Influence of layer thickness and nozzle temperature on the interlocking adhesion strength of additive manufactured multi-material interface

Achieving adequate adhesion strength at multi-material interfaces is always a challenge in material extrusion additive manufacturing (MEAM), especially when the materials have very different chemical affinities. This study investigated the adhesion mechanism of multi-material interfaces in MEAM from a micro-geometric perspective. The vertically printed interface was found to have a smooth surface, while the horizontally printed interface had a micro-zigzag interlocking geometry. The formation of this micro-zigzag interlock is due to the switching of extruders during printing, which mechanically reinforces the interface adhesion strength. Using butt-joint tensile test and microscope observation, it was found that the geometry of this zigzag interlock is significantly influenced by the layer thickness, nozzle temperature and extruder offset. By optimizing the layer thickness and nozzle temperature, the interface adhesion strength between dissimilar materials was increased by 58.2% without significantly increasing the printing time or fabrication complexity.