Debonding of Carbon Fiber–Reinforced Polymer Patches from Cracked Steel Elements under Fatigue Loading

Abstract

This paper summarizes the details of a numerical and experimental research program that was conducted to study the debonding of carbon fiber–reinforced polymer (CFRP) patches from cracked steel members under fatigue loading. A preliminary numerical model was developed to investigate the influence of patch debonding on the fatigue life of cracked steel elements. Results indicated that altering the shape and increasing the size of the debonded region could change the calculated crack growth rate by up to 54 times. To validate the model, six steel edge–notched tension coupons were patched with CFRP materials and tested under fatigue loading, while full-field strain distributions were monitored using a digital image correlation (DIC)–based measurement system. Based on the experimental results the numerical model was refined to incorporate the interfacial traction-separation behavior. A parametric study was conducted using the refined numerical model. The results indicate that the size and shape of the debonded region, and therefore the fatigue crack propagation rate, are not only dependent on the fatigue detail and the crack length, but also on the maximum magnitude of the applied fatigue load and the properties of the bonded interface.