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Acoustically actuated magnetoelectric (ME) antennas based on resonant magnetoelectric coupling within ferromagnetic/piezoelectric ME laminated composites have recently been considered as a promising solution for antenna miniaturization. However, its radiation performance has been theoretically overestimated, since the negative effects on performances due to the magnetization saturation and the nonlinear mechanical behavior that occur from high-field driving have not been paid enough attention. This work presents a unique equivalent-circuit-based numerical method to analyze the near-field resonance radiation performances of ME antennas driven by high electric fields. In this method, we establish an equivalent circuit of the converse magnetoelectric effect for a ME laminated composite to describe the operating principle of acoustically actuated electromagnetic radiation. The equivalent parameters related to resonance characteristics are determined by fitting the circuit model to the data from frequency response measurements of the near-field magnetic flux density. The validity of the model is verified by comparing the theoretical predictions with the experimental results, in the view of the volume fraction dependence of the mechanical resonance-related radiation characteristics of the fabricated ME composites. Based on the proposed model, the influence of driving voltage amplitude on near-field radiation performances is further analyzed by experimental fitting to the model, and the potential limiting factors of ME antennas are discussed according to the driving-amplitude dependence of parameters obtained from the fit. This work provides an effective and engineering-friendly approach to predict the evolution of ME antenna performances, leading a way to improve the performance limit for resonant magnetoelectric coupling. [ABSTRACT FROM AUTHOR]

This study presents photothermal imaging results of subsurface material defects within fiber metal laminates utilizing the virtual wave concept. Therefore, we theoretically analyze the propagation of the virtual wave signal in a hybrid composite laminate via the method of images. For provoking local material damage, the hybrid composite sample is subjected to a defined impact loading. The results obtained from photothermal defect imaging, utilizing rectangular laser pulse excitation, are compared with results obtained from 3D x-ray computed tomography. To sum up, we demonstrate a fast, non-invasive, and easily interpretable reconstruction of defects within macroscopic hybrid composite laminates based on the virtual wave concept. [ABSTRACT FROM AUTHOR]

Purpose: To investigate the influence of immediate dentin sealing (IDS) vs delayed dentin sealing (DDS) on the marginal gaps of machinable monolithic zirconia vs pressable lithium disilicate laminate veneers.Materials and Methods: A total of 40 maxillary lateral incisors were used and received butt-joint laminate veneer preparation. The samples were divided into two groups (n = 20 each) according to ceramic material: pressable lithium disilicate ceramic (PLD) was used in the first group, and machinable monolithic zirconia (MMZ) was used in the second. Each group was then divided into two subgroups according to the bonding protocol: IDS was employed in one, and DDS in the other (n = 10 each). The marginal gap widths were measured using digital microscopy and statistically analyzed.Results: The smallest marginal gaps were observed in MMZ-DDS (57.2 ± 8.4 μm), followed by PLD-DDS (62.4 ± 2.7 μm) and MMZ-IDS (63.5 ± 1.9 μm). The largest marginal gaps were observed in PLD-IDS (81.5 ± 6.3 μm). Two-way ANOVA revealed that the bonding technique (P < .001) and ceramic material (P < .001) both showed significant differences.Conclusions: MMZ produced better marginal accuracy than PLD. IDS seems to have a predisposition to significantly wider marginal gaps than DDS, but these gaps are within the clinically acceptable range. The marginal accuracy of ceramic veneers appears to be related to the bonding technique as well as the material of construction. [ABSTRACT FROM AUTHOR]

Graphene oxide (GO) sheets are widely used as building blocks in flexible electronic devices, structural materials, and energy storage technology owing to physicochemical flexibility and remarkable mechanical properties. GO exists as lamellar structures in these applications and, thus, it urges to enhance interface interaction to prevent interfacial failure. This study explores the adhesion of GO with and without intercalated water utilizing steered molecular dynamics (SMD) simulations. We find the interfacial adhesion energy (γ) depends on the synergistic effect of the types of functional groups, the degree of oxidation (c), and water content (wt). The intercalated monolayer water confined within GO flakes can improve the γ by more than 50% whereas the interlayer spacing is enlarged. The enhancement of adhesion is from the cooperative hydrogen bonding bridges between confined water and functional group on GO. Furthermore, the optimal water content wt = 20% and oxidation degree c = 20% are obtained. Our findings provide an experimentally available way to improve interlayer adhesion through molecular intercalation, which opens the possibility of high-performance laminate nanomaterial-based films for versatile applications. [ABSTRACT FROM AUTHOR]

Highlights Due to recent advancements in textile fabrication, woven fabric reinforcements are used in composite structures as an alternative to traditional unidirectional fiber reinforcing layups. In this paper, experimental work was performed to study the behavior of multiple bolt‐lapped joints under uniaxial tension. Different bolt numbers, composite layups, and fabric configurations were studied. Single‐ and double‐lap configurations were used to investigate the effect of secondary stresses. It was found that the P‐δ curves of lapped joints exhibit four primary stages: a linear elastic stage, followed by a nonlinear hardening stage, then linear hardening leading up to the peak, and finally a softening stage. For double‐lapped non‐woven joints, the curves encompass only the first three stages; however, for woven composites, the last stage is very small. In addition, among the laminates, the non‐woven laminate sustains the highest normalized failure load, except in the staggered case, where the quasi‐isotropic woven laminate exhibits higher strength. Conversely, the bidirectional woven laminate demonstrates the lowest loads and the highest deformation. A study compared bolted joint performance of woven and uni‐based composites. Lapped joints with different bolt arrangements were experimentally studied. P‐δ curves showed elastic, nonlinear, linear hardening, and softening stages. Woven laminates showed higher displacements compared to non‐woven laminates. Secondary bending induced additional stress with less impact on woven samples. Bearing failure predominated, with variations in extent of bearing damage. [ABSTRACT FROM AUTHOR]

(Zr0.8Sn0.2)TiO4 (ZST) microwave dielectric ceramic powder was synthesized by the hydrothermal-molten salt (HMS) method, and the effects of different molding methods on the physical phases, microscopic morphology, and dielectric properties of ZST ceramics were investigated. On this basis, ZST-NZ laminated composites were prepared, and the interfacial diffusion and laminated co-firing behaviors of the composites were studied more systematically. The results show that the heat-pressing process can be used to obtain high-frequency dielectric ceramics with more comprehensive performance. The dielectric properties (1 MHz) were ɛr = 40.5, tanδ = 1.32 × 10−3. ZST-NZ laminated composites have relatively tight interfacial bonding but show significant interfacial diffusion. The mutual diffusion of ZST-NZ composites follows the semi-infinite diffusion coupling model. Based on this diffusion model, the ionic concentration distribution function was established to simulate the interfacial diffusion of ions, and the diffusion coefficients and diffusion activation energies of Fe3+, Zn2+, Sn4+, and Zr4+ were calculated under different conditions. The magnitude of diffusion coefficients in the H-ZST-NZ diffusion couples was in the order of D (Fe3+) > D (Zn2+) > D (Sn4+) > D (Zr4+), and the magnitude of diffusion activation energies at 1275 °C was in the order of Qd (Zr4+) > Qd (Sn4+) > Qd (Zn2+) > Qd (Fe3+). The strong diffusion of Ti and Fe led to the decomposition of ZST and NZ ferrite, producing new TiO2 and Fe3O4 phases, which resulted in the degradation of the dielectric properties of the composites. [ABSTRACT FROM AUTHOR]

