Braided Fabrics Research Articles

Study on the folding damage mechanism of SiC fiber braided fabric based on synchrotron radiation CT and finite-element analysis

Silicon carbide (SiC) fiber exhibits high strength, thermal resistance, and chemical stability, but its insufficient flexural strength renders it unsuitable for use in flexible structural materials. In this study, the microstructure evolution and damage mechanisms of SiC fiber braided fabric were investigated at different braiding angles and folding stages using synchrotron micro computed tomography (µ-CT) and finite-element analysis. Results from synchrotron radiation CT scans indicate that, with an increase in the number of folding cycles, both fiber surface fractures and slippage gradually increased, leading to a looser internal structure and diminished fiber continuity. The SiC fiber braided fabric at 37.8° was predominantly influenced by the folding behavior, exhibiting a higher frequency of fiber breakages. Conversely, the 43.1° SiC fiber braided fabric was primarily affected by inter-bundle abrasion, resulting in looser fiber bundles and increased slippage. In the case of the 41.2° SiC fiber braided fabric, under the combined effects of friction and folding, the highest occurrences of fiber slippage and breakages were observed. Finite-element simulation results reveal that the stress at the folding site of the 40° braided fabric was higher than those of the 45° and 50° braided fabrics, confirming the experimental conclusion that the folding resistance of SiC fiber fabrics is poorest at a braiding angle of around 41° to 42°. This research is of significant importance for a deeper understanding of the folding performance and damage behavior of SiC fiber braided fabric, providing valuable insights for further optimizing material design and applications.

Design and fabrication of highly aligned poly(l‐lactide‐co‐ε‐caprolactone) nanofiber yarns and braided textiles

AbstractAn approach that combines a modified electrospinning method with thermal stretching post‐treatment is designed to fabricate poly(l‐lactide‐co‐ε‐caprolactone) (PLCL) electrospun nanofiber yarns (ENYs). The nanofiber diameter in the PLCL ENYs is found to present an increasing trend with the increasing of polymeric concentration. When the PLCL concentration reaches 13% (w/v), the as‐generated ENYs show bead‐free and uniform nanofibrous structure. Then, a thermally stretching technique is applied to process the primarily‐obtained PLCL ENYs. When the stretching temperature is set as 60 °C, the thermally‐stretched PLCL ENYs present superior fiber orientation and notably enhanced crystallinity, thus resulting in dramatically increased mechanical properties. Finally, the thermally stretched PLCL ENYs are further processed into braided fabrics, and their mechanical properties are found to possess an obviously increased trend with the increasing of ENY numbers, demonstrating the adjustment feasibility of the mechanical properties of ENY‐based textiles by controlling the ENY numbers. Importantly, the in vitro cell studies demonstrate that the ENY‐based braided textiles significantly support the adhesion and proliferation of human dermal fibroblasts (HDFs). In all, the present study provides an easily‐handling strategy to fabricate high performance PLCL ENYs, which shows promising future for the generation of advanced biomedical textiles.

Properties of Multistranded Twisted Graphene Fibers and Their Application in Flexible Light-Emitting Devices.

As a typical carbon-based material electrode, graphene fiber exhibits many advantages, such as good electrical conductivity, lightweight, and strong structural designability. Its demand is increasing in the wearable display field. With the help of fine denier fiber spinning combined with multistranded graphene fibers prepared via twisting and drafting, their petal-like twisted structure endows the fibers with a high specific surface area, enabling them to complete dye adsorption within 30 min. Simultaneously, compared with that of a single fiber with the same thickness, the volume specific resistance of a multistranded twisted graphene fiber is reduced by 2.4 times. During force sensing, the twisted structure of multistranded fibers exhibits varying simultaneity of fiber fracture with excellent resistance sensitivity reaching up to 55%. The multistranded twisted flexible graphene fibers demonstrate excellent robustness. Electroluminescent flexible devices prepared with graphene fibers and fiber braided fabrics with different organizational structures as electrodes emit highly saturated short-wave blue light during long-term multiple use. Therefore, multistranded twisted graphene fibers exhibit considerable potential for future applications in wearable multicolor smart displays and flexible optical signal electronics.

