Ball Impact Test Research Articles

Rigid–flexible coupling design and reusable impact mitigation of the hierarchical-bistable hybrid metamaterials

Mechanical metamaterials with multistable unit cells featured by negative stiffness or quasi-zero stiffness is attracting increasing attention owing to their unique mechanical properties and reusable potential. In this paper, a hierarchical-bistable hybrid metamaterial with rigid–flexible coupling design is proposed, demonstrating excellent mitigation performance and protection against multiple impacts. The metamaterial consists of a multi-layer bistable beams with a central honeycomb and is manufactured by 3D printing. Firstly, the negative stiffness characteristics of the curved beams in the metamaterial are theoretically determined, and the convergence of the finite element model under different mesh sizes is analyzed. And the quasi-zero stiffness characteristics of the metamaterial have been confirmed, along with its more stable and uniform deformation pattern, through the quasi-static compression experiment. Then the buffering performance of the metamaterial is studied in ball impact tests, showing an average improvement of about 65% compared to the rigid control group, while verifying the accuracy of the finite element model. With the analysis of the deformation modes and strain energy, the mitigation mechanism of metamaterials is demonstrated to extend the contact time and disperse the impact load through the layered deformation to reduce the peak response, instead of relying on plastic strain. Finally, the reusability of the metamaterial is explored by the ten-times plate impacts simulation. The results demonstrate that the metamaterial decreases the plastic strain of its structure by 60% while reducing impact response, thereby preventing the premature failure of core components. These results demonstrate the great potential of the proposed metamaterials for various engineering applications, including aircraft or spacecraft landing protection, vehicle pedestrian protection, and the transportation protection of fragile objects or precision instruments.

Preparation of high-performance laminated glass interlayer by modifying epoxy resin composite polyurethane

Laminated glass has been widely used in glass curtain walls, windshields, and other structures due to its high safety, light weight, and aesthetics. The safety of polymer laminated glass depends on the performance of the polymer between the glasses. Polyurethane elastomer (PU) has become a universal polymer material due to its excellent mechanical strength and toughness. The aliphatic thermoplastic polyurethane has attracted people's interest about its application in the field of laminated safety glass due to its transparency and adhesion. In this work, a polyurethane-modified epoxy (EK-PU) composite film with superior bonding strength, mechanical properties, and transparency was successfully achieved. The tensile strength of the PU composite film was confirmed to be 45 MPa, while the bonding strength was 4.73 MPa. The improvement is attributed to the change of microphase separation structure and the introduction of silicone. The excellent impact resistance of the laminated glass based on polyurethane composite film have been confirmed by the falling ball impact test, which is 6.5 times of the common PU film. The laminated glass based on the EK-PU film will be applied in aerospace, defense, and automotive fields.

Strength Enhancement of Polyurethane Film by Solution Annealing.

Recently, polyurethane elastomer (TPU) has attracted more and more attention depending on its excellent optical, mechanical, and retreatment properties. The high strength of polyurethane has always been pursued, which can enable its application in more fields. In this work, an aliphatic polyurethane elastomer membrane (HRPU6) was successfully synthesized, and its strength was obviously improved by solvent annealing technology. The tensile strength and adhesion strength can reach 64.56 and 2.58 MPa, but 36.55 and 1.57 MPa only before solvent annealing, respectively. The impact strength of laminated glass based on HRPU has also been significantly improved after solvent annealing, confirmed through drop ball impact testing. It has been confirmed that the increase in strength of HRPU6 is attributed to the enhancement of hydrogen bonding and the improvement of the phase separation degree.

Sound insulation enhancement of polyvinyl butyral film by blending polyurethane and its laminated safety glass

Laminated glass based on PVB film is widely used in military industry and life depending on its excellent safety performance. However, the insufficient sound insulation performance of PVB film restricts its practical application and has gained much more attention. In this work, a PVB-TPU composites with high strength and excellent sound insulation acoustic performance was designed by melt blending method which is attributed to their molecular entanglement and hydrogen bonding interactions between PVB and TPU molecule chains. It has been showed that the maximum tensile strength and elongation at break of the PVB-TPU blending film reached 34 MPa and 235 % respectively when 10 wt% content of TPU in the system. In addition, 20–41 dB of the sound transmission loss (TL) for the composite film with 1 mm thickness in the range of 2000–6000 Hz was achieved, which was obvious enhanced compared with the existing laminated glass intermediate film. The high impact resistance of the laminated glass based on the PVB-TPU film was confirmed by the falling ball impact test. The high sound insulation and safety laminated glass prepared here will be widely used in more fields.

