Ply Angles Research Articles

Computational Modeling of Hybrid Carbon Fiber/Epoxy Composites Reinforced with Functionalized and Non-Functionalized Graphene Nanoplatelets.

The mechanical properties of aerospace carbon fiber/graphene nanoplatelet/epoxy hybrid composites reinforced with pristine graphene nanoplatelets (GNP), highly concentrated graphene oxide (GO), and Functionalized Graphene Oxide (FGO) are investigated in this study. By utilizing molecular dynamics data from the literature, the bulk-level mechanical properties of hybrid composites are predicted using micromechanics techniques for different graphene nanoplatelet types, nanoplatelet volume fractions, nanoplatelet aspect ratios, carbon fiber volume fractions, and laminate lay-ups (unidirectional, cross-ply, and angle-ply). For the unidirectional hybrid composites, the results indicate that the shear and transverse properties are significantly affected by the nanoplatelet type, loading and aspect ratio. For the cross-ply and angle ply hybrid laminates, the effect of the nanoplate’s parameters on the mechanical properties is minimal when using volume fractions and aspect ratios that are typically used experimentally. The results of this study can be used in the design of hybrid composites to tailor specific laminate properties by adjusting nanoplatelet parameters.

Parametric Study of a Composite Skin for a Twist-Morphing Wing

Although the benefits of morphing wings have been proven in many studies in the last few decades, the wing skin design remains one of the challenges to advancing and implementing the morphing technology. This is due to the conflicting design requirements of high out-of-plane stiffness to withstand aerodynamic loads and low in-plane stiffness to allow morphing with the available actuation forces. Advancements in the design of hybrid and flexible composites might allow for design solutions that feature this balance in stiffness required for this application. These composites offer new design parameters, such as the number of plies, the fiber-orientation angle of each ply in the skin laminate, and the spatial distribution of the plies on the skin surface. This paper presents a parametric study of a composite skin for a twist-morphing wing. The skin is made of periodic laminated composite sections, called “Twistkins”, integrated in an elastomeric outer skin. The twisting deformation is localized in the elastomeric sections between the Twistkins. The design parameters considered are the number of plies in the composite Twistkins, the fiber-orientation angle of the plies, the torsional rigidity of the elastomer, the width ratio, and the number of elastomeric sections. The computational analysis results showed that the torsional compliance can be increased by increasing the width ratio, decreasing the number of elastomeric sections, number of composite plies and the elastomer’s torsional rigidity. However, this would also lead to a decrease in the out-of-plane stiffness. The nonlinearity and rates at which these parameters affect the skin’s behavior are highlighted, including the effect of the fiber-orientation angle of the laminate plies. Hence, the study guides the design process of this twist-morphing skin.

Simulation Analysis of Thermoplastic Composites on Suspension Brackets of Electric Commercial Vehicles

Lightweight is more important in electric commercial vehicles, the static simulation analysis is first carried out on the suspension system bracket using the material of steel under three working conditions in this paper. Taking the suspension system bracket connection plate as an example, the bracket connecting plate model of the suspension system is established with thermoplastic composite materials, which is nine-layer three-dimensional model. The pre-processing, solving and post-processing procedures of the stress analysis of the part are introduced, and the stress distribution of different layers is obtained. Results show that the maximum stress of the steel bracket of the suspension system under three working conditions of triple gravity, acceleration of gravity adding steering inertia, acceleration of gravity adding braking inertia are 189.22, 92.48, and 156.9Mpa for steel, which are all less than the ultimate stress of 235Mpa. The maximum stress of each layer of the thermoplastic composite connecting plate meets the design requirements. In the case of the same ply angle, the bottom layer will bear less and less stress, the base layer will bear very little stress, and the main stress will be borne by the reinforcing material, support is provided for the application of thermoplastic composite materials on automobile chassis.

