Investigation on impact damage evolution under fatigue load and shear-after-impact-fatigue (SAIF) behaviors of stiffened composite panels

Experimental investigation on impact damage evolution under fatigue load and shear-after-impact-fatigue (SAIF) behaviors of stiffened composite panels were conducted in this paper. BVID was introduced into stiffened composite panels at a typical position. Damage areas, in-plane dimensions, dent depths were measured and relationships among the three parameters were determined by plane surface function. All fatigue specimens survived after 106 cycles at the given fatigue load level and the impact damage did not deteriorate or enlarge during fatigue loading. Then SAI (shear-after-impact) and SAIF experiments were conducted with a comparison of shear on virgin specimens. Buckling/failure modes of virgin, impact and impact-fatigue specimens were obtained. Buckling/failure load of impact specimens decreased by 17% and 16% compared to that of virgin specimens respectively. Additionally, fatigue load led a further 4.3% and 6.6% drop in buckling/failure load of impact-fatigue specimens compared to that of pure-impact specimens, although the impact damage area did not deteriorate or enlarge during and after the fatigue treatment.