Evaluation of the Infill Design on the Tensile Response of 3D Printed Polylactic Acid Polymer

Tanner David Harpool; Ibrahim Mohammed Alarifi; Basheer A Alshammari; Abdul Aabid; Muneer Baig; Rizwan Ahmed Malik; Ahmed Mohamed Sayed; Ramazan Asmatulu; Tarek Mohamed Ahmed Ali El-Bagory

doi:10.3390/ma14092195

Evaluation of the Infill Design on the Tensile Response of 3D Printed Polylactic Acid Polymer

Materials (Basel). 2021 Apr 25;14(9):2195. doi: 10.3390/ma14092195.

Authors

Affiliations

¹ Department of Mechanical Engineering, Wichita State University, 1845 Fairmount, Wichita, KS 67260, USA.
² Department of Mechanical and Industrial Engineering, College of Engineering, Majmaah University, Al-Majmaah, Riyadh 11952, Saudi Arabia.
³ Engineering and Applied Science Research Center, Majmaah University, Al-Majmaah, Riyadh 11952, Saudi Arabia.
⁴ Materials Science Research Institute, King Abdulaziz City for Science and Technology, Riyadh 11442, Saudi Arabia.
⁵ Engineering Management Department, College of Engineering, Prince Sultan University, P.O. Box 66833, Riyadh 11586, Saudi Arabia.
⁶ Department of Metallurgy and Materials Engineering, University of Engineering and Technology, Taxila 47050, Pakistan.
⁷ Department of Civil and Environmental Engineering, College of Engineering, Majmaah University, Majmaah 11952, Saudi Arabia.
⁸ Department of Civil Engineering, Faculty of Engineering Assiut University, Assiut 71518, Egypt.
⁹ Department of Mechanical Design, Faculty of Engineering Materia, Helwan University, Cairo 11724, Egypt.

Abstract

The current study explores the effects of geometrical shapes of the infills on the 3D printed polylactic acid (PLA) plastic on the tensile properties. For this purpose, by utilizing an accessible supply desktop printer, specimens of diamond, rectangular, and hexagonal infill patterns were produced using the fused filament fabrication (FFF) 3D printing technique. Additionally, solid samples were printed for comparison. The printed tensile test specimens were conducted at environmental temperature, Ta of 23 °C and crosshead speed, V_C.H of 5 mm/min. Mainly, this study focuses on investigating the percentage infill with respect to the cross-sectional area of the investigated samples. The mechanical properties, i.e., modulus of toughness, ultimate tensile stress, yield stress, and percent elongation, were explored for each sample having a different geometrical infill design. The test outcomes for each pattern were systematically compared. To further validate the experimental results, a computer simulation using finite element analysis was also performed and contrasted with the experimental tensile tests. The experimental results mainly suggested a brittle behavior for solidly infilled specimen, while rectangular, diamond, and hexagonal infill patterns showed ductile-like behavior (fine size and texture of infills). This brittleness may be due to the relatively higher infill density results that led to the high bonding adhesion of the printed layers, and the size and thickness effects of the solid substrate. It made the solidly infilled specimen structure denser and brittle. Among all structures, hexagon geometrical infill showed relative improvement in the mechanical properties (highest ultimate tensile stress and modulus values 1759.4 MPa and 57.74 MPa, respectively) compared with other geometrical infills. Therefore, the geometrical infill effects play an important role in selecting the suitable mechanical property's values in industrial applications.

Keywords: 3D printing; construct stress; finite element analysis; fused filament fabrication (FFF); infill shapes; strain diagrams.