Composite Structures Research Articles

Investigating the use of pixel scrambling and diffusion in secure radiographic inspections

In warhead verification, physical encryption technology could play a critical role in protecting confidential information on geometric structure and isotopic composition of a true warhead. As an important supplement to physical encryption, algorithmic encryption still has great potential in improving defense-in-depth security for nuclear arms control verification. To further supplement feasible nuclear arms control verification technologies, we propose a verification method based on neutron induced fission reactions employing both physical field flux encryption and algorithm encryption. Physical encryption processes the classified geometry or composition information by encrypting the fission neutron signal of the tested item with a randomly shielded mask. Algorithm encryption adopts pixel scrambling, pixel diffusion for secondary encryption. To verify the robustness and security of this new verification method, numerical simulations are performed using the Monte Carlo toolkit Geant4. Verification results indicate a high level of robustness and security with a low level of noise (∼<0.5%).

Layered Double Hydroxides and Metal-Organic Frameworks for Electrocatalytic CO2 Reduction: A Comprehensive Review

Electrocatalytic carbon dioxide (CO2) reduction has emerged as a promising approach for converting CO2 into value-added products and mitigating greenhouse gas emissions. Layered double hydroxides (LDHs) and metal-organic frameworks (MOFs) have attracted significant attention as potential electrocatalysts for CO2 reduction due to their unique structural properties and tunable chemical compositions. In this review, we provide a comprehensive overview of recent advances in the utilization of LDHs and MOFs as electrocatalysts for CO2 reduction. Scrutiny on various catalysts, along with their general design ways for CO2 reduction is presented. This review will provide insight into the up-to-date research progress in MOF-based materials for CO2 conversion. Furthermore, we highlight opportunities in this field and propose future research directions aimed at optimizing the performance of LDHs and MOFs for CO2 reduction applications.

Experimental analysis of hybrid AM60 magnesium composites reinforced with TiC and TiB2 via stir casting

Rapid progress was made in the development of additive manufacturing process, which went commencing being uncomplicated model substitutes to talented additive process. With powders, additive method such as full melting, segment by segment material fusion, and congeal of fine particles may present inimitable opportunities and compensation. Titanium carbide (TiC) and titanium diboride (TiB2) are employed as reinforcements in the creation of AM60-based hybrid metal matrix magnesium composites. Hybrid AM60 nanocomposites were made using well-known additive manufacturing techniques such selective laser melting. The AM60 bar was created from cylindrical type specimens. The reinforcements are increased by percentages two combination of hybrid composites are prepared AM60 with 4 % Titanium carbide (TiC) and titanium diboride (TiB2) and 8 % Titanium carbide (TiC) and titanium diboride (TiB2). Consequences of the reinforcement were evaluated using micro tensile and micro hardness tests. Among the samples and specimens are showed in harmony through ASTM values, micro tensile and micro hardness characteristics are evaluated using Digital tensometer instrument and a Vickers hardness tester. Vickers Hardness Numbers (VHN) for AM60 magnesium alloy with 4, and 8 % reinforcing are 185.9, and 206.8, respectively. The highest ultimate tensile strengths are, respectively, 703.15, and 809.9 MPa. An Optical Micrograph is used to evaluate the bonding structure of composites, while a Field Emission Scanning Electron Microscope (FESEM) is used to evaluate micro tensile specimens. The greater impact of the different reinforcements Titanium carbide (TiC) and titanium diboride (TiB2) has led to more improved tensile and hardness properties.

Facile in-situ fabrication of graphene oxide/poly(ionic liquid) composites and their adsorption performance for methyl orange

This work reveals a facile in-situ fabricating strategy for graphene oxide/poly(ionic liquid) composites toward the effective adsorption of methyl orange in aqueous solution. This synthetic route includes the formation of novel surfactant-free ionic liquid microemulsions and the stable solubilization of graphene oxide. To characterize the designed composites, FTIR, XRD, TGA, SEM, DSC, and XPS analyses were conducted, and the adsorption isotherms/kinetics of the designed composites toward methyl orange were further investigated. Results indicated that graphene oxide/poly(ionic liquid) composites can be in-situ synthesized facilely within the surfactant-free ionic liquid microemulsions, and the network structure of composites can be adjusted effectively by altering the dosage of co-solvent. In addition, the graphene oxide/poly(ionic liquid) composites prepared in situ exhibited a remarkable adsorption performance of methyl orange. These findings indicate the great application potential of graphene oxide/poly(ionic liquid) composites in the field of cationic dye adsorption.

