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The mechanical response of three different structural core sandwich panels in out-of-plane compression and shear has been analyzed. Specific core shapes examined are arc-tangent, wavy trapezoidal and hemispherical. Unit cells consisting of representative elements of the core attached to face sheets were selected for analysis. Both face sheets and core were assumed made from paper. Finite element analysis employing large deformation and rotations and orthotropic elastic–plastic behavior was used. The results show that the arc-tangent and trapezoidal cores are prone to collapse by extensive bending and buckling, whereas the hemispherical core behaved more stably in compression and shear. Core sheets with a hemispherical shape were prepared from copy paper sheets in a specially designed forming machine. Sandwich test specimens were prepared from this core and tested in out-of-plane compression, and the load-displacement response was compared to predictions from finite element simulations. The experimental and finite element results were consistent. [ABSTRACT FROM AUTHOR]

This paper proposes a novel design for a three-dimensional compression-torsion mechanical metamaterial based on the three-period minimal surface (TPMS) theory. Unlike the conventional approach of utilizing chiral or diagonal rod structures to achieve compressive-torsional properties in metamaterials, this paper employs a two-dimensional level of TPMS theory and the synergistic effect of a re-entrant structure to achieve compressive-torsional properties. Theoretical, experimental, and numerical methods were employed to investigate the deformation characteristics and mechanical properties of the proposed structure. The paper investigates the impact of the periodic value of the TPMS on the torsion direction, as well as the influence of unit cell radius r on the deformation characteristics, torsion angle, and Poisson's ratio of the lattice structure. The length of radius r can be appropriately selected to control the torsion angle and negative Poisson's ratio (NPR) effect of the structure. Furthermore, by adjusting the period values of the TPMS, the torsion direction of the structure can be controlled. Finally, the torsion angle, Poisson's ratio, stiffness and specific energy absorption (SEA) were compared with the structure with a diagonal rod microstructure (SDRM). The findings indicate that the proposed structure exhibits superior torsion performance and NPR effect compared to the previously proposed three-dimensional compression-torsion material. This design concept has significant implications for the development of smart devices, aerospace engineering, and conservation engineering applications. [ABSTRACT FROM AUTHOR]

This paper presents a fully coupled thermodynamically consistent diffusion–reaction-deformation cohesive model for pyrolytic carbon (PyC)/SiC interfacial coating in fiber-reinforced composites. Arrhenius function is used to capture the chemical kinetics and the Kuhn-Tucker conditions is exploited to describe the damage evolution of interfacial coating. A strong connection between the diffusion–reaction process and interfacial mechanical deformation is established by the cohesive model, and the rules of the model parameters are discussed in detail. Implementation of the cohesive zone model is conducted in ABAQUS finite element software through the use of UEL subroutines. A mesh convergence for the model is tested and the model is validated by the comparison with the experimental results. A Representative Volume Element (RVE) model for fiber-reinforced composites at different temperatures, equipped with custom cohesive elements, is constructed to investigate the impact of PyC/SiC coating during oxidation. Two-step simulation is adopted to solve the chemo-mechanical behaviors of interfacial coating. The impact of the interfacial coating on stress transfer between the matrix and fibers is highlighted by numerical results that demonstrate an initial decline in mechanical properties followed by an upward trend with increasing temperature. The model also captures the coupling mechanisms between the diffusion–reaction process and the interfacial deformation in the interfacial coating. Theoretical insights for fiber-reinforced composites in chemical environments are provided, guiding the design of interfacial coatings for potential engineering applications. [ABSTRACT FROM AUTHOR]

Deformation of rectangular orthotropic laminate resting on a thin elastic orthotropic foundation with fully fixed bottom plane is studied in this paper. The laminate is subjected to an in-plane uniaxial load uniformly distributed over one of its edges. Models of joint deformation of the laminate and foundation are created based on the equations of plane elasticity for an orthotropic body. The applicability of such equations is justified by the uniformity of edge loading. A laminate model allows for the transverse shear strain, whereas a model created for the foundation considers a nonlinear character of variation of the transverse and axial displacements. A governing system of differential equations modelling the joined deformation of the laminate and foundation is derived using static and kinematic contact conditions. The corresponding boundary value problem is solved using the sweep method. Based on this solution, effects of laminate and foundation thicknesses, and elasticity characteristics on the stress–strain state of the jointed structure are investigated. The model created and the method of its analysis enable the strong oscillating behaviour of stresses and strains to be studied. The results obtained can be utilized for verification of solutions of similar problems found by other numerical methods, including finite-element analyses. [ABSTRACT FROM AUTHOR]

Additive manufactured lattice structures offer great potential for impact resistance applications. They exhibit excellent energy absorption characteristics during the elasto-plastic deformation process, providing protection to internal devices. However, the mechanical response of lattice structures undergoes substantial variations during the deformation process, thereby imposing limitations on their energy absorption behavior. This study introduces a novel twist design to modify the energy absorption behavior of rectangular and hollow cylindrical lattice structures. Powder bed fusion was used to fabricate the twisted lattice structures. The study employed a combination of compressive simulations and experimental investigations to systematically explore the impact of the twist angle on the peak crushing force, energy absorption, and crash load efficiency of the structures. Adjusting the twist angle results in a reduction of the peak crushing force and a transition towards a stable loading profile during the deformation process. Moreover, the crash load efficiency is also reduced. The twist design concept presented in this paper provides insight into designing and optimizing lattice structures for energy absorption applications. [ABSTRACT FROM AUTHOR]

Abstract Extensive studies have been conducted on the use of fibre-reinforced polymer (FRP) as a confining material in hybrid tubular columns for civil construction, where the design of columns is often controlled by the stiffness and/or strength requirements. By contrast, the capacity of sustaining large deformation without losing structural integrity can be critical in some applications such as the standing supports for underground mines. This paper presents the conceptual development of a novel column form with large deformation capacity. The novel column consists of an outer FRP tube, and an infill made of coarse lumps/aggregates, which can be from coal rejects or other waste/recycled materials, as well as calcium sulfoaluminate (CSA)-based cementitious material with high water content. In addition to its large deformation capacity, the new column allows the extensive, direct and easy use of waste materials and eliminates the need for mixing concrete on site or transporting commercial concrete. This paper also presents the results from a series of compression tests on the new columns as well as two similar column forms. These tests demonstrate the very large deformation capacity of the new column and show that an existing stress-strain model for FRP-confined normal concrete can be used to provide reasonable predictions of the behaviour of the confined infill material in the new column. The potential applications of the new column and the needs for future research are also discussed. [ABSTRACT FROM AUTHOR]

