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This paper develops a three-dimensional Finite Element (FE) model using the non-linear explicit code in LS-DYNA to predict the impact behavior of Steel–Concrete–Steel (SCS) sandwich beams with bolt connectors. The accuracy of the developed FE model is validated by comparing the FE-predicted impact force and displacement–time histories with the experimental results of the SCS sandwich beams. The FE prediction shows a close match with the test results. Using the validated FE model, parametric studies are carried out to investigate the influences of different parameters, i.e., spacing of connectors, strength of concrete, presence of endplates, location of impact, mass of drop weight, and height of drop. It is found that the spacing of connectors and the strength of concrete have a limited influence on the impact resistance of the SCS sandwich beams with bolt connectors. However, the concrete strength significantly affects the inertial peak impact force. The SCS sandwich beam without endplates shows higher deformation compared to the beam with endplates, and the location of impact exhibits influence on the impact resistance of the SCS sandwich beams. It is also revealed that the maximum displacements of the SCS sandwich beams could substantially rise with the increase in mass of drop weight and height of drop.

An experimental and statistical study on the impact resistance of ultrahigh-performance concrete (UHPC) is presented. The impact resistance was evaluated by conducting the drop-weight impac...

Impact resistance represents a key property of Fibre Reinforced Concrete (FRC). Recently, the authors proposed a repeated drop-weight test for FRC impact characterization that, among other advantages, is able to distinguish the contribution of different types and dosages of fibres both at cracking and in cracked state. The impacts are applied on a simply supported notched prism of 150 × 150 × 300 mm, being the adopted span length 240 mm, the notch depth 25 mm and the projectile mass 5 kg. An experimental and numerical parametrical study was carried out in order to analyse the effect of the specimen geometry on impact test results. The span length (240, 350 and 500 mm), the notch depth (10, 25 and 50 mm), the specimen width (70, 100 and 150 mm), and the projectile mass (5, 10 and 20 kg) were considered as variables. The numerical model was developed to analyse the stress distribution before the first crack appears (elastic behaviour). In order to corroborate the numerical model, the impact load was measured in some tests with a dynamic load cell. Numerical results concerning the effects of the above-mentioned variables on impact response are presented.

This work investigated the impact performance of hollow reinforced concrete members with inner octagonal steel tube. Experiments on 13 specimens subjected to low-velocity drop weight impact are presented in this article, covering key parameters such as the impact height, boundary condition, axial load ratio and thickness of the inner tube. The dynamic processes, failure patterns, impact force and mid-span deflection histories, and residual mid-span deflections were obtained from the experiments. Flexure-shear was observed as the main failure pattern for all the specimens under impact. It was found that all the key parameters considered had influences on the impact performance of hollow reinforced concrete specimens with inner octagonal steel tube. Effects of these parameters on the impact performance of hollow reinforced concrete members were discussed.

International audience; This paper presents the influence of fabric structures and stab angles on single-pass stab impact and the repeated and multi-angle stabbings of 3-dimensional (3D) warp interlock structural fabrics based on the high-molecular-weight polyethylene (HMWPE) yarns. Five kinds of samples with different structures were experimentally tested using the drop weight stabbing impact equipment at the same impact energy. Radar charts are plotted to demonstrate the differences among different parameters to a better understanding and a more global characterization of single-pass stabbing impact. An image analysis methodology of Structure From Motion (SFM) is used to compare the fabric deformation in Z direction after the stabbing tests. Results indicated that fabric structures have significant effects on the stab impact property that the orthogonal/through-the-thickness interlock fabric has a good stab impact resistance. Besides, the fabric with stab angle of 90° exhibited better single-pass stab impact property than the counterparts with stab angle of 0°. More importantly, the double-pass stabbing tests are compared to the ones of the single-pass stabbing which shows that a better condition occurs when the stab angles are identical in each pass.

In this study, the response of different thin concrete panels of size 600 mm × 600 mm × 40 mm with and without reinforcements subjected to low-velocity impact under drop weight impact is carried out. For the purpose of comparison, concrete panels of different configurations such as simple cement concrete (PCC) free of any kind of reinforcements, textile reinforced concrete (TRC), and reinforced cement concrete (RCC) in addition to panels made with self-compacting concrete (SCC) were casted. The drop hammer impact test consists of a ball (weighing 1.8 kgs) with a drop height 600 mm is considered. The following parameters of the drop weight impact loading test such as number of blows for first crack, ultimate failure, and energy absorption characteristics were examined to arrive at the best configurations among the selected categories. It is observed that the panel made with self-compacting concrete has performed superiorly over all other cases considered in this study.

