Woven Spacer Research Articles

Multi‐layer structure design, fabrication and numerical simulations of 3D woven spacer fabric composites with improved mechanical properties

AbstractThe 3D woven spacer fabric lightweight composites (WSFC) show promising applications in construction, transportation and aerospace. In this study, the 3D WSFC with different structural variations (e.g., layer thicknesses, stacking and face layer thickening) were designed and fabricated. The fracture strengths of single‐layer WSFC in the weft direction with layer thicknesses of 5, 10 and 15 mm were 54.4, 14.3, and 5.4 MPa. In the weft direction, the fracture strengths of double‐ and triple‐stacked 3D WSFCs were 30.6 and 21.7 MPa, which improved 1.1 times and 3.0 times as compared with those of original single‐layer 3D WSFCs, respectively. The double‐ and triple‐stacked WSFC also had large flexural deformation. The 3D WSFC with double‐layer misaligned stacking had the similar flexural strengths in both directions, which obviously reduced the performance differentiation of 3D WSFC in different directions. With the addition of face layer fabric, the mechanical performances of 3D WSFC were notably enhanced, and the damage modes were changed from brittle failure to ductile failure. Furthermore, a multi‐scale model of 3D WSFC with different structural variations was developed for numerical simulation to analyze the stress distribution and damage mechanism.Highlights Stacking design obviously improves mechanical properties of 3D WSFC. WSFC with misaligned stacking has similar flexural strengths. A multi‐scale elastic–plastic damage model for 3D WSFC is established. Damage modes of WSFC are changed with the stacking method.

Mechanical Properties and Damage Mechanism of 3D Woven Spacer Composites Improved with Changing Face Layer Structures: Experimental and Numerical Study

Mechanical Properties and Damage Mechanism of 3D Woven Spacer Composites Improved with Changing Face Layer Structures: Experimental and Numerical Study

Exploring the potential of 3D woven and knitted spacer fabrics in technical textiles: A critical review

Three-dimensional (3D) woven and knitted spacer fabrics have emerged as significant advancements in the field of technical textiles, driven by notable progress made by the textile industry. These unique fabrics possess desirable characteristics that render them suitable for various technical applications. As we look towards the future, spacer fabrics are expected to find innovative applications in various functional products. However, despite the growing interest in their use in the technical textile sector, comprehensive reviews exploring their potential are lacking. Therefore, this review aims to fill this gap in the existing literature by examining the potential of 3D woven and knitted spacer fabrics in technical textiles. It provides a comprehensive exploration of their fabrication techniques, properties, key parameters, and potential applications in technical textiles. This review highlights that woven spacer fabrics exhibit high integrity and stability, making them suitable for composite reinforcement. On the other hand, knitted spacer fabrics offer a higher air-trapping capacity and a double-faced nature, leading to their extensive use in cushions, medical textiles, and protective technical textiles. Additionally, this review provides valuable insights for researchers and manufacturers interested in harnessing the potential of spacer fabrics for various functional products in the field of technical textiles.

Enhancing bending performance in 3D woven spacer composites with lightweight biomimetic integrated double‐spacer structure

AbstractThree‐dimensional woven spacer composites (3DWSCs) with lightweight and excellent mechanical properties have promising application in communication, transportation, aerospace and other fields. However, traditional single‐layer 3DWSCs exhibit insufficient strength, especially when dealing with high thickness, as the pile yarns tend to buckle. In this study, inspired by the structural features of the Thalia dealbata, 3D woven integrated double‐layer glass fiber/epoxy resin spacer composites by mimicking were fabricated. Innovative integrated double‐layer structure design effectively improves the performance and failure mode of 3DWSCs under bending loads. Compared to single‐layer 3DWSCs, the resulting double‐layer 3DWSCs exhibited a 41.79% increase in peak bending load, a 46.85% increase in bending stiffness, and a 99.38% increase in energy absorption. In addition, the double‐layer 3DWSCs showed a low density of 0.52–0.55 g/cm3. This work introduces bioinspired double‐layer 3DWSCs with characteristics of lightweight and superior bending performance, potentially offering novel ideas for the design of high‐performance composites.Highlights Inspired by the structural features of the Thalia dealbata, a 3D integrated woven double‐layer glass fiber/epoxy resin spacer composites by mimicking were fabricated. 3D woven double‐layer spacer composites are lightweight (0.52–0.55 g/cm3) and can effectively improve the bending properties of single‐layer structures. Based on the analysis of the fracture morphology, the significant improvement of the fracture pattern of the single‐layer structure by the double‐layer structure is effectively demonstrated. This study introduces novel design strategies for multi‐layer lightweight composite materials and holds broad applications.

