An Experimental Analysis for Damage Monitoring in Glass Fiber/Epoxy Composites During Fatigue Tests by Acoustic Emission
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TECHNICAL ARTICLE—PEER-REVIEWED
An Experimental Analysis for Damage Monitoring in Glass Fiber/ Epoxy Composites During Fatigue Tests by Acoustic Emission D. Xu . P. F. Liu . Z. P. Chen . S. Q. Zhang
Submitted: 28 June 2020 / in revised form: 2 September 2020 / Accepted: 22 September 2020 Ó ASM International 2020
Abstract As a non-destructive technique, Acoustic emission (AE) can be employed to detect the damage inside the material passively and then locate the damage source. However, fatigue loading poses challenges to AE signal acquisition and processing. In this paper, AE monitoring is performed on glass fiber/epoxy composite laminates under fatigue loads. Due to the intrinsic noise, wavelet packet decomposition is used for noise elimination. Results show that the noise components in original AE signals can be effectively eliminated by the wavelet analysis. Based on the difference of the arrival times, the line positioning method is shown to locate AE sources appearing in the laminates successfully. The peak frequency characteristic of each AE signal is utilized for damage mode classification. The fracture of the laminate is governed by delamination and fiber/breakage, followed by fiber/matrix interface debonding. Keywords Acoustic emission (AE) Failure analysis Composite laminates Fatigue loading
Introduction As a type of clean and renewable energy, wind energy has shown excellent application prospect under the energy crisis around the world. A high-efficiency system for wind D. Xu Z. P. Chen S. Q. Zhang Institute of Chemical Machinery and Process Equipment, School of Energy Engineering, Zhejiang University, Hangzhou 310027, China P. F. Liu (&) Ocean College, Zhejiang University, Zhoushan 316021, China e-mail: [email protected]
power generation depends largely on the superior performance of wind turbine blades. Now, fiber-reinforced composites achieve successful application in the blade due to its high strength/stiffness and low density. However, severe aerodynamic loads and environments, such as elevated temperature, hygrothermal effects, radiation, lightning, typhoon and storms, can increase the uncertainties of damage initiation, evolution and accumulation in the blade. These conditions subject the blades to a variety of stresses, typically including fatigue, bending, shearing and torsion. Therefore, structural health monitoring (SHM) techniques [1–3] should be used to address damage detection, location and identification so as to avoid the premature failure of the blade. Due to complex structures of the wind turbine blade, SHM on the blade poses challenges: (1) Conventional testing techniques are time-consuming and labor-intensive because of large sizes of blades, (2) Planar testing methods on surface structures cannot be implemented, (3) Destructive methods undoubtedly affect the remaining lifetime of the blade. By considering the problems above, acoustic emission (AE) is commonly taken as a dynamic non-destructive testing approach and has been widely applied to defect detection of various com
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