Abstract Terrestrial laser scanning is extensively adopted in the area of high-precision monitoring and three-dimensional measurement. Architectural structures today are increasingly complex and health monitoring plays an important role in guaranteeing their safety. Therefore, how reliability deformation monitoring can be improved is one of the key problems in the field of engineering. This paper combines the three-dimensional laser scanning technology and finite element method (FEM) to investigate the deformation mechanism of arched structures. Within this paper, we simulated arched structures using the FEM, which is consistent with the result of terrestrial laser scanner (TLS) measurement. We aimed at constructing an intelligent and efficient FEM model which can be extensively applied in the monitoring of many constructs, such as bridges and ancient architecture. The focus in this research lies mainly on deformation analysis, which is based on FEM model simulation with the calibration of TLS measurement. [ABSTRACT FROM AUTHOR]

Abstract Nowadays, with the development of demand for construction, the use of composite structures in architectures become more and more popularity. How to improve the intelligent level of deformation monitoring has become one of the key problems. A detailed understanding about deformation behavior is significant for better monitoring of structures, especially in terms of accuracy and detail. The innovation of this paper focuses on that terrestrial laser scanning (TLS) measurement is adopted to investigate deformation of the composite masonry structures. In this paper, deformation segmentation and analysis of the masonry structures are investigated and the deformation tendency is compared and analyzed, based on the intelligent data extraction by window selection method, where high precision 3D laser technology provides reliable experimental data for this research. The deformation of different surfaces of a composite arch is considered and the maximum displacement distribution is analyzed through partially comparing the deformation of different epoch data. [ABSTRACT FROM AUTHOR]

In this paper, the process deformation of 2D SiC/SiC composite materials in the pyrolysis stage of precusor infiltration and pyrolysis process (PIP) is investigated experimentally and computationally through a multiscale study. The pyrolysis process of PCS was described by a kinetic model. The intrinsic properties and behaviors of pyrolysed PCS were characterized experimentally. The macroscopic properties and behaviors of 2D-SiC/SiC composite materials were obtained through the homogenization method. The proposed methodology can successfully predict the process deformation of an L-shaped 2D SiC/SiC composite structure in cyclic PIP process. It is revealed that the pyrolysis of precusor can generate significant chemical shrinkage and stiffness variation, leading to the process deformation of the entire composite structure. Unlike the precusor, the variation of properties and behaviors of composite materials are anisotropic. Furthermore, the cyclic process and the evolution of matrix composition complicate the process deformation. The behavior of composite material is dominated by pyrolysing PCS at first several cycles whereas by pyrolysed SiC at last several cycles. The fundamental understating on process deformation in this paper may benefit the design and the manufacture of SiC/SiC composite materials. [ABSTRACT FROM AUTHOR]

• Novel TPMS-based strut-shell interpenetrating lattice metamaterials are designed. • Strut-shell interpenetrating lattices have superior specific surface area. • Fusion proportion achieves tunable mechanical properties and deformation behavior. • Strut-shell interpenetrating lattices can effectively avoid sharp stress drop. • Interpenetrating lattices have superior densification and energy absorption. Mechanical metamaterials (MMs) are artificially designed structures with superior properties that originate from unit cells. Compared with the widely studied single-morphology MMs, multi-morphology interpenetrating MMs offer, by the virtue of their fused lattice characteristics, the potential for customizable mechanical properties and new application fields. Inspired by the fact that the isosurface of triply periodic minimal surfaces (TPMS) can divide a lattice into two independent regions, this paper proposes a novel TPMS-based strut-shell interpenetrating (TSSI) lattice metamaterial. This study demonstrates that the TSSI lattice has a larger specific surface area than traditional TPMS lattices. Compared with the volume fraction, the fusion proportion parameter is not only more conducive to effectively adjusting the mechanical properties in a wide range and controlling the anisotropy of the lattice metamaterials to achieve elastic isotropy but significantly changes the dominant mechanism of deformation under uniaxial and shear loads. Moreover, the TSSI lattice metamaterial can avoid sharp stress drops due to the mutual support and wrapping of the internal interpenetrating lattices after failure, resulting in a more stable energy absorption efficiency and a maximum increase in energy absorption of 74%. This work provides new opportunities to design lightweight components with a wide range of customizable mechanical properties and superior energy absorption. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel multiscale modeling method was developed for the auxetic behavior of negative Poisson's ratio woven fabric (NPRWF). • The finite element model of NPRWF was innovatively constructed based on the simulated constitutive curve of negative Poisson's ratio yarn (NPRY). • The effectiveness of the theoretical model and the finite element model of NPRWF were verified with good agreement. Auxetic behavior is critical to determining the deformation and mechanical performance of materials. Auxetic mechanisms of the woven fabric have previously not been well understood, especially for those containing negative Poisson's ratio yarn (NPRY). Most theoretical models were developed from the macro geometric structure which lacks analysis of yarn levels. This paper aims to use numeral analysis combined with finite element modeling to investigate the auxetic behavior of the NPRY-based fabric. Firstly, the theoretical model that reveals the relationship between the auxetic behaviors of yarn and NPRY-based fabric was established based on component yarn interweaving rules, deformation, and stress. Following, a strain-dominated deformation simulation was further performed to clarify the micro stress and auxetic mechanism of fabric by calculating the stress–strain response and NPR value. Moreover, the experiments of NPRY-based fabric were also developed to validate the theoretical and simulation results, Results indicate that the model can well predict the auxetic behavior of fabric with an error under 7%. The micro–macro analysis of the auxetic behavior from yarn to fabric provides a fundamental understanding of the auxetic mechanism of NPRY-based fabric. Additionally, the yarn-to-fabric model can used to study the auxetic behavior of NPR fabric with variable parameters thus supplying theoretical guidance for engineering. [ABSTRACT FROM AUTHOR]

Abstract Terrestrial laser scanning (TLS) technology plays an important role in the field of deformation monitoring nowadays, and a lot of the architectures are arched composite structures, which are required to be further understood for their mechanical and physical properties. Only a theoretical numerical analysis is sometimes difficult and defective to achieve, due to varying loads and other factors influencing the stability and reliability of such structures. Therefore, measurements can improve the theoretical analysis in several ways. One of the most important issues is the deformation analysis within load experiments. This paper focuses on the presentation of new possibilities for surface-based measurement techniques and their applicability in the deformation analysis of arched structures. The goal of this paper is to investigate the difference of load-displacement relationships between arched and beam structures though a static load experiment based on high accuracy TLS measurement techniques and the surface analysis method. In this paper, we try to reveal the influencing mechanism of ‘prestressing-like’ force and interpret why arched structures can withstand a surprisingly greater load than beam structures under the same conditions. [ABSTRACT FROM AUTHOR]

