Composite Plates Research Articles

Aspect ratio-dependent volume resistivity in unidirectional composites: Insights from electrical conduction behavior

The electrical properties of carbon fibers serve as the foundation for the multifunctional applications of carbon fiber-reinforced composite structures. In scenarios that exploit the electrical characteristics of materials, accurate estimation of electrical resistivity stands as a critical factor. This study endeavors to elucidate the electrical conduction behaviors in unidirectional composites with different fiber orientation angles (0°, 15°, 30°, 45°, 60°, 75°, and 90°) and aspect ratios, thereby deriving the volume resistivity within an arbitrary Cartesian coordinate system. Employing thermal infrared imaging technology and finite element analysis, we identified distinctive electrical conduction behaviors associated with aspect ratios in carbon fiber composite plates. Notably, a critical aspect ratio exists wherein the diagonal yarn is the only conductive path between two electrodes. Below this critical threshold, no direct conductive path exists, and current flows through the shortest distance between parallel yarns. Conversely, beyond the critical aspect ratio value, multiple yarns form conductive paths between the two electrodes. Based on the electrical conduction behavior of unidirectional composites under different angles and aspect ratios, the volume resistivity with finite boundaries was derived and examined under an arbitrary Cartesian coordinate basis.

Numerical Analysis of SiC and UHMWPE Composite Ballistic Plates against 0.5 Caliber BMG Projectile

The aim of this study was to determine the optimal configuration of silicon carbide-ultrahigh molecular weight polyethylene (SiC-UHMWPE) plates to effectively withstand 0.5 caliber Browning Machine Gun (BMG) projectiles. Six composite plates with varying thicknesses were 3D modeled and assessed for ballistic resistance using finite element analysis in Ansys Explicit Dynamics simulation software. These plates were subjected to high-velocity impacts at 930 m/s using 7.62 mm projectiles. The findings revealed that an 11 mm SiC/80 mm UHMWPE plate provided comparable bullet-stopping performance to a standard 8 mm steel 4340/60 mm UHMWPE plate, but with a significantly lower areal density. The primary mode of failure observed in penetrated samples was petaling, consistent with known behaviors of composite armor under high-impact conditions.

Stress transfer paths and damage modes of layered coal-rock mass under static loading

In order to explore the distribution characteristics of nonlinear mechanical behavior and the tendency of damage and failure of deep in situ coal-rock mass, a layered composite thin plate coal-rock mass model is established based on thin plate theory and finite element method. The continuity of interlayer stress and displacement is maintained by transfer matrix function, and the maximum shear stress is calculated by Mohr-Coulomb strength criterion. The distribution characteristics of stress, displacement, energy and maximum shear stress of coal-rock mass under static load are obtained. The analysis results are as follows : ① The torsional stress concentration areas of τxz and τyz are formed on the boundary of coal-rock interface, and the principal stress concentration areas of σx, σy and σz are formed in the center and center of the boundary, and the shear stress distribution of τxy is formed on the diagonal line. ② The maximum shear stress of the long axis has a strengthening effect on the shear failure, and each layer forms a stress state of alternating tension-shear-compression-shear. It first destroys in the middle of the coal-rock interface and boundary, and then destroys along the long side and short side. ③ The coal-rock mass presents a ′ X ′ -type shear zone along the radial and axial. The shear failure occurs first, followed by the principal stress compression failure. The cracks are preferentially developed in the direction perpendicular to the minimum principal stress, and the stepped ′ V ′ -shaped failure characteristics are formed under the action of shear and tensile stress.

Numerical Study of Ballistic Performance in Level III SiC Ceramic Multilayered UHMWPE Ballistic Plates

This study investigates the ballistic resistance of composite plates composed of a silicon carbide (SiC) strike face and ultra-high molecular weight polyethylene (UHMWPE) layers against 7.62 mm NATO caliber projectiles using Ansys Explicit Dynamics. Five ballistic plate samples were numerically modeled, featuring 40 to 60 UHMWPE layers and a 4 mm SiC strike face. The simulation assessed the plates' response, including backface signature, bullet penetration depth, absorbed kinetic energy, and deformation mechanisms. The findings revealed that increasing the UHMWPE thickness reduces both the backface signature and bullet penetration depth. Plates with 50 to 60 layers of UHMWPE met level III NIJ standards, demonstrating lower backface signatures and bullet penetration compared to those with 40 or 45 layers. Thicker UHMWPE layers were associated with reduced deformation, with the plate featuring 60 layers of UHMWPE and an overall thickness of 25 mm emerging as the optimal configuration for level III ballistic protection.