Highlights The occurrence of process‐induced deformations of composites laminates is challenging for assembly accuracy and may lead to a service life reduction of parts. However, it can be obviously mitigated through different optimization strategies on the basis of the accurate curing process simulation. In this study, a stacking sequence optimization strategy is proposed and applied to multi‐layer thick asymmetric laminates. The shapes of deformed laminate plates are experimentally investigated in virtue of the three‐dimensional coordinate measuring machine. The thermo‐chemical–mechanical behaviors of plates are first verified through the comparisons of model predicted and experimental process‐induced deformations. Then the nonlinear control formula achieved through the regression model is proposed for the direct relationship between stacking sequences and process‐induced deformations. Finally, the required solutions are generated by solving the control formula. With the comparisons between the average deformations before and after optimizations, it is found that the magnitudes of deformations are significantly reduced, especially when the unoptimizated deformations are large. The thermo‐chemical–mechanical behavior can be described in the curing process simulation model. The deformed shapes of multi‐layer thick asymmetric laminate plates are measured by a three‐dimensional coordinate measuring machine. The stacking sequence optimization strategy is implemented by introducing a nonlinear control formula. [ABSTRACT FROM AUTHOR]

Highlights A voronoi user material subroutine (VUMAT) was developed using the three‐dimensional Hashin damage criterion and exponential nonlinear damage evolution method. An interlayer damage model based on the quadratic nominal stress (QUADS) criterion and B‐K fracture criterion was introduced, and a finite element model of Z‐pin reinforced composite laminates under low‐velocity impact was established. The low‐velocity impact behavior of Z‐pin reinforced composite laminates with different impact velocities (0.6 m/s, 0.4 m/s, and 0.3 m/s), different layup forms ([0°/90°]4 and [0°/45°/90°/−45°]2), and different Z‐pin spacing (4 mm, 8 mm, and 16 mm) was studied using ABAQUS. The results indicate that different layup forms have little effect on the low‐velocity impact behavior of Z‐pin reinforced composite laminates. The Z‐pin spacing has a significant influence on the low‐velocity impact behavior of Z‐pin reinforced composite laminates. When the impact velocity is 0.4 m/s, the specific energy absorption of composite laminates with Z‐pin spacing of 16 mm is 85.93% and 87.7% lower than that of composite laminates with Z‐pin spacing of 4 mm and 8 mm. As the Z‐pin spacing decreases (Z‐pin density increases), the impact resistance of Z‐pin reinforced composite laminates first increases and then decreases.• The low‐velocity impact of Z‐pin reinforced composite laminates was studied.• Analyzed the effect of layup forms of laminates on their impact behavior.• Explored the influence mechanism of Z‐pin spacing on the impact behavior.• Studied the energy absorption of different Z‐pin spacing under impact velocity. [ABSTRACT FROM AUTHOR]

A thermo-mechanical progressive analysis model is proposed for predicting fatigue-driven delamination in composite laminated plates. The delamination is simulated based on extended layerwise method (XLWM). The traction-separation law is employed to the heat flux transfer and mechanical load transfer across the delamination front. A thermo-mechanical cohesive zone model (TM-CZM) is developed by Peerlings damage law to simulate the fatigue characteristic of delamination front. In the numerical examples, the effects of mesh lengths, acceleration multipliers, interface strengths, and cyclic temperature load magnitudes on the delamination expansion process are investigated, and the temperature-life curves of composite laminates are determined as well. [ABSTRACT FROM AUTHOR]

For improving the mechanical properties of MgAl 2 O 4 ceramic and maintaining its wide band transparency, the sapphire/MgAl 2 O 4 /sapphire laminated transparent composites with thin sapphire layers were fabricated by brazing with BaO–B 2 O 3 –SiO 2 (BBS) glass filler. The BBS glass filler had an appropriate CTE (coefficient of thermal expansion) value and good wettability on the surface of sapphire and MgAl 2 O 4 ceramics. Joining experiments were first carried out to optimize the preparation process parameters of laminated composites. The results indicated that high bonding temperature promoted mutual dissolution and diffusion of BBS glass and MgAl 2 O 4 ceramic, but led to the intergranular infiltration of glass filler and the formation of pores due to volatilization of B 2 O 3. When the bonding temperature was 1000 °C, the sapphire/MgAl 2 O 4 joints with the best transparency and acceptable shear strength could be obtained. On this basis, the laminated composites with 0.15 mm thick sapphire layers were fabricated by brazing using BBS glass at 1000 °C. The flexural strength of the laminated composite reached 320 ± 10 MPa, which was higher than that of MgAl 2 O 4 (195 ± 15 MPa). The in-line transmittance of laminated composite was 80.9 % at 1000 nm, which was slightly lower than that of MgAl 2 O 4 (82.2 %). [ABSTRACT FROM AUTHOR]

Composite materials play a crucial role in various industries, with plastic composites being particularly significant. This research specifically focuses on producing cotton fabric layers to reinforce polymeric composites. The experiment is designed in two phases. In the first stage, woven fabric is produced using roving as weft insertion instead of the conventional threads or spun yarns. This modification enhances the absorbency of the resin matrix during composite production, leading to improved properties. The second stage of the experiment involves manufacturing composite materials using different fabric structures (plain, twill, and sateen) and varying numbers of fabric layers (1, 3, and 5). This is achieved through a novel process called Vacuum Assisted Resin Transfer Molding (VARTM), which is used for fabric composites instead of the traditional laminated composites. VARTM offers advantages in terms of production efficiency and composite quality. To evaluate the physical and mechanical properties of the resulting composites, several tests are conducted. These include tensile properties testing, bending rigidity testing, measurement of composite thickness, and determination of density. The test results provide valuable insights into the performance of fabric composites under different conditions. Furthermore, the experimental results are compared with simulations conducted using the Finite Element Method (FEM) through COMSOL software. The agreement between the experimental and simulated results confirms the reliability of the proposed approach. [ABSTRACT FROM AUTHOR]

