Outer shell materials

Equation (9.50) is the primitive quasichemical approximation that was used to obtain the results of Figs. 9.1 and 9.2. Primitive emphasizes that the equilibrium constants are obtained with initial neglect of the effects of the outer-shell material, as (9.50)... 

The first point from this development and example is that, although the quasichemical approach is directed towards treating strong attractive - chemical - interactions at short range, it can describe traditional packing problems accurately. The second point is that this molecular-field idea permits us to go beyond the primitive quality noted above of the primitive quasichemical approximation, and specifically to account approximately for the influence of the outer-shell material on the equilibrium ratios Km required by the general theory. This might help with cases of delicate structures noted above with anion hydrates. 

How the latter application of QCT can be formulated has been discussed in some detail [10]. That discussion nearly closes a logical circle PDT —> QCT —> pdt. The final pdt is, however, approximate, as is natural when utilizing a molecular-field description of the influence of the outer-shell material. Specifically,... 

Conduct flammability and impact tests on alternative CH2-ISS outer shell materials select optimum for prototype build... 

The resistance to deformation at the surface can be quantified at the micrometer and nanometer scale. At the micrometer scale, traditional hardness measurements are conducted on a polymer system using a handheld durometer, whereby the penetration tip is varied to properly quantify the Shore hardness. At the nanometer scale, measurements of modulus and depth of penetration are quantified using quasi-static nanoindentation. Increases in stiffiiess at the surface of an American football helmet outer shell material exposed to accelerated weathering (Krzeminski et al., 2014c) and repetitive linear impacts (Krzeminski et al., 2014b) have been quantified using quasi-static nanoindentation. However, Shore A hardness measurements were reported to be overly forceful to quantify shifts in surface mechanical properties of injection-molded American football helmet outer shell materials (Krzeminski et al., 2014b,c). 

Krzeminski, D.E., Fernando, D., Lippa, N.M., Rawlins, J.W., Gould, T.E., Piland, S.G., 2013a. Effects of impact exposure and thermal annealing on mechanical properties of an American football helmet outer shell material. In 37th Annual Meeting of the American Society of Biomechanics. Available from http //www.asbweb.org/conferences/2013/abstracts/203.pdf. 

Table 10.4 shows the effect of two heat sources on various types of fabric. Woven and nonwoven fabrics of different area densities made from aramid and FBI fibre have been compared in terms of their respective thermal protective performance (TPP) indices and the results are shown in Table 10.5. TPP values are the times for a temperature gradient of 25 °C to be generated across the fabric thickness when exposed to a heat source as defined in ASTM D4108. The higher the TPP value, the better the thermal protective property. The original fabric constructional data were published in imperial units and they have been converted to SI units for consistency. Woven fabrics were designed as the outer shell material in firefighters turnout coats, and the needlefelt, nonwoven fabrics could be considered for use as a backing or thermal liner in thermally protective apparel. This work shows that nonwoven fabrics provide...

Table 10.7 lists representative thermal protective performance (TPP) values in seconds (ASTM D4108) for some materials used in structural and proximity clothing. The first two ensembles show the effect of different vapour barriers on the overall thermal performance. The last two materials show the dramatic effect on radiant heat protection of aluminizing the outer shell material. 

Structural Outer Shell Materials, http //www.globetumoutgear.com/tumout-gear/materials/outer-shell... 

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