Composite Construction Research Articles

Surface modification of Luffa and Maize fibers by using alkali medium

Agricultural biomass is a well-known renewable resource that has a high rate of recycling. Two of them are luffa sponge and corn husk/maize fibers. Luffa sponge may be effectively used to reinforce lightweight composite constructions because of its polypore structure. For this race, maize fiber is also appropriate. Surface modifications for both of the fibers are needed for increasing mechanical strength with higher interfacial bonding with the matrix materials of composite manufacturing. This investigation involved treating both materials with 5 g/L, 10 g/L, and 15 g/L of NaOH in order to describe the alterations occurring on their physio-chemical characteristics. The therapy lasted 60 min and was administered at 90 °C. Following that, acetic acid was used to neutralize the samples. The ASTM D1445 technique was used to measure the bundle fibers' breaking force and elongation, and the ASTM D570 procedures were used in order to determine the water absorption variation % in the treated samples. The FTIR test and SEM examination revealed the contaminants that were eliminated from the surface of Luffa and Maize fibers. The test findings demonstrated improved modification behaviors for the 15 g m/L treated fibers, which had an elongation percentage of 3.02% and an equivalent breaking force of 5.12 kg for the Luffa fiber and 5.72 kg for the maize fiber. Natural contaminants were eliminated as a result of variations in functional group intensity shown in the FTIR pictures. However, SEM pictures showed that the surface smoothed out for samples treated with 15 g per liter of NaOH, which may be the cause of the fiber's brittle interlocking with the matrix components. Moreover, water absorbency rose by over 300% compared to the untreated fibers. In summary, samples treated with 10 g/L NaOH might serve as superior reinforced materials of composite for both types of fibers.

FORMATION AND WAYS OF IMPROVEMENT OF CONTINUOUS TEXTILE ORNAMENT

The article discusses the main properties and features of continuous textile ornament, formed in the process of its changes during the change of historical periods. On the basis of concrete examples, the methods of its production are described, and the principles of its plastic organisation are outlined. Special attention is paid to the search for imagery in a continuous ornament based on the plastic connections of compositional construction. The text of the article analyses in detail the plant ornament of modernity, in which a continuous ornament is externally manifested in the form of an endless interweaving of leaves, shoots and flowers on the surface of the fabric, creating images of a blooming meadow, impenetrable swamps or jungles. The modern continuous ornament is considered in the context of stylistic changes of postmodernism and possibilities of computer technologies. The possibilities of improving continuous ornament by using new types of artificial and synthetic fabrics with effects arising from the peculiarities of weaving technologies are determined.

Processable Pickering emulsion for composite cryogel with cellulose nanofibrils and nanochitin

Cryogels that are constructed with cellulose nanofibrils (CNF) are important as green materials for a wide range of applications. However, their utilization is limited by inherent hydrophilicity and insufficient mechanical properties. Herein, a processable CNF/nanochitin (NCh)-stabilized Pickering emulsion that contains polylactide (PLA) in the oil phase is developed to directly produce ternary composite cryogels via freeze-drying. The complexation of CNF with NCh promotes CNF adsorption at the surface of PLA droplets, resulting in formation of uniform Pickering PLA droplets. The CNF/NCh complex-stabilized PLA droplets are easy to be translated to the internal structure of the cryogels, exhibiting lightweight nature and possessing highly porous structure. The interconnected network and lamellar structure formed by the CNF/NCh complexes, associating with inclusion of PLA particles, improve the cryogel structure integrity upon post-processing and endow hydrophilic cryogel with water resistance. This study offers a straightforward and eco-friendly Pickering emulsion template on fabrication of the CNF-based composite cryogel with controllable microstructure and mechanical performance, broadening construction of nanocellulose-based composites.

