CRES installed on CFRP

[ACESENGINEER]

Why is the industry standard in aerospace to not intall CRES (15-5PH, AISI 301, or otherwise) on CFRP. I realize that the materials have significantly different modulas of elasticity and would strain differently, therefore it would not be suggested for doublers and or large fittings, but I can not see the rational for small clips and stiffeners, etc. I see aluminum details installed on 777 floor beams all the time, and it has a much higher coefficient of thermal expansion, so it can't be for that (CRES is actually quite close to Titanium which I understand is very similar to CFRP for modulus and coefficient of thermal expansion). Any advice on this subject would be appreciated.

 

[rb1957]

think corrosion

Quando Omni Flunkus Moritati

 

[ACESENGINEER]

It's not a corrosion issue, they are compatible, we use cres fasteners all over on the beam (collars and nuts primarily). Similar to Titanium as far as corrosion goes and Titanium is also fully compatible.

 

[SWComposites]

What "industry standard" are you citing?

Perhaps it is because CRES is heavy?

 

[PBPouw]

I don't think the question is why the Aerospace standard is not to install Cress on CFRP, it's more that Cress is overall not the preferred fastener material because it is weaker then it's steel equivalent. So the steel variant is smaller / lighter than it's Cress equivalent.

Be careful with conclusions that certain materials corrosion wise go together. Most CFRP panels has an extra glass layer on the outside between a bracket and the panel. Fasteners which holes are drilled through the panel are a different story.............