Browsing by Author "Nassiopoulos, Elias"

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    Cellulose-Based Bio- and Nanocomposites: A Review
    (2011-10-01T00:00:00Z) Kalia, Susheel; Dufresne, Alain; Cherian, Bibin Mathew; Kaith, B. S.; Avérous, Luc; Njuguna, James A. K.; Nassiopoulos, Elias
    Cellulose macro- and nanofibers have gained increasing attention due to the high strength and stiffness, biodegradability and renewability, and their production and application in development of composites. Application of cellulose nanofibers for the development of composites is a relatively new research area. Cellulose macro- and nanofibers can be used as reinforcement in composite materials because of enhanced mechanical, thermal, and biodegradation properties of composites. Cellulose fibers are hydrophilic in nature, so it becomes necessary to increase their surface roughness for the development of composites with enhanced properties. In the present paper, we have reviewed the surface modification of cellulose fibers by various methods. Processing methods, properties, and various applications of nanocellulose and cellulosic composites are also discussed in this paper.
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    Finite element dynamic simulation of whole rallying car structure: Towards better understanding of structural dynamics during side impact
    (2012-06-21) Nassiopoulos, Elias; Njuguna, James A. K.
    Side impact accidents against a tree or pole remain the most dangerous accident scenarios in rally cars. Statistical data shows that 52% of the fatalities between 2004 and 2009 concern crashes against a rigid pole by the track sides, whilst among those more than 60% were side impacts. Despite the present scientific efforts, rallying cars side impacts are still among the least understood primarily due to limited space between the occupant and door sill, evolving safety regulations and vehicle dynamics. In this study, finite element dynamic characteristics of the whole car were studied. The finite element model consisted of the whole car structure and 241 parts including the engines, tyres and the suspension members with 4 different element types and 7 material models. All structural parts were modelled as low-carbon steel with the piecewise- linear-plasticity material model (mat 24). The tyres were modelled with the Blatz-Ko rubber material (mat 07) whilst also rigid and other materials (mat 020, 01, 09, S01 and S02) were used to represent different parts of the model, as the suspension members, suspension links and the engine. A rollcage and two racing seats were modelled with four-node shell elements and the use of piecewise-linear-plasticity and composite-damage materials respectively. A semi- cylindrical pole of 200mm diameter was also designed and modelled as a rigid body. The model was used to first investigate the dynamics of the crash, and later run a wide range of simulations and parametric studies in the cage, the car's floor and the seats. The important findings from the study are presented, conclusions drawn and scope for further development outlined.
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    Localised low velocity impact performance of FLAX/PLA biocomposites
    (Cranfield University, 2015-06) Nassiopoulos, Elias; Njuguna, James; Brighton, James L.
    Natural fibre composites are fast emerging as a viable alternative to traditional materials and synthetic composites. Their low cost, lightweight, good mechanical performance and their environmentally friendly nature makes them an ideal choice for the automotive sector. The automotive industry has already embraced these composites in production of non-structural components. At present, however, research studies into composites made of natural fibres/bio-sourced thermoplastic resins are at infancy stage and such works are rare in the literature. This study therefore focuses on the mechanical properties of poly(lactic) acid (PLA) flax reinforced composites for structural loaded components. The aim was to investigate the performance of flax/PLA biocomposites subjected to localized low velocity impacts. To start with, a detailed literature study was conducted covering biocomposites and PLA in particular. Next, a series of composite samples were manufactured. Morphological and thermal studies were also conducted in order to develop an in-depth understanding of their thermo-mechanical properties, including crystallinity, thermal response and their related transition temperatures. This was followed by localized impact studies. The influence of temperature, water uptake and strain rates to the material tensile strength and modulus, as well as the damage characteristics and limits that lead to failure were studied. Furthermore, in the present work different methods and existing material models to predict the response of biocomposites were assessed. A case study was then performed using these models to understand, develop and improve the side crash performance of a superlight city car prototype. ...[cont.]
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    Tannin-based flax fibre reinforced composites for structural applications in vehicles
    (2012-12-31T00:00:00Z) Zhu, Jinchun; Abhyankar, Hrushikesh; Nassiopoulos, Elias; Njuguna, James A. K.
    Innovation is often driven by changes in government policies regulating the industries, especially true in case of the automotive. Except weight savings, the strict EU regulation of 95% recyclable material-made vehicles drives the manufactures and scientists to seek new 'green materials' for structural applications. With handing at two major drawbacks (production cost and safety), ECHOSHELL is supported by EU to develop and optimise structural solutions for superlight electric vehicles by using bio-composites made of high-performance natural fibres and resins, providing enhanced strength and bio-degradability characteristics. Flax reinforced tannin-based composite is selected as one of the candidates and were firstly investigated with different fabric lay-up angles (non-woven flax mat, UD, [0, 90°]4 and [0, +45°, 90°, −45°]2) through authors' work. Some of the obtained results, such as tensile properties and SEM micrographs were shown in this conference paper. The UD flax reinforced composite exhibits the best tensile performance, with tensile strength and modulus of 150 MPa and 9.6 MPa, respectively. It was observed that during tension the oriented-fabric composites showed some delamination process, which are expected to be eliminated through surface treatment (alkali treatment etc.) and nanotechnology, such as the use of nano-fibrils. Failure mechanism of the tested samples were identified through SEM results, indicating that the combination of fibre pull-out, fibre breakage and brittle resins failure mainly contribute to the fracture failure of composites.