  Extrusion-based 3D printing has become one of the most common additive
manufacturing methods and is widely used in engineering. This contribution
presents the results of flexural creep experiments on 3D printed PLA specimens,
focusing on changes in creep behavior due to physical aging. It is shown
experimentally that the creep curves obtained on aged specimens are shifted to
each other on the logarithmic time scale in a way that the theory of physical
aging can explain. The reason for the physical aging of 3D printed
thermoplastics is assumed to be the special heat treatment that the polymer
undergoes during extrusion. Additionally, results of a long-term flexural creep
experiment are shown, demonstrating that non-negligible creep over long periods
can be observed even at temperatures well below the glass transition
temperature. Such creep effects should be considered for designing components
made of 3D printed thermoplastics.
