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Development and Evaluation of the Mechanical Properties of Coconut Fibre Reinforced Low Density Polyethylene Composite

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Open Journal of Composite Materials 2022年第3期12卷 83-97页

作者： Ahmed mohammed Bukar abubakar mohammed el-jummah Abba Alhaji Hammajam Department of Mechanical Engineering University of Maiduguri Maiduguri Nigeria

This research work developed and evaluated the mechanical properties of coconut fibre reinforced low density polyethylene (LPDE) composite material. The effect of fibre loading on the mechanical properties: tensile, flexural, and impact of the developed composite material have been investigated. Also carried out was the effect of fibre loading on the water absorptivity of the developed material. Sample categories of the developed composite were prepared by varying the fibre contents by weight at 0%, 10%, 20%, and 30%. The aim is to reduce the excessive waste disposal of LDPE materials that are largely found in the form of disposed water package materials (or pure water sachets) that usually affects the environment in the form of pollution. The water retting process was applied in extracting and cleaning fibre (or coir), while the mixed coir-LDPE (or developed composite material) was prepared by Compression Moulding Technique (CMT). The tensile and flexural properties were tested using Hounsfield Monsanto Tensometer (type w) while the impact properties were tested using the Charpy Impact testing machine. The microstructure of the composite was investigated using Scanning electron Microscopy (SEM). The fractured surface morphology of the composite samples indicated a homogeneous mixture of the coir fibre and LDPE matrix. However, weak interfacial bonding between the coir fibre and LDPE matrix was also observed. The analysis of the water absorptivity showed that the developed composite materials have low water absorptivity at low fibre loading. However, at higher fibre loading, the water absorptivity increases significantly.

关键词： Coconut Fibre Low Density Polyethylene Composite Mechanical Properties Water Absorptivity

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The Green Composites: Millet Husk Fiber (MHF) Filled Poly Lactic Acid (PLA) and Degradability Effects on Environment

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Open Journal of Composite Materials 2019年第3期9卷 300-311页

作者： Abba Alhaji Hammajam abubakar mohammed el-jummah Zahari Nur Ismarrubie Department of Mechanical Engineering University of Maiduguri Maiduguri Nigeria Department of Mechanical and Manufacturing Engineering Universiti Putra Malaysia Serdang Selangor Malaysia

This study provides an overview on green composites degradability. Practically, the main drawbacks of using natural fibers are their poor dimensional stability, degradability and high degree of moisture absorption. While, end use of product from natural fiber filled or reinforced composites has become subject of concern to material engineers and scientist. The major properties of natural fiber reinforced polymer composites are greatly dependent on the hydrophilic tendency and dimensional stability of the fibers used, morphology aspect ratio for long fiber, while voids for powder fibers. The effects of chemical treatments on cellulosic fibers that are used as reinforcements for thermoplastics were studied. The chemical source for the treatments is alkalization. The significance of chemically-treated natural fibers is seen through the improvement of mechanical properties. The untreated fiber composites degrade faster in municipal soil compared to treated fiber composites.

关键词： Degradability Composite Fibers Poly Lactic Acid Millet Husk

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Experimental Investigation on the Thermal Properties of Gypsum Plaster-Rice Husk Ash Composite

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Open Journal of Composite Materials 2022年第4期12卷 131-138页

作者： Nuhu Caleb Amulah abubakar mohammed el-jummah Abba Alhaji Hammajam Usman Ibrahim Department of Mechanical Engineering Faculty of Engineering University of Maiduguri Maiduguri Nigeria Department of Mechanical Engineering Faculty of Engineering Nigerian Army University Biu Nigeria Department of Mechanical Engineering Faculty of Engineering Ramat Polytechnic Maiduguri Nigeria

This experimental investigation aims at evaluating the thermal properties of rice husk ash (RHA)—filled gypsum plaster composite for potential applications, as insulating materials. The thermal conductivities of composites of gypsum plaster reinforced with RHA at 0%, 10%, 20%, 30%, and 40% volume fractions were determined experimentally using Lee’s disc method. The experimental results show that integrating RHA reduces the thermal conductivity of gypsum plaster and improves its insulation capacity. The results obtained from the experiments were compared with the Rule of Mixture Model, Maxwell Model, and Russell Model. It was observed that the thermal conductivities obtained from experiments and the theoretical models decreased with an increase in the volume fraction of RHA. The errors associated with the models with respect to experimental results are on the average of 28.7% for Mixture Rule, 31.6% for Russel Model, and 18.8% for the Maxwell Model. An agricultural waste like RHA can be beneficially used for the preparation of composites and, due to improved insulation capability, these composites can be used for applications such as insulation boards and sheathing, hardboard, ceilings of roofs, decorations, etc.

关键词： Rice Husk Ash Thermal Conductivity Gypsum Plaster Lee’s Disc Method Agricultural Waste

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Experimental Investigation on the Thermal Properties of Gypsum Plaster-Rice Husk Ash Composite

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Open Journal of Composite Materials（复合材料期刊） 2022年第4期

作者： nuhu caleb amulah abubakar mohammed el-jummah abba alhaji hammajam usman ibrahim

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Conjugate Heat Transfer Predictions of Gas Turbine Hot Walls Jets Cooling: Influence of Short Hole Grid Resolutions Using Computational Fluid Dynamics*

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Journal of Power and Energy Engineering 2023年第10期11卷 1-16页

作者： abubakar M. el-jummah Shehu A. Abdulrahman Alhaji S. Grema Department of Mechanical Engineering University of Maiduguri Maiduguri Nigeria Department of Mechanical Engineering Nigerian Army University Biu Borno Nigeria Department of Chemical Engineering University of Maiduguri Maiduguri Nigeria

Short hole investigations relevant to gas turbine (GT) hot walls cooling heat transfer techniques, were carried out using computational fluid dynamics (CFD) combined with conjugate heat transfer (CHT) code. The CFD software are commercial ones: ICEM for grid modelling and ANSYS Fluent for the numerical calculation, where symmetrical application prevails. The CFD CHT predictions were undertaken for Nimonic-75 metal walls with square (152.4 mm) arrays of 10 holes, whereby the lumped heat capacitance method was applied in order to determine the surface average heat transfer coefficient (HTC), h (W/m2 K) and the dimensionless Nusselt number, Nu. The major parameters considered for the short hole geometries are the pitch to diameter, X/D and length to diameter, L/D ratios and both were varied with range of D values, but X of 15.24 mm and L of 6.35 mm kept constant. Also applied, are variable mass flux, G (kg/s∙m2) and were used in predicting the flow aerodynamics in the short holes. The predictions were for classic thermal entry length into a round hole, as vena contracta, flow separation and reattachment dominates the holes, hence the development of thermal profile through the depth of the GT hot walls. Additionally, the acceleration of the flow along the wall surfaces as it approaches the holes, was a significant part of the overall heat transfer. This was shown to be independent of the hole length, even though the L/D parameter is a critical component to enhanced heat transfer. The CFD CHT predictions showed that validation of the HTC h, Nu and pressure loss, ∆P are in better agreement with measured data and within reasonable acceptance. The ∆P agreement signifies that the aerodynamics were predicted correctly, which is also the reason why the HTC expressed per wall hole approach surface area and Nu were better predicted. This illustrates how effective and efficient the wall internal heat transfer cooling is for gas turbine hot wall heat transfer

关键词： Lumped Heat Capacitance Thermal Entry Length Symmetrical Application Flow Separation Flow Reattachment

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