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Abstract Aluminium foam sandwich panels (AFSPs) have a high impact resistance and are suitable for a wide range of engineering applications. To improve corrosion resistance, this paper proposes an anti-corrosion sandwich panel with stainless steel as the upper sheet. Drop hammer impact tests were performed on a total of ten AFSPs to investigate their dynamic response and failure patterns. To assess the deformation performance of AFSPs, a laser displacement meter was used to obtain the bottom centre displacement. The effects of the impact energy and the thickness of each component of AFSPs on the peak impact force and deformation performance were studied. Test results showed that the thickness of each component had notable effects on the impactor and bottom displacements. In addition, the effect of the unit mass of the components in AFSPs on decreasing the bottom displacement was discussed. Compared to increasing the aluminium foam and lower sheet thicknesses, increasing the upper sheet thickness was more effective in decreasing the bottom displacement. A finite element model of AFSPs was developed to conduct parameter analysis, indicating that impactors with larger diameters resulted in higher peak forces and reduced deformation of AFSPs.

Flexible materials to achieve deformable wing technology requires high mechanical properties of flexible materials，the existing research on chiral structures as flexible materials to drive deformable wings is based on the case of linear small deformations. In order to investigate the mechanical properties of chiral structures under large deformation conditions，five common chiral system negative Poisson's ratio structures，such as tri-chiral，anti-trichiral，tetra-chiral，anti-tetra-chiral，and hex-chiral structures are taken as the object of study. Based on the theory of cellular structural mechanics，the effect of topological structure and cellular element geometrical parameter on the in-plane compression and energy absorption characteristics of chiral system negative Poisson's ratio structures of the intrinsic model of ideal plastic materials are compared and analysed. The results show that the elastic modulus，plateau stress and energy absorption capacity of the chiral structure are inversely proportional to the cell element parameter α and positively proportional to the cell element parameter β. The topology affects the energy-absorbing properties of chiral structures significantly，i.e.，the energy-absorbing capacity of chiral structures with the same single-cell geometrical parameter is significantly enhanced with the increase in the number of ligaments.

Abstract To enhance the impact resistance of hydraulic columns, a theoretical analysis method was employed to develop a dynamic characteristic analysis model for conventional columns under impact loads. This model facilitated the derivation of key parameters such as equivalent stiffness, maximum retraction amount, and impact duration. A fluid-solid coupling model for the conventional column was constructed using finite element and coupled Eulerian-Lagrangian (CEL) methods. Subsequently, numerical simulation results were compared and analyzed against theoretical predictions. Based on this analysis, an energy-absorbing column was designed, and its fluid-solid coupling model was established to investigate its mechanical response under static and dynamic impact loads.The findings indicate that under a static load of 2000 kN, when superimposed with impact loads of 200 kJ, 400 kJ, and 800 kJ respectively, the peak impact forces on energy-absorbing columns are 89.20%, 91.72%, and 98.42% lower than those on normal columns. The yield displacements of energy-absorbing columns increase by 142.26%, 109.15%, and 108.41% compared to normal columns. Energy absorption in energy-absorbing columns is 152.11%, 171.80%, and 145.18% higher than in normal columns. Furthermore, initial velocities of energy-absorbing columns are consistently lower compared to normal columns. After reaching initial velocity, energy-absorbing columns exhibit reduced oscillations due to interactions between the energy absorber, column, and hydraulic fluid system under impact loads. Unlike normal columns, energy-absorbing columns mitigate stress concentration at the column head through interactions between the energy absorber, emulsion, and column. Additionally, the impact resistance time of energy-absorbing columns is 2.19, 1.64, and 1.85 times longer than that of normal columns.Energy-absorbing columns outperform conventional columns across six metrics: peak impact force, column yield displacement, energy absorption, column movement speed, stress distribution, and impact resistance time, demonstrating superior mechanical properties in impact resistance.

Abstract Engineered Cementitious Composites (ECC) are highly regarded in construction owing to their tensile ductility and crack control capabilities, making them suitable for various structural applications. The accumulation of multi-walled carbon nanotubes (MWCNTs) further enhances their mechanical properties. However, there’s a significant knowledge gap concerning MWCNTs-ECC impact resistance. The objective of this study is to tackle the challenges associated with evaluating, optimizing, and predicting MWCNTs-ECC impact resistance to ensure its safe and widespread use in critical infrastructure by applying response surface methodology (RSM). Moreover, the 13 mixtures of ECC combined with several quantities of PVA fiber and MWCNTs as input elements were utilized to calculate the first (E1) and final (E2) impact energies. The findings demonstrated that the MWCNTs-ECC combinations’ impact resistance improved as the input ingredient concentrations increased. Besides, the optimum E1 and E2 of ECC combined with 1% of PVA fiber were noted by 1398 Joules and 12,956 Joules at 0.065% of MWCNTs on 28 days respectively. Furthermore, Response prediction models for E1 and E2 were created, and after being validated with an analysis of variance (ANOVA), it was determined that they had high R2 readings of 99.30% and 99.07%, correspondingly. The optimization process produced an ideal number of input variables for MWCNTs and PVA fiber, respectively, of 0.066% and 1%, with a desirability value of 100%. Moreover, it is recommended that the usage of 0.066% of MWCNTs in ECC combined with 1.0–1.50% PVA fiber provides optimum results for the construction industry.

Abstract Hydraulic actuated quadruped robots have bright application prospects and significant research values in unmanned area investigation, disaster rescue and other scenarios, due to the advantages of high payload and high power to weight ratio. Among these fields, inevitable collision of robots may occur when contact with unknown objects, step on empty objects, or collapse, all of which have an impact on the working hydraulic system. To overcome the unknown external disturbances, this paper proposes an active disturbance rejection control (ADRC) strategy of double vane hydraulic rotary actuators for the hip joints of the quadruped robots. Considering the order of the valve-controlled actuator model, a three-stage tracking differentiator, a four-stage extended state observer, and a state error feedback controller are designed relatively, and the extended state observer is adopted to observe and compensate the uncertainty of external load torque of the system. The effectiveness of the ADRC method is verified in simulation environment and a single joint experimental platform. Moreover, the impact experiments of the limb leg unit are carried out after introducing the proposed ADRC strategy into hip joint, the limb leg unit of quadruped robots presents better impact resistance ability.