Running ductile fracture is one of the most catastrophic accidents of pipelines for natural gas transportation. Crack arrest toughness is important for preventing crack extension to a long distance along pipeline. Critical crack tip opening angle ( CTOA C ) is a promising parameter for characterizing crack arrest toughness. In this study, a new method is proposed to calculate the CTOA C from the energy-load curves in an instrumented drop weight tearing test (DWTT). Numerical analyses with the Gurson damage model have been conducted to verify the proposed method. It shows that results calculated from the energy-load curves are slightly lower than the results measured from specimen surface. Results calculated from the proposed method also agree well with experimental results reported in the literature.

The major purpose of this study is to provide a framework for determination of energy losses resulting from mechanical impacts of the kind that could occur during nuclear decommissioning of waste material. Measurements have been made of final translational and rotational velocities for impacts between projectiles of different length and a massive barrier. This enabled determination of experimental values of the impact coefficients and energy losses. It was found that the total energy losses could be accurately accounted for by the sum of those pertaining to the normal and tangential processes, thus indicating that these include any losses due to vibration. The results obtained clearly support an Amontons–Coulomb friction model and the previously held contention that there is a limiting value for the impulse ratio at low angles of barrier inclination. Although sliding surfaces are likely to be modified during impact, it is shown that any original contamination on the contacting surfaces results in a very large decrease in impulse ratio or friction coefficient. This represents an important finding in the context of mechanical ignition testing indicating that the state of the impact surfaces and their handling need to be taken into account. The difficulties in establishing appropriate values for the impact coefficients and dealing with the effect of mechanical vibrations on the energy losses are discussed and equations derived for determining the tangential and normal energy losses from known initial velocities.

In this paper we study a new type of interlocking brick recently proposed by the authors. The brick has a symmetrical geometry with four concavo-convex side surfaces for the interlocking purpose. Drop weight tests have been conducted to investigate the mechanical response of interlocking assembly plates by applying different levels of impact force and lateral confining load. The results show that, compared with monolithic plates, the new interlocking assembly plates have significantly improved flexural performance in terms of impact energy absorption capacity. The fracture of individual bricks during the impact always occurs along a load transmission path that is determined by the geometrical constraints of the interlocking bricks. Most importantly, the interlocking design of the plate-like assembly can effectively prevent the propagation and spread of the cracks, so that the damage to a single brick will not lead to a catastrophic failure of the entire structure. Keywords: Interlocking brick, Impact behaviour, Drop weight, Impact test

The response of Glare 3 and Glare 5 to repeated impacts and dropped tools was experimentally investigated using drop weight equipment. Two repetition sequences were tested. The first sequence consisted of successive impacts with the same impact energy, but lower than the first impact. In the second sequence the rebound energy of one impact was taken as the impact energy for the subsequent impact. This sequence represents the drop weight impact. The damage was evaluated using visual inspection and ultrasonic C-scan. Three categories of impact damage were observed: visible deformation without internal or external damage, visible internal damage (C-scan) without external damage, and visible internal and external damages. The “threshold energy” defined as the magnitude of maximum impact energy in successive impacts that caused no further damage after the first impact. For the successive impacts with energy between the threshold energy and the first impact, repeated impacts were observed to cause damage propagation. Successive impacts with impact energy less than the threshold did not reveal any effect on the structural integrity. The dropped tool sequence revealed that the rebound energies do not have a considerable effect; the force–time and force–displacement curves for Glare laminates did not change with successive rebound impacts. Therefore, it can be concluded that damage propagation due to rebound energies is negligible.

In this paper, the impact response of unidirectional cross-ply GF/epoxy laminates with different shape memory alloys (SMAs) positions was investigated. According to vacuum assisted resin injection (VARI) process, we manufactured the laminates without SMAs, the laminates with one layer of SMAs were inserted in 1/8 thickness, in 1/2 thickness, in 14/16 thickness, and in 15/16 thickness of specimen, respectively, the laminates with two layers of SMAs were inserted in the 15/16 and 14/16 thickness, in 15/16 and 1/2 thickness, in 15/16 and 1/8 thickness, in 14/16 and 1/2 thickness, in 14/16 and 1/8 thickness, and in 1/2 and 1/8 thickness of specimen, respectively. The low-velocity impact experiment was performed by Dynatup 9250HV Drop Weight Impact Testing Machine under the impact energy of 28 J to analyze the impact response, and the impact parameters such as contact force (F), displacement (D) and energy (E) of the laminates were obtained. To further observe and analyze the impact damage morphology, we also adopted visual inspection and scanning electron microscope (SEM) technology. The experimental results showed that impact performance of laminates improved by embedding SMAs. By contrast, the impact performance of the laminates with two layers of SMAs was optimum.

