Long beam flexure test, acceptable mode of failure

[audacious2121]

Hi,

I am doing some long beam coupon test using composite panel with build up: Nomex core and phenolic glass fabric skin, purpose of this test is to do qualification of panel process. ASTM D5467 lists out acceptable/ unacceptable failure modes, but coupons which I am testing fails in dis-bond between core and skin, I am understand this is due to lack of proper adhesion between skin and core, but if I use this process and meet all the strength requirements do I have to have acceptable failure ? I am working with part 25 interior components.

Thanks

 

[SWComposites]

1) suggst you use ASTM D7249 instead. It is a more general long beam flex test method
2) both test methods are intended to produce a facesheet failure, not a core or bondline failure
3) the fact that you a re failing in the bondline (unless you are testing a non standard shorter specimen) probably means you have an unacceptable test result and adhesive material.
4) to determine whether the panel is acceptable you will have to discuss the results with your OEM customer, your DER and/or the applicable certification agency