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The aim of this study is to report the effect of delamination on the vibration characteristics of composite sandwich beams. The natural frequencies and corresponding vibration modes of a free-free sandwich beam with delamination of various sizes and locations are predicted using a two-dimensional finite element analysis (FEA). The presence of delam...
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Impact of the composite sandwich made of materials that become defect, how defects after impact in material need to be examined .Is that defected composites and wich still has the strength toremain in use?, then the bending after impact strength testing must be done to answer these questions.Composite sandwich with bamboo fiber-fiber glass reinforc...
Citations
... Significant gains are achieved during finite element investigations in terms of model simplicity in use and model modification, resolution time, and hardware resources. Ref [12] considers how discharge affects the inherent frequencies of the dielectric sandwich. Nomenclature, materials, cell composition, production processes, and honeycomb uses are explained in reference [13]. ...
... Impact load of Al foam increases with increasing impact of velocities. Baba and Gibson [36] studied the effect vibration characteristics of sandwich composite CFRP with foam as core. They concluded that delamination affects the stiffness of the beam and results in changes of natural frequencies. ...
Sandwich structures made up of honeycomb composites have high-strength structural applications because of their low weight and high stiffness. High flexural stiffness is a major aspect in developing structures with several multilayer materials. Statistical tests analyze the behavior of loads to which a body can sustain without failure and dynamic behavior defines the overall failure modes and the vibration characteristics. In this study, static and dynamic responses of honeycomb sandwich structures are performed under static load conditions. The structures made up of carbon fiber reinforcement including various volume fractions of carbon nanotubes (CNT) used as face sheets and aluminum 3003 as core were prepared. Four distinct combinations were examined in this investigation, including one where the face sheet was made primarily of carbon fiber and epoxy without CNT and three others where CNT was added into the matrix with 2 w%, 5 w% and 7.5 w%, respectively. The three-point bending test was performed according to the ASTM standard C393 experimentally and the validation was performed computationally using ANSYS. Free vibration test was carried out analyzing different mode shapes and natural frequencies. In static tests, there was a high correlation between experimental and simulation results. The obtained results reveal the exceptional behavior of the proposed honeycomb structure. The proposed material combination is anticipated to show a high degree of pragmatism in aeronautical applications based on the findings.
... Finally, the accuracy of the theory is confirmed both by published literature and by experiment. Okutan Baba and Gibson [4] reported the delamination effect on the vibration characteristics of composite sandwich beams. Using a two-dimensional finite element analysis (FEA) the natural frequencies and corresponding vibration modes of a free-free sandwich beam with delamination of various sizes and locations are predicted. ...
A high specific stiffness, high specific strength, and tailoring the properties for specific application have attracted the attention of the researchers to work in the field of laminated composites and Sandwich structures. Rapid use of these laminated composites and Sandwich structures necessitated the development of new theories that suitable for the bending, buckling and vibration analysis. Many articles were published on free vibration of beams, plates, shells laminated composites and sandwich structures. In this article, a review on free vibration analysis of shear deformable isotropic beams, plates, shells, laminated composites and sandwich structures based on various theories and the exact solution is presented. In addition to this, the literature on finite element modeling of beams, plates, shells laminated composites and sandwich structures based on classical and refined theories is also reviewed. The present article is an attempt to review the available literature, made in the past few decades on free flexural vibration response of Fiber Metal laminated Composites and Sandwich panels using different analytical models, numerical techniques, and experimental methods.
... During the finite element analyses, substantial advantages were obtained with regard to ease of modeling and model modification, solution time and hardware resources. Reference [3] studied the effect of delamination on the natural frequencies and corresponding modes of a free-free sandwich beam. Reference [4] explained honeycomb manufacturing methods, materials, cell configuration, terminology and uses. ...
In this study free vibration analysis of aluminum honeycomb sandwich structures were carried out experimentally and numerically. The natural frequencies and mode shapes of sandwich structures fabricated with different configurations for clamped-free boundary condition were determined. The effects of lower and upper face sheet thickness, the core material thickness, cell diameter, cell angle and foil thickness on the vibration characteristics were examined. The numerical studies were performed with ANSYS package. While the sandwich structures were modeled in ANSYS the continuum model was used. Later, the numerical results were compared with the experimental findings.
... They analyzed the delaminated beam as seven interconnected EB beams and observed a monotonic relation between the natural frequency and the compressive load. Baba and Gibson [223] used 2D FEA to predict the natural frequencies and corresponding vibration modes of a free-free sandwich beam with delamination of various sizes and locations. Baba and Thoppul [142] made a experimental study to determine the effect of curvatures and debond on the flexural stiffness and strength of composite sandwich beam structures. ...
