国产三代2.5D SiC_(f)/SiC复合材料的界面力学性能

Interfacial Mechanical Properties of the Domestic 3rd Generation 2.5D SiC_(f)/SiC Composite

连续碳化硅纤维增强碳化硅复合材料(SiC_(f)/SiC)是下一代航空发动机的关键结构材料,其界面性能是决定材料力学性能的重要因素之一。为此,本研究表征了国产三代2.5D SiC_(f)/SiC的界面性能,并探究其与材料拉伸性能的关系。利用拉伸加/卸载过程中的迟滞特性定量分析了2.5D SiC_(f)/SiC中各组元残余应力和界面滑动应力(IFSS),根据断口拔出纤维的断裂镜面半径得到了纤维就位强度(σ_(fu))的统计分布,通过纤维推入法得到界面剪切强度(ISS)和界面脱黏能(G_(i))。结果表明:利用宏观结合细观的方法能够较全面地描述SiC_(f)/SiC从初始裂纹萌生到最终脱黏不同阶段的界面力学性能,2.5D SiC_(f)/SiC的IFSS、ISS和Gi分别为56 MPa、(28±5)MPa和(2.7±0.6)J/m2。ISS和Gi较低,表明界面结合较弱,在剪应力作用下易产生裂纹,而IFSS较大,表明界面脱黏后纤维与基体间相对滑动较为困难,阻碍了纤维拔出,不利于发挥纤维的增强作用。根据获得的界面性能和经典ACK模型,较好地预测出比例极限应力,并结合σ_(fu)预测了2.5D SiC_(f)/SiC的拉伸强度。拉伸强度预测值高于实验值,这与界面处径向残余压应力以及纤维承受的残余拉应力有关。

Continuous silicon carbide fiber reinforced silicon carbide composite(SiC_(f)/SiC)is a critical structural material for the development of next-generation aircraft engines.The interfacial property is one of the important factors determining the material mechanical properties.Therefore,this study characterized the interfacial mechanical properties of domestic third-generation 2.5D SiC_(f)/SiC and investigated its relationship with tensile properties.The residual stress of the 2.5D SiC_(f)/SiC constituents and interfacial sliding stress(IFSS)were quantitatively analyzed by hysteresis characteristics during the cyclic tension loading/unloading test.Statistical distributions of the in-situ fiber strength(σ_(fu))were obtained based on the fracture mirror radius of pull-out fibers.Interfacial shear strength(ISS)and interfacial debonding energy(G_(i))were obtained through the push-in method.Results show that combination of macroscopic and microscopic methods can comprehensively describe the interfacial mechanical performance of 2.5D SiC_(f)/SiC from crack initiation to final debonding.The IFSS,ISS,and G_(i)of 2.5D SiC_(f)/SiC are 56 MPa,(28±5)MPa,and(2.7±0.6)J/m²,respectively.Values of ISS and Gi indicate weak interface bonding,causing it susceptible to cracking under shear stress,while the large IFSS suggests that relative fiber sliding is inhibited after interface debonding,hindering fiber pull-out.The obtained interfacial properties can predict the proportional limit stress(sPLS)accurately according to the ACK model.Based on the interfacial properties and the in-situ fiber strength(σ_(fu)),the tensile strength of 2.5D SiC_(f)/SiC is predicted to be higher than the experimental value,which is related to the interfacial radial compressive residual stress and residual tensile stress endured by the fiber.