Issue 47

F. Cucinotta et alii, Frattura ed Integrità Strutturale, 47 (2019) 367-382; DOI: 10.3221/IGF-ESIS.47.27 381 results were finally exploited to validate a FE model purposely developed for such complex and non-isotropic composite materials. The two specimens have been manufactured complying with the same rulebook. However the behaviour during the bending tests is quite different. As shown in Section 2.1, the design idea of the two shipbuilders is different and this discrepancy leads to a different stacking sequence and a final different weight of the two composites (and also to different manufacturing costs). In absolute terms (without considering the respective weights), the A sandwich has a better mechanical behaviour than B sandwich. This difference is annulled or, in some cases, reversed if specific quantities are considered. The same trend is highlighted during the impact tests. These experimental tests suggest that the great flexibility of these materials can lead to different final products designed for the same purpose. In order to find the right compromise (costs, mechanical efficiency, environmental impacts), is fundamental and useful to have a tool, as FE, in preliminary stage, for evaluating different design solutions in different loading conditions and in rapid way. The FE model has been validated through both four-point bending and impact tests. The models provided a reliable representation of the linear behaviour of the material before damage, and an acceptable estimation of the damage growth at higher energy levels. The developed model represents a valuable tool, which can help engineers to make design choices before performing experimental activity, thus allowing to save time and costs and to optimize performances faster. Also, as a future development, the FE model could be exploited in a topological optimization tool to obtain the best layouts for thickness, materials, fibres orientation and core size for specific applications. The experimental and numerical tests showed that there is not a direct correlation between bending and impact properties of the sandwiches. Thus, the importance of a reliable FE model was further highlighted, since the material response under particular conditions cannot be inferred from other testes. It must be underlined that the UIM rules, at the moment, require only four-point quasi static bending tests. Consequently, in order to enhance the safety of drivers by maximizing the impact strength of the cockpit and the ability to absorb energy, the UIM rules could surely be improved, in the future, by providing specific impact characterization compliances. A CKNOWLEDGMENTS he authors wish to thank Mr. Tom Stanley of the Union Internationale Motonautique (UIM) for providing the samples and Mr Sergio Abrami for the precious comments and suggestions. R EFERENCES [1] Ashby, M.F., Bush, S.F., Swindells, N., Bullough, R., Ellison, G., Lindblom, Y., Cahn, R.W., Barnes, J.F. (1987). Technology of the 1990s: Advanced Materials and Predictive Design [and Discussion], Philos. Trans. R. Soc. A Math. Phys. Eng. Sci., 322(1567), pp. 393–407. DOI: 10.1098/rsta.1987.0059. [2] Gibson, R.F. (2010). A review of recent research on mechanics of multifunctional composite materials and structures, Compos. Struct., 92(12), pp. 2793–2810. DOI: 10.1016/j.compstruct.2010.05.003. [3] Kelly, A., Buresch, F.E., Biddulph, R.H. (1987). Composites for the 1990s [and Discussion], Philos. Trans. R. Soc. A Math. Phys. Eng. Sci., 322(1567), pp. 409–23. DOI: 10.1098/rsta.1987.0060. [4] Soutis, C. (2005). Fibre reinforced composites in aircraft construction, Prog. Aerosp. Sci., 41(2), pp. 143–151. DOI: 10.1016/j.paerosci.2005.02.004. [5] Ding, M., Liu, J., Liu, B., Wang, X., Li, T., Cao, D. (2016).On the Development of Automotive Composite Material Rear Bumper Beam. Proceedings of SAE-China Congress 2015, pp. 297–308. [6] Kimpara, I. (1991). Use of advanced composite materials in marine vehicles, Mar. Struct., 4(2), pp. 117–127. DOI: 10.1016/0951-8339(91)90016-5. [7] Timmis, A.J., Hodzic, A., Koh, L., Bonner, M., Soutis, C., Schäfer, A.W., Dray, L. (2015). Environmental impact assessment of aviation emission reduction through the implementation of composite materials, Int. J. Life Cycle Assess., 20(2), pp. 233–243. DOI: 10.1007/s11367-014-0824-0. [8] Witik, R.A., Payet, J., Michaud, V., Ludwig, C., Manson, J.A.E. (2011). Assessing the life cycle costs and environmental performance of lightweight materials in automobile applications, Compos. Part A Appl. Sci. Manuf., 42(11), pp. 1694– 1709. DOI: 10.1016/j.compositesa.2011.07.024. T