Ballistic Loading Research Articles

Impact energy absorption in 3D printed bio-inspired PLA structures

3D printing is an effective technique for designing and producing products with unique shapes that cannot be made using traditional methods. Polylactic acid (PLA) filaments, commonly used in 3D printing, are a promised material for fabricating composites and lightweight structures. This study investigates the fracture and damping properties of biodegradable PLA samples with a bio-inspired structure and different density under dynamical (ballistic) loading. PLA samples were fabricated using a 3D printer and a Fusion Deposition Modeling (FDM) method. A unique computer program for cellular samples with Schwartz-Diamond minimal surface topology was developed. The impact absorption energy under ballistic loading of PLA samples with Schwarz-Diamond surface structure was found to depend on their density and impact velocity. The internal structure of 3D-printed PLA cellular samples with a Schwarz-Diamond triply periodic minimal surface and the fracture mechanism of the cellular samples with different densities were demonstrated using scanning electron microscopy. It was found that the fracture mechanism changed from ductile to quasi-brittle with increasing sample density. This work provides a foundation for understanding the fabrication of plastic cellular products using 3D printing.

Hydrogen susceptibility of Al 5083 under ultra-high strain rate ballistic loading

Abstract The effect of hydrogen on the ballistic performance of aluminum (Al) 5083H131 was examined both experimentally and numerically in this study. Ballistics tests were conducted at a 30° obliquity in accordance with the ballistic test standard MIL-DTL-46027 K. The strike velocities of projectiles were ranged from 240 m s−1 to 500 m s−1 level in the room temperature. Electrochemical hydrogen charging method was utilized to introduce hydrogen into material. Chemical composition of material was analyzed using energy dispersive X-ray (EDX) analysis. Instant camera pictures were captured using high-speed camera to compare H-uncharged and H-charged specimen ballistics tests. The volume loss in partially penetrated specimens were assessed using the 3D laser scanning method. Microstructural examinations were conducted utilizing scanning electron microscopy (SEM). It was observed that with the increased deformation rate, the dominance of the HEDE mechanism over HELP became evident. Furthermore, the experimental findings were corroborated through numerical methods employing finite element analysis (FEM) along with the Johnson–Cook plasticity model and failure criteria. Inverse optimization technique was employed to implement and fine-tune the Johnson–Cook parameters for H-charged conditions. Upon comparing the experimental and numerical outcomes, a high degree of consistency was observed, indicating the effective performance of the model.

Examples of dynamic test procedures for steel fibre reinforced concrete

Abstract The aim of this work is to present some examples of experimental tests, which can be usefull for characterizing the resistance to failure of special steel fibre reinforced concrete – SFRC, intended especially for security use in the framework of ballistic and explosion protection. The first type of the tests was the strain gauge - based characterization of the dynamic response of the SFRC concrete block under ballistic loading. The tests were aimed at measuring the deformation response of a concrete specimen of 500 x 500 x 105 mm in dimensions upon the impact of a projectile. The tests were used to support the development and verification of numerical simulation models. For numerical simulations 3D models of individual projectiles were developed. Four T-type strain gauges were glued according to the geometric scheme on the opposite side of a specimen, i.e. on the side behind the impact of the projectile, and they measured the deflection of the plate after the impact of the projectile. The strain response records obtained from the strain gauges were subsequently used for numerical analyses by the use of the LS-DYNA software. The average maximum deflection of the plate at the impact of the projectile was characterized by the strain 400 µm/m. The second type of the tests was concerned with the method of measuring the quasi-dynamic tensile strength of special concrete specimens using an instrumented Charpy tester. The results compare both the breaking energy and the maximum force achieved for hobby concrete (HB) and hobby concrete with wires (HBD) specimens. These were pilot tests to develop the most suitable testing method. For the HB and HBD specimens the maximum force in the tests was found to be 55 N vs. 600 N, and the breaking energy to be 0.4 J vs. 1.3 J.

