Novel overlapped & staggered interface structure (OS-IS) enhancing the bonding strength between heterogeneous material in fused filament fabrication

In multi-material fused filament fabrication (FFF), heterogeneous material interfaces often constitute structural weak points due to mismatched mechanical properties, thereby limiting the performance of the overall component. To overcome this limitation, a novel overlapped staggered interface structure (OS-IS) was proposed and developed in this study. A series of microstructure analysis, tensile tests, and shear tests were performed on the specimens with these designed heterogeneous interface structures. Results demonstrate that the distinctive geometric configuration of the OS-IS significantly enlarges the contact area between heterogeneous materials, leading to a notable enhancement in interfacial bonding performance. Specifically, compared to the regular interface structure (R-IS), the tensile strength and elongation at break are improved by 29.4 % and 94.8 %, respectively. Moreover, an optimized heat treatment process can effectively enhance interfacial properties. The bio-inspired joint incorporating the OS-IS exhibited a 98.1 % increase in the critical bending-fracture angle compared to the R-IS demonstrating its potential for application such as biomimetic hands. Therefore, this study proposes a novel structural design strategy to overcome interfacial compatibility challenges in multi-material additive manufacturing.