Ballistic Impact Energy Research Articles

A hybrid approach of NiP coating and STF impregnation of UHMWPE fabric for conductive soft body armor

To enhance the ballistic impact performance and impart electrical conductivity into soft armor material made up of UHMWPE fabric, a novel hybrid technique has been devised and incorporated. Initially, the NiP layer was deposited on the UHMWPE fabric surface through the electroless process, subsequently, it was impregnated in the shear thickening fluid (STF) based on nano-silica (40 wt%). The morphology, functional groups, phase structure, thermal stability, breaking load, inter-yarn friction, electro-heating, and ballistic impact performance of the neat (UHM), STF impregnated (UHM-STF), NiP coated(UHM/NiP), and NiP coated STF impregnated (UHM/NiP-STF) fabrics are detailed. The NiP coating enhanced the ballistic impact performance, and thermal stability, and became electrically conductive compared to neat fabric. The ballistic impact test confirmed the enhancement in the energy absorption of UHM-STF (30.84%), UHM/NiP(18.37%), and UHM/NiP-STF(54.82%) compared to UHM. The hybrid technique (UHM/NiP-STF) exhibited higher inter-yarn friction (53.79%) and ballistic impact energy absorption (18.43%) compared to UHM-STF. The significant rise in the impact energy absorption of the UHM/NiP-STF can be ascribed to the synergetic effect of enhanced inter-yarn friction induced by the NiP-coated layer and the shear thickening behavior exhibited by STF. The NiP-coated and STF-impregnated fabrics present a promising prospect for the advancement of soft body armor materials with multifunctional ability.

Influence of Post Weld Cryogenic Treatment on the Ballistic Penetration Resistance of Friction Stir-Welded AZ31B Magnesium Alloy

Influence of post weld cryogenic treatment conditions (deep and shallow) on the ballistic resistance of friction stir welded (FSW) AZ31B magnesium alloy has been investigated. AZ31B welded joints which were prepared by using friction stir welding process were subjected to two types of cryogenic treatment conditions. The microstructural investigation of cryogenic treated joints showed the formation of Mg17Al12 precipitates and conversion of coarse eutectic phase into thin discontinues phase along with halos. In addition, superior microhardness values were noticed for the cryogenically treated joints compared with non-treated joints and base metal. High velocity ballistic experiments were conducted on cryogenically treated and non-treated weld targets using 7.62 mm deformable projectiles at an initial velocity of 450 ± 10 m/s. At the stir zone, the depth of penetration (DOP) of the projectile into the deep cryogenic treated (DCT) target was observed to be 11% and 34 % lesser than the shallow cryogenic treated (SCT) and FSW targets. Thus increase in the ballistic resistance was observed for the post-weld cryogenic treated FSW joints compared to non-treated FSW joints. SEM investigation of the projectile impacted DCT targets showed the formation of cracks, dimples and micro voids at the crater region. It is also noticed that, the Stir Zone (SZ) and Heat Affected Zones (HAZ) of the DCT target has effectively absorbed the ballistic impact energy of the projectile by a ductile fracture and hence DCT can be used to improve the ballistic penetration resistance of the FSW joints at the SZ and HAZ regions.

Ballistic impact performance of composite laminates based on high‐density polyethylene/montmorillonite nanocomposite and Aramide fiber

AbstractNanostructured thermoplastic consisting of high‐density polyethylene (HDPE) modified with exfoliated montmorillonite (MMT) was successfully used as the matrix for the development of composite for ballistic applications. The effect of HDPE and HDPE/MMT as the matrix on the mechanical and ballistic properties of para‐aramid plain‐woven fabric‐based composites was compared with the commercial composite constituted by polyvinyl‐butyral–phenolic resin as the matrix. The dynamic compressive tests using split Hopkinson pressure bar equipment revealed a remarkable increase of maximum compression strength, outstanding dynamic compressive response, and superior tenacity for the composite containing HDPE/MMT as the matrix. Moreover, the ballistic limit of the HDPE/MMT‐based composite was the highest one. Mechanical failures indicated that this matrix was able to interact with a greater fiber volume and was responsible for improving the ballistic impact energy absorption. Thus, the use of MMT in thermoplastic matrix may be considered a promising ballistic solution due to the possibility of combining lightweight and ballistic resistance.

