连续碳纤维增强莫来石基复合材料的性能与失效行为研究
发布时间：2018-08-05 14:25
【摘要】：莫来石(Mullite)陶瓷具有密度低、热膨胀系数低、抗热震性好、耐高温、抗氧化等优点,在高温结构和热防护领域具有广阔的应用前景,但室温下较差的力学性能限制了它的应用。本文在前期研究基础上,以碳纤维布叠层缝合预制件为增强体,以符合莫来石化学计量比的Al2O3-SiO2溶胶为原料,通过浸渍-干燥-热处理技术路线制备C/Mullite复合材料。论文探究了Al2O3-SiO2溶胶的烧结收缩行为和莫来石化行为,在对复合材料工艺进行初步优化的基础上,重点研究分析了C/Mullite复合材料的本征性能,以及在模拟应用环境中的失效行为。所用Al2O3-SiO2溶胶的固含量和陶瓷产率分别为30.7wt.%和18.3wt.%。经过1300℃热处理后,溶胶莫来石化基本完成。凝胶粉末的压片在热处理时,线收缩率随着热处理温度增大而升高,温度越高越有利于粉末烧结。经初步优化,建立了能够避免复合过程中碳纤维布分层开裂的工艺路线。以优化的工艺路线制备得到表观密度、总孔隙率、开孔率分别为2.19g·cm-3、13.4%和11.3%的C/Mullite复合材料。采用不同测试方法表征了C/Mullite复合材料的弯曲强度,三点弯曲强度(228.9±11.0MPa)略高于四点弯曲强度(210.6±8.9MPa),服从m=30.6、λ=238.0的两参数Weibull分布,m值较大,说明复合材料具有较好的均匀性。由于连续碳纤维的引入,复合材料具备纤维断裂、界面脱粘、拔出等增韧机制,断裂韧性达到11.2MPa·m1/2,是单体Mullite陶瓷的4-5倍。C/Mullite复合材料的拉伸强度和拉伸模量分别为119.9MPa和36.6GPa,X方向的压缩强度为128.2MPa,层间剪切强度为28.1MPa。表征了C/Mullite复合材料在室温-1400℃区间内的热物理性能,为材料的工程应用提供基础数据。C/Mullite复合材料的热膨胀系数随温度的升高先增大后减小,在1000℃时达到最大值4.83×10-6K-1;1300℃以后,由于基体进一步烧结收缩,热膨胀系数呈现为负值。C/Mullite复合材料的比热容随温度的升高而增大,温度高于1200℃后趋于稳定,在1200℃时达到最大值1.547J·g-1·K-1,室温时最小,为0.756J·g-1·K-1。C/Mullite复合材料的热扩散率随温度升高呈下降趋势,高温时趋于平稳,室温热扩散率最高,为1.1mm2·s-1,700℃时最低,为0.707mm2·s-1。C/Mullite复合材料的热导率基本上随温度升高而增大,室温时热导率为1.859W·m-1·K-1,1200℃时复合材料热导率达到最大,为2.325W·m-1·K-1。分别研究了C/Mullite复合材料在高温惰性、高温氧化以及高温水汽条件下的性能演变行为。在1200℃和1400℃惰性气氛中热处理1h后,复合材料具有较好的耐高温性能,质量保留率分布别为99.4%和99.2%,强度保留率分别为103.1%和84.6%,当温度升高到1600℃时,由于基体晶粒粗化以及纤维与基体间的碳热还原反应,质量和强度保留率分别显著下降到82.8%和29.3%。C/Mullite复合材料具有较好的抗氧化性能,在1200℃-1600℃静态空气中氧化30min后,强度保留率均在75%左右,复合材料氧化是从材料表面逐渐向内部扩展的过程。C/Mullite复合材料经过1000℃水汽考核30min后,强度保留率为71.3%,当水汽考核温度升高到1200℃和1400℃时,复合材料性能保留率显著下降,不到45%,纤维与基体在高温条件下受到水汽的严重腐蚀,生成挥发性物质导致复合材料失效。研究了C/Mullite复合材料在空气中的抗热震性能,复合材料的质量损失随热震次数增加呈近线性关系增大,经过1200℃?室温和1400℃?室温条件下10次热震(保温10min)后,复合材料强度保留率仅分别为43.9%和25.4%。热震过程中碳纤维的氧化以及由于纤维与基体之间因热膨胀系数不匹配而产生的热应力是复合材料失效的主要原因。初步研究了C/Mullite复合材料的抗烧蚀性能,在氧乙炔焰(中心区温度2727℃)下考核30s后,复合材料的质量烧蚀率和线烧蚀率分别为0.049 g·s-1和0.12 mm·s-1。由于火焰温度过高,莫来石基体分解生成Al2O3和SiO2,在热流以及机械冲刷的作用下,大量SiO2流失。研究成果为后续进一步优化制备工艺和提升综合性能提供了有益借鉴。
[Abstract]:Mullite (Mullite) ceramics have the advantages of low density, low thermal expansion coefficient, good thermal shock resistance, high temperature resistance, anti oxidation and so on. It has a broad application prospect in the field of high temperature structure and thermal protection, but the poor mechanical properties at room temperature limit its application. On the basis of the previous research, the preform is sutured with carbon fiber layer as an augmented body. The C/Mullite composite was prepared by impregnation drying heat treatment technology with the Al2O3-SiO2 sol which conforms to the mullite stoichiometry. The paper explored the sintering shrinkage behavior of Al2O3-SiO2 sol and the behavior of the mullite. On the basis of the preliminary optimization of the composite technology, the C/Mullite composite was studied and analyzed. The intrinsic properties of the material and the failure behavior in the simulated application environment. The solid content and the ceramic yield of the Al2O3-SiO2 sol are 30.7wt.% and 18.3wt.%. respectively after heat treatment at 1300 degrees C. The sol mullite is basically completed. The line shrinkage of the gel powder increases with the increase of heat treatment temperature, and the temperature is higher. It is beneficial to powder sintering. After preliminary optimization, a process route to avoid layered cracking of carbon fiber cloth in the composite process is established. The apparent density, total porosity and opening rate are 2.19g. Cm-3,13.4% and 11.3% C/Mullite composites respectively. C/Mullite composite is characterized by different testing methods. The bending strength of the material, three