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Results of theoretical and experimental studies of the interior ballistics of a powder-driven pulsed cannon are presented. The liquid flow in the facility is considered in quasistationary and nonstationary formulations. Conditions for the applicability of the quasistationary approximation are determined. The effect of the compressibility of the liquid on the performance of the pulsed cannon is evaluated. Calculation results are compared with experimental data obtained on a particular installation.

A novel technique was devised for the selected area observation of residual microstructures in the deformation zones and the detached cap sections of 0.22 calibre bullet holes in thin sheets and laminate thicknesses ranging from 0.03 to 0.54 mm of 304 stainless steel and Inconel 600 by bright- and dark-field transmission electron microscopy. Microhardness measurements over the detached cap and petals, extending radially into the undeformed material, indicated the zone of action to be confined to a region bounded by the deviation of the impact zone from the plane of the plate. This feature was confirmed by electron microscope observations which indicated no defects beyond the bounds of the zone of action so defined. Residual microhardness was observed to increase from the radial bound of the zone of action toward the axis of projectile motion, with maximum hardness values roughly twice the undeformed sheet hardness observed in the petal edges and the detached caps. Dislocation densities were observed to increase correspondingly over this range (∼ 106 to 1011 cm−2), with deformation twins occurring in the petal edges and the detached caps of both materials. An analytical treatment of the specific ballistic perforation examined in this investigation based on the plastic stretching of the target zone of action, fracture and detachment of a cap, and the subsequent petalling of the crater as perforation commences, indicated an absence of high pressure shock effects.

We propose a technology of hardening of the working surfaces of the rollers of dies intended for the treatment of titanium alloys. The detonation deposition of the WC–10Co–4Cr alloy with a thickness of 600 μm and subsequent fusion of this layer with the help of a laser make it possible to increase the hardness of the working layer up to 1057 HV (> 67 HRC). In this case, the wear resistance becomes more than seven times higher as compared with the case of traditional thermal treatment applied for Kh12MFsteel.

We analyze the causes of the in-service loss of integrity of the steel rods of pumps due to the fatigue fracture of their main part as a result of propagation of the surface cracks. To increase the service life of the rods, it is proposed to use a special liquid working medium inhibiting the process of propagation of fatigue cracks as a result of the artificial creation of the effect of crack closure. As a result of scaled-down experiments on the high-cycle fatigue of rods made of 35KhM and 20N2M steels performed after long periods of operation, it was discovered that, on the one hand, a 3% NaCl solution exerts a noticeable negative influence on the fatigue strength and, on the other hand, the working medium exerts a significant positive effect. This effect manifests itself in the increase in the fatigue strength of the rods not only in corrosive media but also in air. For the practical realization of the method under the field conditions, we propose a design of a special chamber, which is fixed on the rod and covers its part.

The engraving of projectile is of great importance during interior ballistics when a gun is fired. In order to investigate the effect of loading speed on the engraving process, quasi-static and dynamic engraving tests are performed, respectively. Small caliber projectiles were engraved by using an MTS809 under predetermined low loading speeds and a specially designed gas gun-based test rig under high loading speeds. The hoop strain of the exterior surface of gun barrel during engraving process was measured. Surface morphology of copper jacket after engraving was observed. Microstructural evolution in cross section of copper jacket was investigated. The present study demonstrates the critical role of strain hardening at low loading speeds and strain rate effect as well as thermal effect at high loading speeds during the engraving process.

Up until the Industrial Revolution, the dynamic mechanical properties of materials were only of importance in warfare, particularly after the powder-driven gun was invented. With the invention of the steam engine, the explosion of steam boilers (which is similar to the explosion of cannon) became a concern. When railways began to be built, the lack of knowledge of the dynamic properties of the iron alloys used in rails and railway bridges was understood to be a problem, but no way of measuring them was devised until the end of the nineteenth century. Ingenious mechanical (and later electromechanical) methods of recording signals onto rotating drums or moving smoked glass plates began to be developed from the middle of the nineteenth century onwards. Optical/photographic methods of recording information from dynamic experiments date from the 1890s. The rod-on-anvil technique (later named after Taylor) was developed in France at the beginning of the twentieth century but not mathematically analysed until the 1940s. The Hopkinson pressure bar was invented just before the start of the First World War and found to be useful in improving British artillery shells. It was then forgotten about until the Second World War when a two-bar version was developed for measuring the dynamic properties of soft materials such as explosives and polyethylene. As the story of high rate mechanical testing from about 1950 onwards is quite well known to the high rate testing community, this date is taken as the end point of this article.

