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The equine hoof wall has outstanding impact resistance, which enables high-velocity gallop over hard terrain with minimum damage. To better understand its viscoelastic behavior, complex moduli were determined using two complementary techniques: conventional (∼5 mm length scale) and nano (∼1 µm length scale) dynamic mechanical analysis (DMA). The evolution of their magnitudes was measured for two hydration conditions: fully hydrated and ambient. The storage modulus of the ambient hoof wall was approximately 400 MPa in macro-scale experiments, decreasing to ∼250 MPa with hydration. In contrast, the loss tangent decreased for both hydrated (∼0.1–0.07) and ambient (∼0.04–0.01) conditions, over the frequency range of 1–10 Hz. Nano-DMA indentation tests conducted up to 200 Hz showed little frequency dependence beyond 10 Hz. The loss tangent of tubular regions showed more hydration sensitivity than in intertubular regions, but no significant difference in storage modulus was observed. Loss tangent and effective stiffness were higher in indentations for both hydration levels. This behavior is attributed to the hoof wall's hierarchical structure, which has porosity, functionally graded aspects, and material interfaces that are not captured at the scale of indentation. The hoof wall's viscoelasticity characterized in this work has implications for the design of bioinspired impact-resistant materials and structures. The outer wall of horse hooves evolved to withstand heavy impacts during gallop. While previous studies have measured the properties of the hoof wall in slowly changing conditions, we wanted to quantify its behavior using experiments that replicate the quickly changing forces of impact. Since the hoof wall's structure is complex and contributes to its overall performance, smaller scale experiments were also performed. The behavior of the hoof wall was within the range of other biological materials and polymers. When hydrated, it becomes softer and can dissipate more energy. This work improves our understanding of the hoof's function and allows for more accurate simulations that can account for different impact speeds. [Display omitted] [ABSTRACT FROM AUTHOR]

The self-wrinkling coating with surface microphase morphology and hierarchical cross-linked structure for impact resistance and mechanical enhancement. [Display omitted] Protective materials are essential for personal, electronic, and military defenses owing to their efficient impact-resistant and energy-absorbing properties. Inspired by the bottom-up fabrication process and energy dissipation mechanism of natural organisms with hierarchical structures, we demonstrated a self-wrinkled photo-curing coating as a new protective material for enhancing the anti-impact property of the substrates. Owing to the self-assembly of polydimethylsiloxane (PDMS) containing polymeric photoinitiator on the surface, the liquid coating formulation was photo-cured by one-step UV irradiation with simultaneous generation of self-wrinkled surface morphology and a gradient cross-linked architecture. The maximum impact resistance height (h max) of the glass substrate coated with plain coating increased from 120 to 180 cm when coated with wrinkled gradient coating. Furthermore, the Young's modulus, fracture stress, and toughness of the wrinkled gradient coating film improved from 39.6 MPa, 2.4 MPa, and 74.1 MJ/cm3 to 235.0 MPa (∼5× increase), 18.5 MPa (∼6.6× increase), and 845.0 MJ/cm3 (∼10.8× increase) compared to the pure coating film as reference. The theoretical simulation and experimental results proved that the surface self-wrinkled morphology and intrinsic hierarchical architecture contribute to the energy dissipation and impact resistance of the cured coating. The photo-curing process, a bottom-up strategy, is conducted in a non-contact mode compared with nano-printing and lithography, enabling bulk materials to be engineered. [ABSTRACT FROM AUTHOR]

The majority of living organisms demonstrate remarkable attributes and have evolved effective mechanisms for synthesizing impact-resistant and damage-tolerant structures. One exemplary instance is the rapid mandible strikes exhibited by trap-jaw ants, which are a highly aggressive species of terrestrial social organisms. An impact-resistant sinusoidal helicoidal architecture is discovered in the mandibles of trap-jaw ants. The bioinspired laminate with a bi-sinusoidal helicoidal structure was manufactured using unidirectional carbon fiber prepreg by mold press forming. This study examines the impact resistance and damage tolerance of a bionic laminate through low velocity impact, computed tomography, and compression after impact tests. The results demonstrate that bionic laminates effectively limit damage propagation within the plane while enhancing energy dissipation capacity. The sinusoidal helicoidal configuration enhances cushioning capability against impact forces, retards penetration under higher loads, hinders crack propagation, and improves residual strength. Bionic laminates provide a valuable solution for damage tolerance through the resistance to through-the-thickness loads. Helicoidal and sinusoidal helicoidal microstructures have been identified in the cross-section of the jaws of trap-jaw ants. The multiple waviness ratio parameters are designed for fabricating a sinusoidal helicoidal structure laminate using unidirectional carbon fiber prepreg through the mold press forming technique. This results in a damage-tolerant mechanism characterized by reduced delamination damage, which leads to a stiffer mechanical response. Meanwhile, it enhances resistance to crack propagation, leading to the formation of discontinuous delamination areas and the accumulation of sub-critical failures. Additionally, the sinusoidal helicoidal structure laminate combines the cushioning performance of bi-sinusoidal arrangements with the enhanced impact resistance of helical arrangements. This design delays penetration at higher loads, resulting in increased residual strength. [Display omitted] [ABSTRACT FROM AUTHOR]

Enamel coating has potential application in steel rebar protection due to its high durability, excellent corrosion resistance, and strong coating/concrete interface bond. The newly developed low temperature enamel (LTE) coating has a substantially lower sintering temperature than that of traditional enamel coatings, whereas its adhesion mechanism to the substrate is expected to vary dramatically. In this study, abrasives of various particle sizes were used to blast steel substrates to create various surface states, to investigate the influence of substrate surface roughening on the interfacial properties of LTE coating. The surface roughness of substrates was quantitatively characterized by a 3D optical profiler. The adhesion, impact resistance, and abrasion resistance of LTE coating under different substrate surface states were investigated by pull-off, falling weight impact, and Taber abrasion test, respectively. The results showed that with increasing substrate surface roughness, the adhesion strength and impact resistance of the LTE coating were greatly improved. Within the investigated range, the substrate surface roughness had negligible influence on abrasion resistance. Overall, appropriate substrate surface roughening can provide the LTE coating with sufficient interface adhesion, impact resistance, and abrasion resistance. [ABSTRACT FROM AUTHOR]

The jackfruit is the largest fruit on the Earth, reaching upwards of 35 kg and falling from heights of 25 m. To survive such high energy impacts, it has evolved a unique layered configuration with a thorny exterior and porous tubular underlayer. During compression, these layers exhibit a progressive collapse mechanism where the tubules are first to deform, followed by the thorny exterior, and finally the mesocarp layer in between. The thorns are composed of lignified bundles which run longitudinally from the base of the thorn to the tip and are embedded in softer parenchymal cells, forming a fiber reinforced composite. The mesocarp contains more lignin than any of the other layers while the core appears to contain more pectin giving rise to variations in compressive and viscoelastic properties between the layers. The surface thorns provide a compelling impact-resistant feature for bioinspiration, with a cellular structure that can withstand large deformation without failing and wavy surface features which densify during compression without fracturing. Even the conical shape of the thorns is valuable, presenting a gradually increasing surface area during axial collapse. A simplified model of this mechanism is put forward to describe the force response of these features. The thorns also distribute damage laterally during impact and deflect cracks along their interstitial valleys. These phenomena were observed in 3D printed, jackfruit-inspired designs which performed markedly better than control prints with the same mass. Many biological materials have evolved remarkable structures that enhance their mechanical performance and serve as sources of inspiration for engineers. Plants are often overlooked in this regard yet certain botanical components, like nuts and fruit, have shown incredible potential as blueprints for improved impact resistant designs. The jackfruit is the largest fruit on Earth and generates significant falling impact energies. Here, we explore the jackfruit's structure and its mechanical capabilities for the first time. The progressive failure imparted by its multilayered design and the unique collapse mode of the surface thorns are identified as key mechanisms for improving the fruit's impact resistance. 3D printing is used to show that these structure-property benefits can be successfully transferred to engineering materials. [Display omitted] [ABSTRACT FROM AUTHOR]

• A double vertical steel tube (DVST) sandwich panel, with a core layer composed of inner and outer vertical circular hollow steel tubes, was proposed. • The dynamic behaviors of the DVST sandwich panel under low-velocity impact was evaluated. • A precise 3D finite element model was developed. • The effectiveness of the DVST sandwich panel as a sacrificial cladding for reinforced concrete (RC) columns under low-velocity impact was investigated. A double vertical steel tube (DVST) sandwich panel, with a core layer composed of inner and outer vertical circular hollow steel tubes, was proposed as a sacrificial cladding to mitigate the damage induced by impact loading to reinforced concrete (RC) column. Through experimental tests and numerical simulations, dynamic behaviors of the DVST sandwich panel under low-velocity impact was evaluated. The impacts of varying inner tube diameters and single-layer versus double-layer configurations on the failure mode and the time-history of impact forces of the DVST sandwich panels were examined. The results indicated that the steel tube of the upper layer in double-layer DVST sandwich panels played a crucial role in absorbing impact energy. Additionally, the effectiveness of the DVST sandwich panel as a sacrificial cladding for RC columns under low-velocity impact was investigated. The findings revealed that the presence of the DVST sandwich panel reduced the energy absorbed by the RC column by approximately 60.1 %, effectively preserving the integrity of the column while minimizing deformation and damage. [ABSTRACT FROM AUTHOR]

