Composite Structures Research Articles

Influence of granite micro particles on the mechanical, damping and antimicrobial properties of silk–sisal hybrid composites

This paper focuses on the effect of granite-micro-filler on static mechanical properties, damping behavior, and physical characteristics of silk-sisal hybrid composite. The composites structures are fabricated by using three layers of plain weaves mat with varying weight percentages (2, 4, and 6 wt%) of granite-micro-filler by hand layer process. The effect of granite-micro-filler on silk-sisal is analyzed and results are compared with pure silk-sisal (without granite-Micro-filler) hybrid composite. The results infer that; the tensile strength and flexural strength value of the developed silk-sisal hybrid composites are increased with the increase in wt% of granite-micro-filler content than pure silk–sisal, approximately 5% and 9% improved value in order by adding 6 wt% granite-micro-filler on silk–sisal. The tensile and flexural fracture morphology analysis indicated that composed plain weave of silk–sisal fiber mat with two (longitudinal and transverse) directions possesses higher mechanical properties and also observed that, granite-micro-filler dispersed on silk–sisal fiber mat and resin with closely packed. The improved damping factor is obtained by adding 6 wt% of granite-micro-filler content, which is approximately 75.8% higher than pure silk–sisal. The physical properties of silk–sisal hybrid composite have also been analyzed and well discussed in this paper.

0D/2D Co-Doping Network Enhancing Thermal Conductivity of Radiative Cooling Film for Electronic Device Thermal Management.

The radiative cooling has great potential for electronic device cooling without requiring any energy consumption. However, a low thermal conductivity of most radiative cooling materials limits their application. Herein, a multishape codoping strategy was proposed to achieve collaborative enhancement of thermal conductivity and radiative properties. The hBN-coated hollow SiO2 particles were prepared based on electrostatic self-assembly technology, which were then mixed with hBN platelets and doped into a poly(vinylidene fluoride-co-hexafluoropropylene) substrate. Discrete dipole approximation theory was employed to reveal the mechanism and optimize the particle size. The results showed that the multishape codoping method can significantly improve the radiative performance, with 94.9% reflectivity and 91.2% emissivity. In addition, this zero-dimensional and two-dimensional composite doping structure facilitated the formation of a thermal conduction network, which enhanced the thermal conductivity of the film up to 1.32 W m-1 K-1. The high thermal conductivity radiative cooling film can decrease the heater temperature from 58.8 to 31.3 °C, with a further reduction of temperature by 7.2 °C compared to the radiative cooling substrates with low thermal conductivity. The net cooling power of the film can reach 102.5 W m-2 under direct sunlight. This work provides a novel strategy for high-efficiency electronic device cooling.

Native Oxide Layer Role during Cryogenic‐Temperature Ion Implantations in Germanium

Herein, the structural properties and chemical composition of Ge samples implanted with tellurium at cryogenic temperatures are analyzed, focusing on the role of the native oxide. For germanium, cryogenic‐temperature implantation is a requirement to achieve hyperdoped impurity concentrations while simultaneously preventing surface porosity. In this work, the critical role of the thin native germanium oxide is demonstrated when performing ion implantations at temperatures close to the liquid nitrogen temperature. The structural and chemical composition of tellurium‐implanted samples as a function of the implanted dose from 5 × 1014 to 5 × 1015 cm−2 is analyzed. After a laser melting process, the incorporated oxygen is diffused to the surface forming again a GeOx layer which retains a large fraction of the total implanted dose. These detrimental effects can be eliminated by a selective etching of the native oxide layer prior to the ion implantation process. These effects have been also observed when implanting on Si substrates. This work identifies key aspects for conducting implantations at cryogenic temperatures, that are otherwise negligible for ion implanting at room temperature.