point bending strength (228.9 + 11.0MPa) is slightly higher than that of four point bending strength (210.6 + 8.9MPa), obeying m=30.6, Weibull distribution of the two parameter of lambda =238.0, and the m value is larger. It shows that the composite has better uniformity. The composite material has fiber fracture, interfacial debonding and pulling out mechanism because of the introduction of continuous carbon fiber. The fracture toughness is 11.2MPa. M1/2. The tensile strength and tensile modulus of the 4-5 times.C/Mullite composite of the single Mullite ceramics are 119.9MPa and 36.6GPa respectively. The compressive strength of the X direction is 128.2MPa, and the interlayer shear strength is 28.1MPa. characterized by the thermal physical properties of the C/Mullite composite in the -1400 room temperature range of room temperature, which is the engineering of the material. The thermal expansion coefficient of.C/Mullite composite material increased first and then decreased with the increase of temperature, reaching the maximum value of 4.83 x 10-6K-1 at 1000 C. After 1300 C, the thermal expansion coefficient presented as negative value.C/Mullite composite material increased with the increase of temperature, and the temperature was higher than 1200. The maximum value of 1.547J. G-1. K-1 at 1200 C, the minimum temperature at room temperature, the thermal diffusivity of 0.756J. G-1 / K-1.C/Mullite composite material decreasing with the temperature, the high temperature tends to be stable, the temperature diffusivity of the room temperature is the highest, which is the lowest in 1.1mm2 s-1700 C. It is the thermal conductivity base of the 0.707mm2 s-1.C/Mullite composite material. As the temperature increases, the thermal conductivity of the composite is maximum at room temperature of 1.859W. M-1. K-11200. 2.325W. M-1. K-1., respectively, to study the behavior of C/Mullite composites under high temperature inert, high temperature oxidation and high temperature water vapor. After heat treatment of 1H at 1200 and 1400 C in inert atmosphere, the properties of the composites are recovered. The material has good high temperature resistance, the distribution of mass retention rate is 99.4% and 99.2%, the retention rate of strength is 103.1% and 84.6% respectively. When the temperature rises to 1600, the retention rate of mass and strength decreases to 82.8% and 29.3%.C/Mullite composites, respectively, due to the grain coarsening of the matrix and the carbon thermal reduction reaction between the fiber and the matrix. With good oxidation resistance, after oxidation of 30min in static air at 1200 -1600 C, the retention rate of the strength is about 75%. The oxidation of the composites is gradually expanding from the surface of the material to the interior of the material. The.C/Mullite composite material is examined by water vapor at 1000 C for 30min, the retention rate of the strength is 71.3%, when the assessment temperature of water vapor rises to 1200 and 140. At 0 C, the performance retention of the composites decreased significantly, less than 45%, and the fiber and matrix were seriously corroded by water vapor under high temperature. The formation of volatile compounds resulted in the failure of the composites. The thermal shock resistance of C/Mullite composites in the air was studied. The mass loss of the composites increased linearly with the increase of the number of thermal shock. After 10 thermal shocks (10min) at room temperature and 1400? Temperature at room temperature and room temperature, the strength retention of the composites is only 43.9% and 