• Dynamic behavior of four typical types of advanced films subject to supersonic micro- and nano-ballistic impact are reviewed. • Specific energy absorptions are summarized and the corresponding energy dissipation mechanisms are provided. • Size effects of impact resistance of the advanced films are discussed. • Some feasible design strategies for improving the impact resistance of the films are introduced. High-performance materials with excellent impact resistance are of fundamental importance in impact protective engineering. With the development of experimental facilities and numerical simulations at the micro- and nano-scales in recent years, some advanced films are found to show extraordinary energy absorption capacities, showing great promise as ideal bulletproof materials. In this paper, we review the dynamic behavior of four typical types of advanced films that are promising candidates as bulletproof materials subject to supersonic micro- and nano-ballistic impact. Their specific energy absorptions are summarized and the corresponding energy dissipation mechanisms are provided. The size effects are discussed. Some feasible design strategies for improving the impact resistance of the films are also introduced. The applications of the advanced films in the future are dicussed and prospected. [ABSTRACT FROM AUTHOR]

• A MSTF-based safety-enhanced battery module design is proposed. • Excellent cooling and anti-impact functions are actively switchable in one system. • Multifunctionality is achieved by a magnetic field that instantly changes the viscosity of MSTF. In this paper, a magnetically controlled multifunctional smart material system based on magneto-sensitive shear thickening fluid (MSTF) is proposed for the safety-enhanced lithium-ion battery (LIB) modules. The rheological behavior of the MSTF can be intelligently manipulated by a magnetic field, allowing its function in the battery module to be actively and rapidly switched between cooling and impact resistance. To quantitatively assess the temperature control and impact resistance of the purposely prepared MSTF, comprehensive experiments are conducted to thoroughly analyze the thermal performance, mechanical response, and electrochemical performance of the battery module integrated with cooling and active impact protection. The results of the cooling test show that the water-based MSTF without a magnetic field has a flowability that gives it similar temperature control to that of a commonly used coolant (water). This suggests that the MSTF can be an effective cooling medium for rapid cooling of LIBs. The results of the impact test indicate that MSTF in a magnetic field can completely avoid battery deformation and significantly reduce the impact force applied to the LIB during impact, due to the fact that the magnetic field can quickly transform the MSTF into a solid-like state, which gives it a significant anti-impact effect. More importantly, the LIBs protected by the MSTF exhibit no rapid capacity degradation or abnormal temperature increase in the subsequent electrochemical cycling tests, while the unprotected or weakly protected LIBs compromise after the impact. With the MSTF, excellent cooling and anti-impact functions can be actively switched in one system, and this innovative integrated design is expected to drive significant advances in safety for battery modules. [Display omitted] [ABSTRACT FROM AUTHOR]

This study investigates the impact resistance of reinforced concrete (RC) beams using various types of high-performance fiber-reinforced cementitious composites (HPFRCCs). A total of ten large-sized RC beams were fabricated and tested under static and impact loading conditions. Four different types of HPFRCCs with 2% by volume of steel, polyvinyl alcohol (PVA), and polyethylene (PE) fibers were considered. Ultra-high-performance fiber-reinforced concrete (UHPFRC) based on steel fibers demonstrated superior compressive and tensile strengths, while high-performance strain-hardening cementitious composite (HP-SHCC) based on PE fibers exhibited the highest strain and energy absorption capacities. The steel-bar reinforced (R-) UHPFRC and HP-SHCC beams showed superior flexural load capacity compared to reinforced normal strength concrete (R-NSC) beams. The highest ductility of 8.02 was found in the R-HP-SHCC beam, almost 5 times higher than that of the R-NSC beam. By drop hammer impact with a kinetic energy of 30 kJ, the R-UHPFRC beam completely failed due to its higher reaction load and lower structural ductility, while other RC beams made of NSC and HPFRCCs withstood the identical impact load. The R-HP-SHCC beam exhibited the best impact resistance, with a 29.1% lower maximum deflection compared to the R-NSC beam, and the largest residual load capacity after the impact damages. The R-HP-SHCC beam, despite being damaged, showed no reduction in flexural stiffness, yet it demonstrated an impressive 5.4% increase in load capacity compared to the undamaged beam. • Ten large-sized RC beams are fabricated and tested under static and impact loads. • Four different types of HPFRCCs with 2% of steel, PVA, and PE fibers are considered. • UHPFRC provides superior mechanical strengths, while HP-SHCC showes the highest ductility. • Almost 5 times higher flexural ductility is achieved in R-HP-SHCC beam compared to R-NSC beam. • R-HP-SHCC beam exhibites the best impact resistance with a 29.1% lower maximum deflection. [ABSTRACT FROM AUTHOR]

Metal cutting is a highly dynamic process, where the loading condition of tool coating is very complex. Excellent static mechanical properties of tool coatings are not enough to meet the dynamic cutting environment, including impact load, cyclic load and so on. The high-frequency and high-temperature cycle impact test device based on ultrasonic vibration was developed in this study. The device performed the high-frequency impact on coating samples through high-frequency reciprocating motion of ultrasonic horn, whose impact frequency could reach 20 kHz. In addition, a high-temperature module was added to perform high-frequency fatigue test at high temperature. Cutting experiments of titanium alloy and impact tests with different temperatures and loads were carried out for the bilayer TiSiN/TiAlN coating. The results of cutting experiments and impact tests were compared and analyzed. The relationship between impact test and cutting experiment was proposed to characterize and evaluate the cutting performance of coated cutting tool by using the high-temperature impact tests. • The high-frequency and high-temperature cycle impact test device based on ultrasonic vibration is developed in this study. • Pre-loading depth is introduced to simulate the actual stress state of the coating tool during cutting.. • It is found that the coating failure mechanism of cutting experiment is similar to that of impact test. [ABSTRACT FROM AUTHOR]

This study is focused on the effects of Class C fly ash (FA), NaOH/Na 2 SiO 3 (SH/SS) ratio and steel fiber (STF) on the freeze–thaw (F-T) cycle, sulfuric acid, thermal conductivity and impact resistance of silica fume (SF) based alkali activated high strength mortars (AAHSMs). In the AAHSM mixtures, FA in different proportions (10 %, 15 %, 20 % and 25 %) is used instead of SF by weight. All the mixtures are prepared with water-to-binder rate of 0.32. F-T cycle results exhibit that the flexural strength (f fs) and compressive strength (f c) values of SF based AAHSMs without and with STF are less affected than those of ordinary Portland cement (OPC) based high strength mortars (OPCHSMs) without and with STF. After 300 F-T cycles, the f fs and f c values of SF based AAHSMs without and with STF are still over 14 MPa and 95 MPa, respectively. After exposure to 20 % sulfuric acid solution for 90 and 180 days, the SF based AAHSMs without and with STF exhibit super performance (i.e., f c values between 78.95 MPa and 96.81 MPa), while the surfaces of OPCHSMs without and with STF are disintegrated. Additionally, the effects of F-T cycle and sulfuric acid solution on SF based AAHSM and OPCHSM are examined with the microstructure analyses. Thermal conductivity results show that the SF based AAHSMs without and with STF perform better than the OPCHSMs without and with STF. The thermal conductivity results of OPCHSMs without and with STF vary between 0.630 W/m.K and 0.697 W/m.K, while the thermal conductivity results of SF based AAHSMs without and with STF range from 0.507 W/m.K and 0.623 W/m.K. Thermal conductivity results are adversely influenced by increasing STF content in the SF based AAHSMs and OPCHSMs. Impact resistance results show that the SF based AAHSMs without and with STF perform better than the OPCHSMs without and with STF. Moreover, the impact resistance values increase, as the amount of STF used in the SF based AAHSMs and OPCHSMs increases. • Effects of Class C FA, NaOH/Na 2 SiO 3 ratio and steel fiber on some durability properties of SF based AAHSMs are exanimated. • SF based AAHSMs are less affected by the freeze-thaw effect than OPCHSMs. • After exposure to sulfuric acid, SF based AAHSMs exhibit super performance, while the surfaces of OPCHSMs are disintegrated. • SF based AAHSMs show better thermal conductivity performance than OPCHSMs. • The impact resistance of SF based AAHSMs is higher than OPCHSMs. [ABSTRACT FROM AUTHOR]

The investigation of available experimental results obtained in the non-instrumented drop weight test recommended by American Concrete Institute on the steel-fiber-reinforced concrete reveals that the data distribution does not match a normal distribution. For this reason, logarithmic scales of the first-crack (number of blows to cause the first visible crack) and failure strengths (number of blows to spread the cracks sufficiently) are adopted to increase the fitness of the normal curve to the frequency histogram. The authors propose a novel model to predict the failure strength and evaluate the steel fiber effect on the post-cracking behavior of steel-fiber-reinforced concrete. The new model improves the prediction of the experimental results obtained in literature review for the various ranges of volume fraction of steel fiber analyzed. The proposed model is compared with other models using statistical parameters and the comparison shows a significant improvement considering different failure states. To verify the performance of the proposed model, in addition to results from another research, an experimental impact test was conducted. Besides, a reliable regression model is developed to validate experimental results. The findings underscore the potential of the proposed model to significantly enhance predictive accuracy, thereby proposing valuable insights for optimizing steel-fiber-reinforced concrete. • Using drop weight test to assess impact response of steel fiber reinforced concrete. • Proposing logarithmic-scale models to predict the failure strength of concrete. • Executing an experimental study to validate the accuracy of the proposed models. [ABSTRACT FROM AUTHOR]

