Effects of Increased Solar Ultraviolet Radiation on Materials

Increased use of fiber reinforced polyester composites in outdoor environments raises questions about environmental durability of these materials, particularly those related to ultraviolet (UV) exposure. In this study, the effect of ultraviolet irradiation on the mechanical properties of glass / polyester composites was investigated. The study focused on the nature of the resin, since photolysis is a surface mechanism, limited to degradation of the mechanical properties of the resin (fibers do not deteriorate). For this purpose, test samples consisting of polyester resin were prepared and processed in the UV chamber by accelerated testing. Three kinds of samples were manufactured. Tensile test samples were prepared according to the ASTM D 638 standard with a nominal thickness of 1 mm. In addition, an alkane sample for the shear test and ASTM D 3410 for the compression test were prepared. In order to obtain the time-dependent mechanical properties of the polyester resin under ultraviolet light, the sample was irradiated at three different time intervals (corresponding to 3 months, 6 months and 12 months) using an artificial UV irradiation chamber. Testing the sample under tensile load showed a maximum strain reduction of maximum 15%, a maximum strength reduction of maximum 30%, and a decrease in tensile elastic modulus of 18% after 100 hr exposure. In addition, significant changes in the shear modulus and strength of the polyester are taken into account. The effect of UV absorber (UVA) on the prevention of mechanical properties of polyester was also investigated. The results show that samples containing UVA additives do not deteriorate after UV irradiation.

After obtaining the properties of the substrate by exposure, the mechanical properties of the glass / polyester composite under ultraviolet light were simulated using micromechanical theory. The simulation results were verified by tensile testing of the ASTM D 3039 [0/90] glass / polyester laminate composite sample. The results show that the shear modulus of the laminate decreases by about 20% due to UV exposure.

Ultraviolet absorbers are used as additives to eliminate the damaging effects of ultraviolet radiation, such as hindered amine light stabilizers (HALS), for use in plastics exposed to intense sunlight ultraviolet radiation. Experimental data on certain resins weathered in the desert climate shows that the use of these additives is effective in preventing polymer degradation due to UV damage. However, due to its limited capacity, degradation of these additives by ultraviolet light remains unclear. In recent years, research has focused on understanding the impact of environmental factors on laminated composites, as composite laminates are used outdoors for many structural applications.

Sunlight, also called sunlight, is a type of radiation that emanates from the sun. Radiation is a part of the electromagnetic spectrum including infrared, visible light, and ultraviolet light. The sunlight incident on the surface of the earth is filtered through the atmosphere and some of the ultraviolet rays are absorbed. In addition to providing light to the earth, sunlight can also function as a radiant heat source to warm the planet. Ionizing radiation is a specific type of radiation having sufficient energy to emit electrons from an atom. Radiation includes ionized particles from alpha or beta decay and electromagnetic waves in the form of gamma radiation. Generally, the energy of alpha and beta decay particles and gamma ray photons is higher than the ionization energy of atoms and molecules. These particles ionize substances to break molecular bonds, which can lead to serious biological damage.

Electromagnetic radiation such as infrared, ultraviolet, x-rays, and gamma rays refers to the spectrum split according to the way each type of radiation interacts with the substance. Radio waves vibrate within the material, near infrared vibrates at the molecular level, ultraviolet rays show excited electrons, x-rays emit core electrons, and gamma rays collide with the substance to produce particles and anti-particle pairs. Antiparticles have the same mass, spin, average lifetime and physical appearance as regular corresponding particles, but their charges have opposite values. Although the radiation type classification scheme is neat and neat, the characteristics between adjacent types of electromagnetic radiation slightly overlap.