Performance evaluation of innovative triangular and spherical ribbed headed studs in composite steel beam-concrete slab junction

Composite structures have now become a popular practice in the construction of bridges and RCC structures. Various advancement has been taken in several decades to ensure the composite action between the concrete and steel interface. Shear connectors were developed to ensure this composite action in between the steel and concrete interface of the composite junction. The two types of connections that are most frequently used in composite construction are headed stud shear connectors and channel connectors. The maximum stress concentration of the headed stud shear connector occurs on the bottom of the headed stud shear connector. As a result of the higher stresses at the bottom of the headed stud shear connector the bending height of the headed stud shear connector varies in between 18 to 33% depending upon the grade of concrete. The present study intends to study the effect of geometric variation in headed stud shear connectors according to the requirement of the cross-section. The geometric variations were made with reference to bending height throughout the shank of headed studs. Based on the stress variation the headed stud shear connector is divided into three different zones. For making these variations the headed stud was distributed into three zones. Zone 1 is the headed region of the connector. Zone 3 is the bottom region with maximum shear concentration and zone 2 is the part of shank connecting the zone 3 and zone 1 of the headed stud shear connector. In present study volume reduction is done in the zone 2 region of the headed stud shear connector and volumetric addition is done in the zone 3 region of the headed stud shear connector. Based on the proposed ideology for creating geometric variations, two different studs are proposed namely spherical ribbed headed studs (SRHS) and triangular ribbed headed studs (TRHS) studs. Performance of the proposed SRHS and TRHS shear connectors was evaluated using six experimental specimen and Finite element analysis. Results show that SRHS and TRHS studs have higher shear carrying capacity, ductility and stiffness compared to conventional headed stud shear connectors.

Rejection of malathion by nanofiltration and reverse osmosis membranes exposed to foulant and two clean-in-place procedures

ABSTRACT This research tested the treatment efficacy of an Energy Savings Nanofiltration 1 Low Fouling (ESNA 1-LF) nanofiltration (NF) and an Energy Saving Polyamide 2 (ESPA2) reverse osmosis (RO) membrane for removing malathion from water. Both membranes are of composite polyamide construction. The study included measuring malathion rejection using both pristine membranes and membranes exposed to a simulated secondary wastewater effluent foulant before and after two types of clean-in-place procedures. Across all conditions studied, malathion rejection ranged from 84 to 95% for the ESNA1-LF NF membrane and 77 to 94% for the ESPA2 RO membrane. Contact angle measurements were also collected for each membrane exposure condition. While the contact angle measurements indicated changes to the hydrophobicity of the selective layer of the membranes, they did not correlate to changes in the performance of malathion rejection. As expected, it was observed that malathion rejection improved with the introduction of foulant. Also, the clean-in-place procedures helped restore flux while maintaining malathion rejection.

An enterprise composite blockchain construction method for business environment.

In order to foster a modern economic system and facilitate high-quality economic development, it is crucial to establish a conducive business environment. Undoubtedly, the evaluation of the business environment for enterprises constitutes a prominent area of research. Nevertheless, ensuring the authenticity and security of the raw data sources provided by participating enterprises poses a challenge, thereby compromising the accuracy of the evaluation. To tackle this issue, an enterprise composite blockchain construction method for business environment is proposed in this paper, which stores the raw data of enterprises by the means of hybrid on-chain and off-chain. Initially, the enhanced hash function SHA256 is introduced to encrypt the raw data of enterprises. The encrypted data is subsequently stored in an off-chain Level DB database, which is based on non-volatile memory. This approach effectively alleviates the burden on communication and storage. Secondly, a composite storage strategy on-chain is adopted: the key values from the Level DB are stored in the DAG-based Conflux public blockchain, while the enterprise state data is stored in the consortium blockchain, so as to provide trusted evidence of business environment evaluation data. Finally, it is demonstrated through a large number of experimental comparisons that the enterprise composite blockchain construction method proposed in this paper exhibits better read and write performance, lower storage efficiency and storage overhead, and outperforms both the before-improved Level DB database and existing blockchain storage models.

CMM 2023, Coimbra, Portugal: XIV Conference on Steel and Composite Construction

CMM 2023, Coimbra, Portugal: XIV Conference on Steel and Composite Construction

Tailoring intrinsic properties for tetrahedral carbon/copper composites construction via electronic interface engineering

