Cooperative enhancement of multi-material interface strength by mechanical interlocking structures and FDM path planning

Multi-material additive manufacturing (MMAM) significantly enhances the design flexibility and performance diversity of manufacturing by integrating materials with different characteristics into a single object. However, augmenting the interface strength of MMAM parts is a crucial step in ensuring the overall quality and performance of the components. In this study, we propose a strategy that combines mechanical interlocking structures with FDM path planning to enhance interface strength. To achieve this goal, we designed three mechanical interlocking structures: Dovetail, Hook, and Cross. These structures not only meet the requirements of continuous extrusion processes but also exhibit non-disassemblable characteristics. Taking into account their slicing profiles and the characteristics of their fracture forms, the interface strength was further enhanced during the forming process by adjusting the nozzle's movement path and controlling the extrusion amount of consumables. The experimental results indicate that, with a layer count of 5 and an embedding distance of 4 mm, all three mechanical interlocking structures exhibit superior tensile performance. Under the collaborative action of path stitching, the interface strength of the three mechanical interlocking structures is enhanced, the Dovetail structure demonstrates a notably superior performance among them, showcasing an average strength limit increase of 304.09% (8.89 MPa). The experimental results not only validate the enhancement of interface strength through the combination of mechanical interlocking structures and FDM path planning but also reveal the relationship between strength limits and contact area. The varied patterns in strength limits resulting from different approaches to increasing the contact area of the two materials provide insights for investigating other structural parameters.