Fiber‐reinforced elastic laminated composites are extensively used in several domains owing to their high specific stiffness and strength and low specific density. Several studies were performed to ascertain the factors that affect the composite plates' dynamic properties. This study aims to derive a mathematical model for the dynamic response of the processed composite material in the form of an annular circular shape made of polyester/E‐glass composite. The mathematical model was developed based on modified classical annular circular plate theory under dynamic loading, and all its formulas were solved using MATLAB 2023. The mathematical model was also verified with real experimental work involving the vibration test of the fabricated composite plate. The composite plate was processed by reinforcing the polyester matrix with E‐glass fibers with a 50% volume fraction each by using the handy lay‐up method. After fabrication, the composite plate was tested with a universal vibration tester, where the plate was impacted and released to free vibration, and the deflection was measured experimentally to compare it with the theoretical value calculated from the derived model. The plate was tested under two boundary conditions, namely, simply and built‐in supported. The findings show good agreement between theoretical and experimental plate deflections at different angles, particularly at built‐in supported boundary conditions. Also, a higher natural frequency was recorded at this condition compared to others, and this may be ascribed to the higher shear stresses involved due to large moments at the ends along with supporting. Meanwhile, the real experimental spectrum of the built‐in condition was higher than others, as the sig view curve revealed. [ABSTRACT FROM AUTHOR]

Highlights Matrix crack propagation and stiffness degradation behaviors of the carbon fiber reinforced polymer/titanium alloy (CFRP/Ti) bolted joint were characterized by a synergistic damage mechanics approach. The parametric study including pre‐tightening torques and interference fit sizes was conducted. The results showed that the joint stiffness degradation exhibited characteristics of local stiffness degradation due to local stress concentration. Stiffness degradation in different plies was caused by matrix crack damage occurring in different directions. The pre‐tightening torque significantly increased the joint stiffness and restrain matrix crack progression, effectively inhibiting the stiffness degradation of the joint. Moreover, the low interference fit level delayed the crack initiation in −45° ply and 45° ply and the crack propagation of the laminate, while promoted the crack initiation in 90° ply. The stiffness degradation of the laminate could be significantly reduced by interference fit. Matrix crack propagation and stiffness degradation behaviors of the CFRP laminate were characterized by a synergistic damage mechanics method. A FE model of the CFRP/Ti double‐lap interference fit bolted joint was established. Influences of pre‐tightening torques on both matrix crack initiation and propagation were investigated. The optimum interference fit size of the matrix damage strengthening was 0.20%–0.60%. [ABSTRACT FROM AUTHOR]

Highlights Composite structures are frequently exposed to varying hygrothermal environments, which can lead to the deterioration of their mechanical properties. This study explores the effects of hygrothermal aging on the mechanical behaviors of twill‐woven carbon fiber composite laminates, with a particular focus on laminates with flame‐retardant epoxy resin (CF_FR)—a relatively underexplored area. The findings reveal several key insights: (1) CF_FR exhibit more pronounced aging damage compared to those with general epoxy resin (CF_G), primarily due to higher moisture absorption, which results in increased surface swelling and internal delamination. (2) Hygrothermal aging enhances the impact resistance of both types of laminates by increasing peak force, particularly at higher temperatures, thereby reducing impact‐induced damage. (3) CF_FR suffers greater reductions in compressive and compression after impact (CAI) strength following aging, with CAI strength decreasing by 36.3% for flame‐retardant laminates and 14.8% for CF_G after immersion at 70°C. (4) Significant local buckling is observed in the swollen regions of CF_FR under compressive loading, indicating an heightened vulnerability to structural instability after aging. These findings offer valuable insights into the performance of composite materials under prolonged moisture exposure, particularly in safety‐critical applications where both flame retardancy and mechanical integrity are crucial. More aging damage is captured from laminates with flame‐retardant epoxy resin Aging temperatures alleviate LVI induced damage and improve the peak force Compressive and CAI strength are affected after prolonged aging conditions CAI strength of CF_FR decreases by 36.3% after exposure to the 70°C water bath Significant local buckling is observed in CF_FR under compressive loading [ABSTRACT FROM AUTHOR]

Highlights The objective of this paper is to analyze the mechanical properties and damage mechanisms of carbon fiber‐reinforced polyamide thermoplastic composite laminates. Four specimens with different ply orientations were designed for open‐hole tensile experiments, and interlaminar toughness experiments including double cantilever beam and end‐notched flexural were carried out. The experimental process was monitored synchronously using acoustic emission, and the strain field changes of the tensile specimens were captured using digital image correlation technology. The unsupervised clustering of the peak frequencies of the acoustic emission signals based on the K‐means++ algorithm was employed to ascertain the peak frequency ranges corresponding to the various damage modes. Typical signals from different specimens were selected, and the gray wolf algorithm was used to optimize the variational modal parameters to decompose the signals. The waveform characteristics, frequency components, and Hilbert spectra of each damage mode were given. The correlation analysis of the intrinsic mode function (IMF) components of the same damage in different specimens demonstrated that the IMF components exhibited high similarity. By analyzing the time series changes in the energy of each damage mode in different specimens, the contribution of different damage modes to the evolution of laminated plate damage was evaluated. The mechanical properties of CF/PA6 laminates were investigated based on open‐hole tensile specimens and pre‐cracked delamination specimens. Unsupervised clustering of AE peak frequencies using K‐means++ to establish the relationship between peak frequencies and damage patterns. AE counts and cumulative energy were used to assess damage evolution. By identifying a single damage signal and providing a more intuitive treatment of the damage energy evolution. [ABSTRACT FROM AUTHOR]

Highlights Artificial intelligence (AI) techniques are increasingly used for structural health monitoring (SHM) of polymer composite structures. However, to be confident in the trustworthiness of AI models, the models must be reliable, interpretable, and explainable. The use of explainable artificial intelligence (XAI) is critical to ensure that the AI model is transparent in the decision‐making process and that the predictions it provides can be trusted and understood by users. However, existing SHM methods for polymer composite structures lack explainability and transparency, and therefore reliable damage detection. Therefore, an interpretable deep learning model based on an explainable vision transformer (X‐ViT) is proposed for the SHM of composites, leading to improved repair planning, maintenance, and performance. The proposed approach has been validated on carbon fiber reinforced polymers (CFRP) composites with multiple health states. The X‐ViT model exhibited better damage detection performance compared to existing popular methods. Moreover, the X‐ViT approach effectively highlighted the area of interest related to the prediction of each health condition in composites through the patch attention aggregation process, emphasizing their influence on the decision‐making process. Consequently, integrating the ViT‐based explainable deep‐learning model into the SHM of polymer composites provided improved diagnostics along with increased transparency and reliability. Autonomous damage detection of polymer composites using vision transformer based deep learning model. Explainable artificial intelligence by highlighting region of interest using patch attention. Comparison with the existing state of the art structural health monitoring methods. [ABSTRACT FROM AUTHOR]

