Si_3N_4/BN复合材料界面应变能释放速率的测试与表征

MEASUREMENT AND CHARACTERIZATION OF INTERFACIAL STRAIN ENERGY RELEASE RATE OF Si_3N_4/BN COMPOSITES BY FOUR-POINT BENDING TEST

提出了一种更为合理、简便地测试与表征Si3N4 /BN复合材料界面应变能释放速率的方法 .借助流延成形和热压烧结工艺 ,制备出具有单一界面层“三明治”结构 ,在单侧基体中点处预制有裂纹源的Si3N4 /BN/Si3N4 试样 ,用四点弯曲加载的方法测出其载荷 -位移曲线 ,进一步求出界面的应变能释放速率值 .分别测出了BN +Si3N4 ,BN +Al2 O3两种界面体系、不同成分界面的应变能释放速率值 ,对于纯BN ,含体积分数分别为 15 % ,2 5 %Si3N4 调节剂的界面 ,其相应的应变能释放速率值分别为 3 7.16,90 .5 8,117.76J/m2 ;含体积分数分别为 16% ,3 6% ,63 %Al2 O3调节剂的界面 ,临界应变能释放速率值分别为 5 3 .95 ,71.86,119.2 1J/m2 .试验结果证明了该种方法的可行性及可靠性 ,与文献所报道的方法进行了对比、分析 。

A new method was developed to measure the interfacial strain energy release rate of Si3N4/BN composites. A kind of sandwich material with a single interlayer was designed and prepared by using tape casting and hot press processing. The source of crack directly connecting the interface was preset on one of the Si3N4 matrices. The load-displacement curves were obtained by the four-point bending test and the interfacial toughness was calculated on the basis of the fracture model of laminated composites. The interfacial toughness of Si3N4/BN composites modified with Si3N4 and the interfacial toughness of Al2O3/BN composites modified with Al2O3 were measured and characterized respectively. The strain energy release rate of pure BN is 37.16 J/m2. For BN interphases modified by Si3N4 with the volume fraction of 15% and 25%, the strain energy release rates are 90.58 J/m2 and 117.76 J/m2 respectively. For BN interphases modified by Al2N3 with the volume fraction of 16%, 36% and 63%, the corresponding critical strain energy release rates are 53.95 J/m2, 71.86 J/m2 and 119.21 J/m2 respectively. The advantages and disadvantages of the new method in comparison with other methods are discussed.