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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]

This work examines the effects of varying weight percentages (0.1, 0.3, and 0.5 wt%) of pristine and functionalized graphene (–COOH, –OH, and –NH2) on the compression and impact strength of carbon fiber-reinforced polymer (CFRP) composite laminates. The laminates were fabricated in two different stacking sequences of carbon fiber in composite laminates, i.e., 0/90° and 0/90/ ± 45° by hand layup technique. Experimental results showed that the inclusion of graphene in epoxy matrix enhances the compressive strength and impact characteristics, namely impact force, displacement, energy profile, and damage behavior of CFRP laminates. Moreover, the orientation of carbon fiber layers in laminates affects the internal damage behavior of specimens and the delamination between fiber layers. The maximum improvements of 38.65 and 76.82% are noticed in the compressive strengths of 0/90° and 0/90/ ± 45° stacked laminates with the reinforcement of 0.1 wt% of pristine and 0.3 wt% of –COOH functionalized graphene to epoxy, respectively. In summary, the test results have shown that using graphene as a reinforcing filler can significantly improve the impact performance of CFRP composites. [ABSTRACT FROM AUTHOR]

The performance of composite materials and structures at high-velocity impacts reaching or exceeding their ballistic limit is crucial for assessing their strength and safety in aerospace applications. In this highly transient impact regime, composite materials are subject to multiple complex failure modes and their properties are susceptible to strain rate effects, making very challenging the simulation and understanding of their ballistic impact performance. This study presents: (1) a multi-scale computational framework for predicting the ballistic limit of composite plates, and (2) experimental results of ballistic impacts on carbon/epoxy plates. The multi-scale model uses a micromechanical approach to account for strain-rate dependency, to calculate micro-stress effects on the matrix and fiber properties, and to predict their coupled effect on effective composite properties. Intralaminar damage initiation and evolution are identified using the maximum stress criterion, but the degradation of properties in the matrix and fibers is predicted with the micromechanics model. Mixed-mode damage laws are implemented to simulate delamination, which guarantees accurate and reliable results. The proposed multi-scale model has been implemented and integrated into ABAQUS/Explicit (VUMAT). Experimental results from high-velocity steel ball impacts on woven IM-65 Carbon/RTM6 epoxy composite plates conducted on a high-speed impact test bench are also presented including non-destructive evaluation of the types of damage and failure. The experimental results are finally used to validate the model predictions for the ballistic limit and the predicted types of damage and failure. [ABSTRACT FROM AUTHOR]

Inspired by the cross-laminated hierarchical structure and flexible interface of high toughness Strombus gigas shell, the "fiber-metal-polymer" laminated composites with different laying modes including cross-laminated structure and interfacial properties were designed, and the corresponding damage and toughening mechanisms were investigated. It shows that the cross-laminated structure, accompanying soft interface modification by metal ultra-thin strip and polymer can optimize the full-field stress distribution and failure behavior, then achieve maximize energy absorption and ensure good strength (ultimate strain and toughness increased to 352% and 127.5%, respectively compared to unidirectional laminated material), which may provide optimization strategies for the design of lightweight composites. [ABSTRACT FROM AUTHOR]

A nonlinear finite element dynamic instability analysis of laminated composite stiffened plates subjected to in-plane harmonic edge loading is presented in this article along with the linear and nonlinear dynamic response study. The eight-noded isoparametric degenerated shell element and a compatible three-noded curved beam element are used to model the stiffened plates. Bolotin method is applied to analyze the dynamic instability regions in linear case. Incremental Harmonic Balance (IHB) method is applied to solve the nonlinear frequency response equations and Newmark-β method is used to solve the linear and nonlinear time history response equations. [ABSTRACT FROM AUTHOR]

Graphene oxide (GO) laminate membranes for water purification have surged in popularity due to their hydrophilicity, high throughput and excellent separation abilities. However, concerns about swelling and stability in water persist. Herein, we prepared high stability, composite reduced graphene oxide (rGO)/graphene oxide (GO) membranes. The composite membranes (i.e. rGO/GO composite membranes) displayed excellent rejection performance for methylene blue (MB) of up to 99.0%, together with ultrahigh water permeance (201.7 L m−2 h−1 bar−1) compared to pristine GO membranes (54.8 L m−2 h−1 bar−1). This study broadens the applications of graphene-based membranes and enhances their performance in water treatment. [ABSTRACT FROM AUTHOR]

The resin is a fundamental factor in determining the performance and usage conditions of its composites. The epoxy vitrimer, which combines both thermoplastic and thermosetting properties, shows significant potential in extending the service life of material. The curing process significantly affects the macroscopic properties of the vitrimer and the resulting carbon fiber reinforced plastics (CFRP). Effective control of curing parameters constitutes the critical factor for the assurance of product quality. In the study, a differential scanning calorimetry (DSC) was utilized to establish a curing kinetics model for a modified, self‐healable epoxy vitrimer based on transesterification. Then the molecular structure, thermodynamic, and mechanical properties of the cured vitrimer were analyzed. Next vitrimeric CFRP (vCFRP) laminates were fabricated, and the tensile and bending properties of the vCFRP laminates were investigated. The results showed the curing process was obtained: 95°C/1 h + 150°C/2 h + 170°C/2 h. The thermodynamic and mechanical properties of cured vitrimer could meet practical requirements. The minimal differences observed in the stress–strain curves of the specimens indicated that the curing process was appropriately configured. The prepared laminates exhibited performance comparable to that of commercial thermosetting composites. [ABSTRACT FROM AUTHOR]

In this paper, the buckling analysis of a five-layer laminated nanocomposite resting on a Kerr foundation is presented. In order to describe the non-continuous behavior of composite plate through its thickness, the displacement field is determined using the Refined Zigzag Theory (RZT). Additionally, the constitutive relations of piezo electromagnetic isotropic materials, orthotropic composites, and Functionally Graded Porous Materials (FGPMs) are presented. With respect to Bi- and Uniaxial loading in the nanoplate, the Hamilton's principle is utilized to derive the equation of motion of this nanoplate. To study the small-scale effect in nanoplates, both Nonlocal Eringen Theory and Nonlocal Strain Gradient Theory (NSGT) are employed to account for nonlocal effects. Finally, the coupled equations of motion are solved using the Differential Quadrature Method (DQM). This paper introduces the newly used Kerr foundation and its effect on the buckling analysis. It also investigates the influence of plate dimensions, piezo electromagnetic terms, boundary conditions, and loading on the dimensionless critical buckling load. [ABSTRACT FROM AUTHOR]

In this study, we address the challenge of hidden damages in FRP composites, such as delamination, matrix cracking, and fibre breakage resulting from transverse low-velocity impact (LVI)—damages often elusive on the surface. Our methodology operates at the meso-scale, depicting laminates as stacked homogenized plies incorporating interfaces. To capture the mechanical behaviour and damages, we extend an existing nonlinear mean-field debonding model (NMFDM), accommodating asymmetric matrix plasticity (AAMP), fibre–matrix interface debonding failure, and in-plane progressive failure. In a key enhancement, we introduce a strain rate term to the AAMP model, addressing strain rate effects associated with LVI loading. Additionally, we incorporate a novel strain-driven 3D failure criteria, offering a more precise assessment of progressive failure subjected to LVI loading. The interfaces between plies are modelled using surface-based cohesive behaviour to capture interaction phenomena. To validate the developed NMFDM, we conduct impact simulations at various energies on a UD composite laminate consisting of AS4/8552 carbon fibre and epoxy matrix. These simulations showcase the predictive capability and accuracy of the NMFDM in capturing the intricate behaviour and damage progression of UD composites subjected to LVI. [ABSTRACT FROM AUTHOR]

