Meijiao Qu

High-energy pulsed lasers induce high-pressure shock waves that drive intense transient particle motion; the evolution of particle velocities is a key parameter for revealing the dynamic response of materials and the bonding state at interfaces. Although photon Doppler velocimetry (PDV) offers high temporal resolution and non-contact measurement advantages, strong non-stationary frequency modulation and a low signal-to-noise ratio cause significant frequency broadening in traditional time-frequency analysis, limiting the accurate extraction of particle velocities. To address this issue, we propose a Demodulation‐based Time‐Frequency Analysis (DTFA) method. This method obtains an instantaneous frequency prior through a frequency-adaptive window and constructs a phase-compensation operator to suppress frequency broadening caused by frequency modulation, thereby mapping the raw signal to an approximately steady-state narrowband domain. By combining a long-window time-frequency transform to extract residual frequencies and performing backward reconstruction to fuse prior and residual information, we achieve high-precision recovery of particle velocities. Simulation and experimental results show that, within a signal-to-noise ratio (SNR) range of 0–20 dB, the root-mean-square (RMS) error of the instantaneous frequency in DTFA is 50%–63% of that in the S-transform, while the average instantaneous equivalent bandwidth is reduced to 54%–80% of the S-transform’s value. For an experimental signal with a bandwidth of only 2.64 MHz, this represents reductions of 42.3% and 25.1% compared to STFT and CWT, respectively. The DTFA maintains continuous and stable velocity evolution even at low signal-to-noise ratios and can identify weak oscillations, providing a new approach for high-precision time-frequency characterization of strongly non-stationary frequency-modulated signals.

This study addresses the critical challenges of interfacial stress mismatch, fiber degradation, and unstable clad geometry in manufacturing continuous carbon fiber-reinforced aluminum composites (Cf/Al) via laser cladding, driven by rapid thermal gradients. A dual-ellipsoid heat source-based thermoelastic–plastic finite element model was developed in Abaqus, integrating phase-dependent material properties and latent heat effects to simulate multi-physics interactions during single-track deposition, resolving transient temperature fields peaking at 1265 °C, and residual stresses across uncoated and Ni-coated fiber configurations. The work identifies an optimal parameter window characterized by laser power ranging from 700 to 800 W, scan speed of 2 mm/s, and spot radius of 3 mm that minimizes thermal distortion below 5% through gradient-controlled energy delivery, while quantitatively demonstrating nickel interlayers’ dual protective role in achieving 42% reduction in fiber degradation at 1200 °C compared to uncoated systems and enhancing interfacial load transfer efficiency by 34.7%, thereby reducing matrix tensile stresses to 159 MPa at fiber interfaces. Experimental validation confirms the model’s predictive capability, revealing nickel-coated systems exhibit superior thermal stability with temperature differentials below 12.6 °C across interfaces and mechanical interlocking, achieving interfacial void fractions under 8%. These results establish a process–structure linkage framework, advancing defect-controlled composite fabrication and providing a digital twin methodology for aerospace-grade manufacturing.

In this study, a combination of theoretical analysis and experimental verification was used to investigate the effects of laser parameters and shock wave shape on the location of layer cracks in carbon fiber‐reinforced plastics specimens. Firstly, the propagation coupling process of trapezoidal, rectangular, and triangular pulses in the material was investigated based on the one‐dimensional stress wave propagation theory. The study analyzed the effects of shock wave pressure amplitude, pulse width, and other factors on the location of layer cracks in the material. Subsequently, laser impact experiments with varying energies and pulse widths were conducted on specimens of different thicknesses to investigate the impact of shock wave pressure amplitude and laser pulse width on the location of layer cracking. The results show that the theoretical analysis of triangular shock waves has broader applicability and can serve as a representative analytical model to describe single‐layer crack damage. Highlights: Laser impact experiments with various specimen thicknesses. Laser pulse width determines the initial location of inter‐laminar cracking. The applicability of the triangular pulsed layer cracking formula. The effect of laser energy on pulse amplitude.

This study explores the effects of laser pulse width and energy on CFRP laminates damage in laser bond inspection technology. Three testing programs were used, including varying laser energy while keeping pulse width constant, altering pulse width while maintaining constant power density, and modifying pulse width while keeping energy constant. The results show that when the pulse width remains constant, increased laser energy has a minimal effect on the initial damage location but leads to gradual interlayer delamination and fiber fracture propagation toward the impact surface. With constant laser energy, a specific threshold for pulse width is observed. When the laser pulse width is below this threshold, it exhibits a positive correlation with the damage characteristics of CFRP laminates, whereas when it exceeds this threshold, it shows a negative correlation. Power density correlates with damage when pulse width is constant, but there is no direct correlation when pulse width varies.Highlights: CFRP laminates underwent laser shock tests with varying pulse widths. Power density is positively correlated with damage under specific conditions. There exists a specific threshold for laser pulse width. In single‐sided laser shock, initial damage spreads within a specified range.