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Real-time frequency determination of acoustic emission for different fracture mechanisms in carbon-epoxy composites
NDT&E International,Vol.
--
=ND T abstracts NDT Abstracts are compiled by AEA Technology are drawn from over 500 British and International
The study of defects
National NDT Centre, Harwell, Oxon, OX1 1 ORA, UK. The entries publications. Each issue concentrates on one or two subject areas.
in composites
by acoustic
Gubanova, G.N.; Tishkin, A.P.; Leksovskii, A.M.; Yudin, V.E.; Svetlichnyi, V.M.; Zaitsev, B.A.; Kudryavtsev, V.V. Relationship between acoustic emission and development of the damage zone in the interlaminar fracture of fiber composites
62028
Krivohodrov, V. Localization of acoustic composites
A study is made of unidirectional carbon-fiber-reinforced composites with both thermosetting and thermoplastic matrices. Experimental data on acoustic emission for unidirectional fiber composites with a crack is presented in the form of an exponential dependence of the number of AE signals on the stress-intensity factor. The increase in the size of the damage zone across the layers of the composite turns out to be linearly dependent on loading ,time (and, thus, on K-lc) in contrast to the usual quadratic dependence along the layers.
6096 1
Gariholdi, E.; Santulli, C.; Stivali, F.; Vedani, M. Evaluation of tensile damage in particulate-reinforced MMC’s by acoustic emission
Scripta Materiala, Vol. 35, No. 2, pp. 273-277 (1996) 61824 Gariholdi, E.; Santulli, C.; Stivali, F.: Vedani, M. Evaluation of damage in MMC’s by acoustic emission technique Forum, Vols. 217-222, Pt. 3, pp.
Ultrasonics, Vol.
34, No. 2-5,
pp. 321-325
(Jun.
and
Wooh, S-C.; Daniel, I.M.; Chun, H-J. Real-time monitoring of damage development in crossply composite laminates by means of ultrasonic and acoustic emission methods
issues
of Progress in Quantitative Nondestructive Evaluation, Vol. 14B. Proceedings of the 21st Symposium on Quantitative Nondestructive Evaluation, Snowmass Village, Colorado (United States), 31 Jul. - 5 Aug. 1994, pp. 1383-l 390. Edited by D.O. Thompson and D.E. Chimenti. Plenum Press (1995) ISBN 0306450623. A real time nondestructive evaluation method was developed and Review
of
1996)
applied to detection of damage evolution in composite materials for the purpose of developing damage accumulation and life prediction models. An attempt was made in an effort to characterize the damage and to correlate the ultrasonic backscattered energy and acoustic emission readings with damage in real time.
60769 Ceysson, 0.; Salvia, M.; Vincent, L. Damage mechanisms characterisation of carbon fibre/epoxy composite laminates by both electrical resistance measurements and acoustic emission analysis
Ceysson, 0.; Salvia, M.; Vincent, L.
Damage mechanisms characterization of carbon fiber/epoxy composite laminates by both electrical resistance measurements and acoustic emission analysis
Scripta Materialia, Vol. 34, No. 8, pp. 1273-1280, It has been shown that it is possible that the
(15 Apr. 1996) electrical resistance measurement allows to monitor in-situ the evolution of various internal damage nucleation and growth in CPRP such as fibre fractures, intraply matrix cracks and interply delaminations. The benefit of this technique relies on its simple usage and its accuracy.
Scripta Materialia, Vol. 34, No. 8, pp. 1273-1280 (IS Apr. 1996) Variation of the electrical conductivity can be taken as an indicator of the evolution of various types of damage in classical longitudinal UD but also in (* 45 degree) CPRP laminates. By comparison with Acoustic Emission, it has been shown that it is possible that the electrical resistance measurement allows one to monitor in-situ the evolution of various internal damage nucleation and growth in CPRP such as fiber fractures, intraply matrix cracks and interply delaminations.
Kwon, O-Y.; Lee, J-H.; Yoon, D-J. Acoustic emission during tensile loading impact-damaged CFRP laminates
de Groot, P.J.; Wljnen, P.A.M.; Janssen, R. B. F. Real-time frequency determination of acoustic emission different fracture mechanisms in carbon-epoxy composites
60765
60965
Journal of Acoustic Emission,
Vol.
of fiber
60869
Composites are formed by the intimate combination of a ductile resin and a brittle fibre reinforcing phase. We consider some issues related to the sources of acoustic emission within composites and the relationship of this emission to fundamental damage mechanisms operative. The philosophy of pattern recognition is considered with regard to quantification and identification of damage.
