Composite Structures Research Articles

Shell element-based prediction of process-induced deformation considering the different fabric parameters and stacking sequences of CFRP woven composites

Herein, we present a finite element method (FEM) based curing analysis for predicting the process-induced deformation (PID) of CFRP woven composites using shell-type elements. This method can efficiently consider various fabric parameters and stacking sequences, even for complex structures. For woven composite plates and L-shaped flanges, FEM-based PID prediction using shell elements reduced computation times by 50–59% compared to solid elements, while maintaining acceptable accuracy with relative errors of 0.17–7.35%. Furthermore, the impacts of various fabric parameters and stacking sequences on the PID of woven composites are analyzed in detail. The main finding is that the variation in material properties due to fabric parameters and stacking sequences significantly impacts the PID of woven composite structures. This prediction method can be applied in the design of composite structures and molds, thereby enhancing the dimensional precision and performance of composite structures.

Uncovering the Interfacial Strengthening Mechanisms of α-Mg/Mg2Sn/β-Li Interfaces Using First-Principle Calculations and HAADF-STEM.

Previously, we reported our new invention of an ultralight (ρ = 1.61 g/cm3) and super high modulus (E = 64.5 GPa) Mg-Li-Al-Zn-Mn-Gd-Y-Sn (LAZWMVT) alloy. Surprisingly, the minor additions of Sn contribute to significant strength and stiffness increases. In this study, we found that Mg2Sn was not only the simple precipitate but also acted as the glue to bind the α-Mg/β-Li interface in a rather complicated way. To explore its mechanism, we have performed first-principle calculations and HAADF-STEM experiments on the interfacial structures. It was found that the interfacial structural models of α-Mg/β-Li, α-Mg/Mg2Sn, and β-Li/Mg2Sn composite interfaces prefer to form α-Mg/Mg2Sn/β-Li ternary composite structures due to the stable formation enthalpy (ΔH: -1.95 eV/atom). Meanwhile, the interface cleavage energy and critical cleavage stress show that Mg2Sn contribute to the interfacial bond strength better than the β-Li/α-Mg phase bond strength (σb(β-Li/Mg2Sn): 0.82 GPa > σb(α-Mg/Mg2Sn): 0.78 GPa > σb(β-Li/α-Mg): 0.62 GPa). Based on the interfacial electronic structure analysis, α-Mg/Mg2Sn and β-Li/Mg2Sn were found to have a denser charge distribution and larger charge transfer at the interface, forming stronger chemical bonds. Additionally, according to the crystal orbital Hamiltonian population analysis, the bonding strength of the Mg-Sn atom pair was 2.61 eV, which was higher than the Mg-Li bond strength (0.39 eV). The effect of the Mg2Sn phase on the stability and interfacial bonding strength of the alloying system was dominated by the formation of stronger and more stable Mg-Sn metal covalent bonds, which mainly originated from the contribution of the Mg 3p-Sn 5p orbital bonding states.

A Novel Model for Shear Strength Prediction of a Steel–UHPC Composite Structure Considering Interface Friction

A Novel Model for Shear Strength Prediction of a Steel–UHPC Composite Structure Considering Interface Friction

Deciphering the ecological impact of azo dye pollution through microbial community analysis in water-sediment microcosms.

The uncontrolled release of untreated dyeing wastewater into aquatic ecosystems poses global environmental risks. It alters native microbial communities and associated ecological processes, often going unnoticed. Therefore, the influence of acid orange 7dye (AO7) contamination on the natural microbial community was investigated using a water-sediment microcosm. Compared to sterile microcosms, complete dye decolourization in natural microcosms showed microbial communities' significance in combating xenobiotic contamination. Proteobacteria dominated the water community, whereas Firmicutes dominated the sediment. AO7 exposure induced notable shifts in the structural composition of the bacterial community in both water and sediment. Niveispirillum exhibited a marked decrease, and Pseudomonas demonstrated a notable increase. The - 9.0 log2FC in Niveispirillum, a nitrogen-fixing bacterium, from 24.4% in the control to 0.1% post-treatment, may disrupt nutrient balance, plant growth, and ecosystem productivity. Conversely, elevated levels of Pseudomonas sp. resulting from azo dye exposure demonstrate its ability to tolerate and bioremediate organic pollutants, highlighting its resilience. Functional profiling via KEGG pathway analysis revealed differential expression patterns under AO7 stress. Specifically, valine, leucine, and isoleucine degradation pathways in water decreased by 52.2%, and cysteine and methionine metabolism ceased expression entirely, indicating reduced protein metabolism and nutrient bioavailability under dye exposure. Furthermore, in sediment, glutathione metabolism ceased, indicating increased oxidative stress following AO7 infusion. However, C5-branched dibasic acid metabolism and limonene and pinene degradation were uniquely expressed in sediment. Decreased methane metabolism exacerbates the effects of global warming on aquatic ecosystems. Further, ceased-butanoate metabolic pathways reflect the textile dye wastewater-induced adverse impact on ecological processes, such as organic matter decomposition, energy flow, nutrient cycling, and community dynamics that help maintain self-purification and ecological balance in river ecosystems. These findings underscore the critical need for more comprehensive environmental monitoring and management strategies to mitigate ecological risks posed by textile dyes in aquatic ecosystems, which remain unnoticed.

