Drop Weight Impact Research Articles

Repeated impact behavior of preplaced aggregate concrete incorporating different fiber types

This research used an experimental approach to examine the impact performance of preplaced fibrous aggregate concrete with various fibre types. Four concrete mixtures were produced with identical quantities except for the type of fiber. The first reference mixture was plain, while the other mixtures were reinforced with 2.5% of polypropylene fibers (PP), short steel fibers (SF1) and long steel fibers (SF2). In accordance with the ACI 544-2R impact test method, six cylindrical discswere tested from each mixture using drop-weight impact loading. The tests' results revealed that adding fibre, irrespective of the type of fiber used, considerably enhanced the impact strength at the cracking (Ncr) and failure (Nf) phases. Compared to their plain concrete specimens, fibrous specimens showed increased Ncr ranging from 395 to 655% and Nf from 727 to 1973%. Steel fibers exhibited higher impact strength by 33 to 151% and higher ductility by 44 to 64% compared to PP fibers. Besides, a longer steel fiber performed better under impact loads than shorter steel fibers, where Ncr and Nf were higher by 14 and 31%, respectively.

Experimental Research on the Impact Resistance of Partially Precast Concrete Beams Strengthened with Bonded Steel Plates

A structure may be exposed to a range of unexpected loads throughout its full life cycle. Partially precast concrete (PC) beams refer to the process of manufacturing concrete beams in which one part of the component is pre−fabricated in a factory and the other part is completed at the construction site. Through the test, it is possible to better ensure the safety and dependability of the PC composite beams under impact load by examining the reinforcement effect, structural toughness, and damage mode of PC composite beams with bonded steel. Additionally, a scientific basis and practical guidance are provided for the actual project. Their impact resistance can significantly affect the overall safety of a structure when subjected to an impact load. Three of the four PC beams used in this investigation were strengthened with steel plates. Residual flexural bearing capacity tests and drop weight impact tests were then conducted. The impacts of steel plate thickness and U−shaped steel plate hoops on the failure mechanism and dynamic response of the component were investigated. The dynamic responses obtained from the experiments included the displacement–time history curve, impact force, and support reaction force. In order to explore the failure mechanism of the partially precast beam during the impact process, a staged analysis was conducted based on the failure mode and dynamic response characteristic values of each curve. Residual flexural bearing capacity tests were used to examine the residual flexural bearing capacity of PC beams strengthened with bonded steel plates. The results of the research reveal that the failure mechanisms of each test beam are bending–shear failures. With the increase in bonded steel thickness, the peak mid−span displacement reduced by 6.55%, the residual mid−span displacement decreased by 29.53%, and the residual flexural bearing capacity improved by 25.02%. With the adoption of U−shaped steel plate hoops, the residual flexural bearing capacity significantly increased while the peak mid−span and residual mid−span displacements both decreased.

Experiment and Numerical Simulation on Damage Behavior of Honeycomb Sandwich Composites under Low-Energy Impact

It is well-established that the honeycomb sandwich composite structures are easily prone to damage under low-energy impact. Consequently, it would lead to a dramatic decrease in structural load-bearing capacity and a threat to overall safety. Both experimental and numerical simulations are carried out to investigate the impact damage behavior of honeycomb sandwich composite specimens. The damage mode, damage parameters, and contact force-time curves of three types of panel materials with T300, T700, and T800 are obtained under different impact energies of 10 J, 20 J, and 40 J by the drop-weight impact experiment. Moreover, digital image correlation (DIC) tests are used to measure the deformation and strain of the lower panel. The experimental results reveal that the degree of damage increases with increasing impact energy. Particularly, the T300 panel specimen exhibits visible fiber fracture when subjected to an impact energy of 40 J. The impact process involves matrix cracking, fiber fracture, and delamination of the upper panel occurring first, followed by immediate crush damage to the honeycomb core and, finally, slight fiber damage to the lower panel. Due to its higher strength, the T800 panel specimen exhibits the highest damage resistance compared to the T700 and T300 panel specimens. To consider the microscopic failure criteria and various types of contact during the impact process, a finite element model of honeycomb sandwich composites is established, and numerical simulation analysis of low-energy impact is performed to determine the damage mode, damage size, and contact-force curves. Comparative analysis demonstrates good agreement between the simulation and experimental results. The findings of this study provide valuable technical support for the widespread application of honeycomb sandwich composites in the aviation field.

