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LITEBUS-MODULAR LIGHTWEIGHT SANDWICH BUS CONCEPT

Final Report Summary - LITEBUS (Modular lightweight sandwich bus concept)

The LITEBUS project was focused on the development of a novel technology to manufacture bus / coach bodies using load carrying sandwich multimaterial panels that have to meet tough design requirements, such as: high static and dynamic performance, high flexural and torsional stiffness, adequate acoustics, crashworthiness, higher safety for passengers, reduced harm to pedestrians in case of accident, fire safety, corrosion resistance, easy repair characteristics and reduced assembly time. As travel by car has increased at a steady rate, of 2 % per year, whereas bus increased 0.9 % and train 0.4 %, the EU White Paper on European Transport Policy for 2010 establishes, as main goal, a shifting of balance from car to public transport, through the development of high quality and safe transport, eliminating the root causes of pollution - the use of individual transportation.

The main overall objectives of the project were to:
- solve the problem of reducing weight and production costs of land transport vehicles through the development of a technology of modular bus / coach construction, using 'all composite' multi-material load carrying sandwich panels instead of a steel / aluminium space-frame lined with sheets of different materials (metallic or non-metallic);
- devise design methodologies that reduce production lead time through reduction of number of components, functional integration, and allowance for dismantling, easy repair and recycling;
- develop high quality urban transport;
- contribute to the shifting of balance between modes of transport;
- contribute to improve road safety;
- contribute to improve quality in the road transport sector.

This project adopted an innovative holistic approach since:
- a new concept structural sandwich material with FRP reinforcements (pultruded sections) and the technology to produce single modular panels was developed;
- new modular vehicle concept architecture, based on the use of structurally resistant composite sandwich panels to produce the structure (lateral, roof and floor panels), instead of the traditional space-frame concept, either in aluminium alloy or steel hollow sections, lined with metallic or composite sheets;
- design of a new product using principles of extended product responsibility (EPR), which extends responsibility to a life cycle stage, taking into account environmental impacts of the product system and principles of design for manufacturing and recycling (that takes into consideration the constraints imposed by the composite sandwich material);
- the new concept reinforced sandwich material and modular panel architecture and respective connections were validated by experimental work, numerical modelling simulation and a rollover test on a bodywork section;
- design, implement, test and evaluate a new structural health monitoring concept relying on novel optical fibre sensing heads and readout equipment, based on in-fibre gratings and micro-cavities for temperature and strain measurements in the body, for composite damage assessment.

During first year the research effort was placed in the development of the bus body concept, materials to be used and respective production technologies. Aspects related with static and dynamic behaviour of the structure, crashworthiness and durability and life cycle cost analysis, although addressed in the identification of the vehicle attributes and specifications did not play the major role of the research effort during the first year.

During the second year, the research work concentrated on the static and dynamic analysis of the proposed structure and design/production of the die to be used in the manufacturing of the pultruded rail floor section and start of pilot production tests. Initial components were manufactured and tested. Particular attention was devoted to the design and production of the pultruded section. Static and fatigue tests on materials and components were performed. A numerical model was developed for composite-composite bonded joints. The activities were developed with the active collaboration of all partners, both during specific work-package meetings, exchanges through email and during the steering committee meetings. A new clamping system was developed to fix the pillars to the lower steel structure of the bus. This system was used in most of the quasi-static tests of the pillar rings and they were used to clamp short straight pillars to test and study the effect of the lateral panels and pultruded profiles on the stiffness of the cell. Residual (survival) space was preserved during the test. The roll-over test validated the proposed new concept of bus body, as far as crashworthiness is concerned. Flexural and torsional stiffness were also demonstrated to be at least equal to equivalent steel bodies.

The main technical achievements were to:
- designing, manufacture and validate of a sandwich material concept with high stiffness and energy absorption suitable for surface transport vehicle;
- generate of new concept vehicle architecture, using systematic product development methodologies and integrated product policy for a more environment friendly vehicle;
- developing a new manufacturing technology for the production of large panels with functional integration. The materials, conceptual design methodologies, design philosophy and assembly methods can be applicable to other industry sectors in particular train rolling stock, ship / boats, and trucks and self-supported refrigerated containers.

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