Stab Resistant Body Armour Research Articles

Minimum depths to essential structures in a UK military population using computed tomography: application to stab-resistant body armour.

Edged weapons are a known domestic threat to the police forces of the UK. This threat is mitigated by wearing stab-resistant body armour that is either worn overtly or covertly depending on role. Although the UK military have traditionally focused their body armour design upon ballistic and fragmentation threats, future roles may require protection against an edged weapon threat. Since 2017, UK police body armour requirements for anatomical coverage for both edged weapon and ballistic threats are now based upon the requirements of UK military. This revised coverage may need additional research to determine minimum distances to essential structures. Three entry locations and penetration vectors were chosen using the limited available information in the literature, in combination with a specialist in edged weapons defence. One hundred twenty CT trauma scans of male military service personnel were subsequently analysed to ascertain minimum distances from skin surface to the first structure encountered that is included in essential coverage (heart, aorta, vena cava, liver and spleen) at 3 specific entry points. Individuals ranged between 18 and 46years, with a mean body mass index of 24.8. The absolute minimum depth from skin surface to a structure within the auspice of essential coverage was 17mm to the liver in entry point 3 and 19mm to the heart in entry point 2. Minimum distances to critical structures were significantly larger than those described in previous studies on civilians. This study will be used to supplement existing evidence to support existing UK police requirements for stab-resistant body armour. Using the weapon entry sites and vectors described in this study, overmatching to a behind armour depth of 17mm would cover all of this population in this study.

The effect of breast size and bra type on comfort for UK female police officers wearing body armour

Within the Police service of England and Wales the wearing of ballistic and stab resistant body armour is common, with most police forces mandating its usage when away from the police station. Of all the serving police officers in England and Wales 29.1% are female (Hargreaves et al., 2017). A survey was developed and then distributed by the Police Federation of England and Wales to all servicing police officers up to the rank of Inspector. The survey returned 2633 responses after cleaning of the data. From the responses it was seen that the predominant bra type worn is underwired (71%) and the predominant UK bra size is 34B (9%). It was also determined that the predominant areas where the body armour either rubbed or caused discomfort were the left and right anterior mammary regions and the posterior lateral sacral region. By understanding the distribution of bra size, type of bra worn and areas of discomfort or rubbing it helps further understand the issues faced by female police officers and how body armour design could be improved.

Comparing the penetrative stab performance of the UK HOSDB P1/B and Stanley Tools 1992 trimming blades on certified body armour specimens

This body of research assessed the penetrative stab performance of the United Kingdom Home Office Scientific Development Branch’s (HOSDB) P1/B certified blades against the readily accessible Stanley Tools 1992 trimming blade. All tests were performed against the HOSDB KR1-E1 impact energy of 24 Joules on HOSDB KR1 certified body armour specimens. Results demonstrated that the Stanley 1992 trimming blade posed a 30% greater stab threat in comparison to the HOSDB P1/B blade. This paper demonstrates the threat imposed by readily available utility blades and a requirement to enhance existing stab resistant body armour test procedures.

DESIGN AND ANALYSIS OF FUSED DEPOSITION MODELING TEXTILE GEOMETRICAL FEATURES FOR STAB RESISTANT APPLICATION

Body armour plays a vital role to provide protection to the law enforcement and correctional officers around the world who are significantly working at risk of encountering assault in daily routine. Despite many modern fiber-based soft body armours have been developed, yet a number of historical issues continue to exist and challenge the current protective solutions. In fact, additive manufacturing (AM) presents a great design freedom and advantages in developing customized user fit lightweight product or part, it also reduces the amount of labour costs, operation time and material waste. This research therefore investigates the feasibility of using AM system to manufacture textile geometrical models, which can be used for the development of novel user fit stab–resistant body armour. Prior to the actual experiments, this paper presents the finite element analysis of a planar and five cross-sectional design of textile models that will be additive manufactured with Fused Deposition Modeling (FDM) system utilizing the commonly used materials such as Acrylonitrile Butadiene Styrene (ABS) and Polycarbonate-ABS (PC-ABS) blend. A comparative analysis is performed between both materials. The purpose of this paper is basically to investigate the relationship between the cross-sectional design of textile models and their protective performance against stabbing. Firstly, a planar model and five textile model with different imbricate scale-linked designs were modeled with a CAD software. These models were simulated tested by a test blade using ANSYS software. The specification of test blade was taken from NIJ Standard-0115.00. The comparative result shows that PC-ABS has better performance to resist the knife threat than ABS due to the addition of ABS provides not only other useful properties, yet reduces the limitations of PC and at the same times without removing other superior mechanical properties. The result shows the knife penetration through the planar model was much larger than the imbricate scale-linked design models. The design of model 5 was the most appropriate as compared to other designs, which the maximum total deformation distributed on its cross section area was the lowest. This implies that the design of model 5 can be used in the experiment later and it might contribute high stab resistant towards the knife threat with impact energy of 24 Joules.

