Question: Airfoil Related Question

[KJ_Lesnick]

How come a fan-blade can be made out of diffusion bonded metal or honeycomb substances and a wing-cannot?

I've been told the reason had to do with shear-stresses, but wouldn't a compressor blade or fan-blade be subjected to similar stresses (if not more so)

 

[CammNut]

A fan blade is a few feet long and less than an inch thick, that's why.

 

[CammNut]

Superplastic forming and diffusion bonding is a good way to produce thin, highly loaded surfaces that would otherwise be a) solid like fan blades and b) hard to fabricate conventionally. Making fan blades hollow rather than solid makes them stronger and lighter, so they can be bigger. Missile fins are another example.

But there is at least one aircraft wing-like application:

"Extensive use of diffusion bonding and superplastic forming is made in the manufacture of the Rafale fighter's highly loaded titanium canard. This incorporates a diffusion-bonded spigot and a hexagonal corrugated core structure. A substantial mass saving is realised compared with other manufacturing methods"

From: http://www.esa.int/esapub/bulletin/bullet79/eaton.htm