How do you design and analyze bonded joints in composite structures?

Bonded joints transfer load through adhesive shear and peel. Joint types: Single lap - Simple but eccentric (peel stresses); Double lap - Symmetric, no eccentricity; Stepped lap - Multiple steps, good for thick laminates; Scarf - Tapered, uniform shear, flush surfaces. Analysis: Volkersen shear lag - Elastic analysis of shear distribution; Goland-Reissner - Includes bending and peel; Hart-Smith - Elastic-plastic adhesive, more realistic; and FEA - Complex geometries, progressive failure. Design guidelines: Overlap length minimum 30x adhesive thickness, Taper adherends to reduce peel, Match adherend stiffness, and Consider bondline defects. Critical factors: Surface preparation (contamination is primary failure cause), Adhesive selection (structural film or paste), Cure conditions (temperature/pressure), and Environmental degradation (hot/wet knockdown 40-60%). Certification: Process specification, NDT acceptance criteria, and Proof test or enhanced inspection for critical joints. Bondline quality cannot be fully verified non-destructively; process control is paramount.