Browsing by Author "Mills, Andrew"

Now showing 1 - 9 of 9
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    Comparative life cycle assessment of aluminium and CFRP composites: the case of aerospace manufacturing
    (Springer, 2024-02-24) Atescan Yuksek, Yagmur; Mills, Andrew; Ayre, David; Koziol, Krzysztof K. K.; Salonitis, Konstantinos
    As climate change intensifies and existing resources are depleted, the need for sustainable industries becomes more important. The aviation industry is actively addressing environmental concerns by enhancing fuel efficiency and adopting lighter materials, especially carbon fibre composites. Research has proven that the use of carbon fibre composites provides cumulative benefits in reducing fuel consumption over the entire life cycle of an aircraft. However, existing studies are lack of a comprehensive exploration of the diverse impacts associated with composite manufacturing processes and recycling methods. To address this gap, a comparative life cycle assessment analysis covering the materials’ manufacturing, operation, and end-of-life phases is conducted. This analysis includes aluminium alloy and five different carbon fibre composite materials produced with varied constituents and manufacturing methods. Composite manufacturing processes, encompassing carbon fibre production, resin selection, and composite manufacturing methods, are considered. Weight savings based on the mechanical properties of utilised composite type are also taken into account. Results highlight the potential to mitigate the environmental impact of composite materials through strategic choices in constituent types, manufacturing processes, and disposal scenarios. Moreover, break-even distances indicate that aluminium becomes more environmentally detrimental than the analysed composite structures beyond a flight distance of 300,000 km.
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    Damage resistance of aricraft wing structure using low cost carbon fibre composite materials
    (Cranfield University, 2010-12) Zhu, Lingang; Mills, Andrew
    This thesis investigated the damage resistance of aircraft wing structure using low cost carbon fibre composites. Experiments had been carried out to investigate their impact behaviour, damage characteristics and residual compression strength. Current aircraft pre-impregnated materials processed by autoclave moulding and also some low-cost fibre preforms using vacuum infusion moulding were compared in this research. Novel tufting technology and veils were taken into consideration to find a cost-efficient method of improving the damage resistance of carbon fibre panels. Initial damage was induced using a falling weight (2.38Kg) apparatus mounting a 16mm hemispherical tip. Various energy levels were applied for different panels, but the energy to thickness ratio was constant. Visual inspection and ultrasonic C-scans were carried out to investigate both exterior and interior damage (fibre fracture, delamination, etc.). Micrographs of the cross-section through the impact point were employed to characterise the fracture mechanisms. The detailed Compression After Impact (CAI) procedure was recorded and presented in this thesis. In order to investigate how much ultimate compression strength was reduced by impact, plain compression strength was also measured. The behaviour of different materials, including damage size, damage shape and construction and residual compression strength were utilised in comparing the different effects on impact of different components such as fibre, fabric, interleaving of toughening layers and through thickness reinforcement. The results show that unidirectional fibre was more sensitive than woven fibre and that tufting and veils were the most affordable and efficient methods to improve the damage resistance of the laminates studied. Over 30% increase in residual compression strength was achieved via these methods.
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    Energy absorption for crashworthiness in carbon-fibre braided composite structures
    (Cranfield University, 2004) Lazarus, Simon David; Mills, Andrew
    In this investigation the effects of material, structural and testing parameters of carbon epoxy braided composite tubes were analysed with respect to their performance in crush and impact conditions. An original method of manufacturing the composite tubes with vacuum infusion together with an expandable foam core to form multi-cellular structures was used. Low cost, 24k tow carbon fibre braids were used and their performance was compared with that of the more expensive l2k tow size fibres. The specimens produced were axially crushed at constant quasi-static low velocities and at higher impact velocities using an instrumented falling weight machine. Load displacement data gathered from such tests were used to evaluate the test specimens with respect to their specific energy absorption values. The effects of a number of parameters including fibre tow size, braid architecture, resin content and loading type were evaluated. From the experimental results analysed from the test specimens it can be concluded that: - The 24k fibre showed lower specific energy absorption values than specimens made from l2k fibre. Epoxy resin content rather than epoxy resin type can significantly affect the specific energy absorption values. In general, specimens tested in impact loading exhibited lower specific energy absorption values than the same specimens test in quasi-static crush. A reasonably good correlation between global density and specific energy absorption for the type of structures examined was found
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    Manufacture of a rotor blade pitch horn using binder yarn fabrics
    (International Committee on Composite Materials, 2009-07-31) Weiland, F.; Weimer, C.; Katsiropoulos, C. V.; Pantelakis, S. G.; Asareh, Mehdi; Cartié, Denis; Mills, Andrew; Skordos, Alexandros A.; Dufort, L.; De Luca, P.; Pickett, A. K.
