Monitoring of damage mechanisms in sandwich composite materials using acoustic emission

Abstract. Composite materials are frequently used due to light weight and high stiffness. However, the use of composite materials is limited due to several micro-mechanical damage mechanisms, which are currently not well understood. Therefore, Acoustic Emission (AE) is frequently suggested for in-situ diagnosis of composite materials in Structural Health Monitoring. Elastic stress waves in the ultrasound regime are recorded using highly sensitive measurement equipment. Based on suitable analysis and interpretation of the waveform data, different micro-mechanical damage mechanisms such as delamination or fiber breakage can be distinguished. Frequently, data-driven approaches are suggested for classification of AE data. In literature, attenuation of AE due to wave propagation is currently the main limiting factor in AE-based diagnosis. In particular, AE is strongly attenuated in composite materials due to dispersion as dominant attenuation mechanism. Furthermore, depending on the source location, which is usually not known a-priori, different propagation paths are obtained in practice. Therefore, the effect of wave propagation on AE is important and can not be neglected to achieve reliable classification. However, the effect of different propagation paths on the classification performance is often not considered explicitly. Due to dependence of wave propagation behavior on waveform characteristics (e.g. frequency), it can be expected that the impact of wave propagation on AE classification performance depends also on the related source mechanism. Therefore, it is worth to study how classification performance of different source mechanisms is effected by wave propagation. In this paper, the dependence of the classification performance on different propagation distances is experimentally investigated in detail. To achieve highly reproducible AE measurements, different artificial AE sources are induced using surface mounted piezo elements. The corresponding waveforms are measured at two different locations. For classification, a convolutional neural network-based classification scheme is established. The pre-trained AlexNet architecture is fine-tuned using measurements obtained using different excitation signals. The classification performance is evaluated with particular focus on the impact of wave propagation. The variations in propagation distance have a strong impact on the classification performance. As main conclusion for AE-based SHM it can be stated that variations in the propagation path should be considered. Furthermore, the underlying source mechanisms should be taken into consideration for reliable performance estimation.

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An Approach to Acoustic Emission Technique Applications to Evaluate Damage Mechanisms in Composite Materials

MATEC Web of Conferences ◽

10.1051/matecconf/20153003009 ◽

2015 ◽

Vol 30 ◽

pp. 03009

Author(s):

C.R. Rios-Soberanis

Keyword(s):

Acoustic Emission ◽

Composite Materials ◽

Acoustic Emission Technique ◽

Damage Mechanisms

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Acoustic Emission and K-S Metric Entropy as Methods for Determining Mechanical Properties of Composite Materials

Sensors ◽

10.3390/s21010145 ◽

2020 ◽

Vol 21 (1) ◽

pp. 145

Author(s):

Lesław Kyzioł ◽

Katarzyna Panasiuk ◽

Grzegorz Hajdukiewicz ◽

Krzysztof Dudzik

Keyword(s):

Mechanical Properties ◽

Acoustic Emission ◽

Composite Material ◽

Composite Materials ◽

Testing Machine ◽

Measurement Data ◽

Entropy Method ◽

Displacement Sensor ◽

Metric Entropy ◽

Plastic Phase

Due to the unique properties of polymer composites, these materials are used in many industries, including shipbuilding (hulls of boats, yachts, motorboats, cutters, ship and cooling doors, pontoons and floats, torpedo tubes and missiles, protective shields, antenna masts, radar shields, and antennas, etc.). Modern measurement methods and tools allow to determine the properties of the composite material, already during its design. The article presents the use of the method of acoustic emission and Kolmogorov-Sinai (K-S) metric entropy to determine the mechanical properties of composites. The tested materials were polyester-glass laminate without additives and with a 10% content of polyester-glass waste. The changes taking place in the composite material during loading were visualized using a piezoelectric sensor used in the acoustic emission method. Thanks to the analysis of the RMS parameter (root mean square of the acoustic emission signal), it is possible to determine the range of stresses at which significant changes occur in the material in terms of its use as a construction material. In the K-S entropy method, an important measuring tool is the extensometer, namely the displacement sensor built into it. The results obtained during the static tensile test with the use of an extensometer allow them to be used to calculate the K-S metric entropy. Many materials, including composite materials, do not have a yield point. In principle, there are no methods for determining the transition of a material from elastic to plastic phase. The authors showed that, with the use of a modern testing machine and very high-quality instrumentation to record measurement data using the Kolmogorov-Sinai (K-S) metric entropy method and the acoustic emission (AE) method, it is possible to determine the material transition from elastic to plastic phase. Determining the yield strength of composite materials is extremely important information when designing a structure.

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Aspects of Strain Rate Effects on Some Composite Materials

10.1115/imece2000-1639 ◽

2000 ◽

Author(s):

Emmanuel O. Ayorinde

Keyword(s):

Acoustic Emission ◽

Composite Materials ◽

Strain Rate ◽

Matrix Cracking ◽

Epoxy Composites ◽

Fiber Architecture ◽

Strain Rate Effects ◽

Rate Effects ◽

General Strain ◽

Ultrasonic Images

Abstract Effects of moderate straining speed on the material and damage characteristics of beam samples of graphite/epoxy and E-glass/epoxy composites were investigated. The basic fiber architecture utilized was unidirectional, axial layup, but data was also obtained for the 45-degree orientation. Ultrasonic and acoustic emission (AE) inspections were utilized. The acoustic emission records show matrix cracking. The ultrasonic images revealed the regions of failure. The results show that in general, strain rate notably affects material and damage properties.

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Investigation of the Staging of Damage Accumulation in Polymer Composite Materials during Bending and Tensile Tests

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.887.116 ◽

2021 ◽

Vol 887 ◽

pp. 116-122

Author(s):

A.A. Bryansky ◽

O.V. Bashkov ◽

Daria P. Malysheva ◽

Denis B. Solovev

Keyword(s):

Acoustic Emission ◽

Composite Materials ◽

Polymer Composite ◽

Loading Rate ◽

Tensile Tests ◽

Mechanical Tests ◽

Rate Effect ◽

Polymer Composite Materials ◽

Static Tension ◽

Point Bend

The paper presents the results of the study of registered acoustic emission (AE) parameters during static deformation and damaging of polymer composite materials (PCM). Mechanical tests were done by a static tension and a static three-point bend, accompanied by an acoustic emission method. The assessment of the loading rate effect on defects formation processes was done by additional static tension test at rate equal half of recommended by the standard and static three-point bend test at rate ten times lower than that calculated by the standard. Clustering by frequency components of the recorded AE signals with a self-organizing Kohonen map was performed. The characteristics of the types of PCM structure damage by the centroids of the obtained clusters are given. Based on the clusters accumulation during mechanical tests, the stages of damage formation for static tension and static three-point bend, the loading rate effect on the process of damage formation are described.

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