In this work, the fabrication of graphene/Al laminate composites was achieved for the first time using the pulse current diffusion bonding method. A complete bonding interface without obvious defects was obtained under the conditions of 530 °C for 10min. The electron backscatter diffraction results revealed that the Al alloy recrystallized under the action of Joule heat, and fine grains were formed at the graphene/Al bonding interface. The transmission electron microscopy results showed that the bonding interface of graphene/Al was composed of graphene/amorphous layer + nanocrystalline MgO and Al 2 O 3 /MgO/Al. This research offers novel insights into the preparation of graphene/metal layer-stack composite materials. [ABSTRACT FROM AUTHOR]

This study investigated the stress concentration phenomenon and the interlaminar stresses of laminated composite spherical, conical, and cylindrical shells using higher-order shear-normal deformation theory (HOSNT) and transverse stress recovery. The proposed theoretical model incorporates laminate deformations that account for the effects of transverse shear and normal strain/stress, thus modeling the deformation of laminated shells more accurately and eliminating the need for the shear correction factor. The governing equations are solved by applying a semi-analytical method based on the simple trigonometric series and a finite-difference method. In order to fulfill boundary conditions at both the bounding surfaces and local stress-equilibrium equations specified by elasticity theory, the transverse shear and normal stresses are reconstructed by integrating along the thickness direction three-dimensional equilibrium equations of elasticity theory with one-step stress recovery. The present mathematic model and computational procedure were validated by comparing obtained numerical results with those available in the literature. The main advantage of the proposed model is that it correctly predicts the stress components near the clamped boundary edges of laminated composite shells, where sharp changes may be observed. Using HOSNT and one-step stress recovery, this study presents the stress distribution of laminated composite shells of revolution in the clamped boundary zones and assesses the influence of main geometric and material parameters on the distribution of nondimensional deflection and stress components. The analysis results indicate that applying HOSNT in conjunction with one-step stress recovery is necessary for investigating the stress state of laminated shells of revolution. [ABSTRACT FROM AUTHOR]

This study analyses the bending of helicoidal laminated composite plates, inspired by biological helicoids. The analysis employed Navier solution-based shear deformation theory. Five helicoidal schemes—recursive, exponential, semi-circular, linear, and Fibonacci—were studied. Plate thickness stress distribution investigations have been done. The helicoidal distribution parameter greatly affects stress variation. Helicoidal designs have homogeneous stress distribution across the thickness of the plate, unlike quasi-isotropic schemes. Helicoidal lamination designs also eliminate stress channeling caused by cross-ply and quasi-isotropic systems. Also, the helicoidal schemes exhibited the lowest value for the transverse shear stresses ( σ ¯ yz ). HIGHLIGHTS: Bending analysis of bio-inspired helicoidal laminated composite (BILC) plates. Kinematics in framework of parabolic shear deformation theory. Stress distribution across thickness of BILC plates for first time are analyzed. BILC plates are effective compared to quasi-isotropic laminates. The study can be used to construct pressure vessels, domes, automobiles, and aerospace structures. [ABSTRACT FROM AUTHOR]

This work presents the experimental results of a quasi-static penetration test of laminates on a polyurea-polyurethane matrix, reinforced with aramid, carbon and flax fibers. A total of 15 series of samples with different reinforcement configurations were prepared. A quasi-static penetration test was performed for coefficient SPR = 5. The SPR = Ds/Dp was calculated as the ratio of the support hole diameter (Ds) to the punch diameter (Dp). A punch with a rounded 9-mm diameter tip was used to penetrate the material. Percentage changes of penetration energy (%E) and maximum load (%P) compared to a non-hybrid laminate were calculated in order to estimate the impact of hybridization on the properties of laminates. The energy absorbed during the quasi-static penetration test was used to calculate the PSS (punch shear strength) of the laminates. Damage analysis was performed after the puncture test. It was observed that both the type of reinforcement and the configuration of the reinforcement layers have a potential impact on the obtained results and the laminate damage mechanism. [ABSTRACT FROM AUTHOR]

Concrete-filled fiber tubes (CFFT) are gaining prominence as a feasible alternative to traditional materials for a variety of structural applications. However, research on structural performance of CFFT beams is still scarce. This paper presents a finite-element (FE) analysis of CFFT beams validated by experimental results from literature. Then, a parametric study investigating structural performance of post-tensioned (PT CFFT) beams was conducted using 34 FE models using ANSYS nonlinear FE software program. The parametric study results showed that both normal-strength concrete (NSC) and high-strength concrete (HSC) filled PT CFFT exhibit identical nonlinear responses. Increasing the prestressed and non-prestressed reinforcement ratio significantly improved the overall performance of PT CFFT beams. Placing the PT tendons at the bottom of PT CFFT beams enhanced the cracking, yielding, and ultimate load-carrying capacities by 7.98%, 12.32%, and 9.03% for NSC-filled PT CFFT beams, respectively. Doubling the axial stiffness of the tube laminate structure increased the ultimate load, energy absorption capacity (EAC), pre-yielding stiffness (Kpre), and post-yielding stiffness (Kpos) by 18.5%, 12.15%, 9.21%, and 8.2%, respectively for NSC-filled PT CFFT beams. Beams with straight PT tendons exhibited increased cracking, yielding, and ultimate load capacity by 10.85%, 14.60%, and 13.58% more than those with curved-profile tendons. The ductility of PT CFFT beams is more sensitive to the amount of prestressed reinforcement ratio and concrete strength has a minimal effect on the structural performance of PT CFFT beams. [ABSTRACT FROM AUTHOR]

This study investigates the residual tensile behaviour of hybrid Carbon Glass fibers reinforced thermoplastic PEEK laminates after they were exposed for 5 min to a hydrogen/oxygen flame. This flame results in a severe thermal aggression characterized by a wall temperature ranging from 900 to 1270 °C and with different heat fluxes (from 200 to 800 kW/m2). The thermally-induced damages were examined by means of microscopic observations and micro CT analyses. The results show that the mass loss linearly depends on the measured heat flux for a 5 min exposure. Depending on the fire testing conditions, the mechanical properties in tension (stiffness and strength) are totally degraded after exposure to the highest heat fluxes (600 and 800 kW/m2) but the retention of the tensile properties is moderate (about −35 to −60% decrease in strength and stiffness, respectively) after exposure to a 200 kW/m2 heat flux. The residual tensile properties of CG/PEEK laminates follow master curves representing the correlations between the mass loss and the changes in the tensile properties regardless the heat flux. These master curves provide a relevant design rule for composite parts to be used under critical service conditions (H 2 /O 2 flame exposure). • The influence of a H 2 /O 2 flame on the behaviour of composite materials was studied. • Wall temperature ranges from 900 to 1270 °C for heat fluxes from 200 to 800 kW/m2. • The mechanical properties are totally degraded after exposure to 600–800 kW/m2. • The changes in the tensile properties are correlated to the mass loss. • Master curves provide a criterion to design composite parts under H 2 /O 2 flame. [ABSTRACT FROM AUTHOR]