Free vibration and transient response of initially compressed CNT-reinforced composite plates

This paper investigates the linear free vibration and nonlinear transient response of carbon nanotube (CNT)-reinforced composite plates subjected to pre-existent compressive load in thermal environments. CNTs are reinforced into matrix according to uniform and functionally graded distributions. The properties of constitutive materials are assumed to be temperature-dependent while the effective properties of nanocomposite are determined using an extended rule of mixture. Governing equations are established within the framework of classical plate theory incorporating von Kármán nonlinearity and initial geometrical imperfection. Analytical solutions of deflection and stress function are assumed to satisfy simply supported boundary conditions, and Galerkin method is applied to obtain a time differential equation including both quadratic and cubic nonlinear terms. Fourth-order Runge–Kutta numerical integration scheme is employed to determine dynamical deflection-time response of nanocomposite plates. Numerical analyses are presented to consider the influences of CNT volume fraction, CNT distribution, initial compressive load, geometrical imperfection, elevated temperature and plate geometry on the natural frequencies and nonlinear dynamical response of nanocomposite plates. The study reveals that the natural frequency and dynamical deflection are strongly decreased and increased when initial compressive load is increased, respectively. Numerical results also find that the natural frequencies are enhanced and dynamical deflection is dropped as a result of increase in volume percentage of CNTs, respectively.

A new nothospecies of Prosthechea (Orchidaceae: Laeliinae) from the Diamantina Plateau, Minas Gerais, Brazil

Based on morphological evidence found in some specimens recently collected in the Diamantina Plateau region, Minas Gerais State, Brazil, a new natural hybrid between Prosthechea calamaria and P. faresiana is described and illustrated as P. ×riopretensis. Both putative parental species are known for the region and their flowering period overlaps. The new nothospecies carries most of the morphological features of P. calamaria, such as short plants (≤ 19 cm height) and inflorescences (≤ 7 cm long), and flowers with a small ovate lip (≤ 1 cm long), but the floral color pattern are remarkably like P. faresiana – sepals and petals covered by longitudinal vinaceous stripes. In addition to a digital composite plate of the taxonomic novelty, further images and a distribution map of the new nothospecies and its putative parents are provided, as well as notes on morphology, phenology, and ecology.

On the role of temperature in the response of air-backed composites to hydrodynamic loading: An experimental study

Understanding the role of temperature in the dynamic response of composite plates is critical for naval systems operating in extreme environments like the Arctic. Despite the advantages of composite materials in improving corrosion resistance and enabling the customization of material properties to their environment, their behavior at cold temperature, especially under dynamic loading, remains elusive. This research gap hinders the effective use of composite materials in extreme environments. Here, we study the dynamic response of air-backed fiberglass epoxy plates under hydrodynamic loading at room temperature and 4∘C. By employing digital image correlation and particle image velocimetry, we investigated the interplay between fluid–structure interactions and cold temperatures. Our findings reveal the critical role of temperature in shaping the dynamic response of air-backed composites through changes in the stiffness and damping properties. At cold temperature, the plate experiences a larger (smaller) deformation in the initial (latter) phase of the dynamic response. Furthermore, we observed a pronounced coupling between the structural response and the flow physics, with peaks of the hydrodynamic loading synchronized with the peak deflections. Our results underscore the importance of considering temperature in the design of naval systems for extreme environments, providing key insights into fluid–structure interactions at cold temperature.