The electronic structure induced interface properties are important for active control of the advanced equipment performance. Nevertheless, it is difficult to reveal the intrinsic mechanism by experiments. In this paper, the interfacial properties and electronic characteristics of eight different stacking ta-C/Cu interfaces were studied via first principles method. The work of adhesion of ta-C/Cu(110)-2nd interface the largest (6.19 J/m2) and its interfacial energy is the smallest (3.74 J/m2), which indicates that it is the most stable structure with the smallest interface formation resistance. In addition, the polar covalent bonds dominated by electronic structures are major contributor of the ta-C/Cu interface properties. During tensile process, the critical strain of ta-C/Cu(110)-2nd is the largest (17.0 %), and the tensile strength of ta-C/Cu(100)-2nd is the largest (61.59 GPa). When all interfaces are fractured under tensile force, the atoms on Cu surfaces are transferred to ta-C surfaces and separated into two free parts. When the energy of one of the wave valleys first reaches the threshold of the lowest plane-averaged potential, the interfacial structure breaks at the interfacial gap corresponding to the wave valley. Changes in interfacial bonding properties can therefore be judged by changes in the magnitude of the electrostatic potential.

Vibration analysis of bio-inspired sandwich composite beam under rotating environment based on the Internet of Things technology

Sandwich composite materials with corrugated cores are mostly used in industries like aircraft, marine construction, automobiles, and construction. Sandwich composite constructions are made for their lightweight, high strength, and high stiffness, and also the sandwich core composite structures are useful for dynamic studies. A novel design inspired by a woodpecker beak microstructure creates fillet edge and champer edge designs. This novel design motivates us to achieve the energy absorbing results starting with free vibration studies followed by rotating environment vibration studies. ASTM E1876 standards, a non-destructive approach, are used to determine the material properties of carbon fiber-polylactic acid (CF-PLA) and glass fiber reinforced polymer (GFRP), along with alternative dynamic method (ADM) for core property evaluation. The hand lay-up technique is used for fabrication and evaluated for free vibration testing with appropriate boundary conditions. Internet of Things technology has been used for analyzing vibrations of sandwich structures in rotating environment setup with 250, 500, 750, and 1000 rpm. It was observed that the fillet edge pattern has a more efficient natural frequency than the champer edge pattern. Furthermore, the parametric evaluations were performed in various ply configurations in numerical simulations for free vibration and the rotating Environment. Also, the effective results are seen in fillet core bioinspired sandwich structure that achieves efficient stiffness in both free vibration and rotational environments, despite various boundary conditions and parametric circumstances. Therefore, the fillet edge 3D printed core design with particular GFRP factsheet orientation brings out the novelty of this research.

Low binder content bricks: a regolith-based solution for sustainable surface construction on the Moon

This work proposes a composite construction material made by a blend of lunar regolith and thermoplastic binders in dry powder form. This solution offers advantages over regolith sintering or melting by requiring lower power consumption and simplifying the manufacturing process. However, its sustainability depends on minimizing the content of the binder material. Drawing from validated concepts used on Earth, such as polymeric concrete and compressed Earth bricks, this paper suggests that binder optimization can be achieved by simplifying and streamlining the manufacturing process, targeting parts with predefined shapes. Standardized elements like bricks or tiles ease production and assembly automation, especially when incorporating interlocking features, simplifying the payload concept transition. After drafting the process with a minimum number of basic steps, this work studies the effects of some process parameters to minimize the weight percentage of the matrix while maintaining reasonable mechanical properties. The compressive and the flexural strength are the targets of an orthogonal array Design of Experiment. Through comparison with reference values for civil engineering, the process demonstrates promising results within an organic phase as low as 10 wt%.

Construction and mechanism analysis of flame-retardant, energy-storage and transparent bio-based composites based on natural cellulose template

With the proposal of sustainable development strategy, bio-based energy storage transparent wood (TW) has shown broad application value in green buildings, cold chain transportation, and optoelectronic device fields. However, its application in most fields is limited due to its own flammability. In this study, epoxy resin, triethyl phosphate (TEP) and polyethylene glycol (PEG) were introduced into delignified balsa wood template by vacuum pressure impregnation, and bio-based TW/PEG/TEP integrating flame retardant, high strength and phase-change energy-storage performance was prepared. TW/PEG composites have no leakage during phase change process and their transparency is up to 95 %. Compared with TW/PEG, the shielding effect of char layer and the inhibition effect in condensed and gas phase significantly decrease the total heat release of TW/PEG/TEP. TW/PEG/TEP biocomposites still maintained a high enthalpy of phase change and a low peak melting temperature, which was conducive to its application around the area of low temperature phase change energy storage. In addition, the tensile strength of TW/PEG/TEP was nearly 4 times higher than that of DW, and its toughness was obviously enhanced. TW/PEG/TEP biocomposites conformed to the current concept of energy-saving and green development. It has the potential to replace traditional petrochemical-based materials and shows excellent application prospects in emerging fields.

