Experimental approach for characterizing the nonlinear, time and temperature-dependent constitutive response of open-cell polyurethane foams

Elastomeric foams are composite materials comprising of a polymeric elastomer and interconnected gas-filled pores, endowing them with exceptional compliance and the ability to undergo large, reversible deformations along with substantial volume change. These foams find extensive utility in contexts demanding compliance and compressibility, such as impact protection and cushioning, spanning a diverse range of applications. Changing temperature can dramatically alter foam stiffness, strength and deformation characteristics specifically around the material's glassy-rubbery transition temperature (Tg$$ {T}_g $$). With the aim of informing new constitutive model developments for elastomeric foams, we conducted a comprehensive series of large deformation, homogeneous compression and tension tests across strain rates from 10-2 s-1 to 100 s-1 and ambient temperatures ranging from -10 degrees C to 50 degrees C covering an even range around the material's Tg$$ {T}_g $$ of 20 degrees C. To achieve precise control of ambient temperatures during mechanical testing, we constructed a custom-designed environmental chamber for controlling the ambient temperature from -10 degrees C to 50 degrees C with a variation of less than 1 degrees C. The obtained digital image correlation based stress-strain data shows significant tension-compression asymmetry as well as significant dependence on strain rate and ambient temperature, especially above and below the glass transition temperature. We provide full access to these data sets for the future development of rate- and temperature-dependent constitutive models.