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Polycondensation Polymers (Step-Reaction Polymerization)
Published in Charles E. Carraher, Carraher's Polymer Chemistry, 2017
Kevlar is used in the manufacture of so-called “bulletproof” clothing used by the military, policemen, and SWAT teams. In truth, most bulletproof clothing is bullet resistant and, unless quite bulky, not able to “stop” most rifle bullets or high-caliber handguns. It is also used in the construction of bullet-resistant facemasks by the military and motorcycle riders and to protect against abrasion by motorcycle riders.
Ballistic Threats and Body Armour Design
Published in Melanie Franklyn, Peter Vee Sin Lee, Military Injury Biomechanics, 2017
Johno Breeze, Eluned A. Lewis, Debra J. Carr
Body armour typically comprises soft and hard elements (Tobin and Iremonger 2006; Carr and Lewis 2014). The soft element of body armour is the familiar waistcoat or vest-like garment worn by the military and police, and is manufactured from high-performance man-made synthetic polymer fibres. These fibres are high-tenacity, high-stiffness and high-cost products. The fibres used in the manufacture of body armour include para-aramids (e.g. Kevlar®, Twaron®) and ultra high molecular weight polyethylene (e.g. Dyneema®, Spectra®). Para-aramids are usually used to manufacture a plain woven fabric, and UHMWPEs are usually used in a cross-ply arrangement. Many layers of fabric are used in body armour. Protection from high-velocity rifle bullets can be provided by the use of hard plates which are usually ceramic faced composite backed (e.g. alumina/para-aramid) or 100% composite (e.g. UHMWPE) (Tobin and Iremonger 2006). The resulting body armour can be heavy (typically in excess of 10 kg), restrictive and increases the thermophysiological burden on the wearer (Carr and Lewis 2014). Thus, efforts to identify new materials and/or systems with improved performance and a lower mass penalty are the primary focus of much research, e.g. the UK MOD initiative Reducing the Burden on the Dismounted Soldier (RBDS). The scope of RBDS was to reduce the load of the solider, whilst also enhancing effectiveness and survivability. Specifically, the Lightweight Personal Protection task aimed to provide a mass saving of 15%–30% (Bruton 2012).
Quantification and health risk assessment of heavy metals in residual floor dust at an indoor firing range: A case study in Trinidad, WI
Published in International Journal of Environmental Health Research, 2022
Christian E. Clarke, Faisal K. Mohammed, Alisha Hamid, Grace-Anne Bent
Lead was the most abundant element in indoor floor dust within the firing range. The observed concentrations ranged from 153.8 mg/g to 339.1.1 mg/g and were of particular concern, as these values were up to 3 × 104 times higher than the control site (13.74 µg/g). Typically, elevated concentrations of Pb in indoor dust have been reported at ‘µg/g’ levels and attributed to external sources such as vehicular emissions and industrialization (Tan et al. 2016). It is evident, therefore, that for this study, the overall contribution to the Pb content in indoor floor dust is significantly related to activities within the range. Generally, Pb deposited on the flooring of indoor firing ranges may be attributed to two main sources: (1) the scrapings created from friction as the bullet passes through the gun barrel upon firing, and (2) disintegration of bullet upon striking the bullet trap (Jackson and Dell 1992b). While the Pb content may be apportioned to shooting activities, the overall accumulation will be dependent on the frequency and type of cleaning procedures utilized. Jackson and Dell (1992b) investigated the effects of different types of ventilation on Pb in air and dust fall at an indoor range and observed that the presence of both a supply fan and an exhaust fan at one particular range had little effect on reducing Pb concentrations. The inability to reduce the Pb concentrations may be possibly attributed to an inefficient ventilation system and may be applicable to the indoor range considered in our study.
A Review on Closed Cell Metal Matrix Syntactic Foams: A Green Initiative towards Eco-Sustainability
Published in Materials and Manufacturing Processes, 2021
Raja Thiyagarajan, M. Senthil kumar
The syntactic foam has extremely high potential applications in the area of defense. The small arm fire, improvised explosive devices and explosion formed penetrators are the threats to the military personal and human lives through terrorist attacks. The metal matrix syntactic foams remain the preferred choice for various defense applications such as military vehicles, ballistic protection, and individual self-protection from arm fire. The defense industries have updated various protections against these threats. The military vehicle needs to have improved lightweight, survivability and self-protection under various environments.[186,198] It is required to bring out the development of a new class of metal-based syntactic foams. That has high energy absorbing characteristics in the defense applications to protect the soldiers from the explosives.[199] The various components such as V-Hull, strike plates and environmental coatings are shown in Fig. 10 developed by cymats to enhance the energy absorbing characteristics and light weight for defense vehicle applications. The developments of foams and syntactic foam in the defense application are highly confidential and have limited information. Although Marx et al.[201] reported on the 50 caliber bullet projectile stopped by using metal foams sandwich structure. It also has better protective strength when compared with the existing one. This remains great evidence to prove that metal-based syntactic foams sandwich structure have enormous potential in the defense-related applications like blast mitigations.
Combustion Characteristics and Mechanisms of Two Gun Barrel Steels by Promoted Ignition Combustion
Published in Combustion Science and Technology, 2023
Caihong Dou, Cheng Zhang, Congzhen Wang, Junyu Chen, Bin Liang, Jinfeng Huang
As the key component of the gun system, gun barrel is served under high temperature and high pressure produced by gunpowder gas and high-speed friction caused by bullet (Hermanson, Conolly, Vezina 2012; Underwood, Vigilante, Mulligan 2007). It causes serious ablation damage included ablation pits, molten layers on the inner barrel after few rounds and to large content depends the lifespan of gun barrel (Chen et al. 2018; Chung, Kong, Nam 1999). In few combustion tests, we found an event where a brief flash was observed and a slight amount of material was consumed at the target materials when the combustion conditions were not conducive for steady state, which is similar as the partial consumed of inner gun barrel after firing (Benz et al. 1986a). Gao et al. (2008) suggested that the melting products found on the ablation surface of gun steel after semi-closed explosive test could be caused by the local combustion reactions. The combustion of metals and ablation damage of the inner barrel have similar characteristics. One is the microstructure after combustion and ablation damage are both composed of oxides and molten layers (Johnston 2005; Shao et al. 2020a). Other is the fire spread of metals and the formation of molten layer during firing are both completed in few seconds (Shao et al. 2020a). Besides, iron could be ignited at the temperature about 600 K below its melting point, which is close to the maximum temperature of inner barrel during firing (Bolobov 2001; Hust and Clark 1973). Based on that, the combustion performance is considered to reflect the anti-ablation performance of gun barrel steel. But there is still a lack of detailed research on the combustion characteristics of gun barrel steel at the present.