Composite sandwich structures are widely used in the aerospace field due to their advantages of high strength, lightweight, and fatigue resistance. However, these structures are prone to damage with very-low-energy impacts. In order to improve the impact resistance of aircraft skin structure, a low-velocity impact resistance of sandwich structure specimens was tested by means of drop hammer impact, and the impact damage area was scanned by ultrasonic C-scan, and obtains the impact damage of specimens with different impact energies and different ply sequences. Combined with the Hashin failure criterion, the finite element equivalent model of composite sandwich structure under low-velocity impact was established. The errors between the simulation results and the C-scan results of the test piece were less than 10%, in which the experimental measurements and numerical predictions were in close agreement. Finally, the finite element equivalent model was applied to optimize the application of model sandwich, which was used for fuselage skin of a certain electric aircraft. The total thickness of the laminate structure remains unchanged before and after optimization, but the impact resistance was significantly enhanced. The ±45° lay-up was beneficial for the structure to absorb the impact energy.

The observation of fibers in salvadora persica roots inspired us to consider the idea of using them as reinforcement to create an innovative composite. The current work focuses on the volumetric mass density, extraction, molding, and mechanical testing of composites and hybrid composites made from salvadora persica roots and glass fibers reinforced with two types of polyester matrix, chosen due their characteristics suitable for use in different orientations. Various extraction and combination methods have been used to identify an optimal approach for obtaining fibers from salvadora persica roots, considering its chemical composition (hemicellulose, pectin, and lignin). In this investigation, the hand lay-up method was used to mold specimens with different geometries. The composite and hybrid composite were combined with a polyester matrix and subjected to various mechanical tests namely; tensile, impact resistance, and water absorption. The results indicate that reinforcing polyester resins with SP fibers, whether long or short, enhances the overall mechanical properties of the composite. Additionally, improved adhesion between salvadora persica roots fibers and resin was observed.

Abstract The high‐speed impact‐resistanct materials are of great significance while their development is hindered by the intrinsic tradeoff between mechanical strength and energy dissipation capability. Herein, the new chemical system of molecular granular material (MGM) is developed for the design of impact‐resistant materials from the supramolecular complexation of sub‐nm molecular clusters (MCs) and hyper‐branched polyelectrolytes. Their hierarchical aggregation provides the origin of the decoupling of mechanical strengths and structural relaxation dynamics. The MCs’ intrinsic fast dynamics afford excellent high‐speed impact‐resistance, up to 5600 s−1 impact in a typical split‐Hopkinson pressure bar test while only tiny boundary cracks can be observed even under 7200 s−1 impact. The high loadings of MCs and their hierarchical aggregates provide high‐density sacrificial bonding for the effective dissipation of the impact energy, enabling the protection of fragile devices from the direct impact of over 200 m s−1 bullet. Moreover, the MGMs can be conveniently processed into protective coatings or films with promising recyclability due to the supramolecular interaction feature. The research not only reveals the unique relaxation dynamics and mechanical properties of MGMs in comparison with polymers and colloids, but also develops new chemical systems for the fabrication of high‐speed impact‐resistant materials.

Roller-compacted concrete pavement (RCCP) is one of the most durable, economical, and practical solutions for the construction of roads for various heavy-duty purposes. To make RCCP more sustainable, different waste materials have been utilized. These materials were densified silica fume (SF), ground granulated blast furnace slag (S), crumb rubber (CR), and recycled steel fibers (RSFs) from waste tires. The weight percentages of replacement for SF and S from cement were 5, and 27.5%, respectively. CR was utilized as a volumetric replacement of sand with 0, 2, 5, and 10%. As a volumetric addition of concrete, RSF with 0.2, 0.4, and 0.6% was utilized. Water content was 6% for all mixtures. The impact resistance test was performed to evaluate the behavior of RCCP to the repeated load on roads. Also, ultrasonic pulse velocity (UPV) (nondestructive) and abrasion resistance tests were performed to validate roller-compacted concrete (RCC) as pavement. There is a substantial increase in impact energy by using 10% of CR and 0.6% of RSF, compared with that of reference specimens. The use of CR and RSF can improve the abrasion resistance of RCC, and this can ensure its applications in pavements. The relationships between impact, abrasion, and UPV were established, and models have been proposed to predict these relationships.

Synergistically enhancing the erosion and impact resistance of contacts poses a significant challenge for cutting-edge electrical equipment. Fortunately, mollusk shells in nature have evolved effective strategies to construct microstructures with superior erosion and impact resistance. Inspired by the structure of nacre, AgSnO2 contact material with hierarchical architectures has been designed and fabricated. The mechanistic link between microstructural evolution and dynamic erosion is studied through experiments combined with Computational Fluid Dynamics (CFD) and Finite Element Method (FEM) simulations. Results show that the reconstructed SnO2 skeleton endowed with a highly continuous and anisotropic ‘flowering'-like structure forms a continuous interpenetrating network with Ag, optimizing the conductive pathways on the molten pool surface. Additionally, the Ag-rich regions in the deeper layers on both sides of the molten pool offers a stable ‘nutrient-supply’ for the continuous ‘flowering’ reconstruction of the skeleton, exhibiting excellent in-situ self-repairing erosion resistance. Benefiting from this synergistic strategy, this skeleton is reconstructed based on its natural structure, which further disperses the stress and deformation concentration while inhibiting interfacial debonding, thereby reducing the formation of cracks and significantly enhancing the impact resistance. This work is expected to breakthrough erosion and impact resistance in extreme condition electrical contact materials through biomimetic microstructure design.

Dynamic mechanical behavior and size-related impact resistance of CNT films are studied by employing laser-induced projectile impact test (LIPIT) and coarse-grained molecular dynamics (CGMD) simulation. The energy dissipation mechanisms of the CNT films are investigated via CGMD simulations. An evident anomalous thickness-dependent effect is directly observed in the experiment, consistent with simulation phenomena. The mechanisms underlying this anomalous thickness-dependent effect are investigated at the atomic scale. The disparities between experiments and simulations are discussed. Our analysis of energy dissipation modes, deformation behaviors during impact, and impact area reveals that kinetic energy change predominantly governs the deformation mode. Meanwhile, a plugging failure mode near the exit face of CNT film is identified at high impact velocity (∼160 m/s), leading to a deterioration in impact resistance and a corresponding reduction in SEA with increasing CNT film thickness. These findings provide a feasible strategy for the protection design of CNT film in broaden protective application scenarios.

This study critically examines the composite material's mechanical properties and performance for 3D-printed shin guards. It contains a thermoplastic polymer matrix with short carbon fibre reinforcement. Shin guard stress and deformation under impact loading were modelled using FEA models. The composite material was 3D-printed and tested for tensile, flexural, and impact properties. The entire cycle of FEA models and careful mechanical testing allows for the development and evaluation of new composite materials and designs. The finite element analysis, such as maximum von Mises stress, is 2890.5 MPa. The carbon fibre-reinforced composite's mechanical properties, including tensile strength, flexural strength, and impact resistance, showed a considerable improvement over those of the unreinforced polymer. The solid design could be heavier and less adaptable than the pattern. Compared to unreinforced polymers, carbon fibre improves strength, stiffness, and impact resistance for the 3D-printed composite. This result thus proves that 3D-printed carbon fibre-reinforced composites could make superior sports protective equipment like shin guards. The FEA calculations and extensive mechanical testing provide a dependable framework for creating and testing these new composite materials and systems.

