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1 – 10 of 466Çağatay Özada, Merve Ünal, Eslem Kuzu Şahin, Hakkı Özer, Ali Riza Motorcu and Murat Yazıcı
This study produced epoxy-filled urea-formaldehyde (UF) microcapsules (MCs) and T-403 amine MCs using the in situ technique. The Taguchi method was used to determine the effects…
Abstract
Purpose
This study produced epoxy-filled urea-formaldehyde (UF) microcapsules (MCs) and T-403 amine MCs using the in situ technique. The Taguchi method was used to determine the effects of the control factors (temperature, stirring speed, core-shell ratio and surfactant concentration) affecting MCs’ core diameter and core content and optimizing their optimum levels with a single criterion. Optimum control factor levels, which simultaneously provide maximum core diameter and core content of MCs, were determined by the PROMETHEE-GAIA multi-criteria optimization method. In addition, the optimized MC yield was analyzed by thermal camera images and compression test.
Design/methodology/approach
Microcracks in materials used for aerospace vehicles and automotive parts cause serious problems, so research on self-healing in materials science becomes critical. The damages caused by micro-cracks need to heal themselves quickly. The study has three aims: (1) production of self-healing MCs, mechanical and chemical characterization of produced MCs, (2) single-criteria and multi-criteria optimization of parameters providing maximum MC core diameter and core content, (3) investigation of self-healing property of produced MCs and evaluation. Firstly, MCs were produced to achieve these goals.
Findings
The optimized micro cures are buried in the epoxy matrix at different concentrations. Thermal camera images after damage indicate the presence of healing. An epoxy-amine MC consisting of a 10% by weight filled aluminum sandwich panel was prepared and subjected to a quasi-static compression test. It was determined that there is a strong bond between the UF shell and the epoxy resin.
Originality/value
The optimization of production factors has been realized to produce the most efficient MCs that heal using less expensive and more accessible methods.
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Dibyendu Adak, Donkupar Francis Marbaniang and Subhrajit Dutta
Self-healing concrete is a revolutionary building material that will generally reduce the maintenance cost of concrete constructions. Self-healing of cracks in concrete structure…
Abstract
Purpose
Self-healing concrete is a revolutionary building material that will generally reduce the maintenance cost of concrete constructions. Self-healing of cracks in concrete structure would contribute to a longer service life of the concrete and would make the material more durable and more sustainable. The cementitious mortar with/without incorporating encapsulates at different percentages of slag replacement with the cement mix improves autogenous healing at different ages. Therefore, this study’s aim is to develop a self-healing cementitious matrix for repair and retrofitting of concrete structures.
Design/methodology/approach
In the present work, waste straw pipes are used as a capsule, filled with the solution of sodium hydroxide (NaOH), sodium silicate (Na2SiO3) and colloidal nano-silica as self-healing activators. An artificial micro-crack on the control and blended mortar specimens at different percentages of slag replacement with cement (with/without encapsulation) is developed by applying a compressive load of 50% of its ultimate load-carrying capacity. The mechanical strength and ultrasonic pulse velocity, water absorption and chloride ion penetration test are conducted on the concrete specimen before and after the healing period. Finally, the self-healing activity of mortar mixes with/without encapsulation is analysed at different ages.
Findings
The encapsulated mortar mix with 10% of slag content has better self-healing potential than all other mixes considering mechanical strength and durability. The enhancement of the self-healing potential of such mortar mix is mainly due to hydration of anhydrous slag on the crack surface and transformation of amorphous slag to the crystalline phase in presence of encapsulated fluid.
Research limitations/implications
The self-healing activities of the slag-based cementitious composite are studied for a healing period of 90 days only. The strength and durability performance of the cracked specimen may be increased after a long healing period.
Practical implications
The outcome of the work will help repair the cracks in the concrete structure and enhances the service life.
Originality/value
This study identifies the addition encapsulates with a self-healing activator fluid that can recover its strength after minor damage.
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Linghuan Li, Shibin Sun, Ronghua Zhuang, Bing Zhang, Zeyu Li and Jianying Yu
This study aims to develop a polymer cement-based waterproof coating with self-healing capability to efficiently and intelligently solve the building leakage caused by cracking of…
Abstract
Purpose
This study aims to develop a polymer cement-based waterproof coating with self-healing capability to efficiently and intelligently solve the building leakage caused by cracking of waterproof materials, along with excellent durability to prolong its service life.
Design/methodology/approach
Ion chelators are introduced into the composite system based on ethylene vinyl acetate copolymer emulsion and ordinary Portland cement to prepare self-healing polymer cement-based waterproof coating. Hydration, microstructure, wettability, mechanical properties, durability, self-healing performance and self-healing products of polymer cement-based waterproof coating with ion chelator are investigated systematically. Meanwhile, the chemical composition of self-healing products in the crack was examined.
