scholarly journals Non-Model-Based Identification of Delamination in Laminated Composite Plates Using a Continuously Scanning Laser Doppler Vibrometer System

2018 ◽  
Vol 140 (4) ◽  
Author(s):  
Da-Ming Chen ◽  
Y. F. Xu ◽  
W. D. Zhu
Keyword(s):  
Composite Structure ◽  
Composite Plate ◽  
Structural Damage ◽  
Laser Doppler Vibrometer ◽  
Laminated Composite ◽  
Composite Plates ◽  
Scanning Laser ◽  
Laminated Composite Plates ◽  
Scanning Laser Doppler Vibrometer ◽  
Local Anomalies

Delamination frequently occurs in a laminated composite structure and can cause prominent local anomalies in curvature vibration shapes associated with vibration shapes of the composite structure. Spatially dense vibration shapes of a structure can be rapidly obtained by use of a continuously scanning laser Doppler vibrometer (CSLDV) system, which sweeps its laser spot over a vibrating surface of the structure. This paper introduces a continuous scanning scheme for general quadrangular scan areas assigned on plates and extends two damage identification methods for beams to identify delamination in laminated composite plates using a CSLDV system. One method is based on the technique that a curvature vibration shape from a polynomial that fits a vibration shape of a damaged structure can well approximate an associated curvature vibration shape of an undamaged structure and local anomalies caused by structural damage can be identified by comparing the curvature vibration shape of the damaged structure with that from the polynomial fit, and the other is based on the technique that a continuous wavelet transform can directly identify local anomalies in a curvature vibration shape caused by structural damage. The two methods yield corresponding damage indices and local anomalies in curvature vibration shapes can be identified in neighborhoods with high damage index values. Both numerical and experimental investigations on effectiveness of the two methods are conducted on a laminated composite plate with a delamination area. In the experimental investigation, delamination identification results from the two methods were compared with that from a C-scan image of the composite plate.

scholarly journals Experimental and Numerical Buckling Analyses of Laminated Composite Plates under Temperature Effects

2010 ◽  
Vol 19 (4) ◽  
pp. 096369351001900 ◽  
Author(s):  
Emin Ergun
Keyword(s):  
Composite Plate ◽  
Numerical Solutions ◽  
Laminated Composite ◽  
Composite Plates ◽  
Buckling Load ◽  
Fibre Reinforcement ◽  
Stacking Sequence ◽  
Laminated Composite Plates ◽  
Different Temperatures ◽  
Good Agreement

The aim of this study is to investigate, experimentally and numerically, the change of critical buckling load in composite plates with different ply numbers, orientation angles, stacking sequences and boundary conditions as a function of temperature. Buckling specimens have been removed from the composite plate with glass-fibre reinforcement at [0°]i and [45°]i (i= number of ply). First, the mechanical properties of the composite material were determined at different temperatures, and after that, buckling experiments were done for those temperatures. Then, numerical solutions were obtained by modelling the specimens used in the experiment in the Ansys10 finite elements package software. The experimental and numerical results are in very good agreement with each other. It was found that the values of the buckling load at [0°] on the composite plates are higher than those of other angles. Besides, symmetrical and anti-symmetrical conditions were examined to see the effect of the stacking sequence on buckling and only numerical solutions were obtained. It is seen that the buckling load reaches the highest value when it is symmetrical in the cross-ply stacking sequence and it is anti-symmetrical in the angle-ply stacking sequence.

Vibroacoustic analysis of a thin laminated composite plate with surface-boned piezoelectric patches and subjected to general boundary conditions

2021 ◽  
Vol 263 (4) ◽  
pp. 2501-2509
Author(s):  
Zhengmin Hu ◽  
Kai Zhou ◽  
Yong Chen
Keyword(s):  
Fourier Series ◽  
Boundary Conditions ◽  
Composite Plate ◽  
Laminated Composite ◽  
Composite Plates ◽  
General Boundary ◽  
General Boundary Conditions ◽  
Acoustic Response ◽  
Laminated Composite Plates ◽  
Laminated Composite Plate

