Composite Shells Research Articles

Vibration optimization of cantilevered bistable composite shells based on machine learning

Bistable composite shells with high storage efficiency have great potential applications in deployable space structures. This paper proposes a constrained vibration optimization approach for improving the bending-mode frequency of cantilevered bistable reeled composite shells (BRCS) with respect to fiber orientation angles using a machine learning (ML) method. First, the bistability and a specific coiled diameter are considered as constraints to classify the input data. The data set of the support vector regression (SVR) model is constructed based on the finite element (FE) simulation results, followed by constricted particle swarm optimization (PSO) to improve the bending-mode vibration frequency of a cantilevered BRCS. A 15.5% improvement of the vibration frequency with respect to the benchmark is achieved at α=59.3° and β=32.2°, which maintains great consistency with published results. Additionally, the optimization approach based on ML is further utilized to improve the vibration frequency of BRCS subjected to constraints of constant arc length and coiled diameter. The vibration frequency is improved by 85.3% with respect to the benchmark shell with optimized parameters of R= 16 mm, γ=358°, and the stacking laminate sequence of [60/80/0/−80/−60]. Evaluation and validation analyses of the ML model demonstrate that vibration optimization using ML yields high computing efficiency and accuracy. This optimization approach has great potential in real-life engineering applications.

Research progress of composite cylindrical shells

AbstractComposite cylindrical shell (CCS) structure are a number of engineering applications in aerospace, civil engineering, ordnance industry, sports equipment and other fields because of their excellent mechanical properties, low density and strong design. In this study, the classification, preparation technology and mechanical test of CCS are summarized. The research on the axial compression strength of CCS is reviewed. The theory of axial compression elasticity and the strength criterion of orthotropic composite materials are analyzed, and the strength criterion is compared. Finally, the basic theory of instability and buckling is deeply analyzed, and the stability theory of CCS is analyzed in detail. In order to provide a new reference for future scientific research and engineering application, the research difficulties are given in the conclusion, and the future research direction is predicted.Highlights Comparing and analyzing the classification, preparation technology and mechanical properties of composite cylindrical shells (CCS) comprehensively. Summarizing and analyzing the axial compression strength of CCS in depth, and analyzing the theory of axial compression elasticity and the strength criterion of orthotropic composite materials thoroughly. Analyzing the basic theory of instability and buckling in depth, and analyzing the stability theory of CCS in detail. Giving the research difficulty of composite cylindrical shell, and predicting the future development direction of CCS.

Magnetorheological elastomer actuated multi-stable gripper reinforced stiffness with twisted and coiled polymer

This study proposes a magnetorheological elastomer actuated multi-stable gripper reinforced stiffness with twisted and coiled polymer. The multi-stable gripper can conform objects with different sizes by means of its stable and adaptive characteristics. The multi-stable gripper is composed of a multi-stable laminated composite shell as the grab unit for supporting, a twisted and coiled polymer as the deformation element for variable stiffness and a magnetorheological elastomer as the smart material for actuation. The magnetorheological elastomer was activated by external magnetic field inducing the gripper change from the first stable state to the second or the third stable state to complete the gripping action. The driving force of the multi-stable laminated composite shell was discussed by the experimental and numerical methods, then the width of deformation and transition element was designed to reduce the driving force. Furthermore, the stiffness of the multi-stable gripper is analysed with respect to the compression, extraction, and gripping performance of the gripper through experiments, and then, the gripping performance was compared with current soft grippers. The experimental results show that the multi-stable gripper exhibits sufficient compliance and adaptability. That is, the multi-stable gripper has a faster response time and larger grasping weight compared with soft grippers.

