The paper analyzes the influence of prestressing force on the natural frequencies on Glass Fibre Reinforced Polymer (GFRP) composite beams. Prestress is introduced by applying initial tensile forces to the fibres embedded in selected layer of the composite material during the manufacturing process. Release of prestressing forces results in deformation and self-equilibrated state of stress of the entire composite which changes both its static properties and dynamic characteristics. The paper is focused on analysis of shifts in natural frequencies corresponding to initial bending modes of the composite beams of various fibre volume fraction and prestressed layer location. The problem is analyzed with the use of finite element simulations and experimental modal analysis. The conducted numerical and experimental work reveals that shifts in the natural frequencies caused by non-axial prestressing can be significant and they are important phenomenon which has to be taken into account during design of the composite material.
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