Composite Material Plate Research Articles

NONLINEAR DYNAMICS ANALYSIS OF ALUMINUM HONEYCOMB SANDWICH PLATE WITH COMPLETED CLAMPED SUPPORTED

Study on the dynamics of aluminum honeycomb sandwich plates of composite structure material plays a key role for the special applications of the aerospace and automotive engineering. The nonlinear dynamics of honeycomb sandwich plate is explored.According to the classical plate theory and the large deformation,the governing equations of motion are established for the honeycomb sandwich plate subjected to the transversal excitation force by using the Hamilton's law of variation principle.The transversal damping is taken into consideration.The method of normalization is utilized to transform the nonlinear vibration equations to nonlinear system with double modes of freedom. Numerical simulation is used directly to investigate the nonlinear responses of the honeycomb sandwich plate.The results indicates that the change of transversal excitation force has a significant effect on the vibration of honeycomb sandwich plate because the hexagon cell of core and the amplitude of the first modal are bigger than the second modal.In the different ranges of transversal excitation force, the honeycomb sandwich plate exists different dynamical phenomena.Single periodic motion appears when the force value is small,and periodic motion,multi-period motion,chaotic motion appears with the increase of force.Experiments are conducted to validate the numerical simulation results.

Reliability of damage mechanism localisation by acoustic emission on glass/epoxy composite material plate

This investigation focuses on the analysis of the Acoustic Emission (AE) wave propagation and velocity evolution in glass/epoxy composite materials according to the fibre orientation. In this work, several piezoelectric sensors were placed on a large composite laminate in the same direction in order to analyse by one measure, the velocity and wave attenuation over a large distance. Then, the measured velocity was compared with the theoretical values of velocity that have been identified by the theoretical model analysis. This last velocity was used during a three-point bending test to analyse the damage localisation on the plate according to the amplitude distribution model developed in the “Laboratory of Roberval at the University of Technology of Compiègne”. The results of the damage localisation on the specimens were compared to the visually observed damage (delaminating, cracks…) and were corrected on the basis of the amplitude correction. Finally, the error ratio of localisation without correction was quantified. The originality of this study was to use the AE results obtained on a large laboratory specimen in order to improve the AE testing on an industrial structure scale.

Sizing of impact damages in composite materials using ultrasonic guided waves

A parametric 2D finite-element inversion scheme is used for sizing cracked zone type strip defect caused by a linear and uniform impact on a composite material plate. The reflection and transmission coefficients produced by mode conversion phenomenon when a pure incident S 0 Lamb wave mode is sent towards the defect are used as input data for the inversion process. The inversion process consists in quantifying two unknown parameters, i.e., width and depth representing the assumed triangular geometry of cracked zone like defect. The inversion scheme consists of a finite element based model, which is used to simulate the Lamb wave scattering for various values of the aimed parameters, and specific post-processing based on Shkerdin's orthogonality relation is applied to predict the needed reflection and transmission coefficients. A laboratory experiment is performed for creating a linear and uniform impact on a carbon epoxy composite plate sample. Then another ultrasonic experiment is performed in laboratory for measuring reflection and transmission coefficients by sending a pure S 0 mode towards the defect. The measured coefficients are then used for the inversion purpose. The two principles used in inversion process give almost similar optimised values for these parameters, showing the usefulness of this technique.

Three-dimensional hybrid model for predicting air-coupled generation of guided waves in composite material plates

