Structure-property relationship of additively manufactured (short carbon fibre-reinforced) polyamide
File(s)
Author(s)
Hou, Yingwei
Type
Thesis or dissertation
Abstract
Additive manufacturing (AM), also known as 3D printing, attracts increasing interests from industry due to its simplicity and low cost. However, 3D printing-induced interfaces which could influence the potential of AM in industrial applications which are required to exhibit high mechanical performance and durability in harsh environment. This thesis investigates the relationship of the manufacturing process-induced interfaces and the properties of printed (short fibre reinforced) polyamide. Partially bonded interfaces induced by the manufacturing process were found between the layers of printed polyamide and short fibre reinforced polyamide (SFRN). The printed SFRN exhibited inferior interfaces compared to polyamide and the resulting mechanical performance was more significantly influenced. The tensile modulus of 3 mm SFRN was decreased as a function of interface density (number of interfaces per unit sample thickness) from 4.57 GPa to 3.88 GPa. This thesis also investigates the moisture absorption of printed polyamide and SFRN. The measured diffusion coefficients of printed SFRN increased as a function of the number of interfaces which increased the moisture absorption kinetics. The influence of moisture absorption on the mechanical performance of printed samples was evaluated. Reduced shear properties indicated the bonding between layers and within layers degraded with absorbed moisture content. The tensile properties of printed samples exposed to moisture decreased more significantly compared to injection moulded samples due to the degraded interfacial property. Moreover, moisture absorption was found to have an irreversible impact on the partially bonded interfaces between adjacent filaments. The resulting tensile and shearing properties of printed samples were not fully recovered after the drying process due to the aggravated interfaces.
Version
Open Access
Date Issued
2022-01
Date Awarded
2022-08
Copyright Statement
Creative Commons Attribution NonCommercial Licence
Advisor
Panesar, Ajit
Lee, Koon-Yang
Publisher Department
Aeronautics
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)