Failure Point
Permanent structural failure resulting from a sustained load below the instantaneous tensile strength of a material defines the limit of endurance. In heavy-duty corrugated packaging, creep rupture occurs when the constant weight of a stacked pallet causes the linerboard fibres to slide past one another until the box walls buckle. This time-dependent deformation progresses through stages of initial strain and steady state flow.
Environmental Influence
Moisture levels in a warehouse environment accelerate the rate at which paper structures reach their breaking point. High humidity or cyclic changes in relative humidity cause the cellulose network to swell and contract, which effectively pumps the molecular bonds toward separation. A container that supports a static load safely at fifty percent humidity might undergo creep rupture in forty-eight hours if the moisture level rises to ninety percent.
Load Calculation
Engineering safety factors for secondary packaging typically account for the duration of storage to prevent the collapse of lower tiers in a stack. Designers calculate the maximum allowable weight by dividing the short-term compression strength by a factor that represents the expected life of the box. If a grade demonstrates high resistance to creep rupture, the shipper can specify a lower grammage without risking the integrity of the supply chain.
Standard testing involves placing a static weight on a sample and recording the time elapsed until the physical structure can no longer support the mass.