A method on the macroscopic length scale is developed to determine frictional energy losses between a homogeneous solid bullet and a twisted barrel. This accounts for the entire interaction between the bullet and the barrel surface, the drag due to the engraving forces, and possible friction-optimized bullet coatings. The method applied is based on the shot’s energy balance which requires as input parameters the bullet and barrel geometries, stress–strain curves of bullet and casing material, and muzzle velocity. The validation is done for a .22lr cartridge fired in a small bore match rifle. Additionally, the model is capable to give an average, system-specific coefficient of friction according to Amontons’ law, which could be an essential quantity for the tribological internal ballistics analysis, especially in the future development of lead-free bullets.

The crater volume has been an important factor in ballistics and has many influences such as material strength, initial projectile velocity, angle of incidence, and nose shape. The goal of this research is to predict the resulting crater volume of a long rod penetration based on the initial projectile velocity and mass. Mooney’s (Bull Seism Soc Am 64(2):473, 1974) displacement equations were used to calculate the elastic crater volume for a given impulse force, P, varying as a delta function in time on the surface of an isotropic, semi-infinite solid. This estimated elastic volume, Velastic is linearly related to the experimental ballistic volume, Vexperimental by an “energy dissipation factor”, k. Velastic = kVexperimental. The energy dissipation factor “lumps” together elastic and plastic deformation mechanisms. Terminal ballistic data for a steel long-rod projectile into “semiinfinite” steel or aluminum target will be compared to the crater volume calculated through the use of k.

To qualitatively understand the deformation processes and damages in the human body caused by high-speed impact, we conducted experimental and computational investigations for bullet penetration into viscoelastic ballistic gelatin blocks. Because it is difficult to measure the strain rate-dependent material properties of viscoelastic gelatin blocks during high-speed impact, the material properties that are indirectly defined by the stress relaxation test were used for the computational simulation. We also conducted some firing experiments and analyzed the deformation processes of the structures. In particular, the passing through times and the shapes of the temporary and permanent cavities inside the ballistic gelatin blocks were analyzed and compared. This data reveals that the employed material models, with some modifications for the FE simulation, are sufficient for predicting the high-speed impact behaviors. To investigate the shapes of the permanent cavities and fragments made by bullets inside the gelatin blocks, two-dimensional sectional images were taken by an industrial CT scanner and a three-dimensional CAD model was constructed based on these images.

In our recent work, a multi-physics computational model for the conventional gas metal arc welding (GMAW) joining process was introduced. The model is of a modular type and comprises five modules, each designed to handle a specific aspect of the GMAW process, i.e.: (i) electro-dynamics of the welding-gun; (ii) radiation-/convection-controlled heat transfer from the electric-arc to the workpiece and mass transfer from the filler-metal consumable electrode to the weld; (iii) prediction of the temporal evolution and the spatial distribution of thermal and mechanical fields within the weld region during the GMAW joining process; (iv) the resulting temporal evolution and spatial distribution of the material microstructure throughout the weld region; and (v) spatial distribution of the as-welded material mechanical properties. In the present work, the GMAW process model has been upgraded with respect to its predictive capabilities regarding the spatial distribution of the mechanical properties controlling the ballistic-limit (i.e., penetration-resistance) of the weld. The model is upgraded through the introduction of the sixth module in the present work in recognition of the fact that in thick steel GMAW weldments, the overall ballistic performance of the armor may become controlled by the (often inferior) ballistic limits of its weld (fusion and heat-affected) zones. To demonstrate the utility of the upgraded GMAW process model, it is next applied to the case of butt-welding of a prototypical high-hardness armor-grade martensitic steel, MIL A46100. The model predictions concerning the spatial distribution of the material microstructure and ballistic-limit-controlling mechanical properties within the MIL A46100 butt-weld are found to be consistent with prior observations and general expectations.

