Process-structure-property optimisation of basalt fibre reinforced thermoplastic composites

• Main Author: Hoo, Ming Shun
• Other Authors: Aravind Dasari
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2021
• Subjects: Engineering::Materials
• Online Access: https://hdl.handle.net/10356/150762
• Institution: Nanyang Technological University

In the present study, various basalt fibre reinforced polymer composites (BFRP) made with different polymeric matrix, processing conditions and reinforcement fabric were studied for their feasibility in replacing glass fibre reinforced polymer composite (GFRP) as a green alternative. The study aims to optimise the manufacturing process and enhance the properties of BFRP for various GFRP applications. The polymer matrix used includes Polypropylene (PP), polycarbonate (PC), and maleic anhydride grafted polypropylene (MAPP). The polymeric matrices displayed varying degree of interfacial adhesion and compatibility with the reinforcement basalt fibres due to differences in polarity between matrix and fibres. The reinforcing basalt fibre are polar by nature and interacts well with polar matrix such as PC and MAPP but display poor interfacial adhesion with the non-polar PP matrix. This resulted in large variation in quality and finishing of BFRP made with PP matrix, which affected the mechanical properties of the composites. To reduce variation and improve quality of BFRP made with PP matrix, simple mechanical control was applied for trial instead of conventional surface modification process. The basalt fibres fabric were taped with high temperature tape to restrict the fibres before the molding process, and the variation and finishing of the PP BFRP improved. Further investigation was done on the melt flow index (MFI) of the polymer matrix to establish the process-property relationship, and to optimise composite properties and quality. The composites were manufactured using hot compression molding with different preconditioning temperature and time, different consolidation temperature and pressure to evaluate the optimum processing conditions for various BFRP. The BFRP panels are then cut to sample size using water jet and tested using an Instron machine to evaluate their mechanical properties. The fibre and matrix volume fractions are obtained using thermogravimetric analysis (TGA) for comparison of theoretical mechanical properties against experimentally measured properties. The cross-sectional surface of the samples was analysed using microscope imaging to observe change in fibre-matrix interaction with changes in processing conditions which is correlated to the BFRP mechanical properties. Unidirectional (UD) basalt fibre polycarbonate (PC) composite showed enhancement in mechanical properties with an increased MFI. The results showed that the optimal MFI at 11.60 g/10mins at 260oC. The mechanical properties recorded showed ultimate tensile strength (UTS) of 708 ± 26 MPa, flexural strength of 1012 ± 43 MPa and elastic modulus of 33.1 ± 1.8GPa. UD basalt fibre PP composite showed improvement in mechanical properties with increased in MFI and pre-conditioning temperature. The mechanical properties of PP BFRP measured UTS of 314 ± 42MPa, flexural strength of 193 ± 14 MPa and elastic modulus of 19.6 ± 3.4 GPa. The higher MFI used for PP BFRP improved the incorporation of PP matrix into the Composite, reducing pores in the composite and increasing the mechanical properties. The MAPP BFRP show great enhancement in mechanical properties while produced using similar conditions as the PP BFRP. The compatiliser improves matrix-fibre adhesion which led to improved mechanical properties. The mechanical properties measured UTS of 412 ± 52 MPa, flexural strength of 287 ± 19 MPa and elastic modulus of 21.4 ± 4.1 GPa.