Numerical and experimental determination of self-healing behavior of the epoxy adhesives reinforced with thermoplastic particles

Adhesive bonding is widely used in bonding different materials. Self-healing of bonded structures is becoming of great interest for the industry. Recently, self-healing process, without the need to identify the damaged areas, which are self-repaired, is under intensive research. One of the methods is based on the addition of microencapsulated healing agent and a catalyst in adhesive. Another method is microvascular network approach. This approach influenced by the vascular network of living organisms. Healing mechanism of this method is similar with the microencapsulated healing method. In this method, differently, healing agent is stored in hollow tubes and fibers. In another method, the thermoplastic particles incorporated into the adhesive are self-repaired by activation of thermoplastic particles with temperature. In this dissertation, it is aimed to investigate self-healing mechanism that facilities to repair the damage of brittle and ductile adhesive that are highly sensitive to defects (voids, micro-cracks) or damages caused by loading. Self-healing of adhesive is going to be examined by experimental and numerical approach in this dissertation. In experimental approach, thermoplastic particles will be incorporated into adhesive. In addition, the temperature of self healing will be chosen above the melting temperature of the thermoplastic material. However, it will be considered the glass transition temperature of adhesive while obtaining the curing temperature. The effects of incorporation thermoplastic particles on glass transition temperature of adhesive are also considered during the experimental approach. Efficiency of self-healing process was based on comparison between healed and unhealed fracture energies. Moreover, in numerical study, changing of healed and unhealed cohesive parameters were obtained by using experimental datas and cohesive zone models. In literature, exponential and potential based (PPR) cohesive zone models were used as the numerical model.