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.

This study suggests an economical and environmentally friendly approach of converting used plastics and discarded tires, two of the most common and non-biodegradable wastes, into value added composites suitable for building applications. Disposal of more than 4 billion tires and 275 million metric tons (MT) of plastics every year is a major environmental, social and health concern. Despite substantial efforts, majority of plastics end up in landfills. Similarly, efforts to recycle and/or recover valuable components from used tires have met with limited commercial success. A simple approach to combine waste plastic and crumb rubber from discarded tire and convert them into composites for various applications has been showcased in this study. Crumb rubber (10–30 %) were added into plastic and compression molded into composites. The composites obtained had tensile strength between 1.8 and 4.8 MPa flexural strength between 6.1 and 14.5 MPa. Considerably high increase of about 60 % was observed for compression and impact resistance with the addition of 20 % rubber. Addition of crumbs also improved the acoustic absorption and thermal resistance. Rubber crumb reinforced waste plastic composites have properties suitable for insulation, pavement blocks and other building applications.

Using origami folding concepts to design novel mechanical metamaterials has recently become a prevalent framework. Inspired by the Kresling origami structure, this study proposes a double-layer Kresling origami metamaterial with reprogrammable shock stiffness. Two combination strategies are constructed, each with different geometric constraints and kinematic compatibility. They are identified as assigned with same torsion direction (ASTD) and assigned with opposite torsion direction (AOTD), respectively. The shock stiffness of two double-layer Kresling origami metamaterials is analyzed using the finite element method, and results indicate that the AOTD metamaterial has superior impact resistance. Furthermore, the programmability of shock stiffness of the metamaterial is carried out comprehensively, and the influence of each design parameter is exhibited in detail. Finally, two prototypes of ASTD and AOTD metamaterials are fabricated, and experimental tests verify the analysis outcomes. This study provides a new approach to constructing mechanical metamaterials with reprogrammable shock stiffness for applications in energy absorption and vibration isolation engineering.

Abstract Structural materials such as ceramics, metals, and carbon fiber‐reinforced plastics (CFRP) are frequently threatened by large compressive and impact forces. Energy absorption layers, i.e., polyurethane and silicone foams with excellent damping properties, are applied on the surfaces of different substrates to absorb energy. However, the amount of energy dissipation and penetration resistance are limited in commercial polyurethane foams. Herein, a distinctive nacre‐like architecture design strategy is proposed by integrating hard porous ceramic frameworks and flexible polyurethane buffers to improve energy absorption and impact resistance. Experimental investigations reveal the bioinspired designs exhibit optimized hardness, strength, and modulus compared to that of polyurethane. Due to the multiscale energy dissipation mechanisms, the resulting normalized absorbed energy (≈8.557 MJ m−3) is ≈20 times higher than polyurethane foams under 50% quasi‐static compression. The bioinspired composites provide superior protection for structural materials (CFRP, glass, and steel), surpassing polyurethane films under impact loadings. It is shown CFRP coated with the designed materials can withstand more than ten impact loadings (in energy of 10 J) without obvious damage, which otherwise delaminates after a single impact. This biomimetic design strategy holds the potential to offer valuable insights for the development of lightweight, energy‐absorbent, and impact‐resistant materials.

Eco-friendly recycled tire-derived rubberized concrete is an environmentally conscious alternative employed in civil engineering for diverse purposes, enhancing the characteristics of concrete. In this paper, the research focuses on examining the drying shrinkage, creep, impact, and post-impact and creep behavior of concrete incorporating rubber. Four groups of cylindrical samples, each with a diameter of 150 mm and a length of 300 mm, were subjected to a consistent load corresponding to 0.25 of the bearing load capacity determined through compression tests on identical concrete mixtures. The testing spanned a year, during which measurements were taken for total strain, dependent strain, creep, and shrinkage. The concrete mixtures were formulated with crumb rubber in place of fine aggregate sand, with varying percentages (0%, 10%, 20%, and 30%). To emphasize distinctions in outcomes across mixtures with different crumb rubber proportions, tests for compression, indirect tension, flexural strength, and impact resistance were carried out at intervals of 28 days, three months, six months, and one year. The examination and contrast of the four combinations demonstrated notable effects on both concrete creep and impact energy due to the addition of rubber particles. Despite this, shrinkage showed minimal influence. In general, there was a decrease in the compressive strength of rubberized concrete. The concrete compressive strength decreased by 25–35%, 45–50%, and 55–65% for rubberized concrete incorporating 10%, 20%, and 30% crumb rubber, respectively. Furthermore, it was observed that creep negatively affects the impact resistance of non-rubberized concrete. Nevertheless, including rubber helps mitigate the effect of creep on the impact resistance, resulting in a reduction ranging from 6% to 12% across rubber percentages from 10% to 30%.

A novel composite double trapezoidal corrugated sandwich plate (CDTCSP) was prepared by mold hot pressing and secondary bonding of carbon fiber reinforced polymer (CFRP) prepregs. The DIT302E drop hammer testing machine with a hammerhead of 5.5 kg was selected to realize the impact test of the new corrugated sandwich structure and the all-composite trapezoidal corrugated sandwich plate (CTCSP) with three different energies of 10 J,30 J, and 50 J by changing the height. The failure modes of the two samples were further studied by experimental investigation along with the finite element model established in Abaqus/Explicit. Based on the verified numerical model, the failure process of CDTCSP under 30 J and 50 J impact energy is analyzed. At the same time, the effects of different impact positions and layup angles on the impact resistance of CDTCSP at 10 J energy were evaluated. It can be observed that as the impact energy increases, the peak load of the composite corrugated sandwich plate decreases. Compared with the traditional ones, the impact position has no noticeable effect on the overall impact resistance of CDTCSP. Based on the analysis of CDTCSP with five different layup parameters, it is found that the matrix compression failure extends along the fiber direction, and the peak load of the sample with all the surfacing layup of ± 45° is 17% larger than that of the sample with 0°.

The impact resistance of the steel fiber reinforced concrete (SFRC) beams after exposure to fire was studied. The SFRC beams were subjected to open flame for 120 min. After cooling to the ambient temperature, the drop-weight impact tests were conducted on the SFRC specimens. The influence of the steel fiber type and fire temperature on the impact-resistant properties was examined. The temperature time history, force time history, and reaction force-deflection curve were obtained. The peak force is discussed and the energy absorption is calculated. The results showed that the influence of steel fiber type on the impact resistance of SFRC was negligible, while the impact resistance and ductility of SFRC decreased significantly after exposure to fire. Compared with the partial fracture of the specimen at room temperature, the specimen after fire showed a more complete fracture under impact load, indicating a larger deflection and more pullout of steel fibers. This means that more friction is needed during the damage process, resulting a higher energy absorption.

