Analysis Of Composite Structures Research Articles

Elastic stiffness of stud connection in composite structures

In composite structures, shear connectors are crucial components to resist the relative slip between the steel and concrete, and thereby to achieve the composite actions. In the service stage, composite structures are usually in elastic state, so the elastic stiffness of the shear connection is a quite important parameter in the structural analysis of composite structures. Nevertheless, the existing studies mainly focus on the load-slip relationship rather than the tangent stiffness at the initial elastic stage. Furthermore, when composite beams subjected to torque or local load, shear connections are affected by both tensile force and shear force. However, the stiffness of shear connections under combined effects appears not to have been discussed hitherto. This paper investigates the initial elastic stiffness of stud connections under combined effects of biaxial forces. The initial expression and the relevant parameters are obtained by establishing a simplified analytical model of the stud connection. Afterwards, parametric finite element analysis is performed to investigate the effects of the relevant factors, including the stud length, stud diameter, elastic modulus of concrete, elastic modulus of steel and volume ratio of reinforcement. The feasibility of the proposed modelling has been proved by comparing with sufficient experimental tests. Based on the analytical analysis and the extensive numerical simulations, design equations for predicting the initial elastic stiffness of stud connections are proposed. The comparison between the equations and the data of finite element models demonstrates that the equations are accurate enough to serve for engineering communities.

Mechanical sensitivity analysis of pipe-liner composite structure under multi-field coupling

Cured-in-place pipe (CIPP) has become one of the most widely used pipeline trenchless rehabilitation technologies because it has the advantages of needing no grouting, rapid curing, and short construction time. However, previous research has not yet revealed the mechanical sensitivity of pipe-liner composite structures. In this paper, a numerical model for a pipe-liner composite structure under multi-field coupling of the traffic load, earth pressure and water flow was first established based on an Abaqus, Fluent and mesh-based parallel code coupling interface (MpCCI). Then, the maximum principal stress of the pipeline, vertical displacement of the pipeline, von Mises stress of the CIPP liner and vertical displacement of the CIPP liner were selected as evaluation indicators, and the CIPP thickness, cover depth, traffic load, corrosion width, corrosion depth, and water quantity were selected as sensitive factors of the pipe-liner composite structure. Finally, the mechanical characteristics of the pipe-liner composite structure were analysed under condition of different sensitive factors; moreover, the sensitivity of the sensitive factors was ranked based on the sensitivity coefficient. The research results are consistent with previous research providing a theoretical basis for the optimal design of wall thicknesses for CIPPs.

Stochastic Finite Element Analysis of Composite Structures with Partially Restrained Connections under Earthquake Loads

The stochastic analysis of composite structures with partially restrained (PR) connections under seismic loads present some interesting and challenging issues to practicing engineers. This paper proposes an efficient, robust, and accurate method for stochastic finite element analysis of concrete–steel composite structures allowing for PR connections. These are followed by suitable numerical example which indicates that employment of such a stochastic finite element analysis. The Kocaeli earthquake in 1999 is considered as a ground motion. The connections parameters and material properties are random variables. It is essential to properly consider the PR connections in the stochastic dynamic analysis and design of the steel-concrete composite structures since design forces change significantly. The assumption that the connections are rigid, which is routinely used in the application, is not proper. The effect of the variability connection stiffness on the composite structures responses is sufficiently important for consideration in structural safety.

High-order three-scale computational method for elastic behavior analysis and strength prediction of axisymmetric composite structures with multiple spatial scales

A novel high-order three-scale (HOTS) computational method for elastic behavior analysis and strength prediction of axisymmetric composite structures with multiple spatial scales is developed in this paper. The multiple heterogeneities of axisymmetric composite structures we investigated are taken into account by periodic distributions of representative unit cells on the mesoscale and microscale. First, the new micro–meso–macro coupled HOTS computational model for elastic problems of axisymmetric composite structures is established based on multiscale asymptotic analysis, which breaks through the traditional multiscale assumptions and includes three main components. Two classes of mesoscopic and microscopic auxiliary cell functions are constructed on the mesoscale and microscale, respectively. The macroscopic homogenization problems are defined on global axisymmetric structures by twice up-scaling procedures from microscale to mesoscale and then from mesoscale to macroscale. Moreover, the asymptotic HOTS solutions are constructed for approximating multiscale elastic problems of axisymmetric structures and the numerical accuracy analysis of the HOTS solutions is given in detail. Then, the strength prediction formulas for axisymmetric composite structures with multiple spatial scales are presented based on the high-accuracy elastic behavior analysis from the proposed HOTS computational model. Furthermore, the corresponding HOTS numerical algorithm based on the finite element method (FEM) is presented for analyzing the mechanical behaviors and predicting the strength of axisymmetric composite structures with multiple spatial scales in detail. Finally, some numerical examples are reported to verify the feasibility and effectiveness of the proposed HOTS computational method. In this study, a unified three-scale computational framework is offered, which enables the simulation of mechanical behaviors of axisymmetric composite structures with multiple spatial scales.

