Abstract

Carbon-carbon composites (C/C composites) is typical high temperature resistant material. Therefore it is applied in solid rocket motor (SRM) throat mostly. Because the throat is mostly single piece and mini-batch, which is not suitable for mold forming. Usually, numerical control machining is still the main method. Due to high strength and heterogeneous composites, the machining damage defects are obvious and quality is poor. Thus, from the perspective of C/C composites ablation resistance, rotary ultrasonic machining technology effect on C/C composites surface defects and damage is investigated. Moreover, the influence of ultrasonic vibration on fiber cutting angle and machined surface morphology is analyzed. Meanwhile, based on comparative experiment, fiber pull-out length and surface porosity are presented as characterization parameters. The results show that ultrasonic vibration not only improves fiber cutting angle effectively, but also reduces pores and cracks on machined surfaces. Moreover, it reduces fiber pull-out length by 10%–50% numerically when along fiber milling. When fiber is perpendicular to the cutting direction, the pull-out length becomes shorter. The above study provides a theoretical basis for subsequent machined damage influence on ablation resistance of C/C throat.

摘要

碳碳复合材料（C/C复合材料）是典型的耐高温材料。因此它主要应用于固体火箭发动机（SRM）喉咙。因为喉部多为单件和小批量，不适合模具成型。通常，数控加工仍是主要方法。由于复合材料强度高、异质性强，加工损伤缺陷明显，质量差。因此，从C/C复合材料抗烧蚀性的角度，研究了旋转超声加工技术对C/C复合材料表面缺陷和损伤的影响。此外，分析了超声波振动对纤维切割角度和加工表面形貌的影响。同时，在对比实验的基础上，提出了纤维拉出长度和表面孔隙率作为表征参数。结果表明，超声振动不仅有效地提高了纤维切割角度，而且减少了加工表面的气孔和裂纹。此外，在纤维铣削过程中，它在数值上减少了 10%–50% 的纤维拉出长度。当纤维垂直于切割方向时，拉出长度变短。上述研究为后续加工损伤对C/C喉部抗烧蚀性的影响提供了理论依据。