Cyclic inelastic performance evaluation of locking bolt demountable shear connectors in steel-concrete composite structures

This study extends the research on the Locking Bolt Demountable Shear Connector (LBDSC), previously introduced and extensively analysed under monotonic loading through both experimental and numerical methods. The focus here shifts towards the inelastic cyclic performance of the LBDSC, a critical aspect for applications in seismic regions. The LBDSC, designed for use in composite floors or decks, such as in-situ solid slabs, profiled deck slabs, or precast slabs in buildings and bridges, features a grout-filled steel tube bolted to the top flange of steel sections. The design incorporates a unique 'locking bolt' technique to counteract the influence of construction tolerances on undesirable initial slip behaviour, significantly facilitating the deconstruction and reuse of steel sections without the need for recycling. Following the Eurocode 4 guidelines, a series of standard push out tests were conducted to explore the LBDSC's inelastic cyclic characteristics. The experimental results confirm the LBDSC's capability for high strength, high initial stiffness, and adequate slip capacity under cyclic loading, with ductile shear failure modes observed at the bolt shank and local concrete crushing above the steel flange. The cyclic loading tests reveal a larger zone of damaged concrete compared to monotonic loading conditions, yet the monotonic and cyclic force-slip curves closely align. Based on these findings, and supported by validated finite element analyses, this paper proposes theoretical monotonic and cyclic models for LBDSC under push out loading, aimed at accurately predicting the load-slip response. These models are intended to facilitate the efficient analyses, design and numerical modelling of composite structures incorporating LBDSCs, and to support the broader adoption of LBDSCs in earthquake-prone areas, promoting sustainable steel-concrete composite construction practices.

Experimental and numerical investigation of damage in multilayer sandwich panels with square and trapezoidal corrugated cores under quasi-static three-point bending

Multilayer composite sandwich panels with corrugated cores have the potential for structural applications requiring high stiffness and strength-to-weight ratios. This study aims to experimentally and numerically investigate the bending response of sandwich panels with novel square and trapezoidal corrugated core configurations fabricated from E-glass fiber-reinforced epoxy composites, both with and without polyurethane foam filling. Quasi-static three-point bending tests were conducted to evaluate and compare the flexural stiffness and maximum load capacity of the panel designs. The cores were manufactured using vacuum-assisted resin transfer molding. Key results showed that changing the core geometry from square to trapezoidal improved the bending stiffness by up to 26 %. Incorporating polyurethane foam further increased the bending stiffness by up to 41 % and maximum load by up to 47 % compared to solid cores. Failure initiation and progression were governed by matrix cracking in the face sheets and cores, followed by core cell wall buckling and delamination. Finite element modeling using ABAQUS captured the progressive damage behavior, exhibiting good agreement with experimental force-displacement responses. Failure modes included matrix cracks, fiber fractures, core buckling and delamination. This study provides valuable insights into the mechanical performance of innovative corrugated core sandwich panel designs under quasi-static bending loads. The validated FE approach also enables virtual testing and optimization of composite sandwich structures.