Energy absorption behavior of aramid/DCPD backing to determining the blunt trauma criterion of a human head in a ballistic helmet

The research involved analyzing a material solution for a 9 mm Full Metal Jacket (FMJ) Parabellum loaded with ballistic impact on a resin laminate strengthened with extra aramid layers. The goal of this research is to determine the impact of material (aramid/DCPD) layer thickness on the energy absorption performance of the laminate for blunt trauma as blunt criterion (BC). For this purpose, aramid fiber laminate with dicyclopentadiene (DCPD) resin matrix was prepared. Laminate samples were tested on the drop test and were subjected to ballistic loads. The ABAQUS/Explicit program and finite element method were used to conduct the study. Individual material systems' optimal solutions were created using numerical analysis, and they were then classified using the mass-efficiency criterion. The numerical results were compared with the experimental using samples prepared according to the modeling methods. Selected results were shown and discussed in the later part of the paper.

Study of rupture behavior of 40Cr ring-scored bursting diaphragms

The rupture diaphragm is a key part of pressure control in the launcher and the reliability of the rupture pressure is directly related to the internal ballistic performance. In order to study the rupture behavior of the 40Cr annular scored diaphragm under internal ballistic conditions and the remaining thickness of the diaphragm’s scoring, the stress-strain curve of the diaphragm is obtained by fitting the internal ballistic loading curve and simulation, the relationship between the rupture pressure and the remaining thickness of the scoring is established and the accuracy of the simulation is verified by the blasting test.

Ballistic impact resistance and flexural performance of natural basalt fiber with carbon and glass fibers in inter‐ply hybrid composites

AbstractThe ballistic and flexural behaviors of basalt (natural fabric), carbon, glass fiber, and their hybrid composites, were investigated in this study. The main objective of the paper was the addition of natural basalt fiber to the carbon and glass fibers with inter‐ply hybrid sequences to search for possible usage to the ballistic loads carrying structures. The composite and hybrid composite plates produced nine layers with cross‐ply stacking sequences ([0/90]9). The ballistic impact tests were conducted using a specially designed ballistic test setup and the flexural tests were performed through the standard three‐point bending test. The results showed that basalt/epoxy absorbed the most energy under ballistic loading among all models. It was observed that the basalt‐glass‐basalt/epoxy (BGB) hybrid composite had an energy absorption capacity very close to the basalt/epoxy composite. When BGB and carbon‐glass‐carbon/epoxy (CGC) hybrid models were compared, the energy absorption capacity of CGC was 62.7% less than BGB. Unlike the ballistic test result, basalt/epoxy had the lowest flexural strength, while carbon/epoxy had the highest flexural strength. Among the hybrid models, it was seen that BGB had the lowest flexural strength, while CGC had the highest flexural strength. The flexural strength of the CGC is 38% higher than BGB. The study found that basalt fiber has high ballistic resistance, whether alone or when combined with commonly used fibers. It also suggests that basalt fiber is a promising candidate for future research and development in the field of protective materials.Highlights Basalt (natural fabric) composite materials behavior. Hybridization of basalt with carbon and glass. Target plates damage resistance according to applied ballistic loads. Target plates damage resistance according to applied flexural loads. Non‐hybrid and hybrid composites plates comparisons.

Ballistic and Charpy impact performance of basalt fiber reinforced polymer composites

AbstractIn this study, the behavior of composite material produced using basalt, a natural fabric, under ballistic and Charpy impact loads was investigated. The damage resistance of target plates under ballistic loads is an important design parameter in the structures that will be exposed to these loads. Cross‐ply fiber‐reinforced composite plates were produced with different numbers of layers. The composite specimens are produced using the vacuum infusion method, cross‐ply laminated with 3, 6, 9, and 12 layers ([0/90]3, [0/90]6, [0/90]9, and [0/90]12). Carbon/Epoxy specimens were also produced in identical sequences to be used as comparison material. The study aimed to understand the absorbed energy under ballistic loads and the required energy level under the Charpy impact loads of Basalt/Epoxy composite specimens with different thicknesses. Ballistic loads are applied to the specimens using a test set‐up including the sample holder mechanism and a firing system. Charpy impact tests were conducted using a standard test machine. According to the results, for 12‐layer specimens, the residual velocity difference between Basalt/Epoxy and Carbon/Epoxy is approximately 1.5 times. For the Basalt/Epoxy plate, increasing number of layers from 3 to 12 increases the amount of energy absorbed approximately 13 times. Although this increase is approximately 19 times for the Carbon/epoxy plate, when Basalt/Epoxy and Carbon/Epoxy plates are compared, Basalt/Epoxy absorbs more energy for all layer numbers. For the Charpy impact cases, it has been observed that Basalt/Epoxy absorbs approximately 34% more energy for flat wise impact and approximately 24% more energy for edgewise impact.Highlights The behavior of composite material produced using basalt, a natural fabric. Cross‐ply fiber‐reinforced composite plates. Effect of different number of layers considered. The damage resistance of target plates under ballistic loads. Comparison of basalt and carbon‐reinforced composites.