ABSTRACT This paper presents the design of a single‐layer, double‐sided frequency selective surface (FSS) with bandpass characteristics at the S‐band (2.45 GHz) and C band (5.8 GHz) for sub‐6‐GHz Industrial Scientific and Medical (ISM) bands. The proposed FSS is based on the concept of complementary FSS that produces additional resonant modes. The FSS is constructed using an ultra‐thin microwave laminate with a thickness of 0.00076λeff calculated at the C‐band. The solid patch on the front side of the FSS unit cell is composed of an octagonal ring connected to four spiral arms while the slotted region on the rear side is complementary to the geometry on the front side. The unit cell size of the proposed FSS element is 0.087λeff × 0.087λeff. The FSS has an ultra‐low profile with at least 40% size reduction compared to the state‐of‐the‐art. The FSS element offers 11.12% (288 MHz) and 11.45% (650 MHz) at 2.45 GHz and 5.8 GHz, respectively, at x‐polarization while 5.8% (142 MHz) and 5.9% (342 MHz) bandwidth in the y‐polarization. The FSS element has a rotational symmetric structure offering enhanced polarization stability and angular independent operation for oblique incidences up to 80°. Furthermore, FSS operation is stable, which is evaluated and presented. The prototype bandpass FSS is fabricated, and the simulation results are validated in real‐time using experiments. [ABSTRACT FROM AUTHOR]

The present study assesses the potential of using machine learning (ML) methods to predict the extent of lightning thermal damage in fiber-reinforced composite laminates using three supervised machine learning (SML) algorithms: (1) linear regression (LR), (2) decision tree (DT)-based, and (3) MLP models. These models were based on the 10 most significant factors that influence the severity of lightning damage, including three current waveform parameters, four material configurations, and three orthogonal electrical conductivities of each composite. All models demonstrated good performance with coefficient of determination (R2) values between 0.84 ~ 0.96. The multilayer perceptron (MLP) regression model trained with the lightning matrix damage dataset showed the most promising results (R2 > 0.94). Additional hyperparameter optimization was performed to improve the prediction performance of the baseline MLP model. The hyperparameter optimization (Adam optimizer, tanh activation function, and three hidden layers with 234 neurons) slightly improved the performance of the baseline MLP model by ~0.02, but achieved faster convergence. This result suggests that the baseline MLP model trained with the lightning matrix damage dataset is sufficiently accurate and robust. This paper highlights that ML-informed regression models can serve as an efficient first pass-estimator of lightning matrix damage in composite laminates, potentially reducing the amount of extremely time-consuming and expensive laboratory-scale lightning tests or streamlining the development of complex lightning damage models for future design. [ABSTRACT FROM AUTHOR]

This paper reports improvement in the tensile, flexural and interlaminar shear strength (ILSS) properties of ADG‐NH2/Epoxy/CFRP composites at low filler content. Five symmetrical CFRP composite laminates were prepared through wet layup process assisted by vacuum bagging technique with varying wt% proportions (0.25, 0.5, 0.75 and 1) of ADG‐NH2/Epoxy. Tensile tests, short beam shear test and flexural tests were carried out as per ASTM D3039, ASTM D2344 and ASTM 790‐10 respectively to assess the effect of the ADG‐NH2 functionalized nano additives on their mechanical properties. The variation in ILSS were studied for varying temperatures (room temperature, 35, 50, 75, 85, & 100°C for each type of ADG‐NH2/Epoxy wt% (neat, 0.25, 0.5, 0.75 & 1)) of ADG‐NH2/Epoxy/CFRP composites. The ILSS was enhanced up to ∼27% for 0.5 wt% of ADG‐NH2 reinforced CFRP at room temperature but reduced with the higher concentrations (0.75 wt% & 1 wt%). It was observed that ILSS reduced with gradual temperature variations up to 100°C w.r.t room temperature. But an increment was observed up to 0.5 wt% for ADG‐NH2 for all temperature. Form the test results, it has been recorded an improvement in mechanical properties that is, the elastic modulus by ∼18%, ultimate tensile strength by ∼21%, % elongation at break by∼19% and toughness by∼28% for the 0.5 wt% of ADG‐NH2 graphene nano additive reinforced CFRP composite laminates as compared to neat epoxy CFRP laminates. Results also show the augmentation in the Max load by ∼24%, flexural strength by ∼33%, flexural modulus by ∼43%, and flexural strain by ∼26% were observed for the 0.5 wt% of ADG‐NH2 graphene nano additive reinforced CFRP composite laminates as compared to neat epoxy CFRP composite laminates. Fractographic studies of fractured surface using SEM analyses shows better adhesion mechanisms which supports the augmentation in mechanical properties with addition of amine functionalized graphene to CFRP laminate. Highlights: Reinforcement of amine functionalized (ADG‐NH2) graphene in the epoxy matrix and incorporation with carbon fibers to enhance the interfacial and flexural properties.Evaluation of temperature effects on interlaminar shear strength properties of amine functionalized CFRP compositesImprovements in tensile, ILSS and flexural properties observed for a low percentage (0.5 wt%) of ADG‐NH2 graphene reinforced CFRP composite laminates.Use of aerospace grade epoxy and resin with amine functionalized graphene for further use in aerospace industry applications. [ABSTRACT FROM AUTHOR]

The insertion of finer Z‐pins is an effective method to reduce the microstructure damage and maintain the in‐plane performance of composite laminates. In this paper, an ultrasound guided insertion process is proposed to achieve the insertion of fine Z‐pins and the influence of Z‐pin material on the mechanical properties of Ø0.11 mm Z‐pin reinforced composite laminates is revealed based on experiments and simulations. For in‐plane mechanical properties, stainless steel Z‐pins help to reduce the loss of compression modulus and compression strength. For the interlaminar mechanical properties, stainless steel Z‐pins and carbon fiber Z‐pins exhibit bilinear and trilinear bridging laws respectively, resulting in the mode‐I maximum load and fracture toughness of carbon fiber Z‐pin reinforced composites being greater than that of stainless steel Z‐pin reinforced composites. By adjusting the insertion spacing, it is found that for unidirectional composite laminates reinforced by Ø0.11 mm carbon fiber Z‐pins with an insertion spacing of 2 mm, the compression strength reduction is only 3.39% while the mode‐I fracture toughness can be improved by 14.4 times in comparison with the unpinned specimens, achieving a better balance between in‐plane performance loss and interlaminar reinforcement effect. Highlights: The effect of Z‐pin material on fine Z‐pin reinforced composites is studied.The compression properties are simulated by the RVE model.The mode‐I fracture properties are simulated by the DCB unit strip model. [ABSTRACT FROM AUTHOR]

