Ceramic matrix composites are ideal for thermo-structural components, where they often encounter complex multiaxial stress states. This study investigated damage evolution in plain-woven SiC/SiC tubes under combined tension-torsion loading using acoustic emission, three-dimensional digital image correlation, and fractography. Results demonstrated that the mechanical behavior was significantly influenced by the stress state. AE analysis revealed this was due to competitive and synergistic tensile-shear interactions, which intensify damage accumulation and drive a transition in the dominant energy dissipation mechanism. To quantify this damage evolution and identify the governing stress type, an AE-based damage initiation criterion and a failure progression envelope model were developed. Fractography further indicated that while the fracture path is governed by the governing stress type, a transition in governing stress type can occur during loading, specifically when tensile and shear stresses co-dominate. This shift directed fracture along the direction of maximum shear stress, consistent with observed fracture angles.

The purpose of this paper is to develop an efficient computational method that predicts the nonlinear dynamic response of C/SiC thermal protection systems (TPS) under time-varying thermal environments with reasonable accuracy. To address thermally induced stiffness evolution, this paper proposes an incremental modal superposition (IMS) method with FEM-based time-dependent modal updating. The IMS method computes response increments in the time-varying modal space and reconstructs the total response in the physical domain, enabling efficient time-domain solution for nonlinear systems. First, a thermal modal test system is established to characterize the dynamic properties of the TPS. Guided by the test, a temperature-dependent finite element model is developed and updated. Thermal–vibration tests are then conducted, and numerical calculations are performed under the same test conditions. The IMS method achieves a 26.5% efficiency improvement over the conventional direct integration method, with only a 1.3% deviation between the predicted and experimental overall RMS responses, demonstrating its clear advantage in efficient response prediction. The dynamic response under combined thermal–vibration–acoustic loads is further analyzed. This study supports efficient dynamic response prediction and strength assessment of composite TPS under extreme service conditions.

The aerodynamic properties of flexible wings can be improved through shape morphing using piezocomposite materials. This study established a piezo-driven flexible wing model and investigated its structural dynamic characteristics under the coupling of structural dynamics and electric field using the Dynamic Mode Decomposition with Control (DMDc) method. By employing this approach, the study examined the dynamic characteristics of wings under multi-field coupling conditions, revealing the nature of the system's complex dynamics. The study concluded the following: Firstly, the DMDc method can effectively capture the structural dynamic characteristics of high aspect ratio wings, including vibration modes and frequency responses, with the best accuracy observed in frequency response capture, the maximum relative error is less than 0.001

Nanoporous materials functionalized liquid (NMFL)-filled structures demonstrate significant potential in the field of energy absorption and cushioning. To thoroughly investigate the behavior of NMFL-filled tubes under axial loading, this study establishes an analytical model based on the ring-shaped crushing hypothesis, deriving analytical expressions for peak stress and mean crushing stress, with the accuracy of the theoretical model validated through finite element analysis. The results show that the crushing process of NMFL-filled tubes exhibits three distinct stages: elastic, yield, and strengthening. For a representative configuration, the FE-predicted peak stress and mean crushing stress in the yield stage are 20.94 MPa and 16.00 MPa, respectively, while the corresponding theoretical predictions are 23.68 MPa and 16.99 MPa. Parametric analysis reveals that the infiltration pressure of the NMFL and the wall thickness of the tube are key parameters controlling the crushing morphology, and global buckling instability occurs when the infiltration pressure exceeds 14 MPa. This study fills the gap in the theoretical modeling of axial crushing for NMFL-filled structures and provides a scientific basis for developing new high-performance cushioning and energy-absorbing materials.

