Fig 6 - uploaded by Hong Hu
Content may be subject to copyright.
Microstructure of fabric's outer layer: a assembly of monofilaments within outer layers, b microstructure of internal side of fabric's outer layer
Source publication
Mechanical properties of a 3D spacer fabric are determined both by mechanical properties of its components and its unique structure. However, at present, there is no well-received method to describe the mechanical performance of a 3D spacer fabric. In this article, numerical methods are used to analyze a compression mechanism of a typical 3D spacer...
Contexts in source publication
Context 1
... and relative positions of respective monofilaments. The geometry models for them are generated as shown in Fig. 5. However, the heights of monofilaments are not as same as the fabric's thickness. According to the structure of the outer layers, the monofilaments are actually laying (2012) 47:3989-3999 3991 down with the wrap of multifilament (Fig. 6). Therefore, the effective height of the geometry models for monofila- ments is defined as 7.192 mm, which subtracts two radi- uses of the monofilaments from the measured overall thickness of the fabric. There are three different shapes of monofilaments in the fabric: monofilament 1, monofilament 2, and monofilament 3. The differences ...
Context 2
... the shapes and dimensions of monofilaments were determined, the boundary conditions of monofilaments have to be defined. Figure 6a shows the structure of the monofilaments in the outer layers by numerical filtering out the multifilaments. In the real fabric, the monofilaments are knitted within the outer layers and wrapped by the multifilament, as shown in Fig. 6b. ...
Context 3
... and dimensions of monofilaments were determined, the boundary conditions of monofilaments have to be defined. Figure 6a shows the structure of the monofilaments in the outer layers by numerical filtering out the multifilaments. In the real fabric, the monofilaments are knitted within the outer layers and wrapped by the multifilament, as shown in Fig. 6b. Due to the nature of the fabrics, there are voids in the structure. It is clear that the structure of the outer layers is complex and discontinuous. When an external load is applied to such kind of structure, the contacts, friction and slide between monofilaments and multifilaments occur. Especially, the contacts between monofilaments ...
Context 4
... and multifilaments are hard to predict, and this could affect the overall mechanical properties significantly. Therefore, the degrees of freedom of monofilaments are very complicated. They are difficult to determine and are affected by both the designed struc- ture and the manufacturing process. According to the geometry model of CT scanning (Fig. 6), the ends of monofilaments are entangled by other monofilaments and are wrapped by multifilaments. When the monofilaments are under loading, their endpoints hardly have any degrees of freedom along translational axes. But their rotational degrees of freedom could exist. The rotational degree of freedom about x axis certainly is ...
Similar publications
For numerous constitutive models are established based on the coaxial theory and validated only under biaxial compression condition, the soil behavior is inaccurately described under the true triaxial condition. A 3D non-coaxial elasto-plasticity model with a novel surface shape was proposed to simulate stress-strain curves before bifurcation and t...
Citations
... 20,21 A constitutive model was developed to characterize quasi-static compression mechanics and predict dynamic impact energy absorptions of spacer fabrics. 22,23 Various finite element (FE) models have been reported to explore the factors affecting the compression properties of spacer fabrics [24][25][26][27][28][29] or to establish geometric structure-property relationships. [30][31][32] However, previous studies have focused only on the deformation of spacer yarns and the interaction between spacer yarns and outer layers. ...
... A precise unit geometric model obtained by X-ray micro-computed tomography (μCT) scanning the fabric presented in Figure 1 is adopted to build a full-size FE model at the yarn level. [24][25][26][27][28][29][30][31][32] The FE model is validated by the compression test results. The partial auxetic mechanism of the 3D mesh fabric is identified from the global to local analysis. ...
The 3D mesh fabric is a key component of automotive seat ventilation systems as it has good compression resistance and creates channels to provide effective circulating airflow. The dimensional inconsistency of fabric sheets by laser cutting to be integrated into car seats and their unrecoverable dimension changes in subsequent cushioning applications are challenging problems. A typical commercialized 3D mesh fabric was observed to shorten and widen under compression, showing an auxetic behavior in the length–thickness section. This counterintuitive partial auxetic behavior accounts for the dimensional variation. A full-size finite element (FE) model of the fabric was established to simulate the complex fabric deformation based on the precise geometry of a unit cell obtained by X-ray micro-computed tomography (μCT) scanning. The FE simulation reproduced the planar dimension change process of the fabric. The underlying mechanism of partial auxeticity was revealed from the global to local analysis, including fabric global deformation, unit meshes deformation and unit cell geometric structure change. It was shown that buckling of initially post-buckled spacer monofilaments drives in-plane movements of monofilament loops to cause partial auxetic behavior. The partial auxeticity weakens in the compression process due to the gradual intercontact and densification of spacer monofilaments. Different constraints on monofilament loops from adjacent unit cells and multifilament inlays make the deformation uneven in the plane of fabric. It is important to fully analyze the dimensional change, especially the partial auxetic deformation, of the 3D mesh fabric under compression for its practical applications.
