Topology Optimization of Additively Manufactured Adherends for increased Adhesive Bond Strength

The limited build space of additive manufacturing (AM) machines constrains the maximum size of AM components, while manufacturing costs rise with geometric complexity. To enhance value and overcome size limitations, it can be more efficient to join non-AM and AM components to meet the requirements by means of a hybrid structure. Adhesive bonding is particularly suitable for such joints, as it imposes no constraints on the joining surface´s geometry or the adherend´s material. To ensure structural integrity, it is conceivable to exploit the design freedom underlying AM processes by optimizing the topology of the AM component to stress the adhesive layer homogenously. This study explores the feasibility of this concept using the example of an axially loaded single-lap tubular joint between a carbon fiber reinforced composite tube and an additively manufactured laser-based powder bed fusion aluminum alloy sleeve. The sleeve topology was optimized using the finite element method, achieving a 75 %P reduction in adhesive stress increase compared to a non-optimized sleeve. Due to the pronounced ductility of the two-component epoxy-based adhesive, the static bond strength remained unaffected, whereas fatigue life significantly improved. The findings demonstrate the feasibility of leveraging AM design freedom to enhance adhesive joint performance, providing a promising approach for hybrid structures in lightweight applications.