Thermomechanical Fatigue of Unidirectional Carbon Fiber/Epoxy Composite in Space

Ali Anvari

doi:10.1155/2020/9702957

Abstract

Thermomechanical fatigue is one of the challenges for spacecrafts during space missions. As a result of the extreme temperature variation in space, thermal cycles are created, and due to the imposed mechanical loads to spacecrafts such as engine loads while they turn on and off, mechanical cycles are created. The worst structural fatigue for spacecrafts occurs when both thermal and mechanical cycles happen, simultaneously. The reason is that both thermal and mechanical cycles could cause stress concentration in the spacecraft structure. Therefore, the probability of crack initiation or propagation in the spacecraft structure increases. In this study, for the first time, novel thermomechanical fatigue relations are introduced to evaluate the safety of unidirectional carbon fiber/epoxy composite in the space environment. This composite material has been used in the spacecraft structure due to its lightweight and high strength. Furthermore, with applying thermal fatigue relations, thermally-safe planets, moons, and asteroids in the solar system for unidirectional carbon fiber/epoxy composite are identified.

Highlights

Unidirectional Carbon Fiber-Reinforced Epoxy (UD CFRE) has been used in many applications such as aerospace, automotive, sporting goods, and ships
One of the failure modes of UD CFRE is due to the thermomechanical fatigue in the space environment. erefore, the effect of thermomechanical fatigue on the mechanical behavior of this material is under extensive study [2]
Design processes have shown that fatigue properties are important characteristics of engineering materials. e reason is the statistics which has indicated that fatigue failures are over 90% of all the failures. e experiments have shown that, at temperatures higher than 100°C, fatigue strength of CFRE decreases significantly. e reduction in the fatigue strength of CFRE is due to the induced defects which causes high stress concentration [6]

Summary

Introduction

Unidirectional Carbon Fiber-Reinforced Epoxy (UD CFRE) has been used in many applications such as aerospace, automotive, sporting goods, and ships. UD CFRE composites have been used in space application due to their best mechanical properties such as low weight and high strength. Since the birth of CFRE, many studies have been provided to evaluate the mechanical properties, failure, and fatigue of this composite [7,8,9,10,11,12,13]. Among these studies, “significance of defects in the fatigue failure of carbon fiber-reinforced plastics” is submitted by Prakash [7]. While thermal and mechanical cycles happen at the same time, the stress concentration which is induced in the structure and the probability of crack initiation and/or propagation in the structure could be higher than when only thermal or mechanical cycle occurs. erefore, an exact analysis to evaluate the thermomechanical fatigue in space missions is required. us, in this study, thermomechanical fatigue of UD CFRE is evaluated

Problem Formulation

Future Work

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Discussion

Conclusions