... Orlik et al. calculated the effective elastic properties of spacer fabrics by using homogenization techniques [23]. Hou et al. conducted an FE study on a spacer fabric by considering the contacts between the spacer monofilaments and outer layers, in which the initial geometries of the spacer monofilaments were calculated from the structural parameters [24]. Liu et al. reported a FE study on a typical spacer fabric based on the precise geometry of a unit cell reconstructed from μCT scanning by considering the interactions among all the fabric components and the material's nonlinearity [4]. ...
Three-dimensional spacer fabric is a type of one-piece sandwich structure consisting of two outer layers and vertical and inclined spacer monofilaments. It behaves like a cushioning material, having linear, plateau, and densification stages under compression. This article elucidates the compression mechanism of a typical spacer fabric in terms of global deformation , local deformation, and internal contact behavior of spacer monofilaments through finite element simulation. While the linear stage is post-buckling of spacer monofilaments with tight constraints, the plateau stage is a combination of post-buckling, torsion, rotation, and contact of spacer monofilaments. The densification stage is attributed to the contact between spacer monofilaments and outer layers, which decreases the effective length to bear the load and enhances the constraints on the spacer monofilaments. The vertical spacer monofilaments with almost triple the normal strains of the inclined ones contribute more to compression resistance.
... 18,19 , but the spacer monofilament geometries were still not realistic, and the material models were linear elasticity. X-ray micro-computed tomography (μCT) was used to scan spacer fabrics with meshed 7,8,[20][21][22][23] or closed outer layers [24][25][26][27] to obtain authentic geometries of spacer monofilaments. The true geometries and material nonlinearity of spacer monofilaments were employed to establish FE models for those fabrics with closed surfaces by treating the outer layers as isotropic and elastic plates. ...
... The true geometries and material nonlinearity of spacer monofilaments were employed to establish FE models for those fabrics with closed surfaces by treating the outer layers as isotropic and elastic plates. [25][26][27] The verified FE models indicate that linear elasticity and plateau stages are mainly a result of post-buckling and rotation of spacer monofilaments, while torsional deformation and contacts among spacer monofilaments dominate in the densification stage. [25][26][27] The outer layers of finished spacer fabrics with closed surfaces are nearly the same as those of the as-knitted fabrics. ...
... [25][26][27] The verified FE models indicate that linear elasticity and plateau stages are mainly a result of post-buckling and rotation of spacer monofilaments, while torsional deformation and contacts among spacer monofilaments dominate in the densification stage. [25][26][27] The outer layers of finished spacer fabrics with closed surfaces are nearly the same as those of the as-knitted fabrics. [11][12][13] By contrast, the outer layers of 3D mesh fabrics, which are initially closed, should be stretched coursewise to form different sizes of meshes in the stentering and heat-setting process. ...
Three-dimensional (3D) mesh fabric is a key component in ventilated car seats for its excellent cushioning and ventilating performance. It is produced by stretching an as-knitted spacer fabric with closed surfaces via stentering and fixing the mesh form via heat-setting. This paper analyzes the effect of stentering and heat-setting processes on the structures and compression properties of a typical and commercial 3D mesh fabric by using X-ray micro-computed tomography (μCT) and finite element (FE) models. The monofilament architectures of the fabric after knitting, stentering, and heat-setting are reconstructed from μCT scanning, and the structural evolution is quantitatively investigated in terms of global dimension change, curvature, and torsion. The results from μCT reconstructions demonstrate that stentering shortens, widens, and thins the fabric due to yarn transfer to shorten monofilament loops and lengthen spacer monofilaments, which are then dispersed, bent, and twisted to increase the curvatures and torsions. The FE simulations indicate that the global and local monofilament architecture deformation shifts the fabric compression mode from constrained post-buckling to concurrent tilting and post-buckling of spacer monofilaments, expanding the plateau stage and decreasing plateau stress. Heat-setting shrinks monofilament and therefore deteriorates its mechanical performance. The fabric is further thinned during the heat-setting process, which also further bends and twists spacer monofilaments to slightly decrease the plateau stress. The structures and cushioning performance of 3D mesh fabrics can be engineered by employing a proper stentering ratio followed by a heat-setting process.
