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Surface decorated wood-based panels with melamine formaldehyde resin (MF) impregnated paper is highly favored by consumers due to its outstanding appearance and durable performance. However, the laminated composites would encounter hygroscopic expansion and damage that affect its service and aesthetics in long-term humid environments. This study aims to construct highly durable superhydrophobic surface to address this issue. Firstly, a controlled micro rough structure on stainless steel plates which were built with sandblasting was successfully duplicated onto the surface of MF impregnated paper laminated medium density fiberboard (MDF) using the embossing method. Following that, a spray treatment with hydrophobic nanoparticles was employed to the laminated composite surface, ultimately resulting in a superhydrophobic coating with a contact angle up to 163°. To confirm the durability of the fabricated superhydrophobic layer, linear abrasion test, water droplet impact test, sand impact test, and tape peeling test were carried out. The results demonstrated that even after severe processed conditions, the contact angle of the decorated surface remained above 150°. And the decorated laminate successfully passed both self-cleaning and dirt resistance challenge, clearly indicating the outstanding durability of superhydrophobic structure. Furthermore, water absorption thickness expansion measurement was done to verify the dimensional stability of the laminate in humid conditions. This research presented a straightforward and cost-effective approach to fabricate highly durable superhydrophobic MF impregnated paper decorated laminates, offering a dependable strategy for research and applications in related domains. [ABSTRACT FROM AUTHOR]

Abstract: We present a model for the laminated composite plate problem based on the Reissner–Mindlin model and first-order lamination theory. The weak problem based on this model is solved with the finite element method using stabilized MITC (mixed interpolation of tensorial components) finite elements. Detailed a priori estimates are given for the mixed finite element formulation of the problem. Explicit bounds for the continuity and coercivity constants of the coupling terms are presented, thus refining earlier results. Furthermore, we present an application of the theory to the paper cockling problem and investigate the effect of boundary conditions on the small-scale deformation of the solution numerically. [Copyright &y& Elsevier]

The graphite-resin composite bipolar plates prepared by the traditional hybrid pressing process exhibit poor conductivity, processability, and wettability due to the graphite flake layer being covered by resin, hindering the formation of a continuous conductive network, which significantly constrains their promotion and application in the field of proton exchange membrane fuel cells (PEMFC). In this paper, an ultra-thin flexible graphite/epoxy composite bipolar plates (BPs) with a thickness of only 0.775 mm is prepared followed by a process of flexible graphite preforming and impregnation curing. The hydrophilicity-modified BPs surface has a contact angle of 59.01° as well as flexural and compressive strengths of 11 MPa and 4 MPa and possesses a high in-plane conductivity of 380 S/cm and a low in-plane specific resistance of 6 mΩ cm2. The electrostack test results show that the hydrophilic runner channel is more conducive to the diffusion and spreading of H 2 O generated from the cathode-side reduction reaction in the flow channel, so that O 2 smoothly passes through the gas diffusion layer to participate in the reduction reaction of O 2 , and exhibits higher electric power at high current density, while the hydrophobically modified BPs has relatively poor overall performance due to ohmic losses. [Display omitted] • A hydrophilic flexible graphite bipolar plate with a contact angle of 59.01° is prepared. • The bipolar plates with excellent flexural strength of 11 MPa and a high in-plane conductivity of 380 S/cm. • The Electricstack has the best overall monolithic voltage and total power when the current density over 1800 mA/cm2. [ABSTRACT FROM AUTHOR]

In order to achieve high efficiency and low damage processing of hard and brittle materials, composite ultrasonic vibration-assisted face grinding (CUVAFG) has been proposed by comprehensively combining the high efficiency of axial ultrasonic vibration grinding (UVAG) and the low damage of elliptic ultrasonic vibration grinding (EVAG). However, the three-dimensional ultrasonic vibration brings about a more complicated machining mechanism than the previous ultrasonic vibration-assisted grinding methodology. Hence, in order to explore the grinding mechanism in deep, this paper first developed a new model of undeformed chip thickness for CUVAFG from the perspectives of the kinematic mechanism and elastic-plastic deformation mechanism. Then the influences of different processing parameters on interference rate and undeformed chip thickness were further confirmed. Finally, CUVAFG experiments of silicon carbide (SiC) ceramics were conducted to study the relationship between the undeformed chip thickness and the resultant grinding forces, specific grinding energy, ground surface morphology and roughness, and subsurface damage. It is found from the experimental results that the critical chip thickness of brittle-ductile transition in CUVAFG is between 0.31 and 0.35 μm. As the undeformed chip thickness is less than the critical value, the grinding forces and the specific grinding energy increases with the undeformed chip thickness, but the ground surface roughness decreases with improved surface morphology and shallow subsurface damage. After exceeding the critical value, the grinding force remains unchanged, the specific grinding energy decreases, and ground surface roughness increases with deteriorated surface morphology and deepened subsurface damage. For the purpose of good machining surface integrity, it is essential to guarantee that the undeformed chip thickness is less than the critical value. The computational and experimental results have demonstrated the contribution of the developed undeformed chip thickness model to understanding the grinding performance of hard and brittle material by CUVAFG. • A novel undeformed chip thickness model that considers the elastic-plastic deformation of workpiece material is proposed. • The interference area and rate are proposed to explain the influence of processing parameters on undeformed chip thickness. • The critical undeformed chip thickness of brittle-ductile transition for silicon carbide by CUVAFG is confirmed in the range of 0.31–0.35 μm. • The depth of the subsurface damage layer increases from 2.1 μm to 66.7 μm with the increase of undeformed chip thickness. • The grinding forces, ground surface roughness, and specific grinding energy are reduced by 30 %, 42 %, and 93 %, respectively. [ABSTRACT FROM AUTHOR]

This study concerns several possible ways of computing the J-integral in the cases of laminated composite plate structures containing delamination. On the one hand, two special types of plate finite element families are provided for advanced fracture mechanical analyses. On the other hand, a numerical algorithm is introduced also that utilizes results derived from solid element models built in commercial finite element software. In order to create plate elements, the first-order (FSDT) and the third-order shear deformation theories (TSDT) are applied with two equivalent single layers. A subparametric element family is created by using the Hermite interpolation with the FSDT that grants the continuity of the derivatives at the element borders. Besides, an isoparametric family is created also with the TSDT employing the Lagrange interpolation scheme. This paper aims to present the compact formulations of calculating the J-integral around the delamination fronts for both plate element families. The calculation of the J-integral is implemented as a matrix multiplication by taking advantage of the properties of plate transition elements. The models yield improved fracture mechanical analyses for delaminated composite plates with linear elastic material behaviour. In addition, computing the J-integral is not available in most commercial finite element software for laminated orthotropic materials, therefore, an appropriate algorithm is presented here for this purpose. To conclude, the models and algorithms are applied to two case studies and subjected to a comprehensive comparison with analytical and formerly used finite element solutions. • A subparametric FSDT plate element family with granted continuity of the derivatives for delaminated plates. • An isoparametric TSDT plate element family that is appropriate for modelling curved delamination fronts. • A robust algorithm for computing the J-integral numerically in solid element models. [ABSTRACT FROM AUTHOR]

