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2.7.9 Positive Definiteness of Material Stiffness Matrix
Positive Definiteness of Material Stiffness Matrix
The positive definiteness of the material stiffness matrix D is tested by Sylvester's criterion, which has been modified regarding the null blocks. If the stiffness matrix D is not positive definite, the non-diagonal components of the material stiffness matrix are consecutively set to zero. In extreme cases, only the positive components from the diagonal remain.