Effect of different aging conditions on the shear performance of joints made between GFRP and glass with a UV absorbance coating

In this experimental study, a series of tensile tests were conducted on double-lap specimens, where UV absorbance laminated glass was adhesively bonded on GFRP polyester pultruded support. Three different types of adhesives were compared, two epoxy and one polyurethane, and both un-aged and aged conditions were investigated. Three ageing conditions, simulating the external environment exposure, were investigated, i.e. temperature/moisture changes (continuous condensation), UV exposure, temperature/moisture changes and UV exposure, in order to test the effectiveness of the UV absorbance film and the durability of the bonding system. This experimental campaign aims to verify if the UV film affects the compatibility of the bonding system between GFRP and glass to be used for structural applications. The experiments showed that the PU adhesive is not the most suitable for structural applications, since it shows a great deformability of the joint with a very small stiffness, if compared with the epoxy ones. With regard to artificial aging, the experiments showed that aging has a different impact on different types of adhesives; in particular a slight effect on the mechanical performances or sensitive reduction of the load carrying capacity and of the joint elongation were observed. In general the continuous condensation produced the worst effects on the specimens, while better results were observed after the UV radiations, even though the beneficial effect of the UV rays, which improve the mechanical behavior of the joint for a further polymerization of the adhesive, are impeded by the UV absorbance film.