increases gradually.The mechanical properties analysis showed that the compressive properties of composites at room temperature showed a downward trend with the increase of temperature.The analysis of high temperature dynamic tensile properties shows that the original aerogel composite material has two near elastic deformation during the stretching process,which corresponds to the original composite and the reorientation of the quartz fiber cluster after the aerogel failure.The fracture of the composite is also considered to be the coupling effect of the fracture of many micro quartz fibers.The tensile strength of the composites decreases with the increase of temperature,and there is a slight increase at 400 C and 700 C.The reason is that the mechanical properties of the aerogel structure in the material decrease sharply at this temperature,causing the fiber cloth in the direction of the composite XY to rotate in the direction of external loading and the consistency of the quartz fiber.The tensile strength and tensile modulus of the composites increased slightly.The thermal conductivity analysis shows that the thermal conductivity of the NQF/Si-PR aerogel composite increases with the increase of temperature,and the thermal conductivity of CM-RT is slightly lower than that of CM-1200 at the same temperature.