Influences of fillers [including multi-walled carbon nanotubes (MWCNTs), SiC nanowires, methyl-polyhedral oligomeric silsesquioxanes (methyl-POSS) and boron phenolic resin] on the characteristics of porous structure in char layers of ethylene propylene diene monomer (EPDM) composites were studied using experimental solid rocket motor (SRM). Comparing to basic formulation (Porosity: 78.25%), char layers of fillers formulation present lower porosity (Ranging from 64.03% to 67.69%) and showed significant trends of overall or local densification. Further analysis revealed different densification mechanisms: CNTs and SiC nanowires can promote chemical vapor deposition (CVD) reaction in char layers and reduce its porosity, which can be referred as “CVD-promotion densification”; boron phenolic resin is relatively high in char yield and char residue would densify the microstructure of char layers, which can be referred as “char residue densification”; methyl-POSS show a combination of both mechanisms, which lead to the lowest mass ablation rate [170.4 g/(m²·s)] and the best ablation performance.

填料[包括多壁碳纳米管 (MWCNTs)、SiC 纳米线、甲基-多面体低聚倍半硅氧烷 (methyl-POSS) 和硼酚醛树脂] 对三元乙丙 (EPDM) 复合材料炭层多孔结构特性的影响使用实验性固体火箭发动机 (SRM) 进行了研究。与基本配方（孔隙率：78.25%）相比，填料配方的炭层孔隙率较低（范围从 64.03% 到 67.69%），并显示出整体或局部致密化的显着趋势。进一步的分析揭示了不同的致密化机制：碳纳米管和碳化硅纳米线可以促进炭层中的化学气相沉积（CVD）反应并降低其孔隙率，这可以称为“CVD促进致密化”；硼酚醛树脂的成炭率较高，炭渣会使炭层微观结构致密化，可称为“炭渣致密化”；甲基 POSS 显示了两种机制的组合，导致最低的质量消融率 [170.4 g/(m² ·s)]和最佳消融性能。