Composite Cylindrical Shells Research Articles

Prediction and optimization of composite shell with cutout under hydrostatic pressure via deep neural networks

Composite cylindrical shells with openings represent an innovative primary structural configuration for submersibles, effectively enhancing their structural performance and, consequently, their endurance capabilities. Under hydrostatic pressure conditions, it is essential to optimize the structural design parameters to improve the buckling load and static strength margins of composite cylindrical shells with openings. However, the stress state around openings is highly complex, making simulation and computational analysis challenging and time-intensive. Therefore, leveraging advanced computational methods to assist in structural design is imperative. This study presents an experimental study on the hydrostatic pressure bearing performance of filament-wound composite shells. Based on the experimental results, an accurate finite element method (FEM) model has been established. This study has developed a data-rich framework, generating a synthetic dataset of strength performance under hydrostatic pressure through 16,996 FEM analysis. Subsequently, machine learning (ML) models have been established to predict strength performance. This study presents the validation of the superiority of Deep Neural Network (DNN) models in predicting structural strength under hydrostatic pressure, and evaluates the prediction error. Additionally, for the first time, the DNN model is applied to estimate the structural performance under hydrostatic pressure, with optimization achieved through the integration of a genetic algorithm. The introducing of DNN greatly accelerates the computational speed compared to full FEM-based optimization procedures. By optimizing representative long and short shell models separately, it is demonstrated that ML-based optimization can replace full FEM-based procedures, facilitating preliminary structural design optimization and offering more efficient design solutions.

Nonlinear vibrations for three-dimensional four-directional braided composite cylindrical shell subjected to aerodynamic force and external excitation

Nonlinear vibrations for three-dimensional four-directional braided composite cylindrical shell subjected to aerodynamic force and external excitation

Vibration characteristics analysis of multi-layer composite cylindrical shell casing with different layer thickness ratios under external pressure using energy method

PurposeAero-engine casings commonly use composite cylindrical shell structures with excellent properties such as corrosion resistance and fatigue resistance. Still, their vibration behavior is relatively complex and may cause fatigue vibration damage, so it is essential to analyze the vibration characteristics of composite cylindrical shells. The purpose of this paper is to analyze the vibration characteristics of multilayer composite cylindrical shells subjected to external pressures and having different interlayer thickness ratios and provide some theoretical basis for the fatigue damage prediction of cylindrical shell casing to ensure the safety and stability of the engine during flight.Design/methodology/approachFirstly, the vibration differential equation with external pressure is established based on Soedel theory considering nonlinear effects, while four symmetric boundary conditions are chosen to constrain the cylindrical shell. Then the Rayleigh–Ritz method, which is more efficient and accurate in calculating large structural systems, is applied to solve the problem, and the theoretical model of three-layer cylindrical shell under external pressure is established. The accuracy of the model is verified by comparing the data with the specialized literature. Subsequently, the effects of different external pressures and different thickness-to-diameter ratios, different length-to-diameter ratios and different interlayer thickness percentages on the natural frequency of multilayer composite cylindrical shells were investigated by control variable analysis.FindingsThe conclusions obtained show that the external pressure increases the natural frequency of the cylindrical shell and that the frequency characteristics of the cylindrical shell vary for different boundary conditions. The effect of length-to-diameter ratio, thickness-to-diameter ratio and the percentage of the thickness of the intermediate layer on the natural frequency of the cylindrical shell are significantly increased under external pressure. Because the presence of external pressure increases the frequency of the cylindrical shell by about 70%, it has almost no effect on the frequency at the minimum number of circumferential waves, and the effect on the frequency at the maximum number of circumferential waves is reduced to about 50%. The frequencies in the SL-SL boundary condition are all in perfect agreement with the S-S boundary condition under the influence of different influencing factors.Originality/valueIn this paper, the effect of external pressure and the natural properties of the cylindrical shell under external pressure on the cylindrical shell’s frequency is considered, emphasizing the effect of different layer thickness ratios on the frequency. This paper aims to summarize the changing law between the natural frequency of the cylindrical shell itself and different design parameters during the flight pressure process. Reliable theoretical predictions are provided for analyzing the vibrational behavior of shells subjected to external pressures in aerospace, as well as a database for the practical production of cylindrical shells.

