Threshold fracture stress of thin ceramic components

Strength is widely used as a design criterion to characterize the mechanical limits of brittle materials. However, depending on the flaw size distribution, measured strength values show considerable scatter. Statistically this spread can be represented for a specific specimen dimension using Weibull statistics with the characteristic strength, Weibull modulus and threshold strength. A comparison of three- and two-parameter Weibull approaches is exemplified using fracture stress results of thin bi-layer ceramic bending specimens taken from solid oxide fuel cell (SOFC) components. Considering statistical parameters and the flaw size limiting thickness of the substrate layer in a SOFC, the three-parameter Weibull statistics is demonstrated to be more appropriate for the fracture characterization of thin ceramic components.