The Necessity of Stab-Resistant Body Armour for Protecting Prison Officers in Saudi Arabia

Protection and comfort are significant aspects for body armour. This study surveyed 102 prison officers in Saudi Arabia about their opinion on the current body armour they may use in terms of protection and comfort. This is to understand the need for protection with body armour and improve protective fabric designs with enhanced comfort performance for future soft body armour. From the information gathered via a questionnaire survey, the risk assessment inside the prison and the percentage of prison officers being attacked were determined. The results revealed that 12% of male and 29% of female prison offices were attacked and protective measures against this violence level cannot be ignored.

Impact of police body armour and equipment on mobility

Body armour is used widely by law enforcement and other agencies but has received mixed reviews. This study examined the influence of stab resistant body armour (SRBA) and mandated accessories on physiological responses to, and the performance of, simulated mobility tasks. Fifty-two males (37 ± 9.2 yr, 180.7 ± 6.1 cm, 90.2 ± 11.6 kg, VO2max 50 ± 8.5 ml kg−1 min−1, BMI 27.6 ± 3.1, mean ± SD) completed a running VO2max test and task familiarisation. Two experimental sessions were completed (≥4 days in between) in a randomised counterbalanced order, one while wearing SRBA and appointments (loaded) and one without additional load (unloaded). During each session participants performed five mobility tasks: a balance task, an acceleration task that simulated exiting a vehicle, chin-ups, a grappling task, and a manoeuvrability task. A 5-min treadmill run (zero-incline at 13 km·h−1, running start) was then completed. One min after the run the five mobility tasks were repeated.There was a significant decrease in performance during all tasks with loading (p < 0.001). Participants were off-balance longer; slower to complete the acceleration, grapple and mobility tasks; completed fewer chin-ups; and had greater physiological cost (↑ %HRmax, ↑ %VO2max, ↑ RER) and perceptual effort (↑ RPE) during the 5-min run. Mean performance decreases ranged from 13 to 42% while loaded, with further decreases of 6–16% noted after the 5-min run. Unloaded task performance was no different between phases.Wearing SRBA and appointments significantly reduced mobility during key task elements and resulted in greater physiological effort. These findings could have consequences for optimal function in the working environment and therefore officer and public safety.

FLEXIBLE STAB RESISTANT CERAMIC-BASED BODY ARMOUR

This paper presents the results of a study on performance of flexible stab resistant ceramic-based composite body armour that our research group has initiated, designed, assembled, and tested. The test outcomes were characterized in terms of the kinetic energy of the stabbing weapon at impact and the depth of penetration of the stab into the armour. A neutral date fitting model that departs from the classical least square approach is proposed. The test results show that the flexible panels are especially suitable for medium and low protection levels and by comparison with rigid panels, the flexible panels allow a deeper penetration which increases with thrust energy.

The development of a quantitative flexibility test for body armour and comparison with wearer trials

In this paper a mechanical flexibility test is developed which can be used to assess multi layer body armour systems. This is compared with a subjective manual test, and then with the results of wearer trials conducted using the recently approved ISO body armour standard ISO 14876-1 (2002). A series of trials was conducted on six different ballistic and/or stab resistant body armour types with a variety of protection levels and constructions. These were tested using the mechanical test system in which the armour was forced through a 200 mm hole by a 100 mm hemispherical plunger. The results of this test were then compared to a second set of trials in which flexibility of the same armour was assessed by manual handling and flexing of the armour. Finally an ergonomic wearer trial was conducted with four armours according to ISO 14876-1 (2002) each armour being assessed by four volunteers and the results compared to flexibility data collected in the first two trials. It was shown that the mechanical flexibility test produced results which were in good agreement with a purely subjective flexibility assessment. These results in turn showed reasonable but not exact correlation with the wearer trials. The ISO wearer trials addressed other factors such as overall comfort and fit of the systems and so the results were not purely a function of flexibility.

