Issue 29

M. Romano et alii, Frattura ed Integrità Strutturale, 29 (2014) 385-398; DOI: 10.3221/IGF-ESIS.29.34 397 C ONCLUSIONS or all evaluated results the standard deviations are generally very low. This is an indicator for constant material quality for all the investigated test panels provided by the manufacturing process as well as for the high reproducibility of the experimental investigations of high-velocity impact loads. The carried out high velocity impact tests showed the respective properties of each single kind of fibre when the monolithic layups have been considered. With a hybrid stacking it is possible to optimize the use of the outstanding material properties of each single kind of reinforcement fibres when energy dissipation issues under high-velocity impact loads are considered. Even though aramid fibres have not been considered as for example described in Muhi, Najim and Moura. 2009 [11] hybridization yields noticeable effects. The effect can directly be lead back to hybridization. The reasons therefore are the relatively high values of the fibre volume content f,s 60%   and at the same time the relatively low standard deviations. These two indicators regarding the composite material imply a high mechanical quality as well as a high degree of reproducibility of the process at the same time. However, aramid fibres should be taken into account in further investigations as even a more distinct enhancement of the energy dissipation capacity can be expected. The initially described idea to enhance transversal deflection due to shear effects and therewith enhance the resulting normal loads in the material can be identified in the evaluated results for the hybrid stacked materials with and without the hexagonal separating layers. The improved relative energy dissipation based on the nominal values as well as standardized to the desired fibre volume content distinctly proves the acting of the aimed structural mechanic effect. Thus, the functional capability of the layer as well as of the hybrid stacked layups can be stated. In further investigations different hybrid layups should be considered additionally. Thereby the focus should lie on the identification of the sensitivity of the energy dissipation properties to the sequential arrangement of the monolithic blocks in the construction of the hybrid stacked layups as basically carried out in Muhi, Najim and Moura. 2009 [11]. A CKNOWLEDGEMENTS he authors would like to thank Mr Marco Vogelsberg and Mr Uwe Riedel from the Laboratory of Ballistics, Weaponry and Munitions at the University of the Bundeswehr Munich as well as Mr Florian Roidl from the Laboratory of Manufacturing Engineering and Machine Tools (LFW) and Mr Bastian Jungbauer, B.Eng. from the Laboratory of Composite Technology (LFT), both at the Ostbayerische Technische Hochschule Regensburg. Further Mrs Carmen Löpelt and Mr Elmar Lauterborn, both from the Wehrwissenschaftliches Institut für Werk- und Betriebsstoffe (WIWeB) Erding are gratefully acknowledged for carrying out the determination of the fibre volume content by chemical extraction. The authors are grateful to the donation of the bearing balls from the company Schaeffler Technologies AG & Co. KG that have exhibited excellent properties as spheric impactors. R EFERENCES [1] Cherif, C., Textile Werkstoffe für den Leichtbau, Techniken-Verfahren-Materialien-Eigenschaften. Springer- Verlag, Berlin/Heidelberg/New York, (2011). [2] Deak, T.; Czigany, T., Chemical Composition and Mechanical Properties of Basalt and Glass Fibers: A Comparison, Textile Research Journal, 79(7) (2009) 645-651. [3] Fadhel, B. M., Numerically Study of Ballistic Impact of Polycarbonate. International Symposium on Humanities, Science and Engineering Research (SHUSER), Kuala Lumpur, (2011) 101-105. [4] Holmquist, T., Johnson, G., Characterization and evaluation of silicon carbide for high-velocity impact, Journal of Applied Physics, 97 (2005) 1-12. [5] Holmquist, T., Johnson, G., Response of silicon carbide to high velocity impact, Journal of Applied Physics, 91( 9) (2002) 5858-5866. [6] Jones, R., Mechanics of Composite Materials, 2nd edition, Taylor & Francis, Philadelphia (Pa.), (1999). F T