Search Results (7)

Auxetic textiles, characterized by a negative Poisson’s ratio, offer considerable promise for innovative applications across multiple fields. In our earlier work, Miura-ori-inspired auxetic fabrics with three different initial dihedral fold angles—30°, 45°, and 60°—were successfully fabricated via jacquard weaving. Their fundamental auxetic behaviors were evaluated, showing deformation characteristics consistent with those in their geometric models. This study further investigates the mechanical properties of Miura-ori-based auxetic woven fabrics. Tensile testing, air permeability measurement, compression performance assessment, and repeated-loading cyclic rope-stretching tests were performed on the three fabric variants. The results show that the fabrics exhibit excellent air permeability, which increases with the proportion of the folded areas; the highest air permeability was observed at Miura-30°. Moreover, Miura-60° exhibited superior compression resistance. The fabrics also demonstrated outstanding structural stability under cyclic tensile loading, exhibiting optimal elastic recovery at the 30° configuration. Collectively, these findings provide a solid theoretical basis for future applications of Miura-ori auxetic woven fabrics. Full article

The assessment of the dynamic mechanical performance of fiber-reinforced composites has gained importance in specific high-tech applications like aerospace and automobiles. However, three dimensional (3D) auxetic reinforcements offering viable performance have remained unexplored. Hence, this study investigates the energy absorption capabilities and high strain impact behaviors of 3D woven fabric-reinforced composites. Three different types of 3D woven reinforcements i.e., warp interlock (Wp), weft interlock (Wt), and bidirectional interlock (Bi) were developed from jute yarn, and their corresponding composites were fabricated using polycarbonate (PC) and polyvinyl butyral (PVB). Out-of-plane auxeticity was measured for reinforcements while composites were analyzed under dynamic tests. Wp exhibited the highest auxeticity with a value of −1.29, Bi showed the least auxeticity with a value of −0.31, while Wt entailed an intermediate value of −0.46 owing to variable interlacement patterns. The dynamic mechanical analysis (DMA) results revealed that composite samples developed with PC resin showed a higher storage modulus with the least tan delta values less than 0.2, while PVB-based samples exhibited higher loss modulus with tan delta values of 0.6. Split Hopkinson pressure bar (SHPB) results showed that, under 2 and 4 bar pressure tests, PVB-based composites exhibited the highest maximum load while PC-based composites exhibited the least. Warp interlock-based composites with higher auxeticity showed better energy absorption when compared with the bidirectional interlock reinforcement based (with lower auxeticity) composites that exhibited lower peak load and energy dissipation. Full article

Auxetic textiles are emerging as an enticing option for many advanced applications due to their unique deformation behavior under tensile loading. This study reports the geometrical analysis of three-dimensional (3D) auxetic woven structures based on semi-empirical equations. The 3D woven fabric was developed with a special geometrical arrangement of warp (multi-filament polyester), binding (polyester-wrapped polyurethane), and weft yarns (polyester-wrapped polyurethane) to achieve an auxetic effect. The auxetic geometry, the unit cell resembling a re-entrant hexagon, was modeled at the micro-level in terms of the yarn’s parameters. The geometrical model was used to establish a relationship between the Poisson’s ratio (PR) and the tensile strain when it was stretched along the warp direction. For validation of the model, the experimental results of the developed woven fabrics were correlated with the calculated results from the geometrical analysis. It was found that the calculated results were in good agreement with the experimental results. After experimental validation, the model was used to calculate and discuss critical parameters that affect the auxetic behavior of the structure. Thus, geometrical analysis is believed to be helpful in predicting the auxetic behavior of 3D woven fabrics with different structural parameters. Full article

Textiles-fibres, yarns and fabrics are omnipresent in our daily lives, with unique mechanical properties that fit the design specifications for the tasks for which they are designed. The development of yarns and fabrics with negative Poisson’s ratio (NPR) is an area of current research interest due to their potential for use in high performance textiles (e.g., military, sports, etc.). The unique braiding technology of interlacement for preparation of braided helically wrapped yarns with NPR effect with later development of auxetic woven fabric made it possible to avoid the slippage of the wrapped component from the core. The applied geometrical configuration and NPR behaviour of the braided helical yarn structure with seven different angles comprising of monofilament elastomeric polyurethane (PU) core with two wrap materials that include multifilament ultra-high molecular weight polyethylene (UHMWPE) and polyethylene terephthalate (PET) fibres were investigated and analysed. The mechanically stable 2D woven textile auxetic fabrics (AF) with various weave patterns such as 2/2 matt and 3/1 twill were developed from the auxetic yarn with PU elastomer core having maximum NPR effect of −1.70 using lower wrapped angle of 9° to study and compare their mechanical responses. The auxetic yarn was used in weft direction and multifilament UHMWPE yarn in warp direction, using semi-automatic loom. Auxeticity of AF was analysed and its various mechanical properties such tensile strength, impact energy absorption, in-plane, and out-of-plane auxeticity, and puncture resistance were studied. Higher energy absorption of 84 Nm for matt fabric was seen compared to twill fabric having an energy of 65 Nm. The puncture resistance capability of matt fabric was better than twill fabric. While twill fabric exhibited better auxetic effect in both in-plane and out-of-plane mode compared to matt fabric. In short, both the twill and matt design AF’s showed unique characteristics which are beneficial in making various protective textiles such as protective helmets, bullet proof shields, cut resistance gloves, blast resistant curtains, and puncture tolerant elastomeric composites. Full article

