Polylactic acid (PLA) is widely used in fused filament fabrication (FFF) 3D printing due to its ease of use, environmental friendliness, affordability, and availability. Pure PLA has limitations despite its popularity, including poor mechanical properties, brittleness, low heat resistance, and a limited processing window. One of the essential methods for physical changes that lead to new properties in PLA is to composite it with materials such as metal powders. For this purpose, in the present study, PLA reinforced with iron microparticle powder was used to fabricate FFF 3D printed samples to study their mechanical properties and to investigate these changes. On the other hand, a key challenge in producing composite parts through FFF 3D printing is finding a correlation between the mechanical properties of the parts and the process parameters. Therefore the effects of nozzle temperature, printing speed, and nominal porosity as the most critical process parameters of the FFF method on the impact strength and specific impact resistance of PLA/iron microparticles composites were investigated. Response surface methodology was used to optimize the experimental design. The results showed that nominal porosity has the most significant effect on the impact resistance, while nozzle temperature had the least effect. Reducing nominal porosity led to improved impact resistance in the samples. The results of multiobjective optimization showed that the lowest nozzle temperature (190°C), the lowest nominal porosity (30%), and the highest printing speed (50mm/s) were the optimal conditions for multiple objectives.
