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One-dimensional high-performance yarns with excellent conductivity and flexibility are of considerable interest in the energy and aerospace industries. However, how to achieve highly conductivity, excellent flexibility, extreme condition durability and high mechanical performance in one fiber material is still a great challenge using economically viable materials and synthesis technologies. Herein, we report electrically conductive yarns (modified polyimide (M-PI)/reduced graphene oxide (RGO) yarns) consisting of RGO coated on the surface of nitrogen plasma M-PI yarns, which are fabricated by combining the N2 plasma pre-treatment and repeated dip-coating and reducing technique. N2 plasma treatment is used to roughen the surface of the PI yarn and introduce functional groups, contributing to improve wettability, which can provide a stronger adhesion of the graphene coating. The dip-coating and reducing process was repeated 10 times to enhance the loading mass of RGO on the PI yarns, then M-PI/RGO yarns with better conductivity property can be obtained. The effects of N2 plasma treatment power and time on the M-PI yarns and M-PI/RGO yarns are investigated and discussed. The results demonstrate that the graphene layer is uniformly and densely coated on the PI yarn when being treated at 200 W for 8 min, and the conductivity of the M-PI/RGO yarn reaches 1.51 × 102 S/m. The M-PI/RGO yarn combine the advantages of RGO and PI yarns, retaining the mechanical properties and thermal stability of PI yarn while exploiting the conductive property of RGO. In addition, the enhanced adhesion between the PI yarn and graphene coating endows the composite yarns with excellent fastness and superior flexibility. This work describes an environmentally friendly, controllable and facile method to develop flexible and conductive functional graphene-coated PI yarns with high-performance properties.

Supplemental Material for Hydrophobic and oleophilic 3D weft-knitted spacer fabrics coated by silica aerogels with five different concentrations by Syed Rashedul Islam, Mohammed Kayes Patoary, Hewan Dawit Estifanos, Ishaq Lugoloobi, Alrayah HD Yousif, Jinhua Jiang and Huiqi Shao in Journal of Industrial Textiles

Soft robots are those that can move like living organisms and adapt to the surrounding environment. Compared with traditional rigid robots, the advantages of soft robots, in terms of material flexibility, human–computer interaction, and biological adaptability, have received extensive attention. Flexible actuators based on light response are one of the most promising ways to promote the field of cordless soft robots, and they have attracted the attention of scientists in bionic design, actuation implementation, and application. First, the three working principles and the commonly used light-responsive materials for light-responsive actuators are introduced. Then, the characteristics of light-responsive soft actuators are sequentially presented, emphasizing the structure strategy, actuation performance, and emerging applications. Finally, this review is concluded with a perspective on the existing challenges and future opportunities in this nascent research frontier.

In this article, the in-plane shear rigidity modulus of five commercially available fabrics of glass warp knitted non-crimp fabrics (WKNCFs) was experimentally investigated by uniaxial bias...

Fiber supercapacitors have attracted significant attention owing to the relevancy in textile electronics. However, the key challenge is to achieve a high output voltage and performance in fiber supercapacitors, while maintaining the high flexibility as fibers. Here, we present a particular type of fiber supercapacitors, based on an overlaid tree topological configuration, by braiding sub-fiber supercapacitor units in an asymmetrical series connection. The tree-like topology-based asymmetric fiber supercapacitors (TTAFSCs) simultaneously achieved a high energy density (22 mWh cm-3 at a power density of 444 mW cm-3) and voltage output, while maintaining outstanding mechanical properties (>1000 bending cycles, capable of loading an object of ~200 g). By continuous braiding of a 6-unit TTAFSC (28 cm length), we were able to achieve a tunable output voltage as high as 9.6 V, which is superior to that achieved by most state-of-the-art fiber supercapacitors. Furthermore, TTAFSCs of ~8 cm long are capable of lightening light-emitting diodes, driving a watch, and powering a display, even at the bent and twisted state. The design of TTAFSCs and fabrication technology acquired represent a genuine breakthrough in textile electronics.