A bifactor representation of the Center for Epidemiological Studies Depression Scale for children: gender and age invariance and implications for adolescents’ social and academic adjustment

BackgroundThe Center for Epidemiological Studies Depression Scale for Children (CES-DC) is a widely used scale for screening depressive symptoms in children and adolescents. This study aims to uncover the optimal factor structure of the DES-DC and presents an alternate conceptualization of adolescent depression by estimating bifactor models and several competing models using a sample of Chinese adolescents.MethodsThe participants were 533 adolescents (49.7% boys, 49.7% girls, 3 participants did not report) between 12 and 18 years of age attending public secondary schools in the middle part of mainland China. Data were collected in classrooms using a questionnaire survey. A structural equation modeling approach was used to estimate and compare a series of competing models for the DES-DC.ResultsA Bifactor exploratory structural equation model (Bi-ESEM) with the best model fit was retained for representing the current data. Tests of measurement invariance demonstrated strict measurement equivalence across gender and age. No gender and age differences have been found in the general depression factor. Findings provided evidence for the composite reliability and construct validity of DES-DC. Depressive symptoms positively related to the Big Five trait neuroticism, negative emotions, loneliness, social anxious behaviors, and disruptive behaviors during school and negatively related to agreeableness, conscientiousness, extraversion, physical health status, school connectedness, and academic self-efficacy.ConclusionsThis study provides support for the one general factor construct of the CES-DC and the continuum concept structure of adolescent depression. Moreover, this research offers empirical evidence for comparing depression symptoms among adolescent populations with diverse genders and age groups. Additionally, the findings replicate and expand upon the implications of depressive symptoms on adolescents’ traits, well-being, social-relational adjustment, and academic adaptation.

When and how to use confirmatory composite analysis (CCA) in second language research

AbstractResearchers in second language (L2) and education domain use different statistical methods to assess their constructs of interest. Many L2 constructs emerge from elements/parts, i.e., the elements define and form the construct and not the other way around. These constructs are referred to as emergent variables (also called components, formative constructs, and composite constructs). Because emergent variables are composed of elements/parts, they should be assessed through confirmatory composite analysis (CCA). Elements of emergent variables represent unique facets of the construct. Thus, such constructs cannot be properly assessed by confirmatory factor analysis (CFA) because CFA and its underlying common factor model regard these elements to be similar and interchangeable. Conversely, the elements of an emergent variable uniquely define and form the construct, i.e., they are not similar or interchangeable. Thus, CCA is the preferred approach to empirically validate emergent variables such as language skills L2 students’ behavioral engagement and language learning strategies. CCA is based on the composite model, which captures the characteristics of emergent variables more accurately. Aside from the difference in the underlying model, CCA consists of the same steps as CFA, i.e., model specification, model identification, model estimation, and model assessment. In this paper, we explain these steps. and present an illustrative example using publicly available data. In doing so, we show how CCA can be conducted using graphical software packages such as Amos, and we provide the code necessary to conduct CCA in the R package lavaan.

Failure investigation of steel and brick aggregate concrete composite construction with angle and channel shear connectors

ABSTRACT This investigation focuses mainly on the failure behaviour and performance of angle and channel shear connectors in composite structures made with steel and brick aggregate concrete. It was observed that both angle and channel shear connectors did not fail themselves. However, in some specimens, localised connector yielding was observed in channel shear connectors. In both cases, concrete strata failed as either concrete crushing and shearing, combined splitting and bending, or complete splitting mode of failure. Crushing and shearing failure was noticed in specimens having smaller web and flange and were brittle in nature as compared to the failure of specimens with larger web and flange. Other parameters, such as shear resistance, energy absorption, and load-slip behaviour, were also investigated. Web height and flange width of both connectors significantly affected the ultimate shear capacity and slip of the brick aggregate concrete specimen. Channel connectors were found more flexible and carried more shear than angle connectors. Channel connectors had an average of 32.41% and 116.17% more ultimate load and slip capacity than the angle connectors in brick aggregate concrete, respectively. The load-carrying capacity, slip, and failure behaviour of the brick aggregate concrete were found similar to those of stone aggregate concrete.

