The technology of continuous fibre-reinforced polymers: a review on extrusion additive manufacturing methods

Additive manufacturing technologies have transitioned from the fabrication of prototypes to final product manufacturing with competitive mechanical performance. The use of materials with high strength to weight ratio, and more specifically continuous fibre-reinforced composites, has demonstrated potential when fabricated through fused filament fabrication (FFF). The development and evaluation of such technologies has attracted a lot of attention in recent years, from both academic researchers and from industry, and a plethora of different techniques for its achievement has been proposed. This review presents different methods of FFF for the fabrication of continuous fibre-reinforced composite components as described in both patent and scholarly research literature. Different print head designs and techniques for combining and depositing polymers reinforced with continuous fibre have been developed including pre-impregnation, the use of multiple nozzles for the separate deposition of the fibre and the matrix material, and in situ impregnation of the reinforcing fibre with the matrix material. This review identifies the challenges associated with each of these approaches such as achieving a successful fibre/matrix impregnation, cutting of the continuous fibres during processing, and the introduction of high-performance thermoplastic polymers as the matrix material.