Face sheet defects in plastic forming of aluminum foam sandwich panel: theoretical models, numerical and experimental studies

In this paper, the theoretical models of face wrinkling and dimpling defects occurred in the plastic forming of aluminum foam sandwich panel (AFSP) were constructed and the influences of AFSP parameters on defect were investigated to predict and avoid the surface forming defects. The wrinkling and dimpling behaviors of shaped AFSPs were analyzed at different scales first, and the analytical models of critical wrinkling and dimpling stresses of face sheet for the forming of AFSP were developed using energy method and differential equilibrium equation method respectively. Finite element simulations of curved AFSPs forming were performed using macroscopic and mesoscopic AFSP models, and plastic forming experiments of spherical and saddle-shaped AFSPs with different core relative densities were conducted. The surface profiles of simulated parts and the face wrinkles and dimples in experimental parts indicated that the established theoretical models can predict the occurrence of face sheet defects in curved AFSPs forming accurately. Furthermore, the effects of geometric and material parameters of AFSP on face wrinkling suggested that the seriousness of face wrinkling can be reduced by decreasing the thicknesses of face sheet and core, and the wrinkling can be suppressed when the elastic Poisson’s ratio of core is close to 0 and 0.5.