A multi phase-field-cohesive zone model for laminated composites: Application to delamination migration

Failure processes in Laminated Fiber-Reinforced Composites (LFRCs) entail the development and progression of different physical mechanisms and, in particular, the interaction between inter-laminar and intra-laminar cracking. Reliable modeling of such complex scenarios can be achieved by developing robust numerical predictive tools that allow for the interaction of both failure modes. In this study, a novel Multi Phase-Field (MPF) model relying on the Puck theory of failure for intra-laminar failure at ply level is coupled with a Cohesive Zone Model (CZM) for inter-laminar cracking. The current computational method is numerically implemented as a system of non-linear coupled equations using the finite element method via user-defined UMAT and UEL subroutines in ABAQUS. The computational tool is applied to qualitatively predict delamination migration in long laminated fiber-reinforced polymers composites comprising 44 cross-ply laminates. The reliability of the current approach is examined via the correlation with experimental results. Finally, the present study is complemented with additional representative examples with the aim of providing further insight into the potential role of different aspects of the system in the delamination migration, including (i) the variation of the ply angle in the migration zone, (ii) the load application point, and (iii) initial crack length.

Numerical and experimental studies of the influence of curing and residual stresses on buckling in thin-walled, CFRP square-section profiles

The study provides the first comprehensive experimental and numerical study of thin-walled, carbon fibre square-section columns subjected to static compression. The profiles were manufactured from unidirectional prepreg tape of Hexcel AS4 high-strength carbon fibres in HexPly® 8552 thermoset resin with ply angles [45/−45/45/−45]s. The dimensions of the columns were: (height × width × length) 80 mm × 80 mm × 240 mm and the wall thickness was 0.92 mm.Advanced Finite Element Models (FEM) of the residual stresses generated during production were used as a basis for simulations of static compression. The deformation predicted by these models showed excellent agreement with 3D scans of the columns. These results also highlighted the residual stress concentrations generated at sample corners during production.It was found that the residual stresses from the autoclaving process significantly enhance the buckling load performance (by ~35%) and that the models provide an effective comparison with the experimental results (<10% error). This demonstrates the importance including residual stresses in FEM of buckling, but also highlights residual stress tailoring as a route to significantly enhance the buckling load capacity of carbon fibre systems used in industrial applications.

Parametric responses of carbon-epoxy composite with delamination using cohesive gap element

This paper focuses on the various parametric responses of the delaminated carbon-epoxy composite beam using a gap element. The analysis is based on the cohesive zone modelling approach, and it is implemented using the finite element software ANSYS APDL. In the study, a zero-thickness cohesive gap element that varies the cohesive stresses with the interfacial opening displacement along the localized fracture process zone is used. The available published results of the double cantilever beam test are used to validate the results obtained from the current analysis. The effects of fracture length, number of layers, angle of plies and thickness on delamination of a composite cantilever beam with edge pull is considered in this paper. The results show that the separation between the composite plies is proportional to the stiffness of the cohesive element, and an increase in the number of layers depicts a transition from anisotropy to orthotropy. Under mode I delamination, composite plies with 450 fibre angles exhibits increased torsional stiffness and global resistance. Also, a comparison between thin and thick laminates demonstrate that a laminate of 5 mm thick dissipates about 85% more energy than a composite laminate of 50 mm thick.

Effect of tensile and compressive nonlinear edge loads on the buckling performance of hybrid metal composite laminates with cutouts

In the current study, the finite element approach has been used to investigate the effect of compression and tension types of nonlinear edge loads on the vibration and buckling performance of interlaminar hybrid fiber metal laminates (HFMLs) with and without cutouts. The effect of various hybridizations in cross ply, angle ply and quasi isotropic laminate schemes is studied extensively. Toward this a 9-noded heterosis plate element has been used to discretize the plate by taking into account the effect of shear deformation and rotary inertia. Since the stress distribution within the plate is highly non-uniform in nature, the dynamic approach has been used to solve the buckling problems. The present study consists of aluminum metal face sheets bounded with four layered hybrid laminate schemes, which includes glass and carbon layers. In which, six different hybrid configurations have been considered. The performance of each hybrid configuration along with different sized and positioned cutouts is well investigated under various nonlinear loading conditions, which are compressive and tensile in nature.

Application of genetic algorithm to optimize the impact resistance of composite laminates

The impact resistance of composite fan hood is of great significance to improve the safety of engine. Taking the fiber reinforced resin matrix composite laminate for Aeroengine fan case as the research object, the maximum loss kinetic energy of impact body as the objective function, and the fiber ply angle as the design variable, the impact resistance of the fiber reinforced composite laminate was optimized. ABAQUS finite element software is used to simulate the high velocity impact of composite laminates, and genetic algorithm is used to optimize the design, and the optimal stacking method is obtained. Through the optimization design, the impact resistance of fiber reinforced composite laminates has been greatly improved.

