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Peridynamic studies of interactions between stress waves and propagating cracks in brittle solids
The dynamic interaction between propagating cracks and stress waves is a complex and challenging problem responsible for the evolution of failure and damage in brittle materials. The peridynamics formulation is used here to study damage and fragmentation induced by impact in a glass plate and intersonic crack propagation in a unidirectional fiber-reinforced composite (FRC). We first show how the peridynamic model is able to explain how cracks form in impact of a thin glass plate. The computational results are compared with those from experiments. Peridynamics captures all of the different types of crack systems seen in experiments, including some fine roughness on the surface of the Hertz cone-crack, when this crack turns and grows transversal through the plate thickness. Understanding how and why various cracks are initiated, and propagate in the brittle material can help us, in the future, understand how to control crack growth and design better protective systems.^ In the second part of the thesis, an improved peridynamic model for FRCs is introduced. We test the model against a well-known experiment in which, under mixed-mode impact loading conditions, a crack reaches intersonic propagation speeds and generates a shock wave as it propagates. These characteristics of brittle fracture in unidirectional FRCs are reproduced by our peridynamic model. Moreover, using a sufficiently small nonlocal region, the model captures the crack propagation speed measured in experiments. We explain why the crack starts propagating long after the first stress wave reaches the tip of the pre-crack. We also provide a critical assessment of other types of peridynamic models for FRCs proposed recently in the literature. In FRCs, the micro-structure and anisotropy lead to complicated stress/strain states that are further influenced by interactions between elastic waves and propagating cracks. We verify these models for wave propagation examples and then use them to model fracture and damage evolution and provide guidance on which models should be used and why. ^
Wang, Yenan, "Peridynamic studies of interactions between stress waves and propagating cracks in brittle solids" (2015). ETD collection for University of Nebraska - Lincoln. AAI3739557.