Comput Mech DOI 10.1007/s00466-007-0164-z ORIGINAL PAPER Detection of stiffness degradation in laminated composite plates by filtered noisy impact testing Sang-Youl Lee · Guillermo Rus · Taehyo Park Received: 18 January 2006 / Accepted: 25 January 2007 © Springer-Verlag 2007 Abstract The purpose of this paper is to detect damage (stiffness degradation) of laminated composite plates from noisy impact response data. The combined finite element method (FEM) with five degrees of free- dom (DOF) and the advanced noise filtering algorithm described in this paper may allow us not only to detect the deteriorated elements but also to find their locations and the extents. A first order shear deformation theory (FSDT) is used to predict the structural behavior and to detect damage of laminated composite plates. The filtering procedure is designed by means of a wavelet decomposition together with a selection of the measur- ing points, and the optimization criterion is constructed on an estimate of the probability of detection using genetic algorithms. All these techniques are applied for the first time to composites. The effects of filtered noise associated with the uncertainty of measurements due to the complex nature of composites are considered for different layup sequences, number of layers, and length– thickness ratios. Several numerical results show that the noise filtering system is computationally efficient in identifying stiffness degradation for complex structures such as laminated composites. S. -Y. Lee · T. Park Department of Civil Engineering, Hanyang University, Seoul 133-791, South Korea e-mail: [email protected] T. Park e-mail: [email protected] G. Rus (B ) Department of Structural Mechanics, University of Granada, Granada 18071, Spain e-mail: [email protected] Keywords Composite plate · Inverse problem · Impact testing · Wavelet analysis · Noise filter · Finite element method 1 Introduction Advanced composite materials are attractive for use in various engineering applications due to their high strength-to-weight and stiffness-to-weight ratios, corro- sion resistance, light weight and potentially high dura- bility. The mechanical behaviors of composite structures with damages are complicated and difficult to analyze for different layup sequences. Structural behavior of laminated composite plates with or without damages has been studied previously by a host of investigators using a variety of approaches [9, 12, 13, 21, 23]. These works, based on forward problems, produce specific responses from known damaged extent and location. Recently, some investigators started turning their attention to the damage detection by solving the inverse problem from static or dynamic responses obtained by the forward procedure. Direct search methods, such as neural networks, genetic algorithms and simulated annealing methods are developed and promisingly applied to the field of structural identification. Among them, genetic algorithms (GA) attract our attention because of the fact that the technique requires signifi- cantly small amount of data in dealing with complex problems, while attaining global convergence as opposed to gradient-based methods. Suh et al. [27] presented a hybrid neuro-genetic technique that is able to identify the location and extent of damage in a beam or frame structure using only the frequency information. Mares
Detection of stiffness degradation in laminated composite plates by filtered noisy impact testing
Jun 15, 2023
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