This paper describes the components and operation of an experimental setup for the visualization of liquid propellant (LP) jet combustion at pressures above 100 MPa. The apparatus consists of an in-line ballistic compressor and LP injector. The ballistic compressor, based on a modified 76 mm gun, provides high-pressure (ca. 55 MPa) clear hot gas for the jet ignition. A piston (projectile) is fired toward a test chamber beyond the barrel’s end, and its rebound is arrested in a transition section that seals the test chamber to the barrel. The LP jet is injected once the piston is restrained, and combustion of the jet further elevates the pressure. At a preset pressure, a disc in the piston ruptures and the combustion gas vents sonically into the barrel. If a monopropellant is used, the jet injection-combustion process then resembles liquid rocket combustion but at very high pressures (ca. 140 MPa). This paper discusses the ballistics of the compression and compares experimental results to those predicted by a numerical model of the apparatus. Experimentally, a pressure of 70 MPa was achieved upon a 12.5 volumetric compression factor by firing a 10 kg piston into 1.04 MPa argon using a charge of 75 g of small-grain M1 propellant.

A mathematical model for a projectile shot at low pressures in the space behind the projectile space is developed. The pressure rise is limited because of the nonsimultaneity of propellant ignition and combustion and the discharge of the propellant combustion products through the gap between the projectile and the walls of the gun barrel. The kinetic characteristics of flame propagation over the propellant particles are determined. A comparison of calculation and experimental data is performed. The calculation results are used in designing 2A85 self-propelled launchers and upgrading 2A30 self-propelled launchers.

An improved procedure for modeling the operation of a light-gas gun is proposed. The motion of working bodies in both the firing chamber and the light-gas chamber is studied within the framework of the mechanics of heterogeneous media. The problem of barrel heating taking into account its melting and removal of thermal ablation products into the medium inside the bore is solved in a coupled formulation. Heat and mass transfer and friction on the barrel surface are calculated using empirical dependences. The deformable piston is considered compressible and elastoviscoplastic. Allowance is made for the presence of a clearance between the lateral surface of the piston and the barrel bore walls and the associated gas flow between the firing and the light-gas chamber. Calculation results are given.

Fiber-reinforced polymer matrix composite materials display quite complex deformation and failure behavior under ballistic/blast impact loading conditions. This complexity is generally attributed to a number of factors such as (a) hierarchical/multi-length scale architecture of the material microstructure; (b) nonlinear, rate-dependent and often pressure-sensitive mechanical response; and (c) the interplay of various intrinsic phenomena and processes such as fiber twisting, interfiber friction/sliding, etc. Material models currently employed in the computational engineering analyses of ballistic/blast impact protective structures made of this type of material do not generally include many of the aforementioned aspects of the material dynamic behavior. Consequently, discrepancies are often observed between computational predictions and their experimental counterparts. To address this problem, the results of an extensive set of molecular-level computational analyses regarding the role of various microstructural/morphological defects on the Kevlar® fiber mechanical properties are used to upgrade one of the existing continuum-level material models for fiber-reinforced composites. The results obtained show that the response of the material is significantly affected as a result of the incorporation of microstructural effects both under quasi-static simple mechanical testing condition and under dynamic ballistic-impact conditions.

