Island‐bridge architecture represents a widely used structural design strategy in the field of stretchable inorganic electronics, where flexible serpentine interconnects function as bridges to accommodate most of the deformation, while the islands residing functional devices exhibit minimal deformation. The mismatch of Young's modulus between the elastic substrate and the rigid islands usually leads to stress concentration, which is named the island effect. This phenomenon can significantly increase the risk of interfacial damage, such as debonding and tearing failure near the island. In this work, the mechanical model of the island effect under equal biaxial stretching is developed based on theoretical analysis, simulation, and experimental measurement. The scaling law of the displacement and strain distributions on the substrate surface illustrates that the ratio of the island radius to the substrate length is the main controlling parameter of the island effect, proved by the experimental and numerical results. The criterion distinguishing whether the island effect problem is axisymmetric is derived from this. Further, the deformation field in periodic array structure is predicted based on the theoretical model, demonstrating its potential for application in flexible electronic devices.

This study investigated the axial tensile performance of adhesively bonded T700/C204 carbon fiber composite and TC4 titanium alloy tubular single-lap joints under three distinct temperature conditions: room temperature, low temperature (−65 °C), and room–low–room-temperature cycling. Two configurations of adhesively bonded joints—composite–composite and composite–titanium—were tested. Specimens were designed to evaluate the influence of spew-fillet and perfect lap configurations on uniaxial tensile bonding strength across varying temperature environments. Analysis of the final failure morphology, stress concentration locations, ultimate failure loads, and load-displacement curves revealed that stress concentration and peeling stress were most pronounced at the ends of the bonded region, which served as the initiation points for failure. The adhesively bonded joints exhibited two distinct failure modes, strongly correlated with material properties and environmental temperature. The titanium alloy tubular joints predominantly experienced adhesive layer failure, while the carbon fiber three-way tubular joints were primarily characterized by fiber-tear failure. Environmental temperature significantly influenced the strength of the adhesively bonded joints. Specifically, the tensile failure limit of the bonded specimens subjected to low-temperature cycling (25~−65~25 °C) was approximately 61% higher than that observed under the room or low-temperature conditions. Furthermore, the experimental results demonstrated that a maximum failure load of 27.522 kN and a shear strength of 10.956 MPa were achieved. Notably, the presence of adhesive spew-fillet had a negligible impact on the bonding strength of the joints.

Scientific balloons provide an inexpensive and reliable platform for near-space scientific experiments. The analysis of the balloon geometry and forces has always been a major concern for balloon designers. Most previous studies have focused solely on the fully inflated shapes and forces of balloons, analyzing only the membrane structure and simplifying the effects of internal and external gases into a gradient pressure difference. This approach lacks consideration of the fluid–structure interaction (FSI) of scientific balloons. This paper utilizes the Coupled Eulerian–Lagrangian (CEL) method in the Abaqus/Explicit simulation environment to analyze the FSI effects of scientific balloons under the influence of internal helium and external air. Three typical working conditions of scientific balloons are selected for simulation analysis. First, a three-dimensional spherical balloon is simulated during the ascent process to verify the correctness of the CEL simulation framework. This also demonstrates the membrane folding characteristics during balloon ascent, which could not be calculated in previous two-dimensional axisymmetric simulations. Next, the study explores balloon shapes that deviate from quasi-static pressure distributions due to the motion of internal helium. These include the “mushroom” shape observed during the dynamic launching of the balloon on the ground and the “sail” shape caused by lateral airflow. The mushroom shape arises from the sudden loss of the bottom constraint, causing the internal helium to move upward while being resisted by the air at the balloon’s top. The simulation successfully replicates the rapid waist transition and the downward concavity at the top due to air resistance, while also providing the corresponding force distribution. For the sail-shaped condition, the simulation analyzes the balloon’s tilt angle and the characteristic upturn of its windward surface. By a comparison with no-wind conditions, this study quantifies the impact of wind on the forces acting on the balloon, offering practical guidance for balloon launching. The CEL simulation framework established in this study not only provides a new tool for the FSI analysis of scientific balloons but also enriches the mechanical analysis results of these balloons.

This paper aims to investigate a new method that uses buoyant gas mixed with air to control the floating height of scientific balloons. Firstly, the static characteristics and thermophysical properties of mixed-gas balloons are analyzed. Subsequently, the inflation model and the thermal-dynamic coupled model are established. Furthermore, based on theoretical research, a GUI program is compiled to simulate the ascent of mixed-gas balloons. Finally, flight tests are conducted. As the balloon volume expands to the maximum, the vertical velocity begins to decay and eventually oscillates around 0 m/s, which is consistent with the simulation. In addition, there is a noticeable shift in which the balloon starts to float after climbing to the target altitude, and the difference values between the test and the simulation are less than 350 m. Moreover, the trajectory results are similar to the prediction, and the errors of the end position are less than 2.5 km in horizontal distance. Consequently, this paper provides guidance for balloon-designated ceiling height technology which can allow a single balloon system to be used for tests at multiple heights.