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Global warming due to human activities (i.e., burning fossil fuels) has led to many issues, such as extreme weather (storm or drought) and rise in sea level making low land uninhabitable. One of the solutions to mitigate the global warming is to promote the use of biobased material. In this work, various dosage of talc powder ranged from 5, 10, 30 and 40 wt% were added into polylactic acid (PLA) to form biobased polymer composites. The biobased polymer composite has the potential to replace fossil-based polymer for sustainable packaging application. The PLA/talc composites were prepared by using melt blending method and compressed into thin sheet for characterisation test. The effect of talc content on the thermal properties and tensile performance of the PLA composites were investigated. Scanning electron microscope was used to study the fracture surface of the composites and the dispersion of talc powder in the matrix. Results showed that the addition of talc ranged from 5 to 30 wt% can enhance the Young's modulus and thermal stability of the composites but there is no improvement in tensile strength and elongation at break due to poor interfacial adhesion. The addition of talc beyond 30 wt% (i.e., 40 wt%) did not show improvement in thermal stability because at high talc content, the formation of agglomerate and voids allows the oxygen to diffuse into the matrix which lead to decomposition process.

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The design and analysis of lattice structures manufactured using Additive Manufacturing (AM) technique is a new approach to create lightweight high-strength components. However, it is difficult for engineers to choose the proper unit cell for a certain function structure and loading case. In this paper, three beam-like lattice structures with triangular prism, square prism and hexagonal prism were designed, manufactured by SLM process using AlSi10Mg and tested. The mechanical performances of lattice structures with equal relative density, equal base area and height, and equal length for all unit cells were conducted by Finite Element Analysis (FEA). It was found that effective Young's modulus is proportional to relative density, but with different affecting levels. When the lattice structures are designed with the same relative density or the same side lengths, the effective Young's modulus of lattice structure with triangular prism exhibits the maximum value for both cases. When the lattice structures are designed with the same base areas for all unit cells, the effective Young's modulus of lattice structures with square prism presents the maximum. FEA results also show that the maximum stress of lattice structures with triangular prisms in each comparison is at the lowest level and the stiffness-to-mass ratio remains at the maximum value, showing the overwhelming advantages in terms of mechanical strength. The excellent agreements between numerical results and experimental tests reveal the validity of FEA methods applied. The results in this work provide an explicit guideline to fabricate beam-like lattice structures with the best tensile and bending capabilities.

This research focused on developing recycled polymer blend filament from post-consumer expanded polystyrene and single-use polypropylene container for fuse filament fabrication (FFF). In this work, recycled polystyrene (rPS)/ recycled polypropylene (rPP) blend was extruded into filament for FFF printing. The increase in printing temperature obviously reduced the air gaps and improved the interlayer adhesion. However, the printed specimen only exhibited optimum tensile strength at printing temperature of 230 C. The printed specimens with rPS/rPP at 80/20 blend ratio showed the lowest tensile strength due to poor printed layers adhesion caused by incompatibility of polymer blend. However, printed specimens with rPS/rPP at 50/50 blend ratio could achieve optimum strength of 32 MPa. The micrographs proved that the voids in printed specimen were smaller or absent when the printing temperature and rPP content in the blend was increased. This means that the increase in print temperature and rPP content displayed a positive effect on the printed specimens. The effect of blend ratio had significantly increased melt flow and crystallinity of rPS/rPP blend when the rPP content was increased in the blend.However, the increase of melt flow and crystallinity led to noticeable warpage on the printed specimen.

Viruses are minuscule parasites that have gained notoriety for causing diseases. However, these harmful pathogens can be inactivated using Ultraviolet-C (UVC) radiation that has a wavelength between 200 – 280 nm. The wavelengths of the UVC are responsible for germicidal effect as the proteins (e.g. RNA and DNA) absorb the maximum radiation in these wavelengths and damage the DNA of the viruses so that they cannot replicate. This project aimed to simulate the UVC light intensity in different room layouts to guide the evaluation of the effectiveness of surface disinfection system which consists of UVC lights. Besides determining the quantity and the installation layout of the UVC lights, the project also aimed to help visualisation of the coverage of UVC radiation and highlight any under-exposed area for optimum room disinfection using a simulation software. DIALux Evo 9.1 was used to simulate the light intensity in different room and lighting layouts. As the software only calculates normal visible light (wavelength 380 – 700 nm) intensity in the unit of Lux, a correlation between Lux and UVC dosage (mJ/cm2) must be established first. A minimum UVC dosage of 40 mJ/cm2 is required to achieve complete surface disinfection of microorganisms. The simulation was able to visualize the coverage of UVC radiation and to determine the optimum placement of UVC lights to ensure sufficient UVC dosage is delivered to every critical surface. The outcome of this project can help to guide the design of UVC room disinfection system especially in hospital wards setting to optimise room disinfection and reducing the risk of infection.

Biocomposites are sustainable composite materials that, owing to their many benefits, have attracted interest of industry. In the present research, the durian husk fiber (DHF) was used as natural fiber in poly(lactic acid) (PLA) biocomposites. This study focused on the effects of fiber and processing aid content on the processing torque, tensile, thermal, and morphological properties of PLA/DHF biocomposites. The biocomposites with high fiber content have strength and modulus that are suitable for nonstructural application. The processing aid used was Ultra-Plast XP519. The addition of Ultra-Plast XP519 significantly improved the processing by lowering the torque, but it brought negative effect on mechanical properties.

In this research, Wire Arc Additive Manufacturing is modelled and simulated to determine the most suitable bead modelling strategy. This analysis is aimed to predict distortion by means of thermomechanical Finite Element Method (FEM). The product model with wire as feedstock on plate as substrate and process simulation are designed in form of multi-layered beads and single string using MSC Marc/Mentat. This research begins with finding suitable WAAM parameters which takes into account the bead quality. This is done by using robotic welding system with 01.2mm filler wire (AWS A5.28 : ER80SNi1), shielding gas (80% Ar/ 20% CO2) and 6mm-thick low carbon steel as base plate. Further, modelling as well as simulation are to be conducted with regards to bead spreading of each layers. Two different geometrical modelling regarding the weld bead are modelled which are arc and rectangular shape. Equivalent material properties from database and previous researches are implemented into simulation to ensure a realistic resemblance. It is shown that bead modelling with rectangular shape exhibits faster computational time with less error percentage on distortion result compared to arc shape. Moreover, by using the rectangular shape, the element and meshing are much easier to be designed rather than arc shape bead.