Evaluation of the effect of structural parameters on the compression behaviour of woven spacer fabrics

In this study, six groups of woven spacer fabrics with different structural parameters such as the spacer yarn pattern (V and W pattern) and spacer yarn density (denting pattern) were produced, and their compressional behaviour was investigated. According to the experimental results, the V-pattern spacer fabrics revealed better compressional resistance compared to the W-pattern spacer fabrics. Besides, it was observed that the spacer fabrics produced with lower spacer yarn density, were more susceptible to compressional forces. Statistical analysis of results demonstrated that all compressional parameters, except relative compressibility and thickness recovery, were affected by the spacer yarn pattern and density. Finally, the compressional behaviour of woven spacer fabric was correlated by three viscoelastic models (Kelvin model, Maxwell model, and three-component model with a nonlinear spring) and also the Van Wyk Theory. The results of curve fitting exhibited that the three-component model with nonlinear spring well fitted the experimental data.

Membrane properties overview in integrated forward osmosis/osmotically assisted reverse osmosis systems

Integration of forward osmosis (FO) and osmotically assisted reverse osmosis (OARO) provides low energy consumption and controlled fouling for brine treatment. This study explains the membrane properties required for cost–optimal OARO-based systems. A detailed model accounting for the relationship between burst pressure, permeate spacer gap, and structural parameters of OARO membranes was implemented with woven and non-woven spacers. Results indicate that the tradeoff between internal concentration polarization (ICP) and permeate–side pressure drop in OARO stages is a crucial consideration for optimal membrane element design. Due to the lower ICP of no-woven spacers, a system using non-woven spacers yielded lower levelized cost of water (LCOW) and specific energy consumption (5.83 $/m3 and 11.65 kWh/m3, respectively) as compared to the system with woven spacers (7.31 $/m3 and 9.90 kWh/m3, respectively) for dewatering a stream of 75 g/L salinity with 70 % water recovery. Sensitivity analysis shows that increasing the maximum pressure in OARO membranes requires a higher membrane structural parameter, aggravating ICP; however, the elevated driving force mitigates adverse effects of ICP. Moreover, a 15 % reduction in LCOW can be achieved if the membrane replacement factor of RO and OARO is reduced from 15 % to 5 %, which accounts for mitigated fouling.

Low velocity impact behaviors and highly residual compressive strength of epoxy foam‐filled 3D woven composites

AbstractIn this work, a new type of epoxy foam‐filled 3D woven spacer composites (FF‐3DWSCs) was designed and manufactured by self‐made 3D loom and foaming technology. The low velocity impact behaviors, residual compressive properties and strengthening mechanisms of epoxy foam were systemically investigated. As the results, the FF‐3DWSCs showed higher impact load of 4000–5200 N than that of 3D woven spacer composites (3DWSCs) (2800–4300 N) at the energy from 10 to 40 J. The residual compressive strength of FF‐3DWSCs (23.85 MPa) was maintained at about 80% after 30 J energy impact. Due to the good compatibility of the epoxy foam and the epoxy resin and the synergistic effect between the pile yarn and the epoxy foam, the interface between epoxy foam and fiber/epoxy was strong. Therefore, the novel FF‐3DWSCs proposed here exhibited excellent impact properties and energy absorption capacity and can be used as a candidate material in the field of high‐performance composites.

Modulation of complex permittivity of carbon nanotubes/epoxy foam composites reinforced by three-dimensional woven spacer fabric

3D woven spacer composites (3DWSC) with integrated structure have immense potential as design platforms for high-performance microwave absorbent materials. In this work, the complex dielectric constant of 3DWSC was modulated by the content of carbon nanotubes (CNTs) in the epoxy foam sandwich. The theoretical model was proposed for predicting the dielectric constant of 3DWSC-CNT/epoxy foam. The error between model prediction, measured results and finite element results was less than 5%. The excellent mechanical properties of 3DWSC-CNT/epoxy foam were demonstrated by compression and impact experiments. The absorption performance and radar cross section (RCS) reduction in the frequency range of 4–18 GHz were calculated by finite element method. The maximum effective absorption bandwidth was 5.5 GHz. The RCS of 3DWSC- CNT/epoxy foam of the same size at 10 GHz was only 1% of that of carbon fiber composites. 3DWSC endowed with microwave absorption function have great potential in the practical application of anti-radar detection.

