Designing Accelerated Creep Buckling Test Protocols for Downgauged Boxboard
Accelerated creep buckling protocols require cyclic humidity chambers and parallel platens to predict thin boxboard stacking failure under dead loads.
Stepped Isostress Method
Accelerated Testing
Prediction of long-term creep behavior in polymeric and cellulose materials can be achieved by subjecting a single specimen to a series of increased stress levels. In the testing of paperboard products, the stepped isostress method is an accelerated test protocol that applies sequential, elevated stress steps to one sample under controlled conditions. This approach reduces the total time needed to construct a complete creep curve for the board.
Stress Progression
Traditional creep testing requires multiple samples run for hundreds of hours under different constant loads. By contrast, the stepped isostress method shortens this process by increasing the load on a single specimen after fixed intervals of time. This step-by-step increase accelerates the creep process in a controlled, measurable manner.
Mathematical Scaling
The data collected from each step is mathematically shifted and combined using a superimposition principle to create a single master curve. This curve represents the long-term deformation behavior of the material under normal storage loads over years. Since paperboard is highly sensitive to temperature and moisture, this method is conducted in a climate-controlled room to isolate the stress effects from environmental changes.
Using this approach allows quality control teams to quickly verify the long-term stability of new paperboard formulations. The resulting curves provide reliable predictions of package performance in global distribution channels.