• The flame retardant can start cross-linking after the EP is exposed to fire, thus forming a dense carbon layer on EP. • The introduction of metals gives the flame retardant a catalytic function, which promotes the carbonising effect of EP and inhibits the release of smoke and poisonous gases. • The mechanical properties of EP can be improved by liquid-phase capping of APP and ZrP with organic long-chain carbonising agents. With the continuous occurrence of aircraft fire events, aircraft composites have received strong attention as they are considered to require excellent fire safety properties. To develop domestically fire safety technology for aircraft epoxy resin (EP), this work synthesized a metal-catalyzed transient cross-linking carbon-forming flame retardant (TcZrA). TcZrA enabled EPs to achieve good fire safety properties. The test results showed that the addition of TcZrA at 5 wt% can lead to an LOI of 29.8 % for the EP composite and a V-0 rating in UL-94. In the CCT test, the PHRR and THR of TcZrA/EP-5 decreased by 62.9 % and 42.3 %, respectively, compared with pure EP. The release of smoke and toxic gases were also reduced. 5 wt% flame retardant can reduce the TSR and TSP of EP composites by 19 % and 18.6 %. Additionally, TcZrA/EP can give EP good impact and deformation resistance, which was reflected in the improvement of glass transition temperature and impact strength. The results of the fire mechanism study showed that TcZrA catalytically promotes the cross-linking structure to start cross-linking into carbon, thus playing a shielding role in the condensed phase, and the generation of a large number of phosphorus-containing compounds can also be in the gas phase to terminate the combustion process. This technology is expected to promote the localization of EP flame retardant technology for aircraft. [ABSTRACT FROM AUTHOR]

Rubber can improve the ductility and durability of concrete and reduce compressive strength. Tests were conducted to investigate the mechanical properties, wear resistance, and impact resistance of modified rubberized concrete (MRC) by mixing basalt fibers (BF), curing agent, and epoxy resin mixture. The results showed that the epoxy polymer improved the flowability of the rubberized concrete. The BF changed the failure mode of the rubberized concrete and enhanced the mechanical properties. When the curing agent-epoxy resin ratio was 4:8, the wear rate of BF 6 E 8 C 4 after 120 times was 4.59 kg/m2, which was 70.02% and 3.77% less than that of BF 2 E 8 C 4 and BF 4 E 8 C 4. The impact strength of BF 6 E 8 C 4 was increased by 256% and 409% compared with the BF 2 E 8 C 4 and BF 4 E 8 C 4 , respectively. By analyzing the mechanism of the synergistic modification of BF and epoxy polymer, it was found that the synergistic work of BF and epoxy polymer could make the internal structure of concrete denser. At last, the wear damage and impact damage models of MRC were established, and the coefficient of determination exceeded 0.92. • The wear resistance and impact resistance of MRC were studied. • The mechanism of synergistic modification of BF and epoxy polymer was revealed. • The wear rate damage and impact damage models were established. [ABSTRACT FROM AUTHOR]

The combination of multi-materials is an alternative way to meet the diverse requirements for various applications. However, the processing difficulty especially in ceramic forming limited the structural innovations. In this paper, a combined methods of ceramic digital light processing (DLP) and metal infiltration is proposed to fabricate the Al 2 O 3 /Al composite structures with controllable ceramic skeletons. The interfacial, compressive and impact resistance properties were studied. The results showed that the Al 2 O 3 grains were closely bonded, and no destructive defects occurred at the interface between Al 2 O 3 and Al. The energy dispersive spectrometer (EDS) and X-ray diffraction (XRD) results showed that the formation of protective phases contributed to the improvement of bonding strength. The compressive tests showed that the composite structures had better capabilities to absorb and resist the applied loads compared with Al structures. Finally, the impact resistance of the structures was discussed, the finite element analysis and the experimental results showed that the composite structures had advantages in dissipating the energy of incident objects and reducing the penetration depth. Based on these results, the damage model of Al 2 O 3 /Al structures was established, and the roles of different materials were revealed. [ABSTRACT FROM AUTHOR]

The horse hoof wall exhibits exceptional impact resistance and fracture control due to its unique hierarchical structure which contains tubular, lamellar, and gradient configurations. In this study, structural characterization of the hoof wall was performed revealing features previously unknown. Prominent among them are tubule bridges, which are imaged and quantified. The hydration-dependent viscoelasticity of the hoof wall is described by a simplified Maxwell-Weichert model with two characteristic relaxation times corresponding to nanoscale and mesoscale features. Creep and relaxation tests reveal that the specific hydration gradient in the hoof keratin likely leads to reduced internal stresses that arise from spatial stiffness variations. To better understand realistic impact modes for the hoof wall in-vivo , drop tower tests were executed on hoof wall samples. Fractography revealed that the hoof wall's reinforced tubular structure dominates at lower impact energies, while the intertubular lamellae are dominant at higher impact energies. Broken fibers were observed on the surface of the tubules after failure, suggesting that the physically intertwined nature of the tubule reinforcement and intertubular matrix improves the toughness of this natural fiber reinforced composite. The augmented understanding of the structure-mechanical property relationship in dynamic loading led to the design of additively manufactured bioinspired structures, which were evaluated in quasistatic and dynamic loadings. The inclusion of gradient structures and lamellae significantly reduced the damage sustained in drop tower tests, while tubules increased the energy absorption of samples tested in compact tension. The samples most similar to the hoof wall displayed remarkably consistent fracture control properties. The horse hoof wall, capable of withstanding large, repeated, dynamic loads, has been touted as a candidate for impact-resistant bioinspiration. However, our understanding of this biological material and its translation into engineered designs is incomplete. In this work, new features of the horse hoof wall are quantified and the hierarchical failure mechanisms of this remarkable material under near-natural loading conditions are uncovered. A model of the hoof wall's viscoelastic response, based on studies of other keratinous materials, was developed. The role of hydration, strain rate, and impact energy on the material's response were elucidated. Finally, multi-material 3D printed designs based on the hoof's meso/microstructure were fabricated and exhibited advantageous energy absorption and fracture control relative to control samples. [Display omitted] [ABSTRACT FROM AUTHOR]

Hedgehog spines with evolved unique structures are studied on account of their remarkable mechanical efficiency. However, because of limitations of existing knowledge, it remains unclear how spines work as a material with a balance of stiffness and toughness. By combining qualitative three-dimensional (3D) structural characterization, material composition analysis, biomechanical analysis, and parametric simulations, the relationship between microstructural characteristic and multifunctional features of hedgehog spines is revealed here. The result shows that the fibers transform from the outer cortex to the interior cellular structures by the "T" section composed of the "L" section and a deltoid. The outer cortex, however, shows an arrangement of a layered fibrous structure. An inward change in Young's moduli is observed. In addition, these spines are featured with a sandwich structure that combines an inner porous core with an outer dense cortex. This feature confirms that the hedgehog spines are a kind of biological functionally graded fiber-reinforced composite. Biomimetic models based on the spine are then built, and the corresponding mechanical performance is tested. The results confirm that the internal cellular structure of the spine effectively improve impact resistance. Furthermore, the transverse diaphragm can prevent ellipticity, which may delay buckling. The longitudinal stiffeners also contribute to promote buckling resistance. The design strategies of the spine proposed here provide inspirations for designing T-joint composites. It also exhibits potential applications in low-density, impact and buckling resistance artificial composites. The spines of a hedgehog are its protective armor that combines strength and toughness. The animal can not only withstand longitudinal and radial forces that are 1 × 106∼ 3 × 106 times the gravity generated by its own weight, but it can also survive unscathed by elastic buckling while dropping to the ground at a speed of up to 15 m/s. Here, we first demonstrate that hedgehog spines are biological graded fiber-reinforced structural composites and reveal their superior impact and buckling resistance mechanism through simulation analysis. Our results broaden the understanding of the relationship among morphology, materials, and function of hedgehog spines. It is anticipated that the survival strategies of hedgehog revealed here could provide inspirations for the development of synthetic composites with impact resistance and structural stability. [Display omitted] [ABSTRACT FROM AUTHOR]

Negative Poisson's ratio (NPR) structures have excellent energy absorption and buffering properties, but they generally have disadvantage of low specific strength, which restricts their wide applications. Therefore, in this study, the carbon fiber reinforced Nylon material (Nylon 12CF) was prepared and used to construct re-entrant hexagonal honeycomb NPR structure. The reinforced (Nylon 12CF) and unreinforced (Nylon 12) specimens were fabricated by 3D printing technology and tested quasi-statically. Then, the quasi-static of the reinforced and unreinforced re-entrant NPR structure and the impact analysis of the composite sandwich panel (CSP) with re-entrant NPR carbon fiber reinforced core are carried out by finite element method. The results show that the NPR structure reinforced with carbon fiber has 112.5% higher failure stress and 113.9% higher energy absorption efficiency than the unreinforced structure. The finite element simulation results are in good agreement with the experimental results. Under the impact load of a 5 kg object with different initial velocities, the maximum of the displacement of the back face sheet's center point of the CSP with reinforced NPR core is smaller than that of CSP with unreinforced NPR core, especially when the impact velocity is 20 m/s. At different initial impact velocities, the CSP of the reinforced NPR structure core all showed high impact resistance, which was about 1.4 times that of the unreinforced NPR structure core. This research provides new ideas for designing more efficient energy-absorbing and impact-resistant structures. • Combining fiber reinforcement with negative Poisson's ratio structure. • Reinforced the re-entrant hexagonal honeycomb structure with carbon fiber. • Fiber reinforced honeycomb structure has better energy absorption effect. • Fiber reinforced honeycomb structure has higher strength. • Fiber reinforced honeycomb sandwich panels have better impact resistance. [ABSTRACT FROM AUTHOR]

