Composite Structures Research Articles

Molecular pathology of skin fragility

The skin's barrier function is primarily maintained by the cohesion of its layers and the specialized stratum corneum. Genetic and autoimmune disorders that result in skin fragility have significantly contributed to understanding the role of various molecular components in the skin. These conditions, characterized by blisters, erosions, wounds, and impaired wound healing, are rare but must be considered in clinical differential diagnoses. Key cutaneous adhesion structures include the epidermal basement membrane, anchoring fibrils, cell-matrix adhesions (e.g., hemidesmosomes and focal adhesions), and cell-cell adhesions (e.g., desmosomes and corneodesmosomes). These multiprotein suprastructures not only provide structural support but also participate in signaling processes and physiological or pathological conditions such as skin aging and wound healing. Additionally, dermal connective tissue plays astructural role and serves as areservoir for proteases, growth factors, and cytokines. Modern techniques like single-cell and spatial transcriptomics, combined with artificial intelligence algorithms, are advancing the molecular mapping of human skin. Moreover, this review highlights the molecular composition of adhesion structures and the specific diseases associated with deficiencies in these components.

How does turbulence intensity affect the fatigue life of composite airfoils based on existing CFD and experimental data?

This research investigates the effect of airflow turbulence intensity on the fatigue life of composite airfoil structures in aerospace engineering. Using advanced Computational Fluid Dynamics (CFD) simulations, this study provides a comprehensive analysis of how varying levels of turbulence intensity—ranging from mild (5%) to severe (30%)—impact the mechanical degradation and fatigue performance of carbon-fiber-reinforced polymers (CFRPs) used in airfoil designs. The research quantifies the relationship between turbulence levels and changes in stress distribution, highlighting critical points of fatigue crack initiation and subsequent propagation. The study includes detailed comparisons of CFD results to experimental data to validate the predictive models and discusses how localized stress fluctuations under high-intensity turbulence accelerate the onset of fatigue failure. We present significant findings that demonstrate a non-linear relationship between turbulence intensity and the reduction in fatigue life, suggesting optimal design modifications for enhanced durability. Furthermore, this paper explores current challenges in merging CFD data with real-world fatigue testing and proposes advanced techniques such as adaptive mesh refinement and hybrid simulation models to improve predictive accuracy and computational efficiency in future research.

A machine learning assisted preliminary design methodology for bolted composite joints in large structures

Abstract Damage initiation hotspots around features, such as bolts and ply drops, must be investigated during the preliminary design phase of large composite structures, such as composite airframes. A global-local modelling approach is commonly employed to perform this investigation, whereby a global low-fidelity model is used to drive high-fidelity local models around the features of interest. However, this methodology is slow, repetitive and expert-dependent. In this investigation, we address these issues by applying machine learning techniques to this global-local modelling framework and demonstrate the time-saving benefit when predicting damage initiation of bolted composite joints. Feature engineering of model inputs and outputs, and appropriate customisation of machine learning methods enables damage initiation prediction. Special consideration is given to the boundary conditions that must be varied to simulate the response of the bolted composite joints. Results show over three orders of magnitude time-saving benefit and satisfactory accuracy of the proposed methodology. This indicates its potential to be developed further into a rapid design and optimisation tool.

Biaxial tubular hybrid braided structures with supreme tensile performance: Experimental and statistical assessments

Biaxial tubular braided structures are increasingly being recognized as superior alternatives to traditional materials in structural engineering due to their enhanced tensile properties and durability. In this study, the mechanical characteristics of these structures are examined, focusing on the influence of braiding angle, yarn hybridization, and layer configurations on tensile behavior. Sixteen diverse specimens, crafted from polyester and basalt yarns using a 32-carrier vertical braiding machine, are explored, incorporating variations across four braiding angles, three hybridizations, and both single and dual-layer setups. Each specimen underwent rigorous uniaxial tensile testing, revealing critical insights into the relationships between structural configuration and mechanical performance. It was found that increasing the braiding angle significantly enhances elongation, strain, and energy absorption capacities. Additionally, a higher basalt yarn content was observed to amplify tensile strength, suggesting potential for tailored structural optimization. Notably, dual-layer configurations were found to outperform single layers in tensile efficiency, underscoring the advantage of layered designs in engineering applications. A significant gap in current literature is filled by this study, as a detailed analysis of biaxial tubular hybrid braids is provided, paving the way for their informed application in advanced composite structures.

