Impact Absorption Research Articles

Comparative Analysis of Mechanical and Thermal Characteristics of 3D‐Printed Polyamide using Material Extrusion and Powder Bed Fusion Process with Industrial and Desktop Printers

AbstractPolyamide (PA) has excellent mechanical properties, making it versatile in various applications, including 3D printing. This paper comprehensively investigates and compares the mechanical, structural, thermal, and geometric properties of 3D‐printed PA12 samples produced with desktop and industrial printers using material extrusion (MEX) and powder bed fusion (PBF) processes. The mechanical tests included tensile, flexural, Charpy impact, Shore hardness, torsion, and water absorption tests. Additionally, scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and melt volume rate (MVR) measurements are conducted. To verify printing accuracy from a biomedical perspective, 3D‐printed prosthetic fingers are subjected to geometric assessments. Industrial PBF samples show significantly higher values for most mechanical properties, including a tensile Young's modulus of 1776 ± 19.42 MPa, while the second highest value is 1419 ± 58.77 MPa (MEX desktop). Furthermore, the MVR of the PBF industrial samples is the highest (18.34 cm3/10 min ± 2.32 cm3/10 min) and this printer exhibits superior performance in printing accuracy than the other printers. The balanced print quality and mechanics make the PBF industrial printer the most recommended for medical device production, but lower‐priced desktop FFF printers can be a good alternative for simple, fast solutions that do not require high precision.

EPIDEMIOLOGY OF INJURIES AND ASSOCIATED RISK FACTORS IN ATHLETES PARTICIPATING IN 2022 AEROBIC GYMNASTICS WORLD CHAMPIONSHIPD CHAMPIONSHIP ATHLETES

Exercise is described as a preventive and therapeutic strategy against various diseases. However, competitive sports practice is associated with an increased risk of injuries, particularly with specialization and more intense training at younger ages. Given the importance of surveillance and epidemiological studies to protect athletes’ health, our study aimed to describe the prevalence of injuries among athletes at the 2022 Aerobic Gymnastics World Championship (WCH) and to understand the intrinsic and extrinsic risk factors that may contribute to these injuries. Athletes participating in WCH 2022 were invited to complete a retrospective injury questionnaire covering the past 12 months of their training schedule. Descriptive statistic data were used to analyze all variables in the study. Seventy-three percent of athletes reported sustaining injuries, with an average of 1.6 ± 1.5 injuries occurring one to three times in the past year. The most common injuries were muscle injuries, joint sprains, stress fractures, and contusions, with the lower limbs being the most affected, followed by the upper body and trunk. Regarding injury risk factors, a significant number of athletes reported experiencing psychological stress (p=0.043) and concerns about individual protection equipment (p=0.042). Given that the type of injury and affected body region seem to be related to sports-specific movements, the impact absorption of the floor and footwear should be studied further. Additionally, injury prevention measures should include coping strategies to manage stress effectively.

Impact Absorption Power of Polyolefin Fused Filament Fabrication 3D-Printed Sports Mouthguards: InVitro Study.

This study aims to evaluate and compare the impact absorption capacities of thermoformed ethylene vinyl acetate (EVA) mouthguards and 3D-printed polyolefin mouthguards used in sports dentistry applications. The objective is to determine whether 3D-printed polyolefin mouthguards offer superior impact toughness compared to traditional EVA mouthguards commonly used in sports settings. Six material samples were assessed: five pressure-formed EVA mouthguards (PolyShok, Buffalo Dental, Erkoflex, Proform, and Drufosoft) and one 3D-printed synthetic polymer (polyolefin). The materials were evaluated using a modified American Society for Testing and Materials (ASTM) D256 Test Method A for Izod pendulum impact resistance of plastics. Polyolefin samples were 3D-printed using fused filament fabrication (FFF) technology. Notably, the FFF process included samples printed with notches placed either parallel or perpendicular to the build direction. This orientation served as a study factor, allowing for comparison of material behavior under different printing conditions. Impact testing was conducted using an Izod impact tester to assess the materials' performance under controlled impact conditions. The study achieved a high power (1.0) in power analysis, indicating strong sensitivity to detect significant differences. Among molded materials, PolyShok showed significantly lower impact toughness compared to others (p = 0.06). The mean impact absorption of EVA materials was 5.4 ± 0.3 kJ/m2, significantly lower than polyolefin materials, which demonstrated 12.9 ± 0.7 kJ/m2 and superior performance (p = 0.0). Horizontal-notched polyolefin samples exhibited higher impact strength compared to vertical-notched samples (p = 0.009). 3D-printed polyolefin mouthguards exhibited significantly higher impact toughness than thermoformed EVA mouthguards. While EVA materials demonstrated structural robustness, their lower impact resistance and observed tearing in other test specimens suggest the need for alternative testing standards to better reflect real-world conditions. 3D-printed mouthguards fabricated with build orientations perpendicular to the direction of impact demonstrate significantly enhanced impact absorption. Further research into manufacturing methods and testing protocols is recommended to optimize mouthguard performance under impact scenarios.