A machine learning model for predicting the ballistic impact resistance of unidirectional fiber-reinforced composite plate

It has been a vital issue to ensure both the accuracy and efficiency of computational models for analyzing the ballistic impact response of fiber-reinforced composite plates (FRCP). In this paper, a machine learning (ML) model is established in an effort to bridge the ballistic impact protective performance and the characteristics of microstructure for unidirectional FRCP (UD-FRCP), where the microstructure of the UD-FRCP is characterized by the two-point correlation function. The results showed that the ML model, after trained by 175 cases, could reasonably predict the ballistic impact energy absorption of the UD-FRCP with a maximum error of 13%, indicating that the model can ensure both computational accuracy and efficiency. Besides, the model’s critical parameter sensitivities are investigated, and three typical ML algorithms are analyzed, showing that the gradient boosting regression algorithm has the highest accuracy among these algorithms for the ballistic impact problem of UD-FRCP. The study proposes an effective solution for the traditional difficulty of the ballistic impact simulation of composites with both high efficiency and accuracy.

Ballistic impact tests and stacked shell simulation analysis of aramid fabric containment system

The plain-woven aramid fabrics have been commonly used to offer the high protection against ballistic threats. This paper deals with the tests and numerical investigations on the ballistic impact responses of aramid fabric containment system. A series of quasi-static tensile tests and dynamic tensile tests are conducted to determine the mechanical performance parameters of plain-woven aramid fabric. A series of ballistic impact tests are further carried out with different projectile velocities to investigate the ballistic behavior of aramid fabric containment system, which are fabricated by wrapping multiple layers around a back-up steel ring. The method of using the explicit dynamic software LS-DYNA to establish the stacked shell finite element model for quantitative analysis of the ballistic impact process is developed and conducted, and the failure mode and containment mechanism are discussed in detail through the test and simulation analysis. The results show that both the peak stress and elastic modulus increase significantly with the increasing of strain rate, but the failure strain increases slightly. The ballistic impact energy is consumed mainly through the large deformation of fabric, inter-yarn friction, and interlaminar friction. The simulation results are in good agreement with the test results, and the deformation and failure mode of aramid fabric containment system are better reproduced, which provides the promising finite element method for analyzing the ballistic impact events. In addition, some comparisons in interlaminar contact, impact position and incident attitude of projectile are further conducted and discussed.

Tucum Fiber from Amazon Astrocaryum vulgare Palm Tree: Novel Reinforcement for Polymer Composites.

The replacement of synthetic fibers by natural fibers has, in recent decades, been the subject of intense research, particularly as reinforcement of composites. In this work, the lesser known tucum fiber, extracted from the leaves of the Amazon Astrocaryum vulgare palm tree, is investigated as a possible novel reinforcement of epoxy composites. The tucum fiber was characterized by pullout test for interfacial adhesion with epoxy matrix. The fiber presented a critical length of 6.30 mm, with interfacial shear strength of 2.73 MPa. Composites prepared with different volume fractions of 20 and 40% tucum fiber were characterized by tensile and Izod impact tests, as well as by ballistic impact energy absorption using .22 ammunition. A cost analysis compared the tucum fiber epoxy composites with other natural and synthetic fiber reinforced epoxy composites. The results showed that 40 vol% tucum fiber epoxy composites increased the tensile strength by 104% and the absorbed Izod impact energy by 157% in comparison to the plain epoxy, while the ballistic performance of the 20 vol% tucum fiber composites increased 150%. These results confirmed for the first time a reinforcement effect of the tucum fiber to polymer composites. Moreover, these composites exhibit superior cost effectiveness, taking into account a comparison made with others epoxy polymer composites.

