High pressure techniques have been introduced to nanomaterials research for about three decades. Most of the studies, especially in the earlier time, were mainly X-ray diffraction (XRD), Raman and infrared spectroscopy investigations on the structural transition and equation of state. In recent years, we extended the explorations for the plastic deformation of nanomaterials by employing radial diamond-anvil cell XRD and transmission electron microscopy (TEM). We have successfully probed the dislocation activities in 3 nm nanocrystals, but also seen that partial dislocations and deformation twinning dominate the plastic deformation below 20 nm. We have observed the reversal in the grain size dependence of grain rotation in nickel, and have found that the strengthening of nickel nanocrystals could be extended down to 3 nm. Compared with the traditional techniques, high pressure techniques are more advantageous in applying mechanical load to nanosized samples and characterizing the structural and mechanical properties in situ or ex situ, which could help to unveil the mysteries of mechanics at the nanoscale and bridge the knowledge on the material mechanics at the multiscale. With these knowledges, more advanced materials could be fabricated for wider and specialized applications.

Graphene oxide (GO) was evenly dispersed in epoxy resin, and vacuum-assisted resin transfer molding was used to prepare reinforced carbon fiber composite materials. Different concentrations (0, 0.03%, 0.07% and 0.10%) were studied tensile properties and micro-adhesive properties of graphene oxide (GO) modified epoxy resin/carbon fiber (EP/CF) laminate at room temperature, explored the threshold for significant improvement of mechanical properties of carbon fiber reinforced composites by low concentration GO. The experimental results show that graphene oxide (GO) has a certain improvement effect on the performance of carbon fiber reinforced epoxy composites. Compared with pure epoxy-based carbon fiber laminates, as the concentration of GO increases, its tensile properties will also increase; GO contained functional groups can improve the degree of bonding between the epoxy-based system and the carbon fiber. Through scanning electron microscopy (SEM), it can be observed that the adhesion of the carbon fiber and the epoxy resin in the GO-laminated board is closer, which makes the meshing effect stronger and improves the tensile strength of composite laminates; mechanical properties of laminates begin to be significantly improved when their content reaches 0.07% when modified by low-concentration GO.

Based on equations of motion and the generalized Maxwell constitutive model, this paper derives the dispersion and dissipation relations of one-dimensional viscoelastic local resonance and Bragg scattering type phononic crystals. The results show that, for the time-harmonic propagation, band gap does not exist in the dispersion relation and the attenuation of wave solely relies on viscous dissipation and periodic modulation, which will enhance the dissipation; on the contrary, for the free wave propagation, there is a band gap in the dispersion relation, but beyond the band gap, the attenuation of wave is still dependent on viscous dissipation and periodic modulation. These results are valuable for the study on stress wave propagation in layered composite materials made of polymers.

The lattice structure is widely used in aerospace, military, and other fields due to its lightweight and excellent energy absorption. This article mainly studies the energy absorption of the bionic BCC (body-centered cubic) structure and discusses its influence by the cross-sectional morphology. In this paper, three different BCC bionic bamboo lattice structures are designed based on the macro-structure and meso-structure of Phyllostachys pubescens. Additionally, the axial compression numerical simulation is carried out on the bionic bamboo lattice structures and original BCC lattice structure, respectively. The results show that both the energy absorption and specific energy absorption of the bionic bamboo lattice structures under quasi-static load are improved by more than 25% compared with the original BCC structure. However, the energy absorption and specific energy absorption of the three bionic bamboo lattice structures are similar. It is also indicated that the relative density of the structure has great influence on its energy absorption and specific energy absorption. During the compression process of the bionic BCC structure, there are wrinkles and collapses inside, which might be an important reason for the stable energy absorption of the bionic structure.

The tightly wound solenoid is the core component of a cascade explosive cylindrical implosion magnetic flux compression device. We designed a solenoid cylinder with composite structure, and carried out two-cascade implosion magnetic flux compression experiment. It is known that the growth of interfacial instability of the solenoid cylinder will determine the amplification of the magnetic field and/or magnetic compressive stress. In the implosion compression event, the projection images of the solenoid by high-speed photography revealed that the inner surface kept in a circle without visible collapse, but cyclic disturbances were observed on the outer surface resulting from explosive detonation. A 2D finite element model was built to study the instability growth of the solenoid under the explosive implosion. The simulation results displayed that the multi-point network detonation of the explosive played an important role on the solenoid instability. The instability growth can be effectively inhibited by both increasing the number of detonation points and introducing a 1–2 mm thick cavity between the explosive cylinder and the solenoid.