61330
in the fracture
1461-1466
(1996) Damage in a 6061-AI/AI0 composite was studied by the acoustic emission technique. Tension and compression tests were performed on the composite after either T4 or T6 aging treatments. The comparative analyses of the acoustic emission evolution and the microstructural observations of the materials tested allowed to investigate the effects of matrix strength and of loading condition on damage accumulation rate. 61611 Hill, R.; Okaroafor, ED.; Priston, A.M. Acoustic emission wave propagation model damage induction in composites
emission
Journal of Acoustic Emission, Vol. 13, No. 3-4, pp. 87-96 (1995) Distribution of acoustic emission (AE) signals within composite materials during deformation is studied. The present research has shown that the AE localization occurs due to two main reasons of a different physical nature: initial distribution of defects in the material and nonlinear dependence of microfracture probability upon applied stress. The dimensionless parameter characterizing AE localization: Parameter of Localization (PL), has been introduced. It is shown that the distribution of internal stress concentrations can be evaluated by the initial part of the PL vs. applied stress curve. This technique can be employed for nondestructive testing. Comparing experimental data with theoretical models has shown that different fracture mechanisms demonstrate a different dependence of PL on applied stress.
61829
Science
emission
loading/unloading tensile testing. Special attention was paid to determine optimal parameters of AE signals to characterize the microscopic fracture process of the composite laminates. Rms voltage of AE signals during the early stage of tensile loading was found to be an effective parameter to quantify the degree of impact damage. A newly defined parameter, integrity ratio, based on the nns voltage is also proposed.
Mechanics of Composite Materials, Vol. 31, No. 6, pp. 561-564 (1995)
Materials
30, No. 2, pp. 1077117, 1997 Elsevier Science Ltd Printed in Great Britain
of low
13, No. 3-4, pp. S83-S88
Composites Science and Technology, Vol. 55, No. 4, pp.
velocity
for
405-412
(1995) Carbon/epoxy material in the form of a unidirectional composite was loaded under different conditions to determine the frequency content of acoustic emission signals. Special specimens, designed to fail under well-defined modes such as matrix cracking, debonding, fibre pull-out and fibre failure, were tested from zero load to failure. The signals analyzed ranged from 50 to 600 kHz. It was concluded that matrix cracking released
(1995)
Carbon fiber/epoxy composite coupons previously damaged by low velocity impact were tested under static tensile loading and the progress of damage was monitored by acoustic emission (AE). The degree of impact damage has been correlated with the AE activity during monotonic or
107
N DT Abstracts frequencies between 90 and 180 kHz. fibre failure frequencies above 300 kHz, debonding frequencies between 240 and 310 kHz and pull-out frequencies between I80 and 240 kHz.
59757 Gariholdi, E.; Vedani, M.; Santulli, C.; Stivali, F. Evaluation of damage in metal matrix composites by means of acoustic emission monitoring
60566 Somiya, S.; Sugiyama, T. Study on fracture mechanisms of AFRP: observation methods and AE methods
Commission of the European Communities, EN-39200-ORA (1995) This report presents the results of tensile tests carried out to evaluate
[O /+45 /9O]s with
Recent Advances in Experimental Mechanics. Proceedings of the 10th International Conference on Experimental Mechanics, Lisbon (Portugal), 18-22 Jul. 1994, Vol. 2. pp. 1313-1317. Edited by J.F.Silva Games, F.B. Branco, et al. Balkema (1994). ISBN 9054103973 Tensile tests for AFRP [0 /f4S /9O]s laminate were conducted in order to analyze the microscopic fracture mechanisms by use of an ultrasonic flaw detector. and to study a relation between these fracture phenomena and the power spectrum characteristic of fracture sound. As a result, it was cleared that cracks occurred in 90 layer in the center grow and progress outwardly to cause delamination between layers in order, and the delamination was evaluated quantitatively. Also, in the analysis by the AE methods, we studied on the power spectra of some AE waves.