A new ballistic material model for 0°/90° cross-plied oriented ultra-high molecular weight (UHMW) polyethylene fiber-based armor-grade composite laminates has been constructed using open-literature data for the fiber and polymeric-matrix material properties and the general experimental/field-test observations regarding the deformation and failure modes in these types of materials. The present model is an extension of our recently developed unit cell-based ballistic material model for the same class of composites (M. Grujicic, G. Arakere, T. He,W.C. Bell, B. A. Cheeseman, C.-F. Yen, and B. Scott, A Ballistic Material Model for Cross-Plied Unidirectional Ultra-High Molecular-Weight Polyethylene Fiber-reinforced Armor-Grade Composites, Mater. Sci. Eng, A 2008, 498(1-2), p 231-241) which was found to be physically sound, but computationally not very efficient. The present model is constructed in such a way that it can be readily integrated into commercial finite element programs like ANSYS/Autodyn (ANSYS/Autodyn version 11.0, User Documentation, Century Dynamics Inc., a subsidiary of ANSYS Inc., 2007), as a User Material Subroutine. To validate the model, a series of transient nonlinear dynamics computational analyses of the transverse impact of armor-grade composite laminates with two types of bullets/projectiles is carried out and the computational results compared with their experimental counterparts. Relatively good agreement is found between the experiment and the computational analysis relative to: (a) the success of the armor panels of different areal densities in defeating the bullets at different initial bullet velocities; (b) postmortem spatial distribution of the damage modes and the extents within the panels; (c) the temporal evolution of the armor-panel back-face bulge; and (d) The existence of three distinct armor-penetration stages (i.e., an initial filament shearing/cutting dominated stage, an intermediate stage characterized by pronounced filament/matrix debonding/decohesion, and a final stage associated with the extensive filaments extension and armor-panel back-face bulging).

A meso-scale ballistic material model for a prototypical plain-woven single-ply flexible armor is developed and implemented in a material user subroutine for the use in commercial explicit finite element programs. The main intent of the model is to attain computational efficiency when calculating the mechanical response of the multi-ply fabric-based flexible-armor material during its impact with various projectiles without significantly sacrificing the key physical aspects of the fabric microstructure, architecture, and behavior. To validate the new model, a comparative finite element method analysis is carried out in which: (a) the plain-woven single-ply fabric is modeled using conventional shell elements and weaving is done in an explicit manner by snaking the yarns through the fabric and (b) the fabric is treated as a planar continuum surface composed of conventional shell elements to which the new meso-scale unit-cell based material model is assigned. The results obtained show that the material model provides a reasonably good description for the fabric deformation and fracture behavior under different combinations of fixed and free boundary conditions. Finally, the model is used in an investigation of the ability of a multi-ply soft-body armor vest to protect the wearer from impact by a 9-mm round nose projectile. The effects of inter-ply friction, projectile/yarn friction, and the far-field boundary conditions are revealed and the results explained using simple wave mechanics principles, high-deformation rate material behavior, and the role of various energy-absorbing mechanisms in the fabric-based armor systems.

High-velocity transverse impact of laminated fiber reinforced composites is of interest in military, marine and structural applications. The overall objective of this work was to investigate the behavior of laminated thermoplastic composites of varying thicknesses under high-velocity impact from an experimental and modeling viewpoint. In order to analyze this problem, a series of ballistic impact tests have been performed on plain weave E-glass/polypropylene (E-glass/PP) composites of different thicknesses using 0.30 and 0.50 caliber right-cylinder shaped projectiles. A gas gun with a sabot stripper mechanism was employed to impact the panels. In order to analyze the perforation mechanisms, ballistic limit and damage evaluation, an explicit three-dimensional finite element code LS-DYNA was used. Material model 162, a progressive failure model based on modified Hashin’s criteria, has been assigned to analyze failure of the laminate. The projectile was modeled using Material model 3 (MAT_PLASTIC_KINEMATIC). The laminates and the projectile were meshed using brick elements with single integration points. The impact velocity ranged from 187 to 332 m s−1. Good agreement between the numerical and experimental results was attained in terms of predicting ballistic limit, delamination and energy absorption of E-glass/PP laminate.