Composite material referred to build speed boats with a lightweight and also endured to support a crushing load. To design and analyze speed boats to support a collision accident, the composite material would be implemented into finite element model. This research had proposed the material model of a fiberglass composite material which used to construct speed boats in Pattaya, Thailand. The rectangular plate of composite material was analyzed according to the drop weight impact test. The orthotropic and isotropic material models were applied to define material properties of the finite element model of the fiberglass plate. The finite element analysis (FEA) results were compared with experimental data. The FEA with isotropic material for modeling the fiberglass material results were in good agreement with experiment. There was an average difference of 0.4195 J when compared the residual energy with the experimental data. Consequently, this fiberglass material model would be used to analyze the speed boat collision in a further work.

Accidents due to low-velocity impact loading are no longer uncommon these days. Accordingly, although evaluation criteria for regulating the global behavior of major structures are required to ensure sufficient impact resistance, to date the criteria have not been specified. Although several studies have suggested empirical formulae for evaluating the deflection of reinforced concrete (RC) beams from drop weight impact tests, the derivation of these formulae suffer limited impact energy ranges and few investigated parameters. To overcome these limitations, 15 RC beams were tested in this study under drop weight impact loading with five variables: impact energy, drop weight momentum, static flexural capacity, cross-section size, and concrete strength. The limitations of the previous studies were experimentally verified, and an empirical formula was newly proposed based on the test results. Furthermore, the validity of both the experimental results and our new empirical formula was analytically verified through parametric studies.

A study of the rate sensitivity of prismatic specimens of steel fiber-reinforced concrete (FRC) is carried out in this contribution. Experimental results are analyzed from impact tests carried out with an instrumented drop weight testing machine. FRC mixes with two types of fibers have been studied, namely short straight fibers and long hook-ended fibers. The experiments have included two amounts of fibers (volumetric fractions of 0.5% and 1.0%), and also companion unreinforced plain concrete specimens are studied. The analysis has focused on the bending properties of the studied mixes, i.e. bending strength and absorbed energy. The study shows that each particular mix of FRC has different rate sensitivity because the dynamic behavior is a consequence of the rate dependence of the mechanisms governing the interaction between fibers and matrix. For the impact strain-rate domain achieved in the tests (1-10 s -1 ), it is shown that the study has to be done in terms of the energy absorption capacity of FRC. According to the results, the rate sensitivity decreases as the amount of fibers increases and, furthermore, the rate sensitivity of FRC mixes with hook-ended fibers is smaller than that of FRC mixes with straight fibers.

The behavior of reinforced and prestressed concrete plates has been studied under drop weight impact loading. The reinforced and prestressed concrete plates having the size 0.8 m x 0.8 m and thickness 100 mm. The impact was applied by dropping a mass of 242.8 kg from a fixed height. The characteristic strength of concrete cubes was 51.38 MPa. The generated impact force and deflection time response were measured and the failure modes of the plate specimens were studied. The results thus obtained for reinforced and prestressed concrete plates were compared and discussed. Prestressed concrete plates were found to have higher impact resistance and performed better in comparison to the conventional reinforced concrete plates. The deflection at bottom surface of prestressed concrete plate has also reduced.

Recently, the demand of the structural safety subjected to impact loading has been increased. For this reason, various studies for predicting the behavior of structures under impact loading have been actively performed. Some researchers have suggested performance based design to predict the behaviors of structures. They conducted drop weight impact test and suggested empirical equations to estimate the maximum or residual deflection of reinforcement concrete (RC) beams under impact loading based on the static flexural capacity and the input impact energy. In these equations, input impact energy is important factor and composed of mass and impact velocity of drop weight. Thus, there are various combinations of mass and impact velocity of drop weight having the same impact energy energy, however, the equation did not include the effect of the combinations. In this study, the behavior of RC beams was investigated considering the combination of mass and impact velocity through the FE analysis using LS-DYNA. The flexural failure type RC beams, which were performed by other researchers, and several combinations of mass and impact velocity of drop weight were used as variables in this analysis. Consequently, it is confirmed that behaviors of RC beams are related to the combination. These results imply that the previous empirical equations and the design of concrete structures subjected to impact loading should consider the combination of mass and impact velocity.

As the chance of unexpected loadings such as impact or blast increases the importance of concrete structures are not designed to resist again the impact or blast loadings and hence strengthening of existing structures might be required per situation. This study investigated the effect of the CFRP (Carbon Fiber Reinforced Polymer) strengthening to the normal concrete beams. The strengthening for the beans was applied with the variable of a width and spacing of the strengthening CFPR wrapping. The impact test was conducted with the drop weight test machine. The drop weight of the hammer was 461 kg and it was dropped from the height of 300mm. The deflection and strain at the concrete in various positions of the beams were measured and compared with the reference beam to investigate the strengthening effect.