The wing fuel tank cover and its surrounding wing outer plate together form a part of the aircraft's aerodynamic shape. During the service process of an aircraft,the fuel tank cover is inevitably hit by foreign objects,ensuring the impact resistance of the fuel tank cover is of great significance for ensuring the safety of the aircraft. In this paper the research progress of impact resistance performance of wing fuel tank cover is systematically introduced from three aspects: airworthiness regulations requirements,common materials and structural forms,assessment methods and evaluation,the current research conclusions are summarized,and the future development of wing fuel tank cover is prospected. The research results can provide theoretical and technical references for the design and manufacturing of new types of masks in the future.

The process of depletion of sources of natural aggregates poses challenges to produce technically and environmentally suitable concrete. Aggregate compositions found in construction and demolition (C&D) waste offer potential alternatives to natural coarse aggregates. Additionally, the utilization of abundantly available natural material like seashore sand, as a replacement for river sand, can present a viable solution to this problem. This research paper investigates the performance of concrete that incorporates 40% recycled coarse aggregates, along with varying percentages of seashore sand as replacements for river sand (0%, 10%, 20%, 30%, 40%, 50%, and 100%). The evaluation focuses on strength properties, including compressive strength tests on cylinders and impact resistance tests, as well as durability properties such as water penetration tests under pressure and sulphate attack tests. The experimental results indicate that concrete incorporating both recycled coarse aggregates and seashore sand replacements yields favorable outcomes in terms of strength and durability when compared to the controlled concrete, particularly at suitable replacement proportions.

In this paper, a liquid-solid origami composite design is proposed for the improvement of impact resistance. Employing this design strategy, Kresling origami composite structures with different fillings were designed and fabricated, namely air, water, and shear thickening fluid (STF). Quasi-static compression and drop-weight impact experiments were carried out to compare and reveal the static and dynamic mechanical behavior of these structures. The results from drop-weight impact experiments demonstrated that the solid-liquid Kresling origami composite structures exhibited superior yield strength and reduced peak force when compared to their empty counterparts. Notably, the Kresling origami structures filled with STF exhibited significantly heightened yield strength and reduced peak force. For example, at an impact velocity of 3 m/s, the yield strength of single-layer STF-filled Kresling origami structures increased by 772.7% and the peak force decreased by 68.6%. This liquid-solid origami composite design holds the potential to advance the application of origami structures in critical areas such as aerospace, intelligent protection and other important fields. The demonstrated improvements in impact resistance underscore the practical viability of this approach in enhancing structural performance for a range of applications.

High entropy alloys have the potential to be used as coating materials in many fields due to their excellent mechanical properties, corrosion resistance and high-temperature stability. Based on the application requirements of high-entropy alloys, this study aims to explore how tungsten carbide can optimize the properties of high-entropy alloys. Through theoretical research and experimental validation, the effects of the organizational structure of high-entropy alloy coatings on their properties and the effects of tungsten carbide content on the properties of high-entropy alloy coatings were investigated. The micro hardness of the coatings is relatively high at low power laser melting, while it decreases with the increase of laser power. After laser melting of different materials, the average impact toughness of the studied materials exceeded 70 J/cm2, and the average values of microhardness of the optimized coatings prepared at laser powers of 1400 W and 1600 W were more than 160 HV0.2. In addition, the properties of the high-entropy alloys were significantly improved when the content of tungsten carbide reached a certain percentage. The composite coatings have excellent wear resistance, corrosion resistance and thermal stability. Overall, the optimized tungsten carbide on high entropy alloys in this study has good performance, which is of great theoretical and practical significance for understanding the performance regulation and optimal design of high entropy alloy coatings.

Automotive safety is a critical concern, and the design of bumpers plays a pivotal role in enhancing impact resistance and overall vehicle safety. Prior research has assessed several materials and structural layouts for car bumpers, emphasizing characteristics, impact resistance, and financial analysis. Further study in this area is necessary since there is a research gap in discovering the ideal bumper design incorporating a spring-supported system and using various materials for more excellent impact resistance at varying speeds. To create a bumper design with a spring-supported system, this study will employ the finite element method (FEM) to undertake structural analysis. It will also evaluate the impact resistance of the bumper at various speeds and utilize various materials. The model has been verified by previous research. To ensure that the design does not exceed the maximum yield strength of the material, it was evaluated based on the average Von Mises stress at the impact location, prioritizing configurations with the lowest stress and most significant displacement. It has been discovered that Aluminium 2024 T-86 may substitute carbon fibre in accidents up to 30 kmph. GMT and SMC can also be substituted in crashes under 25 kmph. Utilizing these materials led to increased deformation followed by decreased absorbed stress, making them ideal for bumper design.

Although Basalt fibre reinforced concrete (BFRC) has a proven record of outstanding behaviour, concerns regarding the decline in its performance beyond certain content remains a major concern. To address this concern, a varying content of Silica Fume (SF) was introduced into the BFRC mix, and their combined influence on concrete's mechanical and impact resistance was investigated using experimental and Response Surface Analysis (RSA). Using regression models developed from experimental results, 13 responses of statistically designed experiments were predicted. The findings revealed significant improvement in the concrete performance with increases between 28% and 65% in compressive strength, 35%–107% in split tensile strength, 11%–46% in flexural strength and 117%–150% in the impact resistance. Therefore, appropriate proportions of BF and SF can be utilised as an eco-friendly sustainable material in concrete.

Rubberized geopolymer concrete (RuGPC) is a new, environmentally safe building material requiring less energy and carbon footmark than normal cement-based systems, which can significantly reduce global warming concerns. Using waste rubber tyres by incorporating them in concrete as a substitute for natural aggregate, helps to reduce pollution and depletion of natural resources. Research shows that incorporating waste crumb rubber in geopolymer concrete (GPC) can reduce carbon dioxide emissions by 90% compared to ordinary Portland cement (OPC) and attain sufficient and mechanical properties and durability. This paper reviews the material properties of RuGPC and the possible structural application. It can be concluded, that RuGPC can substitute normal concrete (NC) particularly due to its impact resistance, and energy absorption performance. However, more research still needs to be conducted to be able to come up with practical design standards and conduct full-scale studies on RuGPC elements structurally to promote its practicability.

