MIXED-MODE FRACTURE-ANALYSIS AND TOUGHNESS OF ADHESIVE JOINTS

A Compact Mixed Mode (CMM) fracture specimen was developed for fractur e toughness determination. It is capable of determining the complete r ange of fracture toughness under pure mode I, pure mode II and mixed m ode I and II loading conditions. Finite element analysis was conducted to provide calibration factors for the stress intensity factor soluti on for the Compact Mixed Mode (CMM) specimen. The finite element resul t, provided empirical correction factors beta(1) for the pure mode I c ase and beta(II) for the pure mode II case which intrinsically take ac count of the substrate-to-adhesive mechanical properties of the test s pecimen. A range of pure mode I, pure mode II and combinations of mode I and II fracture load cases were investigated using the Compact Mixe d Mode (CMM) fracture specimen. With the test results, a failure asses sment diagram for mixed mode fracture toughness was proposed and compa red to theoretical concepts of mixed mode fracture criteria.