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In order to investigate the ballistic performance, failure patterns and energy dissipation of aluminum alloy target plates against the impact of different strength and head shape projectiles, the three-dimensional models of 3 mm thick 6061-T651 aluminum alloy target plates impacted by lightweight-deformable projectiles of different materials were established by Abaqus finite element software, and the modified Johnson-Cook（MJC） constitutive model and the Lode-dependent modified Mhor-Coulomb（MMC） fracture criterion are used for numerical simulation. The results show that the corresponding ballistic limit velocity of the target plates are the highest when the low strength 6061-T651 aluminum alloy are used as the projectile material, and the ballistic limit velocity of the target plates decrease with the increase of the projectiles strength. The impact will cause a more complex failure patterns of the target plates when the projectiles strength is low, and at the same time, the plastic deformation of the projectiles head occur to different degree; the projectiles strength has a significant effect on the energy dissipation ability of the target plates. The ballistic limit velocity corresponding to the lightweight-deformable blunt-head projectiles are higher than that of the ogival-head projectiles.

The traditional Miura-ori was optimized to Miura-ori with platforms by geometric parameters. Two types of impactors were used to conduct low-velocity impact experiments at two specific sites. The damage morphology, response characteristics, and failure mechanism under various energy were systematically investigated. The results reveal that the impact resistance of the node is better than that of the base due to crushing absorbing energy. The impact resistance of the Miura-ori with platforms sandwich structures to the flat-ended impactor is better than that of the hemispherical impactor at the node. Still, the performance at the base is the opposite. [ABSTRACT FROM AUTHOR]

The impact resistance of aluminum alloy circular corrugated sandwich plate is investigated by using the experiments and simulations, and the influence of projectile nose shape and impact velocity on the failure mode and energy dissipation characteristics is analyzed. The experimental results indicate that the projectile nose shape influences the impact resistance of circular corrugated sandwich plates. The ballistic limit velocity (BLV) and energy dissipation of the plate increase as the caliber radius head (CRH) of the projectile increases, and the failure mode gradually changes from shear plugging damage and tensile tearing damage to ductile hole enlargement and petal cracking damage. Numerical simulation results show that the numerical simulation can accurately predict the ballistic limit velocity, failure mode and the impact process. [ABSTRACT FROM AUTHOR]

Highlights The aim of this paper is to explore the effect of polyurethane foam filler on the out‐of‐plane compressive property and low‐velocity impact resistance of the orthogonal corrugated sandwich panel by experimental method. The results show that foam filling increases the energy absorption and specific energy absorption of the orthogonal corrugated sandwich panel by 64.75% and 38.22% under compressive load, respectively. Furthermore, during compression, the filled foam causes the core strut undergo pure buckling failure and gradually folds rather than brittle fracture. Under low‐velocity impact, the strengthening effect of foam filling on the first peak load of the load–displacement of the orthogonal corrugated sandwich panel decreases with the increase of impact energy, while the inhibition effect on the impactor drop increases with the increase of impact energy. The results can provide a reference for the design and optimization of foam‐filled hybrid sandwich structures. The compressive property and low‐velocity impact resistance of the foam‐filled orthogonal corrugated sandwich panel are tested. The effect of foam filling on the mechanical properties of the orthogonal corrugated sandwich panel is obtained by comparing the out‐of‐plane compressive response and low‐velocity impact response of the empty and foam‐filled orthogonal corrugated sandwich panel and foam sandwich panel. Foam filling can improve the load‐bearing property and energy‐absorbing capacity of the orthogonal corrugated sandwich panel and make it more stable progressive damage. [ABSTRACT FROM AUTHOR]

In order to study the effect of PMI foam on the impact resistance of the double-layered plates of aluminum alloy 2 A12-T4, the high-velocity impact experiments were performed to the aluminum alloy double-layered plates and aluminum alloy/PMI/aluminum alloy sandwich panel by using hemispherical-nosed projectiles launched by the one-stage gas gun system. The ballistic limit velocity and damage characteristics of the plates were obtained through the experimental results. The results show that the PMI foam core can restrict the plastic deformation of aluminum alloy plate under the same thickness as the aluminum alloy plate, decrease the absorption of impact energy and reduce the impact resistance of the aluminum alloy 2 A12-T4 double-layered plates by increasing the rigidity of the plate. In addition, the effect of the PMI foam core on the impact resistance of the plates decreases as the increase of velocity of the projectile.

