Flexible Lightweight Research Articles

Innovative radiation shielding material with flexible lightweight and low cost from shrimp shells waste

This study explores an innovative approach to developing radiation shielding materials using shrimp shell waste. The research investigates the feasibility of incorporating shrimp shells into a silicone rubber matrix to create a flexible, lightweight, and cost-effective radiation shielding material. Shrimp shells, rich in calcium carbonate (CaCO3) content of 13.90%, offers promising properties for radiation attenuation. Through a series of experiments and characterization techniques, including X-ray fluorescence (XRF), X-ray diffraction (XRD), and scanning electron microscopy (SEM), the effectiveness of the composite material in attenuating radiation is evaluated. The results demonstrate that as the shrimp shell concentration rose from 25% to 75%, the absorbed radiation increased from 9.27% to 82.39% (40 kVp) and from 1.88% to 30.22% (120 kVp), while the linear coefficient also increased, attributed to the presence of CaCO3. This novel radiation shielding material presents a sustainable solution by repurposing shrimp shell waste while offering a flexible, lightweight, and cost-effective shielding for various radiation applications.

All-Round Passivation Strategy Yield Flexible Perovskite/CuInGaSe2 Tandem Solar Cells with Efficiency Exceeding 26.5.

The perovskite/Cu(InGa)Se2 (CIGS) tandem solar cells (TSCs) presents a compelling technological combination poised for the next generation of flexible and lightweight photovoltaic (PV) tandem devices, featuring a tunable bandgap, high power conversion efficiency (PCE), lightweight flexibility, and enhanced stability and durability. Over the years, the imperative to enhance the performance of wide bandgap (WBG) perovskite solar cells (PSCs) has grown significantly, particularly in the context of a flexible tandem device. In this study, an all-round passivation strategy known as Dual Passivation at Grains and Interfaces (DPGI) is introduced for WBG PSCs in perovskite/CIGS tandem structures. The implementation of DPGI is tailored to improve film crystallinity and passivate defects across the solar cell structure, leading to a substantial performance enhancement for WBG PSCs. Subsequently, both rigid and flexible tandem devices are assembled. Impressively, a fully flexible 4T perovskite/CIGS TSCs is successfully fabricated with a PCE of 26.57%, making it the highest value in this field and highlighting its potential applications in the next generation of flexible lightweight PV tandem devices.

Analysis of the Aeroelastic Dynamics of Lightweight Flexible Variations of the SNL-NRT Turbine

Current trends show that wind turbines are growing in size to meet a rising demand for renewable energy generation, and their upscaled rotors have inherently become more flexible to maintain a proportionally lighter design. This is because larger rotors must be less massive relative to their diameter to minimize the levelized cost of energy (LCOE), which means that blades that are notably less stiff are produced as a result. These structural changes to blades are often reflected in their compromised aeroelastic stability and amplified deformation during operation, which has the potential to decrease the blade’s expected lifetime and the performance of the machine overall. Variations in blade flexibility are also known to influence vortex-wake structures downstream of the turbine, causing patterns of velocity deficit to evolve in ways that affect the performance of other turbines in the farm. This research explores how the increased flexibility of modern utility-scale wind turbine blades influences rotor aeroelastic behavior and interactions with farm flow. High-fidelity simulations of Sandia National Laboratories’ (SNL) National Rotor Testbed (NRT) wind turbine are presented. Flexible variations of the NRT baseline blade are simulated in a variety of realistic operational conditions typically expected at the SNL’s SWiFT facility in Lubbock, Texas. Solutions are then compared to investigate how specific changes to the structural properties of the NRT baseline blade’s design and construction can influence its aeroelastic response at the rotor and the evolution of the turbine’s wake.

Fabrication, characterization and investigation of flexible light weight nylon-6 based silicon rubber composites for radiation attenuation

Lead, the conventional choice for wearable radiation shielding, faces growing health and occupational concerns. This prompts the search for a lighter, more flexible alternative. Nylon 6, prized for its mechanical prowess, emerges as a reinforcement in wearable composites. This study focuses on creating silicon rubber composites using Nylon 6 reinforcement and varying proportions of Bismuth oxide and aluminium fillers. Mechanical Parameters such as Tensile strength and Elongation at break, are studied and the quality of fabrication is assessed using a Scanning Electron Microscope. Studies on various combinations of nylon 6-based silicon rubber with varying percentages of bismuth oxide and aluminium fillers have been studied and radiation parameters have been assessed. TSN-4 (60% wt. bismuth oxide along with 50% wt. aluminium powder) showed the highest tensile strength of 25.13 MPa having 79.3% of elongation at break followed by TSN-1 & TSN-3. The results reveal good mechanical properties as well as satisfactory radiation attenuation properties. The combination of Nylon 6-based with 60% wt. bismuth oxide along with 50% wt. aluminium powder (TSN4) was considered optimal for the energy range from 140 keV to 511 keV with HVL of 2.06 cm, TVL 6.86 cm, and MAC of 0.093 gm/cm2 and also bearing good mechanical properties. Further, the fabricated samples can be compared with the Monte Carlo Simulation method for further improvements in the fabricated composites. The produced composites have the potential to be used as lead-free protective wearables and wearing devices in nuclear medicine following further investigation.

