Papers by Author: Stuart Barnes

Abstract: The objective of this study was to develop clad layer by producing a Silicon Carbide (SiC) particle reinforced Metal Matrix Composite (MMC) using the iron based alloys (P25) as the matrix material. Direct laser cladding was carried out by melting the clad materials and depositing them onto a mild steel substrate. A two gravity feed system was used in this study which contained of SiC particles and iron based powder as separate powders. The intention was to melt the iron based powder and incorporate the SiC particles. Decomposition of SiC particles was observed and only a few SiC particles were found in the clad matrix. Microhardness results showed that laser clad layer had higher hardness which more than 1000 HV and hence potentially better wear resistance that base material. However, most of the SiC had evaporated which created porosity in the melt pool due to the decomposition of SiC and the resultant gas which was trapped in clad layer did not have enough time to escape from the melt pool due to the rapid solidification. Therefore, a blown powder technique is recommended for overcome this problem.

Abstract: Machining of Carbon Fibre Composite (CFC), particularly drilling is frequently employed in many industries especially when dealing with joining, assembly and structural repair of the parts. This paper summarizes the properties of the CFC as well as the appropriate material and geometry of the cutting tool that should be used when drilling of the CFC in order to optimize the drilling performance. In addition, this work also presents the literature review on the relationship between cutting speed, feed rate, tool wear, thrust force and damage of the drilled CFC. The nature and heterogeneous structure of CFC often resulted in difficulty during their machining in terms of rapid tool wear and high thrust force. As a result, this always results in the damage of the drilled parts. Furthermore, higher cutting speed and lower feed rate are also recognized as significant factors which contribute to rapid wear of the cutting tool. Therefore, the use of tungsten carbide cutting tools, cutting fluids and cryogenic machining is seen to be a practical technique in optimizing the drilling performance involving CFC. In general, this work intends to provide a basic guideline and understanding regarding drilling of the CFC.

Abstract: Machining of Carbon Fibre Composites (CFCs) particularly drilling, is frequently employed in industry especially when dealing with joining, assembly and structural repair of the parts. However, the nature and heterogeneous structure of CFCs often results in rapid wear of the cutting tool. This research studied the relationship and compared the effect of drilling a CFC plaque without cutting fluid, with conventional cutting fluid and with cryogenic cooling at constant cutting speed of 94 m/min and feed rate of 0.065 mm/revolution using tungsten carbide twist drill. The conventional cutting fluid was supplied continuously to the drill and the CFC plaque during the drilling cycle; while for the cryogenic cooling tests, the drill tip was immersed in liquid nitrogen for 10 and 30 seconds prior to drilling the CFC. It was found that the tool wear increased with the increasing number of drilled holes at all machining conditions. After drilling of 325 holes, the largest tool wear observed was 181 μm which was produced when drilling the CFC plaque with conventional cutting fluid. The corresponding tool wear for drilling with cryogenic cooling was 164 μm and the smallest tool wear of 155 μm was observed during dry drilling. Dry drilling produced the smallest tool wear because the heat generated reduced the strength of the CFC, particularly polymer matrix. Therefore, this situation led to easier machining of CFC materials; consequently reduced the wear of the tool.

Abstract: The objective of this research was to develop a new form of clad layer by producing a Silicon Carbide (SiC) particle reinforce Metal Matrix Composite (MMC) using the iron based alloys as the matrix material. A 1.2kW continuous wave CO₂ laser was used in this research. A gravity feed system was used with one powder feed which contained different percentages of SiC particles and iron based powder. Experimental results showed that the decomposition of SiC particles was observed and only a few SiC particles were found in the clad matrix. High micro hardness values were found in the SiC clad which were in excess of 1000 HV. However, most of the SiC were evaporated which created porosity in the melt pool. Therefore, blown powder technique is recommended for overcome this problem.