Search Results (44)

Addressing the urgent need for lightweight and reusable energy-absorbing materials in aviation impact resistance, this study introduces an innovative multi-directional braided metamaterial design enabled by 4D printing technology. This approach overcomes the dual challenges of intricate manufacturing processes and the limited functionality inherent to traditional textile preforms. Six distinct braided structural units (types 1–6) were devised based on periodic trigonometric functions (Y = A sin(12πX)), and integrated with shape memory polylactic acid (SMP-PLA), thereby achieving a synergistic combination of topological architecture and adaptive response characteristics. Compression tests reveal that reducing strip density to 50–25% (as in types 1–3) markedly enhances energy absorption performance, achieving a maximum specific energy absorption of 3.3 J/g. Three-point bending tests further demonstrate that the yarn amplitude parameter A is inversely correlated with load-bearing capacity; for instance, the type 1 structure (A = 3) withstands a maximum load stress of 8 MPa, representing a 100% increase compared to the type 2 structure (A = 4.5). A multi-branch viscoelastic constitutive model elucidates the temperature-dependent stress relaxation behavior during the glass–rubber phase transition and clarifies the relaxation time conversion mechanism governed by the Williams–Landel–Ferry (WLF) and Arrhenius equations. Experimental results further confirm the shape memory effect, with the type 3 structure fully recovering its original shape within 3 s under thermal stimulation at 80 °C, thus addressing the non-reusability issue of conventional energy-absorbing structures. This work establishes a new paradigm for the design of impact-resistant aviation components, particularly in the context of anti-collision structures and reusable energy absorption systems for eVTOL aircraft. Future research should further investigate the regulation of multi-stimulus response behaviors and microstructural optimization to advance the engineering application of smart textile metamaterials in aviation protection systems. Full article

Parachute suspension lines shed vortices during descent, and these vortices develop oscillating aerodynamic forces that can induce forced parasitic vibrations of the lines, which can have an adverse impact on the parachute system. Understanding the line’s mechanical behavior can assist in studying the vibrations experienced by the suspension lines. A well-calibrated structural model of the suspension line could be used to help to identify how the braid’s architecture contributes to its mechanical behavior and to explore if and how a suspension line can be designed to mitigate these parasitic vibrations. In the current study, a mesomechanical finite element model of a polyester braided parachute suspension line was constructed. The line geometry was built in the Virtual Textile Morphology Suite (VTMS), and a user material model (UMAT) was implemented in LS-DYNA^® release 14 to describe the material behavior of the individual tows. The material properties were initially calibrated using experimental tension tests on individual tows, which exhibited an initial modulus of ~4100 MPa before transitioning to ~3200 MPa at a stress of 30 MPa. When these properties were applied to the full braid model, slight adjustments were made to account for geometric complexities in the braid structure, improving the correlation between the model and experimental tensile tests. The final calibrated model captured the bilinear tensile behavior of the braid, with an initial modulus of 2219 MPa and a secondary modulus of 1350 MPa, compared to experimental values of 2253 MPa and 1420 MPa, respectively, showing 2% and 5% differences. The calibrated model of the braided cord was then subjected to torsion, and the results showed good agreement with dynamic and static experimental torsion tests, with a difference of 8–19% for dynamic tests and 13–27% for static tests when compared to experimental values. The availability of virtual models of suspension lines can ultimately assist in the design of suspension lines that mitigate flow-induced vibration. Full article

Based on the analysis of the motion law of 3D five-directional circular transverse braided fibers, this paper obtains the angle calculation formula between fibers and the local polar coordinate system in various cell models by transforming the position coordinates of fiber nodes. The stress transformation matrix between the local coordinate system and the global coordinate system of any fiber in the circular braided single cell is derived without considering the physical force on the single-cell micro-hexahedron unit. The calculation formulas of braided parameters such as the overall stiffness matrix and fiber volume content of the circular braided composite material after considering the matrix are derived by using the volume average method; the length of braided knuckles is 2 mm, the inner diameter of inner cells is 7 mm, the number of radial and axial braided yarns is 80, the height of inner cells is 0.5 mm, and the filling coefficient is 0.61. Comparing the results of the numerical prediction model with the experimental results in reference, it is found that the error of the numerical prediction model deduced in this paper is small. Therefore, this model can be used to fully study the effects of braided parameters such as cell inner diameter, cell height, and node length on the mechanical properties of composites. Full article

