Fused deposition modelling (FDM) is a widely used additive layer manufacturing process that deposits thermoplastic material layer-by-layer to produce complex geometries within a short time. Increasingly, fibres are being used to reinforce thermoplastic filaments to improve mechanical performance. This paper reviews the available literature on fibre reinforced FDM to investigate how the mechanical, physical, and thermal properties of 3D-printed fibre reinforced thermoplastic composite materials are affected by printing parameters (e.g., printing speed, temperature, building principle, etc.) and constitutive materials properties, i.e., polymeric matrices, reinforcements, and additional materials. In particular, the reinforcement fibres are categorized in this review considering the different available types (e.g., carbon, glass, aramid, and natural), and obtainable architectures divided accordingly to the fibre length (nano, short, and continuous). The review attempts to distil the optimum processing parameters that could be deduced from across different studies by presenting graphically the relationship between process parameters and properties. This publication benefits the material developer who is investigating the process parameters to optimize the printing parameters of novel materials or looking for a good constituent combination to produce composite FDM filaments, thus helping to reduce material wastage and experimental time.

Composite materials, such as carbon fibre reinforced epoxies, provide more efficient structures than conventional materials through light-weighting, but the associated high energy demand during production can be extremely detrimental to the environment. Biocomposites are an emerging material class with the potential to reduce a product’s through-life environmental impact relative to wholly synthetic composites. As with most materials, there are challenges and opportunities with the adoption of biocomposites at the each stage of the life cycle. Life Cycle Engineering is a readily available tool enabling the qualification of a product’s performance, and environmental and financial impact, which can be incorporated in the conceptual development phase. Designers and engineers are beginning to actively include the environment in their workflow, allowing them to play a significant role in future sustainability strategies. This review will introduce Life Cycle Engineering and outline how the concept can offer support in the Design for the Environment, followed by a discussion of the advantages and disadvantages of biocomposites throughout their life cycle.

Growing environmental concerns and stringent waste-flow regulations make the development of sustainable composites a current industrial necessity. Natural fibre reinforcements are derived from renewable resources and are both cheap and biodegradable. When they are produced using eco-friendly, low hazard processes, then they can be considered as a sustainable source of fibrous reinforcement. Furthermore, their specific mechanical properties are comparable to commonly used, non-environmentally friendly glass-fibres. In this study, four types of abundant natural fibres (jute, kenaf, curaua, and flax) are investigated as naturally-derived constituents for high performance composites. Physical, thermal, and mechanical properties of the natural fibres are examined to evaluate their suitability as discontinuous reinforcements whilst also generating a database for material selection. Single fibre tensile and microbond tests were performed to obtain stiffness, strength, elongation, and interfacial shear strength of the fibres with an epoxy resin. Moreover, the critical fibre lengths of the natural fibres, which are important for defining the mechanical performances of discontinuous and short fibre composites, were calculated for the purpose of possible processing of highly aligned discontinuous fibres. This study is informative regarding the selection of the type and length of natural fibres for the subsequent production of discontinuous fibre composites.

The feasibility of using the HiPerDiF (high performance discontinuous fibre) method to manufacture highly aligned discontinuous fibres intermingled hybrid composites with flax and reclaimed carbon fibres (rCF), and the potential benefits of so doing, are investigated in this paper. It is demonstrated that, despite their hydrophilic nature, flax fibres are not affected by this water-based process. Intermingled flax/rCF hybrid composites are characterised in terms of their tensile and vibrational response. It is concluded that natural/rCF fibre hybrid composites can be a viable solution for those applications where a reduction in primary mechanical properties, e.g., stiffness and strength, is an acceptable trade-off for the enhancement of secondary properties, e.g., noise, vibration, and harshness (NVH) mitigation, and the reduction of monetary costs.