Enhancing photocatalytic hydrogen production in conjugated porous polymers through donor-π-donor fragment insertion

Recent progress in conjugated polymer photocatalysts has opened avenues for enhancing photocatalytic hydrogen production (PHP) activity through structural design. This study highlights the impact of the acceptor-to-donor feed ratio on PHP activity in copolymers, influencing their energy level structures. Five conjugated porous polymers (CPPs) were synthesized by adjusting the acceptor-to-donor molar ratio. Notably, at a 2:1 acceptor-to-donor ratio, the polymer demonstrated a high hydrogen evolution rate (HER) of 61.9 mmol g−1 h−1 under full arc irradiation without co-catalysts and an apparent quantum yield (AQY) of 7.77% at 475 nm. However, further increasing the proportion of the donor unit in the copolymers decreases their HER. Experiments and theoretical simulation characterized that the feed ratios effectively tune the polymer's molecular structure, hydrophilicity, band gap, and the generation and transport efficiency of photo-induced charge carriers, ultimately affecting the hydrogen production kinetics and efficiency. This research demonstrates that tuning the band structure and chemical compositions of CPPs through statistical copolymerization significantly impacts their PHP activity.

Experimental and finite element analysis of ballistic properties of composite armor made of alumina, carbon and UHMWPE

AbstractThe performance of multi‐layer ceramic/composite ballistic armor consisting of Alumina, Carbon fiber, and Ultra High Molecular Weight Polyethylene (UHMWPE) under the impact of 7.62 × 51 M61 caliber armor‐piercing (AP) bullets was examined by experimental and finite element methods. The alumina ceramic thickness used in the experiments is 12 mm. The composite structure thickness used in all samples is 10 mm. Explicit dynamic analyses were also conducted using the Ls‐Dyna to verify the experimental studies. The analysis results were compared with experimental studies and evaluated by considering the damage status of the bullet and armor. According to ballistic test results, partial penetration was observed in all armor produced. The front ceramic layer caused corrosion of the bullet, and a mushrooming effect occurred on it. The carbon fiber layer has dramatically helped as an alternative or support to UHMWPE. Since the results obtained with the carbon fiber ratios used remain within the standards, it will not pose a problem regarding usage. On the contrary, using carbon fiber, which is relatively easier to produce and supply than UHMWPE and more economically suitable, will provide more significant benefits. Experimental and numerical studies have revealed consistent results for all armors.Highlights The effect of a 7.62 × 51 armor‐piercing bullet on ceramic/composite armor was examined. Carbon fiber and UHMWPE hybrid structure was created in different thicknesses. The carbon fiber layer has dramatically helped as an alternative or support to UHMWPE. Using carbon fiber, which is relatively easier to produce and supply than UHMWPE and is more economically suitable. Experimental and numerical studies have revealed consistent results for all armors.

Experimental study on the shear and slip behaviors of perfobond strip connectors with low elastic modulus material wrapped perforated rebars

Adopting Ultra-high performance concrete (UHPC) endows steel-UHPC composite beams with numerous benefits, including high cracking capacity, high durability, light self-weight, etc. However, the cracking load of the steel-UHPC composite beams under negative moments reaches only 13–40 % of their ultimate load, with cracking properties being the primary constraint to the development of steel-UHPC composite beams. This study proposed a novel uplift-restricted and slip-permitted (URSP)-PBL connector to improve the crack resistance in the negative moment regions of continuous steel-UHPC composite beams. A total of ten push-out tests were conducted to investigate the behaviors of the URSP-PBL connector. The effects of perforated rebar diameter, rubber thickness, and row numbers on the URSP-PBL connector were investigated by evaluating the failure mode and the load-slip relationship of the push-out specimens. Additionally, numerical analyses were carried out to investigate the effect of various parameters on the mechanical properties of the connector. Based on the analysis results, a load-slip curve model of the URSP-PBL connector was established as a reference for the promotion of the URSP-PBL connector in steel-UHPC composite structures.