Improved XCT image automatic segmentation for quantitative characterization of the meso-morphological features in the damaged braided composite fabric

Accurately identifying various meso-morphological features and sub-phases within the damaged braided composite fabric is crucial for assessing the mechanical properties of composites under complex loading conditions and different processing parameters. However, obtaining 3D reconstructions that can be quantitatively analyzed is still a challenge, primarily due to the low contrast of the meso-morphological features (yarn tow and matrix crack networks). In this work, a new data enhancement algorithm is proposed to generate a realistic-looking artificial training dataset for enriching the information of the meso-morphological features. Then, the effect of various training networks and training parameters (the size of real and hybrid training dataset, number of epochs) on segmentation performance were examined. Finally, the meso-morphological features were statistically analyzed to accurately evaluate the mechanical properties of the composite material. The work presented here provides an effective tool that enables the quantitative analysis of the dynamic crack evolution process under the axial load of the composite materials.

Folding endurance and damage mechanisms of SiC fiber braided fabrics

Aiming at the issues of poor toughness, low folding endurance, and susceptibility to damage of silicon carbide (SiC) fiber tows during repeated folding process, two-dimensional (2D) SiC fiber braided fabrics with varying braiding angles were prepared in this study. The folding endurance and damage mechanisms of SiC fiber fabrics under different folding conditions were investigated through repeated folding tests, tensile tests, and optical microscope measurements. The results revealed that when the folding angle was (+180°, −180°), the SiC fiber braided fabric with a lower braiding angle (α = 37.8°) exhibited a folding endurance number of 1984 times, while the medium angle fabric (α = 41.2°) had a value of 761 times, and the high angle fabric (α = 43.1°) achieved 1733 times. During the folding process, both interlaced abrasion between fiber tows and external folding loads affected the mechanical properties of SiC fiber tows and their fabrics leading to material damage. Initially, the folding load played a major role in determining fold endurance when there were fewer number of folds; however, as the number of folds increased, the influence of interlaced abrasion became increasingly significant. Ultimately, these combined factors led to progressive damage evolution until failure occurred in the fabrics. Among all tested samples, the SiC fiber braided fabric with a higher braiding angle (α = 43.1°) demonstrated optimal fold endurance performance, and it had superior characteristics such as higher fold endurance numbers along with lower force loss rates for fiber tows after multiple folds and fabric force loss rates following repeated folds.

Improved hyperelastic model for simulating the forming of biaxial braided fabrics

The complex deformation behavior during preforming of composite reinforcements can be effectively predicted by numerical simulation. Most numerical studies generally concern orthogonally woven fabrics. The present work proposes a hyperelastic constitutive model to characterize the anisotropic mechanical properties of non-orthogonal braided reinforcements to simulate the preforming process. Based on the deformation modes, the strain energy was defined by corresponding specific invariants. The coefficients of the hyperelastic constitutive law were identified in the case of non-orthogonal fabrics thanks to the establishment of an energetic model between the second Kirchhoff stress tensor and the tensile load. The constitutive law and energetic model were then validated by means of comparison with the bias-extension test and hemispherical forming test.

Pultrusion molding of continuous fiber reinforced thermoplastic composite pipe using partially-impregnated commingled yarns

Pultrusion molding is one of the high-cycle molding methods for continuous fiber-reinforced plastics using thermoplastic resin, and considering the expansion of industrial applications, shaped parts, such as pipes and L-shapes are more desirable. The following is an example of a product that can be used to achieve this goal. Braided fabrics are one of the most useful preforms for achieving pipe shapes. In this study, commingled yarns and partially impregnated commingled yarns were used as intermediate materials, because excellent impregnation properties and textile workability are required to the fabrication and pultrusion molding of the braided fabrics. However, when forming a pipe shape by pultrusion, the mandrel must be placed in the hollow of the molded product, which causes an increase in pull-out resistance due to shrinkage of the pipe diameter. To solve this problem and achieve high-speed molding of pipe-shaped products by pultrusion molding, this study examined the effects of different intermediate materials and molding conditions on the impregnation state and mechanical properties of molded products, as well as the optimization of the mandrel location. The first part of this study revealed that the impregnation time of partially impregnated commingled yarns is shorter than that of commingled yarns, and as a result, the decrease in void ratio and unimpregnated ratio is smaller, and the decrease in mechanical properties is smaller even if the molding speed is increased. The second part of this study, it was found that the mandrel tip should be positioned so that the temperature of the inner diameter side becomes lower than glass-transition temperature (Tg) during cooling to prevent separating. In addition, it was found that temperature history analysis based on heat conduction calculations is effective in predicting the optimum mandrel position, which varies depending on molding conditions. These results provide a guideline for high-speed pultrusion molding.