Structural forming of soil composites using as a pavement subgrade strengthening

The article substantiates the possibility of obtaining composite materials with improved functional properties to strengthen the subgrade, containing technogenic soil stabilized by an additive based on a gelling polymer. The introduction of technogenic soils into composites will not only reduce the consumption of expensive materials, but also solve a complex of acute environmental problems. Composite materials can be used in the construction of structural layers of road pavements, foundations of buildings and structures, sites for various purposes, for the prevention and elimination of defects in the foundations of engineering structures during their construction, reconstruction and repair, including in permafrost areas. Stabilized technogenic soils are more durable, frost-resistant and waterproof, which makes them applicable for creating impervious curtains in hydraulic structures and sealing storage facilities for hazardous substances. The cryogenic effect on a composite material allows one to vary its properties within a wide range and modify its macroporous structure. Studying the process of structure formation of the resulting organic-inorganic materials, consisting of macromolecules of high-molecular substances and inorganic inclusions that have undergone cryogenic treatment, will make it possible to specifically regulate their performance characteristics. The best values of strength characteristics were obtained for samples with a stabilizing additive concentration of 100g/l. The resulting composite materials are hydrophobic, frost-resistant, characterized by a compressive strength of 2.3-6.5MPa and a thermal conductivity of 0.19-0.20W/(m·K). Data from differential scanning calorimetry and thermogravimetry and IR spectroscopy revealed that the binding of mineral particles by a stabilizing additive occurs due to the formation of organomineral complexes with the participation of clay minerals and the restructuring of hydration shells. SEM data indicate that crystallinity zones formed due to hydrogen bonds of hydroxyl groups of neighboring polymer chains can participate in the formation of the composite structure. An increase in the number of cryogenic treatment cycles promotes additional structuring and strengthening of the polymer phase due to the formation of additional nodes of the supramolecular network, ordering of crystallinity zones and the appearance of compacted areas in the structure. Computed X-ray tomography revealed an increase in the density of the composite upon drying, which helps to increase its strength characteristics. The structure of the sample is characterized by heterogeneity of the pore space, which is characterized by the presence of both fine-porous and large-porous regions, which determines its thermophysical properties.

Topical fluoride varnish application shifts dysbiotic dental plaque microbiome towards eubiosis in children with dental caries

ObjectiveThis study used high-throughput amplicon sequencing to examine the impact of long-term continuous fluoride treatment on the dental plaque microbiota of children aged 8 to 9 with mixed dentition. DesignThe study population consisted of twenty 8–9-year-old children with dental caries. Topical application of fluoride-varnish was weekly administered for one month to all subjects. Clinical indicators and anthropological data, such as the caries index (DMFT and dmft), were documented for every participant at baseline. A baseline assessment and a month after the fluoride varnish treatment were conducted for the salivary pH level and the Patient-Hygiene-Performance (PHP) index. Following application of the fluoride varnish, plaque samples were obtained both one month later and before (baseline) and were then used for 16S rRNA gene-based Next Generation Sequencing. ResultsThe results showed significant differences in the community composition structure (p < 0.01). Notable caries-associated pathogens in the dental plaque microbiome were depleted whilst health associated phylum Proteobacteria was increased in the abundance following fluoride-varnish application. In children with mixed dentition, this study found that after one month of fluoride-varnish treatment, there was a significant decrease in the prevalence of the dominant pathogenic genera, Fusobacterium, Porphyromonas, Capnocytophaga, Neisseria, and Leptrotrichia, along with an increase in certain genera related to healthy oral condition, mostly from the phylum Proteobacteria, such as Areinmonas, Pseudoxanthomonas, and Luteimonas. ConclusionsFluoride-varnish application may shift the community level microecology from dysbiosis to eubiosis. Moreover, application of fluoride-varnish with weekly intervals for one month reduced the caries-causing bacteria while enriching the rise of unique, ubiquitous genera primarily belonging to the Proteobacteria, which may plaque a defensive role against progression of caries. Furthermore, a rising pH level towards neutrality (pH 7) indicated a healthier oral environment following the application of fluoride varnish.

