Fraunhofer Institute for Industrial Mathematics ITWMElectronic textiles (e-textiles) combine classic textile structures with electrical components and thus form a typical area of »smart textiles«. Incorporating conductive yarns, sensors and actuators gives garments new functions – they can actively keep you warm, measure sporting performance or record medical data. In the »SoSeTex« project, together with a team from the Fraunhofer Institute for Reliability and Microintegration IZM, we are researching how the mechanical resilience of electronic textiles can be specifically improved with the help of digital simulations.
Textilstruktur mit digitaler Simulation
© iStockphoto / Fraunhofer ITWM
Developing Smart Textiles Digitally – Challenges With Knitted Fabrics
Project »SoSeTex«: Simulation-Based Optimization of Knitted Structures for Robust and Comfortable E-Textiles
The electrical components of knitted e-textiles in particular are exposed to high mechanical loads. There is a risk of damage when putting them on and taking them off or during washing, which impairs their function. Repairs are costly and it is almost impossible to recycle them by type due to the integrated electronics. Scientists are therefore researching how the structures of e-textiles can be designed to make them more durable and sustainable - both economically and ecologically.
Fraunhofer-Project »SoSeTex«
In the »SoSeTex« project, an interdisciplinary team of textile engineers from Fraunhofer IZM in Berlin and our mathematicians from Fraunhofer ITWM in Kaiserslautern are working on developing a digital tool that evaluates and optimizes the mechanical resilience of e-textiles. The »TexMath« software solution developed at the Fraunhofer ITWM is being used for this purpose. It makes it possible to significantly shorten the prototyping phase and reduce the number of physically produced textile samples.
Project Workflow
Mechanical Tests:
In »TexMath«, the stretching processes of knitted e-textiles are performed virtually. This allows the calculation model to be calibrated and validated.
Material Optimization:
Knitted structures are tested for abrasion resistance and tearing behavior of electrically conductive yarns. Coated yarns are often used to achieve high stretchability of the electrical conductors - but friction can erode the coating over time and reduce conductivity. The simulation shows: The mechanical stress on sensitive conductors can be significantly reduced through a targeted choice of knitting pattern and yarn thickness.
Robust Connections:
Welding points and transitions between conductive yarns and circuit boards are considered to be particularly sensitive and critical points in e-textiles. Local textile reinforcements near the circuit boards and along the conductor paths increase stability. These adjustments are made completely virtually - without any physical prototypes.
The illustration shows the comparison between the real tensile experiment and the simulation. The colors mark the forces acting on the yarns (green = low, red = high). It is already clear here that the conductive yarns in the original design are particularly heavily loaded.
Focus On Longevity
»SoSeTex« is an important building block for the development of durable, highly functional e-textiles. By using innovative digital tools, we are improving the quality and durability of these intelligent textiles and thus contributing to a sustainable textile industry.
Example: Comparison of the Yarn Load in the Tensile Experiment and Simulation
The mechanical load on the yarns in knitted e-textiles was investigated and evaluated in a tensile experiment and in the accompanying simulation. The forces acting on the individual yarns were represented using a color scale: Green stands for low stress and red for high stress. This shows how strongly or weakly the different yarns are stressed during stretching. It is particularly clear that the conductive yarns in the original design are significantly more stressed than others. This uneven distribution of stress can lead to premature material failure and a shortened service life. The knowledge gained forms the basis for targeted design optimizations in order to distribute the load better and more evenly across all yarns, increase mechanical stability and ensure the functionality of the conductive components in the long term.
Partner
Fraunhofer Institute for Reliability and Microintegration IZM
The images show the tensile loads for different knitting designs.
Blue yarns: knitting yarns (not relevant here)
Red yarns: high load on the conductive yarns
Green yarns: low load on the conductive yarns.
The aim of the optimization is to put as little strain as possible on the electric yarns without unnecessarily stiffening the textile.
Example: Reducing the Mechanical Load on Welding Points
A central aim of the »SoSeTex« project is to mechanically relieve particularly sensitive points in e-textiles – such as welding points between conductive yarns and circuit boards. Various reinforcement designs were investigated using digital simulations in order to minimize the stress at these critical points.
Figure A shows the comparison between experimental prototypes and their digital twins. The colors in the digital twin mark different yarn types. In variant 1, the conductor tracks run directly in the normal knitted fabric without additional reinforcement, while in variant 2 a narrow reinforcement zone made of thicker yarn is knitted around the conductor tracks. Variant 3 extends this reinforcement into a wider zone. The color markings in the digital twin make it clear which yarn types were used in each case.
The subsequent mechanical simulations in Figure B show the bending deformation of the textile under its own weight – both in top view (left columns) and in side view (right column). It can be seen that the stresses along the conductor paths can be significantly reduced by the reinforcement zones. Especially in the widely reinforced variant (3), the stress peaks at the welding points are noticeably reduced. These findings enable targeted adjustments to be made to the textile design in order to make sensitive connection points more robust – without the need for physical prototypes. In this way, digital simulation makes a decisive contribution to improving the service life and functional reliability of e-textiles.
Figure A: Experimental and Virtual Prototypes
Figure B: Deformation Under Bending Load
Project Funding and Duration
The »SoSeTex« project ran from October 2021 to September 2024 and is an SME project within the Fraunhofer-Gesellschaft. SME stands for »Small and Medium-sized Enterprises«. The funding supports cooperation with KMU.