Study On Impact Resistance Of Composite Materials Under Low-speed And Ultra-high-speed Impact

With the rapid development of composite materials,it has been widely used in various important occasions due to its good mechanical properties,such as aircraft shell and internal supporting structure,protective shield of space cabin,etc.Composite materials are easily impacted by external loads in engineering applications,among which brittle fiber reinforced composite materials react violently to impact loads,such as falling tools,which may cause severe damage to the structure.In addition,flexible braided composites,as opposed to "brittleness",have been gradually developed and applied to the design of protective structures for spacecraft against hypervelocity impact of space debris,and the foldability of flexible materials plays an important role in improving the effective carrying space of spacecraft.Therefore,it is of great significance to explore the damage degree of "brittle" fiber reinforced composite structure under low-speed impact load and the damage law of flexible braided composite material during ultra-high-speed impact for the safety performance evaluation of future space composite protective structure.The main work of this paper is as follows:Firstly,the low-speed impact damage analysis and residual strength of fiber reinforced composites were studied.In order to explore the damage mechanism of fiber reinforced composites under impact load,the low-speed impact damage test and simulation analysis of composite plate were carried out,the damage mode of composite plate under impact load was studied,and the simulation and test under compression condition were carried out.The subroutine which can accurately describe the damage degree of materials in the process of low-speed impact is written by using the 3Dhashin criterion and the progressive damage theory in fracture damage mechanics for simulation analysis.The residual strength is simulated by using the result model containing impact damage as the initial model of compression simulation.On this basis,a highly reliable impact-compression integrated finite element simulation model is successfully established.Based on the established simulation model,the working conditions under different impact energy are simulated and the residual strength is calculated,and the energy-residual strength prediction curve and semi-empirical formula suitable for fiber reinforced composites are obtained,which has guiding significance for the engineering application of fiber reinforced composites.Secondly,the failure law of flexible braided composite basalt under hypervelocity impact is analyzed and studied.Based on SPH numerical simulation analysis method,combined with Johnson-Cook strength model and Gruneisen equation of state,the damage phenomenon of flexible braided composites during hypervelocity impact was explored.In order to verify the accuracy of this method,the hypervelocity impact test data of aluminum plate under specific working conditions were compared with the simulation results.A plug-in for rapid modeling of braided composites is written to realize rapid modeling and reduce repeated operation time.The simulation results of ultra-high-speed impact between flexible braided composite and aluminum plate are compared,and the difference of damage between them is analyzed.Based on the finite element simulation model,the diffusion law of debris cloud under different plate spacing is explored,which provides reference for the subsequent design of composite protection structure.Finally,based on the above research conclusions,a composite protective structure based on various composite materials is designed by combining "brittle" fiber reinforced composite materials with flexible braided composite materials,which can be used in future alien bases and other occasions.This structure is simulated by hypervelocity impact,and the simulation model is optimized based on SPH-FEM coupling analysis method,which improves the computational efficiency of hypervelocity impact simulation analysis on the basis of ensuring accuracy,so as to evaluate the performance of composite structure.