The paper presents a ballistic performance index for metallic armour materials in terms of the commonly determined mechanical properties such as strength and modulus. The index is derived using an energy-balance approach, where the kinetic energy of the projectile is assumed to be absorbed by the elastic and the plastic deformation involved in the penetration process as well as the kinetic energy imparted to the target material during deformation. The derivation assumes two distinct stages to exist during the penetration of the projectile. At the striking face of the armour, the material is assumed to flow radially in a constrained deformation region but longitudinally at the rear surface leading to typically observed bulging of the armour without constraint. The index is validated using the available experimental and empirical data obtained in the case of small arm projectiles for an impact velocity of about 800 m/sec. This index is expected to facilitate the development of metallic armour, since the number of the ballistic experiments can be reduced significantly and only the promising materials need to be considered.

With the relatively recent introduction of quantitative and volumetric X-ray computed tomography (XCT) applied to ballistic impact damage diagnostics, significant inroads have been made in expanding our knowledge base of the morphological variants of physical impact damage. Yet, the current state of the art in computational and simulation modeling of terminal ballistic performance remains predominantly focused on the penetration phenomenon, without detailed consideration of the physical characteristics of actual impact damage. Similarly, armor ceramic material improvements appear more focused on penetration resistance than on improved intrinsic damage tolerance and damage resistance. Basically, these approaches minimize our understanding of the potential influence that impact damage may play in the mitigation or prevention of ballistic penetration. Examples of current capabilities of XCT characterization, quantification, and visualization of complex impact damage variants are demonstrated and discussed for impacted ceramic and metallic terminal ballistic target materials. Potential benefits of incorporating such impact damage diagnostics in future ballistic computational modeling are also briefly discussed.

A series of depth-of-penetration (DOF) tests are carried out to investigate the ballistic performance of armor ceramics. Based on the experimental results, an improved differential efficiency factor (DEF) is presented, which demonstrates that the general ballistic efficiency index is independent of the ceramic thickness. It is also shown that the density, internal friction, and compression strength of ceramics are crucial factors that affect the ballistic performance of ceramics significantly through the interaction between the long-rod projectiles and thick-tile armor.

Impact responses of extra-soft materials, such as ballistic gelatins and biological tissues, are increasingly in demand. The Kolsky bar is a widely used device to characterize high-rate behavior of materials. When a Kolsky bar is used to determine the dynamic compressive response of an extra-soft specimen, a spike-like feature often appears in the initial portion of the measured stress history. It is important to distinguish whether this spike is an experimental artifact or an intrinsic material response. In this research, we examined this phenomenon using experimental, numerical and analytical methods. The results indicate that the spike is the extra stress from specimen radial inertia during the acceleration stage of the axial deformation. Based on this understanding, remedies in both specimen geometry and loading pulse to minimize the artifact are proposed and verified, and thus capture the intrinsic dynamic behavior of the specimen material.

The penetration of a bullet proof vest worn by a first responder in 2003, resulted in the establishment of a research program designed to investigate the long-term stability and durability of all fibers that are used and have the potential to be used in ballistic applications. The Office of Law Enforcement Standards (OLES) of the National Institute of Standards and Technology (NIST) was charged with conducting this program under the auspices of the National Institute of Justice (NIJ). Because of the urgent need to understand the factors that contributed to this unexpected body armor penetration, the initial focus of this research program is on the ballistic fiber material that composed the compromised vest, i.e., poly[(benzo–[1,2-d:5,4-d′]-benzoxazole-2,6-diyl)-1,4-phenylene] (PBO) fiber. Since data related to the susceptibility of PBO fibers to environmental attack are limited and sometimes contradictory, this review also focuses on the susceptibility of the benzoxazole ring structure, a major component of the PBO chain structure, to environmental exposure conditions. A somewhat detailed discussion of the formation and degradation chemistry of this ring structure is presented to increase the reader’s understanding of how chemical structure and environmental factors may influence ballistic fiber degradation. To balance this discussion, the susceptibility of key linkages in other ballistic fibers to similar conditions is also presented. Therefore, this review seeks to link chemical structure to ballistic performance and provide a fundamental basis for predicting the long-term durability of existing and future ballistic fibers.

