Investigation of curing deformation and drilling effects in composite hat-shaped stiffened panels: Experimental and numerical analysis

This study investigates the curing deformation and drilling effects in composite hat-shaped stiffened panels, which are widely used in aerospace structures for their high strength-to-weight ratio. A numerical path-dependent constitutive model was developed to simulate the curing process, demolding, and drilling operations using ABAQUS, with experimental validation conducted via laser scanning on a full-scale AS4/8552 composite panel (radius: 3000 mm, length: 2000 mm). The results show that the curing deformation exhibits a distinct “X” shape, with a maximum out-of-plane deformation of 2.48 mm in the center and downward edges. Secondary drilling significantly reduced the curing deformation through residual stress relief, whereas pre-reserved holes markedly increased deformation due to stress concentration and reduced stiffness, as confirmed by both experimental and simulation results. Furthermore, an optimal hole size of 300 × 200 mm (3% of panel area) minimized deformation, while larger holes (e.g. 700 × 600 mm) led to a 49.5% reduction in buckling load and increased distortion. These findings provide quantitative guidance for optimizing manufacturing processes to balance stress release and structural integrity in composite stiffened panels.