Combining acoustic emission and digital image correlation analysis for dynamic damage response of woven spacer structure reinforced sandwich composites

This study reveals the dynamic damage process and the bending response of woven spacer structure reinforced sandwich composites (WSRS) by combining the acoustic emission (AE) technique and the digital image correlation (DIC) method. The typical load–displacement curve of six WSRSs was divided into elastic deformation, damage developing, and rapid damage stages. According to AE, the primary failure modes of WSRS were foam failure, interface delamination and core-pile separation, and surface matrix cracking. The failure behavior of the specimens was identified. It revealed that when subjected to bending stress, the load-bearing capacity of WSRS in the weft direction was higher than in the warp direction. While the failure areas were extended, indicating that the core-pile structure played a dominant role. The stress was mainly concentrated in the core layer, increasing the failure degree and damage rate, while the strain nephogram showed superior integrity. Consequently, the weft direction of WSRS exhibited better integrity and load-bearing capacity.

Compressive strength of copper yarn/Kevlar yarn 3D woven spacer hybrid composites and its application for multifunctional composite antennas

Compressive strength of copper yarn/Kevlar yarn 3D woven spacer hybrid composites and its application for multifunctional composite antennas

Compressive properties investigation of “stress transformer” based on high-distance woven spacer fabric design

High-distance woven spacer fabrics have been developed into a variety of special textile products for a wide range of applications. As a type of sandwich structure, their applications are heavily dependent on their compressive properties. In this study, the compressive properties of high-distance woven spacer flexible inflatable composites (HDWSFICs) have been evaluated by varying the indenter diameter, initial inflation pressure, and spacer yarn density. The experimental results showed that the compression process can be divided into three stages, including the Contact Stage, the Stress Transition Stage and the Densification Stage. In the Stress Transition Stage, the HDWSFICs can transform compressive load into tension stress, and especially local stress into integral stress, which can be considered a “Stress Transformer”. The existence of the spacer yarns allows the inflatable composites to bear more than three times the compressive load of the inflatable membrane material itself. The compressive modulus increases with spacer yarn density and initial inflation pressure, thus the stiffness of HDWSFICs can be designed. The findings of this study may provide ideas for the design of a “Stress Transformer” and theoretical references for the development of high-distance woven spacer inflatable composites with excellent mechanical properties.

Enhanced impact resistance of three‐dimensional woven composites with double‐layer core structure

AbstractIn this study, to further improve the anti‐impact property of 3D woven spacer composites (3DWSC), three kinds of integrated 3DWSC with double‐layer cores assembled at different height combinations of 4 + 8 mm, 6 + 6 mm, and 8 + 4 mm, were designed and prepared. And the impact performances and the post‐impact lateral compressive properties of the resulting composites were investigated and compared to the single‐layer 3DWSC of the same height. The results show that among the three combinations, 3DWSC‐4 + 8 has the highest contact force value of 2454.33 N at 10 J, which is 90.60% higher than that of single‐layer 3DWSC. And the residual compressive strength of 3DWSC‐4 + 8 maintains 91.30% after 10 J energy impact, while the retention value of single‐layer 3DWSC is only 68.43%. The above results can be attributed to the fact that the addition of the middle panel in double‐layer 3DWSC is benefical to improve the capacity of the material to withstand transverse load or bending moment and to absorb more energy through its damage compared to the single‐layer 3DWSC. In addition, the SEM images showed that only resin cracks in the double‐layer 3DWSC and no fiber breakage and delamination, indicating exceptional mechanical stability of the as‐prepared double‐layer 3DWSC. This work can serve as a reference for the design and fabrication to multi‐layer 3DWSC, a promising material in the field of high‐performance composites.

Molding and verification of dielectric constant of three-dimensional woven spacer composites

In this paper, a theoretical model was proposed for predicting the dielectric constant of 3DWSCs as a function of the fiber volume fraction and the composites’ structure. In addition, the formula for the dielectric constant of the spacer layer in this model can be extended to other sandwich composites. 3DWSCs with heights of 6mm, 8mm and 10mm were prepared, and their dielectric constant was obtained by experimental measurement, model prediction and finite element simulation. The results showed that the predicted value of the model was in good agreement with the measurement results and the finite element results, and the maximum errors were 2.5% and 4.9%, respectively. The model will increase the feasibility of designing the dielectric properties of 3DWSCs, which was of great help and convenience to its applications such as radome or microstrip antenna.

