Mechanical Properties of Epoxy/Clay Composite Coatings on an X65 Steel Substrate

Abstract

This paper presents the results of a combined experimental and theoretical study of the interfacial and mechanical properties of epoxy/clay composites coatings on a mild steel substrate. This was studied using nano-indentation and Brazil Disk techniques to determine the Young's moduli, hardness values and mode mixity characteristics of the composite coatings. The Young's moduli of the reinforced composites comprising 1, 3, and 5 wt. % of montmorillonite clay particles are shown to improve, respectively, by about 23%, 58%, and 50% while the respective hardness values increased by about 46%, 80%, and 88%, relative to those of pristine epoxy. The measured mechanical properties have also shown to compare favorably with predictions from composite theories (rule-of-mixture and shear lag theories). The interfacial toughness between X65 steel and the epoxy/clay coatings increases with increasing mode mixity. This is associated with crack-tip shielding by crack deflection and crack bridging. The trends in the measured mode-mixity dependence of the interfacial fracture toughness values are consistent with predictions from the simplified zone, normal zone, and row models (at lower mode mixity). The insights from the observations and the measured crack profiles are incorporated into zone and row models for the estimation of crack-tip shielding. The implications of the ABOUT THE AUTHOR Ngasoh Fayen Odette obtained a Bachelor degree in Chemistry and Materials Science from the University of Buea, Cameroon in 2010. She also received her M.Sc in Materials Science and Engineering from the African University of Science and Technology (AUST) in Abuja, Nigeria in 2013. She is actively involved in the research and design of composites using promising materials locally source. She also extensively evaluates the adhesion of such coatings to substrates using fracture mechanic approach such as the interfacial fracture studies, for better understanding of their underlying properties. She is certain that findings from her work will benefit a wide range of research.

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