Mechanical and Viscoelastic Behavior of Flexible Foam Under Combined Shear andCompression

摘要

The room temperature mechanical behavior (shear and normal stresses) of DowCorning Silastic 5370 RTV foam, a flexible, open-cell, polysiloxane foam was investigated under combined shear and compressive strains as functions of strain and time. Compressive stiffness of the foam showed a large dependence on compressive strain, while the shear stifiess was much less dependent on compression and shear. Interestingly, the normal (compressive) stress under shear showed a component that was quadratic in shear strain, decreasing with shear strain at compressions less than 20% (or even going into tension) and increasing with shear strains at compressions greater than 20%. Hysteresis in shear stress and normal stress was observed at high compressions. The foam showed slight viscoelasticity with the stress relaxing as t(Sup -n), as is typical for filled elastomers. The relaxation time exponent, n, showed little dependence on shear strain but became larger with increasing compressive strain indicating faster relaxation of stresses under high compressions. This is consistent with the increased hysteresis seen at larger compressions.