Energies 2021 , 14 , 1095
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In the literature, one can also find investigations on the influence of creasing on the mechanical strength of corrugated paperboard. Creasing is a process, in which fold and perforation lines are manufactured. These lines reduce the strength of corrugated paperboard. In 2008, Thakkar et al. compared the results from the experiments and numerical simulations based on the FEM to investigate the influence of the creasing on the local strength of corrugated paperboard [31]. Later, Beex and Peerlings performed physical and numerical experiments related to influence of creasing and subsequent folding on the mechanical properties of the laminated paperboard [32]. Giampieri et al. [33] proposed a constitutive model for the mechanical response of creased paperboard after folding. The FEM simulations of paperboard creasing and folding useful for the packing industry and important from a practical point of view has been presented by Domaneschi et al. [34]. Awais et al. [35] and Leminena et al. [1] investigated, experimentally and numerically, the influence of the crease on the mechanical properties of the paperboard during the press forming process. However, to the best knowledge of the authors, there are no papers on the influence of perforations on the strength of the whole boxes made of corrugated cardboard. In this paper, a modification of the analytical–numerical approach is proposed for corrugated boxes with perforations. The article verifies the influence of perforation on the compressive strength of corrugated cardboard boxes with a modified analytical formula, through a numerically aided calculation of the critical load. Furthermore, the applicabil- ity of the approach presented in [11,12,20,21] for corrugated cardboard boxes has been extended to cases of the SRPs with different perforations.
2. Materials and Methods 2.1. Ultimate Compressive Strength of a Plate
In order to compute the ultimate load on the box in a static top-to-bottom compres- sion test, see Figure 1c, one can follow an idea presented by Heimerl [36], later used by McKee et al. [3] and recently extended by Garbowski et al. [11,12]. The basis of this ap- proach was the calculation of the ultimate load, P f , of each separated panel (see Figure 1a) using the edge-loaded compressive strength of corrugated board, ECT , and a critical load, P cr , resulting from the buckling phenomenon: P f P cr = k ECT P cr r , (1) where k is a constant, r is an exponent, r ∈ ( 0,1 ) (most often due to empirical fitting r ∈ [ 0.5, 0.75 ] ; [9]), ECT is given in N/mm, and P cr is given in N/mm.
Figure 1. ( a )Apanel b × a separated from corrugated box as a pined plate under in-plane compression; ( b ) corrugated board packaging with perforations; ( c ) box compression test (BCT) press used in laboratory tests [37].
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