Study of bending of triangular cross-section carbon fiber beams


Аuthors

Glazjuk Y. V.1, Demidov A. S.2*, Kashelkin V. V.1**

1. Dollezhal Research and Design Institute of Power Engineering, Moscow, Russia, Malaya Krasnoselskaya ul. 2/8, 107140
2. Moscow Aviation Institute (National Research University), 4, Volokolamskoe shosse, Moscow, А-80, GSP-3, 125993, Russia

*e-mail: demidov@mai.ru
**e-mail: re.entry@g23.relcom.ru

Abstract

The spaceships, which are expected to fly over the next decades, include large structural assemblies. The largest of them is a refrigerator-radiator, which length may exceed one hundred meters. Its load-bearing base should be a frame made of beams of various cross-sections: round, box-shaped and triangular. At present, carbon-based structural materials are considered the most suitable for the beams manufacturing. They demonstrate high mechanical, acceptable technological properties and they are of low density as well. The carbon-based materials specificity is that they exhibit various properties under tension and compression. Such materials are commonly referred to as multi-modular. Obviously, the difference in modularity manifests itself while bending as well. The article considers the stress state of bent solid and thin-walled beams of triangular cross-section. It leads to certain difficulties at stress computing, since the neutral section line position while bending depends on the ratio of Young modules under tension and compression. The problem under consideration is being solved in the article by the analytical method. The cross-section of the bent beam is being divided into two zones by a neutral line. Tension stresses are acting in one of the zones, while compression stresses are acting in the other one. An equilibrium equation is drawn up and formulas for the operating stresses computing are derived. Structurally, the article is divided into five parts and consists of an introduction, analysis of stresses in a bent beam of solid triangular section, the same analysis of a beam of thin-walled triangular section, examples of computing and conclusions. When analyzing the stress state, the K function is used, depending on the ratio of Young's modules for tension and compression, on the shape and size of the beam section, as well as on the neutral line position. The article presents formulas for determining maximum stresses in the cross sections. It includes five figures depicting the view of the refrigerator-radiator section, cross sections of solid and thin-walled beams, graphs of K functions for such beams. The examples include comparative results obtained with and without account for the actual position of the neutral line in the beam section. Conclusions present recommendations on the requirement to account for the difference in modularity of carbon-based materials, which may be useful in engineering practice.

Keywords:

power frame, triangular section beam, carbon fiber, bending, stress state, mechanical properties of carbon fiber

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