Highlights This study delved into the Mode I fracture behavior of laser‐assisted automated fiber placement (AFP) in situ consolidated thermoplastic composite laminates under different curing pressures. In compliance with ASTM D5528 standards, T700 carbon fiber reinforced polyether ether ketone (T700‐CF/PEEK) double cantilever beam (DCB) specimens were fabricated and segregated into three test groups subjected to distinct roller pressures: DCB‐100N, DCB‐500N, and DCB‐1500N. The fracture toughness of these specimens was then inversely characterized by employing an optimized ASTM‐based data reduction methodology. A kind of tri‐linear cohesive zone model (CZM) incorporating the fracture process zone (FPZ) length was developed to simulate delamination behavior, showing good agreement between experimental results and simulation predictions. Compared with the other two test groups, DCB‐1500N specimens have more inter‐laminar bridging fibers and higher propagated toughness. Although the length of fiber bridging area is shorter, the fiber bridging density is higher, so the influence of fiber bridging on toughness is more pronounced in the DCB‐1500N specimens. This study provides theoretical guidance for the impact resistance design of thermoplastic composites (TPCs), offering valuable insights into the intrinsic relationship between material processing and fracture damage mechanisms. Explore the characteristic interlaminar fracture behavior of thermoplastic laminates made by AFP under different curing pressures. Develop a more accurate tri‐linear CZM model to describe the plastic deformation at crack tips and fiber bridging during the delamination process. Unveil the intrinsic relationship between AFP curing pressure and ductile fracture mechanism of thermoplastic composites. [ABSTRACT FROM AUTHOR]

Highlights Processing parameters during the laser‐radiated in‐situ manufacturing process change the thermal history of the thermoplastic composite, which affects porosity and fiber‐resin interfacial bonding quality, and hence the wedge peel strength of the laminate. The effect of different laser powers and consolidation forces on the wedge peel strength of the specimens was investigated. Due to the fiber‐rich area on the tape surface during the laser heating phase as well as the insufficient consolidation force and consolidation length during the consolidation phase, the wedge peel strength decreased due to increased porosity and weak fiber‐resin bonding at the interlayer bonding interface. A conformable consolidation roller of lower hardness was used to improve the wedge peel strength of the laminates, which reduced the initial temperature of the cooling phase, thus inhibiting the void rebound and increasing the bonding strength at the fiber‐resin interface. The cross‐section and peeling surface were characterized by optical microscope and scanning electron microscope. The wedge peel strength of the laminates, with reduced voids and increased interfacial bonding strength between the fibers and the resin, is improved. Mechanism of void formation and evolution in different phases of laser‐radiated in‐situ consolidated laminate. Effect of consolidation roller hardness and deformation on wedge peel strength. [ABSTRACT FROM AUTHOR]

Carbon nanotube (CNT)‐polyetherimide (PEI) hybrid nanofibrous veils were prepared through the electrospinning process to function as an interlayer in carbon fiber reinforced polymer composites (CFRP), and the effects of the addition of the hybrid fiber veils on the interlaminar fracture properties and flexural properties of CFRP were investigated. The results showed that interleaving CNT/PEI hybrid veils can effectively avoid long‐troubled trade‐off between mode‐I interlaminar fracture toughness and in‐plane properties when using thermoplastic toughening materials. Specifically, the GIc value and flexural strength of the laminates were increased by as much as 86.2% and 14.3%, respectively when CNT content was reached up to 0.7 wt% in CNT/PEI hybrid veil. This method adopts ultra‐low PEI and CNT additions, and the limited quantity of these additives demonstrates a notably high interlaminar toughening efficiency while concurrently enhancing the strength, rendering it a promising strategy for both toughening and strengthening. Highlights: PEI is used as a carrier to transport CNT to the CFRP interlaminar layers.PEI‐CNT hybrid fiber veils improve GIC and flexural strength of CFRP.PEI‐CNT hybrid fiber veils impede crack expansion through various mechanisms.This method adopts ultra‐low PEI and CNT additions. [ABSTRACT FROM AUTHOR]

The influence of hygrothermal aging on the mechanical properties of flax fiber‐reinforced polymer (FFRP) composites was studied by examining the mechanical properties and failure mechanism of the composite laminates exposed in distilled water at different temperatures. The resin transfer molding (RTM) process was used to manufacture FFRP laminates, which were then subjected to accelerated aging tests in distilled water at different temperatures. The moisture absorption characteristics of FFRP were analyzed by a water absorption test. Tensile, bending, and low‐velocity impact tests of laminates after different aging conditions were performed. Combined with DSC and FTIR tests, the failure mechanism of FFRP exposure to hygrothermal aging was analyzed. The result indicated that the increase in temperature will accelerate the moisture absorption process of FFRP, and the hygroscopic behaviors at different temperatures conform to Fick's law. In the early stage of hygrothermal aging, the composites undergo post‐curing, and the tensile and bending strengths increase. After that, the tensile and bending strengths are decreased because of the thermo‐oxygen aging of materials and fiber/matrix interface damage. After hygrothermal aging, the impact peak force of FFRP decreases obviously while the absorbed energy increases due to the increase of internal defects and plasticization of composites. The increase of hygrothermal aging temperature aggravates the aging of materials, resulting in a more obvious decline in the tensile, bending, and impact properties of the composites. Highlights: The effect of hygrothermal aging on the mechanical properties of FFRP is investigated.With the increase of hygrothermal aging time, the tensile and bending strength of FFRP increased at the early stage of aging and then decreased.After hygrothermal aging, the impact peak force of FFRP decreases and the absorbed energy increases due to the increase of internal defects and plasticization of composites. [ABSTRACT FROM AUTHOR]

The main objective of the present study is to implement a functionally graded materials (FGM) technique to reduce the hole effect in fiber reinforcement polymers. The tensile and fracture behaviors of conventional and FGM composites containing open holes have been investigated. Open‐hole specimens having different hole sizes have been fabricated using a hand lay‐up technique with different cross‐ply stacking sequences and various numbers of layers to study the open‐hole effect on their tensile strength. On the other hand, a three‐dimensional finite element analysis with the Hashin model was implemented to observe the failure modes along each layer. Experimental and numerical data revealed that the FGM technique enhanced the performance of specimens in the presence of a hole by increasing the fibers around the hole area. Furthermore, the [0°/90°/0°] sequence has more tensile strength than [0°/90°]s and [0°/90°/0°/90°/0°] sequences. It can be concluded that the bearing capacity of cross‐ply laminates is proportionally dependent on the ratio of the number of 0° layers to the number of 90° layers and inversely dependent on the specimen thickness. Highlights: Dense fibers around the open hole improve its strength in laminated composite.The FGM concept has been successfully employed to improve open‐hole strength.The stacking sequence [0°/90°/0°] has better tensile strength than [0°/90°]s.FEA has successfully simulated the FGM concept around the open hole.The open‐hole failure occurred in the same direction as fiber orientation. [ABSTRACT FROM AUTHOR]