In this paper, a semi-analytical model is proposed to deal with the vibroacoustic problems of laminated composite plates with surfaced-boned piezoelectric patches and subjected to general boundary condition using the modified Fourier series method. Based on Kirchhoff plate theory, the dynamic equation of the laminated composite plate is derived using Hamilton's principle. In order to satisfy general boundary conditions, the displacement solution of the plate is expressed in the form of two-dimensional Fourier series and serval auxiliary functions. The acoustic response of the laminated composite plate due to a harmonic concentrated force is obtained with the Rayleigh integral. Besides, the mass and stiffness contribution of the piezoelectric patch are taken into consideration in the present study. Through enough convergent studies and comparative studies, the convergence, accuracy and universality of the proposed method are validated. The developed semi-analytical model can be used for efficient and accurate analysis and design of laminated composite plates equipped with shunted piezoelectric patches. Finally, the effects of the resistor and inductor shunt damping circuits on the vibration and acoustic response is discussed.

scholarly journals Bending Response of Cross-Ply Laminated Composite Plates with Diagonally Perturbed Localized Interfacial Degeneration

2013 ◽  
Vol 2013 ◽  
pp. 1-13 ◽  
Author(s):  
Chee Zhou Kam ◽  
Ahmad Beng Hong Kueh
Keyword(s):  
Composite Plate ◽  
Laminated Composite ◽  
Composite Plates ◽  
Interface Element ◽  
Laminated Composite Plates ◽  
Laminated Composite Plate ◽  
Bending Performance ◽  
Element Approach ◽  
Bending Behavior ◽  
Bending Response

A laminated composite plate element with an interface description is developed using the finite element approach to investigate the bending performance of two-layer cross-ply laminated composite plates in presence of a diagonally perturbed localized interfacial degeneration between laminae. The stiffness of the laminate is expressed through the assembly of the stiffnesses of lamina sub-elements and interface element, the latter of which is formulated adopting the well-defined virtually zero-thickness concept. To account for the extent of both shear and axial weak bonding, a degeneration ratio is introduced in the interface formulation. The model has the advantage of simulating a localized weak bonding at arbitrary locations, with various degeneration areas and intensities, under the influence of numerous boundary conditions since the interfacial description is expressed discretely. Numerical results show that the bending behavior of laminate is significantly affected by the aforementioned parameters, the greatest effect of which is experienced by those with a localized total interface degeneration, representing the case of local delamination.

scholarly journals Operational modal analysis using lifted continuously scanning laser Doppler vibrometer measurements and its application to baseline-free structural damage identification

2019 ◽  
Vol 25 (7) ◽  
pp. 1341-1364 ◽  
Author(s):  
Y.F. Xu ◽  
Da-Ming Chen ◽  
W.D. Zhu
Keyword(s):  
Structural Damage ◽  
Damage Identification ◽  
Laser Doppler Vibrometer ◽  
Laser Doppler ◽  
Scanning Laser ◽  
Mode Shapes ◽  
Modal Parameters ◽  
Experimental Investigations ◽  
Scanning Laser Doppler Vibrometer ◽  
White Noise Excitation

A continuously scanning laser Doppler vibrometer (CSLDV) system is capable of efficient and spatially dense vibration measurements by sweeping its laser spot along a scan path assigned on a structure. This paper proposes a new operational modal analysis (OMA) method based on a data processing method for CSLDV measurements of a structure, called the lifting method, under white-noise excitation and applies a baseline-free method to identify structural damage using estimated mode shapes from the OMA method. The lifting method enables transformation of raw CSLDV measurements into measurements at individual virtual measurement points, as if the latter were made by use of an ordinary scanning laser Doppler vibrometer in a step-wise manner. It is shown that a correlation function with nonnegative time delays between lifted CSLDV measurements at two virtual measurement points on a structure under white-noise excitation and its power spectrum contain modal parameters of the structure, that is, natural frequencies, modal damping ratios, and mode shapes. The modal parameters can be estimated by using a standard OMA algorithm. A major advantage of the proposed OMA method is that curvature mode shapes associated with mode shapes estimated by the method can reflect local anomaly caused by small-sized structural damage, while those estimated by other existing OMA methods that use CSLDV measurements cannot. Numerical and experimental investigations are conducted to study the OMA method and baseline-free structural damage identification method. In the experimental investigation, effects of the scan frequency of a CSLDV system on the two methods were studied. It is shown in both the numerical and experimental investigations that modal parameters can be accurately estimated by the OMA method and structural damage can be successfully identified in neighborhoods with consistently high values of curvature damage indices.

