Mechanism-based development and validation of a structural health monitoring for climate adaptive architectural Cottonid elements

• Applicants: Professor Dr.-Ing. Frank Walther; Professor Dr. Cordt Zollfrank
• Subject Area: Polymeric and Biogenic Materials and Derived Composites ; Synthesis and Properties of Functional Materials
• Term: from 2016 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 325009350

Cottonid is a cellulose-based, sustainably available material, which exhibits new application potential nowadays due to the finite nature of fossil resources. As a function of its material tickness, Cottonid can be used as sustainable, climate adaptive functional material as well as dimensionally stable construction material. These properties define the material as an efficient candidate for the production of architectural elements for conventional structural applications as well as for innovative biomimetic architecture. In the first phase of the joint project, basic relationships between single manufacturing as well as environmental parameters on the material behavior of Cottonid were derived. Further, the manufacturing process was optimized with the aim to increase the hygroscopicity the material. Obtained results allowed to build up a basic understanding of Cottonid‘s interaction with its environment. With regard to the application of Cottonid as architectural element, in the follow-up project the implementation of sensors and sensory elements (assemblies) in the material for a structural health monitoring (SHM) will be explored. The manufacturing principle of Cottonid by layering single paper layers on top of each other has great potential for the integration of SHM sensors. One fundamental question concerning the integration of e.g. fiber optic sensors for temperature and strain measurements (FBG) is, if they withstand the parchmentizing process by maintaining their function. This shall be verified first with physicochemical methods and subsequently investigated in actuation and fatigue experiments as a function of the material thickness. Here, also electrical resistance measurement for assessment of materials‘ moisture content will be considered and further developed. Established SHM methods will further be contrasted with an innovative apporach for intrinsic strain measurement, where Cottonid specimens will be modified with piezoelectric zinc oxide. Accompanying, climate specific strain spectra of different Cottonid variants shall be derived and investigated via long-term experiments, repectively. Finally, the biological degradation behavior of the material is characterized. The optimized manufacturing process from funding phase 1 will be further developed in the follow-up project to realize an application-oriented implementation of SHM sensors for climate adaptive architectural Cottonid elements. Functionality and performance of the instrumented Cottonid elements will be verified via analytical investigations as well as actuation and fatigue experiments to derive essential findings concerning the material behavior and ist long-term behavior under real weather conditions. By the implementation of SHM sensors and the exploration of innovative biomimetic approaches in this field, the follow up project represents a brigde to the intended application of Cottonid elements in architecture and civil engineering.

• DFG Programme: Research Grants