Composite cylindrical shells with auxetic core on elastic foundation: A nonlinear dynamic analysis

This paper investigated vibration analyses of a composite cylindrical shell consisting of a core with negative Poisson's ratios resting on elastic foundation subjected to pre-loaded axial compression and external excitation force. Governing equations are driven based on Donnell's improved shell theory ignoring the shallowness of cylindrical shells and, with the help of Galerkin's method, Volmir's assumption, and Runge-Kutta's fourth-order method, the dynamical analysis of shells is studied. The purpose of this article is to discuss both the linear and nonlinear aspects of the structure's vibration. Furthermore, several parametric examples are presented and discussed to show how different parameters affect the three-layer cylindrical shell oscillation. To ensure the accuracy and the precision of the numerical results, the proposed method is compared with other literature attempts.

Delamination Detection and Localization in Vibrating Composite Plates and Shells Using the Inverse Finite Element Method.

Delamination damage is one of the most critical damage modes of composite materials. It takes place through the thickness of the laminated composites and does not show subtle surface effects. In the present study, a delamination detection approach based on equivalent von Mises strains is demonstrated for vibrating laminated (i.e., unidirectional fabric) composite plates. In this context, the governing relations of the inverse finite element method were recast according to the refined zigzag theory. Using the in situ strain measurements obtained from the surface and through the thickness of the composite shell, the inverse analysis was performed, and the strain field of the composite shell was reconstructed. The implementation of the proposed methodology is demonstrated for two numerical case studies associated with the harmonic and random vibrations of composite shells. The findings of this study show that the present damage detection method is capable of real-time monitoring of damage and providing information about the exact location, shape, and extent of the delamination damage in the vibrating composite plate. Finally, the robustness of the proposed method in response to resonance and extreme load variations is shown.

Automated Fiber Placement Path Planning and Analysis of Pressure Vessels.

The automated fiber placement (AFP) process faces a crucial challenge: the emergence of out-of-plane buckling in thermoplastic prepreg tows during steering, significantly impeding the quality of composite layup. In response, this study introduces a novel approach: the development of equations for wrinkle-free fiber placement within composite pressure vessels. The investigation encompasses a detailed analysis of prepreg trajectories in relation to shell geometry, accompanied by an in-depth understanding of the underlying causes of wrinkling on dome surfaces. Moreover, a comprehensive model for shell coverage, grounded in placement parameters, is meticulously established. To validate the approach, a simulation tool is devised to calculate press roller motions, ensuring the uniform fiber dispersion on the mandrel and achieving flawless coverage of the shell without wrinkles. This innovative strategy not only optimizes the AFP process for composite layup but also remarkably enhances the overall quality of composite shells. As such, this research carries significant implications for the advancement of composite manufacturing techniques and the concurrent improvement in material performance.

Numerical predictions of intralaminar and interlaminar damage in thin composite shells subjected to impact loads

This paper investigates the impact dynamics of thin semicylindrical woven composite laminate shells, with a particular focus on understanding the influence of thickness. Utilizing the finite element (FE) method, the study evaluates both intralaminar and interlaminar damage associated with the impact response. The findings show that the implementation of the explicit FE method, along with a continuum damage mechanics model, for the intralaminar damage, and a surface-based cohesive model, for the interlaminar damage, may be used to correctly predict the load histories, as well as the maximum impact force, maximum displacement, contact time and impact bending stiffness (IBS). The numerical predictions reproduce well the linear response of the maximum impact force and maximum displacement to the thickness variation, as well as the 2nd order polynomial curve of the IBS, with errors ranging from 2.7% to 15.9%. Moreover, the damage areas and the effect of thickness on the damage severity were accurately replicated. These results’ validation enables the prediction of the energy histories and the ensuing energy dissipation forms. According to the findings, the intralaminar damage is around 5 times more significant than the other energy dissipation forms. The accuracy of the simulation creates the possibility for more impact investigations using a similar numerical approach, reducing the expenditures of experimental testing.

