Method for the design of additively manufactured inner channels intended for adhesive application

Abstract

Joining of metal parts manufactured by laser beam powder bed fusion (PBF-LB/M) eliminates the inherent size restriction of this additive manufacturing process and reduces the manufacturing effort. Adhesive bonding presents great potential for joining of PBF-LB/M parts, as there are no constraints on the shape of the connecting surfaces, as long as the adhesive can be applied. The freedom of design underlying the PBF-LB/M process enables the construction of inner channels in the parts, which can facilitate the adhesive application. The adhesive can be injected into a single inlet on the exterior of a part and directed through inner channels before leaking from multiple outlets into the adhesive fill gap between the pre-aligned adherents. To avoid insufficient adhesive distribution and air inclusions in the adhesive fill gap, both of which reduce the bond strength, a methodical approach for the design of inner channels intended for adhesive application by injection is required. This work provides a corresponding design method based on the theory of fluid mechanics. Moreover, an example case of a PBF-LB/M sleeve to be joined to a circular tube is presented. Results from a CFD analysis show that the inner channels designed using the presented method lead to excellent coverage of the adhesive fill gap with adhesive and minimal air inclusions.