基于原位X射线成像的推进剂损伤演化表征

In⁃situ X⁃ray tomography based characterization of propellant damage evolution

为实现对硝酸酯增塑聚醚(NEPE)固体推进剂的细观损伤及其演化行为的可视化表征,基于自主研制的原位力学试验系统与第3代高分辨同步辐射X射线三维成像技术,对拉伸速率为0.1 mm/s下的NEPE固体推进剂单调拉伸过程进行三维成像原位观测和表征,获取初始状态固体推进剂的细微观形貌及其随拉伸载荷的演化特征,提取并分析其内部典型损伤的体积与球度随载荷的演化规律。结果表明:同步辐射原位成像技术能够准确获取NEPE固体推进剂的细观结构特征,可以基于灰度差异对固体推进剂的AP颗粒、Al颗粒、基体以及缺陷等实现特征的准确识别。研究发现,NEPE固体推进剂内部缺陷主要有2种,一种为颗粒内的孔洞,一种为AP颗粒/基体界面的初始脱湿。推进剂细观损伤首先表现为初始的界面脱湿形成的孔隙:在拉伸载荷较小时,推进剂的损伤形式主要表现为较大的AP颗粒脱湿形成的孔隙;在拉伸载荷较大时,除AP颗粒脱湿外可以观察到Al颗粒的脱湿,大量的AP颗粒脱湿后形成的孔隙相互融合,最终导致固体推进剂宏观断裂。对固体推进剂内部孔隙定量化表征的结果表明,孔隙体积随着拉伸载荷增大而增加,而球度变化与初始缺陷相关,有初始缺陷时,球度呈现单调减少的趋势,相反则呈现先增加后减少的变化趋势。

To achieve accurate observation and characterization of the meso-damage and its evolutionary behaviour of the Nitrate Ester Plasticized Polyether(NEPE)solid propellant,an imaging scan test was conducted in the mono⁃tonic stretching process of the NEPE solid propellant at a stretching rate of 0.1 mm/s based on the self-developed insitu monotonic loading test system and the third-generation high-resolution Synchrotron Radiation X-ray Computed To⁃mography(SR-μCT)technology.The meso-morphology of the solid propellant at the initial state and its evolution with the tensile load are obtained,and the evolution of the volume and sphericity of the typical damage within the solid pro⁃pellant with the load is extracted.Results show that the SR-μCT can successfully acquire the mesoscale structure in⁃side the NEPE solid propellant,and identify the AP particles,Al particles,matrix,and defects inside the solid propel⁃lant based on the grayscale difference.Mainly two types of initial defects exist inside the NEPE solid propellant,one being the pores inside the particles and the other the initial debonding at the AP particle/matrix interface.The mesodamage of the solid propellant has firstly appeared as pores formed by initial interface debonding.With the small ten⁃sile load,the meso-damage of the solid propellant has mainly appeared as the pores formed by the debonding of larger AP particles,while the large tensile load enables observation of the Al particle debonding in addition to the debonding of AP particles,and the macroscopic fracture of the solid propellant is due to the fusion of the pores formed by the debonding of a large number of AP particles with each other.The volume of pores increases with increasing tensile load,while the sphericity is related to the initial defects,and those with initial defects show a monotonically de⁃creasing trend,while those without initial defects show a first increasing and then decreasing trend.Current results can enable a deeper understanding of the meso-damage of solid propellants,providing a theoretical basis for the next step of establishing the meso-damage model and constitutive relation.