Effect of Compaction Processing on Residual Stress in Molded Sulfur-Based Components

To address crack initiation and deformation in sulfur-bonded propellant rings caused by concentrated residual stress during compression molding, high-energy ultrasonic vibration was integrated into the compaction process for in-situ stress modulation. Residual stress was non-destructively quantified using the critical refracted longitudinal (LCR) wave time-of-flight method. The effects of molding parameters and ultrasonic excitation on stress distribution and structural integrity were systematically examined across specimens with varying densities. A calibrated stress coefficient of 0.254 was obtained for the batch, with all density groups showing no detectable cracks or porosity, confirming the efficacy of the optimized formulation and processing route. Ultrasonic-assisted molding reduced peak residual stress by 25-40%, while higher-density specimens exhibited more uniform hoop stress distributions with elevated magnitudes. The results reveal a synergistic interaction between material density and process parameters in tailoring the internal stress field, offering mechanistic insights and practical strategies for precision molding sulfur-based energetic composites. The proposed approach provides a viable framework for residual stress management in thermoset polymer systems for defense applications.