Soft robots, formulated by soft and compliant materials, have grown significantly in recent years toward safe and adaptable operations and interactions with dynamic environments. Modeling the complex, nonlinear behaviors and controlling the deformable structures of soft robots present challenges. This study aims to establish a physics-guided deep learning (PGDL) computational framework that integrates physical models into deep learning framework as surrogate models for soft robots. Once trained, these models can replace computationally expensive numerical simulations to shorten the computation time and enable real-time control. This PGDL framework is among the first to integrate first principle physics of soft robots into deep learning toward highly accurate yet computationally affordable models for soft robot modeling and control. The proposed framework has been implemented and validated using three different pneumatic soft fingers with different behaviors and geometries, along with two training and testing approaches, to demonstrate its effectiveness and generalizability. The results showed that the mean square error (MSE) of predicted deformed curvature and the maximum and minimum deformation at various loading conditions were as low as $10^{-4}$ mm $^{2}$ . The proposed PGDL framework is constructed from first principle physics and intrinsically can be applicable to various conditions by carefully considering the governing equations, auxiliary equations, and the corresponding boundary and initial conditions.

To enhance the accuracy of predicting the dynamic response of a supersonic rocket sled along a multikilometer track, a multibody dynamics model of a flexible sled-track system was formulated using finite volume beam elements and multi-degree-of-freedom spring-damper joints. Shear locking was avoided by modifying the constitutive matrix, and the accuracy of the modeling method was validated through modal tests of both the sled and the track. The sled-track interaction model was developed by considering clearance, collision, and friction. A window transfer method was developed to improve computational efficiency. The flexible sled, with a maximum velocity of Mach 2.7, was simulated running along the long flexible track, accounting for the sled's time-varying mass, random track irregularities, oscillating engine thrust, and velocity-dependent aerodynamic forces. A supersonic rocket sled test was also conducted to validate the method. The results showed that the flexible sled-track model developed in this study significantly improved the accuracy of predicting the system's dynamic response compared to traditional rigid sled or track models. The main frequencies of the sled cabin's dynamic responses corresponded to the system's time-varying natural frequencies. The slipper's acceleration exhibited superharmonic responses, with the main frequencies being odd multiples of the fundamental frequency.

As the size decreases, the flight Reynolds number of nano rotors decreases, reaching approximately 104 in magnitude, leading to a sharp decline in their aerodynamic efficiency. Therefore, it becomes crucial to improve the aerodynamic performance of nano rotors at low Reynolds numbers through flow control methods. Existing studies have shown that flexible membranes can improve aerodynamic performance of nano rotors, yet the mechanisms behind this improvement remain unclear. This study uses a dynamic mode decomposition (DMD) framework for analyzing the fluid-structure interactions of flexible membrane rotors, enabling simultaneous examination of fluid and structural variables. Results show that the aerodynamic efficiency of flexible membrane rotors has increased by approximately 7.5% compared to non-membrane rotors. DMD analysis reveals that both membrane and non-membrane rotors are dominated by static modes, which contribute over 65% to the flow field, indicating that the primary mechanism driving the improvement in aerodynamic efficiency is attributed to the static deformation of the membrane. Regarding vibration characteristics, differences in rotor structural properties result in distinct forms of vibration, which excite higher-order aerodynamic modes when coupled with the flow field. This effect becomes more pronounced with increasing collective angles, with higher-order modes contributing up to approximately 35% to the flow field. Research shows that the static deformation of flexible membranes improves aerodynamic performance of nano rotors, while their vibration has a significant impact on flight stability.

This paper investigates the flight configurations that attenuate the adverse effect of drag growth from the perspective of vehicle geometry and magnetic field layout when magnetohydrodynamic (MHD) flow control is applied to the cruise flight of hypersonic vehicles. The high-temperature real gas effects involved in hypersonic flow are modeled using Park’s 7 species chemical reaction model and two-temperature model. Two dimensional Navier-Stocks (NS) equations with MHD terms are solved using the central-upwind scheme of Kurganov with second-order accuracy. Drag and heat flux characteristics of different geometries under MHD control are obtained for RAM-C II flight conditions. The effect of magnetic field layouts on MHD control is analyzed. The shape of cone-cylinder with high magnetic field utilization and magnetic field layout with high magnetic field intensity on either side of the stagnation point are more suitable for applying MHD flow control to hypersonic cruise, which ensure maximum aerodynamic drag reduction and optimal thermal protection effect under the dipole-like magnetic field.

