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Abstract
The high-strain-rate dynamic response of a hydroxyl-terminated polyether (HTPE) propellant during impact loading is essential for assessing the structural reliability and impact safety of HTPE propellant. In this study, a modified split Hopkinson pressure bar (SHPB) apparatus has been developed to research the stress–strain behavior of the HTPE propellant over strain rates ranging from 470 to 5910 s−1 at room temperature, and the validity of the SHPB test is analyzed in detail. Meanwhile, the evolution of deformation to failure of the HTPE propellant was recorded by a high-speed digital camera synchronized with the SHPB test, which revealed the correlation between mechanical response and failure mode. Scanning electron microscopy was applied to investigate the microscopic failure mechanism of the post-test HTPE propellant, which indicated two characteristic failure modes: cracking propagates along the (1) debonding surface and (2) transgranular damage path. Finally, based on the stress–strain plots derived from the SHPB tests, the ultimate stress, strain energy density, and adiabatic temperature-rise effect of the HTPE propellant were seen to show strong strain rate dependence by following an empirical power law function.
Highlights
Sun et al studied the mechanical properties of CMDB propellants under strain rates from 10−4 to 103 s−1 at temperatures from −40 ○C to 0 ○C, and the results indicated that the mechanical performance, such as yield stress, linear elastic modulus, and ultimate strain, depends upon the strain rate and temperature
The prepared hydroxyl-terminated polyether (HTPE) propellant specimen was fabricated in the process of normal casting, which consists of 55.0 wt. % ammonium perchlorate (AP) as the oxidizer, 15.0 wt. % aluminum powder as the fuel, 12.0 wt. % HTPE as the binder, 12.0 wt. % N-butyl-N-(2-nitroxy-ethyl) nitramine (BuNENA) as the plasticizer, 1.5 wt. % isophorone diisocyanate (IPDI) as the cross-linker, and 4.5 wt. % of other additives
The complete stress–strain plot can be divided into four characteristic regions: an initial linear elasticity region corresponding to a uniform deformation without inducing damage followed by a nonlinear increasing region corresponding to germination of debonding and crazing; afterward, a plateau stress region persists until strain of 0.5, accompanied with an almost constant stress level with increasing strain; in this region, crazes develop into cracks and crushing of AP particles occurs, which results in the loss in bearing capacity of the sample; in the end, the fracture region corresponds to the decrease in stress, which means a complete failure of the sample
Summary
As the main energy sources of solid rocket motors (SRMs), solid propellants should withstand a series of severe impact stimulations, such as launch overload, fragment impact, and blast wave, to ensure operational safety and survivability of SRMs. Owing to the advantages of the high energy level and LOVA (Low Vulnerable Ammunition) feature, hydroxyl-terminated polyether (HTPE) propellants are widely considered as the generation of solid propellants for novel tactical missiles. in order to predict the reliability of HTPE propellants under impact loading well, studying the dynamic mechanical response of HTPE propellants is of crucial importance.A HTPE propellant is a highly filled viscoelastic material, which is compounded with a polymeric binder (HTPE), crystal filler [e.g., ammonium perchlorate (AP)], and fuel particle [e.g., aluminum (Al)].7,8 Generally, such viscoelastic materials exhibit very complex mechanical and damage characteristics under dynamic loading. So far, much attention has been paid on the issue of dynamic and quasi-static mechanical properties of solid propellants. A HTPE propellant is a highly filled viscoelastic material, which is compounded with a polymeric binder (HTPE), crystal filler [e.g., ammonium perchlorate (AP)], and fuel particle [e.g., aluminum (Al)].7,8. Such viscoelastic materials exhibit very complex mechanical and damage characteristics under dynamic loading.. Sun et al studied the mechanical properties of CMDB propellants under strain rates from 10−4 to 103 s−1 at temperatures from −40 ○C to 0 ○C, and the results indicated that the mechanical performance, such as yield stress, linear elastic modulus, and ultimate strain, depends upon the strain rate and temperature.. Sun et al studied the mechanical properties of CMDB propellants under strain rates from 10−4 to 103 s−1 at temperatures from −40 ○C to 0 ○C, and the results indicated that the mechanical performance, such as yield stress, linear elastic modulus, and ultimate strain, depends upon the strain rate and temperature. Sunny et al
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