For contact-less, non-destructive testing (NDT) purposes using air-coupled ultrasonic transducers, it is often required to numerically simulate the propagation of ultrasonic waves in solid media, and their coupling through air with specific transducers. At that point, one could simulate the propagation in the air and then in the solid component, using a Finite Element (FE) model. However, when three-dimensional (3D) modeling becomes necessary, such a solution reveals to be extremely demanding in terms of number of degrees of freedom and computational time. In this paper, to avoid such difficulties, the propagation in air from an ultrasonic transmitter to a tested solid plate is modeled in 3D using a closed-form solution. The knowledge of the transducer characteristics (diameter, frequency bandwidth, efficiency in Pa/V) allows the spatial distribution and actual pressure (in Pa) of the acoustic field produced in the air to be predicted, for a given input voltage. This pressure field is applied in turn as a boundary condition in a 3D FE model, to predict the plate response (displacement and stress guided beams) for a given distance between the transmitter and the plate, and for a given angle of orientation of the transmitter with respect to the plate. The FE model is so restricted to modeling of the solid structure only, thus reducing very significantly the number of degrees of freedom and computational time. The material constituting the plate is considered to be an anisotropic and viscoelastic medium. To validate the whole modeling process, an air-coupled ultrasonic transducer is used and oriented at a specific angle chosen for generating one specific Lamb mode guided along a composite plate sample, and a laser probe measures the normal velocity at different locations on the surface of the plate. In the field of NDT, it is generally suitable to excite a pure Lamb mode in order to ease the interpretation of received signals that would represent waves scattered by defects. After a validation step, the numerical model is then used to investigate the effect of the material anisotropy on the purity of the incident guided mode.

Absorbing Properties of Composite Material Plates of Multi-Layer Absorbing Structure

Microwave absorbing material is currently being more and more widely applied in the world. However, conventional absorbent coating material cannot fulfill the complex current requirements of science and technology to have a wide absorption frequency band, and high absorption. This paper describes composite material plates with a multi-layer absorbing structure designed according to impedance-matching and attenuation principles, producing two- and three-layer absorbing structures. Twelve samples were made, containing graphite powder and manganese dioxide at varying concentrations. The results show that in the frequency range 8-18 GHz, the peak absorption of double-layer samples is -12.3dB, the effective bandwidth (R < -10 dB) is 1.8GHz. The absorption peak of three-layer samples is -18 dB, and the effective bandwidth (R < -10 dB) is 8GHz. The findings of this research are useful in improving the absorption bandwidth of absorbing material.

Nonlinear Primary Vibration of Circular Sandwich Plates and Modal Analysis

The nonlinear forced vibration of damped circular sandwich plates is studied. From the movement equations of circular sandwich plate expressed in displacement components, got the relevant nonlinear vibration equation by Galerkin method. The changing of initial deflection, stiffness and a harmonic force which can affect kinetic characteristic of configuration was researched. The FRF of primary resonance periodical solutions were obtained, synchronously modal analysis experiment for composite material plates were tested.

Numerical simulation of the crushing process of a corrugated composite plate

The significant potential of composite materials as highly effective energy absorbers has contributed to their increasing usage in the aerospace, automotive, and railway industries. Traditionally, the development of crashworthiness composites design relies upon laborious and costly experimental testing. Therefore, the ability to simulate accurately the crushing response of composites and their energy absorption mechanisms can significantly reduce the product development cycle and cost. The present work presents a physics-based finite element model of a corrugated carbon–epoxy fabric composite plate subject to quasi-static crushing. The model accounts for both intralaminar (in-plane) and interlaminar (delamination) failure mechanisms. The in-plane response of the fabric plies is modeled using a proposed constitutive model that has been implemented in the commercial finite element code Abaqus/Explicit; and the delamination response of the composite plate is simulated using the cohesive surface capability in Abaqus. The results of the Abaqus/Explicit simulations show very good quantitative and qualitative agreement with the experimental data, thus demonstrating that the proposed methodology and tools can be used for realistic crush simulations of composite structures.

Influence of Hole Strengthening Layer on the Failure Process of Composite Material Plate with a Hole in Connection Structures

In practice,the stress concentration phenomenon in composite plate with holes is very severe.It will lead to various damages.In order to increase the structure strength of composite plate,an extra layer can be laid around the hole to improve the loading capacity.Based on three-dimensional progressive damage theory,with the secondary development language of ANSYS software,a model of open-hole composite material plate containing strengthening structures is developed to calculate the failure process under tensile load.The correctness of this model is verified through its comparison with existing references.Meanwhile,the failure mode of every layer and the influence of different strengthening layer thickness on failure process of each layer are analyzed,and the initial failure load,final failure load and whole failure process of laminated plate are obtained.This provides a certain reference for the research on strengthening structure of composite plate with holes.