A Comparative Analysis of Buckling Pressure Prediction in Composite Cylindrical Shells Under External Loads Using Machine Learning

Composite materials are increasingly utilized in engineering due to their superior properties such as strength, flexibility, and corrosion resistance. However, accurately predicting the buckling pressure of composite cylindrical shells under external loads remains challenging due to the complexities introduced by various stacking methods. This study addressed this challenge by integrating advanced machine learning techniques with simulation-based data generation through finite element analysis (FEA). A comprehensive dataset comprising 1369 simulation results was generated using ANSYS ACP, focusing on cylindrical shells modeled with an 8-mm-thick filament winding technique and T700 material. The stacking angles ranged from −90 degrees to 90 degrees in 5-degree increments. Stacking configurations (inputs) and their corresponding buckling strength (outputs) were generated using ANSYS ACP. Machine learning models, including linear regression, elastic net, polynomial regression, random forest, support vector regression, XGBoost regression, and artificial neural networks, were implemented using Python 3.8 and Scikit-learn (version 0.24.2). A comparative analysis of these methods revealed their model performance, providing insights into the most effective approaches. Additionally, the accuracy of these models was then evaluated on previously unseen input data, allowing for a comparison of their out-of-sample accuracy. The results demonstrated that the random forest model and XGBoost regression achieved superior accuracy with minimal prediction errors. The study highlights the critical role of machine learning in predicting buckling pressure, which is essential for ensuring structural integrity and optimizing performance in marine engineering and other applications involving composite materials.

Machine learning assisted buckling analysis of cantilever bio-inspired helicoidal laminated composite cylindrical shells with cutouts

Buckling behavior of laminated composite shells changes drastically with introduction of cut outs. The present work aims to predict the buckling behavior of bio-inspired helicoidal laminated composite cantilever cylindrical shells using finite element-assisted multi-output Support Vector Machine (SVM) learning algorithm. The model is trained to predict the value for the non-dimensional critical buckling load with the number of layers, geometry of shell, orientation and thickness of each layer, and dimension of circular cut out are adopted as input parameters with critical buckling load for perfect, shell containing one circular or square hole at the center of the length, and shell containing two circular or square hole at the center of the length of the shell are predicted. Thus, single surrogate can predict critical buckling load for five cases in a single rum. Two different types of cut outs i.e., circular and square shaped cut outs are studied. Influence of helicoidal scheme, number of layers, and dimension and number of holes on the buckling behavior of shell is studied. For shell without cut outs, conventional layup schemes such as cross-ply and quasi-isotropic are found to give highest values of the non-dimensional critical buckling load compared to the helicoidal schemes. For shells with cut outs, Fibonacci helicoidal and helicoidal semi-circular (HS3) schemes gives maximum values for the non-dimensional critical buckling loads.

Acoustic Radiation from Double Composite cylindrical Shells with Cyclic Rectangular Rib-Plates: Creeping Waves and Asymptotic Analyses

Acoustic radiation from double composite laminated cylindrical shells with cyclic rectangular rib-plates is analytically investigated by using the Sommerfeld-Watson transform. High-frequency acoustic model of double composite cylindrical shells with rectangular rib-plates is established in terms of creeping waves, geometrical acoustic waves and sound pressure asymptotic integrals. One kind of bending wave boundary layers for the shear deformable rectangular rib-plate is shown. Each set of creeping wave poles for the composite cylindrical shells with rectangular rib-plates is uniformly distributed by the cyclic period. This characteristic still holds for the cyclic structures with the smallest period. Creeping wave poles of the stiffened composite cylindrical shells appear in the entire complex circumferential wavenumber plane. The asymptotic integrals with Airy function are proposed to fast calculate acoustic pressure in the shadow and penumbra regions without making use of creeping wave poles.

Parameter optimisation of piezoelectric vibration absorber in composite cylindrical shells: A multi-modal approach to mitigate stochastic vibration

This paper investigates the stochastic vibration mitigation of composite cylindrical shells using multi-modal piezoelectric vibration absorbers (PVAs). A novel semi-analytical method is proposed to analyse the stochastic vibration characteristics of composite cylindrical shells equipped with PVAs. The vibration behaviour under stochastic excitations is determined using the modified Ritz method and the pseudo excitation method (PEM). Compared to the finite element method (FEM), the proposed model greatly enhances efficiency by eliminating the need for repeated modelling and meshing, thereby facilitating the optimisation of PVAs. The effects of piezoelectric patch layout and circuit parameters on PVA performance are examined in detail using the proposed electro-mechanical model. Additionally, a multi-modal PVA design procedure, combining the semi-analytical model with a surrogate model-based optimisation algorithm, is presented. The superior stochastic vibration suppression performance of the multi-modal PVA is demonstrated by comparing the dynamic responses of the composite cylindrical shell without PVA, with single-modal PVA, and with multi-modal PVA. The proposed optimisation procedure offers a valuable approach for the design of multi-modal PVAs for stochastic vibration control of cylindrical structures.