In China, English as a foreign language (EFL) learning mainly occurs in the classroom, and the resultant lack of practice using English in authentic settings makes it quite difficult for many Chinese learners to learn English words. They may often feel that English words are "difficult to learn and easy to forget." As such, how to effectively teach English vocabulary in classrooms is an essential point for English teachers. Assuming that the goal of vocabulary teaching is to build up students' mental lexicon, this paper first briefly introduces the properties of the mental lexicon and examines differences between the mental lexicon and (print or electronic) dictionaries. More importantly, it then discusses how to teach English vocabulary based on a proper understanding of the organization of the mental lexicon and means of accessing it. Finally, the author poses some suggestions on vocabulary teaching: learning words from context as against word lists, establishing semantic relations between words, providing learners with frequent exposure to words, and teaching morphological knowledge pertaining to the words.

Nowadays, more and more aircraft components are made of composite sandwich structures, and ice impacts are prone to cause internal damage to composite sandwich structures, so it is crucial to study the impact of hail on composite sandwich structures. Since hail impacts may occur several times at a single point, an experimental approach was used to investigate the dynamic response of GFRP/Nomex honeycomb sandwich panels under multiple hail impacts. The dynamic response of the structure was investigated in terms of response rate and deflection‐profile curves using 3D digital image correlation methods, and the effects of impact energy, hail size, and number of impacts on the impact resistance of the honeycomb sandwich structure were explored. The results show that the dynamic response process of sandwich panels can be categorized into the ball‐and‐crown phase, the rebound phase, and the vibration phase. Under the same impact energy, the impact of small‐sized hailstones is more threatening to honeycomb sandwich panels. As the number of impacts increases, the maximum deflection value of the back panel first increases uniformly, and when the layered damage area reaches the threshold value, fiber stripping occurs, and the increment of the maximum deflection value increases significantly. Highlights: Since hail impacts may occur several times in real situations, this study conducted multiple impact experiments for one impact site. The dynamic response and damage pattern of the GFRP/Nomex honeycomb sandwich panels under multiple hail impacts were also investigated.The dynamic response process of GFRP/Nomex honeycomb sandwich panels was categorized into three phases: ball‐crown stage, rebound stage, and vibration stage.With the increase of the number of impacts, fiber stripping and fiber break damage began to occur when the layered damage area of the panel reached the threshold value. The honeycomb core has three main failure modes: cell wall folds, cell wall fracture, and cell wall debonding at the TGPW interface.Small‐diameter hails pose a more significant threat of damage to honeycomb sandwich panels at the same impact energy. [ABSTRACT FROM AUTHOR]

Interlayer hybrid foldcore sandwich structures have been introduced in this study. Both facesheets and foldcores were hybridized in the same ply sequence with two layers of plain woven carbon (C) and two layers of satin woven glass (G) fiber prepregs (Carbon-to-Glass ratio 1:1). Foldcore sandwich structures with six-ply combinations were designed including two symmetric layups (GCCG and CGGC) and four asymmetric layups (CGCG, GCGC, CCGG, and GGCC). The static compression and low-velocity impact performance of foldcore sandwich structures of different ply sequences were investigated. A user-defined material subroutine (VUMAT) was employed to characterize the damage evolution of composite materials based on selected failure criteria. The findings revealed that hybridization was effective in enhancing its energy absorption value of pure carbon fiber foldcore sandwich structures in terms of static compression performance. The damage degree of the interlayer hybrid foldcore sandwich structures increased gradually with the increasing impact energy. Moreover, the damage of facesheet was mainly caused by fiber tensile, matrix tensile damage and delamination, and damage of foldcore was mainly delamination. GCGC sandwich panel with asymmetrical cross-ply sequence has the optimal load bearing capacity, and CGGC sandwich panel with symmetrical layup has a strong energy absorption capacity under high-energy impact load. The foldcore sandwich structure showed smaller peak load, longer crushing distance, and more energy absorption value under larger oblique impact angle. The simulation and experimental results show good agreement in peak force, maximum energy absorption, and damage mode. [ABSTRACT FROM AUTHOR]

