The fracture toughness of dental nanocomposites fabricated by various methods of mixing, silanization, and loadings of nanoparticles had been characterized using fatigue-precracked compact-tension specimens. The fracture mechanisms near the crack tip were characterized using atomic force microscopy (AFM), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). The near-tip fracture processes in the nanocomposties were identified to involve several sequences of fracture events, including: (1) particle bridging, (2) debonding at the poles of particle/matrix interface, and (3) crack deflection around the particles. Analytical and finite-element methods were utilized to model the observed sequences of fracture events to identify the source of fracture toughness in the dental nanocomposites. Theoretical results indicated that silanization and nanoparticle loadings improved the fracture toughness of dental nanocomposites by a factor of 2 to 3 through a combination of enhanced interface toughness by silanization, crack deflection, as well as crack bridging. A further increase in the fracture toughness of the nanocomposites can be achieved by increasing the fracture toughness of the matrix, nano-filled particles, or the interface.

中文翻译：

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通过界面工程和微力学提高牙科纳米复合材料的断裂韧性

通过混合、硅烷化和纳米颗粒负载的各种方法制造的牙科纳米复合材料的断裂韧性已经使用疲劳预裂的紧凑拉伸试样进行了表征。使用原子力显微镜 (AFM)、透射电子显微镜 (TEM) 和扫描电子显微镜 (SEM) 对裂纹尖端附近的断裂机制进行了表征。纳米复合材料中的近尖端断裂过程被确定为涉及几个断裂事件序列，包括：（1）粒子桥接，（2）粒子/基质界面极点处的脱粘，以及（3）粒子周围的裂纹偏转。利用分析和有限元方法对观察到的断裂事件序列进行建模，以确定牙科纳米复合材料中断裂韧性的来源。理论结果表明，通过硅烷化、裂纹偏转和裂纹桥接增强界面韧性的组合，硅烷化和纳米颗粒负载将牙科纳米复合材料的断裂韧性提高了 2 到 3 倍。通过增加基体、纳米填充颗粒或界面的断裂韧性，可以进一步提高纳米复合材料的断裂韧性。