Information on the sintering activation energy is currently focused on evaluation of single-phase ceramic systems. This work shows the results of high-temperature dilatometry measurements of layered and particle composites based on alumina and zirconia. Layered composites with different layer thickness ratios and particle composites with variable composition in the entire concentration range were prepared by electrophoretic deposition allowing manufacturing composites with precious design and strongly bonded interfaces. The phenomena observed during the high-temperature dilatometry measurements are discussed, and the data were used to calculate the sintering activation energies of composites using the modified Master Sintering Curve concept. By covering a wide range of composite designs, it was possible to determine differences in activation energies and to show their dependence on the direction in the case of laminate composites given by the directionally dependent sintering behaviour. Sintering activation energies of layered composites were always higher than for monoliths due to constrained sintering showing maximum sintering activation energies at lower volumes of zirconia in the layers for longitudinal and transversal orientation of the samples. A similar trend was identified in particle composites due to slowed down alumina densification by the pinning effect. Additionally, mechanical properties represented by Vickers hardness and indentation elastic modulus were related to the microstructure developed during sintering. The effects of interconnectivity of phases present in the composites together with other parameters of the microstructure were described. [ABSTRACT FROM AUTHOR]

This research numerically evaluated the eigenvalue responses of the damaged fiber metal laminate (FML) structure. The current numerical model is delved into including crack‐type damage effect on the structural integrity/ stiffness via frequency response. In this regard, a complete mathematical model of FML has been derived through higher‐order shear deformation kinematics for computational purposes. The mathematical model is converted to computer code in the MATLAB platform to predict the eigenvalue responses of FML components with and without damage. The damage influences are considered via circular meshing of finite element steps associated with the isoparametric element (nine nodes and nine degrees of freedom for each node). The solution consistency is checked via convergence, and the results are compared with data available in the open domain. Further, an experimental test is carried out to improve confidence using an in‐house test rig. The experiment was conducted by varying the length of the FML in 0.1 m increments. The results showed good agreement between the numerical and experimental data, with the lowest deviation being 0.29% and the highest 8.97%. The developed numerical model is extended to analyze the influences of design parameters such as geometry shape, aspect ratio (a/b), thickness ratio (a/h) ratio, curvature ratio, and fiber layup sequence on the natural frequency response. [ABSTRACT FROM AUTHOR]

Highlights The CFRP/Ti multi‐bolt joints are commonly used in important structural parts of aircraft. These structure often adopts an integrated drilling method to improve manufacturing efficiency and avoid assembly problems. However, significant differences in material properties between CFRP and titanium alloy can affect hole accuracy, leading to deviations in hole‐size that impact joint performance. In response to these challenges, this study conducted experiments on the hole‐making process for CFRP/Ti laminated multi‐bolt joints and analyzed hole‐size characteristics and precision. The research investigated the effect of hole‐making processes on the static tensile and fatigue performance of CFRP/Ti three‐bolt single‐lap joints specimens and revealed the influence of hole‐size characteristics on load distribution among bolts. Results indicated that titanium alloy chip formation during CFRP hole drilling induced a microcutting effect on CFRP hole walls, resulting in stepped holes. The use of low‐frequency vibration‐assisted drilling improved chip removal and enhanced hole‐making precision. The use of the LDR‐LDR‐CD combined hole‐making process can mitigate the secondary bending phenomenon of critical bolt in CFRP/Ti three‐bolt, single‐lap joints specimens, thereby reducing local stress concentrations. This process combination effectively distributes bolt loads evenly, resulting in a reduction of the bolt load ratio in critical holes by 6.2%, and increases ultimate load and fatigue life by 6.7% and 47.7%, respectively. Therefore, in the hole‐making process of CFRP/Ti multi‐bolt joints, it is crucial to ensure that the precision of critical holes is lower than that of auxiliary holes to decrease the bolt load ratio in critical holes and enhance structural joint performance. Novel method for uniformly distributing load based on controlling drilling precision. The formation process of CFRP/Ti hole diameter characteristics in different processes. The LDR‐LDR‐CD can optimize load distribution, improve ultimate load and fatigue life. [ABSTRACT FROM AUTHOR]

Existing numerical analysis methods often incur high computational costs when directly solving multi-degree-of-freedom systems due to computer capacity limitations. To address this issue, this paper took the composite laminated concentrically stiffened rectangular plate as the research object. The modal synthesis method was employed to reduce the degrees of freedom of the model, enabling the solution of complex dynamic characteristics. In the research process, the domain decomposition theory was used to divide the research object into plate and rib substructures. Based on the spectral Chebyshev method, the substructure dynamic model of the composite laminated rectangular plate was constructed. Subsequently, the function expressions of the complex load excitation on each substructure were derived, and the fixed modal synthesis method was introduced to construct the spectral Chebyshev reduced model of the substructures. According to the artificial spring theory equivalent, the interface force, and the whole reduction model of the composite laminated concentrically stiffened rectangular plate were obtained by assembling the substructure models. The time–domain and frequency–domain dynamic behaviors of composite laminated concentrically stiffened rectangular plates are yielded by solving the whole reduced model. The novelty of this work lies in combining the spectral Chebyshev method with the modal synthesis method. The established reduced model no longer depended on mesh quality and required fewer matrix dimensions and computation time compared to the whole model, while still achieving sufficiently accurate results. Additionally, based on the reduced model, an effective parametric study scheme was proposed to analyze the impact of dimensions and material properties of rib substructures on the dynamic behaviors of the composite laminated concentrically stiffened rectangular plate. These findings can be used to guide the optimal design of laminated concentrically stiffened rectangular plates in engineering practice. [ABSTRACT FROM AUTHOR]

Highlights The extensive use of multidirectional composite laminates requires to understand the delamination behavior at interfaces between plies with different fiber orientations. In this study, double cantilever beam testing was performed to investigate the mode I interlaminar fracture of carbon fiber reinforced polymer laminates with different central interfaces (0//0, 0//+45 and +45//−45). X‐ray microtomography revealed the curved crack front shape that was incorporated to calculate fracture toughness. The fracture toughness varies with the crack length in a typical delamination resistance curve, which can be quantified by an empirical equation. Incorporation of variable fracture toughness into a cohesive zone model can better predict the delamination fracture of the laminate, compared to constant toughness. It was found that the delamination mechanism is independent of central interfaces. However, compared to unidirectional laminates, multidirectional laminates are less resistant to crack initiation, but more resistant to propagation with higher toughness and shorter fiber bridging zone. Mode I interlaminar fracture of CFRP laminates with different central interfaces was investigated experimentally and numerically. Curved crack front shape was incorporated to calculate fracture toughness. Incorporation of variable fracture toughness into a cohesive zone model can better predict the delamination fracture of the laminate. Multidirectional laminates are less resistant to crack initiation but more resistant to propagation with higher toughness and shorter fiber bridging zone. [ABSTRACT FROM AUTHOR]