Compared to their crystalline counterparts, amorphous alloys due to disordered structures are expected to have higher elasticity of deformation. However, in this work, we use the micro-ballistic impact technique to show a smaller dynamic redound of micro-particles on a Zr-based amorphous alloy than that on its corresponding polycrystalline target. We find that the two alloys follow the same rebound law of micro-particle under low impact velocities, but with increasing impact velocity the amorphous alloy exhibits a faster decrease in rebound velocity of micro-particle. This lower rebound results from the easier activations of shear banding in glassy structures, thus contributing to more significant energy dissipation during the micro-particle impact. Further analyses imply that the amorphous alloys and their crystalline counterparts are more favorable in shock wave and projectile protection, respectively. This work is useful in the understanding of the dynamic elasticity and shock energy dissipation of amorphous alloys under micro-particle impacts. [ABSTRACT FROM AUTHOR]

• Inspired by the microstructure of the lobster cuticle, a hybrid-helicoidal composite laminate was proposed to enhance its impact resistance. • Combining various helicoidal structures, such as single-helicoidal and double-helicoidal, improved the toughness and strength. • The effects of helicoidal angle growth rate, position, and thickness on low-velocity impact resistance were analyzed. • The damage mechanisms of bio-inspired helicoidal laminates were detailed revealed. The exoskeleton of the Homarus americanus lobster feature a hybrid-helicoidal structure of chitin-protein fibers, with distinct helicoidal configurations in the exocuticle and endocuticle, exhibiting strong impact resistance. Taking inspiration from this biological structure, combined with single-helicoidal and double-helicoidal structures, various helicoidal configurations of composite laminates were designed. Both linear and nonlinear helicoidal angles, including sinusoidal and exponential configurations, were considered. The interlaminar and intralaminar damage mode were adopted to simulate material damage initiation and evolution. The effect of helicoidal angles, position, thickness and angle variations of endocuticle on low-velocity impact resistance was analyzed, revealing the damage mechanisms of bio-inspired laminates. The results show that bio-inspired hybrid helicoidal structures with special features could significantly enhance the impact resistance of composites, with laminates featuring sinusoidal-exponential double helicoidal structures showing superior performance. Sinusoidal configurations, being less prone to penetration, are more suitable for the exocuticle. The introduction of double-helicoidal configurations could enhance the toughness and strength of the structure. This studying deepened an understanding of failure mechanisms of bio-inspired helicoidal composite laminates under low-velocity impact and provide a design strategies for developing high-performance, impact-resistant composite materials. [ABSTRACT FROM AUTHOR]

Polypropylene fiber (PPF)-based concrete incorporating carbon nanotubes (CNTs) has garnered significant attention in recent literature. However, determining the optimal content of PPF and CNTs remains crucial. Therefore, this study employed response surface methodology (RSM) to systematically optimize the ideal content and interaction between PPF and CNTs, with the aim to achieve the highest concrete strength and impact resistance. Following the recommendation of the ACI committee 544, the drop-weight impact test procedure was refined and utilized to assess the concrete's impact resistance. The study findings revealed that concrete incorporating optimal proportions of PPF (0.3 %) and CNTs (0.1 %) exhibited significantly enhanced strength properties and impact resistance compared to the control sample. The enhancements in compressive, tensile, and flexural strengths were measured at 29 %, 75 %, and 64 %, respectively. Furthermore, the impact energy consumption at the first and failure cracks was significantly higher, i.e., 1433.82 J and 2016.32 J, respectively, compared to 89.61 J for the control concrete. Scanning electron microscopy analysis revealed ribbed calcium silicate hydrate structures with CNTs, which were identified as the primary factor fortifying the stiffness and strength of the concrete matrix. This suggests that the inclusion of both CNTs and PPF holds promise for advancing the development of sustainable concrete materials with improved strength and impact resistance in the future. • Response surface methodology effectively optimized polypropylene fiber and carbon nanotube content. • Concrete with 0.3% polypropylene fibers and 0.1% nanotubes showed remarkable strength and impact resistance. • Strength improvements recorded: 29% in compressive, 75% in tensile, and 64% in flexural. • Utilizing scanning electron microscopy, ribbed calcium silicate hydrate structures with carbon nanotubes were identified. [ABSTRACT FROM AUTHOR]

• A novel composite auxetic reentrant honeycomb structure is designed and fabricated. • The one-stage light gas gun and diffuser-type shock tube were utilized to generate and propagate exponential decaying shock wave. • The effect of gradient form on impact resistance performance was experimentally and numerically investigated. • The effect of relative density of composite reentrant honeycomb structure was analyzed and investigated. The researches on dynamic responses of underwater impulsive loading have been conducted. However, the previous study mainly concentrated on metal sandwich structure and fixed supported boundary. The relative research on composite auxetic re-entrant honeycomb structure and simply supported boundary are rarely. In this paper, the effect of the gradient form and relative density on impact resistance performance of composite auxetic re-entrant honeycomb structure was experimentally and numerically investigated. The one-stage light gas gun was applied to provide initial kinetic energy of the fly plate, and the diffuser-type shock tube was utilized to generate and propagate exponential decaying shock wave. The pressure–time curve was respectively amplified and recorded by the charge amplifier and oscilloscope. The response speed, final deflection of rear panel and failure mode of cores and panels were used to evaluate impact resistance of composite auxetic re-entrant honeycomb structures. Moreover, acoustic-structure interaction algorithm was applied to simulate impact course of specimens in Abaqus/Explicit. The results between experiment and numerical simulation exhibited good consistency. The results indicated that the positive gradient form could excessively slow down response speed of rear panel by dissipating energy of shock wave, and the average gradient demonstrated smaller final displacement of rear panel and less failure compared with graded structures. [ABSTRACT FROM AUTHOR]

In order to promote the use of new sustainable steel fibers (SF) reinforced coal gangue aggregates (CGA) concrete, impact tests were performed in this paper. The impact resistance of steel fiber-reinforced coal gangue concrete was investigated using a self-developed drop-weight facility. The test variables were the CGA replacement rate (0 %, 50 %, and 100 %), the SF volume content (0 %, 0.75 %, and 1.5 %), and the drop height of the drop-weight (0.5 m and 1.0 m). Using 15 kg of hard steel as a drop-weight, the drop-weight impact test was performed on steel fiber-reinforced coal gangue concrete beams with a span of 300 mm; the damage pattern, impact reaction force-time, displacement-time relationships, and energy absorbed by steel fiber-reinforced coal gangue concrete beams were studied. The test shows that, compared with natural aggregate, CGA reduces concrete's static mechanical properties and impact resistance, and adding SF improves the static mechanical properties and impact resistance of coal gangue concrete. As the CGA replacement rate increased from 0 % to 50 % and 100 %, the reaction force of impact of the specimens decreased by 2.54 %− 6.06 % and 3.69 %− 12.33 %. The SF volume content was increased from 0 % to 0.75 % and 1.5 %, and the reaction force of impact of the specimens was increased by 23.05 %− 32.34 % and 72.27 %− 81.84 %, respectively. The impact resistance of steel fiber-reinforced concrete beams under impact loading was investigated numerically using a nonlinear explicit finite element model in LS-DYNA. The Finite Element results were validated with experimental results. Based on the validated finite element model, a parametric study was carried out to investigate the effects of coal gangue replacement rate, steel fiber volume content, and drop height of the drop weight on the behavior of the beams. This study might provide a basis for the future engineering project applications of steel fiber-reinforced coal gangue concrete under impact conditions. • New sustainable coal steel fibers reinforced gangue aggregates (CGA) concrete was investigated. • Impact resistance of this new type of concrete was studied. • Numerical modelling was made to this new type of structure. • Parametric analysis of SFCGC beams was carried out [ABSTRACT FROM AUTHOR]

The impact resistant behaviors of boride reinforced Ti-6Al-4 V functionally graded materials prepared by spark plasma sintering (SPS) with compositional gradients of 90°, 84°, 82°and 79° were investigated based on the experimental test and the finite element method. The material constitutive parameters of the boride reinforced Ti-6Al-4 V alloys with different TiB 2 contents were determined, and the Johnson Holmquist Ceramics (JH-2) model and a cohesive contact model were established and developed to predict the crack propagation and the impact resistance behaviors of the materials. The calculated results agreed well with the split Hopkinson press bar (SHPB) experimental results. The optimum material composition gradient design scheme with a continuous transition property from a high-toughness end to a high-strength end along the thin-thickness direction was determined. The G84 (0, 0, 15, 30 wt% TiB 2) had the best impact resistance, with Young's modulus of 55505±5 GPa, compressive strength of 2045±5 MPa, and microhardness ranging from 535±5HV to 1246±5HV, exhibiting high strength and hardness at a high-strength end that can prolong the interaction time between the impactor and the materials, while the elongation of 39 % at its high-toughness end can cause tensile deformation, consuming impact kinetic energy efficiently. Combined with the experimental and numerical analysis results, the impact resistance and the crack-alleviated mechanisms of boride reinforced Ti-6Al-4 V functionally graded materials were discussed. Reducing the compositional gradient can alleviate the difference in coefficients of thermal expansion between composites, which may lead to strengthen the reflected wave, lower the compression wave, and suppress high-strength end failure efficiently, meaning of relieving the stress concentration under extreme service conditions. Moreover, the effects of the presence of the borides, such as in situ-formed TiB, remained TiB 2 at al. , the dislocation defects and the whisker-like TiB on the armour materials resist fracture and layer cracking were also analyzed. This work provided a method for designing high performance of boride reinforced Ti-6Al-4 V functionally graded materials with high impact resistance and thin thickness. • The boride reinforced Ti-6Al-4 V functionally graded materials exhibiting great promise in good impact resistance were designed and prepared. • The material constitutive parameters of the boride reinforced Ti-6Al-4 V alloys, the Johnson Holmquist Ceramics (JH-2) model and a cohesive contact model were established to predict the impact resistance behaviors of the materials. • The impact resistance and the crack-alleviated mechanisms of boride reinforced Ti-6Al-4 V functionally graded materials were discussed. • This work provided a method for designing high performance of boride reinforced Ti-6Al-4 V functionally graded materials with high impact resistance and thin thickness. [ABSTRACT FROM AUTHOR]

