Honeycomb Panels Construction:

Honeycomb sandwich panels have high torsional and bending rigidity because the structure acts in the same way as an I-beam. The facings of honeycomb panels are similar to flanges of an I-beam, and the core corresponds to the web, but unlike the I-beam, the core gives continuous support to the facing. The chart below demonstrates how dramatically the core strengthens the face material without contributing appreciably to the weight.

Relative Stiffness	100	700	3700
Relative Strength	100	350	925
Relative Weight	100	103	106

While our standard honeycomb panels, which have exposed and visible core between the facings, are suitable for many customers, others may need closures, blocks, cross members, etc. Paneltec can help you design your honeycomb panels with simple cost-effective additions to meet specific requirements.

Edge Close-outs:

Edge close-outs are used in honeycomb panels construction for a variety of reasons including:

1. To act as a structural tie to adjoining or supporting structural members
2. To allow panels to be joined either at angles or flat edgewise
3. To incorporate a hinge or cam lock
4. To seal the panel against moisture or chemical vapors
5. For cosmetic appeal

Edge close outs are co-fab or post-fab depending upon when in the assembly process they are incorporated.

 

Co-fabricated are bonded into the panel.
Post-fabricated are attached to the sandwich panel after it is laid-up and trimmed to size.

 

Treatments you may select:

Post-Fab	Co-Fab
Low cost with two standard angles. Pop-rivet and bond. Special extrusions or castings bonded to panel. Could include doublers. Simplest close out. Legs of channel can be nipped and bent or mitered at corners.	Particle board, foam or wood bonded into panel. Channel bonded into panel. Legs out or in. Tube bonded into panel. Stronger, more costly. Special extrusions can be made to accommodate top and bottom skins. Break metal top and bottom. Can also be made with only one side folded.

 

Internal Blocking

When it is necessary to attach secondary parts to a sandwich panel and these parts are away from the edge, internal blocking or cross members can be provided, using particle board, high density foam, metal bar or tube, etc. Metal blocks can be drilled and tapped.

Sometimes inserts are used instead. The internal block is used when strength requirements are greater. Often inserts are not flush with the panel face--internal blocking is.

Tube	Solid Metal Bar	Particle Board or Wood

Unreinforced honeycomb panels can be drilled and bolted through if body washers, sheet metal or plate doublers are used to spread the compression load. Otherwise the torquing of nut and bolt will dimple or indent the faces.

Paneltec offers these options. In addition we can do post-fabrication machining and some assembly.

Flatness

There are three main factors that affect the flatness of a panel: symmetry, choice of materials, and fixturing in production.

Panels made with matching materials bonded to the two sides of the core will tend to be stable. Changes in ambient temperature and humidity will not affect the flatness of a balanced panel.

Face sheet materials generally don’t vary much in thickness over the area of a sheet and therefore have little effect on flatness. Cores are more likely to vary, particularly polystyrene foam, polypropylene honeycomb, and paper honeycomb. Aluminum honeycomb is manufactured to close tolerances. This is the core to choose if flatness is an issue.

There are also different methods of fixturing panels in the layup process. Paneltec will choose or devise appropriate fixturing to meet your particular requirements. We urge our customers to consider and communicate the degree to which their application is flatness-critical.

By way of example, an aluminum/aluminum panel will yield the best flatness we can offer. We can provide 4’ x 8’ panels that will show less than .010” variation when a 6’ flat bar is applied to the surface. This is achievable when panels are laid up in small batches. Without special attention, quantities of panels can be produced with more relaxed tolerances. We have achieved excellent flatness with larger panels, when required. (See the Fermilab panels in our Projects section.)

Conclusion

We bring you the benefits of our expertise in honeycomb panels fabrication. While we prefer simple design solutions and simple, reliable methods of fabrication, we also employ sophisticated engineering software, CNC machining, laser and water-jet cutting where appropriate. We look for a balance to save you and us headaches and expense.