The current research is focused on the design and development of auxetic woven structures. Finite element analysis based on computational modeling and prediction of axial strain as well as Poisson’s ratio was carried out. Further, an analytical model was used to calculate the same parameters by a foldable zig-zag geometry. In the analytical model, Poisson’s ratio is based on the crimp percentage, bending modulus, yarn spacing, and coefficient of friction. In this yarn, properties and fabric parameters were also considered. Experimental samples were evaluated for the actual performance of the defined auxetic material. Auxetic fabric was developed with foldable strips created in a zig-zag way in the vertical (warp) direction. It is based on the principle that when the fabric is stretched, the unfolding of the folds takes place, leading to an increase in transverse dimensions. Both the analytical and computational models gave close predictions to the experimental results. The fabric with foldable strips created in a zig-zag way in the vertical (warp) direction produced negative Poisson’s ratio (NPR), up to 8.7% of axial strain, and a maximum Poisson’s ratio of −0.41 produced at an axial strain of around 1%. The error percentage in the analytical model was 37.14% for the experimental results. The computational results also predict the Poisson’s ratio with an error percentage of 22.26%. Such predictions are useful for estimating the performance of auxetic woven structures in composite reinforcement. The auxetic structure exhibits remarkable stress-strain behavior in the longitudinal as well as transverse directions. This performance is useful for energy absorption in composite reinforcement. Full article

This paper reports the auxetic behavior of modified conventional non-woven fabric. The auxetic behavior of fabric was achieved by forming rotating square unit geometry with a highly ordered pattern of slits by laser cutting. Two commercial needle-punched non-woven fabric used as lining and the reinforcement fabric for the footwear industry were investigated. The influence of two rotating square unit sizes was analyzed for each fabric. The original and modified fabric samples were subjected to quasi-static tensile load by using the Tinius Olsen testing machine to observe the in-plane mechanical properties and deformation behavior of tested samples. The tests were recorded with a full high-definition (HD) digital camera and the video recognition technique was applied to determine the Poisson’s ratio evolution during testing. The results show that the modified samples exhibit a much lower breaking force due to induced slits, which in turn limits the application of such modified fabric to low tensile loads. The samples with smaller rotating cell sizes exhibit the highest negative Poisson’s ratio during tensile loading through the entire longitudinal strain range until rupture. Non-woven fabric with equal distribution and orientation of fibers in both directions offer better auxetic response with a smaller out-of-plane rotation of rotating unit cells. The out-of-plane rotation of unit cells in non-homogenous samples is higher in machine direction. Full article

Auxetic plied yarns are specially constructed with two types of single yarns of different sizes and moduli. This paper investigates how to use these types of yarns to produce woven fabrics with auxetic effects. Four-ply auxetic yarns were first incorporated into a series of woven fabrics with different design parameters to study their auxetic behavior and percent open area during extension. Effects of auxetic plied yarn arrangement, single component yarn properties, weft yarn type, and weave structure were then evaluated. Additional double helical yarn (DHY) and 6-ply auxetic yarn woven fabrics were also made for comparison. The results show that the alternative arrangement of S- and Z-twisted 4-ply auxetic yarns in a woven fabric can generate a higher negative Poisson’s ratio (NPR) of the fabric. While the higher single stiff yarn modulus of auxetic yarn can result in greater NPR behavior, finer soft auxetic yarn does not necessarily generate such an effect. Weft yarns with low modulus and short float over the 4-ply auxetic yarns in fabric structure are favorable for producing high NPR behavior. The weft cover factor greatly affects the variation of the percent open area of the 4-ply auxetic yarn fabrics during extension. When different kinds of helical auxetic yarns (HAYs) are made into fabrics, the fabric made of DHY does not have the highest NPR effect but it has the highest percent open area, which increases with increasing tensile strain. Full article