Laminate Plate Research Articles

Free vibration analysis of variable stiffness composite laminate (VSCL) plates coupled with fluid

In this article, natural frequencies of variable stiffness composite laminate (VSCL) plates with curvilinear fibers submerged in fluid with different depths of submersion are studied. In each layer of VSCL plate, the fiber-orientation angle changes linearly with respect to the horizontal coordinate. The problem is solved by using the hierarchical finite element method (HFEM) (p-version), with seven degrees of freedom per node and the higher-order shear deformation theory (HSDT) for C0 continuity. The plate theory ensures a zero shear–stress condition at the top and bottom surfaces of plate and does not require a shear correction factor. The fluid/structure interaction is examined in this study, in which the effect of fluid is assumed as pressure acting on the plate. The mathematical model of fluid is given by employing velocity potential and Bernoulli equation. The obtained frequency parameters shown an excellent agreement when compared with experimental and analytical results of available solutions in literature. Accurate results are obtained by increasing the degree of polynomial shape function of HFEM. In order to examine the effect of fluid on VSCL plate, different cases are studied to find out the effect of plate thickness, curvilinear fiber angle and depth of submerged plate.

Effect of backup plate in drilling of composite laminates, analytical and experimental approaches

Delamination is the most severe damage in drilling of composite laminates. Using the backup plate is an appropriate method to control drilling induced delamination. In this paper, an analytical model is applied to determine the critical thrust force and the feed rate for drilling of composite laminates with backup plate. To achieve this aim, the classical laminate plate theory (CLPT), the linear elastic fracture mechanic (LEFM) and the oblique cutting model are used. In analytical models, two separate distributed loads have been exerted by cutting and chisel edges. Based on the model results, the effect of the drill diameter, the chisel edge size, and the backup plate size, on the critical thrust force and the feed rate are investigated. Experimental tests are carried out to prove the analytical model.

Low-velocity impact behaviors of repaired CFRP laminates: Effect of impact location and external patch configurations

Experimental and numerical approaches are used to investigate the effect of impact location and different external patch configurations on the low-velocity impact behaviors of repaired CFRP laminates. Various external patches with different thicknesses (number of layers) and stacking sequences are considered and those patches are used to repair single side of the damaged laminate plates to improve the impact-resistance. To predict the damage initiation and progression of the repaired CFRP laminates under impact loading, a continuum damage mechanics (CDM) model that combines 3D Hashin damage criteria and cohesive zone model (CZM) is proposed. The corresponding drop-weight impact tests are conducted to experimentally obtain the impact response such as impact force and energy. Numerical impact simulations have been performed to study the effect of impact location during the low-velocity impact behaviors of repaired structures. Parametric studies of patch thickness and stacking sequence are also carried out using the low-velocity impact simulation to analyze their effect on the impact-resistance. Finally, this study provides an optimization cafeteria to identify the important design parameter to perform external patch repair based on the simulation results.

Pseudorandom Noise Impulsive Response Analysis and Aerodynamic Forces of Unmanned Aerial Vehicle Structure

This paper concentrated about the effect of both the pseudorandom or random vibration (wind waves) and aerodynamic forces on the wing of unmanned aerial vehicle, which brought the attention of specialists in this field during last years, the performance of wing is improved on a definitive solution for the vibration problems which cause failure in the wings of UAV. The distribution of stresses and distortions with aerodynamic loads is studied. Factors such as tension, pressure and shear stress showed on wing of UAVs due to vibration which caused the structure of wing to break down and then failure. The experimental study was carried out by using wing made of composite material (foam and cover by lamination plate), where airfoil type (NACA Clark y) installed inside wind tunnel of low velocity. It is found that the vibration acceleration at constant wind velocity with variation of attack angle of the wing, it is obtained the relationship between the acceleration and the frequency using the LABVEIW program which analyzed and identified the distribution of forces on the wing. The stress concentration areas is created and found under failure occurs, the aerodynamic force, torsion torque and magnitude of deformation is calculated. It is concluded that the close areas from the root wing (fixed end) is most likely to collapse or break.

