冷却孔排布对SiCf/SiC复合材料拉伸力学性能和损伤演化行为的影响

The influence of cooling hole arrangement on the tensile mechanical properties and damage evolution behavior SiCf/SiC composites

  • 摘要: SiCf/SiC复合材料在航空发动机热端构件中应用广泛,为满足服役要求,需在其表面加工大量冷却孔,但孔的排布间距会削弱构件的力学性能、影响其断裂行为,此关键参数对材料失效行为的影响规律尚不明确。本文采用飞秒激光加工方法,在SiCf/SiC复合材料上加工出不同排布间距的小孔。通过拉伸实验与数字图像相关(DIC)技术研究排布间距对力学性能和拉伸断裂过程的影响,发现材料抗拉强度随孔间距的减小而减小。间距较小时样件从孔处开始沿与其最近的孔斜向断裂,这是由于孔排布密集,不同孔边缘应力集中产生的裂纹更容易连接到一起,且在孔结构加工过程中,连续纤维束被切断导致应力传递路径中断,造成材料拉伸性能的显著降低。通过拉伸模拟结合DIC技术观测了孔排布间距对材料断裂过程中不同阶段的影响,发现初始损伤从孔边缘产生,沿垂直于载荷方向与另一个孔连接,最大应力也随损伤演化过程逐渐从孔边缘向材料内部转移,直到材料发生断裂。该研究揭示了孔排布间距与力学性能及断裂行为的关联机制,为该材料冷却孔的排布设计与加工提供了重要参考。

     

    Abstract: SiCf/SiC composites are widely used in hot-end components of aerospace engines. In order to meet the service requirements, a large number of cooling holes need to be processed. However, the arrangement spacing of these holes will weaken the mechanical properties of the components and affect their fracture behavior. The influence pattern of this critical parameter on material failure behavior remains unclear. Tensile experiment and digital image correlation (DIC) technology are adopted to study the influence of hole arrangement spacing on mechanical properties and tensile fracture process, it is found that the tensile strength of the material decreases with the decrease of hole spacing. When the spacing is small, fracture initiates from the hole edge and propagates along the nearest hole. This is attributed to the dense arrangement of holes, where cracks induced by stress concentrations at different hole edges readily interconnect. Moreover, during hole drilling processes, the continuous fiber bundles are sheared, disrupting stress transfer pathways, resulting in a significant decrease in the tensile properties of the material. The influence of hole spacing on different stages of the material fracture process was analyzed by tensile simulation and DIC technology. It was found that the initial damage was generated from the edge of the hole and propagate perpendicular to the loading direction until connecting with adjacent holes. Throughout damage evolution, the maximum stress gradually transferred from the edge of the hole to the interior of the material until the material fracture occurred. This study reveals the correlation mechanism between hole arrangement spacing and mechanical properties and fracture behavior, which provides an important reference for the arrangement design and processing of cooling hole in such materials.

     

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