Effects of Ultraviolet Radiation on Mechanical Properties of Glass/Polyester Composites

Abstract

The increased use of fiber-reinforced polyester composites in an outdoor environment has led to questions concerning the environmental durability of these materials, particularly as related to ultraviolet (UV) exposure. In this research the effects of UV radiation on mechanical properties of glass/polyester composites were studied. Since the photo degradation is a surface mechanism and is restricted to degradation of mechanical properties of resin (fiber is not degraded), this research is focused on resin properties. For this reason, test samples made of polyester resin were prepared and treated in a UV chamber through accelerated tests. Three types of specimen were manufactured. The tensile testing samples were prepared based on ASTM D638 standard with a nominal thickness of 1 mm. Also, Arcan specimens for shear tests and ASTM D3410 for compression tests were manufactured. To obtain time dependent mechanical properties of polyester resin under UV radiation, samples were radiated in three different time intervals, equivalent to 3, 6 and 12 months, using an artificial UV exposure chamber. Test specimens were tested under tension load and showed a decrease of up to 15% in average failure strain, a decrease of up to 30% in ultimate strength, and 18% decrease in tensile modulus after 100 h exposure. Also, significant changes were considered in shear modulus and strength of polyester. The effect of ultraviolet absorbers (UVA) on preventing polyester mechanical properties degradation is also studied. The results showed that the samples which have UVA additives were not degraded after UV exposure. After obtaining matrix properties due to exposure, mechanical properties of unidirectional laminate of glass/polyester composites under UV radiation were simulated using micromechanics theories. The results of simulation were validated with tensile testing of ASTM D3039 specimens of [0/90]s glass/polyester laminated composites. The results show that shear modulus of this laminate decreased about 20% due to UV exposure.

On erosion issues associated with the leading edge of wind turbine blades

“…The potential effects of UV exposure on the performance of the coating systems was shown in figure 5, however the composite substrate is also based on polymer materials and therefore is also susceptible to the influence of UV exposure. Shokrieh & Bayat [34] showed that through accelerated UV exposure, polyester resin exhibited a decrease of 15% in average failure strain, a decrease of 30% in ultimate strength and an 18% decrease in tensile modulus. When considering a glass fiber reinforced polyester unidirectional composite, under the same exposure, it was found that the shear modulus of the composite decreased by about 20% as a result of such exposure.…”

Effect of UV-Radiation On Fatigue Behaviour of Natural Composite Materials

“…Then, both tensile strength, and shear resistance were experimentally studied for the composite at different UV-exposure time, results indicated more properties degradation is caused by longer exposure time. The fatigue life for epoxy reinforced with E-glass fiber composites was studied in [11]. The multi layers of fibers-epoxy composites was noticed to show degradation in fatigue life after exposed to UV radiation which claimed to the brittleness caused by losing the long chain bond between the fiber and epoxy which leads the micro structure surface crack to propagate through the layers reducing the expected material failure stress.…”

Effects of nano ZnO on strength and stability of unsaturated polyester composites

“…However, the environmental degradation of polymer materials limits their service life and more solid waste is produced which is difficult to recycle. [1][2][3][4][5][6] Some methods, such as surface coating, 12,13 surface film layer, 10,11 and antidegradation additives, [7][8][9] are used to impede the environmental degradation of thermosetting resins, and good results have been obtained to some extent, but there is a limitation in these methods. Organic additives are easy to lose and less effective for thermosetting resins.…”