Numerical Analysis of the Impact Resistance of Composite A-Shaped Sandwich Structures.

This paper focuses on the finite element analysis simulation of the impact properties of composite sandwich structures made of carbon fiber-reinforced polymer lamina. In the existing studies, the composite sandwich structures with A-shaped cores have superior mechanical properties under quasi-static plane compression loads compared to W-shaped, Y-shaped, and X-shaped cores. However, there is limited research on the impact resistance of this structure. This paper studied the resistance of a composite A-shaped core structure to ballistic impact. Using ABAQUS/explicit finite element analysis software, ballistic impact tests for the composite A-shaped core structure were simulated based on the Hashin and Yeh failure criteria with a progressive damage model introduced in the user-defined subroutine VUMAT. First, the composite Y-shaped core sandwich structure was verified via experiments and simulations to determine the accuracy of the method, and then the composite A-shaped sandwich structure was subjected to a series of ballistic impact simulations. With varied impact velocity, the damage to the front and rear face sheet and cores via ballistic loads was simulated to illustrate the overall dynamic response process of the sandwich structure. Subsequently, a curve was fitted using a ballistic limit velocity equation, which was used as the criterion to evaluate the impact resistance of the composite A-shaped core structure. The results showed that, under the same relative density and the same number of component layers, the ballistic limit velocity of the composite A-shaped core sandwich structure was bigger than the composite Y-shaped core sandwich structure. The composite A-shaped core structure had 12.23% higher ballistic limit velocity than the composite Y-shaped core, indicating the impact resistance capabilities of the A-shaped core structure. In addition, the impact location's effect on the impact response was investigated.

Experimental Investigations on the Mechanical Performances of Auxetic Metal-Ceramic Hybrid Lattice under Quasi-Static Compression and Dynamic Ballistic Loading

In recent years, there have been increasing research interests in investigating the compression and ballistic responses of metal-ceramic hybrid structures, mainly making use of the synergistic effects of conventional metal honeycomb structures and infilled ceramic matrix materials. In this paper, a novel hybrid auxetic re-entrant metal-ceramic lattice is designed and manufactured to overcome the intrinsic conflicts between the strength and toughness of architected mechanical metamaterials, synergistic effects of auxetic re-entrant metal honeycombs and infilled ceramic materials are experimentally and numerically studied, and auxetic deformation features and failure modes are characterized with the digital image correlation (DIC) technique as well. It was found that (1) the infilled ceramic matrix of conventional honeycomb frames only endure longitudinal compression or impact loading along the external loading direction, while auxetic metal re-entrant honeycomb components endure both longitudinal and transverse loading due to the negative Poisson′s ratio effect and (2) the collaborative effects of infilled auxetics and the constraint frames’ hybrid structure dramatically moderate the stress concentration state and improve the impact resistance of single-phase ceramic materials. Our results indicate that the auxetic hybrid design exhibits promising industrial application potentials for blast protection engineering.