Effect mechanism of low-velocity impact loading rate on the failure modes transition of steel-UHPC-steel composite plates

This study delved into the transition mechanism of loading rate on the failure mode transition in steel-ultra-high performance concrete-steel (SUHPCS) composite plates under concentrated low-velocity impact loads. A series of drop-weight tests elucidated that, as impact velocity escalated, the composite plate shifts from local punching failure, characterized by circumferential cracks, to overall flexural failure, marked by radial cracks resembling yield lines. Given the constraints in capturing strain data in drop-weight test, a 3D nonlinear structural analysis using Abaqus software was conducted. This numerical simulation method was validated by drop-weight test results in terms of crack patterns and impact force time histories. Moreover, structural dynamic punching and flexural loads at a specific loading rate were obtained with the assistance of the dynamic increase factor (DIF). Failure mode could be judged through comparison between the two critical loads. The discrepancy in strain sensitivity exhibited by steel plates and UHPC accounted for the transition in failure modes of the SUHPCS composite plates. DIFs for UHPC compressive strength and steel plate strength were lower than DIF for UHPC tensile strength, as these factors were around 1.5, 1.7 and 2.6, respectively. Parameter analysis showed that the critical transition impact velocity for a composite plate with a core thickness of 80 mm was 11 m/s, surpassing the 13 m/s threshold for a composite plate with a 100 mm-thick core. Moreover, changes in DIFs of UHPC and steel strengths were less than 2 % with various impact masses and the composite plate maintained the same failure mode.

Study on the Flexural Performance of Ultrahigh-Performance Concrete-Normal Concrete Composite Slabs.

In recent years, there have been an increasing number of examples of using ultrahigh-performance concrete (UHPC) as a pavement layer to form an ultrahigh-performance concrete-normal concrete (UHPC-NC) composite structure to improve the bearing capacity of bridges. In order to study the flexural performance of this kind of structure, this research studied the flexural performance of UHPC-NC composite slabs, with UHPC in the compression zone, using experiments, numerical simulation, and theoretical analysis. The results showed the following. Firstly, after the UHPC-NC interface had been chiseled, there was no obvious slip between the two materials during the test, and the composite plate was always subjected to synergistic stress. Secondly, the composite slabs in the compression zone of the UHPC were all subjected to bending failure, and the cooperative working performance of each part under the bending load was good, indicating that the composite slab had a unique failure mode and a high bearing capacity. Thirdly, increasing the thickness of the UHPC significantly improved the flexural capacity of the composite plate, and the maximum increase was about 15%. Increasing the reinforcement ratio of the tensile steel rebars also had an increasing effect, with a maximum increase of about 181%. Finally, the proposed formula for calculating the flexural capacity of composite slabs with UHPC in the compression zone could accurately predict the bearing capacity of said slabs. The calculated results were in good agreement with the experimental values, and the error was small.

Fumed silica additives enables tunable wettability of the resin for improved composite bipolar plate

Composite bipolar plates (CBP) composed of resin and conductive filler are critical components in proton exchange membrane fuel cell (PEMFC) for achieving mechanical strength and electrical conductivity. The conductive filler entirely enveloped by resin is of significance for the flexibility of the CBP; while connected resin blocks the continued conductive channels and thus weakens the electrical properties of CBP. Herein, we propose a trade-off method between flexibility and conductivity of the CBP by wettability regulations of the resin, in which fumed silica additives are introduced into epoxy as composite adhesives. The abundant hydrogen bonds are demonstrated to be well-formed between epoxy and fumed silica for decreasing surface free energy (SFE) between resin and graphite. As a result, the composite adhesive with 2 % fumed silica delivers moderate wettability enabling much improved CBP, which exhibits high electrical conductivity of 233.33 S cm−1 as well as flexural strength of 66.4 MPa. Moreover, the CBP also delivers improved areal specific resistance (5.34 mΩ cm2), thermal conductivity (10.58 W (m K)−1), and corrosion behaviors (0.0701 A cm−2) which guarantee the operation of the PEMFC. This work provides new insight from the wettability regulation of resins for improved CBP, which is an easy-operating method and has great potential for application in practical CBP fabrication.

