Aerospace structures are prone to impact which affected their residual strength. The aim of this paper to investigate the impact and after-impact behaviour of multi-walled carbon nanotube (MWCNTs) as nanofiller enhanced flax/carbon fibre composites (FLXC) and flax/glass fibre composites (FLXG) hybrid composites. Wet lay-up method was used to fabricate the hybrid composites. The hybrid composites were impacted with impact energies ranging from 5J to 20J, with different types of surface susceptible to the impactor to compare their response under loading. Compression after impact (CAI) testing were done to evaluate the after-impact properties of the hybrid composites. Obtained results found that FLXG composites impacted at glass surface (G-FLX) showed better impact properties compared to C-FLX composites. In another end, it was found that the compressive strength of FLXG composites is higher compared to FLXC composites due to severe damage occurred on FLXC composites surface compared to FLXG composites. Therefore, from the results, it can be concluded that FLXG hybrid composites shows good behaviour to be applied as the interior and functional surfaces inside an aircraft.

Fused Deposition Modelling (FDM) is an actively growing additive manufacturing (AM) technology due to its ability to produce complex shapes in a short time. AM, also known as 3-dimensional printing (3DP), creates the desired shape by adding material, preferably by layering contoured layers on top of each other. The need for low cost, design flexibility and automated manufacturing processes in industry has triggered the development of FDM. However, the mechanical properties of FDM printed parts are still weaker compared to conventionally manufactured products. Numerous studies and research have already been carried out to improve the mechanical properties of FDM printed parts. Reinforce polymer matrix with fiber is one of the possible solutions. Furthermore, reinforcement can enhance the thermal and electrical properties of FDM printed parts. Various types of fibers and manufacturing methods can be adopted to reinforce the polymer matrix for different desired outcomes. This review emphasizes the fiber types and fiber insertion techniques of FDM 3D printed fiber reinforcement polymer composites. A brief overview of fused deposition modelling, polymer sintering and voids formation during FDM printing is provided, followed by the basis of fiber reinforced polymer composites, type of fibers (synthetic fibers vs. natural fibers, continuous vs. discontinuous fiber) and the composites’ performance. In addition, three different manufacturing methods of fiber reinforced thermoplastics based on the timing and location of embedding the fibers, namely ‘embedding before the printing process (M1)’, ‘embedding in the nozzle (M2)’, and ‘embedding on the component (M3)’, are also briefly reviewed. The performance of the composites produced by three different methods were then discussed.

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Fused filament fabrication (FFF) 3D-printed parts are mostly used as prototypes instead of functional parts because they have a weaker mechanical strength compared to their injection molded counterparts. Various methods including a fiber-reinforced polymer composite were proposed to enhance the properties of FFF 3D-printed parts. A new concept to fabricate a polymer composite via FFF 3D printing is proposed, where fiber is deposited during printing, instead of using a premixed composite filament. In order to investigate the workability of this concept, a new device is needed. Firstly, the design requirements were identified, and a fiber doser that can be mounted on a commercial 3D printer was designed. Prototype testing was conducted to improve the design. The improved fiber doser was able to deposit varied fiber contents during FFF 3D printing. Thermogravimetric analysis (TGA) was used to quantify the fiber contents of the fabricated composites. With this newly designed doser, short glass fiber–polylactic acid (PLA) composites with three different fiber contents (1.02 wt.%, 2.39 wt.%, and 4.98 wt.%) were successfully manufactured. A new technique to manufacture a polymer composite is proven; nevertheless, the mechanical and tribological properties of the newly fabricated composites are under investigation and will be reported in a subsequent article.

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