Effects of Test Specimen Sizes on Interlaminar Tension Strength of Ceramic Matrix Composites in Diametral Compression

ABSTRACT The effects of specimen sizes on interlaminar tension (ILT) sizes were assessed in a gas‐turbine grade, 2‐D woven N720/alumina ceramic matrix composite (CMC). A large number of test specimens (>150) with eight different diameters of 5–21 mm were employed for enhanced statistical reproducibility and repeatability of the data. The ILT strengths of the CMC were observed to be insensitive to its specimen sizes. The Weibull size‐effect theory was used to determine effective volume and effective area using a numerical analysis and applied to the prediction of ILT strength and effective volume/area. The prediction was in significant discrepancy with the experimental data. All these outcomes indicated that the oxide/oxide CMC did not exhibit any appreciable size effects, presumably attributed to the characteristics’ uniqueness of the CMC material system reinforced with continuous‐fiber architectures. Other CMC materials also revealed such insensitivity of ILT strength to specimen sizes in either diametral compression or ‘transthickness’ tension. The findings of this work show little to no size effects in ILT strength in gas‐turbine grade CMCs can result in a significant advantage for test economy when considering the costly nature of those CMC materials.