High Velocity Impact Loading Research Articles

Multi-scale analysis of high-speed dynamic friction

Friction occurring at the interface between dissimilar metallic components as a result of high velocity impact or explosive loading can have a profound effect on the subsequent motion. A comprehensive understanding of the involved processes across a wide range of initial conditions remains outstanding. Dry sliding of single crystal silver on copper at high pressure is investigated for a range of sliding speeds using a multi-scale modelling method based upon the domain decomposition approach (molecular dynamics in the near interface region and continuum mechanics elsewhere). The transient solutions reveal detailed observations of the processes that lead to phenomena such as the growth of epitaxial layers of the softer material, shifting of the sliding interface due to formation of shear-bands, development of amorphous structures, and ultimately the resultant motion of the components. Analysis of the results also links these processes to the changes in the state of the material through growth of dislocations and thermal effects.

High Velocity Impact Damage Analysis for Glass Epoxy-Laminated Plates

The ultimate objective of the current work is to examine the effect of thickness on fiberglass reinforced epoxy matrix subjected to high velocity impact loading. The composite material chosen for this research was from type C-glass/epoxy 200 g/m2and type C-glass/epoxy 600 g/m2. This material is used as a composite reinforcement in high performance applications since it provides certain advantages of specific high strength and stiffness as compared to metallic materials. This study investigates the mechanical properties, damage characterisation and impact resistance of both composite structures, subjected to the changes of impact velocity and thickness. For mechanical properties testing, the Universal Testing Machine (UTM) was used while for the high velocity impact, a compressed gas gun equipped with a velocity measurement system was used. From the results, it is found that the mechanical properties, damage characterisation and impact resistance of type C-glass/Epoxy 600 g/m2posses better toughness, modulus and penetration compared to type C-glass/Epoxy 200 g/m2. A general trend was observed on the overall ballistic test results which indicated that as the plate specimen thickness continues to increase, the damage at the lower skin decreases and could not be seen. Moreover, it is also found that, as the plate thickness increases, the maximum impact load and impact energy increases relatively. Impact damage was found to be in the form of perforation, fibre breakage and matrix cracking. Results from this research can be used as a reference in designing structural and body armour applications in developing a better understanding of test methods used to characterise impact behaviour.

Quantification of impact energy dissipation capacity in metallic thin-walled hollow sphere foams using high speed photography

Quantification of energy dissipation capacity in metallic foams is required for their application in transport components subject to high velocity impact loads. In this study, in-situ high speed photography combined with in-house grid tracking codes was used to quantitatively investigate the impact behavior of electrodeposited nickel thin-walled hollow sphere foams in gas gun impact testing at an initial velocity of 60–140 m s−1. The energy dissipated by the foam varied almost linearly with the depth of impacted volume. The compressive plateau stress, which it is difficult to measure directly using conventional experiments, was then calculated for high impact loading velocity. It was found that both the energy dissipation capacity and average plateau strength increase with the initial impact velocity, which may suggest a rate dependency of the foam.

Effects of Short Fiber Reinforcement on the Local Damage of Concrete Plates under High Velocity Impact Loading

This study presents the effects of short fiber reinforcement on the local damage of concrete plates subjected to high velocity impact. In a series of tests, three short fiber composite materials were used. Firstly, static bending tests were conducted to reveal mechanical properties in tension of the short fiber reinforced concrete. Then, high velocity impact tests were carried out to examine the effects of short fiber reinforcement on the local damage of concrete plates. Failure mode and strain behavior on the back surface of the short fiber reinforced concrete plates demonstrated that short fiber reinforcement was very effective in reducing the local damage.

Experimental study of CFRP fluid-filled tubes subjected to high-velocity impact

In recent years, vulnerability against high-velocity impact loads has become an increasingly critical issue in the design of composite aerospace structures. The effects of Hydrodynamic Ram (HRAM), a phenomenon that occurs when a high-energy object penetrates a fluid-filled container, are of particular concern in the design of wing fuel tanks for aircraft because it has been identified as one of the important factors in aircraft vulnerability. The projectile transfers its momentum and kinetic energy through the fluid to the surrounding structure, increasing the risk of catastrophic failure and excessive structural damage. For the present work, water-filled CFRP square tubes were subjected to an impact of steel spherical projectiles (12.5 mm diameter) at impact velocities of 600–900 m/s. The CFRP tubes were filled to different volumes to examine how volume might influence the tank behavior. The composite test boxes were instrumented with six strain gauges and two pressure transducers, and the formation process of the cavity was recorded using a high-speed camera. The damage produced in the tubes was then analyzed, and differences were found according to the testing conditions. This work presents the results of these tests.

