Hygroexpansion-Creep Model for Corrugated Fiberboard

A model was developed for characterizing the creep response of corrugated fiberboard subjected to constant compression load and sinusoidally varying relative humidity. Separate hygroexpansion and mechanosorptive components of deformation during the primary and secondary phases of creep are characterized in terms of six parameters, A0, A, 0, T, μ1, and μ2, Parameters A0, and A are the magnitude and amplitude levels, respectively, of a sinusoidal hygroexpansion response, and 0 is the corresponding phase lag relative to relative humidity. The model makes mechanosorption a function of hygroexpansion and predicts an instantaneous creep rate that varies with the rate of hygroexpansion. An average creep rate of mechanosorption decreases from a value that initiates primary creep to a steady-state value throughout secondary creep. The change occurs exponentially with a time-constant T. Creep constants μ1 and μ2 are proportional to the initial and secondary creep rates, respectively. The model provides a way to characterize cyclic creep data