On the Nonlinear Creep and Recovery of Open Cell Earplug Foams

The compressive creep and recovery of foam earplugs was studied at various applied stresses leading to different final creep strains. Deformation was determined from digital videos of the earplugs via image processing software. Creep could not be modeled by a single exponential in time; creep approximated a power law in time. Nonlinear viscoelasticity was observed: creep compliance depends on stress level. Nevertheless, for strain as high as 24%, recovery follows creep. Recovery does not follow creep at 70% strain. Recovery proceeds to completion given enough time.