Shear deformation characteristics under tensile stress during forming of tubular braided fabrics

Shear deformation characteristics under tensile stress during forming of tubular braided fabrics

Zero-Poisson's-Ratio Honeycomb-Filled Braided Textile Reinforced Conical Tubes: Designing, Manufacturing and Testing

Zero-Poisson's-Ratio Honeycomb-Filled Braided Textile Reinforced Conical Tubes: Designing, Manufacturing and Testing

Low‐velocity impact response and damage tolerance of hybrid biaxial/triaxial braided composite laminates

AbstractThe structural properties of braided composite laminates are significantly affected by the low‐velocity impact (LVI). In this paper, the impact resistance and damage tolerance of triaxial braid structure laminates at different positions were mainly studied. Three hybrid biaxial (B)/triaxial (T) braided composite structures of BBTT, BTTB, and TTBB were designed, and LVI test and post‐impact compression tests were carried out. The results show that the triaxial braided fabric with quasi‐isotropic on the impact side caused more significant matrix cracks along the axis yarn direction, and the matrix damage area and delamination area were larger. For triaxial braided ply with high curl levels, severe fiber fracture and relatively concentrated damage occurred first on the non‐impact side. Interestingly, triaxial braided fabrics exhibited better impact resistance in terms of mechanical response when distributed across the specimen surface. However, a global damage pattern appears at high energy levels, which seriously reduced the residual strength of the structure and showed the worst damage tolerance. The damage quantification analysis of cracks, dent depths, delamination and residual compressive strength caused by the LVI of hybrid shaft number braided laminates was carried out in this work, which provided a valuable reference for engineering failure analysis and rational structure optimization of composite laminates.

Optical inspection of the braid formation zone during manufacturing of preforms from reinforcement fibers for defect detection purposes

Braiding is a highly automated process for manufacturing preforms directly from reinforcement yarns at large production volumes. The quality of braided textiles and the stability of the process can however be negatively affected by defects that occur during braiding. If such defects can be detected from fine process anomalies early during their formation, the process can be interrupted and countermeasures can be introduced before the defect aggravates and gets braided into the product. Current sensor modules for defect detection during braiding however involve problems of either late response times, process impairments or a lack of applicability to braiding of composite parts. In an effort to overcome these drawbacks, the paper at hand proposes to optically monitor the braid formation zone by means of a single camera (no process impairments). An associated image analysis algorithm creates a measure for the angular distance of each individual braiding yarn to its neighboring yarns and tracks the yarns as they rotate around the overbraidable mandrel (typical for braiding of composite parts). Since braiding yarns typically exhibit distinct curvatures as they span from the bobbins towards the center of the braiding machine due to frictional yarn-yarn interaction, a change in yarn curvature and thus in angular yarn distance is an early sign of a defect-characteristic anomaly in yarn tension (early response). If implemented on a real-time capable computing device, an apparatus according to the presented method can be retrofitted to existing production lines for braiding process monitoring. It then contributes to the reduction of error correction times since countermeasures are quicker to implement as long as the defect has not aggravated, yet. Furthermore, scrap material rates can be reduced as anomalies can be detected before they manifest in the braided structure.

Analysis of Thermomechanical Behavior of the Tubular Braided Fabrics with Flax/Polyamide Commingled Yarns.

Flax fibers are widely used as the strongest natural fibers in composite parts with advanced structures. Due to their excellent mechanical properties and recyclability, they have attracted more attention from the aviation and automotive industries, etc. These composite parts are usually obtained by preforming reinforcements or prepregs at high temperatures, and their mechanical behaviors are greatly affected by temperature variations. To improve the understanding of the mechanical properties of flax fiber materials, especially for the braided fabric with non-orthogonal structures, uniaxial tensile tests at different temperatures and tensile speeds were conducted on hollow tubular braided fabrics. The thermomechanical properties of Flax/Polyamide12 (PA12) prepregs were analyzed. The results show that temperature and tensile speed have obvious effects on the strength and shear stiffness of tubular fabrics. The strength and shear stiffness of the fabric decreases as the ambient temperature increases. Meanwhile, the strength of the fabric can also be improved by appropriately increasing the tensile speed. In addition, according to the experimental results, a theoretical model is established to describe the shear angle on the smallest circumference of the fabric, which provides a theoretical basis for the subsequent simulation process. The test results can provide a reference for the manufacture of flax fiber-reinforced composites with tubular structures.