Substantial Global Radial Variations of Basalt Content Near the 660‐km Discontinuity

AbstractMid‐ocean ridges generate basalt and harzburgite, which are introduced into the mantle through subduction as a mechanical mixture, contributing to both lateral and radial compositional heterogeneity. The possible accumulation of basalt in the mantle transition zone has been examined, but details of the mantle composition below the 660‐km discontinuity (hereafter d660) remain poorly constrained. In this study, we utilize the subtle waveform details of S660S, the underside shear‐wave reflection off the d660, to interpret the seismic velocity, density, and compositional structure near, and particularly below, the d660. We identify a significant difference in S660S waveform shape in subduction zones compared to other regions. The inversion results reveal globally enriched basalt at the d660, with a notably higher content in subduction zones, consistent with the smaller impedance jump and S660S peak amplitude. The basalt fraction decreases significantly to less than 10% near 800‐km depth, forming a global harzburgite‐enriched layer and resulting in a steep seismic velocity gradient just below the d660, in agreement with 1D global reference models. The striking compositional radial variations near the d660 verify geodynamic predictions and challenge the applicability of homogeneous radial compositional models in the mantle. These variations may also affect the viscosity profile and, consequently, the dynamics at the boundary between the upper and lower mantle.

Utilizing a combination of experimental and machine learning methods to predict and correlate between accelerated and natural aging of CFRP/AL adhesive joints under hygrothermal conditions

AbstractThis study investigates how carbon fiber reinforced polymer (CFRP)‐to‐aluminum adhesive joints behave under accelerated aging conditions with hygrothermal exposure and compares these findings against naturally aged samples to evaluate material reliability in challenging environments. The CFRP‐to‐aluminum adhesive joints were manufactured and subjected to natural aging for durations ranging from 1 to 3 years with 6‐month intervals, as well as accelerated aging (hygrothermal) for periods ranging from 100 to 1200 h, with intervals of 50 h. Subsequently, the mechanical properties of the joints were evaluated using a three‐point bending test. To forecast natural aging times from accelerated aging data, five machine learning models were utilized: artificial neural network, support vector regression, linear regression, polynomial regression, and random forest regression. Hygrothermal aging significantly degraded the matrix, causing a shift in failure modes from cohesive to mixed types (cohesive, adhesive, and fiber tear failures), leading to a notable decline in bending strength. The study observed a 23.13% strength reduction in samples aged naturally for 3 years and a 24.33% decrease in those subjected to 1000 h of accelerated aging. The random forest regressor demonstrated superior accuracy in predicting natural aging times across different accelerated aging periods. Through the application of machine learning models, this study introduces a novel approach to forecast natural aging durations using data from accelerated aging experiments. This method shows potential for optimizing joints and composite structures, ultimately improving their durability and minimizing the likelihood of failures during operational use.Highlights Studied hygrothermal effects on accelerated aging of carbon fiber reinforced polymer/Aluminum (AL) adhesive joints. Noted strength reduction from hygrothermal aging. Used five machine learning models; random forest regression had the highest accuracy. Analyzed correlation between natural and accelerated aging of dissimilar adhesive joints.

Systematic Evaluation of Macromolecular Carbohydrate-Lectin Recognition Using Precision Glycopolymers.

