Rezultaty
HYCOTRANS is directed towards the development of composite sandwich panels for rail vehicle body-shells and other passenger transportation structures. The research reflects a requirement for lightweight, impact absorbent materials to replace the use of metals in such applications.
The structural sandwich concept involves combining two thin and stiff fibre-reinforced plastic (FRP) faces with a thick and relatively weak foam or honeycomb core. Such structures can be designed to achieve the necessary strength and stiffness for use in load-bearing applications. However, their use in safety critical areas has been severely restricted. Composites are generally brittle in nature, failing in an unpredictable and often catastrophic manner.
HYCOTRANS has overcome this limitation by way of an innovative design approach based on the corrugated 'tied' core sandwich concept. The corrugation represents an integral part of the construction, forming a continuous channel between the upper and lower faces. In the event of a collision, the corrugation is designed to fail at a pre-determined stress level, selected in order to protect passengers from experiencing severe impact forces. Tests conducted on small scale tubular structures at the Advanced Railway Research Centre (ARRC) and the National Technical University of Athens (NTUA) have shown that the resultant collapse mode is one of progressive failure, absorbing large amounts of energy in a stable and reproducible manner. The side impact strength of panels is also suitably high, as demonstrated by ball impact tests conducted at the University of Perugia.
Compared to aluminium and steel carriages, body shells based on composite sandwich panel technology offer numerous advantages. Composite structures lend themselves to higher production, while their non-corrosive properties offer extended service life. The flexibility of composites also means that the complex shapes required for aerodynamic design can be achieved at a significantly lower cost. More fundamentally, significant reductions in vehicle weight can be achieved. These are factors of particular importance to the end-users in the consortium: Ifor Williams Trailers Ltd. (a British trailer builder), Costaferroviaria (an Italian rail vehicle manufacturer) and Irizar (a Spanish bus builder).
In addition to the energy absorbing structural concept a design tool has been developed with the aim of providing the users with a tool for the evaluation of the in-service characteristics of the material (strength, resistance, crashworthiness). The values of the parameters required by the model are extrapolated by experimental tests on samples of different scales, and by results of numerical simulations performed considering configurations not available experimentally.
The study of the structural behaviour indicates that the response of the structure is influenced by the variability of the main parameters that comprise material, geometrical, and structural parameters. In design and manufacturing of advanced materials, it is desirable to find which of the many processing variables mostly contribute to the desired properties of the material. A further development of the predictive tool is envisaged to consider the estimation of the effects on design of the variability (due to the manufacturing process) of the main parameters that characterise the structure.
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