Fraunhofer Institute for Industrial Mathematics ITWM
Fraunhofer Institute for Industrial Mathematics ITWM
Abstandsgewirke werden häufig in medizinischen Bandagen eingesetzt.
© iStockphoto
Abstandsgewirke werden häufig in medizinischen Bandagen eingesetzt.

Advantages of Warp Knitted Spacer Fabrics

Due to the highly resilient, flexible, and strong properties and the superior decompression of warp knitted spacer fabrics the material is perfect for medical bandages, orthotics or sport textiles.

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Modeling the Mechanical Properties of Knitted Spacer Fabrics

DFG Project Modelling of the Structure and the Properties of 3D Warp Knitted Spacer Fabrics and Experimental Evaluation

In this DFG project we analyze warp knited spacer fabrics. Warp knitted spacer fabrics are double knit textiles, in the form of plates or shells that consist of two separate layers of knit fabrics joined by vertical spacer filament yarn. They are used in various products, the areas of application include, for example, the materials used in mattresses and seats.

Through the textile production process and the selection of the thread material the properties of the warp knitted spacer fabrics are variable and adjustable. Up to now the appropriate dimensioning has been possible yet by means of an extremely time-consuming and cost-intensive experimental technique. Furthermore, deformations of the structure generated by reprocessing and using will not be considered at present. This results in problems in fitting accuracy and changed insulation and flowing behaviour of the 3D fabrics as well as the ready-madefunctional components or products.

 

DFG Project: Modeling the Structural Properties of 3D Warp Knitted Spacer Fabrics

In the collaborative DFG project »Modelling of the Structure and the Properties of 3D Warp Knitted Spacer Fabrics and Experimental Evaluation« with the Technical University of Dresden, which is funded by the German Research Foundation (DFG), we work on these explicit problems:

  • Correct design and simulation of spacing knits using mathematical models and algorithms
  • Mechanical and mathematical multiscale modeling, simulation and structural optimization considering the contact of individual fibers
  • Testing methods and arrangements for 3D warp knitted spacer fabrics for charasteric values of space and location
Kompressionsberechnung eines Abstandsgewirkes
© Fraunhofer ITWM
Compression of a Warp Knitted Spacer Fabric
The idea of the research project is the simulation and appropriated designing of the structure of the warp knitted spacer fabric regarding pre-defined using conditions in advance by means of mathematical models and algorithms. This project is organized in two phases.

 

Phase I – Multiscale Modeling for Warp Knitted Spacer Fabrics

In the beginning the project is focused on the multi-scale modelling and simulation of the warp knitted spacer fabric including the structure adaptation in regard to the contact between the single fibres, in particular. For providing the required scale- and direction-resolved data special analytical methods and devices are developed. This is necessary because traditional textile tests methods and devices are not designed for the spacer structure feature, generally.

Phase II – Development of a Software Tool for Virtual Product Development

Subsequently the ready-made aspects like seams, joints and sealed/finished fabric sheets and edges should be considered in the simulation model, in addition to the fabric structure. The aim is the function-adjusted reprocessing of warp knitted spacer fabrics in order to an extended range of features of the ready-made patterns, for instance for the insulation or for the ventilation effect, too, to design. The result consists of a software tool for the virtual product development of function-adjusted spacer fabrics and ready-making technologies. The tool helps to achieve an improved knowledge about the moisture and heat transport mechanisms in textile spacer fabrics.

Lokale axiale Spannungen
© ITWM
Local Stress in a Warp Knitted Spacer Fabric

Realization with TexMath

One advantage of spacer fabrics is their superior decompression. This means these materials are highly resilient, flexible, and strong when subjected to an external pressure load. In the simulation process, we first map the complex structure of the spacer fabric, breaking all the bonds of the spacer filaments. Subsequently, we simulate the tensile, shear, compression and bending properties using TexMath – software we developed for modeling and analyzing textile fabrics. The characteristics are generated from the knitting pattern and the yarn's known force elongation curve, cross section, and frictional properties. Using TexMath, we analyze the textile spatial variations of porosity tensors caused by unequal compression of the structure.

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