Linking microstructure and local mechanical properties in SiC-SiC fiber composite using micromechanical testing
Linking microstructure and local mechanical properties in SiC-SiC fiber composite using micromechanical testing
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DOI：
10.1016/j.actamat.2019.02.001
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发表时间：
2019-04
期刊：
影响因子：
9.4
通讯作者：
Y. Zayachuk;Phani S. Karamched;C. Deck;P. Hosemann;D. Armstrong
中科院分区：
文献类型：
--
作者：
Y. Zayachuk;Phani S. Karamched;C. Deck;P. Hosemann;D. Armstrong
使用纳米压痕和微悬臂梁断裂测试评估 SiC-SiC 纤维增强复合材料（基体、纤维和界面）的局部机械性能。基体的断裂韧性为~4.25 MPa*m1/2，纤维的断裂韧性为~2 MPa*m1/2，界面的断裂韧性为~0.8 MPa*m1/2。研究发现纳米压痕硬度从纤维中心的约 17GPa 到基体的约 40GPa 不等。发现通过微观机械测试获得的值与体积机械性能的现有数据非常一致。复合材料不同成分的机械性能变化可以通过微观结构的变化来解释。该基体具有复杂的分级微观结构，具有细长的晶粒，通常具有孪生特征，从纤维沿主要<111>方向径向生长，并在纤维周围形成多组同心环。纤维含有等轴晶粒，在晶界处有碳沉淀。研究发现，基体中的断裂是穿晶的，而纤维中的断裂既可以是穿晶的，也可以是间晶的；在相间，断裂发生在碳纤维边界处。基体和纤维之间机械性能的差异归因于纤维中碳夹杂物的存在，碳夹杂物降低了硬度和断裂韧性。
Local mechanical properties of SiC-SiC fiber-reinforced composite – matrix, fiber and interphases – were evaluated using nanoindentation and microcantilever fracture testing. The fracture toughness was found to be ∼4.25 MPa*m1/2in the matrix, ∼2 MPa*m1/2in the fibers and ∼0.8 MPa*m1/2at the interphases. Nanoindentation hardness was found to vary from ∼17 GPa in the center of the fibers to ∼40 GPa in the matrix. Values obtained with micromechanical testing were found to be in good agreement with the available data on bulk mechanical properties. The mechanical property variations in the different components of the composite can be explained by the variations in the microstructure. The matrix has complex hierarchical microstructure with elongated grains, often featuring twinning, growing radially from the fibers in predominantly <111> direction and forming sets of concentric rings around them. The fibers contain equiaxed grains with carbon precipitates at the grain boundaries. It was found that in the matrix fracture is transgranular, while in the fibers it can be both trans- and intergranular; at the interphases the fracture occurs at the carbon-fiber boundary. The differences in mechanical properties between the matrix and the fibers are attributed to the presence of carbon inclusions in the fibers, which reduce both hardness and fracture toughness.