Environmental degradation and mechanical behavior of glass fiber reinforced polymer nanocomposites used in offshore applications

Abstract

Present study aims at the variation of mechanical properties of glass fiber/epoxy composite under the effect of temperature, alkalinity, and rate of loading. Glass fiber reinforced polymer (GFRP) with plain epoxy and GFRP with 1–2% variation of Nanoclay were utilized for experimentation. Flexural testing of specimen at optimum percentage of Nanoclay in GFRP and epoxy was performed and after that pre-stretching of GFRP with plain epoxy and GFRP with optimum percentage of Nanoclay was conducted. Combined effect of moisture, alkali, and temperature on the degradation behavior of glass fiber reinforced polymers in different environments was studied. The macroscopic and microscopic behavior of the GFRP composite specimen and pure epoxy and Nanoclay reinforced epoxy exposed to varying hygrothermal loads has also been analyzed. Scanning electron microscope (SEM) was used to study the microscopic behavior of GFRP composites. X-Ray diffraction analysis of epoxy with 1%, 2%, and 3% Nanoclay addition was also performed. Tensile and flexural testing of specimen at different orientations such as 0°, 30°, 45°, 60°, and 90° were also studied. At 0° orientation, maximum average flexural strength of 295.04 MPa and 481.69 MPa was observed for plain glass fiber reinforced polymer and 2% Nanoclay/glass fiber reinforced polymer before hygrothermal loading. At 20% and 50% loading conditions the maximum flexural strength of 46.7 MPa for plain glass fiber reinforced polymer and 147.52 MPa for 2% Nanoclay/glass fiber reinforced polymer was observed before hygrothermal conditions. Maximum degradation in tensile strength (384.78 MPa at 50% loading) for 2% Nanoclay/glass fiber reinforced polymer after hygrothermal loading was observed in NaCl environment. Lower tensile strength observed for 1% of Nanoclay addition in pure epoxy as compared to the 0% and 2% mixing. There is decrease in tensile strength for specimen with 2% of Nanoclay in pure epoxy as compared to the 0% and 1% mixing. Tensile strength changed by moisture as well as mechanical loading of the glass composites. There is lesser degradation and significant increase in tensile strength of glass fiber reinforced polymer nanocomposite was observed when it exposed for lesser time period while tensile strength significantly reduced when specimen was exposed for longer time (3000 hr). After degradation in four different environments (four tanks) for 30 days intervals, SEM analysis of glass fiber reinforced polymer nanocomposite at pre-stretching of 20% and 50% loading was observed. At 20% loading there is lesser damage of glass fiber reinforced polymer nanocomposite with the formation of small irregular lumps were observed while at 50% loading there is significant damage of glass fiber reinforced polymer nanocomposite with the formation of voids of epoxy was clearly observed during SEM analysis.