PhD, EngD and MSc by research theses (SATM)

Permanent URI for this collection

https://dspace.lib.cranfield.ac.uk/handle/1826/8739

Browse

Browsing PhD, EngD and MSc by research theses (SATM) by Supervisor "Abhyankar, Hrushikesh"

Now showing 1 - 7 of 7
  • Thumbnail Image
    ItemOpen Access
    Advanced carbon/flax/epoxy composite material for vehicle applications: vibration testing, finite elements modelling, mechanical and damping characterization.
    (Cranfield University, 2015-05) Ampatzidis, Theofanis; Blackburn, Kim; Abhyankar, Hrushikesh
    Nowadays, research in automotive and construction industries focuses on materials that offer low density along with superior dynamic and static performance. This goal has led to increasing use of composites in general, and carbon fibre (CF) composites in particular. CF composites have been adopted widely in the space industry and motorsports. However, their high stiffness and low density leads to low damping performance, which is responsible for increased levels of noise and reduction in service life. On the other hand, natural fibres (NF) like flax fibres (FF) are capable of delivering a much better damping performance. A hybrid composite comprising of FF and CF can potentially deliver both on strength and higher damping performance. In this study the mechanical and damping properties of CF, FF and their hybrid composites were examined. Composites' anisotropic nature affects their response to vibrations and so traditional damping experimental setups used for metals had to be ruled out. A damping set up based on Centre Impedance Method (CIM) was adopted for the purpose of this study which was based on an ISO standard originally developed for glass laminates. Standard tensile and flexural tests were conducted in order to characterise the performance of the hybrid composite. The experimental work was accompanied by finite elements analysis (FEA). The experimental data and FEA were used to optimize the hybrid structure layup with respect to damping and structural response.
  • Thumbnail Image
    ItemOpen Access
    Development of novel flax bio-matrix composites for non-structural and structural vehicle applications
    (Cranfield University, 2015) Zhu, Jinchun; Abhyankar, Hrushikesh; Zhu, Huijun
    The use of natural fibres (e.g. flax, hemp etc.) instead of synthetic fibres (carbon and glass etc.) as composite reinforcements not only benefits the environment, but also provides economical lightweight products for transports. Although there are a few studies reported in literature on use of flax fibres, there is no comprehensive guide on use of flax fibres with bio-resins to re-engineer bio- composite systems that can be used in vehicle structures. The state-of-art of the current research towards using natural fibre reinforced composites is reviewed by the thesis. The review covers the performances of flax composites, concentrating on the effect of matrix types and existing development methods. The review also identifies the rational of selecting tannin resins and bio-epoxy resins to combine with flax fibre reinforcements. In the experimental work, mimosa tannin resin (natural phenolic resin) and pine- oil derived supersap epoxy resin are selected to manufacture the fully renewable flax composites. By tailoring the fibre configurations and chemical surface treatments, the resultant composites were investigated to provide information for engineers to understand the composite behaviours and properties. Mechanical properties (tension, flexural, shear, impact etc.) and physical properties (moisture, ageing etc.) were assessed through adequate tests and analysing methods. In addition, bio-sandwich structures based on the novel studied composites and commercial bio-foams were evaluated to study the energy absorption which could be very important in vehicle design. Based on the results, flax/supersap epoxy and flax/tannin composites are suitable for possible exterior structural and interior non-structural applications, respectively. The developed flax fibre composites with innovative bio-matrices have a potential to prevail in modern vehicle applications, due to the competitive performances, economic viability and environmental acceptability.
  • Thumbnail Image
    ItemOpen Access
    Manufacturing of novel aerogel based thermal coating systems for carbon/epoxy composite substrates.
    (2018-06) Krishnaswamy, Suryanarayanan; Abhyankar, Hrushikesh; Huang, Zhaorong
    To try and increase the applicability of carbon fibre composites, the present work considers the use of thermal coatings on its surface. After a study on relevant literature pertaining to conventional and alternate thermal barrier coatings, it was believed that YSZ-based and/or aerogel-based systems had the most potential. But successful application of these coatings required additional research, particularly on processing routes and long-term performance. Therefore to try and achieve a more efficient thermal coating on composite substrates, aerogel-based materials were investigated since they showed the most promise. These aerogel/polymer composites were further characterized using different morphological, optical and thermal techniques. The experimental results showed particularly promising trends for aerogel/epoxy materials whose best sample had an aerogel damage coefficient value of 18.3%. Hence, this system was applied as a coating on a carbon fibre reinforced polymer substrate and the whole system showed better thermal performance compared to a pure epoxy coating. The coating and the substrate were subsequently modelled and solved using finite element analysis to determine the most effective system under a cyclic thermal load. Although, the selection of the coating type (double, top or bottom) is dependent on the exact application; the top coating displayed the best performance balance. Nevertheless, both, experimental measurements and simulation results in the current work point to a potential application of the coating in industries such as aerospace, automotive and/or construction.