The finite element analysis method (FEM), for its advantages of lower time and economic costing in predicting the mechanical properties of fabrics, was applied to warp-knitted fabrics. In this paper, two bar warp-knitted fabric knitted with wires was used as reflecting mesh antennas. Firstly the loop unit of the metallic warp-knitted fabric was simulated in 3-D by TexGen software. Secondly the 3-D loop unit model was inputted into ABAQUS software to form a model of the metallic warp-knitted fabric sheet for uni-axial tension analysis. Thirdly numerical results were obtained after setting the parameters in ABAQUS. Finally numerical results were verified by uni-axial tensile experiments on the metallic warp-knitted fabric. The results showed that the simulation was in good agreement with the experimental tensile process, where the transfer of yarns between loops when in low fabric elongation and in yarn elongation when in high fabric elongation were simulated by FEM of warp-knitted fabric in the tensile process. Also the same trend of tensile force was found in experiment and FEM results. Therefore it can be concluded that FEM can be used to predict the mechanical properties of warp-knitted fabric with a complex structure.

Summary Fiber supercapacitors have attracted significant attention because of the relevance for textile electronics. However, the key challenge is to achieve high output voltage and performance of fiber supercapacitors while maintaining the high flexibility of the fibers. Here, we present a fiber supercapacitor, based on an overlaid tree topology configuration, by braiding sub-fiber supercapacitor units in an asymmetrical series connection. The tree-like topology-based asymmetric fiber supercapacitors (TTAFSCs) achieve a high energy density (0.022 Wh cm−3 at a power density of 0.444 W cm−3) with an extendable high voltage output (>9.6 V) while maintaining outstanding mechanical properties (>1,000 bending cycles, capable of loading an object of ∼200 g). TTAFSCs of ∼8 cm in length are capable of lighting light-emitting diodes, driving a watch, and powering a display, even in a bent and twisted state.

The existence of cracks has a great influence on the life span of the envelope material of aerostats, especially for stratospheric airships that operate in harsh environments. Understanding the relationship between fracture mechanism and composite structure of envelope materials is of great significance to the design and development of envelope materials. To explore the fracture mechanism of envelope material, a novel polyimide (PI) envelope was developed by lamination method. Then, the fracture behavior and mechanism of PI envelope with single edge crack was studied and analyzed in detail by means of experimental method and theoretical model analysis. It was found that the crack orientation has no significant effect on the fracture strength of PI envelope, while the increase of crack length will increase the strength loss rate and decrease the crack sensitivity. These phenomena suggest that the fracture strength loss of envelope is mainly determined by the number of cut-off longitudinal yarns. And the stress transfer effect of coating and transverse yarns which causes stress concentration in the crack tip region is another important factor affecting the fracture strength of PI envelope. Besides, the interfacial properties between coating and fibers as well as the size effect of coating also play an important role in the fracture property of PI envelope. Finally, stress intensity factor theory and critical stress field theory were chosen to study the fracture behavior of PI envelope. The calculation results indicated that critical stress field theory can better predict the fracture strength of PI envelope.

A systematic experimental study was performed to detect the compaction and permeability properties of multilayered biaxial and quadriaxial preforms under vacuum pressure. Compression response on ply level showed that the degree of nesting between quadriaxial NCF was more pronounced and the nesting deformation mechanism was affected by the interaction with stitch yarns. Owing to the meso-channels in the fibrous structure and the nesting between layers, the in-plane permeability of quadriaxial NCF did not follow an inverse proportion relationship with the fiber volume fraction. To predict the in-plane permeability of multilayered quadriaxial NCFs, unit cell models at a high level of geometrical details were built, including local variations in yarn cross-sections and the nesting deformation between layers. Numerical methods were implemented, and the prediction results were in very good agreement with the experimental data. Besides, the major contributing parameters to the enhancement of the in-plane permeabilities were identified by investigating the correlation between permeability and structural parameters of quadriaxial NCF. The modeling methodology and the principles established can be applied to the design of the quadriaxial NCF fabrics, where the permeability enhancement was evidenced.