Concurrent level set topology and fiber orientation optimization of fiber-reinforced composite structures

Concurrent level set topology and fiber orientation optimization of fiber-reinforced composite structures

Investigating the effectiveness of carbon nanotubes for the compressive strength of concrete using AI-aided tools

Sustainable development in the building industry can be achieved through the use of versatile cementitious composites. Thus, incorporating nanoparticles into cement composites can create materials with enhanced performance and numerous applications. The utilization of carbon nanotubes (CNTs) in the construction industry has great promise for developing efficient solutions to establish a sustainable ecosystem with diverse characteristics. However, forecasting the characteristics of these composites is a significant challenge due to their intricate composite structure and nonlinear behavior. Designing and conducting laboratory experiments on diverse samples and across multiple age groups is challenging, time-consuming, and costly. Moreover, there is presently a lack of a forecasting model that can predict concrete's compressive strength (fc') with nanoparticles. Three machine learning (ML) techniques, K-nearest neighbor (KNN), linear regression (LR), and artificial neural network (ANN), were used to predict the fc' of nanocomposites containing CNTs in this research. A thorough database consisting of 282 data entities for the CNTs-based concrete and the model's reliability was assessed using the R2 test and statistical error analysis. The ANN model had the most outstanding R2 value of 0.885, while the KNN and LR models had R2 values of 0.838 and 0.744, respectively. Moreover, RReliefF analysis is utilized to evaluate the primary components in predicting concrete outcomes. This research shows that the properties of CNT-based concrete composites are greatly affected by the water-to-binder ratio, followed by the proportions of cement and coarse aggregates. The ML algorithms exhibited superior generalization capabilities, suggesting their enhanced potential for accurate predictions of CNTs-based concrete properties.

Evaluation of the Modal Parameters of a Unidirectional Carbon-Based Composite Structure Using the Influential Factor of Static Loading.

Static loading can significantly alter the dynamics of unidirectional carbon-based composites (UCBCs), with modal parameters varying depending on the orientation of the carbon fibers. In this study, the sensitivity of modal parameters of UCBC structures under uniaxial static loading was investigated. The theoretical static load influential factor was derived from a linearized UCBC model and corresponded to the transformed decoupled response over the mass-normalized static load. Three rectangular UCBC specimens (carbon fiber orientation of 0°, 45°, and 90°) were prepared under fixed-fixed boundary conditions using a jig fixture. Uniaxial static loads between 0 N and 1000 N were applied, and the first three modes of the UCBC specimens were analyzed. An isotropic SUS304 specimen was used as a reference. The linearization assumption about the UCBC structure was preliminarily validated with the Modal Assurance Criterion (MAC). A high influential factor was found for the UCBC specimen when carbon fibers were aligned with the static load direction at the first two resonance frequencies. Therefore, the proposed influential factor is an efficient indicator for determining the sensitivity of the dynamic response of a UCBC structure over a static load case. The variations in the influential factors for the UCBC specimens were more pronounced than for the isotropic specimens.

Novel application of ground penetrating radar for damage detection in thick FRP composites

This paper presents the first successful application of ground penetrating radar (GPR) to the inspection of thick (≥100 mm) fiber-reinforced composites. These thick composites are found in wind/tidal turbine blades and composite-hulled ships, where sufficient non-destructive testing (NDT) remains challenging. Polyester-glass specimens, ranging in thickness from 100 to 120 mm, were created with delamination-mimicking damage. Specimen thickness, damage depth location, antenna orientation and damage dryness were the test variables. Finite-difference time-domain simulations indicated the method’s feasibility, and experimental results confirmed these findings. GPR effectively detected and precisely located dry, in-plane damage, with increased detectability for water-filled damage due to the enhanced contrast of electrical properties that creates the damage response in the signal. This capability is particularly advantageous for marine composites, where extensive damage may lead to water ingress. In a comparison with an ultrasonic inspection, GPR proved superior for the thicker composites (≥100 mm). As the first successful application of GPR to composite structures, these findings significantly advance the field of NDT of these materials.

