Research On The Protective Performance Of Sandwich Composite Structures Under The Combined Action Of Fragmentation And Shock Wave

The explosion-proof safety problem has always been concerned by all countries in the world.The explosion is always accompanied by fragments and shock waves.The two damage elements have different action principles,but both of them can produce serious threats to people and structures.No matter in the field of military or civil,how to analyze and evaluate the load characteristics and damage mechanism of fragments and shock waves has always been an important research content.However,traditional protective structures often have disadvantages such as heavy weight and inconvenient transportation.The emergence of new materials and sandwich structures provides a new direction for the study of light protective structures.New materials such as fiber composite materials and foam metal materials not only overcome the above shortcomings,but also have the advantages of fatigue resistance and higher strength.Therefore,it is of great significance to study the composite materials to meet the requirements of lightweight and efficient anti explosion protection materials.In this paper,the sandwich composite structure is taken as the research object.Two kinds of structures,plate structure and tube structure,are designed respectively.Study on damage mechanism and protective performance of sandwich composite structure under the combined action of fragment shock wave.The main research contents are as follows:Firstly,combining dimensional analysis and detonation theory,the generation and propagation principle of fragments and shock wave are studied,and the motion sequence of fragments and shock wave produced by explosion is analyzed.The results show that the mass ratio of explosive to fragment is the main factor affecting the time sequence of fragment and shock wave motion.In the initial period after initiation,the shock wave moves before the fragment,and then the fragment catches up with the shock wave,moving in front of the shock wave.According to the charge type and parameters,the meeting time of shock wave and fragment can be obtained.Secondly,the theory,simulation and test methods are used to study the protective performance of the sandwich composite structure plate against the combined action of fragment and shock wave.An axial preformed fragment charge model and three kinds of sandwich composite plates composed of aluminum alloy,UHMWPE fiber and aluminum foam were designed.The failure mode and protective performance of sandwich composite plates under the combined action of shock wave and fragment were studied.The failure mode of each layer structure was analyzed.The numerical simulation of the models under different test conditions was carried out The change of fragment velocity,energy absorption of target plate and deformation of target plate are analyzed.The results show that: 1.At a detonation distance of 40 cm,the fragments will act on the target plate before the shock wave,and the fragment load strength is far greater than the shock wave load strength.2.Under three conditions,the structure of "1 mm aluminum alloy panel + 10 mm aluminum foam + 10 mm aluminum foam + 10 mm fiber + 1 mm aluminum alloy backplane" has the best protective performance.The number of the backplane without perforation is 7,and the flexural deformation of the backplane is 26 mm,which is less than the other two Working condition.3.Aluminum alloy panel and fiber layer mainly play the role of resistance to fragment penetration.Aluminum foam itself has weak protection ability for high-speed fragments,but has good energy absorption characteristics for shock wave.When the fiber layer is placed at the end of the core layer,the back plate can play a supporting role in the tensile deformation of the fiber,so as to improve the overall anti penetration performance of the target plate.The numerical simulation results of the three working conditions are basically consistent with the test results.The maximum error between the number of target plate not perforated and the deformation degree of back plate and the test value is 14.2%,which can accurately describe the test phenomenon to a certain extent,and can provide guidance for future experiments.Finally,the protective performance of sandwich composite structure under the combined action of fragments and shock wave is studied by using the method of theory and simulation.In this paper,a charge model of circumferential preformed fragments and three kinds of sandwich structures are designed.The failure mode and protective performance of sandwich composite cylinder under the combined action of shock wave and fragments are simulated by LSDYNA software.The results show that: 1.The fragment and shock wave produced by the explosion of the circumferential preformed fragment charge are similar to that of the axial preformed fragment charge.Under the detonation distance of 20 cm,the shock wave will act on the cylinder wall before the fragment.2.Among the three arrangements,"1mm aluminum alloy panel + 10 mm aluminum foam + 10 mm aluminum foam + 10 mm fiber + 1 mm aluminum alloy backplane" structure has the smallest deformation degree,the best total energy absorption effect of the structure,and the best protective performance can be considered.3.With the increase of shock wave strength,the energy absorption ratio of aluminum foam also increases obviously.When aluminum foam is placed behind the panel,it can effectively absorb the energy generated by the deformation of the panel and reduce the overall deformation of the structure.