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Yarn supercapacitors, as knittable and weavable energy storage devices, are attracting more and more attention in recent years. Similar to various yarns with different physical and mechanical properties available in textile industry, different yarn supercapacitors should be developed as well. However, as a device, stretchable yarn supercapacitors suffer a lot from limited stretchability, complicated and high cost fabrication, which greatly restrict their wide adoptions. Here, we use urethane elastic fiber core spun yarns (UY) with intrinsic high stretchability for the first time, as a wearable scaffold for hosting conductive CNT and electrocapacitive PPy to fabricate large-scale highly stretchable yarn electrodes via a simple two-step process (CNTs dipping and PPy electrodeposition). The yarn supercapacitor keeps the excellent stretchability of the UY without using any extra stretchy substrate or wavy structure as most stretchable yarn supercapacitors used, and at the same time, exhibits a high areal capacitance of 69 mF cm −2 (normalized to two electrodes) as well as a good rate capacity. Furthermore, the capacitive performance of the yarn supercapacitor remains nearly unchanged even at a high strain of 80%. The high-performance stretchable yarn supercapacitor with the use of intrinsically stretchable yarns paves a way for the production of large-size fabrics for wearable electronic applications.

Poisson’s ratio (PR) is defined as the negative ratio between the lateral strain and the longitudinal strain of a material under tensile or compressive loading condition. Auxetic fabrics are those having a negative PR, which means that when their longitudinal strain is positive, their lateral strain is also positive, and vice versa. In this work, tensile and forming properties of auxetic warp-knitted spacer fabrics were investigated and compared with those of the conventional warp-knitted spacer fabrics. Both uniaxial tensile tests and hemispherical compression experiments were conducted, and the relationships of the tensile and forming properties with the auxetic effect were discussed in terms of different fabric structural parameters. The results show that the auxetic warp-knitted spacer fabrics have a prolonged low stress stage in the wale direction, indicating that they are more prone to undergo deformation along the wale direction, and fabric with a longer low stress stage has a better auxetic effect. The results also show that the formability of auxetic warp-knitted spacer fabrics is much better than that of conventional warp-knitted spacer fabrics, due to the much low forming energies required under hemispherical compression, which can be affected by many factors such as auxetic effect, fabric thickness and stiffness, yarn materials and the structure of the spacer layer. When all other parameters are similar, auxetic fabric with a better auxetic effect will have better formability. The study has provided useful information for the design and application of this type of nonconventional spacer fabrics.

Great progress has been made in the research of self-healing materials in recent decades, however, there are still great challenges in achieving high mechanical strength and wide scratch healing simultaneously. Herein, a novel polyurethane elastomer (PUDA) containing polycaprolactone (PCL) soft segments and Diels-Alder (DA) adducting structure was specially designed and synthesized. The experimental results show that the PUDA elastomer after being trained not only had ultrahigh mechanical strength, but also had satisfactory ability in healing of wide scratches. It was found that the elastomer displayed a high tensile strength up to 32.88 MPa, which is unprecedented when compared to those reported self-healing elastomers. The PUDA elastomer material also had excellent healing ability towards wide scratches: an 80-μm-wide scratch could be completely healed after heating at 110°C for 6 min. Furthermore, the elastomer material could also attain more than 100 % recovery of mechanical strength, with its recovered tensile strength reaching up to 34.58 MPa. The developed PUDA elastomer demonstrates quite promising perspective in material science and engineering field, especially for the protection of surface coating.

This paper reports the tensile deformation behavior of an auxetic warp-knitted spacer fabric structure by using the finite element (FE) method. The precise geometry of the outer layer structure of the fabric was firstly obtained from a micro X-ray computerized tomography scan and then inputted to an ANSYS 13.0 software to generate geometrical models. The geometrical models were then meshed using the PLANE 183 element to build FE models. Based on the FE models built, deformation behaviors of the auxetic fabric in the course direction and wale direction were simulated and compared with experimental results. The FE analysis showed that the simulated fabric deformations at different tensile strains were very close to the real fabric deformations and the FE-generated Poisson’s ratio-strain curves agreed well with the experimental ones. Therefore, the FE models could be used for predicting the deformation behaviors of the auxetic warp-knitted spacer fabric stretched in different fabric plane directions.

