3D Printing of Fibre-Reinforced Thermoplastic Composites Using Fused Filament Fabrication-A Review

Abstract

Three-dimensional (3D) printing has been successfully applied for the fabrication of polymer components ranging from prototypes to final products. An issue, however, is that the resulting 3D printed parts exhibit inferior mechanical performance to parts fabricated using conventional polymer processing technologies, such as compression moulding. The addition of fibres and other materials into the polymer matrix to form a composite can yield a significant enhancement in the structural strength of printed polymer parts. This review focuses on the enhanced mechanical performance obtained through the printing of fibre-reinforced polymer composites, using the fused filament fabrication (FFF) 3D printing technique. The uses of both short and continuous fibre-reinforced polymer composites are reviewed. Finally, examples of some applications of FFF printed polymer composites using robotic processes are highlighted.

Keywords: fibre reinforcement; fused filament fabrication; mechanical properties; polymers.

Figure 1

Schematic of FFF process for the printing of parts using the melted polymer filament.

Figure 2

Effect of fibre content and preparation process on (a) tensile strength and (b) modulus of ABS/carbon fibre composites [34].

Figure 3

Scanning electron microscopy (SEM) images of the specimens manufactured using (a) 3D printing and (b) CM methods [33]. These images help to illustrate the differences in interlayer adhesion of 3D printed samples compared to that prepared using CM process.

Figure 4

3D printed circular honeycombs of PLA-PCL/KBF with varying ratios [38]. The PLA-PCL/KBF composite consists of polylactic acid (PLA) as the stiff matrix, polycaprolactone (PCL) as an elastomer phase and silane-treated basalt fibres (KBF) as the reinforcing filler.

Figure 5

Schematics of in-situ fusion techniques: (a) in-nozzle impregnation with polymer and coaxial fibre extrusion, and (b) embedding of continuous carbon fibre (CCF) after 3D printing in a thermal bonding process. Images from [42].

Figure 6

Schematic of ex-situ prepreg process: (a) The extrusion and cooling apparatus for production of the prepreg filament. (b) The printing process utilising the prepreg filament requires no drive gear as the fibre is pulled through the nozzle, extruding the polymer as it moves [42].

Figure 7

Literature values for tensile strength and modulus for short and continuous fibre-reinforced composites, as well as unreinforced polymers for comparison. A comparison between similar additive manufactured (AM) and compression moulded (CM) woven PA66/CF composites is highlighted, with tensile performance being comparable. Key: Author, matrix, reinforcement, fibre % [18,27,29,34,43,46,51,55,56,57,58].

Figure 8

(a) Example of a raster pattern generated for printing tensile testing samples [41]. (b) Objects printed using “spiral” generated by an FFF slicer software [47]. (c) Printer producing a bowl-shaped component from PLA/CF [45].

Figure 9

Comparison of (a) Markforged “Eiger” and (b) Anisoprint “Aura” slicer software for fibre composite printing. The Eiger software facilitates fibre placement in tighter spaces, with blue lines indicating fibre paths.

Figure 10

Modelled fibre layouts (left) and resulting stress heat maps (right). (a) represents an ideal fibre placement scenario with reduced strain concentration [68]. (b) represents a drilled/cut sample with discontinuous fibres resulting in large strain concentrators. (c) represents a cut sample containing fibre vorteces to reduce the strain concentration at the centre hole [67].

Figure 11

The Arevo labs robotic AM system printing a portion of a bicycle frame (left) [71]. The Atropos Robot system printing a glass/epoxy turbine blade without a mould for support (right) [72].