As part of the ‘HEATex’ research project, the Institute for Textile Technology at RWTH Aachen University developed heat-protective textiles as underwear. In addition to experimental tests, the heat transport properties of the multi-layer heat protection textile are simulated under the influence of contact heat. The simulation allows a qualified pre-estimation of the heat protection effect of different layer constructions. The simulation model was carried out with the simulation software ‘Abaqus/CAE’ of the Parisian software company Dassault Systemes SE.
With this approach, the costs and effort of future comparisons can be noticeably reduced. The results of the simulation model show a fundamental similarity to the experimental test results used so far.
Point of fact is that such textiles and materials are extremely important for about 10 per cent of the German workforce: At their workplaces they are exposed to high temperatures (metal, glass, ceramics and steel production as well as forges, foundries, fire departments). During their work assignments, they are regularly scalded and, in worst cases, suffer heat strokes, which occur at a body temperature of over 40 °C. Thermal protection textiles prevent direct contact between external protective clothing and skin and improve the absorption and transport of the body’s own moisture.
How are the thermal protection textiles tested?
In the tests, the textile layers of the undergarments are assumed to be solid materials with isotropic material properties. Air inclusions within textile layers and the use of different materials in a layer are taken into account by adjusting the material parameters. Finally, averaged parameters are used. At 79.2 °C, the final temperature of the simulation is slightly higher than comparable final temperatures measured in in vitro tests with heat protection textiles using contact heat and without pressure. In reality, the textiles are actually surrounded by air. Circulation of the air on the textile caused by temperature differences leads to cooling of the textile by natural convection. This effect is enhanced by forced convection in the form of air movements in the test environment. Finally, according to the authors of the Institute of Textile Technology, a certain inaccuracy in the material parameters leads to the fact that the final temperatures from simulation and tests are of the same order of magnitude despite some simplifications.
With the help of simulation, textiles can be efficiently and quickly pre-estimated in a first step. In addition, the component-based structure of the simulation allows quick changes of material parameters or a change of the layer structure. All in all, this can be used to optimise the development of heat-protective clothing. If such a simulation is used, special attention must be paid to the accuracy of the material parameters used. Other physical effects, such as radiation influences, can be integrated into the simulation if these parameters are known. In addition, the authors recommend minimizing the required computing power by simplifying and exploiting symmetries in the geometry.
A detailed version by Kevin Krause, Paul Grünefeld, Lena Barth, Lukas Lechthaler, Christoph Peiner and Thomas Gries has been published in melliand Textilberichte 1/2020.