| In recent years,with the development of science and technology,the progress of society and the improvement of people’s living standard,there are more and more phenomena of hard collision and high-speed impact in various scenes,and more and more impact scenes are accompanied by higher acceleration value.Some sophisticated microelectronic devices such as batteries,fuses,gyroscopes,and navigation modules are also susceptible to failure of electronic devices,such as breakage of the power leads,damage to the sensor or power module,etc.,in multiple or sustained high acceleration values,all of which will result in the loss of control or destruction of the host aircraft,resulting in enormous economic and potential military irreparable damage.Therefore,the study of high G impact environment,impact elastic wave and protective structure has become an important direction for the industry.Although there has been much progress on the study of high G impact environment at home and abroad,there are still some problems in the following aspects:First,whether it is deduced from theory or actual research,there hasn’t been any detailed study on the influence factors of peak acceleration produced when impact cabin strikes on different liner materials.Second,the impact tests of high acceleration values are basically based on traditional impact testing machine,Hopkinson pressure bar,Marsh drop hammer and air cannon.The measurement accuracy of the four platforms is not high,the experimental risk is higher,and they cover a large area,so they are difficult to adapt to the relevant experimental research requirements;Third,there is no group researching on the influence of the type,quantity and arrangement of the fiber material on the transmission of impact elastic wave and peak acceleration,by using high-performance fibers to fabricate the built-in pod shell that is used to carry the impact cabin.Based on the above-mentioned background,the platform of high acceleration impact test was set up independently,and the G value peak relation of the impact pod on the platform was deduced and corrected based on the Hertz contact theory.The influence of peak value of acceleration on the platform was discussed and studied.The carbon fiber,basalt fiber and aramid 1414 fiber reinforced epoxy resin composite shell were independently designed and installed into the impact chamber,and were used as research objects to study the transmission of impact elastic wave with different fibers and different structures.Based on the built-in capsule shell of carbon fiber reinforced epoxy resin composite material,a built-in floating stage was designed and developed to study the influence of "suspension" on the acceleration and peak time width of the stage.The research content and research results are mainly reflected in the following aspects.(1)The mathematical model of the peak acceleration of the rigid cylinder in the elastic half-space body in Hertz contact theory is expounded.Based on the structure of the impact body of the HALL-1 type microelectronic device with high acceleration impact tester,the relative mathematical models of the Hertz contact theory are deduced;according to the results of the impact test instrument on various liner materials,the relationship between the peak acceleration and the velocity of the impact body is fitted,and the error between the peak acceleration of the deduction and that of the fitting relation is compared and analyzed.In view of the different friction coefficient of the elastic material of the cushion material has a certain correlation with the above error size,the influence of the friction coefficient of the impact cushion material is discussed,and the error correction of the deduction is performed accordingly.The results show that the peak values of the impact acceleration of the impact body are related to the impact velocity V,the mass M,the elastic modulus E1,E2,the Poisson’s ratio v1,v2,the contact radius a and the base radius of the impact body r.The different friction conditions between the multi-layer liner materials and the liner material and the impact body affect the error between the peak acceleration of the Hertz theoretical deduction and that of the fitting relation.Based on the influence of the friction coefficient,liner materials with low coefficient of friction can reduce the error between the peak acceleration of deduction and that of the fitting relation to the allowable range(2)Based on the shell material of the shock-absorbing cabin,the different high-performance fiber materials(carbon fiber,basalt fiber and aramid fiber 1414),different arrangement(horizontal arrangement or vertical arrangement)and the influence of the total amount of fiber on the peak value of G value of suspension stage were studied.The results show that the energy storage capacity of carbon fiber composite shell is weaker than that of the other two kinds of high performance fibers,and the basalt fiber is the strongest;for the same fiber composite shell with the same arrangement,the higher the amount of fiber is,the higher its energy absorption capacity is;Under same fiber arrangement direction,the transmission of impact elastic wave in the carbon fiber composite shell is faster,while slower in the basalt fiber;the transmission of impact elastic wave is faster in the vertical distributed high-performance fiber of the same kind of high performance fiber composite body;all specifications of the high-performance fiber composite shell has a peak reduction of the duration of the peak,compared to the duration of the peak acceleration of the impact cabin,G-value peak duration of the high-performance fiber-reinforced suspension stage is reduced by about 50%(3)Taking the built-in pods and floating pallets of carbon fiber composite shell as the research objects,from the impact of the elastic wave source,the impact of elastic wave transmission,the friction between the floating stage and the polypropylene film wall of the built-in pods,the elastic modulus of the cushion material under the floating stage and other angles,the impact test of the impact velocity of 1.8m/s～5.5m/s was conducted to study the effect of the "suspension"mode of the stage in the built-in capsule on reducing the peak value of the impact acceleration Impact.The results show that the peak value of the G value of the floating platform is directly affected by the elastic wave intensity generated when the impact pod impacting the cushioning material in the impact velocity range of 1.8m/s～5.5m/s,and the greater the intensity of the source shock is,the greater the value of the G peak value of the floating stage;the impact of elastic wave in the transmission process is influenced by the absorption capacity of the liner material under floating stage,and the more energy it absorbs,the smaller the G value of the floating stage is.In addition,the G value of the floating stage is also affected by the friction between the stage and the inner wall of the built-in cabin and the elastic modulus of the cushion material under the stage.The smaller the friction between the floating stage and the inner wall of the built-in cabin is,the smaller the G value of the floating stage is,and the greater the elastic modulus of the under-stage stage cushion material(the experimental range is 9 kPa to 31 kPa)is,the smaller the G value of the floating stage is and the time of G peak value is also relatively lagged behind.The above results can provide relevant experimental evidence and research ideas for the protection of microelectronic devices built in the impact cabin under the condition of high acceleration impact,and have positive practical application value. |
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