This study is based on the finite element method (FEM) considering the Miller model to investigate the blast loading of thermobaric explosives (TBX) in confined spaces and the dynamic response and damage modes of reinforced concrete (RC) slabs. The Miller model considers the secondary reaction of the explosive blast products. It can effectively describe the violent afterburning effect of TBX. In the confined space, wall reflections and Mach reflections of the blast shock wave form a pressure response with long duration and multi-peak oscillations, which creates an approximately uniform load impulse on the surface of the RC slab. The peak pressure of the blast shock wave induces collapse damage, while the uniform load impulse induces bending deformation of the slab. The bending deformed RC slabs showed a large residual displacement, which increased linearly with the increase of the average impulse distributed over the surface of the RC slabs.

In this paper, a novel aluminum foam structure with wave attenuation and ventilation performance suitable for underground space is designed and prepared. It focuses on dynamic response of aluminum foam structure under explosion impact load and ventilation resistance at different wind speeds. Failure modes of each component are analyzed and attenuation mechanism of explosive shock wave are revealed. The results indicate that: under the synergistic action of the crushing behavior of the aluminum foam cells, the rough wall structure of the ventilation holes and the special diagonal square honeycomb-shaped structure, the wave attenuation effect of the aluminum foam structure is significantly improved. The max wave attenuation rate can reach to 99.1%. For this aluminum foam structure, the wind speeds are 4.32 m/s and 9.31 m/s while the ventilation resistances are 119.46 Pa and 641.44 Pa. It indicates its excellent ventilation performance. Therefore, the novel aluminum foam structure has a good application prospect in underground space construction.

The impact from multiple bullets leads to more severe damage to fiber composite laminates, and the dynamic response becomes more complex. However, current research has focused on studying the ballistic limit and single impact response of materials. In this study, an experimental method to investigate the dynamic response and damage modes of fiber composite materials under multi-point asynchronous impacts is proposed. The aim is to reveal the mechanisms behind the differences in ballistic limits and energy absorption of UHMWPE (Ultra-High Molecular Weight Polyethylene) fiber composite panels at different impact distances. Through CT scanning and DIC (Digital Image Correlation) techniques, the delamination area and dynamic response of the laminates were quantitatively analyzed. The results show that the ballistic limit of the second impact is increased by 3.05% when the impact distance is 2.5 times the diameter of the bullet. The maximum difference of energy absorption compared to the first impact was only 3.7% at an impact spacing of 5 times the diameter of the bullet, despite the interference in the damage region. From the perspective of energy absorption, the two impacts are independent. Multiple impact tests are critical for protective materials, and the results of this study provide important insights into UHMWPE fiber laminates in terms of multi-point impact.

This paper investigates the effect of stitch density on the high-velocity impact damage inhibition and CAI (compression after impact) strength of UHMWPE (Ultra-High Molecular Weight Polyethylene) fiber composites. The damage response and compression behavior after impact were quantified and analyzed using CT scanning and DIC (Digital Image Correlation) techniques. The findings reveal that the delamination area of the composite plate with the stitch space of 1 cm reduces by 49.14 % compared to the unstitched sample, and exhibits a 73.05 % higher compressive load than the plate with a 4 cm stitch space. Notably, the 4 cm stitch composite plates demonstrate a significant advantage in energy absorption. However, the sparse stitch structure destroys the original structure inside the composite, resulting in a degradation of CAI performance. The study provides guidance for the practical design of composite materials with enhanced energy absorption and damage resistance.

It has been reported that the ply gap influences the ballistic resistance of spaced multi-ply fabric systems,but its working mechanism was not well-understood. This paper reports the experimental and numerical approaches and results of an investigation on the mechanisms that enable the improved ballistic performance of spaced multi-ply systems. Penetration tests were performed over a range of impact velocities ranging from 200 m/s to 400 m/s. The results confirmed that the ply gap is beneficial to the energy absorption capability of the systems. This is because the front plies tend to absorb more energy when they are not immediately constrained by the rear plies. During a ballistic event, the gap relieves the reflection of the compressive pulse, prolonging the projectile engagement time with the front plies; on the other hand, the rear plies become increasingly less active in dissipating energy as the gap increases.When the gap is sufficiently widened to avoid any interference between the plies before the failure of the front ply, the responses of the whole system no longer vary. It was also found that the ballistic performance of the spaced systems is influenced by ply thickness, impact velocity, and the stacking order of the ply gap.