Polymer-carbon composite bipolar plates (PCCBP) are accepted over graphite bipolar plates (BP) for their use in proton exchange membrane fuel cell (PEMFC), specially in hydrogen fuel cell-powered electric vehicles. This study developed a novel copper fiber-filled PCCBP with epoxy resin as the binder and natural flake graphite (NFG), carbon black (CB), and Cu fiber as filler materials. The fabrication is done by compression molding. Both electrical conductivity and flexural strength increased with the addition of Cu fiber. The composite BP fabricated with 8 vol % Cu fiber, 10 vol % CB, and 42 vol % NFG exhibited electrical conductivity of 169 S/cm, flexural strength of 43 MPa, thermal conductivity of 17 W m−1 K−1 and corrosion current density of 0.972 μA/cm2. The composite also showed acceptable results for contact angle, density and thermal stability tests. This research paper provides insights into further developments of the metal-based PCCBP. • Novel Cu fiber-filled composite bipolar plates were developed for PEM fuel cells. • Effect of content of epoxy resin, carbon black, and copper fiber was investigated. • Enhancement of electrical conductivity and flexural strength achieved concurrently. • Provides insights into future developments of the metal-based PCCBP. [ABSTRACT FROM AUTHOR]

• The ASABH is proposed to attenuate AE reflection waves at the boundary. • The influence of geometric parameters of the ASABH have been revealed. • Compared to ABH, the ASABH has higher security and better adaptability. • The ASABH has a good effect on reducing the AE boundary reflection. Acoustic emission (AE) technology plays a crucial role in dynamic nondestructive testing. To investigate material properties, friction characteristics, damage features, and acoustic source localization, AE tests are commonly conducted on metal or composite plates. However, the reflection of AE waves at the boundary often generates strong interference, significantly impacting AE test results. In response to this challenge, this paper introduces an innovative solution: an additional Spiral Acoustic Black Hole (ASABH) affixed to the test plate's boundary. The ASABH is designed to mitigate the reflection of AE signals, enhancing the signal-to-noise ratio collected by the sensor. The study begins by establishing a finite element model of the ASABH to validate its efficacy in reducing boundary reflection waves. Subsequently, the paper explores the impact of structural geometric parameters—such as length, residual thickness, power exponent, pitch, and extended length—on the reduction effect. The investigation also delves into the variation of attenuation degree when connecting the ASABH to plates with different relative thickness, relative widths, and materials. Finally, the effectiveness of the ASABH in attenuating structural boundary reflection waves is verified through pencil-lead breaking tests conducted on both metal and composite plates. Results indicate that the proposed ASABH effectively mitigates the reflection of AE waves at the structural boundary, demonstrating adaptability and providing valuable insights for ASABH design. [ABSTRACT FROM AUTHOR]

Airplanes are inevitably subjected to various impact loading conditions in the event of emergency landing. An airplane crash scenario is a complex nonlinear impact event which involves large deformation, material fracture, structural failure, and dynamic contact. The impact response becomes more complicated due to the presence of composite materials, which are becoming the dominated choice for aircraft components. However, the impact damage and failure severity of composite fuselage sections can be effectively alleviated with optimized energy absorbing (EA) design. Accordingly, the crashworthy design of fuselage sections has always remained a top priority to prevent catastrophic structural failure and significant casualties. This paper presents a systematic literature review on the impact response and EA design of composite fuselage structures. Firstly, the typical composite materials such as composite tubes, corrugated composite plates, hybrid composite structures and bio-inspired composite materials are introduced to dissipate the impact kinetic energy during a crash. Then, the analytical models and finite element modeling methods of composite bolted joint structures are described to investigate their impact response and failure mode. The crashworthy design of typical composite fuselage structures including sub-cargo support struts, cabin floor support struts, fuselage frame and cabin floor/fuselage frame connection are described in this paper. Finally, an emphasis is placed on the evaluation criteria of the occupant crash safety and the crashworthy evaluation method of fuselage structures. [ABSTRACT FROM AUTHOR]

Since carbon fiber woven composite panels contain complex fiber bundle structures, the aim of this paper is to investigate the factors influencing the macro-equivalent properties and topological flexibility of composite panels resulting from variations in fiber bundle configuration. Firstly, the structural topology optimization design of carbon fiber composite plates was achieved using a multi-scale modeling approach with the variable density method. Nonlinear relationships between carbon fiber bundle configuration parameters and macroscopic equivalent properties, as well as macroscale topological flexibility, were determined using deep learning methods, respectively. The maximum error in the predicted values of the deep learning network model does not exceed 0.5% when compared with the results of the finite element calculations. In addition, utilizing deep learning networks to predict macro-equivalent properties of composites can significantly decrease computational time. The impact of varying the number of filaments in fiber bundles and the spacing of the fiber bundles on the flexibility of the topology was determined using a deep learning network. The optimal topological flexibility, along with its corresponding fiber bundle spacing and number of fiber bundle filaments, are globally searched within the design domain using an adaptive genetic algorithm. The study in this paper can provide a reference for designing fiber bundle configurations of composites for practical applications. [ABSTRACT FROM AUTHOR]

Space debris is a major threat to the safety of spacecraft in orbit, and advanced protective materials with lightweight and high impact resistance are effective passive protection solutions. In order to investigate the hypervelocity impact protection performance of aluminum matrix ceramic ball composite materials plate, this paper has carried out the hypervelocity impact test of aluminum matrix ceramic ball composite materials plate, and verified the accuracy of the numerical model based on the FE-SPH adaptive method, and then carried out a comparative study on the hypervelocity impact protection performance of aluminum plate and aluminum matrix ceramic ball composite materials plate with the same area density. The results show that: compared with the aluminum plate conditions, the composite materials plate has a better ability to broken the projectile. Compared with the aluminum plate, the kinetic energy absorbed by the composite materials plate is increased by 37.04%, and the kinetic energy of the generated debris cloud decreased by 69.57%. The proportion of the internal energy dissipation of the composite materials impact system reaches up to 72.03%. The secondary pollution generated by the composite materials plate is less and the hazardous debris have less threat to the rear wall. The research in this paper can provide reference for the selection of hypervelocity impact protection materials. [ABSTRACT FROM AUTHOR]

In this study, a multilayer high-performance polybenzoxazine/expanded graphite composite bipolar plate with a 'graphite-composites-graphite' structure was prepared by compressing molding. The surface graphite layer and the conductive network were constructed by hot compressing of graphite paper and the polybenzoxazine/expanded graphite composites. The results show that the multilayer synergy makes composite BP reach an in-plane conductivity of 278.85 S cm−1, an area specific resistance of 9.70 mΩ cm2 and a flexural strength of 75.75 MPa. The 'graphite-composites-graphite' structure can make the power density of a single cell assembled by the multilayer composite BP increase by 111.02% and 113.80%. In conclusion, the multilayer bipolar plate with a 'graphite-composites-graphite' structure is a promising polymer composite bipolar plate for the proton exchange membrane fuel cell (PEMFC). [Display omitted] In this study, a multilayer high-performance polybenzoxazine/expanded graphite composite bipolar plate with a 'graphite-composites-graphite' structure was prepared by compress molding. The highlights of our study are summarized as follow: • Multilayer polymer composite bipolar plates are developed by in-situ efficient forming. • The surface enrichment of polymer on polymer composite bipolar plate has been solve. • Composite bipolar plates possess excellent electrical performance and mechanical performance. [ABSTRACT FROM AUTHOR]

