Materials and devices for energy and environment applicationsE
Self-healing materials – from concepts to market
The ability of a material to show autonomous or activated self-repair is of importance in view of costs, sustainability, and safety. This interdisciplinary symposium will present the latest update on various strategies to induce self-healing in structural and functional materials where damage management and self-repair is of relevance.
For a broad range of applications in various classes of materials, the ability of key components to restore the original properties after local contact, damage or fatigue would represent a promising step towards lower costs and enhanced reliability. The last few years have experienced a strong development of activities in a broad range of materials from polymers to metals, as well in academia as in industrial research. The advancing understanding of the underlying mechanisms has fertilised the development of novel approaches, materials, and synthetic procedures from the scratch. At the same time, existing materials and components were screened and optimized for their ability to self-repair, mainly on a more empirical base. The symposium aims to bring together experts from academia and industry interested in the advancement of self-healing materials, and to foster the emerging activities to transfer promising approaches and findings from the lab to application. The program will cover sessions focussing on the important material classes, including polymers, composites, concrete, ceramics, metals, and functional components, as well as on biomimetic, sustainable and comprehensive concepts, and on transfer activities and market considerations. We cordially invite contributions from all related disciplines, i. e. chemistry, physics, material sciences, engineering, mathematics and biomimetics.
One major task for the symposium is to include contributions of young researchers to encourage and support their scientific career. By emphasizing the multidisciplinary character of the field, we are aiming at an intensive exchange on ideas, concepts, and realizations for the future of self-healing materials. It should be realized that Europe is a key continent in this field with 5 EU funded programs and 4 national research programs as well as a number of more isolated research projects. More than in the previous conferences in the field, we address quantification of healing as well as studies on the underlying physics and chemistries. Also conceptual studies to identify potentially attractive self-healing materials on the basis of their general physical properties are expected.
Hot topics to be covered by the symposium:
- Self-healing polymers (intrinsic and extrinsic approaches, polymer dynamics, elastomers & thermoplastics, coatings & bulk polymers)
- Self-healing reinforced polymer composites (carbon, glass, polymeric reinforcements, (multi)functional fillers, morphology & interaction)
- Self-healing concrete and reinforced compounds (autogenous self-healing, polymeric self-healing, microbial self-healing, modelling, characterization)
- Self-healing ceramics (bulk composites ceramics & ceramic coatings, intrinstic and extrinsic mechanisms)
- Self-healing in metals (creep damage, corrosion)
- Functional components, devices, and applications (catalysts, OLEDs, TIM’s)
- Quantification of self-healing properties
- Novel and biomimetic concepts towards self-healing materials
- Sustainability aspects
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Authors : Kazuaki Sanada, Tomonari Suyama, Rikiya Fujisaki
Affiliations : Toyama Prefectural University, Department of Mechanical Systems Engineering Japan
Resume : This study examines the interlaminar shear strength and self-healing of carbon fiber/epoxy laminates fabricated by a tow-spreading technology. Healing is accomplished by incorporating a microencapsulated healing agent and catalyst within a polymer matrix. Self-healing is demonstrated on short beam shear specimens of carbon fiber/epoxy laminates and the healing efficiency was evaluated by the strain energies of virgin and healed specimens. The effect of microcapsule concentration on the interlaminar shear strength and healing efficiency is discussed. The damage area of the healed specimens was also examined by an optical microscope. As the microcapsule concentration increased, the healing efficiency increased and the interlaminar shear strength decreased. Moreover, the change of damage progression path of the each specimen caused a large scatter in the healing efficiency.
Authors : Wataru Nakao, Shunsuke Yoshioka, Teturo Yanaseko
Affiliations : Yokohama National University, Faculty of Engeneering Division of Materials Science and Chemical Engineering, Japan
Resume : Self-healing materials for high temperature use needs advanced material design using backcast on the applications, because self-healing materials exhibit the functions using chemical reaction and chemical reactions often affect strongly the surrounding temperature. Thus, in order to develop the available self-healing ceramics, chemical reaction inducing the self-healing function should be adjusted to be suitable for the service conditions of the application. Furthermore, adequate arrangement of the healing agent in the material is important to maximize the chemical reaction effect to strength recovery behavior. Based on the above concept, fiber-reinforced self-healing ceramics was developed to be available to the turbine blade of jet engine. Thus, the heterogeneous layer consisting of TiSi2 and SiC was employed as the healing agent to adjust the available healing temperature to service temperature. Moreover, the healing agent was arranged at only the interlayer between ceramic fiber bundle and ceramics matrix. The above materials design produces the high active self-healing behavior, by which the introduced cracks was completely re-bonded at 1000 oC for 10 min, and the self-healing function is enough high to apply the middle pressure turbine blade.
