P1 Coral secrets - how do glass flowers of the ocean resist sea wave fatigue

• Applicants: Dr.-Ing. Franziska Schmidt; Professor Dr. Paul Zaslansky
• Subject Area: Polymeric and Biogenic Materials and Derived Composites ; Biomaterials ; Glass, Ceramics and Derived Composites
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 516930787

Stony corals are highly mineralized glassy-crystalline (aragonitic) structures, with a long evolutionary history of successful survival in the wavy environment of the sea. But just how these graceful creatures, where coral and algae reside in extensive porosity, resist fatigue against the cyclic wave loads, is not known. The elaborate flower-shaped geometries and bone-like struts survive decades and centuries of battering wave forces, suggesting that the structure must entail damage resistance that has to date not been investigated, though cracks are known to become arrested. In this project, we propose to learn from natural highly inorganic structures - adapted to cyclic forces in the sea - for inspiration on how to increase mechanical durability and fatigue resistance in highly brittle glass-ceramic 3D structures. On the one side adult coral colonies grown in calm protected waters will be compared with identical species grown in exposed regions of the reef front, where strong wave currents are abundant in relevant niches in the Gulf of Eilat, Israel. The corals will adapt in the months after placement and will then be analysed. Additional lab experiments in aquaria will expose juvenile settled corals to calm versus cyclic wave-flow environments, mimicking the underwater sample growth. Harvested coral samples will be transferred to Berlin for structural, quasistatic and fatigue mechanical testing employing high-resolution 3D imaging via optical, electron and synchrotron X-ray facility beamlines. On the other, engineering side, 3-dimensional glass-ceramic structures will be created by foam replica and additive manufacturing methods with various glass compositions. We will combine silicate based glasses with different crystallization tendencies, heat treated within a range of temperatures to enforce controlled crystallization and to induce stresses inside the system. We will produce biomimetic 3D glass-ceramic structures that mimic morphological and microstructural design features of the corals. We will investigate the influence of material, porosity and microstructure gradients on the mechanical properties and fatigue resistance of the synthetic foams and correlate these findings with the properties and behaviour found in natural corals.

• DFG Programme: Research Units
• Subproject of: FOR 5657: Bioinspired anti-fatigue: enhancing materials science structural properties by abstracting naturally-grown fatigue resistance
• International Connection: Israel
• International Co-Applicant: Professorin Dr. Tali Mass, Ph.D.