Abstract
Bicomponent and multimaterial fused filament fabrication (FFF) with biodegradable polymers offers a sustainable approach to producing structures with tailored mechanical properties. This study investigates the influence of interface geometry and printing parameters on the tensile performance of biodegradable FFF components. UltraFuse PLA Blue and PLA/PHA Shining Silver (Polylactic Acid/Polyhydroxyalkanoate) were used to print samples with four interface configurations: simple “T,” double “2T,” “dovetail,” and “double dovetail,” chosen to evaluate how interlocking complexity affects stress distribution, load transfer, and fracture behavior. Mechanical performance was assessed through uniaxial tensile testing, combined with fracture imaging and surface topography analysis. The results showed that both interface design and printing parameters, such as layer thickness and number of shells, significantly impact tensile strength. Thicker layers reduced filament-to-filament adhesion, particularly along the interface plane, while increasing the number of shells improved filament alignment along the loading direction but introduced potential transverse weaknesses. Among the configurations, the simple “T” interface exhibited the lowest cohesion and strength, whereas the “2T” and dovetail geometries promoted more uniform stress distribution and enhanced fracture resistance. These findings highlight the critical role of interface engineering in improving the mechanical reliability of biodegradable multimaterial FFF parts. Overall, the study demonstrates that simultaneous optimization of interface geometry and process parameters is an effective strategy for enhancing tensile performance, converting structurally vulnerable regions into mechanically robust zones, and providing practical guidance for the design of sustainable, high-performance biodegradable FFF structures.