The aim of the study was to observe and provide a qualitative comparison of the behaviour of mechanically connected and adhesively bonded steel-concrete composite connections under impact load. For this, steel-concrete composites connections were subjected to drop-weight impact test. The number of blows required for crack initiation and final failure (serviceability failure in case of the stud connection) were noticed. It was found that the adhesively bonded connection can resist comparatively higher number (twice) of blows for crack initiation but, the number of blows required for final failure were relatively less. The adhesively bonded connection showed a brittle failure in concrete near the adhesive concrete interface whereas the mechanically connected specimen showed ductile failure due to concrete crushing in composite specimen nearby the studs.

Among the properties of steel fiber-reinforced concrete (SFRC), the volume fraction and shape of steel fibers play an important role when the concrete is subjected to impact and high-velocity loading. In this study, material responses obtained through impact tests, such as the drop weight test, the split Hopkinson pressure bar test, and the swinging pendulum test, are classified and briefly illustrated. The structural responses of several types of fiber-reinforced concrete with steel fibers are introduced and compared. Given the significance of this topic, an up-to-date review of available literature is provided to enhance our current understanding of the behavior of SFRC with varying volume fractions and shapes of steel fibers under different loading rates. The areas where further research is required are highlighted.

This paper focuses on the dynamic behavior of steel beams subjected to falling floor impact loads, and fin-plate connection was used to connect beams and columns. ANSYS/LS-DYNA was employed to establish detailed 3D finite element models (FEM). The accuracy of finite element models was validated against experimental results. Simulation results indicate that the deflection angle of drop weight significantly affected maximum impact force. In addition, six groups of numerical simulations were conducted to study the influence of different parameters on dynamic behavior and impact resistance. The parameters included impact energy, impact location, strength of material, imposed load, distance of bolt holes and thickness of fin-plate. Energy dissipation, maximum displacement, distribution of plastic deformation and internal force at joints were compared in each numerical group. Parametric studies suggest that energy can be used to evaluate the structural resistance of steel beams in impact analyses. Steel beams show different dynamic behaviors under a certain impact energy but different impact masses and impact velocities. A higher impact velocity can slightly improve the energy dissipation rate. Steel beams develop different impact resistances while impact loads are applied at different locations. Besides, high-strength materials are beneficial to reduce the maximum displacement. Inertial effect plays an important role in dynamic behavior. Moreover, decreasing the distance between steel bolts and the thickness of fin-plate may cause premature failure of specimens under lower impact loads.

Impact tests are conducted on concrete beams prestressed with unbonded tendons using a drop-weight facility. These beams are measured comprehensively, including impact load–deformation histories, concrete and tendon strains, and beam cracking process. The interactions between the concrete beam and the tendons are thus systematically analyzed. A model that couples particle elements with finite difference approach (PEM–FDM) is also proposed to simulate the impact behavior of the complete system that is composed of concrete–tendon composites and the loading facility. The comparisons of the test results with those of numerical simulation are satisfactory in terms of load–deformation, concrete and tendon strains, and energy transference among different components. Thus, the main features of the rupture mechanism in structures, including the development of concrete cracking and the yielding effects of tendons, can be reasonably modeled using the PEM–FDM coupling technique.

This work is concerned with the dynamic computational modelling of fibre-reinforced laminated composite panels subjected to low velocity drop-weight impacts. Wings and fuselage of aircraft structures are prone to tool (box) drop impacts during normal shipping and handling of component assembly and maintenance services. Flat nose impacts inflict localised barely visible internal damage that severely reduce compressive residual strength and might result in catastrophic failure during future operations. Hence it is important to have a better understanding of the impact response of composites to mitigate the damage and avert the unexpected failures. Many reported works on the topic are experimental, based on quasi-static indentations that take longer than contact time, and produce global deformations of thin panel where short time effects and through-thickness stresses are neglected. Hence dynamic model is needed to investigate impact behaviour of thick panels for detailed information. The present computational model includes short time effects and utilise through-thickness stresses in mode-based failure criteria to differentiate ply-by-ply failure modes. Cases of laminates up to 7.6 mm thick impacted with flat and round (for comparisons) nose impactors were simulated using ABAQUS™/Explicit dynamic routine. High stress concentration regions were meshed with adaptive meshing techniques using reduced integration elements. Selected simulation results were compared against experimental, intra-simulation results, and the data available in the literature and found to be in acceptable agreement.