Out-of-Plane Instability and Vibrations of a Flexible Circular Arch Under a Moving Load

Flexible lightweight arched structures are finding increasing use as components in smart engineering applications. Such structures are prone to various types of instability under moving transverse loads. Here, we study deformation and vibration of a hinged circular arch under a uniformly moving point load using geometrically-exact rod theory to allow for large pre- and post-buckling deformations. We first consider the quasi-statics problem, without inertia. We find that for arches with relatively large opening angle ([Formula: see text]160[Formula: see text]) a sufficiently large traversing load will induce an out-of-plane flopping instability, instead of the in-plane collapse (snap-through) that dominates failure of arches with smaller opening angle. In a subsequent dynamics study, with full account of inertia, we then explore the effect of the speed of the load on this lateral buckling. We find speed to have a delaying (or even suppressing) effect on the onset of three-dimensional bending–torsional vibrations and instability. Based on numerical computations we propose a power law describing this effect. Our results highlight the role of inertia in the onset of elastic instability.

Effect of impinging behavior annular jet shielding gas and printing substrate on metal droplet stable ejection

Using coaxial shielding gas for low-oxygen protection in metal droplet-based 3D printing helps to promote flexible production and lightweight manufacturing. However, the presence of the printing substrate causes the shielding gas to exhibit complex annular impinging jet characteristics, making the stability of droplet ejection unpredictable. In the present work, the mechanisms of airflow pattern evolution on droplet formation and metal jet deflection were first revealed by incorporating shielding gas simulations, hydrodynamic modeling, and droplet ejection experiments. An innovative airflow disturbance suppression strategy for metal droplet ejection was proposed, which can remarkably reduce the shielding gas disturbance on droplet printing. Results show that the change in deposition distance leads to a transition between two typical airflow patterns, thus affecting the droplet ejection behavior. When the deposition distance exceeds 2.5 mm, metal jets would be stretched even to a secondary break under airflow pattern 1, accelerating droplets. For the deposition distance below 2.5 mm, metal jet shortening and droplet deceleration would occur under airflow pattern 2, deflecting jet trajectory. The negative airflow effect on droplet ejection could be avoided by controlling the deposition distance to the transition region of two airflow patterns. Furthermore, a ball grid array (BGA) chip ball-mounting and two thin-wall tube printing were realized based on metal droplet ejection in annular impinging jet shielding gas. This work provides theoretical and technical guidance for the stable ejection and accurate printing of metal droplets in an opening low-oxygen environment.

Response of flexible structures to air-blast: nonlinear compressibility effects in fluid–structure interaction

This paper presents a coupled model that considers the nonlinear compressibility effect in fluid–structure interaction (FSI) during air-blast loading on flexible structures. In this coupled model, structural behaviour is idealized as a linear single-degree-of-freedom mass-spring-damper system whereas nonlinear fluid compressibility is considered by applying Rankine–Hugoniot jump conditions across a moving plate. The surrounding fluid medium is modelled with an ideal gas equation and hence, this model can be applied for FSI analysis with relatively strong shocks (reflection coefficient of up to 8). The nonlinear compressibility of the fluid medium at the backside of the plate is also considered in this coupled formulation and its effects on the structural responses are examined. Moreover, the negative/underpressure phase of the reflected wave profile, which is typically neglected in a decoupled model, is also considered in the proposed model and its influence on the structural response is also investigated. The study reveals that the nonlinear compressibility of fluid medium significantly influences the coupled FSI phenomena, especially in flexible lightweight structures. Numerical examples are presented to highlight the implications of the nonlinear compressibility effect in FSI on the reflected pressure profile and the response of flexible structures. Parametric dependencies of response on structural mass and natural frequency are examined thoroughly and a response spectrum is obtained. It is envisaged that the lightweight protective structure design under higher blast intensity may benefit from this study.