Waste natural fibers for polymer toughening and biodegradability of epoxy-based polymer composite through toughness and thermal analysis

Polymeric materials are being increasingly used to replace many metallic components due to their beneficial properties such as higher strength-to-weight ratio and corrosion resistance. However, the widespread use of polymers poses a risk to the environment as they are not biodegradable. The addition of the waste jute fiber and sawdust fiber as reinforcement to the epoxy resin improved its toughness and induced the biodegradability of the polymer. To examine the effect of the jute fiber and sawdust fiber on biodegradability, the composites were then kept in the drainage system for one year, and the impact energy and fracture morphology of the as-cast and weathered samples were examined using a drop ball impact test and a Charpy impact test. During the weathering period, weight gain was initially observed due to the water absorption by the porous fibers, but after three months, the composites started to lose weight due to the degradation of the fiber by swelling and microbial attacks. Microorganisms in the drainage system used the fiber as their energy source, which resulted in the deterioration of the fiber and the production of CO2. The production of CO2 was identified by the FTIR analysis of the weathered composite samples. TGA analysis of the as-cast and weathered samples reveals the reduction of the onset thermal degradation temperature of the weathered composites due to the degradation of the composites. The fiber disintegrated through microbial attack and the fiber swelling caused by the absorption of water by jute fiber and sawdust fiber is identified through SEM imaging. The SEM image also reveals the formation of biofilms and the growth of microorganisms at the fibers. A higher growth rate of the microorganisms was observed in the jute fiber composite than in the sawdust fiber composite, as sawdust contains a high level of lignin that protects it from degradation. The results of this study suggest that both sawdust fiber and jute fiber composites induce biodegradability in the epoxy matrix, but jute fiber was more prominent in this regard. The discovery paves the way for using natural fibers in biodegradable polymer composites, reducing polymeric pollution in the environment.

Preparation and application of high sound insulation polyurethane composite film through glass fiber reinforcement

AbstractLaminated glasses have been widely used in buildings, physical protections, and vehicles because of their safety, sound insulation, thermal insulation, and other performance. In recent years, the high sound insulation performance of laminated glass intermediate films in the frequency range of low or high frequencies has attracted more and more attentions. In this work, a glass fiber/polyurethane elastomer composite (PU‐MGF) film with high transparency and impact resistance has been successfully synthesized, 5 dB of the transmission loss increased at 1600–6000 Hz, and 3.6 dB increased at 63–1600 Hz compared with the control polyurethane film. This is a significant progress in the laminated glass industry. In addition, the transmittance of the composite reaches over 75%. The excellent impact resistance of the laminated glass, based on PU‐MGF film, has been confirmed through falling ball impact test, demonstrating its ability to withstand multiple impacts without spattering. The PU‐MGF film prepared in this work exhibits great potential for applications in building windows, transportation, and soundproof devices.

Sound insulation enhancement of PVB/PVDF film by adding LiCl

Polyvinyl Butyral (PVB) has been widely used in laminated glass depending on its excellent adhesion, impact resistance, and transmittance. However, it will provide a quieter environment if its sound insulation characteristics can be improved, especially in the mid to low frequency range. In this paper, PVB/PVDF composite film was prepared by electrostatic spinning and hot pressing. By adding 0.1 % LiCl, the β-phase content and the output voltage of PVDF were increased 15 % and 47 %, respectively. The average transmission loss of PVB/PVDF film has been enhanced for 4.4 dB at 64–1600 Hz. It is attributed to the enhancement of piezoelectric properties of PVDF films by adding LiCl. Moreover, the transmittance and impact resistance of the laminated glass based on PVB/PVDF/LiCl have been confirmed by UV–vis and falling ball impact test.

