scholarly journals Design of self-healing catalysts for aircraft application

2018 ◽  
Vol 9 (6) ◽  
pp. 723-736 ◽  
Author(s):  
Elisa Calabrese ◽  
Pasquale Longo ◽  
Carlo Naddeo ◽  
Annaluisa Mariconda ◽  
Luigi Vertuccio ◽  
...  

PurposeThe purpose of this paper is to highlight the relevant role of the stereochemistry of two Ruthenium catalysts on the self-healing efficiency of aeronautical resins.Design/methodology/approachHere, a very detailed evaluation on the stereochemistry of two new ruthenium catalysts evidences the crucial role of the spatial orientation of phenyl groups in the N-heterocyclic carbene ligands in determining the temperature range within the curing cycles is feasible without deactivating the self-healing mechanisms (ring-opening metathesis polymerization reactions) inside the thermosetting resin. The exceptional activity and thermal stability of the HG2MesPhSyncatalyst, with the syn orientation of phenyl groups, highlight the relevant potentiality and the future perspectives of this complex for the activation of the self-healing function in aeronautical resins.FindingsThe HG2MesPhSyncomplex, with the syn orientation of the phenyl groups, is able to activate metathesis reactions within the highly reactive environment of the epoxy thermosetting resins, cured up to 180°C, while the other stereoisomer, with the anti-orientation of the phenyl groups, does not preserve its catalytic activity in these conditions.Originality/valueIn this paper, a comparison between the self-healing functionality of two catalytic systems has been performed, using metathesis tests and FTIR spectroscopy. In the field of the design of catalytic systems for self-healing structural materials, a very relevant result has been found: a slight difference in the molecular stereochemistry plays a key role in the development of self-healing materials for aeronautical and aerospace applications.

2016 ◽  
Vol 7 (5) ◽  
pp. 656-670 ◽  
Author(s):  
Marialuigia Raimondo ◽  
Felice De Nicola ◽  
Ruggero Volponi ◽  
Wolfgang Binder ◽  
Philipp Michael ◽  
...  

Purpose The purpose of this paper is to describe the first experiments to manufacture self-healing carbon fiber reinforced panels (CFRPs) for the realization of structural aeronautic components in order to address their vulnerability to impact damage in the real service conditions. Design/methodology/approach The developed self-healing system is based on ring-opening metathesis polymerizations reaction of microencapsulated 5-ethylidene-2-norbornene/dicyclopentadiene cyclic olefins using Hoveyda-Grubbs’ first generation catalyst as initiator. In this work, the self-healing resin is infused into a carbon fiber dry preform using an unconventional bulk film infusion technique that has allowed to minimize the filtration effects via a better compaction and reduced resin flow paths. Infrared spectroscopy provides a useful way to identify metathesis products and therefore catalyst activity in the self-healing panel after damage. The damage resistance of the manufactured CFRPs is evaluated through hail and drop tests. Findings The self-healing manufactured panels show, after damage, catalyst activity with metathesis product formation, as evidenced by an infrared peak at 966 cm−1. The damage response of CFRPs, detected in accord to the requirements of hail impact for the design of a fuselage in composite material, is very good. The results are very encouraging and can constitute a solid basis for bringing this new technology to the self-healable fiber reinforced resins for aerospace applications. Originality/value In this paper, autonomically healing CFRPs with damage resistance and self-healing function are proposed. In the development of self-healing aeronautic materials it is critical that self-healing activity functions in adverse weather conditions and at low working temperatures which can reach values as low as −50°C.


