Yubing Hu

In solid rocket motors, the liner serves as a critical interfacial material between the propellant and insulation, and its resistance to plasticizer migration directly affects the long-term structural stability of the propellant grain. In this study, hydroxyl-terminated polybutadiene (HTPB) was used as the matrix and isophorone diisocyanate (IPDI) as the curing agent to prepare composite liners with varying graphene oxide (GO) contents (0, 0.1, 0.3, and 0.5 wt%). The ability of the liners to suppress the migration of dioctyl sebacate (DOS) was systematically investigated. Molecular dynamics (MD) simulations were also conducted by constructing two amorphous cell models, namely DOS/HTPB/IPDI and GO/DOS/HTPB/IPDI, to calculate binding energy and migration coefficient and elucidate the role of GO at the molecular level. Immersion experiments revealed that the incorporation of GO significantly lowered the migration rate of DOS in the liner, with the optimal anti-migration performance achieved at a GO content of 0.3 wt%, which exhibited the lowest equilibrium migration concentration. MD showed that the incorporation of GO reduced the binding energy between DOS and the matrix from 290.998 to 229.264 kcal/mol, while the migration coefficient of DOS decreased from 6.52 × 10⁻¹¹ m²/s to 5.52 × 10⁻¹¹ m²/s, corresponding to a reduction of approximately 15.3%. The combined experimental and simulation results indicate that an appropriate amount of GO forms a two-dimensional physical barrier within the HTPB/IPDI matrix, effectively extending the diffusion pathway of DOS molecules and weakening their affinity with the matrix, thereby significantly enhancing the anti-migration performance of the liner. This work provides both experimental and molecular-level insights for the development of high-performance liner materials with enhanced resistance to plasticizer migration.

To enhance the interfacial performance of 3D-printed short carbon fiber-reinforced polylactic acid (CF/PLA) composites, this study designed and synthesized a series of methoxypolyethylene glycol-polyaniline (PEG-PANI) block copolymers with varying ratios of rigid PANI segments to flexible PEG segments to construct a modulus gradient interfacial layer between the CF and PLA. After introducing the PEG-PANI copolymer onto the surface of continuous carbon fibers (CCFs), modified CF/PLA filaments were prepared via twin-screw pelletization and single-screw extrusion and then formed using fused deposition modeling (FDM). Mechanical testing indicates that the mechanical properties of the composite are optimized when the molar ratio of rigid PANI to flexible PEG units is 1:1. Compared to pure CF/PLA, the interfacial shear strength (IFSS) and impact strength increased by 113.48 and 90.37%, respectively, while tensile strength and flexural strength increased by 46.88 and 32.44%, respectively. Atomic force microscopy peak-force quantitative nanomechanical mapping (AFM-PF-QNM) characterization revealed that the PEG-PANI block copolymer formed a continuous modulus gradient transition zone at the modified interface. This gradient structure facilitates effective stress transfer and uniform load distribution under external forces, thereby significantly improving mechanical compatibility and load-bearing efficiency. This study provides an effective interface control strategy for the development of high-performance FDM-printed composites.

Honeycomb sandwich structures are favored in the aerospace industry for their excellent energy absorption and impact resistance. In this paper, a honeycomb sandwich structure with FMLs as skin panels and CFRP as the honeycomb core was manufactured. The effects of structural parameters, including panel thickness (2/1, 3/2, 4/3), honeycomb cell wall thickness (0.2, 0.4, 0.6 mm), and core cell sizes (5, 10, 15 mm), on the energy absorption ability of the sandwich structures were investigated by drop hammer impact tests under different impact energies (15, 40, 90 J). The results show that the peak impact force and absorbed energy increase significantly with the increase of panel thickness. Other parameters have minimal effects. It is worth noting that the energy absorption ability of the honeycomb core is significantly improved when the cell size is 5 mm under higher energy impact. Then the damage process and energy absorption characteristics of honeycomb sandwich structures under 90 J impact were investigated by finite element simulation. Subsequently, the energy absorption of honeycomb sandwich structures with different core sizes was systematically analyzed. An energy absorption formula for honeycomb cores with cell size smaller than 6 mm is derived to provide guidance for the design of the high impact‐resistant sandwich structures.