Ternary intumescent flame retardant composition containing ionic liquid towards efficiently flame‐retardant polystyrene

AbstractIt is of great importance to enhance ability of charring formation for polystyrene (PS) to overcome non‐charring feature during burning. Here, we demonstrate a kind of ternary intumescent flame retardant composition composed by a novel ionic liquid butyltriphenylphosphonium‐chelated orthoborates (IL) with self‐expanded flame retardant, ammonium polyphosphate (APP) and expandable graphite (EG), to improve flame retardancy of PS. This ternary composition promotes limited oxygen index (LOI) value to 26.6 ± 0.5% and UL‐94 V0 level for PS composite with 15 wt% total loading. In addition, the peak value of heat release rate and smoke production rate of PS composite with ternary composition are separately reduced by 79.7% and 70.7% comparing to neat PS as well as 44.4% and 29.2% to its IL‐free binary counterpart in cone calorimeter test. Meanwhile, the ternary composition displays compact charring bulk constructed by large‐expansion‐volume vermiform expanded graphite. The TG‐FTIR technique is used to analyze gaseous profiles. The rheological property discloses that expansion behavior of the ternary composition contributes to robust viscoelasticity of composite and advantageous network construction at high temperature. Given the fire performance of the ternary composition, the combination of IFR and IL provides an opportunity for rational design and fabrication of functional flame‐retardant system.

Construction of polyurethane composites incorporating borate ester and B-N coordinative bonds: Achieving ultra-high fracture energy, self-healing property, and facile recyclability for wearable sensors

In recent years, there has been a notable surge in research focusing on the utilization of polyurethane (PU) in flexible wearable electronic devices. Consequently, it is essential to incorporate attributes such as high stretch, self-healing, and easy recyclability into PU. However, the suboptimal compatibility of PU with conductive fillers poses a significant challenge. This paper details the synthesis of a highly stretchable, self-healing, and easily recyclable PU elastomer, utilizing borate ester bonds and B-N mating bonds as the composite matrix. Highly conductive flexible composites were fabricated, employing multi-walled carbon nanotubes (CNTs) and graphene nanosheets (GNSs) as fillers. These composites exhibit excellent fracture energy, self-healing ability, and tensile strength due to the synergistic interaction of borate bonds, B-N ligand bonds, and hydrogen bonds. The fracture energy achieves an impressive 109.4 KJ·m−2, with a noteworthy 79% self-healing efficiency. Furthermore, the materials demonstrate mechanical properties, including a tensile strength of 66.5 MPa and an exceptionally high elongation at break of 2792%. The flexible conductive composites present high electrical conductivity (6.86 S/m) and sensitivity (GF：9.45). In its capacity as a flexible conductive composite, it can accurately detect human behaviors, such as finger flexion, facial expressions, throat articulation tests, and more. Therefore, it has potential applications in various fields, including wearables, robotic skin, and health monitoring.

Nickel Hydroxides: Requirements, Targeted Construction and Choice of Characteristics and Industrially Applicable Synthesis for Targeted Use in Electrochemical Devices

AbstractNickel hydroxides (monohydroxides of several modifications and layered double hydroxides, based on nickel hydroxide) have high electrochemical, electrochromic, and electrocatalytic properties that allow them to be effectively used as an active substance in alkaline batteries, hybrid supercapacitors, electrochemical sensors, for electrocatalytic oxidation of organic substances and as an electrochromic device. Each application has its specific requirements for nickel hydroxides which must be defined. For an effective application, it is necessary to carry out a targeted construction of structure and composition, and selection of characteristics of nickel hydroxides and to develop targeted methods and conditions for nickel hydroxide synthesis. The structure, properties, and methods of preparation for use in various fields of nickel hydroxide application have been considered from the targeted ternary points of view: requirements definition, types and characteristics selection, and applying the synthesis method in industry. The 3‐level hierarchical complex of mechanisms for the formation of nickel hydroxides has been described. Also, the contribution of Ukrainian scientists to research in the field of nickel hydroxides is considered.

