Abstract
Constructions based on long fiber composite frames gaining significant and irreplaceable position through almost all traffic sectors. The aim of this presented work is a study of composite rods made by two ways from pre impregnated fibres. In technical practice, one can find applications of so called “prepregs”, especially for so-called wrapping, which is a gradual helical layering of wide tapes. This is a quite simply method with a good quality of final parts, but the using is limited only for straight shapes. Therefore, a method called winding, which is a simultaneous deposition of larger number of fiber filaments was used to handle the problem for curved shapes and fluently changed cross-sections. Even though this method could expand the using of presaturated fibres, in a real case compared with wrapped parts there is evident imperfect alignment and mutually storing of placed fibers. This could be mainly caused by a significant tortuosity and stickiness of the individual fiber strands. The objective the carried work was to experimentally compare the vibrational - modal behavior of two almost identical rods. One was winded and the second kind was wrapped with the same structure of layers, weight and curing parameters. The results of the two compared tubes, that should be theoretically identical, were significantly different. Another step was compilation of a numerical model and verify its suitability for parts created with the two mentioned production methods. The numerical model was in a good agreement with the empirical obtained from the experiment with wrapped parts. However, the using of this standard model also for winded tube is questionable, because of the significantly differences in founded natural frequencies.
Highlights
In recent years using of composite materials is still exponentially growing, thanks to the excellent specific strength, possibilities of customize the properties and achievable weight savings
Methods based on epicyclic winding or helical wrapping are generally used for manufacturing of thin-walled composite parts with circular or oval profiles
The damping in composites involves a variety of energy dissipation mechanisms that depend on vibrational parameters such as frequency and amplitude and these are studied with nondestructive evaluation [7]
Summary
In recent years using of composite materials is still exponentially growing, thanks to the excellent specific strength, possibilities of customize the properties and achievable weight savings. Methods based on epicyclic winding or helical wrapping are generally used for manufacturing of thin-walled composite parts with circular or oval profiles. Those methods are usually used for so-called "wet" form, when bundle of dry placed fibers are impregnated with resin subsequently. It is necessary to create parts shaped, dissected and 3-D curved For this purpose, so-called winding technology in unconventional combination with prepreg materials is used (Fig. 2). -called winding technology in unconventional combination with prepreg materials is used (Fig. 2) This is a process when instead of one wide tape, are around the core placed thin tapes from several coils simultaneously. Typical forced vibration techniques include the free-free beam technique and the piezoelectric ultrasonic composite oscillator technique [9]
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