A novel shear thickening gel with micro-scale hard/soft interface structure and low reaction temperature was proposed in this article. The gel was named TH and used as core material within Kevlar fabrics. Storage modulus of TH was proved to increase by around two orders with increasing of shear frequency, and dynamic properties indicated that TH could dissipate or store more energy. TH can adhere with Kevlar fabrics well and satisfactorily fulfill the gap between fabrics. As a result, shock wave peak pressure and positive impulse decreased markedly. Wavelet decomposition analysis show that high frequency energy was filtered by protection materials. Meanwhile, impact resistance test suggested the existence of TH changed the stress propagation routes and avoided pulling out for Kevlar fabrics. Samples filled with TH demonstrated a better shock wave mitigation ability and impact resistance. Energy dissipation structures with TH have a promising prospect in the application of defending area.

Abstract The high fracture strength and exceptional impact resistance of polymer-based composites are of paramount importance to various industries like aerospace, automotive, and construction. The resin transfer molding (RTM) process is used to produce composite samples of superior quality, minimal porosity, and reduced lamination defects. In the present study, the RTM method was employed to fabricate glass fiber-reinforced composites, aiming to investigate their specific mechanical properties and structural performance. The study initially determined the ballistic limit of the produced samples. Subsequently, experimental investigations were carried out to examine the impact of hole drilling on the tensile strength, flexural strength, and impact resistance of the samples. The results revealed that the produced polymer plate demonstrated a ballistic limit with a pressure of 11 bar and a speed of 104 m/s, leading to ball restriction in the plate. The sample without holes showed the highest fracture force, while samples with three and five holes exhibited reduced fracture forces. Additionally, bending force and impact resistance were lower in samples with multiple holes compared to the sample without holes. The impact resistance of the sample with five holes was the lowest among all configurations. The study revealed that the presence of three holes arranged in a row has a lesser impact on reducing the ultimate tensile force compared to the effect of five holes. Moreover, the bending test results indicated that sample failure occurred on the side under tension, resulting in higher bending forces than tensile forces.

Concrete quality control tests usually focus on the compressive strength of concrete, while neglecting other important properties such as impact and explosion resistance, which are essential for creating resilient concrete structures. Additionally, in the process of refining sugarcane, Bagasse, a yellow fiber that is considered a waste product, is produced. Khuzestan province alone produces around one million tons of Bagasse annually, which leads to environmental concerns. To address these issues, this research investigates the mechanical properties and impact resistance of concrete containing lightweight LECA aggregates and Bagasse fibers under compressive and impact loads. Initially, a target mix scheme is determined, and samples are made and tested after curing without the addition of Bagasse and LECA. Then, samples are made with the mentioned mixing design and the combination of Bagasse and LECA by weight ratio of (Bagasse unit, LECA unit). Additionally, samples using LECA (without Bagasse) with 10%, 20%, and 30% replacement of aggregates are made and tested after curing. Compressive and impact tests are performed on all samples in accordance with regulations using appropriate testing machines and procedures. Results indicate that concrete containing lightweight LECA and Bagasse fibers has a higher impact resistance than ordinary concrete, and that the use of LECA in concrete can create structural lightweight concrete.

The fractal theory can effectively describe the complexity and multi-scale of concrete under impact load and provide a scientific basis for evaluating concrete’s impact resistance. Therefore, based on the fractal theory, this study carried out the fragmentation size analysis by weighing the quality of SFRRAC fragments, disclosed the distribution characteristics of impact fragmentation size of steel fiber reinforced recycled aggregate concrete (SFRRAC) specimens under different recycled coarse aggregate (RCA) replacement ratio, different steel fiber (SF) contents and different impact pressures. The results indicate that the fractal dimension can describe the degree of fragmentation of the specimen. The greater the fractal dimension, the more the amount of fragmentation of the specimen subjected to impact load, the lesser the fragmentation size, and the greater the degree of fragmentation. Under the impact load, the fractal dimension of SFRRAC is between 1.36 and 2.28. As the impact pressure increases, the energy consumption increases, and the fractal dimension decreases. With the growth in replacement ratio, the fractal dimension gradually increases, and the energy consumption is negatively correlated with the fractal dimension. Along with the growth of SF content, the energy consumption gradually increases, and the fractal dimension continuously decreases. A new metric angle is provided to explore the inherent law between the impact-crushing characteristics of SFRRAC and the dynamic load, thereby offering foundational support for the application of SFRRAC in practical engineering.

The TNM alloy, a βo-phase-containing TiAl alloy, has been withdrawn from use as a last-stage turbine blade in commercial jet engines as it suffered frequent impact fractures in service, raising doubts regarding the necessity of the βo-phase in practical TiAl alloys. Here, we evaluate the practical properties required for jet engine blades for various TiAl alloys and investigate the effects of the βo-phase thereupon. First, we explore the influence of the βo-phase content on the impact resistance and machinability for forged Ti–43.5Al–xCr and cast Ti–46.0Al–xCr alloys; the properties deteriorate significantly at increasing βo-phase contents. Subsequently, two practical TiAl alloys—TNM alloy and TiAl4822—were prepared with and without the βo-phase by varying the heat treatment temperature for the former and the Cr concentration for the latter. In addition to impact resistance and machinability, the creep strength is significantly reduced by the presence of the βo-phase. Overall, these findings suggest that the βo-phase is an undesirable phase in practical TiAl alloys, especially those used for jet engine blades, because, although the disordered β-phase is soft at high temperatures, it changes to significantly more brittle and harder βo-phase after cooling.

Traditional cement epoxy pavements suffer from inherent limitations such as terrible tribological properties, poor wear resistance, and weak impact resistance, presenting significant challenges to ensure the safety and continuous operation of urban roads. As a solution, high-performance cement epoxy composite grouting materials have emerged as the preferred option for engineering construction and road maintenance. In this study, CSP/epoxy cement (CSEC) composite materials were prepared by emulsion polymerization. The thermal properties of the materials were characterized, revealing that CSP enhances the thermal properties of epoxy cement (EC) to a certain extent. Furthermore, the frictional properties of CSEC composite materials and pure epoxy cement under different normal loads were investigated. The results indicated that the CSEC composite material exhibited a slight increase in friction coefficient and a notable decrease in wear rate compared to pure epoxy cement (EC). Specifically, the wear rate of CSEC decreased by 14.4% at a load of 20 N, highlighting the enhanced frictional performance facilitated by CSP. Mechanistic analysis attributed the improvement to the unique core-shell structure of CSP, which imparted higher impact resistance and eliminated alleviate residual stresses at the friction interface. This structural advantage further enhanced the wear resistance of materials, making it a promising choice for improving the durability and safety of urban road surfaces.

