Estimating effect of an impact on a composite (sandwich) plate 1

[JBlack68]

To all

I’d like to know if there is a way of estimating the effect of an impact on a composite panel. I am not after some fancy FE analysis. Just a rough idea/back-of-the envelope calc type of approach

Given the mass (of the object) and its drop height I estimated the impact energy at 5J. To which “numbers” should one compare this impact energy too to get an idea what is happening to the panel? I suspect penetrating is unlikely (i.e. going through the panel) I suspect some sort of delamination is possible.

Is it just a matter of comparing the impact energy to some Critical energy release rate?

Thanks
Regards

 

[WKTaylor]

JXB... a few relevant documents

JAMS Impact Damage Formation on Composite Aircraft Structures, 2013 Technical Review, Hyonny Kim, FAA JAMS 2013 Technical Review Meeting, April 9-10, 2013, Everett WA
University of California San Diego

Thesis: DESIGNING COMPOSITE STRUCTURES FOR LOW-VELOCITY IMPACT

http://www.dtic.mil/dtic/tr/fulltext/u2/a225217.pdf

ARC... many topics, this subject...

https://arc.aiaa.org/action/doSearch?AllField=composite+impact+damage++

NTRS... many topics, this subject...

https://ntrs.nasa.gov/?N=0&Ntk=All&Ntt=composite impact damage&Ntx=mode

matchallpartial

Regards, Wil Taylor

o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]

 

[SWComposites]

Predicting the amount of damage in a composite laminate from an impact event is extremely difficult.

Just conduct some tests.

 

[JBlack68]

thanks for the links and confirmation of the difficulty. Still a bit od reading to do. Learnt however that the impactor will have an effect on the result.
Impact Test is planned but not for a while. One could end up end up doing the test(s) and show that while the composite panel is meeting all the (other) requirements, it is damaged from a "minor" impact (BVD most likely) and the customer will have no choice but to replace it.

 

[WKTaylor]

JXB...

When I was working remotely in the 'field' we used one-side Ultrasonic NDI [US-NDI] or 'coin-tap-test' to ID suspected composite damage [area]. This only got-us in the ball-park.

IF cutout-repair was necessary... our rule-of-thumb...

We trimmed-out [routed] the area suggested by US-NDI + a margin [had to know local thickness], +~1T] all-around... then examined the laminate in-detail.

We trimmed-out [routed] the area suggested by tap-test + a margin [had to know local thickness, +~4T-to-6T] all-around... then examined the laminate in-detail.

Usually we were close... but added trimming was almost always necessary.

After the area was trimmed-out to 'solid/undamaged laminate' then we scarfed the edges for build-up patch repair.

A few [more] composite repair documents that include inspection.

AGARD-R-716 Composite Structure Repair

AGARD-CP-530 Debonding/Delamination of Composites

USAF T.O. 1-1-690 General Advanced Composite Repair Processes Manual

SAE R-336 Care and Repair of Advanced Composites

SAE AIR5719 Teaching Points for an Awareness Class on "Critical Issues in Composite Maintenance and Repair

SAE ARP5089 COMPOSITE REPAIR NDT/NDI HANDBOOK

SAE ARP6262 Basic Composite Repair Technician Certification Standard

and the list goes on... butgottagetbacktowork



Regards, Wil Taylor

o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]