Experimental Investigation of the Influence of Notch Geometry on Impact Resistance of Al/Cu Bimetallic Sheets

The impact resistance of bimetallic materials is a critical aspect of engineering, particularly in the aerospace and automotive industries. Notched geometries are often encountered in real-world scenarios due to manufacturing defects or intentional design features. The present work investigates the impact resistance and fracture behavior of Al/Cu bimetallic sheets, focusing on the influence of notches on fracture energy, the fracture process zone, and overall failure mechanisms. For interpretation and analyses purposes, the impact test results were integrated with SEM fractographic analysis and the Essential Work of Fracture (EWF) framework. Four notch dimensions of U and V geometries were tested. Experimental results indicated that U-notches yielded higher fracture toughness and lower stress concentration factors. Conversely, V-notch specimens experienced a 32.5% reduction in toughness and a 25.5% increase in stress concentration as notch depth increased. Also, the Analytical EWF predictions showed good agreement with experimental data provide that Al/Cu obey the fracture ductile behavior. The SEM images emphasized on the ductile fracture nature of the Al/Cu sheet, and U-notches reveal a wider and rougher fracture area shows larger FPZ. As well, as the Al layer exhibited ductile plastic deformation, while the Cu layer showed brittle cleavage and acted as a structural hinge to arrest cracks. These findings provide critical insight into enhancing the use of bimetallic metals under dynamic loading, establishing a basis for future investigations into the relationship between bimetallic parameters and fracture behavior.