Characterization of 6061 T651 aluminum plates subjected to high-velocity impact loads

Ballistic response of single or multi-layered metal armor systems subjected to kinetic energy projectiles was investigated in many experimental, theoretical and numerical studies. In this study, 6061 T651 aluminum plates impacted by 9 mm bullets were investigated. Microstructural investigations have been carried out using optical microscopy. Microhardness values were used to determine the strength behavior of the plates. Influence of the plate thickness and impact velocity on the microstructure has been evaluated. It was concluded from the study that thinner plates are more prone to deformation hardening with high penetration depth values even at low impact velocities while thick plates are more susceptible to thermal softening with less penetration depths. Maximum hardness values were obtained just below the impact zone in both plate thicknesses.

High Rate-Dependent Interaction Diagrams for Reinforced Concrete Columns

Problem statement: There is a need to better understand the rate dependence behavior of reinforced concrete structures in order to improve their response to impact and blast loads. Analysis and design of reinforced concrete structures subjected to seismic loadings has been recommended in many FEMA guidelines. However, reevaluation of design becomes extremely important in cases where large deformations are expected such as blast and impact resistant. Approach: This study presents a numerical model to evaluate reinforced concrete columns submitted to high strain rates expected for seismic, impact and blast loadings. The model utilizes dynamic stress-strain response and considers the effect of strain rate on concrete strength; strain at peak stress; yield and ultimate strength of steel; and slope of the softening portion of the stress-strain curve. Results: Results are presented in the form of interaction diagrams and compared with the available analytical and experimental results. Comparison with available data shows that the proposed model can give consistent prediction of the dynamic behavior of reinforced concrete columns. Conclusion/Recommendations: The established interaction diagrams may be used to design columns to withstand high velocity impact loads. Also, knowledge gained can be used to improve dynamic behavioral models and computer-aided analysis and design of reinforced concrete columns subjected to severe blast loadings.

Numerical algorithms and material models for high-velocity impact computations

This article is the written version of a keynote presentation given at the Hypervelocity Impact Symposium in Williamsburg VA in September 2007, in response to accepting the Distinguished Scientist Award from the Hypervelocity Impact Society. As is the tradition, this article is a summary of the technical work performed throughout the career of the award recipient. It covers a range of numerical algorithms and computational material models for high-velocity impact and other intense impulsive loading conditions.

Structural Characterization of Composite Structural Insulated Panels for Exterior Wall Applications

Structural sandwich composite panels are extensively used for modular panelized construction. This paper includes the structural characterization of the innovative composite structural insulated panels (CSIPs) developed for the exterior walls of a modularized structure. The facesheets of the CSIPs consist of E-glass fibers impregnated with polypropylene matrix, while the core consists of expanded polystyrene foam. The overall panel dimensions including the thickness of the facesheets and the core were obtained using sandwich composite design theories. Uniaxial compressive loading and high velocity impact (HVI) loading are the most important loading criteria for an exterior wall of a structure. The proposed CSIPs were tested for a compressive load of 13.13 kN/m (900 plf) in this study. The deflection at this load was ∼3 mm which was within deflection limits of span/150 as prescribed in ACI 318-05 building design code. The proposed CSIP wall panels were also tested under HVI for the loads prescribed by Fede...

Sandwich structures with textile-reinforced composite foldcores under impact loads

The mechanical behaviour of composite sandwich structures with textile-reinforced composite foldcores, which are produced by folding prepreg sheets to three-dimensional zigzag structures, is evaluated under compression, shear and impact loads. While foldcores made of woven aramid fibres are characterised by a rather ductile behaviour, carbon foldcores with their brittle nature absorb energy by crushing, showing extremely high weight-specific stiffness and strength properties. The impact damage under low and high velocity impact loads tends to be very localised. In addition to regular single-core sandwich structures, a dual-core configuration with two foldcores is also investigated, showing the potential of a two-phase energy absorption behaviour. In addition to experimental testing, finite element models for impact simulations with LS-DYNA have been developed. Despite the high degree of complexity of the models due to the various skin and core failure modes that have to be covered, the results correlate well with test data, allowing for efficient parameter studies or detailed evaluations of damage patterns and energy absorption mechanisms.