Abstract This paper focuses on the adjustment of B-spline approximation to terrestrial laser scanning (TLS) data and its contribution to deformation analysis of composite arched structures. The deformation of an arch structure under static loading conditions are investigated with TLS technology which is accurate, time-efficient, and capable to obtain dense 3D coordinates of point clouds for the measured objects. Highly accurate approximation methods for the point clouds data are extremely important for structural deformation analysis. The innovation of this paper is that parameters of B-spline is optimized with laser tracker (LT) to improve the accuracy of deformation monitoring and analysis, where the result is justified with LT data and the uncertainties are analyzed. It is revealed that optimized B-spline approximation agrees better with LT result. The improvement to the B-spline curve with minimum standard deviation reaches 52%, and its improvement to polynomial approximation reaches 77%. [ABSTRACT FROM AUTHOR]

The Taylor-Hopkinson test is widely used in predicting the dynamic strength of materials. For low-density foam materials, the output bar in the Taylor-Hopkinson test is often made from much weaker materials like polymethylmethacrylate (PMMA) to reduce the wave impedance mismatch between the foam sample and the output bar. These low impedance materials exhibit viscoelastic properties and may affect the dynamic stress prediction of foam samples. In this paper, the shock wave theory for the foam sample in conjunction with the viscoelastic wave propagation in the output bar is employed to illustrate the influence of the viscoelastic output bar on the dynamic response of foam samples in the Taylor-Hopkinson impact. The theoretical model presented in this paper can be degenerated into previous elastic target bar model and rigid target bar model. Finite element simulations are further performed to verify the proposed theory. The influence of material parameters on the final deformation of the foam sample, impact duration and residual velocity of the foam sample are investigated. The results in this paper not only help in understanding the effect of the viscoelastic bar on the dynamic response of foam samples, but also set up guidelines to perform the Taylor-Hopkinson test more precisely. [ABSTRACT FROM AUTHOR]

This paper investigates the vibro-acoustic characteristics of the moderately thick laminated rectangular plate-cavity coupling system by using a modified Fourier series method. In the established model, two boundary conditions of moderately thick laminated rectangular plate are set as uniform elastic supports and non-uniform elastic supports including multi-points elastic supports or partial elastic supports. Besides, the three-dimensional rectangular cavity with rigid walls or impedance walls is discussed in the studied model. The admissible function of the displacements and sound pressure of the coupling system is set as the superposition function combined with Fourier cosine series and Fourier sin series. The Lagrangian energy principle is used to express the coupling system. The vibro-acoustic coupling characteristics can be obtained based on Rayleigh-Ritz technique. It shows good convergence and agreement of the present method by being compared with the finite element method (FEM) and the related literatures. This paper focuses on the study of free and forced vibro-acoustic analysis for the moderately thick laminated rectangular plate-cavity coupling system. Moreover, some results are achieved by discussing the effects of various plate thicknesses, different types of elastic supports, lamination schemes and various impedance boundary conditions on the natural characteristics and responses of the coupling system. [ABSTRACT FROM AUTHOR]

This paper proposes a particle filter-based Bayesian framework for damage prognosis of composite laminates exhibiting concurrent matrix cracks and delamination. Literature shows a number of applications of particle filtering for real-time prognosis of metallic structures and, recently, matrix crack density evolution in composites. The work presented here enhances the methodology proposed in previous papers by extending the Bayesian framework to multiple damage mechanisms, and validates the approach using damage progression data from notched cross-ply CFRP coupons subject to tension-tension fatigue. A multiple damage-mode model for the estimation of the strain energy release rate and the remaining stiffness of damaged laminates constitutes the core of the particle filtering algorithm, thus allowing the prognostic framework to extend for monitoring of simultaneous, coexisting damages. Also, the damage state can be evolved into the future enabling simulation of damage progression and prediction of remaining useful life of the composite material. The proposed prognostic unit successfully predicts damage growth and fatigue life of the laminate, and the results are critically discussed with respect to filtered estimation of damage progression and remaining life prediction. [ABSTRACT FROM AUTHOR]

The problems of a multi-mode buckling approach which is based on Koiter’s theory of a hybrid column are presented in this paper. An interaction of global buckling modes with the local ones is discussed. There are many different local and global buckling modes. Their selected combinations are dangerous and cause a reduction in the load-carrying capacity. All walls of the hybrid column were plane and made of many layers. The outer layers were thermal barriers and made of a TiC ceramic layer or an AL-TiC-type FGM. The inner layers were composed of aluminium layers and a few carbon-epoxy laminate layers. The classical laminate theory is used to define the ABD matrix which described the relations between applied loads and the associated deformations. The layup configuration of the hybrid column is general, so the coupling submatrix B is non-trivial. This submatrix has a significant impact on the value of local buckling load, whereas its effect on the value of global buckling load can be neglected. The main topic discussed in this paper is whether and how individual elements of the B submatrix can change the load-carrying capacity of a hybrid column. A detailed discussion is conducted for simple supported columns with opened cross-sections subjected to mechanical loads only. Thermal effects are neglected. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive review on the development of higher-order continuum models for capturing size effects in small-scale structures. The review mainly focus on the size-dependent beam, plate and shell models developed based on the nonlocal elasticity theory, modified couple stress theory and strain gradient theory due to their common use in predicting the global behaviour of small-scale structures. In each higher-order continuum theory, various size-dependent models based on the classical theory, first-order shear deformation theory and higher-order shear deformation theory were reviewed and discussed. In addition, the development of finite element solutions for size-dependent analysis of beams and plates was also highlighted. Finally a summary and recommendations for future research are presented. It is hoped that this review paper will provide current knowledge on the development of higher-order continuum models and inspire further applications of these models in predicting the behaviour of micro- and nano-structures. [ABSTRACT FROM AUTHOR]

Thermal post-buckling and limit-cycle oscillation characteristics of Functionally Graded Material (FGM) structures are investigated based on the neutral surface concept. In particular, the material properties are non-homogeneous and vary gradually from one surface to the other. Furthermore, the properties are to be considered as temperature-dependent characteristics, and the neutral surface concept is adopted instead of the mid-plane to consider the reference plane due to the asymmetric properties in the thickness direction of model. In the formulation, the First-order Shear Deformation Theory (FSDT) of plate is used, and the geometric nonlinearity is accounted for by the von Karman strain-displacement relations. Also, steady state thermal conduction effects are assumed as a one dimensional heat transfer on the surface of the structure. For the numerical analysis, the Newton-Raphson method is applied to solve the thermal post-buckling behavior, while Newmark's time integration method is employed to resolve the limit-cycle oscillation. In order to validate the analysis results, the results of this paper based on the neutral surface are compared with the data from previous papers using the conventional approach for FGMs model. Finally, effects of the neutral surface on the non-linear thermo-mechanic behavior of structure are discussed in detail. [ABSTRACT FROM AUTHOR]

