Materials 2022 , 15 , 663
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( f ) Figure13. The sensitivity analysis of BS in EB and BE configuration with respect to all layers’ thick- nesses, t i , elastic properties of liners, E i and flute geometric parameters, h i : ( a ) Board1; ( b ) Board2; ( c ) Board3; ( d ) Board4; ( e ) Board5; ( f ) Board6. 4. Discussion The results presented in the study were obtained while using derived analytical or numerical models, in which the experimental data presented in [29] were utilized. All experimental data used in the work are summarized in Tables 1 and 2. The heights of the corrugated layers (E-flute and B-flute) have been corrected and are compiled in Table 3. To the best of our knowledge, there are no other studies in the literature on this subject, although several observations made by various scientific groups have already indicated this phenomenon, e.g., Östlund and Niskanen [66]. The proposed analytical model does not take into account the corrugated layers in the calculation of the bending stiffness of the five-layer corrugated cardboard. Two numerical models were therefore built to validate this assumption. In the first of them, both flat and corrugated layers were used to determine BS. In the second one, the stiffness of the wavy layers was reduced to emulate a situation in which corrugated layers are excluded from the computation. For the comparison, the theoretical model was additionally employed, in which also just flat layers are considered in BS computation. All three models gave almost the same results presented in Figure 10. The differences were between 0.72% and 1.75%. Since the presented model takes into account the influence of initial imperfections in the compressed segment of the corrugated board, the first attention was focused on deter- mining the initial imperfection values. Figures 11 and 12 present BS in two configurations: (a) EB—E wave upwards and (b) BE—B wave upwards, as a function of imperfection value.
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