Terahertz (THz) imaging is increasingly used in the cultural heritage field. In particular, continuous wave (CW) and low frequency THz is

a b s t r a c tShock focusing in water is a phenomenon that can occur during the impact of a shock wave generated by an underwater explosion onto any type of convergent marine structures. To predict the dynamic material response of the marine structure, it is important to understand the shock wave dynamics during the focusing event. In this paper, both experimental investigations and numerical studies of twodimensional shock focusing in water are presented. Here, a convergent geometry given by a logarithmic spiral curve is used to focus the shock waves. In the experiments, the interaction between three types of materials and the shock wave in water is explored by using high-speed photography. Distinct features of such flows are unveiled. Three scenarios have been considered in simulations: a rigid structure where only the water-filled region is taken into account, a fluid-structure interaction problem in which the surrounding material responses are included, and an axisymmetric simulation to determine the threedimensional effects.

In this paper, optical and mechanical excitation thermography were used to investigate basalt fiber reinforced polymer (BFRP), carbon fiber reinforced polymer (CFRP) and basalt-carbon fiber hybrid specimens subjected to impact loading. Interestingly, two different hybrid structures including sandwichlike and intercalated stacking sequence were used. Pulsed phase thermography (PPT), principal component thermography (PCT) and partial least squares thermography (PLST) were used to process the thermographic data. X-ray computed tomography (CT) was used for validation. In addition, signal-to-noise ratio (SNR) analysis was used as a means of quantitatively comparing the thermographic results. Of particular interest, the depth information linked to Loadings in PLST was estimated for the first time. Finally, a reference was provided for taking advantage of different hybrids in view of special industrial applications.

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