Study On Mechanical Properties For Composite Solid Propellant Considering Thermal Ageing And Predictive Damage

The structural integrity and storage life of solid rocker motor highly depend on the the mechanical properties of solid composite propellant. The physical damage and chemical ageing of solid propellant grain may occur in the process of production, transportation and storage. Therefore, the study on the mechanical properties for composite solid propellant under the condition of thermal ageing and predictive damage is important to the propellant’s storage properties and its storage life prediction. In this thesis, the hydroxyl- terminated polybutadiene(HTPB) propellant is choosed as the study object. The ageing rules of HTPB propellant on the predictive damage and thermal aging conditions are investigated, and the ageing model for HTPB propellant is established including the parameters of ageing temperature, ageing time and predictive damage. The research production can be used for structural integrity and life prediction of solid rocker motor.Consider the actual load history of solid propellant grain; the author designed two type program for HTPB propellant, Thermal Aging experiment program and Predictive Damage experiment program. For simulating the physical damage, It takes Pre-strain experiment program and Reciprocating Stretching experiment program. And for simulating the chemical aging, It takes thermal Aging experiment program. In order to get some mechanical mechanical properties, such as strength \ elongation and modulus, the propellant is took unilateral stretching test. Carried out under the conditions of unaged undamaged propellant unilateral stretching test, got the initial propellant mechanical properties..Under the condition of thermal ageing, the HTPB propellant is studyed on the mechanical properties, and is established the ageing model. The study showed that the initial modulus, tensile strength and fracture strength increases with aging time at first increases and then decreases again an increasing trend; Maximum elongation and elongation at break early aging fluctuations, aging late with aging time decreases with an increase; Aging temperature is higher, the more obvious changes in mechanical properties.Under the condition of pre-strain and thermal ageing, the HTPB propellant is studyed on the mechanical properties, and is established the ageing model. The study showed that pre-strain makes propellant strength and elongation decreases, making initial modulus decreases and then increases; with the aging time increases, this effect gradually weakened the mechanical properties of the trend of conventional thermal aging conditions and consistent with the trends; the temperature is the fundamental factor of aging.Prony model using four parameters and improvements include the Arrhenius equation to establish a pre-strain, aging temperature and aging time of maximum elongation propellant aging model.Under the condition of reciprocating stretching and thermal ageing, the HTPB propellant is studyed on the mechanical properties, and is established the ageing model including damage strain-reciprocating stretching frequency-temperature three-factor. The study showed that damage strain and reciprocating stretching frequency badly affect strength of the propellant, but the law is not obvious; Elongation strain injury makes propellant first increases and then decreases, and stretching forth more times, the impact is more obvious; Proposed changes in the mechanical properties of the propellant aging three-factor model combined with Prony series model, Established including damage strain, reciprocating stretching frequency, aging temperature and aging time of the propellant elongation aging model.