Honeycomb fabrics

The consideration of the pressure drop over the monoliths containing a variety of CPSI (cells per in ) for the modeling of honeycomb reactor may be required, since Ap of the reactor strongly depends on CPSI of monolith. Eqn. (7) for the pressure drop of the honeycomb was employed to develop the reactor model describing the performance of the honeycomb fabricated in the present work [8]. and Ke indicate contraction and expansion loss coefficient at the honeycomb inlet and outlet, respectively and o is the ratio of free flow area to frontal area. 

Zhou et modified the plain woven fabrics by manufacturing honeycomb fabrics and by introducing leno structure and double weft insertions at given intervals. This serves to inaease inter-yam friction, via improved yam gripping, between the warp and weft yams. The stmctures are shown in Figs 6.5 and 6.6. It has been found that such structurally modified fabrics led to better ballistic protection than normal plain woven fabrics. 

Aerospace composite adhesives. In addition to molded parts, polyamide-imides are used as the high-strength adhesives and polymer matrix in aerospace composites. One particular area is honeycomb composites [19]. The adhesives and polymer matrix are critical because the ultimate strength of the honeycomb is often directly dependent on the strength of the bond between the honeycomb layers. The polyamide-imide resin is dissolved in an appropriate solvent and applied to the honeycomb fabric, using a bonding technique to achieve the desired... 

Figure 13.12 presents the energy absorption of six 3D Kevlar fabrics with comparison to the 2D plain weave fabric, which is widely used for body amour production for police and military personnel. It was foimd that (a) 3D honeycomb fabrics and the same layer 2D plain fabric The two- and four-layered 3D fabrics performed better than the assembly with the same layer 2D plain woven fabric of similar yam density. The twolayered fabric with lower yam density performed less well than the one with higher yam density, (b) AU the 2D woven fabrics have the ability to absorb more projectile impact energy compared to the three 3D angle-interlock fabrics. 

When comparisons were made on the energy absorbed by the fabric on a per imit impact energy basis, presented in Figure 13.13, the same conclusions were made that 3D honeycomb fabrics performed better than 2D plain weave, and 2D plain weave showed better performance than 3D angle-interlock fabrics. 

The enhanced ballistic performance of the 3D honeycomb fabrics may be attributed to the conjunction area between adjacent layers, which increases the yam friction in the conjunction area and the dimensional stability of the fabric as a whole. The increased yam friction in the conjimction area restrained yams from pulling out of the fabric in comparison to 2D plain woven fabric. Furthermore, both warp and weft yams in the conjunction area are better controlled with higher friction force caused by the higher yam density in the area. The reduced ballistic performance of 3D angle-interlock may be due to the difference in the number of intersections... 

Figure 13.11 Four-layer honeycomb fabric surface and side view.

D honeycomb fabric has also been developed to be used as a device for improving ventilation underneath ballistic body armour (Hearle et al., 1969). The 3D honeycomb woven stmctures used in their study were woven by a conventional loom and composed of three sets of warp yams and one set of weft yam. Each set of the warp yams interlaces with the weft yams, forming plain woven fabric layers. 

Figure 13.14 Vraitilation device made by four-layer honeycomb fabric.

Although mote expensive to fabricate than the pelleted catalyst, and usually more difficult to replace or regenerate, the honeycomb catalyst is more widely used because it affords lower pressure losses from gas flow it is less likely to collect particulates (fixed-bed) or has no losses of catalyst through attrition, compared to fiuidized-bed and it allows a mote versatile catalyst bed design (18), having a weU-defined flow pattern (no channeling) and a reactor that can be oriented in any direction. 

Quite often, NBR adhesives are used to bond various kinds of gasketing (cork, fibre, foam, rubber, metal) to rigid superstructures, such as aircraft. Films cast from solution are often used to fabricate honeycomb structures for aircraft. 

The Mosquito was a laminated wood monocoque design that although unusual, was not new. More uniquely, the monocoque shell was fabricated by gluing plywood skins to balsa wood core. This construction foreshadowed the popular honeycomb core/facesheet aluminum and composite designs of later years. Fuselage halves of the Mosquito were formed in closed wooden female tools (tools... 

Adhesive bonding is an integral part of virtually all composite structure. Early composite matrix resins could in some cases act as an adhesive, such as with self-filleting systems used for honeycomb sandwich fabrication. As composite systems became more optimized for minimum resin content and limited flow, supplementary adhesives became more common. Modern-day composite structure relies on adhesives almost as much as bonded metallic structure. 

Honeycomb core. Honeycomb core used for aluminum bonded sandwich structure is exclusively aluminum. The core is fabricated by printing offset stripes of adhesive (the node adhesive) on aluminum foil, stacking a large number of these foils and then curing the adhesive in a heated press. The resulting block is called a hobe. Slices are machined from the edge of the hobe and then expanded to... 

Use of the ceramic honeycomb packing structure in the recuperator keeps fuel and air substantially isolated as they travel through the recuperator. Various ceramic materials such as cordierite, mullite, alumina and silicon carbide can be used to fabricate honeycomb beds. While metallic materials have the potential to be used in honeycomb bed, corrosion resistance is a major issue... 

Also widely used in boat building, an extruded PP honeycomb, designated Nida-Core, has cost and fabricating advantages over competitive core materials. Nida-Core, developed in France and now available in the USA from Nida-Core Corporation, is produced by an extrusion method and therefore differs from most other honeycombs. Brief details are noted. 

On the other hand, following the development of hybrid combustor configurations that prevent operation of the catalyst module at temperatures above 900-1000 °C, the major drawback of metallic monoliths, namely the limited maximum operating temperature, has been overcome. Accordingly, honeycombs made of metal foils have been adopted in GT catalytic combustors in view of their excellent thermal shock resistance and thermal conductivity properties [9]. In addition, metallic substrates are a promising option for the fabrication of microcombustors. 

Bonding allows thin gauge metals and honeycomb assemblies to be fabricated, resulting in the availability of lighter structures. 

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