Weilong Yin

Structural shape sensing for variable camber wing using FBG sensors

In this paper, a variable camber wing, which comprises a flexible skin, a metal sheet, and a honeycomb structure, is presented. Shape memory polymer (SMP) is selected for the use of flexible skins. Embedded heating wire springs act as the activation system for the SMP. Experimental result shows that the inherent separation does not occur between the heating elements and SMP upon elongation because of elasticity of wire springs. The deformation of SMP skins at different temperature conditions is analyzed in order to establish the relationship between the deformation of the skin and pre-strain applied in the SMP skin. Fibre Bragg Grating (FBG) sensors, with flexibility and small size, are bonded on the surface of the metal sheet to measure the deflection on the some certain points. The relation of the strain on the upper surface of metal sheet and the deflection of the trailing-edge is established to ensure the position of the bonded FBG sensors. The curve shape of the bending metal sheet can be reconstructed using the calibration information.

Structural design and analysis of morphing skin embedded with pneumatic muscle fibers

In this paper, a kind of morphing skin embedded with pneumatic muscle fibers is proposed from the bionics perspective. The elastic modulus of the designed pneumatic muscle fibers is experimentally determined and their output force is tested with internal air pressure varying from 0 to 0.4 MPa. The experimental results show that the contraction ratio of the pneumatic muscle fibers using the given material could reach up to 26.8%. Isothermal tensile tests are conducted on the fabricated morphing skin, and the results are compared with theoretical predictions based on the rule of mixture. When the strain is lower than 3% and in its linear-elastic range, the rule of mixture is proved to possess satisfying accuracy in the prediction of the elastic modulus of the morphing skin. Subsequently, the output force of the morphing skin is tested. It is revealed that when the volume ratio of the pneumatic muscle fibers is 0.228, the contraction ratio can reach up to 17.8%, which is satisfactory for meeting the camber requirement of morphing skin with maximum strain level below 2%. Finally, stress-bearing capability tests of the morphing skin on local uniformly distributed loads are conducted, and the test results show that the transverse stiffness of the morphing skin can be regulated by changing the internal air pressure. Under a uniformly distributed load of 540 Pa, the designed morphing skin is capable of varying by more than two orders of magnitude in the transverse stiffness by changing the internal air pressure.

Design and analysis of morphing wing based on SMP composite

A new concept of a morphing wing based on shape memory polymer (SMP) and its reinforced composites is proposed in this paper. SMP used in this study is a thermoset styrene-based resin in contrast to normal thermoplastic SMP. During heating, the wing curled on the aircraft can be deployed, providing main lift for a morphing aircraft to realize the stable flight. Aerodynamic characteristics of the deployed morphing wing are calculated by using CFD software. The static deformation of the wing under the air loads is also analyzed by using the finite element method. The results show that the used SMP material can provide enough strength and stiffness for the application. Finally, preliminary testing is conducted to investigate the recovery performances of SMP and its reinforced composites. During the test, the deployment and the wind-resistant ability of the morphing wing are dramatically improved by adding reinforced phase to the SMP.

Electrospun silica/nafion hybrid products: mechanical property improvement, wettability tuning and periodic structure adjustment

The sol–gel process and electrospinning were used to fabricate a series of silica/Nafion electrospun hybrid products with no aggregation of the inorganic component. The excellent flexibility of the as-obtained silica/Nafion non-woven membrane and a single hybrid fiber was demonstrated and compared with the brittleness of pure electrospun silica membrane. The difference in wettability between the electrospun silica/Nafion hybrid product and bulk aqueous sol could be caused by the molecular orientation of Nafion during the electrospinning process. The hydrophobic behaviour, improved mechanical performance and good thermal stability made the silica/Nafion hybrid membrane a good candidate for oil–water separation. One-dimensional periodic structures still formed in silica/Nafion hybrid products with a lower Nafion content, although they disappeared completely at a higher Nafion content.

Stiff, Thermally Stable and Highly Anisotropic Wood-Derived Carbon Composite Monoliths for Electromagnetic Interference Shielding

Electromagnetic interference (EMI) shielding materials for electronic devices in aviation and aerospace not only need lightweight and high shielding effectiveness, but also should withstand harsh environments. Traditional EMI shielding materials often show heavy weight, poor thermal stability, short lifetime, poor tolerance to chemicals, and are hard-to-manufacture. Searching for high-efficiency EMI shielding materials overcoming the above weaknesses is still a great challenge. Herein, inspired by the unique structure of natural wood, lightweight and highly anisotropic wood-derived carbon composite EMI shielding materials have been prepared which possess not only high EMI shielding performance and mechanical stable characteristics, but also possess thermally stable properties, outperforming those metals, conductive polymers, and their composites. The newly developed low-cost materials are promising for specific applications in aerospace electronic devices, especially regarding extreme temperatures.