In the past several numerical studies have addressed the ductile mode of fracture propagation. However, the brittle mode of pipeline failure has not received as much attention yet. The main objective of this study is to predict brittle fracture behaviour of API X70 pipeline steel by means of a numerical approach. To this end, the eXtended Finite Element Method (XFEM)-based cohesive segment technique is used to model Drop Weight Tear Test (DWTT) of X70 pipeline steel at -100°C. In this model the dynamic stress intensity factor and crack velocity are calculated at the crack tip at each step of crack propagation.

We carry out significance testing on experimental and computational data sets to determine which material and geometric parameters affect the plastic rotation factor (which is used to estimate the crack-tip-opening angle based on the plastic hinge model) for pipeline steels. It is shown, using the Xue-Wierzbicki damage mechanics model and a statistical analysis, that the rotation factor mainly depends on the Charpy V-notch energy, and empirical fits for the rotation factor are proposed.

In the present study, a finite element impact model was created and analyzed by commercial FEM code ANSYS®-AUTODYN and then validated by drop weight impact experiment. Moreover, models of single- and multilayer panels of plain weave as well as different weaving architectures were designed and created with and without holes to compare impact properties. The influence of the size and location of hole defect on the impact behavior of single-layer Twaron®fabric were investigated, the degree of influence of hole defects with different sizes on the impact behavior and the influence level by different location of the hole defects were well investigated in. In addition, the effect of hole defects on the impact behavior of multi-layer armor panel were studied. Hole defects were less influential in terms of impact contact force and had less severe constraining effect on front layer of the panel when the number of multi-layer armor panels increased. Furthermore, the effect of hole defects on the impact behavior of different weaving architectures (i.e. plain, twill, basket, and satin weave) were analyzed. Plain weave fabric had the highest energy absorption capability in impact scenarios with and without holes among all the woven architectures. Plain weave fabric was the most affected and twill weave was the least affected by hole defects in terms of transverse wave velocity; the satin weave was the most affected and the twill weave was the least affected by hole defects in terms of energy absorption. These findings will provide guidance for engineering of soft body amour and composite materials.

Thirty-one tests under low velocity drop weight impact were carried out to examine the residual failure modes and the time history of the impact forces, global deformations and strains of concrete filled double steel tubular (CFDST) members in this paper. The parameters varied in the testing program include the column type (straight and tapered), the boundary conditions (simply supported and fixed), the axial load level and the impact energy. The results showed that all CFDST members behaved in a ductile manner and the residual deformation consisted of local deformation at the impact section, as well as the overall bending deformation. Compared to hollow double steel tubes, the CFDST members under the same applied impact energy demonstrate superior impact behavior in terms of higher energy absorbed, smaller global deformation and local deformation due to the interaction of the sandwich concrete and double skin steel tubes. The influence of key parameters on the dynamic resistance ability of CFDST is discussed.

The modified Bai–Wierzbicki model allows for precise prediction of ductile fracture failure. For the upper shelf impact toughness assessment of pipeline steels through Battelle drop weight tear test, the model was extended to include strain rate and temperature effects. Through combined experimental and numerical approaches the parameters were adjusted to express the influence of strain rate and temperature on strain hardening. The results from VUMAT implementation of the model agree well with experimental results of pipeline steel x70. To reduce the material parameter calibration effort, an UMAT implementation of the material model was used (in addition to the VUMAT implementation).

This paper presents the impact energy of steel fiber concrete beams at first crack and failure with different replacement ratios of crumb rubber. The test was carried out using simple low velocity drop weight test rig for both normal concrete (NC) and steel fiber concrete (SFC). The crumb rubber with particle size of 1 – 2 mm was added with replacement ratios of 5%, 15%, and 25% by volume of fine aggregate. Six batches consisting of 6 beams (100x100x500 mm) containing 0.5% of hooked end steel fibers were tested under impact load in accordance with ACI Committee 544. The specimens were tested at the age 90 days after curing in water. The results show a reduction in the compressive strength for both NC and SFC with the incorporation of crumb rubber with greater reduction at higher crumb rubber content. However, the measured impact energy for both NC and SFC was foundincreasing with the crumb rubber replacement.

In scope of this study performances of protective layers, proposed to protect the pipes from sudden impact loads such as rock falls, are aimed to be compared. In this study, performance, strength and energy absorption capability of geofoam structures against impact forces are investigated by using drop weight impact testing apparatus. Pipes that are manufactured from steel and composite materials are tested with only 130 mm thick sand protecting layer without any geofoam structure, and with two different geofoam with different thicknesses. Results are presented in a comparative form and the effect of geofoam on the impact behavior of sand layer is investigated. Impact load and accelerations on the pipes are measured with respect to time during experiments. Absorbed energy by the pipes are calculated and compared with each other for determining performance of the different protective structures. From the study, it was observed that the sand and geofoam layers used as protective layers were generally successful by reducing the detrimental effects of impact loads in terms of dissipating impact effects on the pipes and the measured acceleration and displacement levels. The best result is obtained from the 50 mm thick geofoam with sand layer. Finite elements analyses are performed by using ABAQUS software and both test and analysis results are compared to obtain a model that can give an idea to designers. (C) 2015 Elsevier Ltd. All rights reserved.

