3D Simulation of Two-bar Warp-knitted Structures

In this study, 3D computer modeling of simple warp-knitted structures is achieved based on 3D model of warp-knitted loops. Firstly, according to the studying on the geometric structure of warp-knitted loops, Goktepe＇s 3D solid yarn model is developed, and the dimensions of the warp-knitted loops are obtained; then 3D models of stitch defined by eleven given points and in-lay defined by five given points are built with the method of Non-Uniform Rational B-Spline （NURBS） curves and surfaces. Secondly, according to the chain notations of warp-knitted structures, the loop＇s shape can be decided, and with the 3D models the loops can be connected freely and smoothly in some special warp-knitted structures, such as miss-lapping and two- course in-lay. At last, with the tools of Visual C ＋＋ and OpenGL, computer 3D simulation of two-bar warp-knitted fabrics is successfully realized, taking the factor of fabric light and materials into 3D structural model.

Influence of Manufacturing Process of Warp-knitted Vascular Prosthesis on the Wall Homogeneity

This paper reports the evolution of textile structure and mechanical properties of vascular prosthesis in the level of the whole prosthesis and the constituent filaments with respect to the manufacturing process. The tubular wall of the prosthesis is divided circumferentially into three zones; basic line (BL), remeshing line ( RL) and guide line ( GL). Some heterogeneity has been observed on the tubular wall in terms of stitch structure of the prosthesis and linear density of the constituent filaments. The breaking position of the prosthesis under circumferential tensile localizes preferentially in remeshing line that is the weakest zone by warp knitting with double needle bed. Furthermore, the statistical differences of the mechanical properties of the filaments of zone RL, GL and BL have been confirmed too. It is predictable that the deterioration of prosthesis, under physiological loads (periodical pulse blood pressure etc.), could happen firstly in the weaker zone in vivo.

In-plane Tensile Behaviors of Bi-axial Warp-Knitted Composites under Quasi-static and High Strain Rate Loading

The in-plane tensile behaviors of bi-axial warp-knitted(BWK) composites under quasi-static and high strain rates loading were experimentally analyzed in this article. The tensile tests were conducted along warp direction( 0°) and weft direction( 90°) at quasi-static rate of 0. 001 s^(-1) and high strain rates ranging from 1 450 to 2 540 s^(-1),respectively. It is found that the significant strain rate sensitivity can be observed in the stress-strain curves of BWK composites. The fracture morphologies of BWK composites demonstrate that the tensile failure modes are shear failure and fiber breakage under the quasi-static testing condition while interface failure and fibers pullout are at high strain rates.

A Geometric Model of Multiaxial Warp-knitted Preform for Composite Reinforcement

A new geometric model of Multiaxial Warp-Knitted (MWK) performs, which is based on the experimental observations and analysis of basic stitch, is developed to relate the geometric parameters and process variables. The fiber volume fraction and fibre orientation of MWK reinforced composites are described in terms of structural and processing parameters in the model. And this model provides a basis for the prediction of mechanical behavior of the MWK reinforced composites.

Influence of Wires Properties on Warp-Knitted Loop Geometry in Plane Based on Theory of Elastic Rod

Based on classic theory of elastic rod,the warp-knitted loop geometry in plane is independent of yarn properties,while there is a certain gap between the geometrical model and the actual fabrics.According to this problem,further analysis of loop geometry is done based on the theory of elastic rod with theoretical calculation and experiments.The theoretical analysis found that the distance between the contacted points at the loop root affected the loop geometry,and the distance was affected by the ratio of bending rigidity and the friction between yarns.The experiments,forming simple loop by taking the yarn as an elastic rod,found that the bending rigidity affected the loop geometry.Then the relationships between warp-knitted loop geometry in plane of metallic fabrics and wires properties were studied.The results show that metallic fabrics are more suitable for the theory of elastic rod;the friction and bending rigidity of wire yarns affect the loop geometry in plane.Also,the elongation of yarn affects the loop geometry in the actual warp-knitted fabric.

Design of Flexible Electronic Shogging System for High-Speed Warp-Knitting Machine

A flexible electronic shogging system was presented based on rotary type servo motor, which aimed to improve the dynamic response of the shogging drive and decrease the impact of the guide bar during the higher speed running of warp.knitting machine. In this system, the speed control mode, faster response servo motor, no-flat modified trapezoid motion law, and its electronic cam were chosen; the realization standard and method were also introduced in details. The speed response curves of loaded motor indicated that the system could satisfy the technology requirements of high-speed warp- knitting machine which run at the speed of 1 000 r/min in the experiments, and the vibration curves showed that the guide bar had weaker mechanical impact and higher dynamic response characteristics. The results indicated that the flexible electronic shogging system designed following the previous step was successful, and the design principle of the electronic shngging was testified validly.

Development of Warp Knitted Products on RSJ Machine

Products made by Raschel Jacquard(RSJ)high-speed jacquard warp knitting machine are used in ornament and apparel fabrics.However,most products are produced according to the existing samples.The capability of creative design is not enough at home.In this paper,based on the basic features,the knitting methods and the working principles of warp knitting jacquard machines,the rules for manufacturing jacquard products are summarized.The article provides the new thoughts for the development of fabrics,such as the pattern design,changing the cams,power-net and a special technology of without pillar,which were obtained from the practices in a factory.

Positions of Guide Eyes in Circular Warp Knitting Machines

The special lapping requirements were pointed out and the safe range to fix the guide eyes on the circular guide unit was determined by means of Locus Formulas of Warp sections in lapping movement, which were carried out on installing prototype machine. Based on the calculations of the force components acting on lapping points, the positions of the guide eyes in chain overlapping could be used to determine the safe range that could meet the requirements for tricot overlapping. The safe range can ensure the successful lapping and the multi-guide unit designing in circular warp-knitting machines.

Tensile Property of Bi-axial Warp Knitted Structure

The tensile property of bi-axial warp knitted fabrics is tested and compared with that of the plain weave fabric. The results show that there are obvious differences between the tensile property of a bi-axial warp knitted fabric and that of a plain weave fabric.The former can give fuller play to the property of a high modulus yarn than the latter. The tensile strength of a bi-axial warp knitted fabric is linear with the number of yarns in the direction of force.