Periodic free vibrations of composite laminates with curvilinear fibres and CNTs

This article addresses the combined effect of using curvilinear fibres and carbon nanotubes (CNTs) reinforcements in the non-linear modes of vibration of laminated composite plates. To arrive at the material properties of the three-phase composite material, a two-step hierarchic procedure is followed. A modified version of the Halpin–Tsai model is employed to predict the Young’s modulus of the CNT enriched resin and expressions, deduced from equilibria of a unit cell where a fibre is embedded in resin, are applied to obtain the diverse elasticity moduli of the three-phase composite. Moderately large displacements are considered, with von Kármán strain–displacement relations. Although the presented model is an equivalent single layer one, it applies to thick plates, because a Third-order Shear Deformation Theory (TSDT) is followed. The set of autonomous non-linear equations of motion is reduced using static condensation and a modal basis with selected modes, chosen after a convergence analysis. The reduced set of equations of motion is solved by the shooting method. Numerical tests considering plates with diverse curvilinear fibre paths, CNT contents and thicknesses are carried out. The results obtained are thoroughly analysed.

Experimental and numerical investigation of the modal parameters for thin laminated composite plates

In the present work, glass fiber-reinforced (GFR) composite specimens were fabricated using the vacuum-bag molding process. The properties related to the vibrational response of the fabricated composite plates, such as natural frequency, modal density, and damping loss factor (DLF), were investigated through both experimental and numerical approaches. The effects of different parameters, including boundary conditions (BCs), fiber orientations, laminate layer numbers, and aspect ratios, were comprehensively studied. It was found that the experimental and numerical results were in close agreement. For each case, finite element analysis was performed to determine the natural frequencies and mode shapes. Regarding the various BCs, the DLF was observed to be highest (0.47) for fully clamped BC and lowest (0.12) for free-free BC, whereas the modal density was highest (0.068) for cantilever BC and lowest (0.037) for fully clamped BC. In terms of different lamination schemes, the DLF was highest (0.42) for a plate with quasi-isotropic fibers and lowest (0.25) for a plate with unidirectional fibers, while the modal density was highest (0.068) for quasi-isotropic fibers and lowest (0.047) for unidirectional fibers. Regarding the plates with different laminate layers, the highest DLF (0.47) was observed for a plate with 16 layers, while the lowest DLF (0.33) was found in a plate with 8 layers. Conversely, the highest modal density (0.067) was observed for a plate with 8 layers, and the lowest (0.057) was noted for a plate with 16 layers. Lastly, considering aspect ratios, the highest DLF (0.48) was observed for an aspect ratio of 0.5, and the lowest (0.26) for an aspect ratio of 1.5. The highest modal density (0.09) was also observed for an aspect ratio of 0.5, while the lowest modal density (0.045) was for an aspect ratio of 1.5.

Effect of Process Conditions on the Microstructure and Properties of Supercritical Ni-GQDs Plating.

The Ni-GQDs composite plating was created using direct current (DC), single-pulse, and double-pulse power supplies, with GQDs serving as additives under supercritical CO2 conditions. A comparative analysis was conducted to evaluate the effects of different electrodeposition power sources on the microstructure and properties of the Ni-GQDs composite plating. High-Resolution Transmission Electron Microscopy (HRTEM) was employed to investigate the distribution of GQDs within the composite plating as well as to analyze d-spacing and diffraction patterns. Scanning Electron Microscopy (SEM) was utilized to illustrate the surface morphology of the plating and assess its surface quality. The grain size and preferred orientation of the plated layer were examined using X-ray Diffraction (XRD), while Atomic Force Microscopy (AFM) was used to evaluate the roughness of the surface. To compare the abrasion resistance of the various plating types, wear amounts and friction coefficients were measured through friction and wear tests. Additionally, corrosion resistance tests were performed to assess the corrosion resistance of each plating variant. The results indicate that the Ni-GQDs-III composite layers produced via double-pulse electrodeposition exhibit superior surface quality, characterized by smaller grain sizes, enhanced surface flatness, reduced surface roughness, and improved resistance to wear and corrosion.

