What material properties are most important for aerospace structural materials?

Key material properties: Strength - Ultimate tensile strength (UTS), yield strength, compressive strength; Stiffness - Young's modulus (E), critical for deflection-limited designs; Density - Lower is better for weight-critical applications; Specific properties - Strength/density, E/density for comparison; Toughness - Fracture toughness (KIc), energy absorption; Fatigue - S-N curve behavior, crack growth rate (da/dN); Corrosion resistance - General corrosion, stress corrosion cracking, galvanic effects; Elevated temperature - Strength retention, creep resistance, oxidation. Selection trade-offs: High strength often means lower toughness, Stiff materials may be brittle, and Lightweight materials may have manufacturing challenges. Design allowables account for variability (A-basis: 99% probability, 95% confidence; B-basis: 90%/95%). Temperature, environment, and loading affect which properties are critical.