Investigation of modal analysis on glass fiber laminate aluminium reinforced polymer: An experimental study

The present analysis deals with experimental investigation on the vibration behaviour of fiber metal laminates (FMLs) plate. FMLs offer good mechanical properties such as high specific properties in term of strength to weight and stiffness to weight ratio. However, it is observed that very few studies are available on the dynamic behaviour of FMLs. In this experiment, the dynamical behaviour of glass fiber/epoxy and fiber metal laminates was carried out. The specimens have been manufactured using different manufacturing process which is compression mould and vacuum bagging. Free vibration analysis by exciting an impact hammer at the cantilever plate were conducted to determine the dynamical characteristic of the specimens. The stiffness of the material increases, which contributes to the natural frequency increase.

A Fast Forward Simulation Scheme for Eddy Current Testing of Crack in a Structure of Carbon Fiber Reinforced Polymer Laminate

High frequency Eddy Current Testing (ECT) is one of the key non-destructive testing techniques for ensuring integrity of a structure of Carbon Fiber Reinforced Polymer (CFRP) material. An efficient numerical simulator is indispensable to enhance the performance of quantitative ECT for CFRP structures from both point of view of probe optimization and defect sizing. In this paper, a fast forward simulation scheme based on the A-Φ formulation and databases approach is proposed, implemented and experimentally validated for the rapid and high precision simulation of ECT signals due to defects in a CFRP plate by updating an FEM-BEM hybrid code for ECT problem. Comparison of numerical results of the present method with those of the conventional full FEM-BEM code and the experimental results for artificial cracks in CFRP laminate plates indicates that the proposed novel fast forward scheme can predict ECT signals over 300 times faster but without worsening numerical accuracy, which enables it to be applied to efficient reconstruction of cracks in CFRP plates and for probe optimization.

Hygrothermal effects on the behavior of reinforced-concrete beams strengthened by bonded composite laminate plates

The purpose of this paper is to investigate the hygrothermal effects on the behavior of reinforced-concrete beams strengthened by bonded composite laminate plates (theta n/90 m)s. This work is based on a simple theoretical model to estimate the interfacial stresses developed between the concrete beam and the composite with taking into account the hygrothermal effect. Fibre orientation angle effects of number of 90o layers and effects of plate thickness and length on the distributions of interfacial stress in the concrete beams reinforced with composite plates have also been studied.

Theoretical and experimental investigation on the nonlinear vibration behavior of Z-shaped folded plates with inner resonance

As one of the classical complex multibody structures, Z-shaped folded plates are widely applied in several engineering structures. In the present paper, the nonlinear vibration characteristics of a Z-shaped folded plate composed of three carbon-fiber composite plates were analyzed through theoretical and experimental investigation. The nonlinear dynamic model of the Z-shaped plate was developed based on the Hamilton principle, von Kármán equations, and the classical laminate plate theory, and the vibration mode shape functions of the system were calculated in ANSYS. Further, the Galerkin approach was employed to discretize the partial differential equations into a two-degrees-of-freedom nonlinear system, and the effects of transverse excitations on the nonlinear dynamic behavior of the Z-shaped folded plate were investigated through a comprehensive numerical simulation. Moreover, the obtained theoretical results were verified by experimental analysis. In addition, the vibration mode shapes of the Z-shaped folded plate were obtained by operational modal analysis (OMA). The modal parameters were first identified successfully using the PolyMAX method and then validated by modal assurance criterion (MAC). Finally, an excitation-measurement test was designed to measure the nonlinear vibration characteristics of the Z-shaped folded plate.

