To analyze the mechanical properties of jet penetration on a single-cell / multi-cell liquid composite closed structure, the motion equation of jet penetrating a metal target is established, and the energy equation of the penetration system is derived. The simulation results show the radial convergence effect of the liquid in the single-cell increases with the increase of the height of the inner cavity of the closed structure. The radial convergence effect of liquid in multi-cell also has the same phenomenon, but the phenomenon of liquid disjunction appears, which leads to the convergence of liquid into segments. The pressure in the single-cell liquid appears at the bottom of the cell, but the multi-cell liquid appears in the last cell. The pressure distribution of the single-cell is concentrated on the bottom of the cell, and the pressure distribution is circular. The pressure distribution of multi-cell is more uniform, and there is no obvious concentrated distribution phenomenon. The energy of the closed cell structure increases with the increase of the height and the number of the cell.

To research the axial compression properties of unidirectional carbon fiber reinforced epoxy resin composite (UCFREP), the compression experiments at different strain rates were carried out by using the MTS universal electronic testing machine and the equipment of split Hopkinson pressure bar (SHPB). Furthermore, the finite element analysis (FEA) was also used to study the compression properties of UCFREP with different conditions. The true stress-strain curves in quasi-static and dynamic compression were obtained, and the relationship between yield limit and strain rate was coupled. The microstructure of the failure area was observed by scanning electron microscope (SEM). A formula for predicting compression strength of combined buckling under the quasi-static condition was presented. The application range of Chang-Chang failure criterion was discussed by FEA, and the compression failure of UCFREP with different fiber directions was predicted. The results show that UCFREP has the obvious strain rate effect, the mechanical properties at dynamic compression are nonlinear. Shear is the main compression failure mode, which includes the shear cracking of matrix between fibers and the shear buckling of fiber. The direction of the fiber is the main factor that causes the shear cracking, such as the shear cracking shows the feature of 45° when the direction of the fiber is 45°. As a conclusion, increasing the shear strength of matrix and fiber will be a way to increase the compression strength of UCFREP. This paper could be used as a reference to develop the new constitutive model, especially considering the nonlinear effect.

The high-quality (0.78-x)­BiTi0.1Fe0.8Mg0.1O3-0.22CaTiO3-(x)­Na0.5Bi0.5TiO3 nanoscale-thick thin films were prepared successfully on the Pt/Ti/SiO2/Si substrate via the sol–gel method. The influence of Na0.5Bi0.5TiO3 doping on the structure, topography, piezoelectricity, ferroelectricity, and dielectricity of BTFM-CTO-NBT thin films was investigated systematically. The X-ray diffraction and Raman results manifested that NBT doping induced the formation of the tetragonal phase, which existed between the rhombohedral and orthorhombic phases, and the elemental mappings revealed that the distribution of each element was uniform simultaneously. X-ray photoelectron spectroscopy analysis showed that NBT doping could effectively restrain the reduction of Fe3+, thereby reducing the oxygen vacancy concentration. The film had a minimum leakage current of about 3.19 × 10–10 A/cm2, a higher piezoelectric response, a maximum remnant polarization (2P r = 174.64 μC/cm2), and a relatively smaller coercive field (E c = 359.90 kV/cm) as x = 0.05. At the same time, the corresponding film had a maximum dielectric constant (469.6) and a minimum dielectric loss (0.063) at 1 kHz. These insights offer an alternative pathway to enhance the properties of BTFM-CTO thin films.

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