Bierogel, C.: Grellmann, W. Evaluation of thermal and acoustic emission means of local strain measurements 60365
of composites
Proceedings of the 9th Biennial European Conference ECF ‘9, Vama (Bulgaria), 21-25 Sep. 1992. Vol. I, Edited by S. Sedmak, A. Sedmak and D. Ruzic Materials Advisory Services Ltd. (1992) ISBN O-9478
by
on Fracturepp. 242-247. Engineering 17-49-2
(Vol.
1) Insitu-experiments by means of acoustic and thermal and acoustic emission provides a possibility of monitoring damage processes of tibres. interface and matrix. For micromechanical evaluation of damage processes of composites the integral strain isn’t suitable. Measurement of local deformation show that correlations to thermal and acoustic emission are existing.
Wooh, S.C.; Daniel, IN.; Chun, H.J. Real-time ultrasonic and acoustic emission damage in graphite/epoxy laminates 60244
Composites Engineering,
monitoring
Vol. 5, No. 12, pp. 1403-1412
of
(1995)
Progressive failure of a crossply composite laminate under uniaxial tension was characterized by correlating ultrasonic and acoustic emission measurements with damage in real time. Both ultrasonic backscattered
energy and acoustic emission gave consistent results and proved to he sensitive indicators of matrix cracking and other failure mechanisms.The acoustic emission signals were analyzed by investigating the amplitude and count frequency and the corresponding applied strain Loading/unloading tests showed that no additional damage occurs upon reloading up to the previous peak load.
Luo, J-J.; Wooh, S-C.; Daniel, I.M. Acoustic emission study of failure mechanisms in ceramic matrix composite under longitudinal tensile loading 59955
Journal of Composite (1995)
Materials,
Vol. 29, No. 15, pp. 1946-1961
Acoustic emission (AE) measurements were correlated with macroscopic stress-strain behavior and direct microscopic observations of damage mechanisms in a unidirectional ceramic matrix composite under longitudinal tensile loading.
59954 Breval, E.; Srikanth, V.; Suhbarao, E.C. Acoustic emission and microcracking in sapphire, sintered Alsub(2)Osub(J), Al/Alsub(2)0sub(3) composite, and aluminum Journal of the American 2541-2544 (Sep. 1995)
Ceramic
Society,
Vol.
78, No. 9, pp.
damage to metal matrix composites by monitoring acoustic emissions. The aim was to follow damage evolution during the tests by observing mechanical behaviour shown in the stress-strain curves. Aluminium alloy 2014 reinforced with 20% volume alumina particles was subjected to testing along with the non-reinforced alloy 2014 and the results compared. Damage mechanisms occurring in the two materials were then identified by use of fractographic analysis.
59747 Khoroshavina, S.G. Probabilistic models of reliability emission inspection of composites
'108
in the acoustic
Russian Journal of Nondestructive Testing, Vol. 30, No. 10, pp. 742- 750 (Oct. 1994) The acoustic-emission method for the diagnostics and prediction of the quality of composite materials is refined by the introduction of new defectivity parameters based on data from acoustic-emission tests of composites and by the formulation of probabilistic modes of the reliability evaluation of acoustic-emission inspection for these materials. This approach takes into account the probabilities of overrejection and underrejection. The proposed procedure makes possible the transition to a system of active manipulation of technology and to quality control in technological processes for the preparation of composites with predetermined properties.
Prosser. W.H.; Jackson. K.E.; Kellas, S.; Smith, B.T.; 59252 McKeon, J.; Friedman, A, Advanced waveform-based acoustic emission detection matrix cracking in composites
of
Materials Evaluation,
Vol. 53, No.9, pp. 1052-1058 (Sep. 1995) An advanced, waveform based acoustic emission system was used to study the initiation of transverse matrix cracking in cross-ply graphite/epoxy composites. The acoustic emission signals were detected with broad band, high fidelity sensors, and digitized for analysis. Plate wave propagation analysis was used to discriminate noise signals from those generated by cracks. The noise signals were confumed to have originated in the specimen grip region by a new, highly accurate form of location analysis which was independent of threshold setting.
Takashima, K.; Tonda, H.; Bowen, P. Acoustic emission and damage evolution reinforced Ti alloy composite 58998
Journal of Acoustic
Emission,
Vol.
13,
No.
in an SIC fiber 1-2,
pp.
