Folding Angle Research Articles

Flutter Characteristics of a Modified Z-Shaped Folding Wing Using a New Non-Intrusive Model

Unmanned aerial vehicles (UAVs) with folding wings can serve in multiple mission profiles, usually accompanied by sudden changes in flight speed. These bring great challenges to the aeroelastic design of UAVs, especially in the calculation of flutter characteristics. This paper developed a new non-intrusive aeroelastic model to quickly calculate the flutter characteristics of Z-shaped folding wings at different folding angles. First, the original Z-shaped folding wing was designed to be enhanced. Beams and ribs were arranged inside each wing segment to enhance the structural strength performance. Control surfaces were arranged in the middle-wing and outer-wing to enhance the aerodynamic control performance. Second, a parametric aeroelastic model at any folding angle was reconstructed based on the input file of Nastran software for the flutter calculation of the folding wing in the unfolded state. Finally, the effects of parameters such as folding angle, hinge stiffness between different wing segments, and hinge stiffness of the control surfaces on the flutter characteristics of the folding wing were investigated. The results show that the enhancement scheme could significantly increase the flutter speed and flutter frequency of the folding wing. The hinge stiffness between each wing segment had a significant impact on the flutter characteristics of the folding wing, but flutter at the control surface basically did not occur.

Miura Origami‐Inspired Reconfigurable Phase Gradient Metasurface for Linearly and Circularly Polarized Differential Modulation

Miura origami's reconfigurable characteristic and structural asymmetry, combined with electromagnetic (EM) wave manipulation, crashed a unique spark. However, the complexity of the three‐dimensional (3D) origami structure after folding makes it challenging to study the phase regulation mechanism. Here, we propose a reconfigurable phase gradient metasurface based on Miura origami and derive the underlying mechanism of phase modulation in detail under linearly and circularly polarized (LP and CP) incidence. We adopt the one‐dimensional (1D) gradient design along the x direction to verify the idea. The phase calculation formulas are given under LP and CP incidence through the Jones matrix's derivation. The beam deflector angles corresponding to LP and CP waves are identical in the planar state. As the folding angle increases, the phase evolution rules corresponding to the LP and CP waves are discrepant, leading to differential beam steering. Finally, the origami sample is processed for verification, and the experimental data are consistent with the simulation and theoretically calculated values. We believe this work can help analyze the EM behavior of complex 3D origami structures and lay a foundation for designing a multifunctional EM origami metasurface.

Folding angle and wing flexibility influence the flight performance of origami winged fruits

Folding angle and wing flexibility influence the flight performance of origami winged fruits

Parametric Analysis on the Static and Modal Response of Folded Metamaterials

Metamaterials have been studied and analyzed in the past three decades because of their outstanding properties. Generally speaking, a metamaterial is a material that exhibits a mechanical behavior that does not depend only on the bulk material but also on the geometrical configuration in which it lies. This aspect leads to the possibility of tuning and engineering the structural response. One of the most interesting properties is the auxetic behavior of metamaterial. An auxetic material shows a global negative Poisson’s ratio. Shock absorption, acoustic dissipation, and shape morphing are some of the most popular employment for auxetic materials. In this article, we focus on the response of folded material under static and dynamic load conditions. Folded materials consist of folding a sheet under specific geometrical constraints. One of the most famous is the Miura-ori pattern, which comes from the origami-folding technique. The geometrical parameters, such as folding angles and edge lengths, play a fundamental role in achieving the desired auxetic behavior. These geometrical parameters define a unit cell that can be stacked into a periodic structure. This article proposes an experimental parametric study of the thickness impact on the auxetic behavior while edge dimensions and folding angles are fixed. The geometrical complexity of the pattern forced us to use additive manufacturing for the specimen fabrication. In particular, we choose Fused Filament Fabrication (FFF) using polymers like ABS and PLA. Digital Image Correlation (DIC) is used for monitoring the displacement and strain fields onto the Miura-ori surface under tensile load. Finally, Time Averaged Speckle Interferometry is employed for evaluating the modal response by using a quasi-full out-of-plane sensitivity setup.

