Issue 29

M. Romano et alii, Frattura ed Integrità Strutturale, 29 (2014) 385-398; DOI: 10.3221/IGF-ESIS.29.34 395 The relative dissipated kinetic energy of the test panels consisting of the hybrid layups with and without the hexagonal separating layer range from 35 % to 39 %. Confronting the hybrid stacked layup without hexagonal separating layer and the hybrid stacked layup with hexagonal separating layer as a core material a distinct effect can be noticed. The hybrid stacked material with separating layer shows approx. 4 % higher values for the relative dissipated kinetic energy than the hybrid stacked layup without separating layer. In contrast to the monolithic materials the hybrid stacked materials showed the lowest standard deviation. Standardizing the results to a fibre volume content f,s 60%   Fig. 6 illustrates the relative dissipated kinetic energy   diss,rel, f,s 60% E   for each selected type of layup calculated by Eq. (9) as standardized results for the monolithic and hybrid layups with and without the hexagonal separating layer. The relative dissipated kinetic energy diss,rel E and the standardized relative dissipated kinetic energy   diss,rel, f,s E  to desired value of the fibre volume content f,s 60%   vary only slightly when the monolithic materials are considered. The standardized relative dissipated kinetic energy   diss,rel, f,s E  of the monolithic materials, illustrated in Fig. 6, range from 32 % to 43 %. The highest value of the relative dissipated kinetic energy of approx. 43 % is still obtained for the test panels built up of only basalt fabrics. To the test panels consisting of only glass fabrics a value of approx. 38 % is assigned. For the monolithic carbon fibre reinforced layups the standardization yields a value of approx. 32 %. The standard deviations are standardized as well, so that the tendencies in the results based on the nominal values do not change. 31,9% 38,0% 42,7% 33,2% 34,8% 0% 10% 20% 30% 40% 50% 0 1 2 3 4 5 6 Rel. dissipated kin. energy E diss,rel ( φ f,s ) standardized to φ f,s =60% Layup configuration Figure 6 : Relative dissipated kinetic energy   diss,rel, f,s E  of the monolithic and hybrid materials standardized to a fibre volume content f,s 60%   . The relative dissipated kinetic energy diss,rel E and the standardized relative dissipated kinetic energy   diss,rel, f,s E  to the desired value of the fibre volume content f,s 60%   vary only slightly, too, when the hybrid stacked materials are considered. They range from 33 % to 35 %. Because the initial values of the fibre volume content f,e  do not distinctly differ from the desired value of the fibre volume content f,s 60 %   the tendencies are similar to the results obtained for the nominal values. However, the effects caused by the separating layer used as a core material are a little less distinct, yet clearly observable. The hybrid stacked material with separating layer shows approx. 2 % higher values for the standardized relative dissipated kinetic energy than the hybrid stacked layup without separating layer. Because the standard deviations are standardized as well, the tendencies in the results based on the nominal values do not change, as already mentioned before. Description of failure modes – impact surface and outlet areas In the following the characteristic failure modes of the different kinds of layups are confronted with each other. Therefore the fractured surfaces of the impact side as well as of the opposite side are described. Fig. 7 exemplarily shows the