Pusat Pengajian Kejuruteraan Aeroangkasa - Tesis

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Browsing Pusat Pengajian Kejuruteraan Aeroangkasa - Tesis by Author "Awais, Habib"

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    Effects of fabric architecture on mechanical properties of natural fibre (jute, hemp and flax) reinforced polypropylene composites
    (2020-10-01)
    Awais, Habib
    Thermoplastic bio-composites are particularly attractive and ideal materials for weight critical applications. Long natural fibre reinforced thermoplastic composite materials not only offer low weight, better strength than short fibre reinforced composites but are also biodegradable and ecofriendly. The impregnation of resin into the reinforcement is considered as a major concern during the fabrication of thermoplastic composites. Intermediate materials known as commingled fabrics have evolved as an alternative solution to overcome the viscosity constrain and reduce the flow distance. Therefore, in this study, novel commingled fabrics were developed by aligning the polypropylene fibres alongside the reinforcement natural fibres (jute, hemp and flax) using weaving and knitting techniques to assist the fabrication of long fibre reinforced thermoplastic composites and to minimise the melt flow distance of resin. Thermal stability of reinforcing fibres (jute, hemp and flax) was assessed by thermogravimetric analysis (TGA). The strength of individual reinforcing yarn and fabrics was measured by single-strand method and strip method, respectively. A comparative performance evaluation was conducted on natural fibre (jute, hemp and flax) reinforced laminates fabricated using the woven, woven commingled and knitted commingled fabric architectures along with polypropylene matrix by compression moulding. The fibre volume fraction was 35 ± 2 % for all fabricated laminates. The effects of the fabric architecture on the mechanical properties of the fabricated laminates were assessed in terms of tensile, flexural, impact, short-beam shear (SBS) and compression after impact strength (CAI). The results show that flax fibres are more thermally stable than hemp and jute fibres and there is no significant mass loss up to 260 °C. The flax yarns and fabrics show higher tensile strength than hemp and jute yarns and fabrics owing to the difference in chemical composition. The results also show that the knitted commingled laminates display higher mechanical properties compared to the woven and woven commingled laminates. The knitted commingled laminates present higher tensile strength (13 % and 16 %), flexural strength (16.5 % and 14.3 %), Charpy impact strength (12 % and 54 %), SBS strength (20 % and 29 %) and CAI strength (37.9 % and 25.3 %) compared to the woven laminates and woven commingled laminates. The better performance of the knitted commingled laminates was ascribed by the improved wetting of fibres owing to the shortest average matrix flow distance. Although natural fibre reinforced polymer (NFRP) composites are emerging as a viable alternative to metal parts for lightweight components in the automotive and aerospace industry, their use is confined due to their poor performance properties. Currently, fillers are often incorporated in NFRP composites to modify their properties. This study also explores the reinforcing effects of hollow glass microspheres (HGM) as fillers in continuous NFRP composites. Tensile, flexural and impact tests were conducted to investigate the influence of HGM on the mechanical properties of the woven and woven commingled laminates. The results indicate that the loading of 1.5 vol. % HGM improves the tensile and flexural properties, but further addition of HGM (3 vol. %) leads to a decline in these properties; furthermore, the impact strength was significantly improved in woven and woven commingled laminates by the addition of 3 % HGM. The fracture surface morphology reveals the better wetting of fibres and straight yarn configuration in knitted commingled laminates compared to the woven and woven commingled laminates.