Acetylation is a breakthrough in wood modification and has been established on industrial scale. However, concerns have been raised regarding the stability of acetylated wood under elevated temperatures, particularly during post hot-pressing processes to manufacture products such as laminated veneer lumber (LVL). At around 150 °C, the added acetyl groups might cleave off (“de-acetylation”) and by that release sorption sites for water. This would increase the moisture uptake of the modified wood. In this study, the impact of hot-pressing at 150 °C on the stability of acetylated beech veneers and LVL was investigated. Fourier transform infrared (FTIR) spectroscopy showed that the chemical composition of acetylated veneers seemed to be unaffected after the heat treatment. Dynamic vapor sorption (DVS) analysis and long-term storing over saturated salt-solutions in miniature climate chambers, indicated no de-acetylation on the basis of negligible changes in wood-water interactions. The number of hydroxyl groups of heat-treated acetylated samples was similar to that of not heat-treated ones, indicating the persistence of the effects of acetylation. By the present study, a certain resilience of acetylated wood towards elevated temperature, like it may occur during hot-pressing of acetylated veneers, became apparent and illustrated the thermal stability of this chemical modification approach. [ABSTRACT FROM AUTHOR]

ABSTRACT Encouraged by the emerging infrared thermography (IT)–based technique for determining fatigue limit of composite materials, this study introduces a novel approach for the quick fatigue limit determination based on acoustic emission (AE) technology. The AE‐based method expands fatigue testing capabilities beyond the IT‐based methods. Fatigue experiments were conducted for the composite laminates and composite sandwich panels subjected to stepwise increasing cyclic loads. For composite laminate specimens subjected to tension–tension and tension–compression fatigue loads, the fatigue limits obtained by the AE‐based method are in good correlation with those acquired from the IT‐based method as well as the conventional up‐and‐down test procedure. In the tests for out‐of‐plane shearing fatigue limits of composite sandwich panel specimens, where the IT‐based method did not work properly, the AE‐based method performed well and obtained the fatigue limit estimation, which is in line with that derived from the S–N curve data, thereby demonstrating its high adaptability. [ABSTRACT FROM AUTHOR]

Structural sawn timber, sourced from softwood plantations, is widely used in lightweight timber-framed residential housing and in engineered wood products for contemporary mass timber construction. However, a significant proportion of milled timber boards are considered ‘out-of-grade’, failing to attain a structural grade under existing classifications systems due to various stiffness, strength, and/or utility-limiting features. This study investigates the potential of controlled lamination techniques to produce structurally usable laminated timber products from out-of-grade timber, using a minimal number of requisite boards. Numerical and experimental methods were employed to compare different board assignment heuristics, in terms of reducing the stiffness variability in laminated board populations. The results indicate that controlled board locations produced remarkably consistent laminated products, achieving very low variability even with a minimum lamination of only two boards. The findings of this paper suggest that controlled lamination techniques have the potential to transform low-value out-of-grade timber into a valuable resource for value-added applications, challenging the existing market perception that out-of-grade timber lacks structural usability. [ABSTRACT FROM AUTHOR]

This study considered adhesion between thermoplastic and thermoset laminates through interdiffusion at the interface. The influence of the degree of cure of the thermoset at the start of the process was investigated through mechanical testing and microscopy. Increasing the initial degree of cure decreased both interlaminar fracture toughness and interphase thickness. Fracture toughness decreased disproportionately to interphase thickness, attributed to changes in interphase morphology and decreasing surface contact at the interface. A simplified model was developed using gel layer thickness measurement data to predict the level of interdiffusion with increasing initial degree of cure. Compared to thermoset-thermoset co-curing, there was superior bond strength at low initial degrees of cure and a predicted increased sensitivity to the initial degree of cure, suggesting a greater influence of process variability. Hence, for specific property critical applications, the trade-off between the potential manufacturing efficiency gains from semi-curing and the reduced performance would be an important consideration. [ABSTRACT FROM AUTHOR]

The bistable morphing composite laminated shell presents promising potential for aerospace morphing structures design, as it is capable of shape-changing under small energy inputs and maintaining two stable states without external loading. The bistable nonlinearity is distinct from the typical geometrical nonlinearity, as it arises from thermal residual stresses that cannot be equalized. During the derivation of a three-degree-of-freedom nonlinear dynamic model, Sanders' nonlinear strain is incorporated into the strain–displacement relationship, while thermal residual stresses are taken into account in the constitutive relationship. The nonlinear dynamic model effectively captures the snap-through phenomena with orthogonal asymmetry in bistable morphing composite laminated shells. In order to reveal the resonance response and chaotic characteristics due to the interaction of vibrations between degrees of freedom, high-dimensional nonlinear dynamical model is derived by multiple scales method based on the 1:1:1 internal resonance relationship. The resonance response curves reflect the parametric influence law of the dynamical system stability. The nonlinear dynamic behaviors are described by the bifurcation diagrams and the maximum Lyapunov exponent. The significant motions under particular excitation conditions are visualized by phase portraits, time histories and Poincaré maps. [ABSTRACT FROM AUTHOR]

A simple modeling is proposed to estimate the elastic-plastic behavior of two-phase isotropic composites made of interpenetrated co-continuous phases. This nonlinear modeling, without equivalent so far, is based on the extension of an explicit Laminate System (LS) scheme proposed previously for linear elastic behavior of such co-continuous composites. Considering monotonic radial loadings, the effective nonlinear stiffness of bi-continuous elastic-plastic composites is estimated from stepwise linearizing the composite overall and phase behaviors using a classical secant linearization procedure. The efficiency of this proposed modeling is checked on some comparisons with rare experimental literature data and with other classical analytical homogenization estimate schemes. [ABSTRACT FROM AUTHOR]

Highlights In actual service conditions, the composite structures are subjected to the combined effect of Mode‐I and Mode‐II loadings. It has great significance in the aerospace, defense, military, automobile, and marine sectors. This study aims to determine the Mixed Mode‐I/II interlaminar fracture toughness (ILFT) of plain and twill woven carbon, Kevlar monolithic, and interyarn hybrid textile composites under several hybridization schemes. The tailored properties are obtained using the interyarn hybridization of high stiff carbon yarn and high tough Kevlar yarn. The effect of individual yarn in the length direction in different hybrid composite laminates is carefully investigated. The Mixed Mode‐I/II ILFT characterization is experimentally performed using a mixed mode bending (MMB) test specimen on the Instron 8862 system under 45%, 55%, and 65% Mixed Mode ratios (MMRs). The increase in mode mixture percentage decreases the lever length, increases the load‐bearing capacity, and increases the Mixed Mode‐I/II ILFT of the MMB test specimen. Plain woven composites exhibited a higher ILFT than twill woven textile composites. The plain woven carbon–Kevlar hybrid composite laminate with carbon yarn‐in‐length direction shows the highest Mixed Mode‐I/II ILFT after CP laminates. Hybridization significantly increases the Mixed Mode‐I/II ILFT compared to monolithic Kevlar fabric‐reinforced composites. Moreover, the failure mechanisms are investigated using scanning electron microscopy. Mixed Mode‐I/II ILFT of carbon–Kevlar interyarn hybrid textile composites. ILFT at nonlinearity (NL), VIS, and 5%/Max load points for 45%, 55%, and 65% MMR. Advantage of placing carbon yarn‐in‐length direction in hybrid configurations. Effect of carbon–Kevlar interyarn hybridization on Mixed Mode‐I/II ILFT. Fractography of tested specimens to investigate several failure mechanisms. [ABSTRACT FROM AUTHOR]

