Stacking cartons in humid environmental conditions has the potential to cause cartons to fail at loads much less than their overall compressive strength, research from New Zealand Crown research institute Scion suggests.
With a failure rate up to as high as 11 percent of boxes used in the transport and storage of shipments of the world’s 90 million tonnes of packaging worth US$140 billion in 2013, it’s a big issue to get to grips with.
Scion, in association with Miami University, has been working on understanding how corrugated cardboard cartons, commonly used by the meat industry to transport and store products around the world, perform in real supply chain conditions.
Scion packaging research leader Lou Sherman explains placing cartons in stacks during transport and stage, subjects them to constant compressive loads for long periods of time. This can cause significant ‘creep deformation’, especially for boxes at the bottom of the pallets, which are under the highest loadings. Current box compression tests do not take creep deformation into account and so boxes are often not designed correctly.
What the research team – Sadakat Hussain, Douglas Coffin and Christine Todoroki – were looking at was the best ways to measure the creep deformation in different humidity levels to increase understanding in the area.
A novel finding in the paper, published in Packaging Technology and Science (July 2017), was the observation of a transition point where, at high loads, constant humidity was more detrimental than cyclic humidity conditions, but vice-versa for low loads. The fact that cyclic humidity affected the lower applied loads was significant, said the researchers, as this is the way cartons are commonly stacked in real supply chains.
“This highlights the need for both compression testing and cyclic humidity creep testing to give an indication of carton lifetime during the design process,” says Sherman.
More research is required on cyclic humidity creep and boxes made from different corrugated cardboards, the team determined.