In order to improve the maximum bearing capacity of ordinary annual wheeled ultra-high pressure molds, a new spherical arc longitudinally split ultra-high pressure mold structure is proposed. Due to the spherical-arc structure, the circumferential tensile stress of the ultra-high pressure mold that has suffered the most damage is converted into axial stress. Then, the axial stress is reduced by the longitudinal division method, thus improving the ultimate bearing capacity of the ultra-high pressure mold cylinder. Spherical-arc longitudinal splitting of the ultra-high pressure mold can not only reduce the equivalent stress and the maximum tangential stress of the ultra-high pressure mold, but also greatly increase the cavity volume of the mold. The numerical analysis results show that: under the same load condition, the circumferential tensile stress, equivalent stress and maximum tangential stress of the spherical-type longitudinally split ultra-high pressure mold are lower than ordinary annual wheel-type ultra-high pressure molds by 68%, 12.5% and 18.0%, respectively. The radial displacement of the spherical-arc longitudinally split ultra-high pressure mold is also conducive to improving the pressure-holding capacity of the cylinder, and the cavity volume of the spherical-arc longitudinally split ultra-high pressure mold is also increased by about 43% compared to that of the ordinary annual wheel mold. The analysis shows that the spherical-arc longitudinal split structure helps to improve the production efficiency and mold life.

In order to investigate the antiknock performance of polyurea coated steel composite structures and the energy absorption mechanism of polyurea coatings, the 40 and 60 g TNT explosion loading tests were carried out for the uncoated, equal-face coating and back-explosion coating structures with equal surface density and other steel plate thicknesses. Then the polyurea coatings’ effects on the antiknock performance of composite structures and their protective mechanism were analyzed in comparison of the failure modes of composite plates. It was found that the anti-explosion performance decreases with the thickening polyurea coating for the composite structure with uniform surface density, while improves under the same steel plate thickness conditions. In addition, coating on the rear surface proves to be the best. It was also shown that the antiknock performance of polyurea-coated steel composite structures is closely related to the characteristics of constitutive dispersion, interface dispersion and softening effect of the polyurea protective coating.

As an effective structure system for resisting the compression, the nacre composite structure has random Voronoi structure at a microscopic level and good mechanical performance. In this study, a three-dimensional Voronoi model consisting of aluminum/vinyl composite structure was presented to investigate the dynamic responses of nare-like Voronoi model under impact loading. Firstly the stochastic Voronoi model was built using the Voronoi technology, and then the adhesive layers were introduced between random polygonal aluminium sheets to simulate the bonding and delaminating processes. Via the maximum deformation, damage distribution and dissipation energy, the mechanical performances of Voronoi plate model were evaluated and compared with those of the regular plate model. The results showed that the Voronoi model is in favor of energy spreading and absorbing, reducing the stress concentration and making the energy sharing mechanism work better. But the impact damage of the regular plate model is concentrated near the impacting point of the bullet. Finally the influences of adhesive thickness and block size on mechanical performances were discussed. It was indicated that the block size has little effect on the impact resistance of the Voronoi model while the adhesive thickness exerts significant influence on the damage dissipation energy and plastic energy. It was found that the thinner is the adhesive thickness, the better is the impact resistance performance of the model.

Based on the Voronoi model of 2D anisotropic cellular materials, the uniaxial and multiaxial creep behaviors were systematically studied. A large number of numerical simulation results showed that the mechanical properties of the 2D anisotropic cellular materials are greatly dependent on the geometric tensile coefficient R, which represents the degree of anisotropy. Among them, the values of the parameters r₁ and $\nu_{12} $ gradually increase with the increase of R, and the change rule of the parameter r₂ is just the opposite. For 2D anisotropic cellular materials, with the increase of R, the uniaxial steady-state creep rate along the tensile direction increases, while the performance in the other direction decreases gradually. In addition, based on the relationship between characteristic stress and characteristic strain, a theoretical model was established, which can describe the multiaxial creep behavior of 2D anisotropic cellular materials. By comparing the prediction results of the model with the numerical simulation results of the steady-state creep rate of materials under different anisotropic degrees and loading conditions, it was found that these two agree well, which proves the validity of the theoretical model established in this paper.

