5.12 Nondestructive Evaluation – Use of Acoustic Emission for CMCs

Morscher, Gregory N.; Maillet, Emmanuel

doi:10.1016/b978-0-12-803581-8.09998-7

Cited by 4 publications

(3 citation statements)

References 34 publications

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“…The speed of sound (Δt x /x) increases throughout the test as damage develops [6,24]. This was accounted for by determining the Δt x from events which occurred outside the outer sensors, presumably in the grips [25]. There was a period of no AE activity between 100,000 and 130,000 s (Figure 4a).…”

Section: Resultsmentioning

confidence: 99%

“…The AE data were sorted according to the events which triggered the center sensor (#3) first, i.e., the gage section, which was used for post-test analysis. The location along the length was determined from the difference in times of arrival between the outermost sensors (#1 and #2) and the speed of sound as determined by events which occurred in the grip region and crossed the outer two sensors during the test [25]. However, when exact location was required for certain sets of data, manual inspection of waveforms to obtain the exact time of arrival from the time of the first peak were employed as described below.…”

Section: Materials and Methodologymentioning

confidence: 99%

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Damage Determination in Ceramic Composites Subject to Tensile Fatigue Using Acoustic Emission

Morscher

Han

2018

Materials

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Acoustic emission (AE) has proven to be a very useful technique for determining damage in ceramic matrix composites (CMCs). CMCs rely on various cracking mechanisms which enable non-linear stress–strain behavior with ultimate failure of the composite due to fiber failure. Since these damage mechanisms are all microfracture mechanisms, they emit stress waves ideal for AE monitoring. These are typically plate waves since, for most specimens or applications, one dimension is significantly smaller than the wavelength of the sound waves emitted. By utilizing the information of the sound waveforms captured on multiple channels from individual events, the location and identity of the sources can often be elucidated. The keys to the technique are the use of wide-band frequency sensors, digitization of the waveforms (modal AE), strategic placement of sensors to sort the data and acquire important contents of the waveforms pertinent for identification, and familiarity with the material as to the damage mechanisms occurring at prescribed points of the stress history. The AE information informs the damage progression in a unique way, which adds to the understanding of the process of failure for these composites. The AE methodology was applied to woven SiC fiber-reinforced melt-infiltrated SiC matrix composites tested in fatigue (R = 0.1) at different frequencies. Identification of when and where AE occurred coupled with waveform analysis led to source identification and failure progression. For low frequency fatigue conditions, damage progression leading to failure appeared to be due to fiber failure at or near the peak stress of the stress cycle. For higher frequency fatigue conditions, significantly greater amounts of AE were detected compared to low frequency tests a few hours prior to failure. Damage progression leading to failure included AE detected events which occurred on the unloading part of the fatigue cycle near the valley of the stress cycle. These events were associated with 90 tow longitudinal split and shear cracks presumably due to local compressive stresses associated with mating crack surface interactions during unloading. The local region where these occurred was the eventual failure location and the “valley” events appeared to influence the formation of increased local transverse cracking based on AE.

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Section: Resultsmentioning

confidence: 99%

Section: Materials and Methodologymentioning

confidence: 99%

Damage Determination in Ceramic Composites Subject to Tensile Fatigue Using Acoustic Emission

Morscher

Han

2018

Materials

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“…Acoustic emission (AE) detection is a potential NDT method [ 3 ]. AE is an elastic stress wave generated at the occurrence of damage in materials.…”

Section: Introductionmentioning

confidence: 99%

Fiber-Optic Sensor-Based Remote Acoustic Emission Measurement in a 1000 °C Environment

Okabe

2017

Sensors

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Recently, the authors have proposed a remote acoustic emission (AE) measurement configuration using a sensitive fiber-optic Bragg grating (FBG) sensor. In the configuration, the FBG sensor was remotely bonded on a plate, and an optical fiber was used as the waveguide to propagate AE waves from the adhesive point to the sensor. The previous work (Yu et al., Smart Materials and Structures 25 (10), 105,033 (2016)) has clarified the sensing principle behind the special remote measurement system that enables accurate remote sensing of AE signals. Since the silica-glass optical fibers have a high heat-resistance exceeding 1000 °C, this work presents a preliminary high-temperature AE detection method by using the optical fiber-based ultrasonic waveguide to propagate the AE from a high-temperature environment to a room-temperature environment, in which the FBG sensor could function as the receiver of the guided wave. As a result, the novel measurement configuration successfully achieved highly sensitive and stable AE detection in an alumina plate at elevated temperatures in the 100 °C to 1000 °C range. Due to its good performance, this detection method will be potentially useful for the non-destructive testing that can be performed in high-temperature environments to evaluate the microscopic damage in heat-resistant materials.

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Application of a remotely bonded fiber-optic Bragg grating sensor to acoustic emission testing for a carbon-carbon composite at a temperature of 1000 °C

Okabe

2022

Measurement

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5.12 Nondestructive Evaluation – Use of Acoustic Emission for CMCs

Cited by 4 publications

References 34 publications

Damage Determination in Ceramic Composites Subject to Tensile Fatigue Using Acoustic Emission

Damage Determination in Ceramic Composites Subject to Tensile Fatigue Using Acoustic Emission

Fiber-Optic Sensor-Based Remote Acoustic Emission Measurement in a 1000 °C Environment

Application of a remotely bonded fiber-optic Bragg grating sensor to acoustic emission testing for a carbon-carbon composite at a temperature of 1000 °C

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