Highlights The outstanding mechanical performance and flowability of unidirectionally arrayed chopped strands (UACSs) give them an advantage in the manufacture of engineering structures with complex geometry. For the application of practical structures, the impact responses and damage evolution of material under low‐velocity impact must be investigated in advance. In this study, UACS laminates and continuous carbon fiber laminates with a stacking sequence of [0/90]4s and a thickness of 2 mm were fabricated for low‐velocity impact tests at 7, 11, 15, and 20 J. The impact responses and postimpact intralaminar damage area were analyzed according to the experimental results, including impact load responses and ultrasound C‐scan inspections. Moreover, to predict the damage evolution of the internal structure, the 3D finite element models were constructed in ABAQUS using a progressive damage model (PDM) through a user‐material subroutine VUMAT. Compared with continuous carbon fiber laminates, the dissipated energy of UACS laminates increases by approximately 10.64% and 57.37% for the 15 and 20 J, respectively. However, the intralaminar damage area of UACS laminates decreased by 29.96% and 28.16% at 15 and 20 J, respectively, since the discontinuous slits in UACS laminates can guide damage paths and suppress damage propagation. The regularly arrayed short fiber reinforced composite was studied. Revealed the low‐velocity impact responses and predicted the damage evolution. UACS and CFRP laminates have comparable impact performance. Illustrated the slits design can suppress the damage to a relatively small area. [ABSTRACT FROM AUTHOR]

Today, there is a high demand and increasing trend for multifunctional composite materials and components due to the combination of a wide range of favorable properties. However, undesired deformation leading to delamination, curvature, cracks, or even complete fracture frequently occurs during the co‐sintering process of metal–ceramic laminates (MCLs). To solve these issues, experimental work highly relies on the time‐consuming trial‐and‐error principle. This work aims to develop a thermo‐mechanical‐metallurgical model capable of predicting the densification, deformation, and delamination of MCLs during the co‐sintering process. It is found that the developed model successfully considers the inhomogeneous relative density distribution and phase transformation of the steel tape. In addition, a thin interlayer formed by a mixed slurry in the MCLs is modeled as cohesive elements to simulate the delamination process. The developed model is systematically validated by the experimental measurements and observations in terms of densification, deformation, and delamination during the co‐sintering process of the investigated laminate variants. [ABSTRACT FROM AUTHOR]

Jute fiber has emerged as a promising reinforcement material in polymer composites, and researchers are actively exploring hybrid composite materials to overcome its individual mechanical property limitations and enhance overall performance. The paper introduces a unique hybridization of polymer composites that harnesses the advantages of stainless steel and aluminium offering a lightweight material for potential engineering applications. In this study, stainless steel 304 wire mesh (S), aluminium wire mesh (Al) and aluminium perforated sheet (Alp) are used as an additional reinforcement along with jute (J) and glass (G) fibers to fabricate hybrid polymer composites with varying volume fractions of SS304 and Al wire mesh. Seven laminates of hybrid composites namely J/J/J/S/J/J/J, J/J/S/J/J/S/J/J, J/J/J/Al/J/J/J, J/J/Al/J/J/Al/J/J, J/J/J/Alp/J/J/J, G/J/J/J/S/J/J/J/G, (J/J/S/J/J/S/J/J)450 along with virgin composite laminate J/J/J/J/J/J/J/J were fabricated and tested to obtain mechanical and vibration properties. Bonding between metal wire and matrix is investigated and reported through ILLS tests and SEM observations. Experimental findings indicate a notable 24% and 7% increase in tensile and ILSS strength, respectively, with SS304 reinforcement. Moreover, significant improvements in flexural and impact strength, approximately 48% and 33% for J/J/S/J/J/S/J/J, demonstrate the effectiveness of the hybrid approach. The J/J/S/J/J/S/J/J laminate excels in damping capacity under various boundary conditions. The study underscores the potential of metallic reinforcement to enhance the mechanical properties of jute fiber‐reinforced polymer composites, presenting opportunities for the development of lightweight, sustainable, and high‐performance materials in engineering applications. Highlights: Developed jute fiber‐based hybrid polymer composites with metal wire reinforcement.Significant increase in strength and stiffness observed with addition of metal wires.Bonding between metal wire and matrix is investigated through ILLS tests and SEM observations.Vibration damping of all hybrid materials is reported.Study provides valuable data to develop sustainable, lightweight, and cost‐effective materials. [ABSTRACT FROM AUTHOR]

Environmentally‐friendly materials are increasingly sought in use of both structural and non‐structural applications. Most of the prominent places, particulates and fibers are exclusively utilized to reinforce polymeric composites, aiming to enhance their strength and provide effective protection against wear. Currently, one of the most pressing issues encountered in current industries are wear and tear, mostly happens during manufacturing and agricultural operations. To overcome this issue, the current study examines into exploring the effects of different weight ratios (0%, 1%, 3%, 5%, 7%, 9% by wt.%) of fly ash (FA) loading on the abrasive characteristics of Interpenetrating Polymer Networks (IPNs) composites strengthened with E‐Glass fibers. Abrasion tests, conducted in accordance with ASTM D99 standard which involves five control parameters: load, FA content, speed, sliding distance, and surface roughness. Experimental design utilized Taguchi's orthogonal array (L25), with opts ANOVA to identify significant control factors. Results indicate that the addition of FA substantially enhances the wear resistance of particulate‐loaded E‐Glass fiber reinforced IPN composites. Moreover, the specific wear rate is significantly influenced by the applied load and FA content. However experimental data suggests that optimal wear behavior for IPN composites occurs under the conditions of 50 N load, 3% FA content, 300 rpm speed, 4000 m sliding distance, and 0.3 μm disc roughness. Further, scanning electron microscopy was also employed to examine microstructural details to better know the micro‐mechanism behavior happens between the particulates with fiber and matrix reinforcement. Highlights: Utilization of fly ash significantly enhances composite strength.IPN laminates fabricated with 0%–7% particulate loads.IPN laminates thoroughly evaluated through wear testing.DOE guided experimental design using L25 orthogonal array.SEM analysis reveals superior quality of fly ash‐loaded IPN. [ABSTRACT FROM AUTHOR]

Continuous carbon fiber‐reinforced poly(ether‐ether‐ketone) composites (CCF/PEEK) are widely used in aerospace. However, long‐term service to elevated temperatures induces material aging in CCF/PEEK composite structures, significantly reducing their load‐bearing capacity. In this paper, the mechanisms of thermal aging effects on the mechanical properties of CCF/PEEK composites were investigated. Mechanical performance experiments were conducted on three‐point bending, short beam shear, and double cantilever beam specimens after accelerated aging in the range of 250–300°C. The evolution mechanism of crystallization behavior and aging characteristics was revealed through differential scanning calorimetry and thermogravimetric analysis. The results indicated that thermal aging primarily impacted the mechanical properties of CCF/PEEK composites through changes in crystallization and interfacial properties, which were highly sensitive to aging temperature, particularly with crystallization exhibiting temperature−/time‐ dependent behaviors during aging. The thermal aging environment promoted the growth and perfection of the crystals. However, at higher temperatures, further aging caused cross‐linking and degradation, resulting in a significant decrease in crystallinity following an initial increase. Moreover, the rate of oxidation and decomposition of the sizing agent escalated with increasing aging temperature, which led to a significant decline in interfacial properties. Generally, thermal aging at 250°C contributed to the improvement of bending and interlaminar shear properties of the composites. However, at 300°C, a significant decrease in both bending and interlaminar shear properties, as well as mode‐I interlaminar fracture toughness. Highlights: The effect and mechanism of thermal aging on the mechanical properties of continuous carbon fiber‐reinforced poly(ether‐ether‐ketone) composites are investigated within the temperature range of 250–300°C.Thermal aging significantly influences the mechanical properties of the composites primarily by inducing alterations in both crystallization and interfacial properties.The differential scanning calorimetry (DSC) experimental results reveal that the crystallization of the PEEK matrix exhibits temperature−/time‐ dependent behaviors during thermal aging.Further aging at 300°C induces oxidation and decomposition of components such as sizing agents, resulting in interfacial debonding.The experimental results indicate that aging at 250°C is conducive to improving the mechanical properties and thermal stability of the composites. [ABSTRACT FROM AUTHOR]