Green Plate Making Technology Based on Nano-Materials

Laser phototypesetting and computer to plate (CTP) technologies are widely used in print industry. These technologies are based on the complex photosensitive image process. The exposing and development processes result in waste of photosensitive materials and environment pollution. Green plate making technology is not based on photosensitive materials but nano-materials. The image process of the technology is to jet the nano-composite transfer printing material on super hydrophilic print plate with special nano and micro-structure. Then the oleophilic image area and hydrophilic non image area are formed by adjusting interface characters between the nano-composite transfer printing material and super hydrophilic print plate. The plate is used for printing without exposing and development. Without photosensitive image process, the technology has many advantages such as no operation in darkroom, simple process, environmental friendly and low cost. The key problems of print resolution and press life have been solved effectively by preparation of nano composite transfer printing material and super hydrophilic print plate. In this paper, the research process of the nano composite material and the print plate are presented.

Topology optimization of composite material plate with respect to sound radiation

In this paper, topology optimization of composite material plate with respect to minimization of the sound power radiation has been studied. A new low noise design method based on topology optimization is proposed, which provides great guidance for acoustic designers. The structural vibrations are excited by external harmonic mechanical load with prescribed frequency and amplitude. The sound power is calculated using boundary element method. An extended solid isotropic material with penalization (SIMP) model is introduced for acoustic design sensitivity analysis in topology optimization, where the same penalization is applied for the stiffness and mass of the structural volume elements. Volumetric densities of stiffer material are chosen as design variables. Finally, taking a simple supported thin plate as a simulation example, the sound power radiation from structures subjected to forced vibration can be considerably reduced, leading to a reduction of 20 dB. It is shown that the optimal topology is easy to manufacture at low frequency, while as the loading frequency increases, the optimal topology shows a more and more complicated periodicity which makes it difficult to manufacture.

Inverse Method Based on Modal Vibration Testing for Characterizing the Elastic Properties

This paper presents a inverse method to derive the material properties from the resonance frequencies of a free-edge test specimen based on modal vibration test. A mixed numerical experimental identification procedure is used for this purpose. Finite element models of the test plate is simultaneously updating and reproduces the updating frequencies, then optimal procedure is running. The sum of the squared differences between the experimental and the finite element method numerical resonance frquencies is the objective function. To seek practical solutions, here presents a global optimization method--simulated annealing method for the determination of the elastic properties. The inverse method is applied to determine the elastic constants of aluminum , carbon/epoxy , Glass/PP composite material and double coated steel plate. The results indicate that the method can obtain very accurate elastic constants for aluminum , Glass/PP , carbon/epoxy composite material ,but for double coated steel plate , if the individual layer of the three different layers is as isotroptic material having six elastic constants , the method can obtain very accurate results , but if it is as transversely isotropic material having twelve elastic constants, the evaluating elastic constants are bad.

복합재료판 구조물의 고유진동수 위상최적화에 관한 연구

The aim of this research is to construct eigenfrequency optimization codes for plates with Arbitrary Rank Microstructures. From among noise factors, resonance sound is main reason for floor's solid noise. But, Resonance-elusion design codes are not fixed so far. Besides, The prediction of composite material's capability and an resonance elusion by controlling natural frequency of plate depend on designer's experiences. In this paper, First, using computer program with arbitrary rank microstructure, variation on composite material properties is studied, and then natural frequency control is performed by plate topology optimization method. The results of this study are as followed. 1) Programs that calculate material properties along it's microstructure composition and control natural frequency on composite material plate are coded by Homogenization and Topology Optimization method. and it is examined by example problem. 2) Equivalent material properties, calculated by program, are examined for natural frequency. In this paper, Suggested programs are coded using <TEX>$Matlab^{TM}$</TEX>, Feapmax and Feap Library with Homogenization and Topology Optimization method. and Adequacy of them is reviewed by performing the maximization or minimization of natural frequency for plates with isotropic or anisotropic materials. Since the programs has been designed for widely use. If the mechanism between composite material and other structural member is identified, extension application may be possible in field of structure maintenance, reinforcement etc. through application of composite material.