Influence of surface coating on ballistic performance of aluminum plates subjected to high velocity impact loads

Ballistic response of single or multi-layered metal armor systems subjected to high velocity impact loads was investigated in many experimental, theoretical and numerical studies. In this study, influences of plasma spray surface coating on high velocity impact resistance of AA 6061 T651 aluminum plates were analyzed experimentally. Two different types of surface coating were applied to plates using plasma spray. Using 9.00 mm Parabellum bullets, ballistic performance of both uncoated and coated plates was tested. After the impact tests, penetration depth including plate bending on the front face and bulging on the rear face of the target plate was measured. The improvement on the ballistic resistance of the coated plates was clearly observed. The increase in non-perforating projectile velocity and the decrease in penetration depth were both experienced.

Experimental Study of Dynamic Material Properties of Clay Brick and Mortar at Different Strain Rates

It is well known that most construction materials behave differently under highspeed and static loading conditions. The strain rate effect on many materials, such as metals, concrete and rock, has been intensively investigated. However, the strain rate effect on masonry materials, such as clay bricks and mortar mixed with cement, lime and sand, cannot be found in open literature. Understanding the strain rate effects on masonry materials is important for accurately modelling masonry structure damage to high-velocity impact and blast loads. This paper reports experimental results of the strain rate effect on clay bricks and mortar materials. Uniaxial compression tests were carried out on brick and mortar specimens at various strain rates ranging from quasi-static (10-6 /s) to dynamic up to a strain rate of 200 /s. The strain rate effect on the yield and ultimate strength, yield and ultimate strain, elastic modulus, and Poisson’s ratio of clay brick and mortar material are determined from the testing results. Empirical relations of dynamic increase factors (DIF) for the material properties are derived and presented. Discussions and comparisons of the DIF of brick and mortar obtained in this study are also made with other geomaterials, such as concrete and rock.

Numerical simulation of nonlinear elastic wave propagation in piecewise homogeneous media

Systematic experimental work [S. Zhuang, G. Ravichandran, D. Grady, J. Mech. Phys. Solids 51 (2003) 245–265] on laminated composites subjected to high velocity impact loading exhibits the dispersed wave field and the oscillatory behavior of waves with respect to a mean value. Such a behavior is absent in homogeneous solids. An approximate solution to the plate impact in layered heterogeneous solids has been developed in [X. Chen, N. Chandra, A.M. Rajendran, Int. J. Solids Struct. 41 (2004) 4635–4659]. The influence of the particle velocity on many process characteristics was demonstrated. Based on earlier results [A. Berezovski, J. Engelbrecht, G.A. Maugin, Arch. Appl. Mech. 70 (2000) 694–706], numerical simulations of one-dimensional wave propagation in layered nonlinear heterogeneous materials have been performed. The formulated problem follows a conventional experimental configuration of a plate impact. An extension of the high-resolution finite volume wave-propagation algorithm [R.J. LeVeque, Finite Volume Methods for Hyperbolic Problems, Cambridge University Press, 2002] is used. The speed of sound depends nonlinearly on a current stress value in each layer but also on the mismatch properties of layers. Results of numerical simulations capture the experimental data rather well.

Parametric optimization of grid-stiffened composite panels for maximizing their performance under transverse loading

The main focus of this paper is the optimization of geometry to maximize the specific energy absorption of E-glass/polypropylene isogrid composite panels under transverse quasi-static and dynamic impact loading using finite element analysis. The behavior of some of these grid-stiffened composite panels was also analyzed experimentally under high velocity impact loading, and the fluctuations observed in the load–time response during the impact event were attributed to structural resonances of the impactor, the isogrid panel or both combined. Parametric studies of varying the geometry (rib width and thickness; center-to-center distance between rib joints and skin thickness) to maximize specific energy absorption were performed. This study will help in recommending isogrid composite panels for the design and use in applications where impact energy absorption is important, such as in the side doors of automobiles.