Optimizing East-West vertical Façade integrated (T)PV through folding design in the Tropics: A study in an educational building

Appropriate orientation will optimize photovoltaic performance. North and South are found as the optimum orientation for PV and TPV installation in the tropics. In fact, due to its huge area, all sides of vertical façade on a high-rise are potential for (T)PV integration. This encourages study on optimizing the use of east–west façade as BI(T)PV through folding design, aiming to find optimum configuration to serve the needs of energy production while maintaining the function as daylighting aperture. Illuminance, sDA300/50%, daylighting and energy uniformity, and energy substitution are used to assess the performance. Experiment on folding angle, cell coverage ratio, and visible transmittance with simulation as its tool is applied. As the result, certain configurations in 45°, 60°, 75° can provide adequate illuminance level, sDA300/50%, and sufficient energy generation. However, only configuration in 75°- 50 % & 60 % cell coverage ratio − 38 % visible transmittance can promote ≥ 80 % uniformity of energy production.

Accessing quasi-static impact process by 3D-NPR corrugated metamaterials

The conventional impact process is a quintessential impulse process that causes substantial damage due to the high initial impact force. However, the impact effect can be significantly diminished by making the impulse process quasi-statically by using a three-dimensional negative Poisson's ratio corrugated metamaterial (3D-NPRCM) structure. This paper proposes a novel 3D-NPRCM obtained by folding the 2D-NPRCM. This study examines the crashworthiness properties and impact force of 3D-NPRCM subjected to impact using the finite element method (FEM). The results reveal that the sequential matrix structure has the ability to make impact impulse processes quasi-statically. The effects of various folding angles, arrangements, and geometrical parameters on the properties are also explored. Finally, the 3D-NPRCM is employed in an automobile crash box design. Through axial quasi-static compression simulation, the peak crushing force of the 3D-NPRCM crash box is reduced by 25.374 % from 211.652 kN to 157.946 kN, and the energy absorbed is increased by 23.830 % from 11.259 kJ to 13.942 kJ, compared to the conventional crash box. Through cart lateral impact simulation, the peak crushing force of the 3D-NPRCM crash box is reduced by 18.076 % from 206.9 kN to 169.5 kN, and the compressive displacement is decreased by 9.457 % from 235.8 mm to 213.5 mm. This work presents a novel design proposition for a crash box in vehicle engineering and demonstrates a fresh approach to expand the design of three-dimensional mechanical metamaterials.

Multiscale functionalized graphene origami metamaterials enable programming thermoelectric performance of flexible energy harvesters

Origami engineering stands out as one of the prominent approaches for fine tuning the multiphysical properties of energy materials. Employing first-principle calculations at the nanoscale, we explore the mechano-thermoelectric properties of graphene origami metamaterials functionalized by hydrogen (H), nitrogen (N), oxygen (O), and fluorine (F) adatoms. Our computational results reveal that functionalizing carbon (C) atoms induce buckling in the pristine graphene, transitioning carbon atoms from sp2 (for pristine graphene sheet) to hybridized sp3 orbital to fold the graphene origami. The functionalized graphene origami metamaterials, adopting the Miura-ori architecture, exhibit anisotropic mechanical properties and an unprecedented negative Poisson's ratio (NPR) of up to −0.8. Non-symmetrical functionalization breaks the inherent symmetry of graphene, resulting in a robust non-zero electronic band gap. This characteristic makes the graphene origami metamaterial a compelling contender for thermoelectric applications, since they offer an electronic figure of merit that exceed 200 at room temperature (Graphene-H), surpassing that of the majority of 2D thermoelectric materials can offer. Resorting to the finite element approach, we explore the origami-based thermoelectric legs in nanogenerators at mesoscale. The folding capability of origami architectures offer tunable heat insulation in order to realize next generation of thermoelectric legs. Compared to conventional cuboid leg thermoelectric nanogenerators, thermoelectric conversion efficiency of origami metamaterials can be two orders of magnitude higher; an enhancement that is significantly governed by their folding angle. The underlying principles governing the multiphysics performance of multiscale origami-based thermoelectric materials impart novel design concepts for customizing the thermoelectric performance of shape-changing low-dimensional metamaterials and energy-related devices.

