Knife Threat Research Articles

Virtual Hand with Ambiguous Movement between the Self and Other Origin: Sense of Ownership and 'Other-Produced' Agency.

The feeling that a body part is one's own body (sense of ownership; SoO) and the feeling based on the causal relationship between one's will and action (sense of agency; SoA) have been recognized as the basis of our bodily self-consciousness. Previously, the illusory SoO over a fake body part (e.g., rubber hand) was introduced as the rubber hand illusion (RHI). Furthermore, it was determined that one could also evoke a SoA over an object with movements linked to the one's prior intention. On the other hand, the postdictivity of our spontaneity implies that it is essentially inseparable whether actions originate from self or others. In other words, our SoA or daily experiences are obtained in such as inseparable scenario. Previous research, however, has maintained the premise that self- and other-origin movements are perceptually distinguishable. Here, we implement a protocol to make these aspects ambiguous for the participants and to estimate whether they can feel SoO and/or SoA and how. To this end, we employ an experiment using virtual reality, under which participants observe virtual fingers moving very slowly (or quickly or not moving) while their own fingers do not move. For evaluation of the illusory SoO, measurements of skin conductance responses against a knife threat are adopted. Additionally, we introduce face-to-face interviews to determine whether the feelings regarding the slow movement match the conventional SoA definition. Our representative results suggest that the SoO is evoked over the hand, and various attitudes to accept its movement as the participant's own with awareness that they did not originate it are reported by the majority. As the results show, the novelty of this protocol is discovering that in such a situation, the SoO cooperates with an externally produced SoA to establish one's own bodily experience rather than the independence of the SoO and SoA.

Full-body ownership illusion elicited by visuo-vestibular integration.

Vestibular signals allow us to maintain balance and orient ourselves in space. However, the possible contribution of the vestibular sense to the perception of the body as one's own (body ownership) remains poorly understood. The aim of the present study was to investigate how vestibular information contributes to the experience of body ownership using multisensory integration. We conducted 3 studies using a "full-body ownership illusion" induced by virtual reality technology and galvanic vestibular stimulation (GVS); the latter is a technique that allows for the selective stimulation of vestibular afferents. Participants wearing head-mounted displays saw a mannequin's body that was performing a slow swinging movement from a first-person perspective. At the same time, participants were exposed to GVS that elicited vestibular sensations of swinging whole-body movements in the corresponding direction. Perceived ownership of the seen body was measured using questionnaire ratings and skin-conductance responses to a knife threat toward the mannequin. We demonstrated that when participants were exposed to congruent visuo-vestibular information, they perceived a stronger ownership of the mannequin's body compared with when they were exposed to unimodal visual and vestibular conditions or an incongruent visuo-vestibular condition. The findings show that visuo-vestibular congruency is sufficient to increase the feeling of illusory body ownership of a mannequin's body. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

The stab resistance of fabrics impregnated with shear thickening fluids including various particle size of additives

Shear thickening fluid (STF) treated high performance fabrics have attracted much attention in the applications of body protection. In order to improve the contribution of STF treatments, we designed multi-phase STFs and investigated the stab resistance of fabrics impregnated with these novel fluids. Silica and polyethylene glycol (PEG) based STFs were synthesized with various particle size of silicon carbide (SiC) additives to constitute the multi-phase suspension systems. The influence of the additive particles on the thickening behavior of the STFs was analyzed via rheological testing. The stab resistance of the fabrics was investigated in a drop tower against spike and knife threats and therefore, the role of the STFs was discussed in detail. According to this study, multi-phase STFs realized further improvement in the stab resistance of fabrics with respect to single-phase STFs.

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.

Advanced Stab Resistance Fabrics Utilizing Shear Thickening Fluids

A series of shear thickening fluids (STF) were prepared and characterized by Rheometer. The stab resistance of Kevlar and ultrahigh molecular weight polyethylene (UHMWPE) non-woven fabrics impregnated with STF were investigated and found to exhibit significant improvements over neat fabric targets of equivalent weight. Specifically, dramatic improvements in stab resistance (knife threat) were observed. These novel materials could be potentially used to fabricate flexible body armors which provide improved protection against both stab and ballistic threats.

