Degradation due to exposure to ultraviolet (UV) radiation is an important durability challenge with glass fiber reinforced polymer (GFRP) composite. Design and construction guidelines of GFRP suggest using UV protection paint to prevent GFRP degradation. In this study we examine the possible use of multi-walled carbon nanotubes (MWCNTs) dispersed in epoxy matrix to produce UV-resistant GFRP composite. We suggest that MWCNTs can result in a significant improvement to UV degradation resistance in the GFRP. Direct tension tests of GFRP coupons incorporating 0.25 wt%, 0.50 wt%, and 1.0 wt% of MWCNTs show inherent stability and good resistance to UV degradation. Microstructural analysis shows the ability of MWCNTs to resist polymer backbone disassociation caused by UV radiation thus preventing UV degradation in GFRP. Scanning electron microscopy (SEM) images show MWCNTs can resist microcracking caused by UV radiation and thus improve UV degradation resistance of GFRP.

Introduction

Glass fiber reinforced polymers (GFRP) composite represents an excellent material alternative for reinforcing and strengthening reinforced concrete structures because of its high strength-toweight ratio, long-term corrosion resistance, relatively low cost and ease of installation [1]. New manufacturing methods, like pultrusion and filament winding, have made it possible to use GFRP sections as frame and truss elements in FRP structures. GFRP is also used in windmill blades, airplanes and other industrial applications. GFRP is made by reinforcing polymer matrix (typically epoxy, polyester or vinyl ester) with continuous glass fibers. In this composite, the polymer matrix is the weak link and is susceptible to changes in physical properties [2]. When used in construction applications, GFRP bars and sections are prone to different types of environmental exposures including temperature, humidity, and ultraviolet (UV) radiation. It is well documented that GFRP has low resistance to UV radiation [3–۶]. UV radiation experienced by the Earth’s surface has a wavelength range of 290–۴۰۰ nm, which lies within the intensity known to cause bond disassociation in polymers [6,7]. The surface of the polymer degrades because of the photo-initiated oxidation that takes place due to UV exposure. This oxidation breaks the skeletal bonds in the polymers making an adverse impact on its stiffness and strength [6,8].