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.

This chapter details how plasma treatments can be used to tailor the wettability of polymers. A plasma is an excited gas, and exposure of a polymer to a plasma discharge generally results in an enhancement in surface energy and associated with this is an increase in wettability. The effect however can be short lived due to hydrophobic recovery. In this review the use of both low and atmospheric plasmas for the activation of polymers will be discussed, as will the use of these plasmas for the deposition of plasma polymerised coatings. The latter can be used to produce polymer surfaces with tailored functionalities, thus achieving stable water contact angles ranging from superhydrophilic to superhydrophobic, as required.This review briefly introduces plasmas and plasma processing and includes an overview of typical plasma treatment sources. This is followed by a review of the use of plasma discharges to treat polymers and in particular to enhance their surface energy, which is important for example in achieving enhanced adhesive bond strength. The final section of this chapter focuses on the deposition of plasma polymerised coatings and how these can be used to tailor both surface chemistry and morphology. Thus the wettability of polymer surfaces can be controlled.

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This study evaluates the use of a barrel atmospheric plasma system for the treatment of acrylonitrile butadiene styrene and polylactic acid polymer particles. Treatments were carried out in a helium discharge with either oxygen or nitrogen addition. The plasma activated polymer particles were then used to prepare filaments, which in‐turn were then used to fabricated parts by additive manufacturing. The resultant dog bone polymer parts exhibited up to a 22% increase in tensile strength, compared to parts fabricated using unactivated polymer particles. The explanation for the increased mechanical strength is the enhanced activation of the treated polymer particles, as well as the removal of contaminations from the polymer surface.

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