• The impact behaviours of TWIP steel fiber reinforced cementitious composite were investigated. • The effects of varying fiber types, impact heights, and impact times were discussed. • The fractal dimension was applied to quantify the damage degradation process. Twinning-induced plasticity (TWIP) steel fibre is a supermaterial known for its outstanding impact resistance. This paper, for the first time, applied TWIP steel fibre to increase the impact resistance of cementitious composites. The mechanical properties behaviours of TWIP steel fibre-reinforced cementitious composites (T-SFRCC) were investigated and compared with conventional SFRCC with normal steel fiber. The fractal theory was utilized to analyze the deterioration of damage in various SFRCCs subjected to impact loads, displaying TWIP steel fiber could prevent the cracks propagation and fewer fractal dimension compared with others. Results demonstrate that T-SFRCC has comparable compressive strength to SFRCC while exhibiting higher flexural strength. When subjected to impact loading, T-SFRCC demonstrates markedly improved energy absorption and impact toughness, such as better impact force and displacement. Specifically, the energy absorption capacity of T-SFRCC can exceed five times that of SFRCC with corrugated steel fiber, particularly evident when the drop height reaches 1200 mm. The influences of different fiber types and hammer drop methods on the impact resistance of SFRCCs were also discussed, which can provide reference for TWIP steel fiber in the field of cementitious composite materials. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new shear thickening fluid (STF) system consisting of molecular sieves and diols was studied. • The high-temperature Pickering emulsion templating was proposed for the first time to achieve microencapsulation of STF. • The integrity of STF components was guaranteed by the robust barrier formed around the emulsion droplet by the solid stabilizer. • The introduction of STF microcapsules effectively improved the energy absorption and impact resistance of the matrix material. Combining shear-thickening fluid (STF) with matrix material enables the creation of high-performance materials with enhanced impact resistance. However, effectively preventing STF leakage and avoiding potential reactions between the fluid and the matrix material remain notable challenges. Encapsulating STF through emulsion templating offers a viable solution to these issues. Traditional emulsion templating methods require adding extra solvents to STF to counteract the hindrance of shear-thickening on emulsification, accompanied with increased costs and environmental pollution, and difficulties in maintaining the integrity of core components. In this study, we developed STF microcapsules using a novel high-temperature Pickering double emulsion technique. Our investigation into the rheological properties of molecular sieve/diols suspensions demonstrates that the shear thickening effect could be controlled by particle concentration, surface charge of particles and solvent viscosity. Octadecyltrimethoxysilane-modified fumed silica and fumed silica were utilized as stabilizers for STF-in-paraffin primary emulsions and STF-in-paraffin-in-propylene glycol secondary emulsions, respectively. As temperature increased, droplet sizes of the primary emulsion were significantly reduced. The Pickering emulsion approach effectively preserves the STF composition by forming robust barriers at the emulsion interface with silica particles. Typical STF microcapsules were incorporated into a silicone rubber matrix, the composites exhibited a significant decrease in resilience and an enhanced impact resistance with a 20.9% reduction in maximum impact force. This study is the first to suggest the application of the high-temperature Pickering double emulsion technique for the microencapsulation of STF, offering a practical and scalable method without diluting the STF, thereby ensuring the controllability of the core components. [ABSTRACT FROM AUTHOR]

• A new type of 3D-printed fibre-reinforced composite sandwich panel is designed. • The effect of infill patterns on 3D-printed sandwich panels is examined under impact loading. • The inclusion of fibre reinforcement layers provides superior impact resistance. • Composite panels with lower infill density absorb impact energy better. The increasing attention towards 3D-printed fibre-reinforced thermoplastic composite structures is due to their superior characteristics, ability to produce intricate architectures, repeatability, and short lead times. This experimental study aims to investigate the mechanical and dynamic behaviours of 3D-printed composite structures under tensile and impact tests. Different types of samples are designed, including Onyx layers, triangular infill patterns (30 % and 40 % infill density), and continuous carbon fibre layers (two, four, six, and eight layers). Scanning electron microscopy (SEM) and X-ray micro-computed tomography (μCT) analyses are conducted to visualise the morphological characterisation and observe the delamination and damage of the composite structures. The results of the study reveal that the inclusion of carbon fibre reinforcement layers increases the stiffness and tensile strength of the composite structures. Furthermore, the addition of fibre layers in the composite panels provides critical support in damage resistance against impact loading. In contrast, sandwich structures without reinforcement layers are fatally punctured by the impact force, resulting in significant damage on both the impacted and bottom surfaces. The composite sandwich panels with fewer fibre-reinforced layers and lower infill density become softer and absorb impact energy better. [ABSTRACT FROM AUTHOR]

Materials degradation induced by repeated arc erosion and impact poses a considerable challenge for Ag-based contacts. Fortunately, nature has evolved efficient strategies to construct complex gradient-layered structure that exhibit exceptional erosion and impact resistance. Drawing inspiration by the mantis shrimp appendages, a chain-like CuO nanofibre-reinforced Ag-CuO contact material with a gradient-layered scatter-island/chain-skeleton structure was designed and fabricated. Employing a combined experimental and simulation approach, the evolution of the microstructure during the erosion process was investigated. Results indicated that the interaction between the mantis shrimp appendage-like structure and the chain-like CuO nanofibres effectively suppressed the formation of cracks and pores on the contact surface. Particularly, the scatter-island layer not only played a crucial role in maintaining the viscosity of the molten pool and establishing stable electrical and thermal pathways, but also functioned as a "supplement" to continuously supply a steady source of Ag onto the molten pool surface, effectively promoting CuO skeleton restructuring. Meanwhile, the CuO skeleton diffusive-continuous restructuring of the chain-skeleton layer restricted molten pool flow, significantly enhancing contact erosion resistance. Furthermore, the strong synergistic effect between the gradient-layered structures dispersed stress and deformation concentration on the contact surface. It effectively delayed the defects formation and suppressed interfacial debonding, thereby endowing the contact with excellent impact resistance. Our work presents a fascinated route for designing novel biomimetic Ag-based contacts. • A novel Ag-CuO contact with a gradient-layered structure inspired by mantis shrimp appendages was designed and fabricated. • The synergistic reinforcement of the appendages-like structure and chain-like CuO fibres optimized erosion morphology. • Scatter-island layers enhanced electrical and thermal conductivity and acted as "supplements" for CuO skeleton restructuring. • The diffusive-continuous CuO skeleton from the chain-skeleton layer strengthened impact and erosion resistance of contacts. [ABSTRACT FROM AUTHOR]

Lattice and Triply-Periodic-Minimal-Surface (TPMS) structures are widely employed in different engineering disciplines, combining interesting designs with optimal mechanical properties thanks to the capabilities of Additive Manufacturing. In this framework, a technique based on filling a 3D-printed flexible structure with a shear-thickening fluid (STF) is proposed to improve the mechanical response of the resulting bi-phase composite under impact loads in the low-velocity regime up to around 3 m/s. Test data indicate that once the critical shear rate threshold for the fluid is reached, the STF-filled structure can effectively smooth the peak acceleration by 50%, decrease the penetration depth and significantly enhance the energy absorption capability by a remarkable 85%. The proposed hybrid composite paves the way to novel functional applications, exploiting the adaptive behavior of non-Newtonian fillers. To this end, a Finite-Element model is proposed to further investigate and optimize the underlying fluid-structure interaction responsible for improvement of the dynamic compressive response. • STF-filled metamaterial shows a 50% reduction in peak acceleration and a 85% enhancement in the energy absorption capability. • The adaptive behavior under low-speed impact loads is ruled by the shear rate field in the liquid during the deformation. • FE simulations investigate the interaction between solid and liquid phases underlying increased mechanical properties. • Using a non-Newtonian filler leads to the best performance when compared with air- or other liquids-filled configurations. [ABSTRACT FROM AUTHOR]

Shear thickening fluids (STFs) have attracted increasing attention as smart materials with unique rheological properties. However, the preparation of STFs usually relies on a composite system of spherical nanoparticles with polyethylene glycol. In this work, novel multi-phase STFs (ILSTFs) were prepared in an ionic liquid by incorporating nanosized SiO 2 and rod-shaped calcium metasilicate (CaSiO 3) particles as a dispersed phase. Compared to traditional STFs, ILSTFs demonstrate excellent thermal stability. Rheological tests indicate that ILSTFs exhibit continuous shear thickening behavior, resulting in excellent energy absorption and impact wear resistance. In addition, ILSTFs can serve as a new type of lubricant. The tribological properties and impact resistance of ILSTFs were highly correlated with the shear thickening effect, with the multi-phase ILSTF system with CaSiO 3 demonstrating superior impact wear resistance compared to the single-phase system. In this study, finite element analysis (FEA) is further utilized to investigate the local damage evolution and energy absorption rate of STF under impact loading, providing insights into the underlying mechanism. This ionic liquid-based STF holds promise for applications as a flexible filling component in the fields of lubrication technology and impact protection structures. [Display omitted] • A novel multi-phase ILSTF based on ionic liquid as the carrier liquid was constructed. • The multi-phase ILSTF had good thermal stability and significant shear thickening effect. • ILSTF was used as a lubricant for the first time. • Finite element analysis (FEA) revealed the impact resistance mechanism of filled ILSTF in finite space. [ABSTRACT FROM AUTHOR]