In order to investigate the mesoscopic behavior of Al/PTFE reactive materials under shock loading, the shock response of Al/PTFE and Al/Ni reactive materials were investigated via numerical approaches. Two material samples were fabricated by ball mill mixing and cold isostatic pressing, and a Nano-CT system was employed to obtain their mesoscopic images. The 3D mesoscopic finite-element model based on the real configuration was established with the help of image processing and mesh mapping methods, and the numerical Hugoniot results agreed well with the theoretical results. The numerical modeling results indicated that the shock wave is uneven in the mesoscale, and the metal granules were compressed and moved along the impact direction. The PTFE matrix of Al/PTFE melted at high impact velocity, while the Al/Ni remained solid within the impact velocity range of this study.

Inspired by the venation of Royal Water Lily leaves, we conducted numerical simulations on the quasi-static and dynamic compression of layered-gradient honeycomb using the finite element software ABAQUS. Then the relationship of the quasi-static compression plateau stress with the relative density, as well as the relationship of the dynamic compressive strength with the relative density and the impact velocity was analyzed. The results show that: the progressive collapse mode appears at a low impact velocity (10 m/s); the collapse mode presents closely related to the gradient distribution at the impact velocity of 200 m/s, and the initial collapse mode just turns to be progressive. When the shock wave propagates to the far end (fixed end), the layer’s collapse and compaction depend on its static compressive strength, and the compaction occurs in the layer with lower compressive strength in turn.

In order to improve the trajectory stability of the projectile penetrating the steel target, a split penetrator was designed. Through LS-DYNA simulation, the trajectory variation rule of the split penetrator penetrating 14 mm-thick single-layer round steel target at obliquely 15° and different speeds was obtained. The influence of both the thickness and the installation gap of the protective shell on the pitch angle and trajectory deviation of the projectile were also discussed. The results showed that the split penetrator can effectively improve the penetration trajectory stability. When the penetrator speed is 500–700 m/s, the greater the thickness of the protective shell head, the smaller the pitch angle of the projectile and the trajectory deviation. When the penetrator speed is 800 m/s, the deflection angle and trajectory deviation of the projectile with a moderate thickness of the protective shell keep at the minimum. Besides, the installation gap of the protective shell can reduce the deflection of the trajectory by 8%–12% under specific working conditions. This is because when penetrating at low speed, the protective shell is not completely destroyed, and the attenuation of the stress wave increases with the thickness of the head, while at high speed the protective shell is gradually broken to a complete destruction to absorb the impact energy to the greatest extent and improve to the best ballistic stability; By increasing the clearance of the protective shell installation, the damage of the protective shell with a thicker head or at low speed penetration can also be improved.

Taking advantages of the additive manufacturing technology, our work proposes a new small-caliber light metal gun muzzle brake scheme with an impact-type inner wall and reaction-type outer hole feature. On the basis of the finite element simulation model of the after-effective period gunpowder gas evacuation, which was established by means of the three-dimensional non-viscous Euler equation, the muzzle flow field was simulated, the fluid-solid interaction was analyzed, and then the development of muzzle flow field, the characteristics of the muzzle blast wave and overpressure distribution, as well as the efficiency of the muzzle brake and its strength performance were investigated. The results showed that, compared with the traditional structure, the new muzzle brake with the same kind of lightweight titanium alloy material has a higher recoil efficiency, being characteristic of better muzzle overpressure distribution and lower shock wave hazard benefit for the airborne platform. Additionally, its structural strength can meet the operating requirements.