Stress analysis of smart composite plate structures

In the present study, the electro-mechanical responses of smart laminated composite plates with piezoelectric materials are derived using a two-dimensional (2 D) displacement-based non-polynomial higher-order shear deformation theory. The kinematics of the mathematical model incorporates the deformation of laminates which account for the effects of transverse shear deformation and a non-linear variation of the in-plane displacements using inverse sine hyperbolic function of the thickness coordinate. The equilibrium equations are obtained using the minimization of energy principle known as the principle of minimum potential energy (PMPE) which is also based on a variational approach and the solutions are obtained using Navier’s solution technique for diaphragm supported smart laminated composite plates. The responses obtained in the form of deflection and stresses are compared with three dimensional (3 D) solutions and also with different polynomial and non-polynomial based higher-order theories in the literature. The transverse shear stresses are obtained using 3 D equilibrium equations of elasticity to enhance the accuracy of the present results. Various examples are numerically solved to establish the efficiency of the present model.

On the role of large cross-sectional deformations in the nonlinear analysis of composite thin-walled structures

The geometrical nonlinear effects caused by large displacements and rotations over the cross section of composite thin-walled structures are investigated in this work. The geometrical nonlinear equations are solved within the finite element method framework, adopting the Newton–Raphson scheme and an arc-length method. Inherently, to investigate cross-sectional nonlinear kinematics, low- to higher-order theories are employed by using the Carrera unified formulation, which provides a tool to generate refined theories of structures in a systematic manner. In particular, beams and shell-like laminated composite structures are analyzed using a layerwise approach, according to which each layer has its own independent kinematics. Different stacking sequences are analyzed, to highlight the influence of the cross-ply angle on the static responses. The results show that the geometrical nonlinear effects play a crucial role, mainly when higher-order theories are utilized.

Residual life estimation of healthy and cracked composite beam using experimental and numerical modal analysis methods

Preventive maintenance is beneficial to minimize unexpected breakdowns in industries with continuous production. Composite structures are used for naval applications like ship hulls and marine propellers. In most of the industries, composite structural health analysis using experimental and numerical model are available for damage detection and estimate the residual life of composite beams. The present work is focusses on identification of damage and estimate residual life of composite healthy and cracked beams. Free vibrational analysis is carried out on composite beam made of glass fiber reinforced polymer (GFRP) with a different crack orientation. A fast Fourier transform (FFT) spectrum analyzer associated with engineering data management (EDM) software utilized for experimental analysis to detect presence of damage in cracked composite beam. FEM software called Analysis of composite pre/post (ACP) available in ANSYS R3 is used to compare the natural frequency results of healthy composite beam with cracked composite beam with different ply orientations. For validation of numerical modal evaluation, the consequences acquired from ANSYS R3 FEA software are in comparison with experimental results received by impact hammer method. The fatigue life of a damaged composite beam is estimated the use of “Hwang and Han’s” fatigue life equation.

Static analysis of multilayer nonlocal strain gradient nanobeam reinforced by carbon nanotubes

This article presents a comprehensive static analysis of simply supported cross-ply carbon nanotubes reinforced composite (CNTRC) laminated nanobeams under various loading profiles. The nonlocal strain gradient constitutive relation is exploited to present the size-dependence of nano-scale. New higher shear deformation beam theory with hyperbolic function is proposed to satisfy the zero-shear effect at boundaries and parabolic variation through the thickness. Carbon nanotubes (CNTs), as the reinforced elements, are distributed through the beam thickness with different distribution functions, which are, uniform distribution (UD-CNTRC), V- distribution (FG-V CNTRC), O- distribution (FG-O CNTRC) and X- distribution (FG-X CNTRC). The equilibrium equations are derived, and Fourier series function are used to solve the obtained differential equation and get the response of nanobeam under uniform, linear or sinusoidal mechanical loadings. Numerical results are obtained to present influences of CNTs reinforcement patterns, composite laminate structure, nonlocal parameter, length scale parameter, geometric parameters on center deflection ad stresses of CNTRC laminated nanobeams. The proposed model is effective in analysis and design of composite structure ranging from macro-scale to nano-scale.