2018 ◽  
Vol 9 (6) ◽  
pp. 753-767 ◽  
Author(s):  
Panagiota Polydoropoulou ◽  
Christos Vasilios Katsiropoulos ◽  
Andreas Loukopoulos ◽  
Spiros Pantelakis

Purpose Over the last decades, self-healing materials based on polymers are attracting increasing interest due to their potential for detecting and “autonomically” healing damage. The use of embedded self-healing microcapsules represents one of the most popular self-healing concepts. Yet, extensive investigations are still needed to convince on the efficiency of the above concept. The paper aims to discuss these issues. Design/methodology/approach In the present work, the effect of embedded self-healing microcapsules on the ILSS behavior of carbon fiber reinforced composite materials has been studied. Moreover, the self-healing efficiency has been assessed. The results of the mechanical tests were discussed supported by scanning electron microscope (SEM) as well as by Attenuated Total Reflection–Fourier-transform infrared spectroscopy (ATR–FTIR) analyses. Findings The results indicate a general trend of a degraded mechanical behavior of the enhanced materials, as the microcapsules exhibit a non-uniform dispersion and form agglomerations which act as internal defects. A remarkable value of the self-healing efficiency has been found for materials with limited damage, e.g. matrix micro-cracks. However, for significant damage, in terms of large matrix cracks and delaminations as well as fiber breakages, the self-healing efficiency is limited. Originality/value The results obtained by SEM analysis as well as by ATR–FTIR spectroscopy constitute a strong indication that the self-healing mechanism has been activated. However, further investigation should be conducted in order to provide definite evidence.


Polymers ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 201
Author(s):  
Stefano Paolillo ◽  
Ranjita K. Bose ◽  
Marianella Hernández Santana ◽  
Antonio M. Grande

This article reviews some of the intrinsic self-healing epoxy materials that have been investigated throughout the course of the last twenty years. Emphasis is placed on those formulations suitable for the design of high-performance composites to be employed in the aerospace field. A brief introduction is given on the advantages of intrinsic self-healing polymers over extrinsic counterparts and of epoxies over other thermosetting systems. After a general description of the testing procedures adopted for the evaluation of the healing efficiency and the required features for a smooth implementation of such materials in the industry, different self-healing mechanisms, arising from either physical or chemical interactions, are detailed. The presented formulations are critically reviewed, comparing major strengths and weaknesses of their healing mechanisms, underlining the inherent structural polymer properties that may affect the healing phenomena. As many self-healing chemistries already provide the fundamental aspects for recyclability and reprocessability of thermosets, which have been historically thought as a critical issue, perspective trends of a circular economy for self-healing polymers are discussed along with their possible advances and challenges. This may open up the opportunity for a totally reconfigured landscape in composite manufacturing, with the net benefits of overall cost reduction and less waste. Some general drawbacks are also laid out along with some potential countermeasures to overcome or limit their impact. Finally, present and future applications in the aviation and space fields are portrayed.


2014 ◽  
Vol 27 (5) ◽  
pp. 793-806 ◽  
Author(s):  
Eduard Bonet

Purpose – The purpose of this paper is to examine how the boundaries of rhetoric have excluded important theoretical and practical subjects and how these subjects are recuperated and extended since the twentieth century. Its purpose is to foster the awareness on emerging new trends of rhetoric. Design/methodology/approach – The methodology is based on an interpretation of the history of rhetoric and on the construction of a conceptual framework of the rhetoric of judgment, which is introduced in this paper. Findings – On the subject of the extension of rhetoric from public speeches to any kinds of persuasive situations, the paper emphasizes some stimulating relationships between the theory of communication and rhetoric. On the exclusion and recuperation of the subject of rhetorical arguments, it presents the changing relationships between rhetoric and dialectics and emphasizes the role of rhetoric in scientific research. On the introduction of rhetoric of judgment and meanings it creates a conceptual framework based on a re-examination of the concept of judgment and the phenomenological foundations of the interpretative methods of social sciences by Alfred Schutz, relating them to symbolic interactionism and theories of the self. Originality/value – The study on the changing boundaries of rhetoric and the introduction of the rhetoric of judgment offers a new view on the present theoretical and practical development of rhetoric, which opens new subjects of research and new fields of applications.


