Experimental and numerical study on the low-velocity impact behavior of foam-core sandwich panels

This paper presents the results of an experimental and numerical study on the low-velocity impact behavior of foam-core sandwich panels. Panels with polyurethane foam core and plain weave carbon fabric laminated face-sheets were subjected to low-velocity impact with hemispherical steel impactors of different diameters at various energy levels. Digital image correlation technique (a non-contact measuring system) was used to measure the real-time displacement and velocity of the impactor, and the back surface out-of-plane panel deflection time-history. A load sensor was used to record the contact force time-history. Non-destructive inspection and destructive sectioning methods were used to evaluate the internal and external damage on the sandwich panels after impact. The effects of impact variables such as impactor diameter, impact energy, and sandwich panel configuration parameters, such as face-sheet thickness and foam core thickness on the impact behavior and resulting impact damage states were studied. Based on the generalized Schapery theory, a progressive damage model is developed to describe the nonlinear behavior of plain weave carbon laminates during impact. The foam core was modeled as a crushable foam material. Coupon tests were conducted to determine the input parameters for the progressive damage model and the foam crushing properties. Three-dimensional finite element models were implemented to analyze the impact response incorporating the progressive damage model. Results from the numerical models were found to agree well with experimental observations.