Long-Term Ageing on Mechanical Properties of Polyamide 12 Printed by Multi-Jet-Fusion

Abstract

Multi-Jet-Fusion (MJF) is a relatively new powder-based face-sintering additive manufacturing technique that exhibited great potential in high-volume manufacturing due to its rapid printing speed. An extensive amount of work has been conducted on the mechanical properties of MJF-printed polyamide 12 (MJF PA12) by investigating the powder characteristics and build orientations. However, no work has been conducted to study the effect of humidity and physical ageing on the mechanical performance of MJF PA12 specimens. Here, the physical and mechanical properties of different orientated MJF PA12 specimens stored under ambient and dryer condition for 184 days were investigated. It was found that specimens stored under ambient condition exhibited a drop in glass transition temperature due to moisture absorption followed by an increase which could indicate ageing of specimens occurred. The crystallinity of the specimens remains similar over time hence indicating that moisture absorption mainly affects the amorphous phase. The change in mechanical properties, such as tensile modulus and ultimate tensile strength, was more significant for specimens stored in ambient condition than those in dryer condition. It was also found that build orientation does not have a significant impact on moisture absorption rate, glass transition temperature, and the change in trend of mechanical properties. In addition, an artificial neural network was adopted to predict the mechanical properties of the MJF PA12 specimens under the influence of physical ageing, humidity, and build orientations. The neural network adopted in this work has the capability to predict the change in the mechanical properties of differently orientated MJF PA12 with different moisture content over time.

Keywords: Multi-Jet-Fusion, Polyamide 12, Mechanical properties, Storage condition, Long-term ageing, Artificial Neural Network