Equivalent Stiffness Modeling of Fiber-Reinforced Composite Laminates After Impact Fatigue

Based on the homogenization theory of composite materials, this study proposes an equivalent modeling method for calculating the stiffness components of composite laminates with impact damage and post-impact fatigue damage, aiming to provide an efficient and reliable modeling approach for fatigue damage analysis of large composite structures. A solid element model of undamaged laminates was established using the finite element method. Boundary displacement loads were applied according to the constitutive equations of composite laminates, and the stiffness components were calculated by extracting the stress field and deformation field. The finite element simulation results were compared with those from classical laminate theory for validation. The results showed a good consistency between the two methods. The validated method was further applied to analyze the stiffness degradation characteristics of laminates with impact damage and post-impact fatigue damage. The results indicated that with the increase in impact energy and fatigue cycle numbers, all stiffness components showed a varying degree of reduction, among which the shear stiffness decreased the most, indicating that shear properties of the material are most sensitive to interlaminar delamination and matrix crack damage.