The good formability of textile composite materials over complex mold geometries is one of the reasons to make their use expanding in various modern industries. However, different defects in these reinforcements could have occurred during the forming step in the manufacturing process. The defects are arising for many reasons; some are related to the fabric itself and others related to the draping parameters. Understanding the textile structure mechanics and draping behavior is essential to choose the proper reinforcement as well as to attain better simulation. Fabric wrinkles and local out-of-plane bucking of yarns were the fundamental defects in focus. The main objective of this part of the project was to experimentally investigate and compare the draping behavior of six commercially available glass fabrics from the same category of warp-knitted non-crimp fabrics (WKNCFs). The tested fabrics included two stitching patterns: tricot and chain. Also, they were relatively heavy with approximate mass per square meter. A double-dome punching test was performed to implement draping for each fabric; then, the defects were detected and characterized. Punching load-displacement curves were also recorded. In addition, a defect code was designated for the main defects to characterize forming defects at the meso-macroscopic scale. The structure and the number of fabric axes, stacking sequence, and stitching pattern all contribute to defect formation during draping. The studied configurations in this paper can help in studying the simulation of deformed technical fabric and provide a method to minimize and even eliminate the draping defects.

Warp-knitted meshes have been widely used for structural reinforcement of rigid, semi-rigid, and flexible composite materials. In order to meet the performance requirements of different engineering applications, four typical warp-knitted meshes (rectangular, square, circular, and diamond) were designed and developed. The mechanical behaviors of these meshes under mono-axial and multi-axial tensile loads were compared. The influence of the initial notch length and orientation on the mechanical performance was also analyzed. The results showed that the biaxial tensile behavior of warp-knitted meshes tended to be more isotropic. The anisotropy level of the diamond warp-knitted mesh was the lowest (λ = 0.099), while the rectangular one was the highest (λ = 0.502). The notch on a significantly anisotropic mesh was propagated along the direction of larger modulus, while for a not remarkably anisotropic mesh, notch propagation was probably consistent with the initial notch orientation. The breaking strength of warp-knitted meshes with the same initial notch orientation decreased with the increase in notch length in both the wale and course directions. For warp-knitted meshes with the same initial notch length, the breaking strength in the wale direction was kept stable at different notch orientations, while that in the course direction decreased remarkably with notch orientation from 0° to 90°.

Glass warp-knitted fabrics have been widely used as complex structural reinforcements in composites, such as wind turbine blades, boats, vehicles, etc. Understanding the mechanical behavior and formability of these textiles is very necessary for the simulation of forming processes before manufacturing. In this paper, the shear deformation mechanics of glass warp-knitted non-crimp fabrics (WKNCF) were experimentally investigated based on a picture frame testing apparatus equipped to a universal testing machine. Three commercially available fabrics of WKNCFs were tested for four cycles by the picture frame method. The aim was to characterize and compare the shear behavior of relatively high areal density fabrics during preform processing for composites. The energy normalization theory was used to obtain the normalized shear force from the testing machine data; then, the shear stress against the shear angle was fitted by cubic polynomial regression equations. The results achieved from the equations demonstrated that the in-plane shear rigidity modulus was associated with the shear angle. The effect of the shearing cycles and stitching pattern on shear resistance was also analyzed.

In this work, polyimide (PI) was coated onto an ultrafine gilt molybdenum wire in order to protect the gilt surface and prepare an electrically stable wire mesh material which can be widely used in space. The surface of the PI-coated gilt molybdenum wires was characterized using FTIR, SEM, and EDS. Factors such as temperature stability of the PI coating, mechanical properties of the PI-coated gilt molybdenum wires, contact resistance stability, and electromagnetic microwave reflectivity of the their knitted meshes were also investigated. The results indicate that the PI coating conformed uniformly to the surface of the gilt molybdenum wires. The prepared PI coating exhibited excellent temperature stability in the −196 to 300 °C range and could efficiently protect the gilt surface and improve the stability of contact resistance, while the reflection of its wire meshes showed only a slight decrease of 1.4% with the PI coating thickness of 3 μm for electromagnetic microwaves in the S band.

This chapter summarizes the current status of composites reinforced with advanced grid structures. We introduce classification of the mesh structure, its characteristics, structural design and process, molding and performance analysis, and applications for mesh structural composites (or lattice structural composites or grid structural composites). First, we provide a summary of the international status and development of mesh structure composite materials, and then the critical technology involved in mesh structural composites, its processing, testing, and so on are discussed in detail. Principles of structure design and the advantages and disadvantages of various molding process for mesh structural composites are also presented. Information on the structure molding, performance evaluation, and testing methods is also given in detail. Finally, the potential application of diverse mesh structure composites in both aerospace and civil fields is analyzed in association with the main applications of mesh structures.