Laminate Plate Research Articles

A comparative study of finite element modeling techniques for dynamic analysis of elastic-viscoelastic-elastic sandwich structures

Two finite element formulations using different laminate plate theories are developed for the elastic-viscoelastic-elastic sandwich plates. A critical comparison and assessment between them are provided. The dynamic characteristics, namely, the natural frequencies and associated loss factors of the elastic-viscoelastic-elastic sandwich plates are calculated using the two finite element models. The two models are validated through the numerical example and experiment results. Comparisons of the accuracy and computational efficiency of the two finite element models are given. The results show that both of the two finite element models have good accuracy in predicting the natural frequencies and the loss factors with different efficiency. The works in this article have instructive significance in the calculation and application of the elastic-viscoelastic-elastic sandwich structures.

Recurrence Plot and Recurrence Quantification of the Dynamic Properties of Cross-Shaped Laminated Energy Harvester

The paper examines the dynamic properties of bistable cross-shaped laminate plates for broadband energy harvesting applications by converting mechanical vibration energy into the electrical power output. Bistable laminates plates coupled to piezoelectric transducers were excited by application of harmonic excitations and exhibited a range of vibration patterns. The vibration patterns included single-well oscillations and snap-through vibrations of both periodic and chaotic character; such vibration patterns led to a different power output. Classical spectral analysis of measured voltage, displacement and velocity time histories indicated the presence of a variety of nonlinear and chaotic phenomena. As a result, an analysis of the measured displacement and voltage time histories was carried out with the use of the Recurrence Plots and the Recurrence Quantification Analysis methods. The Recurrence Plots method was used for detection of qualitative changes in the dynamic behaviour of the non-linear harvesting system. In order to facilitate interpretation of piezoelectric voltage and laminate displacement, a detailed analysis using Recurrence Plots, Recurrence Quantification Analysis was employed.

Simulation of stress in an innovative combination of composite with metal sheet

In this article research of stress impact in multi-point connection glass epoxy composite with a metal sheet with a rivet nuts was presented. Composite materials are increasingly used because of the good mechanical properties and low price. The laminates are composites of a layer structure, characterized by very high strength in the direction of the fibers, their weakness is not good toughness in a direction perpendicular to the layers. Mainly checking of displacements and stresses generated on the sheet as a result of pneumatic actuators load for composite boards was carried out. Glass-epoxy composite consisting of four layers of glass mat with a weight of 1000 g/m2 and an epoxy resin and hardener HG700 LG700 volume ratio of 38/100 was created. Next composite was fixed with steel plate with a rivet nuts and bolts. A model of laminate samples and plate was simulate in Siemens NX 8.5 software. The simulation results will determine stresses and displacements in conjunction newly designed composite sheet. Strength analysis was performed with the use of the module NX Advanced Simulation. FEM is an advanced method for solving systems of differential equations, based on the division of the field into finite elements for which the solution is approximated by specific functions, and performing the actual calculations only for nodes of this division. Due to the complexity of the created object to simplify the elements made to reduce the calculation time. This article presents the study of stresses and displacements in the composite plates joined with sheet metal, in summary of this article, the authors compare the obtainted results with the computer simulation results in the article: " The study of fix composite panel and steel plates on testing stand".

Critical thrust force predictions during drilling: Analytical modeling and X-ray tomography quantification

In the past, several experimental and analytical studies have been conducted aimed towards predicting the critical thrust force responsible for delamination at the hole exit during drilling. Among these analytical models, few take into account the coupling between bending and stretching often observed in multi-directional (MD) laminates with an un-symmetrical stacking sequence considering the presence of an elliptical crack. In addition, in these analytical models, the tool/composite contact region is modeled without taking into account the chisel edge effect. In the present study, a unique analytical model for critical thrust force prediction has been proposed that explicitly accounts for the effect of the chisel and cutting edges. The interaction zone (composite/chisel edge and composite/principal cutting edge) has been modeled using classical lamination plate theory (CLPT) and linear elastic fracture mechanics (LEFM) principles. In addition, a comparison between the proposed analytical model predictions and experimental results from quasi-static punch tests accompanied with different X-ray tomography observations led to choosing the accurate loading profile developed during drilling.

