Investigation On Power-law Fluid Based Continuous Self-healing Process

Material is susceptible to damage induced by mechanical, thermal impacts. This could lead to the formation of cracks within or in the surface of it. The presence of cracks can deteriorate the performance of the material. It is necessary to repair the cracks to maintain the working life and safety of the material. Under many conditions, active intervention is difficult or even impossible. In response, self-repairing material has been proposed and researched. At present, self-healing materials with microcapsules is the focus of research but the filling of cracks with healing agent is a one-time process. The future development calls for the self-repairing technique based on the use of networks of healing agent. Up to now, investigations on the continuous self-repairing technique focus on Newtonian fluid. But most real healing agents are non-Newtonian fluids. In this thesis continuous self-repairing process based on the power law fluid healing agent (one special non-Newtonian fluid) will be studied.Firstly, the orthogonal flowing network structure is considered. Based on one-dimensional laminar flow model, single object optimization of reducing flow resistance for two scales and multi scales flowing structures is performed when fluid volume and mass flow rate are specified. Two-object genetic algorithm optimization of reducing both flow resistance and fluid volume for multi-scale flowing structures is further carried out when mass flow rate is constant. Three-dimensional numeral simulation and typical experiments are also performed for one two-scale structure. The results show that two-scale structure can reduce flow resistance under invariable mass flow rate and such effect is more notable when the power law index increases. One-dimensional calculation and three-dimensional simulation results agree very well. Besides, experimental results support the reducing resistance effect of the optimized two-scale structures. In the process of designing of continuous self-healing flowing structures, it is suggested that the fluid volume be selected first based on the two-object genetic optimization results and then single object optimization be further performed.Secondly, the author does the two-object genetic algorithm optimization for reducing both system mass and pump power of continuous self-repairing system with alternative pumps. The results show that the optimized structure can reduce power effectively under most conditions. The characteristics of fluids can influence Pareto optimal front greatly and the increase of system's reliability (e.g. increase the number of pumps) causes the increase of power consumption.Finally, the filling of cracks and the spreading on material surface are simulated. The results show that the fluid with large power law index and consistency coefficient has good filling effect. The simulation of flowing and curing with acrylate as the healing agent shows that it is reasonable to decouple the flowing process and the curing process.The results can provide good references for continuous self-repairing system design especially for the optimization of fluid flow paths.