A New Process for Efficient Non-Destructive Metal-Activated Composite Plating of Ni-P-Al2O3 on Titanium Base and Its Performance Research

A new high efficient and non-destructive mental activation process of electroless composite plating was proposed. The process utilized electromagnetic induction equipment to heat the titanium alloy substrate and used its energy to complete the activation process, which could successfully attach the nickel nanoparticles firmly to the surface of the titanium alloy; at the same time, the process pre-activated Al2O3 nanoparticles and added the activated nanoparticles to the plating solution. In the process of plating, the activated titanium substrate was used as the catalytic center of electroless nickel plating (ENP) for electroless composite plating. The new activation process avoided complicated traditional processes such as acid etching and zinc dipping. Such traditional processes require huge doses of chemicals, including various strong acids, so improper waste liquid treatment will cause harm to the environment. The important parameters of the process were optimized by orthogonal experiments. A scanning electron microscope (SEM), an X-ray photoelectron spectroscopy (XPS), an energy dispersive spectrometer (EDS), thermal shock experiments and friction and wear experiments were used to characterize and analyze the surface morphology, composition, binding force and friction coefficient of the coating, and analyze the coating quality by measuring the plating rate and the thickness of the coating. The results showed that the rate of electroless composite plating increased with the increase in Al2O3 nanoparticle concentration. When the concentration of Al2O3 nanoparticles reached 1.5 g/L, the ENP rate decreased with the increase in Al2O3 nanoparticle concentration. The adhesion of the sample was evaluated by the scratch test, which showed that the binding grade of the sample was 0, and the Vickers hardness was 688.5 HV. Results showed that the coating produced by this new process has excellent performance. Therefore, the process is an environmentally friendly and fast activation composite plating process.

Numerical study of composite structures behavior under ballistic impacts

The aim of this paper is to introduce a finite element study of the behavior of composite plates subjected to ballistic impacts. The work studies different configurations of laminated composite structures, with and without reinforcements, subjected to high-speed projectile impacts (400-1000 m/s). The investigation focuses on the response of different composite materials' stacking sequences, as well as the impact of epoxy carbon reinforced with carbon nanotubes and the behavior of hybrid sandwich structures made of Kevlar epoxy and glass epoxy. The purpose is to develop a strategy of composite material damage modelling, identify the effects of multi material hybridization, and the influence of reinforcement by carbon nanotubes, on the structures' resistance to ballistic impacts. Numerical simulation provides a detailed description of plate damage. Results show that composite plates with 2% carbon nanotubes (CNT) displays a better impact energy absorption compared to 1% CNT and plates without CNT. The study also revealed the hybridization sequences offering the greatest energy absorption.

Free Vibration of Composite Rectangular Plates with Internal Crack

In this work, rectangular sheets of composite materials consisting of epoxy with a single layer of fiberglass were studied with the internal crack at angles (0°, 90°) with the x-axis in the presence of nanomaterial TiO2 in proportions (1 wt%, 2 wt%, and 3 wt%), the study was experimental and numerical using the ANSYS. The sample mold was made from plastic using a CNC machine. One case was studied in both the experimental and numerical parts, which is clamped-clamped-free-free (CC-FF). After conducting the test, it was found that the crack negatively affects the rectangular composite plate, as it reduces the value of the natural frequency and increases the value of damping. However, in the case of adding the nanomaterial, it was found that the natural frequency increases with the increase in the percentage of nanomaterials, and the maximum value of the natural frequency was at 3% because it works to increase hardness rectangular plate stiffens and reduces damping. The error rate between the experimental and numerical parts did not exceed (9.717%).

Research on the bonding performance and mechanism of hot-rolled Ti/steel clad plates based on surface state

The interfacial bonding strength of Ti/steel clad plates is a crucial factor that affects their application. However, the effect of the surface state, which is a significant determinant, is often neglected. In this study, various surface treatment processes were employed to create different surface states based on the hot-rolling of double-layer steel billets, and the effects and mechanisms of these surface states on the bonding performance of hot-rolled Ti/steel clad plates were systematically examined. The results showed that the Ti/steel clad plates pretreated with a louver wheel exhibited the highest bonding performance, with the average bonding strength peaking at 328.67 MPa and stabilising at approximately 300 MPa. This strength was approximately 50 % greater than that achieved with wire brush treatment and significantly surpassed the results obtained with sanding belts and diamond grinding discs. The analysis of the surface properties and microstructural characteristics revealed that various surface treatments led to different levels of work hardening and lattice distortion at the surface, and the interface bonding strength depended on the degree of matching between these factors. Proper surface hardening can promote the transformation of lattice distortion energy into a diffusion-driving force of elements on both sides of the interface during rolling, enabling sufficient diffusion of elements on both sides of the interface and obtaining good interface bonding performance. A phenomenological prediction mechanism-based model was established to quantify the relationship between the surface state and the bonding strength. This study elucidats the mechanism by which the surface state of materials influences the interfacial bonding performance of hot-rolled Ti/steel clad plates. These findings have significant implications for enhancing the interfacial properties of these composite plates and for selecting suitable pre-rolling surface treatment processes.