In this paper, a new type of foldcore sandwich panel (tentatively called X‐type foldcore sandwich panel) is proposed by combining the X‐type corrugated sandwich panel and the Miura‐ori sandwich panel. The experimental specimens are prepared by using a glass fiber‐reinforced polymer. To systematically reveal the low‐velocity response mechanism and impact resistance of sandwich panels, a hemispherical impactor is used to impact panels. The effects of impact energy, impact position, diameter of tup, and impact mass on low‐velocity impact performance of X‐type foldcore sandwich panels are considered. The damage morphology, response process, and failure mechanism are analyzed under different working conditions. The results show that under the impact of 75 and 125 J, the impact resistance of the node is better than that of the base. Under 200 J impact, the impact resistance of the base is better than that of the node. Compared with the traditional foldcore sandwich panel, the new configuration reduces the impact resistance difference between two positions (node and base). Highlights: A new foldcore sandwich panel is proposed.The impact effect of energy, mass, position, and tup diameter is investigated.Damage morphology, response process, and impact resistance are analyzed.The new structure reduces differences in impact resistance. [ABSTRACT FROM AUTHOR]

AbstractDue to its superior performance, the foldcore structure has the potential to replace traditional honeycomb materials. Single-ridgeline V-shaped, double-ridgeline M-shaped, and curved S-shaped foldcore structures were designed based on the principle of origami by controlling areal density. Three foldcore sandwich structures were fabricated from GFRP by hot compression molding method, and PU foam-filled foldcore sandwich structures were also prepared by in-situ foaming. The strength analysis models of the three types of foldcore under out-of-plane compression load were established through differentiation and integration. Subsequently, the quasi-static compression performance and failure modes of the foldcore were investigated through experiments. The analysis model has a certain degree of accuracy in predicting the strength of the structure. It was found that the primary failure mode of V-shaped foldcore under out-of-plane compressive loading was wall buckling. In contrast, the M-shaped foldcore had higher buckling resistance and the failure mode changes from buckling to crushing. S-shaped foldcore had a higher compression strength, and its failure mode changed to wall shear fracture. In addition, lightweight foam filling improved the failure stress of the foldcore. [ABSTRACT FROM AUTHOR]

Plant life history is determined by two transitions, germination and flowering time, in which the phosphatidylethanolamine-binding proteins (PEBPs) FLOWERING LOCUS T (FT) and TERMINAL FLOWER1 (TFL1) play key regulatory roles. Compared with the highly conserved TFL1-like genes, FT-like genes vary significantly in copy numbers in gymnosperms, and monocots within the angiosperms, while sporadic duplications can be observed in eudicots. Here, via a systematic analysis of the PEBPs in angiosperms with a special focus on 12 representative species featuring high-quality genomes in the order Lamiales , we identified a successive lineage-specific but systematic expansion of FT-like genes in the families of core Lamiales. The first expansion event generated FT1-like genes mainly via a core Lamiales -specific whole-genome duplication (cL-WGD), while a likely random duplication produced the FT2-like genes in the lineages containing Scrophulariaceae and the rest of the core Lamiales. Both FT1- and FT2 - like genes were further amplified tandemly in some families. These expanded FT-like genes featured highly diverged expression patterns and structural variation, indicating functional diversification. Intriguingly, some core Lamiales contained the relict MOTHER OF FT AND TFL1 like 2 (MFT2) that probably expanded in the common ancestor of angiosperms. Our data showcase the highly dynamic lineage-specific expansion of the FT-like genes, and thus provide important and fresh evolutionary insights into the gene regulatory network underpinning flowering time diversity in Lamiales and, more generally, in angiosperms. [ABSTRACT FROM AUTHOR]