采用动态热机械分析法研究碳化硅纤维单丝的力学性能

Determining the Mechanical Properties of Single Silicon Carbide Fibre by Dynamic Mechanical Analysis

采用动态热机械分析法(DMA)研究了国产KD-SA型碳化硅(SiC)纤维单丝的力学性能。试验对KD-SA型SiC纤维分别进行了1200℃、1300℃、1400℃和1500℃空气环境下的热处理,采用DMA的频率扫描模式测定了未处理和处理后的试样储能模量和损耗角正切。此外,试样的强度也同时使用小载荷万能试验机进行测定。试验发现:经过高温处理的样品,其拉伸强度迅速降低至未处理样品强度的1/2左右。同时,高温处理后,试样的储能模量也远低于未处理试样。高温处理的SiC纤维的力学性能迅速降低,主要归结于高温下的氧化机制。因此,对高温处理样品的截面和表面进行了扫描电镜观察,发现了在高温下,晶粒变大、产生松散结构的现象。最后,高温处理和未经处理样品的储能模量和损耗对频率的依赖性通过DMA试验,并进行了验证和讨论。

In this study,the dynamic mechanical analysis has been used to determine the mechanical properties of home produced KD-SA single silicon carbide fibre.The specimens of this type of KD-SA silicon carbide fibre made in China were heat treated at 1200 ℃、1300 ℃、1400 ℃和 1500 ℃ in air atmosphere respectively.DMA frequency scanning mode was used to test the storage modulus and loss tangent of the specimens untreated and treated respectively.The strength of the specimens were also tested by light-loaded universal testing machine.It was found that the tensile strength and storage modulus of heat-treated specimens diminished significantly compared to untreated specimens,about 1/2 of the latter.The decline if the values was mainly attributed to the oxidation of silicon carbide fibre under high temperature.The cross section and surface of oxidised specimens were observed by scanning electric mirror and it was found that particles enlarged and loosened when heated.The storage modulus and loss of the specimens' dependence on frequency were tested and discussed through DMA.