Experimental Investigation and Parameter Optimization of Low Power CO2 Laser Cutting of a Carbon/Kevlar Fibre-reinforced Hybrid Composite

To overcome the limitations of a singular fibre-reinforcement composite, a number of hybrid composites have been developed consisting of two or more different types of fibres in a common matrix. With the correct combination of dissimilar fibres, a variation of hybrid composite can be obtained possessing improved physical and thermal properties which is previously not possible with a single kind of reinforcement. The use of powerful lasers (several kW) in the cutting of composites is fairly widespread so as to overcome challenges regarding the anisotropic properties of these materials, but at the expense of a large heat affected zone (HAZ), kerf width, and fibre pull-out. The primary aim of this paper is to investigate low-power CO2 laser cutting of a carbon/Kevlar fibre-reinforced hybrid composite. Response surface methodology (RSM) along with Box-Behnken design (BBD) was employed to understand the interactions between the process parameters, such as laser power, cutting speed and standoff distance (SOD), and their effects on the cut quality characteristics including size of the HAZ and kerf characteristics. Following this, process parameter optimization was successfully carried out using ANOVA to minimize the HAZ and kerf width. Qualitative measurement using a scanning electron microscope (SEM) was performed to evaluate the effects of process parameters and fibre orientation on fibre pull-out, HAZ and material decomposition. Difference between the thermal properties of carbon fibres, Kevlar fibres and polymer matrix (epoxy) was found to influence HAZ and kerf width. High thermal conductivity of carbon fibres particularly led to large extent of matrix recession and burning of Kevlar fibres around the cut path

Determination of optimum polymeric coagulant in palm oil mill effluent coagulation using multiple-objective optimisation on the basis of ratio analysis (MOORA)

The main limitation of a conventional palm oil mill effluent (POME) ponding system lies in its inability to completely decolourise effluent. Decolourisation of effluent is aesthetically and environmentally crucial. However, determination of the optimum process parameters is becoming more complex with the increase of the number of coagulants and responses. The primary objective of this study is to determine the optimum polymeric coagulant in the coagulation–flocculation process of palm oil mill effluent by considering all output responses, namely lignin–tannin, low molecular mass coloured compounds (LMMCC), chemical oxygen demand (COD), ammonia nitrogen (NH3-N), pH and conductivity. Here, multiple-objective optimisation on the basis of ratio analysis (MOORA) is employed to discretely measure multiple response characteristics of five different types of coagulants as a function of assessment value. The optimum coagulant is determined based on the highest assessment value and was identified as QF25610 (cationic polyacrylamide). On the other hand, the lowest assessment value was represented by AN1800 (anionic polyacrylamide). This study highlights the simplicity of MOORA approach in handling various input and output parameters, and it may be useful in other wastewater treatment processes as well

Characterization of a Sub-Atmospheric Pressure-Inducing Micropump Based on Flow Rate and Gauge Pressure Measurements

The pumping mechanism in multi-inlet microfluidic channels usually requires multiple micropumps to be separately attached to each inlet. Unfortunately, this may create fluid leakage resulting from a considerably high internal pressure. To address this, a passive sub-atmospheric pressure-inducing micropump is proposed and its performance is characterized as a function of the flow rate and the gauge pressure. With this pump, a sufficiently high flow rate is generated, comparable to some active-piezoelectric micropumps. The gauge pressure is exponentially descending with time and can be crudely classified into three regions of high, moderate, and slow pressure-release times. Overall, the stabilized pressure is identified within 70 s < t £ 300 s for slow rate mixing while rapid mixing is applicable at t £ 70 s

Natural fiber-reinforced composites: types, development, manufacturing process, and measurement