    The use of binder yarn fabrics in rotor blade applications is investigated in this work. A preforming procedure is incorporated in manufacturing, resulting in higher degree of automation and a reduction of process steps. The performance of the process is evaluated with respect to cost savings compared to prepregging technologies.
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    Mapping the effect of variable HPT blade cooling on fuel burn, engine life and emissions for fleet optimization using active control
    (AIAA, 2023-01-19) Pontika, Evangelia; Laskaridis, Panagiotis; Montana Gonzalez, Felipe; Jacobs, Will; Mills, Andrew
    Modern aero engines have increasingly sophisticated control systems. The aim for next-generation aircraft is to have even more adaptive and flexible control systems to enable the optimization of economic aspects, operational aspects and fleet management. Among others, an engine control variable that has the potential to offer various life and fuel burn benefits at different flight phases is the High-Pressure Turbine (HPT) blade cooling air. The HPT blades have demanding cooling requirements to protect their life and decelerate HPT efficiency degradation. However, any engine bleed has a penalty in efficiency and results in increased fuel consumption. Previous generation aircraft have a fixed relative blade cooling flow based on a design choice for a trade-off between life and efficiency. However, with adaptive control systems, there is an opportunity to extract the maximum potential benefit under different flight phases and scenarios. With this opportunity comes the challenge of increased complexity in engine behavior necessitating detailed modeling to quantify effects on lifing, fuel burn and safety. This paper focuses on modeling the performance, lifing and emission effects of variable HPT blade cooling air at take-off, climb and cruise. First, the effect of variable cooling on the Turbine Entry Temperature (TET), Exhaust Gas Temperature (EGT), fuel flow, lifing and NOx emissions are modeled at operating point level while the thrust requirement is achieved. Subsequently, a Design of Experiment is performed at mission level with the relative cooling flow at take-off, climb and cruise as the independent variables to train surrogate, analytical models. The analytical models are applied in the probabilistic modeling of system failure rates under different cooling flows. Optimization of engine control variables, in this case, the HPT blade cooling, requires analytical expressions that can be used in objective functions. These analytical models will inform fleet optimizers and active control systems to facilitate the implementation of fleet decisions such as reducing direct operating costs (fuel cost, maintenance reserves, NOx taxation), meeting NOx requirements of airports and extending Time-on-Wing (TOW). The findings indicate that take-off offers an opportunity to protect HPT life with increased cooling, but caution should be exercised in regard to the damage increase at the downstream non-cooled hot gas path components. A decrease in cooling flow at cruise, which is less detrimental to engine life, can offer significant fuel savings and climb can be investigated for the optimum economic trade-off between life and fuel burn as a response to economic scenarios.
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    Resin transfer moulding: Novel fabrics and tow placement techniques in highly loaded carbon fibre composite aircraft spars
    (Sampe Society for the Advancement of Material, 2007-06-30T00:00:00Z) Mills, Andrew; Patel, Zahir; Dell'Anno, Giuseppe; Frost, Matthew
    A BAE Systems /UK EPSRC funded project Flaviir, is investigating the design and manufacture of low cost carbon fibre composite airframe structures. Novel binder coated unidirectional fibre tapes and tows were developed to enable the design of optimised primary structures. The RTM technique was applied to mould net shape sections of spar components. Various designs of wing attachment lugs were manufactured with a range of reinforcement materials, including non crimp fabric, novel binder coated tapes and conventional unidirectional prepreg. Alongside these, a novel technique termed optimised tow lay up (OTL) was used to reduce the weight. Binder coated carbon fibre tow is placed around the structure in the principal stress directions to increase both bearing strength and overall component stiffness. The novel materials, manufacturing technique and initial element test results are presented.