Laser-energy deposition is a promising method for active flow control in high-speed vehicles due to its superior drag reduction capabilities. However, the challenge of increased heat flux during certain phases and shock issues induced by pulses remains unresolved. Given that magnetohydrodynamic (MHD) flow control offers excellent thermal shielding, and energy deposition can serve as an auxiliary ionization technique to enhance the effectiveness of magnetic control, the feasibility of combining these two methods for drag reduction and thermal protection of hypersonic vehicles was explored. The Navier-Stokes equations with MHD source terms were solved using the finite volume method, with weakly ionized flow modeled by Park's seven-species air model and two-temperature model. The electrical conductivity model based on effective collision frequency and the instantaneous energy deposition model were utilized for simulations. The validity of the algorithm was confirmed by experimental verification. Simulations under RAM-II flight conditions on a hemisphere-cylinder blunt body indicated that applying full-time magnetic control during single-pulse energy deposition effectively mitigates aerodynamic heating from shock interactions and viscous flow while simultaneously decreasing the aerodynamic drag on the blunt body. Additionally, MHD control significantly suppresses the large shock behavior induced by pulse energy deposition through the action of Lorentz forces.

Soft continuum robots are constructed from soft and compliant materials and can provide high flexibility and adaptability to various applications. They have theoretically infinite degrees of freedom (DOFs) and can generate highly nonlinear behaviors, which leads to challenges in accurately modeling and controlling their deformation, compliance, and behaviors. Inspired by animals, embodied intelligence utilizes physical bodies as an intelligent resource for information processing and task completion and offloads the computational cost of central control, which provides a unique approach to understanding and modeling soft robotics. In this study, we propose a theoretical framework to explain and guide distributed sensing enabled embodied intelligence for soft finger manipulation from a physics-based perspective. Specifically, we aim to provide a theoretical foundation to guide future sensor design and placement by addressing two key questions: (1) whether and why the state of a specific material point such as the tip trajectory of a soft finger can be predicted using distributed sensing, and, (2) how many sensors are sufficient for accurate prediction. These questions are critical for the design of soft and compliant robotic systems with embedded sensing for embodied intelligence. In addition to theoretical analysis, the study presents a feasible approach for real-time trajectory prediction through optimized sensor placement, with results validated through both simulation and experiment. The results showed that the tip trajectory of a soft finger can be predicted with a finite number of sensors with proper placement. While the proposed method is demonstrated in the context of soft finger manipulation, the framework is theoretically generalizable to other compliant soft robotic systems.

With reduced size, the flight Reynolds number of the nano rotor decreases, leading to a sharp drop in the aerodynamic efficiency of the nano rotor. Therefore, improving the aerodynamic performance of the nano rotor at low Reynolds numbers through flow control methods becomes imperative. In this study, from the perspective of bionics, flexible materials are employed in nano rotor design. Seven different layouts of flexible membrane rotor blades are designed and fabricated. The influence of leading and trailing edge flexibility, as well as membrane occupancy ratio on rotor blade propulsion characteristics, is explored through propulsion performance tests in hover. Results show that among several layouts proposed in this study, the layout with both reinforced leading and trailing edges of the flexible membrane nano rotor blade exhibits excellent propulsive performance. However, the propulsion performance of the flexible membrane rotors doesn't vary linearly with the ratio of membrane area to the whole rotor area. The appropriate ratio or flexibility can increase the propulsive performance of the rotor, especially at medium and high collective angles. At 7000 RPM and a 20 degrees collective angle, the Figure of Merit of the flexible membrane nano rotor increases up to 4.2% when comparing with the nano rotor without membrane. This improvement becomes more significant with higher collective angles. The structural natural vibration characteristics of each flexible membrane with different layouts are analyzed through modal tests, ensuring the accuracy of the finite element model for flexible membrane rotors. Numerical analysis of the fluid-structure coupling of a flexible membrane rotor with different layouts indicates that rotor structural vibrations is highly consistent with fluctuation of aerodynamic parameters. The deformation of the flexible membrane under aerodynamic forces enhances local blade camber, but reduces angles of attack. This, subsequently, minimizes the size of laminar separation bubbles and the intensity of the blade tip vortices at high collective angles. Consequently, rotor power coefficients decrease, and overall aerodynamic performance improves.

