How are structural adhesives used in modern BIW construction?

Structural adhesives complement traditional spot welding in multi-material BIW: Crash adhesives (toughened epoxy, 30+ MPa shear strength) bond dissimilar materials (aluminum to steel), increase joint stiffness by 20-30%, and improve fatigue life by distributing loads. Hem flange adhesives seal closures while providing structural contribution. Application requires surface preparation (cleaning, primers), controlled bead placement, and oven curing during paint bake. Design must account for peel weakness (use mechanical fasteners in peel-prone areas), thermal expansion mismatch, and repair procedures. Testing per ISO 11003 (lap shear) and impact peel specifications.