A critical challenge in wearable electrothermal textiles is achieving effective insulation while maintaining sheath flexibility, which is essential for enhancing the mechanical properties and durability of conductive materials under everyday conditions, such as washing, stretching, and twisting. In this work, we employ a coaxial tubular braiding technique to coat a high-conductivity carbon nanotube (CNT) yarn with a high-strength insulation layer made of ultra-high-molecular-weight polyethylene (UHMWPE) multifilaments, resulting in a core–sheath-structure CNT yarn with excellent electrothermal performance. By adjusting the number of UHMWPE multifilaments and the sheath braiding angle, we achieve high flexibility, high tensile strength, and abrasion and wash resistance, as well as improved electrical stability for the CNT yarns. Additionally, the CNT yarns with an insulation layer effectively prevent short-circuiting during use and achieve superior thermal management, with a significant increase in steady-state temperature under operational conditions, exhibiting significant potential for applications in wearable electronic devices. Full article

According to the “four-step” braiding technique, this paper analyzed the movement laws of internal space yarns in the projection plane and in space, and established a 3D seven-direction braided composite material solid finite element model by combining the observed yarn directions on the surface and side of the preform. Based on the 3D Hashin criterion, a progressive damage failure analysis method was adopted to study the shear failure mechanism of 3D seven-direction braided composites. The effect of braided angles on the elastic properties and crack propagation path of the fabric was discussed. The failure modes and mechanisms of 3D seven-directional braided composites were also observed and analyzed by electron microscope and scanning electron microscope. The results show that the shear failure mode is mainly caused by matrix failure, interface damage, and fiber fracture and pull-out. The fiber cross-sections at the shear fracture surface are at a certain angle, indicating that the fibers are subjected to both transverse and axial stresses during the shear process. It also can be seen that the initial damage occurs at the interface between the matrix and the fiber bundle. As the crack propagates, tensile damage occurs inside the fiber bundle, forming cracks and eventually leading to the failure of the entire structure. The accuracy of proposed method for predicting 3D seven-directional braided composites was verified by the shear experimental results. Full article

A three-dimensional helix geometry unit cell is established to simulate the complex spatial configuration of 3D braided composites. Initially, different types of yarn factors, such as yarn path, cross-sectional shape, properties, and braid direction, are explained. Then, the multiphase finite element method is used to develop a new theoretical calculation procedure based on the unit cell for predicting the impacts of environmental temperature on the thermophysical properties of 3D four-direction carbon/epoxy braided composites. The changing rule and distribution characteristics of the thermophysical properties for 3D four-direction carbon/epoxy braided composites are obtained at temperatures ranging from room temperature to 200 °C. The influences of environmental temperature on the coefficients of thermal expansion (CTE) and the coefficients of thermal conduction (CTC) are evaluated, by which some important conclusions are drawn. A comparison is conducted between theoretical and experimental results, revealing that variations in temperature exert a notable influence on the thermophysical characteristics of 3D four-directional carbon/epoxy braided composites. The theoretical calculation procedure is an effective tool for the mechanical property analysis of composite materials with complex geometries. Full article

Composites of poly(vinyl alcohol) (PVA) in the shape of braids, in combination with crystals of hydroxyapatite (HAp), were analyzed to perceive the influence of this bioceramic on both the quasi-static and viscoelastic behavior under tensile loading. Analyses involving energy-dispersive X-ray spectroscopy (EDS) and scanning electron microscopy (SEM) allowed us to conclude that the production of a homogeneous layer of HAp on the braiding surface and the calcium/phosphate atomic ratio were comparable to those of natural bone. The maximum degradation temperature established by thermogravimetric analysis (TGA) showed a modest decrease with the addition of HAp. By adding HAp to PVA braids, an increase in the glass transition temperature (Tg) is noticed, as demonstrated by dynamic mechanical analysis (DMA) and differential thermal analysis (DTA). The PVA/HAp composite braids’ peaks were validated by Fourier transform infrared (FTIR) spectroscopy to be in good agreement with common PVA and HAp patterns. PVA/HAp braids, a solution often used in the textile industry, showed superior overall mechanical characteristics in monotonic tensile tests. Creep and relaxation testing showed that adding HAp to the eight and six-braided yarn architectures was beneficial. By exhibiting good mechanical performance and most likely increased biological qualities that accompany conventional care for bone applications in the fracture healing field, particularly multifragmentary ones, these arrangements can be applied as a fibrous fixation system. Full article

