Deformation Phenomenon
Material deformation phenomenon occurs when a hygroscopic material under mechanical load undergoes higher creep when the ambient humidity is changing. This mechano-sorptive effect causes corrugated boxes to fail at load levels that would be safe under constant humidity. It is a fundamental property of cellulose fibres that differentiates them from synthetic polymers or metals.
Bond Rearrangement
Hydrogen bonds within the fibre network are constantly breaking and reforming as water molecules enter and leave the cell wall. When the material is under tension or compression, these bonds reform in a way that accommodates the external stress, leading to permanent deformation. The rate of creep is proportional to the rate of moisture change rather than the absolute moisture level.
This explains why warehouses with poor climate control see high rates of stack failure during seasonal transitions.
Structural Mitigation
Designing for the supply chain requires calculating a safety factor that accounts for this accelerated creep. Simply testing a box at ninety percent humidity is not enough to predict its behavior in a cycling environment. Engineers must specify board grades that have been engineered to minimize this response.
Structural designs that distribute the load away from the most moisture-sensitive areas can also help mitigate the risk. Application of moisture-resistant resins during the sizing process can stabilize the fibre network against these fluctuations.
