Periodic laminated gradient materials with independently controllable wave impedance distributions and minimal physical phase reactions are now being used for quasi-isentropic loading. However, the wave system action time of the currently periodic laminated gradient materials are on the order of nanoseconds due to limitations in preparation technology, which makes it difficult to achieve loading times of significantly larger magnitudes. In this study, the tape casting process was systematically investigated, and large-size Al-Cu periodic laminated gradient materials were successfully prepared using a combined technique of tape casting and low-temperature densification. The quality and quasi-isentropic loading properties were verified through microstructural characterization and dynamic loading experiments. The results show that the gradient structure of the material is well-defined, the interlayer parallelism is high, the layer interface is well bonded, and that no crack defects or intermetallic compounds generated. The material exhibits a densification of 95.8% and a total deformation less than 15 μm. When the Al-Cu periodic laminated gradient material was loaded with a 6 μm-thick Al target at a driving speed of 510.6 m/s, the loading waveform oscillated and increased with a loading time approaching 1 μs. The loading trends of simulation results agree well with the experimental curves through correcting Al/Cu periodic layer thickness and Cu layer wave impedance. The materials demonstrate excellent quasi-isentropic loading characteristics. This study provides theoretical basis, technical support and new preparation techniques for the application of periodic laminated gradient materials.

The shock wave pulse width is one of the essential factors influencing the shock-to-detonation transition in explosives. This study experimentally investigates the pulse width effect on the shock initiation process of the insensitive explosive 1,3,5-triamino-2,4,6-trinitrobenzene (TATB). Shock initiation experiments were conducted on TATB-2 explosives on the gun platform. The pulse width was controlled by varying the thickness of shock flyers. Experimental data including shock wave velocity and particle velocity after wave were recorded using the electromagnetic particle velocity meter and tracer meter. The relationships between pulse width effect, the distance to detonation, and other parameters of TATB-2 explosives were calculated and analyzed. The results demonstrate that pulse width effect significantly affects the detonation build-up process, providing essential references for understanding the shock initiation characteristics of insensitive explosives.

The dynamic response and energy absorption performance of foam aluminum sandwich tubes under lateral explosive loads were systematically investigated using a combination of experimental research and numerical simulation. A series of lateral explosion experiments were conducted using a ballistic pendulum system to analyze the effects of structural geometric parameters, foam aluminum density, and the explosive mass on the deformation mode and blast resistance performance. Based on the experimental results, numerical simulations were performed to further compare the blast resistance performance of foam aluminum sandwich tubes and circular tube core sandwich tubes, comparing gradient and non-gradient designs of circular tube core sandwich tubes. The results show that, the final deformation of circular tube core sandwich tubes is greater than that of foam aluminum sandwich tubes, although the difference is not significant. Among the gradient circular tube core sandwich tubes, the configuration with the largest outer wall thickness and the thinnest middle layer exhibits the best improvement in blast resistance performance. Furthermore, the blast resistance performance of gradient circular tube core sandwich tubes is significantly superior to that of non-gradient structures.

To enhance the dynamic performance of existing concrete-like materials, rubber aggregates were incorporated into a metaconcrete matrix to create a novel impact-resistant material, and the dynamic response of its mesoscopic mechanical model under impact load was simulated. Initially, the content, gradation, distribution, and appropriate material models of the specimen components were systematically calibrated and validated. Subsequently, the wave-damping capacity and the interaction patterns of the components in rubber-based metaconcrete under impact load were analyzed. In particular, the effect of rubber aggregates on the failure modes, damage zones, and extent of damage in metaconcrete under high-amplitude loads was thoroughly examined, and a parameter analysis of the rubber content and particle size was conducted. The numerical results showed that the addition of the rubber aggregates not only makes the damaged area of the concrete show dispersed characteristics, but also effectively reduces the degree of specimen damage. Rubber aggregates enhance the specimen’s toughness and suppress the intensification of damage. However, high rubber content has a detrimental effect on the specimen’s strength, and leads to a trade-off between damage suppression and damage exacerbation. To balance these two effects, it is recommended that rubber aggregates make up 15% to 30% of the total volume of aggregates. These findings demonstrate that incorporating rubber aggregates into metaconcrete can significantly improve its dynamic performance, providing a reference for the design and engineering application of impact-resistant materials in the future.

Shear thickening fluid (STF) impregnated Kevlar fabric is a new type of composite materials which has better impact resistance as compared with neat Kevlar fabric. On the basis of previous work, a dynamic constitutive model for STF impregnated Kevlar fabric is firstly developed by introducing dynamic increase factor (strain rate effect) and residual strength factor in combination with the rheological properties of STF and yarn pull out test results. Numerical simulations of STF impregnated Kevlar fabric at different impact velocities are then conducted using the proposed constitutive model. Finally, the numerical results are compared with the relevant experimental data. It is shown that the present constitutive model can predict well the impact response of STF impregnated Kevlar fabrics in terms of residual velocity, load-displacement curve and damage morphology, lending support to the accuracy and usefulness of the dynamic constitutive model for STF impregnated Kevlar fabric.