A New Type of Wharf and a Study of Its Mechanical Properties by FE (Finite Element) and Experimental Methods

Due to the limitations of planar mode wharfs, this paper proposes a new type of wharf—the three-dimensional cantilevered wharf. The proposed wharf is defined as an improvement of the traditional wharf, extending the traditional wharf upward and cantilevering out to the sea. The three-dimensional cantilevered wharf is a composite truss structure that meets structural and functional requirements. The composite truss structure is formed by connecting the beams of frame structures as a whole. The material consumption of the three-dimensional cantilevered wharf is decreased by controlling stresses and optimizing components. A finite element model of the proposed wharf, with a length of 200 m, width of 105 m, and cantilever length of 80 m, was established to analyze the basic mechanical performance. In this paper, the force distribution of the pile foundation, the vertical force transfer efficiency of web members, the structural stiffness, and the natural frequencies of the proposed wharf are analyzed. Tests regarding the stress and stiffness of different plane cantilever trusses are carried out, and finite element analysis is used for comparison. The test results show that the high-rise cantilever truss has a great in-plane stiffness and a reasonable component stress distribution. Additionally, the three-dimensional cantilevered wharf significantly improves the utilization efficiency of the wharf.

Solar light assisted enhanced photocatalytic activity of smart ternary ZnO:TiO2:SnO2 nanocomposites

In the present study, the smart combinations of metal oxide semiconductors (ZnO:TiO2)1-x(SnO2)x (ZTS) with different SnO2 loadings (as x = 0.0, 0.30, 0.25, 0.20, coded as ZTS0, ZTS1, ZTS2, and ZTS3) were synthesized by employing the simple sol-gel technique. The structural, morphological, optical properties and elemental composition were analyzed by using XRD, Raman spectroscopy, FE-SEM, BET, UV–Vis spectroscopy, IC-PMS, XPS and FTIR of ZTS nanocomposite and proved the formation of smart ternary combination of nanocomposites. Systematic investigation through the characterization emphasised that the acute interfacial combination was established between metal oxide semiconductors. The crystallite size was decreased on adding the amount of SnO2 in the pristine ZTS0 nanocomposites from 23.5 nm to 10.5 nm which was confirmed by Scherrer's equation. The optical energy band gap of the obtained ZTS nanocomposites was found to vary from 3.23 to 3.34 eV on adding the amount of SnO2. The performance of the ZTS nanocomposites as photocatalyst was examined towards organic dyes and the results shows highest degradation of MB and MO dyes with ZTS3 achieving 99 % and 97.3 % degradation efficiency with 1 g/L loading dose. The plausible mechanism was suggested considering the visible light absorption spectra and band diagram resulting in supressed of the recombination rate of charge carriers. The smart combination of ZTS nanocomposites makes it an ideal material for excellent photocatalytic activity for degrading organic contaminants in presence of solar light irradiation.

Mass occurrence of planktic dendroid graptolite synrhabdosomes (Calyxdendrum) from the Early Ordovician Fezouata biota of Morocco

The genus Calyxdendrum is here revised to include planktic dendroid graptolites from the Ordovician (Tremadocian to Sandbian). The mass occurrence of Calyxdendrum amicabilis n. sp. from the Fezouata biota represents one of the few occurrences of synrhabdosomes of dendroid morphology that have ever been discovered. Composite structures, formed from about four to six slender, conical tubaria of the species appear as umbrella-shaped synrhabdosomes. In these, the individual tubaria are connected by their short nemata forming an irregularly shaped proximal membrane. The species is found in the late Tremadocian Sagenograptus murrayi Biozone of the Bou Izargane section in the Ternata plain north of Zagora, Morocco. The mass occurrence is interpreted to represent planktic dendroid colonies transported by low velocity currents or moving actively into different water regions on a wide shallow shelf region. They settled in the “soupy” soft sediment, where they were subsequently compacted in the now lithified mudstone. Planktic dendroids of the genus Calyxdendrum are so far known exclusively from the peri-Gondwana region, but may prove to show a wider biogeographical distribution when better known.

