Research Publications/Outputs

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Browsing Research Publications/Outputs by browse.metadata.cluster "Materials Science and Manufacturing"

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    The effect of curing conditions on bonded repair with boron/epoxy composite patch of aircraft skin
    (2017-07) Malika, Khodja; Hamida, F; Wahid, O; Rossouw, Pierre; Corderley, Gary
    Composite materials are becoming more important in the construction of aerospace structures. Bonded joints fulfil a significant role in the development of new technologies, particularly in the aerospace industry where they give new possibilities for connecting structural elements. The Composite Patch Bonded Repair is a method that can be used for repairing the metallic and composite structures. The method includes the following steps: surface preparation prior to bonding, the placing of Composite Patch and a cure cycle for the composite prepreg and the adhesive film.The primary advantages of composite materials for repair are their high strength, relatively low weight, and corrosion resistance. The purpose of this research is to define the influence of the curing time and temperature on bonded repair structures, by bonding the boron patch composite to the Aluminium 7075-T6 with the use of Structural Adhesive Film FM73K for lower residual stresses by analysis the distortion due the bending curvature. A bending behaviour is observed at the bond area of samples were made for a study of Fatigue crack growth in bonded repair of damaged aircraft structure. Analysis on metallic aircraft structures development and qualification aspect, indicated secondary bending structures curvature from both single side and double side doubler in the repair area did influence the behaviour; they recommended that would require detailed investigation. One way of minimising the level of residual stress is to cure the repair at the lowest possible temperature. FM-73K is a fracture toughened adhesive used for bonded repairs that are typically cured at 120°C for 1 hour. However, during the curing process, adhesively bonded composite/metal laminate structures that are held at elevated temperatures over 120 °C as per data sheet recommendation for material processing, very high residual stresses could build up because of the difference in coefficients of thermal expansion (CTE) for different materials. This thermal mismatch results in delamination or debonding of materials, which facilitates fatigue crack growth in the polymer/metal interface.
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    Effect of milling speed on the formation of Ti-6Al-4V via mechanical alloying
    (2018-10) Daswa, Pfarelo; Gxowa, Zizo; Monareng, Mathibe JI; Mutombo, Kalenda
    Ti-6Al-4V alloys are well known for good corrosion resistance, excellent surface oxide biocompatibility and high specific strength. This paper investigates the influence of milling parameters on the formation of Ti-6Al-4V alloy processed using mechanical alloying. A mixture of CP Ti and master alloy (60Al-40V) powder were milled using a high energy ball mill (HEBM) in order to produce a mechanically alloyed Ti-6Al-4V alloy powder. Milling was carried out at a constant milling time of 5 hours at varying speeds of 800, 900, 1000 and 1100 rpm in order to investigate the influence of speed on the formation of Ti-6Al-4V alloy. Scanning electron microscopy with energy dispersive analysis (EDX) and X-ray diffraction (XRD) were performed on the mechanically alloyed powder to investigate the chemical homogeneity and the formation of alpha (a) and beta (ß) phase during the mechanical alloying of CP Ti and 60Al- 40V.
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    Metal injection moulding of a 17-4 PH stainless steel: A comparative study of mechanical properties
    (2018-10) Machaka, Ronald
    While the metal injection moulding (MIM) of the precipitation-hardenable 17-4 PH stainless steel has found wide-ranging applications in a number of industries and popularity as a workhorse alloy, data on the as-sintered properties ‘that can be expected’ is limited and scattered in the literature. A quantitative comparison of the mechanical properties of assintered 17-4 PH materials prepared via MIM is currently not available in the literature. -5 µm, -15 µ m, and -45 µ m starting 17-4 PH stainless steel powder materials and their bimodal mixtures were used to formulate with feedstocks investigated in this work. This paper compares the as-sintered mechanical properties resulting from the measured tensile tests against those properties reported in the literature, those specified in the ASTM and MPIF standard minimum specification for MIM materials, those properties specified in the material suppliers’ datasheets and the mechanical properties of 17-4 PH wrought material – for completeness. While the as-sintered properties of the CSIR 17-4 PH material are generally lower than expected, the comparison shows that the measured properties are within the industry standard specifications. Findings from this study are a testament that a range of mechanical properties is feasible from the 17-4 PH alloy.