Results of Modified Stenströms Technique Otoplasty and Patients' Satisfaction at King Fahad Armed Forces Hospital (KFAFH).

Background Globally, the prevalence of protruding ears is relatively frequent. Ear deformities manifest due to underdevelopment of the antihelical fold, conchal hypertrophy, and/or an obtuse conchoscaphal angle. The availability of multiple approaches proves that there isn't a single optimal accepted procedure. The Modified Stenström otoplasty technique supports the surgeon in the management of underdeveloped antihelix fold, conchal hypertrophy, and obtuse conchoscaphal angle among other deformities. We are the first to evaluate the clinical effects and measure the satisfaction rate post-otoplasty using the modified Stenström technique with a case series study. Methods Six patients were included in the study with a total of 12 ears operated on between February 2021 and July 2022. Utilizing the modified Stenström technique for bilateral protruding ears. All patients had six postoperative follow-up visits with fixed intervals; one week, three weeks, six weeks, three months, six months, and one year. During their one-year postoperative follow-up appointment, all patients completed thesatisfaction survey questions. Results Six individuals were studied, three males and three females with a mean age of 23.1 (range, 7-53 years old). There were no complications or recurrences observed. Based on the responses we collected, all patients reported a high satisfaction rate at one-year postoperative follow-up. Conclusion The modified Stenström technique yields good naturally appearing ears. It is an easy and safe technique to apply. It has a short recovery period, and no hospital stay is required. All contribute to a high satisfaction rate among studied patients.

Metal-Free Electron Donor-Acceptor Pair Enabled Long-Term Stability of Li-CO2 Battery.

The challenges of Lithium-carbon dioxide (Li-CO2) batteries for ensuring long-term cycling stability arise from the thermodynamically stable and electrically insulating discharge products (e.g., Li2CO3), which primarily rely on their interaction with the active materials. To achieve the optimized intermediates, the bifunctional electron donor-acceptor (D-A) pairs are proposed in cathode design to adjust such interactions in the case of B-O pairs. The inclusion of BC2O sites allows for the optimized redistribution of electrons via p-π conjugation. The as-obtained DO-AB pairs endow the enhanced interactions with Li+, CO2, and various intermediates, accompanied by the adjustable growth mode of Li2CO3. The shift from solvation-mediated mode into surface absorption mode in turn manipulates the morphology and decomposition kinetics of Li2CO3. Therefore, the corresponding Li-CO2 battery got twofold improved in both the capacity and reversibility. The cycling prolongs exceed 1300h and well operates at a wide temperature range (20-50°C) and different folding angles (0-180°). Such a strategy of introducing electron donor-acceptor pairs provides a distinct direction to optimize the lifetime of Li-CO2 battery from local structure regulation at the atomic scale, further inspiring in-depth understandings for developing electrochemical energy storage and carbon capture technologies.

Research on the motion characteristics of the opening process of double joint folding wings

The folding wing mechanism is a system developed for the miniaturization of missile wings to facilitate box (cylinder) storage, transportation, and launching, saving the storage and transportation space of the missile and improving the combat capability of the weapon system. In order to solve the stability problem of the dynamic opening process of wings during missile flight, a theoretical model of a double joint folding wing is proposed. Based on dynamic theory, this paper studies the dynamic process of the folding wing system undergoing rotational opening motion under different initial forces. The influence of the initial angular velocity required for folding wing deployment on the deployment process is analyzed through structural model simulation. Finally, the effect of the folding wing opening action on the flight motion of the full missile is studied, and the dynamic opening process of the folding wing system is simulated by physical experiments. The research results show that the opening motion of the folding wing is sensitive to the initial conditions; during the deformation process, a change in motion type was observed, and the aeroelastic response at certain folding angles may exhibit different motion types. The main impact on the flight motion of the full missile is the change in the aerodynamic force of the missile.