From Ancient Practices to Modern Science: A Review on the Synthesis and Characterization of Ayurvedic Bhasmas

Ayurvedic Bhasma, an ancient form of Indian traditional medicine, represents a unique class of herbo-mineral formulations prepared through a meticulous process involving calcination. This review provides a comprehensive synthesis and characterization of Ayurvedic Bhasmas, focusing on its preparation methods, physicochemical properties, and characterization. The synthesis of Bhasma involves a series of Shodhana (purification), Marana (incineration), and Bhavana (soaking and drying) processes, each contributing to the transformation of raw minerals and herbs into bioavailable nanoparticles with enhanced efficacy and reduced toxicity. The review delves into the intricate processes involved in the production of various bhasmas, prepared in our laboratory as well as reports by other researchers. It also highlights modern scientific techniques used to characterize these formulations, including XRD, SEM, TEM, FTIR, AAS, NAA, DLS etc. These techniques reveal the nanoscale size, crystalline structure, and elemental composition of bhasmas, providing insights into their therapeutic potential and safety profiles.

Investigating the low velocity impact response of additively manufactured tri-material composite structure with application on helmet

Additively manufactured composite structures can be utilized in the production of engineering materials with enhanced mechanical properties. In this work, mono-, bi-, and tri-material structures (MMS, BMS, and TMS, respectively) were fabricated using additively manufactured PLA (poly-lactic acid) lattice frames embedded with Polyurethane (PU) foam and milled glass fibers (MGFs). TMS samples were reinforced with MGFs at 1.25, 2.5, 3.75, and 5.0 vol%, indicated as TMS-1, TMS-2, TMS-3, and TMS-4, respectively. The mechanical response of these composite structures was tested by applying a low-velocity impact load. The effects of MGF content and variations in applied impact energy, and variation in microstructure on the composite samples were investigated. Results revealed an enhanced mechanical response of TMS samples compared to MMS and BMS. Additionally, with increasing applied impact energy, the TMS samples showed an improved corresponding response, with a peak absorbed energy of 96.03% of the applied 60 J energy. Furthermore, to study the applicability of the composite structures in real-life applications, helmet prototypes made of MMS, BMS, and TMS were designed and tested under the applied low-velocity load, showing an improved response of TMS helmet samples compared to the other composite structures.

Dynamic Effect of Ply Angle and Fiber Orientation on Composite Plates

Composite materials have revolutionized industries such as aerospace and automotive with their impressive strength-to-weight ratios and customizable properties. Ply angle and fiber orientation are critical factors that significantly impact the dynamic behavior of composite structures, influencing stiffness, strength, and vibrational characteristics. This research delves into the dynamic characteristics of composite plates, explicitly examining how ply angle and fiber orientation affect vibrational behavior. Through finite element analysis (FEA), composite plates with varying ply angles and fiber orientations were modeled to understand their influence on natural frequencies, mode shapes, and dynamic responses under various loading conditions. The study reveals that cross-ply [0/0/0/0] exhibits the highest stiffness and superior stress handling, while the cross-ply balanced laminate [90/0/0/90] demonstrates better vibrational characteristics. The findings highlight the intricate relationships between design parameters and structural vibrational behavior, offering opportunities for optimizing composite structures. Additionally, harmonic analysis showed that a cut-out increases the natural frequency. The results underscore the importance of optimizing composite plate configurations to enhance vibrational characteristics and align natural frequencies with operational requirements, thereby mitigating resonance-related issues.

Model Test and Numerical Simulation of Two Typical Close-Fitting Pile–Wall Integrated Structures in Deep Excavation

Compared to conventional support methods, the close-fitting pile–wall integration technique features a minimized construction spacing between the retaining pile and the basement retaining wall. This approach leverages the pile stiffness to minimize the wall thickness and enhance underground space utilization. However, it currently lacks significant discussions and measured data about the interaction laws between the pile and the wall. The model test and finite element method (FEM) are employed to study the deformation and internal force interaction laws of two typical close-fitting pile–wall integrated structures, and a comparison with conventional design is conducted. Furthermore, this study separately investigates the impact of sensitivity factors, specifically the pile–wall stiffness ratio and floor plate stiffness, on both structures during the basement construction and serviceability stages. The test results can closely match the numerical simulation. The study results reveal that the wall impacts the bending moment of the pile to some extent. The internal force in the wall is significantly influenced by the lateral deformation of the pile and the floor plate. Compared to conventional designs, this structure significantly reduces the bending moment of the wall, particularly in the composite structure. Additionally, the analysis of sensitivity factors reveals their considerable influence on the pile–wall interaction.