Reliability-based Design Optimization of Laminated Composite Structures under Delamination and Material Property Uncertainties

Delamination is a major type of defects from manufacturing process in laminated composite structures, exhibiting uncertain characteristics which are represented by mixed random variables of continuous in-plane position and delamination size, as well as discrete through-the-thickness position, which should be considered in the design phase of composite structures. Thus, this paper presents a reliability-based design framework for optimal design of composite stacking sequence, for the first time to consider both delamination and material property uncertainties from manufacturing process. Mixed continuous-discrete random variables are involved, and a reliability analysis method is newly proposed to tackle this mixed-variable problem, maintaining high levels of both accuracy and efficiency. The formula of total probability is first employed to formulate the reliability constraint so that discrete and continuous random variables are decoupled; Monte Carlo simulation is then used for reliability analysis with respect to continuous random variables, and a surrogate modelling approach based on Gaussian process regression model is adopted to reduce computation costs. As design variables of ply angles are limited to a discrete set, a genetic algorithm with some proposed improvements is used to handle discrete design variables. Consequently, an optimization framework is devised for composite laminate design under uncertainties from manufacturing process, which is verified via case studies of a cantilever composite plate and can also be extended as a general solution for other composite laminates. With integrated consideration of manufacturing limitations and imperfections as well as structural performances, the presented framework provides a valuable tool in composite structure design.

Nonlinear Damping and Forced Response of Laminated Composite Cylindrical Shells with Inherent Material Damping

In this paper, the nonlinear damping and forced response behaviors of laminated composite cylindrical shells considering the internal damping of composite materials are investigated. Based on Donnell nonlinear shell theory, the dynamic governing equations of composite cylindrical shells with geometrical nonlinearity are established by using the Hamilton principle, in which the inherent material damping is taken into account by complex modulus method. The dependence of nonlinear damping on vibration amplitude and amplitude–frequency response are analytically obtained by the Galerkin method in conjunction with harmonic balance method. By comparing the results of natural frequency and modal damping with those in the literature, the correctness of the above theoretical analysis is verified. Furthermore, the effects of the circumferential wave number, lamination schemes, vibration amplitude and geometric configuration on the nonlinear damping and forced responses of the composite cylindrical shell with unidirectional, angle-ply and cross-ply laminations are analyzed. The results show that the damping dissipation capacity of the composite cylindrical shell is amplitude-dependent, and the effect of the amplitude on the nonlinear damping characteristics gradually decreases with the increase of the length-to-radius ratio. The ply angle not only affects the value of the resonance peak, but also significantly changes the degree of the soft and hard spring characteristics of the composite cylindrical shell. With the increase of internal material damping, the amplitude-frequency curve of the composite cylindrical shell changes from the coexistence of hard and soft characteristics to the only soft characteristics.

Effect of Delamination on Natural Frequencies of E-glass and S-glass Epoxy Composite Plates

The delamination is one of the major modes of failure occurring in the laminated composite due to insufficient bonding between the layers. In this paper, the natural frequencies of delaminated S-glass and E-glass epoxy cantilever composite plates are presented by employing the finite element method (FEM) approach. The rotary inertia and transverse shear deformation are considered in the present study. The effect of parameters such as the location of delamination along the length, across the thickness, the percentage of delamination, and ply-orientation angle on first three natural frequencies of the cantilever plates are presented for S-glass and E-glass epoxy composites. The standard eigenvalue problem is solved to obtain the natural frequencies and corresponding mode shapes. First three mode shape of S-Glass and E-Glass epoxy laminated composites are portrayed corresponding to different ply angle of lamina.

Determining the best practice – Optimal designs of composite helical structures using Genetic Algorithms

Composite helical structures (CHSs) can store and release strain energy through elastic deformation, which have been used in automobile and aerospace structures. The compressive stiffness to weight ratio is the core in the design of these structures, requiring an optimal geometric configuration. Seven state-of-the-art Genetic Algorithms were employed and benchmarked to optimise two conflicting objectives, maximising the compressive stiffness while minimising the weight. All design variables that having effects on the compressive stiffness and weight of CHSs had been considered, which are the helix angle, the number of active coils, the helix diameter, the outer and inner diameter of cross-section, and the ply angle. A quantitative analysis method, mimicked inverted generational distance (mIGD), was used to determine the best practice of Genetic Algorithms. This study shows the selection of the Genetic Algorithm is crucial and multi-objective evolutionary algorithm based on decomposition (MOEA/D) is the best solver on searching the designs of the maximum compressive stiffness and the minimum weight.