... A specialized constitutive model was proposed to capture the complex compression characteristics of spacer fabrics and predict impact behaviour and energy absorption [12,13]. Finite element (FE) methods have also been used to simulate the compression behaviour of spacer fabrics [14][15][16][17][18]. Some FE models conducted parametric studies based on simplified geometric models to examine the structure-property relationships [14,15]. ...
... Some FE models conducted parametric studies based on simplified geometric models to examine the structure-property relationships [14,15]. Precise geometries of spacer monofilaments obtained from Micro X-ray computed tomography (µCT) scanning were adopted to reveal the compression mechanism of spacer fabrics [16][17][18]. ...
Three-dimensional (3D) mesh fabric has a one-piece sandwich structure, consisting of two separate outer layers linked together with a layer of spacer monofilaments. Its intermeshed monofilament architecture provides excellent cushioning and ventilation properties, making the 3D mesh fabric ideal for ventilated car seats. This paper presents a computational study to examine how stentering affects the mesh and monofilament structure of a typical 3D mesh fabric. Experimentally validated finite element (FE) models of the fabric stentering process and its compression following stentering were developed. The structural changes of the fabric in the stentering process were quantitatively analysed in terms of global fabric deformation, mesh deformation, and spacer monofilament deformation. The numerical and experimental results indicate that stentering opens up the meshes differently across the width, with the intermediate mesh being more open and uniform than the two selvage meshes. Stentering sufficiently is essential for obtaining a 3D mesh fabric with uniform meshes. Two adjacent wales of spacer monofilaments are inclined and twisted symmetrically in the stentering process. After stentering, the 3D mesh fabric has more inclined, twisted, and sparse spacer monofilaments, which reduces its compression resistance. By utilising different stentering ratios, 3D mesh fabrics can be engineered to form various monofilament architectures to suit a variety of different applications.
... Spacer yarn is found to have a significant impact on the thickness and compression stiffness of spacer fabric [26,27]. The compression stiffness of the spacer fabric can affect the change in the thickness of the fabric under pressure and hence the distance of the dielectric layer. ...
A five-layer weft-knit with a spacer structure is proposed as a capacitive sensor. The two cotton yarn outer layers provide insulation. The two inner layers that form the parallel electrode plates are separated by using a compressible spacer layer. Four samples with different monofilament yarns in the spacer layer are produced and evaluated. The results show that the pressure sensing range and sensitivity of the fabric sensor vary based on content and thickness of the spacer yarns. The fabric sensor is constructed by using a double-bed knitting machine as a novel means of textile sensor development.
... Some scholars prepared a three-dimensional spacer fabric thermal barrier, and found that its thermal protection performance and air permeability were improved compared with needle punched nonwoven felt. 16 The mechanism of the influence of material, 17 structure, 17 and thickness 18 on the performance of spacer fabric was studied to further optimize the performance of the thermal insulation layer. Yu et al. 19 prepared three-dimensional spacer fabric/hollow microspheres reinforced three-phase composites to obtain fabrics with certain supportability. ...
... Some scholars prepared a three-dimensional spacer fabric thermal barrier, and found that its thermal protection performance and air permeability were improved compared with needle punched nonwoven felt. 16 The mechanism of the influence of material, 17 structure, 17 and thickness 18 on the performance of spacer fabric was studied to further optimize the performance of the thermal insulation layer. Yu et al. 19 prepared three-dimensional spacer fabric/hollow microspheres reinforced three-phase composites to obtain fabrics with certain supportability. ...
The insulating layer of the hollow structure of thermal protective clothing plays a positive role in weight and thermal protection. The relationship between the hole shape and the performance of the hollow structure is of great importance to optimization. This paper focuses on the performance optimization of the honeycomb structure insulation layer. Laser cutting technology was used to cut the hole in the non-woven fabric. The thermal insulation layers of five common three-dimensional sections were prepared by the multi-layer composite method. Compared with the conventional solid fabric system, the honeycomb fabric system has better thermal protection. At the same time, the section structure also affects the thermal protection performance. The developed A-type structure possesses a superior Thermal Protective Performance value in comparison to I-type straight structure. It has lower moisture resistance and higher total heat loss. The thermal protection of A-type section structure, together with excellent thermal and moisture comfort, make it put forward the improvement direction for the structural optimization of commercial nonwovens where the balance between thermal protection and thermal and moisture comfort is the key requirement.
... Several studies have been conducted on the effect of compression properties of weft-knitted spacer fabric. Hou, Hu and Silberschmidt revealed that the mechanical properties of monofilaments directly affect that of the spacer fabric [9]. Hamedi et al. used shape memory alloy as the spacer yarn to increase the energy absorption capacity of the weft-knitted spacer fabric [10]. ...
