Size Effect on Strength of Bimaterial Joints: Computational Approach versus Analysis and Experiment

Metal-composite joints connecting conventional steel to an advanced fiber composite are an attractive structural system for hybrid ship hulls as well as aircraft frames. The objective of this study is to analyze the size effect on the strength of hybrid joints numerically, theoretically and experimentally. In the numerical analysis, linear elastic continuum elements are used for the composite and steel while cohesive fracturing zero-thickness elements are used for the steelcomposite interface. The numerically simulated size effect on the strength of the joints is verified by analytical and experimental studies. Analytical formulation of the asymptote of size effect law is anchored at the large size limit by LEFM (linear elastic fracture mechanics) solutions with complex singularity. A general approximate size effect law, spanning all sizes, is further derived via asymptotic matching. The experimental studies involve testing of geometrically similar specimens with size ratio of 1:4:12. The analytical, numerical and experimental studies all indicate that the strength of metal-composite joints exhibits a strong size effect.