Tensile Testing of 3D Printed Materials

In this research project, first-year students from Kennesaw State University participated in a study to find the effect of the orientation of a part fabricated with additive manufacturing, or 3D printing, on the overall part strength. At the start of this study, students were introduced to the American Society for Testing and Materials (ASTM) standard entitled “Standard Test Method for Tensile Properties of Plastics”. From here, students used Computer-Aided Design (CAD) to design test pieces according to the ASTM standard, sections D638 − 14. Both round and flat sample types were created. All of the samples were fabricated using 3D printers and polylactic acid (PLA) plastic. For the flat samples, each sample set was printed increasing 15 degree intervals of offset from the x axis, from 0 degrees to 90 degrees. The round samples were at the same interval, however the offset was relative to the z axis rather than x. Using these test pieces students were to test the specimens for tensile strength using an MTS Insight material testing machine; parameters for the tests were found in the ASTM standard D638 − 14 section 10. The testing phase consisted of using the MTS machine to gradually increase strain on the sample until it failed and broke. After testing, students were asked to interpret the data for the strain before the test piece broke. This is done by using the raw data - load and displacement - to calculate stress and strain of each sample and entering the results into a chart to illustrate the relationship between the data sets