Carbon/carbon composites are widely used in re-entry engineering applications thanks to their excellent mechanical properties at high temperatures, but they are easily oxidized in the oxygenated atmosphere. It is important to research their residual mechanical properties influenced by oxidation behaviour, in order to ensure the in-service safety. A microscale degradation model is proposed to predict the oxidation behavior based on the mass conservation and diffusion equations, the derived equivalent steady recession rate of composite is employed to evaluate the residual mechanical properties of the oxidized composite theoretically. A numerical strategy is proposed to investigate the oxidation mechanism of this composite. The differences in the degradation rate between the fiber and the matrix resulted in the steady state and an unchanged shape of the front. Residual mechanical properties of composite with three different domains of oxidation were simulated with a multiscale coupled model. The numerical results demonstrated that the mechanical properties of this composite decreased by 24–32% after oxidation for 30 min at 850 °C. Oxidation also caused the stress redistribution inside components, with the stress concentration diminishing their load-bearing capacity. The local areas of increased stress in the pyrocarbon matrix provided new ways for diffusion of oxygen into the pyrocarbon matrix and fibers.

Oxidation behaviour and residual mechanical properties of carboncarbon composites
    Abstract
        Graphical abstract
    1 Introduction
    2 Microscale oxidation mechanism
    3 Mesoscale oxidation mechanism
    4 Mass-loss model based on volume fractions of components
    5 Residual mechanical properties after oxidation
        5.1 Residual elastic modulus
        5.2 Residual tensile strength
    6 Experimental analysis
    7 Calculated results and discussion
        7.1 Oxidation behaviour
        7.2 Mechanical behaviour
    8 Conclusions
    Acknowledgements 
    References

• Meng Han(Faculty of Civil Engineering and Mechanics, Jiangsu University, Zhenjiang 212013, People’s Republic of China)
• Chuwei Zhou(State Key Laboratory of Mechanics and Control of Mechanical Structures, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, People’s Republic of China)
• Vadim V. Silberschmidt(Wolfson School of Mechanical, Electrical and Manufacturing Engineering, Loughborough University, Loughborough LE11 3TU, Leicestershire, UK)
• Qinsheng Bi(Faculty of Civil Engineering and Mechanics, Jiangsu University, Zhenjiang 212013, People’s Republic of China)