This paper is focused on a method for calculating the optimal drape origin on arbitrary surfaces considering a minimal shear-deformation of the applied fiber-reinforced material. The presented method is based on the mesh from a triangulated surface and therefore not restricted by the assumption of a mathematical differentiable surface description. It is shown how the information of the mesh can be used to calculate the point-wise Gaussian-curvature on the given surface. It is further shown how this curvature information can be used to construct a directed planar graph and how this graph can help calculating the optimal drape sequence in order to minimize the shear-deformation of the applied fabric. The paper is concluded by a demonstration of the developed method for different example surfaces. [ABSTRACT FROM AUTHOR]

Based on the refined plate theory, an analytical solution of three-dimensional thermodynamic analysis for a piezoelectric laminated plate under 3D steady temperature field is given in this paper. The refined plate theory has a lot in common with classical plate theory in many aspects, and the involved variables can be expressed as certain function type comparing with other shear deformation theories and exact solution, besides it does not need to use shear correction factor. In this study, the method of separation of variables is used to process the 3D temperature field, subsequently the Galerkin method in conjunction with the double Fourier serial method and Newmark method are applied to determine the closed-form solutions of deflection for thermodynamic problem. The results of this paper show that the fiber orientation, number of layers for laminated plate, thickness ratio between total thickness and thickness of piezoelectric layer, temperature distributed function and geometrical nonlinearity have great influence on the deflection, normal stress and shear stresses of the piezoelectric laminated plate. [ABSTRACT FROM AUTHOR]

• Electromechanical evolution in damaging composites predicted with a multi-physical PD model. • Breakage of a mechanical bond automatically insulates corresponding electricity. • Stochastic model eliminates the explicit representation of micro-scale heterogeneities. • Simulations cost the same as a fully homogenized model. In this paper, a coupled electromechanical peridynamic model is introduced to describe damaging and cracking in conducting composites. In this model, electrical peridynamic bonds and mechanical peridynamic bonds are used to represent the interactions between material points, and the micro-scale heterogeneities are represented by changing the properties and/or distribution of the peridynamic bonds with a stochastically homogenized approach. A significant advantage of this coupled model is that the different mechanical bonds in the stochastically homogenized model are given corresponding electrical properties, and the deformation and breakage of a mechanical bond automatically change or break the corresponding electrical bond connecting the same material points. This multi-physical peridynamic model is utilized to study the electric field evolution in conductive composites during damaging and cracking under different loading configurations (including tensile test and three-point bending test). The model costs the same as a fully homogenized one but simulates the current evolution during material damaging and cracking as observed in a model using the microstructural details. The approach presented in this paper can be applied to other multi-physical problems, especially the ones with damage and fracture involved. [ABSTRACT FROM AUTHOR]

This paper presents the free vibration behavior of carbon nanotube (CNT) reinforced functionally graded composite plates in a thermal environment based on Reddy’s higher-order shear deformation theory (HSDT). The element-free kp-Ritz method is used in this study. Four different types of CNT distributions are considered. The literature reveals that there is a research gap in investigating the mechanical behaviors of CNT reinforced functionally graded composite plates using Reddy’s HSDT in association with any of the mesh-free methods. To the authors’ knowledge, this paper is the first to use this approach to investigate the vibration behavior of CNT reinforced functionally graded composite plates in a thermal environment. The rule of mixture is used to estimate the resulting effective material properties. To verify the reliability of the present model, the obtained numerical results based on a conversion study have been compared with those found in the literature with evident agreement. Moreover, parametric studies have been conducted on the effects of CNT distribution, boundary conditions, plate aspect ratio, plate thickness-to-width ratio and CNT volume fraction on the non-dimensional natural frequencies. Furthermore, the effects of plate aspect ratio and plate thickness-to-width ratio on the sequence of the first six mode shapes have been investigated. [ABSTRACT FROM AUTHOR]

In this paper, the method of reverberation ray matrix (MRRM) is extended to develop an exact and unified solution for the transient response analysis of composite laminated curved beams with arbitrary lamination schemes and general boundary restraints. The effects of shear deformation, rotary inertia and deepness term as well as the Poisson’s effect are considered in the theoretical formulations. Through the Laplace transformation, the governing differential equations are derived in frequency domain via the Hamilton’s principle, and the exact closed form solutions are used to represent the elastic waves propagating in the curved beam. As the main focus of this paper, the artificial spring boundary technique is adopted to simulate general boundary restraints and the scattering matrix is redefined to make the MRRM suitable for different boundary cases. Then, the transient responses of the composite laminated curved beam under general boundary restraints are obtained directly by using the Neumann series expansion and the Fast-Fourier transform (FFT) algorithm. Several numerical cases are presented to test and verify the accuracy, reliability and efficiency of the present solution. Meanwhile, a systematic parameter investigation is performed regarding the influences of elastic restraint parameters, lamination schemes, material properties, geometry parameters and loading types. [ABSTRACT FROM AUTHOR]

In this paper result of detection and localization of artificially initiated delaminations in carbon fiber reinforced polymer (CFRP) samples were presented. Damage detection was based on electromechanical impedance method (EMI). This method utilizes electromechanical coupling of piezoelectric transducer with host structure. Due to this coupling mechanical resonances of structure can be seen in electrical impedance characteristic of a piezoelectric transducer. In the research real part of electrical impedance (resistance) was measured. Delamination in CFRP sample caused frequency shift of certain resonance frequencies visible in resistance characteristic. In this paper also changing temperature effects on EMI method were investigated. In order to remove this temperature induced effects compensation algorithm based on signal cross-correlation was utilized. [ABSTRACT FROM AUTHOR]

This paper presents an efficient uncertainty quantification (UQ) scheme for frequency responses of laminated composite plates. A bottom up surrogate based approach is employed to quantify the variability in free vibration responses of composite cantilever plates due to uncertainty in ply orientation angle, elastic modulus and mass density. The finite element method is employed incorporating effects of transverse shear deformation based on Mindlin’s theory in conjunction with a random variable approach. Parametric studies are carried out to determine the stochastic frequency response functions (SFRF) along with stochastic natural frequencies and modeshapes. In this study, a surrogate based approach using General High Dimensional Model Representations (GHDMR) is employed for achieving computational efficiency in quantifying uncertainty. Subsequently the effect of noise is investigated in GHDMR based UQ algorithm. This paper also presents an uncertainty quantification scheme using commercial finite element software (ANSYS) and thereby comparative results of stochastic natural frequencies are furnished for UQ using GHDMR approach and ANSYS. [ABSTRACT FROM AUTHOR]