Nonlinear vibration characteristics of elastically supported FRP cylindrical shells under temperature gradient conditions: Theoretical and experimental studies

The nonlinear free vibrations of elastically supported fiber-reinforced polymer cylindrical shells (FRPCSs) under temperature gradient conditions are investigated using both theoretical and tested techniques. A dynamic model of the FRPCSs with consideration of such complex thermal conditions is firstly established based on the first-order shear deformation theory in conjunction with Hamilton’s principle, the Galerkin method, the artificial spring technique, etc. Numerical results at room temperature and in a uniform thermal environment with classical or arbitrary boundary conditions are utilized to give a rough validation of this model. Subsequently, a thermal-vibration system is set up to measure the nonlinear natural frequencies of two FRPCS specimens subjected to four different temperature gradient conditions in free-free boundary constraints, and iterative calculations are performed to identify the temperature-dependent material properties. Finally, the detailed comparisons of calculated and experimental results provide a solid validation of the proposed model. This study offers a practical model tool to forecast the nonlinear free vibrations of the FRPCSs in a complex thermal environment, which can be readily adjusted and extended to other forms of composite shells. Also, the predicted and measured results can help assess the structural thermal-vibration behaviors when the temperature gradient effect needs to be considered. Communicated by Makoto Ohsaki.

Buckling performance of stiffened polymer composite cylindrical shell

The buckling of carbon fiber composite cylindrical shells (CF-CCSs) with annular ribs under external pressure was investigated numerically and experimentally. The effects of rib cross-sections, rib geometry and distribution on buckling load and buckling mode were analyzed numerically. In addition, the ribbed polymer composite cylindrical shell was fabricated and tested. The geometry, thickness, buckling load and final collapse mode of the ribbed polymer composite cylindrical shell were measured. Finally, a nonlinear buckling analysis with geometrical imperfections was carried out based on the measured data; the numerical results were in agreement with the experimental results. The results show that different rib cross-sections have limited influence on the load carrying capacity of CF-CCSs, but the distribution of the ribs and the geometry of the ribs have a greater influence on CF-CCSs.

Multi-Scale Modeling and Analysis of Three-Dimensional Woven Composites Shell with Cut-Outs

Advancement in weaving techniques has made woven composites used in the diverse fields of aerospace, automobile, and many more. In the past few decades, textile composites have been considered the best materials, where most of the studies are focused on plain woven composites. The designing of these structures made up of plain-woven composites associated with discontinuities in the form of cut-outs may lead to the failure of the structure. The collapse in the structure will be due to stress concentration or popularly known as stress raisers. Therefore, this research proposes a numerical study based on finite element analysis (FEA) using a multi-scale modeling approach for a three-dimensional (3D) plain-woven composite 3D shell with varied cut-out shapes. The analysis is performed to comprehend the result of fiber orientation on the mechanical behavior of 3D woven composites having circular and elliptical cut-outs. This research proposes a ply stacking sequence that significantly reduces stress concentration primarily at interruptions in the structure. It is concluded that combining different ply layers having fiber orientation of [Formula: see text] in a multilayer composite 3D shell reduces stress concentration around the periphery of circular or elliptical cut-outs.

Low-velocity impact resistance of all composite cylindrical shell panels with a foam filled honeycomb core: Theoretical and experimental investigation

The low-velocity impact resistance of all composite cylindrical shell panels (CCSPs) with a foam filled honeycomb core (FFCHC) is studied experimentally and theoretically. Initially, a dynamical model of the FFCHC-CCSPs is proposed, with the equivalent material properties of the core being determined by combining the Hamilton equivalence theory and the Gibson theory. By using the virtual work principle and quasi-static method, together with the von Karman's theory and the high order shear deformation shell theory, the constitutive relationship related to each damage case is derived. Also, by considering the influence of collapse of the FFCHC, the failure criteria and damage modes are modified. The impact displacement, load and impact energy absorption are solved by using the elastoplastic contact principle and energy principle. Several numerical results from the literature are employed for preliminary validation of the model. Furthermore, the FFCHC-CCSP specimens with and without polyurethane foam are fabricated and the detailed measurements associated with different impact energies are performed to provide a solid validation of the present model as well as to evaluate the structural impact resistance. Finally, the influences of the thickness of FFCHC, wall thickness and side length of honeycomb cell and density of foam on the impact resistance of the FFCHC-CCSP structures are discussed, with some useful conclusions being refined for better impact suppression design and manufacture of such advanced shells.

