基于SEM与数字图像相关方法的HTPB推进剂裂尖扩展过程分析

Analysis of Crack Tip Propagation Process of HTPB Propellant Based on SEM and Digital Image Correlation Method

为了从细观角度获得端羟基聚丁二烯(HTPB)推进剂裂纹的扩展特性并分析裂纹的细观破坏机理,通过原位扫描电镜(SEM)对HTPB推进剂三点弯试验裂纹尖端损伤及扩展过程进行了观察,获得了不同变形阶段的裂纹扩展变形形貌,并采用数字图像相关方法分析了图片序列,获得了推进剂裂纹尖端变形场。结果表明,随着推进剂裂纹的不断张开,当挤压位移达到1mm时,裂尖附近应变极值为0.3474,固体颗粒出现脱湿现象,颗粒周边基体受到了较大的应变作用;当挤压位移为2.5mm时,应变极值达0.4168,颗粒和基体界面产生的微裂纹与主裂纹汇聚导致裂纹的扩展。数字图像相关方法和扫描电镜相结合,可用于推进剂在细观尺度下的变形场测量与裂尖扩展过程的破坏机理分析。

To obtain the crack propagation characteristics of hydroxyl-terminated polybutadiene(HTPB)propellant from a microscopic point of view and analyze the mesoscopic failure mechanism of the crack,the crack tip deformation and expansion process of HTPB propellant three-point bending test were observed by in-situ scanning electron microscopy(SEM).The crack propagation deformation morphology of different deformation stages was obtained.The image sequence was analyzed by a digital image correlation method and the deformation field at propellant crack tip was obtained.Results show that the strain extreme value near the crack tip is 0.347 4 when the extrusion displacement reaches 1 mm as the crack continues to open,the solid particles near the crack tip appear dehumidification and the matrix around the particle is subjected to larger strain.When the extrusion displacement is 2.5 mm,the strain extreme value near the crack tip is 0.416 8,the aggregation of the micro-cracks generated at the interface between the particles and the matrix and the main cracks leads to the crack propagation.The combination of digital image correlation method and scanning electron microscope can be used to measure the deformation field of propellant at the mesoscopic scale and analyzed the failure mechanism of crack tip expansion process.