Damage and failure mechanism of sapphire under ballistic loading based on a modified bond‐based peridynamic model

AbstractTo investigate the dynamic mechanical behaviors of c‐plane and a‐plane sapphire, a novel anisotropic constitutive model and fracture criterion are constructed on the basis of bond‐based peridynamics (BB‐PD) theory. And the concept of strain is introduced in the framework of BB‐PD. After that, the simulations of a‐ and c‐planes of sapphire under spherical and cylindrical impact are conducted. In addition to capturing the distribution of strain and damage, the histories of various fracture types such as the primary fracture front and cracks are monitored for quantitative analysis. The numerical predictions are shown to agree well with previous experimental results, and further reveal the damage and failure mechanisms of sapphire. The different forms of contact between the projectile and the target strongly influence the stress waves generated and energy transferred ultimately affecting the damage development process. The crystal orientation dominates the appearance of anisotropic crack modes. Crack bending and deflection, as well as spalling‐like fracture, are associated with wave reflection and intersection. Moreover, an in‐depth examination of the observed wave splitting phenomenon is performed.

Laminated Glass Plates Subjected to High-Velocity Projectile Impact and Their Residual Post-Impact Performance

This study aims to analyze the performance of laminated glass against ballistic loading and investigates its residual load-bearing capacity. Two groups of specimens were used in quasi-static four-point bending experiments, first without prior ballistic damage and then with it. The main objective was to compare the load-bearing capacity of these two groups to see the effect of ballistic damage. Three different layer compositions were used. The ballistic loading was conducted using an in-service 9 mm bullet fired from a semiautomatic carbine with the glass specimens hanging on steel ropes in a free boundary setup. Numerical simulation and analytical methods were used and validated against the measured response of the undamaged specimens. The simulations were in good agreement with the experimental results. All of the glass specimens were able to withstand the ballistic loading, and the subsequent performance during the quasi-static bending loading was similar to that of the undamaged specimens. The quality of the glass edges seemed to be more important than ballistic damage. The front-plate damage played a negligible role, and the back-plate damage needed to be extensive to influence subsequent performance. Provided that ballistic damage is mainly localized only to the centers of the plates, it did not affect the post-impact loading capacity.

Adiabatic Shear Banding in Nickel and Nickel-Based Superalloys: A Review

This review paper discusses the formation and propagation of adiabatic shear bands in nickel-based superalloys. The formation of adiabatic shear bands (ASBs) is a unique dynamic phenomenon that typically precedes catastrophic, unpredicted failure in many metals under impact or ballistic loading. ASBs are thin regions that undergo substantial plastic shear strain and material softening due to the thermo-mechanical instability induced by the competitive work hardening and thermal softening processes. Dynamic recrystallization of the material’s microstructure in the shear region can occur and encourages shear localization and the formation of ASBs. Phase transformations are also often seen in ASBs of ferrous metals due to the elevated temperatures reached in the narrow shear region. ASBs ultimately lead to the local degradation of material properties within a narrow band wherein micro-voids can more easily nucleate and grow compared to the surrounding material. As the micro-voids grow, they will eventually coalesce leading to crack formation and eventual fracture. For elevated temperature applications, such as in the aerospace industry, nickel-based superalloys are used due to their high strength. Understanding the formation conditions of ASBs in nickel-based superalloys is also beneficial in extending the life of machining tools. The main goal of the review is to identify the formation mechanisms of ASBs, the microstructural evolutions associated with ASBs in nickel-based alloys, and their consequent effect on material properties. Under a shear strain rate of 80,000 s−1, the critical shear strain at which an ASB forms is between 2.2 and 3.2 for aged Inconel 718 and 4.5 for solution-treated Inconel 718. Shear band widths are reported to range between 2 and 65 microns for nickel-based superalloys. The shear bands widths are narrower in samples that are aged compared to samples in the annealed or solution treated condition.

Ballistic perforation and penetration of 6xxx-series aluminium alloys: A review

This study evaluates literature on mechanical response of 6xxx series aluminium alloys under dynamic loads (projectile impacts). It is mainly concerned with the ballistic behaviour of 6xxx series Al alloys fabricated through different sample processing routes involving varied heat treatments at elevated, sub-zero and cryogenic temperatures. Failure and deformation mechanisms leading to dynamic fracture have also been considered. Microstructural evolution, wherever available, is incorporated in this study to understand its influence on energy absorption, and deformation and failure mechanisms under ballistic loads. A brief review of analytical and numerical perforation and penetration models for ballistic impact has been attempted too. These approaches have become more sophisticated incorporating compressibility, better material models, and interface friction effects, etc. over the years. The review also includes semi-empirical and empirical equations proposed based on previous experimental data in some works. However, more investigation is needed to ascertain the applicability of these empirical equations. The deficiencies in available work have thereupon been pointed out for future problems.

