Manan David Tamim, Kim Jeongho, de Melo Renata Marques, Zhang Yu
Department of Civil and, Environmental Engineering, University of Connecticut, 261 Glenbrook Road, U-3037, Storrs, CT 06269.
Department of Civil and Environmental Engineering, University of Connecticut, 261 Glenbrook Road, U-3037, Storrs, CT 06269.
J Eng Mater Technol. 2021 Oct 1;143(4):041006. doi: 10.1115/1.4050972. Epub 2021 May 12.
Dental interfaces are subject to mixed-mode loading. This study provides practical guidance for determining interfacial fracture toughness of dental ceramic systems. We address interfacial fracture of a composite resin cement sandwiched between two dental ceramic materials. Emphasis is placed on sandwich disc specimens with cracks originating from elliptical-shaped flaws near the center, for which analytical fracture mechanics methods fail to predict. The interaction integral method is used to provide accurate finite element solutions for cracks with elliptical-shaped flaws in a Brazil-nut-sandwich specimen. The developed model was first validated with existing experimental data and then used to evaluate the three most widely used dental ceramic systems: polycrystalline ceramics (zirconia), glass-ceramics (lithium disilicate), and feldspathic ceramics (porcelain). Contrary to disc specimens with ideal cracks, those with cracks emanating from elliptical-shaped flaws do not exhibit a monotonic increase in interfacial toughness. Also, interfacial fracture toughness is seen to have a direct relationship with the aspect ratio of elliptical-shaped flaws and an inverse relationship with the modulus ratio of the constituents. The presence of an elliptical-shaped flaw significantly changes the interfacial fracture behavior of sandwich structures. Semi-empirical design equations are provided for fracture toughness and stress intensity factors for interfacial cracks. The developed design equations provide practical guidance for determining interfacial fracture toughness of selected dental ceramic material systems. Those equations take into account four critical factors: size of the elliptical flaw, modulus ratio of constituent materials, loading angle, and applied load.
牙科界面承受混合模式载荷。本研究为确定牙科陶瓷系统的界面断裂韧性提供了实用指导。我们研究了夹在两种牙科陶瓷材料之间的复合树脂水门汀的界面断裂情况。重点关注裂纹源自中心附近椭圆形缺陷的三明治圆盘试样，对于此类试样，解析断裂力学方法无法进行预测。采用交互积分法为巴西坚果三明治试样中带有椭圆形缺陷的裂纹提供精确的有限元解。首先用现有的实验数据对所建立的模型进行验证，然后用于评估三种应用最广泛的牙科陶瓷系统：多晶陶瓷（氧化锆）、微晶玻璃（二硅酸锂）和长石质陶瓷（烤瓷）。与具有理想裂纹的圆盘试样不同，那些裂纹源自椭圆形缺陷的试样的界面韧性并非单调增加。此外，界面断裂韧性与椭圆形缺陷的长径比呈直接关系，与组分的模量比呈反比关系。椭圆形缺陷的存在显著改变了三明治结构的界面断裂行为。给出了界面裂纹断裂韧性和应力强度因子的半经验设计方程。所建立的设计方程为确定所选牙科陶瓷材料系统的界面断裂韧性提供了实用指导。这些方程考虑了四个关键因素：椭圆形缺陷的尺寸、组成材料的模量比、加载角度和施加的载荷。
