Honeycomb sandwich panels

Adhesives with filleting properties are required for honeycomb cores. A modified phenolic is often used with aluminum honeycomb for high strength, while a neoprene- or nitrile-based organic solvent type of adhesive is often used with impregnated paper honeycomb. Epoxy adhesives are also commonly used in the fabrication of honeycomb sandwich panels. 

Soutis C, Spearing SM. Compressive response of notched woven fabric face-sheet honeycomb sandwich panels. J Polym Rubbers Compos 2002 31(9) 392—7. 

Figure 14.3 Typical repair to honeycomb sandwich panel.

Radiography Density variations in bonded components can be detected with X-rays, provided that metallic fillers or other special contrast indicators are present in the adhesive. X-ray inspection of bonded honeycomb sandwich panels may be used for establishing the location of the core, and for checking for damage of the honeycomb. 

Fibrela Honeycomb sandwich panels Ciba-Geigy Ltd. 

Fig. 2. Comparison of destructive tensile strength tests on honeycomb sandwich panels with the predicted strengths using the Fokker bond testa-. A saies of honeycomb constructions is represented, where the foil thicknesses and the cell sizes are both varied ( ), foU thickness 0.007 in. (0.177 mm), ceU size 0.125 in. (3.175 mm) ( ), foil thickness 0.003 in. (0.076 mm), cell size 0.250 in. (6.25 mm) (A), foil thickness 0.002 in. (0.05 mm), cell size 0.1875 in. (4.762 mm) (O), foil thickness 0.001 in. (0.025 mm), ceU size 0.250 in. (6.35 mm). (From R E Clemens, Paper presented at the Amoican Society for Non-destructive Testing Technical Meeting, California, February 1962)...

Davalos, J. F. and Qiao, P. (2001), Modeling and characterization of fiber-reinforced plastic honeycomb sandwich panels for highway bridge applications , Composite Structures, Vol. 52, Issues 3-4, pp. 441 52. 

A cold curing epoxy adhesive developed primarily for bonding load-bearing inserts into honeycomb sandwich panels. Suitable for operation up to 150 6. 

Because of their newness, complete panels for A-300 solar cells are not yet available. Moreover, traditional panel construction with its steel backing is not viable for the robot. Thus, we will construct the solar panels in house, using quarter-inch honeycomb sandwich panels (Nomex core with fiberglass facing). The cell will be encapsulated in silicone. Similar honeycomb composite will be used to make the chassis box (Figure 8). The constraction and joinery of honeycomb panels are mature technologies in the aerospace field, and these materials supply area densities of 1.4 kg/m for solar panels and 2.5 kg/m for chassis walls. 

Manufacturers Comments RT cure. Flame retardant, low density. Edge filler in fire-retardanf honeycomb sandwich panels. ... 

Figure 23 Breaking down of honeycomb sandwich panel bonded with epoxy film. Honeycomb cells break down in different heights. (Colour version of this figure appears...

Figure 33 Pure tensile test on honeycomb sandwich panel — clamps axis must be perfectly aligned in order to avoid any cleavage effect.

Figure 36 Climbing drum peel test for honeycomb sandwich panels (a) specimen configuration (b) climbing drum apparatus (c) typical trace of climbing drum peel test.

For more information about honeycomb and honeycomb sandwich panels, refer to the chapter Sandwich panels in this Handbook. 

Hexcel, in the United States, which started honeycomb production in 1946 supplying glass honeycomb sandwich panels for the construction of the wings of the B 36 in 1949. In Europe, it was not until the early 1950s, with the introduction of Redux 775 Film that de Bruyne s original concept came to fruition with... 

The potential skinning material for honeycomb sandwich panels can cover all the other substrates mentioned above - in flat sheet form - and can be augmented with decorative laminates, based on melamine-formaldehyde, P/F laminates or any other suitable plastic. The latter are to be seen in aircraft interiors. 

Honeycomb Sandwich Panel as laid up before Cure... 

Bonded Honeycomb Sandwich Panel showing Filleting Action of the Adhesive... 

Table 10 Specification data for Redux 319 elfect of multiple cures on metal-to-metal and honeycomb sandwich panels.

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. 

Beam Shear. Here the bondline in a thick-skinned honeycomb sandwich panel is subjected to shear stresses utilising 3- or 4-point loading (Fig. 51). 

Much has been said about the use of bonded honeycomb sandwich panels in spoilers, ailerons, etc. However, the Gulf Stream G5 does not use this technique. Hurel-Hispano manufactures the spoilers for this aircraft from a machined aluminium block (rather than a honeycomb in-fill) to which Redux 119 primed aluminium skins are bonded directly using Redux 319 film adhesive. 

Figure 1.17 Another major use of structural adhesives in the aerospace industry is in making honeycomb sandwich panels where the face skins are bonded to the honeycomb core. This example is from a section of the rudder of Concorde and consists of aluminium alloy core and skins. More recently one has seen the increased use of non-metallic core and skin materials, i.e. carbon-fibre reinforced plastic (CFRP) skins. 

Pyles R (2003) Aging aircraft USAF workload and material consumption life cycle patterns. RAND, Pittsburgh Rao MV, Samuel R, Ramesh K (1990) Dual vacuum stressing technique for holographic NDT of honeycomb sandwich panels. NDT Int 23 267-270 Reynolds WN (1988) Inspection of laminates and adhesive bonds by pulse-video thermography. NDT Int 21 229-232... 

New types of structure utilized As far as the aerospace industry is concerned, one of the most important, novel structures since the early 1950s has been the honeycomb sandwich panel (Fig. 13.16). It could be argued that the woodskinned balsa sandwich panels used in the Mosquito or the metal skinned version used by Chance Vought (Metalite —q.v.) could have been joined by some other method than adhesive... 

Table 13.10 Specification Data for Redux 319 Effect of Multiple Cures on Metal-to-Metal and Honeycomb Sandwich Panels...

A honeycomb structure consists of honeycomb sandwich panels attached either to a frame or in some instances to each other. The honeycomb panels consist of a honeycomb core sandwiched between metallic or composite face sheets. This arrangement permits use of stabilized, lightweight panels to carry most of the structural loads. Secondary supports would mount to inserts bonded within the honeycomb structure in various locations and orientations. Fittings or load spreaders are frequently required to transfer loads into and out of the honeycomb structure. 

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