Pull-out test of hybrid connection in steel-UHPC composite slab

This paper presents an experimental study on tensile behavior of steel and ultra-high performance concrete (UHPC) composite structure connected by different connections including epoxy resin adhesive, headed stud, and hybrid of the former two. Thirty-two pull-out tests are conducted by taking the connection type, specimen size and steel fiber content of UHPC as the main parameters. The influences of these main parameters on the failure mode, load-separation behavior, and ultimate resistance of connection are researched. The failure modes of specimens with hybrid connection are UHPC interface debonding and UHPC cone failure, which is identical with the epoxy resin adhesive connection and headed stud connection, respectively. The tensile resistance ratio of headed stud connection to epoxy resin adhesive connection has a significant influence both on the separation performance and tensile resistance of hybrid connection. An empirical equation for predicting the tensile resistance of hybrid connection was proposed by taking the tensile resistance ratio of headed stud to epoxy resin adhesive. The ratio of predicted to test result was 0.973with standard deviations of 0.070. The pull-out tests and analysis of the hybrid connection in steel-UHPC composite structure were still needed to study to get it improved.

Accelerated corrosion of FeCrAlTi coating by in situ proton irradiation in molten lead-bismuth eutectic

The synergistic effect of simultaneous proton irradiation and LBE corrosion on FeCrAlTi coating is investigated, and the surface morphology, elementary composition, microstructure and crystal structure of the formed oxide scale are systematically analyzed. The results reveal the accelerated LBE corrosion behavior of proton irradiated FeCrAlTi coating, which can be attributed to irradiation produced defects leading to enhanced diffusion, irradiation induced more porous oxide scale resulting in promoted short-circuit diffusion, and irradiation enhanced adsorption energy of O, Pb and Bi on coating surface contributing to intensive interface interaction.

Experimental and numerical investigations on flexural behavior of stress-laminated timber-concrete composite decks with butt joints

Stress-laminated timber (SLT) products are increasingly used in the field of timber bridges. However, existing butt joints and significant vibrations of SLT greatly hinder its application. Allying a concrete slab on the top of an SLT deck to form a composite structure can effectively ameliorate these deficiencies. In this study, the flexural behavior of SLT-concrete composite decks (SCCD) was investigated via four-point bending tests. The test parameters include prestress level, butt joint frequency, and concrete slab thickness. Comparative analysis against the SLT deck revealed substantial improvements in the load-carrying capacity and initial bending stiffness of SCCD, with increases of 30.2 % and 86.2 %, respectively. Additionally, the improvement is more significant when the concrete slab thickness increases. The presence of butt joints reduces the structural performance of SCCD, and its stiffness reduction degree is slightly greater than that of the SLT deck at the same butt joint frequency. Furthermore, a finite element (FE) model for the SCCD was established, and the numerical simulation showed good agreement with the test results in terms of failure modes and bending performance. Finally, the bending stiffness reduction coefficient for the SCCD was recommended by considering various butt joint frequencies based on tests and numerical simulations, which can serve as a reference for practical engineering.

Using a Negative Poisson's Ratio to Mitigate Stress Concentrations in Perforated Composite Plates

Stress concentrations pose a significant challenge in designing and optimizing composite components, often resulting in structural alterations and crack formation. This study delves into a detailed numerical and analytical analysis of stress concentration factors in composite materials, with a specific focus on the influence of negative Poisson's ratio and out‐of‐plane modulus. By exploring the interaction of these material properties, the objective is to devise effective strategies for alleviating stress concentrations in composite structures. Through analytical and numerical simulations, a robust correlation between the customized Poisson's ratio and modulus and the mitigation of stress concentration factors, particularly in epoxy/graphite‐reinforced composites are established. This tailored approach has the potential to enhance energy absorption capabilities and consequently reduce the risk of crack propagation in perforated laminated composite plates. This research findings offer valuable insights into composite material design, presenting innovative solutions for enhancing structural integrity and reducing susceptibility to stress‐related issues.

