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Creep of Epoxy-Clay Nanocomposite at the FRP Interface



Creep of epoxy at the fiber reinforced polymer (FRP) interface can result in offloading of the FRP and inefficient structural strengthening. When the FRP strengthened structure is subjected to sustained loads, creep of epoxy shall be carefully considered and controlled. This paper examines the possible control of creep of epoxy at the FRP interface using nanoclay. In this paper, creep behavior of epoxy-clay nanocomposite at the FRP-steel interface was experimentally measured using double lap shear test. The test involved loading two carbon fibers reinforced polymers laminates (CFRP) bonded to two sides of steel blocks using epoxy under sustained loads and measuring shear creep. The significance of nanoclay loadings of 4% and 10% by weight of epoxy resin on creep behavior at the epoxy-FRP interface was measured. The experiments showed nanoclay loading to have a significant effect on epoxy creep at the FRP-steel interface. A threshold of nanoclay content beyond which nanoclay can limit epoxy creep seems to exist. Microstructure characterization tests were performed to explain the observed effect of nanoclay on creep of epoxy at the FRP interface. Transmission electron microscope (TEM), X-ray diffraction analysis (XRD), 29Si nuclear magnetic resonance (29Si-NMR) and differential scanning calorimetry (DSC) measurements were performed. These measurements showed that nanoclay intercalation rather than exfoliation is necessary to control epoxy creep.

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