25.4%., respectively, the oxidation of carbon fibers in the thermal shock process and the thermal stress caused by the mismatch of thermal expansion coefficient between the fiber and the matrix are the main reasons for the failure of the composites. The preliminary study of C/Mull is made of C/Mull. The ablative properties of ite composites were evaluated by 30s at oxygen acetylene flame (2727 centigrade temperature). The mass ablative rate and line ablation rate of the composites were 0.049 G. S-1 and 0.12 mm. S-1., respectively, because of the high temperature of the flame. The Mullite Matrix decomposed into Al2O3 and SiO2, and a large amount of SiO2 loss was studied under the effect of heat flow and mechanical scour. The results provide a useful reference for further optimizing the preparation process and improving the comprehensive performance.
【学位授予单位】：国防科学技术大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB332
本文编号：2166064
[Abstract]:Mullite (Mullite) ceramics have the advantages of low density, low thermal expansion coefficient, good thermal shock resistance, high temperature resistance, anti oxidation and so on. It has a broad application prospect in the field of high temperature structure and thermal protection, but the poor mechanical properties at room temperature limit its application. On the basis of the previous research, the preform is sutured with carbon fiber layer as an augmented body. The C/Mullite composite was prepared by impregnation drying heat treatment technology with the Al2O3-SiO2 sol which conforms to the mullite stoichiometry. The paper explored the sintering shrinkage behavior of Al2O3-SiO2 sol and the behavior of the mullite. On the basis of the preliminary optimization of the composite technology, the C/Mullite composite was studied and analyzed. The intrinsic properties of the material and the failure behavior in the simulated application environment. The solid content and the ceramic yield of the Al2O3-SiO2 sol are 30.7wt.% and 18.3wt.%. respectively after heat treatment at 1300 degrees C. The sol mullite is basically completed. The line shrinkage of the gel powder increases with the increase of heat treatment temperature, and the temperature is higher. It is beneficial to powder sintering. After preliminary optimization, a process route to avoid layered cracking of carbon fiber cloth in the composite process is established. The apparent density, total porosity and opening rate are 2.19g. Cm-3,13.4% and 11.3% C/Mullite composites respectively. C/Mullite composite is characterized by different testing methods. The bending strength of the material, three point bending strength (228.9 + 11.0MPa) is slightly higher than that of four point bending strength (210.6 + 8.9MPa), obeying m=30.6, Weibull distribution of the two parameter of lambda =238.0, and the m value is larger. It shows that the composite has better uniformity. The composite material has fiber fracture, interfacial debonding and pulling out mechanism because of the introduction of continuous carbon fiber. The fracture toughness is 11.2MPa. M1/2. The tensile strength and tensile modulus of the 4-5 times.C/Mullite composite of the single Mullite ceramics are 119.9MPa and 36.6GPa respectively. The compressive strength of the X direction is 128.2MPa, and the interlayer shear strength is 28.1MPa. characterized by the thermal physical properties of the C/Mullite composite in the -1400 room temperature range of room temperature, which is the engineering of the material. The thermal expansion coefficient of.C/Mullite composite material increased first and then decreased