By incorporating the traditional mortise-and-tenon structure commonly used in timber structures into the porous column, and the effects of jointing mode, height, hole shape and number on the mechanical behavior and energy absorption characteristics of the structure are investigated under the condition of maintaining a uniform porosity in the porous columns. The mechanical behaviors and energy absorption performance of the porous column model are studied through tests and finite element simulation under uniaxial compression. The results show that the mortise-and-tenon porous structure has a better load carrying capacity in the later stage of the concave shape while realizing rapid assembly. The hexagonal hole model has better load carrying capacity and energy absorption characteristics. The load carrying capacity of the single hole model is higher, and the energy absorption characteristics of the porous model are better.

The application of carbon fiber reinforced polymer (CFRP) composite in protective equipment is restricted by its complex penetration behavior and unclear failure mechanism under fragment impact. To overcome the difficulty and high cost of monitoring the penetration process information through experiments, a finite element analysis (FEA) model of CFRP composite under fragment impact is constructed in this study. In this model, a strain-based three-dimensional Hashin failure criterion is adopted, and the rate-dependent relationship of strength is introduced. The effectiveness of the FEA model is verified by comparison with experimental results. The simulation results show significant difference in both initial velocities and impact inclination angles under different TNT equivalents and distances from the explosion point. The inclination angles of fragments with the target plate on y-z and x-z planes are defined as α and β. When β=0°, CFRP composites exhibit pronounced impact velocity sensitivity in the velocity range of 195−392 m/s. The energy absorption capability and impact velocity sensitivity of specimens with different inclination angles β are significantly different. However, the energy absorption capability and impact velocity sensitivity of specimens with different inclination angles α do not show significant differences. When α=0°, the impact velocity sensitivity of CFRP composites in the impact velocity range of 195−392 m/s gradually declines with the increase of inclination angle β. Visualization of the penetration process and failure area indicates that the contact area and time and deformation degree are the crucial reasons for the differences in energy absorption capability and impact velocity sensitivity observed in CFRP composites.

The anti-scour performance of hydraulic support is the key to prevent roadway rock burst. Based on the research foundation of energy absorption components, this paper proposes a new type of energy absorption component filled with aluminum foam, and studies the energy absorption characteristics of the anti-shock column. Through the numerical simulation method, the optimal energy-absorbing performance of the multi-cell tube with different wall thicknesses was selected for seven different ways of aluminum foam filling. The simulation was verified by quasi-static crushing tests, and the filling type of the energy-absorbing component with better energy-absorbing performance (MRYF type) was analyzed. Through the coupling simulation method of drop hammer impact hydraulic system, the impact characteristics of conventional column (no safety valve function) and component energy absorption column (MRYF type energy absorption component function alone) under different impact energy were analyzed. Then the energy absorption characteristics of hydraulic energy absorption column (safety valve acting alone) with hydraulic-component energy absorption column (MRYF type energy absorption component and safety valve acting together) under the action of strong impact energy were compared. The results show that the average bearing capacity of the new energy-absorbing component is increased by 18.11%, the energy absorption is increased by 7.64%, the load mean square error is reduced by 10.75%, the deformation mode is more regular, and the comprehensive energy-absorbing performance is better. Under different impact energy, the peak value of liquid pressure in energy-absorbing column decreases obviously. Under the action of strong impact energy, the peak value of liquid pressure in the hydraulic-component energy absorbing column is reduced by 6.28 MPa compared with the hydraulic energy absorbing column, and the liquid pressure in the column is more stable. Adding new energy absorbing components can reduce energy absorption and the maximum liquid pressure inside the support column under impact load. At the same time, it can reduce the total impact energy applied to the safety valve and improve the adaptability of the safety valve to different impact loads. Further, it improves the impact resistance of the support column under impact load and provides theoretical basis for the design of anti-impact support.

To solve the problems of outlier samples, imbalanced samples, and local optimal of sparrow search algorithm in machine learning rockburst prediction, this paper established a rockburst prediction model from two perspectives of data preprocessing and algorithm improvement. First, based on lithology conditions and stress conditions, selected the maximum tangential stress, compressive strength, tensile strength and elastic energy index of surrounding rock as the characteristic indexes, and used three kinds of machine learning algorithms combined with 5-fold cross-validation method to construct the prediction model. In the data pre-processing stage, collected 174 groups of domestic and international rock burst cases to establish a database; for outlier samples, introduced the local outlier factor (LOF) algorithm to detect and eliminate outlier samples step by step according to the rock burst class; for sample imbalance, the adaptive synthetic sampling method (ADASYN) was introduced to increase the number of minority class samples. Three hybrid strategies were employed to improve sparrow search algorithm (ISSA) was used to optimize the parameters of three machine learning algorithms, namely limit gradient lift tree (XGBoost), random forest (RF) and multi-layer perceptron (MLP). Multiple evaluation indexes such as accuracy rate and precision rate were analyzed and discussed to verify the effectiveness of the model. The results show that the accuracy of the newly constructed optimal model, ISA-XGBoost, reaches 94.12%, indicating high prediction accuracy. In addition to the feature importance analysis of the four feature indexes, it was determined that the maximum tangential stress of the surrounding rock is the most important feature.