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The aim of this study is to determine the effect of environmental factors in
the form of UV radiation and temperature on the amplitude-frequency behaviour of
polymer composites (prepregs) based on a framework of thermosetting epoxy resin
reinforced with high-strength R-glass fibres. Two series of composites with different
fibre arrangements were prepared. The series had fibres arranged at angles of 30°,
45°, and 60°, at symmetric and asymmetric orientations in relation to the central
layer. The composites were subjected to conditioning which simulated a six-month
period of use in the spring and summer in the temperate warm transitional climate
of Central and Eastern Europe. An UV QUV/SPRAY/RP accelerated aging chamber
manufactured by Q - Lab Corporation was used for this purpose, and UV-A 340 lamps
were used to simulate daylight. In addition, varying loads caused by sudden
temperature changes were simulated using the Thermal Shock Chamber T/60/V2
Weisstechnik. Conditioned samples were tested using a TIRAvib 50101
electromagnetic exciter in combination with an LMS Scadias III controller and
Test.Lab software. The results of the tests, in the form of amplitude-frequency
diagrams in resonance regions, indicated that certain changes occurred as a result of
the conditioning, which is a new development in the area of material tests. The
results shed light on the effects of environmental conditions on the stiffness
characteristics of composites, causing dynamic nonlinearities when operating at
resonant frequencies