S&S13
(Jan.-June 1995) Damage evolution in an Sic fiber reinforced Ti alloy composite (SCS6Ti-6AI-4V) has been assessed by acoustic emission (AE), stiffness loss and internal friction (mechanical damping). Damage in the composite was introduced by four point bending through both a series of step-wise monotoiic loading and unloading sequences, and cyclic loading. AE signals were monitored during the tests, and Young’s modulus and internal friction were measured by a flexural resonant method. In both stepwise loading and cyclic loading, the Young’s modulus decreased by only I % before failure of the specimen. However, the internal friction began to increase gradually after loading, and increased rapidly prior to failure in both types of tests. Cumulative AE energy increased with increasing internal friction in both types of tests. These tests suggest that the evolution of damage in such composites can be assessed by a combination of AE monitoring and internal friction measurements.
Anastassopoulos, A.A.; Philippidis, T.P. Clustering methodology for the evaluation of acoustic emission from composites
58994
Journal
A range of materials with brittle to ductile behavior (single-crystal and polycrystalline alumina, aluminum/alumina composite, and metallic aluminum) were investigated by acoustic emission (AE) methods for microcracking during hardness indentations or cooling from elevated temperatures (8OOsup(o)C. During indentation, the extent of crack formation (and the AE counts) decreased in the following order: sapphire, sintered alumina, aluminum/alumina composite with no microcracking in metallic aluminum. During cooling from 8OOsup(o)C, polycrystalline alumina exhibited more extensive microcracking than the aluminum/alumina composite, suggesting that the metallic phase in the aluminum/alumina composite absorbs stresses more than the glassy boundary phase in sintered alumina.
evaluation
of
Acoustic
Emission,
Vol.
13,
No.
1-2,
pp.
1 l-22
(Jan.-Jun. 1995) Partitional clustering is used for the interpretation of acoustic emission (AE) signals from glass fiber/epoxy composite specimens. Two different clustering methods are examined and procedures for numerical validation of the results are investigated. Comparison of clustering results with optical microscopy is used for further validation of the resulting partitions, while the initiation and growth of the different failure mechanisms is successfully characterized by plotting the cumulative events of each of the resulting classes. The proposed method highlights the potential and effectiveness of AE along with data clustering analysis as a powerful stand-alone nondestructive testing technique for the discrimination between various failure mechanisms.
--
=ND T abstracts NDT Abstracts are compiled by AEA Technology are drawn from over 500 British and International
The study of defects
National NDT Centre, Harwell, Oxon, OX1 1 ORA, UK. The entries publications. Each issue concentrates on one or two subject areas.
in composites
by acoustic
Gubanova, G.N.; Tishkin, A.P.; Leksovskii, A.M.; Yudin, V.E.; Svetlichnyi, V.M.; Zaitsev, B.A.; Kudryavtsev, V.V. Relationship between acoustic emission and development of the damage zone in the interlaminar fracture of fiber composites
62028
Krivohodrov, V. Localization of acoustic composites
A study is made of unidirectional carbon-fiber-reinforced composites with both thermosetting and thermoplastic matrices. Experimental data on acoustic emission for unidirectional fiber composites with a crack is presented in the form of an exponential dependence of the number of AE signals on the stress-intensity factor. The increase in the size of the damage zone across the layers of the composite turns out to be linearly dependent on loading ,time (and, thus, on K-lc) in contrast to the usual quadratic dependence along the layers.
6096 1
Gariholdi, E.; Santulli, C.; Stivali, F.; Vedani, M. Evaluation of tensile damage in particulate-reinforced MMC’s by acoustic emission
Scripta Materiala, Vol. 35, No. 2, pp. 273-277 (1996) 61824 Gariholdi, E.; Santulli, C.; Stivali, F.: Vedani, M. Evaluation of damage in MMC’s by acoustic emission technique Forum, Vols. 217-222, Pt. 3, pp.
Ultrasonics, Vol.
34, No. 2-5,
pp. 321-325
(Jun.
and
Wooh, S-C.; Daniel, I.M.; Chun, H-J. Real-time monitoring of damage development in crossply composite laminates by means of ultrasonic and acoustic emission methods
issues
of Progress in Quantitative Nondestructive Evaluation, Vol. 14B. Proceedings of the 21st Symposium on Quantitative Nondestructive Evaluation, Snowmass Village, Colorado (United States), 31 Jul. - 5 Aug. 1994, pp. 1383-l 390. Edited by D.O. Thompson and D.E. Chimenti. Plenum Press (1995) ISBN 0306450623. A real time nondestructive evaluation method was developed and Review
of
1996)
applied to detection of damage evolution in composite materials for the purpose of developing damage accumulation and life prediction models. An attempt was made in an effort to characterize the damage and to correlate the ultrasonic backscattered energy and acoustic emission readings with damage in real time.
