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As a low-density, high-strength material with high energy release potential, Al/Ep cast metal braided tubes have a wide range of application prospects in the combatant shell, which is one of the most important means to realize the integrated destructive effect of kill and blast. In this paper, Al/Ep composites with mass ratios of 3:7, 4:6 and 5:5 were prepared, and the intrinsic model of Al/Ep was established by studying its quasi-static and dynamic mechanical properties. The Al/Ep cast three-dimensional braided metal skeletons were used to obtain the required cast braided tubes with different mass ratios, and the destruction behaviors of the tubes under axial and radial compressive loads were analyzed by a combination of experimental and numerical simulations. The results show that the addition of Al particles can significantly improve the elastic-plastic properties of Al/Ep composites, and the energy storage and absorption capacities are positively correlated with the ratio of the relative contents of Al powder. When the mass ratio of Al powder to epoxy resin is 5:5, the energy absorption of Al/Ep composites is 23.16 MJ/m3, which is optimal among similar specimens and much higher than that of pure epoxy resin materials (the energy absorption of epoxy resin is 9.63 MJ/m3). The strength of binary resin matrix composites is improved, and the intrinsic models of three kinds of different mass ratios of Al/Ep composites are obtained. The intrinsic models of various Al/Ep cast braided tubes with crushing force efficiency CFE, energy absorption capacity, and specific energy absorption SEA decreased with the ratio of mass occupied by the braided filaments.

Aluminum honeycomb framework reinforced Al/PTFE material is a kind of high inert energetic material, which has higher strength and structure advantages than that of pure Al/PTFE material. In order to meet the requirements of special penetration/blasting performance, this paper adds aluminum honeycomb framework with arm length of 1.5 mm into the traditional formula Al/PTFE (mass percentage of Al and PTFE is 26.5% and 73.5%). The energetic material reinforced by aluminum honeycomb framework (20.5% Al/73.5% PTFE/6% aluminum honeycomb) is obtained by cold pressing sintering，and the experimental evaluation of release energy generated by high velocity impact in vacuum was performed by using two-stage light gas gun loading system, transient optical fiber pyrometer measurement system, overpressure measurement system and infrared thermal imager measurement system. Experimental results show that the impact reaction temperature is about 700 °C in vacuum in the velocity range of 0.96–1.5 km/s, and the energy release of the specimen increases with the increase of impact velocity. When the impact velocity is greater than 1.5 km/s, the specimen fully reacts, and the energy released by the complete reaction of the specimen does not exceed 8.3 kJ/g.

To profoundly reveal the protective performance of CFRP/aluminum foam sandwich structure, the high-speed impact simulation models of CFRP, aluminum foam and their sandwich structures are built by ABAQUS/Explicit module. The VUMAT user material subroutine is written for CFRP panel, and Hashin damage criterion is introduced. The elastic constitutive model and macro modeling method for the aluminum foam are chosen. The impact process under different working conditions is numerically simulated and the reliability of the model is verified by one-stage light gas gun loading experiment at the corresponding simulation conditions. At the same time, the protective performance of CFRP/ aluminum foam sandwich structure under different steel projectile shapes, impact velocities and impact angles (the angle between the ballistic and the target normal line) are simulated. The results show that the Mises stress nephogram of CFRP panel is peanut-like with obvious directivity. The stress wave propagates fastest in the direction perpendicular to the fiber. In the impact velocity range of 172−450 m/s, with the increase of impact velocities, the loss of kinetic energy will increase, but the increase of kinetic energy loss will decrease with the increase of impact velocities, and the contact force between the projectile and the sandwich structure will also increase. Thus the sandwich structure will have more serious delamination and fiber breakage, which will consume more kinetic energy. When the velocity of the projectile is greater than 300 m/s, the impact capability of the sandwich structure tends to the upper limit of impact capacity. In the impact velocity range of 170∼300m/s, the sandwich structure has stronger protective performance than ball-nosed projectile when the flat-nosed projectile impact, and the difference of the residual velocity between the two kinds of projectiles is larger. The shape of the projectile has a great influence on the protective performance of the CFRP/ aluminum foam sandwich structure. When the impact velocity is greater than 300m/s, the residual velocities of the two kinds of projectiles are almost the same, and the shapes of the projectile have a gradual effect on the performances of the CFRP/ aluminum foam sandwich structure. The anti-shock performance of sandwich structure under oblique impact is stronger than that of vertical impact. With the increase of impact angles, the transverse deformation of sandwich structure increases, and the anti-shock performance of sandwich structure also increases.

The structures composed by metal fiber and auxiliary elastomer are stretchable and have potential application under larger strain. Nowadays, interfacial failure is still the key problem affecting practicability of the structures. The result of typical pull-out test indicates that three stages exist in this pull-out process: elastic deformation, interfacial debonding and interfacial friction. For the sake of determination of interfacial parameters, a numerical method has been proposed to characterize the damage initiation point by using the slope of force-displacement curve of pull-out experiment. Furthermore, based on the basic material and interfacial parameters, extensive simulations have been conducted to study parametric effect on the general mechanical behavior of structures, including interfacial elastic modulus, failure strength and damage evolution law and friction. The results indicate both interfacial cohesive and friction contribute to the force increasing after damage initiation points.