The effect of knife handle shape on stabbing performance

A quantitative knowledge of stabbing ability is a pre-requisite to establishing protection standards for stab resistant body armour. In order to determine the validity of measurements it is necessary to understand all the mechanisms that determine performance. This paper describes a series of tests that were performed in order to determine the effect of handle size and shape on the forces and impact energy that could be produced during stabbing of an armoured target. It was found that the single largest variable was that of the test participants with all other variables such as handle size and shape having only slight effects on the magnitude of impact energy. The use of a finger guard or hilt was shown to increase the mean energy delivered to the target by approximately 5 J compared to a handle having no guard. It was also found that the characteristics of energy delivery were strongly influenced by the position of the grip relative to this guard. This reinforces the conclusions of previous work (Horsfall et al., 1999; Chadwick et al., 1999) on the serial nature of momentum transfer during a stabbing impact.

Evaluation of test regimes for stab-resistant body armour

Modern lightweight stab-resistant body armour has been developed in response to the operational requirements and the experiences of police forces. While a high degree of protection may be afforded to the wearer, this has usually been achieved at the expense of weight, stiffness, and comfort. The use of a test method to measure the protection level of a proposed design against a target specification is inherent in the design and development process. This study reviews data used to establish recent improvements in standard test methods, and shows that deficiencies in current standards may well lead to over-specification of body armour. It is shown that more detailed characterization of real human stabbing actions is needed and the test situation needs to be viewed as a multibody, dynamic interaction if results are to be obtained that reflect the reality of an attack. The information will be of particular interest to body armour manufacturers and researchers working to improve armour design.

Evaluation of test regimes for stab-resistant body armour

Modern lightweight stab-resistant body armour has been developed in response to the operational requirements and the experiences of police forces. While a high degree of protection may be afforded to the wearer, this has usually been achieved at the expense of weight, stiffness, and comfort. The use of a test method to measure the protection level of a proposed design against a target specification is inherent in the design and development process. This study reviews data used to establish recent improvements in standard test methods, and shows that deficiencies in current standards may well lead to over-specification of body armour. It is shown that more detailed characterization of real human stabbing actions is needed and the test situation needs to be viewed as a multibody, dynamic interaction if results are to be obtained that reflect the reality of an attack. The information will be of particular interest to body armour manufacturers and researchers working to improve armour design.

Ultrasound assessment of the vulnerability of the internal organs to stabbing: determining safety standards for stab-resistant body armour

Stab-resistant body armour may not always prevent the passage of a blade into the human body. The depth to which a knife may ‘safely’ enter the human body before it breaches the internal organs was explored by ultrasound scanning of 25 healthy volunteers. Variations in the minimum skin-to-organ distances for the organs as a function of posture are described. To determine the optimum body coverage by stab-resistant armour, the movement during the breathing cycle and the maximum exposure of the organs beneath the lower costal margin at full inspiration were measured. Although the population studied was small, trends in the vulnerability of the internal organs to the passage of a blade into the body were identified.

A telemetry-based device to determine the force–displacement behaviour of materials in high impact loading situations

Meaningful testing of stab resistant body armour requires the use of realistic body tissue simulants. A device for the determination of the force–displacement behaviour of materials in high impact loading situations has been developed for the testing of such simulants. Force measurement is achieved with the use of electrical foil strain gauges applied to a cylindrical load cell. A piezo-resistive accelerometer (±500 g) is used to calculate the displacement of the device through double integration of its signal, with the impact velocity used as a boundary condition. The signals from the strain gauge circuit and the accelerometer are sampled at 2500 Hz. The data are transmitted to a receiver via telemetry using a 418 MHz FM transmitter and from the receiver to a laptop PC via the serial port. Calibration of the device is described and sample results showing forces up to 2500 N and displacements up to 0.04 m are presented.

An assessment of human performance in stabbing

Stab-resistant body armour is now becoming a standard item of equipment for police officers in the United Kingdom. In the UK these are usually required to have a stab resistance as specified by the Police Scientific Development Branch KR42 standard [G. Parker, PSDB Stab Resistant Body Armour Test Procedure, Police Scientific Development Branch, Publication No 10/93, 1993]. There are several other test standards, all of which specify that body armour must resist penetration by a specific blade type delivered at a specific energy level or range of levels. However, the actual range of energy levels specified varies over almost an order of magnitude and the basis for these levels is not clearly defined. This paper describes tests to determine the energy range and characteristics of stabbing actions that might be directed against stab resistant body armour by an assailant. The energy and velocity that can be achieved in stabbing actions has been determined for a number of sample populations. Volunteers were asked to stab a target using an instrumented knife that measured the axial force and acceleration during the stabbing. The maximum energy obtained in underarm stabbing actions was 64 J whilst overarm stabbing actions could produce 115 J. The loads produced on contact with the target often approached 1000 N.