The design of glass fibre reinforced polymer (GFRP) pultruded members is often governed by deformability and buckling phenomena, preventing the full exploitation of the material potential. Hybridization – the partial replacement of the glass reinforcement with (stiffer) carbon fibres – is a possible approach to improve the performance of GFRP thin-walled profiles. This paper presents an experimental study on the structural behaviour of I-section hybrid fibre reinforced polymer (FRP) pultruded columns made of glass and carbon fibres (GF and CF) embedded in a polyester resin. A bare GFRP reference profile and four series of hybrid C-GFRP profiles, with different types and architectures of CF reinforcement, were designed, manufactured and tested under compression in three different lengths – short, intermediate and long. Particular attention was given to the buckling behaviour of the columns and to the delamination at the interface between GFRP and CFRP layers. In terms of serviceability performance, results obtained confirm the hybridization’s effectiveness in increasing the axial stiffness of GFRP compressive members. In terms of ultimate limit states behaviour, hybridization increased the load carrying capacity of the long columns, which exhibited global buckling. In opposition, for the short and intermediate columns, which failed respectively due to local buckling and a combination of global and local buckling, the load carrying capacity of the hybrid columns was lower than that of the reference profile; such worse performance seems to have been caused by the delamination of the CF layers, owing to the relatively high axial strains that developed in those columns. In a companion paper (Part 2), the experimental data presented and discussed herein is compared with predictions from numerical models and analytical formulae, which also provide further information about the delamination and progressive failure of the hybrid columns. [ABSTRACT FROM AUTHOR]

In this paper the Verchery’s polar method is extended to the conceptual framework of the Reddy’s Third-order Shear Deformation Theory (TSDT) of laminates. In particular, a mathematical representation based upon tensor invariants is derived for all the laminate stiffness matrices (basic and higher-order stiffness terms). The major analytical results of the application of the polar formalism to the TSDT of laminates are the generalisation of the concept of a quasi-homogeneous laminate as well as the definition of some new classes of laminates. Moreover, it is proved that the elastic symmetries of the laminate shear stiffness matrices (basic and higher-order terms) depend upon those of their in-plane counterparts. As a consequence of these results a unified formulation for the problem of designing the laminate elastic symmetries in the context of the TSDT is proposed. The optimum solutions are found within the framework of the polar-genetic approach, since the objective function is written in terms of the laminate polar parameters, while a genetic algorithm is used as a numerical tool for the solution search. In order to support the theoretical results, and also to prove the effectiveness of the proposed approach, some new and meaningful numerical examples are discussed in the paper. [ABSTRACT FROM AUTHOR]

This paper is part II of a study on the CAI responses of laminated composite panels. Panels with three in-plane sizes, two thicknesses, and two stacking sequences were studied using CAI fixtures based on and modified from the industrial standard. The three in-plane sizes are 152.4 mm × 101.6 mm, 177.8 mm × 177.8 mm, and 330.2 mm × 330.2 mm. The two thicknesses are 24-ply and 48-ply. The two stacking sequences are [45/-45/0/90/0/0] ns and [45/0/-45/90] ns. The material system is IM7/977-3. Load–displacement curves, 2D/3D DIC characterization, and ultrasound C-scans are presented. Two types of CAI deformation patterns have been observed. The first type of deformation is mostly in-plane with local buckling, and its corresponding CAI-induced failure concentrates around the impacted plate center. The second type of deformation is with global buckling, and the corresponding CAI-induced failure is unrelated to the LVI-induced damage footprints. Three driving forces for the CAI failure have been identified: LVI-induced damage, global buckling-induced excessive bending, and delamination of the lateral edges. The dominant driving force is dependent on the panel's thickness-to-length/width ratio, which is found to be the most important geometric parameter affecting the CAI behavior. The experimental results imply that the standard coupon-size (152.4 mm × 101.6 mm) CAI test results do not accurately represent the compressive load-carrying capacity of a composite panel subjected to impact damage. The results reported in this paper call for a re-examination and revision of the existing industrial standard ASTM D7137 (2017) to assess CAI load-carrying capacity. [ABSTRACT FROM AUTHOR]

In this paper the Verchery’s polar method is extended to the conceptual framework of the First-order Shear Deformation Theory (FSDT) of laminates. It will be proved that the number of independent tensor invariants characterising the laminate constitutive behaviour remains unchanged when passing from the context of the Classical Laminate Theory (CLT) to that of the FSDT. Moreover, it will also be shown that, depending on the considered formulation, the elastic symmetries of the laminate shear stiffness matrix depend upon those of membrane and bending stiffness matrices. As a consequence of these results a unified formulation for the problem of designing the laminate elastic symmetries in the context of the FSDT is proposed. The optimum solutions are found within the framework of the polar-genetic approach, since the objective function is written in terms of the laminate polar parameters, while a genetic algorithm is used as a numerical tool for the solution search. In order to support the theoretical results, and also to prove the effectiveness of the proposed approach, some novel and meaningful numerical examples are discussed in the paper. [ABSTRACT FROM AUTHOR]

The new piecewise low and high order shear deformation models, which contain the in-plane rigidity and the transverse shear rigidity of the core and skins, are proposed in this paper. The partial differential governing equations are obtained by applying Hamilton’s principle, aiming to attain the natural frequencies for the sandwich panel constituted of orthotropic materials. The frequency equation is explicitly expressed for simply supported rectangular sandwich panel. The effects of the thickness and elastic modulus of the core on the fundamental frequency are also discussed in this paper. The results obtained from the proposed models are compared with those obtained from the classical analytical models, FEM, low and high order shear deformation theory, which verifies the theories have theoretical accuracy and broad application. [ABSTRACT FROM AUTHOR]

