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II.1.10.6 Maximum strain criteria (2D)

The criterion is very similar to maximum stress criterion, except that it is calculated from the mechanical (or equivalent) strain tensor components. The failure index is calculated as follows:

FIMaxStrain = max ϵ11Mech ϵ11all , ϵ22Mech ϵ22all , γ12Mech γ12all ,

in which the ϵ11all and ϵ22all allowables depend on the sign of ϵ11Mech and ϵ22Mech respectively. Ply or laminate passes the test if the three following conditions are satisfied:

ϵ11 ϵ11all,
ϵ22 ϵ22all,
γ12 γ12all.

The reserve factor is calculated as follows:

RFMaxStrain = 1 FoS FIMaxStrain,

and the strength ratio is given by:

SRMaxStrain = FoS FIMaxStrain.

This criterion is referred to as “MaxStrain” criterion in FeResPost.

FeResPost proposes a second version of the criterion where the “total” strain tensor ϵ is used instead of the mechanical strain tensor ϵMech. This version of the criterion is referred to as “MaxTotalStrain” criterion in FeResPost.