Cross-ply Composite Laminates Research Articles

Analytic determination of stress fields in cross-ply symmetric composite laminates

A Hamiltonian state space approach for analytic determination of deformation and stress fields in multilayered cross-ply symmetric laminates under extension and bending is presented, in which the equations of anisotropic elasticity, the end conditions, the traction-free boundary conditions on the bounding planes of the rectangular section, and the interfacial continuity conditions in multilayered laminates are satisfied, regardless of the number of layers. The solutions serve as useful benchmarks for numerical modeling and material characterization of composite laminates.

The initiation of transverse matrix cracking and longitudinal matrix cracking in composite cross-ply laminates: Analysis of a damage criterion

AbstractThe results of stress field distribution in damage cross-ply laminates prompt us to elaborate an energy criterion. This criterion is based on the partial parts’s computation of the strain energy release rate associated with each damage type and for all loading modes. In the related criterion, based on the linear fracture approach, several hypotheses are used to simplify the damage criterion. The main objective with this approach is to estimate the onset of transverse and longitudinal cracking mechanisms and the development of the damage. Only results from numerical simulations are proposed for one material; numerous numerical simulations, with other materials and laminate architectures, give similar evolutions of matrix cracking damage.

A layerwise semi-analytical method for modeling guided wave propagation in laminated and sandwich composite strips with induced surface excitation

A semi-analytical method for the quick and robust solution of guided waves excited in infinite laminated composite strips is presented. In the proposed method, the response of the strip is constructed in time-space domain directly from the governing wave equations, assuming a layerwise variation of the through-the-thickness displacement components. Analytical Fourier transforms, with respect to time and space, provide the transformed response in the frequency-wavenumber domain. Dispersive modal properties for the structure are extracted. Finally, the time transient response of the propagative guided waves is calculated using two inverse Fourier transforms, the first is calculated via the Cauchy's residue theorem, whereas the second is numerically computed. Various numerical results are presented for isotropic, cross-ply composite laminate and sandwich strips and are compared with results from other reported methods as well as with experimental results in composite strips.

Modelling transverse matrix cracking and splitting of cross-ply composite laminates under four point bending

The transverse matrix cracking and splitting in a cross-ply composite laminate has been modelled using the finite element (FE) method with the commercial code Abaqus/Explicit 6.10. The equivalent constraint model (ECM) developed by Soutis et al. has been used for the theoretical prediction of matrix cracking and results have been compared to those obtained experimentally and numerically. A stress-based traction–separation law has been used to simulate the initiation of matrix cracks and their growth under mixed-mode loading. Cohesive elements have been inserted between the interfaces of every neighbouring element along the fibre orientation for all 0° and 90° plies to predict the matrix cracking and splitting at predetermined crack spacing based on experimental observations. Good agreement is obtained between experimental and numerical crack density profiles for different 90° plies. In addition, different mechanisms of matrix cracking and growth processes were captured and splitting was also simulated in the bottom 0° ply by the numerical model.

Fracture characterization of glass fiber composite laminate under experimental biaxial loading

This study proposes a mixed-mode fracture criterion for glass fiber reinforced composite laminates based on numerical and experimental biaxial loading. An optimal cruciform geometry is introduced first based on finite element (FE) simulation. Characterization testing is performed successively on uniaxial and cruciform specimens to determine equivalent loaded area, notch sensitivity behavior and critical fracture toughness properties of cross-ply GFRP laminates. In experimental biaxial testing, two types of crack orientations (0°, 45°) are studied with varying crack lengths. The experimental failure points show that cross-ply GFRP laminates attain higher load bearing capability under biaxial tensile–tensile loading compared to uniaxial testing. Appropriate non-dimensional geometry factor relevant to cruciform shape is determined based on experimental data points and FE simulation. Eventually, a mixed-mode fracture criterion is proposed for cross-ply composite laminate based on the findings from biaxial experimental loading.

