Experimental evaluation and simulation on aging characteristics of aluminised AP-HTPB composite solid propellant

Abstract

The aging behaviour of ammonium perchlorate hydroxyl terminated polybutadiene composite solid propellant was characterised using uni-axial tensile and stress relaxation mechanical property measurements at regular intervals during an accelerated aging period. The measured properties in the tension test were Young's modulus, breaking load and percentage of elongation at the time of break. In stress relaxation test, the load at the end of 180 min of relaxation was recorded and it was selected as one of the indicators for the study of aging behaviour. Scanning electron microscopy examinations were also conducted for the fractured tensile test specimens during the aging period to observe the microscopic structure of the fractured surface of the propellant after tension test. Relaxation tests with 5% constant strain with 3 h hold duration were simulated using a finite element computer program. The reaction forces were collected for the period of hold duration and compared with the experimental results. The simulated results are in good agreement with experimental results.     

Generation and validation of failure assessment diagram for notched strength prediction of solid propellant tensile specimens

Abstract

Failure assessment diagrams are generated utilising the well known inherent flaw model and stress fracture models for accurate prediction of notched tensile strength of different cracked configurations of a solid propellant material. The notched strength estimates from the fracture models are found to be close to the test results. This study indicates that any one of the above fracture models may be used for the generation of a failure assessment diagram used to predict the notched strength of cracked configurations made of solid propellant materials.