Fused filament fabrication of polylactic acid/flax composites: Effects of infill strategy on dynamic and static behavior and energy consumption

Fused Filament Fabrication (FFF) is one of the most widely used Additive Manufacturing (AM) techniques, employing thermoplastic filament to create components. Among its many process parameters, the infill pattern plays a crucial role in determining both the mechanical performance and environmental footprint of printed parts, particularly in energy dissipation and damage behavior under impact. In this context, Natural Fiber Composites (NFCs), such as PLA reinforced with flax, are gaining interest due to their renewable origin, yet their low-velocity impact response and overall process sustainability remain underexplored. This study addresses these gaps by investigating the influence of infill pattern on the flexural and impact behavior of FFF-printed flax-reinforced PLA, while also assessing energy consumption during printing through a gate-to-gate Life Cycle Assessment (LCA). Results show that reducing the infill density of the Solid pattern by 20% leads to a 7.52% reduction in printing energy under constant conditions. Among all tested patterns at 80% infill, the Triangular pattern emerged as the most balanced option, offering favorable mechanical performance with a relatively low environmental impact. These insights aim to support more sustainable design strategies for prototyping and non-structural applications involving biocomposites produced by FFF.