Composite failure vs failure index


Updated by Altair Forum User
Hello,
I have some doubts about composite failure and composite index, relatively to the composite analysis postprocessing. As far as i think, composite failure is a number which should be compared to one according to the composite resistance theories (Tsai-Wu, Hoffman ecc).
But then what does 'failure index' mean? And what 'Plies with Maximum FI'? Which is the relationship between th failure index and the composite failure?
Thank you