with the increase of temperature, reaching the maximum value of 4.83 x 10-6K-1 at 1000 C. After 1300 C, the thermal expansion coefficient presented as negative value.C/Mullite composite material increased with the increase of temperature, and the temperature was higher than 1200. The maximum value of 1.547J. G-1. K-1 at 1200 C, the minimum temperature at room temperature, the thermal diffusivity of 0.756J. G-1 / K-1.C/Mullite composite material decreasing with the temperature, the high temperature tends to be stable, the temperature diffusivity of the room temperature is the highest, which is the lowest in 1.1mm2 s-1700 C. It is the thermal conductivity base of the 0.707mm2 s-1.C/Mullite composite material. As the temperature increases, the thermal conductivity of the composite is maximum at room temperature of 1.859W. M-1. K-11200. 2.325W. M-1. K-1., respectively, to study the behavior of C/Mullite composites under high temperature inert, high temperature oxidation and high temperature water vapor. After heat treatment of 1H at 1200 and 1400 C in inert atmosphere, the properties of the composites are recovered. The material has good high temperature resistance, the distribution of mass retention rate is 99.4% and 99.2%, the retention rate of strength is 103.1% and 84.6% respectively. When the temperature rises to 1600, the retention rate of mass and strength decreases to 82.8% and 29.3%.C/Mullite composites, respectively, due to the grain coarsening of the matrix and the carbon thermal reduction reaction between the fiber and the matrix. With good oxidation resistance, after oxidation of 30min in static air at 1200 -1600 C, the retention rate of the strength is about 75%. The oxidation of the composites is gradually expanding from the surface of the material to the interior of the material. The.C/Mullite composite material is examined by water vapor at 1000 C for 30min, the retention rate of the strength is 71.3%, when the assessment temperature of water vapor rises to 1200 and 140. At 0 C, the performance retention of the composites decreased significantly, less than 45%, and the fiber and matrix were seriously corroded by water vapor under high temperature. The formation of volatile compounds resulted in the failure of the composites. The thermal shock resistance of C/Mullite composites in the air was studied. The mass loss of the composites increased linearly with the increase of the number of thermal shock. After 10 thermal shocks (10min) at room temperature and 1400? Temperature at room temperature and room temperature, the strength retention of the composites is only 43.9% and 25.4%., respectively, the oxidation of carbon fibers in the thermal shock process and the thermal stress caused by the mismatch of thermal expansion coefficient between the fiber and the matrix are the main reasons for the failure of the composites. The preliminary study of C/Mull is made of C/Mull. The ablative properties of ite composites were evaluated by 30s at oxygen acetylene flame (2727 centigrade temperature). The mass ablative rate and line ablation rate of the composites were 0.049 G. S-1 and 0.12 mm. S-1., respectively, because of the high temperature of the flame. The Mullite Matrix decomposed into Al2O3 and SiO2, and a large amount of SiO2 loss was studied under the effect of heat flow and mechanical scour. The results provide a useful reference for further optimizing the preparation process and improving the comprehensive performance.
【学位授予单位】：国防科学技术大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB332
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