Body Armor Panel Research Articles

Numerical investigation of the high-velocity impact performance of body armor panels

The body armor can effectively reduce penetration injuries and save many soldiers’ lives. However, back face deformation (BFD) accompanied by ballistic impacts on body armor can lead to fatal injuries to soldiers on the battlefield. In the study, ballistic tests and finite element models are performed to evaluate the protection of body armor panels. Both soft body armor and ceramic till are validated against the experimental data. Then, the performance of the ultra-high molecular weight polyethylene (UHMWPE) soft armor incorporating the RP #1 clay and foam pad is discussed. The simulation results show that the addition of a foam pad can effectively reduce the maximum clay BFD. At the same time, the performance of the ceramic-UHMWPE panel is studied. The ceramic tile can partly absorb the kinetic energy of the high-velocity projectile and enlarge the contact area between the UHMWPE panel and RP #1 clay, which leads to a lower BFD value. In addition, the effects of the interlaminate strength and the laminate stacking direction of the UHMWPE panel on the BFD are discussed. The current simulation can capture the damage behavior of UHMWPE laminates and ceramic tile well, which can be a guide for the design and improvement of new body armor panels.

Ballistic Performance of Epoxy-Ramie Composite - SiC Layered Body Armor Using Finite Element Analysis

Composite body armor has widely used as bulletproof material combined with hard plates made from ceramic or metals. That replaced the use of full-metals body armor that heavy, rigid, and restricts the user's movement. This study investigates the ballistic performance of SiC-based hard layer body armor on its possible impact position using finite element analysis. The body armor panel consists both of soft and hard layers. The soft layer is made from epoxy-ramie composite which is a natural fiber composite. The hard layer made from hexagonal chip l SiC with 4 mm thickness in an array. There are three possible impact points on the chip which are the center of the chip, between two chips, and between three chips. The soft layer is varied at a range of 6-25 mm depending on its capability to comply with the latest NIJ 0101.07-2019 criteria for RF1. NIJ has several criteria for ballistic performance. This paper discusses panel penetration and Back-face Deformation (BFD) based NIJ. Besides, this paper also discusses the impact of energy absorption and velocity reduction of the bullet by the panel.

Preparation and Impact Resistance Properties of Hybrid Silicone-Ceramics Composites

This article presents the method of preparation a new type of ballistic armor based on hybrid silicone-ceramic (HSC) composites with considerable flexibility. An experimental study on the ballistic behavior of HSC composites connected with soft body armor is presented against FSP.22 fragments. The effect of Al2O3 ceramics on the ballistic performance of HSC composite was investigated, and the fragmentation resistance process of the composite armor combining the HSC composite and soft aramid insert is clarified. Furthermore, impact resistance tests made with a drop tower which allows for a gravity drop of a mass along vertical guides onto a sample placed with an energy of 5 J were performed. The results presented in this paper show that the HSC composites can be successfully used as a hard body armor. However, they do not exhibit the properties of absorbing the impact energy generated during the drop tower tests. The test results show that the ballistic performance of composite armors is influenced by the hardness and Young modulus of ceramics and soft body armor panel. Additionally, in the article, the results of mechanical properties of silicones used for preparation of composites were presented and compiled to determine their role in the performance of impact protection.

Design strategy for optimising weight and ballistic performance of soft body armour reinforced with shear thickening fluid

This study presents some soft armour panel design strategies using shear thickening fluid (STF) reinforced Kevlar® fabric. The effect of size of silica nano and sub-micron particles on the ballistic performance of soft body armour panels against the small arms ammunition (velocity ~ 430 ± 15 m/s) has been analysed. Two STFs, namely STF-500 and STF-100, were prepared by dispersing silica particles of 500 nm and 100 nm diameter, respectively, in polyethylene glycol (PEG) 200. Kevlar® fabrics were impregnated with both the STFs. Multiple layers (20–24) of fabrics were stitched to prepare 13 soft armour panels which were evaluated for back face signature (BFS) against 9 × 19 mm lead core bullet. Soft armour panels comprising of fabrics impregnated with STF-500 yielded lower BFS than the respective panels comprising of fabrics impregnated with STF-100. This study also revealed that STF impregnation of Kevlar® fabrics can reduce the BFS by 2.5 mm–2.8 mm while keeping the areal density of the panel same (5 kg/m2). The areal density of soft armour panel can be reduced further by 10% (4.5 kg/m2), while keeping the BFS comparable to or lower than that of an STF impregnated homogenous panel, by judiciously placing the STF impregnated fabrics at the rear side while neat fabrics are placed at the strike face of the panel. STF impregnated panels were found to stop the impacting bullet earlier than neat panel.

