Assessment of Mechanical Properties of Aged Composite Propellant Using Non‐Destructive Indentation Technique in Solid Propellant Rocket Motor

Ageing study of composite propellant is one of the important aspects for the long term usage of a solid propellant rocket motor (SPRM). The assessment of mechanical properties is essential to predict the structural performance of rocket motors before its flight test. Mostly, the study of ageing behavior of composite propellant is limited to sample level which is subjected to either for normal ageing or accelerated ageing. In the present study, an attempt was made to assess the aging behavior of HTPB based composite propellant at full scale rocket motor level using a non-destructive indentation technique. The mechanical properties of naturally aged HTPB based composite propellant samples were comprehensively studied by both Universal Testing Machine (UTM) and indentation technique. The mathematical correlation was developed using least square method between UTM and indentation data. An attempt was made to establish the method to assess the aging behavior of composite propellant by indentation technique directly. The developed correlation was validated on aged composite propellant samples. Further, indentation technique was used to assess the mechanical properties of the propellant of in-flight fielded SPRM which was 11 years old.