NDI Porosity Allowables - Mechanical Tests
NDI Porosity Allowables - Mechanical Tests
(OP)
Hi All ,
We are currently preparing a justification to support an increase in the NDI porosity design allowable of monolithic and sandwich CFRP laminates .
Part of the justification revolves around a mechanical testing regime of samples that contain a higher level of porosity that seeks to gather relevant data that would support any such process .
We have already considered some matrix dependent tests such as ILSS and we envisage doing a hot / wet campaign as we envisage that these will contribute the greatest ' knock down ' component to any calcualtions . Additionally , we are looking at microscopy and mechanical and thermal fatigue cycles to gain an insight into any micro-cracking issues .
Does anyone else have experience of any further ( particulalrly ) mechanical tests that would be useful to support such a justification ?
Thanks In Advance
We are currently preparing a justification to support an increase in the NDI porosity design allowable of monolithic and sandwich CFRP laminates .
Part of the justification revolves around a mechanical testing regime of samples that contain a higher level of porosity that seeks to gather relevant data that would support any such process .
We have already considered some matrix dependent tests such as ILSS and we envisage doing a hot / wet campaign as we envisage that these will contribute the greatest ' knock down ' component to any calcualtions . Additionally , we are looking at microscopy and mechanical and thermal fatigue cycles to gain an insight into any micro-cracking issues .
Does anyone else have experience of any further ( particulalrly ) mechanical tests that would be useful to support such a justification ?
Thanks In Advance





RE: NDI Porosity Allowables - Mechanical Tests
RE: NDI Porosity Allowables - Mechanical Tests
Just out of curiosity, is the porous material 919/3070P/45 prepreg?
RE: NDI Porosity Allowables - Mechanical Tests
In reverse - Neubaten - no its not a pre-preg application .
RPStress - Thanks for the response . We are aware of the challenge of creating laminates with defined levels of porosity in them . We are not trying to open up the allowable so that we can manufacture to a lesser standard . We are opening it up because we have been set the challenge of quantifying % porosity in our NDI Inspection process . We don't beleive this can be done in sandwich components in high volume production and therefore we are seeking to remove the NDI requirements for porosity by demonstrating that even ( relatively ) high levels of porosity still achieve the required RFs , therefore the NDI inspection issued used to locate FOD and delams only .
RE: NDI Porosity Allowables - Mechanical Tests
RE: NDI Porosity Allowables - Mechanical Tests
RE: NDI Porosity Allowables - Mechanical Tests
I have some test data showing a more or less linear degradation of ILSS with % porosity for a prepreg carbon epoxy. Porosity was between 0.5%–6%. It's not an enormous data set, but there were a reasonable number of specimens.
RE: NDI Porosity Allowables - Mechanical Tests
"Critical Void Content for Polymer Composite Laminates"
AIAA JOURNAL
Vol. 43, No. 6, June 2005
RE: NDI Porosity Allowables - Mechanical Tests
More importantly, many designs are not critical for interlaminar shear stress, so even if porosity has an effect on ILSS, it may not be important. The porosity evaluation should be focused on the properties which are critical for sizing the part.