Characteristic comparison of wound and wrapped composite tubes made from carbon prepreg using modal analysis

Abstract

The lightweight constructions are nowadays often based on composite materials. The best benefits are possible to obtain especially with a dispersion in the form of long fibres. In this study, the main properties of two almost identical composite rods manufactured from preimpregnated carbon fibres using two different methods will be compared. The first one is called “wrapping” which is helical layering of one wide tape in each ply. The main benefit of this method is good quality of final parts, but we are limited only by straight shapes. The second way “winding”, it is simultaneous deposition of several thinner fiber filaments. This method could handle the problem of curved shapes and fluently variable cross-sections. The disadvantage of this method is imperfect alignment of the placed fibers. This could be caused by a significant tortuosity and stickiness of the individual fiber strands. The goal of the carried work was to experimentally compare the vibrational transfer of these two almost identical rods with the same structure of layers, weight and curing parameters. Based on the certified properties of the base fibres and known boundary conditions, the material model and simulation of the vibrational response was created. The results of the empirical model compared with the experimental on the wrapped part were in good agreement. However, the use of this model also for the wound tubes is questionable, because of the found differences in natural frequencies and a shape of the transfer function. As part of the analytical study also the sensitivity analysis on the mesh quality has been done. As the conclusion is possible to say, that for determination of the main modes the mesh in a solved model could be just standard – it means without visible defects. Changes in the results achieved by improving the mesh quality are just really small. The more significant problem is that with using the contemporary knowledge and methods, it is not possible to simply create analytical model of the wound parts. The only option is trying to adjust the mechanical properties of base materials according to the empirical results.