Axisymmetric blockfold origami: a non-flat-foldable Miura variant with self-locking mechanisms and enhanced stiffness

Origami foldcores, especially the blockfold cores, have emerged as promising components of high-performance sandwich composites. Inspired by the blockfold origami, we propose the axisymmetric blockfold origami (ABO), which is composed of both rectangular and trapezoidal panels. The ABO inherits the non-flat-foldability of the blockfold origami, and furthermore, displays self-locking mechanisms and enhanced stiffness. The geometry and folding kinematics of the ABO are formulated with respect to the geometric parameters and the folding angle of the assembly. The mathematical conditions are derived for the existence of self-locking mechanisms. We perform compression test simulations to demonstrate enhanced stiffness and increased load-bearing capacity. We find that the existence of rectangular panels not only dominates the non-flat-foldability of the ABO, but also contributes to the enhancement of the stiffness. Our results suggest the potential applications of the ABO for building load-bearing structures with rotational symmetry. Moreover, we discuss the prospects of designing tightly assembled multi-layered origami structures with prestress induced by the mismatch of successive layers to enlighten future research.

Low-salt organohydrogel electrolytes for wide-potential-window flexible all-solid-state supercapacitors

Flexible supercapacitors have received increasing attention due to their high power density, long cycle life and excellent safety, however, their limited energy density restrains their practical applications. Here, a designed organohydrogel electrolyte strategy boosted the electrochemical potential window (ESW) for flexible all-solid supercapacitor was demonstrated, by which a record-high ESW of 5 V is achieved, accompanied by improved cyclic stability and wider temperature adaptability. Hydrogen-bond of water to DMSO was found to be competitive with cationic hydration, and a wide ESW was achieved at lower salt and DMSO concentrations. DMSO-H2O/alginate/PAAm hydrogel electrolytes were prepared by simple solvent exchange, and it was found that the synergistic interactions between DMSO, water and hydrogel significantly reduced water activity in the hydrogel and realized the high ESW. Moreover, Dimethyl sulfoxide forms abundant hydrogen bonds with water and the hydrogel skeleton, which significantly improves the mechanical properties, freezing resistance, and temperature adaptability of the hydrogel electrolyte. The flexible all-solid-state supercapacitor assembled based on DMSO-H2O/alginate/PAAm hydrogel electrolyte and interdigital electrodes exhibits 2.4 V ESW, stability under different folding angles, adaptability to different temperatures ranging from −20 to 70 °C, and integration performance. The device demonstrates excellent cycling stability and retains 98.66% of capacitance after 10,000 cycles, suggesting that it has the potential to meet the requirements of flexible electronics.

Folding during sheeting improved qualities of dried noodles through gluten network proteins.

The texture properties after cooking for 12 min were selected to optimize the sheeting parameters, and the results were verified using the comprehensive quality of dried noodles. The distribution of water, characteristics of gluten protein, and interaction between gluten network and starch were analyzed to clarify the mechanism of the quality of dried noodles. Results showed that the optimal folding angle was 45°, under this condition, the largest anti-extension displacement perpendicular to the rolling direction and the smallest cooking loss were obtained. The hardness and smoothness of cooked noodles increased by about 14% to 17%. Further, the transverse relaxation time of strongly bound water significantly decreased, while the relative content and binding strength increased. The hydrogen bonds and α-helix contents increased by about 68.8% and 53.1%, respectively. Folding and sheeting enhanced the combination of starch granules and gluten network causing, decreased in the average length and porosity of the gluten network. It is depicted from the results that the method of optimizing the sheeting process based on the texture of dried noodles cooked for 12 min was feasible. And the 45° folding and sheeting could help to improve the quality of dried noodles.

Light- and Solvent-Responsive Bilayer Hydrogel Actuators with Reversible Bending Behaviors.