Modeling of self-oscillating flexible circuits based on liquid crystal elastomers

Deformable and movable flexible circuits are characterized by simple construction, precise control, flexible and versatile morphology, and various functional forms, which can be used to build dynamic circuit systems, achieve the integration of drivers and controllers, and automated control of circuits, etc. Limited to conventional materials, challenges remain in designing novel self-oscillating flexible circuit. In this paper, a concept for a self-oscillating flexible circuit based on electrothermally responsive liquid crystal elastomers (LCEs) is presented, which is capable of generating periodic continuous oscillation under steady applied voltage. The governing equation of the self-oscillating LCE-based flexible circuit is formulated, and numerically calculated by fourth-order Runge-Kutta method with Matlab software. The numerical calculations reveal that the self-oscillating flexible circuit involves two motion patterns, i.e., static pattern and self-oscillation pattern. The self-oscillation arises from the coupling between the electrothermally driven deformation of the LCE film and its motion, and the electrothermal input compensates for the damping dissipation. Moreover, it is found that system parameters affect the self-oscillation of flexible circuit and that there are critical values of these parameters that trigger self-oscillation. Based on the self-oscillating flexible circuit, we conceptualized an automatic control device and a disturbance monitoring device, realizing automatic control of electrical appliances without human intervention and automatic monitoring of external disturbances. The proposed self-oscillating LCE-based flexible circuit features convenient operation, simple construction, flexibility, lightweight, and noiseless operation, rendering it suitable for constructing dynamic circuit systems, achieving actuator-controller integration, and facilitating circuit automation applications.

Lightweight and high-strength polyarylene ether nitrile-based composites for efficient electromagnetic interference shielding

Abstract The proliferation of electronic devices and the widespread adoption of microwave-based technologies have resulted in a notable rise in electromagnetic radiation pollution. In present work, a novel flexible lightweight polyarylene ether nitrile (PEN)-based composite for efficient electromagnetic interference (EMI) shielding was prepared by introducing dual-loss hybrid material (PKMWCNT@Fe3O4) into PEN via non-solvent induce phase separation method and assembling it layer-by-layer with carbon fiber (CF) fabric. The porous morphology of the PEN layer, the electrical conductivity of the CF fabric, and the dual-loss property of the filler enable the material to reflect and absorb electromagnetic waves multiple times, resulting in superior electromagnetic shielding performance. With the addition of PKMWCNT@Fe3O4 at a mass fraction of 50%, the EMI SE T and specific shielding effectiveness SSE/t can reach up to 47.08 dB and 617 dB cm2/g, respectively, indicating absorption dominated shielding mechanism. Furthermore, the material exhibits a lightweight nature with a density of 0.55 g/cm3, and excellent mechanical properties, including a tensile strength of 43.98 MPa and elongation at break of 43.32%. This work presents a new approach to prepare high-performance composites that are both lightweight and resistant to secondary contamination by electromagnetic waves.

Fabrication of Porous Reduced Graphene Oxide Encapsulated Cu(OH)2 Core-shell Structured Carbon Fiber-Based Electrodes for High-Performance Flexible Supercapacitors.

To explore next-generation flexible supercapacitors, lightweight, superior conductivity, low cost, and excellent capacitance are the preconditions for practical use. However, subjected to unsatisfactory conductivity, limited surface areas, and poor porosity leading to long ion transport channels, carbon fiber (CF)-based flexible supercapacitors need to further boost the electrochemical properties. Hence, a porous reduced graphene oxide encapsulated Cu(OH)2 core-shell structured CF-based electrode was fabricated through a scalable approach. The inexpensive Cu(OH)2 nanoarrays were controllably grown in situ on a CF substrate, with residual Cu promoting conductivity. Porous graphene oxide (PrGO), which served as the shell, was realized by Ni nanoparticle etching, which not only provided more active sites for capacitance as well as shortened accessible pathways for the ion transport but also effectively alleviated the exfoliation of the internal active materials. Moreover, thanks to this distinctive core-shell architecture, the extra space between the outer PrGO layer and the internal ordered Cu(OH)2 nanoarrays provided increased space for capacitance storage. The assembled PrGO/Cu(OH)2/Cu@CF electrode exhibited an excellent areal capacitance, reaching up to 722 mF cm-2 at a current density of 0.5 mA cm-2, attributed to its superior structure and materials advantages. The resulting PrGO/Cu(OH)2/Cu@CF//AC//CF asymmetric flexible all-solid-state supercapacitor achieved a high energy density of 0.052 mWh cm-2 and exhibited long-term durability. This work proposes a low-cost and effective way to fabricate hierarchically structured electrodes for wearable CF-based supercapacitors.