Experimental Investigation of the Ballistic Response of Composite Panels Coupled with a Self-Healing Polymeric Layer

AbstractIn this study, multifunctional panels with structural and self-healing capabilities were experimentally investigated under high velocity impact conditions. The panels were composed of two layers, one made of fiber-reinforced plastics (FRP) and the other of a self-healing ionomer, assembled in four different configurations with surface density ranging from 6.85 to 7.49 kg/m2. A total number of 16 impact experiments are reported, where spherical aluminium projectiles with diameters from 2.3 to 4.5 mm were shot at impact velocity, which varied from 2.0 to 2.5 km/s. The panel response was analysed in terms of (1) impact damage; and (2) capability to protect equipment located behind the panel from the cloud of fragments ejected downrange after panel perforation. Successful hole sealing was observed in panels consisting of a carbon FRP laminate and ionomer plate hit by projectiles up to 3.5 mm in diameter. The damage of the target was somewhat smaller when the ionomer was on the panel’s rear side. Suc...

Stress-Distribution around Pin-Loaded Hole for Orthotropic Laminates

Stresses were calculated for orthotropic laminate plate loaded by a frictionless pin in a circular hole of the same diameter. These calculations were based on finite-element analysis for five laminates; 00, [±450]s, [00/900]s,[00/±450]s, and quasi-isotropic [00/±450/900]s. stress distribution, based on nominal bearing stress, were determined for wide ranges of the ratios of width to diameter and edge distance to diameter. Orthotropic had a significant influence on both the magnitude and location of the maximum tensile stress concentration on the boundary of the hole. The laminates with 00 plies developed the peak tensile stress near the ends of the pin-hole contact arc. But the ±450 laminates had peaks where ply fiber were tangent to the hole. The finite width and edge distances strongly influenced the tensile stress concentration. In contrast, the finite widths and edge distances had little effect on bearing stress concentration. For the practical range w/d = 2, the peak tensile stresses were as much as 50 percent larger than the infinite-laminate value. For e/d=1, these stresses were greater 60 percent than infinite-laminate value. In contrast, the finite width and edge distance had little effect on bearing stress concentrations.

Study the Effects of Free Vibration and Effective Elastic Properties with Variation of Layer Orientation of Symmetric Laminate Plates

Study the Effects of Free Vibration and Effective Elastic Properties with Variation of Layer Orientation of Symmetric Laminate Plates

Residual stresses created during curing of a polymer matrix composite using a viscoelastic model

A modified viscoelastic constitutive model is proposed to predict cure-induced residual stresses in polymer matrix composites. The modifications rely on using the inverse of the Deborah number to describe regimes corresponding to a fully relaxed state, a viscoelastic state and an elastic state. The composite is only in a viscoelastic state for limited ranges of the Deborah number. By considering the evolution of the Deborah number during curing of the AS4/3501-6 composite, the composite is in a fully relaxed state when it is cured at high temperature and the degree of cure is lower than 0.73, and no further changes in the viscoelastic characteristics when the degree of cure is higher than 0.8. A 3D simulation of a composite laminate plate is used to predict the evolution of the residual stresses. The analysis reveals that the accurate simulation on the cure-induced residual stress should include the last two states of the entire cure process, and consider the stress relaxation, thermal deformation and chemical shrinkage.

Thermally induced stability and vibration of initially stressed laminated composite plates

In this paper, the thermal effect on the buckling and vibration of laminated composite plates with an arbitrary initial stress is presented. The governing equations including the transverse shear deformation effects are established using the variation method. The initial stress is taken to be a combination of pure bending stress and a uniform normal stress in the example problems. Temperature distribution in the laminate plate is assumed to be combined uniform and linear temperature change in the transverse direction. The effects of various parameters on the thermal induced vibration and stability of laminated composite plates are studied. It is found that the initial stress, rise temperature and elastic modulus cause drastic changes in the thermal vibration and buckling behavior of laminated composite plates.DOI: http://dx.doi.org/10.5755/j01.mech.22.1.8682

NDT evaluation of long-term bond durability of CFRP-structural systems applied to RC highway bridges

The long-term durability of CFRP structural systems applied to reinforced-concrete (RC) highway bridges is a function of the system bond behavior over time. The sustained structural load performance of strengthened bridges depends on the carbon fiber-rein- forced polymer (CFRP) laminates remaining 100 % bon- ded to concrete bridge members. Periodic testing of the CFRP-concrete bond condition is necessary to sustain load performance. The objective of this paper is to present a non-destructive testing (NDT) method designed to evaluate the bond condition and long-term durability of CFRP laminate (plate) systems applied to RC highway bridges. Using the impact-echo principle, a mobile mechanical device using light impact hammers moving along the length of a bonded CFRP plate produces unique acoustic frequencies which are a function of existing CFRP plate-concrete bond conditions. The purpose of this method is to test and locate CFRP plates de-bonded from bridge structural members to identify associated deterio- ration in bridge load performance. Laboratory tests of this NDT device on a CFRP plate bonded to concrete with staged voids (de-laminations) produced different frequen- cies for bonded and de-bonded areas of the plate. The spectra (bands) of frequencies obtained in these tests show a correlation to the CFRP-concrete bond condition and identify bonded and de-bonded areas of the plate. The results of these tests indicate that this NDT impact machine, with design improvements, can potentially pro- vide bridge engineers a means to rapidly evaluate long lengths of CFRP laminates applied to multiple highway bridges within a national transportation infrastructure.