This study investigates the influence of nano clay reinforcement on the mechanical behavior of Kevlar/epoxy composite laminates and sandwich structures subjected to quasi‐static punch shear loading. Three types of composite face sheets were fabricated using hand lay‐up technique: Kevlar/epoxy neat, 0.5, and 1 wt. % of nano clay. The mechanical properties of these composites were characterized through compression, shear, and tensile tests. Sandwich structures were then constructed using the fabricated face sheets and an aluminum honeycomb core. Quasi‐static punch shear tests were performed on the composite laminates and sandwich specimens using hemispherical impactors. Numerical simulations of the punch shear tests were conducted in LS‐Dyna, employing appropriate material models and contact definitions for the constituent materials. Furthermore, to further investigate the failure mechanisms, scanning electron microscopy (SEM) analysis was conducted on the fractured Kevlar/epoxy composite plate specimens. The comparison between the experimental outcomes and numerical data demonstrated a strong correspondence, indicating consistency between the two methodologies. In conclusion, the incorporation of 0.5 wt. % nano clay into the Kevlar/epoxy composite resulted in a 5.09% increase in shear strength and an 11.29% increase in maximum reaction force. The study provides insights into the effect of nano clay reinforcement on the punch shear resistance and energy absorption capabilities of Kevlar/epoxy composites and sandwich structures. Highlights: Proper alignment of the nano clay within the epoxy was achieved.The most efficient rate of nano clay was observed to be 0.5% by weight.The mechanical properties of nano clay‐containing composites were improved.Quasi‐static punch shear tests were performed numerically and experimentally.Numerical results were in close agreement with experimental results. [ABSTRACT FROM AUTHOR]

Though ultra‐high molecular weight polyethylene (UHMWPE) fibers are promising candidates for the design of body armor against ballistic impact, weak interfacial bonding induced by surface inertness of UHMWPE fibers would inevitably result in the fluctuation of impact resistance. Herein, we deploy a scalable 60Co gamma‐ray irradiation strategy to modify the UHMWPE fibers, which not only improves the roughness of the fiber surface, but also creates new chemical bonding between fibers and polyurethane (PU) resin. Surprisingly, the tensile strength of UHMWPE fiber is maintained very well with the introduction of small pores on surface by gamma‐rays, which exhibits greater advantages than other surface modification methods. It should be attributed to the transformation of crystal structures from orthorhombic phase to more stable hexagonal phase in UHMWPE fibers. Because of the improved adhesion between fibers and PU resin, tensile strength of the UHMWPE/PU prepregs is increased by 18.5% after 10 kGy irradiation. Finally, the V50 ballistic performances of UHMWPE/PU laminates are evaluated. Most of the laminates are penetrated at the initial velocity of ~690 m/s except for the UHMWPE/PU laminates irradiated at 10 kGy. In addition, the delamination and back deformation of the irradiated ones are also alleviated significantly, which show great capabilities in not only preventing ballistic impact, but also reducing the injury degree of the wearer. Highlights: A scalable 60Co gamma‐ray irradiation strategy is used to deal with weak interfacial properties of UHMWPE fibers.The roughness of the fiber surface is increased.New chemical bonding between fibers and polyurethane (PU) resin is formed.The tensile strength of UHMWPE fiber is maintained very well.Interfacial properties and ballistic impact limits of laminates are improved. [ABSTRACT FROM AUTHOR]

This study aims to investigate the bending performance and evaluation of aluminum‐carbon fiber reinforced plastic (Al‐CFRP) riveted laminates under varying parameters via self‐pierce riveting and three‐point bending tests. Through the self‐pierce riveting process test, a riveted joint meeting standard requirement was obtained. Based on this joint combination form, Al‐CFRP self‐pierce riveted laminates were prepared. The bending performance test showed the riveted laminate with a span of 80 mm had the greatest bending resistance at a thickness of 2 mm, and the overall strain of the Al‐CFRP self‐pierce riveted laminates was observed by digital image correlation (DIC) technology. Subsequently, validated numerical simulation modeling was conducted by correlating with the test results. On this numerical simulation model basis, further parametric studies and bending performance evaluations (including number of rivets, CFRP lay‐up angle, and laminates width) of the Al‐CFRP self‐pierce riveted laminates were systematically carried out. It was found that the peak load F and bending strength R improved by 1.32% and 26.66%, respectively, while the mass M reduced by 8.99%, for the design variables of var1 of 20 mm, var2 of 6, and var3 of [0/90°]2s. Highlight: An Al‐CFRP riveted laminate structure is proposed to improve the bending properties of riveted laminates by changing the rivet parameters and laminate parameters.The bending properties of riveted laminates with different spans were investigated under three‐point bending loading conditions.The DIC technique observed the changes in the strain field of riveted laminates during bending.The effects of different structural parameters on the bending performance of Al‐CFRP riveted laminates were investigated by numerical simulation.An evaluation method combining the gray correlation degree and the combination assignment method is proposed to obtain the optimum riveted laminate structure under bending load conditions. [ABSTRACT FROM AUTHOR]

Highlights The development of high‐performance ultra‐high molecular weight polyethylene (UHMWPE) fiber laminate is of great significance in the field of bulletproof materials. However, due to the poor heat resistance of UHMWPE fibers, it is challenging to achieve exceptional mechanical properties in laminates prepared via hot‐pressing. In this study, we employ a self‐made ultraviolet (UV) cross‐linked fully drawn yarn of UHMWPE (UVFDY), which exhibits excellent heat resistance, to prepare a UVFDY/unsaturated polyester resin (UPR) laminate through hot‐pressing. The laminate possesses outstanding mechanical properties, which includes high Barcol hardness (~40 HBa), high tensile strength (~800 MPa), and high storage modulus (~13.7 GPa at 25°C), surpassing those of most conventional UHMWPE fiber laminates. Its remarkable mechanical properties are primarily attributed to the highly cross‐linked networks of cured UPR and the stable structures (gel content ~89%, crystallinity ~81.5%, orientation ~93%, and smoother fiber surface) of UVFDY during hot‐pressing. This work not only provides valuable insights into the preparation of high‐performance UHMWPE fiber laminates but also promotes applications for the self‐made UV cross‐linked UHMWPE fiber. Novel laminate possesses high Barcol hardness. The tensile strength and storage modulus of novel laminate are excellent. UV irradiated fiber with high structural stability during hot‐pressing. [ABSTRACT FROM AUTHOR]