Dynamic responses of cross-ply bi-stable composite laminates with piezoelectric layers

In this paper, static and dynamic behavior of bi-stable composite laminates with $$[0-90]_{T}$$ stacking sequence and piezoelectric layers is studied. The governing equations of system were obtained using Rayleigh–Ritz method and Hamilton’s principle. In order to improve the accuracy of results, a set of higher-order shape functions were employed. The dynamic response of the system under various electrical fields applied to the piezoelectric actuators was studied, and the effects of the presented shape functions on short-circuit natural frequency and the lowest electrical field required for snap-through were analyzed. The results obtained from the developed analysis have been compared with the conventional and FEM models. Good correlation was observed between the proposed model and the finite element method.

Reduction of Free Edge Peeling Stress in Composite Laminates under Bending Load

In this paper, a stress function-based approach was proposed to analyze the reduction of free-edge peeling stress in smart composite laminates using piezoelectric actuator under bending load. Electro-mechanically coupled governing equation was obtained by complimentary virtual work principle. The stress state was solved by the generalized eigenvalue procedure. The free-edge peeling stress of smart composite laminates was reduced by the piezoelectric actuation. The reduction rate of peeling stress in cross-ply composite laminate is larger than that in angle ply composite laminate.

Strength evaluation of cross-ply green composite laminates reinforced by bamboo fiber

Steam exploded bamboo (SEB) fibers were treated with alkali solution to remove lignin and hemicelluloses and also to increase the compatibility with biodegradable matrix resin. The fibers were processed by simple hand-lay-up method and hot pressed using dispersion-type biodegradable poly lactic acid (PLA) resin to produce a PLA/bamboo fiber cross-ply (0/90)s laminate composites, whose fiber content varied from 17 up to 68 wt.%. The intermolecular interaction among bamboo fiber and PLA matrix was discussed based on Fourier transform infrared (FTIR) analysis. The results showed that the tensile strength of alkali treated bamboo fiber was comparable with those of common strong natural fibers such as hemp and flax fibers. The composites' strength was similar to that of ordinary glass fiber-reinforced plastics laminate and the specific strength was three times higher than that of mild steel. It was also found that the cross-ply (0/90)s SEB/PLA laminate has the same cracking character as the common cross-ply laminates based on carbon or glass fibers.

Failure analysis of fiber-reinforced composite laminates subjected to biaxial loads

A nonlinear constitutive model for a single lamina is proposed for the failure analysis of composite laminates. In the material model, both fiber and matrix are assumed to behave as elastic-plastic and the in-plane shear is assumed to behave nonlinearly with a variable shear parameter. The damage onset for individual lamina is detected by a mixed failure criterion, composed of the Tsai-Wu criterion and the maximum stress criterion. After damage takes place within the lamina, the fiber and in-plane shear are assumed to exhibit brittle behavior, and the matrix is assumed to exhibit degrading behavior. The proposed nonlinear constitutive model is tested against experimental data and good agreement is obtained. Then, numerical analyses are carried out to study the failure behavior of symmetric angle-ply composite laminates and symmetric cross-ply composite laminates subjected to biaxial loads. Finally, the conclusions obtained from the numerical analysis are given.

Bending analysis of a general cross-ply laminate using 3D elasticity solution and layerwise theory

In this study, the analytical solution of inter- laminar stresses near the free edges of a general (symmetric and unsymmetric layups) cross-ply composite laminate subjected to pure bending loading is presented based on Reddy's layerwise theory (LWT) for the first time. First, the reduced form of displacement field is obtained for a general cross-ply composite laminate subjected to a bend- ing moment by elasticity theory. Then, first-order shear deformation theory of plates and LWT is utilized to determine the global and local deformation parameters appearing in the displacement fields, respectively. One of the main advantages of the developed solution based on the LWT is exact prediction of interlaminar stresses at the boundary layer regions. To show the accuracy of this solution, three-dimensional elasticity bending problem of a laminated composite is solved for special set of boundary conditions as well. Finally, LWT results are presented for edge-effect problems of several symmetric and unsym- metric cross-ply laminates under the bending moment. The obtained results indicate high stress gradients of interlam- inar stresses near the edges of laminates.