The objective of this research is to investigate the potential impact of nanodiamond filler particles on the mechanical and morphological characteristics of epoxy composites that are fortified with ramie and jute fibers. Composed of composite laminates containing nanodiamonds at concentrations of 0.1, 0.3, and 0.5 wt. %, the laminates were produced via vacuum‐assisted resin infusion (VARI to evaluate the alterations in mechanical properties, Vickers hardness, tensile, and flexural tests were conducted on the prepared composites). The findings showed that adding 0.3 wt. % nanodiamonds to epoxy composites significantly improved the hardness of the composites about 18.56% and 34.38%, the tensile strength of the composites about 19.1% and 28.01%, and the flexural strength of the composites about 17.7% and 21.12% for ramie/epoxy and jute/epoxy, respectively. The optimal concentration of nanodiamonds for both types of fibers in order to optimize these properties was calculated to be 0.3 wt. % of nanodiamonds. A micro‐x‐ray CT scan was performed to determine the percentage of porosity in composites. The utilization of scanning electron microscopy (SEM) demonstrated that an increase in the nanodiamond content led to enhanced fiber dispersion and reduced interfacial voids. In contrast, Fourier transform infrared (FTIR) analysis unveils the hydrophobic characteristics, cellulose content, and improved interfacial bonding between the fibers and the epoxy matrix, which is attributed to the robust covalent bonding enabled by the nanodiamonds. Highlights: Adding nanodiamonds (NDs) improved adhesion at fiber‐matrix interface.Mechanical properties peaked for composites with 0.3 wt. % of NDs.Beyond 0.3 wt. % of NDs, agglomerates in composites were observed through SEM.Void percent increased for composites with 0.5 wt. % of NDs. [ABSTRACT FROM AUTHOR]

This study evaluated the effect of multi‐walled carbon nanotubes (MWCNT) addition on the thermomechanical, and electrical responses of unidirectional flax fibers/Elium acrylic modified carbon nanotubes‐based composite. The manufacturing process of these laminated composites involved infusing the nanofillers onto the fibers, ensuring good dispersion of MWCNT within the matrix. Regardless of the rate of incorporated nanotubes, this study revealed a significant deterioration of the mechanical properties in tension and viscoelastic properties of the Elium acrylic resin‐based nanocomposite. The electrical conductivity significantly increased for all nanocomposites and laminated composites. In contrast to the nanocomposite, the unidirectional flax fibers/MWCNT/Elium acrylic composite exhibited a considerable improvement in mechanical properties. An increase in Young's modulus and stress at break of about 27% and 23% respectively, was achieved for the material loaded with 2 wt% of MWCNT. The presence of MWCNT reduces the saturation weight by 5% for the unidirectional composite filled with an amount of 1.5 wt% in MWCNT. Highlights: Improving the electrical properties of nanocomposites and unidirectional fibers (UD) composites.Improving the mechanical properties of Elium/flax/multi‐walled carbon nanotubes (MWCNT) composites.Influence of MWCNTs on the water absorption of UD composites.Influence of MWCNT on the glass transition temperature of nanocomposites.Inhibiting polymerization of MWCNT with Elium. [ABSTRACT FROM AUTHOR]

The research of high‐performance composite pressure vessels in practical application has become the focus of attention, and fiber paths play an important role in the structural performance of composite pressure vessels. Therefore, a method is proposed for determining the optimal geometric parameters of the pressure vessel head shape under a novel variable slippage coefficient non‐geodesic(NVSCNG). First, NVSCNG is used as the dome fiber path design mode, and the classical lamination theory is used to construct a dome stress field model. In addition, on the basis of the Tsai‐Wu failure criterion, the minimum laminate thickness is determined to satisfy the strength constraints. Second, the performance factor (pressure*volume/weight) is used to calculate the structural performance of the dome with variable geometric parameters under the novel variable slippage coefficient fiber path. Moreover, the stability constraints are considered to determine the optimal geometric parameter values of the dome. Finally, the structural properties, stress response and thickness were analyzed under two types of fiber paths based on the optimal dome profile. Results show that compared to the conventional variable slippage coefficient, the performance factor can be maximally improved by nearly 60.94% using the novel variable slippage coefficient, and the thickness of the composite layer at the equator of the dome can be maximally reduced by nearly 34.88%. In addition, the research shows that NVSCNG can improve the structural performance of the dome and realize the lightweight of dome components, which are greatly important in guiding the design of fiber paths for pressure vessels. Highlights: No unconstrained linear problem between NVSCNG and initial winding angle.Optimal dome profile geometry parameters are m = 0.8, rc = 0.5.The dome structural failure is controlled by the longitudinal stresses.Winding angle distribution has a strong influence on dome stress distribution.Higher dimensionless performance factor and lighter mass for NVSCNG. [ABSTRACT FROM AUTHOR]

This paper presents an experimental examination of the compression demeanor of lightweight corrugated core composite (CCC) sandwich panel and corrugated core smart composites (CCSC) sandwich panels subjected to quasi‐static edgewise compression loading. The existence of shape memory alloy (SMA) wires and pre‐strain percentages of SMA are the indicators studied in this article. The fabrication procedure presented and the appraisement of the mechanical properties of the CCC and CCSC sandwich panels are expressed. The core geometry of samples is trapezoid corrugated made of aluminum. The facesheets are four layers of woven glass fiber/ epoxy laminated composite. For evaluation of the efficacy of the presence of SMA wires on mechanical specifications of sandwich panels, three SMA wires with various pre‐strain percentages (0%, 3%, and 6%) are embedded in each composite facesheet. Mechanical properties of all types of CCC and CCSC sandwich panels such as maximum force, critical damage force, specific strength, absorb energy, specific toughness, Young's modulus, and specific stiffness were evaluated. Results showed that the CCC sandwich panel has higher mechanical specifications than the CCSC sandwich panels with 0% and 3% pre‐strain. Also, increasing pre‐strained SMA wires improves all mechanical parameters of CCSC sandwich panels. CCSC sandwich panel with 6% pre‐strain has the highest compression properties than other sandwich panels. Maximum Force, Critical Damage Force, Specific Strength, Absorbed Energy, Specific Toughness, Young's Modulus, and Specific Stiffness of CCSC sandwich panel with 6% pre‐strain are 14.73 kN, 13.6 kN, 9.55 MPa/g, 26.61 kJ, 0.346 MJ/m3g, 4395 MPa and 0.61 kN/mm g, respectively. Highlights: Lightweight CCC sandwich panel and CCSC sandwich panel manufactured.Compression behavior of CCC sandwich panel and CCSC sandwich panel evaluated.Pre‐strained SMA wires improves energy absorption of CCSC sandwich panels.Higher specific toughness was obtained with 6% pre‐strain SMA.Presence of SMA wires with no pre‐strain cannot improve the specific strength. [ABSTRACT FROM AUTHOR]