• The vibration suppression study of the plate structure based on the nonlinear piezoelectric shunt damping is proposed. • The modified Ritz method and complexification-averaging method are adopted to obtain dynamic responses of the system. • The effects of the negative capacitance and nonlinear capacitance on the vibration suppression performance are discussed. This paper proposes a nonlinear piezoelectric shunt damping circuit to mitigate the vibration of the plate structures subjected to the aerodynamic and harmonic excitations. The nonlinear piezoelectric shunt damping circuit consisting of the piezoelectric patch, inductor, resistor, negative capacitor and nonlinear capacitor is considered. Firstly, the governing equations of the electro-mechanical coupling nonlinear system are formulated based on the energy method and modified Ritz method. Furthermore, the complexification-averaging method combined with pseudo arc-length continuation method is adopted to analyze the steady-state response of the coupled system with aerodynamic and harmonic forces. A considerable number of numerical cases are performed to validate the proposed model and the time domain and frequency domain dynamic responses of the plate structures with and without control are further compared to validate the effectiveness of the proposed control strategy. Meanwhile, the energy transfer analysis between the plate structure and external piezoelectric shunt damping circuit is investigated. Finally, the effects of key parameters of the nonlinear piezoelectric shunt damping circuit including the negative capacitance and nonlinear capacitance on the vibration suppression performance of the piezoelectric shunt damping are discussed. [ABSTRACT FROM AUTHOR]

• A bottom-up multiscale model of graphene/PMMA composite is established from atomic scale to macroscopic structure. • The nano scale effects of finite-size graphene on the FG-GRC quadrilateral plate is considered via the multiscale analysis. • The efficiency parameters of graphene/PMMA composite are derived by the extended Halpin-Tsai micromechanics model. • The effects of geometrical parameter, graphene volume fraction and distribution are explored on the vibration behaviors. In this paper, a molecular dynamics (MD)-based multiscale analysis is employed to investigate the free vibration of graphene reinforced laminated composite plates from the atomic scale to the macroscopic behavior. The atomic models of graphene with different sizes, poly (methyl methacrylate) (PMMA) and graphene/PMMA composites with different graphene volume fractions are constructed, and Poisson's ratio as well as elastic moduli are in good agreements with the MD results. Then the efficiency parameters of the Young's and shear moduli of graphene/PMMA composites are derived at the micro scale via the extended Halpin-Tsai micromechanics model, and are employed subsequently to the vibration analysis at the macro scale. Based on the first order shear deformation theory and meshless method, the governing equation of functionally graded graphene reinforced composite (FG-GRC) quadrilateral plates is derived and discretized to analyze the vibration behavior. The effects of geometrical parameter, graphene volume fraction and distribution pattern are investigated on the dimensionless frequency of FG-GRC quadrilateral plates. The multiscale analysis in this paper combines the simulation of material properties at the atomic scale and the response of structure at the macro scale, which provides a feasible way to study the vibration behavior of composite structures. [ABSTRACT FROM AUTHOR]

• The elastothermodynamic damping model of the multi-layer microplate is established. • The generalized orthogonal function method is used to obtain the three-dimensional temperature field function. • The elastothermodynamic damping models under three boundary support conditions are established. Elastothermodynamic damping is one of the most important energy loss mechanisms in micro/nano mechanical resonators, which is related to the high sensitivity and high resonance frequency characteristics of resonators. With the wide application of resonators, multilayer microplate resonators have been applied. In this paper, the elastothermodynamic damping models of three-layer of Kirchhoff–Love microplate under three typical boundary support conditions of Clamped-Clamped-Clamped-Clamped (C-C-C-C), Clamped-Free-Clamped-Free (C-F-C-F) and Clamped-Free-Free-Free (C-F-F-F) are established. Firstly, the thermoelastic mechanical equations of the microplate are given, and then the three-dimensional temperature distribution functions of the microplate are obtained based on the generalized orthogonal function method. Finally, the elastothermodynamic damping models are established based on the composite multilayer plate theory. The model in this paper is compared with the previous model and the finite element results. [ABSTRACT FROM AUTHOR]

In this study, the bioinspired laminated composites with alternating soft Al layers and hard SiCp/Al were fabricated through the tape casting followed by pressure infiltration. In-situ bending and digital image correlation technology (DIC) analysis were carried out on the laminated composites. The results showed that the uniform layers of SiCp/Al and Al were obtained with the thickness of 30 μm and 10 μm, respectively. The interfaces between layers had an intimated combination. The bending deformation process of the laminated composites could be divided into three stages, i.e., crack initiation, crack stable diffusion and crack propagation instability. During deformation, the laminated structure changed the state of strain and strain distribution, further restricted the development of the crack, and the whole materials presented a stepped fracture. This study provides support for preparation and fracture process analysis of biomimetic layered composites prepared by tape casting. [ABSTRACT FROM AUTHOR]

• A semi-analytical model of variable stiffness plates with curvilinear fiber paths described by higher order polynomials is established. • The frequency veering and modal interaction of variable stiffness plates caused by curvilinear fiber paths are studied. • The variation rule of modal coupling vibration for variable stiffness plates at veering regions is analyzed. • The combined effects of material nonlinearity and modal interaction on variable stiffness plates are studied. The coupling forced vibration behaviors of a variable stiffness plate with curvilinear fiber paths at mode veering regions caused by variations of fiber angle have been rarely found in previous papers, especially in the presence of considering the complex material nonlinearity of composite materials. In this paper, the variable stiffness plate of carbon fiber reinforced composites (CFRC) with curvilinear fiber paths is taken as the research object, and the influence of curvilinear fiber paths on its natural characteristics and vibration responses are studied in detail on the basis of considering the material nonlinearity of CFRC. Firstly, it is found that the variations of curvilinear fiber paths can cause complex frequency veering behavior of the variable stiffness plate, and lead to the appearance of irregular modal shapes formed by modal interaction. Then, the forced vibration response of the variable stiffness plate in the frequency veering region is analyzed methodically, and the variation rules of the vibration response under modal interaction is obtained. After analyzing the nonlinear vibration response of the variable stiffness plate under the combined influence of modal interaction and CFRC material nonlinearity, the mechanism of complex nonlinear dynamic behavior of variable stiffness plate in frequency veering region is further investigated. [Display omitted] [ABSTRACT FROM AUTHOR]

