Centro Logístico e Industrial (CLI)

Figures 5.12a – c show the effect of board grade and package design for each vent area. For all the vent areas, packages with BC-flute board had the greatest compression strength while packages with B-flute board had the lowest compression strength. The percentage difference in compression strength between the packages with BC-flute board and the packages with B-flute board for all the designs ranged from 60% to 72% for the 2% vent area, 54% to 65% for the 4% vent area and 49% to 67% for the 8% vent area. For the 2% vent area (Figure 5.12a), no significant difference in the compression strength between the package designs for the B-flute could be observed. However, the compression strength of all the package designs was significantly different from the Control package.

As shown in Figure 5.12b for the 4% vent area, the Standard vent design was the strongest for both B-flute board and C-flute board while for the BC-flute board, the

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Edge vent design was the strongest package. The Alt vent design was the weakest package for the B-flute board while the Multi vent package design was the weakest for both C-flute and BC-flute board grades. For the B-flute board, the compression strength of the weakest package (Alt vent) reduced by about 7% when compared to the strongest package (Standard vent). In comparison with the strongest package (Standard vent) for the C-flute board, the weakest package (Multi vent) reduced by about 9%. Whereas for the BC-flute board, a reduction in compression strength of about 12% was observed for the weakest package (Multi vent) when compared with the strongest package (Edge vent). For the B-flute board, no significant difference in the compression strength between the strongest package and the weakest package while for C-flute and BC-flute boards, there was a significant difference (p<0.05). Figure 5.12c shows the effect of board grade and package design for the 8% vent area. For the B-flute board packages, Multi vent package had the greatest compression strength while the Standard vent package had the lowest compression strength with a 8% difference. No significant difference was observed in the compression strength between all the package designs. In contrast, for the C-flute board packages, the Standard vent package was the strongest while the Multi vent package was the weakest with a difference of about 10%. There was a significant difference (p<0.05) in the compression strength between the strongest package (Standard vent) and the weakest package (Multi vent). For the package designs with BC-flute board, the Edge vent package was the strongest. The compression strength for the Standard, Alt and Multi vent package designs reduced by 8%, 11% and 16%, respectively when compared with the strongest package (Edge vent). Furthermore, the compression strength of the strongest package (Edge vent) was significantly difference (p<0.05) from the compression strength of the weakest package (Multi vent). The results suggest the importance of characterising different boards as well as board components in the design of package vent configuration. Lightweight liners on corrugated boards were observed to displace localised buckling, consequently affected the strength of the board (Popil, 2012). Hence, vent design should be selected with the cognisance of board properties being used in order to improve the strength of the package (Berry et al., 2017).

5.4.4 Comparison between the experimental and numerical compression strength for the package designs

Figures 5.13a – c show the plot of the buckling mode for the Control package with B-flute, C-flute and BC-flute. The buckling load or compression strength for the Control package design with B-flute, C-flute and BC-flute are 4536 N, 8021 N and 8884 N, respectively. The Control package with B-flute corrugated board had the lowest compression strength while the compression strength C-flute board and BC- flute board increased the compression strength of the Control package by 77% and 96%, respectively. Comparing the numerical compression strength of the Control package with B-flute (4334.05±85.22 N) with the experimental compression strength showed a difference of about 5%. For the Control package with C-flute (7268.57±158.47 N) and BC-flute (7945.35±261.29 N), the difference between the

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numerical compression strength and experimental results were about 10% and 11%, respectively.

The plots for the buckling shape of the various package design for all the vent areas (2%, 4% and 8%) evaluated for B-flute, C-flute and BC-flute board packages are shown in Figure 5.14, Figure 5.15 and Figure 5.16, respectively. From the plots, it was observed that buckling originated from the centre of the faces of the package, particularly the lengthwise (long) side of the package. Panyarjun and Burgess (2001) attributed failure of packages to localised crushing of the board on the faces of the package. In addition, it was observed that the width (short) side of the packages was more resistance to buckling. This may be attributed to the lower width-to-height ratio of the short side with compared to length-to-height ration of the long side. Wei et al. (2011) investigated the effect of aspect ratio on the compression strength of corrugated boxes and reported a decrease in compression strength with an increase in the aspect ratio.

Figure 5.17 shows the comparison between the experimental and simulation compression strength for all the package designs. Both experimental and simulation compression strength for all the package designs were shown to be significantly dependent on the percentage of vent area (Pathare et al., 2012b; Émond & Vigneault, 1998). Table 5.4 summarises the percentage difference and the correlation index between the numerical and experimental compression strength for all the package designs, for the different board grades and vent areas. The numerical predictions of the package strength agree reasonably well with the experimental results, although in most cases the model predictions were higher than the experimental results. For the B-flute, C-flute and BC-flute board packages, the range of the percentage difference between the numerical and experimental compression strength was within 8.6%, 9.8% and 11.2%, respectively. Furthermore, a high correlation index was obtained between the numerical and experimental results.