Low-velocity Impact Loading Research Articles

Response of treated recycled aggregate concrete against low-velocity impact loading: Experimental and Weibull statistical analysis

Sustainable and ecologically friendly building practices require increased conservation and recycling of renewable resources. Because of the rise in development and demolition worldwide, using recycled construction materials as aggregate in new concrete can be an essential step towards making the material more environmentally friendly. Removing or fortifying the adherent mortar is the main technique to advance the poor standard of recycled concrete aggregate, which the adherent mortar causes. The study examines the impact performance of recycled aggregate concrete (RAC) comprising different replacement levels (10, 20, 30 and 40 %) of recycled aggregate (RA). Three concentrations (10, 15, and 20 %) of MgSO4 solution were used to pre-treat the RA and subjected to three different immersion times of 5, 10, and 15 days. For this, thirty-seven mixtures were prepared with the combination of RA contents, MgSO4 concentrations and immersion periods. The study was divided into three phases. The physical properties of RA, slump, and compressive strength tests were studied in the first phase. The best thirteen mixtures that exhibited expectational results in the first phase are put forward to the second phase. The effect of RA content, MgSO4 concentration and immersion periods on the impact strength was studied in the second phase. Besides, the differences in the impact test results were studied by Weibull distribution and results were displayed with regard to the probability of survival. The final phase studied the impact response of reinforced concrete slabs under a large mass impact. The findings reveal that the five days of immersion in a 10 % MgSO4 solution has been shown to enhance the impact strength of RAC, whereas a replacement ratio of 20 % is recommended.

Behavior of novel steel-concrete-steel sandwich walls under low-velocity impact loading

This paper reported experimental and analytical studies on impact behaviors of steel-concrete-steel sandwich composite (SCSSC) walls using enhanced C-channels (ECs). Six SCSSC walls, designed with variations in impact energy levels and boundary columns, were tested by drop hammer and simulated by LS-DYNA. The main failure modes of the specimens after impact loading were global flexure and flexure-shear mode. As direct-link connections, the ECs provided strong interfacial shear and tensile resistances, which prevented local failure of SCSSC walls. Under three impact energy levels, boundary CSFT columns increased the ultimate impact resistance of SCSSC walls, and effectively reduces their peak displacements. Refined finite element (FE) models considering the effect of strain rate were established, and verified by reported impact test results. In addition, this study adopted modified two-degree-of-freedom (TDOF) model to estimate the impact force and displacement responses of this type of SCSSC walls. Validations against reported test results confirmed that the TDOF model provided reasonable predictions.

Performance of steel–concrete composite walls with recycled aggregate concrete under low-velocity lateral impact loading

This paper investigates the impact-resistant behaviours of steel–concrete (SC) composite walls experimentally and numerically, which consist of two outer steel plates and infilled recycled aggregate concrete (RAC). Totally eight SC walls were designed and fabricated with different coarse recycled aggregate (CRA) content and steel plate thicknesses. Drop-hammer impact testing was first performed to obtain the failure mode, impact force and deformation. Test results indicated that the impact resistance behaviour of SC walls enhanced considerably with a decrease in CRA content. The tie bars combined with studs were effective to avoid the separation of steel plate from the concrete core. Afterwards, the finite element (FE) models were developed and calibrated, and then used to obtain more information on the full-range motion response, development of stress and strain, and energy absorption. In addition, the influences of different parameters, including the CRA content, material strength, steel plate ratio, tie-bar spacing, impact energy and axial load ratio on the impact resistance performance were assessed. Finally, the displacement response of SC composite walls with RAC was predicted using single-degree of freedom (SDOF) approach.

The Effect of Core Metal Layer Thickness on the Behavior of Carall Under Low Velocity Impact Loading

Fiber metal laminates are the advanced composite materials, in which the metal and FRP layers are stacked alternatively to achieve the desired properties. The presence of FRP layers enhances the fatigue, fracture properties and weight savings. Durability and plasticity of the metal plays a significant role in the design of fiber metal laminates. This study evaluates the role of middle metal layer (core) thickness on the behavior of Carall fiber metal laminates under low velocity impact loading. Two types of Carall 3/2 with middle layer of varying thickness are considered. The metal volume fraction is same for both the laminates. Finite element simulations have been carried out for the laminates considered according to the standard ASTM D7136. Johnson–cook plasticity and damage model and two-dimensional Hashin damage criteria have been used to model the aluminum and CFRP respectively. From the study, it was found that the placement of thicker layer at the middle position in the Fiber metal laminate enhances the impact resistance of Carall. The energy absorption studies also indicate that the presence of thicker layer at the middle position increases the energy absorption capability.