The precise modulation of protein-carbohydrate interactions is critical in glycobiology, where multivalent binding governs key cellular processes. As such, synthetic glycopolymers are useful for probing these interactions. Herein, we developed precision glycopolymers (PGPs) with unambiguous local chemical composition and well-defined global structure and systematically evaluated the effect of polymer length, hydrophobicity, and backbone hybridization as well as glycan density and identity on the binding to both mammalian and plant lectins. Our studies identified glycan density as a critical factor, with PGPs below 50% grafting density showing significantly weaker lectin interactions. Coarse-grained molecular dynamics simulations suggest that the observed phenomena may be due to a decrease in carbohydrate-carbohydrate interactions in fully grafted PGPs, leading to improved solvent accessibility. In functional assays, these PGPs reduced the cell viability and migration in 4T1 breast cancer cells. Our findings establish a structure-activity relationship in glycopolymers, providing new strategies for designing synthetic glycomacromolecules for a myriad of applications.

Wear properties of Al6061/SiC + B4C + TiC hybrid composites produced by vacuum infiltration method

Abstract In the study, hybrid metal matrix composite (HMMC) structures were produced by vacuum infiltration method (VIM) using Al6061 alloy and varying amounts of SiC, B4C, and TiC ceramic powder pairs. Age-hardening processes were applied to these HMMCs. After heat treatment, wear behavior was examined under different loads using the pin-on-disc test method. All Al6061 hybrid composites exhibited better wear performance than unreinforced Al6061. In the wear tests of composite samples, the lowest volume loss and therefore the highest wear resistance were obtained in Al6061 3 wt.% B4C + SiC composites under 5 N force. The lowest wear resistance due to the highest volume loss was determined in Al6061/1 wt.% TiC + B4C composites under 15 N force. Abrasive and adhesive wear characteristics were observed in field emission scanning electron microscopy(FESEM) images of worn surfaces. Additionally, wear debris, smearing, and deep grove formations were determined on the surface. In the EDS analysis performed on the worn surface, O and Fe elements were found in addition to the elements that are likely to be in the structure (such as Al, B, C, Ti, Si, and Mg). The wear tests caused the formation of oxide layers on the sample surfaces.

Mechanical Properties Test and Failure Analysis of Composite Foam Sandwich Structure in Ramp-Down Zone

Mechanical Properties Test and Failure Analysis of Composite Foam Sandwich Structure in Ramp-Down Zone

Combined effect of nitrogen-doped carbon and NiCo2O4 for electrochemical water splitting

Electrocatalytic water splitting for green hydrogen production necessitates effective electrocatalysts. Currently, commercial catalysts are primarily platinum-based. Therefore, finding catalysts with comparable catalytic activity but lower cost is essential. This paper describes spinel-structured catalysts containing nickel cobaltite NiCo2O4, graphene, and additionally doped with heteroatoms. The structure and elemental composition of the obtained materials were analyzed by research methods such as TEM, SEM-EDX, XRD, XPS, and Raman spectroscopy. The electrochemical measurements showed that hybrid materials containing nickel cobaltite NiCo2O4 doped with graphene are highly active catalysts in the hydrogen evolution reaction (Tafel slopes = 91 mV dec−1, overpotential = 468 mV and onset potential = -339 mV), while in the oxygen evolution reaction (Tafel slopes = 51 mV dec−1, overpotential = 1752 mV and onset potential = 370 mV), bare NiCo2O4 without the addition of carbon has a worse activity (for HER: Tafel slopes = 120 mV dec−1, overpotential - does not achieve and onset potential = -404 mV, for OER: Tafel slopes = 54 mV dec−1, overpotential = 1796 mV and onset potential = 410 mV). In terms of stability, comparable results were obtained for each synthesized compound for both the HER and OER reactions.

