3D printing of fibre-reinforced polymer composites via multi jet fusion

• Main Author: Peng, Yong Sheng
• Other Authors: Zhou Kun
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2023
• Subjects: Engineering::Mechanical engineering
• Online Access: https://hdl.handle.net/10356/172632
• Institution: Nanyang Technological University

As one of powder bed fusion technique Multi Jet Fusion (MJF) has been a popular pick across aerospace, automotive and medical industries because of its rapid production cycle and the ability to construct complex structures without the need for supports. However, the mechanical properties of MJF printed polymer parts are insufficient for specialise industrial requirement. In this project, surface modified polyimide (mPI) fibres were mechanically mixed with polyamide 12 (PA12) powder to produce composite powders for MJF. The addition of mPI fibres caused negligible change in the powder flowability and thermal property, ensuring the good printability. With mPI fibre loading fraction of 4% in the X orientation, the MJF-printed PA12/mPI composite parts exhibited significant improvements in the tensile strength and modulus of 55.5 MPa and 1.76 GPa which has an increase of 17% and 4% as compared to pure PA12 printed parts. Using the fibre loading of 8% in Y orientation, the MJF-printed PA12/mPI composite parts exhibited improvements in the tensile strength and modulus of 69 MPa and 2.5 GPa which has an increase of 15% and 10% as compared to pure PA12/PI printed parts and negligible elongation differences. With the same mPI fraction of 8% in the Y orientation has an increase of 42% and 92% as compared to pure PA12 printed parts. The elongation percentage decreases as the mPI or PI fraction increases indicating that the fibre reinforced parts are becoming more brittle with the addition of mPI or PI fibre fraction as compared to pure PA12 printed parts. Annealing treatment has further improved the mechanical properties of the composite parts based on PA12/8%mPI composition in the Y orientation increased by 8.7% in UTS and 12% in modulus as compared to pure PA12/8%PI annealed parts and the elongation differences of the printed part can be neglected. With the addition of GB to mPI loading fraction of 4% in the Y orientation, the MJF-printed PA12/mPI/GB composite parts exhibited significant improvements with the increase loading fraction of 5% GB but decreases as more loading fraction of the GB are added to it, the addition of 5% GB to the composites of PA12/mPI has increased the UTS by 7.2% and modulus by 10% but drastically decreases the elongation by 68%. As the GB loading fraction increases from 5% to 20%, the UTS and elongation gradually decreases while the modulus gradually increases. This indicates that with the increasing amount of GBs, the modulus of the parts keeps increasing at the expense of losing some tensile strength and elongation. The outcome of this project has successfully improved the mechanical properties of MJF parts printed by adding reinforcement materials like PI fibres and GBs to PA12 and provide a new surface modification method for PI fibres to further enhance the mechanical properties of composites material. The project has also successfully developed a new mPI fibres and mPI/GBs reinforced PA12 composites powder for MJF printing.