Influence of thickness on the IZOD impact strength of FDM printed specimens from PLA and PETG

Abstract

Additive manufacturing (AM) is a process that can achieve many parts with complex features in the production. The most important aspect of AM is that there is no more material wastage, which reduces costs. Additive manufacturing is beginning to be used in many fields, in medicine, in automotive, in aircraft, etc. The method of layer-by-layer addition is used for a wide range of materials: plastics, metals, and ceramics. Additive manufacturing materials can be tested by stretching, Charpy or Izod impact, bending, shearing, etc. For plastics, the most widely used process for impact testing is Izod. In the basic process, a specimen with a notch is embedded on one side, fixed with the notch at the base of the embedment, and hit with the Izod pendulum on the unembedded side. Initially, the Izod method was used mainly in the North American area; in Europe, the Charpy method was preferred. The Prusa MK3 printer was used to build the polylactic acid (PLA) and polyethylene terephthalate glycol (PETG) test specimens. A 100% infill density was defined with raster angles of ±45° for the infill. A 0.15 mm layer thickness was considered for printing. Four thicknesses were used for each material: 4, 6, 8 and 10mm. The specimens were tested with the CEAST 9050 pendulum impact system, according to the ISO 180:2000 standard. Brittle fracture was observed for all specimens, independent on thicknesses, and also similar behavior in the elastic zone of deflection for the same type of materials and for the same thickness respectively. The values of the IZOD impact strength have similar results for both materials, but if the PETG specimens allow a higher deflection, the PLA specimens presents a higher impact force.