Paper‐based sensors for real‐time cure monitoring in the production of glass fiber‐reinforced phenol‐formaldehyde composites for aerospace interiors

AbstractThe aerospace industries demand for advanced materials necessitates stringent quality control measures, particularly for composite structures to ensure optimal curing and structural integrity. Traditional methods like differential scanning calorimetry (DSC) and dynamic mechanical analysis, while useful, are limited to laboratory settings. This study explores the use of a printed paper‐based sensor for real‐time cure monitoring of glass fiber‐reinforced phenol‐formaldehyde (PF/GF) prepregs. The sensor, composed of a cellulose paper substrate with screen‐printed electrodes, offers flexibility, ease of integration, and cost‐effectiveness compared to commercial polymer‐based dielectric sensors. Real‐time monitoring with the printed paper‐based sensor was conducted at temperatures ranging from 130 to 180°C, both with and without pressure, and validated against DSC and Fourier‐transform infrared (FTIR) spectroscopy. The results showed a strong correlation between real‐time monitoring and the DSC prediction model, as well as FTIR spectroscopy. Notably, the real‐time monitoring revealed a shorter curing cycle on the production line than the predicted cure kinetic model, which is crucial for large‐scale production, such as fabricating honeycomb panels for aircraft interiors. This research underscores the importance of innovative sensor technologies in improving quality control and manufacturing efficiency in aerospace composites.Highlights Cure Monitoring of PF‐based prepregs was carried out using paper‐based sensor. Sensor offered reproducibility and seamless integration in composites. Sensor data showed a strong correlation with DSC and FTIR spectroscopy results. Paper sensors enable online monitoring of composite in aerospace manufacturing.

Focal volume optics for composite structuring in transparent solids

Abstract Achieving high-level integration of composite micro-nano structures with different structural characteristics through a minimalist and universal process has long been the goal pursued by advanced manufacturing research but is rarely explored due to the absence of instructive mechanisms. Here, we revealed a controllable ultrafast laser-induced focal volume light field and experimentally succeeded in highly efficient one-step composite structuring in multiple transparent solids. A pair of spatially coupled twin periodic structures reflecting light distribution in the focal volume are simultaneously created and independently tuned by engineering ultrafast laser-matter interaction. We demonstrated that the generated composite micro-nano structures are applicable to multi-dimensional information integration, nonlinear diffractive elements, and multi-functional optical modulation. This work presents the experimental verification of highly universal all-optical fabrication of composite micro-nano structures with independent controllability in multiple degrees of freedom, expands the current cognition of ultrafast laser-based material modification in transparent solids, and establishes a new scientific aspect of strong-field optics, namely, focal volume optics for composite structuring transparent solids.

Lightning ablation damage and residual bending performances of scarf-repaired composite laminates with copper mesh protection

The copper mesh provides effective lightning strike protection for composite structures, while its efficiency can be compromised in scarf-repaired composite structures. In this study, after verified by test results, a numerical analysis procedure was employed to predict the lightning ablation damage and residual bending performances of scarf-repaired composite laminates with copper mesh protection. Initially, the ablation damage and bending damage mechanisms of good repaired and poor repaired composite laminates were analyzed. Then, the impact of lightning strike attachment position and repair design parameters including overlap length and thickness of adhesive layer on the lighting protection performances was investigated. The results indicate that ablation damage of composite and adhesive materials near the repair area significantly compromises structural integrity and reduces the bending strength. The predominant bending failure mode of scarf-repaired woven composite laminates after lightning strike is fiber failure in warp direction, accompanied by small areas of matrix failure and delamination failure. The reestablishment level of the electrical path varies with overlap length and thickness of adhesive layer, subsequently affecting the ablation damage area and depth. This study can provide a reference for the design and process control of scarf-repair in copper mesh protected composite structures.