Проектный анализ подкрепленной композитной оболочки

The paper formulates the design calculation problem of a reinforced composite shell as a related problem of two shells — the layered and the lattice (ribbed). The layered shell is formed by a single double-helical monolayer; the lattice shell is made up of longitudinal and transverse ribs. The reinforced shell continuum model is based on a stiffness matrix equal to the sum of stiffness matrices of the quasi-homogeneous layered and ribbed shells, which are rigidly connected to each other and are deformed without slipping. External axial load between the two shells is distributed under the static conditions. The shells’ thickness is determined from the strength condition. The layered skin winding angle is found through iterations in achieving the goal function, for example, the minimum mass of a structure. The ribs transverse dimensions are found from the strength condition with preliminary setting of one of the ribs’ parameters. The obtained relationships make it possible to determine the stress-strain state of reinforced composite cylindrical shells.

Research on explosive damage effects of tungsten fiber-reinforced Zr-based bulk metallic glass matrix composite shell

To expand the application range of explosive fragmentation projectiles, tungsten fiber-reinforced bulk metallic glass matrix composite (WF/Zr-MG) is used as the warhead shell in static explosion experiments, and is compared with 40CrMnSiB steel shells. The experimental results showed that, compared with 40CrMnSiB steel shells, the fragments produced by the WF/Zr-MG shell exhibit a larger aspect ratio, smaller average size, and a greater number of fragments at distances of 3 m and 5 m, with an equal number of fragments at a distance of 8 m. Theoretical calculations showed that the initial velocity of the fragments produced by the WF/Zr-MG shell is lower, but their velocity decay is slower, resulting in a greater determined damage range. The research results showed that WF/Zr-MG can be used as a shell material for explosive fragmentation projectiles, which can enhance their destructive power.

Bending behavior of 3D printed continuous fiber reinforced composite sandwich cylindrical shells

Continuous carbon fiber reinforced composite sandwich cylindrical shells (CFRCSs) have been widely used in aerospace and automotive fields due to their excellent load-bearing performance. However, traditional manufacturing methods involve complex processes and expensive molds. This study uses 3D printing technology to manufacture CFRCSs with sinusoidal, triangular, and trapezoidal core. The sample surface and inside fiber distribution is inspected by the optical microscope and X-ray microscope, respectively. It is found that the samples have the defects of uneven resin distribution, fiber breaking, and fiber waviness. The bending behaviors of CFRCSs are investigated by the three-point bending test. The results show that the CFRCSs with sinusoidal core have the maximum ultimate load of about 3094 N, while those with the triangular core structure have the minimum ultimate load of about 1774 N. The triangular and sinusoidal structures mainly undergo debonding at the junction of the core and the panel and fracture at the core because of the small contact area between the core and panel. In contrast, the trapezoidal structure is mainly brittle fracture with fiber pull-out at the bottom panel and fracture at the top panel. The core type greatly influences the bending mechanical properties of the printed CFRCSs. 3D printing technology can be used to manufacture CFRCSs with required mechanical properties by flexibly designing the core shape.

Free Vibration Analyses of Stiffened Functionally Graded Graphene-Reinforced Composite Multilayer Cylindrical Panel

In this paper, the free vibration response of a stiffened functionally graded graphene nanoplatelet (GPL)-reinforced composite multilayer cylindrical shell panel is studied for the first time. The shell is stiffened by both stringers and rings. Additionally, the effect of reinforcing the shell panel, ring and stinger with GPLs is independently studied. Halpin–Tsai relations are employed to evaluate the mechanical properties of the shell panel, rings and stringers. The first-order shear deformation shell theory, accompanied by the Lekhnitsky smeared stiffener model, using the numerical finite element method and Hamilton principle, is employed to develop the governing motion equations of the shell panel. Four different types of GPL patterns, including FG-A, FG-X, FG-O and UD, are assumed across the thickness of the shell panel, rings and stringers. The effects of different factors, including various weight fractions and patterns of GPLs nanofillers, the geometry of the shell panel and stiffeners and two displacement boundary conditions, on the natural frequencies of the shell panel, have been studied.