Experimental investigation on mechanical behavior of 3D integrated woven spacer composites under quasi-static indentation and compression after indentation: Effect of indenter shapes

This paper presents an experimental study on the mechanical response of 3D integrated woven spacer carbon fiber composites under quasi-static indentation (QSI) and the failure behavior under compression after indentation (CAI). The test specimens are divided into weft direction ones (X-type) and warp direction ones (Y-type). The quasi-static indentation process is conducted using four types of indenters: the hemispherical indenter, the flat indenter, the conical indenter, and the pyramid indenter. A C-scan ultrasonic imaging system and a digital microscope are used to evaluate the damage visibility and penetration resistance of 3D integrated woven spacer composites during the QSI test. The digital image correlation (DIC) is used to perform the CAI analysis. The results indicate that the flat indenter has the largest indentation damage area (395 mm2 for X-type specimens, 398 mm2 for Y-type specimens), and the average indentation damage area caused by the four indenters is less than twice of the maximum cross-sectional area of each indenter. The maximum absorbed energy of two types of 3D integrated woven spacer composites is very similar in QSI tests under the same indenter. It is found that the residual strength of the X-type specimen decreases by 51.7% and that of the Y-type specimen decreases by 35.8% after the flat indenter penetrates the specimen.

Friction and Heat Transfer in Membrane Distillation Channels: An Experimental Study on Conventional and Novel Spacers.

The results of an experimental investigation on pressure drop and heat transfer in spacer-filled plane channels, which are representative of Membrane Distillation units, are presented and discussed. Local and mean heat transfer coefficients were obtained by using Thermochromic Liquid Crystals and Digital Image Processing. The performances of a novel spacer geometry, consisting of spheres that are connected by cylindrical rods, and are hereafter named spheres spacers, were compared with those of more conventional woven and overlapped spacers at equal values of the Reynolds number Re (in the range ~150 to ~2500), the pitch-to-channel height ratio, the flow attack angle and the thermal boundary conditions (two-side heat transfer). For any flow rate, the novel spacer geometry provided the least friction coefficient and a mean Nusselt number intermediate between those of the overlapped and the woven spacers. For any pressure drop and for any pumping power, the novel spacer provided the highest mean Nusselt number over the whole Reynolds number range that was investigated. The influence of buoyancy was also assessed for the case of the horizontal channels. Under the experimental conditions (channel height H ≈ 1 cm, ΔT ≈ 10 °C), it was found to be large in empty (spacer-less) channels that were up to Re ≈ 1200 (corresponding to a Richardson number Ri of ~0.1), but it was much smaller and limited to the range Re < ~500 (Ri < ~0.5) in the spacer-filled channels.

Recent Advances in Woven Spacer Fabric Sandwich Composite Panels: A Review.

Because of the advantageous characteristics of strong integrity, lightweight, high performance, and various designs, woven spacer fabric (WSF) and its composite are extensively used in construction, traffic, and aerospace, among other fields. This paper first describes the WSF structure, including core yarns and cross-linking, and then discusses the influence of the processing parameters, among angle of the wall decisive the failure mode on the plate properties. Moreover, we summarize the molding and filling technology of WSF composite sandwich panels and discuss the process order, resulting in a significant effect on the stiffness of the sandwich composite plate; the current processing is mostly hand lay-up technology. In addition, we introduce the core and matrix material of the sandwich composite plate, which are mainly polyurethane (PU) foam and epoxy resin (70% of matrix material), respectively. Finally, the mechanical properties of WSF composite sandwich panels are summarized, including bending, compression, impact, shear, and peel properties. Factors influencing the mechanical properties are analyzed to provide a theoretical basis for future plate design and preparation.