Application of SMP composite in designing a morphing wing

A new concept of a morphing wing based on shape memory polymer (SMP) and its reinforced composite is proposed in this paper. SMP used in this study is a thermoset styrene-based resin in contrast to normal thermoplastic SMP. In our design, the wing winded on the airframe can be deployed during heating, which provides main lift for a morphing aircraft to realize stable flight. Aerodynamic characteristics of the deployed morphing wing are calculated by using CFD software. The static deformation of the wing under the air loads is also analyzed by using the finite element method. The results show that the used SMP material can provide enough strength and stiffness for the application.

Variable camber wing based on pneumatic artificial muscles

As a novel bionic actuator, pneumatic artificial muscle has high power to weight ratio. In this paper, a variable camber wing with the pneumatic artificial muscle is developed. Firstly, the experimental setup to measure the static output force of pneumatic artificial muscle is designed. The relationship between the static output force and the air pressure is investigated. Experimental result shows the static output force of pneumatic artificial muscle decreases nonlinearly with increasing contraction ratio. Secondly, the finite element model of the variable camber wing is developed. Numerical results show that the tip displacement of the trailing-edge increases linearly with increasing external load and limited with the maximum static output force of pneumatic artificial muscles. Finally, the variable camber wing model is manufactured to validate the variable camber concept. Experimental result shows that the wing camber increases with increasing air pressure and that it compare very well with the FEM result.

Pneumatic artificial muscle and its application on driving variable trailing-edge camber wing

As a novel bionic actuator, pneumatic artificial muscle has high power to weight ratio. In this paper, the experimental setup to measure the static output force of pneumatic artificial muscle was designed and the relationship between the static output force and the air pressure was investigated. Experimental result shows the static output force of pneumatic artificial muscle decreases nonlinearly with increasing contraction ratio. A variable camber wing based on the pneumatic artificial muscle was developed and the variable camber wing model was manufactured to validate the variable camber concept. Wind tunnel tests were conducted in the low speed wind tunnel. Experimental result shows that the wing camber increases with increasing air pressure.

Static aeroelastic deformation of flexible skin for continuous variable trailing-edge camber wing

The method for analyzing the static aeroelastic deformation of flexible skin under the air loads was developed. The effect of static aeroelastic deformation of flexible skin on the aerodynamic characteristics of aerofoil and the design parameters of skin was discussed. Numerical results show that the flexible skin on the upper surface of trailing-edge will bubble under the air loads and the bubble has a powerful effect on the aerodynamic pressure near the surface of local deformation. The static aeroelastic deformation of flexible skin significantly affects the aerodynamic characteristics of aerofoil. At small angle of attack, the drag coefficient increases and the lift coefficient decreases. With the increasing angle of attack, the effect of flexible skin on the aerodynamic characteristics of aerofoil is smaller and smaller. The deformation of flexible skin becomes larger and larger with the free-stream velocity increasing. When the free-stream velocity is greater than a value, both of the deformation of flexible skin and the drag coefficient of aerofoil increase rapidly. The maximum tensile strain of flexible skin is increased with consideration of the static aeroelastic deformation.

Variable densification of reduced graphene oxide foam into multifunctional high-performance graphene paper

Super-flexible, electrically and thermally conductive graphene-based papers are in great demand in the fields of electronics and supercapacitors. However, the applications of graphene-based papers are limited either by their brittleness, small scale, or by their unsatisfactory thermal conductivity. Conventionally, such papers are fabricated by vacuum-assisted filtration, direct evaporation, electrospray coating, or wet spinning. Here we propose a novel strategy, namely, direct densification of reduced graphene oxide foam, to fabricate large-scale multifunctional graphene papers. The graphene paper density could be adjusted by applying different loads. The densities of the graphene papers varied from 0.32 g cm−3 to 1.85 g cm−3. The thermal conductivity, tensile stress, electrical conductivity and electromagnetic interface shielding effectiveness increased with an increase in the density of the graphene paper. When the density of the graphene paper reached 1.85 g cm−3, the tensile stress was up to 50.4 MPa with strain of 4%, the thermal conductivity was 1103 W m−1 K−1 at room temperature and there was high electrical conductivity of 1.1 × 105 S m−1, as well as an electromagnetic interference (EMI) shielding effectiveness of 77.2 dB. Our new strategy is very promising in terms of controlling the thickness, density, and size of graphene paper. Our graphene paper has very high potential for applications.