Comparative study on production and characterisation of extracellular polymeric substances (EPS) using activated sludge fortified with crude glycerol from different biodiesel companies

Extracellular polymeric substances (EPS) are eco-friendly and economical biopolymers with a significant role in pollutant removal, bio-flocculation, settling and dewatering of activated sludge. In this study, growth profile and EPS production by an EPS-producing microbial strain (isolated from wastewater sludge or WWS) was studied using activated sludge fortified with glycerol. The study compared three crude glycerol samples as carbon sources from different biodiesel companies (BIO-LIQ, BIOCARDEL, ROTHSAY) and their effect on EPS production and characterisation was observed. The maximum slime EPS (S-EPS) concentration (12.34 g/L) was produced when sludge fortified with BIO-LIQ crude glycerol was used, higher than pure glycerol (10 g/L) at 72 h. The S-EPS was enhanced (16 g/L) when purified BIO-LIQ glycerol (by acid treatment) was used. It was also observed that S-EPS concentration increased 1.6–2.6 times by using sludge fortified with glycerol as compared to only glycerol (no sludge) as EPS production medium. In addition, the S-EPS produced from different glycerol samples yielded different characteristics in terms of protein-carbohydrate content, flocculation activity and dewaterability. The S-EPS from purified BIO-LIQ glycerol (with sludge) gave maximum flocculation activity and dewaterability i.e. 93.71% and 60.2% respectively. The comparison between Ca(OH)2 and NaOH used as alkaline sludge pre-treatment methods revealed that the EPS produced from Ca(OH)2-treated sludge fortified with glycerol solutions to be better in terms of protein content, flocculation activity and dewaterability. Structural composition analysis using Fourier Transform Infrared Spectroscopy (FT-IR) revealed the presence of distinct functional groups (carboxyl, hydroxyl, amine groups) in the produced S-EPS.

A novel mode-dependent and probabilistic semi-discrete damage model for progressive failure analysis of composite laminates - Part I: Meshing strategy and mixed-mode law

A novel semi-discrete damage model (SD2M) is proposed for the progressive failure analysis (PFA) of composite structures. The presented method utilizes a separation of fiber and matrix failure modes and introduces a material strength distribution to thin strips of matrix-splitting elements in order to capture the progression of transverse crack density. With the proposed meshing strategy, the discreteness is greatly enhanced, while the model remains efficient and simple by using solely continuum elements. The SD2M approach aims to unify desirable features of both smeared and discrete methods and utilizes a practical and simple mesh generation procedure. In addition, a novel mixed-mode law is proposed to capture the damage evolution of matrix cracks. The proposed mixed-mode formulation ensures smooth and simultaneous vanishing of traction components and is suitable for generic softening laws. Applications of SD2M to several examples are presented in part II [1] of this two-part paper.

Natural Component in the Plan Composition Formation of Moscow Historical Settlements

The natural component in the formation of the historical settlements’ plan composition (on the example of the Moscow city) is studied in the article. A scientist Kudryavtsev believes that the main technique in the Russian medieval architects’ arsenal was the reception of the buildings’ location similarity, planning elements and compositional accents to the location of vegetation types on relief elements. This thesis was taken into account during conducting research on the subject to make a historical documentary compositional analysis of urban planning content - Petrov Drawing. The purpose of the analysis was to determine the drawing’s organic geometry of the Moscow 16th century plan, combined with the modern plan to confirm the truth of the town-documentary planning. In this research option, the combination of the compositional structural analysis’ method, which is typical for the art study, and the environmental approach, adopted to address issues of urban planning, are optimal.

