A systematic study on the quality improving of fracture toughness measurement in structural ceramics by laser notching method

•Relationships between Kc and notch characteristics are systematically studied.•A new Kc-ρ relationship is discovered.•The ρ threshold for accurate measurement of fracture toughness is revealed.•The feasibility of laser method for SEVNB testing of small-sized specimens is proved.•Study serves as a guideline in accurate measurement of fracture toughness. The single-edge V-notched beam (SEVNB) method based on the laser notching approach can effectively overcome the shortcoming of time-consuming and avoid large errors in traditional fracture toughness measurement ways, yet there is still a lack of systematic research on the normativity of V-notches as well as the applicability of ceramics with various compositions and microstructures. Taking oxide (ZrO2 and Al2O3), carbide (SiC), nitride (Si3N4) and boride (ZrB2-based) ceramics as the research objects, this paper systematically discussed the effects of notch tip sharpness, relative notch depth (a/W) and equivalent notch angle on the measured value of fracture toughness, thereby clearly defining the range of these parameters that is required for measuring the fracture toughness accurately. Furthermore, in order to give full play to the advantages of the laser notching method, the feasibility of sample miniaturization was also discussed. This study could provide important data reference and theoretical basis for the standardization of laser method in the future.