The physical–chemical method with plasma treatment and polypyrrole grafting was used to improve the low velocity impact resistance of the ultra-high molecular weight polyethylene (UHMWPE) fiber/epoxy laminates. The experimental impact force–time curves and impact force-central displacement curves were recorded. The microscopic void distribution of impact region was quantitatively counted by high-resolution X-ray micro-computed tomography (μCT). Then the residual compressive strengths for the laminates after low velocity impact were explored. Experimental results showed that the impact resistance and residual strength of the laminates treated by the combined plasma treatment and polypyrrole grafting were significantly improved by comparing with the plasma treatment alone, and the void fraction also reduced remarkably. In addition, the impact resistance with single physical plasma treatment method was more affected by the mixture ratio of nitrogen and oxygen.

Developing new high-entropy alloy system has been a subject of significant research interest in recent years. However, it is a challenge to enhance the impact-resistance property in existing high-entropy alloys. Here we proposed a combination strategy of strengthening via second phase and grain refining to build a network microstructure in Co 2 Ni 2 CrVTa 0.3 high entropy alloys that could significantly enhance the ballistic limit velocity from 407.8 m/s to 435.4 m/s. Especially, under a high impact velocity of 750 m/s, the energy absorption of the alloy was evidently larger than that of the Ta-free alloy. The microstructure of Co 2 Ni 2 CrVTa x alloys could be sensitively tuned via Ta addition because of the Ta-induced multi-scale microstructure involving the micro-scale Laves phase and nano-scale L1 2 structure precipitates. This should be the structural mechanism of the enhanced impact-resistance property, and will shed light on the development of alloys with excellent impact-resistance property.

Modern protective materials must not only exhibit an intelligent response behavior, but also possess an excellent energy absorption ability. The applicability of shear-stiffening gel is limited because it generally cannot demonstrate good shape stability, strain sensitivity, and energy dissipation ability simultaneously. In this study, multiple hydrogen bonds and metal coordination bonds are incorporated into a shear-hardening gel to fabricate a new impact-hardening polymer (IHP-Cu) with multi-level energy dissipation pathways, thereby achieving a balance between shape stability, rapid self-healing, and energy dissipation. IHP-Cu maintains a stable shape in its natural state, exhibits significant strain-sensitive behavior at different strain rates, and supports a weight of 400 g at room temperature for 10 s after damage. In compression cycling tests, its energy absorption efficiency exceeded 90%. In the frequency-dependent test (strain rate of 0.1 s−1), its elastic work and viscous dissipation increased by 24 and 12.5 times, respectively, compared to those of the conventional shear-hardening gel. This paper also reveals the energy dissipation mechanism of IHP-Cu, thus providing a theoretical basis and reference for the development and optimization of new protective materials.

Obtaining a robust fiber/matrix interface is crucial for enhancing the mechanical performance of fiber-reinforced composites. This study addresses the issue by presenting a novel physical–chemical modification method to improve the interfacial property of an ultra-high molecular weight polyethylene (UHMWPE) fiber and epoxy resin. The UHMWPE fiber was successfully grafted with polypyrrole (PPy) for the first time after a plasma treatment in an atmosphere of mixed oxygen and nitrogen. The results demonstrated that the maximum value of the interfacial shear strength (IFSS) of the UHMWPE fiber/epoxy reached 15.75 MPa, which was significantly enhanced by 357% compared to the pristine UHMWPE fiber. Meanwhile, the tensile strength of the UHMWPE fiber was only slightly reduced by 7.3%, which was furtherly verified by the Weibull distribution analysis. The surface morphology and structure of the PPy in-situ grown UHMWPE fibers were studied using SEM, FTIR, and contact angle measurement. The results showed that the enhancement of the interfacial performance was attributed to the increased fiber surface roughness and in-situ grown groups, which improved the surface wettability between the UHMWPE fibers and epoxy resins.

The influences of Mg2+ and Ca2+ on the short-term (1800 s) corrosion behavior of X100 pipeline steel were investigated in a sodium chloride (NaCl) solution saturated with CO2. Either Ca2+ or Mg2+ in the solution inhibited the short-term corrosion of X100 pipeline steel, with the corrosion current density decreasing from 262.4 μA cm−2 to 163.5 μA cm−2 or 80.8 μA cm−2. During longer-term (8−48 h) immersion, the Mg2+ inhibited the formation of the protective scale, whereas the Ca2+ accelerated the formation of the scale. Further, an experimental equation establishing the relationship between the precipitation rate of the corrosion scale and the exposure time was proposed to quantitatively study the effects of Mg2+ and Ca2+ on the precipitation rate of the corrosion scale.

