The shock induced equation of state and shear strength of polyvinylidene difluoride

Polyvinylidene difluoride (PVDF) has found application as a piezoelectric stress gauge for the measurement of the shock response of materials. Therefore, it is perhaps surprising that little data concerning its bulk response to shock loading has reached the open literature. In this paper, we examine the behaviour of this polymer, both hydrostatically (equation of state; shock stress, shock velocity and particle velocity), and its deviatoric response (shear strength behind the shock front). Equation-of-state measurements show close agreement with existing data, but also a strong non-linearity in shock velocity at low particle velocities. The calculated hydrodynamic response also agrees well with existing pressure measurements, but is significantly lower than the measured shock stresses, suggesting that the shear strength of this material has a strong positive dependence on the applied shock pressure. Subsequent measurements of the lateral component of stress, which in combination with the known longitudinal stress has been used to calculate the shear strength, has confirmed this.