Low-velocity impact response of viscoelastic material filled FG honeycomb reinforced laminate plate in hygrothermal environments

In the present study, the dynamic response of functionally gradient (FG) honeycomb reinforced and viscoelastic material (VEM) embedded composite laminate plates with low-speed impact in the hygrothermal environment is investigated. The equivalent effective mechanical properties of the two-phase macroscopic constructed layers are determined according to Hill's generalized self-consistent model. The Reddy's high-order shear deformation theory (HSDT) is employed to evaluate the in-plane displacement variables. By combining the extended Hamilton's principle with the finite element method and adopting the Rayleigh's proportional damping, the global mass, damping and stiffness matrices are determined first. Then, the central displacement of the FG honeycomb reinforced laminate plate is obtained with the aid of the Newmark's method. Next, several key factors affecting the central displacement in the whole impact duration are analyzed and compared, such as the hygrothermal effects, the radius of the impactor and the functionally gradient factor. Moreover, the finite element method (FEM) is applied to obtain the mode parameters and to verify the convergence of our analysis. Finally, the LS-DYNA explicit solution is employed to validate the present results.

Residual stress and failure analyses of polymer matrix composites considering thermal cycling and temperature effects based on classical laminate plate theory

The effects of temperature and thermal cycling on the residual stress and failure behavior of different polymer matrix composites have been investigated in this paper. A new algorithm within the framework of the classical laminate plate theory (CLPT) has been presented to calculate the residual stresses. The modified Tsai-Wu failure criterion has been employed to study the failure behavior of different stacking sequences. Numerical results show that the residual stress and failure index of the composites decrease with the increase of the temperature. It has also been established that thermal cycling condition leads to reduction of the residual stresses and increment of the failure index.

Effects of hybridization on the mechanical properties of composites reinforced by piassava fibers tissue

The gradual replacement of conventional materials by composite materials becomes reality when specific properties cannot be achieved by the former. Also, the search for new composites that use natural fibers or a mixture of natural fibers with synthetic fibers as reinforcement is being carried out. Thus, a research was made on the development of two composite laminates, one based on piassava fiber fabric and the other a hybrid composite based on piassava fiber and glass-E fabrics, in order to compare the mechanical behavior of both. The laminate plates were prepared and were processed for specimen manufacture in accordance with the specifications of ASTM D3039 - Uniaxial Tensile Test, and ASTM D790 - Three-point Bending Test standards. Scanning Electron Microscopy (SEM) was also performed to analyze the mechanisms of damage of the specimens. The analysis of the results of the tested specimens show they are satisfactory, as they are very akin to the results of other materials already researched by academy.

Experimental and analytical study of an CF-PEEK Fastener all composites single-lap shear joint under static and fatigue loading

This paper presents a detailed experimental study on carbon fibre (CF) polyether etherketone (PEEK) composite fasteners designed to join conventional high performance composites (CFRP). The failure mechanisms of two CF-PEEK fasteners with countersunk heads joining two laminate plates in a single-lap configuration were investigated under static (tensile) and cyclic loading (tension–tension). The failure process of the bolted joints is described in detail using acoustic emission and microscopic cut views. For comparison the CF-PEEK fasteners were replaced by metal fasteners (Titanium) under the corresponding conditions and loadings. The experimental results are in good agreement with the newly developed “closed-form” model up to the damage point of the joints. This enhanced analytical approach is a closed-form extension of the spring-based method, where bolts and laminates are represented by an arrangement of springs and masses. The model covers in all variables influencing the joint behaviour, such as fastener position, joint material, fastener type, hole diameter, joint thickness, bolt-hole clearance, and bolt torque.