We have developed an optical technique called ballistic imaging to view breakup of the near-field of an atomizing spray. In this paper, we describe the successful use of a time-gated ballistic imaging instrument to obtain single-shot images of core region breakup in a transient, single hole atomizing diesel fuel spray issuing into one atmosphere. We present a sequence of images taken at the nozzle for various times after start of injection, and a sequence taken at various positions downstream of the nozzle exit at a fixed time. These images contain signatures of periodic behavior, voids, and entrainment processes.

This study reports the ballistic penetration performance of a composite material composed of woven Kevlar® fabric impregnated with a colloidal shear thickening fluid (silica particles (450 nm) dispersed in ethylene glycol). The impregnated Kevlar fabric yields a flexible, yet penetration resistant composite material. Fragment simulation projectile (FSP) ballistic penetration measurements at ∼244 m/s have been performed to demonstrate the efficacy of the novel composite material. The results demonstrate a significant enhancement in ballistic penetration resistance due to the addition of shear thickening fluid to the fabric, without any loss in material flexibility. Furthermore, under these ballistic test conditions, the impregnated fabric targets perform equivalently to neat fabric targets of equal areal density, while offering significantly less thickness and more material flexibility. The enhancement in ballistic performance is shown to be associated with the shear thickening response, and possible mechanisms of fabric-fluid interaction during ballistic impact are identified.

The ability of γ-TiAl to withstand potential foreign object damage (FOD) and/or domestic object damage (DOD) is a technical risk to the implementation of γ-TiAl in low-pressure turbine (LPT) blade applications. The overall purpose of the present study was to determine the influence of ballistic impact damage on the high-cycle fatigue strength of γ-TiAl-simulated LPT blades. Impact and specimen variables included ballistic impact energy, projectile hardness, impact temperature, impact location, and leading-edge thickness. The level of damage induced by the ballistic impacting was studied and quantified on both the impact (front) and backside of the specimens. Multiple linear regression was used to model the cracking and fatigue response as a function of the impact variables. Of the impact variables studied, impact energy, had the largest influence on the response of γ-TiAl to ballistic impacting. Backside crack length (BSCL) was the best predictor of remnant fatigue strength for low-energy impacts (

Rain erosion is a major cause of strength and transmission loss in IR ‘windows’ in high velocity flight. The Cavendish Laboratory's Multiple Impact Jet Apparatus (MIJA) is able to simulate high velocity rain impact accurately and reproducibly under laboratory conditions using a series of discrete water jets. Quantitative erosion data in the form of Damage Threshold Velocity (DTV) curves can be obtained, giving the lower limit of damage to the material under study. Damage threshold curves are presented for five different materials carried out using three different nozzle orifice diameters to create the impacting jet. Two approaches are made to predicting the DTV value for each specimen using only data from the standard 0.8 mm nozzle: (i) the ‘cylindrical jet’ approach, in which the impacting jet is considered to have a flat front, and (ii) the drop (‘round-fronted jet’) model. Both methods are found to give predictions well within the bounds of experimental error. The former predicts the damage threshold better when the smaller (0.6 mm) nozzle is used and the drop model the threshold when the larger (1.2 mm) nozzle is used. High-speed photographs of jets from differently-sized orifices are presented validating the use of models for the various nozzle diameters.

Failure of composite beams containing initial delamination is investigated under low-speed impact by a dropping weight. Bolotin's theory of dynamic failure (1992) is used. The start and stop time of growth of a nonsymmetric delamination crack is studied. It is found that the initial extension starts and subsequently continues at the crack tip, which is located closer to the impact point. Then extension is observed on the second crack tip, and finally a synchronous growth of delamination occurs at both crack tips. With constant impact energy, the final size of delamination does not depend on its initial size. The start and stop time of delamination growth increases as the initial defect approaches the beam surface.

The aim of this work is to compare the behavior of untreated glass and glass treated by hydrofluoric acid, as well as to determine factors controlling high ballistic characteristics of the strengthened glass.