Auxetic materials are a kind of non-conventional materials having negative Poisson’s ratio. They laterally expand when stretched or laterally shrink when compressed. Compared to conventional materials, auxetic materials have a number of enhanced properties that could be very interesting for some special applications. This paper reviews the latest achievements in auxetic materials, including their properties, structures and applications. A special discussion on their potential applications in textiles is also made. It is expected that this review could provide some useful information for the future development of auxetic textile materials.

Auxetic spacer fabrics are a novel kind of three-dimensional (3D) fabric structure with a negative Poisson’s ratio. They have found a number of applications in functional garments, protective pads and sportive shoes due to their unusual properties. In this paper, a study on deformation behaviors of 3D spacer fabrics that could be fabricated on a large scale is reported. Through experimental observations of deformation of a basic hexagonal unit at different tensile strains, two different geometrical models are proposed for the fabric structure when extended in the course direction and wale direction, respectively. Based on the geometrical models, two semi-empirical equations between the Poisson’s ratio and tensile strain are established for both tensile directions. The study shows that the established semi-empirical equations fit well with experimental results. Therefore, they could be used in the design and prediction of 3D auxetic spacer fabrics with different values of geometrical parameters.

Auxetic fabrics have gained an increasing attention in the auxetic material area in recent years. Especially, auxetic fabrics fabricated based on both weft-knitted and warp-knitted structures have made some important progress. However, all the knitted auxetic fabrics reported so far are fabricated based on 2D knitted structures, although some of the weft-knitted auxetic fabrics are finally formed into 3D forms. This paper reports a novel kind of 3D auxetic fabric fabricated based on a warp-knitted spacer structure with adoption of a special geometrical configuration which is formed with parallelograms. The auxetic behavior of these fabrics is discussed in terms of tensile direction, geometrical parameter, and repeated extension. The shape fitting ability on a spherical surface is also demonstrated. The results shows that the 3D auxetic fabrics have auxetic behavior in all the fabric plane directions and the highest auxetic effect is obtained when stretched in the weft direction of the fabric. The 3D auxetic fabrics also display an excellent shape fitting ability, which makes them very attractive for various applications where fitting to the human body's shape is highly required, such as bra cups, protectors for knees and elbows, shoes covers, etc.

Flat knitting is a widely used fabric manufacturing technology. Compared with warp knitting and circular knitting, flat knitting is characterized by its higher process flexibility and greater fabric structure variety. In this work, flat knitting technology was exploited to fabricate auxetic fabrics which laterally expand when stretched. Three kinds of geometrical structures, i.e. foldable structure, rotating rectangle and reentrant hexagon, were employed as basic reference structures for the development of these kinds of auxetic fabrics. The weft knitting processes based on these structures were specially developed and auxetic fabrics were fabricated using the computerized flat knitting machines. The Poisson’s ratio-strain curves of the developed fabrics were plotted and compared with those calculated using existing models to demonstrate the variation trends of Poisson’s ratio with the axial strain. The results reveal that except the folded fabric formed with the face loops and reverse loops in a rectangular arrangement, of which the auxetic effect firstly increases and then decreases with the axial strain, the auxetic effects of all other fabrics decrease with an increase of the axial strain. The work also shows that auxetic fabrics can be realized based on knitted structures and that flat knitting technology can provide a simple, but highly effective way of fabricating auxetic fabrics from conventional yarns.

This paper investigates the influence of waterproof fabrics on heat and moisture transfer through a clothing system. The water vapor permeability (WVP) for the outside layer was derived from published experimental data, and was considered to be a factor influencing the mass transfer coefficient at the boundary exposed to the environment. The analysis was carried out by using a mathematical model that describes the coupled heat and moisture transfer in porous textiles. The numerical simulation reveals a significant influence of water proof fabrics on the dynamic moisture content distribution in fabrics⁄fibers, moisture vapor condensations and the liquid transfer behavior inside the clothing. The research has shown the potential usage of the mathematical simulation in evaluating the performance of different waterproof and breathable fabrics in clothing systems, as well as the potential usage in the product development of functional apparel.