Dynamic flow response of rigid polymer foam subjected to direct impact

In this work, the dynamic response of closed-cell PMDI foam specimens with different initial densities subjected to direct impact loading was investigated using a shock-tube apparatus and digital image correlation. Cylindrical foam specimens with different densities were affixed on a rigid frame on one side while the impact load was applied to the other side. The full-field deformation of the polymeric foam specimen during the loading process was captured using stereovision high speed camera system. The load was measured using quartz impact force sensors located between the rigid frame and the specimen, while the full-field displacement and strain distributions were obtained using 3D DIC. A simple one-dimensional model was also proposed to calculate the change of specimen density at any given time during the deformation. The inertia stresses developed during high strain rate deformation were determined using the instantaneous density and the full-field acceleration distribution obtained from the displacement field measured by DIC. By using the load cell data, the calculated inertia stresses and the strain components obtained from DIC, the full field stress-strain distribution over the entire region of interest was extracted. The average stress-strain response of the specimens was also presented as a function of foam density.