Investigation of Bond between Fiber Reinforced Polymer and Concrete Undergoing Global Mixed Mode I/II Loading

Abstract

A novel experimental method using modified double cantilever beam specimens and a customized test frame are introduced to evaluate bond characteristics and toughness of fiber reinforced polymer (FRP) composite overlays and a concrete substrate under mixed mode loading. A computer vision system is used to measure the crack location, near-tip deformations and crack opening displacement during the crack growth process. Digital image correlation is used to determine the crack opening displacement (COD) for flaws growing in the vicinity of the FRP–concrete interface. Results from this study indicate that during crack growth, (1) the Mode I component of COD is dominant for all angles of specimen loading, (2), the magnitude of the local Mode I component of COD is maximized when good bond quality is present and crack extension occurs within the mortar/concrete near the FRP–concrete interface and (3) good agreement exists between independent energy release rate estimates based upon both an approximate elastic double cantilever beam formulation and also use of the measured components of COD in a classical linear elastic expression.