Material characterization and micro-damage detection of additive manufactured poly-lactic-acid products using material extrusion-based technique

The growing application of 3D printing demands the attention of designers regarding the damage mechanism in the products of such kind of additive manufacturing procedure. However, limited detailed studies were available in the related literature. The main contribution of the current work is to explore the failure mechanism of 3D-printed parts via optical tools, such as Scanning Electron Microscopy (SEM) images on a micro-scale and Digital Image Correlation (DIC) images on a macro-scale. Mechanical characterization, e.g., tensile, compression, and torsional properties of 3D-printed specimens were carried out in experimental tests to measure the basic constants in the raster and its perpendicular directions. Also, the fractographic method was utilized to qualitatively analyze the damage initiation and propagation under different loading conditions. The remarkable findings of the current study have pointed out that the 3D-printed products demonstrated orthotropic behavior in various types of experiments. As a result, the average tensile strength, Young modulus, and elongation at breakage measured in filament direction were 38%, 11%, and 47% higher than those in transverse direction. The SEM images of the damaged specimen show that the tensile failure in specimens loaded in filamentary direction was occurred in two-step softening stages. It was affected by the filaments cross-sectional expansion. In torsional specimens, the different damage modes were observed owing to the bond failure of the adjacent filaments as a 3D printing procedure. The results of the compressive specimens subjected to the compressive load in a raster filaments' direction indicate the micro-buckling and kinking whereas when the load applies transversely, there is filament debonding phenomenon accompanied by densification and plasticity were observed.