Mixed-mode I/II fracture properties of selectively laser sintered polyamide

Abstract

Additive manufacturing (AM) is a topical field today and has received the attention of many researchers. However, further research is needed to overcome the many challenges facing AM, especially in the mixed-mode fracture. The results presented in this paper are framing the experimental data obtained for mixed-mode I/II fracture properties of laser sintered polyamide. The experiment was carried out on Semi-Circular Bend (SCB) specimens manufactured from polyamide PA2200 using EOS Formiga P100 laser sintering machine. To achieve the full range of fracture toughness values, from pure mode I to pure mode II, five crack orientations of the SCB specimens (0, 15, 30, 45 and 54°) were considered. Further, crack initiation angle and crack paths of SCB specimens have been assessed in order to identify the fracture phenomena (interlayer and/or intralayer fracture). The main fracture properties (fracture toughness, crack initiation angles and crack paths) were compared with the theoretical predictions of three mixed-mode fracture criteria (Maximum Tensile Stress-MTS, Maximum Energy Release Rate-Gmax and Equivalent Stress Intensity Factor-ESIF). The results underline differences between theoretical approaches and experimental data, especially due to the interlayer fracture phenomenon. However, it was obtained that the Gmax and ESIF criteria show the best match with the experimental data.