<title>Effect of experimental conditions on acousto-ultrasonic reproducibility</title>

Acousto-ultrasonic characterization of C/SiC composites under different loading configurations

“…The effect of experimental boundary conditions, such as transducer contact force, specimen support structure, and material damage state, on individual AU parameters acquired from CMC material specimens was also investigated [3][4]. AU parameters were shown to be sensitive to the contact force and specimen support structure.…”

“…The waveforms were analyzed to produce the measurable parameters: ultrasonic decay rate, M 0 , and f c . These three parameters were chosen based on the results of previous studies illustrating their consistency and ability to be correlated with damage [2][3][4]6]. Secondly, a single operator collected three sets of data from a single specimen, to determine whether the measurements were repeatable for a single operator with the manual setup.…”

“…The waveform is processed to produce a number of measurable parameters. The technique, often called the stress wave factor technique, correlates the measurable parameters, such as ultrasonic decay rate, M 0 and f c , to mechanical properties and damage in composite materials [1][2][3][4][5][6]. Instead of identifying each type of complex, microstructural damage, such as matrix cracking, fiber-matrix debonds, and fiber breakage, the technique is more responsive to distributed damage within the material.…”

“…AU's capabilities in characterizing the degree of damage and damage progression in CMC composite materials have been demonstrated [2][3][4][5]. The effect of experimental boundary conditions, such as transducer contact force, specimen support structure, and material damage state, on individual AU parameters acquired from CMC material specimens was also investigated [3][4].…”

“…However, they were shown to be more sensitive to the damage state of CMC material specimens than to the boundary conditions. AU parameters increased by 400 percent of their state prior to incurring damage [4]. Although f c has shown limited sensitivity to the damage state of a material, it has shown a high level of reproducibility and low standard deviations which makes it a viable parameter to study [2,4].…”