Investigation of composite fabric impregnated with non-Newtonian fluid for protective textiles

Commercial high-performance fibre materials for body armour have very low surface friction and this has become an issue in the effectiveness of ballistic impact energy absorption. Also, the incidence of sports injuries in high contact sports is high. The severity of injuries of police and sportsman can be reduced by wearing enhanced protective clothing that have the ability to absorb the shocks. In this study, a type of non-Newtonian fluid has been developed. It became hardened upon a shock impact which was observed through a drop-on-weight test. The non-Newtonian fluid was successfully applied on to a traditional plain weave body armour fabric made of Twaron®. The treated fabric was studied by scanning electron microscopy and a yarn pulling-out test. It shows that the force to pull out a yarn from the non-Newtonian fluid treated fabric is four times higher than that of the untreated one. The flexibility of the non-Newtonian polymer treated fabric remains unchanged. The polymer can be used for applications where impact protection can be a highly desirable property.

Improving the Impact Resistance Performance of STF Treated Kevlar Fabric Structures

Abstract A continuous increase in the war-conflicts and development in the area of weapons challenges the research community to develop the body armor materials accordingly. The focus is on making the materials light weight and flexible yet improving its impact resistance performance to make the material compatible to use for a longer duration. Application of nano-materials such as nano-fibers, nano-fillers and nano-finishes are turning the concept into reality. Application of shear thickening fluid (STF) has been proved to increase the impact resistance performance of the textile structures to further use it as a body armor material. Present research deals within the same segment where nano-silica based STF was applied on Kevlar woven fabric to make the structure lightweight and flexible while improving its impact resistance performance. It was observed in the earlier studies by the authors that it is difficult to get a fair amount of add-on of STF on Kevlar fabric as it comes with a PTFE coating which hinders its absorbency. Hence, a novel method named as sequential padding is developed in the present study to improve the add-on of STF on Kevlar fabric. Contrary to the conventional process, where Kevlar fabric is treated with STF once using any one pressure, in sequential padding method, the Kevlar fabrics were treated twice using three levels of pressure (0.5, 1 and 2 bar) in various combinations and sequences. STF add-on % and dynamic Impact energy absorption on dynamic impact tester at a fixed velocity of 6 m/s were observed for sequentially padded fabrics and compared with untreated Kevlar fabric and fabrics treated with STF in single step. Low velocity bullet proof tests with 165 m/s were also performed to verify the results It was observed that both add-on% and impact energy absorption of Kevlar fabrics increases significantly with sequential padding process as compared to untreated as well as single step padding process. It was also noted that different combinations and sequences of padding pressures used for STF treatment of Kevlar fabric play a significant role in improving the impact resistance performance. It was noted that impact energy absorption of sequentially padded Kevlar fabric show almost 125% increase in ballistic impact energy absorption (40.62 J) as compared to untreated fabric (18.07 J). Therefore, it is concluded that sequential padding process opens up a new horizon for further improvement in impact performance of body armor materials based on STF treated Kevlar fabrics.

Atomistic-scale simulations of mechanical behavior of suspended single-walled carbon nanotube bundles under nanoprojectile impact

Carbon nanotube fiber (CNTF) is generally considered a strong candidate for the fabrication of bullet-resistant vests due to its excellent combination of extremely high elastic modulus, high yield strain, low density, super toughness, as well as good flexibility. CNTF may also provide effective dissipation of impact energy through fibrillation within the CNTF and through disintegration of the CNTF. In this study, molecular dynamic (MD) simulations are performed to investigate the nanoprojectile impact on suspended single-walled carbon nanotube (SWCNT) bundles. The simulated results show that the fronts of impact-induced longitudinal and transverse waves travel at speeds ranging from 18 to 20 km/s and 1.5 to 1.7 km/s in the bundles that absorb most of the nanoprojectile's initial kinetic energy. The manner in which ballistic impact energy spreads within the CNTF is predicted to be mainly through transverse waves. Acoustic vibrations of the SWCNT bundle caused by the impact-induced longitudinal and transverse waves are revealed. We propose that impact energy can be effectively dampened in a manner of generating acoustic noise and heat. The threshold of the nanoprojectile's incidental kinetic energy is calculated and is used to evaluate the breaking of SWCNT bundle. The destructive role of a lap joint within the SWCNT bundle is demonstrated, as well as the role of local buckling in blocking the propagation of transverse and longitudinal waves. To facilitate the spreading of impact energy over a long distance, we propose that polymers may form an ideal matrix that should be infiltrated in the CNTF through capillary forces to increase the impact strength and to reinforce the wave spreading to release.