Development and analysis of a three-dimensional braided honeycomb structure

This paper presents the design and development of three-dimensional braided honeycomb structures. The basic principles and braiding process are described. The relationship between braiding parameters and honeycomb geometric parameters is established and several three-dimensional (3D) braided honeycomb fabrics are introduced. Based on the principle of the 3D braiding ‘four-step’ method, the interlaced state of yarns can be changed by controlling the movement of yarn carriers, so the separation and combination of the braid can be controlled, then 3D braided honeycomb fabric can be formed. As the number of braiding cycles of wall length increases, the relative density will gradually decrease, but the number of braiding cycles of free wall length has a greater effect on the relative density. When the number of columns of yarns participating in wall thickness increases, the relative density will gradually increase. The relative density also showed a positive correlation with the braiding angle. With the increase of the opening angle, the relative density gradually decreases, although there is a minimum point after which a little increase is observed. This paper provides significant guidance for designing various 3D braided honeycomb structures and evaluating their relative density, and can be a reference for the design and development of new honeycombs structures.

Composite Braided Fabric Coupled with Photothermal and Electrothermal Processes for Stable and Continuous All-Day Desalination

In this study, a carbon fiber/tencel composite braided fabric was used in stable and continuous all-day desalination technology with superior photothermal and electrothermal conversion capability. The desalination performance was regulated by adjusting the braiding parameters. Because the water in carbon fibers is maintained in the capillary state and thus evaporates more easily in clusters, it required less energy to evaporate water off the composite fabric. Under 1 sun illumination, the average evaporation rate and the evaporation efficiency were 1.84 kg m-2 h-1 and 88.8%, respectively. When a small amount of electricity (3 V) was applied, the evaporation rate of the braided fabric was maintained at over 1.88 kg m-2 h-1, and a superior desalination performance during the daytime was achieved. Under continuous all-day operation, most of the organics, metal ions, and contaminants were effectively eliminated from the water, which satisfied the WHO drinkable water standards. Our results can contribute to paving the way for efficient and stable wastewater treatment, seawater desalination, and drinking water collection methods.

Highly Stretchable, Conductive and Long‐Term Stable PEDOT:PSS Fibers with Surface Arrays for Wearable Sensors

Substantial progress has been made in exploring the novel structures and sensing mechanisms for wearable sensors, where high sensitivity plays an essential role. For fiber‐based wearable sensors, the sensitivity mainly depends on the electroconductivity and surface microstructure of fibers. However, preparing highly conductive fibers along with excellent stretchability and long‐term stability via facile and effective approaches is still challenging. Therefore, in this work, wet‐spun poly (3, 4–ethylenedioxythiophene):poly (styrene sulfonate) (PEDOT:PSS) fibers with a superior conductivity of 105 S cm−1 and exceptional stretchability of 132% have been successfully achieved by adding urea and soluble copper salts into a coagulation bath. With the additional copper ions, the formation of a copper complex with fluff‐like arrays morphology occurs spontaneously on the surface of fibers, while the existence of urea not only enhances their electroconductivity and stretchability, but also endows both with long‐term stability. Meanwhile, the obtained fibers reveal fast response time and ultra‐low detection limit to the external stimuli, and braided fabrics decorated with such fibers own potential applications for wearable electronic textiles. More importantly, this work explores the significance of durability for PEDOT:PSS fiber‐based devices, inspiring a unique path for novel fiber design.

Machine learning prediction of mechanical properties of braided-textile reinforced tubular structures

Braided-textile composites have been applied in various engineering fields and used for high-efficiency energy absorbers to meet different loading requirements. However, it’s difficult to accurately forecast the mechanical properties of these braided-textile composites based on theoretical method, which is a big obstacle to the precise design of the energy-absorbing structure. In this research, carbon fiber reinforced composite (CFRC) tubular structures were fabricated by two-dimensional braided textiles, and 160 groups of orthogonal axial compression experiments were carried out.Axial compression behaviors of CFRC tubular structures, including peak force, mean crushing force, energy absorption, specific energy absorption, elastic modulus and other relevant parameters, were tested and collected in a database. The feed forward back propagation (FFBP) algorithm based on artificial neural network (ANN), as an algorithm with high convergence accuracy in machine learning (ML), was adapted to build a prediction model to forecast the overall axial compression properties of those CFRC tubular structures uncollected in the database. By a series of error analyses, the ML method was proven to have high accuracy in predicting the relevant mechanical properties within the range of orthogonal design groups. Although the relative error of marginal sample data (especially single-layer tubes) is large, the mean absolute error (MAE) of training set and test set is only about 5% and 10%, respectively. Our work demonstrates the potential of machine learning methods in predicting the overall mechanical properties and guiding the design of composite materials.