The impact test is a test to measure the material's durabilityagainst shock loads. The impact test simulates the operating conditions of that materialoften found where the load does not always occur slowly but rathercame suddenly. The impact test instrument to be designed in this studyis a Drop Weight Tester (DWT) tool. This impact test apparatus utilizes massobjects and gravitational forces. Design of Drop Weight Tester (DWT) tool, designthe design refers to the ASTM D-5420-04 standard. In this study the designthe impact test apparatus analyzed the strength of the connection as well as the construction deflection forensure design results can be made. On testing Drop Weight Tester, objectsthe test is given a shock load with certain criteria such as altitude, load, dimensionpunch component striker as well as specimen thickness. At the same time it is doneobservation and data collection of the energy absorbed during the test.Specimen used is SPCC and Zincalume material with thicknessdifferent.

In this paper, the low-velocity impact response of patch-repaired CFRP laminates is investigated experimentally and numerically. This study considers various patches of different shapes and sizes placed on the single side of the parent laminate plates. In the low-velocity impact simulation, damage development and the failure process of the repaired laminate plates are analyzed based on continuum damage mechanics (CDM) theory which is derived from 3D Hashin failure criteria, and a cohesive zone model (CZM). In order to validate the proposed numerical approach , impact response such as impact force and energy are predicted from simulation. Moreover, the corresponding drop weight impact tests have been performed, and the numerical prediction is in a good agreement with the experimental measurements. Finally, the influence of patch parameters on repair performance has been analyzed according to the delamination surface area and absorbed energy of the repaired laminates from the low-velocity impact simulation. And, an optimal impact-resistance design of the patch repair is obtained based on the finding results.

This study investigates the impact behavior of concrete beams using drop-weight facility. Different tups were used and varying drop weights and heights were applied. This study measures impact loads, mid-span accelerations, and strains at the top and bottom edges of the beam. To distinguish the inertial and bending components of impact forces, inertial force is formulated based on elastic beam theory. When the strain rate ranges between 0.1 s−1 and 4 s−1, rate effect is significant given corresponding dynamic increase factors ranging from 1.6 to 3.4. Finally, the equilibrium of momentum–impulse and energy conversion are examined.

Quasi-static and dynamic crush tests of a unidirectional carbon fiber reinforced plastic (CFRP) circular tube were performed, and its energy absorption capability was controlled using a double-sided plug. It was revealed in the quasi-static crush test that its energy absorption capability was controlled significantly from 8 to 178 kJ/kg by changing the curvature of the plug. The range of energy absorption covers almost all types of CFRP tube reported in the literature. A dynamic crush test up to 55 km/h was then performed by drop weight impact tests. The energy absorption capability of the CFRP tube in the dynamic crush test was very similar to that in the quasi-static crush test. A simple design concept of energy absorption for a CFRP tube, using the double-sided plug, was proposed.

This work is concerned with physical testing of carbon fibrous laminated composite panels with low velocity drop-weight impacts from flat and round nose impactors. Eight, sixteen, and twenty-four ply panels were considered. Non-destructive damage inspections of tested specimens were conducted to approximate impact-induced damage. Recorded data were correlated to load–time, load–deflection, and energy–time history plots to interpret impact induced damage. Data filtering techniques were also applied to the noisy data that unavoidably generate due to limitations of testing and logging systems. Built-in, statistical, and numerical filters effectively predicted load thresholds for eight and sixteen ply laminates. However, flat nose impact of twenty-four ply laminates produced clipped data that can only be de-noised involving oscillatory algorithms. Data filtering and extrapolation of such data have received rare attention in the literature that needs to be investigated. The present work demonstrated filtering and extrapolation of the clipped data using Fast Fourier Convolution algorithm to predict load thresholds. Selected results were compared to the damage zones identified with C-scan and acceptable agreements have been observed. Based on the results it is proposed that use of advanced data filtering and analysis methods to data collected by the available resources has effectively enhanced data interpretations without resorting to additional resources. The methodology could be useful for efficient and reliable data analysis and impact-induced damage prediction of similar cases’ data.

