Investigation of fatigue crack growth and crack turning on integral stiffened structures under mode I loading

Integral structures have benefits compared to riveted structures, but they offer lower damage tolerance. This investigation analysed possible decrease of crack growth in integral structures by means of design analysis on stringer cross-sections. For this purpose the finite element analysis (FEA) was applied. First the reliability of FEA was proven by comparing calculated crack growth rates (CGR) to test results. Since CGR in linear elastic fracture mechanics is controlled by the stress intensity factors (SIF), different cross-sections were analysed. These configurations were evaluated regarding their crack turning behaviour (T-stress). The SIF was reduced about 18%. Crack turning is more probable when the crack is far away from stringer.