High Temperature Fracture Mechanics

The objective of this project is to develop a capability to model fracture of materials used in hypersonic vehicles that results from hypervelocity impact while exposed to extreme temperatures. Symplectic Engineering’s approach addresses this challenge at two levels. At the computational level, a Relaxed Extended Finite Element approach is pursued to represent (possibly intersecting) fractures lines independent of the underlying computational mesh. This approach is integrated with strategies that facilitate the simulation of shock waves that may develop as a result of extreme pressure engendered by the hypervelocity impact. The other level addressed is that of the material models. In Phase I, Symplectic Engineering chose to consider polycrystalline materials, coated with a silica-based ceramic thermal shield. A viscoplastic model based on multiplicative decompositions of the deformation gradient (mechanical-thermal and elastic-inelastic) will be pursued for the polycrystalline material, and an elastic-brittle model will be adopted for the silica-based ceramic material. The models will be implemented and applied to simulate experiments selected from the literature that will demonstrate the feasibility of the proposed approach. Symplectic Engineering will also propose as set of tests, to be undertaken in Phase II, for the identification of material properties and model validation. Approved for Public Release | 20-MDA-10398 (2 Mar 20)