The new multi-layer pavement system is proposed according to the laboratory impact test. This proposed multi-layer pavement is the combination of High Strength Concrete (HSC), Engineered Cementitious Composite (ECC), and Asphalt Concrete (AC) reinforced with High Strength Geosynthetics (GST), which has good impact resistance. The control specimens with current pavement design will also be investigated for its dynamic behavior under impact load. Results from conventional and proposed multi-layer pavement will be discussed.

Research work carried out so far towards the development of concrete that exhibits improved impact resistance than conventional concrete. There are several situations in which concrete structural elements are subjected to impact loading. The behaviour of concrete under impact loads is far from adequate and there is significant variability in the published literature. The primary reason for this is the lack of a standardized technique of testing concrete under impact. In this project, an attempt is made to study the impact resistance of fibrous concrete using ACI drop weight Impact tester. Two grades of concrete's namely M1 and M2 are consideredin this investigation with 0.5, 1.0, 1.5 and 2.0% dosage of steel fiber. The experimental test results of steel reinforced fiber concrete are compared with plain concrete and conclusions are arrived. Shivaraj et al. (1989) have presented the results of an investigation carried out to determine the flexural, endurance limit and impact strength of steel fiber reinforced refractory concrete at 0.5, 1.0 and 1.5% by volume of fiber. These properties are compared to the same refractory concrete mix without steel fiber. The fatigue strength of increased 61, 159 and 199 to 0.5, 1.0 and 1.5% by volume of steel fiber, respectively. The endurance limit expressed as a percentage of plain concrete modulus of rupture, increased 60, 160 and 200%. When reinforced with 0.50, 1.0 and 1.5% of steel fiber by volume, respectively. The addition of steel fiber also substantially increased the strength of refractory concrete. Lifshitz et al. (1995) have investigated low

The aim of this work is to study the behaviour of two types of composite material when subjected to impacts at different energy levels under low velocity impact events. The composite material used in this study was Glass Fibre Reinforced Polymer (GFRP) which was C-type/600 g/m2 and E-type/600 g/m2. This material was fabricated to produce laminated plate specimens with a dimension of 100 mm 150 mm. Each specimen had 10 layers of GFRP woven roving plies. The low velocity impact test was performed using an IM10 Drop Weight Impact Tester with a 10 mm hemispherical striker cap. The impact energy was set to 14, 28, 42 and 56 joules with velocity ranging from 1.73 m/s to 3.52 m/s. The relationships of impact energy with impact force, displacement and energy absorbed are presented. The comparison and behaviour between the two types of GFRP are discussed.

This work is concerned with physical testing and numerical simulations of flat and round nose drop-weight impact of carbon fibre-reinforced laminate composite panels to predict ply level failure. Majority of the existing studies on impact of composites by spherical nose impactors are experimental, computational models are simplified, and based on classical laminated plate theories where contributions of through-thickness stresses are neglected. Present work considers flat nose impact and contributions from through-thickness stresses and is mainly simulation based. A computational model was developed in ABAQUS™ software using adaptive meshing techniques. Simulation produced (2D model) stresses were numerically integrated using MATALB™ code to predict through-thickness (3D) stresses. Through-the-thickness stresses were then utilised in advanced failure criteria coded in MATLAB™ software to predict ply level failures. Simulation produced results demonstrate that the computational model can efficiently and effectively predict ply-by-ply failure status of relatively thick laminates.

This paper presents low velocity impact testing on fibreglass reinforced polymer. The materials used in this experiment are Type C-glass/Epoxy 600 g/m 2 and Type E-glass/Epoxy 800 g/m 2 . The materials were fabricated into 10 layer laminates. The drop weight low velocity impact tests were performed on 101.6 mm × 152.4 mm (4 in × 6 in) laminated plates using Imatek IM10 ITS Drop Weight Impact Tester in accordance with the Boeing Specification Support Standard Boeing BSS 7260 with variation in incident impact energy. As incident impact energy increases, the damage area also increases. Several damage modes occurred from delamination to matrix cracking. The 10-ply Type C-glass/Epoxy 600 g/m 2 laminate exhibited more severe matrix damage than the 10-ply Type E-glass/Epoxy 800 g/m 2 laminate at the same impact energy level. From this experiment, 10-ply Type Eglass/Epoxy 800 g/m 2 is recommended as the material for low velocity impact, as it has a higher impact resistance compared to 10-ply Type C-glass/Epoxy 600 g/m 2 .

This paper presents the results of an investigation carried out on Ultra High Strength Concrete (UHSC) panels subjected to low velocity projectile impact to assess impact resistance. UHSC panel of size 350 × 350 mm and thickness 15 mm is studied under drop weight impact loading for three different pre-determined drop heights ranging from 100 mm to 300 mm. The response of UHSC panel in terms of acceleration vs time is obtained experimentally. Numerical model has been developed to simulate the impact behaviour of UHSC panel. The Brittle cracking model is used to simulate the behaviour of UHSC panel under impact loading and to perform parametric studies by varying the volume fraction of steel fibres.