A Two‐Dimensional Plum‐Blossom Sensor Array‐Based Multiple Signal Classification Method for Impact Localization in Composite Structures

AbstractThe growing use of composite materials on aircraft structures has attracted much attention for the impact monitoring as a kind of structural health monitoring method. Uniform linear sensor array (ULSA)‐based multiple signal classification (MUSIC) technology is a promising method because of its directional scanning ability and easy arrangement of the sensor array. However, the monitoring range of ULSA‐based MUSIC method is 0°–180°, and its beamforming properties degrade at angles close to 0° and 180°. Besides, the ULSA‐based MUSIC methods proposed require the knowledge of the direction dependent velocity profile obtained by additional experiments. This article presents a novel two‐dimensional (2‐D) plum‐blossom sensor array (PBSA)‐based MUSIC method. First, the velocity propagating at the specific direction is estimated by impact signal itself using PBSA directly. Second, 2‐D PBSA‐based MUSIC method well realizes omnidirectional 0°–360° impact localization of composite structures. Experimental results show its successful performance on epoxy laminate plate and complex composite structure.

Responses of bistable piezoelectric-composite energy harvester by means of recurrences

In this paper we examine the modal response of a bistable electro-mechanical energy harvesting device based on characterization of the experimental time-series. A piezoelectric element attached to a vibrating bistable carbon-fibre reinforced polymer laminate plate was used for the conversion of mechanical vibrations to electrical energy under harmonic excitations at a variety of frequencies and amplitudes. The inherent bistability of the mechanical resonator and snap-through phenomenon between stable states were exploited for energy harvesting. To identify the dynamics of the response of the studied harvesting structure and the associated output power generation we used the Fourier spectrum and Recurrence Quantification Analysis (RQA).

Sound transmission across composite laminate sandwiches: Influence of orthogonal stiffeners and laminate layup

A theoretical model is developed to predict sound transmission loss (STL) across periodically and orthogonally stiffened composite laminate sandwich structures. The first order shear deformation theory (FSDT) is employed to describe the top and bottom composite laminate plates whilst the longitudinal and rotational motion equations are utilized to characterize the reaction forces and moments of the stiffeners. By taking advantage of the periodicity of the sandwich, the governing vibroacoustic equations are favorably solved by employing the method of space harmonic expansion. The validity and feasibility of the proposed theoretical model is qualified through comparisons with finite element simulation results. It is demonstrated that both the stiffeners and laminate layup have significant effects on the vibration and sound radiation behaviors of the structure, especially in the mid and high frequency regimes, enabling further acoustic optimization design.

Detection of low-velocity impact-induced delaminations in composite laminates using Auto-Regressive models

In this paper, the detection of delaminations in carbon-fiber-reinforced-plastic (CFRP) laminate plates induced by low-velocity impacts (LVI) is investigated by means of Auto-Regressive (AR) models obtained from the time histories of the acquired responses of the composite specimens. A couple of piezoelectric patches for actuation and sensing purposes are employed. The proposed structural health monitoring (SHM) routine begins with the selection of the suitable locations of the piezoelectric transducers via the numerical analysis of the curvature mode shapes of the CFRP plates. The normalized data recorded for the undamaged plate configuration are then analyzed to obtain the most suitable AR model using five techniques based on the Akaike Information Criterion (AIC), the Akaike Final Prediction Error (FPE), the Partial Autocorrelation Function (PAF), the Root Mean Squared (RMS) of the AR residuals for different order p, and the Singular Value Decomposition (SVD). Linear Discriminant Analysis (LDA) is then applied on the AR model parameters to enhance the performance of the proposed delamination identification routine. Results show the effectiveness of the developed procedure when a reduced number of sensors is available.

