Detection of interface flaws in Concrete-FRP composite structures using linear and nonlinear ultrasonics based techniques

Saptarshi Sasmal; Sukanya Basu; Chunduri V V Himakar; Tribikram Kundu

doi:10.1016/j.ultras.2023.107007

Detection of interface flaws in Concrete-FRP composite structures using linear and nonlinear ultrasonics based techniques

Ultrasonics. 2023 Jul:132:107007. doi: 10.1016/j.ultras.2023.107007. Epub 2023 Apr 8.

Authors

Saptarshi Sasmal¹, Sukanya Basu², Chunduri V V Himakar³, Tribikram Kundu⁴

Affiliations

¹ Special and Multi-functional Structures Laboratory, CSIR-Structural Engineering Research Centre, India; Academy of Scientific and Innovative Research, Ghaziabad-201002, India. Electronic address: saptarshi@serc.res.in.
² Special and Multi-functional Structures Laboratory, CSIR-Structural Engineering Research Centre, India; Academy of Scientific and Innovative Research, Ghaziabad-201002, India.
³ Post Graduate Project Student, CSIR-Structural Engineering Research Centre, Chennai, India.
⁴ Civil and Architectural Engineering and Mechanics, The University of Arizona, Tucson, AZ 85721, USA.

PMID: 37121183
DOI: 10.1016/j.ultras.2023.107007

Abstract

Timely and appropriate retrofitting of existing structures holds paramount importance to ensure the structural integrity and sustainability. Fiber Reinforced Polymer (FRP) composites with high corrosion resistance, strength and durability, have been increasingly used in recent years for retrofitting of concrete infrastructure. The effectiveness of retrofitting is primarily dependent on the appropriate integrity at the interface between FRP and concrete substrate. Presence of any interface flaw can jeopardize the structural performance. In the present study, investigations are carried out to detect the early stage flaws at the FRP-concrete interface using ultrasonic waves. Artificial flaws of different size are introduced in the adhesive (epoxy) layer of carbon based FRP composite concrete beam. Rayleigh waves (at different frequencies) are generated for measuring the response from different FRP composite-concrete specimens. The specimens consist of three different types of materials, namely, concrete, epoxy and FRP. Two different input excitation frequencies, i.e., 75 KHz and 250 KHz, are tried out during the experimental investigations. The output signals are processed using different linear and nonlinear ultrasonic methods. Numerical simulations are also performed to better understand the wave signals' interactions with the multi-layer composite medium. The results showed that the linear ultrasonic methods are not able to provide a consistent information on presence and extent of flaws. Nonlinear ultrasonic methods showed significantly better performance for characterizing both small and large flaws considered in this investigation. Sensitivity analysis reveals that relatively new and promising nonlinear ultrasonic technique, namely, the Sideband Peak Count-Index (SPC-I) performs remarkably well for detection of flaws in FRP-concrete interface.

Keywords: Energy distribution; Interfacial flaw; Nonlinear ultrasound; Sensitivity; Sideband peak count-index (SPC-I).