Composite Structures Research Articles

Effects of Nanofillers and Synergistic Action of Carbon Black/Nanoclay Hybrid Fillers in Chlorobutyl Rubber

Nanocomposites based on chlorobutyl rubber (CIIR) have been made using a variety of nanofillers such as carbon black (CB), nanoclay (NC), graphene oxide (GO), and carbon black/nanoclay hybrid filler systems. The hybrid combinations of CB/nanoclay are being employed in the research to examine the additive impacts on the final characteristics of nanocomposites. Atomic force microscopy (AFM), together with resistivity values and mechanical property measurements, have been used to characterise the structural composition of CIIR-based nanocomposites. AFM results indicate that the addition of nanoclay into CIIR increased the surface roughness of the material, which made the material more adhesive. The study found a significant decrease in resistivity in CIIR–nanoclay-based composites and hybrid compositions with nanoclay and CB. The higher resistivity in CB composites, compared to CB/nanoclay, suggests that nanoclay enhances the conductive network of carbon black. However, GO-incorporated composites failed to create conductive networks, which this may have been due to the agglomeration. The study also found that the modulus values at 100%, 200%, and 300% elongation are the highest for clay and CB/clay systems. The findings show that nanocomposites, particularly clay and clay/CB hybrid nanocomposites, may produce polymer nanocomposites with high electrical conductivity. Mechanical properties correlated well with the reinforcement provided by nanoclay. Hybrid nanocomposites with clay/CB had increased mechanical properties because of their enhanced compatibility and higher filler–rubber interaction. Nano-dispersed clay helps prevent fracture growth and enhances mechanical properties even more so than CB.

A Comparative Analysis on the Optimization of Carbon Fibre Reinforced Polymer and Glass Fiber Reinforced Polymers as Wrapping Structures on Defected Piping System using Computational Simulation Approach

This study examined the application of carbon fiber reinforced polymer (CFRP) and glass fiber reinforced polymer (GFRP) as wrapping structures for defective pipe systems. The structural behavior and performance of the CFRP and GFRP wrapping structures were assessed using computational simulation methodologies. The goal of the study was to determine the best wrapping material for strengthening the integrity and reliability of piping systems with defects by comparing the results of the simulations. The study evaluated the capability of the proposed composite wrapping structure through CAD simulation. The simulations provided preliminary analysis and visually depicted deformations, aiding in the selection of an optimized lamination orientation for the composite wrapping structure in real-world applications. Eventually, this approach could have alleviated two primary failure modes that were common in composite repair: composite overloading due to excessive thickness and composite delamination from the substrate. The results of this study would have helped enhance effective and efficient pipe repair techniques in a variety of industries by offering useful insights into the selection and use of suitable wrapping structures for repairing defective pipes.

Quasi-static uniaxial compression and low-velocity impact properties of composite auxetic CorTube structure

Auxetic structures are gaining great attention due to their unique contraction deformation characteristics under compression and impact. In this paper, high performance carbon fiber-reinforced composites are used to fabricate the auxetic structure consist of corrugated sheets and tubes (CorTube). The quasi-static uniaxial compression and low-velocity impact properties of composite CorTube structure are explored. The response of the composite CorTube structures under quasi-static compression loads are analyze through a combination of theoretical analysis, simulations, and experimental tests. Additionally, drop-weight impact tests are conducted using a rigid impactor with a hemispherical head to examine the effects of impact energy levels, impact locations, and corrugated sheet thickness on the impact response of CorTube structure. Enhancing corrugated sheet-tube bonding via modified cross members and reducing tube crushing during quasi-static compression are notable findings. The results also highlight the remarkable auxetic properties of the composite CorTube under low-speed impact, and the impact resistance could be enhanced by increasing the corrugated sheet thickness and stiffness. Various failure modes were observed, including cracks, pits, tube crushing, and delamination. Significantly, peak-impacted specimens exhibited greater maximum displacement with lower peak impact forces. This study offers insights into the deformation and failure modes of auxetic CorTube structures under low-velocity impact.

