Residual Strength and Fatigue Lifetime of ... - Solid Mechanics

4.4 Face/Core Fatigue Crack Growth in Sandwich Panels
In this section the 2D fatigue crack growth finite element routine is further developed to account
for 3D fatigue crack growth. Here, instead of having a crack tip and one point of crack
propagation, a crack front propagates in different points in different directions. As schematically
described in Figure 4.10, an iterative procedure is devised to couple the debond propagation
routine and the cycle jump method, including a control criterion to ensure accuracy and
computational efficiency of the simulation as described earlier in this chapter.
Figure 4.10: Route diagram of the 3D fatigue debond growth and cycle jump routines.
Initially, a set of station points defining the debond shape is chosen and the finite element model
of the debonded panel is generated. The debond front is defined by passing a spline through the
station points. To evaluate the direction of debond propagation, the normal and tangential
directions of the debond front at each station point are determined and an orthogonal mesh at the
debond front is imposed. The debond only propagates at the station points used to define the
debond front. The finite element model is solved for the first three cycles. The strain energy
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