Surface Acoustic Wave Sensors for Wireless Temperature Measurements above 1200 Degree Celsius

High-temperature wireless sensing is crucial for monitoring combustion chambers and turbine stators in aeroengines, where surface temperatures can reach up to 1200 °C. Surface Acoustic Wave (SAW) temperature sensors are an excellent choice for these measurements. However, at extreme temperatures, they face issues such as agglomeration and recrystallization of electrodes, leading to loss of conductivity and reduced quality factor, hindering effective wireless signal transmission. This study develops an LGS SAW sensor with a Pt-10%Rh/Zr/Pt-10%Rh/Zr/Pt-10%Rh/Zr multilayer composite electrode structure to address these challenges. We demonstrate that the sensor can achieve wireless temperature measurements from room temperature to 1200 °C with an accuracy of 1.59%. The composite electrodes excite a quasi-shear wave on the LGS substrate, maintaining a Q-factor of 3526 at room temperature, providing an initial assurance for the strength of the wireless interrogation echo signal. The sensor operates stably for 2.18 h at 1200 °C before adhesion loss between the composite electrode and the substrate causes a sudden increase in resonant frequency. This study highlights the durability of the proposed electrode materials and structure at extreme temperatures and suggests future research to improve adhesion and extend the sensor’s lifespan, thereby enhancing the reliability and effectiveness of high-temperature wireless sensing in aerospace applications.

Study on Mechanical Properties of Tunnel Flame Retardant Asphalt Pavement Considering the Ablative Effect

With the widespread utilization of composite pavements in highway tunnel projects, the flammability issue of asphalt layers has garnered increasing attention. Previous research has demonstrated that the addition of flame retardants effectively reduces the occurrence of pavement fires. However, there are few studies combining asphalt flame retardant technology with tunnel composite pavement structures. Therefore, this paper, considering the context of actual engineering projects, uses ABAQUS software to analyze and calculate the mechanical response of the tunnel composite pavement, considering the thickness of various asphalt layers under the ablation depth. Key design indexes such as shear stress and lower tensile strain of the asphalt layer, the bottom tensile stress of the cement concrete subgrade, and interlayer shear stress between the asphalt layer and cement concrete subgrade of composite pavements are analyzed using the nonlinear finite element analysis method. The findings enable the determination of the optimal thickness of the composite pavement asphalt layer combination after ablation, thus contributing to enhancing the safety of tunnel pavements.

Correlated multimodal imaging in life sciences: lessons learnt

Correlated Multimodal Imaging (CMI) gathers information about the same specimen with two or more modalities that–combined–create a composite and complementary view of the sample (including insights into structure, function, dynamics and molecular composition). CMI allows one to reach beyond what is possible with a single modality and describe biomedical processes within their overall spatio-temporal context and gain a mechanistic understanding of cells, tissues, and organisms in health and disease by untangling their molecular mechanisms within their native environment. The field of CMI has grown substantially over the last decade and previously unanswerable biological questions have been solved by applying novel CMI workflows. To disseminate these workflows and comprehensively share the scattered knowledge present within the CMI community, an initiative was started to bring together imaging, image analysis, and biomedical scientists and work towards an open community that promotes and disseminates the field of CMI. This community project was funded for the last 4 years by an EU COST Action called COMULIS (COrrelated MUltimodal imaging in the LIfe Sciences). In this review we share some of the showcases and lessons learnt from the action. We also briefly look ahead at how we anticipate building on this initial initiative.

Mechanical Properties and Deformation Behavior of Open-Cell Type Aluminum Foams with Structural Conditions and Alloy Composition

Mechanical Properties and Deformation Behavior of Open-Cell Type Aluminum Foams with Structural Conditions and Alloy Composition

The influence of geographical location on moisture distribution in wood cross sections: a numerical simulation study using Austria as an example

Wood constantly interacts with the surrounding, locally varying climate, leading to changes in the moisture content. Advanced simulation tools can predict the two-dimensional moisture distributions caused by these changing climate conditions within wood cross sections over time. However, there is a notable absence of systematic simulation results for diverse climatic conditions and various wood cross sections. This study seeks to bridge this gap in research. Here, we present moisture fields in three solid timber and three glued laminated timber cross sections in Austria and show the effect of the location and the altitude on the moisture content distribution. The results reveal decreasing influence of the location on the moisture content development with increasing cross section size, and primarily the altitude affecting the moisture content. In addition, the results are compared with the standard for the design of timber–concrete composite structures (ONR CEN/TS 19103), revealing appropriate values in most of the cases. Only for cross sections with a width of 14 cm and larger, assigned to a specific region, the standard value is assumed underestimated. Furthermore, the distribution of moisture gradients, which are related to the crack depth development, are analyzed for Austria, demonstrating the influence of mountain areas in the moisture gradient development.

