Ballistic Protection Performance Research Articles

Effect of domestic laundering on the fragment protective performance of fabrics used in personal protection

UK Armed Forces wear items of clothing that incorporate fragment protective fabrics (Tier 1 Pelvic Protection) and other items of clothing are under development (e.g. Improved Under Body Armor Combat Shirt). The long-term robustness of such garments is of interest. In this paper four candidate fabrics (knitted silk, ultra-high molecular weight polyethylene felt, para-aramid felt and a woven para-aramid) were investigated. The effect of laundering on 0.24 g chisel-nosed fragment simulating projectile ballistic protective performance was measured on packs containing the candidate fabrics that were representative of clothing layers. Changes in the physical properties (mass, thickness, dimensional change) of candidate fabrics were measured. The ballistic protective performance of two candidate fabrics was unaffected by laundering; for the other two fabrics improved performance was measured. The masses of the specimen packs was unaffected by laundering; however, the thickness of all fabrics increased, relative to dimensional change.

Numerical simulation of the ballistic protection performance of a laminated armor system with pre-existing debonding/delamination

The ballistic protection performance of laminated body armor may be significantly reduced through defects such as debonding/delamination. To understand the effect of a pre-existing defect on body armor performance, a two-dimensional finite element model was developed. The numerical study shows that the laminated armor system with a pre-existing debonding/delamination has poorer ballistic protection performance than that without any imperfection. Also, it was noted that the ballistic protection performance of the laminated armor system with a pre-existing debonding/delamination is sensitive to the changes in the parameters considered such as size, location and pattern of the pre-existing debonding/delamination.

New hybrid foam materials for impact protection

The present paper investigates the dynamic compression and impact behaviour of a new class of open-cell Ni/Al-hybrid metal foams (nickel strengthened aluminium foams) in comparison to pure aluminium foams. In order to determine the characteristics of the pure aluminium and Ni/Al-hybrid foams, dynamic compression tests using a classical split Hopkinson pressure bar have been performed at strain rates up to 5000 s−1. Whereas the pure aluminium foams show only slight strain rate sensitivity, the hybrid foams are highly strain rate sensitive. The stress strain characteristics show a change in the deformation behaviour of the foams from bending dominated failure under quasi-static compression to a failure mode induced by microinertia effects under dynamic loading with additional stretching. As a fact of this additional stretching the hybrid foams are able to dissipate more energy under dynamic loading.Further ballistic impact tests have been performed on foam sandwich panels at impact velocities of 300 m/s. The hybrid foams show a significant improved ballistic protection performance especially in the case of elastomeric fillings. The paper outlines the possible application of Ni/Al-hybrid foams as crash absorber, security panels in case of blast and ballistic impact.

An integrated approach towards future ballistic neck protection materials selection

Ballistic protection for the neck has historically taken the form of collars attached to the ballistic vest (removable or fixed), but other approaches, including the development of prototypes incorporating ballistic material into the collar of an under body armour shirt, are now being investigated. Current neck collars incorporate the same ballistic protective fabrics as the soft armour of the remaining vest, reflecting how ballistic protective performance alone has historically been perceived as the most important property for neck protection. However, the neck has fundamental differences from the thorax in terms of anatomical vulnerability, flexibility and equipment integration, necessitating a separate solution from the thorax in terms of optimal materials selection. An integrated approach towards the selection of the most appropriate combination of materials to be used for each of the two potential designs of future neck protection has been developed. This approach requires evaluation of the properties of each potential material in addition to ballistic performance alone, including flexibility, mass, wear resistance and thermal burden. The aim of this article is to provide readers with an overview of this integrated approach towards ballistic materials selection and an update of its current progress in the development of future ballistic neck protection.

