Self-healing epoxy composites: preparation, characterization and healing performance (original) (raw)
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Robust synthesis of epoxy resin-filled microcapsules for application to self-healing materials
Philosophical transactions. Series A, Mathematical, physical, and engineering sciences, 2016
Mechanically and thermally robust microcapsules containing diglycidyl ether bisphenol A-based epoxy resin and a high-boiling-point organic solvent were synthesized in high yield using in situ polymerization of urea and formaldehyde in an oil-in-water emulsion. Microcapsules were characterized in terms of their size and size distribution, shell surface morphology and thermal resistance to the curing cycles of commercially used epoxy polymers. The size distribution of the capsules and characteristics such as shell thickness can be controlled by the specific parameters of microencapsulation, including concentrations of reagents, stirrer speed and sonication. Selected microcapsules, and separated core and shell materials, were analysed using thermogravimetric analysis and differential scanning calorimetry. It is demonstrated that capsules lose minimal 2.5 wt% at temperatures no higher than 120°C. These microcapsules can be applied to self-healing carbon fibre composite structural materi...
Healing efficiency of epoxy-based materials for structural application
AIP Conference Proceedings, 2012
Several systems to develop self-repairing epoxy resins have recently been formulated. In this paper the effect of matrix nature and curing cycle on the healing efficiency and dynamic mechanical properties of self-healing epoxy resins were investigated. We discuss several aspects by transferring self-healing systems from the laboratory scale to real applications in the aeronautic field, such as the possibility to choose systems with increased glass transition temperature, high storage modulus and high values in the healing functionality under real working conditions.
Advanced Materials Letters, 2017
The objective of this work was to study the effect of incorporating a microencapsulated healing agent in an epoxy matrix and E-glass fiber reinforced composite. Microcapsules were prepared via oil-in-water emulsion polymerization method with dicyclopentadiene as core material and poly(urea-formaldehyde) (PUF) as shell material. The suitable formulation for the epoxy matrix was selected based on the study of the rheological and mechanical properties of various chemical systems. Different amounts of microcapsules were incorporated and the most appropriate processing method (mixing, curing and postcuring cycle) was evaluated. Furthermore, flexural and fracture tests were carried out and the distribution of the capsules as well as the interfacial adhesion with the epoxy matrix were studied. Finally, the processing of fiber reinforced composites, with and without microcapsules, was carried out by compression molding and the mechanical properties of the composites were studied (modulus and maximum flexural strain) from testing three-point bending. The resulting samples with 32 wt. % of fibers and matrices with no microcapsules were compared. Compression molding technique did not affect the integrity of the microcapsules inside the composites.
Effect Of TETA Microcapsules On Self-healing Ability Of Dual Component Epoxy System
Advanced Materials Letters, 2016
To deliver epoxy composites with enhanced self-healing ability, this study investigates healing efficiency of dual component epoxy system consisting of microcapsules containing epoxy (DGEBA) and different variants of hardener (TETA) microcapsules. Morphological investigation under FESEM confirms formation of spherical shaped intact TETA microcapsules at high agitation speed with average size of the ~65.32 µm and reduced wall thickness of ~1.823 µm. Reaction temperature is found to play significant role to tune the roughness of the microcapsule surfaces. The single edge notched bending (SENB) test was performed to evaluate the healing ability. It was found that with incorporation of microcapsules, the fracture toughness decreases but the healing efficiency increases with increase in content of microcapsules. The maximum healing efficiency observed was 65.61%. High concentration of TETA microcapsule (prepared at high agitation speed) in epoxy network gives the essence for their applicability as a potential ingredient to elevate the healing efficiency. To enhance the healing ability further of the composites as well as fibre reinforced composites with unaltered mechanical properties we believe synthesis nanocapsules and their incorporation could have significant impact.
Cure behavior and mechanical properties of structural self-healing epoxy resins
Journal of Polymer Science Part B-polymer Physics, 2010
Advances in the growing use of polymer composites in aerospace applications explore the possibility in the development of smart materials capable of self-repair. In this article, we have formulated and characterized a multifunctional autonomically healing composite inspired by the design of White et al. Microcapsules containing dicyclopentadiene (DCPD) and powders of Grubbs first generation catalyst were embedded in an epoxy formulation and both the epoxy precursor and the composite were cured up to the temperature of 120 C that preserves the activity of the catalyst. The results on the cure behavior of an epoxy matrix for self-healing material and the influence of the components related to self-healing func-tion on the dynamic-mechanical properties are investigated. The presence of catalyst powder causes a slight decrease in the elastic modulus value with respect to the epoxy matrix. At variance, a large recovery in this parameter is gained for the self-healing specimen, proving that well-distributed microcapsules contribute to improve the mechanical properties. V C 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 000: 000-000, 2010
Evaluation of the Mechanical Properties of Microcapsule-Based Self-Healing Composites
International Journal of Aerospace Engineering, 2016
Self-healing materials are beginning to be considered for applications in the field of structural materials. For this reason, in addition to self-healing efficiency, also mechanical properties such as tensile and compressive properties are beginning to become more and more important for this kind of materials. In this paper, three different systems based on epoxy-resins/ethylidene-norbornene (ENB)/Hoveyda-Grubbs 1st-generation (HG1) catalyst are investigated in terms of mechanical properties and healing efficiency. The experimental results show that the mechanical properties of the self-healing systems are mainly determined by the chemical nature of the epoxy matrix. In particular, the replacement of a conventional flexibilizer (Heloxy 71) with a reactive diluent (1,4-butanediol diglycidyl ether) allows obtaining self-healing materials with better mechanical properties and higher thermal stability. An increase in the curing temperature causes an increase in the elastic modulus and a...
Autonomic Healing of Epoxy Using Micro-Encapsulated Dicyclopentadiene
2003
The autonomic healing ability of an epoxy adhesive containing micro-encapsulated dicyclopentadiene (DCPD) was evaluated. The epoxy resin used was Epon 828 cured with either Versamid 140 or diethylenetriamine (DETA). Variables included total weight percent of microcapsules (MCs) and catalyst, as well as the catalyst to DCPD ratio. The degree of healing was determined by the fracture toughness before and after 'healing' using double-cantilever beam analysis. It was found that the degree of self-healing was most directly related to the contact area (i.e. crack width) during healing. Temperature also played a significant role. Observed differences between the results of this study and those in literature are discussed.
2017
Smart self-healing epoxides have attracted immense interest in the industry due to their capability to prevent crack propagation and increase material service life. Self-healing can be achieved via a number of approaches, where microcapsulebased systems are deemed to be the closest to market implementation. The work presented here demonstrates the effect of polymeric microcapsules made of poly(urea-formaldehyde) on the Charpy impact resistance of a standard epoxy matrix. Poly(urea-formaldehyde) microcapsules containing epoxy resin (EPIDIAN 52) and organic solvent (Ethyl phenylacetate) were prepared using in-situ polymerisation in an oil-in-water emulsion as described in the literature. The Charpy impact tests were performed on specimens made of neat epoxy resin (EPIDIAN 52) amine hardener (Z1) as well as for the epoxy filled with microcapsules with 1, 2.5, 5, 10 and 25 wt.%. The test results have shown that the presence of brittle and spherical additives has a detrimental effect on ...