Investigation of a novel hydraulic tunnel composite lining with polyurea coating interlayer

PurposeMultilayer composite liner structures are the primary structural form of hydraulic tunnels. However, the bearing mechanism of multilayer composite liners has not been investigated thoroughly. Many existing design schemes do not properly achieve a balance between structural safety, anti-seepage capacity, and cost effectiveness. Thus, a new composite liner structure type and its theoretical model was proposed.Design/methodology/approachA novel hydraulic tunnel composite liner structure with a polyurea spray coating interlayer was proposed in this study. A theoretical model based on the state-space method was developed and verified using FEM models and existing theoretical models. Parametric analysis was conducted based on the theoretical model to investigate the influence of various variables, including interfacial shear stiffness, inner liner thickness, and outer liner elastic modulus.FindingsIt was concluded that the proposed theoretical model can be used successfully to calculate multilayer composite liner structures with high calculation efficiency. The overall deformation stiffness of the composite liner system increased with the interfacial shear stiffness. The sprayed coating interlayer significantly affects the residual force distribution between the outer and inner liners, which can also be affected by the adjustment of the thickness of the outer and inner liners. Thus, attention should be paid to these factors in the rational design of the proposed composite liner system.Originality/valueWith the development of China’s water conservancy projects, complex geological conditions, high surrounding rock stress, high internal and external water pressures, and other unique application scenarios have gradually increased. This places higher requirements on the bearing performance and impermeability of hydraulic tunnel lining structures. On the other hand, conventional hydraulic tunnel lining structures can hardly achieve a satisfactory balance between economy, structural safety, and impermeability. Thus, the proposed structure has the potential to be used in a wide range of applications.

Composition control of additively manufactured color-graded temporary veneer

ObjectiveThe aim of this study was to design and assess composite resin composition for patient-specific esthetic color-graded temporary veneer. MethodsVarious compositions of composite structures (assorted by Ba2SiO4 filler, TiO2 pigment, and photoinitiator) were prepared via additive manufacturing with 3 s UV exposure (405 nm, 10 W/cm2) per 50 µm thick layer followed by 20 min post-curing treatment after fabrication. The effect of each component on the generated color shades was observed and compared to the commonly used VITA shade guide. The coloration was explored by staining aging treatment under dry, wet, artificial saliva environments, coffee, and cola. The mechanical properties were also evaluated. Color measurement and comparison were done using a colorimeter (lightness (L*), green-red color (a*), and blue-yellow color (b*)), and the changes were calculated by CIEDE2000 (ΔE00), translucency parameter (TP) and whiteness index (WID). The composition color analysis results were then applied to produce a color-graded temporary veneer for mimicking a natural look. ResultMechanically, all composition result in adequate bending strength with maximum achievable strength of 111.64 MPa. At the same time, the composite color was affected by each constituent differently. The L* value, which indicates the color lightness of the composite, was considerably tuned by the TiO2 pigment, whereas Ba2SiO4 filler only triggered minor changes. Photoinitiator concentration significantly affected the yellowness, indicated by the increased b* value. Similar tendency also observed toward the calculated TP and WID as well. Based on these evaluations, color-graded temporary veneer successfully generated, matching the VITA A3, A2, and B1 shades gradation. However, the stability of the composite color decreased at high amounts of Ba2SiO4 and photoinitiator. SignificanceThe study presents a composition guide for fabricating temporary patient-specific color-graded veneer. It provides insights on the effect of the constituent material on dental esthetics.

Influence of mandatory waste classification on environmental and economic impacts of residual waste treatment in Xiamen, China.