Damage analysis of the laminated plate

This paper deals with the development of a numerical simulation methodology for estimating damages in laminate composite plates caused by a low-speed impact. Experimental tests were performed on laminate plates reinforced with weaven carbon fibers and epoxy resin. Three thickness plates were evaluated. The impact loads were transversal and punctual. Two lamina failure criteria were evaluated. The first is the maximum stress. The second is a proposed modification of the Hashin failure criterion. Four lamina degradation criteria were evaluated too. The numerical damaged areas and lengths were similar or greater than the experimental results.

Stress Distribution of Bolted Joints With Different Lay-Up Types

A parametric study of the stress distribution in the composite plates is undertaken to show the effect of different lay-ups. Full 3-D elastic properties are required in the modelling. These properties are calculated using equations taken from the literature and derivation from simple Classical Laminate Plate Theory (CLPT). In previous experimental work, it was shown that tensile failure involved the development of a damage zone at the edge of the hole. In a double-lap joint, it is assumed that uniform stresses are exhibited throughout the plate thickness. Different lay-ups system give different tangential stress distributions and insignificant variation in the radial stress distribution along the hole boundary.

Effect of tool geometry on surface roughness in slotting of CFRP

This paper presents a study of transverse and longitudinal arithmetic average roughness of carbon fiber-reinforced plastic (CFRP) material slotted with three micrograin carbide knurled tools: fine, medium, and coarse toothings. By transverse (respectively longitudinal) arithmetic average roughness, we mean roughness measured perpendicular to the advance direction (respectively in the advance direction). The purpose of this work is to implant a theoretical model of transverse arithmetic average roughness highlighting his dependence on only tool geometry, to validate it experimentally and to define an empirical model of longitudinal arithmetic average roughness for each knurled tool. From the results of ANOVA, it is concluded that feed per tooth makes the highest statistical and physical influence on surface roughness. Experiments show that knurled tool fine toothing is the suitable tool for slotting of CFRP because it produces less damage to the laminate plate.

Introducing CFRP as an alternative material for engine hood to achieve better pedestrian safety using finite element modeling

The increased number of pedestrian injuries and fatal deaths are resulting from road accidents due to the increased urban population and number of private vehicles. In order to address this issue along with other safety measurements, design, and material of engine hood has been a key point for an automotive industry. The most common materials for the manufacturing of engine hood were steel, aluminum and recently, composite materials have been used due to its added advantage for pedestrian safety. In this study, the finite element models of the pedestrian head impact on automotive hood, adult headform, composite laminate plate and sandwich composite plate were created by ABAQUS/Explicit. Simulation results are validated by Euro-NCAP pedestrian head to hood impact tests. The results show that the FEM modeling of the composite laminate plate, sandwich composite plate and engine hood can effectively predict the pedestrian head injury and deformation pattern of the models. This method can be an applicable tool for the vehicle, pedestrian safety evaluation and related development.

Numerical and experimental investigations of S-Glass/Polyester composite laminate plate under low energy impact

This paper deals with an analysis of a low energy impact on unidirectional S-Glass/Polyester composite plate. A set of low energy impact tests was carried out on composite plates in a bending configuration. The impact loads were applied using drop-mass tower. The mechanical responses, such as impact force, bending, energy dissipation and damage are highlighted and analysed. A reliable finite element model is developed to calculate, and then to compare to experiments, all mechanical responses. An analysis of the stress state and damaged surfaces induced by the impact is performed based on the Hashin's damage criterion. The effect of the drop height on the degradation of the composite material is highlighted, particularly the extent of the damaged area. It is shown that the maximum bending and the maximum impact force follow linear evolution with respect to the drop height. Also, the model reproduced well experimental observations, such as damage generated in the inter-plies, the damaged zone extent and other mechanical responses. A parametric study was performed to highlight the effect of relevant design parameters on the mechanical response of the composite laminate to the impact loading.

Semi-analytical modeling of composite beams using the scaled boundary finite element method

The scaled boundary finite element method (SBFEM) is a semi-analytical method in which only the boundary is discretized. The results on the boundary are scaled into the domain with respect to a scaling center which must be “visible” from the whole boundary. For beam-like problems the scaling center can be selected at infinity and only the cross-section is discretized.The current work is devoted to the development of some SBFEM elements for thin-walled beams on the basis of the first order shear deformation theory. The beam sections are considered to be multilayered laminate plates with arbitrary layup. The arbitrary cross-section is discretized with beam-like elements of Timoshenko type. Using the virtual work principle gives a system of differential equations of a gyroscopic type. The solution is given using the matrix exponential function.Knowing the deformation of the beam, the stresses, strains and curvatures can be calculated and a failure criterion can be used to assess the laminate.The SBFEM has been tested and compared with a finite element model and it gives good results.