Free vibration analysis of hygrothermally stable stiffened composite plates with plate-stiffener interfacial debonding

Stiffeners are frequently utilized in many engineering projects because they boost strength while adding only a small amount of weight to the overall structure. The environments that the stiffened composite constructions are typically exposed to are harsh, which can result in damage like interlayer delamination and debond at the plate-stiffener interface, which can cause catastrophic failure. As a result, it is necessary to examine these structures’ dynamic behavior in addition to their stability performance. The current study attempts to investigate the free vibration response of stiffened composite plates with plate-stiffener interfacial debonding under hygrothermal circumstances using a robust finite element (FE) model. The skin and stiffener flange are simulated in the current work using a 9-noded heterosis element to prevent the shear-locking issue. Additionally, to considerably enhance computational performance, the stiffener web is formulated as a 3-noded isoparametric beam element with the torsion correction factor. Additionally, a dummy node is created to represent the debond, and a fictitious spring is added to stop the nodes from interpenetrating one another. Three schemes of hygrothermally stable laminates (θ/(90- θ))s, (22.5/−67.5)s and (77.5/−12.5)s are considered to identify the stiffened plate configuration with improved free vibration characteristics. Further, extensive parametric analyses are conducted on the obtained stiffened plate with improved performance in a hygrothermal environment by considering debond at the skin-stiffener interface. The vibrational behavior of the debonded plate is shown to be significantly more affected by moisture than by temperature. Additionally, the debond has a more obvious impact on the vibration characteristics in the plate with a centrally attached stiffener than in the plate with an eccentricity attached stiffener. As a result, the established FE formulation is anticipated to be trustworthy and computationally effective while effectively analyzing the debonded stiffened panel’s free vibration behavior in a hygrothermal environment.

Dual synergistic effect of the amine-functionalized MIL-101@cellulose sorbents for enhanced CO2 capture at ambient temperature

The development of high carbon dioxide (CO2) sorption capacity materials is necessary for the deployment of the CO2 capture and storage strategy. Metal-organic frameworks (MOFs) have emerged as promising substitutes for traditional liquid and solid CO2 capture sorbents due to their high surface area, tunable pore size, diverse composition, and various physical and chemical properties. However, MOFs feature the intrinsic limitations of powder agglomeration, weak binding affinity, and sluggish diffusion kinetics, thus hindering their industrial application in CO2 capture. Herein, we design an amine-functionalized MIL-101@cellulose (NH2-MIL-101@BM) composite sorbent by anchoring NH2-MIL-101 nanoparticles onto the BM matrix through hydrogen bonding interaction. The dual synergistic effect, origin from the physical sorption synergistic effect and chemisorption synergistic effect proposed between NH2-MIL-101 and BM, not only facilitates the mass transfer of CO2 by reducing the diffusion resistance through hierarchical-pore structure but also offers stronger sorption sites with CO2 by increasing the adsorption energy of metal-CO2 or amine-CO2, which are confirmed by series of characterizations and theory functional calculations. Benefiting from the above merits, the NH2-MIL-101@20 %BM sorbent delivers a superior initial CO2 sorption capacity of 13.4 mmol/g when the BM doping amount is 20 wt% at 25 °C, and also shows good recycle stability even after 15 runs with maintainable structure. This work displays the in-depth mechanism understanding for enhanced CO2 capture, providing value inspiration for future MOF-based composite sorbent construction for CO2 capture at ambient temperatures.

Construction of Mineralization Nanostructures in Polymers for Mechanical Enhancement and Functionalization.

Mineralization capable of growing inorganic nanostructures efficiently, orderly, and spontaneously shows great potential for application in the construction of high-performance organic-inorganic composites. As a thermodynamically spontaneous solid-phase crystallization reaction involving dual organic and inorganic components, mineralization allows for the self-assembly of sophisticated and exclusive nanostructures within a polymer matrix. It results in a diversity of functions such as enhanced strength, toughness, electrical conductivity, selective permeability, and biocompatibility. While there are previous reviews discussing the progress of mineralization reactions, many of them overlook the significant benefits of interfacial regulation and functionalization that come from the incorporation of mineralized structures into polymers. Focusing on different means of assembly of mineralized nanostructures in polymer, the work analyzes their design principles and implementation strategies. Then, their different advantages and disadvantages are analyzed by combining nanostructures with organic substrates as well as involving the basis of different functionalizations. It is anticipated to provide insights and guidance for the future development of mineralized polymer composites and their application designs.