Elastodynamic Behavior of Waves in Thermo-Microstretch Elastic Plate Bordered with Layers of Inviscid Liquid

The elastodynamic behavior of waves in a thermo-microstretch elastic homogeneous isotropic plate bordered with layers of inviscid liquid on both sides subjected to stress-free thermally insulated and isothermal conditions is investigated in the context of Lord and Shulman and Green and Lindsay theories of thermoelasticity. The mathematical model has been simplified by using the Helmholtz decomposition technique, and the frequency equations for different mechanical situations are obtained and discussed. The special cases such as short wavelength waves and regions of the secular equations are also discussed. Finally, the numerical solution is carried out for a magnesium crystal composite material plate bordered with water. The dispersion curves, attenuation coefficients, amplitudes of dilatation, microrotation, microstretch, and temperature distribution for the symmetric and skew-symmetric wave modes are presented graphically.

Effect of shear on deflection and buckling of beams and plates

The paper deals with the influence of shear stresses on bending and buckling of beams and plates of composite materials employing the hypothesis of ‘straight line’. It is assumed that a set of points lying on a line perpendicular to the neutral surface (the mid-plane) before deformation remains on the line and this line is non-perpendicular to the neutral surface after a load's application. This non-orthogonality is caused by the presence of shear stresses. Thus, this approach does not require the section to be normal to the neutral surface as in the classic Kirchhoff hypothesis. It is shown that the latter is inconsistent with the existence of shear stresses. The corresponding differential equations are derived from the non-linear differential equations of the theory of elasticity in Cartesian coordinates. This allows well-founded simplification of the equations for different partial cases and also correct determination of the sections' rotation angles in the equations for buckling. Several solutions for bending and buckling of beams and plates are given while considering the effect of shear stresses. Formulae are derived for the Euler force of compressed beams and simply supported orthotropic plates, which allows calculation of the error resulting from the application of the Kirchhoff hypothesis. For example, it is shown that for h/b < 0.1 (h = plate thickness, b = dimension of smallest side) the error is smaller than 5% and it does not depend on the plate's aspect ratio. Also, a solution is found for bending strength of beams and orthotropic plates subjected to the arbitrarily distributed lateral pressure considering the effect of shear stresses. Formulae for the deflection in the plate's centre are derived as well as for calculating the error when the classic Kirchhoff hypothesis is applied.

Coupled fluid–structure solver: The case of shock wave impact on monolithic and composite material plates

An unstructured adaptive mesh flow solver, a finite element structure solver and a moving mesh algorithm were implemented in the numerical simulation of the interaction between a shock wave and a structure. In the past, this interaction is mostly considered as one-way in the sense that the shock causes a transient load on the structure while it is reflected uneffected by the impact. A fully coupled approach was implemented in the present work which can account for the effects associated with a mutual interaction. This approach included a compressible flow Eulerian solver of second order accuracy in finite volume formulation for the fluid and a Langargian solver in finite element formulation for the solid structure. A novel implementation of advancing front moving mesh algorithm was made possible with the introduction of a flexible and efficient quad-edge data structure. Adaptive mesh refinement was introduced into the flow solver for improved accuracy as well. Numerical results are further validated by theoretical analysis, experimental data and results from other numerical simulations. Grid dependency study was performed and results showed that the physical phenomena and quantities were independent of the numerical grid chosen in the simulations. The results illuminated complicated flow phenomena and structure vibration patterns, which in order to be detected experimentally require capabilities beyond those of the current experimental techniques. The numerical simulations also successfully modelled the aero-acoustic damping effects on the structure, which do not exist in previous numerical models. Further analysis of the results showed that the mutual interaction is not linear and that the non-linearity arises because the wave propagation in the fluid is not linear and it cascades a non-linear and non-uniform loading on the plate. Non-linearity intensifies when the plate is vibrating at high frequency while the wave propagation speed is low.

Wave Propagation in Microstretch Thermoelastic Plate Bordered with Layers of Inviscid Liquid

The propagation of free vibrations in microstretch thermoelastic homogeneous isotropic, thermally conducting plate bordered with layers of inviscid liquid on both sides subjected to stress free thermally insulated and isothermal conditions is investigated in the context of Lord and Shulman (L‐S) and Green and Lindsay (G‐L) theories of thermoelasticity. The secular equations for symmetric and skewsymmetric wave mode propagation are derived. The regions of secular equations are obtained and short wavelength waves of the secular equations are also discussed. At short wavelength limits, the secular equations reduce to Rayleigh surface wave frequency equations. Finally, the numerical solution is carried out for magnesium crystal composite material plate bordered with water. The dispersion curves for symmetric and skew‐symmetric wave modes are computed numerically and presented graphically.

