Experimental investigation of the low-velocity impact response of sandwich plates with functionally graded core

In this study, the mechanical behavior of sandwich plates with functionally graded core under low-velocity impact loads was investigated experimentally. Sandwich plate with functionally graded core has two different structures (metal–ceramic), and the upper and lower surfaces are pure metal (Al) and the internal layers of the plate are manufactured with gradually varying material composition through the plate thickness. The low-velocity impact tests were conducted on both upper and lower surfaces of specimens using CEAST low-velocity impact device, and the contact force–time and the energy–time graphs were plotted. Metallographic and micromechanical examinations were carried out on the specimens after impact tests. As a result of the metallographic and micromechanical examinations, the material composition variation through the specimen thickness was obtained in accordance with the rule of the theoretical mixture. As a result of impact tests (v = 4 m/s) on upper surface (ceramic-rich side), crack damages occurs on the plates with n = 10.0 material composition, whereas the specimens with n = 1.0 and n = 10.0 material compositions have crack damages after impact tests on its lower surfaces (metal-rich side). Impact force on the ceramic-rich upper surface provides to meet the transferred load waves through the plate thickness by metal-rich bottom surface. This situation makes the structure more resistant against damage. Moreover, the upper and lower surfaces of the functionally graded structure reinforced by ductile pure metal layers provide an important contribution to protection of functional integrity of the structure against damage.