Buckling analysis in hybrid cross-ply composite laminates on elastic foundation using the two variable refined plate theory

This paper presents the effect of hybridization material on variation of critical buckling load with different cross-ply laminates plate resting on elastic foundations of Winkler and Pasternak types subjected to combine uniaxial and biaxial loading by using two variable refined plate theories. Governing equations are derived from the principle of virtual displacement; the formulation is based on a new trigonometric shape function of displacement taking into account transverse shear deformation effects vary parabolically across the thickness satisfying shear stress free surface conditions. These equations are solved analytically using the Navier solution of a simply supported. The influence of the various parameters geometric and material, the thickness ratio, and the number of layers symmetric and antisymmetric hybrid laminates material has been investigated to find the critical buckling loads. The numerical results obtained through the present study with several examples are presented to verify and compared with other models with the ones available in the literature.

Partial Strain Energy Release Rate for Study Matrix Cracking Evolution in Composite Cross-Ply Laminates

Matrix cracking is generally the first observed damage in composite laminates. The stress field distribution in the damaged cross ply laminates is analysed through an approach which uses several hypotheses to simplify the damage state. The proposed cracking criterion involves the respective partial part of the 0° and 90° layers to the damage process. The initiation of transverse and longitudinal cracking mechanisms is predicted.

Analytical and experimental investigation of tensile properties of cross-ply and angle-ply GFRP composite laminates

AbstractThe static tensile properties in the form of ultimate failure stress, ultimate failure strain and Young’s modulus of a cross-ply glass fiber-reinforced polymer (GFRP) composite laminate [904, 04]s and an unconventional angle-ply GFRP composite laminate [+67.54, -67.54]s were investigated using the netting analysis, the laminate mixture rule (Hart-Smith 10% rule) and the classical laminate theory (CLT). The findings were then compared to experimental results to determine the accuracy of each analytical technique. It was found that the netting analysis was the best overall method for estimating the cross-ply laminate tensile properties, whereas neither the CLT nor the 10% rule were appropriate for estimating the tensile properties of the unconventional ply angle laminate.

ANALYSIS OF CROSS-PLY LAMINATES WITH PIEZOELECTRIC FIBER-REINFORCED COMPOSITE ACTUATORS USING FOUR-VARIABLE REFINED PLATE THEORY

This study presents an analytical solution for cross-ply composite laminates integrated with a piezoelectric fiber-reinforced composite (PFRC) actuator subjected to electromechanical loading using the four-variable refined plate theory. This theory predicts parabolic variation of transverse shear stresses and satisfies the zero traction on the plate surfaces without using the shear correction factor. Using the principle of minimum potential energy, the governing equations for simply supported rectangular plates are extracted and the Navier method is adopted for solution of the equations. The comparison of obtained results with other common plate theories and the exact solution indicates that besides the simplicity of the presented formulation, it is very accurate in analysis of laminated composite plates integrated with PFRC. Also the effects of the thickness ratio, aspect ratio, number of layers, staking sequence and amount of electrostatic loading on the displacements and stresses are investigated and the obtained findings are reported.

Guided wave interaction with hole damage using the local interaction simulation approach

This paper considers the effects of hole damage on guided wave propagation in isotropic and composite plates using both the local interaction simulation approach (LISA) and experimental methods. Guided wave generation from piezoceramic wafers is modeled using the recently developed LISA hybrid approach. First, holes in isotropic plates are simulated to establish LISAʼs ability to capture the guided wave scattering effects of various hole sizes. Experimental results are compared with the simulations to aid in evaluating the LISA model. Next, hole damage in cross-ply composite laminates is modeled and compared with experimental results. Various hole sizes and azimuthal locations are simulated to determine the effects of varying those parameters. Results from both the isotropic and composite damage studies clearly display the ability of LISA to model hole damage. Both the simulation and experimental results illustrate the advantages and disadvantages of various sensor locations relative to the actuator and damage locations. Finally, the study shows the ability of the LISA model to capture mode conversions resulting from partial thickness holes.

