How do you perform residual strength assessment for damaged composite structures?

Composite residual strength assessment involves: Damage characterization through NDI (ultrasonic C-scan, thermography) to map delamination extent; Analysis method selection based on damage type (notch analogy for impact, delamination buckling for compression); Point stress or average stress criteria for open holes; Delamination growth analysis under fatigue loading using interlaminar fracture mechanics (GIc, GIIc); Environmental knockdowns for hot-wet conditions; Finite element analysis with explicit damage modeling for complex cases; and Correlation with CAI, OHC, and notched strength test data. Assessment determines if damage is within limits of acceptable damage (return to service), requires repair (Type A or B repair), or requires replacement. Results support structural repair manual limits.