scholarly journals Do air-gaps behind soft body armour affect protection?

2017 ◽  
Vol 164 (1) ◽  
pp. 15-18 ◽  
Author(s):  
Lee Tilsley ◽  
D J Carr ◽  
C Lankester ◽  
C Malbon
Keyword(s):  
Ceramic Composite ◽  
Air Gap ◽  
The Body ◽  
Gap Size ◽  
Soft Body ◽  
Air Gaps ◽  
Body Armour ◽  
Ballistic Protection ◽  
Back Face ◽  
Full Metal Jacket

IntroductionBody armour typically comprises a fabric garment covering the torso combined with hard armour (ceramic/composite). Some users wear only soft armour which provides protection from sharp weapons and pistol ammunition. It is usually recommended that body armour is worn against the body with no air-gaps being present between the wearer and the armour. However, air-gaps can occur in certain situations such as females around the breasts, in badly fitting armour and where manufacturers have incorporated an air-gap claiming improvements in thermophysiological burden. The effect of an air-gap on the ballistic protection and the back face signature (BFS) as a result of a non-perforating ballistic impact was determined.MethodsArmour panels representative of typical police armour (400x400 mm) were mounted on calibrated Roma Plastilina No 1 and impacted with 9 mm Luger FMJ (9×19 mm; full metal jacket; Dynamit Nobel DM11A1B2) ammunition at 365±10 m/s with a range of air-gaps (0–15 mm). Whether or not the ammunition perforated the armour was noted, the BFS was measured and the incidence of pencilling (a severe, deep and narrow BFS) was identified.ResultsFor 0° impacts, a critical air-gap size of 10 mm is detrimental to armour performance for the armour/ammunition combination assessed in this work. Specifically, the incidences of pencilling were more common with a 10 mm air-gap and resulted in BFS depth:volume ratios ≥1.0. For impacts at 30° the armour was susceptible to perforation irrespective of air-gap.ConclusionsThis work suggested that an air-gap behind police body armour might result in an increased likelihood of injury. It is recommended that body armour is worn with no air-gap underneath.

Effects of clothing ease and body postures on the air gap and clothing coverage

2019 ◽  
Vol 31 (4) ◽  
pp. 578-594
Author(s):  
Shitan Wang ◽  
Xiuhua Wang ◽  
Yunyi Wang
Keyword(s):  
Air Gap ◽  
The Body ◽  
Upper Body ◽  
Gap Size ◽  
Lower Body ◽  
Content Type ◽  
Body Postures ◽  
Body Regions ◽  
Gap Models ◽  
The Right

Purpose The purpose of this paper is to determine the effects of clothing ease and body postures on the size and distribution of the air gap as well as the body coverage with the clothing. Design/methodology/approach Visual and quantitative analyses were conducted using a 3D body scanner and Geomagic Software. The air gap size and clothing area factor (fcl) in three test coverall and seven selected postures were calculated and compared. Findings The results indicated that both the clothing ease and body postures had a strong effect on the air gap and clothing coverage, especially the more complex the postures, the wider the range of influence. Nevertheless, these effects varied over body regions, being stronger at the lower body than the upper body. The air gap size at the left side of the body was generally larger than the right side. It was also found that the clothing coverage was linearly correlated with the air gap size and could be employed as an indicator to evaluate clothing protective capabilities. Practical implications The findings suggested that greater attention should be paid to the protection and flexibility at the lower body and asymmetrical distribution of the air gap should be considered in the future air gap modeling. Originality/value The outcomes provided useful information to improve the protective clothing and develop more realistic air gap models to simulate the heat and mass transfer.

Experimental Studies on Diesel Engine with Piston Crown Modification Using an Optimum Alternative Fuel

2015 ◽  
Vol 813-814 ◽  
pp. 830-835
Author(s):  
Akkaraju H. Kiran Theja ◽  
Rayapati Subbarao
Keyword(s):  
Diesel Engine ◽  
Combustion Chamber ◽  
Experimental Studies ◽  
Alternative Fuel ◽  
Air Gap ◽  
The Body ◽  
Injection Timing ◽  
Positive Trend ◽  
Piston Crown ◽  
Karanja Oil

The drawbacks associated with bio-fuels can be minimized by making modifications to combustion chamber. Modification of combustion chamber is achieved by providing an air gap in between the crown and the body of the piston with the top crown made of low thermal conductivity material. Experimentation is carried on a diesel engine with brass as piston crown material and karanja as test fuel, which is found to be a better alternative fuel based on the tests carried out prior to modification. Investigations are carried out on the performance of the engine with modified combustion chamber consisting of air gap insulated piston with 2 mm air gap with brass crown when fuelled with karanja oil. Comparative studies are made between the two configurations of engine with and without modification at an injection timing of 29obTDC. Performance, heat balance and emission plots are made with respect to brake power. Fuel consumption increased with modification. The mechanical and volumetric efficiencies are similar in both the cases. Indicated and brake thermal efficiencies got reduced with modification. But, it is good to see that HC and CO emissions are showing positive trend. Thus, the present investigation hints the possibility of improvements while making piston modification and providing air gap insulation.