Investigation on Behaviours along Weak Axes of Steel Beam under Low Velocity Impact Loading: Experimental and Numerical

This study examines the behaviors of structural members in their most vulnerable state (fixed along their weak axes) against sudden loads such as impact loads. To do so, eight supported rectangular hollow steel beam samples were constructed, and a circular head hammer weighing 75 kg was dropped as a free fall along the weak axes of these beams. Each fall had a different drop height (ranging from 250 mm to 2000 mm) and different amounts of energy (ranging from 183 J to 1471 J) in order to compare the structural behaviors of the beams against low velocity impacts with different drop heights and energy levels. Additionally, finite element analyses were conducted to investigate the performances of the rectangular hollow steel beams against impact loading along the weak axes numerically as well as experimentally. Initially, six model verification and mesh convergence analyses were performed to determine the optimum mesh size. After that, eight finite element models were developed with verified data in order to calculate the displacements, accelerations, plastic denting values, distributed stresses, and plastic equivalent strains. Consequently, impact load factors for static analysis were calculated mathematically and compared with the experimental and numerical results. Overall, the results obtained from the FE analyses were in line with the results obtained from experimental and mathematical studies. To sum up, the increases in the drop height of the impact force and the amount of energy in beams placed along their weak axes will increase the amounts of acceleration, maximum deflection, internal stress, residual displacement, and plastic denting in such beams.

Low velocity impact performance of natural fibre reinforced polymer composites: a review

Natural fibre-reinforced polymer composites (NFRPC) are versatile and applicable materials for structural applications that require durability and reliability under various forces. However, these composites are susceptible to crack formation when exposed to low-velocity impact (LVI) loads, compromising their functionality and performance. Therefore, it is essential to investigate the influence of LVI on NFRPC and their characterization methods, testing standards, and failure mechanisms. This paper reviews the latest research and development on the characterization, testing, and modelling of NFRPCs under LVI loads. It also explores the impact behaviour of various natural fibres, such as kenaf, bamboo, mallow, buriti, and curaua, and the effect of fibre hybridization and nanofiller incorporation on the LVI response of NFRPCs. The paper evaluates the properties, failure mechanisms, and applications of NFRPCs in relation to LVI resistance. The paper provides useful information for developing advanced composite systems and achieving material efficiency for various structural applications. Finally, it highlights the potential applications and challenges of NFRPC as LVI-resistant materials for advanced composite systems.

Numerical Modelling of Impact Loads on RC Beams Utilizing Spent Garnet as a Replacement for Fine Aggregate

Spent Garnet (SG) is one of the waste materials that attracts the interest of researchers to use it as a replacement for fine aggregate in concrete materials. As experimental investigation was carried out to assess the performance of a reinforced concrete (RC) beam incorporating SG as a substitute for fine aggregate. The study involved subjecting the beam to low-velocity impact loads within a controlled testing configuration. The primary objective of this study was to determine the optimal proportion of spent garnet (SG) to replace fine aggregates in reinforced concrete (RC) beams subjected to impact loads with a 100 kg impact weight dropped from a height of 1.5m, equivalent to a velocity of 5.4 m/s. To evaluate the effectiveness of SG as a replacement for fine aggregates, RC beams with varying percentages of SG (0%, 10%, 20%, 30%, and 40%) were numerically modelled using the Finite Element Method (FEM) incorporating the Concrete Damage Plasticity (CDP) constitutive model to simulate their behaviour under low-velocity impact loads. The study aimed to comprehensively examine the failure mode of the RC beams. The findings through FEM showed that the inclusion of SG in the concrete mix enhanced the material's behaviour and decreased the failure and damage of the beams as the percentage of SG in the mix increased, indicating its effectiveness as a replacement for fine aggregates, which is consistent with the experimental results.

Experimental and Numerical Evaluation of GFRP-Reinforced Concrete Beams Under Consecutive Low-Velocity Impact Loading

Experimental and Numerical Evaluation of GFRP-Reinforced Concrete Beams Under Consecutive Low-Velocity Impact Loading

The effect of the W-shape stirrups shear reinforcement on the dynamic behavior of RC flat solid slab subjected to the low-velocity impact loading