Structural Analysis of Composite Conical Convex-Concave Plate (CCCP) Using VAM-Based Equivalent Model

Compared with the ordinary foundation plate, the composite conical convex-concave plate (CCCP) has obvious anisotropic characteristics, and there is less research on the relationship between its mechanical properties and structural parameters. In this article, a numerical model for the equivalent stiffness of a typical unit cell with conical convex is established by using the variational asymptotic method. Then, the 3D finite element model (3D-FEM) of CCCP is transformed into 2D equivalent plate model (2D-EPM) with the effective plate properties obtained from the constitutive analysis of unit cell. The accuracy of 2D-EPM is verified by comparing with the displacement, natural frequencies, and buckling results from 3D-FEM under different boundary conditions. Then, the influence of geometric parameters and layup configurations on the effective performances of CCCP are investigated. Finally, the buckling loads and natural frequencies of bidirectional CCCP are compared with those of CCCP by using the present model. The present model is particularly useful in the early design stage of CCCP where many design trade-offs need to be made over a vast design space in terms of material selection, ply angles, and geometric parameters.

Free vibration analysis of composite foils with different ply angles based on beam theory

Previous investigations on composite materials are most based on uniform beam, while solid shape of foils are usually used in ocean and marine industries. To better predict the modal characteristics of composite solid foils, this paper modifies analytical model based on anisotropic thin-walled closed-section beam theory and investigates free vibration characteristics of the composite NACA0009 foil with different ply angles(θ). Good agreement has been obtained between the predicted natural frequencies and those simulated by Finite Element Method. Due to the non-coincidence of the shear center and mass center, the natural frequencies are not the same at opposite ply angles. The modal shapes illustrate the coupling of bending and torsion modes at different ply angles. For the first mode, the modal shapes are mainly the first bending with first torsion shape coupled at different ply angles. When |θ|<10°, the first torsion plays a key role in the second modal shapes, while when |θ|>10°, the main modal shapes of the second mode is changing to the second bending shape. Compared the results with and without coupling effects considered, the variation of natural frequencies may related to the change of modal shapes. By mode decomposition, it is shown that the percentages of uncoupling bending shapes and torsion shapes on each modal shapes with different ply angles.

Three-dimensional exact elasticity solutions for antisymmetric angle-ply laminated composite plates

This paper is concerned with the derivation of the benchmark three-dimensional exact solutions for the static analysis of rectangular antisymmetric angle ply plates. The expressions for the exact solutions of displacements and stresses can be used in a straight forward manner to find the numerical results for any fiber orientation angle. It has been explored that the expressions for the exact solutions of displacements and stresses in the square antisymmetric angle-ply plates with 45° fiber orientation angle cannot be used for other fiber orientation angles and vice versa. Comparison of the exact solutions with the analytical solutions employing the first order shear deformation theory (FSDT) reveals that the FSDT can be efficiently used for thin and two layered thick antisymmetric angle-ply plates.

Vibration and thermal buckling analyses of multi-span composite lattice sandwich beams

Multi-span composite lattice sandwich beams have wide application prospects in the aerospace, high-speed trains and civil engineering fields because of the low specific weight, high specific strength and multifunctional potential. Moreover, the span number and the subspan length have a great influence on the vibration and thermal buckling properties of multi-span beams. Therefore, a simple and effective method is presented to investigate the vibration and thermal buckling behaviors of different multi-span sandwich beams with pyramidal truss core in this study. The first-order shear deformation theory is used to evaluate the strain–displacement relations in the structural modeling. The mode shapes modified by the interpolation function are used to evaluate the vibration modes of the multi-span lattice sandwich beam. The differential equation of motion is formulated by Hamilton’s principle. The natural frequencies of the multi-span sandwich beam with pyramidal truss core are validated through comparing the finite element method results. The parametrical investigations with respect to the ply angle of the composite laminated face sheets and the radius of trusses are conducted. Furthermore, the influences of the span number and subspan length on the vibration and thermal buckling behaviors of the composite lattice sandwich beams are also performed and discussed.

