Mechanics and fracture of hybrid material interface bond

Considering current and future applications of hybrid materials and structures in civil engineering, the strength and durability of interface bond between the conventional materials and composites are critical to development of such products. Conventional methods mostly used for analysis of isotropic materials may not be well suitable or accurate enough for a system made of anisotropic materials with relatively low shear stiffness. A need exists for developing more accurate and explicit analytical solutions for hybrid material interface analysis and related novel experimental characterization techniques.; In this study, a combined analytical and experimental approach to characterize hybrid material interface bond is developed. Using a shear deformable plate theory and an elastic interface model, a mechanics approach for interface analysis of hybrid material bond under general loading is first proposed. The resulting closed-form solution of interface stress distribution is used to compute strain energy release rate (SERB) and stress intensity factor (SIF) of the interface with or without adhesive bond. This approach is then extended to delamination of composite structures under generic loading conditions.; Second, novel experimental approaches for characterization of hybrid material bonded interfaces are presented. To account for the crack tip deformations, a tapered beam on elastic foundation (TBEF) is developed. Based on the TBEF model, analysis and design of two novel fracture specimens, Tapered Double Cantilever Beam (TDCB) and Tapered End Notched Flexure (TENF), are proposed, and they are effectively used in fracture toughness tests of bonded interface under Mode-I and Mode-II loadings, respectively. A constant compliance rate change over certain crack length range is achieved for the TDCB and TENF specimens, and it alleviates the necessity of experimental compliance calibration tests. The fracture toughness data obtained from the experiments are useful to predict potential crack growth of adhesively bonded joints.; In summary, a comprehensive study of mechanics and fracture of hybrid material interface bond is presented. The shear deformable-based mechanics and fracture model developed can be effectively and accurately used to predict the SERR and SIF of hybrid material interface bond, and the analysis and design of novel TDCB and TENF specimens provide useful and efficient techniques to experimentally characterize the hybrid material bonded interfaces.