Reinforced concrete flat solid slabs may experience explosive and impact loads. Reinforced concrete flat solid slabs have been studied under static and dynamic loads. Researchers have widely explored numerous reinforcing strategies to strengthen RC slabs exposed to impact loads, yet gaps remain. Internal anchorage stirrups (W-stirrups shear reinforcement) is still rarely used to strengthen slabs against impact loading. Consequently, this study emphasized the influence of W-stirrups shear reinforcement on the dynamic response and failure modes of RC slabs subjected to impact loads.The first part examined the impact behavior of fully fixed RC flat solid slabs reinforced with W-stirrups shear reinforcement experimentally. Slabs were impacted using portable drop-weight testing equipment. Six 800-x-800-x-90-mm RC slabs were made. Three samples were reinforced with a W-stirrups orthogonally oriented in two directions, whereas three controls were without any type of strengthening. The eccentric vertical displacement of slabs, strain at four points on the W-stirrups, two on main steel, and two on concrete, and acceleration at one point over a slab were measured; also, failure modes were monitored.In the second section, ABAQUS software was used to generate finite element models of slab study samples. Numerical model results matched experimental results. Thus, the suggested finite element model may assess reinforced RC slabs under low-velocity impact loads. Finally, a parametric study was conducted in the third part to address the issue of over-reinforced design in slabs with W-stirrups. The parametric study aimed to determine the optimal steel ratio of flexural and shear reinforcement and its influence on the behavior of RC flat solid slabs reinforced with W-stirrups shear reinforcement.

On the damage and performance degradation of multifunctional sandwich structure embedded with lithium-ion batteries under impact loading

The integration of energy storage and load bearing in composite structures provides an alternative ideal solution for the next generation of delivery equipment due to its potential in improving energy storage efficiency and space utilization significantly. However, the susceptibility to impact during services makes it necessary to understand the damage and performance degradation of this multifunctional composite structure and its interaction behavior under impact loads to ensure structural integrity and safety behavior. This study realized the embedded design of lithium-ion batteries (LIBs) into the composite structure and investigated the mechanical-electrochemical coupling behavior of composites-LIB integrated multifunctional sandwich composite structure under low-velocity impact loads. Experimental results showed that the embedded batteries experienced micro short circuits during the impact-loading process and kept good energy-storage capacity after the transient impact. Furthermore, charge-discharge cycling tests results indicated that the abrupt capacity loss increased with impact energy, and degradation rate rapidly deteriorated under high impact energy. Post-mortem inspection revealed that the damage and densification of active materials and separator contributed to the abrupt capacity loss and performance degradation. This work provides valuable insights for the performance evaluation and structural design of multifunctional energy storage composite structures.

Low energy impact behavior of unidirectional and cross-ply flax/epoxy laminates and comparison with similar glass/epoxy laminates

Unidirectional (UD) and cross-ply flax and glass fiber reinforced composites (FFRC and GFRC)are tested under four out-of-plane low velocity impact loads. A hybrid flax reinforcement was used, denoted UD-mat, which is made of a UD layer of continuous flax fibers bound to a flax fiber mat layer. For the mat binder, two types of short flax fibers are considered: unmodified fibers and refined ones. The laminates made ofrefined fibers show the highest permanent and maximum displacements. Moreover,the peak load for the unidirectional FFRC with refinedfibers is lower than that with unmodified fibers, for example it is 25% lower at 11 J. When comparing with flax fiber laminates, the absorbed energy and energy absorption ratio are on average 40% lower for glass laminates but less damage is observed. Several failure modes are observed in the flax laminates, while the main failure of the glass/epoxy laminates is delamination.

Energy absorption properties of a 3D-printed lattice-core foam composite under compressive and low-velocity impact loading

This experimental work aims to investigate the compression and low-velocity impact characteristics of different lattice structures made via Fused Deposition Modeling (FDM) technology to be used as a skeleton of a lightweight polyurethane foam (PUF) composite. Three frame-unit geometries, namely one cubic cell and two pyramidal cell variants, were firstly considered as reinforcement. A stepwise design rationale was adopted to identify better lattice configurations progressively, focusing on manufacturing aspects such as cell geometry and structural density, as well as efficiency requirements. A square-based pyramid geometry was identified as the most efficient in energy dissipation and, therefore, was selected for further investigations, varying bulk density, to identify the lattice reinforcement to be embedded in the polyurethane foam matrix and generate the PUF composite. The experimental outcomes showed enhanced dissipative capacity of the composite structure under static and dynamic loading conditions, suggesting promising applications to preserve the integrity of objects in accidental collisions.

