Abstract:
Natural fibre composite materials have become increasingly attractive in recent years as a substitute for synthetic materials that are often derived from petrochemicals. At present, the use of natural fibre composites is limited to mainly non-structural components due to poor mechanical performance. The main focus of this research is to develop new manufacturing processes to fully realize the potential of natural fibre composite materials. Solution, powder and aqueous suspension impregnation techniques have been developed to manufacture flax/PLA prepregs. Testing plates were manufactured from these prepregs using compression moulding. It was found that the tensile properties of the plates matched or exceeded those found in the literature. To replace manufacturing steps that were not conducive to large scale manufacturing and gain other benefits such as reduced exposure to temperature and increased manufacturing flexibility, a facility was developed to produce natural fibre thermoplastic tape. The process was based around continuous compression moulding and used an o✏ine solution impregnation process to impregnate the yarn. Flax/PLA tape was successfully produced. To understand how each parameter a↵ected the tape quality, a parametric study was conducted using the Taguchi method of experimental design. Findings from this study were used to develop the second-iteration tape manufacturing facility. The second tape manufacturing facility was based around rollers for tape compression and had an online powder impregnation unit which impregnated flax yarn with a PA12 slurry. Each stage in the facility underwent iterative development until flax/PA12 tape was consistently produced. This facility was also studied parametrically using the Taguchi method of experimental design. A finite element model was developed using LS-DYNA software for the manufacturing stage where PA12 slurry coated yarn is heated. The model was used to predict a forming window for the manufacturing process and investigate alternative materials. Finally, the feasibility of using flax/PA12 tape in the automated tape placement process was investigated. Two di↵erent heating sources were investigated and test plates were produced. Cylindrically wound parts were also produced from flax/PA12 tape using a filament winding process.