Light-responsive hydrogel systems have gained significant attention due to their unique ability to undergo controlled and reversible swelling behavior in response to light stimuli. Combining light-responsive hydrogels with nonresponsive polymers offers a unique self-folding feature that can be used in soft robotic actuator designs. However, simple formulation of such systems with rapid response time is still a challenging task. Herein, we demonstrate a simple but versatile bilayer polymeric design combining light-responsive spiropyran-polyacrylamide (SP-PAAm) with polyacrylamide (PAAm) hydrogels. The photochromic spiropyran in our polymer design is a closed-ring, hydrophobic compound and turns into an open-ring, hydrophilic merocyanine isomer under light irradiation. The swelling degree of SP-PAAm and PAAm hydrogels was evaluated using LED lights with different wavelengths and solvent media (e.g., water, ethanol, DMF, and DMSO). We observed that SP-PAAm hydrogels reached a swelling ratio of ∼370% with the illumination of the blue LED in the DMF medium. By combining light-responsive SP-PAAm hydrogels with nonresponsive PAAm, a proof-of-concept demonstration was performed to demonstrate the applicability of our fabricated platforms. Although fabricated one-armed bilayer hydrogels possessed self-folding ability with a folding angle of ∼40° in 30 min, the four-armed bilayer platforms demonstrated more efficient and rapid folding behavior and reached a folding angle of ∼75° in ∼15 min. Given their simplicity and efficiency, we believe that such polymeric designs may offer new avenues for the fields of polymeric actuators and soft robotic systems.

Bilayer Self‐Folding Method with High Folding Force and Angle by Suppressing Delamination of Shrink Layer

Heat‐shrinkable films commonly serve as active materials for self‐folding owing to their capability to fold all hinges upon heating. For origami‐based electronic devices, the self‐folding of the metal layer is necessary. Nevertheless, the self‐folding angle is low owing to the high bending stiffness of metal layers and the low adhesion of heat‐shrinkable films. Here, we introduce a bilayer self‐folding technique that effectively suppresses delamination of the shrink layer, thereby achieving a high folding force and angle. A polyolefin film mechanically fixed on the metal substrate serves to inhibit delamination, regardless of the adhesive properties of the shrink layer. This is achieved by applying adhesives within holes fabricated on the shrink layer. Conventional methods using an adhesive layer to fix the shrink layer lead to delamination at temperatures above 100°C, resulting in a decrease in self‐folding angles. In contrast, our novel fixing method yields a folding angle of 161° at 140°C, with a shrinkage rate of 69%. To demonstrate the versatility of our proposed technique, we self‐fold various origami structures, including Miura‐ori, scissors, cranes, and tessellation with chip LEDs. The introduced method broadens the range of substrate materials suitable for self‐folding and offers new possibilities for the development of origami devices. © 2024 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC.

Static and Modal Analysis of a Box Structured Satellite Deployment Mechanism with self-actuated Torsion Joint

A brand-new satellite deployment mechanism with boxed structure and self-actuated torsion joints is proposed and an effective method to verify the feasibility of this mechanism is established in this paper. This mechanism has the characteristics of high base frequency, high ratio of deployed and folded space occupation ratio. In order to meet the design requirements, the related analysis and optimization need to be conducted, and several conclusions are obtained. Firstly, the modal analysis of deployment mechanism at folded and fully deployed state is analyzed, and the result showed that the proper wall thickness is the key parameter to satisfy the design requirement and an optimized value could be obtained; Secondly, the heat deformation analysis result showed that the material plays an more important roll on affecting the thermal deformation than structure parameter; Thirdly, Under the torsional moment of the joints, the stress distribution of the deployment mechanism under different folding angle is investigated, it could be clearly found that the maximum stress is always located on the bonded area of the rod and joint, and the maximum stress is increased with the opening angle generally. By combined analysis including thermal, static, and modal, the related characteristics are obtained which could be used for structure optimization and provide an effective solution for the design of box structured satellite unfolding mechanism with self-actuated torsional joints.