Ultra‐lightweight 3D woven spacer integrated composites with stabilization of dielectric and robust mechanical properties at room and elevated temperatures

AbstractPolymer matrix composites with lightweight, low dielectric constant (ε) and dielectric loss tangent (tan δ), high‐temperature resistance, and excellent mechanical properties are urgently needed in the fields of aviation, aerospace, transportation, and wireless communication services. In this work, 3D woven spacer Kevlar/polyimide composites (3DKPC) with excellent dielectric properties and robust mechanical properties were designed and obtained by combining 3D weaving technology and thermal imidization process. Results show that the volume density of the prepared composites is as low as 0.24 g·cm−3, but its compressive strength can be up to 6.24 MPa. The dielectric constant and loss tangent of 3DKPC at room temperature are extremely low, with the value of ~1.32 and 6.9 × 10−3, respectively. Moreover, the compressive strength retention rate is more than 96% and the dielectric constant can be consistently lower than 1.36 when the temperature increases from 25 to 300°C, demonstrating the outstanding mechanical and dielectric stability of 3DKPC. In addition, as an application example of resulting composites, a microstrip antenna with 3DKPC as the substrate material was designed, followed by the simulation of its electromagnetic properties via High Frequency Structural Simulator. The results display that the gain of the microstrip antenna is 6.2 dB, which is superior to those of many other reported microstrip antennas, indicating that the 3DKPC proposed here has great application potential in aerospace, wireless communication, and other fields.

Low-velocity impact and compression after impact behavior of 3D integrated woven spacer composites

Due to their superior overall properties, 3D integrated woven spacer composites overcome the weakness of traditional sandwich composites under low-velocity impact (LVI). The dynamic response of carbon fiber 3D integrated woven spacer composites under LVI and failure behavior under compression after impact (CAI) were experimentally investigated in this work. The impact damage patterns were analyzed using ultrasonic C-scan and micro-CT techniques at various energy, while digital image correlation (DIC) was used for CAI analysis. The results indicate that the impact damaged areas of X-type specimens is 365.1 mm2 under the impact energy of 7 J, while that of Y-type specimens is 371.4 mm2. The maximal absorbed energy is very close for two types of 3D integrated woven spacer composite specimens, which is about 6.99 J. The residual strength of X-type specimens decreases by 38.9% after the impact energy of 7 J, while that of Y-type specimens is reduced by 24.6%. The damage mechanism of the composites under LVI and CAI was obtained, which can provide some guidance for designing more suitable 3D integrated woven spacer composite structures in engineering practice.

Ultra-high compressive strength of 3D woven spacer composites with bulked glass fiber and saturated resin absorption

Three-dimensional woven spacer composites (3DWSCs) have a great potential to applied in aerospace or transportation fields due to their high strength-to-weight and stiffness-to-weight ratios, with excellent skin-core debonding resistance. Among these properties, the compressive strength of the 3DWSCs which is most critical, and still needs to be improved to meet the highly requirements in practical applications. In this study, we designed and manufactured 3DWSCs with highly enhanced compressive strength and energy absorption by adopting bulked glass fibers (BGFs) as pile yarns to weave its core layer to absorb more epoxy resin. Consequently, the specific compressive strength of 3DWSCs woven by BGFs as pile yarns with saturated epoxy resin absorption was 52.54 MPa g−1 cm3, 180% higher than that of the 3DWSCs woven by regular glass fiber (RGFs). Furthermore, the work of fracture of 3DWSCs woven by BGFs as pile yarns with saturated epoxy resin absorption was 14.82 N m, which enhanced 474% compared with that of 3DWSCs woven by RGFs. The failure cross sections depicted multiple brittle fractures of the pile yarns for both composites under compression, which caused multiple peaks in their stress–strain curves.

Low-Velocity Impact Response on Glass Fiber Reinforced 3D Integrated Woven Spacer Sandwich Composites.

This study presents an experimental investigation on the low-velocity impact response of three-dimensional integrated woven spacer sandwich composites made of high-performance glass fiber reinforced fabric and epoxy resin. 3D integrated woven spacer sandwich composites with five different specifications were produced using a hand lay-up process and tested under low-velocity impact with energies of 5 J, 10 J, and 15 J. The results revealed that the core pile’s heights and diverse impact energies significantly affect the stiffness and energy absorption capacity. There is no significant influence of face sheet thickness on impact response. Moreover, the damage morphologies of 3D integrated woven spacer sandwich composites under different impact energies were analyzed by simple visualization of the specimen. Different damage and failure mechanisms were observed, including barely visible damage, visible damage, and clearly visible damage. Moreover, it was noticed that the damage of 3D integrated woven spacer sandwich composites samples only constraints to the impacted area and does not affect the integrity of the samples.