No abstract

PurposeThis 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/approachMicrocracks 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.FindingsThe 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/valueThe optimization of production factors has been realized to produce the most efficient MCs that heal using less expensive and more accessible methods.

The self-healing of micro and macro cracks is vital for eliminating defects such as damage progression and loss of strength in structures. In this study, a polyurethane (PU) based geometrically self-healing sandwich structure was developed. The geometric healing agent, PU resin and activator, were filled into macrocapsules, and these capsules were filled into the Aluminum (Al) honeycomb cells. Self-healing of structural strength, large holes and cracks in developed sandwich structures were investigated by performing quasi-static compression and impact penetration tests. The sandwich structure with a self-healing capsules-filled core was damaged by subjecting it to quasi-static and penetration impact loads, and the healing agents in the broken capsules were mixed. The damage in the specimen was removed by geometric self-healing. Liquid and air permeability tests were applied to the PU foam used as a healing agent. No liquid permeability was observed in the structure. In addition, significant reductions in air permeability were obtained. Scanning electron microscope images were used to explore the characterization of the PU foam structure cells.