Recovered Foam Impact Absorption Systems

The use of foam materials in environments where they come into contact with individuals often results in deterioration, necessitating periodic replacements to maintain safety and hygiene standards. Foam, a lightweight, porous plastic formed by aggregated bubbles, possesses excellent impact-absorbing properties; however, its inherent porosity and susceptibility to wear present challenges. This project aims to develop a technological application for repurposing spent polyurethane (PU) foam from leisure facilities into effective impact absorption systems. By focusing on the reuse of deteriorated foam materials, this initiative seeks to minimize environmental impact while leveraging their beneficial technical characteristics. Addressing issues related to foam degradation, this project endeavors to create sustainable solutions by reintegrating spent foam into new systems. This innovative approach promotes sustainability while enhancing safety through the provision of high-quality, impact-resistant elements. Ultimately, this work aims to contribute to environmental conservation and the advancement of effective impact protection measures in leisure facilities.

Study on Mechanical and Microstructural Evolution of P92 Pipes During Long-Time Operation

To investigate the mechanical properties and microstructure evolution of P92 steel during long-term service, the operated P92 main steam pipes from the first ultra-supercritical units in China were sectioned into samples representing various service durations and stresses (0# (as-received state, 1# (82,000 h, 67.3 MPa), 2# (85,000 h, 78.0 MPa), and 3# (100,000 h, 80.3 MPa)). Thereafter, a comprehensive assessment of their mechanical properties, including tensile strength, impact, hardness, and creep resistance, as well as a detailed microstructure analysis, was carried out. The effect of stress on the aging of material properties during operation is discussed. The results show that the circumferential stress caused by the increase in the internal steam pressure can significantly promote the creep life consumption of P92 steel, resulting in the degradation of mechanical properties and the expedited aging of the microstructure. The Rp0.2 and Rm of the P92 main steam pipe at room temperature and 605 °C decreased with the service time increase, reflecting the influence of stress in operation, which is expected to be used for the residual life evaluation of P92 steel. The relationship between the impact absorption energy (FATT50), Brinell hardness, and the operating time of P92 operating pipes is non-monotonic, indicating that these parameters are not sensitive indicators of material aging due to stress. The evaluation of performance degradation in P92 operating pipes due to stress-induced aging is not reliably discernible through optical metallography alone. To achieve a thorough assessment, the use of transmission electron microscopy (TEM) is essential.

Effect of heat treatment on microstructure and mechanical anisotropy of direct energy deposited Ti-6.0Al-2.5Nb-2.2Zr-1.2Mo alloy

Ti-6.0Al-2.5Nb-2.2Zr-1.2Mo alloy (Ti-6321) exhibits excellent corrosion resistance and impact toughness, which can be used as a deep-sea pressure-resistant hull. However, the alloy tends to have high strength but low plasticity, poor impact toughness, and anisotropic mechanical properties by fabricating by direct energy deposition (DED) technology. In order to improve the impact toughness of DEDed Ti-6321 alloy while reducing its anisotropy of mechanical properties, this study manipulates the microstructure and mechanical properties of the alloy through heat treatment. The research finds that with the increase of the single-stage annealing temperature within the (α+β) two-phase region, the width of the α phase increases, the Ultimate Tensile Strength (UTS) remains essentially unchanged, the Yield Strength (YS) decreases, and the impact absorption energy significantly improves. For double annealing heat treatment at two-phase region, temperature increase at the first-stage annealing enlarges the width and decreases the aspect ratio of the primary α phase. Leading to the decrease of the UTS & YS and increase of the impact absorption energy, with a conversely tendency at 1000 °C. The increase in the second-stage annealing temperature raises the size and volume fraction of the secondary α phase, causing the alloy's UTS and YS to initially rise then fall, with a slight increase in impact absorption energy. The anisotropy in the mechanical properties of DEDed Ti-6321 alloy mainly addressed from the different distribution of α phase orientations at different loading directions, and can be eliminated through sufficient β single-phase zone annealing.

