Bond strength analysis in additive manufacturing of polymer structures on aluminium foam

Abstract Hybrid materials enable innovative and technologically advantageous lightweight design solutions, especially the efficient combination of metals and polymers is a promising approach. This contribution addresses an additive manufacturing (AM) process with polymers on the surface of foamable extruded aluminium profiles. The aim is to individualise aluminium profiles with locally applied polymer components using the foam structure as a mechanical bonding interface. The bond strength of hybrid aluminium foam-polymer composites fabricated via screw extrusion additive manufacturing (SEAM) is investigated and the influence of the key process parameters as well as the properties of the aluminium foam structures are taken into account. Additionally, X-ray microscopy is used to analyse the pore structure, evaluating the pore size distribution, the wall thickness, and the pore filling. The material- and process-dependent bond strength is determined from lap-shear and cross-tension tests. A ductile failure of the specimens was detected, which is caused by mixed failure modes such as cohesive failure and adhesive failure in the polymer and in the aluminum. By minimising the distance between the extruder nozzle and the aluminium foam, the samples with the highest adhesive strength of 5.4 MPa in the cross-tensile test and 7 MPa in the lap-shear test were produced. An inhomogeneous pore distribution shows the highest influence on the tested bond strength, which results in a large scattering of the maximum detected testing force. The aluminium foam-polymer composites show potential for overcoming the problem of joining dissimilar materials to produce hybrid structural components, which could enable further advances for these types of components.