Authors : Seyed Hosein Payandeh GharibDoust, Parinaz Jafarzadeh, Sepideh Khoee
Affiliations : Department of Chemistry, Tehran University, P.O.Box 14155-6455 Tehran, Iran
Resume : Key words: self-healing, response surface methodology, epoxy resin, nanocapsule, urea formaldehyde. Inspired by living systems, self-healing polymers are designed to automatically repair damages in coatings and composites, thus providing a means to significantly extend the service life and reliability of polymeric structural composites. It has been shown that micro/nanocapsules embedment is among the most successful approaches to provide self-healing ability in polymers . Here a model is provided that demonstrate the effect of different synthesis parameters on the properties of nanocapsules containing epoxy resin. The most effective parameters on the properties of nano-capsules such as surfactant concentration, agitation rate and sonication time are selected and the response surface method is used to determine the effect of these parameters on the nanocapsules size and core content. Using the modified variables, nanocapsules with a size of 165 nm and a core content of 68.7% are prepared. Thermogravimetric analyses reveal that the nanocapsules are stable up to 200 °C which makes them applicable for future wide spread use in self-healing coatings and composites.  H. Wei, Y. Wang, J. Guo, N.Z. Shen, D. Jiang, X. Zhang, et al., Advanced micro/nanocapsules for self-healing smart anticorrosion coatings, J. Mater. Chem. A. 3 (2015) 469480. doi:10.1039/C4TA04791E.
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Session 4 : -
Authors : Costantino Creton, Koichi Mayumi, Thomas Guyon, Tetsuharu Narita, Chung Yuen Hui, Jingyi Guo
Affiliations : ESPCI ¨Paris Tech, 10 Rue Vaquelin, 75231 Paris Cedex 05, France; Cornell University, Mechanical and Aerospace Engineering, USA
Resume : It has been well established that combining self-healing bonds with permanent bonds, can significantly increase the fracture toughness of soft hydrogels. Yet the details of how this actually occurs and in particular the link between bond breaking and healing dynamics and fracture properties, is not yet known. In this work we investigate in detail the rheology in small and large strain and the fracture behavior of a model hydrogel based on polyvinyl alcohol crosslinked both chemically with glutaraldehyde, and physically with a borax solution. We carried out a series of crack propagation experiments on prenotched gel samples over a wide range of loading rates and measured both the critical energy release rate where the crack propagates, and the average crack propagation velocity for each case. Using a recently proposed 3D mechanical model to describe the breaking and healing of the reversible bonds we can simulate the energy stored and dissipated ahead of the crack and we attempt to explain quantitatively how the physical bonds affect the fracture process of the hybrid hydrogels.
Authors : M. Grandcolas, N. Rival, H. Bu, S. Jahren, R. Schmid, H. Johnsen
Affiliations : SINTEF Materials and Chemistry, P.O. Box 124 Blindern, N-0314 Oslo, Norway
Resume : The concept of an autonomic self-healing material, where initiation of repair is integrated to the material, is now being considered for engineering applications (LG released in 2014 a mobile phone using a self-healing finish (LG G Flex)) and is a hot topic in the literature (SciFinder: 2090 references were found containing the concept "self-healing material"). Among several concepts/techniques, two are most interesting: i) Capsules: Integration of microcapsules in or at the surface of coatings or fibre-like structures has recently gained much attention. Upon damage-induced cracking, the microcapsules are broken by the propagating crack fronts resulting in release of an active chemical (healing agent) by capillary action, subsequently repairing and avoiding further crack growth. ii) Self-healing polymers: Interestingly, the introduction of dynamic covalent bonds into polymer networks has also recently been used as a powerful approach towards the design of various intrinsically self-healing polymer systems. The idea behind this is to reconnect the chemical crosslinks which are broken when a material fractures, restoring the integrity of the material and thereby prolonging its lifetime. We propose here to integrate both self-healing concepts (capsules, self-healing polymers) in electrospun fibres and coatings. Different capsule preparation approaches have been investigated in SINTEF. The most advanced method to produce capsules is based on emulsification to create a water-in-oil emulsion before polymerization. The healing agent is a polyurethane-based dispersion that was encapsulated in shell materials consisting of urea-benzaldehyde resins. Results showed successful preparation of microcapsules and release of the agent when capsules break. Since capsules are produced in water-in-oil systems we mainly investigated organic solvent based coatings while a major challenge resides in the incorporation of capsules into water-based coatings. We also focused on developing more robust microcapsules to prevent premature rupture of the capsules. The capsules have been characterized in terms of size, and encapsulation and release might be visualized by incorporating fluorescent dyes and examine the capsules by microscopy techniques. Alternatively, Electrospinning is an innovative technique that has attracted enormous attention due to unique properties of the produced nano-to-micro fibers, ease of fabrication and functionalization, and versatility in controlling parameters. Especially roll-to-roll electrospinning is a unique method which has been used in industry to produce nanofibers continuously. Electrospun nanofibers can usually reach a diameter down to 100 nm, depending on the polymer used, which is of interest for the concept with self-healing polymer systems. In this work we proved the feasibility of fabrication of POSS-based (POSS: polyhedral oligomeric silsesquioxanes, tradename FunzioNano) nanofibers via electrospinning. Two different formulations based on aqueous or organic solvents have shown nanofibres with diameter between 200 450nm with low defects. The addition of FunzioNano in the polymer blend also showed enhanced properties in term of wettability, promising for e.g. membrane technology. The self-healing polymer systems developed are here POSS-based materials synthesized to develop dynamic soft brushes.