On the Static Instability of FG-GNP-Reinforced Composite Cylindrical Shells Under Thermo-Mechanical Loading

The nonlinear buckling response of laminated composite cylindrical shells reinforced with graphene nanoplatelets (GNPs) is studied in this paper. The functionally graded (FG) shell reinforced by GNPs is analytically studied under external pressure and uniform temperature rise loadings. It is also assumed that the GNP-reinforced laminated composite shell is in contact with an elastic foundation. Various types of profiles are employed for the GNP distribution patterns in the shell thickness including 10 nanocomposite layers. The nonlinear strain-displacement relations of the shallow cylindrical panel are established utilizing the third-order shear deformation shell theory. Governing equilibrium equations of the laminated GNP-reinforced composite shell are formulated employing the principle of virtual displacement. The coupled system of nonlinear differential equations is solved analytically for the hinged–hinged and fixed–fixed boundaries of the shell using a perturbation-based technique. Correctness of presented formulations and obtained solutions is proved by comparisons with results from previous studies for an isotropic cylindrical shell. Novel numerical results reveal that the material properties, geometrical characteristics and load parameters significantly affect on the buckling behavior of laminated composite cylindrical shells.

Exact solutions of elasticity theories for static analysis of doubly curved antisymmetric angle-ply composite shells

Exact solutions of elasticity theories for static analysis of doubly curved antisymmetric angle-ply composite shells

Ab initio investigation on the ordering mechanism of L12 phase in Al–Zr–Y(Sc) alloy

The L12-Al3Y(Sc) phase promotes the precipitation kinetics of Al3Zr. However, although Al3Y and Al3Sc are both with L12 structures, the mechanisms are not entirely the same due to different structures of the compound composites: Al3(Zr, Sc) has a core-shell structure, while Al3(Zr, Y) does not. Formation mechanisms of core-shell and non-core-shell structures were revealed in this work through analyzing surface energy, interface binding energy, and interface energy. The results showed that the interface energy and the lattice mismatch of Al/Al3Sc and Al/Al3Y are 0.011 J/m2,1.9% and 0.512 J/m2 and 5% respectively. During the growth of Al3(Zr, Sc) with Al3Sc as the heterogeneous core, the interface energy decreased linearly with increasing Zr contents at the interface and eventually a Zr rich shell formed. However, during the formation of Al3(Zr, Y), the interface energy fluctuated with changes in the composition and Zr(Y) content at the interface, eventually forming a composite phase shell of Al3Y(Zr). The diffusion migration energy for Zr atoms in pure Al was 1.102 eV, and it increased by at least 2% near the Al/Al3Sc interface, while it decreased by up to 46.3% near the Al/Al3Y interface. The impact of the L12-Al3Y(Sc) heterogeneous core on the diffusion ability of Zr atoms is crucial for its influence on the kinetics of Al3Zr precipitation.

Buckling analysis of laminated composite elliptical shells using the spline finite strip procedure

According to the first order shear deformation plate assumption, current paper numerically investigates the buckling problem of cylindrical shells with oval cross-section under simply supported boundary condition subjecting to uniform and non-uniform loads via spline finite strip method. Equilibrium governing equations are generated based upon the virtual work's principle. Shell displacement function is assumed to be as dual development of degree 3 spline functions and Lagrange polynomial functions. The analysis method used at any time with any type of loading can calculate deformation and buckling. The step-by-step critical load is calculated using the determinant of the stiffness matrix. In the present paper, it is supposed that the applied linear elastic materials consist of isotropic and non-isotropic materials. Numerical studies are performed to indicate the effects of shell geometry, materials, and layered materials on the buckling load. For the validation purpose, the results of current research are compared with those of previous researches and ABAQUS software.

Fracture Morphology and Fiber Reinforcement Mechanism of Composite Shells with Different Interfaces

Fracture Morphology and Fiber Reinforcement Mechanism of Composite Shells with Different Interfaces