When an aircraft flies through clouds or rainfields at high speed, the extremely high relative velocity between the aircraft and raindrops can cause damage or even detachment of the coating on windward structural surfaces, thereby shortening aircraft service life. Polyurethane coatings offer excellent wear resistance, weather resistance, chemical corrosion resistance, strong adhesion, and good flexibility, and are therefore widely used in aerospace applications. However, research on their rain erosion resistance remains limited. Therefore, this paper investigates the delamination damage  mechanism under high-speed raindrop impact to improve rain erosion resistance.T800 carbon fiber composite laminates were used as the substrate, onto which polyurethane coatings of different interlaminar bond strengths were applied. Based on single-jet and pulsed multi-jet impact test platforms, the influence of interlaminar bond strength between the coating and the substrate on rain erosion damage characteristics and the occurrence mechanism of delamination failure were systematically examined.Under single-jet impact, coatings with low interlaminar bond strength first experience interfacial adhesion failure at the impact center, leading to localized delamination. The reflected stress waves cause significant interfacial stress concentration, resulting in uneven stress transfer and crack propagation along the interface. The characteristic damage morphology includes coating spallation at the impact point, peripheral uplift, and circumferential cracking. By contrast, coatings with higher interlaminar strength better dissipate the impact load and suppress the initiation and growth of microcracks, maintaining coating integrity.Under multiple-jet impacts, the interface is subjected to long-term cyclic loading, making it prone to stress fatigue and the formation of microcracks, which gradually evolve into pronounced delamination. The typical damage morphology appears as elongated delamination bands extending along the carbon fiber orientation, with significant uplift and circumferential cracking at the boundaries, and local carbon fiber fracture may also be observed. Weaker interlaminar bond leads to shorter time to delamination and more severe damage. Based on the experimental results and numerical stress‑response analysis, the delamination mechanism under raindrop impact is clarified: shear waves generated during droplet impact nucleate interfacial microcracks, which continue to propagate and lead to interlaminar cracking and delamination. The stress waves generated by impact reflect at the coating–substrate interface, and under pulsed droplet loading, stress superposition generates high tensile stress. Continuous lateral jet loading further acts on the interface, causing coatings with low interlaminar bond strength to experience delamination after fewer impacts.

In the field of material dynamic mechanical properties research, it is significant to obtain reliable data of materials under complex stress states. To address the challenge of achieving a stable stress ratio during combined loading, this work developed a novel device based on the electromagnetic Hopkinson bar (ESHB) platform. This device uniquely enables unilateral synchronous tension/compression-torsion combined dynamic loading. The paper detailed the device’s configuration and loading principles. The core innovation of this device is the independent generation of trapezoidal tensile/compressive and torsional stress waves. A multi-circuit pulse shaper produced tensile/compressive waves, while shear waves were generated using an electromagnetic clamp with torque storage. Crucially, a high-precision digital delay generator (DDG) ensured wave synchronization. With triggering accuracy within 0.1 μs, it controlled the arrival time difference of these distinct waves at the specimen to within 5 μs. This overcame the challenge posed by their different propagation velocities. Additionally, it described the synchronization control methodology and the wave propagation analysis essential for timing calculations. To validate the apparatus, dynamic tension-torsion experiments were conducted on CoCrFeMnNi high-entropy alloy specimens. The results show that the device is highly reliable and effective. It successfully achieved a stable stress ratio of approximately 1.7 throughout the loading duration. Furthermore, the experiments conclusively showed a key finding. Trapezoidal wave loading significantly enhances stress-ratio stability during combined dynamic loading. This improvement contrasts with the effect of traditional sinusoidal wave loading. This advancement offers a robust and controllable experimental method. It enables the study of materials’ dynamic mechanical responses under complex stress states. These states involve high-strain rates and multiaxial loading. This capability is especially valuable for aerospace, impact engineering, and materials science applications. The successful implementation of constant stress-ratio loading opens avenues for more accurate characterization of material yield criteria and failure mechanisms under dynamic multiaxial conditions.

Aircraft-mounted weapons systems generate intense shock and vibration during combat missions, creating a highly complex, repetitive, and nonstationary environment. Avionic devices and components are susceptible to damage in severe gunfire shock environments and must undergo shock testing. In the absence of measured data, gunfire shock signals synthesized from Shock Response Spectrum (SRS) should serve as input excitation. However, the synthesis of gunfire shock signals presents several challenges, primarily due to the transient and repetitive nature of gunfire shock itself, as well as the inherent non-linearity in the SRS method. This paper presents a novel method for synthesizing gunfire shock signals that match SRS specifications while maintaining realistic temporal characteristics. The proposed method utilizes a shock-waveform dictionary technique to generate single-shot shock signals with controllable features including initial rise time, effective duration, and repetition intervals. These single-shot signals are then duplicated and concatenated to create multi-shot sequences, with low-frequency compensation applied to meet SRS requirements. The method’s effectiveness is demonstrated through a case study simulating the M61A1 aircraft cannon firing at 4000 rounds per minute, achieving an average error of only 0.35 dB compared to SRS specifications. Further validation across two additional cases with varied single-shot durations and repetition intervals underscores the method’s generalizability. The proposed synthesis method provides a practical solution for laboratory testing of avionic equipment under gunfire shock conditions when measured data is unavailable.

