Abstract
Most of the composite materials that are used in aerospace structures have been manufactured using a thermostable matrix, as epoxy resin. The region of stability of these polymers is defined by the glass transition temperature (Tg). However, operating temperatures close and above the Tg can cause a variation in the properties of the polymer and consequently, modify the mechanical properties of the composite material. Therefore, it is necessary to understand the failure mechanisms that occur in the material in order to ensure stability and durability. The effect of temperature and time of exposure on the impact and flexural mechanical responses of carbon/epoxy composites are studied in this work. For that purpose, ageing treatments at temperatures below and above the Tg have been considered and then, impact and flexural tests have been performed. It was observed that thermal ageing cause two different effects: at temperatures below the Tg, there is an increase of the maximum strength because of a post-curing effect; however, the mechanical properties decrease at higher temperatures of thermal ageing due to the thermo-oxidation of the epoxy resin and the loss of adhesion in the matrix/fibre interface.
Highlights
Fibre-reinforced composite materials have become relevant in aerospace, automotive, wind energy, marine and civil engineering applications due to their high specific strength, stiffness and fatigue performance [1,2,3,4,5,6]
Composite structures present an inherent sensitivity to environmental factors compared to metallic structures, so they must be designed considering the influence of factors such as moisture, temperature or UV radiation to ensure the reliability and safety of carbon fibre-reinforced polymer (CFRP) structures [7]
Thermal ageing of reinforced thermoset matrix composites is frequently associated with a physicochemical degradation of the resin that involves several changes on the thermomechanical properties of composites [8]
Summary
Fibre-reinforced composite materials have become relevant in aerospace, automotive, wind energy, marine and civil engineering applications due to their high specific strength, stiffness and fatigue performance [1,2,3,4,5,6]. Composite structures present an inherent sensitivity to environmental factors compared to metallic structures, so they must be designed considering the influence of factors such as moisture, temperature or UV radiation to ensure the reliability and safety of CFRP structures [7]. In many applications, such as aeronautical components, one of the greatest concerns is associated with the long-term ageing effect, since oxidation strongly affects the properties of the polymer matrix, particularity failure performance. Glass transition temperature (Tg ) of a thermoset polymer defines the region where the material present high stability in mechanical and thermal
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