Lamb-Wave-Based Damage Identification in Laminated Composite Plates

2014 ◽  
Vol 1014 ◽  
pp. 3-8
Author(s):  
Zai Lin Yang ◽  
Hamada M. Elgamal ◽  
Jian Wei Zhang
Keyword(s):  
Lamb Wave ◽  
Structural Damage ◽  
Damage Identification ◽  
Lamb Waves ◽  
Laminated Composite ◽  
Composite Plates ◽  
High Sensitivity ◽  
Scattered Wave ◽  
Propagation Path ◽  
Laminated Composite Plates

With advantages including capability of propagation over a significant distance and high sensitivity to abnormalities and inhomogeneity near the wave propagation path, Lamb waves can be energised to disseminate in a structure and any changes in material properties or structural geometry created by a discontinuity, boundary or structural damage can be identified by examining the scattered wave signals. This paper presents an overview of the Lamb-wave-based damage identification in laminated composite plates including the formulation of lamb waves in an isotropic plate.

Neural Network Based Buckling Strength Prediction of Laminated Composite Plate with Central Cutout

2014 ◽  
Vol 592-594 ◽  
pp. 560-564 ◽  
Author(s):  
P. Emmanuel Nicholas ◽  
K.P. Padmanaban ◽  
D. Vasudevan ◽  
I. Joseph Selvaraj
Keyword(s):  
Neural Network ◽  
Finite Element Analysis ◽  
Finite Element ◽  
Composite Plate ◽  
Power Transmission ◽  
Laminated Composite ◽  
Composite Plates ◽  
Inspection System ◽  
Laminated Composite Plates ◽  
Element Analysis

Laminated composite plates are greatly used in many applications where high specific strength and stiffness are mandatory. These structures may have holes in order to accommodate windows and doors if it is used for air craft structures or to provide cables and inspection system if it is used in the applications like power transmission systems and automobiles. The laminated composite plates with holes shall be analyzed using finite element analysis. It is necessary to optimize the parameters like thickness, fiber orientation, material and the stacking sequence to obtain the desired characteristics for these structures. But using finite element analysis makes the process more tedious job. With this in mind it is proposed here to construct the artificial neural network to predict the buckling behavior of the composite plate.

Optimal Design of Laminated Composite Plates for Maximum Buckling Load Using Genetic Algorithm

2005 ◽  
Vol 219 (9) ◽  
pp. 869-878 ◽  
Author(s):  
C. W. Kim ◽  
J. S. Lee
Keyword(s):  
Genetic Algorithm ◽  
Optimal Design ◽  
Uniaxial Compression ◽  
Composite Plate ◽  
Laminated Composite ◽  
Composite Plates ◽  
Buckling Load ◽  
Laminated Composite Plates ◽  
Worst Case ◽  
Case Design

An optimization procedure using a genetic algorithm (GA) is proposed to determine the optimal stacking sequence of laminated composite plates for the maximum buckling load under several different loadings, such as uniaxial compression, shear, biaxial compression, and the combination of shear and biaxial loadings. A series of optimal design is conducted for composite laminates having different aspect ratios, load conditions, and number of plies. Critical buckling load is taken as fitness function and fibre orientations are taken as design variables. A performance index is introduced to represent the effectiveness of optimal design with respect to worst case design. Then, for uniaxial compression loading, postbuckling behaviour is analysed numerically for the optimally designed composite plates as well as the worst case design composite plate. It shows the outstanding postbuckling performance of one of the optimally designed composite plates against the worst case design composite plate. Also, a GA finds the global solution without requiring auxiliary information such as derivatives of the objective function.

Dynamic Analysis of Orthotropic Laminated Composite Plate Under Axial Load on Elastic Foundation

2006 ◽  
Author(s):  
M. T. Ahmadian ◽  
T. Pirbodaghi
Keyword(s):  
Natural Frequency ◽  
Elastic Foundation ◽  
Composite Plate ◽  
Shear Deformation Theory ◽  
Compressive Force ◽  
Laminated Composite ◽  
Free Vibration Analysis ◽  
Composite Plates ◽  
Laminated Composite Plates ◽  
Laminated Composite Plate

In this paper, free vibration analysis of laminated composite plates is carried out using first shear deformation theory and finite element method. Effect of axial tension and compression forces on the natural frequencies of the structure is investigated. Applying elastic foundation under the laminated composite plates has enabled us to achieve desired frequencies. The displacements are based C° – nine plate bending element and each node has three degree of freedom. The equations of motion are derived using Hamilton's principle. Results indicate the tension forces will increase the natural frequency while the compression force reduces the natural frequency. The buckling force of plate is computed by increasing the absolute value of compressive force until the natural frequency tends to zero. Dynamic of moving mass in a circular path on the laminated composite plate is also investigated. Displacement of plate center reveals a sinusoidal pattern in time.

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