Sidewall erosion

The two main approaches employed in chemically induced CD shrink techniques are based on sidewall formation and sidewall erosion, respectively. 

Chemically induced CD shrink techniques based on sidewall erosion rely on chemical reactions that preferentially take place at the sidewalls of already-patterned resist features, leading to their erosion. The hydrophilic overlayer process is a good example of this technique. 

Processing methods include shredding, splitting in halves, cutting sidewall/ beads, and baling. A number of products, in the form of processed tires, can be made from scrap tires that have applications in erosion control, soil conserva-... 

Truck-tire pipes were made by cutting the bead and sidewall from heavy truck tires and stacking and compressing beads/sidewalls [13]. The bead and sidewall are cut from heavy truck tires to make pipes for roadway cross drainage by stacking and compressing the bead/sidewalls to 2.4 m, held in place with rebars wrapped length-wise around the pipe walls and welded [13]. Sidewalls and faces cut from scrap tires can also be used on erosion control structures. 

In the aft end of the motor case, sidewall insulation is necessary in those areas exposed throughout the motor firing and those locations left exposed by recession of the propellant grain front. The materials used in these areas must have performance capabilities similar to the insulator in the forward bulkhead, except improved erosion resistance is required because of the moving gas stream. In general, the sidewall insulator is composed of an elastomer-resin copolymer or charring rubber reinforced with various fibrous compositions. 

Material requirements become more demanding as the gases move into the aft bulkhead section of the nozzle. Increased material rigidity, resistance to erosion and thermal insulations is required. Some degree of surface recession is permitted, since its influence on thrust is small. The aft bulkhead insulator is usually composed of a material similar to that employed in the case sidewall. Both elastomer-modified TS resins and heavily loaded rubber compositors have been employed with success. 

Figure 74 Schematic of the main rotor blade of Westlands Sea King Helicopter (courtesy of Westland Helicopters Limited), (A) BIM manifold, (B) Root doublers, (C) Erosion shield, (D) Packing piece, (E) Heater mat, (F) Outer wraps, (G) Uni-directional nose moulding, (H) Inner wraps, (J) Uni-directional sidewall slab, (K) Uni-directional backwall slab, (L) Skin, (M) Uni-directional sidewall slab, (N) Honeycomb, (O) Closing Channel, (P) CauUc, (R) Dummy skin, (S) Cuff, (colour version of this figure appears on p. xviLi).

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