In this paper, Comprehensive progressive damage analyses are performed
to evaluate the effects of patch sizes and layups on re-starting crack
growth of single-side repaired panels with central inclined cracks under
high cycle fatigue loading. Complicated nonlinear damage behavior of
adhesive bonding, composite patch, mixed-mode cracks and fatigue
loadings require precise numerical tools to consider and analyze the
coupling effects of various damages on fatigue life of such complex
component. For this purpose, two user-written materials subroutines
added to a commercial finite element software to capture adhesive
debonding and composite patch damages under high cycle fatigue. In
progressive damage analysis, high cycle fatigue cohesive zone modeling
used for debonding of patch and high cycle fatigue continuum damage
model used for composite patches. Practical composite patch layups and
sizes are selected in huge number of models and the restarting crack
growth life are predicted. The results shown that the composite plies
angles attached to the cracked panels have dominant effect on restarting
crack growth life. Different combinations of the same layup angles show
completely different restarting crack growth lives. The obtained results
show the possibility of increasing the restarting crack growth life
using an appropriate composite patch layup and geometry dimensions.