Thickness dependency of mechanical properties of laser-sintered polyamide lightweight structures

Laser sintering (LS), as an additive manufacturing process for production of polymer structures, provides the possibility of directly manufacturing personalized, structural motorcycle components for motor sports. To create such lightweight structures, the wall thickness and position limits of the LS systems need to be investigated in detail. Appearing process-related flaws such as different amounts of crystallinity, surface roughness, and defects such as pores exhibit dimensions similar to the wall thickness. To study the process-related effects on the mechanical properties of 450 tensile test specimens in z-direction, the build areas of two LS systems were screened and a detailed wall thickness investigation was conducted. In addition, dynamic mechanical analysis, differential scanning calorimetry, and scanning electron microscopy for several wall thicknesses similar to the spot size were conducted. The investigations showed that the Young's moduli and ultimate tensile strengths of the produced specimens of the two commercial EOS systems, P396 and P770, are similar and evenly distributed. However, distinct differences were found in elongation at break. The scattering of mechanical properties is more in the specimens produced by P770 than in those produced by P396. The Poisson's ratio does not vary between thin- and thick-walled structures. Furthermore, structures with a thickness below 1 mm showed distinctive losses in stiffness, ultimate tensile strength, and elongation at break.