Preparation And Thermal Properties Of Carbon Fiber/Phenolic-silicone Nanocomposites

Lightweight ablative and antioxidant materials are usually composed of a low density,low thermal conductivity resin as the matrix phase and a low density,high porosity carbon fibre fabric as the reinforcing phase,which is characterised by low density,low thermal conductivity,high temperature resistance,micro-ablation,oxidation resistance and long re-entry time.Ablative composites for large windward surfaces.In this study,the design,microstructure modulation,preparation,testing and analysis of the thermodynamic properties of carbon fibre/phenolic-silicone nanocomposites and their performance in aerobic thermal environments were carried out using phenolic resin（PR）aerogels and organosilane/siloxane（Si OC）aerogels as impregnating phases and carbon-bonded carbon fibre composite（CBCF）as reinforcing phase.The evaluation of the performance of the carbon fibre/phenolic-silicone nanocomposites has been carried out.In this paper,phenolic/silicone（PR-Si）hybrid aerogels were synthesized by sol-gel reaction,solvent replacement and atmospheric pressure drying on the basis of phenolic resin,and then the material composites were prepared by impregnating carbon-quartz fibre preforms and carbon-bonded carbon fibre preforms to produce C-QF/PSi,CBCF/PR/Si OC and CBCF/Si OC/PR aerogels,respectively.nanocomposites,and their microstructure,thermal properties,chemical state,ablation resistance and oxidation resistance were investigated,and the ablation/insulation mechanisms of the carbon fibre/phenolic-silicone nanocomposites were explored.Phenolic resin,hexamethylenetetramine and ethylene glycol were mixed with a co-precursor solution consisting of 3-aminopropyltriethoxysilane（APTES）to prepare phenolic/organosilicon（PR/Si）hybrid aerogels by sol-gel reaction.A new lightweight carbon quartz fibre fabric-reinforced phenolic-silicone hybrid aerogel composite with a complete and homogeneous microstructure was prepared by impregnating the carbon quartz fibre hybrid mat（C-QF）as the three-dimensional reinforcing phase of the material with the co-precursor solution of the hybrid aerogel and undergoing copolymerisation-induced nanoscale phase separation,solvent exchange and ambient atmospheric pressure drying（APD）.The effect of the weight ratio of APTES/PR on the mechanical properties of C-QF/PSi was studied by combining C-QF with a density of 0.352 g/cm³ with PSi hybrid aerogels with a density ranging from 0.139 to 0.215 g/cm³,the compressive strength ranges of C-QF/PSi with a density of 0.460～0.516 g/cm³ in the XY and Z directions are12.7～17.01 MPa and 5.96～7.51 MPa,respectively.The thermal conductivity at room temperature in the XY and Z directions is as low as 0.161 W/（m×K）and 0.112W/（m×K）,and the thermal diffusivity at room temperature in the XY and Z directions is as low as 0.374 mm²s^-1 and 0.260 mm²s^-1.The ablation/insulation performance of C-QF/PSi was examined at 300 s of ablation under high temperature oxidised oxygen-acetylene flame conditions,with linear ablation rates as low as0.017 mm/s and peak internal temperatures below 100℃ at 80 mm depth from the ablated surface at temperatures above 2000℃.CBCF/PR/SiOC aerogel composites with different Si OC contents and densities of 0.323-0.381 g/cm³ and porosity of 62.4%-68.5%were prepared by impregnating phenolic resin aerogel and Si OC aerogel in turn with CBCF/PR/Si OC aerogel with a density of 0.184 g/cm³ and 88.5%porosity as the reinforcing phase of the composite.Si OC aerogel composites have a multi-scale pore structure with a homogeneous and complete microstructure.CBCF/PR/Si OC aerogel composites with a density range of0.323-0.381 g/cm³ and a porosity range of 62.4%-68.5%were prepared by continuous modification.The homogeneous and complete microstructure of the NCF/PR aerogel composite,which is distributed in the micropores,mesopores and macropores ranges,directly illustrates the multi-scale pore structure properties of PR aerogels.The effect of the density of the Si OC precursor solution on the mechanical properties of CBCF/PR/Si OC aerogel composites was investigated.The compressive strength ranges of CBCF/PR/Si OC were 2.29±0.27 to 4.13±0.33 MPa and 2.09±0.30to 3.46±0.47 MPa,and the compressive modulus ranges from 109.3±19 to202.78±27 MPa and 68.91±21.33 to 101.79±27.52 MPa in the XY and Z directions,respectively.The thermal conductivity at room temperature is as low as 0.095W/（m×K）and 0.081 W/（m×K）in the XY and Z directions,and the thermal diffusion coefficient at room temperature is as low as 0.322 mm²s^-1 and 0.278 mm²s^-1in the XY and Z directions.The ablation/insulation performance of CBCF/PR/Si OC was examined at 2000 s of ablation under high temperature butane flame conditions,with peak internal temperatures below 385.7℃,257.4℃ and 176℃ at depth positions 8 mm,14 mm and 18.5 mm from the ablated surface at temperatures above1250℃,respectively.CBCF with a density of 0.184 g/cm³ and 88.5%porosity was used as the reinforcing phase,and Si OC aerogel and phenolic resin aerogel were impregnated in turn to produce CBCF/Si OC/PR aerogel composites with a density range of 0.292-0.356 g/cm³ and a ternary interpenetrated structure with a porosity range of 65.6%-75.9%.The effect of different densities of phenolic resin precursor solutions on the mechanical properties of CBCF/Si OC/PR aerogel composites was investigated.The compressive strength ranges of CBCF/Si OC/PR were 2.446 to 4.18 MPa and 1.68 to3.45 MPa,and the compressive modulus ranges from 78.91 to 155.56 MPa and 43.90to 80.99 MPa in the XY and Z directions,respectively.The room temperature thermal conductivity and thermal diffusivity in the XY direction are 0.161-0.183W/（m×K）and 0.374-0.385 mm²s^-1,respectively,and the room temperature thermal conductivity and thermal diffusivity in the Z direction are 0.112-0.133 W/（m×K）and 0.260-0.280 mm²s^-1,respectively.The ablation/insulation performance of CBCF/Si OC/PR was examined at 2000 s of ablation under high temperature butane flame conditions,with peak internal temperatures below 389.1℃,221.3℃,95.8℃ and 64.9℃ at depth positions 10 mm,25 mm,30 mm and 38 mm from the ablated surface at temperatures above 1250℃,respectively.