In this study, the vertical imbibition of water from foam concretes upward were studied with the assistance of staining, which illustrated the way contrast material spread in specimens during CT scans. The 20 x 20 mm2 bottom face of dried rectangular concrete was adopted, and the test was limited to the first 2.5 h. Using cesium (Cs) or iodine (I) as the staining agent, a new-developed X-ray attenuation method (XRAM) was used to obtain the spatial distribution of water. The result showed that Cs and I are equally trustable in tracing water during the early-time imbibition. Besides, two regions, namely "saturated verge" (near the imbibing face) and "unsaturated transport region" (from an inner area), could be recognized from the imbibition path regarding their variant evolving patterns. The saturated verge from the inlet was of constant width, while the scale of the unsaturated transport region kept increasing during imbibition, and the imbibing rate was similar for all specimens in this study. Moreover, even though the imbibition progress in this study was confirmed a diffusion-controlling progress, a broad imbibition front was revealed from the averaged 1D water content profile, which was mainly attributed to the irregular-shaped "saturated verge".

Carbon fiber reinforced plastic (CFRP) have been widely used in recent years for their high specific strength and stiffness. However, due to the high brittleness and low elongation, its application in protection engineering was limited. The introduction of other ductile fibers can ameliorate this shortcoming. In this paper, laminated construction and failure mechanism of twill carbon fiber and ultra-high molecular weight polyethylene (UHMWPE) fiber hybrid composite laminates under ballistic impact were comprehensively studied. Three different interface properties were characterized by peeling test. The simulation results were in good agreement with the ballistic impact experimental results. The sample of 4C4P with carbon fiber in the front and UHMWPE fiber in the back shows the best impact energy absorption performance,with the specific energy absorption increased by 92.22%. Based on the computed tomography (CT) scanning, delamination damage cloud images of the composite laminates were presented for the first time. The improvement of interlayer fracture toughness can enhance the impact resistance of laminates, which mainly depending on the stacking sequence and interface properties. It provided a new idea for the study of impact damage of laminated structures.

With the comprehensive promotion of ultralow emissions and world-class energy consumption standards, the disposal of the spent SCR (selective catalytic reduction of NOx with NH3) catalyst and fly ash has become a new challenge for coal power plants. In this study, a new method of simultaneous utilization of the spent SCR catalyst and fly ash in concrete preparation was developed. The working performance and heavy metal leaching characteristics of concrete prepared by replacing some cement with the spent SCR catalyst/fly ash were investigated. Results suggested that the addition of fly ash could improve the deterioration of concrete fluidity caused by the addition of the spent SCR catalyst. Better working performance was evidenced at 5% of the spent SCR catalyst and less than 10% of fly ash addition. When more than 10% of the spent SCR catalyst was added into concrete, the compressive strength and impermeability of the concrete were significantly worsened, but those could be improved by adding fly ash due to its pozzolanic activity. Leaching characteristics showed that the solidification efficiency of V and As could reach more than 96 and 97%, respectively, which mainly comes from the generation of C-S-H gels by the hydration reaction of cement in the concrete curing process. Results revealed that the method proposed in this study can achieve high-efficiency solidification of heavy metals in spent SCR catalysts. In general, the simultaneous utilization of the spent SCR catalyst and fly ash to replace some parts of the cement for preparing concrete is a promising method for harmless disposal of spent SCR catalysts.

Plastics from waste electrical and electronic equipment (WEEE) have been an important environmental problem because these plastics commonly contain toxic halogenated flame retardants which may cause serious environmental pollution, especially the formation of carcinogenic substances polybrominated dibenzo dioxins/furans (PBDD/Fs), during treat process of these plastics. Pyrolysis has been proposed as a viable processing route for recycling the organic compounds in WEEE plastics into fuels and chemical feedstock. However, dehalogenation procedures are also necessary during treat process, because the oils collected in single pyrolysis process may contain numerous halogenated organic compounds, which would detrimentally impact the reuse of these pyrolysis oils. Currently, dehalogenation has become a significant topic in recycling of WEEE plastics by pyrolysis. In order to fulfill the better resource utilization of the WEEE plastics, the compositions, characteristics and dehalogenation methods during the pyrolysis recycling process of WEEE plastics were reviewed in this paper. Dehalogenation and the decomposition or pyrolysis of WEEE plastics can be carried out simultaneously or successively. It could be ‘dehalogenating prior to pyrolysing plastics’, ‘performing dehalogenation and pyrolysis at the same time’ or ‘pyrolysing plastics first then upgrading pyrolysis oils’. The first strategy essentially is the two-stage pyrolysis with the release of halogen hydrides at low pyrolysis temperature region which is separate from the decomposition of polymer matrixes, thus obtaining halogenated free oil products. The second strategy is the most common method. Zeolite or other type of catalyst can be used in the pyrolysis process for removing organohalogens. The third strategy separate pyrolysis and dehalogenation of WEEE plastics, which can, to some degree, avoid the problem of oil value decline due to the use of catalyst, but obviously, this strategy may increase the cost of whole recycling process.