A low-cost electronic yarn (e-yarn) fabricated with conductive yarns and light-emitting diodes (LEDs) for wearables is presented. As part of ongoing research to develop smart interactive pedestrian clothing, this work demonstrates the design and performance qualities of braided e-yarns to produce red lighting effects. The design process adopted a simple encapsulation process with adhesive tape and a heat contraction tube to secure stainless steel conductive threads to solder pads of the LEDs. These were arranged in series against two stainless steel conductive threads to provide single positive and negative terminals at both ends. The success of these low-cost, flexible, and strong (wash durability) braided e-yarns proved to be a major achievement for integration into woven fabrics for smart pedestrian safety clothing. These braided e-yarns producing the necessary lighting effects are a key safety feature for improving pedestrian visibility and driver recognition at night-time. Full article

For signal transmission and sensing in stretchable structures for human motion monitoring or proprioception of soft robots, textiles with electronically conductive yarns are a promising option. Many recent publications employ silver-plated yarns in knits, braids, wovens for strain or pressure sensing purposes as well as heating fabrics or twisted string actuators. Silver-plated yarns are available in a wide range of base materials, yarn counts and twists. These structural properties significantly influence the electrical and electromechanical behavior of such yarns. However, until now little research has been carried out on the yarns themselves. To close this research gap, several variations of a single yarn type are electromechanically characterized. Additionally, tensile tests with synchronous resistance measurements are performed. From these measurements, sensor metrics are derived and calculated to compare the different variants quantitatively. Full article

Fabrics have been recognized as a necessary component of daily life due to their involvement in garments, home textiles, and industrial textiles. The mechanical performance of textiles was considered essential to meet the end-user requirements for strength and durability. The purpose of this work was to provide an overview of the textile structures and tensile strengths of woven textiles. Different types of textile structures, depending on the weaving methods (woven, braided, knitted, non-woven) and the most common architectures of woven fabrics (plain weave, twill and sateen), were presented. Common materials constituting the textiles’ structures and a comparison in terms of the density, Young’s modulus and tensile strength between natural (plant-based, animal-based, and mineral-based) and synthetic fibers were reported. The mechanical properties of woven textiles were presented for neat and coated textiles, primarily in terms of the tensile strength. Depending on the cases, typical regions in the load–displacement curve (i.e., crimp, elastic, non-linear failure, thread fracture) were highlighted. The impact of the architecture, yarn distance and size, and yarn twisting on the tensile strength of woven fabrics was then illustrated. Full article

This study aims to enable intelligent structural health monitoring of internal damage in aerospace structural components, providing a crucial means of assuring safety and reliability in the aerospace field. To address the limitations and assumptions of traditional monitoring methods, carbon nanotube (CNT) yarn sensors are used as key elements. These sensors are woven with carbon fiber yarns using a three-dimensional six-way braiding process and cured with resin composites. To optimize the sensor configuration, an artificial fish swarm algorithm (AFSA) is introduced, simulating the foraging behavior of fish to determine the best position and number of CNT yarn sensors. Experimental simulations are conducted on 3D braided composites of varying sizes, including penetration hole damage, line damage, and folded wire-mounted damage, to analyze the changes in the resistance data of carbon nanosensors within the damaged material. The results demonstrate that the optimized configuration of CNT yarn sensors based on AFSA is suitable for damage monitoring in 3D woven composites. The experimental positioning errors range from 0.224 to 0.510 mm, with all error values being less than 1 mm, thus achieving minimum sensor coverage for a maximum area. This result not only effectively reduces the cost of the monitoring system, but also improves the accuracy and reliability of the monitoring process. Full article

Fiber materials have advantages such as light weight and high strength, corrosion resistance, fatigue resistance, and easy processing and production, and they are widely applied in the repair and renovation of concrete structures. To promote the construction convenience of fiber materials, fiber raw yarn is continuously braided to form fiber-belt-bars. Based on the existing research, the performance of bonding between fiber-belt-bars and a concrete interface was investigated, and pull-out tests were performed to systematically investigate the effects of the fiber-belt-bar cross-sectional size, anchorage length, concrete strength, and fiber type on the bonding performance. The experimental results show that the bond strength reduces with an increase in the anchorage length, increase in cross-sectional size, and decrease in concrete strength, and the effect of fiber type on the bond strength is not obvious. On this basis, a formula for calculating the average bond strength of fiber-belt-bars is proposed. Experiments and calculations determined that the average bond strength between fiber-belt-bar and concrete with a cross-sectional size of 12 mm × 3 mm is 10–30% higher than that with a cross-sectional size of 20 mm × 3 mm for the same anchorage length. Finally, the minimum anchorage length of the fiber-belt-bar is proposed to provide a valuable reference for the use of fiber-belt-bar in concrete projects. Full article