Highlights It is more and more difficult to identify defects in carbon fiber composite materials due to the difficulty in making defect samples and the single signal analysis method. In order to better solve the problem of defect identification in carbon fiber composite materials, this study uses ultrasonic phased array equipment to quantitatively locate and detect carbon fiber composite laminates with embedded delamination defects, so as to more intuitively and effectively display the appearance of different delamination defects. The time domain analysis of the collected ultrasonic original signal and the time‐frequency domain analysis using wavelet packet are carried out. A total of 6 eigenvalues were extracted to reflect the ultrasonic signals of different delamination defects. By using genetic algorithm to optimize BP neural network, the recognition accuracy of delamination defects of different sizes is more than 95%, and the recognition accuracy of delamination defects of different depths is 100%, so as to realize the effective intelligent recognition of delamination defects of different sizes and depths of carbon fiber composites. This study is of great significance to improve the accuracy and reliability of defect identification of carbon fiber composite materials. The ultrasonic phased array equipment is used to quantitatively locate the carbon fiber composite laminates with embedded delamination defects, so that the appearance of different defects can be displayed more intuitively and effectively. Using time domain analysis and time‐frequency domain analysis based on wavelet packet, the combination of the two can more comprehensively extract the effective features of the defect signal. The BP neural network is optimized by genetic algorithm, and the results can effectively and automatically identify different layered defects, which lays a good foundation for the rapid and accurate identification of more defects in the future. [ABSTRACT FROM AUTHOR]

Accumulative roll bonding (ARB) is a repeated cladding process in which two or more sheets of material are joined together by rolling at temperatures below recrystallization. The present review is focused on ARB of high‐alloy steels, which, among other laminated metal composites (LMCs), deliver the highest mechanical properties. After a brief description of high‐strength steels, history, and state of the art of LMCs, the principal roll bonding mechanism is explained. Further, the methodology of ARB of steels and variable parameters (stacking, temperature, etc.) are discussed. Known examples of steel–steel laminates are summarized with respect to their rolling temperature and mechanical properties. Further, the main toughening mechanisms of steel‐based LMCs are listed. The most promising candidates of high‐alloy steel laminates are presented in more detail. The important deformation mechanisms of twinning‐ and transformation‐induced plasticity (TWIP and TRIP) high‐alloy steels are explained. Microstructural changes and layer bonding as well as mechanical properties and damage behavior of two‐ and four‐layered TRIP/TWIP steel laminates are illustrated, including some specific phenomena, such as deformation lenses. Finally, by summarizing the analyzed data on steel laminates, conclusions and outlook are formulated. [ABSTRACT FROM AUTHOR]

Highlights In this work, the behavior of carbon fiber reinforced polymer composites (CFRPs) interleaved with electrospun veils under low velocity impact (LVI) conditions and extreme environmental temperatures was investigated. 2/2 twill carbon fiber/epoxy laminates were subjected to LVI at three energy levels (10, 20, and 30 J), and three temperatures (−50°C, room temperature, and 100°C). Two interleaved configurations were explored (six veils placed symmetrically with respect to the middle plane of the laminate and with respect to the external layers of the laminate). Particularly at room temperature and up to 20 J, nanofibrous interlayers effectively reduced localized deformation (by about 13.0%) and delamination (by about 12.2%) when positioned in the outer ply interleaved configuration compared to the reference laminate. At 100°C, this effect is maintained at 10 J, preventing an increase in the delaminated area. At −50°C and 10 J, the promotion of delamination prevented back surface fiber failure. Regarding post‐impact flexural properties, the presence of nanoveils ensured superior mechanical properties compared to the corresponding reference laminate impacted at the same conditions, demonstrating their efficacy in enhancing the damage tolerance of the overall laminate. Electrospun veils were interleaved in 20 layers of 2/2 twill carbon/epoxy laminate. Three configurations were tested under LVI at 10 J, 20 J, 30 J, and −50°C, RT, and 100°C. Observed damage modes include delamination, indentation, and back surface fiber cracks. Veils symmetrically placed in external layers limit delamination at 20 J (RT) and 10 J (100°C). Electrospun veils enhanced CFRP bending and residual post‐impact properties at RT and 100°C. [ABSTRACT FROM AUTHOR]

Highlights This work aims to study the effects of bionic spiral stacking sequence, impact energy and impactor shape on the impact resistance of laminates. The finite element model is established based on the stress failure criterion, progressive damage evolution, and the triangle traction‐separation law. The reliability of the finite element model is validated through rigorous comparison with experimental data. The study investigates the influence of laminate layup sequence, impact energy, and impactor shape on the impact resistance of laminates. The results show that during low‐speed impacts, laminate damage is primarily characterized by fiber breakage, matrix cracking, and delamination. Matrix cracking and delamination become more pronounced as the impact energy increases. The design of linear spiral ply and power function spiral ply has a positive effect on the impact resistance of laminates. The impact resistance of laminates is sensitive to the sharpness of the impactor and the level of impact energy. Higher impact energy and sharper impactor shapes lead to increased energy absorption in the laminate, resulting in more pronounced damage failure. The impact resistance of bionic spiral composite laminates is studied. Three biologically inspired stacking sequences were designed. A numerical simulation method is proposed and verified. The low‐velocity impact characteristics of bionic laminates are revealed. [ABSTRACT FROM AUTHOR]

Copper matrix composites can be used to address the issue of heat dissipation in electronic devices. Nevertheless, the thermal conductivity (TC) of carbon fiber (CF)/copper (Cu) composites falls significantly below expectations. This is primarily attributed to the challenge of achieving a well-ordered arrangement of CF within the matrix, coupled with the issue of low interfacial bonding strength. A highly effective and uncomplicated approach to fabricate copper matrix composites featuring a "sandwich structure" of Cu-CF-Cu is introduced in this paper. This configuration, achieved through structural design facilitated by hot-press sintering and vacuum suction filtration, exhibited a three-dimensional graphene-like networks (3D-GLNs) and meticulously ordered CF layers over long distances. More importantly, in comparison to pure copper (350 W m−1 K−1), the laminated composite with 40 vol% CF of the CF layer had an in-plane TC of 510 W m−1 K−1, which was approximately 1.5 times greater than that of pure copper. Additionally, the coefficient of thermal expansion (CTE) of the laminated composite with 45 vol% was 9.98 ppm/K. The in-plane TC of the composite was comparable to that of the graphene/Cu composites with the same content. This underscores the advantages of the structural design, even in cases where the TC of the reinforced phase differs by a factor of two. The aforementioned findings demonstrate that this methodology for developing a unique "sandwich" structure can effectively enhance in-plane TC in CF/metal composites, presenting potential for utilization in electronic packaging requiring efficient directional heat transfer. [ABSTRACT FROM AUTHOR]