2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Fatemeh Narenji Thani ◽  
Ebrahim Mazari ◽  
Somaye Asadi ◽  
Maryam Mashayekhikhi

PurposeConsidering innovation and its improvement as an essential strategy to enable organizations to continue their lives in the new competitive environment leads to a focus on employees' self-development as a factor that affects human resource agility (HRA) and the tendency toward organizational innovation. Consequently, the purpose of the study was to explain the impact of self-development on the tendency toward organizational innovation with the role of the mediator, HRA in higher education institutions as one of the most important and vital organizations in any society.Design/methodology/approachThe study was an applicable one with the quantitative approach using the descriptive–correlative method. The population consisted of 477 nonacademic employees of Kharazmi University among whom 214 ones were selected as the sample group, using a simple random sampling technique. Data were collected through the self-development, HRA and the tendency toward organizational innovation questionnaires and then analyzed using the structural equation modeling approach.FindingsThe study findings revealed a positive impact of self-development on the HRA (γ = 0/79) and HRA on the tendency toward organizational innovation (β = 0/6). Also, self-development with mediating HRA impacts the tendency toward organizational innovation (β = 0/58). Finally, self-development had no direct impact on the tendency toward organizational innovation.Research limitations/implicationsTaking the circumstances of doing this research into consideration, if there were the opportunity to do the research on the staffs of more than one university simultaneously and categorize the university staff into executives, managers and experts, more favorable results could be achieved. Also, considering group and organizational factors with the attention to the self-development approach and its factors would provide more awareness-training information on the higher education system in Iran. For future researches, both the individual and group factors are suggested to be surveyed and compared, to assess the weight and impact of these factors all together and to provide an adequate clarification of the role of the group and the organization. Finally, in future studies, it is also recommended that a qualitative approach be used to reach deeper clarifications on the aspects of these variables in the context of higher education.Practical implicationsThese findings have major practical implications concerning the higher educational settings. The findings of this study must give significant and practical insights for policymakers of universities and other higher education stakeholders, as well as recommendations to the academic community for further research in this area. First, they should recognize that nonacademic staff members are professional employees who contribute to improving organizational innovation. Higher education must focus on designing and implementing successful mechanisms and a well-planned self-development program that can help and promote the self-development approach among all staff. If the above-mentioned programs are designed based on the employees' needs analysis, they will get trained in a way to enhance mental and behavioral flexibility. The programs with such an approach can result in the proactive, adaptive, resilient behavior and agility of HR.Originality/valueThe model for this study has integrated and prioritized the key innovation drivers that would help universities design, adopt and implement policies and practices that facilitate and encourage improvements and adaptation to a fast-paced environment. Furthermore, the convincing reason for the significance of the current research is that although several types of research have been carried out on each of these three variables in different contexts separately, very few studies, like this, have directly examined the correlation between these three variables among the non-academic staff in higher education institutes. So, given the importance of the issue and rare availability of evidence in this regard, the authors were intrigued to discover whether the self-development through the mediation of HRA could reinforce and strengthen the tendency toward organizational innovation and whether HRA could be an appropriate mediator of the relationship between self-development and the tendency toward organizational innovation among the nonacademic staff of Kharazmi University as one of the most prestigious and celebrated universities in Iran.


2021 ◽  
Author(s):  
Ricardo Hungria ◽  
Momen Mousa ◽  
Marwa Hassan ◽  
Omar Omar ◽  
Andrea Gavilanes ◽  
...  

Coatings ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 543
Author(s):  
Dong-Min Kim ◽  
Junseo Lee ◽  
Ju-Young Choi ◽  
Seung-Won Jin ◽  
Kyeong-Nam Nam ◽  
...  

