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Training Network for Self-Healing Materials: from Concepts to Market

Final Report Summary - SHEMAT (Training Network for Self-Healing Materials: from Concepts to Market)

Certain types of synthetic materials are designed to chemically repair cracks and other defects in their structure. Such materials are widely referred to as self-healing, and often offer advantages in durability. The EU-funded 'Training network for self-healing materials: From concepts to market' (SHeMat) focuses on the investigation of these materials. The consortium primarily aims to implement and optimise self-healing effects in various materials, and to foster their commercialisation. In particular, SHeMat intends to develop standardised methods for the characterisation of self-healing potential throughout the materials classes. This goal, unique and central to the SHeMat project, is an important key to unlocking the commercialization of self-healing materials. Furthermore, the project focuses on four types of material: polymers, fibre-reinforced polymer composites, concrete and ceramics. This four-year undertaking concluded at the end of 2015.
15 young researchers have actively contributed to the scientific progress and to the advancement of available approaches for self-healing effects in a broad class of materials from the laboratory towards application. In the accompanying training programme, three training schools on the development, assessment, commercialisation, and sustainability of self-healing materials were organized, and each of them promoted not only the fellows’ professional development but also personal contact, networking, and cooperation. The latter was further fostered by regular secondments of the fellows across the partner institutions and is manifested in several common publications.
In the course of the project, SHeMat successfully progressed towards the applicability of existing self-healing concepts, with inspiration coming from biological systems. Practical solutions were presented for different self-healing coatings on the base of either microcapsules or superabsorbent polymers, while commercial ionomers have been proven to be promising as additives in tire mousse. For bulk polymers, the supramolecular, hydrogen bond based approach was successfully transferred to epoxy systems and their composites. The latter, in particular fibre-reinforced polymers, are of high relevance as T-joints, changes in section, holes etc., all potential locations for self-healing that can be exploited for easier integration. Furthermore, it is at such localised regions where self-healing is likely to offer greatest benefit. It was demonstrated that additives of self-healing features (microcapsules or vascules) with design details typically found in reinforced structures show great promise. More investigation, however, is still required on the means of integration within the industrial manufacturing processes.
Progress is also reported on the development of self-healing concrete towards the market using either porous carrier protected or self-protected bacteria/spores, and biological nitrate reduction was proven to be an eco-friendly, effective pathway for nutrition. Also, in terms of cost efficiacy, the step into real-scale application is getting closer.
Two different classes of ceramic materials were investigated in this project. On the one hand, MAX phase ceramics showing an intrinsic oxidation-induced crack healing were developed and tested under both laboratory and industrial conditions. On the other hand, crack healing oxide ceramics (i.e. alumina) were obtained by doping with carbide-based healing particles, resulting in full strength recovery.
Within the project we learned that the self-healing evaluation of the mechanical restoration in different material classes requires flexible but harmonized parameter sets. It is useful to differentiate between bulk materials and coatings. In order to further the understanding of underlying mechanisms and to validate macroscale quantification studies under service conditions, microstructural and microchemical methodologies are essential. Based on these considerations, new test methods to quantitatively determine the mechanical properties after healing of controlled damage were developed and implemented for the different material classes.
The project results constitute a considerable contribution to the advancement of self-healing materials into industry. It should be pointed out that today, while we are witnessing a few self-healing materials that have successfully entered the market in narrow segments and niche applications, the potential for their larger exploitation is clear. Unlocking the technological and ecological obstacles will allow the wider benefits to be utilised, such as enhanced material durability, improved safety, sustainability and resource protection.

Contact details of the project office:
Fraunhofer Institute for Environmental, Safety and Energy Technology (UMSICHT)
Simone Krause
Osterfelder Strasse 3
D-46047 Oberhausen, Germany

Phone +49 (0)208 8598-1136
Prof. Dr. Annette M. Schmidt
Fraunhofer UMSICHT
& Universität zu Köln
Department für Chemie
Luxemburger Str. 116
D-50939 Köln
Phone + 49 (0)221 470 5410;