Spacer fabrics are commonly used as cushioning materials. Their compression properties are one of the most important concerns in determining their specific end-use. Therefore, it is time and cost- efficient to have another means available that could allow quick and easy modifications to the compression behaviour of spacer fabrics and control them too. In this study, a method that uses an elastic inlay is adopted to modify the physical and compression properties of spacer fabrics. Fifteen samples constructed with different spacer structures and inlay yarns and patterns were fabricated and then evaluated. The results show that spacer fabrics with different thicknesses, densities and compression behaviours can be obtained by using different inlay patterns and elastic yarns. Increasing the number of miss stitches in the inlay pattern can help to increase the thickness and stiffness of spacer fabric and withstand a higher compression strength. However, when the number of miss stitches further increases to 3 miss stitches between every tuck stitch, the irregularity of the spacer structure would increase and could show adverse effects to certain spacer structures. The spacer fabric made by incorporating an elastic inlay can retain air permeability and a lower fabric weight than that made by the knit stitches of elastic yarns together with the surface yarns. By changing the inlay pattern, a spacer fabric with different compression behaviours in different areas of the same fabric can be realised. This novel method can increase the flexibility of creating a spacer fabric with the desired properties.
... Brisa et al. [8] presented an FE model for a vertical spacer monofilament of a thick spacer fabric under compression by taking the contacts between the spacer monofilament and the outer layers into account during the compression process. Hou et al. [9,10] also conducted an FE study on a spacer fabric. In their study, the geometrical shapes of the spacer monofilaments were calculated by a nonlinear buckling analysis from the manufacturing parameters, and the outer layers were modelled as two isotropic planes. ...
This paper aims to identify the underlying physical mechanism for the compression deformation of a warp-knitted spacer fabric with a typical structure with experimental and theoretical studies. Compression tests were carried out to measure the load–displacement relationship of the fabric. The structural features of the spacer yarns were photographed by a microscope at different displacements during the compression test. A theoretical model based on elastica theory was developed to describe the compression behavior of the fabric by introducing the effect of complex geometry of the spacer yarns. A comparison between the experimental results and theoretical calculations was also conducted. Four distinctive stages including initial stage, elasticity stage, plateau stage and densification stage were identified and their underlying physical mechanisms were explained based on experimental observations and theoretical calculations. The model could provide an in-depth understanding on the deformations of spacer yarns of spacer fabrics under compression.
... Furthermore, numerical methods were also used to investigate the compression behavior of 3D spacer fabrics [25,26], syntactic-foam/glass fibre [27] composites, and core properties [28] of pile and foam-filled composites under compression and shear. ...
Three-dimensional woven spacer composites have great potential for use in different parts of automobiles and construction application due to their better mechanical performance. In literature, time-dependent compression and recovery behavior of three-dimensional woven spacer composites was not studied. In this study, three-dimensional woven spacer composites (three thickness levels) were evaluated under static and dynamic (time-dependent) compression and recovery. The static compressive strength of composites was reduced with the increase in sample thickness. Also, the highest amount of energy was absorbed during the fracture of 4 mm (Comp4) thick composite, followed by 10 mm (Comp10) and 20 mm (Comp20) thick composites. Compressibility (%) and resiliency (%) was highest in Comp4 but recovery (%) was a bit lower as compared to the Comp10 and Comp20, while recovery (%) was highest in 10 mm thick composite as compared to the 4 mm and 20 mm thick samples. Moreover, higher value of permanent deformation in thickness with time was observed in Comp20 showing higher creep followed by Comp4 and Comp10. Furthermore, Comp4 showed the highest values of work done during cyclic compression loading–unloading testing, presenting highest toughness.
... He used experimental data of material tests for his analytical model and performed also experiment of bended panel for comparison. Knitted spacer fabric was modelled by finite element method in [7]. ...
3D distance fabrics are modern and promising material for lightweight inflatable structures. The applications are used in sport, boats, tents, construction, military etc. Its advantages are large load capacity per unit weight, stiffness dependent on pressurized air, fail-safe structure. However, the mechanics of inflated fabric panel is not still described enough. This paper gives basic theory and its experimental verification about mechanical behaviour of distance fabrics. The mathematical model of air-inflated distance fabric panel is created based on analytical theory of cylindrical bending of plates. Material data of the fabric required for performing computations of the model are determined from tensile tests. The reliability of the analytical model is experimentally verified. For that purpose the air-inflated fabric panel was made and tested. Results obtained both experimentally and analytically are compared and discussed. The experiment proves the validity of the mathematical model and allows us to predict the behaviour of distance fabrics.