Although rubberized concrete is widely accepted as an eco-friendly building material, its engineering applications are far limited due to its relatively low strength. To address this deficiency, the current study examines the effect of enhancing the strength of rubberized concrete through incorporating basalt fibers (BF) and water-based epoxy resin (ER) at varying proportions. In this study, both experimental testing and numerical simulations were conducted to investigate the mechanical, impact, and abrasion resistance properties of BF-ER composite enhanced rubberized concrete (BERC) using 12 different mix ratios. The evolution of damage in BERC was investigated, and the reinforcing mechanism of the fiber-polymer composite was elucidated through micro-morphology and pore structure analysis. The results indicate that the compressive strength and impact resistance of rubberized concrete are significantly improved due to inclusion of BF-ER, with the former achieving up to 60 % higher than normal rubberized concrete, while the latter attains improvement of 100 %. Due to the energy-absorbing behavior of rubber particles and the enhanced bonding effect provided by fiber-polymer, BERC exhibited a ductile failure mode, characterized by development of more complex cracks. Inclusion of fiber polymer resin has strengthened the weak interfacial transition zone (ITZ) between rubber particles and cement paste, albeit at the cost of increased porosity caused by the multiple interfaces of BF. From the current study, the optimal dosages of BF and ER are determined to be 2 kg/m3 and 4 kg/m3, respectively. The research results have provided useful insights on the application of rubberized concrete in critical engineering structures that require impact and abrasion resistance. • Mechanical properties and microstructures of BF and ER reinforced rubberized concrete were studied. • The influences of epoxy resin content on abrasion resistance of the BERC. • Effects of basalt fiber on compressive behavior and failure mode of rubberized concrete. • The basalt fiber and epoxy resin could be used in rubberized concrete to improve impact resistance. [ABSTRACT FROM AUTHOR]

• The effect of WC addition was investigated on the flow state of molten pool. • The effect of WC addition was discussed on the mechanism of wear. • The effect of WC addition was investigated on the mechanism of impact. Ni45 powder and tungsten carbide (WC) particles were added to laser cladding coatings by to improve the wear resistance and impact resistance of mechanical components. The microstructure and elements of the coatings were assessed using SEM and TEM. A high-speed camera was used to analyse the morphology of the molten pool during the cladding process. The wear resistance and impact resistance of the coatings were tested by a wear and impact testing machine. The reaction of WC in the molten pool releases a large amount of thermal energy, which gives the molten pool a faster flow rate. The flow rate increases rapidly at WC dosages of ≤10 wt% and more slowly at dosages >10 wt%. Flow in the molten pool causes the WC to break the columnar crystals in the pool, which form a large number of coarse cellular crystals. WC causes the coatings to precipitate more rich Cr hard phase and intermetallic compounds, which increases their abrasion resistance and impact performance. The wear rate of the coating containing 12 wt% WC was 91.59% lower than that of the Ni45 coating. However, the impact resistance was decreased by the stress concentration and brittleness of the WC. [ABSTRACT FROM AUTHOR]

• By introducing phosphorus sources to the carbonizing agent, a P/N synergistic integrated flame retardant (TRBPO) was constructed while retaining the cross-linkable groups. • The crosslinkable structure in the flame retardant can generate a crosslinked structure with flame retardant properties when the EP is exposed to fire. • The long-chain structure of TRBPO can improve the impact resistance of EP by dispersing the stress when it is subjected to force. With the development of flame retardant technology, intumescent flame retardant (IFR) systems, and instant cross-linking in case of fire have become important directions for epoxy resin (EP) flame retardancy. A carbonized matrix containing a benzoxazine structure was constructed with the triazine structure, and the integrated flame retardant (TRBPO) was constructed by introducing the phosphorus source through a partial ring-opening reaction. It can maintain its structural characteristics during the curing process of EP. When EP materials are exposed to fire, TRBPO will cross-link in the EP matrix and work as the P/N synergistic IFR system to achieve excellent flame retardancy. The results showed that 5 wt% of TRBPO could make EP composites reach UL-94 rating of V-0 with a PHRR of 303.7 kW/m2, and the TSP and TSR were reduced by 48.5 % and 48.9 %, respectively, compared with pure EP. The introduction of TRBPO has a impact resistance effect on EP, and its excellent stress dispersion effect made the impact strength of 5-TRBPO/EP reached 36.49 KJ/m2. The analysis of the flame retardant mechanism proved that the rapid carbon formation function of IFR and the self-crosslinking flame retardancy of TRBPO in the fire are the main reasons for flame retardancy. In addition, the capture of flammable groups in the gas phase is an important source of flame retardant effect. [ABSTRACT FROM AUTHOR]

[Display omitted] • A bionic impact-resistant organohydrogel was prepared by direct ink writing. • The rheological performance of inks was optimized with printability explored. • The organohydrogel presented favorable rate-enhanced mechanical properties. • The organohydrogel showed good impact resistance for customized protection. The growing safety consciousness towards life and engineering poses demand for efficient anti-impact materials. Decent advances have been made in material development and structure design, whereas the superiority synergism of materials and structures remains challenging. This work develops an advanced impact-resistant shear stiffening gel-polyvinyl alcohol-chitosan (SSG-PVA-CS) organohydrogel by integrating 3D printed customized architectures with strain rate enhanced matrix materials. Following rheological optimization of components, the precursor ink presents shear thinning and yield stress fluid behaviors enabling the direct ink writing (DIW) printing techinique. The printability is systemically explored through finite element modeling assisted flow dynamics analysis and experimental validating, and a quantitative phase diagram is constructed which determines the dependence of parameters on the printing mode and quality. The organohydrogel presents favorable mechanical strength, cyclic durability and rate enhancement effect, which imparts basis of impact resistance to the matrix. The rational structure design effectively reduces the volume density within 0.60 to 0.71 g/cm3 while maintaining considerable attenuation ratios of 73.09 % to 83.55 %, with structure-dependent dynamic mechanical behaviors clarified via finite element analysis. This study provides a reliable approach to fabricate impact-resistance materials with tailored architectures and mechanically functional matrix materials, unlocking paths to break through the performance bottleneck. [ABSTRACT FROM AUTHOR]

Based on single-walled CNT, inspired by weaving operation, mechanical and impacting properties of a new proposed carbon nanotube woven film (CNWF) are systemically investigated via molecular dynamic simulations. From the tensile simulations of CNWF, it is found that CNWF are anisotropic in the axial and transverse directions. In the axial direction, similar to single CNT, CNWF possess extremely high gravimetric tensile strength and gravimetric Young's modulus. However, along the transverse direction, the gravimetric tensile strength and gravimetric Young's modulus of CNWF are nearly 2 orders of magnitude lower than those of single CNT, while CNWF possess super high stretchability which is up to 1228.18%. On the other hand, from the results of impacting simulations, the impact resistance of CNWF is extremely high and could be efficiently tuned by controlling the tensile strain of CNWF. Furthermore, it is found that CNWF could sustain the simultaneous impact of many projectiles with different sizes and selectively filter out projectiles by changing corresponding tensile strain. Therefore, CNWF has great application potential in intercepting the space debris. This work provides in-depth understanding on the mechanical and impact properties of CNWF and brings perceptive insights into the fabrication of strong and multifunctional CNT-based weaving structures. [Display omitted] [ABSTRACT FROM AUTHOR]

In this research, the effects of nanosilica and steel fibers on the impact resistance of ground granulated blast furnace slag based self-compacting alkali-activated concrete were investigated. Nanosilica volume fraction was kept constant at 2%. Two types of hooked-end steel fibers (Kemerix 30/40 and Dramix 60/80) and steel fiber volume contents (0.5% and 1%) were utilized to highlight the combined effects of nanosilica and steel fiber on the impact behavior. The fresh state and mechanical properties such as slump flow, L-box, V-funnel, compressive strength, modulus of elasticity, splitting tensile strength, and flexural strength were evaluated. The microstructure of the samples was examined using a scanning electron microscope. The impact resistance of the specimens was measured by a drop-weight test. Acceleration-time and force-time graphs were plotted and evaluated together with the crack photos of the specimens for the first and failure impactor drops. The incorporations of nanosilica and steel fiber improved splitting tensile strength, flexural strength, impact resistance, and energy absorption capacity, while they decreased compressive strength and modulus of elasticity. For the specimens without nanosilica and with 2% nanosilica, the impact energy improvements were five times and 12.5 times higher for 0.5% short fibrous, 20.5 times and 44.5 times higher for 1% short fibrous, 23.5 times and 31 times higher for 0.5% long fibrous, and 64 times and 144.5 times higher for 1% long fibrous specimens than the specimens without nanosilica and steel fiber, respectively. The long fibers were found more effective in mechanical strength and impact energy than short fibers, and the reinforcing efficiency of fibers enhanced with higher steel fiber volumes. The combined utilization of nanosilica and steel fibers have the potential to delay the crack formation and dissipate energy to the surrounding zones, and this potential increased with higher steel fiber lengths and volume ratios. [ABSTRACT FROM AUTHOR]

This work is about investigated the effectiveness of inclusion of local waste, represented by plastic water drink bottles caps (CPPA), in the concrete as a partial substitute for coarse aggregates. Compressive, flexural and splitting strengths were evaluated for plain concrete. For reinforced concrete (R.C.), bond strength between reinforced bar and surrounding concrete has been evaluated. In additional, impact resistance, energy absorption capacity, mid-span deflection and crack width for Two-way R.C. slab subjected to repeated impact load have been evaluated. Five different content of plastic aggregate were examined; 0%, 15%, 30%, 45%, 60% and 75% of CPPA. Tests Results showed that strengths (compressive, splitting, flexural and bond strengths) improved for plastic content 15% and 30% especially at 15%. While these strengths began to decrease with increasing plastic's content over 30%. For R.C. slabs, number of blows that caused failure increased with increasing plastic content up to 45%, which mean increasing in impact resistance and increasing in energy-absorbed capacity. Based on the experimental results, empirical equations were proposed of calculating splitting, flexural, bond strengths and energy-absorbed capacity for concrete incorporating CPPA. According to results of this investigation, for structural reinforced concrete, 15% and 30% of this type of plastic is recommended to be used as partial replacement of gravel. [ABSTRACT FROM AUTHOR]

