Eccentric impact analysis of pre-stressed composite sandwich plates with viscoelastic cores: A novel global–local theory and a refined contact law

A novel double superposition power-exponential global–local theory and a refined contact law are developed to investigate eccentric low-velocity impact responses of rectangular sandwich plates with viscoelastic cores. The continuity conditions of the transverse normal and shear stresses at the interfaces between layers is satisfied a priori. Stiffness of the underneath layers is considered in the contact law as well, for the first time. The non-linear integro-differential governing equations are solved by a second-order finite element and a special numerical time integration procedure. Effects of the pre-stresses on the indentation and contact force are investigated for the first time. Moreover, effects of the eccentricity on the impact responses of the sandwich plates are discussed in detail, for the first time. Verification of the results is accomplished through comparing present results with experimental results of a known reference. Results show that in the eccentric impacts, the contact force and the absorbed energy increase. Therefore, the failure occurrence can be more likely in the eccentric impacts. Furthermore, by utilizing a viscoelastic core, the apparent stiffness of the contact region increases and consequently the impact force and the absorbed energy increase. Biaxial tension increases the impact force and consequently, leads to premature failures.