Improvement of the low-frequency sound insulation performance of hollow double-leaf panels by inserting a bending panel

Air-borne sound transmission loss of building materials generally follows the mass law. Transmission loss decreases at lower frequencies and is minimal at the fundamental natural frequency f0. On the other hand, transmission loss increases below f0, and is controlled by stiffness. Moreover, the stiffer the materials, the higher the f0. In the other words, even without increasing the mass, increasing the stiffness can improve low-frequency transmission loss. We focus on the fact that flexible lightweight panels are easily stiffened by bending deformation. We conduct a basic study on the effect of inserting a bending panel into hollow double-leaf panels. Experimental results on single panels showed a correspondence between the increase of f0 by bending deformation and the improvement of low-frequency sound insulation performance. In the case of the double-leaf panels with the lightweight bending panel inserted inside, the stronger the bending, the more low-frequency sound insulation performance tended to be improved.

Surrogate-based optimization for the worst-case prediction regarding a flexible structure impacted by wind gusts

The paper is a follow-up of the recent study on the assessment of discrete wind gust parameters impacting a flexible lightweight structure as a first step towards the evaluation of the worst-case scenario caused by strong wind gusts (JWEIA 231, 105207, 2022). The present study goes beyond by suggesting an optimization framework which allows to determine the worst-case scenario automatically. For this purpose, a stochastic response surface algorithm with a surrogate model based on radial basis functions is chosen. The algorithm relies on costly evaluations of the objective function, which consist of CPU-time intensive fully coupled fluid–structure interaction (FSI) high-fidelity simulations including the pre- and post-processing of the results. Besides the parallelization of the coupled FSI solver, a parallel version of the optimization algorithm allows to carry out several costly evaluations simultaneously. The Metric Stochastic Response Surface algorithm determines the worst case fast. Then, it continues to explore the optimization space to ensure that the global extremum is reached. A sensitivity study on relevant parameters of the optimization algorithm is conducted. Typically, for the present FSI setup, an optimization run takes one week with 6 evaluations in parallel to compute 100 different configurations. The worst case is found after about one third of the evaluations. The increase of parallel evaluations drastically reduces the wall-clock time, but the worst case is found later after half of the evaluations. This later finding is due to the parallel nature of the algorithm. Finally, the various sources of uncertainties that arise throughout the entire procedure are assessed and discussed.

Lightweight Flexible Nonlinear Composite (LFNLC) and Elastic Composite, Reinforced Lightweight Concrete as an LFNLC

Lightweight Flexible Nonlinear Composite (LFNLC) and Elastic Composite, Reinforced Lightweight Concrete as an LFNLC

Flexible lightweight Bi2O3-rubber based materials for X-ray protection

The flexible X-ray protective materials are commonly made of lead rubber. They have heavy weight, high biological toxicity, poor flexibility and aging resistance. The "weak absorption zone" in the energy range of 40–88 keV threaten environmental safety and human health. Bi2O3-rubber based flexible X-ray protective materials were prepared by rubber production process. The micromorphology, shore hardness, specific gravity, mechanical properties and radiation protective properties were characterized and analyzed. The results showed that Bi2O3 particles dispersed in natural rubber (R) matrix uniformly. The shore hardness of samples fluctuated between 41° and 46° with the increasing Bi2O3 content, lower than the Level 1 index requirement of the hardness (≤80°) of lead-free composite protective materials. The specific gravity increased from 1.35 g/cm3 to 2.38 g/cm3, which reduced approximately 34% comparing with the commercial protective materials containing Pb. The breaking strength and breaking elongation meet the index requirements in National standard GB 16757-2016. When Bi2O3 content reached 300 parts, the highest lead equivalent and maximum shielding ratio were 0.3012 mmPb and 52.95% respectively. It meets the index requirement of lead equivalent of 0.25 mmPb≤Pb≤0.35 mmPb for the front sheet of protective clothing. The effective shielding range of the protective material R/Bi2O3(100/300) was mainly in the range of incident energy of 65∼100 keV and 164–250 keV, which covered the “weak absorption zone” of lead.

A flexible lightweight self-powered wireless metal detector enabled by triboelectric discharge effect

A flexible lightweight self-powered wireless metal detector enabled by triboelectric discharge effect

Octopus-Inspired Robotic Arm Powered by Shape Memory Alloys (SMA)

Traditional rigid grippers that are used for underwater systems lack flexibility and have lower degrees of freedom. These systems might damage the underwater environment while conducting data acquisition and data sampling. Soft robotics, which is mainly focused on creating robots with extremely soft materials are more delicate for the grasping of objects underwater. These systems tend to damage the underwater ecosystem in the least possible way. In this paper, we have presented a simplified design of a soft arm inspired by the octopus arm actuated by coiled Shape Memory Alloys (SMAs) using completely flexible lightweight material. The characterization arm performance under various load and input current conditions is shown. We hope this work will serve as a basis for the future of underwater grasping utilizing soft robotics.