Soft body armour development by silica particle based shear thickening fluid coated p-aramid fabrics

Soft body armour panels using p-aramid (Technora) fabrics with three different levels of thread densities were developed in this research. Shear thickening fluid (STF) was synthesized using silica nano-particle (100 nm) and polyethylene glycol (PEG). Fabrics were coated with 60% (w/w) STF to improve their resistance against low-velocity bullets (165 m s−1). For neat fabrics, all the bullets fired from 0.38″ calibre revolver pierced the multilayer fabric panel. However, impact energy absorption increased with the increase in thread density in fabric. After coating with shear thickening fluid, panels having four layers of fabric stopped all the bullets fired. It was possible to reduce the weight of panel by 23% after the STF treatment whilst ensuring bullet stoppage.

Determination of Materials for Hybrid Design of 3D Soft Body Armour Panels

In order to optimise the construction of soft body armour panels by hybridization, this study aims to identify materials determination for hybrid panel. Different ballistic characteristics of aramid woven fabrics and Ultra High Molecular Weight Polyethylene uni-directional laminates were investigated through ballistic test and fractorgaphic analysis. With an increasing of total layer numbers in a panel, specific energy absorption of Twaron woven panel shows a decrease trend, and Dyneema UD panel exhibits an increasing trend. Such reverse trend of ballistic performance is due to different failure modes of two materials. According to fractorgraphic analysis, Twaron fabric has large transverse deformation for back layers in a perforated panel. This results in higher energy absorption in back layers. For Dyneema UD, thermal damage is the dominant failure mode, which can result in performance degradation especially for front layers on the strike face. In addition, Dyneema UD exhibits significant advantage of minimize Backface Signature (BFS) and a little higher perforation ratio than that of Twaron woven panels. Based on these findings, an optimized hybrid panel is designed by combing Twaron woven fabric before Dyneema UD. In comparison with other panels with different layer sequences, this hybridization manner exhibited better ballistic performance, including improvement of energy absorption, minimized BFS of the non-perforated panel and reduction of perforation ratio. These findings indicated that material determination for hybrid design should be based on ballistic characteristics of different materials and requirements of different regions in a panel.

Development of comfortable and well-fitted bra pattern for customized female soft body armor through 3D design process of adaptive bust on virtual mannequin

The performance of various protective clothing i.e., soft body armor depends mainly on material type, fabric construction and garment design. However, most female soft body armor has been designed using traditional methods which face poor ballistic protection, less fitness and comfort. These problems mainly arise from corset problem due to using current inaccurate traditional bra sizing system which considers only cup size as a description of complex three dimensional (3D) breast volumes. Besides, female body armor manufacturing using this method enforced to involve different darts to accommodate the natural curvature of the female body, i.e. bust area. This brought the weak parts at the seams while ballistic impact and revealed discomfort due to accumulated fabrics at this area. The current study introduces a novel designing technique for developing female adaptive bust volume on 3D female virtual mannequin. The adaptive bust later used to generate different volumes of breast based on parametrization. The main purpose of our approach is to solve previous design problems by using the computer-aided design (CAD) knowledge in the morphological evolution of the chest and introduced it into a 3D design process for achievement of comfortable and well fitted 3D bra design. During 3D digitized modeling process, various cutting planes in x and y-direction from the bust origin have been intersecting with the bust at several angles. This intersection would help to extract the real surface of the body contour and creates the wireframe mesh on the bust. This wireframe mesh ensued different feature points on 3D expandable bust for defining the different volumes of breast based on their cup sizes. Moreover, 3D bra pattern is developed using the adaptive volume to validate the specific obtained volume. The flattened 2D patterns from the 3D model were also compared to the corresponding traditional 2D pattern. The result indicated that the proposed method is easier to implement and can generate 2D bra patterns with satisfactory fit and comfort. This is due to the 3D pattern derived from the new method which perfectly follows the exact body contours than assuming the measurement, as done into classical 2D graphical method. The study later associates different bust cups with the front part of female body armor panel to determine the possible variation for better performance and optimal comfort. In general, this approach solves previous design problems and helps to customize bra pattern and female body armor front panel patterns using CAD knowledge in the morphological evolution of the female bust volume. Further study is required to develop seamless female front body pattern in association with the respective bust volume. This will help to customize the ballistic vest which attains the required bust volume without involving dart for better comfort, ballistic protection and fitness.

Tuning the structure of 3D woven aramid fabrics reinforced with shear thickening fluid for developing soft body armour

Soft body armour panels have been developed by tuning the structure of 3D woven orthogonal aramid fabrics and reinforcing them with shear thickening fluid (STF). Five 3D woven orthogonal aramid fabric structures were prepared by changing the ratio of stuffer (X direction) to binder (Z direction) yarns and also by changing the relative position of the latter. Two types of ballistic evaluations, namely energy absorption against low velocity (165±10 ms−1) bullets and back face signature (BFS) against high velocity (430±10 ms−1) bullets were carried out for neat and STF impregnated 3D fabrics and their panels. STF impregnation improved impact energy absorption by 3D woven aramid fabrics. Increasing the ratio of stuffer to binder yarns was found to be beneficial in terms of impact energy absorption and resistance against bullet penetration. STF impregnated 3D fabrics having 4:1 stuffer to binder ratio performed the best in ballistic evaluations. Synergistic effect of 3D woven fabric structure and reinforcement of STF was found to be the key for successful design of soft body armour.

