Multi-crack propagation in PMMA plates under dynamic out-of-plane impact

In this paper, the multi-crack propagation within polymethyl methacrylate (PMMA) plates under out-of-plane impact is experimentally investigated. First, the dynamic propagation behaviors of in-plane radial and circular cracks are directly recorded using a non-contact optical measurement platform in which a high-speed imaging system is combined with a low-speed impact loading device. Second, the dynamic energy release rates and crack velocities of multiple cracks are studied using caustics, and the effects of impact speed and plate thickness are studied. Finally, a mathematical model of dynamic energy release rate which is related to the radial crack length is established based on the principle of energy conservation. The fracture mechanism of multi-crack propagation in PMMA plates is quantitatively analyzed.