The Effect of Raster Pattern and Acetic Acid Exposure on the Mechanical and Failure Properties of Additively Manufactured PLA and PLA-wood Composite Specimens

Understanding how additively manufactured components interact with a given environment is critical for the furthering of the technology. Specimens composed of polylactic acid and a polylactic acid-wood composite were made with the additive manufacturing process of fused filament fabrication. The effect of raster pattern as well as exposure to acetic acid (in the form of apple cider vinegar) on mechanical properties was made via tensile testing and dynamic mechanical analysis. Exposure to the apple cider vinegar occurred at a temperature of 60 °C for a duration of 168 h. Differences between sample pools were ascertained by application of the Tukey–Kramer honestly significant difference test to collected data. The relationship between moisture absorption and raster pattern was assessed and found to differ between material types. A comprehensive fracture surface analysis was carried out with scanning electron microscopy which gave insight to the effect of raster pattern and material type on fracture surface morphology. It was also noted that bacterial growth occurred on the PLA-wood composite specimens, but not on the PLA specimens. A key observation made here was the presence of adiabatic shear bands, which is potentially the first time this phenomenon has been observed in the case of fused filament fabrication.