3D printing of continuous flax fibre reinforced biocomposites for structural applications

A Le Duigou,A Barbé,E Guillou,M Castro

doi:10.1016/j.matdes.2019.107884

Abstract

Recently, interest has been increasing in natural fibres as composite reinforcing fillers for polymer-based filaments manufactured with the Fused Deposition Modeling (FDM) process, despite their moderate mechanical properties compared to pure polymer.An innovative way was proposed in the present work to optimize the mechanical properties of biocomposites. It was based on novel continuous flax fibre/PLA (cFF/PLA) composite filaments made with a customized co-extrusion process and printed with a simple and affordable printing machine. The microstructure of the printed cFF/PLA biocomposite evidenced a homogeneous distribution of yarn within the cross section, while the twisted flax yarn led to fibre-rich areas at mesoscale. The cFF/PLA showed tensile modulus and strength values that exceeded the only available published result on continuous natural fibre printed composites by >4.5 times. Tensile properties were in the same range as those for continuous glass fibre/PolyAmide (PA) printed composites, paving the way for the use of biocomposites in structural applications. Their weakest point was their transverse properties that remained poorer than similar flax/PLA thermocompressed composites.

Highlights

Among several AM techniques, Fused Deposition Modeling (FDM - known as Fused Filament Fabrication (FFF)) can be performed on thermoplastic polymers or composites, to allow a filament to be printed in layers
An average diameter of 482 ± 30 μm was measured here, which was slightly higher than commercial continuous glass or carbon/polyamide filaments [16], but significantly thinner than the 1.8 mm discontinuous natural fibre composite filaments that are used commonly with conventional printing devices [10][21]
Even if porosities are mostly located within the flax yarn, the porosity content vp is encouragingly low (2.1 ± 0.6 %) when compared with filaments that are produced including short natural fibre composite (8.4< vp

Summary

Introduction

Among several AM techniques, Fused Deposition Modeling (FDM - known as Fused Filament Fabrication (FFF)) can be performed on thermoplastic polymers or composites, to allow a filament to be printed in layers. Thermoplastic polymers reinforced with natural fibres (wood, flax, hemp, etc.) possess a promising range of specific mechanical properties [3] in combination with a reduced environmental footprint [4]. These biocomposites are most commonly used in manufacturing process such as extrusion, injection moulding, thermoforming, film stacking, vacuum bag moulding, etc. Natural fibres have been attracting interest as composite fillers for 3D printing, but the mechanical properties of the printed parts remain low. Continuous synthetic (glass, carbon or aramid) fibre composites are increasingly being studied due to the high level of performance they can achieve compared to their discontinuous counterparts [11]. 3D Printing can be performed with simultaneous impregnation of polymer and fibres [12][13][14] or on pre-impregnated filaments [15][16][17], the latter exhibiting higher potential for structural applications with significantly improved mechanical performance

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Conclusion