Dislocation response of ECC-RC composite supporting structures of tunnels passing through active fault

To address the problems of the conventional composite supporting structures (CCSSs) such as insufficient anti-dislocation performance and deformation capacity, this study used Engineered Cementitious Composite (ECC) lining sections instead of the traditional lining sections and optimized support design parameters, resulting in the development of novel ECC-RC composite supporting structures (ECSSs) of tunnels passing through active fault. The dislocation response characteristics and their parameter sensitivity of the ECSS was revealed by way of 1/25-scale fault dislocation model tests and finite element analysis. The test results show that the mechanical response characteristics and the failure modes of the CCSS and the ECSS are similar under reverse fault dislocation. Compared with the CCSS, the anti-dislocation performance of the ECSS is significantly improved by introducing of the ECC lining and optimizing the design parameters. The vertical deformation of the ECSS and the range of influence under the same dislocation are significantly decreased, and the strain are reduced to different degrees. This phenomenon shows that by improving the material properties, shortening the spacing of aseismatic joints and optimising the thickness of the shock absorption layer, the stress conditions and applicability under deformation of the structure are improved. The ECSS benefits from the crack resistance and toughening effect of fibres, the degree and scope of cracking of the ECSS are significantly reduced compared with those of the CCSS, and internal and external through cracks and local spalling are absent. The results of finite element analysis show that the overall damage degree of the ECSS is decreased and the damage range is increased by decreasing the strength of the surrounding rock in the fault zone. The fault dislocation response pattern of the ECSS varies depending on the fault type. The damage degree caused by different fault types follows the order of normal fault, strike-slip fault, and reverse fault from large to small. However, the damage range caused by the strike-slip fault is significantly larger compared to normal fault and reverse fault. In the design of fault resistance, the surrounding rock conditions of the fault zone and the form of fault dislocation should be considered.

Electrodeposition in one step: Synthesizing Ir–Co tetradecahedral nanoparticles with high-index (311) crystal planes for enhanced catalytic activity in alkaline hydrogen evolution reaction

Electrochemical water splitting represents a viable route for hydrogen production, but its efficiency critically depends on developing effective electrocatalysts that minimize energy loss and material costs. This study introduces iridium-cobalt (Ir–Co) nanoparticles were synthesized on copper foam (CF) substrates using a one-step electrodeposition method. A comprehensive analysis was conducted on the morphology, chemical composition, and crystal structure of the electrocatalysts, along with a particular study on their electrocatalytic performance in the hydrogen evolution reaction (HER). The results demonstrate that high-index IrCo (311) crystal planes have been detected in the Ir–Co/CF electrocatalysts, which possess a tetradecahedral polycrystalline structure. The size of tetradecahedral nanoparticles is in the range of 180–250 nm. Ir–Co nanoparticles exhibit a balanced composition of approximately 49.8 at% Ir and 50.2 at% Co. The Ir–Co/CF electrocatalyst exhibits superior electrocatalytic activity in 1.0 M KOH solution, requiring only 46.8 mV overpotential to obtain a current density of 10 mA cm−2, with a low Tafel slope of 32.65 mV·dec−1. Additionally, the prolonged stability tests confirm the robustness of the Ir–Co/CF electrocatalyst, highlighting its potential for sustainable energy applications.

Electrochemical and structural performances of carbon and glass fiber-reinforced structural supercapacitor composite at elevated temperatures

Abstract The structural supercapacitor can store electrical energy and withstand structural loads while saving substantial weight in many structural applications. This study investigated the development of a structural supercapacitor with a fiber-reinforced polymer composite system and explored the operating temperature’s influence on its performance. The electrochemical and mechanical properties of structural supercapacitors beyond the ambient temperature have not yet been studied; hence, evaluating parameters such as specific capacitance, energy density, cycle life, and structural performance at elevated temperatures are highly desired. We have designed and manufactured single and parallelly connected multilayer structural supercapacitor composites in this research. Carbon fibers were used as a bifunctional component, acting both as a current collector while acting as a mechanical reinforcement. In addition, glass fibers were added as the separator which is also acting as an integral reinforcement. The electrochemical and mechanical behavior of structural supercapacitors at elevated temperatures up to 85 °C were experimentally investigated. The test results revealed that at room temperature, the developed double-cell structural supercapacitor, which demonstrated an area-specific capacitance of 1.16 mFcm-2 and energy density of 0.36 mWhcm-2 at 0.24 mAcm-2, which are comparable to current achievements in structural supercapacitor research. The structural supercapacitor’s tensile, flexural, and compression strengths were measured as 109.5 MPa, 47.0 MPa, and 50.4 MPa, respectively. The specific capacitance and energy density reached 2.58 mFcm-2 and 0.81 mWhcm-2, while tensile, flexural, and compression strengths were reduced to 70.9 MPa, 14.2 MPa, and 8.8 MPa, respectively, at 85 °C. These findings provide new comprehensive knowledge on structural supercapacitor devices suitable for applications operating within a temperature range from ambient conditions to 85 °C.

