All materials are subjected to physical damage, which will reduce their lifetime. In order to enhance the lifetime of manufactured goods, self-healing materials are being investigated. A key limitation of most of the self-healing approaches is their capability of only repairing once in the same site. Vascular self-healing systems overcome that problem. The channels created serve as a reservoir for the healing agents as well as for its distribution along the material. In this PhD project, a nanovascular network will be created through nanofibres in an epoxy matrix. Two-component chemistry will be used for the self healing; the idea is to create two different networks by electrospinning, and fill each one with one of the healing agents. Upon the occurrence of a crack, both healing agents will be released in the crack, come into contact and react, mending the crack.
The first step is to make nanofibrous mats. In the first stage of the project a single network will be produced. This will be used as a model system to study the flow of the healing agent in the vascular network. In the second stage laminates will be produced to allow for alternating layers of the two healing components. Finally co-electrospinning will be carried out creating a core-shell structure. The nanofibrous webs will be characterized mainly using SEM (diameter of the nanofibres). To produce the nanovascular network, a composite will be made by vacuum assisted resin transfer moulding (VARTM). After the curing of the epoxy, the nanofibres will be removed by dissolution. Then, the healing agents will be infused into the vascular system; this requires a study of the flow properties of the healing agents into the vascular network. This study will be performed by wicking experiments and by confocal laser microscopy if possible. The selection of the healing agents will be based upon their flow into the vascular network. A first screening will be based on their contact angle with the matrix and the reaction kinetics. Upon the occurrence of a crack, the healing agents must flow out, spread along the crack and diffuse into another. The interdifussion of the healing agents needs to be faster than the reaction kinetics. This will be studied by microcalorimetry, AFM and SEM-EDX (model systems, mimicking cracks). This will enable a further selection of healing agents. Finally, an in situ study of the ability of the material to fill a real crack will be carried out.
This innovative PhD project will be executed both at the VUB-FYSC, under the guidance of H. Rahier, and at UGent-Tex under the guidance of K. De Clerck