This paper aims to illustrate the effect of the impact damage on fatigue behavior of CF/PEEK-titanium hybrid laminates. To achieve this end, a fatigue life model was proposed to predict the S–N curves of the laminates at various initial impact energy levels and stress ratios based on the energy dissipation approach. The energy dissipation behavior of the laminates during fatigue loading under different experimental conditions was analyzed through a large amount of post-impact fatigue tests, and the correlation between the initial impact damage and the total fatigue dissipation energy was determined. The full-field axial strain distribution of the titanium layer on the impacted side of the laminate was characterized in terms of initial impact energy level and maximum stress using digital image correlation, and then the post-impact fatigue failure mechanism of CF/PEEK-Ti hybrid laminates was summarized. Finally, the validity of the proposed model was verified by fatigue tests under other conditions of stress ratio and impact energy level. It is worth mentioning that the proposed model is also applicable to other types of FMLs, and can accurately predict the residual fatigue life of laminates after impact with only one set of S–N curve data.

Fiber metal laminates (FMLs) provide a reliable approach for achieving lightweight in high-speed aerospace vehicles. However, the weak interfacial properties between metals and composites could significantly affect the deformation and failure modes of FMLs. In this paper, the low-velocity impact responses and damage mechanisms of CF/PEEK-Ti hybrid laminates with nano-interfacial enhancement by multi-walled carbon nanotubes (CNTs) were characterized and analyzed. The post-impact residual tensile strengths (RTS) were investigated experimentally using quasi-static uniaxial tests combined with digital image correlation, and were evaluated theoretically by developing an analytical prediction model that considers the internal thermal stress and dent geometry. Results show that the initial delamination thresholds of force and displacement during impact can be effectively increased via interfacial enhancement of CNT network. By using a 5% decrease in RTS retention rate as a criterion for damage tolerance, a significant strength decrease starts to appear at 3 J for the sandblasted-only laminates, which is improved to 10 J for the laminates with nano-interfacial enhancement. The proposed unified constitutive model can yield an acceptable prediction for RTS and failure strain of the hybrid laminate after impact, providing a guidance for the structural design and engineering applications of FMLs.