Honeycomb structural panels are widely used in aerospace applications since they offer exceptional strength/stiffness-to-weight ratio. Acoustic turbine tailpipes, exhaust plugs, cones, nozzles, and fan ducts are often brazed as honeycombs.

Honeycomb brazed at edges to perforated face sheets. The perforations are free of braze alloy or other contaminants, so the structure's noise reduction qualities are retained and the mechanical bond is unimpaired. Tailpipes for the McDonnell Douglas 80, Boeing 727, and the Rolls Royce TAY engines, etc. and hushkits for the Pratt & Whitney JT8D engine are brazed by "wallpapering" the skin surfaces with MBF or by using Bräzcor.

Brazing Application
For acoustic or sound attenuation structures, the brazing filler alloy must flow off the honeycomb surfaces to form fillets at all the junctions without clogging the perforations, which are needed for sound absorption. Residues left by other conventional powder containing brazing filler metal clog the perforations due to inferior flow, leading to joint rejects.

Solution
By tack welding the MBF to the face sheets or using Bräzcor™ honeycomb core*, capillary action draws the melted brazing alloy to the thin edges of the honeycomb structure, while keeping it out of the perforations. Joint strength is improved because the foil acts as a spacer to maintain an optimum joint gap. Filler metal flows only in necessary contact area.

* Bräzcor by Alloy Spot Welders is the world's first ready-to-braze metallic honeycomb core. It is manufactured through a patented process which places precisely metered amounts of MBF between the cell nodes during fabrication for clean, precise brazed joints. Bräzcor can be manufactured using heat resistant alloys (Inconel and Hastelloys), titanium-based alloys and stainless steels.