The safety of airport runways is important to guarantee aircraft taking-off, landing, and taxiing, and the comparison of the mechanical response of pavement structures under dynamic and static loading by LS-DYNA has rarely been studied. The purpose of this work is to separate two analysis methods to investigate the mechanical response of rigid airport pavements. Firstly, a tire–road coupling model of an airfield was established to evaluate the suitability of dynamic and static analyses. Then, the effects of landing pitch angles, sinking speeds, and tire pressures on the effective stress, effective strain, and z-displacement of the runway were investigated for both dynamic and static analysis. Finally, the significance of influence factors was analyzed by regression analysis in Statistical Product and Service Solutions (SPSS). The results indicated that the effective stress, effective strain, and z-displacement of the runway increased with a decrease in the landing pitch angle, which also increased with an increase in the sinking speed and tire pressure. It was demonstrated that the difference in pavement mechanical response between dynamic and static analyses progressively widened at high tire pressure and sinking speed. In other words, the static analysis method can be adopted to assess the dynamic mechanical behavior when the landing pitch angle is large and the tire pressure is small. Among the various factors of mechanical response, the effect of tire pressure was the most obvious, followed by sinking speed and landing pitch angle. The work proposes a new approach to understanding the mechanical behavior of runways under complicated and varied conditions, evaluates the applicability of the dynamic and static mechanical analysis methods, identifies key factors in the dynamic and static mechanical analysis of rigid runways, and provides technical support for improving and maintaining the impact resistance of pavement facilities.

The aim of this study is to analyze the ballistic impact behavior of a panel made of Twaron CT736 fabric with a 9 mm Full Metal Jacket (FMJ) projectile. Three shots are fired at different velocities at this panel. The ballistic impact test procedure was carried out in accordance with NIJ 010106. The NIJ-010106 standard is a document that specifies the minimum performance requirements that protection systems must meet to ensure performance. The 9 mm FMJ projectile is, according to NIJ 010106, in threat level II, but the impact velocity is in threat level IIIA. Analysis of macro-photographs of the impact of the Twaron CT736 laminated fabric panel with a 9 mm FMJ projectile involves a detailed examination of the images to gather information about the material performance and failure mechanisms at the macro- or even meso-level (fabric/layer, thread). In this paper, we analyze numerically and experimentally a panel consisting of 32 layers, made of a single material, on impact with a 9 mm FMJ projectile. The experimental results show that following impact of the panel with three projectiles, with velocities between 414 m/s and 428 m/s, partial penetration occurs, with a different number of layers destroyed, i.e., 15 layers in the case of the projectile velocity of 414 m/s, 20 layers of material in the case of the panel velocity of 422 m/s and 22 layers destroyed in the case of the projectile velocity of 428 m/s. Validation of the simulated model is achieved by two important criteria: the number of broken layers and the qualitative appearance. Four numerical models were simulated, of which three models validated the impact results of the three projectiles that impacted the panel. Partial penetration occurs in all four models, breaking the panel in the impact area, with only one exception, i.e., the number of layers destroyed, in which case the simulation did not validate the validation criterion. The performance of Twaron CT736 fabric is also given by the indentation depth values by two methods: according to NIJ 0101.06 and by 3D scanning. The NIJ 010106 standard specifies that a panel provides protection when the indentation depth values are less than 0.44 mm.

The impact resistance of layered polymer structures using polyvinyl butyral (PVB) in combination with Kevlar® fabric and ultra-high molecular weight polyethylene (UHMWPE) were fabricated and tested. Methods of wet impregnation and hot-press impregnation and consolidation of fabric with PVB and UHMWPE were used to manufacture multilayer constructs. All sandwich constructs were fixed to the surface of ballistic clay and subject to a free drop-weight test with a conical impactor having a small contact area. All tests were made at the same impact energy of 9.3 J and velocity of 2.85 m/s. The change in the resistance force was recorded using a piezoelectric force sensor at the time intervals of 40 μs. Using experimental force–time history, the change in the impactor’s velocity, the depth of impactor penetration, the energy transformation at various stages of impactor interaction with the sample, and other parameters were obtained. Three indicators were considered as the main criteria for the effectiveness of a sample’s resistance to impact: (1) minimum deformation, bulging, of the panel backside at the moment of impact, (2) minimum absorption of impact energy per areal density, and (3) minimal or, better yet, no destruction of structural integrity. Under the tested conditions, the rigid Kevlar–PVB–Kevlar sandwich at the frontside and relatively soft but flexible UHMWPE–Kevlar–UHMWPE layers in the middle helped to localize and absorb impact energy, while the backside Kevlar–PVB–Kevlar sandwich minimized local bulging providing the best overall performance. The front layer damage area was very shallow and less than two impactor tip diameters. The backside bulging was also less than in any other tested configurations.

Using the layered design concept of fine-grained diamond in the upper layer and the coarse-fine diamond in contact with the cemented carbide layer in the lower layer, the polycrystalline diamond compact (PDC) with multiple diamond layers for drilling was prepared. The differences in microstructure and performance between the single-layer diamond PDC and the multi-layer diamond PDC with different particle sizes were compared. The internal defects and surface morphology of the PDC were characterized using ultrasonic scanning and scanning electron microscopy (SEM), and the heat resistance, impact resistance and wear resistance of the PDC were tested, respectively. The results show that the comprehensive performance of the multi-layer diamond PDC is good. The surface layer is wear-resistant, while the lower layer is more impact-resistant. The PDC exhibits a more balanced combination of heat resistance, impact resistance and wear resistance. Specifically, the fine-grained diamond layer PDC demonstrates higher wear resistance but lower heat and impact resistance; while the coarse-grained diamond layer PDC exhibits better heat and impact resistance, but poor wear resistance.

Spherical and whisker-like cobalt particles were doped into the diamond powders to synthesize the PDC compacts under the HPHT conditions, to investigate the effect of their morphology on the properties of PDC. It was found that the two morphologies of cobalt powder have significant differences in physical characteristics, such as microstructure, porosity, magnetic properties, and crystallinity. When they were used to synthesize PDC samples, it was found that there were noticeable differences in interface bonding morphology, abnormal growth of interface WC, impact strength, and wear resistance. PDC synthesized with spherical cobalt powder had better comprehensive performance than PDC synthesized with whisker-like cobalt powder.

To promote the application of rubber-cement composites as the main bearing structure and key components in practical engineering under frequent dynamic disturbances, in this work, the split Hopkinson pressure bar (SHPB) cyclic impact tests of rubber-cement composite specimens with four different confine modes were carried out in which the impact load increased sequentially. The relationship between average strain rate, ultimate strain and impact times and the relationship between peak stress, damage energy, ultimate strain and incident energy were analyzed. The results showed that the appropriate confine reinforcement treatment can make rubber-cement composite give full play to its deformation ability when it was completely damaged. Carbon fiber-reinforced polymer (CFRP) sheet and steel cylinder can work together with the rubber-cement composite matrix to resist impact load, which effectively improves the structural strength, damage fracture energy, and cyclic impact resistance of the rubber-cement composite. Finally, based on the effect difference of confine modes, the simplified plane force models of rubber-cement composite specimens with four different confine modes were established, which clearly revealed the completely different impact resistance mechanism of the rubber-cement composites with different constraints under cyclic impact loading.