A novel computational framework for the analysis of bistable composite beam structures

Over the last few years, several studies have shown the potential of multi-stability in engineering applications such as shape-adaptive structures and energy harvesting devices. Due to their highly non-linear mechanics, multi-stable structures are inherently more complex to model than conventional engineering structures. Especially when composite materials are involved, two-dimensional or three-dimensional finite elements solutions are often required in order to have a thorough understanding of the stress field evolution within the structure throughout the snap-through phenomenon. Nevertheless, such modelling strategies yield time-consuming design and optimisation procedures. In order to exploit multi-stability in industrial applications, an enhancement of the existing modelling capabilities is needed. Starting from the state-of-the-art methodologies available in the literature, a novel computational framework is proposed in this study for the analysis of bistable composite beam structures. An advanced structural modelling approach based on Carrera’s Unified Formulation (CUF) is adopted. By harnessing the potential of CUF, a full in-plane stress field (including axial, transverse shear and transverse normal stress) can be accurately yet efficiently predicted with no need to resort to two-dimensional or three-dimensional FEM solutions. Furthermore, the equilibrium paths of slender as well as thicker bistable beams are investigated, showing that refined predictions of the stable geometries and snap-through loads in bistability analyses can be obtained via the proposed advanced one-dimensional formulation. Validation of the proposed modelling approach towards reference solutions and commercial software finite elements is provided.

Experimental and Numerical Buckling Analysis of Carbon Fiber Composite Lattice Conical Structure before and after Lateral Impact

In this research, the numerical and experimental analysis of the carbon fiber composite lattice conical structure has been performed to assess the buckling stability of the structure before and after the lateral impact. In the experimental analysis, the carbon fiber composite lattice conical structure was constructed with the winding method and using elastic molds and metal mandrel. In order to investigate the buckling stability of the structures before each lateral impact, they are subjected to be compressive-axial loading. The rest of the structures first subjected under the axial-compressive loading, then in the next step, a compressive loading is applied to determine the effect of the impact on the compressive strength of the damaged structures. In the numerical analysis, the Abaqus software is used to modeling and performing the mentioned analysis. Finally, the comparison of the results shows that the effect of the lateral impact causes how many reductions will be occurred in the buckling strength. So, it should be considered during the design of the applied structures. On the other hand, the low difference between the numerical and experimental simulations shows that the experimental and numerical methods can be used to analyze the structures with different geometric characteristics and material.

Hybrid Surface Electric Field Volume Magnetic Field Integral Equations for Electromagnetic Analysis of Heterogeneous Dielectric Bodies With Embedded Electrically Conducting Structures

In this article, hybrid surface electric field volume magnetic field integral equations (SEVMIE) for electromagnetic analysis of heterogeneous dielectric bodies with embedded perfect electrical conductor (PEC) structures are presented. These are then solved using a quasi-exact vector moment method employing mixed order edge-based divergence conforming basis functions to expand the current on the PEC surface and node-based linear Lagrangian basis functions to expand the magnetic field within the dielectric region. For an incident plane wave scattered by the combined structure, this procedure results in a linear matrix equation for the surface currents and the volume magnetic fields. The method is demonstrated for three spherical test cases and the results compared to those obtained by a semi-analytic Mie series expansion. The performance is compared to that of the well-known volume surface integral equation (VSIE) method and found to provide more accurate results with approximately one-third the number of degrees of freedom. The method is then demonstrated on the scattering cross section calculation of a heterogeneous composite structure. This new method enables the efficient and accurate analysis of composite structures with large dielectric regions.

Reliability analysis of composite anisogrid lattice interstage structure

Application of composite lattice structures in aerospace application can bring about considerable weight savings, thus allowing for increased payload weight. This study is devoted to reliability analysis of composite anisogrid lattice interstage structure (CALIS) used in typical launch vehicle (LV). CALIS is usually formed in to thin-walled cylindrical or conical shell via helical and circumferential ribs that can act as a lightweight load bearing support structure interfacing any two stages of the LV. Thus, the current study is of practical importance as the interstage structure is acted upon by rather high axial and bending forces emanating from LV external aerodynamics, thrust and inertial forces. As there are always uncertainties associated with the material properties, structural geometry, loading conditions as well as the manufacturing processes, CALIS is faced with stochastic load and strength characteristics. In this sense, CALIS structural reliability is of importance and is thus investigated with respect to material strength, local and global buckling via different reliability techniques. The analytical reliability results are verified against a Monte Carlo simulation and analysis. In addition, a comprehensive sensitivity analysis is performed for some of key CALIS design variables that dominantly affect its structural reliability.

Analysis of antisymmetric cross-ply laminates using high-order shear deformation theories: a meshless approach

For many years finite element method (FEM) was the chosen numerical method for the analysis of composite structures. However, in the last 20 years, the scientific community has witnessed the birth and development of several meshless methods, which are more flexible and equally accurate numerical methods. The meshless method used in this work is the natural neighbour radial point interpolation method (NNRPIM). In order to discretize the problem domain, the NNRPIM only requires an unstructured nodal distribution. Then, using the Voronoi mathematical concept, it enforces the nodal connectivity and constructs the background integration mesh. The NNRPIM shape functions are constructed using the radial point interpolation technique. In this work, the displacement field of composite laminated plates is defined by high-order shear deformation theories. In the end, several antisymmetric cross-ply laminates were analysed and the NNRPIM solutions were compared with the literature. The obtained results show the efficiency and accuracy of the NNRPIM formulation.