To solve the problem of large thermal deformation of reflectors for airborne optical systems, a new lightweight mirror was created using TPMS structure. To ensure that the model performance during optimization is consistent with the actual structural performance, the elasticity and thermal conductivity models of TPMS units were established. Eventually, the thermal deformation of the mirror was greatly reduced. [Display omitted] In recent decades, unmanned aerial vehicle airborne optical systems have gained a booming development. With the continuous pursuit of optical system performance, the thermal deformation of the reflector during temperature change constrains the further improvement of the system performance. Traditional open-back mirrors have difficulty meeting high-performance targets under temperature change. With the rapid development of 3D printing technology, the complex structures represented by TPMS have significantly increased the freedom of optical reflector design. This paper proposes a TPMS structure optimization design approach based on the homogenization performance model, which can accurately describe the TPMS structure performance and obtain structures with outstanding performance with minimal computing cost. A TPMS-filled reflector with a diameter of 400 mm and a height of 60 mm was designed with a mass reduction of about 70 %. Results show that the final shape deviation of the mirror is below 20 nm RMS at room temperature and below 30 nm RMS at 50 ℃. Compared to open-back mirrors, TPMS-filled mirrors perform significantly better at high temperatures. This method helps with the application of TPMS in the design of opto-mechanical structures. [ABSTRACT FROM AUTHOR]

• An innovative 3D auxetic structure (3D CATS) was proposed based on the coupling connection of the tube and auxetic units. • The force responses exhibit multiple stages, and the tube and auxetic units played different roles during different stages. • The interaction between the auxetic units and the tube completely changes the deformation modes of the tube. • The SEA of the structure was significantly superior to most existing 2D and 3D auxetic structures. • Two sets of parameters were introduced to vary the compression displacement and force in the plateau stage. In this paper, a novel 3D composite auxetic tubular structure (3D CATS) connected by a thin-walled (TW) circular tube was proposed, and two sets of parameters h 1 , h 2 , and β , n were introduced to construct structural families with various geometries and mechanical properties. The mechanical responses of the 3D CATS were preliminarily explored through the quasi-static experiment. The good agreement between the experimental results and the finite element (FE) simulation verified the accuracy of the FE model. Subsequently, the coupling mechanism between the tube and auxetic units was revealed by analyzing the deformation modes and force responses. The results indicated that the deformation of auxetic units caused more plastic hinges in the tube to enhance the contact force seriously. Then, the 3D CATS was proved to exhibit better specific energy absorption (SEA) compared with other auxetic structures. Furthermore, the influence of h 1 , h 2 , and β , n on the responses was also discussed. The results showed that h 1 , h 2 can change the compression displacement points and forces, while β , n can adjust the stiffness and forces. The results can provide an important reference for the design and study of variable mechanical properties for innovative 3D auxetic structures with enhanced performance. [ABSTRACT FROM AUTHOR]

Abstract: The use of fibre reinforced polymer (FRP) structural elements, including glass fibre reinforced polymer (GFRP) pultruded profiles, has increased in the last few decades. The high potential of these materials for civil engineering structural applications, particularly for footbridges, stems from their high strength, low self-weight and good durability. However, when designing GFRP structures, the high deformability and the susceptibility to instability phenomena seldom allow the full exploitation of the GFRP material. In order to overcome these limitations, several hybrid structural systems have been proposed, namely GFRP-concrete hybrid systems. In this context, the evaluation of the dynamic characteristics of GFRP-concrete hybrid structural systems is very important, especially for footbridge applications, whose design is generally governed by pedestrian comfort criteria. This paper first presents modal identification experimental tests on a 6.0m long and 2.0m wide GFRP-concrete hybrid footbridge prototype, made of two I-shaped GFRP main girders and a thin steel fibre reinforced self-compacting concrete (SFRSCC) deck. The tests consisted of applying an excitation to the deck with an impact hammer and measuring both the applied excitation and the structure’s response. The natural modes of vibration, frequencies and damping were determined using (i) a conventional input–output modal identification technique, based on the Rational Fraction Polynomial method, and (ii) a simple output-only method directly based on the Fast Fourier Transform (FFT) of the response (mode frequencies only). In the second part of the paper, experimental data are compared with analytical and numerical simulations in order to assess the accuracy of such design tools in predicting the dynamic behaviour of GFRP-SFRSCC hybrid structures, in terms of mode shapes and frequencies. [Copyright &y& Elsevier]

Abstract: Composite sandwich structures are widely used in the high-performance applications where weight reduction is one of the most attractive design parameters. However, structural sandwich components have low resistance to out-of-plane impact due to the thin outer composite skins and the highly deformable cores. The present paper deals with a finite element study on the impact response of sandwich panels, obtained combining phenolic resin-based glass fiber reinforced plastics as skins and phenolic resin-impregnated aramid paper honeycomb structure (Nomex) as core. The numerical analysis has been performed using the LSDYNA software enabling to account for the main sandwich failure modes occurring during impact. The honeycomb core structure and composite skins have been modeled by means of solid and shell elements respectively. The properties of the finite element model have been calibrated on a series of experimental outcomes in order to achieve numerical parameters for both composite facesheet and orthotropic honeycomb material models. The major concerns are related to damage mechanisms, influence of strain-rate effects and energy absorbing capability. The model is validated using the results from experimental impact tests performed on different initial impact conditions. Good agreement was obtained between numerical and experimental results in terms of impact damage and force–displacement trend. [Copyright &y& Elsevier]

Abstract: The solution method presented in this paper is of Trefftz type which uses exponential basis functions (EBFs) to solve composite plate problems. Following its success in the solution of plates using well-known theories (Composite Struct 2011;93:3112–9, 94:84–91 and 2012;94:2263–68), here we aim to apply the method to higher order shear deformation theories. In this paper we demonstrate the way that one can generally evaluate the EBFs for a laminated plate using a Zig–Zag theory. We present explicit relations for three-layer sandwich plates which have a wide range of applications in structural/mechanical engineering fields. The results of our numerical experiments on the bending analysis of composites with different boundary conditions and different configurations are provided and compared with those available in the literature. For further sudies we present some results for sandwich composite plates, including those with soft cores, as new benchmarks using the Zig–Zag theory. [Copyright &y& Elsevier]

Abstract: An exact finite strip for the buckling analysis of moderately thick symmetrically cross-ply laminated composite plates and plate structures is presented in this paper by using First-order Shear Deformation Theory (FSDT). Based on the concept that the so-called strip is effectively a plate, the critical buckling load and out-of-plane deflection mode shape are obtained by solving the Von-Karman’s equilibrium equation exactly. A transcendental stiffness matrix is obtained for an individual strip. The overall stiffness matrix for the whole section is obtained by assembling the individual stiffness matrices. Since the overall stiffness matrix is transcendental, it is not possible to identify a separate geometric stiffness matrix. In this paper a secure method i.e. bisection method is used to find the buckling load and the corresponding buckling mode of the plate structure. [Copyright &y& Elsevier]