Research on size effects in the low‐velocity impact (LVI) and compression after impact (CAI) characteristics of composite laminates

AbstractThe load‐bearing capacity and failure characteristics of composite structures are closely related to their dimensions. In this study, low‐velocity impact, ultrasonic non‐destructive testing, and compression after impact tests were conducted on composite laminates of varying widths to investigate the influence of size effects. Distinct impact response profiles and compression failure modes were characterized. The results indicate that under impact loading, the delamination threshold load (6700 N ~ 7200 N) and the knee‐point energy (40 J) are not affected by width. However, variations in width lead to differences in indentation depth, impact duration, peak load, delamination characteristics, and energy absorption. Furthermore, increasing impact energy further magnifies these differences. Under compression loading, wider laminates exhibit lower residual strength, with the influence of impact energy on residual strength decreasing as width increases. Importantly, the observed compression failure deformation mode transitions from localized buckling to widespread sub‐layer delamination‐induced compression failure. This suggests that changes in width alter the governing mechanical mechanisms of CAI failure. Consequently, the use of a single‐size laminate to represent both LVI and CAI processes is not recommended. Based on experimental results, the reliability of the equivalent damage method in predicting the residual compression strength of laminates of different widths was confirmed, providing valuable insights for practical engineering applications.Highlights Assess the variations in the low‐velocity impact process of laminates with different widths. Evaluate the delamination damage of laminates after impacts by ultrasonic C‐scan techniques. Investigate the effect of variation in widths on the compression behavior of laminates after impact. Validate the feasibility of equivalent damage modeling for calculating residual strength.

Hybrid Inspection Method using Three Dimensional Scanning, Lock-in Thermography and Laser Shearography

The proportion of composite materials (such as CFRP) to the metal used on the modern aircrafts is rising, imposing different kind of failure modes. Since the composite structures are known to be sensitive to the impact loading, there is need for means to assess the sub-surface damage in the structure rapidly. Royal Netherlands Aerospace Centre NLR has an extensive track record on contactless non-destructive inspection (NDI) methods based on optical sensors, such as 3D surface scanning, lock-in thermography and laser shearography. The combination of these methods (multi-domain inspection) enables us to assess the structural integrity of an aircraft outer surface in a short time, reducing inspection costs and the “down time” of the aircraft. Recently, NLR is working towards a 3D oriented mesh environment of an object, enhanced with NDI data, providing sub-surface damage information. By automatically stitching the 3D object images, it is possible to expand this method for a complete scan of an aircraft surface. Furthermore, the thermographic and shearography imaging information has been integrated into the 3D surface accounting for the image distortion from the different measurement angles. In this paper, the results from the various studies will be presented involving integration of the 2D measurements with the 3D scan mesh. Keywords: Thermography, Shearography, 3D scanning, Data fusion

Effects of High-Energy Electron Beam-Modified Fumed Silica on the Structure and Properties of Silicone Rubber Composites

Effects of High-Energy Electron Beam-Modified Fumed Silica on the Structure and Properties of Silicone Rubber Composites

Floristic Composition, Diversity, and Vegetation Structure in Wadi Al-Quwayiyah, Riyadh Region, Saudi Arabya

Floristic Composition, Diversity, and Vegetation Structure in Wadi Al-Quwayiyah, Riyadh Region, Saudi Arabya

Effect of prefabricating process on remelting interfacial properties for thermoplastic composite stiffened structures: Molecular dynamics simulation and experimental verification

The forming interface is the weak link of complex thermoplastic composite structures. Aiming at the bottleneck problem of “weak bonding” at the remelting interface for the “Prefabricating + Remelting bonding” forming process of stiffened structures, through a combination of molecular dynamics (MD) simulation and experimental verification, a study was conducted on the influence of different prefabricating systems on the remelting bonding performance in the subsequent process. The results showed that prolonged high-temperature melting would lead to resin crosslinking reactions in the prefabricating stage and affect the remelting interface's molecular diffusion and penetration. Establishing a time-temperature condition function for the resin not to undergo crosslinking reaction during the prefabricating stage, the negative impact of the prefabricating process on the remelting bonding quality was reduced effectively, which provides theoretical and technical support for the high-quality manufacturing of complex thermoplastic composite structures.

Strength reinforcement of coal fly ash based non-sintered lightweight aggregates by autoclave curing and H2O2-modified basalt fiber addition

Coal fly ash, an industrial solid waste, occupies land and pollutes the environment in long-term stockpiling. Utilization of coal fly ash to produce non-sintered lightweight aggregates is a simple and cheap process with low energy consumption. However, it is still a challenge to produce coal fly ash based non-sintered lightweight aggregates with high mechanical and physical properties. In this work, high strength coal fly ash based non-sintered lightweight aggregates with low initial Ca/Si ratio were produced by autoclave curing and 1 h H2O2-modified basalt fiber addition. The cylinder compressive strength, 1 h water absorption, the bulk density and apparent density of the produced aggregates are 15.52 MPa, 4.85 %, 1089.83 kg/m3 and 1762.43 kg/m3 respectively. By analyzing the phase composition, microstructure and pore structure of the produced aggregates by XRD, SEM, FT-IR and MIP, it suggested that honeycomb-like C-A-S-H gel was formed and filled the pores in the aggregate matrix. Shown in the 3D profiles, a highly rough surface was formed on the basalt fiber after 1 h H2O2-modification. The rough surface provided as anchoring points for the interaction between the aggregate matrix and the fiber. Autoclave curing and basalt fiber modification synergistically improved the mechanical and physical properties of coal fly ash based non-sintered lightweight aggregates through “chemical filling-physical occupancy”.