The addition of graphene nanoplatelets as a nanofiller on the surface of pristine and oxidized carbon fiber for making reinforced polymer composites has shown improvement in monotonic flexural properties. However, the fatigue response of these laminates under bending loads has not been investigated so far. The current study aims to examine the monotonic and fatigue behavior of the graphene nanoplatelets (GNPs) coated bi‐directional pristine and oxidized carbon fiber epoxy composites under bending loads. Eight layers of fabrics were used to manufacture the laminates through vacuum‐assisted resin transfer molding technique (VARTM). An optimum amount of GNP addition on oxidized fiber leads to ~830‐fold enhanced fatigue life at higher stresses as compared to pristine laminates. However, excessive GNP addition on pristine as well as oxidized fiber leads to a deterioration in fatigue life. In‐situ optical microscopic examination was done to observe the crack initiation and propagation of all the specimens with respect to the number of cycles coupled with post‐mortem SEM images of the fracture surfaces. [ABSTRACT FROM AUTHOR]

With the increasing emphasis on environmental protection, there is a growing focus on the synthesis of water‐solvent self‐emulsifying sizing agents. In this study, five types of anionic polyester sizing agents with varying molecular weights were synthesized to explore the effect of molecular weight on the interfacial bonding strength of carbon fiber (CF) reinforced vinyl resin composites. The results demonstrated that the molecular weights of the synthesized sizing agents were precise; the particles in the sizing agents were nanometer‐sized, monodisperse, and exhibited high thermal stability. When the molecular weight was 8000, it exhibited optimal wettability for CF, leading to a substantial improvement in the interlaminar shear strength, reaching 71.8 MPa, which represents a significant increase of 22.7% compared with commercial CFs (CFF). Additionally, the interfacial shear strength was maximized at 13.23 MPa, which was significantly increased by 14.2% compared with CCF. These significant improvements in surface properties and mechanical performance were attributed to the excellent wettability of the CF surface, effective spreading performance of the sizing agent, the presence of double bonds in the sizing agent facilitating reactions with free radicals on the CF surface, and the residual double bonds further undergoing curing with the vinyl resin, promoting the reinforcement of interface bonding. [ABSTRACT FROM AUTHOR]

In this paper, the energy absorption performance of braided composite tubes under combined shear-compression loading is investigated. ABAQUS/Explicit is employed to analyze the energy absorption of braided composite tubes, and quasi-static compression tests are carried out. Braided composite materials absorb energy through the damage accumulation in laminate. Thus, to maximize energy absorption performance, a progressive crushing mode should be induced. While extensive research has been conducted on cases of axial loading, understanding of the energy absorption performance of braided composite tubes under combined shear-compression loading remains limited. Experimental results reveal that under both axial and combined shear-compression loading at 30 degrees, the braided composite tube exhibits a progressive crushing mode. The test results are utilized to validate the finite element model. Through finite element analysis, it is confirmed that the damage accumulation in laminate is maximized due to the induction of a progressive crushing mode. It means that the energy absorption principles of braided composites apply similarly to combined shear-compression loading, allowing for the maintenance of superior energy absorption performance of braided composites under various load angles. [ABSTRACT FROM AUTHOR]

In this research, the vibration damping characteristics of the laminated aluminum sheets (LAS) were evaluated in a sheet specimen and an automotive dash panel and compared with those of the monolithic aluminum sheet (MAS). The LAS was fabricated with two 5xxx series aluminum alloy (AA) sheets (AA5052-O) with a thickness of 0.7 mm by inserting an acryl-based adhesive in between. The automotive dash panels were manufactured by multi-step stamping processes for the LAS and the MAS with a similar thickness. The shaker vibration test in a sheet specimen and the impact hammer test in an automotive dash panel were conducted to measure the frequency response function (FRF) of LAS, compared with those of MAS. The results show that the frequency response function made by the LAS has less noise and fluctuation than that of the MAS in a sheet specimen and an automotive dash panel. The damping ratios in a sheet specimen and an automotive dash panel made by the LAS have higher values than those of the MAS. This proves that the LAS has better vibration damping characteristics and a larger damping effect than the MAS in a sheet specimen and an automotive dash panel. [ABSTRACT FROM AUTHOR]

This research focuses on investigating the buckling strength of thin-walled composite structures featuring various shapes of holes, laminates, and composite materials. A parametric study is conducted to optimize and identify the most suitable combination of material and structural parameters, ensuring the resilience of structure under both mechanical and thermal loads. Initially, a numerical approach employing the finite element method is used to design the C-section thin-walled composite structure. Later, various structural and material parameters like spacing ratio, opening ratio, hole shape, fiber orientation, and laminate sequence are systematically varied. Subsequently, simulation data from numerous cases are utilized to identify the best parameter combination using machine learning algorithms. Various ML techniques such as linear regression, lasso regression, decision tree, random forest, and gradient boosting are employed to assess their accuracy in comparison with finite element results. As a result, the simulation model showcases the variation in critical buckling load when altering the structural and material properties. Additionally, the machine learning models successfully predict the optimal critical buckling load under mechanical and thermal loading conditions. In summary, this paper delves into the study of the stability of C-section thin-walled composite structures with holes under mechanical and thermal loading conditions using finite element analysis and machine learning studies. [ABSTRACT FROM AUTHOR]

The study examines the interactive functions of gesture repetitions as a specific form of interpersonal synchronization in argumentative decision-making processes of peers (1–6 graders). Based on a collection of 13 instances, gesture repetitions are investigated in the process of collaboratively co-constructing arguments. Drawing on multimodal interaction analysis, a description is provided of how gestures are aligned and laminated with other multimodal resources, such as body posture and gaze, into multimodal repetitions during the co-construction of both arguments and counterarguments. The study illustrates the way in which multimodal repetitions serve to mark coherence between the participants' turns and contribute to the argument. As the multimodal resources are highly synchronized with each other, multimodal repetitions also make the collaboration of specific participants publicly visible to all interactants, thereby attaching more importance to the sharedness—and persuasiveness—of the constructed argument. The analysis therefore focuses on both depictive and pragmatic gestures that are conceived as parts of multimodal gestalts (Mondada, 2014), and describes different trajectories of co-constructions that entail interactively successful as well as unsuccessful examples. [ABSTRACT FROM AUTHOR]