The authors carried out numerical examination of the processes taking place in collision of steel cylinders with steel sheets. The ratio of the thickness of the barrier to the diameter of the striker was 1.25, and the ratio of the length of the striker whose diameter was varied from 1.16 to 6.94. Modelling was carried out up to the stage of formation of a knocked- out plug in the barrier. The dependences of the depth and speed of penetration on the initial speed of interaction were examined and differences in the behavior of compact and elongated strikers were investigated.

In recent years the two-stage light gas ballistic apparatus with deformable plastic pistons has become widely used in experimental aerodynamics. The existing methods of calculating such devices either completely neglect friction of the piston on the channel wall [1–3] or use a schematization of the frictional forces [4–6], which does not have a satisfactory physical basis. In a number of studies [7, 8] the friction force was considered constant, and its value was specified not from physical considerations, but to produce the best agreement between calculated and experimental values of object velocity or driving gas pressure. Since friction is such a significant factor, its proper consideration in calculating piston motion parameters requires special study. In this connection, it is useful to consider the operation of only the first stage of the ballistic apparatus, which sets the piston in motion. Below we will consider the problem of the internal ballistics of a one-stage powder-driven apparatus in the column channel of which a piston made of polymer material moves, experiencing friction. The friction model is constructed on the basis of a series of experiments on the slow forcing of polymer specimens compressed in the longitudinal direction through a steel channel. An experimental study was made of the relationship between the gunpowder gas pressure and time within a constant volume chamber, allowing establishment of the true powder-burning law, and its deviation from the geometric law of [9]. Calculated and experimental values of maximum gas pressure and muzzle velocity of a polyethylene piston are compared.

An experimental and analytical study was performed on the mechanics of oblique perforation of metallic plates by projectiles. The purpose was to determine the dependence of the velocity drop on the angle of impact for prescribed mechanical and physical properties of the projectile and the target plate. The ballistic experiments were carried out with 0.22-in.-caliber lead bullets on target plates of commercially pure aluminum and an aluminum alloy which ranged from 2.0 to 6.0 mm in thickness. Transient measurements were taken which included high-speed photographs of the perforation process. The theoretical model that had been developed previously by the authors for the case of normal perforation was modified to include the effects of the angle of impact. The experimental observations for the present test conditions indicate that the main modification to the analysis is the use of the total projectile path as the effective target-plate thickness. Reasonably good agreement between the experimental and theoretical results was obtained.

For ballistically impacted glass/epoxy cross-ply laminated plates with three five-layer unidirectional laminas, high-speed photos were taken from the back of plates, illuminated from the front side. The semitransparency of the plates enabled a Nova high-speed camera to record delamination-crack propagations at speeds of up to 40,000 frames/s. The delamination crack in the fiber direction of the first (second) lamina at the first (second) interface, propagated initially at 300–400 (400–500) m/s which decreased to 200–300 (270–400) m/s during the period of observation, and decelerated to a stop within 100 (300) μs. This last velocity range (270–400 m/s) agreed well with the largest-amplitude flexural-wave velocity measured by strain gages. This is a documentation that delamination is associated with the flexural wave.

We report on the continued development of thermodynamics-based analysis of shock waves propagation with the objective of extracting information related to materials strength at high strain rates and pressures. Building on previous results reported for peak stresses of 10 GPa and 25 GPa, we present a series of three-step gas-gun shock experiments designed to explore the pressure and strain rate dependence of plastic flow in polycrystalline tantalum. These experiments at nominal peak stresses of 50 GPa and 75 GPa show the irreversible deformation before pullback to be almost entirely confined to the shock loading, with negligible plastic relaxation on the post-shock plateau. We also add a reverse-ballistics shot at 25 GPa, which was designed to reveal the pullback response with negligible interference from free-surface effects. General thermodynamic considerations allow us to place bounds on the plastic behavior even for parts of the curve that change far too rapidly for the velocimetric time resolution of (conservatively) ~ 5 ns. To analyze the data, we found it necessary to substantially improve the interpolation/extrapolation scheme in order to improve its robustness, flexibility and range of applicability. We describe the new scheme based on splines, as well as an extension of free-surface corrections to the post-shock rarefaction waves. Reanalysis with the new scheme produces results essentially within the error bars previously reported, showing that the known systematic errors associated with free-surface effects are relatively inconsequential for determining thermodynamic paths.

