No abstract

A micro/macromechanical approach was used to model and simulate crack initiation and crack propagation in particulate composite structures. The approach used both the micromechanical and macromechanical analyses in tandem. The micromechanical analysis was based on a simplified micromechanical model and damage mechanics at the micro-level, and the macromechanical analysis utilized the finite element method. In using these methods, crack initiation and growth in a general shape of composite structure were investigated with an efficient computational effort. It was assumed that a crack initiates and/or propagates when localized damage is saturated. As a result, the crack length was assumed to be the size of the saturated damage zone. Matrix crack initiation and propagation at circular notch tips were simulated using this approach. Modeling and simulation were also conducted for cases of nonuniform particle distribution in particulate composite structures. Predicted results showed a good agreement with the experimental data.

No abstract

This paper summarizes the current progress in characterizing the damage field near the tip of a crack in a composite solid propellant, using the acoustic-imaging technique. The effects of loading history on the damage characteristics near the crack tips are discussed. In addition, the limitations of the acoustic-imaging technique are discussed, and recommendations for future work are presented.

Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and revie«/ing this collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highv»ay, Suite 1204, Arlington, VA 22202-4302. Respondents should be av»are that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid 0MB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS.