What are the design challenges for metal-composite hybrid structures?

Metal-composite hybrid structure challenges include: CTE mismatch (aluminum 23, CFRP 0-2 micro-strain/K) causing thermal stress and fatigue in joints; Galvanic corrosion at metal-CFRP interface requiring isolation; Different failure modes and design methodologies; Load transfer mechanisms at transitions; Certification showing both metallic (AC 25.571) and composite (AC 20-107B) compliance; Manufacturing sequence coordination; Repair of hybrid joints; and Analysis complexity combining metal plasticity with composite damage. Solutions include: glass ply isolation layers, sealant application, gradual stiffness transitions, hybrid-specific joint designs, and extensive testing of interfaces. 787 and A350 successfully integrate hybrid structures through careful attention to these issues.