Micromechanical RVE model application for generalization of smart composite laminate structures with thermoelastic characteristics

A generalization of the piezoelectric composite laminate plate model is investigated. To avoid depending on experimentally determined moduli, a micromechanical model based on the Reduced Volume Element (RVE) was used to calculate the effective moduli of the composite. This study applies the finite element method (FEM) based on the First-order Shear Deformation Theory of Plates (FSDTP). To validate the accuracy of the model, the overall deflection under various loads, voltages, temperatures, and dynamic pressures are calculated with both mechanical moduli. Nonlinear analysis is performed through the Newton-Raphson Iterative method. Furthermore, the active control of the plate with the piezoelectric layers is presented through the transient response using the Newmark method. In all cases, the micromechanical model was in good agreement with the experimental model. Also, an improved shear correction factor (SCF) was implemented to allow for further generalizations in the context of composite plate structures. The factors are shown with various ply-angles of the composite layer. Additionally, the application of Macro-Fiber Composites (MFC) piezoelectric layers instead of isotropic piezoelectric layers is investigated.

Numerical Investigation on Water Blast Response of Freestanding Carbon Fiber Reinforced Composite Sandwich Plates with Square Honeycomb Cores

The dynamic response of freestanding carbon fiber reinforced composite sandwich plates with square honeycomb cores of different relative densities subjected to water blast is investigated by numerical simulations. The constitutive models are validated by quasi-static compression response comparisons of numerical simulations and theoretical calculations. The deformation process, core compression and momentum transmitting characteristics are analyzed and the regulations of the core compression and momentum transmitting for sandwich plates with different core relative densities are revealed. Dynamic response and protection property of composite sandwich plates and mass-equal laminate plates are compared, which indicates that the composite sandwich plates can provide superior protection from water blast than laminate plates.

Experimental study on mechanical properties of aramid fibres reinforced natural rubber/SBR composite for large deformation – quasi-static mechanical properties

ABSTRACTQuasi-static mechanical properties of aramid fibres reinforced natural rubber/SBR composites are comprehensively investigated via scanning electron microscopy (SEM), uniaxial tensile tests, multi-step stress relaxation, and the Mullins experiment. The strength, stiffness, viscoelasticity, and Mullins effect of composites are analysed, and the micro failure mechanism is also explored. It is shown that the samples appear similar to a laminate plate with random short fibres in a plane. The results of the uniaxial tensile tests indicate that the tensile strength and elongation at failure decrease, while the stiffness increases following the addition of a small amount of aramid fibres into the rubber matrix. The multi-step relaxation and Mullins experiments reveal that the aramid-short-fibres weaken the viscoelasticity of rubber composites. Finally, the strain energy of the composite is divided into four parts, and one part is considered with respect to its application to the study of interface destruction between the matrix and fibre.

Snapthrough and free vibration of bistable composite laminates using a simplified Rayleigh-Ritz model

Abstract The snapthrough and free vibration response of bistable cross-ply [ 90 n / 0 n ] composite laminates is investigated. Thin unsymmetric composite laminates possess more than one equilibrium position when cooled to room temperature due to the difference in thermal expansion of the plies. Bistable cross-ply laminates have cylindrical shapes at room temperature provided appropriate side-length-to-thickness ratio is used. The laminate is modelled according to the classical lamination plate theory taking into account the von Karman geometric nonlinearity . The strains and displacements are approximated via a simplified Rayleigh-Ritz model that depends on only four time-dependent parameters for the general dynamic response. The simplified model is validated against experimental and finite element results and an acceptable agreement is obtained. The laminate’s length-to-thickness ratio is key to assess the existence of bistability. The model is used to investigate the snapthrough response of an 8-ply [ 90 4 / 0 4 ] laminate that is subjected to three loading schemes: concentrated moments, normal forces, and tangential forces . The variations of the principal curvatures and the lateral displacement of the laminate with the applied forces are shown. The significance of the force location is also found a crucial element in finding the snapthrough force. The free vibration that takes place in the vicinity of a stable equilibrium position is studied and the variation of the fundamental frequency with the laminate size is presented.

