A new fractal model for predicting the permeability of satin fabrics is proposed mainly based on the fractal theory. The repetitive unit was selected first according to the structural characteristic of a fabric. Then, the tortuosity fractal dimension was figured out after the actual length of a pore channel calculated by the minimum potential energy method. The maximum equivalent diameter, on which the structure fractal dimension can be computed depends, was obtained later by the microscopic measurement technique. Subsequently, the permeability was expressed as the explicit equation of various structural parameters, such as the representative length, the tortuosity fractal dimension, and the structure fractal dimension, which makes the physical meanings of each parameter intuitive and clear. Finally, the permeability of a five-harness fabric and an eight-harness fabric was predicted according to the new fractal models. In order to validate the new model, contrast experiments were designed. The results show that the predicted values agree well with the experimental values, which illustrate that the new method is feasible and effective.

We have studied the friction behavior based on liquid crystal (LC) alignment of a unique tribological system composed of a nematic LC and polyimide (PI). The LC was used as a lubricant and a tribological factor with molecular alignment ability. PI was used as both a rubbing pair part and a LC alignment agent. The LCs used as lubricants included the single LC 5CB and the mixed LCs 5CB–2UTPP3 and 3PEP5–3UTPP4. The PI used as the friction pair was 6FDA-ODA PI, and its counterpart was GCr15 steel. For this system, it was found that under the premise that the nematic phase temperature range of the selected LC meets the operating temperature of the friction test at a suitable ambient temperature, the operating speed and load are controlled to maintain a stable lubricating film thickness between the friction pairs during operation of the system. Moreover, by avoiding excessive or insufficient friction heat generated by the running speed being too high or too low to change the phase state of the LC, with the anchoring energy between the PI and the LC, the LC molecules will align in the rubbing direction, that is, they will arrange parallel to each other along the grooves, which can contribute to achieve superlubricity behavior.

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