The impact responses of typical laminates are investigated numerically in this research. Delamination responses among plies and fibre and/or matrix damage responses within plies are simulated to understand the behaviours of laminates under different impaction conditions. Damage resistance of a laminate is highly dependent upon several factors including geometry, thickness, stiffness, mass, and impact energies (impact velocities), which are here considered by the finite element (FE) method. Three groups of composite laminates are simulated and the numerical results in general are in good agreement with corresponding experiments. Models containing different stacking sequences and impact energies are built to study their influence on impact responses and demonstrate that clustered (or nearly clustered) plies in the laminate can effectively reduce the degree of interface damage. Models containing different indenters and plate shapes are also built to systematically study their influence on the low-speed drop-weight behaviour of composite laminates. Suggestions are proposed for designing impact tests for particular purposes.

It is a challenging task to develop a lightweight, and at the same time, strong material with high energy absorption for applications in military vehicles, which are able to withstand impact and blast with minimum injury to occupants. This paper presents a study on aluminium matrix syntactic foams as a possible core material for a protection system on military vehicles. Experimental work was first carried out which covers sample preparation through pressure infiltration and impact tests on aluminium matrix syntactic foams manufactured. Numerical models were then developed using commercial finite element code ABAQUS/Explicit to simulate the dynamic behaviour of the foam. The effect of strain rate on their compressive behaviour was investigated as these properties are vital in terms of the applications of these materials. Characterisation of the foam behaviour under low velocity impact loading and an identification of the underlying failure mechanisms were also carried out to evaluate the effective mechanical performance. It was found that samples subjected to drop weight impact offered a 20–30% higher plateau stresses than those of the samples subjected to quasi-static compression loading. The degree of correlation between the numerical simulations and the experimental results has been shown to be reasonably good.

Plain GFRP, copper wire embedded GFRP and SMA short fibres included copper wires embedded GFRP laminates have been prepared by hand lay-up method. The mechanical properties like flexural and tensile strength were investigated. To study the impact properties of the laminates an experimental set up was designed and the impact strength of the laminates was studied by drop weight method. Three point bend method was adopted for flexural studies and the tensile strength was found by Instron Machine. It is found that the inclusion of SMA short fibres significantly improved the mechanical properties of the composites.

We modify the Xue–Wierzbicki damage mechanics model to include strain rate effects, implement it in an explicit finite element code and use it to model the dynamic response and failure of X70 pipe steel in the Drop-Weight Tear Test (DWTT). The damage evolution depends on Lode angle, hydrostatic pressure, and strain rate. Strength of the steel is assumed to depend on strain hardening, strain rate and thermal softening. To mitigate the expected mesh dependence of results, we use the non-local integral formulation due to Bazant and Pijaudier-Cabot. A highlight of the computational results is the ability to model the fracture mode transition between impact and static loading: slant fracture for impact loading and flat fracture for static loading of the DWTT specimen. Furthermore, the measured experimental force–displacement curves are in excellent agreement with the computed curves. We estimate the Crack Tip Opening Angle and compare with experimental measurements. Our results also provide insight into the influence of the Lode-angle-dependent damage evolution on modeling slant fracture.

This paper reports on the actual and virtual low velocity impact response of carbon fibre composite laminates. It utilises the contribution of through-thickness stresses, in the prediction of the onset of internal damage created by this type impact scenario. The paper focuses on the damage imparted by the flat nose impactor since this induces a different type of damage and structural response compared to that of the standard test method of using a round nose impactor. Vulnerability of the fibrous composites to vertical drop-weight impact can result in premature failure which is a major concern in their widespread usage. The topic has been of intense research to design more damage tolerant and resistant materials. However, due to materials’ anisotropic and three-dimensional nature and complicated damage mechanisms no standard model could have been achieved. Designers predict consequences of a local impact within the global structural context without full-scale testing. Majority of the existing simulation models neglect through-thickness stresses that are regarded as the major cause of catastrophic failures. Efficient and reliable investigations are required to reduce testing and include through-thickness stresses. Drop-weight impact simulation models were developed herein using ABAQUS™ software. Simulations were carried out to compute in-plane stresses subjected to flat and round nose impacts on laminates of differing thicknesses. These stresses once computed were numerically integrated employing the equilibrium equations to efficiently predict through-thickness stresses. The predicted stresses were then utilised in failure criteria to quantify the coupled and embedded damage. This provides a quick insight into the status and contribution of through-thickness stresses in failure predictions. The computed values were compared to the experimental results and found to be in good agreement.