Assessment of shunted piezoelectric devices for simultaneous noise and vibration reduction: comparison of passive, active and hybrid networks

Structural vibration and noise control of a cavity-backed three-layered smart piezo-coupled rectangular panel system under harmonic or transient loads is achieved by using purely active, passive, and hybrid active/passive piezoelectric shunt networks. Problem formulation is based on the classical lamination plate theory, Maxwell’s equation for piezoelectric materials, linear circuit theory, and wave equation for the enclosed acoustic domain. The orthogonal mode expansions along with the modal coupling theory are employed to obtain the coupled differential equations of the electro-mechanical-acoustic system, which are then put into the convenient state-space form, and subsequently solved numerically in both frequency and time domains. A triple-mode hybrid RLC shunt circuit, in series with an external active voltage source and connected to a single electroded piezoelectric segment, is tuned to the dominant resonance frequencies of the composite structure. The linear quadratic optimal control (LQR) theory is adopted for obtaining the active control gains. The frequency and time domain performances of the passive, active and hybrid multi-modal piezoelectric systems are calculated and discussed in terms of sensor output voltage, local sound pressure, and control effort. It is found that the hybrid control methodology with properly tuned circuit parameters can be an excellent candidate for simultaneous vibration and structure-borne noise control of the cavity-coupled smart panel with decreased control effort. Also, the active control strategy integrated in the hybrid control system is demonstrated to enhance the overall system damping characteristics and improve the control authority at frequencies where the passive shunt network performs weakly. Limiting cases are considered and correctness of the mathematical model is verified by using a commercial finite element software as well as by comparisons with the literature.

Behaviour of plain-woven glass-fiber reinforced polymer laminate plates during symmetrical bending on a circular support – Part II: Numerical analysis

Behaviour of plain-woven glass-fiber reinforced polymer laminate plates during symmetrical bending on a circular support – Part II: Numerical analysis

Modal Analysis of a Compressor Disk

The compressor disk is one of the key parts of the aeroengine. Its structure and strength play an important role in the reliability of the compressor. Most of the damage are caused by resonance stress. At the same time, the dynamic design and analysis of the key components are required because of the rotating state. When the compressor disk is in normal operation, the disk rotates around the rotating shaft in a large scale. Centrifugal inertia force will affect the deformation of the structure, and induce a certain change of natural frequency when compared to the static condition, which has increased complexity to modelling and numerical calculation. In this paper, the effect of dynamic stiffening on the vibration characteristics of disc is studied. In order to derive the equations of motion, Hamilton’s principle is used, and the boundary conditions are obtained at the same time. We studied the natural frequency of the isotropic plate and laminate plate by Ritz method. Using the popular finite element analysis software ANSYS, we carry on simulation computation of vibration modes on a certain type of compressor in the working process. Besides, by investigation of the influence of structure parameter and rotating speed on the forward travelling wave and back travelling wave, we studied the critical speed of the compressor disk, which is essential in the rotator.

Static deflection and thermal stress analysis of non-uniformly heated tapered composite laminate plates with ply drop-off

The effective design of tapered laminated composite structures subject to non-uniform temperature fields requires a thorough understanding of their static behaviour. In this study, a finite element analysis of tapered laminated composite plates with ply drop-off has been carried out to study the static deflection and normal stress patterns developed under non-uniform heating. The study revealed that the nature of the taper configuration, the nature of the applied temperature field and the structural boundary conditions influence the static deflection behaviour and the normal stresses developed in the tapered composite plates. It is found that the static deflection pattern of a tapered plate subject to a particular temperature profile is not sensitive to the nature of the taper configuration. It is also observed that the static deflection pattern of a tapered plate is significantly influenced by the nature of temperature field. Normal stress variation of tapered plates subject to various temperature fields reflects the nature of the temperature profile. Maximum normal stress occurs at locations where the highest temperature exists for that particular temperature field. The stresses are also influenced by the nature of the taper - Taper D plates experience low stresses while Taper B and Taper C plates experience similar values. It was also found that large variations in stresses are observed at resin pockets.