Mechanics Of Bimaterial Interface Beams And Its Application To Fracture Of FRP-concrete Bonded Interfaces

With recent development and application of composite materials and structures in civil engineering, the analysis of fracture mechanisms of interface bond between the conventional materials and composites has received a lot of interest.Split beam type of fracture specimens is commonly used in the delamination evaluation of laminated composites. In this study, based on the conventional composite beam theory, shear deformable bi-layer beam theory and interface deformable multi-layer beam theory, three different joint deformation models (i.e., the rigid joint model, semi-rigid joint model, multi-sub-layer flexible joint model) are first presented. Due to different considerations of the interface displacement compatibility in each sub-layer beam, these joint models show three distinct levels of accuracy in predicting the crack tip deformation. As a validation, an Four-point Bending End-Notched Flexure FRP-concrete beam specimen (4ENF) tapered by aluminum is examined by three joint models; the interface stress, beam deformation and energy release rate (ERR) of 4ENF are derived in this study in the new light of the crack tip deformation as well as the numerical finite element analysis. It is shown that the rigid joint model is the most approximate due to neglecting the crack tip deformation, the semi-rigid model provides better solutions due to partially inclusion of the joint deformation, and the multi-sub-layer flexible joint model is the most accurate because of the fully consideration of the crack tip deformation. The effect of accuracy of the models also indicates the contribution of joint (crack tip) deformation on delamination specimen analysis.Second, a 4ENF beam on two-parameter elastic foundation model (BEF), which incorporates the effect of the crack tip deformation on compliance, is developed to analyze the 4ENF specimen for mode II fracture of bi-material bonding interface. A linear relationship between average compliance and crack length within a certain crack range is obtained for the 4ENF specimen. The accuracy of this model and the linearity of the average compliance-crack length...