High-efficient Numerical Method For Impact Response Of Large Composite Structures And Its Applications

Composite materials are more and more widely used in the aerospace industry.The application of composite in our country lags behind advanced level abroad significantly.The composiste structural design level is one of the main problems that restrict the widely application of composite materials.Numerical simulation is an important approach of composite structural design.The application scope of composite materials gradually transitions to main bearing structure and large complex structure,which puts higher requirements on the computational efficiency of numerical simulation.The purpose of this paper is to investigate the high-efficiency simulation strategies for the impact response of large-scale composite structure,which foucs on the high-efficiency modeling method and high-efficiency optimization design methods to establish an high-efficient numerical method for large-scale composite structure impact response.The anti-bird impact optimization design of composite wing leading edge is as an example to demonstrate the superiority of the algorithms.The high-efficiency numerical method can accelerate the design process of composite structures and improve the design level of impact resistance of composite structures.Significant efficiency improvement is achieved.Efficient element algorithms are an important way to improve the efficiency of numerical simulations,so this paper studies the improved solid shell element,which eliminating the trapezoidal locking,transverse shear locking,Poisson locking and volumetric locking by adopting assumed natural strain method(ANS),enhanced assumed strain method(EAS)and selective reduction integration(B-bar)method.Compared with other solid shell elements adopting multi-parameter EAS method,the new improved solid shell element with single-parameter EAS method has higher computational efficiency.The classical numerical examples show that the new solid shell element proposed in this paper has high accuracy and high efficiency.The high-efficiency solid shell element is applied to the delamination simulation of the composite double cantilever beam model.The numerical results show that the new improved solid shell element has higher calculation accuracy and faster calculation speed than the continuous shell element in Abaqus.The high-efficiency solid shell element can improve the numerical analysis efficiency of composite structures and speed up the design progress.Since the simulation accuracy depends intensively on fine meshes,the numerical analysis of the impact response of large composite structures is costly,which affects the efficiency and design of composite structural analysis.This paper proposes a multi-grade global-local modeling method,especially suitable for simulation of impact response.The response characteristics of different regions in the composite structure is analyzed,and then the composite structure is divided into several local regions.The different local regions adopt different modelling strategies according to the research objectives and response characteristics,which greatly reduces the computational scale and improves the analysis efficiency of the impact response of large composite structures.Based on the analysis model for impact response of composite structure,this paper determines the local region division scheme of wave-controlled impact response and ballistic impact response.Combining analytical model,multi-grade global-local modeling method and simulation strategies for composite material which includs SSE-ABE element,this paper establishes an efficient modeling method for large composite impact response.Efficient modeling methods can establish efficient numerical models,and efficient numerical models can achieve efficient numerical analysis.Efficient modeling and high-efficiency numerical analysis are the means to achieve efficient composite structure optimization design.Therefore,this paper studies the efficient optimization design method of composite structure impact response,and proposes simulation optimization method based on high-efficiency numerical model and theoretical optimization method based on analytical model.The high-efficiency numerical model plays an important role in both optimization methods.Finally,combined with efficient modeling method and efficient optimization design method,this paper establishes an efficient numerical method for large-scale composite impact response.The high-efficiency numerical method for large composite impact response is completely applied to the modeling,numerical analysis and optimization design process of the composite wing leading edge anti-birdstrike problem.Firstly,the birdstrike model of composite wing leading edge is established based on the multi-grade global-local modeling method.The number of elements of the birdstrike model is reduced from 650,000 to 270,000.The model simulation time cost is reduced from 36 hours to 10 hours,which means that the simulation efficiency is improved by 3.6 times.The accuracy of the birdstrike model is almost the same as the original one.The numerical birdstrike model is validated effectively by the birdstrike experiment.Both the numerical analysis and the birdstrike experiment show that the original structure design of the composite wing leading edge does not meet the anti-birdstrike performance requirements.Therefore,the optimization design of the composite wing leading edge is carried out.The optimization design process is based on the theoretical optimization design method,so a birdstrike analytical model is established.The analytical model combines the effective impact kinetic energy and the effective impact kinetic energy density.The weakness factor is used to characterize the severity of the damage caused by the birdstrike.And the corresponding Matlab algorithm to efficiently determine weakness factor is also given.The birdstrike analytical model is used to analyze the birdstrike problem of the composite wing leading edge in this paper.The critical impact position is determined,which is different from that used in the traditional birdstrike study.The high-efficiency numerical analysis results support the conclusion drawn by analytical model,which validate the correctness of the analytical model.Based on the birdstrike analytical model,this paper proposes an anti-birdstrike optimization design scheme for localized strengthening skin with variable thickness.The effective impact energy density distribution function is used to determine the thickness distribution of the localized strengthening skin,and the best anti-birdstrike performance is achieved.The performance of the new optimization scheme is far better than the traditional optimization schemes.The above process is summarized into composite wing skin design process that meets the anti-birdstrike requirements,which can reduce the number of experiment and simulation cost,realize the efficiency of the design of the wing leading edge structure,speed up the design progress,and improve the impact resistance design of composite structures.In this paper,an high-efficient numerical method for the impact response of large composite structures is established,which can significantly improve the efficiency of numerical modeling,numerical analysis and structural optimization design.Its superiority is fully embodied in the research of anti-birdstrike design of composite wing leading edge.