In order to study the factors affecting the anti-elastic energy of the composite double-layer targets, a tungsten alloy spherical fragment with a diameter of 9.5 mm and a mass of 8.05 g was used to penetrate the single layer and the superimposed double Q235 targets with different combinations, which were kept 7.2 mm in total thickness. The experimental results show that the ballistic limit of (3.6 + 3.6) mm targets is the highest, followed by (5.4 + 1.8) mm targets, and (1.8 + 5.4) mm targets, which is the lowest. The ballistic limit of the penetration monolayer 7.2 mm target is basically the same as that of the (5.4 + 1.8) mm superimposed target. It is also found that the failure and energy consumption modes of superimposed targets vary with different arrangements. When both the two layers of the targets produce slug failure, the compression and sag energy dissipations together affect the elastic energy of the targets. However, when the current target is punch failure and the rear target reaming failure, only the sag energy dissipation is the main factor affecting its elastic energy. According to the energy consumption calculation of multiple combination targets, the arrangement of (3.6 + 3.6) mm turns to be the optimal combination under the conditions of this study. The results are of great reference value to the design of protective device.

Due to the difference in physical quantities such as density and pressure, the forming process of explosive formed projectile(EFP) in air and water is quite different. In order to optimize the design scheme of underwater EFP, the simulation study was carried out using AUTODYN finite element software and the specific effects of the seven variables of the charge were discussed in detail. A set of design parameters suitable for underwater EFP charge is produced. According to the simulation results, the optimized design parameters of the EFP charge with a total mass of 1 kg are: the aspect ratio of the explosive is 1.5, the type of explosive is HMX with a higher detonation speed, the material of the liner structure is copper, and the tangential cone angle is 145°, the wall thickness $\delta $ is 2 mm, the length of the air field is 3 times the charge radius, and the initiation radius r is 0.4 times the charge radius. This scheme has a good effect on optimizing EFP speed,aspect ratio and kinetic energy.

Due to the limitation of current numerical simulation model in predicting the fracture of rod-shaped tantalum-tungsten (Ta-W) alloy explosive formed projectile (EFP) during the forming process, the tests of the mechanical properties of Ta-W alloy specimen under different stress, strain rate and temperature conditions were carried out to obtain the parameters of Johnson-Cook failure model. The forming process of Ta-W EFP with typical charge structure was simulated by LS-DYNA software using the Johnson-Cook failure model and adaptive algorithm. X-ray experiment was carried out to verify the effectiveness of the numerical simulation. When the failure model was used in the numerical simulation of rod-shaped EFP molding, the prediction of EFP fracture was better, and the errors between the simulation results and the experiment results were less than 9%. The results revealed that the formation and fracture of rod-shaped EFP can be accurately predicted by the failure model.

A dynamic calculation model for launching a long rod projectile was established in this paper, where the sabot used a new type of glass fiber reinforced polyetherimide composite material, and then the dynamic deformation of the sabot under the light gas gun pressure load was analyzed by the LS-DYNA software. The results show that the maximum stress inside the sabot occurs at the maximum bore pressure. The high stress area is distributed on the outer periphery and the root tooth of the sabot tail. The stresses at the tooth root and tooth tip are different with the overplus of material strength at the sabot head. By improving the structure of the sabot, the mass of the sabot is reduced by 16 g with the extra velocity gain of 612.2 m/s at given launching pressure.

In order to study the explosion resistance of ultra-high performance concrete-filled double skin steel tubes (UHPCFDST) under near-explosive loads, a three-dimensional finite element model of TNT explosives-UHPCFDST columns-air was established. The ALE multi-material fluid-solid coupling algorithm is used to analyze the damage mechanism, energy absorption characteristics and influence parameters of UHPCFDST columns under near-explosion. The calculation results show that the typical failure modes of UHPCFDST columns under near-explosion are plastic deformation and the collapse of the concrete core pillar. The damage process of the concrete core pillar can be divided into three stages. Compared with the ordinary concrete column, the UHPCFDST column has superior anti-blast performance; within a certain range, reducing the cross-section hollow ratio can effectively improve the explosion resistance of UHPCFDST columns; increasing the thickness of inner and outer steel pipes, particularly for the inner pipe, can increase the explosion resistance of UHPCFDST columns. The presence of axial pressure has a great influence on the deformation of the UHPCFDST column. The increase of axial pressure ratio, within a certain range is beneficial to resisting the overall deformation. As the axial pressure continues to increase, local deformation increases and the UHPCFDST column would lose its strength under the combined effects of the near-blast and the axial loads.