Study on drilling characteristics and mechanical properties of CFRP composites

Stacking plates of CFRP composite materials are increasingly used because of their unique characteristics. However, unlike other materials used in metallurgy they have a disadvantage of uneven quality and anisotropy when combined with other composites. Hence, specimens of CFRP stacking plates are manufactured by changing orientation angles throughout three quasi-isotropic plies (0°/45°/90°/−45°) 6s, (0 3°/45 3°/90 3°/−45 3°) 2s, and (0 6°/45 6°/90 6°/−45 6°) s and throughout three cross plies (0°/90°/0°/90°) 6s, (0 3°/90 3°/0 3°/90 3°) 2s, and (0 6°/90 6°/0 6°/90 6°) s. In this study 3-point bending tests and transverse bending tests have been carried out in order to find out mechanical characteristics according to orientation angles by stacking in 6 different types along with the change of stacking composition method of a CFRP composite.

High velocity impact on NCF reinforced composites

In the current paper, a series of high velocity impact tests using ϕ50 and ϕ25 mm ice spheres and 0.32 g granite stones on non-crimp fabric (NCF) composite plates are reported. The impact tests were performed using an air gun and velocities between 100 m/s and 199 m/s. The impact events were monitored using a high-speed camera, with a 20 million frames per second capacity, as well as by a displacement transducer for out-of-plane displacement measurements of the impacted plates. NCF composite plates of two different thicknesses were impacted. The composites were manufactured from carbon fibre and epoxy resin by vacuum infusion. Engineering type models were employed to predict impact response and impact damage formation. Comparison between predicted and resulting damage for the impact test validates the application of a semi-empirical model for predicting impact velocity thresholds for damage formation. Analytical models relying on the assumption of solid impact bodies cannot be employed for these types of impact.

Flexural wave dispersion in orthotropic plates with heavy fluid loading

Orthotropic plates support flexural waves with wavenumbers that depend on their angle of propagation. The present work investigates the effect of fluid loading on this angular dependence, and finds that the effect is relatively small for typical composite plate materials in contact with water. This finding results from an analytical model of the fluid-loaded plate, in which the plate is modeled by classical laminated plate theory and the fluid is modeled as an ideal acoustic fluid. The resulting dispersion relation is a tenth-order polynomial in the flexural wavenumber. Direct numerical solution, as well as analysis at frequencies below coincidence, reveals that the angular dependence of wavenumber is magnified but not significantly distorted by the addition of fluid loading.

Shock wave impact on monolithic and composite material plates: The preferential aeroelastic response

An experimental investigation was carried out to determine the aeroelastic response of thin flat plates during face-on impact with planar shock waves. The experiments were performed in a large-scale shock tube research facility, which had a working section of 12″ in diameter and a length of 80 ft. One aluminum plate, one stainless steal plate and several composite plates were tested in the present investigation. Miniature semi-conductor strain-gauges of high-frequency response were employed to measure locally the strain on the exterior side of the plates and high-frequency response pressure transducers were used to measure time-dependent wall and total pressure. Due to the elastic deformation of the plates and their reverberation, strong acoustic waves were generated on the external side of the impact which carry a significant signature of the plates’ properties. Composite plates were found to suppress several of the modes of the wave patterns while metallic ones demonstrate a rich variety of interacting modes. The amplitude of the excited acoustic waves, however, was higher in the case of composite plates than in the case of steel plates. The frequency content of the strain signals on the surface of composite plates was not always the same with the content of the surface acceleration measured in free vibration experiments. Calculations by using a coupled system of equations between the fluid and solid phases of monolithic materials provided predictions in good agreement with the measured values of modal frequencies. These theoretical results were also in agreement with the classical modal analysis results by using the Poisson–Kirchoff theory for thin plates under axisymmetric or non-axisymmetric conditions.