High-strength steel (HSS) welded H-section beams are increasingly used in steel structures considering their advantage of high strength, but the stability is a concern especially near the supports, where the beams are prone to buckling under the combined actions of bending and shear. In this paper, finite element method was used to analyze the mechanical performance of HSS welded H-section beams under shear and bending-shear loads. A parametrical analysis for the H-section beams under pure shear loads was conducted, and a new shear buckling coefficient calculation method considering the interaction between plates was proposed. This coefficient was then applied to calculate the shear strength, and a design method for shear buckling strength based on the direct strength method (DSM) was proposed. Finally, a new bending-shear interaction curve was developed to predict the ultimate resistance of HSS welded H-section beams under bending-shear combination, and the reliability analysis results demonstrate the feasibility and safety of the design method proposed in this paper for HSS welded H-section beams. [Display omitted] • Calculation method for elastic shear buckling coefficient of H-section beams under shear. • The Direct Strength Method for high strength steel (HSS) welded H-section beams under shear. • A new bending-shear interaction curve for HSS welded H-section beams under bending-shear combination. • Reliability analysis of the new design proposals. [ABSTRACT FROM AUTHOR]

Nonlinear asymmetric bi-stable composite laminates, characterized by multistable nature and rich dynamics, have seen increased application potential recently. This has necessitated a detailed dynamical analysis of bistable laminates. In this manuscript, the nonlinear behaviour of asymmetric [ 0 n / 9 0 n ] bistable laminates with free–free boundary conditions is investigated through simulations and experimental observations. A refined 17 degrees of freedom (dofs) analytical model is developed, fusing Raleigh–Ritz with Hamilton's principle to obtain the governing nonlinear equations of motion. A nonlinear finite element (FE) model is also developed using ABAQUS®. Experiments are conducted by clamping the midpoint of the plate with a shaker and then exciting it. The composite laminate shows many intricate dynamics, such as sub-harmonic and super-harmonic oscillations, intra-well oscillation (periodic and chaotic), and inter-well snap-through (periodic and chaotic snap-through) prominently. The primary focus of this paper is to highlight the potential of bistable laminates by elucidating the existence of large-amplitude vibrations over a broad frequency range under different input and system parameters. Further, it has been observed that attached mass plays a significant role in modifying the response bandwidth for cross-well oscillation for a given excitation frequency and amplitude. Hence fine-tuning of masses can excite different nonlinear dynamic characteristics of the laminate, making it applicable in different engineering fields. • Analytical, numerical and experimental investigations on the dynamics of bistable asymmetric laminate. • Developed a 17 DoF analytical model and a nonlinear finite element model in ABAQUS. • Experiments are carried out to capture nonlinear behaviour at various excitation and system parameters. • Effect of key parameters, i.e., excitation frequency, excitation amplitude, and the inertial mass are studied. • Symmetric, asymmetric modes, intra-well-sub-harmonics & super harmonics and inter-well oscillations are captured and reported. [ABSTRACT FROM AUTHOR]

This paper proposes a study on the thermal buckling of Variable Angle Tow (VAT) composite plates using high-order theories. Here, the governing equations are derived via the principle of virtual work. Under the assumption of linear pre-buckling, the stability problem is reduced to a linear eigenvalue analysis considering proportional geometric stiffness. In contrast, a constant thermal load is assumed to be known along the plate thickness, and the uncoupled thermo-mechanical formulation is used, where the thermal effects are described as external loads. The plate is discretized using the Finite Element Method (FEM) and high-order theories are developed using the Carrera Unified Formulation (CUF). Using the CUF, the equations are expressed as an invariant of the plate theory approximation order. Therefore, Equivalent Single Layer (ESL) and Layer-Wise (LW) models can be easily implemented. Several geometries and lamination cases are considered for verification purposes, including different side-to-thickness ratios and fiber orientations, which result in various anisotropy effects. In addition, the effect of changing constraints and materials is evaluated. Particular attention is paid to the effect of the structural theory approximation on the evaluation of the thermal buckling load. It is shown that the correct evaluation is highly dependent on the edge-to-thickness ratio and on the anisotropy given by both the fiber orientation and the material properties. As a final remark, sensitivity analysis and best fiber angle solutions are discussed to highlight the importance of the LW modeling approach. [ABSTRACT FROM AUTHOR]

· Novel composite ABHs act as efficient trapped-energy resonators. · Highly-localized trapped modes drive strong scattering of composite ABHs in infinite plates. · Large impedance mismatch and intensified interaction between composite ABHs guarantee efficient vibration isolation. · Various lattice configurations achieve significant bandgap performance and expand vibration-damping regions. Drawing upon the advantages of lightweight nature and highly efficient energy harvesting capabilities, acoustic black holes (ABHs) serve as local resonator units with significant potential in constructing phononic plates. In this paper, we introduce a novel composite ABH structure made of different materials, and extends this composite concept to the infinite plate model. Analytical results reveal that the composite ABH exhibits a stronger local resonance effect and more localized trapped modes compared to traditional homogeneous types. By employing linear algebraic equation systems derived from boundary conditions and utilizing the closed-form solutions of the varying-thickness Kirchhoff plate, we compare the wave propagating behaviors of different ABH scatterers. Numerical results highlight that the enhanced trapped modes resulting from material inhomogeneity lead to more pronounced peaks in scattering energy. Moreover, we address the multiple scattering problem for composite ABH array in the infinite plate using the T -matrix relationship between the scattering and exciting energy. Displacement spectra and wave field results demonstrate that the larger impedance mismatch and increased interaction caused by periodic composite ABHs in the plate result in more effective vibration isolation. Our discussion on array configurations concludes that the ABH square array, incorporating both rows and columns, produces a significant bandgap for flexural vibration, while also expanding the larger and more efficient vibration-attenuated region. [Display omitted] [ABSTRACT FROM AUTHOR]

This paper establishes a geometrically nonlinear bending analysis framework using the deep energy method and the classical laminated plate theory (CLPT) for laminated plates. Inspired by the transfer learning technique, a load applied to a laminated plate can be divided into multiple load steps. The network parameters for the current load step, with the exception of the initial step, are initialized by inheriting values from their preceding steps. Including both von Kármán and Green-Lagrange strains, the plate strains are computed using the automatic differentiation and integrated along the thickness direction per laminate plate based on the constitutive theory. By combining the outputs of neural network, the external potential energy can be obtained, and the optimized network parameters are given by minimizing the total system potential energy of the laminated plate. In order to validate the proposed approach, several numerical examples are calculated, and the present solutions are compared with those given by the literature and the Finite Element Analysis (FEA). The results show that the proposed approach is indeed feasible, can reach high levels of precision under varying loads while offering a simplified calculation strategy. [ABSTRACT FROM AUTHOR]

• A shear-deformable beam model designed for the nonlinear buckling of beam-type structures with composite thin-walled cross-sections. • Angle-ply laminate composites are considered. • The large rotation effects and warping of the cross-section are taken into account. • The incremental equilibrium equations are developed using the virtual work principle and the updated Lagrangian formulation. • The transformation rule includes semitangential incremental rotations. This paper introduces an improved shear-deformable beam formulation for nonlinear buckling analysis of laminated composite beam-type structures with thin-walled cross-sections. Each wall of a cross-section is assumed to be a thin symmetric and balanced angle-ply laminate. The incremental equilibrium equations of a straight beam element are derived by applying the virtual work principle within the framework of updated Lagrangian formulation, Hooke's law and the nonlinear displacement field of a thin-walled cross-section, which takes into account restrained warping and large rotation effects. Incremental stress resultants are calculated by the Timoshenko–Ehrenfest beam theory for bending and the modified Vlasov theories for torsion. Shear coupling problems occurring at non-symmetric thin-walled cross-sections and arising from the shear forces-warping torsion moment couplings are considered. As a result, new shear-correction factors for a cross-section composed of thin angle-ply laminates are derived. Force recovering is performed according to the conventional procedure based on the concept of semitangential rotations. The shear-locking occurrence is prevented by applying the Hermitian cubic interpolation functions for deflections and twist rotation, and the associated quadratic functions for slopes and warping. The effectiveness of the proposed geometrically nonlinear shear-deformable beam formulation is validated through the test problems. [ABSTRACT FROM AUTHOR]