Abstract: In this paper, the layerwise model for laminates with imperfect interfaces and enhanced in Part 1 of this work is confronted with experimental results. The model calculations are validated by comparing its sliding predictions in double lap adhesive joints to the sliding measurements performed in a previous paper. The model predictions agree with the experimental results. Finally, the model is applied to the failure analysis in double lap joints and T-peel joints exhibiting adherend, adhesive and cohesive failures. The model calculations and pertinent failure criteria provide accurate predictions and may become a helpful tool suitable to the design of adhesive joints. [Copyright &y& Elsevier]

Abstract In this paper a dynamic mesh method based on diffusion equation and nodal rotation is developed for high-aspect-ratio composite wings. Mesh displacement is described by diffusion equation and calculated by finite element method. The mesh was distorted because the displacement of the mesh nodes is uncoupled in different directions, and its quality diminished due to large deformation. The nodal rotational method is introduced to solve this problem. The technique used the same diffusion equation to describe the rotational angle and is solved by the finite element method. The node nearest the wall boundary is the rotational centre and the corresponding rotational vector is the rotational axis. The new position of the mesh node is obtained by rotating transformation. The mesh deformation of two-dimensional NACA0012 airfoil mesh, three-dimensional spherical mesh and high aspect ratio composite wings are verified for various cases. The results show that the present method is applicable to structural and unstructured/hybrid meshes. The mesh quality is improved and its overlap and negative volume are effectively prevented under large deformation. [ABSTRACT FROM AUTHOR]

Abstract Fiber reinforced polymer matrix composites are increasingly being used to fabricate energy-absorbing aerospace structural components susceptible to impact loading, such as jet engine containment structures subjected to blade-out events. The development and certification of such structures necessitates a detailed understanding of the dynamic behavior of the constituent materials, particularly the strain rate, temperature, and pressure dependent polymer matrix, and their complex interaction. As the rate of deformation increases, the thermodynamic condition transitions from isothermal to adiabatic. The conversion of plastic work to heat causes local adiabatic heating in the polymer matrix, but the rapid nature of impact events does not allow sufficient time for heat to dissipate; ballistic impact events can therefore be regarded as fully adiabatic. Local adiabatic heating can significantly affect the high rate deformation response if thermal softening effects outweigh strain and strain rate hardening effects and therefore, must be explicitly modeled at the appropriate length scale. In this paper, an existing isothermal viscoplastic strain rate and pressure-dependent polymer constitutive formulation is extended to nonisothermal conditions by modifying the inelastic strain rate tensor components to explicitly depend on temperature based on the Arrhenius equation for nonisothermal processes. A methodology based on shifting neat resin dynamic mechanical analysis data is utilized to determine the polymer elastic properties over a range of strain rates and temperatures. Temperature rises due to the conversion of plastic work to heat are computed, assuming adiabatic conditions. It is demonstrated that the modified polymer constitutive model is capable of capturing strain rate and temperature dependent yield as well as thermal softening associated with the conversion of plastic work to heat at high rates of strain. The nonisothermal polymer constitutive model is then embedded within the Generalized Method of Cells micromechanics framework to investigate the manifestation of matrix thermal softening, due to the conversion of plastic work to heat, on the high strain rate response of a T700/Epon 862 unidirectional composite. Adiabatic model predictions for high strain rate composite longitudinal tensile, transverse tensile, and in-plane shear loading are presented. Results show a substantial deviation from isothermal conditions; significant thermal softening is observed for matrix dominated deformation modes (transverse tension and in-plane shear), highlighting the importance of accounting for local adiabatic heating in the polymer matrix in the high strain rate analysis of polymer matrix composite structures. [ABSTRACT FROM AUTHOR]

Abstract The integration of functional material, such as actuator material, is an essential aspect for the multi-functionality and resource efficiency of fiber-reinforced plastics (FRPs). By integrating a textile-based actuator into reinforcing fabrics during the production process, single axis and intrinsic adaptive FRPs can be produced, and these can change their form according to requirements. However, this paper presents the effect of thickness ratio and integrated weft yarn column number in shape memory alloys on the deformation behavior of adaptive FRPs. In order to achieve this aim, shape memory alloys were converted into hybrid yarn in the form of a core-sheath structure before being textile-technologically integrated into the reinforcing fabrics using weaving technology. The thickness variation was achieved by the warp as well as weft yarn density and the type of interlacement. These preforms were infused by a thermosetting resin system. The adaptive FRPs were tested electro-mechanically with respect to their maximum deformation. Results reveal that the maximum deformation of adaptive FRPs is enhanced by increasing the thickness ratio and the integrated weft yarn column number in shape memory alloys. [ABSTRACT FROM AUTHOR]

Abstract In order to predict the effect of projectile impacts on aramid fabrics with a low computational cost a 1-layer mesoscopic model has been developed. This model has been studied with orthotropic and isotropic properties and have been compared each other. Similar results have been obtained in both cases in a range from low to high velocities (up to 1763 m/s). The comparison shows a very good fit for both models in the predictions of residual velocity and absorbed energy which rely on the experimental results of Park et al. (2014). Ballistic limit has been studied on both cases with good result considering experimental results of Rao et al. (2009) and Duan et al. (2005). Finally, the deformation induced by the projectile has been studied too. Furthermore, in this paper are presented the advantages and the limitations of each methodology. [ABSTRACT FROM AUTHOR]

Abstract A semi analytical method is employed to analyze free vibration behaviors of functionally graded (FG) doubly-curved shells of revolution subject to general boundary conditions. The analytical model is established on basis of multi-segment partitioning strategy and first-order shear deformation theory. The displacement functions are made up of the Jacobi polynomials along the axial direction and Fourier series along the circumferential direction. In order to obtain continuous conditions and satisfy general boundary conditions, the penalty method about spring technique is adopted. The solutions about free vibration behaviors of FG doubly-curved shells were obtained by approach of Rayleigh–Ritz. The convergence study and numerical verifications for FG doubly-curved shells with different boundary conditions, Jacobi parameters, spring parameters and truncation of permissible displacement functions are carried out. Through the comparison and analysis, it is obvious that the proposed method has a good stable and rapid convergence property and the results of this paper closely agree with those obtained by published literatures, FEM and experiment. In addition, some interesting results about free vibration characteristics of FG doubly-curved shells are investigated. [ABSTRACT FROM AUTHOR]

