Department of Agricultural Engineering

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    Shear strength at Sisal fibre-polyester resin interfaces: use of inverse gas chromatography to study pretreatment effects
    (Taylor & Francis, 2012-04-02) Price, G J; Pastor, M L; Towo, A N; Packham, D E; Ansell, Martin P.
    Inverse gas chromatography, IGC, has been used to investigate changes to the surface of Sisal fibres on treatment with sodium hydroxide. By determining the retention of a series of alkane probes and of probes with acidic or basic character, it was shown that little change to the chemical nature of the surface occurs as measured by the enthalpy of adsorption of alkane probes or the dispersion component of the surface free energy. This IGC study supports the conclusion of previous work involving S.E.M. which suggested that the major effect of the treatment was the removal of weak or adventitious layers from the substrate surface, thus increasing the interfacial shear strength when incorporated into polyester resin.
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    Weibull analysis of microbond shear strength at sisal fibre-polyester resin interfaces
    (VSP, 2005) Towo, Arnold; Ansell, Martin P.; Pastor, M-L; Packham, D
    An analysis has been made of the tensile strength of sisal fibres and the interfacial adhesion between fibres and polyester resin droplets. Density and microscopy methods were used to determine the cross-sectional area of the sisal fibres. The average tensile strength of treated sisal fibres decreased by a modest amount following treatment with 0.06 M NaOH. However, this treatment resulted in a substantial increase in the interfacial shear strength at the sisal fibre to polyester resin interface. Weibull analysis has been used successfully to analyse variability in tensile strengths and interfacial shear strength using probability of failure plots. Scanning electron microscopy has revealed the shape of resin droplets on the surface of treated and untreated sisal fibres and contact angles are much lower for droplets on treated fibres. Damage to the surface of fibres has been examined following shear testing. Weibull analysis is an effective tool for characterising highly variable fibre properties and evaluating the level of adhesion between polymer resin and the fibre surface.
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    Fatigue of sisal fibre reinforced composites: Constant-life diagrams and hysteresis loop capture
    (Elsevier, 2007-09-06) Towo, Arnold; Ansell, Martin P.
    Composite materials have been manufactured using untreated or 0.06 M NaOH treated sisal fibre bundles in a polyester or epoxy matrix. Mechanical tests have been conducted to establish the static properties of the composites which have been used to calculate the maximum loads used during fatigue testing. Composites containing alkali treated fibre bundles have better mechanical properties than those with untreated fibre bundles. Alkali treatment has the greatest effect for polyester resin matrices. S–N diagrams constructed from fatigue data at stress ratios of R = 0.1 (tension–tension) and R = -1 (reversed loading) show improvement in the fatigue lives of composites following alkali treatment of sisal fibre bundles. Constant-life diagrams for epoxy matrix composites with untreated or alkali treated fibre bundles show the superiority of the alkali treated fibre composites for low cycle fatigue. Composites loaded in tension–tension fatigue (R = 0.1) exhibit hysteresis loops with diminishing loop area with increasing number of cycles. The composites loaded in reversed loading fatigue (R = -1) generate loops with increasing loop area with increasing number of cycles. Failure modes in tension–tension and reversed loading are very different with a distinctive buckling failure mode at R = -1.
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    Main Factors Affecting Development and Transfer of Technologies for R&D Institutions in Tanzania
    (2015) Mwanza, J. S.; Elias, Erasto; Majaja, Bashira A.
    Technologies are essential inputs in pursuit of the developmental goals of any country in particular the developing countries to achieve sustainable development and also have a crucial role to play in achieving the Millennium Development Goals. The majority of the local industries in Tanzania use turnkey plants and process machinery imported from abroad for specific production lines. The imported technology may not be completely fit to the local conditions and it is the duty of the R&D institutions to match it with the local needs and conditions. Therefore, one of the major corrective measures required is to promote technology development and transfer from local R&D institutions to industrial enterprises. This paper focuses on how technological capabilities were enhanced by R&D Institutions in the development and transfer of technologies and the results of the enhancement. The discussion of the findings is based on the preliminary data collected from questionnaires and interviews which was administered to R&D Institutions in Tanzania.
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    Cutting of Sisal
    (1989) Majaja, Bashira A.; Chancellor, W. J.
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    Anthropometric Data Collection of the Tanzanian Worker
    (1984) Majaja, Bashira A.; Bhandari, V. K.
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    Investigation of Motorcycle Design Improvements with Respect to Whole Body Vibration Exposure to the Rider
    (2015-03) Ndimila, Benjamin W.; Majaja, Bashira A.; Elias, Erasto; Nalitolela, Noel G.