The use of tungsten fiber-reinforced tungsten composites (W_f/W) has been demonstrated to significantly enhance the mechanical properties of tungsten (W) by incorporating W-fibers into the W-matrix. However, prior research has been restricted by the usage of single fiber-based textile fabrics, consisting of 150 µm warp and 50 µm weft filaments, with limited homogeneity, reproducibility, and mechanical properties in bulk structures due to the rigidity of the 150 µm W-fibers. To overcome this limitation, two novel textile preforms were developed utilizing radial braided W-yarns with 7 core and 16 sleeve filaments (R.B. 16 + 7), with a diameter of 25 µm each, as the warp material. In this study, bulk composites of two different fabric types were produced via a layer-by-layer CVD process, utilizing single 50 µm filaments (type 1) and R.B. 16 + 7 yarns (type 2) as weft materials. The produced composites were sectioned into KLST-type specimens based on DIN EN ISO 179-1:2000 using electrical discharge machining (EDM) and subjected to three-point bending tests. Both composites demonstrated enhanced mechanical properties with pseudo-ductile behavior at room temperature and withstood over 10,000 load cycles between 50–90% of their respective maximum load without sample fracture in three-point cyclic loading tests. Furthermore, a novel approach to predict the fatigue behavior of the material under cyclic loading was developed based on the high reproducibility of the composites produced, especially for the composite based on type 1. This approach provides a new benchmark for upscaling endeavors and may enable a better prediction of the service life of the produced components made of W_f/W in the future. In comparison, the composite based on fabric type 1 demonstrated superior results in manufacturing performance and mechanical properties. With a high relative average density (>97%), a high fiber volume fraction (14–17%), and a very homogeneous fiber distribution in the CVD-W matrix, type 1 shows a promising option to be further tested in high heat flux tests and to be potentially used as an alternative to currently used materials for the most stressed components of nuclear fusion reactors or other potential application fields such as concentrated solar power (CSP), aircraft turbines, the steel industry, quantum computing, or welding tools. Type 2 composites have a higher layer spacing compared to type 1, resulting in gaps within the matrix and less homogeneous material properties. While type 2 composites have demonstrated a notable enhancement over 150 µm fiber-based composites, they are not viable for industrial scale-up unlike type 1 composites. Full article

Textile reinforcements have established themselves as a convincing alternative to conventional steel reinforcements in the building industry. In contrast to ribbed steel bars that ensure a stable mechanical interlock with concrete (form fit), the bonding force of smooth carbon rovings has so far been transmitted primarily by an adhesive bonding with the concrete matrix (material fit). However, this material fit does not enable the efficient use of the mechanical load capacity of the textile reinforcement. Solutions involving surface-profiled rods promise significant improvements in the bonding behavior by creating an additional mechanical interlock with the concrete matrix. An initial analysis was carried out to determine the effect of a braided rod geometry on the bonding behavior. For this purpose, novel braided rods with defined surface profiling consisting of several carbon filament yarns were developed and characterized in their tensile and bond properties. Further fundamental examinations to determine the influence of the impregnation as well as the application of a pre-tension during its consolidation in order to minimize the rod elongation under load were carried out. The investigations showed a high potential of the impregnated surface-profiled braided rods for a highly efficient application in concrete reinforcements. Hereby, a complete impregnation of the rod with a stiff polymer improved the tensile and bonding properties significantly. Compared to unprofiled reinforcement structures, the specific bonding stress could be increased up to 500% due to the strong form-fit effect of the braided rods while maintaining the high tensile properties. Full article

Thin fiber-shaped pneumatic artificial muscle (PAM) can generate contractile motions upon stimulation, and it is well known for its good compliance, high weight-to-power ratio, resemblance to animal muscle movements, and, most importantly, the capability to be integrated into fabrics and other textile forms for wearable devices. This fiber-shaped device, based on McKibben technology, consists of an elastomeric bladder that is wrapped around by a braided sleeve, which transfers radial expansion into longitudinal contraction due to the change in the sleeve’s braiding angle while being inflated. This paper investigates the effect of material properties on fiber-shaped PAM’s behavior, including the braiding yarn and bladder’s dimensional and mechanical properties. A range of samples with combinations of yarn and bladder parameters were developed and characterized. A robust fabrication process verified through several calibration and control experiments of PAM was applied, which ensured a more accurate characterization of the actuators. The results demonstrate that material properties, such as yarn stiffness, yarn diameter, bladder diameter, and bladder hardness, have significant effects on PAMs’ deformation strains and forces generated. The findings can serve as fundamental guidelines for the future design and development of fiber-shaped pneumatic actuators. Full article