Research And Development Of Optimal Design System For Multilayer Composite Absorbing Materials

Absorbing materials are widely used in military weapons,and become an important means for weapon stealth.By using the coating of absorbing materials,the radar cross section of aircraft,missiles,ships or tanks and armored vehicles can be reduced,and the possibility of military weapons being detected by radar electromagnetic waves can be effectively reduced.At present,the single-layer absorbing material can not meet the requirements of stealth technology such as thinner thickness,lighter weight,wider absorption frequency and stronger absorption ability,so the design of multi-layer composite absorbing material is of great significance.For multilayer composite absorbing materials,due to the complexity and diversity of physical mechanism and optimization objectives,there is still a lack of perfect optimization design system.Genetic algorithm in composite optimization design occupies an important position,however,adopts the roulette method of genetic algorithm to produce a new generation of population chromosome individuals usually has great randomness,aiming at the characteristics of composite material design,based on the roulette wheel selection genetic algorithm combined with using the best way to keep the choice of individual chromosomes into the offspring population,In order to improve the fitness value of the optimal individual in the final population,the crossover and variation of the material type and thickness were carried out by means of crossover and mutation respectively.The main work of this thesis is as follows:1)Based on radar electromagnetic wave incident multilayer composite absorbing material after absorbing materials with different thickness and different kinds of medium interface after the refraction and reflection process to produce the principle of impedance and loss,the ray tracing algorithm is adopted to the given materials of different coating combinations under the different frequency electromagnetic wave produced by the calculation of compound reflectivity.2)For the problem that limiting the maximum thickness of single layer of absorbing material can easily make the thickness of each layer of the optimal individual be the maximum of the limit,the method of limiting the maximum total thickness of multi-layer composite absorbing material is adopted to solve the problem;In order to improve the fitness value of the optimized design results of multilayer composite absorbing materials,the roulette selection method was improved to the roulette selection method for most of the chromosomes in the population,and the best retention method for the other small part,and some chromosomes with the highest fitness value in the population were inherited to the next generation population.Meanwhile,The method of randomly selecting one crossover point and mutation point from the whole chromosome was improved to the method of selecting the crossover point and mutation point respectively for the gene segment encoded by the type and thickness of the absorbing material of each layer on the chromosome.3)Development of multilayer composite absorbing material optimization design system,to provide users with flexible way of parameter Settings in the imported electromagnetic parameters such as the experimental data,the material type and thickness of single layer is obtained by the objective function under the different combinations of fitness value,the improved genetic algorithm for iterative combination way,achieve the best combination of multilayer composite absorbing material determination.In this thesis,the optimal design system of multilayer composite absorbing materials is designed to optimize the different material types and the combination mode of different material thicknesses under the restriction of thickness.The experimental results show that the improved genetic algorithm can effectively increase the fitness value of the optimal individual of the final population and reduce the reflectivity of electromagnetic waves.At the same time,the system can be used to calculate the composite reflectivity of the material at a given thickness,and find the best combination of the material given by the user under the condition of limiting the total thickness of the coating.