This paper aims to present novel exact solutions for the buckling of a laminated plate resting on the viscoelastic foundation with both normal and shear viscoelastic layers. The governing equations of plate buckling are derived using three-dimensional elasticity theory and state-space formulation. The normal and shear layers of the viscoelastic foundations are modeled using the generalized Maxwell model to represent both the elastic and viscose properties of the foundation. To couple the viscoelastic foundation equation with the buckling equation, Boltzmann's superposition principle along with the Laplace transform is utilized. Then, the effects of geometry, relaxation modulus of normal and shear layers, viscosity, and time are investigated on the buckling load. The results reveal that the higher viscosity coefficient leads to a slower rate of change in the buckling loads. In addition, the viscoelastic properties have a significant impact on the buckling behavior of the plate. In this regard, the results show that instead of the expected second mode at a constant aspect ratio, the plate experiences the first mode as time passes. The computed results also show that there is a critical threshold. When the foundation stiffness exceeds this threshold, the conventional method of reducing the aspect ratio to prevent buckling not only proves ineffective in reducing the probability of buckling but also, in fact, leads to an increase in buckling occurrences. In addition to the analytical investigation, a finite element (FE) analysis is carried out to study the buckling response of the composite plate. The finite element results also show a reasonably good agreement with those of the analytical method. • Exact solution for plate buckling on foundation with normal and shear layers. • The effects of viscoelastic spring and dashpot constants on buckling load is studied. • The buckling equations are derived by using the three-dimensional elasticity theory. • Boltzmann's principle and Laplace transform link viscoelastic foundation to buckling. [ABSTRACT FROM AUTHOR]

Fiber reinforced thermoplastic composites have many advantages, such as repeated molding, high toughness, durability and recyclability, which made them a potential substitute as engineering strengthening materials for thermosetting composites. However, their long-term performances under complex service environments are not well understood, hindering its durability design. In the present paper, glass fiber reinforced polypropylene (GFRPP) plate was studied on its mechanical property evaluation subjected to water immersion (distilled water) and bending (bending strains of 0.54 % and 1.04 %) at elevated temperatures (40 °C, 60 °C and 80 °C) up to 180 days. Water uptake, mechanical properties, thermal properties and microstructure tests were further carried out to reveal the effects of water uptake content, immersed temperature and bending loading level on the properties. The results showed the water absorption curve at three temperatures presents a two-stage diffusion behavior. After the longest immersion time of 180 days, the strength retention of plate at 40 °C, 60 °C and 80 °C were 88.2 %, 58.3 % and 31.8 % for tensile strength, 83.6 %, 67.8 % and 47.9 % for flexural strength and 70.6 %, 61.7 % and 41.4 % for in-plane shear strength. Higher immersion temperature accelerated the swelling effects of polypropylene. Higher bending loading levels accelerated the crack or defects formation and propagation in the resin as well as at the interface. When the strength retention rates were 50 %, the longest service life of plate exposed in service environment of Da Lian (T=9.2 °C) were 23.9 years (tensile strength), 12.8 years (flexural strength) and 3.0 years (in-plane shear strength) without the bending strain. Through comparing with thermosetting composites, glass fiber reinforced polypropylene has almost close or higher tensile strength retention rate and service life for certain service conditions. • The maximum water absorption and diffusion coefficient of composites were lower than epoxy or polyurethane based composites. • Higher immersion temperature accelerated the swelling effects of polypropylene. • Higher bending loading levels accelerated the crack or defects propagation in the resin as well as at the interface. • When the strength retention rates were 50 %, the longest service life of tensile strength were 23.9 years. [ABSTRACT FROM AUTHOR]

• Multi-domain features characterize different stages of damage. • VAE for dimensionality reduction and fusion of high-dimensional features. • The proposed semi-supervised model accurately predicts and quantifies damage. • Hyperparameter value functions improve the accuracy and robustness of the model. Accurate monitoring of the damage state of composite structures is crucial. However, uncertainties such as complicated dispersion processes make it difficult to monitor the damage state. In this paper, a semi-supervised model integrating variational auto-encoder (VAE) and Bayesian neural network (BNN) is proposed to predict the damage state. A high-dimensional damage feature set is constructed by extracting different features from Lamb wave signals, which are then fused and downscaled by the VAE model's hidden layer. To avoid overfitting, noise signals are added into the VAE hidden layer to generate diversity samples. Finally, the VAE hidden layer is fed into the BNN network to predict the damage state of the composite plate, and the model's uncertainty is measured with 95% confidence intervals. Experimental validation results on composite plate demonstrate that all experimental measurements fall within the 95% confidence interval, achieving accurate prediction of the damage state of the composite plate. [ABSTRACT FROM AUTHOR]

In this paper, a novel approach to evaluate the neutron shielding performance of multiphase neutron absorber reinforced aluminum matrix composites was proposed through the establishment of a direct relationship between equivalent B areal density (EBAD) of the composite and its thermal neutron shielding coefficient. It was found when the EBAD of the composite was 0.1105 g/cm2, the thermal neutron shielding coefficient will achieve 99%. Based on this proposed approach, (1% Gd+15% B 4 C)/6061Al composite plates were successfully fabricated using vacuum hot pressing method followed hot rolling. The results showed that when the EBAD of the composite was 0.1871 g/cm2, the thermal neutron shielding coefficient was above 99.9%, which was consistent with the theoretical calculation. The 5 mm-thick composite plate also had a good shielding effect on the Am-Be neutron source. Meanwhile the composite possessed a 380 MPa tensile strength as well as an elongation of 5% after hot rolling. In all, the (Gd + B 4 C)/6061Al composite designed in this paper showed better comprehensive performance compared with the literature's. The work of this paper has a great guiding significance for the design and preparation of neutron absorbing composites with high thermal neutron shielding performance as well as high strength and plasticity. Image 1 • EBAD was proposed to evaluate neutron shielding performance of composites. • The direct relationship between EBAD and thermal neutron shielding performance was established. • The idea of equivalent substitution for the design of composites with good performance is of great significance. • (1%Gd+15%B 4 C)/6061Al composite possessed good mechanical and neutron shielding properties. [ABSTRACT FROM AUTHOR]