Stabbing resistance of body armour panels impregnated with shear thickening fluid

This paper presents an investigation on the use of shear thickening fluid (STF) to improve stabbing resistance of soft ballistic body armour. STFs were produced from polyethylene glycol and silica nanoparticles. The effects of silica nanoparticle sizes and silica nanoparticle weight fraction were studied and STFs made with the different compositions were used to impregnate the Twaron® woven fabrics. Systemic investigations into rheological behaviour of STF were carried out experimentally on STFs with different compositions. STF impregnated woven fabric panels were created and tested for stabbing resistance. Stabbing impact tests were conducted on 6 different types of STF impregnated fabric panels against 2 untreated fabric panels, and the results were studied against the benchmark fabrics without STF impregnation. Based on the same number of layers of fabric, the STF impregnation improves the stabbing resistance notably. For same panel areal density, the STF impregnated panels outperform the untreated fabric panel. The results of this research indicate the possibility of lighter ballistic panel materials for higher stabbing protection. It was also found that higher nanoparticle weight fraction and larger nanoparticle size of silica leads to better stabbing resistance performance among the STF impregnated panels.

Multi-layer pattern creation for seamless front female body armor panel using angle-interlock woven fabrics

Angle-interlock woven fabric offers an option for making female body armor as it can form integrally the required dome shapes because of its extraordinary moldability and satisfactory ballistic performance. A mathematical model is created to determine the pattern geometry for the front panel of female body armor, and the front panel can be quickly created using this mathematical model. However, the body armor is multi-layer, which indicates that the relationship between the thickness of the fabric and the pattern block projection for different layers of fabric needs to be investigated, in order to create the whole panel, to improve this novel approach for making seamless female body armor with satisfactory ballistic performance.

Study of energy absorption and failure modes of constituent layers in body armour panels

Abstract This study aims to investigate ballistic resistant efficiency of individual layers in body armour panels in order to further understand the energy absorption and failure modes of the layers and the panel. Finite Element (FE) analysis, in conjunction of experimental methods, was used to quantify the ballistic responses of the individual layers under ballistic impact. Perforated and non-perforated ballistic tests and photographic morphology examination were employed in this study for layer and panel failure mechanisms. The results of the investigation revealed that the fabric layers at different positions in the panel exhibit different transverse deformation and stress distribution. In the perforated panel, energy absorption in each layer increases gradually from the front to the rear of the panel. Comparison with the stand-alone fabric layer revealed that the energy absorption efficiency of the front layers is lower than that of the rear for the perforated panels. Based on the failure modes of different fabric layers in a ballistic panel, it is possible that the construction of the panel be optimised for improved ballistic performance.

Experimental investigation of the influence of wool structures on the stab resistance of woven body armor panels

In the production of body armor panels, multilayer aramid fabrics are normally used. A main problem of these panels is the high weight and consequential lower comfort for the wearer. In a recent survey it was shown that most officers in the United States would prefer an improved comfort and also reduced weight in their ballistic vests. To reduce layers with a concomitance of the same safety standards, the panel has to be improved. One solution is to reduce the slippage of the yarns during the penetration of the knife and with this to increase the absorbed impact energy. The tests showed that the placement of a layer of wool fabric on the top of the aramid panel changes the penetration behavior. The main goal of this work is the investigation of the influence of the woven wool structure over the penetration of aramid panels. For this investigation, the stab resistance of five aramid fabrics with different properties and patterns combined with one layer of wool on the top and bottom of the panel has been tested and compared against pure aramid panels, according to the VPAM test instruction “Stab- and Impact Protection”. In addition, an optical evaluation of the stab tests has been done using a high-speed camera. Also, the stab recess in the aramid layers was evaluated optically, using a digital microscope. The experimental results confirm that wool can increase the stab resistance of body armor panels, but results are dependent on the properties and pattern of the aramid fabrics, too.

Conceptual Mold Design for Multi-curved Natural Fiber Reinforced Composite Body Armor Panel

The development of lightweight and inexpensive body armor products is under on-going attention by both manufacturers and users. In general most body armor panels are made either from ceramic or composite materials using various manufacturing techniques such as manual layup, compression moulding, etc. However, for natural based reinforced composite which the reinforcement material is in powder or particulate form, such technique have to be specifically modified to achieve workability in the actual fabrication process. This paper present a systematic design approach on fabricating a natural based particulate composite mold using compression molding method. A Total Design Method was utilized in generating the concepts of multi-curved body armor molds with different ejection system. The significant criteria in the mold concept design selection were found to be the fabrication process, maintenance and cost. Further analysis such as machining time and fatigue life estimation were done to evaluate the workability of the selected concept design.

