High Temperature Fracture Mechanics

TECHNOLOGY AREA(S): Info Systems, Materials, Weapons OBJECTIVE: Develop a capability to analyze the effects of high temperature environments on the fracture characteristics of high temperature materials in a hypervelocity impact. DESCRIPTION: This topic seeks models, concepts, and studies on the effects of the hypersonic flight regime on the mechanical fracture properties of materials. The aerodynamic heating (2,000 F) produced by extreme velocities in the atmosphere can affect the strength of materials. The goal of this topic is to further the state-of-the-art of modeling methods within fracture models. The materials under consideration could include, but are not limited to, silicon carbide composites, carbon-carbon composites, aluminum, and titanium. The model should characterize the fracture of these materials under high strain rates and high heat loadings simultaneously over short time periods. Previous topics have sought to characterize the fracture of materials after fatigue loading cycles. This topic does not seek that type of characterization; it is concerned with hypervelocity, high-temperature impacts. PHASE I: Develop research and development model(s) for the fracture and mechanics of the aforementioned materials under the impact conditions and the high temperatures resulting from travel at hypersonic velocities (i.e. above Mach 5), incorporating existing test data from the technical literature. Provide a methodology for modeling fracture that is proved out for feasibility via analytical studies that shows results against existing data. Develop a test plan to benchmark the model with empirical data. PHASE II: Implement the model(s) and test plan developed in Phase I for testing against relevant materials in a high-temperature environment. Include comparison against model runs as part of the Phase II effort. Improve the fidelity of the models based on the information gathered in testing. PHASE III: Transition the high temperature fracture modeling capability to an appropriate hydro-code and execute model runs for design and analysis cases of interest to the government. REFERENCES: 1: V.C.D. Dawson, R. Piacesi, and R.H. Waser, "Temperature Yield Strength Correlation of the Crater Size Produced in Aluminum by the Hypervelocity Impact of Aluminum Spheres," 1st AIAA Annual Meeting 1964. 2: H.B. Probst and H.T. McHenry, "A Study of the Impact Behavior of High-Temperature Materials," NACA Technical Note 3894. 3: J.H. Underwood, P.J. Cote, and G.N. Vigilante, "Themomechanical and Fracture Analysis of Silicon Carbide in Cannon Bore Applications," Technical Report ARCCD-TR-03009. 4: O. Heuze, J.C. Goutelle, and G. Baudin, "A New Temperature-Dependent Equation of State for Inert, Reactive, and Composite Materials," AIP Conference Proceedings, 620, 169 (2002). 5: R. Krueger, "Virtual crack closure technique: History, approach, and applications," Appl Mech Rev Vol 57, no 2, p. 109, March 2004. 6: R. Vignjevic, J.C. Campbell, et al, "Modelling Shock Waves in Composite Materials," AIP Conference Proceedings 955, 287 (2007). 7: R.A. Cunningham and H.L. McManus, "effects oKEYWORDS: Hypersonic, Fracture Mechanics, Aerothermodynamics, High-rate Loading, High-temperature Materials, High-temperature Mechanical Properties