Abstract The recent advancement in the manufacture and analysis of Carbon nanotubes (CNT) has persuaded many researchers to use them as the reinforcing phase of a polymer matrix. Nevertheless, it should be recalled that polymers show a viscoelastic behavior, so that their mechanical properties are functions of time due to the intrinsic nature of the material. In this paper, a Maxwell rheological model is employed to describe the time-dependency of the mechanical properties of the matrix in the framework of linear viscoelasticity. The viscoelastic matrix is enriched by both CNTs and oriented fibers to obtain the so-called three-phase composite materials. Such materials represent the main constituents of the plates investigated in this paper by means of the Reissner-Mindlin theory. The transient response, which is analyzed through the Newmark's scheme, is expressed in terms of central deflection and mechanical parameters for several configurations. The effect of the mass fraction of both reinforcing phases is discussed. The solutions are achieved numerically by means of a Finite Element (FE) code which implements the viscoelastic model and the proper homogenization technique in order to deal with three-phase composites. [ABSTRACT FROM AUTHOR]

Abstract The influence of flexural anisotropy or bend-twist coupling on the buckling performance of CFRP composite plates in compression and shear and thin-walled CFRP composite tubes in torsion is examined in this paper using the finite strip method of analysis. The finite strip formulation employed in the analysis procedure is readily able to deal with the many complexities associated with typical laminated composite construction. Lay-up configurations resulting in membrane anisotropy, flexural anisotropy and membrane-flexural coupling are all easily dealt with. The strip perturbation or buckling displacement fields are postulated to vary sinusoidally along the strip length and algebraicly across the strip width and any combination of linearly varying bi-axial tension or compression coupled with in-plane shear loading on the strip can be accommodated. The paper gives an in-depth understanding of the complex buckling mechanics associated with flexural anisotropy in polymer composite construction and highlights the importance of realising the significance of the applied in-plane shear or torque direction on buckling performance. Markedly different stability levels are shown to be in existence for the load cases of positive and negative shear in composite plates and for the clockwise and anticlockwise torsional loading of thin-walled composite tubes. This situation is, of course, not realised in isotropic metal construction or in orthotropic composite construction since such material systems are devoid of the effects of bend-twist coupling. Highlights • The behaviour of CFRP laminates with B-T coupling and in-plane shear is highlighted. • Different shear stability levels of CFRP plates are detailed for +ve and -ve shear. • Different torque stability levels of CFRP tubes are detailed for +ve and -ve torques. • Max interactive compression co-exists with a unique value of negative shear such that the buckling mode is devoid of shear distortion. • The maximum interactive compressive stability of a composite plate with coupling is greater than its stability in pure compression. [ABSTRACT FROM AUTHOR]

Abstract This paper presents in a unified and comparative manner, the formulation of two triangular plate bending composite elements, i.e. DKMT and MITC3 which are published in 1993 and 2004. Both elements have 3 nodes and 5 dof per node (three displacements and two rotations), taking into account transverse shear effects. There are valid for thin to thick composite plates, and give good results in classical benchmark and patch tests. The numerical results using DKMT element show the optimal and uniform convergence for thin and thick plates with an advantage for DKMT compare to MITC3 due to semi quadratic interpolation for the rotation variables The present paper contains new convergence analysis based on the s -norm tests for sandwich plates considering uniform and distorted meshes, and for symmetric and non symmetric composite plates with 3 and 9 layers. As the novelty and main contribution of this article, we propose the shear projection method in the element formulations to show the asymptotic equivalence of DKMT and the MITC3 for thick to thin composite plates. [ABSTRACT FROM AUTHOR]

• The effect of the bolt clearance, friction coefficient, joint type, and other parameters on the maximum bolt clamping force (Pmax) of the composite lapped joint is studied. • A 3D finite element model was built for the simulation of the single and double lapped bolted joint. • The model was validated by using previously published experimental results. • Using the composite plate between two steel plates (double lap), increases the clamping force capacity of the joint significantly. • It was recommended to use washer bolt hole clearance less than or equal to the composite plate bolt hole clearance. • Larger washer clearance can cause earlier damage due to bolt tightening pressure. Laminated glass is made by joining two or more glass layers together using a polymeric interlayer which can significantly minimize the risk of flying shards and dissipate a great deal of energy after the glass cracking stage. In this paper, tensile tests are conducted on three different polymeric films i.e., PVB, EVA, and SentryGlas (SG) at two different strain rates to characterize the mechanical properties of the interlayer. In addition, a static full-scale water chamber was used to study the effect of panel size on the characteristic failure and deflection of the laminated glass windows experimentally. However, due to the high risk and cost of explosion experiments, dynamic modeling of laminated glass window systems is presented in this paper using ANSYS AUTODYN. The accuracy of the dynamic model is verified with previously published experimental data. Material characterization tests showed that SG film has the highest strength, which appeared significantly also in the static panel test and numerical. In addition, the maximum reduction in panel static strength due to size increase was observed in panels with SG and PVB interlayers with a maximum reduction of 58%. However, SG showed a lower dynamic response under blast loads. [ABSTRACT FROM AUTHOR]

Beetle elytron plate (BEP), which is derived from the bionics of Trypoxylus dichotomus 's elytra, is a typical lightweight and high-strength structure with superior and comprehensive mechanical properties. To promote the engineering application of BEPs, this paper explores the vibration characteristics of foam-filled fiber composite BEPs. Through the finite element method (FEM), structural parameters such as the length-to-width ratio, core height-to-thickness ratio, skin thickness and foam density influence the natural frequency and mode. Furthermore, the influence pattern of parameters (such as boundary conditions and the number of stacked layers) toward the first two orders of natural frequencies and modes of the BEP were investigated under controlled total height and controlled single layer height. The results indicate that 1) the ranking of structural parameters on the 1st order frequency from a strong to weak sequence is as follows: length-to-width ratio, core height-to-thickness ratio, foam density and skin thickness; for the 2nd order natural frequency: length-to-width ratio, skin thickness, foam density and core height-to-thickness ratio. 2) Generally, an increase in the length-to-width ratio will reduce the frequency of the BEP, and increases in the core height-to-thickness ratio and skin thickness will raise its frequency. Additionally, foam filling plays a decisive role in local deformation. 3) When the total height of the sandwich plate is controlled, the improvement of the boundary conditions can effectively boost its 2nd-order frequency (approximately 200%), but the 1st-order frequency can be significantly increased (approximately 140%) only when all four sides are improved. 4) In the case of controlling the height of the single layer of the sandwich plate, its frequency gradually increases with the increase in the number of stacked layers. However, when the constraints are weak or there are few stacked layers, increasing the number of stacked layers can effectively boost the vibration frequency. This paper provides references and suggestions for the design and application of sandwich structures, enriching the research on the mechanical properties of BEPs and establishing groundwork for promoting BEPs in engineering practices. • The ranking of structural parameters on the 1st- and 2nd-order natural frequency was ascertained. • The parameter influence pattern of BEP's free vibration was investigated under two stacking ways. • The proposed stacking way of controlling the total height is more economical. • The results provide suggestions for the vibration design of sandwich plates. [ABSTRACT FROM AUTHOR]

