Damage Mechanics Approaches for Sharp and Diffuse Fracture Propagation: Application to Ice Sheet Fracture and Composite Delamination
Jimenez, Stephen Keith
Damage mechanics approaches are developed for the numerical modeling of fracture evolution along sharp (i.e., zero-thickness) and diffuse (i.e., finite-thickness) interfaces and applied to investigate ice sheet fracture and fatigue delamination of composites. Throughout this work, three computational damage mechanics models, namely the cohesive zone model (CZM), creep damage model (CDM), and phase field model (PFM) for brittle fracture, are implemented using the finite element method. The models are extended to incorporate time- and rate- dependent damage mechanisms, thus incorporating the multi-physics nature of fracture. The CZM is a robust methodology for simulating sharp crack growth under non-monotonic mixed-mode loading conditions where the potential crack path is known a priori. The gradient and nonlocal CDM and PFM approaches are suited for modeling the evolution of diffuse crack interfaces for quasi-brittle fracture where the crack paths are not known a priori. The selection of the CZM is motivated by the need to simulate interface degradation in laminate composites subjected to high-cycle fatigue loading, and parametric sensitivity studies are conducted in order to establish a reliable fatigue damage criterion. The creep damage approach is employed to model time-dependent crevasse propagation in polar ice sheets undergoing large creep deformations. The cohesive zone and phase field models are also deployed to model the time-independent, brittle fracture of polar ice sheets by simulating the evolution of water-filled crevasses. The damage mechanics approach is shown to be consistent with theoretical fracture mechanics models for predicting the penetration of crevasses through ice.