In this study, a nanosecond-pulsed ultraviolet laser surface processing technique was used to create periodic microgroove matrix structures on the surface of an ethylene propylene diene monomer (EPDM) substrate for interfacial strengthening with carbon fiber-reinforced composites (CFRP). The effects of surface modification on the mechanical properties of the bonding interface were systematically investigated via mechanical tests combined with multiscale characterization methods. The experimental results demonstrated that laser surface treatment reduced the contact angle of the EPDM surface by 67.8% and increased the surface roughness (S_a) to 26.21 μm. These changes significantly enhanced the material surface wettability and mechanical interlocking effect. Fourier-transform infrared spectroscopy analysis confirmed that the laser treatment increased the prevalence of hydrophilic groups on the EPDM surface. Single-lap shear strength tests revealed that the maximum shear strength of the EPDM/CFRP joint reached 4.84 MPa, which was 325% higher than that of the untreated specimen. In addition, the failure mode shifted from adhesive failure to substrate failure. This study provides a substantial theoretical and experimental basis for optimizing the EPDM/CFRP bonding interface.

Thermoplastic polyurethane (TPU) combines elastomeric and thermoplastic properties but suffers from insufficient rigidity and strength for structural applications. Herein, we developed novel carbon fiber-reinforced TPU (CF/TPU) composites filaments and utilize melt extrusion for 3D printing to maintain elasticity, while achieving enhanced stiffness and strength through multi scale-the control of fiber content and optimization of printing parameters, reaching a rigid–elastic balance. A systematic evaluation of CF content (0–25%) and printing parameters revealed optimal performance to be at 220–230 °C and 40 mm/s for ensuring proper flow to wet fibers without polymer degradation. Compared with TPU, 20% CF/TPU exhibited 63.65%, 105.51%, and 93.69% improvements in tensile, compressive, and impact strength, respectively, alongside 70.88% and 72.92% enhancements in compression and impact energy absorption. This work establishes a fundamental framework for developing rigid–elastic hybrid materials with tailored energy absorption capabilities through rational material design and optimized additive manufacturing processes.

Metal powder fuels are widely used in various fields such as aerospace, pyrotechnics, damage, and renewable energy. Recently, ramjets have gained significant attention due to their beneficial characteristics, including simple design, light weight, and high thrust-to-weight ratio. These features make them well-suited for aircraft, missiles, and unmanned aerial vehicles. However, there is a conspicuous lack of comprehensive research on modification methods and applicability into the metal powder fuels for ramjets, which creates an obstacle to further and widespread application. Therefore, this paper focuses on modifying metal fuels suitable for powder fuel ramjets. First, the effects of metal features, such as crystallinity, microscopic morphology, and particle size, on the ignition and combustion performance of fuel, flowability, and density are summarized. Second, the research discusses the modified materials and techniques of metal fuels, especially those that can be adapted to powder fuel ramjets, and systematically exhibits the properties of these modified metal fuels in terms of oxidation, ignition, and combustion. Third, the present challenges and prospects of powder fuels ramjets are discussed in detail. The paper serves as a comprehensive reference and guidance for the research on powder fuel ramjets.

When the particle size of energetic materials is reduced to the nanoscale, significant changes occur in their properties and behavior. In this work, compression processes of three RDX nanoparticles (A, B, and C) were simulated using ReaxFF-lg. The mechanical, structural, and energetic responses of RDX nanoparticles during compression were revealed and characterized. Simulations reveal that the compression process of the nanoparticles can be divided into three stages: elastic stage, primary damage stage, and sustained damage stage. The temperature increase rate in the elastic phase is much lower than in the primary damage phase. In addition, we found that the smaller nanoparticle B presents a smaller elastic modulus and compressive strength, and it has a slower rate of temperature increase during the primary damage phase. Compared to cuboidal nanoparticles (A and B), the spherical nanoparticle C tends to absorb less energy during the elastic stage and exhibits slower damage rate during the primary damage stage. This is a key factor contributing to the low sensitivity of spherical nanoparticles.