Natural fiber-reinforced polymer composites offer huge benefits in terms of weight and cost savings, and therefore has been employed in numerous automotive interior and exterior parts. Precision cutting of the composite parts is important to minimize material loss with better surface finish. This paper focuses on the types and manufacturing of composites with machinability characteristics of fiber-reinforced composite. Finally, the study concerns the employment of gray relational analysis to determine the optimized cut characteristics in precision cutting of cocoa pod husk fibers-reinforced thermoplastic polyurethane composites. The cut characteristics, namely kerf width (material loss) and surface roughness (surface finish) are optimized as a function of blade speed, feed rate of the blade, and cocoa fiber loading in the composite. A central composite design method is used to determine the multi-performance characteristics of cut using precision linear saw. The set of the optimized processing parameters is determined based on the highest grade at minimum feed rate (12.1 mm s–1), minimum blade speed (2500 rpm), and minimum fiber content (20% by weight). The influence of each parameter on cut quality is also discussed where the effects of feed rate and blade speed were more significant as compared to the fiber content

Towards Three-Dimensional Experimental Investigation on Fish Sperm Mobility in Oily Water By Digital Holographic Microscopy for Environmental Protection

Fish is the primary source of protein and essential nutrients for growing global population. Fish and fisheries products provide sustainable income with multi-dimensional livelihoods for numerous communities across the world. The contribution of fisheries and aquaculture to food security and nutrition is largely affected by environmental quality. Addressing the growing demands for fish, conservation of natural resources and environmental protection are undeniably important. A large variety of studies have been conducted examining physiology of fish sperm, understanding the combined effects of heavy metals, inorganic and organic pollutants on sperm motility, to name but a few. However, there is a limited study concerning the dynamic behaviour of fish sperms in polluted environments and its consequences on historical sperm motility. In this research, a custom-made digital holographic microscope has been successfully designed, calibrated and tested. Digital holographic microscopy (DHM) is a promising three-dimensional fluid flow measurement technique as it can easily provide detailed three-dimensional microscale observation and visualization of flow field in real time. Initial preliminary experiments using 10 μm polystyrene microspheres as fish sperm substitutes flowing in oily water were performed and demonstrated promising results

Laser-assisted high speed machining of aluminium alloy: The effect of ultrasonic induced droplet vegetable-based cutting fluid on surface roughness and tool wear

Laser-assisted high speed milling is a subtractive machining method that employs a laser beam to thermally soften material's surface in order to enhance machinability at high material removal rate with improved surface finish and tool life. Ultrasonic-assisted milling is an advanced manufacturing technology where ultrasonic source is connected with cutting tool, that has demonstrated effectiveness in terms of acquiring good surface topography and high surface finish. Despite this, its application is limited at low speed and is not widely applied for high volume production. Here, an ultrasonic-induced droplet delivery method is employed as an efficient method for laser-assisted high speed milling operation. In this study the effect of ultrasonic-induced droplet cutting fluid on surface roughness and flank wear of 6082 aluminium alloy is experimentally investigated using response surface methodology (RSM) and the results are compared with the conventional droplet cutting fluid. The ultrasonic creates acoustic streaming, acoustic cavitation as well as cavitation bubbles in the cutting fluid. This acoustic energy is able to increase the local temperature of cutting fluid with which the laser power combinedly softens the machined surface, thereby reducing the tool abrasion and surface roughness. The results show a favourable reduction in surface roughness and flank wear by 11.04 and 1.37%, respectively, in comparison to conventional droplet cutting fluid. Clearly, the laser-assisted high speed milling with ultrasonic-induced droplet cutting fluid will be applicable in high production rate manufacturing where it will yield less production time, low operating cost and, at the same time, give better surface finish and longer tool life. © 2021 Old City Publishing. All rights reserved

Fabrication of Flexible Microfluidic Strain Sensor by Laser Micromachining for Hand Motion Tracking