The role of adhesive in the ballistic/structural performance of ceramic/polymer–matrix composite hybrid armor

Transient non-linear dynamics computational finite-element analyses are employed to investigate the role of the adhesive used in ceramic strike-face/composite back-face hybrid armor. The role of the adhesive is investigated under: (a) high loading-rate conditions accompanying impact of an armor-piercing projectile onto the armor structure; and (b) low loading rate conditions associated with the ingress of the loads which are generated at the road/tire contact interfaces and transmitted into the armor structure through the vehicle frame. The high loading-rate conditions were analyzed since they reveal the role of the adhesive under ballistic impact scenarios which controls the overall penetration resistance of the armor. On the other hand, the low loading-rate conditions were analyzed since they may reveal the potential structural damage that armor may experience due to sustained in-service loads. Since structural thermoset-polymer-based adhesives suffer from inadequate ductility, only the case of flexible (elastomer-based) adhesives was considered. The following two specific aspects of the adhesive mechanical response are given special attention: (a) strain rate sensitivity and (b) the degree of volumetric compressibility. The results obtained show that while significant improvements in the ballistic protection performance and durability of hybrid armor can be attained by proper modifications in the adhesive layer mechanical properties, there is no single combination of these properties which simultaneously optimizes all the performance requirements.

A Computational Investigation of the Multi-Hit Ballistic-Protection Performance of Laminated Transparent-armor Systems

Multi-hit ballistic-protection performance of a prototypical laminated glass/polycarbonate transparent armor is investigated using a series of transient nonlinear dynamics analyses of armor impact with a sequence of four M2AP full metal jacket (FMJ) armor-piercing bullets. All calculations were carried out using ABAQUS/Explicit commercial finite element program (ABAQUS Version 6.7, User Documentation, Dessault Systems, 2007), and the computational results obtained were compared to their experimental counterparts obtained by Dolan (Ballistic Transparent-armor Testing Using a Multi-hit Rifle Pattern, Bachelors, Thesis, Kettering University, December 2007). The comparison revealed that (a) The proposed computational procedure can reasonably well account for the observed multi-hit ballistic-protection performance of the laminated transparent armor; (b) The role of prior bullet hits in reducing armor’s ballistic-protection performance is clearly revealed; (c) The role of polycarbonate lamina in preventing glass fragments from entering the vehicle interior is clearly demonstrated; and (d) Experimentally observed inability of the transparent armor to defeat 0.50-caliber Fragment Simulating Projectiles (FSPs) is confirmed.

Finite element analysis of the effect of up-armouring on the off-road braking and sharp-turn performance of a high-mobility multi-purpose wheeled vehicle

A comprehensive finite element investigation is carried out of the effect of up-armouring on the off-road performance of a prototypical high-mobility multi-purpose wheeled vehicle. The effect of up-armouring on the vehicle performance was investigated under the following off-road manoeuvres: straight-line flat-land braking; straight-line off-angle downhill braking; sharp left turn. In each case, the appropriate vehicle performance criteria are identified and the parameters used to quantify these criteria are defined and assessed. The computational results obtained clearly revealed the compromises in vehicle off-road performance caused by the up-armouring employed to improve vehicle blast and ballistic protection performance and survivability. The results obtained are also analysed and explained in terms of general field-test observations in order to judge the physical soundness and fidelity of the present computational approach. Finally, the potential benefits and ramifications of lightweight up-armouring in providing the needed level of blast and/or ballistic performance while causing fewer compromises in the vehicle off-road performance are also discussed.

Elucidating the Design and Impact Properties of Composite Nonwoven Fabrics with Various Filaments in Bulletproof Vest Cushion Layer

Nonwoven materials have been used in ballistic protection applications because they offer the advantages of light and flexible fabrics. This study examined the ballistic protection efficacy of a nonwoven structure with high tenacity polyamide staple fiber as its main component. The nonwoven structure was reinforced with low-melt polyester fiber. High tenacity filaments were laid between two layers of polyamide webs and bonded via needle punching. The impact-resistant properties were assessed using dropped weight and bullet-shooting impact tests. The results of the dropped weight-impact test were used to examine the optimum processing conditions for composite nonwoven fabrics. Furthermore, the results of the bullet-shooting test were used to examine the ballistic protection performance of composite nonwoven fabrics. The experiment's results demonstrated that the cushion structure of composite nonwoven fabric could reduce non-penetration damage and increase the ballistic-resistant properties of bullet-resistant vest.

