Prediction of Storage Life of Propellants having Different Burning Rates using Dynamic Mechanical Analysis (original) (raw)
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Central European Journal of Energetic Materials, 2013
The ageing of double base (DB) rocket propellants, as a consequence of chemical reactions and physical processes that take place over time, has significant effect on their relevant properties, such as chemical composition and mechanical and ballistic properties. The changes of relevant properties limit safe and reliable service life of DB rocket propellants. Accordingly, numerous research efforts have been undertaken to find out reliable methods to measure the changes caused by ageing in order to assess the quality of DB rocket propellants at a given moment of their lifetime, and to predict remaining service lifetime In this work we studied dynamic mechanical properties of DB rocket propellant artificially aged at 80, 85 and 90°C temperature, in order to detect and quantify changes in dynamic mechanical properties caused by ageing, and to investigate possibilities for prediction of service lifetime. Dynamic mechanical properties were studied using a dynamic mechanical analyser (DMA)...
2017
Nitrocellulose (NC) based double base (db) rocket propellants (RP) are further on in use because of adaptable properties in burning rate and the low signature. The slow ageing during storage is often seen as a major disadvantage. However, this is not the case in reality. If properly manufactured with carefully selected ingredients, in-service times up to 20 years at normal thermal loads (10 to 30°C) can be obtained easily. To secure the in-service time handling of db RP motors, one should use the proven ageing indicators: decrease of primary (added at manufacture) stabilizer, decrease of molar mass of NC, heat generation rate determined by heat flow microcalorimetry (HFMC). They are used to determine the state of chemical ageing and to predict residual in-service time. Further ageing indicators are tensile strength at break, mass loss and gas generation. DMA (dynamic mechanical analysis) can answer special questions. On the base of these methods, the adapted concept for the health m...
Artificial ageing of double base rocket propellant
Journal of Thermal Analysis and Calorimetry, 2009
The ageing of double base rocket propellants (DB rocket propellants), which is a consequence of chemical reactions and physical processes that take place over time, has significant effect on their relevant properties (e.g. chemical composition, mechanical properties, ballistic properties, etc.). The changes of relevant properties limit the safe and reliable service life of DB rocket propellants. This is the reason why numerous research efforts are devoted to finding out reliable methods to measure the changes caused by ageing, to assess the quality at a given moment of time, and to predict remaining lifetime of DB rocket propellants. In this work we studied dynamic mechanical properties of DB rocket propellant artificially aged at elevated temperatures, in order to detect and quantify changes in dynamic mechanical properties caused by the ageing. Dynamic mechanical properties were studied using dynamic mechanical analyser (DMA). The results obtained have shown that the ageing causes significant changes of DMA curve's shape and positions. These changes are quantified by following some characteristic points on DMA curves (e.g. glass transition temperatures; storage modulus, loss modulus and tand at characteristic temperatures, etc.). It has been found out that the most sensitive parameters to the ageing process are: storage modulus at viscoelastic and softening region, peak width and height on loss modulus curve, glass transition and softening temperature, and tand at viscoelastic region.
Central European Journal of Energetic Materials, 2021
This work introduces dynamic mechanical thermal analysis (DMTA) as an efficient method for the assessment of the shelf life of solid composite solid propellants in air and nitrogen atmospheres. The samples were aged at three temperatures 323.15, 333.15, and 343.15 K for 60, 120, and 180 days. The two different methods of Arrhenius and Berthelot were used to compare the effects of air and nitrogen atmospheres on the ageing of composite solid propellants. Damping (Tan δ) of composite solid propellants was used to determine the shelf life of the samples based on the loss of half of the physical property Tan δ (50% drop in damping). For the air atmosphere, the calculated activation energy for the degradation reactions of the samples was 86.26 kJ·mol–1. Both models, Arrhenius and Berthelot, confirmed that the shelf lives of the samples under the nitrogen atmosphere are more than four times those in an air atmosphere.
Studies on Stress-Strain Curves of Aged Composite Solid Rocket Propellants
Defence Science Journal, 2012
Mechanical property evaluation of composite solid rocket propellants is used as a quick quality control tool for propellant development and production. However, stress-strain curves from uni-axial tensile testing can be utilised to assess the shelf-life of propellants also. Composite propellants (CP) of two varieties cartridge-loaded (CLCP) and case-bonded (CBCP) are utilized in rocket and missile applications. Both classes of propellants were evaluated for mechanical properties namely tensile strength, modulus and percentage elongation using specimens conforming to ASTM D638 type IV at different ageing time. Both classes of propellants show almost identical variation in various mechanical properties with time. Tensile strength increases with time for both classes of propellants and percentage elongation reduces. Initial modulus is also found to decrease with time. Tensile strength is taken as degradation criteria and it is observed that CLCP has slower degradation rate than CBCP. This is because of two facts-(i) higher initial tensile strength of CLCP (1.39 MPa) compared to CBCP (0.665 MPa) and (ii) lower degradation rate of CLCP (0.0014 MPa/day) with respect to CBCP (0.0025 MPa/day). For the studied composite propellants, a degradation criterion in the form of percentage change in tensile strength is evaluated and shelf life for different degradation criteria is tabulated for quick reference.