Matrix cracking and delamination evolution in composite cross-ply laminates

AbstractThis study followed numerous simulations of the stress field distribution in damaged composite cross-ply laminates, which were subjected to uni-axial loading. These results led us to elaborate an energy criterion. The related criterion, a linear fracture-based approach, was used to predict and describe the initiation of the different damage mechanisms. Transverse crack damage was generally the first observed damage. The second type of damage was longitudinal cracking and/or delamination. The stress field distribution in the damaged cross-ply laminates was analysed through an approach that used several hypotheses to simplify the damage state. The initiation of transverse cracking and delamination mechanisms was predicted. The proposed results concern the evolution of the strain energy release rate associated to the evolution of transverse cracking and delamination. As in several studies in the literature, to quantify the evolution of the damage mechanisms in the present approach, the laminate is su...

Propagation of Ao mode through the front edge of a delamination: Numerical and experimental studies

Numerical and experimental studies carried out on the propagation of ultrasonic Lamb wave and its interaction with the front edge of a delamination in a cross-ply and unidirectional composite laminates are presented in this paper. When the fundamental antisymmetric Lamb mode (Ao) is incident at the leading (front) edge of a delamination, it undergoes reflection and transmission into the sub-laminates. Numerical simulations carried out on the interaction of the Ao mode with the edge of a semi-infinite delamination revealed that during this interaction, So mode is generated and propagate as AoSo (propagation of the So mode due to the incident Ao mode) mode in the top and bottom sub-laminates along with the incident Ao mode, which propagates as AoAo (propagation of the Ao mode due to the incident Ao mode) mode. Transmission factors and power transmission coefficients of AoAo and AoSo modes on an assortment of excitation frequencies — 150 kHz, 175 kHz, 200 kHz and 225 kHz, and thickness ratios were computed. Experimental validation of results arrived through numerical simulations, was also carried out employing air-coupled ultrasonic transducers.

Acoustic Emission Health Assessment with Artificial Intelligence on the Composite Cross Ply Laminates.

Acoustic Emission Health Assessment with Artificial Intelligence on the Composite Cross Ply Laminates.

Analysis of Free Edge Stresses in Composite Laminates Using Higher Order Theories

This paper presents the determination of the interlaminar stresses close to the free edges of general cross-ply composite laminates based on higher order equivalent single-layer theory (HESL). The laminates with finite dimensions were subjected to a bending moment, an axial force, and/or a torque for investigation. Full three-dimensional stresses in the interior and the boundary-layer regions were determined. The computed results were compared with those obtained from Reddy’s layerwise theory. It was found that HESL theory predicts precisely the interlaminar stresses near the free edges of laminates. Besides, high efficiency in terms of computational time is obtainable when HESL theory is used as compared with layerwise theory. Finally, various numerical results were presented for the cross-ply laminates. Also design guidelines were proposed to minimize the edge-effect problems in composite laminates.

The Pulsed Ultrasonic Backscatter Polar Scan and its Applications for NDT and Material Characterization

In a conventional ultrasonic polar scan (UPS) experiment, the amplitude or time-of-flight-diffraction (TOFD) values of the transmitted and/or reflected acoustic pulse are recorded for a wide range of incidence angles, in view of gaining knowledge about the elastic properties at the insonified material spot. Here we apply the pulsed UPS technique and investigate the backscattered signal, resulting in the ultrasonic backscatter polar scan (UBPS). It is shown that a UPBS contains a blueprint of geometrically related features of the insonified material spot which can be of particular interest for various industrial applications. We applied the UBPS for (i) the determination of the stacking sequence of a cross-ply composite laminate, (ii) the semi-quantification of a multidirectional microscopic surface corrugation, (iii) the detection of corrosion in an early stage as well as (iv) the detection and the localization of a closed surface breaking crack.