Viscoelastic Aging of 3d-Printed Pa12 Parts During Repeated Service Loads

A method of multi-step loading test was introduced to investigate the aging of 3D-printed polymer parts in terms of elasticity and viscosity under repeated service loads, where Nylon 12 by the process of powder bed fusion was employed in consideration of its excellent mechanical properties. Two-types of loading, i.e., axial tension on dumbbell-shaped plate coupons and 3-point bending on a cruciform-section beam, are examined on the condition that the generated strains remain in an ordinary service range. Major findings are as follows: alterations in viscoelasticity of the printed parts under repeated service loads are negligible when the loading rates remain the same, in other words, the mechanical properties are repeatable or free from aging, while the degree of loading rates is influential to Young’s modulus as well as viscosity but not to Poisson’s ratio. The repeatability was statistically tested by means of traditional Fisher-Neyman-Pearson’s statistics and also by Bayesian statistics.