Effects of the infill pattern on mechanical properties of fused layer modeling (FLM) 3D printed wood/polylactic acid (PLA) composites

In this paper, possible influences of various infill orientations (deposition angles) on specific material characteristics—such as tensile strength, compressive strength, charpy impact strength and heat deflection temperature (HDT)—of fused layer modeling (FLM) processed test specimens were evaluated. Two specially made wood filaments, made of the same polylactic acid (PLA) polymer but two different wood fiber contents, were used for sample manufacturing and evaluated as a function of fiber content as well as infill orientation. In the context of the wood fiber content, formulations containing 15 wt. % as well as 25 wt. % of fibers were examined. In connection with infill orientation, the influence factor of seven FLM 3D printing infill orientations (deposition angles)—in particular 0°, 15° crossed, 30° crossed, 45° crossed, 60° crossed, 75° crossed and 90°—on several material properties was investigated. It could be proven that there is a direct interaction between the infill orientation (deposition angle) and the resulting mechanical performance of the test specimens. This is not exclusively a direct correlation, but there is a mutual dependency. Apart from that, the analysis showed that the higher the fiber content in the filament, the higher the resulting mechanical properties.