Findings
The results showed that ion chelators could motivate the hydration of C2S and C3S, as well as the formation of hydration products (C-S-H gel) of the waterproof coating to improve its compactness. Compared with the control group, the waterproof coating with ion chelator had more excellent water resistance, alkali resistance, thermal and UV aging resistance. When the dosage of ion chelator was 2%, after 28 days of curing, cracks with a width of 0.29 mm in waterproof coating could fully heal and cracks with a width of 0.50 mm could achieve a self-healing efficiency of 72%. Furthermore, the results reveal that the self-healing product in the crack was calcite crystalline CaCO3.
Originality/value
A novel ion chelator was introduced into the composite coating system to endow it with excellent self-healing ability to prolong its service life. It has huge application potential in the field of building waterproofing.
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Hong-Feng Li, Jun Sun, Xiao-Yong Wang, Lei-Lei Xing and Guang-Zhu Zhang
The purpose of this paper is to add expanded perlite (EP) immobilized microorganisms that replace part of the standard sand in mortar to improve the self-healing ability of mortar…
Abstract
Purpose
The purpose of this paper is to add expanded perlite (EP) immobilized microorganisms that replace part of the standard sand in mortar to improve the self-healing ability of mortar cracks and reduce the water absorption of mortar after healing.
Design/methodology/approach
Bacillus pseudofirmus spores were immobilized with EP particles as self-healing agents. The effects of adding self-healing agents on the compressive strength of mortar specimens were observed. The ability of mortar specimens to heal cracks was evaluated using crack microscopic observation and water absorption experiments. The filler at the cracks was microscopically analyzed by scanning electron microscope and X-ray diffraction experiments.
Findings
First, the internal curing effect of EP promotes the hydration of cement in mortar, which generates more amount and denser crystal structure of Ca(OH)2 at mortar cracks and improves the self-healing ability of mortar. Second, the self-healing ability of mortar improves with the increase of self-healing agent admixture. Adding a self-healing agent of high admixture makes the planar undulation of calcite crystal accumulation at mortar cracks more significant. Finally, the initial crack widths that can be completely healed by adding EP and self-healing agents to the mortar are 200 µm and 600 µm, respectively.
Originality/value
The innovation points of this study are as follows. (1) The mechanism of the internal curing effect of EP particles on the self-healing ability of mortar cracks was revealed by crack microscopic observation tests and microscopic experiments. (2) The effect of different self-healing agent amounts on the self-healing ability of mortar cracks has been studied. (3) The effects of EP particles and self-healing agents on healing different initial widths were elucidated by crack microscopic observation tests.
Graphical abstract
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Evgenia Madia, Konstantinos Tserpes, Panagiota Polydoropoulou and Spyros Pantelakis
The purpose of this study is the investigation of self-healing materials containing encapsulated healing agents embedded in a polymer matrix with dispersed catalysts. In recent…
Abstract
Purpose
The purpose of this study is the investigation of self-healing materials containing encapsulated healing agents embedded in a polymer matrix with dispersed catalysts. In recent years, the high performance and design flexibility of composite materials have led to their widespread use in the aeronautics, space, automotive and marine fields. Simultaneously, as the need for advanced material properties has increased, many studies have been conducted on multifunctional materials, focusing on different fields of their desired capabilities.
Design/methodology/approach
A multiscale model was developed to simulate the effect of microcapsules on the mechanical behavior of the polymer matrix. Furthermore, the effects of microcapsule diameter and microcapsule concentration on the mechanical behavior of the composite were studied. Digimat and Ansys software were used to simulate the self-healing composites.
Findings
There is a trade-off between the efficiency of the microcapsules and the degradation of the properties of the composite material.
Originality/value
The generated model simulated an encapsulated healing agent in a polymeric matrix.
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Massimo Viscardi, Maurizio Arena, Liberata Guadagno, Luigi Vertuccio and Giuseppina Barra
The purpose of this paper is to evaluate the applicative potentiality of functional/self-responsive materials in aeronautics. In particular, the study aims to experimentally…
Abstract
Purpose
The purpose of this paper is to evaluate the applicative potentiality of functional/self-responsive materials in aeronautics. In particular, the study aims to experimentally validate the enhancement of structural performances of carbon fibers samples in the presence of nanofillers, as multi-walled carbon nanontubes or microcapsules for the self-healing functionality.
Design/methodology/approach
The paper opted for a mechanical study. Experimental static and dynamic tests on “blank” and modified formulations were performed in order to estimate both strength and damping parameters. A cantilever beam test set-up has been proposed. As a parallel activity, a numerical FE approach has been introduced to assess the correct modeling of the system.
