Pibo Ma

Design and fabrication of auxetic warp-knitted structures with a rotational hexagonal loop

In this paper, the design, manufacturing and characterization of two-dimensional warp-knitted textiles with auxetic performance is reported. Four warp-knitted structures based on a rotational hexagonal structure are produced, and these structures can lead to a negative Poisson’s ratio mathematically. The testing results have confirmed that the knitting structure of the front bar, as well as let-off values of the front bar’s chain parts, has a great effect, and auxetic properties of the warp-knitted textiles have a complicated relationship with the rotation angle. These novel structures can expand the applied area of auxetic structures.

3-D dynamic behaviors simulation of weft knitted fabric based on particle system

In this work, a particle-based system is introduced to improve the sense of volume and reality of weft knitted fabric. This system is built through cuboid particle system to show the interlaced structures between the stitches. The particles are connected dynamically by the prism and diagonal of the cuboid which are acted as the springs to simulate the dynamic of the particles. The spatial displacement of particles is updated by using velocity-Verlet numerical integration to realize the 3-D dynamic simulation of weft knitted fabric. When simulating the thread, numbers of cylinders are inserted between adjacent bonding points. The coordinate of the cylinders is obtained by filters to make the thread look smooth. The queue template class in the Standard Template Library is also introduced to build the data structure. The spread depth of force is limited to ensure the accuracy of the calculation, and to reduce the amount of computation. The proposed method has provided a vivid and practical simulation with real-time performance.

A review on the impact tension behaviors of textile structural composites

The three-dimensional textile composites have excellent advantages of impact resistance, owing to their more integral microstructure and higher interlaminar shear strength than those of laminated composites. The composites are frequently used under impact loading in the practical application. Researches on the impact behaviors can help in the development and optimization of design for textile structural composites. In this review, the development and features of three types of textile structures, including weaving, knitting, and braiding have been introduced respectively, and the current and future potential applications of these kinds of textile structural composites have been described. The impact tension behaviors and the damage mechanisms of textile structural composites have been introduced. The finite element analysis and frequency domain analysis which to reveal the tensile damage mechanisms of textile structural composites under high strain rates also have been investigated. Furthermore, the future development of impact tension behaviors of textile structural composites is also introduced in this review.

Review on the knitted structures with auxetic effect

Abstract There are now different kinds of geometrical models for auxetic materials, such as re-entrant model, rotating model, nodule and fibril model, chiral model, liquid crystalline model, helical model and rod model for describing the angle-ply composites. Knitting technology, including plane and 3D warp knitting as well as weft knitting, is widely used in the manufacturing fields nowadays and has been adopted in fabric structure designing. Knitted fabrics with negative Poisson’s ratio have great potentials in both apparel and industries. The present article reviews the auxetic principles in general and in the specific context of knitted textile structures with auxetic potential made from conventional fibers.

Knitting Technologies And Tensile Properties Of A Novel Curved Flat-Knitted Three-Dimensional Spacer Fabrics

Abstract This paper introduces a knitting technique for making innovative curved three-dimensional (3D) spacer fabrics by the computer flat-knitting machine. During manufacturing, a number of reinforcement yarns made of aramid fibres are inserted into 3D spacer fabrics along the weft direction to enhance the fabric tensile properties. Curved, flat-knitted 3D spacer fabrics with different angles (in the warp direction) were also developed. Tensile tests were carried out in the weft and warp directions for the two spacer fabrics (with and without reinforcement yarns), and their stress–strain curves were compared. The results showed that the reinforcement yarns can reduce the fabric deformation and improve tensile stress and dimensional stability of 3D spacer fabrics. This research can help the further study of 3D spacer fabric when applied to composites.