Design and mechanical properties analysis of a cellular Waterbomb origami structure

Cellular structures are commonly used to design energy-absorbing structures, and origami structures are becoming a prevalent method of cellular structure design. This paper proposes a foldable cellular structure based on the Waterbomb origami pattern. The geometrical configuration of this structure is described. Quasi-static compression tests of the origami tube cell of this cellular structure are conducted, and load-displacement relationship curves are obtained. Numerical simulations are carried out to analyze the effects of aspect ratio, folding angle, thickness and number of layers of origami tubes on initial peak force and specific energy absorption (SEA). Calculation formulas for initial peak force and SEA are obtained by the multiple linear regression method. The degree of influence of each parameter on the mechanical properties of the single-layer tube cell is compared. The results show that the cellular structure exhibits negative stiffness and periodic load-bearing capacity, as well as folding angle has the most significant effect on the load-bearing and energy-absorbing capacity. By adjusting the design parameters, the stiffness, load-bearing capacity and energy absorption capacity of this cellular structure can be adjusted, which shows the programmable mechanical properties of this cellular structure. The foldability and the smooth periodic load-bearing capacity give the structure potential for application as an energy-absorbing structure.

Miura origami based reconfigurable polarization converter for multifunctional control of electromagnetic waves

Polarization is one of the basic characteristics of electromagnetic (EM) waves, and its flexible control is very important in many practical applications. At present, most of the multifunction polarization metasurfaces are electrically tunable based on PIN and varactor diodes, which are easy to operate and have strong real-time performance. However, there are still some problems in them, such as few degrees of freedom of planar structure control, complex circuit, bulky sample, and high cost. In view of these shortcomings, this paper proposes a Miura origami based reconfigurable polarization conversion metasurface for multifunctional control of EM waves. The interaction between the electric dipoles is changed by adjusting the folding angle θ, thereby tuning the operating frequency of the polarization conversion and the polarization state of the reflected wave. This mechanical control method brings more degrees of freedom to manipulate EM waves. And the processed sample is with lightweight and low cost. To verify the performance of the proposed origami polarization converter, a Miura origami structure loaded with metal split rings is designed and fabricated. The operating frequency of the structure can be tuned in different folding states. In addition, by controlling the folding angle θ, linear-to-linear and linear-to-circular polarization converters can be realized at different folding states. The proposed Miura origami polarization conversion metasurface provides a new idea for reconfigurable linear polarization conversion and multifunctional devices.

Assessing the geometry of defect waviness from borehole data

Within the large, open cut, iron ore mines of the Pilbara region of Western Australia, defect shear strengths often control the slope design where bedding dips shallowly to moderately out of the pit slope. The presence of metre to decametre scale open folding or waviness in these units can contribute to the friction angle of bedding shear strengths, potentially allowing for steeper slope angles and improved economics for the deposit. Traditionally, waviness affecting defect shear strength is assessed from surface mapping, bench mapping or qualitatively from observations in core. Surface mapping of bedrock is often not possible due to detrital cover or a lack of suitable outcrop, while bench mapping is inherently conducted perpendicular to the direction of sliding risk. The use of downhole data from boreholes drilled into the slopes circumvents these issues. The method presented here involves assessing characteristic downhole wavelength, inter-limb angle and amplitude of folding from defect orientation data interpreted from borehole televiewer imaging. The downhole wavelength and defect orientations are transformed to a true down-dip wavelength, dilation angle, and estimated amplitude in the direction of sliding risk. The calculation of down-dip wavelength is critical for assessing the applicability of the associated dilation angle to the scale of the slope and failure mechanism in question. The adoption of defect shear strengths that include a waviness contribution to the friction angle allows for implementation of steeper slope angles in structurally controlled slopes.

High-efficiency light manipulation using a single layer of folded graphene microribbons

Since its one-atom thickness, it remains an open question to enhance light–matter interactions in graphene, which is usually implemented through external resonant structures such as Fabry–Perot cavity. Here, we propose an alternative scheme to enhance light–matter interactions in a single layer of folded graphene microribbons (FGMRs), and remarkably, for normal incidences rather than oblique incidences in most studies. By optimizing structural parameters (e.g., the location of folding axis and folding angle), three light manipulations such as perfect absorption, perfect reflection, and perfect transmission can be achieved independently. More interestingly, any one of the three functionalities can be actively switched to the other via changing material parameters (Fermi level and carrier mobility ), which is actually the most attractive feature of graphene plasmonics. Finally, we show FGMRs can also support triple functionalities, i.e., via changing material parameters, one of the three functionalities can be switched to the second one and then the third one. Our results will be of great interest to fundamental physics and pave the way for graphene plasmonic device applications.