During the launch phase of a multinozzle rocket, the high-level noise induced by the supersonic jet ejected from the nozzles significantly affects the structural safety of the rocket and the reliability of the instruments. Therefore, it is important to predict and suppress the multinozzle rocket jet noise. This study proposes a numerical analysis method that uses the detached eddy simulation model combined with species transport equations, the discrete-phase model, and the acoustic analogy method (FW-H). It aims at a four-nozzle liquid rocket to predict jet and noise environments while considering the physical effect of evaporation and the influence of the launch pad structure. The proposed method was verified by comparing the single-nozzle jet simulation and experiment results. The prediction of the supersonic jet flow field and noise environment at different lift-off heights of the rocket was completed. An annular water jet noise-reduction system was designed to suppress the noise environment at different heights by single-deck and double-deck water injections. The noise attenuation effect of the water injection system was better when the lift-off altitude increased. And the noise suppression effect of the double-deck water injection system was more comprehensive than that of the single-deck water injection system. Furthermore, the reasons for the difference in noise reduction by different layers of water injection were analyzed in detail.

Nano Air Vehicle (NAV) is widely used in the military, production, scientific research, and other fields. Meanwhile rotor thrust control methods widely used currently include using a controllable pitch propeller hub which has a complex structure with large mass, or a variable speed motor which leads to lower energy conversion efficiency. In order to obtain a rotor thrust control method with a simple structure and low additive mass, meanwhile won’t cause overconsumption of energy, a novel electroactive polymer is used as driving material to design a smart nano rotor with continuous variable trailing edge flap. When electric field is applied to the electroactive polymer driver, the continuous variable flaps at the trailing edge of the blades are driven to bending and thus change the thrust of the rotor. The mechanical parameters and electrostriction properties of the electroactive polymer materials were studied by experiments. A fluid-electric-structure multi-field coupling method is used to study the aerodynamic characteristics of a smart nano rotor with a continuous variable trailing edge flap driven by electroactive material under the control of active electric field. It is found that when the control voltage is 1000 V, the blade trailing edge was effectively driven by electroactive polymer to produce bending deformation, which led to the pressure difference between upper and lower blade surfaces increasing significantly. The Thrust of the rotor was increased by 17.20

The slipper is the critical component of a supersonic rocket sled that is in contact with the track. Due to clearance and contact effects, the supersonic slipper-track system displays pronounced nonlinearities. A comprehensive analysis, including bifurcation and chaos detection, is conducted on this system to predict the nonlinear behavior of the slipper. Kinematic and dynamic models of the system are established using the generalized coordinate and Lagrange multiplier methods. This model accounts for slipper-track clearances, track irregularities, and normal contact forces. The dynamic response of the slipper is examined both in time and frequency domain. The bifurcation analysis encompasses various parameters such as slipper velocity and length, and slipper-track clearance. Chaos identification is employed for both qualitative and quantitative assessments, utilizing phase diagrams, Poincar & eacute; sections, the trajectory of the slipper's center, and the largest Lyapunov exponent (LLE). The findings revealed significant nonlinear phenomena, including self-excited vibrations, superharmonic responses, jumping phenomena, strange attractors, and combined frequencies. Notably, this study demonstrated the potential for leveraging chaotic response to mitigate the contact forces on the slipper. These insights contribute to the rationalization of control parameters and the optimization of slipper and track design.

