Investigation of mechanical characteristics of braided carbon fiber

The use of composite materials in various branches of modern industry is rapidly increasing due to their high strength properties, low weight and good manufacturability. A wide variety of materials used, types of reinforcement and internal structures creates a need for studies of the static and dynamic properties of composite materials. Due to the latest advances in technology, composite materials are widely used in a variety of industrial applications. As a result, there is considerable interest in studying and understanding the behavior of composite structures. Analysis of composite structures, study of resonance frequencies, damping factors and modal shapes played an important role in determining the dynamic characteristics of the structure, detecting damage and monitoring the state of the composite structure. In this paper, the results of computational and experimental researches of the Young’s modulus, natural frequencies and modes of vibration, damping properties of the composite material are presented. The researches were carried out on samples of the woven ten-layer carbon fiber reinforced plastic. The investigated carbon fiber reinforced plastic has a plain weave. Samples were cut in three directions: warp (0 °), weft (90 °) and 45 °. Nine samples were prepared for each direction. To study the Young’s modulus, a tensile testing machine was used, and a vibration stand was used to determine the natural frequencies and modes of vibration. Damping properties are calculated by the Oberst method, based on the amplitude-frequency characteristics of the samples. Statistical processing of the experimental results was carried out and the values ​​of the mathematical expectation and variance were obtained. Geometric and finite element models of сarbon fiber reinforced plastic samples were built, their natural frequencies and vibration modes were determined. Comparison of the computational and experimental data with numerous calculations using the finite element method is carried out.

Damping Properties of Hybrid Composites Made from Carbon, Vectran, Aramid and Cellulose Fibers

Hybridization of carbon fiber composites can increase the material damping of composite parts. However, there is little research on a direct comparison of different fiber materials—particularly for carbon fiber intraply-hybrid composites. Hence, the mechanical- and damping properties of different carbon fiber intraply hybrids are analyzed in this paper. Quasi unidirectional fabrics made of carbon, aramid, Vectran and cellulose fibers are produced, and their mechanical properties are analyzed. The material tests show an increased material damping due to the use of Vectran and aramid fibers, with a simultaneous reduction in strength and stiffness.