陶瓷叠层结构增韧设计的数值模拟及实验研究

A NUMERICAL SIMULATION AND EXPERIMENTAL STUDY ON TOUGHENING DESIGN OF MULTILAYER CERAMIC

本研究尝试将微机作为辅助手段引入仿生陶瓷复合材料的增韧设计 .基于多层梁模型 ,采用有限元数值模拟方法模拟了仿生陶瓷叠层结构的断裂行为和裂纹逐次从硬层基片向弱界面层的拐折和扩展 .后处理程序显示了三点弯曲试件的裂纹扩展路径、相应的载荷 -位移曲线和增韧效应 (断裂功大幅度提高 ) .还进一步分析了叠层陶瓷的韧性和强度受试件几何参数 (硬软层层厚比、层数 )和材料性能参数 (断裂应变、Young氏模量比等 )的影响变化趋势 ,据此确定增韧设计中上述各参数的最佳取值 .通过数值计算结果与叠层陶瓷三点弯曲试件断裂功实测值的对比 ,证明了本法的有效性 ,并证明因弱界面层的存在引发主裂纹拐折和这一叠层陶瓷主要耗能增韧机理所决定的叠层梁模型的合理性 .

Computer analysis was introduced as an auxiliary means for toughening design of biotechnological laminated ceramic composites. Based on a multilayer beam model, a finite element method has been used to simulate fracture behaviour, crack kinking and growing from basal sheet of hard layer to weak interface layer in laminated ceramic structure. The post_processing approach offers crack growing path, correlative load_displacement curve for three_point bending and shows toughen_ing effect (the fracture work is significantly increased). The changes in the toughness and strength of laminated ceramic with the specimen's geometric parameters (thickness ratio, layer number) and material properties parameters (fracture strain, Young's moduli, etc ) are analyzed by FEA numerical simulation. The optimum_values of above parameters in toughening design are then determined. The effectiveness of this numerical simulation method is demonstrated by comparing results of the numerical evaluation with experimental measurement of fracture work for Si 3N 4/BN multilayer specimen in the three_point bending test. It is also affirmed the rationality of the multilayer layer beam model. The primary mechanism of absorbing energy and toughening of the laminated ceramic composites is explained by the weak interface layers, which are capable of deflecting main cracks.