As the main component of the aircraft leading edge, the radome is often the first to be hit by raindrops and cause structural damage when passing through a rain field. Rain resistant coating is usually applied to ensure the performance protection requirements. In order to clarify the rain erosion damage mechanism of radome coating and explore the influencing factors and mechanisms of coating material damage under different jet impact conditions, impact tests were conducted on three types of skin coating samples, and the damage mode was observed through electron microscopy characterization. The experimental results show that the typical morphology of rain erosion damage is annular surface peeling damage. The damage area and volume of the three coating samples increase with the continuous increase of raindrop impact velocity. The threshold velocity for initial damage to the coating is about 360 m/s; under the influence of the velocity component, the reduction in impact angle leads to a gradual reduction in the degree of damage to the sample. ABAQUS finite element simulation software was used to establish a constitutive model for coating rain erosion simulation and obtain the propagation law of stress waves during the impact process. The simulation results show that at the 75° impact angle, the jet impacts the surface of the specimen at different velocities, and as the impact velocity increases, the Mises equivalent stress on the surface shows an increasing trend, which is one of the main factors causing damage with increasing velocity. The effectiveness, rain erosion damage mode, and influencing mechanism of the model were verified based on the test results; the dynamic failure mechanism of the sample was further studied, and the stress propagation process at different impact angles was compared, revealing the influence mechanism and damage law of the impact angle on the high-speed raindrop impact of the material.

The dynamic failure behavior of CoCrFeNi High-Entropy Alloy (HEA) under plane biaxial stress was investigated in detail. The dynamic biaxial tensile tests were conducted using an Electromagnetic Biaxial Split Hopkinson Tensile Bar (EBSHTB) system. For comparison, the quasi-static uniaxial and biaxial tensile tests, as well as dynamic uniaxial tensile tests, were performed respectively. A cruciform specimen suitable for large plastic deformation was designed and employed in the experiments. The Finite Element Method (FEM) verified that the improved cruciform specimen could satisfy the basic requirements. The feasibility of the proposed specimen was further confirmed through loading tests. Finally, the quasi-static and dynamic yield loci of the HEA in the first quadrant of the principal stress space were plotted. The results indicate that the alloy exhibits obvious strain hardening effect and strain rate strengthening effect, the yield locus and plastic work contours can be accurately described by Hill’48 criterion.

When an aircraft passes through a rainy area at high speed, the coating on the front edge of the fuselage will be continuously eroded by raindrops, causing the coating to wear, crack or even peel off. This paper uses carbon fiber T300 material as the base material, and at the different impact speeds and impact numbers, water cutting equipment was used to simulate the erosion of the coating caused by the continuous impact of water droplets. The damage morphology of samples at different damage stages was observed by digital microscope and Scanning Electron Microscope (SEM), and the damage evolution curve was established to analyze and reveal the damage behavior and damage mechanism of rain erosion. The results show that the degree of damage experienced an increasing trend with the increase of impact numbers and speed, until circular peel damage was formed; no damage occurred during the incubation period, and the curvature of the damage evolution curve increased significantly after the expansion period and eventually showed a stable expansion trend. The mechanical properties of the coating material were the main influencing factors of its rain corrosion resistance. Moreover, the axially symmetric unsteady contact problem of droplets impacting the surface of a solid deformable body was studied. And the contact area was determined based on the iterative algorithm boundary positioning method. A mathematical model and closed mathematical formula describing the unsteady interaction between a droplet and a solid deformable obstacle were proposed.

The incursion of Unmanned Aerial Vehicles (UAVs) into airports often occurs due to the popularity of drones, which may lead to a threat to aircraft flight safety. Therefore, estimating the dynamic impact load caused by drone strikes is essential. This paper proposes a test method with high precision and low cost involving launching of a UAV to impact a flat plate specimen by using an air gun. The test results of UAVs impacting flat plates at different impact velocities, such as the UAV damage deformation captured by a high-speed camera and strain vs time dynamic response curves of plates, were obtained and analysed. At the same time, a corresponding numerical simulation was carried out by using the explicit finite element software LS-DYNA. The predicted damage to the UAV and strain on the flat plate during the strike process were compared with the test results. The overall trend of the simulation results is in good agreement with the test results, at least for the first three milliseconds of the event. This shows that the numerical simulation model established in this paper is reasonable. The UAV numerical method established in the present paper can be used to carry out numerical simulations and evaluations of the collision safety of UAVs against large aircraft and high-value ground targets. The results show that the local deformation of the impacted target is uneven due to the distribution of concentrated mass components such as motors, battery, and camera. As the impact velocity of the UAV increases, all parts of the UAV are seriously damaged and basically in a fragmented state, and the battery is greatly deformed. The interaction between the UAV and the flat plate specimen is approximately 2.7 ms, and the UAV numerical simulation model established in this paper can well simulate the real UAV impact process.