Stab Resistance of Thermoset-Impregnated UHMWPE Fabrics

The stab resistance of thermoset(TS) impregnated, woven UHMWPE fabric with additional steel fabrics was investigated under dynamic stab testing conditions. Vinyl-ester resin was coated on the UHMWPE fabrics with hand lay-up process to fabricate the composite and the mental fabrics were laminated on the composites. Dynamic stab testing of targets was based on GA68-2008 for stab resistance of body armor. Six uniform specified knives impactor were used for testing. And the samples are found to present significant improvements in stab resistance (knife threat) over neat fabric targets of equal areal density. Photographs show that resin primarily reduces the mobility of yarns and enables them to stop the knife penetration more effectively in the damage zone. These results indicate that the penetration of knives through such multilayer fabrics is effectively prevented and the process could be used to fabricate flexible body armors that provide improved protection against stab threat.

Synthesis, processing and characterization of shear thickening fluid (STF) impregnated fabric composites

Shear thickening is a non-Newtonian fluid behavior defined as the increase of viscosity with the increase in the applied shear rate. The shear thickening fluid (STF) is a combination of hard metal oxide particles suspended in a liquid polymer. This mixture of flowable and hard components at a particular composition, results in a material with remarkable properties. In this manuscript the shear thickening fluid (STF) was prepared by ultrasound irradiation of silica nanoparticles dispersed in liquid polyethylene glycol polymer. The as-prepared STFs have been tested for their rheological and thermal properties. Kevlar and Nylon fabrics were soaked in STF/ethanol solution to make STF/fabric composite. Knife threats and quasistatic penetration tests were performed on the neat fabrics and STF/fabric composite targets for both engineered spike and knife on areal density basis. The results showed that STF impregnated fabrics have better penetration resistance as compared to neat fabrics without affecting the fabric flexibility. This indicates that the addition of STF to the fabric have enhanced the fabric performance and can be used in liquid body armor applications.

Studies on the Fabrication and Stab Resistance Characterization of Novel Thermoplastic-Kevlar Composites

Kevlar has demonstrated the ability to protect well against ballistic threats but has low resistance to puncture. Correctional Kevlar has shown good resistance to puncture. However, the fabric is expensive, difficult to manufacture because of its tight weave construction, and has limited protection against ballistic threats. In an effort to produce materials that are less bulky, more flexible, and resistant to puncture, thermoplastic-Kevlar (TP-Kevlar) composites have been examined. Kevlar fabric was impregnated with thermoplastic film using a hot press to produce the composites. Static and dynamic puncture resistant properties of the TP-Kevlar composites were investigated using a National Institute of Justice (NIJ Standard 0115.00) Stab Tower. The TP-films used in this study were polyethylene, Surlyn, and co extruded-Surlyn, which is a co extrusion of Surlyn and polyethylene. Response of the polyethylene (PE)-Kevlar composites, Surlyn-Kevlar composites, and co extruded (COEX)-Kevlar composites to spike and knife threats under static and dynamic conditions were compared with that of neat Kevlar. The infusion of thermoplastic films into the Kevlar fabric was shown to dramatically increase puncture resistance during quasi-static and dynamic testing with spikes. The TP-film type also made a difference when examining the resistance on a comparative basis of the TP-Kevlar targets. The TP-Kevlar composite targets showed more resistance to quasi-static spike testing than quasi-static knife testing. Weapon comparisons revealed that the TP-Kevlar composite targets had more resistance to dynamic knife testing than dynamic spike testing.

Stab resistance of shear thickening fluid (STF)-treated fabrics

The stab resistance of shear thickening fluid (STF)-treated Kevlar® and Nylon fabrics is investigated and found to exhibit significant improvements over neat fabric targets of equivalent areal density. Specifically, dramatic improvements in puncture resistance (spike threat) are observed under high and low speed loading conditions, while slight increases in cut protection (knife threat) are also observed. Studies on the effect of fabric architecture indicate that STF addition provides benefits analogous to the effect of increasing fabric yarn count, with STF addition primarily reducing the mobility of filaments and yarns in the impact zone. Microscopy shows significant energy dissipation in the damage zone that includes plastic flow of the polymeric filaments, as well as deformation of the filaments due to mechanical interaction with the colloidal particles of the STF. These results indicate that these novel materials could be used to fabricate flexible body armors that provide improved protection against stab threats.