Measurement of the Viscoelastic Bulk Modulus

A new piston-cylinder type pressurizable dilatometer has been developed to measure the time-dependent bulk modulus of viscoelastic materials. The PVT behavior and the glass transition temperature of a polystyrene have been measured as a function of pressure. Preliminary measurements of the time-dependent bulk modulus have also been made. The isothermal bulk modulus is important because its magnitude is directly related to isotropic residual stress development in curing thermoset-reinforced composites; in addition, by comparing the bulk and shear responses, proposed differences in the molecular origins can be explored.