| Having high specific strength and modulus,composite materials are widely used in aerospace structures with the continuous improvement of processing technology and reliability,especially for small and medium-sized UAV,most of which are realized for all-composite airframe structure.For light-weight design of UAV,based on reviewing relevant information of topology and composite structure optimization,this dissertation proposed a topology-size combined optimization method for composite structural optimization.Firstly,the structure layout form is obtained by topology optimization.Then,the structure model of composite material is established and applied by size optimization to obtain the optimized structure of composite material.The optimization strategy is validated by the composite box structure optimization numerical cases.Based on the topology-size combined grading optimization method,considering the general design requirements and engineering experience of the wing,the finite element model is established for a certain type of UAV wing with load simplification,and applied to optimize the structure of the wing.Firstly,the initial model of inner structure of the wing,assuming as solid uniform material,is applied for topology optimization analysis.The layout information of the beam and rib is obtained.Then,the beam and ribs obtained by the topology optimization are replaced by the foam sandwich composite material.Establishing the finite element model with optimized size of the panel,the thickness of the layup at different angles is analyzed and optimized.Finally,the optimization of the pavement sequence is applied to realize the overall optimization design of the wing.Comparing the optimization results within/without foam sandwich,the numerical results show that the foam sandwich composite material has better optimization results and stronger carrying capacity.We optimized the structure of the wings of UAV using the method above.According to the results of topological optimization,we designed the stiffening beam and ribs at the end of the wing,and effectively decreased the weight.With Optistruct software,we finished the free-size optimization design of wing skin with external loading through free-size optimization,group-size optimization and stacking-sequence optimization.We considered conditions of three different thickness of foam,and found that certain thickness of foam could effectively decrease the weight and ensure the strength and stiffness.The optimization method and results obtained in this dissertation can be severed as reference data for structure optimization of UAV. |