Impact performance of egg‐box core sandwich panels made from sisal fibers and castor‐oil‐based polymer

AbstractDeveloping sustainable composites for engineering applications is essential for minimizing environmental impacts and ensuring the long‐term viability of infrastructure and technological advancements. In this context, this work focuses on the manufacture and evaluation of the structural integrity of a sandwich structure composed of aluminum faces and egg‐box‐shaped, sisal fiber‐reinforced epoxy (SFE) or castor‐oil polyurethane (SFC‐O) composites. The sandwich panel is filled with a biobased foam and subjected to dynamic load (drop‐tower) test. For comparison, the base materials SFE and SFC‐O molded into the egg‐box‐shaped cores are also evaluated using Charpy impact tests to establish a potential correlation between their Charpy performance and the drop‐tower behavior of egg‐box sandwich structures. The findings reveal that SFC‐O laminates demonstrate superior Charpy impact resistance (~49%) compared to SFE laminates. Similarly, sandwich structures composed of egg‐box‐castor‐oil composite cores absorb approximately 42.5% more energy than those made with egg‐box‐epoxy cores. The impact behavior of the sandwich structures correlates directly with the impact resistance of the sisal fiber laminates. Overall, the results indicate that the castor‐oil polymer can effectively replace the epoxy polymer matrix phase, enhancing impact absorption and providing an environmentally correct and sustainable solution for fabricating sandwich panels.Highlights Castor‐oil polymer provides laminates with lower density relative to epoxy. Sisal‐castor‐oil‐based laminates possess higher impact resistance than those based on epoxy. Sisal‐castor‐oil‐based panels achieve higher absolute and specific drop‐tower impact properties. Panels subjected to drop‐tower impact tests reveal skin delamination, wrinkling and indentation. Debonding between the foam and egg‐box core is a typical failure mode for epoxy sandwich panels.

Effect of Vinyl Acetate, Glass Fibers Contents, and Buffer Space on EVA's Mechanical Property and Shock Absorption Ability.

The aim of the study was to evaluate the mechanical properties and impact absorption capacity of prototype materials comprising ethylene vinyl acetate (EVA) of different hardness reinforced using different amounts of glass fibers (GFs), considering a buffer space. Six prototype materials were made by adding E-GFs (5 and 10 wt%) to EVA with vinyl acetate (VA) contents of 9.4 wt% ("hard" or HA) and 27.5 wt% ("soft" or SO). Durometer hardness and tensile strength tests were performed to evaluate the mechanical properties of the materials. Moreover, an impact test was conducted using a customized pendulum impact tester to assess the impact absorption capacity (with or without a buffer space) of the specimens. The mechanical properties of the prototypes, namely, durometer hardness, Young's modulus, and tensile strength, were significantly higher in the HA group than in the SO group, regardless of the presence or added amount of GFs. The addition of GFs, particularly in a large amount (10 wt%), significantly increased these values. In terms of the impact absorption capacity, the original hardness of the EVA material, that is, its VA content, had a more substantial effect than the presence or absence of GFs and the added amount of GFs. Interestingly, the HA specimens with the buffer space exhibited significantly higher impact absorption capacities than the SO specimens. Meanwhile, the SO specimens without the buffer space exhibited significantly higher impact absorption capacities than the HA specimens. Moreover, regardless of the sample material and impact distance, the buffer space significantly improved impact absorption. In particular, with the buffer space, the impact absorption capacity increased with the added amount of GFs. The basic mechanical properties, including durometer hardness, Young's modulus, and tensile strength, of the EVA prototype were significantly increased by reducing the amount of VA regardless of the presence or added amount of GFs. Adding GFs, particularly in large amounts, significantly increased the values of aforementioned mechanical properties. Impact absorption was significantly affected by the hardness of the original EVA material and enhanced by the addition of the buffer space. The HA specimen had a high shock absorption capacity with the buffer space, and the SO specimen had a high shock absorption capacity without the buffer space. With the buffer space, impact absorption improved with the amount of added GFs.