In this paper, we present the results related to the development of a technique for low-frequency acoustic non-destructive testing of layered composite structures. The main goal was to detect and pinpoint potential bundles in such structures. To do this, we used as an object of research a manufactured carbon fiber panel consisting of eight layers, with the addition of inclusions between the fourth and fifth layers. By performing a finite element analysis of the effects of an omnidirectional piezoelectric transducer mounted in the center of the panel, we found that the amplitudes of the out-of-plane velocities increase significantly near the lamination regions. Our technique includes the use of a laser vibrometer and a simple method of velocity analysis that allows us to detect and accurately locate lenticular delaminations within the geometry under study. It was found that the results of the simulation were sufficiently like to the experiment. In addition, we also considered a model case, where the defect is located between the first and second layers of the panel. It is noted that the behavior of the velocity field in this case differs from the previous variant, but the average amplitude of the out-of-plane velocity undergoes a slight decrease relative to the case of the defect occurring in the center of the thickness.
In this study, a novel method for detecting the growth of delamination in sandwich structures has been proposed. To this end, we suggested hybridizing the Deep Learning techniques (DL) and Finite Element Method (FEM) for predicting the growth of delamination in this structures. A dataset of simulated delamination growth under different delamination sizes has been produced using the FEM method. Then, a DL model has been trained using this dataset to precisely predict the growth of delamination. This study focused on predicting delamination growth using a tuned and optimized deep learning based regressor. Therefore, to find the ideal set of hyperparameters, the Bayesian optimization algorithm has been used for selecting the best structure and enhancing the regressor performance. Afterward, the model was evaluated and multiple processes were conducted to improve its behavior and solve its stability and overfitting issues. Particularly, an inconsistency between validation loss and training loss has been initially detected in the behaviour of the model, which may indicate overfitting. To tackle this issue, dropout regularization has been added, which improved the consistency between the loss functions but results in less smooth convergence from the expectations. So, in a third study, dropout and L1 regularization has been combined to improve the stability of the model. This combination achieved a consistent and smooth convergence between the validation and training loss functions. The findings highlight the importance of hyperparameter optimization and regularization techniques in improving regression model performance. The study shows the efficiency of Bayesian optimization in hyperparameter tuning and the iterative optimization of a regression model. Furthermore, the outcomes show that the suggested method can identify and predict delamination growth with high accuracy.
The fiber fraction in a composite will have a significant influence on its behavioural aspects and is reported in the current study. With different fiber fractions (0, 12, 24, 36 and 48 wt%) of the areca sheath fiber reinforcing agent, composite specimens were prepared and its physical and mechanical properties were examined. The measured density of the neat epoxy to the higher fiber fraction composite specimen (48 wt%) varies from 1.147 to 0.9524 g/cm³, from which it is evident that the density decreases with increase in the fiber concentration. On the other hand, void fraction for a neat epoxy is 0.26% which increases with the increase in the fiber concentration and is 6.14% for the 48 wt% fiber loaded specimen. An optimum values of investigated mechanical properties such as the hardness (72.56 HRB), Young’s modulus (1.98 GPa), and the Impact strength (4.724 J) have been observed with the increase in fibre fraction. The flexural strength for the neat epoxy is 46.28 MPa starts decreasing with the inclusion of fibers and reaches 12.05 MPa at a higher fraction of 48 wt%. The similar declining behaviour may be observed for the flexural modulus of 0.26 GPa and tensile strength of 14.02 MPa at high fiber fraction.
This paper revisits the problem of free vibration of delaminated composite plates with Lévy type boundary conditions. The governing equations are derived for laminated Kirchhoff plates including through-width delamination. The plate is divided into two subplates in the plane of the delamination. The kinematic continuity of the undelaminated part is established by using the system of exact kinematic conditions. The free vibration analysis of orthotropic simply supported Lévy plates reveals that the delaminated parts are subjected to periodic normal and in-plane shear forces. This effect induces parametric excitation leading to the susceptibility of the plates to dynamic delamination buckling during the vibration. An important aspect is that depending on the vibration mode the internal forces have a two-dimensional distribution in the plane of the delamination. To solve the dynamic stability problem the finite element matrices of the delaminated parts are developed. The distribution of the internal forces in the direction of the delamination front was considered. The mode shapes including a half-wave along the width of the plate accompanied by delamination buckling are shown based on the subsequent superimposition of the buckling eigenshapes. The analysis reveals that the vibration phenomenon is amplitude dependent. Also, the phase plane portraits are created for some chosen cases showing some special trajectories.
