Multi Jet Fusion (MJF) is a pioneering and highly efficient powder bed fusion additive manufacturing technique. However, even with the addition of reinforced glass fibers (GFs), MJF-printed polyamide 12 (PA12) objects still have lower mechanical strength as compared to many commercial polymer composites. In this work, a high-temperature (173 °C, near the onset melting temperature of PA12) annealing process is developed to remarkably enhance the mechanical strength of MJF-printed PA12 and GF/PA12 composites. Specifically, the ultimate tensile strength (UTS)/tensile modulus of PA12 and GF/PA12 specimens are increased by 20.8%/48.5% and 22.8%/30.6%, respectively. The mechanical performance of GF/PA12 specimens is better than that of previously reported MJF- and Selective Laser Sintering (SLS)-printed PA12, glass bead/PA12, and GF/PA12 composites. Moreover, the melting temperatures of both PA12 and GF/PA12 specimens are increased by more than 5 °C after the annealing process. Further experimental results reveal that the crystallinity increase is the primary enhancement mechanism of the high-temperature annealing. It is envisioned that a similar approach can also be applied to other SLS- and MJF-printed polymers and composites for mechanical enhancement.

Multi Jet Fusion (MJF) 是一种开创性的高效粉末床融合增材制造技术。然而，即使添加了增强玻璃纤维 (GF)，与许多商业聚合物复合材料相比，MJF 打印的聚酰胺 12 (PA12) 物体仍然具有较低的机械强度。在这项工作中，开发了一种高温（173°C，接近 PA12 的起始熔化温度）退火工艺，以显着提高 MJF 印刷的 PA12 和 GF/PA12 复合材料的机械强度。具体而言，PA12和GF/PA12试样的极限拉伸强度（UTS）/拉伸模量分别提高了20.8%/48.5%和22.8%/30.6%。GF/PA12 试样的机械性能优于先前报道的 MJF 和选择性激光烧结 (SLS) 印刷 PA12、玻璃珠/PA12 和 GF/PA12 复合材料。此外，PA12 和 GF/PA12 试样的熔化温度在退火过程后都增加了 5°C 以上。进一步的实验结果表明，结晶度的增加是高温退火的主要增强机制。预计类似的方法也可以应用于其他 SLS 和 MJF 打印的聚合物和复合材料，以增强机械性能。