The Influence of the Gradient Infill of PLA Samples Produced with the FDM Technique on Their Mechanical Properties.

Three-dimensional printing is a dynamically developing field of industry. Its main advantage is the small amount of waste, no need to use specialized tools, and easy control of the mechanical properties of the printed model. One of the most popular techniques of 3D printing is FDM. The main factor influencing the mechanical properties of 3D-printed materials is the filling density. The aim of this study was to determine the mechanical properties of porous structures with a porosity gradient of PLA samples printed using the FDM technique. The accuracy of mapping the structures by computed tomography was assessed, and then a static compression test was performed. It has been shown that the strength properties increased with the increase in the filling density. The highest value of compression strength, amounting to 41.2 MPa, was observed for samples made of PLA with an 80% filling degree, whereas the lowest value of compression strength was found in PLA-T samples with a filling degree of 10%, reaching only 0.6 MPa. It was found that not only the core filling density, but also the outer layers, influences the mechanical properties. The assessment of spatial architecture allowed for a qualitative and quantitative assessment. The obtained images from the computed tomograph showed that the designed sample models were correctly reproduced in the entire volume.