A study of earthquake-induced vibration on laminated composite plates using finite element method

This study presents the dynamic response of an eight-noded composite plate under earthquake excitation. Koyna earthquake excitation frequency is considered for the present study. Central displacement and stresses at various positions are studied extensively. Variation in response under different boundary conditions and varying geometric conditions are presented. The ply angle in a lamina and the number of layers in a plate are also varied to observe their effect on displacement and stress. In almost all the cases, 45° lamination shows maximum displacement response, whereas 0°/90° lamination scheme always shows maximum normal stress values. On the other hand, inplane shear gives maximum response whenever a − 45° layer is present. The effect of plan dimension on displacement is also presented here. The displacement response is maximum when the plate becomes square for both cross- and angle-ply laminations. The displacement response with change in total thickness of the plate is presented in this article. The response increases drastically as the plate becomes thinner for angle and cross-ply laminations. The plate becomes unstable as the side to thickness ratio increases beyond 50. The variation of stresses for cross- and angle-ply laminated plates across their layers is reported here with different boundary conditions. A very important observation made through this comparison as a 45° clamped laminated plate should be designed under transverse shear stress, whereas the simply supported plate should be designed under inplane shear stress.

Structural Design and Mechanical Performance Analysis of Carbon Fiber Closed Fixtures for UHV Transmission Lines

The closed clamp is a standard tool for the insulator replacement in ultrahigh voltage (UHV) transmission lines, which is mainly made of titanium alloy material and weighs more than 27 kg that greatly reduces the working efficiency for operators. Due to the lightweight demand, carbon fiber composite materials are applied to design a new type of clamp, in which mechanical properties of new fixtures need to be fulfilled while considering poor impact resistance and low interlaminar shear strength of carbon fiber composite materials. To excavate a high-strength ply structure, finite element progressive damage strength analysis is employed to evaluate the mechanical properties of three different ply angles of the carbon fiber closed fixture, in which Tsai–Wu strength theory is thought as the strength judgment basis for carbon fiber composite materials. After comparison with the displacement-load curves, the three different ply angles fail to meet the strength requirements. So, a carbon fiber laminate structure with an outer cladding for carbon fiber closed fixtures is raised and verified. The analysis results show that the laminate structure meets the strength requirements. Destructive test of the new closed clamp is conducted to verify the correctness of the proposed method, and the weight is reduced by 36.46%.

Investigation of effect of different geometric parameters on fundamental natural frequency of composite laminate plate

Composite materials have remarkable properties such as high strength to weight ratio, wear resistance, good electrical and thermal properties compared to metals. A laminated composite material consists of several layers of a composite laminas made of matrix and fibers. Each layer with different fiber orientations may have similar or dissimilar material properties. In this study, the effect of the fiber orientations on the fundamental natural frequency of laminated composite plate is investigated. The problem is analyzed and solved using the finite element method and Matlab. A variety of boundary conditions are used in the analysis. Numerical results were obtained for orthotropic symmetric laminated plate. Fundamental natural frequency of composite plates depends upon various characteristics like aspect ratio, boundary condition and fiber orientation. The effect of cut outs on fundamental natural frequency is analysed. It is observed that the ply angles are playing major role while deciding the fundamental natural frequency of composite laminate plate.

In-situ effect in cross-ply laminates under various loading conditions analyzed with hybrid macro/micro-scale computational models

In this work, multi-scale finite element analyses based on three-dimensional (3D) hybrid macro/micro-scale computational models subjected to various loading conditions are carried out to examine the in-situ effect imposed by the neighboring plies on the failure initiation and propagation of cross-ply laminates. A detailed comparative study on crack suppression mechanisms due to the effect of embedded laminar thickness and adjacent ply orientation is presented. Furthermore, we compare the results of in-situ transverse failure strain and strength between the computational models and analytical predictions. Good agreements are generally observed, indicating the constructed computational models are highly accurate to quantify the in-situ effect. Subsequently, empirical formulas for calculating the in-situ strengths as a function of embedded ply thickness and different ply angle between embedded and adjacent plies are developed, during which several material parameters are obtained using a reverse fitting method. Finally, a new set of failure criteria for σ22-τ12, σ22-τ23, and σ11-τ12 accounting for the in-situ strengths are proposed to predict laminated composites failure under multi-axial stress states. This study demonstrates an effective and efficient computational technique towards the accurate prediction of the failure behaviors and strengths of cross-ply laminates by including the in-situ effects.