Effects of textile structure and projectile geometry on ballistic performance of UHMWPE textiles

The ballistic performances of three ultrahigh molecular weight polyethylene (UHMWPE) textile structures (2D braided, 2D triaxial braided and 3D orthogonal woven) are studied. The tensile strength of UHMWPE yarn is first measured by quasi-static tensile experiment. By inputting the measured material parameters, numerical models including macro-meso model and mesoscopic models are established and these numerical models are validated by a ballistic experiment of 2D braided textile. The ballistic performances of three textile structures under impact of three different head-shape projectiles (flat, sharp and hemispherical nose) are investigated, using the macro-meso model. Based on the analysis of ballistic limit, failure mode and energy dissipation, we demonstrate that the 2D triaxial braided (2D3A) textile has better ballistic performance than the 2D textile. All three textile structures show the least ballistic damage by flat projectile, followed by sharp and hemispherical projectile.

Effect of silane coupling treatments on mechanical properties of epoxy based high‐strength carbon fiber regular (2 x 2) braided fabric composites

AbstractBraiding technique is one of the most cost‐effective and versatile methods to manufacture braided preforms for producing textile reinforced composites. Carbon fiber is one of the most common reinforcing fibers having high strength and modulus used in high‐performance composites. In this study, epoxy resin was modified with 3‐aminopropyltriethoxysilane (APTES) and 3‐aminopropylmethyldimethoxysilane (APMDMS) in order to enhance interfacial adhesion between matrix and carbon fiber. Composites were produced by vacuum‐assisted resin infusion method using braided fabrics which were manufactured from a high‐strength standard modulus type of carbon fiber (T700S) by using a radial braiding machine. Epoxy resin was treated with silane at different concentrations from 0.0% to 1.0%. According to the mechanical results, the ideal (optimum) concentration of APTES and APMDMS for the matrix modification has been around 0.5 wt% of the epoxy system. Also, the mechanical properties of APTES‐treated epoxy composites are slightly higher than those of APMDMS‐treated epoxy composites at the same concentration. When it is compared to silane untreated composite, 0.5 wt% of APTES/APMDMS silane treated epoxy/carbon braided composites have led to an increase of 7.71/6.16% and 7.65/6.05% in tensile and flexural strength while the corresponding increase has resulted in 17.48/13.51% and 16.63/13.33% in terms of tensile and flexural modulus, respectively. Impact testing results indicate that 0.5 wt% of APTES and APMDMS composites are improved 6.87% and 4.31% compared to untreated composites, respectively.

Surface engineering via self-assembly on PEDOT: PSS fibers: Biomimetic fluff-like morphology and sensing application

Wearable sensors based on fibers or textiles are attracting widespread attention due to their potential applications in wearable health monitoring and care systems, where high sensitivity plays an essential role in the development of electroconductive fibers. Though the great progress has been made in designing novel structures and understanding sensing mechanism, how to prepare conductive fibers with high sustainability and conductivity via a facile and efficient method is still a challenge. Herein, inspired by the spider’s fluff, an ion-induced self-assembly is proposed and performed to obtain continuous and large-scale fabrication of poly (3, 4-ethylenedioxythiophene): poly (styrene sulfonate) (PEDOT: PSS) fibers with an array microstructure. The formation of copper complex with fluff-like shape occurs spontaneously on the surface of PEDOT fibers without any additional post-treatment or harsh condition, which is difficult to achieve by other approaches. Benefiting from the fluff-like array, these biomimetic PEDOT: PSS-Cu2+ fibers possess a near 5-fold increase in specific surface area compared to that of pristine PEDOT: PSS fibers, which endows it with a good pressure sensitivity with ultralow detection limit (~82 Pa) and fast response time (47 ms). We further demonstrate their potential applications for airflow detection, real-time information transmission, and gravity/pressure sensing while decorating such biomimetic fibers to braided fabrics. More importantly, this work sheds light on the formation mechanisms of microstructures on the fiber, inspiring a unique path for conventional wet-spinning technology and novel fiber-surface design in order to achieve its outstanding sensitivity.

Effect of fiber architecture on the impact resistance of composite panels subjected to metallic projectile

Experiments using a single-stage gas gun were conducted to evaluate the resistance of three types of composite panels to high-velocity impacts from metallic projectiles: panels reinforced with unidirectional tape or formed from plain-woven fabric or two-dimensionally braided fabric. The critical penetration velocity, deformation, and failure morphologies were examined by virtue of high-speed photography, 3D digital image correlation technology and non-destructive testing methods. In addition, a normalized quantity was introduced to assess the energy absorption capacity of the panels. Laminates stacked by angle-ply unidirectional tapes contained impacts at higher velocities than other panels, and the energy absorption capacities of the plain-woven and braided composite panels are comparable. The results provide insights into the impact failure behavior of composite panels and can aid in the selection of materials for aeroengine casings.