Static properties and impact resistance performance of U-shaped PU-modified concrete under repeated drop-weight impact load

Static properties and impact resistance performance of U-shaped PU-modified concrete under repeated drop-weight impact load

Experiment and analysis of drop-weight damping control of MR semi-active impact resistance-based hydraulic actuator

The impact vibration caused by sudden changes in the external load of hydraulic actuators reduces the service life of hydraulic components and limits the high-precision applications of hydraulic actuators. Therefore, to improve the underdamped characteristics and impact resistance of valve-controlled cylinder systems, a semi-active impact resistance control of hydraulic actuator based on magnetorheological damper (MRD) is proposed. Firstly, based on the shear force characteristics of magnetorheological fluid, a multi-stage flow channel MRD is designed, which is connected in series with the hydraulic actuator to form a hydraulic damping actuator (HDA). Meanwhile, based on the mechanical experimental data, the parameters of MRD dynamic model are identified to ensure the accuracy of MRD output force. Secondly, a drop weight impact model is established, and a sliding mode controller which can track the command current in real time is designed, so as to realize the resistance force coupling between the MRD and the hydraulic actuator for improving the impact resistance control effect. Then the dynamic performance test and impact resistance simulation program are established to verify the excellent dynamic performance and impact resistance effect of the HDA with the sliding mode control. Finally, the drop weight impact experimental platform is built. The experimental results show that under the impact with a height of 200 mm, the dynamic offset of the HDA is only −1.25 mm, and the time to return to the original position is 0.08 s, which validate the excellent performance of the proposed scheme in improving the underdamped characteristics of the valve-controlled cylinder system and the dynamic response performance of the hydraulic actuator.

Full-field deformation and failure analysis for compression after impact of carbon fibre reinforced polymer laminates

Residual compressive strength after impact is a critical design factor in assessing damage tolerance of carbon fibre-reinforced polymers (CFRP) for structural applications in aircraft. This study investigated compression after impact (CAI) performance of quasi-isotropic CFRP laminates by measuring 3D deformation and strain using three-dimensional digital image correlation (3D DIC). Before the CAI, these test panels were subjected to drop-weight impact testing with energy levels representing visible impact damage (VID). During the CAI testing, deformation behaviours throughout the full loading sequence were captured by twin-camera imaging systems at the front and back faces of panels at standard speed. A single-camera high-speed imaging system captured ultimate failure behaviours at the sample front face. The single-camera high-speed system used four planar mirrors to achieve 3D DIC measurements. This study investigated the effect of boundary conditions on the compressive behaviours of the test panels, where the effect of additional support plates at the front and back surfaces to reduce the unsupported area was compared with the boundary condition of standard anti-buckling guides. The panels with added supports were found to experience deformations dominated by local buckling and final out-of-plane displacements in an S-shaped profile. These panels also exhibited residual strength reductions correlating to impact damage levels and ultimate failure initiating at the damaged region and propagating rapidly along the transverse axis. In comparison, the panels without added supports exhibited failure dominated by global buckling as manifested by large out-of-plane displacements, which had an arc-shaped profile. The DIC measurements were compared against those of mounted biaxial strain gauges. The single-camera high-speed system was shown not only to be feasible for high strain rate testing applications; it also offered a significant cost saving compared to an equivalent twin-camera high-speed system.

Mechanical properties of sustainable concrete comprising various wastes

Due to the rapid increase of pollution around the world, the disposal of waste materials such as granite powder (GP), iron powder (IP), brick powder (BP), and waste plastic particles (PP) is a major environmental problem in the entire world. Utilizing these industrial waste materials has many advantages for the construction industry regarding cost-effectiveness and the sustainability of natural resources. This investigation examined the addition of GP, IP, BP, and PP as a fine aggregate with ratios of 5%, 10%, 15%, and 20% of sand in producing and assessing sustainable concrete. The static properties, i.e., compressive, tensile, flexural strength, and dynamic properties using the drop-weight impact test, were evaluated of such materials. The results showed that using IP as a partial replacement enhances both static and dynamic properties of concrete; the enhancement kept increasing up to 20% of IP, and the compressive, tensile, flexural strength, and impact energy increased by 8.4%, 12.5%, 8.5, and 125%, respectively. Therefore, IP can be suggested to replace sand by up to 20%. Using PP up to 15% enhanced the impact energy at failure by about 225%. It also observed that the optimum value for GP and BP was 10%. When using 10% GP the increase in the compressive, tensile, flexural strength, and impact energy was 11.7%, 25%, 21.5%, and 100%, respectively, while it increased by 12.9%, 7.6%, 15.4%, and 63% respectively when using BP.