    Various studies on motorcycle rider whole body vibration (WBV) exposure indicate that the vibration magnitude in the vertical direction is the most severe as compared to magnitudes in lateral and transverse directions. For the sake of understanding and doing evaluation of the vibration environment of the motorcycle rider and various motorcycle component bodies, a mathematical model was developed. The main intention was to investigate the physics of motorcycle suspensions, study vibration magnitudes in vertical direction in terms of displacement and acceleration on a cyclist depending on motorcycle and road parameters, also attempt to determine the location of the rider’s seat with least vibration magnitudes. In this case, analytical methods for studying response to harmonic base excitation of the rider and other component bodies of a motorcycle were applied with the aim to analyze their vibrational behaviour. The two wheeled motorcycle with a rider model was introduced. The equations of motion for the model were formulated. The matrix form of the equations was written solved and simulations were done. The vibration behaviour in vertical direction of various component bodies of the motorcycle model was observed.
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    Evaluation and Optimization of Sisal Harvesting Systems
    (1984) Shine, S. J.; Bhandari, V. K.; Majaja, Bashira A.
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    Application of Web 2.0 Tools in Delivering Library Services: A Case of Selected Libraries in Tanzania
    (2012) Muneja, Paul S.; Abungu, Apollo K.; Makori, E. O.
    This paper explores the adoption and application of Web 2.0 tools in delivering library services in selected libraries in Tanzania. The paper investigates the ways in which librarians are adopting the tools to enhance services. The study examines Web 2.0 tools used by libraries in delivering their services, factors influencing the use of Web2.0 tools, challenges and prospects in their usage. The findings reveal that librarians in Tanzania have started using various Web 2.0 tools in varying degrees and the most common tool is Facebook. The findings also reveal that most librarians are motivated to use these tools because they are free and open source and relatively easy to apply. Sharing resources, communication and promotion of services were the main reasons why this tools are used. Challenges include unreliable power and internet access. Advantades included, increase in resources awareness, better communication and interest in library usage. Recommendations suggest that institutions should develop policies that adopt the use of emerging technologies and alternatives to reliable power sources such as solar and generators.
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    (American Society of Agricultural Engineers, 1997) Majaja, B. A.; Chancellor, W. J.
    With current renewed interest in natural fibers, traditional suppliers of sisal such as those in Tanzania are looking to reestablish high production levels despite the shortage of field workers for laborious and hazardous harvest operations. Cutting force and energy determinations made with Agave sisalana leaves indicated that these parameters were well within the capabilities of workers even at a work rate twice that of current levels. Measurements of leaf bending resistance, friction coefficients, and mass distribution were made to assist designers of equipment to handle sisal leaves. Physical simulations of cutting operations with worker aids aimed at obviating the stooping currently required of harvest workers, indicated that only tools powered by some external energy source could match or exceed the current traditional work rate of one leaf per 2.9 s. Among the design concepts formulated for in-field leaf handling, collection and transport devices, there was an indication that an inverted umbrella type leaf catcher may have economic potential. Because the cutting operation is complex and selective, it was concluded that the most immediate potential for sisal harvest mechanization would involve manually operated cutting mechanisms using worker aids, combined with mechanized infield collection, handling and transport of leaves.
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    Fatigue evaluation and dynamic mechanical thermal analysis of sisal fibre–thermosetting resin composites
    (Elsevier, 2007-08-10) Towo, Arnold N; Ansell, Martin P.
    Sisal composites were manufactured in a hot press from as-received and 0.06 M NaOH treated sisal fibres with polyester and epoxy resin matrices. Tensile tests were conducted on the composites to establish loading levels for fatigue testing. A fatigue evaluation of the sisal fibre–thermosetting resin composites was undertaken at loading levels of 75%, 60%, 50% and 35% of static tensile strength and at an R ratio of 0.1. S–N curves for the composites are presented for untreated and 0.06 M NaOH treated sisal fibres. Epoxy matrix composites have a longer fatigue life than polyester matrix composites. The effect of chemical treatment on fatigue life is significantly positive for polyester matrix composites but has much less influence on the fatigue life of epoxy matrix composites. Dynamic mechanical thermal analysis (DMTA) was conducted on samples from failed epoxy resin fatigue specimens and the influence of fatigue history on the Tanδ peak temperatures and Tg of the composites is examined. Significant shifts in Tg are observed following fatigue testing. The fatigue performance of natural fibre composites suggests that they are suitable for use in dynamically loaded structures and may be used as a substitute for Glass Fibre Reinforced Plastic composites in fatigue.