Creep behavior of polyamide 12, produced by selective laser sintering with different build orientations

The successful use of components produced by selective laser sintering as a rapid manufacturing process requires a comprehensive understanding of the material. In this study, the effect of specimen build orientation on mechanical properties of selective laser-sintered polyamide 12 was investigated in detail. Samples were printed with an orientation of 0 degrees, 15 degrees, 45 degrees, and 90 degrees to the build platform. In addition to quasi-static tensile tests, creep tests under different loads (5 MPa, 10 MPa, 15 MPa, and 20 MPa) and for different times (10 h and 1000 h) with and without relaxation were performed. Creep behavior was analyzed using the Burgers model. Therefore, the elastic strain, the relaxant strain, the viscous strain, and the total deformation were determined. Results show that the build orientation has no significant influence on the long-term creep behavior, at small stresses. Short-term creep and relaxation tests show that the elastic and viscous strain are only slightly influenced by the build orientation. However, the viscoelastic strain is affected by the build orientation. Furthermore, the deformations resulting from creep and relaxation have no significant influence on the mechanical behavior as shown by tensile tests.