Three-Dimensionally Printed Polypropylene Sheets: Insights on Mechanical and Interface Shear Behavior

Abstract

Three-dimensional (3D) printing technology is replacing most of the conventional manufacturing processes of civil engineering materials because of the control that can be offered on the properties of the materials produced. 3D printing is particularly beneficial for printing polymeric geosynthetics, which are used in soils to perform various functions. Various controlling parameters that affect the strength and surface features of the printed geosynthetics are not understood so far. This study highlights the importance of various printing controls on the mechanical response of 3D-printed polypropylene (PP) sheets, which are close to geomembranes used for landfill liners and barrier systems. The number of layers used to achieve the thickness, speed of printing, and orientation of printing were varied, and the mechanical response of printed sheets were compared. The printed PP sheets were tested for tensile strength using strip tension tests and interface shear response with sand using direct shear tests. Results showed that speed of printing did not have a significant effect on the mechanical response of printed PP sheets. An increase in the number of layers for the same thickness caused an increase in tensile strength but decreased the interface shear strength. Orientation of printing is the major factor that influenced the mechanical response of the printed sheets among the parameters considered. Among the three printing orientations used, diagonal printing produced PP sheets of highest tensile strength and interface shear strength compared to horizontal and vertical printing. Sheets printed in the horizontal direction showed least tensile strength and interface shear strength. Reasons for these variations were investigated through image analysis to bring out important recommendations for 3D printing of PP sheets for geotechnical applications.