What are the key considerations in designing bonded joints for aircraft structures?

Bonded joint design considerations include: Joint geometry (lap, scarf, stepped lap) selection based on load and manufacturing; Adherend preparation (surface treatment critical for bond durability); Load transfer through adhesive shear - peak stress at ends requires tapering; Peel stress minimization (thin bondlines, avoid T-joints, use mechanical fasteners for peel-critical); Environmental durability (hot-wet degradation, requires testing); Inspection difficulty (no reliable NDI for bond quality, hence design for bondline failure detectable by other means); and Certification approach - often requires mechanical fasteners as backup or fail-safe feature. Adhesive allowables include knockdowns for porosity, temperature, and environment.