Kinetic Dissipation in Ballistic Tests of Soft Body Armors

The objective of this study was to assess the amount of energy transferred to the backing material of oil-based clay (i.e. kinetic dissipation) in ballistic tests of soft body armor panels. To determine the relationship between penetration depth (or dent volume) and impact velocity (or energy), weight dropping test with a series of steel spheres was carried out at low impact velocities, and direct shooting with a 5.56 mm NATO fragment simulating projectile (FSP) was carried out at high impact velocities. At high and low impact velocities, the volume of the dent made in the oil-based clay was proportional to the velocity of the impactor. The change in dent volume per the change in impact velocity was found to be proportional to the 1.5th power of the mass of the impactor, while the energy absorption per unit dent volume increased linearly with the impact velocity. The relationship between trauma depth (or dent volume) and kinetic dissipation of a soft body armor panel subjected to a 9 mm bullet at 436 m/s is presented, where the trauma diameter approached that of a 1.043 kg steel ball.

Temperature and humidity aging of poly( p-phenylene-2,6-benzobisoxazole) fibers: Chemical and physical characterization

In recent years, poly( p-phenylene-2,6-benzobisoxazole) (PBO) fibers have become prominent in high strength applications such as body armor, ropes and cables, and recreational equipment. The objectives of this study were to expose woven PBO body armor panels to elevated temperature and moisture, and to analyze the chemical, morphological and mechanical changes in PBO yarns extracted from the panels. A 30% decrease in yarn tensile strength, which was correlated to changes in the infrared peak absorbance of key functional groups in the PBO structure, was observed during the 26 week elevated temperature/elevated moisture aging period. Substantial changes in chemical structure were observed via infrared spectroscopy, as well as changes in polymer morphology using microscopy and neutron scattering. When the panels were removed to an ultra-dry environment for storage for 47 weeks, no further decreases in tensile strength degradation were observed. In a follow-on study, fibers were sealed in argon-filled glass tubes and exposed to elevated temperature; less than a 4% decrease in tensile strength was observed after 30 weeks, demonstrating that moisture is a key factor in the degradation of these fibers.

The method of neutron imaging as a tool for the study of the dynamics of water movement in wet aramid-based ballistic body armour panels

A new non-destructive method based on neutron imaging (neutron radiography) to determine the exact water content in aramid-based soft body armour panels is presented. While investigating the ballistic resistance of aramid-based body armour panels under a wet condition, it is important to precisely determine their water content and its chronological development. Using the presented method, the influence of water amount and location on impact testing as well as its time dependence was shown. In the ballistic panels used, spreading of water strongly depended on the kind of quilting. Very fast water migration could be observed when the panels were held vertically. Some first results regarding the water distribution in wet panels immediately after the impact are presented. On the basis of the presented results, requirements for a standard for testing the performance of ballistic panels in the wet state are deduced.

Microscopical Study of a Multilayer Nylon Body Armor Panel After Impact

A body armor panel consisting of twelve identical layers of 2 X 2 basket weave nylon fabric was investigated after impact by a fragment simulator .22-caliber steel missile in the range of 330-420 m. sec. (1100-1400 ft. sec.) striking velocities. The kinetic energy of the projectile was either slightly higher or lower than that the panel could absorb (706,000 g.-cm.). Completely and partially penetrated holes were investigated. The area surrounding the bullet holes was studied to learn about the various types of deformations and damages in each layer. The microscopic observations were obtained at various magni fications (5, 10, and 200 X) from cross sections of the panel and from individual layers removed from the panel. Cross sections at various levels were made in three directions, either perpendicular or parallel to the panel surface. In these sections the distortion of the fabric pattern, alignment of extended, unravelted. and broken yarns into the direction of bullet move ment, compression of yarns, softening, heat relaxation, fusion, decomposition, and fibrillation of nylon filaments were observed. It was recognized that the permanent damage was localized to a small area close to the path of the fast-moving missile. After separating the panel into individual layers, the stoppage of the projectile was studied. A slight dissipation of the stress was observed in those layers which were exposed to the bullet after it was stowed down. Some damages to nylon filaments were caused by the transient and localized heat generated during the impact of the missile. Fibrillation indicates the vigorous movements of filaments which took place in the panel during penetration. The restriction of permanent deformations and defects to small regions was explained by the presence of cross yarns. They prevent the propagation oi the stress from the impacted spot to any considerable length along the yarns.