Honeycomb peel

Honeycomb peel at 75°F Honeycomb peel at 75°F after 30 days exposure at 95°F, 100 percent R.H. Honeycomb peel at 75°F after 30 days salt spray exposure at 95°F Flatwise tensile at 75°F Flatwise tensile at 180°F 45 lb-in/3 inch 75 lb-in/3 inch 75% of actual room temperature peel strength 75% of actual room temperature peel strength 900 psi 1100 psi 500 psi 750 psi... 

Figure 46 Lap-shear and honeycomb peel performance of Redux 312.

Honeycomb Peel A conventional thin-skinned honeycomb sandwich panel is tested in peel using the so-called climbing drum peel rig (Fig. 50). Applying a measurable torque to the drum forces it to climb the specimen and, hence, peel off the bonded skin enough specimens are tested to be able to assess the adhesive bond to both top and bottom skins in the sandwich. 

In addition to epoxy-phenolic adhesives three-part epoxy-phenolic-nitrile rubber systems are used in metal-metal edge joints and honeycomb constructions [208], These add toughness not available in most EP systems and improve peel strengths. When used on honeycomb, the NR-P is normally applied to the aluminum skin and the EP to the honeycomb for assembly. Service temperature limitations are those imposed by the NR-P part. 

Table 1 contains the metal-to-metal engineering property requirements for Boeing Material Specification (BMS) 5-101, a structural film adhesive for metal to metal and honeycomb sandwich use in areas with normal temperature exposure. The requirements are dominated by shear strength tests. Shear strength is the most critical engineering property for structural adhesives, at least for the simplistic joint analysis that is commonly used for metal-to-metal secondary structure on commercial aircraft. Adhesive Joints are purposefully loaded primarily in shear as opposed to tension or peel modes as adhesives are typically stronger in shear than in Mode I (load normal to the plane of the bond) loading. 

Fig. 10. Climbing drum peel apparatus (honeycomb shown). Reproduced by permission of the Boeing Company.

If an assembly is destructively inspected, the verification film is used to identify potential problem areas for particular attention. These areas and others randomly selected are cross-sectioned to determine bondline thickness (Fig. 22), bond details are peeled apart to inspect for voids and honeycomb core bonds are... 

A pressure of 25 psi and temperature of 175°C are required for 1 h to cure the epoxynylon adhesive. Because of their excellent filleting properties and high peel strength, epoxy-nylon adhesives are often used to bond aluminum skins to honeycomb core in aircraft structures. In these applications, climbing drum peel strengths in excess of 150 lb/in have been achieved. 

Figure 26-5 649 Specular reflection illumination reveals the honeycomb appearance of the normal cornea and the black zones in the endothelium caused by guttata arrow). (B) TransiUumination revealing orange-peel dimpling characteristic of central corneal guttata arrow). (Courtesy of Pat Caroline.)...

Paxillus involutus is a large brown mushroom, ranging from 3" to 7" wide, recognized by a broadly depressed cap, inrolled cap margin from which the species name and common name is derived. The stem is stout and lumpy honeycomb gills with the tendency for all parts of the mushroom to bruise brown. The gills are also easily peeled from the cap and sometimes... 

Finally, another way to tune the pore shape is to apply directional mechanical forces such as shrinking [109] or stretching [73] to viscoelastic honeycomb films or to orientate the humid airflow [110]. In addition peeling-off the top surface of honeycomb films, exhibiting an organized hexagonal pattern of spherical pores, produced pincushion structures at the origin of surface hydrophobicity [86, 111, 112]. 

Yabu, H., Shimomura, M. Mesoscale pincushions, microrings, and microdots prepared by heating and peeling of self-organized honeycomb-patterned films deposited on a solid substrate. Langmuir 22, 4992-4997 (2006)... 

Three-way catalysts used in exhaust-gas catalytic converters of automobiles contain platinum, palladium, rhodium, zirconium, and cerium. Oki et al. have developed a method which concentrates these metals by means of a two-step crushing procedure (Kim et al., 2010 Oki et al. 2010). The process makes it possible to increase concentration of rare-earth metals by a factor of five by first demolishing the honeycomb structure, and then peeling off the surface. To date, no process leading to recovery of individual rare-earth metals has been described. 

Adhesives are designed for specific applications. For example, a honeycomb structure adhesive (requiring good filleting around the cells) would have different flow characteristics than one used for metal-to-metal joining. In addition, the type of stress (e.g., shear or peel) on the bonded area varies and will depend upon the design of the structure. 

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