Numerical model of curved composite tiles under low-velocity impact loading

In recent years, composite structures have seen widespread application across diverse industries, including automotive and aerospace, owing to their favourable strength-to-weight ratio. However, these structures, particularly high-pressure vessels, are susceptible to extreme loadings such as impact forces, resulting in visible and latent damage, ultimately leading to catastrophic failures. Hence, it is imperative to assess such damages diligently. Given the cost implications associated with experimental investigations, numerical methodologies emerge as a potent means for conducting relevant analyses. This paper will introduce a numerical model approach to conducting virtual tests to assess curved carbon fibre composite tiles subjected to low-velocity impact. The primary focus of this study is to consider the impact-induced delamination on composite tiles through a numerical model. The composite tiles are conducted to 90J impact loading. Specifically, the study evaluates filament winding structures’ interface properties (shear resistance) variability during manufacturing. Notably, the parameter of shear resistance significantly impacts the anticipation of intralaminar damage (delamination) after impact loading. Three-point bending tests were performed to calibrate the composite material’s shear interface properties, followed by low-velocity impact tests on the curved composite tiles. The findings indicate that the shear resistance values, which ranged from 14.25 MPa to 60 MPa, play a critical role in predicting delamination, with lower shear resistance leading to increased damage areas. The results underscore the importance of accurately calibrating interface properties to enhance the predictive accuracy of numerical models for curved composite structures under impact loading.

Programmable viscosity metamaterials: Designing fluid properties using temporal superposition of shear and acoustics

Metamaterials are composite structures whose extraordinary properties arise from a mesoscale organization of their constituents. Here, we introduce a different material class—viscosity metafluids. Specifically, we demonstrate that we can rapidly drive large viscosity oscillations in shear-thickened fluids using acoustic perturbations with kHz to MHz frequencies. Because the timescale for these oscillations can be orders of magnitude smaller than the timescales associated with the global material flow, we can construct metafluids whose resulting time-averaged viscosity is a composite of the thickened, high-viscosity and dethickened, low-viscosity states. We show that viscosity metafluids can be used to engineer a variety of unique properties including zero, infinite, and negative viscosities. The high degree of control over the resulting viscosity, the ease with which they can be accessed, and the variety of exotic properties achievable make viscosity metafluids attractive for uses in technologies ranging from coatings to cloaking to 3D printing. Published by the American Physical Society 2024

2D heterostructures of graphene oxide and MoS2 to improve sensitivity performance of flexible pressure sensor with shell biological structure

Inspired by the multilayer structure of the shellfish, a novel two-dimensional (2D) composite structure consisting of graphene oxide, MoS2 and graphene oxide (G/M/G) was integrated to the flexible pressure sensing. The composite structure was prepared by the vacuum suction filtration in order to imitate the high toughness of shellfish. Based on the strategy of strain engineering, a comprehensive experimental bench capable of meeting different strain conditions was connected to a push–pull meter and an LCR digital bridge, and then a computer was used to record the changes in transducer capacitance when an external load was applied to the meter. Graphene oxide (GO) and G/M/G supercells were constructed, and density functional theory (DFT) simulations of the initial energy band structure under strain-free conditions were carried out to determine the relationship between the band gap, conductivity, capacitance, and sensitivity of the G/M/G structure based on band gap theory, and to easily understand the mechanism of the shellfish heterostructure leading to enhanced sensitivity of the sensors. Using two-point bending and axial tensile tests, a flexible pressure sensing device was designed to realize positive strains in the ranges of 0%–5 % and 5%–50 %. The results show that the sensitivity of both GO and G/M/G capacitive pressure sensors decreased with increased strain, and the sensitivity of the G/M/G sensors was significantly improved by 75%–102 % compared to the GO sensors at the same strain. The parallel-plate capacitor model and crack growth theory well explain the experimental results at small and large strains. Our results provide new concepts for the design of novel flexible sonar with high sensitivity and large strain operating range by a simple vacuum filtration method, which can be extended to the design of other high-performance 2D flexible electronic devices.

Layered/Olivine Composite Structure-Induced Stable Gradient Interfacial Chemistry toward High-Temperature Lithium-Ion Batteries.