60769 Ceysson, 0.; Salvia, M.; Vincent, L. Damage mechanisms characterisation of carbon fibre/epoxy composite laminates by both electrical resistance measurements and acoustic emission analysis
Ceysson, 0.; Salvia, M.; Vincent, L.
Damage mechanisms characterization of carbon fiber/epoxy composite laminates by both electrical resistance measurements and acoustic emission analysis
Scripta Materialia, Vol. 34, No. 8, pp. 1273-1280, It has been shown that it is possible that the
(15 Apr. 1996) electrical resistance measurement allows to monitor in-situ the evolution of various internal damage nucleation and growth in CPRP such as fibre fractures, intraply matrix cracks and interply delaminations. The benefit of this technique relies on its simple usage and its accuracy.
Scripta Materialia, Vol. 34, No. 8, pp. 1273-1280 (IS Apr. 1996) Variation of the electrical conductivity can be taken as an indicator of the evolution of various types of damage in classical longitudinal UD but also in (* 45 degree) CPRP laminates. By comparison with Acoustic Emission, it has been shown that it is possible that the electrical resistance measurement allows one to monitor in-situ the evolution of various internal damage nucleation and growth in CPRP such as fiber fractures, intraply matrix cracks and interply delaminations.
Kwon, O-Y.; Lee, J-H.; Yoon, D-J. Acoustic emission during tensile loading impact-damaged CFRP laminates
de Groot, P.J.; Wljnen, P.A.M.; Janssen, R. B. F. Real-time frequency determination of acoustic emission different fracture mechanisms in carbon-epoxy composites
60765
60965
Journal of Acoustic Emission,
Vol.
of fiber
60869
Composites are formed by the intimate combination of a ductile resin and a brittle fibre reinforcing phase. We consider some issues related to the sources of acoustic emission within composites and the relationship of this emission to fundamental damage mechanisms operative. The philosophy of pattern recognition is considered with regard to quantification and identification of damage.
61330
in the fracture
1461-1466
(1996) Damage in a 6061-AI/AI0 composite was studied by the acoustic emission technique. Tension and compression tests were performed on the composite after either T4 or T6 aging treatments. The comparative analyses of the acoustic emission evolution and the microstructural observations of the materials tested allowed to investigate the effects of matrix strength and of loading condition on damage accumulation rate. 61611 Hill, R.; Okaroafor, ED.; Priston, A.M. Acoustic emission wave propagation model damage induction in composites
emission
Journal of Acoustic Emission, Vol. 13, No. 3-4, pp. 87-96 (1995) Distribution of acoustic emission (AE) signals within composite materials during deformation is studied. The present research has shown that the AE localization occurs due to two main reasons of a different physical nature: initial distribution of defects in the material and nonlinear dependence of microfracture probability upon applied stress. The dimensionless parameter characterizing AE localization: Parameter of Localization (PL), has been introduced. It is shown that the distribution of internal stress concentrations can be evaluated by the initial part of the PL vs. applied stress curve. This technique can be employed for nondestructive testing. Comparing experimental data with theoretical models has shown that different fracture mechanisms demonstrate a different dependence of PL on applied stress.
61829
Science
emission
loading/unloading tensile testing. Special attention was paid to determine optimal parameters of AE signals to characterize the microscopic fracture process of the composite laminates. Rms voltage of AE signals during the early stage of tensile loading was found to be an effective parameter to quantify the degree of impact damage. A newly defined parameter, integrity ratio, based on the nns voltage is also proposed.