Findings
The paper provides practical and empirical insights about how self-responsive materials react to mechanical solicitations. It suggests that reinforcing a sample positively affects the samples properties since they, de facto, improve the global structural performance. This work highlights that the addition of carbon nanotubes strongly improves the mechanical properties with a simultaneous slight enhancement in the damping performance. Damping properties are, instead, strongly enhanced by the addition of self-healing components. A balanced combination of both fillers could be adopted to increase electrical conductivity and to improve global performance in damping and auto-repairing properties.
Practical implications
The paper includes implications for the use of lightweight composite materials in aeronautics.
Originality/value
This paper fulfills an identified need to study new lightweight self-responsive smart materials for aeronautical structural application.
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– The purpose of this work was to prepare a catalyst-free microcapsules as self-healing agent in an automotive clearcoat to improve the scratch resistance of coatings.
Abstract
Purpose
The purpose of this work was to prepare a catalyst-free microcapsules as self-healing agent in an automotive clearcoat to improve the scratch resistance of coatings.
Design/methodology/approach
In this research, microcapsule with isophorone diisocyanate (IDPI) core and polyurethane shell were prepared and used in self-healing coatings. Microcapsules synthesised were characterised by thermal gravimeter and infrared spectra. The microcapsules were dispersed in an acrylic-melamine clearcoat, and the scratch resistance was evaluated.
Findings
The triplex product and the formed polyurethane bonds were confirmed by thermal gravimeter and infrared spectra. In addition, smooth spherical particles with a diameter of 1.5 to 1.7 micronmeters were observed by a scanning electron microscope. The microcapsules dispersed in an acrylic-melamine clearcoat increased the scratch resistance of coatings. Also, the self-healing feature of those coatings was proved.
Research limitations/implications
The size of microcapsules can affect its dispersion in the clearcoat and consequently affect the properties of the cured films.
Practical implications
The self-healing coatings are interested for many industries such as building and automotive industries. The reported data can be used by the formulators working in the R & D departments.
Social implications
Self-healing systems are considered as one of the smart coatings. Therefore, the developing of its knowledge can help to extend its usage to different applications.
Originality/value
The application of microcapsules in the coating as healing agents is a great challenge, which has been hardly investigated so far. In the current research, the effect of polyurethane-IDPI microcapsules in an automotive clearcoat as a self-healing coating was investigated.
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– This paper aims to provide an introduction to smart materials, with an emphasis on their capabilities and applications.
Abstract
Purpose
This paper aims to provide an introduction to smart materials, with an emphasis on their capabilities and applications.
Design/methodology/approach
Following an introduction, this paper first considers what smart materials are and what they can do. It then discusses existing and emerging applications of shape changing, self-actuating, self-healing, self-diagnostic and self-sensing materials.
Findings
Although difficult to define unambiguously, smart materials offer a range of unique characteristics and have been used in a multitude of products, ranging from household goods and novelty items to automotive components and medical devices. They are the topic of extensive research and all manner of new applications will emerge in the future, reflecting both technological developments and a growing awareness of their capabilities.
Originality/value
This paper provides an insight into the rapidly developing technology and applications of smart materials.
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Hua Huang, Yaqiong Fan, Huiyang Huang and Runlan Guo
As an efficient self-healing intelligent material, the encapsulation-based self-healing resin mineral composite (SHC) has a broad application prospect.
Abstract
Purpose
As an efficient self-healing intelligent material, the encapsulation-based self-healing resin mineral composite (SHC) has a broad application prospect.
Design/methodology/approach
Aiming at the cracking performance of SHC, the dynamic load condition is employed to replace the traditional static load condition, the initial damage of the material is considered and the triggered cracking process and influencing factors of SHC are analyzed based on the extended finite element method (XFEM). In addition, the mechanism of matrix cracking and microcapsule triggered cracking process is explained from the microscopic point of view, and the cracking performance conditions of SHC are studied. On this basis, the response surface regression analysis method is used to obtain a second-order polynomial model of the microcapsule crack initiation stress, the interface bonding strength and the matching relationship between elastic modulus. Therefore, the model could be used to predict the cracking performance parameters of the microcapsule.
Findings
The interfacial bonding strength has an essential effect on the triggered cracking of the microcapsule. In order to ensure that the microcapsule can be triggered cracking normally, the design strength should meet the following relationship, that is crack initiation stress of microcapsule wall < crack initiation stress of matrix < interface bonding strength. Moreover, the matching relationship between elastic modulus has a significant influence on the triggered cracking of the microcapsule.
Originality/value
The results provide a theoretical basis for further oriented designing of the cracking performance of microcapsules.
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Panagiota Polydoropoulou, Christos Vasilios Katsiropoulos, Andreas Loukopoulos and Spiros Pantelakis
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…
Abstract
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.
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