Fracture Behavior of Closed-cell Polyvinylchloride Foam Subjected to Low-velocity Impact

Abstract

Mode I impact fracture experiments were carried-out on three grades of Divinycell foam using single edge notched bend (SENB) specimens. A drop-weight rig was used to perform the low-velocity impact fracture tests. SENB specimens were tested at various impact potential energies by varying the drop-height in order to determine the critical impact potential energy at which the crack growth initiates from the notch tip. Three-dimensional linear-elastic finite element simulations of impact behavior of the SENB specimen were carried-out. The virtual crack closure technique was applied to analyze the strain energy release rate under impact loading. The mode I impact fracture toughness was characterized in terms of the critical dynamic strain energy release rate at the onset of crack growth from the notch tip. It was found that the impact fracture toughness increases rapidly with increasing the foam density. SENB specimens were tested also under static loading. The mode I static fracture toughness was extracted from the test data by the virtual crack closure technique in conjunction with finite element simulations. It was found that the impact fracture toughness is between 20.5% and 28.2% lower than the static one for the different grades. This finding indicates that the static fracture toughness should not be used in the fracture mechanics based design of rigid foam structures which are subjected to impact loading during their lifetime.