Various types of strain sensors have been developed for providing reliable monitoring of human health. Microfluidic strain sensors is favourable for such an application due to its outstanding performance under a variety of three-dimensional deformations on the basis of elastic channel deformation. In this study, we report for the first time laser-machined micro-channels on fabricated epoxy substrate. Fabrication of flexible microfluidic sensor using soft clear epoxy is investigated. A ratio of 100:30 of epoxy resin-to-hardener results in a flexible and elastic epoxy layer. Laser micromachining (ablation) technique at varying parameters is conducted using Taguchi Experimental Design. Low number of passes for both kerf depth and kerf width gives an optimum response, while laser power and laser cutting speed differs for kerf width and kerf depth. Microstructure imaging is carried out using scanning electron microscopy for heat-affected zone examination

Modelling of Water-Assisted Flame Synthesis of Carbon Nanotube using Counterflow Diffusion

Research on carbon nanotubes (CNTs) has been performed extensively. On top of that, water-assisted synthesis of CNT has started to emerge with captivating effect towards growth of CNT. The present study investigates a baseline inlet condition for water assisted case utilizing diffusion flame that imitates the temperature distribution and growth region of CNT without water vapor, on the basis of experimental data of non-water assisted high yield CNTs. To affirm the effect of water vapor, 35% to 70% of water vapor has been added replacing the fuel side nitrogen content. The results prove that water vapor suppresses the flame where the maximum temperature drops with increasing concentration. Consequently, this affects the length and growth region of CNTs. The region width has been reduced for about 7.4% to 18.5% with water vapor. This shows that excessive water poorly affects the growth of CNTs. On the other hand, the region has also shifted for about 0.64 mm to the fuel side (5.7%) from the origin when 70% of water vapor was added. Following this, the impact of catalyst towards CNT growth is subsequently presented whereby a comparison is made between Fe and Co to synthesize CNT using flame synthesis. Based on the result, Fe possess better activation for the CNTs to grow as compared to Co. A significant difference between the predicted CNT length for Fe (147 μm) and Co (56 μm) is attributed to their diffusivity values

A Feasibility Study Of Low-Power Laser Trepanning Drilling Of Composite Using Modified DVD Writer

In the present study, laser cutting of cotton fiber composite laminate is experimented using a modified DVD writer drive. A 250 mW diode laser is initially extracted from a DVD writer drive, and then regulated by a custom-made laser driver circuit designed using a Proteus® software. Experimental tests are carried out using multi-pass laser trepanning drilling at different drilling speeds and standoff distances (SODs). The cut quality is evaluated by measuring the extent of both oxide and resolidified resin regions. It was discovered that high speed of trepanning drilling and positive SOD significantly improve cut quality. Furthermore, positive and negative SODs require relatively high number of passes at different drilling speeds. From SEM micrographs, it is found out that the crack formation and fiber protruding happen in the drilling area due to thermal stresses and matrix vaporization

Laser-Assisted High Speed Machining of 316 Stainless Steel: The Effect of Water-Soluble Sago Starch Based Cutting Fluid on Surface Roughness and Tool Wear

Laser-assisted high speed milling is a subtractive machining method that employs a laser to thermally soften a difficult-to-cut material’s surface in order to enhance machinability at a high material removal rate with improved surface finish and tool life. However, this machining with high speed leads to high friction between workpiece and tool, and can result in high temperatures, impairing the surface quality. Use of conventional cutting fluid may not effectively control the heat generation. Besides, vegetable-based cutting fluids are invariably a major source of food insecurity of edible oils which is traditionally used as a staple food in many countries. Thus, the primary objective of this study is to experimentally investigate the effects of water-soluble sago starch-based cutting fluid on surface roughness and tool’s flank wear using response surface methodology (RSM) while machining of 316 stainless steel. In order to observe the comparison, the experiments with same machining parameters are conducted with conventional cutting fluid. The prepared water-soluble sago starch based cutting fluid showed excellent cooling and lubricating performance. Therefore, in comparison to the machining using conventional cutting fluid, a decrease of 48.23% in surface roughness and 38.41% in flank wear were noted using presented approach. Furthermore, using the extreme learning machine (ELM), the obtained data is modeled to predict surface roughness and flank wear and showed good agreement between observations and predictions