How Do Cracks Initiate and Grow in a Thin Glass Plate? A Peridynamic Analysis

In this report, we present peridynamic simulation results and experimental evidence for the origin and evolution of cracks in a thin glass plate that is impacted near its center, at moderate speeds (150m/s), by a small steel projectile. A polycarbonate thin backing plate is used to preserve location of glass fragments. In the computational model the tape used on the sides to hold the two plates together is absent. Upon impact, a series of circular cracks form on the strike face, followed by radial cracks advancing from the impact site towards the boundaries, driven by elastic deformations induced behind the Rayleigh wave. At the same time, a through-thickness Hertz-crack grows, as well as cracks parallel to the sides of the plates, induced by waves reflected from the boundaries reinforcing surface waves emanated from the impact region. We present evidence gathered from our simulations for the origin and evolution of these cracks, and confirm these results with fractography experiments of post-mortem samples. The results provide evidence of the predictive capabilities of the peridynamic model for simulating complex dynamic fracture behavior in brittle targets and offer arguments for what the sufficient ingredients in a model for dynamic brittle fracture should be. Presented at the U.S. National Congress on Theoretical and Applied Mechanics, June 17 2014.