An ingenious composite microstructure of mantis shrimp appendage for improving impact resistance

Mantis shrimp appendage, as an important weapon for hunting, have remarkable impact resistance due to their unique microstructure. In this study, the appendages were subjected to falling ball impact tests and their fracture surfaces were observed by scanning electron microscopy. It was observed that the outer layer was prone to brittle fracture, while the inner layer was more flexible and turned the brittle fracture into a ductile fracture. Our study supported the idea that the unique microstructures in the appendages act as barriers against crack growth and therefore play a leading role in the toughening of the entire appendage structure. Based on the bionic inspiration of the appendage microstructure, a bionic composite structure was designed, which consists of a rigid outer layer and a flexible inner layer. The fibers in the flexible layer show a longitudinal and sinusoidal arrangement to provide shielding to the crack tip when the fracture occurs. The toughening mechanism of the microstructure was further corroborated through finite element simulations, which demonstrated that the longitudinal arrangement of fibers played a pivotal role in spreading stress concentration and thereby delaying the fracture process. The sinusoidal arrangement of fibers was also found to be instrumental in not only bridging the rigid and flexible layers, but also in directing the deviation of the crack path. This work was enlightening for the structural design of impact-resistant composites.

Dynamic Response Study of Piezoresistive Ti3C2-MXene Sensor for Structural Impacts.

MXenes are a new family of two-dimensional (2D) nanomaterials. They are inorganic compounds of metal carbides/nitrides/carbonitrides. Titanium carbide MXene (Ti3C2-MXene) was the first 2D nanomaterial reported in the MXene family in 2011. Owing to the good physical properties of Ti3C2-MXenes (e.g., conductivity, hydrophilicity, film-forming ability, elasticity) various applications in wearable sensors, energy harvesters, supercapacitors, electronic devices, etc., have been demonstrated. This paper presents the development of a piezoresistive Ti3C2-MXene sensor followed by experimental investigations of its dynamic response behavior when subjected to structural impacts. For the experimental investigations, an inclined ball impact test setup is constructed. Stainless steel balls of different masses and radii are used to apply repeatable impacts on a vertical cantilever plate. The Ti3C2-MXene sensor is attached to this cantilever plate along with a commercial piezoceramic sensor, and their responses for the structural impacts are compared. It is observed from the experiments that the average response times of the Ti3C2-MXene sensor and piezoceramic sensor are 1.28±0.24μs and 31.19±24.61μs, respectively. The fast response time of the Ti3C2-MXene sensor makes it a promising candidate for monitoring structural impacts.

Dynamic mechanical properties, interface structure evolution and deformation behaviors of PVA-carbon fiber reinforced concrete with negative Poisson’s ratio design

Based on the advantages of negative Poisson's ratio (NPR) materials in controlling deformation and absorbing energy, this paper combines NPR design with the preparation of fiber reinforced concrete (FRC) to optimize the anti-dynamic load performance of FRC. In this paper, a helical auxetic yarn (Hay) with NPR effect is obtained by wrapping carbon fiber (CF) on polyvinyl alcohol fiber (PVAF) at a certain angle, and it is mixed into concrete in different forms to obtain auxetic fiber concrete. In order to explore the influence of auxetic fiber on the anti-dynamic load performance of concrete, split Hopkinson pressure bar (SHPB) test and dropping ball impact test are carried out on different FRC. The impact resistance of FRC under different impact velocities is tested, and the impact resistance behavior of FRC is analyzed by digital speckle correlation method (DSCM). The results show that in SHPB test, the anti-impact strength of the layered auxetic fiber concrete is 19.1 % higher than that of the plain concrete (PC), and its fracture energy is increased by 25.8 %. In the dropping ball impact test, its fracture energy is 5 ∼ 9 times that of PC. In addition, the results of scanning electron microscopy (SEM) and DSCM test show that the incorporation of auxetic fiber has a positive effect on improving the generation and development of internal cracks in concrete, which is expected to provide a reference for the application of NPR materials in explosion resistance, penetration resistance and impact resistance of building structures.