  • Thumbnail Image
    ItemOpen Access
    Mathematical modelling and simulation of continuous, highly precise, metal/eco-friendly polymerization of Lactide using alternative energies for reaction extrusion
    (Cranfield University, 2016-07) Dubey, Satya P.; Abhyankar, Hrushikesh; Brighton, James L.
    Polylactic acid (PLA) is one of the most promising bio-compostable and biodegradable thermoplastic made from renewable sources. PLA, is typically obtained by polymerising lactide monomer. The technique mainly used for ring opening polymerization (ROP) of Lactide is based on metallic/bimetallic catalyst (Sn, Zn, and Al) or other organic catalysts in suitable solvent. However, the PLA synthesized using such catalysts may contain trace elements of the catalyst, which may be toxic. In this work, reactive extrusion experiments using stannous octoate Sn(Oct)2 and tri-phenyl phosphine (PPh)3 were considered to perform ROP of lactide monomer using ultrasound as an alternative energy (AE) source for activating and/or boosting the polymerization. Mathematical model of ROP of lactide, was developed to estimate the impact of reaction kinetics and AE source on the polymerization process. Ludovic® software, a commercial code was used. It was adopted for the simulation of continuous reactive extrusion of PLA. Results from experiments and simulations were compared to validate the simulation methodology. Results indicate that the application of AE source in reaction process boost the PLA formation rate. Result obtained through Ludovic simulation and experiments were validated. It was shown that there is a case for reducing the residence time distribution (RTD) in Ludovic due to the ‘liquid’ monomer flow in the extruder. This change in the parameters resulted in validation of the simulation. However, it was concluded that the assumption would have to be established by doing further validations.The simulation model includes the details of kinetics of reactions involved with in the process and helps to upscale the reaction output. This work also estimates the usefulness and drawbacks of using different catalysts as well as effect of alternative energies and future aspects for PLA production.
  • Thumbnail Image
    ItemOpen Access
    Mechanical properties and impact energy absorption of hybrid thermoplastic nanocomposite structures
    (2016-01) Silva, Francesco; Abhyankar, Hrushikesh; Brighton, James L.
    This thesis focuses on the mechanical properties and the impact energy absorption capabilities of injection moulded hybrid three-phase polymer composites. Its main aim is to investigate the effect of different micro and nano sized filers on the mechanical properties; such as stiffness, strength, ductility, impact resistance and energy absorption capability; of short-fibre reinforced thermoplastic composites. Extensive experimental and numerical investigations were core to the research. Six different, three-phase composites, were manufactured by the integration of two types of nano-reinforcements (either nano-silica or nano-clay), or micro glass-spheres, into two types of short glass-fibre reinforced thermoplastic matrices (either Polypropylene (PP) or Polyamide (PA6)). The materials were characterized using Transmission Electron Microscopy (TEM), Wide Angle X Ray Diffraction (WAXD) and optical microscopy. The effect of matrix and reinforcement material on the mechanical properties and the energy absorption capabilities of polymer composites were studied in detail. The results are compared with the properties of standard two-phase glass-fibre reinforced polymer composites. Initial experiments focused on quasi-static uniaxial tensile and compression tests, as well as quasi-static crash tests of the conical structures. Subsequently, dynamic drop weight impact crash tests of the conical structures were conducted to investigate the influence of the nano reinforcement on the energy absorption capabilities of the polymer composites. To study propagation of the dynamic cracks and the energy absorbing mechanism, the impact event was recorded using a high-speed camera. The fracture surface was investigated with scanning electron microscopy (SEM). Furthermore, improved simulation tools were developed to accurately and effectively model nanocomposite structures subjected to dynamic loads. A constitutive model with orthotropic yield, strain rate sensitivity and strain energy density based failure criterion, was developed and implemented into Ls Dyna Finite Element (FE) code. The results show that by changing the filler and the matrix material, it is possible to control the mechanical properties and the energy absorption capability of the glass-fibre reinforced polymer nanocomposites. An increase in the mechanical properties (stiffness, strength or ductility) of PA6 composites was observed. Furthermore, nano-silica and glass-spheres reinforcements were found to improve the energy absorption capabilities of PA6 composites by changing the mode of failure, whereas nano-clay reinforcement caused a decrease in that capability. Little or negative influence of the nano-fillers was observed, when combined with PP based composites. The experimental findings were used to generate, calibrate and validate the user defined material model. The structural FE modelling proved that the model was capable of accurately and effectively representing the nanocomposite structures subjected to static and dynamic loads. Furthermore, it provided a valuable input for better understanding of the structural failure mechanism, observed in the three-phase nanocomposite structures.