Reprint of: Projectile penetration into sand: Relative density of sand and projectile nose shape and mass

Compacted granular materials, like sand, have a tendency to dilate and expand under shear loading. Such tendency of dilation is beneficial to inhibit projectile penetration. Furthermore, the higher the striking velocity of a given projectile, the higher is the peak strength of the sand sample. Different nose shapes (spherical, flat, hemispherical, conical and ogival) and mass (7g, 15g and 20g) of projectiles were fired into sand samples of relative densities ranging from medium dense to very dense state (60%, 75% and 90%). Results showed that the pointed ogival head projectile had the lowest ballistic limit, whereas the blunt flat head projectile required the highest ballistic energy to defeat the sand block. Despite visible effect of nose shape, the mass of projectile has a larger influence on the amount of absorbed energy. On the other hand, initial compaction of the sand alters the depth of penetration marginally. This is attributed to the projectile impact which compacts the sand as the projectile penetrates through the sand sample. A strong linear correlation between projectile nose shape, mass and ballistic impact energy was established in this study, which allows protective engineers to easily design sand barriers to defeat a range of projectiles. Furthermore, it was found that the energy absorption of sand remains high even when subjected to striking velocities way beyond its ballistic limit. This opens up avenues for sand barriers to be used as sacrificial layer of a composite lightweight protective barrier.

Projectile penetration into sand: Relative density of sand and projectile nose shape and mass

Compacted granular materials, like sand, have a tendency to dilate and expand under shear loading. Such tendency of dilation is beneficial to inhibit projectile penetration. Furthermore, the higher the striking velocity of a given projectile, the higher is the peak strength of the sand sample. Different nose shapes (spherical, flat, hemispherical, conical and ogival) and mass (7g, 15g and 20g) of projectiles were fired into sand samples of relative densities ranging from medium dense to very dense state (60%, 75% and 90%). Results showed that the pointed ogival head projectile had the lowest ballistic limit, whereas the blunt flat head projectile required the highest ballistic energy to defeat the sand block. Despite visible effect of nose shape, the mass of projectile has a larger influence on the amount of absorbed energy. On the other hand, initial compaction of the sand alters the depth of penetration marginally. This is attributed to the projectile impact which compacts the sand as the projectile penetrates through the sand sample. A strong linear correlation between projectile nose shape, mass and ballistic impact energy was established in this study, which allows protective engineers to easily design sand barriers to defeat a range of projectiles. Furthermore, it was found that the energy absorption of sand remains high even when subjected to striking velocities way beyond its ballistic limit. This opens up avenues for sand barriers to be used as sacrificial layer of a composite lightweight protective barrier.

Ballistic impact properties of mixed multi-layered amorphous surface alloyed materials fabricated by high-energy electron-beam irradiation

The objective of this study is to investigate ballistic impact properties of multi-layered amorphous surface alloyed materials fabricated by high-energy electron-beam irradiation. The mixture of Zr-based amorphous alloy powders and LiF+MgF2 flux powders was deposited on a Ti alloy substrate, and then electron beam was irradiated on this powder mixture to fabricate an one-layered surface alloyed material. On top of this layer, the powder mixture was deposited again and then irradiated with electron beam whose beam current was decreased to fabricate the multi-layered surface alloyed material. In the mixed multi-layered surface alloyed materials fabricated with LM1 alloy powders and LM2 or LM10 alloy powders, the surface region consisted of amorphous phases, together with a small amount of crystalline particles, whereas the center region was complicatedly composed of amorphous phases, crystallized phases, and dendritic β phases. Since the surface region mostly composed of amorphous matrix was quite hard, the alloyed materials sufficiently blocked the travel of a projectile. When cracks formed at the surface region propagated into the center region, the formation of many cracks or debris was accelerated, which could beneficially work for absorbing the ballistic impact energy, thereby leading to the higher ballistic impact properties than the surface alloyed materials fabricated with LM1 or LM2 alloy powders.