The state-of-the-art layered oxide as the cathode material for lithium-ion batteries has attracted wide attention; however, harsh operations of high-energy and high-safety energy-storage technology at high temperature is challenging owing to the aggravated structural instability and parasitic reactions at the cathodes. Herein, the layered/olivine composite structure architecture is designed at the grain surface to govern constant electrochemistry in a harsh environment, and a gradient LiF interlayer is developed onto the cathodes to suppress the interfacial degradation. By a combination of interfacial-sensitive characterizations and theoretical analysis at the cathode/interface, the formation mechanism of this special interphase induced by the composite structure cathode is revealed. The composite structure cathode could deliver an excellent high-temperature cycling stability with 90.8% retention for 300 cycles in the half cell and 95.6% retention for 1000 cycles in the pouch cell and simultaneously enhances ∼51% of the thermal stability, which broadens the approaches for developing high-stable cathodes that work in extreme environments.

A Monte Carlo Approach for Simulating Electrical Conductivity in Highly Porous Ceramic Composites: Impact of Internal Structure.

Porous ceramic composites play an important role in several applications. This is due to their unique properties resulting from a combination of various materials. Determination of the composite properties and structure is crucial for their further development and optimization. However, composite analysis often requires complex, expensive, and time-demanding experimental work. Mathematical modeling represents an effective tool to substitute experimental approach. The present study employs a Monte Carlo 3D equivalent electronic circuit network model developed to analyze a highly porous composite on the basis of minimum easily obtainable input parameters. Solid oxide cell electrodes were used as a model example, and this study focuses primarily on materials with a porosity of 55% and higher, characterized by deviation of behavior from those of lower void fraction share. This task is approached by adding to the original Monte Carlo model an additional parameter defining the void phase coalescence phenomenon. The enhanced model accurately simulates electrical conductivity for experimental samples of up to 75% porosity. Using sample composition, single-phase properties, and experimentally determined conductivity, this model allows us to estimate data of the internal structure of the material. This approach offers a rapid and cost-effective method to study material microstructure, providing insights into properties, such as electrical conductivity and heat conductivity. The present research thus contributes to advancing predictive capabilities in understanding and optimizing the performance of composite materials with potential in various technological applications.

Correction: Climate impact and energy use of structural battery composites in electrical vehicles—a comparative prospective life cycle assessment

Correction: Climate impact and energy use of structural battery composites in electrical vehicles—a comparative prospective life cycle assessment

Fabrication of an Antibacterial/Anticoagulant Dual-Functional Surface for Left Ventricular Assist Devices via Mussel-Inspired Polydopamine Chemistry.

Infections and thrombosis remain unsolved problems for implanted cardiovascular devices, such as left ventricular assist devices. Hence, the development of surfaces with improved blood compatibility and antimicrobial properties is imperative to reduce complications after artificial heart implantation. In this work, we report a novel approach to fabricate multifunctional surfaces for left ventricular transplanted ventricular assist devices (LVADs) by immobilizing nitric oxide (NO) generation catalysts and heparin and reducing silver nanoparticles in situ. The general view, structure, and chemical compositions of the pure/modified surfaces were characterized using digital imaging, scanning electron microscope (SEM), atomic force microscope (AFM), water contact angle (WCA), X-ray photoelectron spectroscopy (XPS), and inductively coupled plasma (ICP). All of the results demonstrated that the AgNPs and heparin were successfully immobilized on the surface. The Cu ions and NO release experimental results showed that the immobilized copper ions could catalyze the production of NO from S-nitrosothiols within the biological system. Meanwhile, due to the synergistic anticoagulant effect of NO and surface-immobilized heparin, the fabricated modified surfaces exhibited antiplatelet adhesion activities and good hemocompatibility. Finally, the antimicrobial activity of the samples was evaluated by Escherichia coli and Staphylococcus aureus, and cytocompatibility was measured using human umbilical vein endothelial cells (HUVECs). The results demonstrated that silver nanoparticles (AgNPs) immobilized by surface reduction reaction did not cause any significant inhibition of cell proliferation while providing stable and effective antimicrobial properties. We envision that this simple surface modification strategy with bifunctional activities of antimicrobial and anticoagulant will find widespread use in clinically used indwelling left ventricular assist devices.