On tailoring morphing mechanics of a bistable composite cylindrical shell through elastic fibre prestressing

A bistable composite cylindrical shell is a thin-walled structure that can change shape between two stable configurations under small energy input, showing great potential to be applied to space deployable mechanics. The internal stress level within a cylindrical shell plays a vital role in determining its morphing mechanics, whilst tailoring the internal stress is tricky for traditional composite manufacturing methods. In this paper, we devise a novel biaxial elastic fibre prestressing (EFP) method to systematic design and produce prestrained carbon-based composite cylindrical shells, with tailorable bistability and morphing mechanics, as well as improved load-carrying capabilities. A biaxial fibre stretching rig was devised to apply tensions on both directions of a plain-weave carbon prepreg simultaneously; prestrained cylindrical shell samples were produced with various prestrain levels to fully evaluate the fibre prestraining effects; a finite element model was established and showed good agreement with experimental observations. The fibre prestraining mechanisms were then proposed. It is found that EFP is effective in tailoring the internal strain/stress level within a composite cylindrical shell, which in turn altering the structural morphing mechanics, and able to significantly lower the maximum tensile strain during shape-changing, thus improve the load-carrying capability. These findings are expected to facilitate structural design of the deployable composite structures and flexible mechanical hinges, by allowing further design freedoms in terms of morphing mechanics and load-carrying capability.

The Effect of the Layup on the Stability of Composite Cylindrical Shells

Fiber reinforced plastic laminated composites have conquered greater and greater territory in the field of engineering in the past decades for their high strength to weight ratio. By varying the layup structure their behavior can easily be modified. One of the applications, that is investigated in this article is the slit tube or cylindrical shell, that used as a structural element undergoes bending. These shells indifferent from their material may experience the snap-through phenomenon (this depends both on the material and geometry) in which the shell flattens and loses its stability to bending. Depending on the layup bistable behavior also can be achieved, i.e., the shell would have two different shapes that are in equilibrium without any constraint. In this article the effect of the layup is investigated both on the bistable behavior and the snap-through phenomenon. Geometric limitations for the bistability are calculated based on a simple beam model from the literature. The same model is used to find the snap-through moment for these shells as a function of the orientation angle. It is also proven that the flattening of the shell cannot be evaded by changing the layup structure. The results are confirmed by FE simulations where applicable.

Inverse design method of deployable cylindrical composite shells for solar sail structure

The deployable cylindrical composite shell (DCCS) applied in the solar sail structure requires suitable geometric parameters to have high storage capacity and large sunlight area. However, it is difficult to obtain the suitable geometric parameters of DCCS. An inverse design method combining the advantages of radial basis function artificial neural network (RBFANN) and multi-island genetic algorithm (MIGA) is proposed to obtain the geometric parameters of DCCS in this paper. RBFANN has the ability of self-learning and nonlinear problem solving, MIGA has the ability of global optimization. The specimens of DCCS were manufactured based on the obtained geometric parameters. The coiling radius, driving characteristics of specimens were studied by experiment and finite element simulation, and the numerical results are in good agreement with the experimental results, which verify the effectiveness of the inverse design method. The inverse design method proposed in this paper can effectively obtain the geometric parameters of DCCS, which also can guide the design of solar sail structure.

Quantum computing with error mitigation for data-driven computational homogenization

As a crossover frontier of physics and mechanics, quantum computing is showing its great potential in computational mechanics. However, quantum hardware noise remains a critical barrier to achieving accurate simulation results due to the limitation of the current hardware. In this paper, we integrate error-mitigated quantum computing in data-driven computational homogenization, where the zero-noise extrapolation (ZNE) technique is employed to improve the reliability of quantum computing. Specifically, ZNE is utilized to mitigate the quantum hardware noise in two quantum algorithms for distance calculation, namely a Swap-based algorithm and an H-based algorithm, thereby improving the overall accuracy of data-driven computational homogenization. Multiscale simulations of a 2D composite L-shaped beam and a 3D composite cylindrical shell are conducted with the quantum computer simulator Qiskit, and the results validate the effectiveness of the proposed method. We believe this work presents a promising step towards using quantum computing in computational mechanics.