Analysis of stability of naturally aged single base propellants
African Journal of Pure and Applied Chemistry, 2021
In this work chemical changes in 42 years old single base propellant induced by natural aging were evaluated. The sample was stored for a long time under uncontrolled conditions. The chemical stability was tested using High performance liquid chromatography (HPLC), High-performance thin-layer chromatography (HPTLC), the vacuum stability test (VST), SEM/EDX and visual analysis by Stereo Microscope. Heat flow calorimetry (HFC) method was used for analysis of thermal behavior of the sample. Visual changes in appearance of the 42 years old propellant sample surface were apparent. HPLC analysis showed that the sample contains very low effective stabilizer content (<0.2%) and VST measured very high gas release (ΔVST gas >2 ml/g). Therefore, the propellant is classified as very unstable. Although the effective stabilizer is almost completely consumed, the sample demonstrated very good thermal properties measured using HFC where the heat flow limit of 114 μW/g was not exceeded. The presence of inorganic stabilizers which could contribute to stability was examined using SEM/EDX. The results showed only presence of C, O and N and traces of Si. It could be assumed that even though all the parent DPA is almost consumed, the remaining daughter stabilizer products continue to protect the propellant from possible self-ignition for a long period of time.
Dynamic mechanical analysis of double base rocket propellants
Biuletyn Wojskowej Akademii Technicznej, 2016
The article presents dynamic mechanical analysis (DMa) for solid rocket propellants testing. Principles of operation and measured values are briefly described. The authors refer to the previous research of PtFe material and literature data providing information about proper experimental conditions and influence of measurement frequency, load amplitude, and heating rate on the results of DMa tests. The experimental results of solid double-base rocket propellant testing obtained on the netzsch DMa 242 device are presented. Mechanical properties such as the dynamic storage modulus E´, the dynamic loss modulus E˝ and tan(δ) were measured within temperature range from (-120°c) to (+90°c) at the heating rate of 1 k/min. The test sample was subjected to a dual cantilever multi-frequency test. special attention was paid to determination of the glass transition temperature of the tested propellant in reference to the nato standardization agreement 4540 as well as influence of the measurement frequency on the glass transition.
Problemy Mechatroniki, 2015
The paper presents results of Dynamic Mechanical Analysis (DMA) of double-base (DB) solid rocket propellant with special attention paid to determining the glass transition temperature. The presented experiments were carried out with the use of Netzsch DMA 242C analyzer with the dual cantilever operation mode. Advantages and drawbacks of the DMA method, measured values, as well as important characteristics of solid double-base rocket propellants were briefly described. Obtained values of the storage modulus E', the loss modulus E", and tanδ were represented in dependence on temperature. The glass transition temperature of the tested propellant was determined according to NATO standard 4540 [7] at the peak of the loss modulus curve.
Study of Mechanical Properties of Naturally Aged Double Base Rocket Propellants
2010
Various chemical reactions and physical processes (such as stabilizer consumption, migration and evaporation of nitroglycerine, decomposition of nitroglycerine and nitrocellulose, etc.) take place in double based rocket propellants grains over the time, even under ambient storage conditions. The overall effect of these reactions and processes are changes of physical, chemical, thermal, ballistic and mechanical properties of rocket propellants with storage time, i.e. the reduction of the propellants performances and safe service life. The aim of this work was to evaluate the mechanical changes of rocket propellants-sustainers, built in in-service antitank guided missiles systems, induced by natural ageing at ambient conditions during up to 35 years of storage. The mechanical and viscoelastic properties were tested using a dynamic mechanical analyser, an uniaxial tensile and compression tester, and a notch toughness tester. The results have shown that the changes of the studied mechanical and viscoelastic properties are evident, although the results of the tests are rather scattered (as a consequence of measuring uncertainty, different ageing histories of propellants, etc.) or changes of some properties are not too pronounced. For example, after 15 years of storage at ambient conditions the glass transition temperature increases for about 5 °C, the tan δ in the glass transition region decreases for about 5%, the storage and loss modulus at 25 °C increase for about 15%, Young modulus at 23 °C increases up to 30%, the notch toughness at-30 °C decreases up to 15%, etc. Along with these tests, the stabilizer content determination and proving ground ballistic tests were also done.
Analysis of the aging process of double-base propellants without an organic stabilizer
Scientific Technical Review, 2014
This paper describes studying the chemistry of the double-base propellant aging process of the grains from the START motor of the Soviet ground-to-air missile system, S-125 'Neva'. This system was introduced in the armament of the Army of Serbia, in the early seventies of the last century and it is still in use. In order to determine the extent of degradation of propellants and then assess their chemical stability, ten methods were used. Modern analytical methods confirmed that typical organic propellant stabilizers are not present in the tested propellants. Therefore, the chemical stability of this propellant had to be additionally tested by the methods which are not based on measuring the consumption of stabilizers such as: microcalorimetry method of heat flux measuring, vacuum stability test, heat storage test at 100ºC, methyl violet test at 120ºC and mass loss test.