Ballistic loading and survivability of optical fiber sensing layers for soft body armor evaluation

The authors previously demonstrated the use of FBG sensors in Kevlar mats behind body armor to measure the transient back face deformation (BFD) during ballistic testing. This paper presents a novel sensor system based on a Fiber Bragg Grating embedded in silicone mats to improve the survivability of the body armor in-situ strain sensing layers. Due to the large amount of deformation, a relative slip between the optical fibers and the supporting structure is needed to maintain the performance of the sensors and determine the relationship between the measured strain and deformation shape. Two silicone materials were tested, Smooth-Sil 950 and Sorta-Clear 40, in both 1 mm and 2 mm thicknesses to evaluate their survivability and impact on BFD. To enhance slipping between the fibers and surrounding silicone a thin layer of petroleum jelly was placed on the fibers prior to being cast in the silicone mats. The 1 mm Sorta-Clear 40 mats performed best in silicone survivability, FBG survivability and minimal impact on the BFD. The new system improves on key deficiencies that were found from inserting the fibers directly into the Kevlar with minimal to no impact on the back face deformation.

Assessment of ballistic impact damage on aluminum and magnesium alloys against high velocity bullets by dynamic FE simulations

Abstract The shape of the projectile seems to determine the effect of a ballistic impact and failure mechanism. In this study, the numerical analysis of ballistic impact with different projectile shapes, i.e., ogive, blunt, conical, and hemispherical is performed. The target is a circular sandwich plate with an outer diameter of 315 mm, which is composed of three layers with a thickness of 1 mm for each layer. These layers will be filled with different materials such as 1100-H12 aluminum alloy, ZK61m magnesium alloy, and 6061-T651 aluminum alloy. The target plate in the numerical analysis consists of two parts: the inner and outer zones. In the inner zone, the selected element size is set to fine, while in the outer zone, it is set to be coarser, and the size will increase along with the direction and the diameter of the circle. This numerical simulation uses the Johnson–Cook material model and is applied to ABAQUS/Explicit software. The simulation configurations are validated based on previous experiments by comparing the residual velocity values after the projectile has penetrated the target plate. The simulation results will obtain energy absorption values for each variation of the target plate. The energy absorption values are affected by stress and strain in radial, circumferential, axial, and shear deformation. The energy absorption value determines the strength of each variation of the target plate. Then the target plate will compare which arrangement is the strongest when receiving ballistic loads.

Characterization of adhesive joints under ballistic shear impact

In this paper, we study the ballistic impact strength and energy absorption of single lap joints in predominantly shear (Mode II) loading. The behavior of two adhesives, namely a methacrylate and an epoxy, with steel adherends is presented. The developed ballistic shear test is analogous to the static single lap-shear joint test and uses an apparatus that is commonly used in ballistic penetration tests. The testing approach is coupled with a non-linear finite element parametric study to estimate the mechanical properties of the adhesives under ballistic loading. The finite element stress analysis results indicate that the shear failure stresses of both adhesives are much greater under ballistic loading than under static loading. In addition, the shear ballistic tests also show greater strength and energy absorption than the adhesive joints tested in Mode-I dominant ballistic impact. Though both the epoxy and methacrylate adhesives used in this study have similar static shear strengths, the shear strength of the epoxy under ballistic shear was found to be significantly higher than that for the methacrylate.

