The surface fracture toughness is an important mechanical parameter for studying the failure behavior of air plasma sprayed (APS) thermal barrier coatings (TBCs). As APS TBCs are typical multilayer porous ceramic materials, the direct applications of the traditional single edge notched beam (SENB) method that ignores those typical structural characters may cause errors. To measure the surface fracture toughness more accurately, the effects of multilayer and porous characters on the fracture toughness of APS TBCs should be considered. In this paper, a modified single edge V-notched beam (MSEVNB) method with typical structural characters is developed. According to the finite element analysis (FEA), the geometry factor of the multilayer structure is recalculated. Owing to the narrower V-notches, a more accurate critical fracture stress is obtained. Based on the Griffith energy balance, the reduction of the crack surface caused by micro-defects is corrected. The MSEVNB method can measure the surface fracture toughness more accurately than the SENB method.

表面断裂韧性是研究空气等离子喷涂 (APS) 热障涂层 (TBC) 失效行为的重要力学参数。由于APS TBC是典型的多层多孔陶瓷材料，直接应用忽略这些典型结构特征的传统单边缺口梁（SENB）方法可能会导致误差。为了更准确地测量表面断裂韧性，应考虑多层和多孔特性对 APS TBC 断裂韧性的影响。在本文中，开发了一种具有典型结构特征的改进单边 V 型缺口梁 (MSEVNB) 方法。根据有限元分析（FEA），重新计算多层结构的几何因素。由于更窄的 V 形缺口，可以获得更准确的临界断裂应力。基于格里菲斯能量平衡，修正了微缺陷引起的裂纹表面的减少。MSEVNB 方法比 SENB 方法能更准确地测量表面断裂韧性。