Abstract In this paper, we present the development of completely 2D formulation for bending of functionally graded plates subjected to stationary thermal loading. Consistently with the assumptions made in plate bending theories, the temperature field in 3D domain is expanded into low order power-law series with respect to transversal coordinate and the original 3D formulation (governing equation and boundary conditions) is recast according to physical principles into 2D formulation. A unified formulation is developed using the assumptions of three plate bending theories such the Kirchhoff-Love theory for bending of thin plates (KLT) and the shear deformation plate theories of the 1st and 3rd order (FSDPT, TSDPT) valid for thick plates too. The derivation is performed with assuming the power-law gradation of material coefficients (such as the Young modulus, linear thermal expansion coefficient, and heat conduction coefficient) across the plate thickness. For variation of material coefficients and plate thickness within the mid-plane, arbitrary continuous function is allowed. In numerical simulations, the derived formulation is implemented numerically by using the strong formulation and mesh-free Moving Least Square-approximation. The original PDE with high order derivatives are decomposed into a system of 2nd order PDE. [ABSTRACT FROM AUTHOR]

Abstract Application of high strength concrete (HSC) is an effective way to reduce the column size in high-rise and large-span structures, resulting in more available floor space. The concern on the brittleness of HSC can be alleviated by providing some confinement to it. To this end, carbon fiber reinforced polymer (CFRP) and steel tube are found to be very effective. This paper presents experimental and theoretical studies on the axial behavior of CFRP-steel composite tubed HSC columns. Totally, 25 specimens were tested to investigate the influences of CFRP layers, diameter-to-thickness ratio of steel tube, and concrete strength on the load bearing capacity and deformation behavior of such composite members. The observed failure modes, stress-strain relationships, stresses of steel tubes, and deformations of concrete are discussed. The experimental results indicate that with enough CFRP sheets the load bearing capacity and deformation behavior of core concrete are significantly improved, especially the ductility of specimens with concrete strength of 105 MPa. Calculation methods for the axial load bearing capacity of a CFRP-steel composite tubed HSC column are presented and discussed. [ABSTRACT FROM AUTHOR]

Abstract The excellent mechanical properties of Carbon Fiber Reinforced Plastics (CFRP) have great influence on the deformation and failure of the components. The accurate prediction of the mechanical properties of CFRP is always a necessary but tough task, especially the transverse elastic modulus and shear modulus. This paper proposed an approach to predict the mechanical properties of CFRP based on cross-scale simulation. Firstly, the structural representative volume element (RVE) of unidirectional CFRP (UD-CFRP) is established in ABAQUS software at microscopic level considering periodic boundary conditions. The macroscopic mechanical properties of UD-CFRP are predicted by applying the different loading conditions for RVE in each direction. Secondly, based on the homogenization theory, the mesoscopic simplified RVE of multidirectional CFRP (MD-CFRP) is established according to the dimension of structural RVE. The mechanical properties of CFRP with the change of the angle and the different stacking sequence of UD-CFRP are also predicted through the mesoscopic simplified RVE. Finally, a series of experiments have been carried out, which showed that the results of the prediction approach and the experiments are in good agreements. [ABSTRACT FROM AUTHOR]

Abstract A fundamental problem investigated in this paper is computational homogenization of two-component particulate and fibrous composites with material characteristics treated as symmetric but non-Gaussian random processes. Homogenization method is based on equity of deformation energies for the real multi-component and the homogenized Representative Volume Elements (RVE) of the given composite structure. The iterative generalized stochastic perturbation technique is used to provide the additional Taylor expansions about expected values and to finally derive analytical formulas for the basic probabilistic characteristics of the effective tensor components. These expansions use polynomial response functions relating this tensor components with real material characteristics determined through the series of the Finite Element Method homogenization tests and the Least Squares Method. Applicability of this stochastic strategy and its Stochastic Finite Element Method implementation are verified for two well-known probability distributions, i.e. the uniform and the triangular one, to model uncertainty in Young modulus of some composite components. Validation of this approach is carried out using two alternative methods – statistical one known as the Monte-Carlo simulation as well as the semi-analytical one using the same polynomial responses as the perturbation approach, but finally processed using classical analytical probability integrals. This study generally confirms applicability of the proposed probabilistic method to homogenize composite structures with linear elastic and isotropic components exhibiting uniform and triangular uncertainties in their elastic properties. [ABSTRACT FROM AUTHOR]

Abstract This paper is dedicated to study the elastic buckling behavior of isotropic, laminated composite and sandwich beams subjected to various axially varying in-plane loads and boundary conditions (BCs). The formulation of the problem is derived by using the Ritz method with the displacement field based on a shear and normal deformable beam theory (SNDBT). Polynomial functions are employed to present the displacement field. The convergence studies are performed and then obtained results are compared with those of reported works. Results from extensive analysis are presented for different BCs, aspect ratios, orthotropy ratios, fiber angles and loading conditions. It is observed that the type of the axially variable in-plane load significantly affects the critical buckling loads and mode shapes of the beams depending on the BCs. The normal deformation effect depends on not only the aspect ratio but also BCs and the fiber orientation angles. [ABSTRACT FROM AUTHOR]

Abstract The purpose of the paper is to predict the electromechanical behavior of composite shell structures with embedded piezoelectric layers using 3D-shell model based on a discrete double directors shell element. The implementation is applicable to the analysis of isotropic and functionally graded shells with integrated piezoelectric layers. The third-order shear deformation theory is introduced in the present method to remove the shear correction factor and improve the accuracy of transverse shear stresses. The present results were compared with reference solutions from literature in order to verify the accuracy of the present formulation and excellent agreement was found. A parametric study is carried out to highlight the influence of material composition and curvature radius on the deflection and axial stress along the thickness. [ABSTRACT FROM AUTHOR]

Abstract Design of materials and structures with quite low coefficient of thermal expansion (CTE), even zero or negative CTE is important for industrial application where drastic temperature changes are encountered. In this paper, making use of the bending of bi-material beam and the unique deformation mechanism of chiral lattice structures, five sets of chiral lattice composite structures with tailorable CTEs are proposed, where synergic effects of rigid node rotation and bi-material ligament bending deformation are responsible for giant range of structural deformation due to temperature change, from positive CTE to negative CTE through adjusting the geometrical parameters of composite bi-material chiral unit cell, and the relationship between unit cell geometric parameters and CTEs of the structure are studied systematically through finite element analysis. Finally, design of bi-material cylindrical shells consisting of anti-tetra chiral unit cells are proposed, and its axial CTEs with different number of the unit cells along the circumferential are studied systematically, demonstrating the robust range of CTEs can be generated through adjusting the geometrical parameters of chiral bi-material unit cells. The proposed chiral structures demonstrated promising application potentials in industrial fields, such as: aerospace and microelectronics, where extremely high structural accuracy is required during harsh working temperature environment. [ABSTRACT FROM AUTHOR]