Auxetic materials are attracting increasing interest due to their extraordinary or even abnormal mechanical properties. Different from the traditional truss-lattice structures, this paper proposes a series of novel auxetic plate-lattice structures with an excellent auxetic effect. Utilizing a dual-materials glue-free assembly design involving hyperelastic and plastic materials, these plate-lattices exhibit numerous advantages such as disassembly, assembly, replacement, recyclability, reusability, excellent energy absorption, high specific stiffness, and impact resistance performances. Quasi-static/dynamic tests and simulations are conducted to assess mechanical properties, including elastic constants, deformation modes, and mechanical responses. Simultaneously, the effect of the principal geometric parameter, concave angle, on the structural response was analyzed with various impact velocities. Findings suggest that the concave angle influences the structural elastic constants under compressive loading. The stress–strain response exhibits a distinct dual-plateau phenomenon. Taking the A65 (concave angle is 65°) configuration as an example, the stress on the second plateau is approximately 2.7 times that of the first plateau, significantly enhancing the structure's energy absorption capability. Under dynamic impact loadings, different configurations and varying impact velocities affect the structure's energy absorption performance. This paper introduces a series of assemblable plate-lattice structures with an auxetic effect, offering design insights and guidance tailored to the convenient transportation, unconventional structures, and rapid assembly needs of lightweight, impact-resistant mechanical metamaterials. [ABSTRACT FROM AUTHOR]

In this study, an inverse design framework was constructed to explore gradient honeycomb structures (HCS) with high impact resistance. By establishing the relationship between the height of the cell and the cell-wall angle, HCS with different gradient modes were designed. The developed machine learning (ML) framework consisted of a forward regression model based on neural network (NN) and an inverse optimization model based on generative adversarial network (GAN). The regression model surrogated finite element analysis (FEA) to rapidly provide corresponding mechanical properties for the generated data of GAN. To ensure that the generated data met the desired design targets, additional physical constraints were incorporated into the generator of the GAN. This ensured that the network output not only consisted of valid data but also exhibited superior impact resistance. The results demonstrated that the trained ML model optimized both specific energy absorption (SEA) and initial peak stress of HCS. It even discovered high-performance gradient designs that outperformed the original data, with a maximum energy absorption 49.5% higher than that of uniform HCS. Moreover, the gradient modes and structural parameters of superior designs were identified, which is of great significance for the gradient design of HCS under impact loading. As a general design approach, this ML framework holds significant potential for the optimization design of metamaterials in other structures or with different mechanical properties. • A inverse design framework for finding high impact resistance HCS is proposed. • Using NN surrogate FEA to accelerate the prediction of structural performance. • The design of desired properties can be obtained by introducing physical constraints. • The multi-layer HCS with different gradient modes is evaluated. [ABSTRACT FROM AUTHOR]

The mechanical shock and thermal damage generally exist together in hazardous environment, whereas traditional single protective materials are difficult to achieve all-round protection under extreme environment. Herein, to realize the integration of multifunctional abilities about impact resistance, flame-retardant and sensing performance, a "solid-liquid host-guest" structural shear thickened composite sponge is proposed, which flame-retardant shear thickening fluids with an extraordinary thickening ratio of 2183.95 % continuously disperse in 3D sponge matrix. The resulting composite sponge effectively attenuates the impact force by nearly 80 % with the thickness of only 4 mm via a cooperation between the effect of shear hardening and structure densification. Meanwhile, after burning on the alcohol flame for 12 s, the composite sponge with 7 wt.% fire-retardant additive maintains a complete morphology and realizes self-extinguishing with a reliable flame-retardant ability. Attributed to the good electrical conductivity of shear thickening fluid, the composite sponge serves favorably in human body monitoring, impact sensing and fire warning. In a word, this multifunctional lightweight composite sponge is expected to realize the integration of early warning and protection, which is a competitive candidate material for the intelligent protection in complex environments. [Display omitted] • A new type of conductive shear thickening fluid was prepared. • The sensing performance endows P-STF sponge with human body monitoring function. • The P-STF sponge protects against both impact and thermal hazards. • The P-STF sponge achieves the integration of protection and early warning. [ABSTRACT FROM AUTHOR]

• Impact resistance of architected composites is amplified by positive hybrid design. • Lamellar bottom enhances toughness; Brick-mud top guarantees flexural stiffness. • Declining volume ratio of cohesive and adhesive phases promotes energy dissipation. • Increasing gradient in material property contributes rigidity-toughness coupling. In recent decades, architected composite materials have received increasing attention due to its promising potential in improving the impact resistance performance compared with bulk materials. Some ingenious microstructures of biomaterials can enlighten the design of novel architected composite materials, such as nacre, conch shell and dactyl club of mantis shrimp, which have been extensively applied. Here, in order to further enhance the impact resistance of architected composite materials, hybrid architectures are proposed based on nacre-like brick-mud and sponge-like lamellar architectures. Then, their impact resistance performances and mechanism are investigated by combining experiment with finite element simulation. The results show that through positive hybrid design inspired of the dactyl club, the lamellar bottom makes the hybrid architecture retain excellent toughness, and the brick-mud top guarantees large flexural stiffness, thereby achieving rigidity-toughness coupling and boosting the energy absorption dramatically. Moreover, as the decline of volume ratio of soft phases within and between brick-mud layers, the energy absorption of brick-mud architecture gradually increases owing to the rising damage resistance. Further, the rigidity-toughness coupled effect can be optimized by positively hybridizing multiple architectures with larger variation in flexural stiffness and toughness, even achieving 375 % improvement in energy absorption compared with the basic brick-mud architecture. [Display omitted] [ABSTRACT FROM AUTHOR]

Shear thickening fluids (STFs) are a unique type of fluids that can quickly transform into a solid-like state when subjected to forces (rate dependent). These fluids are created by dispersing micro and nanoparticles within a medium. When the force is removed, they return to their original liquid state. Shear thickening fluids can absorb a significant amount of impact energy, making them useful for reducing vibrations and serving as a damper. This study provides a comprehensive and brief overview of existing literature on shear thickening fluids, including their properties, classification, and the rheological mechanisms behind the shear thickening behaviour. It also examines the use of these fluids in various applications, such as improving resistance to stabs and spikes, protecting against low- and high-velocity impacts, and as a new medium for energy dissipation in industries such as battery safety, vibration control and adaptive structures. Lastly, this work reviews the promising combination of STFs with cork. Given the sustainability of cork and its energy absorption capacity, cork-STF composites are a promising solution for various impact-absorbing applications. Overall, the paper underscores the versatility and potential of STFs, and advocates for further research and exploration. [Display omitted] • Shear thickening fluids enhance composites energy absorption • Shear thickening colloidal suspensions perform well as sandwich structure interface • Cork composites are highly sustainable • Promising combination of shear thickening fluids with cork composites [ABSTRACT FROM AUTHOR]

• Dynamic damage of CF/BMI impacted by titanium alloy flyer at high speed are studied by experiment and numerical simulation, and the real model of CF/BMI were established. • CF/BMI were modeled by TexGen, and VUMAT subroutine interface in Fortran environment, the Hashin failure criterion were implanted into the numerical simulation. • Time history curve of strain, macroscopic damage process and microscopic damage morphology were obtained. In this paper based on the turbofan engine fan casing, the rectangular cross-section TC4 flyer high-speed impact carbon fiber/bismaleimide (CF/BMI) composite laminate was used to simulate the impact of failed blade fragments on the casing. Based on mechanical properties tests and equivalent mechanics theory, the mechanical properties parameters of laminates were obtained. The mesoscopic CF/BMI laminates model was built by TexGen. The Hashin failure criterion was implanted into the VUMAT subroutine. ABAQUS/Explicit was used to simulate the normal penetration and oblique penetration of ballistic impact experiments to obtain the strain time history curves, macroscopic damage process and mesoscopic damage morphology. The reliability of the numerical simulation method was verified by ballistic impact test. On this basis, the mechanical response and impact damage characteristics of flyer penetrating CF/BMI laminates under different impact velocities (260 m/s, 300 m/s), incident angles (45°, 60°, 90°) and flyer flight attitudes were studied. The damage characteristics of CF/BMI laminates under high-speed impact of flyer were obtained by combining the dynamic response analysis of two components of carbon fiber layer and bismaleimide resin in the laminates. [ABSTRACT FROM AUTHOR]

