ABSTRACT
A more realistic compression unit, used in many experiments, is a piston-in-cylinder compression cell [194,195,196]. Dunlop [194] employed the piston-in-cylinder apparatus to estimate the van Wyk’s model parameters. He stated that there was considerable difficulty in obtaining the parameters required to characterise the compression properties of wool by means of conventional piston-in-cylinder apparatus. Young and Dricks [196] studied the energy required to compress wool fibres from the initial volume vo to the final volume v. They adapted the conventional method of conducting compression tests on fibrous masses by employing a ‘piston-in-cylinder’ arrangement, as shown in Figure 33. They performed the experiments and measured the energy required for the compression of samples from the load compression and relaxation curves. Although they claimed that boundary friction effects were eliminated by using pressure plate, the fibre-to-metal (cylinder wall) friction effect was still in the experiment. Therefore, the results are also overestimated due to the friction between the fibres and the cylinder wall. However, the method is potentially useful for estimating the compression characteristics of fibres. On the other hand, Yuksekkaya and Oxenham [197-202] proposed another type of compression-testing unit to measure the frictional properties of fibres. The instrument is a basic piston cylinder application with high sampling data acquisition connection. Figure 34 shows the picture of their proposed instrument. In their experiment, they have reported that it would be possible to distinguish the surface differences on fibre samples.