Understanding the interface fracture mechanism by composite BFPMPC mortar and cement concrete bending beam

This study aims to utilize basalt fiber-reinforced polymer-modified magnesium phosphate cement (BFPMPC) mortar as an overlay for rapidly repairing surface defects such as raveling and delamination on Portland cement concrete (PCC) pavements, thereby swiftly restoring traffic flow and enhancing pavement service durability. Initially, double layered three-point bending fracture (DLTPB) tests were conducted on composite BFPMPC and PCC specimen with different predetermined crack lengths. The flexural strength was measured, fracture parameters were obtained based on the double-K fracture criterion, and crack propagation paths were determined using digital image correlation (DIC) methods. Subsequently, the fracture behavior of the composite beam was predicted by boundary effect model, and the interface microstructure between BFPMPC and PCC was characterized using nanoindentation, nano-scratch, and SEM/EDS techniques. Finally, by analyzing the fracture characteristics of the composite specimens, the crack propagation model was established and validated by finite element analysis (FEA). The results indicated that BFPMPC mortar overlay can enhance the flexural strength of composite structure. The unstable fracture toughness, cohesive fracture toughness, and fracture energy decreased with increase of crack length-to-height ratio (a0/D), while the initiation fracture toughness increased with increase of a0/D. DIC measurements provided insights into the morphology of the crack tip and the length of the fracture process zone (FPZ). The boundary effect model predictions aligned with the fracture characteristics of the specimens, which were controlled by nonlinear fracture criteria. Nanoindentation tests revealed that the mechanical properties of the interface are influenced by multiple sub-interfaces, with the elastic modulus relationship being ITZ-4 > ITZ-2 > ITZ-3 > ITZ-1. Further analysis of scratch hardness and scratch fracture toughness confirmed that the BFPMPC-PCC interface exhibited high fracture toughness, which was crucial for improving structural resistance to fracture. SEM/EDS observations revealed significant cracks at the interface between BFPMPC and ordinary Portland cement (OPC), while cracks between BFPMPC and coarse aggregates were smaller. Subsequently, the fracture analysis model for composite specimens was proposed to finely reveal interface fracture failure, and the FEA results exhibited a high degree of consistency with experimental results.

Design of polyimide/carbon nanotube@Ag@polyimide/graphene composite aerogel for infrared stealth and electromagnetic interference protection

CHATGPT artificial intelligence is taking the world by storm, and countless electronic devices will generate massive amounts of electromagnetic interference (EMI). Hence, there is a pressing demand for materials exhibiting high thermal conductivity and superior EMI shielding effectiveness (SE). Thus, we construct a polyimide/carbon nanotube@Ag@polyimide/graphene (PCAPG) composite aerogel with porous, layered, and homogeneous structures in one, which provides a new idea for the multi-interface polarization interaction and special structure of anti-EMI materials. PCAPG has high thermal conductivity of ∼ 0.259 W (mK)-1 at 25 °C, excellent EMI SE of ∼ 90.28 dB and specific shielding effectiveness (SSE) of ∼ 940.42 dB cm3 g−1. The synergistic EMI attenuation mechanism of the PCAPG composite structure is analyzed using an aerogel unit. This composite aerogel provides a viable solution for infrared stealth, promoting heat dissipation from electronic components and reducing electromagnetic interference.

Stacking sequence optimization of composite laminates for maximum fundamental frequency using Bayesian optimization computational framework

A computational framework combined with the commercial finite element software Abaqus and Bayesian optimization algorithm is proposed. The proposed computational framework leverages the Gaussian process based-probabilistic capability in Bayesian optimization as a surrogate model for minimizing the computational cost of objective function evaluations in the finite element analysis. The optimization problem in this work is to enhance the maximum fundamental frequency of the composite laminates, which is one of the critical parameters in the design for composite structures. The optimization of stacking sequence selection is investigated and validated by the results obtained from literatures. The effectiveness and efficiency of the proposed Bayesian optimization computational framework in maximizing the fundamental frequency of composite laminates are demonstrated by comparing the optimized results from different optimization techniques through a series of cases including the 8-layer rectangular plates with 11 different boundary conditions and the 10 to 20-layer trapezoidal plates with the same boundary condition. The proposed framework developed in this work has highly potential as an engineering tool to address a broader range of structural optimization in vibration problems.

