To investigate the flow mechanism of feather-like rough airfoils based on swift wings, computational simulations were employed to explore their overall aerodynamic characteristics in comparison to equivalent smooth airfoils. The study focused on angles of attack ranging from 0° to 20° at low Reynolds numbers. The results reveal that the rough airfoil exhibits higher lift and lower drag compared to the smooth airfoil at moderate angles of attack ranging from 6° to 10°, resulting in significantly improved aerodynamic efficiency. Notably, at an angle of attack of 8°, the aerodynamic efficiency is increased by 19%. However, at angles of attack smaller than 6°, the increase in drag outweighs the increase in lift, leading to lower aerodynamic efficiency for the rough airfoil. Conversely, when the angle of attack exceeds 16°, both airfoils experience separated flow-dominated flow fields, resulting in comparable effective aerodynamic shapes and similar aerodynamic efficiencies. Furthermore, the study found that increasing the Reynolds number results in greater pressure differences in the flow field, leading to higher aerodynamic efficiency. These preliminary conclusions are valuable for elucidating the flight mechanisms of bird-feather-like wings and can inform the design or morphing design of bio-inspired micro aerial vehicles in the near future.

In the field of gun launched missile extended range rocket, the propellant grain in the rocket needs to withstand significant launch loads during their firing phase, and also bear the high pressure caused by ignition, and the impact of launch overloads and ignition shocks on the structural integrity of propellants becomes very important. So this work investigated the dynamic initiation fracture toughness of the composite modified double-base (CMDB) propellant by both experiments and numerical simulations. The dynamic mechanical properties test of the cracked straight through flattened Brazilian disc (CSTFBD) specimens were conducted using a modified Split Hopkinson pressure bar (SHPB). By comparing the results of quasi static and dynamic numerical simulations, it was found that dynamic fracture initiation toughness can be determined by time-to-fracture using the quasi-static theory. The numerical simulation results combined with the ZWT constitutive model agree well with the experimental results, indicating that ZWT constitutive model is suitable for numerical simulation calculation of propellant structural integrity under dynamic load, and provides a theoretical basis for propellant structural integrity analysis under dynamic load. During the measurement of the mechanical response, the fracture surfaces of the dynamic test specimens were observed by electron microscopy scanning. Then the evolution of the microstructure synchronously was obtained. The scanning electron microscope (SEM) results revealed that fracture modes and breakage of the ammonium perchlorate (AP) particles in the surface layer played an important role in determining the failure mechanism, which revealed the failure mechanism of the propellant under dynamic load. The result of experimental measurement showed the influence of loading rate on the dynamic fracture initiation toughness of CMDB propellant.

The aluminium–magnesium fuel-rich propellant is one of the classified propellant used in the solid rocket ramjet. The weapons with the rocket ramjet are under high overload by launching, the mechanical properties of the propellant should be studied under high strain rate. The uniaxial compressive mechanical curves of the aluminium–magnesium fuel-rich propellant under high strain rates have been obtained with the modified split Hopkinson pressure bar in this paper. Four groups of stress–strain curves were obtained at different strain rates of 2600, 3300, 4500 and 5100 s−1. The experimental results show that the mechanical properties of the aluminium–magnesium fuel-rich propellant are rate-dependent, and the Mg–Al fuel-rich propellant has the mechanical properties of viscoelastic material. With the increase of strain rate, the modulus of the aluminium–magnesium fuel-rich propellant obviously increases. The underlying mechanism of the significant rate sensitivity was investigated by adopting the scanning electron microscope from a micro-structure point of view.

Aiming at the application of C/C composite in nozzle throat lining of solid rocket motor, the thermochemical ablation of C/C composites under CO2 or N2 different confining pressures is studied by using a continuous laser ablation test device, and some useful conclusions are obtained. In CO2 confining pressure environment, with the increase of pressure, the heat absorption effect of thermochemical reaction becomes more obvious, and the surface temperature of the sample decreases. The temperature at 1MPa and 2MPa decreases by 12% and 23% respectively, compared with the maximum temperature in N2 environment because there is no chemical reaction between N2 and C/C composites. The sample surface is carbonized after endothermic, and forms a large number of holes.

In order to predict the maximum elongation of composite modified double base (CMDB) propellants under different aging time, temperature and strain rate, systematic uniaxial tensile characterization was performed across six controlled temperatures (233.15 K, 253.15 K, 273.15 K, 283.15 K, 298.15 K, 323.15 K) and three decades of strain rates (3.3 × 10⁻⁴ s⁻¹, 3.3 × 10⁻³ s⁻¹ and 3.3 × 10⁻²s⁻¹) through accelerated aging protocols. The maximum elongation of CMDB propellants under different temperatures and strain rates during aging was obtained, and the aging mechanism of CMDB propellants was analyzed in combination with scanning electron microscopy experiments. The elongation master curve was constructed based on time-temperature equivalent principle, and the elongation master curve model considering aging effect was established combining with existing theories. The results show that the maximum elongation of CMDB propellant decreases monotonically with the aging time, and the microscopic damage in the tensile section gradually increases. The aging time has little effect on the temperature and rate-related properties of the material. By comparing the predicted results of the elongation master curve model considering the aging effect with the experimental results, It is shown that the elongation master curve model considering the aging effect can describe the elongation master curve under different aging time.