Effect of Low-Temperature Tempering Temperature on the Mechanical Properties of NM500 Wear-Resistant Steel

Abstract In order to explore the effect of low temperature tempering heat treatment temperatures on Brinell hardness (HB), impact absorption energy (KV2) and tensile mechanical properties of NM500 wear-resistant steel, isothermal tempering heat treatment of NM500 wear-resistant steel sheets after quenching were carried out at 200~260 °C. The microstructures, Brinell hardness, -20 °C impact energies and tensile mechanical properties of NM500 wear-resistant steel after tempered were analyzed by optical microscope, Brinell hardness tester, pendulum impact testing machine and tensile testing machine respectively. The results show that when the tempering temperature increases from 200 °C to 260 °C, the Brinell hardness of NM500 wear-resistant steel decreases from 490 HBW to 460 HBW, the offset yield strength (Rp0.2) decreases from 1396.3MPa to 1351.0MPa, and the tensile strength (Rm) decreases from 1708.5 MPa to 1615.0 MPa. However, the low temperature tempering temperature has no significant effect on the microstructure and elongation after fracture. According to GB/T 24186-2022, 200~220 °C is the suitable low temperature tempering temperature range for NM500 wear-resistant steel.

Characterization of the Aluminium-Based Metal Foam Properties for Automotive Applications

AbstractMetal foams are solids where the gas is filled inside uniformly in the metal matrix. Blowing agent supplies air inside the parent metal, and metal foam has emerged to be a promising material because of its low density, high absorption capacity, low thermal conductivity and high strength which finds its huge applications in automobile components. The present work deals with the application of the aluminium metal foam with different densities 200 and 400 kg/m3 in automobiles. Various tests such as toughness, hardness, bending and compression are carried out for four chosen densities, and the values are compared with the aluminium base metal. The result showed that the hardness value increased significantly by 24.48% with the rise in the density from 200 to 400 kg/m3. Maximum modulus of resilience for the low-density specimen is found to be 2.21 MJ/m3. Surface topography showed irregular pore shapes with discontinuity, resulting in a loss of cell integrity with the neighbouring cell walls. This affected the performance of the foam significantly. Thermal experiments were carried out to determine the thermal conductivity where thermal conductivity increased by 122% with the rise in the density from 200 to 400 kg/m3. Based on the results, it is concluded that aluminium foam with density 400 kg/m3 can be recommended for use in automobile applications due to its lightweight properties, which contribute to improving fuel efficiency, impact absorption capacity and the vehicle’s speed. Additionally, the air trapped within the foam cells serves as a sound barrier and insulator in cars.

Direct ink writing of non-sintered ceramic with biomimetic cellular structure

Cellular ceramics are highly valued for their exceptional mechanical properties and low density, making them suitable for applications like thermal insulation, impact absorption, and biomedical implants. However, high-temperature sintering required for densification can cause issues like shrinkage, loss of precision, and degradation of functional additives. This work reports a novel approach for fabricating 3D printed cellular ceramics under ambient conditions using CO2-cured γ-C2S ink via direct ink writing. The printed green body is converted into a dense matrix of CaCO3 and silica gel upon exposure to a CO2-rich environment without high temperature sintering. The non-sintered cellular ceramics achieve high compressive and specific strength comparable to sintered counterparts, with the square-shaped structure exhibiting the best performance of 104 and 171 MPa in terms of in-plane and out-of-plane compressive strength, respectively. Further, the in-situ analysis reveals distinct deformation modes and crack propagation patterns across structures, providing insights into structure-property relationships to guide the design of high-strength non-sintered cellular ceramics.

Effect of microstructure evolution on impact toughness in advanced ultra-high strength steel

The microstructure evolution and strength-toughness matching relationship of advanced ultra-high strength steel were studied under the tempering temperature range of 200–400 °C. The Charpy impact absorption energy of U-notch and V-notch focused on the crack initiation and crack propagation processes, respectively. The peak impact absorption energy of the U-notch appeared at 300 °C due to reduced stress concentration from low GND (Geometrically Necessary Dislocations) density. The optimal mechanical properties were found after tempering at 250 °C, where martensitic blocks hindered crack propagation, resulting in the peak impact energy of V-notch.

Towards greener wind power: Nanodiamond-treated flax fiber composites outperform standard glass fiber composites in impact fatigue tests

Wind energy is facing two major problems, recyclability of wind turbine blades, primarily made from fiberglass, and rain erosion on the blade’s leading edges. Here, we show that flax fiber reinforced epoxy composites have less impact fatigue damage than glass fiber (GF) composites made with the same resin. The novel treatment of flax with non-toxic nanodiamonds even boosts its outstanding performance. Nanodiamond-treated flax fiber (FFND) composites exhibit a damage incubation period up to 17 times as long as GF composites and have at least 74% less mass loss. This is connected to lower initial impact pressure, less shock wave reflections and better impact absorption of flax composites. The nanodiamonds act as fiber sizing, strengthening the fibers and their matrix interface. This delays fracturing and results in less erosion, making the biodegradable FFND a promising replacement for GF towards a fabrication of more sustainable and longer lasting wind turbine blades.

