Browsing by Author "Silva, Francesco"
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Item Open Access The effect of nanoclay on dust generation during drilling process of polyamide 6 nanocomposites(Hindawi Publishing Corporation, 2012-06-10T00:00:00Z) Sachse, Sophia; Silva, Francesco; Zhu, Huijun; Irfan, Adeel; Leszczynska, Agneska; Pielichowski, Krzysztof; Ermini, Valentina; Blazquez, Maria; Kuzmenko, Oleksandr; Njuguna, James A. K.During the past decade, polymer nanocomposites have emerged as a novel and rapidly developing class of materials and attracted considerable investment in research and development worldwide. However, there is currently a lack of information available in the literature on the nano and ultrafine particle emission rates from these materials. In this study, influence of nanoclay on mechanical drilling of PA6 composites, in terms of dust generation has been reported. With the help of real-time characterization, submicrometer-sized particles (5.6-512 nm) size distribution and number concentration emitted from polyamide 6/nanoclay composites during mechanical drilling is studied. Total particle concentration for the PA6/nanoclay composites was 20,000 cm-3, while unreinforced panel measured a total concentration of approximately 400,000 cm-3. While the airborne particle concentration for the PA6/ nanoclay composites was 20 times lower than for the PA6 matrix, the concentration of deposited nanoparticles doubled for the nanocomposite. The results clearly shows that more particles in the size range between 175-350 nm are generated, during drilling of the nanocomposites and this particles deposit in a shorter time. It is likely that the presence of nanoclay in some way retains the formation of high quantity of airborne particles and promotes particle deposition.Item Open Access The Influence of Multiscale Fillers Rein forcement into Impact Resistance and Energy Absorption Properties of Polyamide 6 and Polypropylene Nanocomposite Structures(2013-09-01T00:00:00Z) Silva, Francesco; Njuguna, James A. K.; Sachse, Sophia; Pielichowski, Krzysztof; Leszczynska, Agneska; Giacomelli, MarcoThree-phase composites (thermoplastic polymer, glass-fibres and nano-particles) were investigated as an alternative to two-phase (polymer and glass-fibres) composites. The effect of matrix and reinforcement material on the energy absorption capabilities of composite structures was studied in details in this paper. Dynamic and quasi-static axial collapse of conical structures was conducted using a high energy drop tower, as well as Instron universal testing machine. The impact event was recorded using a high-speed camera and the fracture surface was investigated with scanning electron microscopy (SEM). Attention was directed towards the relation between micro and macro fracture process with crack propagation mechanism and energy absorbed by the structure. The obtained results indicated an important influence of filler and matrix material on the energy absorption capabilities of the polymer composites. A significant increase in specific energy absorption (SEA) was observed in polyamide 6 (PA6) reinforced with nano-silica particles and glass-spheres, whereas addition of montmorillonite (MMT) caused a decrease in that property. On the other hand, very little influence of the secondary reinforcement on the energy absorption capabilities of polypropylene (PP) composites was found.Item Open 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.Item Open Access Nanocomposites for vehicle structural applications(2011-11-14T00:00:00Z) Njuguna, James A. K.; Silva, Francesco; Sachse, Sophia; Lin, TAdvancements in the nanotechnology industry promise to offer improvements in capabilities across a spectrum of applications. This is of immense strategic importance to the high performance sector which has historically leveraged technological advances. The uses of polymer nanocomposites in structures have several predictable impacts on structural design and applications, primarily by providing a safer, faster, and eventually cheaper transportation in the future. In this chapter, special attention is focused on the reinforcement of key properties of polymer nanocomposites for potential high performance structural applications. Further insight is provided on developments in both theoretical and experimental investigations providing valuable fundamental elements in strength and stiffness, impact resistant and energy absorption performance, thermal properties, age and durability performance and structural health monitoring of polymer nanocomposites for vehicular structural needs. A brief overview of modeling and simulation of nano-reinforced materials is also given reflecting its importance in vehicular structures.