Experimental study of heat and moisture transfer in vertical air gap under protective clothing against dry and wet heat exposures

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Yun Su ◽  
Miao Tian ◽  
Yunyi Wang ◽  
Xianghui Zhang ◽  
Jun Li
Keyword(s):  
Natural Convection ◽  
Protective Clothing ◽  
Moisture Transfer ◽  
Heat Exposure ◽  
Air Gap ◽  
Gap Size ◽  
Heat And Moisture Transfer ◽  
Content Type ◽  
Wet Heat ◽  
Heat And Moisture

PurposeThe purpose of this paper is to study heat and steam transfer in a vertical air gap and improve thermal protective performance of protective clothing under thermal radiation and hot steam.Design/methodology/approachAn experiment-based model was introduced to analyze heat and moisture transfer in the vertical air gap between the protective clothing and human body. A developed test apparatus was used to simulate different air gap sizes (3, 6, 9, 12, 15, 18, 21 and 24 mm). The protective clothing with different air gap sizes was subjected to dry and wet heat exposures.FindingsThe increase of the air gap size reduced the heat and moisture transfer from the protective clothing to the skin surface under both heat exposures. The minimum air gap size for the initiation of natural convection in the dry heat exposure was between 6 and 9 mm, while the air gap size for the occurrence of natural convection was increased in the wet heat exposure. In addition, the steam mass flux presented a sharp decrease with the rising of the air gap size, followed by a stable state, mainly depending on the molecular diffusion and the convection mass transfer.Originality/valueThis research provides a better understanding of the optimum air gap under the protective clothing, which contributes to the design of optimum air gap size that provided higher thermal protection against dry and wet heat exposures.

Optimal designing of soft body armour materials using shear thickening fluid

2013 ◽  
Vol 46 ◽  
pp. 191-198 ◽  
Author(s):  
Abhijit Majumdar ◽  
Bhupendra Singh Butola ◽  
Ankita Srivastava
Keyword(s):  
Shear Thickening ◽  
Soft Body ◽  
Shear Thickening Fluid ◽  
Body Armour ◽  
Optimal Designing

scholarly journals Effect of Air Gap on Electrical Tree in Epoxy Resin Under High Frequency Bipolar Square-Wave Voltage

Materials ◽  
2020 ◽  
Vol 13 (24) ◽  
pp. 5722
Author(s):  
Shihang Wang ◽  
Chuang Zhang ◽  
Hang Fu ◽  
Jiao Xiang ◽  
Jianying Li ◽  
...  
Keyword(s):  
Epoxy Resin ◽  
High Frequency ◽  
Air Gap ◽  
Heat Accumulation ◽  
Air Gaps ◽  
Square Wave ◽  
Electrical Tree ◽  
Electrical Trees ◽  
Voltage Frequency ◽  
Tree Characteristics

Insulation fails quickly under high-frequency AC high voltage, especially bipolar square-wave voltage with a high dV/dt. It is of great significance to study the failure mechanism of epoxy casting insulation under such kind of voltage. In this paper, pin-plane epoxy casting insulation samples with air gaps were prepared, and the relation between the electrical trees under the high frequency bipolar square-wave voltage and the air gap conditions and voltage frequencies (1~20 kHz) were studied. Results indicated that, with the presence of air gaps, the electrical trees were bush-type and had a relatively slow growth rate, which was different from the fast-growing branch-type trees in the samples without air gap. The electrical tree characteristics related with the size of air gap and voltage frequency were also studied. The electrical tree grew faster under higher voltage frequency or with a smaller air gap. Results proved that discharge introduced a lot of defects for the surface layer of the epoxy resin samples and hence induced the possibility of multi-directional expansion of electrical trees. In addition, the resulting heat accumulation and unique charge transport synergistically affected the electrical tree characteristics under the high frequency bipolar square-wave voltage.

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

2019 ◽  
Vol 110 (10) ◽  
pp. 1515-1518 ◽  
Author(s):  
Abhijit Majumdar ◽  
Animesh Laha ◽  
Debarati Bhattacharjee ◽  
Ipsita Biswas ◽  
Sanjeev Verma
Keyword(s):  
Silica Particle ◽  
Shear Thickening ◽  
Soft Body ◽  
Shear Thickening Fluid ◽  
Body Armour ◽  
Aramid Fabrics
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