Quantification of alloy atomic composition sites in 2D ternary MoS2(1-x)Se2x and their role in persistent photoconductivity, enhanced photoresponse and photo-electrocatalysis

Engineering transition metal dichalcogenides-based semiconducting two-dimensional (2D) layered materials for photo(electro)chemical (PEC) hydrogen evolution reaction (HER) by water splitting is an enduring challenge. Here, alloy-assisted photoconductivity and photoresponse from CVD-grown MoS2(1-x)Se2x (MSSE) 2D ternary atomic layered alloy-based photodetector device is presented for the realization of PEC HER. The explicit role of ‘S–Se’ and ‘Se2’ atomic alloy sites including chalcogen-induced vacancy defects on the photoconductivity/photoresponse and PEC HER performance of MSSE 2D alloy is investigated. Alloy formation, atomic site-by-site ‘Se’ composition and atomic structure are characterized using Raman/Photoluminescence (PL) spectroscopy, high-angle annular dark field (HAADF)- scanning transmission electron microscopy (STEM) extensively and supported with Auger Electron Spectroscopy (AES) mapping. Further, the local density and concentration of S–Se, Se2 atomic sites and defects were quantitatively estimated using HAADF-STEM image analysis in correlation with AES and it is found between the range of ∼15–20 % in MSSE alloy. A 10-fold high photoresponsivity in the case of MSSE concerning as-grown MS having fast photocurrent growth time and the prolonged decay time originates from the ‘Se’ and this alloy assisted states to enhance the PEC performance of MSSE alloy. The enhanced PEC HER activity of MSSE alloy was identified in terms of overpotential and current density. In addition, increased density of states as a function of ‘Se’ alloying, shifts in a p-band centre and lowers ΔGH* according to density functional theory calculations, which makes MSSE alloy an efficient HER activity. Further, the PEC stability and presence of the ‘S–Se’ and ‘Se2’ alloying and their role towards HER have been correlated by the spectral line shape analysis of PL and Raman spectra from post-PEC HER catalysts. These experimental and theoretical findings establish the role of chalcogen, and transition metal-based 2D alloy, leading to the design of new PECs of engineered 2D atomic layer interfaces.

Community assembly of ectomycorrhizal fungal communities in pure and mixed Pinus massoniana forests

Ectomycorrhizal (EcM) fungi play an important role in nutrient cycling and community ecological dynamics and are widely acknowledged as important components of forest ecosystems. However, little information is available regarding EcM fungal community structure or the possible relationship between EcM fungi, soil properties, and forestry activities in Pinus massoniana forests. In this study, we evaluated soil properties, extracellular enzyme activities, and fungal diversity and community composition in root and soil samples from pure Pinus massoniana natural forests, pure P. massoniana plantations, and P. massoniana and Liquidambar gracilipes mixed forests. The mixed forest showed the highest EcM fungal diversity in both root and bulk soil samples. Community composition and co-occurrence network structures differed significantly between forest types. Variation in the EcM fungal community was significantly correlated with the activities of β-glucuronidase and β−1,4-N-acetylglucosaminidase, whereas non-EcM fungal community characteristics were significantly correlated with β-1,4-glucosidase and β-glucuronidase activities. Furthermore, stochastic processes predominantly drove the assembly of both EcM and non-EcM fungal communities, while deterministic processes exerted greater influence on soil fungal communities in mixed forests compared to pure forests. Our findings may inform a deeper understanding of how the assembly processes and environmental roles of subterranean fungal communities differ between mixed and pure plantations and may provide insights for how to promote forest sustainability in subtropical areas.

The structural motif transformations in 71-atom PtAlCu nanoalloys: A combined Atomistic−DFT study

The structural motif transformations are vital for the catalytic performance of nanoalloys. A growing body of evidence suggests that Pt-based binary and ternary heterogeneous catalysts are being designed to reduce cost and increase efficiency. The present study aimed to explore the relationship between composition, stress, and the structural families of 71-atom PtnAl52Cu19-n (n = 0–19) nanoalloys, combining Gupta and DFT calculations. We present evidence of the relationship between structural motif transformations, composition and pressure. Also, the segregation phenomena of nanoalloys were confirmed. Our general results are that PtAlCu nanoalloys have three different motifs (Ih, chiral Dh, and daisy) on the surface and 19-atom Dh motif in the inner site, and the daisy motif plays a role in promoting contract or deformation.