Mandatory waste classification has been widely considered as an effective solution for reducing the production and treatment amount of municipal solid waste. However, there is limited evidence regarding whether and how waste classification can affect the composition of residual waste (RW) and its environmental economic impacts. Here, an accounting method recommended by the Intergovernmental Panel on Climate Change, field surveys and cost-benefit analysis was utilized to investigate the changes in RW composition, environmental impacts and economic benefits under the waste classification policies implementation in Xiamen, China. This study found that: (1) The implementation of waste classification policies led to a significant increase in recyclable content from 17% to 51% and a decrease in organic content from 56% to 32%. (2) Waste classification effectively reduces greenhouse gas emissions from landfilling and incineration by an additional 0.34 tCO2-eq t-1 RW. (3) The introduction of mechanical recycling achieves a saving of 0.47 tCO2-eq t-1 RW at 40% recycling efficiency, a 4.5-fold increase compared to business as usual (BAU). (4) The operational benefits (900 yuan t-1 RW) from the recyclables sorting system offset the total expenses of investment, operation and waste disposal. The study successfully demonstrated that RW source-classified management can optimize the structure of waste composition, reduce environmental emissions and offer detailed guidance for the development of solid waste management systems in other cities in China.

Energetic properties of core–shell B@PVDF/AP composite micro-units prepared by electrostatic spraying technology

In this study, to improve the ignition and combustion performance of fuel boron (B) powder. The core–shell B@ polyvinylidene fluoride (PVDF)/ ammonium perchlorate (AP) composite micro-unit with the effect of erosion activation is successfully prepared by simple and controllable electrostatic spraying technology. The results of morphology and structural composition show that PVDF and AP are tightly wrapped on the surface of B, forming a uniform shell, which effectively prevents moisture absorption and oxidation of B during storage and transportation. The results of the thermal analysis show that the hydrofluoric acid (HF) gas generated by the decomposition of PVDF at about 100 °C in advance has a pre-ignition reaction (PIR) with the boron oxide (B2O3) film on the surface of B. The PIR generates boron fluoride (BF3) gas and breaks the B2O3 film. This reduces the initial oxidation temperature of B by 12.6 % and enhances the oxidation activity of B powder. In addition, the oxygen (O2) released by AP improves the combustion performance of B and strengthens the effect of erosion activation. It is also found that all samples can be successfully ignited and burned continuously, which improves the ignition and combustion performance of B powder. It is worth noting that the ignition delay time of the composite micro-unit sample with the stoichiometric ratio of B/PVDF/AP of 2: 1: 2 can be shortened to 0.454 s at most, which is 17 % lower than that of the physical mixed sample. Moreover, its combustion intensity and flame temperature also reach the best. These results show that the core–shell B@PVDF/AP composite micro-unit provides a great strategy for application in solid propellant and pyrotechnics.

Coupling interface, electronic and conjugation effects in C-COFs/TiO2 composite structure toward boosting photocatalytic hydrogen evolution

Hydrogen energy, recognized as a pivotal clean energy source, has attracted considerable attention in the realm of photocatalytic hydrogen production. Nevertheless, inorganic materials were difficult to regulate band gaps, resulting in limited photogenerated carrier rates. Additionally, organic materials frequently suffer from insufficient stability and a propensity for electron recombination. Therefore, fully utilizing the interface effect will become an important breakthrough for novel and efficient catalysts. Herein, hydroxylate covalent organic frameworks (H-COFs) were formed by direct synthesis method, in addition, titanium dioxide (TiO2) was used as an inorganic substrate, and TiO2 was transformed titanium acid under weakly acidic conditions, meanwhile, chloride covalent organic frameworks (C-COFs) growth on TiO2 surface by interface effect when H-COFs were formed into C-COFs under titanium acid. The structure characteristics, photoelectric performance, bandgap width and stability of C-COFs/TiO2 were confirmed through characterization analysis. C-COFs/TiO2 exhibit strong stability, conjugation effects, electron deficiency effects, and catalytic efficiency. Hydrogen production rate up to 5598 μmol g−1 h−1 by C-COFs/TiO2 as photocatalyst. C-COFs/TiO2 lead to 161 times improvement in photocatalytic activity for TiO2 and 3.6 times improvement in photocatalytic activity for H-COFs. The catalytic reaction mechanism was obtained by utilizing experimental data and DFT calculation. This synergistic integration of organic inorganic combined catalyst provides a foundational framework for advancing research into novel photocatalysts.