Validation of an in-house-designed tensile testing machine for the mechanical characterization of 3D-printed specimens

Additive manufacturing is gaining greater and greater popularity in recent years: thanks to a dramatic reduction of costs and increasing print quality, more and more people are attracted to 3D printing, even for the production of end-use load-bearing parts. Today, there are no universally-accepted norms that guide the engineer through the uncertain task of predicting the mechanical behavior of 3D-printed parts. Even though there are numerous reports and articles in literature regarding this topic, the designer will have to rely mostly on his own mechanical tests. This paper describes the design of an in-house-built machine for 3D-printed material tensile testing. The accuracy of this test-rig has been verified through comparison of results on different 3D-printed specimens: these were realized through Fused Deposition Modelling (FDM) and were divided into four distinct sets, based on the material and their orientation on the buildplate. Some samples were printed in PLA, others in XTCF-20™: a composite material made of a matrix of Amphora™ polymer reinforced with 20% in weight carbon short fibers. PLA samples were printed flat on the buildplate, on one side and standing: this affects directly the orientation of the plastic fibers. Tensile tests were performed both on ours and on a high-end commercial testing machine, following the ISO 527 norm. Maximum stress, strain at maximum stress and Young’s modulus were calculated for each tested specimen: these measures allowed to compare the results of the two testers. Results proved coherent, thus validating the in-house machine, which was realized for a fraction of the cost of an equivalent commercial model.