MSD in Honeycomb Panels 3

[rotorguy]

I am looking for some information on the analysis of MSD in honeycomb panels. In am trying to find a way to asses what are acceptable damage limits or panel residual strength.

In addition, I am also looking for info on the analysis of repairs to the same panel types. (ie potted insert repairs)

Thanks...

 

[SuperStress]

I think you need to be more specific in regards to the types of panels and the types of damage.

Are you looking at aluminum/aluminum, fiberglass/nomex, or something else?

Are you concerned with skin damage? Core damage? Disbonds?

Potted insert strengths are extremely dependent on installation procedures, so developing "standard" repairs can be a difficult task.

Can you provide more info?

SuperStress

 

[Eap2n]

Hi,

For potted inserts a great reference is ESA PSS-03-1202, "Insert Design Handbook". We ran a series of tests a while back and the failure loads all fell within 5% of what was predicted with the ESA methodology. For sandwich panels in general (including damage assesment) try "The Handbook of Sandwich Construction" by Zenkert.

Erik

 

[rotorguy]

SuperStress,

What I am interested in specifically is Aluminum face sheets and aluminum core. The damage I am concerned with is mostly impact damage, multiple denting of the face, sharp, non-sharp and various sizes. My objective is to be able to asses what acceptable damage limits would be. Any info would be appreciated.


Eap2n,

Thanks for the reference material on potted insert repairs; I will definitely take a look.

Cheers, Rotorguy

 

[Eap2n]

Hi,

The FAA also has a good paper available on the web which might be of help to you:

"Review of Damage Tolerance for Composite Sandwich Airframe Structures"
research.faa.gov/aar/tech/docs/techreport/99-49.pdf

Erik

 

[SuperStress]

I don't have any information better than what Erik posted above.

Thanks for the link!

SuperStress

 

[Eap2n]

"My objective is to be able to asses what acceptable damage limits would be."

As far as I know there is still a great deal of work going on to determine what "acceptable" damage from impacts should be for sandwich aerostructures. NASA Langley did a lot of work to try to establish industry curves for the relationship between impactor size, mass, shape, and velocity and the corresponding loss in compressive stiffness of composite sandwich wing panels. You can find most of these papers for free directly through the NASA tech report server or google.

We are currently finishing up certification of the tailcone APU flap for the airbus a380 which is made entirely from nomex honeycomb panels, and it is turning out to be very difficuly to come to some agreement with airbus regarding what damage they will accept for an event such as hail impact. We modelled a number of different impact events with FEM to get a qualitative feel of what types of damage occur, but without a well-defined acceptance criteria its all kind of meaningless.

Erik

 

[rotorguy]

Thanks very much for all the info. This should be good to get me started. I appreciate the references.

Cheers,

 

[Eap2n]

I forgot to mention one other reference which I think will help:

"Loading, Degradation and Repair of F-111 Bonded
Honeycomb Sandwich Panels – Preliminary Study"

http://www.dsto.defence.gov.au/corporate/reports/DSTO-TR-1041.pdf