Numerical analysis of ballistic impact through FE and SPH methods

In the defense and aerospace industries, structures are designed to resist ballistic impact loads. Experimental analysis of ballistic impact has been conducted successfully for many years, and alternatively, numerical techniques have been employed to reduce the experimental cost. In this study, the ballistic impact of metallic materials is addressed with both finite element (FE) and smoothed particle hydrodynamics (SPH) methods. A single-shot ballistic impact model consisting of a deformable plate and a rigid projectile is developed. These two methods are compared using Johnson-Cook (JC) and Modified Mohr-Coulomb (MMC) damage models. Lode parameter dependent MMC damage criterion is implemented in the user-defined field (VUSDFLD) for damage analysis. Various numerical setups with varying target thickness, impact velocity, projectile nose shape and impact angle of the projectile, are generated. The damage response of the plate target according to the impact angle and the nose shape and the effect of ballistic impact parameters on the residual velocity is discussed in detail. The results are compared with the experimental results from the literature. FE method is found to be more consistent than SPH method in the prediction residual velocity. MMC damage model is better in agreement with experimental data than JC damage model. A linear decrease in residual velocity is observed with increasing thickness of target except the JC model used with FE method. Moreover, blunt projectiles are more sensitive to change in the impact angle than hemispherical and ogival projectiles. Increase in impact angle cause a reduction in residual velocity for all three projectile.

Pre-twinned magnesium for improved ballistic performance

Despite promise as a lightweight structural and armor material, widespread adoption of Mg alloys remains limited. For instance, the highly anisotropic properties, arising both from the fundamental deformation mechanisms and strong texture developed during processing of wrought Mg products, result in poor performance under ballistic loading. In an effort to improve the impact performance, a novel pre-compression process was developed to introduce twins into a rolled AZ31B plate. Through sequential compression along plate transverse direction (TD) and rolling direction (RD) the resistance to penetration by a 0.30-cal fragment simulating projectile, as characterized by its V50, was increased by 13% offering equivalent protection of a plate 16% heavier than the pre-twinned plate. In addition, the dominant failure mechanism was found to change from discing to ductile hole growth. Through examination of the pre-compressed microstructures and microhardness measurements the origins of the improved performance were identified as the introduction of stable twins.

Impact of nozzle profile on ballistic performance and structural loads

A nozzle is a device that is designed to regulate the direction and characteristics of the combustion gas products of jet engines. So, the nozzle performance has a significant impact on the mission achievement. This paper is concerned with the internal ballistics of the nozzle aiming to estimate pressure and thermal loads on its walls. Computational fluid dynamics is applied to analyse the effect of changing nozzle internal profile on the resulting thrust, flow energy losses, and nozzle wall structure. Area ratios at the inlet, critical, and exit sections are considered as constraints for the examined design. Two different sets with 4 different profiles for each are investigated. The results show thrust, entropy losses across the nozzle and the static pressure and temperature at nozzle wall. Bell shape profiles produce better performance compared to other profiles. Changing the internal profile of the nozzle causes significant change in pressure and temperature loads acting on nozzle wall structure.

Role of anisotropy in the ballistic response of rolled magnesium

Rolled magnesium alloys exhibit pronounced tension-compression asymmetry as well as anisotropy in yield and strain-hardening behavior. Although differences in the mechanical response are reasonably well-understood, it is not clear to what extent anisotropy alters the deformation and failure of plates subjected to ballistic loading conditions. In this work, the role of texture and anisotropy in the ballistic response is investigated using a combined experimental–computational approach. Sphere impact experiments are performed on rolled magnesium plates cut from orientations that exhibit differing mechanical responses. The complex failure process is characterized by in situ diagnostics, including ultra-high-speed Digital Image Correlation and Photonic Doppler Velocimetry, and compared with simulations performed on polycrystalline aggregates using a polycrystal plasticity model for hcp metals. The anisotropic deformation behavior arises from deformation mechanisms with disparate strength and strain hardening behavior, which is well captured in the model. The occurrence of low-strength extension twinning is shown to govern the initial anisotropic deformation and bulging of the plate. When compared with post-mortem 3D X-ray microscopy, regions that experience intense basal slip are shown to be sites for damage initiation that leads to eventual fracture. The combination of experiments and simulations suggest that at low to intermediate ballistic loading rates, material orientation plays a crucial role in dictating eventual fracture and failure in strongly anisotropic metals such as in rolled magnesium alloys.