Impact behavior of high-strength steel beam with circular web openings

A drop-weight impact testing machine was used to conduct an impact test on 9 specimens in order to examine the impact resistance of high-strength steel beams with circular web openings (HSSBCWO). The experimental results indicated that the dynamic response of HSSBCWO is significantly affected by the change of impact energy and opening height. A coefficient β is proposed to assess the severity of localized deformation in HSSBCWO, and the range of β values for the specimens of test are found to be approximately between 0.5 and 0.8. Within the range of impact energy designed for the experiment, HSSBCWO primarily absorbed energy through localized plastic deformation. A finite element model which can predict the dynamic response of HSSBCWO under impact load is established. The results show that the optimal ratios of opening height to beam height and spacing between openings to beam height for the HSSBCWO are determined to be 0.50 and 0.93, respectively. Furthermore, a damage evaluation system for HSSBCWO under impact load was established, utilizing the ratio of mid-span residual displacement to calculated beam span Dr / L0 as the damage assessment index, with impact energy, opening height, and spacing between opening as the main control parameters.

Compressive strength and impact strength of preplaced aggregate fibre reinforced concrete

A new form of concrete composites known as prepacked aggregates fiber reinforced concrete (PAFRC) has recently attracted the research community's attention. Preparing PAFRC involves inserting and packing coarse aggregate fibers in a mold. Afterward, a cement grout that has a high flowability is injected into the gaps between the particles to complete the construction. This study aimed to examine PAFRC's resistance to impact using a drop weight impact test. Four mixtures were prepared with three different dosages (1, 3 and 5%) of steel fibres. All of the specimens were put through an impact test as per the recommendations of the ACI Committee 544. The impact resistance of PAFRC specimens dosed with 1, 3, and 5% steel fibres was increased by 7.86, 20.64, and 30.57 times, respectively, compared to those without fibres. The information that was gleaned from this analysis serves as a baseline for more extensive scientific research into PAFRC when it is being affected by an impact.

Investigating the Mechanical and Durability Properties of Geopolymer Concrete Based on Granulated Blast Furnace Slag as Green Concrete

Geopolymer concretes (GPCs) are known as green, environmentally friendly, sustainable concretes in the development of the structural industry with superior mechanical performance and durability compared to ordinary Portland cement concrete (OPCC). This type of concrete emits less CO2 than OPCC and aims for efficient waste management while reducing environmental impacts. In this experimental research, 5 mixed designs were made of GPC based on granulated blast furnace slag (GBFS), which contains 0-8% Nano silica (NS) and 1-2% polyolefin fibers (POFs). A mixed design was also made of OPCC to compare with GPC. The tests of compressive strength, tensile strength, drop weight impact (DWI), Ultrasonic Pulse Velocity (UPV), water permeability and microstructural examination by scanning electron microscope (SEM) images and X-ray fluorescence (XRF) spectroscopy were performed on concrete samples and the results were analyzed and compared. The results obtained in this laboratory research, while overlapping with each other, indicate the superiority of mechanical properties and durability of GPC compared to OPCC.

Cost-Effective Engineered Cementitious Composites with Hybrid PVA and Basalt/PP Fiber: A Study on Compressive, Tensile and Impact Performance.

Currently, oil-coated PVA fibers are the most commonly used material in ECC research. However, the high price limits the application of PVA-ECC in practical engineering. In order to reduce the cost, one of the methods is to partially replace the PVA fibers in ECC. In order to demonstrate the feasibility of PVA/BF-ECC and PVA/PP-ECC, polyvinyl alcohol fibers (PVA), basalt fibers (BFs) and polypropylene fibers (PP) were added at 0.5%, 1.0% and 1.5% by volume of PVA in addition to 1% by volume of PVA. Subsequently, tensile, compression and drop-weight impact tests were conducted on single or hybrid fiber concrete. The results showed that the post-peak compression toughness, tensile strength, and initial cracking impact strength of PVA/BF-ECC and PVA/PP-ECC increased significantly with the increase in the volume ratio of BF and PP fibers, while the performance of PVA-ECC materials with the same fiber volume ratio decreased slightly. Therefore, the cost can be reduced by designing hybrid PVA/BF-ECC materials that meet the performance requirements. The experimental evidence presented in this study demonstrates the feasibility and reasonable prospect of the new hybrid PVA/BF-ECC.

