Hydroxyl‐terminated polybutadiene (HTPB) solid propellant was widely used in carrier rocket and guided missiles, owing to its excellent mechanical properties. The material of HTPB subjected to complex load such as in the process of manufacturing, storage and transportation. Therefore, the mechanical properties of HTPB had important implications for the safety of structure and service life. The purpose of this work is to study the effects of different loading ratios and loading speeds on the biaxial tension of hydroxyl‐terminated polybutadiene (HTPB) solid propellant with a proper kind of biaxial tensile specimen and a high volume fraction three dimensional particle filling model of the material. The proper kind of biaxial tensile specimen with which the stresses in its central part could be obtained with the loads acted on each loading direction was designed and used in the study, and the strains in its central parts were obtained with digital image correlation (DIC) method. The stress‐strain relationship at each direction could be obtained by experiments. Experimental results indicated that the loading speed remarkably influenced the biaxial tensile behaviors of HTPB propellant at room temperature and at different loading ratios. The finite element simulation results demonstrated the accuracy of the biaxial experiment. Based on the experimental results, the particle debonding in biaxial experiments were analyzed and an equivalent Poisson's ratio parameter was proposed to evaluate the degree of debonding. The highly volume fraction three dimensional particle filling model provides a good simulation with experimental results and the equivalent Poisson's ratio parameter can conveniently and accurately determine the debonding of particles which is meaningful to the structure integrity assessment of HTPB solid propellant.

Solid rocket propellants based on hydroxyl-terminated polybutadiene (HTPB), in which HTPB acts as the polymeric binder and fuel matrix, are widely used in aerospace propulsion. During storage, transport, and service, these composite energetic materials are exposed to sustained mechanical loads as well as environmental variations, which may induce time-dependent inelastic deformation. Such creep deformation can alter the grain geometry, affect combustion stability, and reduce the structural reliability of rocket motors. In this work, room-temperature tensile creep tests were conducted on an HTPB-based solid propellant under different stress levels. Several viscoelastic and power-law constitutive models were compared, and a composite time-hardening creep model was established to describe the experimental strain–time response. The model was further implemented in Abaqus through a Fortran user subroutine for finite element simulation. The results provide a useful basis for creep deformation assessment, formulation optimization, and structural reliability analysis of HTPB-based propellants.

The purpose of this work is to study the effects of different loading rate ratios and loading speeds on the biaxial tension of hydroxyl-terminated polybutadiene (HTPB) solid propellant. A proper kind of biaxial tensile specimen with which the stresses in its central part can be obtained with the loads acted on each loading direction is designed and used in the study, and the strains in its central parts are obtained with the digital image correlation (DIC) method. The stress and strain relationship at each direction can be obtained by experiments. The uniaxial stress vs. strain curves and the biaxial stress vs. strain curves were obtained, and it was found that the loading speed remarkably influenced the biaxial tensile behaviors of HTPB propellant. The Mises equivalent stress and strain could be used to describe the biaxial tension stress and strain state, and the exponential constitutive model obtained in the study could be used to predict the stress vs. strain curve under different test conditions.

As the level of engineering technology increases, the mechanical problems posed in the area of mechanics become complex and diverse. The traditional measurement methods and content of past measurements no longer meet the needs, so more advanced experimental methods are needed to accurately measure the three-dimensional shape of objects and their deformations. Nitrate ester plasticized polyether (NEPE) propellants, are the highest energy solid propellant that have been applied in public reports in the world. Due to the material properties of the material itself, its mechanical properties cannot be accurately measured by conventional methods. This paper proposes a simple and highly accurate optical measurement method to study the volume change rate, Poisson’s ratio and true stress-strain curves of NEPE at different displacement loading rates of NEPE. In this paper, the strain of solid propellant NEPE in three directions during unidirectional stretching was measured by defocusing method and digital image correlation(DIC) method and the volume change rate, Poisson’s ratio and true stress-strain curves of NEPE under different stretching rates were obtained. The measured damage initiation engineering strain of NEPE at different tensile strain rates is 0.4687.

Distributed Internet of Things (IoT) nodes powered by wind energy harvesters (WEHs) have enabled long-term, maintenance-free environmental monitoring in remote and extreme scenarios. However, the large fluctuations in wind speed may cause structural fatigue and dynamical instability of conventional WEHs. To achieve stable and durable operation under high wind speeds (up to 25 m/s), this study reports a Feynman-sprinkler-like WEH (FSL-WEH). In contrast to conventional WEHs that rely on turbine blades directly driven by the wind, the FSL-WEH harnesses the reaction force generated by airflow expelled through Feynman nozzles to produce rotational motion. Simulation and experiments indicate that the FSL-WEH achieves a maximum power output of 4.34 W and a peak power density of 66.77 kW/m³ at a wind speed of 25 m/s. Moreover, the FSL-WEH successfully powers an environmental monitoring system, which wirelessly transmits temperature and humidity data to connected terminals, validating the operational reliability and durability of the device in extremely high wind speeds and high-humidity conditions. This study provides a promising solution for scavenging wind energy to power distributed environmental sensor networks under high-wind, high-humidity conditions.