This paper presents an innovative methodology employing the One-dimensional Convolutional Gated Recurrent Unit neural network (1D-CGRU) algorithm for the analysis of laminated composites using the Refined Zigzag theory (RZT). The RZT methodology is utilized to assess laminated plate structures and generate essential data, forming the basis for training the 1D-CGRU model. The synergistic application of RZT and 1D-CGRU demonstrates exceptional global–local accuracy in predicting the mechanical behavior of laminated composite plates. For efficient data generation, RZT not only provides high precision, but also exhibits computational efficiency, making it suitable for finite element simulations with a C0-continuous kinematic approximation. Additionally, the 1D-CGRU model integrates the strengths of a One-dimensional Convolutional Neural Network (1D-CNN) for spatial feature extraction and dimensionality reduction, coupled with a Gated Recurrent Unit (GRU) network for discerning temporal relationships and mapping them to the target domain. Furthermore, quantitative accuracy measurements, including Mean Squared Error (MSE), Root Mean Squared Error (RMSE), and Mean Absolute Error (MAE), are used to validate the superior performance of the 1D-CGRU model compared to other surrogate models. For angle-ply and cross-ply composite laminates, the 1D-CGRU model achieves remarkable accuracy (98.15% and 99.45%, respectively) with low RMSE values. These results highlight the potential of the proposed framework to enhance predictive analysis for laminated composite structures, offering valuable insights for engineering applications and design optimizations. [ABSTRACT FROM AUTHOR]

New types of laminated composites are continuously being developed to meet various requirements involved in engineering applications. Before mass production of these new composite materials can take place, it is necessary to identify their elastic properties. Although current identification methods based on vibration tests and optimization algorithms are highly accurate, their high computation cost is a drawback. To address this issue, this paper proposes a new method to identify orthotropic elastic properties of multi-layered composite plates. The proposed method is based on the Modal Stability Procedure, using the experimental vibration frequencies and corresponding numerical mode shapes of structures. It converges after only two or three iterations without requiring an optimization algorithm. Therefore, the computational cost of the proposed method is significantly lower than that of optimization-based methods. The effectiveness and robustness of this method are demonstrated through three examples with different material, stacking sequences, and geometries including curved plate. [ABSTRACT FROM AUTHOR]

• A semi-analytic method combining Chebyshev-Ritz is utilized to build the database. • An ANN model based on the genetic algorithm optimization (GA-ANN) is proposed to determine the delamination parameters. • Sensitivity analysis is taken into account by adding different levels of noise to the system and prediction errors are discussed. • Mapping between delamination parameters and vibration response is studied. • Effect of delamination length and position on natural frequency is investigated. Delamination is a frequent failure mode of laminated fiber-reinforced polymer (FRP) composites structure in aeronautical and other industries, leading to changes in vibration characteristics. Vibration-based techniques evaluate and compare the dynamic response between damaged and undamaged structures, and guarantee the non-destructive measurement with reliability and repeatability. Previous studies typically concentrate on using finite element method to obtain vibration characteristics and enhance the database for intelligent algorithms. This paper presents a semi-analytical result using the Chebyshev−Ritz method to expand delamination prediction. Vibration frequency serves as a global damage indicator, and multi-order frequency characteristics are utilized to identify the delamination length and location of FRP composite plates. A database of natural frequencies corresponding to damage parameters for FRP laminated plates is generated based on the established model using the region approach. An intelligent approach, known as a genetic algorithm optimization-based back-propagation (GA-BP) artificial neural network, is utilized for system identification. The network model is subjected to a sensitivity analysis, where artificial noise is added to vibration frequency to distinguish between the actual structure and the numerical model. The results indicate that the GA-BP algorithm shows good accuracy and stable performance against the standard neural networks for delamination analysis. [ABSTRACT FROM AUTHOR]

• A unified electromechanical dynamic model for moving composite laminated plates with piezoelectric shunt damping circuits (PSDC) is developed. • An electric-mechanical coupling based vibration control method is developed. • The relationship between the optimal circuit parameters and the moving speed are investigated. This paper presents a modified variational modeling method and develops an electro-mechanical coupling based vibration control method for moving composite plate structures. Unlike the stationary structures, movement will introduce new challenges for both vibration analysis and control of the laminated plate. Based on the modified variational method, electromechanically coupled dynamic models for the moving plate with piezoelectric patches and control circuits are developed. To release limitations to the admissible functions, modified variational principles are derived for the interface and boundary constraints in both directions of the moving plate. On the basis of first-order shear deformation theory (FSDT), the energy functional expressions of the axially moving laminated plates are formulated and the governing equations are obtained. To suppress the vibration, a piezoelectric shunt damping circuit (PSDC) with negative capacitance is proposed and the control circuit parameters are optimized using the differential evolution (DE) algorithm. Through numerous numerical examples, the high accuracy, good efficiency, and flexibility in constructing admissible functions of the proposed modeling method are demonstrated. The developed PSDC possesses much better vibration suppression properties for the moving laminated plates than the series R-L PSDC. Effects of the moving speed and negative capacitance on the optimal circuit parameters are also examined. The appropriate values of the negative capacitance are shown to be near the capacitance of the patches. [ABSTRACT FROM AUTHOR]

In this paper, the effective elastic behavior of three-layer quasicrystal composite plates are forecasted. Firstly, effective properties of the first and third layers quasicrystal composite plates containing ellipsoidal inclusions are obtained according to the Mori-Tanaka model. Secondly, the three-layer composite plates effective behavior parameters are computed by employing the general matrix approach. The numerical examples reveal the influence of the inclusions geometry and volume fraction on the three-layer quasicrystal composite plates effective behavior parameters. The findings indicate that changing the elastic constants of the phason field and phonon-phason coupling field of inclusions will affect the effective behavior parameters of the three-layer quasicrystal composite plates. The increase in layers to some extent reduces the effective behavioral parameters. [ABSTRACT FROM AUTHOR]

Guided wave propagation (GWP) is commonly employed for the design of SHM systems. However, GWP is sensitive to variations in the material properties, often leading to false alarms. To address this issue, uncertainty quantification (UQ) is employed to improve the reliability of the predictions. Computational structural mechanics is a useful tool for the simulation of GWP. Even so, the application of UQ methods requires numerous solutions, while large-scale, transient GWP simulations increase the computational cost. In this paper, we propose a machine learning (ML)-based reduced order model (ROM), annotated as BO-ML-ROM , to decrease the computational time of the GWP simulation. The ROM is integrated with a Bayesian optimization (BO) framework to adaptively sample the data for the ROM training. The results showed that BO outperforms one-shot sampling methods, both in terms of accuracy and speed. The developed ROM, which is orders of magnitude faster than the original solver, is then applied for forward uncertainty quantification of the GWP in an aluminum plate and a composite panel under varying material properties. The UQ analysis reveals the higher impact of the uncertainties in the wave reflections. Furthermore, to compute the influence of the material properties on the predictions, a sensitivity analysis (SA) is performed using the variance-based Sobol' indices and the Shapley additive explanations, where it is shown that the uncertainties in the elastic properties have a varying influence across time. The predicted results reveal the efficiency of BO-ML-ROM for the simulation of the GWP and demonstrate its utility for UQ and SA. [ABSTRACT FROM AUTHOR]

