Highly aligned discontinuous fibre thermoplastic filaments as feedstock for fused deposition modelling
: production, printing and performance

  • Knight Krajangsawasdi

Student thesis: Doctoral ThesisDoctor of Philosophy (PhD)

Abstract

Fused deposition modelling (FDM), a thermoplastic layer-by-layer additive manufacturing technique also known as 3D printing, can quickly build complex geometries, reducing design limitations and production costs of conventional manufacturing methods. Using a fibrous reinforcement strengthens the thermoplastic matrix, allowing FDM to be used in more structural complex-shape small-size applications. Aligned discontinuous fibre composites (ADFRC) incorporate a high-performance reinforcement architecture that, owing to a sufficient fibre length and high alignment, results in mechanical performance comparable to those of continuous fibre composites as well as higher formability and fewer manufacturing defects.
DcAFF (Discontinuous Aligned Fibre Filament) is a novel ADFRC filament developed for 3D printing aiming to achieve both high mechanical performance and formability. The ADFRC used in this thesis is produced with the High Performance Discontinuous Fibre (HiPerDiF) technology. The DcAFF filament was studied in three main areas: production, printing, and performance. A high production rate filament-forming machine was designed to compress the high aspect ratio cross-section of the tape outputted by the HiPerDiF into a square cross-section filament before its pultrusion to obtain a circular cross-section filament. The designed filament-forming process ensures that a large fraction of the fibres in the final product is well aligned with the longitudinal axis of the filament and the void content is minimised. The printability of the DcAFF filament is relatively good in straight rasters, but there are some discrepancies between the desired and deposited raster at sharp deposition turnings. This discrepancy was minimized with a first-order lag relationship and PI controller that offered an additional path to compensate for the turning corner. The DcAFF material was evaluated with different testing approaches: tensile, open-hole and short beam shear. Overall, considering the information available in the literature for 3D printed composites using the same matrix, i.e. PLA, DcAFF shows mechanical performances superior to those reinforced with short fibres and comparable to those employing continuous ones. It is concluded that the use of ADFRC in DcAFF filament is sufficient to provide performance comparable to continuous fibre composites and relatively better formability compared to the 3D printing of continuous fibre. This paves the way for this material as a candidate for high-performance 3D printing.
Date of Award3 Oct 2023
Original languageEnglish
Awarding Institution
  • University of Bristol
SupervisorDmitry Ivanov (Supervisor), Marco Longana (Supervisor), Ian Hamerton (Supervisor) & Ben K S Woods (Supervisor)

Keywords

  • Fused deposition modelling
  • 3D printing
  • Aligned discontinuous fibre composites
  • Additive manufacturing

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