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

The Alpha STAR Corporation and the University of Akron STTR Phase II proposal will establish ASTM standards test methods to determine relevant ceramics matrix composites (CMC) delamination crack growth resistance (CGR) material properties (Mode I & Mode II)under service load temperature conditions. Phase Ii will expand on Phase I results, conclusions & recommendations. Emphasis will be on testing techniques and quality specimen preparation that will result in lower test scatter/higher accuracy and high temperature testing with improved non-visual measurements using AE/ER (acoustic emission and electrical resistivity). Phase II will test several class of CMC's coupons (e.g., SiC/SiC, Sic/SiNc, Oxide/Oxide), and ASTM approved test standards with round-robin verification including simple data analysis methods (e.g. modified bean equation). A significant reduction in design time and cost will be achieved by using validated & calibrated virtual testing software that can rapidly assess durability & damage tolerance (D&DT) and reliability of CMC structures based on FAA recommended building block strategy. Robust design optimization technique integrated with multi-scale modeling (damage and fracture evolution) will be used to maximize the ASTM design performance and address the CMC test issues (e.g., zig-zag crack pattern, blunt/sharp notch width effect.