On the use of different types of standardized dogbone specimens for tensile tests of PLA printed by MEX: A comparative analysis

The mechanical properties of 3D-printed parts produced by material extrusion (MEX) have been extensively investigated in recent years. However, there are no standards defining the test conditions and specimens' geometry, specifically for the parts obtained by this technology. The dogbone specimens, as defined by ISO 527-2 and ASTM D638, are mainly used for tensile tests of 3D printed polymers. This study presents a comparative analysis of four types of dogbone specimens made from polylactic acid (PLA) by material extrusion. Experimental results showed only slight variations (up to 2,34%) in the ultimate tensile strength (UTS) across the different types of specimens. On the other hand, they revealed the occurrence of failure at the boundary of the gauged section of the specimens, caused by a stress concentration in this area (as shown by numerical simulations) combined with irregularities and voids generated by the 3D printing strategy.