Normal concrete-polyurethane grout (NC-PUG) composite U-shaped and beam specimens were developed in this study to evaluate the capability and efficacy of PU grouting material prepared from mixing bio-based polyurethane (PU) and quartz sand as a coating material. The composite specimens were subjected to dynamic and flexural loads using U-shaped drop-weight impact test (USDWIT) and three-point bending test, respectively. Various PUG overlaid thicknesses and configurations were adopted to improve the impact and flexural behavior of the concrete. Weibull distribution analysis was performed on the USDWIT result. The result indicated that the reference NC-PUG beam exhibited the highest load-carrying capacity of 18.26 kN and the lowest ultimate deflection of 0.52 mm compared to the composite NC-PUG specimens. While, the NC beam retrofitted with a 10 mm thickness overlaid at the top surface (NC-PUGT10) revealed a reduced ultimate load-carrying capacity compared to the reference NC-PUG specimen. The impact performance of the composite U-shaped NC-PUG specimen have remarkably improved due to the influence of PU grouting materials overlaid, with a higher ductility index, which tends to change the brittle nature of concrete to a ductile state. The energy absorption capacity at the failure stage of the NC-PUGT5 is 16 times that of the reference U-shaped NC-PUG specimen. The NC-PUGTB5 and NC-PUGT10 revealed impact strength, which is 52.28 times and 68.1 times more than the reference specimens, respectively. Reliability analysis indicated that about 80% of the U-shaped NC-PUG specimen can withstand 63 impact times at the failure stage. The finding showed that retrofitting concrete structures with PUG material is a promising and sustainable method to protect the concrete structure against dynamic loads

AbstractThe scientific community has taken a particular interest in the study of low-velocity impact (LVI) behavior of fiber-reinforced polymer (FRP) composites due to its application across various domains. LVI is a serious threat to composites since it generates a variety of internal damages as well as complex failure mechanisms, resulting in a significant drop in composite structural characteristics. Several parameters, including fabric architecture, resin toughness, environmental conditions, stacking sequence, and hybridization can affect the impact resistance and damage tolerance of FRP composites. Furthermore, polymer composites in outdoor applications are exposed to various hygrothermal conditions. This results in moisture absorption and leads to physiochemical changes in the matrix material through various mechanisms such as plasticisation, hydrolysis and swelling. The long-term exposure to such environments causes the material property degradation, which affects the overall LVI performance and durability of the structures. Hence, it is crucial to critically review the influence of various parameters and hygrothermal ageing on the LVI response of FRP composites. This paper reviews the primary factors affecting LVI behavior, following, a comprehensive review on the hygrothermal effect on LVI behavior of FRP composites.

ObjectivesThe addition of thermoplastic phase materials between the layers of traditional marine composite laminates can effectively improve the impact resistance properties of marine composites. This study carries out experiments to explore the impact damage characteristics of such materials. MethodsThe thermoplastic/thermoset interface of laminates is observed with an optical microscope, and the bonding mode of the two-phase materials is analyzed. Composite laminates with different structures are impacted at low velocity with three different energies. The damage morphology of each specimen is observed via ultrasonic C-scan and electron microscopy to obtain the impact response and damage mechanism of each specimen. ResultsThe results show that marine composite laminates embedded with PEI film have better damage resistance than carbon fiber laminates. Under 8 J and 12 J of impact energy , the delamination damage is reduced by 19% and 39% respectively, and they showed better integrity after 12 J impact. ConclusionsEmbedding PEI thermoplastic film inside laminates can improve their toughness and significantly reduce internal delamination damage. Compared with carbon fiber laminates and double-sided coated laminates, PEI thermoplastic film can significantly improve the impact resistance of internal film embedded laminates.

Fiber-reinforced polymer (FRP) is the most promising technique in the present era to bring sustainability, reliability, and pseudo ductility to concrete structures due to its superior properties. Thermoplastic and thermoset polymers are the most thrown-out synthetic waste that contributes to environmental pollution for a long time. To address this issue an attempt was made to utilize High-Density Polyethylene Fiber (HDPE) fillers of size 40x2 mm has been incorporated in concrete. This investigation aims to estimate the integrity effect of HDPE fillers incorporation and wrapping of concrete with Basalt fiber mats (BFM) and Geo-textile fiber mats (GFM) on split tensile strength, shear strength, and impact resistance as per standards. Results indicate that the addition of an optimum quantity of HDPE has a significant effect on improving the tensile, shear, and impact strengths. Adding HDPE fillers in the range of 0.5 - 1.5% in concrete samples wrapped with Basalt and Geo-textile fiber mats showed an increased tensile strength of up to 14.06% and 7.40% respectively with that conventional concrete. Further, wrapping of concrete using Basalt fiber and geotextile fiber mats showed a 4.16% and 20% increase in shear strength for 0.5% HDPE-incorporated concrete samples. Higher impact resistance was also observed for HDPE-added and fiber-wrapped concrete samples

Article highlights Compressive, tensile, and flexural capacity waste rubber tires-based concrete were discussed. The durability properties of waste rubber tires-based concrete were discussed. The suitability of waste rubber tires-based concrete for roadside barriers were discussed.

For many years, several research has been conducted to investigate the use of tyre rubber waste as a substitute for concrete fine and coarse aggregates to decrease its unfavourable impacts on the environment. This resulted in producing crumb rubber concrete (CRC) with limited compressive strength. CRC strength enhancement approaches were introduced mostly through pre-treating the rubber aggregate using chemicals before using in concrete with impractical methodologies and contradictory findings. In the current research, the performance of CRC containing high contents of heat pre-treated rubber and magnetized water (MW), prepared in magnetic field strength of 1.4 T, was investigated. Rubber content, heating temperature, heating time, MW content, and water magnetizing time were the variables in this experimental investigation. Measurements of the concrete workability, mechanical properties, impact resistance, and microstructure analyses were conducted in this study. Water characterization before and after magnetization was also carried out. Promising performance was shown by CRC contained heat pre-treated rubber at 200 °C for 2 h and 100% MW treated for 24 h. These conditions resulted in compressive strength recovery of 74% and impact resistance enhancements of 2.2 times at first crack and 92% at ultimate failure when using rubber content of 40%. The microstructural analyses showed that rubber heat pre-treatment burnt out most of the unwanted materials in rubber aggregate, created an outer hard shell on the rubber particles, and decreased the zinc presence in rubber from 8.32% to 1.89%, which all resulted in CRC compressive strength and impact resistance enhancements.