• High-velocity impact performance of AA 7475-T7351 aluminum plates impacted by spherical and cubical projectiles. • Predicting impact velocity limits that lead to liquid (fuel) leaks from impacted aluminum plates. • Effect of different impact orientations of a cubical projectile on the ballistic and leakage velocity limits of aluminum plates. This paper presents numerical and experimental findings of high-velocity impact tests conducted on thin AA 7475-T7351 aluminum plates subjected to the impact of small cubical and spherical projectiles. The investigation includes an examination of the influence of different impact angles, namely edge-on, corner-on, and face-on orientations, on the target performance. Following each impact test, the damaged plates underwent a leakage test, to determine the leakage threshold caused by the impact event. To gain a deeper insight into the failure modes and penetration mechanisms of thin-walled aluminum plates, finite element models were developed for various impact scenarios. The results revealed that both the shape and orientation of the projectile significantly impact the ballistic and liquid leakage limit velocities of targets. Notably, the cubical projectile exhibited lower ballistic and leakage limits than the spherical projectile. In terms of the leakage limit, a clear correlation was identified between the sharpness of the projectile's nose and leakage limit velocity. As the projectile's nose became sharper, the consistent trend was a decrease in leakage limit velocity i.e. the corner-on impact orientation (having the sharpest nose) exhibited the lowest leakage limit velocity, while the face-on impact orientation (having a blunt nose) displayed the highest leakage limit velocity. However, in contrast to the leakage limit velocity, a definitive relationship between the projectile nose sharpness and ballistic limit velocities was not observed. This is evident as the corner-on impact orientation, associated with the sharpest nose, registered the highest ballistic limit velocity, while the edge-on impact orientation, with an intermediate nose sharpness, recorded the lowest ballistic limit velocity. [ABSTRACT FROM AUTHOR]

This paper aims to assess the impact responses of hyperelastic materials that have the potential to be effective in reducing loads and drag during water impact. Using experimental and numerical methods, the mechanisms of energy conversion and stress distribution induced by the deformation behaviors of hyperelastic spheres impacting rigid and water surfaces are investigated. By comparing the impact events of rigid spheres, the elastic waves propagating inside the hyperelastic spheres over a single deformation cycle are analyzed to evaluate the impact resistance. The results show that the energy loss into the fluid is responsible for more kinetic energy loss in hyperelastic sphere during water impact. The drag reduction effect of hyperelastic spheres during water entry depends on the deformation behavior. Additionally, an analysis is conducted on the strain energy density of hyperelastic spheres during water entry. The initial change in kinetic energy is studied as a function of the dimensionless ratio of material shear modulus to impact hydrodynamic pressure. • Energy dynamics in hyperelastic spheres impacting rigid and water surfaces are elucidated. • The drag reduction in water of hyperelastic spheres is contingent on a specific range of material properties. [ABSTRACT FROM AUTHOR]

Impacts on structural materials can cause greater safety hazards, and it will be difficult to reinforce the original structure. Therefore, it is important to investigate a coating that can improve the impact resistance of materials. Polyurea coatings with excellent mechanical properties have become a widely used protective coating military and residential applications. However, it is still a significant challenge to prepare polyurea elastomers with high strength, toughness, tear and impact resistance. In this work, two polyurea elastomers (BPU1000 and BPU650) with different soft segment molecular weights of high mechanical strength and toughness are fabricated by introducing the rigid benzene ring structure between the soft and hard segment. Moreover, the hard segment units are cross-linked by reversible hydrogen bonding, which promotes a significant increase in stiffness, strength, toughness and tearing. Compared to the unmodified coating, BPU1000 and BPU650 showed significantly improved tensile strength and toughness. Specifically, the tensile strengths of BPU1000 and BPU650 are 36.93 MPa and 37.78 MPa and the toughness is 230.78 MJ/m3 and 156.29 MJ/m3, respectively. The drop hammer and penetration experiments show that BPU1000 and BPU650 possess excellent impact resistance, much higher than the previously reported elastomers, which provides a new choice for the application of polyurea coatings for structural protection. • Benzocaine modified PTMG polyurea coatings with excellent mechanical properties are prepared. • The prepared polyurea coatings showed significant impact and excellent energy dissipation. • The polyurea coatings with ultra strength, toughness and impact resistant provides a good choice for ballistic protection and explosive resistance application. [ABSTRACT FROM AUTHOR]

The application of shear thickening fluids (STFs) in impact protection has attracted increasing attention as an innovative material capable of promptly perceiving and reacting to external stimuli. Herein, we synthesized the zeolitic imidazolium ester-like skeletal structure material ZIF-8 and employed it to create a new multi-phase STF. This involved incorporating ZIF-8 particles as a third dispersed phase and using a single-phase SiO 2 -based STF as the base liquid. The critical shear thickening rates of multi-phase STFs that contain ZIF-8 are lower, while their peak viscosities are higher. Additionally, a new method to characterize the mechanical properties of STF was established by constructing a light-load impact testing platform. The ZIF-8-based multi-phase STFs exhibit excellent energy dissipation ability, and an increased ZIF-8 content can improve the resistance to impact wear and energy absorption ability of the STFs. In particular, the impact crater volume is only 574 µm3 (reduced by 89.76%) when the ZIF-8 content is 7.5 wt%. The mechanism study shows that the nanoparticles inside the multi-phase STF are able to form a stable frictional contact network, thereby bolstering the shear thickening effect and rapid responsiveness during the impact process. This study introduces novel concepts for the design of impact protection materials. [Display omitted] • A novel device and method for evaluating the mechanical properties of STF under low-load conditions was developed. • Novel multiphase shear thickening fluids (STFs) were prepared by dispersing ZIF-8 into SiO 2 -based suspensions. • The incorporation of ZIF-8 improved the shear thickening properties of the STF. • The multi-phase STF exhibited notable wear resistance. [ABSTRACT FROM AUTHOR]

Compared with traditional impact-resistant materials, nanocarbon materials have the advantages such as light weight, large specific volume for energy dissipation and their exceptional thermal stability for the extreme-environmental working potentials. However, based on the commonly used fabrication method, the general nanocarbon structures (e.g. carbon nanotube (CNT) array) are always constructed with the weak interaction between units. Therefore, when they are subjected to impact, the impact energy cannot be transferred throughout the whole loose and discontinuous structure efficiently, which results in the degradation of their impact-resistant capabilities. To address the above issue, we fabricated a nanocarbon "cushion" with the combination of a diamond like carbon (DLC) film and multi-wall CNT (MWCNT) array. The DLC film was deposited successfully onto the as-grown MWCNT array through enhanced glow discharge plasma immersion ion implantation and deposition (EGD-PIII&D) method to form a continuous upper layer which is vital to distribute and transfer the impact energy loading. The new nanocarbon system has high specific dissipated energy up to ∼2.22 kJ/m3, which is almost twice as much as that of the commercial polyurethane sponge. We anticipate that this study will provide new insights to develop novel nanocarbon materials for impact resistance in high-tech edge applications. Image 1 • A nanocarbon "cushion" by combining a diamond like carbon film and a multi-wall CNT array was firstly reported. • The structure design of nanocarbon cushions enables the release of impact energy throughout the whole material. • The specific dissipated energy of nanocarbon cushions is about 2-fold higher than that of commercial polyurethane sponges. • The nanocarbon cushions are promising to address the protective issues in the specific high-tech fields. [ABSTRACT FROM AUTHOR]

Discarding PET plastic (dPET) causes serious environmental pollution and enormous fossil resources waste. Processing techniques have mainly focused on the conversion of dPET into monomers, with minimal reports highlighting their transformation into high–value materials. This work intends to transform dPET into a high–performance material with potential alternative value in harsh production environments. The soft and hard segments of the thermoplastic polyester elastomeric (TPEE) molecular structure are reacted and cross–linked with dPET using a facile one–pot process, and two main polymers, (C 8 H 4 O 4) n and ((C 16 H 18 O 4) 0.76 ·(C 4 H 8 O) 0.24) n are generated after the reaction. Through chemical reactions between TPEE and dPET, new characteristic products and chemical bond–crossing structures are formed, while the resulting product particles or multiple TPEE particles are anchored by the high viscosity of dPET, which endows the material with superior tensile strength (34.21 MPa) and impact resistance. The glass transition temperature (T g) of the material implies that neither the molecular chain nor the chain segments can move, while only the atoms or groups composing the molecule vibrate at their equilibrium positions. The development of this new treatment method may contribute to the reduction of environmental pollution and the improvement of the high–value conversion and utilization of dPET. [Display omitted] • An innovative strategy to convert dPET into functional materials was developed. • The fabricated material showed excellent tensile strength and impact resistance. • (C 8 H 4 O 4) n and (C 16 H 18 O 4) 0.76 ·(C 4 H 8 O) 0.24) n were generated after polymerization. • Newly formed long–chain polymer is responsible for superior tensile strength. • This study gives a new alternative approach to high-value utilization of dPET. [ABSTRACT FROM AUTHOR]

• The design of the bionic structure is inspired by the lotus stem. • Distribution of porous layer can improve energy absorption. • Mechanism of mechanical property enhancement of bionic structure revealed. • Compared to reference structures, the bionic structure has significant advantages. • The bionic lotus stem structure has advantages over the five bionic structures proposed in recent years. Lotuses could survive in heavy storms while long and slender lotus stems have porous structure. 12 or 13-wells cross section structure and its distribution along lotus stems were identified by sampling random lotuses from nature. 4 bionic 12-wells structured bars and 1 bionic 13-wells structured bar were fabricated by 3D printing technology with toughness resin. 1 hollow circular tube and 1 hollow square tube were prepared for reference. All the bionic bars and tubes were subjected to three-point bending experiments and transverse loading experiments to investigate mechanical properties referred to the effects of cross section structures and their axial gradient distribution. The results of the transverse loading experiments showed that the peak crushing force (PCF) of the 13-wells original structure (Os-13w) was reduced by about 82.46 % and the crushing force efficiency (CFE) was increased by about 300.00 % compared with the reference square tube. The results of three-point bending experiments showed that the specific energy absorption (SEA) and CFE of the 12-wells original structure (Os-13w) increased by about 90.71 % and 173.33 %, respectively, and the PCF decreased by about 29.28 % compared with the reference circular tube. Simulation of the experiments explained why the bionic 12-wells structured bar had better mechanical performance than the referenced tubes. In addition, comparisons are made with some novel bionic structures of recent years. [ABSTRACT FROM AUTHOR]