Although self-healing protective coatings have been widely studied, systematic research on healing performance of the coating according to damage width has been rare. In addition, there has been rare reports of self-healing of the protective coating having damage width wider than 100 µm. In this study, self-healing performance of a microcapsule type self-healing protective coating on cement mortar was studied for the coating with damage width of 100–300 µm. The effect of capsule-loading (20 wt%, 30 wt% and 40 wt%), capsule size (65-, 102- and 135-µm-mean diameter) and coating thickness (50-, 80- and 100-µm-thick undercoating) on healing efficiency was investigated by water sorptivity test. Accelerated carbonation test, chloride ion penetration test and scanning electron microscope (SEM) study were conducted for the self-healing coating with a 300-µm-wide damage. Healing efficiency of the self-healing coating decreased with increasing damage width. As capsule-loading, capsule size or coating thickness increased, healing efficiency of the self-healing coating increased. Healing efficiency of 76% or higher was achieved using the self-healing coating with a 300-µm-wide scratch. The self-healing coating with a 200-µm-wide crack showed healing efficiency of 70% or higher. The self-healing coating having a 300-µm-wide scratch showed effective protection of the substrate mortar from carbonation and chloride ion penetration, which was supported by SEM study.


Polymers ◽  
2018 ◽  
Vol 11 (1) ◽  
pp. 41 ◽  
Author(s):  
Ali Berkem ◽  
Ahmet Capoglu ◽  
Turgut Nugay ◽  
Erol Sancaktar ◽  
Ilke Anac

The self-healing ability can be imparted to the polymers by different mechanisms. In this study, self-healing polydimethylsiloxane-graft-polyurethane (PDMS-g-PUR)/Vanadium pentoxide (V2O5) nanofiber supramolecular polymer composites based on a reversible hydrogen bonding mechanism are prepared. V2O5 nanofibers are synthesized via colloidal route and characterized by XRD, SEM, EDX, and TEM techniques. In order to prepare PDMS-g-PUR, linear aliphatic PUR having one –COOH functional group (PUR-COOH) is synthesized and grafted onto aminopropyl functionalized PDMS by EDC/HCl coupling reaction. PUR-COOH and PDMS-g-PUR are characterized by 1H NMR, FTIR. PDMS-g-PUR/V2O5 nanofiber composites are prepared and characterized by DSC/TGA, FTIR, and tensile tests. The self-healing ability of PDMS-graft-PUR and composites are determined by mechanical tests and optical microscope. Tensile strength data obtained from mechanical tests show that healing efficiencies of PDMS-g-PUR increase with healing time and reach 85.4 ± 1.2 % after waiting 120 min at 50 °C. The addition of V2O5 nanofibers enhances the mechanical properties and healing efficiency of the PDMS-g-PUR. An increase of healing efficiency and max tensile strength from 85.4 ± 1.2% to 95.3 ± 0.4% and 113.08 ± 5.24 kPa to 1443.40 ± 8.96 kPa is observed after the addition of 10 wt % V2O5 nanofiber into the polymer.


2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
Jing Xu ◽  
Xianzhi Wang ◽  
Junqing Zuo ◽  
Xiaoyan Liu

Protective carrier is essential for the self-healing of concrete cracks by microbially induced CaCO3 precipitation, owing to the harsh conditions in concrete. In this paper, porous ceramsite particles are used as microbial carrier. Heat treatment and NaOH soaking are first employed to improve the loading content of the ceramsite. The viability of bacterial spores is assessed by urea decomposition measurements. Then, the self-healing efficiency of concrete cracks by spores is evaluated by a series of tests including compressive strength regain, water uptake, and visual inspection of cracks. Results indicate that heat treatment can improve the loading content of ceramsite while not leading to a reduction of concrete strength by the ceramsite addition. The optimal heating temperature is 750°C. Ceramsite particles act as a shelter and protect spores from high-pH environment in concrete. When nutrients and spores are incorporated in ceramsite particles at the same time, nutrients are well accessible to the cells. The regain ratio of the compressive strength increases over 20%, and the water absorption ratio decreases about 30% compared with the control. The healing ratio of cracks reaches 86%, and the maximum crack width healed is near 0.3 mm.


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