A cylindrical shell model with distributed springs for a rotating tire

In a companion paper (Vol. 248, Article 108227), we demonstrated the dependence of tire parameters on the modal characteristics of a stationary tire. For a more realistic scenario, when tire rotation is considered, the modal characteristics are veered due to centrifugal, Coriolis, and gyroscopic effects. In this paper, we study the forced vibration response of a rotating tire and also consider the effect of static load on modal characteristics. The tire tread is modeled as a cylindrical shell and the sidewall is modelled using distributed springs in axial, circumferential, and radial directions. The tire inflation pressure is accounted for, which generates pre-stresses in the tire belt in circumferential and axial directions. The material model incorporates an orthotropic composite structure of the tire with multiple stacked layers of steel belt reinforcing. The governing equations of motion of the rotating shell are derived and further reduced to the corresponding eigenvalue problem. Galerkin’s projection with orthogonal basis functions is used to obtain the natural frequencies and associated mode shapes. For the forced vibration, the tire is excited by a harmonic point load at a fixed location, and the response is calculated by superimposing the basis functions of the free vibration problem. The analytical model predictions are compared against the computation finite element (FE) model developed in ABAQUS® and experimental modal testing results. To understand the effects of rotation on wave propagation, dispersion relations were obtained, and the wave number spectrum of the rotating tire was compared with that of the stationary one. Finally, to understand the dependence of natural frequencies on tire rotation and normal load, Campbell diagrams and frequency response functions (FRFs) were obtained from the proposed model. The model shows a fairly good agreement with experimental results and FE simulations.

Geometrically nonlinear topology and fiber orientation optimization of composite structures using membrane-embedded model

The membrane-embedded model can be efficiently used in the finite element analysis of composite structures considering geometrical nonlinearity because of its practicability. This paper extends this model to the topology and fiber orientation optimization considering geometrical nonlinearity. The discrete design variables of topology and fiber orientation are continuous by the solid isotropic material with penalization method and bi-value coding parameterization method. An optimized interpolation scheme for the membrane-embedded model is constructed for geometrical nonlinearity. The filtering function is added to improve the convergence of the fiber orientation. To reduce the computational complexity, topology and fiber orientation are independently updated at each iteration during the optimization process. Numerical examples demonstrate the effectiveness of the proposed method for membrane-embedded composite considering geometrical nonlinearity.

Three-dimensional porous structured cobalt- and nitrogen-doped carbon nanotube electrocatalyst derived from cobalt-based zeolitic imidazolate framework nanoleaves for high performance zinc-air battery

The development of efficient and cost-effective electrocatalysts to overcome the intrinsic sluggish kinetics of the oxygen reduction reaction (ORR) in zinc-air batteries is crucial. In this study, we introduce a strategy that integrates a template-assisted synthesis with subsequent thermal treatment to fabricate an active and stable cobalt-based nitrogen-doped carbon electrocatalyst, denoted as Co-N-CNT. The strategy adjusts the disordered architecture of the zeolitic imidazolate framework (ZIF) through the synergistic effect of bimetallic species, restricted the growth of zeolitic imidazolate framework nanoleaves (ZIF-L) using salt templates, and directed the transformation from a two-dimensional blade-like morphology to a three-dimensional multi-tiered composite structure. Notably, the Co-N-CNT-800 sample, synthesized at an optimized pyrolysis temperature of 800 °C, exhibits a half-wave potential of 0.89 V and demonstrates stability with sustained cycling over 21 h, which is comparable to the performance of commercial Pt/C electrocatalysts. Moreover, when employed as the cathode in zinc-air batteries, Co-N-CNT-800 not only surpasses Pt/C in terms of power density but also exhibits long-term charge/discharge stability. This findings offer a viable pathway for the design of active and cost-effective ORR electrocatalysts, holding promise for applications in the electrochemical energy storage and conversion systems.

