SPP 1568

Description:

"Self-healing materials" are able to partially or completely heal mechanical damage inflicted on them (in particular crack formation) in situ and to such a degree that the original functionality is restored - not necessarily the outer or inner microstructure. These materials would greatly improve materials' reliability and lifetime by reversing damage development once or even multiple times. Self-healing ability is not limited to one specific material class: it is applicable to concrete, to polymers (and their composites), to metals and ceramics. However, up to now there is no cross-disciplinary, concept-driven, coordinated approach to the design and understanding of self-healing materials.

The main objective is to elucidate fundamental cross-disciplinary, material-independent princi-ples and design strategies and to apply the knowledge gained to new approaches in the different material classes. The ultimate goal is to provide a new generation of adaptive high-performance materials that can be used for various applications in technology and medicine.

Fundamental scientific questions and challenges concern the influence of the hierarchical structural order on the damage process (localisation by hierarchical borders), damage detection and signal transmission by complex 3-dimensional structures (detection), local stimulation of reaction processes in crack planes (activation) and efficiency of the achievable damage regeneration. Methodical questions include the generation and registration of the material damage being a prerequisite for evaluating the achieved healing efficiency, the activation of the healing reaction by external energy (laser beam, inductive or resistive heating, ultrasonically induced friction), the modelling and simulation of healing reactions by thermodynamic, reaction mechanistic, and kinetic approaches as well as the development of suitable manufacturing processes.

The research programme will be devoted to three material classes (polymers and composites, ceramics and concrete, metals). The investigation of the basic principles for all classes and the application of the principles for synthesis/fabrication of self-healing materials will be in the centre of interest. The interdisciplinary integration of the different material classes occurs in three cross-sectional areas:

  • Investigation of fundamental principles:
    Chemical and physical processes will be investigated that lead to local crack healing without the subsequent intentional addition of additional substances. Such processes will include, e.g., chemical reactions (e.g., polymerisations, redox reactions, cross-linking reactions, but not limited to these reactions), phase transitions (e.g., martensitic transformation), flow and sinter processes as well as stress relaxation.
  • Material realisation (synthesis/fabrication and characterisation):
    The synthesis and fabrication of self-healing materials (based on the fundamental con-cepts) will be investigated. One challenge will be the utilisation of bio-inspired structural models. The combination of top-down approaches (melt and powder methods, generative methods) and bottom-up approaches (self-organisation, directed addition, spinodal segregation, eutectic solidification) seem to be exceptionally promising. Being an important target, investigations on optimising material properties will first aim at mechanical properties, the extension of the lifetime, and reliability under static and cyclic stress.

  • Research projects targeting requirements of potential applications:
    This part will be of particular interest only in the second funding period.