Ballistic Impact Properties of Zr-Based Amorphous Alloy Composites Reinforced with Woven Continuous Fibers

This study aims at investigating ballistic impact properties of Zr-based amorphous alloy (LM1 alloy) matrix composites reinforced with woven stainless steel or glass continuous fibers. The fiber-reinforced composites with excellent fiber/matrix interfaces were fabricated without pores and misinfiltration by liquid pressing process, and contained 35 to 41 vol pct of woven continuous fibers homogeneously distributed in the amorphous matrix. The woven-STS-continuous-fiber-reinforced composite consisted of the LM1 alloy layer of 1.0 mm in thickness in the upper region and the fiber-reinforced composite layer in the lower region. The hard LM1 alloy layer absorbed the ballistic impact energy by forming many cracks, and the fiber-reinforced composite layer interrupted the crack propagation and blocked the impact and traveling of the projectile, thereby resulting in the improvement of ballistic performance by about 20 pct over the LM1 alloy. According to the ballistic impact test data of the woven-glass-continuous-fiber-reinforced composite, glass fibers were preferentially fragmented to form a number of cracks, and the amorphous matrix accelerated the fragmentation of glass fibers and the initiation of cracks. Because of the absorption process of ballistic impact energy by forming very large amounts of cracks, fragments, and debris, the glass-fiber-reinforced composite showed better ballistic performance than the LM1 alloy.

Correlation of Microstructure and Ballistic Performance of Multilayered Zr-based Amorphous Surface Composites Fabricated by High-Energy Electron-Beam Irradiation

In this study, multilayered, Zr-based amorphous surface composites were fabricated by high-energy electron-beam irradiation; the correlation of their microstructure, hardness, compressive properties, and fracture properties with ballistic performance was investigated. The mixture of Zr-based amorphous powders and LiF + MgF2 flux powders was deposited on a pure Ti substrate or a plain carbon steel substrate, and then an electron beam was irradiated on this powder mixture to fabricate a one-layered surface composite. The multilayered surface composite was fabricated by an irradiating electron beam several times again onto the powder mixture deposited on the one-layered surface composite. The microstructural analysis results indicated that a small amount of fine crystalline particles was distributed homogeneously in the surface composite layer. Because the surface composite layers absorbed the ballistic impact energy by forming many cracks or microcracks, the surface composite plates were not perforated during the ballistic impact test. On the one hand, in the surface composite without containing ductile β phases, the composite layer was cracked completely and fallen off from the substrate. On the other hand, a small amount of fragmentation was found in the impacted area of the composite containing β phases because it had the sufficient hardness and fracture toughness simultaneously for effectively blocking the traveling of a projectile, thereby improving ballistic performance.

Ballistic performance of armour ceramics: Influence of design and structure. Part 1

The use of advanced ceramics for armour systems allows the defeating of the projectile and ballistic impact energy dissipation providing adequate ballistic protection. The development of lightweight and inexpensive ceramics and armour designs is under ongoing attention by both ceramic armour manufacturers and armour users. This paper summarizes the results of extensive studies of ballistic performance of different armour ceramics, mostly obtained during development, as well as of the materials manufactured by other recognized armour ceramic suppliers, and the designed ceramic-based armour systems. The studied armour ceramics include homogeneous oxide and carbide ceramics and heterogeneous ceramic materials. Composition, structure and main properties of the considered ceramics, which affect ballistic performance, are examined and analyzed. Only a combination of all relevant physical properties and microstructure, including the ability to dissipate ballistic energy, as well as optimization of manufacturing processes, should be considered for proper selection and evaluation of ceramic armour. Ballistic performance of the studied ceramics as function of their structure and properties, armour system design and type of projectile has been discussed.

