TiB_2基陶瓷复合材料超高速撞击损伤行为研究

Damage Behavior of TiB_2-based Ceramic Composites under Hypervelocity Impact

为了提高航天器对空间碎片的防护能力,设计了以TiB_2基陶瓷复合材料为缓冲屏的Whipple式防护构型(单层TiB_2基陶瓷缓冲屏以及TiB_2基陶瓷/铝合金缓冲屏),利用二级轻气炮在2.88~7.32 km/s的撞击速度范围内开展超高速撞击实验,并对上述缓冲屏与典型全铝合金缓冲屏进行比较验证。通过分析不同撞击速度下缓冲屏的穿孔、后墙损伤、碎片云结构特征,并结合SEM微观损伤形貌和EDS元素分布模式,重点阐述了不同缓冲屏材料特性与结构特性对碎片云形成以及后墙撞击成坑之间的作用关系。研究表明,单层TiB_2基陶瓷复合材料缓冲屏可以有效破碎铝合金弹丸获得更加细小的碎片云颗粒,由于碎片云动能被有效分散到更为广泛的细小碎片颗粒当中,从而获得比等面密度典型全铝缓冲屏更为优异的防护性能,且防护性能随着撞击速度的增加而有所提高。相反的,TiB_2基陶瓷/铝合金缓冲屏由于异质材料之间波阻抗的明显差异,在超高速撞击下会导致陶瓷前面板的严重断裂并造成铝合金后板的花瓣状破坏,且损伤程度随着撞击速度和弹丸尺寸的增加而增加,由于不能有效细化碎片云颗粒,其防护效能反而低于等面密度典型全铝缓冲屏。

In order to improve the protective capability of spacecraft shielding configuration for hypervelocity impact of space debris, the Whipple-based shield configuration within the thin-plate bumpers of TiB_2-based ceramic composites were manufactured（i.e. the monolayer bumper of ceramic plate, the double-layer bumper of ceramic/metal plate）. The hypervelocity impact experiments were carried out on a two-stage light-gas gun to compare the above novel bumpers with the typical aluminum alloy bumper under the impact velocity of 2.88~7.32 km/s. The perforation characteristics of front bumper, the damage characteristics of rear wall and the structural characteristics of debris were studied by combining the SEM fracture morphology and EDS elements distribution, especially, the relationship among the material properties and structure features of various bumpers, the formation process of debris clouds, the cratering mechanics of rear wall was discussed. The results show that the monolayer ceramic bumper can effectively smash the projectile to smaller pieces in debris cloud. Since the impact kinetic energy of projectile fragments is distributed into the smaller particles of expanded debris cloud, the protective capability of the monolayer ceramic bumper exceeds the typical aluminum alloy with equal areal density. Moreover, the protective capability of the monolayer ceramic bumper is obviously promoted with the increasing impact velocity. On the other hand, for the double-layer ceramic/metal bumper, due to the difference in acoustic impedance between the ceramic and aluminum, the impact wave could causes serious fracture in the front ceramic plate as well as the curling deformation of rear aluminum plate, and the damage degree of ceramic/metal bumper increases at higher impact velocity. Because of the larger impact fragments and the smaller expanding bubble of the debris cloud, the protective capability of the double-layer ceramic/metal bumper is worse than the traditional aluminum bumper on the contrary.