INTERNAL CHARACTERIZATION OF DYNAMICALLY STRESSED MATERIALS

NASA HAS A STRONG INTEREST IN DEVELOPING ADVANCED STRUCTURALMATERIALS FOR VARIOUS SYSTEM SPPLICATIONS. IN PRACTICE, THEDEVELOPMENT OF NEW, OR THE IMPROVEMENT OF OLD, MATERIALS SYSTEMS IS AN ITERATIVE PROCESS IN WHICH THE RATE OF PROGRESS IS INTIMATELY RELATED TO THE UNDERSTANDING OF THE PROPERTIES AND BEHAVIOR OF THE MATERIALS AS A FUNCTION OF THEIR MICROSTRUCTURE. A NOVEL NDE INSTRUMENT WEDDING THE CAPABILITIES OF COMPUTED TOMOGRAPHY (CT) AND A LOAD FRAME ISPROPOSED. CT IS A NONINVASIVE RADIOGRAPHIC TECHNIQUE THAT PROVIDES QUANTITATIVE SPATIAL AND DENSITY INFORMATION ABOUT THE INTERNAL STRUCTURE OF MATERIALS. BY ALSO INCORPORATING ACOUSTIC EMISSION TRANSDUCERS, THE INSTRUMENT WOULD ENABLE THE USER TO FOCUS ATTENTION ON THE CROSS SECTION OF THE SAMPLE WHERE THE MOST INTERESTING DAMAGE IS OCCURRING DURINGSTRESS TESTING. SUCH AS INSTRUMENT WOULD PROVIDE A UNIQUE METHOD OF STUDYING THE GRADUAL ACCUMULATION OF DAMAGE IN A SPECIMEN BY MAKING IT POSSIBLE TO WATCH THE MOVEMENT AND PROPAGATION OF CRACKS AND DELAMINATIONS IN NEAR REAL TIME PRIOR TO FAILURE. PHASE I WILL IDENTIFY THE IMAGING CHARACTERISTICS THAT THE PROPOSED INSTRUMENT NEEDS TO HAVE AND CONCEPTUALIZE AN ENGINEERING DESIGN OF A DEVICE SUITABLEFOR PHASE II IMPLEMENTATION.