TL-Detector: Lightweight Based Real-Time Traffic Light Detection Model for Intelligent Vehicles

With the leap-forward development of intelligent driving, traffic light detection with high accuracy and high speed is important for intelligent transportation systems to ensure safety. However, existing methods encounter difficulties in balancing the detection speed and accuracy. This paper aims to present a flexible and robust lightweight model TL (Traffic Light)-Detector for real-time detection of traffic light. The model is composed of three parts. An enhanced backbone network combined with G-module is proposed to generate abundant information and reduce computational load, and the coordinate attention mechanism is introduced to focus on location features thereby strengthening the feature extract ability. The lightweight neck promotes multi-scale feature information aggregation for feature fusion to build a lightweight feature fusion network. The lightweight detection head adopts anchor-free mechanism to eliminate the hyperparameters related to the anchor. The dataset TL2022 of traffic light is built based on real traffic sceneries. Experimental results show that TL-Detector has the best comprehensive performance. TL-Detector achieves a detection speed of 277 FPS and a precision of 73.24% with only 0.72 GFLOPs. The experiments on LaRA (La Route Automatisee) public traffic light dataset show the excellent generalization ability. It indicates that TL-Detector can effectively achieve accurate and real-time detection for traffic lights.

Lightweight Flexible Solid-State Supercapacitor Based On Metal–Graphene-Textile Composite Electrodes

Lightweight Flexible Solid-State Supercapacitor Based On Metal–Graphene-Textile Composite Electrodes

SERS with Flexible β-CD@AuNP/PTFE Substrates for In Situ Detection and Identification of PAH Residues on Fruit and Vegetable Surfaces Combined with Lightweight Network.

The detection of polycyclic aromatic hydrocarbons (PAHs) on fruit and vegetable surfaces is important for protecting human health and ensuring food safety. In this study, a method for the in situ detection and identification of PAH residues on fruit and vegetable surfaces was developed using surface-enhanced Raman spectroscopy (SERS) based on a flexible substrate and lightweight deep learning network. The flexible SERS substrate was fabricated by assembling β-cyclodextrin-modified gold nanoparticles (β-CD@AuNPs) on polytetrafluoroethylene (PTFE) film coated with perfluorinated liquid (β-CD@AuNP/PTFE). The concentrations of benzo(a)pyrene (BaP), naphthalene (Nap), and pyrene (Pyr) residues on fruit and vegetable surfaces could be detected at 0.25, 0.5, and 0.25 μg/cm2, respectively, and all the relative standard deviations (RSD) were less than 10%, indicating that the β-CD@AuNP/PTFE exhibited high sensitivity and stability. The lightweight network was then used to construct a classification model for identifying various PAH residues. ShuffleNet obtained the best results with accuracies of 100%, 96.61%, and 97.63% for the training, validation, and prediction datasets, respectively. The proposed method realised the in situ detection and identification of various PAH residues on fruit and vegetables with simplicity, celerity, and sensitivity, demonstrating great potential for the rapid, nondestructive analysis of surface contaminant residues in the food-safety field.

Flexible thermoelectric energy harvesting system based on polymer composites

Flexible and easy processing lightweight thermoelectric materials for energy harvesting applications have shown an increasing interest. Thermoplastic polyvinylidene fluoride (PVDF) and elastomer styrene-ethylene/butylene-styrene (SEBS) polymers reinforced with thermoelectric ceramics, including bismuth sulfide (Bi2S3), bismuth telluride (Bi2Te3) and antimony telluride (Sb2Te3), and electrically conductive carbon nanotubes (CNT) have been developed, tailoring their thermal and electrical properties for thermoelectric device applications. The Seebeck coefficient of the composites increases with thermoelectric ceramic filler content for semicrystalline PVDF composites, slightly decreasing for amorphous SEBS composite. Thermoelectric power factor and figure-of-merit in the polymer composites increases up to 9 orders of magnitude with respect to the pristine polymer, up to a maximum value of 10−3 µW/(m·K2) and 10−6, respectively, for the PVDF/CNT/Bi2Te3 composite. A device composed by 2 printable p-n thermocouples based on PVDF/50Bi2S3 and PVDF/50Bi2Te3 can generate power in the order of the nW and charge a capacitor with 5 V. Theoretical modeling allows to evaluate different thermoelectric configurations, the effect of the number of thermocouples and the influence of the temperature gradient on device performance.