Tear properties and meso-scale mechanism of multi-axial warp-knitted fabric from various architectures: Studied by photography

Tear properties tests of three kinds of multi-axial warp-knitted (MWK) fabric: triaxial fabrics (−45 °/90 °/+45 ° and −45 °/0 °/+45 °) and biaxial fabric (−45 °/+45 °) were respectively implemented along the orientations of 0 °, 45 ° and 90 °. Load-displacement curves were well obtained. The high-speed camera was employed to observe the whole tear damage process and series of still images were picked up to analyze the meso-scale mechanism of the extension and displacement of tows on oriented layers. The results indicated the tear properties of MWK fabric are closely related to the orientations of the layers and the deformation mechanism of the layers. Stitching yarns incarnated significant effects in restricting the deformation procedures of tows.

Transverse impact characterization of carbon woven fabric-foam sandwich composites with carbon nanotubes

Different contents of carbon nanotubes were incorporated in an epoxy matrix that was then reinforced with carbon woven fabric and foam to manufacture the carbon woven fabric-foam sandwich composites. The transverse impact characterizations of the sandwich composites were reported. The split Hopkinson pressure bar apparatus were employed to test the transverse impact behaviors. The impact wave signals were recorded and the impact load versus displacement curves and impact damages of the sandwich composites were observed to analyze the energy absorption and the impact damage mechanisms. It was found that the failure area and energy absorption is increased as the increase of impact velocity and decrease of carbon nanotubes content. The main failure modes are foam breakage and the interface delamination between the woven fabric and foam.

3D simulation model of warp-knitted patterned velvet fabric

Purpose Realistic geometric description is essential for simulating physical properties of warp-knitted velvet fabrics, which are widely used for home-textiles and garments. The purpose of this paper is to provide an approach to the description of patterned piles and propose a customized simulation model to realize highly real-time simulation of warp-knitted velvet fabrics in three dimensions. Design/methodology/approach Based on knitting technology and structure features, a mathematical model to qualify forming possibility of piles is conducted by assessing underlaps of pattern bars and pile ground bars. When the pile areas and ground areas are classified, a three-dimensional (3D) space coordinate is built, of which the z-axis is divided into equal spaces to form certain multi-layer textured slices. Color and transparency of piles on each textured slice can be computed and generated by mapping to 3D geometrical grid layers with particular mapping relationship. Moreover, piles’ deflection and spatial collision are also taken into account to make sure high uniformity with real fabrics. Findings According to the models built, a simulator special for warp-knitted patterned velvet fabrics is programed via Visual C++ and the models are proven practical and easily implemented by comparing simulated effect of one sample with real fabric. Research limitations/implications Because of present limited research, 3D simulation of patterned velvet fabrics knitted on double-needle bar Raschel machine as well as 3D shadow effect will be studied in the further research. Practical implications The paper includes implications for designing patterned velvet products and shows convenience to instantly see finished effect without sampling on machine. Originality/value This paper fulfills a featured simulation method for warp-knitted patterned velvet fabrics in 3D dimensions for the first time.

Computer-Aided Design Method of Warp-Knitted Jacquard Spacer Fabrics

Abstract Based on a further study on knitting and jacquard principles, this paper presents a mathematical design model to make computer-aided design of warp-knitted jacquard spacer fabrics more efficient. The mathematical model with matrix method employs three essential elements of chain notation, threading and Jacquard designing. With this model, the processing to design warp-knitted jacquard spacer fabrics with CAD software is also introduced. In this study, the sports shoes which have separated functional areas according to the feet structure and characteristics of movement are analysed. The results show the different patterns on Jacquard spacer fabrics that are seamlessly stitched with jacquard technics. The computer-aided design method of warp-knitted jacquard spacer fabrics is efficient and simple.

Mechanical properties of co-woven-knitted fabric/epoxy composites incorporating carbon nanotubes

The mechanical properties of co-woven-knitted (CWK)/epoxy resin composites with various carbon nanotubes (CNTs) contents along different directions had been investigated. The tensile failure mode of CWK composites with various CNTs contents also was reported. The results indicate that the stress strain curves are influenced by the CNTs contents obviously, and the failure stress, failure strain and absorbed energy composites with various CNTs contents are linearly increased with the CNTs contents. The tensile failure modes of CWK composites with various CNTs contents tend to be in shear deformation and fiber breakage together, and the failure modes of CWK composites with high CNTs contents mainly are resin shear deformation.