Analysis On Protection Mechanism Of Basalt Fabric And Ballistic Limit Of Its Stuffed Shielding Structure

China is ready to launch the core cabin of space station in2018at the thirdphase of the manned spaceflight program, and began to establish the space station.The space station needs to run decade in low earth orbit of350km/s~400km/s, inthis period, it will rendezvous and dock with cargo spacecraft and mannedspacecraft repeatedly. Currently growing space debris pose a serious threat to thelong-term safe operation of the space station in orbit. Due to a longer running timein orbit, too much larger exposed area and higher safety indicators for the spacestation, traditional aluminum materials and single shielding structure cannot meetthe protection design requirements of the space station with non-penetratingprobability greater than0.9. So, China intends to use the stuffed shieldingstructure consisting of basalt fabrics and Kevlar fabrics as the main protectivestructure of the space station. The thesis studies the protection mechanism ofbasalt fabric and ballistic limit of its stuffed shielding structure by hypervelocityimpact tests and theoretical analysis method. The main research works includes:Primarily, hypervelocity impact damage tests of basalt fabric were carried bytwo-stage light gas gun facilities, hypervelocity damage of basalt filaments andprojectile were observed with digital microscope. The damage morphologicaldiversity of basalt filaments was discovered; some remaining aluminum meltingparticles and aluminum soften strips were found around the perforation of basaltfabric. Based on these phenomena, the melting-initiation threshold velocity andsoften-initiation threshold velocity of aluminum projectile were obtained withimpacting onto basalt fabric.Secondly, based on the micro-damage of basalt filaments and hypervelocityimpact damage of projectile, the cumulative damage model of projectile was built.The cumulative damage model considered the process of aluminum projectileimpacting basalt fabric as the process of basalt filaments impacting aluminumprojectile; with increasing of shock numbers of basalt filaments, the increasingcumulative effect of shock pressure, impact temperature and internal energy wasanalyzed. By the cumulative damage model of projectile, the propagation law ofshock wave in projectile and basalt filaments and the cumulative effect of impacttemperature and remained specific internal energy were analyzed; the theoreticalvalues of the melting-initiation threshold velocity and soften-initiation thresholdvelocity of aluminum projectile were confirmed. And it was confirmed that themulti-shock of basalt filaments and the woven structure of basalt fabric were themain reasons that causing the erosion damage on the front surface of the projectile.Thirdly, ballistic limit and protection performance of the stuffed shieldingstructure consisting of basalt fabrics and Kevlar fabrics were investigated byhypervelocity impact tests with the projectile with different diameters, andhypervelocity impact damage and protection mechanism of Basalt/Kevlar stuffedshielding structure were also analyzed. The experimental ballistic limit pointswere fitted to the ballistic limit curves, and compared with ballistic limit curves ofNextel/Kevlar stuffed shielding structure with the same areal density, theprotection capability of Basalt/Kevlar stuffed shielding structure was better.Finally, the paper discussed the possibility of building ballistic limit equationby dimensionless method and elastic-plastic theory. In ballistic region, the stuffedshielding structure is equivalent to the rear wall of a certain thickness, the ballisticlimit equation was built using dimensionless method; in liquefaction/gasificationregion, considering the effect of bump thickness, position of stuffed layer and totalprotection spacing, ballistic limit equation was established by dimensionlessmethod; ballistic limit equations of shatter regime was built with interpolationmethod. According the damage morphology and failure mode of rear wall, it wasdiscussed that the possibilities of establishing ballistic limit equations byelastic-plastic theory.Basalt fabric and its stuffed shielding structure were selected as the mainprotection material and the main protection structure of China’s space station, thethesis investigated their hypervelocity damage and protection mechanism,obtained the protection performance data and discussed the methods of buildingballistic limit equation. It will provide theory basis for selecting and developingprotection materials，and provide technical support for China’s manned spacestation.