Development and verification of a meso-scale based dynamic material model for plain-woven single-ply ballistic fabric

A meso-scale unit-cell based continuum material constitutive model has been developed for plain-woven single-ply ballistic fabric materials. This model, due to its computational efficiency, is suitable for use in computational analyses of the ballistic-protection performance of multi-layer body-armor vests. The model utilizes the continuum-level in-plane and out-of-plane deformation-state of the material, an energy minimization procedure and a simple account of yarn slip to update the structure/architecture of the fabric unit cell. Forces and moments developed within the structural components of the unit cell are then used to compute the continuum-level stress state at the material points associated with the unit cell in question. The model is implemented in a user-material subroutine suitable for use within commercial finite-element programs. To validate the model, a series of transient non-linear dynamic analyses of the impact of a square-shaped fabric patch with a spherical projectile is carried out and the computed results compared with their counterparts obtained using a more traditional finite-element approach within which yarns and yarn weaving are modeled explicitly. The results obtained show that the material model provides a reasonably good description for the fabric deformation and fracture behavior under a variety of boundary conditions applied to fabric edges and under varying fictional conditions present at the yarn/yarn and projectile/fabric interfaces. In addition, the overall ballistic energy absorption capacity of the fabric as well as its yarn-strain energy, yarn-kinetic energy, and frictional sliding contributions are predicted with reasonable accuracy by the proposed material model for fabric.

The effect of a carbon-nanotube forest-mat strike face on the ballistic-protection performance of E-glass reinforced poly-vinyl-ester-epoxy composite armour

In the present work, a ballistic material-model development approach is combined with transient non-linear dynamics simulations of the projectile/armour interactions to explore the armour-hard-facing potential of multi-walled carbon nanotube (MWCNT) reinforced, poly-vinyl-ester-epoxy (PVEE)-matrix composite mats. This approach is applied to improving the ballistic-protection performance of E-glass fibre-mat reinforced PVEE-matrix laminate armour. Two different architectures of the MWCNT-reinforced/PVEE-matrix composite mats were considered: (a) a MWCNT-ply mat structure in which the MWCNT reinforcements are aligned parallel to the armour faces and (b) a MWCNT-forest mat structure in which the MWCNT reinforcements are aligned orthogonally to the armour faces. The projectile/armour interaction simulation results showed that, at low volume fractions of MWCNTs, both armour architectures yield no discernable increase in the armour ballistic-protection performance as measured by the armour. On the other hand, at high MWCNT volume fractions of MWCNTs, the first armour architecture remained ineffective whereas the second showed a minor improvement in the ballistic-protection performance relative to the corresponding monolithic armour. These results were rationalized using published experimental observations pertaining to the effect of MWCNTs on the in-plane and the through-the-thickness properties of fibre-mat/polymer-matrix composite materials.

Ballistic-protection performance of carbon-nanotube-doped poly-vinyl-ester-epoxy matrix composite armor reinforced with E-glass fiber mats

In the present work, a material model development approach and transient non-linear dynamics simulations of the projectile/armor interactions are employed to explore the role of multi-walled carbon-nanotube (MWCNT) reinforcements in improving the ballistic-protection performance of poly-vinyl-ester-epoxy matrix (PVEE)/E-glass fiber matrix reinforced laminate armor. Two different architectures of the composite-laminate armor are considered: (a) a hybrid armor consisting of a 100 μm-thick high MWCNT-content PVEE-matrix MWCNT-reinforced lamina sandwiched between two PVEE-matrix/E-glass mat reinforced laminas and (b) a monolithic E-glass mat reinforced composite laminate with a low MWCNT-content MWCNT-doped PVEE-matrix. The projectile/armor interaction simulation results show that both armor architectures yield a minimal (∼6%) increase in the ballistic-protection as measured by the armor V50, a velocity at which the probability of armor penetration by a given fragment is 50%. The results obtained are rationalized using a simple analysis of the effect of MWCNTs on the in-plane and the through-the-thickness properties of the armor.

Mechanics of integral armor: discontinuous ceramic-cored sandwich structure under tension and shear

An integral armor sandwich structure consisting of S2-glass-reinforced face sheets with adhesively bonded discontinuous ceramic tiles provides potential optimal ballistic protection and structural performance at minimum weight for composite armored vehicle applications. The structural response is investigated by defining an idealized unit cell subjected to tensile and in-plane shear membrane loading. In the model, an admissible stress system that satisfies equilibrium and all boundary and interface conditions is constructed, and the principle of minimum complementary energy is employed to find an optimal approximation. Typical stress variations are presented, and their implications for progressive damage and failure of the structure are discussed. Based on the stress and deformation fields in the core and face sheet, the overall effective stiffness of the structure can be evaluated. By selecting some critical parameters, such as the core length and the adhesive stiffness and thickness, an optimized design for the structure can be achieved.