Due to the influence of many factors, distribution cables are often densely placed at the bottom of the cable trench. As a result, it is easy for distribution cables to become the thermal bottleneck of the whole transmission line. To address this dilemma, this paper establishes a finite element simulation model of a cable trench to analyze the hot spots of cables with different arrangements in the cable trench. Then, the model’s accuracy is verified based on real temperature rise experiments. For an arrangement with overheating risk, the ampacity improvement method of filling the cable trench with high-thermal-conductivity material was proposed, and the ampacity improvement effect under different filling ratios was assessed. Finally, combined with the analysis of economic benefit and cost, the method of determining the optimal filling ratio was used, and the impact resistance of the cables under the impact of new energy load was analyzed. The results indicate that, for the case of the optimal filling ratio, the cables in the dense cable trench showed superior impact resistance. The investigations in this paper make significant contributions to the promotion of the maximum utilization of cables.

To improve the shock resistance of personal protective equipment and reduce casualties due to shock wave accidents, this study prepared four types of carbon fiber/polymethacrylimide (PMI) foam sandwich panels with different face/back layer thicknesses and core layer densities and subjected them to quasi-static compression, low-speed impact, high-speed impact, and non-destructive tests. The mechanical properties and energy absorption capacities of the impact-resistant panels, featuring ceramic/ultra-high molecular-weight polyethylene (UHMWPE) and carbon fiber/PMI foam structures, were evaluated and compared, and the feasibility of using the latter as a raw material for personal impact-resistant equipment was also evaluated. For the PMI sandwich panel with a constant total thickness, increasing the core layer density and face/back layer thickness enhanced the energy absorption capacity, and increased the peak stress of the face layer. Under a constant strain, the energy absorption value of all specimens increased with increasing impact speed. When a 10 kg hammer impacted the specimen surface at a speed of 1.5 m/s, the foam sandwich panels retained better integrity than the ceramic/UHMWPE panel. The results showed that the carbon fiber/PMI foam sandwich panels were suitable for applications that require the flexible movement of the wearer under shock waves, and provide an experimental basis for designing impact-resistant equipment with low weight, high strength, and high energy absorption capacities.

Polyureas have been widely applied in many fields, such as coatings, fibers, foams and dielectric materials. Traditionally, polyureas are prepared from isocyanates, which are highly toxic and harmful to humans and the environment. Synthesis of polyureas via non-isocyanate routes is green, environmentally friendly and sustainable. However, the application of non-isocyanate polyureas is quite restrained due to their brittleness as the result of the lack of a soft segment in their molecular blocks. To address this issue, we have prepared polyester polyureas via an isocyanate-free route and introduced polyester-based soft segments to improve their toughness and endow high impact resistance to the polyureas. In this paper, the soft segments of polyureas were synthesized by the esterification and polycondensation of dodecanedioic acid and 1,4-butanediol. Hard segments of polyureas were synthesized by melt polycondensation of urea and 1,10-diaminodecane without a catalyst or high pressure. A series of polyester polyureas were synthesized by the polycondensation of the soft and hard segments. These synthesized polyester-type polyureas exhibit excellent mechanical and thermal properties. Therefore, they have high potential to substitute traditional polyureas.

Conventional cushioning materials such as silicone sheets which have been recommended for resisting impact generally cause discomfort to the wearer from heat and perspiration. With the increasing need for personal protective equipment, textile–silicone composite structures are proposed in this study to reduce acute impact and moisture while enhancing thermal comfort. The influence of the composite structure and thickness on the mechanical and thermal properties of textile–silicone materials are systematically investigated. The results show that an additional knitted powernet fabric as a composite material can significantly improve the tensile properties of silicone rubber by up to 315%. However, only a slight improvement is found in the thermal conductivity (up to 16%), compression elasticity (up to 18%) and force reduction performance (up to 3.6%). As compared to inlaid spacer fabric, which has also been used for cushioning and preserving thermal comfort, the textile–silicone composites have higher tensile and compression elasticity, exhibit force reduction with the largest difference of 43% and are more thermally conductive, with increases more than 38%. The findings of this study introduced a cost-effective new silicone–textile composite for optimal impact protection and wear comfort for protective applications.

Concrete materials are subjected to a complex coupled environment of temperature, humidity, and salt ions when in a coastal area during the summer. Geopolymer concrete (GPC), as one of the best alternatives to ordinary silicate concrete, was explored in this study to investigate its mechanical damage under wet-hot-salt environment, and to understand the strengthening mechanism of its mechanical properties by polyvinyl alcohol fibers (PF), which are crucial for the application of GPC in coastal engineering. To achieve this, a series of experiments were conducted to investigate the effect of wet-hot-salt coupled environment and PF content on the mechanical properties of fiber-reinforced geopolymer concrete containing nano-SiO2 (PF-GPC). In the experimental design, a coupled environment of 45 °C temperature, 100% humidity, and 5% NaCl solution content was firstly established for simulation acceleration test by an environmental simulation test chamber. Then different PF volume contents (from 0% to 0.8%) were considered for the cube compressive strength test, split tensile test, elastic modulus test and impact test. The results indicated that the wet-hot-salt environment significantly weakened the mechanical properties of GPC specimens, while the addition of appropriate content of PF effectively mitigated the degradation caused by the wet-hot-salt environment. The compressive strength, splitting tensile strength and elastic modulus of PF-GPC reached their maximum value at a PF content of 0.6%. Particularly, the addition of PF significantly improved the impact resistance of PF-GPC in wet-hot-salt coupled environment, with the highest impact resistance indices observed at a PF content of 0.4%. Moreover, the correlation between the elastic modulus and compressive strength of PF-GPC in wet-hot-salt environment was established by using the power function equation. And based on the applicability of the two-parameter Weibull distribution in the impact life model, an impact damage evolution equation of PF-GPC was established and validated under the wet-hot-salt conditions, which can provide valuable guidance for the design of GPC structures under different damage probabilities. The findings of this study indicated that PF-GPC can be applied in the wet-hot-salt environment, which is important for the low-carbon sustainable development of building materials.

Abstract Walnut shell is lightweight material with high‐strength and toughening characteristics, but it is different from other nut shells’ microstructure with two or three short sclerotic cell layers and long bundle fibers. It is essential to explore the fracture resistance biomechanism of lightweight walnut shell and how to prevent damage of bionic structure. In this study, it is found that the asymmetric mass center and geometric center dissipated impact energy to the whole shell without loading concentration in the loading area. Diaphragma juglandis is a special structure improved walnut shell's toughening. The S‐shape gradient porosity/elastic modulus distribution combined with pits on single auxetic sclerotic cells requires higher energy to crack expansion, then decreases its fracture behavior. These fantastic findings inspire to design fracture resistance devices including helmets, armor, automobile anti‐collision beams, and re‐entry capsule in spacecraft.