What are the design considerations for composite aircraft structures?

Composites offer weight savings but require different design approaches. Design considerations: Layup design - Ply orientation, stacking sequence, symmetric/balanced laminate rules; Joining - Bonded joints, mechanical fasteners, or hybrid; composites don't yield so stress concentrations are critical; Damage tolerance - Impact damage (barely visible), delamination growth analysis, inspection requirements; Environmental - Moisture absorption effects on properties, temperature limits; Manufacturing - Layup methods (hand, ATL, AFP), cure cycles, tooling requirements. Advantages: 20-25% weight reduction, corrosion resistance, fatigue-resistant, tailored stiffness. Challenges: Higher raw material cost, More complex analysis (anisotropic properties), Damage detection more difficult, and Limited field repair capability. Certification: Building block approach (coupons to components to aircraft), Specific composite requirements (AC 20-107B). Modern aircraft (787, A350) are majority composite by weight.