A minimalist elastic metamaterial with meta-damping mechanism

A novel elastic mechanical metamaterial with extreme damping performance has been achieved skillfully by coupling snap-through and pseudo-constant-force behaviors. The proposed meta-damping mechanism is systematically expounded to tailor synthetical force–displacement response for programming hyper energy dissipations. Within this framework, detailed designs in functional sub-structures and collaborative design strategy combined with parametric optimization in integrated structure are further presented synthetically. By additive manufacturing and loading–unloading cyclic experiments, the physical realization of meta-damping elastic metamaterials reveals the extraordinary specific damping capacity (Ψ=7.03), which exceeds any research reported previously and is immensely close to the theoretical limit. Remarkably, this minimalist design method, with only two necessary functional components, reconciles the contradiction between load-bearing and damping dissipation, with strong multi-directional and periodic expansibility. This work has far-reaching implications on the compact design of recoverability, reusability, frequency-independent, material-independent elastic mechanical metamaterials for superior dynamic applications such as impact absorption, vibration reduction, and energy trapping.

Effect of forefoot transverse arch stiffness on foot biomechanical response--based on finite element method.

The plantar vault, comprising the transverse and longitudinal arches of the human foot, is essential for impact absorption, elastic energy storage, and propulsion. Recent research underscores the importance of the transverse arch, contributing over 40% to midfoot stiffness. This study aimed to quantify biomechanical responses in the ankle-foot complex by varying the stiffness of the deep metatarsal transverse ligament (DTML). Using CT image reconstruction, we constructed a complex three-dimensional finite element model of the foot and ankle joint complex, accounting for geometric complexity and nonlinear characteristics. The focus of our study was to evaluate the effect of different forefoot transverse arch stiffness, that is, different Young's modulus values of DTML (from 135MPa to 405MPa), on different biomechanical aspects of the foot and ankle complex. Notably, we analyzed their effects on plantar pressure distribution, metatarsal stress patterns, navicular subsidence, and plantar fascial strain. Increasing the stiffness of the DTML has significant effects on foot biomechanics. Specifically, higher DTML stiffness leads to elevate von Mises stress in the 1st, 2nd, and 3rd metatarsals, while concurrently reducing plantar pressure by 14.2% when the Young's modulus is doubled. This stiffening also impedes navicular bone subsidence and foot lengthening. Notably, a 100% increase in the Young's modulus of DTML results in a 54.1% decrease in scaphoid subsidence and a 2.5% decrease in foot lengthening, which collectively contribute to a 33.1% enhancement in foot longitudinal stiffness. Additionally, doubling the Young's modulus of DTML can reduce the strain stretch of the plantar fascia by 38.5%. Preserving DTML integrity sustains the transverse arch, enhancing foot longitudinal stiffness and elastic responsiveness. These findings have implications for treating arch dysfunction and provide insights for shoe developers seeking to enhance propulsion.

DESCRIPTIVE OSTEOLOGY OF THE PELVIC LIMB OF EQUINE

The pelvic limb of equines performs vital functions such as weight support, locomotion, and impact absorption. Its main bones include the ilium, ischium, pubis, femur, patella, tibia, fibula, and the bones of the tarsus, metatarsus, and phalanges. The ilium, ischium, and pubis form the pelvis, which connects the limb to the trunk and supports the body’s weight. The femur, the largest bone of the limb, articulates with the pelvis and tibia, allowing for wide and powerful movements. The patella, located in front of the knee, facilitates limb extension. The tibia and fibula, situated in the leg, support and distribute weight, while the bones of the tarsus, metatarsus, and phalanges form the foot structure, essential for impact absorption and propulsion. Studying the osteology of the pelvic limb is fundamental for veterinarians and students, as it allows for a detailed understanding of the structure and function of the bones, facilitating the diagnosis and treatment of injuries, and improving animal management and welfare practices. However, detailed information on the osteology of the equine pelvic limb is scarce in scientific articles, being mostly dispersed in specialized books. This hinders quick and practical access to the necessary knowledge. Based on this, this article aims to fill this gap by offering a comprehensive and accessible description of the anatomy of the bones of the equine pelvic limb. By consolidating this information, it is hoped to contribute to the advancement of knowledge and the improvement of practices in the field.

