Abstract
Composite materials have been used increasingly for various space applications due to the favorable characteristic of high modulus to density ratio and potential for near-zero coefficient of thermal expansion. In composite system, depending on the orientation of fibers, strength and stiffness can be changed so that the optimum structure can be accomplished. This is because the coefficient of thermal expansion (CTE) of carbon fibers is negative. For spacecraft and orbiting space structure, which are thermally cycled by moving through the earth' shadow for at least 5 years, it is necessary to investigate the change of properties of the material over time. In this study, thermal aging of epoxy matrix/high modulus carbon fiber composite materials are accelerated to predict the long term creep property. Specimens are tested at various temperatures of 100~140�� with dynamic mechanical analysis to obtain creep compliances that are functions of time and temperature. Using Time Temperature Superposition method, creep compliance curves at each temperature are shifted to the reference temperature by shift factor and a master curve is generated at the reference temperature. This information is useful to predict the long term thermal aging of high modulus composite material for spacecraft application.
Highlights
Polymer matrix composite(PMC) materials play a key role in lightweight spacecraft structure[1] with high specific stiffness, corrosion resistance, design flexibility, reducing number of assemblies and fasteners, and high resistance to fatigue damage
High modulus pitch based carbon fibers are currently available with high thermal conductivity for satellite
Even though the creep behavior of composite material is sensitive to various space environment, the creep in this study is accelerated by temperature change while other variables are kept constant
Summary
Polymer matrix composite(PMC) materials play a key role in lightweight spacecraft structure[1] with high specific stiffness (modulus-to-density ratio), corrosion resistance, design flexibility, reducing number of assemblies and fasteners, and high resistance to fatigue damage. By proper arrangement of reinforced fiber, the optimum condition for dimensional stability can be achieved This is important since the mechanical and dimensional stability during transport into orbit and flight through the earth' shadow is required for an often lengthy mission. The long-term performance of composite materials must be investigated to understand the degradation of properties during the intended service life of the spacecraft[2]. The degradation of polymer matrix composites comes from radiation, temperature, thermal cycling, atomic oxygen, micrometeoroids, and contamination. Thermal aging of epoxy matrix/high modulus carbon fiber composite materials are accelerated to predict the long term creep property. High modulus pitch based carbon fibers are currently available with high thermal conductivity for satellite. Even though the creep behavior of composite material is sensitive to various space environment, the creep in this study is accelerated by temperature change while other variables are kept constant
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