Interlaminar Mode I and Mode II Fracture Toughnesses in Ceramic Matrix Composites (CMCs)

Ceramic Matrix Composite (CMC)'s are highly susceptible to interlaminar shear failure at elevated temperatures. Therefore, interlaminar properties, critical design limitation of CMC should be assessed accurately with appropriate test methods to ensure overall structural reliability/integrity of components in Naval gas turbine engines. AlphaSTAR proposes to develop rigorous, precise, and innovative test methods, and validated FEM based Fracture Toughnesses (FT) methodology, that guides tests, and assist customization of the standardized delamination growth CMC test methods. To address the need a comprehensive/systematic approach is proposed that involves the application of the latest advanced FT analysis/modeling and experimental techniques. The focus in Phase I is on:1) room/elevated temperatures modeling of technically sound and marketable testing technique for accurate characterization of delamination resistance such as crack tip micro-cracks; crack growth resistance (Mode I/II, mixed mode), as well as predicting high temperature FT when only tests are available at room temperature; and 2) to identify/implement modifications to ASTM test methods working with OEM design engineers. Following the initial redesign of test method and testing in Phase I, further development, data generation on one or more specific materials, and efforts for standardization of procedures will be pursued in Phase II.