Novel one-dimensional/two-dimensional composite films: Ag nanowires/ZnO nanowalls

We synthesized novel Ag nanowires/ZnO nanowalls composite films successfully, which integrated the beneficial characteristics of one-dimensional Ag nanowires and two-dimensional ZnO nanowalls. And the resulting Ag nanowires/ZnO nanowalls composite films exhibited outstanding photoelectric properties and enhanced light trapping abilities. The evenly distributed and interlaced Ag nanowires/ZnO nanowalls composite structures were clearly observed. By measuring the total transmittance (TT), diffuse transmittance (DT) and sheet resistance of the composite films, it can be seen that the haze value at 550 nm is 0.26, and the sheet resistance value is 42.5 Ω/sq. These indicated that the photoelectric and light trapping properties of the Ag nanowires/ZnO nanowalls composite films were enhanced significantly compared with those of the simplex films.

Stability of Thin-Walled Composite Structures with Closed Sections Under Compression

Stability of Thin-Walled Composite Structures with Closed Sections Under Compression

Geometrically Engineered Heating Arrays Enabled by Electric-Field-Driven 3D Printing for On-Demand Thermal Patterning

Arbitrary and high-precision thermal patterning has long been desired in the field of thermal functional materials. However, existing thermal patterning strategies have not been widely applied, either hampered by the difficulty in fabricating anisotropic metamaterials or limited by complex thermal manipulation. We propose an on-demand thermal patterning scheme that sandwiches geometrically engineered heating arrays between a substrate and an encapsulation layer to form composite structures and control the omnidirectional transfer of the heat flux generated by the heating arrays. These heating arrays are digitally assembled from multiple heater cells of varying widths and continuously printed using electric-field-driven 3D printing. A design strategy for thermal patterning with good uniformity within individual regions and high contrast between regions is proposed. The performance of the on-demand thermal patterning is verified via high-precision thermal printing. The proposed scheme provides a general and reproducible method for designing thermal functional materials, with potential applications in thermochromics, messaging, thermal camouflage, and illusions.

Real-Time Phased Array Ultrasonic Monitoring of Debonding Growth Under Cycling Loading in CFRP

Carbon Fibre Reinforced Polymer (CFRP) composites are widely employed in diverse industries due to their specific stiffness and strength, and corrosion resistance. However, over time, service-induced damage can initiate a failure that can threaten the operation’s safety and reliability, especially in critical industries like aerospace applications. The challenge lies in identifying and monitoring the defects before they escalate into serious issues. Non-Destructive Testing (NDT) methods play a pivotal role in this scenario, aiming to detect and evaluate defects without causing harm to the material. Detecting flaws in composite materials such as CFRP remains a complex task. Traditional NDT methods often struggle to effectively pinpoint and assess defects within these intricate structures. However, recent advancements in ultrasonic testing, especially Phased Array Ultrasonic Testing (PAUT), show promise in examining the internal composition of CFRP composites with higher accuracy and reliability. This study aims to demonstrate the applicability of PAUT for real-time monitoring of debond growth under dynamic loading. The loading was applied to the test specimens up to one million cycles, and 64 elements 2 MHz linear phased array probe was attached to the specimen. The acquired signals were analyzed and could also be recorded for offline processing or archiving. To validate the credibility of the findings, the performance of PAUT was compared to Acoustic Emission (AE), a well-established method for detecting and analysing high-frequency signals emitted by materials undergoing deformation or damage. Encouragingly, both methods exhibited similar trends in capturing the growth of debond. Furthermore, to verify the final defect lengths, post-test ultrasonic C-Scans utilizing the through transmission technique were conducted, complemented by visual inspections. These assessments served to confirm the accuracy and reliability of the results obtained through Phased Array Ultrasonic Testing. Real-time monitoring of composite structures using phased array technology comprises a valuable tool for real- time assessment of debonding in the composite. As industries continue to rely on Carbon Fibre Reinforced Polymer composites for multifaceted applications, the utilization of advanced Non-Destructive Testing methodologies like Phased Array Ultrasonic Testing emerges as a cornerstone in guaranteeing their continued integrity and performance.

Compositionally Equivariant Representation Learning.

