Fiber induced time-lag during water droplet adsorption on carbon fiber reinforced silicon carbide (C/SiC) surfaces

Many of the advantages that make C/SiC functional materials desirable are also largely responsible for the machining difficulties encountered. The time-lag of water droplet adsorption (WDA) arised from the complex fabricated carbon fiber precast body may cause cooling condition deterioration in near dry machining of C/SiC, which then gives rise to a lower machinability with respect to the surface integrity. However, little attention has been devoted to the fiber induced time-lag of WDA on C/SiC surfaces. In this study, theoretical models of WDA of two typical C/SiC surfaces, namely, pillar fiber ending and circle fiber ending C/SiC surfaces, were first established. Uni-directional C/SiC was fabricated to experimentally simulate the WDA process on these two typical surfaces. The complete WDA process on a single sample was analyzed first. Considering the stochastic shape of the flow channel, WDA experiments conducted on two typical C/SiC surfaces were repeated 2000 times. The frequency occurrence of the water droplet adsorption time (WDAT) of these 2000 experiments was fitted using the normal distribution function. The statistical evaluation methods indicated that the WDAT of a pillar fiber ending C/SiC surface lagged behind the WDAT of a circle fiber ending C/SiC surface. Furthermore, the time-lags were dependent on both the volume of the water droplet volume and increase in temperature. A critical discussion was conducted regarding the prevention of the WDA time-lag on C/SiC surfaces, and it is suggested that reducing the tiny droplet diameter of cooling mists and spray mists in advance and properly improving the cutting heat can limit, to some extent, the fiber induced time-lag of the WDA of C/SiC surfaces, which is an important factor for optimizing the cooling supply of near dry machining of C/SiC composites.