The determination and verification of repair tolerance of patch-repaired laminates based on progressive failure analysis method was studied. The axial tensile tests of intact, perforated, and repaired specimens of T700SC/EC240A composite laminates were carried out. The damage process of composite laminates under tensile load was numerically simulated using the progressive damage degradation model of 3D Hashin–Ye failure criterion. A method for determining the repair tolerance of patch-repaired laminates was proposed, and the upper and lower limits of repair the composite laminates were derived. The result verified by the strength index of Boeing Company showed that the method for determining the repair tolerance proposed is reasonable and feasible. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive investigation on optimum layer thickness and fiber orientations of laminated composite plates against buckling under complex loading conditions by using a new optimization procedure that effectively utilizes computational efforts. In this proposed procedure, a finite element model of the laminated composite plates is developed for the buckling analysis and the interior point optimization procedure is used to maximize the buckling coefficient, aiming to determine the optimum values of fiber orientation angles and thickness. In optimization scenarios, the laminated composite plates are subjected to single and complex loading conditions, including compression, shear, bending and a combination of two or more of these loading types. The computational performance of the proposed optimization procedure is evaluated to investigate and present the effect of various factors including the number of layers, length-to-thickness ratios, aspect ratios, and boundary conditions on the optimum buckling analysis. [ABSTRACT FROM AUTHOR]

This paper presents the delamination impact over the dynamic response of the variable angle tow (VAT) composite plates. The VAT plates with various fiber angles are constrained to different boundary conditions for parametric investigation, while delamination is made to present over two different locations with varying sizes. A comparative stochastic vibration study is performed to evaluate the contribution of composite properties to delaminated and intact plates. The randomness in the material properties is modeled with the efficient Latin hypercube sampling method. The polynomial neural network-based surrogate model, considered an efficient substitute for computationally expensive Monte Carlo simulation, is employed in the present work to examine the stochastic behavior of VAT plates. The contribution of the composite properties on the uncertain vibration characteristics is evaluated. It is observed from the investigations that the sensitivity of the composite properties varies significantly with the delamination. Lastly, a failure probability estimation is carried out with a developed polynomial neural network-based surrogate model to provide safe design estimation for various cases. [ABSTRACT FROM AUTHOR]

In this paper, a meshfree Jacobi point interpolation (MJPI) approach for the free vibration and stationary stochastic response analyses of heated composite laminated plate with varying thickness and curvilinear fiber is developed. The theoretical formulations for heated composite laminated plate with varying thickness and curvilinear fiber are established by using Hamilton's principle in framework of first order shear deformation theory. The effect of thermal stress generated by the temperature variation is considered based on the thermo-elastic theory. The displacement components of the plate are approximated by using the MJPI shape function. The boundary conditions considered in this study are achieved by using the artificial spring technique. The accuracy and reliability of the proposed MJPI shape function are confirmed by comparing with numerical results from the published literature and finite element software ABAQUS. Several comparisons show that the differences between the numerical results from current method, reference and ABAQUS software are less than 1%. Finally, the effects of different parameters such as temperature difference, fiber direction coefficient, thickness gradient and thickness power index on the free vibration and stationary stochastic response of the composite laminated plate are investigated. [ABSTRACT FROM AUTHOR]

This work presents a unique technique for optimising composite laminates used as structural components, which is critical for situations where failure might result in disastrous effects. Unlike traditional surrogate‐based optimisation approaches, this methodology combines the accurate modelling capabilities of finite element (FE) analysis with the iterative refining capacity of metaheuristic algorithms. By combining these two methodologies, our method intends to improve the design process of laminated shell structures, assuring robustness and dependability is crucial. Compared to existing benchmark solutions, the current FE shows a <1% error for cylindrical and spherical shells. The prime objective of this study is to identify the optimum ply angles for attaining a high fundamental frequency. The problem is NP‐hard because the possible ply angles span a wide range (±90°), making it difficult for optimisation algorithms to find a solution. Seven popular metaheuristic algorithms, namely the genetic algorithm (GA), the ant lion optimisation (ALO), the arithmetic optimisation algorithm (AOA), the dragonfly algorithm (DA), the grey wolf optimisation (GWO), the salp swarm optimisation (SSO), and the whale optimisation algorithm (WOA), are applied to and compared on a wide range of shell design problems. It assesses parameter sensitivity, discovering significant design elements that influence dynamic behaviour. Convergence studies demonstrate the superior performance of AOA, GWO, and WOA optimisers. Rigorous statistical comparisons assist practitioners in picking the best optimisation technique. FE‐GWO, FE‐DA, and FE‐SSA methods surpass the other techniques as well as the layerwise optimisation strategy. The findings obtained, employing the GWO, DA, and SSA optimisers, demonstrate ~3% improvement over the existing literature. With respect to conventional layup designs (cross‐ply and angle‐ply), the current optimised designs are better by at least 0.43% and as much as 48.91%. [ABSTRACT FROM AUTHOR]

In this article, the nonlinear dynamic instability of stiffened laminated composite plates is studied in the finite element (FE) framework subjected to uniform in-plane harmonic patch loading. The harmonic load is applied to the two opposite sides of the stiffened plate. The linear and nonlinear time-history response analysis is also studied. The skin and the stiffener are modeled using an eight-node isoparametric degenerated shell element and a three-node curved beam element, respectively. A system of matrices is developed by considering the Green–Langrange strain–displacement relationship. In the linear case, the Bolotin method is used to analyze the dynamic instability region (DIR). The nonlinear instability behavior of the laminated composite stiffened plate is studied by applying the Incremental Harmonic Balance Method (IHB). The Newmark-β method is used to solve the linear and nonlinear time-history response equations to understand the instability behavior of the stiffened plates. The effect of the parameters such as the length of the in-plane loading patch, varying number of stiffeners in x -direction and the position of the patch on the nonlinear vibrations and nonlinear dynamic response is examined. [ABSTRACT FROM AUTHOR]

This study investigates the vibration behavior of delaminated cylindrical shells composed of symmetric cross-ply composite material are partially or completely filled with fluid. An incompressible, non-viscous and irrotational internal fluid is considered. The classical shell theory and Helmholtz's equation with the velocity potential function are employed to derive the governing equation for the vibration of delaminated symmetric cross-ply laminated cylindrical shells. The primary focus is to understand the impact of varying fluid heights, densities and velocities on the natural frequencies of the shells, as well as the effects of shell length, thickness-to-radius ratio, and delamination's position in the thickness and circumferential directions. The study findings indicate that the natural frequencies decrease considerably as the height of the fluid increases and that the delamination position significantly influences the observed frequency variations. Moreover, the internal fluid density and shell length affected natural frequencies. This research contributes not only to our knowledge of the behavior of cylindrical shells with delamination and fluid filling but can also assist in designing structures that mitigate undesirable vibrations and promote the creation of more efficient and dependable structures. [ABSTRACT FROM AUTHOR]