Effect of infill pattern on fatigue characteristics of 3D printed polymers

Abstract

The effect of the structure that is printed inside an object, known as infill pattern, on fatigue life of 3D printed specimens made of ABS was investigated in this paper. There are several infill pattern geometries, each with benefits and compromises between material usage, printing time or mechanical strength of the obtained part. Standard specimens with 100 % infill rate and rectilinear 0° and 90°, grid 0°–90° and ± 45°, triangular 60°, fast honeycomb, full honeycomb and wiggle infill patterns were tested. Following the completion of tensile tests to determine the ultimate tensile strength (UTS) of specimens, axial fatigue tests for each combination of infill pattern were conducted to measure the fatigue life for 90 %, 75 %, 60 %, 45 % and 40 % UTS. Comparative evaluation of the measured values revealed the strong influence of the printing patterns upon fatigue life. A simple mathematical model of the fatigue proprieties has been proposed for each infill patterns, statistical data shows that the proposed model ensures reasonably accurate prediction of fatigue life. The examination of fracture areas using electronic microscopy indicated the microstructural interaction between filaments underlying the main failure mechanisms, crazing, delamination and disbonding of the filaments and layers and their fracture. The results indicate that pattern with inclined filaments about tensile axis (grid±45°, rectilinear 0° and triangular 60°) have the maximum fatigue life compared with those with most of the filaments perpendicular to tensile direction (fast honeycomb, full honeycomb and rectilinear 90°). The pattern like grid 0°–90° and wiggle are very close to the first group, having filaments inclined (wiggle) or along and perpendicular to the tensile direction (grid 0°–90°).