Mechanics of Composite Materials, Vol. 31, No. 6, pp. 561-564 (1995)
Materials
30, No. 2, pp. 1077117, 1997 Elsevier Science Ltd Printed in Great Britain
of low
13, No. 3-4, pp. S83-S88
Composites Science and Technology, Vol. 55, No. 4, pp.
velocity
for
405-412
(1995) Carbon/epoxy material in the form of a unidirectional composite was loaded under different conditions to determine the frequency content of acoustic emission signals. Special specimens, designed to fail under well-defined modes such as matrix cracking, debonding, fibre pull-out and fibre failure, were tested from zero load to failure. The signals analyzed ranged from 50 to 600 kHz. It was concluded that matrix cracking released
(1995)
Carbon fiber/epoxy composite coupons previously damaged by low velocity impact were tested under static tensile loading and the progress of damage was monitored by acoustic emission (AE). The degree of impact damage has been correlated with the AE activity during monotonic or
107
N DT Abstracts frequencies between 90 and 180 kHz. fibre failure frequencies above 300 kHz, debonding frequencies between 240 and 310 kHz and pull-out frequencies between I80 and 240 kHz.
59757 Gariholdi, E.; Vedani, M.; Santulli, C.; Stivali, F. Evaluation of damage in metal matrix composites by means of acoustic emission monitoring
60566 Somiya, S.; Sugiyama, T. Study on fracture mechanisms of AFRP: observation methods and AE methods
Commission of the European Communities, EN-39200-ORA (1995) This report presents the results of tensile tests carried out to evaluate
[O /+45 /9O]s with
Recent Advances in Experimental Mechanics. Proceedings of the 10th International Conference on Experimental Mechanics, Lisbon (Portugal), 18-22 Jul. 1994, Vol. 2. pp. 1313-1317. Edited by J.F.Silva Games, F.B. Branco, et al. Balkema (1994). ISBN 9054103973 Tensile tests for AFRP [0 /f4S /9O]s laminate were conducted in order to analyze the microscopic fracture mechanisms by use of an ultrasonic flaw detector. and to study a relation between these fracture phenomena and the power spectrum characteristic of fracture sound. As a result, it was cleared that cracks occurred in 90 layer in the center grow and progress outwardly to cause delamination between layers in order, and the delamination was evaluated quantitatively. Also, in the analysis by the AE methods, we studied on the power spectra of some AE waves.
Bierogel, C.: Grellmann, W. Evaluation of thermal and acoustic emission means of local strain measurements 60365
of composites
Proceedings of the 9th Biennial European Conference ECF ‘9, Vama (Bulgaria), 21-25 Sep. 1992. Vol. I, Edited by S. Sedmak, A. Sedmak and D. Ruzic Materials Advisory Services Ltd. (1992) ISBN O-9478
by
on Fracturepp. 242-247. Engineering 17-49-2
(Vol.
1) Insitu-experiments by means of acoustic and thermal and acoustic emission provides a possibility of monitoring damage processes of tibres. interface and matrix. For micromechanical evaluation of damage processes of composites the integral strain isn’t suitable. Measurement of local deformation show that correlations to thermal and acoustic emission are existing.
Wooh, S.C.; Daniel, IN.; Chun, H.J. Real-time ultrasonic and acoustic emission damage in graphite/epoxy laminates 60244
Composites Engineering,
monitoring
Vol. 5, No. 12, pp. 1403-1412
of
(1995)
Progressive failure of a crossply composite laminate under uniaxial tension was characterized by correlating ultrasonic and acoustic emission measurements with damage in real time. Both ultrasonic backscattered
energy and acoustic emission gave consistent results and proved to he sensitive indicators of matrix cracking and other failure mechanisms.The acoustic emission signals were analyzed by investigating the amplitude and count frequency and the corresponding applied strain Loading/unloading tests showed that no additional damage occurs upon reloading up to the previous peak load.
Luo, J-J.; Wooh, S-C.; Daniel, I.M. Acoustic emission study of failure mechanisms in ceramic matrix composite under longitudinal tensile loading 59955
Journal of Composite (1995)
Materials,
Vol. 29, No. 15, pp. 1946-1961
Acoustic emission (AE) measurements were correlated with macroscopic stress-strain behavior and direct microscopic observations of damage mechanisms in a unidirectional ceramic matrix composite under longitudinal tensile loading.
59954 Breval, E.; Srikanth, V.; Suhbarao, E.C. Acoustic emission and microcracking in sapphire, sintered Alsub(2)Osub(J), Al/Alsub(2)0sub(3) composite, and aluminum Journal of the American 2541-2544 (Sep. 1995)
Ceramic
Society,
Vol.