Experimental and numerical analysis of residual compression strength after Low-Velocity Impact of carbon/epoxy composite plate

A composite laminate is susceptible to Low-Velocity Impact (LVI) load, leading to Barely Visible Impact Damage (BVID) accompanied by invisible damage in the form of delamination. Such delamination is significantly reduced the compression strength of the composite laminate plate. The present work provides an experimental and numerical analysis, based on finite elements, on residual compression strength after the low-velocity impact of carbon/epoxy composite plate. Five specimens of 16 layers Unidirectional carbon/epoxy composite plate with fiber orientation [+450/900/-450/00/+450/900/-450/00]s have been tested subject to low-velocity impact load, with a single use of impact energy value of 2.75 Joule/mm, followed by compression test. Moreover, another similar five specimens tested compression before impact to measure its compression strength. Experimental results were observed to identify the profile and size of total-projection delamination after impact and after compression and compression-strength before and after impact. The Finite Element analysis is based on the utilization of cohesive zone elements with Benzeggagh-Kenane fracture criterion to predict the initiation and propagation of delamination, Kirchhoff based formulation of continuing shell element to model stiffness of the laminate, and Hashim-Rotem damage mechanism to predict intralaminar damages.

Energy absorption investigation of SFRFC-filled double circular tubes under quasi-static compression and low velocity impact loading

The filled thin-walled tube (FTT) is a common energy absorption device, which consists of two important parts: filled materials and thin-walled tubes. According to existing researches, the filled materials significantly influence the mechanical properties of FTTs, especially the energy absorption capacity. In this study, a novel design of FTTs is proposed and studied, which adopts the double aluminum (Al) pipe and is filled with the steel fiber reinforced foamed concrete (SFRFC). Firstly, specimens with different steel fiber contents of 0, 0.5, 1, 1.5, and 2% are prepared and tested under quasi-static compression, and the influence of dynamic velocity (4.4, 6.2and 7.6 m/s) are investigated; then, the numerical modeling is conducted to study the influence of structural parameters on the energy absorption properties of the proposed SFRFC FTTs under quasi-static compression loadings. Results show that an appropriate content of steel fiber can prolong the stress platform under quasi-static compression loadings, and stabilize the fluctuation during dynamic plastic buckling. The thickness、diameter、aspect ratio of SFRFC FTTS have a significant effect on the SEA and CFE, especially the thickness of the inner tubes, which means the geometry parameters obviously affect the crashworthiness characteristics of SFRFC FTTs. According to the results of this research, it can be concluded that SFRFC is an excellent and potential energy adsorption filled material for FTTs, which can obviously improve the mechanical properties of filled thin-walled tubes under quasi-static and low velocity impact loadings.

The influence of composite core thickness on the perforation resistance of titanium-based FMLs

Fibre metal laminates (FMLs) have been widely used as structural materials in aerospace applications due to their superior properties compared to traditional fibre reinforced composites. FMLs are hybrid materials consisting of alternating sheets of metal and plain composite. The aim of this study is to investigate the impact response of FMLs that have potential applications in the next generation of aircraft. Here, the influence of the thickness of the composite core in a 2/1 (metal/composite/metal) titanium alloy-based fiber metal laminate were investigated under low velocity impact conditions. It is shown that increasing the thickness of the composite core resulting in higher values of impact force and absorbed energy. The FMLs offered a much higher specific perforation energy than that offered by the plain composite for a given thickness of composite core.Explicit finite element (FE) models were developed to predict the response of the laminates under low velocity impact loading, which were then validated by comparing the numerical predictions with the corresponding experimental results. The resulting FE predictions showed good agreement with the experimental data in terms of the load-displacement trace, peak impact force, absorbed energy and perforation mechanisms.

Failure Modes Behavior of Different Strengthening Types of RC Slabs Subjected to Low-Velocity Impact Loading: A Review

Concrete is brittle; hence, it is incredibly likely that concrete buildings may fail in both local and global ways under dynamic and impulsive stresses. An extensive review investigation was carried out to examine reinforced concrete (RC) slab behavior under low-velocity impact loading. Significant past research studies that dealt with experimental and numerical simulations and analytical modeling of the RC slabs under impact loading have been presented in this work. As a result, numerous attempts to define failure behavior and to assess concrete structures’ vulnerability to lateral impact loads have been made in the literature. Based on analytical, numerical, and experimental studies carried out in previous research, this article thoroughly reviewed the current state of the art regarding the responses and failure behaviors of various types of concrete structures and members subjected to low-velocity impact loading. The effects of different structural and load-related factors were examined regarding the impact strength and failure behavior of reinforced concrete slabs reinforced with various types of strengthening procedures and exposed to low-velocity impact loads. The reviews suggested that advanced composite materials, shear reinforcement, and hybrid techniques are promising for effectively strengthening concrete structures.