Research on Auxetic Lattice Structure for Impact Absorption in Machines and Mechanisms

Research on Auxetic Lattice Structure for Impact Absorption in Machines and Mechanisms

Build and raster orientation effects on CFRP onyx/aramid impact absorption

Composite materials fabricated via additive manufacturing are becoming more relevant in ready-for use products used in engineering applications like aerospace structures, propellers, electric vehicles, or sandwich cores. Continuous Fiber Reinforced Polymeric (CFRP) composites are 3D-printed composites with tailor-made properties due to the capability of the printing process to deposit matrix and fiber whenever required. However, CFRP products behave differently and have lower mechanical properties than traditional composites. This study aimed to analyze the impact strength of CFRP specimens with gyroid infill and the effects of two build (flat and on-edge) and two raster (0° and 45°) orientations on impact behavior. The gyroid infill helps to obtain a light-weight structure and it has been used in energy absorption applications showing excellent mechanical behavior in thermoplastic 3D-products. The specimens were manufactured using Onyx as the matrix and aramid fiber as the reinforcement materials. The impact energy absorption of CFRP composites was measured using unnotched Izod impact specimens. The impact tests results were statistically analyzed, revealing that the build orientation directly and significantly affects the impact behavior, resulting in higher impact absorption when flat orientation is used to produce CFRP composites. The impact strength of CFRP composites increased 8 times, and 2 times for flat and on-edge oriented specimens, respectively compared to pure Onyx specimens. The variation in impact energy absorption between raster orientations in both build orientations was not significant, the difference in flat-oriented specimens at 0° and 45° was only 0.2 J, and between on-edge-oriented specimens at 0° and 45° was only 0.089 J. Also, the after impact specimens were analyzed to categorize the different failure modes observed. The after-impact analysis showed poor impregnation between aramid and onyx layers, causing delamination, fiber bridging, and fiber exposure failures. The combination of Aramid, Onyx, and a non-solid infill (gyroid) demonstrated positive results in impact behavior, obtaining high-impact absorption (165 kJ/m2) with no more than 56 % of fiver volume. The impact properties information of CFRP composites made with aramid fibers is still very scarce, joined to the lack of information on the impact properties of CFRP composites with non-solid infill, like gyroids or sinusoidal path infills. The results of this research open the possibility of using non-solid infill in CFR process that can be used to manufacture and test ready-for-use CFRP products in tasks that require high-strength, low-weight structures and impact energy absorption.

Topology optimised novel lattice structures for enhanced energy absorption and impact resistance

ABSTRACT This study evaluates topologically optimized lattice structures for high strain rate loading, crucial for impact resistance. Using the BESO (Bidirectional Evolution Structural Optimisation) topology optimisation algorithm, CompIED and ShRIED topologies are developed for enhanced energy absorption and impact resistance. Micromechanical simulations reveal CompIED surpasses theoretical elasticity limits for isotropic cellular materials, while the hybrid design ShRComp achieves theoretical maximum across all relative densities. Compared to TPMS, truss, and plate lattices, the proposed structures exhibit higher uniaxial modulus. Manufactured via fused deposition modeling with ABS thermoplastic, their energy absorption capabilities are assessed through compression tests and impact simulations. The ShRComp lattice demonstrates superior energy absorption under compression compared to CompIED. Impact analyses of CompIED and ShRComp sandwich structures at varying velocities show exceptional resistance to perforation and higher impact absorption efficiency, outperforming other classes of sandwich structures at similar densities. These findings position these new and novel topologies as promising candidates for impact absorption applications.

Intelligently optimized arch-honeycomb metamaterial with superior bandgap and impact mitigation capacity

Engineering applications concurrently face challenges related to vibration, impact, load-bearing and energy absorption. Here, an arch-honeycomb metamaterial with split-ring resonators is proposed for wave attenuation and impact mitigation, with better energy absorption and lower initial peak stress. The split-ring resonators effectively induce bandgaps below 3 kHz, and the mechanisms of bandgap generation and polarization are studied through mode shapes, frequency contours and equivalent mass densities. Subsequently, a machine learning-based optimization framework is introduced to tailor the bandgaps, leading to a 155.59% increase in bandgap width. Furthermore, superior vibration isolation and impact mitigation are confirmed through experiments. Obvious attenuation peaks are observed in the bandgaps of the acceleration transmission spectrum in frequency domain. In time domain, the impact test demonstrates peak weakening and delay. The metamaterials offer advantages in wave attenuation, impact mitigation, load-bearing and energy absorption, providing valuable insights for the advancement of multifunctional metamaterials and their practical engineering applications.