Photochromic safety-glass based on polyurethane interlayer film blend with perovskite quantum dot

In recent years, photochromic glass has been widely used in smart windows, depending on its thermal insulation, concealment and intelligent controllability. However, the safety requirements of photochromic glass are still one of the problems to be solved in practical applications. In this work, a photochromic composite film based on polyurethane/perovskite quantum dots (HPU) has been got by casting blending extrusion process. Then laminated safety glass based on the HPU intermediate films are constructed by hot pressing process, the glass of which shall be coated with a layer of acrylate hot-melt adhesive (PA) before use. Under ultraviolet light, it can be displayed in green from colorless within 0.5 s, and transmittance of laminated glass is almost the same as that of single-layer glass under natural light. The safety of laminated glass based on the glass/PA/HPU/PA/glass structure is evaluated by falling ball impact test. There are no glass fragments falling off and splashing when they are impacted by a 50 g of steel ball falling freely from a height of 1 m. The excellent environmental stabilities have been confirmed by fluorescence spectrum tracking. The intelligent photochromic safety-glass mentioned in this work has great application potential in the fields of building windows, automotives and optical devices.

Optimal Mixture of Materials and Condition in Producing Flat Glasses for Automobile Windscreens in Nigeria

The selection of materials is an essential element for engineering designers. This study investigated the optimal mixture of materials and condition in producing flat glasses for automobile windscreens in Nigeria. To achieve this, 10 pairs of compositions of material mixtures and cullet (broken glasses) were used. The standard material mixture (80/20 wt. % of material mix/cullet) from the local industry was modified to have batches of up to 60/40 wt. % material mix/cullet. These material mixtures were used to produce flat glasses by adopting procedures of industrial float glass process of Pilkington Brothers in variable conditions of annealing temperature and time. The average density of each pair of flat glass was measured using water displacement method, and each pair was later laminated to produce a total of 10 automobile windscreens. The windscreens were subjected to 2.25kg drop ball impact test from a height of 4m at 900. The study revealed that the density of the flat glass produced was significantly (p< 0.01) related to squared composition (wt. %) of cullet (R2=97.65%). The highest and lowest densities of 2.23g/cm3 and 1.95g/cm3 were obtained at cullet inclusions of 40 wt. % and 20 wt. % respectively at constant annealing temperature (5500C) and time (60 min). The optimal batch obtained composed of 40 wt. % cullet inclusion, annealed at 5000C for 50 minutes. Increased cullet composition was found to reduce the melting temperature of the batch mixture and fractured characteristics of the windscreens produced. Employing this design in the windscreens manufacturing industry saves production cost, facilitates a competitive market, enhance the quality of windscreens, reduce emissions and curb environmental degradation.

Experimental Study on the Vibration Reduction Performance of the Spindle Rotor of a Rubbing Machine Based on Aluminium Foam Material

Larger vibration and noise often exist in agricultural machinery due to the harsh working environment and high power. The rubbing machine is one of the indispensable pieces of equipment in the agriculture and livestock industry, and it is affected by the vibration of large constraints on its promotion and use. To reduce the vibration of the rubbing machine, the vibration characteristics of the spindle rotor were first analysed by modal simulation, thus determining the larger contributions to the spindle rotor vibration. Second, aluminium foam material was installed in the large deformation part of the spindle rotor. Its vibration reduction and energy absorption characteristics were used to optimise the vibration reduction design by increasing the damping. Third, a steel ball impact test was conducted to analyse the vibration characteristics of the optimised spindle rotor. The results show that the maximum impact accelerations were reduced by 28.4% and 64.75% in the axial and radial directions, respectively, and the impact energies were reduced by 67.3% and 90.65% in the axial and radial directions within 2 s of impact collision, respectively, indicating that the optimised spindle rotor damping increased significantly. In addition, the vibration reduction effect of the optimised rubbing machine was verified by a bench test. By measuring the change degree of the static component of the spindle rotor vibration, the axial, radial, and vertical vibrations of the spindle rotor were improved by 5.78%, 10.32%, and 23.96%, respectively. Therefore, optimising the spindle rotor with aluminium foam material can reduce the vibration generated during the impact of the material on the spindle rotor. The rubbing machine’s vibration, damping, and energy absorption were also realised in real working conditions.