Parametric Study of PEKK Based Fiber Metal Laminates Used in Aerospace Applications

Numerical analyses offer a cost-effective and efficient alternative to experimental investigations, and Finite Element (FE) models have become a popular tool to simulate the behavior of Fiber metal laminates (FMLs) under impact loads. This study verified the reliability of the proposed FE models to predict the perforation response of ‎the FMLs investigated under low-velocity impact loadings. The validation of ‎the FE models was assessed through comparison with the corresponding results of the ‎experimental work. The results showed that the proposed simulations are capable of predicting the dynamic response of the laminates investigated with a high degree of success. The parametric studies were conducted on 2/1 titanium FMLs based on 2-ply composite cores and 2/1 aluminum FMLs based on 4-ply composite cores under impact with a variety of loading conditions. The developed FE models were then used to explore the structural behavior of the fiber metal laminates investigated with an extended variation of parameters, i.e., projectile striking angle, impact locations, the geometry of the projectile, and velocity. The results of the FE models are presented in terms of load-displacement traces, energy absorption, and failure modes. The findings of this study contribute to the understanding of the structural behavior of FMLs under impact loads and can inform the design and optimization of FMLs for various engineering applications. The use of FE models provides a cost-effective and efficient means of exploring the structural behavior of FMLs under different impact conditions, which can reduce the need for costly and time-consuming experimental investigations.

Investigation on lateral impact resistant performance of aluminum foam-filled 6082-T6 aluminum alloy circular tubes: Experimental and numerical study

Nowadays, the aluminum alloy building structure is at risk of the accidental impact loadings, which seriously threatens the personal security and the safety of the property. However, the existing research on the local lateral impact performance of the aluminum foam-filled tube applied to building structures is limited. In this study, impact tests on 9 aluminum foam-filled tubes with fixed boundaries were conducted by using a drop hammer impact test device to investigate the dynamic performance of the foam-filled tube under local lateral low-velocity impact loadings. The failure modes, impact force histories, displacement histories, and permanent deformation of the foam-filled tubes were obtained and compared with those of the empty tubes under the same impact loading. The finite element (FE) model was also established via the software ANSYS/LS-dyna and the accuracy of the FE method was verified against impact test results. Based on the experimental and numerical results, the aluminum foam-filled aluminum tube shows better lateral impact resistant performance than the empty tube due to the support effect of the aluminum foam on the tube wall by good energy absorption and deformation characteristics. Especially, filling the aluminum foam prevents the generation of cracks for the composite tube near the impact position when the impact energy is high. The influence law of the aluminum foam filler and its density, shape of hammer head on the lateral impact resistant performance of the aluminum foam-filled composite tube was then investigated based on the experimental and numerical results by consideration of the damage level, energy absorption, impact force–lateral displacement relationship, and permanent deformation. By filling the aluminum foam into the empty tube, the energy absorption is improved by up to 67.2% and 44.9%, respectively, when the hammer displacement reaches 20 mm and 40 mm within the impact load condition conducted in this study.

Dynamic response of reinforced concrete beams subjected to low velocity impact loads using nonlinear finite element analysis

Dynamic response of reinforced concrete beams subjected to low velocity impact loads using nonlinear finite element analysis

Compressive and splitting tensile impact properties of rubberised one-part alkali-activated concrete

This paper presents an experimental assessment of the compressive and splitting tensile properties of rubberised one-part alkali-activated concrete under quasi-static and low-velocity impact loading. An optimised mix design, employing blast furnace slag and fly ash as precursors and anhydrous sodium metasilicate as a solid activator, is used as a reference. Rubber contents of up to 60% volumetric replacement of total natural aggregates are considered. Quasi-static tests are performed using servo-hydraulic machines, whilst the impact tests are performed in an instrumented drop-weight loading rig. Digital image correlation is used to get displacement measurements under both quasi-static and impact loading conditions. Three impact velocities of 5, 10, and 15 m/s are considered, giving rise to strain-rates in the range of 3–270 s−1. The quasi-static results show shape- and size-dependency and characteristically lower compressive and splitting tensile strengths with higher rubber content. The dynamic properties are notably influenced by the rubber content, with a higher ratio resulting in greater impact duration under compressive loading, reduced peak compressive strength, and reduced peak splitting tensile strength. The shape of the stress-strain response under compressive loading changes with rubber addition, showing two major peaks as opposed to a single peak for the non-rubberised specimens. The dynamic mechanical properties are also strain-rate dependent, exhibiting an increase with higher strain-rates. The rubberised specimens exhibit higher strain-rate sensitivity in splitting tension than compression, signified by higher dynamic increase factors for a given strain-rate and lower critical transition strain-rates. A higher rubber content in the mix also result in reduced critical transition strain-rates for the compressive strength, axial crushing strain, and splitting tensile strength. Based on the results of this study, analytical expressions are provided for predicting the dynamic increase factors for the compressive strength, axial crushing strain, elastic modulus, and splitting tensile strength.