Impact fracture of glass‐flake reinforced polypropylene

The impact resistance of glass‐flake reinforced polypropylene was analyzed over a wide range of loading rates and glass‐flake concentrations. It was found that the dynamic fracture toughness, K d , of the composite is strongly rate‐dependent. When impact velocity is increased, K d first decreases, attains a minimum value, and then increases with impact speed. The increase in K d with loading rate is attributed to the blunting effect at the crack tip, induced by adiabatic heating. The addition of glass flakes substantially increases the dynamic fracture toughness of polypropylene. The increase in K d with glass‐flake content is also more pronounced when the loading rate is increased. The blunting effect was found to increase with glass‐flake concentration up to 30 percent by weight, leading to a stronger increase in K d with glass‐flake content from 0 to 30 percent. Above 30 percent, the blunting effect diminishes with concentration.