  • Thumbnail Image
    ItemOpen Access
    Nanoparticle reinforced polyamide 66 glass fibre composites for automotive under-the-bonnet-applications.
    (2016-10) Butterworth, Ian; Abhyankar, Hrushikesh; Brighton, James L.
    This work focus on an engine oil pan application which expects component materials operate at elevated temperatures due to returning oil heating up during operation. Mechanical properties of thermoplastic composites are known to be temperature dependent with performance losses elevated temperatures. A pilot study was conducted to benchmark the current state-of-the-art glass reinforced polyamide materials at elevated temperatures to address a gap in this knowledge. Experiments included tensile, 3-point flexural, and gas gun impact where conducted at elevated temperatures 23°C, 65°C, 90°C and 120°C. Experimental results demonstrated the trade-off in the mechanical properties of the two materials especially when one of the materials had been impact modified with an elastomer (PA66-GF-E). PA66-GF-E mechanical and impact performance can be considered fit of purpose as a suitable material for an oil pan application but is more expensive. As an extra compounding step is required to graft the elastomer to the PA66 matrix. Literature studies into replacements for the elastomer suggested nanoparticles as they can be compounded at the same time as the GF and in turn eliminate secondary compounding costs. Six 3-phase nanocomposite where then compounded using a twin screw extruder. Additions of OMMT and SiO2where done in 2, 3 and 4wt.% for each nanocomposite. Testing of the 3-phase nanocomposites indicated the GF reduction has reduced mechanical strength in all results, but still demonstrates each nanomaterial and volume has been successful. Thermomechanical testing and aging suggests an optimised SiO2 in wt.% of 2 or 3 could replace an elastomer as an impact modifier. OMMT grades did not have a significant improvement to over the SiO2 grades to consider suitable for the oil pan application. However this work does builds a strong case for further work to continue developing 3-phase nanocomposites by improving the compounding setup.
  • Thumbnail Image
    ItemOpen Access
    A study of emission of nanoparticles during physical processing of aged polymer-matrix nanocomposites
    (Cranfield University, 2016-11) Gendre, Laura; Abhyankar, Hrushikesh; Brighton, James L.
    Nanotechnology research and its commercial applications have experienced an exponential rise in the recent decades. Although there are a lot of studies with regards to toxicity of nanoparticles, the exposure to nanoparticles, both in terms of quality and quantity, during the life cycle of nanocomposites is very much an unknown quantity and an active area of research. Unsurprisingly, the regulations governing the use and disposal of nanomaterials during its life cycle are behind the curve. This work aims to assess the quantity of nanoparticles released along the life cycle of nanocomposites. Machining operations such as milling and drilling were chosen to simulate the manufacturing of nanocomposites parts, and impact testing to recreate the end-of-life of the materials. Several studies have tried to simulate different release scenarios, however these experiments had many variables and in general were not done in controlled environments. In this study, a reliable method was developed to assess the release of nanoparticles during machining and low velocity impact of nanocomposites. The development and validation of a new prototype used for measurement and monitoring of nanoparticles in a controlled environment is presented, as along with release experiments on different nanocomposites. Every sample tested was found to release nanoparticles irrespective of the mechanical process used or the type of material tested. Even neat polymers released nanoparticles when subjected to mechanical forces. The type of matrix was identified to play a major role on the quantity of nanoparticles release during different process. Thermoset polymers (and especially polyester) were found to release a higher number concentration of particles, mainly due to their brittle properties. A polyester sample was found to release up to 48 times more particles than a polypropylene one during drilling. The nanofiller type and percentage used to reinforce the polymer is also a key point. For example, the addition of 2 wt.% of nano-alumina into polyester increases the number concentration of particles by 106 % following an impact. The nanofiller chosen and its quantity affect the mechanical properties and machinability of the composites and therefore its nanoparticles release potential. The mechanical process and the process parameters chosen were also found to be crucial with regards to the nanoparticles released with different trends observed during drilling and impact of similar materials. Finally, thermal ageing of nanocomposites increases the number concentration of nanoparticles released (by 8 to 17 times after 6 weeks).