Mixed Mode I/II Fracture Performance and Mode Mixity of GFRP‐Balsa Interfaces in Sandwich Structures

This study focuses on lightweight balsa‐core composite sandwich structures suitable for engineering applications and investigates the interface peeling performance of glass fiber reinforced polymer and balsa wood sandwich beams through single‐leg bending beam tests. The mixed Mode I/II interface peeling process and failure mode of the sandwich beams were characterized. The mechanism of the interface peeling failure under static loads was analyzed. The influence of span‐to‐depth ratio, number of face sheet layers, fiber laying angle, and processing method on interface peeling performance was summarized. The strain energy release rate for mixed Mode I/II fracture was calculated using classical plate theory and an energy‐based method. Based on the elastic foundation beam theory, the Mode I strain energy release rate was derived, and the mode mixity was determined by decomposing the total mixed‐mode energy release rate.