Identification Method for Material Constants in Johnson–Cook Model Associated With Strain-Rate and Temperature Sensitivities Using Ball Impact and Indentation Tests

Abstract The Johnson–Cook (JC) flow stress model can simply express the strain-rate and temperature dependencies of the flow stress. We previously proposed a concept of a simple identification method for material constants in the JC model associated with the strain-rate and temperature sensitivities (JC parameters C and m) at high-strain rates. However, several issues still exist in our method for practical use. In this study, we modified our method to identify both the JC parameters C and m. The fundamental concept was formulated based on the requirement that the normalized indentation depths obtained from the ball impact and instrumented ball indentation tests are equal to each other. In addition, the conversion factor was derived to transfer from the impact velocity to the strain rate. The ball indentation and impact analyses based on a finite element method were conducted to verify the established method. The analysis results obtained under idealized conditions demonstrated that C and m can be accurately identified using the established method, even at exceeding 104 s−1. Changes in the radius of the impactor are more effective in obtaining different strain rates than changes in the impact velocity because the identification accuracy can be ensured at lower than 200 m/s.

Modeling of Falling Ball Impact Test Response on Solid, Veneer, and Traditional Engineered Wood Floorings of Several Hardwoods

Hardness is a key mechanical property of flooring materials. In this study, the performance of veneer floorings (with a top layer thickness of 0.6 mm) was investigated by dynamic hardness tests, comparing it with those of traditional engineered wood floorings (with a top layer thickness of 3 mm) and solid wood floorings. Two hardwoods commonly used on wood flooring, viz. Quercus robur L. and Hymenaea courbaril L., and two fast-growing hardwoods, Eucalyptus globulus Labill. and Eucalyptus grandis W. Hill ex Maiden, were tested as top layers. To compare their usage properties, a dynamic impact hardness test involving steel balls with three diameters and five different drop heights was carried out, measuring the footprint diameter (FD) and the indentation depth (ID). The data from 4800 impacts, corresponding to 180 different individual groups (4 hardwood species × 3 ball diameters × 5 drop heights × 3 floor types) were analyzed. The results showed that the general response in terms of both FD and ID was better in the engineered wood floorings than in solid wood floorings, and that the veneer floorings (0.6 mm) showed better behavior than traditional engineered wood floorings (3.0 mm). Furthermore, for the veneer floorings, the two fast-growing hardwood species tested, which have significantly different densities, showed similar behavior to traditional hardwoods, suggesting that they would be suitable for valorization in the wood flooring industry.

Preparation of biological antifreeze protein-modified emulsified asphalt coating and research on its anti-icing performance

Natural organisms use their own biological antifreeze proteins (AFP) to cope with cold environments. Based on this natural phenomenon, we herein use biological AFP and asphalt-based materials to prepare road anti-icing coating materials and subsequently study its storage stability and anti-icing performance. The storage stability test, fluorescence microscope analysis, scanning electron microscope analysis, and infrared spectrum analysis demonstrated that when the AFP powder content was not more than 5%, it was evenly dispersed in the emulsified asphalt, had good stability, did not undergo a chemical reaction, and retained the molecular activity of AFP. Combined with the anti-icing, pull-out, and falling ball impact tests, the addition of biological AFP powder demonstrates obvious anti-icing performance; furthermore, with an increase in the powder content, the anti-icing effect is improved. The road performance test showed that the coating had good durability and spalling resistance. When the spraying amount of the coating on the asphalt pavement is ≤ 0.4 kg/m2, the BPN value and TD value meet the requirements of the specification. The application of a biological AFP-modified emulsified asphalt coating can significantly improve the anti-icing performance of roads and does not harm ecological environments.

