Failure Mechanism of Empty and Concrete-Filled CFRP Box Beams

Abstract

This paper highlights the failure mechanism of beams composed of carbon fiber-reinforced polymer (CFRP) box with and without infill concrete, and subjected to four point bending and axial load. In an experimental study performed with 20 small scale beams from five types of CFRP laminates, the beams failed near a loading plate. This study employs finite-element analysis to investigate the failure mechanism. Concrete is modeled as an isotropic material capable of cracking in tension and crushing in compression. CFRP is modeled as an orthotropic material with linear constitutive relation, and Tsai-Wu failure criterion is employed for CFRP. The analysis reproduces the observed beam failure. Local bending of top flange governs the failure of empty beams. CFRP failure near loading plate governs the failure of filled beams. Failure of CFRP occurs with more than 60% contribution by longitudinal compressive stress and the rest by in-plane shear stress. The contribution of the longitudinal compression increases with an increase in axial load. Moreover, the beams with more fibers in the transverse direction fail by longitudinal compression.