Honeycomb Sandwich Panels
If you are wondering what honeycomb sandwich panels are, then no worries. They are super strong and lightweight panels made from two components.
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Face sheets or skins, and some type of filler honeycomb core. The skins lie on the top and bottom side of the honeycomb sandwich panel. They are the primary load bearing members for membrane or in-plane forces and moments. The honeycomb sandwich core on the other hand is mainly used to keep the skins apart. Also it has to transfer out of plane or transverse shear forces from one skin to the other, without getting crushed. This is called core shear failure. The core is porous in most aircraft structural applications with a honeycomb cell structure (one of the strongest nature has ever made). Thus the weight to thickness penalty ratio is minimized and at the same time giving us some pretty strong panels that can take a lot of load.
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Many industries use honeycomb sandwich panels in various forms, shapes and sizes and material configurations (both metallic and non metallic). Industries such as commercial and business jets, military applications, rotor crafts, some high end boats, yachts, even high end automotive applications use these panels.
The objective is to minimize weight and maximize strength and stiffness. These panels have excellent fire resistance capabilities critical to retard fires on aircraft, in compliance with FAA regulations.
Materials used in Honeycomb Sandwich Panels:
- Common Material: The facings, or skins of honeycomb sandwich panels are made from a variety of different materials. For non metallic, high stiffness and light weight panels, the most common facing material used is a woven fiberglass cloth or fabric. It is typically procured by panel manufacturers in the form of a 'prepreg' (short form for pre-impregnated with resin). This prepreg is ready to go into a mold or an autoclave oven to be cured as part of a panel build up or a laminate layup
- Other Materials: Other facing materials include clad Aluminum Alloy 2024 or 7075 sheets (metallic honeycomb sandwich panels), carbon fiber prepregs etc.
- Thickness: Each fiberglass prepreg ply typically comes with a structural adhesive ply on one side. The total nominal ply thicnkess is generally about 0.01". The most common nonmetallic honeycomb sandwich panels use two plies. Thus, the total nominal facing thickness on each side of the panel is about 0.02"
- Common Material: The core of the honeycomb sandwich panels is the main reason for their rigidity and high stiffness to weight ratio. It is also manufactured from various materials. The most common in interior applications is the 'nomex' aramid paper fiber core. The video below shows the manufacturing process of the core material
- Manufacturing Process Video: Having trouble with the video player above? Watch it on Youtube, click this link: Honeycomb Sandwich Panels
- Other Materials: The core is also made from other lightweight materials such as Kevlar, Fiberglass, Carbon fiber etc.
- Thickness: The most common panel thickness used in cabin interior honeycomb sandwich panels is 0.5" nominal. Therefore, since the total facing thickness on both sides combined is 0.04", the core nominal thickness is 0.46"
Probably one of the first names that comes to mind when we talk about panel manufacturers is HEXCEL. Here are some useful links to the Hexcel panel specs and other documents:
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