Fabrication of Cellular Composite Structures with Continuous Fiber Reinforcement and Different Infill Patterns Using Fused Filament Fabrication

Additive manufacturing (AM), also known as 3D printing, is a process of creating three-dimensional objects with complex geometries that is utilized in various engineering applications. Continuous carbon fiber (CCF) is a high-performance material that offers a range of benefits in terms of strength, weight, and durability. Fused filament fabrication (FFF) is a type of AM that uses a thermoplastic filament as a material with which to create a three-dimensional object, and it has been widely used in various applications, as it enables the faster, cheaper, and more customizable production of parts and products. Lightweight cellular composite structures consists of small, repeating unit cells that are interconnected to form a larger structure, and they are employed in high engineering applications. In this study, cellular composite structures were fabricated using FFF technology, considering two types of infill paths design (grid and triangular) manufactured at three infill density levels (20%, 40%, and 60%). After the fabrication process, tensile and flexural properties were experimentally investigated, and the influence of the infill pattern and density on the cellular composite parts were studied. The achieved results demonstrated that the infill design pattern and its density had great influence on the mechanical properties of the cellular structure. The obtained results also showed that the lightweight cellular composite parts had great potential for use in structural applications.

Efficacy and mechanism of activation peroxymonosulfate for tetracycline degradation by AC-MIL-101(Fe)-derived magnetic CuO/Fe2O3/CuFe2O4

In this work, magnetic CuO/Fe2O3/CuFe2O4 (CFC-0.50) composites were prepared by using a complex of the metal–organic skeleton AC-MIL-101(Fe) and Cu as a precursor. The compositional structure of the catalysts was observed via XRD, FTIR, SEM, and TEM, and the physicochemical properties of the catalyst materials were analyzed via characterization methods such as BET and VSM. Degradation experiments using TC as the target antibiotic were performed to screen the optimal catalyst, CFC-0.50, by modulating different doping ratios of Cu/AC-MIL-101(Fe) to study the effects of changes in key parameters of the catalyst environment on the degradation efficiency of TC and to investigate the stability and applicability of CFC-0.50. The reaction mechanism of the CFC-0.50/PMS/TC system was proposed by using XPS to study the chemical shape of the catalyst before and after the reaction and supplemented by quenching experiments, EPR, and EIS and LSV. The intermediate products of the reaction system were analyzed via LCMS, and possible degradation pathways were proposed.

Transparent Superhydrophobic and Self-Cleaning Coating.

Surface roughness and low surface energy are key elements for the artificial preparation of biomimetic superhydrophobic materials. However, the presence of micro-/nanostructures and the corresponding increase in roughness can increase light scattering, thereby reducing the surface transparency. Therefore, designing and constructing superhydrophobic surfaces that combine superhydrophobicity with high transparency has been a continuous research focus for researchers and engineers. In this study, a transparent superhydrophobic coating was constructed on glass substrates using hydrophobic fumed silica (HF-SiO2) and waterborne polyurethane (WPU) as raw materials, combined with a simple spray-coating technique, resulting in a water contact angle (WCA) of 158.7 ± 1.5° and a sliding angle (SA) of 6.2 ± 1.8°. Characterization tests including SEM, EDS, LSCM, FTIR, and XPS revealed the presence of micron-scale protrusions and a nano-scale porous network composite structure on the surface. The presence of HF-SiO2 not only provided a certain roughness but also effectively reduced surface energy. More importantly, the coating exhibited excellent water-repellent properties, extremely low interfacial adhesion, self-cleaning ability, and high transparency, with the light transmittance of the coated glass substrate reaching 96.1% of that of the bare glass substrate. The series of functional characteristics demonstrated by the transparent superhydrophobic HF-SiO2@WPU coating designed and constructed in this study will play an important role in various applications such as underwater observation windows, building glass facades, automotive glass, and goggles.

Formation mechanism and properties of superhydrophobic surface of ship plate steel

Superhydrophobic surface of ship plate steel was constructed by chemical etching and low surface energy modification. Formation mechanism and properties of the superhydrophobic surface were investigated through SEM, FT-IR, electrochemical analysis and anti-icing evaluation. Corrosion and dissolution of ferrite creates a high-roughness surface with a micro-nano composite structure, and a monomolecular layer of low surface energy material covers steel surface through chelation coordination of stearic acid and Fe, which endows ship plate steel surface with superhydrophobicity. Compared with bare steel, the superhydrophobic surface shows high corrosion resistance, while 75.2% of surface icing is prevented, achieving the purpose of anti-water, anti-icing and corrosion resistance of ship plate steel. In addtion, the simple and cost-effective preparation technique is conducive to large-scale industrial applications in the future.