The project “auXteX” was carried out within the larger consortium futureTEX (Verbundvorhaben 29) and funded under the German grant code 03ZZ0629D. Partner 4, the Institute for Concrete Construction at the Hochschule für Technik und Wirtschaft Leipzig (HTWK Leipzig), led the investigation of auxetic effects in textile half‑finished products for use in building construction. The overall project period ran from 1 July 2018 to 31 October 2022, but the HTWK Leipzig work phase was extended to 31 October 2023 because of pandemic‑related delays, resulting in a ten‑month extension. The consortium included several other research institutions and industry partners, with which the HTWK Leipzig exchanged knowledge and integrated complementary expertise into the joint effort.

Technically, the project set out to demonstrate and qualify auxetic behavior in textile structures through experiments and finite‑element method (FEM) simulations. Initially, a requirement catalogue was produced that defined the essential specifications for auxetic effects in the context of concrete construction, identifying key application areas such as linear sealing of building envelopes and anchoring of non‑metallic reinforcements. The study focused on weaving and the Kmail process to create rope‑like auxetic elements, where an elastic roving core is encircled by a stiff fiber such as carbon or aramid. The core material was required to be as elastic and thick as possible while exhibiting low transverse compressibility, a constraint that guided the selection of suitable polymers.

The HTWK Leipzig developed and validated several FEM models to capture the auxetic response of these rope‑like structures under transverse compression. The simulations confirmed that the auxetic effect could be induced by the interaction between the elastic core and the stiff surrounding fiber. Parallel to the numerical work, the consortium supplied prototype half‑finished textiles, which were tested on custom‑designed rigs. Mechanical testing revealed the auxetic behavior, and the results were used to refine the design of preferred variants. These variants were then integrated into binder systems—both cementitious and polymeric—to assess their performance in concrete elements. The integration process involved the development of test bodies and preforms, followed by laboratory and in‑situ experiments on concrete panels.

The final phase produced demonstrators and prototype concrete elements that showcased the practical potential of auxetic textiles under realistic loading conditions. Although the report does not provide specific numerical performance figures, it documents that the auxetic effect was measurable and that the developed prototypes met the predefined requirements for sealing and anchoring functions. The project therefore established a proof of concept for auxetic textiles in building construction and identified clear pathways for further development and industrial application.