Smart analysis of sandwich foldable cylinders as gymnastic accessories

A novel smart analysis of sandwich composite cylindrical shell is presented in this article. It is assumed that the sandwich shell is manufactured from the graphene origami reinforced copper core between two intelligent layers. The proposed structure in this article can be used as an idealized model for cylinder shapes in gymnastic sport and physical therapy units. The virtual work principle in the piezo elasticity framework and the cylindrical coordinate system is extended to derive governing equations. To arrive at more accurate results, a third order shear deformable model is extended for kinematic relations. The electro elastic responses are explored using the analytical method to seek impact of main parameters of the composite structure such as foldability parameter, graphene content percent, and applied electric potential on the electro elastic strain, deformation and stress results.

Bending Analysis of Multiwall Carbon Nanotube Reinforced Functionally Graded Composite Cylindrical Shell

The curved structural components of aircraft, automobiles, and marine vessels, such as cylindrical panels, are primarily exposed to loading, which can result in bending failure, particularly in lightweight structures. The bending analysis of cylindrical panels made of functionally graded multiwall carbon nanotube (FG-MWCNT) epoxy composites is subjective in this study. In the first section, FG-MWCNT composite cylindrical panels are simulated in the ANSYS software. There are three methods for distributing uniaxially aligned reinforcements. The material properties of the carbon nanotubes uniformly distributed and functionally graded over the thickness of the shell structure are estimated using an extended rule of mixture micromechanical model that incorporates certain useful characteristics. To demonstrate the effectiveness and applicability of the proposed finite element approach, deflection data are presented. The analysis of the shell structure's bending includes an investigation of the impact of CNT volume fraction, boundary condition, lengthto-thickness ratio, and other geometrical factors

Vibration response analysis of multilayer functionally graded graphene platelets reinforced composite cylindrical shell under moving random loads

Vibration response analysis of multilayer functionally graded graphene platelets reinforced composite cylindrical shell under moving random loads

Buckling Analysis of Variable Stiffness Composite Cylindrical Shells Under Axial Compression Considering Imperfection Sensitivity

Thin-walled composite cylindrical shells are nowadays widely used as primary structures in the aerospace industry. The so-called variable stiffness (VS) composite cylindrical shells with flexible stiffness tailoring characteristics have been made possible by existing AFP techniques. Considering the inherent imperfection sensitivity property of axially compressed thin-walled cylindrical shells, the buckling behaviors of the axially compressed VS composite cylindrical shells with initial geometric imperfections and delamination imperfections are investigated respectively in this paper. The design buckling loads of the axially compressed VS composite cylindrical shells are first determined by the probing method, which is verified by comparing with the existing test data and numerical simulation results. Additionally, a parametric study is conducted to investigate the effects of delamination imperfections on the buckling loads. The constraint delamination sizes of the VS composite cylindrical shells based on the design buckling load in this paper are given. Furthermore, the effects of continuously variable fiber angles on the buckling loads are investigated considering the imperfection sensitivity. The specific VS composite cylindrical shells with both high- buckling loads and low-imperfection sensitivity are obtained. Results indicate that the effects of imperfection sensitivity need to be carefully considered in buckling design of the axially compressed VS composite cylindrical shells.

Vibration analysis of functionally graded carbon nanotube‐reinforced composite open cylindrical shells with damping film embedded

AbstractIn the present study, a discrete layer model was established to explore the vibration performance of Functionally Graded Carbon Nanotube‐Reinforced Composite (FG‐CNTRC) open cylindrical shells with damping film embedded based on the first‐order shell theory. There are four configurations of stacking arrangements considered for FG‐CNTRC open cylindrical shells with damping film embedded. The equivalent structural parameters of the top and bottom FG‐CNTRC panels are generated by implementing the extended mixing rule. Governing equations are derived based on the Hamilton principle and solved with the Naiver solution. Subsequently, after verifying the validity of this paper's solution by comparing it with the published literature, a parametric elaborated investigation discloses the variation patterns of vibration performance of four FG‐CNTRC open cylindrical shells with damping film embedded. The conclusions of the study can be used as a useful guide about open cylindrical composite shell structures with the design of high strength and damping.Highlights Discrete layer vibration model was bulit based on first‐order shell theory. Vbration performance of FG‐CNTRC open sandwich shells was studied. Variation patterns of frequency and loss factor was disclosed.

