۱- Introduction

۲- Formulation of bond behavior of CFRP-to-stainless steel

۳- Experimental test and calibration

۴- Test results and discussions

۵- Further parametric study and discussions of bond strength

۶- Conclusion

References

Abstract

Steel structures using stainless steel are recently accepted as more sustainable and durable systems. Although much research has been conducted on steel structures strengthened by carbon fiber-reinforcement polymer (CFRP) material, these steel structures are often made of conventional mild steel and thus existing prediction and analysis specified for mild steel cannot be directly extended for that of stainless steel. Therefore, this study aims to develop a new prediction model for determining the bond behavior of CFRP-to-stainless steel. Load time-history bond behavior was formulated in a piecewise manner to account for varying elastic, elastoplastic and debonding stages. A total of 22 stainless steel plates bonded with CFRP laminates were fabricated and tested to calibrate the model and further quantify the critical design parameters, including layers and anchorage length. Observation of the experiment showed that debonding failure between the adhesion layer and the CFRP sheets was dominant, partially suggesting the linear stress-strain relation for the CFRP and stainless steel. Comparison of results predicted by the proposed model to the test ones demonstrated that the proposed model has a high accuracy in prediction of bond stress and bond strength.

Introduction

In recent years, the stainless steel, due to its excellent ductility and superior resistance to corrosion, becomes emerging structural material as alternative for more sustainable and durable structures. Accordingly, some countries, including those in Europe and the United States, have developed the relevant design codes and specifications to the stainless steel [1–۳]. Similar to the traditional mild steel, the stainless-steel structures could be strengthened and retrofitted by the use of the CFRP composite sheets that have been widely accepted as effective materials in civil engineering structures [4–۹]. As identified [8,10–۱۹], the selection and proper design of the CFRP composites to a structure are highly associated with the performance of the interfacial bond between the CFRP and steel substrate, that is, CFRP-to-steel interface. Literature review reveals that most studies either through experimental tests or analytical modeling have been conducted particularly on the bond behavior between the CFRP material and steel. From experimental standpoint [10–۱۴], bond behavior was studied through the tests of adhesion strength of FRP to the mild steel components, for instance, Damatty and Abushagur [11] carried out the experiments involving shear lap testing of FRP sheets bonded to hollow steel sections to address the in-plane and out-of-plane behavior of the FRP sheets. Teng et al. [12] has presented an experimental study on the behavior of CFRP-to-steel bonded interfaces through testing of single-lap bonded joints. Nozaka [7] has analyzed and compared the stress distribution in the adhesive layer between a prototype repaired bridge girder and various specimens to determine an appropriate specimen and test setup for assessing the effective bond length of the adhesive. Zeng et al. [14] experimentally calibrated the mechanism of the debonding failure of CFRP strengthened H-section beams. Besides the mechanical properties, more recent studies have devoted to the longterm durability and various environmental conditions. Chandrathilaka et al. [15] presented their very recent study on bond behavior of the CFRP to steel under elevated temperature and discussed the impacts of the exposure of various temperature on bond curing. Yu et al. [16] reported the experimental study on long-term bond-slip behavior under coupled marine conditional and fatigue loading, and stated the bond reduction under laboratory accelerated durability tests. Other investigations [12,17–۲۴] were carried out on the analytical modeling of nonlinear interfacial stress, bond-slip relation, and debonding behavior. Wu et al.