Evaluation of Dispersion Methods and Mechanical Behaviour of Glass Fibre Composites with Embedded Self-Healing Systems

Abstract

The present paper is focused on evaluating the most suitable dispersion method in the epoxy matrix of two self-healing systems containing dicyclopentadiene (DCPD) and 5-ethylidene-2-norbornene (ENB) monomers encapsulated in a urea-formaldehyde (UF) shell, prior to integration, fabrication and impact testing of specimens. Both microstructural analysis and three-point bending tests were performed to evaluate and assess the optimum dispersion method. It was found that ultrasonication damages the microcapsules of both healing systems, thus magnetic stirring was used for the dispersion of both healing systems in the epoxy matrix. Using magnetic dispersion, 5%, 7%, 10%, 12% and 15% volumes of microcapsules were embedded in glass fibre composites. Some of the samples were subjected to thermal cycling between −20 °C and +100 °C for 8 h, to evaluate the behaviour of both healing systems after temperature variation. Impact test results showed that the mechanical behaviour decreases with increasing microcapsule volume, while for specimens subjected to thermal cycling, the impact strength increases with microcapsule volume up to 10%, after which a severe drop in impact strength follows. Retesting after 48 h shows a major drop in mechanical properties in specimens containing 15% MUF-ENB microcapsules, up to total penetration of the specimen.

A Microvascular System Self-Healing Approach on Polymeric Composite Materials

“…Also, as seen in the previous work performed by the authors [ 11 , 12 ], even though the microencapsulation of healing agents leads to an 80–85% recovery of mechanical properties, the integration of microcapsules within the matrix and the composite material acts as an induced damage and thus reduces the mechanical properties of the specimen, as compared to the reference ones. This is mainly due to the microcapsule dimensions and volume used, and the fact that after breakage, the microcapsule shells are left within the material, further acting as a stress concentrator for other mechanical loads to which the structure can be subjected to.…”

Preparation of two‐component micro‐encapsulated epoxy self‐healing materials based on Pickering emulsion method

“…As observed in Figure 11a, the flexural strength reached up to 132 MPa at the microcapsule content of 5 wt%, which was only 7.2 MPa less than the sample without the addition of microcapsules, again maintaining 95% of the flexural strength, and 80% of the feedstock at the 10 wt% microcapsule content. Self‐healing materials prepared by Vintila et al 34 when the content of the microcapsules was 5 wt% were used, the self‐healing material had a bending stress of 80% of the feedstock. However, the addition of small‐sized microcapsules affected the bending stress of the self‐healing material to a lesser extent.…”

“…In this study, GO was amphiphilic, because GO surface contained a large number of hydroxyl, carboxyl and other oxygen‐containing functional groups and sp 2 hybrid layers structure, meanwhile, BN was hydrophobic, because BN was composed of sp 2 hybrid layers and arranged in a honeycomb pattern, so GO and BN could be used to stabilize Pickering emulsion 24,31–34 . A schematic diagram of the synthesis of two microcapsules was shown in Figure 1a, where TEPA and IPDI were polymerized at the oil–water interface to form a PU shell, then the epoxy microcapsules and microcapsules of amines were prepared.…”