78, No. 9, pp.
damage to metal matrix composites by monitoring acoustic emissions. The aim was to follow damage evolution during the tests by observing mechanical behaviour shown in the stress-strain curves. Aluminium alloy 2014 reinforced with 20% volume alumina particles was subjected to testing along with the non-reinforced alloy 2014 and the results compared. Damage mechanisms occurring in the two materials were then identified by use of fractographic analysis.
59747 Khoroshavina, S.G. Probabilistic models of reliability emission inspection of composites
'108
in the acoustic
Russian Journal of Nondestructive Testing, Vol. 30, No. 10, pp. 742- 750 (Oct. 1994) The acoustic-emission method for the diagnostics and prediction of the quality of composite materials is refined by the introduction of new defectivity parameters based on data from acoustic-emission tests of composites and by the formulation of probabilistic modes of the reliability evaluation of acoustic-emission inspection for these materials. This approach takes into account the probabilities of overrejection and underrejection. The proposed procedure makes possible the transition to a system of active manipulation of technology and to quality control in technological processes for the preparation of composites with predetermined properties.
Prosser. W.H.; Jackson. K.E.; Kellas, S.; Smith, B.T.; 59252 McKeon, J.; Friedman, A, Advanced waveform-based acoustic emission detection matrix cracking in composites
of
Materials Evaluation,
Vol. 53, No.9, pp. 1052-1058 (Sep. 1995) An advanced, waveform based acoustic emission system was used to study the initiation of transverse matrix cracking in cross-ply graphite/epoxy composites. The acoustic emission signals were detected with broad band, high fidelity sensors, and digitized for analysis. Plate wave propagation analysis was used to discriminate noise signals from those generated by cracks. The noise signals were confumed to have originated in the specimen grip region by a new, highly accurate form of location analysis which was independent of threshold setting.
Takashima, K.; Tonda, H.; Bowen, P. Acoustic emission and damage evolution reinforced Ti alloy composite 58998
Journal of Acoustic
Emission,
Vol.
13,
No.
in an SIC fiber 1-2,
pp.
S&S13
(Jan.-June 1995) Damage evolution in an Sic fiber reinforced Ti alloy composite (SCS6Ti-6AI-4V) has been assessed by acoustic emission (AE), stiffness loss and internal friction (mechanical damping). Damage in the composite was introduced by four point bending through both a series of step-wise monotoiic loading and unloading sequences, and cyclic loading. AE signals were monitored during the tests, and Young’s modulus and internal friction were measured by a flexural resonant method. In both stepwise loading and cyclic loading, the Young’s modulus decreased by only I % before failure of the specimen. However, the internal friction began to increase gradually after loading, and increased rapidly prior to failure in both types of tests. Cumulative AE energy increased with increasing internal friction in both types of tests. These tests suggest that the evolution of damage in such composites can be assessed by a combination of AE monitoring and internal friction measurements.
Anastassopoulos, A.A.; Philippidis, T.P. Clustering methodology for the evaluation of acoustic emission from composites
58994
Journal
A range of materials with brittle to ductile behavior (single-crystal and polycrystalline alumina, aluminum/alumina composite, and metallic aluminum) were investigated by acoustic emission (AE) methods for microcracking during hardness indentations or cooling from elevated temperatures (8OOsup(o)C. During indentation, the extent of crack formation (and the AE counts) decreased in the following order: sapphire, sintered alumina, aluminum/alumina composite with no microcracking in metallic aluminum. During cooling from 8OOsup(o)C, polycrystalline alumina exhibited more extensive microcracking than the aluminum/alumina composite, suggesting that the metallic phase in the aluminum/alumina composite absorbs stresses more than the glassy boundary phase in sintered alumina.
evaluation
of
Acoustic
Emission,
Vol.
13,
No.
1-2,
pp.
1 l-22
(Jan.-Jun. 1995) Partitional clustering is used for the interpretation of acoustic emission (AE) signals from glass fiber/epoxy composite specimens. Two different clustering methods are examined and procedures for numerical validation of the results are investigated. Comparison of clustering results with optical microscopy is used for further validation of the resulting partitions, while the initiation and growth of the different failure mechanisms is successfully characterized by plotting the cumulative events of each of the resulting classes. The proposed method highlights the potential and effectiveness of AE along with data clustering analysis as a powerful stand-alone nondestructive testing technique for the discrimination between various failure mechanisms.