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    Shear Driven Deformation and Damage Mechanisms in High-performance Carbon Fibre-reinforced Thermoplastic and Thermoset Composites
    (Cranfield University, 2020-11-03 17:38) Yazdani Nezhad, Hamed; Mills, Andrew; Hernandez, Thibault
    The underpinning data related to monolithic and cyclic testing of thermoplastic and thermoset carbon fibre-reinforced polymer composites for description of shear driven deformation and damage mechanisms at micro-scale, related to high-performance aerospace grade structures undergoing high mechanical strains.
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    Surface structured bonded composite-metal joint
    (Cranfield University, 2014-04) Di Giandomenico, Vincenzo; Mills, Andrew; Ayre, David
    The design of structural joints is one of the critical challenges for the development of composite lightweight aircraft and motorsport structures. Despite the universal reliance upon mechanical fastening and adhesive bonding, the disadvantages of both when applied to high stiffness composites are considerable. For bolting and riveting these include added weight as laminates are thickened to account for stress concentrations. For bonding these include chemical uncertainties of the bonding process, inability to inspect for adhesive application quality and vulnerability to catastrophic failure. These concerns stimulated the drive for the development of new hybrid metal/composite joints which combine onlythe advantages of adhesive bonding and of mechanical interlocking by means of the pin-locking concept. This research project investigated the performance of several hybrid joint configurations obtained with the permutations of two different plate designs (double-scarf and double-stepped) and two surface feature shapes (spike and “shark teeth” pins). Tensile mechanical performance testing using the Digital Image Correlation (DIC) technique was carried on to examine the influence of the metal fitting geometry on the joint performance and strain distribution. The pins were manufactured using the processes of micro-machining (MM) and electron beam melting (EBM). The experimental results show a progressive pin failure advancing from the end of the overlap. Both surface features provide an increase in mechanical performance of the joint. Pin geometry such as the diameter, base width, length and shape critically affect the strength of the joint. The highest values of tensile strength are obtained with shark teeth pins which cause a severe reduction in stress concentration at the joint overlap edges and provide a more even strain distribution across the joining area increasing the joint strength. The plate design affects the strain distribution at high loads and can be modified so as to reduce the peel stress. The manufacturing process (EBM or MM) does not affect joint strength significantly (for spike pins) and the process choice can be made on economic grounds. The results provide a strong basis for more detailed stepped lap joint optimisation using tailored surface features designs to assist with the provision of robust, safe, very high strength and weight optimised joints.
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    Sustainable sandwich composites manufactured from recycled carbon fibers, flax fibers/PP skins, and recycled PET core
    (MDPI, 2020-11-23) Jiang, Qihong; Chen, Guiyong; Kumar, Abhideep; Mills, Andrew; Jani, Krutarth; Rajamohan, Vasudevan; Venugopal, Barathan; Rahatekar, Sameer S.
    European union end of life vehicle directive mandates the use of more sustainable/recyclable materials in automotive industries. Thermoplastics matrix-based composites allow recyclability of composites at the end of life; however, their processing technology is more challenging than thermoset composites. Manufacturing process and mechanical testing of sustainable sandwich composite made from sustainable materials: flax, recycled carbon fiber, polypropylene, and recycled PET foam are presented in this article. High pressure compression molding with adhesive thermoplastic polymer film was used for manufacturing sandwich composite skin. The recycled PET foam core was integrated/joined with the skin using a thermoplastics adhesive film. A three-point bending test was conducted to compare the flexural properties. The results show that such sustainable sandwich composites will be an excellent material for truck side panel to operate in adverse wind/storm conditions. The sustainable sandwich composite can potentially be an excellent candidate for the fabrication of light-duty, lightweight, and low-cost engineering structures in automotive industry to meet the EU end of life requirements.