Proposal of estimation method for strain rate dependency of flow stress based on ball impact test

Proposal of estimation method for strain rate dependency of flow stress based on ball impact test

Lipophilic modification of T-ZnOw and optical properties of T-ZnOw/PVB composite films

In order to protect the articles in buildings from ultraviolet radiation and save air-conditioning energy, polyvinyl butyral laminated glass are employed and produced in large quantities. Several inorganic particles with blocking effect have been doped into PVB, such as TiO2, ZnO, and ATO. T-ZnOw is a widely used functional structural material with excellent absorption properties. Herein, T-ZnOw was lipophilic modified with silane coupling agent KH-570, and T-ZnOw/PVB composite films were prepared via subsequent solution blending. As per the FTIR spectrum, a characteristic peak of Si–O–Zn at 1165 cm−1 was observed, indicating that T-ZnOw was successfully modified by KH-570. T-ZnOw before and after modification was separately mixed with the St/H2O mixed solution. The modified T-ZnOw could be dispersed in styrene instead of water, displaying a certain lipophilicity. On the other hand, from a microscopic perspective, the SEM images suggest that filling the filler in the form of a suspension can disperse the modified T-ZnOw in PVB in an independent four-needle form, which contributes toward improvement of the agglomeration of T-ZnOw in the PVB matrix. The UV–Vis–NIR spectrum shows that the addition of T-ZnOw reduced the UV transmittance of T-ZnOw/PVB composite films from 50.84 to 25.77%, resulting in a decrease in near-infrared transmittance from 82.14 to 43.22%. The ultraviolet and near-infrared light barrier properties of composite films were more than twice that of the ordinary PVB films. Moreover, the modified T-ZnOw endowed composite films with stronger ultraviolet light and near-infrared light-blocking properties, or better visible light transmittance. And the falling ball impact test proved that there was no clear relationship between the thickness of the film and the adhesion. This work proposes a new solution and preparation method for the production of energy-saving glass. Therefore, it is expected that using composite films instead of traditional PVB films to make laminated glass can greatly contribute toward energy conservation and environmental protection.

Elastic Wave Attenuation Characteristics and Relevance for Rock Microstructures

We investigated elastic wave attenuation characteristics using a PCI-2 acoustic emission system. A lead-break test was employed to carry out attenuation experiments in granite, marble, red sandstone, and limestone. Because the centroid frequency variation of the red sandstone differs significantly from the other rocks, a pendulum steel ball impact test was also performed to study the attenuation characteristics of elastic waves in red sandstone. The results show that the elastic wave signal amplitude decreases with increasing propagation distance for all four rock types. In granite and red sandstone, the peak frequency of the elastic wave declines abruptly after the propagation exceeds 800 and 100 mm, respectively, and remains almost unchanged in marble and limestone. The attenuation of centroid frequency in granite, limestone, and marble shows the same trend; however, in red sandstone, when the elastic wave propagation exceeds a certain distance, the variation of centroid frequency shows an upward tendency. The main influence of elastic wave attenuation in rock is the packing state of mineral particles: less tightly packed rocks consistently have a higher attenuation coefficient. The secondary cause of attenuation is the development of structures such as joints and stratifications. More developed interior structures lead to higher attenuation coefficients. Sensor selection is also very important in rock attenuation tests. We recommend use of a wide resonant frequency sensor or sensors with different resonant frequencies along the elastic wave propagation path.

Hybrid woven carbon-Dyneema composites under drop-weight and steel ball impact

In this study, the impact behavior and damage mechanism of novel carbon-Dyneema hybrid fabric reinforced plastic composites are investigated using drop-weight and steel ball impact tests. The force-displacement response, energy absorption and damage mechanisms of the hybrid composite were analyzed and compared with those of woven carbon laminates. The experimental results suggest that the impact resistance of the hybrid composites has been improved when benchmarked with carbon fiber composites. The Dyneema fibers suppress the splitting of bottom surfaces during impact but are susceptible to buckling due to the low compressive strength of Dyneema fibers. A multi-scale approach is proposed for modelling impact damage of hybrid woven composite accounting for the interweave patterns. A meso-scale representative volume element of the interwoven hybrid structure is analyzed and discretized into several sub-sections, each regarded as a type of laminate. Then, a macro-scale impact model is established based on the homogenized effective properties of the sub-sections using continuum shell elements. The failure of the material is modelled using energy-based continuum damage mechanics. Overall, the numerical simulations show good agreement with experimental data in terms of impact force history and damage features, providing insight into the impact damage behavior of hybrid composites.