Laminated metal composites have become a key strategy for the design and manufacture of metal parts with multiple combinations of excellent properties. This paper utilizes the differences in mechanical properties and recrystallization behavior of component metals to prepare a novel 316 L/(316 L-2.5 wt%Gd)/316 L neutron shielding laminated metal composites (LMCs) through composite rolling and solution treatment processes. LMCs have an excellent combination of properties: high strength (tensile strength: 571.36 MPa), sufficient tensile ductility (fracture elongation: 60 %) and high neutron shielding properties (thermal neutron shielding rate: > 90 %). Specifically, compared to the non-composite 316 L-2.5 wt%Gd neutron shielding material, the strength of the hot-rolled LMCs has increased by 2.0 times, and the elongation at fracture has improved by 3.3 times. After solid solution treatment, the elongation of LMCs is further increased, which is 6 times higher than non-composite 316 L-2.5 wt%Gd neutron shielding materials. The specially designed soft-hard matched 316 L/(316 L-2.5 wt%Gd) heterogeneous interfaces achieved good metallurgical bonding, with significant differences in grain sizes and strains. The main reasons for the enhanced strength and plasticity of LMCs are the geometric constraints caused by the layered structure composed of ductile and brittle metallic components, as well as the back-stress strengthening and strain hardening induced by deformation incompatibility at the heterogeneous interface. • 316 L/(316 L-2.5 wt%Gd) heterogeneous interfaces with different grain sizes and obvious differences in strains were constructed. • Heterogeneous structure and interfacial constraints synergistically enhance the strength and plasticity of 316 L/(316 L-2.5 wt%Gd)/316 L laminated composites. • Provides a promising solution to the difficult problem of mutual constraints between neutron shielding properties and mechanical properties. [ABSTRACT FROM AUTHOR]

Although various two-dimensional (2D) theories have been developed for analysis of laminated shell structures in the last two decades, most of these models are not efficient. There are many 2D laminate theories that yield quasi three-dimensional (3D) results, but they are computationally expensive due to the high number of variables required for defining their displacement fields. Developing efficient shell theories that consider the compromise between accuracy and the computational cost is a key issue. In this paper, an efficient laminate shell theory is developed that has only seven displacement field variables. Displacement fields of the laminated shell are obtained based on the global-local (GL) double superposition concept. A quadrilateral shell element with eight nodes is formulated for solving the dynamic equations of motion. The accuracy of the proposed shell theory and developed finite element (FE) formulation has been evaluated through free vibration analysis of various cross-ply, angle-ply, and soft-core sandwich shells. Results show that vibrating behaviors of laminated shells with different ranges of length-to-thickness and curvature ratios can be accurately predicted by using the presented shell theory. • A new shear deformation theory is proposed for free vibration analysis of laminated shells. • The proposed shell formulation is constructed based on the concept of double superposition theory. • Dynamic equations of motion are solved using an eight-node quadrilateral shell element. • The proposed shell theory can accurately predict natural frequencies of laminated shells. • The proposed shell finite element model is computationally low cost. [ABSTRACT FROM AUTHOR]

The paper presents a numerical-analytical method developed to determine the stresses formed in composite plates near the tips of curved cracks by means of the Williams series. The coefficients of the terms of the Williams series and T-stresses have been calculated based on the derivatives of the displacement discontinuity of the crack edges. It has been shown that the calculations can be simplified implementing the Green's solutions by the Lekhnitskii method. The numerical algorithms based on Lobatto quadrature formulas have been used to solve the singular equations and determine both the coefficients the Williams power series and T -stresses. The proposed approach has been used to analyze rectilinear and curvilinear cracks in composite plates. In addition, the Green's solutions have been implemented to investigate the cracks located in a half-plane, near an elliptical hole, in rectangular plates, and in strip. One- and two-period problems have been considered for plates with cracks in the present calculations. The high accuracy of the performed calculations of the stresses near the crack tips in composite plates using elementary formulas contained by the Williams series has been confirmed on the test examples. • The article has been revised taking into account the comments of the editor, who recommended reducing the scope of the article. At the same time, it was necessary to supplement this article according to your comments. Therefore, part of the results was removed from the previous version of the article. • In the work, the research was performed using the Lekhnitskyi method. The basic equations in this method are valid simultaneously for the general case of anisotropy and orthotropic materials. Therefore, the solutions obtained in the work can be used for materials with general anisotropy (and not only orthotropic ones). In the revised version of the article, examples of calculation of SIF and T-stresses for a material with general anisotropy have been added. • In the revised version of the article, the review of the literature on the topic of the article has been expanded. It follows that a significant number of scientific works have been devoted to the development of refined methods for obtaining stresses near the tips of cracks based on Williams series, which indicates the actuation of the topic. • The developed methods apply to materials with general anisotropy (and not only orthotropic ones), which is illustrated in the revised version of the article. • In the literature, the Somigliana representation, from which hypersingular integral equations are obtained, is mainly used to study stresses near cracks. • Singular integral equations are more widely used to calculate stresses near cracks in isotropic plates (this is indicated in the authors' article). Such equations are easier to solve numerically. Effective methods of controlling the accuracy of calculations have been developed for them. • For anisotropic materials, such singular equations are used only in a few works, in particular in the authors' articles. Even fewer such studies were performed with the additional use of Green's functions. Therefore, we do not agree with the reviewer's statement that such methods are well known. • Singular integral equations are used in this article primarily because they are based on it is easier to determine T-stresses and coefficients for terms in the Williams series. [ABSTRACT FROM AUTHOR]

For the pursuit of lightweight structures with excellent mechanical performance, sandwich structures with lightweight cores and strengthened face sheets have become popular in the advanced engineering fields in recent years. In this paper, the nonlinear static and dynamic responses of the sandwich plate constructed with the aluminum pyramidal lattice core and functionally graded graphene platelets reinforced composite (FG-GPLRC) face layers are analyzed. The partial differential equations of the pyramidal lattice sandwich plate considering the geometric nonlinearity are achieved based on the Reddy's third order shear deformation theory (TSDT), which are solved by the combination of finite element model, Raphson's method and Newmark numerical integration method. Four different types of the impact loads including the step loading, triangular loading, half-sine loading and exponential loading with the same peak value and duration time are investigated. The influences of the thickness-to-truss radium ratio and the angle of the truss core, as well as the weight fraction and distribution patterns of graphene platelets (GPLs) over the face sheets under different impact loads and different boundary conditions are analyzed. According to the numerical results, it is concluded that the sandwich plate with higher weight fraction of GPLs, lower thickness-to-truss radium ratio, and higher angle of the truss core can exhibit better performance in both static and dynamic loading conditions. The FG-X distribution of GPLs presents the best dynamic performance as compared to the other GPL distributions. The combination of lightweight truss core with the advanced GPLRC face sheets is instructive for potential applications and further research. • A pyramidal lattice sandwich plate subjected to blast loadings is described theoretically. • Static and dynamic behaviors of the sandwich plate are both investigated. • Sandwich plate with functionally graded graphene platelets reinforced faces is considered. • Four different impact loadings with the same peak value and duration time are discussed. • Effects of distribution parameters of lattice core and GPLs in face sheets are examined. [ABSTRACT FROM AUTHOR]