Authors : Elke Gruyaert, Ghislain Louis, Damien Betrancourt, Yusuf Ersan Cagatay, Christine Lors, Denis Damidot, Nele De Belie
Affiliations : Magnel Laboratory For Concrete Research, Technologiepark Zwijnaarde 904, 9052 Ghent, Belgium; Ecole des Mines de Douai, Boulevard Lahure 741, 59500 Douai, France
Resume : CaCO3 precipitation is one of the main mechanisms to heal cracks in bacterial based self-healing concrete or self-healing concrete incorporating superabsorbent polymers (SAPs), but also in traditional concrete, cracks can be healed autogenously due to CaCO3 precipitation. To study the mechanical properties of the CaCO3 precipitated in the cracks of these three types of concrete, the indentation technique was used. A scanning electron microscope (SEM) equipped with a special stage to combine the indentation technique with SEM/EDS (energy dispersive X-ray spectroscopy), was used in this study. The advantage of this system is that the location of the indentation test can be accurately determined and it is known for certain for which phase the mechanical properties are measured and calculated. The results show that there is no significant difference in the Martens hardness of the calcite formed in autogenously healed specimens and specimens incorporating bacteria or SAPs. Furthermore, the mechanical properties of the cement paste were also measured and the influence of the strength class of the cement (CEM I 42.5 N vs. CEM I 52.5 N) and presence of SAPs was investigated. This work was supported by the SHeMat project "Training Network for Self-Healing Materials: from Concepts to Market" within the scope of the Seventh Framework Programme [FP7/2007-2013] under grant agreement no 290308 by the European Commission's Marie Curie programme.
Authors : Ali Behnood, Christian Simon, Emmanuel Cailleux, Yegor Morozov, Fatima Montemor, Sviatlana. Lamaka, Kim Van Tittelboom, Nele De Belie
Affiliations : Magnel Laboratory for Concrete Research, Department of Structural Engineering, Faculty of Engineering and Architecture, Ghent University, Technologiepark Zwijnaarde 904, B-9052 Ghent, Belgium; SINTEF Materials and Chemistry, Forskningsveien 1, 0314, Oslo, Norway; Belgian Building Research Institute, Avenue Pierre Holoffe 21, B-1342, Limelette, Belgium; Centro de Quimica Estrutural, Instituto Superior Técnico, Universidade de Lisboa, Portugal 5Magnesium Innovation Centre, Institute of Materials Research, Helmholtz-Zentrum Geesthacht, Germany
Resume : Recently, self-healing concrete has been introduced as a novel construction material which can result in a considerable reduction in annual maintenance costs of concrete structures such as bridges, tunnels and retaining walls. Although many research works have been done for optimizing properties of self-healing concrete, the bottleneck for its valorisation is the encapsulation method of the healing agent because the capsules have to demonstrate multifunctional properties. They (i) have to protect the healing agent over long time, (ii) have to release the healing agent upon crack formation and (iii) should not affect the fresh concrete workability and the early and long term mechanical properties. Moreover, it is essential that capsules can easily be mixed in concrete and/or can survive during concrete casting. Consequently, the concrete production process is not remarkably affected and the processing costs will almost not increase. In addition, the capsules should provide good barriers against both oxygen and water to protect the healing agent. These requirements may cause difficulties in finding a suitable encapsulation material because the capsules should not be broken during concrete preparation whereas they should break immediately upon crack formation. Although no commercial product seems suitable for these purposes, within the CAPDESIGN project it is aimed to develop, optimize and test novel types of capsules for application in self-healing concrete. Hybrid nanoparticles developed at SINTEF will be used to improve both mechanical properties and barrier properties of the capsules. Within this project, it is also the aim to develop capsules which can be applied to the concrete via an innovative placement technique. The advantage of capsules which survive during mixing/operation are (i) decreasing the cost of self-healing concrete, (ii) facilitating production of self-healing concrete by companies, (iii) open the possibility to valorise self-healing concrete. Consequently, mass production of self-healing concrete structures which do not require maintenance costs will result into a lot of economic, environmental and social advantages such as less traffic jams or higher safety levels.