The micro co-axial rotor UAV has the advantages of high hovering efficiency and compact structure in various applications, but its attitude control system has the characteristics of strong nonlinearity and coupling, and the design of the controller is the most difficult point in the design of this type of aircraft. In this paper, a control system is designed based on reinforcement learning algorithm for a micro co-axial rotor UAV that uses aerodynamic rudder surface for attitude control. Firstly, according to the reinforcement learning theory and the characteristics of the UAV, the main formulas of the control system is designed. Secondly, digital model of the UAV and training environment are established, the controller basically meets the control requirements after the training experiments were conducted. Judging by the performance of the reinforcement learning controller, it effectively improved the control accuracy and efficiency comparing with the existing PID controller. This research implements the combination of reinforcement learning algorithm and the controller of micro co-axial rotor UAV, and provides an idea to build an intelligent controller for complex micro-aircraft.

In order to develop the ability to analyze the gouging effect of rocket sled test with high confidence level, a simulation and verification study on gouging effect of hypersonic rocket sled was carried out based on real gouging data in orbit. Firstly, the parameter description of typical gouging phenomenon was obtained by the analysis of real gouging data of rocket sled test in orbit, and the closed-loop verification of gouging mechanism based on adiabatic shear theory is completed through the detection of chemical composition and metallographic microstructure. Secondly, the Johnson-Cook constitutive model parameters were obtained by static tensile test and Hopkinson bar test based on the principle of high temperature double synchronization. Finally, the simulations of gouging effect under three vertical speed conditions of 1.75 m/s 2.00 m/s and 2.25 m/s were carried out using material point method. The simulation results in terms of gouging morphology were basically consistent with the ones obtained by real tests. The comparison between the results of simulation and real tests shows that the consistency between measurement and simulation is the best when the vertical speed of the slipper is 2 m/s, and the deviations of the length and depth of the gouging pit are 1.8% and-3.9%, which are not more than 5%. The applicability of the material point method in analyzing gouging is verified. The method and parameter value can be used as a reference for the gouging safety evaluation in the design stage of hypersonic rocket sled test.

Precisely predicting the aerodynamic characteristics and the flow field of a high-speed rocket sled under-ground effects is of great significance to the design and evaluation of the sled.The finite volume method was used to study the influence of turbulence model on the calculation accuracy of rocket sled aerodynamic characteristics, and a high-precision numerical method for the rocket sled aerodynamic characteristics based on the realizable k-ε turbulence model was established.In combination with the wind tunnel test, the influence of Reynolds number and ground effects on the flow field characteristics of a high-speed rocket sled was studied, and the aerodynamic characteristics of the sled were analyzed.The results showed that the drag coefficient decreased with the increasing Reynolds number, while the lift and pitching moment coefficients increased. However, the Reynolds number had little influence on the aerodynamic characteristics of the sled.Ground effects could induce the interference between shock waves, the interference between the shock wave and the boundary layer, the shock wave repeated reflection, and other complex aerodynamic phenomena in the flow field of the rocket sled, which significantly improved the lift and pitch moment coefficients, but had little influence on the drag coefficient.This study provided a basis for the design of the aerodynamic shape of a high-speed rocket sled and the evaluation of the stability.

The dynamic response of a hypersonic rocket sled was studied by considering the time-varying friction coefficient and the gap caused by wear between the slipper and track. A multibody dynamic model for a hypersonic rocket sled system was established by considering the time-varying mass and moment of inertia, nonlinear aerodynamic loads, engine thrust, track irregularity, and nonlinear contact force. As for the wear calculation, the ductile and shear criteria were used as the material damage criteria, and slipper wear was determined by the number of damaged elements. A rocket sled test was also carried out, and the dynamic response of the sled was measured. The results showed that the computational sliding displacement and velocity of the third-stage sled matched well with the test values. The computational root mean square (RMS) values of the vertical acceleration of the third-stage sled front slipper considering friction and wear matched better with the test values than with the case without considering friction and wear, which underestimated the RMS value by approximately 20.1% at Mach 5. The importance of considering friction and wear and the correctness of the computational method were validated. It is also found that the kinetic friction coefficient decreased with an increase in the product of the pressure and velocity. The wear height of the slipper increased almost linearly with the sliding displacement. The test results showed that the vertical acceleration power spectral density of the third-stage sled front slipper increased with time in the full frequency band below 2000 Hz. This study will guide the design and optimization of hypersonic rocket sleds.