Deep learning models often need sufficient supervision (i.e., labelled data) in order to be trained effectively. By contrast, humans can swiftly learn to identify important anatomy in medical images like MRI and CT scans, with minimal guidance. This recognition capability easily generalises to new images from different medical facilities and to new tasks in different settings. This rapid and generalisable learning ability is largely due to the compositional structure of image patterns in the human brain, which are not well represented in current medical models. In this paper, we study the utilisation of compositionality in learning more interpretable and generalisable representations for medical image segmentation. Overall, we propose that the underlying generative factors that are used to generate the medical images satisfy compositional equivariance property, where each factor is compositional (e.g., corresponds to human anatomy) and also equivariant to the task. Hence, a good representation that approximates well the ground truth factor has to be compositionally equivariant. By modelling the compositional representations with learnable von-Mises-Fisher (vMF) kernels, we explore how different design and learning biases can be used to enforce the representations to be more compositionally equivariant under un-, weakly-, and semi-supervised settings. Extensive results show that our methods achieve the best performance over several strong baselines on the task of semi-supervised domain-generalised medical image segmentation. Code will be made publicly available upon acceptance at https://github.com/vios-s.

A PEDOT: PSS/GO fiber microelectrode fabricated by microfluidic spinning for dopamine detection in human serum and PC12 cells.

Rapid and accurate in situ determinationof dopamine is of great significance in the study of neurological diseases. In this work, poly (3,4-ethylenedioxythiophene): poly (styrenesulfonic acid) (PEDOT: PSS)/graphene oxide (GO) fibers were fabricated by an effective method based on microfluidic wet spinning technology. The composite microfibers with stratified and dense arrangement were continuously prepared by injecting PEDOT: PSS and GO dispersion solutions into a microfluidic chip. PEDOT: PSS/GO fiber microelectrodes with high electrochemical activity and enhanced electrochemical oxidation activity of dopamine were constructed by controlling the structure composition of the microfibers with varying flow rate. The fabricated fiber microelectrode had a low detection limit (4.56 nM) and wide detection range (0.01-8.0 µM) for dopamine detection with excellent stability, repeatability, and reproducibility. In addition, the PEDOT: PSS/GO fiber microelectrode prepared was successfully used for the detection of dopamine in human serum and PC12 cells. The strategy for the fabrication of multi-component fiber microelectrodes isa new and effective approach for monitoring the intercellular neurotransmitter dopamine and has highpotential as an implantable neural microelectrode.

Microstructural evolution and investigation of mechanical properties of Al 7055 –Nano Si3N4 composites

In this paper an attempt has been made to develop the aluminium based metal matrix composites. Al7055 were chosen as base material and hard ceramic particulate nano silicon nitride as reinforcement. The composites were fabricated by using bottom pouring stir casting technique by varying weight percentage of Si3N4 in steps of (3 wt%, 6 wt% & 9 wt%) respectively and particle size of 30, 60 and 90nm. Morphological characterization of composites was conducted by using HRFESEM. The SEM result reveals that there is homogeneous distribution between the matrix and reinforcement. EDS mapping for prepared composites were done to identify the presence of alloying elements and phase distribution. XRD analysis is conducted for validation of the structural composition. Mechanical tests like tensile, micro Vickers hardness and impact test were performed on developed composites. The ultimate tensile strength of the composites at 9 wt% and particle size of 90 nm found to be diminishing due to severe agglomeration. The hardness value increases at 9 wt% and particle size of 30 nm. The toughness of the composites increased at 30 nm reinforcement size and 6 wt% as compared to higher weight percentage developed composites. Corrosion test were conducted as per ASTM G31 by weight loss method for different samples by dipping composite samples in 50 g Hcl solution for duration of 6 h and it was found that the corrosion resistance of the composites was higher while increasing the wt% of Si3N4 as compared to base matrix..

Effects of Susac syndrome on the central vascular structure of the retina-An optical coherence tomography angiography study

Susac syndrome (SS)describes an endotheliopathy of vessels in the central nervous system. Retinal involvement plays acentral role in the manifestation of the disease. This case-control study investigated the macular microvasculature in patients with chronic SS compared to controls using optical coherence tomography angiography (OCTA). 12eyes of 12patients with SS were compared with age-matched healthy control subjects with regard to their OCT angiographic parameters. The flow density (FD) of different macular layers, foveal avascular zone (FAZ) parameters and central retinal thickness and volume values were compared between the two groups. The FD of the choriocapillaris was reduced in Susac patients compared to healthy controls. The FD values of the superficial and deep capillary plexus of the inner retina, parameters of the FAZ as well as central retinal thickness and volume showed no significant differences between the two groups. Treated chronic SS does not appear to significantly affect the vascular and structural composition of the central inner retina; however, differences in the choriocapillaris indicate changes in deeper, highly vascularized capillary layers.