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In inertial confinement fusion, electromagnetic pulses (EMPs) can be produced during high-power laser interacting with solid targets, which are intimately related to laser intensity and laser energy. In this study, EMPs generated by hybrid laser pulses coupling with targets are recorded and analyzed. The results indicate that a single picosecond laser gives birth to the most intense EMPs, but they are remarkably suppressed when a nanosecond laser-shooting target is triggered before the picosecond and femtosecond laser. One possible hypothesis is proposed based on x-rays inducing pre-ablation that generates pre-plasma at the surfaces of the picosecond target and femtosecond target, leading to a sharp drop both in the energy and number of the emitting hot electrons and protons. The findings will deepen our understanding of the mechanism of EMPs’ generation and will also open a new avenue to regulate EMPs by hybrid laser pulses.

In this paper, an improved method for measuring displacement in digital speckle correlation technology, which is based on an iterative and spatial-gradient algorithm, is developed. After obtaining full-field displacement, both finite element method and 2D generalized cross-validation (GCV) algorithm are adopted for smoothing the displacement field, and then the strain field can be obtained from the smoothed displacement field. The method is estimated by simulated speckle patterns and three-point bending experiment. All the results show the improved method can obtain a reasonable estimation of displacement and strain fields in digital speckle correlation method.

The crack tip (mode I, mode I + II) stress singularities in orthotropic composites are studied by the method of reflective caustic. Based on the caustic parametric equations and its initial curves surrounding the crack tip derived by the elastic crack solutions of composites and the principle of reflective caustic, theoretical caustics and initial curves at mode I and mixed mode (I + II) crack tip of fibre orthotropic composites are simulated. Influences of material orientation on crack tip singularities in composites are analysed. The static experimental caustics of mode I and mixed mode I + II crack tip in composites are obtained when the initial crack direction is parallel to the main axis of the orthotropic material, i.e. θ = 0°. The results indicate that the experimental caustics obtained from the actual fibre composites have a remarkable difference compared with the simulation caustics based on the fracture theory of continuum orthotropic composites, which provide an important physical foundation for understanding the singular stress characterizations at the crack tip of composite materials.

Applications of the digital speckle correlation method (DSCM) for the full-field deformation measurement of carbon fiber/epoxy composite pressure vessel were investigated and the basic principles of displacement measurement by the DSCM are briefly given. The full-field displacement and strain distribution of a composite pressure vessel were evaluated under internal pressure. The results of the average strain value show a good agreement with the results from conventional electronic strain gauge technology. The results reveal that the DSCM is suitable for deformation measurement of composite pressure vessels in real engineering practice.