This criterion is adapted to the qualification of laminates with unidirectional plies. This criterion distinguishes two failure modes: one fiber failure mode in direction 1 and one matrix failure mode. Three versions of the Puck criterion are distinguished.
The first version of Puck failure index is calculated as follows:
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in which the allowables and depend on the signs of and respectively. Ply passes the failure criterion if the two following conditions are satisfied
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The reserve factor is simply given by:
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and the strength ratio is given by:
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This criterion is referred to as “Puck” criterion in FeResPost.