Authors : J. Feiteira, E. Gruyaert, N. De Belie
Affiliations : Magnel Laboratory for Concrete Research, Ghent University, Technologiepark-Zwijnaarde 904, 9052 Ghent, Belgium
Resume : Self-healing concrete aims at the autonomous healing of small cracks, with widths in the order of a few hundred micrometers. This way, the service life of reinforced concrete structures can be extended and their watertightness guaranteed for longer periods, while costly and potentially complex repair works can be avoided. As with other emerging concrete technologies, this novel repair technique poses new challenges regarding the conception of new test methods that are able to assess its performance in realistic conditions and able to continuously monitor it. Thus, this paper presents results of applying the transmission of ultrasonic shear waves for continuous monitoring of small scale cement mortar specimens cracked and healed with encapsulated precursors of flexible polymers. Preliminary results on larger concrete specimens showed already that this technique successfully detects the continuous hardening of the precursors after rupture of the capsules and further filling of the crack, corresponding to an increase of the amplitude of shear waves transmitted through the healed crack. Additionally, the reverse was observed when failure occurred, due to rupture of the polymers matrix or to its detachment from the crack walls. In this study, the transmission of ultrasonic shear waves is used to assess the limits of the elongation of the polymers bridging the cracks and their resistance to fatigue while healing a moving crack induced by cyclic loads. The polymer precursors used include moisture curing polyurethanes forming solid films or foams with closed-cell structure. ACKNOWLEDGEMENTS The research has received funding from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement n° 309451 (HEALCON).
Authors : Rami Alghamri, Abir Al-Tabbaa
Affiliations : Department of Engineering, University of Cambridge, Cambridge, United Kingdom
Resume : Utilization of expansive agents and mineral admixtures as an approach for self-healing of cementitious composites has been the subject of extensive research over the last two decades. However, it has been consistently shown that the main challenges of this approach are the significant loss in workability of fresh concrete and the occurrence of early reactions with cementitious materials, which would decrease the self-healing efficiency. Therefore, this work aims to study the influence of incorporating coated pellets with different cargoes of expansive minerals into the cementitious composites on the crack self-healing performance with the elapse of time. Four different types of pellets containing (1) Blend of high reactive Magnesium Oxide (MgO) and Bentonite, (2) Blend of MgO and Silica fume, (3) Low reactive MgO and (4) Medium reactive MgO were used. The first two types were developed in the laboratory while the latter two are commercial pellets. All of them are with (1-2) mm diameter and they were coated by a film layer of polyvinyl alcohol (PVA) to control the time of autonomic healing. These coated pellets were added to mortar mixes as partial sand replacement. Controlled width cracks of 300 µm were induced in three prism specimens from each mix after 7 days of curing in water. Then monitoring of cracks closure using optical microscope images was applied every 7 days for 28 days. Thereafter, the specimens were re-cracked by three point bending test to examine their flexural strength recovery. The results indicate that the mortar samples containing the coated pellets possessed promising crack self-healing performance compared to the control samples with superiority to those developed in laboratory.
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Authors : A. Kotrotsos, A. Baltopoulos, S. Tsantzalis, X. Tsilimigkra, P. Tsokanas, D. H. Turkenburg, H. R. Fischer, V. Kostopoulos
Affiliations : Applied Mechanics Lab., Department of Mechanical Engineering and Aeronautics, University of Patras. Patras University Campus, GR 265 00 Patras, Greece
Resume : The extension of the working life and safety of the fiber reinforced plastics (FRPs), are lately under investigation. In that sense, the development of a new class of cross-linked polymers capable of healing internal cracks and delaminations through thermo-reversible bonds is currently proposed. In the present investigation, bis-maleimide (BMI) prepolymer powder with particle size of 100μm was successfully incorporated in the mid-plane of CFRPs. Reference and samples with 60, 120 and 240 grams per square meter (gsm) were produced and tested under mode I and mode II remote loading conditions. All the samples contain 22 layers of UD carbon pre-preg, while the manufacturing root was that of autoclave. The incorporation of the BMI-prepolymer powder was predefined along the crack propagation region, according to AITM 1.0005 and 1.0006 standards. After the manufacturing process all the samples were tested under mode I and II fracture tests and the results were compared against the reference one. The modified with BMI powder composites showed a slight increase for the interlaminar fracture energy both in mode I and II (GIC & GIIC). After the crack propagation up to a certain length, the samples were heated and fractured again several times in order to calculate the healing efficiency. It was shown the higher the BMI gsms, the higher the healing efficiency value under mode I experiments while all the mode II samples showed high healing efficiency values.
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