Ballistic performance of armour ceramics: Influence of design and structure. Part 2

The use of advanced ceramics for armour systems allows the defeating of the projectile and ballistic impact energy dissipation providing adequate ballistic protection. The development of lightweight and inexpensive ceramics and armour designs is under ongoing attention by both ceramic armour manufacturers and armour users. This paper summarizes the results of extensive studies of ballistic performance of different armour ceramics, mostly obtained during development, as well as of the materials manufactured by other recognized armour ceramic suppliers, and the designed ceramic-based armour systems. The studied armour ceramics include homogeneous oxide and carbide ceramics and heterogeneous ceramic materials. Ballistic performance of the studied ceramics as function of their structure and properties, armour system design and type of projectile has been discussed. Depending on the requirements for ballistic protection, armour systems may be designed to various configurations and weights based on the most suitable ceramic materials and backing. The examples of successful designs of lightweight armour systems with adequate ballistic performance, including satisfactory multi-hit performance, have been demonstrated.

Yarn Pull-Out as a Mechanism for Dissipating Ballistic Impact Energy in Kevlar® KM-2 Fabric

The energy absorbed in ballistic fabrics is modeled by assuming yarn pull-out, including yarn uncrimping and translation, as the primary energy absorption mechanism. Using a semi-empirical model of yarn pull-out based on laboratory tests, predictions of fabric ballistic performance are compared to ballistic test results. The study demonstrates that quasi-static pull-out results can be correlated quantitatively with yarn pull-out during ballistic impact.

Yarn Pull-Out as a Mechanism for Dissipating Ballistic Impact Energy in Kevlar® KM-2 Fabric

Yarn pull-out can be an important energy absorption mechanism during the ballistic impact of woven Kevlar® fabric. This study reports the effects of fabric length, number of yarns pulled, arrangement of yarns, and transverse tension on the force-displacement curves for yam pull-out tests on Kevlar® KM-2 fabric under laboratory conditions. A semi-empirical model is presented for predicting the yam pull-out force and energy as a function of pull-out distance, including both yarn uncrimping and subsequent yam translation. This model is found to replicate the experimental data with a high degree of accuracy, and should prove useful for understanding ballistic experiments and improving computational modeling of fabrics.

A study of the influence of controlled corona treatment on UHMWPE fibres in reinforced vinylester composites

AbstractIn order to illuminate the mechanisms of corona discharge treatment on ultra‐high molecular weight polyethylene (UHMWPE) fibre, the effects of corona treatment power and time are discussed in detail. The surface‐roughness and tensile‐failure characteristics of the polyethylene fibre were determined by a scanning electron microscope (SEM). The photos from the SEM showed that the size and number of the micro‐pits on the fibre surface increase with increase of corona power. The oxygen‐containing groups on the fibre surface could be detected by Fourier‐transform infrared attenuated total reflectance and also increased gradually with increase of corona power. The T‐peel strength of composites increased from the corona treatment, and then showed a maximum value at a corona treatment time about 0.1 s with increase of treatment time. However, the tensile strength of the fibre was reduced with increase of corona power and the failure mechanism obviously changed after the treatment. The ballistic impact energy absorption of UHMWPE fibre/vinylester composite was obtained after fragment simulating projectiles (FSP) impact tests. After 6‐kW corona treatment for 0.075 s, the impact energy absorbed by the laminate reached a maximum value. Copyright © 2003 Society of Chemical Industry

The effect of ballistic impacts on the high-cycle fatigue properties of Ti-48Al-2Nb-2Cr (atomic percent)

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 (<0.74 J), whereas Hertzian crack length (HCL) (impact side damage) was the best predictor for higher-energy impacts. The impacted γ-TiAl samples displayed a classical mean stress dependence on the fatigue strength. For the fatigue design stresses of a sixth-stage LPT blade in a GE90 engine, a Ti-48Al-2Nb-2Cr LPT blade would survive an impact of normal service conditions.