The effect of knife blade profile on penetration force in flesh simulants

A series of stab-penetration tests were carried out using model knife blades with different degrees of sharpness. Target blocks of flesh simulant were penetrated by the knife blades at constant low velocity and the penetration force was monitored. PSDB 10/93, a test protocol for stab-resistant body armour, recommends a modelling clay (Roma Plastilina) as a flesh simulant. From the stab-penetration tests it was found that Roma Plastilina has poor resemblance to flesh, and a simulant such as gelatine is more realistic. Bowie knife blades are specified in the test protocol while kitchen knives appear to be the most common in real incidents. More importantly, no required blade sharpness is specified in the test protocol, an aspect that could lead to inconsistencies in test results.

Safety standards for stab-resistant body armour: a computer tomographic assessment of organ to skin distances.

The protective properties of knife-resistant armour are quantified by the distance a test blade penetrates beyond a test sample into clay at a given energy. At present there are two proposed standards: penetration to 5 mm and penetration to 20 mm. Armour made to the higher standard specification (5mm) is necessarily heavier as it offers more protection. To determine the safety of these standards a retrospective review of 71 consecutive computerised tomographic (CT) scans was made. The minimum distance from the skin to the vital organs was measured. No organ would have been breached at 5 mm of knife penetration deep to body armour. 41% of pleurae, 61% of livers, 64% of femoral arteries, 25% of spleens and 6% of hearts would have been breached at a depth of 20 m of knife penetration. There was no significant difference in the minimum skin to organ distances between male and female subjects. The 20 mm standard does not offer adequate protection against knife attacks.

Safety standards for stab-resistant body armour: a computer tomographic assessment of organ to skin distances

The protective properties of knife-resistant armour are quantified by the distance a test blade penetrates beyond a test sample into clay at a given energy. At present there are two proposed standards: penetration to 5 mm and penetration to 20 mm. Armour made to the higher standard specification (5 mm) is necessarily heavier as it offers more protection. To determine the safety of these standards a retrospective review of 71 consecutive computerised tomographic (CT) scans was made. The minimum distance from the skin to the vital organs was measured. No organ would have been breached at 5 mm of knife penetration deep to body armour. 41% of pleurae, 61% of livers, 64% of femoral arteries, 25% of spleens and 6% of hearts would have been breached at a depth of 20 mm of knife penetration. There was no significant difference in the minimum skin to organ distances between male and female subjects. The 20 mm standard does not offer adequate protection against knife attacks.

Delinquent gangs: A psychological perspective : by Arnold P. Goldstein Research Press (2612 North Mattis Avenue, Champaign, Illinois 61821), 313 pp., softcover— $19.95

Body armour is used widely by law enforcement and other agencies but has received mixed reviews. This study examined the influence of stab resistant body armour (SRBA) and mandated accessories on physiological responses to, and the performance of, simulated mobility tasks. Fifty-two males (37 ± 9.2 yr, 180.7 ± 6.1 cm, 90.2 ± 11.6 kg, VO2max 50 ± 8.5 ml kg−1 min−1, BMI 27.6 ± 3.1, mean ± SD) completed a running VO2max test and task familiarisation. Two experimental sessions were completed (≥4 days in between) in a randomised counterbalanced order, one while wearing SRBA and appointments (loaded) and one without additional load (unloaded). During each session participants performed five mobility tasks: a balance task, an acceleration task that simulated exiting a vehicle, chin-ups, a grappling task, and a manoeuvrability task. A 5-min treadmill run (zero-incline at 13 km·h−1, running start) was then completed. One min after the run the five mobility tasks were repeated.There was a significant decrease in performance during all tasks with loading (p < 0.001). Participants were off-balance longer; slower to complete the acceleration, grapple and mobility tasks; completed fewer chin-ups; and had greater physiological cost (↑ %HRmax, ↑ %VO2max, ↑ RER) and perceptual effort (↑ RPE) during the 5-min run. Mean performance decreases ranged from 13 to 42% while loaded, with further decreases of 6–16% noted after the 5-min run. Unloaded task performance was no different between phases.Wearing SRBA and appointments significantly reduced mobility during key task elements and resulted in greater physiological effort. These findings could have consequences for optimal function in the working environment and therefore officer and public safety.