Progressive damage analysis of composite laminates subjected to low-velocity impact using 2D layer-wise structural models

The present work deals with the progressive damage analysis of composite laminates subjected to low-velocity impact. We develop a numerical model using higher-order structural theories based on the Carrera Unified Formulation (CUF) with Lagrange polynomials and resulting in a 2D refined layer-wise model. To model damage, we use a combination of the continuum damage-based CODAM2 intralaminar damage model to account for fibre and matrix damage within the ply, and cohesive elements to account for delamination between successive composite plies. We carry out numerical assessments for the case of a linear elastic composite plate subjected to impact, to compare the current framework with standard approaches based on 3D finite element (FE) analysis. We, then, consider the elastoplastic analysis of a bimetallic laminated plate to compare the performance of the proposed layer-wise model and 3D-FE approaches, for the case of nonlinear impact analysis. The final assessment considers progressive damage due to low-velocity impact, and the results are compared with available literature data. The numerical predictions show a good correlation with reference experimental and simulation results, thus validating the current framework for impact analysis of composite structures. Comparisons of the proposed layer-wise structural models with those based on 3D finite elements demonstrate the improved computational efficiency of the CUF models in terms of model size and analysis time.

Multiscale model of micro curing residual stress evolution in carbon fiber-reinforced thermoset polymer composites

In this study, the micro curing residual stresses of carbon fiber-reinforced thermoset polymer (CFRP) composites are evaluated using a multiscale modeling method. A thermochemical coupling model is developed at the macroscale level to obtain the distributions of temperature and degree of cure. Meanwhile, a representative volume element model of the composites is established at the microscale level. By introducing the information from the macroscale perspective, the curing residual stresses are calculated using the microscale model. The evolution of curing residual stresses reveals the interaction mechanism of fiber, matrix, and interphase period during the curing process. Results show that the curing residual stresses mostly present a tensile state in the matrix and a compressive state in the fiber. Furthermore, the curing residual stresses at different locations in the composites are calculated and discussed. Simulation results provide an important guideline for the analysis and design of CFRP composite structures.

Analytical analysis of sound transmission in passive damped multilayered shells

An analytical shell model is here proposed for the sound transmission analysis of composite multilayered structures embedding viscoelastic sheets. The present analytical solution, based on the Navier approach, is developed starting from the Principle of Virtual Displacements, through the use of advanced layer-wise higher-order models and by considering real viscoelastic frequency-dependent materials with fractional derivative constitutive models. Several simply-supported shell structures with isotropic and cross-ply composite layers embedding viscoelastic frequency-dependent sheets are considered and the results of the passive noise reduction analysis are given in terms of acoustic parameters based on Rayleigh integral method. Moreover a comprehensive study on different types of time loads is taken into account, considering impulse time load, time-window load histories, space–time dependent loads.

A cross-sectional aeroelastic analysis and structural optimization tool for slender composite structures

A fully open-source available framework for the parametric cross-sectional analysis and design optimization of slender composite structures, such as helicopter or wind turbine blades, is presented. The framework—Structural Optimization and Aeroelastic Analysis (SONATA)—incorporates two structural solvers, the commercial tool VABS, and the novel open-source code ANBA4. SONATA also parameterizes the design inputs, postprocesses and visualizes the results, and generates the structural inputs to a variety of aeroelastic analysis tools. It is linked to the optimization library OpenMDAO. This work presents the methodology and explains the fundamental approaches of SONATA. Structural characteristics were successfully verified for both VABS and ANBA4 using box beam examples from literature, thereby verifying the parametric approach to generating the topology and mesh in a cross section as well as the solver integration. The framework was furthermore exercised by analyzing and evaluating a fully resolved highly flexible wind turbine blade. Computed structural characteristics correlated between VABS and ANBA4, including off-diagonal terms. Stresses, strains, and deformations were recovered from loads derived through coupling with aeroelastic analysis. The framework, therefore, proves effective in accurately analyzing and optimizing slender composite structures on a high-fidelity level that is close to a three-dimensional finite element model.