On the Shear Bands and Shear Localizations in Elastohydrodynamic Lubrication Films

On the Shear Bands and Shear Localizations in Elastohydrodynamic Lubrication Films

HIGH VELOCITY IMPACT DYNAMIC RESPONSE OF STRUCTURES USING SPH METHOD

This paper presents the dynamic response of structures under high velocity impact loading using Smooth Particle Hydrodynamics (SPH) approach. The SPH equations governing the elastic and elasto-plastic large deformation dynamic response of solid structure are derived. The proposed additional stress points are introduced in the formulation in order to mitigate the tensile instability inherent in the SPH approach. The incremental rate approach is combined with the leap-frog scheme of time integration forming solution algorithm adopted in present study. Examples on high velocity impact of the solids are presented and results from the proposed SPH approach compared with available finite element solution illustrating that the transient dynamic response under high velocity impact can be effectively solved by the proposed SPH approach.

Performance of stitched/unstitched woven carbon/epoxy composites under high velocity impact loading

In this paper, response of stitched/unstitched woven fabric carbon/epoxy composite laminates subjected to high velocity impact loading is discussed. Aerospace grade plain and satin weave carbon fabrics were used to manufacture the laminate using a toughened SC-15 epoxy resin system with an affordable vacuum assisted resin infusion molding process. For fabrication of stitched laminates, a 3-cord Kevlar thread was used to stitch the fabric preform in lock stitch fashion in an orthogonal grid of size 12.7 and 25.4 mm with 6 mm stitch spacing. Unstitched laminates used in the study were made of 7, 17 and 37 layers whereas the stitched laminates were made of 7 and 17 layers. Four laminates of each type were subjected to high velocity impact loading at different velocity to determine the ballistic limit. The ensuing damage was characterized through ultrasonic NDE. Results of the study indicate that the damage was well contained within the stitch grid incase of stitched laminates. However, ballistic limit was higher for the unstitched laminates. Ballistic limit increased with the increase in the thickness of the laminate. Further, satin weave laminates exhibited higher ballistic limits in most of the cases.

Intermediate Velocity Impact Response of Carbon/Epoxy Composites with Polycarbonate Facing

Woven fabric composites are increasingly being used in composite structures for applications in the aircraft, marine, and automotive industries. With emerging low-cost processing techniques for composite materials, the role of fabric architectures in sustaining low, intermediate, and high velocity impact loads is a subject of interest. An example of a low-cost process is the out-of-autoclave, vacuum assisted resin transfer molding (VARTM) technique. The present study evaluates the intermediate velocity impact response of two commonly used structural carbon fabric laminates produced from plain and 2/2 twill woven fabrics, processed using VARTM. A series of impact tests have been performed on the all plain, all twill and hybrid plain-twill weave carbon/epoxy laminates. All laminates studied were covered with a polycarbonate facing in order to enhance the impact resistance of the carbon/epoxy laminates. The perforation mechanism, ballistic limit, and damage evolution of each laminate has been studied. The results from the experiments are reported.

High-velocity impact loading of thick GFRP blocks

High-velocity impact loading of thick GFRP blocks

High-velocity impact loading of thick GFRP blocks

In previous depth of penetration experiments with tungsten long rod projectiles was found that the ballistic resistance of a relatively thick - up to the penetrator length - glass fibre reinforced plastic block grows with increasing penetration depth. This penetration behaviour significantly differs from that of other inert armour materials. Until now, no significant difference between unconfined and totally confined GFRP configurations has been found. Newest experiments with up to semi-infinite thick GFRP blocks show a change in the penetration process: For thicknesses significantly higher than the penetrator length the protective power may saturate. During the late penetration phase the shortening and deceleration of the projectile induce a change of penetration mechanism from erosion to rigid body penetration. Additionally, the projectile may break into several individually tumbling parts. Reflected tension waves and, probably, pyrolysis effects may cause increasing precursory damage. These effects together are likely to explain the reduction of the ballistic resistance increase during the late penetration phase. Based on these experimental results the published working hypothesis on the governing mechanism of the GFRP penetration behaviour had to be completed. A new approach based on a hyperbolic tangent function seems to satisfactorily describe the observed thickness dependent phenomena.