To investigate the dynamic compressive behavior of zirconium filaments/aluminum/polytetrafluoroethylene (mass fraction of Zr fiber/Al/PTFE of 3%/23.5%/73.5%) active materials, traditional formula Al/PTFE active materials (Al/PTFE mass fraction of 26.5%/73.5%) and Al/Zr/PTFE active materials were prepared by cold pressing sintering process. The microscopic morphology and impact reaction behavior of the material by scanning electron microscopy (SEM) and high-speed camera are observed. The dynamic compressive experiments of the two materials are carried out by using separate Hopkinson bar (SHPB) test system. The results show that the Al/PTFE by adding active metal zirconium (Zr) filaments can improve the dynamic compressive properties of conventionally Al/PTFE. The failure strength of active material is increased from 32 MPa to 110 MPa comparing with conventionally Al/PTFE active materials, and the increase is about 243.75%. When the strain rate is 2500–4000 s−1, Al/Zr/PTFE specimens exhibit the same elastic–plastic mechanical behavior as conventionally Al/PTFE specimens. The behavior of the two specimens can also be divided into three stages: compressive deformation, crack generation and hot spot initiation (there are microscopic holes around Zr fibers, and the collapse and expansion of holes is the main reason for the formation of hot spots).

In view of the wide demands of sandwich structure with aluminum honeycomb material as core layer in many important fields such as automobile manufacturing, transportation, aerospace, protection engineering as well as ship, etc. In order to reveal the interacting duration and microscopic characteristics generated by high-velocity impact on Carbon Fiber Reinforced Plastics/Aluminum honeycomb core sandwich panel (CFRP/Al HC SP), a series of experiments about combined type and split type targets impacted by cylindrical steel projectiles at the velocity of nearly 300m/s have been performed by using one-stage light gas loading system and related velocity measurement systems established by ourselves. The residual velocities and the interacting duration are measured during the process of the projectile piercing through combined type target and each part of the split target, respectively. Meanwhile, the simulations have been conducted under the corresponding experimental conditions, and the microscopic characteristics of the CFRP specimens have also been analyzed by using scanning electron microscopy (SEM). The results shows that the total interacting duration on the whole combined type structure is 164.5 μs, and duration consumed in the front CFRP panel, Al HC and the rear CFRP panel in combined target are 32.5 μs, 91.7 μs and 40.3 μs, respectively. The damage morphology, residual velocity and interacting duration in each parts of the combined type target obtained by numerical simulation of ABAQUS/Explicit module are basically consistent with the experiments, and the crack, delamination, fracture and drawing wire of carbon fiber filaments have been given by cylindrical solid steel projectile impacting on CFRP panel at the given experimental conditions. Keywords: High-velocity impact, CFRP/Al HC SP structure, Interacting duration, ABAQUS/Explicit module, Microscopic characteristics

In order to deeply reveal the microscopic damage mode and microscopic damage mechanism of Carbon Fiber Reinforced Plastic laminates (CFRP laminates) impacted vertically by the ice projectile at high velocity. In this paper, the loading system of the one-stage light gas gun, the liquid nitrogen circulating cooling system, the impact pressure measuring system and the high speed camera acquisition system are used, and the experiments of the spherical ice projectile (simulated hail ice, SHI) with diameter of 11 mm impacting CFRP laminates vertically at the velocity of 50-200 m/s were carried out. The impact pressure of the SHI impacting the target, the strain of X-Y in the two main directions at the impact point were measured, and the deflection/ time history curve at the impact point during the impact process was obtained. By using ABAQUS/Explicit finite element software, the numerical simulation of high-velocity vertical impact of SHI on CFRP laminates was compared with the image acquisition results of the high speed camera at different moments during the impact process, and the failure morphology and process of SHI was analyzed. At the same time, the delamination of the target obtained by numerical simulation is compared with the cracking of the CFRP fiber reinforcement and the delamination of the epoxy resin interface obtained by microscopic SEM observation, the correctness of using cohesion model to describe the micro-damage of CFRP laminates induced by SHI impacting vertically at high speed was verified. The damage failure threshold of CFRP laminates under the impact load of SHI under given experimental conditions was obtained. By establishing a three-point simply supported physical model, the ultimate deflection of laminated plates subjected to delamination failure was analyzed. Based on the measurement of strain and deflection at impact point, the valuable reference for the prediction of delamination failure in CFRP laminates can be provided, then the detection of the micro-damage to the surface composite part of the aircraft will be realized by the control of the sensor. Keywords: CFRP laminates, Cohesion model of ice projectiles, Microscopic damage model, Microscopic damage mechanism, Delamination failure prediction

In view of the wide demands of sandwich structure with porous material as core layer in many important fields such as protection engineering, aerospace, automobile manufacturing and ship, etc. In order to reveal the energy absorption and damage characteristics of high velocity impact aluminum foam core and CFRP/aluminum foam core structure, the quasi-static loading system, one-stage light gas gun loading system, the impact pressure testing system and the high-speed camera acquisition system were used to perform the quasi-static compression experiments of aluminum foam and the projectiles with different materials impacting on the aluminum foam core and CFRP/aluminum foam sandwich structure at the speeds of 100–300 m/s. The influences of impact velocity and projectile’ density on the damage characteristics of CFRP/aluminum foam sandwich structure and the attenuation effect of shock wave in sandwich structure have been studied. The experimental results showed that the curve of stress and strain has three typical zones similar to porous materials: elastic zone, yield platform zone and compaction zone under quasi-static compression loading. Due to its brittle and low tensile strength of aluminum foam material, the single aluminum foam plate has poor ballistic performance under the high-speed impact of projectiles with different materials. Therefore, closed cell aluminum foam needs to be combined with high strength panels to form sandwich structure to improve its ballistic performance. Keywords: High velocity impact, Aluminum foam core, CFRP/aluminum foam sandwich structure, Energy dissipation, Damage characteristics