A fuzzy set approach to interlaminar cracks simulation problems

A numerical approach to the assessment of the fatigue life has been developed. In the 3-D finite element analysis non-linearities due to both large rotations and face contact have been considered. The model is mechanistic and uses energy release rates for prediction of delamination growth and of critical delamination sizes that induce buckling and final failure of the structure. The increments of the delaminated area have been optimized in order to study both the effects of variations of the area and of the shape of the curve surrounding the delaminated region. The uncertainty in the response (a fatigue life prediction) is modelled with the use of the fuzzy set approach and it is associated with pre-selected variations in material parameters characterizing the delamination initiation and material degradation of a laminate due to matrix cracking. Numerical tests have been performed for cross-ply laminated plate subjected to compression and having a single embedded delamination located at the plate center.