The diol and dicarboxylic acid in polyester synthesis are significant independent variables that relate directly to the structure–property-dependent variables of polyesters. The choice of the stereoisomers of the diol in the polyester synthesis can significantly alter the mechanical and thermal performance. Terephthalate polyesters prepared from the proper ratio of 2,2,4,4-tetramethyl-1,3-cyclobutanediol (CBDO) and 1,3-propanediol have superior impact resistance when compared to ballistics grade polycarbonate. In addition these polymers exhibit very strong self-healing behavior that is activated by heat. These copolymers were all produced with a mixture of cis and trans isomers with a ratio of 43/57, respectively. This study reports research conducted to determine the structure–property relationships that can be attributed to the stereoisomers of the CBDO monomer. The polyester prepared with 99 % cis (CBDO) monomer has significantly improved mechanical and thermal performance when compared with the polyester prepared with a 43:57 mixture of cis and trans isomers or 100 % trans isomer. Thermal gravimetric analysis and differential scanning calorimetry demonstrated that the cis CBDO polymer exhibit a much higher T g (99 °C for cis and 69 °C for the trans 84.5 °C for the mixed polymer) and better thermal stability than the trans form of the polymer (onset of decomposition of trans at 345 and 360 °C for cis). Dynamic mechanical analysis and the Notched Izod demonstrated that the cis form of the polymer was much tougher than the trans form. Wide angle X-ray diffraction showed that the trans form was semicrystalline and the cis form was amorphous. The Notched Izod impact was 1070 J/m for the cis CBDO-based copolymer with the trans form having an impact factor of 841 J/m with the mixed polymer exhibiting an intermediate value of 944 J/M. Molecular modeling supports the experimental evidence that the choice of stereoisomers for the diol significantly influences the molecular architecture of the polyesters. The molecular architecture of polyesters in addition to polar attraction and molecular weight variables provides a dramatic increase in mechanical and thermal performance.

This review considers the link between the damage tolerance of composite laminates and the nature and organization of the fibre reinforcement. This embraces composites made from unidirectional prepregs through composites based on a variety of textile forms such as woven fabrics, multiaxial fabrics, braids and knits. The objective has been firstly to detail how the differing varieties of composite exhibit different properties under impact conditions and under subsequent loading after impact. This includes both fracture mechanisms and data such as energy absorption, and peak failure loads. The second objective is to describe the links that have been found between these properties and the specific fibre architectures and damage development processes in the various composite forms. The post impact compression properties are highlighted as this is the area of greatest interest by end-users. The review describes the different forms of textiles that are used for composite reinforcement, considers different impact conditions (e.g. low velocity and ballistics), general materials variables such as fibre and resin type, and ultimately looks at specific textile systems. Some consideration is also given to the value and role of numerical modelling in the field of damage formation and damage tolerance. Clear differences have been found in the literature between composites based on different textile forms in terms of damage states after impact and the consequences of this damage on subsequent properties. While the literature is clearly incomplete at this time there is sufficient information available to indicate that control of fibre organization by the use of textiles may be an effective method of optimizing composite properties for specific end use properties.

Deflagrations caused by interactions of charcoal with potassium nitrate were discovered in 9th-century China. This led quickly to the development of primitive fuzes and ballistics. Roger Bacon, a 13th-century Franciscan monk experimented in England with gunpowder. The 18th-century saw the manufacture of charcoal by the cylinder method and the development of Waltham Abbey as the centre for gunpowder production which peaked to about 20 000 barrels per year at the time of the Battle of Waterloo. Methods of gunpowder manufacture changed little over the centuries until recent times. Whereas sulphur and nitre are reproducible ingredients, a mystery enshrined optimum specifications for gunpowder charcoal. Within recent years the application of modern analytical techniques has removed some of this mystery and anatomical features and physical properties have been characterized.