Composite structure is widely used in various technological fields because of its superior material properties. Composite structure detection technology has been exploring efficient and fast damage detection technology. In this paper, imagebased NDT technology is proposed to detect composite damage using deep learning. A data set was established through literature, which contained images of damaged and non-damaged composite material structures. Then, five convolutional neural network models Alexnet, VGG16, ResNet-34, ResNet-50, and GoogleNet were used to automatically classify the damage. Finally, the performance of five pre-trained network architectures is evaluated, and the results show that RESNET-50 technology can successfully detect damage in a reasonable computation time with the highest accuracy and low complexity using relatively small image datasets. [ABSTRACT FROM AUTHOR]

CFRP is characterized by its anisotropic properties. Therefore, further structural weight reduction might be achieved by introducing the fiber direction as a design variable. For this study, steering fiber laminates defined by a Bezier curve are applied to a skin panel of CFRP stiffened panels. Then, simultaneous optimization of the fiber paths and stringer dimensions is performed to minimize the panel weight. We propose a new surrogate model that combines two neural networks and Latin hypercube sampling. Stiffness, manufacturability, and buckling load are introduced as constraints. Also, optimization is performed using the surrogate model and a genetic algorithm (GA). Furthermore, the stringer dimensions and fiber directions are optimized for straight fiber laminates. Comparison of steering fiber laminates and straight fiber laminates demonstrated that the introduction of steering layup into skin plates can reduce the stringer weight by up to 25.6%. An effective method for designing the geometric dimensions and layup path is provided. [ABSTRACT FROM AUTHOR]

This research investigates the statistics in terms of mean and coefficient of variance of thermal buckling temperature of shape memory alloy (SMA) fiber-reinforced composite laminated plate using polynomial chaos (PC). The basic mathematical formulation is adopted based on Co finite element method (FEM) in conjunction with secant function-based shear deformation theory. The uncertain input system properties in material and geometrical parameters are modeled as random variables. The effects of SMA fiber and location, pre-strain, loading, modes, temperature distribution, modulus ratio, fiber orientation, length-to-thickness ratio, aspect ratio, and various boundary conditions on the statistics of critical temperature are analyzed. The small amount of random change in input system parameters significantly affects the variance and reliability of SMA fiber-reinforced composite laminated plate thermal buckling temperature under uniform and non-uniform temperature variations. The present PC simulation's results are compared with independent Monte Carlo simulation and those existing in the literature. [ABSTRACT FROM AUTHOR]

In the present article, the panel flutter behavior of nanocomposite hybrid laminated quadrilateral panel is studied. A three-phase carbon-nanotube (CNT)/polymer/fiber laminated composite is considered where the probable agglomeration of the CNT phase in the nano-matrix mixture is also addressed. Diverse use of fiber phase material in different plies is assumed in the context of hybrid laminated composite. A combination of nanocomposite polymer matrix, tow-steered curvilinear reinforcing fibers within the plies, and hybrid multi-material laminate is considered. The panel flutter behavior of the arbitrary quadrilateral hybrid laminated nanocomposite plate is formulated by a non-uniform rational B-splines-type isogeometric analysis method based on the first-order shear deformation plate theory. The nonideal mixture of the nanocomposite is also concerned about through applying a micromechanics approach. Representative results are obtained and compared with those available in the literature to demonstrate the quality of the proposed formulation. The effects of different parameters including the layup, mixture quality, boundary condition, geometry, and flow direction on the flutter behavior are investigated by performing parametric studies. [ABSTRACT FROM AUTHOR]

This article aims to investigate the fatigue life prediction methodologies of composite laminates and lay the groundwork for establishing fatigue life evaluation technology for composite structures. By extending the Hashin criterion to the fatigue failure criterion, an empirical equation for the fatigue life of unidirectional laminates with various fiber orientation is simply created. In view of the influence of the stiffness reduction coefficient of the failure layer, the failure sequence of each layer in the laminate is determined under time-varying loads. On the basis of the equivalence principle of fatigue damage, the equivalent life of the failure layer to the remaining layers in laminate is determined by considering the effects of load interaction, variable loading, and load cycles on damage. In combination with equivalent life, the fatigue life prediction model for composite laminates is constructed, and the proposed model agrees will with the test data. [ABSTRACT FROM AUTHOR]

In this paper, a one-dimensional thermodiffusion laminated beam system with delay feedback is studied. The existence of a solution for our system is discussed within the context of the semigroup approach. In addition, under different boundary conditions, two results of stability properties independent of initial data are investigated. [ABSTRACT FROM AUTHOR]

Currently, sustainability plays a central role in the response to global challenges, strongly influencing decisions in various sectors. From this perspective, global efforts to explore inventive and eco-friendly solutions to address the demands of industrialization and large-scale production are being made. Bio-based composites needed for lightweight applications benefit from the integration of natural fibers, due to their lower specific weight compared to synthetic fibers, contributing to the overall reduction in the weight of such structures without compromising the mechanical performance. Nevertheless, challenges arise when using natural fibers in composite laminates and hybridization seems to be a solution. However, there is still a lack of knowledge in the literature regarding the strategies and possibilities for reducing laminate thickness, without sacrificing the mechanical performance. This work aims to fill this knowledge gap by investigating the possibility of reducing the laminate thickness in hybrid flax/basalt composites made of plies, organized in the same stacking sequence, through only varying their number. Tensile, Charpy, flexural, and drop-weight tests were carried out for the mechanical characterization of the composites. The results obtained confirm the feasibility of achieving thinner hybrid composites, thus contributing to sustainability, while still having acceptable mechanical properties for structural applications. [ABSTRACT FROM AUTHOR]

Deep Eutectic Solvents (DESs) show promising abilities for the delamination of multilayer packaging films that are used in food packaging and in pharmaceutical blister packs. Due to the complexity of their structure, the recycling of such materials is a challenging task, leading to the easiest or cheapest disposal option of either landfill or incineration. Towards the development of 'green' solvents for efficient waste management and recycling, this research focuses on the preparation of a range of hydrophobic and hydrophilic DESs based on carboxylic acids in combination with various naturally derived aliphatic and aromatic organic compounds as well as amino acids. Chemical and physical characterization of the solvents was undertaken using differential scanning calorimetry, rheometry, and density measurements for the determination of their properties. Subsequently, batches of solvent were tested against different types of consumer packaging to evaluate the ability of the DES to delaminate these structures into their component materials. The laminate packaging waste products tested were Al/PE, PE/Al/PET, Al/PE/paper, and PVC/PE/Al. Separated films were collected and studied to further examine the effect of solvent delamination on the materials. Depending on the DES formulation, the results showed either partial or full delamination of one or more of the packaging materials, albeit there were challenges for certain solvent systems in the context of delivering a broad delamination efficiency. Variables including temperature, agitation rate, mixing time, and solvent ratios were investigated via a Design of Experiments process to assess the effects of these parameters on the delamination outcome. The results showed that the DESs presented in this research can offer an efficient, low-energy, affordable, and green option for the delamination of laminate packaging materials. [ABSTRACT FROM AUTHOR]