A unified impact displacement prediction model for geometrically similar RC beams: from test specimen to prototype component

Drop hammer impact tests based on the reduced-scale model are the most commonly accepted technique to investigate the impact response of reinforced concrete (RC) beams. However, the scale of RC beam prototypes in actual engineering is much larger than that of test specimens in the laboratory. Whether the analytical results obtained from the small-scaled specimens can be fully extrapolated and evolved to large/full-scaled geometrically similar prototype components needs further discussion. Given a structural scale factor, this study applied numerical simulations on four series of geometrically similar RC beams under different impact energy combinations. The effects of structural scales and energy combinations on the beams' damage modes, midspan displacement response, and energy absorption were numerically investigated. The results indicate that there is a scaling effect on the impact displacement of geometrically similar RC beams, which is influenced by the energy combination. A dimensionless displacement analytical model was developed for single-scaled RC beams under drop weight impact using Buckingham's π-theorem, and it was validated by several drop weight impact results. Then, a unified impact displacement prediction model for geometrically similar RC beams was proposed by considering the coupling effect of structural scales and impact energy combinations. Moreover, the numerical parametric study results preliminarily evaluated the accuracy and safety of the present model. It's worth stating that the proposed model provides a reference for designing and verifying the prototype members.

Dynamic mechanical behaviors of coral sand under drop weight impact

Dynamic mechanical behaviors of coral sand under drop weight impact

Effect of temperature on ignition mechanism of Ammonium Perchorate (AP) particles under drop weight impact

AbstractThe experimental analysis of ignition responses of mildly impacted Ammonium Perchorate (AP) particles was performed based on an optimized drop‐weight system equipped with a High‐Speed Camera (HSC). The experimental results suggested that the jetting phenomena observed by HSC is the result of the energy released by gaseous products, which push the pulverized or melted particles to splash radially. In the process of complex stress stimulation, AP particles experienced four stages of compaction, solid phase transition, sputtering, and ignition. In addition, with the increase in temperature, AP particle sensitivity increased. At room temperature, AP particles are insensitive particles. When the temperature is 50 °C, the ignition threshold of AP particles is 40 cm. However, when the temperature increases to 100 °C, the ignition threshold is 35 cm. Finally, particle friction and rapid gas compression are the main reasons for the ignition of AP particles during impact loading.

Experimental and analytical studies on a novel steel-PU foam-concrete-tube multilayer energy absorbing panel under impact loading by a cylinder head

A novel steel-polyurethane foam-concrete-tube multilayer energy absorbing panel (SFCTMEAP) was proposed in this paper, and it could be attached to the surface of the protected structure to mitigate impact loading. The impact tests on the SFCTMEAP were performed via using a drop-weight impact test machine. The investigated parameters in the impact tests included the thickness of concrete core as well as thickness and width of the steel tube. All tested specimens exhibited a combined failure mode, consisting of the local indentation of energy absorbing panel and the collapse of polyurethane foam-filled steel tubes. The energy absorbing performance of SFCTMEAP under impact loading was discussed in detail. Additionally, a three-degree-of-freedom model was proposed to obtain the displacement response of the SFCTMEAP, and the analytically-calculated displacement–time histories agreed well with the experimental results.

Investigations on the quasi-static/dynamic mechanical properties of 3D printed random honeycombs under in-plane compression

The aim of this study was to reveal the effects of inertia and base material strain rate on the mechanical properties of 3D-printed random honeycombs. First, random honeycombs were established with various meso-structural parameters based on the Voronoi technique and then manufactured by 3D printing. Quasi-static compression tests were performed using a universal test machine. The results indicated that the random honeycombs exhibited a more uniform deformation mode which led to a gentle stress–strain curve when compared with the regular honeycombs. Furthermore, the strain rate effect of the base material was determined by Split Hopkinson Pressure Bar (SHPB) tests. Finite element models considering the base material strain rate were verified by the quasi-static compression and drop weight impact tests. Dynamic simulations were carried out to determine the critical velocity between the deformation mode and clarify its mechanisms. The second critical velocities increase as the cell size and cell wall thickness increased or as the strain rate effect of the base material is considered. The effects of inertia and base material strain rate on the mechanical properties were discussed. The dynamic stress enhancement is dominated by the strain rate effect of the base material and the inertia effect in the random and shock modes, respectively. Finally, an empirical model that includes the inertia effect and strain rate effect of the base material was proposed based on the 1D shock wave theory and the Johnson–Cook material model.

Effect of Activator Concentrations on the Postfire Impact Behavior of Alkali-Activated Slag Concrete

