Determining the Stages of Deformation and Destruction of Composite Materials in a Static Tensile Test by Acoustic Emission

Abstract

Composite materials are used in many industries. They are construction materials that are being used more and more often, which makes it necessary to accurately identify the process of their destruction. Recent decades have resulted in an intensive increase in diagnostic tests of structures and mechanical elements. Non-destructive testing (NDT) represents a group of test methods (surface and volumetric) that provide information about the properties of the tested element without changing its structure. The method of acoustic emission (AE) is also being used more frequently. Thanks to the ability to detect and locate signal sources, as well as to perform tests during operation, it is a method that is increasingly used in industry. In this article, the acoustic emission was used to analyze the changes occurring in composite materials. Obtained parameters helped to determine the signals originating from fibre delamination, fibre cracking, etc., as well as the starting point of these changes and the stress values at which these changes occurred. The analysis of acoustic emission signals recorded during the tests helped to determine the values of amplitudes characteristic for the destruction mechanisms of considered composite materials. Signals with an amplitude in the range of 30–41 dB may indicate elastic–plastic deformation of the matrix. Signals with an amplitude in the range of 42–50 dB indicate matrix cracks with the accompanying phenomenon of fibre delamination. Signals with amplitudes greater than 50 dB indicate fibre breakage. Based on the test results, the permissible stress was determined; when exceeded, the mechanisms of damage to the structure of composite materials accumulate. This stress limit for the tested material is 70 MPa. The use of the acoustic emission method in mechanical tests may contribute to a greater knowledge of composite materials used as a construction material, as well as determine the stresses allowable for a given structure.

Deep Learning Approach for Damage Classification Based on Acoustic Emission Data in Composite Materials

“…Initial damage mode identification efforts only used one or a few features of the waveform to describe the emitting damage mode [67,68]. In recent years, based on our prior knowledge of AE signals, deep learning methods have been developed by combining feature evaluation algorithms [17,23,24]. While these low-dimensional representations are useful for indicating broader trends in damage mode shifts, they obstruct the high-fidelity characterization of signals [69].…”

“…A large number of AE features, including energy, duration, hits, amplitude, signal strength, peak frequency, rise time, and so on, can be extracted from the AE's electrical signal [18,[20][21][22][23]. All of these features can be used individually or together to [24,25] describe material and structural damage. When AE features are employed in certain combinations, damage mode identification can be achieved, and the AE characteristics of a specific damage mode can thus be discovered [17,[24][25][26][27].…”

“…All of these features can be used individually or together to [24,25] describe material and structural damage. When AE features are employed in certain combinations, damage mode identification can be achieved, and the AE characteristics of a specific damage mode can thus be discovered [17,[24][25][26][27]. Other analysis methods are also used to seek more evidence of damage during AE data analysis, including cluster analysis [28], principal component analysis (PCA) [29], correlation coefficients, modal acoustic emissions [30,31], etc.…”

Acoustic Emission Signal Characterisation of Failure Mechanisms in CFRP Composites Using Dual-Sensor Approach and Spectral Clustering Technique

“…However, these methods have several limitations regarding real-time evaluation, difficult feasibility or the voluminal portion of the material, which can be tested in real time. Hence, the acoustic emission method [ 7 ] has been used in a large number of studies [ 8 , 9 , 10 , 11 ] because it offers a practical and effective solution compared to the methods listed above. The AE method belongs to a group of NDT methods that are fully supported by international standards for applications in technical practice.…”

Identification of Multiple Mechanical Properties of Laminates from a Single Compressive Test

“…Delamination is an important damage mechanism for this kind of material [4,5]. It is of great significance to obtain the mechanical properties of the laminate with delamination efficiently for evaluating the state of the laminate and predicting the remaining life [6][7][8]. The ability to obtain a single mechanical property, such as the elastic property and the interlaminar property, has formed a variety of standards.…”