Stably Grafting Polymer Brushes on Both Active and Inert Surfaces Using Tadpole-Like Single-Chain Particles with an Interactive "Head".

We report a "grafting to" method for stably grafting high-molecular-weight polymer brushes on both active and inert surfaces using tadpole-like single-chain particles (TSCPs) with an interactive "head" as grafting units. The TSCPs can be efficiently synthesized through intrachain cross-linking one block of a diblock copolymer; the "head" is the intrachain cross-linked single-chain particle, and the "tail" is a linear polymer chain that has a contour length up to micrometers. When grafted to a surface, the "head", integrating numerous interacting groups, can synergize multiple weak interactions with the surface, thereby enabling stable grafting of the "tail" on both active and traditionally challenging inert surfaces. Because the structural parameters and composition of the "heads" and "tails" can be separately adjusted over a wide range, the interactivity of the "heads" with the surface and properties of the brushes can be controlled orthogonally, accomplishing surface brushes that cannot be achieved by existing methods.

Multi-Scale Study of a Phase Change Material on a Tropical Island for Evaluating Its Impact on Human Comfort in the Building Sector

Our study explores the utilization of a phase change material (PCM) to optimize energy efficiency and thermal comfort in buildings in tropical climates. Employing a comprehensive multi-scale approach, this research encompasses both microscopic and macroscopic analyses to rigorously evaluate the PCM’s performance under various environmental conditions. It evaluates the effect of PCMs on ambient conditions in the face of temperature variations and high humidity, utilizing experimental methods at different scales (microscopic and macroscopic). Microscopic analyses reveal the composite structure of the PCM, consisting of microencapsulated paraffin within a cellulose fiber matrix. At a macroscopic scale, experiments using two real-scale test cells evaluated thermal performance and its influence on thermal comfort. Temperature and humidity data were meticulously collected over an extended period to assess the PCM’s impact on indoor regulation. We employed type T thermocouples and flux meters to monitor thermal dynamics and energy flux across the building walls. This setup facilitated a detailed comparison of temperature variations and thermal comfort metrics between the PCM-equipped test cell and a control cell. The results indicate a seasonal duality of the PCM: beneficial in winter for thermal regulation but problematic in summer due to excessive heat retention. The conclusions highlight the importance of carefully selecting and adapting PCMs for tropical climates, thus providing valuable insights for designing sustainable buildings in regions facing similar climatic challenges.

Non-destructive evaluation and Structural Health Monitoring of impact induced damage in composite structures using ultrasonic approaches and shearography

Non-destructive evaluation and Structural Health Monitoring of impact induced damage in composite structures using ultrasonic approaches and shearography

Metal-enhanced fluorescence (MEF) effect based on silver nanoparticles with different UV spectra on a surface carbon dot-based novel dry platform

In this work, to enhance the fluorescence quantum yield of carbon dots (CDs), a novel metal-enhanced fluorescence (MEF) structure was designed by decorating CDs on silver nanoparticle (AgNPs) film. The glass slide-AgNPs (GS-AgNPs) structure was fabricated using the electrostatic adsorption method, and the AgNPs-CDs structures were prepared by the direct drying method, which then formed the GS-AgNPs-CDs composite structure. In this structure, the MEF effect was found to be size dependent by changing the 5 types of AgNPs with different sizes. And the MEF effect also decreased as the distance between the AgNPs and CDs increased by using polyvinylpyrrolidone (PVP) to separate the AgNPs and CDs. This hybrid structure can be used as a fluorescence detection platform and the recorded fluorescence intensity of GS-AgNPs 428 nm-CDs achieved a maximum enhancement factor (EF) of 31.72. Considering the high enhancement factor, this system may become promising to find potential applications in biochemical assay fields.