New analytical model for multi-layered composite plates with imperfect interfaces under thermomechanical loading

AbstractA new analytical model for thermoelastic responses of a multi-layered composite plate with imperfect interfaces is developed. The composite plate contains an arbitrary number of layers of dissimilar materials and is subjected to general mechanical loads (both distributed internally and applied on edges for each layer) and temperature changes, which can vary from layer to layer and along two in-plane directions. Each layer is regarded as a Kirchhoff plate, and each imperfect interface is described using a spring-layer interface model, which can capture discontinuities in the displacement and stress fields across the interface. Unlike existing models, the governing equations and boundary conditions are simultaneously derived for each layer by using a variational procedure based on the first and second laws of thermodynamics, which are then combined to obtain the global equilibrium equations and boundary conditions for the multi-layered composite plate. A general analytical solution is developed for a symmetrically loaded composite square plate with an arbitrary number of layers and imperfect interfaces by using a new approach that first determines the interfacial normal and shear stress components on one interface. Closed-form solutions for two- and three-layer composite square plates are obtained as examples by directly applying the general analytical solution. Numerical results for two-, three- and five-layer composite plates under different loading and boundary conditions predicted by the current model are provided, which compare well with those obtained from finite element simulations using COMSOL, thereby validating the newly developed analytical model.

A new species of Aspalathus (Fabaceae, Crotalarieae) from the Cape Floristic Region, South Africa

A new species from the Western Cape, South Africa is described: Aspalathus praetermissa—a highly localized and critically endangered endemic, occurring between Elandsbaai, Redelinghuys, and Paleisheuwel. This species is morphologically similar to A. quinquefolia subsp. virgata, but differs in having small, 5.5–6.0 mm long, pale yellow flowers (versus flowers 7–10 mm long, bright yellow); more extensive pubescence on wing petals as well as keel petals, blade not flaring apically (versus wing petals partially pubescent to glabrous, flaring apically). A composite plate and map for A. praetermissa are presented, and a taxonomic key to the A. quinquefolia complex.

A quasi-3D SinZZ model-driven multi-field Chebyshev FEM for nonlinear vibration control in multilayer multiferroic composite plates

This paper presents an advanced numerical method for modeling and mitigating nonlinear vibrations in thin multilayered fiber-reinforced multiferroic composite plates, addressing complex multi-physical interactions. The proposed methodology leverages a multi-physical coupling Chebyshev finite element formulation, utilizing high-order shape functions derived from Chebyshev polynomials. By integrating the strengths of spectral element methods and Legendre spectral finite element methods, this approach effectively overcomes challenges such as shear locking and spurious zero energy modes while ensuring high convergence rates in multi-physical problems. A quasi-3D refined model, incorporating the Murakami zig-zag model and sinusoidal shear deformation theory, is employed to accurately capture the nonlinear Von Kármán strain–displacement relationship and the magneto-electro-elastic coupling in multilayer structures with thickness-dependent material properties. To suppress nonlinear vibrations, the study utilizes a closed-loop multiphysical Chebyshev finite element model for time-domain analysis of viscoelastically damped systems, employing the Golla–Hughes–McTavish model. The results underscore the significant influence of multiferroic properties and the strategic distribution of ferroelectric fibers within the substrate on the dynamic behavior of the plate. The numerical validation, supported by rigorous verification, demonstrates the robustness of the proposed method in effectively simulating and controlling multilayer fiber-reinforced multiferroic composite plates. Additionally, this research highlights the potential for significant vibration reduction through semi-active damping mechanisms, offering valuable insights for practical applications in industries where precision and stability are critical.