Changing concrete ingredients significantly affects its performance due to changing the type of hydration products formed. The stability of these hydration products will dominate concrete impact behavior before and after exposure to fire. Limited research had explored the role of activators, as the main ingredient of alkali-activated slag concrete (AASC), on impact performance. Hence, this study highlights the effects of activator characteristics on the impact behavior of AASC at an ambient condition (23°C) and after exposure to elevated temperatures (200°C, 400°C, and 600°C). Conventional ordinary portland cement (OPC) concrete was also tested for general performance comparison. Besides the drop weight impact test, compressive and indirect splitting tensile strength, shrinkage, ultrasonic pulse velocity and water absorption tests were conducted to evaluate AASC performance. In addition, thermogravimetric analysis (TGA), X-ray diffraction (XRD), and scanning electron microscopy (SEM) were used to confirm and analyze findings. Results confirmed the better impact performance of AASC compared to OPC concrete. Activator concentrations showed contrary effects on AASC performance at ambient and elevated temperatures. High activation levels improved strength and impact capacity at ambient temperature, showing lower internal defects and higher hydration product formation. Conversely, lowering the activation level at elevated temperatures was preferable and resulted in a higher residual strength and impact absorption capacity. This was ascribed to the high unreacted slag particle crystallization to akermanite at higher temperatures, leading to strength gain, fewer hydration products to decompose, and high microstructure ductility that accommodated the thermal incompatibility. Hence, designing AASC while focusing only on maximizing strength can be misleading based on the targeted performance and exposure conditions.

Experimental investigation into the transverse impact performance of high-strength circular CFST members

Both high-strength steel and high-strength concrete are gaining increasing use in the construction industry. At the same time, the benefits of composite construction are also being increasingly recognized and exploited. In the present study, high-strength steel and high-strength concrete are considered in combination in high-strength concrete-filled high-strength steel tubular (HSCFST) members, with a focus on their behaviour under transverse impact loading, resistance to which is important for resilient infrastructure. Tests on thirteen HSCFST specimens and six reference CFST specimens under drop weight impact loading are presented. Hot-finished high-strength S890 steel sections were employed for the outer tubes of the HSCFST specimens, while hot-finished S355 steel tubes were used for the reference CFST specimens. Two core concrete strengths of approximately 60 MPa and 100 MPa were considered. The instantaneous impact force and deformation histories of the specimens were recorded at high frequencies throughout the impact process. A single-degree-of-freedom (SDOF) model was developed and used to facilitate the analysis of the experimental results. The dynamic moment capacities of the test specimens were obtained using the developed SDOF model and a dynamic increase factor (Rd) was introduced to quantify the enhancement in moment capacity relative to the static values. The influence of the test parameters on the dynamic increase factors was then analysed. The test results indicated that Rd is positively correlated with the impact velocity and negatively correlated with the steel grade, steel ratio and specimen length, while being insensitive to the concrete strength.

Crashworthiness analysis and multi-objective optimization of spatial lattice structure under dynamic compression

A spatial lattice structure is proposed to improve the structural crashworthiness and energy absorption. First, a single-cell structure is proposed via a bionic honeycomb, and then the single-cell structure is arrayed to form a spatial lattice structure. The finite element model of the spatial lattice structure for crashworthiness analysis is established. The theoretical model of the plateau stress of the lattice structure under compressive conditions is derived, and its accuracy is verified by the corresponding finite element analysis. After that, the effect of geometrical parameters of single-cell structure on crashworthiness is analyzed. Then, geometrical parameters of single-cell structure and number of single-cell in the X, Y, and Z directions are used as design variables, the mass, and overall size are used as constraints, and specific energy absorption and collision peak force are used as optimization objectives. The multi-objective crashworthiness optimization of spatial lattice structure is carried out, and the optimal lattice structure design is determined via the gray relational analysis coupling entropy weight method. The validity of the finite element model and optimal design is verified by the drop weight impact test. The crashworthiness optimization of spatial lattice structures has important guiding significance for the design of energy-absorbing structures.

Experimental investigation of hybridization effect of Kevlar and Glass fibers on CFRP composite under low velocity impact

This paper experimentally investigates the effect of Kevlar and glass fibers on carbon fibers epoxy composite to enhance the impact strength under low velocity impact (LVI). Experiments were conducted on various combinations of Kevlar, glass, and carbon FRP composites to study the dynamic impact behavior using a drop-weight impact tester. Five varieties of the hybrid composite were selected for experimentation using a drop-weight impact tower Instron, CEAST 9340. Out of five combinations, the first sample contains only carbon fiber with a different orientation, and the other four contain interplay hybrid fibers (Kevlar-carbon-Kevlar, Glass-carbon-Glass, Kevlar-carbon-glass, and glass-carbon-kevlar) 8-ply composite. The carbon fiber layers are inserted within each hybrid composites to investigate how the Kevlar and glass fiber qualities affect the impact resistance of CFRP composite. The analytical modeling results were compared with experimental results, which are in good agreement. The delamination and damage location were detected using an advanced ultrasonic C-scan. The damage area of laminates is measured using ImageJ software. The analysis shows that the amount of absorbed energy increased in a hybrid laminate having Kevlar at outer surface locations.