Nonlinear Vibrations of Composite Cylindrical–Cylindrical Shells with Bolt Loosening Connection

The nonlinear vibrations of composite cylindrical–cylindrical shells with bolt loosening connections are investigated. First, a theoretical model of such a combined shell is developed, with a multisegmental virtual material ring technique being adopted to replicate the partial bolt looseness in the bolted connection zone of two single shells. Furthermore, to consider the nonlinear vibration issue of such a bolted connection zone affected by external excitation amplitude, the equivalent Young’s modulus of the virtual material is defined, and the equation of motion is derived to solve nonlinear vibration parameters. Finally, three single composite cylindrical shells are connected with 12 bolts to form two combined shell specimens, and experimental tests are carried out to validate the model and examine the nonlinear vibration characteristics of such combined shells. Also, the impact of partial bolt loosening parameters on the nonlinear vibration behaviors is investigated with some important findings being summarized. The analysis methods, modeling techniques, test methods and important conclusions proposed in this study provide a useful reference for the study of the vibration issues of bolted composite shells.

Natural Vibrations and Stability of Composite Cylindrical Shells Containing a Quiescent Fluid

This paper presents the results of investigation of the natural vibrations and stability of circular vertical multilayered cylindrical shells, fully or partially filled with a quiescent compressible fluid subjected to hydrostatic and external static loads. The behavior of the elastic structure and fluid medium is described based on the classical shell theory and Euler’s equations. The linearized equations of motion of the shell, together with the corresponding geometrical and physical relations are reduced to a system of ordinary differential equations with respect to new unknowns. The acoustic wave equation is transformed to a system of differential equations using the method of generalized differential quadrature. The solution of the formulated boundary value problem is developed using Godunov’s orthogonal sweep method. The dependences of the lowest vibration frequencies and critical external pressure on the ply angle and the filling level of two-layer and three-layer cylindrical shells are analyzed in detail. It is demonstrated that, in contrast to the ply angle and a given combination of boundary conditions, the lay-up scheme of composite materials plays different parts in the problems of maximizing the fundamental frequency of vibrations and extending the stability boundaries.

The Vibration Characteristics Analysis of Fiber-Reinforced Thin-Walled Conical–Cylindrical Composite Shells with Artificial Spring Technique

In this paper, the vibration characteristics (free vibration and forced vibration) of fiber-reinforced thin-walled conical–cylindrical composite shells (FTCCS) are analyzed by combining theory and experiment. Based on the classical shell theory and Kirchhoff–Love assumption, the overall structure of the FTCCS is theoretically modeled. The artificial spring technology is used to simulate the arbitrary boundary conditions at the joint, which is divided into a main spring and a secondary spring. At the same time, the displacement functions of the two sub-structure shells of the FTCCS are established by the orthogonal polynomial method, and the energy function of the FTCCS is constructed according to the continuity condition of the bolt joint. Then, the vibration characteristics of the FTCCS are solved using the Rayleigh–Ritz method and the modal superposition method. Finally, the TC300/epoxy resin-based fiber-reinforced thin-walled conical–cylindrical composite shells are selected as the research object, and the rationality of the mathematical model is verified by pulse, frequency sweeping and resonance excitation tests. The experimental results show that the errors between the natural frequency and the resonance displacement calculated by the theory and the experimental results are 1.75–4.76% and 3.79–9.28%, which confirms the rationality of the proposed model. By changing the length of the shell, the lamination angle and the semi-cone angle of the conical shell, the vibration characteristics parameters under different conditions are calculated to evaluate the influence of three physical parameters on the vibration characteristics of the FTCCS.

Postbuckling behaviour of anisotropic shear deformable laminated cylindrical shells with general imperfection distribution subjected to torsion

Composite cylindrical shells belong to typical basic structure in engineering, whose buckling and postbuckling behaviours determine the stability and safety of overall structures under complex service loadings. In this paper, a nonlinear mechanical model for anisotropic laminated composite cylindrical shells with general distributed initial imperfection is derived to analyse the buckling and postbuckling behaviours under torsional loads, in which the general distributed imperfections are represented by a generic two-dimensional imperfection function reconstructed by using measured data. Based on a higher order shear deformation shell theory, the governing equations are established with consideration of von Kármán–Donnell-type of kinematic nonlinearity and the coupling effects of extension/twist, extension/flexural and flexural/twist. By using a two-step perturbation technique, a new set of explicit solutions is obtained to determine the buckling loads and postbuckling equilibrium paths of the torsional composite cylindrical shells. Furthermore, the internal quantitative relationship between the shear stress with torsional characteristics along with an associate compressive stress of anisotropic laminated shell is for the first time obtained. Numerical analyses are performed to validate the accuracy and effectiveness of the present explicit solutions, and obtain the postbuckling response of different types of imperfections, anisotropic laminated cylindrical shells with different values of shell parameters.